Similarities in electronic properties of organic charge-transfer solids and layered cobaltates

The apparently counterintuitive carrier concentration-dependent electronic properties of layered cobaltates have attracted wide interest. Here we point out that very similar carrier-concentration dependence has previously been noted in strongly correlated quasi-one dimensional (quasi-1D) organic charge-transfer solids. The normal states of both families can be understood, over the entire range of carrier concentration of interest, within the extended Hubbard Hamiltonian with significant intersite Coulomb interaction. As with the charge-transfer solids, superconductivity in the cobaltates appears to be limited to bandfilling of one-quarter. We point out further that there exist other families of correlated superconductors, such as spinels, where too strong correlations, geometric lattice frustration and bandfilling of one-quarter seem to be the essential features of the unconventional superconductors.     

Decision tree SAR models for developmental toxicity based on an FDA/TERIS database

Humans are exposed to thousands of environmental chemicals for which no developmental toxicity information is available. Structure-activity relationships (SARs) are models that could be used to efficiently predict the biological activity of potential developmental toxicants. However, at this time, no adequate SAR models of developmental toxicity are available for risk assessment. In the present study, a new developmental database was compiled by combining toxicity information from the Teratogen Information System (TERIS) and the Food and Drug Administration (FDA) guidelines. We implemented a decision tree modeling procedure, using Classification and Regression Tree software and a model ensemble approach termed bagging. We then assessed the empirical distributions of the prediction accuracy measures of the single and ensemble-based models, achieved by repeating our modeling experiment many times by repeated random partitioning of the working database. The decision tree developmental SAR models exhibited modest prediction accuracy. Bagging tended to enhance the accuracy of prediction. Also, the model ensemble approach reduced the variability of prediction measures compared to the single model approach. Further research with data derived from animal species- and endpoint-specific components of an extended and refined FDA/TERIS database has the potential to derive SAR models that would be useful in the developmental risk assessment of the thousands of untested chemicals.     

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd3Bx (x=0.25, 0.50 and 0.75)

We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd₃B_x (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd₃ leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd₃. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd₃B_x with that of stoichiometric compositions GdPd₃B_xC_1−x. The comparative study of GdPd₃B_x and GdPd₃B_xC_1−x confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.     

Effect of AEE788 and/or Celecoxib on colon cancer cell morphology using advanced microscopic techniques

Analysis of changes in cancer cell morphology and cytoskeletal element induced by external stimuli is focus of current cancer chemotherapeutic studies. Cancer cell cytoskeleton is complex network of interwoven protein fibers composed of microtubules, microfilaments and intermediate filaments. These interwoven protein fibers are responsible for maintaining cell morphology, movement, adhesion and transmembrane signal transmission. In this study, morphological and cytoskeletal changes induced by AEE788 and/or Celecoxib on colon cancer cell HCT 15 were analyzed using advanced microscopic techniques. Cell proliferation assay was used for determining IC₅₀ of AEE788 and/or Celecoxib on HCT 15. Confocal microscopic analysis of AEE788 and/or Celecoxib treated HCT 15 was performed using Rhodamine-Phalloidin (actin stain) and Hoechst 33342 (nuclear stain). Atomic force (AFM) and scanning electron microscopic (SEM) studies were also performed to analyze cell morphology and cell wall extension (filopodia and lamellipodia). In addition, quantitative analysis of morphological parameters was studied using cellular image processing technique. This is the first report that combination of AEE788 and Celecoxib additively increase growth inhibition and cell death on human colon cancer cell HCT 15 as estimated by cell proliferation assay. Morphological analysis of AEE788 or Celecoxib treated HCT 15 cell for 24 h have not revealed significant change in morphology under phase contrast microscopy. But, slight morphological changes were observed in combination (AEE788 + Celecoxib) treated HCT 15 for 24 h. In contrast, high resolution confocal laser fluorescence and atomic force microscopic studies have revealed cell shrinkage, disorganized actin filament and, loss of filopodia and lamellipodia. These changes were more prominent in combination of AEE788 and Celecoxib treated HCT 15 than either drug alone. These results may suggest antiproliferative and antimetastatic activity of AEE788 and/or Celecoxib. Quantitative analysis of morphological parameters using cellular image processing technique have shown decrease in mean area, perimeter, compactness and eccentricity of combination drug treated cells than either drug alone. These results further support the confocal and AFM study. Scanning electron microscopic study of AEE788 and/or Celecoxib treated HCT 15 has also shown morphological changes and loss of filopodia and lamellipodia. In conclusion, this investigation of morphological and cytoskeletal changes using advanced microscopic techniques present a significant foundation for evaluating anticancer activity of a drug and form a new strategy for evaluating effect of AEE788 and/or Celecoxib on colon cancer.     

Fluorometric and isothermal titration calorimetric studies on binding interaction of a telechelic polymer with sodium alkyl sulfates of varying chain length

Steady-state fluorescence measurements and isothermal titration calorimetric experiments have been performed to study the interaction between a telechelic polymer, pyrene-end-capped poly(ethylene oxide) (PYPY), and sodium alkyl sulfate surfactants having decyl, dodecyl, and tetradecyl hydrocarbon tails. Fluorometric results suggest polymer-surfactant interaction in the very low range of polymer concentrations. The relative variation in the excimer to monomer pyrene emission intensities with varying surfactant concentration reveals that initial addition of surfactant favors intramolecular preassociation until the surfactant molecules start binding with the ethylene oxide (EO) chain. With the growing number of surfactant aggregates along the EO chain, the association becomes hindered due to the polyelectrolyte effect. The results from microcalorimetric titrations in the low concentration range of PYPY solution (approximately 10(-6) M) with alkyl sulfates suggest two kinds of surfactant-polymer interactions, one with the polymer hydrophobic end groups and the other with the ethylene oxide backbone. The overall polymer-surfactant interaction starts at a much lower surfactant concentration for the hydrophobically modified polymers compared to that in the case of unsubstituted poly(ethylene oxide) homopolymer. From the experiments critical aggregation concentration values and the second critical concentration where free micelles start forming have been determined. An endeavor has been made to unveil the mechanism underlying the corresponding associations of the surfactants with the polymer.     

Gauge-invariant inflaton in the minimal supersymmetric standard model

We argue that all the necessary ingredients for successful inflation are present in the flat directions of the Minimally Supersymmetric Standard Model. We show that out of many gauge-invariant combinations of squarks, sleptons, and Higgs bosons, there are two directions, LLe and udd, which are promising candidates for the inflaton. The model predicts more than 10(3) e-foldings, with an inflationary scale of H(inf) approximately O(1-10) GeV, provides a tilted spectrum with an amplitude of delta(H) approximately 10(-5) and a negligible tensor perturbation. The temperature of the thermalized plasma could be as low as T(rh) approximately O(1-10) TeV. Parts of the inflaton potential can be determined independently of cosmology by future particle physics experiments.     

Triphenylphosphine chalcogenides as efficient ligands for room temperature palladium(II)-catalyzed Suzuki-Miyaura reaction

A simple catalytic system based on PdCl₂ and triphenylphosphine chalcogenides (PPh₃X; X = O, S, Se) is found to be highly effective (up to 97% isolated yield) in the room temperature Suzuki-Miyaura reactions. Under the same experimental conditions, triphenylphosphine chalcogenides as ligands show superior activities compared to free triphenylphosphine.     

Non‐covalent dimers of the lysine containing protonated peptide ions in gaseous state: electrospray ionization mass spectrometric study

Study of the non‐covalent molecular complexes in gas phase by electrospray ionization mass spectrometry (ESI‐MS) represents a promising strategy to probe the intrinsic nature of these complexes. ESI‐MS investigation of a series of synthetic octapeptides containing six alanine and two lysine residues differing only by their positions showed the formation of non‐covalent dimers, which were preserved in the gas phase. Unlike the monomers, the dimers were found to show only singly protonated state. The decrease in the solvent polarity from water to alcohol showed enhanced propensity of formation of the dimer indicating that the electrostatic interaction plays a crucial role to stabilize the dimer. Selective functionalization studies showed that ε‐NH₂ of lysine and C‐terminal amide (? CONH₂) facilitate the dimerization through intermolecular hydrogen bonding network. Copyright © 2010 John Wiley & Sons, Ltd.     

Oxidation of propane to acrylic acid and acetic acid over alkaline earth-doped Mo-V-Sb-Ox catalysts

Alkaline earth metal (Mg, Ca, Sr and Ba)-doped Mo-V-Sb-Ox catalysts, prepared by a dry-up method, have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions. The catalysts have been characterized by N2 adsorption-desorption, temperature-programmed desorption (TPD) of NH3, SEM and XRD. Influence of water vapor on the catalytic performance, particularly on the selectivities to acetic acid and acrylic acid, has also been studied. The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-Ox catalysts. The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals, which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid. The catalytic activity and product selectivities were found to be influenced by the reaction temperature, C3H8/O2 ratio and space velocity. A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.