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The understanding of swimming physiology and knowledge on the metabolic costs of swimming are important for assessing effects of environmental factors on migratory behavior. Swim tunnels are the most common experimental setups for measuring swimming performance and oxygen uptake rates in fishes; however, few can realistically simulate depth and the changes in hydrostatic pressure that many fishes experience, e.g. during diel vertical migrations. Here, we present a new hyperbaric swimming respirometer (HSR) that can simulate depths of up to 80 m. The system consists of three separate, identical swimming tunnels, each with a volume of 205 L, a control board and a storage tank with water treatment. The swimming chamber of each tunnel has a length of 1.40 m and a diameter of 20 cm. The HSR uses the principle of intermittent-flow respirometry and has here been tested with female European eels (Anguilla anguilla). Various pressure, temperature and flow velocity profiles can be programmed, and the effect on metabolic activity and oxygen consumption can be assessed. Thus, the HSR provides opportunities to study the physiology of fish during swimming in a simulated depth range that corresponds to many inland, coastal and shelf waters., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: The number of soft-tissue filler injections performed in the United States is constantly increasing and reflects the high demand for enhanced facial and body attractiveness. The objective of the present study was to measure the viscoelastic properties of soft-tissue fillers when subjected to different testing frequencies. The range of tested frequencies represents clinically different facial areas with more [lips (high frequency)] or less [zygomatic arch (low frequency)] soft-tissue movement., Methods: A total of 35 randomly selected hyaluronic acid-based dermal filler products were tested in an independent laboratory for their values of G', G″, tan δ, and G* at angular frequencies between 0.1 and 100 radian/second., Results: The results of the objective analyses revealed that the viscoelastic properties of all tested products changed between 0.1 and 100 radian/second angular frequency. Changes in G' ranged from 48.5 to 3116 percent, representing an increase in their initial elastic modulus, whereas changes in G″ ranged from -53.3 percent (i.e., decrease in G″) to 7741 percent (i.e., increase in G″), indicating both an increase and a decrease in their fluidity, respectively., Conclusions: The increase in G' would indicate the transition from a "softer" to a "harder" filler, and the observed decrease in G″ would indicate an increase in the filler's "fluidity." Changes in the frequency of applied shear forces such as those occurring in the medial versus the lateral face will influence the aesthetic outcome of soft-tissue filler injections., Competing Interests: Disclosure:The authors have no commercial associations or financial disclosures that might pose or create a conflict of interest with the methods applied or the results presented in this article. The laboratory testing procedures were financially supported by Adoderm, Langenfeld, Germany. No financial support was received for data interpretation or manuscript conception., (Copyright © 2021 by the American Society of Plastic Surgeons.)

Background: Currently, the diagnostic ability of uroflowmetry, the most widely used urodynamic test available for initial assessment of patients with lower urinary tract symptoms (LUTS), is considered limited by its inability to accurately discriminate between the underlying mechanisms of this condition. To improve the diagnostic accuracy of uroflow, we developed a mathematical formula that calculates the flow resistive forces index (QRF), a novel measure of bladder outflow/urethral resistance, and assessed its clinical applicability compared to the maximum flow rate (Q max )., Materials and Methods: A cross-sectional observational study was conducted in a cohort of 61 adult men presenting with voiding dysfunction symptoms, who all underwent free uroflowmetry followed by pressure flow study. The development of the mathematical formula which contains five key uroflowmetry variables (voided volume, flow time, Q max , average flow rate, and peak flow time) was based on the assumption that urine volume momentum changes during voiding, the concept of diphasic uroflow pattern (acceleration/deceleration), and the urethral resistance factor (URA) equation. Study subjects were classified either as obstructed or nonobstructed according to established urodynamic criteria (linearized passive urethral resistance relation, LinPURR; Abrams-Griffiths number, AGN [also called bladder outlet obstruction index, BOOI]; and URA). Univariate linear correlations, binary logistic regression model, and receiver operating characteristic (ROC) curve statistical analysis were employed (SPSS-22, MedCalc, GraphPad [P < .05])., Results: Outflow obstruction was diagnosed in 50.8% (1 in 2) patients. Univariate analysis, and bivariate linear correlation, binary logistic regression, and ROC curve analyses showed that the QRF was a strong independent predictor of bladder outlet/outflow obstruction (BOO), significantly outperforming Q max ., Conclusions: QRF index accurately predicts BOO, significantly outperforming the currently widely used bladder outlet obstruction estimator Q max . Despite potential study limitations (mainly small cohort size and lack of control group), we anticipate that with further study and proper clinical validation, QRF could become a valuable complement to uroflowmetry., (© 2020 John Wiley & Sons Australia, Ltd.)

We aimed to evaluate the accuracy and interchangeability of stroke volume and cardiac output measured by electrical velocimetry and transthoracic echocardiography during cesarean delivery.We enrolled 20 parturients in this prospective observational study. We recorded the stroke volume and cardiac output using both methods and compared the values at seven specific time points. We analyzed the data using linear regression analysis for Pearson's correlation coefficients and Bland-Altman analysis to determine percentage errors. We conducted a trending ability analysis based on the four-quadrant plot with the concordance rate and correlation coefficient.We recorded 124 paired datasets during cesarean delivery. The correlation coefficients of the measured cardiac output and stroke volume between the two methods were 0.397 (P < .001) and 0.357 (P < .001). The 95% limits of agreement were -1.0 to 8.1 L min for cardiac output and -10.4 to 90.4 ml for stroke volume. Moreover, the corresponding percentage errors were 62% and 60%. The concordance correlation coefficients were 0.447 (95% CI: 0.313-0.564) for stroke volume and 0.562 (95% CI: 0.442-0.662) for cardiac output. Both methods showed a moderate trending ability for stroke volume (concordance rate: 82% (95% CI: 72-90%)) and cardiac output (concordance rate: 85% (95% CI: 78-93%)).Our findings indicated that electrical velocimetry monitoring has limited accuracy, precision, and interchangeability with transthoracic echocardiography; however, it had a moderate trending ability for stroke volume and cardiac output measurements during cesarean delivery.

Background: The delayed graft function (DGF) in kidney transplantation (KT) is a risk factor for long-term poor graft survival. The pathogenesis is multifactorial but mainly related to an ischemia-reperfusion injury. However, the graft hemodynamics have been recently identified as a key aspect for early DGF risk assessment and potential therapeutic intervention., Methods: A pilot study on 20 single kidney grafts from donor after brain death with intraoperative measurement of graft arterial flowmetry, 30 minutes after reperfusion. Exclusion criteria were grafts with multiple arteries or severe atherosclerosis of the recipient's external iliac artery., Results: KT recipients with DGF (n = 4, 20%) were homogenous with controls (n = 16) in terms of cold ischemia time, donor age, recipients' hemodynamic parameters, renal artery, and recipients' external iliac artery diameters. Nonetheless, at transplant, the kidney grafts that developed DGF were characterized by a significantly higher renal artery resistive index (DGF vs no-DGF 0.96 ± 0.04 vs 0.77 ± 0.13, P = .02), as well as lower flow extraction rate (24.8% ± 11.8 vs 59.2% ± 21.1, P < .01)., Conclusions: Intraoperative arterial graft flowmetry seems to be an effective tool to identify grafts at high risk of DGF., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Major hemodynamic changes are frequently noted during liver transplantation (LT). We evaluated the performance of electrical velocimetry (EV) as compared to that of TEE in SV optimization during liver transplantation. This was an observational study in 32 patients undergoing LT. We compared SV values measured simultaneously by EV (SV EV ) and TEE (SV TEE ) at baseline 30 min after induction, at the end of dissection phase, 30 min after anhepatic phase, 30 min after reperfusion. We also evaluated the reliability of EV to track changes In SV before and after 49 fluid challenges. Finally, the SV variation (SVV) and pulse pressure variation (PPV) were tested as predictors for volume responsiveness, defined as an increase in SV ≥ 10% after 250 ml of colloid. For 112 paired SV data, the overall correlation was 0.76 and bias (limits of agreement) 0.3 (- 29 to 29) ml percentage error 62%. The EV was able to track changes in SV with a concordance rate of 97%, and a sensitivity and specificity of 93% to detect a positive fluid challenge. The AUC values (with 95% confidence intervals) for SVV and PPV were 0.68 (0.52-0.83) and 0.72 (0.57-0.86), respectively, indicating low predictive capacity in these setting. The absolute values of SV derived from EV did not agree with SV derived from TEE. However, EV was able to track the direction of changes in SV during hemodynamic management of patients undergoing liver transplantation.Clinical trial registration: Clinicaltrials.gov Identifier: NCT03228329 prospectively Registered on 13-July-2017.

In the present work it is aimed to obtain closed-form exact solutions for the fully developed momentum, thermal and concentration layers through a concentric annulus filled with various nanoparticle mixtures of water-based nanofluids in the presence of wall slip nanofluid velocity. The thermal boundary conditions of either both walls at fixed temperatures or of the inner wall at prescribed temperature and of the outer wall at specified heat flux are considered. Initially, the classical single phase model is adopted leading to simple formulas for the nanofluid flow and heat transfer. Then, the two-phase model of Buongiorno is considered by modifying it to incorporate the effects of nanoparticle volume fraction distribution in the full governing equations. This complex model also yields analytical formulas with regard to the momentum and thermal transport of nanoparticles of different nanofluids flowing in the concentric annuli. The essential features of nanofluids concerning the velocity, temperature and nanoparticle concentration fields as well as the rate of heat transfer are easily captured via the presented cute formulae. Particularly, the effects of Brownian and thermophoretic diffusivities as numerically examined in the literature can be investigated analytically by means of the derived solutions here valid under two distinct thermal conditions. Both models successfully explain the enhancement of heat transfer character of nanofluids by analysing the obtained exact Nusselt numbers involving several parameters of physical interest., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: The indocyanine green retention rate at 15 min (ICGR15) is a marker of the liver function and is useful for planning hepatectomy. To clarify the ICGR15 and the related clearance value (ICGK) calculated by a dye-dilution cardiac output flowmetry (DCOF), we examined the correlation and clinical significance of the ICGR15 values determined by DCOF and those determined with the conventional blood sampling (BS) procedure., Methods: We extracted liver function parameters, including the ICGR15 modified value and ICGK, and the extent of hepatectomy from the clinical and surgical records of 63 patients with various liver diseases in whom the ICGR15 (actual value), R15m (mean), and K (clearance rate per minute) were measured by DCOF., Results: All the patients were classified as Child-Pugh grade A. Hepatic complications were observed in 10 (16%) patients, but there was no mortality. The mean values of ICGR15 determined by BS (R15-BS) and DCOF (R15-DCOF) were 12.2 ± 8.1% and 11.2 ± 8.7%, respectively. The mean R15m determined by DCOF (R15m-DCOF) was 15.7 ± 10.2%. Significant differences were observed between R15-BS and R15-DCOF (1.1 ± 4.8%; p = 0.002) and R15m-DCOF (4.0 ± 5.9%; p < 0.001). The difference between R15-BS and R15m-DCOF was greater than that between R15-BS and R15-DCOF. Correlation between R15-BS and R15-DCOF was significant r = 0.839 (p < 0.001)., Conclusions: The ICGR15 measured by DCOF shows comparable reliability and stability to the BS method, which is useful for planning hepatectomy.

This study evaluated the flow properties of viscosity and flow rate for water and two common pediatric liquids. The flow properties of the test liquids are of interest to create a cup simulation model and "smart" prototype training cup. Two objective methods of determining flow properties were utilized: a rheometer to assess viscosity and a modified version of the International Dysphagia Diet Standardization Initiative (IDDSI) to assess flow rate. Rheometer results concluded that the pediatric supplements were less than 50 cP at all shear rates evaluated and exhibited shear-thinning properties, placing both liquids into the "thin" category. The IDDSI, which was performed according to standardized protocol and also with experimental modifications of varying syringe volumes, determined that all three test liquids had greater than 1 mL/s flow rate across all syringe types/sizes. The experimental modification of the IDDSI with 60 mL syringe volume was found to be the most consistent and applicable with discrete values obtained across all liquids tested. A flow rate factor equation can be determined with the use of a 60 mL syringe, with our laboratory setup, to create the cup simulation model. This computer-generated cup simulation model also aims to integrate engineering with clinical practice to develop a "smart" prototype training cup equipped with software to control flow rate.

Introduction and Hypothesis: The objective was to evaluate the intra-individual variability of uroflowmetry (UFM) in healthy control subjects and women suffering from stress, urge, and mixed urinary incontinence., Methods: A total of 35 healthy controls (group A) and 105 women suffering from urinary incontinence were enrolled in the study. Thirty-five women suffered from stress urinary incontinence (group B), 35 women suffered from mixed urinary incontinence (group C), and 35 women with overactive bladder both dry and wet (group D). All participants were asked to perform UFM measurement three times. The following parameters were analyzed: voided volume (VV), peak flow (Q max ), average flow (Q ave ), volume-corrected peak flow cQ max (cQ max  = Q max / 2 √ VV), volume-corrected average flow (cQ ave  = Q ave / 2 √ VV), and postvoid residual volume (PVR). Statistical analysis was performed using the analysis of variance on repeated measurements. Relative error was calculated using variation coefficients reported as a percentage of the average. All descriptive characteristics were reported as means ± standard deviation (SD). p values ≤0.05 were considered statistically significant., Results: No statistically significant intra-individual difference in any of the recorded parameters was identified among the three UFM recordings in groups A, C, and D. The intra-individual variability of the following parameters reached statistical significance in patients suffering from stress urinary incontinence (group B): Q max (p = 0.0016), Q ave (p = 0.0005), and cQ ave (p = 0.0389). A significant difference was only observed in comparison between the first and second consecutive recordings., Conclusions: This study provides evidence supporting the high yield and good intra-individual reproducibility of UFM.

In this paper, we present an analytical study of pressure-driven flow of micropolar non-Newtonian physiological fluids through a channel comprising two parallel oscillating walls. The cilia are arranged at equal intervals and protrude normally from both walls of the infinitely long channel. A metachronal wave is generated due to natural beating of cilia and the direction of wave propagation is parallel to the direction of fluid flow. Appropriate expressions are presented for deformation via longitudinal and transverse velocity components induced by the ciliary beating phenomenon with cilia assumed to follow elliptic trajectories. The conservation equations for mass, longitudinal and transverse (linear) momentum and angular momentum are reduced in accordance with the long wavelength and creeping Stokesian flow approximations and then normalized with appropriate transformations. The resulting non-linear moving boundary value problem is solved analytically for constant micro-inertia density, subject to physically realistic boundary conditions. Closed-form expressions are derived for axial velocity, angular velocity, volumetric flow rate and pressure rise. The transport phenomena are shown to be dictated by several non-Newtonian parameters, including micropolar material parameter and Eringen coupling parameter, and also several geometric parameters, viz eccentricity parameter, wave number and cilia length. The influence of these parameters on streamline profiles (with a view to addressing trapping features via bolus formation and evolution), pressure gradient and other characteristics are evaluated graphically. Both axial and angular velocities are observed to be substantially modified with both micropolar rheological parameters and furthermore are significantly altered with increasing volumetric flow rate. Free pumping is also examined. An inverse relationship between pressure rise and flow rate is computed which is similar to that observed in Newtonian fluids. The study is relevant to hemodynamics in narrow capillaries and also bio-inspired micro-fluidic devices., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objectives/hypothesis: To assess the accuracy and reliability of the flow coupler relative to the implantable arterial Doppler probe in postoperative monitoring of head and neck free flaps., Study Design: Retrospective single-institution study, April 2015 to March 2017., Methods: Both the venous flow coupler and arterial Doppler were employed in 120 consecutive head and neck free flap cases. When Doppler signal loss occurred, flaps were evaluated by physical exam to determine whether signal loss was a true positive necessitating operating room takeback. Sensitivity, specificity, and false positive rate (FPR) were recorded for each device. Logistic regression was conducted to identify user trends over time., Results: Eleven of 120 patients (9.2%) required takeback, 10 from venous thrombosis and one from arterial thrombosis. Permanent signal loss (PSL) occurred in the flow coupler in all takebacks; PSL occurred in the arterial Doppler only in the case of arterial thrombosis. Salvage rate was 9/11 (81.8%). For the flow coupler, sensitivity was 100%, specificity 86.4%, and FPR 13.6%. For the arterial probe, sensitivity was 9.1%, specificity 97.1%, and FPR 2.9%. A 4.1% decrease in false positives with each additional flow coupler use was observed., Conclusions: Monitoring the vein via flow coupler has high sensitivity in identifying vascular compromise compared to the arterial probe, especially for venous thrombosis. There is moderate FPR; this decreases with increased usage and, when supplemented with physical examination, does not result in unnecessary takebacks. The flow coupler can be a valuable tool in postoperative monitoring of head and neck free flaps., Level of Evidence: 4. Laryngoscope, 128:812-817, 2018., (© 2017 The American Laryngological, Rhinological and Otological Society, Inc.)

Obstacles and swimming fish in flow create a wake with an alternating left/right vortex pattern known as a Kármán vortex street and reverse Kármán vortex street, respectively. An energy-efficient fish behavior resembling slaloming through the vortex street is called Kármán gaiting. This paper describes the use of a bioinspired array of pressure sensors on a Joukowski foil to estimate and control flow-relative position in a Kármán vortex street using potential flow theory, recursive Bayesian filtering, and trajectory-tracking feedback control. The Joukowski foil is fixed in downstream position in a flowing water channel and free to move on air bearings in the cross-stream direction by controlling its angle of attack to generate lift. Inspired by the lateral-line neuromasts found in fish, the sensing and control scheme is validated using off-the-shelf pressure sensors in an experimental testbed that includes a flapping device to create vortices. We derive a potential flow model that describes the flow over a Joukowski foil in a Kármán vortex street and identify an optimal path through a Kármán vortex street using empirical observability. The optimally observable trajectory is one that passes through each vortex in the street. The estimated vorticity and location of the Kármán vortex street are used in a closed-loop control to track either the optimally observable path or the energetically efficient gait exhibited by fish. Results from the closed-loop control experiments in the flow tank show that the artificial lateral line in conjunction with a potential flow model and Bayesian estimator allow the robot to perform fish-like slaloming behavior in a Kármán vortex street. This work is a precursor to an autonomous robotic fish sensing the wake of another fish and/or performing pursuit and schooling behavior.

Introduction: International prostate symptom score is a validated questionnaire used to evaluate the lower urinary tract symptoms in benign prostatic hyperplasia. Visual prostate symptom score is a new simplified symptom score with pictograms to evaluate the same. We evaluated the correlation of visual prostate symptom score with international prostate symptom score and uroflowmetry parameters in Nepalese male patients with lower urinary tract symptoms., Methods: Male patients aged ≥40 years attending the Urology clinic were enrolled in the study. They were given international prostate symptom score and visual prostate symptom score questionnaires to complete providing assistance whenever needed. Demographic data, examination findings and uroflowmetry parameters were noted. Correlation and regression analysis was used to identify correlation of the two scoring systems and uroflowmetry parameters., Results: Among the 66 patients enrolled, only 10 (15.15%) patients were able to understand English language. There was a statistically significant correlation between total visual prostate symptom score and international prostate symptom score (r= 0.822; P<0.01). The correlations between individual scores of the two scoring systems related to force of urinary stream, frequency, nocturia and quality of life were also statistically significant. There was also a statistically significant correlation of both scores with maximum flow rate and average flow rate., Conclusions: There is a statistically significant correlation of visual prostate symptom score with international prostate symptom score and uroflowmetry parameters. IPSS can be replaced with simple VPSS in evaluation of lower urinary tract symptoms in elderly male patients.

This communication deals with the properties of heat source/sink in a magneto-hydrodynamic flow of a non-Newtonian fluid immersed in a porous medium. Shrinking phenomenon along with the permeability of the wall is considered. Mathematical modelling is performed to convert the considered physical process into set of coupled nonlinear mathematical equations. Suitable transformations are invoked to convert the set of partial differential equations into nonlinear ordinary differential equations which are tackled numerically for the solution computations. It is noted that dual solutions for various physical parameters exist which are analyzed in detail., Competing Interests: The authors have declared that no competing interests exist.

Introduction: Uroflowmetry is a first-line tool in the evaluation of children with lower urinary tract symptoms. Unfortunately, there is a tremendous amount of intra- and interobserver variation in defining the shape of curves. Regrettably, one observer can see one flow as a tower and the other can call it a bell. Here lies the major flaw with the interpretation of uroflow shapes. Previously, we have shown that there is a good correlation between the calculated flow index (FI) and the shape of a flow curve (bell, tower and plateau) in normal children., Objective: Our hypothesis was to show that the FI-defined shapes were as good or better than the present system of grading flow curves. If so this would help remove subjectivity from the field of uroflow assessment and make studies objective and easily compared., Study Design: Consecutive uroflows of children who were being evaluated for lower urinary tract symptoms from two centers were reviewed and compared alongside those of presumed normal voiders; the shape of the curves were read by the same experienced readers at each institution. Only curves that were read as bell, plateau, and tower were compared with the curve patterns derived from the quantitative methods derived by one of the authors. FI was derived by taking the actual Qmax/estimated Qmax., Results: There were 591 males and 1039 females who had uroflow studies, of these 409 and 819, respectively were read as either bell, towers, or plateaus The highest kappa value for males was 0.71 (CI 0.64-0.79) using a 3 × 3 matrix indicating substantial agreement. In females the highest kappa was 0.52 (CI 0.46-0.59) in the group 2 patients using the receiver operating characteristic cutoffs but the 1 SD cutoff was close with a kappa value of 0.51, which indicates moderate agreement (Table)., Discussion: Using the FI method we saw that there was substantial to moderate agreement using a quantitative method to define flow shapes based on the kappa values that were obtained in this study. The one fundamental flaw with shape determination in both visual and FI-derived methods is that the cutoffs are arbitrary since the visual defined shapes are the basis for the FI shapes., Conclusion: Our findings clearly showed that a FI-derived method of defining shapes is as accurate as visual inspection or more depending on the study. The greatest disagreement occurs in those grey or transition zones between plateau, bell and tower. This system could be useful in removing much of the ambiguity and difficulty in reading flows., (Copyright © 2016 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.)

Purpose: To test the milk flow rates and variability in flow rates of bottle nipples used after hospital discharge., Study Design and Methods: Twenty-six nipple types that represented 15 common brands as well as variety in price per nipple and store location sold (e.g., Babies R' Us, Walmart, Dollar Store) were chosen for testing. Ten of each nipple type (n = 260 total) were tested by measuring the amount of infant formula expressed in 1 minute using a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated. Flow rates of nipples within brand were compared statistically., Results: Milk flow rates varied from 1.68 mL/min for the Avent Natural Newborn Flow to 85.34 mL/min for the Dr. Brown's Standard Y-cut. Variability between nipple types also varied widely, from .03 for the Dr. Brown's Standard Level 3 to .37 for MAM Nipple 1 Slow Flow., Clinical Implications: The extreme range of milk flow rates found may be significant for medically fragile infants being discharged home who are continuing to develop oral feeding skills. The name of the nipple does not provide clear information about the flow rate to guide parents in decision making. Variability in flow rates within nipples of the same type may complicate oral feeding for the medically fragile infant who may not be able to adapt easily to change in flow rates. Both flow rate and variability should be considered when guiding parents to a nipple choice., Competing Interests: None

Two-phase outflows refer to situations where the interface formed between two immiscible incompressible fluids passes through open portions of the domain boundary. We present several new forms of open boundary conditions for two-phase outflow simulations within the phase field framework, as well as a rotational pressure correction based algorithm for numerically treating these open boundary conditions. Our algorithm gives rise to linear algebraic systems for the velocity and the pressure that involve only constant and time-independent coefficient matrices after discretization, despite the variable density and variable viscosity of the two-phase mixture. By comparing simulation results with theory and the experimental data, we show that the method produces physically accurate results. We also present numerical experiments to demonstrate the long-term stability of the method in situations where large density contrast, large viscosity contrast, and backflows occur at the two-phase open boundaries.

The goal of this study is to validate a new, continuous, noninvasive stroke volume (SV) method, known as transbrachial electrical bioimpedance velocimetry (TBEV). TBEV SV was compared to SV obtained by cardiac magnetic resonance imaging (cMRI) in normal humans devoid of clinically apparent heart disease. Thirty-two (32) volunteers were enrolled in the study. Each subject was evaluated by echocardiography to assure that no aortic or mitral valve disease was present. Subsequently, each subject underwent electrical interrogation of the brachial artery by means of a high frequency, low amplitude alternating current. A first TBEV SV estimate was obtained. Immediately after the initial TBEV study, subjects underwent cMRI, using steady-state precession imaging to obtain a volumetric estimate of SV. Following cMRI, the TBEV SV study was repeated. Comparing the cMRI-derived SV to that of TBEV, the two TBEV estimates were averaged and compared to the cMRI standard. CO was computed as the product of SV and heart rate. Statistical methods consisted of Bland-Altman and linear regression analysis. TBEV SV and CO estimates were obtained in 30 of the 32 subjects enrolled. Bland-Altman analysis of pre- and post-cMRI TBEV SV showed a mean bias of 2.87 % (2.05 mL), precision of 13.59% (11.99 mL) and 95% limits of agreement (LOA) of +29.51% (25.55 mL) and -23.77% (-21.45 mL). Regression analysis for pre- and post-cMRI TBEV SV values yielded y = 0.76x + 25.1 and r(2) = 0.71 (r = 0.84). Bland-Altman analysis comparing cMRI SV with averaged TBEV SV showed a mean bias of -1.56% (-1.53 mL), precision of 13.47% (12.84 mL), 95% LOA of +24.85% (+23.64 mL) and -27.97% (-26.7 mL) and percent error = 26.2 %. For correlation analysis, the regression equation was y = 0.82x + 19.1 and correlation coefficient r(2) = 0.61 (r = 0.78). Bland-Altman analysis of averaged pre- and post-cMRI TBEV CO versus cMRI CO yielded a mean bias of 5.01% (0.32 L min(-1)), precision of 12.85% (0.77 L min(-1)), 95% LOA of +30.20 % (+0.1.83 L min(-1)) and -20.7% (-1.19 L min(-1)) and percent error = 24.8%. Regression analysis yielded y = 0.92x + 0.78, correlation coefficient r(2) = 0.74 (r = 0.86). TBEV is a novel, noninvasive method, which provides satisfactory estimates of SV and CO in normal humans.

Animal studies have shown that injection pressures > 75 kPa indicate probable intrafascicular needle tip position. This study describes the flow/pressure characteristics of seven common needle systems. A syringe pump delivered flow rates of 5, 6.67, 10, 13.3, 15 and 20 ml.min(-1) through these needle systems, while keeping the needle tips open to atmosphere. A pressure transducer connected between the syringe and needle provided a real-time graphical display for analysis. Mean plateau pressures increased linearly with flow and with decreasing needle diameter (2.7-92 kPa). Flow rates > 17 ml.min(-1) and needle sizes 22 G and smaller produced mean plateau pressures > 75 kPa. Pressure monitors upstream from the needle may produce false-positive alarms at high flow rates due to needle resistance, and unreliable readings due to non-laminar flow. We recommend injection rates ≤ 15 ml.min(-1) (0.25 ml.s(-1) ) to reduce the effect of factors upstream from the needle tip as a cause of high pressure readings., (© 2014 The Association of Anaesthetists of Great Britain and Ireland.)

A supersonic separator has been introduced to remove water vapour from natural gas. The mechanisms of the upstream and downstream influences are not well understood for various flow conditions from the wellhead and the back pipelines. We used a computational model to investigate the effect of the inlet and outlet flow conditions on the supersonic separation process. We found that the shock wave was sensitive to the inlet or back pressure compared to the inlet temperature. The shock position shifted forward with a higher inlet or back pressure. It indicated that an increasing inlet pressure declined the pressure recovery capacity. Furthermore, the shock wave moved out of the diffuser when the ratio of the back pressure to the inlet one was greater than 0.75, in which the state of the low pressure and temperature was destroyed, resulting in the re-evaporation of the condensed liquids. Natural gas would be the subsonic flows in the whole supersonic separator, if the mass flow rate was less than the design value, and it could not reach the low pressure and temperature for the condensation and separation of the water vapor. These results suggested a guidance mechanism for natural gas supersonic separation in various flow conditions.

We present an optically encoded photoacoustic (PA) flow imaging method based on optical-resolution PA microscopy. An intensity-modulated continuous-wave laser photothermally encodes the flowing medium, and a pulsed laser generates PA waves to image the encoded heat pattern. Flow speeds can be calculated by cross correlation. The method was validated in phantoms at flow speeds ranging from 0.23 to 11  mm/s. Venous blood flow speed in a mouse ear was also measured.

The wharf roach Ligia exotica is a small animal that lives by the sea and absorbs water from the sea through its legs by virtue of a remarkable array of small blades of micron scale. We find that the imbibition dynamics on the legs is rather complex on a microscopic scale, but on a macroscopic scale the imbibition length seems to simply scale linearly with elapsed time. This unusual dynamics of imbibition, which usually slows down with time, is advantageous for long-distance water transport and results from repetition of unit dynamics. Inspired by the remarkable features, we study artificially textured surfaces mimicking the structure on the legs of the animal. Unlike the case of the wharf roach, the linear dynamics were not reproduced on the artificial surfaces, which may result from more subtle features on the real legs that are not faithfully reflected on the artificial surfaces. Instead, the nonlinear dynamics revealed that hybrid structures on the artificial surfaces speed up the water transport compared with non-hybrid ones. In addition, the dynamics on the artificial surfaces turn out to be well described by a composite theory developed here, with the theory giving useful guiding principles for designing hybrid textured surfaces for rapid imbibition and elucidating physical advantages of the microscopic design on the legs.

Hypothesis: Droplet size in microfluidic devices is affected by wettability of the microfluidic channels. Three-dimensional countercurrent flow focusing using assemblies of chemically inert glass capillaries is expected to minimize wetting of the channel walls by the organic solvent., Experiments: Monodispersed polycaprolactone and poly(lactic acid) particles with a diameter of 18-150 μm were produced by evaporation of solvent (dichloromethane or 1:2 mixture of chloroform and toluene) from oil-in-water or water-in-oil-in-water emulsions produced in three-dimensional flow focusing glass capillary devices. The drop generation behaviour was simulated numerically using the volume of fluid method., Findings: The numerical results showed good agreement with high-speed video recordings. Monodispersed droplets were produced in the dripping regime when the ratio of the continuous phase flow rate to dispersed phase flow rate was 5-20 and the Weber number of the dispersed phase was less than 0.01. The porosity of polycaprolactone particles increased from 8 to 62% when 30 wt% of the water phase was incorporated in the organic phase prior to emulsification. The inner water phase was loaded with 0.156 wt% lidocaine hydrochloride to achieve a sustained drug release. 26% of lidocaine was released after 1 h and more than 93% of the drug was released after 130 h., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Magnetic fields are increasingly being utilized in endoscopy and gastric transport control. In this regard, the present study investigates the influence of a transverse magnetic field in the transient peristaltic rheological transport. An electrically-conducting couple stress non-Newtonian model is employed to accurately simulate physiological fluids in peristaltic flow through a sinusoidally contracting channel of finite length. This model is designed for computing the intra-bolus oesophageal and intestinal pressures during the movement of food bolus in the digestive system under magneto-hydro-dynamic effects. Long wavelength and low Reynolds number approximations have been employed to reduce the governing equations from nonlinear to linear form, this being a valid approach for creeping flows which characterizes physiological dynamics. Analytical approximate solutions for axial velocity, transverse velocity, pressure gradient, local wall shear stress and volumetric flow rate are obtained for the non-dimensional conservation equations subject to appropriate boundary conditions. The effects of couple stress parameter and transverse magnetic field on the velocity profile, pressure distribution, local wall shear stress and the averaged flow rate are discussed with the aid of computational results. The comparative study of non-integral and integral number of waves propagating along the finite length channel is also presented. Magnetic field and non-Newtonian properties are found to strongly influence peristaltic transport., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Purpose: To investigate retrospectively the use of catheter-based intraaccess blood flow measurements as an adjunct to physical examination and fistulography in hemodialysis access interventions., Materials and Methods: Among 1,540 dialysis interventions performed at a single institution in a 2.5-year period, 104 qualifying catheter-based flow measurements were made in 70 mature native fistula interventions in 55 patients and 34 graft interventions in 31 patients. The flow rate threshold prompting intervention was generally 600 mL/min, but some variation existed depending on the clinical setting., Results: The most common indication for measurement of blood flow was to determine the hemodynamic significance of a fistula inflow stenosis (n = 25), of which only four had subsequent intervention. Other common indications included decision-making resulting in further angioplasty or stent implantation of noninflow lesions (fistulas, n = 10; grafts, n = 23) versus termination of the procedure (n = 23), problem-solving in cases in which there was no visible lesion to explain the clinical indicator of access failure (n = 17), evaluation for high-flow-related cardiac risk in aneurysmal fistulas (n = 13), suboptimal evaluation of the inflow (n = 8), and suboptimal physical examination (n = 6). Overall, flow measurements supported a decision to perform angioplasty (n = 11) or stent placement (n = 3) in 17% of fistula interventions and 35% of graft interventions., Conclusions: The major benefit of flow measurement was to support a decision to withhold further angioplasty or stent placement., (Copyright © 2013. Published by Elsevier Inc.)

Probing the physical properties of heterogeneous materials is essential to understand the structure, function and dynamics of complex fluids including cells, mucus, and polymer solutions. Particle tracking microrheology is a useful method to passively probe viscoelastic properties on micron length scales by tracking the thermal motion of beads embedded in the sample. However, errors associated with active motion have limited the implementation to dynamic systems. We present a simple method to decouple active and Brownian motion, enabling particle tracking to be applied to fluctuating heterogeneous systems. We use the movement perpendicular to the major axis of motion in time to calculate rheological properties. Through simulated data we demonstrate that this method removes directed motion and performs equally well when there is no directed motion, with an average percent error of <1%. We use this method to measure glycerol-water mixtures to show the capability to measure a range of materials. Finally, we use this technique to characterize the compliance of human sputum. We also investigate the effect of a liquefaction agent used to prepare sputum for diagnostic purposes. Our results suggest that the addition of high concentration sodium hydroxide increases sample heterogeneity by increasing the maximum observed creep compliance.

In the present study, a nasal powder of the antidiuretic peptide desmopressin (DDAVP) formulated as chimera agglomerates was studied to improve drug bioavailability and provide a flexible drug product. Firstly, DDAVP was spray-dried along with mannitol and lecithin to produce primary microparticles capable of instantaneous dissolution in water. The chimera agglomerates were spontaneously formed by mechanically vibrating the microparticles on two stacked sieves. Agglomerate formation and strength were favored by the presence of lecithin. Drug content and dissolution rate remained unmodified after agglomeration. However, owing to the agglomerate larger size, powder flowability was greatly improved in comparison with the original microparticles, allowing accurate powder dosing into the nasal delivery device. DDAVP in vitro permeation across excised rabbit nasal mucosa from the agglomerates was significantly higher than that obtained from a commercial liquid nasal spray. In rats, intranasal DDAVP agglomerates allowed for efficient administration with almost 80% of the loaded powder emitted from the device into the animal nose. The administration of DDAVP agglomerates induced a significant reduction in urine production. Moreover, the antidiuretic effect of agglomerates did not significantly differ from the one induced by an intravenous injection of DDAVP at a ten-fold lower dose., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The left ventricle (LV) pumps oxygenated blood from the lungs to the rest of the body through systemic circulation. The efficiency of such a pumping function is dependent on blood flow within the LV chamber. It is therefore crucial to accurately characterize LV hemodynamics. Improved understanding of LV hemodynamics is expected to provide important clinical diagnostic and prognostic information. We review the recent advances in numerical and experimental methods for characterizing LV flows and focus on analysis of intraventricular flow fields by echocardiographic particle image velocimetry (echo-PIV), due to its potential for broad and practical utility. Future research directions to advance patient-specific LV simulations include development of methods capable of resolving heart valves, higher temporal resolution, automated generation of three-dimensional (3D) geometry, and incorporating actual flow measurements into the numerical solution of the 3D cardiovascular fluid dynamics.

Cell migration is commonly quantified by tracking the speed of the cell layer interface in wound healing assays. This quantification is often hampered by low signal to noise ratio, in particular when complex substrates are employed to emulate in vivo cell migration in geometrically complex environments. Moreover, information about the cell motion, readily available inside the migrating cell layers, is not usually harvested. We introduce Cell Image Velocimetry (CIV), a combination of cell layer segmentation and image velocimetry algorithms, to drastically enhance the quantification of cell migration by wound healing assays. The resulting software analyses the speed of the interface as well as the detailed velocity field inside the cell layers in an automated fashion. CIV is shown to be highly robust for images with low signal to noise ratio, low contrast and frame shifting and it is portable across various experimental settings. The modular design and parametrization of CIV is not restricted to wound healing assays and allows for the exploration and quantification of flow phenomena in any optical microscopy dataset. Here, we demonstrate the capabilities of CIV in wound healing assays over topographically engineered surfaces and quantify the relative merits of differently aligned gratings on cell migration.

Flows through tubular structures are common in many fields, including blood flow in medicine and tubular fluid flows in engineering. The analysis of such flows is often done with a strong reference to the main flow direction along the tubular boundary. In this paper we present an approach for straightening the visualization of tubular flow. By aligning the main reference direction of the flow, i.e., the center line of the bounding tubular structure, with one axis of the screen, we are able to natively juxtapose (1.) different visualizations of the same flow, either utilizing different flow visualization techniques, or by varying parameters of a chosen approach such as the choice of seeding locations for integration-based flow visualization, (2.) the different time steps of a time-dependent flow, (3.) different projections around the center line , and (4.) quantitative flow visualizations in immediate spatial relation to the more qualitative classical flow visualization. We describe how to utilize this approach for an informative interactive visual analysis. We demonstrate the potential of our approach by visualizing two datasets from two different fields: an arterial blood flow measurement and a tubular gas flow simulation from the automotive industry., (© 2011 IEEE)

The aim of this work is to demonstrate that uncontrolled initial moisture content in microcrystalline cellulose (MCC) can profoundly affect high shear wet granulation (HSWG) process. We show that granule tabletability is reduced by approximately 50% when initial moisture content in MCC increases from 0.9% to 10.5% while all other processing parameters remain unchanged. An important observation is that granule tableting performance deteriorates significantly when initial moisture content increases from 2.6% to 4.9%, which is considered normal variation in moisture content for typical MCC (3-5%). The deteriorated tabletability is largely caused by increased granule size. On the other hand, granule flowability improves continuously with increasing initial moisture content in MCC. The improved flowability is mainly a result of granule size enlargement. Clearly, moisture content of raw materials for a HSWG process must be carefully monitored and controlled to ensure a robust manufacturing process as required by the quality-by-design principle., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Roll compaction is gaining importance in pharmaceutical industry for the dry granulation of heat or moisture sensitive powder blends with poor flowing properties prior to tabletting. We studied the influence of microcrystalline cellulose (MCC) properties on the roll compaction process and the consecutive steps in tablet manufacturing. Four dissimilar MCC grades, selected by subjecting their physical characteristics to principal components analysis, and three speed ratios, i.e. the ratio of the feed screw speed and the roll speed of the roll compactor, were included in a full factorial design. Orthogonal projection to latent structures was then used to model the properties of the resulting roll compacted products (ribbons, granules and tablets) as a function of the physical MCC properties and the speed ratio. This modified version of partial least squares regression separates variation in the design correlated to the considered response from the variation orthogonal to that response. The contributions of the MCC properties and the speed ratio to the predictive and orthogonal components of the models were used to evaluate the effect of the design variation. The models indicated that several MCC properties, e.g. bulk density and compressibility, affected all granule and tablet properties, but only one studied ribbon property: porosity. After roll compaction, Ceolus KG 1000 resulted in tablets with obvious higher tensile strength and lower disintegration time compared to the other MCC grades. This study confirmed that the particle size increase caused by roll compaction is highly responsible for the tensile strength decrease of the tablets., (Copyright © 2011 Elsevier B.V. All rights reserved.)

An inhaler design methodology was developed and then used to design a new dry powder inhaler (DPI) which aimed to fulfill two main performance requirements. The first requirement was that the patient should be able to completely empty the dry powder from the blister in which it is stored by inspiratory effort alone. The second requirement was that the flow resistance of the inhaler should be geared to optimum patient comfort. The emptying of a blister is a two-phase flow problem, whilst the adjustment of the flow resistance is an aerodynamic design problem. The core of the method comprised visualization of fluid and particle flow in upscaled prototypes operated in water. The prototypes and particles were upscaled so that dynamic similarity conditions were approximated as closely as possible. The initial step in the design method was to characterize different blister prototypes by measurements of their flow resistance and particle emptying performance. The blisters were then compared with regard to their aerodynamic performance and their ease of production. Following selection of candidate blisters, the other components such as needle, bypass and mouthpiece were dimensioned on the basis of node-loop operations and validation experiments. The final shape of the inhaler was achieved by experimental iteration., (Copyright © 2011 Elsevier B.V. All rights reserved.)

We sought to validate center-specific published medians and estimate the effects of sonologist and Doppler measurement techniques on middle cerebral artery (MCA) peak systolic velocity (PSV) values. We studied 154 gravidas with normal singletons who underwent MCA PSV measurement at 18 to 35 weeks' gestation by one of three experienced sonologists. Pregnancies complicated by a known fetal anomaly (structural or aneuploidy), amniotic fluid volume disturbance, intrauterine growth restriction, multiple gestation, or isoimmunization were excluded. MCA PSV was measured using both manual caliper and auto-trace techniques. Regression models of log-transformed PSV values and gestational age were developed. Although auto-trace medians were significantly lower than those obtained with manual calipers ( P < 0.0001), they more closely approximated published medians used in clinical practice. Minimal intersonologist differences (maximum mean difference <3 cm/s) were statistically significant ( P < 0.01). Compared with manual caliper, auto-trace measurement yielded significantly lower medians. However, center-specific medians obtained by our sonologists using auto-trace more closely approximated published standards. Estimated interobserver variability suggested that different sonologists may utilize the same median values. We suggest that centers that utilize Doppler velocimetry for the prediction of fetal anemia examine their measurement protocol and consider formal confirmation of their own center-specific median values., (Copyright Thieme Medical Publishers.)

The glide is a major part of starts, turns and the stroke cycle in breaststroke. Glide performance, indicated by the average velocity, can be improved by increasing the glide efficiency, that is, the ability of the body to minimise deceleration. This paper reviews the factors that affect glide efficiency. In the first part of the review the sources of resistive force are reviewed including surface friction (skin drag), pressure (form) drag and resistance due to making waves (wave drag). The effect of body surface characteristics on the skin drag, the effect of the depth of the swimmer on wave drag, and the effects of posture and alignment, body size and shape on the form drag are reviewed. The effects of these variables on the added mass, that is, the mass of water entrained with the body are explained. The 'glide factor' as a measure of glide efficiency that takes into account the combined effect of the resistive force and the added mass is described. In the second part methods of quantifying the resistive force are reviewed. Finally, the 'hydro-kinematic method' of measuring glide efficiency is evaluated., (Copyright 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Numerical studies on fluid-structure interaction have primarily relied on decoupling the solid and fluid sub-domains with the interactions treated as external boundary conditions on the individual sub-domains. The finite element applications for the fluid-structure interactions can be divided into iterative algorithms and sequential algorithms. In this paper, a new computational methodology for the analysis of tissue-fluid interaction problems is presented. The whole computational domain is treated as a single biphasic continuum, and the same space and time discretisation is carried out for the sub-domains using a penalty-based finite element model. This procedure does not require the explicit modelling of additional boundary conditions or interface elements. The developed biphasic interface finite element model is used in analysing blood flow through normal and stenotic arteries. The increase in fluid flow velocity when passing through a stenosed artery and the drop in pressure at the region are captured using this method.

Recently, there has been growing interest in the development of photoacoustic flow measuring methods aimed to study microvascular blood flow in biological tissue. Here, we describe the M-mode photoacoustic particle flow imaging, using an optical resolution photoacoustic microscope equipped with a high-repetition-rate pulsed dye laser. We studied the flow of a diluted dyed particle suspension in a small tube embedded in a nonscattering medium as well as in a scattering medium simulating biological tissue. Potentially, the method can be applied to detect the flow speed of single red blood cells in a capillary.

An essential requirement for any practical fully integrated lab-on-a-chip device is the ability to mix two or more fluids thoroughly and efficiently, i.e., in a reasonable amount of time. This paper presents a way to improve mixing in microfluidic systems combining alternate flows with obstacles using passive mixers. Numerical simulations show that the layers of high and low solute concentration, created by the alternate flow, are split into smaller chunks of fluid, due to the obstacles inserted in the mixing channel, increasing the contact area between high and low concentration regions and decreasing the critical mixing length. This improvement can lead to shorter mixing channels and to low-cost mixers fabricated by planar lithographic technology.

A 3D computational fluid dynamic (CFD) model is presented to simulate transient rolling adhesion and deformation of leukocytes over a P-selectin coated surface in shear flow. The computational model is based on immersed boundary method for cell deformation, and stochastic Monte Carlo simulation for receptor/ligand interaction. The model is shown to predict the characteristic 'stop-and-go' motion of rolling leukocytes. Here we examine the effect of cell deformation, shear rate, and microvilli distribution on the rolling characteristics. Comparison with experimental measurements is presented throughout the article. We observe that compliant cells roll more stably, and have longer pause times due to reduced bond force and increased bond lifetime. Microvilli presentation is shown to affect rolling characteristics by altering the step size, but not pause times. Our simulations predict a significant sideway motion of the cell arising purely due to receptor/ligand interaction, and discrete nature of microvilli distribution. Adhesion is seen to occur via multiple tethers, each of which forms multiple selectin bonds, but often one tether is sufficient to support rolling. The adhesion force is concentrated in only 1-3 tethered microvilli in the rear-most part of a cell. We also observe that the number of selectin bonds that hold the cell effectively against hydrodynamic shear is significantly less than the total adhesion bonds formed between a cell and the substrate. The force loading on individual microvillus and selectin bond is not continuous, rather occurs in steps. Further, we find that the peak force on a tethered microvillus is much higher than that measured to cause tether extrusion.

Obstruction of the microcirculation is the most important cause of painful crisis in sickle cell disease (SCD). Extensive microvascular obstruction has been observed in mouse models of SCD. A technique to determine the extent of the microcirculatory obstructions in humans may be helpful in the clinical setting and for research purposes. Therefore, we measured sublingual microcirculation longitudinally in patients with SCD admitted with painful crisis. Sublingual microcirculation was recorded with side-stream darkfield (SDF) imaging and semi-quantified with a microvascular flow index (MFI) on a range from 0 to 4 (arbitrary units; from 0 (no flow) to 4 (hyperdynamic flow)). Thirteen consecutive adult sickle cell patients admitted with painful crises were included and provided 47 measurements of MFI in 14 episodes of painful crisis. Seven patients provided baseline measurements and seven healthy controls were studied. The mean (+/-standard error of the mean) MFI during painful crisis was 2.6+/-0.1 and did not change during the painful crisis. The mean MFI of patients with SCD during steady state (2.7+/-0.1) and the mean MFI of the controls (2.7+/-0.1) were not different from the mean MFI during painful crisis. During painful crisis irregular microvascular perfusion, expressed by the distribution width of the microvascular blood flow velocity, correlated negatively (r=-0.484; P=0.002) with hemoglobin concentration. We conclude that sublingual microcirculatory blood flow velocity is not disturbed in sickle cell patients during painful crisis.

Background and Objective: The purpose was to study the agreement between cardiac output measurements with electrical velocimetry vs. intermittent thermodilution before and after coronary artery bypass graft surgery., Methods: Cardiac output was measured simultaneously with electrical velocimetry and intermittent thermodilution before and immediately after coronary artery bypass graft surgery, and in the intensive care unit. Measurements were performed in three different body positions. The results were analysed according to Bland and Altman., Results: The mean bias of all 150 paired measurements in 16 patients was 0.21 +/- 0.78 L min(-1), and the mean error was 40%. Before skin incision the mean bias was 0.04 +/- 0.41 L min(-1), and the mean error was 25%. After skin closure the mean bias was 0.57 +/- 0.92 L min(-1), and the mean error was 42%. In the intensive care unit the mean bias was 0.26 +/- 0.68 L min(-1), and the mean error was 32%., Conclusions: The agreement between cardiac output measurements with electrical velocimetry and intermittent thermodilution was clinically acceptable only before skin incision in coronary artery bypass graft surgery. The mean error was unacceptably high immediately after skin closure and was at a borderline level in the intensive care unit. Thus, the overall accuracy of cardiac output measurements with the electrical velocimetry technique during coronary artery bypass graft surgery is not clinically unacceptable.

The density profiles in a fluid interacting with the two identical solid walls of a closed long slit were calculated for wide ranges of the number of fluid molecules in the slit and temperature by employing a nonlocal density functional theory. Using argon as the sample fluid and considering the walls composed of solid carbon dioxide, it is shown that the density profile corresponding to the stable state of the fluid considerably changes its shape with increasing average density rho(av) of the fluid inside the slit. Temperature dependent critical values rho(sb1) and rho(sb2) of rho(av) were identified, such that for rho(sb1)

An optimized closure approximation for both simple and molecular fluids is presented. A smooth interpolation between Perkus-Yevick and hypernetted chain closures is optimized by minimizing the free energy self-consistently with respect to the interpolation parameter(s). The molecular version is derived from a refinement of the method for simple fluids. In doing so, a method is proposed which appropriately couples an optimized closure with the variant of the diagrammatically proper integral equation recently introduced by this laboratory [K. M. Dyer et al., J. Chem. Phys. 123, 204512 (2005)]. The simplicity of the expressions involved in this proposed theory has allowed the authors to obtain an analytic expression for the approximate excess chemical potential. This is shown to be an efficient tool to estimate, from first principles, the numerical value of the interpolation parameters defining the aforementioned closure. As a preliminary test, representative models for simple fluids and homonuclear diatomic Lennard-Jones fluids were analyzed, obtaining site-site correlation functions in excellent agreement with simulation data.

The dynamics of fluid vesicles in simple shear flow is studied using mesoscale simulations of dynamically triangulated surfaces, as well as a theoretical approach based on two variables: a shape parameter and the inclination angle, which has no adjustable parameters. We show that, between the well-known tank-treading and tumbling states, a new "swinging" state can appear. We predict the dynamic phase diagram as a function of the shear rate, the viscosities of the membrane and the internal fluid, and the reduced vesicle volume. Our results agree well with recent experiments.

We provide a direct experimental test of the fluctuation-dissipation theorem (FDT) in an aging colloidal glass. The use of combined active and passive microrheology allows us to independently measure both the correlation and response functions in this nonequilibrium situation. Contrary to previous reports, we find no deviations from the FDT over several decades in frequency (1 Hz-10 kHz) and for all aging times. In addition, we find two distinct viscoelastic contributions in the aging glass, including a nearly elastic response at low frequencies that grows during aging.

The aerated stirred reactor (ASR) has been widely used in biochemical and wastewater treatment processes. The information describing how the activated sludge properties and operation conditions affect the hydrodynamics and mass transfer coefficient is missing in the literature. The aim of this study was to investigate the influence of flow regime, superficial gas velocity (U(G)), power consumption unit (P/V(L)), sludge loading, and apparent viscosity (mu(ap)) of activated sludge fluid on the mixing time (t(m)), gas hold-up (epsilon), and volumetric mass transfer coefficient (k(L)a) in an activated sludge aerated stirred column reactor (ASCR). The activated sludge fluid performed a non-Newtonian rheological behavior. The sludge loading significantly affected the fluid hydrodynamics and mass transfer. With an increase in the U(G) and P/V(L), the epsilon and k(L)a increased, and the t(m), decreased. The epsilon, k(L)a, and t(m), were influenced dramatically as the flow regime changed from homogeneous to heterogeneous patterns. The proposed mathematical models predicted the experimental results well under experimental conditions, indicating that the U(G), P/V(L), and mu(ap) had significant impact on the t(m), epsilon, and k(L)a. These models were able to give the t(m), epsilon, and k(L)a values with an error around +/-8%, and always less than +/-10%., (Copyright 2005 Wiley Periodicals, Inc.)

Purpose: Parameters derived from uroflowmetry are frequently used in the evaluation and reassessment of children presenting with lower urinary tract dysfunction. Since current nomograms have been constructed from 1 to 2 voids per child, variability of flow parameters is unknown. We evaluate intraindividual variability of flow parameters in children free of lower urinary tract symptoms., Materials and Methods: Children between 4 and 16 years old (mean age 9.8) who were hospitalized but not suffering from urinary tract infection, pyelonephritis or neurological disturbance, and who had neither structural abnormality of the urinary tract nor acute pain or disorientation voided spontaneously over a flowmeter on 4 to 6 occasions. Post-void urine was estimated by ultrasound within 5 minutes of micturition to confirm complete emptying., Results: A total of 98 subjects provided a mean of 4.4 traces each. Neither maximum nor average flow rate showed great intraindividual variability (maximum flow rate r >0.8, average flow rate r >0.74). Flow rates significantly correlated with flow duration, volume voided and patient age. Initial flow curves were bell-shaped in 63% of cases, staccato in 30% and intermittent in 6%. These proportions did not change with subsequent voids. There was no significant difference between genders with respect to staccato voiding, although boys demonstrated 70% of intermittent voids and were significantly older than girls., Conclusions: In normal children there is minimal variability in flow rates and the phenomenon of staccato voiding is seen approximately 30% of the time, despite no significant levels of post-void residual urine.

Objectives: To evaluate a novel method for the determination of bladder wall tension (BWT) and to correlate these findings with postoperative persistent residual urine, postoperative uroflow, International Prostate Symptom Score, and quality-of-life index in patients with bladder outlet obstruction., Methods: In 28 male patients with prostate enlargement or bladder neck sclerosis undergoing surgical treatment, the preoperative BWT was determined after urodynamic investigation and ultrasound determination of bladder weight. The patients were divided into two groups: group 1 (n = 24), postoperative residual urine volume less than 50 mL; and group 2 (n = 4), persistent residual urine volume greater than 50 mL. Five patients in group 1 were unobstructed in accordance with the Abrams-Griffiths nomogram. This group was compared separately with group 2, in which all 4 patients were also classified as unobstructed., Results: The preoperative BWT in group 1 was 5.2 +/- 4.1 N/cm(2), significantly different from the preoperative BWT in group 2 (0.98 +/- 0.3 N/cm(2)). The BWT in the 5 unobstructed patients in group 1 (3.4 +/- 1.3 N/cm(2)) was significantly greater than that in patients in group 2. BWT was the sole parameter that was distinctly different between these 5 patients and the patients in group 2, with a significant influence on postoperative uroflow, International Prostate Symptom Score, and quality-of-life index., Conclusions: The results of this pilot study show that the determination of BWT allows further evaluation of the detrusor function. Especially in patients classified as unobstructed according to the Abrams-Griffiths nomogram, preoperative determination of the BWT could become a supplemental and important parameter with predictive value for postoperative success in patients with prostate enlargement or bladder neck sclerosis.