Improvement in physical properties of poly(vinyl chloride) by radiation-induced graft copolymerization with mixed monomers

Gamma-ray-induced graft copolymerization of butadiene with vinyl monomers onto PVC was attempted to improve the physical properties of PVC. The Izod impact strength was increased from 2 kg·cm/cm² to more than 100 kg·cm/cm² by grafting ca. 10% butadiene. But the tensile strength and melt flow were decreased by the grafting. The electron micrograph showed that the mass of polybutadiene in the graft copolymer had a convenient diameter (0.1–1 μ) for absorbing the impact energy. The weatherability of PVC grafted with butadiene was improved by cografting of butadiene with acrylates and methacrylates which had long side chains.     

Magnetic resonance imaging of acute cerebellar ataxia: report of a case with gadolinium enhancement and review of the literature

INTRODUCTION: Intervention studies to reduce cigarette sales to minors have been conducted primarily in suburban settings. Little is known about sociocultural factors influencing cigarette sales to minors in urban settings. This study sought to determine sociodemographic and cultural factors that may play a role in cigarette sales and in efforts to reduce sales to minors in urban areas. METHODS: Merchant education and follow-up surveys were conducted in small local stores in predominantly African-American urban census tracts in Baltimore. The stores had prior evidence of cigarette sales to minors. RESULTS: Merchants reported hostility (66%) and foul language (64%) when they requested youth identification. Youthful-oriented advertising of cigarettes was highly prevalent in all stores and moreso in stores owned and staffed by Asian merchants. Advertising with specific youthful content was predictive (OR = 3.97; 95% CI = 1.70, 9.23; P = .0014) of higher requests for cigarettes from minors. CONCLUSIONS: Youth-oriented cigarette advertising is a prevalent environmental risk for urban youth. Differences between Asian and African-American merchants suggest socioethnic factors may be an influential component of illegal sales and educational campaigns to reduce smoking among minors.     

Niobium‐Catalyzed Highly Enantioselective Aza‐Diels–Alder Reactions

Niobium‐based chiral Lewis acid was found to be highly effective catalyst for aza‐Diels–Alder reactions of imines with Danishefsky‘s dienes. The reactions proceed in high yield with high enantioselectivity for both aromatic and aliphatic imines. The developed methodology was applied to total synthesis of (+)‐anabasine.     

Transverse vibrations of linearly tapered beams with ends restrained elastically against rotation subjected to axial force

It is the object of this investigation to examine the effect of an axial force on the frequencies of linearly tapered beams with ends restrained elastically against rotation. The buckling of the system is also discussed. The fundamental eigenfrequencies of the beams with two types of linear tapers are obtained numerically by means of the Ritz method. Numerical results for various taper ratios are shown in graphs and tables against the axial forces and the degrees of end fixity.     

Role for preliminary and continuous hemodialysis during extracorporeal circulation in infants and children

The efficacy of both preliminary and continuous hemodialysis during extracorporeal circulation (ECC) was evaluated in the pediatric population. Preliminary hemodialysis of the priming solution was initiated in eight children (HD-I group), while both preliminary and continuous hemodialysis during ECC was performed in another eight children (HD-II group). The control group which consisted of eight children did not undergo hemodialysis. Urine volume during ECC, perfusion pressure, and water balance were measured and compared among the three groups. In the HD-I and HD-II groups, the total urine volume during ECC was greater than in control group, but there was no significant difference. In the control group, the perfusion pressure temporally decreased after the pump was operating for five minutes, but the perfusion pressures remained stable in the HD-I and HD-II groups. Therefore, preliminary hemodialysis appears to prevent the "initial drop" seen in perfusion pressures. Water balance in the control group tended to be in positive balance, but both the HD-I and HD-II groups appeared to be in negative balance. Significant differences between HD-I and HD-II in contrast to the control group (p < 0.05) and p < 0.04, respectively) were observed. Preliminary hemodialysis is useful during ECC in infants and children because by maintaining perfusion pressure urine output remains adequate while a net negative water balance is achieved. Preliminary hemodialysis will increase the continuous hemodialysis in infants who are subjected to prolonged extracorporeal circulation.     

Reduction in microalbuminuria in diabetics by eicosapentaenoic acid ethyl ester

Eicosapentaenoic acid (EPA) ethyl ester (1.8 g/d) was administered to 16 diabetic patients (5 insulin-dependent and 11 noninsulin-dependent diabetics) for 6 mon. EPA in total plasma fatty acids increased from 4.0±2.4 mol% (mean±SD) to 7.5±3.1 mol% (p<0.001). Albumin excretion, measured with spot urine, was significantly reduced from 65 to 36 mg/g creatinine (geometric means, p<0.001). Fasting blood sugar levels, glycohemoglobin, body weight and blood pressure did not change significantly during the study. There were also no significant changes in serum levels of creatinine, urea nitrogen, total cholesterol and triglycerides. Although no overt hemorrhage was observed in the patients, hematocrit was reduced from 42.6±2.8% to 41.0±3.9% (p<0.02). Ten other similar diabetic patients (4 insulin-dependent and 6 non-insulin-dependent diabetics) were followed as a reference group, not concomitantly, for 6 mon with neither EPA ethyl ester nor placebo. The parameters mentioned above were not changed significantly in this group during 6 mon. EPA administration might retard the appearance of overt diabetic nephropathy.     

Insights from ab initio molecular dynamics simulations for a multicomponent oxide glass

It remains a challenge to establish structural models of multicomponent oxide glass systems. In this study, we have investigated 68.3SiO₂–16.1B₂O₃–4.2Al₂O₃–11.4Na₂O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against ¹⁷O solid‐state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, and coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five‐coordinate Si (Si^V) and Al (Al^V). The Si^V–O bond lengths and O–Si^V–O angle distribution in the glass indicated 1.718 Å and three peaks at 90°, 120°, and 175°, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that Si^V and Al^V were found to preferentially contribute to the formation of small ring sizes.     

Label-free protein biosensor based on aptamer-modified carbon nanotube field-effect transistors

We have fabricated label-free protein biosensors based on aptamer-modified carbon nanotube field-effect transistors (CNT-FETs) for the detection of immunoglobulin E (IgE). After the covalent immobilization of 5'-amino-modified 45-mer aptamers on the CNT channels, the electrical properties of the CNT-FETs were monitored in real time. The introduction of target IgE at various concentrations caused a sharp decrease in the source-drain current, and a gradual saturation was observed at lower concentrations. The amount of the net source-drain current before and after IgE introduction on the aptamer-modified CNT-FETs increased as a function of IgE concentration. The detection limit for IgE was determined as 250 pM. We have also prepared CNT-FET biosensors using a monoclonal antibody against IgE (IgE-mAb). The electrical properties of the aptamer- and antibody-modified CNT-FETs were compared. The performance of aptamer-modified CNT-FETs provided better results than the ones obtained using IgE-mAb-modified CNT-FETs under similar conditions. Thus, we suggest that the aptamer-modified CNT-FETs are promising candidates for the development of label-free protein biosensors.     

Reconstruction of Cracks with Multiple Eddy Current Coils Using a Database Approach

This paper presents some recent studies dealing with flaw reconstruction using eddy current testing. The locations of parallel planar cracks in an Inconel 600 plate specimen are determined and the shapes of them are reconstructed at the same time using the signals from a multi-pancake coil probe. The reconstruction strategy, consisting of a data base used fast forward solver and a first order optimization algorithm, relies on the minimization of the nonlinear least square residual function. Validity of the inverse analysis method is investigated with respect to the influence of the arrangement of scanning paths. The efficiency of the computation is also discussed.