An in situ transport measurement of interfaces between SrTiO3(1 0 0) surface and an amorphous wide-gap insulator

We have explored the transport properties of the interface between a SrTiO₃(1 0 0) single crystal and a CaHfO₃ wide-gap insulator layer deposited by pulsed laser deposition. The electrical transport measurements were done in situ during the heterojunction fabrication and consistently showed an enhancement of interface conductivity. A conducting interface was always obtained, independent of deposition parameters (laser pulse rate, laser fluence, oxygen pressure, and substrate termination). The conduction was attributed to plume-induced photocurrent in SrTiO₃. The current decay rate after insulator film fabrication was strongly influenced by substrate termination. An exponential relaxation-type photocurrent decay was clearly seen on SrO-termination, whereas a nearly constant conductivity was seen for up to 24 h on TiO₂-terminated surfaces.     

Hyperfine fields at surfaces and interfaces

Magnetism and hyperfine fields at transition metal surfaces are discussed using state-of-the-art local spin density methods. Emphasis is placed on recent results obtained for the Fe(001), Ni(001), Cr(001) and Ag/Fe(001) ferromagnetic surfaces, and for the Knight shift in Pt(001).     

EFFECTS OF CAFFEINE ON DNA REPAIR OF UV-IRRADIATED DICTYOSTELIUM DISCOIDEUM

Abstract— Caffeine enhances the UV-killing of amoeboid cells of NC-4, but UV-irradiated γs-13 is insensitive to caffeine. UV-irradiated NC-4 becomes insensitive to the effect of caffeine during a postirradiation incubation in buffer for about 90 min, but γs-13 remains unchanged in the sensitivity to caffeine throughout the incubation for 180 min. Amoeboid cells of γs-13 can remove pyrimidine dimers as well as NC-4 even in the presence of caffeine. Caffeine inhibits rejoining of strand-breaks of DNA in UV-irradiated NC-4, but the rejoining in γs-13 is insensitive to caffeine.     

Polarizations of spin 32 particles and 7Li58Ni interactions

New representations of polarizations of spin $\text{3}\text{2}$ particles are proposed for elastic scattering. They are useful in investigating spin-dependent interactions. The application to ⁷Li⁵⁸Ni scattering gives weak spin-orbit interactions and rather strong tensor ones of ⁷Li.     

It takes more than an imine: the role of the central atom on the electron-accepting ability of benzotriazole and benzothiadiazole oligomers

We report on the comparison of the electronic and photophysical properties of a series of related donor-acceptor-donor oligomers incorporating the previously known 2H-benzo[d][1,2,3]triazole (BTz) moiety as the acceptor and the recently reported BTzTD acceptor, a hybrid of BTz and 2,1,3-benzothiadiazole (BTD). Although often implied in the polymer literature that BTz has good acceptor character, we show that this moiety is best described as a weak acceptor. We present electrochemical, computational, and photophysical evidence supporting our assertion that BTzTD is a strong electron acceptor while maintaining the alkylation ability of the BTz moiety. Our results show that the identity of the central atom (N or S) in the benzo-fused heterocyclic ring plays an important role in both the electron-accepting and the electron-donating ability of acceptor moieties with sulfur imparting a greater electron-accepting ability and nitrogen affording greater electron-donating character. We report on the X-ray crystal structure of a BTzTD trimer, which exhibits greater local aromatic character in the region of the triazole ring and contains an electron-deficient sulfur that imparts strong electron-accepting ability. Additionally, we examine the transient absorption spectra of BTzTD and BTz oligomers and report that the BTz core promotes efficient intersystem crossing to the triplet state, while the presence of the thiadiazole moiety in BTzTD leads to a negligible triplet yield. Additionally, while BTz does not function as a good acceptor, oligomers containing this moiety do function as excellent sensitizers for the generation of singlet oxygen.     

First measurement of the rho spectral function in high-energy nuclear collisions

We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.     

Kaonic nuclear state search via reaction at rest on He target

Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon S⁰(3115) obtained in KEK PS-E471. In contrast to the previous proton spectrum, no narrow (20 MeV) peak structure was found either in the inclusive ⁴He(stopped K⁻, p) or in the semi-inclusive ⁴He(stopped K⁻, pX^±) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to S⁰(3115), has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure.     

Intact-sheet double-layer ablation induced by femtosecond-laser excitation of graphite

Structural changes of graphite surfaces induced by femtosecond (fs) laser excitation at a fluence regime above 75 mJ/cm² are reported. Direct imagings of excited surfaces by means of scanning tunneling microscopy have revealed that fs-excitations induce nanometer-scaled craters, together with sp³-type interlayer-bonded domains. The nano-craters are characterized by atomically-flat bottom and two atomic-steps in depth, indicating the exfoliation of fragmentary intact-sheets of double-layer of graphite. The theoretical simulation has shown that the required energy for the double-layer ablation is much lowered by the help of interlayer-bond formation, compared to the sequential removal of individual graphene layers. Based on the experimental and theoretical results, the exfoliation of double graphite layers, that is a novel mode of laser-ablation observed first, indicates clearly that the formation of strong interlayer bonds between the two atomic layers is a crucial step in the ablation process.