text:
\section{Introduction}
\label{sec_1}

Carbon nanotubes (CNTs) have exceptional strength and stability, and they can exhibit either
metallic or semiconducting properties depending on the rolling direction (chirality)
and diameter[\onlinecite{Mintmire}].
Due to these structural and electronic properties, many studies have expected the applications of CNTs
in future nanoelectronic devices[\onlinecite{Zhang,Wind,Javey03}].
Attention has focused especially on field-effect transistors (FETs).
With the continuous improvement of scaling and contacts,
high performances of carbon nanotube field-effect transistors (CNFETs)
have been reported[\onlinecite{Wind,Javey03,Derycke,Chen,Franklin}].

CNFET has a significant potential to replace conventional silicon-based circuitry due to its
smaller size,  better electrostatics, and higher
mobility. And nanoelectronic devices will promisingly be used in future space technology and weapons technology.
The space radiation and nuclear radiation are known to cause defects in solids[\onlinecite{Dienes,Dartyge,
Gusarov,Luneville,Jin,Narayanan}].
And the fabrication process
of CNFETs introduces also defects in the oxide or at the nanotube-oxide interface[\onlinecite{Chan}].
A defect in gate oxide may trap a current carrier on a carbon nanotube and then detrap it.
A charge state of the defect may keep for some time and then change into another charge state due to the
random trapping or detrapping. Such random charge-state switching
will cause a random current switching between two (or more) levels, i.e., random telegraph signals
(RTSs)[\onlinecite{Rall,Kirton,Uren,Liu06}].

RTSs due to individual defects in CNFETs have been observed in experiments[\onlinecite{Liu,Liu06,Liu08,Chan,Lee}],
and giant RTS values of 60\% or more have recently been detected[\onlinecite{Liu08}].
Some experiments[\onlinecite{Chan}] measured RTSs even at low drain bias of 50 mV due to defects
at the nanotube-oxide interface or in the oxide.
Theoretical studies have also indicated that a single defect in the gate dielectric of a CNFET may cause
a substantial current change in CNFETs[\onlinecite{Heinze,Neophytou,Wang}].
When there are many defects with different time constants, the superposition of RTS leads to
a low frequency 1/f noise[\onlinecite{Dutta, Weissman,Collins,Lin,Ishigami}].
Therefore,  CNFETs need not only to be provided with the resistance to radiations but also to be designed with low noise.
Clearly, studying the effect of individual defects is important for understanding the microscopic aspect of
1/f noise in CNFETs  as well as for designing a CNFET with low noise.

SiO$_2$ is a commonly used gate dielectric for the conventional metal-oxide-semiconductor field-effect transistors
(MOSFETs) and CNFETs. To improve continuously the performances of the FETs,
the thickness limit of SiO$_2$ will soon be reached and a new dielectric material with a
high dielectric constant is needed to replace SiO$_2$. The FET gate stack scaling with various
materials of high dielectric constant have widely been studied[\onlinecite{Wilk,Gusev}].
Usually, the band gap decreases as the dielectric constant increases.
Simply employing thinner HfO$_2$ ($\epsilon \approx$ 16) or other materials
with high dielectric constant is not a solution because the thinner HfO$_2$ or
other materials of high dielectric constant will cause unacceptably high levels of
gate leakage current[\onlinecite{Lee}].

TiO$_2$ has a large dielectric constant that ranges from 40 to 86[\onlinecite{Brown,Rausch,Fuyuki}] and
its band gap is between 3.0 $\sim$ 3.5 eV[\onlinecite{Pascual,Fuyuki}],
depending on the crystalline structure. A considerable gate leakage current occurs if TiO$_2$-only
gate dielectric is used due to small band gap and thermionic emission.
SiO$_2$ has a band gap of 9 eV, which is much larger than the band gap of TiO$_2$.
It has been known that composite gate oxides with TiO$_2$ and SiO$_2$ can reduce effectively the gate leakage
current within a range of appropriate gate voltages[\onlinecite{Campbell,Kim}].
Recently, composite gate dielectrics have been studied to reduce gate leakage current[\onlinecite{Campbell,Lu,Cho,Choi}].

As pointed out in Ref.[\onlinecite{Wang}], using a sigle gate oxide
with large dielectric constant or small thickness
can reduce the RTS noise amplitude. However, for a compiste structure of gate insulators how the RTS noise
amplitude depends on dielectric constants and thicknesses of inner and outer insulators is unknown up to now.
In this work, we will investigate systematically how the composite gate dielectrics affect
the amplitude of the RTS noise. This paper is organized as follows.
In section \ref{sec_2} we show the device setup for simulations
and give a brief overview of our methodology.
In section \ref{sec_3} we present our calculation results
for the dependence of the RTS noise amplitude on
the nanotube radius and parameters of composite gate dielectrics,
and discuss also how to reduce the amplitude of the noise caused by  a charge in composite gate dielectrics.
Finally, conclusions will be given in section \ref{sec_4}.

\section{Methodology}
\label{sec_2}

The insets of Fig.\ref{current-exp} show the cylindrical geometry of a CNFET considered for calculations,
which is similar to the device used in Refs.[\onlinecite{Leonard,Heinze,Wang}].
In the present work, we consider a zigzag (n,0) semi-conducting carbon nanotube,
where the index n will be defined in the calculation.
Source and drain leads are separated from the CNT in the radial
direction by a van der Waals distance of 0.3 nm.
The CNT is surrounded by a dielectric oxide, whose dielectric constant and thickness will be defined according
to the request of calculations.
The CNT is divided into three regions: semi-infinite source and drain regions having uniform potentials,
and a self-consistent scattering region.
The scattering lengths of the CNT inside the source and drain leads
are both defined as 24 nm. The channel length
between the source and drain leads is 200 nm unless otherwise specified.
The thickness of the gate oxide will be defined below.
The work function of the metal source and drain leads is chosen to be 1 eV larger than
the work function of the CNT, which is measured from midgap.
This gives an ohmic p-type contact,
as obtained in recent experiments[\onlinecite{Javey03,Appenzeller}].
The temperature is fixed at $290 K$.

At an appropriate gate voltage, if a drain bias is applied a source-drain current will occur.
The drain voltage is related to the Fermi levels of the source and drain leads by
the expression of $V_{D} = (\mu_{S} - \mu_{D})/e$.
The electron (or hole) transport properties can be calculated using the non-equilibrium Greens function method.
The retarded Greens function of the scattering region plays an important role in the theory.
It can be expressed as[\onlinecite{Datta}]
\begin{equation}
\displaystyle\bigg[\ (E\ + i0^+)I\ -\ H\ -\Sigma^{r}_{S}(E)\
             -\Sigma^{r}_{D}(E)\ \bigg]G^{r}(E)\ =\ I,
\label{Green-function}
\end{equation}
where $I$ is the identity matrix, $H$ is the Hamiltonian for the scattering region of the CNT, and
$\Sigma^{r}_{S,D}$ denote retarded self-energies of the source and drain leads, respectively.
We describe the Hamiltonian of a CNT using a tight-binding approximation with one $\pi $
orbital per carbon atom[\onlinecite{Heinze,Wang,Leonard,Guo}].
The nonequilibrium Greens function can easily be calculated using a mode-based method in Ref.[\onlinecite{Guo}].

The charge distribution in the scattering region can be evaluated
using the density matrix[\onlinecite{Brandbyge,Rocha}].
Then, the discrete charges on the CNT are broadened by a Gaussian along the nanotube
direction and in the radial direction with $\sigma\ =\ $0.07 nm, which is about half the C-C bond length[\onlinecite{Heinze}].
The charge of the defect is approximately treated as a point charge,
smeared by a Gaussian along the nanotube axis and in the
radial direction with $\sigma\ =\ $0.05 nm[\onlinecite{Heinze}], and is placed midway between the source and drain leads.
Scattering from the Coulomb potential of the charged defect is treated neglecting band mixing.

The potential along a CNT can be obtained from the solution of the Poisson equation
at a finite drain voltage[\onlinecite{Brandbyge}]. It is found from Eq.(\ref{Green-function}) that
the Greens function $G^{r}(E)$ will be changed due to the potential,
which is included in the Hamiltonian $H$ of the CNT.
Therefore, the Greens function of the scattering region $G^{r}(E)$,
the charge on the CNT, and the potential along the CNT
must be determined self-consistently.

If the Greens function $G^{r}(E)$ is obtained from self-consistent calculations,
one can calculate the current through the system using the well-known
Landauer-B\"{u}ttiker formula[\onlinecite{Buettiker,Meir,Datta}]
\begin{equation}
I\ =\ \displaystyle\frac{2e}{h}\int dE T(E)
                   \displaystyle\bigg[\ n_{F}(E - \mu_{S})\
                    -\ n_{F}(E - \mu_{D}) \ \bigg]\ ,
\label{current}
\end{equation}
where the factor of 2 is due to the degeneracy of spin and $n_{F}$ is the Fermi function.
The transmission between the source and drain leads in Eq.(\ref{current})
can be determined using the following
expression[\onlinecite{Meir,Datta,Svizhenko}]
\begin{equation}
T(E)\ =\ tr\displaystyle\bigg( \Gamma_{S}(E)G^{r}(E)
                              \Gamma_{D}(E)G^{a}(E)
                              \displaystyle\bigg)\ ,
\label{transmission}
\end{equation}
where $\Gamma_{S,D}$ is defined by the formula of
$\Gamma_{S,D}\ =\ i
  \displaystyle\bigg[\ \Sigma^{r}_{S,D}(E)\ -\ \Sigma^{a}_{S,D}(E)\ \bigg] $.

For a p-type CNFET, the hole emission and capture by a defect in the gate oxide
will cause randomly the current switchings between $I_0$ and $I_Q$, i.e. RTSs.
The amplitude of such RTS noise is defined as the relative
current change due to the charge of the defect[\onlinecite{Wang}]
\begin{eqnarray}
A_{RTS}=(I_0-I_Q)/I_0\ ,
\end{eqnarray}
where $I_Q$ and $I_0$ are the current with and without the charge.

\section{Numerical Results}
\label{sec_3}

In this section, we investigate in detail how the amplitude of the RTS noise due to a single defect
depends on the nanotube radius and how the RTS noise amplitude relys on the parameters of composite gate dielectrics,
such as, thicknesses and dielectric constants of the inner insulator and the outer insulator.
The nanotube-direction position of the charge is fixed in the middle of the channel.

\subsection{\bf Dependence of $A_{RTS}$ on $R_{CNT}$}
\label{sec_3a}

To demonstrate the validity of our model, we calculate the current through a
CNFET of sylindrical geometry with a zigzag (14,0) carbon nanotube and a 10 nm-thick HfO$_2$ dielectric.
The channel length in the calculation is defined as 40 nm. The obtained result for $V_d = -0.1$ V is shown
in Fig.\ref{current-exp}. A recent experiment[\onlinecite{Franklin}] measured the current at $V_d = -0.1$ V through
a CNFET with a cylindrical geometry of gate electrode. In the experiment, the carbon nanotube was 1 nm in diameter
and 40 nm in length, and the gate oxide was 10 nm-thick HfO$_2$.
The experimental result is also displayed in Fig.\ref{current-exp} for comparison.
Clearly, our calculation results are in quite good agreement with experimental
data[\onlinecite{Franklin}].
The good agreement between theoretical results and experimental data justifies our model.

We consider a commonly used insulator of SiO$_2$ ($\epsilon = 3.9$) as a gate oxide of a CNFET
and investigate the dependence of
$A_{RTS}$ on the nanotube radius.
For different zigzag (n,0) carbon nanotubes, where the index n is 13, 17, 20, 25, and 29,
we calculate the current through the device at the drain voltage of -50 mV and at different gate voltages from -3 V to 0.5 V.
For the gate radius of $R_g = 16$ nm, the obtained result is shown
in panel (a) of Fig.\ref{diff_nanotube} as a function of the applied gate voltage.
The (13,0) zigzag nanotube gives the large value of on-off current ratio, $I_{on}/I_{off}\ \approx 10^{11}$, while
the (29,0) zigzag nanotube gives a much lower on-off current ratio, $I_{on}/I_{off}\ \approx 10^4$.

For a positive charge of Q = +1e located at a radial distance of 0.4 nm from the nanotube wall (i.e., at the nanotube-oxide
interface), we calculate the amplitude of the RTS noise due to the positive charge for a gate radius of $R_g\ =\ 16$ nm,
a dielectric constant of 3.9, and zigzag (n,0) carbon nanotubes with the index n being 13, 17, 20, 25, and 29.
From the calculated current through a CNFET with and without charged defect in the device,
we calculate the amplitude of the RTS noise due to the charged defect.
The obtained results are shown as a function of gate voltage $V_g$ in Fig.\ref{diff_nanotube}.
It is clear that the smaller the nanotube is, the bigger the amplitude of the RTS noise is.

In order to understand the dependence of the RTS noise amplitude on the nanotube radius,
we calculate the potential along the nanotube and show the result
in Fig.\ref{poten-trans}(a).
In the absence of any scatterer, the potential in the channel is almost constant in midchannel, as expected for
a long-channel ballistic device. A positively charged trap right at the nanotube-oxide interface causes an extra barrier
for hole transport, giving a shift in the plot of transmission vs energy in Fig.\ref{poten-trans}(b).
This shifts the voltage threshold of the device, as seen in Fig.\ref{diff_nanotube}.
Comparing the potential for the (13,0) nanotube and the potential for the (29,0) nanotube,
concerning the hole transmission the potential barrier of the former
is much larger than that of the latter.
This gives a less abrupt turn-on of transmission with energy
for the (13,0) nanotube as shown in Fig.\ref{poten-trans}(b).
Therefore, we expect a larger amplitude of the RTS noise for the (13,0) nanotube.

From the above calculations of current through idea CNFETs (i.e., without any charged defect) for different
carbon nanotube radii, one can see that
a smaller semi-conducting nanotube gives a larger value of on-off current ratio $I_{on}/I_{off}$.
However, the RTS noise amplitude for a smaller semi-conducting nanotube is larger,
which suggests one to make an intermediate choice
between different nanotube radii.
In the following, we use a zigzag (17,0) carbon nanotube, which has a radius of 0.67 nm, to study the RTS noise in FETs.

\subsection{\bf Role of composite gate insulators}
\label{sec_3b}

The amplitude of the RTS noise is known to decrease with the gate dielectric thickness.
However, if the gate dielectric is too thin the gate leakage current will occur because of direct tunneling
between the bands of the semi-conducting nanotube and
the Fermi level of the gate electrode.
Composite gate insulators may be used to prevent or reduce
the gate leakage current[\onlinecite{Campbell,Kim}].
The question then arises: how does the amplitude of the RTS noise due to a charged defect
depend on the parameters of the composite gate insulators?
To answer this question, we will investigate the current reduction due to a charged defect in
a composite gate insulators as
shown in Fig.\ref{device_setup_2}. For convenience, we denote the thickness and dielectric constant of the inner insulator
as $t_1$ and $\epsilon_1$, respectively. The outer insulator is supposed as SiO$_2$,
whose thickness and dielectric constant are denoted by $t_2$
and $\epsilon_2$ ($\epsilon_2$ = 3.9), respectively.

As an example, we use 1 nm-thick HfO$_2$
for the inner insulator (i.e., $\epsilon_1 = 16, t_1 = 1$ nm) and 2 nm-thick SiO$_2$ for the outer
insulator (i.e., $\epsilon_2 = 3.9, t_2 = 2$ nm) in the composite structure. We calculate the current through the device
without any charged defect (Q = 0) and the current for a charge of Q = +1e located at
the nanotube-insulator interface.
From the results of the current $I_0$ for Q = 0 and the current $I_Q$ for
Q = +1e,  we calculate the relative current reduction $(I_0 - I_Q)/I_0$ due to the charge of Q = +1e.
The obtained result of the current $I_0$ is shown as black solid curve in panel (a) of
Fig.\ref{current_cgi_eps16}. The calculated relative current reduction is shown as black solid curve in panel (b) of
Fig.\ref{current_cgi_eps16}. The relative current reduction due to the charge of Q = +1e
is estimated as 91\% in the turn-region and 4\% in the on-state.
We enlarge the thickness of the inner gate insulator HfO$_2$ to 13 nm (i.e., $\epsilon_1 = 16, t_1 = 13$ nm)
and keep the same thickness of the outer insulator SiO$_2$
as before (i.e., $\epsilon_2 = 3.9, t_2 = 2$ nm). The current for Q = 0 and Q = +1e
and the relative current reduction due to the charge of Q = +1e are calculated.
The obtained result of the current for Q = 0 and
that for the relative current reduction are shown in  panels (c) and (d) of
Fig.\ref{current_cgi_eps16}, respectively.
The relative current reduction in the turn-on region is around 80\%,
which is decreased by about 11\% as compared with the corresponding result for $t_1 = 1$ nm obtained before.
The comparison of panels (b) and (d) of Fig.\ref{current_cgi_eps16} represents that the relative current reduction
due to a charge in composite gate dielectrics increases with the decreasing total thickness of composite gate dielectrics
if the outer insulator is unchanged.
For comparison sake, the results of relative current reduction for 3 nm-thick SiO$_2$ and
3 nm-thick HfO$_2$ are shown in panel (b) of Fig.\ref{current_cgi_eps16},
and the corresponding results for 15 nm-thick SiO$_2$ and 15 nm-thick HfO$_2$ are shown in panel (d) of Fig.\ref{current_cgi_eps16}.
As expected, the relative current reduction due to a charge in single gate dielectric of SiO$_2$ or HfO$_2$
decreases if the gate dielectric gets thinner.
Apparently, the dependence of the relative current reduction due to a charge in composite gate dielectrics
on the thickness of the composite gate dielectrics is contradictory to the
dependence of the relative current reduction caused by a charge in a single gate dielectric
on the thickness of the single gate dielectric.

To see more clearly, we consider another example of composite gate dielectrics, which
is a combination of the inner insulator with $\epsilon_1 = 40, t_1 = 1 $ nm and
the outer insulator of 2 nm-thick SiO$_2$ (namely $\epsilon_2 = 3.9, t_2 = 2 $ nm).
We calculate the current through the device
for Q = 0 and Q = +1e. From the results of the current $I_0$ for Q = 0 and the current $I_Q$ for
Q = +1e,  we calculate the relative current reduction due to the charge of Q = +1e.
The obtained results of the current $I_0$ and
the relative current reduction are shown in panels (a) and (b) of Fig.\ref{current_cgi_eps40}, respectively.
To examine the dependence of the relative current reduction on the thickness of the inner insulator, we
calculate also the current for composite insulators with $\epsilon_1 = 40, t_1 = 13 $ nm
and $\epsilon_2 = 3.9, t_2 = 2 $ nm.
The results for the current $I_0$ and the relative current reduction are shown
in in panels (c) and (d) of Fig.\ref{current_cgi_eps40}, respectively.
The relative current reduction $(I_0 - I_Q)/I_0$ for $t_1 = 1 $ nm is estimated as 84\% in the turn-on region
and 0.4\% in the on-state.
And the relative current reduction decreases apparently to 49\% in the turn-on region
and 0.1\% in the on-state if $t_1 = 13 $ nm.

To understand why the relative current reduction due to a charge in composite gate dielectrics
increases with the decreasing total thickness of composite gate dielectrics,
in Fig.\ref{poten-trans_1} we show the potential along the nanotube for Q = 0  and for Q = +1e
located at the nanotube-insulator interface of a CNFET with the composite gate insulators.
Clearly, as the inner insulator thickness $t_1$ increases from 1 nm to 13 nm,
the potential barrier for hole transport due to Q = +1e decreases.
The screening of the impurity charge contains the screening by the composite gate insulators
and the screening by the gate electrode.
From the top panel of Fig.\ref{poten-trans_1}, it is found that
the total screening effect of the impurity charge in the composite gate insulators
decreases if the full thickness of the composite gate dielectrics becomes smaller and
the thickness of the outer insulator maintains unchanged.
The screening of the impurity charge by the gate electrode increases
with the decreasing thickness of the composite gate dielectrics because the screening by the gate electrode
becomes stronger when the gate electrode is closer to the impurity charge[\onlinecite{Wang}].
The screening by the composite gate dielectrics is dependent on the effective
dielectric constant of the composite gate dielectrics.

In order to know the screening of the impurity charge by the composite gate dielectrics,
we discuss the effective dielectric constant of the composite insulators.
We consider the device in Fig.\ref{device_setup_2} as a cylindrical capacitor, which contains
a solid cylindrical conductor of radius $R_0 \approx R_{CNT} + 0.3 \approx 1$ nm, surrounded by a coaxial cylindrical conductive
shell of inner radius $R_2 = R_g$. The length of both cylinders is the channel length $L_c$
and we take this length to be much larger than $R_2 - R_0$. If there is no gate dielectric,
the capacitance of the device is expressed as $C_0$. And then, we suppose the two insulators with dielectric
constants of $\epsilon_1$ and $\epsilon_2$
($\epsilon_1 > \epsilon_2$) exist between the two cylindrical conductors and the radius of the interface between the
two insulators is defined as $R_1$. In this case, the corresponding capacitance is written as $C_x$. The effective
dielectric constant of the composite insulators may be defined as $\bar{\epsilon} = C_x/C_0$. If the length of both conductors
in the capacitor is much larger than the distance between the two conductors, i.e., $L_c >> R_2 - R_0$,
the effective dielectric constant may be estimated as
\begin{equation}
\begin{array}{rcl}
\bar{\epsilon} & \ = \ & \displaystyle \left[\frac{1}{\epsilon_1} +
       ( -\frac{1}{\epsilon_1} + \frac{1}{\epsilon_2} )\ln\frac{R_2}{R_1}
       /\ln\frac{R_2}{R_0} \right]^{-1} \\
             \ & \ = \ & \displaystyle \left[\frac{1}{\epsilon_1} +
       ( -\frac{1}{\epsilon_1} + \frac{1}{\epsilon_2} )\ln(1 + \frac{t_2}{R_0 + t_1})
       /\ln(1 + \frac{t_1}{R_0} + \frac{t_2}{R_0}) \right]^{-1} \ ,
\end{array}
\label{eff_dielec}
\end{equation}
where $\epsilon_1$ and $\epsilon_2$ are the dielectric constants of the inner and outer insulators, respectively,
and $t_1$ and $t_2$ are the thicknesses of the inner and outer insulators, respectively, i.e.,
$t_1 = R_1 - R_0$ and $t_2 = R_2 - R_1$.
One may use Eq.(\ref{eff_dielec}) to explain qualitatively the dependence of
the effective dielectric constant of composite gate insulators (as shown in Fig.\ref{device_setup_2}) on the
thickness of the inner insulator $t_1$.
It is clear from Eq.(\ref{eff_dielec}) that if $\epsilon_1 > \epsilon_2$, $t_1$ increases and $t_2$ keeps unchanged,
the effective dielectric constant of the composite insulators increases.
So, the screening of the impurity charge by the composite insulators increases if the full thickness of the composite insulators
gets larger and the outer insulator maintains the same thickness.
On the contrary, the screening of the impurity charge by the gate electrode decreases
with the increasing thickness of the composite insulators.
From results shown in the top panel of Fig.\ref{poten-trans_1}, we conclude that
the screening of the impurity charge by the composite insulators increases
with the full thickness of the composite insulators faster than the screening of the impurity charge by the gate electrode
decreases with the increasing full thickness of the composite insulators,
so that the summing-up screening effect of the impurity charge increases
with the full thickness of the composite insulators
if the thickness of the outer insulator is kept the same.

Since the screening of the impurity charge in the composite insulators is sophisticatedly dependent on
the thickness of the inner insulator $t_1$ and the thickness of the outer insulator $t_2$,
we investigate how the relative current reduction depends on
the thickness of the inner insulator $t_1$ within a wide range of $t_1$
when the thickness of the outer insulator is fixed.
We consider different thicknesses of the inner insulator from $t_1 = 1$ nm to $t_1 = 24$ nm and define
$\epsilon_2 = 3.9$ and $t_2 = 2$ nm.
And we calculate the relative current reduction at the gate voltage of $V_g = -0.1$ V, at which
the relative current reduction has a maximal value as compared with
the relative current reductions at other gate voltages (see panels (b) and (d) of Figs.\ref{current_cgi_eps16}
and \ref{current_cgi_eps40}).
In the middle panel of Fig.\ref{RTS_cgi}, we use solid diamonds to show the obtained results of
the relative current reduction $(I_0 - I_Q)/I_0$ as a function of the inner insulator thickness $t_1$.
For comparison, we show the relative current reductions at the
gate voltage of $V_g = -0.1$ V for a single gate insulator with a dielectric constant of
3.9, 40, and 80 in the top panel of Fig.\ref{RTS_cgi} as a function of the thickness of the gate oxide.
And the relative current reduction for $\epsilon = 3.9, 40$, and $80$
increases nearly to the saturation value of 100\%, 49\%, and 30\%, respectively,
if the thickness of the gate oxide $t_{ox} \stackrel{>}{\sim} 11$ nm.
From Fig.\ref{RTS_cgi}, one can find that for composite gate dielectrics
the relative current reduction increases with the decreasing
thickness of the inner insulator $t_1$. If $t_1 > 20$ nm, the relative current reduction
decreases approximately to the saturation value of 49\%, which is the same with the saturation value of
$(I_0 - I_Q)/I_0$ for a single gate oxide of $\epsilon = 40$.
The reason is that if the thickness of the inner insulator $t_1$ is large enough,
the effective dielectric constant of the composite insulators $\bar{\epsilon}$ is nearly
the same with the $\epsilon_1$, as one can easily see from Eq.(\ref{eff_dielec}).
Furthermore, from the top panel of Fig.\ref{RTS_cgi} we can see that the relative current reduction for a single gate insulator
increases nearly to its saturation value if the thickness of the gate oxide $t_{ox} \stackrel{>}{\sim} 11$ nm, and this
indicates that the screening of the impurity charge by the gate electrode becomes very weak if the thickness of the gate oxide
is large enough.

Fixing the thickness of the outer insulator as $t_2\ =\ $ 1 nm, we calculate the relative current reduction
for different thicknesses of the inner insulator $t_1$ and show
the results of the relative current reduction at $V_g = -0.1$ V as a function of the inner insulator
thickness $t_1$ in the middle panel of Fig.\ref{RTS_cgi}.
To compare the results for the outer insulator thicknesses of $t_2 = 1$ nm and $t_2 = 2$ nm,
in the bottom panel of Fig.\ref{RTS_cgi}
we show the results of the relative current reduction as a function of the ratio $t_1/t_2$. It is
found that for $t_2 = 1$ nm and $t_2 = 2$ nm, the dependences of the relative current reduction
on the ratio $t_1/t_2$ are almost the same.

For comparison sake, we consider a composite structure of a inner insulator with $\epsilon_1 = 80$
and an outer insulator with $\epsilon_2 = 3.9$ (as for SiO$_2$),
calculate the relative current reduction at $V_g = -0.1$ V for different inner-insulator thicknesses $t_1$
fixing the outer insulator thickness as $t_2 = 1$ nm (or $t_2 = 2$ nm),
and the obtained results are shown as open triangles (or solid triangles) in Fig.\ref{RTS_cgi}.
It is found from Fig.\ref{RTS_cgi} that if $t_1/t_2 \stackrel{>}{\sim} 10$
the relative current reduction at $V_g = -0.1$ V reaches approximately saturation. And the saturation
value of the relative current reduction is
around 49\% and 30\% for $\epsilon_1 = 40$ and $\epsilon_1 = 80$, respectively.
Such amplitudes of the RTS noise in the turn-on region are much smaller than
the corresponding RTS noise amplitude for the SiO$_2$-only gate oxide.

\section{Conclusions}
\label{sec_4}

In this work, we calculate current through a ballistic p-type carbon nanotube transistor, using
the nonequilibrium Green function method in a tight-binding approximation.
The obtained current for an idea CNFET (i.e., without any charged defect) is in good agreement
with experimental result[\onlinecite{Franklin}].
From the calculated current through a CNFET with and without charged defect in the device,
we evaluate the amplitude of the random-telegraph-signal noise
due to the defect.
We have investigated the dependence of the RTS noise amplitude due to a single postive charge
on the nanotube radius.
It is found that the RTS noise amplitude increases with the decreasing nanotube radius.

We consider as gate dielectrics a composite structure of an inner insulator with a large dielectric constant
and an outer insulator with a dielectric constant of 3.9 (as for SiO$_2$) as shown in Fig\ref{device_setup_2}.
We have studied the relative current reduction due to a charged impurity in the composite gate insulators.
The screening of the impurity charge includes the screening of the impurity charge by the gate electrode
and the screening of the impurity charge by the composite gate insulators.
The screening effect of the impurity charge by the gate electrode increases with the decreasing full thickness
of the composite gate insulators. On the contrary, the screening of the impurity charge by the composite gate insulators
diminishes if the full thickness of the composite gate insulators gets smaller and the thickness of the outer insulator remains the same.
This is because when the thickness of the outer insulator is fixed the effective constant constant of the composite gate insulators
diminishes with the decreasing thickness of the inner insulator.
Since the former screening effect varies with the full thickness of the composite gate insulators slower than the latter
screening effect, the summing-up screening effects of the impurity charge weakens with the decreasing full thickness
of the composite gate dielectrics if the thickness of the outer dielectric remains unaltered.

The relative current reduction due to the impurity charge in a p-type CNFET
increases with the decreasing ratio of the inner-insulator thickness to the outer-insulator thickness.
If the inner insulator is very thin, even though its dielectric constant is as large as 80, the amplitude
of the RTS noise caused by the charge of Q = +1e may amount to around 80\% in the turn-on region.
If the thickness of the inner gate insulator is much larger than the thickness of the outer gate insulator,
the RTS noise caused by the charge of Q = +1e in the composite gate insulators of
a p-type CNFET may be reduced greatly.
If we use a combination of the inner insulator with a dielectric constant of 80 and
the outer insulator with a dielectric constant of 3.9 (as for SiO$_2$)
and the inner insulator is much thicker than the outer insultor, the RTS
noise amplitude due to a charge of Q = +1e may be reduced
to no more than 30\% in the turn-on region and 0.1\% in the on-state.

Since a single defect in the gate oxide of a CNFET may cause a large amplitude of RTS noise, it is important to
establish the effective methods to resist radiations;
on the other hand, CNFETs may also be used for detecting radiations.

\begin{acknowledgments}
We are grateful to S. Heinze for useful discussions.
N-PW acknowledges financial support from The National Natural Science Foundation of China
under Grant No. 61176081 and K.C. Wong Magna Fund in Ningbo University.
\end{acknowledgments}

redpajama_set_name: RedPajamaArXiv


Invited Presenters: Shari Manning, Ph.D. and Kathrine Comtois, Ph.D., M.P.H.
Watch Shari Manning explain what this fabulous training has to offer!
Daily breakfast, lunch, beverages, and afternoon snacks are included in the cost of your registration.
DBT in Action: Case Based Training© is for individuals who have been practicing DBT Individual Psychotherapy in the context of a comprehensive program. This training will build on existing skills and provide opportunities for feedback and consultation designed to increase the capacities necessary for certification in Dialectical Behavior Therapy.
Participants will follow a client named "Lisa" through Stage 1 DBT. Participants will function as "Lisa's" individual therapist and conduct sessions that include pre-treatment, commitment, chain analysis and the interventions that are chosen as part of solution analysis. Strategies will be identified, coached and strengthened by the trainers and other participants. As some participants conduct DBT individual therapy sessions and/or presenting cases, other participants will identify strategies in individual therapy sessions, looking for what is DBT and what is not, and focus on the provision of effective DBT consultation.
Additionally, participants will bring a case formulation of one DBT individual therapy client to the training for consultation.
This workshop will include power point slides and handouts, but the vast majority of the training will be interactional: demonstrating and discussing the effective use of DBT's principles and strategies in individual therapy, consultation team, and skills groups; then having participants practice with coaching and feedback. Taking the DBT practice of participants "to another level" is accomplished by focused, practical, experiential teaching (role-plays, practice exercises) with lots of feedback and discussion; with use of case examples from the instructors and the participants, and the occasional use of a video from the instructors.
Choices Counseling & Skills Center and Institute for Girls' Development are thrilled to have these dynamic and experienced trainers join us to provide Treatment Implementation Collaborative's phenomenal training on DBT case conceptualization!


Something went wrong with my addon and I don't have a log again.
I'm really sorry but something went wrong and I don't have a log file.
As far as I know the addon that toggles logging on/off was on yet no logfile was created.
Ops, forgot to upload them at the end of the night.


Working a full-time job can be stressful. Having kids can be stressful. When you combine the two, it can be enough to make you lose your sanity. If you are a working mom, you might sometimes feel as if you are totally stressed and overwhelmed. This is normal, but there are things that you can do to make things a little bit easier on yourself. Try these tips, and you might see that it will make a big difference in your mental health and overall happiness.
First of all, a lot of people feel as if they have to try to handle everything themselves. It can be easy to have too much pride to want to ask for help, but there is nothing wrong with having others help you every now and then. If you have a family member who doesn't mind picking your kids up every now and then to give you a break, take them up on their offer. If you need help with keeping your house clean, don't be ashamed to hire someone for the job. With a little help, you might find that your household will run a lot more smoothly and that things will be a whole lot easier on you.
It can be tough to keep your home neat and organized when you feel as if you're always on the go. However, keeping things organized can really help you make your days a whole lot easier. After all, the last thing that you probably have time for is finding your child's shoes when you're already running late in the morning.
Using a planner or calendar –whether you choose an old-fashioned option or if you use an application on your smartphone — can help you stay organized. You can track everything from your work schedule to your children's extracurricular activity schedules to when your bills need to be paid. This can help you avoid forgetting the important things and can help you compile a daily to-do list so that you can focus on taking care of everything.
It can be tempting to want to stay up late to watch TV or browse the internet, particularly if you don't get much time to yourself during the day. However, getting in the habit of going to bed earlier can be a good thing, and it can help you ensure that you are getting enough sleep every night. After all, ensuring that you are properly rested is important for your health and can help you get more things done during the day.
If possible, try to wake up a little while before your kids do in the morning. This can give you a chance to write out a daily to-do list while enjoying your morning coffee, and it can also give you time to shower and get ready for the day without having to corral your kids just yet. Plus, you might find that having a little bit of time to yourself in the morning is actually a relaxing start to an otherwise long and stressful day.
Preparing healthy meals for your kids is important, but it can be challenging to do. Doing what you can to make meal prep easier, such as cooking things ahead and stashing them in the freezer or learning a few slow cooker recipes, can save you a lot of time and help you ensure that you get a tasty yet healthy meal on the table for yourself and your kids every night. This can help you avoid the cost and unhealthy side effects of hitting up a drive-through or ordering pizza every night.
If you are like many working parents, you might feel as if all of your time is dedicated to working and taking care of your kids. Make sure that you pencil in some "me" time for yourself here and there, even if it's just a few minutes to enjoy a nice, relaxing hot bath.
It might sound like a joke, but it's not a bad idea to seek therapy if you are a busy, hardworking mom who feels like you have a lot on your plate. Going to therapy does not mean that there is anything wrong with you; it is just a tool that you can use to get help in coping with your day-to-day life. Focusing on your mental health is important for your own sake and for the sake of your children, so it's definitely something to consider.
As you can see, there are a few foolproof tips that you can follow if you want to keep yourself sane as a working mom. It's true that things might still get more than a little stressful every now and then, but if you follow these tips, you can help make things at least a little easier for yourself.


Lovely Gothic leggings from Devil Fashion. Featuring lace paneling on both thighs, these leather look leggings are simple, but effective. Made from 95% Polyester and 5% Elastane, these leggings are perfectly stretchy, generously sized, and a great way to complete your Gothic look.
Full retail price is £22.99. You will save £3 by shopping with LB!


text:
Braywick is a linear suburb in the southern portion of the unparished area of Maidenhead and formerly in the civil parish of Bray in the English county of Berkshire. It is incorrectly called Bray Wick on Ordnance Survey maps.

Geography

Natural conservation areas
Braywick Park is a park and local nature reserve on the west side of the York Stream. Adjoining this, on the east side of York Stream, is a site of Special Scientific Interest (SSSI) called Bray Meadows.

Notable people
Arthur Dillon (1750–1794) was an Irish Catholic aristocrat born in England who inherited the ownership of a regiment that served France under the Ancien Régime during the American Revolutionary War and then the French First Republic during the War of the First Coalition.

References

External links

Villages in Berkshire
Maidenhead
Bray, Berkshire

redpajama_set_name: RedPajamaWikipedia


Use the above link to make an appointment during Brad's office hours. Note: the link only works for active FIT Google accounts. All others, please email for appointment times.
As our culture becomes more and more visual, photographs play a bigger role in communicating ideas. Photographs are used to sell products, tell a story, or convey a mood. Therefore, talented and skilled photographers are in high demand. What makes a great photo? In FIT's Photography Department, the focus is not solely on a pretty or well-composed image. We are interested in the very essence of photographs and how they communicate complex ideas.
Whether your interest is in advertising, fashion, photojournalism/documentary, or fine art photography, our faculty of professional photographers will prepare you with the skills and knowledge you need to reach your goals as a visual artist. You'll study the latest techniques, learn about camera formats, lighting, and photo styling, and become proficient in both digital and analog technologies. Frequent critiques help you identify your strengths and weaknesses, shaping your identity as an individual creative artist.
Classrooms are professionally equipped photography studios, darkrooms, and digital editing labs.
create a network of contacts through seminars, guest lectures, and industry events.
explore museums, galleries, and photo studios in New York City, the center of the art world and your extended classroom.
develop a portfolio of work that meets the highest professional standard.
gain an international perspective on photography with study abroad opportunities in Europe and India.


text:
static const AVOutputFormat * const muxer_list[] = {
    NULL };

redpajama_set_name: RedPajamaGithub


text:
Q: failed command: READ FPDMA QUEUED, Freezes and IO errors on Ubuntu 18.04 Here is the latest error that I got:
Mar 31 12:16:17 hristo-ws kernel: ata5.00: exception Emask 0x1 SAct 0x70000 SErr 0x0 action 0x6 frozen
Mar 31 12:16:17 hristo-ws kernel: ata5.00: irq_stat 0x40000008
Mar 31 12:16:17 hristo-ws kernel: ata5.00: failed command: READ FPDMA QUEUED
Mar 31 12:16:17 hristo-ws kernel: ata5.00: cmd 60/00:80:90:4d:10/01:00:06:00:00/40 tag 16 ncq dma 131072 in
                                           res 40/00:84:90:4d:10/00:00:06:00:00/40 Emask 0x1 (device error)
Mar 31 12:16:17 hristo-ws kernel: ata5.00: status: { DRDY }
Mar 31 12:16:17 hristo-ws kernel: ata5.00: failed command: READ FPDMA QUEUED
Mar 31 12:16:17 hristo-ws kernel: ata5.00: cmd 60/08:88:b8:9c:b1/00:00:07:00:00/40 tag 17 ncq dma 4096 in
                                           res 40/00:01:00:4f:c2/00:00:00:00:00/00 Emask 0x5 (timeout)
Mar 31 12:16:17 hristo-ws kernel: ata5.00: status: { DRDY }
Mar 31 12:16:17 hristo-ws kernel: ata5.00: failed command: READ FPDMA QUEUED
Mar 31 12:16:17 hristo-ws kernel: ata5.00: cmd 60/08:90:c8:20:25/00:00:06:00:00/40 tag 18 ncq dma 4096 in
                                           res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x5 (timeout)
Mar 31 12:16:17 hristo-ws kernel: ata5.00: status: { DRDY }
Mar 31 12:16:17 hristo-ws kernel: ata5: hard resetting link
Mar 31 12:16:17 hristo-ws kernel: ata5: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Mar 31 12:16:17 hristo-ws kernel: ata5.00: configured for UDMA/133
Mar 31 12:16:17 hristo-ws kernel: ata5.00: device reported invalid CHS sector 0
Mar 31 12:16:17 hristo-ws kernel: ata5: EH complete
Mar 31 12:16:17 hristo-ws kernel: ata5.00: exception Emask 0x0 SAct 0x14 SErr 0x0 action 0x0
Mar 31 12:16:17 hristo-ws kernel: ata5.00: irq_stat 0x40000008
Mar 31 12:16:17 hristo-ws kernel: ata5.00: failed command: READ FPDMA QUEUED
Mar 31 12:16:17 hristo-ws kernel: ata5.00: cmd 60/00:10:90:4d:10/01:00:06:00:00/40 tag 2 ncq dma 131072 in
                                           res 41/40:00:90:4d:10/00:01:06:00:00/40 Emask 0x409 (media error) <F>
Mar 31 12:16:17 hristo-ws kernel: ata5.00: status: { DRDY ERR }
Mar 31 12:16:17 hristo-ws kernel: ata5.00: error: { UNC }
Mar 31 12:16:17 hristo-ws kernel: ata5.00: configured for UDMA/133
Mar 31 12:16:17 hristo-ws kernel: sd 4:0:0:0: [sdc] tag#2 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Mar 31 12:16:17 hristo-ws kernel: sd 4:0:0:0: [sdc] tag#2 Sense Key : Medium Error [current]
Mar 31 12:16:17 hristo-ws kernel: sd 4:0:0:0: [sdc] tag#2 Add. Sense: Unrecovered read error - auto reallocate failed
Mar 31 12:16:17 hristo-ws kernel: sd 4:0:0:0: [sdc] tag#2 CDB: Read(10) 28 00 06 10 4d 90 00 01 00 00
Mar 31 12:16:17 hristo-ws kernel: print_req_error: I/O error, dev sdc, sector 101731728

What could this mean? And how to fix it?

A: Your computer tries to communicate with the disk on ata5 that failed.

*

*Check the SMART data from your disk to see if your disk turned bad

*And check the connections / cables to your drive

redpajama_set_name: RedPajamaStackExchange


Island Squeeze by I Love Salts by Mad Hatter Juice is the ultimate nicotine salt blend featuring a blast of tropical guavas followed by a healthy mix of vine-ripened strawberries and exotic kiwis to create a tasty vape. The beautiful tropic blend of guava, strawberry, and kiwi will have you feeling calm and vaping refreshed.
Every time you take in some vapor, you're treated to the ripe, tangy and sweet fruity trio of juices as they soak each taste bud, making your mouth water instantly. Once you let it go, you thirst, and cravings will be quenched.
Island Squeeze from I Love Salts comes in a 30ml Unicorn gorilla bottle. The smooth and nice throat hit you get will keep you stranded where you are. In this case, that's not a bad thing.


Earlier this month the U.S. attorney for the Southern District in New York charged 26 people with taking part in a mortgage fraud scheme companies that brokered loans with a total face value of more than $200 million. Many of the defendants worked for Galina Zhigun, who owns a Brooklyn-based mortgage brokerage called AGA Capital, which later became Lending Universe. The indictment said that the the scammer companies earned at least $4 million in commissions and fees. Lenders lost at least $4.5 million because they relied on false information.
So what kind of business was Lending Universe? After the jump, watching a video they produced to show you how easy it is to get a loan. And then write yourself a note not to trust mortgage brokers who play first person shooter games where they gun down lenders.
Want to play yourself? Click here. Don't forget to shoot the cat.


text:
Virtual tours held monthly via Zoom, click here for more info!
Join us for our Annual Winter Open House! Held virtually January 31, 2021. Click here for more info!
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Reimagining Education
Welcome to The Attic Learning Community, nurturing in children a sense of self, a passion for learning, community, and childhood.
Join us for a Virtual Tour - available every month via Zoom!
The Attic is a unique and innovative pre-K through 12th progressive learning community located in Woodinville, WA. Our mission is to nurture in all children a sense of self, a passion for learning, community, and childhood.
Ask yourself: What is your greatest hope for your child?
At The Attic, our greatest hope is that children will be authentic—that they will truly know who they are, and that they will be empowered to bring their unique gifts into the world. We support them in fulfilling this hope through our unique paradigm that sees education as founded on trusting each individual child's long-term growth and development. With this vision at the heart of our work, we nurture autonomy and a sense of self as we foster a passion for learning, community, childhood.
Sense of Self
Passion for Learning
The Attic is a vibrant, thriving, multi-age community of learners. We have a rich history of innovation in education, and we continue to foster our unique vision today on our beautiful campus in Woodinville, WA.
Our Community >>
Our Campus >>
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The Attic's core program attends to the needs of the whole child, encompassing academics, social/emotional growth, and community across all ages.
EXPLORE OUR CORE PROGRAM >>
Teens Steer Their Own Education
Student to Teacher Ratio
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Multiage
Primary – High School
The Attic was founded
Outdoor Preschool founded in
Balance of Childhood and Academics
Acre Campus on Rowlands Creek
Join Us in Reimagining Education...
The Attic is a model learning community. As we launch into our third decade, our next learning edge is to explore the most effective ways to reimagine and impact education beyond our four walls. Whether you are new to the field of teaching, a kid-at-heart committed to making schools healthier places for children, a seasoned educator, or an artist or investor wanting to create a brighter future for all, we invite you to join us in reimagining education.
Collaborate >>
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24023 51st Ave SE
Woodinville, WA 98072
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Our trust in the child is at the center of our community's culture and our core academic program. We support autonomy, self-knowledge, and intrinsic motivation as foundational to flourishing in life. We see every child as a naturally innovative, resourceful, and whole person. Children come to us innately prepared to be creative, curious, lifelong learners.
From a very young age, Attic learners are given freedom to self-advocate, to make decisions, and to have a voice in the community and in their own education. Out of this autonomy, a strong sense of self develops. Attic kids see themselves as learners! They are readers, writers, problem-solvers, mathematicians, scientists, and artists. They are community builders and friends. They are responsible for themselves and their futures.
We nurture this sense of self-confidence and agency by stressing collaboration over competition and by encouraging intrinsic motivation to learn without external rewards and punishment. We do not grade, and we do not test. Our teens leave The Attic having retained their innate childhood sense of self-confidence, curiosity, and creativity, prepared to launch into adult life as passionate and self-determined individuals.
At The Attic, we know that the most important agent of learning is the learner. We understand that learning looks different for everyone, and the cornerstone of education is respect for each learner's individual developmental journey. We see learning as a continuum—and knowledge as a lifelong road one walks. We focus not on "benchmarks" or externally defined mileposts, such as age or grade-level, but on learning to learn, and on celebrating what can be learned deeply when a child is given time. Our goal is that each Attic child sees him/her/themself as a capable, confident, self-directed learner.
Our approach to teaching and learning is influenced by Piaget's constructivist theory. Piaget identified three types of knowledge: social, physical, and logical-mathematical. Autonomy, Piaget said, is the aim of education. Children are naturally curious, creative constructors of their own knowledge. They learn by seeing, doing, thinking, and being in relationship. They learn in unique ways and on their own developmental schedule. Teaching in accordance with this understanding of learning means creating a safe environment—free from rewards and punishments, and nurtured by the love of a close community—in which these inherent traits can grow and thrive.
At The Attic, we value community as an essential element of education.
At The Attic the child is at the heart of all we do. Learning here is teacher-supported, but child-driven. With that in mind, play is integral to our educational philosophy and is an active and vivid part of our approach to academics. We value and encourage learning with joy, with creativity, and with new eyes. Our mission is to support children to become their true selves, to nurture their innate passion for learning, to surround them with acceptance as they take on the unique challenges of growing up, and to love them throughout their educational journey.
We prioritize long-term goals for our children in everything we do, educating with the whole-child in mind. This means gifting each learner with trust, acceptance, time, autonomy, choice, and authentic opportunities to learn.
At the very center of an Attic education is the child.
In community, we are stronger and more innovative. In community, we can learn and grow knowing we are safe to take risks, to be ourselves, and to meet challenges—all because we are loved, just as we are.
The Attic is a multi-age community of learners, where children have authentic opportunities to develop deep relationships with other learners of all ages. This community gives younger children the gift of role models, and older children the gift of leadership. Our kids mentor one another, problem-solve together, and see one another as equals. Through their relationships with each other, they learn how to participate in civil discourse, collaborative work, conflict resolution, and healthy friendships. Our culture is one of acceptance, of cooperation, and of mutual respect for all.
The Attic Learning Community
For more information, please contact the Development Office.
Annual Winter Open House
Come learn about our progressive, child-centered approach to education! Our Annual Winter Open House will be held virtually this year – via Zoom. RSVP at the link below to sign up!
We are currently accepting applications for Fall 2020 and 2021. Tours are held monthly online. More info available on our Admissions Page.
Learn more and RSVP

redpajama_set_name: RedPajamaCommonCrawl


If there's one thing that can't be missed while visiting the beautiful Bordeaux & Dordogne area, it's – you guessed it - the wine it's famous for. Bordeaux wine is a synonym to quality for sommeliers and the Dordogne hosts some of the world's most famous vineyards, a must for vino-philiacs who want to experience true variety and authenticity.
The Bordeaux wine region is the world's largest and oldest of its kind, stretching over an impressive 112,000 hectares, providing 7,000 winegrowers, 300 wine merchants and 93 brokers. An awe-inspiring five million hectolitres are produced here annually, 89% of which are red. The Medoc wine region north of the city of Bordeaux is known for its Margaux, Pauillac and Saint Julien reds, whilst the southern Graves region is home to the premiere Cotes de Bordeaux, such as the Cabernet Sauvignon and Malbec reds. Reds from the Gironde are some of the best of Bordeaux, including Cabernet Franc and Petit Verdot grape varieties. Head east to Pomerol and UNESCO World Heritage village St Emillion to find fantastic cellars and celebrated aged Petrus wines.
The Dordogne region includes some of the most famous vineyards such as the Bergerac situated on the northern banks of the Dordogne River, renowned for its Bergerac, Pecharmant, Monbazillac, Saussignac, Rosette and Montravel. Local wines can be tasted in numerous cellars throughout the region, with 'Chateaux at Monbazillac' as a popular choice. Additionally, many of the beautifully historic wine-producing châteaux scattered along the Dordogne River have been turned into fabulous hotels that are well worth a visit.
But don't just take our word for it - get a taste of Bordeaux and the Dordogne for yourself.
Harriet and Kate L are our 'Wine Tour in Bordeaux & the Dordogne' experts and as seasoned travellers they have the inside track on the most memorable adventures.


Set on the stunning Jimbour Plains, Big Skies is an annual event celebrating the sights, tastes and unique experiences of the Western Downs.
The Big Skies festival boasts nine days of fantastic events from Saturday 27 April to Sunday 5 May. Kicking off with the Dalby Picnic Races, Big Skies also features tours of the historical Jimbour House, camp bonfires, an outdoor cinema, regional tours and more. The 2019 festival will come to an end with the best Aussie rock west of the Great Divide at Day on the Plain. The show stopping rock concert will feature Jon Stevens, John Paul Young, Ross Wilson, Pseudo Echo and Deni Hines.


The 14-acre rhododendron and azalea gardens at Stody Lodge near Holt in North Norfolk will be welcoming the public through its gates once again next May.
These exceptional gardens are popular with both local and national coach tours thanks to its warm welcome and extraordinary explosion of colour that provide a great day out for even non-garden lovers.
Visitors to these gardens, a hidden gem in North Norfolk, will be amazed by the riot of colour thanks to its extensive collection of over 200 varieties of rhododendrons and azaleas. This intensity of colour is softened by beautiful magnolias, camellias, ornamental and specimen trees, late daffodils and bluebells. There are also beautiful rhododendron-lined woodland pathways to explore and expansive lawns and magnificent yew hedging to enjoy.
Stody Lodge also boasts a little-known national treasure: its exceptional four-acre Azalea Water Gardens which is widely believed to be the largest single planting of vividly coloured azalea mollis (over 2,000 plants) in the UK.
London architect Walter Sarel was commissioned to design Stody Lodge and its gardens in 1932 by the 1st Viscount Rothermere, the British newspaper proprietor and founder of the Daily Mail and Daily Mirror. The gardens' original design have been protected as much as possible whilst developing new areas, deepening the herbaceous borders and adding interest around the lodge.
Stody Lodge Gardens is proud of the warm welcome it extends to all its visitors. It offers delicious homemade teas in aid of local charities, a plant stall by the local award-winning Edgefield Nurseries, and good wheelchair access to most areas of the garden. Dogs on leads are also welcome.
Stody Lodge Gardens is open 1pm-5pm on Sunday 6th, Sunday 13th, Sunday 20th, Sunday 27th and Bank Holiday Monday 28th May 2018.
Entrance is £6, children under 12 free, payable by cash or cheque.


It's hard to imagine seeing 15,000 Corvettes in one place. But then again, it's also hard to imagine how Mike Yager, a former tool-and-die maker, was able to turn a business run out of the trunk of his car into a multi-million-dollar industry leader in Corvette parts and accessories. Nonetheless, he did, and it's Mid America Motorworks, the company he created, that hosts Corvette Funfest. An annual customer appreciation party usually thrown in September, Funfest draws 15,000 Corvettes to the Mid America corporate campus in Effingham, Illinois, effectively quadrupling the town's population over a long weekend.
"You've got to come," the Mid America folks told me last year when I was covering the Walter Mitty Challenge. And come I did. Having penciled in the September 19-21 dates on my mental calendar, when the 18th rolled around, I fueled up my blacked-out Crown Vic Police Interceptor and headed north through Tennessee and Kentucky to Effingham. Perhaps it was a travesty to drive a Ford, but what Corvette get-together is complete without a Crown Vic in the rearview?
Funfest has traditionally been held on the corporate campus of Mid America Motorworks, which contains the Performance Choice manufacturing facility, Mike Yager's MY Garage museum, and a seemingly endless collection of automotive memorabilia.
Theoretically, I could have flown, but somehow it seemed wrong not to drive. Besides, the nearest airport is in Indianapolis. So after 10 hours of road construction, accident cleanups, and endless cups of coffee, I straggled into the Fairfield Inn, past the framed Funfest Corvette Challenge poster on an easel in the lobby. Fortunately, my reservations were made a couple of months earlier: Many of the hotels have special event rates for Funfest, but if they don't have any rooms left, the rate hardly matters.
Now is a good time to point out that Funfest isn't a car show; it's called a "customer appreciation party," and that's pretty accurate. The leading item at the top of the calendar of events reads, "All Day...Have Fun." There's no cost to attend, and there's a vast spectrum of things to do over the Friday, Saturday, and Sunday that comprise the event. From tours of Mid America's facilities to displays set up by Corvette-parts vendors (many of whom will do installations on the spot) and autograph sessions and seminars with some of the top names in the hobby, the only hard part is trying to see everything. In addition, every year Funfest has a theme, usually related to one or more of the cars that reside in Mike Yager's MY Garage museum. Last year, it was Corvette Summer; this year the chosen cars were the Corvette Challenge cars from 1988 and 1989.
Although traffic flow is carefully managed through color-coded gates, it takes some time for the flow of Corvettes to make its way onto the grounds. Expect to idle a while and enjoy the view--you won't get many chances to see this many Vettes in one place.
Not long after its introduction in 1984, the C4 Corvette went on to absolutely flog the competition in the SS class of the SCCA's Showroom Stock Endurance Championship. With a record of 19-0 during its three years of dominance, the Corvette won the '87 manufacturer's title by 81-7, understandably upsetting other manufacturers--specifically, Porsche, who wasn't used to getting its clock cleaned so monotonously. "While we would be content to thrash our competition eternally," the poster announcing the Corvette Challenge read, "the gruesome sight proved to be too brutal for the SCCA." Sort of. It was actually too brutal for the boys from Stttgart, who threatened to take their toys and go home if SCCA didn't ban the Corvette from competition.
So, with Teutonic efficiency, the best Corvette yet was thrown out on its ear. Enter John Powell, who was running a race series in Canada. Largely by force of personality, he convinced Goodyear, Exxon, and the then-much-smaller Mid America to put up a total of $1 million to start a new, Corvette-only race series. With sponsorships in hand, he approached Chevrolet and asked them to produce 50 factory race cars for the series he had named the Corvette Challenge. Although the General had been conscientiously aloof from racing for decades, Powell's persuasive power carried the day. On March 29th, five months after being tossed out of SCCA, the identical factory racers were delivered to their teams at Chevrolet's Central Office in Warren, Michigan.
"Install Alley" is the area where aftermarket components purchased at Funfest are installed on-site while you wait. Exhaust systems are a particularly popular upgrade, with Billy Boat, Borla, and Corsa all exhibiting at Funfest.
Identical in every specification and dyno-tested to prove it, the Challenge cars even had their engines sealed with a special green paint to ensure horsepower parity between competitors. If ever there was a race series about drivers, this was it. And if they thought the SCCA was brutal, that was nothing compared to the Corvette Challenge, which has also been described as "close-order combat." With a million dollars in prize money up for grabs, no equipment advantage whatsoever, and young, aggressive drivers who usually didn't own the cars they were pounding on, the word "intense" barely begins to describe the fierceness of the competition. Perhaps the best way to explain it is to say that Steve Wiedman, who was Mid America's motorsports director at the time and worked the GM parts truck at each race, was also responsible for keeping fresh Mid America stickers on the Challenge cars' front bumpers. The problem? The logos were often scuffed up by other competitors' wheels.
The '88 and '89 Corvette Challenge grew out of the C4's competitive dominance, which eventually led to the car's ouster from the SCCA. Two years of raucous driving later, the series was canceled, making instant collectibles out of the Chevrolet-produced factory racers.
The series drew so much attention that ESPN contracted to cover the series in 1989. What makes this significant is that it marked the first time a network had displayed real-time performance data--such as engine rpm, gear selection, and speed--alongside the in-car video footage of the race. Commonplace now, this was the height of technology at the time, and mind-numbingly difficult to put together.
Unlike the '88 Challenge cars, the '89s had exhaust pipes that exited through the rear bodywork. Adding a little extra exhaust noise certainly didn't hurt the popularity of the series.
Other seminars offered during Funfest included interior installation demos for C3, C4, and C5 Corvettes and a broad selection of performance-related topics. Mike Wood of Nitrous Express gave a seminar on the basics of nitrous, and braking was covered in a presentation by Baer Brakes, whose techs did while-you-wait installations on brake systems purchased at Funfest. Automotive writer Dave Emanuel spoke on tuning and tweaking the C5 and C6, and fellow writer Richard Newton covered suspension and autocrossing. I was fortunate enough to get to spend some time talking with both Emanuel and Newton, which brings up another of the wonderful things about Funfest: Between seminars and autograph sessions--and just plain running into folks while you're walking around--it gives you the opportunity to meet some of the biggest names in the Corvette hobby. From Bob Bondurant and Reeves Callaway, to noted Corvette restorer Kevin Mackay and Corvette Chief Engineer Tom Wallace, Funfest provides a unique chance to interact with people you otherwise might only read about.
Mike Yager, founding father of Mid America. In addition to being a part of the Corvette Challenge panel discussion, Yager could be found autographing copies of his Corvette Bible, presenting the Celebrity Choice awards, and generally serving as the host of Funfest.
It also puts you in the same place with some truly unbelievable cars, such as the new ZR1, which GM engineers brought to Funfest in triplicate. Not only did the good folks from GM show off the supercharged, 638hp beast in walk-around tech briefings, but they also offered rides. This went over swimmingly until one of the ZR1s--the yellow one, predictably--was pulled over during a demo. I don't know the exact speed, but word on the street was that it was running about a hundred...over.
Editor Jay Heath referred to this event in a previous issue as possibly apocryphal. Being of an inquisitive mind myself, I did my best to ascertain the actual facts of the encounter. Mike Yager referred to the exact speed as "about a buck over," high enough to make it what Illinois law refers to as a "general offense" (read: jail time). Although I later overheard the passenger who was in the car at the time say they were doing 120, I decided that going straight to the source--the driver, whose name I'm not printing here--would be best.
Yager mans the autograph table, flanked by super-tuner Reeves Callaway (left) and Vehicle Line Executive Tom Wallace. Other luminaries on hand included Bowling Green Assembly Plant Manager Paul Graham, race legend Bob Bondurant, former Corvette Chief Engineer Dave McLellan, and Corvettes at Carlisle honcho Lance Miller.
He shrugged when I asked him what happened. "You know, it's a ZR1. They wanted to know about the car."
"How fast were you going?"
"I don't know, I was watching the road." He raised his hands helplessly. "That's what you're supposed to do, right?"
With all of the seminars and exhibitors--and the tours of Mid America's Performance Choice manufacturing facility and the MY Garage Museum--it's tough to take the time to simply walk down the rows and rows of Corvettes parked side-by-side. But it's something worth doing; you'll see every generation, from stock, fully restored C1s to restomods that have virtually no actual Corvette parts in them. You can always pony up the $20 for a helicopter ride that will circle you around the area and give you a bird's-eye view, but it's in getting right there next to them that you get a real sense of the broad variety of Corvettes that show up.
The new ZR1 was one of the stars of the show. GM engineers provided both walk-arounds of the car as well as rides--all well and good until that nasty incident with the Sheriff's deputy.
Not only do you get to see what others have done with their cars, there's also the opportunity for your car to be recognized, because walking with you down those aisles will likely be one of the celebrity judges. Made up of members of the motoring press and a variety of VIPs from the hobby, the judges get to pick their favorite cars from those who attend, and their selections are announced at the end of every day. From a beautifully restored '54 that was trailered there to a supercharged Callaway C6 Pace Car, the cars selected are as individual as the owners who created them and the judges that chose them (look for an upcoming article on the '68 restomod selected by Editor Heath).
Watching the proud owners as they receive their awards from Mike Yager, you get a new sense of what this event--and the hobby--is all about. Steve Wiedman put it best when we were talking about the Corvette Challenge cars: "It's about the people. It revolves around the cars, but it's really about the people."
Special thanks to Ed Baumgarten, Valerie Corrie, Lori Worman, and Mike and Laurie Yager.


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Warming Arctic climate constrains life in cold-adapted mammals
Despite the growth in knowledge about the effects of a warming Arctic on its cold-adapted species, how these changes affect animal populations is poorly understood. Research efforts have been hindered by the area's remoteness and complex logistics required to gain access.
A new study led by Joel Berger, professor in the Department of Fish, Wildlife and Conservation Biology at Colorado State University, has uncovered previously unknown effects of rain-on-snow events, winter precipitation and ice tidal surges on the Arctic's largest land mammal, the muskoxen.
The warmer climate is stressing mothers and young muskoxen, said Berger, also a senior scientist with the Wildlife Conservation Society. Rain-on-snow events occurring in the winter -- when muskoxen gestate -- and unusually dry winter conditions have also led to underdeveloped skeletal growth in juvenile muskoxen. This effect can be traced back to their pregnant mothers.
"When rain-on-snow events occur in the Arctic, due to warming temperatures, and the snow freezes again, this leads to mothers not being able to access food for adequate nutrition," said Berger. "The babies then, unfortunately, pay the price."
The smaller size observed in juvenile and young adult muskoxen is associated with poorer health and fitness, due to delayed puberty, and increased mortality, according to the research team.
In addition, scientists documented a mass mortality event due to a one-time extreme ice event caused by a tidal surge. In February 2011, an historically high tidal surge resulted in at least 52 muskoxen being submerged at the northern coast of Bering Land Bridge peninsula.
Researchers also found historical records documenting deaths due to rapid freezing and thawing during winter at a range of single sites of whales -- 170 Beluga and 150 narwhals -- and sea otters along the Aleutian Islands.
"Unlike polar bears, which are on the world's stage, no one really knows about muskoxen or cares," said Berger. "They roamed with wooly mammoths but still survive. Muskoxen are feeling the heat, just as we humans are feeling the extremes of climate. These wild weather swings have massive impacts on us. Solutions are clear, but we fail to respond by changing our consumptive ways."
Measuring a muskox, tracking temperatures
The research team analyzed head size of juvenile muskoxen using digital photo data over the span of seven years and at three sites in Alaska and Russia. They also compiled winter weather data for the Alaskan sites from the closest weather stations maintained by the National Oceanic and Atmospheric Administration. Data used to calculate rain-on-snow events on Wrangel Island, located in the Arctic Ocean, between the Chukchi Sea and East Siberian Sea, were from the Federal Hydro-meteorological Service of Russia, whose records date back to 1926.
Berger acknowledged the role his research plays "in a challenging political era." His collaborators include Russian scientists in Asia and the Alaskan Arctic. Berger is not only a researcher, but he also serves as a diplomat of sorts, working closely with Russian research counterparts and the government. He praised them for their active engagement and willingness to share data.
"To better understand how species like the muskoxen are responding to a changing Arctic, we must collaborate, so that we can document rare and often tragic events, and gain additional insight from local people," said Berger.
The study, "Climate degradation and extreme icing events constrain life in cold-adapted mammals," was published in Scientific Reports, an online open access journal from the publishers of Nature.
Co-authors of the study include Cynthia Hartway, Wildlife Conservation Society and South Dakota State University; Alexander Gruzdev, Wrangel Island World Heritage Site; and Michael Johnson, U.S. Forest Service in Juneau, Alaska.
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South Sudan army downplays severity of discontent with General Thomas Cirilo
April 7, 2016 (JUBA) – South Sudanese army (SPLA) has downplayed severity of anger of its deputy chief of general staff for logistics, General Thomas Cirilo Swaka, over land grabbing in Juba and warned media outlets against publishing stories about the matter.
Lt. Gen. Thomas Cirilo Swaka, the ex-SPLA deputy chief of general staff for training (youtube photo)
Local media outlets in the national capital published a story last week, alleging that General Swaka has declared to fight against land grabbers in defence of lands of his Bari community in Juba and its surrounding areas.
This followed an incident of land grabbing last month in his home village located southwest of Juba, where new settlers identified to be members of the South Sudan's largest ethnic group, the Dinka, particularly from Bor and Apadang sections attempted to illegally occupy it.
However, a press statement issued on Thursday by the SPLA spokesperson, Brigadier Lul Ruai Koang, denied the depicted situation, saying General Swaka has not declared to fight for his community.
"SPLA GHQs [General Headquarters] has noted with great concern malicious rumors that had been circulating on social and print media outlets against Lt. Gen. Thomas Cirilo Swaka, Deputy Chief of General Staff for Logistics. The Down Daily Newspaper on Tuesday 29 March 2016 Vol.1 Issue 046 published a story on its front page" I will fight along Bari community against land grabbers." This attention capturing headline was said to have been uttered by Gen. Thomas Cirilo," the statement partly reads.
"On the same note, SPLA warns some reckless media agencies that legal action will be taken against institutions found defaming our officers in particular and the army in general," said the SPLA spokesperson.
He said the army was compelled by severity of "these potentially damaging allegations against this high ranking officer", and therefore the SPLA high command through the office of the Spokesperson has concluded that a press conference was necessary in order to "clear the air and put some records straight."
It was not clear why it took the SPLA high command up to 9 days to respond to the allegations published since 29 March, 2016.
In the statement the army's spokesman pointed out that, as a professional military officer, General Thomas Cirilo does not receive directives from his community to confront land grabbers who had threatened indigenous people in the area.
Brig. Koang said General Swaka did not threaten to leave the army for Rajaf in order to fight land grabbers, but admitted that the General does visit the village where the land grabbing was taking place.
"I hereby confirm that he stays at his official residence in Juba not in Rajaf where he is reported to be monitoring the situation. However, it's good to underscore that the Gen. does go to his village especially over the weekends," he said.
Brig. Koang who conducted a press conference on Thursday in Juba said the army's General Headquarters "condemns in the strongest terms possible deliberate acts aimed at defaming and tarnishing images" of officers from the army.
Last month, reports indicated that General Swaka was angered by an attempt to grab lands in his home village, prompting the army to chase away land grabbers from the village.
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Egyptian police arrest 7 Sudanese trying to sneak into Israel
ICG urges international mobilization to break Sudan's Abyei deadlock


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