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.     

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.     

Effectiveness of tumor electrochemotherapy as a function of electric pulse strength and duration

The aim of this study was to evaluate the effectiveness of electrochemotherapy (ECT) as a function of various combinations of pulse strength and duration. C57Bl mice bearing LLC tumors were injected i.p. with bleomycin (BLM) at doses 5 mg/kg in 0.2 ml of physiological saline. Thirty minutes later, tumors were positioned between plate electrodes and were pulsed with eight-square wave electric pulses with an individual pulse strength of 900, 1100, 1300 or 1500 V/cm and duration of 0.1, 0.25, 0.5 or 1 ms. Effectiveness of ECT was estimated by measuring inhibition of tumor growth and by estimating extent of necrosis in histological slices of the treated tumors. At pulse strength of 900 V/cm and duration of 0.1 ms, electrochemotherapy was ineffective. Noticeable inhibition of tumor growth (threshold of ECT) was obtained when pulse duration at this field strength was increased up to 0.25 ms. Further increase of pulse strength and/or duration resulted in progressive enhancement of antitumor effects. Using tumor doubling time (DT) as a criteria, we showed that the same efficacy of ECT could be achieved using various pairs of values for pulse strength and duration. Largest antitumor efficacy of ECT was obtained at pulse strength of 1500 V/cm and duration of 1 ms. These pulse conditions applied alone neither significantly suppressed tumor growth nor induced noticeable side effects of the surrounding tissues. The results of this study thus suggest that the effectiveness of electrochemotherapy can be enhanced (in comparison to widely accepted conditions of electrochemotherapy--8 pulses of 1300 V/cm, 0.1 ms) if 1500-V/cm, 1-ms electric pulses are used. Our study also implicates that other pulse conditions could be found for this enhanced ECT.     

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.     

Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

Nonlinear oscillations in marine hydroids

Irregular oscillations in a colony of marine hydroids Podocoryne carnea were investigated. Quantitative characteristics were obtained as a result of long term (10-12 h) monitoring of oscillations at arbitrary sites. The sliding window spectra as well as the pulse-to-pulse dynamics argue the transient chaotic behavior of hydroid colony. The significant change of amplitudes and frequencies in intact colony oscillations after feeding and long sustained oscillations of stolons separated from colony suggest that the irregular activity could be determined by the network of pacemakers residing in stolon wall cells. These are influenced mechanically by the amount of digesting food and/or by chemical action of nutrients inside the stolon lumen. The possible correlation of these oscillations which can evoke Ca(2+) waves in stolon wall cells is discussed.