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.     

Crystallographic report: Aquadicylcohexyltin(IV) bis(2‐picolinate) ethanol solvate

The tin atom in the title compound is in a distorted pentagonal bipyramidal geometry defined by two sets of nitrogen and oxygen donors derived from the carboxylate ligands, two carbon atoms from the cyclohexyl substituents and an oxygen atom from the coordinated water molecule; C? Sn? C 170.85(15)°. Extensive hydrogen bonding occurs in the lattice. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and Structure of Bis(para‐methoxyphenyl)selenoxide and its Monohydrate. Theoretical Considerations of the Hydration of Diorganoselenium Oxides

The title compound was prepared by base hydrolysis of (p‐MeOC₆H₄)₂SeCl₂ in water and isolated as the crystalline monohydrate, (p‐MeOC₆H₄)₂SeO·H₂O, in which the water molecule is associated via hydrogen‐bonding. Water‐free (p‐MeOC₆H₄)₂SeO was obtained crystalline after drying and recrystallisation from toluene. Both crystal phases were investigated by single crystal X‐ray diffraction. Preliminary DFT calculations at the B3LYP/LANL2DZdp level of theory suggest that the hydrogen bonded complexes R₂SeO·H₂O (R = H, Me, Ph) are by 2.79, 3.36 and 11.10 kcal mol^?1 more stable than the corresponding elusive diorganoselenium dihydroxides R₂Se(OH)₂. The hydrogen bond energies of R₂SeO·H₂O (R = H, Me, Ph) are 5.98, 7.18 and 5.89 kcal mol^?1.     

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.     

Crystallographic report: 1,4‐Bis[(phenyldichlorostannyl)ethyl]benzene,p‐(Cl2PhSnCH2CH2)2C6H4

An ‘S’ conformation, stabilized by intramolecular C? H···π interactions, is found in centrosymmetric p‐(Cl₂PhSnCH₂CH₂)₂C₆H₄. The dinuclear species features distorted tetrahedral tin centres, with the greatest distortion manifested in the C? Sn? C angle of 134.32(16) °. Copyright © 2002 John Wiley & Sons, Ltd.     

Transients from a mixture of [(R(O)Sn)2C(CH3)2]2 and (RCl2Sn)2C(CH3)2 [R = (SiMe3)2CH]: an identification in situ by 1D 119Sn and 2D 1H?119Sn HMQC NMR spectroscopy and electrospray mass spectrometry

The reaction of the 2,2‐bis(organodichlorostannyl)propane [(Me₃Si)₂CH(Cl₂)Sn]₂CMe₂ (A) with the corresponding organotin oxide {[(Me₃Si)₂CH(O)Sn]₂CMe₂}₂ (B) does not provide the corresponding normally expected tetraorganodistannoxane {[(Me₃Si)₂CH(Cl)SnCMe₂Sn(Cl)CH(SiMe₃)₂]O}_n but a complex reaction mixture. One major product, namely the 2,4,6,8‐tetraorgano‐2,6‐dichloro‐1,5,9‐trioxa‐2,4,6,8‐tetrastannabicyclo[3.3.1]nonane derivative [(Me₃Si)₂CHSnCMe₂Sn(Cl)CH(SiMe₃)₂]₂O₃ (C) was identified in situ by 2D ¹H? ¹¹⁹Sn and ¹H? ¹³C heteronuclear multiple quantum coherence and heteronuclear multiple bond correlation NMR spectroscopy as well as electrospray mass spectrometry. Compound C is proposed to be in equilibrium with an ionic species C′, the cation of which has an adamantane‐type structure. Copyright © 2003 John Wiley & Sons, Ltd.