Polymerization and photoinitiation behavior in the light-cured dental composite resins

The polymerization behavior and photoinitiation process in the visible light-cured dental composite resins were studied using ESR and IR spectroscopies. The concentration of methacryl propagating radical corresponded to the transmittance of irradiated light. While the radical was stable and long-lived in the cured resin, its concentration quickly decreased in the oral cavity due to the ventilation of atmospheric oxygen accompanied by respiration. Camphorquinone radical in the presence of tertiary amine easily initiated the radical polymerization. A decrease in monomer consumption was explained by the inhibition effect of oxygen in the photoinitiation process. Post-curing by the residual radical proceeded effectively in the deeper part of the resin.     

Spectral and related properties about the Emden-Fowler equation −Δu=λe u on circular domains

The first author is on leave from the Department of Mathematics, Chiba Institute of Technology, Narashino 275, Japan     

A microporous membrane-based continuous generation system for trace-level standard mixtures of atmospheric gases.

A reliable and convenient system to generate accurate and stable standard gas mixtures of various atmospheric compounds at parts-per-billion levels has been developed. The system is of simple design; the generator is a coil consisting of an inner tube of microporous polytetrafuluoroethylene (PTFE) membrane tubing and an outer tube of silicone tubing. An aqueous solution of the given compound continuously flows through the inner microporous tube and the purge gas flows through the annulus between the inner and outer tubes. In addition to the generation of gas mixtures based on Henry's law, the proposed flow-type system offers generation based on chemical reactions, leading to a distinct advantage of the availability of continuous sources of various compounds. The generation system was tested for preparing standard gas mixtures of HCHO and H2O2 on the basis of Henry's law, and those of HNO2, NO, and SO2 on the basis of chemical reactions. A stable generation of the desired low concentrations of various kinds of gas mixtures can be readily achieved by adjusting the concentration of the solution without the use of high-dilution flow.     

Simultaneous Determination of Imidazole Amino Acids, Aromatic Amino Acids, and Creatinine by Dual-Mode Gradient HPLC Using a Low-Capacity Sulfo-Functionalized Poly(Ethylstyrene-Divinylbenzene) Resin Column

This paper presents a low-capacity cation-exchange chromatography method for the analysis of UV-absorbing dipeptides and amino acids. A newly marketed low-capacity cation-exchange column packed with sulfo-functionalized highly cross-linked macroreticular poly(ethylstyrene-divinylbenzene) copolymer was used for the simultaneous determination of imidazole amino acids, aromatic amino acids, and creatinine in urine samples. A dual-mode binary gradient chromatography method was established using two solvents, A: 15 mM H₃PO₄/5 mM ethylenediamine and B: 15 mM H₃PO₄/5 mM ethylenediamine/40 (v/v) % CH₃CN at 40 °C, with an optimized time program for changing the delivery ratio of A/B and the flow rate. Good chromatograms were obtained within an acceptable cycle time of 25 min. The quantification data were satisfactory for all analytes, showing the relative standard deviations (RSD) of retention times between 0.08 and 1.68 %; RSDs of area intensities between 0.23 and 2.60 %; and linear regression lines with r ² more than 0.9994. The method could determine the creatinine ratios of the diagnostic markers on the single chromatographic run, which enabled to discriminate disease from health. For example, the creatinine ratios for phenylketonuria were significantly higher than those for controls. The method can provide highly cost-efficient information or useful knowledge for clinical and pharmaceutical studies.     

Preparation of highly dispersible and tumor-accumulative, iron oxide nanoparticles Multi-point anchoring of PEG-b-poly(4-vinylbenzylphosphonate) improves performance significantly

This paper describes the preparation of iron oxide nanoparticles, surface of which was coated with extremely high immobilization stability and relatively higher density of poly(ethylene glycol) (PEG), which are referred to as PEG protected iron oxide nanoparticles (PEG-PIONs). The PEG-PIONs were obtained through alkali coprecipitation of iron salts in the presence of the PEG-poly(4-vinylbenzylphosphonate) block copolymer (PEG-b-PVBP). In this system, PEG-b-PVBP served as a surface coating that was bound to the iron oxide surface via multipoint anchoring of the phosphonate groups in the PVBP segment of PEG-b-PVBP. The binding of PEG-b-PVBP onto the iron oxide nanoparticle surface and the subsequent formation of a PEG brush layer were proved by FT-IR, zeta potential, and thermogravimetric measurements. The surface PEG-chain density of the PEG-PIONs varied depending on the [PEG-b-PVBP]/[iron salts] feed-weight ratio in the coprecipitation reaction. PEG-PIONs prepared at an optimal feed-weight ratio in this study showed a high surface PEG-chain surface density (≈0.8 chainsnm(-2)) and small hydrodynamic diameter (<50 nm). Furthermore, these PEG-PIONs could be dispersed in phosphate-buffered saline (PBS) that contains 10% serum without any change in their hydrodynamic diameters over a period of one week, indicating that PEG-PIONs would provide high dispersion stability under in vivo physiological conditions as well as excellent anti-biofouling properties. In fact we have confirmed the prolong blood circulation time and facilitate tumor accumulation (more than 15% IDg(-1) tumor) of PEG-PIONs without the aid of any target ligand in mouse tumor models. The majority of the PEG-PIONs accumulated in the tumor by 96 h after administration, whereas those in normal tissues were smoothly eliminated by 96 h, proving the enhancement of tumor selectivity in the PEG-PION localization. The results obtained here strongly suggest that originally synthesized PEG-b-PVBP, having multipoint anchoring character by the phosphonate groups, is rational design for improvement in nanoparticle as in vivo application. Two major points, viz., extremely stable anchoring character and dense PEG chains tethered on the nanoparticle surface, worked simultaneously to become PEG-PIONs as an ideal biomedical devices intact for prolonged periods in harsh biological environments.     

Evaluation of TA10 broth for recovery of heat- and freeze-injured Salmonella from beef

The Bacteriological Analytical Manual (BAM) Salmonella pre-enrichment broth [lactose (LAC) broth], buffered peptone water, and universal pre-enrichment (UP) broth were compared with TA10 broth, developed in our laboratory, for recovery of heat- and freeze-injured Salmonella (55 degrees C for 2-20 min and -20 degrees C for 2 months, respectively) from beef. Beef samples were contaminated with single Salmonella serovars, and contamination levels of 0.44 to <0.001 most probable number (MPN)/g and 0.74 to 0.14 MPN/g were used for heat- and freezing-induced injury studies, respectively. Twenty test portions (25 g) of the contaminated beef were pre-enriched in each broth, and the BAM Salmonella culture method was used thereafter. There was a significant difference (chi2 = 7.73) in recovery of heat-injured Salmonella between TA10 broth and LAC broth, 189 (67.5%) versus 156 (55.7%) positive samples, respectively, determined by plating onto selective agars and identification by biochemical tests. For the recovery of freeze-injured Salmonella, there was a significant difference (chi2 = 24.7) between TA10 and LAC broth, 189 (72.7%) versus 133 (51.2%) positive samples, respectively. TA10 broth was more effective than LAC broth and UP broth for recovery of freeze-injured Salmonella. The results indicate that TA10 broth should be used instead of LAC broth for testing of beef that may be contaminated with heat- and freeze-injured Salmonella spp.     

Comparison of two methods for determination of tomato paste solids: vacuum oven versus microwave oven

Two analytical procedures used to determine total, soluble, and insoluble solids in tomato paste were evaluated. The microwave oven (MO) method was compared to the vacuum oven (VO) method. The VO method is tedious and measured the three solids fractions in the paste directly, while the MO method measured the total solids directly but used an equation to calculate the water-soluble and -insoluble solids. The MO method was faster and less labor-intensive, and yielded small but statistically significant higher values for total and insoluble solids and lower statistically significant values for soluble solids.     

Synthesis of oligonucleotides possessing versatile probes for PET labelling and their rapid ligand-free click reaction

We synthesised aryl acetylene derivatives as versatile probes for labelling of oligonucleotides. RNA oligomers bearing an aryl acetylene molecule rapidly reacted with benzylazide derivatives under ligand-free click reaction conditions.     

Preparation of gold colloid using pyrrole-2-carboxylic acid and characterization of its particle growth

Gold colloid was prepared by reduction of tetrachloroaurate using pyrrole-2-carboxylic acid in the presence of α-methoxy-ω-mercaptoethyl-poly(ethylene glycol). The shape and size of the obtained gold colloids were monitored by absorption spectroscopy and transmission electron microscopy during the reduction reaction. In the early stage of the reducing reaction, large fluffy particles with diameters >100 μm were observed. Some of these large particles had rectangular parallelepiped shapes. However, the mean particle size decreased with increasing time. Eventually, these large, non-round-shaped particles disappeared almost completely, and uniform round-shaped particles with a mean diameter of 10.5 nm became dominant.     

Permeation flux of organic molecules through silica-surfactant nanochannels in a porous alumina membrane.

The permeation fluxes of phenol, benzene sulfonate (BS) and benzene disulfonate (BDS) through a porous anodic alumina membrane with the perpendicularly oriented silica-surfactant nanochannel assembly membrane (NAM) were measured in water-ethanol mixture media. The permeation flux depended on solute charges and on solvent composition. As the ethanol ratio increased, the fluxes of BS and BDS increased and the flux of phenol decreased. The results of extraction/elution experiments also depended on the solute charges and the solvent composition. Chromatographic experiments in n-hexane showed that dipole and hydrophobic interactions affect the retention of solutes. Permeation of the solute across the NAM in water-ethanol mixture is likely to be determined by various factors such as dipole interaction, hydrophobic interaction, solvation, and anion-exchange efficiencies.