Optimization of Fusion Pellet Launch Velocity in an Electrothermal Mass Accelerator

Electrothermal mass accelerators, based on capillary discharges, that form a plasma propelling force from the ablation of a low-z liner material are candidates for fuelling magnetic fusion reactors. As lithium is considered a fusion fuel and not an impurity, lithium hydride and lithium deuteride can serve as good ablating liners for plasma formation in an electrothermal plasma source to propel fusion pellets. A comprehensive study of solid lithium hydride and deuteride as liner materials to generate a plasma to propel cryogenic fuel pellets is presented here. This study was conducted using the ETFLOW capillary discharge code. Relationships between propellants, source and barrel geometry, pellet volume and aspect ratio, and pellet velocity are determined for pellets ranging in volume from 5 to 100 mm³.     

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride]: II. A novel cholinergic channel modulator with effects on cognitive performance in rats and monkeys

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride], a novel ligand at neuronal nicotinic acetylcholine receptors with reduced adverse effects and improved oral bioavailability relative to (-)-nicotine, was tested in a variety of cognitive tests in rats and monkeys. Administered acutely, ABT-089 only marginally improved the spatial discrimination water maze performance of septal-lesioned rats. However, more robust improvement (45% error reduction on the last training day) was observed when ABT-089 was administered continuously via subcutaneous osmotic pumps (minimum effective dose: 1.3 micromol/kg/day). Continuous infusion of (-)-nicotine produced comparable improvement in the spatial discrimination water maze performance of septal-lesioned rats, but a 40-fold higher dose of (-)-nicotine was required (62 micromol/kg/day). Continuous infusion of ABT-089 to aged rats enhanced spatial learning in a standard Morris water maze, as indexed by spatial bias exhibited during a probe trial conducted after 4 days of training, but not when they were subsequently trained in a two-platform spatial discrimination water maze. The compound induced a small impairment in young rats on the standard water maze, but not on the two-platform task. A probe trial conducted after additional training in the standard water maze revealed no age or drug effects. ABT-089 did not affect performance of either the aged or young rats during inhibitory (passive) avoidance training. Also, continuous infusion of ABT-089 did not affect responses to acoustic startle or prepulse inhibition of acoustic startle in young, aged or septal-lesioned rats and did not affect locomotor activity in either sham-lesioned or septal-lesioned rats. In monkeys, acute administration of ABT-089 modestly improved the delayed matching-to-sample performance of mature, adult monkeys and more robustly improved performance in aged monkeys. Improved performance in the aged monkeys was restricted to the longest delay intervals and was not accompanied by changes in response latencies.     

Conformation and unfolding thermodynamics of epidermal growth factor and derivatives

Mouse submaxillary epidermal growth factor (EGF) is a 53-residue single chain peptide hormone of known amino acid sequence which contains three disulfides, five tyrosines, and two tryptophans. Circular dichroic (CD) spectra have been obtained and resolved for EGF, several well-characterized chemical and enzymic derivatives, and related low molecular weight model compounds. Assignments have been made to most of the resolved bands; these include the peptide, aromatic, and disulfide chromophores. From a comparison of the rotational strength of the 213-nm resolved CD band in native EGF with that of standard proteins, EGF is estimated to contain about 22% beta structure and no alpha helicity. A derivative of EGF lacking the five carboxyl-terminal residues (prepared by limited trypsin digestion) and the cyanogen bromide derivative, in which there is a single main-chain cleavage at residue 21, have spectra properties indicative of approximately 10 and 12% beta structure, respectively. The near-ultraviolet CD spectra of the derivatives are similar to, albeit not identical with, that of EGF. The rotational strengths characteristic of the side-chain chromophores in EGF and these derivatives are several-fold higher than the corresponding values in low molecular weight model compounds. Thus, it appears that EGF and these modified forms contain a stable (and similar) tertiary structure. In contrast, the S-aminoethylated derivative of EGF exhibits a drastically altered CD spectrum relative to EGF indicating a different conformation(s). Equilibrium studies on the guanidinium hydrochloride (GdmCl) mediated reversible unfolding of EGF showed that the transition midpoint is quite high (i.e., 6.89 M GdmCl at 25.0 degrees C), thus, indicating considerable stability. From these data a rough estimate of 16 kcal/mol can be made for the unfolding free energy (delta G degrees) of EGF in the absence of denaturant. Interestingly, EGF exhibits greater stability characteristics than several proteins two to four times its size. The cyanogen bromide derivative of EGF exhibited greatly reduced stability characteristics, e.g., the transition midpoint occurred at 4.19 M GdmCl (25.0 degrees C) and delta G degrees was estimated to be approximately 4 kcal/mol. Thus, a single main-chain cleavage reduced the stability of EGF by about 70%. Thermal transitions of EGF and the cyanogen bromide derivative in the presence of concentrated GdmCl are characterized by a relatively high enthalpy of about 25 kcal/mol at 40 degrees C and a low (probably zero) heat capacity. From these thermodynamic parameters one can calculate that the large reduction in delta G degrees due to scission of the single peptide bond between residues 21 and 22 can be attributed almost completely to a change in entropy; e.g., at 40 degrees C the apparent entropy of unfolding of EGF is 20.4 cal mol-1 deg-1 while that of the cyanogen bromide derivative is 66.4 cal mol-1 deg-1.     

Comparison of scales of amino acid side chain properties by conservation during evolution of four proteins

As the amino acid sequence of a given protein changes alongthe phylogenetic tree, enough of the overall folding patternmust be conserved to ensure that the protein still fulfils itsbiological function. Eighteen published scales which tabulatevarious side chain properties are compared here by computingthe variance of each scale when applied to each of several proteinfamilies. The conservation of each scale of side chain propertiesis examined for the 20 627 residues in 60 mammalian myoglobins,31 mammalian ribonucleases, insulin A and B chains (29 sequenceseach), 29 vertebrate and 28 plant cytochrome c's. Those scaleswhich are the most highly conserved through the evolution ofeach protein family may well be the best predictors of proteinfolding patterns. The mean-area-buried scale and the optimizedmatching hydrophobicities scale are more conserved than otherscales. An additional result is the relatively poor conservationacross evolution of the Chou-Fasman secondary structure predictors.     

Structure-activity studies related to ABT-594, a potent nonopioid analgesic agent: effect of pyridine and azetidine ring substitutions on nicotinic acetylcholine receptor binding affinity and analgesic activity in mice

Analogs of A-98593 (1) and its enantiomer ABT-594 (2) with diverse substituents on the pyridine ring were prepared and tested for affinity to nicotinic acetylcholine receptor binding sites in rat brain and for analgesic activity in the mouse hot plate assay. Numerous types of modifications were consistent with high affinity for [3H]cytisine binding sites. By contrast, only selected modifications resulted in retention of analgesic potency in the same range as 1 and 2. Analogs of 2 with one or two methyl substituents at the 3-position of the azetidine ring also were prepared and found to be substantially less active in both assays.     

Prominent Roles of Impurities in Ionic Liquid for Catalytic Conversion of Carbohydrates

Impurities present in commercially available ionic liquids display prominent catalytic functions toward carbohydrate conversion. Little conversion was observed at 180?°C with high purity [EMIM]Cl ionic liquid whereas significant conversion was observed for ionic liquids of lower purity levels. Addition of metal halides to high purity [EMIM]Cl catalyze cellulose conversion with drastically different product selectivities dependent on the metal ions. CuCl₂ is an active catalyst for hydrolyzing cellulose and further degrading the products. CrCl₂ is an active and a selective catalyst for the formation of 5-hydroxymethylfurfural (5-HMF). CrCl₂ also helps stabilize the 5-HMF product. FeCl₂ does not show catalytic activity. Metal impurities in ionic liquid correlate to the activities observed when similar metals were added to high purity ionic liquids.     

Analysis and modeling of a two-phase jet pump of a thermal management system for aerospace applications

Jet pumps are devices capable of pumping fluids to a higher pressure by inducing the motion of a secondary fluid employing a high-speed primary fluid. The main components of a jet pump are a primary nozzle, secondary fluid injectors, a mixing chamber, a throat, and a diffuser. The work described in this paper models the flow of a two-phase primary fluid inducing a secondary liquid (saturated or subcooled) injected into the jet pump mixing chamber. The model is capable of accounting for phase transformations due to compression, expansion, and mixing. The model is also capable of incorporating the effects of the temperature and pressure dependency in the analysis. The approach adopted utilizes an isentropic constant-pressure mixing in the mixing chamber and at times employs iterative techniques to determine the flow conditions in the different parts of the jet pump.     

Enabling renewable energy—and the future grid—with advanced electricity storage

Environmental concerns about using fossil fuels, and their resource constraints along with energy security concerns, have spurred great interest in generating electrical energy from renewable sources. The variable and stochastic nature of renewable sources, however, makes solar and wind power difficult to manage, especially at high levels of penetration. Electrical energy storage (EES) is necessary to effectively use intermittent renewable energy, enable its delivery, and improve the reliability, stability, and efficiency of the electrical grid. While EES has gained wide attention for hybrid and electrical vehicle needs, public awareness and understanding of the critical challenges in energy storage for renewable integration and the future grid is relatively lacking. This paper examines the benefits and challenges of EES, in particular electrochemical storage or battery technologies, and discusses the fundamental principles, economics, and feasibility of the storage technologies.     

Functional characterization of the novel neuronal nicotinic acetylcholine receptor ligand GTS-21 in vitro and in vivo

(2.4)-Dimethoxybenzylidene anabaseine dihydrochloride (GTS-21), a compound that interacts with rat neuronal nicotinic acetylcholine receptors (nAChRs), was evaluated using human recombinant nAChRs in vitro and various pharmacokinetic and behavioral models in rodents, dogs and monkeys. GTS-21 bound to human alpha 4 beta 2 nAChR (K1-20 nM) 100-fold more potently than to human alpha 7 nAChR, and was 18- and 2-fold less potent than (-)-nicotine at human alpha 4 beta 2 and alpha 7 nAChR, respectively. Functionally. GTS-21 stimulated [5H]dopamine release from rat striatal slices with an EC50 of 10 +/- 2 microM (250-fold less potent and 70% as efficacious as (-)-nicotine), an effect blocked by the nAChR antagonist dihydro-beta-erythroidine. However, GTS-21 did not stimulate human alpha 4 beta 2 nor human ganglionic nAChRs significantly. In vivo, GTS-21 had no adverse effect on dog blood pressure (< or = 2.5 micromol/kg i.v. bolus infusion), in marked contrast with (-)-nicotine, GTS-21 (-62 micromol/kg.s.e.) also did not cross-discriminate significantly with (-)-nicotine in rats and did not reduce temperature or locomotion in mice. Neither was it active in the elevated plus maze anxiety model (0.19-6.2 micromol/kg.IP) in normal mice. However, GTS-21 did improve learning performance of monkeys in the delayed matching-to-sample task (32-130 nmol/kg.i.m.).