18,084 research outputs found
Power supply Patent
Power supply with automatic power factor conversion syste
The magnetic field at milliarcsecond resolution around IRAS20126+4104
IRAS20126+4104 is a well studied B0.5 protostar that is surrounded by a ~1000
au Keplerian disk and is where a large-scale outflow originates. Both 6.7-GHz
CH3OH masers and 22-GHz H2O masers have been detected toward this young stellar
object. The CH3OH masers trace the Keplerian disk, while the H2O masers are
associated with the surface of the conical jet. Recently, observations of dust
polarized emission (350 um) at an angular resolution of 9 arcseconds (~15000
au) have revealed an S-shaped morphology of the magnetic field around
IRAS20126+4104. The observations of polarized maser emissions at milliarcsecond
resolution (~20 au) can make a crucial contribution to understanding the
orientation of the magnetic field close to IRAS20126+4104. This will allow us
to determine whether the magnetic field morphology changes from arcsecond
resolution to milliarcsecond resolution. The European VLBI Network was used to
measure the linear polarization and the Zeeman splitting of the 6.7-GHz CH3OH
masers toward IRAS20126+4104. The NRAO Very Long Baseline Array was used to
measure the linear polarization and the Zeeman splitting of the 22-GHz H2O
masers toward the same region. We detected 26 CH3OH masers and 5 H2O masers at
high angular resolution. Linear polarization emission was observed toward three
CH3OH masers and toward one H2O maser. Significant Zeeman splitting was
measured in one CH3OH maser (\Delta V_{Z}=-9.2 +/- 1.4 m/s). No significant (5
sigma) magnetic field strength was measured using the H2O masers. We found that
in IRAS20126+4104 the rotational energy is less than the magnetic energy.Comment: 9 pages, 5 figures, 2 tables, accepted by Astronomy & Astrophysic
EVN observations of 6.7-GHz methanol maser polarization in massive star-forming regions II. First statistical results
Magnetic fields have only recently been included in theoretical simulations
of high-mass star formation. The simulations show that magnetic fields play an
important role in the formation and dynamics of molecular outflows. Masers, in
particular 6.7-GHz CH3OH masers, are the best probes of the magnetic field
morphologies around massive young stellar objects on the smallest scales of
10-100 AU. This paper focuses on 4 massive young stellar objects,
IRAS06058+2138-NIRS1, IRAS22272+6358A, S255-IR, and S231, which complement our
previous 2012 sample (the first EVN group). From all these sources, molecular
outflows have been detected in the past. Seven of the European VLBI Network
antennas were used to measure the linear polarization and Zeeman-splitting of
the 6.7-GHz CH3OH masers in the star-forming regions in this second EVN group.
We detected a total of 128 CH3OH masing cloudlets. Fractional linear
polarization (0.8%-11.3%) was detected towards 18% of the CH3OH masers in our
sample. The linear polarization vectors are well ordered in all the massive
young stellar objects. We measured significant Zeeman-splitting in
IRAS06058+2138-NIRS1 (DVz=3.8+/-0.6 m/s) and S255-IR (DVz=3.2+/-0.7 m/s). By
considering the 20 massive young stellar objects towards which the morphology
of magnetic fields was determined by observing 6.7-GHz CH3OH masers in both
hemispheres, we find no evident correlation between the linear distributions of
CH3OH masers and the outflows or the linear polarization vectors. On the other
hand, we present first statistical evidence that the magnetic field (on scales
10-100 AU) is primarily oriented along the large-scale outflow direction.
Moreover, we empirically find that the linear polarization fraction of
unsaturated CH3OH masers is P_l<4.5%.Comment: 13 pages, 8 figures, 7 tables, accepted by Astronomy & Astrophysic
On some geometric features of the Kramer interior solution for a rotating perfect fluid
Geometric features (including convexity properties) of an exact interior
gravitational field due to a self-gravitating axisymmetric body of perfect
fluid in stationary, rigid rotation are studied. In spite of the seemingly
non-Newtonian features of the bounding surface for some rotation rates, we
show, by means of a detailed analysis of the three-dimensional spatial
geodesics, that the standard Newtonian convexity properties do hold. A central
role is played by a family of geodesics that are introduced here, and provide a
generalization of the Newtonian straight lines parallel to the axis of
rotation.Comment: LaTeX, 15 pages with 4 Poscript figures. To be published in Classical
and Quantum Gravit
Jamming under tension in polymer crazes
Molecular dynamics simulations are used to study a unique expanded jammed
state. Tension transforms many glassy polymers from a dense glass to a network
of fibrils and voids called a craze. Entanglements between polymers and
interchain friction jam the system after a fixed increase in volume. As in
dense jammed systems, the distribution of forces is exponential, but they are
tensile rather than compressive. The broad distribution of forces has important
implications for fibril breakdown and the ultimate strength of crazes.Comment: 4 pages, 4 figure
Association Between Air Pollution and Low Birth Weight: A Community-Based Study
The relationship between maternal exposure to air pollution during periods of pregnancy (entire and specific periods) and birth weight was investigated in a well-defined cohort. Between 1988 and 1991, all pregnant women living in four residential areas of Beijing were registered and followed from early pregnancy until delivery. Information on individual mothers and infants was collected. Daily air pollution data were obtained independently. The sample for analysis included 74,671 first-parity live births were gestational age 37-44 weeks. Multiple linear regression and logistic regression were used to estimate the effects of air pollution on birth weight and low birth weight (< 2,500 g), adjusting for gestational age, residence, year of birth, maternal age, and infant gender. There was a significant exposure-response relationship between maternal exposures to sulfur dioxide (SO2) and total suspended particles (TSP) during the third trimester of pregnancy and infant birth weight. The adjusted odds ratio for low birth weight was 1.11 (95% CI, 1.06-1.16) for each 100 micrograms/m3 increase in SO2 and 1.10 (95% CI, 1.05-1.14) for each 100 micrograms/m3 increase in TSP. The estimated reduction in birth weight was 7.3 g and 6.9 g for each 100 micrograms/m3 increase in SO2 and in TSP, respectively. The birth weight distribution of the high-exposure group was more skewed toward the left tail (i.e., with higher proportion of births < 2,500 g) than that of the low-exposure group. Although the effects of other unmeasured risk factors cannot be excluded with certainty, our data suggests that TSP and SO2, or a more complex pollution mixture associated with these pollutants, contribute to an excess risk of low birth weight in the Beijing population.National Institute of Environmental Health Sciences (ES05947, ES08337); National Institute of Child Health & Human Development (R01 HD32505); Department of Health and Human Services (MCJ-259501, HRSA 5 T32 PE10014
Temporal response to harmonic driving in electroconvection
The temporal evolution of the spatially periodic electroconvection (EC)
patterns has been studied within the period of the driving ac voltage by
monitoring the light intensity diffracted from the pattern. Measurements have
been carried out on a variety of nematic systems, including those with negative
dielectric and positive conductivity anisotropy, exhibiting "standard EC"
(s-EC), those with both anisotropies negative exhibiting "non-standard EC"
(ns-EC), as well as those with the two anisotropies positive. Theoretical
predictions have been confirmed for stationary s-EC and ns-EC patterns.
Transitions with Hopf bifurcation have also been studied. While traveling had
no effect on the temporal evolution of dielectric s-EC, traveling conductive
s-EC and ns-EC patterns exhibited a substantially altered temporal behavior
with a dependence on the Hopf frequency. It has also been shown that in
nematics with both anisotropies positive, the pattern develops and decays
within an interval much shorter than the period, even at relatively large
driving frequencies.Comment: 19 pages, 5 figure
Weak disorder expansion for localization lengths of quasi-1D systems
A perturbative formula for the lowest Lyapunov exponent of an Anderson model on a strip is presented. It is expressed in terms of an energy-dependent doubly stochastic matrix, the size of which is proportional to the strip width. This matrix and the resulting perturbative expression for the Lyapunov exponent are evaluated numerically. Dependence on energy, strip width and disorder strength are thoroughly compared with the results obtained by the standard transfer matrix method. Good agreement is found for all energies in the band of the free operator and this even for quite large values of the disorder strength
Information Content in Decays and the Angular Moments Method
The time-dependent angular distributions of decays of neutral mesons into
two vector mesons contain information about the lifetimes, mass differences,
strong and weak phases, form factors, and CP violating quantities. A
statistical analysis of the information content is performed by giving the
``information'' a quantitative meaning. It is shown that for some parameters of
interest, the information content in time and angular measurements combined may
be orders of magnitude more than the information from time measurements alone
and hence the angular measurements are highly recommended. The method of
angular moments is compared with the (maximum) likelihood method to find that
it works almost as well in the region of interest for the one-angle
distribution. For the complete three-angle distribution, an estimate of
possible statistical errors expected on the observables of interest is
obtained. It indicates that the three-angle distribution, unraveled by the
method of angular moments, would be able to nail down many quantities of
interest and will help in pointing unambiguously to new physics.Comment: LaTeX, 34 pages with 9 figure
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