4,397 research outputs found
Extending Hamiltonian Operators to Get Bi-Hamiltonian Coupled KdV Systems
An analysis of extension of Hamiltonian operators from lower order to higher
order of matrix paves a way for constructing Hamiltonian pairs which may result
in hereditary operators. Based on a specific choice of Hamiltonian operators of
lower order, new local bi-Hamiltonian coupled KdV systems are proposed. As a
consequence of bi-Hamiltonian structure, they all possess infinitely many
symmetries and infinitely many conserved densities.Comment: 13 pages, late
Study protocol for investigating the clinical performance of an automated blood test for glial fibrillary acidic protein and ubiquitin carboxy-terminal hydrolase L1 blood concentrations in elderly patients with mild traumatic BRAIN Injury and reference values (BRAINI-2 Elderly European study): a prospective multicentre observational study
Computed tomography; Neurosurgery; Trauma managementTomografia computaritzada; Neurocirurgia; GestiĂł del traumaTomografĂa computarizada; NeurocirugĂa; GestiĂłn del traumaIntroduction Two blood brain-derived biomarkers, glial fibrillar acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), can rule out intracranial lesions in patients with mild traumatic brain injury (mTBI) when assessed within the first 12 hours. Most elderly patients were excluded from previous studies due to comorbidities. Biomarker use in elderly population could be affected by increased basal levels. This study will assess the performance of an automated test for measuring serum GFAP and UCH-L1 in elderly patients to predict the absence of intracranial lesions on head CT scans after mTBI, and determine both biomarkers reference values in a non-TBI elderly population.
Methods and analysis This is a prospective multicentre observational study on elderly patients (≥65 years) that will be performed in Spain, France and Germany. Two patient groups will be included in two independent substudies. (1) A cohort of 2370 elderly patients (1185<80 years and 1185≥80 years; BRAINI2-ELDERLY DIAGNOSTIC AND PROGNOSTIC STUDY) with mTBI and a brain CT scan that will undergo blood sampling within 12 hours after mTBI. The primary outcome measure is the diagnostic performance of GFAP and UCH-L1 measured using an automated assay for discriminating between patients with positive and negative findings on brain CT scans. Secondary outcome measures include the performance of both biomarkers in predicting early (1 week) and midterm (3 months) neurological status and quality of life after trauma. (2) A cohort of 480 elderly reference participants (BRAINI2-ELDERLY REFERENCE STUDY) in whom reference values for GFAP and UCHL1 will be determined.
Ethics and dissemination Ethical approval was obtained from the Institutional Review Boards of Hospital 12 de Octubre in Spain (Re#22/027) and Southeast VI (Clermont Ferrand Hospital) (Re# 22.01782.000095) in France. The study’s results will be presented at scientific meetings and published in peer-review publications.This study was supported by a grant from the European Institute of Innovation and Technology (EIT) Health (BP 2022–2024). EIT Health is supported by EIT, a body of the European Union. BioMérieux is responsible for the development and manufacturing of the VIDAS GFAP and VIDAS UCH-L1 assays. BioMérieux will provide in-kind support to this study by supplying the assays for measuring UCH–L1 and GFAP necessary for this study
Impacts of tectonic subsidence on basin depth and delta lobe building
Channel avulsions on river deltas are the primary means to distribute sediment and build land at the coastline. Many studies have detailed how avulsions generate delta lobes, whereby multiple lobes amalgamate to form a fan-shaped deposit. These studies often assume steady subsidence and uniform basin depth. In nature, however, lobe building is disrupted by variable subsidence, and progradation of lobes into basins with variable depth: conditions that are prevalent for tectonically active areas. Herein, we explore sediment dispersal and deposition patterns across scales using measurements of delta and basin morphology compiled from field surveys and remote sensing, collected over 150 years, from the Selenga Delta (Baikal Rift Zone), Russia. Tectonic subsidence events, associated with earthquakes on normal faults crossing the delta, displace portions of the topset several meters below mean lake level. This allogenic process increases regional river gradient and triggers lobe-switching avulsions. The timescale for these episodes is shorter than the predicted autogenic lobe avulsion timescale. During quiescent periods between subsidence events, channel-scale avulsions occur relatively frequently because of in-channel sediment aggradation, dispersing sediment to regional lows of the delta. Avulsion settings for the Selenga Delta preserve discrete stratal packages that could contain predominately deep channels. Exploring the interplay between tectonic subsidence and sediment accumulation patterns will improve interpretations of stratigraphy from active margins and basin models
Effects of Noise, Correlations and errors in the preparation of initial states in Quantum Simulations
In principle a quantum system could be used to simulate another quantum
system. The purpose of such a simulation would be to obtain information about
problems which cannot be simulated with a classical computer due to the
exponential increase of the Hilbert space with the size of the system and which
cannot be measured or controlled in an actual experiment. The system will
interact with the surrounding environment, with the other particles in the
system and be implemented using imperfect controls making it subject to noise.
It has been suggested that noise does not need to be controlled to the same
extent as it must be for general quantum computing. However the effects of
noise in quantum simulations and how to treat them are not completely
understood. In this paper we study an existing quantum algorithm for the
one-dimensional Fano-Anderson model to be simulated using a liquid-state NMR
device. We calculate the evolution of different initial states in the original
model, and then we add interacting spins to simulate a more realistic
situation. We find that states which are entangled with their environment, and
sometimes correlated but not necessarily entangled have an evolution which is
described by maps which are not completely positive. We discuss the conditions
for this to occur and also the implications.Comment: Revtex 4-1, 14 pages, 21 figures, version 2 has typos corrected and
acknowledgement adde
The peculiar velocity field in a quintessence model
We investigate the evolution of matter density perturbations and some
properties of the peculiar velocity field for a special class of exponential
potentials in a scalar field model for quintessence, for which a general exact
solution is known. The data from the 2-degree Field Galaxy Redshift Survey
(2dFGRS) suggest a value of the today pressureless matter density Omega_M0 =
0.18 +- 0.05.Comment: 11 pages, 3 figure
A Variational Method in Out of Equilibrium Physical Systems
A variational principle is further developed for out of equilibrium dynamical
systems by using the concept of maximum entropy. With this new formulation it
is obtained a set of two first-order differential equations, revealing the same
formal symplectic structure shared by classical mechanics, fluid mechanics and
thermodynamics. In particular, it is obtained an extended equation of motion
for a rotating dynamical system, from where it emerges a kind of topological
torsion current of the form , with and
denoting components of the vector potential (gravitational or/and
electromagnetic) and is the angular velocity of the accelerated frame.
In addition, it is derived a special form of Umov-Poynting's theorem for
rotating gravito-electromagnetic systems, and obtained a general condition of
equilibrium for a rotating plasma. The variational method is then applied to
clarify the working mechanism of some particular devices, such as the Bennett
pinch and vacuum arcs, to calculate the power extraction from an hurricane, and
to discuss the effect of transport angular momentum on the radiactive heating
of planetary atmospheres. This development is seen to be advantageous and opens
options for systematic improvements.Comment: 22 pages, 1 figure, submitted to review, added one referenc
Strategy for investments from Zipf law(s)
We have applied the Zipf method to extract the exponent for seven
financial indices (DAX, FTSE; DJIA, NASDAQ, S&P500; Hang-Seng and Nikkei 225),
after having translated the signals into a text based on two letters. We follow
considerations based on the signal Hurst exponent and the notion of a time
dependent Zipf law and exponent in order to implement two simple investment
strategies for such indices. We show the time dependence of the returns.Comment: submitted to Physica A;Proceedings ICE02, Bali, Aug.28-31, 200
Appearance of the weight-bearing lateral radiograph in retrocalcaneal bursitis
Background and purpose A retrocalcaneal bursitis is caused by repetitive impingement of the bursa between the Achilles tendon and the posterosuperior calcaneus. The bursa is situated in the posteroinferior corner of Kager's triangle (retrocalcaneal recess), which is a radiolucency with sharp borders on the lateral radiograph of the ankle. If there is inflammation, the fluid-filled bursa is less radiolucent, making it difficult to delineate the retrocalcaneal recess. We assessed whether the radiographic appearance of the retrocalcaneal recess on plain digital (filmless) radiographs could be used in the diagnosis of a retrocalcaneal bursitis. Methods Whether or not there was obliteration of the retrocalcaneal recess (yes/no) on 74 digital weight-bearing lateral radiographs of the ankle was independently assessed by 2 observers. The radiographs were from 24 patients (25 heels) with retrocalcaneal bursitis (confirmed on endoscopic calcaneoplasty); the control group consisted of 50 patients (59 heels). Results The sensitivity of the test was 83% for observer 1 and 79% for observer 2. Specificity was 100% and 98%, respectively. The kappa value of the interobserver reliability test was 0.86. For observer 1, intraobserver reliability was 0.96 and for observer 2 it was 0.92. Interpretation On digital weight-bearing lateral radiographs of a retrocalcaneal bursitis, the retrocalcaneal recess has a typical appearanc
X-ray emission from isolated neutron stars
X-ray emission is a common feature of all varieties of isolated neutron stars
(INS) and, thanks to the advent of sensitive instruments with good
spectroscopic, timing, and imaging capabilities, X-ray observations have become
an essential tool in the study of these objects. Non-thermal X-rays from young,
energetic radio pulsars have been detected since the beginning of X-ray
astronomy, and the long-sought thermal emission from cooling neutron star's
surfaces can now be studied in detail in many pulsars spanning different ages,
magnetic fields, and, possibly, surface compositions. In addition, other
different manifestations of INS have been discovered with X-ray observations.
These new classes of high-energy sources, comprising the nearby X-ray Dim
Isolated Neutron Stars, the Central Compact Objects in supernova remnants, the
Anomalous X-ray Pulsars, and the Soft Gamma-ray Repeaters, now add up to
several tens of confirmed members, plus many candidates, and allow us to study
a variety of phenomena unobservable in "standard'' radio pulsars.Comment: Chapter to be published in the book of proceedings of the 1st Sant
Cugat Forum on Astrophysics, "ICREA Workshop on the high-energy emission from
pulsars and their systems", held in April, 201
A supernova constraint on bulk majorons
In models with large extra dimensions all gauge singlet fields can in
principle propagate in the extra dimensional space. We have investigated
possible constraints on majoron models of neutrino masses in which the majorons
propagate in extra dimensions. It is found that astrophysical constraints from
supernovae are many orders of magnitude stronger than previous accelerator
bounds. Our findings suggest that unnatural types of the "see-saw" mechanism
for neutrino masses are unlikely to occur in nature, even in the presence of
extra dimensions.Comment: Minor changes, matches the version to appear in PR
- …