Linear acceleration emission: 2 Power spectrum

The theory of linear acceleration emission is developed for a large amplitude electrostatic wave in which all particles become highly relativistic in much less than a wave period. An Airy integral approximation is shown to apply near the phases where the electric field passes through zero and the Lorentz factors of all particles have their maxima. The emissivity is derived for an individual particle and is integrated over frequency and solid angle to find the power radiated per particle. The result is different from that implied by the generalized Larmor formula which, we argue, is not valid in this case. We also discuss a mathematical inconsistency that arises when one evaluates the power spectrum by integrating the emissivity over solid angle. The correct power spectrum increases as the 4/3rd power of the frequency at low frequencies, and falls off exponentially above a characteristic frequency. We discuss application of linear acceleration emission to the emission of high frequency photons in an oscillating model for pulsars. We conclude that it cannot account for gamma-ray emission, but can play a role in secondary pair creation.Comment: 25 pages; Accepted for publication in Ap

Effectiveness analysis of ship formation air defence based on deep belief network

Aiming at the problem of strong subjectivity and insufficient data utilisation in the traditional ship formation combat effectiveness analysis method, this study proposes a performance analysis fitting model based on deep belief network (DBN), which effectively reconstructs the combat model and improves the accuracy of the effectiveness analysis of the combat system. Firstly, the ship formation air defence effectiveness analysis index system is constructed, and then the structure and training method of the performance analysis fitting model are introduced. Finally, based on the formation of air defence combat, the performance analysis fitting model based on DBN and its comparative experiments are simulated and analysed. Simulation results verify the applicability and effectiveness of the model and method

Trauma-focused psychotherapies for post-traumatic stress disorder: A systematic review and network meta-analysis.

IntroductionMeta-analytic reviews suggest similar outcomes across trauma-focused psychotherapies for adults with post-traumatic stress disorder (PTSD). However, this conclusion may be premature due to suboptimal statistical-review methodologies. Network meta-analysis (NMA) allows a detailed rank-ordering of the efficacy of established psychotherapy interventions derived from indirect evidence as well as results from direct head-to-head comparisons.ObjectiveWe sought to determine the efficacy and attrition rates of psychotherapy interventions for PTSD by applying NMA.MethodsWe searched EMBASE, PsychINFO, PTSDPubs and PubMed for randomised controlled trials that compared psychotherapies either head-to-head or against controls for adults with PTSD. A frequentist NMA was used to compare direct and indirect effects to determine the efficacy and attrition rates of psychotherapy interventions.ResultsOf the 5649 papers identified, 82 trials comprising of 5838 patients were included. The network comprised 17 psychotherapies and four control conditions. Network estimates indicated superior efficacy of meta-cognitive therapy and cognitive processing therapy over other psychotherapies (ESs between = 0.26 and 2.32). Written exposure therapy and narrative exposure therapy were associated with lower risk of drop out when considered alongside other psychotherapies. Confidence in the network meta-analytic estimates was considered moderate for both outcomes.ConclusionsIn broad terms, therapeutic commensurability was evident. Nevertheless, with additional studies and larger sample sizes, meta-cognitive and written exposure therapies could indeed differentiate themselves from other approaches as having favourable efficacy and acceptability respectively. These findings may inform clinical decision-making, as well as guide future research for PTSD

Parallel Computing on a PC Cluster

The tremendous advance in computer technology in the past decade has made it possible to achieve the performance of a supercomputer on a very small budget. We have built a multi-CPU cluster of Pentium PC capable of parallel computations using the Message Passing Interface (MPI). We will discuss the configuration, performance, and application of the cluster to our work in physics.Comment: 3 pages, uses Latex and aipproc.cl

Dynamical generation and dynamical reconstruction

A definition of `dynamical generation', a hotly debated topic at present, is proposed and its implications are discussed. This definition, in turn, leads to a method allowing to distinguish in principle tetraquark and molecular states. The different concept of `dynamical reconstruction' is also introduced and applies to the generation of preexisting mesons (quark-antiquark, glueballs, >...) via unitarization methods applied to low-energy effective Lagrangians. Large $N_{c}$ arguments play an important role in all these investigations. A simple toy model with two scalar fields is introduced to elucidate these concepts. The large $N_{c}$ behavior of the parameters is chosen in order that the two scalar fields behave as quark-antiquark mesons. When the heavier field is integrated out, one is left with an effective Lagrangian with the lighter field only. A unitarization method applied to the latter allows to `reconstruct' the heavier `quarkonium-like' field, which was previously integrated out. It is shown that a Bethe-Salpeter (BS) analysis is capable to reproduce the preformed quark-antiquark state. However, when only the lowest term of the effective Lagrangian is retained, the large $N_{c}$ limit of the reconstructed state is not reproduced: instead of the correct large $N_{c}$ quarkonium limit, it fades out as a molecular state would do. Implications of these results are presented: it is proposed that axial-vector, tensor and (some) scalar mesons just above 1 GeV obtained via the BS approach from the corresponding low-energy, effective Lagrangian in which only the lowest term is kept, are quarkonia states, in agreement with the constituent quark model, although they might fade away as molecular states in the large $N_{c}$ limit.Comment: 14 pages, 3 figure