Magnetoresistance in LaFe11.2Co0.7Si1.1 compound

Magnetoresistance has been studied in LaFe/sub 11.2/Co/sub 0.7/Si/sub 1.1/ compound. The ferromagnetic ordering at Curie temperature T/sub C/ of 274 K was found being accompanied by a drastic negative lattice expansion due to the strong structural and magnetic interplay. Such a simultaneous magnetic and lattice change would cause changes in transport properties. The measured transport properties indicate that the transition can be induced by temperature or applied magnetic field. The sample shows a metallic character below T/sub C/, whereas the electrical resistance decreases dramatically and then recovers the metal-like behavior above T/sub C/. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase of field leads to an increase of resistance at temperatures near but above T/sub C/, which is a result of the field-induced metamagnetic transition from paramagnetic to ferromagnetic state.published_or_final_versio

Magnetocaloric effect in itinerant electron metamagnetic systems La(Fe1-xCox)11.9Si1.1

The NaZn13-type compounds La(Fe1–xCox)11.9Si1.1 (x=0.04, 0.06, 0.08) were successfully synthesized, in which the Si content is the limit that can be reached by arc-melting technique. TC is tunable from 243 to 301 K with Co doping from x=0.04 to 0.08. Great magnetic entropy change S in a wide temperature range from ~230 to ~320 K has been observed. The adiabatic temperature change Tad upon changing magnetic field was also directly measured. Tad of sample x=0.06 reaches ~2.4 K upon a field change from 0 to 1.1 T. The temperature hysteresis upon phase transition is small, ~1 K, for all samples. The influence of Co doping on itinerant electron metamagnetic transition and magnetic entropy change is discussed. ©2005 American Institute of Physics.published_or_final_versio

Differential Effects of Tyrosine Kinase Inhibitors on Volume-sensitive Chloride Current in Human Atrial Myocytes: Evidence for Dual Regulation by Src and EGFR Kinases

To determine whether protein tyrosine kinase (PTK) modulates volume-sensitive chloride current (I Cl.vol) in human atrial myocytes and to identify the PTKs involved, we studied the effects of broad-spectrum and selective PTK inhibitors and the protein tyrosine phosphatase (PTP) inhibitor orthovanadate (VO 4 -3). I Cl.vol evoked by hyposmotic bath solution (0.6-times isosmotic, 0.6T) was enhanced by genistein, a broad-spectrum PTK inhibitor, in a concentration-dependent manner (EC 50 = 22.4 μM); 100 μM genistein stimulated I Cl.vol by 122.4 ± 10.6%. The genistein-stimulated current was inhibited by DIDS (4,4′-diisothiocyanostilbene-2,2′-disulfonic acid, 150 μM) and tamoxifen (20 μM), blockers of I Cl.vol. Moreover, the current augmented by genistein was volume dependent; it was abolished by hyperosmotic shrinkage in 1.4T, and genistein did not activate Cl - current in 1T. In contrast to the stimulatory effects of genistein, 100 μM tyrphostin A23 (AG 18) and A25 (AG 82) inhibited I Cl.vol by 38.2 ± 4.9% and 40.9 ± 3.4%, respectively. The inactive analogs, daidzein and tyrphostin A63 (AG 43), did not alter I Cl.vol. In addition, the PTP inhibitor VO 4 -3 (1 mM) reduced I Cl.vol by 53.5 ± 4.5% (IC 50 = 249.6 μM). Pretreatment with VO 4 -3 antagonized genistein-induced augmentation and A23- or A25-induced suppression of I Cl.vol. Furthermore, the selective Src-family PTK inhibitor PP2 (5 μM) stimulated I Cl.vol, mimicking genistein, whereas the selective EGFR (ErbB-1) kinase inhibitor tyrphostin B56 (AG 556, 25 μM) reduced I Cl.vol, mimicking A23 and A25. The effects of both PP2 and B56 also were substantially antagonized by pretreatment with VO 4 -3. The results suggest that I Cl.vol is regulated in part by the balance between PTK and PTP activity. Regulation is complex, however. Src and EGFR kinases, distinct soluble and receptor-mediated PTK families, have opposing effects on I Cl.vol, and multiple target proteins are likely to be involved.published_or_final_versio

Template-free synthesis of Nd0.1Bi0.9FeO3 nanotubes with large inner diameter and wasp-waisted hysteresis loop

published_or_final_versio

Substrate co-doping modulates electronic metal-support interactions and significantly enhances single-atom catalysis

Transitional metal nanoparticles or atoms deposited on appropriate substrates can lead to highly economical, efficient, and selective catalysis. One of the greatest challenges is to control the electronic metal–support interactions (EMSI) between the supported metal atoms and the substrate so as to optimize their catalytic performance. Here, from first-principles calculations, we show that an otherwise inactive Pd single adatom on TiO2(110) can be tuned into a highly effective catalyst, e.g. for O2 adsorption and CO oxidation, by purposefully selected metal–nonmetal co-dopant pairs in the substrate. Such an effect is proved here to result unambiguously from a significantly enhanced EMSI. A nearly linear correlation is noted between the strength of the EMSI and the activation of the adsorbed O2 molecule, as well as the energy barrier for CO oxidation. Particularly, the enhanced EMSI shifts the frontier orbital of the deposited Pd atom upward and largely enhances the hybridization and charge transfer between the O2 molecule and the Pd atom. Upon co-doping, the activation barrier for CO oxidation on the Pd monomer is also reduced to a level comparable to that on the Pd dimer which was experimentally reported to be highly efficient for CO oxidation. The present findings provide new insights into the understanding of the EMSI in heterogeneous catalysis and can open new avenues to design and fabricate cost-effective single-atom-sized and/or nanometer-sized catalysts

The abnormal electrical and optical properties in Na and Ni codoped BiFeO3 nanoparticles

published_or_final_versio

Genetic relationships among alfalfa gemplasms resistant to common leaf spot and selected Chinese cultivars assessed by sequence-related amplified polymorphism (SARP) markers

Genetic relationships among 26 alfalfa cultivars, of which, 12 were of high resistance to common leaf spot (CLS), were assessed using sequence-related amplified polymorphism (SRAP) markers. 34 SRAP primer combinations were selected for fingerprinting of these cultivars and a total of 281 bands were observed, among which 115 were polymorphic (40.93%). Based on molecular data, 26 cultivars were classified into 5 groups. Group I included 12 Chinese cultivars, most of which had a low CLS resistance and were planted in cold and/or drought region in China, while 10 of 11 cultivars with a high CLS resistance were put in group II or group IV respectively. Furthermore, the clustering pattern was, on the whole, consistent with their CLS resistance or geographic origins. In addition, there was a low genetic diversity among alfalfa cultivars from China. In conclusion, SRAP markers may serve as a quick tool to analyze the genetic relationships and genetic diversity among alfalfa cultivars in conjunction with DNAbulking method. The information produced by this study on the genetic relationships and genetic diversity among 26 cultivars could be useful to select parents in a CLS resistance breeding program of alfalfa.Key words: Lucerne, SRAP, Medicago sativa, common leaf spot, genetic relationship

Abnormal variation of band gap in Zn doped Bi0.9La0.1FeO3 nanoparticles: Role of Fe-O-Fe bond angle and Fe-O bond anisotropy

published_or_final_versio