text:
\section{Introduction}
\label{sec:level1}

Quantifying the dynamics of a suspension of microscopic particles consists in measuring and analyzing the motion of those particles at the individual level or as a group. Like hockey for Canadians or cricket for Indians and Pakistanis, quantifying the dynamics of a suspension of microscopic particles is the national sport of a large community of researchers in physics and biology. For example, a century ago, Perrin has characterized the motion of small particles in a liquid, an experiment that evidenced the Brownian motion and firmly proved the existence of atoms \cite{22_perrin2014atomes}. More recently, the motion of tracer particles has been used extensively in soft matter\cite{pt1990witten, pt1964reiner} to extract the mechanical properties such as viscosity or elasticity of fluids, gels\cite{Mason1997, Chen2010}, pastes, cell cytoplasm\cite{Fabry2001,Lau2003} and foods at scales unreachable by macroscopic techniques. In the past decade, the study of the collective motion of fish schools, bird flocks and bacteria swarms has lead to the emergence of a new field, active matter \cite{Bricard2013}.

Video Particle Tracking (VPT) and Dynamic Light Scattering (DLS) are two of the most well-known techniques to characterize the dynamics of a suspension of microscopic particles and that have been widely described in a teaching context. VPT consists in tracking the position of an individual particle as a function of time to digitalize its trajectory. It provides precise information on a limited region of interest of a sample \citep{Crocker1996,ajp2013catipovic,Maurer2014}. DLS consists in shining a laser through the particle suspension and monitoring the fluctuations of scattered intensity as a function of time\cite{ajp1969clark}. It yields average information about the dynamics of a sample \citep{18_sartor2003dynamic, ajp1999goldburg,ajp1969clark}.

Here, we present a tutorial for an alternative method called Differential Dynamic Microscopy (DDM) recently proposed by Cerbino and Trappe \cite{2_DDM}. DDM is intuitive as it deals with real-space video of the moving objects like VPT, however it uses digital Fourier transform to obtain the same kind of information as DLS.  Contrary to tracking algorithm, DDM algorithm is straightforward to implement at the programming level of most undergraduate students. We believe lab work on DDM is a great opportunity to become familiar with a microscope and with reciprocal units, the range of accessible wavenumbers and other nitty-gritty details necessary to tame the power of the Fourier transform\cite{ajp1976higgins, ajp2001whiford}. We have joined to this article movies of suspensions with different types of particles and the DDM codes in Matlab and Python so that the reader may reproduce the image analysis proper to DDM, see EPAPS.

In this article, we show how to apply DDM to two sets of different micrometer particles, colloids at first, then motile bacteria, i.e.bacteria that can self propel. In section \ref{sec:materials}, we present the materials and method we use to prepare the samples as well as the acquisition parameters. Section \ref{sec:ddm} presents the DDM principle and algorithm. In section \ref{sec:BrownSection}, we use DDM to characterize the Brownian motion of colloidal particles which has been widely studied in a teaching context~\cite{ajp1997lemons, ajp2006newburgh, ajp2006bergstein} and we determine the diffusion coefficient of the particles. In section \ref{sec:BactSection}, we apply DDM to \textit{salmonella} bacteria and show that it is possible to characterize entangled dynamics where the bacteria both diffuse and ``swim". In particular we determine the proportion of motile bacteria, their diffusion coefficient as well as their velocity. This last example highlight the impact of physical techniques on biology. Finally in section~\ref{sec:didac}, we focus of the didactic aspect of the lab work.

\section{Materials and methods}
\label{sec:materials}
\subsection{Colloidal particles}

We use polystyrene spheres (Density of polystyrene, $\rho_\text{c}$ = $\SI{1040}{\kilogram\per\meter\cubed}$) with a catalog radius of $R=\SI{0.50}{\micro\meter}$  (FluoSpheres\circledR{} F-13082 from Thermo Fisher Scientific) and a 10\% polydispersity. The commercial dispersion is diluted 50 times in deionized water (at $T=\SI{20}{\degree C}$ the viscosity of water is $\eta =\SI{1.002}{\milli\pascal\second}$, and its density is $\rho_\text{s}=\SI{1000}{\kilogram\per\meter\cubed}$) so that the distance between two individual particles is large compared to $R$, typically $20 R$. This concentration remains sufficiently high to observe enough particles in the camera field of view and to accumulate satisfactory statistics. Polystyrene refractive index is $\approx 1.6$, larger than the one of water $\approx 1.3$, so the particles are visible in bright field microscopy.

To observe the Brownian motion of particles in a Newtonian fluid, several conditions are required \citep{16_CollSusp}. The particle has to be colloidal, meaning that its size has to be far larger than the size of the solvent molecules, it is the case for the suspension we used (molecular diameter of water \citep{17_marcus1998properties}  $\SI{0.34}{\nano\meter}$). Furthermore, colloidal particles have to be in the dilute regime to avoid interaction between them. This is checked once the sample is made. As our particles do not have long distance interaction, we estimate that the sample is dilute when the mean distance between particles is higher than at least 10 $R$. Finally, the thermal agitation should be the physical process that dominates the dynamics of the colloidal particles. We ensure that the solvent is not flowing by using an immobile, sealed and thin optical cell with negligible temperature gradient. The sedimentation motion can be characterized by the P\'eclet number \citep{12_patankar1980numerical, ajp2009saka}: $\text{Pe}_\text{g} = \frac{E_\text{g}}{E_\text{th}}$, where $E_\text{g} = \frac{4 \pi R^3}{3}  (\rho_\text{c} - \rho_\text{s}) g  \times 2R$ is the variation of potential energy for a difference of altitude equal to the diameter $2R$ of the particle, $E_\text{th} = k_\text{B} T$ is the thermal energy, $\rho_\text{c}$ and $\rho_\text{s}$ the respective densities of the particle and the surrounding solution, $g$ the acceleration of gravity, $k_\text{B}$ the Boltzmann constant and $T$ the temperature. Here we have $\text{Pe}_\text{g} \approx 0.1$, indicating that the sedimentation can be neglected over Brownian motion. Equivalently in the time domain, our particle respectively sediments and diffuses on a distance equal to its own diameter on respective characteristic times $\tau_\text{s}=9\eta/(8(\rho_\text{c}-\rho_\text{s}) R)\approx\SI{100}{\second}$ and $\tau_\text{d}=24\pi\eta R^3/k_BT\approx\SI{2}{\second}$, so we have $\tau_\text{s}\gg\tau_\text{d}$. Absence of both flow and sedimentation will be verified \textit{a posteriori}. In presence of a flow the trajectory of the particle, that should be random, is biased in the direction of the flow.

\subsection{Bacteria}
In section \ref{sec:BactSection}, we study the motion of non-pathogenic bacteria \textit{Salmonella Typhimurium SJW1103}  (American Type Culture Collection, Manassas, VA, U.S.A.) \citep{21_fabrega2013salmonella}. This bacterium has the shape of a rod of length of $\SI{2}{\micro\meter}$ and diameter of $\SI{1}{\micro\meter}$ with flagella that insure self propulsion\citep{5_berg2000motile}. The global motion of this bacterium can be split into two modes~\cite{Nelson2004}. In the ``tumble'' mode, the motors rotate clockwise and independently, causing the bacterium to move erratically. In the ``run'' mode, the motors are synchronized and rotate counter-clockwise leading the bacterium to move ballistic and straight forward. As we gently mixed the culture medium during growth, the nutrient medium can be considered homogeneous in our samples and the bacteria are moving isotropically.

\textit{Salmonella Typhimurium SJW1103}  are stored in a freezer at $\SI{-80}{\degree C}$ in a mixture of water ($\simeq \SI{33}{\%} w$) and glycerol ($\simeq 66\% w$). First, using a sterile inoculation loop, we streak bacteria from the storage solution on a sterile agar/LB plates  ($\SI{500}{\milli\liter}$ of LB/agar was made of $\SI{5}{\gram}$ of NaCl, $\SI{5}{\gram}$ of Tryptone, $\SI{2.5}{\gram}$ of Yeast Extract, $\SI{7.5}{\gram}$ of Agar). Second, the agar plates are closed and placed in an incubator at $\SI{37}{\degree C}$. The agar plates are oriented such that the LB/agar gel is at the top, to prevent the condensation from disturbing the development of the bacteria. After $\simeq$ 12 hours, we observe the formation of monoclonal circular colonies. Third, Using an inoculation loop, we take a monoclonal colony of bacteria from LB/Agar plate and disperse it in a \textsc{Falcon} tube with $\simeq \SI{5}{\milli\liter}$ TN growth medium. The TN growth medium is sterile and composed of $\SI{4}{\gram\per\liter}$ of bacto-tryptone, $\SI{2.5}{\gram\per\liter}$ of NaCl and $0.4\% w$ of glycerol diluted in water. The \textsc{Falcon} tubes have an oxygen permeable cap which allows the bacteria to breath and limits evaporation. Those bacteria are pre-cultured for a night at $\SI{32}{\degree C}$ at a shaking speed of 300 rpm in an Incu-Shaker 10L. Finally, we collected $\SI{50}{\micro\liter}$ of the solution of bacteria with a sterile pipette and we put it in a new \textsc{Falcon} tube filled with $\simeq \SI{5}{\milli\liter}$ of TN growth medium. The tube is then placed in the Incu-Shaker 10L at 300 rpm and $\SI{32}{\degree C}$ for 1h30. Around this time the optical density (OD) at $\SI{600}{\nano\meter}$ is around OD=0.5 and most bacteria are ``swimming". It is important to grow bacteria in a nutrient poor media and to collect them early on, at low concentrations, otherwise the bacteria tend not to develop a flagella. More details about bacteria preparation can be obtained in ref\cite{Schwarz2015, ajp2010hagen}.

\subsection{Microscope slide}
For the microscope observations, the aqueous suspension of colloids or bacteria are enclosed in a home made hermetic optical cell, Fig.\ref{fig:Slide}.a and observed at room temperature, $T=\SI{20}{\degree C}$. The cell is composed of a  glass slide (\textsc{RS France}) and a cover slip (\textsc{Menszel-gl\"aser}) spaced by two stripes of paraffin film (\textsc{Bemis}) creating a gap between the glass slide and the cover slip of approximately $\SI{125}{\micro\meter}$. The optical cell is briefly heated on a hot plate so that the paraffin welds to the slide and the cover slip. The suspension of colloids or bacteria is then introduced into the slit by capillarity, and the slit is immediately sealed at both extremity using ultraviolet-cured glue (Norland Optical).

\begin{figure}
\includegraphics[width=\figwidth]{Lamelle_Photos.pdf}
\caption{Experimental setup. (a) Schematics of the microscope cell used to study the motion of particles, namely, colloids and bacteria. (b) Typical bright field image of our colloidal suspension. (c) idem with bacteria.}
\label{fig:Slide}
\end{figure}

\subsection{Microscope and acquisition parameters}

The colloidal and bacterial suspensions are observed with light field microscope\cite{Mignard2015} (\textsc{nikon Eclipse Ti}) in bright field with an objective $10 \times$ of numerical aperture $N.A. = 0.3$, Fig.\ref{fig:Slide}.b-c. The focus is made in the middle of the microscope slide in $z$-direction so that we observe only particles able to move in the 3 dimensions. Images are acquired with a camera (\textsc{Hamamatsu ORCA-Flash 2.8}).

The images $I(\vec{r}, t)$ depends on the time $t$ when it was acquire. $\vec{r}$ is the coordinate of the pixels of the image.  $I(\vec{r}, t)$ is coded in $\SI{8}{bits}$  grey-scale: each pixel intensity is proportional to the incoming light intensity from the sample and varies linearly from  0 (black) to 255 (white). Using an exposure time of $\SI{1}{\milli\second}$, we adjusted the brightness of the microscope light in order to have a maximum number of pixel around a value of $\sim 120$ which minimize the amount of saturated pixels.

{The choice of the acquisitions parameters is a compromise between the spatial and the temporal resolution. With the $10\times$ objective, a pixel corresponds to $dL=\SI{0.645}{\micro\meter}$, a bit smaller than the optical resolution of the microscope, $\lambda/(2N.A.)\approx\SI{0.8}{\micro\meter} $. Bacteria or colloidal particles are about $\SI{1}{\micro\meter}$ and therefore correspond to a few pixels on the camera. We chose a $(\SI{512}{px})^2$ field of view which is large enough to capture the motion of 100 of particles and small enough to reach high acquisition frequencies, up to $\SI{400}{\hertz}$. At $\SI{400}{\hertz}$, it is impossible to directly send the data from the camera to the computer during the capture, so we have to temporarily save the acquisition on the buffer of the camera, and, once it is over, we send the data from the buffer of the camera to the computer. The camera buffer memory limits  to 4000 the number of images in one stack. To cover a wide range of time scales, we chose to acquire a first stack of $N$=4000 images at $\SI{400}{\hertz}$ and a second similar stack at $\SI{4}{\hertz}$. With this procedure, we cover time scales between $\SI{2.5e-3}{\second}$ and $\SI{1000}{\second}$ and length scales between $dL=\SI{0.645}{\micro\meter}$ and $L=\SI{330}{\micro\meter}$.

$\hat{I}(\vec{q}, t)$ is the numerical 2D Fourier transform of $I(\vec{r}, t)$ obtained using Fast Fourier Transform (FFT) algorithm which is widespread and included in most high-level languages. $\vec{q}$ refers to the wave vector which norm is $q=2\pi/r$. $\hat{I}(q, t)$=$ \left\langle\hat{I}(\vec{q},t) \right\rangle_{\vec{q}}$ is the radial average of  $\hat{I}(\vec{q},t)$  obtained by averaging the value of all the pixels that are between $q$ and $q+dq$ from the center of this 2D spectrum. In Fourier space, the wave number increment, which also corresponds to the minimum wave number, is related to the image size, $dq=2\pi/L=\SI{0.019}{\micro\meter^{-1}}$. The maximum wave number is $q_{max}=2\pi/(2dL)=\SI{4.87}{\micro\meter^{-1}}$. Indeed according to the Nyquist–Shannon sampling theorem, the smallest wavelength measurable corresponds to a sinusoidal wave of period 2 pixels: 1 pixel for the positive part of sinusoidal wave and 1 pixel for the negative.

\section{Differential dynamic microscopy}
\label{sec:ddm}

\subsection{Autocorrelation function $f$}
\label{sec:ddm1}

Differential Dynamic Microscopy (DDM) aims at obtaining the auto-correlation function $f$\cite{ajp1995passmore} from a stack of images $I(\vec{r}, t)$. $f$ is sensitive to the dynamics of the system and measures the similarity of the statistical properties of images separated by a lag time $\Delta t$. In Fourier space, the expression of $f$ is simple,  thanks to the Wiener-Khintchine theorem. It is the product between the Fourier transform conjugate of the images at time $t$,  $\hat{I}^*(\vec{q}, t)$, and the Fourier transform of the image at time $t+\Delta t$, $\hat{I}(\vec{q}, t+\Delta t)$ normalized by the square norm of $\hat{I}(\vec{q}, t)$:
\begin{equation}
f(q, \Delta t) =\frac{\left\langle \hat{I}^*(\vec{q}, t) \hat{I}(\vec{q}, t+\Delta t) \right\rangle_{t, \vec{q}}}{\left\langle | \widehat{I}(\vec{q},t)|^2  \right\rangle_{t, \vec{q}} }
\label{eq:f}
\end{equation}
As the colloidal or the bacteria display stationary ergodic and  isotropic dynamics, we average over the initial time $t$ and the orientation of the wavevector $\vec{q}$ as symbolized by the brackets, so that $f$ no longer depends on $t$ and $\vec{q}$  but only on the lag time $\Delta t$ and the wave number $q$ respectively.

For such systems, $f$ shows interesting general properties. $f$ decays with $\Delta t$ from 1 when the system has not changed ($\Delta t=0$) to 0 when the system has changed completely $(\Delta t\rightarrow\infty)$. The decay of $f(q, \Delta t)$ and its characteristic time $\tau(q)$ depend on the length scale via $q$. $\tau(q)$ is longer for large length scales, i.e. smaller $q$ because larger structures need longer time to decorrelate. The combined dependence of $f$ with $q$ and $\Delta t$ contains information about the physical origin of the decorrelation process. Based on dimension analysis, a diffusion process is characterized by its diffusion coefficient $D$ which scale as $[D]=[\text{length}]^2/[\text{time}]$ so that $f$ collapses on a master curve when plotted as a function of $q^2\Delta t$ (dimension of the inverse of the diffusion coefficient). In contrast, a ballistic process is characterized by its velocity $v$ which scale as $[v]=[\text{length}]/[\text{time}]$ and  $f$ collapses on a master curve when plotted as a function of $q\Delta t$ (dimension of the inverse of the velocity).

\subsection{DDM principle}

In DDM, $f$ is obtained as follow. First, we consider the difference between two images separated by $\Delta t$,

\begin{equation}
\Delta I(\vec{r},t, \Delta t) = I(\vec{r}, t+\Delta t) - I(\vec{r}, t),
\label{eq:DI}
\end{equation}

The subtraction remove all static artifacts such as dirt on the slide or on the microscope lenses. Second, we compute the DDM matrix $\mathcal{D}$: the squared normed  ensemble averaged on $t$ of the numerical 2D spatial Fourier transform $\widehat{\Delta I}$. The calculation of $\mathcal{D}$ allows us to recover $f$ as defined in Eq.\eqref{eq:f} thank to cross product term:

\begin{align*}
\mathcal{D}(\vec{q},\Delta t) \equiv& \left\langle \left|\widehat{\Delta I}\right|^2 \right\rangle_t\\
 =& \left\langle \left|\widehat{I}(\vec{q},t+\Delta t) - \widehat{I}(\vec{q},t)\right|^2 \right\rangle_t \\
=& \left\langle \left|\widehat{I}(\vec{q},t+ \Delta t)\right|^2 + \left|\widehat{I}(\vec{q},t)\right|^2\right. \\
&\left.- 2 \, \widehat{I}^*(\vec{q},t) \widehat{I}(\vec{q},t+\Delta t) \right\rangle_t\\
=& \underbrace{2\left\langle | \widehat{I}(\vec{q},t)|^2  \right\rangle_t}_{\equiv A(\vec{q})} \bigg[ 1-\underbrace{\frac{\left\langle \hat{I}^*(\vec{q}, t) \hat{I}(\vec{q}, t+\Delta t) \right\rangle_t}{\left\langle | \widehat{I}(\vec{q},t)|^2  \right\rangle_t }}_{f(\vec{q}, \Delta t)} \bigg]
\addtocounter{equation}{1}\tag{\theequation} \label{eq:DDM}
\end{align*}
}

Third, we radial average $\mathcal{D}(\vec{q},\Delta t)$ and therefore drop the dependence on the orientation of the wavevector $\vec{q}$. The contribution of the dark, shot and read-out noise\cite{Mignard2015,Joubert2011} of the camera add some noise to each images and is taken into account by adding a supplementary term $B(q)$. $B(q)$ is decorrelated  at all time and therefore independent of $\Delta t$.

\begin{equation}
\mathcal{D}(q,\Delta t) = A(q)\left[1-f(q, \Delta t)\right] + B(q)
\label{eq:D2f}
\end{equation}

The DDM matrix does not directly yield $f$. Ones need to correctly evaluate $A(q)$ and $B(q)$ to get $f$. Two different strategy can be adopted. Strategy 1: $A(q)$ and $B(q)$ are measured independently based on the properties of $\mathcal{D}$: at short times $f$=1, $\mathcal{D}(q,\Delta t\rightarrow 0) = B(q)$, and long times, $f$=0, $\mathcal{D}(q,\Delta t\rightarrow \infty) = A(q)+B(q)$. This first method give access directly to the autocorrelation function $f$ which can then be fitted. It is however necessary to measure small enough and  long enough lag time $\Delta t$ with respect to the derecorrelation time $\tau$ otherwise $B$ is overestimated and $A+B$ is underestimated, respectivel. Strategy 2 consists in fitting directly $\mathcal{D}$ with $A$ and $B$ as free parameters and a model for $f$. This last method is less demanding on the range of the lag time $\Delta t$ but it requires a model for $f$ and therefore prevent a scaling approach in the first place as described in section \ref{sec:ddm1}.

\subsection{DDM algorithm}
\label{sec:ddmalgo}

\begin{figure*}
	\includegraphics[width=\linewidth]{Graph.pdf}\\
	\caption{DDM principle. a) Schematic of the DDM algorithm. b) Image differences $\Delta I(\vec{r}, t,\Delta t=100 \text{ s})$. c) Square of the Fourier transform $|\widehat{\Delta I}|^2$ of the image in  (b). d) DDM matrix averaged and projected on $q$ for different lag times $\Delta t$. e) DDM matrix radial averaged and projected on $\Delta t$ for different $q$.  The results are obtained with the colloidal suspension.}
	\label{fig:D}
\end{figure*}

The DDM algorithm consists in two nested loops on $\Delta t$ and $t$ respectively, see Fig.~\ref{fig:D}a. At each iteration, we first open the couple of images $I(\vec{r},t)$ and $I(\vec{r},t+\Delta t)$, calculate $\Delta I(\vec{r},t, \Delta t)$ via Eq.~\eqref{eq:DI}, see Fig.~\ref{fig:D}b, and its Fourier spectrum $\left|\widehat{\Delta I}(\vec{r},t, \Delta t)\right|^2$, see Fig.~\ref{fig:D}c.  The loop on $t$ allows to compute at a fixed $\Delta t$ the time-averaged $\mathcal{D}(\vec{q}, \Delta t)$. This radial average yields $\mathcal{D}(q, \Delta t)$, see Fig.~\ref{fig:D}d. We then iterate on $\Delta t$.

A few tricks are performed to reduce calculation time. The role of the inner loop on $t$ is to gather statistics. At most it runs over $N-\Delta t$ couples of images which can be very expensive for short $\Delta t$. We found that limiting this number to 300 was enough provided that the initial times $t$ are evenly sampled across the accessible time window. Again to save calculation time, we logarithmically sampled $\Delta t$ with 10 points per decades which reduces the number of iteration of the outer loop from $N-1$=3999 to 10log$N$=35. With those optimizations, the calculation time falls to a few minutes.

We run the DDM procedure on both stacks of images at $\SI{400}{\hertz}$ and $\SI{4}{\hertz}$ independently. We then merged the two sets of data by scaling the data at $\SI{4}{\hertz}$ so that both values at $\SI{0.25}{\second}$ are equal. We average the values of $\mathcal{D}$ at $\SI{4}{\hertz}$ and $\SI{400}{\hertz}$ in the overlap interval, from $\SI{0.25}{\second}$ to $\SI{10}{\second}$. We thus obtain $\mathcal{D} (q, \Delta t)$, see Fig.~\ref{fig:D}e, for $\Delta t$ from $\SI{2.5e-3}{\second}$ to $\SI{1000}{\second}$ a range of $\Delta t$ wide enough to correctly measure or fit $A$ and $B$.

The final step consist in analyzing $\mathcal{D}$ (Eq.~\ref{eq:D2f}) to extract information on dynamics of the observed dispersion. In the following, for both colloidal and bacteria suspensions, we decided to display $f$ rather than $\mathcal{D}$ because it is easier to interpret and to compare to DLS experiments which also yields $f$. We will use strategy 1 to apprehend the scaling properties of $f$ and strategy 2 to fit $f$ with the appropriate model. $\mathcal{D}$ is fitted in logarithmic scale in order not to attribute too much weight on points with high intensity and we dismiss timescales above \SI{200}{\second} where the statics is poor because $\mathcal{D}$ is averaged less than 4 times.

\section{Brownian motion and DDM}
\label{sec:BrownSection}

\subsection{The Brownian motion of colloids}
The Brownian motion is the unceasing and random motion of small particles suspended in a fluid at rest. It is due to the shocks between the solvent molecules and the colloidal particles~\cite{13_brown1828brief,9_einstein1906theory, 14_sutherland1905lxxv, 10_von1906kinetischen,ajp1997lemons,22_perrin2014atomes} and has often been reviewed in the litterature~\cite{ajp1997lemons,Nelson2004, ajp2006newburgh, ajp2006bergstein, Pearle2010}. For spherical Brownian particles  diffusing in the  background solvent, the autocorrelation function is\cite{18_sartor2003dynamic, ajp1999goldburg,ajp1969clark,8_berne2000dynamic}:
\begin{align}
f(q, \, \Delta t) &= \exp(-\Delta t/\tau_\text{d})
\label{eq:fdiff}\\
\text{with }\tau_\text{d} &= \frac{1}{Dq^2}.
\label{eq:relax}
\end{align}
$\tau_\text{d}$ is the characteristic diffusion time of the exponential decay and $D$ the diffusion coefficient of the particles. $D$ is increasing with the temperature $T$ and decreasing with the radius $R$ of the particle and the viscosity $\eta$ of the solvent according to the \textsc{Stokes-Einstein} formula \cite{Nelson2004, 16_CollSusp, ajp1997lemons, ajp2007jia}:
\begin{equation}
D = \frac{k_\text{B} T}{6 \pi \eta R}
\label{eq:se}
\end{equation}

\subsection{Results}
\label{sec:resultcolloid}
Using strategy 1, from the short and long times values of $\mathcal{D}(q,\Delta t)$, we estimate $A(q)$ and $B(q)$ and isolate $f$, Fig.\ref{fig:ISF}.a. As shown in  Fig.\ref{fig:ISF}.b, $f$ collapse on a master curve when plotted as a function of $\Delta t q^2$. This scaling is compatible with a diffusive process and justified by Eq.~\ref{eq:fdiff}.

Now we use the strategy 2. We incorporate the model in Eq. \eqref{eq:D2f} for $f$ in $\mathcal{D}$ and fit $\mathcal{D}$. The initial parameters for the fit are:
\begin{equation}
\left\{
\begin{array}{rcl}
A_0 &=& \mathcal{D} (q,\Delta t_\text{max}) - \mathcal{D} (q,\Delta t_\text{min}) \\
B_0 &=& \mathcal{D} (q,\Delta t_\text{min}) \\
\tau_\text{d} &=& \SI{1}{\second}
\end{array}
\right.
\end{equation}
where $\Delta t_\text{max}$ and $\Delta t_\text{min}$ are respectively the maximum and the minimum interval of time between two images.

\begin{figure}
	\includegraphics[width=\figwidth]{ISFColloides3.pdf}\\
	\caption{Autocorrelation function extracted from the DDM matrix $\mathcal{D}$ at various $q$ versus $\Delta t$ (a) and $\Delta tq^2$ (b). Lines are exponential fits to the data according to Eq.~\ref{eq:fdiff}.}
	\label{fig:ISF}
\end{figure}

\begin{figure}
	\includegraphics[width=\figwidth]{DiffusionColloids2.pdf}\\
	\caption{Characteristic Brownian diffusion time and the parameters $A(q)$, $B(q)$ versus $q$. (a) $\tau_\text{d}$ ($\circ$) and its fit (\textcolor{red}{\textbf{---}}) using Eq.\ref{eq:relax}. (b)  ($A$ (\textcolor{blue}{+}), $B$ (\textcolor{blue}{.})) measured with strategy 1  and ($A$ ($\Box$), $B$ ($\diamond$))  fitted with strategy 2. The red dashed line is a fit of $A(q)$ following the model in Ref\citep{3_DDM3D}. The vertical black dash lines delimite regime 1, 2 and 3. Fits are performed in regime 2.}
	\label{fig:FitDiffColl}
\end{figure}

The fit results are displayed  as a function of $q$ in Fig.\ref{fig:FitDiffColl}. We observe 3 regimes:
\begin{itemize}
\item[\textbf{(1)}] Insufficient statistics. The radial average is performed on very few pixels (4 pixels for $q = q_\text{min}$ which correspond to the central cross of the Fourier transforms).  Also, at small $q$ the characteristic time is comparable to the duration of the experiment, $\SI{1000}{\second}$.
\item[\textbf{(2)}] Statistics are good and the signal-to-noise ratio is low enough.
\item[\textbf{(3)}] For  $q>\SI{3.5}{\per\micro\meter}$, $A(q)$ (signal) is too close to $B(q)$ (noise), to yield a consistent fit. This sets the spatial resolution of DDM to  $\frac{2\pi}{3.5} = \SI{1.8}{\micro\meter}$.
\end{itemize}

We fit $\tau_\text{d}(q)$ in regime (2) according to (Eq.~\ref{eq:relax}), which corresponds in logarithmic scale to a straight line of slope -2 and of intercept $-\log(D)$, Fig.\ref{fig:FitDiffColl}.a. Our measurements yield a diffusion coefficient of $D_\text{fit} = \SI{0.39}{\micro\meter\squared\per\second}$. We estimate the DDM experiment precision by repeating the exact same experiments 5 times. We obtain an average value $D_\text{fit}$ = 0.40 $\pm$ 0.02 $\mu$m$^2$/s with a relative precision of 5\%. The relative precision is comparable to the DLS technique\cite{Kayori2008}. Using the Stokes-Einstein formula with our experimental conditions and taking into account that the manufacturer stipulate a 10\% polydispersity on the colloidal radius we obtain $D_\text{E}$ = 0.42 $\pm$ 0.04 $\mu$m$^2$/s. The values $D_\text{E}$ and $D_\text{fit}$ are consistent.

There are many sources of uncertainties that may be reduced to increase the precision of the DDM results. First, statistics may be improved by increasing the number of particles in the field of view and the number of images in the time average. Second, DDM intrinsically deals with the static noise, thanks to the image subtraction process (Eq. \ref{eq:DI}), and the camera noise, $B$. To optimize the quality of the  measurement of $B$,one needs to measure fast enough so that $f$ remains almost completely correlated at short times. Otherwise $B$ is underestimated and consequently so is $\tau_\text{d}$.Third, $f$ needs to be properly normalized. One needs to measure long enough so that $f$ becomes completely decorrelated at long times otherwise $A+B$ is underestimated and consequently $\tau_\text{d}$ is overestimated. Experimentally this is easily checkable. One needs to observe for each $q$ two plateaus of the DDM matrix $\mathcal{D}$ at short and long lag times $\Delta t$, Fig.\ref{fig:D}e. The width of the range of $\Delta t$ is less critical for strategy 2 as all the parameters are fitted. Four, the choice of the region (2) where we fit the characteristic time also need to be properly estimated. Five, the results are model dependent. Ones need in fact to take the proper model for $f$. For example, the model in Eq.~\eqref{eq:fdiff}  considers that the particles are monodisperse. This is not exactly the case: the manufacturer stipulate a 10\% polydispersity. This could be refine by integrating a size polydispersity in the model for $f$. DDM is all the more precise that the experimentalists have some good knowledge about the system they study and have also first validated their procedure on a simple system like the one presented in this section.

 Fig.\ref{fig:FitDiffColl}.b shows the parameters $A(q)$ and $B(q)$. The noise level $B(q)$ seems constant for every $q$: the camera is adding a white noise to each images. With bright field, due to the depth of field of the objective in the $z$-direction, we are imaging a volume projected on $xy$ plane. The depth of field is an issue mostly on the large length scales (small $q$) due to the disappearance of particles from the $z$-field, which leads to underestimate the characteristic times\cite {4_Martinez20121637}. Taking into account the 3D nature of the experiment,  F. Giavazzi et al.\citep{3_DDM3D} have shown that it is possible to model $A(q)$.

In this section, we have verified and dissected the DDM procedure. We have shown that we obtain via the intermediate scattering function quantitative information on the 3D dynamics of a hundreds of colloidal particles simultaneously on length scales ranging from $\sim \SI{2}{\micro\meter}$ to $\sim \SI{200}{\micro\meter}$ and on time scales ranging from the millisecond to the minutes. This exact experiment can also be exploited in a different manner, thanks to the Stokes Einstein formula, Eq.\eqref{eq:se}. Provided  that we know $T$ and take for hydrodynamics radius of the particles $R= \SI{0.5}{\micro\meter}$, we can measure the viscosity of the solvant $\eta$. In our experiment, we find $\eta$= 1.07 mPas. Compared to a classical rheology experiment, DDM is actually better suited to measure small viscosity ($\sim$ mPas) of a solvent that we have on limited quantities ($\sim$ 50 $\mu L$). Finally, provided that this time we know $T$ take  $\eta$= 1.02 mPas, we can measure $R$ for particles size ranging from tens of nanometers to a few microns \cite{2_DDM}.  In our experiment, we find $R= \SI{0.53}{\micro\meter}$. Given the robustness and high throughput of DDM, DDM is appropriate for screening purposes.

\section{Bacteria and DDM}
\label{sec:BactSection}

\subsection{Motile Bacteria}

\textit{The Salmonella Typhimurium SJW1103} dispersion has a more complex dynamics than colloidal dispersion. We used the same acquisition parameters and algorithm as for the colloids. We extracted $f$ from the DDM matrix using the strategy 1 where $A$ and $B$ are measure experimentally. Contrary to the colloidal case, $f(q, \Delta t)$ shows a two step decay which corresponds to two decorrelation mechanisms, Fig.\ref{fig:ISFBacteria}.a. The first decorrelation mechanism, for small $\Delta t$, is due to a ballistic motion of the bacteria: the first decays of $f$ collapses on a master curve as we scale $f$ with the abscissa  $\Delta t q$, see Fig.\ref{fig:ISFBacteria}.b. On the contrary, the second decorrelation mechanism observed at large $\Delta t$, is due to a diffusion process:  the second decays of $f$ collapse when plotted as a function of $\Delta t q^2$, see Fig.\ref{fig:ISFBacteria}.c.

Based on the scalings properties of the $f$, we turn to a model that takes into account the Brownian motion of bacteria due to $k_BT$, the mean velocity and the velocity distribution during the run, the fact that some of our bacteria are motile and some are not. Considering these new conditions, it can be shown that an adequate $f$ is \citep{1_BactMobil}:

\begin{align}
f(q, \Delta t) &= \exp\left(-\frac{\Delta t}{\tau_\text{d}}\right)\left[(1-\alpha) + \alpha \mathcal{P}(q, \Delta t)\right],\label{eq:fbact}\\
\mathcal{P}(q, \Delta t) &= \int_{0}^{\infty} P(v)\, \text{sinc}(\Delta t/\tau_\text{r}) \mathrm{d}v,\\
\text{with } &\tau_\text{d} = 1/(Dq^2) \text{ and } \tau_\text{r}=1/(q\overline{v}),\label{eq:taus}
\end{align}
with $\tau_\text{d}$ the characteristic Brownian diffusion time and $\tau_\text{r}$ the characteristic run time. The expression of $\tau_\text{d}$ and $\tau_\text{r}$ justify the scaling proposed in Fig. \ref{fig:ISFBacteria}.b and c.

$\alpha$ is the fraction of motile bacteria. $\text{sinc}(\Delta t/\tau_\text{r})$ is the $f$ of an isotropic population of swimmers at velocity $v$. The distribution of velocity $P(v)$ and the integral $\mathcal{P}(q, \Delta t)$ over $v$ take into account that all bacteria do not move at the same velocity. Following Wilson et al.\cite{1_BactMobil}, we chose a Schulz distribution for $P(v)$ which is peaked around the average velocity $\overline{v}$ and going to 0 when $v \rightarrow \infty$:
\begin{equation}
P(v) = \frac{v^Z}{Z!} \left(\frac{Z+1}{\overline{v}}\right)^{Z+1} \exp\left[-\frac{v(Z+1)}{\overline{v}}\right],
\end{equation}
with $Z$ is a parameter related to the standard deviation $\sigma$ of the velocity distribution $P(v)$:
\begin{equation}
Z = \left( \frac{\overline{v}}{\sigma} \right)^2 -1.
\label{eq:sig}
\end{equation}
The integral $\mathcal{P}$ can be formally calculated:
\begin{equation}
\mathcal{P}(q, \Delta t) = \frac{\sin\left(Z\tan^{-1}\theta\right)}{Z\theta\left(1+\theta^2\right)^{Z/2}}\text{, with }\theta = \frac{\Delta t}{\tau_r(Z+1)}.
\end{equation}

\begin{figure}
	\includegraphics[width=\figwidth]{ISF_Fonction_TetTq2etTq_Bact2.pdf}\\
	\caption{Autocorrelation function $f$ extracted from $\mathcal{D}$ at various $q$ versus $\Delta t$ (a), $\Delta tq$ (b) and $\Delta tq^2$ (c). Lines are fit to the data according to Eq.~\eqref{eq:fbact}.}
	\label{fig:ISFBacteria}
\end{figure}

\subsection{Results}
Using strategy 2, the fit of $\mathcal{D}(q, \Delta t)$ with Eq.~\eqref{eq:fbact} as model for $f$ requires 6 parameters. Even though the 2 decays of $f$ are well separated in time, we initialize the fit with values very close to the results so that the fit converges:
\begin{equation}
\left\{
\begin{array}{rcl}
A_0 &=& \mathcal{D} (q,\Delta t_\text{max}) - \mathcal{D} (q,\Delta t_\text{min}) \\
B_0 &=& \mathcal{D} (q,\Delta t_\text{min}) \\
\tau_\text{d0} &=& 1/(0.1 q^{2})\\
\tau_\text{r0} &=& 1/(10 q)\\
\alpha_0 &=& 0.5\\
Z_0 &=& 1
\end{array}
\right.
\end{equation}

The fit-output parameters are displayed as a function of $q$ in Fig. \ref{fig:FitParametersBacteria}. Their values are quite robust : repeating this experiment five consecutive times, yields a 6\% relative deviation. We limit the $q$ range to the regime (2) set by the colloid experiment where the statistics and the signal to noise are optimal. Fig. \ref{fig:FitParametersBacteria}a display the run and the diffusion time as the function of $q$ which are fitted in logarithmic scale by straight lines of respective slopes -1 (ballistic) and -2 (diffusion). The intercept of $\tau_\text{d}$ yields a diffusion coefficient of  $D = \SI{0.28}{\micro\meter\squared\per\second}$. The \textsc{Stokes-Einstein} relation considering spherical bacteria of diameter $\SI{1.5}{\micro\meter}$, $\eta = \SI{1}{\milli\pascal\second}$ and $T=\SI{293}{\kelvin}$, yields $D_\text{SE} = \SI{0.28}{\micro\meter\squared\per\second}$, a very good agreement even though we are not considering the real shape of bacteria. Fitting $\tau_\text{r}$ and using the mean value of $\sigma$ (Fig. \ref{fig:FitParametersBacteria}c-d) yields the mean velocity and the standard deviation of the bacteria in the ''run" state: $\overline{v}$ = 21.2 $\pm$ 11.3 $\mu$m/s. The \textit{Salmonella Typhimurium SJW1103}  are faster than \textit{E. Coli} ($\overline{v} \approx \SI{10}{\micro\meter\squared\per\second}$)\cite{4_Martinez20121637}. In Fig.~\ref{fig:FitParametersBacteria}b, we show the fraction of motile bacteria as a function of $q$. Our bacteria suspension displays a higher fraction of motile bacteria, $\alpha\approx$ 0.8 than \textit{E. Coli} ($\alpha\approx 0.6$)\cite{4_Martinez20121637}. This is why we chose this species rather than \textit{E. Coli}. DDM permits to measure the velocity along the trajectories of the bacteria on relevant length scales, up to $\sim 30 \mu$m, a clear advantage compared to the typical DLS experiment where the smallest $q$ only go down to $\sim$ 6 $\mu$m$^{-1}$, corresponding to $\sim$ 1 $\mu$m in real space, roughly size of a bacterium. We note that $\alpha$, $Z$ and $\sigma$ are expected to be constant as the statistical properties of the bacteria dispersion and should not change over the duration of the experiment nor with $q$. This is roughly what we observe.

\begin{figure}
	\includegraphics[width=\figwidth]{VitesseDiffusionParams2.pdf}\\
	\caption{Fit parameters for the motile bacteria as a function of $q$  as extracted from the fit of the measurements of the DDM matrix $\mathcal{D}$. (a) characteristic time for the diffusion, $\tau_d$ (\textcolor{red}{$\circ$}), and balistic motion, $\tau_r$ (\textcolor{blue}{$\circ$}). (b) Fraction of motile bacteria $\alpha$. (c) $Z$. Inset: Shulz velocity distribution, $P$ for $<Z>$=2.4. (d) Standard deviation of the Shulz distribution $\sigma$ obtained from Eq. \eqref{eq:sig}.}
	\label{fig:FitParametersBacteria}
\end{figure}

\section{Didactic considerations}
\label{sec:didac}
We had the chance to test this lab work on an unusually long format: 48h spread on 6 days. However, provided that the DDM code is already written~\cite{code_github}, and the acquisition parameters given to the students, the colloid part of this paper can be accomplished in a regular lab class of 8h. In this reduced format the students can make the sample, use the microscope and the camera, put in practice the concept of diffusion, build a Peclet number, understand the importance of the auto-correlation function and get Fourier Transform. A similar lab class on bacteria is more involved and probably to be kept for students who have already done the lab class on colloids.

An other option is a physics-inspired computer project~\cite{ajp2005spencer, ajp2014deutsh}. In this case, the students start from the movies in EPAPS and have to write the DDM code. Before any coding, we discuss with the students how to translate the principle of DDM into an algorithm, section \ref{sec:ddm}. To keep the code structured and readable for us we give them the signature of each function to code with predefined input and output. Students have to first produced a non optimized version of the algorithm to run on only 100 images. In this way the students can feel that unoptimized  calculations are heavy and unpractical for longer movies and can then optimise the algorithm as explained in section~\ref{sec:ddmalgo}. All along this process, we discuss the nitty-gritty of the Fourier transform, units conversion and the Nyquist–Shannon sampling theorem.

\section{Conclusion}
\label{sec:cl}
Differential Dynamic Microscopy (DDM) is a microscopy technique that probes the dynamics of a system of particles using a microscope, a camera and numerical computations. We exposed this technique in the well-known case of simple Brownian motion before applying it to the more complex case of the motile bacteria. We have shown how to extract physically relevant information from DDM based on scaling and how to obtain quantitative values such as the diffusion coefficient or the velocity.

DDM is based  on microscopy and can therefore benefit from  more advanced techniques than bright field imaging. For example, it is possible to use fluorescence microscopy to tell apart colloidal probes in a crowed medium\cite{Hendricks2015}, confocal microscopy\cite{Lu2012}, or polarized light microscopy\citep{20_reufer2012differential}. Apart from colloidal Brownian motion, DDM has also been used to characterize ellipsoidal particles\citep{20_reufer2012differential}, kinetics of phase separation\cite{Gao2015}, aggregation\cite{Ferri2011} and other species of bacteria, such as \textit{E. Coli} or \textit{C. Reinhardtii}\cite{4_Martinez20121637}. Even macroscopic systems, like human crowds shot from above, could be studied by DDM. In that sense, DDM opens much more possibilities than dynamic light scattering and can be used in various contexts both in the lab and in the classroom.

\section*{EPAPS}
\label{sec:epaps}
EPAPS are accessible as zip file at: \url{http://perso.ens-lyon.fr/thomas.gibaud/ddm} and  contains 4 movies and a note describing each movies. Each movies are obtained with bright field microscopy and are composed of 4000 images of size = $(\SI{512}{px})^2$.  $\SI{1}{px}$ represent $\SI{0.645}{\micro\meter}$. Movie 1 and 2 capture the dynamics of the colloidal dispersion at $f_{acq}$=400 and 4 Hz. Movie 3 and 4 capture the dynamics of the \textit{Salmonella} dispersion at $f_{acq}$=400 and 4 Hz.

We have attributed a DOI \href{http://dx.doi.org/10.5281/zenodo.30559}{10.5281/zenodo.30559}\cite{code_github} to the codes which are accessible at GitHub.

\begin{acknowledgments}
The authors would like to thank the students who endured the initial versions of this lab work: Alicia Damm, Florine Dubourg, D.G. himself, Paul Haddad, Gabriel Rigon and Sylvie Sue.
This work was supported by the ENS Lyon, the Agence Nationale de la Recherche fran\c{c}aise (ANR-11-PDOC-027) and ML thanks the Region Rh\^one Alpes and
the Programme d'Avenir Lyon - Saint Etienne (PALSE NoGELPo) for postoctoral grant.
\end{acknowledgments}

\bibliographystyle{apsrev4-1}

redpajama_set_name: RedPajamaArXiv


1. Heat the Intense 35 Belgian milk couverture chocolate to the correct temperature for processing.
2. Use the piping bag to apply a layer of Belgian milk couverture chocolate into a flexipan chocolate mould.
3. Tip: Of course, you can also use different shapes.
1. After the hardening, remove the chocolate shapes from the mat.
2. Place the chocolate shapes on a baking tray covered with paper.
3. Create a velvety effect on the chocolate surface using an airbrush and a 50/50 mix of milk chocolate and cocoa butter.
1. Blow some gold sparkle over the velvet-sprayed moulds.
1. Heat the Emotion 58 Belgian dark couverture chocolate to the correct temperature for processing.
4. Level the mould with a scraper.
1. Using a skewer, make a zigzag line slightly higher than half way up the chocolate egg.
2. Place the mould in the refrigerator for several minutes and then remove the chocolate eggs from the mould.
1. Briefly melt the edges of two chocolate egg halves on a hot plate, or on the bottom of a hot pan, and stick them together immediately.
1. Powder the chocolate eggs with gold sparkles, using a brush.
1. Use a little bit of Belgian milk couverture chocolate to stick the golden chocolate egg on the moulded chocolate.
1. Place the burnished almonds in a food processor and chop in fine pieces.
2. Add the Belgian milk couverture chocolate dots and chop finely together with the almonds.
3. Depending on the amount of fat in the almond, you can optionally add nut oil.
1. Once you have an oily paste, you can add the butter.
2. Use a kitchen cutter to further chop the mass into a nice smooth gianduja.
1. Fill half of the chocolate egg with the chocolate almond gianduja.
1. Heat the chocolate to the correct temperature for processing.
2. Mix the Belgian dark couverture chocolate with the Crispy crunchies and break into large pieces on a baking tray with paper.
3. Apply a layer of Crispy crunchies on the chocolate almond gianduja after the chocolate has hardened.
1. Heat the Belgian milk couverture chocolate to the correct processing temperature.
2. Spread the chocolate up to 3 mm thick with a glazing knife.
3. Using the skewer, make an incision along the Easter bunny's head.
4. Tip: if you want to produce a large quantity, it is easier to make a cutter of the image with an iron band.
1. Create the parts that make the Easter bunny's face using modelling chocolate.
2. Tip: marzipan is also a good option.
3. The eyes are made of white chocolate. Another possibility is to make the eyes with modelling chocolate or marzipan.
1. Stick the chocolate parts, such as ears, eyes, nose and teeth, on the chocolate Easter bunny step by step, using Belgian dark couverture chocolate.
2. Garnish the eyebrows and mouth contouring with Belgian dark couverture chocolate.
1. Make the Easter bunny's hands from little balls of modelling chocolate.
2. Stick them on the edge of the chocolate egg.
1. Stick the Easter Bunny faces on the chocolate egg with Belgian dark couverture chocolate.
1. The Easter Bunny in a filled chocolate egg is ready to be presented!


text:
Supplemental Issues
Collections - French
Collections - English
Authors & Reviewers
Careers & Locums
About CFP
About the CFPC
Directives pour les blogues
Mainpro+ Credits
About Mainpro+
http://www.cfpc.ca/Canadianfamilyphysician/
https://www.cfpc.ca/Login/
Careers and Locums
Follow cfp Template on Twitter
OtherCollege
Francine Lemire
Canadian Family Physician September 2015, 61 (9) 816;
Roles: EXECUTIVE DIRECTOR AND CHIEF EXECUTIVE OFFICER
At its June 2015 meeting, the Federation of Medical Regulatory Authorities of Canada approved the physician practice improvement (PPI) framework for the purposes of consultation. The CFPC has been a collaborator in the work that led to the framework's creation. Much of the philosophy behind PPI is consistent with the principles that have guided us up to now: namely that the maintenance of competence is a dynamic process, influenced by a physician's context and scope of practice; that it must be based on a physician's identified learning needs; and that, above all, it must have an effect on practice and ultimately benefit our patients and communities.
The PPI framework is notably improved from earlier work around revalidation in 2 distinct areas: there is a shift in focus toward quality improvement; and there is coverage of several dimensions of a physician's practice—administrative, educational, and research roles as well as clinical roles. As outlined in documents circulated at the June meeting, the 5 steps in the PPI process are as follows:
Understand your practice.
Assess your practice and determine your learning needs.
Create your plan.
Implement your plan.
Evaluate the outcomes.
The final step guides the beginning of the next cycle.
The 7 principles of PPI include transparency (processes and procedures are clear and can be understood by all stakeholders, including physicians and the public); relevance (PPI applies to the physician's competence within the scope of his or her practice, and uses fair and consistent tools and processes); inclusivity (PPI applies to all licensed physicians and participation is mandatory); transferability (it is recognized by all licensing authorities in Canada and will not inhibit mobility within Canada); formative nature of the process (it is constructive and educational); efficiency (there is consideration of cost and administrative burden for physicians and redundancy is minimized); and integration (it relies on collaboration by and among stakeholders).
The CFPC's Maintenance of Certification has consisted, up to now, of meeting our requirements for continuing professional development (CPD) by participating in the Mainpro® program. Is this enough? Should there be a separate recertification process, which could include Mainpro participation as one of its components?
This area of exploration was recently stimulated by a meeting of the leadership of the CFPC and the American Academy of Family Physicians. In the United States, family physicians recertify every 10 years.1 Regular assessment modules are completed online throughout the 10-year cycle, with a multiple-choice recertification examination as the culmination of all these activities. The assessment tools allow evaluation of knowledge. Given the variety of contexts and scopes of practice, there is concern that assessment of knowledge is only one facet of competence. In the United Kingdom, physicians must recertify every 5 years through a process that includes quality improvement initiatives, patient surveys, and multisource feedback, done yearly.2 Anecdotally, some express concern that while the recertification cycle in the United Kingdom has increased transparency and accountability, and aims to improve patient safety, the relatively short cycle and the volume of demands on the average GP can challenge their daily work and elements of the clinical care they provide.
Meeting the CFPC's CPD requirements is associated with satisfactory performance in practice.3 The medical profession widely accepts CPD as an important component of maintaining competence but it is also beginning to recognize that our standards need to be strengthened. Peer reviews, audits, multisource feedback, specialty-specific clinical indicators, personal development plans, implementation of clinical guidelines, formalized peer networks, and analysis of and reflection on incidents and complaints, are some of the tools and approaches that have been suggested.4
Internal preliminary discussion at the CFPC (written communication with I. Oandasan, P. Eisener-Parsche, J. Meuser; July 2015) on this topic is generating definite viewpoints. We are mindful that competence is not maintained; "it evolves, and changes over time, experience, and setting." You will be glad to hear that there is no appetite for examinations; given the complexity I have described, "to find a single set of assessment elements that could be applied to the validation of the diversity of practices that characterize our discipline seems difficult to imagine."
The need for us to consider these questions arises in part owing to a changing environment, where patient safety, transparency, and accountability are more prominent than ever before. We are early in our reflection on this journey and welcome your feedback at info{at}cfpc.ca.
I thank Eric Mang and Cheri Nickel for their assistance with this article.
Cet article se trouve aussi en français à la page 815.
Copyright© the College of Family Physicians of Canada
Royal KD,
Puffer JC
. A closer look at recertification pass rates. Ann Fam Med 2013;11(4):389-90.
Burge S
. Recertification in the medical specialties: a way forward. Clin Med 2007;7:232-4.
Goulet F,
Hudon E,
Gagnon R,
Gauvin E,
Lemire F,
Arsenault I
. Effects of continuing professional development on clinical performance. Results of a study involving family practitioners in Quebec. Can Fam Physician 2013;59:518-25.
Shaw K,
Armitage M,
Starke I
. Specialist recertification: a survey of Members and Fellows. Clin Med 2008;8:155-6.
Collections - Française
Authors and Reviewers
Copyright © 2021 by The College of Family Physicians of Canada

redpajama_set_name: RedPajamaCommonCrawl


text:
Rienzi is an early opera by Richard Wagner in five acts, with the libretto written by the composer after Edward Bulwer-Lytton's novel of the same name (1835). Written between July 1838 and November 1840, it was first performed at the Hofoper, Dresden, on October 20, 1842, and was the composer's first success.
The opera is set in Rome and is based on the life of Cola di Rienzi (1313–1354), a late medieval Italian populist figure who succeeds in outwitting and then defeating the nobles and their followers and in raising the power of the people. Magnanimous at first, he is forced by events to crush the nobles' rebellion against the people's power, but popular opinion changes and even the Church, which had urged him to assert himself, turns against him. In the end the populace burns the Capitol, in which Rienzi and a few adherents have made a last stand.
Rienzi – Rene Kollo
Irene – Cheryl Studer
Wolfgang Sawallisch – Conductor
Recorded at the Bavarian State Opera, live in 1983.
Rene Kollo
Rienzi
Bavarian Stata Opera and Chorus; Richard Wagner, conductor Cheryl Studer Wolfgang Sawallisch


Let's start with some basics. An informal interview is one that occurs in an informal setting and is generally positioned as a casual exchange of dialogue. You may have a friend of a friend that works at XYZ company, and she knows someone, and recommends you meet this guy from the P Department, and there you go, a meeting is born.
All is good right? But what do you wear? Can you be candid during the session or put on your professional face? Find out.
Since this is an informal meeting, you may want to gauge how you should dress by a) the company culture (ie. If you apply for a job as a funeral director, then suit up), b) the type of job that which you are applying, and c) information provided by your contact (ie. Keep it casual says your contact).
To be candid or not to be..
You may be thinking that you can get away with speaking your mind, but remember that old saying, loose lips, sink ships. You don't want to sink this ship, so play it safe and find a happy medium between formal interview, and meeting with a buddy. Keep things professional, but you can relax and enjoy the meeting, without worrying about some of details one would commonly find in a sit-down grilling session.
Make sure you bring your resume, and something from which to record notes. It's still important to be on-top of your game, so stay sharp and think about the nature of the meeting and what you want to accomplish before the end of the session. These meetings are a great way to get insight into the job via an off-the-record setup.
Getting to know more about the job seems like a good idea, but just keep in mind this person could affect the chances of getting a job with this company. When in doubt fall back to the formal interview planning techniques that we provided, and you'll do fine.
Hope you enjoyed this article, and good luck with your interview!


text:
Client Login Translator Login
Clinical Trials and Patient Recruit
Culture Corner
ESL Tips and Tricks
Global Training Group
On Language
Reader's Corner
Translation Buyer Tips
Translations Group
aiatranslations
Alysa Salzberg
Translate hieroglyphics with Google
Although it's not perfect, Google Translate has become known as an easy way to translate over a hundred different languages. And now, the bot has a cousin who translates something you might not expect: hieroglyphics.
Google Arts & Culture's Fabricius translator was launched on July 15, the anniversary of the 1799 discovery of the Rosetta Stone, the first tool (albeit non-digital) that allowed us to translate hieroglyphics.
First, let's get this out of the way: This is a totally fun way to spend time. However, Google has taken things to another level, offering their software to academics the world over.
That has ruffled some feathers – but not because of issues like academic tradition or snobbery. Instead, there is a real issue here. Machine translation like Google Translate works with algorithms, which means that right now, it's not a perfect translator for this newly acquired language.
And even with time, it will never be perfect, simply because machines are not human beings. If hieroglyphics refer to an obscure name or place, or need a great deal of context to be
understood, a computer can't do that.
Additionally, Egyptologist Dr Roland Enmarch points out that since hieroglyphics were carved, drawn, or painted by hand, not typed by a machine, computers may have trouble understanding subtle variations of the same symbol.
So, translating entire tablets, wall paintings, and parchments of complex hieroglyphic passages is something better left to the experts.
But on the other hand, if you want to translate your name into hieroglyphics, or test Google to see if it can tell you what a single set of symbols mean, go right ahead.
There's even a fun option that allows you to translate with emoji – a truly amazing meeting of a very old language that used pictures, and a very new one.
And Google's initiative is admirable; with options like ready-made hieroglyphic messages to send to friends, and information and resources about Ancient Egypt, Fabricius might at the very least be a way for people to learn more about a fascinating language and society.
Read on for more information about Google's Fabricius hieroglyphics translator, from how to use it, to what Egyptologists think of it.
A screengrab of Fabricius in action.
Contact Our Writer – Alysa Salzberg
What we still get wrong about introverts
How 2020 changed our language
Does language influence our emotions?
FREE QUOTE? Click here
4387 W. Swamp Road #556
Doylestown, PA 18938 USA
© 2019 by aiaTranslations


I was very nervous about starting at Tha Rue Jang school, but the teachers were very friendly and welcomed me almost as family.
The children's English skills were very limited but over the course of my stay we found many ways to communicate without language. I was teaching computer studies, but I hope I also helped with their English and confidence speaking English. Occasionally I found things challenging or difficult to deal with.
The accommodation was set up as a share house situation. This suited me fine as it gave me a lot of freedom to do my own thing.
I really like the town of Trat. It is large enough that you can buy pretty much anything you need, but small enough that it feels like a community. It is very clean and easy to get around on a bicycle. I found the Thai people to be very friendly and welcoming. To me it felt like a place to live and call home, not just a place to visit. Some people may find the pace a little slow here, but for me it suited me fine. I always found something to do. From riding my bicycle down around the lake to drinking in local bars or dancing in the night club, spending a day relaxing on a beach or heading to the nearby islands.
I was very nervous about starting at Tha Rue Jang school, but the teachers were very friendly and welcomed me almost as family. The children's English skills were very limited but over the course of my stay we found many ways to communicate without language. I was teaching computer studies, but I hope I also helped with their English and confidence speaking English. Occasionally I found things challenging or difficult to deal with. But there wasn't anything that I could not work through with the help of the teachers, and the support of Meaw.
I am going to miss the children of this school so much. Everywhere I walked in the school I was met by calls of "Hello Teacher" and grinning smiling faces.
In my heart I will always have the name Kru Lahn. I am not sure how much I was able to teach the kids in my five months, but I hope I was able to keep some of them from falling behind and inspire others to continue studying computers. Also I hope I was able to reduce the workload of the ever hard working Kru Pook.
Volunteering in Thailand was an experience beyond anything I could have hoped for when I signed up for this project.
It gave me the opportunity to meet some wonderful people and make great friendships. To be able to become part of a community and learn about the culture and how life is lived in this part of the world was such a privilege. I know that I could not achieve this as traveller and it was exactly what I was looking for when I decided to volunteer. My one piece of advice to future volunteers is, don't buy your return ticket first. You may find that it is very hard to leave this place.


 Ahmber - Meaning of Ahmber, What does Ahmber mean?
[ syll. ah-(m)ber, ahm-b-er ] The baby girl name Ahmber is pronounced as AA-MB-er †. Ahmber is derived from Arabic origins. Ahmber is a form of the Dutch and English name Amber.
Ahmber is not regularly used as a baby girl name. It is not ranked within the top 1000. In 2017, within the family of girl names directly linked to Ahmber, Amber was the most widely used.
Baby names that sound like Ahmber include Aamber, Ambar (English), Ambre (French), Ambrea, Ambur (English), Ambyre, Anbar, Anbarr, Anbarre, Ambria (English), Amparo (Spanish), Annie Pier, Annie-Pier, Anupriya (Indian), and Ambyr.
† approx English pronunciation for Ahmber: AA as in "odd (AA.D)" ; M as in "me (M.IY)" ; B as in "be (B.IY)" ; ER as in "hurt (HH.ER.T)"


Hold the Babysitter!!! Our awards night has now been rescheduled to Saturday 5th April. The tickets we've given out will still be valid so please hold onto them. Apologies for any inconvenience.
Cuala 1995's please fill in our Online Form NOW!
Calling all Cuala 1995?s! Now that you are graduating to the Adults Section, we need to update your contact details and learn about your playing plans and availability for 2014. Please complete our online form.


text:
Rao score test
Calyampudi Radhakrishna Rao (2009), Scholarpedia, 4(10):8220. doi:10.4249/scholarpedia.8220 revision #121946 [link to/cite this article]
Curator: Calyampudi Radhakrishna Rao
Leo Trottier
Juan Pablo Carbajal
Anil Bera
Dr. Calyampudi Radhakrishna Rao, Pennsylvania State University
Rao's Score test is an alternative to Likelihood Ratio and Wald tests. These three tests are referred to in statistical literature on testing of hypotheses as the Holy Trinity. All these tests are equivalent to the first order of asymptotics, but differ to some extent in the second order properties. No one is uniformly superior to the others. Some related tests are Neyman's C(α) and Neyman–Rao tests.
5 Recommended reading
Let \(X = (x_1,\ldots, x_n)\) be an iid sample from a probability density function \( p(x,\theta) \ ,\) where \(\theta\) is an \(r\)- vector parameter. Let
\[ P(X,\theta) = p(x_1,\theta) \ldots p(x_n,\theta) \]
The score vector of Fisher is \[ S (\theta) = \left[ s_1(\theta), \ldots, s_r(\theta) \right]' \quad s_j(\theta) = \frac{1}{P}\frac{\partial P}{\partial \theta_j} \quad j = 1, \ldots, r \]
The Fisher information matrix of order \(r \times r\) is defined by
\[ I(\theta) =( i_{jk} (\theta)),\quad i_{jk}(\theta) = E ( s_j(\theta) s_k(\theta)). \]
The Rao's score(RS) test for a simple hypothesis \(H_0: \theta = \theta_0\ ,\) introduced in Rao (1948), is \[\tag{1} RSS = S (\theta_0)^\prime \left[I (\theta_0)\right]^{-1} S(\theta_0) \]
which has an asymptotic chi-square distribution on r degrees of freedom. Test (1) uses only \( \theta_0 \ ,\) the null value of \(\theta\!\ ,\) unlike the Wald test. Consider the composite hypothesis \[ H_0 : H(\theta) = C \] where
\[\tag{2} H(\theta)^\prime = (h_1(\theta),\ldots, h_t(\theta) ), \quad C^\prime=(c_1, \ldots, c_t), \quad t \leq r, \]
\( h_1,\ldots,h_t \) are given functions and \( c_1, \ldots,c_t \) are given constants. Let \(\hat{\theta}\) be the maximum likelihood estimate (mle) of \( \theta\!\) under the restriction (2). The RS test for the composite hypothesis (2) is \[ RSC = S (\hat{\theta})^\prime [I (\hat{\theta})]^{-1} S (\hat{\theta}). \]
An alternative way of expressing the RSC is as follows. Note that the restricted mle \(\hat{\theta}\) is a solution of \[\tag{3} S (\theta) + [ G(\theta)]^\prime \lambda = 0, \quad H (\theta) = C \]
where \( G(\theta)=((\partial h_i/\partial \theta_j )) \) and \(\lambda\) is a \(t\)-vector of Lagrangian Multipliers, so that \( [S (\hat{\theta}) ]^\prime = -\lambda^\prime G(\hat{\theta})\ .\) Substituting in (3), we have \[\tag{4} RSC =\lambda^\prime[ A(\hat{\theta} )]\lambda \]
where \[ A(\theta) = G (\theta) [I (\theta)]^{-1}[ G (\theta)]^\prime \]
Silvey (1959) expressed RSC in the form (4) and called it the Lagrangian Multiplier (LM) test. Neyman (1979) considered the special case of a composite hypothesis \[\tag{5} H : \theta_1 = \theta_{10},\theta_2, \ldots, \theta_r. \]
where \(\theta_{10}\) is given and the rest are arbitrary.
The RSC for (5) is known as Neyman's \(C(\alpha)\) test in statistical literature. Hall and Mathiason (1990) considered a more general composite hypothesis of the form. \[\tag{6} H : \theta_1 = \theta_{10},\ldots, \theta_q = \theta_{qo}, \ldots, \theta_{q+1}, \ldots, \theta_r. \]
where \(\theta_{10},\ldots, \theta_{qo} \) are all given and the rest are arbitrary.
The RSC for(6) is termed as Neyman – Rao test by them.
In the early years of my appointment at the Indian Statistical Institute, I had the opportunity of interacting with the staff and research scholars and discussing with them new problems in statistics arising out of consultation work. One of the scholars, S.J. Poti, by name, asked me about testing a simple hypothesis \( H : \theta = \theta_0 \) concerning a single parameter \(\theta\) when there is some prior information about the alternative such as \(\theta > \theta_0\ .\) I suggested a procedure by which local power on the right side of \(\theta_0\) is maximized leading to a test of the form \(P^\prime(\theta)/ P (\theta) > \lambda \) where \(P^\prime/ P \) is Fisher's score. The result was published in Rao and Poti (1946). They also proposed a general test of the form \((P^\prime/ P)^2 > \lambda \) which is likely to have good local power on either side of \(\theta_0\ .\) Two years later, I was working on a problem at Cambridge University, UK, which involved testing of simple and composite hypotheses concerning multiple parameters when there is information that alternatives are close to those specified by the null hypothesis. This led to combining the individual tests criteria based on the Fisher's scores \(s_1(\theta), \ldots, s_r(\theta) \) into a single criterion. Following methods used in multivariate analysis, I arrived at statistics of the form (1) and (2), which were approved by R.A. Fisher, my thesis advisor when I was working at Cambridge University during 1946-48. The paper (Rao,1948), containing the general discussion of score tests is published in the proceedings of the Cambridge Philosophical Society.
A comprehensive account of the applications of RS tests in econometrics is given in Godfrey (1988). Some applications to statistical inference are given in Bera and Jarque (1981), Breusch and Pagan (1979), Breush (1978), Godfrey (1978 a,b), Byron (1968), Bera and Ullah (1991) and in a series of papers in Vol. 97, pp 1-200, 2000 of J. Statistical Planning and inference. Comparison with likelihood ratio and Wald tests in terms of power and other properties are summarized in Rao(2005), which also gives references to some key papers and recent developments on RS tests, suggesting modifications in particular applications.
Bera, A.K.and Jarque, C.M. (1981), Working papers in Economics and Econometrics 40, Australian National University.
Bera, A.K. and Ullah, A (1991) J.Quantitative Economics 7, 189-220.
Bera, A.K. and Bilias, Y (2001), J Statistical Planning and Inference 97 9-44,
Bruesch, T.S. (1978), Australian Economic papers 17, 334-355.
Bruesch, T.S. and Pagan, A.R. (1979), Econometrics 47, 1287-1294.
Byron, R.P. (1968) Australian Economic Papers 7, 227-248.
Godfrey, L.G. (1978 a), Econometrika 46, 227-236.
Godfrey, L.G. (1978 b), Econometrika 46, 1303-1310.
Godfrey, L.G. (1988), Misspecification tests in Econometrics, Cambridge University Press.
Hall, H.J and Mathiason, D.J. (1990), Int. Statistical Review 58, 77-99.
Neyman, J (1979), Sankhya A 41, 1-21.
Rao, C.R. (1948), Proc. Camb.Philos. Soc. 44,50-57.
Rao,C.R. (2005), In Advances in Ranking and Selection, Multiple Comparisons and Reliability, Birkhauser,3-20.
Calyampudi Radhakrishna Rao (2008) Cramér-Rao bound. Scholarpedia, 3(8):6533.
Calyampudi Radhakrishna Rao (2008) Rao-Blackwell theorem. Scholarpedia, 3(8):7039.
Calyampudi Radhakrishna Rao (2009) Second order efficiency. Scholarpedia, 4(3):7084.
Bing Li (2001), J.Statistical Planning and Inference 97, 57-66.
Chandra T.K. and Joshi, S.N. (1983), Sankhya A 45, 226-246.
Ghosh J.K. and Mukherjee R. (2001), J. Statistical Planning and Inference 97, 45-55.
Taniguchi, M. (2001), J Statistical Planning and Inference 97, 191-200.
Calyampudi R. Rao's web page
The C.R. Rao Advanced Institute of Mathematics, Statistics and Computer Science
Chronology of Probabilists and Statisticians http://www.math.utep.edu/Faculty/mleung/probabilityandstatistics/chronology.htm
Figures from the history of Probabilists and Statisticians http://www.economics.soton.ac.uk/staff/aldrich/figures.htm
Cramér-Rao bound, Rao-Blackwell theorem, Fisher-Rao Metric, Second Order Efficiency.
Reviewed by: Dr. Anil Bera, University of Illinois at Urbana Champaign, IL
Retrieved from "http://www.scholarpedia.org/w/index.php?title=Rao_score_test&oldid=121946"
Eponymous
"Rao score test" by Calyampudi Radhakrishna Rao is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Permissions beyond the scope of this license are described in the Terms of Use


With the season of Thanksgiving being here, I wanted to make sure I shared how thankful I am for the blessing of generations of grandparents I had the honor to meet. I'm 34 years old and have physically met my Great Great Grandmother, both Great Grandmothers, one Great Grandfather, both Grandmothers, and both Grandfathers. Most of my friends don't even know their grandparents so I don't take them for granted. I'm the oldest of 9 on my mother's side and second oldest of 9 on my father's side. My sister and younger cousins were too young to share the memories I have of some of my grands. Though I was young to, the pictures I have display moments I hope to never forget.
The picture below was taken at my parents wedding. My mom's parents are on the far left and my dad's parents on the far right with the greats in the middle. The only one missing from this photo is my great grandfather who I know was there but my parents are unaware of the reason he didn't make the shot. What a treasure to have captured this moment in time.
Here is a picture of me and my Great Grandma Carrie. I don't have too many memories of her because I was very young when she was living, but I do have a few pictures with her.
These are my Grandma Shirley's parents. There names were Grandma Marie and Grand Daddy Shepherd. The woman above in the picture with me is my Grandma Marie's mother. I have plenty of memories with these two. You will see me in a family picture below sitting on my mother's lap while surrounded by my granny's. I remember visiting them at their home in DC . Whether it was for a family event or just to stop by and see how everyone was doing. Grandma would always offer me something to eat as granny's often do. Not that my parents didn't feed me or offer me food, but I think it's in the make up of a Grandmother….Lol! I do recall her being able to talk your ear off if you let her. I just never really understood what she was talking about. She always use to give me these big hugs and pat you on the back. At least she thought it was a pat. I thought she left a hole when she was done, but it was all out of love of course.
Grandma Cherry! This was my grandfathers mom on my mother's side. She lived in Virginia all my life. While I don't have many memories of her, I remember how much my grandfather looked like her. The way she smelled and the way she laughed and talked. I remember seeing her at the family reunions she was able to attend. I wish I had the opportunity to spend more time with her to build more memories, but I'm thankful for the moments I was able to share.
These are my mom's parents. My Grandma Shirley and Poppi is what I called them. The below picture is one of my favorites of them. I love a good black and white! What a stunning pic of them on their wedding day! They kept me during my younger years. The memories I have with them are uncountable, but just to name a few: My grandmother making breakfast in the mornings. Me flying down the hill in the back yard on paper bags with my cousins and my sister while also jumping in the piles of leaves we raked together. My Grandparents cat (Tabi) whom I apparently terrorized during my younger years. Again, my grandmother would ask me if I was hungry then make me something to eat no matter my response. My Grandfather was so comical to me. He was always very cool, calm, and collective. I remember him sitting in his chair in the family room watching a tennis match or reading the news paper. He made sure there was a fire in the fire-place during the colder months and would let me help. I remember him letting me help him water the grass. The root beer floats he use to make me were so tasty. All the card games played on their dining room table. The large natural Christmas tree in the front yard my grandfather use to decorate every year. One of my fondest memories of being in their home was the living room being covered in wrapping paper after all 9 grand kids unwrapped their Christmas gifts. Lastly, but surely not least, the holidays we spent together as a family in their home.
In this picture is my grandparents, my parents and my mother's brother and two sisters.
Grandma Sarah and Pompsi! These are my dad's parents. My Grandma Sarah is my last living grandparent. I remember their home in DC where we would often go to visit them. I will never forget the oatmeal cream pies Granny use to keep in the pantry for us to eat. I would sneak to get more cookies every time, but she doesn't need to know that. I remember the time me and my cousin stayed over and made brownies with my granny. We licked the bowl of brownie mix clean and ended up getting sick that night. They kept my sister when she was young. She thought Pompsi was the greatest thing in life. He spoiled her rotten! He was hilarious! He would fall asleep in mid conversation. When we asked if he was listening, he would always say he was just resting his eyes but that he could still hear us. We were pretty sure he was sleeping. I remember the holidays spent with my dad's side of the family in their home when Grandma Sarah would fill the table with yummy goodness! During my middle school years we lived in the same apartment complex as them and me and my sister would go visit every day if they weren't already watching us while our parents were gone. Whenever it would storm, Granny would make us go in the closet and be quiet…no metal forks and no TV…we might get struck by lightning! I remember that flannel robe my grandfather would always wear ALL year round. No clue how he managed that one. Lastly, but by far not least, I recall all the times my grandmother should have told our parents on us but never did. She said as long as we weren't in any danger she would never tell. They later moved in with us which is the home my family and Grandma Sarah live in today.
I like to call them Sarah & Louise! My two granny's…I love that I was able to get so many pictures of them together. I made sure of it every time they got together. Aren't they just the cutest?
This entry was posted in Family and tagged Family, Generations, Grandparents, Memories. Bookmark the permalink.
It's settled Brittney looks just like your aunt!! Wow!


text:
runit_service "chef-solr" do
  action :disable
end

redpajama_set_name: RedPajamaGithub


text:
Development of Nuclear Waste and Sustainability in Russia
Posted on December 3, 2013 by ZiegZag4
From the radiation of its food to the radiation of its rivers, Russia has built itself into a competitive nuclear power through a tumultuous history of trial and error.[1] Much of the initial funding for Soviet nuclear energy came in an effort to match the United States' atomic project. But, after developing "the bomb", nuclear resources in the USSR were applied to a number of areas. These often gave poor results. From such failures, modern Russia has striven to provide a nuclear industry that is safe, clean, and sustainable. In fact, the head of Rosatom's used fuel management has set a goal of 100% efficiency in the company's fuel cycle; where all spent fuel is reprocessed into the system — no waste.[4] To understand these, at first, outlandish expectations, we should consider the damages and adaptations that the industry has incurred since its inception in the 1940s.
In the earliest days of the Soviet nuclear industry, one of the most practiced efforts was the irradiation of food. This gave food stuffs a much longer shelf life and they exhibited fewer incidents of contamination due to bacteria or spoiling. But, this also exposed many citizens to harmful levels of radiation after sustained consumption.
In an effort to appease the growing "green movements" in the Soviet Union, Stalin once pursued an aggressive hydro-electric policy. To map the currents in possible rivers, the Soviets had opted to use radioactive isotopes instead of foreign nutrients. These isotopes gave far more accurate readings than the nutrients which would dissolve more quickly in the water. Unfortunately, these tests also irradiated the sites on which they were conducted.
In an effort to store industrial byproducts in a safe manner, the Soviet Union began to put barrels of waste under the Arctic ice. They thought that the metal barrels would isolate the waste from the environment while still allowing the nuclear waste to cool down. Now, Russia has begun to take responsibility for the incident and is trying to excavate them from beneath the ice. The trouble here is that the area is inaccessible during from late fall to spring as the ice begins to freeze too thick for Russia's icebreakers.
Many of the efforts during the Soviet era to remedy environmental damage came as a result of grass root environmental movements. Following Gorbachev's "glas'nost", many citizens began speaking out.[2] Other factors, such as better education and a growing middle-class, have also been credited with influencing environmental activism in the late Soviet period.[3] What is interesting is how the green movements began to recede after the collapse of the Soviet Union. Henry, in Red to Green, implies this is the product of government assimilation of environmental practices. In the 1990s, the Russian Green Party is established and large funds are diverted to repair environmental damages from the Soviet era. Russia has also taken responsibility for much of the Bloc's environmental damages. Perhaps this accountability has made the green Soviet activists obsolete. In modern Russia there are still environmental hazards; the significant decline in incidents is still watched closely by the green organizations. But, the grass root aspect of Soviet environmentalism has lessened.
Reckless practices by the nuclear industry created a strong green movement in the USSR which survives, in some form, in Russia today. Many of these citizen whistle-blowers were responsible for stopping projects, such as the irradiation of food, which tested nuclear potential on ignorant Soviet citizens. The Chernobyl incident, though another blunder by the Soviet Union, also served to shape the young nuclear industry into a safer and better regulated industry than many other nations'. From the 1950s into the 1980s the USSR had been storing waste in containment pools on-site and burying large amounts in underground containment centers. Both of these practices were accepted by many Western agencies as well. But, after the international community began investigating Chernobyl, citizens began reporting violations of Soviet nuclear law in the areas around the containment sites. With international pressure, the USSR reformed their waste storage practices into secure and modern facilities based in Siberia.[4] These projects reflect much of the work regarding the Yucca Mountains in the United States.
Here is a video detailing Russia's modern nuclear industry.
The Adobe Flash Player is required for video playback.
Get the latest Flash Player or Watch this video on YouTube.
Given these policy revisions, much of the pre-Chernobyl nuclear damage was left unattended until the fall of the Soviet Union. As one of its efforts to become a respectable world power, Russia began funding massive environmental clean-up projects. These are costing the country billions of rubles and figures in the nuclear industry are now stressing the economic efficiency of leak prevention and safety. In recent agreements between nuclear countries, Russia has been designated a stable recycler of nuclear waste.[5] This has given Russia the recognition of a safe and efficient destination; a safer and more efficient option than other nuclear powers, such as the United States.
Currently, Russian methods of handling nuclear waste are very similar to other nuclear countries in the West. The policies include water-submersion or dry-holding pools on site of many reactors. Without the ability to process the mass quantities of waste, spent nuclear fuel is building up in many Western countries. Russia's nuclear industry is currently able to process 2,500 tonnes of waste each year by reprocessing spent nuclear waste so it can be utilized in the generation of more energy. The current series of reactors are designed to consume primarily 'fresh' uranium.[6] But, there are already a number of BN-800 and VVER-1200 series reactors, designed to consume primarily re-purposed uranium, which are nearing the end of their construction. These will make the possibility of a Russian founded Global Nuclear Energy network a viable option for energy sustainability in Eurasia.
The opening to this episode of Spotlight gives a short biography on Rosatom in Russia today.
An agreement signed in 2000 between the U.S. Department of Energy and Russia's Federal Atomic Energy Agency, Rosatom, laid the foundation for disposal of spent U.S. waste and weaponized uranium in Russia in exchange for funds to enhance the country's nuclear industry.[7] This increased responsibility for disposal of nuclear waste has galvanized the industry to produce such models as the BN-800 to meet growing global demand for Russia's reprocessing ability. Rosatom has, also, laid the goal of having a 100 percent sustainable nuclear industry by 2020.[8] This program would increase domestic demand, too. As it stands, Russia is reprocessing much of the United States' nuclear waste and storing it for later use in the BN-800 and VVER-1200 reactors in addition to
purchasing and developing its own 'fresh' uranium. Effectively, Russia appears to be stockpiling used uranium (potential energy) which the U.S. is paying for the country to import. This is a very effective economic policy for Russia, but this system is dependent on developing the consumption of reprocessed nuclear waste instead of increasing output of energy. Many of these new reactor series had their designs and construction paid for by the 2000 Agreement. Because the emphasis was on the consumption of United States' waste and not expanding Russian energy supply, this dictated the evolution of the Russian nuclear energy industry. Also telling is that the United States is the country exporting its waste to Russia. The United States has long been a leading nuclear power when considering total energy output and uranium consumption. This would make the United States one of the largest waste producers then, as well. That the United States has to purchase the services of another nuclear power is interesting, and Russia is using this to its advantage.
A report by the Center for Strategic and International Studies prescribes a "Decade of Stabilization" in post-Soviet Russia ending in a loosely planed international nuclear energy network.[9] This plan prescribes foreign powers' purchase of nuclear plant in post-Soviet states; most being maintained by France, United States, and Germany. The outlines for this transition have strong imperialist leanings by giving such domestic influence to foreign powers, but the idea is something that Rosatom seems keen on.[10] Granted in Rosatom's plan, Already Russia is one of the largest energy providers in Eastern Europe, holding a large supply of fossil fuels and other raw materials. If Russia establishes a global nuclear energy market, its energy exports will most likely increase. Russia has begun reaching out to other nuclear powers, offering itself as a viable disposer of nuclear waste. If Russia successfully transitions to a nuclear industry which largely consumes the reprocessed nuclear wastes of other countries, then Russia will establish itself as both an energy producer and as a nuclear waste disposer.
By establishing a global nuclear network, Russia will have a larger market for its nuclear energy and its waste disposal. In a global market in which Russia is the primary disposer of nuclear waste, Russia would control the costs of its competition by influencing overhead costs of waste disposal. At the same time, Russia would be able to continue producing energy for the world market primarily from the waste that it is being paid to import by other countries.
Aside from Russian economic gains, all partners in a global nuclear energy network would benefit from Russia's specialization in nuclear waste consumption. Russia is developing reactors focused on waste consumption and not energy production, while other countries are trying to maximize energy output in their nuclear industries. By joining a global network each country will be able to utilize the specializations of the other countries, improving the efficiency (and, ultimately, the sustainability) of each independent nuclear agency.
While Russia's nuclear agency was founded on the unattainable goals set in the Soviet era, the mistakes made during its infancy has helped mature this field to one of the most developed in the world. While there is still evidence of its grandiose mentality, as evidenced by its floating fleet of nuclear reactors, nuclear energy in Russia is kept in reasonable check by better government regulation and an attentive population. Now, even the government's Rosatom is helping the population stay informed on the nuclear conditions in Russia. Recently, they launched a map on their site fed by real-time radiation readings from around each nuclear plant. This site is public and open to continuous access. After the events of Chernobyl and other nuclear incidents like it, the nuclear industry has had to work to alleviate global and domestic concerns. If we consider how the international community has pursued nuclear partnerships with Russia, it seems safe to say that the industry has succeeded. Now, when we consider Russia's nuclear industry, it may seem that "100%" efficiency might not be as far a reach as we thought.
[1] Paul R. Josephson, Red Atom: Russia's Nuclear Program from Stalin to Today, 146-166.
[2] Laura A. Henry, Red to Green: Environmental Activism in Post-Soviet Russia, 39-40.
[3] Karl Qualls, "Chernobyl and Ecocide," Class lecture, Russia – Quest for the Modern from Dickinson College, Carlisle, PA, November 25 2013.
[4] World Nuclear Association, "Russia's Nuclear Fuel Cycle."
[5] Guy Lunsford, "Status of Russian Plutonium Disposition," Proceedings of the Institute of Nuclear Matierials Management.
[6] Here I use 'fresh' to mean this is its first cycle of consumption, not yet reprocessed uranium.
[8] World Nuclear Association. Nuclear Power in Russia. Last modified September 2013.
[9] Robert Ebel, ed., Nuclear Energy Safety Challenges in the Former Soviet Union: A Consensus Report of the CSIS Congressional Study Group on Nuclear Energy Safety Challenges in the Former Soviet Union.
[10] World Nuclear Association. Russia's Nuclear Fuel Cycle. Last modified August 23, 2013.
Full bibliographyhere.
This entry was posted in HIST254-Archive and tagged classsourcing, Eurasia, h254, industry, Nuclear, Putin, Radiation, Red Atom, Rosatom, Russia, Soviet, soviet union, Stalin, Sustainability, Waste by ZiegZag4. Bookmark the permalink.
4 thoughts on "Development of Nuclear Waste and Sustainability in Russia"
smythk on December 8, 2013 at 2:44 pm said:
Do you think any countries have any reticence towards supplying their nuclear waste to Russia, given the short and long term effects of Chernobyl? Has the development of Russia's nuclear waste industry come so far that it could be considered better than the United State's disposal of nuclear waste? It's very interesting to see the change in Russian nuclear policies post-Chernobyl and their drastic improvement in the disposal of nuclear waste.
ZiegZag4 on December 12, 2013 at 1:59 am said:
My project tries to allude to what you were getting at in your response; that Russia's program is superior to the United States' in some ways. I would argue that Russia has come so far in the time since Chernobyl. It was such a dramatic event that the global community responded to the USSR's nuclear regulation. Given how much the industry has had to adapt and yet be careful of the wary public watching, I would say that it should not be surprising that Russia has emerged as a top nuclear power. I suggest you look at my third diagram where it shows a relation between public trust/education with regards to (1) legislation and (2) existing technology and safety.
ZiegZag4 on December 15, 2013 at 12:53 am said:
Here is a recent article from NPR on the nuclear disarmament agreement which is supplying Russia with much of its weaponized uranium to be reprocessed, but from a U.S. perspective.
http://goo.gl/Bq4oVk
CrisisMaven on June 17, 2014 at 3:31 pm said:
Why would the "irradiation of food" have exposed the populace to radioactivity? To my knowledge, gamma irradiation of normal foodstuffs does not induce nuclear chemical reactions that "enrich" the food with radioactive nuclides by transforming normal isotopes like the irradiation with e.g. alpha particles or neutrons would. Rather the drawbacks are often that the food degenerates just as with heat treatment or starts tasting "funny". However, that Rosatom will try and adopt a fully closed fuel cycle and thus "no waste" policy should be treated with suspicion. So far any such attempts at e.g. transmutation have been as elusive as the use of fusion – all these projects are to mature in the next fifty years. When these fifty years are reached then it's another fifty.


further news and update will be posted on the thesilent.com from now on.
PAYPAL is not supported anymore.
Disabling char merger maybe cause of all lol DB crash.
Races overhaul added special ability stat.
Other skillset or race specific abilities in progress.
This is a messed up php 4. something code it need to be updated to 5.6.
Back thenmy skills aren't as good and clean as today I'll try to find some time to redo the whole thing.
from now on a new server will be created every year.
When the game was in beta and perl back then.
Mollie Payment option added calling 400 credits for 3 euro, I think it's for Netherlands and Belgium users only?
The amount of credits can be changed in the future just a testing fase now.
Devlab Fusion of xp, life, str, dex, agi, intel, conc, cont, weapon, spell, heal, helm, shield, amulet, ring, armor, belt, pants, hand and feet made possible.
Now it's possible to fuse any stats or equipment with other char.
For testing purpose it's released on Devlab first at a price of 5 credits the final price to be determined.
Member info now shows natural stats.
It should be working but not tested yet please post your outcome in forums. Use at your own risk!!!
Added global login on lordsoflords.com main site for all servers, not all worlds are working yet.
Added Global Player Seeker (GPS), easier track down cheaters or finding your friend.
Sorry for the inconvinience and delay.
I kinda messed up the Mysql migration to the new server everything should be working again.
If their are still errors email me.
The new server with 4 times more bandthwidth at 10TB bandwidth will have the same hardware specs but for the half the price as this one.
This server with php4, mysql4 and apache 1 wil be upgraded.
New server will have php5, mysql 5 and apache 2.
There will be some workaround on that server, I'll try to get a version of lordsoflords running on that IP to test if everything will work.
Giving myself a month to fit all scripts in php 5.
Bugs, suggestions, seen a cool game feature elsewhere that we want to have, yeah say whatever but say usefull thing or get deleted.
Wil be experimenting with new version of LAMP server for a few weeks.
I haven't done anything lately but making sushi's at www.sushidetoren.com.
Since I have started this fast food & sushi bar thing, I don't had much time left for my other hobbies including golf, computers, games, programming, etc..
Worlds Meadow, Meadow2, Eidolon, Xedon and pdarpg.
These games can now be playing on your smartphone or other browser enabled PDA at www.pdarpg.com.
PDARPG world is launched with this new pdarpg.com domain and only playable there.
Timer change and a floating reply box added to the forums.
Changed the site layout of lordsoflords.com.
Watch out for fake Admin silents in the game!
Fake one's are Silent my name is SilenT, the T is the difference.
Most of my in game accounts are deleted due to inactivity.
The only way to communicate to me is contacting me at lol_silent[at]hotmail.com.
Allot non collected funds here, I got an logged IP only.
Please send me your server and username to let me manual give you the credits that belong to you!


Did you hear about MSNBC's white supremacist commentator?
For years, Pat Buchanan has passed off white supremacist ideology as legitimate mainstream political commentary. And MSNBC continues to pay him and give him a platform on national TV to do it.
Buchanan has the right to express his views, but he's not entitled to a platform that lets him broadcast bigotry and hate to millions. If MSNBC wants to be seen as a trusted, mainstream source of news and commentary, it needs to fire Buchanan now.
If Buchanan didn't have a powerful media platform, he'd be just another person with outdated, extremist ideas. But it's irresponsible and dangerous for MSNBC to promote his hateful views to an audience of millions.
Yeah, I got that directly from Color of Change. Pat is a wierdo. Didn't know he was regular contributor on MSNBC. He;s more a Fox kind of guy. I have mixed feelings about being a censor of what MSNBC can or cannot air. I wish Fox would have Rachel Maddow or some of the other MSNBC regulars from time to time. Convince me I should sign the petition.
I signed the petition, mostly because as an occasional viewer of MSNBC I figured I have the right to tell them what kind of stuff is too offensive to air. I wouldn't add Fox News to my cable package for any reason, but I did e-petition advertisers on Glenn Beck's show to tell them how people felt about financial supportors of his free-association chalkboard show.
I guess there is a difference between consumers trying to influence programming on a network (with the rather weak instrument of internet petitions) and a lobbying campaign of a numerous or rich political/religious/economic group to do the same. So I wouldn't call it being a censor of what MSNBC can or cannot air, as it's not talking about the power of censorship, but I think MSNBC thinks of Pat Buchanan in that all-too-common way corporate news does now of a necessary "balance" to Rachel Maddow; in the same way that when a guest on the dangers of global warning, or the drawbacks of capital punishment is interviewed, somewhere an authouritative-sounding proponent of the opposite opinion must be found, whether they are employed by British Petroleum, veterinary pentobarbital manufacturers, or not. A little push from viewers and other consumers can only benefit a cable TV news station.
Wow, what sensitivity you folks have. Pat is not racist. He is an intellectual who values the contributions of Western Civilization. Don't be so offended so easily. You know what, Rap music offends me. Should we take it off the airways?