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Notes: The present study introduces the concept of a new scanning dual-capillary-tube viscometer (SDCV) for viscosity measurements of both Newtonian and non-Newtonian fluids, including whole blood, over a wide range of shear rates. The flow rate and pressure drop measurements that are usually required for the operation of a capillary-tube viscometer are replaced with two measurements of liquid-height variation with time. Using a charge-coupled device sensor array, one could measure the variation of fluid levels at each riser tube, h1(t) and h2(t), from which the test fluid viscosity was calculated. The feasibility and accuracy of the SDCV technique has been demonstrated for a standard-viscosity oil and for bovine blood by comparing results against established viscosity measurement techniques. A power-law viscosity model was used to correlate the data for the latter. The dual-capillary-tube viscometer extends the shear rate range as low as 0.1 s−1 for both the viscosity of mineral oil (9.9 cP at 25 °C) and bovine blood with 3% ethylenediaminetetraacetic acid at room temperature. © 2000 American Institute of Physics.

Notes: The present study introduces a new scanning capillary tube viscometer for measuring fluid viscosity continuously over a range of shear rates including a low shear regime. Using a charge-coupled device sensor array, one could measure the changes in fluid level in a rising tube h(t) from which viscosity and shear rate were mathematically calculated. The concept of the new scanning capillary tube viscometer was validated by measuring viscosities of Newtonian fluids and comparing the results with those obtained with reference data and a rotating viscometer. Furthermore, the present method overcomes one of the major drawbacks of the capillary tube viscometer, the inability to produce viscosity data in a low shear range, by extending the shear rate range as low as 5 s−1 for water and diluted glycerin solutions at room temperature. © 1999 American Institute of Physics.

Notes: Abstract: We have investigated the effects of fetal hypophysectomy (HX) with or without thyroxine (T4) replacement on the plasma concentrations of free methionine-enkephalin (free Met-Enk), noradrenaline, and adrenaline in late gestation sheep fetus. Plasma adrenaline concentrations were significantly higher in intact fetal sheep (1.05 ± 0.12 pmol/L) between 125 and 140 days of gestation when compared with the HX + saline (0.64 ± 0.10 pmol/L) and HX + T4 (0.61 ± 0.08 pmol/L) groups. During the first 15 days of the T4 or saline infusion, the plasma concentrations of free Met-Enk were significantly higher in the HX + T4 group (392 ± 40 pmol/L) than in the HX + saline group (299 ± 43 pmol/L). At this stage of gestation, however, circulating concentrations of free Met-Enk were significantly higher in intact fetal sheep (556 ± 51 pmol/L) than in either of the HX groups. Between 125 and 140 days of gestation, plasma free Met-Enk concentrations were similar and significantly higher in the intact and HX + T4 groups than those measured in the HX + saline fetal sheep. We conclude that the decrease in circulating free Met-Enk concentrations after removal of the fetal pituitary is primarily a consequence of functional athyroidism.

Notes: Soil microbes produce exudates which upon drying become water-repellent, thus altering hydraulic properties. The influence of microbial activity caused by adding plant nutrients on the hydraulic characteristics of soil aggregates is reported. Soil aggregates were collected from a field that had been fertilized with different amounts of nitrogen. Aggregates were also incubated with different nutrient treatments in the laboratory. Their sorptivity, hydraulic conductivity and water repellency were measured with a new device. Adding nitrogen was found to decrease sorptivity and hydraulic conductivity because of increased water repellency in the field. In the laboratory studies, the addition of nutrients caused severe water repellency in the soil aggregates. Respiration studies identified a large increase in biological activity following nutrient amendment which produces water-repellent materials.

Notes: The production of exudates by plant roots and microbes in the rhizosphere, together with intense wetting and drying cycles due to evapotranspiration, stimulate changes in soil structure. We have attempted to separate these two processes using an experimental model with bacterial exopolysaccharides (dextran and xanthan) and root mucilage analogues (polygalacturonic acid, PGA), and up to 10 cycles of wetting and drying. To characterize the soil structure, tensile strength, water sorptivity and ethanol sorptivity of the amended soils were measured, and thin sections were made. Xanthan and PGA induced greater tensile strength of the amended soil, suggesting that they increased the bond energy between particles. Porosity increased with each cycle of wetting and drying, and this increase was less pronounced for the PGA 2 g l−1 than for the xanthan and dextran. This suggests that PGA stabilized the soil against the disruptive effect caused by the wetting and drying. The PGA was the only polysaccharide that influenced water sorptivity and repellency, resulting in slower wetting of the treated soil. Wetting and drying led to an increase of the sorptivity and a decrease of the repellency for all treatments with the exception of the PGA-amended soils. The PGA may therefore stabilize the soil structure in the rhizosphere by increasing the strength of bonds between particles and decreasing the wetting rate.〈section xml:id="abs1-2"〉〈title type="main"〉Influence de mucilages racinaire et microbiens modèles sur la structure du sol et le transport d'eau〈section xml:id="abs1-3"〉〈title type="main"〉RésuméLa production d'exsudats par les plantes et les microbes de la rhizosphère ainsi que les cycles d'humectation–dessiccation très intense due à l'évapotranspiration, entraînent des modifications de la structure du sol. Notre objectif a été de séparer ces deux processus en utilisant un modèle expérimental avec des polysaccharides bactériens (dextran et xanthan) et un analogue d'exsudat racinaire (acide polygalacturonique, APG), et jusqu'à dix cycles d'humectation et dessiccation. Afin de caractériser la structure du sol, la résistance en traction ainsi que l'infiltration de l'eau et de l'éthanol dans le sol amendé par les différents polymères ont été mesurés, et des lames minces ont été réalisées. Le xanthan et l'APG ont provoqué la plus forte augmentation de la résistance en traction, ce qui serait attribuable à une plus grande énergie de liaison entre les particules de sol. La porosité a augmenté avec chaque cycle d'humectation–dessiccation pour tous les traitements et cette augmentation a été moins prononcée pour l'APG 2 g l−1 par rapport au xanthan et au dextran. Cela suggère que l'APG a stabilisé le sol contre la déstructuration provoquée par les cycles d'humectation–dessiccation. L'APG a été le seul polysaccharide qui a influencé– dans le sens d'une diminution – l'infiltration de l'eau dans le sol amendé. Les cycles d'humectation–dessiccation ont entraîné une augmentation de l'infiltration de l'eau dans le sol amendé par les différents polymères à l'exception de l'APG. Ce dernier stabiliserait donc la structure du sol dans la rhizosphère en augmentant la force de liaison entre les particules et en diminuant la vitesse d'humectation du sol.

Notes: Summary During a national study of Hunter's syndrome, visits were made to 33 sets of parents who had had a total of 44 affected sons, 27 with the severe, and 17 with the mild, form of the disease. Information about the behavioural pattern in a further 22 boys was obtained from hospital records. Serious behavioural disturbance was reported in 36 of the 38 severely affected boys, in contrast to those mildly affected, who were generally well behaved but often had serious psychological problems. The effects upon the parents of these boys are discussed. A plea is made that all possible long-term support should be offered both to the families and to the boys themselves.

Notes: The article considers the modeling of regions where the susceptibility is 0.01–10 ppm different from the majority of the space of interest. These calculations are of use in MR imaging, for example, in one possible application, the susceptibility of an haemorrhagic deposit could be adduced. Two methods are considered. Firstly, the use of finite element modeling using double precision arithmetic in conjunction with carefully set convergence limits. Secondly, a method which considers the induced polarity in the region of enhanced susceptibility, and calculates the difference field. The work is validated initially by calculating analytically the field perturbation produced by a sphere of susceptibility of 1×10−8 and comparing the results with the two methods given above. It is shown that excellent agreement is obtained. As a further confirmation the field produced by a short cylindrical object was measured experimentally using a MR scanner and again the applicability of both modeling techniques was confirmed. © 1996 American Institute of Physics.