Subunit stoichiometry of a core conduction element in a cloned epithelial amiloride-sensitive Na+ channel

The molecular composition of a core conduction element formed by the alpha-subunit of cloned epithelial Na+ channels (ENaC) was studied in planar lipid bilayers. Two pairs of in vitro translated proteins were employed in combinatorial experiments: 1) wild-type (WT) and an N-terminally truncated alphaDeltaN-rENaC that displays accelerated kinetics (tauo = 32 +/- 13 ms, tauc = 42 +/- 11 ms), as compared with the WT channel (tauc1 = 18 +/- 8 ms, tauc2 = 252 +/- 31 ms, and tauo = 157 +/- 43 ms); and 2) WT and an amiloride binding mutant, alphaDelta278-283-rENaC. The channels that formed in a alphaWT:alphaDeltaN mixture fell into two groups: one with tauo and tauc that corresponded to those exhibited by the alphaDeltaN-rENaC alone, and another with a double-exponentially distributed closed time and a single-exponentially distributed open time that corresponded to the alphaWT-rENaC alone. Five channel subtypes with distinct sensitivities to amiloride were found in a 1alphaWT:1alphaDelta278-283 protein mixture. Statistical analyses of the distributions of channel phenotypes observed for either set of the WT:mutant combinations suggest a tetrameric organization of alpha-subunits as a minimal model for the core conduction element in ENaCs.     

Impacting the future of power engineering: a focus at thepre-college level

The power industry is undergoing many new and exciting challenges. It is expected that these challenges will continue to exist and new ones will arise as the systems are pushed for greater efficiencies and economics. Therefore, as the workforce evolves from one generation to the next, it will be of paramount importance to have a continuing flow of competent power engineers available for the industry. However, to accomplish this is no small matter. The power industry must compete for students among declining engineering enrollments and what some students may view as more “glamorous” engineering professions. Therefore, it is incumbent upon the power engineering educators to seek methods of ensuring that the flow of competent power engineers is there to meet the needs of the future power industry. The purpose of this paper is to illustrate an approach taken to start to attract students at the pre-college level (high school) to careers in electric power engineering. This paper summarizes the results of a workshop designed to work with science teachers to help them better understand electricity and magnetism, show them ways of teaching these basic sciences, and relate how these skills are used by practicing electrical power engineers     

An improved fault analysis algorithm for unbalanced multi-phasepower distribution systems

The results of an improved method for fault calculations in unbalanced multi-phase power distribution systems containing nonutility generators and large induction motor loads are presented in this paper. The method utilizes a combined time- and frequency-domain analysis approach to produce results that are superior to those obtained in “classical” fault analysis without the large increase in computer time with complete time-domain solutions. Sources and loads can be represented by either classical frequency-domain models or detailed differential equation models. The potentially unbalanced power distribution system is represented by an admittance matrix formed using a linear graph-based application of AC circuit theory. The time-domain differential equation source and load models are interfaced with the frequency-domain distribution system model using time series analyses to estimate equivalent voltage and current phasors from discrete data sets     

Microfluidic transendothelial electrical resistance measurement device that enables blood flow and postgrowth experiments

Transendothelial electronic resistance (TEER) measurements are performed across a cell layer immobilized on a microfluidic device that also enables the cell layer to interact with a flowing stream of red blood cells (RBCs). A bipolar pulsed square wave potential is applied across a monolayer of bovine pulmonary artery endothelial cells, and the resulting current response is measured and integrated. The overall impedance of the cell layer provides an indicator of cell layer integrity. After cell seeding on the device, a decrease in TEER signal from 22.3 ± 1.6 μC to 3.5 ± 0.4 μC (corresponding to a resistance of 40.9 ± 2.9 Ω·cm(2) to 259.1 ± 27.4 Ω·cm(2)) was observed after 8 h of cell growth. Intracellular nitric oxide (NO) production by the immobilized endothelial cells that had reached confluence was 34% higher than those cells that had not reached confluence, as indicated by the integrated TEER system. Importantly, this NO production by the confluent endothelium was stimulated by ATP released from RBCs flowing under the endothelial cells. In this construct, the described microfluidic device enables both a TEER-based evaluation of cell layer integrity and molecularly communicated interactions of these cells with a flowing stream of blood components.     

The fracture and fatigue of composite structures

Successful design of laminated composite structures is critically dependent upon knowledge of the structural failure mechanisms. An experimental program has been executed to determine the fracture and lifetime characteristics of the material and attachment concepts. The lifetime characteristics have been determined by using a digital computer to stimulate a random load history and closed loop control of the test equipment. Both the fracture and lifetime characteristics observed indicate a need for a change in rational for the design of composite structures. These physical characteristics and their relationship to the design of composite structures will be discussed.     

An observer-based psychoacoustic procedure for use with young infants.

This article describes an observer-based technique for assessing auditory capacities of infants from 3 to 12 months of age. This technique, referred to as the Observer-based Psychoacoustic Procedure (OPP), combines features of the Forced-choice Preferential Looking technique developed by Teller (1979) and of Visual Reinforcement Audiometry (Moore, Thompson, & Thompson, 1975). The rationale behind the procedure and the specific techniques used in its application are detailed here. Psychometric functions and thresholds for pure-tone detection and frequency discrimination obtained with OPP are also presented. The results for 6-month-olds are compared with results from previous studies employing a visually reinforced head-turn procedure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fact-oriented modelling for data analysis

Abstract. Although entity-relationship modelling is the most popular means of specifying the conceptual schema for the data perspective of an information system, an alternative design approach known as fact-oriented modelling appears to offer advantages. This paper provides an overview of fact-oriented modelling, including some recent revisions and an evaluation of how the method has coped with large-scale practical applications. One distinguishing feature of the approach is its emphasis on natural verbalization of information examples in terms of elementary facts. This notion of elementarity is clarified to cater for a problematic case involving compositely identified object types. Finally, the algorithm for mapping a conceptual to a relational schema is revised to cater for lazy object types.     

Experimental investigation on the effects of study and testing on student learning, retention, and ratings of instruction.

Measures of learning and retention were obtained in ongoing college-level classes along with student ratings of instruction. Analyses of the resulting data from 90 undergraduates show that Ss who studied for and took a test not only achieved more but also retained their learning longer than Ss who "studied in order to learn rather than for a test." However, ratings of the method of instruction were lower when Ss were tested. It is concluded that testing is valuable in the learning process, but teachers who test might expect less positive evaluations from their students. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)