1,337 research outputs found
The Salinity Distribution in Young Sea-Ice
When undertaking a study of the lateral variation of the salinity of sea-ice it is necessary to select an area of ice with a known history. The field measurements reported here were made in North Star Bay, Thule, northwestern Greenland .... The sampling for the sheet ice grid was started at 1100 on November 6 and by 2100 the 2-, 4-, 8- and 16-foot grids were completed. The 32-, 64- and 128-foot grids were completed the following morning. ... Sampling of the pancake ice was started at 0900 on November 9 and completed by the evening of the same day. ... the standard deviation of the salinity values from closely spaced cored samples in sheet ice is always equal to or greater than ±0.3 per mil. In pancake ice, the standard deviation is usually ±1.0 per mil. ... this uncertainty will produce a standard deviation of approx. ±4 to 6 per cent of the total brine volume in the sheet ice and ±11 to 19 per cent of the total brine volume in pancake ice. This then accounts for a considerable proportion of the scatter observed in studying the strength properties of sea-ice
Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space
Stability analysis of the Bianchi type I universe in pure gravity theory is
studied in details. We first derive the non-redundant field equation of the
system by introducing the generalized Bianchi type I metric. This non-redundant
equation reduces to the Friedmann equation in the isotropic limit. It is shown
further that any unstable mode of the isotropic perturbation with respect to a
de Sitter background is also unstable with respect to anisotropic
perturbations. Implications to the choice of physical theories are discussed in
details in this paper.Comment: 5 pages, some comment adde
The Effect of Nitrided Layer on Antibacterial Properties for Biomedical Stainless Steel
AbstractPlasma nitriding of AISI type 303 austenitic stainless steel using microwave system at various input powers was conducted in present study. The nitrided layers were characterized via scanning electron microscopy, transmission electron microscopy and Vickers microhardness tester. The anti-bacterial property of this nitrided layer was also evaluated. The analytical results revealed the hardness of AISI type 303 stainless steel could be enhanced with nitriding process. The microstructure of the nitrided layer comprised of nitrogen-expanded Îł phase. Bacterial test demonstrated the nitrided layer processed the excellent an ti-bacterial properties. The enhanced hardness and anti-bacterial properties make the nitrided AISI type 303 austenitic stainless steel the potential material in the biomedical applications
Friedmann Equation and Stability of Inflationary Higher Derivative Gravity
Stability analysis on the De Sitter universe in pure gravity theory is known
to be useful in many aspects. We first show how to complete the proof of an
earlier argument based on a redundant field equation. It is shown further that
the stability condition applies to Friedmann-Robertson-Walker spaces
based on the non-redundant Friedmann equation derived from a simple effective
Lagrangian. We show how to derive this expression for the Friedmann equation of
pure gravity theory. This expression is also generalized to include scalar
field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte
Androgens and coronary artery disease
This chapter reviews data that examine the relationship between androgens and coronary artery disease (CAD) in men. Androgens can exert both beneficial and deleterious actions on a myriad of factors implicated in the pathogenic mechanisms of atherosclerosis and CAD. Androgen/androgen receptor (AR) can modulate arterial disease and vascular function via genomic (AR) or non-genomic mechanisms in animal models and in vitro experimental studies. The diversity and complexity of the actions of testosterone (and its metabolites E2 and DHT) and DHEA on the vasculature reflect the multiple cellular targets in the vessel wall, differences between species, gender, concomitant disease and, most importantly, level/dosage of testosterone exposure. At present, it is not possible to determine the net effect of androgens on CAD pathogenesis and clinical outcomes. While observational clinical studies showed a consistent association between low testosterone and CAD (risk factors, events and mortality), and some experimental studies may suggest positive effects of androgens on CAD risk factors, body composition and individual vascular mechanisms, it is hazardous to suggest that manipulation of the androgenic milieu will result in clinical benefits in a complex multifactorial condition such as CAD. This ongoing uncertainty also underlines recent concerns regarding the possibility of adverse cardiovascular side effects in androgen treatment of endocrine and non-endocrine conditions, hampering efforts to exploit the potential therapeutic benefits of testosterone for men in the treatment of osteoporosis, sarcopaenia, chronic debilitating disease and obesity-related hypoandrogenism in the ageing male population. Large-scale prospective randomised placebo-controlled trials of sufficient size and duration are urgently needed to assess not only the benefits in terms of meaningful clinical benefits and patient-important outcomes but also to document the risks of serious adverse events in testosterone treatment. In the meantime, for patients with established pathological hypogonadism, there are no substantive data to suggest that physiological testosterone therapy is associated with increased cardiovascular risk and their management should not deviate from current recommended practice. For complete coverage of this and related topics, please visit www.endotext.org
Measurement of lowâdensity lipoprotein cholesterol levels in primary and secondary prevention patients: Insights from the PALM registry
Background The 2013 American College of Cardiology/American Heart Association Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults recommended testing low-density lipoprotein cholesterol ( LDL -C) to identify untreated patients with LDL -C â„190 mg/dL, assess lipid-lowering therapy adherence, and consider nonstatin therapy. We sought to determine whether clinician lipid testing practices were consistent with these guidelines. Methods and Results The PALM (Patient and Provider Assessment of Lipid Management) registry enrolled primary and secondary prevention patients from 140 US cardiology, endocrinology, and primary care offices in 2015 and captured demographic data, lipid treatment history, and the highest LDL -C level in the past 2 years. Core laboratory lipid levels were drawn at enrollment. Among 7627 patients, 2787 (36.5%) had no LDL -C levels measured in the 2 years before enrollment. Patients without chart-documented LDL -C levels were more often women, nonwhite, uninsured, and non-college graduates (all P\u3c0.01). Patients without prior lipid testing were less likely to receive statin treatment (72.6% versus 76.0%; P=0.0034), a high-intensity statin (21.5% versus 24.3%; P=0.016), nonstatin lipid-lowering therapy (24.8% versus 27.3%; P=0.037), and had higher core laboratory LDL -C levels at enrollment (median 97 versus 92 mg/dL; P\u3c0.0001) than patients with prior LDL -C testing. Of 166 individuals with core laboratory LDL -C levels â„190 mg/dL, 36.1% had no LDL -C measurement in the prior 2 years, and 57.2% were not on a statin at the time of enrollment. Conclusions In routine clinical practice, LDL -C testing is associated with higher-intensity lipid-lowering treatment and lower achieved LDL -C level
Quantum Monte Carlo treatment of elastic exciton-exciton scattering
We calculate cross sections for low energy elastic exciton-exciton scattering
within the effective mass approximation. Unlike previous theoretical
approaches, we give a complete, non-perturbative treatment of the four-particle
scattering problem. Diffusion Monte Carlo is used to calculate the essentially
exact energies of scattering states, from which phase shifts are determined.
For the case of equal-mass electrons and holes, which is equivalent to
positronium-positronium scattering, we find a_s = 2.1 a_x for scattering of
singlet-excitons and a_s= 1.5 a_x for triplet-excitons, where a_x is the
excitonic radius. The spin dependence of the cross sections arises from the
spatial exchange symmetry of the scattering wavefunctions. A significant
triplet-triplet to singlet-singlet scattering process is found, which is
similar to reported effects in recent experiments and theory for excitons in
quantum wells. We also show that the scattering length can change sign and
diverge for some values of the mass ratio m_h/m_e, an effect not seen in
previous perturbative treatments.Comment: 6 pages, 6 figures. Revision has updated figures, improved paper
structure, some minor correction
Caregiversâ Health Literacy and Their Young Childrenâs Oral-healthârelated Expenditures
Caregiversâ health literacy has emerged as an important determinant of young childrenâs health care and outcomes. We examined the hypothesis that caregiversâ health literacy influences childrenâs oral-health-careârelated expenditures. This was a prospective cohort study of 1,132 child/caregiver dyads (childrenâs mean age = 19 months), participating in the Carolina Oral Health Literacy Project. Health literacy was measured by the REALD-30 (word recognition based) and NVS (comprehension based) instruments. Follow-up data included child Medicaid claims for CY2008-10. We quantified expenditures using annualized 2010 fee-adjusted Medicaid-paid dollars for oral-healthârelated visits involving preventive, restorative, and emergency care. We used descriptive, bivariate, and multivariate statistical methods based on generalized gamma models. Mean oral-healthârelated annual expenditures totaled 81, restorativeâ22. Among children who received services, mean expenditures were: emergency hospital-basedâ106, and restorative careâ40; 95% confidence interval, -32, 111). Nevertheless, with both instruments, emergency dental care expenditures were consistently elevated among children of low-literacy caregivers. These findings provide initial support for health literacy as an important determinant of the meaningful use and cost of oral health care
Haploinsufficiency of the murine Col3a1 locus causes aortic dissection: a novel model of the vascular type of EhlersâDanlos syndrome
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