Spacecraft nitrogen generation

Two spacecraft nitrogen (N2) generation systems based on the catalytic dissociation of hydrazine (N2H4) were evaluated. In the first system, liquid N2H4 is catalytically dissociated to yield an N2 and hydrogen (H2) gas mixture. Separation of the N2/H2 gas mixture to yield N2 and a supply of H2 is accomplished using a polymer-electrochemical N2/H2 separator. In the second system, the N2/H2 gas mixture is separated in a two-stage palladium/silver (Pd/Ag) N2/H2 separator. The program culminated in the successful design, fabrication, and testing of a N2H4 catalytic dissociator, a polymer-electrochemical N2/H2 separator, and a two-stage Pd/Ag N2/H2 separator. The hardware developed was sized for an N2 delivery rate of 6.81 kg/d (15lb/day). Experimental results demonstrated that both spacecraft N2 generation systems are capable of producing 6.81 kg/d (15lb/day) of 99.9% pure N2 at a pressure greater than or equal to 1035 kN/m(2) (150 psia)

Experiments on H2-O2MHD power generation

Magnetohydrodynamic power generation experiments utilizing a cesium-seeded H2-O2 working fluid were carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments were conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments, it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator. Peak power densities of greater than 100 MW/cu M were achieved

A two-stage, two-organism process for biohydrogen from glucose

H2 can potentially be produced in a two-stage biological process: the fermentation of glucose by Escherichia coli HD701 and the photofermentation of the residual medium by Rhodobacter sphaeroides O.U. 001. In a typical batch fermentation, E. coli consumed glucose and produced H2, organic end-products and biomass. Organic end-products and residual glucose were removed during subsequent photofermentation by R. sphaeroides, with associated growth and neutralization of pH. However, photoproduction of H2 did not occur during photofermentation of the residual liquor per se due to the presence of fixed nitrogen compounds. Nevertheless, this two-stage approach could be applied to dispose of sugar-containing industrial wastes, H2 being used for on-site power generation

Light-Driven Hydrogen Production from Aqueous Solutions Based on a New Dubois-Type Nickel Catalyst

In this work, we report a new photocatalytic system that links multifunctional semiconductor nanocrystals with emerging water-soluble molecular catalysts made of earth-abundant elements for H2 generation [Ni(P2RN2R′)2(BF4)2]4−, R = Ph, R′ = [PhSO3]− (NiS). This noble metal free hybrid exhibits remarkable catalytic activity with a turnover number of 511 for H2 production and a photon-to-H2 conversion efficiency of 12.5%. The mechanistic insight into such high efficiency in this photocatalytic system was examined using a combination of steady-state emission and time-resolved absorption spectroscopy

Catalytic-Dielectric Barrier Discharge Plasma Reactor For Methane and Carbon Dioxide Conversion

A catalytic - DBD plasma reactor was designed and developed for co-generation of synthesis gas and C2+ hydrocarbons from methane. A hybrid Artificial Neural Network - Genetic Algorithm (ANN-GA) was developed to model, simulate and optimize the reactor. Effects of CH4/CO2 feed ratio, total feed flow rate, discharge voltage and reactor wall temperature on the performance of catalytic DBD plasma reactor was explored. The Pareto optimal solutions and corresponding optimal operating parameters ranges based on multi-objectives can be suggested for catalytic DBD plasma reactor owing to two cases, i.e. simultaneous maximization of CH4 conversion and C2+ selectivity, and H2 selectivity and H2/CO ratio. It can be concluded that the hybrid catalytic DBD plasma reactor is potential for co-generation of synthesis gas and higher hydrocarbons from methane and carbon dioxide and showed better than the conventional fixed bed reactor with respect to CH4 conversion, C2+ yield and H2 selectivity for CO2 OCM process

First description of a histamine receptor of class 2 (HRH2) in a protochordate: expression during blastogenesis and role in regulation of ciliary beat frequency

Histaminergic receptors belong to the family of seven-transmembrane \u3b1-helix domain receptors classified in mammals into four distinct classes. Despite being widely studied in vertebrates, few data are available on the invertebrate receptors, with only predicted H1 and H2 sequences for non-chordate deuterostomes. We report the first transcript evidence of an H2 receptor for histamine in the colonial ascidian Botryllus schlosseri showing a high degree of conservation with HRH2 mammalian and other vertebrate orthologous proteins. The transcript and protein localisation during blastogenic development through in situ hybridisation and immunohistochemistry has been described. The mRNA expression appears first in the ciliary tissues of the alimentary system in filter-feeding adults and the buds, with a particular intensity in the pharynx. Transcription is activated very early, beginning from the inner layer of the disc of the secondary bud. From one generation to the next, the transcript signals become more and more intense at the level of the emergence of primordia of the branchial and peribranchial chambers and, finally, in the cells bordering the stigmata, dorsal lamina, and non-glandular ciliated zones of the endostyle. The translated H2 receptor appears as soon as the primordia of branchial and peribranchial chambers form in the secondary bud, and, in the primary buds, is found mainly in the protostigmata before the two layers of branchial and peribranchial epithelial tissue perforate to form the stigmata. In the adult zooid, the H2 receptor is expressed by ciliated mucous cells involved in food progression throughout the whole length of the alimentary canal. The observation of the effects of histamine and histamine-receptor antagonist (ranitidine) and agonist (dimaprit) drugs on explanted branchial tissue has provided confirmation concerning the receptor class and its role in regulating the ciliary beat frequency. The involvement in the local regulation of ciliary activity is of particular concern for evolutionary considerations because HRH2 seems to have been conserved in the pharynx and its developmental derivatives (e.g. upper respiratory tract and middle ear of mammals) during the evolution of chordates