Current evaluation of the tripropellant concept

An analytical study was conducted to determine the specific-impulse advantages of adding metals to conventional liquid-bipropellant systems. These tripropellant systems theoretically offer higher specific impulse and increased propellant density compared with bipropellant systems. Metals considered were Be, Li, and Al. Bipropellant systems were H2/O2, N2H4/N2O4, RP-1/O2, and H2/F2. Thermochemical calculations were performed for sea-level expansion from 6.895-MN/sq. m. (1000-psia) chamber pressure over a wide range of mixture ratios and propellant compositions. Three-dimensional plots characterize the specific impulse of each tripropellant system. Technology issues pertinent to metallized propellant systems are discussed

P19-26. Directing macaque immune responses with an anti-dendritic cell HIV Gag p24 fusion protein vaccine

International audiencen.

Summary of EC Superelement Results for OH Inter-Module Connecting Forces

The purpose of this report is to summarize the OH module connecting forces found as a result of the super-element modeling of the EC internal module structure. Although not presented here, this approach can also provide MH connecting forces and assembly deflections. This report includes only information on the OH connecting forces for various assumed connector schemes. The super-element machinery is in place to model other connector ideas, and provide information on overall deflections, MH connecting forces, and primary module stresses

Summary of ANSYS and Strain Gauge Results for the EC Calorimeter OH and MH Modules

The OH and MH modules of the EC calorimeter consist essentially of metal boxes containing calorimetry plates. These plates can contribute to the module behavior only in compression, with this effect being enhanced if the plates are compressively preloaded against the skin of the box prior to assembly. The finite element method can be applied in the analysis of these modules. Its advantages are: 1. The structural components can be modeled with less simplification than beam theory allows. The angled faces of the OH modules can be represented exactly, and the shear deflections inherent in short, deep beams will be a natural part of the solution. 2. The finite element method can be subjected to any number of realistic loadings. 3. With proper mesh density relevant stresses can be extracted. The disadvantages of the method are that exact modeling of the internal plates is difficult, time consuming, and computationally expensive. It is of interest, then, to verify how well a simple model of the structural components only (i.e., the skin, endplates, and any structural internal plates) predicts deflections and stresses which can be relied on for design purposes. The finite element modeling of the OH and MH EC modules has been under constant review since the technique was first applied to these structures. Early verification attempts were based on comparison of finite element deflection predictions with measured module deflections. These comparisons were not entirely successful, due primarily, in the author's opinion, to the difficulty of measuring the actual module deflections with acceptable accuracy. It was proposed in October, 1986, that verification be based on stress, rather than deflection. The purpose of this report is to summarize the results of four experiments which were conducted to determine the accuracy with which ANSYS finite element models could predict the stresses in the OH and MH EC modules as measured by strain gauges. The three comparisons with actual module prototypes show that ANSYS can predict with good accuracy the stresses in those regions far from discontinuities where the stress gradient is low. In all regions, but particularly those of high gradient, ANSYS will tend to overestimate the stress. The comparison with the skin-only module shows that the basic approach is sound and exhibits the behavior expected from a finite element analysis. Finite element analysis can clearly be a useful part of the module design process when augmented by experimental and closed-form analytical techniques

P18-08. Characterization of CD34+ derived dendritic cells generated in vitro and transfected with HIV gene as potential therapeutic vaccine in macaque

International audiencen.

Unique Structural Modifications Are Present in the Lipopolysaccharide from Colistin-Resistant Strains of \u3ci\u3eAcinetobacter baumannii\u3c/i\u3e

Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause severe infections, including hospital-acquired pneumonia, wound infections, and sepsis. Multidrug-resistant (MDR) strains are prevalent, further complicating patient treatment. Due to the increase in MDR strains, the cationic antimicrobial peptide colistin has been used to treat A. baumannii infections. Colistin-resistant strains of A. baumannii with alterations to the lipid A component of lipopolysaccharide (LPS) have been reported; specifically, the lipid A structure was shown to be hepta-acylated with a phosphoethanolamine (pEtN) modification present on one of the terminal phosphate residues. Using a tandem mass spectrometry platform, we provide definitive evidence that the lipid A isolated from colistin-resistant A. baumannii MAC204 LPS contains a novel structure corresponding to a diphosphoryl hepta-acylated lipid A structure with both pEtN and galactosamine (GalN) modifications. To correlate our structural studies with clinically relevant samples, we characterized colistin-susceptible and -resistant isolates obtained from patients. These results demonstrated that the clinical colistin-resistant isolate had the same pEtN and GalN modifications as those seen in the laboratory-adapted A. baumannii strain MAC204. In summary, this work has shown complete structure characterization including the accurate assignment of acylation, phosphorylation, and glycosylation of lipid A from A. baumannii, which are important for resistance to colistin

Place-exchange mechanism of Pt (111) oxidation/reduction as observed by synchrotron X-ray scattering

Structural changes in the Pt(111) single crystal surface associated with incipient electrochemical oxidation/reduction were studied by {ital in}{ital situ} synchrotron x-ray reflectivity. It was shown that lifting of Pt atoms of the surface layer occurs, substantiating the long-standing hypothesis of a place-exchange mechanism for solution/metal interface oxidation. It was also shown that, for a charge transfer of {approx_lt}1.7 e{sup -}/Pt atom, the initially flat surface structure could be recovered by electrochemical reduction. In constrast, the surface was irreversibly roughened for amounts of charge transfer exceeding {approx}1.7 e{sup -}/Pt, but the roughening involved only the atoms in the top layer of the original flat surface. A detailed mechanism is proposed for the place-exchange mechanism and the subsequent roughening of the electrode surface

\u3ci\u3eStaphylococcus aureus\u3c/i\u3e Hyaluronidase Is a CodY-Regulated Virulence Factor

Staphylococcus aureus is a Gram-positive pathogen that causes a diverse range of bacterial infections. Invasive S. aureus strains secrete an extensive arsenal of hemolysins, immunomodulators, and exoenzymes to cause disease. Our studies have focused on the secreted enzyme hyaluronidase (HysA), which cleaves the hyaluronic acid polymer at the β-1,4 glycosidic bond. In the study described in this report, we have investigated the regulation and contribution of this enzyme to S. aureus pathogenesis. Using the Nebraska Transposon Mutant Library (NTML), we identified eight insertions that modulate extracellular levels of HysA activity. Insertions in the sigB operon, as well as in genes encoding the global regulators SarA and CodY, significantly increased HysA protein levels and activity. By altering the availability of branched-chain amino acids, we further demonstrated CodY-dependent repression of HysA activity. Additionally, through mutation of the CodY binding box upstream of hysA, the repression of HysA production was lost, suggesting that CodY is a direct repressor of hysA expression. To determine whether HysA is a virulence factor, a ΔhysA mutant of a community-associated methicillin-resistant S. aureus (CA-MRSA) USA300 strain was constructed and found to be attenuated in a neutropenic, murine model of pulmonary infection. Mice infected with this mutant strain exhibited a 4-log-unit reduction in bacterial burden in their lungs, as well as reduced lung pathology and increased levels of pulmonary hyaluronic acid, compared to mice infected with the wild-type, parent strain. Taken together, these results indicate that S. aureus hyaluronidase is a CodY-regulated virulence factor

Prospective surveillance of invasive group a streptococcal disease, Fiji, 2005-2007.

We undertook a prospective active surveillance study of invasive group A streptococcal (GAS) disease in Fiji over a 23-month period, 2005-2007. We identified 64 cases of invasive GAS disease, which represents an average annualized all-ages incidence of 9.9 cases/100,000 population per year (95% confidence interval [CI] 7.6-12.6). Rates were highest in those >65 years of age and in those <5 years, particularly in infants, for whom the incidence was 44.9/100,000 (95% CI 18.1-92.5). The case-fatality rate was 32% and was associated with increasing age and underlying coexisting disease, including diabetes and renal disease. Fifty-five of the GAS isolates underwent emm sequence typing; the types were highly diverse, with 38 different emm subtypes and no particular dominant type. Our data support the view that invasive GAS disease is common in developing countries and deserves increased public health attention