Secondary ferroic properties of partial mixed ferroelectric ferroelastics

Nineteen types of phase transitions in nonmagnetic crystals that exhibit only partial mixed ferroelectric-ferroelastic properties in the low-temperature phase are analyzed. A crystal-physical method is used to establish that all partial mixed ferroelectric ferroelastics are full ferroelastoelectrics and partial ferrobielastics except for the crystals undergoing the $\overline 4 3m \to 3$ phase transition, which results in the appearance of both full ferroelastoelectric and full ferrobielastic properties. The possible appearance of partial mixed ferroelectric-ferroelastic properties in perovskite-like crystals is discussed.     

Search for the standard model Higgs boson in the diphoton decay channel with 4.9 fb(-1) of pp collision data at √s=7 TeV with ATLAS

A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9 fb(-1) collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of √s=7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110-150 GeV, this significance becomes 1.5 standard deviations. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges of 113-115 GeV and 134.5-136 GeV.     

Search for scalar bottom quark pair production with the ATLAS detector in pp collisions at sqrt[s]=7 TeV

The results of a search for pair production of the scalar partners of bottom quarks in 2.05 fb(-1) of pp collisions at sqrt[s]=7 TeV using the ATLAS experiment are reported. Scalar bottom quarks are searched for in events with large missing transverse momentum and two jets in the final state, where both jets are identified as originating from a bottom quark. In an R-parity conserving minimal supersymmetric scenario, assuming that the scalar bottom quark decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits are obtained in the b(1) - χ(1)(0) mass plane such that for neutralino masses below 60 GeV scalar bottom masses up to 390 GeV are excluded.     

Application of coherent four-wave mixing for two-dimensional mapping of the spatial distribution of excited atoms in a laser-produced plasma

An experimental technique for the two-dimensional mapping of the relative populations of excited states of atoms and ions in a low-temperature plasma of optical breakdown is developed on the basis of coherent four-wave mixing (FWM) with hyper-Raman resonances. The possibility to extract information concerning the spatial distribution of the populations of excited atomic and ionic states from two-dimensional maps of the FWM intensity allowing for phase mismatch and one-photon absorption is considered. Conditions when FWM in a plasma occurs in the phase-matched regime and is not subject to a considerable influence of one-photon absorption are experimentally determined.     

Effect of the loading rate on the mechanical properties of polycrystalline samples of a ZrO2-3 mol. % Y2O3 solid solution

The dependence of the bending strength and fracture toughness of polycrystalline samples of a solid solution of ZrO₂-3 mol. % Y₂O₃ on the traverse rate of a test machine has been studied in the velocity interval of 0.005–50 mm/min. It is shown that the strength and the fracture toughness are virtually constant in the interval of loading rates of 0.05–5 mm/min. An increase of the loading rate to 50 mm/min is accompanied by a significant decrease (by a factor of 2 or 3) in both the strength and the fracture toughness. When the loading rate is decreased to 0.005 mm/min, a slight increase (10–15%) in the fracture toughness and a comparable decrease in the strength is observed. An experiment has also been done to see how the mechanical properties measured at a loading rate of 0.5 mm/min are affected by holding polycrystalline samples of a solid solution of ZrO₂-3 mol. % Y₂O₃ under load for several hours. Holding the samples under a load causes a significant increase (by 30–50%) in both the strength and the fracture toughness. The observed phenomena are explained in terms of the variation of the amount of Y₂O₃, which stabilizes the metastable tetragonal phase of a solid solution of ZrO₂. Fiz. Tverd. Tela (St. Petersburg) 39, 880–884 (May 1997)     

Luminescence of excitons in slightly asymmetric double quantum wells

We report the first studies of exciton luminescence spectra from asymmetric double quantum wells (DQWs) of very similar width. The DQWs were of GaAs/AlGaAs and the differences in widths of the coupled wells were one or two monolayers. The coupled direct and indirect exciton states anticross with a resonance splitting of 1.33 meV. An additional luminescence line appearing at low temperatures is identified as a localized indirect exciton. Fiz. Tverd. Tela (St. Petersburg) 39, 735–739 (April 1997)     

Triterpene and steroid glycosides of theMelilotus genus and their genins I. Melilotosides A,B, and C from the roots ofMelilotus albus

Three new triterpene glycosides of the oleanane series — melilotosides A, B, and C — and the nonglycosylated soyasapogenol B have been isolated from the roots of the plant Melilotus albus Medik. (Leguminosae). The structures of the glycosides have been shown on the basis of chemical transformations and spectral results. Melilotoside A has the structure of soyasapogenol B 3-O-α-L-arabinopyranoside, melilotoside B that of soyasapogenol B 3-O-[O-β-D-galactopyranosyl-(1→2)-α-L-arabinopyranoside], and melilotoside C that of soyasapogenol B 3-O-[O-α-L-rhamnopyranosyl-(1→2)-O-β-D-galactopyranosyl-(1→2)-α-L-arabinopyranoside.     

Triterpene glycosides of Astragalus and their genins. XXIII. Cyclocanthogenin from Astragalus tragacantha

The epigeal part of the plantAstragalus tragantha Habl. (Leguminosea) has yielded (in addition to cyclosieversigenin, cyclocyclosiversioside F, and -sitosterol -D-glucopyranoside) a new methylsteroid of the cycloartane series — cyclocanthogenin — the structure of which has been established on the basis of chemical transformations and spectral characteristics, and also of a chemical correlation with the structure of cycloasgenin C, as 24S-cycloartane-3,6,16,24,25-pentaol.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 817–824, November–December, 1987.