853 research outputs found
Extrinsic properties of automorphism groups of formal groups
We prove two conjectures on the automorphism group of a one-dimensional
formal group law defined over a field of positive characteristic. The first is
that if a series commutes with a nontorsion automorphism of the formal group
law, then that series is already an automorphism. The second is that the group
of automorphisms is its own normalizer in the group of all invertible series
over the ground field. A consequence of these results is that a formal group
law in positive characteristic is determined by any one of its nontorsion
automorphisms.Comment: 15 page
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Determinant of HIV-1 mutational escape from cytotoxic T lymphocytes.
CD8+ class I-restricted cytotoxic T lymphocytes (CTLs) usually incompletely suppress HIV-1 in vivo, and while analogous partial suppression induces antiretroviral drug-resistance mutations, epitope escape mutations are inconsistently observed. However, escape mutation depends on the net balance of selective pressure and mutational fitness costs, which are poorly understood and difficult to study in vivo. Here we used a controlled in vitro system to evaluate the ability of HIV-1 to escape from CTL clones, finding that virus replicating under selective pressure rapidly can develop phenotypic resistance associated with genotypic changes. Escape varied between clones recognizing the same Gag epitope or different Gag and RT epitopes, indicating the influence of the T cell receptor on pressure and fitness costs. Gag and RT escape mutations were monoclonal intra-epitope substitutions, indicating limitation by fitness constraints in structural proteins. In contrast, escape from Nef-specific CTL was more rapid and consistent, marked by a polyclonal mixture of epitope point mutations and upstream frameshifts. We conclude that incomplete viral suppression by CTL can result in rapid emergence of immune escape, but the likelihood is strongly determined by factors influencing the fitness costs of the particular epitope targeted and the ability of responding CTL to recognize specific epitope variants
Variasi Temperatur Pencampuran Terhadap Parameter Marshall Pada Campuran Lapis Aspal Beton
This study was conducted to determine the effect of temperature variations on the mixing processof the asphalt concrete AC-WC (Asphalt Concrete-Wearing Course) subtle gradations in themiddle limit and lower limit of the Marshall parameters with reference to specifications of BinaMarga, 2010.From the results of experiments conducted that the optimum asphalt content is used to middle limitusing a asphalt content of 5,7% and 6,8% for the lower limit after that mixing was done usingtemperature variation of 120 o C, 130 o C, 140 o C, 150 o C, and 160 o C.To a mixture of Laston AC-WC subtle gradations middle limit grading 5,7% asphalt contentmixing temperature using a temperature of 120 o C, 130 o C, 140 o C, 150 o C, 160 o C and still meet allstandards of marshall parameters. Ideal mixing temperature variations in the middle limit ofmixing temperature 150 o C-160 o C. While the lower limit to the level of 6,8% asphalt contentmixing temperatures between 120 o C-160 o C did not meet the specifications, because the MQ valuebelow the minimum value of 250 kg / mm
Evidence of Three Mechanisms Explaining the Radius Anomaly of Hot Jupiters
The radii of hot Jupiters are still not fully understood and all of the
proposed explanations are based on the idea that these close-in giant planets
possess hot interiors. We approach the radius anomaly problem by adopting a
statistical approach. We infer the internal luminosity for the sample of hot
Jupiters, study its effect on the interior structure, and put constraints on
which mechanism is the dominant one. We develop a flexible and robust
hierarchical Bayesian model that couples the interior structure of exoplanets
to their observed properties. We apply the model to 314 hot Jupiters and infer
the internal luminosity distribution for each planet and study at the
population level ({\it i}) the mass-luminosity-radius distribution and as a
function of equilibrium temperature the distributions of the ({\it ii}) heating
efficiency, ({\it iii}) internal temperature, and the ({\it iv}) pressure of
the radiative-convective-boundary (RCB). We find that hot Jupiters tend to have
high internal luminosity leading to hot interiors. This has important
consequences on the cooling rate and we find that the RCB is located at low
pressures. Assuming that the ultimate source of the extra heating is the
irradiation from the host star, we illustrate that the heating efficiency
follows a Gaussian distribution, in agreement with previous results. We discuss
our findings in the context of the proposed heating mechanisms and illustrate
that ohmic dissipation, advection of potential temperature, and thermal tides
are in agreement with certain trends inferred from our analysis and thus all
three models can explain aspects of the observations. We provide new insights
on the interior structure of hot Jupiters and show that with our current
knowledge it is still challenging to firmly identify the universal mechanism
driving the inflated radii.Comment: 27 pages and 12 figures. Accepted in A&A. Source code can be found at
https://github.com/psarkis/bloatedHJs and data at
https://www.space.unibe.ch/research/research_groups/planets_in_time/numerical_data/index_eng.htm
Banach Analytic Sets and a Non-Linear Version of the Levi Extension Theorem
We prove a certain non-linear version of the Levi extension theorem for
meromorphic functions. This means that the meromorphic function in question is
supposed to be extendable along a sequence of complex curves, which are
arbitrary, not necessarily straight lines. Moreover, these curves are not
supposed to belong to any finite dimensional analytic family. The conclusion of
our theorem is that nevertheless the function in question meromorphically
extends along an (infinite dimensional) analytic family of complex curves and
its domain of existence is a pinched domain filled in by this analytic family.Comment: 19 pages, This is the final version with significant corrections and
improvements. To appear in Arkiv f\"or matemati
Determinants of HIV-1 Mutational Escape From Cytotoxic T Lymphocytes
CD8+ class I–restricted cytotoxic T lymphocytes (CTLs) usually incompletely suppress HIV-1 in vivo, and while analogous partial suppression induces antiretroviral drug-resistance mutations, epitope escape mutations are inconsistently observed. However, escape mutation depends on the net balance of selective pressure and mutational fitness costs, which are poorly understood and difficult to study in vivo. Here we used a controlled in vitro system to evaluate the ability of HIV-1 to escape from CTL clones, finding that virus replicating under selective pressure rapidly can develop phenotypic resistance associated with genotypic changes. Escape varied between clones recognizing the same Gag epitope or different Gag and RT epitopes, indicating the influence of the T cell receptor on pressure and fitness costs. Gag and RT escape mutations were monoclonal intra-epitope substitutions, indicating limitation by fitness constraints in structural proteins. In contrast, escape from Nef-specific CTL was more rapid and consistent, marked by a polyclonal mixture of epitope point mutations and upstream frameshifts. We conclude that incomplete viral suppression by CTL can result in rapid emergence of immune escape, but the likelihood is strongly determined by factors influencing the fitness costs of the particular epitope targeted and the ability of responding CTL to recognize specific epitope variants
Outer Membrane Vesicles of a Human Commensal Mediate Immune Regulation and Disease Protection
Commensal bacteria impact host health and immunity through various mechanisms, including the production of immunomodulatory molecules. Bacteroides fragilis produces a capsular polysaccharide (PSA), which induces regulatory T cells and mucosal tolerance. However, unlike pathogens, which employ secretion systems, the mechanisms by which commensal bacteria deliver molecules to the host remain unknown. We reveal that Bacteroides fragilis releases PSA in outer membrane vesicles (OMVs) that induce immunomodulatory effects and prevent experimental colitis. Dendritic cells (DCs) sense OMV-associated PSA through TLR2, resulting in enhanced regulatory T cells and anti-inflammatory cytokine production. OMV-induced signaling in DCs requires growth arrest and DNA-damage-inducible protein (Gadd45α). DCs treated with PSA-containing OMVs prevent experimental colitis, whereas Gadd45α^(−/−) DCs are unable to promote regulatory T cell responses or suppress proinflammatory cytokine production and host pathology. These findings demonstrate that OMV-mediated delivery of a commensal molecule prevents disease, uncovering a mechanism of interkingdom communication between the microbiota and mammals
Spread of imipenem-resistant Acinetobacter baumannii co-expressing OXA-23 and GES-11 carbapenemases in Lebanon
© 2015 The Authors. Objectives: The acquisition of carbapenemases by Acinetobacter baumannii is reported increasingly worldwide, but data from Lebanon are limited. The aims of this study were to evaluate the prevalence of imipenem-resistant A. baumannii in Lebanon, identify resistance determinants, and detect clonal relatedness. Methods: Imipenem-resistant A. baumannii were collected from nine Lebanese hospitals during 2012. Antimicrobial susceptibility, the cloxacillin effect, and ethylenediaminetetraacetic acid (EDTA) synergy were determined. Genes encoding carbapenemases and insertion sequence IS. Aba1 were screened via PCR sequencing. IS. Aba1 position relative to genes encoding Acinetobacter-derived cephalosporinases (ADCs) and OXA-23 was studied by PCR mapping. Clonal linkage was examined by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Results: Out of 724 A. baumannii isolated in 2012, 638 (88%) were imipenem-resistant. Of these, 142 were analyzed. Clavulanic acid-imipenem synergy suggested carbapenem-hydrolyzing extended-spectrum β-lactamase. A positive cloxacillin test indicated ADCs, while EDTA detection strips were negative. Genotyping indicated that 90% of isolates co-harbored blaOXA-23 and blaGES-11. The remaining strains had blaOXA-23, blaOXA-24, blaGES-11, or blaOXA-24 with blaGES-11. ISAba1 was located upstream of blaADC and blaOXA-23 in 97% and 100% of isolates, respectively. ERIC-PCR fingerprinting revealed 18 pulsotypes spread via horizontal gene transfer and clonal dissemination. Conclusion: This survey established baseline evidence of OXA-23 and GES-11-producing A. baumannii in Lebanon, indicating the need for further surveillance
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