Superconductivity Near a Quantum Critical Point in Ba(Fe,Co)2As2

We will examine the possible link between spin fluctuations and the superconducting mechanism in the iron-based high temperature superconductor Ba(Fe,Co)2As2 based on NMR and high pressure transport measurements.Comment: Invited paper to m2s-IX (2009

Influence of Sea Surface Temperature on the Gonadal development of Sea urchin Temnopleurus toreumaticus from the Gulf of Mannar, South East Coast of India

This study was conducted for a 20 months period from October 2013 to May 2015 in Gulf of Mannar, south east coast of India. During the investigation the abiotic factors viz., Sea surface temperature (SST), Daylight photoperiod and atmospheric temperature data were collected from International comprehensive Ocean Atmospheric Database (ICOADS) and the reproductive cycle of the sea urchin was studied from the monthly sampling of sea urchin collected from Vedalai landing centre in Gulf of Mannar. The gonads were studied to calculate Gonad index as well histological to categories them into four different stages of the development and this data was compared with abiotic factors to study the influence of it on the reproductive behaviour of sea urchin. The data were analyzed statistically through Pearson correlation and it was found negative between mean monthly gonad index and day length photoperiod, as well as with SST. This clearly indicates that the gonadal development in sea urchin is very much influenced by these two abiotic factors; however other nutritional factors might play greater role in the development gonad

NMR measurements of intrinsic spin susceptibility in LaFeAsO(0.9)F(0.1)

We will probe the intrinsic behavior of spin susceptibility chi_(spin) in the LaFeAsO(1-x)F(x) superconductor (x ~ 0.1, Tc ~ 27K) using 19-F and 75-As NMR techniques. Our new results firmly establish the pseudo-gap behavior with Delta_(PG)/kB ~ 140K. The estimated magnitude of chi_(spin) at 290K, ~1.8x10^(-4) [emu/mol-Fe], is approximately twice larger than that in high Tc cuprates. We also show that chi_(spin) levels off below ~50K down to Tc.Comment: Invited paper to the Proceedings of the International Symposium on Iron-oxypnictide Superconductors (June 28-29, 2008, Tokyo). J. Phys. Soc. Jpn. Suppl. (in press

Evaluation of periphyton quantity on different natural substrates in Earthen lined pond

Experiments were conducted in outdoor earthen lined pond to study periphyton quantity on three types of natural substrates such as split bamboo pole, coconut coir and coconut shell, which was placed inside the earthen lined pond filled with seawater for duration of 45 days. Observations were made in every 15th day for growth of periphyton both qualitatively and quantitatively on the three natural substrates and physico-chemical properties of selected pond water such as transparency, water temperature, salinity, pH, Dissolved oxygen, Ammonia (NH3-N), Nitrite (NO2-N), Nitrate (NO3-N), BOD and Chlorophyll ‘a’ were recorded during periphyton samplings. The periphy-ton quantity (34562 ± 671 cells / cm2) observed for coconut coir was higher than the split bamboo pole (33104 ± 810 cells / cm2), and coconut shell (21194 ± 872 cells / cm2) in the final day of the experiment. One way ANOVA of the data collected clearly affirmed that significant differences were observed (P < 0.05) in periphyton quantity among the three substrates tested. A total 16 phyto-periphytic microalgae (Bacillariophyceae – 10 types, Dinophyceae – 4 types and Cyanophyceae – 2 types) and 10 Zoo-periphyton (Copepod- 4 types, Meroplankton – 4 types and Tintin-nidae – 2 types) were recorded from these three substrates. Among the different phyto-periphytic microalgae, Bacil-lariophyceae group were found to be more (Split bamboo pole – 72%, Coconut coir – 73% and Coconut shell – 71%) on three substrates studied. Further, coconut coir was found to be best substrate than split bamboo pole and coconut shell, which can be utilized by fin and shellfishes as natural food

भारत में शूलचर्मी पालन में संभावनाएं

Prospects of Echiniculture in Indi

Pressure effects on the electron-doped high Tc superconductor BaFe(2-x)Co(x)As(2)

Application of pressures or electron-doping through Co substitution into Fe sites transforms the itinerant antiferromagnet BaFe(2)As(2) into a superconductor with the Tc exceeding 20K. We carried out systematic transport measurements of BaFe(2-x)Co(x)As(2) superconductors in pressures up to 2.5GPa, and elucidate the interplay between the effects of electron-doping and pressures. For the underdoped sample with nominal composition x = 0.08, application of pressure strongly suppresses a magnetic instability while enhancing Tc by nearly a factor of two from 11K to 21K. In contrast, the optimally doped x=0.20 sample shows very little enhancement of Tc=22K under applied pressure. Our results strongly suggest that the proximity to a magnetic instability is the key to the mechanism of superconductivity in iron-pnictides.Comment: 5 figure

Interplay between magnetism and superconductivity and appearance of a second superconducting transition in alpha-FeSe at high pressure

We synthesized tetragonal alpha-FeSe by melting a powder mixture of iron and selenium at high pressure. Subsequent annealing at normal pressure results in removing traces of hexagonal beta- FeSe, formation of a rather sharp transition to superconducting state at Tc ~ 7 K, and the appearance of a magnetic transition near Tm = 120 K. Resistivity and ac-susceptibility were measured on the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic transition visible in ac-susceptibility shifts down under pressure and the resistive anomaly typical for a spin density wave (SDW) antiferromagnetic transition develops near the susceptibility anomaly. Tc determined by the appearance of a diamagnetic response in susceptibility, increases linearly under pressure at a rate dTc/dP = 3.5 K/GPa. Below 1.5 GPa, the resistive superconducting transition is sharp; the width of transition does not change with pressure; and, Tc determined by a peak in drho/dT increases at a rate ~ 3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition develops. This effect cannot be explained by possible pressure gradients in the sample and is inherent to alpha-FeSe. The dependences drho(T)/dT show a signature for a second peak above 3 GPa which is indicative of the appearance of another superconducting state in alpha-FeSe at high pressure. We argue that this second superconducting phase coexists with SDW antiferromagnetism in a partial volume fraction and originates from pairing of charge carriers from other sheets of the Fermi surface

High temperature superconductivity (Tc onset at 34K) in the high pressure orthorhombic phase of FeSe

We have studied the structural and superconducting properties of tetragonal FeSe under pressures up to 26GPa using synchrotron radiation and diamond anvil cells. The bulk modulus of the tetragonal phase is 28.5(3)GPa, much smaller than the rest of Fe based superconductors. At 12GPa we observe a phase transition from the tetragonal to an orthorhombic symmetry. The high pressure orthorhombic phase has a higher Tc reaching 34K at 22GPa.Comment: 15 pages, 4 figure

INFLUENCE OF SELECTED FEED ADDITIVES ON THE GROWTH AND GONADAL MATURATION OF GOLDFISH (CARRASSIUS AURATUS)

The present investigation was designed to study the influence of selected feed additives, viz., fish meal, shrimp head meal and soy flour on the growth and gonadal maturation of goldfish, Carassius auratus. The feeding trial was carried out for 60 days and the sampling was carried out once in a fortnight. The fish meal, at 30 per cent concentration had the highest mean body weight gain (1.966 g) and specific growth rate (0.320 %/day), which ranked first among all the concentrations tried. The mean body weight gain was five folds higher in 30% concentration when compared to control. In the case of gonadal maturation, the fishes fed with 40% yielded the best results in both male and female. The shrimp head meal, at 40% concentration yielded the best result with regard to the growth of the goldfish. With regard to breeding performance of goldfish fed with different concentration of shrimp head meal diet, 20% concentration yielded the best result followed by 40% concentration. The mean body weight gain of 1.351 g was observed at 30% concentration of soy flour fed fishes. These results indicated that fish meal at 30% concentration is the best for the better growth of goldfish