820 research outputs found
Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
The problem of proton-antiproton motion in the --
system is investigated by means of the variational method. We introduce a
modified nuclear interaction through mass-scaling of the Born-Oppenheimer
potential. This improved treatment of the interaction includes the nondivergent
part of the otherwise divergent adiabatic correction and shows the correct
threshold behavior.
Using this potential we calculate the vibrational energy levels with angular
momentum 0 and 1 and the corresponding nuclear wave functions, as well as the
S-wave scattering length. We obtain a full set of all bound states together
with a large number of discretized continuum states that might be utilized in
variational four-body calculations. The results of our calculations gives an
indication of resonance states in the hydrogen-antihydrogen system
Nuclear targeting of the serine protease granzyme A (fragmentin-1)
Cytolytic granule-mediated target cell killing is effected in part through synergistic action of the membrane-acting protein perforin and serine proteases such as granzymes A (GrA) or B (GrB). In the present study we examine GrA cellular entry and nuclear uptake in intact mouse myeloid FDC-P1 cells exposed to perforin using confocal laser scanning microscopy, as well as reconstitute GrA nuclear uptake in vitro. GrA alone was found to be able to enter the cytoplasm of intact cells but did not accumulate in nuclei. In the presence of perforin, it specifically accumulated in the cell nuclei, with maximal levels about 2.5 times those in the cytoplasm after 2. 5 hours. In vitro, GrA accumulated in the nucleus and nucleolus maximally to levels that were four- and sixfold, respectively, those in the cytoplasm. In contrast, the active form of the apoptotic cysteine protease CPP32 did not accumulate in nuclei in vitro. Nuclear/nucleolar import of GrA in vitro was independent of ATP and not inhibitable by the non-hydrolyzable GTP analog GTPgammaS, but was dependent on exogenously added cytosol. Importantly, GrA was found to be able to accumulate in the nucleus of semi-intact cells in the presence of the nuclear envelope-permeabilizing detergent CHAPS, implying that the mechanism of nuclear accumulation was through binding to insoluble factors in the nucleus. GrB was found for the first time to be similar in this regard. The results support the contention that GrA and GrB accumulate in the nucleus through a novel nuclear import pathway, and that this is integral to induction of the nuclear changes associated with cytolytic granule-mediated apoptosis.David A. Jans, Lyndall J. Briggs, Patricia Jans, Christopher J. Froelich, Gayathri Parasivam, Sharad Kumar, Vivien R. Sutton and Joseph A. Trapan
Resonant Formation of Molecules in Deuterium: An Atomic Beam Measurement of Muon Catalyzed dt Fusion
Resonant formation of molecules in collisions of muonic tritium
() on D was investigated using a beam of atoms,
demonstrating a new direct approach in muon catalyzed fusion studies. Strong
epithermal resonances in formation were directly revealed for the
first time. From the time-of-flight analysis of fusion
events, a formation rate consistent with times the theoretical prediction was obtained. For the largest
peak at a resonance energy of eV, this corresponds to a rate
of s, more than an order of magnitude larger
than those at low energies.Comment: To appear in Phys. Rev. Let
Time dependence of breakdown in a global fiber-bundle model with continuous damage
A time-dependent global fiber-bundle model of fracture with continuous damage
is formulated in terms of a set of coupled non-linear differential equations. A
first integral of this set is analytically obtained. The time evolution of the
system is studied by applying a discrete probabilistic method. Several results
are discussed emphasizing their differences with the standard time-dependent
model. The results obtained show that with this simple model a variety of
experimental observations can be qualitatively reproduced.Comment: APS style, two columns, 4 figures. To appear in Phys. Rev.
The biology of cytotoxic cell granule exocytosis pathway: granzymes have evolved to induce cell death and inflammation
The granule exocytosis pathway of cytotoxic lymphocytes (Tc and NK cells) is critical for control of tumor development and viral infections. Granule-associated perforin and granzymes are key components in Tc cell-mediated function(s). On the basis of studies that showed granzymes A, B, C, K and M, to induce apoptosis in vitro, all granzymes were thought to also induce cell death in vivo. This review summarizes our present understanding of the biological processes elicited by purified granzyme A and granzyme as well as the processes induced by the more physiologically relevant cytotoxic cells secreting these proteases. The combined evidence supports the concept that the granule secretion pathway is not mono-specific but rather poly-functional including induction of pro-inflammatory cytokines, besides their widely appreciated apoptotic properties
Sedimentology and geochemistry of an urban coastal lake system: Coombabah Lake Nature Reserve, Gold Coast, Queensland
Combined treatment with memantine and galantamine-CR compared with galantamine-CR only in antidementia drug naive patients with mild-to-moderate Alzheimer's disease
Introduction: Several studies have tested the N-methyl-D-aspartate–receptor antagonist memantine as an add-on to pre-existing treatment with acetylcholinesterase inhibitors. The objective of this study was to evaluate the efficacy and safety of a combined memantine and galantamine-CR de novo regimen compared with galantamine-CR only treatment in never treated patients with mild-to-moderate Alzheimer's disease (AD). Methods: Antidementia drug–naïve participants (n = 232) with probable, mild-to-moderate AD, and mini-mental state examination scores between 15 and 26 (inclusive) were randomized to receive either 20 mg/day memantine plus 24 mg/day galantamine-CR or 24 mg/day galantamine-CR plus placebo in a 52-week, prospective, double-blind, controlled trial. The primary outcome measurement was the change on the Alzheimer's disease assessment scale-cognition score. Secondary measures comprised the Alzheimer's Disease Cooperative Study-activities of daily living inventory and the clinical dementia rating. Results: At the end of the trial, there were no statistically significant differences between the galantamine-CR/memantine combination and galantamine-CR only group in primary and secondary outcome measurements. The incidence and the severity of adverse events were similar between the groups. Discussion: In this trial, memantine in combination with galantamine-CR did not show an advantage with respect to cognition, function, and behavior in previously never treated patients with mild-to-moderate AD. There were no significant differences in tolerability and safety between the groups. Thus, a de novo combination treatment results in no significant improvement in disease progression (current controlled trials number: NCT01921972)
X-ray emission during the muonic cascade in hydrogen
We report our investigations of X rays emitted during the muonic cascade in
hydrogen employing charge coupled devices as X-ray detectors. The density
dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha,
K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of
liquid hydrogen density. In this density region collisional processes dominate
the cascade down to low energy levels. A comparison with recent calculations is
given in order to demonstrate the influence of Coulomb deexcitation.Comment: 5 pages, Tex, 4 figures, submitted to Physical Review Letter
Resummation of the Divergent Perturbation Series for a Hydrogen Atom in an Electric Field
We consider the resummation of the perturbation series describing the energy
displacement of a hydrogenic bound state in an electric field (known as the
Stark effect or the LoSurdo-Stark effect), which constitutes a divergent formal
power series in the electric field strength. The perturbation series exhibits a
rich singularity structure in the Borel plane. Resummation methods are
presented which appear to lead to consistent results even in problematic cases
where isolated singularities or branch cuts are present on the positive and
negative real axis in the Borel plane. Two resummation prescriptions are
compared: (i) a variant of the Borel-Pade resummation method, with an
additional improvement due to utilization of the leading renormalon poles (for
a comprehensive discussion of renormalons see [M. Beneke, Phys. Rep. vol. 317,
p. 1 (1999)]), and (ii) a contour-improved combination of the Borel method with
an analytic continuation by conformal mapping, and Pade approximations in the
conformal variable. The singularity structure in the case of the LoSurdo-Stark
effect in the complex Borel plane is shown to be similar to (divergent)
perturbative expansions in quantum chromodynamics.Comment: 14 pages, RevTeX, 3 tables, 1 figure; numerical accuracy of results
enhanced; one section and one appendix added and some minor changes and
additions; to appear in phys. rev.
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