Relating indices of knowledge structure coherence and accuracy to skill-based performance: Is there utility in using a combination of indices?

The authors examined the relative criterion-related validity of knowledge structure coherence and two accuracy-based indices (closeness and correlation) as well as the utility of using a combination of knowledge structure indices in the prediction of skill acquisition and transfer. Findings from an aggregation of 5 independent samples (N = 958) whose participants underwent training on a complex computer simulation indicated that coherence and the accuracy-based indices yielded comparable zero-order predictive validities. Support for the incremental validity of using a combination of indices was mixed; the most, albeit small, gain came in pairing coherence and closeness when predicting transfer. After controlling for baseline skill, general mental ability, and declarative knowledge, only coherence explained a statistically significant amount of unique variance in transfer. Overall, the results suggested that the different indices largely overlap in their representation of knowledge organization, but that coherence better reflects adaptable aspects of knowledge organization important to skill transfer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling semiconductor heterojunctions in equilibrium

Computation of the equilibrium electrostatic potential and energy band diagram of semiconductor devices with nonuniform composition is considered. We first establish the relationship between the electrostatic potential and the energy band edges and then derive a Poisson-Boltzmann equation for the electrostatic potential. Although the equation is more general, we consider only the simple example of an abrupt heterojunction diode in detail. An analytical solution for doubly-intrinsic, abrupt heterojunctions is also presented. The modeling approach is then generalized to include Fermi-Dirac statistics for free carriers. We also discuss the application of the formulation to a variety of heterojunction devices (e.g. heavily doped silicon and gate-modulated devices).     

Scaling the microwave plasma-assisted chemical vapor diamond deposition process to 150–200 mm substrates

The scale up of two microwave plasma assisted chemical vapor deposition processes from 75 mm to 200 mm substrates is investigated. A thermally floating 2.45 GHz reactor is scaled up by increasing its physical size by a factor of 2.7 and exciting the reactor with 915 MHz microwave energy. Two processes are investigated, 1) the deposition of ultananocrystalline diamond films (UNCD) and 2) the deposition of polycrystalline diamond films (PCD). Gas chemistries of argon/methane/hydrogen were used for UNCD deposition and hydrogen/methane was used for PCD deposition. Experimental pressures range from 40–110 Torr while microwave power input ranged from 1.9–7 kW resulting in steady state substrate temperatures from 630–950 °C. Uniform deposition was demonstrated over 150–200 mm substrates, i.e. thickness variations of 4% over 150 mm and 6% over 200 mm were achieved with deposition rates ranging from 30–460 nm/h. Low temperature deposition at 633 °C was achieved and thereby demonstrated the potential of integrating the process with temperature sensitive materials. A comparison of the power densities between the two reactors indicates that the large reactor operates at five to nine times lower discharge power densities than smaller reactors suggesting improved deposition efficiencies.     

A combined current density technique for the electrochemical oxidation of perfluorooctanoic acid (PFOA) with boron‐doped diamond

Perfluoroalkyl substances (PFAS) have unique properties that limit their degradability in the environment. One of these PFAS is an acid (PFOA). Electrochemical oxidation is a promising method for remediation, but energy costs are high. To limit the energy consumption, this study used a boron‐doped diamond (BDD) electrode stack and a combined current density technique that employed 50 mA/cm² for the first 0.25 hours then lowered the current density to 1, 5, or 10 mA/cm². This technique is similar to one developed previously; however, that method was only developed for compounds comprising of carbon, oxygen and nitrogen, whereas PFAS have the addition of fluorine. For the degradation of PFOA, the combined current density of 50 and 5 mA/cm² (50&5) allowed for a 37% reduction in energy usage to obtain 75% defluorination compared to using 50 mA/cm² alone. Further investigation into remediating an ion‐exchange regeneration solution shows great promise.     

cDNA of eight nuclear encoded subunits of NADH:ubiquinone oxidoreductase: human complex I cDNA characterization completed

Brief elevation in postsynaptic calcium in hippocampal CA1 neurons leads to prolonged changes in synaptic strength. The calcium may enter the postsynaptic neuron via different routes, such as voltage-gated calcium channels or glutamate receptor channels of N-methyl-D-aspartate type, and/or be released from intracellular stores. The manner in which the synapse is altered, leading to the expression of an enhanced/depressed synaptic strength, is still unclear. The present study, performed using whole-cell recording from CA1 pyramidal cells of three- to five-week-old guinea-pigs, shows that postsynaptic depolarization alone, allowing for calcium influx through voltage-gated calcium channels, leads to a synaptic potentiation characterized by an altered time-course of the evoked excitatory synaptic response, an unaltered coefficient of variation of that response and a decreased paired-pulse facilitation likely related to a postsynaptic mechanism. These characteristics contrasted with those of long-term potentiation induced via activation of N-methyl-D-aspartate receptor channels, where the time-course was unaltered, the coefficient of variation was decreased and no change in paired-pulse facilitation was observed. Synapses can thus have mechanistically separate, but co-existent, potentiations of synaptic transmission initiated from separate sources for postsynaptic calcium.     

Manufacturing cost analysis of optoelectronic integrated circuits

A modified version of a recently proposed cost model for millimeter and microwave integrated circuits is applied to the cost analysis of optoelectronic integrated circuits. The particular example that is examined is a four-function receiver module for optical interconnects. On the basis of this analysis, it is concluded that the lowest receiver module cost, for any level of production, is achieved by integrating the receiver at the rate of two functions per chip, rather than a full single-chip integration of the receiver. This observation is the result of the loss of functional yield and a reduction of the number of die per wafer incurred by the increased die size     

The first nuclear-encoded complex I mutation in a patient with Leigh syndrome

Nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase (complex I) is the largest multiprotein enzyme complex of the respiratory chain. The nuclear-encoded NDUFS8 (TYKY) subunit of complex I is highly conserved among eukaryotes and prokaryotes and contains two 4Fe4S ferredoxin consensus patterns, which have long been thought to provide the binding site for the iron-sulfur cluster N-2. The NDUFS8 cDNA contains an open reading frame of 633 bp, coding for 210 amino acids. Cycle sequencing of amplified NDUFS8 cDNA of 20 patients with isolated enzymatic complex I deficiency revealed two compound heterozygous transitions in a patient with neuropathologically proven Leigh syndrome. The first mutation was a C236T (P79L), and the second mutation was a G305A (R102H). Both mutations were absent in 70 control alleles and cosegregated within the family. A progressive clinical phenotype proceeding to death in the first months of life was expressed in the patient. In the 19 other patients with enzymatic complex I deficiency, no mutations were found in the NDUFS8 cDNA. This article describes the first molecular genetic link between a nuclear-encoded subunit of complex I and Leigh syndrome.     

Boron doped diamond deposited by microwave plasma-assisted CVD at low and high pressures

Boron doped diamond is deposited over a range of pressures and chemistries including pressures from 35–120 Torr and gas chemistries including hydrogen–methane–diborane and argon–methane–hydrogen–diborane mixtures. The diamond deposition system is a 2.45 GHz microwave resonant cavity system. Diborane (B₂H₆) gas chemistry has been utilized with flow rates of 2.5–100 ppm. At low pressures of 35 Torr polycrystalline films are deposited using a feed gas mixture of hydrogen and 0.5% methane. At moderate pressures of 95 Torr, diamond films are grown using 60% Ar, 39% H₂ and 1% CH₄. For the high pressure experiments of 120 Torr, polycrystalline films are deposited using 98% H₂ and 2% CH₄. The deposition rate ranges from 0.3 to 1.6 μm/h. This investigation describes the relationship of the diborane flow rate and pressure versus the resulting film morphology, electrical properties, and morphology of the deposited films. The deposition of boron-doped polycrystalline diamond is done on 5 cm diameter silicon and silicon dioxide coated substrates. The resistivity spatial variation across the wafer was ± 5% indicating a good uniformity.     

The influence of the surface texture of hydrogen-free tetrahedral amorphous carbon films on their wear performance

Hydrogen-free and predominantly tetrahedrally bonded amorphous carbon thin films (ta-C) are excellent coatings to protect surfaces from wear due to their low coefficient of friction and high hardness. Since these coatings may be several times harder than common engineering materials counterpart wear can be significant. Therefore the surface texture of the ta-C coating is critical to wear applications. While the surface roughness is an important factor, the paper shows that other surface texture parameters have to be considered as well to predict the wear performance of the coating. Wear data are compared of as deposited, polished and brushed ta-C coatings. The results show that typically referenced average values for the surface roughness such as R_a and R_z may prove insufficient to reliably predict the wear behavior of the coating. Additional parameters describing the surface texture such as the “Skewness” (R_sk) and “Kurtosis” (R_ku) can provide relevant information. For example, a brushed ta-C surface with an average roughness of R_a = 31 nm showed a tenfold improved wear performance over a polished ta-C surface with an average roughness of R_a = 10 nm. This phenomenon is explained by analyzing the R_sk and R_ku data, which prove to more closely capture the post-treatment specific changes to the surface texture of the coatings.     

化妆品防腐效能测试

防腐体系通常是配方师设计配方时最后考虑的部分，同时却也是问题产生时最先被想到的因素。在化妆品工业领域中，防腐体系在保护产品安全和消费者健康方面发挥着极为重要的作用。可是，大众却对防腐体系有着众多的非议和误解。因此，即使是很有经验的配方师，在为配方设计防腐体系时也经常加量过高过低甚至选用不当。