Soil, grain and water chemistry and human selenium imbalances in Enshi district, Hubei Province, China

Many elements which are essential to human and other animal health in small doses can be toxic if ingested in excess. Selenium (Se), a naturally occurring metalloid element is found in all natural materials on earth including rocks, soils, waters, air, plant and animal tissues. Since the early 1930’s, it has been recognised that Se toxicity causes hoof disorders and hair loss in livestock. Se was also identified as an essential trace element to humans and other animals in the late 1950’s. It forms a vital constituent of the biologically important enzyme glutathione peroxidase which acts as an anti-oxidant preventing cell degeneration. Se deficiency has been implicated in the aetiology of several diseases including cancer, muscular dystrophy, muscular sclerosis and cystic fibrosis. Se can be assimilated in humans through several pathways including food, drinking water and inhalation of Se-bearing particles from the atmosphere. In the majority of situations, food is the most important source of Se, as levels in water are very low. The narrow range between deficiency levels (<40 pg per day) and toxic levels in susceptible people (> 900 pg per day) makes it necessary to carefully control the amount of Se in the diet. In China, Se deficiency has been linked to an endemic degenerative heart disease known as Keshan Disease (KD) and an endemic osteoarthropathy which causes deformity of affected joints, known as Kaschin-Beck Disease. These diseases occur in a geographic belt stretching from Heilongjiang Province in north-east China to Yunnan Province in the south-west. In the period between 1959 and 1970, peak KD incidence rates exceeded 40 per 100 000 (approximately 8500 cases per annum) with 1400 - 3000 deaths recorded each year. Incidence rates have since fallen to less than 5 per 100 000 with approximately 1000 new cases reported annually (Levander, 1986). Se toxicity (selenosis) resulting in hair and nail loss and disorders of the nervous system in the human population, has also been recorded in Enshi District, Hubei Province and in Ziyang County, Shanxi Province. China possesses one of the best epidemiological databases in the world on Se-related diseases which has been used in conjunction with geochemical data to demonstrate a significant geochemical control on human Se exposure. However, the precise geographical areas at risk and the geochemical controls on selenium availability have yet to be established

The histone methyltransferase Setd7 promotes pancreatic progenitor identity

Cell fate specification depends on transcriptional activation driven by lineage-specific transcription factors as well as changes in chromatin organization. To date, the interplay between transcription factors and chromatin modifiers during development is not well understood. We focus here on the initiation of the pancreatic program from multipotent endodermal progenitors. Transcription factors that play key roles in regulating pancreatic progenitor state have been identified, but the chromatin regulators that help establishing and maintaining pancreatic fate are less well known. Using a comparative approach, we identify a critical role for the histone methyltransferase Setd7 in establishing pancreatic cell identity. We show that Setd7 is expressed in the prospective pancreatic endoderm of Xenopus and mouse embryos prior to Pdx1 induction. Importantly, we demonstrate that setd7 is sufficient and required for pancreatic cell fate specification in Xenopus Functional and biochemical approaches in Xenopus and mouse endoderm support that Setd7 modulates methylation marks at pancreatic regulatory regions, possibly through interaction with the transcription factor Foxa2. Together, these results demonstrate that Setd7 acts as a central component of the transcription complex initiating the pancreatic program

Bound magnetic polaron driven low-temperature ferromagnetism in Cu1−xMnxO compounds

AbstractPartial Mn atoms have been confirmed to enter the CuO lattice and form the Cu1−xMnxO compounds in the case of doping with 0≤x≤0.2 by the sol–gel method. With increasing Mn content, magnetism is observed. The magnetic critical transition temperature increases with enhanced magnetism, which obeys the bound magnetic polaron theory. The electronic transportation shows an insulating behavior as the band-gap decreases. Our results may indicate that CuO may be used as a candidate of magnetic semiconductor

Computation of protein geometry and its applications: Packing and function prediction

This chapter discusses geometric models of biomolecules and geometric constructs, including the union of ball model, the weigthed Voronoi diagram, the weighted Delaunay triangulation, and the alpha shapes. These geometric constructs enable fast and analytical computaton of shapes of biomoleculres (including features such as voids and pockets) and metric properties (such as area and volume). The algorithms of Delaunay triangulation, computation of voids and pockets, as well volume/area computation are also described. In addition, applications in packing analysis of protein structures and protein function prediction are also discussed.Comment: 32 pages, 9 figure

Landau levels and magnetopolaron effect in dilute GaAs:N

The magnetic-field dependence of the energy spectrum of GaAs doped with nitrogen impurities is investigated. Our theoretical model is based on the phenomenological Band Anticrossing Model (BAC) which we extended in order to include magnetic field and electron - phonon interaction. Due to the highly localized nature of the nitrogen state, we find that the energy levels are very different from those of pure GaAs. The polaron correction results in a lower cyclotron resonance energy as compared to pure GaAs. The magneto-absorption spectrum exhibits series of asymmetric peaks close to the cyclotron energy

Vortex Matter in Mesoscopic Superconducting Disks and Rings

Phase transitions between different (i.e. giant and multi-vortex) superconducting states and between the superconducting-normal state of mesoscopic disks and rings are studied in the presence of an external magnetic field by solving the two non-linear Ginzburg-Landau equations self-consistently. The flux through a circular disk with a hole in the middle is not quantized.Comment: 8 pages, 10 figures; to appear in Physica C (proceedings of the conference on Vortex matter, Crete (september 1999

Well-posedness of the Ericksen-Leslie system

In this paper, we prove the local well-posedness of the Ericksen-Leslie system, and the global well-posednss for small initial data under the physical constrain condition on the Leslie coefficients, which ensures that the energy of the system is dissipated. Instead of the Ginzburg-Landau approximation, we construct an approximate system with the dissipated energy based on a new formulation of the system.Comment: 16 page

Holstein polarons in a strong electric field: delocalized and stretched states

The coherent dynamics of a Holstein polaron in strong electric fields is considered under different regimes. Using analytical and numerical analysis, we show that even for small hopping constant and weak electron-phonon interaction, the original discrete Wannier-Stark (WS) ladder electronic states are each replaced by a semi-continuous band if a resonance condition is satisfied between the phonon frequency and the ladder spacing. In this regime, the original localized WS states can become {\em delocalized}, yielding both `tunneling' and `stretched' polarons. The transport properties of such a system would exhibit a modulation of the phonon replicas in typical tunneling experiments. The modulation will reflect the complex spectra with nearly-fractal structure of the semi-continuous band. In the off-resonance regime, the WS ladder is strongly deformed, although the states are still localized to a degree which depends on the detuning: Both the spacing between the levels in the deformed ladder and the localization length of the resulting eigenfunctions can be adjusted by the applied electric field. We also discuss the regime beyond small hopping constant and weak coupling, and find an interesting mapping to that limit via the Lang-Firsov transformation, which allows one to extend the region of validity of the analysis.Comment: 10 pages, 13 figures, submitted to PR

Identification of rice chromosome segment substitution line Z322-1-10 and mapping QTLs for agronomic traits from the F₃ population

Chromosome segment substitution lines (CSSLs) are powerful tools to combine naturally occurring genetic variants with favorable alleles in the same genetic backgrounds of elite cultivars. An elite CSSL Z322-1-10 was identified from advanced backcrosses between a japonica cultivar Nipponbare and an elite indica restorer Xihui 18 by SSR marker-assisted selection (MAS). The Z322-1-10 line carries five substitution segments distributed on chromosomes 1, 2, 5, 6 and 10 with an average length of 4.80 Mb. Spikilets per panicle, 1000-grain weight, grain length in the Z322-1-10 line are significantly higher than those in Nipponbare. Quantitative trait loci (QTLs) were identified and mapped for nine agronomic traits in an F3 population derived from the cross between Nipponbare and Z322-1-10 using the restricted maximum likelihood (REML) method in the HPMIXED procedure of SAS. We detected 13 QTLs whose effect ranging from 2.45% to 44.17% in terms of phenotypic variance explained. Of the 13 loci detected, three are major QTL (qGL1, qGW5-1 and qRLW5-1) and they explain 34.68%, 44.17% and 33.05% of the phenotypic variance. The qGL1 locus controls grain length with a typical Mendelian dominance inheritance of 3:1 ratio for long grain to short grain. The already cloned QTL qGW5-1 is linked with a minor QTL for grain width qGW5-2 (13.01%) in the same substitution segment. Similarly, the previously reported qRLW5-1 is also linked with a minor QTL qRLW5-2. Not only the study is important for fine mapping and cloning of the gene qGL1, but also has a great potential for molecular breeding