Raman studies of nonlinear phenomena in fullerene crystallites

The resonant Raman scattering of C₆₀ crystallites is monitored as a function of excitation intensity at 514.5 nm. At low intensities, a strong line at 1468 cm^–1 is observed. No feature at 1459 cm^–1 is observable. With increasing intensities, the 1468 cm^–1 line shifts continuously and reversibly to lower frequencies. The mode softening is nonlinearly dependent on the input intensity and is accompanied by a nonlinear increase in the Raman intensity. The spectral changes are discussed in terms of a nonlinear reduction in force constant and increase in bond polarisability as a result of an increased intermolecular delocalisation of the -electron cloud. The nonlinear changes are associated with the nonlinear luminescence and photoconductive response observed in fullerenes and are contrasted to the irreversible phototransformation recently discussed.     

Two new eudesmane derivatives from Verbesina virginica

<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods.     

Gamma and enclosure dosimetry for TL/ESR dating with the new Al2O3: C TL dosemeter

Al₂O₃: C manufactured by LAIKS-CORUND, Ekaterinenburg, Russia, offers several advantages for the measurement of environmental radiation: stability, low self-dose, high sensitivity and energy deposition features under gamma and beta irradiation very similar to quartz and quartz-like TL minerals. In the present work those properties were tested for in situ gamma dosimetry, by comparison with other dosimetric techniques. It was confirmed that this phosphor is very well adapted to this purpose. On the other hand, the new alumina can be made insensitive to external alpha radiation by means of thermal treatments. This α-insensitized alumina is very interesting for enclosure dosimetry in the perspective of quartz inclusion dating. In this technique, the quartz grains to be dated are faithfully simulated by alumina: the phosphor allows us to measure directly the dose that would be experienced by quartz grains (HF etched, as usual). However, because the attenuation of beta radiation by coarse grains must be taken into account in inclusion dating, the role of this factor was theoretically and experimentally—with Al₂O₃—explored. The preliminary experiments indicated that enclosure dosimetry with this new alumina was a promising technique.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Present status and prospects for Spin-Echo Small-Angle Neutron Scattering (SESANS) at PIK neutron source

We discuss the present status and the prospects of Spin-Echo Small-Angle Neutron Scattering (SESANS) against the background of the available expertise and the neutron source PIK at PNPI (Gatchina). Two options for SESANS instruments are reviewed: (1) monochromatic with π-flipping permalloy foils and (2) with adiabatic radio frequency spin flippers in a white beam, combined with time-of-flight data collection. A software tool for quantitative prediction of the technical properties of option (2) is developed. For both options, we show that a SESANS instrument which can compete with instruments elsewhere, is realistic. For option (2), we suggest a perspective of spin-echo-length range such that neutron interference experiments become feasible.     

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g⁻¹ for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g⁻¹ fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h⁻¹ recorded initial deposits of 5.20 and 10.05 μg g⁻¹ and 0.33 and 0.48 μg g⁻¹ for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.