2,798 research outputs found
Peritonsillar Abscess with Uvular Hydrops
The use of ultrasound by emergency physicians has improved the evaluation of pharyngeal infections. We present a unique case of concomitant peritonsillar abscess and uvular hydrops in which ultrasound provided accurate, timely information in the evaluation
Far-flung Filaments of Ejecta in the Young Supernova Remnant G292.0+1.8
New optical images of the young SNR G292.0+1.8, obtained from the 0.9-m
telescope at CTIO, show a more extensive network of filaments than had been
known previously. Filaments emitting in [O III] are distributed throughout much
of the 8 arcmin diameter shell seen in X-ray and radio images, including a few
at the very outermost shell limits. We have also detected four small complexes
of filaments that show [S II] emission along with [OIII]. In a single long-slit
spectrum we find variations of almost an order of magnitude in the relative
strengths of oxygen and sulfur lines, which must result from abundance
variations. None of the filaments, with or without [S II], shows any evidence
for hydrogen, so all appear to be fragments of pure SN ejecta. The [S II]
filaments provide the first evidence for undiluted products of oxygen burning
in the ejecta from the supernova that gave rise to G292.0+1.8. Some oxygen
burning must have occurred, but the paucity of [S II]-emitting filaments
suggests that either the oxygen burning was not extensive or that most of its
products have yet to be excited. Most of the outer filaments exhibit radial,
pencil-like morphologies that suggest an origin as Rayleigh-Taylor fingers of
ejecta, perhaps formed during the explosion. Simulations of core-collapse
supernovae predict such fingers, but these have never before been so clearly
observed in a young SNR. The total flux from the SNR in [OIII] 5007 is 5.4 *
10**-12 ergs/cm**2/s. Using a distance of 6 kpc and an extinction correction
corresponding to E(B-V) = 0.6 (lower than previous values but more consistent
both with our data and radio and X-ray estimates of NH), this leads to a
luminosity of 1.6 * 10**35 ergs/s in the 5007 Ang. line.Comment: 32 pages including 10 figures, and 3 tables, accepted for publication
in AJ. Vol 132, July 2006. Higher resolution versions of the figures and a
pdf of the manuscript can be found at
http://www-int.stsci.edu/~long/papers/g292_optical
Adenovirus RIDα regulates endosome maturation by mimicking GTP-Rab7
The small guanosine triphosphatase Rab7 regulates late endocytic trafficking. Rab7-interacting lysosomal protein (RILP) and oxysterol-binding protein–related protein 1L (ORP1L) are guanosine triphosphate (GTP)–Rab7 effectors that instigate minus end–directed microtubule transport. We demonstrate that RILP and ORP1L both interact with the group C adenovirus protein known as receptor internalization and degradation α (RIDα), which was previously shown to clear the cell surface of several membrane proteins, including the epidermal growth factor receptor and Fas (Carlin, C.R., A.E. Tollefson, H.A. Brady, B.L. Hoffman, and W.S. Wold. 1989. Cell. 57:135–144; Shisler, J., C. Yang, B. Walter, C.F. Ware, and L.R. Gooding. 1997. J. Virol. 71:8299–8306). RIDα localizes to endocytic vesicles but is not homologous to Rab7 and is not catalytically active. We show that RIDα compensates for reduced Rab7 or dominant-negative (DN) Rab7(T22N) expression. In vitro, Cu2+ binding to RIDα residues His75 and His76 facilitates the RILP interaction. Site-directed mutagenesis of these His residues results in the loss of RIDα–RILP interaction and RIDα activity in cells. Additionally, expression of the RILP DN C-terminal region hinders RIDα activity during an acute adenovirus infection. We conclude that RIDα coordinates recruitment of these GTP-Rab7 effectors to compartments that would ordinarily be perceived as early endosomes, thereby promoting the degradation of selected cargo
Political conservatism predicts asymmetries in emotional scene memory
Variation in political ideology has been linked to differences in attention to and processing of emotional stimuli, with stronger responses to negative versus positive stimuli (negativity bias) the more politically conservative one is. As memory is enhanced by attention, such findings predict that memory for negative versus positive stimuli should similarly be enhanced the more conservative one is. The present study tests this prediction by having participants study 120 positive, negative, and neutral scenes in preparation for a subsequent memory test. On the memory test, the same 120 scenes were presented along with 120 new scenes and participants were to respond whether a scene was old or new. Results on the memory test showed that negative scenes were more likely to be remembered than positive scenes, though, this was true only for political conservatives. That is, a larger negativity bias was found the more conservative one was. The effect was sizeable, explaining 45% of the variance across subjects in the effect of emotion. These findings demonstrate that the relationship between political ideology and asymmetries in emotion processing extend to memory and, furthermore, suggest that exploring the extent to which subject variation in interactions among emotion, attention, and memory is predicted by conservatism may provide new insights into theories of political ideology
Stochastic Approach to Enantiomeric Excess Amplification and Chiral Symmetry Breaking
Stochastic aspects of chemical reaction models related to the Soai reactions
as well as to the homochirality in life are studied analytically and
numerically by the use of the master equation and random walk model. For
systems with a recycling process, a unique final probability distribution is
obtained by means of detailed balance conditions. With a nonlinear
autocatalysis the distribution has a double-peak structure, indicating the
chiral symmetry breaking. This problem is further analyzed by examining
eigenvalues and eigenfunctions of the master equation. In the case without
recycling process, final probability distributions depend on the initial
conditions. In the nonlinear autocatalytic case, time-evolution starting from a
complete achiral state leads to a final distribution which differs from that
deduced from the nonzero recycling result. This is due to the absence of the
detailed balance, and a directed random walk model is shown to give the correct
final profile. When the nonlinear autocatalysis is sufficiently strong and the
initial state is achiral, the final probability distribution has a double-peak
structure, related to the enantiomeric excess amplification. It is argued that
with autocatalyses and a very small but nonzero spontaneous production, a
single mother scenario could be a main mechanism to produce the homochirality.Comment: 25 pages, 6 figure
Perceptions of Cancer Risk/Efficacy and Cancer-Related Risk Behaviors : Results From the HCHS/SOL Sociocultural Ancillary Study
This study evaluated the associations among perceived risk, perceived efficacy, and engagement in six cancer-related risk behaviors in a population-based Hispanic/Latino sample. Interviews were conducted with 5,313 Hispanic/Latino adults as part of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Sociocultural Ancillary Study. Participants were recruited from the study's four field centers (Bronx, NY; Chicago, IL; Miami, FL; San Diego, CA) between February 2010 and June 2011. Perceived risk and perceived efficacy were assessed with questions drawn from the Health Interview National Trends Survey. More than half of the sample endorsed perceived risk of cancer associated with the six evaluated behaviors, as well as general perceived efficacy for preventing cancer. Adjusted logistic regression analyses demonstrated significant differences across Hispanic/Latino background groups for perceived risk associated with high consumption of alcohol and saturated fat, low consumption of fruits and vegetables, and insufficient exercise but not with smoking or low consumption of fiber. Differences were also found for the belief, "It seems like everything causes cancer" but not for other perceived efficacy items. Perceived cancer risk and perceived efficacy for preventing cancer were neither independently nor interactively associated with engagement in cancer-related risk behaviors after controlling for sociodemographic covariates. Results suggest that perceptions of risk and efficacy with regard to cancer vary across Hispanic/Latino background groups, and therefore background group differences should be considered in prevention efforts. Perceived risk and perceived efficacy were not related to cancer-related risk behaviors among Hispanics/Latinos. Further work is needed to evaluate determinants of cancer-related risk in this population
FAPRI 1999 U.S. Agricultural Outlook
Crop Production/Industries, Livestock Production/Industries,
Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity
The atmospheric deposition of both macronutrients and micronutrients plays an important role in driving primary productivity, particularly in the low-latitude ocean. We report aerosol major ion measurements for five ship-based sampling campaigns in the western Pacific from similar to 25 degrees N to 20 degrees S and compare the results with those from Atlantic meridional transects (similar to 50 degrees N to 50 degrees S) with aerosols collected and analyzed in the same laboratory, allowing full incomparability. We discuss sources of the main nutrient species (nitrogen (N), phosphorus (P), and iron (Fe)) in the aerosols and their stoichiometry. Striking north-south gradients are evident over both basins with the Northern Hemisphere more impacted by terrestrial dust sources and anthropogenic emissions and the North Atlantic apparently more impacted than the North Pacific. We estimate the atmospheric supply rates of these nutrients and the potential impact of the atmospheric deposition on the tropical western Pacific. Our results suggest that the atmospheric deposition is P deficient relative to the needs of the resident phytoplankton. These findings suggest that atmospheric supply of N, Fe, and P increases primary productivity utilizing some of the residual excess phosphorus (P*) in the surface waters to compensate for aerosol P deficiency. Regional primary productivity is further enhanced via the stimulation of nitrogen fixation fuelled by the residual atmospheric iron and P*. Our stoichiometric calculations reveal that a P* of 0.1 mu mol L-1 can offset the P deficiency in atmospheric supply for many months. This study suggests that atmospheric deposition may sustain similar to 10% of primary production in both the western tropical Pacific
A Brief History of AGN
Astronomers knew early in the twentieth century that some galaxies have
emission-line nuclei. However, even the systematic study by Seyfert (1943) was
not enough to launch active galactic nuclei (AGN) as a major topic of
astronomy. The advances in radio astronomy in the 1950s revealed a new universe
of energetic phenomena, and inevitably led to the discovery of quasars. These
discoveries demanded the attention of observers and theorists, and AGN have
been a subject of intense effort ever since. Only a year after the recognition
of the redshifts of 3C 273 and 3C 48 in 1963, the idea of energy production by
accretion onto a black hole was advanced. However, acceptance of this idea came
slowly, encouraged by the discovery of black hole X-ray sources in our Galaxy
and, more recently, supermassive black holes in the center of the Milky Way and
other galaxies. Many questions remain as to the formation and fueling of the
hole, the geometry of the central regions, the detailed emission mechanisms,
the production of jets, and other aspects. The study of AGN will remain a
vigorous part of astronomy for the foreseeable future.Comment: 37 pages, no figures. Uses aaspp4.sty. To be published in
Publications of the Astronomical Society of the Pacific, 1999 Jun
The group II intron ribonucleoprotein precursor is a large, loosely packed structure
Group II self-splicing introns are phylogenetically diverse retroelements that are widely held to be the ancestors of spliceosomal introns and retrotransposons that insert into DNA. Folding of group II intron RNA is often guided by an intron-encoded protein to form a catalytically active ribonucleoprotein (RNP) complex that plays a key role in the activity of the intron. To date, possible structural differences between the intron RNP in its precursor and spliced forms remain unexplored. In this work, we have trapped the native Lactococcus lactis group II intron RNP complex in its precursor form, by deleting the adenosine nucleophile that initiates splicing. Sedimentation velocity, size-exclusion chromatography and cryo-electron microscopy provide the first glimpse of the intron RNP precursor as a large, loosely packed structure. The dimensions contrast with those of compact spliced introns, implying that the RNP undergoes a dramatic conformational change to achieve the catalytically active state
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