7,371 research outputs found
Fluid thrust control system
A pure fluid thrust control system is described for a pump-fed, regeneratively cooled liquid propellant rocket engine. A proportional fluid amplifier and a bistable fluid amplifier control overshoot in the starting of the engine and take it to a predetermined thrust. An ejector type pump is provided in the line between the liquid hydrogen rocket nozzle heat exchanger and the turbine driving the fuel pump to aid in bringing the fluid at this point back into the regular system when it is not bypassed. The thrust control system is intended to function in environments too severe for mechanical controls
Precise Determination of |V{us}| from Lattice Calculations of Pseudoscalar Decay Constants
Combining the ratio of experimental kaon and pion decay widths, Gamma(K to mu
antineutrino{mu} (gamma)) / Gamma(pi to mu \antineutrino (gamma)), with a
recent lattice gauge theory calculation of f{K}/f{pi} provides a precise value
for the CKM quark mixing matrix element |V{us}|=0.2236(30) or if 3 generation
unitarity is assumed |V{us}|=0.2238(30). Comparison with other determinations
of that fundamental parameter, implications, and an outlook for future
improvements are given
Research on mechanisms of alloy strengthening. Part 1 - Strengthening through fine particle dispersion. Part 2 - Control of structure and properties by means of rapid quenching of liquid metals /splat cooling/ Semiannual report
Alloy strengthening mechanisms - strengthening by fine particle dispersion, and structure and properties control by rapid quenching or splat cooling of liquid metal
SSOR Preconditioning of Improved Actions
We generalize local lexicographic SSOR preconditioning for the
Sheikholeslami-Wohlert improved Wilson fermion action and the truncated perfect
free fermion action. In our test implementation we achieve performance gains as
known from SSOR preconditioning of the standard Wilson fermion action.Comment: 3 pages, Latex, 3 figures, Talk presented at Lattice'9
Adaptive mesh refinement approach to construction of initial data for black hole collisions
The initial data for black hole collisions is constructed using a
conformal-imaging approach and a new adaptive mesh refinement technique, a
fully threaded tree (FTT). We developed a second-order accurate approach to the
solution of the constraint equations on a non-uniformly refined high resolution
Cartesian mesh including second-order accurate treatment of boundary conditions
at the black hole throats. Results of test computations show convergence of the
solution as the numerical resolution is increased. FTT-based mesh refinement
reduces the required memory and computer time by several orders of magnitude
compared to a uniform grid. This opens up the possibility of using Cartesian
meshes for very high resolution simulations of black hole collisions.Comment: 13 pages, 11 figure
Gel transitions in colloidal suspensions
The idealized mode coupling theory (MCT) is applied to colloidal systems
interacting via short-range attractive interactions of Yukawa form. At low
temperatures MCT predicts a slowing down of the local dynamics and ergodicity
breaking transitions. The nonergodicity transitions share many features with
the colloidal gel transition, and are proposed to be the source of gelation in
colloidal systems. Previous calculations of the phase diagram are complemented
with additional data for shorter ranges of the attractive interaction, showing
that the path of the nonergodicity transition line is then unimpeded by the
gas-liquid critical curve at low temperatures. Particular attention is given to
the critical nonergodicity parameters, motivated by recent experimental
measurements. An asymptotic model is developed, valid for dilute systems of
spheres interacting via strong short-range attractions, and is shown to capture
all aspects of the low temperature MCT nonergodicity transitions.Comment: 12 pages, LaTeX, 5 eps figures, uses ioplppt.sty, to appear in J.
Phys.: Condens. Matte
Varicella vaccination in pediatric oncology patients without interruption of chemotherapy
AbstractBackgroundMorbidity and mortality from primary varicella-zoster virus (VZV) infection is increased in immunocompromised children. Vaccination of VZV-seronegative cancer patients with live-attenuated varicella vaccine is safe when chemotherapy is interrupted. However, VZV vaccination without interruption of chemotherapy would be preferable.ObjectiveTo vaccinate VZV-seronegative pediatric oncology patients with live-attenuated VZV vaccine without interrupting their chemotherapy.Study-designWe performed a single-center prospective cohort study.ResultsThirty-one patients with either a hematological malignancy (n=24) or a solid tumor (n=7) were vaccinated early during their course of chemotherapy. VZV IgG seroconversion occurred in 14 of the 31 patients (45%) after one vaccination. Only 20 patients were revaccinated after 3 months. These were patients who did not seroconvert (5 patients) and patients who serocoverted (15 patients) to induce or sustain seropositivity. Of these 20 patients the final seroconversion rate was 70%. Seven out of the 31 patients (23%) developed a mild rash of which 5 were treated with antivirals and recovered completely without interrupting chemotherapy, and 2 recovered untreated. Of these 31 immunized patients 26 were available for cellular testing. After one vaccination 20 of 26 patients (77%) tested positive for VZV-specific CD4+ T cells, of which 7 patients had remained VZV-seronegative. After the second vaccination 11 of 11 patients showed VZV-specific CD4+ T cells to sustain positivity, although 4 remained VZV-seronegative.ConclusionsThis study indicates that live-attenuated VZV vaccine can be safely administered to closely monitored pediatric oncology patients without interruption of chemotherapy and adaptive immunity was induced despite incomplete seroconversion
- …