3,345 research outputs found
Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant
We here present a high sensitivity gravity-gradiometer based on atom
interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are
launched in fountain configuration and interrogated by a Raman interferometry
sequence to probe the gradient of gravity field. We recently implemented a
high-flux atomic source and a newly designed Raman lasers system in the
instrument set-up. We discuss the applications towards a precise determination
of the Newtonian gravitational constant G. The long-term stability of the
instrument and the signal-to-noise ratio demonstrated here open interesting
perspectives for pushing the measurement precision below the 100 ppm level
Multifractal properties of resistor diode percolation
Focusing on multifractal properties we investigate electric transport on
random resistor diode networks at the phase transition between the
non-percolating and the directed percolating phase. Building on first
principles such as symmetries and relevance we derive a field theoretic
Hamiltonian. Based on this Hamiltonian we determine the multifractal moments of
the current distribution that are governed by a family of critical exponents
. We calculate the family to two-loop order in a
diagrammatic perturbation calculation augmented by renormalization group
methods.Comment: 21 pages, 5 figures, to appear in Phys. Rev.
The central engine of GRB 130831A and the energy breakdown of a relativistic explosion
Gamma-ray bursts (GRBs) are the most luminous explosions in the universe, yet
the nature and physical properties of their energy sources are far from
understood. Very important clues, however, can be inferred by studying the
afterglows of these events. We present optical and X-ray observations of GRB
130831A obtained by Swift, Chandra, Skynet, RATIR, Maidanak, ISON, NOT, LT and
GTC. This burst shows a steep drop in the X-ray light-curve at s
after the trigger, with a power-law decay index of . Such a rare
behaviour cannot be explained by the standard forward shock (FS) model and
indicates that the emission, up to the fast decay at s, must be of
"internal origin", produced by a dissipation process within an
ultrarelativistic outflow. We propose that the source of such an outflow, which
must produce the X-ray flux for day in the cosmological rest frame,
is a newly born magnetar or black hole. After the drop, the faint X-ray
afterglow continues with a much shallower decay. The optical emission, on the
other hand, shows no break across the X-ray steep decrease, and the late-time
decays of both the X-ray and optical are consistent. Using both the X-ray and
optical data, we show that the emission after s can be explained
well by the FS model. We model our data to derive the kinetic energy of the
ejecta and thus measure the efficiency of the central engine of a GRB with
emission of internal origin visible for a long time. Furthermore, we break down
the energy budget of this GRB into the prompt emission, the late internal
dissipation, the kinetic energy of the relativistic ejecta, and compare it with
the energy of the associated supernova, SN 2013fu.Comment: Accepted for publication by MNRAS. 21 pages, 3 figures, 8 tables.
Extra table with magnitudes in the sourc
Lighting during grow-out and Salmonella in broiler flocks
<p>Abstract</p> <p>Background</p> <p>Lighting is used during conventional broiler grow-out to modify bird behaviour to reach the goals of production and improve bird welfare. The protocols for lighting intensity vary. In a field study, we evaluated if the lighting practices impact the burden of <it>Salmonella </it>in broiler flocks.</p> <p>Methods</p> <p>Conventional grow-out flocks reared in the states of Alabama, Mississippi and Texas, USA in 2003 to 2006 were sampled 1 week before harvest (<it>n </it>= 58) and upon arrival for processing (<it>n </it>= 56) by collecting feathered carcass rinsate, crop and one cecum from each of 30 birds, and during processing by collecting rinsate of 30 carcasses at pre-chilling (<it>n </it>= 56) and post-chilling points (<it>n </it>= 54). Litter samples and drag swabs of litter were collected from the grow-out houses after bird harvest (<it>n </it>= 56). Lighting practices for these flocks were obtained with a questionnaire completed by the growers. Associations between the lighting practices and the burden of <it>Salmonella </it>in the flocks were tested while accounting for variation between the grow-out farms, their production complexes and companies.</p> <p>Results</p> <p>Longer relative duration of reduced lights during the grow-out period was associated with reduced detection of <it>Salmonella </it>on the exterior of birds 1 week before harvest and on the broiler carcasses at the post-chilling point of processing. In addition, starting reduced lights for ≥18 hours per day later in the grow-out period was associated with decreased detection of <it>Salmonella </it>on the exterior of broilers arriving for processing and in the post-harvest drag swabs of litter from the grow-out house.</p> <p>Conclusions</p> <p>The results of this field study show that lighting practices implemented during broiler rearing can impact the burden of <it>Salmonella </it>in the flock. The underlying mechanisms are likely to be interactive.</p
Determinants of avoidable deaths from ischemic heart disease in East and West Germany
Objective: Within Germany, a significant decrease in avoidable mortality from ischemic heart disease (IHD) has been observed since the early 1990s. The objective of this paper is to identify the specific reasons that have led to the decrease in the number of avoidable deaths from IHD in West and East Germany from 1996 to 2004. Methods: We analyzed the mortality rate from IHD of the male population aged less than 65 years on the regional level of German counties over the 1996–2004 period. Methodologically, after adjusting for a number of health structure variables, the socioeconomic structure of each region, and yearly time trends in avoidable mortality, we accounted for unobservable differences among regions by using a fixed-effect estimator. Results: Our main result reveals that the number of intracardiac catheter facilities, an important diagnostic tool for IHD, significantly accounts for decreases in avoidable mortality from IHD. This is important, as the modernization of the East German health sector included a considerable catching-up process in the number of IC facilities provided relative to West Germany. Conclusion: Our results suggest that the modernization of the East German health sector may have contributed to saving people from premature deaths
"They go for gender first"
There have been many recent media reports about the online harassment of women journalists working in technology, particularly the video gaming industry. However, little research has focused on this aspect, by looking at specific occupations, or analysing the implications for women and society. This paper is a feminist study of the experiences of sexist abuse of a sample of women journalists writing about technology. It is a commentary on the results of a questionnaire-based study of 102 women (and their approximately 300 comments) that work in what has emerged as one of the frontlines of the struggle for gender equality. The research looks at the extent of the abuse, the harm it causes and how women are reacting to it. Most of the participants have experienced abuse, many have changed their working practices and some have disguised their identity to avoid it. An examination of their comments suggests that sexist abuse is now often normalised, alongside a new kind of "invisible" feminism. It also reveals a mood of defiance and an appetite for radical change to address the problems of exclusion and loss of identity. Overall, results indicate that the abuse is damaging women’s lives and impacting journalism and society in a negative way
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
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