Mahler's work on Diophantine equations and subsequent developments

We discuss Mahler's work on Diophantine approximation and its applications to Diophantine equations, in particular Thue-Mahler equations, S-unit equations and S-integral points on elliptic curves, and go into later developments concerning the number of solutions to Thue-Mahler equations and effective finiteness results for Thue-Mahler equations. For the latter we need estimates for p-adic logarithmic forms, which may be viewed as an outgrowth of Mahler's work on the p-adic Gel'fond-Schneider theorem. We also go briefly into decomposable form equations, these are certain higher dimensional generalizations of Thue-Mahler equations.Comment: 26 pages. This paper will appear in "Mahler Selecta", a volume dedicated to the work of Kurt Mahler and its impac

Electronic structure of fully epitaxial Co2TiSn thin films

In this article we report on the properties of thin films of the full Heusler compound Co2TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600{\deg}C. The films are well ordered in the L21 structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 \mu_B on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L3/L2 edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co2TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.Comment: 11 pages, 8 figure

High-resolution record of stable isotopes in soil carbonates reveals environmental dynamics in an arid region (central Iran) during the last 32 ka

Although central Iran is pivotal for palaeoclimatic correlations, palaeoenvironmental data for this region is very sparse and a reliable chronology for pedogenic features is lacking. We therefore tried to answer the question how the environmental conditions and, in particular, the climate developed over time by using the isotopic signatures of pedogenic carbonates. We present a chronology of pedogenic carbonates in association with stable carbon and oxygen isotopes in both the matrix and coating carbonates of a relict palаeosol (Baharan palaeosol) in central Iran to understand the dynamics of environmental changes in this region during the late Quaternary. The palаeosol experienced several episodes of leaching during pedogenesis as reflected in its morphology (carbonate coatings under the rock fractions) and geochemical characteristics (Ba/Sr ratios). The δ$^{18}$O values of both the matrix and coating carbonates in the upper 60 cm (especially in the upper 20 cm) of the pedon are enriched (∼4‰) compared to the subsoil and are mainly related to the impact of evaporation. Moreover, the δ$^{13}$C values of the carbonates are in isotopic disequilibrium with the modern vegetation cover (desert shrubs) of the study area and are enriched in different degrees. The carbonates in the top 60 cm are formed by the input of atmospheric CO$_{2}$ and calcareous dust while deeper carbonates formed in an environment exhibiting a higher contribution of C$_{4}$ plants. Based on the radiocarbon chronology of carbonate coatings, it seems that three main stages of palaeoenvironmental changes occurred in the region during the last 32 ka. The first stage lasted ca. 5,000 years (between 31.6 and 26.0 ka) and was accompanied by deep leaching under sub-humid climatic conditions and the expansion of C$_{4}$ plants. Under the dominance of semi-arid conditions during the second stage until the late Holocene, a gradual increase in the δ$^{18}$O values and aridity occurred in the region. The last phase in the late Holocene was characterised by the establishment of an arid and evaporative environment with a sparse vegetation cover. A climatic correlation using the oxygen isotopic composition of secondary carbonates from the Baharan palaeosol, Soreq Cave (the Levant) and Hoti Cave (Oman; both having speleothems records) suggested a climatic connection between central Iran and the eastern Mediterranean during the late Pleistocene and between central Iran and northern Oman during the late Holocene

Population-wide administration of single dose rifampicin for leprosy prevention in isolated communities: A three year follow-up feasibility study in Indonesia

Background: Indonesia ranking third in the world, regarding leprosy burden. Chemoprophylaxis is effective in reducing risk of developing leprosy among contacts. 'Blanket approach' is an operational strategy for leprosy post-exposure prophylaxis in which all members of an isolated community, high endemic for leprosy are screened and given a single dose of rifampicin (SDR) in the absence of signs and symptoms of leprosy. The objective is to assess the operational feasibility of a population-wide 'blanket' administration of SDR for leprosy prevention in isolated communities in a remote island. Methods: A prospective follow-up study was conducted in the year 2014, 2015 and 2016 in Lingat village of Selaru Island, Indonesia. During the first two visits, screening and SDR were provided, whereas only screening was conducted during the third visit. The demographic and clinical data were used for a descriptive analysis of the project coverage and leprosy epidemiology. Results: During the first two visits, 1671 persons (88%) were screened, 1499 (79%) received SDR, and 213 (11%) were excluded based on the exclusion criteria. During the first two visits, 43 (2.6%) cases were diagnosed with leprosy with a rate of 2263 per 100,000 population. The prevalence was highest in the age groups 15-24 and 25-49 years. Total, 14 (33%) cases had MB and 29 (67%) PB leprosy. Two cases (5%) had grade 2 disability. During the third visit, 10 new leprosy cases, with no grade 2 disability, were detected out of 1481 screened persons at the rate of 484 cases per 100,000 population (n = 2065 population in 2016). Among those screened during the third visit, there was a 50% reduction of leprosy among those who had previously received SDR compared to those who had not. Conclusion: With adequate planning and some additional investment, it is feasible to implement a blanket approach of chemoprophylaxis in a remote island of Indonesia, although effort needs to be made to cover as many people as possibl

A SNP based linkage map of the turkey genome reveals multiple intrachromosomal rearrangements between the Turkey and Chicken genomes

<p>Abstract</p> <p>Background</p> <p>The turkey (<it>Meleagris gallopavo</it>) is an important agricultural species that is the second largest contributor to the world's poultry meat production. The genomic resources of turkey provide turkey breeders with tools needed for the genetic improvement of commercial breeds of turkey for economically important traits. A linkage map of turkey is essential not only for the mapping of quantitative trait loci, but also as a framework to enable the assignment of sequence contigs to specific chromosomes. Comparative genomics with chicken provides insight into mechanisms of genome evolution and helps in identifying rare genomic events such as genomic rearrangements and duplications/deletions.</p> <p>Results</p> <p>Eighteen full sib families, comprising 1008 (35 F1 and 973 F2) birds, were genotyped for 775 single nucleotide polymorphisms (SNPs). Of the 775 SNPs, 570 were informative and used to construct a linkage map in turkey. The final map contains 531 markers in 28 linkage groups. The total genetic distance covered by these linkage groups is 2,324 centimorgans (cM) with the largest linkage group (81 loci) measuring 326 cM. Average marker interval for all markers across the 28 linkage groups is 4.6 cM. Comparative mapping of turkey and chicken revealed two inter-, and 57 intrachromosomal rearrangements between these two species.</p> <p>Conclusion</p> <p>Our turkey genetic map of 531 markers reveals a genome length of 2,324 cM. Our linkage map provides an improvement of previously published maps because of the more even distribution of the markers and because the map is completely based on SNP markers enabling easier and faster genotyping assays than the microsatellitemarkers used in previous linkage maps. Turkey and chicken are shown to have a highly conserved genomic structure with a relatively low number of inter-, and intrachromosomal rearrangements.</p

A snow forecasting decision tree for significant snowfall over the interior of South Africa

Snowfall occurs every winter over the mountains of South Africa but is rare over the highly populated metropolises over the interior of South Africa. When snowfall does occur over highly populated areas, it causes widespread disruption to infrastructure and even loss of life. Because of the rarity of snow over the interior of South Africa, inexperienced weather forecasters often miss these events. We propose a five-step snow forecasting decision tree in which all five criteria must be met to forecast snowfall. The decision tree comprises physical attributes that are necessary for snowfall to occur. The first step recognises the synoptic circulation patterns associated with snow and the second step detects whether precipitation is likely in an area. The remaining steps all deal with identifying the presence of a snowflake in a cloud and determining that the snowflake will not melt on the way to the ground. The decision tree is especially useful to forecast the very rare snow events that develop from relatively dry and warmer surface conditions. We propose operational implementation of the decision tree in the weather forecasting offices of South Africa, as it is foreseen that this approach could significantly contribute to accurately forecasting snow over the interior of South Africa. SIGNIFICANCE : • A method for forecasting disruptive snowfall is provided. It is envisaged that this method will contribute to the improved forecasting of these severe weather events over South Africa. • Weather systems responsible for snowfall are documented and the cloud microphysical aspects important for the growth and melting of a snowflake are discussed. • Forecasting methods are proposed for the very rare events when snow occurs over the interior of South Africa when the air is relatively dry and somewhat warmer.This paper emanates from the work that J.H.S. conducted to obtain his MSc at the University of Pretoria under the supervision of L.D.South African Weather Service; University of Pretoriahttp://www.sajs.co.za/am2016Geography, Geoinformatics and Meteorolog

A snow forecasting decision tree for significant snowfall over the interior of South Africa

Snowfall occurs every winter over the mountains of South Africa but is rare over the highly populated metropolises over the interior of South Africa. When snowfall does occur over highly populated areas, it causes widespread disruption to infrastructure and even loss of life. Because of the rarity of snow over the interior of South Africa, inexperienced weather forecasters often miss these events. We propose a five-step snow forecasting decision tree in which all five criteria must be met to forecast snowfall. The decision tree comprises physical attributes that are necessary for snowfall to occur. The first step recognises the synoptic circulation patterns associated with snow and the second step detects whether precipitation is likely in an area. The remaining steps all deal with identifying the presence of a snowflake in a cloud and determining that the snowflake will not melt on the way to the ground. The decision tree is especially useful to forecast the very rare snow events that develop from relatively dry and warmer surface conditions. We propose operational implementation of the decision tree in the weather forecasting offices of South Africa, as it is foreseen that this approach could significantly contribute to accurately forecasting snow over the interior of South Africa. SIGNIFICANCE : • A method for forecasting disruptive snowfall is provided. It is envisaged that this method will contribute to the improved forecasting of these severe weather events over South Africa. • Weather systems responsible for snowfall are documented and the cloud microphysical aspects important for the growth and melting of a snowflake are discussed. • Forecasting methods are proposed for the very rare events when snow occurs over the interior of South Africa when the air is relatively dry and somewhat warmer.This paper emanates from the work that J.H.S. conducted to obtain his MSc at the University of Pretoria under the supervision of L.D.South African Weather Service; University of Pretoriahttp://www.sajs.co.za/am2016Geography, Geoinformatics and Meteorolog

Coverage of harm reduction services and HIV infection: A multilevel analysis of five Chinese cities

__Background:__ Since 2003, a harm reduction program for injecting drug users has been rolled out countrywide in China. It entails services for condom promotion, a needle and syringe program (NSP), and methadone maintenance treatment (MMT). However, it remains unknown if and to what extent the coverage of these services at city level is related to a reduced risk of HIV infection among drug users. __Methods:__ We wished to quantify the extent to which city-level characteristics (such as NSP and MMT service coverage) and individual-level determinants (e.g., self-reported exposure to NSP and MMT services, knowledge, motivation, and skills) were associated with the risk of HIV infection among drug users. In 2006, we conducted an integrated serological and behavioral survey among drug users in five cities of Yunnan Province, China (N = 685), constructing a multilevel logistic regression model with drug users clustered within these cities. __Results:__ Drug users who reported having received NSP or MMT services were about 50% less likely to be infected with HIV than those who reported not having received them (OR 0.45, 95% CI, 0.26-0.83 for NSP and 0.48, 95% CI, 0.31-0.73 for MMT). Despite a between-city variation of HIV infection risk (ICC 0.24, 95% CI 0.08-0.54), none of the city-level factors could explain this difference. Individual-level determinants such as perceived risk of infection and use of condoms were not associated with HIV infection. __Conclusions:__ Although people who had used NSP or MMT services were less likely to be HIV infected, this study found no relationship between city-level coverage of HIV prevention programs and variations in HIV infection between cities. This may have been due to the low number of cities in the analysis. Future research should include the analysis of data from a larger number of cities, which are collected widely in China through integrated behavioral and serological surveys