text:
\section{Introduction}

There are reasons to suspect that the vacuum in
quantum gravity may determine a preferred rest frame
at the microscopic level. However, if such a frame
exists, it must be very effectively concealed from
view. Numerous observations severely limit the
possibility of Lorentz violating physics among the
standard model fields~\cite{Mattingly:2005re}. The
constraints on Lorentz violation in the gravitational
sector are generally far weaker.

To allow for gravitational Lorentz violation without
abandoning the framework of general relativity (GR),
the background tensor field(s) breaking the symmetry
must be dynamical. Einstein-\ae ther theory is of this
type. In addition to the spacetime metric tensor field
$g_{ab}$ it involves a dynamical, unit timelike vector
field $u^a$. Like the metric, and unlike other
classical fields, the unit vector cannot vanish
anywhere, so it breaks local Lorentz symmetry down to
a rotation subgroup. It defines a congruence of
timelike curves filling all of spacetime, like an
omnipresent fluid, and so has been dubbed the ``\ae
ther". This paper aims to provide a review of what has
been learned about this theory, the status of
observational constraints, and some currently open
issues.

A primary motivation for studying Einstien-\ae ther
theory---``\ae -theory " for short---is the quantum
gravity suspicion mentioned above. A secondary aim is
to develop a viable and reasonably natural foil
against which to compare gravitational observations,
in an era when numerous alternate gravity theories
have already been either ruled out or severely
constrained. A third source of interest is the
theoretical laboratory it offers for studying
diffeomorphism invariant physics with preferred frame
effects.

The action involving metric and \ae ther is highly constrained
by diffeomorphism invariance, locality,
and the unit constraint on $u^a$.
The only term with no derivatives is
the cosmological constant, there are no terms with
one derivative (other than a total divergence),
and there are five terms with two derivatives,
\begin{equation} S = -\frac{1}{16\pi G}\int \sqrt{-g}~ (R+K^{ab}_{mn} \nabla_a
u^m \nabla_b u^n)~d^{4}x. \label{action} \end{equation}
Here $R$ is the Ricci scalar, and the tensor
$K^{ab}_{mn}$ is defined by
\begin{equation} K^{ab}_{mn} = c_1 g^{ab}g_{mn}+c_2\delta_m^a\delta_n^b
+c_3\delta_n^a\delta_m^b +c_4u^au^bg_{mn}, \end{equation}
where the $c_i$ are dimensionless
coupling constants.  Like general relativity,
pure classical \ae -theory
defined by this action is
scale-free.
(The metric signature is $({+}{-}{-}{-})$,
the speed of light defined by the metric $g_{ab}$
is unity, and the \ae ther is taken to be dimensionless.)
The term $R_{ab}u^au^b$ can be expressed as the
difference of the $c_3$ and $c_2$ terms, up to a total
derivative, so is not independent.
In computations the unit timelike constraint on the
\ae ther is usually
imposed by adding a Lagrange multiplier term
$\lambda(g_{ab}u^au^b-1)$ to the action.
The covariant derivative
operator $\nabla_a$ involves derivatives of the metric
through the connection components, and the unit
vector is nowhere vanishing, hence
the terms quadratic in
$\nabla_a u^m$ are quadratic in derivatives of
both \ae ther and metric perturbations, so the
metric and \ae ther modes are coupled.
The field equations are written out in detail
in many of the references, beginning with
Ref.~\cite{Eling:2003rd}. It is noteworthy that
the \ae ther stress tensor includes second derivative
terms arising from the variation of the metric in the
connections. In all phenomenology work to date, it has
been assumed that the \ae ther is aligned
at large
scales with the rest frame of the microwave background
radiation.

The restriction to no more than two derivatives is
motivated by the standard precepts of effective field
theory~\cite{Burgess:2003jk}: higher derivatives would
be suppressed by one power of a small length scale for
each extra derivative. The natural size of the
coupling constants $c_i$ depends on unknown physics at
high energies. If the Planck scale is the only
relevant scale then the $c_i$ are naturally all of
order unity. If on the other hand there is an
additional scale or scales characterizing the Lorentz
violating physics, then the $c_i$ might be naturally
smaller and could differ from each other in order of
magnitude. Note that although the $c_4$ term in the
action is quartic in the \ae ther field, it makes a
quadratic contribution to the kinetic terms for metric
and \ae ther perturbations when expanded around a flat
background with a constant \ae ther of unit norm.

Einstein-\ae ther theory is similar to the
vector-tensor gravity theories studied long ago by
Will and Nordvedt~\cite{willnord}, but with the
crucial difference that the vector field is
constrained to have unit norm. This constraint
eliminates a wrong-sign kinetic term for the
length-stretching mode~\cite{Elliott:2005va}, hence
gives the theory a chance at being viable. An
equivalent theory using the tetrad formalism was first
studied by Gasperini~\cite{Gasperini}, and in the
above form it was introduced by Jacobson and
Mattingly~\cite{Jacobson:2000xp}. Related
vector-tensor gravity theories are that of Kostelecky
and Samuel~\cite{Kostelecky:1989jw} which corresponds
to the Maxwell-like special case of \ae -theory
($c_3=-c_1$, $c_2=c_4=0$), both with a fixed norm and
with a symmetry breaking potential for the vector, of
Gripaios~\cite{Gripaios:2004ms} which has all
two-derivative terms and a symmetry breaking potential
for the vector, and the generalized Einstein-\ae ther
theories of Zlosnik, Ferreira and
Starkman~\cite{Zlosnik:2006zu} and of
Zhao~\cite{Zhao:2007ce}, in which the \ae ther kinetic
terms of (\ref{action}) are replaced by functions
thereof. Kanno and Soda~\cite{Kanno:2006ty} introduced
dependence of the coupling parameters on a scalar
field that has its own dynamics, and studied
inflationary cosmology for one such model. Other
theories involving scalar fields in addition to a
vector field with a Maxwell-like action for the vector
are Bekenstein's TeVeS~\cite{Bekenstein:2004ne} and
Moffat's STVG~\cite{Moffat:2005si}.

\subsection{Matter couplings}
Lorentz-violating (LV) effects in the matter sector
are produced by couplings of the matter to the \ae
ther. (More complicated Lorentz symmetry breaking
patterns require LV extensions of general relativity
with other symmetry breaking fields~\cite{Bluhm:2004ep}.) Such
effects have been highly constrained by
observations~\cite{Mattingly:2005re},
so if they exist they are very weak. In this review I
will therefore assume that matter couples universally
to the metric $g_{ab}$. This assumption is motivated
by phenomenology, but goes against the
precepts of effective field theory since the Lorentz
violation in the gravitational sector would presumably
induce Lorentz violating terms in the matter action
via loop effects. Supersymmetry could conceivably provide a
natural suppression of these terms, as discussed briefly
in section~\ref{Frontiers}.

\subsection{Metric redefinitions}

When investigating aspects of the theory that do not
involve matter, it can be helpful to exploit the
metric redefinition $g'_{ab} = g_{ab}+(\zeta-1) u_a u_b$,
which ``stretches" the metric tensor in the \ae ther
direction by a positive factor $\zeta$.
(A negative factor would return a Euclidean signature metric.)
The action (\ref{action})
for ($g'_{ab}$, $u'^a = u^a/\sqrt{\zeta}$) takes the same
form as that for ($g_{ab}$, $u^{a}$), with new
coefficients $c'_i$. The relation between the $c'_i$
and $c_i$ was worked out in~\cite{Foster:2005ec}, and
is conveniently given in terms of certain combinations
with simple scaling behavior:
\begin{eqnarray}
c'_{14} &=& c_{14}\nonumber\\
c'_{123} &=& \zeta c_{123}\nonumber\\
c'_{13}-1 &=& \zeta (c_{13}-1)\nonumber\\
c'_1-c'_3-1 &=& \zeta^{-1}(c_1-c_3-1). \label{redef} \end{eqnarray}
Note that in the absence of matter couplings
a one-parameter set of
Einstein-\ae ther theories is actually
pure vacuum GR in disguise~\cite{BarberoG.:2003qm,Foster:2005ec}:
the parameters
$c_i'$ all vanish if $c_{14}=c_{123}=2c_1-c_1^2+c_3^2=0$,
and $\zeta>0$ provided $c_{13}<1$.

\section{Newtonian and post-Newtonian limits}
\label{NPN}

In the weak-field, slow-motion limit \ae -theory
reduces to Newtonian gravity~\cite{Carroll:2004ai},
with a value of  Newton's constant $G_{\rm N}$ related
to the parameter $G$ in the action (\ref{action})  by
\begin{equation} G_{\rm N}=\frac{G}{1-c_{14}/2}, \label{GN}\end{equation}
where $c_{14}\equiv c_1+c_4$. (Similar notation is  used below for
other additive combinations of the $c_i$.) As long as  $c_{14}<2$,
the Newtonian limit is thus recovered. If $c_{14}>2$ gravity is
repulsive. This suggests the possibility of resolving
singularities by anti-gravity if the coupling coefficients $c_i$
were not constants~\cite{Gasperini}. Here I discuss only the
theory with constant coefficients.

All parameterized post-Newtonian (PPN)
parameters~\cite{willLR} of ae-theory except the
preferred frame parameters $\alpha_{1,2}$ agree with
those of GR for any choice of the $c_i$.  In
particular, the Eddington-Robertson-Schiff parameters
$\beta$ and $\gamma}\def\G{\Gamma$ are both unity~\cite{Eling:2003rd}, the
Whitehead parameter $\xi$
vanishes~\cite{Foster:2005dk}, and the five
energy-momentum conservation parameters $\alpha_3,
\zeta_{1,2,3,4}$ vanish simply because the theory is
derived from a lagrangian. The parameter $\alpha_2$ was
found for small $c_i$ in~\cite{Graesser:2005bg}, and
the exact values of $\alpha_1$ and $\alpha_2$ were found
in~\cite{Foster:2005dk}:
\begin{eqnarray}
    \alpha_1&=& \frac{-8(c_3^2 + c_1c_4)}{2c_1 - c_1^2+c_3^2}\label{alpha1}\\
    \alpha_2&=&\frac{\alpha_1}{2}
    -\frac{(c_1+2c_3-c_4)(2c_1+3c_2+c_3+c_4)}{c_{123}(2-c_{14})}\label{alpha2} \end{eqnarray}
(This particular way of expressing $\alpha_2$ was given
in~\cite{Foster:2006az}.) In deriving the PPN parameters,
the $00$-component of the metric perturbation and the
$0$-component of the aether perturbation are expanded
to $O(2)$ in the Newtonian potential, while the
$0i$-components of the metric and $i$ components of
the aether are truncated at their lowest order,
$O(1.5)$.\footnote{The 0-component of the
aether is expanded explicitly only to $O(1)$
in Ref.~\cite{Foster:2005dk},
but the contribution of the $O(2)$ part is
implicitly incorporated by use of the identity (A.26).}

Observations currently impose the strong constraints
$\alpha_1 \lesssim 10^{-4}$ and $\alpha_2\lesssim 4\times
10^{-7}$~\cite{willLR}. Since \ae -theory has four
free parameters $c_i$, we may set $\alpha_{1,2}$
exactly to zero by imposing the
conditions~\cite{Foster:2005dk}
\begin{eqnarray}
 c_2&=&(-2c_1^2-c_1c_3 + c_3^2)/3c_1 \label{zeroalphac2}\\
 c_4&=&-c_3^2/c_1 \label{zeroalphac4}.
\end{eqnarray}
 With
(\ref{zeroalphac2}, \ref{zeroalphac4}) satisfied, {\it all} the PPN
parameters of \ae -theory are equivalent to those of GR.

The
parameters $\alpha_{1,2}$ can also be set to zero by imposing
$c_{13}=c_{14}=0$, but this case is pathological, as discussed in
section \ref{special}.  Also discussed there is the case $c_{123}=0$,
for which $\alpha_2$ can diverge. Another special case occurs
when $2c_1-c_1^2 -c_3^2=0$, for which $\alpha_1$ diverges unless
also $c_3^2+c_1c_4=0$ in which case it is indeterminate.
Together these imply $c_{14}=2$, so
Newton's constant (\ref{GN}) diverges in this case.

\section{Homogeneous isotropic cosmology}

Assuming spatial homogeneity and isotropy, $u^a$
necessarily coincides with the 4-velocity of the
isotropic observers, and automatically satisfies its
field equation. The \ae ther stress tensor is
constructed purely form the spacetime geometry and is
identically conserved. It is just a certain
combination of the Einstein tensor and the stress
tensor of a perfect fluid with energy density
proportional to the inverse square of the scale
factor, like the curvature term in the Friedman
equation~\cite{Mattingly:2001yd,Carroll:2004ai},
\begin{equation} T^{\mbox{\scriptsize \ae ther}}_{ab}= -\frac{c_{13}+3c_2}{2}
\Bigl[G_{ab}-\textstyle{\frac16}{}^{(3)}R(g_{ab}+2u_au_b)\Bigr].
\end{equation}
The latter contribution plays no important
cosmological role since the spatial curvature is
small, while the former renormalizes the gravitational
constant appearing in the Friedman equation,
yielding~\cite{Carroll:2004ai}
\begin{equation} G_{\rm cosmo}=\frac{G}{1+(c_{13}+3c_2)/2}. \end{equation}
Since $G_{\rm cosmo}$ is not the same as $G_{\rm N}$
the expansion rate of the universe differs from what
would have been expected in GR with the same matter
content. The ratio is constrained by the observed
primordial ${}^4$He abundance to satisfy $|G_{\rm
cosmo}/G_{\rm N} - 1|\lessim1/8$~\cite{Carroll:2004ai}. When
the PPN parameters $\alpha_{1,2}$ are set to zero by
(\ref{zeroalphac2}, \ref{zeroalphac4}), it turns out
that $G_{\rm cosmo}=G_{\rm N}$, so this
nucleosynthesis constraint is automatically
satisfied~\cite{Foster:2005dk}.

\section{Linearized wave modes}
\label{modes}

When linearized about a flat metric and constant \ae
ther, \ae -theory possesses five massless modes for
each wave vector: two spin-2, two spin-1, and one
spin-0 mode. The squared speeds of these modes
relative to the \ae ther rest frame are given
by~\cite{Jacobson:2004ts}
\begin{eqnarray}\label{speeds}
\mbox{spin-2}\qquad&&1/(1-c_{13})\label{s2}\\
\mbox{spin-1}\qquad&&(2c_1- c_1^2+
c_3^2)/2c_{14}(1-c_{13})\label{s1}\\
\mbox{spin-0}\qquad&&c_{123}(2-c_{14})/c_{14}(1-c_{13})(2+c_{13}+3c_2)\label{s0}
\end{eqnarray}
The corresponding polarization tensors were found in
one gauge in Ref.\ \cite{Jacobson:2004ts} and in
another gauge in Ref.\ \cite{Foster:2006az}. The
former gauge choice for the metric and \ae ther
perturbations $h_{ab}$ and $v^a$ is $h_{0i}=0$ and
$v^i\!,\!{}_{i}=0$. In this gauge the nonzero components of
the polarization for waves in the 3-direction are
given by
\begin{eqnarray}\label{pols}
\mbox{spin-2}\qquad&&h_{12},\quad h_{11}=-h_{22}\label{pol2}\\
\mbox{spin-1}\qquad&&v_I,\quad h_{3I}= \left[
{2c_{14}c_{13}^2}/{(2c_1- c_1^2+
c_3^2)}\right]^{1/2}\, v_I\label{pol1}\\
\mbox{spin-0}\qquad&& v_0,\quad h_{00}=-2v_0,\quad
h_{11}=h_{22}=-c_{14}v_0,\qua
h_{33}=[2c_{14}(1+c_2)/c_{123}]\, v_0,
\label{pol0}\end{eqnarray}
where the index $I$ takes only the transverse values
$1,2$.

The energy of the spin-2 modes is always positive,
while for the spin-1 modes it has the sign of $(2c_1
-c_1^2 +c_3^2) /(1-c_{13})$, and for the spin-0 modes
it has the sign of
$c_{14}(2-c_{14})$~\cite{Eling:2005zq,Foster:2006az}.
(These reduce to the results of Ref.\
\cite{Lim:2004js} in the decoupling limit where
gravity is turned off.) Under the metric redefinition
$g_{ab}\rightarrow g_{ab}+(\zeta-1)u_au_b$, (\ref{redef})
can be used to verify that the squared speeds all
scale as $1/\zeta$ as expected, and the signs of the
energy are invariant.

Several constraints are imposed by stability
conditions on the linearized modes. The squared speeds
correspond to (frequency/wavenumber)${}^2$, so must be
non-negative to avoid imaginary frequency
instabilities. They must moreover be greater than or
equal to unity, to avoid the existence of vacuum
\v{C}erenkov radiation by
matter~\cite{Elliott:2005va}. (The existence of ultra
high energy cosmic rays, which propagate near the
metric light cone, requires that the metric and \ae
ther modes propagate at no less than an extremely
small amount below the metric speed of light.) And the
mode energy densities should be positive, to avoid
dynamical instabilities.

With the $\alpha_{1,2}=0$ conditions
(\ref{zeroalphac2}, \ref{zeroalphac4}) imposed, the squared speeds
expressed in terms of $c_\pm\equiv c_1\pm c_3$ are
\begin{eqnarray}\label{zaspeeds}
\mbox{spin-2}\qquad&&1/(1-c_+)\\
\mbox{spin-1}\qquad&&(c_++c_--c_+c_-)(c_++c_-)/4c_+c_-(1-c_+)
\label{s1za}\\
\mbox{spin-0}\qquad&&c_+/3c_-(1-c_+), \end{eqnarray}
the sign of the spin-1 mode energy is that of
$(c_++c_--c_+c_-)/(1-c_+)$, and $c_{14}=2c_+c_-/(c_++c-)$. The
conditions that the squared spin-2 and spin-0 mode speeds be
greater than or equal to unity then restrict $c_\pm$ to the region
\begin{eqnarray}\label{superluminal}
0&\le& c_+\le1\label{sl1}\\
0&\le& c_-\le c_+/3(1-c_+).\label{sl2} \end{eqnarray}
Some algebra shows that the inequalities $0\le
c_+\le1$ and $0\le c_-$ also ensure that the squared
spin-1 mode speed (\ref{s1za}) is also greater than or
equal to unity. They also imply $0\le c_{14}<2$, hence
the condition for attractive gravity mentioned in
section \ref{NPN} need not be separately imposed. Also
the energies of the spin-0 and spin-1 modes are then
positive. That is, when $\alpha_{1,2}=0$ all of the
requirements for all of the modes are met and gravity
is attractive if and only if  and $c_\pm$ are
restricted by the inequalities (\ref{sl1},
\ref{sl2})~\cite{Foster:2005dk}. The allowed range is
the shaded region in Fig.~1
\begin{figure}[htb]\label{c+c-plane}
\begin{center}\hspace{-1.2cm}
\includegraphics[width=4in]{c+c-plane}
\end{center}
\caption {The shaded region
satisfies the stability, \v{C}erenkov, and positive energy
constraints (\protect\ref{sl1}, \protect\ref{sl2}) on $c_\pm$ after
having imposed the vanishing
of the PPN parameters $\alpha_{1,2}$ by the conditions
(\protect\ref{zeroalphac2}, \protect\ref{zeroalphac4}).
The dashed curve is the locus where the
net radiation power from a source with
weak self-field matches that of GR. The four dotted curves
are contours of fixed $c_{14}$.}
\end{figure}

Interestingly, if the mode speeds are instead required to be {\it
less} than unity (sub-luminal), then the spin-1 and spin-0 energy
densities are negative. Hence not only the \v{C}erenkov
constraint, but also energy positivity (together with
$\alpha_{1,2}=0$) requires mode speeds greater than unity.

\section{Primordial perturbations}

The behavior of primordial cosmological perturbations
in ae-theory has been studied in
Refs. \cite{Lim:2004js,Li:2007vz}. The coupling to the
\ae ther modifies the spin-2 perturbations in two
ways: it changes their propagation speed, as already
discussed above for perturbations of flat space, and
it changes their amplitude, since that is determined
by the ``bare" $G$ in the action (\ref{action}) rather
than by the measured Newton constant $G_{\rm N}$. The
result is that, given the same $G_{\rm N}$,  and
assuming the PPN parameters $\alpha_{1,2}$ vanish, the
power in these perturbations differs from that in GR
by the factor $(1-c_{14}/2)(1-c_{13})^{1/2}$. When the
stability constraints (\ref{sl1}, \ref{sl2}) are
satisfied this factor is smaller than unity, hence
these spin-2 perturbations are even more difficult to
detect than in GR.

Perturbations of the \ae ther can be decomposed into
spin-0 and spin-1 modes, both of which decay by
themselves as the universe expands. In the presence of
a scalar inflaton, however, the spin-0 \ae ther mode
is sourced and no longer decays away. For single
scalar field slow-roll inflation, it turns out that
the power spectrum is generally modified, but it is
unchanged when the PPN parameters vanish.

The late time evolution of the primordial
perturbations is modified, since anisotropic photon
and neutrino stresses in the radiation dominated epoch
source the spin-1 mode. This leads to modified matter
and CMB spectra~\cite{Li:2007vz}. The effect is rather
small however, and is degenerate with matter-galaxy
bias and with neutrino masses.

Primordial perturbations are thus difficult to distinguish in
ae-theory and GR.

\section{Radiation damping and strong self-field effects}

Two-body dynamics and radiation in ae-theory have been
analyzed for purely weak fields in
Ref.~\cite{Foster:2006az}, and including strong self
gravity effects in Ref.~\cite{Foster:2007gr}. In
general the radiation includes not only spin-2 waves
sourced by a varying quadrupole moment, but also
spin-1 waves sourced by quadrupole and dipole moments
and spin-0 waves sourced by quadrupole, dipole, and
monopole moments. As seen in section \ref{modes}, the
waves of different spin propagate in general at
different speeds relative to the \ae ther rest frame.
Direct observation of all of these waves is in
principle possible with existing gravitational wave
antennas~\cite{willLR}. With waves of sufficient
amplitude from multiple sources, and a network of
detectors, the \ae ther rest frame and the wave speeds
(\ref{s2})-(\ref{s0}) and polarizations
(\ref{pol2})-(\ref{pol0}) could all be measured.

\subsection{Weak fields}
If the fields are weak everywhere (including inside
the radiating bodies),
 and
the PPN parameters $\alpha_{1,2}$ vanish, then the dipole
source vanishes and the monopole source is uncoupled
to the fields. In this regime therefore all radiation
is sourced by the quadrupole, as in GR. The net power
radiated in spin-0, spin-1, and spin-2 modes in this
case is given by $(G_{\rm N} {\mathcal
A}/5)\dddot{Q}_{ij}^2$, where $Q_{ij}$ is the
quadrupole moment and
 ${\mathcal A}={\mathcal A}[c_i]$ is a
 function of the coupling parameters $c_i$
that reduces to unity in the case of GR. Agreement
with the damping rate of GR (confirmed to $\sim 0.1\%$
in binary pulsar systems~\cite{willLR}) can be
achieved by imposing the condition ${\mathcal
A}[c_i]=1$, which is consistent with the constraints
(\ref{sl1}, \ref{sl2}), as shown by the dashed line in
Fig.~1

\subsection{Strong field effects}
For compact sources with strong internal fields such
as neutron stars or black holes, terms of higher order
in $Gm/d$ (where $m$ and $d$ are the mass and
characteristic size of the source) can play an
important role in the dynamics and radiation. Since
background fields and radiation fields vary little
over compact source dimensions, these strong field
effects can be handled using an ``effective source"
dynamics specified by a worldline action
integral~\cite{Foster:2007gr}
\begin{equation} S=-m_0\int d\tau\; [1
+\sigma(v^au_a-1)+\sigma'(v^au_a-1)^2+\dots],
\label{effectiveaction} \end{equation}
where $v^a$ is the 4-velocity of the body, $u_a$ is
the local background value of the \ae ther, and $\sigma$
and $\sigma'$  are a constants characterizing the body,
called a ``sensitivity parameters" or just
``sensitivities". A similar technique was introduced
by Eardley~\cite{Eardley} for scalar-tensor gravity,
in which the first sensitivity measures the dependence
of the action on the local background value of the
scalar field. The ellipses in (\ref{effectiveaction})
stand for all other invariants that can be formed from
the particle worldline and the background fields. All
of these are of higher order in the velocity relative
to the \ae ther or involve more derivatives and are
hence suppressed. Among other things, the
sensitivities determine the dependence of energy on
velocity, $E=m_0 + {\textstyle{\frac{1}{2}}} (1+\sigma)m_0v^2
+\textstyle\frac38(1+\sigma-\sigma')m_0v^4+\dots$. (This is
obtained by expressing the action
(\ref{effectiveaction}) in the form $\int dt (T-V)$
where $V=m_0$, and reading off $E=T+V$.) At lowest
order in binding energy $\Omega$, $\sigma$ is given by
\begin{equation} \sigma= (\alpha_1-\textstyle{\frac{2}{3}}\alpha_2)(\Omega/m)
+ \mathcal{O}\Bigl(f[c_i](G_{\rm N}m/d)^2\Bigr), \end{equation}
where $f[c_i]$ scales as $c_i$ for
$c_i\ll1$.\footnote{This corrects an error in version
1 of Ref.\ \cite{Foster:2007gr}, where $\sigma$ is said to
scale as $c_i^2$. (Also the a prefactor $c_{14}$ in
Eqn. (70) should be deleted.) As a result of this
correction, the likely constraints on $c_i$ are an
order of magnitude stronger, as stated
here~\cite{bzf-pc}.} Note that the leading term
vanishes when $\alpha_{1,2}$ vanish. The higher order
terms in $\sigma$ have not yet been computed, nor have
even the lowest order terms in $\sigma'$ (which will also
scale as $c_i$). They presumably differ for black
holes and stars, and will depend on the equation of
state of the star.

Nonzero sensitivities lead to a number of
phenomena that are constrained by observations,
including dependence of dynamics on the ambient
\ae ther vector,
modified post-Newtonian
two-body dynamics, modified quadrupole sourced
radiation, and both monopole and dipole sourced
radiation. When $\alpha_{1,2}=0$, all of these constraints
are met provided the sensitivities are less than $\sim
0.001$, which will certainly be the case if
$c_i\lesssim 0.01$~\cite{Foster:2007gr}. To be more
precise would require knowing the actual dependence of
the sensitivities on the $c_i$. It is conceivable that
the constraints will be much weaker.

To determine the strong field constraints just
mentioned, it is necessary to make some assumption
about the speed $V$ of the observed systems with
respect to the background \ae ther frame.  It was
argued in Ref.~\cite{Foster:2007gr} that neglect of
terms involving this speed is justified provided
$V\lesssim 10^{-2}$, which is easily satisfied for any
known proper motion relative to the rest frame of the
microwave background radiation.

\section{Spherically symmetric stars and black holes}

Unlike GR, \ae -theory has a spherically symmetric
mode, corresponding to radial tilting of the \ae ther, and
there is a three-parameter family of
spherically symmetric static vacuum solutions~\cite{Eling:2006df}.
If asymptotic flatness is imposed and the mass
fixed, there remains a one-parameter
family~\cite{Eling:2003rd,Eling:2006df}, whereas
GR has the unique Schwarzschild solution.
As explained below, the evidence suggests that
only two solutions in this one-parameter family
are astrophysically relevant,
at least provided the couplings are not too large.

The total energy of an asymptotically flat
solution of \ae -theory
receives a contribution from the asymptotic
$1/r$ falloff of the
\ae ther~\cite{Eling:2005zq,Foster:2005fr}.
The \ae ther normalization condition locks this
contribution to that of the metric, so the energy can be
expressed in terms of the metric alone.
It turns out
to be just $E=r_0/G_{\rm N}$, where
$r_0$ is the coefficient of the $1/r$ term in
the $g^{rr}$ inverse metric component\footnote{This
is the asymptotic Misner-Sharp energy~\cite{Hayward:1994bu},
covariantly defined by
$r_0=\lim_{r\rightarrow\infty} (r/2)(1-g^{ab}r_{,a}r_{,b})$,
where $r$ is the area radius.}
and $G_{\rm N}$ is Newton's constant (\ref{GN}).
That is, it agrees with the Newtonian mass in the
Newtonian limit, which is inevitable given that the
theory has a Newtonian limit.  This is how the mass of the
solutions discussed below is determined.

\subsection{Static vacuum \ae ther}
The solution outside a static star is the unique
vacuum solution for a given mass in which the \ae ther
is aligned with the Killing
vector~\cite{Eling:2006df}. This ``static \ae ther"
vacuum solution depends on the $c_i$ only through the
combination $c_{14}$, and was found analytically (up
to inversion of a transcendental
equation)~\cite{Eling:2006df}. It has a globally
timelike Killing vector, and is asymptotically flat.
The spatial slices have a minimal area 2-sphere,
inside of which the 2-spheres flare out to infinite
area at a singularity on a would-be Killing horizon
with vanishing surface gravity. The affine parameter
distance to the singularity is finite along radial
null geodesics. (The minimal two sphere is a property
of the vacuum solution only; it never occurs in the
presence of a matter source.) Although this static
wormhole indicates the presence of a negative
effective energy density in the field equation (i.e.
the Einstein tensor has this property), all solutions
in this family have positive total mass. In
Ref.~\cite{Seifert:2007fr} it was found that this
static \ae ther solution is stable to linear
perturbations under the same conditions as for flat
spacetime, with the exception of the case $c_{123}=0$.

\subsection{Neutron stars}

The solution inside a fluid star has been found by
numerical integration, both for constant
density~\cite{Eling:2006df} and for realistic neutron
star equations of state~\cite{Eling:2007xh}. The
maximum masses for neutron stars range from about 6 to
15\% smaller than in GR when $c_{14}=1$, depending on
the equation of state. The corresponding surface
redshifts can be as much as 10\% larger than in GR for
the same mass. Measurements of high gravitational
masses or precise surface redshifts thus have the
potential to yield strong joint constraints on
$c_{14}$ and the equation of state.

Sufficiently compact stars can have around them an
innermost stable circular orbit (ISCO), which occurs
in the Schwarzscild solution of GR at the radius
$6G_{\rm N}M$. The ISCO in the static \ae ther
solution lies at a radius larger by approximately the
factor $(1+0.03\, c_{14})$, with orbital frequency
lower by the factor $(1-0.04\, c_{14})$. These small
differences would likely be difficult to measure in
practice.

\subsection{Black holes}
For black holes the \ae ther cannot be aligned with
the Killing vector, since the latter is not timelike
on and inside the horizon. Instead, the \ae ther is at
rest at spatial infinity and flows inward at finite
radii. The condition of regularity at the spin-0
horizon (where the outgoing spin-0 waves propagate at
constant radius) selects a unique solution from the
one-parameter family of spherical stationary solutions
for a given mass~\cite{Eling:2006ec}. This is because
the coefficient of the second radial derivative term
in a field equation vanishes at the spin-0 horizon,
which forces the second derivative to blow up unless
the rest of the terms also vanish. Generically this
regularity condition does not hold, but the solution
can be tuned to satisfy it. When a black hole forms
from collapse of matter, the spin-0 horizon develops
in a nonsingular region of spacetime, where the
evolution should be regular. This motivated the
conjecture that collapse produces a black hole with
nonsingular spin-0 horizon, which has been confirmed
for some particular examples in numerical simulations
of collapse of a scalar field~\cite{Garfinkle:2007bk}.

The black holes with nonsingular spin-0 horizons are
rather close to Schwarzschild outside the horizon for
a wide range of couplings; for instance, the ISCO
radius differs by a  factor $(1 + 0.043 c_1 + 0.061
c_1^2)$, in the case with $c_3=c_4=0$ and $c_2$ fixed
so that the spin-0 speed is unity~\cite{cte-pc}. (This
expansion is accurate at least when $c_1\le0.5$. No
solution with regular spin-0 horizon exists in this
case when $c_1 \; \raisebox{-.8ex}{$\stackrel{\textstyle >}{\sim}$}\; 0.8$.) Inside the horizon the
solutions differ more, but like Schwarzschild they
contain a spacelike singularity. Black hole solutions
with singular spin-0 horizons have been studied in
Ref.\ \cite{Tamaki:2007kz}. These solutions can differ
much more outside the horizon. Quasi-normal modes of
black holes in \ae -theory have been investigated in
Refs.\ \cite{Konoplya:2006rv}.

\section{Special values of $c_i$}
\label{special}

It would be interesting if there existed a symmetry of
the action restricting the values of the coupling
parameters $c_i$, but none has been identified. Values
for which the PPN parameters $\alpha_{1,2}$ vanish
evidently lead to more symmetry in the weak field
limit, but this does not appear to extend to a
symmetry of the full theory.  A microscopic theory
might predict a particular relation or hierarchy
between the coefficients, but no such theory is
in hand. Hence any prior imposition
of restrictions would be unjustified.
Nevertheless, we
may ask from a purely phenomenological perspective
whether some simplifying restrictions could be
compatible with observations. The answer is negative.
It appears that, unless {\it all} of the parameters
are much smaller than unity, then
in order to be compatible with all of
the theoretical and observational constraints (leaving
aside the radiation reaction and strong self-field effects),
most likely {\it none} of the $c_i$, nor $c_{13}$,
$c_{14}$, or $c_{123}$ can vanish. We now discuss
these special cases in some detail.

\begin{itemize}

\item The first case to be examined in
detail~\cite{Kostelecky:1989jw,Jacobson:2000xp} was
$c_{13}=c_2=c_4=0$, i.e.\ the ``Maxwell action" (with
the unit constraint on the vector). The PPN result for
$\alpha_2$ (\ref{alpha2}) is infinite in this case, and
the spin-0 mode speed is zero. The perturbation series
used in the PPN analysis is thus evidently not
applicable. Independently of that, however, other
problems with this case have been identified, such as
the formation of shock
discontinuities~\cite{Jacobson:2000xp,Clayton:2001vy}
and a possibly related
instability~\cite{Seifert:2007fr}.
This case is equivalent to Maxwell theory
in a special gauge if
it is further restricted to the sector in which the
Lagrange multiplier field vanishes (see
~\cite{Nambu68, Jacobson:2000xp,
Chkareuli:2007da,Bluhm:2007bd} and references therein).
However, this equivalence
holds only if one abandons the notion that the vector
is itself physical. The shock discontinuities and
instabilities of the vector can then be regarded as
gauge artifacts, but the theory is no longer
that of a Lorentz-violating vector field.

\item The mode speeds (\ref{speeds}) are all equal to unity
if
$c_{13}=c_4=0$ and $c_2=c_1/(1-2c_1)$.
In this case the PPN parameters
become $\alpha_1=-4c_1$ and $\alpha_2=0$,
so the observational
constraint on $\alpha_1$
imposes the stringent condition
$|c_1|\lesssim 2.5\times 10^{-5}$, and the other
parameters are then similarly small.
Positivity of the spin-1 and spin-0 mode energies
imposes $0<c_1<1$. With small positive $c_1$, the
remaining constraints can be satisfied as well.

\item The case $c_1=c_3=0$ is evidently not
covered by the existing PPN analysis, since $\alpha_1$
(\ref{alpha1}) is indeterminate and the spin-1 mode
speed is zero. (If $c_2=0$ then also the spin-0 speed
vanishes. If $c_4=0$ then the spin-1 speed is
indeterminate and the spin-0 speed is infinite, but
the energy of both modes is zero.) It
appears that the post-Newtonian order of some field
quantities must be modified in this case, which could
be interesting to examine ab initio.

\item Assuming that (i) $\alpha_{1,2}=0$,   (ii) the
speed constraints
(\ref{sl1}, \ref{sl2}) are satisfied, (iii) the spin-1 mode
speed (\ref{s1}) is not infinite with finite energy,
and  (iv) putting aside the case
$c_1=c_3=0$ which is not covered by existing
PPN analyses, the only viable
case in which {\it any} of $c_i$,
$c_{13}$, $c_{14}$, or $c_{123}$ vanishes is
the special case
$c_3=c_4=2c_1+3c_2=0$, with $2/3<c_1<1$.
This large value of $c_1$
is probably inconsistent with the strong field constraints from
orbital binaries, but as mentioned above those are not yet
precisely known because the sensitivity parameters have not yet
been computed for neutron stars, so this case is not yet ruled
out. All the other special cases contradict one or more of
the conditions (i)-(iv), which can be seen as follows.
We halt when a case is reduced to a previous case.

\begin{itemize}

\item $c_1=0$:  $\alpha_1=0$ then implies also $c_3=0$. As stated above,
the case $c_1=c_3=0$ requires a new analysis.

\item $c_{13}=0$: The speed constraint (\ref{sl2}) then implies
also $c_-=0$, so $c_1=c_3=0$.

\item  $c_{14}=0$: $\alpha_1=0$  then implies $c_3^2= c_1^2 $, so either
$c_+ = 0$ or $c_- = 0$. In either case, the spin-1 speed diverges
unless $c_1=0$.

\item $c_{123}=0$: The denominator of the second term in
$\alpha_2$ vanishes (\ref{alpha2}), so either $\alpha_2$ diverges
or,  if the numerator also vanishes, it is indeterminate.
When $\alpha_1=0$, $\alpha_2$ becomes
\begin{equation}
\alpha_2=-\frac{c_{13}^2(3c_1c_{123}-c_{13}^2)}{c_1^2c_{123}(2-c_{14})},
\end{equation}
so the numerator vanishes in this case only if $c_{13}=0$.
(This also implies $c_{14}=0$.)

\item $c_2=0$: $\alpha_{1,2}=0$ implies (\ref{zeroalphac2}),
which can be written as
\begin{equation}
c_2  = -c_+(c_+ + 3c_-)/6c_1.
\label{za2'}
\end{equation}
Thus either $c_+ = 0$ (covered above) or
$c_+ + 3c_- = 0$. In the latter case,  either $c_+$ or
$c_-$ is negative, violating the speed constraints.

\item $c_3=0$: $\alpha_1=0$ implies $c_1=0$ (covered above) or
$c_4=0$. In the latter case,   (\ref{zeroalphac2}) or (\ref{za2'})
then implies that $2c_1 + 3c_2=0$.

\item $c_4=0$:  $\alpha_1=0$ then implies $c_3=0$.

\end{itemize}

\end{itemize}

\section{Frontiers}
\label{Frontiers}

A number of questions remain open regarding phenomenology
of \ae -theory, as well as more fundamental issues. In this
section some of these are briefly outlined.

\begin{itemize}

\item The most pressing issue is to compute the
sensitivity parameters for neutron stars and black
holes, so that strong field effects on radiation
damping rates, waveforms, and post-Newtonian dynamics
can be evaluated. To determine the sensitivities for a
given compact object one might compute (presumably
numerically) the exact solution for the object moving
at some velocity with respect to the asymptotic
aether, and match e.g.\ multipole moments of the
asymptotic fields to those of the corresponding
solution derived from the worldline action
(\ref{effectiveaction}). It may be adequate to solve
for linear perturbations of the exact, static
solutions, rather than finding the exact moving
solutions, but this may not be any more convenient.

\item Spherical collapse of a star to a black hole
would be accompanied by a pulse of spin-0
radiation, since the \ae ther must adjust from the
static configuration (parallel to the Killing vector)
to the black hole configuration (flowing across the
horizon). This radiation may be much stronger than
that of ordinary gravitational waves arising from
asphericity of supernova core collapse. Moreover, it
could in principle be measured by gravitational wave
detectors, as seen from the polarization components
(\ref{pol0}).

\item  Rapidly rotating black holes,
unlike the non-rotating ones, might turn out to be
very different from the Kerr metrics of GR. If so,
this could provide an interesting observational
signature to detect or constrain. It may be that the
easiest way to determine such solutions would be by
numerical simulation of axisymmetric collapse.

\item Although the linear perturbations all
have positive energy for
coupling parameters within in a certain range,
the total, nonlinear energy has not been
shown to be always positive in this range.
(The positive energy theorem of GR does not
apply since the
\ae ther stress tensor does not satisfy the
dominant energy condition.)
Even a spherically
symmetric result in this regard would be useful. The
question of energy positivity was addressed in
Ref.~\cite{Clayton:2001vy}, but attention was
restricted there to the case where the coupling to
gravity is neglected, and only some special cases were
examined.

\item Supersymmetry could potentially allow for a naturally
suppressed Lorentz violation in the matter
sector~ \cite{GrootNibbelink:2004za}.
To include gravity in such a
scheme would require a Lorentz violating supergravity.
Can \ae -theory be supersymmetrized?
The argument~\cite{Deser:1977hu} that supergravity
has positive energy and therefore so must GR would
presumably extend to
\ae -theory. Therefore, supersymmetrizability is
likely only possible at most for
those parameter ranges for which
\ae -theory has positive energy.

\item
Black hole thermodynamics remains a puzzle  in \ae
-theory. It has not been possible to identify the
entropy and a corresponding ``first law" of black hole
mechanics, despite the existence of an identity
relating mass and angular momentum variations to a
horizon integral~\cite{Foster:2005fr}. The difficulty
is related to the fact that the \ae ther necessarily
diverges at the bifurcation surface, so the methods
usually employed~\cite{Wald:1993nt} are not applicable.
One might expect that the problem is related to the fact
that, in a theory with multiple limiting speeds, no
unique horizon is selected. However, even for the
cases mentioned in section \ref{special} for which the
mode speeds are all equal to unity, the entropy has
not yet been identified.

A further important issue is the status of the
generalized second law of thermodynamics. It has been
argued that in a theory with more than one limiting
speed, both quantum Hawking
radiation~\cite{Dubovsky:2006vk} and classical energy
extraction~\cite{Eling:2007qd} methods can be
exploited to violate the generalized second law of
thermodynamics. This suggests that there may be some
deep problem with such theories, including ae-theory
(with unequal mode speeds).

\item Lorentz-violating matter fields can be consistently
coupled to gravity using \ae -theory. In this way
gravitational back-reaction of such fields is well
defined. This has been studied in a cosmological
setting~\cite{Jacobson:2000gw}, and the issue of
renormalization of the corresponding quantum stress tensor has
recently been seriously tackled~\cite{Lopez Nacir:2007jx}.
Counter-terms renormalizing the \ae -theory action are
generally required. Such analyses should enable the
quantum back reaction to cosmological expansion as
well as to Hawking radiation to be studied.

\item Quantization of ae-theory may be instructive to
investigate. The dynamical unit timelike vector field
determines a time flow with respect to which evolution
can be referred.  This ``material reference system"
could perhaps be
employed~\cite{Brown:1994py,Brown:1995fj} to address
the ``problem of
time"~\cite{Isham:1992ms,Kuchar:1999br} in canonical
quantum gravity.

\item Vacuum ae-theory in 1+1 dimensions might provide
a useful simplified model for studying quantum
effects. The classical theory has been
investigated~\cite{Eling:2006xg}, where the full
solution space was mapped out. The solutions include
de Sitter and anti-de Sitter spacetimes, with a
uniformly accelerated \ae ther that is invariant under
a two-dimensional subgroup of SO(2,1) generated by a
boost and a null rotation. (The \ae ther becomes
infinitely stretched on certain Killing horizons in
these solutions.) The only other solution is a
peculiar one with singularities and no Killing
vectors.

\end{itemize}

\section{Conclusion}

Einstein-\ae ther theory provides a theoretical
laboratory in which gravitational effects of possible
Lorentz violation can be meaningfully studied without
abandoning the generally covariant framework of
general relativity. It is striking that \ae -theory
can match observations to the degree that it can.
While of course starting with four free parameters
$c_{1,2,3,4}$ makes this easier, the freedom to choose
these parameters might have already been used up in
setting the PPN parameters to agree with those of GR.
Instead, only two parameters need be fixed at that
stage, leaving $c_1$ and $c_3$ free. Then, despite
possessing three distinct types of linearized wave
modes, all positive energy, stability and vacuum
\v{C}erenkov requirements on the modes are met within
a large common region of the $(c_1,c_3)$ space. Within
this same parameter space, the dynamics of the
cosmological scale factor and perturbations differ
little from GR, and non-rotating neutron star and
black hole solutions are quite close to those of GR
(but may be distinguishable with future observations).

Additional constraints arise from the observed
radiation damping rate in binaries. For systems with
weak self-fields, a constraint of order $10^{-3}$
would be imposed on one combination of the two
parameters $c_{1}$ and $c_3$. Current observations
involve pulsars which possess strong self-fields.
Presuming that the sensitivity parameters for neutron
stars turn out to have the expected magnitude, such
binaries will exhibit
effects constraining both the parameters to be less
than around $10^{-2}$, in addition to the stronger
radiation damping constraint on one combination. It
may turn out that observations of multiple systems
with different combinations of sensitivities will
constrain both parameters separately at the $10^{-3}$
level.

\section*{Acknowledgments}
I am grateful to C.T.\ Eling, B.Z.\ Foster, B.\ Li, E.\ Lim,
D.\ Mattingly, I.\ Rothstein
and T. Sotiriou
for helpful discussions and comments on drafts of
this article. This work was supported by NSF grant
PHY-0601800.

redpajama_set_name: RedPajamaArXiv


Dogs being better humans than humans.
If life ever gets you down, find a dog and train that dog to do a jig with you. We're not kidding.
A special friendship between human and canine, more specifically, between Instagram user Mary (my_aussie_gal) and her pup Secret, shows just how much better at friendship dogs are than humans.
You've got your standard adorable puppy shots, but the post that truly takes the cake is a short but deeply satisfying video of Mary teaching her pet a dancing duet.
Secret, who is one year old, also dabbles in prodigious piano playing — we'd like to see a one year old human with this level of pitch perfection.
Dancing, playing or swinging. Dogs friends are better than human friends.


The school year continues to unfold for our new Praise Academy in Allendale/Lakeside. Eight students attend the school and they range from fifth grade down to pre-school. "We've been organizing and re-organizing our schedule as we understand more fully what works best for our students," said Joan Pingel, head of school. The staff, Joan Pingel, Colleen Bowar and Kevin McShane, has developed a set of routines that that proven very helpful for the students. "The kids weren't accustomed to routines and it's been really helpful for them to know the daily routine. They've come to depend on it," said Joan.
The staff recently instituted a time for free play. The students needed some help to begin to use their imaginations for play. "It took a little coaching but it's been wonderful to see how play time has awakened their imaginations," Joan said.
Another highlight for Joan was teaching a six year old to write his name. He arrived for school this year with no experience with letters but had a real determination to learn how to write his name and though it took some time and a lot of effort, he succeeded. It took much more time and effort than the student expected, but that yielded some real improvement in his interest in learning more things and his determination to push through some harder work.
The school day begins with faculty prayer at 7:15 am. The school provides breakfast for the students at 8:00 am followed by group morning prayer. The morning is divided into two class sessions separated by a time for physical education. At noon a neighbor comes and prepares lunch. In the early afternoon the younger students have a nap time and class time continues for the older students.
The CIM team pitches in to help out in a variety of ways — preparing breakfast, picking up kids for school, and helping out where needed. "This school is a full CIM effort," said David Zimmel, coordinator for the CIM team. "It has been a real blessing to the team (and the Shreveport branch) to be able to help so much with the school. I think everyone on the team is helping out every week, and most of branch is helping in one way or another. Working with our kids in the neighborhood has always been one of the big ways we experience serving Christ, but it is just wonderful to be able to help out every week and to be a part of something that has started so well. It is also amazing to see the dedication, creativity and expertise of teachers. They are working terrifically hard to get this started and it is really impressive."


Following the irrigation scheduling experiment in Morocco during the SPOT4-Take5 experiment (Le Page et al, 2014), a Web tool owing to help the irrigation decision making is under development (http://osr-cesbio.ups-tlse.fr/Satirr). The tool is functional on three Landsat8 tiles: Marrakech in Morocco, Kairouan in Tunisia, Toulouse, France.
As the tool is addressing irrigators, the idea is to set an irrigated plot of the simplest and fastest possible way. After drawing his plot on a base map, the user answers to 4 questions. He chose his culture among 7 options currently parameterized (corn, wheat, olive ...), its soil among the 12 USDA typical soils, the sowing date and irrigation method (flooding, sprinkler or drip). This rough initialization is adequate launch the service although, at any time, the user can change the plot contours or refine parameterization if he knows the soils, the peculiarities of its crop, etc.
Initially the server makes an approximation of an average behavior of the plant. For this, a monthly climatology is compiled (multi-annual average of weather parameters) and then interpolated to daily values, while the average behavior of the plant is extracted from FAO-56 Tables "FAO Irrigation and Drainage No. 56 : Guidelines for Computing Crop Water Requirements" (Allen et al, 1998). In a second step, the satellite images already on the server are examined and the relationship between NDVI and Basal Crop coefficient (Kcb) and percent of ground covered by vegetation (Fraction cover, Fc) are determined at each date by averaging on the plot.
Past weather is populated by measurements on the nearest synoptic station of the World Meteorological Organization and synthesized in the form of daily reference evapotranspiration (ET0) and rainfall. Forecasts are obtained by the API of the Norwegian Meteorological Institute.
Finally, a water balance very close to the one described in the FAO-56 is calculated by combining typical crop behavior and climate, satellite imagery, weather data and forecasts and projection into the future of crop development. The goal is to propose a date and dose of irrigation.
In addition to updating the weather (measures and forecasts), the server will check every day for the availability of new images (only Landsat8 for the time being). If there is availability, the tile is downloaded, it is then corrected for atmospheric effects using the information provided by the nearest photometer from the Aeronet network using the SMAC code (Rahman & Dedieu, 1994), then a cloud mask is created and NDVI is calculated. This image is stored as the original file is discarded to not overload the server.
All parameterization / measures / prediction are stored in a postgres / postgis database that links with a web client interface. The user can view the results in tables or graphs, and add its own irrigation in another dedicated interface.
Adaptation to Sentinel-2: the transition to S2 should not be a hassle. However, it will be necessary to adjust the calculation of the tiles to download, the download code and format reading.
Use of Sentinel-1: In the current state, the well-performance of water balance is based on the actual information of irrigation provided by the user. We plan to test the use of S1 images to determine the irrigation dates.
Access to local agro-weather stations: As part of the development of the Environmental Information System in Cesbio, telemetry of several weather stations has been settled up (eg, see http://trema.ucam.ac .ma) (Jarlan et al, 2015), we have to make these stations accessible through a standardized web service like Sensor Web.
Introduction of collective irrigation network. The PhD work of Kharrou (2013) and Belaqziz (2013, 2014) have shown that remote sensing can be used to optimize water rotations of an irrigated command. We plan to offer the possibility of introducing a set of plots to associate it with a distribution network and ultimately offer an optimized arrangement of the water rotation. However, at present, this goal is more into the order of a challenge!
We are currently working on a procedure to introduce wheat yield using remote sensing data (J. Toumi PhD Thesis) and further expect to input an early wheat yield prediction into the tool.
If you want to try it out, be my guest, it's free. If you want to try it out on other regions, please contact me!
Le Page M., J. Toumi, S. Khabba, O. Hagolle, A. Tavernier, M. Kharrou, S. Er-Raki, M. Huc, M. Kasbani, A. Moutamanni, M. Yousfi, and L. Jarlan, "A Life-Size and Near Real-Time Test of Irrigation Scheduling with a Sentinel-2 Like Time Series (SPOT4-Take5) in Morocco," Remote Sens., vol. 6, no. 11, pp. 11182–11203, Nov. 2014.
Allen R., L. Pereira, D. Raes, and M. Smith, FAO Irrigation and Drainage n°56: Guidelines for Computing Crop Water Requirements, no. 56. FAO, 1998, pp. 273–282.
Rahman H. and G. Dedieu, "SMAC: a simplified method for the atmospheric correction of satellite measurements in the solar spectrum," Int. J. Remote Sens., vol. 15, no. 1, pp. 123–143, 1994.
Kharrou M.H., M. Le Page, A. Chehbouni, V. Simonneaux, S. Er-Raki, L. Jarlan, L. Ouzine, S. Khabba, and A. Chehbouni, "Assessment of Equity and Adequacy of Water Delivery in Irrigation Systems Using Remote Sensing-Based Indicators in Semi-Arid Region, Morocco," Water Resour. Manag., vol. 27, no. 13, pp. 4697–4714, Sep. 2013.
Belaqziz S., S. Mangiarotti, M. Le Page, S. Khabba, S. Er-Raki, T. Agouti, L. Drapeau, M. H. Kharrou, M. El Adnani, and L. Jarlan, "Irrigation scheduling of a classical gravity network based on the Covariance Matrix Adaptation – Evolutionary Strategy algorithm," Comput. Electron. Agric., vol. 102, pp. 64–72, Mar. 2014.
Belaqziz S., S. Khabba, S. Er-Raki, L. Jarlan, M. Le Page, M. H. Kharrou, M. El Adnani, and A. Chehbouni, "A new irrigation priority index based on remote sensing data for assessing the networks irrigation scheduling," Agric. Water Manag., vol. 119, pp. 1–9, Mar. 2013.
Jarlan L., S. Khabba, S. Er-raki, M. Le Page et al, "Remote sensing of water resources in semi-arid Mediterranean basins: The Joint International Laboratory TREMA," Int. J. Remote Sens., vol. (under review), 2015.
CESBIO contributes to an international joint laboratory in Morocco, called TREMA, "Télédétection et Ressources en Eau en Méditerranée semi-Aride", which means "Remote Sensing and Water Resources in Semi-Arid Mediterranean". This year, this laboratory has embarked on an ambitious experiment of irrigation scheduling by satellite imagery, on a wheat plot near Marrakech. This experiment was already described in March, and it gave very promising results.
The main objective of the experiment was to see if the logistics of irrigation scheduling by water balance model were feasible in real conditions. For this, a farmer accepted to play our game on two four hectares plots of wheat: Irrigation of the reference plot was driven by the farmer in the usual way. The test plot irrigations was driven by our tool SAMIR (FAO-56 model forced by satellite imagery).
Since the sowing late December to the harvest in early June, a weather station installed on a reference culture has given us the daily reference evapo-transpiration measurements. On the other hand, to control a posteriori the quality of our estimates of water requirements for irrigation, two flux measuring stations were set up. We also acquired a series of images SPOT5 early in the season to compensate for the slightly late start of SPOT4 experience (TAKE5) which began in February.
In addition to a clear weather throughout the season, we were able to benefit from the excellent work of the SPOT4 (TAKE5) team which provided us with the georeferenced images very quickly. The NDVI evolutions were thus available in a relatively short time. As an end user, the Office of Agricultural Haouz allowed us to perform the irrigation of the test plot in the best conditions while being subjected to the constraints of the canal system.
On the ground, everything did not work as well as we planned. Following a misunderstanding with the farmer, we completely missed the second irrigation and the fertilizer application was not timely. Indeed, the study plot is installed on a heavy clay soil that forms a crust. We were not aware that, a few days after sowing, a specific irrigation is needed to ease the emergence of plants. On the other hand, the farmer applied nitrogen fertilizer on two plots just after irrigation of the reference parcel and relatively far from the irrigation of the test plot. Under these conditions the nitrogen is relatively less soluble, and our test plot lacked fertilizers.
Our experiment has been seriously hampered by the misunderstandings with the farmer. But despite the bad start, the experiment was pursued to its end.
This plot shows the changes throughout the course of the experiment of the water supply from rainfall and irrigation, the evapo-transpiration ETobs measured in the field and the Evapo-Transpiration ET estimated by SAMIR model, using the vegetation status from SPOT4 (Take5) images. On this plot, the dates of irrigation were suggested by the model.
To our surprise, the results are extremely promising. Indeed, despite a 20% lower biomass compared to the plot driven by the farmer, we got a equivalent performance in grain yield. This can be explained by the fact that, although the average number of wheat blades was much lower on the test plot, it is very likely that the reference plot, irrigated by the traditional method, has suffered water stress in late March limiting the filling of grain.
This full-scale experiment finally turned out to be very instructive. First, imaging/weather/irrigation logistics worked great : the weather data transmission, the reception and the geometric and radiometric correction of images, the model runs and irrigation decision were largely automated. The SPOT4 (Take5) data, that prefigure those of Sentinel-2, proved perfectly suited to this application. Unfortunately, the clay crust has severely limited the emergence of culture. Yet this phenomenon, well-known to our farmer, taught us to cultivate humility , and we will consider the introduction of the risk in a decision support system. Finally, the functional constraints of the gravity irrigation system have taught us that our tool should be more flexible to recommend an irrigation period instead of a single date, and that we should link the service to weather forecasts.
Following this experiment, we started developing a Web service (SAT-IRR) that should shortly provide the essential functions of an irrigation decision support with a simplified interface.
Although different, the terms land use and land cover are often used as synonymous. From Wikipedia Land cover is the physical material at the surface of the earth. Land covers include grass, asphalt, trees, bare ground, water, etc. There are two primary methods for capturing information on land cover: field survey and analysis of remotely sensed imagery. and Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It also has been defined as "the arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it" (FAO, 1997a; FAO/UNEP, 1999).
A precise knowledge of land use and land cover is crucial for many scientific studies and for many operational applications. This accurate knowledge needs frequent information updates, but may also need to be able to go back in time in order to perform trend analysis and to suggest evolution scenarios.
Satellite remote sensing offers the possibility to have a global point of view over large regions with frequent updates, and therefore it is a very valuable tool for land cover map production.
However, for those maps to be available in a timely manner and with a good quality, robust, reliable and automatic methods are needed for the exploitation of the available data.
The automatic approaches to land cover map production using remote sensing imagery are often based on image classification methods.
unsupervised: the image pixels are grouped by similarity and the classes are identified afterwards.
Supervised classification often yields better results, but it needs reference data which are difficult or costly to obtain (field campaigns, photo-interpretation, etc.).
Until recently, fine scale land cover maps have been nearly exclusively produced using a small number of acquisition dates due to the fact that dense image time series were not available.
The focus was therefore on the use of spectral richness in order to distinguish the different land cover classes. However, this approach is not able to differentiate classes which may have a similar spectral signature at the acquisition time, but that would have a different spectral behaviour at another point in time (bare soils which will become different crops, for instance). In order to overcome this problem, several acquisition dates can be used, but this needs a specific date selection depending on the map nomenclature.
For instance, in the left image, which is acquired in May, it is very difficult to tell where the rapeseed fields are since they are very similar to the wheat ones. On the right image, acquired in April, blooming rapeseed fields are very easy to spot.
May image. Light green fields are winter crops, mainly wheat and rapeseed. But which are the rapeseed ones?
April image. Blooming rapeseed fields are easily distinguished in yellow while wheat is in dark green.
If one wants to build generic (independent from the geographic sites and therefore also from the target nomenclatures) and operational systems, regular and frequent image acquisitions have to be ensured. This will soon be made possible by the Sentinel-2 mission, and it is right now already the case with demonstration data provided by Formosat-2 and SPOT4 (Take 5). Furthermore, it can be shown that having a high temporal resolution is more interesting than having a high spectral diversity. For instance, the following figure shows the classification performance results (in terms of index, the higher the better) as a function of the number of images used. Formosat-2 images (4 spectral bands) and simulated Sentinel-2 (13 bands) and Venµs (12 bands) data have been used. It can be seen that, once enough acquisitions are available, the spectral richness is caught up by a fine description of the temporal evolution.
Systems with similar spatial resolution (SPOT or Landsat) have longer revisit periods and fewer and larger spectral bands. Systems with similar temporal revisit have either a lower spatial resolution (MODIS) or narrower swaths (Formosat-2).
The kind of data provided by Sentinel-2 allows to foresee the development of land cover map production systems which should be able to update the information monthly at a global scale. The temporal dimension will allow to distinguish classes whose spectral signatures are very similar during long periods of the year. The increased spatial resolution will make possible to work with smaller minimum mapping units.
However, the operational implementation of such systems will require a particular attention to the validation procedures of the produced maps and also to the huge data volumes. Indeed, the land cover maps will have to be validated at the regional or even at the global scale. Also, since the reference data (i.e. ground truth) will be only available in limited amounts, supervised methods will have to be avoided as much as possible. One possibility consists of integrating prior knowledge (about the physics of the observed processes, or via expert rules) into the processing chains.
Last but not least, even if the acquisition capabilities of these new systems will be increased, there will always be temporal and spatial data holes (clouds, for instance). Processing chains will have to be robust to this kind of artefacts.
Danielle Ducrot, Antoine Masse and a few CESBIO interns have recently produced a a large land cover map over the Pyrenees using 30 m. resolution multi-temporal Landsat images. This map, which is real craftsmanship, contains 70 different classes. It is made of 3 different parts using nearly cloud-free images acquired in 2010.
70-class land cover map obtained from multi-temporal Landsat data.
In his PhD work, Antoine works on methods allowing to select the best dates in order to perform a classification. At the same time, Isabel Rodes is looking into techniques enabling the use of all available acquisitions over very large areas by dealing with both missing data (clouds, shadows) and the fact that all pixels are not acquired at the same dates.
These 2 approaches are complementary: one allows to target very detailed nomenclatures, but needs some human intervention, and the other is fully automatic, but less ambitious in terms of nomenclature.
A third approach is being investigated at CESBIO in the PhD work of Julien Osman: the use of prior knowledge both quantitative (from historical records) and qualitative (expert knowledge) in order to guide the automatic classification systems.
We will give you more detailed information about all those approaches in coming posts on this blog.
The atmospheric effects : how they work.
Here are two SPOT4 (Take5) images, acquired with a time gap of 5 days above Morocco. Because of atmospheric effects, the second image has less contrast and is"hazier" than the first one.
Atmospheric absorption : in blue, the surface reflectance of a vegetation pixel, as a function of wavelength. In red, the reflectance of the same pixel at the top of atmosphere.
The air molecules absorb the light within thin absorption bands. Within these absorption bands, the reflectance measured by the satellite is lessened, and in some cases, the light may be completely absorbed and the apparent reflectance at the top of atmosphere (TOA) is zero. (for instance, at 1.4µm, in the figure on the right. Such a property is used to detect high clouds with Sentinel-2 or Landsat-8).
Thankfully, the satellite designers usually choose to locate the spectral bands away from strong absorption bands (but beware of satellite designers ). Within the satellite channels, the absorption is generally sufficiently low so that an approximate knowledge of the absorbent abundance is enough to obtain an accurate correction of absorption. Information on absorbing gases (ozone, water vapour) concentration may be found in weather analyses.
The air molecules scatter the light. A photon that passes close to a molecule will be deflected in another direction. As the air molecules are very small compared to visible light wavelengths, they will mainly scatter short wavelengths (in the blue range). The blue sky results from the scattering of sun light by air molecules, since the blue light in the sun spectrum is much scattered while the other wavelengths are mainly transmitted to the ground. A cloud also scatters the light, but its large particles (droplets, crystals) scatter all wavelengths, which explain its white colour.
Apart from clouds and air molecules, scattering may be due to aerosols. Aerosols are particles of diverse nature (sulphates, soot, dust...), suspended in the atmosphere. Their abundance, type and size are extremely variable, and their effect on light is also variable. Small aerosols will mostly scatter blue light, while larger aerosols will scatter all wavelengths. Some aerosols may also absorb light. All this variability makes the correction of their effect very tricky.
The above video, provided by NASA, gives an idea of the way aerosol properties may change from one day to the other, within a two years period. The colour gives an idea of aerosol types, while the colour intensity provides the aerosol optical thickness.
When aerosol quantity increases, ρatm increases while Td decreases. These two variables also depend on view and sun angles. The closer to vertical, the lower value of ρatm and the higher value of Td .
The above model should only be applied to a uniform landscape. But above a standard landscape, a heavy loaded atmosphere will also blur the images. This is explained in another post.
Several models may be used to perform atmospheric corrections. For, approximate corrections, the SMAC model should be one of the simplest. SMAC be downloaded from the CESBIO site. The difficulty in using any atmospheric correction model lies in providing the necessary information on aerosol properties. We will talk about that in another post.
Other more accurate models may be used. In our case, in the MACCS processor, we pre-compute "Look-up Tables " using an accurate radiative transfer code (Successive Orders of Scattering), that simulates the light propagation through the atmosphere. But the use of a complex model is only justified if it is possible to obtain an accurate knowledge of the aerosol optical properties.
We have now received all the L1A images of the SPOT4(Take5) experiment taken between January the 31st and March the 10th, for which at least some part of the surface is visible. We ortho-rectify these images to obtain level 1C products, but sometimes, the cloud cover is still too high to process the image. We can use all these productions to derive some statistics about cloud cover.
Proportion of images processed at Level 1A and Level 1C for the sites selected by each agency.
Between 40% and 50% of the images taken are sufficiently clear so that the ortho-rectification is feasible. When the production of all cloud masks (level2A) is finished, we will be able to compute the number of cloud free observations for each pixel.
After having looked at all the images in Europe or North Africa, we can confirm that all the pixels of these sites have been observed at least once without clouds, except for 3 sites : CAlsace, EBelgium and CTunisia (!). For the site in Alsace, we had to wait until the 4th of March, and until the 10th of March for the site in Tunisia. And up to now, only a little part of the site in Belgium has been observed, on the 8th of March.
In France, despite a very cloudy month of February, the 5 days repetitivity enabled to observe nearly each site at least once. But if SPOT4 had only imaged one out of two overpasses, only the sites in Versailles, Provence and the Alps would have been observed in any case.
This result confirms that it is absolutely necessary to launch both Sentinel-2 satellites with a short time interval, so enable the numerous operational applications that need to rely on a monthly clear observation. And it would be a pity if the recent GMES/Copernicus budget cuts resulted in delaying the Sentinel-2B satellite, reducing the repetitivity to only 10 days for several long years.
Now that you know almost everything on our cloud detection method and on our shadow detection method, we can show you the first results obtained by Mireille Huc (CESBIO) with SPOT4(Take5) time series. As the method is multi-temporal, it needs an initialisation phase, and we had to wait until we had a sufficient number of images to produce the masks. These first results are not (yet) perfect, but are already quite presentable.
The images shown below are a series of 6 Level 1C images, expressed in Top of Atmosphere reflectance, with the contours of several masks orverlayed : the clouds are circled in green, their shadows in black, the water and snow mask are respectively circled in blue and pink. You may click twice on the images to see the details of the masks. These images were acquired in Provence (France), each of them is made from 4 (60x60 km²) SPOT Images obtained on the same day, ortho-rectified, then merged.
Most clouds are detected, including very thin clouds, while the number of false cloud detections is very low. Most large cloud shadow are also detected, even if a few of them were missed. The water mask is also quite accurate with nearly no false detections, taking into account it is produced at 200m resolution. The snow is well classified when the snow cover is high, but often, pixels with a moderate snow cover are classified as clouds. This is a classical difficulty with snow masks.
However, we know that your sharp eyes will have noticed some very thin clouds partly missed by our classification in the North East of the first image, a few false cloud detections on the 3rd and the 5th images (the ground dries and becomes brighter and whiter), some missed cloud shadows for some small clouds once in a while (we know why, it is an initialisation problem, but quite long to explain...). The cloud detection threshold for water pixels (the method is different from the cloud detection above land), is maybe a little to low, as some bright Camargue Lakes are wrongly classified as cloudy. But after all, for a first run, the result is not bad, and we will refine all the parameters when we have a sufficient number of images.
On the Fourth Image, only two of the 4 (60*60 km²) images are available, because the two others are too cloudy to be ortho-rectified, as we need to see the surface to take ground control points. In fact, the ortho-rectification step is the first of our cloud masking steps.
The clouds are circled in green, their shadows in black, the water and snow mask are respectively circled in blue and pink. You may click twice on the images to see the details of the masks.
The THEIA Land Data Centre is a French inter-agency initiative designed to promote the use of satellite data, primarily for environmental research on land surfaces but also for public policy monitoring and for management of environmental resources. Its objective is to foster the use of remote sensing data to measure the impact of human pressure and climate on ecosystems and local areas, to observe, quantify and model water and carbon cycles, to follow the evolution of societies and of their activities, including agricultural practices, and to understand the dynamics of biodiversity.
Within the Land Data Centre, CNES set up a production centre named MUSCATE. This centre aims are providing users with ready-to-use products derived from time series of images acquired over large areas. Sentinel-2 will of course be the spearhead of the production centre, but before the launch of the Sentinel-2, MUSCATE will already begin to produce data from the SPOT4 (Take 5) experiment. At the same time, the processing centre also prepares the production of all Landsat data acquired over mainland France from 2009 to 2011.
MUSCATE production centre already exists in the form of a prototype developed by CNES with strong support from Cap Gemini. This prototype is already able to handle LANDSAT, SPOT, FORMOSAT-2, Sentinel-2 and Venμs data, using processors developed by CNES for geometric processing , and developed by CESBIO for cloud detection  and for atmospheric correction . Simultaneously, the development of an operational production facility is being specified.
Level 2A (ortho-rectified surface reflectance after atmospheric correction, along with a mask of clouds and their shadows, as well as a mask of water and snow).
Level 3A (bi-monthly or monthly composite products of surface reflectances, obtained as the weighted average surface reflectance of non-cloudy pixels obtained during the period). Up to now, Level 3A chain is only available for Venμs satellite.
The data produced by MUSCATE will be freely distributed to research laboratories on the one hand, and to the French public institutions on the other, they will be if possible distributed freely to a wider community. The Land Data Center is also building a distribution server to make all these data available.
: Baillarin, S., P. Gigord, et O. Hagolle. 2008. « Automatic Registration of Optical Images, a Stake for Future Missions: Application to Ortho-Rectification, Time Series and Mosaic Products ». In Geoscience and Remote Sensing Symposium, 2008, 2:II‑1112‑II‑1115. doi:10.1109/IGARSS.2008.4779194.
: Hagolle, Olivier, Mireille Huc, David Villa Pascual, et Gérard Dedieu. 2010. « A multi-temporal method for cloud detection, applied to FORMOSAT-2, VENµS, LANDSAT and SENTINEL-2 images ». Remote Sensing of Environment 114 (8) (août 16): 1747‑1755. doi:10.1016/j.rse.2010.03.002.
: Hagolle, O, G Dedieu, B Mougenot, V Debaecker, B Duchemin, et A Meygret. 2008. « Correction of aerosol effects on multi-temporal images acquired with constant viewing angles: Application to Formosat-2 images ». REMOTE SENSING OF ENVIRONMENT 112 (4) (avril 15): 1689‑1701. doi:10.1016/j.rse.2007.08.016.
Changing SPOT4 orbit : easy ?
choose the new orbit (2 to 6 days repeat cycle) minimizing fuel consumption : We must keep enough fuel to be able to reduce the altitude of the satellite, so that it burns in the atmosphere after a period of less than 25 years. The finally chosen orbit provides a 5 days repeat cycle, resulting in a very low fuel consumption. This orbit also provides the exact repeatability of the two satellites Sentinel-2.
choose the strategy change orbit. The date of optimal maneuver is January 29, but it corresponds to the end of a full moon, and it is prohibited to maneuver SPOT4 during the full moon. It is not due to superstition, but only because of a potential blinding of star sensors used to determine the orientation of the satellite. But a detailed analysis of recent full moons in the same period last year showed that the maneuver could still be executed on January 29 without any risk.
check that the ground segment (designed 15 years ago) can handle the new orbit. The ground segment programs the satellite and the acquisitions, manages the old tape recorders, coordinates the data download to the receiving station, while avoiding interference with other satellites. Because the satellite is no longer on its nominal orbit, all the conditions of interference are to be recalculated.
the usual programming system at SpotImage will not work on this orbit, we will have to use CNES programming system, more flexible but less automated. It takes one hour and a half to program the 42 sites observed over 5 days, but someone will have to do it every 5 days.
find internal and external staff (and budgets) to extend the life of SPOT4 for 5 months.
prepare the MUSCATE production center that will provide level 1C and 2A users. This production facility will be implemented within the Land Data Centre.
Many thanks to Didier Roumiguières, Sylvia Sylvander, Laurence Houpert, Jean-Marc Walter, Jordane Sarda (CS-SI), Aurélie Moussy-Soffys, Frédéric Daniaud (CS-SI), Michel Moulin, Benoît Boissin, Selma Cherchali, Françoise Schiavon, Marc Leroy, Jerôme Bijac (Astrium geo) and to all CNES and Astrium-Geo people who contributed to the acceptation SPOT4(Take5) experiment.
Paul Desmond's Take 5 jazz standard was written in an unusual 5 beat rythm.
At the end of life of each satellite, CNES issues a call for ideas for short-term experiments taking place before de-orbiting the satellite. CESBIO took the opportunity to set up the Take 5 experiment at the end of SPOT4' life : this experiment will use SPOT4 as a simulator to give us a hint of the time series that ESA's Sentinel-2 mission will provide.
The first Sentinel-2 satellite should be launched within the next two years, and the second satellite should follow 18 months later. Together, these satellites will provide us every fifth day with high-resolution images of all land areas... or of the clouds that cover them. Despite these clouds, users will be guaranteed access to cloud-free data at least once per month. The arrival of these data should therefore cause a revolution in the use of remote sensing data.
ESA is providing datasets simulating the spectral bands of the instrument, but these airborne data are not multi-temporal, and only cover small areas.
-CNES and the Israel Space Agency are developing the VENµS project, whose goal is to provide high repeatability time series, but its launch is only scheduled for late 2014.
CESBIO provided time series of FORMOSAT-2 images and LANDSAT, but in the first case, the data only cover areas of 20 * 20 km, whereas in the second case, the repeatability of the data is much lower than expected from Sentinel-2.
Level 2A (Data ortho-rectified surface reflectance after atmospheric correction, along with a mask of clouds and their shadows, as well as a mask of water and snow).


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Q: problem with data output from the database node js this code renders the page and prints the text to the console, but does not increase the value in the database
 result.findOneAndUpdate({name:'score7'} ,{$inc:{text2:"11"}});
console.log('123');
next();
}, function (req, res) {
result.find({$or:  [{name:'police'} ,  {name:'score7'}]}, function(err, data){
    res.render('result_other', {result: data, title: 'Отчет из police'});
});
});```

A: $inc accepts only numeric values, and can only operate on fields containing numbers.
Assuming the text2 fields contains a number, {$inc:{text2:11}} should work.

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The most dangerous places in North Wales to be a police officer revealed
Home Office figures reveal the places in Wales with the most police attacks - and the north features pretty prominently
Harri Evans
Michael Goodier
Katie-Ann Gupwell
The job clearly has its risks (Image: South Wales Echo)
North Wales is a pretty dangerous place for police officers, according to recent Home Office figures.
Out of the top 10 most dangerous places in Wales for police officers to ply their trade, Wrexham, Denbighshire, Conwy and Gwynedd all make the list with Wrexham topping the list based on attacks per 100,000 people.
According to the figures reported by Wales Online, the county saw 130 assaults (95 per 100,000) around 36% of which resulted in an injury between June 2018 and the end of May 2019.
Denbighshire rounded off the top three with 74 assaults (78 per 100,000) with Conwy coming fifth with 74 assaults (63 per 100,000) and Gwynedd eighth with 68 assaults (55 per 100,000).
Assaults on police officers in Wales has risen over the past two years with statistics showing there were 694 in the 12 months to June 2017 which increased to 857 by June 2018, and 995 in the 12 months to June 2019.
However this is not limited to Wales. With England taken into consideration as well, the figures are even more dramatic, showing a rise from 18,220, 27,237 and 30,513 in the same time frame.
Police attacks have risen over the past two years (Image: Peter Byrne/PA Wire)
The full list is as follows:
1. Wrexham - 130 assaults (95 per 100,000 people)
2. Merthyr Tydfil - 48 assaults (80 per 100k people)
3. Denbighshire - 74 assaults (78 per 100k people)
4. Cardiff - 231 assaults (63 per 100k people)
5. Conwy - 74 assaults (63 per 100k people)
6. Ceredigion - 45 assaults (62 per 100k people)
7. Newport - 89 assaults (58 per 100k people)
8. Gwynedd - 68 assaults (55 per 100k people)
9. Carmarthenshire - 102 assaults (54 per 100k people)
10. Pembrokeshire - 61 assaults (49 per 100k people)
Chief Inspector Mark Williams, of North Wales Police, said: "Assaults on police officers are never accepted as part of the job and will always encourage our staff to report and record these offences so that we can take positive action against those responsible.
"As a force, we put the safety and welfare of our officers at the top of our agenda and are continuously reviewing assaults on police to ensure the front line has the necessary information, training and equipment to carry out the role a safely as possible."
National Chair of the Police Federation of England and Wales, John Apter, said: "The rise in assaults on our officers is completely unacceptable and must never be seen as just part of the job.
"The recent surge of severe, high-profile attacks is a serious concern and the Federation will continue to push for increased protections for officers including a wider roll-out of Taser.
"But Taser is just part of the solution; there must also be a stronger legal deterrent.
"My colleagues feel failed by the criminal justice system that should be there to support them when the thugs who attack them are let off with little more than a slap on the wrist.
"We welcome the Government's pledge to double the current maximum sentencing to 24 months - something we initially fought hard for through our Protect the Protectors campaign - and I will be discussing this with the Home Secretary when I meet with her in the coming weeks to ensure those who attack my colleagues are dealt with severely."
AngleseyCrossbow murder accused 'claimed he was near victim's house for outdoor sex with man'Mold crown court heard Terence Whall claimed he had been having an affair with a man called Barry Williams

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Some Insights into the Transfer of Power Upon Retirement
Jane S. Howze, J.D.
We've had numerous opportunities over the years to conduct searches for executives who will be replacing a retiree, or soon-to-be retiree. The process of retiring can be awkward for both the retiree and the company. As is true with most things in life, there are no absolutes, and every organization must determine the best plan for everyone involved.
Not surprisingly, when exiting executives can't wait to hit the door—whatever their reasons—it makes for a crisp transition. Conversely, when retiring executives don't have a plan for their new life in retirement, or worse, they don't want to retire, the change of control can be difficult for everyone, at both a professional and a very personal, emotional level.
No two clients handle the setting of an executive's retirement timetable in the same way, and we hear strong opinions about timing formed through experience in the trenches.
Two weeks? Too fast. Executives tell us that there simply is not enough time to even learn what questions to ask, much less absorb the knowledge dump in that amount of time, even when those leaving remain available.
An extended transition, while seemingly well-intended, creates more problems than solutions.
Two quarters to two years? Too slow. Many times, an extended transition, while seemingly well-intended, creates more problems than solutions. For one, the retiring executives must continue to find ways to remain relevant to the organization and validate themselves and their (usually large) paychecks. Perhaps more critical is the impact such delays have on the troops who are uncertain about to whom to look for directives and leadership. Despite everyone's best intentions, employees will most often pursue familiar routes of problem solving and communications until forced to do otherwise.
That said, a longer transition can help, especially when the outgoing executive is able to manage certain matters while the new executive deals with bigger issues, like getting up to speed on the organization, its business strategy, its people, and its potential needs.
Worst case? Undefined transition schedules that leave the organization in a state of limbo. A mandate for change can be made especially difficult when the creator of those policies and procedures is still around. If the trains are running on time, installing a new leader doesn't imply wholesale change. Either way, the ambiguity creates a tightrope upon which the entire organization is perched, trying to balance potentially competing loyalties, questions about authority and chain of command, and employees' uncertainty about their own future vis-à-vis the organization and their new manager.
Undefined transition schedules leave the organization in a state of limbo.
Just right. We have found some consensus indicating that a one- to two-month transition period is just right. This seems to allow for both the outgoing and incoming executives, and the people on their teams, to implement an effective, efficient, and respectful change of control that honors the contributions of those leaving while conferring credibility on the new leader.
Announcing the transition
How an organization handles the messaging of retiring executives and their replacements seems to play a significant role in how smoothly the transition occurs. One major corporate client begins planning at the highest levels six months before the selected retirement date, makes a formal announcement two months out, and then the retiree is gone. Some organizations prefer to ease the executive into retirement, being careful to not offend anyone or intimate anything less than a stellar performance by the retiree, and a longer overlap is often viewed as more appreciative of their contribution.
So much seems tied to the frequency with which an organization may deal with these situations. Generally speaking, larger organizations have standardized procedures and smaller organizations almost have to reinvent the wheel each time.
Interestingly, a couple of themes consistently surface as we speak to both outgoing and incoming executives: (1) treat people with respect, and (2) remember that this is just one piece of a continuing story.
They express it in various ways: what goes around comes around, karma, the Golden Rule. Call it what you will, the message is clear: We would be wise to remember that we will all be the retiree someday.
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Rachel Curtis participated in the 2010, 24 hour Relay For Life fund raiser for the Cancer Council ACT, held at the AIS athletics track at Bruce.
The ACT Corrective Services Probation and Parole Officer volunteered as part of a relay team that circled the track for 24 hours to support relatives with cancer and to remember other relatives who have succumbed to the disease.
"Relay For Life is an overnight, community event where teams of 10 or more keep a baton moving in a relay-style walk or run," Rachel explains.
"I expect to be mainly walking. That better suits my fitness regime," she adds with a grin.
Born in London, Rachel came to Australia backpacking in her early 20s.
After spending three months in Sydney, she hit Canberra, got into a relationship and decided to stay. That was nine years ago and she has settled nicely.
"I found Canberra so much more personal than my hometown of London and decided this was a good place to be."
Rachel has received considerable support from her Corrections colleagues and with her relay team has exceeded their target of $1000 for the Cancer Council ACT.


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LSU researcher receives $325,000 grant to study Cercospora leaf blight
Graduate student Nelomie Galagedara works on collecting spore samples in the field — photo by Maria Izabel Costa de Novaes/LSU AgCenter
Cercospora leaf blight has been a bane to soybean farmers in the Mid-South region for more than two decades, costing the industry more than $250 million in the past five years alone. Now, thanks to a three-year, $324,988 research grant from the National Institute of Food and Agriculture, Louisiana State University AgCenter plant pathologist Sara Thomas-Sharma and her team are trying to develop long-term solutions to the problem.
In her project summary for the NIFA grant, Thomas-Sharma laid out three research objectives to assist soybean producers in protecting their crop. First is to determine the importance of air-borne spores in the disease cycle and identify environmental predictors associated with disease development. Second is develop tools to monitor resistance to commonly used fungicides. And third is to integrate improved fungicide application timing and host resistance in Cercospora disease management.
Thomas-Sharma said the collaborative grant among Louisiana, Arkansas and Mississippi is meant to assist growers directly.
"Management of this disease has had a lot of challenges because much was not understood about where it was coming from," she said. "We have reason to believe that it is coming in as spores, so the first objective is to set up spore traps to try and understand when the peaks may occur."
Enlisting spore traps
The spore traps are set up in multiple locations and come in two different types: one surprisingly simple, the other more complex. The simple trap consists of a wind vane containing a microscope slide coated with petroleum jelly that catches the spores when the vane moves. The other, more expensive type is connected to a power source that sucks air onto a paraffin-coated tape.
Thomas-Sharma's second objective addresses the question of resistance to some of the less-expensive commercial fungicides. Until now, there have been few in-depth surveys in the Mid-South on where resistance does and does not occur.
"If there is no resistance problem in a certain area, it makes more sense for the grower to just apply the cheaper fungicide," she said. "But if there is, applying the cheaper fungicide won't do any good and will just be a waste of money, so we're developing a method where we can quickly monitor the level of resistance throughout the three states."
According to Thomas-Sharma, Cercospora comes late in the growing season, close to when pods are maturing. The leaves begin to turn a purple color, then get leathery and burnt, causing a reduction in yield because there are no leaves to provide photosynthesis.
Target spore peaks
Thomas-Sharma's third objective is to target the spore peaks identified in the first objective for timing fungicide applications better. She said growers are currently advised to spray crops during the reproductive growth stage (R3 to R5). She wants to determine if it's possible to accurately time the application when the spores are high to get better control of the disease.
"This is where we're trying to put the results from the first objective into use," she said. "If you have a susceptible variety, and have to use a fungicide, when is the best time to do it to provide the most protection to the crop and does it necessarily depend on growth stage."
Currently, Cercospora is a bigger problem in the South than it is in the Midwest or other larger U.S. soybean-producing regions. While Thomas-Sharma's research focuses primarily on the Mid-South area, the disease could become a bigger problem for more northern regions in the future, she said.
"There is always a concern that with weather patterns changing that the disease can move," Thomas-Sharma said. "So there is a broader long-term impact of the research as well."
She said her goal is to come up with answers for growers on how to manage Cercospora to better protect their bottom lines. She said it's almost a given these days that soybean growers in the South will get the disease on their crops; the question is how to minimize its effects.
For her personally, the NIFA grant represents the third time being the charm.
"This is my third try submitting a fairly similar proposal," she said. "It feels good to see the work and effort finally materialize into something the growers can actually use."
The LSU AgCenter contributed this article.
LSU AgCenter
University of Arkansas Soybean Economic Notes, Sept. 10, 2021
Taproot decline emerges as new problem for Alabama soybean growers


text:
Jeff Foxworthy Is Downsizing, but You Can't Buy Any of His Stuff
By Katie Garrity
If you've scoured eBay to try and find some of the best possessions of your favorite celebrities, you're looking in the wrong place! Some celebs have estate sales and auctions where they sell off their possessions whether to downsizing or financial issues.
Jeff "You Might Be a Redneck" Foxworthy is having an estate sale at his Georgia home, and you could have the opportunity to buy some of his things! So, why is Jeff Foxworthy having an estate sale? We have the details!
Jeff Foxworthy is moving out of his Johns Creek, Ga. home.
According to TMZ, the Blue Collar Comedy Tour star is moving out of his 12,000 square ft mansion in Johns Creek, Ga. and downsizing to a smaller home. He and his wife, Pamela, decided to move to somewhere a bit cozier for them and are selling many of their personal items including autographed memorabilia.
"Among Jeff's items up for grabs include autographed memorabilia from various comedy and entertainment projects, TV scripts, sports collectibles, fine furnishings, a Renaissance billiards table, and 2 white-tailed deer mounts," TMZ reported.
The sale also features Atlanta memorabilia, including a Chipper Jones signed bat, Braves World Series framed tear sheets and Michael Vick signed jersey.
Due to huge demand for appointments, the sale's last day was canceled.
Atlanta locals were encouraged to make an appointment online to set up a time to browse through Jeff's items, however, due to large demand, the last day of the estate sale has been canceled.
"Regrettably, Saturday, Aug. 8 — the final day of our Jeff Foxworthy estate sale – HAS BEEN CANCELLED due to the tremendous traffic the sale has generated within the Country Club of the South community. We also are unable to add additional appointments to Friday's schedule because slots were previously filled," the estate sale website states.
Interestingly enough, Jeff hosts a show about items you'd find at an estate sale.
The timing of Jeff's estate sale is interesting considering his new A&E show recently premiered which has a lot in common with items that could be found at an estate sale just like Jeff's. The show has been called a virtual twist on the classic television show Antique's Roadshow.
The series premiere of @whatsitworthae starts RIGHT NOW on @aetv ! Watch and tweet along using the hashtag #WhatsItWorthAE!
A post shared by Jeff Foxworthy (@realjefffoxworthy) on Aug 4, 2020 at 5:56pm PDT
On What's It Worth?, Jeff Foxworthy scours the country in search of hidden treasures held by everyday people who are hoping to strike it big. From the comfort of their homes, Jeff Foxworthy and a team of experts visit different states and towns o examine a variety of heirlooms, trinkets, and treasures to help people determine if they are sitting on a gold mine, or if they are just holding on to items for sentimental value.
"The on-going partnership with Jeff Foxworthy, a one of a kind collector, in both What's It Worth? and What's It Worth? Live allows us to expand on the traditional genre with a modern and digital twist," Elaine Frontain Bryant, Executive Vice President and Head of Programming for A&E Network said, according to Slanted.
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