Determining the extent of reaction by29Si NMR of abrasion-resistant hybrid sol-gel coatings based on triethoxysilane functionalized organics

Diethylenetriamine, melamine, and low molecular weight branched polyethylenimine were functionalized separately with 3-isocyanatopropyltriethoxysilane. Coatings on polycarbonate were prepared from these compounds through the sol-gel process. The extent of reaction and the relative species concentration of the trifunctional silicon atom were obtained from²⁹Si CP-MAS NMR measurements. The sol-gel reaction was found to be limited by vitrification. A variety of silicon species was present in the vitrified coating. The extent of reaction could be increased by increasing the curing temperature, curing for longer times, and increasing the acid concentration. The extent of reaction was also found to be related to the basicity of the functionalized organic backbone.     

Superparamagnetic flexible substrates based on submicron electrospun Estane® fibers containing MnZnFe?Ni nanoparticles

Flexible, elastomeric, and superparamagnetic substrates were prepared by electrospinning a solution of elastomeric polyurethane containing ferrite nanoparticles (～14 nm) of Mn? Zn? Ni. The flexible mats were characterized in terms of fiber morphology and magnetic properties. Field emission scanning electron microscopy (FESEM) indicated that the diameter of these composite fibers was ～300–500 nm. Furthermore, the back‐scattered electron FESEM images indicated agglomeration of the nanoparticles at higher wt % (ca. 17–26 wt %) loading in the electrospun fibers. The induced specific magnetic saturation and the relative permeability were found to increase linearly with increasing wt % loading of the ferrite nanoparticles on the submicron electrospun fibers. A specific magnetic saturation of 1.7–6.3 emu/g at ambient conditions indicated superparamagnetic behavior of these composite electrospun substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4935–4942, 2006     

Transient sorption by symmetrical multilaminate slabs in well-stirred semiinfinite and finite baths

Equations describing the sorption kinetics of symmetrical slabs with 2-N laminae each with constant diffusion and partition coefficients in well-stirred semiinfinite and finite baths are presented. Their application is illustrated using slabs with N = 3.     

Mercury exposure may suppress baseline corticosterone levels in juvenile birds

Mercury exposure has been associated with a wide variety of negative reproductive responses in birds, however few studies have examined the potential for chick impairment via the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis regulates corticosterone levels during periods of stress. We examined the relationship between baseline fecal corticosterone metabolite concentrations and mercury concentrations in down feathers of recently hatched (<3 days) and blood of older (15-37 days) Forster's tern (Sterna forsteri) chicks in San Francisco Bay, California. Baseline fecal corticosterone metabolite concentrations were negatively correlated with mercury concentrations in blood of older chicks (decreasing by 81% across the range of observed mercury concentrations) while accounting for positive correlations between corticosterone concentrations and number of fledgling chicks within the colony and chick age. In recently hatched chicks, baseline fecal corticosterone metabolite concentrations were weakly negatively correlated with mercury concentrations in down feathers (decreasing by 45% across the range of observed mercury concentrations) while accounting for stronger positive correlations between corticosterone concentrations and colony nest abundance and date. These results indicate that chronic mercury exposure may suppress baseline corticosterone concentrations in tern chicks and suggests that a juvenile bird's ability to respond to stress may be reduced via the downregulation of the HPA axis.     

Accurate automatic analysis of cardiac cine images

Acquisition of noncontrast agent cine cardiac magnetic resonance (CMR) gated images through the cardiac cycle is, at present, a well-established part of examining cardiac global function. However, regional quantification is less well established. We propose a new automated framework for analyzing the wall thickness and thickening function on these images that consists of three main steps. First, inner and outer wall borders are segmented from their surrounding tissues with a geometric deformable model guided by a special stochastic speed relationship. The latter accounts for Markov-Gibbs shape and appearance models of the object-of-interest and its background. In the second step, point-to-point correspondences between the inner and outer borders are found by solving the Laplace equation and provide initial estimates of the local wall thickness and the thickening function index. Finally, the effects of the segmentation error is reduced and a continuity analysis of the LV wall thickening is performed through iterative energy minimization using a generalized Gauss-Markov random field (GGMRF) image model. The framework was evaluated on 26 datasets from clinical cine CMR images that have been collected from patients with eleven independent studies, with chronic ischemic heart disease and heart damage. The performance evaluation of the proposed segmentation approach, based on the receiver operating characteristic (ROC) and Dice similarity coefficients (DSC) between manually drawn and automatically segmented contours, confirmed a high robustness and accuracy of the proposed segmentation approach. Furthermore, the Bland-Altman plot is used to assess the limit of agreement of our measurements of the global function parameters compared to the ground truth. Importantly, comparative results on the publicly available database (MICCAI 2009 Cardiac MR Left Ventricle Segmentation) demonstrated a superior performance of the proposed segmentation approach over published methods.     

Process modeling of the low‐temperature evolution and yield of polycarbosilanes for ceramic matrix composites

The volatilization of polycarbosilanes is important to the processing and performance of polymer infiltration and pyrolysis‐based ceramic matrix composites. Low molecular weight (MW) polycarbosilane is often present in preceramic polymers and enhances viscosity for the purpose of composite infiltration. Due to the volatility of low MW chains, a model was developed to semi‐empirically determine the MW distribution and then predict the mass yield and evolution of the MW distribution as a function of temperature and time for StarPCS^? SMP‐10. The enthalpy of vaporization, the temperature dependence of the enthalpy of vaporization, the temperature dependence of the normal boiling point and a representation of the molecular weight distribution were fit using a series of thermogravimetric measurements, involving isothermal holds on a particular batch of SMP‐10. Once calibrated for SMP‐10 in this fashion, the molecular weight distribution of different batches of SMP‐10 could be fit using a thermogravimetric measurement involving a reduced temperature‐time series. The model was then predictive of mass loss over time for temperatures below the onset of curing (>90°C). Understanding this volatilization enables improved SiC yield, reduced processing time and minimizing void/bubble formation.     

Metaperceptions of bias in intimate relationships.

Meta-awareness of bias in intimate partner judgments was investigated in 3 studies. In Study 1, participants rated fictional partners in happier relationships as more positively biased in their partner perceptions. In Study 2, participants thought their judgments of their own current partners were positively biased and that they were judged by their partners in a positively biased fashion. Using a sample of couples, Study 3 showed that metaperceptions of bias were anchored to actual levels of bias at the individual and relationship levels. In addition, positive bias was accentuated for traits that were more relevant to mate evaluation. These findings (as expected) suggest that positive bias in partner judgments can be a normative and consciously accessible feature of intimate relationships. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Recovery of delayed alternation in rats after lesions in medial frontal cortex and septum.

Two experiments using contingently reinforced T-maze alternation with 48 male Long-Evans and hooded rats found that (a) normal Ss, after achieving high accuracy in alternation with brief (0 sec) intertrial intervals (ITIs), dropped to chance levels with longer ITIs (90 sec) but reacquired effective alternation with additional practice; (b) small lesions in mediodorsal pregenual cortex had no effect on postoperative retention of alternation at either short or long ITIs; (c) however, small lesions in posterodorsal septum temporarily disrupted alternation at brief ITIs, whereas at long ITIs Ss chose randomly and never recovered; and (d) large lesions in medial frontal cortex disrupted retention of alternation at brief ITIs of 10 sec but significant recovery did occur with additional experience. Implications regarding task difficulty and locus of lesion for recovery of function are discussed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)