First-principles investigation of spin polarized conductance in atomic carbon wire

We analyze spin-dependent energetics and conductance for one dimensional (1D) atomic carbon wires consisting of terminal magnetic (Co) and interior nonmagnetic (C) atoms sandwiched between gold electrodes, obtained employing first-principles gradient corrected density functional theory and Landauer's formalism for conductance. Wires containing an even number of interior carbon atoms are found to be acetylenic with sigma-pi bonding patterns, while cumulene structures are seen in wires containing odd number of interior carbon atoms, as a result of strong pi-conjugation. Ground states of carbon wires containing up to 13 C atoms are found to have anti-parallel spin configurations of the two terminal Co atoms, while the 14 C wire has a parallel Co spin configuration in the ground state. The stability of the anti-ferromagnetic state in the wires is ascribed to a super-exchange effect. For the cumulenic wires this effect is constant for all wire lengths. For the acetylenic wires, the super-exchange effect diminishes as the wire length increases, going to zero for the atomic wire containing 14 carbon atoms. Conductance calculations at the zero bias limit show spin-valve behavior, with the parallel Co spin configuration state giving higher conductance than the corresponding anti-parallel state, and a non-monotonic variation of conductance with the length of the wires for both spin configurations.Comment: revtex, 6 pages, 5 figure

Ultrasonic techniques for repair of aircraft structures with bonded composite patches

This is a paper on a research and development project to demonstrate a novel ultrasonic process for the field application of boron/epoxy (B/Ep) patches for repair of aircraft structures. The first phase of the project was on process optimization and testing to develop the most practical ultrasonic processing techniques. Accelerated testing and aging behavior of precured B/Ep patches, which were ultrasonically bonded to simulated B-52 wing panel assemblies, were performed by conducting flight-by-flight spectrum loading fatigue tests. The spectrum represented 2340 missions/flights or 30 years of service. The effects of steady-state applied temperature and prior exposure of the B/Ep composite patches were evaluated. Representative experimental results of this phase of the project are presented

Effect of dietary supplementation of marigold oleoresin on growth, survival and total muscle carotenoid of Koi carp, Cyprinus carpio L.

The experiment was conducted to evaluate the effect of dietary supplementation of carotenoid (marigold oleoresin) on growth, survival and total body carotenoid of Koi carp (Cyprinus carpio). The experiment was carried out in 12 fiber aquarium tanks of size 12"×6"×6"(20l capacity). Each tank was stocked with15 fishes of uniform size. The marigold oleoresin were as dietary supplement at levels 60, 120, 180, 240, 300 ppm/kg of the feed and designated as treatment T1, T2, T3, T4 and T5 respectively and diet without marigold oleoresin supplementationserved as a control (T0). The result of the experiment showed that there was significant difference found in absolute growth rate and specific growth rate of the fish (P >0.05). However, 180ppm marigold oleoresin fed fishes showed higher mean weight gain of 3.98±0.22g and lower feed conversion ratio (FCR) of 2.81±0.04 than the other treatment groups. The body coloration and total carotenoid concentration of muscle tissue (30.16±0.60?g/g) was significantly higher in fish fed with 180 ppm marigold oleoresin diet. The study showed that incorporation of 180ppm of marigold oleoresin in diet was found better to enhance the growth and coloration in C. carpio

Superconducting and normal-state interlayer-exchange-coupling in La0.67_{0.67}Sr0.33_{0.33}MnO3{3}-YBa2_{2}Cu3_{3}O7−La_{7}-La_{0.67}SrSr_{0.33}MnO MnO{3}$ epitaxial trilayers

The issue of interlayer exchange coupling in magnetic multilayers with superconducting (SC) spacer is addressed in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) - YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) - La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) epitaxial trilayers through resistivity, ac-susceptibility and magnetization measurements. The ferromagnetic (FM) LSMO layers possessing in-plane magnetization suppress the critical temperature (T$_{c})$ of the c-axis oriented YBCO thin film spacer. The superconducting order, however, survives even in very thin layers (thickness d$_{Y} \sim$ 50 {\AA}, $\sim$ 4 unit cells) at T $<$ 25 K. A predominantly antiferromagnetic (AF) exchange coupling between the moments of the LSMO layers at fields $<$ 200 Oe is seen in the normal as well as the superconducting states of the YBCO spacer. The exchange energy J$_{1}$ ($\sim$ 0.08 erg/cm$^{2}$ at 150 K for d$_{Y}$ = 75 {\AA}) grows on cooling down to T$_{c}$, followed by truncation of this growth on entering the superconducting state. The coupling energy J$_{1}$ at a fixed temperature drops exponentially with the thickness of the YBCO layer. The temperature and d$_{Y}$ dependencies of this primarily non-oscillatory J$_{1}$ are consistent with the coupling theories for systems in which transport is controlled by tunneling. The truncation of the monotonic T dependence of J$_{1}$ below T$_{c}$ suggests inhibition of single electron tunneling across the CuO$_{2}$ planes as the in-plane gap parameter acquires a non-zero value.Comment: Accepted for publication in Phys. Rev.

Substantial increase in yield predicted by wheat ideotypes for Europe under future climate

A substantial increase in food production is needed for global food security. Europe is the largest wheat producer, delivering 35% of wheat globally, but its future genetic yield potential is yet unknown. We estimated the genetic yield potential of wheat in Europe under 2050 climate by designing in silico wheat ideotypes based on genetic variation in wheat germplasm. To evaluate the importance of heat and drought stresses around flowering, a critical stage in wheat development, sensitive and tolerant ideotypes were designed. Ideotype yields ranged from 9 to 17 t ha−1 across major wheat growing regions in Europe under 2050 climate. Both ideotypes showed a substantial increase in yield of 66−89% compared to current local cultivars under future climate. Key traits for wheat improvements under future climate were identified. Ideotype design is a powerful tool for estimating crop genetic yield potential in a target environment, along with the potential to accelerate breeding by providing target traits for improvements

Phase transitions and ordering of confined dipolar fluids

We apply a modified mean-field density functional theory to determine the phase behavior of Stockmayer fluids in slitlike pores formed by two walls with identical substrate potentials. Based on the Carnahan-Starling equation of state, a fundamental-measure theory is employed to incorporate the effects of short-ranged hard sphere - like correlations while the long-ranged contributions to the fluid interaction potential are treated perturbatively. The liquid-vapor, ferromagnetic liquid - vapor, and ferromagnetic liquid - isotropic liquid first-order phase separations are investigated. The local orientational structure of the anisotropic and inhomogeneous ferromagnetic liquid phase is also studied. We discuss how the phase diagrams are shifted and distorted upon varying the pore width.Comment: 15 pages including 8 figure

Melanosis and quality attributes of chill stored farm raised whiteleg shrimp (Litopenaeus vannamei)

Loss of market value of shrimp is mainly due to the formation of black spot called melanosis. A study was conducted for 14 days to determine the extent of melanosis and quality changes during that period of freshly har-vested whiteleg shrimp (Litopenaeus vannamei) under chilled storage (2?). Among quality parameters, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBAR-S), were varied from 13.17 mg % to 44.50 mg % and 0.04to 2.57 mg malondehaldehyde/kg of fat respectively whereas melanosis score and metric chroma (C) exhibited significant increases during chilled storage (P&lt;0.05). There was a slight increase in moisture, crude fat and pH from 73.96 % to 74.57 %, 1.05 % to 1.14 % and 6.52 to 7.60 respectively at 14th day of storage. Loss of protein from 22.51 % to 21.28 % may be due to decrease in available amino acids during chilled storage and total plate count (TPC) showed gradual increase of bacterial load up to 1.73*107 log CFU/g at the end of chilled storage. The sensory analysis by panellists indicated, the acceptability of white leg shrimp was up to 6 days in chilled condition and formation of black spot is one of the major parameter for rejection by the panellists

Vitrification of a monatomic 2D simple liquid

A monatomic simple liquid in two dimensions, where atoms interact isotropically through the Lennard-Jones-Gauss potential [M. Engel and H.-R. Trebin, Phys. Rev. Lett. 98, 225505 (2007)], is vitrified by the use of a rapid cooling technique in a molecular dynamics simulation. Transformation to a crystalline state is investigated at various temperatures and the time-temperature-transformation (TTT) curve is determined. It is found that the transformation time to a crystalline state is the shortest at a temerature 14% below the melting temperature Tm and that at temperatures below Tv = 0.6 Tm the transformation time is much longer than the available CPU time. This indicates that a long-lived glassy state is realized for T < Tv.Comment: 5pages,5figures,accepted for publication in CEJ

Rings and rigidity transitions in network glasses

Three elastic phases of covalent networks, (I) floppy, (II) isostatically rigid and (III) stressed-rigid have now been identified in glasses at specific degrees of cross-linking (or chemical composition) both in theory and experiments. Here we use size-increasing cluster combinatorics and constraint counting algorithms to study analytically possible consequences of self-organization. In the presence of small rings that can be locally I, II or III, we obtain two transitions instead of the previously reported single percolative transition at the mean coordination number $\bar r=2.4$, one from a floppy to an isostatic rigid phase, and a second one from an isostatic to a stressed rigid phase. The width of the intermediate phase $~ \bar r$ and the order of the phase transitions depend on the nature of medium range order (relative ring fractions). We compare the results to the Group IV chalcogenides, such as Ge-Se and Si-Se, for which evidence of an intermediate phase has been obtained, and for which estimates of ring fractions can be made from structures of high T crystalline phases.Comment: 29 pages, revtex, 7 eps figure