Effects of polysulfides on the polymerization of methyl methacrylate

The effect of organic sulfur compounds on the radical polymerization of methyl methacrylate initiated by azobisisobutyronitrile at 50°C. has been studied. The sulfur compounds used were benzene-type polysulfides (C₆H₅CH₂? S_n? CH₂C₆H₅; n = 0–4), benzyl mercaptan, and sulfur (S₈). All sulfur compounds studied, except dibenzyl, dibenzyl monosulfide, and dibenzyl disulfide, were found to behave as retarders under these experimental conditions. Chain-transfer constants of these compounds were determined from rate measurements and from the conventional method based on numberaverage degree of polymerization. Chain-transfer constants of benzyl-type polysulfides were less than those of mercaptan and sulfur and increased with increasing sulfur. The correlation of the reactivities of sulfur compounds as transfer agents and their molecular structures is discussed.     

Improved liquid chromatographic separation of different proteins by designing functional surfaces of cattle bone-originated apatite

Spherical particles of cattle bone-originated hydroxyapatite (r-HAp) were prepared by dissolution-precipitation, spray-drying using a two fluid-nozzle apparatus, and subsequent heat treatment. The product had effective pore structures for liquid chromatographic separation of albumin, myoglobin, ribonuclease, lysozyme and cytochrome c. The activated surfaces of the r-HAp particles were easily prepared with desired proportions of P- and C-sites and appropriate acid-basic strength for selective protein adsorption by optimizing the synthesis conditions. Liquid chromatography columns packed with the particles exhibited high resolution and durability in protein separation, reflecting stable distribution of pore size.     

Plutonium and cesium isotopes in river waters in Japan

Concentrations of cesium isotopes and plutonium in river water samples in Japan, collected during the period from June 1985 to February 1987, have been measured. The total¹³⁷Cs concentrations in the Japanese river waters ranged from 0.063 to 1.89 mBq·l^–1. The portion of particulate¹³⁷Cs to total was observed to be less than 10 to 35%. The total^239,240Pu concentrations ranged from 0.56 to 1.93 Bq·l^–1. Particulate^239,240Pu occupied 13 to 95% of the total. After the Chernobyl fallout, elevated¹³⁷Cs concentrations were observed in the Japanese river waters as well as the detection of¹³⁴Cs, whereas there was no effect on the river plutonium from the Chernobyl fallout. The partition coefficients of¹³⁷Cs and plutonium between suspended particulate and dissolved phases in the Japanese rivers were determined: from 1.0·10⁴ to 3.2·10⁵ and from 4.1·10⁴ to 2.3·10⁶ for¹³⁷Cs and plutonium, respectively. The result suggests that these radionuclides, especially plutonium, are tightly associated with soil particles and/or suspended matter.     

Pr(OTf)3-promoted Chichibabin pyridine synthesis of isodesmosine in H2O/MeOH

1,2,3,5-Tetrasubstituted pyridinium amino acid isodesmosine is a crosslinking amino acid of elastin and is an attractive biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD). Herein, we report an application of the Chichibabin pyridine synthesis to the total synthesis of isodesmosine. Specifically, the appropriate protected lysine and the corresponding aldehyde were reacted using Pr(OTf)₃ in H₂O/MeOH.     

Effects of collision between two plumes on plume expansion dynamics during pulsed laser ablation in background gas

Si and Ge targets were simultaneously irradiated by individual two pulsed lasers, and two plumes from the targets were collided head-on with expectation to prepare hybrid nanoparticles. We investigate effects of He background gas pressure on plume collision dynamics. Three characteristic behaviors of plume expansion dynamics are observed at low, middle, and high background gas pressure regions. Interaction between the two atomic species during plume expansion was small and the effect of collision was hardly observed at a low background gas pressure, 130 Pa, while spatial evolution of the plume was suppressed at middle pressure, 270 Pa, due to collision of the two plumes. At high pressure, 2700 Pa, plume expansion is suppressed by background gas and the effect of a direct collision of two plumes was small. These results indicate that plume collision dynamics, which governs nanoparticle formation, and the mixture of Si and Ge species can be varied by background gas pressure. The deposit near the center of two targets was nanoparticles that were composed of Si and Ge.     

HCC-to-liver contrast on arterial-dominant phase images of EOB-enhanced MRI: comparison with dynamic CT

The purpose of this study was to assess the efficacy of arterial-dominant phase images of gadolinium–ethoxybenzyl–diethylenetriamine pentaacetic acid (EOB)-enhanced magnetic resonance imaging (MRI) for evaluation of arterial blood supply in hepatocellular carcinoma (HCC) in comparison with that of multiphasic dynamic computed tomography (CT). This study comprised 30 patients (22 men and 8 women, mean age: 68.0 years) with 40 pathologically proven HCCs (well differentiated: 3, moderately differentiated: 30, poorly differentiated: 7, mean diameter: 45.1 mm), all of whom underwent EOB-enhanced MRI and dynamic CT preoperative assessment. Regions of interest were placed over HCCs and the adjacent normal liver, and signal intensities or CT values were measured by two experienced abdominal radiologists on the arterial-dominant phase images of EOB-enhanced MRI and dynamic CT images. HCC-to-liver contrasts [Michelson's contrast: C_M=(S_HCC− S_Liver)/(S_HCC+ S_Liver)] were calculated and compared among the modalities. HCC-to-liver contrasts were also visually scored on a 5-point scale and compared. The mean C_M and visual score for dynamic CT were significantly higher than those for EOB-enhanced MRI. Good agreements were obtained among the two observers. Dynamic CT is a more suitable modality than EOB-enhanced MRI for evaluation of arterial blood supply in HCC. This should be taken into account for diagnosis and management of HCC.     

Differentiation of AB‐FUBINACA positional isomers by the abundance of product ions using electron ionization–triple quadrupole mass spectrometry

Mass spectrometric differentiation of structural isomers is important for the analysis of forensic samples. Presently, there is no mass spectrometric method for differentiating halogen positional isomers of cannabimimetic compounds. We describe here a novel and practical method for differentiating one of these compounds, N‐(1‐amino‐3‐methyl‐1‐oxobutan‐2‐yl)‐1‐(4‐fluorobenzyl)‐1H‐indazole‐3‐carboxamide (AB‐FUBINACA (para)), and its fluoro positional (ortho and meta) isomers in the phenyl ring by electron ionization–triple quadrupole mass spectrometry. It was found that the three isomers differed in the relative abundance of the ion at m/z 109 and 253 in the product ion spectra, while the detected product ions were identical. The logarithmic values of the abundance ratio of the ions at m/z 109 to 253 (ln(A₁₀₉/A₂₅₃)) were in the order meta < ortho < para and increased linearly with collision energy. The differences in abundances were attributed to differences in the dissociation reactivity between the indazole moiety and the fluorobenzyl group because of the halogen‐positional effect on the phenyl ring. Our methodology, which is based on the abundance of the product ions in mass spectra, should be applicable to determination of the structures of other newly encountered designer drugs. Copyright © 2016 John Wiley & Sons, Ltd.     

Transient Current Dependent on Nematic Director Orientation

Transient currents induced by the polarity reversal of an applied DC voltage in nematic liquid crystals have been studied experimentally and theoretically. The experimental results of transient currents in the cells with various treated substrate surfaces have been presented. In the theoretical studies, the presence of adsorbed charge layers on the substrate surfaces and a spatial distribution of carrier mobility dependent on a director orientation have been assumed. By one dimensional mobility distribution of drift sheet carrier across the cell, the carrier transport process and the generation mechanism of the transient current with or without peaks can be well understood. The experimental results on transient currents have been successfully explained from the interpretation of the different adsorbed charge ratio which is the ratio of adsorbed charges to the total amount of the charges in the cell.     

Field-induced alignment of the nematic director: studies of nuclear magnetic resonance spectral oscillations in the limit of fast director rotation

Time-resolved NMR spectroscopy is a powerful method to investigate field-induced rotation of the director in a nematic liquid crystal. The method requires that the director does not rotate significantly during the acquisition of the free induction decay and hence the NMR spectrum. We have extended the method to systems where this is not the case and the observed NMR spectra are now found to contain novel oscillatory features. To understand these oscillations, we have developed a model combining both director and spin dynamics. In addition to increasing the information content of the time-resolved NMR spectra, it also proves possible to determine the field-induced relaxation time from a single spectrum.