Pneumoconiosis In The Chrome Mining Industry Of Rhodesia

A CAJM article showing the effects of chrome mining dust on the health of the miners' lungs

A gap in the spectrum of the Neumann-Laplacian on a periodic waveguide

We will study the spectral problem related to the Laplace operator in a singularly perturbed periodic waveguide. The waveguide is a quasi-cylinder with contains periodic arrangement of inclusions. On the boundary of the waveguide we consider both Neumann and Dirichlet conditions. We will prove that provided the diameter of the inclusion is small enough in the spectrum of Laplacian opens spectral gaps, i.e. frequencies that does not propagate through the waveguide. The existence of the band gaps will verified using the asymptotic analysis of elliptic operators.Comment: 26 pages, 6 figure

Optical manipulation of silicon microparticles in biological environments

Manipulation of micron-scale silicon particles has been investigated with optical tweezers implemented using a two-dimensional scanning trap driven with acousto-optic modulators. Spheres of latex, Poly(methyl methacrylate) (PMMA), silica, and silver-coated PMMA have been utilized to calibrate transverse trapping forces. The goal of this work is to non-invasively manipulate 10-20μm silicon-based devices in and around cells

Hopf algebras and Markov chains: Two examples and a theory

The operation of squaring (coproduct followed by product) in a combinatorial Hopf algebra is shown to induce a Markov chain in natural bases. Chains constructed in this way include widely studied methods of card shuffling, a natural "rock-breaking" process, and Markov chains on simplicial complexes. Many of these chains can be explictly diagonalized using the primitive elements of the algebra and the combinatorics of the free Lie algebra. For card shuffling, this gives an explicit description of the eigenvectors. For rock-breaking, an explicit description of the quasi-stationary distribution and sharp rates to absorption follow.Comment: 51 pages, 17 figures. (Typographical errors corrected. Further fixes will only appear on the version on Amy Pang's website, the arXiv version will not be updated.

Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths

We review observations of several classes of neutron-star-powered outflows: pulsar-wind nebulae (PWNe) inside shell supernova remnants (SNRs), PWNe interacting directly with interstellar medium (ISM), and magnetar-powered outflows. We describe radio, X-ray, and gamma-ray observations of PWNe, focusing first on integrated spectral-energy distributions (SEDs) and global spectral properties. High-resolution X-ray imaging of PWNe shows a bewildering array of morphologies, with jets, trails, and other structures. Several of the 23 so far identified magnetars show evidence for continuous or sporadic emission of material, sometimes associated with giant flares, and a few possible "magnetar-wind nebulae" have been recently identified.Comment: 61 pages, 44 figures (reduced in quality for size reasons). Published in Space Science Reviews, "Jets and Winds in Pulsar Wind Nebulae, Gamma-ray Bursts and Blazars: Physics of Extreme Energy Release

MAP2-mediated binding of chromaffin granules to microtubules

AbstractWe have examined the interaction of chromaffin granules from bovine adrenal modulla with microtubules. Chromaffin granules were mixed with microtubules made of phosphocellulose-purified tubulin, and pelleted through a 1.6 M sucrose cushion at 12000 × g for 10 min. Both components (granules and microtubules) were pelleted when added together but not separately. This result indicates that granules form a heavy complex with the microtubules. Such a complex was visualized by an electron microscopy of the granule/microtubule mixture. Treatment of the granules with trypsin abolished their ability to interact with the microtubules. The binding of the granules to the microtubules: (i) was not sensitive to ATP: and (ii) was completely inhibited by the cleavage of C-terminal peptides of α- and β-subunits of tubulin with subtilisin. These relationships suggest that the granule binding is mediated by one of the structural microtubule-associated proteins rather than by microtubule-dependent translocators. For identification of protein(s) mediating the binding, the granules were solubilized with Triton X-100, soluble proteins were mixed with the microtubules, and microtubules with bound proteins were pelleted through a glycerol cushion. At least one granule protein interacting with the microtubules was found in the pellet. This protein was identified as MAP2 according to its electrophoretic mobility and reactivity with a MAP2 antibody. Affinity chromatography of solubilized proteins on a column containing taxol-stabilized microtubules also revealed MAP2 as a protein of chromaffin granules interacting with the microtubules

A spatial measure of neighborhood-level racial isolation applied to low birthweight, preterm birth, and birthweight in North Carolina

Research on racial residential segregation (RRS) and birth outcomes has focused on RRS at a broad geographic scale, in an aspatial framework, and in northern US cities. We developed a spatial measure of neighborhood level racial isolation of blacks. We examined the association between this new measure and low birthweight, preterm birth, and birthweight in the southern state of North Carolina. Natality data were obtained from the North Carolina Detailed Birth Record 1998–2002 files. Using multiple regression with cluster corrected standard errors, infants born to black and white mothers living in black isolated neighborhoods had, on average, decreased birthweight, and increased odds of low birthweight and preterm birth compared to their counterparts in less isolated areas. White mothers in predominantly black neighborhoods experienced greater increases in odds of each poor birth outcome than did black mothers. Black isolation may be proxying concentrated socioeconomic disadvantage, including disamenities in the built environment