Oscillation frequency dependence of nonclassical rotation inertia of solid 4He

The nonclassical rotational inertia fraction of the identical cylindrical solid 4He below 300 mK is studied at 496 and 1173 Hz by a double resonance torsional oscillator. Below 35 mK, the fractions are the same at sufficiently low rim velocities. Above 35 mK, the fraction is greater for the higher than the lower mode. The dissipation peak of the lower mode occurs at a temperature approximately 4 mK lower than that of the higher mode. The drive dependence of the two modes shows that the reduction of the fraction is characterized by critical velocity, not amplitude or acceleration.     

Proton-coupled electron transfer in ruthenium(II)-pterin complexes: formation of ruthenium-coordinated pterin radicals and their electronic structures

Ruthenium(II)-pterin complexes were prepared using tetradentate and tripodal tris(2-pyridylmethyl)amine (TPA) and tris(5-methyl-2-pyridylmethyl)amine (5-Me3-TPA) as auxiliary ligands together with 2-(N,N-dimethyl)-6,7-dimethylpterin (Hdmdmp) and 6,7-dimethylpterin (Hdmp) as pterin derivatives for ligands. Characterization was made by spectroscopic methods, X-ray crystallography, and electrochemical measurements. The pterin ligands coordinated to the ruthenium centers as monoanionic bidentate ligands via the 4-oxygen of the pyrimidinone moiety and the 5-nitrogen of the pyrazine parts. The striking feature is that the coordinated dmp- ligand exhibits a quinonoid structure rather than a deprotonated biopterin structure, showing a short C-N bond length for the 2-amino group. Those complexes exhibit reversible two-step protonation for both pterin derivatives coordinated to the ruthenium centers to give a drastic spectral change in the UV-vis spectroscopy. Doubly protonated Ru(II)-pterin complexes were stabilized by pi-back-bonding interaction and exhibited clear and reversible proton-coupled electron transfer (PCET) to give ruthenium-coordinated neutral monohydropterin radicals as intermediates of PCET processes. Those ESR spectra indicate that the unpaired electron delocalizes onto the PCET region (N5-C6-C7-N8) of the pyrazine moiety.     

Surface-modified carbon black for As(V) removal

This paper reports the results of the adsorption performance of As(V) removal by a commercial carbon black and its H2SO4-modified form in a single-ion situation. The influence of different process parameters and the physicochemical principles involved were studied in detail. Acid modification caused morphological changes in the virgin carbon black as evidenced by BET surface area measurements and SEM study. FTIR spectra showed the introduction of sulfonic acid group in the parent carbon due to H2SO4 treatment. TGA analysis revealed higher weight loss characteristics of the modified carbon, demonstrating the creation of functional groups. The point of zero charge (pH pzc) of the modified carbon black is highly acidic (3.5) compared to commercial carbon black (6.4). It directly infers the generation of acidic functional moieties in the carbon black. The adsorption experiments were carried out following batch equilibrium techniques. The kinetics and thermodynamics of adsorption were investigated to unveil the mechanism and nature of the adsorption process, respectively. The kinetic parameters of different models were calculated and discussed. The kinetics of adsorption can be expressed by a pseudo-second-order model and intraparticle diffusion was not the rate-determining step. Dependence of pH on adsorption showed maximum metal uptake in the range of 4-5 and inferred surface complexion as the principal mechanism of adsorption. The equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin-Kaganer-Radushkevich (DKR) isotherm equations and the corresponding isotherm parameters were calculated and discussed in detail.     

Phellifuropyranone A: a new furopyranone compound isolated from fruit bodies of wild Phellinus linteus

A new furopyranone, phellifuropyranone A, was isolated from fruit bodies of wild Phellinus linteus as well as phelligridin G, and their chemical structures were determined by various spectroscopic methods including measurement of NMR spectra. Phellifuropyranone A together with meshimakobnol A and meshimakobnol B showed antiproliferative activity against mouse melanoma cells and human lung cancer cells in vitro.     

Catalytic Oxidation of Xylene in Air using TiO<Subscript>2 </Subscript>under Electron Beam Irradiation

The oxidation of xylene and its irradiation byproducts in air using TiO₂ was studied under electron beam (EB) irradiation for the purification of ventilation gases emitted from paint factories. EB irradiation experiments were mainly performed under two different conditions: a TiO₂ pellet layer was placed in an irradiation or a non-irradiation space. The results revealed that xylene was decomposed and CO was formed in the gas phase of the irradiation space irrespective of the presence of TiO₂ pellets, while CO₂ was produced in the gas phase of the irradiation space and on the surface of TiO₂ pellets. The total CO₂ concentration increased when the pellet layer was in the non-irradiation space. On the other hand, the concentration of CO₂ produced on the surface of the TiO₂ pellets in the irradiation space was higher than that in a non-irradiation space.     

Completely dispersible PEGylated gold nanoparticles under physiological conditions: modification of gold nanoparticles with precisely controlled PEG-b-polyamine

A novel water-soluble, biocompatible polymer, poly(ethylene glycol)-block-poly((2-N,N-dimethylamino)ethyl methacrylate) (PEG-b-PAMA), possessing controlled molecular weight with a narrow molecular weight distribution, was synthesized by the atom-transfer radical polymerization (ATRP) method. PEG-b-PAMA having a short PAMA chain length was successfully synthesized under suitable polymerization conditions. Gold nanoparticles (GNPs) were modified using PEG-b-PAMA prepared under a variety of PEGylation conditions. Under alkaline conditions (pH >10) and an [N]/[GNP] ratio of more than 3300, the PEGylated GNPs (PEG-GNPs) showed complete dispersion stability, avoiding coagulation. The amino groups of the PAMA segment of the block copolymers were completely deprotonated above pH 10. This means that PEG-b-PAMA interacted with the GNP surface via multipoint coordination of the tertiary amino groups of PAMA, not electrostatically. The effect of the number of amino groups in the PAMA segment on GNP surface modifications was investigated by zeta potential and dynamic light scattering (DLS) measurements. When the PEG-GNPs were prepared in excess polymer solution, almost the same diameter was observed regardless of the PAMA chain length. After the PEG-GNPs were purified by centrifugation, the zeta potentials of all PEG-GNPs were shielded to almost 0 mV, indicating the effective modifications of the GNP surface by PEG-b-PAMA regardless of the chain length. However, the particle size and particle size distribution of the purified PEG-GNPs were strongly affected by the PAMA chain length. PEG-GNPs with longer PAMA segments underwent coagulation after purification, whereas PEG-GNPs with shorter PAMA segments increased their dispersion stability. The experimental results of the thermal gravimetric analysis confirmed that the PEG density on the GNP surface increased as the AMA units decreased to 3. Thus, the dispersion stability depended significantly on the PEG density on the GNP surface. GNPs modified with PEG-b-PAMA having short AMA units showed excellent dispersion stability under a variety of pH conditions. The excellent dispersion stability of the obtained PEG-GNP was also confirmed both in bovine serum albumin (BSA) solution and 95% human serum.     

High-performance thin-layer chromatography/mass spectrometry for rapid analysis of neutral glycosphingolipids

Direct coupling of high-performance thin-layer chromatography (HPTLC) to matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MS) was shown to be a reliable and reproducible method to obtain structural information and fundamental properties of glycosphingolipids (GSLs). We report a protocol for the preparation of neutral GSL extracts from mouse tissues and demonstrate the applicability of HPTLC/MS to these preparations. The protocol consists of lipid extraction and ion exchange chromatography followed by a mild alkaline treatment and a reversed-phase cartridge extraction. Possible structures for each GSL are proposed based on HPTLC/MS analyses. This fast and simple method can be used to screen neutral GSL extracts obtained from tissues and cells without isolation and purification into individual GSLs.     

Elongational flow opto-rheometry for polymer melts

Polymer melt elongation is one of the most important procedures in polymer processing. To understand its molecular mechanisms, we constructed an elongational flow opto-rheometer (EFOR) in which a high precision birefringence apparatus of reflection-double path type was installed into a Meissner's new elongational rheometer of a gas cushion type (commercialized as RME from Rheometric Scientific) just by mounting a small reflecting mirror at the center of the RME's sample supporting table. The EFOR enabled us to achieve simultaneous measurements of tensile stress (t) and birefringence n(t) as a function of time t under a given constant strain rate within the range of 0.001 to 1.0s^–1. (t) can be monitored upto the maximum Hencky strain (t) of 7 as attained, in principle, with RME, while the measurable range of the phase difference in the birefringence was 0 to 250 (0 to 79 100 nm for He-Ne laser light) within the accuracy of ±0.1 (±31.6 nm) up to (t) 4. The performance was tested on an anionically polymerized polystyrene (PS) and a low density polyethylene (LDPE). For both polymers (t) first followed the linear viscoelasticity rule in that the elongational viscosity, , is three times the steady shear viscosity, 3 _o(t), at low shear rate , but the _E (t) tended to deviate upward after a certain Hencky strain was attained. The birefringence n(t) was a function of both Hencky strain and strain rate in such a way that the stress-optical law holds with the stress-optical coefficient C(t) = n(t)/(t) being equal to the ones reported from shear flow experiments. Interestingly, however, for PS elongated at low strain rates the C(t) vs (t) relation exhibited a strong nonlinearity as soon as (t) reached steady state. This implies that the tensile stress reaches the steady state but the birefringence continues to increase in the low strain-rate elongation. For the PS melt elongated at high strain rates, on the other hand, C(t) was nearly a constant in the entire range observed. For LDPE with long-chain branchings, (t) exhibited tendency of strain-induced hardening after certain critical strain, but C(t) was nearly a constant in the entire range of (t) observed.