During the course of my Bluetooth security research, I found that the BlueZ utility bccmd could be used to poll a Bluetooth adapter based on the Cambridge Silicon Radio (CSR) chipset for a random number. Bluetooth devices use random numbers as part of the pairing process, to generate initialization keys based on the user's PIN and the MAC addresses of the devices pairing. With bccmd you can direct a specific Bluetooth adapter to generate a random number on the fly, which is reported back to the software.
Now, I wasn't going to lie to myself. I was positive pretty much from the start that the pseudorandom number generator (PRNG) in a Bluetooth adapter is probably not very good, and would be unlikely to outperform a decent PRNG algorithm on the computer. But I couldn't help but be curious about just how well the PRNG in one of these devices could perform. Even if it didn't outperform the operating system's built-in PRNG, it had a certain advantage of being a dedicated piece of hardware. In theory, the generation of random numbers in an external device, even if it is only a software PRNG running on it, is slightly more secure than using the default OS's PRNG, if for no other reason than the fact that it is not part of the OS itself. It should be less susceptible to the environmental factors that can hinder the effectiveness of the OS's generator. For example, Linux's PRNG uses things like keyboard and mouse activity to generate entropy, but what if the machine is headless? By pushing random number generation to another device, even if the objective quality of the numbers is no better, it may still be less prone to attack.
Also, the PRNG in some software implementations and operating systems is not very good in the first place. For example, take a look at this interesting discovery about the PHP rand() function on Windows. To be fair, this was a combination of a few problems, but it does show how PRNGs that are actively being used in the field can end up being defective. In these cases, the Bluetooth PRNG could conceivably outperform what is already in place.
But really, the biggest draw here was the fact that devices with the CSR chipset can be had for as little as $3 shipped from retailers like DealExtreme. Having a dedicated PRNG hardware device for $3, even one that isn't terribly good, is just too cool not to look into.
In theory, this should work with any Bluetooth USB adapter based on the CSR chipset, but in my testing I found that some adapters simply wouldn't return any data when queried. I was never able to find out the exact reason for this, so there is a bit of luck involved with finding hardware that will work consistently with these methods. In my own testing, I used 2 AIRcable XR's, and SKUs 11825, 16229, and 12696 from DealExtreme.
If you are going to buy hardware to experiment with, I would probably suggest SKU 16229; it is the cheapest option I have found but out of all the devices I tested had the most unreliable performance. With DX's BULKRATE program, you can get 10 of these shipped for under $30, which is good, because you are going to want multiples in case some of them don't want to play nice. If you are into Bluetooth research in general and are going to do other things with it, it is worth it to get a second-hand Host XR on eBay. The Host XR was easily the most reliable out of all the devices I used.
Besides the devices shown here, I have done some (minimal) testing with the internal Bluetooth devices in Dell laptops, and found those to work fairly well. If anyone tries to duplicate these results on their own, I would be interested in hearing about what devices you used and how reliable they were.
Oh. So it took just shy of 30 seconds to generate about 4,800 random digits. Now, considering any real analysis of random numbers takes millions of digits to even approach statistical accuracy, we have a little bit of a problem on our hands. At this rate, it would take nearly two hours to create just 1 million digits, which still isn't enough to do any serious testing with.
Clearly I had an issue. I proved that random numbers could be pulled en masse from a bog-standard Bluetooth adapter, but the rate at which this Bash script was doing it was way too low for a statistical analysis. I needed to do it much much faster, and when you need speed you certainly don't want Bash. Rather reluctantly, as I am not a terribly good nor experienced programmer, I came to realize the only way to get the speed I needed was to open up the source for bccmd itself, and modify it.
Getting the source for bccmd was easy enough, I just got it from the Slackware /source directory on my nearest mirror (which happens to be about 10 feet from where I am sitting). I used bccmd from the BlueZ 3.x branch, as that is what I do all of my testing and work with.
Ah, now that was more like it. It took the modified bccmd almost half the time to run 1000 iterations as did the simple Bash proof of concept. I began work refining my little modification, until it rapidly turned into a complete rewrite, keeping only the one or two functions that provided the BlueZ transport and commands. bt_rng was born.
I realized pretty early on that the biggest problem with using Bluetooth adapters as a source of random number was that the adapter takes it's sweet time responding no matter how fast the computer itself is. I am not sure if the delay is in BlueZ, or the processing time it takes the meager adapter's hardware to calculate a number (probably a bit of both), but I know that it is the absolute speed-limit. So if one adapter can only output data at a specific rate...the only way to get data faster would be to use more adapters.
To do this I needed to make bt_rng multithreading. Basically, the function that requests a random number from the adapter would break off from the main program and run on it's own in the background. The main program could then spawn another copy of the function, or thread, pointing at a different adapter. Assuming BlueZ could hold it together, I figured it would be possible to poll at least 2 adapters simultaneously, and possibly more. Though from my previous research I knew BlueZ seems to destabilize once you get more than 2 or 3 Bluetooth devices in the same machine.
This was a fine idea, but the only problem was I never wrote a multithreaded application before. As I mentioned earlier, I am not a terribly good programmer either, so I was worried that my inexperience and lack of skill would be enough to stop this concept dead in it's tracks. But luckily for me I found this excellent page which gave a very clear overview on how to do multithreaded applications in a standards-compliant way. After only a few tries, I had a basic multithreaded version of bt_rng up and running.
As I expected, past a 2 adapters things start to get a little shaky, and devices start to time out. bt_rng supports and can work with up to 4 threads on 4 separate devices, but I have found that 2 seems to give the best balance of performance and stability. Any more, and the auto-correction routine (which involves throttling down the thread) tends to slow down overall performance.
As you can see, performance is up a bit. Two devices during 500 iterations each completes in about 10.5 seconds, compared to 16 seconds for a single device. This is not completely unexpected, but still disappointing. The auto-correction adds a few seconds to overall runtime, which is unfortunately a necessary evil. Auto-correction only becomes more frequent as the number of devices increases, so runtime actually gets worse with too many devices going at once. This was certainly better than the old code, but was fundamentally flawed; if I couldn't run more than 2 devices on a machine without incurring performance penalties, there was only one other option.
If I was limited to 2 devices per machine, then the next step was to run 2 devices on multiple machines at the same time. I am sure a more experienced programmer would have built some parallel processing functions into the application itself, but my solution was a little more mundane. I would simply export the bt_rng program over NFS, and have multiple client machines execute it from there. As all of them will be writing to the same output file on the NFS export, they will be collectively working together to overcome the issues incurred running multiple devices on each machine.
In addition, as each client will have opened the file in append mode there will be an interleaving effect due to multiple processes writing to the same file simultaneously. In other words, node 1 might inject it's data into the output file chronologically after node 4, but before node 3. In theory, this should help to compensate for any bias in one particular adapter or node.
Running bt_rng on a cluster is the only way to generate large amounts of random data in a realistic time frame, but it is still by no means quick. The previous examples showed us that, roughly, a machine running 2 bt_rng threads would take 10 seconds to complete 1000 iterations, or 1 second to complete 100. Using this as a very rough metric of speed, we can calculate per-node runtime for a given number iterations.
For example, say we had 2 nodes in the cluster, each running 2 devices. Let's also say that each node was set to run 4 million iterations. Given a speed of 100 iterations per second, we can expect each node to be running for a minimum of just under 6 hours. This time can vary slightly depending on the number of autocorrections required, so between 6 and 6.5 hours would be a good estimate. But since we have 2 nodes running in parallel, the end result will be 8 million iterations in 6 to 6.5 hours.
Once I had a system setup were I could generate significant random digits from the devices I was able to start doing serious analysis on the data. Take a look at the Evaluating Entropy Research Page for information on the software and methods used in the following section. Go ahead, I'll wait.
The first runs show that bt_rng has a very good ratio for the digits 1 through 9, but occurrences of 0 are significantly lower than the others. This is sort of a flaw in bt_rng, though one that I can't immediately figure out a better solution for. Basically, some incompatible Bluetooth devices just put out 0 every time you request a random number, so bt_rng interprets this as a hardware problem and exits. So the only zeros that appear in the output are the leading zeros, hence the lower probability.
To get around this problem, by default bt_rng will only deal with digits between 1 and 8. This does cut down a bit on throughput, but gives much better results as can be seen in the above chart. The statistical probability of getting a 1 through 8 is almost perfectly equal, which is considerably better than I thought it would be.
Entropy = 1.000000 bits per byte.
of this 20741323 byte file by 87 percent.
Arithmetic mean value of data bytes is 48.4999 (127.5 = random).
Serial correlation coefficient is 0.000393 (totally uncorrelated = 0.0).
This looks...exceptionally good. Bias is very low, and the serial correlation coefficient is excellent. I then set Spectra to run through and generate a 1920x1080 image of the data set, which also looked good, no noticeable pattern in the data. Click here to view.
Frankly, the output surprised me. This was an incredible improvement over the previous runs, though I wanted to see just how good these numbers were compared to known-good sources and comparable PRNGs. For the known good data I once again used files from Random.org, and for the PRNG I just wrote up a simple C program to generate 0's and 1's with a time-seeded rand().
There isn't a whole lot going on here, but if you look closely you will notice that the bt_rng and rand() data have a slightly more dense look to them, with some clusters of black here and there. This is a bit more evident on the rand() sample. What this basically means is that the Random.org data is better spread out than the other two, which is to be expected. But bt_rng doesn't exhibit any glaringly obvious repeating pattern, which is very impressive considering how close the spread was in the last test. I have to admit, I almost expected Spectra to show that the entire file generated by bt_rng was alternating 0's and 1's.
Well, I am not entirely sure how to grade this one. On one hand, bt_rng is able to generate some apparently high-quality random numbers through commodity Bluetooth adapters. On the other hand, it takes at least a half a dozen of those adapters and 2 or 3 computers running for ~12 hours to do it. But for argument's sake, I was also generating many more numbers than the average installation would require as I was testing millions of digits at a time. For a home server that is tasked with encryption, one or two adapters could very well be enough to generate enough random data to meet demand. I'm also not sure how to evaluate bt_rng's ability to resist attacks or flaws in the operating system's PRNG. My gut still tells me this would be somewhat less exploitable, but more testing would be necessary to say for sure.
At the end of the day, I learned a lot about parallel computing tasks, multi-threading applications, and repurposing proven GPL'd code for new programs. Plus there were a lot of graphs, so I think that deserves bonus points. In total I think enough went right, or at least sufficiently un-terrible to keep this one out of the "Fails" department.
As a blind Starfleet Chief Engineer once said, "But you don't have to take my word for it." You can download stable(ish) versions of bt_rng from the Downloads section.
You will notice that there is a 1.x series and a 2.x series of bt_rng in the Downloads. bt_rng 2.x is the new series that takes into account advice and information I got after this project hit HackaDay, most notably from Simon Cooper of LavaRND fame. bt_rng 2.x uses a much more accurate and efficient algorithm, and drops the multiple output modes from 1.x. I will keep the older 1.x series up for the sake of completion, but for all practical purposes only 2.x should be used for any real work.
I would be exceptionally interested to hear from anyone who plays with this code on their own systems, or is bored enough to actually setup their own bt_rng cluster for evaluation.
For those of you who are feeling somewhat less masochistic, I have also put up the output file from the cluster's 20 hour run. That is 20,741,323 random bytes for you to enjoy. Test it for entropy, print it out and make wallpaper, whatever you want. Let me know if you find anything interesting. You can get it from the bt_rng Download directory.


text:
HomeDown Memory LaneDown Memory Lane for July 4
Down Memory Lane for July 4
By Jan Clatterbuck July 3, 2019 Down Memory Lane 0
Approximately eighty 5-year-old children will enroll in Rappahannock's first kindergarten program in September 1976, according to a report submitted by the County School Board to the State Department of Education.
The report "investigates various aspects" of implementing the kindergarten program, according to School Board Chairman I.R. Kilby.
The State Standards of Quality Act, passed by the legislature in 1972, requires all Virginia counties to set up a kindergarten program by 1976 or lose state funds. Rappahannock will receive no additional money from the state to fund the kindergarten program.
A tractor-trailer spilled its cargo of cement over the banks of the Covington River at Rediviva early Thursday morning when it overturned. According to Trooper W. A. Buntin, the driver said he was forced off the road by another vehicle, lost control of the rig and turned over. The 1971 Diamond Reo was driven by William Allen Anderson, who received minor scratches.
For the first time since the establishment of the Rappahannock Farmers' Co-operative, its volume of business topped the million dollar mark in 1973.
This was disclosed in a report by the local Co-op manager, Gordon Thornhill, at the annual membership meeting Monday evening at Graves Mountain Lodge. Total for the past year stood at $1,012,703.67, according to Mr. Thornhill.
At last Wednesday's meeting, the Rappahannock planning commissioners gave the go-ahead to a five-lot subdivision near Amissville and tabled a request for approval of a single five-acre lot near Flint Hill, pending legal advice.
The commissioners authorized Zoning Administrator David Konick to give preliminary plat approval to Wallace Judd for five lots on Route 637 near Amissville.
Initially Judd proposed six lots but the layout didn't meet ordinance requirements that each lot be served by a 50-feet right-of way and have 2580 feet of road frontage. Accordingly, Judd revised the preliminary plat, eliminating one lot to ensure that each of the five acre plus parcels had the necessary road frontage.
At its December meeting, the Rappahannock County School Board decided not to honor the request of Robert Judd, a California contractor, who proposed to demolish the old Scrabble School building for materials to be used in building a Rappahannock retirement home. The board did so on the advice of Commonwealth's Attorney Douglas Baumgardner, who advised them that the rights to the property were in dispute.
Rappahannock County merchants experiencing the ups and downs of seasonal business report an encouraging trend this Christmas shopping season.
A combination of good weather, new marketing techniques, and appeals to local customers has resulted in many shops experiencing their best Christmas sales to date.
"We've had a dramatic increase in our shop sales," reports Cheri Woodard of Faith Mountain Herbs in Sperryville. "Our catalog sales are way up too. — 110 percent over last year."
Cheri said that, indirectly, the catalog has boosted her store sales. "This was a surprising reaction," she said. "People come in, catalog in hand, asking to buy items that were offered by mail order. I think that with the catalog, they plan to stop by here on their next trip." Cheri said that the most popular Christmas items this year were her herb wreaths, corn husk wreaths and herb jars.
Wild Ideas: Bugs! Bugs! Bugs!
School news for July 4

redpajama_set_name: RedPajamaCommonCrawl


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Previous articleAlkaline Water Racks Up $6 Million in Sales – in Two Months.
Next articleA88 (WTER) Infused Beverage Division, Inc., and American Nutritional Products Inc. Enter into Production Agreement.


text:
Q: How does one write custom accessor methods in Perl6? How does one write custom accessor methods in Perl6?
If I have this class:
class Wizard {
    has Int $.mana is rw;
}

I can do this:
my Wizard $gandalf .= new;
$gandalf.mana = 150;

Let's say I want to add a little check to a setter in my Perl6 class without giving up the $gandalf.mana = 150; notation (in other words, I don't want to write this: $gandalf.setMana(150);). The program should die, if it tries to set a negative mana. How do I do this? The Perl6 documentation just mentions it is possible to write custom accessors, but does not say how.

A: With more recent versions of Rakudo there is a subset named UInt that restricts it to positive values.
class Wizard {
  has UInt $.mana is rw;
}

So that you're not stuck in a lurch if you need to something like this; here is how that is defined:
( you can leave off the my, but I wanted to show you the actual line from the Rakudo source )
my subset UInt of Int where * >= 0;

You could also do this:
class Wizard {
  has Int $.mana is rw where * >= 0;
}

I would like to point out that the * >= 0 in the where constraint is just a short way to create a Callable.
You could have any of the following as a where constraint:
... where &subroutine # a subroutine that returns a true value for positive values
... where { $_ >= 0 }
... where -> $a { $a >= 0 }
... where { $^a >= 0 }
... where $_ >= 0 # statements also work ( 「$_」 is set to the value it's testing )

( If you wanted it to just not be zero you could also use ... where &prefix:<?> which is probably better spelled as ... where ?* or ... where * !== 0 )

If you feel like being annoying to people using your code you could also do this.
class Wizard {
  has UInt $.mana is rw where Bool.pick; # accepts changes randomly
}

If you want to make sure the value "makes sense" when looking at all of the values in the class in aggregate, you will have to go to a lot more work.
( It may require a lot more knowledge of the implementation as well )
class Wizard {
  has Int $.mana; # use . instead of ! for better `.perl` representation

  # overwrite the method the attribute declaration added
  method mana () is rw {
    Proxy.new(
      FETCH => -> $ { $!mana },
      STORE => -> $, Int $new {
        die 'invalid mana' unless $new >= 0; # placeholder for a better error
        $!mana = $new
      }
    )
  }
}

A: You can get the same accessor interface that saying $.mana provides by declaring a method is rw.  Then you can wrap a proxy around the underlying attribute like so:
#!/usr/bin/env perl6
use v6;

use Test;
plan 2;

class Wizard {
    has Int $!mana;

    method mana() is rw {
        return Proxy.new:
            FETCH => sub ($) { return $!mana },
            STORE => sub ($, $mana) {
                die "It's over 9000!" if ($mana // 0) > 9000;
                $!mana = $mana;
            }
    }
}

my Wizard $gandalf .= new;
$gandalf.mana = 150;
ok $gandalf.mana == 150, 'Updating mana works';
throws_like sub {
    $gandalf.mana = 9001;
}, X::AdHoc, 'Too much mana is too much';

Proxy is basically a way to intercept read and write calls to storage and do something other than the default behavior.  As their capitalization suggests, FETCH and STORE are called automatically by Perl to resolve expressions like $gandalf.mana = $gandalf.mana + 5.
There's a fuller discussion, including whether you should even attempt this, at PerlMonks.  I would recommend against the above -- and public rw attributes in general.  It's more a display of what it is possible to express in the language than a useful tool.

redpajama_set_name: RedPajamaStackExchange


Cederberg, a small mountainous region in the Western Cape province of South Africa is not only beautiful but is also home to the magical healing herb, rooibos. This herb's fresh needle-like leaves, packed with vitamin C, are used to make a herbal tea called rooibos. Also known as bush tea in Southern Africa or red bush tea in Great Britain, rooibus tea is available in two forms. The fermented version of this tea has a reddish-brown colour, and the unfermented version is green with a malty and slightly grassy flavour. This tea, which has been a beloved drink in South Africa for centuries, has numerous health benefits that make it one of the best beverages to consume. Wondering what these benefits are? Read on.
Rooibos tea is rich in many minerals such as iron, calcium, potassium, copper, manganese, zinc, magnesium, and alpha hydroxy acid. It does not contain caffeine, and has low tannin levels compared to black or green tea. The antioxidants present in rooibos tea boost the strength of the immune system as well as the digestive system, prevent premature ageing and also aid weight loss.
Rooibos tea contains alpha hydroxy acid and zinc, which can reduce the signs of wrinkles, and other premature aging symptoms. Apply some red tea powder on your skin to relieve acne, pimples, sunburn or related skin conditions.
Removing caffeine from your diet helps improve your Stress levels, mood, and heart health. Rooibos tea is completely caffeine-free. Drinking it before you go to bed can help you sleep better.
Rooibos tea contains orientin and luteolin, flavonoids that increase the mineral content in bones. It is also rich in minerals like calcium, manganese, and fluoride that help maintain a good bone structure, stronger teeth, and reduce the chances of arthritis, osteoporosis, and chronic joint pain.
Rooibos tea is a bronchodilator - a substance that dilates the bronchi and bronchioles and increases airflow to the lungs making breathing easier. With the decrease of resistance in the respiratory airway, it helps combat the symptoms of asthma, and common cardiovascular diseases including atheroschelorsis and heart attacks.
This tea is a rich source of antispasmodic agents, which can ease severe stomach cramps and abdominal pains. It activates potassium in the body without antagonizing the activities of calcium. This can reduce the presence of hyperactivity in the gastrointestinal tract, and thus prevent diarrhea and other intestinal issues.
Rooibos tea is known to relieve stress, nervous tension, and high blood pressure. It contains chrysoeriol and quercetin, flavonoids that decrease blood pressure and improve blood circulation.
Aspalathin is one of the rare antioxidants found in rooibos tea can help balance blood sugar, improve insulin resistance and glucose absorption by the muscles, and boost insulin secretion from the pancreas.
Quercetin, an anti-inflammatory antioxidant found in rooibos tea, reduces blood pressure and hunts free radicals. It increases the HDL cholesterol (good cholesterol) and prevents the LDL cholesterol (bad cholesterol) from binding to the walls of arteries and blood vessels, protecting you from heart attacks, strokes and several heart conditions.
Quercetin is known to block the immune cells that trigger allergic reactions. In many parts of South Africa, rooibos tea is seen as an effective curative to treat allergies like eczema, hay fever, and allergy-related bronchitis.


If you're looking for a bigger and faster electric mini dirt bike for your up and coming rider, you've got to check out the Monster Moto 1000 Watt Electric Mini Bike. This mini bike packs a powerful punch and will leave its competitors in the dust with its 1000 watt motor and top speed of 17 mph. One of the nicest things about this Monster Moto mini bike is that it ships basically completely assembled. All that you will need to do is attach the handlebars and get it charged up. Let's go ahead and take a closer look at our Monster Moto 1000 Watt Electric Mini Bike Review!
Let's kick things off with this Monster Moto electric mini bike review by answering some of the most frequently asked questions about this kids electric dirt bike.
Who is the Monster Moto 1000 Watt Mini Bike designed for?
This electric mini bike is designed for riders ages ages 14 and up with a maximum rider weight of 185 pounds.
How big is the Monster Moto 1000 Watt Mini Bike?
How fast is this Monster Moto Mini Bike?
The Monster Moto 1000 watt electric mini bike has a top speed of 17 mph with up to 45 minutes of continuous use on a full charge. This makes this Monster Moto mini bike one of the faster stock electric mini bikes currently on the market.
How much does this electric mini bike cost?
The Monster Moto 1000 watt dirt bike is going to run you around $400. The only other kids electric dirt bike that rivals the Monster Moto 1000 watt at this price point would be the Razor MX650. If you'd like to read through our comparison review of these dirt bikes, check out our article on Best Electric Dirt Bikes Under $500.
COST – Let us save you the search, you will not find another electric mini bike of this quality at a better price.
MOTOR – As we've hit on multiple times throughout this review, we love the powerful 1000 watt motor on this mini bike. You'll find a number of different electric mini bikes with motors ranging from 250 watts to 650 watts, but the Monster Moto 1000 watt is in a league of its own.
SUSPENSION – Or should we say, lack of suspension. Now this isn't a deal breaker by any means but it could make for a smoother ride. We also want to reiterate that Monster Moto has done a nice job of compensating for this by adding a larger off road tire than most other electric dirt bikes.
The MX650 has a 650 watt motor and the Monster Moto 1000 is powered by a 1000 watt motor.
Top speed for both of these electric dirt bikes is about the same (17 mph).
Monster Moto 1000 is about 10 pounds heavier than the MX650.
Range on a full charge is about the same as well (40-45 minutes).
Razor MX650 has both front and rear suspension and the Monster Moto 1000 does not have any suspension.
Bottom line, if you're looking for a larger, more powerful mini bike you can't go wrong with the Monster Moto 1000 Watt!
Check out the Monster Moto 1000 Watt Electric Mini Bike in action!
So what are you waiting for? Get your Monster Moto electric mini bike TODAY!
Be sure to check out some of the other great Monster Moto products and dirt bikes available through Wild Child Sports!


text:
\section{Introduction}
Understanding friction is an actual scientific and technological
problem ~\cite{BowdenOxford1954,SingerKluwer1992,PerssonKluwer1996}.
Friction is a complex phenomenon of fundamental interest in many
scientific areas that occur at all length
scales~\cite{GneccoSpringer2007,
  UrbakhNature2004,BormuthScience2009,UrbakhNature2010}. Its
comprehension at the nanoscale is fundamental for instance for the
manipulation of nanoparticles and the miniaturization of moving
devices as nano-electromechanical systems (NEMs).  With the
development of experimental techniques such as the force friction
microscope (FFM) and the surface force apparatus (SFA), experimental
and theoretical studies of friction at the atomic scale have received
an increasing interest in the last years.  Furthermore, as the
frictional interface between two surfaces involves complex
interactions among many asperities, the atomic force microscope is an
exceptional tool to better understand friction at nanoscale level
since it can be described essentially as a single asperity dragged
along a surface~\cite{GneccoSpringer2007, UrbakhNature2004,
  SzlufarskaJPhysD2008}.

So far, most theoretical studies describing force friction microscopy
(FFM) experiments have focused on the behavior of defect{-}free and
perfect periodic surfaces with or without the inclusion of thermal
effects~\cite{JohnsonTribolLett1998,GneccoPRB2000,SangPRL2001,MedyanikPRL2006}.
However, the study of the effect of substrate disorder or defects on
atomic friction is particularly important since atomically flat
surfaces represent ideal models and defects of different kind are
always present. A recent study in a one-dimensional model indicates
that small uncertainties in the interaction effective potential
between the FFM tip and the surface can produce strong changes in the
frictional behavior of the tip~\cite{OFajardoPRB2010}. Other results
shows that other kind of imperfections in the substrate potential also
modify the frictional behavior at atomic scale~\cite{TshiprutPRL2009,
  BraimanPRE,ReguzzoniPNAS2009}. Reguzzoni {\it et al} studied friction in
the sliding of a xenon monolayer on a copper
substrate~\cite{ReguzzoniPNAS2009}. They found that the onset of slip
of the monolayer is strongly affected by the presence of vacancy-type
defects within the monolayer. H\"{o}lscher et al analyzed the load
dependence of atomic friction at atomic-scale surface
steps~\cite{HolscherPRL2008}.

In order to better characterize atomic-scale friction under
realistic surface potentials we present here results for the effect of
{\em surface defects} on atomic friction and its interplay with
thermal effects. By surface defects we refer to absorbed molecules,
vacancies or inclusion of attractive or repulsive atoms into the
perfect lattice. We will use a minimalistic model which focuses
in a small number of the most relevant degrees of freedom and emphasizes
the nonlinear nature of frictional dynamics.
We consider the one-dimensional case and focus on the
stick-slip region of the friction force versus dragging velocity
curve. The same problem has been studied previously by Tshiprut {\it et
al}~\cite{TshiprutPRL2009}. We present results for the mean value of
the friction force and the slip length and for the slip length
probability distribution functions (PDFs) for a range of values of the
corrugation potential amplitude, density of defects, temperature, and
damping.  We present results for four different types of defects. Our
results indicate that the presence of defects may strongly modify the
frictional behavior at atomic scale. The observed changes in the
friction force result from local changes of the potential profile,
which in many cases produce also significant changes in the PDFs of
the slip lengths.  We have compared our results with the defect-free
case and evaluated how the inclusion of defects locally modify the
slip length that the tip performs. To finish we make a detailed
comparison of the results obtained for {\it surface disorder} and {\it
  surface defects}. We also observe that the effect of surface
disorder on averaged quantities is screened at enough strong thermal
fluctuations. On the contrary, for the surface defects problem we
found significant effects even at high temperatures.

\section{Model}
We study a generalized Prandtl-Tomlinson model which includes the
thermal effects\cite{SangPRL2001},
\begin{equation}
\eqalign{ M\frac{\rmd ^{2}x}{\rmd t^{2}}+M\gamma \frac{\rmd x}{\rmd t}+\frac{\partial U(R,x)}{\partial x} = \xi(t), \cr
U(R,x)=\frac{k}{2}\left[ R(t)-x \right]^{2}+V(x).}\label{eq2}
\end{equation}

Here the tip is modeled as a single particle dragged by an elastic
spring over a one-dimensional substrate potential. $U(R, x)$ accounts
for the tip effective potential and it includes the elastic coupling of
the tip with a support which moves at constant velocity $v_s$
($R(t)=R_0+v_s t$), and the tip{-}surface interaction $V(x)$.  $M$ and
$x$ are the effective mass and the lateral position of the tip and $k$
is an effective spring constant. $\xi (t)$ is the random noise term
which satisfies the fluctuation{-}dissipation relation $\langle \xi
(t) \xi (t ') \rangle = 2M \gamma k_{\rm B}T \delta (t-t') $ with $
\gamma $ the microscopic friction coefficient and $ k_{\rm B} $ the
Boltzmann constant.

\begin{figure}[!t]
\centering
\includegraphics[scale=0.25]{1.eps}
\caption{Tip-surface potential $V(\widetilde{x})/U_0$ for (a) the perfect lattice,
  (b) the type I defect-in-minima lattice, (c) the type I defect-in-maxima lattice,
  (d) the type II defect-in-minima lattice and
  (e) the type II defect-in-maxima lattice.}
\label{Fig1}
\end{figure}

\begin{figure}[t]
\centering
\includegraphics[scale=0.31]{2.eps}
\caption{ Average friction force versus corrugation
  potential amplitude $U_0$ in the low driving velocity region
  ($v_s=10$ nm/s). $T=0$ and $\gamma=10^5$s$^{-1}$. (a) results for
  the defect-free (solid circles), type I defects-in-maxima (solid
  squares), and type I defects-in-minima (open squares)lattices. (b)
  results for the defect-free (solid circles), type II
  defects-in-maxima (open squares), and type II defects-in-minima
  (solid squares) lattices.  The density of defects is $d=30\%$.}
\label{Fig2}
\end{figure}

\begin{figure}[h]
\centering
\includegraphics[scale=0.31]{3.eps}
\caption{ Figures (a) to (c) show the local effects of
  the inclusion of defects on the instantaneous position and friction
  force of the tip for $U_0=0.27$ eV. The density of defects is $d=30\%$,
  $T=0$ and $\gamma=10^5$s$^{-1}$. (a) stands for the perfect lattice,
  (b) for type I in minima and (c) for type I in maxima.}
\label{Fig3}
\end{figure}

We model surface defects by including gaussian terms in the standard
tip{-}surface interaction potential,
\begin{equation}
 V(x)=-U_0\left[ 1.0+\cos \left( \frac{2\pi}{a} x\right) \right] +\sum_{j}A_0\rme^{-\frac{(x-x_j)^2}{2\sigma^2}}.
\label{defect}
\end{equation}
$A_0$ gives the amplitude of the defect potential and $\sigma$ its
range. $a$ and $U_0$ are the lattice spacing and the amplitude of the
defect-free surface potential, respectively. In theory, this amplitude
can be changed by varying the normal
load~\cite{MedyanikPRL2006,SocoliucPRL2004}.

We will show below results for the four kind of defects shown in
figures~\ref{Fig1}(b)-(e). Panel (a) shows the potential profile for a
perfect lattice. As in~\cite{TshiprutPRL2009} we model the inclusion
of atoms of different nature by introducing a random series of
gaussian terms located in the minima ($x_{j}=na$) of the otherwise
perfect lattice (see figure~\ref{Fig1}(b) where $A_0=-0.71 U_0$ and
$\sigma=0.2 a$). The absence of atoms in the substrate is modeled
introducing gaussian terms located randomly in the maxima
[$x_j=(2n+1)a/2$] of the lattice (see figure~\ref{Fig1}(c) where
$A_0=-2.0 U_0$ and $\sigma=0.2 a$). Figure~\ref{Fig1}(d) stands for
defects located in the minima with $A_0=+2.0 U_0$ and $\sigma=0.2 a$;
and figure~\ref{Fig1}(e) for defects in the maxima with $A_0=+0.71 U_0$
and $\sigma=0.2 a$. For the first two kinds of defects,
figures~\ref{Fig1}(b)-(c), $A_0<0$ and we will refer to them as type I
defects. For the last two cases, figures~\ref{Fig1}(d)-(e), $A_0>0$ and
we will refer to them as type II defects.

\begin{figure}[!t]
\centering
\includegraphics[scale=0.7]{4.eps}
\caption{ Average friction force and average length slip versus
  density of defects centered in minima (gray) or in maxima
  (black). Type I defects are continuous lines and
  type II dashed ones. We show results for  $Uo= 0.27$ eV, $U_0=0.38$ eV,
  $U_0=0.58$ eV. $T=0$ K and $v_s=10$nm/s.}
\label{Fig4
\end{figure}

\begin{figure}[tb]
\centering \includegraphics[scale=0.25]{5.eps}
\caption{ Probability density functions (PDF) of the
  slip length for the perfect (black dashed line) and the
  defect-in-minima (density 30\%, solid blue line) lattices at $T=0$ K
  and (a) $ Uo= 0.27$ eV, (b) $U_0=0.38$ eV, (c) $U_0=0.58$ eV and (d)
  $U_0=0.88$ eV.}
\label{Fig5
\end{figure}

To obtain dimensionless equations, energy can be measured in units of
the corrugation potential amplitude $U_0$, space in units of the
lattice spacing ($\widetilde{x}=2\pi x/a$) and time in units of the
natural frequency for oscillations of the tip in the surface potential
($\tau=\omega_p t$ with $\omega_p=2\pi\sqrt{U_0/Ma^2}$). Then
$\widetilde{\gamma}=\gamma / \omega_p$, $\widetilde{k}=1/\Theta=k a^2
/(4\pi^2U_0)$ and $\widetilde{v_s}=v_s\sqrt{M /U_0}$ are the
dimensionless damping, spring constant and velocity respectively. Some
of our results will be shown as a function of $U_0$. From the above
relations we see that a change in $U_0$ produces a change in both the
dimensionless damping and velocity of the system.

We have performed detailed numerical simulations of the dynamics of
the system at different parameter values.  We will present results for
the mean friction force $\langle F \rangle$, with $F(t)= k
[R(t)-x(t)]$, mean slip length $\langle L \rangle$ and slip length
PDFs.  Following the work by Tshiprut et al~\cite{TshiprutPRL2009},
we have used $M= 5.0\times 10^{-11}$Kg, $a=0.45$nm, $k=1.5$N/m,
$\gamma=10^{5}$s$^{-1}$ (except in section V where we change the
damping) and $U_0$ in the 0.2eV to 1.2eV range (then
$\widetilde{\gamma}$ goes from 0.3 to 0.1 and $\Theta$ from 4 to
25). For $v_s$ we have used 10nm/s,~\cite{Comentario1}. Our simulations
were performed using an stochastic Runge-Kutta
method with dimensionless time step 0.01. Averages were computed after
a sliding distance of 2000 lattice constants.  An evolution of this
length allows to obtain results of the average quantities with
reliable statistics. We will show also the Probability Distribution
Function of the slip lengths.

\section{Surface defects without temperature}

Here we consider the effect of surface defects in the deterministic
dynamics of the system, $T=0$~K. We focus on the stick-slip region of
the force versus velocity characteristic curve. The well-known
behavior of the friction force as a function of the potential
amplitude for the defect-free
lattice~\cite{GneccoSpringer2007,UrbakhNature2004,SzlufarskaJPhysD2008,JohnsonTribolLett1998,GneccoPRB2000,SangPRL2001,MedyanikPRL2006,OFajardoPRB2010,TshiprutPRL2009}
is presented in figure~\ref{Fig2} (solid circles). There, the friction
force has been computed in the low driving velocity region ($v_s=10$
nm/s) with $U_0$ ranging from 0.25 to 1.2 eV.  A series of
discontinuities can be seen. They mark transitions between different
dynamical states characterized by a well defined mean value of the
length of the slip
events~\cite{JohnsonTribolLett1998,MedyanikPRL2006,OFajardoPRB2010,NakamuraPRB2005}.
Regions numbered as 1, 2, 3 and 4 in the figure correspond,
respectively, to regions characterized approximately by one, two,
three and four-lattice constant jumps. The value of the normalized
parameter $\Theta$ in the first four regions is: $ 1.0 < \Theta_{1}
\leq 6.66 \leq \Theta_{2} \leq 11.45 \leq \Theta_{3} \leq 16.03 \leq
\Theta_{4} \leq 20.61$.  For values of $\Theta < 1$, the tip
slides smoothly and stick-slip events do not appear.

Figure~\ref{Fig2} also presents the result for surface defects with
density $d=30\%$. As expected, in general the presence of type I
defects in the potential minima or type II defects in the potential
maxima increases the friction. On the contrary the suppression of
potential maxima, type II defects in potential minima or type I
defects in potential maxima, decreases friction. Thus, a system with
both types of defects will suffer a certain balance of both
effects. However, the dynamics of the system is much more complex and
this is not always the case. For type I in minima defects for
instance, it is easy to see the presence of two competing effects: a
deep potential causes a longer stick and then high friction, but it
can also cause longer slips, which reduce friction. Depending on the
parameter values the first or the second mechanism is the more
important one. Furthermore, close to the transition points surface
defect effects are difficult to predict. In addition, significant
changes are observed for large values of the potential $U_0$.  There,
the effective damping is smaller~\cite{Comentario2} and the dynamics
is more sensitive to small changes in the substrate potential.

\begin{figure}[tb]
\centering
\includegraphics[scale=0.31]{6.eps}
\caption{ Average friction force versus corrugation
  potential amplitude $U_0$ at $T=0$, $50$ and $300$ K. (a) Type I
  defect-in-minima and (b) type I defect-in-maxima case. Open symbols
  are the defect-free lattice and solid ones for surface defect
  ones. In all the cases $v_s=10$nm/s.}
\label{Fig6
\end{figure}

\begin{figure*}[tb]
\centering
\includegraphics[scale=0.55]{7.eps}
\caption{ Average value of the friction force and the
  slip length versus temperature for different potential corrugation
  amplitudes $U_0$ for the defect-in-minima, defect-in-maxima and
  perfect (continuous black line) cases.  Type I defect-in-minima
  (solid circles), type I defect-in-maxima (solid squares), type II
  defect-in-minima (open circles) and type II defect-in-maxima (open
  squares). $U_0=$0.27, 0.38, 0.58 and 0.88 eV; panels (a) to (d)
  respectively.  As usually $v_s=10$nm/s.}
\label{Fig7
\end{figure*}

Figures~\ref{Fig3}(a)-(c) show the effect of the surface defects on
the instantaneous position of the tip (top) and friction force
(bottom). Figure~\ref{Fig3}(a) stands for the perfect sinusoidal
potential. This case is characterized by a regular tip dynamics with a
characteristic slip length and a periodic friction force.  The
inclusion of type I defects in potential minima, figure~\ref{Fig3}(b),
produces a significant change in the slip lengths and friction forces.
Finally, type I defects in maxima, figure~\ref{Fig3}(c), produce a
strong reduction of the slip length and a reduction of the stick
phase. We have checked that as expected such reduction is complete if
we totally remove the potential maximum.

Figures~\ref{Fig2} and~\ref{Fig3} were computed for a density of 30\%
of defects.  In figure~\ref{Fig4} we study the value of the mean
friction force and mean slip length as a function of the density of
defects (solid lines are for type I defects and dashed lines for type
II ones) for three values of the potential amplitude: $U_0=0.27$,
$0.38$ and $0.58$eV (marked in figure~\ref{Fig2}). We observe a
significant modification of the friction force. As it can be seen in
the figure, this change sometimes is associated to an important change
of the mean slip length, and other times is due to the modification of
the potential profile without change of $\langle L \rangle$. Figure
also shows that the friction force and the slip length change linearly
with the density of defects. Due to computational reasons, in what
follows we will show results for a density of defects $d=30\%$.

In order to get a better insight of the findings showed in
figure~\ref{Fig4}, we have computed slip length PDFs at different values
of $U_0$, figure~\ref{Fig5} for $d=30\%$. We show results for the
defect-free and type I defect-in-minima cases, other type of defects
can be understood in a similar way. For $U_0=0.27$ eV
[figure~\ref{Fig4}(a)], for the defect free case a single peak with
$\langle L \rangle$ close to one is found~\cite{Comentario3} [black dashed line in
  figure~\ref{Fig5}(a)]. For the lattice with defects the slip length
PDF (blue line) presents significant modifications. Now we see a
second peak in the distribution, located near to $L/a=1.65$ and a
decrease of the original one located at $L/a=0.73$. Thus the average
slip length is increased and the friction force reduced. Larger
densities produce an additional increase of the second peak and
reduction of the first one.

For $U_0=0.38$ eV the mean slip length $L/a \simeq 1.65$ for all the
defect density studied, figure~\ref{Fig4}(b). The corresponding PDF are
also slightly modified as seen in figure~\ref{Fig5}(b). However, we
observe an important increase of the friction force which in this case
is ascribed to the increase in the potential barriers associated to
the defects.

In the third case, $U_0=0.58$ eV, figure~\ref{Fig4}(c), we observe both
effects: an important modification of the slip length PDF with an
increase of the slip length mean value and also an increase of the
friction force.

Finally, the last case shown in Figure 5(d), corresponds to a small
normalized damping and there the dynamics of the tip is different.  At
low values of the normalized damping tip oscillations exist between
the accessible wells.  This effect introduces additional changes in
the friction force and the slip length.  These two combined effects,
defects and low normalized damping, produce a slightly modified slip
length but a significant change in friction force.

\begin{figure*}[tb]
\centering
\includegraphics[scale=0.25]{8a.eps}
\includegraphics[scale=0.25]{8b.eps}
\includegraphics[scale=0.25]{8c.eps}
\includegraphics[scale=0.25]{8d.eps}
\caption{ Slip length PDFs for the defect-free lattice
  (black dashed line) and the type I defect-in-minima one (blue line)
  at: (a) $U_0= 0.27$, (b) $U_0=0.38$, (c) $U_0= 0.58$, and (d)
  $U_0=0.88$ eV. For each potential value above we show the PDF at
  $T=10$, $100$, $300$ and $400$ K.}
\label{Fig8
\end{figure*}

\section{Surface defects with temperature}

In this section we will present results on the combined effect of
surface defects and temperature in the friction force of the
system. Theoretical and experimental results have shown that thermal
effects are fundamental to understand friction at this
scale~\cite{GneccoPRB2000,SangPRL2001,TshiprutPRL2009,SillPRL2003,SchirmeisenApplPhysLett2006,RiedoNanotech2004,OFajardoPRB2010}.
Previous studies show that the main temperature effect is a reduction
of the friction force in the stick-slip region. This reduction, which
has been observed at high temperatures, is explained in terms of
thermally activated jumps of the tip~\cite{GneccoPRB2000,SangPRL2001}.
Recently, it has been also observed that, at low temperatures, thermal
fluctuation can increase the friction force, which reaches a maximum
and then
decreases~\cite{OFajardoPRB2010,TshiprutPRL2009,SchirmeisenApplPhysLett2006}.
This effect is understood in terms of a reduction of the mean length
of the slip events which dominates at low temperatures.

\begin{figure*}[tb]
\centering
\includegraphics[scale=0.7]{9a.eps}
\includegraphics[scale=0.7]{9b.eps}
\caption{ Average friction force and average length
  slip versus density of defects centered in minima (gray) or in
  maxima (black) . Type I defects are continuous lines and type II
  dashed ones. We show results for $ Uo= 0.27$ eV, $U_0=0.38$ eV,
  $U_0=0.58$ eV at $v_s=10$nm/s and $T=100$K (left) and 300K (right).}
\label{Fig9
\end{figure*}

Due to the important role played by temperature it is natural to
consider now the combined effect of thermal fluctuations and surface
defects in the response of the system. Figures~\ref{Fig6},~\ref{Fig7},~\ref{Fig8},
and~\ref{Fig9} summarize the main results.  In figure~\ref{Fig6}(a) we
compare at $T=0$, $50$ and $300$ K, the average friction force versus
the potential amplitude $U_0$ for the defect-free lattice (open
symbols) and the type I defect-in-minima. In figure~\ref{Fig6}(b) we
show the same comparison for the type I defect-in-maxima
case. Differences are clearly visible in all the studied temperature
range.  This effect is also studied in figure~\ref{Fig7} where we show
the average friction force $\langle F \rangle$ and slip length
$\langle L \rangle$ as a function of the system temperature for four
different values of $U_0$ corresponding to the four different
dynamical states marked in figure~\ref{Fig2}.

The inclusion of surface defects does not modify the two main
competing thermal effects already reported in the literature. The low
$U_0$ and high temperature regimens are dominated by a monotonic
decreasing of friction due to thermal activation without modification
of the mean slip length. At low temperatures and high $U_0$ values,
friction increases due to the reduction of the mean slip
length~\cite{OFajardoPRB2010}. However we observe that at a given
temperature the friction force for the type I defect-in-minima case is
bigger than for the defect-free one which in turns is also bigger than
for the type I defect-in-maxima lattice.
\begin{figure*}[tb]
\centering
\includegraphics[scale=0.26]{10a.eps}
\includegraphics[scale=0.26]{10b.eps}
\caption{ The mean friction force and mean slip length
  versus normalized damping at $T=0$ K for perfect lattice (open
  symbols), defects in minima of lattice and defects in maxima of
  lattice. (a) Type I defects and (b) type II defects.  Combined
  effect of surface defects and temperature (circles for $T=0$,
  diamonds for $100$ and squares for $300$ K) on the mean friction
  force and mean slip length as a function of normalized damping for
  defects in minima and defects in maxima of lattice. (c),(e) for type
  I and (d),(f) for type II defects. In all cases $U_0=0.27$ eV and
  $30$ \% for density of defects.}
\label{Fig10
\end{figure*}

In figure~\ref{Fig8} we show the change in the probability distribution
functions by the combined effect of defects and temperature. We
present results for type I defect-in-minima. The figure shows the
results for the same $U_0$ values used in figure~\ref{Fig5} but now at
four different temperature values. In the first case ($U_0=0.27$ eV),
figure~\ref{Fig8}(a), temperature suppress the second peak of the PDF. In
this case temperature affects more importantly the defect-free case
and moves apart the location of the peaks.  For $U_0=0.38$ eV,
figure~\ref{Fig8}(b), temperature activates a second peak close to
$\langle L \rangle=1$. As temperature increases the original one
decreases and disappears for the defect-free lattice case.  For
$U_0=0.58$ eV, figure~\ref{Fig8}(c), at zero temperature the main peak
is observed close to $\langle L \rangle=3$. At higher temperatures we
observe first the appearance of a second peak close to $\langle L
\rangle=2$, which will become the more important one, and later a
third one close to $\langle L \rangle=1$. At $U_0=0.88$ eV,
figure~\ref{Fig8}(d), the normalized damping is smaller and dynamics is
more complex and oscillations between adjacent wells are possible.

An important consequence of figures~\ref{Fig7} and ~\ref{Fig8} is that
although the PDF for the lattice with and without defects can be quite
similar (especially at low $T$) the mean friction force is very
different due to reduction of the effective barrier of the system.

Finally, we have studied again the dependence of the friction force
and mean slip length as a function of the density of defects in the
surface. In figure~\ref{Fig4} we showed the results for the zero
temperature case. Now, in figure~\ref{Fig9} we plot the similar results
for $T=100$K and $T=300$K. As we can see in the figures at all the
temperatures, both, the mean friction force and the mean slip length
depend almost linearly on the density of defects for the studied range

\section{Damping effect}

The effect of coupling of the system to many other degrees of freedom
is modeled by assuming the existence of a heat bath at a given
temperature and satisfying the fluctuation-dissipation relation. The
dissipation associated with this coupling is controlled by the damping
parameter, with temperature being a well-controlled parameter. However
to determine the correct value of the effective damping for the tip is
a much more complex and difficult question. Thus, it is important to
study the dynamics of the system for different values of the damping
in order to check the robustness of the results against changes of
this important parameter of the dynamics of the system.

A critical damping value is usually defined above which the tip
oscillations disappear (overdamped dynamics). In this case all the
deterministic slips have a length close to one lattice
constant. However, there are experimental evidences which indicate
that the damping of the system is below this critical value. In this
case the dynamics is more complex and
richer~\cite{KerssemakersApplPhysLett1995,RRothTribolLett2009}. We
have studied first in the regular case the effect of the damping
parameter on the friction force for values of $\widetilde{\gamma}$
crossing the critical value. Then we analyze how this behavior is
affected when surface defects are included. In figure~\ref{Fig10}(a) we
observe a series of steps in the friction force versus damping curve
(open symbols). Close to the discontinuities a small change in the
damping can produce a large change in the friction force. Every step
in figure corresponds to a slip close to one or two lattice sites
respectively.  In the overdamped limit only the first available
minimum (site 1) is reached. When smaller values of the damping are
achieved the tip can reach a further minimum (site 2). If damping is
reduced again the tip can move through 1 to 2 and then oscillates back
to 1 where is trapped. At small damping the tip oscillates back and
forth between both minima before reaching an equilibrium value. Then,
by decreasing the value of the damping more transitions are observed.
For other values of the parameters (larger $U_0$), more complex
situations are found. In these cases dynamics results from the
interplay between a larger number of minima than that shown in
figure~\ref{Fig10}.

When surface defects are included (full symbols), additional slight
modifications are observed. Figure~\ref{Fig10}(a) shows the change of
the friction force and the mean slip length as a function of the
damping for a density of $30$\% of defects and it compares to the
regular case curve. With inclusion of the thermal effects (diamond
symbols, $100$ K), the steps are strongly smoothed, see
figure~\ref{Fig10}(b). At higher temperatures steps are strongly smoothed
or even suppressed (square symbols, $300$ K).

\section{Discussion and conclusions}

We have studied the effect of the presence of four different types of
surface defects on atomic friction. Our results show that significant
changes can be observed even at high temperature. As expected,
differences are more important for $U_0$ values close to deterministic
dynamical transition points of the system.
\begin{figure*}[tb]
\centering
\includegraphics[scale=0.21]{11a.eps}
\includegraphics[scale=0.21]{11b.eps}
\caption{ Friction force and mean slip length dependence
  on the amplitude of the defect potential $A_0$ for defects in minima
  and in maxima at $T=0$ (black triangles), 100 (grey circles) and 300K
  (red squares)}
\label{Fig11
\end{figure*}

As we have seen, for surface defects, the change in the mean friction
force can not be understood in terms of the change in the mean slip
length.  In order to understand our numerical results we have done an
study of the probability distribution function of the slip length. A
rich scenario where jumps of very different length may coexist is
found.

We have identified two main different mechanisms which modify the mean
friction force of the system when defects are considered. First,
defects modify locally the potential profile in a way that change
importantly the instantaneous friction force that the tip experiences
when crosses one defect. Second, the presence of defect also changes
the slip length probability distribution which also changes the mean
friction force.

With respect to the density of defects in the system, our results show
an almost linear dependence on this parameter. We will discuss now on
a different point which is related with the amplitude of the defect
potential given by $A_0$. We have chosen $A_0=-0.71U_0$ for type I
defect in minima and $A_0= 0.71U_0$ for type II defect in maxima and
$A_0=-2U_0$ for type I defect in maxima and $A_0= 2U_0$ for type II
defect in minima. Those values were chosen to get the potential
profiles showed in figure~\ref{Fig1}. However other values of $A_0$ can
be of interest for a particular real situation. Figure~\ref{Fig11}
shows the results of the mean friction force and mean slip length
dependence on the defect amplitude coefficient $A_0$. Type I defects
correspond to $A_0<0$ values and type II to $A_0>0$ values. Results
are given for three temperature values (0, 100 and 300K) and two $U_0$
values (0.27eV and 0.38ev), showing two different physical
situations. The figure shows that the friction force also depends
importantly on this parameter in a way that is comparable to the
effect of temperature or density defects. Figure also shows that, as
expected, results for defect in minima and in maxima with different
sign of $A_0$ are very similar. This was also shown in
figures~\ref{Fig4}, \ref{Fig7} and \ref{Fig9} for instance.

\begin{figure*}[tb]
\centering
\includegraphics[scale=0.35]{12.eps}
\caption{ (a) Mean friction force versus corrugation
  potential amplitude $U_0$ at $T=0$ K. We compare the effects from
  two representative types of surface defects on the friction
  force-corrugation potential curve of the perfect lattice (open
  circles): type I surface defects in maxima (solid triangles up), in
  minima (solid triangles down) and the effect of surface disorder (solid
  diamonds). In (b) the similar comparison at $T=300$ K.}
\label{Fig12
\end{figure*}

To finish, we find interesting to compare our results for surface
defects to the recently studied effect of surface
disorder~\cite{OFajardoPRB2010}. There, surface disorder was modeled
including a small second harmonic term in the standard tip{-}surface
interaction potential,
\begin{equation}
 V(x)=-U_o \left[ 1.0 + \epsilon\ \sin\left( \frac{2\pi x}{b}\right)
   \right] \cos\left( \frac{2\pi x}{a}\right).
\label{disorder}
\end{equation}
Thus the surface disorder changes the potential profile, introduces a
distribution of barrier heights and moves slightly the positions of
the potential maxima and minima.

Figure~\ref{Fig12} compares the results obtained for the case of the
perfect lattice, surface disorder and surface defects. It shows the
results for $T=0$K y $T=300$K and at different values of $U_0$. The
figure shows results for type I defects in minima and maxima. Similar
results for other types of defects are found.  At low temperature we
found that it is not easy to distinguish between the presence of
defects and disorder.  However, an analysis of instantaneous
quantities such as force and tip position allows to discriminate both
situations. At high enough temperature our results indicate that the
role of the surface disorder is screened by the thermal effects but
the presence of surface defects modifies the friction force of the
system. In the regular and in the lattice with disorder the mean value
of the barrier that the tip experiences is the same. However the
presence of surface defects increases or decreases, depending on the
type of the defects, the value of such mean barrier.

Our model accounts for the effect of adsorbed molecules or vacancies
in the lattice, but it could be used also to study artificially
designed grooves or ridges. Our results show that a significant
density of defects in a sample may change the friction force curve at
any temperature and thus such presence affects a comparison between
numerical and experimental results.

However, it is important to point that friction is a very general phenomenon which occurs in several
problems. Because of that, the study of simple models is important
since it allows for understanding basic effects that can be relevant
or realized in different kind of systems. This is the case for
instance of the motion of a single colloidal particle in a colloidal
system. There are now experiments and simulations where a single
colloidal particle can be driven through other particles or quenched
disorder and the effective friction and drag measured for varied
temperature, density, pull rate and so forth~\cite{HabdasEurophys04,ReichhardtPRL04,ReichhardtPRE08,MejiaSoft11}.
Some similar variations on the system can be rapidly realized
by driving a single particle over a random, periodic or
combination of periodic and random substrates in 1D, 2D and even 3D
so that some of the results from the present work
could be tested more directly on real systems.

Another system where the results of the present paper could be applied
is that of vortices in type-II superconductors. Very recent
experiments drag individual vortices over random or periodic
pinning arrays~\cite{HoffmanAPL08,AuslaenderNature09,ReichhardtNature09}. It would be interesting to make a periodic 1D or 2D
pinning potential and drag a single vortex. This experiment could then
be repeated for adding additional defects that could act like
attractive or repulsive sites.

\ack

The authors acknowledge financial support from Spanish MICINN through project
No. FIS2008-01240, cofinanced by FEDER funds. O. Y. Fajardo acknowledges financial
support from FPU grant by Spanish MICINN.

\section*{References}

redpajama_set_name: RedPajamaArXiv


text:
Die Jugend-Olympiamannschaft aus Neuseeland für die I. Olympischen Jugend-Sommerspiele vom 14. bis 26. August 2010 in Singapur bestand aus 54 Athleten.

Athleten nach Sportarten

Badminton

Basketball
Jungen
James Ashby
Ben Fraser
Michael Karena
Reuben Te Rangi
 3 × 3: 14. Platz

Boxen
Jungen
Joseph Parker
 Superschwergewicht:

Gewichtheben
Jungen
Joshua Milne
 Leichtgewicht: 9. Platz

Hockey
Mädchen
Amy Barry
Erin Goad
Rachel McCann
Elley Miller
Kayla Wilson
Georgia Barnett
Jessica Chisholm
Michaela Curtis
Sarah Matthews
Kate McCaw
Rhiannon Dennison
Rose Keddell
Danielle Sutherland
Lydia Velzian
Jamie Bolton
Samara Dalziel

Judo
Mädchen
Haley Baxter
 Klasse bis 63 kg: 9. Platz
 Mixed  (im Team Belgrad)

Leichtathletik

Radsport
Sarah McDonald
Denay Cottam
Sam Shaw
Trent Woodcock
 Mannschaft: 20. Platz

Reiten
Jake Lambert
 Springen Einzel: 21. Platz
 Springen Mannschaft:  (im Team Australasien)

Ringen
Mädchen
Tayla Ford
 Freistil bis 60 kg: 7. Platz

Rudern

Schießen
Mädchen
Jenna Mackenzie
 Luftgewehr 10 m: 13. Platz

Schwimmen

Segeln

Tischtennis

Triathlon

Weblinks
Übersicht der Athleten in der Olympedia

Neuseeland
Sommerspiele 2010

redpajama_set_name: RedPajamaWikipedia


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text:
War, Chaos & Irony in Libya: The West's 'Most Successful' Mission
© AP Photo / Mohamed Ben Khalifa
https://sputniknews.com/world/201508281026312531/
More than 200 people are feared dead after two boats full of migrants sank in the Mediterranean off the coast of Libya.
The tragic scenes have become commonplace in the country, which western governments only four years ago claimed was a striking example of successful foreign intervention.
Authorities are continuing their efforts to retrieve bodies from the water after the vessels capsized shortly after leaving Libya's coastal city of Zuwara, en-route to Italy.
W/ four days remaining in the month, IOM calculates 18,000 #migrants have arrived in Italy from Libya, about 400 died pic.twitter.com/1LTJq2h2DL
— IOM (@IOM_news) 28 августа 2015
The coastal port has become known as a major people-smuggling hub as huge numbers of migrants and asylum seekers from war-torn and poverty-stricken countries in the Middle East and Africa hope of reaching Europe.
Chaos in Libya
© Flickr / Thierry Ehrmann
Western Legacy in Libya Leaves a Hole Filled by Migrants Fleeing for Europe
The seemingly free-reign that people smugglers and human traffickers have in Libya is indicative of the state of lawlessness engulfing the North African country, which has been locked in a four-year civil war.
Already suffering from the outbreak of conflict between rebel groups and government forces of former leader Muammar Gaddafi, a NATO-led alliance, headed by the UK and France, engaged in a bombing campaign to oust the then leader.
Following Gaddafi's death at the hands of an anti-government Libyan rebel group in 2011, many Western leaders praised the success of their military campaign in the country, with then NATO Secretary General Anders Fogh Rasmussen labelling the campaign "one of the most successful in NATO history."
EXCLUSIVE: Libyan PM Blames Turkey and Qatar for Forcing Political Islam on His Country
However instead of a democratic revolution promised and preached by Western governments, Libya descended into an ever-increasingly fragmented state, epitomized by conflict between various rebel groups as they fought for control of the country.
The fighting become so severe that the country's internationally recognized government was forced to flee Libya's capital of Tripoli for the eastern city of Tobruk.
On top of this, a number of Islamist groups have taken advantage of the chaos in Libya, with groups like ISIL and Ansar al-Sharia seizing control of various cities and districts across the country, further exacerbating human trafficking concerns.
The West to Blame
Many have criticized the Western intervention in Libya, arguing that the NATO bombing campaign helped to destabilize the country, thus contributing to Libya's current predicament.
Others, such as Nigel Farage, leader of the British political party UKIP, have said that UK Prime Minister David Cameron and others involved in the bombing of Libya "directly caused" the migrant crisis engulfing the country, and in turn, Europe.
UK under doctrine of supposed humanitarian intervention bombed Iraq Libya UK 12,000 refugees Germany 800,000 per yr Remember that next time
— Mark Wayne (@orwell4ever) 28 августа 2015
"It was the European response that caused this problem in the first place. The fanaticism of [former French president Nicolas] Sarkozy and Cameron to bomb Libya — what they have done is to destabilize Libya, to turn it into a country of much savagery and a place where for Christians the situation is virtually impossible.
"We ought to be honest and say we have directly caused this problem. There were no migrants coming across from Libya in these quantities before we bombed the country and got rid of Gaddafi, however bad he may have been."
With increased numbers of migrants risking the perilous voyage from Libya to Europe, many have criticized the West for creating Libya's problems and then merely walking away, without addressing the issues left behind.
Did anyone tell Cam that his intervention with Sarko in Libya would open gates to this hell?
— Denis MacShane (@DenisMacShane) 28 августа 2015
The EU's immigration policy has been accused of not offering enough legal avenues for people to resettle in Europe, therefore forcing many to try and seek asylum "illegally."
With an anti-immigration rhetoric sweeping across Europe, and EU countries squabbling to come to an agreement to help re-settle refugees stranded by the migrant crisis, the situation continues to worsen in Libya — leaving many to ponder the results of one of the West's "most successful" foreign interventions.
Serbian NGO Chief Wants EU to Adopt Common Stance on Migrants
Merkel Vows to Improve Conditions for Migrants by October
Some 50 Migrants Found Dead in Smuggler Boat Off Libyan Coast
boat, death toll, migration, European Union, Libya, United Kingdom


text:
1. Are there any resorts in Armenia?
There are resorts in such cities of Armenia as Tsaghkadzor, Sevan, Dilijan, Djermuk, Aghveran, Vanadzor, etc. The information about many resorts is available here.
2. Where in Armenia would you suggest spending summer/winter vacations?
In summer the nature of Armenian reaches its peak of bloom in Sevan, Dilijan, Djermuk and Aghveran. Tsaghkadzor is the best place for spending an active winter vacation and engaging in winter sports.
3. What kind of hotels are there in Yerevan?
There are many 3- to 5-star category hotels in Yerevan. The information about hotels in Yerevan can be found here.
4. What is the weather like in Armenia?
The weather in Armenia is mild in winter and hot in summer. In summer the temperature fluctuates between +22C to +36C. The winters are mainly cold, the average temperature is between -15C to -1C.
5. What is the temperature like in Tsaghkadzor?
In summer +25C ~ +35C (75F ~ 95F), in winter -15C ~ -5C (5F ~ 25F).
6. Which are the traditional Armenian dishes?
The traditional and most popular Armenian dishes are: dolma (minced meat, wrapped in cabbage or stuffed in eggplants, peppers and tomatoes), barbeque, qyufta, khash. The Armenian bread (lavash) is the integral part of the Armenian meal.
7. Where can I buy souvenirs?
Souvenirs can be purchased in Vernissage which is located in the centre of Yerevan, close to the Republic Square. Numerous traditonal and contemporary art exhibits are sold here. There are also many other souvenir shops on Abovyan and Tumanyan streets.
8. What kind of museums, galleries, concert-halls, theatres and cinemas are there in Armenia?
You can get detailed information at the web-pages http://www.port.am/afisha (in Armenian and Russian), http://www.armeniainfo.am (in English), http://www.museums.am (in English) or http://www.toms.am.
9. Which is the oldest church in Armenia?
The oldest church in Armenia is the Mother See of Holy Etchmiadzin, which was founded in 303.
10. What can I see in Matenadaran?
Old Armenian parchment manuscripts and books are kept in Matenadaran. Those are unique and do not have analogues in the whole world. The first printed Armenian book, the smallest and the biggest Armenian books can also be found in Matenadaran. For details visit http://www.matenadaran.am.
11. Is it possible to be hosted by Armenian families for a few days to get acquainted with Armenian everyday life?
The Armenians are very hospitable and the guest is always welcome in the Armenian family. For accommodating details contact us at: contact@hyurservice.com.
12. Is it possible to experience the Armenian village life?
We will be pleased to organize a tour to the Armenian villages, where you will have the opportunity to have dinner with the locals, get acquainted with their everyday life, bake lavash, churn out yogurt, etc.
13. What does "Khachkar" (cross-stone) mean?
"Khachkar" is a piece of art which is a kind of symbol for Armenia and the Armenians. It is a carved, usually vertically erected flat stone, on one side of which the main element of the composition - the cross is engraved. Around the cross usually trimmings, eternity symbols, images of flora and fauna, as well as people in the form of icons are depicted. Khachkars are usually erected near monasteries and churches, in cemeteries, close to roads. There are khachkars everywhere in Armenia, and especially in Noratus village there are many khachkars of high level of art.
14. Which is the best place to see and to take photos of Mount Ararat?
The monastic complex of Khor Virap is located very close to Mount Ararat and from there you can easily take photos.
15. What is the currency in Armenia? Can I use dollars or euros in the shops?
The national currency of Armenia is called "Dram" (AMD). The shops trade only in Dram.
16. Where can I exchange money?
There are currency exchange offices everywhere in Yerevan, especially in the big stores and central places. Banks exchange currency, too.
17. For which services in Yerevan is it possible to use bank cards?
Bank cards are accepted in all banks, hotels and many centrally located shops and restaurants in Yerevan.
18. Are there any ATMs in Yerevan?
There are ATMs on Abovyan, Tigran Mets, Tumanyan, Isahakyan streets and Baghramyan and Komitas avenues, as well as near the banks.
19. Can I hire a car with a driver?
Yes, of course. You can get acquainted with the conditions and the pricelist by visiting "Vehicles with driver" section of our web-site.
20. Is it true, that there is an established tax to be paid at the airport when leaving Armenia?
No, starting from April 2009, you do not need to pay 10000 AMD airport tax anymore when leaving Armenia.
21. Which airlines operate flights to Armenia?
Armenian, Russian and Ukraine airlines operate direct flights from almost all the big cities of CIS countries. "Flydubai", "Air France", "Atlasjet", "Aeroflot", "Aseman", "Austrian Airlines", "Czech Airlines", "Siberia Airlines" and other air companies operate direct flights from Dubai, Paris, Istanbul, Moscow, Tehran, Vienna, Prague and from other cities. The timetable of the flights is presented on the web-page of Zvartnots International Airport.
22. Is it possible to get a visa at the airport of Yerevan?
Yes, it is possible. Upon arrival it is necessary to apply to the corresponding department of the airport. In general the procedure lasts 20-25 minutes. The citizens of the CIS member-states, the EU member-states and the Schengen Acquis states do not need visa to travel to Armenia. For the visitors under 18 years old visa is free of charge. By the expiration of the visa dates it should be prolonged at the Passport and Visa Department (Yerevan, 13a, Mashtots Ave).
Visa can be also obtained prior to the arrival (online) by applying to the Ministry of Foreign Affairs of Armenia: http://www.mfa.am/eVisa.
More detailed information regarding visa provision can be found at the web-page of Ministry of Foreign Affairs.
23. What is the maximum amount of foreign currency, allowed to be taken to and out of Armenia?
Any amount of foreign currency can be taken to Armenia. In case of taking more than 5.000.000 AMD (or equivalent currency) out of the country, customs declaration should be filled in.
24. Should a visa to Artsakh be obtained? Citizens of which countries should have the visa?
The visa to Artsakh is necessary for all foreign country citizens, except for the ones from CIS countries and Argentina.
25. Where in Armenia is it possible to make International calls? Do they sell any telephone cards?
International calls can be made in the post offices. There are also telephone cards sold everywhere, which allow to make a call by fixed and mobile phones.
26. What kind of restaurants are there in Yerevan?
There are Armenian ("Afrikyanneri pandok" - 39, Sayat-Nova Ave. and 1, Pushkin Str.), Georgian ("Mimino" - 7, Alek Manukyan Str.), Arabian ("Lagonid" - 37, Nalbandyan Str.), Chinese ("Beijing" - 33, Sayat-Nova Ave. and 9, Tumanyan Str.), Italian ("Ai Leoni" - 40, Tumanyan Str. and "Gusto" - 11, Abovyan Str.), Mexican ("Cactus" - 42, Mashtots Ave) and many other restaurants in Yerevan.
27. What means of public transportation can be found in Yerevan?
The following means of public transportation are available in Yerevan: metro (100 AMD), taxicabs (100 AMD per 1 km, the minimum fare is 600 AMD), buses (100 AMD) and minibuses (100 AMD). Taxicabs, buses and minibuses connect Yerevan and the adjacent areas.
28. What is the electricity system in Armenia?
The electricity in Armenia is 220 volt, 50 Hz , as in almost all of Europe. The Armenian socket standard is CEE, mostly without lines. The outlet adaptors for the standards of different countries can be purchased in almost all home appliances and electronics stores in Yerevan.
In case you have other questions, please send them to our e-mail address: contact@hyurservice.com.


Originally published by Capital Press June 11, 2018.
Under the California Endangered Species Act (CESA), the California Department of Fish and Wildlife (CDFW) is required to conduct status reviews of species listed as either threatened or endangered every five years. The department has unlawfully failed to conduct these five-year status reviews for 231 out of the 235 listed species, and apparently has no intention of conducting the reviews.
In 2016, the California Cattlemen's Association, with the help of the Pacific Legal Foundation, filed a lawsuit against the CDFW to compel them to conduct the mandatory five-year reviews. The status reviews are extremely important, because they can be crucial to the recovery of listed species. Californians have a vital interest in seeing species recover, for both economic and environmental reasons.
However, without up-to-date information on species, we lack the sound scientific analysis needed to determine if the department's programs are making progress toward their stated goal of restoring threatened and endangered species.
Since the lawsuit was filed, CDFW officials have dragged their feet, effectively delaying the 231 overdue status reviews for more than two years. They recognize the reviews are mandatory, but claim they do not need to complete them because it would cause species to go extinct. Yet when pressed on this point, department officials cannot point to anything, other than a lack of resources that would make their contention true.
There are two reasons why the department is wrong about its requirement to complete the five-year reviews.
First, the CDFW fears its other activities will come to a screeching halt because of the resources needed to conduct these five-year status reviews. But the department bases its resource estimates on the wrong type of status review. This confusion between two types of status reviews is like equating traveling from San Diego to Sacramento on foot with traveling there by car. Even though the word "traveling" is the same, the two modes of transportation make the trip extremely different in terms of time required. Similarly, conducting a five-year review is much less time consuming than conducting the extensive status review the department claims it has to undertake.
The department incorrectly argues that to comply with the five-year status review requirement, it needs to undertake what is called a 12-month status review. This more intensive type of review, which requires significant investment of resources and collaboration with outside scientists, ultimately concludes with a recommendation to list or not list the species. These reviews often require multiple CDFW scientists and biologists to review complex and challenging questions related to the species' legal status. Also, many of these reviews undergo peer review, which adds to the time required for completion.
By contrast, the process for the five-year status review requirement is much less intensive, requiring only 90 days to complete. The five-year review is statutorily equivalent to what is called a petition evaluation, which the department conducts whenever stakeholders petition to list or delist a species under CESA. To complete a five-year status review, the department would only need to evaluate and compile information it has on hand to analyze whether a change in a species' status is warranted.
Second, the California legislature recognized there would be resource constraints when it enacted the five-year status review requirement. In fact, the wise stewardship of taxpayer resources was a key rationale for the requirement: legislators understood that tracking the progress of species listed under the CESA was necessary to efficiently and effectively allocate funds to those species most deserving of protection. The legislature, understanding the importance of these reviews, has not repealed or relaxed the requirement that the five-year reviews be conducted.
This five-year status review requirement ensures that the CDFW is periodically checking in on listed species. These reviews play an important role in the conservation of threatened and endangered species, because they compile crucial information about how a species is doing, current population levels, the potential threats and harms the species might face, and how the recovery programs are actually working. This allows officials to make decisions based upon the most up-to-date data and analysis.
The five-year reviews also protect property owners from unnecessary regulatory burdens imposed because of species that are no longer threatened, and they protect taxpayers by ensuring the department is efficiently handling its resources and attending to those species that face the most serious threats of harm.
The federal government recognizes the value of regular reviews in endangered species management. The U.S. Fish and Wildlife Service implements a similar five-year review requirement to ensure species listed under the federal Endangered Species Act are those that actually warrant protection. The federal review revealed that at least seven of the species listed under CESA may be eligible for reclassification or delisting. But because the CDFW has failed to complete its five-year reviews, we have no idea whether these actions might be appropriate at the state level as well.
Californians care deeply about the conservation, protection, and enhancement of our state's threatened and endangered species, and we have entrusted that vital responsibility to the CDFW. By abdicating its responsibility to conduct regular status reviews of endangered and threatened species, the department is failing to uphold its end of the bargain. It's time for the CDFW to follow the law and conduct the five-year status reviews as required.


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I'm addicted again, I don't want to be I'm not proud of it but I am. I'm not 100% sure how it happend, it was a combanation of no will power and yummy treats at work, on the road, and Easter. My face is breaking out, I'm tired and I'm getting migrains again, I need to change.
This should be a good start, hopefuly I'll be back on track in no time.


text:
Three Charged in Hit & Run, Weapons Offences
Three Charged in Hit &…
BreachDrugs & AlcoholFirearms and Weapons relatedTraffic & Motor vehicle incidents
Three adults are charged in connection to alleged Weapons and Hit & Run incidents that happened on Sunday evening, June 7th.
This investigation began at approximately 8:20 p.m., Sunday, June 7, 2020, when police received a report of a collision, in the area of the 3100 block Lakeshore Drive, where one vehicle, believed to have an impaired driver and a number of passengers, left the scene. The complainant reported seeing a firearm on the lap of the driver. While police were looking for the vehicle, a second call came in reporting an impaired driver at a location in the 1300 block of Broadway Avenue. It was the same suspect vehicle. Police conducted surveillance and then attempted a traffic stop in the area of Victoria Avenue and Arcola Street. The suspect vehicle fled, and was followed to College Avenue and Osler Street, where four people jumped out of the vehicle and scattered. Patrol and canine members apprehended all four passengers; two were released without charge. Of the remaining two: a female and male were arrested, allegedly in possession of weapons and in breach of court-ordered conditions. The suspect vehicle ended up in the area of the 2100 block Elphinstone where it became inoperable after hitting two other vehicles and a tree. The driver fled on foot and was apprehended by a canine team. The driver was taken to hospital for treatment of dog bite injuries and cleared. The driver and two of the passengers were charged.
Twenty-three year-old Tyrone Lane EAGLE, of Regina, is charged with:
3 X Hit & Run [320.16(1) CC];
Refusal to comply with demand [320.15(1) CC; and
Operate Conveyance Dangerous to Public [320.13(1) CC].
EAGLE made his first court appearance on these charges in Provincial Court at 9:30 a.m. on Monday, June 8, 2020.
Twenty-one year-old Justine Lonnie Mae LITTLETENT, of Regina, is charged with:
Possession of a Weapon for a Purpose Dangerous to Public Peace (machete) [88 CC]; and
Breach of Probation [733.1(1) CC]; and
Breach of Undertaking [145(5)(a) CC].
LITTLETENT was released with a court date of August 20, 2020.
Nineteen year-old Aiden MCNAB-MOOSEMAY, of no fixed address, Regina, is charged with:
Possession of a Weapon for a Purpose Dangerous to Public Peace (bear spray) [88 CC]; and
Breach of Probation [733.1(1) CC].
MCNAB-MOOSEMAY made his first court appearance on these charges in Provincial Court at 9:30 a.m. on Monday, June 8, 2020.
Categories: Breach, Drugs & Alcohol, Firearms and Weapons related, Traffic & Motor vehicle incidents June 8, 2020
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