Numerical study of transient natural convection in a cavity with multiple adiabatic blocks

This study deals with the solution of a problem of unsteady natural convection in a thermally driven square enclosure with four adiabatic square blocks placed inside. The governing equations are solved numerically using higher order compact schemes. Results are in good agreement with the established results for some special cases. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transport properties of nanocrystalline silicon and silicon–germanium

We report on the minority carrier lifetime, diffusion length and mobility in nanocrystalline Si and (Si,Ge) p⁺nn⁺ devices. The devices were fabricated on stainless steel using VHF plasma deposition techniques. Minority carrier lifetime was measured using junction reverse recovery techniques. The minority carrier lifetime was found to be well correlated with the inverse of defect density and increased with increasing measurement temperature. Simultaneous measurement of diffusion length and lifetime yielded values for hole mobility.     

Am原子及其离子Amq+(q=1~6)的K,L,M-X射线跃迁能和跃迁几率的理论研究(英文)

使用基于Dirac-Hartree-Fock方法的Grasp2K程序包,计算了Am原子及离子的K,L,M-X射线的跃迁能和跃迁速率。在计算中,包括了Breit相互作用、真空极化和自能等重要效应。目前研究结果与已有的其他实验和理论结果相对误差约为0.04%。此外,我们还首次计算了从Am1+到Am6+离子的K,L,M-X射线的跃迁能和跃迁速率。相对于中性原子,来自低离化态的跃迁能相对于中性的相应跃迁线的能量仅有轻微的偏移,这反映出外层电子几乎不影响内壳层的跃迁性质。Transition energies and rates of K, L, and M X-ray lines from electric-dipole transition of americium have been calculated using GRASP2K code based on the Dirac-Hartee-Fock method. The effects of the Breit interaction, vacuum polarization and self energy were taken into account. It is found that the present results agree within 0.04% with other experimental and theoretical values. Furthermore, we also calculated transition energies and rates of the K-, L-, and M-shell hole states of americium ions with charge states Am1+-Am6+ for the first time. It is found that the transition energies and rates change slightly relative to the corresponding results of americium atoms, which indicates that the outermost electrons can hardly affect inner-shell transition properties.     

X‐ray crystal of diprotonated tetra‐(2‐pyridyl)pyrazine (H2TPPZ), aqua Fe3+‐phen crystal and new lanthanide complexes of TPPZ and their biochemical studies

New complexes derived from M³⁺ salts with polyazine as monometallic such as [Fe (TPPZ)Cl₃].½H₂O (1) , [Cr (TPPZ)₂Cl₂]Cl.2EtOH (2) , [La (TPPZ)(NO₃)₂(H₂O)₂]NO₃.H₂O (3) in addition to [Fe (Phen)₃]3Cl.7H₂O (4) were isolated. Three bimetallic, [H₂TPPZ][(AuCl₄)₂]. H₂O (5) , [Ce₂(TPPZ)EtOH (NO₃)₃]3NO₃ (6) and [Nd₂TPPZCl₂(H₂O)₄]4Cl.CHCl₃. 4H₂O (7) and mixed ligand complexes, [Fe (TPPZ)(Phen)₂]Cl₃ (8) , [Fe (TPPZ) (Phen)₂][TPPZCl₃] (9) , [La₂(TPPZ)(Phen)₂(EtOH)₂]6Cl.CHCl₃.EtOH.H₂O (10) and [Nd₂(TPPZ)(Phen)Cl₄]2Cl.3H₂O (11) were synthesized and characterized. Crystal data of (4) is tetragonal, I4₁/a, a = b 35.951 (3) Å, c = 11.9055 (8) Å, α = 80.201 (2)° β = 78.846 (2)°, γ = 89.687 (2)° V = 741.06 (5)ų, Z = 1 while triclinic, P1, a = 7.3913 (3) Å, b = 9.7344 (4) Å, c = 10.6577 (4) Å, α = β = γ = 90°, V = 741.06 (5)ų and Z = 170 for (5) . Analyses, spectral and cyclic voltammetry studies indicate the bonding and the redox properties. Anticancer studies promised to be effective in lanthanides and some complexes were screened against antibacterial or antifungal.     

Phototransformations of some 3‐cyclohexenyloxychromenones: Synthesis of Spirocyclic compounds

The phototransformation of the 3‐cyclohexenyloxychromenones by irradiation with a pyrex‐filtered light from a 125 W Hg vapor lamp under an inert atmosphere into the spirocyclic fused xanthenones was described. The efficacy of the protocol depended upon the position (o‐, m‐, or p‐) of the cyclohexenyloxy group appended to the 2‐aryl moiety on the chromenone nucleus, which was further invoked by steric, electronic, and proximity considerations. The structure(s) of the substrates and photoproducts were established using the spectroscopic (IR and NMR) data.     

Stereoselective total syntheses of (−)-pseudohygrophorone A12 and (−)-pseudohygrophorone B12

Abstract

Stereoselective total syntheses of anti-fungal cyclohexenones (?)-pseudohygrophorone A¹² and (?)-pseudohygrophorone B¹² were achieved. Salient features of these syntheses are the diastereoselective addition of dodecylmagnesium bromide to highly oxygenated ketone derived from (?)-quinic acid and α-oxidation of the enone.     

Carbon dioxide production in the oxidation of organic acids by Cerium(IV) under aerobic and anaerobic conditions

The stoichiometry of CO₂ production during the ceric oxidation of various organic acids is measured under conditions with organic acid excess. Measurements utilize a photometric methodology. For anaerobic conditions stoichiometries [CO₂]_produced:[Ce(IV)]_reduced of about 0 (malonic acid), 0.5 (e.g., glyoxylic acid), and 1.0 (oxalic acid) are found. Oxalic acid showed an oxygen-induced decrease of CO₂ production, while other compounds such as malonic acid increased the amount of produced CO₂ or showed no changes (e.g., tartronic acid). In the case of mesoxalic acid the stoichiometry is increased from about 0.5 to 2.0 due to the presence of molecular oxygen. The results are discussed on the basis of simple reaction mechanisms demonstrating that useful information on reaction pathways and intermediates can be extracted from these simple measurements. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 899–902, 1998     

General proportional mean residual life model

By considering a covariate random variable in the ordinary proportional mean residual life (PMRL) model, we introduce and study a general model, taking more situations into account with respect to the ordinary PMRL model. We investigate how stochastic structures of the proposed model are affected by the stochastic properties of the baseline and the mixing variables in the model. Several characterizations and preservation properties of the new model under different stochastic orders and aging classes are provided. In addition, to illustrate different properties of the model, some examples are presented.     

Synthesis and Solid-State Structure of Cyclobutyltellurium(IV)-Containing Dimeric Tungstoarsenates(III)

The cage-like cyclobutyltellurium(IV)-containing tungstoarsenate(III) dimers [(C₄H₈Te-OH)₂(C₄H₈Te)₆{As₂W₁₇O₆₁(H₂O)}₂]^14? (1) and [{(C₄H₈Te)₂W₂O₅(H₂O)₂As₂W₁₉O₆₇(H₂O)}₂]^16? (2) were synthesized in moderately acidic aqueous medium by reaction of C₄H₈TeI₂ with the lacunary tungstoarsenates(III) [B-α-AsW₉O₃₃]^9? and [As₂W₁₉O₆₇(H₂O)]^14?, respectively. Polyanion 1 was isolated as a mixed cesium-guanidinium salt Cs_8.5(C(NH₂)₃)_5.5[(C₄H₈TeOH)₂(C₄H₈Te)₆{As₂W₁₇O₆₁(H₂O)}₂]·60H₂O (1a), whereas 2 crystallized as a mixed cesium-potassium salt Cs₉K₇[{(C₄H₈Te)₂W₂O₅(H₂O)₂As₂W₁₉O₆₇(H₂O)}₂]·90H₂O (2a). Single crystal X-ray analysis demonstrated that 1a and 2a crystallized in the triclinic space group \( P \bar{1} \), with a = 12.7738(8) Å, b = 18.7490(14) Å, c = 21.9831(14) Å, α = 111.155(4)^o, β = 93.312(3)^o, γ = 99.530(4) and Z = 1 for 1a and a = 19.309(6) Å, b = 24.674(8) Å, c = 26.071(8) Å, α = 63.218(17)°, β = 89.26(16)^°, γ = 79.948(17)^° and Z = 2 for 2a. The polyanion salts 1a and 2a were characterized by solid state NMR (¹H, ¹³C, ¹²⁵Te), FT-IR, TGA-DSC, and elemental analysis.     

Bis(2-Hydroxy-3-Isopropyl-6-Methyl-Benzaldehyde)Ethylenediamine: A Novel Cation Sensor

Novel substituted phenol-based new symmetrical bis(2-hydroxy-3-isopropyl-6-methyl-benzaldehyde)ethylenediamine (1) has been designed and synthesized. The compound 1 fluorometrically recognized Cu²⁺ ion in CH₃OH/H₂O (90:10, v/v) by exhibiting an increase in emission upon complexation. In addition, Cu²⁺ gave rise to a change in colour of the solution of compound 1, which was clearly visible to the naked eye under UV irradiation. The association constant (K) of compound 1 with Cu²⁺ ion was computed with the Benesi-Hildebrand plot and Scatchard plot at 43,000 M^?1 and 43,011 M^?1 respectively.