917 research outputs found
Social and structural conditions for the avoidance of advance care planning in neuro-oncology: a qualitative study
BACKGROUND: Primary brain tumours newly affect >260â000 people each year worldwide. In the UK, every year >10â000 people are diagnosed with a brain tumour while >5000 die annually from the disease. Prognoses are poor, cognitive deterioration common and patients have prolonged palliative needs. Advance care planning (ACP) may enable early discussion of future care decisions. Although a core commitment in the UK healthcare strategy, and the shared responsibility of clinical teams, ACP appears uncommon in practice. Evidence around ACP practice in neuro-oncology is limited. OBJECTIVES: We aimed to elicit key social and structural conditions contributing to the avoidance of ACP in neuro-oncology. DESIGN: A cross-sectional qualitative study design was used. SETTING: One tertiary care hospital in the UK. PARTICIPANTS: Fifteen healthcare professionals working in neuro-oncology participated in this study, including neuro-oncologists, neurosurgeons, clinical nurse specialists, allied healthcare professionals and a neurologist. METHOD: Semi-structured interviews were conducted with participants to explore their assumptions and experiences of ACP. Data were analysed thematically using the well-established framework method. RESULTS: Participants recognised the importance of ACP but few had ever completed formal ACP documentation. We identified eight key factors, which we suggest comprise three main conditions for avoidance: (1) difficulties being a highly emotive, time-intensive practice requiring the right 'window of opportunity' and (2) presence and availability of others; (3) ambiguities in ACP definition, purpose and practice. Combined, these created a 'culture of shared avoidance'. CONCLUSION: In busy clinical environments, 'shared responsibility' is interpreted as 'others' responsibility' laying the basis for a culture of avoidance. To address this, we suggest a 'generalists and specialists' model of ACP, wherein healthcare professionals undertake particular responsibilities. Healthcare professionals are already adopting this model informally, but without formalised structure it is likely to fail given a tendency for people to assume a generalist role
Expansion of W 3(OH)
A direct measurement of the expansion of W 3(OH) is made by comparing Very
Large Array images taken about 10 yr apart. The expansion is anisotropic with a
typical speed of 3 to 5 km/s, indicating a dynamical age of only 2300 yr. These
observations are inconsistent with either the freely expanding shell model or a
simple bow shock model. The most favored model is a slowly expanding shell-like
HII region, with either a fast rarefied flow or another less massive diffuse
ionized region moving towards the observer. There is also a rapidly evolving
source near the projected center of emission, perhaps related to the central
star.Comment: LaTeX file, 28 pages, includes 8 figures. To appear in ApJ in
December 10 (1998) issue. Also available at
http://www.submm.caltech.edu/~kawamura/w3oh_pp.p
Gate-controlled Guiding of Electrons in Graphene
Ballistic semiconductor structures have allowed the realization of
optics-like phenomena in electronics, including magnetic focusing and lensing.
An extension that appears unique to graphene is to use both n and p carrier
types to create electronic analogs of optical devices having both positive and
negative indices of refraction. Here, we use gate-controlled density with both
p and n carrier types to demonstrate the analog of the fiber-optic guiding in
graphene. Two basic effects are investigated: (1) bipolar p-n junction guiding,
based on the principle of angle-selective transmission though the graphene p-n
interface, and (2) unipolar fiber-optic guiding, using total internal
reflection controlled by carrier density. Modulation of guiding efficiency
through gating is demonstrated and compared to numerical simulations, which
indicates that interface roughness limits guiding performance, with
few-nanometer effective roughness extracted. The development of p-n and
fiber-optic guiding in graphene may lead to electrically reconfigurable wiring
in high-mobility devices.Comment: supplementary materal at
http://marcuslab.harvard.edu/papers/OG_SI.pd
(Sub)mm Interferometry Applications in Star Formation Research
This contribution gives an overview about various applications of (sub)mm
interferometry in star formation research. The topics covered are molecular
outflows, accretion disks, fragmentation and chemical properties of low- and
high-mass star-forming regions. A short outlook on the capabilities of ALMA is
given as well.Comment: 20 pages, 7 figures, in proceedings to "2nd European School on Jets
from Young Star: High Angular Resolution Observations". A high-resolution
version of the paper can be found at
http://www.mpia.de/homes/beuther/papers.htm
A Census of the High-Density Molecular Gas in M82
We present a three-pointing study of the molecular gas in the starburst
nucleus of M82 based on 190 - 307 GHz spectra obtained with Z-Spec at the
Caltech Submillimeter Observatory. We present intensity measurements,
detections and upper limits, for 20 transitions, including several new
detections of CS, HNC, C2H, H2CO, and CH3CCH lines. We combine our measurements
with previously-published measurements at other frequencies for HCN, HNC, CS,
C34S, and HCO+ in a multi-species likelihood analysis constraining gas mass,
density and temperature, and the species' relative abundances. We find some 1.7
- 2.7 x 10^8 M_sun of gas with n_H2 between 1 - 6 x 10^4 cm^-3 and T > 50 K.
While the mass and temperature are comparable to values inferred from mid-J CO
transitions, the thermal pressure is a factor of 10 - 20 greater. The molecular
interstellar medium is largely fragmented and is subject to ultraviolet
irradiation from the star clusters. It is also likely subject to cosmic rays
and mechanical energy input from the supernovae, and is warmer on average than
the molecular gas in the massive star formation regions in the Milky Way. The
typical conditions in the dense gas in M82's central kpc appear unfavorable for
further star formation; if any appreciable stellar populations are currently
forming, they are likely biased against low mass stars, producing a top-heavy
initial mass function.Comment: 15 pages (using emulateapj.cls), 6 figures, Astrophysical Journal, in
pres
Interaction of Wilson loops in confining vacuum
Nonperturbative and perturbative interaction mechanisms of Wilson loops in
gluodynamics are studied within the background field formalism. The first one
operates when distance between minimal surfaces of the loops is small and may
be important for sea quark effects and strong decay processes. The second
mechanism -- perturbative interaction in nonperturbative confining background
is found to be physically dominant for all loop configurations characteristic
of scattering process. It reduces to perturbative gluon exchanges at small
distances, while at larger distances it corresponds to the t-channel exchange
of (reggeized) glueball states.
Comparison to other approaches is made and possible physical applications are
discussed.Comment: LaTeX, 25 pages, 5 EPS-figure
ZrTe2/CrTe2: an epitaxial van der Waals platform for spintronics
The rapid discovery of two-dimensional (2D) van der Waals (vdW) quantum
materials has led to heterostructures that integrate diverse quantum
functionalities such as topological phases, magnetism, and superconductivity.
In this context, the epitaxial synthesis of vdW heterostructures with
well-controlled interfaces is an attractive route towards wafer-scale platforms
for systematically exploring fundamental properties and fashioning
proof-of-concept devices. Here, we use molecular beam epitaxy to synthesize a
vdW heterostructure that interfaces two material systems of contemporary
interest: a 2D ferromagnet (1T-CrTe2) and a topological semimetal (ZrTe2). We
find that one unit-cell (u.c.) thick 1T-CrTe2 grown epitaxially on ZrTe2 is a
2D ferromagnet with a clear anomalous Hall effect. In thicker samples (12 u.c.
thick CrTe2), the anomalous Hall effect has characteristics that may arise from
real-space Berry curvature. Finally, in ultrathin CrTe2 (3 u.c. thickness), we
demonstrate current-driven magnetization switching in a full vdW topological
semimetal/2D ferromagnet heterostructure device.Comment: Includes new data (ST-FMR) and calculations (spin Hall conductivity
Stochastic Theory of Relativistic Particles Moving in a Quantum Field: II. Scalar Abraham-Lorentz-Dirac-Langevin Equation, Radiation Reaction and Vacuum Fluctuations
We apply the open systems concept and the influence functional formalism
introduced in Paper I to establish a stochastic theory of relativistic moving
spinless particles in a quantum scalar field. The stochastic regime resting
between the quantum and semi-classical captures the statistical mechanical
attributes of the full theory. Applying the particle-centric world-line
quantization formulation to the quantum field theory of scalar QED we derive a
time-dependent (scalar) Abraham-Lorentz-Dirac (ALD) equation and show that it
is the correct semiclassical limit for nonlinear particle-field systems without
the need of making the dipole or non-relativistic approximations. Progressing
to the stochastic regime, we derive multiparticle ALD-Langevin equations for
nonlinearly coupled particle-field systems. With these equations we show how to
address time-dependent dissipation/noise/renormalization in the semiclassical
and stochastic limits of QED. We clarify the the relation of radiation
reaction, quantum dissipation and vacuum fluctuations and the role that initial
conditions may play in producing non-Lorentz invariant noise. We emphasize the
fundamental role of decoherence in reaching the semiclassical limit, which also
suggests the correct way to think about the issues of runaway solutions and
preacceleration from the presence of third derivative terms in the ALD
equation. We show that the semiclassical self-consistent solutions obtained in
this way are ``paradox'' and pathology free both technically and conceptually.
This self-consistent treatment serves as a new platform for investigations into
problems related to relativistic moving charges.Comment: RevTex; 20 pages, 3 figures, Replaced version has corrected typos,
slightly modified derivation, improved discussion including new section with
comparisons to related work, and expanded reference
Bispectrum speckle interferometry observations and radiative transfer modelling of the red supergiant NML Cyg: Multiple dust-shell structures evidencing previous superwind phases
(abridged) NML Cyg is a highly evolved OH/IR supergiant and supposed to be
among the most luminous supergiants in the galaxy. We present the first
diffraction limited 2.13micron observations of NML Cyg with 73mas resolution.
The speckle interferograms were obtained with the SAO 6m telescope, image
reconstruction is based on the bispectrum speckle interferometry method.
Radiative transfer calculations have been carried out to model the spectral
energy distribution, our 2.13micron visibility function, and mid-infrared
visibility functions. The observed dust shell properties do not appear to be in
accordance with single-shell models but seem to require multiple components.
Considering previous periods of enhanced mass-loss, various density
enhancements in the dust shell were taken into account. An extensive grid of
models was calculated for different locations and strenghts of such superwind
regions in the dust shell. To match the observations from the optical to the
sub-mm domain requires at least two superwind regions embedded in the shell.
The best model includes a dust shell with a temperature of 1000K at its inner
radius of 6.2Rstar, a close embedded superwind shell extending from 15.5Rstar
to 21.7Rstar with amplitude 10 (factor of density enhancement), and a far-out
density enhancement at 186Rstar with amplitude 5. The angular diameter of the
inner dust-shell rim amounts to 105mas. Within the various parts of the dust
shell, 1/r^2 density distributions could be maintained differing only in their
amplitude A. The present-day mass-loss rate was determined to be 1.2 10^-4
Msol/yr. The inner embedded superwind shell corresponds to a phase of enhanced
mass-loss which began ~59yr ago and lasted for ~18yr, and the outer superwind
region to a high mass-loss period which terminated 529yr ago.Comment: 12 pages including 13 PostScript figures, also available from
http://www.mpifr-bonn.mpg.de/div/ir-interferometry/publications.html;
accepted for publication in Astronomy & Astrophysic
Rheumatoid Arthritis is an Autoimmune Disease Triggered by Proteus Urinary Tract Infection
Rheumatoid arthritis (RA) is a chronic and disabling polyarthritic disease, which affects mainly women in middle and old age
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