Effect of Coldfog on the Corona Induced Degradation of Silicone Rubber Samples

Corona is an unavoidable phenomena in high voltage power transmission system, in spite of suitably designed insulator accessories and transmission line hardware. It is a proven fact that the continuous occurrence of corona can subject the polymeric insulator to a severe degradation. Further, moisture in the air has a positive influence on the corona activity. This paper presents the methodology to evaluate the corona performance of the silicone rubber housing material with simultaneous application of cold fog. Analysis conducted after corona treatment by the Fourier Transform Infrared Spectroscopy (FTIR) present an interesting results showing a higher hydroxylation of sample surface under the moisture application than in the normal condition for both AC and DC excitation. FTIR spectrum also indicates the presence of nitric acid on the treated surface with coldfog application. Results obtained from SEM analysis are also presented.

Enantio sensing property of helicin, the derivative of a natural product: Discrimination of amines and amino alcohols

The chiral sensing property of helicin (the derivative of natural product obtained by partial oxidation of salicin, extracted from willow tree (Salix helix)) is reported. The use of helicin as a chiral derivatizing agent for the discrimination of amines and amino alcohols is convincingly established using H-1 NMR spectroscopy. The large chemical shift separation achieved between the discriminated peaks facilitated the accurate quantification of enantiomeric composition. The consistent trend observed in the shifting of imine proton peak (Delta delta) of helicin in all the derivatized molecules might aid the determination of spatial configuration. (C) 2015 Elsevier B.V. All rights reserved.

Enantio sensing property of helicin, the derivative of a natural product: Discrimination of amines and amino alcohols

The chiral sensing property of helicin (the derivative of natural product obtained by partial oxidation of salicin, extracted from willow tree (Salix helix)) is reported. The use of helicin as a chiral derivatizing agent for the discrimination of amines and amino alcohols is convincingly established using H-1 NMR spectroscopy. The large chemical shift separation achieved between the discriminated peaks facilitated the accurate quantification of enantiomeric composition. The consistent trend observed in the shifting of imine proton peak (Delta delta) of helicin in all the derivatized molecules might aid the determination of spatial configuration. (C) 2015 Elsevier B.V. All rights reserved.

Enantio sensing property of helicin, the derivative of a natural product: Discrimination of amines and amino alcohols

The chiral sensing property of helicin (the derivative of natural product obtained by partial oxidation of salicin, extracted from willow tree (Salix helix)) is reported. The use of helicin as a chiral derivatizing agent for the discrimination of amines and amino alcohols is convincingly established using H-1 NMR spectroscopy. The large chemical shift separation achieved between the discriminated peaks facilitated the accurate quantification of enantiomeric composition. The consistent trend observed in the shifting of imine proton peak (Delta delta) of helicin in all the derivatized molecules might aid the determination of spatial configuration. (C) 2015 Elsevier B.V. All rights reserved.

Quercetin, a Natural Flavonoid Interacts with DNA, Arrests Cell Cycle and Causes Tumor Regression by Activating Mitochondrial Pathway of Apoptosis

Naturally occurring compounds are considered as attractive candidates for cancer treatment and prevention. Quercetin and ellagic acid are naturally occurring flavonoids abundantly seen in several fruits and vegetables. In the present study, we evaluate and compare antitumor efficacies of quercetin and ellagic acid in animal models and cancer cell lines in a comprehensive manner. We found that quercetin induced cytotoxicity in leukemic cells in a dose-dependent manner, while ellagic acid showed only limited toxicity. Besides leukemic cells, quercetin also induced cytotoxicity in breast cancer cells, however, its effect on normal cells was limited or none. Further, quercetin caused S phase arrest during cell cycle progression in tested cancer cells. Quercetin induced tumor regression in mice at a concentration 3-fold lower than ellagic acid. Importantly, administration of quercetin lead to -5 fold increase in the life span in tumor bearing mice compared to that of untreated controls. Further, we found that quercetin interacts with DNA directly, and could be one of the mechanisms for inducing apoptosis in both, cancer cell lines and tumor tissues by activating the intrinsic pathway. Thus, our data suggests that quercetin can be further explored for its potential to be used in cancer therapeutics and combination therapy.

Electromagnetic Shielding Properties of Nano Carbon Filled Silicone Rubber Composites

Electromagnetic shielding has become important for various electrical systems because of the electromagnetic pollution caused by the large scale use of electronic devices operating at different frequencies and power levels. Traditionally used metallic shields lack flexibility and hence may not be the right choice for certain applications. In such situations, filled polymer composites provide a good alternative for electromagnetic shielding applications. Being polymer based, they are easy to manufacture and can be molded into the required geometry and shape. In this study, the shielding properties of multiwalled carbon nanotubes and carbon nanofibers filled silicone rubber are studied. The conductivity and the shielding effectiveness of the composites were measured at different filler loadings. Both the fillers are able to make the base polymer conducting even at very low filler loadings. The conductivity and the shielding effectiveness improved when the filler loading was above the percolation threshold.

Effects of heat-treatment processes on the electroless Ni-B coating and its natural aging mechanism

A Ni-B coating was prepared with EN using potassium borohydride reducing agent. The as-plated micro-structure of the coating was confirmed from XRD to be a mixture of amorphous and supersaturated solid solution. Three kinds of phase transformation were observed from the DSC curve. Different from the previous works, the formation of Ni4B3 and Ni2B was found during some transformation processes. The key factors which influence the variation of micro-hardness and micro-structure in deposits are the formation, the size and amount of Ni3B, Ni4B3 and Ni2B. Aging of the deposits treated under some heat treatment conditions occurred at room temperature. Changes of the micro-hardness indicated aging phenomena evidently. the natural aging phenomena are concerned with various kinds of decomposition of borides, especially with Ni4B3 phase. The extent of natural aging depends on the formation and the quantity of Ni(4)B3 and Ni2B.

Numerical Simulation of Nox Formation in Coal Combustion with Inlet Natural Gas Burning

A full two-fluid model of reacting gas-particle flows and coal combustion is used to simulate coal combustion with and without inlet natural gas added in the inlet. The simulation results for the case without natural gas burning is in fair agreement with the experimental results reported in references. The simulation results of different natural gas adding positions indicate that the natural gas burning can form lean oxygen combustion enviroment at the combustor inlet region and the NOz concentration is reduced. The same result can be obtained from chemical equilibrium analysis.

Experimental investigation on the chaotic phenomena in the wake of a natural thermal convection flow

Chaotic phenomena in the wake of thermal convection flow fields above a heating flat plate were investigated experimentally. A newly developed electron beam fluorescence technique (EBF) was used to simultaneously measure density fluctuation at 7 points in a cross section above the plate. Correlation dimensions, intermittence coefficients, Fourier spectrum have been obtained for different Grashof numbers. Spatial distribution of correlation dimensions are presented. The experimental result shows that there is a certain relationship between the density fluctuation and the Gr number. And time-spacial characteristic of chaos evolution is also given.

Comparación de parámetros reproductivos bajo inseminación artificial y monta natural en cerdas, (Cofradia, G.E.P.)

Este experimento se realizó en la Granja Experimental Porcina (G.E.P), Cofradía, Masaya, con 82 cerdas del cuarto parto, 30 servidas a través de inseminación artificial (I.A) y 52 cerdas por monta natural (M.N); iniciando en mayo de 1,995 hasta mayo de 1,996 con el objetivo de evaluar los parámetros reproductivos y económicos en ambos sistemas de monta. Los dos grupos de cerdas reproductoras estaban compuestos por las razas LANDRACE, YORKSHIRE y DUROC. Las variables evaluadas fueron: Tasa de concepción (T.C) y tasa de parición (T.P), números de crías por partos (N.C.P), peso vivo promedio del lechón en la camada al nacer (P.V.L.C), relación beneficio-costo (B-C). Los resultados finales comprobados al 5% de significancia estadísticas fueron: T.P en I.A con 56.66% menor que en M.N con 76.92%, en N.C.P para I.A con 7.06, menor que en M.N de 8.725, P.V.L.C en I.A de 1.85 kg, similar a 1.74 kg, en MN. Para la relación B-C en I.A fue de 0.53 córdobas y para M.N de 0.56 córdobas.

Comparación de índices productivos y reproductivos de monta natural e inseminación artificial con semen congelado en cerdos

El presente trabajo de tesis se realizó en la granja experimental porcina MAGFOR-Misión China de la república de Taiwán, ubicada en Cofradía. El estudio consistió en la evaluación de los parámetros reproductivos en grupos de cerdas obtenidos por inseminación artificial y grupos obtenidos a través de la monta natural, también se aborda el tema de la consanguinidad y sus consecuencias como un factor negativo en la fijación de caracteres indeseables, esto sucede en las poblaciones en las que existe una alta homocigosis debido al origen común del material genético (padres emparentados). Las variables evaluadas en el presente trabajo fueron: tamaño de la camada al nacimiento, peso promedio de los lechones al nacimiento, peso promedio de los lechones al destete e intervalo parto parto. para el análisis estadístico se elaboraron tablas de contingencias por cada una de las variables con base en los promedios. Para la variable tamaño de la camada al nacimiento se obtuvo para el tratamiento inseminación artificial un promedio de 9.16 lechones y para la monta natural un promedio de 9.89 lechones al contrastar las medias de los dos tratamientos se obtuvo un valor de t de 0.88 que comparado con el valor tabulado al 5% resulto no significativo al observar el comportamiento de las diferentes razas ,la yorkshire obtuvo los mayores promedios en inseminación el caso especifico de esta habían muy pocos ejemplares 6 . Se trabajo en condiciones normales de producción lo cual pudo influir en estos resultados debido al tamaiio de la muestra en esta raza. Los resultados para la variable peso promedio de los lechones al nacimiento, arrojaron un promedio de 1.76 Kg. para las camadas obtenidas por inseminación artificial y 1.67kg para las obtenidas por el método de monta natural en las observaciones de los promedios por razas, se obtuvo el mayor peso a favor de la raza Landrace con 1.99 Kg. seguido de la raza duroc con 1.85 Kg. en el tratamiento de inseminación artificial, y para la monta natural el menor peso lo obtuvo la raza duroc con 1.44 Kg. y elmayor peso fue también la raza Landrace. la raza Yorkshire mostró un comportamiento similar tanto en inseminacion artificial, como en monta natural. Para la variable peso promedio de los lechones al destete, se obtuvo un peso promedio de 7.39 Kg. para los lechones obtenidos por el método de inseminacion artificial y un peso promedio de 6.71 Kg. en el caso de lechones obtenidos por monta natural al evaluar las razas, la raza Landrace obtuvo el mayor peso al destete con 8.01 Kg. como era de esperar al obtener los mayores promedios en peso al nacimiento esto fue para las camadas obtenidas por inseminacion artificial. en el caso. de los lechones obtenidos mediante la monta natural el mayor peso correspondió a la raza Hampshire pudiendo haber influido el numero de lechones, ya que esta fue la que presento el menor numero la raza Yorkshire tuvo en este caso un comportamiento similar en los dos tratamientos. Para la variable intervalo parto-parto, en el caso de las cerdas servidas por el método de inseminacion artificial presentaron un IPP de 5.52 meses o sea 167 días y las cerdas servidas por monta natural obtuvieron un IPP de5.01 meses o 152 días. En la prueba de hipótesis tanto como el contraste de varianza, los resultados fueron significativos y una diferencia de 15 días vacíos en una hembra eleva los costos de producción de una manera considerable por esta razón un IPP como el de la inseminación artificial solo se justifica en la granja experimental porcina en un numero especifico de cerdas elite y como apoyo al mejoramiento genético del hato porcino de esta así como del hato nacional.

Effects of Natural Convection on the Characteristics of a Long Laminar Argon Plasma Jet Issuing Horizontally into Ambient Air

Three-dimensional modeling results show that the appearance of the long laminar plasma jet is less influenced by natural convection even as it is issuing into ambient air horizontally. However, plasma parameter distributions may deviate from axi-symmetry

Large strain field near a crack tip in a rubber sheet

The distribution of stress-strain near a crack tip in a rubber sheet is investigated by employing the constitutive relation given by Gao (1997). It is shown that the crack tip field is composed of two shrinking sectors and one expanding sector. The stress state near the crack tip is in uniaxial tension. The analytical solutions are obtained for both expanding and shrinking sectors.