Zinc oxide : From dilute magnetic doping to spin transport

During the past years there has been renewed interest in the wide-bandgap II-VI semiconductor ZnO, triggered by promising prospects for spintronic applications. First, ferromagnetism was predicted for dilute magnetic doping. In comprehensive investigation of ZnO:Co thin films based on the combined measurement of macroscopic and microscopic properties, we find no evidence for carrier-mediated itinerant ferromagnetism. Phase-pure, crystallographically excellent ZnO:Co is uniformly paramagnetic. Superparamagnetism arises when phase separation or defect formation occurs, due to nanometer-sized metallic precipitates. Other compounds like ZnO:(Li,Ni) and ZnO:Cu do not exhibit indication of ferromagnetism. Second, its small spin-orbit coupling and correspondingly large spin coherence length makes ZnO suitable for transporting or manipulating spins in spintronic devices. From optical pump/optical probe experiments, we find a spin dephasing time of the order of 15 ns at low temperatures which we attribute to electrons bound to Al donors. In all-electrical magnetotransport measurements, we successfully create and detect a spin-polarized ensemble of electrons and transport this spin information across several nanometers. We derive a spin lifetime of 2.6 ns for these itinerant spins at low temperatures, corresponding well to results from an electrical pump/optical probe experiment.publishe

Allelic Variant in the Anti-Müllerian Hormone Gene Leads to Autosomal and Temperature-Dependent Sex Reversal in a Selected Nile Tilapia Line

<div><p>Owing to the demand for sustainable sex-control protocols in aquaculture, research in tilapia sex determination is gaining momentum. The mutual influence of environmental and genetic factors hampers disentangling the complex sex determination mechanism in Nile tilapia (<i>Oreochromis niloticus</i>). Previous linkage analyses have demonstrated quantitative trait loci for the phenotypic sex on linkage groups 1, 3, and 23. Quantitative trait loci for temperature-dependent sex reversal similarly reside on linkage group 23. The anti-Müllerian hormone gene (<i>amh</i>), located in this genomic region, is important for sexual fate in higher vertebrates, and shows sexually dimorphic expression in Nile tilapia. Therefore this study aimed at detecting allelic variants and marker-sex associations in the <i>amh</i> gene. Sequencing identified six allelic variants. A significant effect on the phenotypic sex for SNP <i>ss831884014</i> (p<0.0017) was found by stepwise logistic regression. The remaining variants were not significantly associated. Functional annotation of SNP <i>ss831884014</i> revealed a non-synonymous amino acid substitution in the <i>amh</i> protein. Consequently, a fluorescence resonance energy transfer (FRET) based genotyping assay was developed and validated with a representative sample of fish. A logistic linear model confirmed a highly significant effect of the treatment and genotype on the phenotypic sex, but not for the interaction term (treatment: p<0.0001; genotype: p<0.0025). An additive genetic model proved a linear allele substitution effect of 12% in individuals from controls and groups treated at high temperature, respectively. Moreover, the effect of the genotype on the male proportion was significantly higher in groups treated at high temperature, giving 31% more males on average of the three genotypes. In addition, the groups treated at high temperature showed a positive dominance deviation (+11.4% males). In summary, marker-assisted selection for <i>amh</i> variant <i>ss831884014</i> seems to be highly beneficial to increase the male proportion in Nile tilapia, especially when applying temperature-induced sex reversal.</p></div

Effect of SNP <i>ss831884014</i> genotypes, temperature treatment (28°C vs. 36°C from 10–20 dpf) and their interaction on the phenotypic sex in Nile tilapia.

<p>(The effects were estimated using a GLM with binominal error distribution and logit link function and were validated using a GLM with identity link function; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104795#pone.0104795.e001" target="_blank">Equation 1</a>: Linear regression model ; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104795#pone.0104795.e006" target="_blank">Equation 2</a>: Fixed effect model .</p><p>Effect of SNP <i>ss831884014</i> genotypes, temperature treatment (28°C vs. 36°C from 10–20 dpf) and their interaction on the phenotypic sex in Nile tilapia.</p

Relationship between male proportion and genotype at <i>amh</i> variant <i>ss831884014</i> in Nile tilapia, reared at 28°C or 36°C from 10 to 20 days post fertilisation.

<p>Linear least-square regression of the genotypic values (LSmean male proportion) for genotypes C/C, G/C, and G/G at locus <i>ss831884014</i> of the <i>amh</i> gene (Scaffold <i>GL831234.1</i>). The genotypic values were derived from the regression models by either excluding the interaction between SNP and treatment (LSmeans 1: red and blue line) or by including the interaction between SNP and treatment (LSmeans 2: red and blue triangles) as effect class. Numbers of individuals per genotype were 26/79/20 and 114/144/47 for genotypes C/C, G/C, and G/G, for the control group (28°C) and the group reared at high temperature (36°C), respectively.</p

Dominance and additive effects of the variant <i>ss831884014</i> on the male proportion in Nile tilapia reared at 28°C or 36°C from 10–20 dpf.

<p>(Values given brackets are standard errors of the estimates; ¹⁾ Parameters were derived from GLM with binominal error distribution and logit link function; ²⁾ Dominance and homozygous additive allele effects were derived from back transformed LSmeans; ³⁾ Parameters were derived from GLM with identity link function).</p><p>Dominance and additive effects of the variant <i>ss831884014</i> on the male proportion in Nile tilapia reared at 28°C or 36°C from 10–20 dpf.</p

Allele frequencies, polymorphism information content (PIC), heterozygosity and allelic diversity for four allelic variants in the <i>amh</i> gene detected in a genetically all-female (XX) Nile tilapia population.

<p>(¹ Initially 93 individuals were Sanger-sequenced for the <i>amh</i> gene. The genotyped sample was comprised of three families including the corresponding three dams and sires; ² In total 337 individuals were investigated using the FRET-assay, in order to obtain a total of 430 genotypes at SNP <i>ss831884014</i> (including the before mentioned Sanger-sequenced individuals)).</p><p>Allele frequencies, polymorphism information content (PIC), heterozygosity and allelic diversity for four allelic variants in the <i>amh</i> gene detected in a genetically all-female (XX) Nile tilapia population.</p

Functional annotation of six allelic variants in the Nile tilapia <i>amh</i> gene.

<p>(¹The annotation of functional effects was carried out using <i>SNP</i>Eff 2.0.5 (<a href="http://SNPeff.sourceforge.net/" target="_blank">http://SNPeff.sourceforge.net/</a>) using the <i>Oreochromis niloticus</i> genome sequence deposited in the Ensembl database (scaffold <i>GL831234.1</i>)).</p><p>Functional annotation of six allelic variants in the Nile tilapia <i>amh</i> gene.</p

Experimental design to obtain a genetically female (XX) population in order to study temperature effects on the male proportion in a selected line of Nile tilapia.

<p>Experimental design to obtain a genetically female (XX) population in order to study temperature effects on the male proportion in a selected line of Nile tilapia.</p