Retinal neurostimulator for a multifocal vision prosthesis.

A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously.     

固化剂对环氧树脂/蒙脱土纳米复合材料中蒙脱土剥离行为的影响

采用阳离子交换的方法对蒙脱土进行了有机改性，使蒙脱土由亲水性变成亲油性，并使其层间距由原来的1．2nm扩大到2．2nm。分别使用甲基四氢苯酐和4，4’-二胺基二苯基甲烷为固化剂，制备两种环氧树脂／蒙脱土纳米复合材料，并用x一射线衍射仪和透射电镜(TEM)分析有机蒙脱土在环氧树脂中的剥离行为。研究表明，固化剂的选择对有机蒙脱土的剥离行为有很大的影响，用固化剂甲基四氢苯酐和促进剂苄基二甲胺后，有机蒙脱土容易被剥离而得到剥离型的纳米复合材料，而用4，4’-二胺基二苯基甲烷固化剂未能使有机蒙脱土剥离后形成插层型纳米复合材料。     

Time-Dependent Reliability Analysis of FRP Rehabilitated Pipes

The goal of this paper is to present work that demonstrates the application of probabilistic modeling to evaluate the long-term performance of fiber-reinforced polymer (FRP) rehabilitated piping components. The time-dependent reliability index is evaluated for a fully deteriorated piping component rehabilitated with FRP considering the demands of internal fluid pressure, external soil pressure, and traffic loading. Carbon FRP (CFRP) and glass FRP (GFRP) composites are compared and the influence of material deterioration, fiber volume fraction (FVF), and variation in thickness of the composite are assessed using a first order reliability method and compared to a steel pipe under similar loading. A CFRP rehabilitation scheme having a FVF greater than 40% would be needed to exceed the as-built reliability index of a steel pipe under time-dependent composite deterioration, while no practical GFRP FVF can achieve the performance of steel pipe in the presence of time-dependent composite deterioration. Variations in the coefficient of variation (COV) can adversely affect the safety of both FRP rehabilitation schemes where an increase in COV from 10 to 30% result in decreases in the reliability index by 39.4% for CFRP (40% FVF) and 39.7% for GFRP (40% FVF).     

The Distribution of Fatty Acid Biomarkers of Dairy Intake across Serum Lipid Fractions: The Prospective Metabolism and Islet Cell Evaluation (PROMISE) Cohort

Circulating fatty acids (FA) derived largely from dairy consumption have most commonly been measured in total human serum or phospholipid (PL) fractions, and have been used as validated biomarkers of dairy intake in a growing number of epidemiological studies. Nevertheless, measurement and characterization of a wider spectrum of FA biomarkers of dairy across the four major serum lipid fractions is lacking. This study aimed to (1) quantify FA biomarkers of dairy in PL, triacylglycerol (TAG), cholesteryl ester (CE), and unesterified fatty acid (FFA) serum lipid fractions; and (2) identify potential demographic and metabolic factors that may modify the proportions of these FA across serum fractions. Baseline data from 444 adults in the PROMISE cohort were analyzed. FA biomarkers, 15:0, t16:1n-7, 18:2-c9,t11, and t18:1n-7 were quantified from serum. Dairy intake was estimated using the validated Canadian Diet History Questionnaire. Our results show that t18:1n-7 was the most abundant FA biomarker in all fractions except CE, where 18:2-c9,t11 was the most abundant. Positive correlations within fractions, and across FA in the PL, CE, and FFA fractions were found, however, TAG FA were negatively correlated with the other fractions. PL and CE FA were positively associated with dairy intake, and negatively associated with markers of dysmetabolism while, in contrast, these markers were predictors of higher TAG dairy FA. This study is the first to demonstrate distinct proportions of dairy FA in different serum lipid fractions. PL and CE FA marked dairy intake in this cohort, while TAG FA appeared to be markers of dysmetabolism.