590 research outputs found
Multi-Use Seismic Stations Offer Strong Deterrent to Clandestine Nuclear Weapons Testing
As the United States and other nations push for the signing of a Comprehensive Test Ban Treaty, representatives are meeting in Geneva this year to develop an International Seismic Monitoring System to verify compliance with the treaty's restrictions. In addition to the official monitoring system, regional networks developed for earthquake studies and basic research can provide a strong deterrent against clandestine testing. The recent release of information by the U.S. Department of Energy (DoE) on previously unannounced nuclear tests provides an opportunity to assess the ability of multi-use seismic networks to help monitor nuclear testing across the globe.
Here we look at the extent to which the formerly unannounced tests were recorded and identified on the basis of publicly available seismographic data recorded by five seismic networks. The data were recorded by networks in southern Nevada and northern California at stations less than 1500 km from the Nevada Test Site (NTS), and two networks in the former Soviet Union at stations farther than 1500 km from the NTS
Measuring the cosmic ray acceleration efficiency of a supernova remnant
Cosmic rays are the most energetic particles arriving at earth. Although most
of them are thought to be accelerated by supernova remnants, the details of the
acceleration process and its efficiency are not well determined. Here we show
that the pressure induced by cosmic rays exceeds the thermal pressure behind
the northeast shock of the supernova remnant RCW 86, where the X-ray emission
is dominated by synchrotron radiation from ultra-relativistic electrons. We
determined the cosmic-ray content from the thermal Doppler broadening measured
with optical spectroscopy, combined with a proper-motion study in X- rays. The
measured post-shock proton temperature in combination with the shock velocity
does not agree with standard shock heating, implying that >50% of the
post-shock pressure is produced by cosmic rays.Comment: Published in Science express, 10 pages, 5 figures and 2 table
The non-Abelian dual Meissner effect as color-alignment in SU(2) lattice gauge theory
A new gauge (m-gauge) condition is proposed by means of a generalization of
the Maximal Abelian gauge (MAG). The new gauge admits a space time dependent
embedding of the residual U(1) into the SU(2) gauge group. This embedding is
characterized by a color vector . It turns out that this vector
only depends of gauge invariant parts of the link configurations. Our numerical
results show color ferromagnetic correlations of the field in
space-time. The correlation length scales towards the continuum limit. For
comparison with the MAG, we introduce a class of gauges which smoothly
interpolates between the MAG and the m-gauge. For a wide range of the gauge
parameter, the vacuum decomposes into regions of aligned vectors . The
''neutral particle problem'' of MAG is addressed in the context of the new
gauge class.Comment: 15 pages, 6 figures, LaTeX using eps
Modified iterative versus Laplacian Landau gauge in compact U(1) theory
Compact U(1) theory in 4 dimensions is used to compare the modified iterative
and the Laplacian fixing to lattice Landau gauge in a controlled setting, since
in the Coulomb phase the lattice theory must reproduce the perturbative
prediction. It turns out that on either side of the phase transition clear
differences show up and in the Coulomb phase the ability to remove double Dirac
sheets proves vital on a small lattice.Comment: 14 pages, 8 figures containing 23 graphs, v2: 2 figures removed, 2
references adde
Bond graphs in model matching control
Bond graphs are primarily used in the network modeling of lumped parameter physical systems, but controller design with this graphical technique is relatively unexplored. It is shown that bond graphs can be used as a tool for certain model matching control designs. Some basic facts on the nonlinear model matching problem are recalled. The model matching problem is then associated with a particular disturbance decoupling problem, and it is demonstrated that bicausal assignment methods for bond graphs can be applied to solve the disturbance decoupling problem as to meet the model matching objective. The adopted bond graph approach is presented through a detailed example, which shows that the obtained controller induces port-Hamiltonian error dynamics. As a result, the closed loop system has an associated standard bond graph representation, thereby rendering energy shaping and damping injection possible from within a graphical context
Design and implementation of a twin-family database for behavior genetics and genomics studies.
In this article we describe the design and implementation of a database for extended twin families. The database does not focus on probands or on index twins, as this approach becomes problematic when larger multigenerational families are included, when more than one set of multiples is present within a family, or when families turn out to be part of a larger pedigree. Instead, we present an alternative approach that uses a highly flexible notion of persons and relations. The relations among the subjects in the database have a one-to-many structure, are user-definable and extendible and support arbitrarily complicated pedigrees. Some additional characteristics of the database are highlighted, such as the storage of historical data, predefined expressions for advanced queries, output facilities for individuals and relations among individuals and an easy-to-use multi-step wizard for contacting participants. This solution presents a flexible approach to accommodate pedigrees of arbitrary size, multiple biological and nonbiological relationships among participants and dynamic changes in these relations that occur over time, which can be implemented for any type of multigenerational family study
Bone Mineral Density in Transgender Individuals After Gonadectomy and Long-Term Gender-Affirming Hormonal Treatment
Introduction: Establishing the influence of long-term, gender-affirming hormonal treatment (HT) on bone mineral density (BMD) in transgender individuals is important to improve the therapeutic guidelines for these individuals. Aim: To examine the effect of long-term HT and gonadectomy on BMD in transgender individuals. Methods: 68 transwomen and 43 transmen treated with HT who had undergone gonadectomy participated in this study. Dual-energy x-ray absorptiometry (DXA) scans were performed to measure BMD at the lumbar spine and total hip. Laboratory values related to sex hormones were collected within 3 months of performing the DXA scan and analyzed. Main Outcome Measure: BMD and levels of sex hormones in transwomen and transmen. Results: In transwomen, the mean BMD values at the lumbar spine and total hip at the first DXA scan were, respectively, 0.99 ± 0.15 g/cm2 (n = 68) and 0.94 ± 0.28 g/cm2 (n = 65). In transmen, the mean BMD values at the lumbar spine and total hip at the first DXA scan were, respectively, 1.08 ± 0.16 g/cm2 (n = 43) and 1.01 ± 0.18 g/cm2 (n = 43). A significant decrease in total hip BMD was found in both transwomen and transmen after 15 years of HT compared with 10 years of HT (P =.02). Conclusion: In both transwomen and transmen, a decrease was observed in total hip bone mineral density after 15 years of HT compared to the first 10 years of HT. Dobrolińska M, van der Tuuk K, Vink P, et al. Bone Mineral Density in Transgender Individuals After Gonadectomy and Long-Term Gender-Affirming Hormonal Treatment. J Sex Med 2019; 16:1469–1477
Morphology of synchrotron emission in young supernova remnants
In the framework of test-particle and cosmic-ray modified hydrodynamics, we
calculate synchrotron emission radial profiles in young ejecta-dominated
supernova remnants (SNRs) evolving in an ambient medium which is uniform in
density and magnetic field. We find that, even without any magnetic field
amplification by Raleigh-Taylor instabilities, the radio synchrotron emission
peaks at the contact discontinuity because the magnetic field is compressed and
is larger there than at the forward shock. The X-ray synchrotron emission
sharply drops behind the forward shock as the highest energy electrons suffer
severe radiative losses.Comment: 8 pages, 6 figures, Accepted for publication in A&
Status of center dominance in various center gauges
We review arguments for center dominance in center gauges where vortex
locations are correctly identified. We introduce an appealing interpretation of
the maximal center gauge, discuss problems with Gribov copies, and a cure to
the problems through the direct Laplacian center gauge. We study correlations
between direct and indirect Laplacian center gauges.Comment: Presented by S. Olejnik at the NATO Advanced Research Workshop
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", Jan.
21-27, 2002, Stara Lesna, Slovakia. 10 pages, 3 figures (8 EPS files), uses
crckapb.st
- …