1,477 research outputs found
Modern seawater acidification: The response of foraminifera to high-CO<inf>2</inf> conditions in the Mediterranean Sea
The seas around the island of Ischia (Italy) have a lowered pH as a result of volcanic gas vents that emit carbon dioxide from the sea floor at ambient seawater temperatures. These areas of acidified seawater provide natural laboratories in which to study the long-term biological response to rising CO2 levels. Benthic foraminifera (single-celled protists) are particularly interesting as they have short life histories, are environmentally sensitive and have an excellent fossil record. Here, we examine changes in foraminiferal assemblages along pH gradients at CO2 vents on the coast of Ischia and show that the foraminiferal distribution, diversity and nature of the fauna change markedly in the living assemblages as pH decreases. Ā© 2010 Geological Society of London
Use of cumulative mortality data in patients with acute myocardial infarction for early detection of variation in clinical practice: observational study
OBJECTIVES: Use of cumulative mortality adjusted for
case mix in patients with acute myocardial infarction
for early detection of variation in clinical practice.
DESIGN: Observational study.
SETTING: 20 hospitals across the former Yorkshire
region.
PARTICIPANTS: All 2153 consecutive patients with
confirmed acute myocardial infarction identified
during three months.
MAIN OUTCOME MEASURES: Variable lifeĀadjusted
displays showing cumulative differences between
observed and expected mortality of patients; expected
mortality calculated from risk model based on
admission characteristics of age, heart rate, and
systolic blood pressure.
RESULTS: The performance of two individual hospitals
over three months was examined as an example. One,
the smallest district hospital in the region, had a series
of 30 consecutive patients but had five more deaths
than predicted. The variable lifeĀadjusted display
showed minimal variation from that predicted for the
first 15 patients followed by a run of unexpectedly
high mortality. The second example was the main
tertiary referral centre for the region, which admitted
188 consecutive patients. The display showed a period
of apparently poor performance followed by
substantial improvement, where the plot rose steadily
from a cumulative net lives saved of - 4 to 7. These
variations in patient outcome are unlikely to have
been revealed during conventional audit practice.
CONCLUSIONS: Variable lifeĀadjusted display has been
integrated into surgical care as a graphical display of
riskĀadjusted survival for individual surgeons or centres.
In combination with a simple risk model, it may have a
role in monitoring performance and outcome in
patients with acute myocardial infarction
Timelapse ultrasonic tomography for measuring damage localization in geomechanics laboratory tests.
Variation of mechanical properties in materials can be detected non-destructively using ultrasonic measurements. In particular, changes in elastic wave velocity can occur due to damage, i.e., micro-cracking and particles debonding. Here the challenge of characterizing damage in geomaterials, i.e., rocks and soils, is addressed. Geomaterials are naturally heterogeneous media in which the deformation can localize, so that few measurements of acoustic velocity across the sample are not sufficient to capture the heterogeneities. Therefore, an ultrasonic tomography procedure has been implemented to map the spatial and temporal variations in propagation velocity, which provides information on the damage process. Moreover, double beamforming has been successfully applied to identify and isolate multiple arrivals that are caused by strong heterogeneities (natural or induced by the deformation process). The applicability of the developed experimental technique to laboratory geomechanics testing is illustrated using data acquired on a sample of natural rock before and after being deformed under triaxial compression. The approach is then validated and extended to time-lapse monitoring using data acquired during plane strain compression of a sample including a well defined layer with different mechanical properties than the matrix
Improving interval estimation of binomial proportions
In this paper, we propose one new confidence interval for the binomial proportion; our interval is based on the Edgeworth expansion of a logit transformation of the sample proportion. We provide theoretical justification for the proposed interval and also compare the finite-sample performance of the proposed interval with the three best existing intervalsāthe Wilson interval, the AgrestiāCoull interval and the Jeffreys intervalāin terms of their coverage probabilities and expected lengths. We illustrate the proposed method in two real clinical studies
Monotonicity of quantum ground state energies: Bosonic atoms and stars
The N-dependence of the non-relativistic bosonic ground state energy is
studied for quantum N-body systems with either Coulomb or Newton interactions.
The Coulomb systems are "bosonic atoms," with their nucleus fixed, and the
Newton systems are "bosonic stars". In either case there exists some third
order polynomial in N such that the ratio of the ground state energy to the
respective polynomial grows monotonically in N. Some applications of these new
monotonicity results are discussed
Occurrence of methicillin-resistant Staphylococcus aureus in surface waters near industrial hog operation spray fields
Industrial hog operations (IHOs) have been identified as a source of antibiotic-resistant Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). However, few studies have investigated the presence of antibiotic-resistant S. aureus in the environment near IHOs, specifically surface waters proximal to spray fields where IHO liquid lagoon waste is sprayed. Surface water samples (n = 179) were collected over the course of approximately one year from nine locations in southeastern North Carolina and analyzed for the presence of presumptive MRSA using CHROMagar MRSA media. Culture-based, biochemical, and molecular tests, as well as matrix-assisted laser desorption/ionization-time of flight mass spectrometry were used to confirm that isolates that grew on CHROMagar MRSA media were S. aureus. Confirmed S. aureus isolates were then tested for susceptibility to 16 antibiotics and screened for molecular markers of MRSA (mecA, mecC) and livestock adaptation (absence of scn). A total of 12 confirmed MRSA were detected in 9 distinct water samples. Nine of 12 MRSA isolates were also multidrug-resistant (MDRSA [i.e., resistant to ā„ 3 antibiotic classes]). All MRSA were scn-positive and most (11/12) belonged to a staphylococcal protein A (spa) type t008, which is commonly associated with humans. Additionally, 12 confirmed S. aureus that were methicillin-susceptible (MSSA) were recovered, 7 of which belonged to spa type t021 and were scn-negative (a marker of livestock-adaptation). This study demonstrated the presence of MSSA, MRSA, and MDRSA in surface waters adjacent to IHO lagoon waste spray fields in southeastern North Carolina. To our knowledge, this is the first report of waterborne S. aureus from surface waters proximal to IHOs
A Complete Supersymmetric SO(10) Model
A complete supersymmetric SO(10) model is constructed, which is the most
general consistent with certain , discrete, and flavor symmetries.
The desired vacuum of the theory has vevs which lie in particular directions of
group space. This leads to both doublet triplet splitting and to the generation
of just four operators for charged fermion masses. The model illustrates how
many features of superunification become related in the context of a complete
theory. The features discussed here include: the weak mixing angle prediction,
the doublet-triplet splitting problem, proton decay, the generation of the
parameter, neutrino masses and the generation of the operators which lead
to charged fermion mass predictions.Comment: 18 page
A Way to Reopen the Window for Electroweak Baryogenesis
We reanalyse the sphaleron bound of electroweak baryogenesis when allowing
deviations to the Friedmann equation. These modifications are well motivated in
the context of brane cosmology where they appear without being in conflict with
major experimental constraints on four-dimensional gravity. While suppressed at
the time of nucleosynthesis, these corrections can dominate at the time of the
electroweak phase transition and in certain cases provide the amount of
expansion needed to freeze out the baryon asymmetry without requiring a
strongly first order phase transition. The sphaleron bound is substantially
weakened and can even disappear so that the constraints on the higgs and stop
masses do not apply anymore. Such modification of cosmology at early times
therefore reopens the parameter space allowing electroweak baryogenesis which
had been reduced substantially given the new bound on the higgs mass imposed by
LEP. In contrast with previous attempts to turn around the sphaleron bound
using alternative cosmologies, we are still considering that the electroweak
phase transition takes place in a radiation dominated universe. The universe is
expanding fast because of the modification of the Friedmann equation itself
without the need for a scalar field and therefore evading the problem of the
decay of this scalar field after the completion of the phase transition and the
risk that its release of entropy dilutes the baryon asymmetry produced at the
transition.Comment: 19 pages, 3 figures; v2: minor changes, remark added at end of
section 5 and in caption of figure 1; v3: references added, version to be
publishe
Quantum gates with neutral atoms: Controlling collisional interactions in time dependent traps
We theoretically study specific schemes for performing a fundamental
two-qubit quantum gate via controlled atomic collisions by switching
microscopic potentials. In particular we calculate the fidelity of a gate
operation for a configuration where a potential barrier between two atoms is
instantaneously removed and restored after a certain time. Possible
implementations could be based on microtraps created by magnetic and electric
fields, or potentials induced by laser light.Comment: 10 pages, 3 figure
On Black Hole Detection with the OWL/Airwatch Telescope
In scenarios with large extra dimensions and TeV scale gravity ultrahigh
energy neutrinos produce black holes in their interactions with the nucleons.
We show that ICECUBE and OWL may observe large number of black hole events and
provide valuable information about the fundamental Planck scale and the number
of extra dimensions. OWL is especially well suited to observe black hole events
produced by neutrinos from the interactions of cosmic rays with the 3 K
background radiation. Depending on the parameters of the scenario of large
extra dimensions and on the flux model, as many as 28 events per year are
expected for a Planck scale of 3 TeV.Comment: 8 pages, including 7 color figures, three figure captions corrected,
minor changes for clarification, one reference adde
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