We report measurements with the Very Long Baseline Array of the proper motion of Sgr A* relative to two extragalactic radio sources spanning 18 yr. The apparent motion of Sgr A* is −6.411 0.008 mas ...yr−1 along the Galactic plane and −0.219 0.007 mas yr−1 toward the North Galactic Pole. This apparent motion can almost entirely be attributed to the effects of the Sun's orbit about the Galactic center. Removing these effects yields residuals of −0.58 2.23 km s−1 in the direction of Galactic rotation and −0.85 0.75 km s−1 toward the North Galactic Pole. A maximum-likelihood analysis of the motion, both in the Galactic plane and perpendicular to it, expected for a massive object within the Galactic center stellar cluster indicates that the radiative source, Sgr A*, contains more than about 25% of the gravitational mass of 4 × 106 deduced from stellar orbits. The intrinsic size of Sgr A* is comparable to its Schwarzschild radius, and the implied mass density of pc−3 is very close to that expected for a black hole, providing overwhelming evidence that it is indeed a supermassive black hole. Finally, "intermediate mass" black holes more massive than 3 × 104 between approximately 0.003 and 0.1 pc from Sgr A* are excluded.
Hydrological connections between river channels and their adjacent floodplains facilitate the flux of organisms and nutrients and access to increased habitat and new resources. Hydrological ...connections also deliver water subsidy and potentially disturb (through hydraulic forces) floodplain ecosystems. This study investigates the role of hydrological connectivity as a driver of patterns in wetland plant assemblages in billabongs on the floodplain of an Australian dryland river, exploring indirectly the relative importance of the mechanisms of flux, subsidy and disturbance. Wetland plants were surveyed in billabongs across gradients of hydrological connectivity and depth. Surveys were accompanied by experiments examining germination from the soil seed banks of each site under submerged and waterlogged conditions. The patterns in extant and germinant plant communities in relation to connectivity and depth gradients were used to infer the relative importance of the connectivity-related mechanisms of flux, subsidy and hydraulic disturbance in structuring wetland plant communities. Depth influenced both extant and germinating plant communities. Shallow billabongs supported a greater diversity and abundance of plants, and greater numbers and diversity of germinable seeds in the seed bank. Germination of seeds was greater in waterlogged soils than submerged soils. Thus, the main controls of plant abundance in wetlands appear to be availability of waterlogged soil habitat for germination and absence of light limitation for growth. Hydrological connectivity did not influence the abundance of plants or germinable seeds, but did influence species presence-absence in growing vegetation; this effect did not extend to the germinating community. Thus, hydrological connection does not appear to influence wetland vegetation by facilitating the movement of propagules between habitats. Instead, the patterns observed are consistent with hydrological connection providing a cue for germination through the delivery of water, and by modifying hydraulic habitat.
Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and ...lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.
Epidemiology of ovarian cancer： a review Reid, Brett M; Permuth, Jennifer B; Sellers, Thomas A
Cancer biology & medicine,
02/2017, Letnik:
14, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Ovarian cancer （OC） is the seventh most commonly diagnosed cancer among women in the world and the tenth most common in China. Epithelial OC is the most predominant pathologic subtype, with five ...major histotypes that differ in origination, pathogenesis, molecular alterations, risk factors, and prognosis. Genetic susceptibility is manifested by rare inherited mutations with high to moderate penetrance. Genome-wide association studies have additionally identified 29 common susceptibility alleles for OC, including 14 subtype-specific alleles. Several reproductive and hormonal factors may lower risk, including parity, oral contraceptive use, and lactation, while others such as older age at menopause and hormone replacement therapy confer increased risks. These associations differ by histotype, especially for mucinous OC, likely reflecting differences in etiology. Endometrioid and clear cell OC share a similar, unique pattern of associations with increased risks among women with endometriosis and decreased risks associated with tubal ligation. OC risks associated with other gynecological conditions and procedures, such as hysterectomy, pelvic inflammatory disease, and polycystic ovarian syndrome, are less clear. Other possible risk factors include environmental and lifestyle factors such as asbestos and talc powder exposures, and cigarette smoking. The epidemiology provides clues on etiology, primary prevention, early detection, and possibly even therapeutic strategies.
NGC 4258 is a critical galaxy for establishing the extragalactic distance scale and estimating the Hubble constant ( ). Water masers in the nucleus of the galaxy orbit about its supermassive black ...hole, and very long baseline interferometric observations of their positions, velocities, and accelerations can be modeled to give a geometric estimate of the angular-diameter distance to the galaxy. We have improved the technique to obtain model parameter values, reducing both statistical and systematic uncertainties compared to previous analyses. We find the distance to NGC 4258 to be 7.576 0.082 (stat.) 0.076 (sys.) Mpc. Using this as the sole source of calibration of the Cepheid-SN Ia distance ladder results in km s−1 Mpc−1, and in concert with geometric distances from Milky Way parallaxes and detached eclipsing binaries in the LMC we find km s−1 Mpc−1. The improved distance to NGC 4258 also provides a new calibration of the tip of the red giant branch of mag, with reduced systematic errors for the determination of compared to the LMC-based calibration, because it is measured on the same Hubble Space Telescope (HST) photometric system and through similarly low extinction as SN Ia host halos. The result is km s−1 Mpc−1, in good agreement with the result from the Cepheid route, and there is no difference in when using the same calibration from NGC 4258 and the same SN Ia Hubble diagram intercept to start and end both distance ladders.
Background: School readiness, conceptualized as three components including emotional self‐regulation, social competence, and family/school involvement, as well as absence of conduct problems play a ...key role in young children's future interpersonal adjustment and academic success. Unfortunately, exposure to multiple poverty‐related risks increases the odds that children will demonstrate increased emotional dysregulation, fewer social skills, less teacher/parent involvement and more conduct problems. Consequently intervention offered to socio‐economically disadvantaged populations that includes a social and emotional school curriculum and trains teachers in effective classroom management skills and in promotion of parent–school involvement would seem to be a strategic strategy for improving young children's school readiness, leading to later academic success and prevention of the development of conduct disorders.
Methods: This randomized trial evaluated the Incredible Years (IY) Teacher Classroom Management and Child Social and Emotion curriculum (Dinosaur School) as a universal prevention program for children enrolled in Head Start, kindergarten, or first grade classrooms in schools selected because of high rates of poverty. Trained teachers offered the Dinosaur School curriculum to all their students in bi‐weekly lessons throughout the year. They sent home weekly dinosaur homework to encourage parents’ involvement. Part of the curriculum involved promotion of lesson objectives through the teachers’ continual use of positive classroom management skills focused on building social competence and emotional self‐regulation skills as well as decreasing conduct problems. Matched pairs of schools were randomly assigned to intervention or control conditions.
Results: Results from multi‐level models on a total of 153 teachers and 1,768 students are presented. Children and teachers were observed in the classrooms by blinded observers at the beginning and the end of the school year. Results indicated that intervention teachers used more positive classroom management strategies and their students showed more social competence and emotional self‐regulation and fewer conduct problems than control teachers and students. Intervention teachers reported more involvement with parents than control teachers. Satisfaction with the program was very high regardless of grade levels.
Conclusions: These findings provide support for the efficacy of this universal preventive curriculum for enhancing school protective factors and reducing child and classroom risk factors faced by socio‐economically disadvantaged children.
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•Ideal mass spectrometer for MALDI MSI would satisfy the ‘4S-criteria for performance’ (speed, specificity, spatial resolution and sensitivity).•Quantification MALDI MSI is achieved ...by spotting calibration curves onto control tissue sections or by using mimetic tissue models.•Stable isotope standards are most commonly used for signal normalization in quantitative MSI.•Further Validation and multi-site studies are required for best practices in wet lab, ‘big data’ processing and reporting.•Besides drug disposition studies, investigation of target engagement, PK/PD and drug-induced toxicity is drawing more attention.
Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) has emerged as a key technology for label-free bioanalysis of the spatial distribution of biomolecules, pharmaceuticals and other xenobiotics in tissue sections. Recent advances in instrumentation, sample preparation, multimodal workflows, quantification, analytical standardization and ‘big data’ processing have led to widespread utilization of MALDI MSI in pharmaceutical research. These developments have led to applications of the technology in drug discovery beyond drug disposition analysis, most notably in pharmacodynamic biomarker research and in toxicology.
Critical illness polyneuropathies (CIP) and myopathies (CIM) are common complications of critical illness. Several weakness syndromes are summarized under the term intensive care unit-acquired ...weakness (ICUAW). We propose a classification of different ICUAW forms (CIM, CIP, sepsis-induced, steroid-denervation myopathy) and pathophysiological mechanisms from clinical and animal model data. Triggers include sepsis, mechanical ventilation, muscle unloading, steroid treatment, or denervation. Some ICUAW forms require stringent diagnostic features; CIM is marked by membrane hypoexcitability, severe atrophy, preferential myosin loss, ultrastructural alterations, and inadequate autophagy activation while myopathies in pure sepsis do not reproduce marked myosin loss. Reduced membrane excitability results from depolarization and ion channel dysfunction. Mitochondrial dysfunction contributes to energy-dependent processes. Ubiquitin proteasome and calpain activation trigger muscle proteolysis and atrophy while protein synthesis is impaired. Myosin loss is more pronounced than actin loss in CIM. Protein quality control is altered by inadequate autophagy. Ca(2+) dysregulation is present through altered Ca(2+) homeostasis. We highlight clinical hallmarks, trigger factors, and potential mechanisms from human studies and animal models that allow separation of risk factors that may trigger distinct mechanisms contributing to weakness. During critical illness, altered inflammatory (cytokines) and metabolic pathways deteriorate muscle function. ICUAW prevention/treatment is limited, e.g., tight glycemic control, delaying nutrition, and early mobilization. Future challenges include identification of primary/secondary events during the time course of critical illness, the interplay between membrane excitability, bioenergetic failure and differential proteolysis, and finding new therapeutic targets by help of tailored animal models.
Abstract
Over the past decade, the BeSSeL Survey and the VERA project have measured trigonometric parallaxes to ≈250 massive, young stars using VLBI techniques. These sources trace spiral arms over ...nearly half of the Milky Way. What is now needed are accurate distances to such stars that are well past the Galactic center. Here we analyze the potential for addressing this need by combining line-of-sight velocities and proper motions to yield three-dimenensional (3D) kinematic distance estimates. For sources within about 10 kpc of the Sun, significant systematic uncertainties can occur, and trigonometric parallaxes are generally superior. However, for sources well past the Galactic center, 3D kinematic distances are robust and more accurate than can usually be achieved by trigonometic parallaxes.
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