A Homemade Autosampler/Injector Commutator for Flow Injection Analysis

An autosampler/injector commutator for flow injection analysis (FIA) was constructed with electronic components of used equipments. The apparatus is controlled by commercially available multifunctional interface (PCL711B) connected to a personal computer, and the software was written in Visual Basic language. The system was applied to water analysis and it presented satisfactory results. The low cost and simplicity are the principal characteristics of the autosampler/injector commutator

Characterization of ferroeletric polymers: methodology and results

Neste trabalho, foram desenvolvidos e implementados três métodos experimentais, o método de corrente constante - CC (adaptado a partir do triodo de corona à corrente constante), o método de rampa de tensão - RT (adaptado a partir do método bipolar de medida de histerese elétrica) e o método para medida do coeficiente piroelémco pela técnica da temperatura oscilante (função senoidal). Os métodos foram empregados no estudo das polarizações elétricas apresentadas pelo PVDF, PVF, o copolímero P(VDF-TrFE) e a blenda P(VDF-TrFE) - PMMA. Verificou-se através de medidas de difratometia de raios-x, medida da polarização ferroelétrica (obtida pelos métodos CC e RT) e medida do coeficiente piroelétrico que parte da polarização elétrica relaxa após a remoção do campo elétrico e está associada a efeitos não hereditários. Foi estudada a dependência desta polarização com o campo elétrico aplicado (taxa de subida do campo e campo máximo), com o tempo de curto circuito que a amostra foi submetida entre processos de polarização consecutivos e o tipo de amostra. Foram determinados e comparados a polarização remanescente e o campo coercitivo dos materiais citados, obtidos pelos métodos CC e RT.In this work three experimental setups were developed, the constant current method (CC) (derived from the corona mode with constant current), the ramp voltage method (RT) (derived from the bipolar hysteresis measurements) and measurement of the pyroeletric coefficient employing a sinusoidal temperature variation. These methods were used to study the ferroelectric polarization in polymers such as PVDF, PVF, copolymer of P(VDF-TrFE) and P(VDF-TrFE) - PMMA blend. From x-ray, electric polarization and pyroelectric measurements it was found that part of the total polarization decays after removing the electric field. The dependence of such decaying polarization on the rate of increasing of the electric field, on the maximum field applied to the sample and the time interval of short-circuit between successive measurements was investigated. The value of the remanent polarization and the coercive field was determined for polymeric materials listed above and a comparison of the results obtained using the CC and RT method was performed

Characterization of ferroeletric polymers: methodology and results

Neste trabalho, foram desenvolvidos e implementados três métodos experimentais, o método de corrente constante - CC (adaptado a partir do triodo de corona à corrente constante), o método de rampa de tensão - RT (adaptado a partir do método bipolar de medida de histerese elétrica) e o método para medida do coeficiente piroelémco pela técnica da temperatura oscilante (função senoidal). Os métodos foram empregados no estudo das polarizações elétricas apresentadas pelo PVDF, PVF, o copolímero P(VDF-TrFE) e a blenda P(VDF-TrFE) - PMMA. Verificou-se através de medidas de difratometia de raios-x, medida da polarização ferroelétrica (obtida pelos métodos CC e RT) e medida do coeficiente piroelétrico que parte da polarização elétrica relaxa após a remoção do campo elétrico e está associada a efeitos não hereditários. Foi estudada a dependência desta polarização com o campo elétrico aplicado (taxa de subida do campo e campo máximo), com o tempo de curto circuito que a amostra foi submetida entre processos de polarização consecutivos e o tipo de amostra. Foram determinados e comparados a polarização remanescente e o campo coercitivo dos materiais citados, obtidos pelos métodos CC e RT.In this work three experimental setups were developed, the constant current method (CC) (derived from the corona mode with constant current), the ramp voltage method (RT) (derived from the bipolar hysteresis measurements) and measurement of the pyroeletric coefficient employing a sinusoidal temperature variation. These methods were used to study the ferroelectric polarization in polymers such as PVDF, PVF, copolymer of P(VDF-TrFE) and P(VDF-TrFE) - PMMA blend. From x-ray, electric polarization and pyroelectric measurements it was found that part of the total polarization decays after removing the electric field. The dependence of such decaying polarization on the rate of increasing of the electric field, on the maximum field applied to the sample and the time interval of short-circuit between successive measurements was investigated. The value of the remanent polarization and the coercive field was determined for polymeric materials listed above and a comparison of the results obtained using the CC and RT method was performed

Quantifying zooplankton species: use of richness estimators

ABSTRACT Richness estimators (Jackknife 1, Bootstrap, Chao 1 and ACE) were used to relate zooplankton species richness with amount of water collected per sample and number of samples throughout the year for the limnetic region of Sapucai River compartment of Furnas reservoir, state of Minas Gerais, Brazil. Seven 100 L samples were collected in sequence using a motor pump, and seven 70 L samples were collected in sequence using a plankton net (68 μm mesh size) in vertical hauls, to totalize 450 L, in three stations of the reservoir. Twelve monthly samplings were carried out over a year. The assessment of richness was made by analyzing the asymptotic behavior of the estimator curves. The samplings reached the asymptote from 350 L of collection with trawls and 400 L using a suction motor pump and reached the plateau on the 8th collection, which included both dry and rainy seasons. Regardless of the type of sampling, the volume of 400 L and eight sessions throughout the year is enough to register 90% of the zooplankton richness in the environment

Morphological abnormalities in cladocerans related to eutrophication of a tropical reservoir

In zooplankton communities, morphological changes in Cladocera (Crustacea: Branchiopoda) may be resulting from water pollution by anthropogenic activities and/or natural events. The removal of vegetation cover, urbanization, agriculture and sewage release accelerate the eutrophication process in the aquatic environment. The present study seeks to demonstrate the occurrence of morphological abnormalities in cladocerans and relate the changes in the morphology and species composition to the physical and chemical parameters of the water. Samplings were made monthly in five stations on the Sapucaí River compartment of Furnas Reservoir, located in the state of Minas Gerais, Brazil, from July 2013 to February 2014. The Furnas Reservoir has intense occupation of the surrounding areas by agriculture, urban and industrial activities and the installation of net cage fish cultures, which contribute to the water quality deterioration. Cladocerans samples were collected using a suction pump and plankton net (68 μm mesh size) and concentrated from a volume of 400 L. The measures of physical and chemical parameters of the water were obtained by a Horiba U-50 multi-sensor on the surface of water column and the density and morphology of Cladocera were made by microscopy. Twenty-three species of Cladocera were recorded with high organism densities of Chydoridae family species. Morphological abnormalities were observed in Daphnia gessneri, Ceriodaphnia silvestrii, Bosmina longirostris, Bosmina tubicen and Chydorus pubescens. The highest densities of C. pubescens with abnormalities were observed at sampling stations which had littoral characteristics and influences of sewage release. For C. pubescens, abnormalities were observed and classified into two types. The type 1 abnormality was considered an increase of length of intestine and size of its intestinal loop, whereas for type 2 was considered the occurrence of an intestine prolapse. The morphological abnormalities in cladocerans were described and compared to the ones described in the literature. From the results, it may observe that the abnormalities were probably resulting from continuous eutrophication process which has been occurring in the reservoir due to anthropogenic activities around the reservoir and a decrease in the water volume of the reservoir, caused by an unusual dry weather period in this region in the last years.</p

Alona iheringula Sinev & Kotov, 2004 (Crustacea, Anomopoda, Chydoridae, Aloninae): life cycle and DNA barcode with implications for the taxonomy of the Aloninae subfamily.

Knowledge of reproductive rates and life cycle of the Cladocera species is essential for population dynamic studies, secondary production and food webs, as well as the management and preservation of aquatic ecosystems. The present study aimed to understand the life cycle and growth of Alona iheringula Kotov & Sinev, 2004 (Crustacea, Anomopoda, Chydoridae), a Neotropical species, as well as its DNA barcoding, providing new information on the Aloninae taxonomy. The specimens were collected in the dammed portion of the Cabo Verde River (21°26'05″ S and 46°10'57″ W), in the Furnas Reservoir, Minas Gerais State, Brazil. Forty neonates were observed individually two or three times a day under controlled temperature (25±1°C), photoperiod (12 h light/12 h dark) and feeding (Pseudokirchneriella subcapitata at a concentration of 105 cells.mL-1 and a mixed suspension of yeast and fish feed in equal proportion). Individual body growth was measured daily under optical microscope using a micrometric grid and 40× magnification. The species had a mean size of 413(±29) µm, a maximum size of 510 µm and reached maturity at 3.24(±0.69) days of age. Mean fecundity was 2 eggs per female per brood and the mean number of eggs produced per female during the entire life cycle was 47.6(±6.3) eggs per female. The embryonic development time was 1.79(±0.23) days and the maximum longevity was 54 days. The species had eight instars throughout its life cycle and four instars between neonate and primipara stage. The present study using molecular data (a 461 bp smaller COI fragment) demonstrated a deep divergence in the Aloninae subfamily

Ferroelectric switching and dielectric response of P(VDF-TrFE)/PMMA blends

The ferroelectric and the dielectric behaviors of binary blends formed by an equi-molar Poly(vinylidene fluoride trifluoroethylene) copolymer [P(VDF-TrFE)] and Poly(methyl methacrylate) [PMMA] were investigated, for several PMMA compositions. For 40 wt.% or more PMMA contents, the blends are completely amorphous. Below this value, they crystallize in the usual Cm2m polar structure of P(VDF-TrFE). The ferroelectric switching characteristics and the dielectric response of the blends demonstrate the formation of dynamically stable ferroelectric domains. Moreover, the blended films are highly transparent in the optical region. Therefore, thin films of these binary blends are good candidates as host materials for nonlinear optical applications

Dinâmica dos compostos de enxofre em uma represa da zona rural de monte Belo, Minas Gerais, Brasil

Foram feitas determinações de sulfato e sulfeto em amostras de água de uma represa localizada na Fazenda Lagoa, Instituto Sul-mineiro de Proteção Ambiental, Monte Belo, Minas Gerais. A concentração média de sulfato foi 13,47 ppm. Obtiveram-se concentrações para sulfeto de 5,5 a14,3 ppb. Nota-se estratificação da coluna d’água na represa e correlação entre os teores de compostos de enxofre, parâmetros físico-químicos e teores de ferro e alumínio. Variações sazonais típicas do ecossistema foram observadas. Os processos de oxirredução constituem importantes mecanismos de reciclagem do enxofre na represa, postulando-se que sejam típicos desse ambiente, i.é., lagoa mesotrófica