1,787 research outputs found

    The TRENDS High-Contrast Imaging Survey. VI. Discovery of a Mass, Age, and Metallicity Benchmark Brown Dwarf

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    The mass and age of substellar objects are degenerate parameters leaving the evolutionary state of brown dwarfs ambiguous without additional information. Theoretical models are normally used to help distinguish between old, massive brown dwarfs and young, low mass brown dwarfs but these models have yet to be properly calibrated. We have carried out an infrared high-contrast imaging program with the goal of detecting substellar objects as companions to nearby stars to help break degeneracies in inferred physical properties such as mass, age, and composition. Rather than using imaging observations alone, our targets are pre-selected based on the existence of dynamical accelerations informed from years of stellar radial velocity (RV) measurements. In this paper, we present the discovery of a rare benchmark brown dwarf orbiting the nearby (d=18.69±0.19d=18.69\pm0.19 pc), solar-type (G9V) star HD 4747 ([Fe/H]=−0.22±0.04-0.22\pm0.04) with a projected separation of only ρ=11.3±0.2\rho=11.3\pm0.2 AU (ξ≈\theta \approx 0.6"). Precise Doppler measurements taken over 18 years reveal the companion's orbit and allow us to place strong constraints on its mass using dynamics (msin⁥(i)=55.3±1.9MJm \sin(i) = 55.3\pm1.9M_J). Relative photometry (ΔKs=9.05±0.14\Delta K_s=9.05\pm0.14, MKs=13.00±0.14M_{K_s}=13.00\pm0.14, Ks−Lâ€Č=1.34±0.46K_s - L' = 1.34\pm0.46) indicates that HD 4747 B is most-likely a late-type L-dwarf and, if near the L/T transition, an intriguing source for studying cloud physics, variability, and polarization. We estimate a model-dependent mass of m=72−13+3MJm=72^{+3}_{-13}M_J for an age of 3.3−1.9+2.33.3^{+2.3}_{-1.9} Gyr based on gyrochronology. Combining astrometric measurements with RV data, we calculate the companion dynamical mass (m=60.2±3.3MJm=60.2\pm3.3M_J) and orbit (e=0.740±0.002e=0.740\pm0.002) directly. As a new mass, age, and metallicity benchmark, HD 4747 B will serve as a laboratory for precision astrophysics to test theoretical models that describe the emergent radiation of brown dwarfs.Comment: Accepted to Ap

    The TRENDS High-contrast Imaging Survey. VIII. Compendium of Benchmark Objects

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    The physical properties of faint stellar and substellar objects often rely on indirect, model-dependent estimates. For example, the masses of brown dwarfs are usually inferred using evolutionary models, which are age dependent and have yet to be properly calibrated. With the goal of identifying new benchmark objects to test low-mass stellar and substellar models, we have carried out a comprehensive adaptive optics survey as part of the TaRgetting bENchmark-objects with the Doppler Spectroscopy high-contrast imaging program. Using legacy radial velocity measurements from the High Resolution Echelle Spectrometer at Keck, we have identified several dozen stars that show long-term Doppler accelerations. We present follow-up high-contrast observations from the campaign and report the discovery of 31 comoving companions, as well as 11 strong candidate companions, to solar-type stars with well-determined parallax and metallicity values. Benchmark objects of this nature lend themselves to orbit determinations, dynamical mass estimates, and independent compositional assessment. This compendium of benchmark objects will serve as a convenient test group to substantiate theoretical evolutionary and atmospheric models near the hydrogen fusing limit

    The TRENDS High-contrast Imaging Survey. VIII. Compendium of Benchmark Objects

    Get PDF
    The physical properties of faint stellar and substellar objects often rely on indirect, model-dependent estimates. For example, the masses of brown dwarfs are usually inferred using evolutionary models, which are age dependent and have yet to be properly calibrated. With the goal of identifying new benchmark objects to test low-mass stellar and substellar models, we have carried out a comprehensive adaptive optics survey as part of the TaRgetting bENchmark-objects with the Doppler Spectroscopy high-contrast imaging program. Using legacy radial velocity measurements from the High Resolution Echelle Spectrometer at Keck, we have identified several dozen stars that show long-term Doppler accelerations. We present follow-up high-contrast observations from the campaign and report the discovery of 31 comoving companions, as well as 11 strong candidate companions, to solar-type stars with well-determined parallax and metallicity values. Benchmark objects of this nature lend themselves to orbit determinations, dynamical mass estimates, and independent compositional assessment. This compendium of benchmark objects will serve as a convenient test group to substantiate theoretical evolutionary and atmospheric models near the hydrogen fusing limit

    Melatonin: the placental antioxidant and anti-inflammatory

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    Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine hormone with many physiological and biological roles. Melatonin is an antioxidant, anti-inflammatory, free radical scavenger, circadian rhythm regulator, and sleep hormone. However, its most popular role is the ability to regulate sleep through the circadian rhythm. Interestingly, recent studies have shown that melatonin is an important and essential hormone during pregnancy, specifically in the placenta. This is primarily due to the placenta’s ability to synthesize its own melatonin rather than depending on the pineal gland. During pregnancy, melatonin acts as an antioxidant and anti-inflammatory, which is necessary to ensure a stable environment for both the mother and the fetus. It is an essential antioxidant in the placenta because it reduces oxidative stress by constantly scavenging for free radicals, i.e., maintain the placenta’s integrity. In a healthy pregnancy, the maternal immune system is constantly altered to accommodate the needs of the growing fetus, and melatonin acts as a key anti-inflammatory by regulating immune homeostasis during early and late gestation. This literature review aims to identify and summarize melatonin’s role as a powerful antioxidant and anti-inflammatory that reduces oxidative stress and inflammation to maintain a favorable homeostatic environment in the placenta throughout gestation

    Feasibility and acceptability of Technology-Supported Sexual Health Education among adolescents Receiving inpatient Psychiatric Care

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    Mental illness in adolescence is associated with high-risk sexual behaviors including multiple sex partners, infrequent or inconsistent condom use, and nonuse of contraception. Inpatient psychiatric care represents a promising setting to provide sexual health education. This pilot study investigates the feasibility and acceptability of online sexual health education in this group by assessing usability and impact on short-term psychosocial outcomes. We administered online modules on healthy relationships, pregnancy prevention, condom use, and sexually transmitted infection (STI) prevention to youth. We evaluated outcomes using a single group, pre/post-intervention design. One quality improvement session assessed staff acceptability of the programming. Participants included 51 inpatients (mean age = 15.3; 61% female; 57% Hispanic or Latino; 55% heterosexual). Overall, the program was feasible to administer and highly acceptable to youth (84-89% liked the modules, 98-100% found them easy to use, 96-100% found them credible, 91-98% said information would lead to healthier dating relationships, and 78-87% would refer to a friend). Youth who completed modules demonstrated improvement in several outcomes: attitudes and norms towards violence

    Social Vulnerability of the People Exposed to Wildfires in U.S. West Coast States

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    Understanding of the vulnerability of populations exposed to wildfires is limited. We used an index from the U.S. Centers for Disease Control and Prevention to assess the social vulnerability of populations exposed to wildfire from 2000–2021 in California, Oregon, and Washington, which accounted for 90% of exposures in the western United States. The number of people exposed to fire from 2000–2010 to 2011–2021 increased substantially, with the largest increase, nearly 250%, for people with high social vulnerability. In Oregon and Washington, a higher percentage of exposed people were highly vulnerable (\u3e40%) than in California (~8%). Increased social vulnerability of populations in burned areas was the primary contributor to increased exposure of the highly vulnerable in California, whereas encroachment of wildfires on vulnerable populations was the primary contributor in Oregon and Washington. Our results emphasize the importance of integrating the vulnerability of at-risk populations in wildfire mitigation and adaptation plans

    Social Vulnerability of the People Exposed to Wildfires in US West Coast States

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    Understanding of the vulnerability of populations exposed to wildfires is limited. We used an index from the U.S. Centers for Disease Control and Prevention to assess the social vulnerability of populations exposed to wildfire from 2000-2021 in California, Oregon, and Washington, which accounted for 90% of exposures in the western United States. The number of people exposed to fire from 2000-2010 to 2011-2021 increased substantially, with the largest increase, nearly 250%, for people with high social vulnerability. In Oregon and Washington, a higher percentage of exposed people were highly vulnerable (\u3e40%) than in California (~8%). Increased social vulnerability of populations in burned areas was the primary contributor to increased exposure of the highly vulnerable in California, whereas encroachment of wildfires on vulnerable populations was the primary contributor in Oregon and Washington. Our results emphasize the importance of integrating the vulnerability of at-risk populations in wildfire mitigation and adaptation plans

    Self‐management for adults with epilepsy: Aggregate Managing Epilepsy Well Network findings on depressive symptoms

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    ObjectiveTo assess depressive symptom outcomes in a pooled sample of epilepsy self‐management randomized controlled trials (RCTs) from the Managing Epilepsy Well (MEW) Network integrated research database (MEW DB).MethodsFive prospective RCTs involving 453 adults with epilepsy compared self‐management intervention (n = 232) versus treatment as usual or wait‐list control outcomes (n = 221). Depression was assessed with the nine‐item Patient Health Questionnaire. Other variables included age, gender, race, ethnicity, education, income, marital status, seizure frequency, and quality of life. Follow‐up assessments were collapsed into a visit 2 and a visit 3; these were conducted postbaseline.ResultsMean age was 43.5 years (SD = 12.6), nearly two‐thirds were women, and nearly one‐third were African American. Baseline sample characteristics were mostly similar in the self‐management intervention group versus controls. At follow‐up, the self‐management group had a significantly greater reduction in depression compared to controls at visit 2 (P < .0001) and visit 3 (P = .0002). Quality of life also significantly improved in the self‐management group at visit 2 (P = .001) and visit 3 (P = .005).SignificanceAggregate MEW DB analysis of five RCTs found depressive symptom severity and quality of life significantly improved in individuals randomized to self‐management intervention versus controls. Evidence‐based epilepsy self‐management programs should be made more broadly available in neurology practices.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151320/1/epi16322_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151320/2/epi16322.pd
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