Rheological studies of nickel oxide and quartz/hematite mixture systems

This study aimed to investigate the rheology of two-mineral mixture systems as a function of pH and solid concentration. Single minerals (nickel oxide, quartz and hematite) and two-mineral systems (nickel oxide–quartz and nickel oxide–hematite) were studied. Rheology tests were conducted to investigate the effect of pH and solid concentration on shear yield stress of suspensions while zeta potential measurements of suspensions were used to explain the rheology results. Rheology results indicated that single mineral experiments showed that 5 and 10 vol.% of quartz and hematite had no shear yield stress whereas the one of nickel oxide was positive value. Shear yield stress of nickel oxide–quartz mixture and nickel oxide–hematite mixtures increased as increasing pH and solid concentration, and the value was higher than the one obtained with only nickel oxide. These results obtained with two-mineral mixture systems were explained by electrokinetic properties of the minerals, i.e. zeta potential of the minerals.     

A localised experimental–numerical technique for determining mixed mode strain energy release rates

Composite structures are being used increasingly in the aerospace industry due to their superior specific stiffness and strength. One key issue associated with such structures is delamination, and how to effectively predict this. A new method which is derived from localised test displacement data is presented to determine the mixed mode strain energy release rates of layered structures with a pre-existing crack. Images taken during experimentation of the vicinity of the crack tip are analysed at low load and high load to determine the displacement changes across the load variation. These displacements are applied as boundary conditions to a simple local numerical model including a constraint at the crack tip. The forces and displacements at the crack tip are taken as output data and combined with the Virtual Crack Closure Technique to predict strain energy release rates. Initial validation of the localised experimental–numerical technique (LENT) shows that applying experimental data to a numerical model does give reasonable agreement thus far in the established trends, and hence LENT is promising for use in determining mixed mode strain energy release rates and mode mixity ratios.     

A randomized,double-blind trial on the bioavailability of two CoQ10 formulations

The bioavailability of a single, 100 mg, dose of reduced Coenzyme Q10 (CoQH-CF) and Coenzyme Q10 formulation was compared in individuals of >60 years. Significantly higher (P < 0.001) plasma concentrations were demonstrated for the CoQH-CF formulation at 5, 6, 8, 12, 24, 48 and 72 h post-dose compared to the CoQ10 formulation. The area under the curve (AUC) of reduced and total Coenzyme Q10 was significantly higher (P < 0.001) in subjects administered CoQH-CF resulting in 4.3-fold higher plasma AUC_{0–72 h} (430% increase) in subjects receiving CoQH-CF compared to subjects receiving Coenzyme Q10. Oxidized Coenzyme Q10 in plasma was higher (P < 0.001) in subjects receiving CoQH-CF compared to subjects receiving Coenzyme Q10 resulting in a 3.3-fold higher plasma AUC_{0–72 h} (329% increase). Total CoQ10 reached maximum plasma concentrations 15.5 ± 19.6 h after supplementation with CoQH-CF and 26.5 ± 25.8 h after supplementation with Coenzyme Q10, respectively. Thus, reduced Coenzyme Q10 liquid soft gel formulation was found to be superior to the commercial formulation of Coenzyme Q10 for bioavailability.     

Screening for noncovalent ligand-receptor interactions by electrospray ionization mass spectrometry-based diffusion measurements

The application of a novel method for the identification of low-molecular-weight noncovalent ligands to a macromolecular target is reported. This technique is based on the measurement of analyte diffusion coefficients by electrospray mass spectrometry (ESI-MS) (Clark et al., Rapid Commun. Mass Spectrom. 2002, 16, 1454-1462). Potential ligands have large diffusion coefficients as long as they are free in solution. Binding to a macromolecular target, however, drastically reduces the diffusional mobility of any ligand species. Mixtures containing six different saccharides [ribose, rhamnose, glucose, maltose, maltotriose, and N,N',N'-triacetylchitotriose (NAG(3))] were screened for noncovalent binding to lysozyme. Of these six compounds, only NAG(3) is known to bind to the protein. In "direct" binding tests, NAG(3) shows a significantly reduced diffusion coefficient in the presence of the protein. No changes were observed for any of the other saccharides. In a second set of experiments, the use of a "competition" screening method was explored in which mixtures of candidate saccharides were tested for their ability to displace a reference ligand from the target. The addition of NAG(3)-containing mixtures significantly increased the diffusion coefficient of the reference ligand NAG(4) (N,N',N',N'-tetraacetylchitotetrose), whereas mixtures that did not contain NAG(3) had no effect. These data clearly indicate the potential of ESI-MS-based diffusion measurements as a novel tool to screen compound libraries for binding to proteins and other macromolecular targets. In contrast to conventional ESI-MS-based ligand-receptor binding studies, this method does not rely on the preservation of noncovalent interactions in the gas phase.     

Supportive friendships moderate the association between stressful life events and sexual risk taking among African American adolescents.

Objective: This study examined whether uncontrollable stressful life events were associated with sexual risk taking among adolescents across a 1-year period, and whether supportive friendships modified associations. Design: Participants were 159 sexually active African American adolescents (57% male; mean age [SD] = 17.0 [1.5] years at baseline). Participants were recruited for in-person interviews through random digit dialing in one inner-city neighborhood characterized by high rates of poverty and crime relative to the surrounding city. Main Outcome Measures: Dependent variables included substance use before sexual activity and inconsistent condom use. Results: Among adolescents who reported low levels of supportive friendships, uncontrollable stressors were associated with greater levels of sexual risk taking over time. In contrast, uncontrollable stressors were not associated with sexual risk taking among adolescents who reported high social support from friends; risk taking was typically moderate to high among these adolescents. Conclusion: Different processes may explain sexual risk taking among adolescents with varying levels of social support from friends. Adolescents with low support may be prone to engagement in health risk behavior as a stress response, while adolescents with high support may engage in risk behavior primarily due to peer socialization of risk. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to recognize talkers from natural, sinewave, and reversed speech samples.

In 5 experiments, the authors investigated how listeners learn to recognize unfamiliar talkers and how experience with specific utterances generalizes to novel instances. Listeners were trained over several days to identify 10 talkers from natural, sinewave, or reversed speech sentences. The sinewave signals preserved phonetic and some suprasegmental properties while eliminating natural vocal quality. In contrast, the reversed speech signals preserved vocal quality while distorting temporally based phonetic properties. The training results indicate that listeners learned to identify talkers even from acoustic signals lacking natural vocal quality. Generalization performance varied across the different signals and depended on the salience of phonetic information. The results suggest similarities in the phonetic attributes underlying talker recognition and phonetic perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of biodegradable core–clad borosilicate glass fibers with round and rectangular cross-section

Here, we report on core–clad bioactive borosilicate fibers, that we have prepared both with round and rectangular cross-section profile. The exposed approach, which relies on the stacking and drawing of glass slabs, demonstrates our ability to develop bioactive-based glass fibers with tailored cross-section profiles. Tens-of-meters-long fibers were successfully drawn, although suffering from elevated losses in the case of the rectangular ones. The response of the fibers in simulated body fluid was studied for both geometries. We found that a round cladding can act as protective layer, tempering effects of the corrosion. We also noticed that rectangular fibers are more prone to degradation, the enhanced corrosion beginning from their sharp corners as they accumulated residual tensile stress during drawing. To the best of our knowledge, this is the first report on the effect of residual tensile stresses from surface tension deformations applied to the corrosion of rectangular fibers. As geometry plays a critical role on the biodegradation behavior of the fiberglass, we believe the enclosed results could lead to the design of fiber devices with tailored cross-section profile in order to tune their rate of degradation on solely based geometrical effects.