Effects of Ketone Bodies on Brain Metabolism and Function in Neurodegenerative Diseases

Under normal physiological conditions the brain primarily utilizes glucose for ATP generation. However, in situations where glucose is sparse, e.g., during prolonged fasting, ketone bodies become an important energy source for the brain. The brain’s utilization of ketones seems to depend mainly on the concentration in the blood, thus many dietary approaches such as ketogenic diets, ingestion of ketogenic medium-chain fatty acids or exogenous ketones, facilitate significant changes in the brain’s metabolism. Therefore, these approaches may ameliorate the energy crisis in neurodegenerative diseases, which are characterized by a deterioration of the brain’s glucose metabolism, providing a therapeutic advantage in these diseases. Most clinical studies examining the neuroprotective role of ketone bodies have been conducted in patients with Alzheimer’s disease, where brain imaging studies support the notion of enhancing brain energy metabolism with ketones. Likewise, a few studies show modest functional improvements in patients with Parkinson’s disease and cognitive benefits in patients with—or at risk of—Alzheimer’s disease after ketogenic interventions. Here, we summarize current knowledge on how ketogenic interventions support brain metabolism and discuss the therapeutic role of ketones in neurodegenerative disease, emphasizing clinical data.     

Experimental and numerical assessment of gate-lag phenomena in AlGaAs-GaAs heterostructure field-effect transistors (FETs)

Gate-lag effects are characterized in AlGaAs-GaAs heterostructure field-effect transistors (HFETs) by means of measurements and numerical device simulations. Gate lag increasingly affects device switching at increasing ungated recess extension, suggesting that responsible deep levels be located at the ungated, recess surface of the HFET. Gate lag diminishes by making the off-state gate-source voltage less negative and by increasing the drain bias. Increasing the temperature makes the turn-on transient faster at low drain bias, while slightly delaying it at high drain bias. Numerical device simulations accounting for acceptor-like traps at the ungated surface predict gate-lag phenomena in good agreement with experiments, reproducing correctly the observed bias and temperature dependences. Simulations show that surface states behave, during the turn-on transient, as hole traps capturing holes attracted at the ungated surface by the negative trapped charge.     

Positive temperature dependence of the electron impact ionizationcoefficient in In0.53Ga0.47As/InP HBTs

Impact ionization is a major limiting factor to the maximum operating voltage of InGaAs-based, high-speed transistors. In this work, data on the positive temperature dependence of the electron impact ionization coefficient α_n in In_0.53Ga_0.47As at medium-low electric fields are reported for the first time. The increase of α_n with temperature is opposite to the behavior normally observed in most semiconductors. This anomalous behavior implies the onset of a positive feedback between power dissipation and avalanche generation which may adversely affect the power handling capability of In_0.53Ga _0.47As-based devices, and which should be taken into account in device thermal modeling. In the experimental procedure, based on the measurement of the multiplication factor M-1 in npn In_0.53Ga _0.47As/InP Heterojunction Bipolar Transistors (HBT), particular care has been taken in order to rule out possible spurious, temperature-dependent contributions to the measured multiplication current     

Systematic characterization of Cl2 reactive ion etchingfor improved ohmics in AlGaN/GaN HEMTs

Pre-metal-deposition reactive ion etching (RIE) was performed on an Al_0.3Ga_0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs     

The impacts of a GTL plant on Brazil's oil products supply and refinery expansion

This paper assesses the impacts of a GTL plant on the expansion of Brazil's oil refining segment. The GTL plant (50,000 bpd) was sized to start up operations in 2015, producing diesel and naphtha through the indirect route (FT-synthesis). This plant will consume the non-associated natural gas production from the recent discoveries at the Santos Basin (around 419 Bm³), and the associated gas production from the Campos Basin. Both basins are located in the Southeast of Brazil, the most populated, rich and industrialized region of the country. Two different criteria for refinery expansion were simulated in order to meet oil product demand scenarios. Findings show that depending on the refinery expansion criteria considered GTL will play a fundamental hole to meet the oil product demand forecast to Brazil in the next 10 years.     

Influence of impact-ionization-induced base current reversal onbipolar transistor parameters

In this paper we describe a set of measurements representing a complete characterization of impact-ionization effects in bipolar transistors. We demonstrate that impact-ionization significantly influences the dependence of base resistance on current and voltages applied to the device. A dc method for the simultaneous extraction of all parasitic resistances in bipolar transistors is presented. The method can separate the influence of current-crowding on the base resistance from that of base width and conductivity modulation; the collector parasitic resistance is measured in the active region. Starting from the parameters extracted by means of these techniques, a complete and accurate circuit-model of impact-ionization effects can be defined     

Impact of parental discipline methods on the child's internalization of values: A reconceptualization of current points of view.

It is generally argued that parental use of specific discipline techniques (e.g., reasoning vs power assertion) differentially affects a child's internalization. This article offers an expanded formulation. Internalization as a result of discipline is proposed to be based on a child's accurate perception of the parental message and acceptance or rejection of it. Mechanisms promoting acceptance are perceptions of the parent's actions as appropriate, motivation to accept the parental position, and perception that a value has been self-generated. Features of the misdeed, discipline technique, child, and parent that affect accurate perception and acceptance–rejection are outlined. Other goals besides internalization, such as movement beyond the parent's position, maintenance of the child's self-esteem, and maintenance of the parent–child relationship, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Economic Comparison of NdFeB and Hard Ferrites in Automotive Applications

With the increasing use of electric motors in automobiles—in some cases as many as 100 electric motors per vehicle—alternatives to ferrite magnetic materials are under consideration. If more powerful magnetic materials could be implemented, size reductions in these motors could result in curb weight reductions that lead to improved fuel economy. NdFeB magnets are attractive as potential replacement materials, due to their higher flux density and thus smaller required size; however, high material costs have limited their implementation. To investigate the economic competitiveness of alternative magnetic materials, technical cost models (TCMs) were developed and used to examine the manufacturing economics related to the production of both NdFeB and ferrite magnets. Results from the TCMs are used to identify the cost drivers and opportunities for cost reductions. Subsequent investigations will include effects on vehicle fuel efficiency, and the environmental impact of magnet manufacture and disposal.     

A profile of science in Brazil

The Brazilian contribution to publications in science and humanities increased from 0.29% of the worldwide total in 1981 to 0.46% in 1993. In science, but not in humanities, Brazilian publications tend to follow the world publication trend; thus, during the period 1981–1993, 57.9% of Brazilian publications were in life sciences, 35.4% in exact sciences, 3.9% in earth sciences and 2.9% in humanities. The ten institutions with the largest number of publications are universities, which account for half of the all Brazilian publications. The total number of authors on the Brazilian 1981–1993 publications was 52,808. Among these 57.8% appear in only one publication and 17.5% have their publications cited more than 10 times.     

Project Preserve: A Program to Retain Minorities in Engineering

A national effort, begun in 1972 to increase the numbers of minorities in engineering, has made substantial progress, but the attrition for minority students is still estimated at 70%. To address the problem, Project Preserve was designed to confirm, by demonstration, the results of previous research showing that the combination of explicit cognitive development, close relationships with faculty, and strong bonds to an institution can raise the performance and retention of minority engineering students. The project enrolled over 100 minority engineering students who had been dismissed from freshman engineering studies on other campuses or placed on academic probation, but whose high school grades and SAT scores were indicative of success. They were channeled into participating institutions chosen for their record of basic support services, willingness to augment or restructure those services, and for variation among institutional variables: Xavier University of Louisiana (XU), California State University at Northridge (CSUN), and City College of the City University of New York (CCNY). A 2 1/2 hour battery of evaluation instruments was given to 79 students upon entry and to 26 students upon their attaining Junior status after two years in the program. The results demonstrated that: (1) an admirable 64% of would-be drop outs had achieved Junior status or were still enrolled in engineering at the conclusion of two years; (2) cognitive growth occurred on basic memory skills and one critical thinking skill, but there were institutional differences in the extent of intellectual development, with Xavier producing the most change; (3) closer relationships to faculty were outcomes; (4) the most positive feelings about, or bonding to, the institution occurred at Xavier University, while the most evidence of social participation and connectedness occurred at CSUN.