Production of niobium powder by electronically mediated reaction (EMR) using calcium as a reductant

Explored in this study is an electronically mediated reaction (EMR) route for the production of niobium powder using calcium as a reductant for niobium oxide (Nb2O5). Feed material, Nb2O5, and reductant calcium alloy containing aluminum and nickel were charged into electronically isolated locations in a molten salt (e.g. CaCl2) at 1173 K. The current flow through an external path between the feed and reductant locations was monitored. A current approximately 0.4 A was measured during the reaction in the external circuit connecting cathode and anode location. Niobium powder with low aluminum and nickel content was obtained although liquid Ca–Al–Ni alloy was used as the reductant. This clearly demonstrates that niobium metal powder can be produced by an electronically mediated reaction (EMR), without direct physical contact between feed (Nb2O5) and reductant (calcium). Mechanism of calciothermic reduction of Nb2O5 in the molten salt is discussed using an isothermal chemical potential diagram.

Thermodynamic properties of calcium titanates: CaTiO3, Ca4Ti3O10, and Ca3Ti2O7

The chemical potentials of CaO in two-phase fields (TiO2 + CaTiO3), (CaTiO3 + Ca4Ti3O10), and (Ca4Ti3O10 + Ca3Ti2O7) of the pseudo-binary system (CaO + TiO2) have been measured in the temperature range (900 to 1250) K, relative to pure CaO as the reference state, using solid-state galvanic cells incorporating single crystal CaF2 as the solid electrolyte. The cells were operated under pure oxygen at ambient pressure. The standard Gibbs free energies of formation of calcium titanates, CaTiO3, Ca4Ti3O10, and Ca3Ti2O7, from their component binary oxides were derived from the reversible e.m.f.s. The results can be summarised by the following equations: CaO(solid) + TiO2(solid) → CaTiO3(solid), ΔG° ± 85/(J · mol−1) = −80,140 − 6.302(T/K); 4CaO(solid) + 3TiO2(solid) → Ca4Ti3O10(solid), ΔG° ± 275/(J · mol−1) = −243,473 − 25.758(T/K); 3CaO(solid) + 2TiO2(solid) → Ca3Ti2O7(solid), ΔG° ± 185/(J · mol−1) = −164,217 − 16.838(T/K). The reference state for solid TiO2 is the rutile form. The results of this study are in good agreement with thermodynamic data for CaTiO3 reported in the literature. For Ca4Ti3O10 Gibbs free energy of formation obtained in this study differs significantly from that reported by Taylor and Schmalzried at T = 873 K. For Ca3Ti2O7 experimental measurements are not available in the literature for direct comparison with the results obtained in this study. Nevertheless, the standard entropy for Ca3Ti2O7 at T = 298.15 K estimated from the results of this study using the Neumann–Koop rule is in fair agreement with the value obtained from low-temperature heat capacity measurements.

Retention characteristics of Cu2+, Pb2+, and Zn2+ from aqueous solutions by two types of low lime fly ashes

The technical feasibility of utilization of fly ash as a low-cost adsorbent for the removal of metals from water has been studied. For two types of fly ashes, the retention capacities of copper, lead, and zinc metal ions have been studied. Contact time, initial concentration, and pH have been varied and their effect on retention mechanism has been studied. The dominant mechanisms responsible for retention are found to be precipitation due to the presence of calcium hydroxide, and adsorption due to the presence of silica and alumina oxide surfaces in the fly ash. First-order kinetic plots have revealed that the rate constant increases with increase in the initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions considered under different conditions. X-ray diffraction studies revealed the formation of new peaks corresponding to respective metal ions precipitates under alkaline conditions.

Identification of miRNAs from French bean (Phaseolus vulgaris) under low nitrate stress

Objective: In this study, we report the role of miRNAs involved under nitrogen starvation from widely grown vegetable crop, French bean. In recent years, a great deal of attention has been paid to the elucidation of miRNAs involved in low nitrate stress. Methods: To identify miRNAs expressed under stress, cDNA libraries were analyzed. Results: We reported the nine potential miRNAs with 67 targets involved in nutrient transporters and other stress specific genes. Among the miRNA sequences obtained 6 sequences belong to miR172 family, one with miR169. RT-PCR analysis of expression of miR172 family was induced upon low nitrate stress while miR169 family was repressed. In addition, Pvu-SN7b and Pvu-miR16 may be new members of miRNA172 and miR169 families, respectively. Conclusion: The targets of Pvu-SN7b were major protein kinases, one among which is the Protein Kinase CK2. CK2 Kinase is found to involve in transcription-directed signaling, gene control and cell-cycle regulation. Other targets of Pvu-SN7b were involved in DNA-dependent transcription regulation, photo-periodism, calcium-mediated signaling. Pvu-miR16 targets Thymidine kinase, the key enzyme of deoxy-nucleotide synthesis. The cleavage of these targets affects cell proliferation there by affecting nodule formation. Pvu-miR8 inhibits translation of its target protein Pre-protein translocase, a membrane-bound protein transporter involved in trans-membrane protein transportation. Together these results denote the response and role of miRNAs to nitrate-limiting conditions in French bean.

The influence of mesoporous silica in low T-g cyclic olefin copolymer nanocomposite films: Mechanical and moisture barrier studies

In this study, mesoporous silica-cyclic olefin copolymer nanocomposite films were fabricated by solution casting. With an increase in silica loading, the stiffness of the matrix increased. The nanocomposite film shows increased strain to failure with moisture after aging by matrix plasticization. The storage modulus and loss factor for samples with silica content show better results compared with pristine polymer, as indicated by dynamic mechanical analysis. The interaction between filler-polymer chain exhibit hydrophobicity compared to the neat polymer. Water absorption studies at room temperature and near the T-g of the polymer (similar to 64 degrees C) were carried out. The nanocomposites up to 4 wt% filler reduces the water diffusion by forming hydrogen and chemical bonding. The result by calcium degradation test method for moisture permeability and Schottky structured organic device encapsulation under weathering condition confirms the effective reinforcement effect of silica particles in the matrix. (C) 2014 Elsevier Ltd. All rights reserved.

Phase stability of silver particles embedded calcium phosphate bioceramics

In this paper, we report the compositional variation-dependent phase stability of hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) on doping with silver. The transformation of hydroxyapatite to (beta/alpha) tricalcium phosphate phases during sintering has been explored using Raman spectroscopy and X-ray diffraction techniques. The optical absorption spectroscopy analysis reveals the presence of Ag+ ions at low doping levels. As the doping increases, abundance of Ag particles is enhanced.

Twinning induced enhancement of fracture toughness in ultrafine grained Hydroxyapatite-Calcium Titanate composites

Despite being highly bioactive and biocompatible, the limitations of monolithic hydroxyapatite (HA) include extremely low fracture toughness, poor electrical conductivity. While addressing these issues, the present study demonstrates how CaTiO3 (CT) addition to HA can be utilized to obtain a combination of long crack fracture toughness (1.7 MPa m(1/2) SEVNB technique) and flexural strength of 98-155 MPa (3-point bending) and a moderate tensile strength (diametral compression) of 17-36 MPa. The enhancement in fracture resistance in spark plasma sintered HA-CT composites has been explained in reference to the observed twin morphology. TEM reveals the presence of twins in CT grains due to 1800 rotation about 101]. The measured properties along with our earlier reports on biocompatibility and electrical properties make HA-CT suitable for bone tissue engineering applications. When compared with other competing HA-based biocomposites, HA-CT composites are found to have a better combination of properties useful for medium load bearing implant applications. (C) 2015 Elsevier Ltd. All rights reserved.

Hypoxic and low pH water in the nearshore marine environments of Monterey Bay, California: characterizing a decade of oxygen and pH, and drivers of variability.

A decade-long time series recorded in southern Monterey Bay, California demonstrates that the shallow, near-shore environment (17 m depth) is regularly inundated with pulses of cold, hypoxic and low pH water. During these episodes, oxygen can drop to biologically threatening levels, and pH levels were lower than expected. Weekly water chemistry monitoring revealed that the saturation state of aragonite (the more soluble form of calcium carbonate) was often below saturation and had a moderate positive relationship with pH, however, analytical and human error could be high. Pulses of hypoxia and low pH water with the greatest intensity arise at the onset of the spring upwelling season, and fluctuations are strongly semidurnal (tidal) and diurnal. Arrival of cold, hypoxic water on the inner shelf typically occurs 3 days after the arrival of a strong upwelling event and appears to be driven by upwelling modulated by internal tidal fluctuations. I found no relationship between the timing of low-oxygen events and the diel solar cycle nor with terrestrial nutrient input. These observations are consistent with advection of hypoxic water from the deep, offshore environment where water masses experience a general decline of temperature, oxygen and pH with depth, and inconsistent with biochemical forcing. Comparisons with concurrent temperature and oxygen time series taken ~20 km away at the head of the Monterey Canyon show similar patterns but even more intense hypoxic events due to stronger semidiurnal forcing there. Analysis of the durations of exposure to low oxygen levels establishes a framework for assessing the ecological relevance of these events. Increasing oceanic hypoxia and acidification of both surface and deep waters may increase the number, intensity, duration and spatial extent of future intrusions along the Pacific coast. Evaluation of the resiliency of nearshore ecosystems such as kelp forests, rocky reefs and sandy habitats, will require consideration of these events.

Associação de componentes dietéticos com desordens alimentares e seus agravos em adolescentes atletas tenistas e não atletas

Adolescentes apresentam rápido crescimento e intensas mudanças corporais que os tornam vulneráveis em termos nutricionais. A prática de restrições alimentares, bastante comum entre adolescentes, pode levar a inadequações nutricionais que parecem ser o primeiro sinal para o início de uma desordem alimentar (DA). A participação feminina no esporte e o número de casos de DA em adolescentes atletas de modalidades que exigem exposição do corpo, agilidade e leveza dos movimentos, como o tênis, têm aumentado nos últimos anos. As DA podem levar a complicações de saúde como irregularidades menstruais (IM) e baixa densidade mineral óssea (DMO), caracterizando a Tríade da Mulher Atleta (TMA). Desta forma, acredita-se que alguns componentes dietéticos podem ter associação com DA e seus agravos. O objetivo do presente estudo foi avaliar a associação de componentes dietéticos com desordens alimentares, irregularidades menstruais e composição corporal em adolescentes atletas tenistas e não atletas do sexo feminino. Trata-se de estudo do tipo transversal. Foram realizadas avaliações do desenvolvimento puberal pela auto-aplicação dos critérios de Tanner; da composição corporal pela absortometria radiológica de dupla energia (DXA); dos parâmetros dietéticos por registro alimentar de três dias alternados; das DA pela aplicação de três questionários validados (Eating Attitudes Test - EAT-26, Bulimic Investigatory Test, Edinburgh- BITE e o Body Shape Questionnaire - BSQ); do ciclo menstrual por questionário validado e da DMO também pelo DXA. A Tríade da Mulher Atleta (TMA) foi estabelecida pela presença concomitante de DA e/ou baixa disponibilidade de energia (BDE), IM e baixa DMO. Foram realizadas associações por meio de correlações de Spearman entre as variáveis numéricas de componentes dietéticos com DA e composição corporal. Também foram realizadas associações por meio do teste qui-quadrado, teste exato de Fisher ou prova binomial para as variáveis categóricas de adequação dos componentes dietéticos com DA e seus agravos. Participaram do estudo 75 adolescentes (25 tenistas, 50 não atletas) apresentando desenvolvimento puberal similar. Atletas obtiveram melhor perfil da composição corporal quanto ao tecido adiposo. Quanto à ingestão de macronutrientes, os carboidratos merecem destaque. Em ambos os grupos, a maioria das participantes apresentaram baixa ingestão de carboidratos, sendo este percentual de inadequação significativamente maior para as atletas. Os micronutrientes que obtiveram maior percentual de inadequação foram folato e cálcio em ambos os grupos. Verificou-se que 92%, 32% e 24% das atletas e 72%, 8% e 30% das não atletas preencheram critérios para DA e/ou BDE, IM e baixa massa óssea, respectivamente. Apesar de adolescentes atletas tenistas e não atletas apresentarem prevalência de DA similares, as não atletas apresentaram maior insatisfação com a imagem corporal pelo teste BSQ. No entanto, as atletas parecem estar em situação mais grave uma vez que apresentaram maior prevalência de BDE e de IM. A DMO e a prevalência de TMA foram similares entre os grupos. Foi verificada associação inversa e significativa entre alguns componentes dietéticos (principalmente energia e carboidratos) e os escores do teste BSQ. Foi possível concluir que a baixa ingestão de alguns componentes dietéticos, principalmente energia e carboidratos, podem funcionar como marcadores para desordens alimentares em ambos os grupos a fim de previnir posteriores consequências à saúde

Efeito da suplementação dietética com cálcio sobre a plasticidade ontogenética no modelo de superalimentação pós-natal

A obesidade está relacionada com o desenvolvimento da diabetes, estresse oxidativo, esteatose hepática, alteração da sensibilidade hormonal e redução da capacidade termogênica pelo tecido adiposo marrom (TAM). Na obesidade, alterações do sistema dopaminérgico mesocorticolímbico podem levar ao vício por alimentos palatáveis. Todas estas características contribuem para o baixo gasto energético e o alto consumo alimentar. Para estudar os efeitos em longo prazo da obesidade infantil, utilizamos o modelo de redução do tamanho da ninhada. Para induzir a superalimentação neonatal, o tamanho da ninhada foi reduzido para 3 filhotes machos de PN3 21 (grupo SL). O grupo controle permaneceu com 10 filhotes (grupo NL). Em PN120, o grupo SL foi dividido em: SL que recebeu ração controle e SL-Ca que recebeu dieta controle suplementada com 10g/kg de CaCO3. Os sacrifícios ocorreram em PN120 e PN180. Durante todo o período experimental, avaliamos o consumo alimentar e peso corporal. Em PN175, avaliamos a preferência alimentar dos animais por uma dieta rica em açúcar ou em lipídio. Avaliamos os hormônios por ELISA, RIA e quimioluminescência; o conteúdo proteico por Western blotting no fígado, tecido adiposo branco (TAB) e marrom (TAM), adrenal e regiões cerebrais; as atividades enzimáticas no soro e no fígado por cinética enzimática. Em PN21, PN120 e PN180, avaliamos in vivo a atividade simpática do TAM. Ao desmame, os ratos SL apresentaram maior estado pró-oxidativo no fígado e plasma e menor sensibilidade às catecolaminas no TAB. Na idade adulta, a suplementação é capaz de melhorar o estado pró-oxidativo no fígado e plasma, a sensibilidade à insulina e a microesteatose no fígado. Tanto a alteração de metabolismo/ação da vitamina D e do glicocorticóide no tecido adiposo como a menor capacidade termogênica do TAM contribuem para a maior adiposidade dos animais do grupo SL. A suplementação com cálcio corrigiu parte dessas alterações. A superalimentação pós-natal levou a redução da via dopaminérgica e a maior preferencia por gordura, enquanto a suplementação com cálcio normalizou esta via apenas a nível hipotalâmico e corrigiu a preferência alimentar. Nossos dados destacam o impacto benéfico da suplementação dietética com cálcio, que pode ter um papel nutricional promissor para auxiliar a perda de peso e minimizar os distúrbios relacionados a obesidade e a síndrome metabólica dos animais obesos que foram superalimentados na lactação.

Food preference and intake pattern of Penaeus monodon (Fab.) in semi-intensive culture system

P. monodon juveniles prefer natural food than artificial feed in their initial stage of rearing. However, the percentage preference towards artificial feed increases as the days of culture/average body weight increases. Consumption of artificial feed was high during evening meal (1700h) and low during night meal (2200h). The index of intestine fullness was high (8.4±0.7) during initial stage of rearing, compared to that of final stage of rearing (4.9±0.4), probably due to low nutritional value of intake material and low water depth at initial stage. At all stage of rearing omnivorous feeding habit was established and no evidence of diet periodicity in feeding activity was observed.

Necessity of dietary calcium supplement in file fish (Monacanthus cirrhifer)

File fish, Monacanthus cirrhifer, juveniles with initial mean body weight of 0.27g were fed purified diets with or without calcium (Ca) supplement for 10 weeks at a water temperature of 27.0±1.4°C. Growth was significantly low in fish fed diet without Ca supplement than fish fed diet with Ca supplement. Feed efficiency and condition of fish were also significantly decreased in absence of a dietary Ca supplementation, Minerals contents of bone were similar in both the treatment groups and did not appear as a suitable indicator of Ca requirement. It appeared that Ca supplement to the purified diet is necessary for file fish for their proper growth and feed utilization.

Low-field magnetoresistance in La0.7Ca0.3MnO 3 manganite compounds prepared by the spray drying technique

Calcium-substituted lanthanum manganite compounds were synthesized by the spray drying technique. This method - whose main advantages are versatility, high reproducibility and scalability - yields small grain materials of high homogeneity and displaying low-field magnetoresistance effects. We report about the physical and chemical characterizations of these samples in order to investigate the potential interest of spray drying for the production of materials for low-field magnetoresistance applications. We have studied the dependence of the low-field magnetoresistance on the temperature and duration of the thermal treatment applied to the pelletized powders. The issue of the shape anisotropy (demagnetisation effects) influence on the magnetoresistance properties has also been dealt with. © 2005 Springer Science + Business Media, Inc.

Gasoline fuelled partially premixed compression ignition in a light duty multi cylinder engine: A study of low load and low speed operation

The objective of this study was to examine the operating characteristics of a light duty multi cylinder compression ignition engine with regular gasoline fuel at low engine speed and load. The effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented. The measurements used in this study included gaseous emissions, filter smoke opacity and in-cylinder indicated information. It was found that stable, low emission operation was possible with raised intake manifold pressure and temperature, and that fuel stratification can lead to an increase in stability and a reduced reliance on increased temperature and pressure. It was also found that the auto-ignition delay sensitivity of gasoline to intake temperature and pressure was low within the operating window considered in this study. Nevertheless, the requirement for an increase of pressure, temperature and stratification in order to achieve auto-ignition time scales small enough for combustion in the engine was clear, using pump gasoline. Copyright © 2009 SAE International.

Measurements of intake separation hysteresis in a model fan and nacelle RIG

A 1/20-scale, low speed model rig representing the fan and nacelle of a high bypass ratio jet engine has been tested under crosswind conditions. The flow conditions under which the intake flow separates and reattaches have been found to exhibit considerable hysteresis. This phenomenon has been examined by a careful test procedure in which the crosswind angle has been slowly increased and then decreased. Measurements of the hysteresis associated with separation and reattachment are presented for independent variations in stream-tube contraction ratio, ground clearance, fan operating point and Reynolds number. The results reveal that particular care must be taken to allow for any hysteresis when testing intakes under crosswind conditions. They also indicate that separation hysteresis is particularly sensitive to fan operating point and the position of the ground plane. These findings suggest that it is important for high Reynolds number intake tests and calculations to include a ground plane and a model of the downstream turbomachinery. © 2002 by the author(s).