24 research outputs found
CopperâCobalt Oxide Nanoparticles with Tailored Cobalt Oxidation State and Lattice Oxygen Vacancy for Low-Temperature Ignition of Ammonium Dinitramide Monopropellants
Ammonium dinitramide (ADN) ionic liquid monopropellants
are recognized
as suitable green substitutes for hydrazine and have attracted considerable
research interest. However, the cold-start capability of a monopropellant
is a critical requirement in propulsion applications, and ADN monopropellants
are not cold-start capable. In this study, we introduce non-noble
metal oxide-based Cu-incorporated Co3O4 (CuâCo3O4) spinel nanoparticles for the low-temperature
catalytic ignition of an ADN-based liquid monopropellant variant,
LMP 103X. The Cu incorporation reduces the particle size and enhances
the surface properties of Co3O4. The catalytic
activity of CuâCo3O4 for the decomposition
of LMP 103X monopropellant was investigated by using a simultaneous
thermal analyzer. The CuâCo3O4 nanoparticles
enhanced the reaction rate and showed better catalytic performance
by lowering the decomposition temperature from 178 to 132 °C,
with sudden decomposition of the entire propellant sample. More grain
boundaries observed in CuâCo3O4 possibly
enhanced the adsorption and transport of reactant species across the
catalyst. The synergistic effect of the high Co3+/Co2+ ratio, oxygen vacancies, pore volume, grain boundaries,
and segregation of CuO enhanced the catalytic activity of the Cu-incorporated
Co3O4. The efficiency of the catalyst is analyzed
by the oxidation states of the transition metals, the abundance of
active sites, and oxygen vacancies appearing on their surfaces
Characterization of nuclease-resistant ribozymes directed against hepatitis B virus RNA
Hepatitis B virus (HBV) is responsible for \u3eâ350 million cases of chronic hepatitis B worldwide and 1.2 million deaths each year. To explore the use of ribozymes as a novel therapy for HBV infection, nucleaseâresistant ribozymes that target highly conserved regions of HBV RNA were screened in cell culture. These synthetic ribozymes have the potential to cleave all four major HBV RNA transcripts and to block the HBV lifecycle by cleavage of the pregenomic RNA. A number of the screened ribozymes demonstrate activity in cell culture systems, as measured by decreased levels of HBV surface antigen, HBV e antigen and HBV DNA. In addition, a lead antiâHBV ribozyme maintains activity against a lamivudineâresistant HBV variant in cell culture. Treatment of HBV transgenic mice with lead antiâHBV ribozymes significantly reduced viraemia compared with salineâtreated animals and was as effective as treatment with lamivudine. In conclusion, the therapeutic use of a ribozyme alone or in combination with current therapies (lamivudine or interferons) may lead to improved HBV therapy