Central mode and spin confinement near the boundary of the superconducting phase in YBa2Cu3O6.353 (Tc=18 K)

We have mapped the neutron scattering spin spectrum at low-energies in YBa2Cu3O6.353 (Tc=18 K) where the doping ~0.06 is near the critical value (pc=0.055) for superconductivity. No coexistence with long range ordered antiferromagnetism is found. The spins fluctuate on two energy scales, one a damped spin response with a ~2 meV relaxation rate and the other a central mode with a relaxation rate that slows to less than 0.08 meV below Tc. The spectrum mirrors that of a soft mode driving a central mode. Extremely short correlation lengths, 42+-5 Angstrom in-plane and 8+-2 Angstrom along the c direction, and isotropic spin orientations for the central mode indicate that the correlations are subcritical with respect to any second order transition to Neel order. The dynamics follows a model where damped spin fluctuations are coupled to the slow fluctuations of regions with correlations shortened by the hole doping.Comment: 5 pages 4 figures. One figure revised and some text revision. Accepted PRB Rapids February 14, 200

Dynamical Properties of a Haldane Gap Antiferromagnet

We study the dynamic spin correlation function of a spin one antiferromagnetic chain with easy-plane single-ion anisotropy. We use exact diagonalization by the Lancz\H os method for chains of lengths up to N=16 spins. We show that a single-mode approximation is an excellent description of the dynamical properties. A variational calculation allows us to clarify the nature of the excitations. The existence of a two-particle continuum near zero wavevector is clearly seen both in finite-size effects and in the dynamical structure factor. The recent neutron scattering experiments on the quasi-one-dimensional antiferromagnet NENP are fully explained by our results.Comment: 14 pages, SphT/92-135 plain tex with Postscript figures included. Postscipt file available by anonymous ftp at amoco.saclay.cea.fr by get pubs.spht/92-135.ps local_file (290 kb) or get pubs.spht/92-135.ps.Z local_file.Z (compressed - 120 kb

Spin dynamics near the critical doping in weakly-superconducting underdoped YBa2Cu3O6.35 (Tc=18K)

Using neutron scattering we have determined the magnetic structure and fluctuations in the YBa2Cu3O6.35 superconductor (Tc=18 K). The long-range ordered collinear spins of the insulating antiferromagnet are replaced by a commensurate central mode arising from slow, isotropically polarized, short-range spin correlations. The inelastic spectrum up to 30 meV is broad in wave vector and commensurate. In contrast to the the resonance peak of higher Tc superconductors, the spins exhibit a single overdamped spectrum whose rate of relaxation decreases on cooling and saturates at 5 meV below 50 K. As the relaxation rate saturates the quasi-static spin correlations grow and become resolution limited in energy. The spin susceptibility at high temperatures illustrates that the dominant energy scale is set by the temperature. At low temperatures, the scale length is geometric and not linked by velocity to dynamic widths. There is no observable suppression of the spin fluctuations or central mode upon the onset of superconductivity. The spins respond not to coherent charge pairs but to hole doping allowing coexistence of glassy short range spin order with superconductivity. Since the physics of the weakly superconducting system YBCO6.35 must connect continuously with that in more strongly superconducting YBCO6.5, we find that neither incommensurate stripe-like spin modulations nor a well-defined neutron spin resonance are essential for the onset with doping of pairing in a high temperature cuprate superconductor.Comment: 22 pages, 19 figures, accepted for publication in Phys. Rev.

CIRSE Standards of Practice on Conducting Meetings on Morbidity and Mortality

This CIRSE Standards of Practice document is developed by an expert writing group under the guidance of the CIRSE Standards of Practice Committee. It aims to assist Interventional Radiologists in their daily practice by providing best practices for conducting meetings on morbidity and mortality.info:eu-repo/semantics/publishedVersio

Impact of Six Genetic Modifications of Corn on Feed Cost and the Consumption of Traditional Feed Ingredients

There is excitement about the potential profit and economic development opportunities from genetic modifications of grain. This excitement is manifested in huge industry consolidations through buyouts, joint ventures, and mergers of chemical, seed and agribusiness companies. State and federal government agencies and private organizations have developed programs to encourage and facilitate the production, handling, processing, and marketing of genetically modified grains. Huge investments are being allocated to research and development of new commodities and specialty grains. A large share of these research and development funds are being invested in modifying com because of the large amount of com produced in the United States and its diversity of uses. About 80 percent of the U.S. corn crop is used in animal feeds domestically and abroad; therefore, genetic modifications of com for animal feed are believed to have major profit and development potential

Long-Term and Global Tradeoffs between Bio-Energy, Feed, and Food

Projections of U.S. ethanol production and its impacts on planted acreage, crop prices, livestock production and prices, trade, and retail food costs are presented under the assumption that current tax credits and trade policies are maintained. The projections were made using a multi-product, multi-country deterministic partial equilibrium model. The impacts of higher oil prices, a drought combined with an ethanol mandate, and removal of land from the Conservation Reserve Program (CRP) relative to baseline projections are also presented. The results indicate that expanded U.S. ethanol production will cause long-run crop prices to increase. In response to higher feed costs, livestock farmgate prices will increase enough to cover the feed cost increases. Retail meat, egg, and dairy prices will also increase. If oil prices are permanently $10-per-barrel higher than assumed in the baseline projections, U.S. ethanol will expand significantly. The magnitude of the expansion will depend on the future makeup of the U.S. automobile fleet. If sufficient demand for E-85 from flex-fuel vehicles is available, corn-based ethanol production is projected to increase to over 30 billion gallons per year with the higher oil prices. The direct effect of higher feed costs is that U.S. food prices would increase by a minimum of 1.1% over baseline levels. Results of a model of a 1988-type drought combined with a large mandate for continued ethanol production show sharply higher crop prices, a drop in livestock production, and higher food prices. Corn exports would drop significantly, and feed costs would rise. Wheat feed use would rise sharply. Taking additional land out of the CRP would lower crop prices in the short run. But because long-run corn prices are determined by ethanol prices and not by corn acreage, the long-run impacts on commodity prices and food prices of a smaller CRP are modest. Cellulosic ethanol from switchgrass and biodiesel from soybeans do not become economically viable in the Corn Belt under any of the scenarios. This is so because high energy costs that increase the prices of biodiesel and switchgrass ethanol also increase the price of corn-based ethanol. So long as producers can choose between soybeans for biodiesel, switchgrass for ethanol, and corn for ethanol, they will choose to grow corn. Cellulosic ethanol from corn stover does not enter into any scenario because of the high cost of collecting and transporting corn stover over the large distances required to supply a commercial-sized ethanol facility.biofuels, corn acreage, crop prices, ethanol production, food prices, Resource /Energy Economics and Policy,

U.S. Proposal for WTO Agriculture Negotiations: Its Impact on U.S. And World Agriculture

The Food and Agricultural Policy Research Institute (FAPRI) analyzed the latest U.S. proposal to the Doha round of WTO negotiations (see Appendix 1, U.S. Proposal for WTO Agriculture Negotiations, USTR, October 10, 2005). While the U.S. proposal provides many concrete steps to reduce farm support and trade distortions, it does not provide all necessary information for quantitative analysis of the proposal. FAPRI, through consultations with economists and staffers of the U.S. Senate Committee on Agriculture, Nutrition and Forestry, Office of the United States Trade Representative, and U.S. Department of Agriculture, elaborated a complementary set of policy assumptions to carry the quantitative analysis. The analysis is conducted in deviation from the baseline of the FAPRI 2005 U.S. and World Agricultural Outlook. New policies put in place since the 2005 baseline was established have been accommodated to separate the impact of the policy scenario from the full set of policy assumptions.

Arsenic trioxide down-regulates antiapoptotic genes and induces cell death in mycosis fungoides tumors in a mouse model

Background: Mycosis fungoides (MF) is the most frequent cutaneous T-cell lymphoma (CTCL). Arsenic trioxide (As2O3) has recently been shown to be effective against leukemias, so we studied whether As2O3 induces apoptosis of CTCL cells in vitro. We further investigated if As2O3 is effective in a MF mouse model. Material and methods: Annexin V/7-amino-actinomycin-D stainings were carried out to investigate if As2O3 induced apoptosis of CTCL cell lines. To study the underlying mechanisms, the effects of As2O3 on various transcription factors and apoptosis regulating proteins were analyzed by western blots, electrophoretic mobility shift assays and transcription factor enzyme-linked immunosorbent assays. The ability of As2O3 to induce tumor regression was investigated in a MF mouse model. Results: As2O3-induced apoptosis was paralleled by a reduction of the DNA-binding activities of transcription factors of the NFkB and signal transducer and activator of transcription gene families and reduced expression of the antiapoptotic proteins bcl-1, bcl-xL and mcl-1. Local injections of 200 μM As2O3 into tumors caused complete remissions in five of six mice and one partial remission. Conclusions: As2O3 induced apoptosis of CTCL cells by the down-regulation of transcription factors that stimulate the expression of antiapoptotic genes. Local injection of As2O3 into MF tumor-bearing mice resulted in tumor regressio