Comparison of two low-hazard organic solvents as individual and cosolvents for the fabrication of polysulfone membranes

Petroleum-derived solvents commonly used in membrane fabrication are often hazardous and toxic, so the investigation of safer alternatives is important. In this study, two low-hazard solvents, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv® PolarClean) and gamma-valerolactone (GVL), were investigated as sole solvents and as cosolvents to cast polysulfone membranes via nonsolvent induced phase inversion. Normalized viscosity was introduced as an indicator of dope solution homogeneity and was used to compare the required time of mixing to achieve full dissolution of the polymer in the different solvents/solvent mixtures. All dope solutions made with low-hazard solvents were found to be more viscous than those made with traditional solvents, which meant additional mixing time was needed, and that fabricated membranes were morphologically different. With respect to operation, membranes cast from dope solutions containing equal amounts of PolarClean and GVL displayed the most similar flux curves and solute rejection to those made using the traditional solvent tested.     

Founder BRCA1 and BRCA2 mutations in Ashkenazi Jews in Israel: frequency and differential penetrance in ovarian cancer and in breast-ovarian cancer families

Germ-line BRCA1 and BRCA2 mutations account for most of familial breast-ovarian cancer. In Ashkenazi Jews, there is a high population frequency (approximately 2%) of three founder mutations: BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT. This study examined the frequency of these mutations in a series of Ashkenazi women with ovarian cancer unselected for family history, compared with the frequency of these mutations in families ascertained on the basis of family history of at least two affected women. Penetrance was compared, both according to the method of family ascertainment (i.e., on the basis of an unselected ovarian cancer proband vs. on the basis of family history) and for the BRCA1 founder mutations compared with the BRCA2 6174delT mutation. There was a high frequency (10/22; [45%]) of germ-line mutations in Ashkenazi women with ovarian cancer, even in those with minimal or no family history (7/18 [39%]). In high-risk Ashkenazi families, a founder mutation was found in 59% (25/42). Families with any case of ovarian cancer were significantly more likely to segregate a founder mutation than were families with site-specific breast cancer. Penetrance was higher in families ascertained on the basis of family history than in families ascertained on the basis of an unselected proband, but this difference was not significant. Penetrance of BRCA1 185delAG and BRCA1 5382insC was significantly higher than penetrance of BRCA2 6174delT (hazard ratio 2.1 [95% CI 1.2-3.8]; two-tailed P = .01). Thus, the high rate of germ-line BRCA1/BRCA2 mutations in Ashkenazi women and families with ovarian cancer is coupled with penetrance that is lower than previously estimated. This has been shown specifically for the BRCA2 6174delT mutation, but, because of ascertainment bias, it also may be true for BRCA1 mutations.     

Miniaturized electrochemical flow cells

Several novel types of miniaturized electrochemical flow cells are described. The flow cells are fabricated in fluorinated ethylene propylene using a novel technique where channels with inner diameters down to 13 microm are integrated with electrodes. The channel is formed by shrinking and simultaneous melting of a heat shrink/melt tubing around a channel template (a tungsten wire) and electrodes followed by removal of the channel template. The technique allows incorporation of different electrode materials of different sizes. The electrode configuration consists of one or two working electrodes inside the channel and a counter electrode located in the channel outlet reservoir. Electrode configurations with different channel and working electrode sizes, different electrode materials including carbon fibers, glassy carbon rods, poly(tetrafluoroethylene)/carbon composite material, and platinum wires, and different arrangements have been assembled. Hydrodynamic voltammograms in dual-electrode (generator-collector) experiments indicate good potential control for cells with 25-microm channels, while there is some iR drop in cells with 13-microm channels. Cells prepared with a cylindrical working electrode tangent and perpendicular to a flow channel show a flow rate dependence consistent with thin-layer cell behavior. Electrode areas can be made in the range of 10(-10)-10(-8) m2.     

The effect of silica on the thermal decomposition of sodium sulphate

The effect of NaCl and SiO₂ on the evolution of SO₂ and SO₃ from Na₂SO₄ at 850°C has been studied by mass spectrometry. NaCl lowers the melting point of Na₂SO₄ and increases SO₂ evolution. The evolution of SO₃ appears to result from a chemical reaction between Na₂SO₄ and SiO₂.     

Family influences on school achievement in low-income, African American children.

The authors examined the achievement-related beliefs and behaviors of parents of economically disadvantaged African American youth, and the relations among parental factors and children's academic self-concept and achievement. Forty-one children and their primary caregivers were interviewed. Parents reported on their academic-related beliefs and behaviors. Children completed measures of academic self-concept and 2 standardized achievement tests: 1 during the summer and 1 at the end of the following school year. Significant and positive relations were found between parental belief and behavior measures within the domains of reading and math; however, parental beliefs were more strongly linked with child outcomes than were parents' achievement-oriented behaviors. The relation between parental beliefs and child outcomes was not mediated by children's academic self-concept. Results are discussed in light of models of family influences on achievement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermal denaturation of ribonuclease A characterized by water 17O and 2H magnetic relaxation dispersion

Water oxygen-17 and deuteron nuclear magnetic relaxation dispersion (NMRD) measurements were used to characterize ribonuclease A (RNase A) in the course of thermal denaturation at pH 2 and 4. The structure and dynamics of the protein were probed by specific long-lived water molecules, by the short-lived surface hydration, and by labile side-chain hydrogens. The NMRD data show that native RNase A contains at least three water molecules with a mean residence time of 8 ns at 27 degreesC and an activation enthalpy of ca. 40 kJ mol-1. These water molecules are identified with some or all of six ordered water molecules partly buried in surface pockets in the crystal structure of RNase A. The loss of the 17O dispersion at higher temperatures demonstrates that, in the thermally denatured protein, these surface pockets are either not present or undergoing large structural fluctuations on a subnanosecond time scale. The relaxation dispersion step vanishes monotonically and essentially in concert with the CD denaturation curves, thus ruling out the existence of equilibrium intermediates with a substantial amount of non-native and long-lived hydration water. The NMRD data show that thermally denatured RNase A has a relatively compact but highly flexible structure. The global solvent exposure and the hydrodynamic volume of the denatured protein are much less than for maximally unfolded disulfide-intact RNase A. The NMRD data show that thermal denaturation is accompanied by a large reduction of the mean-square orientational order parameter of side-chain O-H bonds, implying that, in the denatured state, these side chains sample a wide distribution of conformational states on a subnanosecond time scale.     

JFET/SOS devices. II. Gamma-radiation-induced effects

For pt.I see ibid., vol.35, no.3, p.353-8 (1988). Enhancement-mode and depletion-mode JFETs have been fabricated on silicon-on-sapphire (SOS) substrates. When these devices are irradiated under bias with a ⁶⁰Co source, their drain currents increase, and their threshold voltages shift in such a way that the devices become more difficult to pinch off. These effects can be explained by positive charge trapping at the silicon-sapphire interface. Gate-to-drain leakage currents also increase, and can be traced to interface effects at the gate edges rather than to the passivating oxide. These effects were studied as a function of dose rate and postirradiation annealing. Deep-level transient spectroscopy (DLTS) was performed prior to and following both irradiation and anneal on both the gate-drain and gate-source p-n junctions. DLTS trap bands were observed whose characteristics depended on the depth of the depletion layer and on the total gamma dose received. The DLTS spectra suggest that a continuum of levels is responsible for the bands, and that the emission kinetics are influenced by band bending at the Si-sapphire interface. The major bands correspond in temperature with steps in capacitance-temperature curves