1,158 research outputs found
The two-loop five-particle amplitude in supergravity
We compute for the first time the two-loop five-particle amplitude in
supergravity. Starting from the known integrand, we perform an
integration-by-parts reduction and express the answer in terms of uniform
weight master integrals. The latter are known to evaluate to non-planar
pentagon functions, described by a 31-letter symbol alphabet. We express the
final result for the amplitude in terms of uniform weight four symbols,
multiplied by a small set of rational factors. The amplitude satisfies the
expected factorization properties when one external graviton becomes soft, and
when two external gravitons become collinear. We verify that the soft
divergences of the amplitude exponentiate, and extract the finite remainder
function. The latter depends on fewer rational factors, and is independent of
one of the symbol letters. By analyzing identities involving rational factors
and symbols we find a remarkably compact representation in terms of a single
seed function, summed over all permutations of external particles. Finally, we
work out the multi-Regge limit, and present explicitly the leading logarithmic
terms in the limit. The full symbol of the IR-subtracted hard function is
provided as an ancillary file.Comment: 22 pages, 1 figure, 8 ancillary file
Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources
Radiation from the highly-charged ions contained in the plasma of
Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of
X-rays. Because the ions have a relatively low kinetic energy ( eV)
transitions can be very narrow, containing only small Doppler broadening. We
describe preliminary accurate measurements of two and three-electron ions with
Z=16--18. We show how these measurement can test sensitively many-body
relativistic calculations or can be used as X-ray standards for precise
measurements of X-ray transitions in exotic atoms
On the characterisation of a Bragg spectrometer with X-rays from an ECR source
Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source
have been used to determine the response function of a Bragg crystal
spectrometer equipped with large area spherically bent silicon (111) or quartz
(10) crystals. The measured spectra are compared with simulated ones
created by a ray-tracing code based on the expected theoretical crystal's
rocking curve and the geometry of the experimental set-up.Comment: Version acceptee (NIM
Cost-effective scat-detection dogs: unleashing a powerful new tool for international mammalian conservation biology
Recently, detection dogs have been utilized to collect fecal samples from cryptic and rare mammals. Despite the great promise of this technique for conservation biology, its broader application has been limited by the high cost (tens to hundreds of thousands of dollars) and logistical challenges of employing a scat-detection dog team while conducting international, collaborative research. Through an international collaboration of primatologists and the Chinese Ministry of Public Security, we trained and used a detection dog to find scat from three species of unhabituated, free-ranging primates, for less than $3,000. We collected 137 non-human primate fecal samples that we confirmed by sequencing taxonomically informative genetic markers. Our detection dog team had a 92% accuracy rate, significantly outperforming our human-only team. Our results demonstrate that detection dogs can locate fecal samples from unhabituated primates with variable diets, locomotion, and grouping patterns, despite challenging field conditions. We provide a model for in-country training, while also building local capacity for conservation and genetic monitoring. Unlike previous efforts, our approach will allow for the wide adoption of scat-detection dogs in international conservation biology
Characterization and social correlates of fecal testosterone and cortisol excretion in wild male Saguinus mystax
Reproductive success in male primates can be influenced by testosterone (T) and cortisol (C). We examined them in wild Saguinus mystax via fecal hormone analysis. Firstly, we wanted to characterize male hormonal status over the course of the year. Further we tested the influence of the reproductive status of the breeding female, social instability, and intergroup encounter rates on T levels, comparing the results with predictions of the challenge hypothesis (Wingfield et al., 1990). We also tested for interindividual differences in hormonal levels, possibly related to social or breeding status. We collected data during a 12-mo study on 2 groups of moustached tamarins at the Estación Biológica Quebrada Blanco in northeastern Peru. We found fairly similar T and C levels over the course of the year for all males. Yet an elevation of T shortly after the birth of infants, during the phase of ovarian inactivity of the group’s breeding female, was evident. Hormonal levels were not significantly elevated during a phase of social instability, did not correlate with intergroup encounter rates, and did not differ between breeding and nonbreeding males. Our results confirm the challenge hypothesis (Wingfield et al., 1990). The data suggest that reproductive competition inmoustached tamarins is not based on endocrinological, but instead on behavioral mechanisms, possibly combined with sperm competition.Deutsche Forschungsgemeinschaft (HE 1870/10-1,2
Gebiss: an ImageJ plugin for the specification of ground truth and the performance evaluation of 3D segmentation algorithms.
Background: Image segmentation is a crucial step in quantitative microscopy that helps to define regions of tissues, cells or subcellular compartments. Depending on the degree of user interactions, segmentation methods can be divided into manual, automated or semi-automated approaches. 3D image stacks usually require automated methods due to their large number of optical sections. However, certain applications benefit from manual or semi-automated approaches. Scenarios include the quantification of 3D images with poor signal-to-noise ratios or the generation of so-called ground truth segmentations that are used to evaluate the accuracy of automated segmentation methods.
Results: We have developed Gebiss; an ImageJ plugin for the interactive segmentation, visualisation and quantification of 3D microscopic image stacks. We integrated a variety of existing plugins for threshold-based segmentation and volume visualisation.
Conclusions: We demonstrate the application of Gebiss to the segmentation of nuclei in live Drosophila embryos and the quantification of neurodegeneration in Drosophila larval brains. Gebiss was developed as a cross-platform ImageJ plugin and is freely available on the web at http://imaging.bii.a-star.edu.sg/projects/gebiss
A model of management academics' intentions to influence values
Business schools face increased criticism for failing in the teaching of management studies to nurture their students’ values. Assuming that individual academics play an important role in shaping the value-related influence of business schools, I model management academics’ intentions to influence values. The suggested model encompasses academics’ economic and social values as internal variables, as well as perceived support for attempting to influence values and academic tenure as social and structural variables. A test with empirical data from 1,254 management academics worldwide reveals that perceived external support is most relevant for explaining intentions. Moreover, academics’ social values, but not their economic ones, contribute to an explanation of their intentions to influence values. The results reveal how important it is for academics to believe that their colleagues, higher education institutions, and other stakeholders support their value-related behavioral intentions
Tick-, mosquito-, and rodent-borne parasite sampling designs for the National Ecological Observatory Network
Parasites and pathogens are increasingly recognized as significant drivers of ecological and evolutionary change in natural ecosystems. Concurrently, transmission of infectious agents among human, livestock, and wildlife populations represents a growing threat to veterinary and human health. In light of these trends and the scarcity of long-term time series data on infection rates among vectors and reservoirs, the National Ecological Observatory Network (NEON) will collect measurements and samples of a suite of tick-, mosquito-, and rodent-borne parasites through a continental-scale surveillance program. Here, we describe the sampling designs for these efforts, highlighting sampling priorities, field and analytical methods, and the data as well as archived samples to be made available to the research community. Insights generated by this sampling will advance current understanding of and ability to predict changes in infection and disease dynamics in novel, interdisciplinary, and collaborative ways. (Résumé d'auteur
All master integrals for three-jet production at NNLO
We evaluate analytically all previously unknown nonplanar master integrals
for massless five-particle scattering at two loops, using the differential
equations method. A canonical form of the differential equations is obtained by
identifying integrals with constant leading singularities, in space-time
dimensions. These integrals evaluate to -linear combinations of
multiple polylogarithms of uniform weight at each order in the expansion in the
dimensional regularization parameter, and are in agreement with previous
conjectures for nonplanar pentagon functions. Our results provide the complete
set of two-loop Feynman integrals for any massless scattering process,
thereby opening up a new level of precision collider phenomenology.Comment: 6 pages, 1 figure, 5 ancillary files; v2: references added; full
boundary values in s12 physical region included; v3: values of the master
integrals in the ancillary files update
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