Laser-induced shape transformation of gold nanoparticles below the melting point: the effect of surface melting

Relatively large gold nanoparticles (mean diameter of major axis 38.2 nm, mean aspect ratio 1.29) in aqueous solution were found to undergo shape transformations from ellipsoids to spheres at ca. 940 degrees C, which is much lower than their melting point, ca. 1060 degrees C. The shape transformation of gold nanoparticles induced by a single pulse of a Nd:YAG laser (lambda = 355 nm, pulse width = 30 ps) was directly observed by a transmission electron microscope (TEM). Analysis of the experimental data showed that the threshold energy for photothermally induced shape transformation was on the order of 40 fJ for a particle, which is smaller than the energy, 67 fJ, required for its complete melting. Estimations based on the heat balance and surface melting model revealed that the temperature which particles reach after a single laser pulse was about 940 degrees C, with the thickness of the liquid layer on the surface of the solid core being 1.4 nm. We also examined thermally induced shape transformation of gold nanoparticles on Si substrates; above 950 degrees C they changed their shapes to spheres, which supported our estimation. Due to the surface melting of particles, their shape transformation occurs at a temperature much lower than their melting point.     

Kinetics of reaction of methyl α-eleostearate with phenol

The kinetics of addition reactions between methyl α-eleostearate which forms the main chain of tung oil and phenol when catalyzed by an acid, p-toluene sulfonic acid, have been studied. The addition reactions, carried out with phenol was shown to be second order with regard to methyl α-eleostearate concentration and first order with regard to phenol concentration. The reactions were additions of two phenol molecules to one methyl α-eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step is rate determining: ((1)) ((2)) The apparent reaction rate constant (l/mol min) was found to be 0.036 and its value was nearly equal to that in the case of m-cresol. The apparent activation energie (kcal/mol) was found to be 4.76 and its value was larger than that in the case of m-cresol.     

Introduction of large sample volumes in capillary supercritical fluid chromatography

A splitless injection method using make-up flow was developed for SFC. Dilution of sample solvent with carbon dioxide mobile phase was very effective for focusing the solutes onto the column. Injection of a 4.5-μl sample volume on a 100-μm i.d. capillary column became possible.     

Cationic graft copolymerization of styrene onto chlorinated butyl rubber

The graft copolymerization of styrene onto chlorinated butyl rubber (Cl-IIR) with stannic chloride as cationic catalyst was studied in cyclohexane, and the rate of polymerization, per cent grafting and grafting efficiency were obtained. Polymerization was carried out in a sealed tube. The product was precipitated in methanol and dried. The increase in weight of Cl-IIR used was regarded as styrene conversion, and the increase in weight after extraction by boiling acetone as the weight of grafted styrene. Grafting was confirmed by fractional dissolution and infrared spectra. The rate of polymerization of styrene was proportional to concentrations of styrene, Cl-IIR and SnCl₄. The per cent grafting increased with styrene and SnCl₄ concentration, but was constant with Cl-IIR concentration. It also increased with time and with halogen content in the polymer. The addition of a polar solvent such as nitrobenzene greatly promoted the grafting reaction and the per cent grafting was 200%.     

A comparison of the analysis of covariance (ANCOVA) and range-based approaches for assessing batch-to-batch variability of the stability of pharmaceutical products

Stability data were generated by the Monte Carlo method, and batch-to-batch variability was evaluated by analysis of differences in slope and intercept according to the analysis of covariance (ANCOVA) approach recommended in the FDA Guidance. Using the same generated data, batch-to-batch variability was also evaluated by assessing the equivalence of shelf lives estimated for individual batches based on the range (Range-based approach) in order to compare the ability of the two approaches to detect stability differences among batches. The results of the study indicated that the Range-based approach can detect a 30% difference in the slope of degradation curves among batches with a similar beta error as the ANCOVA approach, provided that degradation data are obtained with assay errors below 0.5. The range-based approach appears to be useful as an alternative method to ANCOVA, if it is modified such that the variance of estimates is taken into account.     

Surface tension of fluoroalkanes in a liquid phase

The parachor assigned to fluorine atoms in fluorinated alkanes was examined. The values vary systematically with the number of fluorine atoms in the molecule. Partially fluorinated alkanes show large values, while perfluoroalkanes give a smaller value which is constant for all the perfluoroalkanes examined in this work. The molecular structure seems to be important for the intermolecular interaction of this series of compounds, and may be responsible for the deviation from the parachor additivity rule.     

Oviposition-stimulatory activity against Ostrinia zealis by essential oil of root part from Cirsium japonicum DC

The essential oil components from root part of Cirsium japonicum and oviposition-stimulatory activity against Ostrinia zealis by root essential oil were investigated. The main component of fresh root essential oil was aplotaxene (75.14%) and of dried root stock was found to be palmitic acid (14.42%). The root oil was significantly more active than the control against O. zealis.     

Hydrolytic reaction by zinc finger mutant peptides: successful redesign of structural zinc sites into catalytic zinc sites

To redesign a metal site originally required for the stabilization of a folded protein structure into a functional metal site, we constructed a series of zinc finger mutant peptides such as zf(CCHG) and zf(GCHH), in which one zinc-coordinating residue is substituted into a noncoordinating one. The mutant peptides having water bound to the zinc ion catalyzed the hydrolysis of 4-nitrophenyl acetate as well as the enantioselective hydrolysis of amino acid esters. All the zinc complexes of the mutant peptides showed hydrolytic activity, depending on their peptide sequences. In contrast, the zinc complex of the wild-type, zf(CCHH), and zinc ion alone exhibited no hydrolytic ability. These results clearly indicate that the catalytic abilities are predominantly attributed to the zinc center in the zinc complexes of the mutant peptides. Kinetic studies of the mutant peptides demonstrated that the catalytic hydrolysis is affected by the electron-donating ability of the protein ligands and the coordination environment. In addition, the pH dependence of the hydrolysis strongly suggests that the zinc-coordinated hydroxide ion participates the catalytic reaction. This report is the first successful study of catalytically active zinc finger peptides.     

Synthesis of phidolopin, 7-(4-hydroxy-3-nitrobenzyl)-1,3-dimethylxanthine from the bryozoan phidolopora pacifica

A total synthesis of a biologically active compound, phidolopin, was accomplished and its regioisomer was also synthesized.     

Performance of the OP correlation functional in relation to its formulation: Influence of the exchange component and the effect of incorporating same‐spin correlations

In the present study, we have investigated two significant features of the OP correlation functional, namely the incorporation of the exchange functional into itself, and the inclusion of only opposite‐spin (OS) effects. To explore the latter feature, we have compared OP with B95 and a new functional introduced in the present study – the OPB method that combines OP with the same‐spin (SS) component of B95. In general, we find that B95 and OPB perform comparably. Our comparisons of the various DFT procedures suggest that the incorporation of a meta‐GGA (e.g., TPSS) into OP and OPB does not necessarily lead to a chemically more accurate procedure than the use of a related GGA (e.g., PBE). An important finding is the more notable (and somewhat more consistent) improvement in performance with the incorporation of SS correlation, particularly for longer‐range chemical properties. Nonetheless, on average across our test sets of over 800 systems, the difference between the performances of OP versus B95 or OPB is not exceedingly large. By drawing a parallel between these DFT methods and the wavefunction scaled‐MP2‐type methods, we reason that one can further develop the OP functional, and perhaps a wider range of correlation functionals by combining it with the technique of range separation. © 2016 Wiley Periodicals, Inc.