Strange-quark Current in the Nucleon from Lattice QCD

The contribution of the strange-quark current to the electromagnetic form factors of the nucleon is studied using lattice QCD. The strange current matrix elements from our lattice calculation are analyzed in two different ways, the differential method used in an earlier work by Wilcox and a cumulative method which sums over all current insertion times. The preliminary results of our simulation indicate the importance of high statistics, and that consistent results between the varying analysis methods can be achieved. Although this simulation does not yet yield a number that can be compared to experiment, several criteria useful in assessing the robustness of a signal extracted from a noisy background are presented.Comment: 12 pages, 9 figures, Presented at EMI 200

Interaction effects in thermocapillary bubble migration

Two bubbles migrating along their line of centers under the influence of an imposed thermal gradient are considered in the quasi-static limit. Results are reported for representative values of the governing parameters

The effect of acoustic fields on the efficiency of solar cells

Acoustic field effects on gallium arsenide, silicon solar cells, and photoresistive devices with and without light exposur

Flight 1 technical report for experiment 74-36: Thermal migration of bubbles and their interaction with solidification interfaces

Specimens of gas saturated carbon tetrabromide were directionally solidified in a transparent furnace using a gradient freeze technique. The original temperature gradient was 5 C/cm and the cooling rate was 40 C/h. Progress of the experiment was monitored photographically. Gas bubbles were generated at the advancing solidification front in each of the three specimens. The gas bubbles were observed to increase in size, coalesce, and eventually be grown into the solid specimen under low gravity conditions. No bubble detachment from the interface was observed. Identical specimens processed in the laboratory showed bubble nucleation, bubble growth, and eventual bubble detachment due to buoyancy forces. Examination of the specimens showed a significantly greater void content in the low gravity processed samples. The grain size was observed to be finer in the low gravity processed samples

Demographics and Outcomes of Pulmonary Hypertension Patients in United States Emergency Departments

Introduction: Pulmonary hypertension (PH) is a common, yet under-diagnosed, contributor to morbidity and mortality. Our objective was to characterize the prevalence of PH among adult patients presenting to United States (US) emergency departments (ED) and to identify demographic patterns and outcomes of PH patients in the ED.Methods: We analyzed the Nationwide Emergency Department Sample (NEDS) database, with a focus on ED patients aged 18 years and older, with any International Classification of Diseases, Clinical Modification (ICD)-9-CM or ICD-10-CM diagnosis code for PH from 2011 to 2015. The primary outcome was inpatient, all-cause mortality. The secondary outcomes were hospital admission rates and hospital length of stay (LOS).Results: From 2011 to 2015, in a sample of 121,503,743 ED visits, representing a weighted estimate of 545,500,486 US ED visits, patients with a diagnosis of PH accounted for 0.78% (95% confidence interval [CI], 0.75- 0.80%) of all US ED visits. Of the PH visits, 86.9% were admitted to the hospital, compared to 16.3% for all other ED visits (P <0.001). Likewise, hospital LOS and hospital-based mortality were higher in the PH group than for other ED patients (e.g., inpatient mortality 4.5% vs 2.6%, P < 0.001) with an adjusted odds ratio (aOR) of 1.34 (95% CI, 1.31–1.37). Age had the strongest association with mortality, with an aOR of 10.6 for PH patients over 80 years (95% CI, 10.06–11.22), compared to a reference of ages 18 to 30 years.Conclusion: In this nationally representative sample, presentations by patients with PH were relatively common, accounting for nearly 0.8% of US ED visits. Patients with PH were significantly more likely to be admitted to the hospital than all other patients, had longer hospital LOS, and increased risk of inpatient mortality

Fast Mesh Refinement in Pseudospectral Optimal Control

Mesh refinement in pseudospectral (PS) optimal control is embarrassingly easy --- simply increase the order $N$ of the Lagrange interpolating polynomial and the mathematics of convergence automates the distribution of the grid points. Unfortunately, as $N$ increases, the condition number of the resulting linear algebra increases as $N^2$; hence, spectral efficiency and accuracy are lost in practice. In this paper, we advance Birkhoff interpolation concepts over an arbitrary grid to generate well-conditioned PS optimal control discretizations. We show that the condition number increases only as $\sqrt{N}$ in general, but is independent of $N$ for the special case of one of the boundary points being fixed. Hence, spectral accuracy and efficiency are maintained as $N$ increases. The effectiveness of the resulting fast mesh refinement strategy is demonstrated by using \underline{polynomials of over a thousandth order} to solve a low-thrust, long-duration orbit transfer problem.Comment: 27 pages, 12 figures, JGCD April 201

The sun's magnetic sector structure

The synoptic appearance of solar magnetic sectors is studied using 454 sector boundaries observed at earth during 1959-1973. The sectors are clearly visible in the photospheric magnetic field. Sector boundaries can be clearly identified as north-south running demarcation lines between regions of persistent magnetic polarity imbalances. These regions extend up to about 35 deg of latitude on both sides of the equator. They generally do not extend into the polar caps. The polar cap boundary can be identified as an east-west demarcation line marking the poleward limit of the sectors. The typical flux imbalance for a magnetic sector is about 4 x 10 to the 21st power Maxwells