Distortion maps for genus two curves

Distortion maps are a useful tool for pairing based cryptography. Compared with elliptic curves, the case of hyperelliptic curves of genus g > 1 is more complicated since the full torsion subgroup has rank 2g. In this paper we prove that distortion maps always exist for supersingular curves of genus g>1 and we construct distortion maps in genus 2 (for embedding degrees 4,5,6 and 12).Comment: 16 page

Measurement Invariance, Entropy, and Probability

We show that the natural scaling of measurement for a particular problem defines the most likely probability distribution of observations taken from that measurement scale. Our approach extends the method of maximum entropy to use measurement scale as a type of information constraint. We argue that a very common measurement scale is linear at small magnitudes grading into logarithmic at large magnitudes, leading to observations that often follow Student's probability distribution which has a Gaussian shape for small fluctuations from the mean and a power law shape for large fluctuations from the mean. An inverse scaling often arises in which measures naturally grade from logarithmic to linear as one moves from small to large magnitudes, leading to observations that often follow a gamma probability distribution. A gamma distribution has a power law shape for small magnitudes and an exponential shape for large magnitudes. The two measurement scales are natural inverses connected by the Laplace integral transform. This inversion connects the two major scaling patterns commonly found in nature. We also show that superstatistics is a special case of an integral transform, and thus can be understood as a particular way in which to change the scale of measurement. Incorporating information about measurement scale into maximum entropy provides a general approach to the relations between measurement, information and probability

Global Hot Gas in and around the Galaxy

The hot interstellar medium traces the stellar feedback and its role in regulating the eco-system of the Galaxy. I review recent progress in understanding the medium, based largely on X-ray absorption line spectroscopy, complemented by X-ray emission and far-UV OVI absorption measurements. These observations enable us for the first time to characterize the global spatial, thermal, chemical, and kinematic properties of the medium. The results are generally consistent with what have been inferred from X-ray imaging of nearby galaxies similar to the Galaxy. It is clear that diffuse soft X-ray emitting/absorbing gas with a characteristic temperature of $\sim 10^6$ K resides primarily in and around the Galactic disk and bulge. In the solar neighborhood, for example, this gas has a characteristic vertical scale height of $\sim 1$ kpc. This conclusion does not exclude the presence of a larger-scale, probably much hotter, and lower density circum-Galactic hot medium, which is required to explain observations of various high-velocity clouds. This hot medium may be a natural product of the stellar feedback in the context of the galaxy formation and evolution.Comment: 11 pages, invited talk in the workshop "The Local Bubble and Beyond II

Protein components of the microbial mercury methylation pathway

Mercury (Hg) in the environment and the resulting methylmercury (CH3Hg+) produced by microorganisms has emerged as a global concern in the last 50 years after a series of high profile, large scale contamination events, increased burning of fossil fuels, and a more recent major escalation of widespread use of Hg in artisanal gold mining. The Hg cycle in the environment is complex and still not completely known. Among the many different forms of Hg present in the environment, Hg, mainly as Hg(II), has been known to be converted to the more toxic CH3Hg+ by microorganisms. CH3Hg+ accumulates in the aquatic food chain and humans are eventually exposed to the toxic CH3Hg+ through their diets. When exposed to elevated levels of CH3Hg+, symptoms include mainly neurological pathologies along with reduced kidney and liver function. However, until recently the mechanism of the conversion of Hg(II) to CH3Hg+ in microorganisms was not known. It has now been shown that a pair of genes, hgcA and hcgB, present in a variety of microorganisms, are necessary for bacterial Hg methylation to occur. The structure and functions of the proteins encoded by these genes are still being explored, and here new data are shown for residues in these proteins that suggest key structural elements necessary for the Hg methylation reaction. Also presented are data from other possible proteins in the carbon flow and cobalamin assembly pathways leading up to Hg methylation by HgcA and HgcB. The new work described here is significant in that it not only adds to the expanding base of knowledge of microbial Hg methylation with the identification of hgcA and hgcB, but also shows specific catalytic residues of HgcA and HgcB that can be further studied in organisms that methylate Hg. These data and the mutants designed to facilitate its acquisition can be used in future efforts to identify other members of the Hg methylation pathway. These data and constructs will also aid in future attempts to determine if the two genes evolved for the sole purpose of methylating Hg(II) or to support the life cycle of the organism harboring these genes in another, yet to be determined capacity

Cavity-enhanced absorption using an atomic line source: application to deep-UV measurements

Optical cavities are commonly used to increase the sensitivity of absorption measurements, but have not been extensively used below 300 nm, mainly owing to the limited light sources at these wavelengths. While some progress has been made using cavity ring-down spectroscopy, these systems rely on complex and expensive lasers. Here we investigate an approach combining Cavity-Enhanced Absorption Spectroscopy (CEAS) with an inexpensive low vapour pressure mercury lamp for sensitive absorption measurements at 253.7 nm. We demonstrate that the CEAS absorption in our system is 50 times greater than the absorption found in a single-pass configuration; using this approach, we obtained limits of detection of 8.1 pptv (66 ng m(-3)) for gaseous elemental mercury and 8.4 ppbv for ozone. We evaluate the performance of the system and discuss potential improvements and applications of this approach

Modeling the Local Warm/Hot Bubble

In this paper we review the modeling of the Local Bubble (LB) with special emphasis on the progress we have made since the last major conference "The Local Bubble and Beyond (I)" held in Garching in 1997. Since then new insight was gained into the possible origin of the LB, with a moving group crossing its volume during the last 10 - 15 Myr being most likely responsible for creating a local cavity filled with hot recombining gas. Numerical high resolution 3D simulations of a supernova driven inhomogeneous interstellar medium show that we can reproduce both the extension of the LB and the OVI column density in absorption measured with FUSE for a LB age of 13.5 - 14.5 Myr. We further demonstrate that the LB evolves like an ordinary superbubble expanding into a density stratified medium by comparing analytical 2D Kompaneets solutions to NaI contours, representing the extension of the local cavity. These results suggest that LB blow-out into the Milky Way halo has occurred roughly 5 Myr ago.Comment: 8 pages, 3 figures, to appear in the proceedings of "The Local Bubble and Beyond II", Philadelphia, USA, April 21-24, 200

Preliminary - Representative Farm Analysis of House of Representatives Draft Concept Paper for 2002 Farm Bill

Agricultural and Food Policy,

Ternatin and improved synthetic variants kill cancer cells by targeting the elongation factor-1A ternary complex.

Cyclic peptide natural products have evolved to exploit diverse protein targets, many of which control essential cellular processes. Inspired by a series of cyclic peptides with partially elucidated structures, we designed synthetic variants of ternatin, a cytotoxic and anti-adipogenic natural product whose molecular mode of action was unknown. The new ternatin variants are cytotoxic toward cancer cells, with up to 500-fold greater potency than ternatin itself. Using a ternatin photo-affinity probe, we identify the translation elongation factor-1A ternary complex (eEF1A·GTP·aminoacyl-tRNA) as a specific target and demonstrate competitive binding by the unrelated natural products, didemnin and cytotrienin. Mutations in domain III of eEF1A prevent ternatin binding and confer resistance to its cytotoxic effects, implicating the adjacent hydrophobic surface as a functional hot spot for eEF1A modulation. We conclude that the eukaryotic elongation factor-1A and its ternary complex with GTP and aminoacyl-tRNA are common targets for the evolution of cytotoxic natural products