Two-component model for the chemical evolution of the Galactic disk

In the present paper, we introduce a two-component model of the Galactic disk to investigate its chemical evolution. The formation of the thick and thin disks occur in two main accretion episodes with both infall rates to be Gaussian. Both the pre-thin and post-thin scenarios for the formation of the Galactic disk are considered. The best-fitting is obtained through $\chi^2$-test between the models and the new observed metallicity distribution function of G dwarfs in the solar neighbourhood (Hou et al 1998). Our results show that post-thin disk scenario for the formation of the Galactic disk should be preferred. Still, other comparison between model predictions and observations are given.Comment: 23 pages, 7 figure

Advanced post-acceleration methodology for pseudospark-sourced electron beam

During its conductive phase, a pseudospark discharge is able to generate a low energy electron beam with a higher combined current density and brightness compared with electron beams formed from any other known type of electron source. In this paper, a configuration is proposed to post-accelerate an electron beam extracted from a single-gap pseudospark discharge cavity in order to achieve high quality high energy intense electron beams. The major advancement is that the triggering of the pseudospark discharge, the pseudospark discharge itself, and the post-accelerating of the electron beam are all driven by a single high voltage pulse. An electron beam with a beam current of ∼20 A, beam voltage of 40 kV, and duration of ∼180 ns has been generated using this structure. The beam energy can be adjusted through adjusting the amplitude of the voltage pulse and the operating voltage of the whole structure, which can be varied from 24 to 50 kV with an efficient triggering method under fixed gas pressure below ∼10 Pa

Long-term trends in Indigenous deaths from chronic diseases in the Northern Territory: a foot on the brake, a foot on the accelerator

Objective: To examine trends in Northern Territory Indigenous mortality from chronic diseases other than cancer. Design: A comparison of trends in rates of mortality from six chronic diseases (ischaemic heart disease [IHD], chronic obstructive pulmonary disease [COPD], cerebrovascular disease [CVD], diabetes mellitus [DM], renal failure [RF] and rheumatic heart disease [RHD]) in the NT Indigenous population with those of the total Australian population. Participants: NT Indigenous and total Australian populations, 1977–2001. Main outcome measures: Estimated average annual change in chronic disease mortality rates and in mortality rate ratios. Results: DeathratesfromIHDandDMamongNTIndigenouspeoplesincreased between 1977 and 2001, but this increase slowed after 1990. Death rates from COPD rose before 1990, but fell thereafter. There were non-significant declines in death rates from CVD and RHD. Mortality rates from RF rose in those aged 50 years. The ratios of mortality rates for NT Indigenous to total Australian populations from these chronic diseases increased throughout the period. Conclusions: Mortality rates from IHD and DM in the NT Indigenous population have been increasing since 1977, but there is evidence of a slower rise (or even a fall) in death rates in the 1990s. These early small changes give reason to hope that some improvements (possibly in medical care) have been putting the brakes on chronic disease mortality among Aboriginal and Torres Strait Islander peoples

Solving variational inequalities defined on a domain with infinitely many linear constraints

We study a variational inequality problem whose domain is defined by infinitely many linear inequalities. A discretization method and an analytic center based inexact cutting plane method are proposed. Under proper assumptions, the convergence results for both methods are given. We also provide numerical examples to illustrate the proposed method

Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity

In various astrophysical contexts, we analyze self-similar behaviours of magnetohydrodynamic (MHD) evolution of a quasi-spherical polytropic magnetized gas under self-gravity with the specific entropy conserved along streamlines. In particular, this MHD model analysis frees the scaling parameter $n$ in the conventional polytropic self-similar transformation from the constraint of $n+\gamma=2$ with $\gamma$ being the polytropic index and therefore substantially generalizes earlier analysis results on polytropic gas dynamics that has a constant specific entropy everywhere in space at all time. On the basis of the self-similar nonlinear MHD ordinary differential equations, we examine behaviours of the magnetosonic critical curves, the MHD shock conditions, and various asymptotic solutions. We then construct global semi-complete self-similar MHD solutions using a combination of analytical and numerical means and indicate plausible astrophysical applications of these magnetized flow solutions with or without MHD shocks.Comment: 21 pages, 7 figures, accepted for publication in APS