Dendritic cavitands: preparation and electrochemical properties

A new series of dendrimers containing a central cavitand core with four appended Fréchet-type dendrons, linked to the core through 4,4'-bipyridinium (viologen) subunits, have been synthesized, characterized and their electrochemical properties investigated using cyclic voltammetric measurements.     

Isobaric analog resonances in the 82se+p system investigated by (p,p'γ) angular correlations and low-lying states in 83Se

Low-lying states in ⁸³Se have been studied through proton-induced isobaric analog resonance (IAR) reactions. Excitation functions for elastic and inelastic proton scattering were measured in the bombarding energy range 4.5– to 7.7 MeV. Angular distributions of proton inelastic scattering cross sections for the reaction ⁸²Se(p, p')⁸²Se(0.655 MeV 2⁺) and angular correlations of the inelastic protons and the associated 2⁺-0⁺ de-excitation γ-rays were measured on observed resonance peaks. In the analysis for the inelastic scattering, direct reaction contributions to the IAR were taken into account. Correlations between the low-lying states in ⁸³Se and the excited 2⁺ core state are discussed.     

Synthesis,optical and electrochemical properties of arylenevinylene‐based π‐conjugated polymers with imidazolium units in the main chain

Arylenevinylene‐based π‐conjugated polymers containing imidazolium cationic units in the main chain and their model compounds were synthesized and characterized in terms of optical and electrochemical properties. 9,9‐Bisoctylfluorene, 2,5‐bisdodecyloxybenzene, and 3‐dodecylthiophene were introduced as arylene units with different donor characteristics to evaluate the effect on the highest occupied molecular orbital‐lowest unoccupied molecular orbital (HOMO‐LUMO) gap energy. The UV–vis and fluorescence spectra of cationic polymers and model compounds with iodide counter anion exhibited a significant blue shift with respect to the parent neutral molecules. X‐ray single crystal analysis for model compounds revealed that the effective π‐conjugation length of cationic model compounds decreased compared to the neutral model compounds by means of twisted conformation directed by CH‐π interactions between N‐methyl groups of imidazolium and neighboring aryl units. The cyclic voltammetry measurement suggested the negative shift of LUMO levels by the conversion of imidazole to imidazolium, indicating the electron‐accepting characteristics of cationic imidazolium unit. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Similarity laws of the wind wave and the coupling process of the air and water turbulent boundary layers

The statistical properties of growing wind waves are known to obey certain self-similarity laws. One of these is expressed as the -power law relation between the significant wave-height and the significant wave period in nondimensional forms. Recent experiments on turbulence above and below laboratory wind waves indicate that both the air and the water layers have a structure which is similar to that of the turbulent boundary layer over a rough solid wall. The continuity of the momentum flux through the air and water boundary layers combined with the -power law of wind waves means that all the characteristic velocities related to the air-water boundary process are proportional to one another. Our laboratory experimental data on the several characteristic variables concerned support this picture. The state of local equilibrium as expressed by the -power law is thought to be brought about by the “breaking adjustment of the wind wave” which is required by the overall continuity of the velocity and the momentum flux across a thin surface layer. The above proportionality of the characteristic velocities provides a physical basis for the observed friction velocity scaling of the ocean mixed layer.     

Modeling of argon discharge characteristics of planar-type surface wave plasmas in an electron fluid model

The planar-type surface wave plasma (SWP) device permits the generation of high-density and uniform processing plasmas via 2.45-GHz microwave power without the application of an external magnetic field. In the present study, the discharge characteristics in the SWP device were analyzed using a two-dimensional numerical simulation code, and the results were compared with experimental observations. The simulation code is based on the finite-difference time-domain (FDTD) method for the microwave field and on the electron fluid model for the argon discharge plasma. Experimental measurements were performed, and they showed that the surface-wave discharge at a filling pressure of 10-100 mtorr has characteristic electron-density distributions that have a peak at approximately 2 cm from the surface. This characteristic of the electron density profiles, as well as the electron temperature profiles in the plasma, is reproduced by the simulation code, albeit with some discrepancies. In order to reduce the effects of these discrepancies, intentional changes in the electron heat conductivity were introduced, and the adiabatic assumption was found to result in a reasonable electron temperature profile. The effects of the alumina window thickness were also investigated in the simulation.     

Mechanical interaction between cellulose microfibrils and matrix substances in wood cell walls induced by repeated wet-and-dry treatment

We measured the lattice spacing of the cellulose in sugi (Cryptomeria japonica D. Don) and hinoki (Chamaecyparis obtusa Endl.) cell walls under wet and dry conditions. We gave all specimens repeated wet-and-dry treatments and tried to induce substantial changes in the microstructure of the wood cell wall. Macroscopic dimensions, measured using a micrometer, showed well-known behaviors, that is, shrinkage by drying and swelling by wetting, which were unaffected after the repeated wet-and-dry treatments in both longitudinal and tangential directions. On the other hand, lattice spacing, measured using an X-ray diffractometer, showed different results. In particular, d ₂₀₀ lattice spacing expanded considerably with drying in the early stages of repeated wet-and-dry treatments. The d ₂₀₀ lattice spacing in the dried specimen then became gradually smaller in the later stages, whereas no such dynamic change was observed in d ₀₀₄ lattice spacing throughout the repeated wet-and-dry treatments. Once the d ₂₀₀ lattice spacing in the dried specimen had become smaller after giving wet-and-dry treatments, it did not recover, even after soaking in distilled water for 1 month. These results suggest that repeated drying and re-swelling caused structural changes in the wood cell wall, specifically an interfacial separation between cellulose microfibrils and matrix substances.     

Selective targeting of lysosomal cysteine proteases with radiolabeled electrophilic substrate analogs

BACKGROUND: The lysosomal cysteine proteases of the papain family are some of the best studied proteolytic enzymes. Small-molecule inhibitors and fluorogenic substrate mimics have been used to probe the physiological roles of these proteases. A high degree of homology between family members and overlap in substrate specificity have made elucidating individual protease function, expression and activity difficult. RESULTS: Using peptide vinyl sulfones and epoxide as templates, we have generated probes that can be tagged with radioactive iodine. The resulting compounds covalently label various cathepsins and several unidentified polypeptides likely to be proteases. MB-074 was found to be a highly selective probe of cathepsin B activity. Probes that labeled several cathepsins were used to examine the specificity and cell permeability of the CA-074 family of inhibitors. Although CA-074 reportedly acts in vivo, we find it is unable to penetrate cells. Esterifying CA-074 resulted in a cell-permeable inhibitor with dramatically reduced activity and specificity for cathepsin B. The probes were also used to monitor protease activity in primary human tumor tissue and cells derived from human placenta. CONCLUSIONS: We have generated a highly selective cathepsin B probe and several less specific reagents for the study of cathepsin biology. The reagents have several advantages over commonly used fluorogenic substrates, allowing inhibitor targets to be identified in a pool of total cellular enzymes. We have used the probes to show that cathepsin activity is regulated in tumor tissues and during differentiation of placental-derived cytotrophoblasts to invasive cells required for establishing blood circulation in a developing embryo.     

Preparation of Titania Containing Mixed Oxides and Their Catalytic Activities

Titania containing catalysts were prepared by conventional procedures (coprecipitation, hydrogel kneading and titania precipitation) and a complexing-agent assisted sol-gel method. The effect of preparation methods on their properties and catalytic activities in the oxidation of olefins and decomposition of cumene hydroperoxide were examined. The sol-gel method gave the best dispersion of titania. In contrast, with the kneading and titania precipitation method, titania formed crystalline particles. The sol-gel catalysts are more effective for epoxydation of olefins because of the high dispersibility of Ti in them. However, the most active catalysts in the decomposition of cumene hydroperoxide are kneading ones.     

57Fe Mössbauer study YBa2Cu3−xFexO7−y

Mössbauer measurement is made on the system YBa₂Cu_3?xFe_xO_7?y (0.03≤x≤1.0) at various temperatures. It is found that the sites occupied by Fe ions can be classified into major two and minor one groups. The isomer shifts for the major two groups are nearly zero relative to metallic iron, and their quadrupole splittings are large (about 1.9 and 1.1 mm/s). By comparison of the spectra measured before and after a heat-treatment in vacuum, it is concluded that the Fe ions with the largest quadrupole splitting occupy the pyramidal sites, and the other the planer sites. Two different hyperfine magnetic fields (240 and 442 k0e) are observed at 1.7 K for the specimen with x=0.2. It is proposed that the valence states of Fe ions of the major two groups are pentavalent.