Immunogenic properties of rabbit haemorrhagic disease virus structural protein VP60 expressed by a recombinant baculovirus: an efficient vaccine

We have constructed a recombinant baculovirus containing the gene encoding the structural protein VP60 from the Spanish field isolate AST/89 of rabbit haemorrhagic disease virus (RHDV). Infection of cultured Spodoptera frugiperda Sf9 cells with this recombinant virus resulted in the production of high yields of VP60 protein which did not seem to assemble to form virus like particles, but was antigenically similar to the corresponding viral protein obtained from purified virions. A VP60-dose study showed that the recombinant protein was able to elicit a protective response in rabbits against a nasal challenge with 100 LD50 of RHDV. The effective dose able to protect 50% of the animals in the absence of adjuvant was found to be 10-25 micrograms of recombinant VP60.     

Electrostatic interactions in collagen-like triple-helical peptides

Collagen-like peptides with potential for ion pair formation were studied to investigate the role of electrostatic interactions in the triple-helix conformation. Three peptides--(POG)10, the EK-containing peptide (POG)4EKG(POG)5, and T3-487, a peptide with 18 residues of type III collagen and a C-terminal (GPO)4 tail--all form stable triple helices in aqueous solution, with melting temperatures of 58, 46, and 26 degrees C, respectively, at neutral pH. The thermal stabilities of these peptides correlate with their imino acid content, which is 66%, 60%, and 41%, respectively. Variation of pH over the range of 1-13 led to 8-9 degrees C changes in the Tm of the EK-containing peptide and peptide T3-487, with the greatest stability seen at pH values where both acidic and basic residues are ionized. Equilibrium ultracentrifugation shows these peptides are largely trimeric at low temperature, with no hexamers or larger aggregates, indicating that the pH-dependent stability arises from intramolecular interaction. Computer modeling indicates both intrachain ion pairs and interchain ion pairs can form and stabilize the triple helix. Studies of the pH dependence of the thermal stability of (POG)10 and the N-terminal acetylated form of T3-487 indicate that repulsion of the three charged N-terminal or C-terminal ends has a destabilizing effect. Taking into account these end effects, the energy contribution of two oppositely charged residues in a triple helix which are sterically capable of participating in ion pairs and backbone hydrogen bonding is 0.5-1 kcal/mol ion pair. It is possible that the stabilizing influence of ion pairs arises indirectly, through elimination of like charge repulsion, formation of ion pairs in the single chain form, or solvent effects.     

Pure H2 Production by Decomposition of Methane Over Ni Supported on Hydroxyapatite Catalysts

The catalytic decomposition of CH₄ for the production of pure H₂ is carried out over Ni supported on hydroxyapatite [Ca₅(PO₄)₃(OH)] catalysts at 650 °C and atmospheric pressure. CH₄ decomposition activity is decreased with time on stream and finally deactivated completely. The physicochemical properties of the fresh catalysts are characterized by XRD, DTA/TG, TPR and SEM techniques along with CHNS analyses of the used samples. It is found that the 30 wt% Ni/HAp displayed higher H₂ production rates over the other Ni loadings, which is correlated with Ni metal surface area measured by O₂ pulse chemisorption. IICT communication number: 051211.     

Preparation and characterization of sodium bearing perovskite phases

Ceramic waste-forms constitute a major alternative to glass for immobilization of radionuclides in solid phase, with advantage of greater stability in the presence of water at moderate temperature. CaZrO₃ and SrZrO₃ with ABO₃ perovskite structure are suitable host matrices for fixation of sodium and neodymium. Three new phases with compositions Na_0.5Nd_0.5ZrO₃, Ca_0.44Na_0.28Nd_0.28ZrO₃ and Sr_0.6Na_0.2Nd_0.2ZrO₃ have been synthesized and characterized as orthorhombic phases. The crystal structure of Ca_0.44Na_0.28Nd_0.28ZrO₃ was derived from the crystallographic parameters of CaZrO₃ using X-ray powder diffraction data in the orthorhombic system by Rietveld profile method. Preliminary leaching studies carried out in a digestion bomb showed low leachability of sodium and neodymium in water at 70 °C from Ca_0.44Na_0.28Nd_0.28ZrO₃ matrix as compared to that from Sr_0.6Na_0.2Nd_0.2ZrO₃ matrix.     

Calculation of thermodynamic parameters of U–Pu–N system with carbon and oxygen impurities

Mixed nitride fuels are being considered for advanced FBR, but very little is known about the thermodynamic properties of these fuels. For an overall composition of the nitride fuel with small amounts of oxygen and carbon impurities, thermodynamic properties, e.g. carbon activity and partial pressures of nitrogen, carbon-monoxide, plutonium and uranium, were calculated in present work. These calculations were based on standard Gibbs free energies of the binary compounds, present in this multi-component system (U,Pu)–C–N–O. For an over all composition of the fuel, stable phase-field was determined by minimization of the Gibbs free energy of the system. The fabrication experiences of various workers, reported in literature, have shown that depending on the impurity content, nitride fuel can exist in two phase fields, mono-nitride phase in equilibrium with sesquinitride phase or mono-nitride phase in equilibrium with dioxide phase. Therefore, in present calculations special attention was given to the thermodynamic behavior of these two phase-fields. A comparison of calculated thermodynamic properties indicated that nitride fuel with dioxide as second phase will be superior to the one with sesquinitride.     

Investigation of Magnetocaloric Behavior of Nanocrystalline Nd0.67A0.33MnO3, (A = Ca,Sr, Ba and Pb)

Colossal magnetoresistive (CMR) materials with the compositional formula, Nd_0.67A_0.33MnO₃ (where A = Ca, Sr, Ba, and Pb) in the nanocrystalline form were prepared by the PVA gel technique. After characterizing the samples structurally, a systematic investigation of magnetization has been undertaken, over a temperature range 10–300 K at 0.05 T magnetic field. An effort has been made to calculate the magnetocaloric behavior of all the samples theoretically using the experimental magnetization data. Other important parameters such as maximum entropy change, full width at half-maximum, relative cooling power, and maximum adiabatic temperature change under 0.05 T were also computed. The observed behavior has been explained qualitatively.     

Microstructural Characterization and Mechanical Properties of Powder Metallurgy Dual Phase Steel Preforms

In order to improve the mechanical properties of powder metallurgy (P/M) ferrite-pearlite steel, a dual phase (DP) ferrite-martensite steel was produced through intercritical annealing of sintered P/M preforms. Mi-crostructures of the sintered and DP steels were examined with optical, scanning and transmission electron microscopes. Mechanical properties were evaluated through hardness measurements and compression tests. Microstructural studies revealed that sintered steel contained polygonal ferrite-pearlite while the DP steel contained polygonal, lath and acicular ferrite along with lath-type martensite as microstructural constituents. In DP steels, with increasing mean preform density, the microstructure contained fine and continuous network of martensite colonies with minimum porosity. The work hardening rate vs plastic strain plots (Jaoul-Crussard analysis) of both the steels revealed typical three stage deformation behaviour for low and high mean preform densities. Compression tests revealed that, DP P/M steel displayed higher strength-plasticity combination than the sintered steel.