Turbulent spots in boundary layers in a free-piston shock-tunnel flow

In this paper, experiments to detect turbulent spots in the transitional boundary layers, formed on a flat plate in a free-piston shock tunnel how, are reported. Experiments indicate that thin-film heat-transfer gauges are suitable for identifying turbulent-spot activity and can be used to identify parameters such as the convection rate of spots and the intermittency of turbulence.

Numerical modelling of tide-induced beach water table fluctuations

Field studies have shown that the elevation of the beach groundwater table varies with the tide and such variations affect significantly beach erosion or accretion. In this paper, we present a BEM (Boundary Element Method) model for simulating the tidal fluctuation of the beach groundwater table. The model solves the two-dimensional flow equation subject to free and moving boundary conditions, including the seepage dynamics at the beach face. The simulated seepage faces were found to agree with the predictions of a simple model (Turner, 1993). The advantage of the present model is, however, that it can be used with little modification to simulate more complicated cases, e.g., surface recharge from rainfall and drainage in the aquifer may be included (the latter is related to beach dewatering technique). The model also simulated well the field data of Nielsen (1990). In particular, the model replicated three distinct features of local water table fluctuations: steep rising phase versus flat falling phase, amplitude attenuation and phase lagging.

Simulation of mixing in unsteady flow through a periodically obstructed channel

Fluid mixing in steady and unsteady Bow through a channel containing periodic square obstructions has been studied using a finite-difference simulation to determine fluid velocities, followed by the use of passive marker particle advection to look at fluid transport out of the cavities formed between each of the obstructions. The geometry and Bow conditions were chosen from the work by Perkins (1989, M.S. Thesis, Lehigh University; 1992, Ph.D. Thesis, Lehigh University); who investigated heat transfer enhancement due to unsteady flow through such an obstructed channel. Particle advection shows that Bow regimes which are predicted to give good mixing based on snapshots of instantaneous streamline contour plots were not necessarily able to efficiently mix fluid which started in the cavity regions throughout the channel. The use of Poincare sections shows regular regions existing under these conditions which inhibit efficient fluid transport. These regular regions are found to disappear when the unsteady Bow velocity is increased. (C) 1997 Elsevier Science Ltd.

Low birth weight in response to salt restriction during pregnancy is not due to alterations in uterine-placental blood flow or the placental and peripheral renin-angiotensin system

A number of studies conducted in humans and in animals have observed that events occurring early in life are associated with the development of diseases in adulthood. Salt overload and restriction during pregnancy and lactation are responsible for functional (hemodynamic and hormonal) and structural alterations in adult offspring. Our group observed that lower birth weight and insulin resistance in adulthood is associated with salt restriction during pregnancy On the other hand, perinatal salt overload is associated with higher blood pressure and higher renal angiotensin II content in adult offspring. Therefore, we hypothesised that renin-angiotensin system (RAS) function is altered by changes in sodium intake during pregnancy. Such changes may influence fetoplacental blood flow and thereby fetal nutrient supply, with effects on growth in utero and, consequently, on birth weight. Female Wistar rats were fed low-salt (LS), normal-salt (NS), or high-salt (HS) diet, starting before conception and continuing until day 19 of pregnancy, Blood pressure, heart rate, fetuses and dams` body weight, placentae weight and litter size were measured on day 19 of pregnancy. Cardiac output, uterine and placental blood flow were also determined on day 19. Expressions of renin-angiotensin system components and of the TNF-alpha gene were evaluated in the placentae. Plasma renin activity (PRA) and plasma and tissue angiotensin-converting enzyme (ACE) activity, as well as plasma and placental levels of angiotensins I, II, and 1-7 were measured. Body weight and kidney mass were greater in HS than in NS and LS dams. Food intake did not differ among the maternal groups. Placental weight was lower in LS dams than in NS and HS dams. Fetal weight was lower in the US group than in the NS and HS groups. The PRA was greater in IS dams than in NS and HS dams, although ACE activity (serum, cardiac, renal, and placental) was unaffected by the level of sodium intake. Placental levels of angiotensins I and II were lower in the HS group than in the ISIS and IS groups. Placental angiotensin receptor type 1 (AT(1)) gene expression and levels of thiobarbituric acid reactive substances (TBARS) were higher in HS dams, as were uterine blood flow and cardiac output. The degree of salt intake did not influence plasma sodium, potassium or creatinine. Although fractional sodium excretion was higher in HS dams than in NS and LS dams, fractional potassium excretion was unchanged. In conclusion, findings from this study indicate that the reduction in fetal weight in response to salt restriction during pregnancy does not involve alterations in uterine-placental perfusion or the RAS. Moreover, no change in fetal weight is observed in response to salt overload during pregnancy. However, salt overload did lead to an increase in placental weight and uterine blood flow associated with alterations in maternal plasma and placental RAS. Therefore, these findings indicate that changes in salt intake during pregnancy lead to alterations in uterine-placental perfusion and fetal growth. (C) 2008 Elsevier Inc. All rights reserved.

Peritoneal Dialysis in Acute Kidney Injury: Lessons Learned and Applied

Peritoneal dialysis (PD) is a simple, safe, gentle, and efficient renal replacement therapy (RRT) method. It is able to correct acute kidney injury (AKI)-induced metabolic, electrolytic, and acid-base disorders and volume overload both in and out the intensive care unit setting. Some PD modalities, such as high-volume PD and continuous flow PD, can provide RRT doses and efficiency comparable to extracorporeal blood purification methods. PD is particularly suitable for children, patients with refractory heart failure or hemodynamically instable, conditions where systemic anticoagulation should be avoided, patients with difficulty for vascular access and hypo- and hyperthermia conditions. In the following manuscript, PD technical aspects and the possible advantages and limitations of this RRT method will be discussed, and the more recent literature on clinical experience with PD for treatment of AKI will be reviewed.

Genetic population structure of the catadromous perciform: Macquaria novemaculeata (Percichthyidae)

Genetic population structure in the catadromous Australian bass Macquaria novemaculeata was investigated using samples from four locations spanning 600 km along the eastern Australian coastline. Both allozymes and mtDNA control region sequences were examined. Population subdivision estimates based on allozymes revealed low levels of population structuring (G(st)=0.043, P<0.05). However, mtDNA indicated moderate levels of geographic population structure (G(st)=0.146, P<0.01). Phylogenetic analysis of mtDNA control region sequences (mean sequence divergence 1.9%) indicated little phylogeographic structuring. Results suggested that genotypic variation within each river population, while bring affected primarily by genetic drift, was also prevented from more significant divergence by homogenizing levels of gene flow-synonymous with a one-dimensional stepping-stone model of population structure. The catadromous life history of Macquaria novemaculeata was considered to br influential on the pattern of population structure displayed. Results were compared to the few population genetic studies involving catadromous fishes, indicating that catadromy alone is unlikely to be a good predictor of population structure. A more comprehensive suite of biological characteristics than simple life-history traits must be considered fully to allow reliable predictive models of population structure to be formulated. (C) 1997 The Fisheries Society of the British Isles.

Nitric oxide modulates lipopolysaccharide-induced endothelial platelet endothelial cell adhesion molecule expression via interleukin-10

We have shown previously that nitric oxide (NO) controls platelet endothelial cell adhesion molecule (PECAM-1) expression on both neutrophils and endothelial cells under physiological conditions. Here, the molecular mechanism by which NO regulates lipopolysaccharide (LPS)-induced endothelial PECAM-1 expression and the role of interleukin (IL)-10 on this control was investigated. For this purpose, N-(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg/day for 14 days dissolved in drinking water) was used to inhibit both constitutive (cNOS) and inducible nitric oxide (iNOS) synthase activities in LPS-stimulated Wistar rats (5 mg/kg, intraperitoneally). This treatment resulted in reduced levels of serum NO. Under this condition, circulating levels of IL-10 was enhanced, secreted mainly by circulating lymphocytes, dependent on transcriptional activation, and endothelial PECAM-1 expression was reduced independently on reduced gene synthesis. The connection between NO, IL-10 and PECAM-1 expression was examined by incubating LPS-stimulated (1 mu g/ml) cultured endothelial cells obtained from naive rats with supernatant of LPS-stimulated lymphocytes, which were obtained from blood of control or L-NAME-treated rats. Supernatant of LPS-stimulated lymphocytes obtained from L-NAME-treated rats, which contained higher levels of IL-10, reduced LPS-induced PECAM-1 expression by endothelial cells, and this reduction was reversed by adding the anti-IL-10 monoclonal antibody. Therefore, an association between NO, IL-10 and PECAM-1 was found and may represent a novel mechanism by which NO controls endothelial cell functions.

Hydraulic tracer studies in a pilot scale subsurface flow constructed wetland

Current design procedures for Subsurface Flow (SSF) Wetlands are based on the simplifying assumptions of plug flow and first order decay of pollutants. These design procedures do yield functional wetlands but result in over-design and inadequate descriptions of the pollutant removal mechanisms which occur within them. Even though these deficiencies are often noted, few authors have attempted to improve modelling of either flow or pollutant removal in such systems. Consequently the Oxley Creek Wetland, a pilot scale SSF wetland designed to enable rigorous monitoring, has recently been constructed in Brisbane, Australia. Tracer studies have been carried out in order to determine the hydraulics of this wetland prior to commissioning it with sealed sewage. The tracer studies will continue during the wetland's commissioning and operational phases. These studies will improve our understanding of the hydraulics of newly built SSF wetlands and the changes brought on by operational factors such as biological films and wetland plant root structures. Results to date indicate that the flow through the gravel beds is not uniform and cannot be adequately modelled by a single parameter, plug flow with dispersion, model. We have developed a multiparameter model, incorporating four plug flow reactors, which provides a better approximation of our experimental data. With further development this model will allow improvements to current SSF wetland design procedures and operational strategies, and will underpin investigations into the pollutant removal mechanisms at the Oxley Creek Wetland. (C) 1997 IAWQ. Published by Elsevier Science Ltd.

Regional Blood Flow Distribution and Oxygen Metabolism During Mesenteric Ischemia and Congestion

Background. Acute mesenteric ischemia is a potentially fatal vascular emergency with mortality rates ranging between 60% and 80%. Several studies have extensively examined the hemodynamic and metabolic effects of superior mesenteric artery occlusion. On the other hand, the cardiocirculatory derangement and the tissue damage induced by intestinal outflow obstruction have not been investigated systematically. For these reasons we decided to assess the initial impact of venous mesenteric occlusion on intestinal blood flow distribution, and correlate these findings with other systemic and regional perfusion markers. Methods. Fourteen mongrel dogs were subjected to 45 min of superior mesenteric artery (SMAO) or vein occlusion (SMVO), and observed for 120 min after reperfusion. Systemic hemodynamics were evaluated using Swan-Ganz and arterial catheters. Regional blood flow (ultrasonic flow probes), intestinal O(2)-derived variables, and mesenteric-arterial and tonometric-arterial pCO(2) gradients (D(mv-a)pCO(2) and D(t-a)pCO(2)) were also calculated. Results. SMVO was associated with hypotension and low cardiac output. A significant increase in the regional pCO(2) gradients was also observed in both groups during the ischemic period. After reperfusion, a progressive reduction in D(mv-a)pCO(2) occurred in the SMVO group; however, no improvement in D(t-p)CO(2) was observed. The histopathologic injury scores were 2.7 +/- 0.5 and 4.8 +/- 0.2 for SMAO and SMVO, respectively. Conclusions. SMV occlusion promoted early and significant hemodynamic and metabolic derangement at systemic and regional levels. Additionally, systemic pCO(2) gradient is not a reliable parameter to evaluate the local intestinal oxygenation. Finally, the D(t-a)pCO(2) correlates with histologic changes during intestinal congestion or ischemia. However, minor histologic changes cannot be detected using this methodology. (C) 2010 Elsevier Inc. All rights reserved.

Effects of Exercise Training on Myocardial Blood Flow Reserve in Patients With Heart Failure and Left Ventricular Systolic Dysfunction

Exercise training has been shown to be effective in improving exercise capacity and quality of life in patients with heart failure and left ventricular (LV) systolic dysfunction. Real-time myocardial contrast echocardiography (RTMCE) is a new technique that allows quantitative analysis of myocardial blood flow (MBF). The aim of this study was to determine the effects of exercise training on MBF in patients with LV dysfunction. We studied 23 patients with LV dysfunction who underwent RTMCE and cardiopulmonary exercise testing at baseline and 4 months after medical treatment (control group, n = 10) or medical treatment plus exercise training (trained group, n = 13). Replenishment velocity (0) and MBF reserves were derived from quantitative RTMCE. The 4-month exercise training consisted of 3 60-minute exercise sessions/week at an intensity corresponding to anaerobic threshold, 10% below the respiratory compensation point. Aerobic exercise training did not change LV diameters, volumes, or ejection fraction. At baseline, no difference was observed in MBF reserve between the control and trained groups (1.89, 1.67 to 1.98, vs 1.81, 1.28 to 2.38, p = 0.38). Four-month exercise training resulted in a significant increase in beta reserve from 1.72 (1.45 to 1.48) to 2.20 (1.69 to 2.77, p <0.001) and an MBF reserve from 1.81 (1.28 to 2.38) to 3.05 (2.07 to 3.93, p <0.001). In the control group, 13 reserve decreased from 1.51 (1.10 to 1.85) to 1.46 (1.14 to 2.33, p = 0.03) and MBF reserve from 1.89 (1.67 to 1.98) to 1.55 (1.11 to 2.27, p <0.001). Peak oxygen consumption increased by 13.8% after 4 months of exercise training and decreased by 1.9% in the control group. In conclusion, exercise training resulted in significant improvement of MBF reserve in patients with heart failure and LV dysfunction. (C) 2010 Elsevier Inc. All rights reserved. (Am J Cardiol 2010;105:243-248)

Impact of gender on benefits of exercise training on sympathetic nerve activity and muscle blood flow in heart failure

We compared the effects of exercise training on neurovascular control and functional capacity in men and women with chronic heart failure (HF). Forty consecutive HF outpatients from the Heart Institute, University of Sao Paulo, Brazil were divided into the following four groups matched by age: men exercise-trained (n = 12), men untrained (n = 10), women exercise-trained (n = 9), women untrained (n = 9). Maximal exercise capacity was determined from a maximal progressive exercise test on a cycle ergometer. Forearm blood flow was measured by venous occlusion plethysmography. Muscle sympathetic nerve activity (MSNA) was recorded directly using the technique of microneurography. There were no differences between groups in any baseline parameters. Exercise training produced a similar reduction in resting MSNA (P = 0.000002) and forearm vascular resistance (P = 0.0003), in men and women with HF. Peak VO(2) was similarly increased in men and women with HF (P = 0.0003) and VE/VCO(2) slope was significantly decreased in men and women with HF (P = 0.0007). There were no significant changes in left-ventricular ejection fraction in men and women with HF. The benefits of exercise training on neurovascular control and functional capacity in patients with HF are independent of gender.

Derivation and external validation of a simple prediction model for the diagnosis of type 2 Diabetes Mellitus in the Brazilian urban population

A risk score model was developed based in a population of 1,224 individuals from the general population without known diabetes aging 35 years or more from an urban Brazilian population sample in order to select individuals who should be screened in subsequent testing and improve the efficacy of public health assurance. External validation was performed in a second, independent, population from a different city ascertained through a similar epidemiological protocol. The risk score was developed by multiple logistic regression and model performance and cutoff values were derived from a receiver operating characteristic curve. Model`s capacity of predicting fasting blood glucose levels was tested analyzing data from a 5-year follow-up protocol conducted in the general population. Items independently and significantly associated with diabetes were age, BMI and known hypertension. Sensitivity, specificity and proportion of further testing necessary for the best cutoff value were 75.9, 66.9 and 37.2%, respectively. External validation confirmed the model`s adequacy (AUC equal to 0.72). Finally, model score was also capable of predicting fasting blood glucose progression in non-diabetic individuals in a 5-year follow-up period. In conclusion, this simple diabetes risk score was able to identify individuals with an increased likelihood of having diabetes and it can be used to stratify subpopulations in which performing of subsequent tests is necessary and probably cost-effective.

Interconnected-tubes model of hepatic elimination

The distributed-tubes model of hepatic elimination is extended to include intermixing between sinusoids, resulting in the formulation of a new, interconnected-tubes model. The new model is analysed for the simple case of two interconnected tubes, where an exact solution is obtained. For the case of many strongly-interconnected tubes, it is shown that a zeroth-order approximation leads to the convection-dispersion model. As a consequence the dispersion number is expressed, for the first time, in terms of its main physiological determinants: heterogeneity of flow and density of interconnections between sinusoids. The analysis of multiple indicator dilution data from a perfused liver preparation using the simplest version of the model yields the estimate 10.3 for the average number of interconnections. The problem of boundary conditions for the dispersion model is considered from the viewpoint that the dispersion-convection equation is a zeroth-order approximation to the equations for the interconnected-tubes model. (C) 1997 Academic Press Limited.

Application of inter simple sequence repeat (ISSR) markers to plant genetics

Microsatellites or simple sequence repeats (SSRs) are ubiquitous in eukaryotic genomes. Single-locus SSR markers have been developed for a number of species, although there is a major bottleneck in developing SSR markers whereby flanking sequences must be known to design 5'-anchors for polymerase chain reaction (PCR) primers. Inter SSR (ISSR) fingerprinting was developed such that no sequence knowledge was required. Primers based on a repeat sequence, such as (CA)(n), can be made with a degenerate 3'-anchor, such as (CA)(8)RG or (AGC)(6)TY. The resultant PCR reaction amplifies the sequence between two SSRs, yielding a multilocus marker system useful for fingerprinting, diversity analysis and genome mapping. PCR products are radiolabelled with P-32 or P-33 via end-labelling or PCR incorporation, and separated on a polyacrylamide sequencing gel prior to autoradiographic visualisation. A typical reaction yields 20-100 bands per lane depending on the species and primer. We have used ISSR fingerprinting in a number of plant species, and report here some results on two important tropical species, sorghum and banana. Previous investigators have demonstrated that ISSR analysis usually detects a higher level of polymorphism than that detected with restriction fragment length polymorphism (RFLP) or random amplified polymorphic DNA (RAPD) analyses. Our data indicate that this is not a result of greater polymorphism genetically, but rather technical reasons related to the detection methodology used for ISSR analysis.