8,853 research outputs found
Comparison of Monomethylhydrazine/Hydroxypropylcellulose and Hydrocarbon/Silica Gels
Experimental studies have been performed to investigate rheology and droplet burning with different types of gelled propellants. Monomethylhydrazine has been gelled with organic hydroxypropylcellulose. JP-8 and RP-1 hydrocarbon gels have been produced with inorganic fumed silica particles. Rheological characterization showed the differences in terms of viscosity and yield stress behavior due to different types of gelling agents. Herschel-Bulkley and Carreau-Yasuda models have been used to characterize the gels with inorganic and organic gelling agents, respectively. First experiments with the Monomethylhydrazine/hydroxypropylcellulose gels showed a typical swelling process during combustion with a flexible viscous droplet surface. Contrary to that, the hydrocarbon/silica gels burned while a rigid silica structure was built, which remained unburned. Burning drop measurements have been compared to the d^2-squared law
A combined approach for comparative exoproteome analysis of Corynebacterium pseudotuberculosis
Background: Bacterial exported proteins represent key components of the host-pathogen interplay. Hence, we
sought to implement a combined approach for characterizing the entire exoproteome of the pathogenic
bacterium Corynebacterium pseudotuberculosis, the etiological agent of caseous lymphadenitis (CLA) in sheep and
goats.
Results: An optimized protocol of three-phase partitioning (TPP) was used to obtain the C. pseudotuberculosis
exoproteins, and a newly introduced method of data-independent MS acquisition (LC-MSE) was employed for
protein identification and label-free quantification. Additionally, the recently developed tool SurfG+ was used for in
silico prediction of sub-cellular localization of the identified proteins. In total, 93 different extracellular proteins of
C. pseudotuberculosis were identified with high confidence by this strategy; 44 proteins were commonly identified
in two different strains, isolated from distinct hosts, then composing a core C. pseudotuberculosis exoproteome.
Analysis with the SurfG+ tool showed that more than 75% (70/93) of the identified proteins could be predicted as
containing signals for active exportation. Moreover, evidence could be found for probable non-classical export of
most of the remaining proteins.
Conclusions: Comparative analyses of the exoproteomes of two C. pseudotuberculosis strains, in addition to
comparison with other experimentally determined corynebacterial exoproteomes, were helpful to gain novel
insights into the contribution of the exported proteins in the virulence of this bacterium. The results presented
here compose the most comprehensive coverage of the exoproteome of a corynebacterial species so far
Utilisation of Mucuna Beans (Mucuna pruriens (L.) DC ssp. deeringianum (Bart) Hanelt) to Feed Growing Broilers
Performance of broilers fed on diets containing mucuna beans (MB) (Mucuna pruriens (L.) DC ssp. deeringianum (Bart) Hanelt) with different treatments were studied in three experiments. First experiment: three sorghum diets using 0 and 280g/kg of MB raw or soaked were evaluated. Second experiment: three sorghum diets using 0 and 280g/kg of MB raw or boiled were evaluated. Third experiment: six maize diets: maize only, three diets containing 280g/kg of MB raw, soaked or boiled, one containing soybean and a balanced diet (control) were evaluated. Experiment one: the birds fed on the 0g MB/kg showed a higher live weight gain (LWG) and a lower feed:gain ratio (FG) (p 0.01) than birds fed on the MB diets. There were no differences for any of the variables studied between the birds fed on the MB diets. Experiment two: the birds fed on the 0g MB/kg performed better (p 0.01) than birds fed on the MB diets. However, birds fed on the boiled MB diet had a higher LWG and a lower FG (p 0.01) than birds fed on the raw and soaked MB diet. Experiment three: the birds fed on the control diet obtained a higher LWG (p 0.01) than birds fed on the remainder treatments. The birds fed on the raw MB diet had a lower FG (p 0.01) than birds on the remainder treatments. However, birds fed on the boiled MB had a higher LWG and feed intake than birds fed on raw and soaked MB diets and only maize diet (p 0.01), but, lower (p 0.01) in comparison to birds fed on the soybean diet. The birds on the raw and soaked MB diets performed worst (p 0.01), even in comparison to birds fed on only maize (p 0.01). The results from these experiments indicated that inclusion of 280g MB/kg in the diet affected adversely the poultry performance. However, utilisation of MB boiled improved the broilers performance compared to birds fed on the raw and soaked MB diets
Fecundity, spore recruitment and size in Gelidium sesquipedale (Gelidiales,Rhodophyta)
Gelidium sesquipedale fecundity was quantified by counting tetrasporangial sori and cystocarps per meter squared
and by estimating the number of spores contained inside them . These were obtained by regression on a size metric
of reproductive structures . Tetrasporangial sori length and cystocarp thickness were the best estimators of spore
number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds
was monitored.
No clear seasonal pattern of reproduction was found . Tetraspore production peaked in March 1990 with 10.4
x 106 spores m-2, whereas the carpospore peak was lower, 4.9 x 10 5 spores m-2 in July 1989. Recruitment
followed tetraspore peaks . The probability of a G. sesquipedale tetraspore making the transition to a recruit was
4.7 x 10-5. Frond length was significantly related to tetrasporangial sori number, while cystocarp number was
only related to frond branching order. Minimum size for reproduction was 6.9 cm for gametophytes and 5.4 cm for
tetrasporophytes; very rarely were cystocarpic fronds smaller than 9 cm, while tetrasporic fronds were often longer
than 15 cm . Cystocarpic fronds were significantly shorter and had more branches than tetrasporic fronds
Atomic Bose-Fermi mixtures in an optical lattice
A mixture of ultracold bosons and fermions placed in an optical lattice
constitutes a novel kind of quantum gas, and leads to phenomena, which so far
have been discussed neither in atomic physics, nor in condensed matter physics.
We discuss the phase diagram at low temperatures, and in the limit of strong
atom-atom interactions, and predict the existence of quantum phases that
involve pairing of fermions with one or more bosons, or, respectively, bosonic
holes. The resulting composite fermions may form, depending on the system
parameters, a normal Fermi liquid, a density wave, a superfluid liquid, or an
insulator with fermionic domains. We discuss the feasibility for observing such
phases in current experiments.Comment: 4 pages, 1 eps figure, misprints correcte
An HST search for planets in the lower Main Sequence of the globular cluster NGC 6397
Searches for planetary transits carried out in open and globular clusters
have yielded to date only a handful of weak, unconfirmed candidates. These
results have been interpreted either as being insignificant, or as evidence
that the cluster chemical or dynamical environment inhibits the planetary
formation or survival. Most campaigns were limited by small sample statistics
or systematics from ground-based photometry. In this work we performed a search
for transiting planets and variables in a deep stellar field of NGC 6397 imaged
by HST-ACS for 126 orbits. We analyzed 5,078 light curves, including a pure
sample of 2,215 cluster-member M0-M9 dwarfs. The light curves have been
corrected for systematic trends and inspected with several tools. No
high-significance planetary candidate is detected. We compared this null
detection with the most recent results from Kepler, showing that no conclusive
evidence of lower planet incidence can be drawn. However, a very small
photometric jitter is measured for early-M cluster members (<~2 mmag on 98% of
them), which may be worth targeting in the near future with more optimized
campaigns. Twelve variable stars are reported for the first time.Comment: 10 pages, 6 figures, 1 table; accepted for publication in A&A on
February 16, 2012. Typos corrected. One figure and a short final note adde
Stability of Unconventional Superconductivity on Surfaces of Topological Insulators
Superconductivity on the surface of topological insulators is known to be
anisotropic and unconventional in that the symmetry is the mixture of s-wave
and nodeless p-wave component. In contrast to Anderson's theorem for the
insensitivity of the s-wave superconducting critical temperature to the
nonmagnetic (time-reversal symmetric (TRS)) impurities, anisotropic
superconductors including nodeless p-wave one are in general fragile even with
small concentration of the TRS impurities. By employing the Abrikosov-Gor'kov
theory, we clarify that this type of unconventional superconductivity emergent
on the surface state of the strong topological insulators robustly survive
against TRS impurities
Magneto-optical trap for metastable helium at 389 nm
We have constructed a magneto-optical trap (MOT) for metastable triplet
helium atoms utilizing the 2 3S1 -> 3 3P2 line at 389 nm as the trapping and
cooling transition. The far-red-detuned MOT (detuning Delta = -41 MHz)
typically contains few times 10^7 atoms at a relatively high (~10^9 cm^-3)
density, which is a consequence of the large momentum transfer per photon at
389 nm and a small two-body loss rate coefficient (2 * 10^-10 cm^3/s < beta <
1.0 * 10^-9 cm^3/s). The two-body loss rate is more than five times smaller
than in a MOT on the commonly used 2 3S1 -> 2 3P2 line at 1083 nm. Furthermore,
we measure a temperature of 0.46(1) mK, a factor 2.5 lower as compared to the
1083 nm case. Decreasing the detuning to Delta= -9 MHz results in a cloud
temperature as low as 0.25(1) mK, at small number of trapped atoms. The 389 nm
MOT exhibits small losses due to two-photon ionization, which have been
investigated as well.Comment: 11 page
Protecting forests at the expense of native grasslands: Land-use policy encourages open-habitat loss in the Brazilian cerrado biome
The agricultural conversion of natural habitats is one of the main drivers of biodiversity loss worldwide. In the âŒ2 million km2 Brazilian cerrado biome, a global biodiversity hotspot, vast areas have been converted into croplands and cattle pastures. Because the cerrado biome is overwhelmingly contained within private lands, Brazil's environmental legislation should serve as a decisive instrument in protecting these natural ecosystems. We assessed the role of Legal Reserves (LRs), legally defined as the minimum proportion of private landholdings set aside to protect natural vegetation, in the conservation of the cerrado biome. We assume that the property-scale allocation of LRs is primarily based on economic decision-making, creating a bias against cerrado protection. We therefore assessed the area ratio between forest vegetation (FV) and grassland vegetation (GV) areas across LRs within 48,762 landholdings, 9 formal protected areas (PAs) and 34 Indigenous Lands (ILs) within the cerrado (sensu lato) of the 903,357-km2 state of Mato Grosso, Brazil. We show that there are 7.26 ha of forest lands for each hectare of native grasslands within private RLs of the cerrado biome within Mato Grosso, a ratio almost three-fold larger than that found in formal PAs and ILs. ILs protect in absolute values (hectares) six-fold more native grassland vegetation than PAs. We discuss the policy relevance of this severe land-use bias in maintaining the heterogeneity of cerrado habitats for biodiversity conservation within private properties, which account for 90% of the entire cerrado biome
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