Multi-component ab2 metal hydride alloys for nickel metal hydride battery applications

Compared to the mish metal-based AB5 MH alloy commonly used in Ni/MH batteries, the transition metal-based AB2 MH alloy not only reduces the rare earth dependency, it also has higher specific energy. In order to further improve the performance of AB2 MH alloy, it\u27s crucial to full understand its multi-phase nature, which includes the main C14/C15 Laves phases and the secondary non-Laves phases. In order to optimize the gaseous phase and electrochemical advantages of both the C14 and C15 Laves phases, a study was established to recognize the factors that affect the C14/C15 phase abundance. Average electron density (e/a) was proven to be an influential parameter in determining the C14/C15 phase abundance: as e/a increased, C14/C15 became less/more dominant, respectively. However, with different A-site composition, a shift in e/a was observed in the C14/C15 phase abundance vs. e/a relationship. The average chemical potential for electronic charge of A atoms (Φ * A) was found to show a nearly perfect linear correlation to the C14/C15 threshold with various selections of A-site elements. The combination of e/a and Φ * A can be used to predict the C14/C15 phase abundance and assist future AB2 MH alloy design process. Four non-Laves phase alloys, Zr8Ni21, Zr7Ni10, Zr9Ni11, and ZrNi, commonly seen in AB2 MH alloys were studied. Annealing treatment was adopted on each alloy to change the abundances of various phases. Annealing suppressed secondary phases except for the case of Zr9Ni11, where its secondary ZrNi phase increased. As the Zr/Ni ratio increased, the maximum gaseous phase hydrogen storage capacity increased but maximized at Zr : Ni = 9 : 11. Comparing the properties before and after annealing, it was clear that the natures of constituent phases influenced the gaseous phase storage. The highest full discharge capacity was obtained at Zr : Ni = 7 : 10, which is a compromise between the hydrogen desorption rate and the theoretical maximum gaseous phase hydrogen storage. As the Zr/Ni ratio increased, the amount of metallic Ni in the surface oxide decreased, therefore the high-rate dischargeablity decreased. Among all alloys, the unannealed Zr7Ni10 demonstrated the best gaseous phase hydrogen storage and electrochemical capacities, and the unannealed Zr8Ni21 showed excellent HRD and activation. Zr8Ni21 alloy was then chosen based on its promising performance to be further modified for the purpose of developing alternative MH alloys for Ni/MH batteries. Zr8Ni19 X 2 alloys (X = Ni, Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf) were prepared and studied. The effect of annealing on these alloys was also investigated. Only the main phase of the annealed Sn-substitution remained Zr8Ni21-structured while those of other substitutions turned into Zr7Ni10 or Zr2Ni7. Annealing generally suppressed secondary phases except for the case of Zr8Ni19Sn2, where the major phase transformed from Zr2Ni7 to Zr8Ni21. Both the maximum gaseous phase hydrogen storage and electrochemical full discharge capacities followed the increasing order of B/A ratio of the main phase. After annealing, all alloys except for the Sn-substituion showed degradation in full discharge capacity due to the reduction in number and abundance of the catalytic secondary phases. Among all alloys, the as-cast Hf-substituted Zr8Ni21 alloy demonstrated the best overall gaseous phase hydrogen storage and electrochemical properties

Recommendations for the management of indeterminate HIV PCR results within South Africa’s early infant diagnosis programme

Indeterminate HIV PCR results represent missed diagnostic opportunities within South Africa’s early infant diagnosis programme. These results not only delay diagnosis and appropriate management but are also a source of confusion and apprehension amongst clinicians and caregivers. We describe the extent of indeterminate HIV PCR results within South Africa’s early infant diagnosis programme and provide recommendations for the management of these cases, both in terms of laboratory practice and the clinical care of the infants.They also thank the United Nations Children’s Emergency Fund (UNICEF) for partial funding of this work. A.H.M. acknowledges the Discovery Foundation for financial support.http://www.sajhivmed.org.zaam2016Medical Virolog

Genetic Structure of Plasmodium falciparum and Elimination of Malaria, Comoros Archipelago

Elimination interventions should be implemented simultaneously throughout the entire archipelago

Pattern of the Divergence of Olfactory Receptor Genes during Tetrapod Evolution

The olfactory receptor (OR) multigene family is responsible for the sense of smell in vertebrate species. OR genes are scattered widely in our chromosomes and constitute one of the largest gene families in eutherian genomes. Some previous studies revealed that eutherian OR genes diverged mainly during early mammalian evolution. However, the exact period when, and the ecological reason why eutherian ORs strongly diverged has remained unclear. In this study, I performed a strict data mining effort for marsupial opossum OR sequences and bootstrap analyses to estimate the periods of chromosomal migrations and gene duplications of OR genes during tetrapod evolution. The results indicate that chromosomal migrations occurred mainly during early vertebrate evolution before the monotreme-placental split, and that gene duplications occurred mainly during early mammalian evolution between the bird-mammal split and marsupial-placental split, coinciding with the reduction of opsin genes in primitive mammals. It could be thought that the previous chromosomal dispersal allowed the OR genes to subsequently expand easily, and the nocturnal adaptation of early mammals might have triggered the OR gene expansion

Morphological and allozyme variation in a collection of Cucumeropsis mannii Naudin (Cucurbitaceae) from Côte d'Ivoire

peer reviewe

Hydrides of Laves type Ti–Zr alloys with enhanced H storage capacity as advanced metal hydride battery anodes

The present work was focused on the studies of the effect of variation of stoichiometric composition of Ti–Zr based AB2±x Laves phase alloys by changing the ratio between A (Ti + Zr) and B (Mn + V + Fe + Ni) components belonging to both hypo-stoichiometric (AB1.90, AB1.95) and over-stoichiometric (AB2.08) alloys further to the stoichiometric AB2.0 composition to optimize their hydrogen storage behaviours and performances as the alloy anodes of nickel metal hydride batteries. AB2-xLa0.03 Laves type alloys (A = Ti0.15Zr0.85; B = Mn0.64–0.69V0.11–0.119Fe0.11–0.119Ni1.097–1.184; x = 0, 0.05 and 0.1) were arc melted and then homogenized by annealing. The studies involved probing of the phase-structural composition by X-Ray diffraction (XRD), together with studies of the microstructural state, hydrogen absorption–desorption and thermodynamic characteristics of gas–solid reactions and electrochemical charge-discharge performance, further to the impedance spectroscopy characterization. The alloys were probed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and XRD. These studies concluded that the alloys contained the main C15 FCC Laves type AB2 intermetallic co-existing with a secondary C14 hexagonal Laves phase and a small amount of LaNi intermetallic

Corncrake conservation genetics at a European scale: the impact of biogeographical and anthropological processes

Understanding patterns of genetic structure, gene flow and diversity across a species range is required if we are to determine the genetic status and viability of small peripheral populations. This is especially crucial in species distributed across a large range where spatial heterogeneity makes it difficult to predict the distribution of genetic diversity. Although biogeographical models provide expectations of how spatially structured genetic variation may be at the range scale, human disturbance may cause strong deviations from these theoretical predictions. In this study, we investigated genetic structure and demography at a pan-European scale, in the corncrake Crex crex, a grassland bird species strongly affected by agricultural changes. We assessed population structure and genetic diversity, as well as demographic trends and direction of gene flow, in and among 15 contemporary populations of this species. Analyses revealed low genetic structure across the entire range with high levels of genetic diversity in all sites. However, we found some evidence that the westernmost populations were, to a very limited extent, differentiated from the rest of the European population. Demographic trends showed that population numbers have decreased in western Europe and remained constant across eastern Europe. Results may also suggest asymmetric gene flow from eastern to western populations. In conclusion, we suggest that the most likely scenario is that contrasting demographic regimes between eastern and western populations, driven by heterogeneous human activity, has caused asymmetric gene flow that has buffered small peripheral populations against genetic diversity loss, but also erased any genetic structure that may have existed. Our study highlight the need of coordinated actions at the European scale to preserve source populations and ensure the maintenance of reproductive productivity in the most threatened sites, in order to avoid losing any adaptive potential and too strongly relying on sink source populations whose future is uncertain

Grafting versus seed propagated apricot populations: two main gene pools in Tunisia evidenced by SSR markers and model-based Bayesian clustering

Apricot was introduced into the Mediterranean Basin from China and Asian mountains through the Middle-East and the Central Europe. Traditionally present in Tunisia, we were interested in accessing the origin of apricot species in the country, and in particular in the number and the location of its introductions. A set of 82 representative apricot accessions including 49 grafted cultivars and 33 seed propagated ‘Bargougs’ were genotyped using 24 microsatellite loci revealing a total of 135 alleles. The model-based Bayesian clustering analysis using both Structure and InStruct programs as well as the multivariate method revealed five distinct genetic clusters. The genetic differentiation among clusters showed that cluster 1, with only four cultivars, was the most differentiated from the four remaining genetic clusters, which constituted the largest part of the studied germplasm. According to their geographic origin, the five identified groups (north, centre, south, Gafsa oasis and other oases groups) enclosed a similar variation within group, with a low level of differentiation. Overall results highlighted the distinction of two apricot gene pools in Tunisia related to the different mode of propagation of the cultivars: grafted and seed propagated apricot, which enclosed a narrow genetic basis. Our findings support the assumption that grafting and seed propagated apricots shared the same origin

Genetic diversity of a large set of horse breeds raised in France assessed by microsatellite polymorphism

After the recent publication of our article (Leroy, Genetics Selection Evolution 2009 41:5), we found several errors in the published Table Three, concerning the computation of contribution to within-breed diversity (CW). We apologize to the readers for these errors, which are corrected in the present erratum

GC Content Increased at CpG Flanking Positions of Fish Genes Compared with Sea Squirt Orthologs as a Mechanism for Reducing Impact of DNA Methylation

Background: Fractional DNA methylation in sea squirts evolved to global DNA methylation in fish. The impact of global DNA methylation is reflected by more CpG depletions and/or more A/T to G/C changes at CpG flanking positions due to context-dependent mutations of methylated CpG sites. Methods and Findings: In this report, we demonstrate that the sea squirt genes have undergone more CpG to TpG/CpA substitutions than the fish orthologs using homologous fragments from orthologous genes among Ciona intestinalis, Ciona savignyi, fugufish and zebrafish. To avoid premature transcription, the TGA sites derived from CGA were largely converted to TGG in sea squirt genes. By contrast, a significant increment of GC content at CpG flanking positions was shown in fish genes. The positively selected A/T to G/C substitutions, in combination with the CpG to TpG/CpA substitutions, are the sources of the extremely low CpG observed/expected ratios in vertebrates. The nonsynonymous substitutions caused by the GC content increase have resulted in frequent amino acid replacements in the directions that were not noticed previously. Conclusion: The increased GC content at CpG flanking positions can reduce CpG loss in fish genes and attenuate the impact of DNA methylation on CpG-containing codons, probably accounting for evolution towards vertebrates. © 2008 Wang, Leung.published_or_final_versio