10,461 research outputs found
Analysis of severe atmospheric disturbances from airline flight records
Advanced methods were developed to determine time varying winds and turbulence from digital flight data recorders carried aboard modern airliners. Analysis of several cases involving severe clear air turbulence encounters at cruise altitudes has shown that the aircraft encountered vortex arrays generated by destabilized wind shear layers above mountains or thunderstorms. A model was developed to identify the strength, size, and spacing of vortex arrays. This model is used to study the effects of severe wind hazards on operational safety for different types of aircraft. The study demonstrates that small remotely piloted vehicles and executive aircraft exhibit more violent behavior than do large airliners during encounters with high-altitude vortices. Analysis of digital flight data from the accident at Dallas/Ft. Worth in 1985 indicates that the aircraft encountered a microburst with rapidly changing winds embedded in a strong outflow near the ground. A multiple-vortex-ring model was developed to represent the microburst wind pattern. This model can be used in flight simulators to better understand the control problems in severe microburst encounters
Evidence for Antiferromagnetic Order in LaCeCuO from Angular Magnetoresistance Measurements
We investigated the in-plane angular magnetoresistivity (AMR) of -phase LaCeCuO (LCCO) thin films () fabricated by a pulsed laser deposition technique. The in-plane
AMR with shows a twofold symmetry instead of the
fourfold behavior found in other electron-doped cuprates such as PrCeCuO and NdCeCuO. The twofold AMR
disappears above a certain temperature, . The is well above
for ( K), and decreases with increasing doping,
until it is no longer observed above at . This twofold AMR
below is suggested to originate from an antiferromagnetic or spin
density wave order.Comment: to be published in Phys. Rev. B, Vol. 80 (2009
Reliable solid-state circuits Semiannual report no. 2, Jun. 1 - Nov. 30, 1965
Pulse width modulator and other microminiaturized electronic equipment for space age application
Dissecting the Workforce and Workplace for Clinical Endocrinology, and the Work of Endocrinologists Early in Their Careers
[Excerpt] No national mechanism is in place for an informed, penetrating, and systematic assessment of the physician workforce such as that achieved by the National Science Foundation (NSF) for the periodic evaluation of the nation’s scientists and engineers. Likewise, knowledge of the workforce for clinical research is enigmatic and fragmentary despite the serial recommendations of “blue-ribbon” panels to establish a protocol for the recurrent assessment of clinical investigators early in their careers. Failure to adopt a national system for producing timely, high-quality data on the professional activities of physicians limits the application of improvement tools for advancing clinical investigation and ultimately improving clinical practice.
The present study was designed as a pilot project to test the feasibility of using Web-based surveys to estimate the administrative, clinical, didactic, and research work of subspecialty physicians employed in academic, clinical, federal, and pharmaceutical workplaces. Physician members of The Endocrine Society (TES) were used as surrogate prototypes of a subspecialty workforce because of their manageable number and investigative tradition. The results establish that Web-based surveys provide a tool to assess the activities of a decentralized workforce employed in disparate workplaces and underscore the value of focusing on physician work within the context of particular workplaces within a subspecialty. Our report also provides a new and timely snapshot of the amount and types of research performed by clinically trained endocrinologists and offers an evidenced-based framework for improving the investigative workforce in this medical subspecialty
Spectral Properties of the Core and the VLBI-Jets of Cygnus A
We present a detailed VLBI study of the spectral properties of the inner core
region of the radio galaxy Cygnus A at 5 GHz, 15 GHz, 22 GHz, 43 GHz and 86
GHz. Our observations include an epoch using phase-referencing at 15 GHz and 22
GHz and the first successful VLBI observations of Cygnus A at 86 GHz. We find a
pronounced two-sided jet structure, with a steep spectrum along the jet and an
inverted spectrum towards the counter-jet. The inverted spectrum and the
frequency-dependent jet-to-counter-jet ratio suggest that the inner counter-jet
is covered by a circum-nuclear absorber as it is proposed by the unified
scheme.Comment: 2 pages, 2 figures, Proceedings of the 7th EVN Symposium held in
Toledo, Spain in October 2004, needs evn2004.cl
Bromination of Graphene and Graphite
We present a density functional theory study of low density bromination of
graphene and graphite, finding significantly different behaviour in these two
materials. On graphene we find a new Br2 form where the molecule sits
perpendicular to the graphene sheet with an extremely strong molecular dipole.
The resultant Br+-Br- has an empty pz-orbital located in the graphene
electronic pi-cloud. Bromination opens a small (86meV) band gap and strongly
dopes the graphene. In contrast, in graphite we find Br2 is most stable
parallel to the carbon layers with a slightly weaker associated charge transfer
and no molecular dipole. We identify a minimum stable Br2 concentration in
graphite, finding low density bromination to be endothermic. Graphene may be a
useful substrate for stabilising normally unstable transient molecular states
Subaqueous cryptodome eruption, hydrothermal activity and related seafloor morphologies on the andesitic North Su volcano
© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Volcanology and Geothermal Research 323 (2016): 80-96, doi:10.1016/j.jvolgeores.2016.04.041.North Su is a double-peaked active andesite submarine volcano located in the eastern
Manus Basin of the Bismarck Sea that reaches a depth of 1154 m. It hosts a vigorous
and varied hydrothermal system with black and white smoker vents along with several
areas of diffuse venting and deposits of native sulfur. Geologic mapping based on ROV
observations from 2006 and 2011 combined with morphologic features identified from
repeated bathymetric surveys in 2002 and 2011 document the emplacement of a
volcanic cryptodome between 2006 and 2011. We use our observations and rock
analyses to interpret an eruption scenario where highly viscous, crystal-rich andesitic
magma erupted slowly into the water-saturated, gravel-dominated slope of North Su. An
intense fragmentation process produced abundant blocky clasts of a heterogeneous
magma (olivine crystals within a rhyolitic groundmass) that only rarely breached through
the clastic cover onto the seafloor. Phreatic and phreatomagmatic explosions beneath
the seafloor cause mixing of juvenile and pre-existing lithic clasts and produce a
volcaniclastic deposit. This volcaniclastic deposit consists of blocky, non-altered clasts
next, variably (1-100 %) altered clasts, hydrothermal precipitates and crystal fragments.
The usually applied parameters to identify juvenile subaqueous lava fragments, i.e.
fluidal shape or chilled margin, were not applicable to distinguish between pre-existing
non-altered clasts and juvenile clasts. This deposit is updomed during further injection of
magma and mechanical disruption. Gas-propelled turbulent clast-recycling causes clasts
to develop variably rounded shapes. An abundance of blocky clasts and the lack of
clasts typical for the contact of liquid lava with water is interpreted to be the result of a
cooled, high-viscosity, crystal-rich magma that failed as a brittle solid upon stress. The
high viscosity allows the lava to form blocky and short lobes. The pervasive volcaniclastic cover on North Su is partly cemented by hydrothermal precipitates. These
hydrothermally-cemented breccias, crusts and single pillars show that hydrothermal
circulation through a thick layer of volcaniclastic deposits can temporarily increase slope
stability through precipitation and cementation.The RV Melville work was funded by a combination of
the US National Science Foundation grant OCE-0327448 and a collaborative research
funding grant from Nautilus Minerals for the ABE surveys. The RV Sonne research
cruise was funded through the BMBF (Grant G03216a). Additional funding, including
salary support for JT, was provided by the German DFG Research Centre/Excellence
Cluster ―The Ocean in the Earth System‖. WB acknowledges support from DFG
research grant BA1605/4-1.2018-05-1
Insights into the Carbon chemistry of Mon R2
Aiming to learn about the chemistry of the dense PDR around the ultracompact
(UC) HII region in Mon R2, we have observed a series of mm-wavelength
transitions of C3H2 and C2H. In addition, we have traced the distribution of
other molecules, such as H13CO+, SiO, HCO, and HC3N. These data, together with
the reactive ions recently detected, have been considered to determine the
physical conditions and to model the PDR chemistry. We then identified two kind
of molecules. The first group, formed by the reactive ions (CO+, HOC+) and
small hydrocarbons (C2H, C3H2), traces the surface layers of the PDR and is
presumably exposed to a high UV field (hence we called it as "high UV", or
HUV). HUV species is expected to dominate for visual absorptions 2 < Av < 5
mag. A second group (less exposed to the UV field, and hence called "low UV",
or LUV) includes HCO and SiO, and is mainly present at the edges of the PDR (Av
> 5 mag). While the abundances of the HUV molecules can be explained by gas
phase models, this is not the case for the studied LUV ones. Although some
efficient gas-phase reactions might be lacking, grain chemistry sounds like a
probable mechanism able to explain the observed enhancement of HCO and SiO.
Within this scenario, the interaction of UV photons with grains produces an
important effect on the molecular gas chemistry and constitutes the first
evidence of an ionization front created by the UC HII region carving its host
molecular cloud. The physical conditions and kinematics of the gas layer which
surrounds the UC HII region were derived from the HUV molecules. Molecular
hydrogen densities > 4 10^6 cm^(-3) are required to reproduce the observations.
Such high densities suggest that the HII region could be pressure-confined by
the surrounding high density molecular gas.Comment: 32 pages, 8 figures. Accepted by Astrophysical Journa
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