9,303 research outputs found
Prophylactic tracheostomy in aged and poor risk general surgical patients
The most common postoperative complications are those involving respiration, and they are especially dangerous to patients classified as poor risks because of age or other handicaps. Among the 11 patients whose histories are given, some who were nearly moribund from respiratory difficulties were saved by tracheostomy; others made good recoveries from major surgery under conditions that would have been hopeless without the help afforded by prophylactic tracheostomy. If this possibility is foreseen, an orderly procedure can be carried out in the operating room instead of desperate measures on the ward. Scrupulous care of the tracheostomy is essential; this includes aseptic precautions, humidification of the inhaled air or oxygen, and the systematic but gentle use of suction to aspirate accumulating mucus. © 1959, American Medical Association. All rights reserved
A Universal Stellar Initial Mass Function? A Critical Look at Variations
Few topics in astronomy initiate such vigorous discussion as whether or not
the initial mass function (IMF) of stars is universal, or instead sensitive to
the initial conditions of star formation. The distinction is of critical
importance: the IMF influences most of the observable properties of stellar
populations and galaxies, and detecting variations in the IMF could provide
deep insights into the process by which stars form. In this review, we take a
critical look at the case for IMF variations, with a view towards whether other
explanations are sufficient given the evidence. Studies of the field, local
young clusters and associations, and old globular clusters suggest that the
vast majority were drawn from a "universal" IMF: a power-law of Salpeter index
() above a few solar masses, and a log normal or shallower
power-law () between a few tenths and a few solar masses
(ignoring the effects of unresolved binaries). The shape and universality of
the IMF at the stellar-substellar boundary is still under investigation and
uncertainties remain large, but most observations are consistent with a IMF
that declines () well below the hydrogen burning limit.
Observations of resolved stellar populations and the integrated properties of
most galaxies are also consistent with a "universal IMF", suggesting no gross
variations in the IMF over much of cosmic time. There are indications of
"non-standard" IMFs in specific local and extragalactic environments, which
clearly warrant further study. Nonetheless, there is no clear evidence that the
IMF varies strongly and systematically as a function of initial conditions
after the first few generations of stars.Comment: 49 pages, 5 figures, to appear in Annual Reviews of Astronomy and
Astrophysics (2010, volume 48
The polymeric stability of the Escherichia coli F4 (K88) fimbriae enhances its mucosal immunogenicity following oral immunization
<p>Only a few vaccines are commercially available against intestinal infections since the induction of a protective intestinal immune response is difficult to achieve. For instance, oral administration of most proteins results in oral tolerance instead of an antigen-specific immune response. We have shown before that as a result of oral immunization of piglets with F4 fimbriae purified from pathogenic enterotoxigenic Escherichia coli (ETEC), the fimbriae bind to the F4 receptor (F4R) in the intestine and induce a protective F4-specific immune response. F4 fimbriae are very stable polymeric structures composed of some minor subunits and a major subunit FaeG that is also the fimbrial adhesin. In the present study, the mutagenesis experiments identified FaeG amino acids 97 (N to K) and 201 (I to V) as determinants for F4 polymeric stability. The interaction between the FaeG subunits in mutant F4 fimbriae is reduced but both mutant and wild type fimbriae behaved identically in F4R binding and showed equal stability in the gastro-intestinal lumen. Oral immunization experiments indicated that a higher degree of polymerisation of the fimbriae in the intestine was correlated with a better F4-specific mucosal immunogenicity. These data suggest that the mucosal immunogenicity of soluble virulence factors can be increased by the construction of stable polymeric structures and therefore help in the development of effective mucosal vaccines.</p></p
Automatic estimation of harmonic tension by distributed representation of chords
The buildup and release of a sense of tension is one of the most essential
aspects of the process of listening to music. A veridical computational model
of perceived musical tension would be an important ingredient for many music
informatics applications. The present paper presents a new approach to
modelling harmonic tension based on a distributed representation of chords. The
starting hypothesis is that harmonic tension as perceived by human listeners is
related, among other things, to the expectedness of harmonic units (chords) in
their local harmonic context. We train a word2vec-type neural network to learn
a vector space that captures contextual similarity and expectedness, and define
a quantitative measure of harmonic tension on top of this. To assess the
veridicality of the model, we compare its outputs on a number of well-defined
chord classes and cadential contexts to results from pertinent empirical
studies in music psychology. Statistical analysis shows that the model's
predictions conform very well with empirical evidence obtained from human
listeners.Comment: 12 pages, 4 figures. To appear in Proceedings of the 13th
International Symposium on Computer Music Multidisciplinary Research (CMMR),
Porto, Portuga
The "Solar Model Problem" Solved by the Abundance of Neon in Stars of the Local Cosmos
The interior structure of the Sun can be studied with great accuracy using
observations of its oscillations, similar to seismology of the Earth. Precise
agreement between helioseismological measurements and predictions of
theoretical solar models has been a triumph of modern astrophysics (Bahcall et
al. 2005). However, a recent downward revision by 25-35% of the solar
abundances of light elements such as C, N, O and Ne (Asplund et al. 2004) has
broken this accordance: models adopting the new abundances incorrectly predict
the depth of the convection zone, the depth profiles of sound speed and
density, and the helium abundance (Basu Antia 2004, Bahcall et al. 2005). The
discrepancies are far beyond the uncertainties in either the data or the model
predictions (Bahcall et al. 2005b). Here we report on neon abundances relative
to oxygen measured in a sample of nearby solar-like stars from their X-ray
spectra. They are all very similar and substantially larger than the recently
revised solar value. The neon abundance in the Sun is quite poorly determined.
If the Ne/O abundance in these stars is adopted for the Sun the models are
brought back into agreement with helioseismology measurements (Antia Basu 2005,
Bahcall et al. 2005c).Comment: 13 pages, 3 Figure
Towards the glueball spectrum from unquenched lattice QCD
We use a variational technique to study heavy glueballs on gauge
configurations generated with 2+1 flavours of ASQTAD improved staggered
fermions. The variational technique includes glueball scattering states. The
measurements were made using 2150 configurations at 0.092 fm with a pion mass
of 360 MeV. We report masses for 10 glueball states. We discuss the prospects
for unquenched lattice QCD calculations of the oddballs.Comment: 19 pages, 4 tables and 8 figures. One figure added. Now matches the
published versio
Experimental observation of nonlinear Thomson scattering
A century ago, J. J. Thomson showed that the scattering of low-intensity
light by electrons was a linear process (i.e., the scattered light frequency
was identical to that of the incident light) and that light's magnetic field
played no role. Today, with the recent invention of ultra-high-peak-power
lasers it is now possible to create a sufficient photon density to study
Thomson scattering in the relativistic regime. With increasing light intensity,
electrons quiver during the scattering process with increasing velocity,
approaching the speed of light when the laser intensity approaches 10^18
W/cm^2. In this limit, the effect of light's magnetic field on electron motion
should become comparable to that of its electric field, and the electron mass
should increase because of the relativistic correction. Consequently, electrons
in such high fields are predicted to quiver nonlinearly, moving in figure-eight
patterns, rather than in straight lines, and thus to radiate photons at
harmonics of the frequency of the incident laser light, with each harmonic
having its own unique angular distribution. In this letter, we report the first
ever direct experimental confirmation of these predictions, a topic that has
previously been referred to as nonlinear Thomson scattering. Extension of these
results to coherent relativistic harmonic generation may eventually lead to
novel table-top x-ray sources.Comment: including 4 figure
Substance P induces localization of MIF/α1-inhibitor-3 complexes to umbrella cells via paracellular transit through the urothelium in the rat bladder
BACKGROUND: Macrophage migration inhibitory factor (MIF) is released into the intraluminal fluid during bladder inflammation in the rat complexed to α1-inhibitor-3 (A1-I3; a rodent proteinase inhibitor in the α-macroglobulin family). The location of A1-I3 in the bladder had not been investigated. Therefore, we examined the location of A1-I3 and MIF/A1-I3 complexes in the bladder and changes due to experimental inflammation. METHODS: Anesthetized male rats had bladders removed with no treatment (intact) or were injected with Substance P (SP; s.c.; saline vehicle). After one hour intraluminal fluid was removed, bladder was excised and MIF and A1-I3 levels were determined using ELISA and/or western-blotting. MIF co-immunoprecipitation determined MIF/A1-I3 complexes in the bladder. Bladder sections were immunostained for A1-I3 and MIF/A1-I3. RESULTS: A1-I3 immunostaining was observed in interstitial spaces throughout the bladder (including submucosa) but not urothelium in intact and saline-treated rats. RT-PCR showed that the bladder does not synthesize A1-I3, therefore, A1-I3 in the interstitial space of the bladder must be plasma derived. In SP-treated rats, A1-I3 in the bladder increased and A1-I3 was observed traversing through the urothelium. Umbrella cells that do not show MIF and/or A1-I3 immunostaining in intact or saline-treated rats, showed co-localization of MIF and A1-I3 after SP-treatment. Western blotting demonstrated that in the bladder MIF formed non-covalent interactions and also binds covalently to A1-I3 to form high molecular weight MIF/A1-I3 complexes (170, 130 and 75-kDa, respectively, verified by co-immunoprecipitation). SP-induced inflammation selectively reduced 170-kDa MIF/A1-I3 in the bladder while increasing 170 and 130-kDa MIF/A1-I3 in the intraluminal fluid. CONCLUSION: A1-I3 and MIF/A1-I3 complexes are resident in bladder interstitium. During SP-induced inflammation, MIF/A1-I3 complexes are released from the bladder into the lumen. Binding of MIF/A1-I3 complexes to urothelial cells during inflammation suggests these complexes participate in the inflammatory reaction through activation of receptors for MIF and/or for A1-I3
Crohn's Disease Exacerbation Induced by Edwardsiella tarda Gastroenteritis
Exacerbations of Crohn's disease are not infrequently associated with bacterial gastroenteritis. The recognition of synchronous infections in such patients is vital for the initiation of appropriate antimicrobial therapy. Furthermore, the detection of active bacterial infections may lead the clinician to delay starting biological therapy. We report here a man presenting with an exacerbation of his Crohn's disease during a trip to Thailand. Stool cultures were positive for the unusual gut pathogen Edwardsiella tarda. The patient's symptoms resolved with concurrent antibiotic and steroid therapy. This finding demonstrates the value of performing stool culture in all patients presenting with exacerbations of inflammatory bowel diseases
Stable Heterogeneity for the Production of Diffusible Factors in Cell Populations
The production of diffusible molecules that promote survival and growth is common in bacterial and eukaryotic cell populations, and can be considered a form of cooperation between cells. While evolutionary game theory shows that producers and non-producers can coexist in well-mixed populations, there is no consensus on the possibility of a stable polymorphism in spatially structured populations where the effect of the diffusible molecule extends beyond one-step neighbours. I study the dynamics of biological public goods using an evolutionary game on a lattice, taking into account two assumptions that have not been considered simultaneously in existing models: that the benefit of the diffusible molecule is a non-linear function of its concentration, and that the molecule diffuses according to a decreasing gradient. Stable coexistence of producers and non-producers is observed when the benefit of the molecule is a sigmoid function of its concentration, while strictly diminishing returns lead to coexistence only for very specific parameters and linear benefits never lead to coexistence. The shape of the diffusion gradient is largely irrelevant and can be approximated by a step function. Since the effect of a biological molecule is generally a sigmoid function of its concentration (as described by the Hill equation), linear benefits or strictly diminishing returns are not an appropriate approximations for the study of biological public goods. A stable polymorphism of producers and non-producers is in line with the predictions of evolutionary game theory and likely to be common in cell populations
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