Gaseous optical contamination of the spacecraft environment: A review

Interactions between the ambient atmosphere and orbiting spacecraft, sounding rockets, and suborbital vehicles, and with their effluents, give rise to optical (extreme UV to LWIR) foreground radiation which constitutes noise that raises the detection threshold for terrestrial and celestial radiations, as well as military targets. Researchers review the current information on the on-orbit optical contamination. Its source species are created in interaction processes that can be grouped into three categories: (1) Reactions in the gas phase between the ambient atmosphere and desorbates and exhaust; (2) Reactions catalyzed by exposed ram surfaces, which occur spontaneously even in the absence of active material releases from the vehicles; and (3) Erosive excitative reactions with exposed bulk (organic) materials, which have recently been identified in the laboratory though not as yet observed on spacecraft. Researchers also assess the effect of optical pumping by earthshine and sunlight of both reaction products and effluents

Photometric analysis of a space shuttle water venting

Presented here is a preliminary interpretation of a recent experiment conducted on Space Shuttle Discovery (Mission STS 29) in which a stream of liquid supply water was vented into space at twilight. The data consist of video images of the sunlight-scattering water/ice particle cloud that formed, taken by visible light-sensitive intensified cameras both onboard the spacecraft and at the AMOS ground station near the trajectory's nadir. This experiment was undertaken to study the phenomenology of water columns injected into the low-Earth orbital environment, and to provide information about the lifetime of ice particles that may recontact Space Shuttle orbits later. The findings about the composition of the cloud have relevance to ionospheric plasma depletion experiments and to the dynamics of the interaction of orbiting spacecraft with the environment

Body Composition of Older Female Subjects: New Approaches and their Limitations

Criterion values for body composition include N and K measurements and (in epidemiological surveys) Wt/ht2. Methods of estimating body fat (skinfold data and hydrostatic weighing) have been evaluated against these criteria in a sample of 12 older but moderately active female subjects (age 48-58 years, average body fat by hydrostatic weighing 30.1%). In this age group, the hydrostatic estimate is less closely correlated with criterion values than is a skinfold estimate. It is suggested that this reflects difficulties in determining the density of older subjects, and uncertainties concerning change in the density of lean tissue with age. Potassium estimates of body fat are strengthened by simultaneous consideration of N and Ca data, while N estimates are strengthened by consideration of K and Ca figures. Nevertheless, the simple anthropometric criterion (wt/ht2) yields a higher correlation with skinfold data than do estimates derived from N and/or K, in part because of uncertainty regarding age-related changes in body composition. Moreover, wt/ht2 estimates of body fat cannot be strengthened by considering whole body counter estimates of body fat. Within the limitations imposed by this small sample of healthy older women, anthropometric data thus seem preferable to either hydrostatic or whole body counter estimates of body fat

Glyco-Engineering Cell Surfaces by Exo-Enzymatic Installation of GlcNAz and LacNAz Motifs

Exo-enzymatic glyco-engineering of cell-surface glycoconjugates enables the selective display of well-defined glyco-motifs bearing bioorthogonal functional groups, which can be used to study glycans and their interactions with glycan-binding proteins. In recent years, strategies to edit cellular glycans by installing monosaccharides and their derivatives using glycosyltransferase enzymes have rapidly expanded. However, analogous methods to introduce chemical reporter-functionalized type 2 LacNAc motifs have not been reported. Herein, we report the chemo-enzymatic synthesis of unnatural UDP-GlcNAc and UDP-GalNAc nucleotide-sugars bearing azide, alkyne, and diazirine functionalities on the C2-acetamido group using the mutant uridylyltransferase AGX1F383A. The unnatural UDP-GlcNAc derivatives were examined as substrates for the human GlcNAc-transferase B3GNT2, where it was found that modified donors were tolerated for transfer, albeit to a lesser extent than the natural UDP-GlcNAc substrate. When the GlcNAc derivatives were examined as acceptor substrates for the human Gal-transferase B4GalT1, all derivatives were well tolerated and the enzyme could successfully form derivatized LacNAcs. B3GNT2 was also used to exo-enzymatically install GlcNAc and unnatural GlcNAc derivatives on cell-surface glycans. GlcNAc- or GlcNAz-engineered cells were further extended by B4GalT1 and UDP-Gal, producing LacNAc- or LacNAz-engineered cells. Our proof-of-concept glyco-engineering labeling strategy is amenable to different cell types and our work expands the exo-enzymatic glycan editing toolbox to selectively introduce unnatural type 2 LacNAc motifs

Single-cell RNA-sequencing reveals transcriptional dynamics of estrogen-induced dysplasia in the ovarian surface epithelium.

Estrogen therapy increases the risk of ovarian cancer and exogenous estradiol accelerates the onset of ovarian cancer in mouse models. Both in vivo and in vitro, ovarian surface epithelial (OSE) cells exposed to estradiol develop a subpopulation that loses cell polarity, contact inhibition, and forms multi-layered foci of dysplastic cells with increased susceptibility to transformation. Here, we use single-cell RNA-sequencing to characterize this dysplastic subpopulation and identify the transcriptional dynamics involved in its emergence. Estradiol-treated cells were characterized by up-regulation of genes associated with proliferation, metabolism, and survival pathways. Pseudotemporal ordering revealed that OSE cells occupy a largely linear phenotypic spectrum that, in estradiol-treated cells, diverges towards cell state consistent with the dysplastic population. This divergence is characterized by the activation of various cancer-associated pathways including an increase in Greb1 which was validated in fallopian tube epithelium and human ovarian cancers. Taken together, this work reveals possible mechanisms by which estradiol increases epithelial cell susceptibility to tumour initiation

IN SEARCH OF CREATIVE EXPRESSION: THE DIALECTICS OF RACE, POLITICS, AND LITERATURE IN CARIBBEAN DUB POETRY / IEŠKANT KŪRYBINĖS IŠRAIŠKOS: RASĖS, POLITIKOS IR LITERATŪROS DIALEKTIKA KARIBŲ DUB ŽANRO POEZIJOJE

This article examines dub poetry as an artistic form located along several borderlines, both spatial and cultural. Formulated by poets of African descent, the creative language of dub poets was often conceptualized through the framework of identity politics and an anti-colonial approach. Yet from the 1980s, dub poetry became institutionalized simultaneously within the pop culture industry and in “respectable” venues such as academic research, a process that calls its initial political orientation into question. In light of its differentiated formations, audiences, mediating devices, and forms of reception, however, we might view and evaluate dub poetry not exclusively through the prism of political speech, but also as a cultural form. Based on texts, recordings and performance analysis this article is a call to acknowledge dub poetry, and artistic expression in general, as the result of aesthetic decisions rather than exclusively moral ones. Santrauka Straipsnyje tyrinėjama dub žanro poezija kaip meninė forma, vyraujanti ties kai kuriais paribiais – tiek erdviniais, tiek kultūriniais. Formuluota Afrikos nuosmukio laikotarpio poetų, kūrybinė dub žanro poetų kalba politikos ir antikolonijiniu požiūriais dažnai buvo konceptualizuojama ieškant tapatumo. Nuo XX a. 9-ojo dešimtmečio dub poezija tapo institucionalizuota tiek popkultūros industrijoje, tiek „gerbiamose“ srityse, tokiose kaip akademiniai tyrimai – tai procesas, kvestionuojantis savąją vidinę politinę orientaciją. Šio proceso diferencijuotų formacijų, auditorijų, medijuojančių priemonių ir priėmimo formų fone vis dėlto galima į dub poeziją žvelgti ir ją vertinti ne išimtinai per politinės kalbos prizmę, bet ir kaip kultūrinę formą. Pagrįstas tekstų, įrašų ir performansų analize, šis straipsnis – tai kvietimas pripažinti dub poeziją ir meninę išraišką apskritai ne tiek kaip išskirtinai moralinių, kiek estetinių sprendimų rezultatą. Reikšminiai žodžiai: juodumas, Karibų dub žanro poezija, Jamaika, performansas, rasė, regis