High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb

CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number of measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high ($\sim$ 47\%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47\% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane is strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.Comment: 6 pages, 4 figure

Crossover of cation partitioning in olivines: a combination of ab initio and Monte Carlo study

We report studies based on a combination of ab initio electronic structure and Monte Carlo (MC) technique on the problem of cation partitioning among inequivalent octahedral sites, M1 and M2 in mixed olivines containing Mg<SUP>2+</SUP> and Fe<SUP>2+</SUP> ions. Our MC scheme uses interactions derived out of ab initio, density functional calculations carried out on measured crystal structure data. Our results show that there is no reversal of the preference of Fe for M1 over M2 as a function of temperature. Our findings do not agree with the experimental findings of Redfern et al. (Phys Chem Miner 27:630-637, 2000), but are in agreement with those of Heinemann et al. (Eur J Mineral 18:673-689, 2006) and Morozov et al. (Eur J Mineral 17:495-500, 2005)

EFFECTS OF THEAFLAVINS ON GASTRIC CANCER CELL LINE

  Objective: The objective of this study was to evaluate the anticarcinogenic effects of theaflavins (TFs), component of black tea, on human gastric cancer cell line.Materials and Methods: Cell viability was assessed by WST-1 reagent. Acridine orange (AO) and ethidium bromide (EB) fluorescence staining method were used to detect apoptotic cells, if any, followed by flow cytometric detection. To evaluate the molecular basis for understanding the apoptotic pathway, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were measured. Pro- and anti-apoptotic protein and gene expressions were detected by western blot and real-time techniques.Results: TFs-treated AGS cell indicated apoptosis-mediated cell death. The presence of TFs induced the generation of ROS and which in turn changes the MMP with the elevated level of cyt c, activation of caspase-9, caspase-3, and PARP cleavage. Our study also showed that TFs treatment altered the Bax/Bcl2 ratio and upregulated the expression of p53.Conclusion: All these observations lead to the fact that TFs developed potential chemopreventive effects through the induction of apoptosis through mitochondria-mediated death cascade in the human gastric cancer cell

Tunable Surface Plasmon Resonance in Sn-Doped Zn–Cd–O Alloyed Nanocrystals

Aliovalent ion doped n-type semiconductor nanocrystals (NC) have presently gained high interest in semiconductor research for their potential applications in plasmonics, transparent conducting oxide (TCO), and high speed optical device. For most of the cases the plasmonic absorbance band appears in the near infrared region (NIR) but it is rarely observed in visible wavelength for aliovalent ion doped semiconductor nanocrystals. In this article, we report the synthesis of Sn-doped ZnO monodispersed nanocrystals and their unique plasmonic absorbance property which is tunable from the visible to the NIR region (550 nm to >3000 nm) by varying the Sn dopant concentration and the degree of Cd-alloying. We have studied the surface enhanced Raman spectroscopy (SERS) of the 4-mercaptopyridine (4-MPy) molecule using Sn:ZnO NC thin film as SERS substrate and found a high enhancement factor value. A TCO thin film with a good figure of merit value has been prepared by Sn:Zn–Cd–O alloyed NCs by taking advantage of high electron density and high mobility of electrons of doped alloyed NCs. Application as SERS substrate and TCO are excellent features of Sn-doped Zn_1–<i>x</i>Cd_<i>x</i>O NCs