Oxynitride glass fibers

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future

Shaped Charge Jet Penetration of Alon® Ceramic Assessed by Proton Radiography and Computational Simulations

AbstractThis work describes the use of proton radiography and continuum simulations to investigate the mechanics of a copper jet penetrating unconfined ALON® transparent ceramic. Use of proton radiography enabled characterization of the jet and ceramic material at 21 time steps, in situ, throughout the penetration process. These radiographs provide time-evolution data pertaining to the material densities, cavity growth, and material failure. The data were compared to legacy analytical penetration models and to a simulation of the event computed using a continuum multi-physics code. These comparisons revealed additional insights into the penetration mechanics as well as strengths and weaknesses of the computational algorithms and material models used in the simulations

Hypodontia: genetics and future perspectives

Tooth development is a complex process of reciprocal interactions that we have only recently begun to understand. With the large number of genes involved in the odontogenic process, the opportunity for mutations to disrupt this process is high. Tooth agenesis (hypodontia) is the most common craniofacial malformation with patients missing anywhere from one tooth to their entire dentition. Hypodontia can occur in association with other developmental anomalies (syndromic) or as an isolated condition (non-syndromic). Recent advances in genetic techniques have allowed us to begin understanding the genetic processes that underlie the odontogenic process and to identify the mechanisms responsible for tooth agenesis. Thus far two genes have been identified by mutational analysis as the major causes of non-syndromic hypodontia; PAX9 and MSX1. Haploinsufficiency of either has been observed to cause the more severe forms of hypodontia whilst point mutations cause hypodontia to varying degrees of severity. With the prevalence of hypodontia having been observed to have increased during the 20th century, the future identification and analysis of its genetic basis is essential to allow us to better treat the condition. The clinician can facilitate this process by collaborating with the human geneticist and referring patients/families with familial hypodontia for investigative research

Pressure Induced Densification and Compression in a Reprocessed Borosilicate Glass

Pressure induced densification and compression of a reprocessed sample of borosilicate glass has been studied by X-ray radiography and energy dispersive X-ray diffraction using a Paris-Edinburgh (PE) press at a synchrotron X-ray source. The reprocessing of a commercial borosilicate glass was carried out by cyclical melting and cooling. Gold foil pressure markers were used to obtain the sample pressure by X-ray diffraction using its known equation of state, while X-ray radiography provided a direct measure of the sample volume at high pressure. The X-ray radiography method for volume measurements at high pressures was validated for a known sample of pure α-Iron to 6.3 GPa. A sample of reprocessed borosilicate glass was compressed to 11.4 GPa using the PE cell, and the flotation density of pressure recovered sample was measured to be 2.755 gm/cc, showing an increase in density of 24%, as compared to the starting sample. The initial compression of the reprocessed borosilicate glass measured by X-ray radiography resulted in a bulk modulus of 30.3 GPa in good agreement with the 32.9 GPa value derived from the known elastic constants. This method can be applied to variety of amorphous materials under high pressures

An overview of tobacco related cancers in Patan district, Gujarat state

ABSTRACT: Tobacco is the single most important cause of avoidable morbidity and early mortality in many countries. In India approximately 700,000-900,000 new cancers are diagnosed every year. Nearly half of all cancers in men and one fifth of cancers in women are tobacco related cancers. The present study was conducted to examine the proportion of tobacco related cancers, their age distribution and geographical variations in Patan district, Gujarat. All new cases of tobacco related cancers diagnosed during the year 2011 were included in the study. Apart from Gujarat Cancer & Research Institute, cancer data were also obtained from government hospitals, private hospitals& consultants, pathology laboratories and death registration units of Patan district and other districts. During the year 2011, a total of 472 new cases (Males: 310; Females: 162) were registered. Among them 214 cases were tobacco related cancers with a male preponderance (189 cases). Majority of the cases were in the age group of 35-64 years. Tongue Cancer was the commonest site in both sexes. Patan taluka had highest tobacco related cancers. This study implies an urgent need for tobacco control among the population of Patan district as tobacco is the most common risk factor of cancer occurrence

Research Subsidies, Population Control Policies, and Growth

Several R&D-based growth models without scale effects claim that subsidies to R&D are not conductive for economic growth while a faster growing population is. Yet, in an effort to maintain high growth rates, most OECD countries continue to subsidize R&D, while several developing countries are trying to control the size of their population. Are these countries misguided? This study introduces an R&D-based growth model that is characterized by complementarities between technology and human capital. The model is free of scale effects and consistent with the above-mentioned policies. By applying the model to US data the study uncovers a possible explanation for the productivity slowdown. Copyright � 2007 The Author; Journal compilation � 2007 Blackwell Publishing Ltd.