Application of an Equilibrium Vaporization Model to the Ablation of Chondritic and Achondritic Meteoroids

We modeled equilibrium vaporization of chondritic and achondritic materials using the MAGMA code. We calculated both instantaneous and integrated element abundances of Na, Mg, Ca, Al, Fe, Si, Ti, and K in chondritic and achondritic meteors. Our results are qualitatively consistent with observations of meteor spectra.Comment: 8 pages, 4 figures; in press, Earth, Moon, and Planets, Meteoroids 2004 conference proceeding

Solvent extraction studies with intermediate-burnup Fast Flux Test Facility fuel in the Solvent Extraction Test Facility

In Campaign 8, two batches of irradiated fuel from the Fast Flux Test Facility (FFTF) were processed, using 30% TBP-NPH, in the Solvent Extraction Test Facility (SETF). The burnups were about 36 and 55 MWd/kg with 1.3- and 1-year cooling times, respectively. The latter fuel had the highest burnup and shortest cooling time of any fuel ever handled in the SETF. No major problems were noted during the operation of the mixer-settlers, and low uranium and plutonium losses (<0.02%) were achieved. Zirconium and ruthenium decontamination factors (DFs) were improved by increasing the number of scrub stages and increasing the peak solvent loading in the coextraction-coscrub bank. The use of an in-line photometer to measure the uranium and plutonium concentrations in a process stream permitted high solvent loadings of heavy metals to be achieved in the extraction bank while maintaining low losses to the aqueous raffinate. The investigation of two flowsheet options for making separate uranium and plutonium products (organic backscrub and selective uranium extraction) that was started in Campaign 7 was continued. High-quality products were again obtained (uranium and plutonium DFs of {similar_to}0{sup 4}). Plutonium reoxidation was still extensive even though hydrazine was added to the aqueous strip for the organic backscrub flowsheet. Two different plutonium oxalate precipitation procedures [Pu(III) and Pu(IV)] were used in the preparation of the plutonium oxide products; this was done so that the fuel fabrication characteristics of the oxide from the two procedures could be compared. A total of {similar_to}50 g of plutonium was recovered and shipped to the fuel refabrication program

Cooperation, Norms, and Revolutions: A Unified Game-Theoretical Approach

Cooperation is of utmost importance to society as a whole, but is often challenged by individual self-interests. While game theory has studied this problem extensively, there is little work on interactions within and across groups with different preferences or beliefs. Yet, people from different social or cultural backgrounds often meet and interact. This can yield conflict, since behavior that is considered cooperative by one population might be perceived as non-cooperative from the viewpoint of another. To understand the dynamics and outcome of the competitive interactions within and between groups, we study game-dynamical replicator equations for multiple populations with incompatible interests and different power (be this due to different population sizes, material resources, social capital, or other factors). These equations allow us to address various important questions: For example, can cooperation in the prisoner's dilemma be promoted, when two interacting groups have different preferences? Under what conditions can costly punishment, or other mechanisms, foster the evolution of norms? When does cooperation fail, leading to antagonistic behavior, conflict, or even revolutions? And what incentives are needed to reach peaceful agreements between groups with conflicting interests? Our detailed quantitative analysis reveals a large variety of interesting results, which are relevant for society, law and economics, and have implications for the evolution of language and culture as well

Identification and Preliminary Characterization of a Chitinase Gene in the Autographa californica Nuclear Polyhedrosis Virus Genome

AbstractA functional chitinase gene (chiA) has been identified in the genome of the Autographa californica nuclear polyhedrosis virus (AcMNPV). It is expressed in the late phase of virus replication in insect cells. High levels of both endo- and exochitinase activity were detected by 12 hr p.i. and remained stable throughout infection. An AcMNPV chiA protein-specific antibody was prepared using recombinant material prepared in bacteria. This was used to demonstrate that a product of approximately 58 kDa was synthesised in virus-infected cells. Immunofluorescence analysis of virus-infected cells showed that most chitinase was located in the cytoplasm. Primer extension analysis of mRNA from AcMNPV-infected cells confirmed that transcription initiated from a baculovirus late start site (TAAG), 14 nucleotides upstream from the putative translation initiation codon. The predicted protein sequence of the AcMNPV chiA shares extensive sequence similarity with chitinases from bacteria and, in particular, the Serratia marcescens chitinase A (60.5% identical residues). Phylogenetic analyses indicate that AcMNPV, or an ancestral baculovirus, acquired the chitinase gene from a bacterium via horizontal gene transfer

Preliminary phytochemical screening and In vitro antioxidant activities of the aqueous extract of Helichrysum longifolium DC

<p>Abstract</p> <p>Background</p> <p>Many oxidative stress related diseases are as a result of accumulation of free radicals in the body. A lot of researches are going on worldwide directed towards finding natural antioxidants of plants origins. The aims of this study were to evaluate <it>in vitro </it>antioxidant activities and to screen for phytochemical constituents of <it>Helichrysum longifolium </it>DC. [Family Asteraceae] aqueous crude extract.</p> <p>Methods</p> <p>We assessed the antioxidant potential and phytochemical constituents of crude aqueous extract of <it>Helichrysum longifolium </it>using tests involving inhibition of superoxide anions, DPPH, H₂O₂, NO and ABTS. The flavonoid, proanthocyanidin and phenolic contents of the extract were also determined using standard phytochemical reaction methods.</p> <p>Results</p> <p>Phytochemical analyses revealed the presence of tannins, flavonoids, steroids and saponins. The total phenolic content of the aqueous leaf extract was 0.499 mg gallic acid equivalent/g of extract powder. The total flavonoid and proanthocyanidin contents of the plant were 0.705 and 0.005 mg gallic acid equivalent/g of extract powder respectively. The percentage inhibition of lipid peroxide at the initial stage of oxidation showed antioxidant activity of 87% compared to those of BHT (84.6%) and gallic acid (96%). Also, the percentage inhibition of malondialdehyde by the extract showed percentage inhibition of 78% comparable to those of BHT (72.24%) and Gallic (94.82%).</p> <p>Conclusions</p> <p>Our findings provide evidence that the crude aqueous extract of <it>H. longifolium </it>is a potential source of natural antioxidants, and this justified its uses in folkloric medicines.</p

Thioflavine-T and Congo Red reveal the polymorphism of insulin amyloid fibrils when probed by polarization-resolved fluorescence microscopy.

International audienceAmyloid fibrils are protein misfolding structures that involve a β-sheet structure and are associated with the pathologies of various neurodegenerative diseases. Here we show that Thioflavine-T and Congo Red, two major dyes used to image fibrils by fluorescence assays, can provide deep structural information when probed by means of polarization-resolved fluorescence microscopy. Unlike fluorescence anisotropy or fluorescence detected linear dichroism imaging, this technique allows to retrieve simultaneously both mean orientation and orientation dispersion of the dye, used here as a reporter of the fibril structure. We have observed that insulin amyloid fibrils exhibit a homogeneous behavior over the fibrils' length, confirming their structural uniformity. In addition, these results reveal the existence of various structures among the observed fibrils' population, in spite of a similar aspect when imaged with conventional fluorescence microscopy. This optical nondestructive technique opens perspectives for in vivo structural analyses or high throughput screening

The O/OREOS Mission - Astrobiology in Low Earth Orbit

The O/OREOS (Organism/Organic Exposure to Orbital Stresses) nanosatellite is the first science demonstration spacecraft and flight mission of the NASA Astrobiology Small- Payloads Program (ASP). O/OREOS was launched successfully on November 19, 2010, to a high-inclination (72), 650-km Earth orbit aboard a US Air Force Minotaur IV rocket from Kodiak, Alaska. O/OREOS consists of 3 conjoined cubesat (each 1000 cu.cm) modules: (i) a control bus, (ii) the Space Environment Survivability of Living Organisms (SESLO) experiment, and (iii) the Space Environment Viability of Organics (SEVO) experiment. Among the innovative aspects of the O/OREOS mission are a real-time analysis of the photostability of organics and biomarkers and the collection of data on the survival and metabolic activity for micro-organisms at 3 times during the 6-month mission. We will report on the spacecraft characteristics, payload capabilities and first operational phase of the O/OREOS mission. The science and technology rationale of O/OREOS supports NASAs scientific exploration program by investigating the local space environment as well as space biology relevant to Moon and Mars missions. It also serves as precursor for experiments on small satellites, the International Space Station (ISS), future free-flyers and lunar surface exposure facilities