Prospects of Spin Catalysis on Spin-Polarized Graphene Heterostructures

Extreme points on potential energy surfaces of Ni adatom on free-standing graphene and top:fcc and hcp:fcc graphene/ Ni(111) heterostructures in different spin states were studied using periodic boundary conditions density functional theory approach. It was found that the spin states of the substrates strongly influence the energy of the Ni adatom extreme points on potential energy surface by decreasing (top:fcc heterostructure) or increasing (hcp:fcc heterostructure) the total energies of Z1, Z1 , and Z2 Ni adatom coordinations on graphene. This phenomenon offers unique possibilities to control the potential energy surfaces of transition metal adatoms and promote surface chemical reactions using induced spin polarization of graphene substrates

Thermal evolution of defects in as-grown and electron-irradiated ZnO studied by positron annihilation

Vacancy-type defects in as-grown ZnO single crystals have been identified using positron annihilation spectroscopy. The grown-in defects are supposed to be zinc vacancy (VZn)-related defects, and can be easily removed by annealing above 600 °C. VZn-related defects are also introduced in ZnO when subjected to 3 MeV electron irradiation with a dose of 5.5×1018 cm−2. Most of these irradiation-induced VZn are annealed at temperatures below 200 °C through recombination with the close interstitials. However, after annealing at around 400 °C, secondary defects are generated. A detailed analysis of the Doppler broadening measurements indicates that the irradiation introduced defects and the annealing induced secondary defects belong to different species. It is also found that positron trapping by these two defects has different temperature dependences. The probable candidates for the secondary defects are tentatively discussed in combination with Raman scattering studies. After annealing at 700 °C, all the vacancy defects are annealed out. Cathodoluminescence measurements show that VZn is not related to the visible emission at 2.3 eV in ZnO, but would rather act as nonradiative recombination centers

Microvoid formation in hydrogen-implanted ZnO probed by a slow positron beam

ZnO crystals were implanted with 20–80 keV hydrogen ions up to a total dose of 4.4×1015 cm−2. Positron lifetime and Doppler broadening of annihilation radiation measurements show introduction of zinc vacancy-related defects after implantation. These vacancies are found to be filled with hydrogen atoms. After isochronal annealing at 200–500 °C, the vacancies agglomerate into hydrogen bubbles. Further annealing at 600–700 °C causes release of hydrogen out of the bubbles, leaving a large amount of microvoids. These microvoids are annealed out at high temperature of 1000 °C. Raman spectroscopy for the implanted sample shows the enhancement of vibration modes at about 575 cm−1, which indicates introduction of oxygen vacancies. These oxygen vacancies disappear at temperatures of 600–700 °C, which is supposed to contribute to the hydrogen bubble formation. Cathodoluminescence measurements reveal that hydrogen ions also passivate deep level emission centers before their release from the sample, leading to the improvement of the UV emission

Rutherford Backscattering Investigation of the Corrosion of Borosilicate Glass

The RBS spectra from Frit 21 borosilicate glasses doped with 5 wt % UO/sub 2/, SrO, or Cs/sub 2/O show that: during the initial stages of leaching (0 to 3 h) there is a substantial (300 to 500%) enhancement in the concentration of U, Sr, Ca, and Ti in the outer surface layer and that this enhancement is accompanied by a large depletion of Na, Si, and Cs; and upon further leaching under static conditions (24 h) the leached surface layer composition is indistinguishable from the unleached surface. Other borosilicate glasses such as PNL 76-68 may eventually show the same behavior if the final equilibrium pH value is greater than 9. The technique of Rutherford backscattering depth profile analysis can be a powerful tool for investigating the initial stages of glass corrosion

Conformal invariance: from Weyl to SO(2,d)

The present work deals with two different but subtilely related kinds of conformal mappings: Weyl rescaling in $d>2$ dimensional spaces and SO(2,d) transformations. We express how the difference between the two can be compensated by diffeomorphic transformations. This is well known in the framework of String Theory but in the particular case of $d=2$ spaces. Indeed, the Polyakov formalism describes world-sheets in terms of two-dimensional conformal field theory. On the other hand, B. Zumino had shown that a classical four-dimensional Weyl-invariant field theory restricted to live in Minkowski space leads to an SO(2,4)-invariant field theory. We extend Zumino's result to relate Weyl and SO(2,d) symmetries in arbitrary conformally flat spaces (CFS). This allows us to assert that a classical $SO(2,d)$-invariant field does not distinguish, at least locally, between two different $d$-dimensional CFSs.Comment: 5 pages, no figures. There are slight modifications to match with the published versio

Propiedades ópticas de películas de dióxido de vanadio como recubrimiento termocrómico en ventanas

The optical properties of vanadium dioxide (VO2) thin film have been studied for the potential application of intelligent windows. The results show that VO2 film deposited on sapphire substrates exhibits good thermochromic effects, its IR transmittance changes 60% before and after phase transition, and has less thickness dependence than UV transmittance. Doping can significantly reduce transition temperature, such as to 30°C for 1.5% Mo doped VO2.Se han investigado las propiedades ópticas del dióxido de vanadio (VO2) aplicado como películas delgadas para posibles aplicaciones en ventanas inteligentes. Cuando el VO2 se deposita sobre sustratos de zafiro da lugar a efectos termocrómicos considerables; así, su transmitancia en el infrarrojo cambia en un 60 % después de la transición de fase del dióxido de vanadio, teniendo una dependencia menor con el espesor que la transmitancia en el ultravioleta. El efecto de aditivos sobre estas películas de dioxido de vanadio da lugar a una disminución de la temperatura de dicha transición responsable del efecto termocrómico, de manera que se produce a 30°C con el 1,5 % de adición de Mo

Imatinib and Nilotinib Reverse Multidrug Resistance in Cancer Cells by Inhibiting the Efflux Activity of the MRP7 (ABCC10)

One of the major mechanisms that could produce resistance to antineoplastic drugs in cancer cells is the ATP binding cassette (ABC) transporters. The ABC transporters can significantly decrease the intracellular concentration of antineoplastic drugs by increasing their efflux, thereby lowering the cytotoxic activity of antineoplastic drugs. One of these transporters, the multiple resistant protein 7 (MRP7, ABCC10), has recently been shown to produce resistance to antineoplastic drugs by increasing the efflux of paclitaxel. In this study, we examined the effects of BCR-Abl tyrosine kinase inhibitors imatinib, nilotinib and dasatinib on the activity and expression of MRP7 in HEK293 cells transfected with MRP7, designated HEK-MRP7-2.We report for the first time that imatinib and nilotinib reversed MRP7-mediated multidrug resistance. Our MTT assay results indicated that MRP7 expression in HEK-MRP7-2 cells was not significantly altered by incubation with 5 microM of imatinib or nilotinib for up to 72 hours. In addition, imatinib and nilotinib (1-5 microM) produced a significant concentration-dependent reversal of MRP7-mediated multidrug resistance by enhancing the sensitivity of HEK-MRP7-2 cells to paclitaxel and vincristine. Imatinib and nilotinib, at 5 microM, significantly increased the accumulation of [(3)H]-paclitaxel in HEK-MRP7-2 cells. The incubation of the HEK-MRP7-2 cells with imatinib or nilotinib (5 microM) also significantly inhibited the efflux of paclitaxel.Imatinib and nilotinib reverse MRP7-mediated paclitaxel resistance, most likely due to their inhibition of the efflux of paclitaxel via MRP7. These findings suggest that imatinib or nilotinib, in combination with other antineoplastic drugs, may be useful in the treatment of certain resistant cancers

ACAP-A/B Are ArfGAP Homologs in Dictyostelium Involved in Sporulation but Not in Chemotaxis

Arfs and Arf GTPase-activating proteins (ArfGAPs) are regulators of membrane trafficking and actin dynamics in mammalian cells. In this study, we identified a primordial Arf, ArfA, and two ArfGAPs (ACAP-A/B) containing BAR, PH, ArfGAP and Ankyrin repeat domains in the eukaryote Dictyostelium discoideum. In vitro, ArfA has similar nucleotide binding properties as mammalian Arfs and, with GTP bound, is a substrate for ACAP-A and B. We also investigated the physiological functions of ACAP-A/B by characterizing cells lacking both ACAP-A and B. Although ACAP-A/B knockout cells showed no defects in cell growth, migration or chemotaxis, they exhibited abnormal actin protrusions and ∼50% reduction in spore yield. We conclude that while ACAP-A/B have a conserved biochemical mechanism and effect on actin organization, their role in migration is not conserved. The absence of an effect on Dictyostelium migration may be due to a specific requirement for ACAPs in mesenchymal migration, which is observed in epithelial cancer cells where most studies of mammalian ArfGAPs were performed

Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP