3,282 research outputs found
Molecular outflow launched beyond the disk edge
One of the long-standing problems of star formation is the excess of angular
momentum of the parent molecular cloud. In the classical picture, a fraction of
angular momentum of the circumstellar material is removed by the
magneto-centrifugally driven disk wind that is launched from a wide region
throughout the disk. In this work, we investigate the kinematics in the
envelope-disk transition zone of the Class I object BHB07-11, in the B59 core.
For this purpose, we used the Atacama Large Millimeter/submillimeter Array in
extended configuration to observe the thermal dust continuum emission
( 1.3 mm) and molecular lines (CO, CO and HCO),
which are suitable tracers of disk, envelope, and outflow dynamics at a spatial
resolution of AU. We report a bipolar outflow that was launched at
symmetric positions with respect to the disk (80~AU in radius), but was
concentrated at a distance of 90--130~AU from the disk center. The two outflow
lobes had a conical shape and the gas inside was accelerating. The large offset
of the launching position coincided with the landing site of the infall
material from the extended spiral structure (seen in dust) onto the disk. This
indicates that bipolar outflows are efficiently launched within a narrow region
outside the disk edge. We also identify a sharp transition in the gas
kinematics across the tip of the spiral structure, which pinpoints the location
of the so-called centrifugal barrier.Comment: 5 pages, 5 figures, Accepted for publication in A&A Letter
Tensile and flexural ultimate strength of fiber-reinforced ceramic-matrix composites
International audienceA constitutive equation has been derived for fiber reinforced ceramic-matrix composites, based on fiber breakage and distributed fiber pull-out. Length-dependent and length-independent regimes, governed by the size of the specimen, are differentiated, The constitutive equation is used to predict the ultimate strength of fiber-reinforced ceramic-matrix composites subjected to tensile and flexural loadings
MEMS practice, from the lab to the telescope
Micro-electro-mechanical systems (MEMS) technology can provide for deformable
mirrors (DMs) with excellent performance within a favorable economy of scale.
Large MEMS-based astronomical adaptive optics (AO) systems such as the Gemini
Planet Imager are coming on-line soon. As MEMS DM end-users, we discuss our
decade of practice with the micromirrors, from inspecting and characterizing
devices to evaluating their performance in the lab. We also show MEMS wavefront
correction on-sky with the "Villages" AO system on a 1-m telescope, including
open-loop control and visible-light imaging. Our work demonstrates the maturity
of MEMS technology for astronomical adaptive optics.Comment: 14 pages, 15 figures, Invited Paper, SPIE Photonics West 201
Density functional theory of phase coexistence in weakly polydisperse fluids
The recently proposed universal relations between the moments of the
polydispersity distributions of a phase-separated weakly polydisperse system
are analyzed in detail using the numerical results obtained by solving a simple
density functional theory of a polydisperse fluid. It is shown that universal
properties are the exception rather than the rule.Comment: 10 pages, 2 figures, to appear in PR
Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency
Leaf senescence in winter deciduous species signals the transition from the active to the dormant stage. The purpose of leaf senescence is the recovery of nutrients before the leaves fall. Photoperiod and temperature are the main cues controlling leaf senescence in winter deciduous species, with water stress imposing an additional influence. Photoperiod exerts a strict control on leaf senescence at latitudes where winters are severe and temperature gains importance in the regulation as winters become less severe. On average, climatic warming will delay and drought will advance leaf senescence, but at varying degrees depending on the species. Warming and drought thus have opposite effects on the phenology of leaf senescence, and the impact of climate change will therefore depend on the relative importance of each factor in specific regions. Warming is not expected to have a strong impact on nutrient proficiency although a slower speed of leaf senescence induced by warming could facilitate a more efficient nutrient resorption. Nutrient resorption is less efficient when the leaves senesce prematurely as a consequence of water stress. The overall effects of climate change on nutrient resorption will depend on the contrasting effects of warming and drought. Changes in nutrient resorption and proficiency will impact production in the following year, at least in early spring, because the construction of new foliage relies almost exclusively on nutrients resorbed from foliage during the preceding leaf fall. Changes in the phenology of leaf senescence will thus impact carbon uptake, but also ecosystem nutrient cycling, especially if the changes are consequence of water stress
The LKB1-AMPK-α1 signaling pathway triggers hypoxic pulmonary vasoconstriction downstream of mitochondria
International audienceHypoxic pulmonary vasoconstriction (HPV), which aids ventilation-perfusion matching in the lungs, is triggered by mechanisms intrinsic to pulmonary arterial smooth muscles. The unique sensitivity of these muscles to hypoxia is conferred by mitochondrial cytochrome c oxidase subunit 4 isoform 2, the inhibition of which has been proposed to trigger HPV through increased generation of mitochondrial reactive oxygen species. Contrary to this model, we have shown that the LKB1-AMPK-α1 signaling pathway is critical to HPV. Spectral Doppler ultrasound revealed that deletion of the AMPK-α1 catalytic subunit blocked HPV in mice during mild (8% O2) and severe (5% O2) hypoxia, whereas AMPK-α2 deletion attenuated HPV only during severe hypoxia. By contrast, neither of these genetic manipulations affected serotonin-induced reductions in pulmonary vascular flow. HPV was also attenuated by reduced expression of LKB1, a kinase that activates AMPK during energy stress, but not after deletion of CaMKK2, a kinase that activates AMPK in response to increases in cytoplasmic Ca2+ Fluorescence imaging of acutely isolated pulmonary arterial myocytes revealed that AMPK-α1 or AMPK-α2 deletion did not affect mitochondrial membrane potential during normoxia or hypoxia. However, deletion of AMPK-α1, but not of AMPK-α2, blocked hypoxia from inhibiting KV1.5, the classical "oxygen-sensing" K+ channel in pulmonary arterial myocytes. We conclude that LKB1-AMPK-α1 signaling pathways downstream of mitochondria are critical for the induction of HPV, in a manner also supported by AMPK-α2 during severe hypoxia
Eculizumab is a safe and effective treatment in pediatric patients with atypical hemolytic uremic syndrome
Atypical hemolytic uremic syndrome (aHUS) is caused by alternative complement pathway dysregulation, leading to systemic thrombotic microangiopathy (TMA) and severe end-organ damage. Based on 2 prospective studies in mostly adults and retrospective data in children, eculizumab, a terminal complement inhibitor, is approved for aHUS treatment. Here we prospectively evaluated efficacy and safety of weight-based dosing of eculizumab in eligible pediatric patients with aHUS in an open-label phase II study. The primary end point was complete TMA response by 26 weeks. Twenty-two patients (aged 5 months-17 years) were treated; 16 were newly diagnosed, 12 had no prior plasma exchange/infusion during current TMA symptomatology, 11 received baseline dialysis, and 2 had prior renal transplants. By week 26, 14 achieved a complete TMA response, 18 achieved hematologic normalization, and 16 had 25% or better improvement in serum creatinine. Plasma exchange/infusion was discontinued in all, and 9 of the 11 patients who required dialysis at baseline discontinued, whereas none initiated new dialysis. Eculizumab was well tolerated; no deaths or meningococcal infections occurred. Bone marrow failure, wrist fracture, and acute respiratory failure were reported as unrelated severe adverse events. Thus, our findings establish the efficacy and safety of eculizumab for pediatric patients with aHUS and are consistent with proposed immediate eculizumab initiation following diagnosis in children
Maternal perinatal mental health and offspring academic achievement at age 16:the mediating role of childhood executive function
Background: Elucidating risk pathways for under-achieving at school can inform strategies to reduce the number of
adolescents leaving school without passing grades in core subjects. Maternal depression can compromise the quality
of parental care and is associated with multiple negative child outcomes. However, only a few small studies have
investigated the association between perinatal maternal depression and poor academic achievement in adolescence.
The pathways to explain the risks are also unclear. Method: Prospective observational data from 5,801 parents and
adolescents taking part in a large UK population cohort (Avon-Longitudinal-Study-of-Parents-and-Children) were
used to test associations between maternal and paternal depression and anxiety in the perinatal period, executive
function (EF) at age 8, and academic achievement at the end of compulsory school at age 16. Results: Adolescents of
postnatally depressed mothers were 1.5 times (1.19, 1.94, p = .001) as likely as adolescents of nondepressed
mothers to fail to achieve a âpassâ grade in math; antenatal anxiety was also an independent predictor of poor math.
Disruption in different components of EF explained small but significant proportions of these associations:
attentional control explained 16% (4%, 27%, p < .001) of the association with postnatal depression, and working
memory explained 17% (13%, 30%, p = .003) of the association with antenatal anxiety. A similar pattern was seen for
language grades, but associations were confounded by maternal education. There was no evidence that paternal
factors were independently associated with impaired child EF or adolescent exams. Conclusion: Maternal postnatal
depression and antenatal anxiety are risk factors for adolescents underachieving in math. Preventing, identifying,
and treating maternal mental health in the perinatal period could, therefore, potentially increase adolescentsâ
academic achievement. Different aspects of EF partially mediated these associations. Further work is needed, but if
these pathways are causal, improving EF could reduce underachievement in math
Middle Jurassic fossils document an early stage in salamander evolution
Salamanders are an important group of living amphibians and model organisms for understanding locomotion, development, regeneration, feeding, and toxicity in tetrapods. However, their origin and early radiation remain poorly understood, with early fossil stem-salamanders so far represented by larval or incompletely known taxa. This poor record also limits understanding of the origin of Lissamphibia (i.e., frogs, salamanders, and caecilians). We report fossils from the Middle Jurassic of Scotland representing almost the entire skeleton of the enigmatic stem-salamander Marmorerpeton. We use computed tomography to visualize high-resolution three-dimensional anatomy, describing morphologies that were poorly characterized in early salamanders, including the braincase, scapulocoracoid, and lower jaw. We use these data in the context of a phylogenetic analysis intended to resolve the relationships of early and stem-salamanders, including representation of important outgroups alongside data from high-resolution imaging of extant species. Marmorerpeton is united with Karaurus, Kokartus, and others from the Middle JurassicâLower Cretaceous of Asia, providing evidence for an early radiation of robustly built neotenous stem-salamanders. These taxa display morphological specializations similar to the extant cryptobranchid âgiantâ salamanders. Our analysis also demonstrates stem-group affinities for a larger sample of Jurassic species than previously recognized, highlighting an unappreciated diversity of stem-salamanders and cautioning against the use of single species (e.g., Karaurus) as exemplars for stem-salamander anatomy. These phylogenetic findings, combined with knowledge of the near-complete skeletal anatomy of Mamorerpeton, advance our understanding of evolutionary changes on the salamander stem-lineage and provide important data on early salamanders and the origins of Batrachia and Lissamphibia
Using lâCarnitine as a Pharmacologic Probe of the Interpatient and Metabolic Variability of Sepsis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162752/2/phar2448_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162752/1/phar2448.pd
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