671 research outputs found
Guidelines for fabrication of hybrid microcircuits
Document is summary of approaches that may be taken in designing hybrid microcircuits similar to those for aerospace application
Kinetic Energy Decay Rates of Supersonic and Super-Alfvenic Turbulence in Star-Forming Clouds
We present numerical studies of compressible, decaying turbulence, with and
without magnetic fields, with initial rms Alfven and Mach numbers ranging up to
five, and apply the results to the question of the support of star-forming
interstellar clouds of molecular gas. We find that, in 1D, magnetized
turbulence actually decays faster than unmagnetized turbulence. In all the
regimes that we have studied 3D turbulence-super-Alfvenic, supersonic,
sub-Alfvenic, and subsonic-the kinetic energy decays as (t-t0)^(-x), with 0.85
< x < 1.2. We compared results from two entirely different algorithms in the
unmagnetized case, and have performed extensive resolution studies in all
cases, reaching resolutions of 256^3 zones or 350,000 particles. We conclude
that the observed long lifetimes and supersonic motions in molecular clouds
must be due to external driving, as undriven turbulence decays far too fast to
explain the observations.Comment: Submitted to Phys. Rev. Letters, 29 Nov. 1997. 10 pages, 2 figures,
also available from http://www.mpia-hd.mpg.de/theory/preprints.html#maclo
Stress in nurses : stress-related affect and its determinants examined over the nursing day
Peer reviewedPostprin
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
Proton Spin Structure in the Resonance Region
We have examined the spin structure of the proton in the region of the
nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum
transfer of Q^2 = 1.3 GeV^2. Using the Jefferson Lab polarized electron beam, a
spectrometer, and a polarized solid target, we measured the asymmetries
A_parallel and A_perp to high precision, and extracted the asymmetries A_1 and
A_2, and the spin structure functions g_1 and g_2. We found a notably non-zero
A_perp, significant contributions from higher-twist effects, and only weak
support for polarized quark--hadron duality.Comment: 6 pages, 4 figures, REVTeX4, similar to PRL submission, plots
colorized and appenix added, v3: minor edit, matches PR
Control of star formation by supersonic turbulence
Understanding the formation of stars in galaxies is central to much of modern
astrophysics. For several decades it has been thought that stellar birth is
primarily controlled by the interplay between gravity and magnetostatic
support, modulated by ambipolar diffusion. Recently, however, both
observational and numerical work has begun to suggest that support by
supersonic turbulence rather than magnetic fields controls star formation. In
this review we outline a new theory of star formation relying on the control by
turbulence. We demonstrate that although supersonic turbulence can provide
global support, it nevertheless produces density enhancements that allow local
collapse. Inefficient, isolated star formation is a hallmark of turbulent
support, while efficient, clustered star formation occurs in its absence. The
consequences of this theory are then explored for both local star formation and
galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28
figures, in pres
Heterochromatin: A Rapidly Evolving Species Barrier
Recent work has shown that changes in the sequence composition of heterochromatin, or in the factors that maintain that heterochromatin, may play an important role in speciation
Is Violent Radicalisation Associated with Poverty, Migration, Poor Self-Reported Health and Common Mental Disorders?
BACKGROUND: Doctors, lawyers and criminal justice agencies need methods to assess vulnerability to violent radicalization. In synergy, public health interventions aim to prevent the emergence of risk behaviours as well as prevent and treat new illness events. This paper describes a new method of assessing vulnerability to violent radicalization, and then investigates the role of previously reported causes, including poor self-reported health, anxiety and depression, adverse life events, poverty, and migration and socio-political factors. The aim is to identify foci for preventive intervention. METHODS: A cross-sectional survey of a representative population sample of men and women aged 18-45, of Muslim heritage and recruited by quota sampling by age, gender, working status, in two English cities. The main outcomes include self-reported health, symptoms of anxiety and depression (common mental disorders), and vulnerability to violent radicalization assessed by sympathies for violent protest and terrorist acts. RESULTS: 2.4% of people showed some sympathy for violent protest and terrorist acts. Sympathy was more likely to be articulated by the under 20s, those in full time education rather than employment, those born in the UK, those speaking English at home, and high earners (>£75,000 a year). People with poor self-reported health were less likely to show sympathies for violent protest and terrorism. Anxiety and depressive symptoms, adverse life events and socio-political attitudes showed no associations. CONCLUSIONS: Sympathies for violent protest and terrorism were uncommon among men and women, aged 18-45, of Muslim heritage living in two English cities. Youth, wealth, and being in education rather than employment were risk factors
The Dynamical Structure and Evolution of Giant Molecular Clouds
Giant molecular clouds (GMCs) are the sites of star formation in the Galaxy. Many of their properties can be understood in terms of a model in which the GMCs and the star-forming clumps within them are in approximate pressure equilibrium, with turbulent motions treated as a separate pressure component
The relationship between tumour T-lymphocyte infiltration, the systemic inflammatory response and survival in patients undergoing curative resection for colorectal cancer
There is increasing evidence that both local and systemic inflammatory responses play an important role in the progression of a variety of common solid tumours. The aim of the present study was to examine the relationship between tumour T-lymphocyte subset infiltration, the systemic inflammatory response and cancer-specific survival in patients with colorectal cancer. In all, 147 patients undergoing potentially curative resection for colorectal cancer were studied. Circulating concentrations of C-reactive protein were measured prior to surgery. CD4+ and CD8+ T-lymphocyte infiltration of the tumour was assessed using immunohistochemistry and a point counting technique. When patients were grouped according to the percentage tumour volume of CD4+ T-lymphocytes, there was no difference in terms of age, sex, tumour site, stage and tumour characteristics. However, there was an inverse relationship between percentage tumour CD4+ T-lymphocytes and C-reactive protein (P<0.01). On univariate analysis, both C-reactive protein concentrations (P<0.001) and percentage tumour volume of CD4+ (P<0.05) T-lymphocytes were associated with cancer-specific survival. The results of the present study show that low tumour CD4+ T-lymphocyte infiltration is associated with elevated C-reactive protein concentrations and both predict poor cancer-specific survival
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