An efficient method for joint hypocenter determination for large groups of earthquakes

The number of seismic events that can be located simultaneously by the Joint Hypocenter Determination method is limited generally by the amount of computer time and computer memory available. To find directly the hypocenters of M earthquatkes and the station corrections to N stations requires solving a system of 4M + N equations in 4M + N unknowns. This paper presents a method of solving this system of equations which is considerably more efficient than Guassian elimination.     

Neurturin and GDNF promote proliferation and survival of enteric neuron and glial progenitors in vitro

Signaling through the c-Ret tyrosine kinase and the endothelin B receptor pathways is known to be critical for development of the enteric nervous system. To clarify the role of these receptors in enteric nervous system development, the effect of ligands for these receptors was examined on rat enteric neuron precursors in fully defined medium in primary culture. In this culture system, dividing Ret-positive cells differentiate, cluster into ganglia containing neurons and enteric glia, and create extensive networks reminiscent of the enteric plexus established in vivo. Glial cell-line-derived neurotrophic factor (GDNF) and neurturin both potently support survival and proliferation of enteric neuron precursors in this system. Addition of either neurturin or GDNF to these cultures increased the number of both neurons and enteric glia. Persephin, a third GDNF family member, shares many properties with neurturin and GDNF in the central nervous system and in kidney development. By contrast, persephin does not promote enteric neuron precursor proliferation or survival in these cultures. Endothelin-3 also does not increase the number of enteric neurons or glia in these cultures.     

Susceptibility of Chlamydia trachomatis to chlorhexidine gluconate gel

To identify topical antimicrobial preparations which may be effective in preventing the transmission of sexually transmitted diseases, we examined the activity of chlorhexidine gluconate (CHG) against Chlamydia trachomatis. Chlamydial elementary bodies were incubated with dilutions of CHG gel for various times from 0 to 120 min. An aliquot of each dilution was further diluted and was inoculated onto McCoy cell monolayers in individual wells in a 96-well microtiter plate. The cultures were incubated for 48 h, and the chlamydial inclusions were stained and counted. CHG gel diluted fourfold (0.0625% CHG) killed C. trachomatis serovar D, and CHG gel diluted eightfold (0.0313% CHG) killed serovar F immediately upon exposure. CHG gel diluted 16-fold (0.0156% CHG) killed serovar D, and CHG gel diluted 32-fold (0.0078% CHG) killed serovar F after 120 min of exposure. Alteration of the pH over the range of from 4 to 8 did not significantly affect its activity. The addition of 10% whole human blood decreased the CHG gel activity at 0 min but had no significant effect after 120 min of exposure. We conclude that CHG gel may be effective topically against C. trachomatis at concentrations that can be used and under conditions that are found in the female genital tract and that further studies of its antimicrobial efficacy and toxicity in vivo are warranted.     

The identification of asbestos

Techniques are described for identifying and distinguishing between the six varieties of asbestos. When the fibres are large and numerous, as is the case for insulation materials, simple optical or X-ray methods suffice. For environmental samples one must normally resort to electron microscopic techniques for a positive identification. When asbestiform minerals are to be distinguished from other fibrous silicates it is often necessary to use both electron diffraction and X-ray spectrometry.     

Towards a formal taxonomy of hybrid uncertainty representations

In this paper we present some ideas about how to formally relate various uncertainty representations together in a taxonomic structure, capturing both syntactic and semantic generalization. Fuzziness and nonspecificity are presumed as primitive concepts of uncertainty, and transitive and intransitive methods operating with nonspecificity and fuzziness are introduced to generate a base class of hybrid uncertainty representational forms. Additive, maximal, and interval constraints then complete the characterization of the most important hybrid forms.     

Recommended Dielectric Tests and Test Procedures for Converter Transformers and Smoothing Reactors

The dielectric conditions which are unique to converter transformers and smoothing reactors are examined. Both steady state and transient situations are discussed. Two additional tests are recommended for this equipment - a long term dc applied potential test and a polarity reversal test. Formulae are developed to calculate proposed test levels, and guidelines are presented concerning allowable partial discharge levels during the tests.     

Dielectric rod leaky-wave antennas for millimeter-wave applications

Dielectric rod leaky-wave antennas have the property of being frequency scannable. Bounds are derived for the proper range of spacing of perturbations along the rod to avoid an intrusion upon a grating lobe when frequency scanning. In addition some experimental results are reported on sidelobe levels and polarizations in the far field for these antennas made from a material withepsilon_{r}= 2.33at 81.5 GHz.     

Mechanical properties of fibres of linear polyester-and polyetherurethanes in relation to details of their chemical structures

Elastic fibres soluble in dimethylformamide were made from essentially linear polyester- and polyetherurethanes. The molecular structures of the polyurethanes were varied by using as chain extenders aliphatic diamines with a successively increasing number of carbon atoms. Mechanical investigations resulted in modulus, stress relaxation and creep data which oscillated with increasing number of carbon atoms of the diamines used. These results and the temperature- and time-dependence of these data can be explained by a model proposing the existence of hard segment domains in a matrix of soft but crystallisable polyester or polyether material.