3,951 research outputs found

    A Cenozoic-style scenario for the end-Ordovician glaciation

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    The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these remarkable claims arise from undersampling of incomplete geological sections that led to apparent temporal correlations within the relatively coarse resolution capability of Palaeozoic biochronostratigraphy. We examine exceptionally complete sedimentary records from two, low and high, palaeolatitude settings. Their correlation framework reveals a Cenozoic-style scenario including three main glacial cycles and higher-order phenomena. This necessitates revision of mechanisms for the end-Ordovician events, as the first extinction is tied to an early phase of melting, not to initial cooling, and the largest δ13C excursion occurs during final deglaciation, not at the glacial apex

    Thermochronological constraints on the timing and magnitude of Miocene and Pliocene extension in the central Wassuk Range, western Nevada

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    Apatite fission track and (U-Th)/He thermochronological data provide new constraints on the timing of faulting and exhumation of the Wassuk Range, western Nevada, where east dipping normal faults have accommodated large-magnitude ENE-WSW oriented extension. Extensional deformation has resulted in the exhumation of structurally coherent fault blocks that expose sections of preextensional mostly granitic upper crust in the Grey Hills and central Wassuk Range. These fault blocks display westward tilts of ∼60° and expose preextensional paleodepths of up to ∼8.5 km, based on the structural reconstruction of tilted preextensional Tertiary andesite flows that unconformably overlie Mesozoic basement rocks. Apatite fission track and (U-Th)/He thermochronological data from the fault blocks constrain the onset of rapid footwall exhumation at ∼15 Ma. Fission track modeling results indicate rapid fault block exhumation occurred between ∼15 and 12 Ma, which is in agreement with Miocene volcanic rocks that bracket the tilting history. In addition, fission track and (U-Th)/He data suggest reduced rates of cooling following major extension, as well as renewed cooling related to active, high-angle faulting along the present-day range front starting at ∼4 Ma. Thermochronological data from structurally restored fault blocks indicate a preextensional Miocene geothermal gradient of 27° ± 5°C/km. The thermochronological constraints on the timing of extensional faulting and the eruptive history in the Wassuk Range imply a model for extension where crustal heating and volcanism precede the onset of rapid large magnitude extension, and where synextensional magmatism is suppressed during the highest rates of extension

    On the Hadronic Contribution to Light-by-light Scattering in gμ−2g_\mu-2

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    We comment on the theoretical uncertainties involved in estimating the hadronic effects on the light-by-light scattering contribution to the anomalous magnetic moment of the muon, especially based on the analysis and results of T. Kinoshita, B. Ni\v zi\'c, and Y. Okamoto, Phys.\ Rev.\ D31, 2108 (1985). From the point of view of an effective field theory and chiral perturbation theory, we suggest that the charged pion contribution may be better determined than has been appreciated. However, the neutral pion contribution needs greater theoretical insight before its magnitude can be reliably estimated.Comment: 9 pages, no figures, U. Michigan UM-TH-93-18. (Input phyzzm to compile.) Revised version has minor changes in text. To be published in Phys. Rev. D, Comments sectio

    Aging and the visual perception of exocentric distance

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    AbstractThe ability of 18 younger and older adults to visually perceive exocentric distances was evaluated. The observers judged the extent of fronto-parallel and in-depth spatial intervals at a variety of viewing distances from 50cm to 164.3cm. Most of the observers perceived in-depth intervals to be significantly smaller than fronto-parallel intervals, a finding that is consistent with previous studies. While none of the individual observers’ judgments of exocentric distance were accurate, the judgments of the older observers were significantly more accurate than those of the younger observers. The precision of the observers’ judgments across repeated trials, however, was not affected by age. The results demonstrate that increases in age can produce significant improvements in the visual ability to perceive the magnitude of exocentric distances

    Continuity of medication management in Medicaid patients with chronic comorbid conditions: An examination by mental health status

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    Patients with serious mental illness (SMI) often have comorbid cardiometabolic conditions (CMCs) that may increase the number of prescribers involved in treatment. This study examined whether patients with SMI (depression and schizophrenia) and comorbid CMCs experience greater discontinuity of prescribing than patients with CMCs alone

    Payments for ecosystem services and the fatal attraction of win-win solutions

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    In this commentary we critically discuss the suitability of payments for ecosystem services and the most important challenges they face. While such instruments can play a role in improving environmental governance, we argue that over-reliance on payments as win-win solutions might lead to ineffective outcomes, similar to earlier experience with integrated conservation and development projects. Our objective is to raise awareness, particularly among policy makers and practitioners, about the limitations of such instruments and to encourage a dialogue about the policy contexts in which they might be appropriate. © 2013 Wiley Periodicals, Inc

    R-values in Low Energy e^+e^- Annihilation

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    This presentation briefly summarizes the recent measurements of R-values in low energy e^+e^- annihilation. The new experiments aimed at reducing the uncertainties in R-values and performed with the upgraded Beijing Spectrometer (BESII) at Beijing Electron Positron Collider (BEPC) in Beijing and with CMD-2 and SND at VEEP-2M in Novosibirsk are reviewed and discussed.Comment: 17 pages, 10 figures, invited presentation at the XIX International Symposium on Lepton and Photon Interactions at High Energy, Stanford University, August 199

    Do primary care medical homes facilitate care transitions after psychiatric discharge for patients with multiple chronic conditions?

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    Primary-care-based medical homes may facilitate care transitions for persons with multiple chronic conditions (MCC) including serious mental illness. The purpose of this manuscript is to assess outpatient follow-up rates with primary care and mental health providers following psychiatric discharge by medical home enrollment and medical complexity

    Disparities in Medicare beneficiaries’ receiving medication synchronization

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    Background Medication synchronization (med-sync) aligns patients’ monthly or quarterly chronic medications to a predetermined single pickup date at a community pharmacy. The study objective was to examine med-sync enrollment disparities based on Medicare beneficiaries’ predisposing, enabling, and need characteristics. Methods This was a retrospective cohort study using a Medicare dataset of beneficiaries receiving medications from pharmacies that self-identified as providing med-sync. Medicare beneficiaries who were continuously enrolled in fee-for-service medical and pharmacy benefits during the study period (2014–2016) were included. Study cohorts (med-sync and non–med-sync patients) were defined, and bivariate and multivariable logistic regression analyses were performed. Andersen’s Health Services Utilization Model guided our inclusion of predisposing, enabling, and need characteristics to examine for association with med-sync enrollment. Results A total of 170,180 beneficiaries were included, of which 13,193 comprised the med-sync cohort and 156,987 comprised the non–med-sync cohort. Bivariate logistic regression analysis revealed statistically significant differences (P \u3c 0.05) in cohorts based on age, geographic region, type of residence, number of unique chronic medications, comorbidities, outpatient visits, and inpatient hospitalizations. Beneficiaries had higher odds of being enrolled in med-sync with increasing age (adjusted odds ratio [AOR] 1.003 [95% CI 1.001–1.005]) and if they resided in the Northeast (AOR 1.094 [95% CI 1.018–1.175]), South (AOR 1.109 [95% CI 1.035–1.188]), and West (AOR 1.113 [95% CI 1.020–1.215]) than those in the Midwest. Beneficiaries residing in nonmetro areas had lower odds of enrollment (AOR 0.914 [95% CI 0.863–0.969]) than those in metro areas. Beneficiaries with previous fewer inpatient hospitalizations (AOR 0.945 [95% CI 0.914–0.977]) were more likely to be enrolled, and those with more outpatient visits (AOR 1.003 [95% CI 1.001–1.004]) were more likely to be enrolled. Those taking a higher number of oral chronic medications (AOR 1.005 [95% CI 1.002–1.008]) had greater odds of enrollment in med-sync. Conclusions Med-sync program expansion opportunities exist to address potential enrollment disparities based on age, geographic region, metropolitan area, and prior health utilization. Further studies are needed to develop and examine strategies among pharmacies to improve med-sync enrollment outreach to these subgroups of patients
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