Dielectric Properties Of Lead Potassium Lithium Niobate (Pb1,85K1,15Li0,15Nb5O15) With Tetragonal Tungsten Bronze (TTB) Type Structure

A new tungsten bronze ceramic oxide, Pb2-xK1+xLixNb5O15 (PKLN) (x =0.15) was prepared by high temperature solid-state reaction route. Structural and electrical properties are investigated using X-ray diffraction and dielectric measurements. Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. The dielectric permittivity and the loss tangent of the sample have been measured in a frequency range 1Hz–1MHz and a temperature range 35–550 °C. Studies of dielectric properties show that the compound exhibits an anomaly at 425°C (usually called transition temperature).The electrical parameters of the material were studied using complex impedance spectroscopy showing that the compound exhibits non-Debye of relaxation process. In the paraelectric phase, activation energy was determined and the value is Eτ = 0.68 eV. The present ceramic is promising candidate for high dielectric constant and low loss dielectric ceramic.A new tungsten bronze ceramic oxide, Pb2-xK1+xLixNb5O15 (PKLN) (x =0.15) was prepared by high temperature solid-state reaction route. Structural and electrical properties are investigated using X-ray diffraction and dielectric measurements. Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. The dielectric permittivity and the loss tangent of the sample have been measured in a frequency range 1Hz–1MHz and a temperature range 35–550 °C. Studies of dielectric properties show that the compound exhibits an anomaly at 425°C (usually called transition temperature).The electrical parameters of the material were studied using complex impedance spectroscopy showing that the compound exhibits non-Debye of relaxation process. In the paraelectric phase, activation energy was determined and the value is Eτ = 0.68 eV. The present ceramic is promising candidate for high dielectric constant and low loss dielectric ceramic

Cadmium accumulation and interactions with zinc, copper, and manganese, analysed by ICP-MS in a long-term Caco-2 TC7 cell model

The influence of long-term exposure to cadmium (Cd) on essential minerals was investigated using a Caco-2 TC7 cells and a multi-analytical tool: microwave digestion and inductively coupled plasma mass spectrometry. Intracellular levels, effects on cadmium accumulation, distribution, and reference concentration ranges of the following elements were determined: Na, Mg, Ca, Cr, Fe, Mn, Co, Ni, Cu, Zn, Mo, and Cd. Results showed that Caco-2 TC7 cells incubated long-term with cadmium concentrations ranging from 0 to 10 lmol Cd/l for 5 weeks exhibited a significant increase in cadmium accumulation. Furthermore, this accumulation was more marked in cells exposed long-term to cadmium compared with controls, and that this exposure resulted in a significant accumulation of copper and zinc but not of the other elements measured. Interactions of Cd with three elements: zinc, copper, and manganese were particularly studied. Exposed to 30 lmol/l of the element, manganese showed the highest inhibition and copper the lowest on cadmium intracellular accumulation but Zn, Cu, and Mn behave differently in terms of their mutual competition with Cd. Indeed, increasing cadmium in the culture medium resulted in a gradual and significant increase in the accumulation of zinc. There was a significant decrease in manganese from 5 lmol Cd/l exposure, and no variation was observed with copper. Abbreviation: AAS – Atomic absorption spectrometry; CRM– Certified reference material; PBS – Phosphate buffered saline without calcium and magnesium; DMEM – Dubelcco’s modified Eagle’s medium

Untersuchungen über die chemische Zusammensetzung des menschlichen Gehirns

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Monocyclic Quinone Structure‐Activity Patterns: Synthesis of Catalytic Inhibitors of Topoisomerase II with Potent Antiproliferative Activity

The monocyclic 1,4-benzoquinone, HU-331, the direct oxidation product of cannabidiol, inhibits the catalytic activity of topoisomerase II but without inducing DNA strand breaks or generating free radicals, and unlike many fused-ring quinones exhibits minimal cardiotoxicity. Thus, monocyclic quinones have potential as anti-cancer agents, and investigation of the structural origins of their biological activity is warranted. New syntheses of cannabidiol and (±)-HU-331 are here reported. Integrated synthetic protocols afforded a wide range of polysubstituted resorcinol derivatives; many of the corresponding novel 2-hydroxy-1,4-benzoquinone derivatives are potent inhibitors of the catalytic activity of topoisomerase II, some more so than HU-331, whose monoterpene unit replaced by a 3-cycloalkyl unit conferred increased anti-proliferative properties in cell lines with IC50 values extending below 1 mM, and greater stability in solution than HU-331. The principal pharmacophore of quinones related to HU-331 was identified. Selected monocyclic quinones show potential for the development of new anticancer agents

Phytoplankton of Lake Kivu

peer reviewedThis chapter reviews taxonomic composition, biomass, production and nutrient limitation of the phytoplankton of Lake Kivu. Present Lake Kivu phytoplankton is dominated by cyanobacteria – mainly Synechococcus spp. and thin filaments of Planktolyngbya limnetica – and by pennate diatoms, among which Nitzschia bacata and Fragilaria danica are dominant. Seasonal shifts occur, with cyanobacteria developing more in the rainy season, and the diatoms in the dry season. Other groups present are cryptophytes, chrysophytes, chlorophytes and dinoflagellates. According to a survey conducted in the period 2002–2008, the composition of the phytoplankton assemblage was quasi homogeneous among lake basins. The mean euphotic depth varied between 17 and 20 m, and the increase in the ratio between mixed layer depth and euphotic depth to about 2 in the dry season may have selected for diatoms and cryptophytes, which tended to present their maximal development in this season, when cyanobacteria slightly decreased. Mean chlorophyll a concentration was 2.16 mg m−3, and the mean daily primary production was 0.62 g C m−2 day−1 (range, 0.14–1.92), i.e. in the same range as in other large oligotrophic East African Rift lakes. Seston elemental ratios indicated a moderate P deficiency during the dry, mixed season and a severe P limitation during part of the rainy, stratified season; the C:N ratio indicated a moderate N limitation throughout the year. Nutrient addition assays pointed to a direct N limitation and co-limitation by P during rainy seasons and P or N limitation during dry seasons depending on the year. Thus, phytoplankton ecology in Lake Kivu does not differ from that of other Rift lakes, where seasonal variations result in a trade-off between low light with high nutrient supply and high light with low nutrient supply. Phytoplankton production in Lake Kivu is also similar to that of other Rift lakes, and nutrient limitation of phytoplankton growth may occur as a result of variable availability of N and P, as in Lakes Tanganyika and Malawi, even though the extent of P limitation seems greater in Lake Kivu

Avaliação do desempenho do método do ensaio por enzimas imuno-adsorvidas (ELISA) em leite em pó reconstituído contaminado experimentalmente com aflatoxina M1 Evaluation of competitive enzyme-linked immunosorbent assay (ELISA) in milk powder contaminated with known concentrations of aflatoxin M1

O desempenho do ensaio por enzimas imuno-adsorvidas (ELISA), mediante o emprego de conjuntos de reativos produzidos em escala comercial, para determinação de aflatoxina, foi avaliado em condições experimentais, através de análises repetidas, em amostras de leite em pó reconstituído contaminadas com concentrações conhecidas da fração M1 da toxina. Para os níveis de 0,10; 0,20; 0,50; e, 1,00 ng/ml, os percentuais de recuperação foram: 83,0%; 87,5%; 103,0%; e, 111,8%, respectivamente. O desvio-padrão relativo, para as referidas concentrações, foi, respectivamente, 65,5%; 31,8%; 10,9% e 13,6% (n=10, para cada nível de contaminação). Os resultados obtidos demonstram que o método é apropriado para pesquisas e levantamentos sobre a ocorrência de aflatoxina M1 em leite, sobretudo nas faixas de concentração entre 0,20 - 1,00 ng/ml.<br>The evaluation of commercially available test systems of competitive enzyme-linked immunosorbent assay (ELISA), for Aflatoxin M1 (AFM1) was performed in experimental conditions, through repeated analysis, in samples of milk powder contamined with known concentrations of the toxin. Recoveries of AFM1 added to milk at levels of 0.10, 0.20, 0.50 and 1.00 ng/ml were 83.0%, 87.5%, 103.0% and 111.8% respectively. Relative standard deviations for the above mentioned concentrations were 65.5%, 31.8%, 10.9% and 13.6%, respectively (n =10, per spiking level). According to these results the ELISA is appropriate for AFM1 research and/or surveying, mainly for concentrations between 0.20 - 1.00 ng/ml