A Continuum Reaction Field Theory of Polarizable, Nondipolar, Quadrupolar Solvents: Ab Initio Study of Equilibrium Solvation in Benzene

A continuum theory to describe solvation in nondipolar quadrupolar solvents is developed by accounting for electronic polarizability. A general Hamiltonian for a solute–solvent system in an arbitrary nonequilibrium configuration is obtained in terms of two field variables—densities of the solvent quadrupole and induced dipole moments. Equilibrium solvation is studied by optimizing this Hamiltonian with account of cavity boundaries. As an application, electronic structures and free energies of small molecules in benzene are examined with ab initio methods. Solvation stabilization due to solvent quadrupole moments is found to be substantial; for the solutes considered here, it is comparable to and often in excess of that arising from solvent-induced dipole moments.     

Lewis acid-mediated cross-coupling reaction of 7-azaindoles and aldehydes: Cytotoxic evaluation of C3-linked bis-7-azaindoles

The synthesis of 3,3′-bis-7-indolylmethane derivatives is important for their further development as pharmaceutical compounds and other synthetic purposes. Herein, we describe the zinc- or acid-mediated cross-coupling reaction of 7-azaindoles with aldehydes, such as paraformaldehyde, alkyl aldehydes, aryl aldehydes, enal, and α-ketoaldehyde, providing the corresponding C3-linked bis-7-azaindole derivatives, which are a crucial class towards the development of novel bioactive compounds. High levels of site selectivity and functional group tolerance were observed. Synthesized 3,3′-bis-7-azaindole derivatives were evaluated against human breast adenocarcinoma cells (MCF-7) and human ovarian carcinoma cells (SKOV-3), respectively. Notably, compounds 3s and 4e displayed promising anticancer properties competitive with anticancer doxorubicin as a positive control.     

Chemiluminescent Probe for the In Vitro and In Vivo Imaging of Cancers Over‐Expressing NQO1

Activatable (turn‐on) probes that permit the rapid, sensitive, selective, and accurate identification of cancer‐associated biomarkers can help drive advances in cancer research. Herein, a NAD(P)H:quinone oxidoreductase‐1 (NQO1)‐specific chemiluminescent probe 1 is reported that allows the differentiation between cancer subtypes. Probe 1 incorporates an NQO1‐specific trimethyl‐locked quinone trigger moiety covalently tethered to a phenoxy‐dioxetane moiety through a para‐aminobenzyl alcohol linker. Bio‐reduction of the quinone to the corresponding hydroquinone results in a chemiluminescent signal. As inferred from a combination of in vitro cell culture analyses and in vivo mice studies, the probe is safe, cell permeable, and capable of producing a “turn‐on” luminescence response in an NQO1‐positive A549 lung cancer model. On this basis, probe 1 can be used to identify cancerous cells and tissues characterized by elevated NQO1 levels.     

Measuring particle size distribution using LED-illumination

A particle/droplet image analysis (PDIA) system employing LED-illumination was designed. Freezing the moving droplets using high speed camera instead of stroboscopic illumination, the system had no requirement to synchronize the backlight and the camera. It featured low cost, low power consumption and simple optical configuration in comparison to laser-based systems. Only focused droplets in images were counted. Given the sample size of the system was relatively small, an upper-limit lognormal distribution was used to fit the actual data to represent the spray patterns. The accuracy of the diameter measurement was verified using precisely manufactured balls. Comparisons with two laser-based systems were given and the system’s capacity to distinct spray patterns were demonstrated in nozzle classification experiments.     

Application and New Developments in Polymer‐Dispersed Liquid Crystal Simulation Studies

Polymer‐dispersed liquid crystals (PDLCs) represent an important new class of materials with electro‐optic applications such as flexible displays, large‐area devices projection displays, electrically switchable windows, etc. On considering such applications of these materials, many studies have been performed on the experimental side. Similarly, research on the simulation side for the PDLCs is of the fundamental interest too. The present article contains a short review on the present and past simulation studies of PDLCs. Various molecular simulation approaches applied to PDLC systems by different groups are reviewed here. In addition some new findings of the bulk phases are also extensively described.

     

Surface Structure and Stereocomplex Formation of Enantiomeric Polylactide Blends Using Poly(dimethyl siloxane) as a Probe Polymer

In the stereocomplex between enantiomeric poly(l-lactide) (l-PLA) and poly(d-lactide), crystallites formed as a result of stereocomplexation, equimolar l- and d-lactide unit sequences are packed side by side. The stereocomplex exhibits a melting temperature higher by about 50 °C than that of each homopolymer. In this study, we attempt to obtain further insight into the stereocomplex-induced surface structure of enantiomeric PLA blend films. The design of the blend systems is based on principles of surface segregation of multicomponent polymeric systems with a low surface energy, triblock copolymer (l-PLA-b-PDMS-b-l-PLA) of l-PLA and poly-(dimethyl siloxane). (l-PLA-b-PDMS-b-l-PLA/l-PLA) blend films showed the surface segregation of PDMS, regardless of blend composition while the surface composition of PDMS in the (l-PLA-b-PDMS-b-l-PLA/d-PLA) blend films was strongly depended on blend composition or a degree of complexation. These results are likely due to strong interaction between d- and l-lactide unit sequences, which prevents the surface segregation of PDMS.     

A new approach to an N/G/1 queue

We propose a new approach that gives a one-step computational algorithm to directly obtain the queue length distribution of an N/G/1 queueing system. The new approach is based on the supplementary variable method and the matrix–analytic method. We shall show that this approach enables us to derive the joint distribution of the queue length and the elapsed service time. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct, stereospecific generation of (Z)-disubstituted allylic alcohols

A one-pot method to prepare highly functionalized (Z)-disubstituted allylic alcohols is introduced. Hydroboration of a variety of 1-bromo-1-acetylenes with dicyclohexyl borane, reaction with t-BuLi, and transmetalation to zinc generates a (Z)-disubstituted vinylzinc reagent. In situ reaction of this reagent with aldehydes generates (Z)-disubstituted allylic alcohols in high yields (81-97%). Addition to chiral protected alpha- or beta-oxygenated aldehydes proceeds with diastereoselectivities between 6:1 and 18:1. The anti-Felkin product is obtained in most cases.     

Effect of CdS deposition temperature for thermally grown Cu(In,Ga)Se2 and two-step chalcogenized Cu(In,Ga)(S,Se)2 absorbers on solar cell performances

CdS buffer layer of varying thickness ranging from 23 to 58 nm deposited at different substrate temperature were prepared as n-type junction partner for thermally grown Cu(In,Ga)Se₂ and two-step chalcogenized Cu(In,Ga)(S,Se)₂ photovoltaic absorber films and the effect of deposition temperature and time on the CdS growth behavior and solar cell performance were evaluated. High deposition temperature resulted in a thicker CdS layer and more importantly lower density and shallower depth of open voids, which attributed to the improved open-circuit voltage and fill factor due to reduced interface recombination. The solar cell efficiency of thermally grown absorber saturated at about 30 nm thickness of CdS, while that of chalcogenized absorber gradually increased with CdS thickness up to 60 nm without significant loss of short-circuit current density.     

Dynamic stability analysis of shear-flexible composite beams

Dynamic stability behavior of the shear-flexible composite beams subjected to the nonconservative force is intensively investigated based on the finite element model using the Hermitian beam elements. For this, a formal engineering approach of the mechanics of the laminated composite beam is presented based on kinematic assumptions consistent with the Timoshenko beam theory, and the shear stiffness of the thin-walled composite beam is explicitly derived from the energy equivalence. An extended Hamilton’s principle is employed to evaluate the mass-, elastic stiffness-, geometric stiffness-, damping-, and load correction stiffness matrices. Evaluation procedures for the critical values of divergence and flutter loads of the nonconservative system with and without damping effects are then briefly introduced. In order to verify the validity and the accuracy of this study, the divergence and flutter loads are presented and compared with the results from other references, and the influence of various parameters on the divergence and flutter behavior of the laminated composite beams is newly addressed: (1) variation of the divergence and flutter loads with or without the effects of shear deformation and rotary inertia with respect to the nonconservativeness parameter and the fiber angle change, (2) influence of the internal and external damping on flutter loads whether to consider the shear deformation or not.