Experiments shed new light on nickel-fluorine reactions

Isotopic tracer experiments and scale-impingement experiments show fluorine to be the migrating species through the nickel fluoride scale formed during the fluorination of nickel. This is in contrast to nickel oxide scales, where nickel is the migrating species

Iron-Magnesium Alloy Bioabsorbable Blood Stent

Bioabsorbable materials are fairly new and proper alloys for implantation in the body have not yet been established. There are a few polymers that have showed promise, but they do not provide the proper mechanical support that metal does. These materials would be used to create devices such as blood stents and orthopedic screws. Investigation into the properties of different alloys can help to establish a material that can be used for implanted devices that are only needed for a limited amount of time. In order to investigate these alloys many different experiments will to be run to test the different properties. This includes corrosion tests, and cytotoxicity tests. Corrosion will be tested by using potentiondynamic polarization tests to accelerate the rate of corrosion. Cytotoxicity tests will be performed by incubating the cells with the material for a certain period of time to establish that the material does not cause cell death. The corrosion test showed that the alloy that was cold worked had a reduced corrosion rate as compared to the samples that were quenched. The cytotoxicity tests are currently underway and it is hoped that they will show no decrease in cell death when compared to a control. Cold working and changing the microstructure appears to reduce the corrosion rate. More investigation into what properties influence the corrosion rate of materials is needed. The cytotoxicity will hopefully increase cell growth meaning that when implanted it will encourage recovery and reconstruction of the damaged area

Bt maize: a tool for improving food safety of grains at harvest

A new EU (European Union) regulation came into force in 2007 with Regulation (EC) No. 1126/2007 which established maximum levels for fumonisins B1 and B2 (4000 ppb), deoxynivalenol (1750 ppb) and zearalenone (350 ppb) in maize and maize products. In order to evaluate French maize food safety, studies were carried out by the national Biological Risk Monitoring (BRM) Network. In this study, field trials involving 84 plots were conducted with Bt maize (MON 810) and its isogenic non-Bt counterpart in 2005 and 2006 in South-western France. Mycotoxin levels were determined in grain at harvest. Fumonisins B1 and B2, deoxynivalenol, and zearalenone were analyzed by LC-MS-MS and the results treated statistically using non parametric tests for mycotoxins and analysis of variance test for weather variables. As the climate was homogenous inside the experimental area, the transgenic event introduced into the maize was the only key parameter which differed between Bt and non-Bt maize plots. Our results showed that all mycotoxin families were not impacted in the same way. The efficacy of Bt maize reduced mycotoxins more than 90% for fumonisins and more than 50% for zearalenone although deoxynivalenol was lightly increased. Therefore a competition between the different Fusarium spp. which produced fumonisins or trichothecenes is hypothesized. According to Regulation (EC) No. 1126/2007, 93% of the maize of Bt maize plots were able to be commercialized compared to only 45% for non-Bt maize plots. The results of this work showed that Bt maize improved food safety and constituted an useful tool to reduce significantly mycotoxin levels in harvested and stored grains. Keywords: Bt (MON810) maize, Fumonisins B1 and B2, Deoxynivalenol (DON), Zearalenone, EC regulation 1126/2007 threshold

Evaluation of a Tetracycline-Inducible Promoter in Staphylococcus aureus In Vitro and In Vivo and Its Application in Demonstrating the Role of sigB in Microcolony Formation

An inducible promoter system provides a powerful tool for studying the genetic basis for virulence. A variety of inducible systems have been used in other organisms, including pXyl-xylR-inducible promoter, the pSpac-lacI system, and the arabinose-inducible PBAD promoter, but each of these systems has limitations in its application to Staphylococcus aureus. In this study, we demonstrated the efficacy of a tetracycline-inducible promoter system in inducing gene expression in S. aureus in vitro and inside epithelial cells as well as in an animal model of infection. Using the xyl/tetO promoter::gfpuvr fusion carried on a shuttle plasmid, we demonstrated that dose-dependant tetracycline induction, as measured by bacterial fluorescence, occurred in each of the above environments while basal activation under noninduced conditions remained low. To ascertain how the system can be used to elucidate the genetic basis of a pathogenic phenotype, we cloned the sigB gene downstream of the inducible promoter. Induction of SigB expression led to dose-dependent attachment of the tested strain to polystyrene microtiter wells. Additionally, bacterial microcolony formation, an event preceding mature biofilm formation, also increased with tetracycline induction of SigB

Treg depletion followed by intracerebral CpG-ODN injection induce brain tumor rejection

Using brain lymphoma model, we demonstrate that immunotherapy combining Treg depletion (using anti-CD25 mAb PC61) followed by intracranial CpG-ODN administration induced tumor rejection in all treated mice and led to the establishment of a memory antitumor immune response in 60% of them. This protective effect was associated with a recruitment of NK cells and, to a lesser extent, of dendritic cells, B cells and T lymphocytes. NK cell depletion abolished the protective effect of the treatment, confirming a major role of NK cells in brain tumor elimination. Each treatment used alone failed to protect brain tumor bearing mice, revealing the therapeutic benefit of combining Treg depletion and local CpG-ODN injection

LABORATORY INVESTIGATIONS IN SUPPORT OF FLUID BED FLUORIDE VOLATILITY PROCESSES. PART I. THE FLUORINATION OF URANIUM DIOXIDE-PLUTONIUM DIOXIDE SOLID SOLUTIONS

Work in the development of fluid-bed fluoride volatility processes is described. In these processes, uranium and plutonium in spent nuclear fuels are converted into hexafluoride compounds in a fluid-bed reactor. The uranium and plutonium hexafluorides are volatile and can be separated from fission products, cladding, and alloying materials by techniques such as vaporization and distillation. The experimental work was directed toward devising a fluorination procedure for uranium and plutonium dioxides which would result in a high degree of removal of uranium and plutonium as hexafluorides. In these experiments synthetic mixtures made up to simulate a charge for a fluidized bed reactor (100 kg U, 0.4 kg Pu, approximates 1 kg F.P., and 30 kg inert solids) were used. High-purity recrystallized alumina was found to be a suitable material for use as the fluidized inert solid. After a 10-hr fluorination period at 450 deg C, the concentrations of residual uranium and plutonium on the alumina were 0.01 and 0.03 wt%, respectively. A reaction temperature of 450 deg C was found to be optimum, since experiments at 500 and 550 deg C resulted in plutonium retentions on the alumina of 0.060 and 0.090 wt%, respectively. At all these temperatures, the residual uranium content of the residue was less than 0.01 wt%. When fission product element oxides, in quantities that would be expected in a Dresden-type fuel after 100,000 Mwd/ton burnup and 30 days of cooling, were added to the uranium dioxide-plutonium dioxide-- alumina and the mixture was fluorinated at 450 deg C for 10 hr, the concentration of plutonium on the alumina increased to a value of 0.065 U%. Additional recovery of the plutonium retained on the alumina was obtained by either pyrohydrolysis followed by refluorination at 450 deg C for 10 hr, or by refluorination alone at 550 deg C for 10 hr. These procedures reduced the residual plutonium content of the alumina to less than 0.02 wt%. Experiments were also performed to determine the feasibility of using the same batch of alumina as the inert solid for the fluorinations of five batches of the urania--plutonia solid solution. Experiments were performed in which the solid solution of plutonium dioxide in uranium dioxide was oxidized prior to fluorination. The oxidation resulted in a powdered mixture of uranosic oxide and plutonium dioxide. Fluorination of this oxide mixture in alumina resulted in the removal of essentially all of the uranium in a reaction time of 2 hr at 450 deg C when 10 vol% fluorine was used. When this fluorination was followed by a second fluorination period of 5 hr at 550 deg C with 75 vol% fluorine, the plutonium content of the alumina was 0.011 wt%. When both fluorination periods were extended to 10 hr each, the retention of plutonium was 0.007 wt%, which corresponded to a removal of 99.5% of the plutonium contained in the solid mixture. During the first part of the fluorination period, in which the major portion of the uranium is removed from the mixture of uranium dioxide, plutonium dioxide, alumina, and representative fission product element oxides, a low ternperature (450 deg C) and a low concentration of fluorine (10 vol% fluorine in nitrogen) are desirable. However, in order to remove the plutonium efficiently during the last portion of the fluorination period, it is desirable to use a higher temperature (550 deg C) and a higher fluorine content of the gas mixture (75 vol% fluorine in nitrogen). (auth