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Search Results: 1 - 10 of 263045 matches for " B. K. Hamilton "
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Recent Results in Semileptonic B Decays With BaBar
B. K. Hamilton
Statistics , 2011,
Abstract: In this note, recent results of studies of semileptonic B meson decays from \babar\ are discussed and preliminary results given. In particular, a recent measurement of $\mathcal{B}(B \to D^{(*)}\tau \nu)$ and the ratio $\mathcal{B}(B \to D^{(*)}\tau \nu)/\mathcal{B}(B \to D^{(*)}\ell \nu)$ is presented. For the $D^*$ mode, a branching fraction of $1.79\pm0.13\stat\pm0.17\syst$ is found, with a ratio of $0.325\pm0.023\stat\pm0.027\syst$. For the $D$ mode, the results are $1.04\pm0.12\stat\pm0.14\syst$ and $0.456\pm0.053\stat\pm0.056\syst$, respectively. In addition, a study of $B_s$ production and semileptonic decays using data collected in a center-of-mass energy region above the \Y4S resonance is discussed. The semileptonic branching fraction $\mathcal{B}(B_s \to \ell \nu X)$ is measured to be $9.9{}^{+2.6}_{-2.1}\stat{}^{+1.3}_{-2.0}\syst$.
用生物反应器生产l-氨基酸
b.k.hamilton,梅芳
中国生物工程杂志 , 1986,
Abstract: 现已有几种l-氨基酸是用生物反应器中的酶或全细胞生产的。最早采用这种技术的例子之一是日本l-天冬氨酸的生产。最近放大了由肉桂酸和氨生产l-苯丙氨酸的生物反应器法,产物效价达60克/升以上,原料转化率约为90%。
Field-guided proton acceleration at reconnecting X-points in flares
B. Hamilton,K. G. McClements,L. Fletcher,A. Thyagaraja
Physics , 2003, DOI: 10.1023/A:1024204928413
Abstract: An explicitly energy-conserving full orbit code CUEBIT, developed originally to describe energetic particle effects in laboratory fusion experiments, has been applied to the problem of proton acceleration in solar flares. The model fields are obtained from solutions of the linearised MHD equations for reconnecting modes at an X-type neutral point, with the additional ingredient of a longitudinal magnetic field component. To accelerate protons to the highest observed energies on flare timescales, it is necessary to invoke anomalous resistivity in the MHD solution. It is shown that the addition of a longitudinal field component greatly increases the efficiency of ion acceleration, essentially because it greatly reduces the magnitude of drift motions away from the vicinity of the X-point, where the accelerating component of the electric field is largest. Using plasma parameters consistent with flare observations, we obtain proton distributions extending up to gamma-ray-emitting energies (>1MeV). In some cases the energy distributions exhibit a bump-on-tail in the MeV range. In general, the shape of the distribution is sensitive to the model parameters.
The JNK- and AKT/GSK3β- Signaling Pathways Converge to Regulate Puma Induction and Neuronal Apoptosis Induced by Trophic Factor Deprivation
Kristin K. Ambacher, Kristen B. Pitzul, Meera Karajgikar, Alison Hamilton, Stephen S. Ferguson, Sean P. Cregan
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046885
Abstract: The AKT, GSK3 and JNK family kinases have been implicated in neuronal apoptosis associated with neuronal development and several neurodegenerative conditions. However, the mechanisms by which these kinase pathways regulate apoptosis remain unclear. In this study we have investigated the role of these kinases in neuronal cell death using an established model of trophic factor deprivation induced apoptosis in cerebellar granule neurons. BCL-2 family proteins are known to be central regulators of apoptosis and we have determined that the pro-apoptotic family member Puma is transcriptionally up-regulated in trophic factor deprived neurons and that Puma induction is required for apoptosis in vitro and in vivo. Importantly, we demonstrate that Puma induction is dependent on both JNK activation and AKT inactivation. AKT is known to regulate a number of downstream pathways, however we have determined that PI3K-AKT inactivation induces Puma expression through a GSK3β-dependent mechanism. Finally we demonstrate that the JNK and AKT/GSK3β pathways converge to regulate FoxO3a-mediated transcriptional activation of Puma. In summary we have identified a novel and critical link between the AKT, GSK3β and JNK kinases and the regulation of Puma induction and suggest that this may be pivotal to the regulation of neuronal apoptosis in neurodegenerative conditions.
Synthetic Sex Pheromone in a Long-Lasting Lure Attracts the Visceral Leishmaniasis Vector, Lutzomyia longipalpis, for up to 12 Weeks in Brazil
Daniel P. Bray,Vicky Carter,Graziella B. Alves,Reginaldo P. Brazil,Krishna K. Bandi,James G. C. Hamilton
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002723
Abstract: Current control methodologies have not prevented the spread of visceral leishmaniasis (VL) across Brazil. Here, we describe the development of a new tool for controlling the sand fly vector of the disease: a long-lasting lure, which releases a synthetic male sex pheromone, attractive to both sexes of Lutzomyia longipalpis. This device could be used to improve the effectiveness of residual insecticide spraying as a means of sand fly control, attracting L. longipalpis to insecticide-treated animal houses, where they could be killed in potentially large numbers over a number of weeks. Different lure designs releasing the synthetic pheromone (±)-9-methylgermacrene-B (CAS 183158-38-5) were field-tested in Ara?atuba, S?o Paulo (SP). Experiments compared numbers of sand flies caught overnight in experimental chicken sheds with pheromone lures, to numbers caught in control sheds without pheromone. Prototype lures, designed to last one night, were first used to confirm the attractiveness of the pheromone in SP, and shown to attract significantly more flies to test sheds than controls. Longer-lasting lures were tested when new, and at fortnightly intervals. Lures loaded with 1 mg of pheromone did not attract sand flies for more than two weeks. However, lures loaded with 10 mg of pheromone, with a releasing surface of 15 cm2 or 7.5 cm2, attracted female L. longipalpis for up to ten weeks, and males for up to twelve weeks. Approximately five times more sand flies were caught with 7.5 cm2 10 mg lures when first used than occurred naturally in non-experimental chicken resting sites. These results demonstrate that these lures are suitably long-lasting and attractive for use in sand fly control programmes in SP. To our knowledge, this is the first sex pheromone-based technology targeting an insect vector of a neglected human disease. Further studies should explore the general applicability of this approach for combating other insect-borne diseases.
The Allegro gravitational wave detector: Data acquisition and analysis
E. Mauceli,Z. K. Geng,W. O. Hamilton,W. W. Johnson,S. Merkowitz,A. Morse,B. Price,N. Solomonson
Physics , 1996, DOI: 10.1103/PhysRevD.54.1264
Abstract: We discuss the data acquisition and analysis procedures used on the Allegro gravity wave detector, including a full description of the filtering used for bursts of gravity waves. The uncertainties introduced into timing and signal strength estimates due to stationary noise are measured, giving the windows for both quantities in coincidence searches.
Caloric curves and critical behavior in nuclei
J. B. Natowitz,R. Wada,K. Hagel,T. Keutgen,M. Murray,A. Makeev,L. Qin,P. Smith,C. Hamilton
Physics , 2001, DOI: 10.1103/PhysRevC.65.034618
Abstract: Data from a number of different experimental measurements have been used to construct caloric curves for five different regions of nuclear mass. These curves are qualitatively similar and exhibit plateaus at the higher excitation energies. The limiting temperatures represented by the plateaus decrease with increasing nuclear mass and are in very good agreement with results of recent calculations employing either a chiral symmetry model or the Gogny interaction. This agreement strongly favors a soft equation of state. Evidence is presented that critical excitation energies and critical temperatures for nuclei can be determined over a large mass range when the mass variations inherent in many caloric curve measurements are taken into account.
Linear frictional forces cause orbits to neither circularize nor precess
B. Hamilton,M. Crescimanno
Physics , 2007, DOI: 10.1088/1751-8113/41/23/235205
Abstract: For the undamped Kepler potential the lack of precession has historically been understood in terms of the Runge-Lenz symmetry. For the damped Kepler problem this result may be understood in terms of the generalization of Poisson structure to damped systems suggested recently by Tarasov[1]. In this generalized algebraic structure the orbit-averaged Runge-Lenz vector remains a constant in the linearly damped Kepler problem to leading order in the damping coe
Higher titers of some H5N1 and recent human H1N1 and H3N2 influenza viruses in Mv1 Lu vs. MDCK cells
Sara B Hamilton, Diane E Wyatt, Brett T Wahlgren, Maureen K O'Dowd, Jane M Morrissey, Deirdre E Daniels, John A Lednicky
Virology Journal , 2011, DOI: 10.1186/1743-422x-8-66
Abstract: The 50% tissue culture infectious dose and plaque forming titer of many influenza A subtype H1N1, H3N2, and H5N1 viruses was higher in Mv1 Lu than in MDCK cells.The yields of influenza subtype H1N1, H3N2, and H5N1 viruses can be higher in Mv1 Lu cells than in MDCK cells.The infectivity of influenza viruses can differ among the various primary cells and continuous cell lines used for such measurements [1,2]. As the term "infectivity" has many meanings in virology, in this manuscript, infectivity is broadly defined as the ability of a virus particle to enter a host cell and form viable progeny virions. Measures of infectivity depend not only on the inherent susceptibility of a particular type of cell for a given influenza virus, but also on the methodology used for infecting the cells [such as the length of time the virus is left in contact with the cells, as the affinity/avidity of a virus for its receptor(s) may vary according to cell type], the quasispecies distribution within a particular influenza virus stock, and other variables.Accurate viable virus counts are essential for inhalation exposure studies with aerosolized viruses [3], for correlation of viable count to genome equivalence in level of detection studies, and other relevant work with influenza viruses. Quantitative RT-PCR methods are not suitable, as they do not distinguish between viable and non-viable virus particles. Indeed, infectious influenza virus particles comprise a minor subpopulation of biologically active particles (BAP) within a viral population [4]. The other BAP include interferon suppressing particles [4,5], defective interfering particles [4,6], and noninfectious cell-killing particles [4,7].Madin-Darby canine kidney (MDCK) epithelial cells are widely used for the isolation of human influenza A and B viruses and the determination of influenza A virus titers [1,8-11]. However, we (S. Hamilton and J. Lednicky, unpublished) and others [2,12] have observed that all things equal, the cytopa
Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography
J. F. Hamilton, A. C. Lewis, C. Bloss, V. Wagner, A. P. Henderson, B. T. Golding, K. Wirtz, M. Martin-Reviejo,M. J. Pilling
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2003,
Abstract: Photo-oxidation products from the reaction of a series of alkyl-benzenes, (benzene, toluene, p-xylene and 1,3,5-trimethyl-benzene) with hydroxyl radicals in the presence of NOx have been investigated using comprehensive gas chromatography (GCxGC). A GCxGC system has been developed which utilises valve modulation and independent separations as a function of both volatility and polarity. A number of carbonyl-type compounds were identified during a series of reactions carried out at the European Photoreactor (EUPHORE), a large volume outdoor reaction chamber in Valencia, Spain. Experiments were carried as part of the EXACT project (Effects of the oXidation of Aromatic Compounds in the Troposphere). Two litre chamber air samples were cryo-focused, with a sampling frequency of 30 minutes, allowing the evolution of species to be followed over oxidation periods of 3-6 hours. To facilitate product identification, several carbonyl compounds, which were possible products of the photo-oxidation, were synthesised and used as reference standards. For toluene reactions, observed oxygenated intermediates found included the co-eluting pair a-angelicalactone/4-oxo-2-pentenal, maleic anhydride, citraconic anhydride, benzaldehyde and p-methyl benzoquinone. In the p-xylene experiment, the products identified were E/Z-hex-3-en-2,5-dione and citraconic anhydride. For 1,3,5-TMB reactions, the products identified were 3,5-dimethylbenzaldehyde, 3,5-dimethyl-3H-furan-2-one and 3-methyl-5-methylene-5H-furan-2-one. Preliminary quantification was carried out on identified compounds using liquid standards. Comparison of FTIR and GCxGC for the measurement of the parent aromatics generally showed good agreement. Comparison of the concentrations observed by GCxGC to concentration-time profiles simulated using the Master Chemical Mechanism, MCMv3, demonstrates that this mechanism significantly over-predicts the concentrations of many product compounds and highlights the uncertainties which exist in our understanding of the atmospheric oxidation of aromatics.
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