9,771 research outputs found
Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)
The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of
(Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect
(MOKE). A transient MOKE signal followed by low amplitude oscillations was
evidenced, with a strong dependence on applied magnetic field, temperature and
ps-ASP amplitude. Careful interferometric measurement of the layer's thickness
variation induced by the ps-ASP allowed us to model very accurately the
resulting signal, and interpret it as the strain modulated reflectivity
(differing for probe polarizations), independently from dynamic
magnetization effects.Comment: 6 pages, 5 figure
The Dutch version of the Child Posttraumatic Cognitions Inventory:validation in a clinical sample and a school sample
With the inclusion of trauma-related cognitions in the DSM-5 criteria for posttraumatic stress disorder (PTSD), the assessment of these cognitions has become essential. Therefore, valid tools for the assessment of these cognitions are warranted
Quantitation of Human Immunodeficiency Virus Provirus and Circulating Virus: Relationship with Immunologic Parameters
Virologic and seroimmunologic parameters were determined in 56 persons infected with human immunodeficiency virus (HIV). The provirus level varied from 10 to 100,000/106 CD4+ lymphocytes, and genomic HIV RNA was detectable in 39 of 56 patients at a relative concentration varying from 10 to >250 copies/ml, of serum. Provirus expressed as copies per 106 CD4+ lymphocytes and as circulating virus per milliliter of serum increased with disease progression and decrease of CD4+ cell concentration. The mean provirus concentration expressed per milliliter of blood varied little among categories of patients with various levels of CD4+ cells, but there was a progressive increase of circulating HIV genomic RNA. These virologic data suggest that during the course of HIV infection, an increasing proportion of the remaining CD4+ lymphocytes harbor the HIV genome and produce infectious virus. Finally, there was a marked correlation between increased provirus and genomic RNA concentration and three seroimmunologic markers: decrease in CD4+cell count, p24 antigenemia, and disappearance of antibodies to HIV core antige
Family Dynamics and Personal Strengths among Dementia Caregivers in Argentina
This study examined whether healthier family dynamics were associated with higher personal strengths of resilience, sense of coherence, and optimism among dementia caregivers in Argentina. Caregivers are usually required to assist individuals with dementia, and family members have typically fulfilled that role. Personal strengths such as resilience, sense of coherence, and optimism have been shown to protect caregivers from some of the negative experiences of providing care, though the family-related variables associated with these personal strengths are largely unknown. Hierarchical multiple regressions investigated the extent to which family dynamics variables are associated with each of the caregiver personal strengths after controlling for demographic and caregiver characteristics. A sample of 105 caregivers from Argentina completed a set of questionnaires during a neurologist visit. Family dynamics explained 32% of the variance in resilience and 39% of the variance in sense of coherence. Greater family empathy and decreased family problems were uniquely associated with higher resilience. Greater communication and decreased family problems were uniquely associated with higher sense of coherence. Optimism was not found to be significantly associated with family dynamics. These results suggest that caregiver intervention research focused on the family may help improve caregiver personal strengths in Argentina and other Latin American countries
Radiative hydrodynamics simulations of red supergiant stars: II. simulations of convection on Betelgeuse match interferometric observations
Context. The red supergiant (RSG) Betelgeuse is an irregular variable star.
Convection may play an important role in understanding this variability.
Interferometric observations can be interpreted using sophisticated simulations
of stellar convection. Aims. We compare the visibility curves and closure
phases obtained from our 3D simulation of RSG convection with CO5BOLD to
various interferometric observations of Betelgeuse from the optical to the H
band in order to characterize and measure the convection pattern on this star.
Methods. We use 3D radiative-hydrodynamics (RHD) simulation to compute
intensity maps in different filters and we thus derive interferometric
observables using the post-processing radiative transfer code OPTIM3D. The
synthetic visibility curves and closure phases are compared to observations.
Results. We provide a robust detection of the granulation pattern on the
surface of Betelgeuse in the optical and in the H band based on excellent fits
to the observed visibility points and closure phases. Moreover, we determine
that the Betelgeuse surface in the H band is covered by small to medium scale
(5-15 mas) convection-related surface structures and a large (30 mas)
convective cell. In this spectral region, H2O molecules are the main absorbers
and contribute to the small structures and to the position of the first null of
the visibility curve (i.e. the apparent stellar radius).Comment: 11 pages, Accepted for publication on A&
Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror
We present experimental results showing the diffuse reflection of a
Bose-Einstein condensate from a rough mirror, consisting of a dielectric
substrate supporting a blue-detuned evanescent wave. The scattering is
anisotropic, more pronounced in the direction of the surface propagation of the
evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure
Improving Interferometric Null Depth Measurements using Statistical Distributions: Theory and First Results with the Palomar Fiber Nuller
A new "self-calibrated" statistical analysis method has been developed for
the reduction of nulling interferometry data. The idea is to use the
statistical distributions of the fluctuating null depth and beam intensities to
retrieve the astrophysical null depth (or equivalently the object's visibility)
in the presence of fast atmospheric fluctuations. The approach yields an
accuracy much better (about an order of magnitude) than is presently possible
with standard data reduction methods, because the astrophysical null depth
accuracy is no longer limited by the magnitude of the instrumental phase and
intensity errors but by uncertainties on their probability distributions. This
approach was tested on the sky with the two-aperture fiber nulling instrument
mounted on the Palomar Hale telescope. Using our new data analysis approach
alone-and no observations of calibrators-we find that error bars on the
astrophysical null depth as low as a few 10-4 can be obtained in the
near-infrared, which means that null depths lower than 10-3 can be reliably
measured. This statistical analysis is not specific to our instrument and may
be applicable to other interferometers
Dynamics and Instabilities of Planar Tensile Cracks in Heterogeneous Media
The dynamics of tensile crack fronts restricted to advance in a plane are
studied. In an ideal linear elastic medium, a propagating mode along the crack
front with a velocity slightly less than the Rayleigh wave velocity, is found
to exist. But the dependence of the effective fracture toughness on
the crack velocity is shown to destabilize the crack front if
. Short wavelength radiation due to weak random
heterogeneities leads to this instability at low velocities. The implications
of these results for the crack dynamics are discussed.Comment: 12 page
Abundances of Baade's Window Giants from Keck/HIRES Spectra: I. Stellar Parameters and [Fe/H] Values
We present the first results of a new abundance survey of the Milky Way bulge
based on Keck/HIRES spectra of 27 K-giants in the Baade's Window (, ) field. The spectral data used in this study are of much higher resolution
and signal-to-noise than previous optical studies of Galactic bulge stars. The
[Fe/H] values of our stars, which range between -1.29 and , were used to
recalibrate large low resolution surveys of bulge stars. Our best value for the
mean [Fe/H] of the bulge is . This mean value is similar to the
mean metallicity of the local disk and indicates that there cannot be a strong
metallicity gradient inside the solar circle. The metallicity distribution of
stars confirms that the bulge does not suffer from the so-called ``G-dwarf''
problem. This paper also details the new abundance techniques necessary to
analyze very metal-rich K-giants, including a new Fe line list and regions of
low blanketing for continuum identification.Comment: Accepted for publication in January 2006 Astrophysical Journal. Long
tables 3--6 withheld to save space (electronic tables in journal paper). 53
pages, 10 figures, 9 table
RF spectroscopy in a resonant RF-dressed trap
We study the spectroscopy of atoms dressed by a resonant radiofrequency (RF)
field inside an inhomogeneous magnetic field and confined in the resulting
adiabatic potential. The spectroscopic probe is a second, weak, RF field. The
observed line shape is related to the temperature of the trapped cloud. We
demonstrate evaporative cooling of the RF-dressed atoms by sweeping the
frequency of the second RF field around the Rabi frequency of the dressing
field.Comment: 7 figures, 8 pages; to appear in J. Phys.
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