6,174 research outputs found
Molecular CO outflows in the L1641-N cluster: kneading a cloud core
We present results of 1.3mm interferometric and single-dish observations of
the center of the L1641-N cluster in Orion. Single-dish wide-field continuum
and CO(2-1) observations reveal the presence of several molecular outflows
driven by deeply embedded protostellar sources. At higher angular resolution,
the dominant millimeter source in the cluster center is resolved into a pair of
protostars (L1641-N-MM1 and MM3), each driving a collimated outflow, and a more
extended, clumpy core. Low-velocity CO line-wing emission is widely spread over
much of the cluster area. We detect and map the distribution of several other
molecular transitions (13CO, C18O, 13CS, SO, CH3OH, CH3CN, and OCS). CH3CN and
OCS may indicate the presence of a hot corino around L1641-N-MM1. We
tentatively identify a velocity gradient over L1641-N-MM1 in CH3CN and OCS,
oriented roughly perpendicular to the outflow direction, perhaps indicative of
a circumstellar disk. An analysis of the energy and momentum load of the CO
outflows, along with the notion that apparently a large volume fraction is
affected by the multiple outflow activity, suggests that outflows from a
population of low-mass stars might have a significant impact on clustered (and
potentially high-mass) star formation.Comment: 16 pages plus 10 figures accepted by AJ, full resolution version
available at http://www.eso.org/~tstanke/preprints.htm
Evaluation of the health-related quality of life of children in Schistosoma haematobium-endemic communities in Kenya: a cross-sectional study.
BACKGROUND: Schistosomiasis remains a global public health challenge, with 93% of the ~237 million infections occurring in sub-Saharan Africa. Though rarely fatal, its recurring nature makes it a lifetime disorder with significant chronic health burdens. Much of its negative health impact is due to non-specific conditions such as anemia, undernutrition, pain, exercise intolerance, poor school performance, and decreased work capacity. This makes it difficult to estimate the disease burden specific to schistosomiasis using the standard DALY metric.
METHODOLOGY/PRINCIPAL FINDINGS: In our study, we used Pediatric Quality of Life Inventory (PedsQL), a modular instrument available for ages 2-18 years, to assess health-related quality of life (HrQoL) among children living in a Schistosoma haematobium-endemic area in coastal Kenya. The PedsQL questionnaires were administered by interview to children aged 5-18 years (and their parents) in five villages spread across three districts. HrQoL (total score) was significantly lower in villages with high prevalence of S. haematobium (-4.0%, p<0.001) and among the lower socioeconomic quartiles (-2.0%, p<0.05). A greater effect was seen in the psychosocial scales as compared to the physical function scale. In moderate prevalence villages, detection of any parasite eggs in the urine was associated with a significant 2.1% (p<0.05) reduction in total score. The PedsQL reliabilities were generally high (Cronbach alphas ≥0.70), floor effects were acceptable, and identification of children from low socioeconomic standing was valid.
CONCLUSIONS/SIGNIFICANCE: We conclude that exposure to urogenital schistosomiasis is associated with a 2-4% reduction in HrQoL. Further research is warranted to determine the reproducibility and responsiveness properties of QoL testing in relation to schistosomiasis. We anticipate that a case definition based on more sensitive parasitological diagnosis among younger children will better define the immediate and long-term HrQoL impact of Schistosoma infection
Sliding charge density wave in manganites
The so-called stripe phase of the manganites is an important example of the
complex behaviour of metal oxides, and has long been interpreted as the
localisation of charge at atomic sites. Here, we demonstrate via resistance
measurements on La_{0.50}Ca_{0.50}MnO_3 that this state is in fact a
prototypical charge density wave (CDW) which undergoes collective transport.
Dramatic resistance hysteresis effects and broadband noise properties are
observed, both of which are typical of sliding CDW systems. Moreover, the high
levels of disorder typical of manganites result in behaviour similar to that of
well-known disordered CDW materials. Our discovery that the manganite
superstructure is a CDW shows that unusual transport and structural properties
do not require exotic physics, but can emerge when a well-understood phase (the
CDW) coexists with disorder.Comment: 13 pages; 4 figure
Hydrodynamic behavior in expanding thermal clouds of Rb-87
We study hydrodynamic behavior in expanding thermal clouds of Rb-87 released
from an elongated trap. At our highest densities the mean free path is smaller
than the radial size of the cloud. After release the clouds expand
anisotropically. The cloud temperature drops by as much as 30%. This is
attributed to isentropic cooling during the early stages of the expansion. We
present an analytical model to describe the expansion and to estimate the
cooling. Important consequences for time-of-flight thermometry are discussed.Comment: 7 pages with 2 figure
Dynamic Impedance of Two-Dimensional Superconducting Films Near the Superconducting Transition
The sheet impedances, Z(w,T), of several superconducting a-Mo77Ge23 films and
one In/InOx film have been measured in zero field using a two-coil mutual
inductance technique at frequencies from 100 Hz to 100 kHz. Z(w,T) is found to
have three contributions: the inductive superfluid, renormalized by nonvortex
phase fluctuations; conventional vortex-antivortex pairs, whose contribution
turns on very rapidly just below the usual Kosterlitz-Thouless-Berezinskii
unbinding temperature; and an anomalous contribution. The latter is
predominantly resistive, persists well below the KTB temperature, and is weakly
dependent on frequency down to remarkably low frequencies, at least 100 Hz. It
increases with T as e-U'(T)/kT, where the activation energy, U'(T), is about
half the energy to create a vortex-antivortex pair, indicating that the
frequency dependence is that of individual excitations, rather than critical
behavior.Comment: 10 pages, 10 figs; subm PR
Time correlations and 1/f behavior in backscattering radar reflectivity measurements from cirrus cloud ice fluctuations
The state of the atmosphere is governed by the classical laws of fluid motion
and exhibits correlations in various spatial and temporal scales. These
correlations are crucial to understand the short and long term trends in
climate. Cirrus clouds are important ingredients of the atmospheric boundary
layer. To improve future parameterization of cirrus clouds in climate models,
it is important to understand the cloud properties and how they change within
the cloud. We study correlations in the fluctuations of radar signals obtained
at isodepths of winter and fall cirrus clouds. In particular we focus on three
quantities: (i) the backscattering cross-section, (ii) the Doppler velocity and
(iii) the Doppler spectral width. They correspond to the physical coefficients
used in Navier Stokes equations to describe flows, i.e. bulk modulus,
viscosity, and thermal conductivity. In all cases we find that power-law time
correlations exist with a crossover between regimes at about 3 to 5 min. We
also find that different type of correlations, including 1/f behavior,
characterize the top and the bottom layers and the bulk of the clouds. The
underlying mechanisms for such correlations are suggested to originate in ice
nucleation and crystal growth processes.Comment: 33 pages, 9 figures; to appear in the Journal of Geophysical Research
- Atmosphere
Dislocation Loop Formation and Growth under In Situ Laser and/or Electron Irradiation
Vacancies and interstitial atoms are primary lattice (point) defects that cause observable microstructural changes, such as the formation of dislocation loops and voids in crystalline solids. These defects' diffusion properties determine the phase stability and environmental resistibility of macroscopic materials under ambient conditions. Although in situ methods have been proposed for measuring the diffusion energy of point defects, direct measurement has been limited. In this study, we propose an alternative in situ method to measure the activation energy for vacancy migration under laser irradiation using a pulsed laser beam from a laser-equipped high-voltage electron microscope (laser-HVEM). We made in situ observations that revealed the formation and growth of vacancy dislocation loops in an austenitic stainless steel during laser irradiation. These loops continued to grow when thermal annealing was performed after laser irradiation at the same temperature. We anticipate that laser-HVEM will provide a new method for investigating lattice defects
Evolution of edge states in topological superfluids during the quantum phase transition
The quantum phase transition between topological and non-topological
insulators or between fully gapped superfluids/superconductors can occur
without closing the gap. We consider the evolution of the Majorana edge states
on the surface of topological superconductor during transition to the
topologically trivial superconductor on example of non-interacting Hamiltonian
describing the spin-triplet superfluid 3He-B. In conventional situation when
the gap is nullified at the transition, the spectrum of Majorana fermions
shrinks and vanishes after the transition to the trivial state. If the
topological transition occurs without the gap closing, the Majorana fermion
spectrum disappears by escaping to ultraviolet, where Green's function
approaches zero. This demonstrates the close connection between the topological
transition without closing the gap and zeroes in the Green's function. Similar
connection takes place in interacting systems where zeroes may occur due to
interaction.Comment: 5 pages, 2 figures, JETP Letters style, version submitted to JETP
Letter
Hidden Order in the Cuprates
We propose that the enigmatic pseudogap phase of cuprate superconductors is
characterized by a hidden broken symmetry of d(x^2-y^2)-type. The transition to
this state is rounded by disorder, but in the limit that the disorder is made
sufficiently small, the pseudogap crossover should reveal itself to be such a
transition. The ordered state breaks time-reversal, translational, and
rotational symmetries, but it is invariant under the combination of any two. We
discuss these ideas in the context of ten specific experimental properties of
the cuprates, and make several predictions, including the existence of an
as-yet undetected metal-metal transition under the superconducting dome.Comment: 12 pages of RevTeX, 9 eps figure
Majorana Neutrino Mixing
The most plausible see-saw explanation of the smallness of the neutrino
masses is based on the assumption that total lepton number is violated at a
large scale and neutrinos with definite masses are Majorana particles. In this
review we consider in details difference between Dirac and Majorana neutrino
mixing and possibilities of revealing Majorana nature of neutrinos with
definite masses
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