Hydrogen Pentagraphenelike Structure Stabilized by Hafnium: A High-Temperature Conventional Superconductor

The recent discovery of H3S and LaH10 superconductors with record high superconducting transition temperatures Tc at high pressure has fueled the search for room-temperature superconductivity in the compressed superhydrides. Here we introduce a new class of high Tc hydrides with a novel structure and unusual properties. We predict the existence of an unprecedented hexagonal HfH10, with remarkably high value of Tc (around 213–234 K) at 250 GPa. As concerns the novel structure, the H ions in HfH10 are arranged in clusters to form a planar “pentagraphenelike” sublattice. The layered arrangement of these planar units is entirely different from the covalent sixfold cubic structure in H3S and clathratelike structure in LaH10. The Hf atom acts as a precompressor and electron donor to the hydrogen sublattice. This pentagraphenelike H10 structure is also found in ZrH10, ScH10, and uH10 at high pressure, each material showing a high Tc ranging from 134 to 220 K. Our study of dense superhydrides with pentagraphenelike layered structures opens the door to the exploration of a new class of high Tc superconductors

Systematic Analysis of Sequences and Expression Patterns of Drought-Responsive Members of the HD-Zip Gene Family in Maize

Background: Members of the homeodomain-leucine zipper (HD-Zip) gene family encode transcription factors that are unique to plants and have diverse functions in plant growth and development such as various stress responses, organ formation and vascular development. Although systematic characterization of this family has been carried out in Arabidopsis and rice, little is known about HD-Zip genes in maize (Zea mays L.). Methods and Findings: In this study, we described the identification and structural characterization of HD-Zip genes in the maize genome. A complete set of 55 HD-Zip genes (Zmhdz1-55) were identified in the maize genome using Blast search tools and categorized into four classes (HD-Zip I-IV) based on phylogeny. Chromosomal location of these genes revealed that they are distributed unevenly across all 10 chromosomes. Segmental duplication contributed largely to the expansion of the maize HD-ZIP gene family, while tandem duplication was only responsible for the amplification of the HD-Zip II genes. Furthermore, most of the maize HD-Zip I genes were found to contain an overabundance of stress-related ciselements in their promoter sequences. The expression levels of the 17 HD-Zip I genes under drought stress were also investigated by quantitative real-time PCR (qRT-PCR). All of the 17 maize HD-ZIP I genes were found to be regulated by drought stress, and the duplicated genes within a sister pair exhibited the similar expression patterns, suggesting their conserved functions during the process of evolution

Performances zootechniques de Tryonomys swinderianus en captivité en zone daltitude

In order to improve on the reproductive performances of grasscutters (Tryonomys swinderianus) in captivity, a study was conducted in the grasscutter distribution centre at CIPCRE1 Bafoussam, Cameroon. The reproductive performances of 53 gestating females (37 in the first and 16 in the second) were studied. The major results showed that the average litter size at first litter was 4.44 ± 1.41 which increased on second birth. A mortality rate of 7% was observed in the first litter which significantly (p<0.05) increase to 11% in the second litter. The number of grasscutters born alive per litter (4.12 ± 1.68) remains relatively unchanged in the two litters. A sex ratio of 0.92:1 and 1.06:1 was observed in the first and second litter respectively. The post natal mortality rate (36%) decreased with litter number and varies inversely with the female weight at reproductive maturity. The birth and weaning weight (138 ± 21 and 533 ± 84 g respectively) were higher in the second litter with weaning rate of 97%. The mortality rate of 70% was observed in the study which resulted from respiratory, gastro-intestinal tract diseases and some accidental cases. Metabolic diseases were more frequent in the males grasscutters. However, death rate in the females was twice that of the males.Dans le but de contribuer à l"amélioration des performances de reproduction des aulacodes (Tryonomys swinderianus) en captivité, une étude a été menée en 2004 à la station de diffusion des aulacodes du CIPCRE1 à Bafoussam (ouest-Cameroun). Un total de 53 mises bas (37 en première et 16 en seconde) a été suivi pour les performances de reproduction. Les principaux résultats ont été les suivants : la durée de gestation a été de 158 ± 6 jours. La taille de la portée, de 4,44 ± 1,41 petits en moyenne, a été plus élevée à la seconde mise-bas. Le taux de mortinatalité, de près de 7 % à la première, était significativement plus élevé (11%) à la seconde mise-bas. Le nombre de petits nés vivants par portée (4,12 ± 1,68) est resté relativement inchangé pour les deux mise-bas. Le sex-ratio, de 0,92/1 à la première, a été plus élevé à la seconde mise-bas (1,06/1). Le taux de mortalité post natal (30%) a baissée avec le numéro de mise-bas, variant inversement au poids à la mise en reproduction des femelles. Le poids à la naissance et au sevrage (138 ± 21 et 633 ± 84 g respectivement) ont été plus élevé à la seconde mise bas, le taux de sevrage étant de 97%. Les principales causes de morbidité et de mortalité ont été: les affections respiratoires, gastro-intestinales et les accidents, dont 70% des mortalités totales. Les maladies liées à l"alimentation ont été plus fréquentes chez les mâles que chez les femelles. Par contre, les reproductrices mouraient pratiquement deux fois plus que les reproducteurs

Design Principles for High-Temperature Superconductors with a Hydrogen-Based Alloy Backbone at Moderate Pressure.

Hydrogen-based superconductors provide a route to the long-sought goal of room-temperature superconductivity, but the high pressures required to metallize these materials limit their immediate application. For example, carbonaceous sulfur hydride, the first room-temperature superconductor made in a laboratory, can reach a critical temperature (T_{c}) of 288 K only at the extreme pressure of 267 GPa. The next recognized challenge is the realization of room-temperature superconductivity at significantly lower pressures. Here, we propose a strategy for the rational design of high-temperature superconductors at low pressures by alloying small-radius elements and hydrogen to form ternary H-based superconductors with alloy backbones. We identify a "fluorite-type" backbone in compositions of the form AXH_{8}, which exhibit high-temperature superconductivity at moderate pressures compared with other reported hydrogen-based superconductors. The Fm3[over ¯]m phase of LaBeH_{8}, with a fluorite-type H-Be alloy backbone, is predicted to be thermodynamically stable above 98 GPa, and dynamically stable down to 20 GPa with a high T_{c}∼185  K. This is substantially lower than the synthesis pressure required by the geometrically similar clathrate hydride LaH_{10} (170 GPa). Our approach paves the way for finding high-T_{c} ternary H-based superconductors at conditions close to ambient pressures

Hydrogen Pentagraphenelike Structure Stabilized by Hafnium: A High-Temperature Conventional Superconductor.

The recent discovery of H_{3}S and LaH_{10} superconductors with record high superconducting transition temperatures T_{c} at high pressure has fueled the search for room-temperature superconductivity in the compressed superhydrides. Here we introduce a new class of high T_{c} hydrides with a novel structure and unusual properties. We predict the existence of an unprecedented hexagonal HfH_{10}, with remarkably high value of T_{c} (around 213-234 K) at 250 GPa. As concerns the novel structure, the H ions in HfH_{10} are arranged in clusters to form a planar "pentagraphenelike" sublattice. The layered arrangement of these planar units is entirely different from the covalent sixfold cubic structure in H_{3}S and clathratelike structure in LaH_{10}. The Hf atom acts as a precompressor and electron donor to the hydrogen sublattice. This pentagraphenelike H_{10} structure is also found in ZrH_{10}, ScH_{10}, and LuH_{10} at high pressure, each material showing a high T_{c} ranging from 134 to 220 K. Our study of dense superhydrides with pentagraphenelike layered structures opens the door to the exploration of a new class of high T_{c} superconductors