Optimization of Mass Transfer Processes in the Zone of the Air Electrode of a Fuel Cell with a Solid Polymer Electrolyte

A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally.     

Lysine-containing calcium hydroxylapatite: Synthesis and physicochemical characterization

The CaCl₂-(NH₄)₂HPO₄-NH₂(CH₂)₄NH₂CHCOOH-NH₃-H₂O system at 25°C is studied using Tananaev’s solubility (residual concentrations) method and pH measurements. Lysine-containing calcium hydroxylapatite Ca₁₀(PO₄)₆(OH)_1.9[NH₂(CH₂)₄NH₂CHCOO]_0.1 · 6H₂O is identified using chemical analysis, thermogravimetry, powder X-ray diffraction, and IR spectroscopy.     

Mass spectrometry of π-complexes of transition metals : V. Dimeric (π-cyclopentadienyl)dicarboxylatovanadium complexes

Mass spectra of dimeric (π-cyclopentadienyl)dicarboxylatovanadium complexes [π-C₅H₅V(OOCR)₂]₂, have been studied. The principal paths of fragmentation of the trihaloalkyl derivatives involve the formation of VHal bonds, whereas VO bonds are formed during decomposition of acetato and formato complexes. An unusual increase in stability of dimeric and monomeric ions of the alkyl derivatives is observed in going from R = CH₃ to R = CF₃. With aromatic complexes, only ions containing a single metal atom occur.     

Antiferromagnetic complexes involving metal---metal bonds III. Synthesis, structure and magnetic properties of heterotrinuclear complexes of the type M(CO)5L (M = Cr, Mo and w) containing [(C5H5CrSCMe3)2S] as unusual antiferromagnetic ligand L

Isostructural heterotrinuclear complexes (C₅H₅CrSCMe₃)₂S · M(CO)₅ (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C₅H₅CrSCMe₃)₂S (I) (with the Cr---Cr bond 2.689 Å long and with the exchange parameter −2J = 430 cm⁻¹) and metal hexacarbonyls, M(CO)₆, where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) Å). Its geometry remains practically unaffected by the complex formation (the Cr---Cr bond length in III and IV is 2.73(1) Å). The exchange parameter, −2J (410, 440 and 440 cm⁻¹ in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct Cr---Cr exchange. The Cr---Cr bond length may thus be correlated with the observed overall exchange coupling.     

First experiments on transmutation studies of129I and237Np using relativistic protons of 3.7 GeV

First experiments on the transmutation of long-lived¹²⁹I and²³⁷Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:¹²⁹I(n,)¹³⁰I and²³⁷Np(n,)²³⁸Np. The isotopes¹³⁰I (T _1/2-12.36 h) and²³⁸Np (T _1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (¹²⁹I(n,))=(10±2)b and (²³⁷Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna.     

Beta-decay strength measurement,total beta-decay energy determination,and dcay-scheme completeness testing by total absorption <Emphasis Type="Italic">γ</Emphasis>-ray spectroscopy

Applications of total absorption γ-ray spectroscopy and its combination with high-resolution nuclear spectroscopy methods for measurements of a β-decay strength function S _β (E), determination of the total β-decay energy Q _β , and testing of decay-scheme completeness are presented.     

Transmutation of 129I, 237Np, 238Pu, 239Pu, and 241Am using neutrons produced in target-blanket system ‘Energy plus Transmutation’ by relativistic protons

Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution has also been studied using a set of threshold detectors. Results of transmutation studies of ¹²⁹I, ²³⁷Np, ²³⁸Pu, ²³⁹Pu and ²⁴¹Am are presented.