5,358 research outputs found
Multi-level study of C3H2: The first interstellar hydrocarbon ring
Cyclic species in the interstellar medium have been searched for almost since the first detection of interstellar polyatomic molecules. Eleven different C3H2 rotational transitions were detected; 9 of which were studied in TMC-1, a nearby dark dust cloud, are shown. The 1 sub 10 yields 1 sub 01 and 2 sub 20 yields 2 sub 11 transitions were observed with the 43 m NRAO telescope, while the remaining transitions were detected with the 14 m antenna of the Five College Radio Observatory (FCRAO). The lines detected in TMC-1 have energies above the ground state ranging from 0.9 to 17.1 K and consist of both ortho and para species. Limited maps were made along the ridge for several of the transitions. The HC3N J = 2 yields 1 transition were mapped simultaneously with the C3H2 1 sub 10 yields 1 sub 01 line and therefore can compare the distribution of this ring with a carbon chain in TMC-1. C3H2 is distributed along a narrow ridge with a SE - NW extension which is slightly more extended than the HC2N J = 2 yields 1. Gaussian fits gives a FWHP extension of 8'5 for C3H2 while HC3N has a FWHP of 7'. The data show variations of the two velocity components along the ridge as a function of transition. Most of the transitions show a peak at the position of strongest HC3N emission while the 2 sub 21 yields 2 sub 10 transition shows a peak at the NH3 position
Voltage-controlled electron tunnelling from a single self-assembled quantum dot embedded in a two-dimensional-electron-gas-based photovoltaic cell
We perform high-resolution photocurrent (PC) spectroscopy to investigate
resonantly the neutral exciton ground-state (X0) in a single InAs/GaAs
self-assembled quantum dot (QD) embedded in the intrinsic region of an
n-i-Schottky photodiode based on a two-dimensional electron gas (2DEG), which
was formed from a Si delta-doped GaAs layer. Using such a device, a single-QD
PC spectrum of X0 is measured by sweeping the bias-dependent X0 transition
energy through that of a fixed narrow-bandwidth laser via the quantum-confined
Stark effect (QCSE). By repeating such a measurement for a series of laser
energies, a precise relationship between the X0 transition energy and bias
voltage is then obtained. Taking into account power broadening of the X0
absorption peak, this allows for high-resolution measurements of the X0
homogeneous linewidth and, hence, the electron tunnelling rate. The electron
tunnelling rate is measured as a function of the vertical electric field and
described accurately by a theoretical model, yielding information about the
electron confinement energy and QD height. We demonstrate that our devices can
operate as 2DEG-based QD photovoltaic cells and conclude by proposing two
optical spintronic devices that are now feasible.Comment: 34 pages, 11 figure
Reconfigurable Boolean Logic using Magnetic Single-Electron Transistors
We propose a novel hybrid single-electron device for reprogrammable low-power
logic operations, the magnetic single-electron transistor (MSET). The device
consists of an aluminium single-electron transistors with a GaMnAs magnetic
back-gate. Changing between different logic gate functions is realized by
reorienting the magnetic moments of the magnetic layer which induce a voltage
shift on the Coulomb blockade oscillations of the MSET. We show that we can
arbitrarily reprogram the function of the device from an n-type SET for
in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane
magnetization orientation. Moreover, we demonstrate a set of reprogrammable
Boolean gates and its logical complement at the single device level. Finally,
we propose two sets of reconfigurable binary gates using combinations of two
MSETs in a pull-down network
Poisoning with the recreational drug paramethoxyamphetamine ("death")
The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.Objective: To describe the clinical features of paramethoxyamphetamine (PMA; "death") poisoning and to compare these with those of people with self-reported "ecstasy" poisoning. Design: Retrospective casenote review. Participants and setting: 22 patients who presented to the Emergency Department of the Royal Adelaide Hospital (RAH), a major metropolitan teaching hospital, between 1 January 1996 and 31 December 1998 with PMA poisoning identified through urine drug screens; and 61 patients with self-reported ecstasy poisoning between 1 September 1997 and 31 December 1998 found through the hospital databases. Results: Patients with PMA poisoning presented with tachycardia (64%), hyperthermia (temperature > 37.5ºC; 36%), coma (41%), seizures (32%), arrhythmias (23%), and QRS intervals 100 ms (50%) with greater frequency and often greater severity than those with self-reported ecstasy poisoning. Two patients with PMA poisoning presented with severe hypoglycaemia (blood glucose level, 7.5 mmol/L). Conclusions: At our hospital, PMA poisonings accounted for most of the severe reactions among people who believed they had taken ecstasy. Hypoglycaemia and hyperkalaemia may be specific to PMA poisoning. PMA toxicity should be suspected with severe or atypical reactions to "ecstasy", and confirmed by chromatographic urine drug screens.Liang Han Ling, Colin Marchant, Nicholas A. Buckley, Michael Prior and Rod J. Irvin
Composition and Distribution of Extracellular Polymeric Substances in Aerobic Flocs and Granular Sludge
Extracellular polymeric substances (EPS) were quantified in flocculent and aerobic granular sludge developed in two sequencing batch reactors with the same shear force but different settling times. Several EPS extraction methods were compared to investigate how different methods affect EPS chemical characterization, and fluorescent stains were used to visualize EPS in intact samples and 20-µm cryosections. Reactor 1 (operated with a 10-min settle) enriched predominantly flocculent sludge with a sludge volume index (SVI) of 120 ± 12 ml g–1, and reactor 2 (2-min settle time) formed compact aerobic granules with an SVI of 50 ± 2 ml g–1. EPS extraction by using a cation-exchange resin showed that proteins were more dominant than polysaccharides in all samples, and the protein content was 50% more in granular EPS than flocculent EPS. NaOH and heat extraction produced a higher protein and polysaccharide content from cell lysis. In situ EPS staining of granules showed that cells and polysaccharides were localized to the outer edge of granules, whereas the center was comprised mostly of proteins. These observations confirm the chemical extraction data and indicate that granule formation and stability are dependent on a noncellular, protein core. The comparison of EPS methods explains how significant cell lysis and contamination by dead biomass leads to different and opposing conclusions
Projected free energies for polydisperse phase equilibria
A `polydisperse' system has an infinite number of conserved densities. We
give a rational procedure for projecting its infinite-dimensional free energy
surface onto a subspace comprising a finite number of linear combinations of
densities (`moments'), in which the phase behavior is then found as usual. If
the excess free energy of the system depends only on the moments used, exact
cloud, shadow and spinodal curves result; two- and multi-phase regions are
approximate, but refinable indefinitely by adding extra moments. The approach
is computationally robust and gives new geometrical insights into the
thermodynamics of polydispersity.Comment: 4 pages, REVTeX, uses multicol.sty and epsf.sty, 1 postscript figure
include
Varenicline and suicidal behaviour: a cohort study based on data from the General Practice Research Database
Objective To determine whether varenicline, a recently licensed smoking cessation product, is associated with an increased risk of suicide and suicidal behaviour compared with alternative treatments bupropion and nicotine replacement therapy
Evaluating Aspen Responses to Changes in Elk Abundance, Distribution and Behavior Following Wolf Reestablishment in West-Central Yellowstone National Park
The reintroduction of wolves to Yellowstone National Park created a unique “natural experiment” to study trophic interactions in a large-scale terrestrial system among wolves, elk, and aspen. This study utilized data from a long-term elk demography study that was established prior to wolf reintroduction. Significant changes in the abundance and distribution of the Madison headwaters elk herd were observed following wolf reestablishment. The spatial arrangement of these changes made it possible to directly test for the occurrence of a density-mediated trophic cascade. The objectives of this study were to answer the following questions: 1) was there a marked decrease in browsing pressure on aspen where elk densities declined, and 2) was there a corresponding plant-growth response indicating that aspen were released from browsing pressure? Historical browsing conditions and aspen height were observed for 31 aspen stands to assess the occurrence of a density-mediated trophic cascade following wolf reintroduction. Browse conditions and aspen morphology in stands where elk densities declined dramatically following wolf reintroduction were compared to stands that experienced persistent heavy browsing throughout this period. A major decline in browsing pressure along with a modest increase in aspen height and leader longevity was detected, supporting the hypothesis of a density-mediated trophic cascade. However, the magnitude of the growth response was weak, suggesting that browsing was not the dominant limiting factor to aspen growth in the study area and that aspen may be more strongly limited by bottom-up regulation
Center-of-mass motion and cross-channel coupling in time-dependent Hartree-Fock theory
We provide a discussion of issues related to the center-of-mass motion and
cross-channel coupling in applications of the time-dependent Hartree-Fock
(TDHF) theory to heavy-ion collisions. We find that the entrance channel
dynamics of a heavy-ion collision as described by TDHF does not seem to be
significantly influenced by these effects, whereas the long-time evolution may
be less reliable.Comment: 4 pages, 4 figure
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