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A T Watson

Publications and source records attributed to A T Watson.

122 records · Page 7Linked to original sources
PubMed2001

Measurement of the decays B--> phiK and B--> phiK*.

We have observed the decays B--> phiK and phiK(*) in a sample of over 45 million B mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are B(B+--> phiK+) = (7.7(+1.6)(-1.4)+/-0.8)x10(-6), B(B0--> phiK0) = (8.1(+3.1)(-2.5)+/-0.8)x10(-6), B(B+--> phiK(*+)) = (9.7(+4.2)(-3.4)+/-1.7)x10(-6), and B(B0--> phiK(*0)) = (8.7(+2.5)(-2.1)+/-1.1)x10(-6). We also report the upper limit B(B+--> phipi(+))<1.4x10(-6) ( 90% C.L.).

Journal Article↗
PubMed2001

Observation of CP violation in the B(0) meson system.

We present an updated measurement of time-dependent CP-violating asymmetries in neutral B decays with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. This result uses an additional sample of Upsilon(4S) decays collected in 2001, bringing the data available to 32 x 10(6) BB macro pairs. We select events in which one neutral B meson is fully reconstructed in a final state containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2 beta, is derived from the decay time distributions in such events. The result sin2 beta = 0.59+/-0.14(stat)+/-0.05(syst) establishes CP violation in the B(0) meson system. We also determine absolute value of lambda = 0.93+/-0.09(stat)+/-0.03(syst), consistent with no direct CP violation.

Journal Article↗
PubMed2001

Measurement of CP-violating asymmetries in B0 decays to CP eigenstates.

We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23x10(6) Upsilon(4S)-->BbarB decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events in which one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay time distributions in such events. The result is sin2beta = 0.34+/-0.20 (stat)+/-0.05 (syst).

Journal Article↗
PubMed2001

Chlamydomonas nuclear mutants that fail to assemble respiratory or photosynthetic electron transfer complexes.

We are using a molecular-genetic approach to investigate the role of nuclear genes in the biogenesis of the electron transfer complexes of mitochondria and chloroplasts. Our analysis of nuclear mutants of the green alga Chlamydomonas that are defective in respiration or photosynthesis has led to the identification of genes encoding factors required for the expression of specific organellar genes, and genes encoding structural components of the complexes.

Animals↗
PubMed1995

Characterization of fractured permeable porous media using relaxation-weighted imaging techniques.

The inversion time (TI) weighted inversion-recovery spin-echo (IRSE) imaging technique was used for laboratory characterization of fractures and porous matrix in permeable media. The method is based on the fact that relaxation rates in fractures and those in surrounding porous matrix are substantially different. Thus, by selectively suppressing imaging signals from either fractures or porous matrix, one can highlight fluid distributions in either of these regions so that fractures can be unambiguously identified and surrounding porous structures can be characterized. The advantages over conventional NMR spin-echo imaging are demonstrated with various fractured porous rock types. A technique to speed acquisitions of images of fluid distributions in porous matrix is also demonstrated.

Calcium Carbonate↗
PubMed1994

Measurements and analysis of fluid saturation-dependent NMR relaxation and linebroadening in porous media.

NMR T1, T2 and spectral linewidth measurements were conducted in rock samples with different saturations obtained by drainage experiments. Saturation dependent T1 was found to follow a power-law relationship and the inverse of linewidth to follow a linear dependence with saturation. These phenomena can be explained by considering that the fluids are distributed in different sized pores for different saturation states. A method is proposed for calculating wetting phase relative permeabilities using T1 data at various saturations.

Magnetic Resonance Spectroscopy↗
PubMed1993

The use of agarose gels for quantitative determination of fluid saturations in porous media.

The use of agarose gel reference standards for quantifying petrophysical properties in porous media is described. The specific interest is to determine the values of fluid saturations and porosity in oil bearing rocks; the MRI methodology for estimating these properties is discussed. It is shown that the relaxation times of the gel reference standard and the relaxation times of the fluid contained in the porous media affect the estimation process. The determination of porosity and fluid saturations can be greatly simplified if the relaxation times of the reference standard and the relaxation times of the fluid are closely matched. Gel concentration of paramagnetic impurities in the form of copper ions is used to control the longitudinal relaxation properties. The relaxation properties of agarose gels, as a function of agarose and paramagnetic impurity concentrations, have been measured at 2.0 T. The data are well fitted by a simple polynomial in agarose concentration and paramagnetic impurity concentration. Finally, a one-dimensional imaging example of use of agarose gels as reference phantoms is discussed.

Engineering↗
PubMed1992

Quantitative NMR imaging of multiphase flow in porous media.

Quantitative description of multiphase flow in porous media and local saturation distributions at steady states are of fundamental importance for petroleum recovery. The use of MRI provides an unprecedented means for obtaining such information. In this paper, profile imaging techniques for quantitative evaluation of fluid saturations during flow experiments in porous media are developed. The procedures for overcoming problems arising from very short, fluid saturation-dependent and spatial variation of T2, which are common in porous media, were addressed. The general methods developed should also be applicable to similar inhomogeneous biological systems. Experimental NMR imaging measurements of two-phase displacement were conducted in several limestones and sandstones representing various different types of pore structures, including a macroscopically homogeneous structure, a laminated structure, and a sample that exhibits porosity at different scales. The advantages of using each different type of profile imaging sequence to investigate flow in different types of porous structures are demonstrated. Images showing many features of multiphase flow, including nonuniform flow through different bedding structures, are obtained during the flow experiments. The use of profile images for obtaining many important petrophysical properties, such as permeability, porosity, saturation, and pore structural information, is discussed.

Geological Phenomena↗
PubMed1991

Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris.

Glutamine synthetase (GS) activity increased over three-fold in developing primary leaves of Phaseolus vulgaris L. This increase was shown to be the result of differential expression of three members of the GS gene family: gln-alpha and gln-beta, which encode cytosolic GS polypeptides, and gln-delta, which encodes the chloroplast-located GS. The gln-delta gene was the most highly expressed GS gene and was regulated in a complex manner with two different transcripts accumulating differentially during leaf development. This gene was expressed weakly in the dark and was induced strongly by light; this induction was shown not to be an indirect effect of photorespiration. In the long term, gln-delta showed increased expression in photorespiring compared with non-photorespiring leaves. However, in the short term, there was no induction of gln-delta following transfer of plants to photorespiratory conditions. These results suggest that regulation of gln-delta by photorespiration was the result of indirect, long-term effects on cellular metabolism. In general, in all these experiments, analysis of cytosolic versus chloroplastic GS polypeptides and of the GS isoenzyme profiles showed the same pattern of changes in abundance as that observed for the mRNAs suggesting that regulation of GS gene expression occurred primarily at the mRNA level. However, it was noteworthy that the delta isoenzyme remained at a high abundance in older leaves, grown in both light and dark, despite a decrease in abundance of gln-delta mRNA.

Blotting, Northern↗
PubMedDate not supplied

Estimation of porous media flow functions using NMR imaging data.

Nuclear magnetic resonance (NMR) imaging data measured during two-phase displacement experiments on porous rock core samples are used in an inverse problem methodology to estimate the two-phase flow functions relative permeability and capillary pressure. Nuclear magnetic resonance imaging data contain valuable information about variation of fluid states within the core sample and are therefore important for accurate estimation of these properties. A precise agreement between measured data, which also includes pressure drop across the core samples, and the data simulated by using the estimated flow functions is found, indicating accurate flow function estimates.

Alkanes↗
PubMedDate not supplied

The effect of wait time on T2 distributions from NMR experiments.

Nuclear magnetic resonance (NMR) relaxation curves for both T1 and T2 on two brine-saturated core plugs have been measured at 1 MHz. T2 distributions were extracted from Carr-Purcell-Meiboom-Gill (CPMG) measurements using different wait times between consecutive echo sequences. The analysis was performed with both a limited number of exponentials and a continuous B-spline basis. The distributions depend strongly on wait time. The distributions were generally restored to the true distributions when a wait time correction was applied.

Humans↗
PubMedDate not supplied

NMR characterization of hydrocarbon gas in porous media.

Laboratory investigations of nuclear magnetic resonance (NMR) relaxation properties of methane gas in bulk and in porous media are reported. Measurements were performed for methane alone and together with water in glass bead packs and Bentheimer sandstone. Results indicate that surface relaxation effects can be significant and that diffusion effects dominate observed T2 relaxation.

Gases↗
PubMedDate not supplied

Quantitation of barbiturates by a modification of the EMIT-tox serum barbiturate assay.

A modification of the Syva EMIT-tox Serum Barbiturate Assay was developed to provide a rapid and practical method for quantitating serum barbiturates. Standard curves for eight selected barbiturates were run using specific sets of standards for each. Correlation coefficients, slopes, and y-intercepts for the curves of best fit were determined by the least-squares method. Between-run and within-run precision analysis indicated acceptable reproducibility for barbiturate concentrations in high therapeutic to toxic serum levels. A case report describing the use of this method for the determination of serum pentobarbital concentrations during therapy for intracranial hypertension is presented. The modified EMIT assay may be useful for monitoring barbiturate blood levels in overdose, and when used for therapy of ischemic brain damage.

Antibody Specificity↗