572 research outputs found
First results of the BATSE/COMPTEL/NMSU rapid burst response campaign
The Imaging Compton Telescope (COMPTEL) on board the Compton Gamma Ray Observatory regularly observes gamma‐ray bursts which occur inside the instrument’s ∼1 sr field‐of‐view. COMPTEL images bursts in the 0.75–30 MeV energy range with a typical location accuracy of 1–3 degrees, depending on burst strength, position, duration, and spectrum. COMPTEL’s imaging capability has been exploited in order to search for fading gamma‐ray burst counterparts at other wavelengths through the establishment of a BATSE/COMPTEL/NMSU rapid burst response campaign. This campaign utilizes near real‐time identification and preliminary burst location by BATSE, accelerated COMPTEL imaging, and a world‐wide network of observers to search COMPTEL error boxes as quickly as possible. Timely, deep searches for lingering counterpart emission of several bursts per year are the realized goal of this campaign. During its first year of operation, the rapid response program has been successfully applied to two strong bursts: GRB 930131 and GRB 930309. These bursts were imaged in record time only hours after their occurrence. Subsequently, several observations were made at radio and optical observatories world‐wide
Weather on the Nearest Brown Dwarfs: Resolved Simultaneous Multi-Wavelength Variability Monitoring of WISE J104915.57-531906.1AB
We present two epochs of MPG/ESO 2.2m GROND simultaneous 6-band ()
photometric monitoring of the closest known L/T transition brown dwarf binary
WISE J104915.57-531906.1AB. We report here the first resolved variability
monitoring of both the T0.5 and L7.5 components. We obtained 4 hours of focused
observations on the night of UT 2013-04-22, as well as 4 hours of defocused
(unresolved) observations on the night of UT 2013-04-16. We note a number of
robust trends in our light curves. The and light curves appear to be
anticorrelated with and for the T0.5 component and in the unresolved
lightcurve. In the defocused dataset, appears correlated with and
and anticorrelated with and , while in the focused dataset we measure
no variability for at the level of our photometric precision, likely due to
evolving weather phenomena. In our focused T0.5 component lightcurve, the
band lightcurve displays a significant phase offset relative to both and
. We argue that the measured phase offsets are correlated with atmospheric
pressure probed at each band, as estimated from 1D atmospheric models. We also
report low-amplitude variability in and intrinsic to the L7.5
component.Comment: 14 pages, 5 figures, accepted to ApJ Letter
Quantum Cloning and Distributed Measurements
We study measurements on various subsystems of the output of a universal 1 to
2 cloning machine, and establish a correspondence between these measurements at
the output and effective measurements on the original input. We show that one
can implement sharp effective measurement elements by measuring only two out of
the three output systems. Additionally, certain complete sets of sharp
measurements on the input can be realised by measurements on the two clones.
Furthermore, we introduce a scheme that allows to restore the original input in
one of the output bits, by using measurements and classical communication -- a
protocol that resembles teleportation.Comment: submitted to Phys. Rev.
The Star Formation Rate in the Reionization Era as Indicated by Gamma-ray Bursts
High-redshift gamma-ray bursts (GRBs) offer an extraordinary opportunity to
study aspects of the early Universe, including the cosmic star formation rate
(SFR). Motivated by the two recent highest-z GRBs, GRB 080913 at z = 6.7 and
GRB 090423 at z = 8.1, and more than four years of Swift observations, we first
confirm that the GRB rate does not trace the SFR in an unbiased way. Correcting
for this, we find that the implied SFR to beyond z = 8 is consistent with
LBG-based measurements after accounting for unseen galaxies at the faint end of
the UV luminosity function. We show that this provides support for the
integrated star formation in the range 6 < z < 8 to have been alone sufficient
to reionize the Universe.Comment: 4 pages, 4 figures; modified to match version accepted for
publication in ApJ Letter
Antalarmin
In the molecule of the title compund [systematic name: N-butyl-N-ethyl-2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-amine], C24H34N4, the pyrrolopyrimidine ring system is nearly planar, its five- and six-membered rings forming a dihedral angle of 5.3 (2)°. The benzene ring is nearly orthogonal to the central ring system. The N atom carrying the ethyl and n-butyl groups is flattened pyramidal
On reminder effects, drop-outs and dominance: evidence from an online experiment on charitable giving
We present the results of an experiment that (a) shows the usefulness of screening out drop-outs and (b) tests whether different methods of payment and reminder intervals affect charitable giving. Following a lab session, participants could make online donations to charity for a total duration of three months. Our procedure justifying the exclusion of drop-outs consists in requiring participants to collect payments in person flexibly and as known in advance and as highlighted to them later. Our interpretation is that participants who failed to collect their positive payments under these circumstances are likely not to satisfy dominance. If we restrict the sample to subjects who did not drop out, but not otherwise, reminders significantly increase the overall amount of charitable giving. We also find that weekly reminders are no more effective than monthly reminders in increasing charitable giving, and that, in our three months duration experiment, standing orders do not increase giving relative to one-off donations
Ground-state fidelity of Luttinger liquids: A wave functional approach
We use a wave functional approach to calculate the fidelity of ground states
in the Luttinger liquid universality class of one-dimensional gapless quantum
many-body systems. The ground-state wave functionals are discussed using both
the Schrodinger (functional differential equation) formulation and a path
integral formulation. The fidelity between Luttinger liquids with Luttinger
parameters K and K' is found to decay exponentially with system size, and to
obey the symmetry F(K,K')=F(1/K,1/K') as a consequence of a duality in the
bosonization description of Luttinger liquids.Comment: 13 pages, IOP single-column format. Sec. 3 expanded with discussion
of short-distance cut-off. Some typos corrected. Ref. 44 in v2 is now
footnote 2 (moved by copy editor). Published versio
GRB Polarimetry with POET
POET (Polarimeters for Energetic Transients) represents a concept for a Small Explorer (SMEX) satellite mission, whose principal scientific goal is to understand the structure of GRB sources through sensitive X‐ray and γ‐ray polarization measurements. The payload consists of two wide field‐of‐view (FoV) instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2–15 keV and a high energy polarimeter (Gamma‐Ray Polarimeter Experiment or GRAPE) that would measure polarization in the 60–500 keV energy range. The POET spacecraft provides a zenith‐pointed platform for maximizing the exposure to deep space. Spacecraft rotation provides a means of effectively dealing with any residual systematic effects in the polarization response. POET provides sufficient sensitivity and sky coverage to measure statistically significant polarization (for polarization levels in excess of 20%) for ∼80 GRBs in a two‐year mission. High energy polarization data would also be obtained for SGRs, solar flares, pulsars and other sources of astronomical interest
BMP4 gene therapy enhances insulin sensitivity but not adipose tissue browning in obese mice
Bone morphogenetic protein 4 (BMP4) adeno-associated viral vectors of serotype 8 (AAV8) gene therapy targeting the liver prevents the development of obesity in initially lean mice by browning the large subcutaneous white adipose tissue (WAT) and enhancing energy expenditure. Here, we examine whether this approach could also reduce established obesity. Dietary-induced obese C57BL6/N mice received AAV8 BMP4 gene therapy at 17-18 weeks of age. They were kept on a high-fat diet and phenotypically characterized for an additional 10-12 weeks. Following termination, the mice underwent additional characterization in vitro. Surprisingly, we observed no effect on body weight, browning of WAT, or energy expenditure in these obese mice, but whole-body insulin sensitivity and glucose tolerance were robustly improved. Insulin signaling and insulin-stimulated glucose uptake were increased in both adipose cells and skeletal muscle. BMP4 also decreased hepatic glucose production and reduced gluconeogenic enzymes in the liver, but not in the kidney, in addition to enhancing insulin action in the liver. Our findings show that BMP4 prevents, but does not reverse, established obesity in adult mice, while it improves insulin sensitivity independent of weight reduction. The BMP antagonist Noggin was increased in WAT in obesity, which may account for the lack of browning
Social preferences, accountability, and wage bargaining
We assess the extent of preferences for employment in a collective wage bargaining situation with heterogeneous workers. We vary the size of the union and introduce a treatment mechanism transforming the voting game into an individual allocation task. Our results show that highly productive workers do not take employment of low productive workers into account when making wage proposals, regardless of whether insiders determine the wage or all workers. The level of pro-social preferences is small in the voting game, while it increases as the game is transformed into an individual allocation task. We interpret this as an accountability effect
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