4,565 research outputs found
Disoriented Chiral Condensates, Pion Probability Distributions and Parallels with Disordered System
A general expression is discussed for pion probability distributions coming
from relativistic heavy ion collisions. The general expression contains as
limits: 1) The disoriented chiral condensate (DCC), 2) the negative binomial
distribution and Pearson type III distribution, 3) a binomial or Gaussian
result, 4) and a Poisson distribution. This general expression approximates
other distributions such as a signal to noise laser distribution. Similarities
and differences of the DCC distribution with these other distribution are
studied. A connection with the theory of disordered systems will be discussed
which include spin-glasses, randomly broken objects, random and chaotic maps.Comment: 5 pages, 1 figure include
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A Case Report of Cognitive Processing Therapy Delivered over a Single Week.
Although evidence-based treatments for posttraumatic stress disorder (PTSD), such as Cognitive Processing Therapy (CPT), have been developed and widely disseminated, the rate of veterans engaging in and completing these therapies is low. Alternative methods of delivery may be needed to help overcome key barriers to treatment. Delivering evidence-based therapies intensively may address practical barriers to treatment attendance as well as problems with avoidance. This report details the case of a combat veteran who received 10 sessions of Cognitive Processing Therapy delivered twice per day over a single, five-day work week (CPT-5). Post-treatment, the veteran reported large and clinically meaningful decreases in PTSD and depression symptom severity as well as in guilt cognitions, which is a purported mechanism of successful treatment. These effects persisted six weeks after treatment ended. Despite the intensive nature of the treatment, the veteran found CPT-5 tolerable and could cite many benefits to completing therapy in one work week. In conclusion, CPT-5 holds promise as a way to efficiently deliver an evidence-based therapy that is both clinically effective and acceptable to patients, although more rigorous clinical trials are needed to test this treatment delivery format
Diffusion and Trapping on a one-dimensional lattice
The properties of a particle diffusing on a one-dimensional lattice where at
each site a random barrier and a random trap act simultaneously on the particle
are investigated by numerical and analytical techniques. The combined effect of
disorder and traps yields a decreasing survival probability with broad
distribution (log-normal). Exact enumerations, effective-medium approximation
and spectral analysis are employed. This one-dimensional model shows rather
rich behaviours which were previously believed to exist only in higher
dimensionality. The possibility of a trapping-dominated super universal class
is suggested.Comment: 20 pages, Revtex 3.0, 13 figures in compressed format using uufiles
command, to appear in Phys. Rev. E, for an hard copy or problems e-mail to:
[email protected]
Dislocation-Mediated Melting: The One-Component Plasma Limit
The melting parameter of a classical one-component plasma is
estimated using a relation between melting temperature, density, shear modulus,
and crystal coordination number that follows from our model of
dislocation-mediated melting. We obtain in good agreement
with the results of numerous Monte-Carlo calculations.Comment: 8 pages, LaTe
Adsorption-desorption kinetics in nanoscopically confined oligomer films under shear
The method of molecular dynamics computer simulations is employed to study oligomer melts confined in ultra-thin films and subjected to shear. The focus is on the self-diffusion of oligomers near attractive surfaces and on their desorption, together with the effects of increasing energy of adsorption and shear. It is found that the mobility of the oligomers near an attractive surface is strongly decreased. Moreover, although shearing the system forces the chains to stretch parallel to the surfaces and thus increase the energy of adsorption per chain, flow also promotes desorption. The study of chain desorption kinetics reveals the molecular processes responsible for the enhancement of desorption under shear. They involve sequences of conformations starting with a desorbed tail and proceeding in a very fast, correlated, segment-by-segment manner to the desorption of the oligomers from the surfaces.
Development of a Core outcome set for fetal Myelomeningocele (COSMiC): study protocol
BACKGROUND: Open spina bifida (OSB) is one of the most common congenital central nervous system defects and leads to long-term physical and cognitive disabilities. Open fetal surgery for OSB improves neurological outcomes and reduces the need for ventriculoperitoneal shunting, compared to postnatal surgery, but is associated with a significant risk of prematurity and maternal morbidity. Fetoscopic surgery comes with less maternal morbidity, yet the question remains whether the procedure is neuroprotective and reduces prematurity. Comparison of outcomes between different treatment options is challenging due to inconsistent outcome reporting. We aim to develop and disseminate a core outcome set (COS) for fetal OSB, to ensure that outcomes relevant to all stakeholders are collected and reported in a standardised fashion in future studies. METHODS: The COS will be developed using a validated Delphi methodology. A systematic literature review will be performed to identify outcomes previously reported for prenatally diagnosed OSB. We will assess maternal (primary and subsequent pregnancies), fetal, neonatal and childhood outcomes until adolescence. In a second phase, we will conduct semi-structured interviews with stakeholders, to ensure representation of additional relevant outcomes that may not have been reported in the literature. We will include patients and parents, as well as health professionals involved in the care of these pregnancies and children (fetal medicine specialists, fetal surgeons, neonatologists/paediatricians and allied health). Subsequently, an international group of key stakeholders will rate the importance of the identified outcomes using three sequential online rounds of a modified Delphi Survey. Final agreement on outcomes to be included in the COS, their definition and measurement will be achieved through a face-to-face consensus meeting with all stakeholder groups. Dissemination of the final COS will be ensured through different media and relevant societies. DISCUSSION: Development and implementation of a COS for fetal OSB will ensure consistent outcome reporting in future clinical trials, systematic reviews and clinical practice guidelines. This will lead to higher quality research, better evidence-based clinical practice and ultimately improved maternal, fetal and long-term childhood outcomes. TRIAL REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO) CRD42018104880 . Registered on December 5, 2018. Core Outcome Measures in Effectiveness Trials (COMET): 1187
Dielectric Properties of the Quasi-Two-Dimensional Electron Liquid in Heterojunctions
A quasi-two-dimensional (Q2D) electron liquid (EL) is formed at the interface
of a semiconductor heterojunction. For an accurate characterization of the Q2D
EL, many-body effects need to be taken into account beyond the random phase
approximation. In this theoretical work, the self-consistent static local-field
correction known as STLS is applied for the analysis of the Q2D EL. The
penetration of the charge distribution to the barrier-acting material is taken
into consideration through a variational approach. The Coulomb from factor that
describes the effective 2D interaction is rigorously treated. The longitudinal
dielectric function and the plasmon dispersion of the Q2D EL are presented for
a wide range of electron and ionized acceptor densities choosing GaAs/AlGaAs as
the physical system. Analytical expressions fitted to our results are also
supplied to enable a widespread use of these results.Comment: 39 pages (in LaTeX), including 8 PostScript figure
Viscosity and Rotation in Core-Collapse Supernovae
We construct models of core-collapse supernovae in one spatial dimension,
including rotation, angular momentum transport, and viscous dissipation
employing an alpha-prescription. We compare the evolution of a fiducial 11
M_sun non-rotating progenitor with its evolution including a wide range of
imposed initial rotation profiles (1.25<P_0<8 s, where P_0 is the initial,
approximately solid-body, rotation period of the iron core). This range of P_0
covers the region of parameter space from where rotation begins to modify the
dynamics (P_0~8 s) to where angular velocities at collapse approach Keplerian
(P_0~1 s). Assuming strict angular momentum conservation, all models in this
range leave behind neutron stars with spin periods <10 ms, shorter than those
of most radio pulsars, but similar to those expected theoretically for
magnetars at birth. A fraction of the gravitational binding energy of collapse
is stored in the free energy of differential rotation. This energy source may
be tapped by viscous processes, providing a mechanism for energy deposition
that is not strongly coupled to the mass accretion rate through the stalled
supernova shock. This effect yields qualitatively new dynamics in models of
supernovae. We explore several potential mechanisms for viscosity in the
core-collapse environment: neutrino viscosity, turbulent viscosity caused by
the magnetorotational instability (MRI), and turbulent viscosity by entropy-
and composition-gradient-driven convection. We argue that the MRI is the most
effective. We find that for rotation periods in the range P_0<~5 s, and a range
of viscous stresses, that the post-bounce dynamics is significantly effected by
the inclusion of this extra energy deposition mechanism; in several cases we
obtain strong supernova explosions.Comment: accepted to ApJ, references added, discussion tightened, 26 pages, 11
figures, emulateap
Entropy in general physical theories
Information plays an important role in our understanding of the physical
world. We hence propose an entropic measure of information for any physical
theory that admits systems, states and measurements. In the quantum and
classical world, our measure reduces to the von Neumann and Shannon entropy
respectively. It can even be used in a quantum or classical setting where we
are only allowed to perform a limited set of operations. In a world that admits
superstrong correlations in the form of non-local boxes, our measure can be
used to analyze protocols such as superstrong random access encodings and the
violation of `information causality'. However, we also show that in such a
world no entropic measure can exhibit all properties we commonly accept in a
quantum setting. For example, there exists no`reasonable' measure of
conditional entropy that is subadditive. Finally, we prove a coding theorem for
some theories that is analogous to the quantum and classical setting, providing
us with an appealing operational interpretation.Comment: 20 pages, revtex, 7 figures, v2: Coding theorem revised, published
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