Synthesis and size control of silver nanoparticles using reverse micelles of sucrose fatty acid esters

Silver nanoparticles were prepared in reverse micelles of sucrose fatty acid esters. The TEM image showed that the obtained silver nanoparticles displayed a wide variety of shapes. The size of silver nanoparticles was strongly dependent upon a kind of reducing agents and tended to increase with an increase in reaction temperature. Moreover, the size of silver nanoparticles was controlled by using sucrose fatty acids at a different esterification degree or by mixing sucrose fatty acid monoesters with polyoxyethylene sorbitan fatty acid monoesters. The resultant silver colloid could be preserved for at least 1 month without precipitation.     

Novel One-pot Three-component Coupling Reaction with Trimethylsilylmethyl-phosphonate, Acyl Fluoride, and Aldehyde through the Horner-Wadsworth-Emmons Reaction

A novel three-component coupling between trimethylsilylmethylphosphonate, acyl fluoride, and aldehyde has been developed. A sequential nucleophilic addition of lithio-trimethylsilylmethylphosphonate to the acyl fluoride and Horner-Wadsworth-Emmons reaction of an aldehyde with the lithio-β-ketophosphonate generated in situ by desilylation at the α-position of the α-silyl-β-ketophosphonate by fluoride took place cleanly in a one-pot operation. Various E- and Z-enones were obtained in high yields with high stereoselectivities by this one-pot procedure.     

Role of complex defects in photocatalytic activities of nitrogen-doped anatase TiO(2)

Deep impurity states associated with a substitutional nitrogen at an oxygen site (N(O)) are believed to be the source of the visible-light absorption of nitrogen-doped titanium dioxide (TiO(2)). Our comprehensive study using density functional theory (DFT) plus onsite Coulomb interaction (U) reveals that a titanium atom at an interstitial site (Ti(i)) is highly mobile and strongly binds with N(O). Hybridizations of N p with Ti d states of Ti(i) give rise to a new band at the valence band edge, eliminating the hole-trapping centers originated from the deep N(O) states. The suggested mechanism explains the photocatalytic oxidation reactions as well as the visible-light absorption observed on N-doped anatase TiO(2).     

Theory for trivial trajectory parallelization of multicanonical molecular dynamics and application to a polypeptide in water

Trivial trajectory parallelization of multicanonical molecular dynamics (TTP-McMD) explores the conformational space of a biological system with multiple short runs of McMD starting from various initial structures. This method simply connects (i.e., trivially parallelizes) the short trajectories and generates a long trajectory. First, we theoretically prove that the simple trajectory connection satisfies a detailed balance automatically. Thus, the resultant long trajectory is regarded as a single multicanonical trajectory. Second, we applied TTP-McMD to an alanine decapeptide with an all-atom model in explicit water to compute a free-energy landscape. The theory imposes two requirements on the multiple trajectories. We have demonstrated that TTP-McMD naturally satisfies the requirements. The TTP-McMD produces the free-energy landscape considerably faster than a single-run McMD does. We quantitatively showed that the accuracy of the computed landscape increases with increasing the number of multiple runs. Generally, the free-energy landscape of a large biological system is unknown a priori. The current method is suitable for conformational sampling of such a large system to reduce the waiting time to obtain a canonical ensemble statistically reliable.     

Enhanced catalase-like activity of manganese salen complexes in water: effect of a three-dimensionally fixed auxiliary

A new Mn(Salen) complex bearing an ureido group as an auxiliary that is three-dimensionally fixed by a cyclopentane ring fused to the Salen structure was developed. This compound exhibited considerably higher catalase-like activity than the original Mn(Salen), i.e., the cyclopentane-fused Mn(Salen) without the auxiliary, under near-physiological conditions.     

Oxygen‐Assisted Synthesis of Mesoporous Palladium Nanoparticles as Highly Active Electrocatalysts

Mesoporous Pd nanoparticles (MPNs) enclosed by high‐index facets have been successfully prepared by taking advantage of successive oxygen adsorption and desorption caused by the oxidative etching effect. The as‐prepared MPNs exhibit excellent performance toward formic acid electro‐oxidation, which is due to the synergetic effect between the diffusion‐feasible tubular mesochannels and the high index facets.     

Assignment of Absolute Configuration of Bromoallenes by Vacuum-Ultraviolet Circular Dichroism (VUVCD)

A new application of vacuum-ultraviolet circular dichroism (VUVCD), which enables the measurement of CD spectra in the vacuum-ultraviolet region (140–200 nm), for the assignment of the absolute configurations of bromoallenes is described. Bromoallene moieties are found in natural products obtained from many marine organisms. To date, the absolute configuration of bromoallenes has been assigned almost exclusively with Lowe’s rule, which is based on specific rotation. However, exceptions to Lowe’s rule have been reported arising from the presence of other substituents with large specific rotations. For the unambiguous assignment of the absolute configuration of the bromoallene moiety with its characteristic absorption wavelength at 180–190 nm due to the π–π* transition, VUVCD was applied to four pairs of bromoallene diastereomers prepared by modifying the synthetic scheme of omaezallene. The VUVCD spectra clearly showed positive or negative Cotton effects around 180–190 nm according to the configuration of the bromoallene employed, revealing the potential of VUVCD for determining absolute stereochemistry.     

Quantum Field Theory of Crystals and Dislocations

We present a quantum field theoretical treatment of crystals from the view point of the spontaneous breakdown of the spatial translation invariance. It is proved that at least three massless Goldstone particles exist and they are identified as the acoustic phonons. We carry out the boson transformation to show that the classical phenomenological theory of crystals can be derived. The classical momentum and stress tensor are expressed in terms of the classical displacement field. The method is extended to a microscopic derivation of the theory of crystal dislocations. It is shown that the Burgers vector is quantized and is a special case of the so-called topological quantum number. An explicit expression of a general solution of the dislocation is obtained.