2,742 research outputs found
Habitability: CAMELOT 4
During 1988 to 1989 the NASA/USRA Advanced Design Program sponsored research and design efforts aimed at developing habitability criteria and at defining a habitability concept as a useful tool in understanding and evaluating dwellings for prolonged stays in extraterrestrial space. The Circulating Auto sufficient Mars-Earth Luxurious Orbital Transport (CAMELOT) was studied as a case in which the students would try to enhance the quality of life of the inhabitants by applying architectural design methodology. The study proposed 14 habitability criteria considered necessary to fulfill the defined habitability concept, which is that state of equilibrium that results from the interaction between components of the Individual Architecture Mission Complex, which allows a person to sustain physiological homeostatis, adequate performance, and acceptable social relationships. Architecture, design development, refinements and revisions to improve the quality of life, new insights on artificial gravity, form and constitution problems, and the final design concept are covered
Searching for the signatures of terrestial planets in solar analogs
We present a fully differential chemical abundance analysis using very
high-resolution (R >~ 85,000) and very high signal-to-noise (S/N~800 on
average) HARPS and UVES spectra of 7 solar twins and 95 solar analogs, 24 are
planet hosts and 71 are stars without detected planets. The whole sample of
solar analogs provide very accurate Galactic chemical evolution trends in the
metalliciy range -0.3<[Fe/H]<0.5. Solar twins with and without planets show
similar mean abundance ratios. We have also analysed a sub-sample of 28 solar
analogs, 14 planet hosts and 14 stars without known planets, with spectra at
S/N~850 on average, in the metallicity range 0.14<[Fe/H]<0.36 and find the same
abundance pattern for both samples of stars with and without planets. This
result does not depend on either the planet mass, from 7 Earth masses to 17.4
Jupiter masses, or the orbital period of the planets, from 3 to 4300 days. In
addition, we have derived the slope of the abundance ratios as a function of
the condensation temperature for each star and again find similar distributions
of the slopes for both stars with and without planets. In particular, the peaks
of these two distributions are placed at a similar value but with opposite sign
as that expected from a possible signature of terrestial planets. In
particular, two of the planetary systems in this sample, containing each of
them a Super-Earth like planet, show slope values very close to these peaks
which may suggest that these abundance patterns are not related to the presence
of terrestial planets.Comment: Accepted for publication in The Astrophysical Journa
\u3cem\u3eluxS\u3c/em\u3e in bacteria isolated from 25- to 40-million-year-old amber
Interspecies bacterial communication is mediated by autoinducer-2, whose synthesis depends on luxS. Due to the apparent universality of luxS (present in more than 40 bacterial species), it may have an ancient origin; however, no direct evidence is currently available. We amplified luxS in bacteria isolated from 25- to 40-million-year-old amber. The phylogenies and molecular clocks of luxS and the 16S rRNA gene from ancient and extant bacteria were determined as well. Luminescence assays using Vibrio harveyi BB170 aimed to determine the activity of luxS. While the phylogeny of luxS was very similar to that of extant Bacillus spp., amber isolates exhibited unique 16S rRNA gene phylogenies. This suggests that luxS may have been acquired by horizontal transfer millions of years ago. Molecular clocks of luxS suggest slow evolutionary rates, similar to those of the 16S rRNA gene and consistent with a conserved gene. Dendograms of the 16S rRNA gene and luxS show two separate clusters for the extant and ancient bacteria, confirming the uniqueness of the latter group
Tropical Cyclone Landfall Frequency and Large-Scale Environmental Impacts along Karstic Coastal Regions (Yucatan Peninsula, Mexico)
Tropical cyclones (TCs) are natural systems that develop over ocean basins and are key components of the atmospheric activity during the warm season. However, there are still knowledge gaps about the combined positive and negative TC impacts on the structure and function of coastal socio-ecosystems. Using remote sensing tools, we analyzed the frequency, trajectory, and intensity of 1894 TCs from 1851-2019 to identify vulnerable hotspots across the Yucatan Peninsula (YP), Mexico. A total of 151 events hit the YP, with 96% of landings on the eastern coast. We focused on three major hurricanes (Emily and Wilma, 2005; Dean, 2007) and one tropical storm (Stan, 2005) to determine the impacts on cumulative precipitation, vegetation change, and coastal phytoplankton (Chl-a) distribution across the YP. Despite a short inland incursion, Wilma\u27s environmental damage was coupled to strong winds (157-241 km/h), slow motion (4-9 km/h), and heavy precipitation (up to 770 mm). Because of an extensive footprint, Wilma caused more vegetation damage (29%) than Dean (20%), Emily (7%), and Stan (2%). All TCs caused a Chl-aincrease associated to submarine discharge and upwelling off the peninsula coastlines. Disaster risk along the coast underscores negative economic impacts and positive ecological benefits at the regional scale
Plasma-wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials
Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong
bursts of fast charged particles which will deposit tens of kJ m and
implant more than 10 particles m in a few microseconds at a
repetition rate of some Hz. Large chamber dimensions and resistant
plasma-facing materials must be combined to guarantee the chamber performance
as long as possible under the expected threats: heating, fatigue, cracking,
formation of defects, retention of light species, swelling and erosion. Current
and novel radiation resistant materials for the first wall need to be validated
under realistic conditions. However, at present there is a lack of facilities
which can reproduce such ion environments.
This contribution proposes the use of ultra-intense lasers and high-intense
pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By
target normal sheath acceleration, ultra-intense lasers can generate very short
and energetic ion pulses with a spectral distribution similar to that of the
inertial fusion ion bursts, suitable to validate fusion materials and to
investigate the barely known propagation of those bursts through background
plasmas/gases present in the reactor chamber. HIPIB technologies, initially
developed for inertial fusion driver systems, provide huge intensity pulses
which meet the irradiation conditions expected in the first wall of LIF
chambers and thus can be used for the validation of materials too
Enhancing a de novo enzyme activity by computationally-focused ultra-low-throughput screening
Directed evolution has revolutionized protein engineering. Still, enzyme optimization by random library
screening remains sluggish, in large part due to futile probing of mutations that are catalytically neutral
and/or impair stability and folding. FuncLib is a novel approach which uses phylogenetic analysis and
Rosetta design to rank enzyme variants with multiple mutations, on the basis of predicted stability. Here,
we use it to target the active site region of a minimalist-designed, de novo Kemp eliminase. The
similarity between the Michaelis complex and transition state for the enzymatic reaction makes this
system particularly challenging to optimize. Yet, experimental screening of a small number of active-site
variants at the top of the predicted stability ranking leads to catalytic efficiencies and turnover numbers
( 2 104 M 1 s 1 and 102 s 1) for this anthropogenic reaction that compare favorably to those of
modern natural enzymes. This result illustrates the promise of FuncLib as a powerful tool with which to
speed up directed evolution, even on scaffolds that were not originally evolved for those functions, by
guiding screening to regions of the sequence space that encode stable and catalytically diverse
enzymes. Empirical valence bond calculations reproduce the experimental activation energies for the
optimized eliminases to within 2 kcal mol 1 and indicate that the enhanced activity is linked to better
geometric preorganization of the active site. This raises the possibility of further enhancing the stabilityguidance
of FuncLib by computational predictions of catalytic activity, as a generalized approach for
computational enzyme designKnut and Alice Wallenberg Foundation (Wallenberg Academy Fellowship)
2018.0140Human Frontier Science Program
RGP0041/2017FEDER Funds/Spanish Ministry of Science, Innovation and Universities
BIO2015-66426-R
RTI2018-097142-B-100FEDER/Junta de Andalucia - Consejeria de Economia y Conocimiento
E.FQM.113.UGR18Swedish National Infrastructure for computing (SNAC)
2018/2-3
2019/2-
A Hot Uranus Orbiting the Super Metal-rich Star HD77338 and the Metallicity - Mass Connection
We announce the discovery of a low-mass planet orbiting the super metal-rich
K0V star HD77338 as part of our on-going Calan-Hertfordshire Extrasolar Planet
Search. The best fit planet solution has an orbital period of 5.7361\pm0.0015
days and with a radial velocity semi-amplitude of only 5.96\pm1.74 m/s, we find
a minimum mass of 15.9+4.7-5.3 Me. The best fit eccentricity from this solution
is 0.09+0.25-0.09, and we find agreement for this data set using a Bayesian
analysis and a periodogram analysis. We measure a metallicity for the star of
+0.35\pm0.06 dex, whereas another recent work (Trevisan et al. 2011) finds
+0.47\pm0.05 dex. Thus HD77338b is one of the most metal-rich planet host stars
known and the most metal-rich star hosting a sub-Neptune mass planet. We
searched for a transit signature of HD77338b but none was detected. We also
highlight an emerging trend where metallicity and mass seem to correlate at
very low masses, a discovery that would be in agreement with the core accretion
model of planet formation. The trend appears to show that for Neptune-mass
planets and below, higher masses are preferred when the host star is more
metal-rich. Also a lower boundary is apparent in the super metal-rich regime
where there are no very low-mass planets yet discovered in comparison to the
sub-solar metallicity regime. A Monte Carlo analysis shows that this, low-mass
planet desert, is statistically significant with the current sample of 36
planets at around the 4.5\sigma\ level. In addition, results from Kepler
strengthen the claim for this paucity of the lowest-mass planets in super
metal-rich systems. Finally, this discovery adds to the growing population of
low-mass planets around low-mass and metal-rich stars and shows that very
low-mass planets can now be discovered with a relatively small number of data
points using stable instrumentation.Comment: 25 pages, 15 figures, 5 tables, accepted for publication in Ap
The lack of the TetR-like repressor gene BCG_2177c (Rv2160A) may help mycobacteria overcome intracellular redox stress and survive longer inside macrophages when surrounded by a lipid environment
Mycobacteria, like other microorganisms, survive under different environmental variations by expressing an efficient adaptive response, oriented by regulatory elements, such as transcriptional repressors of the TetR family. These repressors in mycobacteria also appear to be related to cholesterol metabolism. In this study, we have evaluated the effect of a fatty acid (oleic–palmitic–stearic)/cholesterol mixture on some phenotypic and genotypic characteristics of a tetR-mutant strain (BCG_2177c mutated gene) of M. bovis BCG, a homologous of Rv2160A of M. tuberculosis. In order to accomplish this, we have analyzed the global gene expression of this strain by RNA-seq and evaluated its neutral-lipid storage capacity and potential to infect macrophages. We have also determined the macrophage response by measuring some pro- and anti-inflammatory cytokine expressions. In comparison with wild-type microorganisms, we showed that the mutation in the BCG_2177c gene did not affect the growth of M. bovis BCG in the presence of lipids but it probably modified the structure/composition of its cell envelope. Compared to with dextrose, an overexpression of the transcriptome of the wild-type and mutant strains was observed when these mycobacteria were cultured in lipids, mainly at the exponential phase. Twelve putative intracellular redox balance maintenance genes and four others coding for putative transcriptional factors (including WhiB6 and three TetR-like) were the main elements repeatedly overexpressed when cultured in the presence of lipids. These genes belonged to the central part of what we called the “genetic lipid signature” for M. bovis BCG. We have also found that all these mycobacteria genotypic changes affected the outcome of BCG-infected macrophages, being the mutant strain most adapted to persist longer inside the host. This high persistence result was also confirmed when mutant-infected macrophages showed overexpression of the anti-inflammatory cytokine TGF-ß versus pro-inflammatory cytokines. In summary, the lack of this TetR-like repressor expression, within a lipid environment, may help mycobacteria overcome intracellular redox stress and survive longer inside their host
Inhibition of IL-34 Unveils Tissue-Selectivity and Is Sufficient to Reduce Microglial Proliferation in a Model of Chronic Neurodegeneration
The proliferation and activation of microglia, the resident macrophages in the brain,
is a hallmark of many neurodegenerative diseases such as Alzheimer’s disease (AD)
and prion disease. Colony stimulating factor 1 receptor (CSF1R) is critically involved
in regulating microglial proliferation, and CSF1R blocking strategies have been recently
used to modulate microglia in neurodegenerative diseases. However, CSF1R is broadly
expressed by many cell types and the impact of its inhibition on the innate immune
system is still unclear. CSF1R can be activated by two independent ligands, CSF-1 and
interleukin 34 (IL-34). Recently, it has been reported that microglia development and
maintenance depend on IL-34 signaling. In this study, we evaluate the inhibition of IL-34
as a novel strategy to reduce microglial proliferation in the ME7 model of prion disease.
Selective inhibition of IL-34 showed no effects on peripheral macrophage populations in
healthy mice, avoiding the side effects observed after CSF1R inhibition on the systemic
compartment. However, we observed a reduction in microglial proliferation after IL-34
inhibition in prion-diseased mice, indicating that microglia could be more specifically
targeted by reducing IL-34. Overall, our results highlight the challenges of targeting the
CSF1R/IL34 axis in the systemic and central compartments, important for framing any
therapeutic effort to tackle microglia/macrophage numbers during brain disease
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