9,390 research outputs found
The dense gas in the largest molecular complexes of the antennae: HCN and HCO+ observations of NGC 4038/39 using ALMA
We present observations of the dense molecular gas tracers , , and in the transition using the Atacama Large Millimeter/submillimeter Array. We supplement our data sets with previous observations of , which trace the total molecular gas content. We separate the Antennae into seven bright regions in which we detect emission from all three molecules, including the nuclei of NGC 4038 and NGC 4039, five super giant molecular complexes in the overlap region, and two additional bright clouds. We find that the ratio of , which traces the dense molecular gas fraction, is greater in the two nuclei ( ) than in the overlap region ( ). We attribute this to an increase in pressure due to the stellar potential within the nuclei; a similar effect to what has been seen previously in the Milky Way and nearby spiral galaxies. Furthermore, the ratio of does not vary by more than a factor of 1.5 between regions. By comparing our measured ratios to photon dominated region (PDR) models including mechanical heating, we find that the ratio of is consistent with mechanical heating contributing gsim5%–10% of the PDR surface heating to the total heating budget. Finally, the ratio of varies from ~1 in the nucleus of NGC 4038 down to ~0.5 in the overlap region. The lower ratio in the overlap region may be due to an increase in the cosmic ray rate from the increased supernova rate within this region
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In vitro evidence of cellular adaptation to ozone toxicity in the rat trachea.
Adaptation to prolonged ozone (O3) exposure occurs in the tracheal epithelium of rats and is marked by the presence of ciliated cells with uniform short cilia but is not accompanied by shifts in cell populations, altered characteristics of epithelial secretory cell products, increased cell turnover, or elevated tracheal superoxide dismutase activity. The purpose of this study was to test the hypothesis that adaptation is a result of alterations intrinsic to epithelial cells or to the cells and their matrix, and not due to systemic or neural influences. Rats were preexposed to either filtered air (FA) or 0.96 ppm O3 for 8 hr/night for 60 days, and then their tracheae were removed and exposed to 3 ppm O3 in an explant culture system where behavioral, nasal, exudative, and secretory product influences can be eliminated. After exposure to 3 ppm O3 in vitro, quantitative electron microscopic evaluation demonstrated that the epithelia from the FA preexposure group had significantly more necrotic cells and sloughed cells and fewer ciliated cells than the epithelia from the O3 preexposure group. Thus previous exposure to ozone in vivo induces a change in tracheal epithelium which confers resistance to ozone-induced injury in the explant exposure system
The forms and functions of switch reference in A’ingae
This paper examines switch reference (SR) in A’ingae, an understudied isolate language from Amazonian Ecuador. We present a theoretically informed survey of SR, identifying three distinct uses of switch reference: in clause chaining, adverbial clauses, and so-called ‘bridging’ clause linkage. We describe the syntactic and semantic properties of each use in detail, the first such description for A’ingae, showing that the three constructions differ in important ways. While leaving a full syntactic analysis to future work, we argue that these disparate properties preclude a syntactic account that unifies these three constructions to the exclusion of other environments without SR. Conversely, while a full semantic account is also left to future work, we suggest that a unified semantic account in terms of discourse coherence principles appears more promising. In particular, we propose that switch reference in A’ingae occurs in all and only the constructions that are semantically restricted to non-structuring coordinating coherence relations in the sense of Segmented Discourse Representation Theory
Absorbate-Induced Piezochromism in a Porous Molecular Crystal
Atmospherically stable porous frameworks
and materials are interesting
for heterogeneous solid–gas applications. One motivation is
the direct and selective uptake of pollutant/hazardous gases, where
the material produces a measurable response in the presence of the
analyte. In this report, we present a combined experimental and theoretical
rationalization for the piezochromic response of a robust and porous
molecular crystal built from an extensively fluorinated trispyrazole.
The electronic response of the material is directly determined by
analyte uptake, which provokes a subtle lattice contraction and an
observable bathochromic shift in the optical absorption onset. Selectivity
for fluorinated absorbates is demonstrated, and toluene is also found
to crystallize within the pore. Furthermore, we demonstrate the application
of electronic structure calculations to predict a physicochemical
response, providing the foundations for the design of electronically
tunable porous solids with the chemical properties required for development
of novel gas-uptake media
Effects of Heat-Producing Elements on the Stability of Deep Mantle Thermochemical Piles
©2020. American Geophysical Union. All Rights Reserved. Geochemical observations of ocean island and mid-ocean ridge basalts suggest that abundances of heat-producing elements (HPEs: U, Th, and K) vary within the mantle. Combined with bulk silicate Earth models and constraints on the Earth's heat budget, these observations suggest the presence of a more enriched (potentially deep and undepleted) reservoir in the mantle. Such a reservoir may be related to seismically observed deep mantle structures known as large low shear velocity provinces (LLSVPs). LLSVPs might represent thermochemical piles of an intrinsically denser composition, and many studies have shown such piles to remain stable over hundreds of Myr or longer. However, few studies have examined if thermochemical piles can remain stable if they are enriched in HPEs, a necessary condition for them to constitute an enriched HPE reservoir. We conduct a suite of mantle convection simulations to examine the effect of HPE enrichment up to 25× the ambient mantle on pile stability. Model results are evaluated against present-day pile morphology and tested for resulting seismic signatures using self-consistent potential pile compositions. We find that stable piles can form from an initial basal layer of dense material even if the layer is enriched in HPEs, depending on the density of the layer and degree of HPE enrichment, with denser basal layers requiring increased HPE enrichment to form pile-like morphology instead of a stable layer. Thermochemical piles or LLSVPs may therefore constitute an enriched reservoir in the deep mantle
A novel feature selection-based sequential ensemble learning method for class noise detection in high-dimensional data
© 2018, Springer Nature Switzerland AG. Most of the irrelevant or noise features in high-dimensional data present significant challenges to high-dimensional mislabeled instances detection methods based on feature selection. Traditional methods often perform the two dependent step: The first step, searching for the relevant subspace, and the second step, using the feature subspace which obtained in the previous step training model. However, Feature subspace that are not related to noise scores and influence detection performance. In this paper, we propose a novel sequential ensemble method SENF that aggregate the above two phases, our method learns the sequential ensembles to obtain refine feature subspace and improve detection accuracy by iterative sparse modeling with noise scores as the regression target attribute. Through extensive experiments on 8 real-world high-dimensional datasets from the UCI machine learning repository [3], we show that SENF performs significantly better or at least similar to the individual baselines as well as the existing state-of-the-art label noise detection method
Methods for identifying surgical wound infection after discharge from hospital: a systematic review.
Background: Wound infections are a common complication of surgery that add significantly to the morbidity of patients and costs of treatment. The global trend towards reducing length of hospital stay post-surgery and the increase in day case surgery means that surgical site infections (SSI) will increasingly occur after hospital discharge. Surveillance of SSIs is important because rates of SSI are viewed as a measure of hospital performance, however accurate detection of SSIs post-hospital discharge is not straightforward. Methods: We conducted a systematic review of methods of post discharge surveillance for surgical wound infection and undertook a national audit of methods of post-discharge surveillance for surgical site infection currently used within United Kingdom NHS Trusts. Results: Seven reports of six comparative studies which examined the validity of post-discharge surveillance methods were located; these involved different comparisons and some had methodological limitations, making it difficult to identify an optimal method. Several studies evaluated automated screening of electronic records and found this to be a useful strategy for the identification of SSIs that occurred post discharge. The audit identified a wide range of relevant post-discharge surveillance programmes in England, Scotland and Wales and Northern Ireland; however, these programmes used varying approaches for which there is little supporting evidence of validity and/or reliability. Conclusion: In order to establish robust methods of surveillance for those surgical site infections that occur post discharge, there is a need to develop a method of case ascertainment that is valid and reliable post discharge. Existing research has not identified a valid and reliable method. A standardised definition of wound infection ( e. g. that of the Centres for Disease Control) should be used as a basis for developing a feasible, valid and reliable approach to defining post discharge SSI. At a local level, the method used to ascertain post discharge SSI will depend upon the purpose of the surveillance, the nature of available routine data and the resources available
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