Effect of Hydrogen on Pristine Amorphous V2O5 Thin Film

Sequentially deposited layer by layer up to five vanadium oxide film is deposited on glass and silica substrates at 300 k by vacuum thermal evaporation technique. The deposited samples subjected to reduction process in the preparation situe by hydrogen gas at 473k for 10 minutes and 573 k for 10, 20 minutes. The XRD investigation of the samples demonstrates that the pristine sample is amorphous while those reduced are crystalline. The existed phases in virgin samples are educated by Raman spectroscopy which indicates the single V2O5 phase. The different phases in the reduced sample are identified by analyzing their XRD patterns. The electrical resistance of the reduced samples is measured as a function of temperature during heating and cooling cycles. The transition temperature from semiconducting to metal state is defined by the derivative of dR/d

Antioxidant activities and flavonoid contents of selected plants belonging to Family Loranthaceae

The methanolic extract of three parasitic plants belonging to family Loranthaceae (Plicosepalus acacia, Plicosepalus curviflorus and Phragmanthera austro arabica) were investigated for their antioxidant activity. The free radical and nitrogen oxide scavenging abilities were evaluated using diphenyl-1-picrylhydrazyl (DPPH), and Griess reagent was used to determine the total antioxidant activity. The three extracts showed comparable activities. The three activities ranged from 18 to 56% of the activity of standard ascorbic. The total flavonoid contents were determined and calculated in terms of quercetin which was detected in all the examined extracts. The quercetin concentration was determined using high performance thin layer chromatography using CHCl3 : MeOH : glacial acetic acid (8.5: 1.5: 0.1) for development. The maximum sensitivity was obtained when the plates were scanned at 360 nm. The concentration of quercetin varied from 0.157 (P. austro arabica) to 0.062 g% (P. acacia) and P. curviflorus contained 0.115 g% w/w quercetin. All validation parameters were found to be satisfactory regarding accuracy, precision, limits of detection and quantitation.Key words: Loranthaceae, antioxidant, spectrophotometry, high performance thin layer chromatography (HPTLC), flavonoids, quercetin, ascorbic acid

Power System Stabilizer Driven by an Adaptive Fuzzy Set for Better Dynamic Performance

This paper presents a novel application of a fuzzy logic controller (FLC) driven by an adaptive fuzzy set (AFS) for a power system stabilizer (PSS).The proposed FLC, driven by AFS, is compared with a classical FLC, driven by a fixed fuzzy set (FFS). Both FLC algorithms use the speed error and its rate of change as input vectors. A single generator equipped with FLC-PSS and connected to an infinite bus bar through double transmission lines is considered. Both FLCs, using AFS and FFS, are simulated and tested when the system is subjected to different step changes in the reference value. The simulation results of the proposed FLC, using the adaptive fuzzy set, give a better dynamic response of the overall system by improving the damping coefficient and decreasing the rise time and settling time compared with classical FLC using FFS. The proposed FLC using AFS also reduces the computational time of the FLC as the number of rules is reduced.

Caracterización de aceite de semilla de girasol extraído enzimáticamente así como de los residuos proteínicos

Sunflower seed oil was enzymatically extracted with six different enzymes: cellulase, hemicellulase, animal proteinase, acid proteinase, pectinase and pectinex under the following conditions: substrate concentration in phosphate buffer (0.5M, pH 5) 30%, enzyme concentration 2% (E/S), temperature 50°C and time 3 hours. The obtained oils were analyzed for physicochemical properties and fatty acid profiles. The protein residues were analyzed for amino acid compositions. The results showed that the enzymatic extraction with cellulase or hemicellulase could maintain good oil quality of the extracted oils as their levels of linoleic and oleic acids recorded similar values to those of the control oil extracted with organic solvents. Also the level of iodine value was in the same level of control. On the other hand, the use of proteases in the enzymatic extraction of sunflower seed oil caused some reductions in the levels of the unsaturated fatty acids as well as the iodine value. The pectinases showed a similar trend to that of the proteinase with the least recovery of linoleic acid among the different oils under study. Similarly, the use of cellulases did not change the amino acid composition of the protein residue as compared to the control, in the contrary to the extraction with the proteinases which caused reduction of some amino acids from the protein residues especially lysine, leucine, iso-leucine, alanine, arginine and aspartic. In that respect the use of pectinases behaved similar to cellulases.Aceite de semilla de girasol fue extraído enzimáticamente con seis enzimas diferentes: celulasa, hemicelulasa, proteinasa animal, proteinase acida, pectinasa y pectinex bajo las condiciones siguientes: concentración de sustrato en tampón fosfato (0,5M, pH 5) 30%, concentración enzimática 2% (E/S), temperatura 50°C y tiempo 3 horas. Los aceites obtenidos fueron analizados por sus propiedades fisicoquímicas y perfiles de ácidos grasos. Los residuos proteínicos fueron analizados por sus composiciones en aminoácidos. Los resultados mostraron que la extracción enzimática con celulasa o hemicelulasa podían proporcionar buena calidad en los aceites, ya que sus niveles de ácidos linoleico y oleico registraron valores similares a los del aceite control extraído con disolventes orgánicos. También el valor de índice de iodo fue similar al del control. Por otro lado, el uso de proteasas en la extracción enzimática de aceite de semilla de girasol causó algunas reducciones en los niveles de ácidos grasos insaturados, así como en el índice de iodo. Las pectinasas mostraron una tendencia similar a la de las proteinases con la menor obtención de ácido linoleico entre los diferentes aceites en estudio. Del mismo modo, el uso de celulasas no cambió la composición de aminoácidos del residuo proteínico comparado con el control, por el contrario la extracción con proteinasas causó una disminución de algunos aminoácidos, especialmente lisina, leucina, isoleucina, alanina, arginina y aspártico. A este respecto, el uso de pectinasa se portó de manera análoga al de celulasas

La radiación-γ mantiene la calidad de la mantequilla de vaca

This investigation aims to study the use of gamma irradiation for keeping the quality of cows’ butter. Fresh butter samples were exposed to gamma irradiation at doses of 0, 2.5 and 5 kGy followed by refrigerated storage and the effects of these treatments on the microbiological aspects and lipid characteristics of butter samples were studied. Moreover, fatty acid profiles and unsaponifiable matter constituents were determined by gas chromatographic analysis, while the stability of butter was determined by rancimat. The results indicated that gamma irradiation at 2.5 kGy dose reduced the counts of total bacteria, lipolytic bacteria, coliforms, molds and yeasts, however, these counts gradually increased during cold storage. Also irradiation at 5 kGy dose greatly reduced the total bacterial count which gradually increased upon storage, while completely eliminated the other determined microorganisms. Irradiation treatments increased the acid value and peroxide value of butter, while the iodine number was not altered. Moreover, gas chromatographic analysis showed that gamma irradiation slightly increased the total volatile fatty acids, total saturated fatty acids and total hydrocarbons, while slightly decreased the total unsaturated fatty acids and total sterols. In addition, irradiation of butter decreased its stability as determined by rancimat and upon storage of both irradiated and non irradiated butter samples, the acid value gradually increased, while a flexuous changes in the peroxide value were observed. The present study proved that 2.5 and 5 kGy gamma irradiation doses could keep the quality of cows’ butter and increased its shelf life at 4±1ºC for 8 and 12 weeks as compared to 4 weeks for non irradiated butter (based on the visual appearance of mold growth on the surface of samples) without any effects on its sensory properties.En esta investigación se estudió el uso de la radiación gamma para mantener la calidad de la mantequilla de vaca. Muestras de mantequilla fresca fueron expuestas a diferentes dosis de radiación gamma (0, 2.5 y 5 kGy) y guardadas en frío. Se determinaron parámetros microbiológicos y lipídicos, incluyendo el análisis de ácidos grasos y constituyentes del insaponificable mediante cromatografía gaseosa, y la estabilidad de la mantequilla por rancimat. Los resultados indicaron que la radiación gamma a la dosis de 2.5 kGy reducía el número total de bacterias, bacterias lipolíticas, coliformes, hongos y levaduras, aunque la recuperación era gradual con el tiempo de almacenamiento. A la dosis de 5 kGy, el efecto sobre el número total de bacterias fue más acentuado, hubo una recuperación gradual, pero el resto de microorganismos estudiados desaparecieron completamente. Los tratamientos de irradiación aumentaron la acidez y los peróxidos en la mantequilla, sin alterar el índice de yodo. La radiación gamma aumentó ligeramente el total de ácidos grasos volátiles, de ácidos grasos saturados y de hidrocarburos; mientras que redujo ligeramente el total de ácidos grasos insaturados y el de esteroles. La irradiación de la mantequilla afectó negativamente su estabilidad, aumentando gradualmente la acidez tanto en las muestras irradiadas como en las no irradiadas. Con el presente estudio se demuestra que la irradiación gamma a las dosis de 2.5 y 5 kGy podría mantener la calidad de la mantequilla de vaca e incrementar su vida útil si se mantiene a 4±1ºC durante 8 y 12 semanas cuando se compara con la mantequilla no irradiada y almacenada durante 4 semanas (basado en la apariencia visual del crecimiento de hongos en la superficie de las muestras), sin efectos sobre las propiedades sensoriales

Glucose metabolism abnormalities among pediatric acute lymphoblastic leukemia survivors: Assessment and relation to body mass index and waist to hip ratio

AbstractBackgroundAs survival rates of pediatric acute lymphoblastic leukemia (ALL) improve, attention is turning to side and late effects of therapy including glucose metabolism abnormalities.ObjectiveTo asses the presence of abnormal glucose metabolism in pediatric ALL survivors and its possible relation to body mass index (BMI), waist to hip ratio and treatment related factors.Subjects and methodsRetrospective study with a prospective follow-up of 12 ALL survivors who had been off chemotherapy for >9months was done. Fifteen healthy sex and age matched children were involved as controls. Body mass index (BMI) waist to hip ratio (WHR), and Oral glucose tolerance test (OGTT) were performed with assessment of glycated hemoglobin (Hb A1C) and insulin sensitivity indices.ResultsAt study time the mean BMI, WHR, all components of the OGTT (except the 2h post load glucose), all indices of insulin sensitivity and the mean Hb A1C% were significantly higher compared to those of the controls. Two survivors (16.6%) developed transient hyperglycemia during therapy, one (8.3%) had pre-diabetes, seven (58.3%) had a risk level of Hb A1C but no one had diabetes mellitus (DM) or insulin resistance (IR). At study time the two survivors with transient hyperglycemia during therapy had a significantly high WHR compared to the remainders. WHR of the survivors at study time correlated significantly with fasting plasma glucose and area of insulin under the curve (AUC). The 2h post-prandial plasma glucose correlated with the duration after therapy completion.ConclusionsWHR may play a better role than BMI in the prediction of insulin resistance in those patients. Hb A1C may increase earlier than other indices of glucose tolerance

Condiciones de optimización para la extracción enzimática de aceite de girasol

Sunflower seed oil was extracted with an enzymatic processes using different hydrolytic enzymes: cellulase, hemicellulase, animal proteinase, acid proteinase, pectinase and pectinex, as compared to enzyme - free aqueous extraction. All the hydrolytic enzymes enhanced oil extraction from sunflower seeds. The most optimal conditions for oil extraction from sunflower seeds were: 2% enzyme concentration, 30% substrate concentration and 3 hrs period. Using Boganov and Buchkov equation showed that time must be prolonged to get higher yields. The maximum yield during 3 hrs extraction with enzymatic process ranged between 44,5%-57,1% of the soxhlet extractable oil. The potency of the investigated enzymes in extracting oil was in the following order: acid proteinase > cellulase > hemicellulase > animal proteinase > pectinex > pectinase when compared at the previous optimal conditions.Aceite de semilla de girasol fue extraído mediante un proceso enzimático usando diferentes enzimas hidrolíticos: celulasa, hemicelulasa, proteinasa animal, proteinasa acida, pectinasa y pectinex, comparando con la extracción acuosa libre de enzima. Todos los enzimas hidrolíticos incrementan la extracción de aceites de semilla de girasol. Las condiciones óptimas para la extracción de aceite a partir de semillas de girasol fueron: 2% de concentración de enzima, 30% de concentración de sustrato y un período de 3 horas. La ecuación de Boganov y Buchkov mostró que el tiempo debe ser prolongado para alcanzar altos rendimientos. El máximo rendimiento durante tres horas de extracción con proceso enzimático osciló entre el 44,5%-57,1% del aceite extraído con soxhlet. La potencia de los enzimas investigados en la extracción de aceite siguió el orden: proteinasa acida > celulasa > hemicelulasa > proteinasa animal > pectinex > pectinasa cuando fue previamente comparado con las condiciones óptimas

Analytical modeling for the heat transfer in sheared flows of nanofluids

We developed a model for the enhancement of the heat flux by spherical and elongated nano- particles in sheared laminar flows of nano-fluids. Besides the heat flux carried by the nanoparticles the model accounts for the contribution of their rotation to the heat flux inside and outside the particles. The rotation of the nanoparticles has a twofold effect, it induces a fluid advection around the particle and it strongly influences the statistical distribution of particle orientations. These dynamical effects, which were not included in existing thermal models, are responsible for changing the thermal properties of flowing fluids as compared to quiescent fluids. The proposed model is strongly supported by extensive numerical simulations, demonstrating a potential increase of the heat flux far beyond the Maxwell-Garnet limit for the spherical nanoparticles. The road ahead which should lead towards robust predictive models of heat flux enhancement is discussed.Comment: 14 pages, 10 figures, submitted to PR