13,182 research outputs found
Social Media Users\u27 Guide
Mass Communication Professor Susan Currie Sivek shares ideas and suggestions for how to take control of social media and use it to your advantage
A Compound model for the origin of Earth's water
One of the most important subjects of debate in the formation of the solar
system is the origin of Earth's water. Comets have long been considered as the
most likely source of the delivery of water to Earth. However, elemental and
isotopic arguments suggest a very small contribution from these objects. Other
sources have also been proposed, among which, local adsorption of water vapor
onto dust grains in the primordial nebula and delivery through planetesimals
and planetary embryos have become more prominent. However, no sole source of
water provides a satisfactory explanation for Earth's water as a whole. In view
of that, using numerical simulations, we have developed a compound model
incorporating both the principal endogenous and exogenous theories, and
investigating their implications for terrestrial planet formation and
water-delivery. Comets are also considered in the final analysis, as it is
likely that at least some of Earth's water has cometary origin. We analyze our
results comparing two different water distribution models, and complement our
study using D/H ratio, finding possible relative contributions from each
source, focusing on planets formed in the habitable zone. We find that the
compound model play an important role by showing more advantage in the amount
and time of water-delivery in Earth-like planets.Comment: Accepted for publication in The Astrophysical Journa
Business orientation and the food security status of small scale producers in the Venda region, South Africa
Questions addressed in this paper are: How to determine the food status of rural households; and does an agribusiness orientation enhance the food security status of farm families. A study was conducted on two groups of small scale black farmers in the Venda region: one group, agribusiness directed and generally more progressive towards technology, produces mangos and other subtropical fruits (cash crop farmers); the other group concentrates on locally consumed and sold vegetables (food crop farmers). Their food status was quantitatively determined by means of household energy, protein and fat balances and food security determinants were identified. More than 80% of the households had a negative balance for energy, protein or fat. Business orientation and farming type in this particular case study does not influence the energy, protein and fat coverage significantly. The marginal nature of farming by these small holders could explain this finding. Significant predictors of food security status were rather factors such as the household size and the availability of outside sources of income and cash to spend on food.Agribusiness, Food Security and Poverty,
Amplification of surface plasmon polaritons in the presence of nonlinearity and spectral signatures of threshold crossover
We describe effects of nonlinearity on propagation of surface plasmon
polaritons (SPPs) at an interface between a metal and an amplifying medium of
the externally pumped two-level atoms. Using Maxwell equations we derive the
nonlinear dispersion law and demonstrate that, the nonlinear saturation of the
linear gain leads to formation of stationary SPP modes with the intensities
independent from the propagation distance. Transition to the regime of
stationary propagation is similar to the threshold crossover in lasers and
leads to narrowing of the SPP spectrum.Comment: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-34-18-286
Quantum Correlation Without Classical Correlations
We show that genuine multiparty quantum correlations can exist on its own,
without a supporting background of genuine multiparty classical correlations,
even in macroscopic systems. Such possibilities can have important implications
in the physics of quantum information and phase transitions.Comment: 4 pages, no figures; v2: presentation improved, results unchanged,
published versio
Neuropilin-1 Controls Endothelial Homeostasis by Regulating Mitochondrial Function and Iron-Dependent Oxidative Stress.
The transmembrane protein neuropilin-1 (NRP1) promotes vascular endothelial growth factor (VEGF) and extracellular matrix signaling in endothelial cells (ECs). Although it is established that NRP1 is essential for angiogenesis, little is known about its role in EC homeostasis. Here, we report that NRP1 promotes mitochondrial function in ECs by preventing iron accumulation and iron-induced oxidative stress through a VEGF-independent mechanism in non-angiogenic ECs. Furthermore, NRP1-deficient ECs have reduced growth and show the hallmarks of cellular senescence. We show that a subcellular pool of NRP1 localizes in mitochondria and interacts with the mitochondrial transporter ATP-binding cassette B8 (ABCB8). NRP1 loss reduces ABCB8 levels, resulting in iron accumulation, iron-induced mitochondrial superoxide production, and iron-dependent EC senescence. Treatment of NRP1-deficient ECs with the mitochondria-targeted antioxidant compound mitoTEMPO or with the iron chelator deferoxamine restores mitochondrial activity, inhibits superoxide production, and protects from cellular senescence. This finding identifies an unexpected role of NRP1 in EC homeostasis
High power impulse magnetron sputtering discharges: Instabilities and plasma self-organization
We report on instabilities in high power impulse magnetron sputtering plasmas which are likely to be of the generalized drift wave type. They are characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron and cause periodic shifts in floating potential. The azimuthal mode number m depends on plasma current, plasma density, and gas pressure. The structures rotate in × direction at velocities of ∼10 km s−1 and frequencies up to 200 kHz. Collisions with residual gas atoms slow down the rotating wave, whereas increasing ionization degree of the gas and plasma conductivity speeds it up
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