Space station propulsion technology

The objectives of this program are to provide a demonstration of hydrogen/oxygen propulsion technology readiness for the initial operational capability (IOC) space station application, specifically gaseous hydrogen/oxygen and warm hydrogen thruster concepts, and to establish a means for evolving from the IOC space station propulsion system (SSPS) to that required to support and interface with advanced station functions. These objectives were met by analytical studies and by furnishing a propulsion test bed to the Marshall Space Flight Center for testing

Abundances in Stars from the Red Giant Branch Tip to the Near the Main Sequence in M71: I. Sample Selection, Observing Strategy and Stellar Parameters

We present the sample for an abundance analysis of 25 members of M71 with luminosities ranging from the red giant branch tip to the upper main sequence. The spectra are of high dispersion and of high precision. We describe the observing strategy and determine the stellar parameters for the sample stars using both broad band colors and fits of H$\alpha$ profiles. The derived stellar parameters agree with those from the Yale$^2$ stellar evolutionary tracks to within 50 -- 100K for a fixed log g, which is within the level of the uncertainties.Comment: Minor changes to conform to version accepted for publication, with several new figures (Paper 1 of a pair

Chemical Abundance Inhomogeneities in Globular Cluster Stars

It is now clear that abundance variations from star-to-star among the light elements, particularly C, N, O, Na and Al, are ubiquitous within galactic globular clusters; they appear seen whenever data of high quality is obtained for a sufficiently large sample of stars within such a cluster. The correlations and anti-correlations among these elements and the range of variation of each element appear to be independent of stellar evolutionary state, with the exception that enhanced depletion of C and of O is sometimes seen just at the RGB tip. While the latter behavior is almost certainly due to internal production and mixing, the internal mixing hypothesis can now be ruled out for producing the bulk of the variations seen. We focus on the implications of our new data for any explanation invoking primordial variations in the proto-cluster or accretion of polluted material from a neighboring AGB star

Imaging of Oxidation-Specific Epitopes in Atherosclerosis and Macrophage-Rich Vulnerable Plaques

Oxidative stress, and in particular oxidation of lipoproteins, is a hallmark of atherosclerosis. Upon entry of lipoproteins into the vessel wall, a cascade of pro-atherogenic pathways is initiated whereby the reaction of reactive oxygen species with substrates amenable to oxidation, such as polyunsaturated fatty acids, generates a variety of oxidation-specific epitopes on lipoproteins, proteins in the vessel wall, and apoptotic macrophages. Several of these oxidation-specific epitopes have been well characterized and specific murine and fully human antibodies have been generated in our laboratory to detect them in the vessel wall. We have developed radionuclide, gadolinium and iron oxide based MRI techniques to noninvasively image oxidation-specific epitopes in atherosclerotic lesions. These approaches quantitate plaque burden and also allow detection of atherosclerosis regression and plaque stabilization. In particular, gadolinium micelles or lipid-coated ultrasmall superparamagnetic iron oxide particles containing oxidation-specific antibodies accumulate within macrophages in the artery wall, suggesting they may image the most unstable plaques. Translation of these approaches to humans may allow a sensitive technique to image and monitor high-risk atherosclerotic lesions and may guide optimal therapeutic interventions

Online resources and apps to aid self-diagnosis and help seeking in the perinatal period: A descriptive survey of women's experiences.

OBJECTIVE:Assess the role of online resources and apps for women's help seeking and staff's response to concerns in the perinatal period. DESIGN:Online survey. Descriptive analysis of women's use and experiences of digital resources for self-diagnosis and help seeking, drawing on numerical and free-text responses. SETTING:Two tertiary referral centres and one district general hospital in two UK geographic locations. PARTICIPANTS:632 postnatal women, surveyed over a 4 month period. MEASUREMENTS:Women's access to digital devices; frequency and type of health concerns experienced after 22 weeks' gestation; variability in use and experiences of websites/apps; perceptions of staff's response to concerns after help-seeking. FINDINGS:1254 women were approached over a 4-month period; 632 participated (response rate: 50%). Women reported a 'mix and match' blended use of digital resources to both learn about, and self-diagnose/self-triage for potential complications in pregnancy as an adjunct to care provided by maternity staff. Over half the participants experienced concerns about themselves or their baby after 22 weeks. The top concern was fetal movements, reported by 62%. Women used 91 different digital resources to help with understanding and decision-making, in addition to seeking support from family, friends and healthcare professionals. Enabling features of staff responses were identified from free-text responses (n = 292) by women who sought professional help regarding their health concerns, and influencing factors at clinical, organisational and digital level. KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE:Online information retrieval and digital self-monitoring is increasingly integral to women's self-care during pregnancy and offers opportunities to support escalation of care and shared decision-making. Further work should assess optimal inclusion of this 'digital work' into clinical consultations

Wheelchair rugby players maintain sprint performance but alter propulsion biomechanics after simulated match play

The study aimed to explore the influence of a sports-specific intermittent sprint protocol (ISP) on wheelchair sprint performance and the kinetics and kinematics of sprinting in elite wheelchair rugby (WR) players with and without spinal cord injury (SCI). Fifteen international WR players (age 30.3 ± 5.5 years) performed two 10-s sprints on a dual roller wheelchair ergometer before and immediately after an ISP consisting of four 16-min quarters. Physiological measurements (heart rate, blood lactate concentration, and rating of perceived exertion) were collected. Three-dimensional thorax and bilateral glenohumeral kinematics were quantified. Following the ISP, all physiological parameters significantly increased (p ≤ 0.027), but neither sprinting peak velocity nor distance traveled changed. Players propelled with significantly reduced thorax flexion and peak glenohumeral abduction during both the acceleration (both -5°) and maximal velocity phases (-6° and 8°, respectively) of sprinting post-ISP. Moreover, players exhibited significantly larger mean contact angles (+24°), contact angle asymmetries (+4%), and glenohumeral flexion asymmetries (+10%) during the acceleration phase of sprinting post-ISP. Players displayed greater glenohumeral abduction range of motion (+17°) and asymmetries (+20%) during the maximal velocity phase of sprinting post-ISP. Players with SCI (SCI, n = 7) significantly increased asymmetries in peak power (+6%) and glenohumeral abduction (+15%) during the acceleration phase post-ISP. Our data indicates that despite inducing physiological fatigue resulting from WR match play, players can maintain sprint performance by modifying how they propel their wheelchair. Increased asymmetry post-ISP was notable, which may be specific to impairment type and warrants further investigatio

Linearly scaling direct method for accurately inverting sparse banded matrices

In many problems in Computational Physics and Chemistry, one finds a special kind of sparse matrices, termed "banded matrices". These matrices, which are defined as having non-zero entries only within a given distance from the main diagonal, need often to be inverted in order to solve the associated linear system of equations. In this work, we introduce a new O(n) algorithm for solving such a system, being n X n the size of the matrix. We produce the analytical recursive expressions that allow to directly obtain the solution, as well as the pseudocode for its computer implementation. Moreover, we review the different options for possibly parallelizing the method, we describe the extension to deal with matrices that are banded plus a small number of non-zero entries outside the band, and we use the same ideas to produce a method for obtaining the full inverse matrix. Finally, we show that the New Algorithm is competitive, both in accuracy and in numerical efficiency, when compared to a standard method based in Gaussian elimination. We do this using sets of large random banded matrices, as well as the ones that appear when one tries to solve the 1D Poisson equation by finite differences.Comment: 24 pages, 5 figures, submitted to J. Comp. Phy

Oxygen Abundances in Two Metal-Poor Subgiants from the Analysis of the 6300 A Forbidden O I Line

Recent LTE analyses (Israelian et al. 1998 and Bosegaard et al. 1999) of the OH bands in the optical-ultraviolet spectra of nearby metal-poor subdwarfs indicate that oxygen abundances are generally higher than those previously determined. The difference increases with decreasing metallicity and reaches delta([O/Fe]) ~ +0.6 dex as [Fe/H] approaches -3.0. Employing high resolution (R = 50000), high S/N (~ 250) echelle spectra of the two stars found by Israelian et al. (1998) to have the highest [O/Fe]-ratios, viz, BD +23 3130 and BD +37 1458, we conducted abundance analyses based on about 60 Fe I and 7-9 Fe II lines. We determined from Kurucz LTE models the values of the stellar parameters, as well as abundances of Na, Ni, and the traditional alpha-elements, independent of the calibration of color vs $T_{eff}$ scales. We determined oxygen abundances from spectral synthesis of the stronger line (6300 A) of the [O I] doublet. The syntheses of the [O I] line lead to smaller values of [O/Fe], consistent with those found earlier among halo field and globular cluster giants. We obtain [O/Fe] = +0.35 +/- 0.2 for BD +23 3130 and +0.50 +/- 0.2 for BD +37 1458. In the former, the [O I] line is very weak (~ 1 mA), so that the quoted [O/Fe] value may in reality be an upper limit. Therefore in these two stars a discrepancy exists between the [O/Fe]- ratios derived from [O I] and the OH feature, and the origin of this difference remains unclear. Until the matter is clarified, we suggest it is premature to conclude that the ab initio oxygen abundances of old, metal-poor stars need to be revised drastically upward.Comment: 38 pages, 5 tables, 14 figures To appear in July 1999 AJ Updated April 16, 1999. Fixed typo

On the Delta V_HB_bump parameter in Globular Clusters

We present new empirical estimates of the Delta V_HB_bump parameter for 15 Galactic globular clusters (GGCs) using accurate and homogeneous ground-based optical data. Together with similar evaluations available in the literature, we ended up with a sample of 62 GGCs covering a very broad range in metal content (-2.16<=[M/H]<=-0.58 dex). Adopting the homogeneous metallicity scale provided either by Kraft & Ivans (2004) or by Carretta et al. (2009), we found that the observed Delta V_HB_bump parameters are larger than predicted. In the metal-poor regime ([M/H]<=-1.7, -1.6 dex) 40% of GCs show discrepancies of 2sigma (~0.40 mag) or more. Evolutionary models that account either for alpha- and CNO-enhancement or for helium enhancement do not alleviate the discrepancy between theory and observations. The outcome is the same if we use the new Solar heavy-element mixture. The comparison between alpha- and CNO-enhanced evolutionary models and observations in the Carretta et al. metallicity scale also indicates that observed Delta V_HB_bump parameters, in the metal-rich regime ([M/H]=>0), might be systematically smaller than predicted