Charge order suppression and antiferromagnetic to ferromagnetic switch over in Pr_0.5Ca_0.5MnO_3 nanowires

We have prepared crystalline nanowires (diameter ~ 50 nm, length ~ a few microns) of the charge ordering manganite Pr_0.5Ca_0.5Mn_O3 using a low reaction temperature hydrothermal method and characterized them using X-ray diffraction, transmission electron microscopy, SQUID magnetometry and electron magnetic resonance measurements. While the bulk sample shows a charge ordering transition at 245 K and an antiferromagnetic transition at 175 K, SQUID magnetometry and electron magnetic resonance experiments reveal that in the nanowires phase, a ferromagnetic transition occurs at ~ 105 K. Further, the antiferromagnetic transition disappears and the charge ordering transition is suppressed. This result is particularly significant since the charge order in Pr_0.5Ca_0.5MnO_3 is known to be very robust, magnetic fields as high as 27 T being needed to melt it.Comment: 12 pages including 4 figures. submitted to Applied Physics Letter

The Role of Middlemen inEfficient and Strongly Pairwise Stable Networks

We examine the strong pairwise stability concept in network formation theory under collective network benefits.Strong pairwise stability considers a pair of players to add a link through mutual consent while permitting them to unilaterally delete any subset of links under their control.We examine the properties of strongly pairwise stable networks and find that players in middleman positions, who have the power to break up the network into multiple components, play a critical role in such networks.We show that for the component-wise egalitarian rule there is no conflict between the efficient and stable networks when these middlemen have no incentive to break up the network. Finally, we examine efficiency and stability in middleman-free networks.networks;stability

Equipartition of Current in Parallel Conductors on Cooling Through the Superconducting Transition

Our experiments show that for two or more pieces of a wire, of different lengths in general, combined in parallel and connected to a dc source, the current ratio evolves towards unity as the combination is cooled to the superconducting transition temperature Tc, and remains pinned at that value below it. This re-distribution of the total current towards equipartition without external fine tuning is a surprise. It can be physically understood in terms of a mechanism that involves the flux-flow resistance associated with the transport current in a wire of type-II superconducting material. It is the fact that the flux-flow resistance increases with current that drives the current division towards equipartition.Comment: Revised version of J.Phys. Condens.Matter; vol. 18(2006) L143-L147 14 pages including 3 figures; provided an explanation in terms of the physical mechanism of flux flow induced resistance that is proportional to the impressed current. We are adding a simple, physically robust derivation of our equipartition without taking resort to the minimum dissipation principl

Equipartition of current in parallel conductors on cooling through the superconducting transition

Our experiments show that for two or more pieces of a wire, of different lengths in general, combined in parallel and connected to a dc source, the current ratio evolves towards unity as the combination is cooled to the superconducting transition temperature Tc, and remains pinned at that value below it. This redistribution of the total current towards equipartition without external fine-tuning is a surprise. It can be physically understood in terms of a mechanism that involves the flux-flow resistance associated with the transport current in a wire of type-II superconducting material. It is a fact that the flux-flow resistance increases with the current that drives the current division towards equipartition

A Wave-function for Stringy Universes

We define a wave-function for string theory cosmological backgrounds. We give a prescription for computing its norm following an earlier analysis within general relativity. Under Euclidean continuation, the cosmologies we discuss in this paper are described in terms of compact parafermionic worldsheet systems. To define the wave-function we provide a T-fold description of the parafermionic conformal field theory, and of the corresponding string cosmology. In specific examples, we compute the norm of the wave-function and comment on its behavior as a function of moduli.Comment: 30 pages, 3 figures, v3: references adde

Crystal structure and magnetic properties of spin-1/21/2 frustrated two-leg ladder compounds (C4_4H14_{14}N2_2)Cu2X6_2X_6 (XX= Cl and Br)

We have successfully synthesized single crystals, solved the crystal structure, and studied the magnetic properties of a new family of copper halides (C$_4$H$_{14}$N$_2$)Cu$_2X_6$ ($X$= Cl, Br). These compounds crystallize in an orthorhombic crystal structure with space group $Pnma$. The crystal structure features Cu$^{2+}$ dimers arranged parallel to each other that makes a zig-zag two-leg ladder-like structure. Further, there exists a diagonal interaction between two adjacent dimers which generates inter-dimer frustration. Both the compounds manifest a singlet ground state with a large gap in the excitation spectrum. Magnetic susceptibility is analyzed in terms of both interacting spin-$1/2$ dimer and two-leg ladder models followed by exact diagonalization calculations. Our theoretical calculations in conjunction with the experimental magnetic susceptibility establish that the spin-lattice can be described well by a frustrated two-leg ladder model with strong rung coupling ($J_0/k_{\rm B} \simeq 116$ K and 300 K), weak leg coupling ($J^{\prime\prime}/k_{\rm B} \simeq 18.6$ K and 105 K), and equally weak diagonal coupling ($J^{\prime }/k_{\rm B} \simeq 23.2$ K and 90 K) for Cl and Br compounds, respectively. These exchange couplings set the critical fields very high, making them experimentally inaccessible. The correlation function decays exponentially as expected for a gapped spin system. The structural aspects of both the compounds are correlated with their magnetic properties. The calculation of entanglement witness divulges strong entanglement in both the compounds which persists upto high temperatures, even beyond 370~K for the Br compound.Comment: 13 pages, 9 figures, 2 table

Neural network and its application in aquaculture

In the-past decades the researchers and managers have used empirical, statistical models or complicated mathematical models predict the consequences of management regimes or actions, and to assist in decision making

Coconut (Cocos nucifera)-based farming system: a viable land use option for small and marginal farmers in coastal Odisha

An investigation was carried out during 2012-2013 in Puri district of Odisha to study the composition, structure and role of coconut (Cocos nucifera L.) based farming in 15 different holding sizes, i.e. 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 and 1.5 acre. The experiment was laid out in randomised block design with three replications. The smaller holdings were found close to houses as homegardens and comparatively larger holdings were found little away from the houses. The composition was found very diverse consisting of perennial trees, annual crops and seasonal crops. The coconut based agroforestry systems of various sizes are playing important role for the household which include productive role, protective and ameliorative role, recreational and educational role as well as developmental role giving various kinds of tangible and intangible benefits. As the natural forest cover is less in coastal Odisha, a substantial quantity of fuel wood was found to be derived from homegarden and the contribution of fuel wood production increased with increase of holding size up to 1.2 acre. The net return varied from Rupees 5 617 to Rupees 32 850/annum showing the income level increased with increase in holding size, while the economics was calculated on acre basis, the net income ranged from Rupees 56 167 to Rupees 21 900 indicating decreasing trend towards higher holding sizes. In terms of market orientation, the smaller unit sizes were found more subsistence and less commercial than bigger holding sizes and vice versa. The coconut based agroforestry system of size 0.8 acre (perennials-coconut, siris, rain tree, eucalyptus, acacia, areca nut, mango, sissoo, teak, jackfruit, bamboo, guava, pomegranate, papaya, drumstick, bael, citrus, banana, curry leaf ; seasonals-pine apple, yam, arrowroot, turmeric, ginger, brinjal, okra, bitter gourd, ridge gourd, chilli, greens, cowpea, tomato, cauliflower, pumpkin; mushroom-paddy straw/oyster; fish- rohu, silver crap, grass crap; cattle, buffalo, goat, poultry, duck) was found to be the best among the holding sizes studied with regard to viability of landuse

Gene transfer in Indian major carps by electroporation

The rainbow trout growth hormone gene has been successfully tranferred into three species of Indian major carps rohu (Labeo rohita), mrigal (Cirrhinus mrigala) and catla (Catla catla) through electroporated sperm cell. At 0.5kV/cm (25μF capacitance, a resistance, and 2 pulses) the gene transfer efficiency was 25% for rohu, 23% for mrigal and 13% for catla. This is the first report on gene transfer in Indian major carps