2,258 research outputs found
Landau levels in a 2D noncommutative space: matrix and quaternionic vector coherent states
The behavior of an electron in an external uniform electromagnetic background
coupled to a harmonic potential, with noncommuting space coordinates, is
considered in this work. The thermodynamics of the system is studied. Matrix
vector coherent states (MVCS) as well as quaternionic vector coherent states
(QVCS), satisfying required properties, are also constructed and discussed
Two generalizations of the PRV conjecture
Let G be a complex connected reductive group. The PRV conjecture, which was
proved independently by S. Kumar and O. Mathieu in 1989, gives explicit
irreducible submodules of the tensor product of two irreducible G-modules. This
paper has three aims. First, we simplify the proof of the PRV conjecture, then
we generalize it to other branching problems. Finally, we find other
irreducible components of the tensor product of two irreducible G-modules that
appear for "the same reason" as the PRV ones
The BCS theory of q-deformed nucleon pairs - qBCS
We construct a coherent state of q-deformed zero coupled nucleon pairs
distributed in several single-particle orbits. Using a variational approach,
the set of equations of qBCS theory, to be solved self consistently for
occupation probabilities, gap parameter Delta, and the chemical potential
lambda, is obtained. Results for valence nucleons in nuclear degenerate sdg
major shell show that the strongly coupled zero angular momentum nucleon pairs
can be substituted by weakly coupled q-deformed zero angular momentum nucleon
pairs. A study of Sn isotopes reveals a well defined universe of (G, q) values,
for which qBCS converges. While the qBCS and BCS show similar results for Gap
parameter Delta in Sn isotopes, the ground state energies are lower in qBCS.
The pairing correlations in N nucleon system, increase with increasing q (for q
real).Comment: 8 pages, REVTEX, 3 eps figure
Unconventional continuous phase transition in a three dimensional dimer model
Phase transitions occupy a central role in physics, due both to their
experimental ubiquity and their fundamental conceptual importance. The
explanation of universality at phase transitions was the great success of the
theory formulated by Ginzburg and Landau, and extended through the
renormalization group by Wilson. However, recent theoretical suggestions have
challenged this point of view in certain situations. In this Letter we report
the first large-scale simulations of a three-dimensional model proposed to be a
candidate for requiring a description beyond the Landau-Ginzburg-Wilson
framework: we study the phase transition from the dimer crystal to the Coulomb
phase in the cubic dimer model. Our numerical results strongly indicate that
the transition is continuous and are compatible with a tricritical universality
class, at variance with previous proposals.Comment: 4 pages, 3 figures; v2: minor changes, published versio
Lattice realizations of unitary minimal modular invariant partition functions
The conformal spectra of the critical dilute A-D-E lattice models are studied
numerically. The results strongly indicate that, in branches 1 and 2, these
models provide realizations of the complete A-D-E classification of unitary
minimal modular invariant partition functions given by Cappelli, Itzykson and
Zuber. In branches 3 and 4 the results indicate that the modular invariant
partition functions factorize. Similar factorization results are also obtained
for two-colour lattice models.Comment: 18 pages, Latex, with minor corrections and clarification
Autoresuscitation (Lazarus phenomenon) after termination of cardiopulmonary resuscitation - a scoping review.
Autoresuscitation describes the return of spontaneous circulation after termination of resuscitation (TOR) following cardiac arrest (CA). We aimed to identify phenomena that may lead to autoresuscitation and to provide guidance to reduce the likelihood of it occurring.
We conducted a literature search (Google Scholar, MEDLINE, PubMed) and a scoping review according to PRISMA-ScR guidelines of autoresuscitation cases where patients undergoing CPR recovered circulation spontaneously after TOR with the following criteria: 1) CA from any cause; 2) CPR for any length of time; 3) A point was reached when it was felt that the patient had died; 4) Staff declared the patient dead and stood back. No further interventions took place; 5) Later, vital signs were observed. 6) Vital signs were sustained for more than a few seconds, such that staff had to resume active care.
Sixty-five patients with ROSC after TOR were identified in 53 articles (1982-2018), 18 (28%) made a full recovery.
Almost a third made a full recovery after autoresuscitation. The following reasons for and recommendations to avoid autoresuscitation can be proposed: 1) In asystole with no reversible causes, resuscitation efforts should be continued for at least 20 min; 2) CPR should not be abandoned immediately after unsuccessful defibrillation, as transient asystole can occur after defibrillation; 3) Excessive ventilation during CPR may cause hyperinflation and should be avoided; 4) In refractory CA, resuscitation should not be terminated in the presence of any potentially-treatable cardiac rhythm; 5) After TOR, the casualty should be observed continuously and ECG monitored for at least 10 min
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Accelerating the Configuration Tuning of Big Data Analytics with Similarity-aware Multitask Bayesian Optimization
One of the key challenges for data analytics deployment is configuration tuning. The existing approaches for configuration tuning are expensive and overlook the dynamic characteristics of the analytics environment (i.e. frequent changes in workload due to receiving evolving input sizes or change in the underlying cluster environment). Such workload/environment changes can cause significant performance degradation, with retuning the configuration to accommodate those changes can yield up to 85\% potential execution time saving.
We propose SimTune, an approach that accommodates such changes through efficient configuration tuning.
SimTune combines
workload characterization and Multitask Bayesian optimization to identify similarity across workloads and accelerate finding near-optimal configurations. Our experimental results show that SimTune reduces the search time for finding
close-to-optimal configurations by 56-73\% (at the median) when compared to existing state-of-the-art techniques. This means that the
amortization of the tuning cost happens significantly faster, enabling
practical tuning in the rapidly changing environment of distributed analytics.Google Cloud, Amazon AW
Performance Assessment of Out-of-Hospital Use of Pelvic Circumferential Compression Devices for Severely Injured Patients in Switzerland: A Nationwide Retrospective Cross-Sectional Study.
Patients with severe pelvic fractures carry a greater risk of severe bleeding, and pelvic compression devices (PCCD) are used to stabilize the pelvis on the pre-hospital scene. The aim of this study was to describe the use of PCCD in the pre-hospital setting on a nationwide scale (Switzerland) and determine the sensitivity, specificity and rates of over- and under-triage of the current application practices. The secondary objective was to identify pre-hospital factors associated with unstable pelvic fractures.
Retrospective cross-sectional study using anonymized patient data (1 January 2015-31 December 2020) from the Swiss Trauma Registry (STR). Based on AIS scores, patients were assigned a unique principal diagnosis among three categories (unstable pelvic fracture-stable pelvic fracture-other) and assessed for use or not of PCCD. Secondarily, patient characteristics, initial pre-hospital vital signs, means of pre-hospital transport and trauma mechanism were also extracted from the database.
2790 patients were included for analysis. A PCCD was used in 387 (13.9%) patients. In the PCCD group, 176 (45.5%) had an unstable pelvic fracture, 52 (13.4%) a stable pelvic fracture and 159 (41.1%) an injury unrelated to the pelvic region. In the group who did not receive a PCCD, 214 (8.9%) had an unstable pelvic fracture, 182 (7.6%) a stable pelvic fracture and 2007 (83.5%) an injury unrelated to the pelvic region. The nationwide sensitivity of PCCD application was 45.1% (95% CI 40.1-50.2), the specificity 91.2% (95% CI 90-92.3), with both over- and under-triage rates of 55%. The prevalence of unstable fractures in our population was 14% (390/2790). We identified female sex, younger age, lower systolic blood pressure, higher shock index, pedestrian hit and fall ≥3 m as possible risk factors for an unstable pelvic fracture.
Our results demonstrate a nationwide both over- and under-triage rate of 55% for out-of-hospital PCCD application. Female gender, younger age, lower blood pressure, higher shock index, pedestrian hit and fall >3 m are possible risk factors for unstable pelvic fracture, but it remains unclear if those parameters are relevant clinically to perform pre-hospital triage
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