180 research outputs found
Comparative Signature-Tagged Mutagenesis Identifies Pseudomonas Factors Conferring Resistance to the Pulmonary Collectin SP-A
The pulmonary collectin, surfactant protein A (SP-A), is a broad spectrum opsonin with microbicidal membrane permeabilization properties that plays a role in the innate immune response of the lung. However, the factors that govern SP-A's microbial specificity and the mechanisms by which it mediates membrane permeabilization and opsonization are not fully understood. In an effort to identify bacterial factors that confer susceptibility or resistance to SP-A, we used comparative signature-tagged mutagenesis to screen a library of 1,680 Pseudomonas aeruginosa mutants for evidence of differential pulmonary clearance in SP-A-sufficient (SP-A(+/+)) and SP-A-deficient (SP-A(−/−)) mice. Two SP-A-sensitive P. aeruginosa mutants harboring transposon insertions in genes required for salicylate biosynthesis (pch) and phosphoenolpyruvate-protein-phosphotransferase (ptsP) were recovered. The mutants were indistinguishable from the parental wild-type PA01 with regard to opsonization by SP-A, but they exhibited increased susceptibility to SP-A-mediated membrane permeabilization. These results suggest that bacterial gene functions that are required to maintain membrane integrity play crucial roles in resistance of P. aeruginosa to the permeabilizing effects of SP-A
LOLA: Lunar Optical Long-baseline Array. 1992-1993 space design
In the fall of 1992, the design and analysis of a lunar-based optical interferometer telescope array was initiated by a group of students in the Department of Aerospace Engineering at Virginia Tech. This project was undertaken at the suggestion of the Space Exploration Initiative Office at the NASA Langley Research Center. The original array design requirements, listed below, centered on the primary objective of resolving earth-type planets about stars out to a distance of ten parsecs: spectrum coverage spanning wavelengths from five nm to five mm, with a primary operating mode in the visible spectrum; a total collecting area providing a signal-to-noise ratio (SNR) of no less than 10.0 for a median wavelength of 500 nm; the individual array elements must be identical and have a maximum optical diameter of 2.0 m; and lunar site selection is limited to ten degrees north and south of the lunar equator on the lunar far side while not closer than 15 degrees to either near-side limb. Following construction by astronaut crews, array operation will be conducted from earth and astronomical observations will not be conducted during the lunar day. The entire system is designed for minimum achievable mass. The majority of the original design requirements for the telescope array were met
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Detection and Quantification of Microparticles from Different Cellular Lineages Using Flow Cytometry. Evaluation of the Impact of Secreted Phospholipase A2 on Microparticle Assessment
Microparticles, also called microvesicles, are submicron extracellular vesicles produced by plasma membrane budding and shedding recognized as key actors in numerous physio(patho)logical processes. Since they can be released by virtually any cell lineages and are retrieved in biological fluids, microparticles appear as potent biomarkers. However, the small dimensions of microparticles and soluble factors present in body fluids can considerably impede their quantification. Here, flow cytometry with improved methodology for microparticle resolution was used to detect microparticles of human and mouse species generated from platelets, red blood cells, endothelial cells, apoptotic thymocytes and cells from the male reproductive tract. A family of soluble proteins, the secreted phospholipases A2 (sPLA2), comprises enzymes concomitantly expressed with microparticles in biological fluids and that catalyze the hydrolysis of membrane phospholipids. As sPLA2 can hydrolyze phosphatidylserine, a phospholipid frequently used to assess microparticles, and might even clear microparticles, we further considered the impact of relevant sPLA2 enzymes, sPLA2 group IIA, V and X, on microparticle quantification. We observed that if enriched in fluids, certain sPLA2 enzymes impair the quantification of microparticles depending on the species studied, the source of microparticles and the means of detection employed (surface phosphatidylserine or protein antigen detection). This study provides analytical considerations for appropriate interpretation of microparticle cytofluorometric measurements in biological samples containing sPLA2 enzymes
Prognosis of cirrhotic patients admitted to intensive care unit: a meta-analysis
and METAREACIR GroupInternational audienceBackgroundThe best predictors of short- and medium-term mortality of cirrhotic patients receiving intensive care support are unknown.MethodsWe conducted meta-analyses from 13 studies (2523 cirrhotics) after selection of original articles and response to a standardized questionnaire by the corresponding authors. End-points were in-ICU, in-hospital, and 6-month mortality in ICU survivors. A total of 301 pooled analyses, including 95 analyses restricted to 6-month mortality among ICU survivors, were conducted considering 249 variables (including reason for admission, organ replacement therapy, and composite prognostic scores).ResultsIn-ICU, in-hospital, and 6-month mortality was 42.7, 54.1, and 75.1%, respectively. Forty-eight patients (3.8%) underwent liver transplantation during follow-up. In-ICU mortality was lower in patients admitted for variceal bleeding (OR 0.46; 95% CI 0.36–0.59; p 19 at baseline (OR 8.54; 95% CI 2.09–34.91; p 26 (OR 3.97; 95% CI 1.92–8.22; p < 0.0001; PPV = 0.75), and hepatorenal syndrome (OR 4.67; 95% CI 1.24–17.64; p = 0.022; PPV = 0.88).ConclusionsPrognosis of cirrhotic patients admitted to ICU is poor since only a minority undergo liver transplant. The prognostic performance of general ICU scores decreases over time, unlike the Child–Pugh and MELD scores, even recorded in the context of organ failure. Infection-related parameters had a short-term impact, whereas liver and renal failure had a sustained impact on mortality
Multi-Messenger Astronomy with Extremely Large Telescopes
The field of time-domain astrophysics has entered the era of Multi-messenger
Astronomy (MMA). One key science goal for the next decade (and beyond) will be
to characterize gravitational wave (GW) and neutrino sources using the next
generation of Extremely Large Telescopes (ELTs). These studies will have a
broad impact across astrophysics, informing our knowledge of the production and
enrichment history of the heaviest chemical elements, constrain the dense
matter equation of state, provide independent constraints on cosmology,
increase our understanding of particle acceleration in shocks and jets, and
study the lives of black holes in the universe. Future GW detectors will
greatly improve their sensitivity during the coming decade, as will
near-infrared telescopes capable of independently finding kilonovae from
neutron star mergers. However, the electromagnetic counterparts to
high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus
demand ELT capabilities for characterization. ELTs will be important and
necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve
The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought
We use moderate-resolution optical spectrophotometry and the new MARCS
stellar atmosphere models to determine the effective temperatures of 74
Galactic red supergiants. From these we find a new effective temperature scale
that is significantly warmer than those in the literature. We show that this
temperature scale, along with the newly derived bolometric corrections, gives
much better agreement between our red supergiants and stellar evolutionary
tracks. This agreement provides an independent verification of our new
temperature scale. The combination of effective temperature and bolometric
luminosities allows us to calculate stellar radii; the coolest and most
luminous stars have radii of roughly 1500 solar radii (7 AU), in excellent
accordance with the largest stellar radii predicted from current evolutionary
theory. We find that similar results are obtained for the effective
temperatures and bolometric luminosities using only the de-reddened V-K colors,
providing a powerful demonstration of the self-consistency of the MARCS models.Comment: 32 pages, 16 figures; Accepted by the Astrophysical Journa
A Revised Age for Upper Scorpius and The Star-Formation History Among the F-Type Members of the Scorpius-Centaurus OB Association
We present an analysis of the ages and star-formation history of the F-type
stars in the Upper Scorpius (US), Upper Centaurus-Lupus (UCL) and Lower
Centaurus-Crux (LCC) subgroups of Scorpius-Centaurus. We find that 1) our
empirical isochrones are consistent with the previously published age-rank of
the Sco-Cen subgroups, 2) LCC and UCL appear to reach the main sequence turn-on
at spectral types ~F4 and ~F2, respectively. An analysis of the A-type stars
shows US reaching the main sequence at about spectral type ~A3. 3) The median
ages for the pre-main sequence members of UCL and LCC are 16 Myr and 17 Myr,
respectively, in agreement with previous studies, however we find that 4) Upper
Sco is much older than previously thought. The luminosities of the F-type stars
in US are typically a factor of ~2.5 less luminous than predicted for a 5 Myr
old population for four sets of evolutionary tracks. We reexamine the
evolutionary state and isochronal ages for the B-, A-, and G-type Upper Sco
members, and the evolved M supergiant Antares, and estimate a revised mean age
for Upper Sco of 11+/-1+/-2 Myr (statistical, systematic). Using radial
velocities and Hipparcos parallaxes we calculate a lower limit on the kinematic
expansion age for Upper Sco of >10.5 Myr (99% confidence). However, the data
are statistically consistent with no expansion. We reevaluate the inferred
masses for the known substellar companions in Upper Sco using the revised age.
Specifically, we estimate the mass of 1RXS J1609-2105b to be 14^{+2}_{-3} Mjup,
suggesting that it is a brown dwarf rather than a planet. Finally, we find the
fraction of F-type stars exhibiting Ha emission and/or a K-band excess
consistent with accretion to be 0/17 (<19%; 95% C.L.) in US at ~11 Myr, while
UCL has 1/41 (2^{+5}_{-1}%; 68% C.L.) accretors and LCC has 1/50 (2^{+4}_{-1}%;
68% C.L.) accretors at ~16 Myr and ~17 Myr, respectively. [Abridged]Comment: Accepted for publication in ApJ. Formatted with emulateapj, 28 pages,
16 figures, 14 table
High-Resolution Melting System to Perform Multilocus Sequence Typing of Campylobacter jejuni
Multi-locus sequence typing (MLST) has emerged as the state-of-the-art method for resolving bacterial population genetics but it is expensive and time consuming. We evaluated the potential of high resolution melting (HRM) to identify known MLST alleles of Campylobacter jejuni at reduced cost and time. Each MLST locus was amplified in two or three sub fragments, which were analyzed by HRM. The approach was investigated using 47 C. jejuni isolates, previously characterized by classical MLST, representing isolates from diverse environmental, animal and clinical sources and including the six most prevalent sequence types (ST) and the most frequent alleles. HRM was then applied to a validation set of 84 additional C. jejuni isolates from chickens; 92% of the alleles were resolved in 35 hours of laboratory time and the cost of reagents per isolate was 100 for sequence-based typing. HRM has the potential to complement sequence-based methods for resolving SNPs and to facilitate a wide range of genotyping studies
Periodic Density Functional Theory Investigation of the Uranyl Ion Sorption on Three Mineral Surfaces: A Comparative Study
Canister integrity and radionuclides retention is of prime importance for assessing the long term safety of nuclear waste stored in engineered geologic depositories. A comparative investigation of the interaction of uranyl ion with three different mineral surfaces has thus been undertaken in order to point out the influence of surface composition on the adsorption mechanism(s). Periodic DFT calculations using plane waves basis sets with the GGA formalism were performed on the TiO2(110), Al(OH)3(001) and Ni(111) surfaces. This study has clearly shown that three parameters play an important role in the uranyl adsorption mechanism: the solvent (H2O) distribution at the interface, the nature of the adsorption site and finally, the surface atoms’ protonation state
The tundra phenology database: more than two decades of tundra phenology responses to climate change
Observations of changes in phenology have provided some of the strongest
signals of the effects of climate change on terrestrial ecosystems. The International
Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to
measure plant phenology in tundra study areas across the globe. Today, this valuable collection
of phenology measurements depicts the responses of plants at the colder extremes of
our planet to experimental and ambient changes in temperature over the past decades.
The database contains 150 434 phenology observations of 278 plant species taken at 28 study
areas for periods of 1\u201326 years. Here we describe the full data set to increase the
visibility and use of these data in global analyses and to invite phenology data contributions
from underrepresented tundra locations. Portions of this tundra phenology database have
been used in three recent syntheses, some data sets are expanded, others are from entirely
new study areas, and the entirety of these data are now available at the Polar Data Catalogue
(https://doi.org/10.21963/13215)
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