Superconducting tantalum disulfide nanotapes; growth, structure and stoichiometry

Superconducting tantalum disulfide nanowires have been synthesised by surface-assisted chemical vapour transport (SACVT) methods and their crystal structure, morphology and stoichiometry studied by powder X-ray diffraction (PXD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and nanodiffraction. The evolution of morphology, stoichiometry and structure of materials grown by SACVT methods in the Ta-S system with reaction temperature was investigated systematically. High-aspect-ratio, superconducting disulfide nanowires are produced at intermediate reaction temperatures (650 degrees C). The superconducting wires are single crystalline, adopt the 2H polytypic structure (hexagonal space group P6(3)/mmc: a = 3.32(2) angstrom, c = 12.159(2) angstrom; c/a = 3.66) and grow in the <2<(1)over bar>(1) over bar0> direction. The nanowires are of rectangular cross-section forming nanotapes composed of bundles of much smaller fibres that grow cooperatively. At lower reaction temperatures nanowires close to a composition of TaS3 are produced whereas elevated temperatures yield platelets of 1T TaS2

A combined XAS and XRD Study of the High-Pressure Behaviour of GaAsO4 Berlinite

Combined X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) experiments have been carried out on GaAsO4 (berlinite structure) at high pressure and room temperature. XAS measurements indicate four-fold to six-fold coordination changes for both cations. The two local coordination transformations occur at different rates but appear to be coupled. A reversible transition to a high pressure crystalline form occurs around 8 GPa. At a pressure of about 12 GPa, the system mainly consists of octahedral gallium atoms and a mixture of arsenic in four-fold and six-fold coordinations. A second transition to a highly disordered material with both cations in six-fold coordination occurs at higher pressures and is irreversible.Comment: 8 pages, 5 figures, LaTeX2

NaIrO3 - A pentavalent post-perovskite

Sodium iridium(V) oxide, NaIrO3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO3, the much-studied structural analogue of the high-pressure post-perovskite phase of MgSiO3. Among the oxide post-perovskites, NaIrO3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO6 octahedra separated by layers of NaO8 bicapped trigonal prisms. NaIrO3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides.Comment: 22 pages, 5 figures. Submitted to Journal of Solid State Chemistr

Thermal design of air cooled condenser of a solar adsorption refrigerator

The objective of this paper is to study the design of a condenser of a solar adsorptionrefrigerator which will be tested in the region of Biskra (Algeria). The LMTD (log mean temperaturedifference) method is used to calculate the size of the condenser applying experimental dataobtained from the literature. For this purpose, a calculation code has been developed todetermine the total heat transfer area of the heat exchanger. Therefore, we present a comparisonbetween calculated and experimental results obtained from the literature. This comparisonallowed the validation of the calculation method by applying the same experimental conditions.The discussion of the results indicates that we cannot use the ambient air in free convection modeas a cooling fluid if its temperature exceeds 30°C. This problem presents the greatest obstacleespecially in the Saharan regions, such as in Biskra, where the average ambient air temperatureduring the summer exceeds 35°C. As a solution, we propose in this article the improvement of theheat transfer by the air-forced convection mode. Thus, it is established that the use of the air fancan extend the operating temperature limits of the condenser above 35°C

Improved crystal structure solution from powder diffraction data by the use of conformational information

The effect of introducing conformational information to the DASH implementation of crystal structure determination from powder diffraction data is investigated using 51 crystal structures, with the aim of allowing increasingly complex crystal structures to be solved more easily. The findings confirm that conformational information derived from the Cambridge Structural Database is indeed of value, considerably increasing the chances of obtaining a successful structure determination. Its routine use is therefore encouraged

Diversity of cereal pests (wheat and barley) grown in arid climate in Ziban region (provence of Biskra – southeastern Algeria)

This study investigated cereal pests (wheat and barley) grown in southeastern Algeria’s arid climate. Using three sampling techniques (yellow pan traps and Pitfall traps, a comprehensive collection of insect specimens was obtained, comprising 2526 individuals taxonomically classified into 20 distinct species, 15 genera, ten families, and six orders. Homoptera and according to quantitative analysis, Thysanoptera was the most dominant taxa, with six and four occurrences, respectively. In contrast, the dominant species were Mayetiola destructor (Say 1817) (Diptera, Cecidomyiidae) with 412 specimens, Rhopalosiphum maidis (Fitch 1856) (Homoptera, Aphididae) with 404 specimens then Oulema melanopa (Linné 1758) (Coleoptera, Chrysomelidae) with 342 specimens. The observed and expected species richness diversity parameters were comparatively more significant in the cereal ecosystem cultivated in the El Outaya location than in the Sidi Okba location. (Kruskal–Wallis, df = 3, P = 0.019). The results obtained from the Generalised Linear Models (GLM) indicated a statistically significant variation in species richness across the different sites and crops (wheat and barley) (df = 3, Mean Square = 47.70, F = 3.58, P = 0.020).While there were very significant differences in the average number of individuals per species (N/S ratio) (df = 3, mean square = 22.08, F = 5.526, P = 0.002). Species richness extrapolation revealed that diversity is anticipated as the number of individuals captured increases, however, at a slower rate as the sampled population increases. The species distribution showed that some insect species are found at all phenological stages and all sampling sites.  Article history: Received 2 June 2024; Revised 29 October 2024; Accepted 1 November 2024; Available online 10 December 202

Mylabrini diversity and host plants in a Saharan oasis ecosystem with an updated checklist of Meloidae from Algeria (Coleoptera)

The Mylabrini and Lyttini species (Meloidae family) of the oasis of Ouled Djellal were recorded: Croscherichia litigiosa (Chevrolat, 1840), C. gilvipes (Chevrolat, 1840), and Mylabris impressa Chevrolat, 1840, Alosimus cfr. viridissimus (Lucas, 1846). The host plants feed by these species are recorded. Moreover, an updated checklist of the blister beetles from Algeria is published

Improved performance of crystal structure solution from powder diffraction data through parameter tuning of a simulated annealing algorithm

Significant gains in the performance of the simulated annealing algorithm in the DASH software package have been realised by using the irace automatic configuration tool to optimise the values of three key simulated annealing parameters. Specifically, the success rate in finding the global minimum in intensity chi squared space is improved by up to an order of magnitude. The general applicability of these revised simulated annealing parameters is demonstrated using the crystal structure determinations of over 100 powder diffraction data sets