913 research outputs found
Quantum Dynamics of the Slow Rollover Transition in the Linear Delta Expansion
We apply the linear delta expansion to the quantum mechanical version of the
slow rollover transition which is an important feature of inflationary models
of the early universe. The method, which goes beyond the Gaussian
approximation, gives results which stay close to the exact solution for longer
than previous methods. It provides a promising basis for extension to a full
field theoretic treatment.Comment: 12 pages, including 4 figure
Gender Disparities in Alcohol Use Disorder Treatment Among Privately Insured Patients with Alcohol‐Associated Cirrhosis
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147837/1/acer13944_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147837/2/acer13944.pd
Use of Native Grassland in Small-Scale Dairy Systems in the Highlands of Central Mexico. A Case Study
Small-scale dairy systems in Mexico comprise 78% of specialized dairy farms and provide 37% of national production. They are small farms with herds 3-35 cows plus replacements, and rely on family labour (Posadas-Domínguez et al., 2014).
In the highlands, many farms have native grasslands, grazed during the rainy season, and supplemented with other feeds as maize straw, maize grain and maize ears. Native grasslands have not been studied in this context. This is a case study on the use of native grassland in a small-scale dairy farm. The objective was to determine how native grasslands are integrated in feeding milking dairy cows, and the feeding costs involved
Aspects of Magnetic Field Configurations in Planar Nonlinear Electrodynamics
In the framework of three-dimensional Born-Infeld Electrodynamics, we pursue
an investigation of the consequences of the space-time dimensionality on the
existence of magnetostatic fields generated by electric charges at rest in an
inertial frame, which are present in its four-dimensional version. Our analysis
reveals interesting features of the model. In fact, a magnetostatic field
associated with an electric charge at rest does not appear in this case.
Interestingly, the addition of the topological term (Chern-Simons) to
Born-Infeld Electrodynamics yields the appearance of the magnetostatic field.
We also contemplate the fields associated to the would-be-magnetic monopole in
three dimensions.Comment: 8 page
Design, development and verification of the 30 and 44 GHz front-end modules for the Planck Low Frequency Instrument
We give a description of the design, construction and testing of the 30 and
44 GHz Front End Modules (FEMs) for the Low Frequency Instrument (LFI) of the
Planck mission to be launched in 2009. The scientific requirements of the
mission determine the performance parameters to be met by the FEMs, including
their linear polarization characteristics.
The FEM design is that of a differential pseudo-correlation radiometer in
which the signal from the sky is compared with a 4-K blackbody load. The Low
Noise Amplifier (LNA) at the heart of the FEM is based on indium phosphide High
Electron Mobility Transistors (HEMTs). The radiometer incorporates a novel
phase-switch design which gives excellent amplitude and phase match across the
band.
The noise temperature requirements are met within the measurement errors at
the two frequencies. For the most sensitive LNAs, the noise temperature at the
band centre is 3 and 5 times the quantum limit at 30 and 44 GHz respectively.
For some of the FEMs, the noise temperature is still falling as the ambient
temperature is reduced to 20 K. Stability tests of the FEMs, including a
measurement of the 1/f knee frequency, also meet mission requirements.
The 30 and 44 GHz FEMs have met or bettered the mission requirements in all
critical aspects. The most sensitive LNAs have reached new limits of noise
temperature for HEMTs at their band centres. The FEMs have well-defined linear
polarization characteristcs.Comment: 39 pages, 33 figures (33 EPS files), 12 tables. Planck LFI technical
papers published by JINST:
http://www.iop.org/EJ/journal/-page=extra.proc5/1748-022
Dirac-like Monopoles in Three Dimensions and Their Possible Influences on the Dynamics of Particles
Dirac-like monopoles are studied in three-dimensional Abelian Maxwell and
Maxwell-Chern-Simons models. Their scalar nature is highlighted and discussed
through a dimensional reduction of four-dimensional electrodynamics with
electric and magnetic sources. Some general properties and similarities of them
when are considered in Minkowski or Euclidian space are mentioned. However, by
virtue of the structure of the space-time in which they are considered a number
of differences among them take place. Furthermore, we pay attention to some
consequences of these objects when acting upon usual particles. Among other
subjects, special attention is given to the study of a Lorentz-violating
non-minimal coupling between neutral fermions and the field generated by a
monopole alone. In addition, an analogue of the Aharonov-Casher effect is
discussed in this framework.Comment: 20 pages. Latex format. No figures. Accepted for publication in Phys.
Rev.
How the central domain of dystrophin acts to bridge F-actin to sarcolemmal lipids
Dystrophin is a large intracellular protein that prevents sarcolemmal ruptures by providing a mechanical link between the intracellular actin cytoskeleton and the transmembrane dystroglycan complex. Dystrophin deficiency leads to the severe muscle wasting disease Duchenne Muscular Dystrophy and the milder allelic variant, Becker Muscular Dystrophy (DMD and BMD). Previous work has shown that concomitant interaction of the actin binding domain 2 (ABD2) comprising spectrin like repeats 11 to 15 (R11-15) of the central domain of dystrophin, with both actin and membrane lipids, can greatly increase membrane stiffness. Based on a combination of SAXS and SANS measurements, mass spectrometry analysis of cross-linked complexes and interactive low-resolution simulations, we explored in vitro the molecular properties of dystrophin that allow the formation of ABD2-F-actin and ABD2-membrane model complexes. In dystrophin we identified two subdomains interacting with F-actin, one located in R11 and a neighbouring region in R12 and another one in R15, while a single lipid binding domain was identified at the C-terminal end of R12. Relative orientations of the dystrophin central domain with F-actin and a membrane model were obtained from docking simulation under experimental constraints. SAXS-based models were then built for an extended central subdomain from R4 to R19, including ABD2. Overall results are compatible with a potential F-actin/dystrophin/membrane lipids ternary complex. Our description of this selected part of the dystrophin associated complex bridging muscle cell membrane and cytoskeleton opens the way to a better understanding of how cell muscle scaffolding is maintained through this essential protein
Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance
We give the calibration and scientific performance parameters of the Planck
Low Frequency Instrument (LFI) measured during the ground cryogenic test
campaign. These parameters characterise the instrument response and constitute
our best pre-launch knowledge of the LFI scientific performance. The LFI shows
excellent stability and rejection of instrumental systematic effects;
measured noise performance shows that LFI is the most sensitive instrument of
its kind. The set of measured calibration parameters will be updated during
flight operations through the end of the mission.Comment: Accepted for publications in Astronomy and Astrophysics. Astronomy &
Astrophysics, 2010 (acceptance date: 12 Jan 2010
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