740 research outputs found
Parameter estimation supplement to the Mission Analysis Evaluation and Space Trajectory Operations program (MAESTRO)
This Parameter Estimation Supplement describes the PEST computer program and gives instructions for its use in determination of lunar gravitation field coefficients. PEST was developed for use in the RAE-B lunar orbiting mission as a means of lunar field recovery. The observations processed by PEST are short-arc osculating orbital elements. These observations are the end product of an orbit determination process obtained with another program. PEST's end product it a set of harmonic coefficients to be used in long-term prediction of the lunar orbit. PEST employs some novel techniques in its estimation process, notably a square batch estimator and linear variational equations in the orbital elements (both osculating and mean) for measurement sensitivities. The program's capabilities are described, and operating instructions and input/output examples are given. PEST utilizes MAESTRO routines for its trajectory propagation. PEST's program structure and subroutines which are not common to MAESTRO are described. Some of the theoretical background information for the estimation process, and a derivation of linear variational equations for the Method 7 elements are included
Radio astronomy Explorer-B in-flight mission control system development effort
A description is given of the development for the Mission Analysis Evaluation and Space Trajectory Operations (MAESTRO) program to be used for the in-flight decision making process during the translunar and lunar orbit adjustment phases of the flight of the Radio Astronomy Explorer-B. THe program serves two functions: performance and evaluation of preflight mission analysis, and in-flight support for the midcourse and lunar insertion command decisions that must be made by the flight director. The topics discussed include: analysis of program and midcourse guidance capabilities; methods for on-line control; printed displays of the MAESTRO program; and in-flight operational logistics and testing
Frequency splitting of polarization eigenmodes in microscopic Fabry-Perot cavities
We study the frequency splitting of the polarization eigenmodes of the
fundamental transverse mode in CO2 laser-machined, high-finesse optical
Fabry-Perot cavities and investigate the influence of the geometry of the
cavity mirrors. Their highly reflective surfaces are typically not rotationally
symmetric but have slightly different radii of curvature along two principal
axes. We observe that the eccentricity of such elliptical mirrors lifts the
degeneracy of the polarization eigenmodes. The impact of the eccentricity
increases for smaller radii of curvature. A model derived from corrections to
the paraxial resonator theory is in excellent agreement with the measurements,
showing that geometric effects are the main source of the frequency splitting
of polarization modes for the type of microscopic cavity studied here. By
rotating one of the mirrors around the cavity axis, the splitting can be tuned.
In the case of an identical differential phase shift per mirror, it can even be
eliminated, despite a nonvanishing eccentricity of each mirror. We expect our
results to have important implications for many experiments in cavity quantum
electrodynamics, where Fabry-Perot cavities with small mode volumes are
required.Comment: 10 pages, 6 figure
Characterization of the monocyte-specific esterase (MSE) gene
Carboxylic esterases are widely distributed in hematopoietic cells. Monocytes express the esterase isoenzyme (termed 'monocyte-specific esterase', MSE) that can be inhibited by NaF in the alpha-naphthyl acetate cytochemical staining. We examined the expression of MSE in normal cells and primary and cultured leukemia-lymphoma cells. The MSE protein was demonstrated by isoelectric focusing (IEF); MSE mRNA expression was investigated by Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). The following samples were positive for MSE protein and Northern mRNA expression: 20/24 monocytic, 4/32 myeloid, and 1/20 erythroid-megakaryocytic leukemia cell lines, but none of the 112 lymphoid leukemia or lymphoma cell lines; of the normal purified cell populations only the monocytes were positive whereas, T, B cells, and granulocytes were negative; of primary acute (myelo) monocytic leukemia cells (CD14-positive, FAB M4/M5 morphology) 14/20 were Northern mRNA and 11/14 IEF protein positive. RT-PCR revealed MSE expression in 29/49 Northern-negative lymphoid leukemia-lymphoma cell lines. The RT-PCR signals in monocytic cell lines were on average 50-fold stronger than the mostly weak trace expression in lymphoid specimens. On treatment with various biomodulators, only all-trans retinoic acid significantly upregulated MSE message and protein levels but could not induce new MSE expression in several leukemia cell lines; lipopolysaccharide and interferon-gamma increased MSE expression in normal monocytes. Analysis of DNA methylation with sensitive restriction enzymes showed no apparent regulation of gene expression by differential methylation; the MSE gene is evolutionarily conserved among mammalian species; the half-life of the human MSE transcripts was about 5-6 h. The extent of MSE expression varied greatly among different monocytic leukemia samples. However, the MSE overexpression in a significant number of specimens was not associated with gene amplification, gross structural rearrangements or point mutations within the cDNA region. Taken together, the results suggest that MSE expression is not absolutely specific for, but strongly associated with cells of the monocytic lineage; MSE is either not expressed at all or expressed at much lower levels in cells from other lineages. The biological significance, if any, of rare MSE messages in lymphoid cells detectable only by the hypersensitive RT-PCR remains unclear. Further studies on the regulation of this gene and on the physiological function of the enzyme will no doubt be informative with respect to its striking overexpression in some malignant cells and to a possible role in the pathobiology of monocytic leukemias
Is ethnic density associated with health in a context of social disadvantage? Findings from the Born in Bradford cohort.
YesObjectives
In this study we aimed to test the associations between area-level ethnic density and health for Pakistani and White British residents of Bradford, England.
Design
The sample consisted of 8610 mothers and infant taking part in the Born in Bradford cohort. Ethnic density was measured as the percentage of Pakistani, White British or South Asian residents living in a Lower Super Output Area. Health outcomes included birth weight, preterm birth and smoking during pregnancy. Associations between ethnic density and health were tested in multilevel regression models, adjusted for individual covariates and area deprivation.
Results
In the Pakistani sample, higher ethnic density was associated with lower birth weight (b -0.82, 95% CI -1.63; -0.02), and higher South Asian density was associated with a lower probability of smoking during pregnancy (OR 0.99, 95% CI 0.98; 1.00). Pakistani women in areas with 50-70% South Asian residents were less likely to smoke than those living in areas with less than 10% South Asian residents (OR 0.39, 95% CI 0.16;0.97). In the White British sample, neither birth weight nor preterm birth was associated with ethnic density. The probability of smoking during pregnancy was lower in areas with 10-29.99% compared to < 10% South Asian density (OR 0.79, 95% CI 0.64; 0.98).
Conclusion
In this sample, ethnic density was associated with lower odds of smoking during pregnancy but not with higher birth weight or lower odds of preterm birth. Possibly, high levels of social disadvantage inhibit positive effects of ethnic density on health.Hall Dorman studentship , also Wellcome and NIH
Shear Viscosity in a Perturbative Quark-Gluon-Plasma
Among the key features of hot and dense QCD matter produced in
ultra-relativistic heavy-ion collisions at RHIC is its very low shear
viscosity, indicative of the properties of a near-ideal fluid, and a large
opacity demonstrated by jet energy loss measurements. In this work, we utilize
a microscopic transport model based on the Boltzmann equation with quark and
gluon degrees of freedom and cross sections calculated from perturbative
Quantum Chromodynamics to simulate an ideal Quark-Gluon-Plasma in full thermal
and chemical equilibrium. We then use the Kubo formalism to calculate the shear
viscosity to entropy density ratio of the medium as a function of temperature
and system composition. One of our key results is that the shear viscosity over
entropy-density ratio becomes invariant to the chemical composition of
the system when plotted as a function of energy-density instead of temperature.Comment: 11 pages, 8 figures: version #2 contains some revisions and added
references to clarify relationship to previously published wor
Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC
The stochastic dynamics of c and b quarks in the fireball created in
nucleus-nucleus collisions at RHIC and LHC is studied employing a relativistic
Langevin equation, based on a picture of multiple uncorrelated random
collisions with the medium. Heavy-quark transport coefficients are evaluated
within a pQCD approach, with a proper HTL resummation of medium effects for
soft scatterings. The Langevin equation is embedded in a multi-step setup
developed to study heavy-flavor observables in pp and AA collisions, starting
from a NLO pQCD calculation of initial heavy-quark yields, complemented in the
nuclear case by shadowing corrections, k_T-broadening and nuclear geometry
effects. Then, only for AA collisions, the Langevin equation is solved
numerically in a background medium described by relativistic hydrodynamics.
Finally, the propagated heavy quarks are made hadronize and decay into
electrons. Results for the nuclear modification factor R_AA of heavy-flavor
hadrons and electrons from their semi-leptonic decays are provided, both for
RHIC and LHC beam energies.Comment: 4 pages, 2 figures (3 eps files); submitted for publication in the
proceedings of "Quark Matter 2011", 23-28 May 2011, Annecy (France
Age-0 walleye \u3ci\u3eSander vitreus\u3c/i\u3e display length-dependent diet shift to piscivory
The ontogenetic diet shift to piscivory can be energetically beneficial for fish growth and allows larger, more energetically profitable prey to be consumed. A shift to piscivory may be easier for longer individuals within a cohort due to larger gape size, and an early shift is likely advantageous, potentially leading to increased growth rates and survival. Such length-dependent ontogenetic diet shifts may explain the intracohort variability in length that is common for age-0 walleye (Sander vitreus). The objectives of this study were to describe seasonal intracohort variability in length, identify the timing of the shift to piscivory and determine if the onset of piscivory was length-dependent in age-0 walleye. Walleye initially fed on zooplankton, but shifted to piscivory during July of 2010 and June of 2011. The onset of piscivory in age-0 walleye was associated with length-dependent differences during both years, in which longer individuals within the cohort became piscivorous earlier than shorter individuals within the same cohort. Intracohort variability in length was detected and increased postontogenetic diet shift. Age-0 walleye that experience a growth advantage could benefit from increased survival and feeding opportunities
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