Measuring miscible fluid displacement in porous media with magnetic resonance imaging

The development of new quantitative magnetic resonance imaging (MRI) technologies open new opportunities for measurements of mass transport in porous media. The current work examines a simple miscible displacement process of H2O and D2O in porous media samples. Laboratory measurements of dispersion in porous media traditionally monitor the effluent intensity of an injected tracer. We employ MRI to obtain quantitative water saturation profiles, and to measure dispersion in rock core plugs. The saturation profiles are modeled with PHREEQC, a fluid transport modeling program. We demonstrate how independent magnetic resonance measurements can be employed to estimate three important input parameters for PHREEQC, mobile porosity, immobile porosity, and dispersivity. Bulk Carr Purcell Meiboom Gill (CPMG) T2 distribution measurements were undertaken to estimate mobile and immobile porosity. Bulk alternating-pulsed-gradient-stimulated-echo (APGSTE) measurements were undertaken to measure dispersivity. The imaging method employed, T2 mapping Spin Echo Single Point Imaging (SE-SPI), also provides information about the pore size distributions in the rock cores, and how the fluid occupancy of the pores changes during the displacement process.

Evaluating the corrosion behaviour of magnesium alloy in simulated biological fluid by using SECM to detect hydrogen evolution

Scanning electrochemical microscopy (SECM) in surface generation/tip collection mode is investigated as an assessment tool for studying the corrosion behaviour of magnesium in simulated biological fluid. The technique provides a local map of hydrogen (H2) evolution which alone can be used as a direct measure of corrosion. The H2 generated during corrosion of magnesium is oxidized at the probe(i.e. a Pt ultra micro-electrode);with the magnitude of the current generated due to oxidation being indicative of the intensity of H2 evolution at a local scale on the magnesium surface. This method was calibrated using a cathodically polarized Pt disk to simulate H2 evolution in a controlled condition on a homogeneous surface. Potential interference from dissolving Mg or high local pH was also investigated. The technique was implemented for studying H2 evolution at the surface of AZ31 as a model Mg alloy.SECM results combined with SEM-EDX and profilometry data revealed that local domains of higher H2 evolution on the surface of AZ31 are in close proximityof the observed pitting sites.

A review of computational fluid dynamics applications in pressure-driven membrane filtration

Ongoing advances in computational performance and numerics have led to computational fluid dynamics (CFD) becoming a ubiquitous modelling tool. However, CFD methods have only been adopted to simulate pressure-driven membrane filtration systems relatively recently. This paper reviews various approaches to describing the behaviour of these systems using CFD, beginning with the hydrodynamics of membrane channels, including discussion of laminar, turbulent, and transition flow regimes, with reference to the effects of osmotic pressure, concentration polarisation, and cake formation. The use of CFD in describing mass transfer through the membrane itself is then discussed, followed by some concluding comments on commercial membrane simulation packages and future research directions in membrane CFD. © 2013 Springer Science+Business Media Dordrecht.

Titanium dioxide nanotube films for electrochemical supercapacitors: Biocompatibility and operation in an electrolyte based on a physiological fluid

Growing interest in developing devices that can be implantable or wearable requires the identification of suitable materials for the components of these devices. Electrochemical supercapacitors are not the exception in this trend, and identifying electrode materials that can be not only suitable for the capacitive device but also biocompatible at the same time is important. In addition, it would be advantageous if physiological fluids could be used instead of more conventional (and often corrosive) electrolytes for implantable or wearable supercapacitors. In this study, we assess the biocompatibility of films of anodized TiO2 nanotubes subjected to the subsequent annealing in Ar atmosphere and evaluate their capacitive performance in a physiological liquid. A biocompatibility test tracking cell proliferation on TiO2 nanotube electrodes and electrochemical tests in 0.01 M phosphate-buffered saline solution are discussed. It is expected that the study will stimulate further developments in this area.

Fluid intake, hydration, work physiology of wildfire fighters working in the heat over consecutive days

PURPOSE: (i) To evaluate firefighters' pre- and post-shift hydration status across two shifts of wildfire suppression work in hot weather conditions. (ii) To document firefighters' fluid intake during and between two shifts of wildfire suppression work. (iii) To compare firefighters' heart rate, activity, rating of perceived exertion (RPE), and core temperature across the two consecutive shifts of wildfire suppression work. METHOD: Across two consecutive days, 12 salaried firefighters' hydration status was measured immediately pre- and post-shift. Hydration status was also measured 2h post-shift. RPE was also measured immediately post-shift on each day. Work activity, heart rate, and core temperature were logged continuously during each shift. Ten firefighters also manually recorded their food and fluid intake before, during, and after both fireground shifts. RESULTS: Firefighters were not euhydrated at all measurement points on Day one (292±1 mOsm l(-1)) and euhydrated across these same time points on Day two (289±0.5 mOsm l(-1)). Fluid consumption following firefighters' shift on Day one (1792±1134ml) trended (P = 0.08) higher than Day two (1108±1142ml). Daily total fluid intake was not different (P = 0.27), averaging 6443±1941ml across both days. Core temperature and the time spent ≥ 70%HRmax were both elevated on Day one (when firefighters were not euhydrated). Firefighters' work activity profile was not different between both days of work. CONCLUSION: There was no difference in firefighters' pre- to post-shift hydration within each shift, suggesting ad libitum drinking was at least sufficient to maintain pre-shift hydration status, even in hot conditions. Firefighters' relative hypohydration on Day one (despite a slightly lower ambient temperature) may have been associated with elevations in core temperature, more time in the higher heart rate zones, and 'post-shift' RPE.

Noradrenaline, but not neuropeptide Y, is elevated in cerebrospinal fluid from the third cerebral ventricle following audiovisual stress in gonadectomised rams and ewes

There are sex differences in the activation of the hypothalamo-pituitary-adrenal axis in response to stress, but the source of these differences is unknown. The hypothalamo-pituitary-adrenal axis is regulated by corticotropin-releasing hormone and arginine-vasopressin neurones located in the paraventricular nucleus and these, in turn, are regulated by neural systems that include afferent noradrenergic and neuropeptide Y (NPY)-producing neural pathways. We tested the hypothesis that concentrations of noradrenaline and NPY will be elevated in cerebrospinal fluid (CSF) sampled from the third cerebral ventricle in response to stress, and these responses will differ in males and females. We collected concurrent samples of CSF (1 ml) from the third ventricle and blood (5 ml) from the jugular vein from gonadectomised rams (n = 7) and ewes (n = 5) at 10-min intervals for 3 h. This procedure was conducted on a day when no stress was imposed and on a day when audiovisual stress was imposed for 5 min after 1 h of sampling. Following the audiovisual stress, plasma concentrations of cortisol and CSF concentrations of noradrenaline were elevated (p < 0.05), but CSF concentrations of NPY did not change. Adrenaline was not detected in samples of CSF. The rise in plasma cortisol following the stress was greater (p < 0.05) in ewes than in rams, but there were no sex differences in the rise in noradrenaline. Basal concentrations of NPY in the CSF were higher (p < 0.05) in rams than in ewes. We conclude that the sex differences in the stress-induced activity of the hypothalamo-pituitary-adrenal axis in sheep are not likely to be due to differences in the level of noradrenergic and/or NPY input to the hypothalamus.

Corrosion protection afforded by praseodymium conversion film on Mg alloy AZNd in simulated biological fluid studied by scanning electrochemical microscopy

Surface passivation of AZNd Mg alloy with Pr(NO3)3 is studied using scanning electrochemical microscopy (SECM) in surface generation/tip collection (SG/TC) and AC modes. Corrosion protection afforded by the Pr treatment and the degradation mechanism in a simulated biological environment was examined on a local scale and compared with non-treated AZNd. SG/TC mode results revealed a drastic decrease in H2 evolution due to the Pr treatment. Mapping the local insulating characteristics using AC-SECM showed higher conductivity of the surface where H2 evolution was most favorable.

Fluid mixing in droplet-based microfluidics with a serpentine microchannel

The hydrodynamics and mixing process within droplets travelling along a three dimensional serpentine microchannel are studied using a computational fluid dynamics simulation based on the volume-of-fluid approach. The fluid mixing within the droplet follows symmetric circulations in the straight section, which generates axial mixing. In the winding section, the asymmetric circulations lead to the reorientation of the fluids within the droplet, thus enhancing the mixing efficiency. The mixing performance is controlled by the spatial distribution of the mixing components and the circulation period within the droplet. The best mixing occurs when the droplet size is comparable with the channel width. When the droplet size is less than two times the channel width, the asymmetric circulations make it easy for the fluid to distribute in the axial direction, which leads to a fast mixing process. For larger droplets, the long circulation period becomes more significant, which causes lower mixing efficiency.

Manejo nutricional e digestibilidade no quilotórax canino

O quilotórax corresponde ao acúmulo de fluido linfático em um ou em ambos os espaços pleurais, resultante do extravasamento de linfa do ducto torácico ou de uma de suas divisões principais. Este pode estar associado à ascite quilosa em pacientes com distúrbios linfáticos sistêmicos, como na linfangiectasia, em decorrência de defeitos no transporte linfático-venoso do quilo da cavidade torácica para a circulação sistêmica. A linfangiectasia intestinal é um distúrbio obstrutivo que envolve o sistema linfático do órgão e revela-se como a causa mais comum de enteropatias associadas à má absorção e perda de proteínas em cães. São apresentados no presente relato o controle clínico com o uso de dieta caseira com baixa gordura e a quantificação da função digestiva, por meio da determinação da digestibilidade do alimento, em um cão acometido por quilotórax secundário à linfangiectasia intestinal. A dieta caseira incluiu arroz, peito de frango, cenoura, carbonato de cálcio, levedura de cerveja, suplemento vitamínico e mineral e sal. O ensaio de digestibilidade foi conduzido pelo método de coleta total de fezes. A dieta caseira foi eficaz em interromper o acúmulo de efusão quilosa torácica, restabelecer as concentrações de proteína total e albumina e promover ganho de peso no paciente. Os resultados da digestibilidade demonstraram menor aproveitamento de todos os nutrientes no cão com linfangiectasia em relação ao controle sadio.

Evaluation of electrophoretic profile and albumin quota in the cerebrospinal fluid of dogs with distemper showing or not neurvous signs

Estudaram-se o perfil eletroforético das proteínas liquóricas e a cota de albumina em cães sem e com cinomose na fase neurológica e não-neurológica. A punção da cisterna magna para a obtenção de amostras de liquor realizou-se em 30 cães. Analisaram-se teores de proteínas totais, cota de albumina e fracionamento eletroforético das proteínas liquóricas em gel de agarose. Os resultados foram semelhantes nos cães normais e nos cães com cinomose sem sinais neurológicos e significativamente elevados no grupo de cães com cinomose apresentando sinais neurológicos. O estudo do quadro protéico do líquido cérebroespinhal foi útil e contribuiu significativamente na detecção de lesões ao sistema nervoso central e de danos à barreira hematoencefálica durante a fase neurológica da cinomose.

Physical-chemical analysis of the cerebrospinal fluid of healthy dogs submitted to different storage periods and temperatures

Disfunções envolvendo o sistema nervoso são de grande importância na Medicina Veterinária, pois tratam-se de enfermidades de elevada incidência e com poucos subsídios auxiliares no seu diagnóstico, prognóstico e na avaliação de terapias empregadas. Ainda hoje, o diagnóstico baseia-se, em grande parte, no histórico e no exame clínico neurológico. Dessa forma, a análise dos constituintes do fluido cefalorraquidiano torna-se uma das poucas alternativas de acesso clínico ao sistema nervoso central (SNC). Mesmo com a grande utilidade do exame físico-químico e citoscópico do liquor na neurologia veterinária, poucos são os estudos sobre a estabilidade dos seus constituintes sob estocagem. Dessa forma, o presente trabalho teve como finalidade verificar a influência da temperatura e do tempo de conservação nas características físico-químicas do liquor de cães hígidos. Para tanto, foram coletadas amostras de LCR, através da punção da cisterna cerebelo-medular de cães clinicamente sadios, as quais foram submetidas à análise da densidade específica, do pH, da glicorraquia, das proteínas totais e das atividades das enzimas creatina quinase (CK) e aspartato aminotransferase (AST), após conservá-las em diferentes temperaturas (25°C, 4°C e -4°C) e por diferentes períodos de tempo (logo após a colheita, 24 horas, 48 horas, uma semana e um mês). Dentre os resultados obtidos, foi possível verificar, principalmente, que houve estabilidade dos parâmetros estudados por até um mês de estocagem nas amostras mantidas sob a temperaturas de congelamento de -4°C.

Peritoneal fluid changes in horses subjected to small colon distension

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Serum magnesium levels in healthy dogs submitted to the administration of cisplatin with fluid therapy

Cisplatin is an antineoplastic drug that is used to treat carcinomas and osteosarcomas in dogs. However, it can cause kidney damage which in turn leads to the loss of electrolytes. Concentration of magnesium was evaluated in the blood serum of eight dogs that had undergone therapy with cisplatin. The dogs were divided into two groups. Group 1 was supply with cisplatin (70 mg/m(2), iv) and to prevent nephrotoxcity, saline solution at 0.9% was administered (25 ml/kg/hour, iv in three hours). The animals in Group 2 were not supplied with cisplatin. There was no significant difference (P < 0.05) between the two groups and the results obtained indicated that the protocol used for Group 1 did not cause changes in the serum concentrations of magnesium. Therefore, it can be concluded that the administration of cisplatin does not cause variations if it is combined with the fluid therapy.