3,743 research outputs found
KOI-1003: A new spotted, eclipsing RS CVn binary in the Kepler field
Using the high-precision photometry from the Kepler space telescope,
thousands of stars with stellar and planetary companions have been observed.
The characterization of stars with companions is not always straightforward and
can be contaminated by systematic and stellar influences on the light curves.
Here, through a detailed analysis of starspots and eclipses, we identify
KOI-1003 as a new, active RS CVn star---the first identified with data from
Kepler. The Kepler light curve of this close binary system exhibits the
system's primary transit, secondary eclipse, and starspot evolution of two
persistent active longitudes. The near equality of the system's orbital and
rotation periods indicates the orbit and primary star's rotation are nearly
synchronized ( days; days). By assuming the secondary star is on the main sequence, we suggest
the system consists of a subgiant primary and
a main-sequence companion. Our work gives a
distance of pc and an age of Gyr,
parameters which are discrepant with previous studies that included the star as
a member of the open cluster NGC 6791.Comment: 21 pages, 19 figures, accepted to Ap
Privileges and Immunities of Non-Profit Organizations
And now abideth, faith home and charity, these three; but the greatest of these is charity. This unsubtle reference to the word charity describes superficially the field of non-profit or not-for-profit corporation law. The objective of this paper is not to delve into the intricacies and complexities of the non-profit area, but rather to make manifest a few of the many privileges and immunities granted to non-profit corporations
Privileges and Immunities of Non-Profit Organizations
And now abideth, faith home and charity, these three; but the greatest of these is charity. This unsubtle reference to the word charity describes superficially the field of non-profit or not-for-profit corporation law. The objective of this paper is not to delve into the intricacies and complexities of the non-profit area, but rather to make manifest a few of the many privileges and immunities granted to non-profit corporations
Gate-Controlled Electron Spin Resonance in a GaAs/AlGaAs Heterostructure
The electron spin resonance (ESR) of two-dimensional electrons is
investigated in a gated GaAs/AlGaAs heterostructure. We found that the ESR
resonance frequency can be turned by means of a gate voltage. The front and
back gates of the heterostructure produce opposite g-factor shift, suggesting
that electron g-factor is being electrostatically controlled by shifting the
equilibrium position of the electron wave function from one epitaxial layer to
another with different g-factors
Formation of Pillars at the Boundaries between H II Regions and Molecular Clouds
We investigate numerically the hydrodynamic instability of an ionization
front (IF) accelerating into a molecular cloud, with imposed initial
perturbations of different amplitudes. When the initial amplitude is small, the
imposed perturbation is completely stabilized and does not grow. When the
initial perturbation amplitude is large enough, roughly the ratio of the
initial amplitude to wavelength is greater than 0.02, portions of the IF
temporarily separate from the molecular cloud surface, locally decreasing the
ablation pressure. This causes the appearance of a large, warm HI region and
triggers nonlinear dynamics of the IF. The local difference of the ablation
pressure and acceleration enhances the appearance and growth of a multimode
perturbation. The stabilization usually seen at the IF in the linear regimes
does not work due to the mismatch of the modes of the perturbations at the
cloud surface and in density in HII region above the cloud surface. Molecular
pillars are observed in the late stages of the large amplitude perturbation
case. The velocity gradient in the pillars is in reasonably good agreement with
that observed in the Eagle Nebula. The initial perturbation is imposed in three
different ways: in density, in incident photon number flux, and in the surface
shape. All cases show both stabilization for a small initial perturbation and
large growth of the second harmonic by increasing amplitude of the initial
perturbation above a critical value.Comment: 21 pages, 8 figures, accepted for publication in ApJ. high resolution
figures available upon reques
Optimal rotations of deformable bodies and orbits in magnetic fields
Deformations can induce rotation with zero angular momentum where dissipation
is a natural ``cost function''. This gives rise to an optimization problem of
finding the most effective rotation with zero angular momentum. For certain
plastic and viscous media in two dimensions the optimal path is the orbit of a
charged particle on a surface of constant negative curvature with magnetic
field whose total flux is half a quantum unit.Comment: 4 pages revtex, 4 figures + animation in multiframe GIF forma
Hall-effect and resistivity measurements in CdTe and ZnTe at high pressure: Electronic structure of impurities in the zincblende phase and the semi-metallic or metallic character of the high-pressure phases
We carried out high-pressure resistivity and Hall-effect measurements in
single crystals of CdTe and ZnTe up to 12 GPa. Slight changes of transport
parameters in the zincblende phase of CdTe are consitent with the shallow
character of donor impurities. Drastic changes in all the transport parameters
of CdTe were found around 4 GPa, i.e. close to the onset of the cinnabar to
rock-salt transition. In particular, the carrier concentration increases by
more than five orders of magnitude. Additionally, an abrupt decrease of the
resistivity was detected around 10 GPa. These results are discussed in
comparison with optical, thermoelectric, and x-ray diffraction experiments. The
metallic character of the Cmcm phase of CdTe is confirmed and a semi-metallic
character is determined for the rock-salt phase. In zincblende ZnTe, the
increase of the hole concentration by more than two orders of magnitude is
proposed to be due to a deep-to-shallow transformation of the acceptor levels.
Between 9 and 11 GPa, transport parameters are consistent with the
semiconducting character of cinnabar ZnTe. A two orders of magnitude decrease
of the resistivity and a carrier-type inversion occurs at 11 GPa, in agreement
with the onset of the transition to the Cmcm phase of ZnTe. A metallic
character for this phase is deduced.Comment: 20 pages, 4 figure
TGF beta 1 attenuates expression of prolactin and IGFBP-1 in decidualized endometrial stromal cells by both SMAD-dependent and SMAD-independent pathways
Background: Decidualization (differentiation) of the endometrial stromal cells during the secretory phase of the menstrual cycle is essential for successful implantation. Transforming Growth Factor beta 1 (TGF beta 1) canonically propagates its actions via SMAD signalling. A role for TGF beta 1 in decidualization remains to be established and published data concerning effects of TGF beta 1 on markers of endometrial decidualization are inconsistent.
Methodology/Principal Findings: Non-pregnant endometrial stromal cells (ESC) and first trimester decidual stromal cells (DSC) were cultured in the presence or absence of a decidualizing stimulus. Incubation of ESCs with TGF beta 1 (10 ng/ml) down-regulated the expression of transcripts encoding the decidual marker proteins prolactin (PRL), insulin-like growth factor binding protein-1 (IGFBP-1) and tissue factor (TF). TGF beta 1 also inhibited secretion of PRL and IGFBP-1 proteins by ESCs and surprisingly this response preceded down-regulation of their mRNAs. In contrast, DSCs were more refractory to the actions of TGF beta 1, characterized by blunted and delayed down-regulation of PRL, IGFBP-1, and TF transcripts, which was not associated with a significant reduction in secretion of PRL or IGFBP-1 proteins. Addition of an antibody directed against TGF beta 1 increased expression of IGFBP-1 mRNA in decidualised cells. Knockdown of SMAD 4 using siRNAs abrogated the effect of TGF beta 1 on expression of PRL in ESCs but did not fully restore expression of IGFBP-1 mRNA and protein.
Conclusions/Significance: TGF beta 1 inhibits the expression and secretion of decidual marker proteins. The impact of TGF beta 1 on PRL is SMAD-dependent but the impact on IGFBP1 is via an alternative mechanism. In early pregnancy, resistance of DSC to the impact of TGF beta 1 may be important to ensure tissue homeostasis
Spectroscopy of a Cooper-Pair box in the Autler-Townes configuration
A theoretical spectroscopic analysis of a microwave driven superconducting
charge qubit (Cooper-pair box coupled) to an RLC oscillator model is performed.
By treating the oscillator as a probe through the backreaction effect of the
qubit on the oscillator circuit, we extract frequency splitting features
analogous to the Autler-Townes effect from quantum optics, thereby extending
the analogies between superconducting and quantum optical phenomenology. These
features are found in a frequency band that avoids the need for high frequency
measurement systems and therefore may be of use in qubit characterization and
coupling schemes. In addition we find this frequency band can be adjusted to
suit an experimental frequency regime by changing the oscillator frequency.Comment: 13 pages, 7 figures. v2: Revised version after referee comments.
Accepted for publication by Physical Review
A First-Principles Approach to Insulators in Finite Electric Fields
We describe a method for computing the response of an insulator to a static,
homogeneous electric field. It consists of iteratively minimizing an electric
enthalpy functional expressed in terms of occupied Bloch-like states on a
uniform grid of k points. The functional has equivalent local minima below a
critical field E_c that depends inversely on the density of k points; the
disappearance of the minima at E_c signals the onset of Zener breakdown. We
illustrate the procedure by computing the piezoelectric and nonlinear
dielectric susceptibility tensors of III-V semiconductors.Comment: 4 pages, with 1 postscript figure embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/is_ef/index.htm
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