There will be ''tears in the bubbles'' at Dawn Salon on Friday.
Owner Jenny Hyslop (70) is retiring this week, ending a hairdressing career in Dunedin that has spanned 55 years.
For the past 25 years, it has been something of a double-act with Joy Rowe - her first apprentice - working part-time in the St Kilda salon.
Mrs Rowe (62) was also retiring, saying it ''wouldn't feel right'' working with anyone else.
Inside the modest exterior of the salon, on Prince Albert Rd, lies a workplace where hilarity - and sometimes wine - has flowed freely.
A large part of its market was catering for an older clientele and Mrs Hyslop acknowledged work was not as busy these days as clients had their final cuts.
The pair often felt like they were part of the family of their long-standing clients. When they attended funerals of special customers, they could usually identify family members - despite having never met them - because they had heard so much about them.
Mrs Hyslop, who grew up in Dunedin, followed in her mother's hairdressing footsteps and served her apprenticeship at Mark Everett Salon in the 1960s.
She had a break for 16 years while raising a family, just cutting the neighbours' hair and her own children's.
Then, 27 years ago, Mrs Hyslop bought Dawn Salon, an existing business which had long been known by that name.
Asked if she had ever been tempted to switch to a more modern name, she said some of her clients told her initially not to change it as it had always been called that.
The salon is finally undergoing a name change - it will be known as Studio 24 when new owner Kim Thompson takes over on April 1.
Mrs Hyslop said the business had become very much ''a community thing'' in latter times, particularly as it had been quieter. Often, people called in for coffee, rather than a cut.
Their location, next to a laundromat, also provided plenty of entertainment. People would sometimes take their clothes off on the street and stand in their underwear.
Mrs Hyslop was looking forward to retirement, saying she was ''ready for sitting down and not doing so much''.
Troubled by some health issues, Mrs Rowe quipped that her surgeons would be ''delighted'' that she was retiring.
The pair acknowledged it would also be ''weird'' to hang up their scissors at the end of what was shaping up to be a very busy week.
''There'll be tears in the bubbly,'' Mrs Hyslop said.


text:
What Is Window Film?
Window film is a polyester film generally made of PET, Polyethylene Terephthalate, the same polymer used to manufacture water bottles. For example most films are applied to the interior surface of a glass window in a home, commercial building or car. They have a scratch resistant coating on the outer surface to protect the film.
There are many types of window films. Some are clear and feature multiple layers of PET to offer protection from shattering glass; others are tinted with metals, dyes or pigments to reduce the visible light transmitted through the glass and block heat coming through from the sun. There are even decorative window films that can replicate the look of frosted glass or etched patterns.
What are the benefits of window film?
Window films have many benefits depending on your choice of film.
For example: Safety, Security and Intruder window films can improve home security by both strengthening the integrity of the glass against breakage and helping hold dangerous broken pieces of the shattered glass in place making it much safer.
Tinted window films, also called solar control films, can do the following:
Significantly reduce solar heat gain and temperature inside your home
Reduce air conditioning costs
Decrease your home's environmental emissions
Increase occupant comfort
Reduce glare to visibility inside, especially for computer and TV screens
Provide daytime privacy
Block up to 99% of UV radiation
Offer significant fade protection for furniture, carpets, woodwork and other interior furnishings
How is window film installed?
The installation process starts with thoroughly cleaning your windows to remove even the smallest pieces of dirt. A piece of film is cut to approximately the size of your window, its inner release liner is removed and an application solution is sprayed on the film's adhesive to activate it. The application solution is also sprayed on the window .Next the film is installed on the glass and all the application solution is squeegeed out from between the glass and the film. The installer will do some final edge trimming to ensure the film fits perfectly.
How long will the film last?
This depends on the film type, glass type, window construction, orientation and geographical location of the building. All Manchester Window Films are covered by a warranty for a specified time. Most installations receive a 10-year warranty. There are some speciality films that have different terms, for example, exterior films carry a warranty of 4-10 years on vertical glass and 2-5 years on sloped glass. Decorative films have a 7- year coverage. The warranty coverage is based on extensive internal testing and our years of experience in the field. It is common that we see films last well beyond their warranty period, sometimes as long as 15-20 years.
View This Service

redpajama_set_name: RedPajamaCommonCrawl


My current project, the quilt "Jane Austen's Bonnet" by Brenda Ryan, is coming along nicely!
I began work on some of the pretty pictures this time, and I have included two of them here.
Firstly, a pretty Regency lady!
The back of a pretty Regency lady!
The stitches I have used are: split stitch, backstitch, colonial knots, running stitch, stem stitch, blanket stitch, and satin stitch. There is also a little bit of ribbon embroidery in the hair.
The stitches I have used here are: back stitch, running stitch, stem stitch, colonial knots, and satin stitch. This one is also beaded and has two bows done with ribbon embroidery.
With all of these diamonds, I am stitching a quick running stitch around the outside of the piece to mark the stitching line, which I hope will be useful when I put the quilt together.
Stay tuned for Part Four of this series.


A meal at Sticks'n'Sushi is not the most direct route to sainthood.
We have both the angelic and the wicked on our menu.
A menu without tuna would probably be best — but also a mockery of the sushi tradition. Instead, we have reduced the tuna on our menus, so it can be your choice to opt in or opt out.
Our vegetarian menus can look any nutrition expert straight in the eye.
On the other hand, don't eat our ebi bites if you are on a diet.
And some of our sauces were discovered in the river of sin.
We translate that into taking care of ourselves whilst taking care to enjoy while there's time. Below we have made a list that gives an overview of what is what.
Organic. Free range. And, at the time of this writing, we're in negotiations to have our own pig farm where animal welfare will be far better than the law requires.
One word. One supplier. Aarstiderne. That should tell you all you need to know about the quality, the level we have and that the origins are organic. And if not, please ask the waiter, who will be happy to answer your questions.
The food of nuns and monks. No fats to be had. Nothing to provoke a dietitian. Unless you finish it off with a slice of Marcel cake for dessert.
It goes without saying that you can't sell sushi without knowing where the net was cast and about the welfare of the stock. What kind of fish and where did it come from? That knowledge is available to you in any of our restaurants. We supply ocean-sized explanations in every sense of the word. Take, for example, that of our mackerel, which is pole caught by Icelandic fishermen and belongs to a select crowd of only 10% of the total catch. And there's more where they came from.
We use plastic — but we don't like it. Therefore, a course has been set: a gradual phase-out will end with total cessation by 2022. Meanwhile, we'll use what's known as PET, which isn't quite an optimal solution — but it's far from the worst.
There's less meat on the menu. And one day cow will be replaced entirely by veal, lamb and free-range pork from our own endeavours. Until then, meat goes on the list of possible improvements. But we're serving this indulgence with our eyes open and head up.
Ideally, it shouldn't appear on any menu anywhere in the world, at least not until the stock improves. But eliminating tuna from a sushi menu would be committing Harikiri given our roots. We've chosen a consistent compromise: On our side, we've removed tuna from several of our items. But we've made it a possible option from yours.
Beware. They look like little cherubs and taste divine. But the truth is that they're more of a snack than a meal.


being a musician can be stressful.
Between the career uncertainty, performance anxiety, and the standards we put on ourselves, being a musician can be a uniquely stressful experience. This is why musicians suffer from higher than normal rates of anxiety and depression. Music Made Well was started to help musicians of all levels develop strategies to take better care of their mental health, get connected to resources, and start a conversation that removes the stigma around mental health issues in the musician community.


text:
\section{Introduction}

Microscopic and mesoscopic organisms such as bacteria operate at length scales where
swimming motion takes place at very low Reynolds number \cite{N2}. In his `scallop' theorem of
microscopic swimming Purcell argued that swimming strategies can only be successful in
this regime if they involve a cyclic and non time reversible motion
\cite{P77,SW89}.
The driving of
helically shaped bacterial flagella by a reversible rotary engine and the beating motion
of elastic rod-like flagella utilized by eukaryotic cells are examples
of biological mechanisms which
break time reversible invariance, thus allowing microscopic organisms to move in a
controlled fashion. In an exciting recent development Dreyfus {\em et al.} \cite{DB05a}
have demonstrated for the first time the controlled swimming motion of a fabricated,
micrometer size device.

Several authors have described models of swimmers at low Reynolds number. Simple models
which comprise linked spheres or connected rods that move by changing the distances or directions
between the components are considered in \cite{P77,BK03,NG04,AK05,DB05b}.
For one dimensional motion analytic results for the swimming velocity and efficiency can
be obtained.
Felderhof \cite{F06} used the Oseen tensor formalism to model microscopic swimmers using a
bead spring model. Gauger and Stark \cite{GS06} used a similar method to model the experimental
elastic filament of Dreyfus {\em et al.} \cite{DB05a}. Both of these approaches are distinct from the
one we use, in that the actuation of the beads is described in terms of forces,
whereas we define swimming in terms of a predefined shape change.
Propulsion by a non time reversible pattern of surface distortions is addressed in
 \cite{SS96,Y06a,PB06}. Another possible swimming mechanism, mediated by an asymmetric
distribution of reaction products, is proposed in \cite{GL05}.

Increasingly, quantitative experiments on bacterial dynamics are appearing in the
literature. Transient collective motion has been observed in collections of swimming
cells \cite{DC04}. Bacteria near solid boundaries have been shown to swim in
circles \cite{LD06} and those near an obstacle to reverse their swimming
direction \cite{CD06}. Experiments have been performed to determine the dependence of the
chemotactic response of \emph{Dictyostelium discoideum} cells swimming
in a concentration
gradient \cite{B06}.

Although simple, analytical models can provide considerable help in understanding these
results there are many new features inherent or accessible in real biological systems
that remain to be explored. These include more complicated swimming mechanisms, interactions between
densely packed swimmers and the effect of boundaries and obstacles. There will
increasingly be a need to develop numerical methods to probe the behavior of more
complicated structures and situations where analytic approaches become intractable.

In numerical approaches published so far Hernandez-Ortiz {\em et al.} have considered
the swimming motion of a collection of force dipoles \cite{HS05}. They
observe the large scale coherent vortex motion that has been seen in
experiments.
Ramachandran {\em et al.} have described swimmers, modeled as force dipoles,
interacting with a fluid described by a lattice Boltzmann
algorithm \cite{RK06}.
Work on swimmers propelled by a flexible filament modeled
hydrodynamics through an anisotropic friction coefficient \cite{L03, LC03}.

Our first aim in this paper is to explore new ways in which simulation
methods can be applied to the motion of swimmers in a low Reynolds
number solvent. We model the hydrodynamic interactions by using
the Oseen tensor approximation \cite{Oseenref}, a lattice
Boltzmann algorithm \cite{S01,Y06} and multiparticle collision
dynamics \cite{MK99}. The approaches are validated by solving the
equations of motion for a linear three bead swimmer where an
analytic solution is available for comparison \cite{NG04}. We discuss
the relative merits and demerits of the three approaches.

Secondly, we extend the linear model to more general three bead microstructures. We use an
Oseen tensor approach to demonstrate that they can move in a controlled fashion in three
dimensions by changing both the length of and the angle between their arms and we discuss the
efficiencies of the various swimming modes. We also show that multibead linear
structures are highly efficient swimmers.

We then consider the swimming motion of driven elastic filaments. Our model, solved using
multiparticle collision dynamics, mirrors the behavior of the swimming device introduced
by Dreyfus {\em et al.} \cite{DB05a}. In the conclusion, we consider future directions in
which the modeling approaches might be useful in understanding the swimming of bacteria
and of fabricated microstructures.

\section{Numerical Approaches}
\label{numsec}

The swimmers we consider are composed of $N$ spheres,
of fixed radius $R$ and with
positions given by ${\bf r}_{i}$, where
$i = 1...N$. The spheres are linked
by rods that are sufficiently thin to neglect any
hydrodynamic effect. Internal forces and torques act to change
the lengths and/or angles between the rods, causing the swimmer
to change shape. These shape changes, when coupled to the fluid,
lead to directed motion. We now describe three different numerical
approaches used to simulate the fluid.

\subsection{Oseen tensor}

\label{OseenT}

The Oseen tensor allows us to consider the hydrodynamic interaction, in the
limit of zero Reynolds number, between spheres that are spaced far
apart ({\em i.e.} at distances significantly larger than their radii, $R$) \cite{Oseenref}.
A sphere pushed by a force will move, and so set up a flow
field. Any surrounding spheres will be advected
with the resulting local fluid velocity.
Furthermore, since the Reynolds number is very low,
the time taken to set up the flow fields is much smaller than
that needed for a given sphere to move a significant fraction of
$R$ \cite{N1}. Therefore, the hydrodynamic
interaction can be approximated as instantaneous.
Since the Stokes equation (the Navier-Stokes equation without
the inertial term, as is appropriate in the low Reynolds number limit)
is linear, the velocity fields produced by each of the spheres simply add up.
This allows us to write
\begin{equation}
{\bf v}_i = \sum_{j = 1}^N {\bf H}_{ij} {\bf F}_j
\label{oseen}
\end{equation}
where ${\bf v}_i$ is the velocity of sphere $i$ and ${\bf F}_j$ is the
force on sphere $j$. The Oseen tensor ${\bf H}_{ij}$ is \cite{Oseenref}
\begin{equation}
{\bf H}_{ij} =
\begin{cases}
\frac{{\bf I}}{6\pi\eta R},  &\text{if $i = j$}, \\
\frac{1}{8\pi\eta | r_{ij} |} \left( {\bf I} +
  \frac{{\bf r}_{ij} {\bf r}_{ij}}{ |
    r_{ij} |^2} \right) &\text{otherwise},
\end{cases}
\label{oseent}
\end{equation}
where $\eta$ is the fluid viscosity, ${\bf I}$ is the identity matrix,
and ${\bf r}_{ij} = {\bf r}_j - {\bf r}_i$
is the vector between spheres $i$ and $j$.
For a swimmer, the forces ${\bf F}_i$ are not external, but rather internal
forces mediated through the links that connect the spheres.
They are subject to the constraints
\begin{equation}
\sum_{i=1}^N {\bf F}_i = 0, \quad  \sum_{i=1}^{N} {\bf F}_i \times {\bf r}_i = 0
\label{constraint}
\end{equation}
which state that no external forces or torques act on the swimmer.

\begin{figure}
\begin{center}
\includegraphics[width=3in]{oseen4.eps}\\
\end{center}
\caption{
(a) The swimmer at time $t$.
(b) The swimmer {\it shape} defined at time $t+\delta t$. The lengths
of the two links connecting sphere $3$ have decreased.
(c) The shape at $t+\delta t$ is translated by a vector
$\Delta {\bf r}$
and rotated by an angle $\Delta \theta$ around its center of mass.
These operations preserve the link lengths, thus leaving the shape
unchanged. The parameters $\Delta {\bf r}$ and $\Delta \theta$ are
chosen to improve upon the accuracy of the constraints in equation
(\ref{constraint}). This procedure is performed iteratively until
the necessary accuracy is achieved.
}
\label{figoseen}
\end{figure}

The swimming motion is defined as a periodic {\it shape} change
and, from this information, the algorithm must determine the
trajectory of the swimmer through the fluid.
To illustrate how this works we begin by considering a
swimmer whose motion is confined to a two dimensional plane.
Figure \ref{figoseen} shows the procedure for the case $N = 3$.
At a given time $t$, the position of the spheres ${\bf r}_i$ are
known, as shown in figure \ref{figoseen}(a).
The new shape of the swimmer at the next time step
$t+\delta t$ is shown in figure \ref{figoseen}(b).
We have chosen, for illustrative purposes, a swimming step where
the lengths of the two links connecting sphere 3 have decreased.

The shape of the swimmer in figure \ref{figoseen}(b) is defined
through the three quantities $|r_{12}^\prime|$, $|r_{23}^\prime|$,
and $|r_{31}^\prime|$. However, this information does not determine
the absolute positions of the spheres.
To find these, it is necessary to enforce the
conservation conditions stated in equation (\ref{constraint}). This
is performed in the following iterative manner.

We take the first approximation for ${\bf r}_i(t+\delta t)$ to be
${\bf r}_i^\prime$. This does not, in general, obey
equation (\ref{constraint}), as will be apparent below. Our aim is to
move the spheres in such a way as to successively improve the
accuracy of equation (\ref{constraint}). To do this, we consider translating
the swimmer by a vector $\Delta {\bf r} = (\Delta x, \Delta y)^T$,
and rotating it about its center of mass by an angle $\Delta \theta$,
as illustrated in Figure \ref{figoseen}(c). Note that these operations
do not change the shape of the swimmer.
In doing this, we introduce new position coordinates
${\bf r}_i^{\prime \prime}$ defined by
\begin{eqnarray}
{\bf r}_i^{\prime \prime} = {\bf r}^\prime_{cm} + {\bf \Delta r} + {\bf R} \left( {\bf
r}^\prime_i - {\bf r}^\prime_{cm} \right)
\label{better}
\end{eqnarray}
where ${\bf R}$ is a clockwise rotation matrix around an angle
$\Delta \theta$ and
${\bf r}^\prime_{cm} = \sum_{i=1}^N {\bf r}_i^\prime/N$ is the center
of mass position of the swimmer.
The unknown displacement ${\bf \Delta r}$ and angle $\Delta \theta$
are chosen to improve upon the accuracy of the constraints in equation
(\ref{constraint}). To calculate them we note that
the velocity of sphere $i$ can be related to its displacement over
time $\delta t$ by
\begin{eqnarray}
{\bf v}_i &=& \frac{{\bf r}_i^{\prime \prime} -  {\bf r}_i}{\delta t} \nonumber\\
&\approx& \frac{{\bf r}_{i}^\prime -  {\bf r}_i + {\bf \Delta r} + \Delta \theta |{
r}_i^\prime - { r}_{cm}^\prime| \hat{\bf r}_i^\theta}{\delta t}. \label{v}
\end{eqnarray}
The unit vector $\hat{\bf r}_i^\theta$ lies in the direction a given point moves
under an infinitesimal rotation (which can be calculated by
rotating the vector ${\bf r}^\prime_i - {\bf r}^\prime_{cm}$ by
$90^o$ clockwise and normalizing it).

Substituting expression (\ref{v}) into equation (\ref{oseen}), and
numerically inverting the resulting matrix equation using Gaussian
elimination, we obtain an expression for the forces acting on
each sphere of the form
\begin{eqnarray}
{\bf F}_i = {\bf a}_i + {\bf b}_i \Delta x + {\bf c}_i \Delta y + {\bf d}_i \Delta \theta
\label{F}
\end{eqnarray}
where ${\bf a}_i$, ${\bf b}_i$, ${\bf c}_i$, and ${\bf d}_i$
are constant vectors.
Using this, the three constraints in equation (\ref{constraint})
can, after some rearranging, be written
\begin{eqnarray}
{\bf A}
\left(
\begin{array}{c}
\Delta x \\
\Delta y \\
\Delta \theta
\end{array}
\right)
=
\left(
\begin{array}{c}
e_1 \\
e_2 \\
e_3
\end{array}
\right),
\label{A}
\end{eqnarray}
where the matrix ${\bf A}$ and the column vector ${\bf e}$ are
constants. Finally, this matrix equation can be inverted to obtain
the values of $\Delta x$, $\Delta y$, and $\Delta \theta$ which are then
used in equation (\ref{better}) to obtain a better approximation,
${\bf r}^{\prime\prime}$, to the sphere positions at time
$t+\delta t$.
Repeating the procedure gives rapid
convergence to the correct solution. Typically a single iteration
improves the accuracy of equation (\ref{constraint}) by a factor
of $\sim 10$.

The approach is easily generalized to a swimmer moving in three
dimensions. In this case there are three
displacement parameters $\Delta x$, $\Delta y$, $\Delta z$, and three
rotation parameters $\Delta \theta_{xy}$ $\Delta \theta_{yz}$,
$\Delta \theta_{zx}$ (where, for example, $\Delta \theta_{xy}$ is a rotation in the
$x$-$y$ plane). These six unknowns can be determined using the six
constraints in equation (\ref{constraint}). The method is the same as
above, except equations (\ref{better}-\ref{F}) now contain the
corresponding extra terms, and ${\bf A}$ in equation (\ref{A})
becomes a six by six matrix.

The computation for one time step scales as $N^3$. For low to moderate values of $N$ the
method is very fast. However, for $N \gtrsim 100$, it quickly becomes very computationally
intensive.

\subsection{Lattice-Boltzmann}

\label{latboltsec}

The lattice Boltzmann algorithm is now a widely used mesoscopic
modeling technique for simulating the behavior of complex fluids \cite{S01,Y06}.
The method consists of an evolution equation for a mass density
distribution function $f_k({\bf s},t)$, which can be considered as a
simplified, discretized version of Boltzmann's transport equation.
The distribution function is defined at positions, ${\bf s}$, which
lie on a cubic lattice
with a distance $\delta s$ between nearest neighbor points.
Its value is updated simultaneously and discretely in
time, with time step $\delta t$. We define $c = \delta s / \delta t$.
The subscript $k$ denotes a particular velocity
direction ${\bf e}_k$.
The velocity vectors ${\bf e}_k$
must be chosen such that ${\bf e}_k \delta t$ lies between lattice sites.
In this study all simulations are performed in three dimension using a
$15$ velocity model. This has a zero velocity vector
${\bf e}_0 = (0,0,0)$, six nearest neighbor velocity vectors
${\bf e}_{1-6}$ in the directions $(\pm c,0,0)$, $(0,\pm c,0)$, and
$(0,0,\pm c)$, and eight velocity vectors ${\bf e}_{7-14}$ in the
diagonal directions $(\pm c, \pm c, \pm c)$.
From $f_k$ we can calculate the mass density $\rho$ and momentum
density $\rho {\bf u}$:
\begin{eqnarray}
\rho=\sum_k f_k,&\ \ \ \ \ \ &\rho u_{\alpha}=\sum_k f_k e_{k \alpha}.
\label{5.3}
\end{eqnarray}

Evolution in time is given by
\begin{eqnarray}
 f_k({\bf s} + {\bf e}_k \delta t , t+\delta t) = f_k({\bf s}, t) - \frac{1}{\tau} \Bigl[
f_k({\bf s}) - f_k^{eq}({\bf s}) \Bigr]
\label{latbolt}
\end{eqnarray}
where we use the Bhatnagar-Gross-Krook approximation, which uses a
single parameter $\tau$ to determine the
rate of relaxation toward equilibrium.
A suitable choice for the equilibrium distribution function is
\begin{eqnarray}
f^{eq}_k &=& \rho w_k \left( 1 + \frac{3 e_{k\alpha} u_\alpha}{c^2} + \frac{9
(e_{k\alpha} u_\alpha)^2}{2c^4} - \frac{3 u^2}{2 c^2} \right)
\label{fequ}
\end{eqnarray}
where the weight factors are
$w_0 = \frac{2}{9}$, $w_{1-6} = \frac{1}{9}$,
and $w_{7-14} = \frac{1}{72}$.
Note that this distribution satisfies
\begin{eqnarray}
\sum_k f_k^{eq} = \rho,&\ \ \ \ \ \
&\sum_k f_k^{eq}e_{k \alpha}= \rho u_{\alpha},
\label{ncons}
\end{eqnarray}
such that mass and momentum are conserved in time. This can be seen
by summing the zeroth and first velocity moments of equation (\ref{latbolt}), and
using the relations in (\ref{5.3}).

Applying the Chapman-Enskog expansion to the lattice Boltzmann
equation (\ref{latbolt}) \cite{Y06} gives
the continuity equation for the total density,
\begin{equation}
\partial_t \rho +\partial_\alpha( \rho u_\alpha) = 0
\label{conteqn}
\end{equation}
and the Navier-Stokes equation for the fluid momentum,
\begin{eqnarray}
\partial_{t}(\rho u_\alpha) +  \partial_\beta ( \rho u_\alpha u_\beta) = -
\partial_\alpha \left( \rho c_s^2 \right) + \partial_\beta \left(  \nu \rho
\partial_\beta u_\alpha \right)
\label{nsfinal2}
\end{eqnarray}
where the kinematic viscosity is
\begin{eqnarray}
\nu = \frac{(\delta s)^2}{3 \delta t} \left(\tau - \frac{1}{2} \right)
\end{eqnarray}
and the speed of sound is $c_s = c/\sqrt{3}$. At low Reynolds numbers the fluid
is, to a very good approximation, incompressible, {\em i.e.} $\nabla.{\bf u} = 0$.
(In the simulations, the difference between the maximum and minimum density within
the system was found to be no more that $0.04\%$ of the average density.)

For simplicity, we do not explicitly consider a solid-fluid interface but define
the swimmer to comprise of the fluid region within the spheres which make up the
swimmer \cite{N3}. The swimmer-fluid interaction is incorporated into the lattice
Boltzmann algorithm after finding the fluid velocities in equation (8), but before
calculating the equilibrium distributions in equation (10). This interaction is generated in three
stages. Firstly, the total linear and angular momentum of the swimmer are calculated:
\begin{eqnarray}
{\bf P} = \sum_j \rho_j {\bf u}_j, \quad {\bf L} = \sum_j {\bf s}_j \times \rho_j {\bf u}_j,
\end{eqnarray}
where the sum $j$ runs over all the lattice sites contained within the swimmer.
Secondly, the new positions of the spheres are calculated. This procedure is
analogous to that described for the Oseen tensor method in Section \ref{OseenT}. In this, we know
the positions of the spheres at time $t$ and the swimmer {\it shape} at time
$t+\delta t$. The algorithm works out how this new shape is oriented with respect to
the original, such that linear and angular momentum are conserved, {\em i.e.}
\begin{eqnarray}
\sum_i m_i {\bf v}_i = {\bf P}, \quad \sum_i {\bf r}_i \times m_i {\bf v}_i = {\bf L},
\end{eqnarray}
where $m_i = \sum_j \rho_j$ and
\begin{eqnarray}
{\bf v}_i = \frac{{\bf r}_i(t+\delta t) - {\bf r}_i(t)}{\delta t}
\end{eqnarray}
are the mass and velocity of sphere $i$, respectively. Thirdly, the
motion of the swimmer is coupled back to the fluid.
Lattice sites within a given sphere are set to the velocity of that sphere,
{\em i.e.} ${\bf u}_j = {\bf v}_i, \,\,\, {\bf s}_j \in \text{Sphere}\,\, i$. These
updated velocities are then used in calculating the equilibrium distributions
(\ref{fequ}). Through repeated iteration of the lattice Boltzmann equation (9),
the fluid within and immediately adjacent to the spheres is
strongly coupled to move with the same velocity as the spheres, thus giving the correct boundary condition.

To avoid unwanted lattice effects, the radius $R$ of each sphere must be
sufficiently large to accurately resolve its shape on the cubic grid. In this study
we choose $R=3\delta s$, such that each sphere contains approximately $113$ lattice
sites. Note that in this procedure we neglect the effect of rotation on the spheres, assuming that all parts of a given sphere travel at the same velocity.
This assumption is justified because the hydrodynamic interactions between rotating spheres is rather weak.
(The Oseen tensor (\ref{oseent}) decays as $r^{-1}$, whereas the flow field around a rotating sphere decays at a much faster rate of $r^{-3}$.)
In the case of modeling more than one swimmer, it is necessary to add hard core
potentials between spheres to prevent them from overlapping.

\subsection{Multiparticle Collision Dynamics}

\label{SRDsec}

An alternative mesoscale approach, which solves the equations
of {\em fluctuating} hydrodynamics
is the multiparticle collision dynamics (also known as stochastic rotation
dynamics) algorithm introduced by
Malevanets and Kapral \cite{MK99}.
The fluid is represented by a large number of point-like
particles of mass $m$, with position $\mathbf{r}_k(t)$, and
velocity $\mathbf{v}_{k}(t)$ at time $t$, where $k$ is
the particle index. The particles move in continuous space, and
at discrete time intervals, $\delta t$. Particle positions are updated
according to

\begin{equation}
\mathbf{r}_k(t+\delta t) = \mathbf{r}_k(t) + \mathbf{v}_k(t)\delta t.
\label{eq:SRD1}
\end{equation}
At each time step the particles also undergo a multiparticle collision
that locally conserves mass, momentum, and energy. To perform the collision,
the simulation box is divided into a grid of cubic cells, with sides
of length $a$. The average number of particles per cell will be
denoted by $\gamma$. The velocities of the particles in each cell are
then rotated about the center of mass velocity of the cell,
$\mathbf{v}_{cm}$
\begin{equation}
\mathbf{v}_k(t+\delta t) = \mathbf{v}_{cm}(t) +
\mathbf{R}\left[\mathbf{v}_k(t) - \mathbf{v}_{cm}(t)\right] .
\label{eq:SRD2}
\end{equation}
$\mathbf{R}$ is a rotation matrix through a
fixed angle, $\alpha$, about an axis that is generated randomly for each cell in the
simulation at each time step. The position of the cubic grid is chosen randomly at each
time step -- this leads to substantially improved Galilean invariance in the algorithm
 \cite{IK01}. In the continuum limit, the multiparticle collision dynamics algorithm
recovers the thermohydrodynamic equations of motion and thus acts as a Navier-Stokes
solver. Conveniently, the dependence of the transport coefficients of the fluid on the
simulation parameters is known analytically \cite{IK03,PY05}. Thus, it is a relatively
simple task to choose values that result in a low Reynolds number fluid.

We couple a swimmer to the multiparticle collision dynamics solvent
by considering it to be composed of a number of particles,
and including these solute particles in the solvent collision step
(\ref{eq:SRD2}). In this way the swimming microstructure can exchange
momentum with the solvent. In general, the equations of motion of
the microstructure are solved using a velocity Verlet molecular
dynamics algorithm. Precise details of how specific swimmers
are dealt with using this approach are given in later sections
of the paper.

\section{Linear Three Sphere Swimmer}
\label{1-D}

Recently, Najafi and Golestanian~\cite{NG04} proposed a one-dimensional
swimmer comprising three connected spheres. Their model is perhaps the
simplest example of a controlled, cyclic motion that breaks time
reversibility. The swimmer consists of a central sphere that is
connected to two other spheres by arms that are separated by an
angle of $180^o$, are of negligible thickness, and whose
length can be changed by, for example, the action of engines located
on the central sphere. The microstructure moves by shortening and
extending the lengths of the arms in a periodic and time irreversible
manner, as shown in Figure \ref{fig:gol1}. The relevant parameters
for this model
are $D$, the distance between the central sphere and an outer sphere
at the maximum arm length, $\varepsilon$, the distance the arm shortens,
$W$, the speed at which the arms change their lengths, and $R$, the
radius of the spheres. The result of this cyclic, time
irreversible motion is a net translation of the swimmer along the
line linking the three spheres; we define $\Delta$ as the distance
the swimmer translates in one complete cycle.

\begin{figure}
\begin{center}
\includegraphics[width=3in,height = 4.9in]{gol_motion2.eps}
\end{center}
\caption{The four step, cyclic motion of the linear three sphere
swimmer \cite{NG04}.}
\label{fig:gol1}
\end{figure}

\subsection{Analytic Theory}

Because of the simplicity of the shape deformations of the linear three
sphere swimmer, it is possible to calculate analytically the total
net displacement, $\Delta$, of the swimmer during each complete cycle
of its motion, in the limit of $\varepsilon \ll D$ and $R \ll D$.
We summarize the argument of Najafi and Golestanian \cite{NG04}
 and correct their formula for the displacement
of the swimmer, which we shall need for comparison to the numerical
results.

Each of the four
steps of the stroke can, by a simple transformation, be converted into
one particular auxiliary stroke. In the auxiliary stroke one arm
has a fixed length, $\delta$, where $\delta$ is either $D$ or
$D - \varepsilon$, and the other arm changes length from
$D$ to $D - \varepsilon$.
We choose the {\em x}-axis to be parallel to the line linking the spheres
and directed away from sphere $2$ (see Figure \ref{fig:gol1}).
During the auxiliary stroke $v_1 = v_3$ and
$W = v_2 - v_1$, and thus the velocity of the middle sphere,
in the limit that the swimmer undergoes small deformations, is

\begin{equation}
\begin{aligned}
v_1(\delta) &\approx \frac{-W\left(H_{11}-H_{23}-H_{12}\right)}
                   {\left(3H_{11}-2\left(H_{12}+H_{13}+H_{23}\right)\right)}\\
            &\approx
            -\frac{W}{3}\left[1-\frac{R}{2(D-Wt)}+\frac{R}{\delta}
                              -\frac{R}{2(\delta+D-Wt)}\right],
\end{aligned}
\label{eq:th8}
\end{equation}
ignoring terms of order $(R/D)^2$ and greater.
The elements of the Oseen tensor for each pair of spheres
follow from equation (\ref{oseent}).
Integrating (\ref{eq:th8}) gives the
displacement over the auxiliary stroke,

\begin{equation}
\Delta_a(\delta) = \int^{\varepsilon/W}_0 v_1(\delta)\,dt.
\label{eq:th9}
\end{equation}
This can then be used to calculate the total displacement after the four step cycle, to second order in $\varepsilon / D$, as

\begin{eqnarray}
\Delta  &=& 2 \left[ \Delta_a(D) - \Delta_a(D - \varepsilon) \right] \nonumber \\
        &=& \frac{7}{12} R
      \left[
      \left(\frac{\varepsilon}{D}\right)^2 +
      \left(\frac{\varepsilon}{D}\right)^3
      \right],
\label{eq:th13}
\end{eqnarray}

We note here that this expression differs from that given by
Najafi and Golestanian~\cite{NG04} who reported
\begin{equation}
\Delta = 2.8 R \left(\frac{\varepsilon}{D}\right)^3.
\label{eq:th12}
\end{equation}
In equation (\ref{eq:th12}) the displacement, $\Delta$, is proportional
to $(\varepsilon / D)^3$. If one considers the transformation
$\varepsilon \rightarrow \chi = -\varepsilon$ and
$D \rightarrow G = D - \varepsilon$, this corresponds to a swimmer
undergoing exactly the same
continuous motion as that
shown in Figure \ref{fig:gol1}, only with
the swimming stroke
beginning at the third step in the cycle.
Thus, the swimmer must move in the same direction.
However, equation (\ref{eq:th12}) suggests that the swimming direction
is reversed under this transformation, which is clearly incorrect.

In the following section, we summarize the results of
numerical simulation studies of the motion of the
linear three sphere swimmer at low Reynolds number in order
to validate and compare the use of these approaches in the study of
swimming microstructures.

\subsection{Numerical Results}

\label{results}

\begin{figure}
\begin{center}
\includegraphics[width=3.4in,height = 3in]{Delta_vs_epsilon.eps}
\end{center}
\caption{
The shift per cycle of the linear three sphere swimmer, $\Delta$,
as a function of the
sphere displacement amplitude, $\varepsilon$. The inset shows a magnified
view of the region of the graph below $\varepsilon/D = 0.2$.
The parameters
$D=25$ and $R=3$ were used in the Oseen tensor and lattice Boltzmann
approaches. In the multiparticle collision dynamics simulations we
used $D=3.0 a$. The solid line was obtained by numerically solving
the Oseen tensor equation, outlined in section \ref{OseenT}. The
crosses mark results obtained from lattice Boltzmann simulations,
presented in section \ref{latboltsec}. The error bars show the distribution
of results using multiparticle collision dynamics from section \ref{SRDsec}.
 The dashed line is the theoretical expression given in equation (\ref{eq:th13})
and the dot-dashed line is the expression proposed by Najafi {\em et al}.~\cite{NG04}
reproduced in equation (\ref{eq:th12}).
}
\label{figgolelb}
\end{figure}

Figure \ref{figgolelb} gives the results for a single linear three sphere
swimmer, using each of the three methods presented in Section
\ref{numsec}. This graph shows how the total displacement of the
swimmer over one swimming cycle, $\Delta$, varies as a function
of the amplitude of the stroke, $\varepsilon$. The parameters used
were $D=25$ and $R=3$ for the Oseen tensor and lattice Boltzmann
approaches and $D = 3.0a$ for the multiparticle collision dynamics
simulations.

The solid line in Figure \ref{figgolelb} is obtained by directly
solving the Oseen tensor interaction between the spheres,
as outlined in Section \ref{OseenT}. The dashed line shows the
theoretical curve, equation (\ref{eq:th13}), which is correct to
third order in $\varepsilon/D$.
These two curves converge in the limit of small $\varepsilon/D$,
as expected.
The dot-dashed line is equation (\ref{eq:th12}), the
expression proposed by Najafi and Golestanian~\cite{NG04}.
This appears to give good agreement for larger values of
$\varepsilon/D$. This is misleading, however, as in the
limit of small $\varepsilon/D$ it does not converge to the theoretical
solution (this is seen most clearly within the inset), and it should
not be valid at higher values of $\varepsilon/D$ due to the
assumptions made in the derivation.

The lattice Boltzmann simulations
were performed using a lattice
of size $L_x=200$, $L_y=100$, and $L_z=100$, with periodic
boundary conditions. Initially, the
swimmer was placed in the middle of the box, aligned parallel to
the $x$ direction. The relaxation parameter was chosen to be
$\tau = 1$.
 The simulations were run for one complete
swimming cycle, which corresponded to $t_{max}=102400 \delta t$ time steps.
The maximum speed of spheres is approximated by $4\varepsilon/t_{max}$.
Using this together with $R$, which gives a characteristic length scale
for the problem, the Reynolds number can be expressed as $Re = 4 \varepsilon R/\nu
t_{max}$.
The largest displacement used ($\varepsilon=19$) gives
$Re = 0.013$. This was checked to be sufficiently low by running a
limited number of simulations using $t_{max}=204800 \delta t$ time steps,
and finding that these results agreed to within $1\%$. Furthermore,
we checked that finite size effects were not important by performing
simulations using a lattice of size $L_x=300$, $L_y=150$, and
$L_z=150$, with results again agreeing within this tolerance.

The results from the lattice Boltzmann simulations are denoted by the
crosses in Figure \ref{figgolelb}. They agree well with the full
Oseen tensor result (solid curve) at small
$\varepsilon/D$ and deviate as $\varepsilon/D$ gets increasingly
large. This is because the Oseen tensor approximation that the
spheres are far apart breaks down in this limit (the spheres
intersect each other if $\varepsilon/D > 0.76$ for the parameters
used).

Simulations using multiparticle collision dynamics are
intrinsically noisy. If we simply use a molecular dynamics algorithm
to solve the equations of motion for the swimmer and include
the particles that make up the swimmer in the solvent collision
step then, without further correction, the microstructure will rotate,
and not stay aligned along one particular axis. Although this
behavior would be realistic for a nanoscale microstructure in a
solvent, it does not easily allow for an accurate comparison
of swimming speed with theory.
To constrain the motion to one dimension, the transverse
velocities of the three particles that comprise the swimmer
were adjusted to the average velocity of the particles
after each collision step.
Changes in the arm lengths were undertaken by adding an
extra velocity to each particle, such that
the total momentum of the microstructure remained unchanged
during the arm length change.

For the multiparticle collision dynamics solvent we used the
following parameters: Particle temperature
$kT = 0.005$, time step $\delta t = 0.01$, cell size $a = 1.0$, rotation angle
$\alpha = 135^o$, average number of particles per cell $\gamma = 10$,
and particle mass $m = 10$. These result in a Reynolds number for the
microstructure of
$\sim 10^{-5}$. These parameters both ensure a low Reynolds
number and minimize fluctuations in the solvent with
a high Schmidt number. In our simulations, we employed a
simulation box of dimensions $30a \times 8a \times 8a$ with
periodic boundary conditions and checked for finite size
effects.
For the swimmer we used a mass of
$5 m$ for each sphere.
Due to the nature of the swimmer--solvent interaction in our
implementation of the multiparticle collision dynamics
algorithm, it is difficult to define the effective hydrodynamic
radii of the spheres. However, comparison with the Oseen tensor and
lattice Boltzmann simulation results suggests the parameters
used lead to $R/D \sim 0.12$.
The simulations were conducted for a total time of $t_{max} = 2.72
\times 10^5 \delta t$ time steps, and one period of motion took
$6.8 \times 10^3 \delta t$. The period must be sufficiently long to
allow the solvent to couple with the swimmer.
20 runs were performed for each parameter set and the results are denoted by the
error bars in Figure \ref{figgolelb}, which are spread one standard
error on either side of the average
of the 20 runs. The results are compatible with, but much less
precise than, those obtained by the methods without intrinsic
fluctuations.

\begin{figure}
\begin{center}
\includegraphics[width=3.2in,height = 5.5in]{efficiencygolenew.eps}
\end{center}
\caption{ The percentage efficiency of a linear three sphere swimmer
as a function of (a) the sphere displacement amplitude, $\varepsilon$, for fixed $D=5R$, and
(b) the maximum arm length, $D$, for fixed minimum separation $D-\varepsilon=4R$.
}
\label{effi}
\end{figure}

~\\

By changing the parameters, $D$ and $\varepsilon$, it is not
only possible to change the swimmer displacement, $\Delta$, but also
the efficiency of the swimmer. We define this efficiency to be the
energy required for an external force to move the individual spheres
by the distance $\Delta$ in a time $P$ divided by the work done by the
swimmer in performing the corresponding cyclic shape change:
\begin{eqnarray}
\text{Efficiency} = \frac{6\pi\eta N \Delta^2/P }{\sum_{i=1}^N \int_0^P \mathbf{F}_i . \mathbf{v}_i
dt}.
\label{effic}
\end{eqnarray}
Using the Oseen tensor approach, the forces on the spheres,
$\mathbf{F}_i$, are calculated through equation (\ref{F}),
so this quantity is easily obtainable.
The line in figure \ref{effi}(a) shows how the swimming
efficiency is changed as a function of
$\varepsilon$, whilst keeping $D=5R$ fixed. Note that this curve
terminates when $\varepsilon = D-2R$, since beyond this the spheres
unphysically overlap at some point within the swimming cycle.
Furthermore, the Oseen tensor method tends to overestimate the efficiency when the spheres get close,
because it does not include the viscous dissipation resulting from lubrication effects.
Figure \ref{effi}(a) illustrates a general feature of swimmers, namely that small amplitude motion
results in inefficient swimming.
The curve in figure \ref{effi}(b) shows the efficiency against $D$, assuming a fixed mimumum sphere separation of $D-\varepsilon = 4R$.
We find that the swimmer becomes
increasingly
efficient as $D$ increases, approaching a limit of around $8\%$.

We now summarize the relative advantages and disadvantages of the
three numerical methods. The Oseen tensor approach is particularly
advantageous for swimmers comprising small numbers of spheres because
it is computationally very fast (simulations taking only minutes
instead of days using lattice Boltzmann or multiparticle collision
dynamics). This is primarily because it is not necessary to
explicitly solve a set of fluid dynamics equations. However the
simulation time scales as $N^3$ so lattice Boltzmann becomes more
efficient for large numbers of swimmers.

The Oseen tensor formalism is also limited because it
assumes that the interacting spheres are spaced
far apart, compared to their radii. This means, for instance,
that it would not be appropriate
to use this method to study the movement of a swimmer close to a wall
or in a confined geometry.
On the other hand, the lattice Boltzmann
algorithm can address these problems, providing an exact
solution to any fluid flow problem given sufficient resolution. In practice it is limited
by computational power. To avoid spurious lattice effects, the
sphere radius must be significantly larger than the lattice size,
necessitating the need for large systems. Moreover, to obtain a
sufficiently low Reynolds number, the cyclic swimming motion must
be performed over a great number of time steps, further increasing
the computational burden.

Multiparticle collision dynamics is advantageous because it
is unconditionally stable, unlike the lattice Boltzmann method, and
this allows somewhat lower Reynolds numbers to be obtained more
easily. One can also use a molecular dynamics approach to
treat the microstructure allowing
for great flexibility in the swimmer models it is possible to consider.

Additionally, as this method inherently contains noise it will
be appropriate for studying very small scale structures, for which
Brownian fluctuations are important. However, if the
fluctuations are unphysical the noise is
undesirable, necessitating long time averages.

For the remainder of this paper, we concentrate on using the Oseen
tensor and multiparticle collision dynamics approaches to study more
complex swimming motions.

\section{Generalized Three Sphere Swimmers}

\label{otherthree}

\begin{figure}
\begin{center}
\includegraphics[width=3.6in,height = 3.2in]{newfig.eps}
\end{center}
\caption{
Alternative cyclic motion for a three sphere swimmer, allowing
the microstructure to translate in two dimensions. Possible extensions
to this scheme include allowing the angle $\alpha$ to change as the
arm lengths change.
}
\label{fig3general}
\end{figure}
The swimmer described in Section \ref{1-D} is constrained to move
in one dimension along its axis.
Using the same basic elements one can design a number of other
three sphere swimmers that can move their individual
components and centers of mass in two or three dimensions. To extend the
original design we allow the angle between the two arms of the
swimmer to change \cite{DB05b}. When the change in angle takes place, the
spheres may move radially with the arm lengths
constant, or the arm lengths may change at the same time, thus allowing
for a number of different motions. In Figure \ref{fig3general} we show
one of many possible alternative schemes of motion for swimmers of this
type, which we will refer to as
generalized three sphere swimmers.
\begin{figure}
\begin{center}
\includegraphics[width=3.2in,height = 2.7in]{delta_vs_angle.eps}
\end{center}
\caption{
The position shift over one cycle, $\Delta$, as a function of swimmer angle $\alpha$ for
the swimmer defined in Figure~\ref{fig3general}.
Other parameters were $D = 5R$ and $\varepsilon = 2R$.
}
\label{newswim}
\end{figure}

We first concentrate
on the motion shown in Figure \ref{fig3general}, and the case where the arms
rotate at fixed length.
If the swimmer employs a
symmetric motion with arm lengths $D_{12} = D_{13}$ and
$\varepsilon_{12} = \varepsilon_{13}$, the net translation of the swimmer
is along the {\em x}-axis (defined in the figure). Thus, the microstructure
remains a one dimensional swimmer while its individual
elements are moving in two dimensions.
Interestingly, the direction that the microstructure
translates varies with $\alpha$,
for fixed $D$ and $\varepsilon$,
as shown in Figure \ref{newswim}.
For $D = 5R$ and $\varepsilon = 2R$ the outer two spheres do not
intersect for $\alpha > 39^o$, and there
is a transition from backward motion to forward motion at $\alpha = 77^o$.
Intuitively it is not obvious what causes this reversal of direction.
We found that the maximum efficiency of this swimmer (with efficiency defined by equation
(\ref{effic})), occurs at $\alpha = 138^o$.
This corresponds to an efficiency of $1.8 \%$, which is considerably
less than the $\sim 8 \%$ found for the linear three sphere swimmer in the
previous section.
It seems plausible that the linear three sphere swimmer is the most
efficient three sphere swimmer possible.
\begin{figure}
\begin{center}
\includegraphics[width=3.2in,height = 2.7in]{anglech.eps}
\end{center}
\caption{The angular change in the orientation of the generalized
three sphere swimmer over one complete swimming cycle, $\Delta \theta$,
as a function of the swimmer displacement amplitude, $\varepsilon_{13}$.
Other parameters were fixed to be $\varepsilon_{12} = 3 R$ and $D_{12} = D_{13} = 6R$.
The inset shows the movement of the center of mass of the swimmer at
a fixed point in the cycle, over the course of 9 swimming cycles.}
\label{anglechange}
\end{figure}

If one instead defines an
asymmetric motion, with $D_{12} \neq D_{13}$ and/or
$\varepsilon_{12} \neq \varepsilon_{13}$, the microstructure will
move its center of mass in two dimensions.
The swimmer rotates and translates, as shown for
$D_{12} = D_{13} = 6$, $\varepsilon_{12} = 3$ and $\varepsilon_{13}$
as variable
in Figure \ref{anglechange}. As the difference between $\varepsilon_{12}$ and
$\varepsilon_{13}$
becomes greater,
the angular rotation about the center of mass of the microstructure
for each swimming cycle increases.
Thus, it is a relatively easy step to imagine a
manufactured device that can switch between symmetric and asymmetric
cyclic motions,
perhaps in response to an external stimulus or experimental condition,
to enable movement in a controlled fashion in two dimensions.
A three
sphere swimmer, that can change the angle between its two arms, could
simply adopt the efficient swimming motion of Section
\ref{1-D}, where $\alpha = 180^o$, to move in a straight line,
and then vary $\alpha$ to adopt a structure allowing it to turn.

To extend the movement of such a microstructure to three
dimensions, the angle between the arms could be changed
along another plane, perpendicular to the original one.
One strategy to do this might be to employ a double-jointed structure
where the angle between the arms could be changed from
$\alpha = 180^o$ in either of two perpendicular planes.
It is of interest that this microstructure
is the first low Reynolds number swimmer to be proposed theoretically
that can move in a controlled fashion in three dimensions,
without employing numerous one dimensional swimming devices placed
perpendicular to each other.

\section{Extended, Linear, One Dimensional Swimmers}
\label{extended}

To extend the linear three sphere swimmer of Section \ref{1-D} one can
simply add more spheres to the microstructure, the simplest extension
being the four sphere case. For the four sphere microstructure shown in
Figure \ref{fig4linear}i), we analyzed through Oseen tensor based
numerical simulations all possible cyclic
motions that are made up of a discrete number of steps. At the end of each step
the distance between neighboring spheres is either $D$ (an extended rod) or
$D-\varepsilon$ (a contracted rod). If a rod changes length during a step then it
does so at a constant speed $W$.
In this analysis we allowed for more
than one rod length changing simultaneously.

Out of this subset of
possible swimmers the swimming strategy shown in Figure
\ref{fig4linear} is the most efficient. This optimal swimming strategy proceeds as
follows: Starting from the fully extended conformation, i), the
distance between spheres $1$ and $2$ is reduced to
$D - \varepsilon$, ii). In the next two steps the distance
between spheres $2$ and $3$ is reduced to $D - \varepsilon$,
iii), and the distance between spheres $3$ and $4$ is reduced to
$D - \varepsilon$, iv), the fully contracted conformation.
The microstructure then sequentially extends, first by extending the
distance between spheres $1$ and $2$ to $D$, v), then extending
the distance between spheres $2$ and $3$ to $D$, vi), and
finally by extending the
distance between spheres $3$ and $4$ to $D$, completing the
cycle and taking the conformation back to the original starting
configuration i).
For the case $D = 5R$ and $\varepsilon = 2R$, the four
sphere microstructure using the optimal swimming strategy has a
swimming efficiency of 6.9 \% compared to 4.5 \% for the
three sphere swimmer using the same parameters.

\begin{figure}
\begin{center}
\includegraphics[width=3.0in,height = 5.0in]{linear.eps}
\end{center}
\caption{
The most efficient cyclic swimming
strategy for an extended, linear, four sphere
microstructure.
}
\label{fig4linear}
\end{figure}
Extending to the five sphere case, we analyzed all possible cyclic
swimming strategies using Oseen tensor based numerical simulations,
and found that the analogous swimming strategy
to that in Figure \ref{fig4linear} was optimal,
resulting in a swimming efficiency of 8.8 \% for the
$D = 5R$ and $\varepsilon = 2 R$ case. We studied this optimal
swimming strategy for microstructures with up to 200 spheres and the
swimming efficiency as a function of the number of spheres is
shown in Figure \ref{fig:beads}.
\begin{figure}
\begin{center}
\includegraphics[width=3in,height = 2.5in]{eff_vs_nbeads.eps}
\end{center}
\caption{Percentage efficiency against the number of spheres for a microstructure
adopting the swimming strategy depicted in Figure \ref{fig4linear}.
}
\label{fig:beads}
\end{figure}
The curve indicates a logarithmic growth in the efficiency
as a function of sphere number.
This would imply that for a sufficiently large number of spheres
the efficiency will go above one.
Although counter intuitive, from our definition of efficiency in
equation (\ref{effic}), this is perfectly possible, and does not violate
any physical principles. However, as the number of spheres is increased, the physical size of the spheres and rods
would have to be made proportionately smaller, to ensure that finite Reynolds number
effects do not become important.

\section{Filament Swimmers Using Multiparticle Collision
Dynamics}
\label{filament}

As an example of using multiparticle collision dynamics to investigate a more complicated
swimmer we consider the motion of a filament modeled as beads connected by springs and
interacting through Lennard-Jones forces. The filament is driven by a sinusoidally
oscillating force applied at one end. The model was motivated by the man-made microscopic
swimmer of Dreyfus {\em et al.} where a red blood cell is attached to a filament
consisting of superparamagnetic colloids, that are connected to each other using DNA
 \cite{DB05a}. Two magnetic fields are used experimentally, one to align the filament and
the other to actuate one end of it in a sinusoidal manner. This actuation results in a
series of waves, originating at the tail of the filament, propagating towards the red
blood cell at the head. Because the perpendicular and parallel friction coefficients of
the microstructure are not equal ($\zeta_\perp / \zeta_\parallel \approx 2$), a net
translation, in the opposite direction to the propagation of the wave, occurs along the
alignment direction of the filament.

In the multiparticle collision dynamics simulation we model the filament as a number of
Lennard-Jones beads, representing the superparamagnetic colloids, connected to each
other by FENE springs, representing the DNA linkers. Instead of a magnetic
field, we simply apply an equal and opposite force to each end of the filament to align
it along an axis, and apply a sinusoidal actuating force, perpendicular to the aligning
forces, to one end of the filament (see Figure \ref{fig:filament}(a)).

Lowe \cite{L01} proposed a dimensionless parameter to
characterize naturally flexible filaments,
the `sperm number', defined as
\begin{equation}
S_p = L / \left( \frac{\kappa}{\zeta_\perp \omega} \right)^{1/4}
\end{equation}
where $L$ is the length, $\kappa$ is the bending
rigidity, and $\zeta_\perp$ is the perpendicular friction
coefficient for the filament, and $\omega$ is the angular
frequency of the actuation or driving. For our model filament
in a multiparticle collision dynamics solvent we calculate
the bending rigidity from the change
in energy of the structure as a function of the curvature
of the filament \cite{LC03}. We determine the friction coefficients
by applying a known force to each bead, in a direction perpendicular
or parallel to the alignment, and measuring the resulting velocity of the
microstructure (with no actuation). We can then measure how the
velocity of the microstructure depends on $S_p$ by
changing the angular frequency of the actuation.

For the multiparticle collision dynamics solvent we use
the following parameters:
$kT = 1.0$, $\delta t = 1.0$, $a = 1.0$, $\alpha = 120^o$, $\gamma = 5$,
and $m = 4$
resulting in a Reynolds number for the microstructure of
$\sim 10^{-2}$. For the microstructure we use a mass of
$4 m$ for each bead and a molecular dynamics time step of
$0.002 \delta t$. The average distance between the
centers of mass of each bead is $\approx 1.0 a$, and we
use 10 beads to represent the filament.
The simulations are conducted over $t_{max} = 200000 \delta t$
solvent time steps, and
we average the results over 10 runs for each data point.

In Figure \ref{fig:filament} we show
the swimming velocity of the microstructure, scaled by
$L \omega$, as a function of $S_p$. As predicted by theory
for naturally flexible filaments \cite{WG98}, we observe a
maximum in the scaled swimming velocity of the filament between
the high (dominated by viscous friction) and low (dominated
by internal elasticity) $S_p$ regimes. This reproduces the
behavior demonstrated for the man-made swimmer
of Dreyfus {\em et al.} \cite{DB05a}, and we also observe very similar
scaled speeds in our simulations to those found experimentally.

\begin{figure}
\begin{center}
\includegraphics[width=3.3in,height = 3.0in]{filament3.eps}
\end{center}
\caption{(a) Model filament used in the multiparticle collision
dynamics simulations. The
filament is composed of Lennard-Jones beads that are connected
by FENE springs. An aligning force, $F_{align}$, is applied to
both ends of the filament, and a sinusoidal force,
$F_{actuate} = F_{max} \sin(\omega t)$, is used to actuate one
end of the microstructure, leading to wave propagation from
right to left in the diagram.
(b) Scaled swimming velocity as a function of the sperm
number for the flexible filament. To obtain this plot, $F_{max}$ is varied
for different frequencies of actuation such that the integral of
$F_{actuate}$ over half of the period is equal.
}
\label{fig:filament}
\end{figure}

To verify that the filament in the simulations
swims through the mechanism of wave propagation, we also
modeled a 2 bead microstructure under the influence of aligning
and actuating forces. We find that this microstructure does not
swim as it is impossible for a 2 bead filament to move in a
time irreversible fashion.

\section{Conclusions}

In this paper we have described three different methods for
simulating low Reynolds number swimmers: An Oseen tensor approach, lattice Boltzmann and
multiparticle collision dynamics. In Section \ref{1-D}, each of
these methods was used to model a very simple, linear swimmer
comprising three linked spheres. Analytic results are available for
this system \cite{NG04} and hence we were able to validate the
approaches and identify the strengths and weaknesses of each
method. For swimmers made up of a small number of spheres the Oseen
tensor approach is very fast. However as the number of spheres
increases, or as multiple swimmers are considered, lattice Boltzmann
becomes more efficient. Moreover the Oseen tensor does not accurately
take into account short range hydrodynamic interactions. Lattice
Boltzmann is able to deal with spheres close to each other or to a
surface, but at the expense of an increasingly fine lattice
resolution. We found that multiparticle collision dynamics is in
general a less useful approach as the intrinsic noise tends to
dominate the results. This method will be of use when modeling
nanoscale systems where fluctuations are an intrinsic component of the
physics.

Subsequently, in Section \ref{otherthree}, we proposed a new three
sphere swimmer, which has the advantage of being able to turn, and
control its trajectory in a three dimensional manner. These ideas may
be of use in the design and fabrication of artificial microswimmers.
Section \ref{extended} extended the one dimensional three sphere
swimmer aiming to search for the most efficient swimming strategy for
a larger number of spheres. We found that the efficiency increases
logarithmically with the sphere number.

In Section
\ref{filament}, we looked at modeling a filament swimmer
that moves due to the propagation of waves along its length. Using multiparticle
collisional dynamics we were able to reproduce the behavior
observed experimentally.

There are many directions in which it would be fruitful to pursue the
simulations. We are currently considering interactions between two or
more swimmers, and it would be of interest to consider the effect of
boundaries and obstacles on swimming behavior.
Continuum hydrodynamic theories have recently been proposed to
describe concentrated solutions of swimmers \cite{SR02,LM05}. These have led to results
very suggestive of swimming behavior but it is hard to pin down the
phenomenological parameters in the equations of motion. Simulations of
increasing numbers of swimmers are needed to try to bridge the gap
between the microscopic and continuum approaches.

There is enormous scope presented by more realistic
biological problems such as the chemotactic responses of bacteria or
random tumbling during a swimming cycle. Moreover simulations of this
type may be important in designing artificial microswimmers for
applications as diverse as drug delivery or mixing fluids within
microchannels.

redpajama_set_name: RedPajamaArXiv


I have been involved in voluntary work for over 30 years.
I am one of the founder members of Unity Youth Club and Football Team, which was formed in 1977. Unity Youth club and Football team was formed specifically for the young black youth in Gloucester and was based at the Chequers Bridge Centre.
In 1979 I completed a part time youth leaders course held at Cowley Manor, and went on to became a Part Time Youth leader at Unity Youth Club and at Matson Youth Club, which was based in Matson Lane.
In 1988 Danny Williams and I formed D&D Promotions. We specialised in bringing Reggae Bands, Singers, DJ's and Sound Systems to the Black Community of Gloucester that would not normally come and perform in Gloucester.
In 1990 elected to the Jamaican Sports and Social club Management committee. A member of the management committee for 5 years. During that time held various position on the committee, Entertainment's Manager, Fixtures Secretary of the clubs Domino team, responsible for liasing with the Clubs Architect when the club was refurbished 1993-4.
At present I am the chairperson of the Gloucester FM community radio management committee, which was formed in 1999.


We are delighted to announce that the Vault 2014 Asia Pacific Consulting Rankings are here! As a region that is home to around two-thirds of the world's population, and a number of rapidly developing economies, Asia-Pacific is key to the future of the global economy. That presents opportunities for anyone in the consulting industry, from those looking to leverage manpower in the region to provide offshore services to clients elsewhere in the world, to those seeking to identify business opportunities within the region itself.
The data from this year's survey indicate that, despite some concerns over the slowing of growth in the region, Asia-Pac-based consultants remain bullish about business prospects in the region. It also demonstrated that firms are aware that, to take advantage of those opportunities, there is a greater need than ever to attract and retain the best talent possible. That can be seen most clearly in McKinsey's improved showing in the Best to Work For categories, which saw it emerge as the top firm in the region. But the level of competition in the industry means that firms such as Bain, Crescendo Partners, BCG, Booz & Company, Oliver Wyman, Mercer and Accenture—which all performed strongly this year—are also great places for those looking to start or further a consulting career in the Asia-Pacific region.
As mentioned, McKinsey dominated the Vault Asia Pacific Consulting Rankings, earning the title of the Top Consulting Firm, based on an overwhelmingly strong performance in the Best to Work For rankings, where it took the top spot in 12 of 22 categories. McKinsey also remained the Most Prestigious Consulting firm and continued to shine in the Practice Area Rankings, taking the No. 1 spot in eight separate categories. The impressive performance pushed McKinsey past last year's top firm, Bain & Company, which also performed strongly in all categories.
The rankings are based on the results of Vault's annual Consulting Survey conducted earlier this year. More than 500 consulting professionals of all levels across the Asia Pacific region assessed their peer consulting firms on a scale of 1 to 10 based on prestige and practice area strengths (respondents were unable to rate their own employers and rated only firms with which they were familiar). Consultants also rated their own firm on a variety of "best to work for" factors in such categories as firm culture, compensation, overall satisfaction and hours, among others. For the purpose of the Asia Consulting Ranking, a weighted formula was used to combine findings from both prestige and best to work for ratings to create the overall "Top Consulting" category.
Supporting McKinsey & Company's first-place finish, one employee pointed to the firm's "quality of clients and work," "fantastic people," and "collaborative culture." Another survey respondent praised the firm's career development initiatives, stating that McKinsey offers "the fastest learning and development curve of any firm I know of. But the real development that the firm and I are proud of is personal; I can't imagine any other institution investing as much in my personal development."
Last year's top firm — Bain & Company — came in a close second place. Bain consultants expressed great loyalty to their firm. "Bain has come a long way in the 10 years I have been working there — there is a constant effort to make the workload sustainable," said one firm employee, while another added, "I feel like with Bain I am able to carve out a path which allows me to follow my passion."
Crescendo Partners made their debut in the rankings this year at No. 3, with strong best to work for category scores. The Australia-based firm's employees appreciate Crescendo's "great work-life balance," "large exposure to clients at a junior level," "travel opportunities," and "steep learning curve." One survey respondent noted that "Crescendo understands the importance of balancing a fun environment with one that is constantly striving for excellence."
Crescendo's emergence in this year's rankings forced Booz & Company and Oliver Wyman down one spot each, to No. 4 and No. 5, respectively. A.T. Kearney remained in the No. 6 spot. Moving up to No. 7 was Alvarez & Marsal, a firm that was also new to the rankings this year. "This is a great place to learn leadership skills," said one Alvarez & Marsal consultant. "It will make you a better manager than any of the top strategy firms."
L.E.K. Consulting made a big jump from No. 13 to No. 8 this year. "L.E.K. has made a real effort to improve work/life balance and I have seen a significant improvement over the last two years," explained one survey respondent. "Hours have also dropped a bit despite record revenues. Most importantly, travel is kept to a bare minimum, so you can actually maintain a life in your home city rather than living out of hotels."
Rounding out the Top 10 are OC&C Strategy Consultants and Roland Berger Strategy Consulting, both of which dropped two spots, to No. 9 and No. 10, respectively.
Now more than ever, job applicants are putting job satisfaction over prestige. Name value is no longer enough for candidates who want better benefits, more pay, and a superior work-life balance. With respect to these quality of life standards, no two firms performed better than McKinsey and Crescendo Partners. In each of the 22 Best to Work For categories featured in this year's rankings, the No. 1 spot was occupied by one of the two firms.
McKinsey took the top spot in 12 categories, including Formal Training, Informal Training, International Opportunities, Internal Mobility, Client Interaction, Benefits, Green Initiatives, Philanthropy, Innovation in the Industry, Hiring Process and Business Outlook.
The firm's turnaround in Best to Work For scores challenges conventional wisdom about the firm, according to one employee who said the best part of working at McKinsey is the "coworker relationships. People across different levels are friendly with each other. It was a pleasant surprise, as McKinsey typically gives the image of being a cut-throat company."
Proving that boutique outfits can compete with the bigger players when it comes to employee satisfaction, the remaining 10 categories belonged to Crescendo Partners. The firm was ranked No. 1 in Overall Satisfaction, Firm Culture, Promotion Policies, Ability to Challenge, Supervisor Relationships, Work Hours, Travel Requirements, Work-Life Balance, Compensation and Firm Leadership.
"Crescendo Partners understands the needs of each and every one of its employees, particularly when it comes to work/life balance," said one consultant at the firm. "For example, past employees have had arrangements to finish early on time to pick up children from school, part time arrangements, etc. Further, working hours and conditions are very favorable — there is a culture of not working on weekends."
Other news coming out of the Best to Work For Rankings surrounded the sheer volume of favorable Business Outlook scores from consultants at firms surveyed this year. "The outlook scores were promising across the region," noted Stott. "With the recent surge in the Japanese economy, coupled with the improving global outlook, consultants seem genuinely optimistic about the future, and there's a palpable sense of anticipation about the future. It's definitely an exciting time for the consulting industry."
Enjoying where you work is important, but prestige still matters to job seekers looking to have the biggest and best names on their resume. According to industry insiders, McKinsey & Company still reigns as the most prestigious firm in the consulting world, once again edging out Boston Consulting Group and Bain.
Survey respondents described McKinsey as the "cream of the crop," a "known leader," "prestigious," "innovative," and the "firm to beat."
The firm also performed strongly in the Practice Area Rankings, retaining their No. 1 spot in Management Consulting, Economic Consulting, Energy Consulting, and Financial Consulting. The firm also overtook Accenture for the top spot in Operations Consulting and Boston Consulting Group for No. 1 for Healthcare Consulting. McKinsey also ranked No. 1 in Strategy Consulting, a category won by Arthur D. Little last year. Rounding out the firm's impressive accomplishments, McKinsey was ranked No. 1 for Retail Consulting, which, along with specific IT Consulting categories, was ranked for the first time in the Asia-Pacific region this year.
Vault's 2014 Consulting Rankings are Here!


Figuring out the cities and towns that will be in the dark the longest during the solar eclipse on Aug. 21 is like figuring who made the final cut for the NCAA Basketball Tournament.
Greer made the cut for eclipse totality at 2:38 p.m. for 1 minute, 25 seconds. Spartanburg is not in the path of totality and Greenville is.
Greenville Health System (GHS) made DiversityMBA Magazine's 50 Out Front list, which recognizes companies' hiring and support of women and minority managers. GHS has made the list six consecutive years.
GHS is No. 27 on the list.


r.series.accumulate Makes each output cell value a accumulationfunction of the values assigned to the corresponding cells in the input raster map layers.
r.series.interp Interpolates raster maps located (temporal or spatial) in between input raster maps at specific sampling positions.
See also the corresponding keyword series for additional references.


text:
Oil and Gas Lawyer Blog
Published By John McFarland
EPA Grades Railroad Commission on Regulation of Injection Wells
By John McFarland
The EPA has issued a report evaluating the Texas Railroad Commission's regulation of injection wells: EPAreviewRRC The report criticizes the RRC in three areas, discussed below.
Injection wells, permitted by the RRC, are used to dispose of oilfield waste – produced water, frac water, and other fluids. These liquid wastes are injected into underground reservoirs determined to have no useable groundwater or producible hydrocarbons. Called Class II injection wells, Texas has more than 56,000 such wells – a third of all Class II injection wells in the U.S.
Injection of waste underground is governed by the Safe Drinking Water Act passed by Congress in 1974. That act allows states to take responsibility for permitting and regulation of injection wells if the state's program meets the requirements of the SDW Act and the EPA. Texas has been regulating injection wells under authority delegated by the EPA since 1982. As part of that delegation, the EPA evaluates Texas' performance each year and issues an annual report with its findings.
By and large, the EPA report finds that the RRC's regulation of injection wells meets or exceeds the requirements of the Act. But the RRC is criticized in three respects.
First, the EPA says that
RRC representatives have publicly indicated that available scientific data do not support a causal relationship between Class II waste disposal wells in North Texas and recorded earthquakes. In light of findings from several researchers, its own analysis of some cases, and the fact that earthquakes in some areas diminished following shut-in or reduced injection volume in targeted wells, EPA believes there is a significant possibility that North Texas seismic activity is associated with disposal wells.
The EPA pointed out that there has been significant seismic activity in the DFW area, in and around Azle, Cleburne and DFW Airport, and that the RRC has worked with disposal well operators to reduce injection volume, and that seismic activity in these three areas has substantially diminished. The EPA report reminds the RRC that it participated in an EPA/State UIC National Technical Workgroup on injection-induced seismic activity that resulted in a report issued in February 2015, recommending strategies for managing and minimizing induced seismic activity, and EPA commended the RRC "for its influential involvement" and for "solidifying RRC authority to take appropriate action related to injection well operations." The report concludes:
EPA is concerned with the level of seismic activity during 2015 in the Dallas/Ft. Worth area because of the potential to impact public health and the environment, including underground sources of drinking water. EPA recommends close monitoring of injection activity through daily recording and reporting of accurate injection pressures and volumes from area disposal wells coupled with appropriate data analysis methods, in a coordinated effort to detect possible correspondence with seismic activity.
(The EPA report was issued by its Dallas Regional Office, which undoubtedly experienced the quake activity in that area.) In a letter responding to the EPA's report, the RRC said that the report's statement that "RRC has publicly stated that available scientific data do not support a correlation between recorded earthquakes and Class II waste disposal" should be stricken from the report "because it is taken out of context and is, therefore, false and misleading." The RRC's letter says that "The Commission's actions demonstrate a clear recognition of the potential correlation between injection and seismic activity." In its final report, the EPA modified but did not eliminate its reference to statements by Railroad Commissioners that scientific data do not support a correlation between quakes and injection wells. It appears that the RRC, like Oklahoma before it, has had to admit (despite pressure from the industry) the link between injection wells and seismic activity — although, in two recent show cause hearings, the RRC found no link between two injection wells near the town of Azle and the quakes in that area.
Second, EPA is concerned about increased pressures related to injection wells disposing of fluids into the Rodessa Formation in East Texas. It notes that the RRC has responded to the pressure build-up by increased monitoring of wells in the area and special reporting requirements for these wells, and it recommends continued monitoring of wells injecting into the Rodessa.
Third, the report comments on the RRC's efforts in "Identification and Delineation of Aquifer Exemptions." Any aquifer that contains water with less than 10,000 milligrams per liter (mg/l) of total dissolved solids (TDS) is considered under federal law a potential source of drinking water. Injection wells can be permitted into such formations only by "special exemption," if it is determined that the aquifer water is not "reasonably expected to supply a public water system" — for example, if the waters are too deep or are already polluted. When the EPA delegated to the RRC the responsibility for regulating injection wells, it required that the RRC keep up with any injection wells permitted into such aquifers. The report says the RRC has failed to identify what injection wells are operating in aquifers that have this special exemption. The RRC has said it is working to identify those wells and aquifers, but that doing so is "very resource intensive." The EPA "recommends continue high prioritization of this effort."
Aquifers with "brackish" water have recently become more important as potential sources of drinking water. Groundwater is generally not used for human consumption without treatment unless it contains less than 500 mg/l of TDS. The principal "solid" in water is typically salt, NaCl. Seawater contains around 35,000 mg/l of TDS. Water between 1,000 and 10,000 mg/l of TDS is considered "brackish" water.
As Texas' population has grown and demands for water have increased, cities have looked to underground brackish water as a potential source of drinking water. San Antonio is completing a desalination plant to treat brackish water produced from the Wilcox formation. So injection of contaminated waters into water reservoirs whose water contains less than 10,000 mg/l of dissolved solids has become more important to groundwater districts, cities and other users looking for sources of potable water. Not surprisingly, environmental groups have jumped on EPA's criticism of the RRC's failure to identify injection wells in "exempt" aquifers.
For more on the issue of aquifer exemptions, see Jim Malewitz's article in the Texas Tribune.
Posted in: Energy and the Environment and Texas Railroad Commission
Updated: August 26, 2016 9:05 am
John McFarland is a shareholder at Graves, Dougherty, Hearon & Moody in Austin Texas specializing in representation of landowners and mineral owners in oil and gas matters in Texas.
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Copyright © 2015 – 2020, John McFarland


Go to the Import tab.
Click Choose Files to select the Comma-Separated Value (CSV) file containing your customer information from your file system.
The mapping screen appears. This screen allows you to map a column in the CSV file to a field in the customer file of the Virtual Contact Center CRM. The column names from the CSV file are available in the pull-down menu, as shown below. Select a column name of the CSV file from the pull-down menu, and map it to the matching field in the Virtual Contact Center customer file.
The summary page opens and shows the mappings selected.
Click Start to initiate the import.
Click Back to modify the settings.
On initiating the import, the progress is displayed on the screen. The import is committed to the database in increments of 100 records at a time. Statistics about the import are displayed as well.
You can save the import report on the local file system.


Dharma is a stunning white wolf born in the spring 2004. You can view a sibling of hers at the Calgary Zoo In Alberta...Dharma is a serious and intense young female and teaches me how truly sensitive these creatures are to everything. She is a teacher in her own right. She always wants to be the leader and have everyone follow. Little does she know the ways she gets outsmarted ;0) Dhama personifies and enforces ALL the reasons why no wolf makes a pet!
and scroll down to the section on seasonal aggression. If caretakers of wolves are not VERY experienced, such as ourselves at AWA, they could wind up in some serious altercation and possible injury/harm to the caretaker.
For more info on this please go here www.wildsentry.org and click on essays and links.
Dharma is a perfect example of how variant personalities can be from one wolf to the next. As easy going as legend is, Dharma takes the world VERY seriously. Just like people, wolves can get moody, but wolves can be highly reactive, or even overreact at times, depending on the situation and the surrounding circumstances.
In the wrong inexperienced hands, all of what makes a wolf a wolf, can be potentially dangerous. It must be pointed out that though dharma is what I consider *tame* to a certain degree (some other experts may agree or argue this point) she still retains inherent wild tendencies, regardless of being raised in a captive situation. Wolves are NOT domesticated, no matter how many generations of them have been raised in captivity,/domestic situations.
I have heard the term *domestic* wolves, but IF this term is used, this should not be a referral, and taken to mean *domesticated*. There are some lines of wolves that can inherit and pass on more tractable traits, like Legend and Tibet (these types of wolves are great working in film etc) but even they do not become *dogs* nor can you make them into one .
Though wolves do not display any known behaviors not also found in the typical domestic dog, what varies is the frequency, and intensity of the behaviors and in which context those behaviors may be expressed.
Dharma's space, needs and wants are respected at all times. Why argue with a wolf? Through many years of studying and analyzing wolf behavior (ethology), wolf language becomes easily read. They certainly are far from unpredictable. Any training done with the wolves at AWA is done because it gives them something to do, and it can help give the people working with the wolf somewhat of an upper hand when it comes to having to take them to the vet, get a lead on them, or prepare them for getting any blood work done, training helps to give *any canine* guidance even wolves, to a point.
Contrary to popular belief wolves can be trained to a certain degree, wolves like to work and use their minds, and training helps them to accomplish this. If one works with the wolf and is attentive to the wolfs needs and desires it is not as hard as some may think to get the wolf to do what you want them to do. Though training can help shape even alter the nature of wolves through nurturing, nature certainly plays a big part in what a wolf is truly all about, and in the end this must be taken into consideration if one wishes to be dealing with such creatures in their daily lives.
Wolves are magnificent to watch and dharma is no exception when it comes to what a wolf is. One cannot push themselves onto a wolf, it is disrespectful of the wolfs own personal space, just as people need it so do wolves. When we are feeling icky do we want people to grab us out of the blue regardless of our feelings? Wolves are tolerant to a degree but as with all animals including the human animal wolves have their snapping points too. They will come to you on their time and will display affection when they see fit to do so. They do not live their lives to please humans the way dogs do. Wolves are independent animals and this independence makes them survivors.
Their teeth, their brain size, their legs, their chests, their nails, feet, tail, ears, coat are all designed to aid the wolf in surviving in the wild. In the classrooms I have taught the kids differences between our domestic bunny rabbits we have as pets and the wild jack rabbits. Jacks Rabbits (Hares) are *designed* with more exaggerated features their feet size and leg size for hopping faster and farther distances in one leap, their ear size for hearing predators better, the same thing can be said about wolves, they are exaggerated souped up canines (liken this comparison between a 3 cylinder car and a ferrari), and they are souped up for VERY specific reasons. I am honored to share their world, and never lose sight of the fact that their lessons are constant.
Sheri Gordon is a phenom artist check her out!
Please Note: We are not provincially, or federally funded. We work to support the outreach work, any programs, and the wolves out of our own pockets, NOT the other way around Through your sponsorship and buying wolf gifts from us, you are not supporting US the human caretakers, any funds ALWAYS 100% go towards future educational programs, & expansion/enrichment for the wolves only, we work jobs like everyone else to support ourselves. The wolves are not bred for profit, nor do we make a living off their lives. We believe if wild has to be in captivity, that they should have jobs to help their wild brethren via educating with their wild messages. We believe in keeping wild; wild and thus actively participate via partaking ourselves in, and financially supporting other worthy wildlife rehab organizations, & wildlife/habitat conservation organizations.


text:
Q: Can I declare a variable that is used in a line and discarded right after? Suppose I have this code:
int a = 1;
int b = 2;
string s = (a + b == 3 ? "3" : array[a + b]);

I would like to declare a "local" variable to store (a+b) so that I don't need to compute it twice. I imagine something like that:
int a = 1;
int b = 2;
string s = (c == 3 ? "3" : array[c]) where c = a + b;
//from now on, c doesn't exist anymore

I know where doesn't exist. I tried to use using var c = a + b but I don't think it's possible. Is there a way?

A: What you want to do reminds me of Kotlin's scope functions, specifically let. You can write an extension method for this:
static class ScopeFunctions
{
    public static U Let<T, U>(this T x, Func<T, U> func) => func(x);
}

Usage:
string s = (a + b).Let(x =>
    (x == 3 ? "3" : array[x])
);

x becomes the "'local' variable to store (a+b) so that I don't need to compute it twice" that you "discard right after", as x will be out of scope outside the lambda.

redpajama_set_name: RedPajamaStackExchange


I have won awards in 3 states and have been a cabinetmaker for 45 years. I have used many different brands over the years, nothing holds a candle to Porter Cable routers!!!! Nothing!
A really good deal. Couldn't be better.
CPO pricing and shipping were outstanding. This is a great router that belongs in every shop, hobbyist to professional.
I needed this router to start using my dovetail jig and now I'm cutting dovetails with ease.
I purchased the router mainly for dovetails and the Dhandle makes it excellent for that purpose and probably for other jobs. I also have a 3 1/2 H.P. Porter Cable Router and there is no stopping it. I highly recommend both for anyone who is considering purchasing a router. I was also pleased with how quick I received my purchase.
Great balance, easy to change bits, easy to dial in depth of cut, plenty of power for most things. I have three Porter Cable routers of this size and one big one, they are all great.
I love the D handle 691 router. My last one finally got too hard to tighten and I have to "trust" my settings as I work with expensive hardwoods in trim work and furniture. My last one went about 20 years. This new one has some minor improvements and I got it slightly cheaper than what I paid 20 years ago.
I have 5 routers. One is a production router, PC of course, and 3 other PC routers. I have liked to use the plunge features of the others machines, but the D-handle routers provides unparalleled control compared to any other. I use two routers for the routing of each of the pins and tails when dovetail routing. If you have never tried a D-handle router before, you will impressed with the control it offers. I love mine and can honestly recommend it to you.
Reconditioned Router which looks and runs like new. Love the D-Handle. Very easy to handle and control.
Will the Porter Cable 6931 plunge base fit this router?


text:
The Upload: Your tech news briefing for Thursday, ...
The Upload: Your tech news briefing for Thursday, April 23
Facebook's mobile traffic dominates... Google, Box step up enterprise tools... Russian malware targeted the White House
IDG News Service staff (IDG News Service) on 23 April, 2015 21:54
What if your whole online experience is just Facebook?
Facebook's mobile shift shows through in financial results
It doesn't seem so long ago that analysts were fretting over Facebook's mobile playbook, but now the social media giant is monetizing a user base that is increasingly on smartphones and tablets. In reporting its financial results Wednesday, it said that a solid majority of its advertising revenue for the first quarter came from users on mobile devices, the New York Times reports.
Facebook gives Android phones souped-up caller ID
Facebook wants to move even closer to the core functions of your Android smartphone, with a new dialer app called Hello that uses Messenger to call your friends. The company also says it can give you better security with enhanced call-blocking, and uses the Facebook database to identify callers, PC World reports.
Google, Box boost enterprise efforts
Google is stepping up its efforts make its Chrome browser and Chromebook computers central to the workplace, it said Wednesday. It will let Chromebook users access files stored on the Box cloud services as easily as they can access Google's own services. And for its part, Box wants to move beyond its legacy as a storage, sync and sharing service and toward its higher calling as a platform company, with a new Developer Edition that will allow enterprises to build applications on top of its service without using the Box user interface or requiring users to have a Box account.
...And Google rolls out Project Fi mobile phone service
As expected, Google took the wraps off its own-brand mobile phone service Wednesday, and it's an MVNO offering with a twist. Called Project Fi, it combines traditional wireless service from Sprint and T-Mobile with Wi-Fi, using about a million wireless hotspots, the New York Times reported. It's only available to users of Google's Nexus 6 phone, though, and costs $20 per month plus $10 per gigabyte of data.
Malware clues point to Russia in White House, State Department hacks
The hackers who got into White House and U.S. State Department systems last year used malware that bears strong similarities to cyberespionage tools suspected to be of Russian origin, say researchers from Kaspersky Lab. The malware has a lot in common with tools used to attack NATO members and European governments over the past two years; Moscow-based Kaspersky didn't say it, but others believe those tools are the work of the Russian government.
Comcast merger with Time Warner Cable hits a roadblock at the FCC
The planned merger of two behemoths in the U.S. broadband Internet access and cable TV markets has hit a snag: the Federal Communications Commission wants to hold hearings on whether the $45 billion deal is in the public interest, the Wall Street Journal reports. It said that the would-be partners also met on Wednesday with officials of the Justice Department, where there is concern about the effect on competition if one company controls 57 percent of the market for broadband Internet service and 30 percent of the pay-TV market.
Cyberthreat bill passes U.S. House vote
Legislation that encourages sharing of cyberthreat information passed the U.S. House in a 307 to 116 vote on Wednesday, despite concerns that the law could expose consumers' private information. The Protecting Cyber Networks Act shields companies from customer lawsuits when they voluntarily share data on hacks. Privacy advocates also have concerns about the National Cybersecurity Protection Advancement Act, which is scheduled for a vote on Thursday. If that passes as well, the two bills will be combined and sent on to the Senate.
Don't have a Tesla in the driveway? Put one in your house
Electric-car maker Tesla Motors knows something about battery technology, and now it's aiming to bring that to consumers and utilities in a new way. Next week it will announce battery lines aimed at those markets, to make it easier to store power from renewable sources like solar panels, Computerworld reports.
Fold is a new content management system from the MIT Media Lab that helps authors add context to their stories in a richer form than hyperlinks.
What's next for Moore's law on its 50th anniversary? Chip analyst David Kanter lays out some ideas for how Intel can keep up the growth in processor power.
More from ASUS
Tags mobilebusiness issuesGoogleFacebookintelsprintt-mobilecomcastComponentsTime Warner CableBoxTesla Motors
IDG News Service staff


Forrest Glenn Co-op in Spring Hill, Florida, is a resident-owned 55+ and very active adult community of Manufactured Homes and an Easy Life Style. We are in Hernando County, a major expanding part of Florida. No pets over 25 pounds or 17" tall. Option available to purchase share in park ownership for $35,000 or pay lot rental of $350 per month. The village was first built in the mid 90's under private ownership. Forrest Glenn is over 45 acres. The residents purchased the village in 2005. Paved streets, lawn service, boat and camper storage.