Gas-rich dwarf galaxies in dense and sparse environments

Dwarf irregular galaxies (generically labelled Im for the present purposes) pose an enigma to students of galaxy evolution. In nearby groups and the Virgo cluster, Im galaxies are at least as abundant as spiral galaxies, and their low surface brightnesses and high gas-to-stars ratios suggest that (at least in the stochastic self-propagating star formation scenario) there should be significant numbers of HI clouds with masses approaching 10(exp 8) solar mass which have undergone very little or no star formation. To date, however, no clouds with so little star formation that they would not be recognized as Im galaxies on high-quality photographic plates have been identified. There have been suggestions that such dwarfs may be tidally disrupted in regions of high galactic density, but may be prevalent in low density regions. We offer data from three parallel programs relevant to this issue. (1) A large number of Im galaxies throughout the Local Supercluster have been mapped in the HI spectral line using the Arecibo Radiotelescope, and we can establish the frequency with which HI disks much more extended than their optically visible portions are found. (2) Our extensive mapping of spiral and dwarf galaxies in the Virgo cluster allows us to set stringent limits on the density of star-free Hi clouds in that cluster. (3) We have conducted a sampling of the void in the distribution of galaxies toward the super galactic pole, optimized for finding low-mass HI clouds at redshifts out to approximately 2000 km/s

Contamination control by use of ethylene oxide

The uses of ethylene oxide as a decontaminating agent for planetary quarantine related applications are reported. Aspects discussed include: applications and limitations, chemical and physical properties, germicidal activity, methods of applications, and effects on personnel

Method of identifying clusters representing statistical dependencies in multivariate data

Approach is first to cluster and then to compute spatial boundaries for resulting clusters. Next step is to compute, from set of Monte Carlo samples obtained from scrambled data, estimates of probabilities of obtaining at least as many points within boundaries as were actually observed in original data

A computer program for a line-by-line calculation of spectra from diatomic molecules and atoms assuming a Voight line profile

Computer program predicts the spectra resulting from electronic transitions of diatomic molecules and atoms in local thermodynamic equilibrium. The program produces a spectrum by accounting for the contribution of each rotational and atomic line considered

Hot temperatures and morbidity : a systematic review and meta–analysis

Extreme temperatures have been shown to have a detrimental effect on health. Hot temperatures can increase the risk of mortality, particularly in people suffering from cardiorespiratory diseases. Given the onset of climate change, it is critical that the impact of temperature on health is understood, so that effective public health strategies can correctly identify vulnerable groups within the population. However, while effects on mortality have been extensively studied, temperature–related morbidity has received less attention. This study applied a systematic review and meta–analysis to examine the current literature relating to hot temperatures and morbidity

Figurative Sculpture in Paper Clay.

The artist discusses her Master of Fine Arts exhibition at East Tennessee State University, Carroll Reece Museum, Johnson City, Tennessee, March 9 - 17, 2001. The exhibition marked her return to organic, gestural work. Works are figurative, ceramic, sculpture, made of paper clay, ranging from 8-inch, wall mounted, bas-relief to life sized, full round figures. Most are slab constructed, unglazed or lightly glazed with soda wash. Topics discussed: the artist\u27s development, including the influences of Stephen De Staebler, in his treatment of the individual in mass culture, and of Mary Frank, in psychological content and in the use of negative space; similarities with sensuality in Georgia O\u27Keeffe\u27s flower paintings; paper clay technique and the work of Rosette Gault; ceramic workshops in Appalachia; mythology and feminism as inspiration; the effect of nature and environment on art; and Georges Jeanclos. Includes images and discussion of seventeen works

Biological Electron Transfer Mediators in Model Membrane Systems

The overall objective of this research was to create chemically well-defined liquid redox membranes, each of which would be capable of mediating a process of continuous electron transfer between an aqueous reductant on one side and an aqueous oxidant on the other. The transport of electrons between the two otherwise separate aqueous phases would be effected by membrane-bound reversible redox-active carrier molecules. It has been proposed that such molecules function in certain electron transfer processes associated with biological membranes. In particular, the isoprenoid benzoquinone coenzyme Q is thought to carry electrons (and protons) across the inner mitochondrial membrane during respiration, whilst the related naphthoquinone vitamin K acts as a carrier in photosynthetic and bacterial electron transfer. Since these two molecules were also found to possess all the attributes required of 'ideal' carriers, they were chosen for incorporation in all the redox membranes investigated during this research, in the hope that their behaviour in these simple model systems could be used to elucidate their biological function. Preliminary investigations were carried out to find suitable aqueous reductants and reducible substrates. A wide variety of common redox reagents, and several biological molecules, were tested for their ability to reduce coenzyme Q10 and vitamin K1, or to reoxidise their quinol forms, in biphasic reactions in which the quinone/quinol in hexane solution was equilibrated anaerobically over the aqueous reagent. A number of criteria were specified defining 'ideal' reductants, substrates and carriers, and control experiments were performed to assess the ideality of the reagents used. In general terms, coenzyme Q was found to be reduced by a wider range of reductants than vitamin K, while dihydrovitamin K was much more easily reoxidised than reduced coenzyme Q. Both quinones reacted readily at pH 7 with reduced methyl viologen and flavin mononucleotide free radicals, which behaved as ideal reductants. Electron paramagnetic resonance spectroscopy revealed the presence of semiquinone free radical species of coenzyme Q and vitamin K at the hexane/aqueous interface during these reactions. To establish continuous membrane-mediated electron transfer processes, experiments were conducted in an H-shaped reaction vessel in which the quinone solution (in hexane) formed a bridge between the aqueous reductant and aqueous oxidant in the lower limbs. Reduced methyl viologen, in large molar excess over the quinone and substrate, was routinely used as a reductant, and the kinetics of reduction of various substrates were followed spectrophotometrically. Both coenzyme Q and vitamin K were shown to function as reversible electron carriers in these bulk membrane systems, but the rate of substrate reduction was always very much slower when coenzyme Q was used. For this reason, more detailed studies were restricted to vitamin K as electron carrier. The kinetics of reduction of methylene blue by dihydrovitamin K were first order with respect to the oxidised dye, and the measured rate constant was consistent with diffusion control on the substrate side of the interface. The reaction was inhibited to varying degrees by the addition of different amphipathic phospholipids to the membrane. With cytocnrome c as substrate, the biphasic reaction with dihydrovitamin K was no longer diffusion-controlled, but was determined by mechanistic factors. The very slow, apparently zero-order reaction was greatly stimulated by the addition of the mitochondrial phospholipid cardio-lipin to the membrane, and the variation of the reaction rate with ionic strength of the aqueous phase could be explained in terms of binding between the acidic phospholipid and the basic protein. Such interactions are proposed to be of importance in the functional organisation of the mitochondrial membrane. Having established the abilities of coenzyme Q and vitamin K to act as electron carriers across a bulk hydrocarbon phase, attempts were made to improve the biological model by reducing the thickness of the membrane to the dimensions of a lipid bilayer. The two model systems studied were planar bimolecular lipid membranes (BLM) and closed unilamellar lipid vesicles (liposomes). The stabilities and thicknesses of a large number of BLM formed from a selection of amphipathic lipids and lipid mixtures were examined, and 'recipes' were found for membrane-forming solutions which yielded stable bilayers containing either vitamin K or coenzyme Q. A membrane cell was developed, allowing electron transfer across ultrathin membranes to be followed spectrophotometrically. Unfortunately, the instability of lipid bilayers within the apparatus did not allow kinetics experiments to be performed using BLM. However, electron transfer across thicker lens membranes, mediated by vitamin K, was demonstrated. (Abstract shortened by ProQuest.)