1,213 research outputs found

    Are there optical differences between storm-time substorms and isolated substorms?

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    We have performed an extensive analysis of auroral optical events (substorms) that occurred during the development of the main phase of magnetic storms. Using images from the Earth Camera on the Polar spacecraft (Frank et al., 1995), we compared the optical emission features of substorms occurring during 16 expansion phases of magnetic storms with the features of isolated substorms occurring during non-storm times. The comparison used two techniques, visual inspection and statistical comparisons. The comparisons were based on the common characteristics seen in isolated substorms that were initially identified by Akasofu (1964) and quantified by Gjerloev et al. (2008). We find that when auroral activity does occur during main phase development the characteristics of the aurora are very dissimilar to those of the classical isolated substorm. The primary differences include the lack of a surge/bulge, lack of bifurcation of the aurora, much shorter expansion phases, and greater intensities. <br><br> Since a surge/bulge and bifurcation of the aurora are characteristics of the existence of a substorm current wedge, a key component of the magnetosphere-ionosphere current system during substorms, the lack of this component would indicate that the classical substorm model does not apply to the storm time magnetosphere-ionosphere current system. Rather several of the analyses suggest that the storm-time substorms are associated more closely with the auroral oval, at least spatially, and, therefore, probably with the plasma sheet dynamics during the main phase development. These results then must call into question the widely held assumption that there is no intrinsic difference between storm-time substorms and classical isolated substorms

    Vegetational Areas of Texas.

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    Comparison of the Thermal Stability in Equal-Channel-Angular-Pressed and High-Pressure-Torsion-Processed Fe–21Cr–5Al Alloy

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    Nanostructured Steels Are Expected to Have Enhanced Irradiation Tolerance and Improved Strength. However, They Suffer from Poor Microstructural Stability at Elevated Temperatures. in This Study, Fe–21Cr–5Al–0.026C (Wt%) Kanthal D (KD) Alloy Belonging to a Class of (FeCrAl) Alloys Considered for Accident-Tolerant Fuel Cladding in Light-Water Reactors is Nanostructured using Two Severe Plastic Deformation Techniques of Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT), and their Thermal Stability between 500–700 °C is Studied and Compared. ECAP KD is Found to Be Thermally Stable Up to 500 °C, Whereas HPT KD is Unstable at 500 °C. Microstructural Characterization Reveals that ECAP KD Undergoes Recovery at 550 °C and Recrystallization above 600 °C, While HPT KD Shows Continuous Grain Growth after Annealing above 500 °C. Enhanced Thermal Stability of ECAP KD is from Significant Fraction (\u3e50%) of Low-Angle Grain Boundaries (GBs) (Misorientation Angle 2–15°) Stabilizing the Microstructure Due to their Low Mobility. Small Grain Sizes, a High Fraction (\u3e80%) of High-Angle GBs (Misorientation Angle \u3e15°) and Accordingly a Large Amount of Stored GB Energy, serve as the Driving Force for HPT KD to Undergo Grain Growth Instead of Recrystallization Driven by Excess Stored Strain Energy

    Determining the 7Li(n,gamma) cross section via Coulomb dissociation of 8Li

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    The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction 8Li(gamma,n)7Li. A 69.5 MeV/nucleon 8Li beam was incident on a Pb target, and the outgoing neutron and 7Li nucleus were measured in coincidence. The deduced (n,gamma) excitation function is consistent with data for the direct capture reaction 7Li(n,gamma)8Li and with low-energy effective field theory calculations.Comment: Accepted for publication in Phys. Rev.

    PMTCT option b+ does not increase preterm birth risk and may prevent extreme prematurity: A retrospective cohort study in Malawi

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    Objective: To estimate preterm birth risk among infants of HIV-infected women in Lilongwe, Malawi, according to maternal antiretroviral therapy (ART) status and initiation time under Option B+. Design: A retrospective cohort study of HIV-infected women delivering at ≥27 weeks of gestation, April 2012 to November 2015. Among women on ART at delivery, we restricted our analysis to those who initiated ART before 27 weeks of gestation. Methods: We defined preterm birth as a singleton live birth at ≥27 and <37 weeks of gestation, with births at <32 weeks classified as extremely to very preterm. We used log-binomial models to estimate risk ratios and 95% confidence intervals for the association between ART and preterm birth. Results: Among 3074 women included in our analyses, 731 preterm deliveries were observed (24%). Overall preterm birth risk was similar in women who had initiated ART at any point before 27 weeks and those who never initiated ART (risk ratio = 1.14; 95% confidence interval: 0.84 to 1.55), but risk of extremely to very preterm birth was 2.33 (1.39 to 3.92) times as great in those who never initiated ART compared with those who did at any point before 27 weeks. Among women on ART before delivery, ART initiation before conception was associated with the lowest preterm birth risk. Conclusions: ART during pregnancy was not associated with preterm birth, and it may in fact be protective against severe adverse outcomes accompanying extremely to very preterm birth. As preconception ART initiation appears especially protective, long-term retention on ART should be a priority to minimize preterm birth in subsequent pregnancies

    Increasing confidence and changing behaviors in primary care providers engaged in genetic counselling.

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    BackgroundScreening and counseling for genetic conditions is an increasingly important part of primary care practice, particularly given the paucity of genetic counselors in the United States. However, primary care physicians (PCPs) often have an inadequate understanding of evidence-based screening; communication approaches that encourage shared decision-making; ethical, legal, and social implication (ELSI) issues related to screening for genetic mutations; and the basics of clinical genetics. This study explored whether an interactive, web-based genetics curriculum directed at PCPs in non-academic primary care settings was superior at changing practice knowledge, attitudes, and behaviors when compared to a traditional educational approach, particularly when discussing common genetic conditions.MethodsOne hundred twenty one PCPs in California and Pennsylvania physician practices were randomized to either an Intervention Group (IG) or Control Group (CG). IG physicians completed a 6 h interactive web-based curriculum covering communication skills, basics of genetic testing, risk assessment, ELSI issues and practice behaviors. CG physicians were provided with a traditional approach to Continuing Medical Education (CME) (clinical review articles) offering equivalent information.ResultsPCPs in the Intervention Group showed greater increases in knowledge compared to the Control Group. Intervention PCPs were also more satisfied with the educational materials, and more confident in their genetics knowledge and skills compared to those receiving traditional CME materials. Intervention PCPs felt that the web-based curriculum covered medical management, genetics, and ELSI issues significantly better than did the Control Group, and in comparison with traditional curricula. The Intervention Group felt the online tools offered several advantages, and engaged in better shared decision making with standardized patients, however, there was no difference in behavior change between groups with regard to increases in ELSI discussions between PCPs and patients.ConclusionWhile our intervention was deemed more enjoyable, demonstrated significant factual learning and retention, and increased shared decision making practices, there were few differences in behavior changes around ELSI discussions. Unfortunately, barriers to implementing behavior change in clinical genetics is not unique to our intervention. Perhaps the missing element is that busy physicians need systems-level support to engage in meaningful discussions around genetics issues. The next step in promoting active engagement between doctors and patients may be to put into place the tools needed for PCPs to easily access the materials they need at the point-of-care to engage in joint discussions around clinical genetics

    Guidelines for implementation of cystic fibrosis newborn screening programs: Cystic Fibrosis Foundation workshop report

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    Newborn screening for cystic fibrosis offers the opportunity for early intervention and improved outcomes. This summary, resulting from a workshop sponsored by the Cystic Fibrosis Foundation to facilitate implementation of widespread high quality cystic fibrosis newborn screening, outlines the steps necessary for success based on the experience of existing programs. Planning should begin with a workgroup composed of those who will be responsible for the success of the local program, typically including the state newborn screening program director and cystic fibrosis care center directors. The workgroup must develop a screening algorithm based on program resources and goals including mechanisms available for sample collection, regional demographics, the spectrum of cystic fibrosis disease to be detected, and acceptable failure rates of the screen. The workgroup must also ensure that all necessary guidelines and resources for screening, diagnosis, and care be in place prior to cystic fibrosis newborn screening implementation. These include educational materials for parents and primary care providers; systems for screening and for providing diagnostic testing and counseling for screen-positive infants and their families; and protocols for care of this unique population. This summary explores the benefits and risks of various screening algorithms, including complex situations that can occur involving unclear diagnostic results, and provides guidelines and sample materials for state newborn screening programs to develop and implement high quality screening for cystic fibrosis

    Heparin cofactor II in atherosclerotic lesions from the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study

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    Heparin cofactor II (HCII) is a serine protease inhibitor (serpin) that has been shown to be a predictor of decreased atherosclerosis in the elderly and protective against atherosclerosis in mice. HCII inhibits thrombin in vitro and HCII-thrombin complexes have been detected in human plasma. Moreover, the mechanism of protection against atherosclerosis in mice was determined to be the inhibition of thrombin. Despite this evidence, the presence of HCII in human atherosclerotic tissue has not been reported. In this study, using samples of coronary arteries obtained from the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study, we explore the local relationship between HCII and (pro)thrombin in atherosclerosis. We found that HCII and (pro)thrombin are co-localized in the lipid-rich necrotic core of atheromas. A significant positive correlation between each protein and the severity of the atherosclerotic lesion was present. These results suggest that HCII is in a position to inhibit thrombin in atherosclerotic lesions where thrombin can exert a proatherogenic inflammatory response. However, these results should be tempered by the additional findings from this, and other studies, that indicate the presence of other plasma proteins (antithrombin, albumin, and α1-protease inhibitor) in the same localized region of the atheroma
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