Nanoscale Au-ZnO heterostructure developed by atomic layer deposition towards amperometric H2O2 detection

Nanoscale Au-ZnO heterostructures were fabricated on 4-in. SiO2/Si wafers by the atomic layer deposition (ALD) technique. Developed Au-ZnO heterostructures after post-deposition annealing at 250 degrees C were tested for amperometric hydrogen peroxide (H2O2) detection. The surface morphology and nanostructure of Au-ZnO heterostructures were examined by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. Additionally, the electrochemical behavior of Au-ZnO heterostructures towards H2O2 sensing under various conditions is assessed by chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that ALD-fabricated Au-ZnO heterostructures exhibited one of the highest sensitivities of 0.53 mu A mu M(-1)cm(-2), the widest linear H2O2 detection range of 1.0 mu M-120mM, a low limit of detection (LOD) of 0.78 mu M, excellent selectivity under the normal operation conditions, and great long-term stability. Utilization of the ALD deposition method opens up a unique opportunity for the improvement of the various capabilities of the devices based on Au-ZnO heterostructures for amperometric detection of different chemicals

A Monte Carlo test of linkage disequilibrium for single nucleotide polymorphisms

<p>Abstract</p> <p>Background</p> <p>Genetic association studies, especially genome-wide studies, make use of linkage disequilibrium(LD) information between single nucleotide polymorphisms (SNPs). LD is also used for studying genome structure and has been valuable for evolutionary studies. The strength of LD is commonly measured by <it>r</it>², a statistic closely related to the Pearson's <it>χ</it>²statistic. However, the computation and testing of linkage disequilibrium using <it>r</it>²requires known haplotype counts of the SNP pair, which can be a problem for most population-based studies where the haplotype phase is unknown. Most statistical genetic packages use likelihood-based methods to infer haplotypes. However, the variability of haplotype estimation needs to be accounted for in the test for linkage disequilibrium.</p> <p>Findings</p> <p>We develop a Monte Carlo based test for LD based on the null distribution of the <it>r</it>²statistic. Our test is based on <it>r</it>²and can be reported together with <it>r</it>². Simulation studies show that it offers slightly better power than existing methods.</p> <p>Conclusions</p> <p>Our approach provides an alternative test for LD and has been implemented as a R program for ease of use. It also provides a general framework to account for other haplotype inference methods in LD testing.</p

Fixed Points of Difference Operator of Meromorphic Functions

Let f be a transcendental meromorphic function of order less than one. The authors prove that the exact difference Δf=fz+1-fz has infinitely many fixed points, if a∈ℂ and ∞ are Borel exceptional values (or Nevanlinna deficiency values) of f. These results extend the related results obtained by Chen and Shon

A gene-based approach for testing association of rare alleles

Rare genetic variants have been shown to be important to the susceptibility of common human diseases. Methods for detecting association of rare genetic variants are drawing much attention. In this report, we applied a gene-based approach to the 200 simulated data sets of unrelated individuals. The test can detect the association of some genes with multiple rare variants

Comparisons of mutation rate variation at genome-wide microsatellites: evolutionary insights from two cultivated rice and their wild relatives

<p>Abstract</p> <p>Background</p> <p>Mutation rate (μ) per generation per locus is an important parameter in the models of population genetics. Studies on mutation rate and its variation are of significance to elucidate the extent and distribution of genetic variation, further infer evolutionary relationships among closely related species, and deeply understand genetic variation of genomes. However, patterns of rate variation of microsatellite loci are still poorly understood in plant species. Furthermore, how their mutation rates vary in di-, tri-, and tetra-nucleotide repeats within the species is largely uninvestigated across related plant genomes.</p> <p>Results</p> <p>Genome-wide variation of mutation rates was first investigated by means of the composite population parameter θ (θ = 4Nμ, where N is the effective population size and μ is the mutation rate per locus per generation) in four subspecies of Asian cultivated rice <it>O. sativa </it>and its three related species, <it>O. rufipogon</it>, <it>O. glaberrima</it>, and <it>O. officinalis</it>. On the basis of three data sets of microsatellite allele frequencies throughout the genome, population mutation rate (<b><it>θ</it></b>) was estimated for each locus. Our results reveal that the variation of population mutation rates at microsatellites within each studied species or subspecies of cultivated rice can be approximated with a gamma distribution. The mean population mutation rates of microsatellites do not significantly differ in motifs of di-, tri-, and tetra-nucleotide repeats for the studied rice species. The shape parameter was also estimated for each subspecies of rice as well as other related rice species. Of them, different subspecies of <it>O. sativa </it>possesses similar shape parameters (<b><it>α</it></b>) of the gamma distribution, while other species extensively vary in their population mutation rates.</p> <p>Conclusion</p> <p>Through the analysis of genome-wide microsatellite data, the population mutation rate can be approximately fitted with a gamma distribution in most of the studied species. In general, different population histories occurred along different lineages may result in the observed variation of population mutation rates at microsatellites among the studied <it>Oryza </it>species.</p

Compensation and price delegation for heterogeneous sales force

A heterogeneous sales force may not be as desirable as a homogeneous sales force for two reasons: premiums are required for all except from one agent type, and only the highest type would work as hard as though they were from a homogeneous sales force. This study revisits the heterogeneous sales force compensation and price delegation problem with type-dependent reservation. We find that an equilibrium separating or pooling compensation contract always exists. Different types of agents may receive premiums, and there are scenarios when no premiums are paid. Retaining centralized pricing provides a tool for regulating agent behavior. More than one or even all agent types may work as hard as though they were members of a homogeneous sales force. These findings differ from existing results and their driving force is the dynamics between the differences in reservations and agents’ effort costs arising from concealing their true types

A new measure of population structure using multiple single nucleotide polymorphisms and its relationship with FST

<p>Abstract</p> <p>Background</p> <p>Large-scale genome-wide association studies are promising for unraveling the genetic basis of complex diseases. Population structure is a potential problem, the effects of which on genetic association studies are controversial. The first step to systematically quantify the effects of population structure is to choose an appropriate measure of population structure for human data. The commonly used measure is <it>Wright's </it>F_ST. For a set of subpopulations it is generally assumed to be one value of F_ST. However, the estimates could be different for distinct loci. Since population structure is a concept at the population level, a measure of population structure that utilized the information across loci would be desirable.</p> <p>Findings</p> <p>In this study we propose an <it>adjusted C parameter </it>according to the sample size from each sub-population. The new measure C is based on the <it>c parameter </it>proposed for SNP data, which was assumed to be subpopulation-specific and common for all loci. In this study, we performed extensive simulations of samples with varying levels of population structure to investigate the properties and relationships of both measures. It is found that the two measures generally agree well.</p> <p>Conclusion</p> <p>The new measure simultaneously uses the marker information across the genome. It has the advantage of easy interpretation as one measure of population structure and yet can also assess population differentiation.</p