Universal distribution of magnetic anisotropy of impurities in ordered and disordered nano-grains

We examine the distribution of the magnetic anisotropy (MA) experienced by a magnetic impurity embedded in a metallic nano-grain. As an example of a generic magnetic impurity with partially filled $d$-shell, we study the case of $d^{1}$ impurities imbedded into ordered and disordered Au nano-grains, described in terms of a realistic band structure. Confinement of the electrons induces a magnetic anisotropy that is large, and can be characterized by 5 real parameters, coupling to the quadrupolar moments of the spin. In ordered (spherical) nano-grains, these parameters exhibit symmetrical structures and reflect the symmetry of the underlying lattice, while for disordered grains they are randomly distributed and, - for stronger disorder, - their distribution is found to be characterized by random matrix theory. As a result, the probability of having small magnetic anisotropies $K_L$ is suppressed below a characteristic scale $\Delta_E$, which we predict to scale with the number of atoms $N$ as $\Delta_E\sim 1/N^{3/2}$. This gives rise to anomalies in the specific heat and the susceptibility at temperatures $T\sim \Delta_E$ and produces distinct structures in the magnetic excitation spectrum of the clusters, that should be possible to detect experimentally

Simulations of a weakly conducting droplet under the influence of an alternating electric field

We investigate the electrohydrodynamics of an initially spherical droplet under the influence of an external alternating electric field by conducting axisymmetric numerical simulations using a charge-conservative volume-of-fluid based finite volume flow solver. The mean amplitude of shape oscillations of a droplet subjected to an alternating electric field for leaky dielectric fluids is the same as the steady-state deformation under an equivalent root mean squared direct electric field for all possible electrical conductivity ratio $(K_r)$ and permittivity ratio $(S)$ of the droplet to the surrounding fluid. In contrast, our simulations for weakly conducting media show that this equivalence between alternating and direct electric fields does not hold for $K_r \ne S$. Moreover, for a range of parameters, the deformation obtained using the alternating and direct electric fields is qualitatively different, i.e. for low $K_r$ and high $S$, the droplet becomes prolate under alternating electric field but deforms to an oblate shape in the case of the equivalent direct electric field. A parametric study is conducted by varying the time period of the applied alternating electric field, the permittivity and the electrical conductivity ratios. It is observed that while increasing $K_r$ has a negligible effect on the deformation dynamics of the droplet for $K_r<S$, it enhances the deformation of the droplet when $K_r>S$ for both alternating and direct electric fields. We believe that our results may be of immense consequence in explaining the morphological evolution of droplets in a plethora of scenarios ranging from nature to biology.Comment: 10 pages, 8 figure

Identification des sources de tolérance au stress hydrique sur des espèces sauvages de la famille des Cucurbitacées en cutlture in vitro

Identification of tolerance sources to the water stress on wild species of the cucurbitaceous family in in vitro culture. The objective of this survey is to identify sources of tolerance to the water stress. This will permit to choose the adequate material allowing the transfer of genes governing the drought tolerance to the gene pool of the main cultivated species. Indeed, a method has been developed to evaluate the water stress tolerance in vitro. It is based on the capacity of the calus recuperation after dehydration under a laminar flux hot until a loss of 50% of their fresh weight as a basis. The study included nine accessions of wild species and three cultivated varieties of the cucurbitaceous family. It comes out that the three cultivated varieties (melon, cucumber and watermelon), as well as some wild species accessions are sensitive to the water stress. The wild accessions of Cucumis africanus (L4), Cucumis dipsaceus, Citrullus colocynthis (Saudi Arabia) and Citrullus colocynthis (Niger) are obviously tolerant

Live cell imaging with protein domains capable of recognizing phosphatidylinositol 4,5-bisphosphate; a comparative study

<p>Abstract</p> <p>Background</p> <p>Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)<it>P</it>₂] is a critically important regulatory phospholipid found in the plasma membrane of all eukaryotic cells. In addition to being a precursor of important second messengers, PtdIns(4,5)<it>P</it>₂also regulates ion channels and transporters and serves the endocytic machinery by recruiting clathrin adaptor proteins. Visualization of the localization and dynamic changes in PtdIns(4,5)<it>P</it>₂levels in living cells is critical to understanding the biology of PtdIns(4,5)<it>P</it>₂. This has been mostly achieved with the use of the pleckstrin homology (PH) domain of PLCδ1 fused to GFP. Here we report on a comparative analysis of several recently-described yeast PH domains as well as the mammalian Tubby domain to evaluate their usefulness as PtdIns(4,5)<it>P</it>₂imaging tools.</p> <p>Results</p> <p>All of the yeast PH domains that have been previously shown to bind PtdIns(4,5)<it>P</it>₂showed plasma membrane localization but only a subset responded to manipulations of plasma membrane PtdIns(4,5)<it>P</it>₂. None of these domains showed any advantage over the PLCδ1PH-GFP reporter and were compromised either in their expression levels, nuclear localization or by causing peculiar membrane structures. In contrast, the Tubby domain showed high membrane localization consistent with PtdIns(4,5)<it>P</it>₂binding and displayed no affinity for the soluble headgroup, Ins(1,4,5)P₃. Detailed comparison of the Tubby and PLCδ1PH domains showed that the Tubby domain has a higher affinity for membrane PtdIns(4,5)<it>P</it>₂and therefore displays a lower sensitivity to report on changes of this lipid during phospholipase C activation.</p> <p>Conclusion</p> <p>These results showed that both the PLCδ1PH-GFP and the GFP-Tubby domain are useful reporters of PtdIns(4,5)<it>P</it>₂changes in the plasma membrane, with distinct advantages and disadvantages. While the PLCδ1PH-GFP is a more sensitive reporter, its Ins(1,4,5)P₃binding may compromise its accuracy to measure PtdIns(4,5)<it>P</it>₂changes. The Tubby domain is more accurate to report on PtdIns(4,5)<it>P</it>₂but its higher affinity and lower sensitivity may limit its utility when phospholipase C activation is only moderate. These studies also demonstrated that similar changes in PtdIns(4,5)<it>P</it>₂levels in the plasma membrane can differentially regulate multiple effectors if they display different affinities to PtdIns(4,5)<it>P</it>₂.</p

Ramsey Goodness of Bounded Degree Trees

Given a pair of graphs G and H, the Ramsey number R(G, H) is the smallest N such that every red-blue coloring of the edges of the complete graph KN contains a red copy of G or a blue copy of H. If a graph G is connected, it is well known and easy to show that R(G, H) ≥ (|G| − 1)(χ(H) − 1) + σ(H), where χ(H) is the chromatic number of H and σ(H) is the size of the smallest color class in a χ(H)-coloring of H. A graph G is called H-good if R(G, H) = (|G| − 1)(χ(H) − 1) + σ(H). The notion of Ramsey goodness was introduced by Burr and Erd˝os in 1983 and has been extensively studied since then. In this paper we show that if n ≥ Ω(|H| log4 |H|) then every n-vertex bounded degree tree T is H-good. The dependency between n and |H| is tight up to log factors. This substantially improves a result of Erd˝os, Faudree, Rousseau, and Schelp from 1985, who proved that n-vertex bounded degree trees are H-good when n ≥ Ω(|H| 4 ). MSC: 05C05, 05C5

The Role of Housefly (Musca Domestica) in Mechanical Transmission of Intestinal Parasites in Maiduguri Metropolis, North Eastern Nigeria.

Housefly is the best known and most widely distributed insects accounting for 90% of all flies in human habitation. A study was undertaken to determine the role of housefly (Musca domestica) in the transmission of human intestinal parasites in Maiduguri metropolis. A total of 1151 Houseflies were collected using insect sweep net, from four different breeding sites and were examined for human intestinal parasites using Formol-saline concentration techniques. The highest fly abundance recorded was 453 (39%) while the least recorded was 135 (12%) houseflies. Four intestinal parasites were isolated from fly external body with the following frequency of infection in their external surfaces respectively; Ascaris lumbricoides 22(2%), Hookworm 21(1.8%), Trichuris trichiura 3(0.3%), Hymenolepis nana 1(0.09%) and the transmission rate from four sampling sites was (0.8%) Abattoir, (2.0%) open defecation area, (1.3%) Maiduguri main market and (1.6%). Housefly was found to be a potential mechanical transmitter of parasitic infection and significantly contribute to the spread of food borne parasitic diseases, since this research detected the presence of four gastrointestinal parasites in flies’ exoskeleton and therefore its role in disease transmission cannot be over emphasized. Keywords: Housefly, Intestinal parasites, Maiduguri, Mechanical transmission, Nigeri

A remark on Hamilton cycles with few colors

Akbari, Etesami, Mahini, and Mahmoody conjectured that every proper edge colouring of Kn with n colours contains a Hamilton cycle with ≤O(logn) colours. They proved that there is always a Hamilton cycle with ≤8n−−√ colours. In this note we improve this bound to O(log3n)

Household food consumption and nutritional status of children aged 6 to 59 Months in Zinder, Niger Republic

Malnutrition exists in both urban and rural areas in Niger. An analysis of food and nutrition situation was carried out in the urban&nbsp; municipality of Zinder in order to contribute to a better understanding of the situation. This work was done from February to March 2018, at the household level, sampled by probabilistic method. The study involved 168 children from 6 to 59 months selected from 150 households in 15neighborhoods in the urban municipalities of Zinder. An analysis of the Food Consumption Score and Household Food Diversity Score showed acceptable food consumption and high food diversity respectively in58.7% and 67.3% of households. Furthermore, the results showed that the socio-economic characteristics that determined Score of food consumption were the main activities of heads of households and their wives. Food diversity was generally acceptable, although 2.7 % of households still had low dietary diversity in the study area. Also, food diversity remained low overall for nearly 8.9% of children with a rate of 6.0% for&nbsp; households headed by a woman. Nevertheless, the latter female-headed households had an estimated 13.7% of children with average individual food diversity. The prevalence of acute global malnutrition is 13.1% with the severe form at3%. It should be noted that girls were much more affected by this severe form (3.4%) compared to 2.5% for boys. However, stunting was more prevalent in males than in females with 57.5% and 46.6%,respectively. Moderate form accounting for 28.4% in females compared to 17.5% in males. This&nbsp; nutritional status reflects the relatively acceptable food situation in which these children lived. Furthermore, the appreciation of different foods and modes of consumption have shown on the one hand that the diet remains monotonous. On the other hand, this analysis revealed that cereal-based dishes accompanied by vegetable/leafy sauces predominated in these households in the study area. This situation exposes the members of these households and especially young children to the risk of malnutrition. Key words: Characterization, food consumption, food diversity, nutritional status, children, household, socioeconomics, Zinde

Planar Rayleigh scattering results in helium-air mixing experiments in a Mach-6 wind tunnel

Planar Rayleigh scattering measurements with an argon—fluoride excimer laser are performed to investigate helium mixing into air at supersonic speeds. The capability of the Rayleigh scattering technique for flow visualization of a turbulent environment is demonstrated in a large-scale, Mach-6 facility. The detection limit obtained with the present setup indicates that planar, quantitative measurements of density can be made over a large cross-sectional area (5 cm × 10 cm) of the flow field in the absence of clusters