Caffeine Versus Methylphenidate and d-Amphetamine in Minimal Brain Dysfunction: A Double-Blind Comparison

The authors compared the efficacy of caffeine, methylphenidate, and d-amphetamine in children with minimal brain dysfunction using a double-blind crossover design. The slight improvement with caffeine was not significantly better than placebo. Both prescription drugs resulted in significant improvement and were significantly superior to caffeine. The authors suggest that the discrepancy between these results and an earlier, more optimistic report may stem from the use in this study of pure caffeine rather than whole coffee

Design and Application of Variational Representations

Variability is an important and widely studied topic across domains such as version control, software product lines, and metaprogramming. This dissertation presents an investigation into the process of systematically adding variability to data structures and programs, leading to guidelines for variational data structures and implications for programs that create, manipulate, and otherwise consume them. In particular, it focuses on the tradeoffs between expressiveness and efficiency that must be managed when designing these structures and programs. While more general and expressive variational programs can simplify the work programmers need to do, they are inevitably less efficient than approaches tailored to specific scenarios and domains. This means that these approaches to variability are more appropriate for a certain class of applications than others. While efficiently consuming variational data remains a challenge, concentrating on domains that focus on generating variational artifacts has been effective. We demonstrate this directly with two example application domains, namely variational pictures and variational data visualization

Two stage catalytic combustor

A catalytic combustor (14) includes a first catalytic stage (30), a second catalytic stage (40), and an oxidation completion stage (49). The first catalytic stage receives an oxidizer (e.g., 20) and a fuel (26) and discharges a partially oxidized fuel/oxidizer mixture (36). The second catalytic stage receives the partially oxidized fuel/oxidizer mixture and further oxidizes the mixture. The second catalytic stage may include a passageway (47) for conducting a bypass portion (46) of the mixture past a catalyst (e.g., 41) disposed therein. The second catalytic stage may have an outlet temperature elevated sufficiently to complete oxidation of the mixture without using a separate ignition source. The oxidation completion stage is disposed downstream of the second catalytic stage and may recombine the bypass portion with a catalyst exposed portion (48) of the mixture and complete oxidation of the mixture. The second catalytic stage may also include a reticulated foam support (50), a honeycomb support, a tube support or a plate support

3D Progressive Damage Modeling for Laminated Composite Based on Crack Band Theory and Continuum Damage Mechanics

A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads

Effect of ion implantation on the oxygen overpotential of Ni anodes

This work investigates the use of ion implantation for decreasing the oxygen-overpotential of nickel anodes. It is part of a search for improved electrocatalysts to increase the energy efficiency of the H2O electrolysis process for producing H2 gas. A series of Ni electrodes were implanted at room temperature with various doses of 50 keV Ag+, Li+, He+, or Kr+ ions. Polarization measurements were then made in a suitable electrolysis cell over a wide range of current densities, using aqueous KOH solution (30%) at 80 °C as electrolyte. In the case of Ag+ implants, Rutherford backscattering (RBS) measurements were performed before and after electrolysis in order to monitor the amount and depth distribution of the Ag atoms. For Li+ or He+ implantation, we observe a negligible change in the measured polarization curves. For high dose Kr+ implants (I0^18 ions cm^(-2)) the Ni electrode exhibits an increase in overpotential, indicating that excessive damage and/or sputtering of the surface causes some deterioration in electrode behaviour. For Ag+ implants, on the other hand, we observe a large (20–40%) reduction in the total overpotential at implant doses of 0.3–4*10^16 Ag+ cm^(-2). Furthermore, RBS measurements show that prolonged electrolysis at higher current density (24–28 h at 1A/cm^(-2)) produces only a small loss of Ag and shifts its depth profile to significantly larger depths. Supplementary nuclear microanalyses, using the 16O(d, p )17O reaction, show that the shift in Ag profile is correlated with the growth of an anodic nickel oxide (+carbon) layer during electrolysis. In one set of runs, the Ni electrodes were thermally oxidized before Ag+ implantation in order to form an 400 Å layer of NiO at the surface. In this case, we observe a somewhat smaller reduction in overpotential following Ag+ implantation; furthermore, a large loss of Ag into the electrolyte occurs during the subsequent electrolysis

High-Temperature Structures, Adhesives, and Advanced Thermal Protection Materials for Next-Generation Aeroshell Design

The next generation of planetary exploration vehicles will rely heavily on robust aero-assist technologies, especially those that include aerocapture. This paper provides an overview of an ongoing development program, led by NASA Langley Research Center (LaRC) and aimed at introducing high-temperature structures, adhesives, and advanced thermal protection system (TPS) materials into the aeroshell design process. The purpose of this work is to demonstrate TPS materials that can withstand the higher heating rates of NASA's next generation planetary missions, and to validate high-temperature structures and adhesives that can reduce required TPS thickness and total aeroshell mass, thus allowing for larger science payloads. The effort described consists of parallel work in several advanced aeroshell technology areas. The areas of work include high-temperature adhesives, high-temperature composite materials, advanced ablator (TPS) materials, sub-scale demonstration test articles, and aeroshell modeling and analysis. The status of screening test results for a broad selection of available higher-temperature adhesives is presented. It appears that at least one (and perhaps a few) adhesives have working temperatures ranging from 315-400 C (600-750 F), and are suitable for TPS-to-structure bondline temperatures that are significantly above the traditional allowable of 250 C (482 F). The status of mechanical testing of advanced high-temperature composite materials is also summarized. To date, these tests indicate the potential for good material performance at temperatures of at least 600 F. Application of these materials and adhesives to aeroshell systems that incorporate advanced TPS materials may reduce aeroshell TPS mass by 15% - 30%. A brief outline is given of work scheduled for completion in 2006 that will include fabrication and testing of large panels and subscale aeroshell test articles at the Solar-Tower Test Facility located at Kirtland AFB and operated by Sandia National Laboratories. These tests are designed to validate aeroshell manufacturability using advanced material systems, and to demonstrate the maintenance of bondline integrity at realistically high temperatures and heating rates. Finally, a status is given of ongoing aeroshell modeling and analysis efforts which will be used to correlate with experimental testing, and to provide a reliable means of extrapolating to performance under actual flight conditions. The modeling and analysis effort includes a parallel series of experimental tests to determine TSP thermal expansion and other mechanical properties which are required for input to the analysis models

Stress coping style does not determine social status, but influences the consequences of social subordination stress

Chronic stress exposure may have negative consequences for health. One of the most common sources of chronic stress is stress associated with social interaction. In rodents, the effects of social stress can be studied in a naturalistic way using the visual burrow system (VBS). The way an individual copes with stress, their “stress coping style”, may influence the consequences of social stress. In the current study we tested the hypothesis that stress coping style may modulate social status and influence the consequences of having a lower social status. We formed 7 VBS colonies, with 1 proactive coping male, 1 passive coping male, and 4 female rats per colony to assess whether a rat's coping style prior to colony formation could predict whether that individual is more likely to become socially dominant. The rats remained in their respective colonies for 14 days and the physiological and behavioral consequences of social stress were assessed. Our study shows that stress coping style does not predict social status. However, stress coping style may influence the consequences of having a lower social status. Subordinate passive and proactive rats had distinctly different wound patterns; proactive rats had more wounds on the front of their bodies. Behavioral analysis confirmed that proactive subordinate rats engaged in more offensive interactions. Furthermore, subordinate rats with a proactive stress coping style had larger adrenals, and increased stress responsivity to a novel acute stressor (restraint stress) compared to passive subordinate rats or dominant rats, suggesting that the allostatic load may have been larger in this group

From infancy to adolescence: fifteen years of continuous treatment with hydroxyurea in sickle cell anemia

Despite documented laboratory and clinical benefits of hydroxyurea for children with sickle cell anemia (SCA), the drug\u27s long-term safety and efficacy remains poorly defined. The HUSOFT trial and extension study examined feasibility, toxicity, and hematological efficacy of hydroxyurea in infants with SCA.This report describes HUSOFT participants who have continued hydroxyurea therapy for 15 years. With IRB approval, medical records were reviewed for clinical, laboratory, and growth parameters.Twenty-eight infants enrolled in the original 2-year HUSOFT study received open-label liquid hydroxyurea at 20 mg/kg/day; 17 completed the extension study with dose escalation to 30 mg/kg/day. Eight of these 17 (6 girls and 2 boys, all HbSS) have continued on daily hydroxyurea for at least 15 years (median age at last follow-up 17.6 years) without interruption. All hematologic indices (Hb concentration, mean corpuscular volume (MCV), fetal hemoglobin) showed sustained effect after 15 years. The median maximum tolerated dose of hydroxyurea has decreased from 30 to 26 mg/kg/day (range 19.5-31.2); neutropenia [absolute neutrophil count (ANC) \u3c 1.0 x 10/L] prompting temporary drug discontinuation occurred a total of 10 times in 4 subjects and there was no severe neutropenia (ANC \u3c 0.5 x 10/L). Growth rates over 15 years continued at the 50th percentile for both height and weight, and puberty occurred without delay (age range 10-14 years). There were 5.1 vaso-occlusive events (pain and acute chest syndrome)/100 patient years, 7.3 packed red blood cell transfusions/100 patient years. No malignancies, strokes, or deaths occurred. At last follow up, all subjects were at appropriate grade level (10-12 grade) with no history of repeated grades.A cohort of young teenagers with SCA who initiated treatment in infancy have had sustained and continued hematological benefits for a decade and a half. Growth and sexual development are normal and comparable to the general pediatric population. Continuous hydroxyurea therapy since infancy appears safe and efficacious in SCA

Electrical design of TNS

The electrical design of the ORNL-Westinghouse next step (TNS) fusion reactor was begun in 1976, using a set of ground rules which were based on the overall program objectives. These objectives were to identify the design of reasonably-priced reactors, which would achieve ignition and be technology forcing. The term ''technology forcing'' was understood to mean the desirability of a large number of ignited D-T pulses and the incorporation of superconducting toroidal field (TF) coils, if at all possible. A trade study methodology was developed to compare different machine sizes and TF coil technologies and to aid in the selection of system and subsystem design approaches. The logic which led from the program objectives to the design ground rules and from the ground rules to the circuit selection is described below. The circuit design approaches were generalized and these models were incorporated into a computer program (COAST) which was used to examine the cost of overall tokamak systems as key design parameters were varied