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Search Results: 1 - 10 of 160012 matches for " William B. White "
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Identification of cave minerals by Raman spectroscopy: new technology for non-destructive analysis
White William B.
International Journal of Speleology , 2006,
Abstract: The usual tools are X-ray powder diffraction, the optical microscope, and the scanning electron microscope. X-ray diffraction gives a definitive fingerprint by which the mineral can be identified by comparison with a catalog of reference patterns. However, samples must be ground to powder and unstable hydrated minerals may decompose before analysis is complete. Raman spectroscopy also provides a fingerprint useful for mineral identification but with the additional advantage that some a-priori interpretation of the spectra is possible (distinguishing carbonates from sulfates, for example). Because excitation of the spectra is by means of a laser beam, it is possible to measure the spectra of samples in sealed glass containers, thus preserving unstable samples. Because laser beams can be focused, spectra can be obtained from individual grains. New technology has reduced the size of the instrument and also the sensitivity of the optical system to vibration and transport so that a portable instrument has become possible. The sampling probe is linked to the spectrometer by optical fibers so that large specimens can be examined without damage. Comparative spectra of common cave minerals demonstrate the value of Raman spectra as an identification technique.
Speleothem microstructure/speleothem ontogeny: a review of Western contributions
White William B.
International Journal of Speleology , 2012,
Abstract: Mineral ontogeny is the study of the growth and development of mineral deposits in general and, in the present context, speleothems in particular. Previous researchers, mainly in Russia, have developed a nomenclatural hierarchy based on the forms and habits of individual crystals and the assembly of individual crystals into both monomineralic and polymineralic aggegates (i.e. speleothems). Although investigations of the growth processes of speleothems are sparse, there is a large literature on growth processes of speleothem minerals and related crystals in the geochemical and materials science literature. The purpose of the present paper is to sort through the various concepts of crystal growth and attempt to relate these to observations on speleothems and to the Russian conceptual framework of mineral ontogeny. For calcite, the most common mineral in speleothems, the activation energy for two dimensional nucleation (required for the growth of large single crystals) is almost the same as the activation energy for three- dimensional nucleation (which would result in the growth of many small crystals). Calcite growth is highly sensitive to minor impurities that may poison growth in certain crystallographic directions or may poison growth altogether. Extensive recent research using the atomic force microscope (AFM) provides many details of calcite growth including the transition from growth on screw dislocations to growth by two-dimensional nucleation. The deposition of aragonite speleothems requires metastable supersaturation curve and is usually ascribed to the impurities Mg2+ and Sr2+. AFM studies reveal that Mg2+ poisons calcite growth by blocking deposition sites on dislocations, thus allowing supersaturation to build up past the aragonite solubility curve. Sr2+ precipitates as a Sr-rich nucleus with the aragonite structure which acts as a template for aragonite growth. The different morphology of gypsum speleothems can be explained by the different growth habit of gypsum. Examples of twinned growth, dendrite growth, and spherulitic growth are common in the crystal growth literature and can be used to interpret the corresponding cave forms. Interpretation of monomineralic aggregate growth follows from individual crystal mechanisms. Interpretation of polymineralic aggregate growth requires knowing the evolving chemistry which in turn requires new methods for the sampling and analysis of microliter or nanoliter quantities of fluid.
Effects of Telmisartan with Hydrochlorothiazide versus Valsartan with Hydrochlorothiazide in Patients with Moderate-to-Severe Hypertension
Ravi Marfatia,William B. White,Helmut Schumacher
International Journal of Hypertension , 2012, DOI: 10.1155/2012/976828
Abstract: Combination therapy is recommended for patients with blood pressure (BP) significantly above goal by recent consensus guidelines around the globe. The use of angiotensin II receptor blockers (ARBs) alone or in combination with a thiazide diuretic is a preferred treatment strategy due to both efficacy and safety considerations. However, there are few data known about the benefits of ARB-diuretic combination therapy in patients with moderate-to-severe hypertension. We performed a subanalysis from two large clinical trials that compared the antihypertensive effects of telmisartan 80 mg versus valsartan 160 mg, both combined with hydrochlorothiazide (HCTZ) 25 mg in a subpopulation of 725 patients with moderate-to-severe hypertension (systolic BP SBP ≥ 160 mm Hg). Treatment with telmisartan-HCTZ induced significantly greater reductions in BP (−31.1/−18.3 mm Hg) than valsartan-HCTZ (−28.4/−16.3 mm Hg; SBP =0.0265, diastolic BP =0.0041). More patients receiving the telmisartan combination achieved a BP goal < 140/90 mm Hg than those receiving valsartan-HCTZ. There were similar safety and tolerability data for the two active treatment groups. These findings support the use of longer-acting ARBs combined with higher doses of thiazide diuretic to improve BP control in patients with moderate-to-severe hypertension.
Measurement of luminescent banding in speleothems: some techniques and limitations
Crowell Bryan E.,White William B.
International Journal of Speleology , 2012,
Abstract: Speleothems, especially flowstone and cylindrical stalagmites, exhibit phosphorescence which is often banded on the scale of a few tens of micrometers. The luminescence bands are paleoclimatic records with a very high temporal resolution. A technique has been developed using a laser source and a high resolution Raman spectrometer with microscope and computer-controlled translation stage for both luminescence profiles and luminescence spectroscopy. Luminescence intensity could be measured as a function of traverse distance with a spatial resolution of 2 – 3 μm. Potential sources of error include loss of intensity due to radiation damage by the laser beam, irregularities, cracks, and inclusions on the polished speleothem surface, and defocusing of the beam along the traverse path.
Effects of Telmisartan with Hydrochlorothiazide versus Valsartan with Hydrochlorothiazide in Patients with Moderate-to-Severe Hypertension
Ravi Marfatia,William B. White,Helmut Schumacher
International Journal of Hypertension , 2012, DOI: 10.1155/2012/976828
Abstract: Combination therapy is recommended for patients with blood pressure (BP) significantly above goal by recent consensus guidelines around the globe. The use of angiotensin II receptor blockers (ARBs) alone or in combination with a thiazide diuretic is a preferred treatment strategy due to both efficacy and safety considerations. However, there are few data known about the benefits of ARB-diuretic combination therapy in patients with moderate-to-severe hypertension. We performed a subanalysis from two large clinical trials that compared the antihypertensive effects of telmisartan 80?mg versus valsartan 160?mg, both combined with hydrochlorothiazide (HCTZ) 25?mg in a subpopulation of 725 patients with moderate-to-severe hypertension (systolic BP SBP ≥ 160?mm?Hg). Treatment with telmisartan-HCTZ induced significantly greater reductions in BP (?31.1/?18.3?mm?Hg) than valsartan-HCTZ (?28.4/?16.3?mm?Hg; SBP , diastolic BP ). More patients receiving the telmisartan combination achieved a BP goal < 140/90?mm?Hg than those receiving valsartan-HCTZ. There were similar safety and tolerability data for the two active treatment groups. These findings support the use of longer-acting ARBs combined with higher doses of thiazide diuretic to improve BP control in patients with moderate-to-severe hypertension. 1. Introduction The angiotensin II receptor blockers (ARBs) are effective antihypertensive agents with tolerability profiles similar to placebo [1–4]. The use of ARBs and/or angiotensin converting enzyme (ACE) inhibitors, alone or in combination with a calcium channel blocker or with a thiazide diuretic, has become the cornerstone of hypertension management [2, 5, 6]. A series of landmark clinical trials have demonstrated that ARBs reduce cardiovascular (CV) morbidity and mortality in a variety of types of hypertensive patients [7–13]. In seeking to improve blood pressure (BP) control, use of hydrochlorothiazide (HCTZ) at 25?mg rather than 12.5?mg in combination with ARBs and ACE inhibitors is recognized as an effective and well-tolerated strategy [1, 2, 14]. Two independent and identically designed trials were previously conducted to evaluate the benefits and safety of two single-pill combination (SPC) therapies: telmisartan 80?mg plus HCTZ 25?mg (T80/H25) and valsartan 160?mg plus HCTZ 25?mg (V160/H25) in patients with stages 1 and 2 hypertension [15, 16]. A pooled analysis of these two studies provided support for the use of ARBs with this higher 25?mg dose of thiazide diuretic; furthermore, the analysis demonstrated that T80/H25 resulted in greater reductions in
Candoluminescence of cave gypsum
Sweet John R.,Hess John W.,White William B.
International Journal of Speleology , 2010,
Abstract: A selection of gypsum specimens from a variety of caves as well as CaSO4 synthesized in the laboratory emit both a green and yellow candoluminescence when excited by a hydrogen diffusion flame. The green emission is attributed to dehydration of gypsum to bassanite and the yellow emission appears upon further dehydration to anhydrite. The source of the luminescence is ascribed to minor concentrations of Mn2+ in the gypsum.
Safety and Tolerability of Edivoxetine for Long-Term Treatment of Major Depressive Disorder in Adult Patients  [PDF]
Tina M. Oakes, James M. Martinez, Mary Anne Dellva, Celine Goldberger, Beth A. Pangallo, Mark E. Bangs, Jonna Ahl, William B. White
Open Journal of Psychiatry (OJPsych) , 2014, DOI: 10.4236/ojpsych.2014.42017
Abstract:

This 12-month open-label, but dose-blinded extension phase, evaluated the safety and tolerability of flexibly-dosed edivoxetine (6, 9, 12 or 18 mg once daily) in patients (N = 397) with major depressive disorder, who completed the 10-week randomized, double-blind, placebo-controlled acute phase of the study.All patients were treated with edivoxetine during the extension phase. The mean age of the patients was 45 years, and most were white females. Safety evaluations included assessment of treatment-emergent adverse events (TEAEs), laboratory and vital sign measures, and suicidality. Within-group t-tests based on a 2-sided significance level of 0.05 and 95% confidence levels were used to assess whether changes from baseline were statistically significant from zero. The overall completion rate was 54%. Adverse event was the most common (14.4%) reason for discontinuation, which included blood pressure increased (1.3%), heart rate increased (1.3%), anxiety (1.0%), and tachycardia (1.0%). At least 1 TEAE was reported by 72.3% of patients, of which headache (10.8%) and hyperhidrosis (10.1%) were the most common; 2.8% of patients had ≥1 serious adverse events, and there were no completed suicides. No

Metals in New Zealand Undaria pinnatifida (Wakame)  [PDF]
Leo Hau, John Robertson, William Lindsey White
Open Journal of Marine Science (OJMS) , 2014, DOI: 10.4236/ojms.2014.43016
Abstract:
Undaria pinnatifida, Wakame is a popular edible seaweed in its native Asia and was first recorded in New Zealand in Wellington Harbor in 1987. It is classified as an unwanted species under the Biosecurity Act 1993, but there is growing interest in harvesting this seaweed for human consumption. The aim of this study was to evaluate the concentrations of metals in U. pinnatifida from several locations (Marlborough Sounds and Wellington harbor) and across seasons. In brief, the highest monthly mean concentration of metals found in New Zealand wild U. pinnatifida was Ca (16.97g·kg-1), K (48.48 g·kg-1), Mg (9.47 g·kg-1), P (12.05 g·kg-1), Cr (1.04 mg·kg-1), Cu (3.78 mg·kg-1), Mn (14.61 mg·kg-1), Ni (2.78 mg
Dark-field transmission electron microscopy and the Debye-Waller factor of graphene
Brian Shevitski,Matthew Mecklenburg,William A. Hubbard,E. R. White,Ben Dawson,M. S. Lodge,Masa Ishigami,B. C. Regan
Physics , 2012, DOI: 10.1103/PhysRevB.87.045417
Abstract: Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary.
Using a neural network to backtranslate amino acid sequences
White,Gilbert; Seffens,William;
Electronic Journal of Biotechnology , 1998,
Abstract: a neural network (nn) was trained on amino and nucleic acid sequences to test the nn?s ability to predict a nucleic acid sequence given only an amino acid sequence. a multi-layer backpropagation network of one hidden layer with 5 to 9 neurons was used. different network configurations were used with varying numbers of input neurons to represent amino acids, while a constant representation was used for the output layer representing nucleic acids. in the best-trained network, 93% of the overall bases, 85% of the degenerate bases, and 100% of the fixed bases were correctly predicted from randomly selected test sequences. the training set was composed of 60 human sequences in a window of 10 to 25 codons at the coding sequence start site. different nn configurations involving the encoding of amino acids under increasing window sizes were evaluated to predict the behavior of the nn with a significantly larger training set. this genetic data analysis effort will assist in understanding human gene structure. benefits include computational tools that could predict more reliably the backtranslation of amino acid sequences useful for degenerate pcr cloning, and may assist the identification of human gene coding sequences (cds) from open reading frames in dna databases.
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