text:
A Lifelong Friendship – Betty Hodges Hughes and Betty Jackson Stewart
Council paves way for creation of two Special Districts
By Leslie Scott
It's a typical weekday morning at the Cotton Gin with breakfast crowds gathering and in a crowd of people, there are two ladies there that are as much a part of Prosper as the business itself. Betty Stewart and Betty Hughes have known each other most of their lives. Friends since they were young, these two have a friendship, not just of longevity, but of depth as well.
As we sat down to breakfast, immediately these two ladies began talking about the pictures and books Betty Hughes brought to show. Affectionately called an Annual by both, we began our visit by talking about their high school years and how they met and developed such a long friendship. Betty Hughes has a twinkle in her eye when she begins, "Betty [Stewart] was three grades ahead and I knew her and she was a majorette. She'd already graduated and then I was a majorette my senior year. I wasn't really that good, she could twirl, but I couldn't twirl. But back then they didn't care. Just as long as you had long legs!" Betty Stewart disputes this by saying, "I didn't have long legs." Not to be deterred, Betty Hughes continues, "but anyway- we stayed in touch. When we moved to Prosper we just hung out. Cousins through marriage – so we are just kind of backdoor relatives – we just all call each other cousins."
Carrying on a conversation with these two is almost like talking to a set of siblings, in particular a set of twins. When asked of their favorite memories together, it's a swinging pendulum of answers. Both immediately say their most recent favorite memories are with the late Jim Hughes and late Bill Hays. Betty Hughes says, "We went to Branson the spring before Jim died" and Betty Stewart finished with, "we went to Swenson's lodge together for a weekend. We both went to the same school for 12 years, both go to the Methodist church, historical society together, there's so many memories we have together."
When asked what attributes they appreciate in the other, Stewart says of Hughes, "She's more like a sister to me, because I've never had any sisters. And if I need anything, I feel like I can call her – we're just good friends." And Hughes says, "She's always been there for me and if I need something, I just call Betty. When she doesn't have a broken arm or broken leg!" Laughing ensues and Stewart replies, "Lately I've been more broken than anything. I played basketball and volleyball and tennis and rode horses and barrel raced and never had a broken bone. And after I got into my late 70s and early 80s, I've had broken bones. It's catching up to me, but I've been lucky all these years and really blessed."
These two both hesitated and thought for a bit when questioned on any guilty pleasures. Stewart says "I love to travel." Hughes says, "She likes to travel but I don't, I'm a homebody – home and a good book, but I know I need to get out for socialization." There were no hesitations when asked of their proudest achievement or accomplishment, as Hughes said, "Our kids," and Stewart answered, "Kids and grandkids." Family is important to both of these women. Betty Stewart is the mother of an only daughter, "We didn't plan it that way, it just so happened we only had one. Doctor didn't know if they could save me or the baby, so decided that meant only one. I have two grandkids and three great-grandkids – three boys. Our daughter didn't like to be an only child and said she would have more – and she had a girl and a boy." Hughes adds, "I have a son and a step-daughter – but 6 grandchildren!" These two also had accomplished careers as well as raising families. Betty Stewart worked for TXU Energy for 37½ years and Betty Hughes began her teaching career in 1959 and had various teaching and administration positions.
A lively volley of back and forth ensues between them when asked about their upbringing and siblings. Stewart begins, "I just had two brothers and always wished for a sister." And Hughes joyfully adds, "I did too. People asked what do you think of him [her baby brother] and I said I want to send him back and get a girl. You always wish for the opposite."
As we gloss through the pages of their school Annual books, they are continuously complimentary to each other. Betty Hughes takes the lead flying through the pages going back in time. There's a photo of Betty Stewart, "there she is, look at her long pretty hair!" Stewart glances and the photo and says, "That's just the way it does – it used to just flip like that and I didn't do anything to it." When asked if they wore much makeup Stewart says, "not very much, maybe a little lipstick. I can't remember putting makeup on." Hughes points out a picture of herself and Stewart says, "Oh that's a good one of you too!" The word Favorite is at the top of the pages these ladies are on in several books which is the equivalent to today's prom queen. They both look amazing and when asked if they still have those dresses Hughes laughs, "Yeah, sure – no, I hold on to a lot of things but not that. I don't even know or remember how we afforded to have those dresses."
Their Annuals are full of photos and accomplishments of each of them:
Betty Jackson: Basketball 4 years, Basketball Co-captain '53, Sophomore Favorite , High School Favorite '51, District Journalism Contest '51-52, Best Athlete '52-53, Nominee for the DAR '53, Pep Squad: Majorette '51-52, Head Majorette '52-53, Business manager of the "Eagle" '52-53, FHA Club 3 years, Librarian 1 year, Journalism Club, Typist of the Static, Delegate to State Journalism Contest, Austin '51-52, Choral Club, FHA Officer 3 years, Freshman Class President.
Betty Hodges: FHA Reporter '52-53, FHA Treasurer '54-55, FHA 4 years, Pep squad 4 years, Majorette '55-56, Class Favorite '53-54, Princess of Royal Court '55-56, Annual Staff 2 years, Static Staff 2 years.
The ladies gloss through the pages stopping here and there to explain junior / senior banquettes, the low number of students in each class, pausing at a photo of Ann Hays, Bill Hays' wife who Stewart says was "like a sister to me," and they jump forward to who their classmates became and where they live. They both say they remember where the photos were taken, the memories being made, and what they were doing at the time. Hughes says "My class still meets every month, but hers has a reunion every once in a while." There are moments while going through the book that are not so happy. Stewart says, "Bill was my travelling partner and now I don't really have anyone to travel with. Most people are working, or they don't like to travel. I'm sure if Bill was alive we would be travelling." And Hughes says, "I know we're eventually all going to go, but losing our friends and loved ones, that's hard."
These ladies have seen many changes through the years and seem to embrace them. Hughes says about technology, "I like it, I still have my flip phone, but I like it. And I like my computer except when it breaks down." Stewart is an optimist, "I think everything has changed for the good. And I do love all the building in Prosper. I know it's a lot of traffic, but just think when all those stores go in we don't have to drive very far, that's a blessing there." Hughes followed with, "you know the Mayor said some people don't want many drive-through places, but I like them. If I don't have her [Betty], or someone to do something with, I can just go grab food and go home and get my book and eat while I'm doing that. I know some people like places they want to sit together as a family too, but I like drive up places to eat."
Both Betty's have observed Prosper growing and evolving throughout their lives. Stewart points out, "there were 250 people here when we were growing up." Hughes gets that twinkle in her eye again when she says, "I wish I had that sign, the population sign." Stewart says wistfully, "I never thought Prosper would grow like it has, you know Prosper is a wonderful town."
Betty Stewart and Betty Hughes have always seemed to be destined to be lifelong friends. Whether related through marriage, neighbors that lived across the street from each other at one time, travel companions, or best friends, they seem to be more sisters than not. These two have experienced great joy, sorrow, humor, and the everyday details of life together. When told that they just can't seem to get away from each other, Stewart immediately responds with a chuckle, "and we don't want to!"
cedarbrookmediagroup January 8, 2018


Make all your sound and vision streaming sources the best they can be, with the powerful Pioneer VSX933.
With power now standing at a mighty 135 watts per channel, the Pioneer VSX933 is more punchy-sounding than ever. 7.2 surround sound immerses you, giving you cinema sound surround that no soundbar can compete with.
Dolby Atmos uses ceiling or upwards firing speakers to produce a multi-dimensional, immersive sound that's a match for the finest cinemas. DTS:X literally pushes the boundaries of what you can expect from home cinema. It renders images in three dimensions that conventional processing can't match. DTS Neural:X upmixer supports Dolby formats, giving you DTS surround whatever the format.
Designed to get the most from Dolby Atmos speakers, Reflex Optimiser uses Phase Control technology for improved focus. By aligning the frequencies from ceiling or upward-firing speakers, the sound is more 'together', making it sound more natural and less disjointed.
Already one of the best-equipped AV receivers for streaming music, the Pioneer VSX-933 features more streaming options than ever. Integrated Amazon Prime Music (via firmware update) joins Spotify, TIDAL and Deezer to make this the best choice of AV receiver for music streaming. There's also Google Chromecast built-in. This lets you stream music, podcasts and audio apps, including Google Play, at the touch of a button.
DTS Play-Fi is a premium, wireless control system that brings everything under one 'roof'. Download the free app and you'll not only have access to Internet radio but also popular music apps such as Spotify, Tidal, Deezer and Napster. As well as bringing all your streaming sources together, Play-Fi offers the potential for full multi-room music. Simply add other Play-Fi compatible sources and you'll quickly be able to build up a comprehensive music system around your home - all under the control of a single app.
Streaming music between rooms from any source, including records and CDs, is easy with FlareConnect. When used with compatible FlareConnect speakers, you can listen to your treasured vinyls and CDs in any room. Music selection, speaker grouping and playback control is all built-in to the Pioneer Remote App for effortless smartphone or tablet control.
The Pioneer VSX-933 is the perfect partner for your HDR-equipped TV and video sources. It supports HDR10, Dolby Vision, HLG and HDCP 2.2, which means you can play UHD Blu-ray discs and stream UltraHD video in the highest quality. It's also equipped with 4K upscaling, giving you the most detailed picture on your 4K TV from all sources. The HDMI sockets allow 4K pass-through, for hassle free switching and viewing without the receiver needing to be on.
With an extra two HDMI sockets over the older model, the VSX933 can now support the most complex AV systems. Games consoles, set-top TV boxes, cameras, video streamers and Blu-ray players can all be accommodated, without the need for HDMI switching units.
When it comes to connecting older sources, the VSX-933 has everything covered – right down to your turntable. Legacy sources such as DVD players or older games consoles connect via digital optical, coaxial component and composite inputs. As well as a turntable input there are four line level ones – ideal for a CD player, music streamer and other music sources. With USB sockets at both the front and rear, connecting a media device and playing back your digital music library is easily achieved.
Another great new feature with the Pioneer VSX-933 is Zone 2 active and passive audio outputting. Use the active outputs to power standard speakers in a second room. Alternatively, RCA phono outputs let you use your own choice of active speakers or amp/speaker combo in another room.
Raise your home entertainment game, with the all-powerful Pioneer VSX933.


Today we are announcing some significant changes to our Developer Program. Over the past several years, we've seen some exciting applications from our developer community. While many delivered value back to our members and LinkedIn, not all have.
As such, we've taken steps to refocus the Developer Program from primarily open APIs to partnership integrations that we believe provide the most value to our members, developers and business. And we're seeing great success from this approach with partners such as Samsung, WeChat, Evernote and our Sponsored Updates partner program.
Allowing members to represent their professional identity via their LinkedIn profile using our Profile API.
Enabling members to post certifications directly to their LinkedIn profile with our Add to Profile tools.
Enabling members to share professional content to their LinkedIn network from across the Web leveraging our Share API.
Enabling companies to share professional content to LinkedIn with our Company API.
The developer community continues to be a priority for LinkedIn. We want to continue providing tools needed to create great products around the use cases we support. So today, we're releasing a new Mobile SDK for Android that allows developers to build applications that make it easy for members to login with their LinkedIn credentials and deep link to view member profiles within the LinkedIn app. We will continue to introduce new opportunities, such as the LinkedIn Economic Graph Challenge, where we will be working closely with developers to help further our company's vision.


So the White Witch project is finally moving again. This began life way back in 2012 when I was commissioned to write a short film script for Reeltime Pictures - a spin-off from an early 1970s Dr Who Episode The Daemons and starring the original actress Damaris Hayman.
Script delivered and all went quiet for a while for a variety of reasons. But now I've signed a contract for the story in the accompany anthology (to be published by Telos Ltd) and things are moving forwards. A couple of weeks ago, I went to Lincoln to record a short interview for Reeltime Pictures, the story is delivered and there's music by Linzi Gold - and we're all set for a release in November 2017.
You can pre-order the DVDs from Galaxy Four.


Polaroid introduces the instant colour camera.
Texas Instruments launches the pocket calculator.
first major coin-operated electronic video game.
Class Motto: Who so neglects learning in youth, loses the past and is dead for the future.


text:
\section{\label{sec:intro} Introduction}
Optical polarization plays a key role in the quantification of numerous physical processes with applications in Atomic and Molecular Optical Physics~\cite{garcia2018improving}, Astronomy \cite{marshall2016polarization}, Imaging \cite{losurdo2009spectroscopic}, and Material Science \cite{capelle2017polarimetric}. Monitoring the polarization of time dependent light from a process can reveal insight into a physical system. Furthermore, several optical technologies, such as optical isolators and photonic waveguides require a precise tuning of the input polarization state. Having a portable, real-time polarimeter is thus a useful tool across many research and industrial optical settings.

This paper presents an affordable, integrated polarimeter system capable of real-time visualization and acquisition of the polarization state and an optical field. The system is easily calibrated to accommodate a broad range of light levels and wavelengths.

\subsection{\label{subsec:quant}Quantifying Polarization}

The polarization state of a quasi-monochromatic plane wave, traveling in the $\hat{z}$ direction can be completely specified by the magnitude ($E_x$, $E_y$) and relative phase ($\phi = \phi_y-\phi_x$) of its transverse components:

\begin{equation}
\label{eq:monochrome}
\vec{E}(\vec{r},t) = \left(E_x\hat{x} + E_ye^{-i\phi}\hat{y}\right)e^{i(kz-\omega t - \phi_x)}
\end{equation}

Equation~\ref{eq:monochrome} describes a parametric plot at a fixed location $z$ between $E_x(t)$ and $E_y(t)$ which generally describes \textit{elliptical polarization}~\cite{Goldstein_03}. In the special cases that the two fields are perfectly in phase, ($\phi = n\pi$), or in quadrature $\phi = (2n+1)\pi/2$ (for integer $n$), the ellipse becomes degenerate (\textit{linear polarization}), or has zero eccentricity (\textit{circular polarization}) respectively. Any polarization state may be uniquely quantified as a superposition of either horizontal and vertical linear polarization, $+45^\circ$ and $-45^\circ$ linear polarization, or right and left circular polarization.

The polarization ellipse evolves at optical frequencies of hundreds of THz, and thus can not be imaged directly, but can be completely specified by the \textit{Stokes parameters}. Denoting $I_{H(V)}$, $I_{+(-)}$, and $I_{R(L)}$ as the intensity of the Horizontal(Vertical), $+45^\circ (-45^\circ)$, and Right(Left) circular polarizations respectively, these parameters are given by \cite{Goldstein_03}:

\begin{subequations}
\begin{align}
S_0 &= \langle E_xE_x^*\rangle +\langle E_yE_y^*\rangle &= I_H + I_V \label{eq:defstokesa}\\
S_1 &= \langle E_xE_x^*\rangle - \langle E_yE_y^*\rangle &= I_H - I_V \label{eq:defstokesb}\\
S_2 &= \langle E_xE_y^*\rangle + \langle E_yE_x^*\rangle  &= I_+ - I_- \label{eq:defstokesc}\\
S_3 &= i(\langle E_xE_y^*\rangle - \langle E_yE_x^*\rangle) &= I_R - I_L \label{eq:defstokesd}
\end{align}
\end{subequations}

\noindent where the angled brackets denote time averaging over a short measurement time.

The Stokes parameters may be measured via intensity and are thus readily accessible using standard photodetection techniques. These parameters can be encompassed in a single vector known as the \textit{Stokes Vector}.

\begin{equation}
\label{eq:def_stokes_vec}
\vec{S} \equiv \left(S_0,S_1,S_2,S_3\right)
\end{equation}

The Stokes vector is useful in mathematically representing polarizing elements using the Mueller formalism~\cite{Goldstein_03}in which polarization transformations are represented by a $4\times4$ ``Mueller matrix''.

An additional benefit of the Stokes formalism is the quantification of polarization of light with non-constant polarization \cite{born2013principles}. If the relative phases and amplitudes in equation~\ref{eq:monochrome} are not constant over the averaging process, $S_1$, $S_2$ and $S_3$ will diminish. In the limit of rapid variation the Stokes parameters become $S_{unp} = (1,0,0,0)$ and the light is said to be ``unpolarized''. Often the light is partially polarized and is somewhere in between. This is quantified by the ``degree of polarization'' \cite{born2013principles}:

\begin{equation}
\label{eq:def_dop}
P \equiv \frac{\sqrt{S_1^2 + S_2^2 + S_3^2}}{S_0}
\end{equation}

Generally we can factor the light into a mixture of polarized and non-polarized light, $S = PS_{pol} + (1-P)S_{unp}$.

We can also specify the polarization directly from the parameters of the ellipse. The polarization ellipse can be completely specified by the Stokes parameters in equation~\ref{eq:defstokesa}--d: The angle of rotation $\psi$ of the ellipse with respect to the $x$ axis, and the ellipticity angle give by the ratio of the semi-minor to semi-major axes of the ellipse $\tan\chi = \pm b/a$ are given by \cite{Goldstein_03}:

\begin{equation}
\label{eq:defellipse}
\tan2\psi = \frac{S_2}{S_1}, \hspace{20pt}\sin2\chi = \frac{S_3}{S_0}
\end{equation}

A third method of quantifying polarization is on the surface of the unit sphere known as the Poincar\'{e} sphere. In this formalism, the azimuthal angle $\phi$ and polar angle $\theta$, in spherical coordinates are related to the normalized Stokes parameters via \footnote{Here, we use the ISO standard \textit{80000-2:2019} for the polar angle which is the angle from the polar axis. Other works use the compliment of this angle and give $S_3 = \sin{\theta}S_0$}:

\begin{equation}
\label{eq:defpoincare}
\tan\phi = \frac{S_2}{S_1}, \hspace{20pt}\cos\theta = \frac{S_3}{S_0}
\end{equation}

Note that each of the parameters in equations~\ref{eq:defstokesa}--d, equations~\ref{eq:defellipse}, or equations~\ref{eq:defpoincare} are sufficient to reconstruct the polarization state.
A device which reconstructs the polarization state by measuring the Stokes parameters is known as a \textit{Stokes Polarimeter} which is the focus of this work. Figure~\ref{fig:our_swp}c shows these three visualizations, using our polarimeter.

\subsection{\label{subsec:swp}Stokes Polarimeters}

Equations~\ref{eq:defstokesa}--d imply that by taking multiple polarization measurements we may extract the Stokes parameters and thus completely characterize the polarization state. Such measurements generally fall into two categories: time-dependent and spatial modulation polarimeters. In spatial modulation techniques, the beam is sent to a spatially varying polarizing element and detected on a CCD array. Previously, micro-mirror arrays have been used to split the light into four beams corresponding to the Stokes measurements \cite{zhao_19}, and conical mirrors creating a continuous signal based upon total internal reflection \cite{hawley_19} have been used.

In time dependent measurements, a polarizing element is varied with time as the intensity is recorded. These typically involve a linear polarizer and a modulated birefringent element, which can be a liquid crystal variable retarder \cite{bueno_00}, or a quarter waveplate taken at discrete points \cite{berry_77,schaefer2007measuring}, or continuously \cite{bobach2017note}. This ``Spinning Waveplate Polarimeter'' (SWP) is the approach described in this work.

Previous works have considered a precisely calibrated quarter-waveplate, but this this can be difficult to achieve in practice and limits the applicability. Instead, we assume a waveplate with arbitrary retardance $\delta$, rotated an angle $\theta$ to the horizontally aligned polarizer. Performing the matrix multiplication in the Mueller matrix formalism, we find an intensity after the polarizer to be:

\begin{align}
\label{eq:swp_intensity}
I(\theta) &= \frac{1}{2}\left[S_0 + \left(\frac{1+\cos\delta}{2}\right)S_1\right] + \left(\frac{\sin\delta}{2}S_3\right)\sin2\theta \nonumber \\
& + \left(\frac{1-\cos\delta}{4}S_1\right)\cos4\theta + \left(\frac{1-\cos\delta}{4}S_2\right)\sin4\theta
\end{align}

Note that in the case of an ideal quarter waveplate ($\delta = \pi/2$), the expression simplifies to the expression in previous works \cite{berry_77}:
\begin{equation}
\label{eq:swp_intensity_basic}
I(\theta) = \frac{2S_0 + S_1}{4} + \frac{S_3}{2}\sin2\theta + \frac{S_1}{4}\cos4\theta + \frac{S_2}{4}\sin4\theta
\end{equation}

Thus, with knowledge of $\delta$ and $I(\theta)$, the Stokes parameters may be obtained algebraically with four discrete measurements. A more robust method however is to acquire data continuously while spinning the polarimeter at a constant rate $\theta(t) = \omega t$, and extract the Fourier components at DC, $2\omega$ and $4\omega$.

\section{\label{sec:our_pol}Our Polarimeter}
\subsection{\label{subsec:mech}Physical Construction}
Our SWP consists of a XD-3420 12V/24V high speed motor, connected by a timing belt to an internally threaded rotating tube (Thorlabs SM05M20) mounted in a low friction ball bearing (see figure~\ref{fig:our_swp}). The ball bearing is press-fit into the main base. The upper timing belt gear contains a small magnet that is picked up by a hall sensor and provides our reference angle and acquisition triggering. The tube contains a 0.5 inch, polymer zero order waveplate (Thorlabs WPQ05ME-780) that threads into the tube. A 3D printed adapter plate containing a thick polarizing sheet directly houses the photodetection circuitry. We use an OPT101 photodiode with integrated transimpedance gain of $100~\text{k}\Omega$, followed by a second non-inverting opamp stage with a variable gain from $G=1$ to $G=11$ via an accessible one-turn $10~\text{k}\Omega$ potentiometer. The motor is controlled by a standard PWM controller. As discussed shortly, our algorithm allows us to run in open loop configuration which simplifies the construction. Our photodiode and Hall-sensor trigger outputs are sent into a Raspberry Pi 4 computer which houses a 12 bit, 100 ksps data acquisition (DAQ) hat (Measurement Computing MCC 118).

\begin{figure}[ht]
\caption{a) Mechanical design of our SWP. b) Photograph of the SWP mounted on an optics table. The photodiode signal goes directly to the Raspberry Pi with MCC118 ADC attached. c) Screen capture of the heads-up display shown by the analysis program while running.}
\label{fig:our_swp}
\begin{center}
\includegraphics[width = 0.7\textwidth]{fig1}
\end{center}
\end{figure}

\subsection{\label{subsec:acquisition}Data Acquisition and Processing}
In order to process the raw data, we use the API provided by the DAQ hat~\footnote{Available at https://github.com/mccdaq/daqhats} to acquire a fixed number of samples for processing. We typically acquire 1000 samples at 20~ksps with a SWP rotation rate of 4500 to 5500 RPM, corresponding to several complete rotations.

To process this raw data, we divide the trace into $N$ segments corresponding to full rotations and assume a linear phase increase between trigger events. Each segment thus corresponds to equally spaced samples between $0$ and $2\pi$ rad. We numerically integrate each segment to extract the Fourier coefficients and use equation~\ref{eq:swp_intensity} to determine the Stokes parameters. We average the result of several segments to minimize statistical errors, and refresh the display at a rate of 4~Hz.

\subsection{\label{subsec:calib}Calibration and Experimental Imperfections}

\subsubsection{Waveplate Alignment Offset Calibration}

The angle $\theta$ in equation~\ref{eq:swp_intensity} refers to the physical angle between the transmission axis of the analysis polarizer and the fast axis of the waveplate. The angles of the magnetic trigger with respect to the polarization axis must therefore be known in order to set a phase reference of the trace. This may be accomplished with a simple procedure based on the fact that the $\cos2\theta$ component of the signal is nominally precisely zero. If however, there is a phase offset $\theta \rightarrow \theta + \Delta\theta$, a nonzero cosine quadrature will appear since $\sin(\theta+\Delta\theta) = \cos\Delta\theta\sin\theta + \sin\Delta\theta\cos\theta$. We thus acquire a single rotation, and minimize the $\cos2(\theta+\Delta\theta)$ curve over all possible phase delays $\Delta\theta$, recording the delay at which minimum value occurs. This is the offset angle between the magnetic sensor and the polarization axis which is used in reconstructing the polarization state. This entire process is automated with a simple script that takes seconds to run.

\subsubsection{Imperfect Waveplates}

The dispersive and birefringent nature of a waveplate leads to a wavelength dependent phase shift between slow and fast axes $\delta(\lambda)$ which can deviate greatly from the condition for a QWP of $\delta = \pi/2$. Referencing equation~\ref{eq:swp_intensity} we see that any deviation in $\delta$ will lead to an incorrect reconstruction of the polarization state, but knowing $\delta$, this can be corrected.

Our device allows for a fast, efficient measurement of the phase $\delta$, modulo $2\pi$. Since our system is monolithic containing its polarizer internally, we devise an \textit{in situ} measurement of retardance which is insensitive to loss and finite polarization extinction ratio of commercial polarizers. By sending in light which is linearly polarized with respect to the internal polarizer, we expect an photodiode signal given by\footnote{This is derived by multiplying the Mueller matrix of a $\delta$ phase waveplate to a horizontal polarizer, with a horizontally polarized Stokes vector as an input.}

\begin{equation}
\label{eq:calpol_v_t}
V(\theta) = \left(\cos^4\theta + \sin^4\theta + 2\cos^2\theta\sin^2\theta\cos\delta\right)V_0
\end{equation}

\noindent\ldots where $V_0$ is the voltage in the absence of the polarizer. The location of the maxima and minima can be used to extract the phase. Differentiating to find the extrema, we find the condition $\left[\sin4\theta\left(\cos\delta -1\right)\right] = 0$, so that $\theta = \frac{n\pi}{4}$. Noting that even $n$ yield maxima and odd $n$ give maxima, we can plug these values back into equation~\ref{eq:calpol_v_t} to note:

\begin{equation}
\label{eq:calpol_final}
\delta = \arccos\left(2\frac{V_{min}}{V_{max}}-1\right)
\end{equation}

We perform this quick calibration before each use by means of an automated script. We find little day-to-day variation for a particular wavelength, but an large variation with wavelength. Our polarizer shows a phase of  $\delta \approx \pi/2$ or $\lambda/4$ at $\lambda = 780~$nm, but $\delta \approx 1.91$ at $\lambda = 635~$nm corresponding to a $\lambda/3.29$-plate.

\subsubsection{Technical Noise}
Owing to the averaging process intrinsic to Fourier analysis, random errors tend to not affect the accuracy of our system. Non-random errors on the other hand, such as a constant dc offset \textit{will} systematically bias the determination of the polarization state.
This is evident from equation~\ref{eq:swp_intensity} where it is seen that an additional constant will lead to an overestimate of the sum of $S_0$ and $S_3$, generally underestimating the degree of polarization.
A DC bias may be due either to unpolarized background light or dark current in the photodetector. This may be accounted for by directly subtracting the constant DC signal present while blocking the light source under test. This is performed on the fly with a Python script, and typically takes a few seconds, allowing for recalibration whenever the background conditions change.

Another source of experimental error which has plagued previous designs \cite{arnoldt2011rotating} is non-constant rotation of the QWP.
In extracting the sine and cosine quadratures we are integrating along polarimeter angle and so this angle must be known at all points along the trace. This may be inferred by linear interpolation between triggers. If the angular velocity is not constant however, there will be a residual error. Since our SWP rotates at up to $6000$~RPM, the system is intrinsically inertially stable and significant changes to the angular speed will be gradual, over several periods. We verify this by observing the residual error from the fit of the measured voltage to the theoretical curve using a linearly polarized state.

\section{\label{sec:applications} Performance and Applications}
\subsection{Determining the Polarization State for Various Inputs}
In order to test the functionality of our SWP system for partially and fully polarized light, we send in numerous known polarization states for calibration.
We begin with incoherent, unpolarized light from a light emitting diode with $\lambda = 663 \pm 9$~nm. As we would expect, the output is unpolarized, showing a degree of polarization equal to $2.1\%$ (figure~\ref{fig:multistate}a).
\begin{figure}[ht]
\caption{a) With unpolarized light such as an LED, the DOP is nearly 0. When a linear polarizer is included, the light is seen to be linearly polarized. c) Partial polarization by reflections via a glass microscope slide shows partial polarization. d) Shows the raw signal for several periods when a waveplate is placed after the microscope slide, with the corresponding ellipse to the right.}
\label{fig:multistate}
\begin{center}
\includegraphics[width = 0.7\textwidth]{fig2}
\end{center}
\end{figure}

Next, we place a linear polarizer aligned horizontally after the LED and find a normalized Stokes vector of $(1.000,0.931,-0.031,0.006)$ with a degree of polarization of 93.1\%~\footnote{The reason for non-unity DOP is the finite polarization extinction ratio of the polarizer.}
For a source of partially polarized light, we reflect the initially non-polarized LED light off a class microscope slide at an angle of $71^\circ$ with respect to the normal (figure~\ref{fig:multistate}c). As predicted from the Fresnel equations~\cite{HechtBook}, we observed partially vertically polarized light. with a $DOP = 29.8\%$.
A general polarization state can be created by inserting a waveplate in the path of the partially polarized reflected light. This, along with the raw data is displayed in figure~\ref{fig:multistate}d.

\subsection{Application: Extremely Affordable waveplates}
A significant barrier to advanced experiments in atomic-optical physics in undergraduate teaching labs is the sheer number of optical components required. Certain experiments such as Pound-Drever Hall laser stabilization and Magneto optical trapping require many quarter wave plates, each of which can cost hundreds of dollars. It was noted in \cite{wieman1995inexpensive} that good quality waveplates may be constructed using overhead transparency paper as there is high transmission and suitable birefringence.
By sending linear polarized light through the material in question and observing the polarization ellipse, our real-time SWP allows for a quick determination of regions with retardance appropriate for a QWP.
Figure~\ref{fig:circpol} shows a typical trace obtained with $S_3/S_0 = -0.93$ corresponding to left handed, approximately circularly polarized light.

\begin{figure}[ht]
\caption{Stokes parameters (left) and polarization ellipse (right) for a sheet of transparency paper used as a quarter wave plate at $45^\circ$.}
\label{fig:circpol}
\begin{center}
\includegraphics[width = 0.75\textwidth]{fig3}
\end{center}
\end{figure}

\subsection{Application: Time Dependant polarization mapping}

The real-time nature of our SWP allows for in-situ characterization of time dependent polarization states. Our acquisition rate is limited by the mechanical rotation rate of the device which is typically 100~Hz if we use one rotation of data. This sets the maximum polarization sample rate for our device for non-graphical operation, although a reduced rate is preferable for averaging and numerical accuracy. For graphical display, we find that the visualization on the Raspberry Pi becomes the bottle neck, and sets the update rate to around 10 frames per second. In figure~\ref{fig:rt_poincare}a we shows the measured Stokes parameters for regular sample intervals while rotating a linear polarizer with an input circular polarizations state from a $650~$nm laser sent through a quarter waveplate.

We also can acquire and visualize the trajectory of a polarized state on the Poincar\'{e} sphere in real-time by keeping a buffer of the last $N$ points and plotting these along with the current location. Figure~\ref{fig:rt_poincare}b shows such an example for acquiring data at 4 fps while rotating the transparency paper by hand.

\begin{figure}[ht]
\caption{Time dependent measurements of the Polarizations state. a) Shows the measured Stokes parameters when an elliptically polarized beam is sent through a rotating polarizer. b) Shows the corresponding trajectory on the Poincar\'{e} sphere.}
\label{fig:rt_poincare}
\begin{center}
\includegraphics[width = 0.7\textwidth]{fig4}
\end{center}
\end{figure}

\section{Conclusions}

We have presented a real-time, fully integrated polarimeter based on affordable components that can be constructed by anyone with access to basic machining tools. We have described a single-shot calibration procedure that allows the use of an waveplate with non-ideal retardance, thus yielding a wide range of analysis wavelengths. By extending the analysis to partially polarized light, our device allows for an online visualization of an input optical state of arbitrary polarization. This has potential for visual demonstration in educational settings as well for providing a convenient heads-up display for in-lab calibration procedures. We also envision application in determining polarization dependent physical quantities such as concentration of optically active substances in a solution and stress induced birefringence metrology.

\noindent \textbf{Acknowledgments}:\textit{
We thank the University of Victoria, Faculty of Science Machine Shop and the Dept. of Physics \& Astronomy Electronics Shop for assistance with the design and construction of the device. We gratefully acknowledge internal support from Department of Physics \& Astronomy at the University of Victoria for funding this research.}

redpajama_set_name: RedPajamaArXiv


text:
Spiders flee — oh, what a tangled web they treed
These trees are loaded with spiders and their webs after flooding in Sindh, Pakistan.Russell Watkins / UK Department for International Development
April 15, 2011, 10:42 PM UTC / Source: LiveScience
By By Wynne Parry
Floods that swamped parts of Pakistan last summer created millions of unusual refugees – spiders. Now the British government has creepy photos showing the trees blanketed by spider webs.
In July, 10 years' worth of rain fell in one week, affecting 20 million people and leaving behind water that spanned an area the size of England, according to the United Kingdom's Department for International Development, which responded to the crisis.
Four months later, on Dec. 7, a photographer in the southern province of Sindh captured images of trees cocooned in gauzy webs made by spiders marooned in their branches by the flood waters. Much of the area remained under water as it was taking a long time for the flood water to recede, according to the department.
Residents of the province said they had never seen this phenomenon before, but credited the spiders with reducing the mosquito population, which appeared lower than would normally be expected given the amount of stagnant water left behind by the flood.
All mosquitoes need water to complete their life cycles, so stagnant water left by the floods could have led to lots of the pesky insects hatching.
You can follow writer Wynne Parry on Twitter.
Secret Weapons: A Bug's Arsenal
Natural Disasters: Top 10 U.S. Threats
By Wynne Parry

redpajama_set_name: RedPajamaCommonCrawl


text:
Posted inNews, Politics, State
Janet Mills reaches deal with tribes on domestic violence bill hanging over sovereignty talks
by Caitlin Andrews February 26, 2020 February 26, 2020
Gov. Janet Mills speaks at the signing ceremony to establish Indigenous Peoples' Day, Friday, April 26, 2019, at the State House in Augusta. William J. Nicholas Sr., Governor of the Passamaquoddy Tribe-Indian Township, left, and Clarissa Sabattus, Tribal Chief of Houlton Band of Maliseet Indians attend the event. Credit: Robert F. Bukaty | AP
AUGUSTA, Maine — After months of negotiations, Gov. Janet Mills' administration on Wednesday reached an agreement with tribes and lawmakers over a domestic violence bill that has been a major hurdle in wider tribal sovereignty negotiations.
Leaders of the four federally recognized tribes in Maine and Gov. Janet Mills have tried for months to agree on a bill passed by the Legislature last year that will allow the Penobscot Nation and the Passamaquoddy tribe to prosecute certain domestic violence crimes under the federal Violence Against Women Reauthorization Act of 2013.
Mills held the bill since last summer, citing concerns that the constitutional rights of non-native defendants wouldn't be protected in tribal courts. Tribal leaders have pushed back, saying federal law gives equivalent protections to non-native defendants and that including more specific language would undermine the tribes' sovereign rights.
Those issues were settled Wednesday, when a new version of the measure was unanimously endorsed by the Legislature's Judiciary Committee on Wednesday. Linda Pistner, deputy legal counsel for Mills, said the governor was "pleased" to support the measure after meeting with tribal chiefs earlier in the day. It will go to the House and Senate for votes.
Pistner said the Democratic governor has always been supportive of the bill's goal, but her final approval was secured with the addition of an explicit statement saying constitutional rights would apply to non-native defendants in tribal proceedings. The bill would require 12-person juries in those cases; the Penobscot Nation has juries of six.
"I'm thrilled that we are going to send the message that native women's lives matter just as much as yours or mine," said Rep. Rachel Talbot-Ross, D-Portland, the bill's sponsor, "and we're going to make sure the tribal courts have the sovereign jurisdictional rights to prosecute anyone who violates them."
The new version would also give tribes jurisdiction over crimes committed on reservations and current and future trust lands. It allows the Passamaquoddy to prosecute crimes between members of federally recognized tribes on its land, which the Penobscot Nation is allowed to do. Tribal courts have no jurisdiction over crimes committed between non-native people.
Since taking office in early 2019, Mills made efforts to repair Maine's fraught relations with the tribes, including banning Native American mascots from public schools and signing a bill to tighten water-quality standards. But tribal leaders feared the governor's hesitation on the domestic violence bill has raised concerns about their broader efforts to regain self-governance over criminal matters and other areas through changes to state law.
Those fears were borne out two weeks ago when Mills raised concerns about land jurisdiction and taxation issues and the "sweeping nature" of a bill from a state task force on tribal relations that proposes 22 changes to Maine law that would overhaul tribal sovereignty provisions.
The federal domestic violence bill passed with the aim of ensuring crimes committed against tribal women on tribal land are prosecuted. Nearly half of tribal women will experience rape, phyiscal violence or stalking by an intimate partner in their lifetime, according to the U.S. Department of Justice. Since the 2013 law was reauthorized, 18 tribes have implemented it, according to the National Congress of American Indians.
But Maine's tribes are boxed out due to state law that essentially treats tribes like municipalities under the state's jurisdiction after a 1980 land-claim settlement. It included provisions saying the state's tribes couldn't benefit from federal law unless that law specifically mentions them. Proposed bills to reauthorize the domestic violence bill in Congress do mention Maine tribes — but negotiations on the issue have stalled in the Senate.
Other criminal recommendations include giving the Houlton Band of Maliseets and the Passamaquoddy tribe the same jurisdiction over crimes committed on their lands granted to the Penobscot Nation and giving tribes concurrent jurisdiction over crimes committed by natives against non-natives. A work session on the omnibus bill is scheduled for next week.
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Professor O'Sullivan is a consultant paediatric pathologist working at OLCHC, which houses the national paediatric oncology-haematology unit. Her specific interest is in paediatric solid tumours and, in the research setting, the genetics, epigenetics and biology of these tumours. Professor O'Sullivan's group particularly focuses on sarcomas and paediatric renal tumours. They have characterised several novel chromosomal translocations and studied the biological impact these have on cell biology. The work has benefits in terms of diagnosis, prognosis, biological understanding and novel therapeutic development for these rare cancers, which are all too often neglected despite their aggressive behaviour.
Antonio has been a post-doctoral researcher in Professor O'Sullivan's group since 2015, having completed his PhD at the University of Madrid.
Professor O'Sullivan's group identified and characterised in 2012 the then only known genetic mutation recurrently seen in Clear Cell Sarcoma of Kidney (CCSK), and have been working on the biologic implications of that mutation (YWHAE-NUTM2 fusion) since then, with very exciting results. Recently, one further mutation was identified in CCSK – this is within the BCOR gene which has a role in epigenetic regulation of gene transcription. Professor O'Sullivan's group have now studied a very large cohort of cases of CCSK collected from international sources to total 159 tumours for these two genetic mutations. Their findings show distinct subsets of CCSK with the BCOR and YWHAE alterations. They have adopted several technical approaches specifically to investigate the epigenetic effect of BCOR ITD in cells. Their studies on YWHAE-NUTM2 are already advanced and they will be uniquely positioned to draw comparisons between the molecular mechanisms in their contributions to CCSK oncogenesis.
Malignant rhabdoid tumour (MRT), one of the most aggressive human cancers, afflicts very young children and has extremely poor outcomes. Despite its highly malignant nature, MRT bears mutations in just one gene known as SMARCB1. This gene encodes a protein that is important in the organization of the DNA (the genetic blueprint) within the cell thereby having a major influence on which genes are actively expressed within that cell. We have a number of aims, including working out what cell type rhabdoid tumour arises from, as this is not known and can be important in choosing best treatment. The DNA within a cell is arranged into a structure called chromatin and the precise arrangement is quite dynamic and highly regulated. SMARCB1 is a subunit of a multiprotein complex involved in this regulation of chromatin's organisation. Therefore, we aimed to work out what exactly happens in terms of DNA organisation when SMARCB1 is inactivated (as occurs in the MRT tumour cell setting) and how this contributes to the cancer developing, but then also to establish what happens when we put SMARCB1 back into the tumour cells that are missing it. Revealing the changes in the chromatin that follow on from loss of, and reintroduction of, SMARCB1 would allow for the identification of vulnerabilities in the MRT cancer cell that could be targeted in new treatments for MRT.
Project Title: Characterization of novel chromosomal translocations in sarcomas with emphasis on t (17;19) and t (10; 17) as initial investigations.


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