4,078 research outputs found
Effects of Boron Purity, Mg Stoichiometry and Carbon Substitution on Properties of Polycrystalline MgB
By synthesizing MgB using boron of different nominal purity we found
values of the residual resistivity ratio () from 4 to
20, which covers almost all values found in literature. To obtain high values
of , high purity reagents are necessary. With the isotopically pure boron
we obtained the highest 20 for the stoichiometric compound. We also
investigated MgB samples with 0.8 1.2. For the range
MgB up to MgB we found average values
of between 14 and 24. For smaller variations in stoichiometry () . All of our data point to the conclusion that high
() and low () are intrinsic
material properties associated with high purity MgB. In addition we have
performed initial work on optimizing the formation of carbon doped MgB
via the use of BC. Nearly single phase material can be formed by reaction
of nominal Mg(BC) for 24 hours at . The
for this composition is between and (depending on
criterion).Comment: accepted to Physica C, special MgB2 issu
Data Hiding with Deep Learning: A Survey Unifying Digital Watermarking and Steganography
Data hiding is the process of embedding information into a noise-tolerant
signal such as a piece of audio, video, or image. Digital watermarking is a
form of data hiding where identifying data is robustly embedded so that it can
resist tampering and be used to identify the original owners of the media.
Steganography, another form of data hiding, embeds data for the purpose of
secure and secret communication. This survey summarises recent developments in
deep learning techniques for data hiding for the purposes of watermarking and
steganography, categorising them based on model architectures and noise
injection methods. The objective functions, evaluation metrics, and datasets
used for training these data hiding models are comprehensively summarised.
Finally, we propose and discuss possible future directions for research into
deep data hiding techniques
Dominin and Segon Form Multiprotein Particles in the Plasma of Eastern Oysters (Crassostrea virginica) and Are Likely Involved in Shell Formation
Dominin and segon are two proteins purified and characterized from the plasma of eastern oysters Crassostrea virginica, making up about 70% of the total plasma proteins. Their proposed functions are in host defense based on their pathogen binding properties and in metal metabolism based on their metal binding abilities. In the present study, the two proteins were further studied for their native states in circulation and extrapallial fluid and their possible involvement in shell formation. Two-dimensional electrophoresis confirmed that the oyster plasma was dominated by a few major proteins and size exclusion chromatography indicated that these proteins were present in circulation in a morphologically homogenous form. Density gradient ultracentrifugation in Cesium Chloride isolated morphologically homogenous particles of about 25 nm in diameter from the plasma and extrapallial fluids. Polyacrylamide gel electrophoresis identified dominin, segon and an unidentified protein as the principal components of the particles and the three proteins likely formed a multiprotein complex that associated to form the particle. Additionally, three major proteins extracted from shell organic matrix were identified based on the apparent molecular weight in SDS-PAGE to correspond to the three major proteins of plasma and protein particles. Moreover, the hemocyte expression of dominin and segon genes measured by real-time RT-PCR increased significantly upon the initiation of shell repair and were significantly greater in younger oysters. These findings suggest that dominin and segon form protein particles by association with each other and perhaps some other major plasma proteins and play a significant role in oyster shell formation
COPD Maintenance Therapy with Tiotropium/Olodaterol Compared with Tiotropium: An Analysis in the Absence of Additional ICS Therapy
On the Core of Dynamic Cooperative Games
We consider dynamic cooperative games, where the worth of coalitions varies
over time according to the history of allocations. When defining the core of a
dynamic game, we allow the possibility for coalitions to deviate at any time
and thereby to give rise to a new environment. A coalition that considers a
deviation needs to take the consequences into account because from the
deviation point on, the game is no longer played with the original set of
players. The deviating coalition becomes the new grand coalition which, in
turn, induces a new dynamic game. The stage games of the new dynamical game
depend on all previous allocation including those that have materialized from
the deviating time on.
We define three types of core solutions: fair core, stable core and credible
core. We characterize the first two in case where the instantaneous game
depends on the last allocation (rather than on the whole history of
allocations) and the third in the general case. The analysis and the results
resembles to a great extent the theory of non-cooperative dynamic games.Comment: 25 page
Jamming in complex networks with degree correlation
We study the effects of the degree-degree correlations on the pressure
congestion J when we apply a dynamical process on scale free complex networks
using the gradient network approach. We find that the pressure congestion for
disassortative (assortative) networks is lower (bigger) than the one for
uncorrelated networks which allow us to affirm that disassortative networks
enhance transport through them. This result agree with the fact that many real
world transportation networks naturally evolve to this kind of correlation. We
explain our results showing that for the disassortative case the clusters in
the gradient network turn out to be as much elongated as possible, reducing the
pressure congestion J and observing the opposite behavior for the assortative
case. Finally we apply our model to real world networks, and the results agree
with our theoretical model
The deep look onto the hard X-ray sky: The Swift - INTEGRAL X-ray (SIX) survey
The super-massive black-holes in the centers of Active Galactic Nuclei (AGNs)
are surrounded by obscuring matter that can block the nuclear radiation.
Depending on the amount of blocked radiation, the flux from the AGN can be too
faint to be detected by currently flying hard X-ray (above 15 keV) missions. At
these energies only ~1% of the intensity of the Cosmic X-ray Background (CXB)
can be resolved into point-like sources that are AGNs. In this work we address
the question of the undetected sources contributing to the CXB with a very
sensitive and new hard X-ray survey: the SIX survey that is obtained with the
new approach of combining the Swift/BAT and INTEGRAL/IBIS X-ray observations.
We merge the observations of both missions. This enhances the exposure time and
reduces systematic uncertainties. As a result we obtain a new survey over a
wide sky area of 6200 deg^2 that is more sensitive than the surveys of
Swift/BAT or INTEGRAL/IBIS alone. Our sample comprises 113 sources: 86 AGNs
(Seyfert-like and blazars), 5 galaxies, 2 clusters of galaxies, 3 Galactic
sources, 3 previously detected unidentified X-ray sources, and 14 unidentified
sources. The scientific outcome from the study of the sample has been properly
addressed to study the evolution of AGNs at redshift below 0.4. We do not find
any evolution using the 1/V_max method. Our sample of faint sources are
suitable targets for the new generation hard X-ray telescopes with focusing
techniques.Comment: ApJS accepte
A new lysozyme from the eastern oyster, Crassostrea virginica, and a possible evolutionary pathway for i-type lysozymes in bivalves from host defense to digestion
Background. Lysozymes are enzymes that lyse bacterial cell walls, an activity widely used for host defense but also modified in some instances for digestion. The biochemical and evolutionary changes between these different functional forms has been well-studied in the c-type lysozymes of vertebrates, but less so in the i-type lysozymes prevalent in most invertebrate animals. Some bivalve molluscs possess both defensive and digestive lysozymes. Results. We report a third lysozyme from the oyster Crassostrea virginica, cv-lysozyme 3. The chemical properties of cv-lysozyme 3 (including molecular weight, isoelectric point, basic amino acid residue number, and predicted protease cutting sites) suggest it represents a transitional form between lysozymes used for digestion and immunity. The cv-lysozyme 3 protein inhibited the growth of bacteria (consistent with a defensive function), but semi-quantitative RT-PCR suggested the gene was expressed mainly in digestive glands. Purified cv-lysozyme 3 expressed maximum muramidase activity within a range of pH (7.0 and 8.0) and ionic strength (I = 0.005-0.01) unfavorable for either cv-lysozyme 1 or cv-lysozyme 2 activities. The topology of a phylogenetic analysis of cv-lysozyme 3 cDNA (full length 663 bp, encoding an open reading frame of 187 amino acids) is also consistent with a transitional condition, as cv-lysozyme 3 falls at the base of a monophyletic clade of bivalve lysozymes identified from digestive glands. Rates of nonsynonymous substitution are significantly high at the base of this clade, consistent with an episode of positive selection associated with the functional transition from defense to digestion. Conclusion. The pattern of molecular evolution accompanying the shift from defensive to digestive function in the i-type lysozymes of bivalves parallels those seen for c-type lysozymes in mammals and suggests that the lysozyme paralogs that enhance the range of physiological conditions for lysozyme activity may provide stepping stones between defensive and digestive forms. Š 2010 Xue et al; licensee BioMed Central Ltd
Angular fluctuations in the CXB: Is Fe 6.4 keV line tomography of the large-scale structure feasible?
AGN are known to account for a major portion, if not all, of the cosmic X-ray
background radiation. The dominant sharp spectral feature in their spectra is
the 6.4 keV fluorescent line of iron, which may contribute to as much as ~ 5-10
% of the CXB spectral intensity at ~ 2-6 keV. Owing to cosmological redshift,
the line photons detected at the energy E carry information about objects
located at the redshift z=6.4/E-1. In particular, imprinted in their angular
fluctuations is the information about the large-scale structure at redshift z.
This opens the possibility of performing the Fe K_alpha line tomography of the
cosmic large-scale structure. We show that detection of the tomographic signal
at ~100 sigma confidence requires an all-sky survey by an instrument with an
effective area of ~10 m^2 and field of view of ~1 deg^2. The signal is
strongest for objects located at the redshift z~1 and at the angular scales
corresponding to l ~ 100-300, therefore an optimal detection can be achieved
with an instrument having a rather modest angular resolution of ~ 0.1-0.5 deg.
For such an instrument, the CCD-type energy resolution of ~ 100-200 eV FWHM is
entirely sufficient for the optimal separation of the signals coming from
different redshifts. The gain in the signal strength that could potentially be
achieved with energy resolution comparable to the line width is nullified by
the photon counting and AGN discreteness noise. Among the currently planned and
proposed missions, these requirements are best satisfied by LOFT, even though
it was proposed for an entirely different purpose. Among others, clear
detection should be achieved by WFXT (~ 20-35 sigma) and ATHENA (~ 10-20
sigma). eROSITA, in the course of its 4 years all-sky survey, will detect the
tomographic signal only marginally.Comment: minor additions, accepted for publication in A&
Size effect on properties of varistors made from zinc oxide nanoparticles through low temperature spark plasma sintering
Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8-nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at roomtemperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as-prepared ceramics are based on scanning electron microscopy and X-ray diffraction analysis. The nonlinear electrical characteristics are evidenced by currentâvoltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 8C
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