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Search Results: 1 - 10 of 107171 matches for " Lee W; "
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Gravitational radiation from mergers of black hole neutron star binaries
W. H. Lee,W. Kluzniak
Physics , 1997,
Abstract: Angular momentum loss via the emission of gravitational waves must eventually drive compact binaries containing black holes and/or neutron stars to coalesce. The resulting events are primary candidate sources for detectors such as VIRGO and LIGO. We present calculations of gravitational radiation waveforms and luminosities for the coalescence of a black hole-neutron star binary, performed in the quadrupole approximation using a Newtonian smooth particle hydrodynamics code. We discuss the dependence of the waveforms and the total emitted luminosity as well as the final configuration of the system on the initial mass ratio and the degree of tidal locking.
Black hole neutron star coalescence as a source of gamma-ray bursts
W. H. Lee,W. Kluzniak
Physics , 1997, DOI: 10.1063/1.55453
Abstract: We present the results of hydrodynamic (SPH) simulations showing the coalescence of a black hole with a neutron star to be a promising theoretical source of short duration gamma-ray bursts. The favorable features of the process include rapid onset, millisecond variability, a duration much longer than the dynamical timescale, and a range of outcomes sufficient to allow variety in the properties of individual gamma-ray bursts. Interestingly, the process of coalescence differs rather markedly from past predictions.
Simulations of binary coalescence of a neutron star and a black hole
W. Kluzniak,W. H. Lee
Physics , 1997, DOI: 10.1086/311151
Abstract: We present the results of Newtonian hydrodynamic simulations of the coalescence of a binary consisting of a black hole with a neutron star. The calculations show that for a wide range of initial conditions the core of the neutron star survives the initial mass transfer episode. We therefore identify black hole-neutron star binaries as the astrophysical production site of low mass neutron stars unstable to explosion. The relevance of the simulations to the theory of gamma-ray bursts is also discussed.
The Role of Atypical Protein Kinase C in CSF-1-Dependent Erk Activation and Proliferation in Myeloid Progenitors and Macrophages
Angel W. Lee
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025580
Abstract: Colony stimulating factor-1 (CSF-1 or M-CSF) is the major physiological regulator of the proliferation, differentiation and survival of cells of the mononuclear phagocyte lineage. CSF-1 binds to a receptor tyrosine kinase, the CSF-1 receptor (CSF-1R). Multiple pathways are activated downstream of the CSF-1R; however, it is not clear which pathways regulate proliferation and survival. Here, we investigated the role of atypical protein kinase Cs (PKCζ) in a myeloid progenitor cell line that expressed CSF-1R (32D.R) and in primary murine bone marrow derived macrophages (BMMs). In 32D.R cells, CSF-1 induced the phosphorylation of PKCζ and increased its kinase activity. PKC inhibitors and transfections with mutant PKCs showed that optimal CSF-1-dependent Erk activation and proliferation depended on the activity of PKCζ. We previously reported that CSF-1 activated the Erk pathway through an A-Raf-dependent and an A-Raf independent pathway (Lee and States, Mol. Cell. Biol. 18, 6779). PKC inhibitors did not affect CSF-1 induced Ras and A-Raf activity but markedly reduced MEK and Erk activity, implying that PKCζ regulated the CSF-1-Erk pathway at the level of MEK. PKCζ has been implicated in activating the NF-κB pathway. However, CSF-1 promoted proliferation in an NF-κB independent manner. We established stable 32D.R cell lines that overexpressed PKCζ. Overexpression of PKCζ increased the intensity and duration of CSF-1 induced Erk activity and rendered cells more responsive to CSF-1 mediated proliferation. In contrast to 32D.R cells, PKCζ inhibition in BMMs had only a modest effect on proliferation. Moreover, PKCζ -specific and pan-PKC inhibitors induced a paradoxical increase in MEK-Erk phosphorylation suggesting that PKCs targeted a common negative regulatory step upstream of MEK. Our results demonstrated that CSF-1 dependent Erk activation and proliferation are regulated differentially in progenitors and differentiated cells.
β2 adrenergic agonists in acute lung injury? The heart of the matter
Jae W Lee
Critical Care , 2009, DOI: 10.1186/cc8171
Abstract: In their manuscript, Briot and colleagues [1] assessed the role of terbutaline, a β2 agonist, on lung microvascular permeability in an acute lung injury (ALI) in vivo model to uncover the underlying mechanisms of therapeutic benefit. The authors used a recently developed broncho-alveolar lavage technique [2] to repeatedly measure (every 15 minutes) the time-course of capillary-alveolar leakage of a macromolecule, fluorescein-labeled dextran (FITC-D70), in 19 oleic acid (OA) lung injured dogs. With OA injury, the transport rate of coefficient of FITC-D70, used as a measure of permeability, from blood to alveoli increased sharply and peaked at 30 minutes. Thereafter, FITC-D70 leakage decreased gradually until the end of the experiment at 4 hours. Surprisingly, the infusion of terbutaline, given following 90 minutes of OA injury, interrupted the recovery phase, further aggravating FITC-D70 leakage. The authors discovered that with the onset of terbutaline infusion at 0.25 μg/kg/minute, the β2 inotropic effect of the drug significantly [3] increased the cardiac output and pulmonary artery pressure by 50% and 30%, respectively, while decreasing the pulmonary vascular resistance by 40%. With increased pulmonary vascular recruitment, the authors surmised that the terbutaline infusion increased perfusion surface area or recruited leaking capillaries from hypoxic vasoconstriction, which led to an aggravation of FITC-D70 leakage into the alveoli.Previously, β2 agonist therapy was considered promising for ALI based on several characteristics seen in both animal and human models: the ability to increase the rate of vectorial salt and water transport by increased intracellular cAMP, leading to improved alveolar fluid clearance (AFC) [4,5] - clinically, impaired AFC in patients with ALI is associated with higher mortality [6]; the ability to improve lung endothelial permeability to protein [7]; and the anti-inflammatory properties of β2 agonists. Maris and colleagues [8] demonstr
Approximate pexiderized gamma-beta type functions
Young W Lee
Journal of Inequalities and Applications , 2013, DOI: 10.1186/1029-242X-2013-14
Abstract: MSC: 39B72, 38B22, 39B82.
The midpoint set of a cantor set
Ken W. Lee
International Journal of Mathematics and Mathematical Sciences , 1978, DOI: 10.1155/s016117127800054x
Abstract: A non-endpoint of the Cantor ternary set is any Cantor point which is not an endpoint of one of the remaining closed intervals obtained in the usual construction process of the Cantor ternary set in the unit interval. It is shown that the set of points in the unit interval which are not midway between two distinct Cantor ternary points is precisely the set of Cantor nonendpoints. It is also shown that the generalized Cantor set C , for 1/3< <1, has void intersection with its set of midpoints obtained from distinct members of C .
The No Child Left Behind Act and the legacy of federal aid to education.
Lee W. Anderson
Education Policy Analysis Archives , 2005,
Abstract: The No Child Left Behind Act of 2001 (NCLB) builds on a tradition of gradually increasing federal involvement in the nation's public school systems. NCLB both resembles and differs from earlier federal education laws. Over the past five decades, conservatives in Congress softened their objections to the principle of federal aid to schools and liberals downplayed fears about the unintended consequences of increased federal involvement. The belief in limited federal involvement in education has been replaced by the presumption by many legislators that past federal investments justify imposing high stakes accountability requirements on schools.
Improved Error Estimate for the Valence Approximation
W. Lee,D. Weingarten
Physics , 1998, DOI: 10.1016/S0920-5632(97)00956-0
Abstract: We construct a systematic mean-field-improved coupling constant and quark loop expansion for corrections to the valence (quenched) approximation to vacuum expectation values in the lattice formulation of QCD. Terms in the expansion are evaluated by a combination of weak coupling perturbation theory and a Monte Carlo algorithm.
Scalar Quarkonium Masses
W. Lee,D. Weingarten
Physics , 1996, DOI: 10.1016/S0920-5632(96)00624-X
Abstract: We evaluate the valence approximation to the mass of scalar quarkonium for a range of different parameters. Our results strongly suggest that the infinite volume continuum limit of the mass of $s\overline{s}$ scalar quarkonium lies well below the mass of $f_J(1710)$. The resonance $f_0(1500)$ appears to the best candidate for $s\overline{s}$ scalar quarkonium.
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