929 research outputs found
NUV/Blue spectral observations of sprites in the 320-460 nm region: (2PG) Emissions
A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98
aircraft sprite observation campaign during July 1998. In this wavelength range
video rate (60 fields/sec) spectrographic observations found the NUV/blue
emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG)
present in the spectrum is confirmed by observations of a co-aligned, narrowly
filtered 427.8 nm imager and is in agreement with previous ground-based
filtered photometer observations. The synthetic spectral fit to the
observations indicates a characteristic energy of ~1.8 eV, in agreement with
our other NUV observations.Comment: 7 pages, 2 figures, 1 table, JGR Space Physics "Effects of
Thunderstorms and Lightning in the Upper Atmosphere" Special Sectio
UV solar irradiance in observations and the NRLSSI and SATIRE-S models
Total solar irradiance and UV spectral solar irradiance have been monitored
since 1978 through a succession of space missions. This is accompanied by the
development of models aimed at replicating solar irradiance by relating the
variability to solar magnetic activity. The NRLSSI and SATIRE-S models provide
the most comprehensive reconstructions of total and spectral solar irradiance
over the period of satellite observation currently available. There is
persistent controversy between the various measurements and models in terms of
the wavelength dependence of the variation over the solar cycle, with
repercussions on our understanding of the influence of UV solar irradiance
variability on the stratosphere. We review the measurement and modelling of UV
solar irradiance variability over the period of satellite observation. The
SATIRE-S reconstruction is consistent with spectral solar irradiance
observations where they are reliable. It is also supported by an independent,
empirical reconstruction of UV spectral solar irradiance based on UARS/SUSIM
measurements from an earlier study. The weaker solar cycle variability produced
by NRLSSI between 300 and 400 nm is not evident in any available record. We
show that although the method employed to construct NRLSSI is principally
sound, reconstructed solar cycle variability is detrimentally affected by the
uncertainty in the SSI observations it draws upon in the derivation. Based on
our findings, we recommend, when choosing between the two models, the use of
SATIRE-S for climate studies
Treatment Options for Carbapenem-Resistant Enterobacteriaceae Infections
This article provides a comprehensive review of currently available treatment options for infections due to carbapenem-resistant Enterobacteriaceae (CRE). Antimicrobial resistance in Gram-negative bacteria is an emerging and serious global public health threat. Carbapenems have been used as the ālast-lineā treatment for infections caused by resistant Enterobacteriaceae, including those producing extended spectrum Ć-lactamases. However, Enterobacteriaceae that produce carbapenemases, which are enzymes that deactivate carbapenems and most other Ć-lactam antibiotics, have emerged and are increasingly being reported worldwide. Despite this increasing burden, the most optimal treatment for CRE infections is largely unknown. For the few remaining available treatment options, there are limited efficacy data to support their role in therapy. Nevertheless, current treatment options include the use of older agents, such as polymyxins, fosfomycin, and aminoglycosides, which have been rarely used due to efficacy and/or toxicity concerns. Optimization of dosing regimens and combination therapy are additional treatment strategies being explored. Carbapenem-resistant Enterobacteriaceae infections are associated with poor outcomes and high mortality. Continued research is critically needed to determine the most appropriate treatment
Leukocyte function and health status of calves supplemented with vitamins A and E
Forty-four Holstein calves were fed milk
replacers with varied concentrations of vitamins
A and E from 3 to 45 d of age to determine their
effects on concentrations of plasma vitamin A
(retinol and retinyl palmitate) and vitamin E (a-
tocopherol), lymphocyte and neutrophil functions,
and health of calves. Plasma a-tocopherol was
unaffected by increased vitamin A supplementation.
Fecal scores, and eye and nose membrane
responses were improved with increased vitamin
A and lower vitamin E concentration, whereas the
same treatment tended to reduce neutrophil
cytotoxic and bactericidal activity by 6 wk of age.
Increased supplemental vitamin E tended to
enhance neutrophil functions. However, age
appeared to have an effect on response to both
vitamins
Exploring tandem ruthenium-catalyzed hydrogen transfer and SNAr chemistry
A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives
Retrotransposon activation contributes to neurodegeneration in a Drosophila TDP-43 model of ALS
Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two incurable neurodegenerative disorders that exist on a symptomological spectrum and share both genetic underpinnings and pathophysiological hallmarks. Functional abnormality of TAR DNA-binding protein 43 (TDP-43), an aggregation-prone RNA and DNA binding protein, is observed in the vast majority of both familial and sporadic ALS cases and in ~40% of FTLD cases, but the cascade of events leading to cell death are not understood. We have expressed human TDP-43 (hTDP-43) in Drosophila neurons and glia, a model that recapitulates many of the characteristics of TDP-43-linked human disease including protein aggregation pathology, locomotor impairment, and premature death. We report that such expression of hTDP-43 impairs small interfering RNA (siRNA) silencing, which is the major post-transcriptional mechanism of retrotransposable element (RTE) control in somatic tissue. This is accompanied by de-repression of a panel of both LINE and LTR families of RTEs, with somewhat different elements being active in response to hTDP-43 expression in glia versus neurons. hTDP-43 expression in glia causes an early and severe loss of control of a specific RTE, the endogenous retrovirus (ERV) gypsy. We demonstrate that gypsy causes the degenerative phenotypes in these flies because we are able to rescue the toxicity of glial hTDP-43 either by genetically blocking expression of this RTE or by pharmacologically inhibiting RTE reverse transcriptase activity. Moreover, we provide evidence that activation of DNA damage-mediated programmed cell death underlies both neuronal and glial hTDP-43 toxicity, consistent with RTE-mediated effects in both cell types. Our findings suggest a novel mechanism in which RTE activity contributes to neurodegeneration in TDP-43-mediated diseases such as ALS and FTLD
Identification of the lipopolysaccharide modifications controlled by the Salmonella PmrA/PmrB system mediating resistance to Fe(III) and Al(III)
Iron is an essential metal but can be toxic in excess. While several homeostatic mechanisms prevent oxygen-dependent killing promoted by Fe(II), little is known about how cells cope with Fe(III), which kills by oxygen-independent means. Several Gram-negative bacterial species harbour a regulatory system ā termed PmrA/PmrB ā that is activated by and required for resistance to Fe(III). We now report the identification of the PmrA-regulated determinants mediating resistance to Fe(III) and Al(III) in Salmonella enterica serovar Typhimurium. We establish that these determinants remodel two regions of the lipopolysaccharide, decreasing the negative charge of this major constituent of the outer membrane. Remodelling entails the covalent modification of the two phosphates in the lipid A region with phosphoethanolamine and 4-aminoarabinose, which has been previously implicated in resistance to polymyxin B, as well as dephosphorylation of the Hep(II) phosphate in the core region by the PmrG protein. A mutant lacking the PmrA-regulated Fe(III) resistance genes bound more Fe(III) than the wild-type strain and was defective for survival in soil, suggesting that these PmrA-regulated lipopolysaccharide modifications aid Salmonella's survival and spread in non-host environments
Massively distributed authorship of academic papers
Wiki-like or crowdsourcing models of collaboration can provide a number of benefits to academic work. These techniques may engage expertise from different disciplines, and potentially increase productivity. This paper presents a model of massively distributed collaborative authorship of academic papers. This model, developed by a collective of thirty authors, identifies key tools and techniques that would be necessary or useful to the writing process. The process of collaboratively writing this paper was used to discover, negotiate, and document issues in massively authored scholarship. Our work provides the first extensive discussion of the experiential aspects of large-scale collaborative researc
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