2,256 research outputs found

    On OH line formation and oxygen abundances in metal-poor stars

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    The formation of the UV OH spectral lines has been investigated for a range of stellar parameters in the light of 3D hydrodynamical model atmospheres. The low atmospheric temperatures encountered at low metallicities compared with the radiative equilibrium values enforced in classical 1D hydrostatic model atmospheres have a profound impact on the OH line strengths. As a consequence, the derived O abundances using 3D models are found to be systematically lower by more than 0.6 dex at [Fe/H] =-3.0 compared with previous 1D analyses, casting doubts on the recent claims for a monotonic increase in [O/Fe] towards lower metallicities. In fact, taken at face value the resulting 3D LTE trend is in rough agreement with the conventional [O/Fe] plateau. Caution must, however, be exercised in view of the remaining assumptions in the 3D calculations. We have verified that the stellar parameters remain essentially unchanged with 3D model atmospheres provided that the infrared flux method (Delta T_eff <~ 20 K), Hipparcos parallaxes (Delta {log } g <~ 0.05) and Fe ii lines (Delta [Fe/H] <~ 0.1 dex) are utilised, leaving the 3D O abundances from OH lines largely intact (Delta [O/H] <~ 0.05 dex). Greater concern stems from possible departures from LTE in both the line formation and the molecular equilibrium, which, if present, would increase the derived O abundances again. Non-LTE line formation calculations with 1D model atmospheres suggest no significant steepening of the [O/Fe] trend even if the abundance corrections amount to about 0.2 dex for all investigated stellar parameters. We note, however, that the 3D case may not necessarily be as metallicity-independent. The apparent lack of laboratory or theoretical rate coefficients at the relevant temperatures for the involved molecular reactions unfortunately prevents a quantitative discussion on the possible effects of non-equilibrium chemistry

    Demonstrating Failure To Discharge Plaintiffs Duty To Mitigate In A Wrongful Termination Case: An Empirical Approach

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    In a wrongful termination case, the defendant has the burden of proving that the plaintiff did not adequately discharge his or her duty to mitigate damages.  The defendant may satisfy its burden by proving that the claimant failed to exercise “reasonable care and diligence” in seeking a job; and it must do so by a preponderance of the evidence.  On the other hand, the amount of any award turns on the difference between the plaintiff’s pre- and post-termination earnings.  Thus, there is a conflict between the potential increased damages award made possible by remaining jobless and the legal duty to mitigate.  It is reasonable to assume that a plaintiff may perceive an incentive to stay out of the workforce to enhance the damage award.  In this paper we empirically establish the expected joblessness duration period for a plaintiff’s population cohort in a wrongful termination lawsuit; we also calculated the estimated duration period’s associated standard error.  To illustrate the procedure we discuss a hypothetical case study and use uncensored data on joblessness duration from the Bureau of Labor Statistics’ Displaced Workers Survey.This process enables us structure a hypothesis test examining whether the plaintiff’s period of joblessness is statistically significantly different from the predicted test statistic in a manner consistent with case law.  Succinctly, we are able to empirically assess the soundness of the duration of a plaintiff’s job search and thereby enhance the robustness of present-day approaches

    Width and dual width of subsets in polynomial association schemes

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    AbstractThe width of a subset C of the vertices of a distance-regular graph is the maximum distance which occurs between elements of C. Dually, the dual width of a subset in a cometric association scheme is the index of the “last” eigenspace in the Q-polynomial ordering to which the characteristic vector of C is not orthogonal. Elementary bounds are derived on these two new parameters. We show that any subset of minimal width is a completely regular code and that any subset of minimal dual width induces a cometric association scheme in the original. A variety of examples and applications are considered

    Multiple Palaeoproterozoic carbon burial episodes and excursions

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    Organic-rich rocks (averaging 2–5% total organic carbon) and positive carbonate-carbon isotope excursions (View the MathML source and locally much higher, i.e. the Lomagundi-Jatuli Event) are hallmark features of Palaeoproterozoic successions and are assumed to archive a global event of unique environmental conditions following the c. 2.3 Ga Great Oxidation Event. Here we combine new and published geochronology that shows that the main Palaeoproterozoic carbon burial episodes (CBEs) preserved in Russia, Gabon and Australia were temporally discrete depositional events between c. 2.10 and 1.85 Ga. In northwest Russia we can also show that timing of the termination of the Lomagundi-Jatuli Event may have differed by up to 50 Ma between localities, and that Ni mineralisation occurred at c. 1920 Ma. Further, CBEs have traits in common with Mesozoic Oceanic Anoxic Events (OAEs); both are exceptionally organic-rich relative to encasing strata, associated with contemporaneous igneous activity and marked by organic carbon isotope profiles that exhibit a stepped decrease followed by a stabilisation period and recovery. Although CBE strata are thicker and of greater duration than OAEs (100 s of metres versus metres, ∌106 years versus ∌105 years), their shared characteristics hint at a commonality of cause(s) and feedbacks. This suggests that CBEs represent processes that can be either basin-specific or global in nature and a combination of circumstances that are not unique to the Palaeoproterozoic. Our findings urge circumspection and re-consideration of models that assume CBEs are a Deep Time singularity

    Neighborhood disadvantage across the transition from adolescence to adulthood and risk of metabolic syndrome

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    This study investigates the association between neighborhood disadvantage from adolescence to young adulthood and metabolic syndrome using a life course epidemiology framework. Data from the United States-based National Longitudinal Study of Adolescent to Adult Health (n = 9500)and a structural equation modeling approach were used to test neighborhood disadvantage across adolescence, emerging adulthood, and young adulthood in relation to metabolic syndrome. Adolescent neighborhood disadvantage was directly associated with metabolic syndrome in young adulthood. Evidence supporting an indirect association between adolescent neighborhood disadvantage and adult metabolic syndrome was not supported. Efforts to improve cardiometabolic health may benefit from strategies earlier in life

    Scale-dependent bias and the halo model

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    We use a simplified version of the halo model with a power law power spectrum to study scale dependence in galaxy bias at the very large scales relevant to baryon oscillations. In addition to providing a useful pedagogical explanation of the scale dependence of galaxy bias, the model provides an analytic tool for studying how changes in the Halo Occupation Distribution (HOD) impact the scale dependence of galaxy bias on scales between 10 and 1000 Mpc/h, which is useful for interpreting the results of complex N-body simulations. We find that changing the mean number of galaxies per halo of a given mass will change the scale dependence of the bias, but that changing the way the galaxies are distributed within the halo has a smaller effect on the scale dependence of bias at large scales. We use the model to explain the decay in amplitude of the baryon oscillations as k increases, and generalize the model to make predictions about scale dependent galaxy bias when redshift space distortions are introduced.Comment: 13 pages, 2 figures; corrected typos, extended discussion of redshift space distortions, matches published versio

    Visible Sector Supersymmetry Breaking Revisited

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    We revisit the possibility of "visible sector" SUSY models: models which are straightforward renormalizable extensions of the Minimal Supersymmetric Standard Model (MSSM), where SUSY is broken at tree level. Models of this type were abandoned twenty years ago due to phenomenological problems, which we review. We then demonstrate that it is possible to construct simple phenomenologically viable visible sector SUSY models. Such models are indeed very constrained, and have some inelegant features. They also have interesting and distinctive phenomenology. Our models predict light gauginos and very heavy squarks and sleptons. The squarks and sleptons may not be observable at the LHC. The LSP is a stable very light gravitino with a significant Higgsino admixture. The NLSP is mostly Bino. The Higgs boson is naturally heavy. Proton decay is sufficently and naturally suppressed, even for a cutoff scale as low as 10^8 GeV. The lightest particle of the O'Raifeartaigh sector (the LOP) is stable, and is an interesting cold dark matter candidate.Comment: 23 pages, 3 figures, LaTe

    Kesiapan Sekolah Dalam Menerapkan Kurikulum Merdeka di Rote Ndao

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    Salah satu bentuk pembangunan pendidikan nasional adalah perubahan kurikulum. Perkembangan terakhir adalah kurikulum mandiri. Perubahan kurikulum ini ditengarai mengabaikan efisiensi maksimal siswa dalam&nbsp; belajar. Oleh karena itu penelitian ini berfokus untuk mengkaji implementasi kurikulum otonom di SD GMIT Kabupaten Rote Barat. Metode yang digunakan adalah penelitian dengan menggunakan metode purposive sampling. Sumber yang digunakan dalam penelitian ini adalah 30 responden. Berdasarkan hasil di atas dapat disimpulkan bahwa kesiapan sekolah untuk mengimplementasikan kurikulum mandiri di sekolah GMIT di Kecamatan Rote Ndao Kabupaten Rote&nbsp; Barat berada pada level yang cukup siap beraksi. Hal ini disebabkan faktor sosialisasi yang masih kurang pemahaman guru, dukungan referensi dan persiapan kurikulum merdeka yang kurang

    Association Between Immigration History and Inflammatory Marker Profiles Among Older Adult Mexican Americans

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    Foreign-born Hispanics have better cardiometabolic health upon arrival in the US than their US-born counterparts, yet this advantage diminishes as duration of residence in the US increases. Underlying mechanisms explaining this paradox have been understudied. Using data from the Sacramento Area Latino Study on Aging (SALSA), this study examined immigration history (immigrant generation and duration of US residence) in relation to biomarkers of inflammation (interleukin-6 (IL-6), soluble forms of type 1 and 2 receptors of tumor necrosis factor-alpha (sTNF-R1 and sTNF-R2), C-reactive protein (CRP), leptin, adiponectin) in a sample of 1,290 predominantly Mexican-origin immigrants. Second and ≄3rd generation immigrants had higher IL-6 and leptin levels than 1st generation immigrants living in the US for less than 15 years (2nd generation percent difference = 45.9; 95% CI: 24.7, 70.7 and 3rd generation percent difference = 41.8; 95% CI: 17.7, 70.4). CRP and sTNF-R1 levels were higher among ≄3rd generation immigrants than 1st generation immigrants with less than 15 years of US residency. Worse inflammatory profiles were observed among Mexican-origin immigrants with longer US immigration histories, independent of health, and behavioral factors. Additional research is warranted to understand the factors that shape trajectories of biological risk across generations of Hispanics

    Feasibility and clinical outcomes when using practice guidelines for evaluation of fever in returning travelers and migrants : a validation study.

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    BACKGROUND: Practice guidelines for examining febrile patients presenting upon returning from the tropics were developed to assist primary care physicians in decision making. Because of the low level of evidence available in this field, there was a need to validate them and assess their feasibility in the context they have been designed for. OBJECTIVES: The objectives of the study were to (1) evaluate physicians' adherence to recommendations; (2) investigate reasons for non-adherence; and (3) ensure good clinical outcome of patients, the ultimate goal being to improve the quality of the guidelines, in particular to tailor them for the needs of the target audience and population. METHODS: Physicians consulting the guidelines on the Internet (www.fevertravel.ch) were invited to participate in the study. Navigation through the decision chart was automatically recorded, including diagnostic tests performed, initial and final diagnoses, and clinical outcomes. The reasons for non-adherence were investigated and qualitative feedback was collected. RESULTS: A total of 539 physician/patient pairs were included in this study. Full adherence to guidelines was observed in 29% of the cases. Figure-specific adherence rate was 54.8%. The main reasons for non-adherence were as follows: no repetition of malaria tests (111/352) and no presumptive antibiotic treatment for febrile diarrhea (64/153) or abdominal pain without leukocytosis (46/101). Overall, 20% of diversions from guidelines were considered reasonable because there was an alternative presumptive diagnosis or the symptoms were mild, which means that the corrected adherence rate per case was 40.6% and corrected adherence per figure was 61.7%. No death was recorded and all complications could be attributed to the underlying illness rather than to adherence to guidelines. CONCLUSIONS: These guidelines proved to be feasible, useful, and leading to good clinical outcomes. Almost one third of physicians strictly adhered to the guidelines. Other physicians used the guidelines not to forget specific diagnoses but finally diverged from the proposed attitudes. These diversions should be scrutinized for further refinement of the guidelines to better fit to physician and patient needs
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