Last successful backup of WhatsApp to iCloud was on 10th April 2019, since then the process keeps hanging.  My iCloud is as good as unused, it has 4.5 GB/5 GB available, so I doubt space is the issue.  Status is "Backing up..." and its hung at "Uploading: 0%"  What did I try:   Updated iOS to 12.3.1. Updated WhatsApp to version 2.19.61. Deleted WhatsApp data from iCloud Drive and tried to backup again. Instead of getting stuck at 0% it then got stuck at 3%. In iCloud Drive, turned WhatsApp "Off" and "On" Hard reset on iPhone   Nothing works! Anyone tips or the same problem?

I am not sure if this is the case, but when you do iCloud Backup of your phone, it will backup Whatsapp. ( I am unsure if this include the Photos and Video )   Then Whatsapp itself has backup option to backup itself in iCloud Drive Backup.   Is that a double Backup? Because i see 2.1GB inside the iCloud Backup, and then 1.7Gb inside document and settings.


I performed a dose-response experiment and I have estimated the LC50 and a confidence interval. I've been asked to provide results expressed in several units (mg/kg and mg/L).  I assume that I can transform my LC50, but I'm not sure about what happens with my confidence limits, as variance is implied in their calculation. However, . Sorry if this is a too basic question, but can I simply transform them as I do with my LC50?  That is, if (a) I transform my confidence limits from mg/kg to mg/L and (b) I fit a new regression on the mg/L values, will I obtain the same LC50 and the same confidence limits? Why?  Edit: I estimated the LC50 by a probit regression. CI calculations are based on Fieller's theorem.

Purpose: Construct a 95% confidence interval for $\theta$.   A common strategy is to construct a confidence interval for $\log(\theta)$ and then exponentiate.  Why is it valid?   My concern is that $E(\log(\theta)) \neq \log(E(\theta))$ and $Var(\log(\theta)) \neq \log(Var(\theta))$...   Do people use this back transformation because it has proven to work fine? What about other transformations (e.g. logit)?


I want to access the sql server using the amazon web services. How do I do it? I have tried this using mysql.connecter in python.  import mysql.connecter conn=mysql.connector.connect(host="hostname",database="datbasename",user="root",password="a") if conn.is_connected():     print('connected to mysql database')

How do I connect to a MySQL database using a python program?


Strangely, when deleting a list of comments on my post (my comments) it says something along the lines of not being able to vote on comments for five seconds.  Since there was only three comments total (two mine, one another user's) even if I did vote, it wouldn't make sense because there is only one comment that I'm allowed to vote on, and since not being able to vote every 5 seconds implies that there was more than one comment that I could vote on, which is false.  I'm using the latest version of Google Chrome on Mac OS X, if that helps.  EDIT: Just found this question:

I had an old question that I revisited in order to link it in a new answer. I noticed that in the comments Steven A Lowe had a funny comment that I -- at the time -- had responded to with "why can't I upvote comments?"  Well, of course, now I can.  So, I voted Steven's comment up then went to delete mine. I got the warning box that I can only submit comment votes once every 5 seconds. This seems like a bug to me. Deleting is not the same as voting.


if I leave my sour tasting oranges in the refrigerator will they ripen and turn sweet?

Sometimes when I buy oranges or grapefruits I find out that they are rather unripe when I get them home. How do I ripen them?


I submitted a paper about 20-25 days ago in this conference  knowing about IEEE involvement here.  Today I have got an acceptance email for my paper, The astonishing thing to me is, I knew at least 1-2 month is required to review this type of conference paper.  The conference date is 8 September, 2017 which is very near. Is there anyone who can assure me that this conference is not scam?

I recently received an invitation to a conference and I'm trying to determine how reputable it is. Is there a good way to go about this?


I have this issue when I search to install Gimp:  $ sudo apt-get install gimp  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  gimp : Depends: libgimp2.0 (>= 2.10.18) but it is not going to be installed         Depends: libgimp2.0 (<= 2.10.18-z) but it is not going to be installed         Depends: libgegl-0.4-0 (>= 0.4.22) but it is not going to be installed E: Unable to correct problems, you have held broken packages.   Nothing change after apt update & upgrade. Do you have a solution for me? Thanks to  Best,

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


I know this is a common problem but even after like four days of reading through different forums I wasn't able to fix it. I'm fairly new to Linux, by the way, so sorry in advance. Here's the situation:  I have an old Toshiba Satellite C660 with Windows 7. A week ago I installed Ubuntu 16.04 as the second OS, using the method of creating a new partition by shrinking an existing one. Even though Ubuntu installed just fine, ever since that time when I start the laptop I have about 50% chance of just getting a black screen. No BIOS splash screen, no recovery mode, nothing. I have to do a hard reboot and then it starts normally, BIOS splash screen, then grub loader etc. The weird thing is, it really only happens in about 50% of cases and at other times it boots normally. Even though I can always start the system eventually by doing the hard reboot, it's very annoying.  What I tried so far: Boot-Repair on recommended mode Updating / reinstalling the grub Editing the grub file in different ways (quiet splash, nomode set, etc.)  I don't know if it's related but my brightness keys don't work either.   I use integrated graphics: Mobile Intel® GM45 Express Chipset.  The output of sudo lshw -c display:  *-display:0                     description: VGA compatible controller        product: Mobile 4 Series Chipset Integrated Graphics Controller        vendor: Intel Corporation        physical id: 2        bus info: pci@0000:00:02.0        version: 07        width: 64 bits        clock: 33MHz        capabilities: msi pm vga_controller bus_master cap_list rom        configuration: driver=i915 latency=0        resources: irq:29 memory:f2800000-f2bfffff memory:d0000000-dfffffff ioport:1800(size=8) memory:c0000-dffff   *-display:1 UNCLAIMED        description: Display controller        product: Mobile 4 Series Chipset Integrated Graphics Controller        vendor: Intel Corporation        physical id: 2.1        bus info: pci@0000:00:02.1        version: 07        width: 64 bits        clock: 33MHz        capabilities: pm bus_master cap_list        configuration: latency=0        resources: memory:f2100000-f21fffff   Thank you guys in advance for any help. Apart from this issue I'm having a blast using Ubuntu and learning all this new stuff, it's really awesome.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I am getting an error when I try to access my NTFS drive from ubuntu.  Unable to access “My Drive”  Error mounting /dev/sda6 at /media/ubuntu/Media Center: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000,dmask=0077,fmask=0177" "/dev/sda6" "/media/rolindroy/Media Center"' exited with non-zero exit status 14: The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Failed to mount '/dev/sda6': Operation not permitted The NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting), or mount the volume read-only with the 'ro' mount option   Any help would be greatly appreciated!

Whenever I boot Ubuntu, I get a message that it cannot mount my windows partition, and I can choose to either wait, skip or manually mount.  When I try to enter my Windows partition through Nautilus I get a message saying that this partition is hibernated and that I need to enter the file system and properly close it, something I have done with no problem so I don't know why this happens.    Here's my partition table, if any more data is needed please let me know.     Device Boot      Start         End      Blocks   Id  System /dev/sda1            2048    20000767     9999360   83  Linux /dev/sda2        20002814   478001151   228999169    5  Extended /dev/sda3   *   478001152   622532607    72265728    7  HPFS/NTFS/exFAT /dev/sda4       622532608   625141759     1304576   82  Linux swap / Solaris /dev/sda5        20002816   478001151   228999168   83  Linux


Take these two sentences for example:     This is to compensate for the fluctuating character length in the sentence.   vs.     This is to compensate for the fluctuating characters length in the sentence.   Which is correct? I would assume the latter but it sounds a bit awkward when spoken compared to the former.

Sorry for the title, it is not very evident and intuitive but I really do not how to tell it better...  Well, you know, several times, or better, many times, we use this form:  If I want to say:      "development of special weapons was   the first point in Hitler's   program..."   I will say this (a better form):      "special weapon development was..."   OK...  is it      "special weapon development"   or      "special weapons development" (note   the plural...)   what's the grammar rule in order to understand how to use this very used form?


$$z=(1+i)^{1+i}$$  I'm having trouble with this one. I got as far as the below, but then I got stuck. Could someone give me a hint??  $$\ln(z)=(1+i)\ln(1+i)$$    After reading the hints + suggested answer:  $$z=(1+i)^{1+i}$$ $$z=e^{(1+i)ln(1+i)}$$ $$z=e^{(1+i)ln|1+i|+(arg(1+i)+2\pi k)i}$$ $$z=e^{ln(\sqrt{2})+\pi i/4+2\pi ik+iln(\sqrt{2})-\pi /4-2\pi k}$$  Is it ok to leave my final answer like this?

The question says to find all the values of $(1+i)^{(1-i)}$  I have trouble figuring out firstly, exactly what values are being looked for. I can toy around with the equation a bit to try to make it look "acceptable" (i.e $ax + byi$ format) but get stuck along the way. So I need help with:  a) figuring out what values are needed. i.e. what does the question $mean$ and some brief background or diagram that explains, in a practical sense, what I'm supposed to be looking for.   b) the algebra that can lead me to a reasonable solution.  --  MY ATTEMPT:  $$ (1+i)^{(1-i)} = (1+i)^{(1-i)}.\frac{(1+i)^{(1+i)}}{(1+i)^{(1+i)}} = \frac{(1+i)^2}{(1+i)^{(1+i)}} = *$$  *is where I get stuck.


Let me start by saying that I'm aware you're supposed to capitalize the first letter after an apostrophe at the beginning of the sentence. My question is can I not. I have this inspiring piece of dialogue: “’kay" and I really much prefer it with the 'k' lowercase. Is that completely incorrect, or can I make the stylistic choice?

A new Victorian-set British novel begins sentences containing h-dropping with lower-case e's, as in " 'e took my money, 'e did." This seems incorrect but I'm at a loss to find the rule.


This is a long shot, but wondering if anyone can help. Trying to recall a sci-fi author. One of his books was about a world that was all vertical, people lived on this eternal cliff (I think they caught up-draughts and down-draughts to go up and down the cliff).   Another story by the same author was about a criminal who was imprisoned in a giant, inescapable structure in distant space (I think that had a red cover).

I'm trying to find a book about a city built on the side of an infinite wall - infinitely tall as well as infinitely long. There was a picture of it on the cover. The city is built on platforms jutting out, and if you fell off, you'd be gone forever. Unfortunately, I can't remember the title, the author, the publisher or anything else but the setting, but I think the plot might have been a detective story.


What are the logical reasons to place following action buttons at the left side or the right side of the form?

We have been puzzling over where to put the submit button, on the left or the right. In researching, we noticed that many sites put buttons on the bottom right in dialogue boxes, and on the bottom left in forms.  It makes sense: in a dialogue box it seems to denote finality, being in the endpoint of the window for left–right readers; in a form, the bottom right could be in a different position relative to the rest of the form if the window is resized.  It seems to be a convention, but I don't see anyone talking about this specific phenomenon in the following questions, nor the articles referenced therein:        So, is this level of button position optimization worth it if it creates an inconsistency in button placement? Is this a good way to go?


More precisely, let $F_1, F_2$ be fields, and we have none zero homomorphisms $f: F_1 \to F_2$ and $g: F_2 \to F_1$ (actually both are monomorphism since $F_1, F_2$ are fields), is there a possibility that $F_1$ is not isomorphic to $F_2$?

My question has been asked for groups I think, but there are no free fields, and fields seem more rigid than groups, so I feel like here the answer may be positive.  The question is the following : suppose we have field morphisms $L\to K\to L$ (I don't know if this is the used convention but I take my morphisms to have $f(1)=1$; and so they are embeddings), must we then have $L\simeq K$ ?   Now obviously the first thing is that, as in Cantor-Bernstein's theorem, the morphism $L\to K$ need not be itself the isomorphism (consider the field $\mathbb{Q}(X_n)_{n\in \mathbb{N}}$ which has plenty of non surjective embeddings into itself). So one would have to construct the isomorphism, not prove that the given morphisms are isomorphisms.  More generally, the question that naturally arises from this is : given a class of universal algebras (of one given type), under what conditions do we have "$A$ can be embedded in $B$ and conversely $\implies A\simeq B$" ?   The answer for the class of fields is the answer to my first question, and for the class of groups, the answer is no (see the question "When can two groups be embedded in eachother ?")


First of all excuse me for this stupid question. This is something with that I am stuck and didn't get anything around.  I am in need of decimal format where if value is something like-  15000.45 should go to => 15,000 150000.44 should go to => 150,000   Note-  I want to eliminate points value after period (.)  I've gone through input mask-   but couldn't find any helper mask.  Another resource I tried-     But they are replacing point value replaced by comma, i.e. if value is something 15000.34 then it converts it to 15000,34  I also tried it giving custom format as-  value.ToString("0,00") but doesn't help.  Please assist!

I want to add a comma in the thousands place for a number.     String.Format()?


I have this table:  CREATE TABLE [Entree] (     [RowId] [int] IDENTITY(1,1) NOT NULL,     [Name] [nvarchar](250) NOT NULL,     [Description] [nvarchar](250) NULL,     [FK_InspirationSource] [int] NOT NULL,     [Type] [int] NOT NULL,     [PriceRangeType] [int] NOT NULL,     [SoldCount] [int] NOT NULL,     [HolidaySpecial] [bit] NULL,     [DiscountApplicable] [bit] NULL,     [DateCreated] [datetime] NULL,     [LastModified] [datetime] NULL,     [Enabled] [tinyint] NOT NULL,     [BirthDate] [smalldatetime] NULL,     [IG_Int1] [int] NULL,     [IG_Int2] [int] NULL,     [IG_Int3] [int] NULL,     [IG_Int4] [int] NULL,     [IG_Int5] [int] NULL,     [IG_Int6] [int] NULL,     [IG_Int7] [int] NULL,     [IG_Int8] [int] NULL   and in C# code, corresponds to a Entree object with the respectable fields. IG_Int s specify bunch of other properties of the entree in cooking process.  Now, we want to have Derived_Entree objects. In the code, DerivedEntree is an Entree too. So DerivedEntree : Entree.   DerivedEntree has more columns. ParentEntreeId (FK to Entree), ExtraProcessingStep.   So for example, an entree would be "Snail Ravioli" and Derived Entree would be "Broiled snail ravioli".   If there were a separate table, it would be  CREATE TABLE [DerivedEntree] (     [RowId] [int] IDENTITY(1,1) NOT NULL,     [FK_Entree] [int] NOT NULL,     [ExtraProcessingStep] [int] NOT NULL )   and add FK_DerivedEntree in Entree table.  So whenever a new entree is entered, a row is inserted to the Entree table, and when a new DerivedEntree is entered, it is inserted to both tables. This is to satisfy the requirement that every Entree has to have a unique Id (which will be a RowId in Entree table)  Instead of adding a separate table, another option is to add those two columns (FK_Entree and ExtraProcessingStep) to the Entree tables and store them there.  What is a more standard practice? I thought about adding additional table because of FK_Entree but perhaps having a foreign key to itself is a common practice?

What are the best practices for modeling inheritance in databases?  What are the trade-offs (e.g. queriability)?  (I'm most interested in SQL Server and .NET, but I also want to understand how other platforms address this issue.)


I've been asked to show that if $G$ is a non-abelian group of order $p^3$, then the derived or commutator subgroup is equal to the centre, $G'$=$Z(G)$. I know that since $G'$ is a subgroup of $G$, it must have order $1$, $p$, $p^2$ or $p^3$. If I can show that |$G'$| = $p^2$, then it is abelian and a maximal proper subgroup, so it must be the centre of $G$. However I'm unsure of how to go about proving this. Thanks for your help.

Let $p$ be a prime number and $G$ a non abelian group or order $p^3$. Prove that $Z(G) = [G,G]$.   I have already figured out that $|Z(G)| = p$, and that $G'=[G,G] \lhd G$.  Also, $|G'| = p$ or $p²$.  I suppose I'd have to prove that $G' \subset Z(G)$, but I've been trying and I have no idea how. Any hints? Thanks!


I have Woocommerce shop with several product categories, custom taxonomies and ACF meta fields. So one product has one category, terms of taxonomies and meta fields values.   For example, we have categories "Washing machines" and "Fridges" and taxonomy "Brand" with terms "Siemens", "Bosch". On product page with specific category or specific category page I need to show terms of taxonomy "Brand", that have products in this specific category. So, on every page I should check the current category and list only nesessary taxonomy terms.  Meta fields are configured to show only in one product category, so we can say, that one ACF field is attached to one category. But taxonomies are attached to the whole post type.  So, the problem is how to quickly get the terms of taxonomy from posts that have specific term of another taxonomy? I can get posts by special query like that  $args = array( 'post_type' => array('post','reviews'), 'paged' => $paged, 'tax_query' => array(   array(     'taxonomy' => 'category',     'terms' => 'android',     'field' => 'slug'   ),   array(     'taxonomy' => 'review_category',     'terms' => 'android',     'field' => 'slug'   ), ) ); query_posts($args);   But I can't do this query on every page load. Is there an easier way to solve the problem?

So I have custom taxonomy called "shape" and another one called "color". If I want to get the list terms under shape that contain posts that are also present in terms under color, how do I do that?   Example, I have a post under custom post type toy called Ball which is present in both shape Circle and color Red. I want to retrieve the term name Circle via $wpdb query. I'd like to emphasize that I want to retrieve the list of terms and not the posts.


I am a Filipino citizen in Jeddah, Saudi Arabia, and booked for a holiday trip to Costa Rica.    My flight is     Jeddah -> Madrid via Saudi Airlines 24 hour layover Madrid -> SJO (Costa Rica) via Iberia     My return trip is  - SJO (Costa Rica) -> Madrid via Iberia  - layover  - Madric -> Jeddah via Saudi Airlines  I will be entering and leaving Madrid twice during the round trip flights.    I  would like to know what type of Schengen visa is appropriate to apply for me to pass Madrid twice with out any hassles in Madrid airport immigration?

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


There are some SE sites I am simply not at all interested in, and never will be.   Is it possible for me to filter certain sites from showing up in the Hot Network Questions list, and if not, can this be considered?  Perhaps a setting in the profile?  Also, once I view a certain Hot Question - Can it be prevented from showing up in the future days?

I was going to make a filter for the "" by excluding some sites from it.  I noticed  which talks about "negative filtering" but does not explain how one can do it or if it is possible.  There does not seem to be a way to do this, though.  On the filter page, my only options are:  So how can I do "All sites except [list]"? It would also be nice if this could include similar functionality with the meta checkbox.  Something like "All main & meta sites except..."


I want to prove that each element of the "Proper Lorentz group" , defined below $O_{\uparrow}^{+}(1,3) = \{\Lambda \in O(1,3) | \det (\Lambda) = 1 , \Lambda_{00} \geq 1 \}$ has an inverse and it is closed with respect to multiplication. For proving that each element has an inverse, I should prove if $\Lambda_{00} \geq 1$ then $(\Lambda^{-1})_{00} \geq 1$ ? It seems strange, How can I prove this? any hint? I also have the same problem with multiplication. Plaese help me.

Orthochronous Lorentz transform are Lorentz transforms that satisfy the conditions (sign convention of Minkowskian metric $+---$) $$ \Lambda^0{}_0 \geq +1.$$ How to prove they form a subgroup of Lorentz group? All books I read only give this result, but no derivation.  Why is this condition $ \Lambda^0{}_0 \geq +1$ enough for a Lorentz transform to be orthochronous?  The temporal component of a transformed vector is  $$x'^0=\Lambda^0{}_0 x^0+\Lambda^0{}_1 x^1+\Lambda^0{}_2 x^2+\Lambda^0{}_3 x^3,$$ the positivity of $\Lambda^0{}_0$ alone does not seem at first glance sufficient for the preservation of the sign of temporal component.  And how to prove that all Lorentz transform satisfying such simple conditions can be generated from $J_i,\ K_i$?    For those who think that closure and invertibility are obvious, keep in mind that $$\left(\bar{\Lambda}\Lambda \right)^0{}_0\neq \bar{\Lambda}^0{}_0\Lambda^0{}_0,$$ but instead $$\left(\bar{\Lambda}\Lambda \right)^0{}_0= \bar{\Lambda}^0{}_0\Lambda^0{}_0+\bar{\Lambda}^0{}_1\Lambda^1{}_0+\bar{\Lambda}^0{}_2\Lambda^2{}_0+\bar{\Lambda}^0{}_3\Lambda^3{}_0.$$  And I'm looking for a rigorous proof, not physical "intuition".


Let order of a group be $108$. Show that there exist a normal subgroup of order $27$ or $9$.  Can we solve without sylow's throrems ? And by sylow's..i need both methods. Thanks

Exercise from Herstein:Abstract Algebra.   Please do it without group action as I don't know it. In Herstein there is no mention of Group Action as in the answer given          Show that a group of order $108$ has  a normal subgroup of order $9$ or $27$.      Attempt: $108=2^2\times 3^3$. If $n_2$ denotes the number of Sylow $2$ subgroups then $n_2=1+2k| 27\implies n_2=1,3,9,27.$  If $n_3$ denotes the number of Sylow $3$ subgroups then $n_3=1+3k| 8\implies n_3=1,2,4,8.$  If $n_3=1\implies $ the group has a normal subgroup of order $27$ but how to neglect the other choices.  I am confused totally .Please help.


A question says:      "Which $n \in \Bbb N$ should the numbers $1991$, $1805$, $2146$ be divided into, so that there will be the same remainders left?"   I arranged them in order: $1805,1991,2146.$ Then did subtraction: $1991-1805=186,$ $2146-1991=155,$ then $186-155=31.$ This last result is the answer. But I am skeptical about my way of finding the answer (and which seems to be a little bit stranger to me), as it wouldn't work in some cases. I would like  1) to know your thoughts on my method, 2) you to provide some hints in order to show the right way of solving this.

If three numbers 112, 232, and 400 are each divided by the number D, each of their quotients will have the same remainder R. Find R where R>1  How should I approach this?


I am having issues with a data layer that is not lining up with my other data layers!  What do I do?    I have all the parcel polygons, parcel pts. Jurisdiction polygons from Ashtabula county that all line up (I received these data layers all from the same source...from Ashtabula county).  Then I bring in a data layer for street centerlines from OGRIP (where I have obtained all my other street centerline data from that works great!)    How do I get these to work?  The extents on the street centerline data are completely different from the other data layers.    The projected coordinate systems are the same in all the layers?

I put 4 different layers into my ArcMap document, but only one of them will show up on the map! I should be seeing the other 3 layers as well. When I do a Zoom to layer, I can see one layer, but I cannot figure out how to make the other 3 show up at once on top of each other.  Before I opened ArcMap, I used ArcCatalog where I right-clicked 3/4 of the shapefiles and  clicked Properties → Coordinate system → Import and then clicked on my Trees layer, which has the coordinate system I want the other 3 to have. But when I opened ArcMap the 4 layers did not overlap, nor could I move them above or below each other.


I have a really big city in Minecraft, but I carelessly went to the Nether and lost my portal!   I am really far away from it. I have been wandering for days!   I don't have a duplicate of my lux city and I would want to find it because I spent months making the city.

No, actually I didn't, but that was a close call and I'm really curious how would one go about that one.  On my third or fourth visit to the Nether, I still didn't realize the risk, and didn't place marks that would help me get back to the origin (currently I like to use flint and iron to create big flaming arrows towards the exit, visible from afar.) I wandered past one hill, and then I couldn't locate the place I came from. I wisened up and started placing marks in form of torches, towers of netherrack with glowstones on top etc. The bunch of wood I had in my stash has proven invaluable as I ran out of steaks, and had to craft a bowl and start making mushroom soup. I realized the fastest way back would be to simply die, but since I had no clue where I was, that would mean losing my quite precious equipment, which cost me a lot of time and effort to gather and enchant, for that trip specifically. I also knew I had traveled rather far from the portal before starting placing marks, so the chances of finding it again by going in any random direction were rather slim.  By sheer luck I found one of the caverns I had explored before, and found my way back, but that was really a close call and I'd prefer to know any hints what to do in Nether if you're already lost (no Obsidian to build a new portal, not willing to die and forgot the direction to the exit.)


There’s a question about , but the answer does not include LaTeX2e. Searching for “LaTeX2e”, “LaTeX2e lettering” or “LaTeX2e writing” didn’t yield the answer, and neither did trying out the commands \LaTeX2 and \LaTeX2e.  How to set LaTeX2e (and while we’re at it: LaTeX3) in a document?

I'm looking after a macro to write the (La)TeX logo (with parentheses), i.e. something similar to \TeX, \LaTeX, but where the output includes ()'s.


I'm changing the default setting for arp_ignore on an ubuntu 16.04 server, from it's default value 0 to 1.  My understanding of the /proc/sys/net/ipv4/conf/ directory is that files under all will affect all interfaces, and default will affect newly created interfaces.  After changing the value of /proc/sys/net/ipv4/conf/all/arp_ignore to 1, the other files are still set to 0:  cat /proc/sys/net/ipv4/conf/*/arp_ignore 1 0 0 0   Does the value of /proc/sys/net/ipv4/conf/all/arp_ignore just override the interface specific files rather than changing their values?

In sysctl, the /proc/sys/net/ipv[46]/conf/ keys have the following subkeys: all, default, and a key for each network interface. For example, on a machine with a single network interface eth0, it will look like this:  iserv ~ # ll /proc/sys/net/ipv[46]/conf/ /proc/sys/net/ipv4/conf/: insgesamt 0 dr-xr-xr-x 0 root root 0 12. Sep 23:30 all/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 default/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 eth0/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 lo/  /proc/sys/net/ipv6/conf/: insgesamt 0 dr-xr-xr-x 0 root root 0 12. Sep 23:30 all/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 default/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 eth0/ dr-xr-xr-x 0 root root 0 12. Sep 23:30 lo/   All the respective settings exist in each key separately. For example, if I want to disable IPv6 Router Advertisements with the accept_ra value, this value exists four times:  iserv ~ # sysctl -a 2>/dev/null | grep "accept_ra " net.ipv6.conf.all.accept_ra = 1 net.ipv6.conf.default.accept_ra = 1 net.ipv6.conf.lo.accept_ra = 1 net.ipv6.conf.eth0.accept_ra = 1   My question now is: which of these values do I need to change? I figured all (to change all existing interfaces) and default (to change all new interfaces that may appear later), but changing these still leaves the value at 1 for lo and eth0:  iserv ~ # sysctl -w net.ipv6.conf.all.accept_ra=0 net.ipv6.conf.all.accept_ra = 0 iserv ~ # sysctl -w net.ipv6.conf.default.accept_ra=0 net.ipv6.conf.default.accept_ra = 0 iserv ~ # sysctl -a 2>/dev/null | grep "accept_ra "   net.ipv6.conf.all.accept_ra = 0 net.ipv6.conf.default.accept_ra = 0 net.ipv6.conf.lo.accept_ra = 1 net.ipv6.conf.eth0.accept_ra = 1   Will the machine now accept Router Advertisements on eth0, or will it not?


How could the following integral be solved in a good manner?  $$\int \frac{\sin(x)}{x}\;\mathrm{d}x$$  Regards:

I want to know if the function sinx/x is integrable and if it is, then what's its integral?  My high school book says its a non-integrable function while WolframAlpha says its integral is Si(x) + constant   Please shed some light on this topic and explain from basic level like what is Si(x), who used it for the first time etc.


I'm on a network with two internet connections. One is a WAN access to a corporate network (with custom firewall rules), the second is a direct internet connection.  By default, all communications are directed to the wan connexion (default route to the wan router). I can set up routes to the direct internet connexion, based on a classic target network/ip/mask to a specific router.  Is it possible to have a custom route for a specific application, and not a specific IP adress ? In fact, I don't know what are the outbound IP addresses used by the APP, and I have to make it use directly the internet connection. The application unfortunately does not support proxy server (and the protocol is proprietary).

Suppose network interface 1 (net1) and 2 (net2) are both connected to the Internet. I want application 1 (app1) to use net1, and application 2 (app2) to use net2. How can it be done under Windows?  If you need a concrete example of the above situation, consider:   A laptop with Windows 7 net1 = A wired connection to a Verizon Internet modem net2 = A wireless connection to a Comcast Internet modem app1 = Internet Explorer app2 = Firefox I'd like to have "IE use Verizon but not Comcast", and "Firefox use Comcast but not Verizon"   It doesn't have to be done via the routing table. If you've other ideas, please let me know!


I have a simple html snippet.

Click Symptom

Click Remedy

  Now for the click action... $(document).on("click", ".hit", function (ev) { if($(this).parents(".symptom"))     alert("Symptom Clicked"); if($(this).parents(".remedy"))     alert("Remedy Clicked"); });  $(this) is supposed to refer only the element that I have clicked. Why does it alert both the alert statements even if the if conditions do not satisfy?

How can I check the existence of an element in jQuery?  The current code that I have is this:  if ($(selector).length > 0) {     // Do something }   Is there a more elegant way to approach this? Perhaps a plugin or a function?


WARNING: Graphic  All I remember about this fantasy horror book is the following:  There is a killer that can stop time. He is searching (or chasing) the protagonist. There is one graphic sequence, where the killer stops time, and is going after the main hero, and the world around them is frozen - they move past frozen people, and the killer rips off their limbs and such (I think there is also reference to how much pain they will feel once they "wake" up).  I was reading S.K and Koontz at the time, but I don't know if it was either of them. I think the book had the word "train" in the title...  P.S.: If this is the wrong place  to ask, can someone refer me to the proper one? I've been meaning to find this out for a long time, but always put it aside.

I read the story over ten years ago while I was still trying to learn English, so I can only vaguely remember that the story is about a cop trying to track down a criminal who had superhuman abilities. Some of his abilities were pyrokinesis, using his mind to form a golem from earth and roam around while he stays in the room and stopping time. Eventually the cop was able to catch the criminal and shot him dead.   If anyone could identify the book I would be very grateful. I'd love to read it for nostalgic purposes.


fids@fids-NDiSM323:~$ java-version java-version: command not found fids@fids-NDiSM323:~$ java -versin The program 'java' can be found in the following packages:  * default-jre  * gcj-4.6-jre-headless  * gcj-4.7-jre-headless  * openjdk-7-jre-headless  * openjdk-6-jre-headless Try: sudo apt-get install <selected package> fids@fids-NDiSM323:~$ sudo apt-get install default-jre [sudo] password for fids:  Reading package lists... Done Building dependency tree        Reading state information... Done Package default-jre is a virtual package provided by:   oracle-java9-installer 9b111+9b111arm-1~webupd8~1   oracle-java8-installer 8u77+8u77arm-1~webupd8~4   oracle-java6-installer 6u45-0~webupd8~8   oracle-java7-installer 7u80+7u60arm-0~webupd8~1 You should explicitly select one to install.  E: Package 'default-jre' has no installation candidate

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


Having HTML code

   with CSS styles  * {     border: none;     margin: 0;     padding: 0; } table {     position: absolute;     left: 50%;     top: 50%;     width: 110px;     height: 92px;     margin-left: -55px;     margin-top: -46px; } img {     width: 110px;     height: 92px; }   accessible in ,  I would expect to have no margin, no padding and no border in the table content. However table height is not same as the image height. There are some extra pixels somewhere in td element.  What is a problem here? Is it style or html code?

I've created a map system for a game that runs on the principle of drawing the picture of the map from tiles. There are many reasons for this which I won't go into here but if you really want to know then I'm sure you can find out how to contact me ;)  I have  so you can see exactly where the problem lies and the source. The issue is the line between the top 2 tiles and the bottom 2 tiles, I can't figure out why it's gone like this and any help would be appreciated.  In the source is a marker called "stackoverflow", if you search for "stackoverflow" when viewing source then it should take you to the table in question.  I have also uploaded an .


I migrate from Ubuntu Server 14 to Ubuntu Server 16 I now I have problems because I'm not undertand that.   I hope that somebody can answer me.

A lot of my scripts stopped working after installing Ubuntu 15.10 and I have trouble remembering this new name as I was used to ethx and wlanx for years. Is there a reason for this change? Do I have to get used to this or can I just rename it and go back to good old eth0?  $ ifconfig  enp0s25   Link encap:Ethernet  HWaddr 77:5a:5e:a6:86:d5         inet addr:192.168.31.239  Bcast:192.168.31.255  Mask:255.255.255.0       inet6 addr: fe80::725a:b6ff:fea6:86d7/64 Scope:Link       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1       RX packets:4833 errors:1332 dropped:0 overruns:0 frame:666       TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0       collisions:0 txqueuelen:1000        RX bytes:3266446 (3.2 MB)  TX bytes:1046654 (1.0 MB)       Interrupt:20 Memory:d3500000-d3520000


According to , apt-get install sublime-text was the right way to install Sublime.  Unfortunately, I can't find it in Lubuntu 18.10.  user@linux:~$ sudo apt show sub subcommander            subiquity-tools         subread                 substance-flamingo-doc  subtle subcommander-doc        subliminal              subread-data            substance-swingx        subunit subdownloader           subliminal-nautilus     substance               substance-swingx-doc    subuser subiquity               submux-dvd              substance-doc           subtitlecomposer        subversion subiquitycore           subnetcalc              substance-flamingo      subtitleeditor          subversion-tools user@linux:~$    I've already updated the system (sudo apt update && sudo apt upgrade), but still can't find it. What seems to be the issue here?

I've just installed a fresh copy of Ubuntu 18.10 on my system. I updated the OS via sudo apt-get update and sudo apt-get upgrade commands. After that I installed Google Chrome.  These are the only things I've done prior to installing the Sublime Text 3 text editor .  I obtained the install commands from Sublime Text's download web page. Then I proceeded to install the editor using them.  wget -qO - https://download.sublimetext.com/sublimehq-pub.gpg | sudo apt-key add - sudo apt-get install apt-transport-https echo "deb https://download.sublimetext.com/ apt/stable/" | sudo tee /etc/apt/sources.list.d/sublime-text.list sudo apt-get update sudo apt-get install sublime-text   The installation completed without any hiccups, but when I try to launch the application, it fails to do so.    You can see on the taskbar that the application is starting up, and the mouse pointer shows the loading animation (that doesn't show up on the screenshot though), but Sublime Text 3 doesn't start.  I don't get any errors or anything. I've even rechecked if I was missing any dependencies via terminal, and checked for updates and upgrades one more time, but nothing was missing. I've tried googling the issue, but haven't found anything.  EDIT: The solution to this issue, which I've tested on multiple PCs (that worked on all of them), is executing this command:  sudo apt-get install libgtk2.0-0


I was checking in my console. When i checked empty object directly like {} == {} , it show false.  Why it's showing false ? shouldn't it show true as both are equal ?

A strict equality operator will tell you if two object types are equal. However, is there a way to tell if two objects are equal, much like the hash code value in Java?  Stack Overflow question  is similar to this question, but requires a more academic answer. The scenario above demonstrates why it would be necessary to have one, and I'm wondering if there is any equivalent solution.


I was making some tweaks in my touchpad settings. Then by mistake I turned the touchpad OFF. Now I don't have a spare mouse and My touchpad isn't working. How can I turn that back ON?

Yesterday, suddenly my touchpad on my MSI Laptop started to not respond. In other words, in Login screen, touchpad is working as expected. However, in Desktop screen, after I have logged in, touchpad is not working.  How can I enable touchpad in Desktop?


I wanted to insert an icon in my GUI. I have already tried inserting one but I need help and want to make it transparent. Can I make the icon transparent in any way? Any help would be appreciated.

How to remove tkinter icon from title bar in it's window


I have seen some programs in python has [::] in the code. But I can't understand why to use and when to use this. Could you please provide some description in a simple language? Thanks in advance.

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


Until a few days ago, I only ever used Texstudio (on windows) to create LaTeX documents, relying entirely on the build and compile button to sort everything out for me. I've been trying to understand how one might compile a latex document without an IDE, and have discovered that this is achieved simply by typing pdflatex filename.tex into a command line, provided that the appropriate binaries folder is in included in the "PATH" environment variable. However, citations and bibtex/biber require that you run bibtex and pdflatex in the order latex>bibtex>latex>latex. So I hypothesised that this is exactly what the build part of the Texstudio button "build and view" does. But this doesn't seem to be the case. This is my messagelog after pressing build and compile on my template.tex file:  Process started: bibtex.exe "template"  This is BibTeX, Version 0.99d (MiKTeX 2.9) The top-level auxiliary file: template.aux The style file: biblatex.bst Database file #1: template-blx.bib Database file #2: testbib.bib Biblatex version: 3.0  Process exited normally      Process started: pdflatex.exe -synctex=1 -interaction=nonstopmode "template".tex  Process exited normally   So Texstudio seemingly runs bibtex followed by pdflatex. I tried doing this manually via the command prompt but bibtex responded "I couldn't open the file template.aux", which is a file created only after having run pdflatex at least once. This implies that Texstudio is running pdflatex before running bibtex even though it doesn't mention so in the message log. I have not changed Texstudio settings to add anything extra to the compilation order. So I'm stumped as to what's going on. Thanks for any help.

I've browsed the forums and found a number of posts that have addressed this issue, but none of the solutions seem to work for me. I have the following script that I just copied from the bibtex home page to get familiar with it. Instead of the citation number I get a question mark. I compile using Latex+Bibtex+Latex+Latex+PDFLatex+ViewPDF just as has been previously suggested and the problem persists.   \documentclass[11pt]{article} \usepackage{cite}  \begin{document}  \title{My Article} \author{Nobody Jr.} \date{Today} \maketitle  Blablabla said Nobody ~\cite{Nobody06}.  \bibliography{mybib} \bibliographystyle{plain} \end{document}   My bibliography (Bib.bbl)  @misc{ Nobody06, author = "Nobody Jr", title = "My Article", year = "2006" }    Looking at previous posts one thing that is concerning is that my .bbl looks empty as shown below. Further, I don't have a .blg  \begin{thebibliography}{}  \end{thebibliography}


I can create a symlink:  > mklink bravo.png alfa.png symbolic link created for bravo.png <<===>> alfa.png         However this is on a virtual machine. For some reason if I create one on my actual computer I am getting this:        Notice:   No thumbnail image If I double click the symlink in the virtual machine, it opens alfa.png in Photo Viewer, as expected. However if I double click the symlink on my computer it presents the “Open with” window. The symlink says “PNG image” in the virtual machine, it says “SYMLINK File” on my computer.   I think some registry setting is the culprit here, but I am not sure which one.

On Windows 7 I created a symbolic link to an executable using:  mklink Test.exe C:\Path\to\source.exe   But when I try to run it by double clicking on it, i get the "open with" dialog.  Running it from a command window works. The path is right.   Is there any way a symbolic link will be treated like the file it points to (e.g. executable or batch scripts)?


When passing vectors to functions, which method should be used: reference or pointer?  I see there are (many/all?) cases where any of the two would do the job. Even in those cases, are there any differences in the way the two methods perform?  I do not see if there are cases where only one of the two would work. Is there any such case?  EDIT: The question cited (about general differences pointers vs. references) as containing the answer to this OP is very much related, but I doubt it is a dupe. The differences between pointers and references, as for passing to functions, can surely be inferred from the answers there, but they are also probably much more specific than the general differences asked about there. So not all of the answers there may be relevant here. Moreover, some answers there may be only partially relevant here.

I know references are syntactic sugar, so code is easier to read and write. But what is the difference between a pointer variable and a reference variable?


I often see that a method is called with a second pair of parentheses.  For example the connect function in redux.  connect(   mapStateToProps,   mapDispatchToProps )(TodoItem)   Or this function from antd  const prefixSelector = getFieldDecorator('prefix', {       initialValue: '86',     })(       <Select style={{ width: 70 }}>         <Option value="86">+86</Option>         <Option value="87">+87</Option>       </Select>     );const prefixSelector = getFieldDecorator('prefix', {       initialValue: '86',     })(       <Select style={{ width: 70 }}>         <Option value="86">+86</Option>         <Option value="87">+87</Option>       </Select>     );   What happens here and how is this concept called so that i can research it further?

I've seen references to curried functions in several articles and blogs but I can't find a good explanation (or at least one that makes sense!)


I am a calculus 3 student (just starting multivariable calculus) and going to start out with linear algebra. I also am pretty knowledgable on classical mechanics (such as the Lagrangian, Hamiltonian equations, and Possion brackets) and quantum mechanics. At this level, what are some good resources to learn about string theory and quantum gravity? I would like it to be free, online resources that include some math that is at my level.

I am in the last year of MSc. and would like to read string theory. I have the Zwiebach Book, but along with it what other advanced book can be followed, which can be a complimentary to Zwiebach. I would like a more mathematically rigorous book or lecture notes along with Zwiebach.   Specifically, mention whether the book discusses string theory   Rigorously? Intuitively?   What's the scope of the book? Does it cover the advanced materials, e.g. Matrix string theory, F-theory, string field theory, etc. Maybe even String Phenomenology?


Microsoft just release the new Skype client. I downloaded it from   The compressed folder has a usr folder with a lot of other files in it. How do I install it ?   sindre@selite:~/Install$ tree usr  usr ├── bin │   └── skypeforlinux └── share     ├── applications     │   └── skypeforlinux.desktop     ├── doc     │   └── skypeforlinux     │       └── third-party_attributions.html     ├── icons     │   └── hicolor     │       ├── 1024x1024     │       │   └── apps     │       │       └── skypeforlinux.png     │       ├── 16x16     │       │   └── apps     │       │       └── skypeforlinux.png     │       ├── 256x256     │       │   └── apps     │       │       └── skypeforlinux.png     │       ├── 32x32     │       │   └── apps     │       │       └── skypeforlinux.png     │       └── 512x512     │           └── apps     │               └── skypeforlinux.png     ├── pixmaps     │   └── skypeforlinux.png     └── skypeforlinux         ├── blink_image_resources_200_percent.pak         ├── content_resources_200_percent.pak         ├── content_shell.pak         ├── icudtl.dat         ├── libffmpeg.so         ├── libnode.so         ├── LICENSES.chromium.html         ├── locales         │   ├── am.pak         │   ├── ar.pak         │   ├── bg.pak         │   ├── bn.pak         │   ├── ca.pak         │   ├── cs.pak         │   ├── da.pak         │   ├── de.pak         │   ├── el.pak         │   ├── en-GB.pak         │   ├── en-US.pak         │   ├── es-419.pak         │   ├── es.pak         │   ├── et.pak         │   ├── fake-bidi.pak         │   ├── fa.pak         │   ├── fil.pak         │   ├── fi.pak         │   ├── fr.pak         │   ├── gu.pak         │   ├── he.pak         │   ├── hi.pak         │   ├── hr.pak         │   ├── hu.pak         │   ├── id.pak         │   ├── it.pak         │   ├── ja.pak         │   ├── kn.pak         │   ├── ko.pak         │   ├── lt.pak         │   ├── lv.pak         │   ├── ml.pak         │   ├── mr.pak         │   ├── ms.pak         │   ├── nb.pak         │   ├── nl.pak         │   ├── pl.pak         │   ├── pt-BR.pak         │   ├── pt-PT.pak         │   ├── ro.pak         │   ├── ru.pak         │   ├── sk.pak         │   ├── sl.pak         │   ├── sr.pak         │   ├── sv.pak         │   ├── sw.pak         │   ├── ta.pak         │   ├── te.pak         │   ├── th.pak         │   ├── tr.pak         │   ├── uk.pak         │   ├── vi.pak         │   ├── zh-CN.pak         │   └── zh-TW.pak         ├── natives_blob.bin         ├── pdf_viewer_resources.pak         ├── resources         │   ├── app.asar         │   ├── app.asar.unpacked         │   │   └── node_modules         │   │       ├── keyboard-layout         │   │       │   └── build         │   │       │       └── Release         │   │       │           └── keyboard-layout-manager.node         │   │       ├── keytar         │   │       │   └── build         │   │       │       └── Release         │   │       │           └── keytar.node         │   │       ├── @paulcbetts         │   │       │   ├── cld         │   │       │   │   └── build         │   │       │   │       └── Release         │   │       │   │           └── cld.node         │   │       │   └── spellchecker         │   │       │       └── build         │   │       │           └── Release         │   │       │               └── spellchecker.node         │   │       ├── slimcore         │   │       │   └── bin         │   │       │       ├── sharing-indicator.node         │   │       │       └── slimcore.node         │   │       └── sqlite3         │   │           └── lib         │   │               └── binding         │   │                   └── node_sqlite3.node         │   ├── default_app.asar         │   └── electron.asar         ├── skypeforlinux         ├── snapshot_blob.bin         ├── ui_resources_200_percent.pak         ├── version         └── views_resources_200_percent.pak  41 directories, 87 files   (Question is for new Skype for Ubuntu 17.10. Old answers does not help.)

I want to install Skype, but I can't locate it in Software Center or by using Synaptic Package Manager. Can anyone help me?


I am trying to compare two sets   #logical operators  set1 = {1,2,3,4,5,6}  set2 = {1,2,3,4,5,6,7}  # is operator is_set1_set2_same = set1 is set2  print(is_set1_set2_same)   This result is as expected "False"  set2.remove(7) is_set1_set2_same = set1 is set2  print(is_set1_set2_same)   Question : I was expecting the output of this one should be "True", but i see its "False" , When I print two sets i see exactly same. Please let me know if i am missing something here on sets.  set3 = set1  is_set1_set3_same =  set1 is set3  print(is_set1_set3_same)   This results as expected "True"

My  has failed me.  In Python, are the following two tests for equality equivalent?  n = 5 # Test one. if n == 5:     print 'Yay!'  # Test two. if n is 5:     print 'Yay!'   Does this hold true for objects where you would be comparing instances (a list say)?  Okay, so this kind of answers my question:  L = [] L.append(1) if L == [1]:     print 'Yay!' # Holds true, but...  if L is [1]:     print 'Yay!' # Doesn't.   So == tests value where is tests to see if they are the same object?


If $A$, $B$ are square matrices and $I-AB$ is invertible how do I prove that $I-BA$ is invertible?   This is exercise 8 of section 6.2 in Linear Algebra by Hoffman and Kunze.    My thoughts.  If $A$ and $B$ are invertible then $AB$ and $BA$ are similar, so we can use that to show that $I-AB$ and $I-BA$ are similar, and hence if $I-AB$ is invertible then so is $I-BA$.  However, $A$ and $B$ are not given to be invertible, so I am not able to apply this idea to show that $I-AB$ and $I-BA$ will be similar in general. Can anyone give me a hint to prove this in the general case?    EDIT: As pointed out in the comments below, it is not true in general that $I-AB$ and $I-BA$ are similar. @JulianRosen gave the example $$ A = \begin{bmatrix} 0 & 1 \\ 0 & 0 \end{bmatrix}, \quad B = \begin{bmatrix} 0 & 0 \\ 0 & 1 \end{bmatrix}. $$ So, my original approach was completely incorrect. However, it is still true that $I-AB$ invertible implies $I-BA$ invertible.

The problem is from  Algebra by Artin, Chapter 1, Miscellaneous Problems, Exercise 8. I have been trying for a long time now to solve it but I am unsuccessful.      Let $A,B$ be $m \times n$ and $n \times m$ matrices. Prove that $I_m - AB$ is invertible if and only if $I_n - BA$ is invertible.    Please provide with only a hint.


How to improve quality of bokeh especially lights?

How can I render bokeh circles?  Nothing I do seems to work.   I tried using an empty as the focus point for a cube, with some point lamps in the background with about 2000 strength, but it doesn't work. It just makes everything blurry.  I also raised the blades to 4/5/6/12, and it doesn't make a difference.  I'm using Blender 2.74.


When using the Stack Exchange iOS app, the edit button for suggesting edits appears to be missing when viewing posts from a per-site meta.     App Version: 1.6.4 Device: iPad mini 2G (Wi-Fi) OS Version: Version 10.3 (Build 14E277)

I love the  that was recently added onto Stack Exchange. However, this feature seems to be missing in per-site metas.  For instance:  Server Fault Meta:    DBA Meta    The parent websites, do have the edit/improve this post link however.


I am trying to create a small program that is able to print out the largest value of a attribute in an XML file. I have wrote the following code:  public class GetMaxLog {     public static void main(String[] args) throws Exception {      DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();     factory.setNamespaceAware(true);      DocumentBuilder builder = factory.newDocumentBuilder();     Document doc = (Document)builder.parse("FILE");      XPathFactory xpathfactory = XPathFactory.newInstance();     XPath xpath = xpathfactory.newXPath();      XPathExpression expr = xpath.compile("//PasswordVault/User[@id = 1]//Log[not(@LOG < ../Log/@LOG)]/LOG/text()");      Object result = expr.evaluate(doc, XPathConstants.NODESET);     NodeList nodes = (NodeList) result;         //returns the element at tag value 0 thus only the first set of data         System.out.println(nodes.item(0).getNodeValue());  }   }  And the XML file looks like this.  <?xml version="1.0" encoding="UTF-8"?> <PasswordVault>   <User id="1">     <Log LOG="1">       <AccountType>afsdgsd</AccountType>       <Username>asdas</Username>       <Password>dsgsdg</Password>       <E-mail>aadfaf</E-mail>     </Log>     <Log LOG="10">       <AccountType>afsdgsd</AccountType>       <Username>asdas</Username>       <Password>dsgsdg</Password>       <E-mail>aadfaf</E-mail>     </Log>   </User> </PasswordVault>   There is a NullPointerException error when i run the program. I am trying to find the largest LOG value and then print it out.I think that my query within Xpath is incorrect .Could anyone help me fix this query and the NullPointerException error also.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


All I can remember is that he had to pilot the ship through some supernova or other anomaly to save the other passenger.

I thought it was The Tommyknockers by Stephen King, but after a check with Wikipedia, it appears that's not the case.  What I remember about the story (a TV movie I think, but definitely based on a book) was that the world is created anew every night, and that the old, used up, Earth was eaten nightly by some scary creatures.  The major plot point involved some protagonists not getting onto the new world at midnight, and having to escape from the monsters that were eating up yesterday's planet.  Does this ring a bell for anyone? I'm finding it very hard to Google for.


Does anyone know how can I contribute (as User Experience Designer) to the development process on GitHub?  I want to know how someone could include UX Research, Usability Testing, Contextual Inquiries and other planning and/or strategical activities from UX or AI point-of-view in the common process of projects being developed using GitHub.  Example:  All the work in GitHub is based in code production, branches, pull requests, etc. I trying to find examples of projects where a UX Designer has contributed in environment like this, how the deliverables have worked, common approaches to user testing, better ways to communicate with developers etc.

I'd like to exercise some of my UX/UI knowledge by contributing to a couple of the FOSS projects that I've used over the years. I've found that these projects usually have a huge deficiency in the area of UX.   I've also found the task of contributing very daunting. I setup some user scenarios and testing for a bug tracking suite and tried to submit my findings, but couldn't get a response from anyone on the team, including the UX/UI team "lead."  A fork of that same project has resulted in some UI changes, but they're still missing UX and I'd like to chip in. What am I up against? Will the scenarios, wireframes, suggestions, and testing data be useful to a team of donation developers? Does anyone have experience with this?


After following the code for the solution of  I am struggling to get the second line of the captions to stay centered. Normally the first line of text is always centered but once there are two or more lines the text switches to the "justified" alignment (block text). I have tried putting both \begin{center} and \centering within the minipage but neither do anything to the captions, nor do they produce any errors.  Here's my code. Although I checked all the packages and commands and don't think they interfere but I'll add them just in case anyone notices a problem.  \documentclass{article} \usepackage[margin=0.75in]{geometry} \usepackage[utf8]{inputenc} \usepackage{multicol} \usepackage{amsmath} \usepackage{hyperref} \usepackage{gensymb} \usepackage{float} \usepackage{biblatex} \usepackage{mwe} \usepackage{natbib} \usepackage{graphicx}  \renewcommand\thesection{\Alph{section}} \newcommand{\HRule}[1]{\rule{\linewidth}{#1}}  \begin{document}  \begin{figure}[H] \centering \begin{minipage}{0.45\textwidth}     \centering     \includegraphics[width=\textwidth]{log-hhcf.png}     \caption{Logarithmic graph for HHCF gold sample.}     \label{log-hhcf} \end{minipage}\hfill \begin{minipage}{0.45\textwidth}     \centering     \includegraphics[width=\textwidth]{hhcf.png}     \caption{HHCF for gold sample with all the relevant fitted lines and functions.}     \label{hhcf} \end{minipage} \end{figure}  \end{document}   I get this:    Anyone know another way to center the text of the captions on my figures?

I'm having a problem with centering my figure captions. Particuarly, I know that we can use \usepackage[justification=centering]{caption} to center captions, however, I'm interested in just centering a specific caption. I've read the caption manual but no luck, so my question is: How can I center a specific caption?


I had Windows 8 installed on my laptop (64-bit) and when I installed ubuntu on it I made a huge mistake and removed windows 8 and every file with it. What done is done.. I've been running ubuntu 13.04 for a month now and I would like to install windows 8 again alongside ubuntu.  I want it to be a dual boot, so when I start my laptop I can choose between the two. Installing windows 8 will be legit from a website from my university, I can just download it for free.   How to do this??  (- Do I need to use a harddrive/cd to put Windows on?)  Thx in advance!

I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go  for UEFI only!


I'm an international student who recently applied to CS Ph.D. programs in the US and this thought's been eating me up. My undergrad background isn't actually in CS. I was originally a literature major and did a CS double major. I wasn't familiar with anything, so my GPA tanked. It's around 3.1-3.2/4.0. If you take the CS-only courses, then it's actually around 2.95/4.0. I'm a master's student right now, and I've managed to maintain a GPA of around 3.8-3.9/4.0. Aside from my UGPA I think my application isn't _that_ bad - good GRE/TOEFL scores, publications as a coauthor, and good LoR's. However, I've been consistently hearing that the undergrad GPA is "what matters most" and that it may keep me from having a person even reading my application. I personally think that's asinine and doesn't make any sense, but I suppose I'm not in a position to be voicing my opinion on that. I'm just wondering what the point of working hard to turn things around is if someone's application won't even be looked at. The anxiety's been even worse because I've been hearing of people who chose the same POI's as me getting interviews, and I  haven't been hearing anything yet. I was hoping that people more knowledgeable than I am may be able to provide their two cents. Thanks.

When applying to a PhD program in the US, how does the admissions process work? If an applicant is weak in a particular area, is it possible to offset that by being strong in a different area?  Note that this question originated from this . Please feel free to edit the question to improve it.


I ask meta exchange to run a script to see who downvoted me, as I suspect the same person, because I had many downvotes all at the same time, after an argument with someone.  I'd like to know if I can ask it publicly, as I think maybe some moderators seems to know some users and won't make the check.

I don't like such kind of questions on Meta, so I will try to make it a good question and describe all with a details.  Today I down-voted  added a comment with explanations why I down-voted it, and flag it as non constructive (my flag was marked as helpful). An hour later  was downvoted, without any comment left about the reason. Yes, that wasn't my best answer, but in my opinion it answers the question. Well, even if somebody considered my answer incorrect he could add the correct answer, or up-vote the competitive ones. I checked the  who made competitve answer, and he didn't get any rep today for that answer.   It was my second down-vote on Stack Overflow, so I was a little bit down, after that. I think who could considered my answer so completely wrong, and that I thought that maybe it was revenge down-vote. So I checked  of the user I down-voted today, and it was clear that he down-voted some answers today. After I checked that that user cast only 19 downvotes in 8 months, so chances were very big that this was revenge down-voting.  I came to this meta, and searched what I should do in this case. I found that most questions about down-votes, were closed as duplicates. After I found , and found that a team member of Stack Exchange suggested to cast a flag for moderator attention, and explain the situation there.  I did that, and create next flag:     I think after I down-voted this question (and a comment about this), the OP down-voted me in revenge; it's clear from his today's reputation and from timing of my down-vote of his question, and time when one of my answers was downvoted. I cannot be 100% sure about that, but if somebody can check this, and point him that it's not the good way to do.   As you can see, I didn't ask for returning any reputation, or banning that user, I just wanted, somebody to point him, that he did wrong. And after I get this respons on my flag: "declined - flags should only be used to make moderators aware of content that requires their intervention." So in the end I also lost 10 points of the flag weight.  After describing all situation in details, I want to know were exactly I was wrong here. And what should I do next time something like this happens?


I recently bought a new computer, an HP, but something weird is happening. Every time I install some software that has a “Company” field, it automatically fills it with “Hewlett-Packard”. While the computer is HP, that doesn't mean I work for HP. Is there a way I can change this to a company I really work for?

how do I change the registered name in Windows 7 to my own name?


This is what happen last time   I follow what rumtscho said and went a bit out of the track. and this is my result:   the hole is quite big which is not what I want. The process and recipe that I used for this you can read it below the rumtscho answer (the comment part of the answer). I knead it for 60 mins. anyone please help me achieve what I want.  I also tried the second recipe which is this one:   and this is the result:   it is still very far away from what I want which is this(the below one I bought it from bakery shop and this is what I want):   anyone please help me I feel something went really wrong.

I would like to make the dense&soft bread like the bottom one and the taste is plain not sweet. What techniques will make bread closer to the one I want? I also want it to be chewy, not just soft.


Let $P,Q,R$ be subspaces of a vector space $V$ such that $V=P \cup Q \cup R$ , then is it true that one of $P,Q,R$ must be equal to $V$ ? I know the result about subspaces that tells that if for subspaces $A,B$ , $A \cup B$ is also a subspace then $A \subseteq B$ or $B \subseteq A$ , but for this three union case I cannot make any headway , Please help . Thanks in advance

Prove that the union of three subspaces of V is a subspace iff one of the subspaces contains the other two.  I can do this problem when I am working in only two subspaces of $V$ but I don't know how to do it with three.   What I tried is: If one of the subspaces contains the other two, Then their union is obviously a subspace because the subspace that contains them is a subspace. (Is this sufficient??).  If the union of three subspaces is a subspace..... How do I prove that one of the subspaces must contain the other two from here?  *When proving this for two I said that there is an element in one of the subspaces that is not the other and proved by contradiction that one of the subspaces must be contained in the other. How would I do this for three?


I understand the principles of asynchronous functions, but something is not clear to me: Scoping in asynchronous functions.  Example:      var path = "/my/folder/to/public/data";     http.createServer(function(request, response){             /* some malicious code is executed, however */             path = "/my/folder/to/private/data"     });      /* go on, go on, go on, wait here because of an synchronous function. */     /* while code execution is here, the callback-function of the server is called. */      fs.readFile(path+"myfile.txt", function(err, content){             console.log(content);     });   So, this is only an example. But how does it behave with the scopes/vars?

How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves?  I have seen  given on Wikipedia, but unfortunately it did not help.


I was taught that when you form a comma-separated list, they should have the same form (singular or plural).  I encountered the sentence below and I can't tell if it is grammatically correct.     I understand that all other company policies, handbooks, standard operating procedures, work instructions, and other mandatory documentation that relates to computer system security is available to me. [emphasis added]   It has a list of pluralized nouns (policies, handbooks, etc). This would usually go with the form are. However the item in this list (documentation) is a mass singular noun and would use the form is.  So in the sentence above:   Is the use of is correct? Can plural nouns and mass singular be used together like this (in other words, sound documentation be changed to documents)?

I was surfing the internet the other day when I found this phrase: Instead your precious time and attention is wasted. To my ears, it sounds wrong. But I'm not a native English speaker, so I consulted with a number of them, and some of them said that it was "is" because the adjective modifies only the noun "time" and not "attention". Others said it "is" because that's just how it is. But I still believe it should be "are". Any help is appreciated.


I want to have something like this:  public class Stream {     public startTime;     public endTime;      public getDuration()     {         return startTime - endTime;     } }   Also it is important that for example if the startTime it's 23:00 and endTime 1:00 to get a duration of 2:00.  Which types to use in order to accomplish this in Java?

How do I get a method's execution time?   Is there a Timer utility class for things like timing how long a task takes, etc?     Most of the searches on Google return results for timers that schedule threads and tasks, which is not what I want.


I've notices in the last weeks that the StackOverflow  became very slow. It takes several seconds to load and from time to time it doesn't load at all.  Did you notice the same? I don't think it's a problem of my network, because the other site sections are running fine as before.

In the last few weeks, the 'review' button at the top of stackoverflow.com has become very slow. I can count to 20 in some cases (but not always).   In a perhaps related phenomenon, I believe that test questions in the queue often trigger a level of extreme slowness all their very own. If I click on a queue, or 'next' after a review, and the periods sit there throbbing for a good long time, chances are that what will show up will be a review audit.


I have been trying to make my footer go at the bottom for the past 2 hours and I can't quite get it fixed at the bottom part. My html code is in here ``https://pastebin.com/UE7NfbWB while I only use bootstrap for my css and I didn't change or add something major, just adding some colors. The red rectangular area is the free space like something is jammed in it.

I have a simple 2-column layout with a footer that clears both the right and left div in my markup.  My problem is that I can't get the footer to stay at the bottom of the page in all browsers.  It works if the content pushes the footer down, but that's not always the case.


A Diceware passphrase is constructed from a set of words chosen from a 7776-word database, using five dice throws to choose each word. The argument is that each word in the phrase adds about 12.92 bits of entropy since $\log_2(7776)≈12.92$. As Arnold Reinhold, the creator of Diceware, , the entropy comes from the size of the database, not from the way in which the elements are represented. So, in principle, it does not matter whether a 7-word passphrase is formed as 7 English words from a Diceware database, the original 7 five-dice throws (in effect 7 five-digit base six numbers with each digit increased by 1), or seven Chinese characters chosen from a database of 7776 Chinese characters. Each would have an entropy of about 90 bits.  Is it not the case, however, that using English words in place of the underlying dice-throw numbers reduces the entropy of the passphrase. The words in the standard Diceware database have an average length of 4.2 characters. This means that the average length of a 7-word passphrase would be about 30 characters. It is said that letters in English text have an entropy of about 1.3 bits each due to the redundancy of the language. This would imply that, analyzed as English text, the passphrase would only have an entropy of 38 bits. Arguably a Diceware passphrase is not typical English text, but presumably one could do a similar analysis to determine the redundancy of text drawn from the Diceware database, but, if my argument is correct, each letter in the passphrase would have to have at least 3 bits of entropy in order not to downgrade the entropy of the underlying Diceware elements.   Reinhold himself glosses over this. He :      But, you might ask, Diceware is made up mostly of English words. Doesn't that redundancy affect it at all? Well, it does. The seven word Diceware passphrase we talked about above would average about 30 letters in length (36 if you count the spaces between the words). If those letters were selected randomly, you would get 4.7 bits of strength per letter. That would work out to a lot more than the 90 bits Diceware claims for a seven word passphrase. The difference is the redundancy of English at work. However English redundancy does not affect the calculation that each Diceware word has 12.9 bits of randomness, which is based entirely how many different words there are in the Diceware list. You can rely on that number.   The redundancy of English does not affect the entropy of the Diceware passphrase, so long as you can rely on each letter having 4.7 bits of entropy, or indeed at least 3 bits. But I don't see what guarantee there is that this is the case.  Note that this question is not answered by  since this question raises a different argument not considered in that question. The underlying issue is similar, but the question asked about it is different.

I use some diceware pass phrases in some places but I have one question that I can't find the answer to.  Let's say I roll the dice and get $N$ words with a total of $M$ letters and that I don't put spaces in between the words.  An attacker wishing to brute force my secret could have to try $7776^N$ times to break it as a diceware pass phrase OR $26^M$ to break it as a "normal" password (assuming I get only words with letters).  But the attacker trying to break it as a normal password could assume that it is made up of English words and then they'd know that some letters and combinations of letters are more common.  So my $M$ letters will not have the entropy of letters selected at random but some lower entropy.  My question is, what $M$ do I need to make up the same entropy as the $N$ words?


I would like to start a Photography course soon but I don't have a camera and I don't know what specs to look for when buying one. This will be my first camera and I really don't know a lot about digital cameras and/or photography. I would like to have like an "all-rounder" camera for a beginner but good enough to take a Photography course.  Can anyone help me telling me which specs I need to look for?   Any guidance is welcome. Thanks!

I am thinking of buying a digital SLR camera. What things should I be looking for?


Sorry for the noob question, but I'm trying to hack together an ad hoc dynamic dns to reliably connect two machines in different geographic regions. My issue is every command I try (ifconfig, iwconfig, netstat, etc.) gives me the IP address from behind the subnet (so for example 10.0.0.1) but I need to be able to tell the other machine what my current external IP is, not what it is to the other machines on my subnet. How can I do this?  Bonus points for tips on how to do it in Python

I can find my IP address using ifconfig or hostname -i command.  But how do I find my Public IP?  (I have a static public IP but I want to find it out using unix command)


I have a Wordpress site which I want to vertically center content in the Jumbotron div (site uses Bootstrap framework) No tables if possible as it ruins other functionality in the jumbotron.   EDIT: The child div is centered but the content inside is not  html  ...

                            <?php echo $content ?>  (function to generate content not shown)

   css  .jumbotron {  position: relative; min-height: 600px;  width: 100%; border-radius: 0 !important; margin: 0; padding: 0; background-size: cover; background-repeat: no-repeat; background-position: center center; }  #s-text {  position: absolute;  text-align: center; margin: auto; max-width: 60%; top: 0; right: 0; left: 0; bottom: 0;  transform:translateY(-50%)  }     .jumbotron {   position: relative;   min-height: 600px;   width: 100%;   margin: 0;   padding: 0;   border-radius: 0 !important;   background-size: cover;   background-repeat: no-repeat;   background-position: center center; } #s-text {   position: absolute;   display: inline-block;   text-align: center;   margin: auto;   max-width: 60%;   top: 50%;   right: 0;   left: 0;   bottom: 0;   transform: translateY(-50%) } #s-text p {   position: relative;   font-weight: 500;   font-size: 1em;   line-height: 1.4em;   color: #fff; } <link href="//netdna.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet" />

content content content content content content content content content content content content content content content content content content content content content

I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


Please give me some examples, this is an exam question of a 1st year math module.

Give an example of a finite, non-commutative ring, which does not have a unity.    I can't think of any thing which fits this question. I was thinking $M_2(\mathbb{R})$ but it has the identity. Any help is appreciated.


I am using the following command to make references to equations of the form "Eq. (X.X)"  \let\originaleqref\eqref \renewcommand{\eqref}{Eq.~\originaleqref}   (see: )  But there is still annoying issue to deal with. Sometimes i want to refer to a bunch of consecutive equations, so the form should be     "Eqs. (X.X) - (X.Z)"   or sometimes to just two equations in the form     "Eqs. (X.X) and (X.Y)".   Additionally i would be absolutely nice if the command would get "oh i have three (four, five...) equations to reference, so i do this":     "Eqs. (X.X), (X.Y) and (X.Z)".   So it seperates all, but not the last mentioned equation with commas, and adds before the last equation an "and". This should be the behavior, if the equations are given in a way telling the command that they should be not(!) be written in the consecutive way as described above.  I provide an MWE just because i have to, although I know, this is not including an possible solution. I apologize for this behavior since i am using this forum for a while, but I have absolutely no glue how to acchieve this.  \documentclass{scrartcl} \usepackage{amsmath} \let\originaleqref\eqref \renewcommand{\eqref}{Eq.~\originaleqref} \begin{document} \begin{equation} 1 \label{eq:1} \end{equation}  \begin{equation} 2 \label{eq:2} \end{equation}  \begin{equation} 3 \label{eq:3} \end{equation} Refer to the first equation: \eqref{eq:1} \\ Refer to the first and second equations: \\ %todo Goal: Eqs. (1) and (2) Refer to the first to third equations: \\ %todo Goal: Eqs. (1) - (3) Refer to the first, second and third equation: \\ %todo Goal: Eqs. (1), (2) and (3) \end{document}

I have occasionally wanted to refer to a range of equations in my document.  So far, I've been using Equations~\eqref{firstEquation}~--~\eqref{lastEquation}, which produces something like "Equations (5) - (12)".  I recognize that this could make it harder to maintain the document if equations get shifted around, but I still prefer it to something like "Equations (5), (6), (7), (8), (9), (10), (11), and (12)".  Is there a standard or accepted way to refer to a range of equations like this?  Or should I just keep doing whatever looks best to me?


It is well known that $a^n-1$ is prime Mersann formula  for some pimes $p$ , I would like to show this implication if $a^n-1$ is prime for $n >1$   with $a$ is a positive integer then $a=2$ ?  Edit: I edited the question as it is related to the precedent question   Note : I have tried to show that for $a$ is odd it's obvious no integer $a$ satisfy $(a^n-1)$ which means it's not prime for an odd integer $a$

I was doing some basic Number Theory problems and came across this problem :     Show that if $a$ and $n$ are positive integers with $n\gt 1$ and $a^{n} - 1$ is prime, then $a = 2$ and $n$ is prime   My Solution : (Sloppy)        $a^{n}-1$ = $(a-1)$ . $(a^{n-1} + a^{n-2} + ... + a + 1)$   This means that $(a-1)$ | $(a^{n}-1)$    But $(a^{n}-1)$ is prime   So , $(a-1)$ = 1 $\Rightarrow$ $a = 2$   Now , let $n$ be composite   $n = kl$ , where $1 \lt k \lt n$ and $1 \lt l \lt n$   Now , $a^{kl}-1$ = $(a^{k}-1)$ . $(a^{k.{(l-1)}} + a^{k.{(l-2)}} + ... + a^k + 1)$   This means that $2^{n} -1$ is composite    Hence , we have achieved a contradiction      My Question : Am I correct ?


The speed of light decreases when it travels from an optically rarer medium to a denser medium, similarly it increases back when it travels from rarer medium to a denser medium. The speed of light in glass is 2 x 10^8 m/s while in air is 3 x 10^8 m/s, from where does a photon get energy to speed up by 10^8 m/s if it travels from glass to air.

As I learned today in school, my teacher told me that when light enters a glass slab it slows down due to the change in density and it speeds up as it goes out of the glass slab. This causes a lateral shift and the light emerges out from the point different than that from where it should have actually emerged from.  Okay so what I mean to ask is, when light enters point A on glass slab and emerges from point C why does the light speed up? Where does it get the energy it has lost when it entered the glass slab?  P.S.: Also, if I place a very very very large glass slab and make a beam of light pass through it will the light never come out as all the energy was lost in place of heat?


I am new to drupal, currently I am creating a new module for forms. Inside of module I have added the code as follows .  $form['first name'] = array(     '#type' => 'textfield',     '#title' => t('First Name'),     );     In this case I wanted to use place holders for text fields. So how can I do ?

Is there a way to convert a regular form and add placeholders with a module, or should this be done with a form template or with jQuery?


I want to generate consecutive alphabetic strings from an integer index, which serve as automatic object names. I know how to generate base-26 from int32, which requires 7 digits. But this is not exactly what I want because for low indices I would still get 7 digits where I would like to get short names starting with a, b, c...  Suppressing leading zeros (a's) is also not an option because then the transition from one-digit to two-digit names is irregular:  a,..., z, ba, bb, bc,...,zy, zz, baa, bab,...  like in this code:      public static string autoVarName(int i)     {         string result = "";          do         {             int j = i % 26;             result = (char)('a'+j) + result;             i /= 26;         }         while (i>0);          return result;     }   What I would like to get is rather similar to how Excel generates column names:  a,..., z, aa, ab, ac,...,zy, zz, aaa, aab,...  I can't seem to be able to wrap my head around how to do this. Any search has just brought up true base-26 numbers. Does anyone know how to modify the above code to get what I want?

How do you convert a numerical number to an Excel column name in C# without using automation getting the value directly from Excel.  Excel 2007 has a possible range of 1 to 16384, which is the number of columns that it supports. The resulting values should be in the form of excel column names, e.g. A, AA, AAA etc.


Give the option to users to not see questions from some communities on the "Hot Network Questions" tab.

I was going to make a filter for the "" by excluding some sites from it.  I noticed  which talks about "negative filtering" but does not explain how one can do it or if it is possible.  There does not seem to be a way to do this, though.  On the filter page, my only options are:  So how can I do "All sites except [list]"? It would also be nice if this could include similar functionality with the meta checkbox.  Something like "All main & meta sites except..."


How do you downgrade from KDE 5 to KDE 4 or downgrade from Kubuntu 15.04 to Kubuntu 14.10.  KDE 5 has been giving errors since I installed it, now I want to downgrade it.

I just installed a new version of Ubuntu and I want to roll it back to the previous version.  How can I do that? Is that even possible?


I am PhD Biologist. I have 5 populations of infected moth larvae (3 inbred, and 2 outbred). The infection in this case is spread vertically (from mother or father to offspring). Normally the virus is spread horizontally.  Analyses through GLM, GLMMs and (arcsine transformed) LMMs reveals that there is no significant difference between these populations. (Note: as block and day larvae were analysed for infection through PCR where ordered events, it could be argued that they are fixed or random effect hence GLM and GLMM analysis. Arcsine tranfomed LMMs are occasionally used for proportional data when events or very rare or very common.)   I suspect that the generally low infection rate may mean that although the number of larval hosts is high, the number of infected hosts is low, leading to a small sample size. Hence the non-significant result. Would it be the case that if the experiment were repeated, an unfeasably large sample size would be needed to show any difference between the populations? Therefore, would looking at a similar moth virus, with a greater rate of vertical transmission be a better idea, than pursuing it in this system?  I want to do a power analyses of the to verify this, for the write up. I understand that power analyses is done in the planning of experiments. Could it give you an idea of whether an unfeasably large sample size is needed to show an effect?  I have had no experience of doing this, so if anybody could point me to books or webpages that could help I would be grateful.   The data is available under the name fulldata .

This question is in response to an answer given by @Greg Snow in regards to a  I asked concerning power analysis with logistic regression and SAS Proc GLMPOWER.  If I am designing an experiment and will analze the results in a factorial logistic regression, how can I use  ( and  ) to conduct a power analysis?  Here is a simple example where there are two variables, the first takes on three possible values {0.03, 0.06, 0.09} and the second is a dummy indicator {0,1}. For each we estimate the response rate for each combination (# of responders / number of people marketed to). Further, we wish to have 3 times as many of the first combination of factors as the others (which can be considered equal) because this first combination is our tried and true version. This is a setup like given in the SAS course mentioned in the linked question.    The model that will be used to analyze the results will be a logistic regression, with main effects and interaction (response is 0 or 1).   mod <- glm(response ~ Var1 + Var2 + I(Var1*Var2))   How can I simulate a data set to use with this model to conduct a power analysis?  When I run this through SAS Proc GLMPOWER (using STDDEV =0.05486016  which corresponds to sqrt(p(1-p)) where p is the weighted average of the shown response rates):    data exemplar;   input Var1 $ Var2 $ response weight;   datalines;     3 0 0.0025  3     3 1 0.00395 1     6 0 0.003   1     6 1 0.0042  1     9 0 0.0035  1     9 1 0.002   1; run;  proc glmpower data=exemplar;   weight weight;   class Var1 Var2;   model response = Var1 | Var2;   power     power=0.8     ntotal=.     stddev=0.05486016; run;   Note: GLMPOWER only will use class (nominal) variables so 3, 6, 9 above are treated as characters and could have been low, mid and high or any other three strings. When the real analysis is conducted, Var1 will be used a numeric (and we will include a polynomial term Var1*Var1) to account for any curvature.  The output from SAS is     So we see that we need 762,112 as our sample size (Var2 main effect is the hardest to estimate) with power equal to 0.80 and alpha equal to 0.05. We would allocate these so that 3 times as many were the baseline combination (i.e. 0.375 * 762112) and the remainder just fall equally into the other 5 combinations.


How can i import *.sql in mysql database using php  how can i do this please help me to fix this issue thanks here's my code :   if (mysql_connect('localhost', 'root', '')) {     print_success("Connection &agrave; la base de donn&eacute;e r&eacute;ussie.")   ; } else print_error(mysql_error()) ;   mysql_query(" CREATE SCHEMA IF NOT EXISTS ".$_SESSION['dbname']." DEFAULT CHARACTER SET utf8 COLLATE utf8_swedish_ci ; ") or print_error(mysql_error()) ;    // Création du User/Password $_SESSION['dbuser'] = "user".$_SESSION['subdomain']; $_SESSION['dbpassword'] = substr(md5($_SESSION['subdomain'].$_SESSION['subdomain']),0,12);  @mysql_query(" DROP USER ".$_SESSION['dbuser']." ; ") ;   mysql_query(" CREATE USER ".$_SESSION['dbuser']." IDENTIFIED BY '".$_SESSION['dbpassword']."'; ") or print_error(mysql_error()) ;   if(WEBSERVER) mysql_query(" GRANT ALL PRIVILEGES ON ".$_SESSION['dbname'].".* TO '".$_SESSION['dbuser']."'@'localhost' IDENTIFIED BY '".$_SESSION['dbpassword']."' ; ") or print_error(mysql_error()) ;  else mysql_query(" GRANT ALL PRIVILEGES ON ".$_SESSION['dbname'].".* TO '".$_SESSION['dbuser']."'@'10.0.66.%' IDENTIFIED BY '".$_SESSION['dbpassword']."' ; ") or print_error(mysql_error()) ;  $sqlFile = "Database.sql"; $command='mysql -h localhost -u root ".$_SESSION['dbname']." < ' .$sqlFile;   It create an empty database, and dump the sql file at the current database which duplicate items!

I'm creating an installation script for an application that I'm developing and need to create databases dynamically from within PHP. I've got it to create the database but now I need to load in several .sql files. I had planned to open the file and mysql_query it a line at a time - until I looked at the schema files and realised they aren't just one query per line.  So, how do I load an sql file from within PHP (as phpMyAdmin does with its import command)?


Let $S = \mathbb{Z}$ and $a ∼ b ⇐⇒ 3|(a + 2b)$.  Show that $∼$ is an equivalence relation. Determine all equivalence classes for $∼$.  Part $1$ was pretty simple to prove, however I can't figure out how to proceed with part $2$. I'm thinking of either doing classes by the coefficient $m$ such that $3m = a+2b$ (ex: $cl(1) = (1,1) , (-1,2), (-3,3)... $  for $(a,b)$ ), by the sum of $a+2b$ (ex: $cl(0) = (-2,1)$ because $-2+2(1) = 0$ ), or just a single class where this relation exists (ex: all the values of $(a,b)$ where $3|(a + 2b)$. The last one wouldn't partition the set $S$ obviously, because it would only take the values divisible by $3$. As a follow up thought, all $3$ of my methods seem incorrect to me, as the set $S$ is only $\mathbb{Z}$, which implies that we are only looking for single integer values in each class, not the $(a,b)$ coordinates that I put in my classes. Any help is appreciated. Thank you!

Take the relation $R$ to be defined on the set of integers:  $$aRb \iff 5 \mid (a + 4b)$$  As part of a larger proof, I have to show that $R$ is both symmetric and transitive. I'm lost.  I see the first steps, but I can't find how to progress further. Here's what I have at this point:    Proof of Symmetry  We have to prove that if $5 \mid (a + 4b)$, then $5 \mid (b + 4a)$. Clearly, this is true if $a = b$, but apart from that, it's unclear in my mind.  Proof of Transitivity  We have to prove that if $5 \mid (a + 4x)$ and $5 \mid (x + 4b)$, then $5 \mid (a + 4b)$.    I've fiddled around with sample values, but I still don't see it. I'm pretty lost here. Thoughts?


The question:  The definite article 'the' has many usages. However, I cannot quite understand one usage, that is, 'used to mark a noun as being used generically'. What does it mean by 'noun being used generically'? Can anyone please shed some light on this and set some examples.  An example for this use is 'The dog is a quadruped.'  How can I  distinguish if the author is expressing a generic noun/idea instead of specifying something in front of 'the'?     Readers Note:  Readers interested in this question might like this question here:   -   That question is about using generic noun phrases with nationalities.

Sentences are:   "The rainforests are in danger." "Rainforests are in danger."  So in this case, I think that they are both correct sentences...but:  "Guitars are musical instruments."  "The guitars are musical instruments."  In this case, we are still making generic statements about a plural noun, but the second one sounds bizarre. This for a student. I'm not sure WHY it's awkward. Why do we opt for "The guitar is a musical instrument."  Thanks in advance :)


Here is the stream "airportFilteredList" i am having trouble with, it should print the country name that matches the filter of the given "Turkey" string but it doesn't print anything to the console, using count() on the stream gives a value of 0  public void getFilteredAirportList(String filteredText){       System.out.println(filteredText); //returns Turkey          Predicate<Airport> filterCountry = u -> u.getCountry() == filteredText;      Stream<Airport> airportFilteredList = airportList.stream().filter(filterCountry);      airportFilteredList.forEach(u -> System.out.println(u.getCountry()));  }   I made a general stream without the filter as well from the same list but it works well and returns all country names of the airports.  public void getAirportList(){     Stream <Airport> airportStream = airportList.stream();     airportStream.forEach(u -> u.getCountry()); //returns Turkey }   The ArrayList from which the Airport objects are retrived  ArrayList<Airport> airportList = new ArrayList<Airport>();  public void createAirport(String airport, String country, String continent,         String airfield_length) {     airportList.add(new Airport(airport, country, continent,             airfield_length));  }   The full source code is at

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I use the package  and it is fine, but when I use this  \hyperlink{label}{go to bla bla}  \newpage  \hypertarger{label}{}  a lot of bla bla   then, when I click on go to bla bla, I don't arrive on the real top of the newpage but at the top of all my blabla-writting, which is an effect I don't like.     Would you know how to jump to the real top of the newpage?

hyperref provides the command \hyperlink, with syntax:  \hyperlink{name}{text}   where name is the name of a hypertext object, and text is used as the link to jump to the defined mark. Page anchors, e.g., page.12, can also be used as hypertext objects. For example,  Click \hyperlink{page.23}{here} to jump to page 23.   This was proposed by Martin Scharrer as a solution to  .  I would  like to link a string of text to a page (by page number) using \hyperlink, but being able to refer to an implicit page anchor page.<number> whose ''number'' is not known in advance. That is, use a value of the counter page, which is only set later in the document, in the argument of \hyperlink.  Here's a hypothetical solution:  \documentclass{article}  \usepackage[pageanchor]{hyperref} % option is the default anyway  %% Martin Scharrer's patch for hyperref %% available at https://tex.stackexchange.com/a/19416/9237 \makeatletter \let\orig@Hy@EveryPageAnchor\Hy@EveryPageAnchor \def\Hy@EveryPageAnchor{%     \begingroup     \hypersetup{pdfview=Fit}%     \orig@Hy@EveryPageAnchor     \endgroup } \makeatother   \def\getpageref{???}   % \getpageref extracts the numeric value of \pageref{key}                        % for use in the first argument of \hyperlink  \begin{document}  See \hyperlink{page.\getpageref{lkd}}{this page} for further clarification.  \newpage  This is the linked page.\label{lkd}  \end{document}   I know how to achieve a similar solution by simply using \label and then \pageref (or \autopageref), but I am interested in making use of a hyperref patch proposed  by Martin to make all page anchors be displayed in full page mode. (This patch only seems to work with \hyperlink.)