3,301 research outputs found
X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180
The bright, soft X-ray spectrum Seyfert 1 galaxies Ark 564 and Ton S180 were
monitored for 35 days and 12 days with ASCA and RXTE (and EUVE for Ton S180).
The short time scale (hours-days) variability patterns were very similar across
energy bands, with no evidence of lags between any of the energy bands studied.
The fractional variability amplitude was almost independent of energy band. It
is difficult to simultaneously explain soft Seyferts stronger variability,
softer spectra, and weaker energy-dependence of the variability relative to
hard Seyferts. The soft and hard band light curves diverged on the longest time
scales probed, consistent with the fluctuation power density spectra that
showed relatively greater power on long time scales in the softest bands. The
simplest explanation is that a relatively hard, rapidly-variable component
dominates the total X-ray spectrum and a slowly-variable soft excess is present
in the lowest energy channels of ASCA. Although it would be natural to identify
the latter with an accretion disk and the former with a corona surrounding it,
a standard thin disk could not get hot enough to radiate significantly in the
ASCA band, and the observed variability time scales are much too short. The
hard component may have a more complex shape than a pure power-law. The most
rapid factor of 2 flares and dips occurred within ~1000 sec in Ark 564 and a
bit more slowly in Ton S180. The speed of the luminosity changes rules out
viscous or thermal processes and limits the size of the individual emission
regions to <~15 Schwarzschild radii (and probably much less), that is, to
either the inner disk or small regions in a corona
Unit Killing Vector Fields on Nearly Kahler Manifolds
We study 6-dimensional nearly Kahler manifolds admitting a Killing vector
field of unit length. In the compact case it is shown that up to a finite cover
there is only one geometry possible, that of the 3--symmetric space
Ultrafast transport of laser-excited spin polarized carriers in Au/Fe/MgO(001)
A time domain approach to probe hot carrier-induced spin dynamics is
demonstrated. The experiments are performed in epitaxial Au/Fe/MgO(001), where
spin-polarized hot carriers are excited in the Fe layer by 35 fs laser pulses.
They propagate to the Au surface where the transient spin polarization is
detected by magneto-induced second harmonic generation. Different energies of
majority and minority hot carriers excited in the exchange-split Fe band
structure lead to their spindependent lifetimes in Au. Accordingly, two
spin-polarized current contributions which propagate superdiffusively at
different velocities result in a spin current pulse of about 100 fs duration.Comment: 5 pages, 4 figure
Validity of the international physical activity questionnaire short form (IPAQ-SF): A systematic review
<p>Abstract</p> <p>Background</p> <p>The International Physical Activity Questionnaire - Short Form (IPAQ-SF) has been recommended as a cost-effective method to assess physical activity. Several studies validating the IPAQ-SF have been conducted with differing results, but no systematic review of these studies has been reported.</p> <p>Methods</p> <p>The keywords "IPAQ", "validation", and "validity" were searched in PubMed and Scopus. Studies published in English that validated the IPAQ-SF against an objective physical activity measuring device, doubly labeled water, or an objective fitness measure were included.</p> <p>Results</p> <p>Twenty-three validation studies were included in this review. There was a great deal of variability in the methods used across studies, but the results were largely similar. Correlations between the total physical activity level measured by the IPAQ-SF and objective standards ranged from 0.09 to 0.39; none reached the minimal acceptable standard in the literature (0.50 for objective activity measuring devices, 0.40 for fitness measures). Correlations between sections of the IPAQ-SF for vigorous activity or moderate activity level/walking and an objective standard showed even greater variability (-0.18 to 0.76), yet several reached the minimal acceptable standard. Only six studies provided comparisons between physical activity levels derived from the IPAQ-SF and those obtained from objective criterion. In most studies the IPAQ-SF overestimated physical activity level by 36 to 173 percent; one study underestimated by 28 percent.</p> <p>Conclusions</p> <p>The correlation between the IPAQ-SF and objective measures of activity or fitness in the large majority of studies was lower than the acceptable standard. Furthermore, the IPAQ-SF typically overestimated physical activity as measured by objective criterion by an average of 84 percent. Hence, the evidence to support the use of the IPAQ-SF as an indicator of relative or absolute physical activity is weak.</p
RESPON OVARIUM SAPI PERANAKAN ONGOLE DAN SAPI LIMOUSIN TERHADAP INDUKSI FOLLICLE STIMULATING HORMONE
OVARIAN RESPONSE OF ONGOLE CATTLE GRADE AND LIMOUSINE CATTLE BREED ON THE FOLLICLE STIMULATING HORMONEINDUCTION.Objectives of this study were to evaluate the effect of Follicle stimulating hormone (FSH) utilization and follicle wave synchronization on ovarian response and transferred embryo.This study was using secondary data of embryo products at “Balai Embrio Ternak Cipelang-Bogor”. Data were taken using types of donor female, day and date conducting super ovulation, semen code, number of corpus luteum, numbers of embryo grades (A,B,C,D), numbers of transferred embryo and numbers of unfertile ovum. This study involved Limousine and Ongle grade cattle cows experiencing in super ovulation process, with body condition scores of 3.0 to 4.0, fed grass and nutritious concentrates. The FSH was used in super ovulation by the institution called Folltropin-Vand PGF2alfa (Lutalyse). Semen was originated from bull used by the embryo transfer institution. Results showed that number of left and right luteum corpus (LC) inducing FSH were not significantly different on both cattle breeds, but number of left LC of FSH induction was significantly higher at Limousine Breed. The quality of embryo successfully transferred using FSH induction was significantly higher compared with degenerative embryo and unfertile in both cattle Breeds. The quality of degenerative embryo and unfertile egg cell was not significantly different in both breeds. Proportions of embryo successfully transferred were 85.4 percents in Ongole Grade 87.4 percents in Limousine Breed. The values of Response rateshowing comparison of female donor number responding to the number of female done of super ovulation were 100 percents. Values of recovery ratein both Breed cows showed also 100 percents.Keywords: Follicle Stimulating Hormoneinduction, ovarian response, Limousine cattle Breed, Ongole cattle Grade
Scaling Laws and Transient Times in 3He Induced Nuclear Fission
Fission excitation functions of compound nuclei in a mass region where shell
effects are expected to be very strong are shown to scale exactly according to
the transition state prediction once these shell effects are accounted for. The
fact that no deviations from the transition state method have been observed
within the experimentally investigated excitation energy regime allows one to
assign an upper limit for the transient time of 10 zs.Comment: 7 pages, TeX type, psfig, submitted to Phys. Rev. C, also available
at http://csa5.lbl.gov/moretto/ps/he3_paper.p
Quantum state engineering on an optical transition and decoherence in a Paul trap
A single Ca+ ion in a Paul trap has been cooled to the ground state of
vibration with up to 99.9% probability. Starting from this Fock state |n=0> we
have demonstrated coherent quantum state manipulation on an optical transition.
Up to 30 Rabi oscillations within 1.4 ms have been observed. We find a similar
number of Rabi oscillations after preparation of the ion in the |n=1> Fock
state. The coherence of optical state manipulation is only limited by laser and
ambient magnetic field fluctuations. Motional heating has been measured to be
as low as one vibrational quantum in 190 ms.Comment: 4 pages, 5 figure
Towards automatic pulmonary nodule management in lung cancer screening with deep learning
The introduction of lung cancer screening programs will produce an
unprecedented amount of chest CT scans in the near future, which radiologists
will have to read in order to decide on a patient follow-up strategy. According
to the current guidelines, the workup of screen-detected nodules strongly
relies on nodule size and nodule type. In this paper, we present a deep
learning system based on multi-stream multi-scale convolutional networks, which
automatically classifies all nodule types relevant for nodule workup. The
system processes raw CT data containing a nodule without the need for any
additional information such as nodule segmentation or nodule size and learns a
representation of 3D data by analyzing an arbitrary number of 2D views of a
given nodule. The deep learning system was trained with data from the Italian
MILD screening trial and validated on an independent set of data from the
Danish DLCST screening trial. We analyze the advantage of processing nodules at
multiple scales with a multi-stream convolutional network architecture, and we
show that the proposed deep learning system achieves performance at classifying
nodule type that surpasses the one of classical machine learning approaches and
is within the inter-observer variability among four experienced human
observers.Comment: Published on Scientific Report
The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHa 198 and LkHa 225S
Observations of outflows associated with pre-main-sequence stars reveal
details about morphology, binarity and evolutionary states of young stellar
objects. We present molecular line data from the Berkeley-Illinois-Maryland
Association array and Five Colleges Radio Astronomical Observatory toward the
regions containing the Herbig Ae/Be stars LkHa 198 and LkHa 225S. Single dish
observations of 12CO 1-0, 13CO 1-0, N2H+ 1-0 and CS 2-1 were made over a field
of 4.3' x 4.3' for each species. 12CO data from FCRAO were combined with high
resolution BIMA array data to achieve a naturally-weighted synthesized beam of
6.75'' x 5.5'' toward LkHa 198 and 5.7'' x 3.95'' toward LkHa 225S,
representing resolution improvements of factors of approximately 10 and 5 over
existing data. By using uniform weighting, we achieved another factor of two
improvement. The outflow around LkHa 198 resolves into at least four outflows,
none of which are centered on LkHa 198-IR, but even at our resolution, we
cannot exclude the possibility of an outflow associated with this source. In
the LkHa 225S region, we find evidence for two outflows associated with LkHa
225S itself and a third outflow is likely driven by this source. Identification
of the driving sources is still resolution-limited and is also complicated by
the presence of three clouds along the line of sight toward the Cygnus
molecular cloud. 13CO is present in the environments of both stars along with
cold, dense gas as traced by CS and (in LkHa 225S) N2H+. No 2.6 mm continuum is
detected in either region in relatively shallow maps compared to existing
continuum observations.Comment: 14 pages, 10 figures (5 color), accepted for publication in Ap
A role for SNX5 in the regulation of macropinocytosis
Background: The mechanisms and components that regulate macropinocytosis are poorly understood. Here we have investigated the role of sorting nexin 5 (SNX5) in the regulation of macropinocytic activity
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