758 research outputs found
The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad Line Region in Mrk 50
We present dynamical modeling of the broad line region (BLR) in the Seyfert 1
galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN
Monitoring Project (LAMP) 2011. We model the reverberation mapping data
directly, constraining the geometry and kinematics of the BLR, as well as
deriving a black hole mass estimate that does not depend on a normalizing
factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is
a nearly face-on thick disk, with a mean radius of 9.6(+1.2,-0.9) light days, a
width of the BLR of 6.9(+1.2,-1.1) light days, and a disk opening angle of
25\pm10 degrees above the plane. We also constrain the inclination angle to be
9(+7,-5) degrees, close to face-on. Finally, the black hole mass of Mrk 50 is
inferred to be log10(M(BH)/Msun) = 7.57(+0.44,-0.27). By comparison to the
virial black hole mass estimate from traditional reverberation mapping
analysis, we find the normalizing constant (virial coefficient) to be log10(f)
= 0.78(+0.44,-0.27), consistent with the commonly adopted mean value of 0.74
based on aligning the M(BH)-{\sigma}* relation for AGN and quiescent galaxies.
While our dynamical model includes the possibility of a net inflow or outflow
in the BLR, we cannot distinguish between these two scenarios.Comment: Accepted for publication in ApJ. 8 pages, 6 figure
The Berkeley Sample of Stripped-Envelope Supernovae
We present the complete sample of stripped-envelope supernova (SN) spectra
observed by the Lick Observatory Supernova Search (LOSS) collaboration over the
last three decades: 888 spectra of 302 SNe, 652 published here for the first
time, with 384 spectra (of 92 SNe) having photometrically-determined phases.
After correcting for redshift and Milky Way dust reddening and reevaluating the
spectroscopic classifications for each SN, we construct mean spectra of the
three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We
compare measures of line strengths and widths made from this sample to the
results of previous efforts, confirming that O I {\lambda}7774 absorption is
stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb
SNe in the first 30 days after peak brightness, though the widths of nebular
emission lines are consistent across subtypes. We also highlight newly
available observations for a few rare subpopulations of interest.Comment: 13 pages; 14 figures; 3 tables. Accepted for publication in MNRA
The structure of the graviton self-energy at finite temperature
We study the graviton self-energy function in a general gauge, using a hard
thermal loop expansion which includes terms proportional to T^4, T^2 and
log(T). We verify explicitly the gauge independence of the leading T^4 term and
obtain a compact expression for the sub-leading T^2 contribution. It is shown
that the logarithmic term has the same structure as the ultraviolet pole part
of the T=0 self-energy function. We argue that the gauge-dependent part of the
T^2 contribution is effectively canceled in the dispersion relations of the
graviton plasma, and present the solutions of these equations.Comment: 27 pages, 6 figure
Study of nucleon resonances with electromagnetic interactions
Recent developments in using electromagnetic meson production reactions to
study the structure of nucleon resonances are reviewed. Possible future works
are discussed.Comment: 25 pages, 19 figure
Laboratory-induced cue reactivity among individuals with prescription opioid dependence
Prescription opioid (PO) dependence is a critical health problem. Although examination of drug cue reactivity paradigms has advanced the understanding of risk factors for relapse for a variety of substances (e.g., cocaine, alcohol, nicotine), no PO specific drug cue paradigm has been developed. The current study addressed this gap in the literature and evaluated the ability of a newly developed PO drug cue paradigm to elicit subjective, physiological, and neuroendocrine changes among PO-dependent participants (n = 20) as compared to controls (n = 17). The drug cue paradigm included an induction script, viewing and handling paraphernalia (e.g., bottle of oxycontin pills, pill crusher) and watching a video depicting people using POs as well as places related to POs (e.g., pharmacies). Consistent with hypotheses, the PO group demonstrated significant pre- to post-cue increases on subjective ratings of craving, difficulty resisting POs, stress, and anger. The control group did not demonstrate significant changes on any of the subjective measures. Both the PO group and the control group evidenced significant pre- to post-cue increases in physiological responses (e.g., blood pressure, skin conductance), as expected given the arousing nature of the drug cue stimuli. The PO group, but not the control group, evidenced a significant pre- to post-cue increase in heart rate and salivary cortisol levels. The development and validation of a drug cue paradigm for POs may help inform future research and treatment development efforts for patients with PO dependence
Ab-initio prediction of the electronic and optical excitations in polythiophene: isolated chains versus bulk polymer
We calculate the electronic and optical excitations of polythiophene using
the GW approximation for the electronic self-energy, and include excitonic
effects by solving the electron-hole Bethe-Salpeter equation. Two different
situations are studied: excitations on isolated chains and excitations on
chains in crystalline polythiophene. The dielectric tensor for the crystalline
situation is obtained by modeling the polymer chains as polarizable line
objects, with a long-wavelength polarizability tensor obtained from the
ab-initio polarizability function of the isolated chain. With this model
dielectric tensor we construct a screened interaction for the crystalline case,
including both intra- and interchain screening. In the crystalline situation
both the quasi-particle band gap and the exciton binding energies are
drastically reduced in comparison with the isolated chain. However, the optical
gap is hardly affected. We expect this result to be relevant for conjugated
polymers in general.Comment: 15 pages including 4 figures; to appear in Phys. Rev. B, 6/15/200
Reverberation Mapping of the Kepler-Field AGN KA1858+4850
KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among
the brightest active galaxies monitored by the Kepler mission. We have carried
out a reverberation mapping campaign designed to measure the broad-line region
size and estimate the mass of the black hole in this galaxy. We obtained 74
epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m
telescope from February to November of 2012, and obtained complementary V-band
images from five other ground-based telescopes. We measured the H-beta light
curve lag with respect to the V-band continuum light curve using both
cross-correlation techniques (CCF) and continuum light curve variability
modeling with the JAVELIN method, and found rest-frame lags of lag_CCF = 13.53
(+2.03, -2.32) days and lag_JAVELIN = 13.15 (+1.08, -1.00) days. The H-beta
root-mean-square line profile has a width of sigma_line = 770 +/- 49 km/s.
Combining these two results and assuming a virial scale factor of f = 5.13, we
obtained a virial estimate of M_BH = 8.06 (+1.59, -1.72) x 10^6 M_sun for the
mass of the central black hole and an Eddington ratio of L/L_Edd ~ 0.2. We also
obtained consistent but slightly shorter emission-line lags with respect to the
Kepler light curve. Thanks to the Kepler mission, the light curve of
KA1858+4850 has among the highest cadences and signal-to-noise ratios ever
measured for an active galactic nucleus; thus, our black hole mass measurement
will serve as a reference point for relations between black hole mass and
continuum variability characteristics in active galactic nuclei
Uncoupling the functions of CALM in VAMP sorting and clathrin-coated pit formation.
CALM (clathrin assembly lymphoid myeloid leukemia protein) is a cargo-selective adaptor for the post-Golgi R-SNAREs VAMPs 2, 3, and 8, and it also regulates the size of clathrin-coated pits and vesicles at the plasma membrane. The present study has two objectives: to determine whether CALM can sort additional VAMPs, and to investigate whether VAMP sorting contributes to CALM-dependent vesicle size regulation. Using a flow cytometry-based endocytosis efficiency assay, we demonstrate that CALM is also able to sort VAMPs 4 and 7, even though they have sorting signals for other clathrin adaptors. CALM homologues are present in nearly every eukaryote, suggesting that the CALM family may have evolved as adaptors for retrieving all post-Golgi VAMPs from the plasma membrane. Using a knockdown/rescue system, we show that wild-type CALM restores normal VAMP sorting in CALM-depleted cells, but that two non-VAMP-binding mutants do not. However, when we assayed the effect of CALM depletion on coated pit morphology, using a fluorescence microscopy-based assay, we found that the two mutants were as effective as wild-type CALM. Thus, we can uncouple the sorting function of CALM from its structural role
Fast left prefrontal rTMS acutely suppresses analgesic effects of perceived controllability on the emotional component of pain experience
The prefrontal cortex may be a promising target for transcranial magnetic stimulation (TMS) in the management of pain. It is not clear how prefrontal TMS affects pain perception, but previous findings suggest that ventral lateral and medial prefrontal circuits may comprise an important part of a circuit of âperceived controllabilityâ regarding pain, stress and learned helplessness. While the left dorsolateral prefrontal cortex is a common TMS target for treating clinical depression as well as modulating pain, little is known about whether TMS over this area may affect perceived controllability. The present study explored the immediate effects of fast TMS over the left dorsolateral prefrontal cortex on the analgesic effects of perceived pain controllability. Twenty-four healthy volunteers underwent a laboratory pain task designed to manipulate perception of pain controllability. Real TMS, compared to sham, suppressed the analgesic benefits of perceived-control on the emotional dimension of pain, but not the sensory/discriminatory dimension. Findings suggest that, at least acutely, fast TMS over the left dorsolateral prefrontal cortex may interrupt the perceived-controllability effect on the emotional dimension of pain experience. While it is not clear whether this cortical area is directly involved with modulating perceived controllability or whether downstream effects are responsible for the present findings, it appears possible that left dorsolateral prefrontal TMS may produce analgesic effects by acting through a cortical âperceived controlâ circuit regulating limbic and brainstem areas of the pain circuit
Black Holes in the Early Universe
The existence of massive black holes was postulated in the sixties, when the
first quasars were discovered. In the late nineties their reality was proven
beyond doubt, in the Milky way and a handful nearby galaxies. Since then,
enormous theoretical and observational efforts have been made to understand the
astrophysics of massive black holes. We have discovered that some of the most
massive black holes known, weighing billions of solar masses, powered luminous
quasars within the first billion years of the Universe. The first massive black
holes must therefore have formed around the time the first stars and galaxies
formed. Dynamical evidence also indicates that black holes with masses of
millions to billions of solar masses ordinarily dwell in the centers of today's
galaxies. Massive black holes populate galaxy centers today, and shone as
quasars in the past; the quiescent black holes that we detect now in nearby
bulges are the dormant remnants of this fiery past. In this review we report on
basic, but critical, questions regarding the cosmological significance of
massive black holes. What physical mechanisms lead to the formation of the
first massive black holes? How massive were the initial massive black hole
seeds? When and where did they form? How is the growth of black holes linked to
that of their host galaxy? Answers to most of these questions are work in
progress, in the spirit of these Reports on Progress in Physics.Comment: Reports on Progress in Physics, in pres
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