Molecule‐specific determination of atomic polarizabilities with the polarizable atomic multipole model

Recently, many polarizable force fields have been devised to describe induction effects between molecules. In popular polarizable models based on induced dipole moments, atomic polarizabilities are the essential parameters and should be derived carefully. Here, we present a parameterization scheme for atomic polarizabilities using a minimization target function containing both molecular and atomic information. The main idea is to adopt reference data only from quantum chemical calculations, to perform atomic polarizability parameterizations even when relevant experimental data are scarce as in the case of electronically excited molecules. Specifically, our scheme assigns the atomic polarizabilities of any given molecule in such a way that its molecular polarizability tensor is well reproduced. We show that our scheme successfully works for various molecules in mimicking dipole responses not only in ground states but also in valence excited states. The electrostatic potential around a molecule with an externally perturbing nearby charge also exhibits a near‐quantitative agreement with the reference data from quantum chemical calculations. The limitation of the model with isotropic atoms is also discussed to examine the scope of its applicability. © 2012 Wiley Periodicals, Inc.     

Thermoanalytical investigations on the solid-state synthesis of Sr-doped praseodymium alkaline-earth cobalt oxides

In this study, the formation and characteristics of Sr-doped praseodymium alkaline-earth cobalt oxide were studied as a function of the strontium content (x). PrBa_1?x Sr _x Co₂O_5+d ceramics with x?=?0.0, 1/16, 1/8, 1/4, and 1/2.5 were prepared by solid-state reaction method from Pr₆O₁₁, BaCO₃, SrCO₃, and Co₃O₄. The solid-state reaction mechanisms were analyzed by differential thermal analysis (DTA) and thermogravimetry (TG) techniques to characterize properly the distinct thermal events occurring during synthesis of layered perovskite-type PrBa_1?x Sr _x Co₂O_5+d oxides. The X-ray diffraction (XRD) results were used to assist the interpretation of DTA?CTG analyses. The TG, DTA, and XRD results for the mixtures showed that the solid-state reaction between precursors was completed in a temperature range between 800 and 1000?°C. The strong influence of strontium contents (x) on the solid-state reaction temperatures and PrBa_1?x Sr _x Co₂O_5+d structure was found.     

Characteristic profiles of the inclusion complex of omeprazole/peracylated-β-cyclodextrin formed in supercritical carbon dioxide

Inclusion properties of the drug omeprazole (OMP) with peracetylated-beta-cyclodextrin (PAc-β-CD) prepared by green method, following supercritical carbon-dioxide (scCO₂), were characterized through thermal (TGA and DSC), crystalline (XRD), NMR spectroscopic and dissolution studies. Comparison amongst PAc-β-CD, OMP, physical binary mixture (equimolar ratio of OMP: PAc-β-CD) and the solid inclusion complex (OMP/PAc-β-CD) revealed scCO₂ as a successful technique for inclusion complex formation as well, identified characteristics performances of PAc-β-CD/OMP interactions. For instance, absence of characteristic DSC or XRD peaks of either chemical in the complex was quite noticeable with the shift of proton peaks in ¹H NMR spectra. The formed inclusion complex also showed an important dissolution performance of OMP for controlled release applications partly due to the hydrophobic nature of PAc-β-CD.     

A highly selective chemodosimeter for the rapid detection of Hg2+ ions in aqueous media

A novel S,S′-diallyl carbohydrazonodithioate derivative 3 of rhodamine B hydrazone was developed as a chemodosimeter for selective detection of mercury ions based on Hg²⁺ promoted cyclization. The allyl groups of 3 play a key role in the binding and selection of Hg²⁺ ions. The probe responds selectively to Hg²⁺ over various other competitive cations with marked chromo- and fluorogenic changes. The formation of stable oxadiazole derivative 8 was a strong driving force for this high selectivity. Practically, this probe is more promising because of the remarkable high selectivity, faster response, low detection limit, and aqueous solubility of 3.     

Synthesis of triphenylamine-based thiophene-(N-aryl)pyrrole-thiophene dyes for dye-sensitized solar cell applications

Two new triphenylamine-based metal-free organic dyes (TPTDYE-1 and TPTDYE-2) containing 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole as a new π-conjugated chromophore were synthesized for dye-sensitized solar cell (DSSC) applications. TPTDYE-1 containing three donor groups around the acceptor group was found to show relatively narrow absorption band from 300 nm to 470 nm while TPTDYE-2 having extended π–π delocalization between the donor and acceptor group showed broad absorption band from 300 nm to 550 nm. The electrochemical studies indicate that the HOMO–LUMO energy gap of TPTDYE-1 is considerably wider than that of TPTDYE-2. The dye-sensitized solar cell performance of each dye was investigated, and the TPTDYE-2-sensitized cell was found to show a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 75%, a short-circuit photocurrent density (J_sc) of 13.50 mA/cm², an open-circuit voltage (V_oc) of 0.72 V, and a fill factor (FF) of 0.69, corresponding to an overall conversion efficiency of 6.71% under simulated AM 1.5 irradiation (100 mW/cm²). Under the same condition the TPTDYE-1-sensitized cell showed the same IPCE value of 75% with a promising conversion efficiency of 6.00%, a J_sc of 11.11 mA/cm², a V_oc of 0.76 V, and a FF of 0.71.     

Comparative resin kinetics using in situ fluorescence measurements

The aminolysis of a novel activated ester resin was utilized for kinetic study via continuous in situ fluorescence measurements. A variety of resin compositions (polystyrene, JandaJel, ArgoPore, TentaGel, NovaGel, and PEGA) and solvents (dimethylformamide, acetonitrile, tetrahydrofuran, 1,2-dichlorethane, and toluene) were tested to compare their effects on the reaction rate. A linear relationship between the reaction rate and (solvent polarity x swelling of resin) was elucidated for the aminolysis reaction.     

CDK5-dependent inhibitory phosphorylation of Drp1 during neuronal maturation

Mitochondrial functions are essential for the survival and function of neurons. Recently, it has been demonstrated that mitochondrial functions are highly associated with mitochondrial morphology, which is dynamically changed by the balance between fusion and fission. Mitochondrial morphology is primarily controlled by the activation of dynamin-related proteins including dynamin-related protein 1 (Drp1), which promotes mitochondrial fission. Drp1 activity is regulated by several post-translational modifications, thereby modifying mitochondrial morphology. Here, we found that phosphorylation of Drp1 at serine 616 (S616) is mediated by cyclin-dependent kinase 5 (CDK5) in post-mitotic rat neurons. Perturbation of CDK5 activity modified the level of Drp1^S616 phosphorylation and mitochondrial morphology in neurons. In addition, phosphorylated Drp1^S616 preferentially localized as a cytosolic monomer compared with total Drp1. Furthermore, roscovitine, a chemical inhibitor of CDKs, increased oligomerization and mitochondrial translocation of Drp1, suggesting that CDK5-dependent phosphorylation of Drp1 serves to reduce Drp1''s fission-promoting activity. Taken together, we propose that CDK5 has a significant role in the regulation of mitochondrial morphology via inhibitory phosphorylation of Drp1^S616 in post-mitotic neurons.     

Enhanced interfacial adhesion,mechanical, and thermal properties of natural flour-filled biodegradable polymer bio-composites

This study examined the interfacial adhesion, mechanical, and thermal properties of compatibilizing agent-treated and non-treated biocomposites as a function of the type of compatibilizing agent. The tensile strength, interfacial adhesion, and heat deflection temperature (HDT) of maleic anhydride-grafted poly(butylene succinate) (PBS-MA) and maleic anhydride-grafted poly(lactic acid) (PLA-MA)-treated biocomposites are greater than those of untreated maleic anhydride-grafted poly(styrene-b-ethylene-co-butylene-b-styrene) triblock copolymer (SEBS-MA) and maleic anhydride-grafted polypropylene (MAPP)-treated biocomposites. The storage modulus (E′) values and the tan δ_max temperatures (T _g) of PBS-MA and PLA-MA-treated biocomposites were slightly higher than that of the untreated biocomposites.