Magnetic fields in primordial accretion disks

Magnetic fields are considered as a vital ingredient of contemporary star formation, and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations, and are subsequently amplified by the small-scale dynamo, leading to a strong tangled magnetic field. Here we explore how the magnetic field provided by the small-scale dynamo is further amplified via the $\alpha-\Omega$ dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop.~III star with $10$~M$_\odot$ and an accretion rate of $10^{-3}$~M$_\odot$~yr$^{-1}$, and a supermassive star with $10^5$~M$_\odot$ and an accretion rate of $10^{-1}$~M$_\odot$~yr$^{-1}$. For the $10$~M$_\odot$ Pop.~III star, we find that coherent magnetic fields can be produced on scales of at least $100$~AU, which are sufficient to drive a jet with a luminosity of $100$~L$_\odot$ and a mass outflow rate of $10^{-3.7}$~M$_\odot$~yr$^{-1}$. For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least $1000$~AU. The jet luminosity corresponds to $\sim10^{6.0}$~L$_\odot$, and a mass outflow rate of $10^{-2.1}$~M$_\odot$~yr$^{-1}$. We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.Comment: Accepted for publication in Astronomy & Astrophysics, comments are still welcom

An Assessment of Dynamic Behavior in the U.S. Catfish Market: An Application of the Generalized Dynamic Rotterdam Model

The generalized dynamic Rotterdam model was used in estimating U.S. demand for disaggregated catfish. The overall goal was to examine habit persistence in consumption and to determine the adjustment process in demand. Results indicated that it took up to 1 month for catfish-product demand to fully adjust to changes in expenditures and prices. Additionally, habit persistence played a role in demand where present consumption of a given product was positively affected by past consumption of that product. Consequently, U.S. catfish demand was significantly more elastic in the long-run.catfish, demand, dynamics, partial adjustment, Rotterdam model, Agribusiness, Consumer/Household Economics, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, C51, Q11, Q13, Q17,

Witnessing the birth of a supermassive protostar

The detection of $\rm z>6$ quasars reveals the existence of supermassive black holes of a few $\rm 10^9~M_{\odot}$. One of the potential pathways to explain their formation in the infant universe is the so-called direct collapse model which provides massive seeds of $\rm 10^5-10^6~M_{\odot}$. An isothermal direct collapse mandates that halos should be of a primordial composition and the formation of molecular hydrogen remains suppressed in the presence of a strong Lyman Werner flux. In this study, we perform high resolution cosmological simulations for two massive primordial halos employing a detailed chemical model which includes $\rm H^-$ cooling as well as realistic opacities for both the bound-free $\rm H^-$ emission and the Rayleigh scattering of hydrogen atoms. We are able to resolve the collapse up to unprecedentedly high densities of $\rm \sim 10^{-3}~g/cm^3$ and to scales of about $\rm 10^{-4}$ AU. Our results show that the gas cools down to $\rm \sim$ 5000 K in the presence of $\rm H^-$ cooling, and induces fragmentation at scales of about 8000 AU in one of the two simulated halos, which may lead to the formation of a binary. In addition, fragmentation also occurs on the AU scale in one of the halos but the clumps are expected to merge on short time scales. Our results confirm that $\rm H^-$ cooling does not prevent the formation of a supermassive star and the trapping of cooling radiation stabilises the collapse on small scales.Comment: Accpeted version, to appear in MNRAS, comments are still welcome and high resolution version is available at http://www2.iap.fr/users/latif/DCBH.pd

Inter-country Comparisons of Poverty Based on a Capability Approach: An Empirical Exercise

We argue that inter-country comparisons of income poverty based on poverty lines uniformly reflecting the costs of the basic requirements of human beings are superior to the existing money-metric approaches. In this exercise, we implement a uniform approach to poverty assessment based on basic human capabilities for three countries: Nicaragua, Tanzania, and Vietnam. We compute standard errors of the resulting poverty estimates and compare the incidence of poverty across these three countries. The choice of approach affects both cardinal estimates and ordinal rankings of poverty across countries and over time. Meaningful and coherent inter-country poverty comparisons can be advanced through international co-ordination in survey design and in the construction of income poverty lines that uniformly reflect the costs of the basic requirements of human beings.Poverty, Inter-Country comparisons, Capability approach

Market Integration for Shrimp and the Effect of Catastrophic Events

Seasonal unit-root testing and seasonal cointegration methods are employed to investigate the price transmission in U.S. shrimp markets. ARIMA and Vector Error Correction Models (VECM) are used to identify the effect of catastrophic events on individual price series in one region and the spillover effects in the price series for other regions. Results showed that a cointegrating relation exists between neighboring states, specifically between Alabama and Mississippi and Louisiana and Texas. Cointegrating relations also exist between the Gulf States and the Pacific region, but not the Atlantic region, and the price of imported shrimp is cointegrated with each of the domestic shrimp price series. Finally, while Katrina had an effect on shrimp prices in Gulf States, the effect was not long lasting.catastrophic events, cointegration, market integration, seasonal unit-roots, spillover effects, Marketing, Risk and Uncertainty, C13, Q11, Q13,

Nickel oxide photocathodes prepared using rapid discharge sintering for p-type dye-sensitized solar cells

This paper compares the photoelectrochemical performances of nickel oxide (NiO) thin films processed using two different sintering procedures: rapid discharge sintering (RDS) and conventional furnace sintering (CS). Prior to sintering, NiO nanoparticles were sprayed onto substrates to form loosely adherent nanoparticulate coatings. After RDS and furnace sintering the resultant NiO coatings were sensitized with erythrosine B dye and corresponding p-type dyesensitized solar cells were fabricated and characterized. NiO electrodes fabricated using the RDS technique exhibited a fourfold enhancement in electroactivity compared to CS electrodes. A possible explanation is the smaller sintered grain size and more open mesoporous structure achieved using the microwave plasma treatments

The Impact of Domestic and Import Prices on U.S. Lamb Imports: A Production System Approach

As U.S. lamb imports increased relative to domestic production, and the relative share of chilled to frozen lamb imports increased, importers of chilled lamb have become less responsive to domestic and import prices, while the direct opposite is the case for frozen lamb imports. From 1990 to 2003, chilled lamb imports from Australia and New Zealand became less and less responsive to U.S. prices, and frozen imports became more responsive. Unconditional own-price elasticities also show that, over time, imports of chilled lamb became less responsive to import prices while frozen imports became more responsive to import prices.lamb, demand, imports, trade, import demand, production, International Relations/Trade,