The Structural Phase Transition of the Relaxor Ferroelectric 68%PbMg1/3Nb2/3O3-32%PbTiO3

Neutron scattering techniques have been used to study the relaxor ferroelectric 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 denoted in this paper as 0.68PMN-0.32PT. On cooling, these relaxor ferroelectrics have a long-range ordered ferroelectric phase and the composition is close to that at which the ferroelectric structure changes from rhombohedral to tetragonal. It was found that above the Burns temperature of about 600K, the transverse optic mode and the transverse acoustic mode are strongly coupled and a model was used to describe this coupling that gave similar parameters to those obtained for the coupling in PMN. Below the Burns temperature additional quasi-elastic scattering was found which increased in intensity as the sample was cooled down to the ferroelectric transition temperature but then decreased in intensity. This behaviour is similar to that found in PMN. This scattering is associated with the dynamic polar nano-regions that occur below the Burns temperature. In addition to this scattering a strictly elastic resolution limited peak was observed that was much weaker than the corresponding peak in pure PMN and which decreased in intensity on cooling below the ferroelectric phase whereas for PMN, which does not have a long-range ordered ferroelectric phase, the intensity of this component increased monotonically as the sample was cooled. The results of our study are compared with the recent measurements of Stock et al. [PRB 73 064107] who studied 0.4PMN-0.6PT. The results are qualitatively consistent with the random field model developed to describe the scattering from PMN

THE STUDY OF CADMIUM UPTAKE BY WATER HYACINTH (EICHHORNIA CRASSIPES) USING A NATURAL MODELLING APPROACH

The results of the investigation on the accumulation of cadmium by water hyacinth, depending on the conditions of pollutant exposure and the presence of various additives are discussed. The main specialty of this study is that all the experiments were carried out in natural conditions using the approach based on the application of the capacities called minicosms. It allowed estimating hit consequences of pollutant on ecosystem most really having made experiment in the conditions as much as possible close to the natural. In this article a very important problem of an accuracy and reliability of the results of trace elements determination in plants is also debated. As a result of carried investigations it was shown that the degree of cadmium extraction by hyacinth from contaminated natural water while maintaining the viability of the plants depends on the way of pollutant introducing into the reservoir and the maximum (about 79%) value is observed in the case of it’s gradual entry

Mercury species in solid matter of dispersion of the Ursk tailing dispersion train (Ursk village, Kemerovo region, Russia)

Mercury species are highly toxic, and methylmercury is the most dangerous for environment and biota. The purpose of this study is to evaluate the distribution of mercury speciations (HgX2 (were X is O, SO24-, Cl and et al.), CH3Hg+, HgS) in diffuse halation high-sulfide waste of piles at the Ursk massive sulfide ore deposits which are being mined since the 1940s. To determine the mercury speciation, the method of thermal analysis with atomic absorption spectrometry as detector was applied

Mercury species in solid matter of dispersion of the Ursk tailing dispersion train (Ursk village, Kemerovo region, Russia)

Mercury species are highly toxic, and methylmercury is the most dangerous for environment and biota. The purpose of this study is to evaluate the distribution of mercury speciations (HgX2 (were X is O, SO24-, Cl and et al.), CH3Hg+, HgS) in diffuse halation high-sulfide waste of piles at the Ursk massive sulfide ore deposits which are being mined since the 1940s. To determine the mercury speciation, the method of thermal analysis with atomic absorption spectrometry as detector was applied

Comparative characteristics of qualitative indicators of amaranth and corn silage

Silage is the main juicy food and a source of vitamins for animals in the winter-stall period. In order to expand the range of forage crops for the production of high – protein silage in the work used non-traditional forage culture amaranth, which is the content of protein balanced by the number of essential amino acids (especially lysine, methionine and tryptophanus), oils, micro – and macro-elements, vitamins and biologically active substances far superior to traditional forage plants, including legumes. Amaranth belongs to the group of plants hard-ensilage because the level of sugar in its green mass does not exceed the minimum required for the silage process, but the use of starter cultures, contributing to the creation of optimal conditions for the normal flow of fermentation processes, can solve this problem. The comparative characteristic of qualitative indicators of a silo from amaranth paniculate and from maize as raw materials of the most widespread for preparation of green forages is carried out in work. It is established that in the phase of milk-wax ripeness of seeds amaranth has the best technological properties for silage harvesting, as the total loss of nutrients in the silage of amaranth in this phase is minimal. The content of "raw" protein, which is an important indicator in the conditions of protein deficiency in traditional fodder crops, in the amaranth silage of paniculata is almost 2 times higher than in the corn silage. Based on the evaluation of the quality of silage on dry matter content, organic acids, crude protein, degree of acidity and organoleptic indicators it can be concluded that the silage of amaranth is more balanced in terms of key indicators of quality compared to corn silage

Role of P on amorphization, microstructure, thermo-physical and soft magnetic properties of Fe-rich FeB(P)SiNbCu melt-spun alloys

The influence of P on amorphizing ability, as-quenched microstructure, thermo-physical and soft magnetic properties of Fe-rich (i) Fe81B15-xPxSi2Nb1Cu1 (ii) Fe82B14-xPxSi2Nb1Cu1 and (iii) Fe83B13-xPxSi2Nb1Cu1 (x = 0, 2, 4, 6, 8 at%) melt-spun alloys are investigated. The substitution of P improves amorphization of alloys and restricts the formation of hetero-amorphous microstructure for Fe 83 at% ribbons at around (x = 8). The improvement in short range ordering of P containing clusters with varying Fe content has been discussed within the framework of Cluster-Glue atom model and supported by experimental thermal parameters. The optimal P content in Fe-rich alloys in the range of 4 <= x <= 6 delivered favourable thermal properties of high primary and secondary crystallization onset temperature viz; T-x1, T-x2 and temperature span Delta T between these onsets. The P substitution drastically restricts the precipitation of secondary crystallites with reduced enthalpy of secondary crystallisation (Delta H-2) during annealing and favourably assists in attaining maximum magnetic moment during the primary crystallization stage. Moreover, the P substitution (4-8 at%) effects refinement of alpha-Fe nanocrystallites and promotes low coercivity (H-c < 20 A/m) in nanocomposite alloys. On contrary, the P substitution linearly reduces saturation magnetization (M-s) by weakening ferromagnetic exchange coupling and ferromagnetic dilution. An optimal content of 4 at% P offers favourable combination of low H-c and High M-s in both amorphous and nanocomposite state

Development of novel electrochemical and optical Lab-on-a-chip platforms for contaminants and biomarkers sensing /

Bibliografia.La detección de contaminantes peligrosos requiere especial atención debido a su posible toxicidad, baja concentración en muestras reales y, en la mayoría de los casos, una imposibilidad de llevar a cabo la detección a través de un metodo tan específico como el inmunoensayo. Una de las estrategias orientadas a la fácil detección de compuestos nocivos es el uso de plataformas microfluídicas llamadas Lab-on-a-chip. En el Capítulo 3, una innovadora plataforma microfluídica en miniatura es desarrollada para la detección simultánea y extracción de polibromodifenil éteres (PBDEs). La plataforma consiste en un chip microfluídico de polidimetilosiloxano (PDMS) para el paso de la inmunoreacción, un chip de PDMS con un electrodo serigrafiado de carbono (SPCE) integrado para la detección, y un chip de PDMS-óxido de grafeno reducido (rGO) para la adsorción física y posterior eliminación de residuos de PBDE. La detección se basó en un inmunoensayo competitivo entre PBDE y PBDE modificado con Peroxidasa de Rábano Silvestre (HRP-PBDE) seguido de un monitoreo de oxidación enzimática de o-aminofenol (o-AP), utilizando voltamperometría de onda cuadrada y resolución anódica (SW-ASV). PBDE fue detectado con una buena sensibilidad y un límite de detección similar al obtenido a través de una prueba colorimétrica comercial (0.018 ppb), pero con la ventaja de utilizar volúmenes reactivos más bajos y un tiempo de análisis reducido. Con el objetivo de diseñar un sistema de detección apropiado para compuestos tóxicos como PBDEs, un compósito de óxido de grafeno reducido y PDMS ha sido desarrollado y optimizado para obtener mayor adsorción (basados en hidropobicidad e interacción π-π entre moléculas de rGO y PBDE) comparado con los PDMS sin modificación. Este sistema se puede aplicar perfectamente para detectar cualquier análito utilizando el inmunoensayo apropiado y facilitar el funcionamiento en matrices tan complejas como el agua marina. En el Capítulo 4 se desarrolla un dispositivo LOC para la preconcentración y la detección simultánea de metales pesados. Dicho dispositivo consta de un electrodo serigrafiado de carbono, un chip de PDMS y otro de GO-PDMS. El chip de GO-PDMS fue fabricado y los factores más esenciales fueron optimizados, incluidos la concentración de GO y aquella del curador de PDMS. Se descubrió que la habilidad de adsorción es inversamente proporcional a la concentración de curador de PDMS en el compósito y proporcional a la concentración de GO. El mecanismo de adsorción está basado en una reacción de complejación , donde grupos activos de oxígeno con cargas negativas se pueden enlazar con metales bivalentes como el Pb. La adsorción más alta fue obtenida en pH=7. El GO-PDMS tiene una capacidad relativamente grande de adsorción, ya que incluso las muestras que contienen niveles más altas que 500 ppb (mayores a 500 ppb) son totalmente adsorbidas, teniendo en cuenta que tal concentración es muy alta. El proceso de desorción ha sido también optimizado. Gracias a ello, metales que habían sido previamente adsorbidos se pueden liberar y detectar en voltamperometría de Onda Cuadrada y Resolución Anódica. El límite de detección de esta técnica (utilizando electrodos serigrafiados de carbono) fue de 0.5 ppb para el plomo (Pb). Esto significa que utilizando una plataforma de preconcentración GO-PDMS, se pueden cuantificar cantidades más bajas de Pb, ya que las muestras preconcentradas mostraron una corriente de hasta 30 veces más alta que las no preconcentradas. Esta plataforma se puede utilizar para la detección mejorada de metales pesados y también para su eliminación