Studies on the valence electronic structure of Fe and Ni in Fe x Ni1−x alloys

K _β-to-K _α X-ray intensity ratios of Fe and Ni in pure metals and in Fe _x Ni_1−x alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 keV γ-rays from a ²⁴¹Am point source, to understand as to why the properties of permalloy Fe_0.2Ni_0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe_0.2Ni_0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties.     

Franck-Condon simulation of the single-vibronic-level emission spectra of HPCl/DPCl and the chemiluminescence spectrum of HPCl, including anharmonicity

Restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] potential energy functions (PEFs) were calculated for the X (2)A" and A (2)A' states of HPCl employing the augmented correlation-consistent polarized-valence-quadruple-zeta (aug-cc-pVQZ) basis set. Further geometry optimization calculations were carried out on both electronic states of HPCl at the RCCSD(T) level with all electron and quasirelativistic effective core potential basis sets of better than the aug-cc-pVQZ quality, and also including some core electrons, in order to obtain more reliable geometrical parameters and relative electronic energy of the two states. Anharmonic vibrational wave functions of the two states of HPCl and DPCl, and Franck-Condon (FC) factors of the A (2)A'-X (2)A" transition were computed employing the RCCSD(T)/aug-cc-pVQZ PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the single-vibronic-level (SVL) emission spectra of HPCl and DPCl reported by Brandon et al. [J. Chem. Phys. 119, 2037 (2003)] and the chemiluminescence spectrum reported by Bramwell et al. [Chem. Phys. Lett. 331, 483 (2000)]. Comparison between simulated and observed SVL emission spectra gives the experimentally derived equilibrium geometry of the A (2)A' state of HPCl of r(e)(PCl) = 2.0035 +/- 0.0015 A, theta(e) = 116.08 +/- 0.60 degrees, and r(e)(HP) = 1.4063+/-0.0015 A via the iterative Franck-Condon analysis procedure. Comparison between simulated and observed chemiluminescence spectra confirms that the vibrational population distribution of the A (2)A' state of HPCl is non-Boltzmann, as proposed by Baraille et al. [Chem. Phys. 289, 263 (2003)].     

Asymmetric synthesis of dimethyl-1,2-bis-(diphenylphosphino)-1,2-ethanedicarboxylate by means of a chiral palladium template promoted hydrophosphination reaction

An optically pure C₂-symmetrical diphosphine ligand containing two ester functional groups at the two chiral carbon stereogenic centres was prepared efficiently from the asymmetric hydrophosphination reaction between diphenylphosphine and dimethyl acetylenedicarboxylate in the presence of an organopalladium(II) complex derived from (S)-N,N-dimethyl-1-(1-naphthyl)ethylamine.     

Preparation of large monodispersed spherical silica particles using seed particle growth

To obtain large-sized, monodispersed spherical particles of silica by sol precipitation, a seed particle growth method was attempted. The formation of secondary particles during seed particle growth causing a multimodal distribution of particle size was suppressed via fine adjustment of the reaction conditions, such as TEOS, ammonia, and water concentrations, as well as operational conditions such as feeding time and agitation speed. Among the reaction conditions, an increase of TEOS concentration promoted secondary particle formation, resulting in bimodal particle distribution. However, secondary particle formation was depressed with increasing ammonia and water concentrations. In addition, long feeding time (low feed flow rate) and rigorous agitation significantly reduced secondary particle formation because they contributed to the slow generation of supersaturation and rapid seed particle growth, respectively.     

Continuous microfluidic reactors for polymer particles

This article provides an overview of our work in the area of the synthesis of polymer particles in continuous microfluidic reactors. The method includes (a) the generation of highly monodisperse monomer droplets in a microfluidic flow-focusing device and (b) in-situ solidification of these droplets by means of photopolymerization. We discuss the effect of monomer properties on the emulsification process, the effect of the polymerization rate on the production of high-quality particles, the role of the material of the microfluidic device in droplet formation, and the synthesis of particles with different shapes and compositions. We also demonstrate the production of highly ordered arrays of polymer particles achieved by photopolymerization of the dynamic lattices of monomer droplets in microfluidic channels. The article is concluded with a summary of future research directions in the production of polymer colloids in microfluidic reactors.     

Calcium is involved in photomovement of cyanobacterium Synechocystis sp. PCC 6803

The unicellular cyanobacterium Synechocystis sp. PCC 6803 (Syn6803) exhibits photomovement through gliding motility. For a better understanding of photomovement in Syn6803, we examined the effects of Ca2+ on photoorientation and motility using a computer-assisted videomicroscope motion analysis system. When calcium ion was chelated from the basic motility medium by adding 0.5 mM ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), the photoorientation was completely inhibited, whereas the gliding motility remained approximately 70% of the control. Photoorientation impaired by EGTA was nearly recovered within 30 min upon addition of 1 mM Ca2+. The recovery of photoorientation by Ca2+ was mimicked by either Mn2+ or Mg2+ but not by Ba2+ or Sr2+. Lanthanum ion at 10 microM completely inhibited both phototactic orientation and gliding motility of Syn6803. Furthermore, pimozide (voltage-gated L-type calcium channel inhibitor), orthovanadate (calcium efflux blocker) and A23187 (calcium ionophore) partially inhibited phototactic orientation and gliding motility. Interestingly, photoorientation was prevented with increasing concentrations of calmodulin antagonist such as trifluoperazine (TFP) and chlorpromazine, but gliding motility was inhibited in proportion to the concentration of TFP. The results we present strongly indicate that Ca2+ plays a significant role in regulating the photomovement of Syn6803.     

Interpolymetallic assembly of d8-d10 sulfide aggregates from [Pt2(PPh3)4(mu-S)2] and group 12 metals

A series of heterometallic Pt-M (M=Zn and Cd) sulfide aggregates with growing nuclearities (Pt2M), (Pt4M), and (Pt4M2), viz., [ZnPt2Cl2(PPh3)4(mu3-S)2] (2), [CdPt2Cl2(PPh3)4(mu3-S)2] (3), [Pt2(PPh3)4(mu3-S)2]2[ZnSO4]2 (4), [Pt2(PPh3)4(mu3-S)2]2[CdSO4]2.H2O (5), [CdPt4(PPh3)8(mu3-S)4][ClO4]2 (7), and [ZnPt4(PPh3)8(mu3-S)4][ClO4]2 (8), have been prepared from Pt2(PPh3)4(mu-S)2 (1) with appropriate zinc and cadmium substrates. The structures have been determined by single-crystal X-ray diffraction. The supporting anions play an active role in the structural assembly process. An unexpected disintegration complex [Pt2(S2CH2)Cl(PPh3)4][PF6] (6) has also been isolated and characterized by single-crystal X-ray diffraction. The mechanism of the formation of 6 is proposed.     

Logit tree models for discrete choice data with application to advice-seeking preferences among Chinese Christians

Logit models are popular tools for analyzing discrete choice and ranking data. The models assume that judges rate each item with a measurable utility, and the ordering of a judge’s utilities determines the outcome. Logit models have been proven to be powerful tools, but they become difficult to interpret if the models contain nonlinear and interaction terms. We extended the logit models by adding a decision tree structure to overcome this difficulty. We introduced a new method of tree splitting variable selection that distinguishes the nonlinear and linear effects, and the variable with the strongest nonlinear effect will be selected in the view that linear effect is best modeled using the logit model. Decision trees built in this fashion were shown to have smaller sizes than those using loglikelihood-based splitting criteria. In addition, the proposed splitting methods could save computational time and avoid bias in choosing the optimal splitting variable. Issues on variable selection in logit models are also investigated, and forward selection criterion was shown to work well with logit tree models. Focused on ranking data, simulations are carried out and the results showed that our proposed splitting methods are unbiased. Finally, to demonstrate the feasibility of the logit tree models, they were applied to analyze two datasets, one with binary outcome and the other with ranking outcome.