Landau theory of compressible magnets near a quantum critical point

Landau theory is used to investigate the behaviour of a metallic magnet driven towards a quantum critical point by the application of pressure. The observed dependence of the transition temperature with pressure is used to show that the coupling of the magnetic order to the lattice diverges as the quantum critical point is approached. This means that a first order transition will occur in magnets (both ferromagnets and antiferromagnets) because of the coupling to the lattice. The Landau equations are solved numerically without further approximations. There are other mechanisms that can cause a first order transition so the significance of this work is that it will enable us to determine the extent to which any particular first order transition is driven by coupling to the lattice or if other causes are responsible.Comment: 12 pages including 5 figures, to be presented at MMM-Intermag conference and accepted for publication in Journal of Applied Physic

Theory of magnetism with temporal disorder applied to magnetically doped ZnO

A dynamic model of the asymmetric Ising glass is presented: an Ising model with antiferromagnet bonds with probabilities q arranged at random in a ferromagnetic matrix. The dynamics is introduced by changing the arrangement of the antiferromagnetic bonds after n Monte Carlo steps but keeping the same value of q and spin configuration. In the region where there is a second order transition between the ferromagnetic and paramagnetic states the dynamic behaviour follows that expected for motional narrowing and reverts to the static behaviour only for large n. There is a different dynamic behaviour where there is a first order transition between the ferromagnetic and spin glass states where it shows no effects of motional narrowing. The implications of this are discussed. This model is devised to explain the properties of doped ZnO where the magnetisation is reduced when the exchange interactions change with time.Comment: Paper was presented at MMM 2008 and is accepted for publication in J.A.

A Potts model for the distortion transition in LaMnO3_3

The Jahn-Teller distortive transition of \lmo is described by a modified 3-state Potts model. The interactions between the three possible orbits depends both on the orbits and their relative orientation on the lattice. Values of the two exchange parameters which are chosen to give the correct low temperature phase and the correct value for the transition temperature are shown to be consistent with microscopy theory. The model predicts a first order transitions and also a value for the entropy above the transition in good agreement with experiment. The theory with the same parameters also predicts the temperature dependence of the order parameter of orbital ordering agreeing well with published experimental results. Finally, the type of the transition is shown to be close to one of the most disordered phases of the generalised Potts model. The short range order found experimentally above the transition is investigated by this model.Comment: 16 pages, 7 figures and no tables. Re-submitted to Phys. Rev.

Study of Optical, Electrical and Photocatalysis Properties of SrMnO3 Synthesized by Solid-State Reaction

SrMnO3 was prepared by solid-state reaction method to obtain powder then thin films by a thermal evaporation method. XRD diffraction, Optical and electrical properties were investigated. Photocatalysis process was implemented as an interesting application of SrMnO3. XRD diffraction results were used to study the compound structure and to calculate some other parameters such as crystallite size, D, microstrain, e, and dislocation density, d. XRD results revealed that SrMnO3 has a polycrystalline structure such as hexagonal structure for SrMnO3 phase and tetragonal structure for MnO2 phase. The optical energy band for the powder and thin film were equal to 2.28 eV and 2.92 eV respectively, which candidates this compound to be a solar cell transparent window, especially for deposited thin films. The electrical resistivity behaved as semiconductor-like where it decreases with the temperature with electrical activation energy equal 0.960 eV when heating and 0.663 eV when cooling. The result of the Methylene blue absorption showed that the SrMnO3 powder does work very well as a Photocatalyst. The efficiency of the powder of SrMnO3 as a Photocatalyst increases with the illumination time and its best value is about 56% at 120 min

Study of Optical, Electrical and Photocatalysis Properties of SrMnO3 Synthesized by Solid-State Reaction

SrMnO3 was prepared by solid-state reaction method to obtain powder then thin films by a thermal evaporation method. XRD diffraction, Optical and electrical properties were investigated. Photocatalysis process was implemented as an interesting application of SrMnO3. XRD diffraction results were used to study the compound structure and to calculate some other parameters such as crystallite size, D, microstrain, e, and dislocation density, d. XRD results revealed that SrMnO3 has a polycrystalline structure such as hexagonal structure for SrMnO3 phase and tetragonal structure for MnO2 phase. The optical energy band for the powder and thin film were equal to 2.28 eV and 2.92 eV respectively, which candidates this compound to be a solar cell transparent window, especially for deposited thin films. The electrical resistivity behaved as semiconductor-like where it decreases with the temperature with electrical activation energy equal 0.960 eV when heating and 0.663 eV when cooling. The result of the Methylene blue absorption showed that the SrMnO3 powder does work very well as a Photocatalyst. The efficiency of the powder of SrMnO3 as a Photocatalyst increases with the illumination time and its best value is about 56% at 120 min

Influence of Annealing Temperature on Structural, Electrical, and Magnetic Properties of Nd0.7Ca0.3MnO3

In this paper, we investigated the effect of annealing temperature on the electrical and magnetic properties of polycrystalline Nd0.7Ca0.3MnO3 synthesized using the well-known solid-state reaction technique. After the formation of the required Perovskite crystal structure phase, another annealing treatment has been done. The selected annealing temperatures are 700, 800, and 900°C for 12 hours. Structural refinement of the X-ray diffraction patterns showed the formation of a single orthorhombic crystal structure phase the of P b n m space group in Nd0.7Ca0.3MnO3 without any impurity peaks. From magneto-resistance measurements, we found that NCMO samples have high-colossal magnetoresistance (CMR). Moreover, the under-investigated NCMO samples showed a high power factor. The resistivity data in the insulating region (T \u3eTMI) were analyzed by considering, the Mott-variable range hopping model. The phase transition temperature showed dependence on the grain size, where Curie temperature (TC) increases with an increase in the grain size

Metabolic profiling of Ochradenus baccatus Delile. utilizing UHPLC-HRESIMS in relation to the in vitro biological investigations

Ochradenus baccatus Delile (Resedaceae) is a desert plant with edible fruits native to the Middle East. Few investigators have reported antibacterial, antiparasitic and anti-cancer activities of the plant. Herein we evaluated the cytotoxic activity of O. baccatus using four cell lines and a zebrafish embryo model. Additionally, liquid chromatography coupled with mass spectroscopy was performed to characterize the extract’s main constituents. The highest cytotoxicity was observed against human cervical adenocarcinoma (HeLa), with CC50 of 39.1 μg/mL and a selectivity index (SI) of 7.23 (p < 0.01). Metabolic analysis of the extract resulted in the annotation of 57 metabolites, including fatty acids, flavonoids, glucosinolates, nitrile glycosides, in addition to organic acids. The extract showed an abundance of hydroxylated fatty acids (16 peaks). Further, 3 nitrile glycosides have been identified for the first time in Ochradenus sp., in addition to 2 glucosinolates. These identified phytochemicals may partially explain the cytotoxic activity of the extract. We propose O. baccatus as a possible safe food source for further utilization to partially contribute to the increasing food demand specially in Saharan countries.Medical University of Lublin | Ref. DS28Universidade de Vigo/CISU

Prioritization of zoonoses for multisectoral, One Health collaboration in Somalia, 2023

Background: The human population of Somalia is vulnerable to zoonoses due to a high reliance on animal husbandry. This disease risk is exacerbated by relatively low income (poverty) and weak state capacity for health service delivery in the country as well as climate extremes and geopolitical instability in the region. To address this threat to public health efficiently and effectively, it is essential that all sectors have a common understanding of the priority zoonotic diseases of greatest concern to the country. Methods: Representatives from human, animal (domestic and wildlife), agriculture, and environmental health sectors undertook a multisectoral prioritization exercise using the One Health Zoonotic Disease Prioritization (OHZDP) tool developed by the United States CDC. The process involved: reviewing available literature and creating a longlist of zoonotic diseases for potential inclusion; developing and weighting criteria for establishing the importance of each zoonoses; formulating categorical questions (indicators) for each criteria; scoring each disease according to the criteria; and finally ranking the diseases based on the final score. Participants then brainstormed and suggested strategic action plans to prevent, and control prioritized zoonotic diseases. Results: Thirty-three zoonoses were initially considered for prioritization. Final criteria for ranking included: 1) socioeconomic impact (including sensitivity) in Somalia; 2) burden of disease in humans in Somalia); 3) availability of intervention in Somalia; 4) environmental factors/determinants; and 5) burden of disease in animals in Somalia. Following scoring of each zoonotic disease against these criteria, and further discussion of the OHZDP tool outputs, seven priority zoonoses were identified for Somalia: Rift Valley fever, Middle East respiratory syndrome, anthrax, trypanosomiasis, brucellosis, zoonotic enteric parasites (including Giardia and Cryptosporidium), and zoonotic influenza viruses. Conclusions: The final list of seven priority zoonotic diseases will serve as a foundation for strengthening One Health approaches for disease prevention and control in Somalia. It will be used to: shape improved multisectoral linkages for integrated surveillance systems and laboratory networks for improved human, animal, and environmental health; establish multisectoral public health emergency preparedness and response plans using One Health approaches; and enhance workforce capacity to prevent, control and respond to priority zoonotic diseases