Distribution of microphytobenthic biomass in Martel Inlet, King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10-60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10-20 m depth (136.2 +/- A 112.5 mg Chl a m(-2), 261.7 +/- A 455.9 mg Phaeo m(-2)), intermediate at 20-30 m (55.6 +/- A 39.5 mg Chl a m(-2), 108.8 +/- A 73.0 mg Phaeo m(-2)) and lower ones at 40-60 m (22.7 +/- A 23.7 mg Chl a m(-2), 58.3 +/- A 38.9 mg Phaeo m(-2)). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 +/- A 3.2 (10-20 m) to 0.7 +/- A 1.0 (40-60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.

Evaluation of Microorganisms with Sulfidogenic Metabolic Potential under Anaerobic Conditions

The aim of this work was to identify groups of microorganisms that are capable of degrading organic matter utilizing sulfate as an electron acceptor. The assay applied for this purpose consisted of running batch reactors and monitoring lactate consumption, sulfate reduction and sulfide production. A portion of the lactate added to the batch reactors was consumed, and the remainder was converted into acetic, propionic and butyric acid after 111 hours of operation These results indicate the presence of sulfate-reducing bacteria (SRB) catalyzing both complete and incomplete oxidation of organic substrates. The sulfate removal efficiency was 49.5% after 1335 hours of operation under an initial sulfate concentration of 1123 mg/L. The SRB concentrations determined by the most probable number (MPN) method were 9.0x10(7) cells/mL at the beginning of the assay and 8.0x10(5) cells/mL after 738 hours of operation.

Transesterification of Palm Oil Catalyzed by Pseudomonas fluorescens Lipase in a Packed-Bed Reactor

Transesterification of palm oil with ethanol catalyzed by Pseudomonas fluorescens lipase immobilized on epoxy-polysiloxane-polyvinyl alcohol composite (epoxy-SiO2-PVA) was performed in a continuous packed-bed reactor (PBR). Two strategies were used for improving the miscibility of the substrates: the addition of the organic solvent tert-butanol and the surfactant Triton X-100. Results were compared to those obtained in a solventless reactor, which displayed a biphasic system that passed through the reactor. Using this system, the ethyl ester yield of 61.6 +/- 1.2% was obtained at steady state. Both Triton X-100 and tert-butanol systems were found to be suitable to promote the miscibility of the starting materials; however, the use of Triton X-100 reduced the yield to levels lower than 20%, because of the enzyme desorption from the support surface, as confirmed by scanning electron microscopy analysis. The best performance was found for the reactor running in the presence of tert-butanol which resulted in a stable operating system and an average yield of 87.6 +/- 2.5%. This strategy also gave high biocatalyst operational stability, revealing a half-life of 48 days and an inactivation constant of 0.6 X 10(-3) h(-1).

Horizontal gene transfer confers fermentative metabolism in the respiratory-deficient plant trypanosomatid Phytomonas serpens

Among trypanosomatids, the genus Phytomonas is the only one specifically adapted to infect plants. These hosts provide a particular habitat with a plentiful supply of carbohydrates. Phytomonas sp. lacks a cytochrome-mediated respiratory chain and Krebs cycle, and ATP production relies predominantly on glycolysis. We have characterised the complete gene encoding a putative pyruvate/indolepyruvate decarboxylase (PDC/IPDC) (548 amino acids) of P. serpens, that displays high amino acid sequence similarity with phytobacteria and Leishmania enzymes. No orthologous PDC/IPDC genes were found in Trypanosoma cruzi or T. brucei. Conservation of the PDC/IPDC gene sequence was verified in 14 Phytomonas isolates. A phylogenetic analysis shows that Phytomonas protein is robustly monophyletic with Leishmania spp. and C. fasciculata enzymes. In the trees this clade appears as a sister group of indolepyruvate decarboxylases of gamma-proteobacteria. This supports the proposition that a horizontal gene transfer event from a donor phytobacteria to a recipient ancestral trypanosome has occurred prior to the separation between Phytomonas. Leishmania and Crithidia. We have measured the PDC activity in P. serpens cell extracts. The enzyme has a Km value for pyruvate of 1.4 mM. The acquisition of a PDC, a key enzyme in alcoholic fermentation, explains earlier observations that ethanol is one of the major end-products of glucose catabolism under aerobic and anaerobic conditions. This represents an alternative and necessary route to reoxidise part of the NADH produced in the highly demanding glycolytic pathway and highlights the importance of this type of event in metabolic adaptation. (C) 2012 Elsevier B.V. All rights reserved.

Effect of cellulose physical characteristics, especially the water sorption value, on the efficiency of its hydrolysis catalyzed by free or immobilized cellulase

Cellulase, an enzymatic complex that synergically promotes the degradation of cellulose to glucose and cellobiose, free or adsorbed onto Si/SiO(2) wafers at 60 degrees C has been employed as catalyst in the hydrolysis of microcrystalline cellulose (Avicel), microcrystalline cellulose pre-treated with hot phosphoric acid (CP), cotton cellulose (CC) and eucalyptus cellulose (EC). The physical characteristics such as index of crystallinity (I(C)), degree of polymerization (DP) and water sorption values were determined for all samples. The largest conversion rates of cellulose into the above-mentioned products using free cellulase were observed for samples with the largest water sorption values; conversion rates showed no correlation with either IC or DP of the biopolymer. Cellulose with large water sorption value possesses large pore volumes, hence higher accessibility. The catalytic efficiency of immobilized cellulase could not be correlated with the physical characteristics of cellulose samples. The hydrolysis rates of the same cellulose samples with immobilized cellulase were lower than those by the free enzyme, due to the diffusion barrier (biopolymer chains approaching to the immobilized enzyme) and less effective contact between the enzyme active site and its substrate. Immobilized cellulase, unlike its free counterpart, can be recycled at least six times without loss of catalytic activity, leading to higher overall cellulose conversion. (C) 2011 Elsevier B.V. All rights reserved.

Flow Boiling Characteristics for R1234ze(E) in 1.0 and 2.2 mm Circular Channels

Experimental flow boiling heat transfer results are presented for horizontal 1.0 and 2.2 mm I. D. (internal diameter) stainless steel tubes for tests with R1234ze(E), a new refrigerant developed as a substitute for R134a with a much lower global warming potential (GWP). The experiments were performed for these two tube diameters in order to investigate a possible transition between macro and microscale flow boiling behavior. The experimental campaign includes mass velocities ranging from 50 to 1500 kg/m(2) s, heat fluxes from 10 to 300 kW/m(2), exit saturation temperatures of 25, 31 and 35 degrees C, vapor qualities from 0.05 to 0.99 and heated lengths of 180 mm and 361 mm. Flow pattern characterization was performed using high speed videos. Heat transfer coefficient, critical heat flux and flow pattern data were obtained. R1234ze(E) demonstrated similar thermal performance to R134a data when running at similar conditions. [DOI: 10.1115/1.4004933]

Water-assisted Flow of Heavy Oil in a Vertical Pipe: Pilot-scale Experiments

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

Amazon Rainforest Exchange of Carbon and Subcanopy Air Flow: Manaus LBA Site-A Complex Terrain Condition

On the moderately complex terrain covered by dense tropical Amazon Rainforest (Reserva Biologica do Cuieiras-ZF2-02 degrees 36'17.1 '' S, 60 degrees 12'24.4 '' W), subcanopy horizontal and vertical gradients of the air temperature, CO2 concentration and wind field were measured for the dry and wet periods in 2006. We tested the hypothesis that horizontal drainage flow over this study area is significant and can affect the interpretation of the high carbon uptake rates reported by previous works at this site. A similar experimental design as the one by Tota et al. (2008) was used with a network of wind, air temperature, and CO2 sensors above and below the forest canopy. A persistent and systematic subcanopy nighttime upslope (positive buoyancy) and daytime downslope (negative buoyancy) flow pattern on a moderately inclined slope (12%) was observed. The microcirculations observed above the canopy (38 m) over the sloping area during nighttime presents a downward motion indicating vertical convergence and correspondent horizontal divergence toward the valley area. During the daytime an inverse pattern was observed. The microcirculations above the canopy were driven mainly by buoyancy balancing the pressure gradient forces. In the subcanopy space the microcirculations were also driven by the same physical mechanisms but probably with the stress forcing contribution. The results also indicated that the horizontal and vertical scalar gradients (e. g., CO2) were modulated by these micro-circulations above and below the canopy, suggesting that estimates of advection using previous experimental approaches are not appropriate due to the tridimensional nature of the vertical and horizontal transport locally. This work also indicates that carbon budget from tower-based measurement is not enough to close the system, and one needs to include horizontal and vertical advection transport of CO2 into those estimates.

Assessment of a UASB reactor for the removal of sulfate from acid mine water

A bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactor was used to study the treatment of acid mine drainage through the biological reduction of sulfate. The reactor was fed with acid mine drainage collected at the Osamu Utsumi uranium mine (Caldas, MG, Brazil) and supplemented with ethanol as an external carbon source. Anaerobic granular sludge originating from a reactor treating poultry slaughterhouse wastewater was used as the inoculum. The reactor's performance was studied according to variations in the chemical oxygen demand (COD)/SO42- ratio, influent dilution and liquid-phase recirculation. The digestion of a dilution of the acid mine drainage resulted in a 46.3% removal of the sulfate and an increase in the effluent pH (COD/SO42- = 0.67). An increase in the COD/SO42- ratio to 1.0 resulted in an 85.6% sulfate reduction. The reduction of sulfate through complete oxidation of the ethanol was the predominant path in the reactor, although the removal of COD was not greater than 68% in any of the operational stages. The replenishment of the liquid phase with tap water positively affected the reactor, whereas the recirculation of treated effluent caused disequilibrium and decreased efficiency. (C) 2012 Elsevier Ltd. All rights reserved.

Feasibility Study of a Solar Reactor for Phenol Treatment by the Photo-Fenton process in Aqueous Solution

Solar reactors can be attractive in photodegradation processes due to lower electrical energy demand. The performance of a solar reactor for two flow configurations, i.e., plug flow and mixed flow, is compared based on experimental results with a pilot-scale solar reactor. Aqueous solutions of phenol were used as a model for industrial wastewater containing organic contaminants. Batch experiments were carried out under clear sky, resulting in removal rates in the range of 96100?%. The dissolved organic carbon removal rate was simulated by an empirical model based on neural networks, which was adjusted to the experimental data, resulting in a correlation coefficient of 0.9856. This approach enabled to estimate effects of process variables which could not be evaluated from the experiments. Simulations with different reactor configurations indicated relevant aspects for the design of solar reactors.

Expanding the horizontal capabilities of CRT monitors using artificial inter-pixel steps for neuroscience experiments

This article describes the development of a visual stimulus generator to be used in neuroscience experiments with invertebrates such as flies. The experiment consists in the visualization of a fixed image that is displaced horizontally according to the stimulus data. The system is capable of displaying 640 x 480 pixels with 256 intensity levels at 200 frames per second (FPS) on conventional raster monitors. To double the possible horizontal positioning possibilities from 640 to 1280, a novel technique is presented introducing artificial inter-pixel steps. The implementation consists in using two video frame buffers containing each a distinct view of the desired image pattern. This implementation generates a visual effect capable of doubling the horizontal positioning capabilities of the visual stimulus generator allowing more precise and movements more contiguous. (C) 2011 Elsevier Inc. All rights reserved.

Geometrical and kinematic properties of interfacial waves in stratified oil-water flow in inclined pipe

The stratified oil-water flow pattern is common in the petroleum industry, especially in offshore directional wells and pipelines. Previous studies have shown that the phenomenon of flow pattern transition in stratified flow can be related to the interfacial wave structure (problem of hydrodynamic instability). The study of the wavy stratified flow pattern requires the characterization of the interfacial wave properties, i.e., average shape, celerity and geometric properties (amplitude and wavelength) as a function of holdup, inclination angle and phases' relative velocity. However, the data available in the literature on wavy stratified flow is scanty, especially in inclined pipes and when oil is viscous. This paper presents new geometric and kinematic interfacial wave properties as a function of a proposed two-phase Froude number in the wavy-stratified liquid-liquid flow. The experimental work was conducted in a glass test line of 12 m and 0.026 m id., oil (density and viscosity of 828 kg/m(3) and 0.3 Pa s at 20 degrees C, respectively) and water as the working fluids at several inclinations from horizontal (-20 degrees, -10 degrees, 0 degrees, 10 degrees, 20 degrees). The results suggest a physical relation between wave shape and the hydrodynamic stability of the stratified liquid-liquid flow pattern. (C) 2011 Elsevier Inc. All rights reserved.

Drag reduction phenomenon in viscous oil-water dispersed pipe flow: Experimental investigation and phenomenological modeling

An experimental study on drag-reduction phenomenon in dispersed oil-water flow has been performed in a 26-mm-i.d. Twelve meter long horizontal glass pipe. The flow was characterized using a novel wire-mesh sensor based on capacitance measurements and high-speed video recording. New two-phase pressure gradient, volume fraction, and phase distribution data have been used in the analysis. Drag reduction and slip ratio were detected at oil volume fractions between 10 and 45% and high mixture Reynolds numbers, and with water as the dominant phase. Phase-fraction distribution diagrams and cross-sectional imaging of the flow suggested the presence of a higher amount of water near to the pipe wall. Based on that, a phenomenology for explaining drag reduction in dispersed flow in a flow situation where slip ratio is significant is proposed. A simple phenomenological model is developed and the agreement between model predictions and data, including data from the literature, is encouraging. (c) 2011 American Institute of Chemical Engineers AIChE J, 2012

Two-Phase Frictional Pressure Drop and Flow Boiling Heat Transfer for R245fa in a 2.32-mm Tube

Experimental two-phase frictional pressure drop and flow boiling heat transfer results are presented for a horizontal 2.32-mm ID stainless-steel tube using R245fa as working fluid. The frictional pressure drop data was obtained under adiabatic and diabatic conditions. Experiments were performed for mass velocities ranging from 100 to 700 kg m−2 s−1 , heat flux from 0 to 55 kW m−2 , exit saturation temperatures of 31 and 41◦C, and vapor qualities from 0.10 to 0.99. Pressures drop gradients and heat transfer coefficients ranging from 1 to 70 kPa m−1 and from 1 to 7 kW m−2 K−1 were measured. It was found that the heat transfer coefficient is a strong function of the heat flux, mass velocity, and vapor quality. Five frictional pressure drop predictive methods were compared against the experimental database. The Cioncolini et al. (2009) method was found to work the best. Six flow boiling heat transfer predictive methods were also compared against the present database. Liu and Winterton (1991), Zhang et al. (2004), and Saitoh et al. (2007) were ranked as the best methods. They predicted the experimental flow boiling heat transfer data with an average error around 19%.

Horizontal distribution of invertebrate larvae around the oceanic island of Gran Canaria: the effect of mesoscale variability

In October 1991, the horizontal distribution of invertebrate larvae was studied in the waters surrounding the island of Gran Canaria (Canary Islands). The cruise was typified by the presence of three recurrent mesoscale hydrographic structures: a cyclonic eddy southwest of the island, a warm lee region downstream of the island and the offshore boundary of an upwelling filament from the African coast reaching the southeast of the island. Decapod larvae were the most abundant group. In general, a rather high spatial variability was found. The horizontal distribution of the invertebrate larvae groups showed that the highest values of abundance occurred in an elongated zone around the island oriented in the overall direction of flow, leeward and windward of the island, while the lowest values occurred off the eastern and western flanks of the islands. On the other hand, Stomatopoda and Mollusca larvae showed a distribution associated with the boundary of the upwelling filament and decapod larvae of pelagic species were distributed around the eddy structure. Our results suggest specific retention mechanisms for the larvae of neritic invertebrate populations that are related to the particular physical oceanography around Gran Canaria. Se estudió la distribución horizontal de las larvas de invertebrados alrededor de la isla de Gran Canaria (Islas Canarias) en octubre de 1991. La campaña se caracterizó por la presencia de tres fenómenos oceanográficos de mesoescala recurrentes: un remolino ciclónico al suroeste de la isla, la estela cálida a sotavento de la misma y el borde de un filamento proveniente del afloramiento africano situado al sureste de Gran Canaria. Las larvas de crustáceos decápodos fueron las más abundantes. En general, las larvas de los diferentes taxa estudiados mostraron una gran variabilidad en cuanto a su distribución espacial. La distribución horizontal de las larvas de los diferentes grupos de invertebrados mostró que las densidades más altas se registraban alrededor de la isla en la banda cercana y orientada hacia el suroeste, en la dirección del flujo, mientras que los valores más bajos se encontraron en el norte y en los flancos este y oeste de la isla. Por otro lado, las larvas de estomatópodos y moluscos presentaron una distribución asociada al frente del filamento, mientras que las larvas de decápodos pelágicos se distribuyeron en torno al remolino ciclónico. Los resultados obtenidos sugieren la existencia de mecanismos de retención específicos para el mantenimiento de las poblaciones insulares, relacionados con los procesos físicos de mesoescala predominantes