SINGAPORE – The National University of Singapore (NUS) and the Singapore Maritime Institute (SMI) announced on Friday (June 29) the setting up of an S$18 million research centre to help Singapore's maritime and port industries to develop innovative capabilities, and enhance their global competitiveness.
The new Centre of Excellence in Modelling and Simulation for Next Generation Ports (C4NGP) will be part of NUS' engineering faculty, and will collaborate with companies in Singapore's maritime and port sectors to improve their technical know-how, efficiency and productivity, the two institutions said.
The C4NGP will also work with companies to ensure that its R&D efforts are aligned with industry needs.
The centre aims to focus on the following areas over the next five years: designing and building maritime systems, conducting navigational channel capacity studies, studying various port terminal systems, and examining land transport-related systems.
About 20 NUS researchers are expected to work on projects in these areas.
Professor Freddy Boey, NUS senior vice-president of graduate education and research translation, said the centre will work closely with the industry to "co-create cutting-edge solutions that could advance these sectors".
The C4NGP governing board, chaired by Prof Boey, will comprise members from key stakeholders such as the Maritime and Port Authority of Singapore (MPA), and the SMI, along with other industry partners.
The centre will also be jointly led by Associate Professor Chew Ek Peng and Associate Professor Lee Loo Hay from the Department of Industrial Systems Engineering and Management at NUS' Faculty of Engineering.
The agreement to set up the new centre was signed on Friday by the dean of NUS Faculty of Engineering, Professor Chua Kee Chaing, and executive director of SMI Toh Ah Cheong.


We have enclosed a $50 donation to the Aquatic Club (OAC) to honor the many hours both of you donate to the youth swimmers in our community. Since you have taken over the leadership of OAC including coaching, it has grown in the number of swimmers in the program and the number of meets OAC sponsors. Both of you have spent countless hours of your time coaching swimmers, managing OAC and officiating at swim meets. Your dedication and hard work has come to the attention of SSSSH. Attached is a little explanation of SSSSH and Hal Reichle.
Hello, My name is Sandi. I was reading through the June 9, 2003 issue of People magazine. I saw the write up on Hal, and all of the kind deeds others were doing in his honor. I had a question…I wanted to know how I could get an issue of the news letter of good deeds that the family issues, and also, wanted to let them know how great I felt reading the article. I am a mother of a disabled child and this story just was amazing. The kindness this gentleman had, and the friends that carried his message was more than words could say. Any information on how I could become more involved I would enjoy reading. Thank you in advance, Sandra.
I just heard about Hal Reichle on my local radio station. They gave me your mailing address and the website address. I immediately logged on to your website and read your stories. My heart feels so warm - I love to hear about people like this. I've been let down a lot in my 30 years and it truly warms my heart knowing that there are good people in this world.
Because of my heartbreaks in my past, I have built a hard exterior and am often miss-trusting of others who cross my everyday path. Stories like this and knowing that there are good people in this world makes me feel empowered and a little less threatened.
I worked in downtown Seattle on a major construction site. I worked with about 300 tradesmen. Our working day usually ended about 3pm.
As you may know, traffic in downtown Seattle during rush hour can be the ultimate nightmare. On this particular summer day, my then boy friend (now husband - we worked together) were on our long trek home, traveling on the busy back roads of Seattle, when we were stopped by a traffic light. A blind lady was trying to cross the street. She had her cane and seemed to be looking for the curb to step up and be on her way. Unfortunately, because of other local construction, the curbs were torn out and all that remained was safety fencing along the perimeters of the construction sites; this was on all four corners of this stoplight.
While traffic stood still through maybe three green lights - I waited patiently to see if any other respectable bystander would assist this lady. Now knowing that traffic in Seattle during rush hour on a hot summer day can cause irritability - I am not surprised that no one ran to her rescue.
I could see that she was frustrated and beginning to cry - as was I, feeling for her. So, out of nowhere, I jumped out of my car, leaving my door open, and ran to her rescue. She was very shaken, as some of the less patient, shall I say "people" had been honking at her-and shaken, rightfully so - I would be. After I introduced myself, calmed her down, and explained to her why she could not find the curb; I grabbed her arm, and asked her for instruction on how to help her. She said, "let me hold on to the back of your arm", firmly adjusting her hand on the backside of my right elbow, and instructing me to lead her and she will follow. When we arrived in the safe part of the block, she thanked me, hugged me and said, "god bless you" - I let her go on her way and hurried back to my car.
However, those "impatiens's", started to continue on there way - this upset me, so I snapped and pointed for them to stop - while I settled safely back in my car. They obliged. Then off we all continued into the mayhem of workday, rush hour traffic in downtown Seattle.
I share this story all the time, I think of this lady everyday. I hope she feels as warm hearted about me, as I do about her. This situation could have been terrible. But, because of my (I guess - I am still a little skeptical) giving spirit, I jumped to her rescue.
My sweet grandma said (when I shared this story with her - she is now gone) "darling, you are now 'for sure' going to heaven".
Thank you for letting me share this with you - and I hope you share this story with others.
To: Secret Society of Serendipitous Service for Hal.
I know this woman, she helps people all the time. Her name is Joanie O'Rourke and she works for Hampton County (South Carolina) recycle. I don't know much about her except that she is always smiling and she helps the old folks a lot. She don't have much. I found out that she was wanting to go to Australia and had been saving for over 2 years. Well she had it all stolen from her truck back in February (03). I had just found out about it. When I asked her about it she said she guessed the person that took it needed it more. I want to find a way to help her make her dream come true. Maybe if you folkes up there prayed for her, she can go and be with her friend in Australia. I put in a note at the church too. I hope it helps her. Thank you for your prayers.
I was grocery shopping about two months ago and while at the checkout, I could see an elderly woman outside standing beneath the canopy for protection from the rain. She had with her one of those metal pushcarts that people in urban areas use so often to easily carry bags/packages while walking. When I saw her speaking to some kids, I thought that she might have been asking for the time while she was waiting for her taxi to arrive. As I was exiting the supermarket, she approached me and actually asked me for a ride back to her home which was about a mile away. Against what I had been taught as a child about not giving rides to strangers, and considering that she was so elderly and fragile looking, I consented to give her a ride. When I finally finished loading her groceries and big metal pushcart (which I noticed she was actually using more as a walker) it really began to downpour.
On the short ride home, I just kept thinking to myself how this woman, an Italian immigrant, had no family left or children nearby to help her with such little things such as grocery shopping. She was completely alone. During the ride, she thanked me profusely for my act of kindness that didn't even take 10 minutes out of my day but meant the world to her.
When putting flowers on the graves of my parents, I noticed the grave of a boy who died of heart disease when we were in the 7th grade, more than four decades ago. Knowing his family would arrive within days to decorate his grave for Memorial Day, I wrote a note to the boy, telling him I remembered how beautiful and nice he was and that I would never forget him. I mounted it to a stick, and stuck it in the ground by his stone where his loved ones would find it and know they weren't the only ones who mourned him after all these years. I did it for the family. I did it for Hal.
Several years ago, just a few weeks after the September 11 attacks, my husband and I took a trip to Italy. We were somewhat apprehensive about leaving the country and we were more observant of those around us. We were particularly interested in the thoughts and reactions of other Americans traveling abroad.
On our last night in Siena, we found a casual, bustling restaurant popular with the locals and were lucky to get a table. The food and wine were excellent and we were enjoying ourselves when we noticed a table of American college students nearby. Each of us observed to ourselves that they seemed to be ordering sparingly to save money. For some reason, my husband asked if I thought we should pick up their check. I had been thinking the same thing, so we did exactly that when we paid our own bill. We asked the waiter not to tell them that their bill was paid until after we had left. It was our hope that this would allow them to order a little more.
We still wonder what moved us to do that, but we agree it was one of the most fun things we have done on the spur of the moment. Maybe it was the spirit of Hal Reichle?
I was delighted to see the article about Hal in our local newspaper. My daughter went to High School with Hal and I am also a Hiram grad.
In the few months I performed 2 anonymous acts of kindness.The first was to buy several bags of groceries for a mother with small children who was a visitor to a local soup kitchen when her assistance check was delayed. I also gave money to a family whose home had been flooded. In both instances, I was able to get help to them without their knowledge of who did it.
Our mens' baseball league has a group of "Angels in the Outfield" who, in honor of the spirit of SSSSH, provided for a young woman on a tight budget to travel to Georgia to attend to her mother, who had open-heart surgery. Also, for her loss of earnings for the time she was out.
I sent a poem like this, laminated, along with a pretty good sized stuffed animal (bear). He is the "softy" referred to in the poem. My friend from church told me about her very ill friend. I told my friend I'd pray for her and send her get well cards. However, the poem and bear went anonymously. Neither my friend nor the sick lady knows where the poem and bear came from. Bye!
I plan soon on sending an anonymous gift card to a grocery store, to a friend of mine.
I saw your story this Thanksgiving weekend on TV and loved it!!!! It is something I have been a fan of for a long time. The only truly anonymous thing I have done was in a casino when I had a pot load of nickels, I hate playing nickels slots so I dumped all my nickels into a rather disheveled mans bucked without stopping or looking back. I have helped others with the stipulation no one else ever know and it never be discussed. I like your idea better and will promote it it.
Thanks again for the cards!
A group of my friends have decided to send Christmas stockings filled with misc. goodies to soldiers stationed in Iraq and Kuwait. I packaged up my 4 stockings the other day and sent them off. We send them to one certain person stationed in Kuwait who works in such a capacity as they have contact with units that pass thru their area on their way to Iraq. This individual will distribute them accordingly. I dropped a Reichle card in each of the stockings along with Christmas wishes and Thank Yous for their giving of theirselves. No return addresses available for them to contact.
As I was watching the video pic on ABC it just reminded me of myself. I've often offered to help or tried to help individuals that can't help themselves. I am an owner of a printing firm here in NY. If there is anything I could do to help you, please feel free to contact me or e-mail me. If you need leaflets to pass or cards, whatever it may be.
On Christmas Eve night a few years back I was out getting gas when I saw a poor migrant family pull up in an old, beat-up truck. There were several kids inside and they were obviously poor. I decided to perform a "random act of kindness" for them and pay for their gas. Then I hung out in the store to see their reaction. When the man began to pay for his gas the clerk tried telling him his gas was already paid for by a stranger. The man still insisted on paying, and eventually the man became angry and went to get his wife to come in, leaving the kids in the car by the pump. There was great agitation as the man and his wife kept arguing with the clerk, and before long there was a huge line backed up. The problem: the man and his wife didn't speak or understand anything in English, and the clerk didn't speak Spanish. The man was getting angry because he just wanted to pay for his gas and leave, but when the clerk wouldn't take his money he figured the clerk either didn't understand him or was just giving him a hard time. I felt so bad. In the end, the man insisted on dropping his money on the counter and walking out the door. The money ended up going to pay for someone else's gas that night. I have since taken several courses in Spanish, and I will see about asking an old teacher about translating the "Reichle Cards." Anyone know French? America is a big "melting pot!"
I saw your spot on Good Morning America last week and I am so excited. This is such a wonderful thing. I can't wait to "pull a Hal", it is just a matter of time and place. This is what makes life worth living, as Hal knew!
Saw the story on Good Morning American last week and was very moved. I will carry on Hale's efforts and hand out your card. This is quite a great thing you are doing for a friend.
I was sent the home web page of the SSSSH... and thought that it was so interesting.. and well. I always thought that this entire thought was orginated with the Christian belief. I know that in my humble life, I look back and find a few places I could say I was being SSSSHed. but as of this time in the stream of things.. I do have one thing I like to give. Me and my knowledge. I work at a Free Health clinic.. I am a Nurse for many years.. kinda retired/disabled.. but there is an entire crew that gives of their time each week.. several days a week to provide needed medical services to those who are in the most need. I am very proud to say, that it has been a joy in my life.. and being able to search out, and locate different programs to benefit my patients. So.. all of those who have a momem to spare, and this is a great way to be involved in SSSSH. Me and my husband of 35 years have been doing this sevice for many years... and I feel it makes me qualified to be a proud SSSSSH.
I am doing a speech in my communications class on doing good deeds for others. I saw a show on GMA regarding your organization. I would love to mention your organization in my speech and add any comments you might want to add.
I think this is a wonderful thing you are doing, I'm sure Hal is very proud.
I found out about a grandmother who was raising 4 grandchildren alone, ages 1 -7 years. She has very little money and had nothing for them for Christmas. She also needed a crib and other necessities. I was able to give her some money and toys for the children's Christmas through a kind man who was delivering donated items to her home.
Hello. I am a Hiram a Hiram Student. I pulled a Reichle in Hal's honor. Here's what I did, while eating lunch at a fast-food restaurant in downtown Cleveland, I saw a man asking people for money outside the door. I purchased a meal for him and gave it to him as I left.
Can you believe how many responses you have had since November?? The media actually does send out positive messages! I, too, was one that didn't write down the address. It took me two days to figure out how to search for you. I have turned many people on to your website at my workplace. We work for a school that in the past has been a school that was more in of a position to help than to need help. With the growth in our area, we are now seeing a change in our children, their families and their needs. Some of the kids in our lives not only see the need to help but so many have reached out to help with what little they have themselves, they must be angels Hal has sent to us. I wish I had known Hal, but I know a bunch of people that he would be proud of, including everyone who has taken part in this group. Thank you for helping people find a way to go out and be a part of something has been lost in our day and time; trust, sincere goodwill and just simply doing what should be done!
I don't even remember where I read about SSSSh, but I checked out the website and loved it. I printed out the cards and I was on a mission within days. I am in the Army, and have been for 11 years. I went onto our Air Force base the other day to get some uniforms altered for Christmas. I live in the Northeast and it's VERY cold right now. My mom was with me for the ride that day. After doing my errand, I stopped at Dunkin Donuts for a big box of Joe. My mother was very confused. I gave her the card and she was ever more confused, so I explained who Hal was and what he did, and that we were going to pull a Reichle. She was so excited. As we were leaving the base, I stopped at the gate where the poor freezing soldiers were standing and letting cars pass. They asked if anything was wrong and I handed them the coffee and bag of condiments with the card taped to the box. I told them that 'a soldier down the street wanted me to give this to you'. He looked so confused!!! I got in the car and we left, watching in the rear view the whole time. They read the card and high fived one another. They must have loved that hot coffee being so cold! A Reichle for Hal's fellow Air Force guys!! Enjoy guys!
In honor of Hal Reichle, we gave $100 gift certificate to Giant Eagle anonymously to a woman with 5 children (who lives paycheck-to-paycheck) so she and her family could enjoy a nice Christmas dinner.


text:
\section{Introduction}

The remarkable recent progress in the fabrication techniques of
nanometric semiconductor structures has stimulated a rapid
development of the emerging field of mesoscopic physics \cite{mitin,
davies, datta}. In particular, the fabrication of devices of a size
shorter than the electron coherence length has motivated the study
of systems where the conduction electrons exhibit a fully quantum
mechanical behaviour. Such systems are the electron analogue of
optical devices. For instance, a multichannel quantum wire can be
regarded as the electron counterpart of an electromagnetic waveguide
\cite{datta}.

On the other hand, there is an active research on the coherent
dynamics of the electron spin in mesoscopic systems \cite{ssqc} due
to its potential applications to the control of electron transport
in so-called ``spintronic" devices \cite{dattadas}, as well as in
the implementations of quantum information processing devices
\cite{lossdiv}. Such interest is justified by the long decoherence
times/distances exhibited by electron spin in semiconductors
\cite{ssqc}.

In this paper, we consider a 1D wire with two spin-1/2 magnetic
impurities embedded at fixed positions. The 1D wire could be
realized by a semiconductor quantum wire \cite{davies} or a
single-wall carbon nanotube \cite{nanotube}, while each impurity
could be implemented by means of a single-electron quantum dot
\cite{ssqc}. Conduction electrons entering the wire undergo multiple
scattering by the two impurities before being reflected or
transmitted. At each scattering event the electron and impurity
spins elastically interact via an exchange coupling which can induce
a spin-flip. If the two impurities were static, the present system
would reduce to the electron analogue of a Fabry-Perot (FP)
interferometer with partially silvered mirrors \cite{rossi}, with
the impurities playing the role of the two mirrors. It follows that
our system can be considered as a generalized FP interferometer
where each mirror has a quantum degree of freedom: the spin.

Since scattering with magnetic impurities is a well-known source of
electron decoherence \cite{datta}, one would expect that, when
mirrors with internal degrees of freedom are considered, the typical
resonance condition found in a standard FP interferometer
\cite{rossi} would be modified. The expected loss of electron
coherence is due to the fact that -- contrary to scattering by
static impurities which give rise to well fixed phase-shifts --
scattering by magnetic impurities causes an uncertainty in the phase
shift of the scattered electron \cite{imry,imrybook}. Equivalently,
decoherence can be regarded as a consequence of the unavoidable
entanglement arising between the electron and impurity spin degrees
of freedom \cite{imry, schulman}.

In the present paper, we analyze the case where \emph{two} magnetic
impurities are embedded in the wire. In \cite{ciccarello} we have
investigated how non-local correlations arising when the scatterers
are in an entangled state affect the wire transmittivity. In the
present paper, we will extend our analysis providing all the details
of our approach and expand the discussion of the possible
applications. In particular, we will show that perfect resonance,
i.e.\ perfect transmittivity for suitable electron wave vectors,
appears for the singlet maximally entangled state of the impurity
spins. Remarkably, these resonant wave vectors turn out to be
independent on the electron-impurity coupling constant. Moreover,
when this resonant condition is fulfilled, perfect transmittivity is
obtained for all possible electron spin states. On the contrary, a
large inhibition of electron transmission through the interferometer
is observed for the case of the triplet maximally entangled state.
As we have pointed out in a recent work, the above behaviour of the
singlet and triplet entangled states suggests a novel potential use
of entanglement as a tool to modulate the conductance of a 1D wire
\cite{ciccarello}.

This paper is organized as follows. In section
\ref{system_approach}, we describe in detail the system and the
approach used to derive all the transmission amplitudes needed to
calculate the single electron transmittivity for any arbitrary
initial spin state. In section \ref{one_spin_up}, we discuss the
transmission properties of the interferometer for initial spin
states with only one impurity spin up. Perfect ``transparency"   is
exhibited for the singlet state of the impurities. Section
\ref{conservation} is devoted to the explanation of this phenomenon.
In section \ref{ent_controlled}, we show how our results suggest a
possible use of entanglement of the impurity spins as a tool to
modulate the transmission of the wire. In section
\ref{aligned_spins} we investigate the transmission properties of a
different family of impurity spin states, namely the one for which
both spins are aligned. We show that, in this case, entangled states
exhibit no relevant interference effects. Finally, in section
\ref{ent_gen} we propose a scheme to generate maximally entangled
states of the impurity spins via electron scattering. The form that
an initial spin state must have in order to have perfect
transparency is derived in \ref{appendix}.

\section{System and approach} \label{system_approach}

Our system consists of a clean 1D wire into which two spatially
separated, identical spin-1/2 magnetic impurities are embedded. We
assume that single conduction electrons can be injected into the
wire. Due to the presence of an exchange interaction, each
conduction electron undergoes multiple scattering with the
impurities before being transmitted or reflected. Let us also assume
that the electron spin state can be prepared at the input of the
wire and measured at its output (this could be achieved through
ferromagnetic contacts at the source and drain of the wire
\cite{ssqc}). To be more specific, consider a 1D wire along the
$\hat{x}$ direction with the two magnetic impurities, labeled 1 and
2, embedded at $x=0$ and $x=x_0$, respectively, as illustrated in
figure \ref{wire}.
\begin{figure}
 \includegraphics [scale=0.6]{Fig1}
 \caption{1D wire with two magnetic impurities, labeled 1 and
2, embedded at $x=0$ and $x=x_0$, respectively.}
\label{wire}
\end{figure}
Assuming that the conduction electrons are injected one at a time
(this allows us to neglect many-body effects) and that they can
occupy only the lowest subband, the Hamiltonian can be written as
\begin{equation} \label{H}
H=\frac{p^{2}}{2m^*}+ J \, \mbox{\boldmath$\sigma$}\cdot
\mathbf{S}_{1} \,\delta(x)+ J \, \mbox{\boldmath$\sigma$} \cdot
\mathbf{S}_{2}\,\delta(x-x_{0})
\end{equation}
where $p=-i \hbar \nabla$, $m^*$ and $\bm{\sigma}$  are the electron
momentum operator, effective mass and spin-1/2 operator
respectively, $\mathbf{S}_{i}$ ($i=1,2$) is the spin-1/2 operator of
the $i$-th impurity and  $J$ is the exchange spin-spin coupling
constant between the electron and each impurity. All the spin
operators are in units of $\hbar$. Since the electron-impurity
collisions are elastic, the energy eigenvalues are simply
$E=\hbar^{2} k^2/2m^*$ ($k>0$) where $k$ is a good quantum number.
As the total spin Hilbert space is 8D and considering left-incident
electrons, it turns out that to each value of $k$ there corresponds
an 8-fold degenerate energy level. Let
$\mathbf{S}=\bm{\sigma}+\mathbf{S}_{1}+\mathbf{S}_{2}$ be the total
spin of the system. Since $\mathbf{S^2}$ and $S_z$, with quantum
numbers $s$ and $m_s$, respectively, are constants of motion, $H$
can be block diagonalized, each block corresponding to an eigenspace
of fixed $s$ (for three spins 1/2, the possible values of $s$ are
$1/2, 3/2$) and $m_s=-s,...,s$ (from now on the subscript $s$ in
$m_s$ will be omitted). Let us rewrite equation (\ref{H}) in the
form
\begin{equation} \label{H2}
H=\frac{p^{2}}{2m^*}+\frac{J}{2}
\left(\mathbf{S}_{e1}^{2}-\frac{3}{2}\right)
\delta(x)+\frac{J}{2}\left(\mathbf{S}_{e2}^{2}-\frac{3}{2}\right)
\delta(x-x_{0})
\end{equation}
where $\mathbf{S}_{ei}=\bm{\sigma}+\mathbf{S}_{i}$ ($i=1,2$) is the
total spin of the electron and the $i$-th impurity. Note that in
general $\mathbf{S}_{e1}^{2}$ and $\mathbf{S}_{e2}^{2}$ do not
commute.

Here we choose as spin space basis the states $\ket{s_{e2}; s, m}$,
common eigenstates of $\mathbf{S}_{e2}^{2}$, $\mathbf{S}^{2}$ and
$S_z$ \cite{nota1}, to express, for a fixed $k$, each of the eight
stationary states of the system as an 8D column. Since
$\mathbf{S}_{e1}^{2}$ and $\mathbf{S}_{e2}^{2}$ do not commute, the
latter in general is not a constant of motion and thus $s_{e2}$ in
general is not a good quantum number.

To determine the transmission properties of the interferometer for a given arbitrary initial spin state, we have to calculate the
transmission probability amplitudes $t_{s_{e2}}^{(s'_{e2};s)}$ that an electron prepared in the incoming state
$\ket{k}\ket{s'_{e2}; s, m}$ is transmitted in the state $\ket{k}\ket{s_{e2}; s, m}$. The calculation of
$t_{s_{e2}}^{(s'_{e2};s)}$ requires the exact stationary states of the system to be derived. To do this, we properly generalize
the quantum waveguide theory approach of reference \cite{amjphys} for an electron scattering with a single magnetic impurity to
the case of two impurities. Note that due to the form of $H$ (see equation \ref{H2}) coefficients $t_{s_{e2}}^{(s'_{e2};s)}$ do
not depend on $m$, as it will be more clear in the following. We first consider the subspace $s=3/2$ and then the subspace
$s=1/2$.

\subsection{Subspace $s=3/2$} \label{subspace_s32}
In this 4D subspace ($m=-3/2,-1/2,1/2,3/2$), both $s_{e1}$ and $s_{e2}$ can assume only the value 1. It follows that in this
subspace $\mathbf{S}_{e1}^{2}$ and $\mathbf{S}_{e2}^{2}$ effectively commute. The states $\ket{s_{e2}; s, m} = \ket{1; 3/2, m}$
are thus also eigenstates of $\mathbf{S}_{e1}^{2}$ and the effective electron-impurities potential $V$ in equation (\ref{H2})
reduces to
\begin{equation} \label{V32}
V=\frac{J}{4} \, \delta(x)+\frac{J}{4}\, \delta(x-x_{0})
\end{equation}
Note that the two impurities behave as if they were static and the scattering between electron and impurities cannot flip the
spins. The four stationary states take therefore the simple product form
\begin{equation}
\ket{\Psi_{k,1;3/2,m}} = \ket{\phi_{k}}\ket{1; 3/2, m}
\end{equation}
where the second index in the left-hand side stand for $s_{e2}=1$
and where $\ket{\phi_{k}}$ describes the electron orbital degrees of
freedom. To determine the wave function $\phi_{k}(x)$, we split the
$\hat{x}$ axis into the three domains $x<0$, $0<x<x_{0}$ and
$x>x_{0}$ labeled I, II and III, respectively. Solving the
Schr\"{o}dinger equation, the wave function $\phi_{k,i}(x)$ in each
domain $i=I, II, III$ is readily written as
\begin{eqnarray}
\phi_{k,I}(x)&=&A_{I}e^{ikx}+B_{I}e^{-ikx}\
\label{wavefunction1}\\
\phi_{k,II}(x)&=&A_{II}e^{ikx}+B_{II}e^{-ikx}
\label{wavefunction2}\\
\phi_{k,III}(x)&=& t_{1}^{(1;3/2)}e^{ikx}
\label{wavefunction3}
\end{eqnarray}
Setting $A_{I}$ to unity, the other four coefficients appearing in
equations (\ref{wavefunction1}) -- (\ref{wavefunction3}) can be
found by requiring the wave function to be continuous at the two
boundaries $x=0$ and $x=x_0$ and its derivative $\phi'_{k}(x)$ to
exhibit a jump at the same points according to
\begin{eqnarray}
\phi'^{+}_{k}(0)-\phi'^{-}_{k}(0)&=&\frac{2m^*}{\hbar^2} \frac{J}{4}\,\phi_{k}(0)\label{jumps32_1}\\
\phi'^{+}_{k}(x_0)-\phi'^{-}_{k}(x_0)&=&\frac{2m^*}{\hbar^2} \frac{J}{4}\,\phi_{k}(x_0) \label{jumps32_2}
\end{eqnarray}
The last conditions are easily found integrating the Schr\"{o}dinger
equation across each impurity (see e.g. \cite{mao}). This yields the
following result for the transmission amplitude $t_{1}^{(1;3/2)}$
\begin{equation}\label{t3/2}
t_{1}^{(1;3/2)}=\frac{64}{64+\pi\rho(E)J\,[16i+(e^{2ikx_0}-1)\rho(E)J]}
\end{equation}
where $\rho(E)=(\sqrt{2m^{*}/E})/\pi\hbar$ is the density of states
per unit length of the wire \cite{mitin, davies}. $t_{1}^{(1;3/2)}$
is thus a function of the two dimensionless parameters $kx_0$ and
$\rho(E)J$. Note that it does not depend on $m$ due to the effective
form (\ref{V32}) of $V$.

\subsection{Subspace $s=1/2$}  \label{subspace_s12}

In this 4D subspace $s_{e1},s_{e2}=0,1$ and thus
$\mathbf{S}_{e1}^{2}$ and $\mathbf{S}_{e2}^{2}$ do not commute and
$s_{e2}$ is not a good quantum number. This is a signature of the
fact that in this space spin-flip may occur. In each of the 2D
$m=-1/2,1/2$ subspaces, the two stationary states are thus of the
form
\begin{equation}  \label{ansatz}
\ket{\Psi_{k,s_{e2}';1/2,m}}=\sum_{s_{e2}=0,1}\ket{\varphi_{k,s_{e2}',s_{e2}}}\ket{s_{e2};
1/2, m}
\end{equation}
where we have used the labeling index $s_{e2}'=0,1$ to indicate that
the incident spin state of (\ref{ansatz}) is $\ket{s_{e2}';1/2,m}$
and where $\ket{\varphi_{k,s_{e2}',s_{e2}}}$ describe the electron
orbital degrees of freedom (from now on we omit the index $k$). Note
that in the case $s=3/2$ discussed in subsection \ref{subspace_s32}
$s'_{e2}$ and $s_{e2}$ coincide.

For a fixed $s'_{e2}=0,1$ the two wave functions
$\varphi_{s'_{e2},0}(x)$ and $\varphi_{s'_{e2},1}(x)$ in each domain
$i=I,II,III$ turn out to take a form analogous to
(\ref{wavefunction1}) -- (\ref{wavefunction3})
\begin{eqnarray}
\varphi_{s'_{e2},s_{e2},I}(x)&=&A_{s_{e2},\,I}^{(s'_{e2})}\,e^{ikx}+B_{s_{e2},\,I}^{(s'_{e2})}\,e^{-ikx}
\label{wavefunction_II_1}\\
\varphi_{s'_{e2},s_{e2},II}(x)&=&A_{s_{e2},\,II}^{(s'_{e2})}\,e^{ikx}+B_{s_{e2},\,II}^{(s'_{e2})}\,e^{-ikx}
\label{wavefunction_II_2}\\
\varphi_{s'_{e2},s_{e2},III}(x)&=&t_{s_{e2}}^{(s'_{e2};1/2)}\,e^{ikx} \label{wavefunction_II_3}
\end{eqnarray}
with $s_{e2}=0,1$. According to the above definition of $s'_{e2}$, the stationary state corresponding to a given $s'_{e2}$ is
obtained by setting $A_{0,\,I}^{(s'_{e2}=0)}=1$, $A_{1,\,I}^{(s'_{e2}=0)}=0$ and $A_{0,\,I}^{(s'_{e2}=1)}=0$,
$A_{1,\,I}^{(s'_{e2}=1)}=1$. In each case, one has to determine the remaining eight coefficients $B_{0,\,I}^{(s'_{e2})},
A_{0,\,II}^{(s'_{e2})}, B_{0\,,II}^{(s'_{e2})}, t_{0}^{(s'_{e2};1/2)}, B_{1,\,I}^{(s'_{e2})}, A_{1,\,II}^{(s'_{e2})},
B_{1\,,II}^{(s'_{e2})}, t_{1}^{(s'_{e2};1/2)}$.
To do this, we need eight constrains. Four of these are obtained imposing the continuity of both $\varphi_{s'_{e2},0}(x)$ and
$\varphi_{s'_{e2},1}(x)$ at $x=0$ and $x=x_0$. The other four constrains come from appropriate boundary conditions for the
derivatives of $\varphi_{s'_{e2},0}(x)$ and $\varphi_{s'_{e2},1}(x)$ at the impurities' sites. To derive these, we insert the
ansatz (\ref{ansatz}) into the Schr\"{o}dinger equation
\begin{eqnarray}\label{scrhrodinger}
\fl\Biggl\{\frac{p^2}{2m^{*}}+\frac{J}{2}
\left(\mathbf{S}_{e1}^{2}-\frac{3}{2}\right) \delta(x)+\frac{J}{2}
\left(\mathbf{S}_{e2}^{2}-\frac{3}{2}\right) \delta(x-x_0)-E\Biggl\}
\sum_{s_{e2}=0,1}\ket{\varphi_{s_{e2}',s_{e2}}}\ket{s_{e2}; 1/2, m}=0\nonumber\\
\end{eqnarray}
We now project both sides of equation (\ref{scrhrodinger}) onto
$\ket{0; 1/2, m}$ and $\ket{1; 1/2, m}$. This yields the two
equations
\begin{eqnarray}
\fl\nonumber\left\{
-\frac{\hbar^2}{2m^{*}}\frac{d^2}{dx^2}+\frac{J}{2}\, \left[\langle
0 \left|\mathbf{S}_{e1}^{2}\right|0 \rangle-\frac{3}{2} \right]
\delta(x)-\frac{3J}{4}\, \delta(x-x_0) -\frac{\hbar^2k^2}{2m}
\right\} \ket{\varphi_{s_{e2}',0}} \nonumber \\+\frac{J}{2} \langle
1 \left|\mathbf{S}_{e1}^{2}\right|0 \rangle
\,\delta(x)\ket{\varphi_{s_{e2}',1}}= 0 \label{coupledeqs1} \\
 \fl \nonumber\left\{-\frac{\hbar^2}{2m^{*}}\frac{d^2}{dx^2}+\frac{J}{2}
 \left[ \,\langle 1 \left|\mathbf{S}_{e1}^{2}\right|1 \rangle-\frac{3}{2} \right]
 \delta(x)+\frac{J}{4}\,\delta(x-x_0)-\frac{\hbar^2k^2}{2m}\right\} \ket{\varphi_{s_{e2}',1}}
\nonumber \\+\frac{J}{2} \langle 1 \left|\mathbf{S}_{e1}^{2}\right|0
\rangle \,\delta(x)\ket{\varphi_{s_{e2}',0}}=0\label{coupledeqs2}
\end{eqnarray}
where $\ket{0}$ and $\ket{1}$ stand for $\ket{0; 1/2, m}$ and
$\ket{1; 1/2, m}$, respectively. The matrix elements of
$\mathbf{S}_{e1}^{2}$ appearing in (\ref{coupledeqs1}) --
(\ref{coupledeqs2}) can be computed through a change of the coupling
scheme expressing basis states $\ket{s_{e2}; 1/2, m}$ in terms of
$\ket{s_{e1}; 1/2, m}$ by means of $6j$ coefficients. This yields
\begin{equation} \label{matrix_coeff}
\langle 0 \left|\mathbf{S}_{e1}^{2}\right|0 \rangle=\frac{3}{2}
\,\,\,\,\,\,\,\,\,\,\, \langle 1\left|\mathbf{S}_{e1}^{2}\right|0
\rangle= \langle 0\left|\mathbf{S}_{e1}^{2}\right|1
\rangle=\frac{\sqrt{3}}{2} \,\,\,\,\,\,\,\,\,\, \langle 1
\left|\mathbf{S}_{e1}^{2}\right|1 \rangle=\frac{1}{2}
\end{equation}
Using (\ref{matrix_coeff}) and integrating both equations
(\ref{coupledeqs1}) and (\ref{coupledeqs2}) across $x=0$ and
$x=x_0$, we end with the four equations
\begin{eqnarray}
\Delta \varphi_{s_{e2}',0}'(0)= \frac{2m^*J}{\hbar^{2}} \frac{\sqrt{3}}{4}\,\varphi_{s_{e2}',1}(0)\label{boundcondacc1}\\
\Delta \varphi_{s_{e2}',1}'(0)=-\frac{2m^*J}{\hbar^{2}}\frac{1}{2}\,\varphi_{s_{e2}',1}(0) +  \frac{2m^*J}{\hbar^{2}}\frac{\sqrt{3}}{4} \,\varphi_{s_{e2}',0}(0)\label{boundcondacc2} \\
\Delta \varphi_{s_{e2}',0}'(x_0)=-\frac{2m^*J}{\hbar^{2}}\frac{3}{4}\,\varphi_{s_{e2}',0}(x_0)  \label{boundcondacc3}\\
\Delta
\varphi_{s_{e2}',1}'(x_0)=\frac{2m^*J}{\hbar^{2}}\,\frac{1}{4}\,\varphi_{s_{e2}',1}(x_0)\label{boundcondacc4}
\end{eqnarray}
where $\Delta
\varphi'_{s_{e2}',s_{e2}}(x)=\varphi_{s_{e2}',s_{e2}}^{'+}(x)-\varphi_{s_{e2}',s_{e2}}^{'-}(x)$.

Equations (\ref{boundcondacc1}) -- (\ref{boundcondacc4}) represent
the appropriate boundary conditions for the derivatives of
$\varphi_{s'_{e2},0}(x)$ and $\varphi_{s'_{e2},1}(x)$ at the
impurities' sites. Note that these imply a coupling between
$\ket{\varphi_{s'_{e2},0}}$ and $\ket{\varphi_{s'_{e2},1}}$, as
witnessed by equations (\ref{boundcondacc1}) and
(\ref{boundcondacc2}) and ultimately by the terms proportional to
$\langle 1\left|\mathbf{S}_{e1}^{2}\right|0 \rangle$ appearing in
(\ref{coupledeqs1}) and (\ref{coupledeqs2}). This coupling thus
results from non commutation of $\mathbf{S}_{e1}^{2}$ and
$\mathbf{S}_{e2}^{2}$.

As equations (\ref{boundcondacc1}) -- (\ref{boundcondacc4}) are
added to the matching conditions of $\varphi_{s'_{e2},0}(x)$ and
$\varphi_{s'_{e2},1}(x)$ at $x=0$ and $x=x_0$ a linear system of 8
equations is obtained. Once this is solved for $s'_{e2}=0$ and
$s'_{e2}=1$, the following transmission amplitudes
$t_{s_{e2}}^{(s'_{e2};1/2)}$ are obtained
\begin{eqnarray}\label{t0t1_1}
 t^{(s_{e2}'; 1/2)}_{0}&=&\frac{1}{\delta}\left[-64\,e^{2ikx_0}\pi^2(\rho(E)J)^2\left(2(1-s_{e2}')+\sqrt{3}s_{e2}'\right)\right. \\
 &+ &\left.64(\pi\rho(E)J-8i) \left(2(4i+\pi\rho(E)J)(1-s_{e2}')+\sqrt{3}\pi \rho(E)Js_{e2}'\right)\right]\nonumber \\
\nonumber \\
\label{t0t1_2} t^{(s_{e2}';
1/2)}_{1}&=&\frac{64}{\delta}\left[\sqrt{3}\pi\rho(E)J
\left(-8i+3(e^{2ikx_0}-1)\pi
\rho(E)J\right)(1-s_{e2}')  \right. \\
&+&\left.\,8s_{e2}'(8-3i\pi\rho(E)J) \right] \nonumber
\end{eqnarray}
with
\begin{eqnarray} \label{delta}
\delta &=&\left\{4096+\pi  \rho(E)J \left[-2048 i+\left(e^{2 i k
x_0}-1\right) \pi  \rho(E)J  \right.\right.\nonumber \\
&\times &\left.\left. \left(-128+96 i \pi \rho(E)J +9 \left(e^{2 i k
x_0}-1\right) \pi ^2 (\rho(E)J) ^2\right)\right]\right\}
\end{eqnarray}
As in the case $s=3/2$, the coefficients
$t_{s_{e2}}^{(s'_{e2};1/2)}$ are functions of $kx_0$ and $\rho(E)J$
and, moreover, they again do not depend on $m$ as suggested by the
notation here adopted. The latter circumstance is due to the form
(\ref{H2}) of $H$ and to the fact that $6j$ coefficients -- and thus
matrix elements (\ref{matrix_coeff}) appearing in
(\ref{coupledeqs1}), (\ref{coupledeqs2}) -- do not depend on $m$
(see e.g. \cite{weissbluth}).

As a further signature of non conservation of $\mathbf{S}_{e2}^2$ in
the present subspace note that $t^{(s_{e2}'; 1/2)}_{s_{e2}}\neq 0$
for $s_{e2}\neq s_{e2}'$.

\subsection{Calculation of transmittivity for an arbitrary spin
state} \label{calcul_chi}

It is important to stress again that our calculated transmission
amplitudes $t^{(s_{e2}'; 1/2)}_{s_{e2}}$ are exact at {\em all}
orders in the electron-impurity coupling constant $J$. This follows
from our quantum waveguide theory approach which addresses the
determination of the stationary states through resolution of the
Schr\"{o}dinger equation. This approach is different from the
perturbative one adopted in \cite{yasser} where  only a finite
number of electron multiple reflections between the two impurities
are taken into account performing a few iterations of the Fermi
Golden rule.

The knowledge of all coefficients $t_{s_{e2}}^{(s'_{e2};s)}$
completely describes the transmission properties of our system. Here
we are mainly interested in calculating how an electron with a given
wave vector $k$ and for some initial electron-impurities spin state
$\ket{\chi}$ is transmitted through the wire. Thus assuming to have
the incident wave $\ket{k}\ket{\chi}$, with $\ket{\chi}$ being an
arbitrary spin state, it is straightforward to see that
$\ket{k}\ket{\chi}$ is the incoming part of the stationary state
\begin{equation}\label{sviluppochi}
\ket{\Psi_{k,\chi}}=\sum_{s_{e2}',s,m} \langle s_{e2}';s,m
\ket{\chi} \ket{\Psi_{k,s_{e2}';s,m}}
\end{equation}
where $s_{e2}'=1$ for $s=3/2$ , while $s_{e2}'=0,1$ for $s=1/2$. It
follows that the transmitted part $\ket{\Psi_{k,\chi}}_t$ of
(\ref{sviluppochi}) provides the transmitted state into which
$\ket{k}\ket{\chi}$ evolves after multiple scattering. To calculate
$\ket{\Psi_{k,\chi}}_t$ we simply replace each stationary state
$\ket{\Psi_{k,s_{e2}';s,m}}$ in (\ref{sviluppochi}) with its
transmitted part, express the latter in terms of amplitudes
$t^{(s_{e2}'; s)}_{s_{e2}}$ and rearrange (\ref{sviluppochi}) as a
linear expansion in the basis $\ket{s_{e2};s,m}$. This yields
\begin{equation}\label{sviluppochi_t}
\ket{\Psi_{k,\chi}}_t=\ket{k}  \sum_{s_{e2},s,m}
\gamma_{s_{e2},s,m}(\chi) \ket{s_{e2},s,m} \nonumber \\
\end{equation}
with
\begin{equation} \label{alpha_coeff}
\gamma_{s_{e2},s,m}(\chi) =\sum_{s_{e2}'} t^{(s_{e2}'; s)}_{s_{e2}}
\langle s_{e2}';s,m \ket{\chi}
\end{equation}
Coefficients (\ref{alpha_coeff}) fully describe how an incoming wave
$\ket{k}\ket{\chi}$ is transmitted after scattering. For instance,
the total electron transmittivity $T$ can be calculated as
\begin{equation} \label{T}
T =\sum_{s_{e2},s,m} |\gamma_{s_{e2},s,m}(\chi)|^2
\end{equation}

\section{Transmission properties for one impurity spin up-states} \label{one_spin_up}

In this section, we investigate how the electron transmission is affected by an initial spin state of the two impurity spins
belonging to the family
\begin{equation} \label{family2}
\ket{\Psi (\vartheta , \varphi)} = \cos\vartheta\ket{\uparrow\downarrow} +
e^{i\varphi}\sin\vartheta\ket{\downarrow\uparrow}
\end{equation}
with $\vartheta\in[0,2\pi]$ and $\varphi\in[0,\pi]$. This family
describes all the states with only one impurity spin up, including
both maximally entangled and product states. Following the
calculation scheme illustrated in subsection (\ref{calcul_chi}), the
electron transmittivity $T$ when the injected electron spin state is
$\ket{\uparrow}$ can thus be computed setting
$\ket{\chi}=\ket{\uparrow}\ket{\Psi (\vartheta , \varphi)}$. The behaviour
of $T$ when the impurities are prepared in the product states
$\ket{\uparrow\downarrow}$ ($\vartheta=0$) and $\ket{\downarrow\uparrow}$ ($\vartheta=\pi/2$) is
plotted in figures 2(a) and (b), respectively.
\begin{figure}[htbp]
              {\hbox{ {\includegraphics[scale=0.7]{Fig2a}}
{\includegraphics[scale=0.7]{Fig2b}
              }}}
\caption{\footnotesize {Electron transmittivity $T$ as a function of
$kx_{0}$ when the electron is injected in the state $\ket{\uparrow}$ with
the impurities prepared in the state $\ket{\uparrow\downarrow}$ (a) and
$\ket{\downarrow\uparrow}$ (b). Dotted, dashed and solid lines stand for
$\rho(E)J=1,2,10$, respectively.}}
\end{figure}
A behaviour similar to a FP interferometer with partially silvered
mirrors \cite{rossi}, with equally spaced maxima of transmittivity,
is exhibited. In figure 2(a) principal maxima occur around a value
of $kx_{0}\neq n\pi$ ($n$ integer) which tends to $kx_{0} =n \pi$
for increasing values of $\rho(E)J$, while in figure 2(b) they occur
at $kx_{0} =n \pi$. As $\rho(E)J$ is increased, maxima become lower
and sharper. Remarkably, in both cases the electron and impurities
spin state is changed after the scattering (as resulting from the
calculated coefficients $\gamma_{s_{e2},s,m}(\chi)$) and the
electron undergoes a loss of coherence, since we always have $T<1$
\cite{datta,imry,joshi}. The above product impurity spins states
thus lead to the typical decoherent behaviour encountered with
magnetic impurities which avoids a perfect resonance condition $T=1$
to occur (see the Introduction).

We now consider maximally entangled spin states belonging to the
family (\ref{family2}) for $\vartheta = \pi/4$. Let us start with
the triplet state $\ket{\Psi^{+}} = (\ket{\uparrow\downarrow}
+\ket{\downarrow\uparrow})/\sqrt{2}$ (see figure 3(a)). A behaviour  similar to
the case of figure 2 is exhibited. Again the transmitted spin state
differs from the incident one, this indicating occurrence of
spin-flip. In particular, when $kx_{0} =n \pi$, the transmitted
state turns out to be a linear combination of
$\ket{\uparrow}\ket{\Psi^{+}}$ and $\ket{\downarrow}\ket{\uparrow\s}$.
\begin{figure}[htbp]
              {\hbox{ {\includegraphics[scale=0.7]{Fig3a}}
{\includegraphics[scale=0.7]{Fig3b}
              }}}
\caption{\footnotesize {Electron transmittivity $T$ as a function of
$kx_{0}$ when the electron is injected in the state $\ket{\uparrow}$ with
the impurities prepared in the state $\ket{\Psi^{+}}$ (a) and
$\ket{\Psi^{-}}$ (b). Dotted, dashed and solid lines stand for
$\rho(E)J=1,2,10$, respectively.}}
\end{figure}

A striking behaviour however appears when the impurity spins are
prepared in the maximally entangled state $\ket{\Psi^{-}} =
(\ket{\uparrow\downarrow} -\ket{\downarrow\uparrow})/\sqrt{2}$: as shown in figure 3(b), the
wire becomes ``transparent" for $kx_{0}= n\pi$. In other words,
perfect transmittivity $T=1$ is reached at $kx_{0}= n\pi$ regardless
of the value of $\rho(E)J$, with peaks getting narrower for
increasing values of $\rho(E)J$. Furthermore, under the resonance
condition $kx_{0}= n\pi$, the spin state $\ket{\uparrow}\ket{\Psi^{-}}$ is
transmitted unchanged. Note that this occurs even if
$\ket{\uparrow}\ket{\Psi^-}$ belongs to the $s=1/2$ subspace where
spin-flip is allowed (see subsection \ref{subspace_s12}).
Importantly, this phenomenon takes place regardless of the electron
spin state. Indeed, in \ref{appendix} we demonstrate that the only
spin state $\ket{\chi}$ allowing perfect transparency of figure 3(b)
to occur is of the form
\begin{equation} \label {chi_transparent}
\ket{\chi}=\left(\alpha\ket{\uparrow}+\beta\ket{\downarrow}\right)\ket{\Psi^{-}}
\end{equation}
with arbitrary complex values of $\alpha$ and $\beta$.

\section{Conservation of $\mathbf{S}_{12}^2$} \label{conservation}

The effect of perfect transparency presented in the previous section
is clearly due to constructive quantum interference. In this section
we show how this phenomenon can be quantitatively analyzed in terms
of Hamiltonian symmetries. Let $\delta_{k}(x)$ and
$\delta_{k}(x-x_0)$ be the effective representations of $\delta(x)$
and $\delta(x-x_0)$, respectively, in a subspace of fixed energy
$E=\hbar^{2} k^2/2m^*$. Using the matrix representations of electron
orbital operators $\delta_{k}(x)$ and $\delta_{k}(x-x_0)$ in the
basis $\left\{ \ket{k},\ket{-k}\right\}$, it is straightforward to
prove that $\delta_{k}(x)=\delta_{k}(x-x_0)$ for $kx_{0}=n\pi$. When
this occurs the non-kinetic part $V$ of $H$ in equation (\ref{H})
assumes the effective representation
\begin{equation}\label{Vk}
V=J \, \mbox{\boldmath$\sigma$}\cdot \mathbf{S}_{12}
\,\delta_{k}(x)=\frac{J}{2}\left(\mathbf{S}^2-\bm{\sigma}^2-\mathbf{S}_{12}^2\right)\,\delta_{k}(x)
\end{equation}
with $\mathbf{S}_{12}=\mathbf{S}_{1}+\mathbf{S}_{2}$ being the total
spin of the two impurities. This means that for electron wave
vectors fulfilling the condition $kx_{0}=n\pi$, the operator
$\mathbf{S}_{12}^2$ (with quantum number $s_{12}$) becomes a
constant of motion whatever the strength of $J$. This is physically
reasonable since the condition $kx_{0}=n\pi$ implies that the
electron is found at $x=0$ and $x=x_0$ with equal probabilities and,
as a consequence, the two impurities are equally coupled to the
electron spin.

Furthermore, from equation (\ref{Vk}) it follows that $V$ vanishes
for $s=1/2$ and $s_{12}=0$. This is the case for the initial state
(\ref{chi_transparent}) as this is an eigenstate of $\mathbf{S}^{2}$
and $\mathbf{S}_{12}^{2}$ with quantum numbers $s=1/2$ and
$s_{12}=0$, respectively (see also \ref{appendix}). Therefore, when
this state is prepared and $kx_{0}=n\pi$, no spin-flip occurs and
the wire becomes transparent: an effective quenching of the
electron-impurities coupling takes place. This explains the results
of figure 3(b).

The same behaviour however does not occur for the state
$\ket{\uparrow}\ket{\Psi^+}$ ($\ket{\downarrow}\ket{\Psi^+}$) belonging to the
degenerate 2D eigenspace of $\mathbf{S}_{12}^{2}$ and $S_{z}$ with
quantum numbers $s_{12}=1$ and $m=1/2$ ($m=-1/2$), respectively.
Since the orthogonal state $\ket{\downarrow}\ket{\uparrow \uparrow}$ ($\ket{\uparrow}\ket{\downarrow
\downarrow}$) lies in the same eigenspace it follows that, when $kx_{0}=
n\pi$, the transmitted spin state will result in a linear
combination of $\ket{\uparrow}\ket{\Psi^+}$ and $\ket{\downarrow}\ket{\uparrow \uparrow}$
($\ket{\downarrow}\ket{\Psi^+}$ and $\ket{\uparrow}\ket{\downarrow \downarrow}$), implying
spin-flip and decoherence in agreement with typical behaviour of
magnetic impurities. This explains the decoherent behaviour of
figure 3(a).

\section{Entanglement controlled transmission and maximally entangled states QND scheme}
\label{ent_controlled}

The deeply different behaviours exhibited by $\ket{\Psi^-}$ and
$\ket{\Psi^+}$ at $kx_0=n\pi$ suggest that, in this regime, electron
transmission through the wire is strongly affected by the relative
phase $\varphi$ between the impurity spin states $\ket{\uparrow\downarrow}$ and
$\ket{\downarrow\uparrow}$ appearing in (\ref{family2}). In figure 4 we thus plot
the transmittivity $T$ when the electron is injected in an arbitrary
spin state $(\alpha\ket{\uparrow}+\beta\ket{\downarrow})$ with the impurities
prepared in a state (\ref{family2}) as a function of $\vartheta$ and
$\varphi$, for $kx_{0}= n\pi$ and $\rho(E) J=10$. Note how the
electron transmission indeed depends crucially on $\varphi$. The
maximum value of $T$ occurs when the impurities are prepared in the
singlet state $\ket{\Psi^{-}}$, while its minima occur for the
triplet state $\ket{\Psi^{+}}$.
\begin{figure}
 \includegraphics [scale=0.8]{Fig4}
 \caption{\label{teta_phi} Electron transmittivity $T$ at $kx_{0}=n\pi$ and $\rho(E)J=10$
 when the electron is injected in an arbitrary spin
state $(\alpha\ket{\uparrow}+\beta\ket{\downarrow})$ with the impurities prepared
in the state
$\cos{\vartheta}\ket{\uparrow\downarrow}+e^{i\varphi}\sin{\vartheta}\ket{\downarrow\uparrow}$.}
\end{figure}
In agreement with what was discussed in section \ref{conservation},
denoting by $T_{\Psi^{\pm}}$ the transmittivity for
$\ket{\Psi^{\pm}}$, decoherence effects cause $T_{\Psi^+}<1$ (it
gets smaller and smaller for increasing values of $\rho(E) J$) while
$T_{\Psi^{-}}=1$ due to occurrence of perfect transparency. To
explain why $T_{\Psi^-}$ and $T_{\Psi^+}$ are, respectively, maxima
and minima of $T$, we observe that the set of states (\ref{family2})
is spanned by $\ket{\Psi^{-}}$ and $\ket{\Psi^{+}}$. Since these two
states belong to orthogonal eigenspaces of the constant of motion
$\mathbf{S}_{12}^2$ a linear combination of them cannot exhibit
quantum interference effects and reduces to a statistical mixture.
This ensures that the transmittivity for a generic state
(\ref{family2}) will have intermediate values between $T_{\Psi^+}$
and $T_{\Psi^-}$.

The most remarkable result emerging from the above discussion is
that, within the set of initial impurity spins states
(\ref{family2}), maximally entangled states $\ket{\Psi^{-}}$ and
$\ket{\Psi^{+}}$ have the relevant property of maximizing or
minimizing electron transmission. We have chosen $\rho(E)J=10$ to
better highlight this behaviour, but this happens for any value of
$\rho(E)J$. This result suggests the appealing possibility to use
the relative phase $\varphi$ as a control parameter to modulate the
electron transmission in a 1D wire \cite{ciccarello}.

According to what was discussed in section \ref{conservation},
perfect transparency ensures that, once $\ket{\Psi^{-}}$ is set for
obtaining high conductivity of the device, this impurity spins state
will not be lost during transport of electrons through the wire.
However, the same is not true for the low conductivity-state
$\ket{\Psi^+}$ which is instead affected by spin-flip events and in
general will be destroyed by electron scattering (see section
\ref{conservation}). For the above entanglement
controlled-modulation to be correctly performed, it is thus required
that $\ket{\Psi^+}$ can be protected from spin-flip events. To
achieve this, conservation of $\mathbf{S}_{12}^2$ can again be
fruitfully used together with proper spin-filtering.

Assume thus that the electrons are injected in a fixed spin state,
let us say $\ket{\uparrow}$. As discussed in section \ref{conservation},
in the regime $kx_0=n\pi$ conservation of $\mathbf{S}_{12}^2$
implies that $\ket{\uparrow}\ket{\Psi^+}$ is transmitted (or reflected) as
a linear combination of $\ket{\uparrow}\ket{\Psi^+}$ and
$\ket{\downarrow}\ket{\uparrow\s}$. It follows that if the electrons are analyzed
at the output of the wire in the same incoming spin state
$\ket{\uparrow}$, the state $\ket{\Psi^+}$ of the impurity spins is
protected from spin-flip \cite{nota_spin_filtering}.

Let us denote by $T_{+}$ the spin-polarized transmission amplitude
that the electron is transmitted in the state $\ket{\uparrow}$. In figures
5(a) and (b) we have plotted $T$ and $T_{+}$, respectively, for an
initial impurity spins state (\ref{family2}) with the electron
injected in the state $\ket{\uparrow}$ and for $kx_0=n\pi$ and
$\rho(E)J=2$. Note how $T_{\Psi^+}$ turns out to be lowered in
figure 5(b) compared to 5(a). This is better visible in Fig. 5(c),
where  both $T$ and $T_{+}$, for $\varphi=0$, are plotted: in both
cases maxima and minima occur for $\ket{\Psi^-}$ and $\ket{\Psi^+}$,
respectively, but while maxima coincide, minima are lowered in the
spin-filtered case. Spin-filtering thus allows the entanglement
controlled-transmission task to work even more efficiently.
\begin{figure}[htbp]
\begin{center}
              {\hbox{ {\includegraphics[scale=0.6]{Fig5a}}
{\includegraphics[scale=0.6]{Fig5b}}{\includegraphics[scale=0.6]{Fig5c}}}}
\caption{\footnotesize {Electron transmittivity $T$ (a) and
conditional electron transmittivity $T_+$ (b) at $kx_{0}=n\pi$ and
$\rho(E)J=2$ when the electron is injected in the state $\ket{\uparrow}$
with the impurities prepared in the state
$\cos{\vartheta}\ket{\uparrow\downarrow}+e^{i\varphi}\sin{\vartheta}\ket{\downarrow\uparrow}$. A
comparison between $T$ (solid line) and $T_+$ (dashed line) for
$\varphi=0$ is detailed in Fig. 5(c).}}
\end{center}
\end{figure}
We have found that $T_{+}\simeq T$ for high values of $\rho(E)J$ as
in figure 3 for $\rho(E)J=10$. Thus in these cases no spin-filtering
is required to protect $\ket{\Psi^+}$.

Finally, we point out that the result showed in figure 4 opens the
possibility of a new maximally entangled states detection scheme.
Indeed, electron transmission can be regarded as a probe to detect
maximally entangled singlet and triplet states of two localized
spins within the family (\ref{family2}). In particular, it should be
clear from the above discussion that use of spin-filtering makes the
above setup  a quantum non-demolition (QND) detection scheme both
for $\ket{\Psi^-}$ and $\ket{\Psi^+}$. In particular, for the state
$\ket{\Psi^-}$, such scheme works as a QND even without
spin-filtering.

\section{Transmission properties for aligned impurity spins states}
\label{aligned_spins}

Not all the sets of maximally entangled states exhibit the effects
described in sections \ref{one_spin_up}, \ref{conservation} and
\ref{ent_controlled}. To show this, in this section, we consider a
different family of impurity spins states
\begin{equation} \label{uu_dd}
\ket{\phi (\vartheta , \varphi)} = \cos\vartheta\ket{\uparrow\s} +
e^{i\varphi}\sin\vartheta\ket{\downarrow\g}
\end{equation}
where again $\vartheta\in[0,2\pi]$ and $\varphi\in[0,\pi]$. Family
(\ref{uu_dd}) describes all the states in which the impurity spins
are aligned.

The transmittivity $T$ for an electron incoming in the up spin state
is shown in figures 6 (a), (b) and (c) for the cases $\vartheta = 0$
(a), $\vartheta = \pi /2$ (b) and $\vartheta = \pi /4$ with
arbitrary $\varphi$ (c). Note how the maximum of $T$ in the case of
figure 6(c) has an intermediate value between the maximum of $T$ of
figure 6(a) and the one of figure 6(b). Additionally, the results of
figure 6(c) do not depend on the value of $\varphi$. The above
behaviour can be easily understood once one realizes that, in the
case of the initial spin state (\ref{uu_dd}) the two impurities
indeed behave as if they were prepared in the mixed state
\begin{equation}
\rho=\cos^2 \vartheta \ket{\uparrow \uparrow} \langle {\uparrow \uparrow}|+\sin^2 \vartheta
\ket{\downarrow \downarrow} \langle {\downarrow \downarrow}|
\end{equation}
The phase $\varphi$ thus plays no role for the present family of
states and no  interference effect occurs. The reason for this is
that $\ket{\uparrow}\ket{\uparrow\s}$ and $\ket{\uparrow}\ket{\downarrow\g}$ are eigenstates
of the constant of motion $S_z$ with different quantum numbers
$m=3/2$ and $m=-1/2$, respectively. Therefore, unlike the set of
states (\ref{family2}), no quantum interference effects are
possible.

Additionally, note that while in the cases of figures 6 (b) and (c)
a loss of electron coherence is exhibited similarly to the cases of
figures 2(a), 2(b) and 3(a), a coherent behaviour completely
analogous to a FP interferometer with partially silvered mirrors
\cite{rossi} is observed when the impurities are prepared in the
state $\ket{\uparrow\s}$ with the electron injected in the state
$\ket{\uparrow}$, as illustrated in figure 6(a). Indeed, the spin state
$\ket{\uparrow}\ket{\uparrow\s}$ belongs to the non degenerate eigenspace
$s=3/2$, $m=3/2$ where spin-flip does not occur and the impurities
behave as if they were static (see subsection \ref{subspace_s32}).
However, we emphasize that at variance with perfect transparency
induced by the impurities' singlet state shown in figure 3(b), here
$T=1$ for values of $kx_0$ \emph{depending} on $\rho(E)J$ and only
when the electron spin is initially aligned with the spins of the
impurities.

The effect of transparency presented in figure 3(b) thus requires
neither the knowledge of the coupling constant $J$ nor any
constraint on the electron spin state to be observed.
\begin{figure}
              \includegraphics [scale=1]{Fig6a_Fig6b_Fig6c}\caption{\footnotesize
{Electron transmittivity $T$ as a function of $kx_{0}$ when the
electron is injected in the state $\ket{\uparrow}$ with the impurities in
the initial state $\ket{\uparrow\s}$ (a), $\ket{\downarrow\g}$ (b) and
$(\ket{\uparrow\s} +e^{i\varphi}\ket{\downarrow\g})/\sqrt{2}$ for arbitrary
$\varphi$ (c). Dotted, dashed and solid lines stand for
$\rho(E)J=1,2,10$, respectively. }} \label{fig1}
\end{figure}

\section{Generation of entangled states} \label{ent_gen}

To observe the entanglement dependent electron transmittivity
discussed in \ref{one_spin_up}, \ref{conservation} and
\ref{ent_controlled} one must be able to prepare the maximally
entangled states $\ket{\Psi^-}$ and $\ket{\Psi^+}$. In particular
this is required to observe the entanglement controlled
transmittivity illustrated in section \ref{ent_controlled}. Although
in our Hamiltonian model (\ref{H}) there is no direct interaction
between the two impurities, an indirect coupling via the electron
spin takes place, as it is implicit in the non-kinetic part of $H$.
In this section we thus show how electron-impurities scattering
itself can be used to generate the desired entanglement between the
impurity spins.

We first observe that it is enough to be able to generate only one
of the two states $\ket{\Psi^-}$ and $\ket{\Psi^+}$ since they can
be easily transformed into each other by simply introducing a
relative phase shift by means of a local field.  In the following,
we therefore show how the triplet state $\ket{\Psi^+}$ can be
generated by electron scattering. Generation of entangled states of
two magnetic impurities via electron scattering in 1D systems has
been recently investigated in \cite{yang, yasser, giorgi, nakazato}.
The basic idea is to inject an electron in the state $\ket{\uparrow}$ with
the two impurities prepared in the state $\ket{\downarrow\g}$. Due to
conservation of $S_z$ the transmitted spin state is of the form
\begin{equation}\label{ABC}
A \ket{\uparrow}\ket{\downarrow\g}+B\ket{\downarrow}\ket{\uparrow\downarrow}+C\ket{\downarrow}\ket{\downarrow\uparrow}
\end{equation}
It follows that if the transmitted electron is analyzed in the down
spin state $\ket{\downarrow}$ the two impurities are projected in the
entangled state $B\ket{\uparrow\downarrow}+C\ket{\downarrow\uparrow}$ (apart from a
normalization factor) with probability $|B|^2+|C|^2$. For a fixed
electron energy, this state is not maximally entangled for any
strength of the electron-impurity coupling constant $J$
\cite{yasser}. However in \cite{yasser} the role played by the
distance $x_0$ between the impurities was not taken into account. In
the remaining of this section we will therefore consider an improved
entanglement generation scheme \cite{ciccarello} making use of the
exact knowledge of the energy eigenstates developed above. In
particular we will consider the regime $kx_0=n\pi$. In this case, in
addition to $S_z$, also $\mathbf{S}_{12}^2$ becomes a constant of
motion. It follows that the transmitted spin state will be of the
form (see also section \ref{conservation})
\begin{equation}\label{ABC2}
A' \ket{\uparrow}\ket{\downarrow\g}+B'\ket{\downarrow}\ket{\Psi^+}
\end{equation}
An output filter selecting only transmitted electrons in the state
$\ket{\downarrow}$ can thus be used to project the impurities into the state
$\ket{\Psi^{+}}$. Note that at variance with the analysis  discussed
in \cite{yasser}, this scheme ensures that a maximally entangled
state is always generated whatever the value of $J$. Furthermore, we
also know that this is the maximally entangled triplet state
$\ket{\Psi^+}$. The spin-polarized probability $T_{-}$ for the
electron to be transmitted in the state $\ket{\downarrow}$ - that is to
project the impurities into $\ket{\Psi^+}$ - is plotted in figure 7
as a function of $\rho(E)J$.
\begin{figure}
 \includegraphics [scale=0.8]{Fig7}
 \caption{\label{P} Spin-polarized electron transmittivity $T_{-}$ at $kx_{0}=n\pi$ as a function of
 $\rho(E)J$ when the electron is injected in the state $\ket{\uparrow}$ with the impurities prepared in the state
 $\ket{\downarrow\g}$.}
\end{figure}
A probability larger than 20\% can be reached with $\rho(E)J\simeq
1$.

\section{Conclusions}

To discuss the possibility to observe the effects presented in this
paper, in particular the entanglement controlled transport, let us
assume an electron effective mass of $0.067\,m_0$ (as in GaAs
quantum wires) and two quantum dots -- each one of size 1 nm -- as
the impurities. Furthermore, the electron wavelength must be large
enough for the contact electron-dot potential of our Hamiltonian
model (\ref{H}) to be valid. This constraint implies that the
electron energy must not exceed 2 meV. In this case, requiring that
$\rho(E)J\simeq 1$ (i.e., as shown in section \ref{ent_gen}, the
optimal condition for generating entangled states of the impurities)
we obtain $J\simeq$ 1 eV{\AA}, which appears to be a reasonable
value of the electron-impurity coupling constant.

To prevent many-body effects, whose occurrence would make the single
electron-approach adopted in this work not valid, electrons could be
shot over an additional tunnel barrier before interacting with the
impurities as proposed in \cite{dalibard, schomerus}. This would
allow the injection of single electrons within a narrow energy range
well separated from the Fermi energy. Alternatively, this task could
be accomplished using a single-electron turnstile \cite{kouwenhoven}
as suggested e.g.\ in \cite{schomerus, jefferson}.

Finally we would like to comment on the effects of decoherence on
the interference phenomena described above. Some of the most
interesting features of electron spin in semiconductor
nanostructures are the long decoherence times, which is typically
larger than 100 nanoseconds (but can exceed in some cases the
microsecond) and the long coherence lengths, which can be longer
than 100 micrometers. Our approach is therefore able to predict an
observable effect. For instance for an electron energy of 2 meV, the
resonance condition $kx_0 =n\pi$ implies that $x_0$ must be in the
order of 100 nm. A coherence length of this order of magnitude is
common in a GaAs quantum wires at low temperatures (e.g.  see
\cite{Ferry}). Of course a stationary state approach to scattering
like the one we have used must be complemented with a dissipative
map for the evolution of the impurity spins when one is interested
in the steady state which can be obtained by the repeated injection
and detection of electrons in the wire.

In summary, in this paper we have considered a 1D wire with two
embedded spin-1/2 magnetic impurities. This system can be regarded
as the electron analogue of a Fabry Perot  interferometer in which
the two mirrors have internal spin degrees of freedom. Adopting an
appropriate quantum waveguide theory approach, we have derived all
the necessary transmission amplitudes at all orders in the
electron-impurity coupling constant. This has allowed us to
calculate the electron transmission properties for an arbitrary
initial spin state of the overall system. The typical behaviour is a
loss of electron coherence induced by spin-flip events due to
scattering by the magnetic impurities. However, when the maximally
entangled singlet state of the impurity spins is prepared, we have
found that perfect transparency of the wire is obtained regardless
of the electron spin state at wave vectors which do not depend on
the electron-impurity coupling constant. In the same regime, we have
found that electron transmittivity is maximized (minimized) by the
singlet (triplet) entangled states of the impurity spins. This
suggests a novel use of entanglement as a tool to modulate the
conductivity of a 1D wire. Additionally, the electron transmission
can be thought as a probe to detect maximally entangled singlet and
triplet states of two localized spins. When spin-filtering is
performed, this is a QND detection scheme for both these states,
while it works as a QND detection scheme for the singlet state even
without spin-filtering. These behaviours have been explained in
terms of the Hamiltonian symmetries, showing that appropriate
electron wave vectors allow for an effective conservation of the
squared total spin of the two impurities. Finally, we have proposed
a scheme to generate maximally entangled states via electron
scattering regardless of the electron-impurity coupling constant.

\section{Acknowledgments}

The authors thank the support from CNR (Italy) and GRICES
(Portugal). YO and VRV thank the support from Funda\c{c}\~{a}o para
a Ci\^{e}ncia e a Tecnologia (Portugal), namely through programs
POCTI/POCI and projects POCI/MAT/55796/2004 QuantLog and
POCTI-SFA-2-91, partially funded by FEDER (EU) as well as the
SQIG-IT EMSAQC initiative.

redpajama_set_name: RedPajamaArXiv


ICAM-1 which is expressed by endothelial cells and leukocytes are observed as first markers in diseases such as transplant rejection, diabetes and atherosclerosis and in infections caused by various pathogens. In the present study, it is aimed to reveal the age-related changes in the expression of ICAM-1 on rats. Therefore, a total of 30 albino rats were taken at the age of 6, 18 and 24 months without gender discrimination. Rats were fed with standard pellet feed during the study. Afterwards, rats were sacrificed and tissue samples were collected from their rats, and the samples were evaluated under the light microscope by staining with immnunohistochemical method. It was determined that the expression of both aortic endothelial cells and endothelial cells in the media layer had been significantly increased based on the age.
KEY WORDS: ICAM-1; Rat; Aortic endothelium; Age.
KETANI, S.; KARAKOÇ, Z.; KETANI, M. A. & KILINÇ, M. Age-related changes in the expression of ICAM-1 in the aorta of Wistar albino rats. Int. J. Morphol., 34(4):1482-1486, 2016.


The Classics for the Advancing Pianist series provides motivating, enjoyable literature of substantial quality for developing keyboard artists. The pieces in these books, written by Edward MacDowell and ordered in a logical progression from volume to volume, help the performer work within his or her abilities while developing playing and listening skills. This standard teaching repertoire will help build technique and musicianship, as well as offer hours of personal enjoyment. Titles: The Brook, Op. 32, No. 2 * Hungarian, Op. 39, No. 12 * Improvisation, Op. 46, No. 4 * Scotch Poem, Op. 31, No. 2 * Shadow Dance, Op. 39, No. 8 * Sung Outside the Prince's Door, Op. 4, No. 1 * To a Water Lily, Op. 51, No. 6 * To an Old White Pine, Op. 62, No. 7. "Hungarian, Op. 39, No. 12," "Improvisation, Op. 46, No. 4," "Scotch Poem, Op. 31, No. 2," and "Shadow Dance, Op. 39, No. 8" are Federation Festivals 2016-2020 selections.


text:
Exciting Changes At Vimy Hockey!
Vimy Hockey is in the midst of some exciting changes.
Ryan Marsh, Vimy Hockey Campus Director for almost 10 years, has been plucked from our ranks by the Edmonton Oil Kings and new bench boss (and former Vimy Hockey Teacher/Instructor) Steve Hamilton. Mr. Marsh will be the new Assistant Coach for the Oil Kings, who will work to defend their Memorial Cup Championship this season.
Mr. Marsh will still be working with Vimy Hockey in an Associate Director role and will continue to provide Vimy Hockey and it's student-athletes with his knowledge and expertise gleaned from running the premiere Hockey Academy in Alberta for almost a decade.
Academic and Athletic Development would like to thank Mr. Marsh for his years of service and dedication to Vimy Hockey and the student-athletes of Donnan and Vimy Ridge Academy.
AAD is also extremely proud to announce Nathan Dempsey as the new Campus Director for Vimy Hockey.
Mr. Dempsey is a former professional hockey player with stops in Europe, the AHL and the NHL, including time with the Toronto Maple Leafs, Chicago Blackhawks, Los Angeles Kings and Boston Bruins.
Because of his hockey resume, Nathan has a unique opportunity to articulate to Vimy Hockey student-athletes what it takes to get to the highest levels of hockey. Mr. Dempsey is passionate about not only building sport-specific skills, but also the character and other mental skills required to create a complete student-athlete.
If you have any questions for Mr. Dempsey he can be reached at Nathan.dempsey@epsb.ca.
Scholarship Donors
Vimy Hockey Welcome 19-20
Gregorowich Hire
Esso Cup 2019

redpajama_set_name: RedPajamaCommonCrawl


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redpajama_set_name: RedPajamaGithub


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text:
Created by: Eberhard Scholz
News no.: 2016059
Nominate now: CAMPUS PRIZE for sustainable research honors theses
The initiators of the new "CAMPUS PRIZE: research for a sustainable future" are convinced that this kind of research deserves the awarding of a prize. The award was launched by the KELLNER & STOLL FOUNDATION FOR CLIMATE AND ENVIRONMENT, the Leibniz Center for Tropical Marine Ecology (ZMT) and the University of Bremen. The prize money amounts to 2,000 Euro and will be awarded annually.
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KELLNER & STOLL – STIFTUNG FÜR KLIMA UND UMWELT
Dr. Rita Kellner-Stoll und Reiner Stoll
E-mail: infoprotect me ?!campuspreisprotect me ?!.de
Bis zum 31. Oktober 2016 können Lehrende Abschlussarbeiten nominieren, die zur nachhaltigen Nutzung von Ressourcen und zum Schutz von Umwelt, Klima und Meere beiträgt.


Not my type of movies, but as chick-flicks go, this one is okay. The plot is not that complicated, and there are no surprises in the movie at all. The acting is just above average, despite Jennifer Lopez' earlier performances on other movies.


On this page, you can find Haywire and Narrative bottle shots and tasting notes as well as hi-res images of our vineyards and winery. All that and more can be found below. If you still can't find what you are looking for, email office@okanagancrushpad.com for assistance.


^ 杨柳. 美国银行称440亿美元收购美林证券. 新华网. 2008年9月15日 [2008-09-15]. (原始内容存档于2008年9月16日).
^ Bank of America Finishes Merger of Merrill Lynch Into Parent. Bloomberg. 21 January 2013 [1 October 2013].
^ 美銀刪「美林」100多年歷史畫下句點 | 鉅亨網 - 美股. 鉅亨網. 2019-02-26 [2019-02-26] (中文(台灣)).


Wow, it seems so long ago that I frequented the Changeling forums here. With the 20th anniversary editions bringing life back to the games, it would be great to see this place thriving again! I'm not sure if there's anyone around who would remember me, but if so, hello again!
With the release of C20 and the forthcoming CtL Second Edition, I'm pushing Shadownessence out there as the place to come for Changeling fans - both Dreaming and Lost - to come and raise Childlings and teach the Wilders something about the days when the Grumps were the Childlings here.
Let the Balefires warm your soul, let your tears fall where they may, and learn to laugh and play again.
oh, and for anyone who frequents the Facebook Dreaming/Lost Group, I go by Alaina Milare there.


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Trying to pull too much from Santa Anita is a challenge as the Arcadia track has a far larger facility and seating capacity than boutique Keeneland will be able to offer.
Seeing firsthand how aspects like the quarantine barn are handled are the types of things that will be invaluable toward Keeneland's preparation. Beasley said that all of next year's Breeders' Cup horses will be housed in the Rice Road area barns in order to be able to restrict access to the public.
Keeneland traditionally has an open backstretch policy; the public is welcome.
"I just went over with the quarantine people this morning to see if there was anything different than what we had in the past, get up to speed to all that," Beasley said. "Then there are things like the European horses come out on the turf and there can't be other horses at that time, all those little things. We have foreign horses there (at Keeneland) but we don't get them in numbers you have here."
With the 2015 Breeders' Cup horses slated to be in the Rice Road barns, Beasley said Keeneland is already working on contingency plans to take care of the horsemen — like Charlie LoPresti, trainer of two-time Horse of the Year Wise Dan — who regularly keep horses in those barns.
"The good thing is you're working with Breeders' Cup who does this at every track so they've got protocols," Beasley said.
Aktabantay out of Juvenile Turf; Faithful Creek in
After Aktabantay trained well over the course Thursday morning, trainer Hugo Palmer announced that the Group III winner has been withdrawn from Friday's Breeders' Cup Juvenile Turf because of a sore foot.
"He worked and moved really well this morning and I was growing in confidence about his chances in Friday's race," Palmer said. "Unfortunately, that confidence did not last long as he was found to have a sore foot when he returned back to the barn and I had to make the decision to scratch him."
"We are now looking forward to the spring and we will be aiming him at the 2,000 Guineas," Palmer added.
The defection of Aktabantay allows Faithful Creek to draw in for trainer Brian Meehan with jockey Kieren Fallon slated to ride.
The son of Bushranger has pleased Meehan, who has been trackside for the past two days.
"We are obviously pleased to be getting a run but not in circumstances like this," Meehan said. "Kieren Fallon, who will be on board tomorrow, got on the horse this morning and said that he gave him a really nice feel and we have the horse in really great shape."
Related stories from Lexington Herald Leader
Breeders' Cup Distaff pits Untapable against tough lineup of veterans
Fans watch the seventh race at Keeneland Race Course in Lexington, Ky., Saturday, October 25, 2014. Photo by Matt Goins Herald-Leader
How did Mark Casse celebrate winning the Preakness?
War of Will's trainer says Preakness win not revenge
2 horses killed at Del Mar in collision during training on 2nd day of meet.
MORE HORSES
Heat prompts NYRA to cancel racing Saturday at Saratoga
Maximum Security leads field of 7 in Haskell Invitational
Racing fans flocking to Saratoga as usual
Best In Show pulls 27-1 upset in Meadowlands Pace
Mariano Rivera honored at Saratoga Race Course
Saratoga Race Course opens Thursday with the Schuylerville


A specialised lesson with Stratford Teachers focuses on one language topic.
Each 30-minute lesson is divided into an explanation by the teacher and time for you to practise using the language. After the lesson, you receive a short, written summary of the topic and a quiz so you can test yourself.
We offer four categories of specialised lessons.
Grammar Many people try to learn English grammar from books. A quick explanation by a teacher is often quicker and more efficient. Our teachers can help you to understand why you make mistakes and how to correct those mistakes.
Vocabulary Vocabulary is difficult to learn when it is very different or very similar to your language. Our teachers can quickly identify your mistakes and show you how to correct them.
Pronunciation Pronunciation mistakes are the main cause of misunderstanding. Our teachers can show you the correct way to produce the sounds and rhythm of English.
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