2,501 research outputs found
The Bouvia Case Revisited: An Introduction to the Bioethical Topics of Individual Rights, Acts of Conscience, and the Right to Die
After a series of court appeals Elizabeth Bouvia won her right to die in 1986. Twenty-five years after the Bouvia case, issues of individual rights, acts of conscience for health care professionals, and the right to die continually inform health care practice and public policy. This article examines these three vital issues in the context of their relevance today, as well as the progression of health policy in regard to these topics since the Bouvia case. The complexity of the Bouvia case keeps it in the forefront of bioethics and health law studies; it begs one to consider how the Bouvia case will be viewed and discussed in another 25 years, as well as how it will continue to inform issues of individual rights, acts of conscience, and the right to die
Chemical abundances in the protoplanetary disk LV2 (Orion): clues to the causes of the abundance anomaly in HII regions
Optical integral field spectroscopy of the archetype protoplanetary disk LV2
in the Orion Nebula is presented, taken with the VLT FLAMES/Argus fibre array.
The detection of recombination lines of CII and OII from this class of objects
is reported, and the lines are utilized as abundance diagnostics. The study is
complemented with the analysis of HST Faint Object Spectrograph ultraviolet and
optical spectra of the target contained within the Argus field of view. By
subtracting the local nebula background the intrinsic spectrum of the proplyd
is obtained and its elemental composition is derived for the first time. The
proplyd is found to be overabundant in carbon, oxygen and neon compared to the
Orion Nebula and the sun. The simultaneous coverage over LV2 of the CIII]
1908-A and [OIII] 5007-A collisionally excited lines (CELs) and CII and OII
recombination lines (RLs) has enabled us to measure the abundances of C++ and
O++ for LV2 with both sets of lines. The two methods yield consistent results
for the intrinsic proplyd spectrum, but not for the proplyd spectrum
contaminated by the generic nebula spectrum, thus providing one example where
the long-standing abundance anomaly plaguing metallicity studies of HII regions
has been resolved. These results would indicate that the standard
forbidden-line methods used in the derivation of light metal abundances in HII
regions in our own and other galaxies underestimate the true gas metallicity.Comment: Accepted by MNRAS November 8; 16 pages, 9 figs; typos corrected,
error in FWHMs in table 4 corrected in this versio
Dynamical Instability of a Rotating Dipolar Bose-Einstein Condensate
We calculate the hydrodynamic solutions for a dilute Bose-Einstein condensate
with long-range dipolar interactions in a rotating, elliptical harmonic trap,
and analyse their dynamical stability. The static solutions and their regimes
of instability vary non-trivially on the strength of the dipolar interactions.
We comprehensively map out this behaviour, and in particular examine the
experimental routes towards unstable dynamics, which, in analogy to
conventional condensates, may lead to vortex lattice formation. Furthermore, we
analyse the centre of mass and breathing modes of a rotating dipolar
condensate.Comment: 4 pages, including 2 figure
Explosive Disintegration of a Massive Young Stellar System in Orion
Young massive stars in the center of crowded star clusters are expected to
undergo close dynamical encounters that could lead to energetic, explosive
events. However, there has so far never been clear observational evidence of
such a remarkable phenomenon. We here report new interferometric observations
made with the Submillimeter Array (SMA) that indicate the well known enigmatic
wide-angle outflow located in the Orion BN/KL star-forming region to have been
produced by such a violent explosion during the disruption of a massive young
stellar system, and that this was caused by a close dynamical interaction about
500 years ago. This outflow thus belongs to a totally different family of
molecular flows which is not related to the classical bipolar flows that are
generated by stars during their formation process. Our molecular data allow us
to create a 3D view of the debris flow and to link this directly to the well
known Orion H "fingers" farther outComment: Accepted by ApJ Letters The 3D movie can be found in:
ftp://ftp.mpifr-bonn.mpg.de/outgoing/lzapata/movie.gi
Atomic Bloch-Zener oscillations for sensitive force measurements in a cavity
Cold atoms in an optical lattice execute Bloch-Zener oscillations when they
are accelerated. We have performed a theoretical investigation into the case
when the optical lattice is the intra-cavity field of a driven Fabry-Perot
resonator. When the atoms oscillate inside the resonator, we find that their
back-action modulates the phase and intensity of the light transmitted through
the cavity. We solve the coupled atom-light equations self-consistently and
show that, remarkably, the Bloch period is unaffected by this back-action. The
transmitted light provides a way to observe the oscillation continuously,
allowing high precision measurements to be made with a small cloud of atoms.Comment: 5 pages, 2 figures. Updated version including cavity heating effect
Integral field spectroscopy of selected areas of the Bright Bar and Orion-S cloud in the Orion Nebula
We present integral field spectroscopy of two selected zones in the Orion
Nebula obtained with the Potsdam Multi-Aperture Spectrophotometer (PMAS),
covering the optical spectral range from 3500 to 7200 A and with a spatial
resolution of 1". The observed zones are located on the prominent Bright Bar
and on the brightest area at the northeast of the Orion South cloud, both
containing remarkable ionization fronts. We obtain maps of emission line fluxes
and ratios, electron density and temperatures, and chemical abundances. We
study the ionization structure and morphology of both fields, which ionization
fronts show different inclination angles with respect to the plane of the sky.
We find that the maps of electron density, O+/H+ and O/H ratios show a rather
similar structure. We interpret this as produced by the strong dependence on
density of the [OII] lines used to derive the O+ abundance, and that our
nominal values of electron density-derived from the [SII] line ratio-may be
slightly higher than the appropriate value for the O+ zone. We measure the
faint recombination lines of OII in the field at the northeast of the Orion
South cloud allowing us to explore the so-called abundance discrepancy problem.
We find a rather constant abundance discrepancy across the field and a mean
value similar to that determined in other areas of the Orion Nebula, indicating
that the particular physical conditions of this ionization front do not
contribute to this discrepancy.Comment: 15 pages, 10 figures. Accepted for publication in MNRA
Vortex in a trapped Bose-Einstein condensate with dipole-dipole interactions
We calculate the critical rotation frequency at which a vortex state becomes
energetically favorable over the vortex-free ground state in a harmonically
trapped Bose-Einstein condensate whose atoms have dipole-dipole interactions as
well as the usual s-wave contact interactions. In the Thomas-Fermi
(hydrodynamic) regime, dipolar condensates in oblate cylindrical traps (with
the dipoles aligned along the axis of symmetry of the trap) tend to have lower
critical rotation frequencies than their purely s-wave contact interaction
counterparts. The converse is true for dipolar condensates in prolate traps.
Quadrupole excitations and centre of mass motion are also briefly discussed as
possible competing mechanisms to a vortex as means by which superfluids with
partially attractive interactions might carry angular momentumComment: 12 pages, 12 figure
On an exact solution of the Thomas-Fermi equation for a trapped Bose-Einstein condensate with dipole-dipole interactions
We derive an exact solution to the Thomas-Fermi equation for a Bose-Einstein
condensate which has dipole-dipole interactions as well as the usual s-wave
contact interaction, in a harmonic trap. Remarkably, despite the non-local
anisotropic nature of the dipolar interaction the solution is an inverted
parabola, as in the pure s-wave case, but with a different aspect ratio.
Various properties such as electrostriction and stability are discussed.Comment: 11 pages, 5 figure
Exploring the effects of high-velocity flows in abundance determinations in H II regions. Bidimensional spectroscopy of HH 204 in the Orion Nebula
We present results from integral field optical spectroscopy with the Potsdam
Multi-Aperture Spectrograph of the Herbig-Haro (HH) object HH 204, with a
spatial sampling of 1 x 1 arcsec^2. We have obtained maps of different emission
lines, physical conditions and ionic abundances from collisionally excited
lines. The ionization structure of the object indicates that the head of the
bow shock is optically thick and has developed a trapped ionization front. The
density at the head is at least five times larger than in the background
ionized gas. We discover a narrow arc of high T_e([N II]) values delineating
the southeast edge of the head. The temperature in this zone is about 1,000 K
higher than in the rest of the field and should correspond to a shock-heated
zone at the leading working surface of the gas flow. This is the first time
this kind of feature is observed in a photoionized HH object. We find that the
O^+ and O abundance maps show anomalous values at separate areas of the bow
shock probably due to: a) overestimation of the collisional de-excitation
effects of the [O II] lines in the compressed gas at the head of the bow shock,
and b) the use of a too high T_e([N II]) at the area of the leading working
surface of the flow.Comment: 12 pages, 7 Postscript figures, accepted for publication in MNRA
Physical Conditions in Barnard's Loop, Components of the Orion-Eridanus Bubble, and Implications for the WIM Component of the ISM
We have supplemented existing spectra of Barnard's Loop with high accuracy
spectrophotometry of one new position. Cloudy photoionization models were
calculated for a variety of ionization parameters and stellar temperatures and
compared with the observations. After testing the procedure with recent
observations of M43, we establish that Barnard's Loop is photoionized by four
candidate ionizing stars, but agreement between the models and observations is
only possible if Barnard's Loop is enhanced in heavy elements by about a factor
of 1.4. Barnard's Loop is very similar in properties to the brightest
components of the Orion-Eridanus Bubble and the Warm Ionized Medium (WIM). We
are able to establish models that bound the range populated in low-ionization
color-color diagrams (I([SII])/I(H{\alpha}) versus I([NII])/I(H{\alpha})) using
only a limited range of ionization parameters and stellar temperatures.
Previously established variations in the relative abundance of heavy elements
render uncertain the most common method of determining electron temperatures
for components of the Orion-Eridanus Bubble and the WIM based on only the
I([NII])/I(H{\alpha}) ratio, although we confirm that the lowest surface
brightness components of the WIM are on average of higher electron temperature.
The electron temperatures for a few high surface brightness WIM components
determined by direct methods are comparable to those of classical bright H II
regions. In contrast, the low surface brightness HII regions studied by the
Wisconsin H{\alpha} Mapper are of lower temperatures than the classical bright
HII regions
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