SMMR Simulator radiative transfer calibration model. 2: Algorithm development

Passive microwave measurements performed from Earth orbit can be used to provide global data on a wide range of geophysical and meteorological phenomena. A Scanning Multichannel Microwave Radiometer (SMMR) is being flown on the Nimbus-G satellite. The SMMR Simulator duplicates the frequency bands utilized in the spacecraft instruments through an amalgamate of radiometer systems. The algorithm developed utilizes data from the fall 1978 NASA CV-990 Nimbus-G underflight test series and subsequent laboratory testing

Torsional oscillations of a magnetar with a tangled magnetic field

We propose a scenario for the quasi-periodic oscillations observed in magnetar flares wherein a tangled component of the stellar magnetic field introduces nearly isotropic stress that gives the fluid core of the star an effective shear modulus. In a simple, illustrative model of constant density, the tangled field eliminates the problematic Alfv\'en continuum that would exist in the stellar core for an organized field. For a tangled field energy density comparable to that inferred from the measured dipole fields of $\sim 10^{15}$ G in SGRs 1806-20 and 1900+14, torsional modes exist with fundamental frequencies of about 20 Hz, and mode spacings of $\sim 10$ Hz. For fixed stellar mass and radius, the model has only one free parameter, and can account for {\em every} observed QPO under 160 Hz to within 3 Hz for both SGRs 1806-20 and 1900+14. The combined effects of stratification and crust stresses generally decrease the frequencies of torsional oscillations by $<10$% for overtones and increase the lowest-frequency fundamentals by up to 50%, and so the star can be treated as having constant density to a generally good first approximation. We address the issue of mode excitation by sudden readjustment of the stellar magnetosphere. While the total energy in excited modes is well within the energy budget of giant flares, the surface amplitude is $< 10^{-3}$ of the stellar radius for global oscillations, and decreases strongly with mode frequency. The 626 Hz QPO reported for SGR 1806-20 is particularly problematic to excite beyond a surface amplitude of $10^{-6}$ of the stellar radius.Comment: 14 pages, 3 figure

Social epidemiology

Social epidemiology is the branch of epidemiology concerned with understanding how social and economic characteristics influence states of health in populations. There has been a resurgence recently in interest among epidemiologists about the roles that social and economic factors play in determining health, leading to valuable synergies with the social sciences. The determinants of health commonly studied in social epidemiology include absolute poverty, income inequality, as well as race and discrimination. Recently, social epidemiologists have been at the forefront of conceptual developments within the discipline that view the determinants of health at different levels of social organization. © 2008 Copyright © 2008 Elsevier Inc. All rights reserved

SMMR simulator radiative transfer calibration model. 1: Derivation

There are no author-identified significant results in this report

Regulation of hematopoietic stem cell activity by inflammation

Hematopoietic stem cells (HSCs) are quiescent cells with self-renewal capacity and the ability to generate all mature blood cells. HSCs normally reside in specialized niches in the bone marrow that help maintain their quiescence and long-term repopulating activity. There is emerging evidence that certain cytokines induced during inflammation have significant effects on HSCs in the bone marrow. Type I and II interferons, tumor necrosis factor, and LPS directly stimulate HSC proliferation and differentiation, thereby increasing the short-term output of mature effector leukocytes. However, chronic inflammatory cytokine signaling can lead to HSC exhaustion and may contribute the development of hematopoietic malignancies. Pro-inflammatory cytokines such as G-CSF can also indirectly affect HSCs by altering the bone marrow microenvironment, disrupting the stem cell niche and leading to HSC mobilization into the blood. Herein, we review our current understanding of the effects of inflammatory mediators on HSCs, and we discuss the potential clinical implications of these findings with respect to bone marrow failure and leukemogenesis