Hand–arm vibration in a group of hand‐operated grinding tools

Vibration acceleration was triaxially and basicentrically measured, and digital‐audio‐tape‐recorded with each axis separately evaluated using both the ANSI S3.34 and ACGIH hand‐arm vibration (HAV) guidelines, for two pairs of pneumatic handheld grinders commonly used in metal fabrication operations including shipyards. Each tool pair consisted of a new and used grinder of the same model, performing the same simulated grinding tasks using new small grinding wheels, carbide burrs, wire brushes, and flap wheels. The results of this limited study showed, primarily, that the HAV standards were not exceeded, but there was a consistent tendency for the acceleration levels to increase between new and used tools, ranging from 11% to 66% on the Z‐axis, 13% to 66% on the Y‐axis, 44% to 58% on the X‐axis, when tasks involved using grinding wheels and carbide burrs (hard implements). The results were mixed when using disposable wire brushes and flap wheels (softer implements). The overall results suggest the need for and implementation of a regular tool vibration monitoring and maintenance program as a primary element to help maintain tool acceleration levels to a minimum. © 2002 Wiley Periodicals, Inc.     

Recognition and analysis of local structure in polycrystalline configurations

A method is described for obtaining information about the local order existing in monoatomic model solids or real materials based on their atomistic configurations. An efficient algorithmic implementation is provided. The shape of the polyhedra formed by ‘relevant’ neighbors of each atom enter a pattern recognition method to resolve the type of the (usually non-ideal) crystal structure to which atoms surrounded by their relevant neighbors belong: hexagonal close-packed, face-centered cubic or body-centered cubic. Further, this approach allows for the analysis of icosahedral structure which preferably occurs in amorphous solids. Results of a molecular dynamics computer simulation illustrate how this method can be applied to contribute to an understanding of the mechanical and structural properties of solids (i) undergoing a steady shear stress and (ii) upon increasing temperature.     

Serum response of Escherichia coli strains causing dyspepsia and urinary tract infection: relation to alpha-hemolysin production and O type

A total of 109 alpha-hemolytic and 104 nonhemolytic Escherichia coli isolates from children with dyspepsia and urinary tract infections were investigated for resistance to the bactericidal activity of human serum. A significantly higher proportion of serum resistance was found in alpha-hemolytic E. coli isolates than in nonhemolytic isolates (P < 0.01). An association between the titer of alpha-hemolysin produced and serum resistance was found.     

A fast and stable Poisson-Schrödinger solver for the analysis of carbon nanotube transistors

When the coupled Schrödinger-Poisson system is solved iteratively with appropriate numerical damping, convergence problems are likely to occur. We show that these problems are due to inappropriate energy discretization for evaluating the carrier concentration. By using an adaptive method the self-consistent loop becomes stable, and most of the simulations converge in a few iterations. We applied this approach to investigate the behavior of carbon nanotube field effect transistors.     

Optimization of pseudomorphic HEMT's supported by numericalsimulations

Measurements and simulations of three different pseudomorphic high electron mobility transistors (PHEMT's) are presented. The PHEMT's possess the same epitaxial structure but different geometrical properties. For the simulations, the generic device simulator MINIMOS-NT is employed. This simulator is not restricted to planar device surfaces but is able to model complex surface topologies including the effect of passivating dielectric layers. Mixed hydrodynamic and drift-diffusion simulations are demonstrated. They include the DC characteristics as well as the bias-dependent gate capacitances. Thus, bias-dependent current-gain cutoff frequencies f_T can be calculated. The results compare very well with the values obtained by small-signal parameter extractions from S-parameter measurements. Although a single consistent set of parameters is used for the simulations of all three devices, their characteristics are reproduced with an accuracy to our knowledge not reported before. Therefore, the DC and RF properties of PHEMT's with geometries significantly different from the measured devices can be reliably predicted     

VOC Emissions after Building Renovations: Traditional and Less Common Indoor Air Contaminants,Potential Sources,and Reported Health Complaints

Abstract Volatile organic compounds (VOCs) were measured in the air of 51 renovated rooms in Schleswig-Holstein. The buildings examined were of different types – private flats, schools, kindergartens, office buildings – the only common characteristic being that they had all been renovated within the last two years. Among the dominating substances in the 46/51 complaint cases were well-known substances such as alkylbenzenes or monoterpenes at high concentrations but also less common substances, i.e. those which have only recently been reported as indoor air contaminants, for example phenoxyethanol, 2-(2-butoxyethoxy)-ethylacetate (butyldiglycolacetate) or longifolene (Mohr, 1994) at remarkable concentrations. A tentative investigation was made to identify the simultaneous occurrences of the different substances, especially the uncommon ones with their potential sources, as well as health impairments. Finally, VOC emissions from two carpet glues, suspected during the investigations of playing a role as a potential source of the less common substances, were carefully measured under test chamber conditions. This additional laboratory experiment was made to verify the tendency shown in the field study that modern ecological building materials contain less volatile and less common substances but with increased indoor persistence, that could partially account for the increasing number of complaints in relation to the SBS phenomenon.     

Detection of infrequent and multiple K-ras mutations in human tumors and tumor-adjacent tissues

A sensitive method was developed and applied to examine the distribution of K-ras gene mutations in histologically differing areas of lung tissues obtained from lung cancer patients. This method, which combines polymerase chain reaction (PCR), mutation allele enrichment (MAE), and denaturing gradient gel electrophoresis (DGGE), allows detection of one K-ras mutant allele present in 10(4) to 10(5) wild-type alleles. It was applied to analyze mutations in codon 12 of the K-ras gene in 43 tissue sites microdissected from paraffin-embedded sections obtained from 8 archival cases of lung cancer, all previously shown to have codon 12 K-ras mutations by direct sequencing. In four cases, mutations were detected only in the tumor, while in the other four cases, the same mutations were also found in tissues adjacent to tumors, using the MAE + DGGE method. No mutations were detected among normal-appearing cells in areas distant from the tumors in any of the cases studied. These findings demonstrate that K-ras mutations can be detected at low frequencies in normal-appearing cells from tissues adjacent to the tumor in some lung cancer cases. In addition, this approach also allowed detection of multiple mutations in colorectal tissues obtained from colorectal cancer patients. Thus, the MAE + DGGE method may be applicable to study of K-ras mutations in premalignant or morphologically suspicious lesions in bronchial mucosa or other types of human cancer.