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Sample records for continuous aortic flow

  1. Management of aortic insufficiency in the continuous flow left ventricular assist device population.

    PubMed

    Holtz, Jonathan; Teuteberg, Jeffrey

    2014-03-01

    With the current generation of continuous-flow (CF) left ventricular assist devices (LVADs), patients are able to be supported for longer periods of time. As a result, there has been increasing focus on long-term complications from prolonged mechanical circulatory support, such as acquired aortic insufficiency (AI). In the presence of an LVAD, AI leads to a blind circulatory loop, with a portion of LVAD output regurgitating through the aortic valve (AV) into the left ventricle and back again through the device, limiting effective forward flow and ultimately leading to organ malperfusion and increased left ventricular diastolic pressures. The AV also experiences abnormal biomechanics as a result of limited valve opening in the presence of a CF LVAD. Increased shear stress, elevated transvalvular pressure gradients, and decreased valve open time all contribute to acquired AI. The prognosis of moderate to severe AI in LVAD patients is generally poor and leads to a higher rate of AV replacement and potentially reduced survival. However, there are no evidence-based guidelines for management of this challenging population. In severe AI, experts generally advocate AV replacement or repair, while lesser degrees of AI can be managed medically and/or with adjustments in pump parameters. PMID:24193452

  2. Electric analog model of the aortic valve for calculation of continuous beat-to-beat aortic flow using a pressure gradient.

    PubMed

    Graen, M D; Ewert, D L; Glower, J S; Gray, L A; Koenig, S C

    1999-01-01

    The objective was to develop a technique for calculating continuous, beat-to-beat aortic flow (AoF) using only left ventricular pressure (LVP) and aortic pressure (AoP). An electric analog model of the aortic valve was developed that includes resistance (R), inertance (L), and compliance (C) parameters, and resulting second order differential equations were derived. Aortic flow, AoP, and LVP recorded in eight subjects during a 5 day period and during lower body negative pressure (LBNP) were used to validate the model. Resistance, L, and C were estimated using a least-squares fit to the measured AoF on day 0 and during 0 mm Hg LBNP. For days 1-4, AoF was calculated using measured values of AoP and LVP and the R, L, and C values from day 0. Similarly, for LBNP, AoF was calculated using measured values of AoP and LVP, and the R, L, and C values from 0 mm Hg LBNP. The calculated and measured AoF were compared. Differences in cardiac output between the calculated and measured flows were less than 13.1+/-17% across days and under minor altered physiologic conditions (LBNP). Waveform morphology for the calculated AoF also agreed well with the measured AoF. Spectral analysis showed differences in magnitude and phase between measured and calculated aortic flow for the first five harmonics across days, less than 20+/-6% and 25+/-14 degrees, respectively. Preliminary evaluation indicates that our model works well for calculating flow through a biologic valve using LVP and AoP. We speculate that it may perform better for a mechanical valve, and if so it may be possible to develop an instrumented mechanical valve capable of continuous LVP, AOP, and AoF measurements. PMID:10360724

  3. Analysis of flow within a left ventricle model fully assisted with continuous flow through the aortic valve.

    PubMed

    Yano, Tetsuya; Funayama, Masanori; Sudo, Seiichi; Mitamura, Yoshinori

    2012-08-01

    Blood compatibility of a ventricular assist device (VAD) depends on the dynamics of blood flow. The focus in most previous studies was on blood flow in the VAD. However, the tip shape and position of the VAD inflow cannula influence the dynamics of intraventricular blood flow and thus thrombus formation in the ventricle. In this study, blood flow in the left ventricle (LV) under support with a catheter-type continuous flow blood pump was investigated. The flow field was analyzed both numerically and experimentally to investigate the effects of catheter tip shape and its insertion depth on intraventricular flow patterns. A computational model of the LV cavity with a simplified shape was constructed using computer-aided design software. Models of catheters with three different tip shapes were constructed and each was integrated to the LV model. In addition, three variations of insertion depth were prepared for all models. The fully supported intraventricular flow field was calculated by computational fluid dynamics (CFD). A transparent LV model made of silicone was also fabricated to analyze the intraventricular flow field by the particle image velocimetry technique. A mock circulation loop was constructed and water containing tracer particles was circulated in the loop. The motion of particles in the LV model was recorded with a digital high-speed video camera and analyzed to reveal the flow field. The results of numerical and experimental analyses indicated the formation of two large vortices in the bisector plane of the mitral and aortic valve planes. The shape and positioning of the catheter tip affected the flow distribution in the LV, and some of these combinations elongated the upper vortex toward the ventricular apex. Assessment based on average wall shear stress on the LV wall indicated that the flow distribution improved the washout effect. The flow patterns obtained from flow visualization coincided with those calculated by CFD analysis. Through these

  4. Concomitant Aortic Valve Procedures in Patients Undergoing Implantation of Continuous-Flow LVADs: An INTERMACS Database Analysis

    PubMed Central

    Robertson, Jason O.; Naftel, David C.; Myers, Susan L.; Prasad, Sunil; Mertz, Gail D.; Itoh, Akinobu; Pagani, Francis D.; Kirklin, James K.; Silvestry, Scott C.

    2014-01-01

    Background Management of existing aortic insufficiency (AI) and mechanical aortic valves in patients undergoing left ventricular assist device (LVAD) implantation remains controversial. Surgical options to address these issues include closure, repair or replacement of the valve. Methods Continuous flow LVAD/BiVAD patients entered into the INTERMACS database between June 2006 to December 2012 were included (n=5,344). Outcomes were compared between patients who underwent aortic valve (AV) closure (n=125), repair (n=95) and replacement (n=85). Results Among patients that underwent an aortic valve procedure, actuarial survival was significantly reduced for AV closures (63.2%) compared to AV repairs (76.8%) and replacements (71.8%, p=0.0003). Differences were greater between groups when only INTERMACS level 1-2 patients were analyzed (p=0.003). After multivariate adjustment, aortic valve closure remained a significant risk factor for mortality (HR=1.87, 95% CI=1.39-2.53, p<0.0001). At six to twelve months postoperatively, moderate to severe AI developed in 19%, 5%, 9% and 10% of patients with available echocardiography who underwent repair, closure, replacement and no intervention, respectively (p<0.0001). Competing outcomes demonstrate that at 1-year fewer patients with aortic valve closures were transplanted compared to patients with repairs/replacements (14% vs. 19%). No differences were observed between groups with respect to cause of death, re-hospitalization, right heart failure or stroke. Conclusions AV closure was associated with increased mortality when compared to repair or replacement in patients with AI that underwent LVAD insertion. The reasons for this association require further investigation. This is the largest study to date to examine concomitant AV procedures in patients undergoing LVAD insertion. PMID:25511747

  5. Replacement of the aortic valve with a bioprosthesis at the time of continuous flow ventricular assist device implantation for preexisting aortic valve dysfunction

    PubMed Central

    Chamogeorgakis, Themistokles; Mountis, Maria; Gonzalez-Stawinski, Gonzalo V.

    2015-01-01

    Left ventricular assist device (LVAD) implantation has become a mainstay of therapy for advanced heart failure patients who are either ineligible for, or awaiting, cardiac transplantation. Controversy remains over the optimal therapeutic strategy for preexisting aortic valvular dysfunction in these patients at the time of LVAD implant. In patients with moderate to severe aortic regurgitation, surgical approaches are center specific and range from variable leaflet closure techniques to concomitant aortic valve replacement (AVR) with a bioprosthesis. In the present study, we retrospectively analyzed our outcomes in patients who underwent simultaneous AVR and LVAD implantation secondary to antecedent aortic valve pathology. Between January 2004 and June 2010, 144 patients underwent LVAD implantation at a single institution. Of these, 7 patients (4.8%) required concomitant AVR. Five of the 7 patients (71%) survived to hospital discharge and suffered no adverse events in the perioperative period. One-year survival for the discharged patients was 80%, and no prosthetic valve-related adverse events were observed in long-term follow-up. Given our experience, we conclude that bioprosthetic AVR is a plausible alternative for end-stage heart failure patients at the time of LVAD implantation. PMID:26424939

  6. Coronary Flow Impacts Aortic Leaflet Mechanics and Aortic Sinus Hemodynamics

    PubMed Central

    Moore, Brandon L.; Dasi, Lakshmi Prasad

    2016-01-01

    Mechanical stresses on aortic valve leaflets are well-known mediators for initiating processes leading to calcific aortic valve disease. Given that non-coronary leaflets calcify first, it may be hypothesized that coronary flow originating from the ostia significantly influences aortic leaflet mechanics and sinus hemodynamics. High resolution time-resolved particle image velocimetry (PIV) measurements were conducted to map the spatiotemporal characteristics of aortic sinus blood flow and leaflet motion with and without physiological coronary flow in a well-controlled in vitro setup. The in vitro setup consists of a porcine aortic valve mounted in a physiological aorta sinus chamber with dynamically controlled coronary resistance to emulate physiological coronary flow. Results were analyzed using qualitative streak plots illustrating the spatiotemporal complexity of blood flow patterns, and quantitative velocity vector and shear stress contour plots to show differences in the mechanical environments between the coronary and non-coronary sinuses. It is shown that the presence of coronary flow pulls the classical sinus vorticity deeper into the sinus and increases flow velocity near the leaflet base. This creates a beneficial increase in shear stress and washout near the leaflet that is not seen in the non-coronary sinus. Further, leaflet opens approximately 10% farther into the sinus with coronary flow case indicating superior valve opening area. The presence of coronary flow significantly improves leaflet mechanics and sinus hemodynamics in a manner that would reduce low wall shear stress conditions while improving washout at the base of the leaflet. PMID:25636598

  7. Ascending aortic blood flow dynamics following intense exercise.

    PubMed

    Kilgour, R D; Sellers, W R

    1990-10-01

    The purpose of this study was to compare and contrast aortic blood flow kinetics during recovery from intense aerobic (maximal oxygen uptake test) and anaerobic (Wingate anaerobic power test) exercise. Fifteen healthy male subjects (VO2max = 56.1 +/- 5.8 mk/kg/min) participated in this study. Beat-to-beat peak aortic blood flow velocity (pkV) and acceleration (pkA) measurements were obtained by placing a 3.0 MHz continuous-wave ultrasonic transducer on the suprasternal notch at rest and during recovery (immediately post-exercise, 2.5 min, and 5.0 min) following the two exercise conditions. Peak velocity and acceleration significantly increased (p less than 0.01) from rest to immediately post-exercise and remained elevated throughout the 5-min recovery period. No differences were observed between the aerobic and anaerobic tests. Stroke distance significantly declined (p less than 0.01) immediately following exercise and progressively rose during the 5-min recovery period. The results indicate that: 1) aortic blood flow kinetics remained elevated during short-term recovery, and 2) intense aerobic and anaerobic exercise exhibit similar post-exercise aortic blood flow kinetics. PMID:2262232

  8. Blood flow characteristics in the aortic arch

    NASA Astrophysics Data System (ADS)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Mihaiescu, Mihai; Fuchs, Laszlo; Gutmark, Ephraim; Backeljauw, Philippe; Gutmark-Little, Iris

    2012-11-01

    The purpose with this study is to investigate the flow characteristics of blood in the aortic arch. Cardiovascular diseases are associated with specific locations in the arterial tree. Considering atherogenesis, it is claimed that the Wall Shear Stress (WSS) along with its temporal and spatial gradients play an important role in the development of the disease. The WSS is determined by the local flow characteristics, that in turn depends on the geometry as well as the rheological properties of blood. In this numerical work, the time dependent fluid flow during the entire cardiac cycle is fully resolved. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different Red Blood Cell loading. Data obtained through Cardiac Magnetic Resonance Imaging have been used in order to reconstruct geometries of the the aortic arch. Here, three different geometries are studied out of which two display malformations that can be found in patients having the genetic disorder Turner's syndrome. The simulations show a highly complex flow with regions of secondary flow that is enhanced for the diseased aortas. The financial support from the Swedish Research Council (VR) and the Sweden-America Foundation is gratefully acknowledged.

  9. Steady flow in abdominal aortic aneurysm models.

    PubMed

    Budwig, R; Elger, D; Hooper, H; Slippy, J

    1993-11-01

    Steady flow in abdominal aortic aneurysm models has been examined for four aneurysm sizes over Reynolds numbers from 500 to 2600. The Reynolds number is based on entrance tube diameter, and the inlet condition is fully developed flow. Experimental and numerical methods have been used to determine: (i) the overall features of the flow, (ii) the stresses on the aneurysm walls in laminar flow, and (iii) the onset and characteristics of turbulent flow. The laminar flow field is characterized by a jet of fluid (passing directly through the aneurysm) surrounded by a recirculating vortex. The wall shear stress magnitude in the recirculation zone is about ten times less than in the entrance tube. Both wall shear stress and wall normal stress profiles exhibit large magnitude peaks near the reattachment point at the distal end of the aneurysm. The onset of turbulence in the model is intermittent for 2000 < Re < 2500. The results demonstrate that a slug of turbulence in the entrance tube grows much more rapidly in the aneurysm than in a corresponding length of uniform cross section pipe. When turbulence is present in the aneurysm the recirculation zone breaks down and the wall shear stress returns to a magnitude comparable to that in the entrance tube. PMID:8309237

  10. Pulsatile blood flow in Abdominal Aortic Aneurysms

    NASA Astrophysics Data System (ADS)

    Salsac, Anne-Virginie; Lasheras, Juan C.; Singel, Soeren; Varga, Chris

    2001-11-01

    We discuss the results of combined in-vitro laboratory measurements and clinical observations aimed at determining the effect that the unsteady wall shear stresses and the pressure may have on the growth and eventual rupturing of an Abdominal Aortic Aneurysm (AAA), a permanent bulging-like dilatation occurring near the aortic bifurcation. In recent years, new non-invasive techniques, such as stenting, have been used to treat these AAAs. However, the development of these implants, aimed at stopping the growth of the aneurysm, has been hampered by the lack of understanding of the effect that the hemodynamic forces have on the growth mechanism. Since current in-vivo measuring techniques lack the precision and the necessary resolution, we have performed measurements of the pressure and shear stresses in laboratory models. The models of the AAA were obtained from high resolution three-dimensional CAT/SCANS performed in patients at early stages of the disease. Preliminary DPIV measurements show that the pulsatile blood flow discharging into the cavity of the aneurysm leads to large spikes of pressure and wall shear stresses near and around its distal end, indicating a possible correlation between the regions of high wall shear stresses and the observed location of the growth of the aneurysm.

  11. Experimental validation of Doppler echocardiographic measurement of volume flow through the stenotic aortic valve.

    PubMed

    Otto, C M; Pearlman, A S; Gardner, C L; Enomoto, D M; Togo, T; Tsuboi, H; Ivey, T D

    1988-08-01

    In aortic stenosis, evaluation of aortic valve area by the continuity equation assumes that the volume of flow through the stenotic valve can be measured accurately in the left ventricular outflow tract. To test the accuracy of Doppler volume-flow measurement proximal to a stenotic valve, we developed an open-chest canine model in which the native leaflets were sutured together to create variable degrees of acute aortic stenosis. Left ventricular and aortic pressures were measured with micromanometer-tipped catheters. Volume flow was controlled and varied by directing systemic venous return through a calibrated roller pump and back to the right atrium. Because transaortic volume flow will not equal roller pump output when there is coexisting aortic insufficiency (present in 67% of studies), transaortic flow was measured by electromagnetic flowmeter with the flow probe placed around the proximal descending thoracic aorta, just beyond the ligated arch vessels. In 12 adult, mongrel dogs (mean weight, 25 kg), the mean transaortic pressure gradient ranged from 2 to 74 mm Hg, and transaortic volume flow ranged from 0.9 to 3.2 l/min. In four dogs, electromagnetic flow that was measured distal to the valve was accurate compared with volume flow determined by timed collection of total aortic flow into a graduated cylinder (n = 24, r = 0.97, electromagnetic flow = 0.87 Direct +0.13 l/min). In eight subsequent dogs, electromagnetic flow was compared with transaortic cardiac output measured by Doppler echocardiography in the left ventricular outflow tract as circular cross-sectional area [pi(D/2)2] x left ventricular outflow tract velocity-time integral x heart rate.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2969311

  12. Aortic Blood Flow Reversal Determines Renal Function: Potential Explanation for Renal Dysfunction Caused by Aortic Stiffening in Hypertension.

    PubMed

    Hashimoto, Junichiro; Ito, Sadayoshi

    2015-07-01

    Aortic stiffness determines the glomerular filtration rate (GFR) and predicts the progressive decline of the GFR. However, the underlying pathophysiological mechanism remains obscure. Recent evidence has shown a close link between aortic stiffness and the bidirectional (systolic forward and early diastolic reverse) flow characteristics. We hypothesized that the aortic stiffening-induced renal dysfunction is attributable to altered central flow dynamics. In 222 patients with hypertension, Doppler velocity waveforms were recorded at the proximal descending aorta to calculate the reverse/forward flow ratio. Tonometric waveforms were recorded to measure the carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities, to estimate the aortic pressure from the radial waveforms, and to compute the aortic characteristic impedance. In addition, renal hemodynamics was evaluated by duplex ultrasound. The estimated GFR was inversely correlated with the aortic pulse wave velocity, reverse/forward flow ratio, pulse pressure, and characteristic impedance, whereas it was not correlated with the peripheral pulse wave velocity or mean arterial pressure. The association between aortic pulse wave velocity and estimated GFR was independent of age, diabetes mellitus, hypercholesterolemia, and antihypertensive medication. However, further adjustment for the aortic reverse/forward flow ratio and pulse pressure substantially weakened this association, and instead, the reverse/forward flow ratio emerged as the strongest determinant of estimated GFR (P=0.001). A higher aortic reverse/forward flow ratio was also associated with lower intrarenal forward flow velocities. These results suggest that an increase in aortic flow reversal (ie, retrograde flow from the descending thoracic aorta toward the aortic arch), caused by aortic stiffening and impedance mismatch, reduces antegrade flow into the kidney and thereby deteriorates renal function. PMID:25916721

  13. A laboratory model of the aortic root flow including the coronary arteries

    NASA Astrophysics Data System (ADS)

    Querzoli, Giorgio; Fortini, Stefania; Espa, Stefania; Melchionna, Simone

    2016-08-01

    Cardiovascular flows have been extensively investigated by means of in vitro models to assess the prosthetic valve performances and to provide insight into the fluid dynamics of the heart and proximal aorta. In particular, the models for the study of the flow past the aortic valve have been continuously improved by including, among other things, the compliance of the vessel and more realistic geometries. The flow within the sinuses of Valsalva is known to play a fundamental role in the dynamics of the aortic valve since they host a recirculation region that interacts with the leaflets. The coronary arteries originate from the ostia located within two of the three sinuses, and their presence may significantly affect the fluid dynamics of the aortic root. In spite of their importance, to the extent of the authors' knowledge, coronary arteries were not included so far when modeling in vitro the transvalvular aortic flow. We present a pulse duplicator consisting of a passively pulsing ventricle, a compliant proximal aorta, and coronary arteries connected to the sinuses of Valsalva. The coronary flow is modulated by a self-regulating device mimicking the physiological mechanism, which is based on the contraction and relaxation of the heart muscle during the cardiac cycle. Results show that the model reproduces satisfyingly the coronary flow. The analysis of the time evolution of the velocity and vorticity fields within the aortic root reveals the main characteristics of the backflow generated through the aorta in order to feed the coronaries during the diastole. Experiments without coronary flow have been run for comparison. Interestingly, the lifetime of the vortex forming in the sinus of Valsalva during the systole is reduced by the presence of the coronaries. As a matter of fact, at the end of the systole, that vortex is washed out because of the suction generated by the coronary flow. Correspondingly, the valve closure is delayed and faster compared to the case with

  14. The relation between transaortic pressure difference and flow during dobutamine stress echocardiography in patients with aortic stenosis

    PubMed Central

    Takeda, S; Rimington, H; Chambers, J

    1999-01-01

    OBJECTIVE—To investigate the relation between transaortic pressure difference and flow in patients with aortic stenosis.
METHODS—50 asymptomatic patients with all grades of aortic stenosis were studied using dobutamine stress echocardiography. Individual plots of mean pressure drop against flow were drawn. Comparisons were made between grades of aortic stenosis as defined by the continuity equation.
RESULTS—A significant linear relation between pressure difference and flow was found in 34 patients (68%). There was a significant curvilinear relation in four (8%), while no significant regression line could be fitted in 12 (24%). In the 34 patients with linear fits, the slopes (mean (SD)) were 0.08 (0.07) in mild, 0.10 (0.04) in moderate, and 0.22 (0.16) in severe aortic stenosis (p = 0.0055).
CONCLUSIONS—Transaortic pressure difference can be related directly to flow in many patients with all grades of aortic stenosis. However, there are individual differences in slope and intercept suggesting that resistance calculated at rest may not always be representative. Raw pressure drop/flow plots may be an alternative method of describing valve function.


Keywords: aortic stenosis; continuity equation; resistance; Doppler echocardiography PMID:10377300

  15. A numerical analysis of the aortic blood flow pattern during pulsed cardiopulmonary bypass.

    PubMed

    Gramigna, V; Caruso, M V; Rossi, M; Serraino, G F; Renzulli, A; Fragomeni, G

    2015-01-01

    In the modern era, stroke remains a main cause of morbidity after cardiac surgery despite continuing improvements in the cardiopulmonary bypass (CPB) techniques. The aim of the current work was to numerically investigate the blood flow in aorta and epiaortic vessels during standard and pulsed CPB, obtained with the intra-aortic balloon pump (IABP). A multi-scale model, realized coupling a 3D computational fluid dynamics study with a 0D model, was developed and validated with in vivo data. The presence of IABP improved the flow pattern directed towards the epiaortic vessels with a mean flow increase of 6.3% and reduced flow vorticity. PMID:24962383

  16. Development of Minimally-Invasive Aortic Pressure and Flow Instrumentation

    NASA Technical Reports Server (NTRS)

    Ewert, Dan

    1996-01-01

    To better understand the mechanisms underlying the effects of microgravity on the cardiovascular system, cardiovascular models have been developed. These computational models estimate changes in cardiovascular parameters such as total peripheral resistance and systemic arterial compliance, and require high quality aortic pressure and flow measurements as their input. Many of these measurements are obtained in experimental animals and therefore the invasiveness of the instrumentation must be as kept to a minimum. These considerations are the primary motivation behind this work.

  17. Theoretical analysis of magnetic field interactions with aortic blood flow

    SciTech Connect

    Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.

    1996-04-01

    The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.

  18. Asymmetric reactions in continuous flow

    PubMed Central

    Mak, Xiao Yin; Laurino, Paola

    2009-01-01

    Summary An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed. PMID:19478913

  19. Continuous flow photochemistry.

    PubMed

    Gilmore, Kerry; Seeberger, Peter H

    2014-06-01

    Due to the narrow width of tubing/reactors used, photochemistry performed in micro- and mesoflow systems is significantly more efficient than when performed in batch due to the Beer-Lambert Law. Owing to the constant removal of product and facility of flow chemical scalability, the degree of degradation observed is generally decreased and the productivity of photochemical processes is increased. In this Personal Account, we describe a wide range of photochemical transformations we have examined using both visible and UV light, covering cyclizations, intermolecular couplings, radical polymerizations, as well as singlet oxygen oxygenations. PMID:24890908

  20. Monolithic Continuous-Flow Bioreactors

    NASA Technical Reports Server (NTRS)

    Stephanopoulos, Gregory; Kornfield, Julia A.; Voecks, Gerald A.

    1993-01-01

    Monolithic ceramic matrices containing many small flow passages useful as continuous-flow bioreactors. Ceramic matrix containing passages made by extruding and firing suitable ceramic. Pores in matrix provide attachment medium for film of cells and allow free movement of solution. Material one not toxic to micro-organisms grown in reactor. In reactor, liquid nutrients flow over, and liquid reaction products flow from, cell culture immobilized in one set of channels while oxygen flows to, and gaseous reaction products flow from, culture in adjacent set of passages. Cells live on inner surfaces containing flowing nutrient and in pores of walls of passages. Ready access to nutrients and oxygen in channels. They generate continuous high yield characteristic of immobilized cells, without large expenditure of energy otherwise incurred if necessary to pump nutrient solution through dense biomass as in bioreactors of other types.

  1. Aortic stenosis in adults. Non-invasive estimation of pressure differences by continuous wave Doppler echocardiography.

    PubMed Central

    Hegrenaes, L; Hatle, L

    1985-01-01

    The peak and mean aortic transvalvar pressure differences measured invasively and non-invasively by continuous wave Doppler echocardiography were compared in 87 consecutive patients with aortic stenosis. The mean values were calculated from the maximal velocities of the aortic jet recorded with a spectral display of the Doppler frequency shifts and by applying a modified Bernoulli equation. Technically satisfactory velocity curves for estimating the mean pressure differences could not be obtained in three patients and invasive measurements were not obtained in two. In all patients the peak transvalvar pressure difference was calculated since the aortic jet was identified non-invasively. The peak and mean pressure differences measured invasively and non-invasively correlated well--with only minor underestimation of the pressure differences measured with the Doppler technique--regardless of age, sex, and the presence or absence of aortic valvar regurgitation, or other valvar lesions. With a systematic search for the highest velocities in the aortic jet and with on line spectral analysis of the Doppler frequencies the peak and the mean aortic pressure differences can be determined non-invasively with a high degree of precision in almost all patients. Images PMID:4052281

  2. Induction of continuous expanding infrarenal aortic aneurysms in a large porcine animal model

    PubMed Central

    Kloster, Brian O.; Lund, Lars; Lindholt, Jes S.

    2015-01-01

    Background A large animal model with a continuous expanding infrarenal aortic aneurysm gives access to a more realistic AAA model with anatomy and physiology similar to humans, and thus allows for new experimental research in the natural history and treatment options of the disease. Methods 10 pigs (group A) underwent infrarenal aortic dissection, balloon dilatation, infusion of elastase into the lumen and placement of a stenosing cuff around the aorta. 10 control pigs (group B) underwent a sham procedure. The subsequent 28 days the AP-diameters of the aneurysms were measured using ultrasound, hereafter the pigs were euthanized for inspection and AAA wall sampling for histological analysis. Results In group A, all pigs developed continuous expanding AAA's with a mean increase in AP-diameter to 16.26 ± 0.93 mm equivalent to a 57% increase. In group B the AP-diameters increased to 11.33 ± 0.13 mm equivalent to 9.3% which was significantly less than in group A (p < 0.001). In group A, a significant negative association between the preoperative weight and the resulting AP-diameters was found. Histology shoved more or less complete resolution of the elastic tissue in the tunica media in group A. The most frequent complication was a neurological deficit in the lower limbs. Conclusion In pigs it's possible to induce continuous expanding AAA's based upon proteolytic degradation and pathological flow, resembling the real life dynamics of human aneurysms. Because the lumbars are preserved, it's also a potential model for further studies of novel endovascular devices and their complications. PMID:25685342

  3. Blood flow in the rabbit aortic arch and descending thoracic aorta.

    PubMed

    Vincent, P E; Plata, A M; Hunt, A A E; Weinberg, P D; Sherwin, S J

    2011-12-01

    The distribution of atherosclerotic lesions within the rabbit vasculature, particularly within the descending thoracic aorta, has been mapped in numerous studies. The patchy nature of such lesions has been attributed to local variation in the pattern of blood flow. However, there have been few attempts to model and characterize the flow. In this study, a high-order continuous Galerkin finite-element method was used to simulate blood flow within a realistic representation of the rabbit aortic arch and descending thoracic aorta. The geometry, which was obtained from computed tomography of a resin corrosion cast, included all vessels originating from the aortic arch (followed to at least their second generation) and five pairs of intercostal arteries originating from the proximal descending thoracic aorta. The simulations showed that small geometrical undulations associated with the ductus arteriosus scar cause significant deviations in wall shear stress (WSS). This finding highlights the importance of geometrical accuracy when analysing WSS or related metrics. It was also observed that two Dean-type vortices form in the aortic arch and propagate down the descending thoracic aorta (along with an associated skewed axial velocity profile). This leads to the occurrence of axial streaks in WSS, similar in nature to the axial streaks of lipid deposition found in the descending aorta of cholesterol-fed rabbits. Finally, it was observed that WSS patterns within the vicinity of intercostal branch ostia depend not only on local flow features caused by the branches themselves, but also on larger-scale flow features within the descending aorta, which vary between branches at different locations. This result implies that disease and WSS patterns in the vicinity of intercostal ostia are best compared on a branch-by-branch basis. PMID:21593030

  4. Effects of Aortic Irregularities on the Blood Flow

    NASA Astrophysics Data System (ADS)

    Gutmark-Little, Iris; Prahl-Wittberg, Lisa; van Wyk, Stevin; Mihaescu, Mihai; Fuchs, Laszlo; Backeljauw, Philippe; Gutmark, Ephraim

    2013-11-01

    Cardiovascular defects characterized by geometrical anomalies of the aorta and its effect on the blood flow are investigated. The flow characteristics change with the aorta geometry and the rheological properties of the blood. Flow characteristics such as wall shear stress often play an important role in the development of vascular disease. In the present study, blood is considered to be non-Newtonian and is modeled using the Quemada model, an empirical model that is valid for different red blood cell loading. Three patient-specific aortic geometries are studied using Large Eddy Simulations (LES). The three geometries represent malformations that are typical in patients populations having a genetic disorder called Turner syndrome. The results show a highly complex flow with regions of recirculation that are enhanced in two of the three aortas. Moreover, blood flow is diverted, due to the malformations, from the descending aorta to the three side branches of the arch. The geometry having an elongated transverse aorta has larger areas of strong oscillatory wall shear stress.

  5. Flow Behavior in the Left Heart Ventricle Following Apico-Aortic Bypass Surgery

    NASA Astrophysics Data System (ADS)

    Shahriari, Shahrokh; Jeyhani, Morteza; Labrosse, Michel; Kadem, Lyes

    2013-11-01

    Apico-aortic bypass (AAB) surgery is an alternative for transcatheter aortic valve implantation (TAVI) to reduce left ventricle (LV) overload in patients with severe aortic stenosis (AS). It consists in connecting the apex of the LV to the descending thoracic aorta with a valved conduit. Postoperative flow assessments show that two thirds of the outflow is conducted from the LV apex to the conduit, while only one third crosses the native aortic valve. In this study, we performed high speed particle image velocimetry (PIV) measurements of flow pattern within an in vitro elastic model of LV in the presence of a very severe AS, before and after AAB. Results indicate that AAB effectively relieves the LV outflow obstruction; however, it also leads to abnormal ventricular flow patterns. Normal LV flow dynamics is characterized by an emerging mitral jet flow followed by the development of a vortical flow with velocities directed towards the aortic valve, while measurements in the presence of AAB show systolic flow bifurcating to the apical conduit and to the aortic valve outflow tract. This study provides the first insight into the LV flow structure after AAB including outflow jets and disturbed stagnation regions.

  6. Blood flow characteristics in the ascending aorta after TAVI compared to surgical aortic valve replacement.

    PubMed

    Trauzeddel, Ralf Felix; Löbe, Ulrike; Barker, Alex J; Gelsinger, Carmen; Butter, Christian; Markl, Michael; Schulz-Menger, Jeanette; von Knobelsdorff-Brenkenhoff, Florian

    2016-03-01

    Ascending aortic blood flow characteristics are altered after aortic valve surgery, but the effect of transcatheter aortic valve implantation (TAVI) is unknown. Abnormal flow may be associated with aortic and cardiac remodeling. We analyzed blood flow characteristics in the ascending aorta after TAVI in comparison to conventional stented aortic bioprostheses (AVR) and healthy subjects using time-resolved three-dimensional flow-sensitive cardiovascular magnetic resonance imaging (4D-flow MRI). Seventeen patients with TAVI (Edwards Sapien XT), 12 with AVR and 9 healthy controls underwent 4D-flow MRI of the ascending aorta. Target parameters were: severity of vortical and helical flow pattern (semiquantitative grading from 0 = none to 3 = severe) and the local distribution of systolic wall shear stress (WSSsystole). AVR revealed significantly more extensive vortical and helical flow pattern than TAVI (p = 0.042 and p = 0.002) and controls (p < 0.001 and p = 0.001). TAVI showed significantly more extensive vortical flow than controls (p < 0.001). Both TAVI and AVR revealed marked blood flow eccentricity (64.7 and 66.7 %, respectively), whereas controls showed central blood flow (88.9 %). TAVI and AVR exhibited an asymmetric distribution of WSSsystole in the mid-ascending aorta with local maxima at the right anterior aortic wall and local minima at the left posterior wall. In contrast, controls showed a symmetric distribution of WSSsystole along the aortic circumference. Blood flow was significantly altered in the ascending aorta after TAVI and AVR. Changes were similar regarding WSSsystole distribution, while TAVI resulted in less helical and vortical blood flow. PMID:26493195

  7. Valve morphology effect in aortic coarctation flow using realistic silicon models and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Marrufo, Oscar; Solis-Najera, Sergio; Pibarot, Philippe; Kadem, Lyes; Kesharvarz-Motamed, Zahra; Rodriguez, Alfredo O.; Garcia, Julio

    2014-11-01

    Aortic valve morphology and phenotype may alter the aortic wall structure and its normal flow hemodynamics. However, the relationship between altered flow patterns and progression of wall pathology is often not fully understood in patients with aortic coartation and needs larger experimental work. In this study, we introduced a compatible experimental setup with magnetic resonance imaging (MRI) using a realistic aortic coarctation (AoCo) silicon model which can replicate physiological flow conditions (pressure, flow-wave, and systemic load). We evaluated the aortic valve hemodynamics of a normal tricuspid valve and a stenotic bicuspid valve using valve effective orifice area (EOA), peak and mean transvalvular pressure gradient (TPG). AoCo severity was assessed by the AoCo pressure gradient. For the tricuspid valve we obtained an EOA = 1.89 cm2, a peak TPG = 10 mmHg, and a mean TPG = 5 mmHg. For the bicuspid valve we obtained an EOA = 1.03 cm2, a peak TPG = 37 mmHg and a mean TPG = 13 mmHg. Furthermore, AoCo with tricuspid valve led to a peak AoCo pressure gradient (PG) = 11 mmHg and a mean PG = 5 mmHg. AoCo with bicuspid valve led to a peak PG = 6 mmHg and a mean PG = 3 mmHg. Aortic flow reattachment was more evident in presence of bicuspid valve and helical flow was present in all cases. This study showed that silicon prototyping in combination with MRI velocity measurements could successfully be used to assess hemodynamic effects of aortic valve morphology in aortic coarctation flow.

  8. Continuous flow dielectrophoretic particle concentrator

    DOEpatents

    Cummings, Eric B.

    2007-04-17

    A continuous-flow filter/concentrator for separating and/or concentrating particles in a fluid is disclosed. The filter is a three-port device an inlet port, an filter port and a concentrate port. The filter separates particles into two streams by the ratio of their dielectrophoretic mobility to their electrokinetic, advective, or diffusive mobility if the dominant transport mechanism is electrokinesis, advection, or diffusion, respectively.Also disclosed is a device for separating and/or concentrating particles by dielectrophoretic trapping of the particles.

  9. Effect of aortic balloon inflation on ventilation and brain stem blood flow in piglets.

    PubMed

    Green, G A; Darnall, R A; Bierd, T B; Adams, J M

    1989-05-01

    Increases in brain stem blood flow (BBF) during hypoxia may decrease tissue PCO2/[H+], causing minute ventilation (VE) to decrease. To determine whether an increase in BBF, isolated from changes in arterial PO2 and PCO2, can affect respiration, we obstructed the thoracic aorta with a balloon in 31 intact and 24 peripherally chemobarodenervated, anesthetized, spontaneously breathing newborn piglets. Continuous measurements of cardiorespiratory variables were made before and during 2 min of aortic obstruction. Radiolabeled microspheres were used to measure BBF before and approximately 30 s after balloon inflation in eight intact and five denervated animals. After balloon inflation, there was a rapid increase in mean blood pressure in both the intact and denervated animals, followed within 10 s by a decrease in tidal volume and VE. In the intact animals, the decrease in VE after acute hypertension can be ascribed to a baroreceptor-mediated reflex. After peripheral chemobarodenervation, however, acute hypertension continued to produce a decrease in VE, which cannot be explained by baroreceptor stimulation. In these denervated animals, aortic balloon inflation was associated with an increase in BBF (13.1 +/- 2.7%; P less than 0.05). We speculate that the increase in BBF during hypoxia may contribute to the decrease in ventilation observed after carotid body denervation. PMID:2501276

  10. Doppler assessment of fetal aortic isthmus flow in twin

    PubMed Central

    Lee, Soon Pyo; Lee, Chae Min; Jung, Sun Young; Park, Han Na

    2015-01-01

    Objective The purpose of this study was to investigate the aortic isthmus (AoI) flow difference between larger fetus and smaller fetus of twin; and to evaluate the predictive value of early diagnosis of hemodynamic change in twin growth. Methods This prospective study on 49 pairs of twin fetuses was performed to obtain AoI blood flow data. Cases with structural or chromosomal abnormalities and co-twin death were excluded. The interval from examination to delivery was within 4 weeks and 3 cases over 4 weeks interval were re-examined. Assessment of fetal AoI Doppler parameters were peak systolic velocity (PSV), end-diastolic velocity, times-averaged maximum velocities, pulsatility index (PI), and resistance index (RI). According to the direction of the diastolic flow in the AoI, antegrade and retrograde flow were made and was used to analyze the perinatal outcomes of each fetus. The predictive value of AoI Doppler parameters in predicting fetal growth was obtained by using ANOVA and logistic regression analysis of quantitative variables in each fetus of twins. Results There were significant differences in the gestational weeks at delivery, birth weight and the incidence of growth discordance over 20% or more between monochorionic twin and dichorionic twin. The AoI PI and RI were significantly higher in smaller fetus than in larger regardless of chorionicity. Retrograde flow was noted in 8 of 98 cases (8.2%) and the only one case was of the larger fetus and the others were smaller fetuses of twin. Significant correlations were found between the AoI PI and birthweight (P=0.018) and between the PSV and growth discordance (P=0.032). In monochorionic twin, linear correlation was shown between the AoI PI and birthweight (P=0.004) and between AoI PI and growth discordance (P=0.031). Also, the meaningful correlation between the PSV and birthweight (P=0.036) was found by using logistic regression analyses. Conclusion On the basis of our observation, AoI PI has revealed their

  11. Hemodynamic Study of Flow Remodeling Stent Graft for the Treatment of Highly Angulated Abdominal Aortic Aneurysm

    PubMed Central

    Yeow, Siang Lin; Leo, Hwa Liang

    2016-01-01

    This study investigates the effect of a novel flow remodeling stent graft (FRSG) on the hemodynamic characteristics in highly angulated abdominal aortic aneurysm based on computational fluid dynamics (CFD) approach. An idealized aortic aneurysm with varying aortic neck angulations was constructed and CFD simulations were performed on nonstented models and stented models with FRSG. The influence of FRSG intervention on the hemodynamic performance is analyzed and compared in terms of flow patterns, wall shear stress (WSS), and pressure distribution in the aneurysm. The findings showed that aortic neck angulations significantly influence the velocity flow field in nonstented models, with larger angulations shifting the mainstream blood flow towards the center of the aorta. By introducing FRSG treatment into the aneurysm, erratic flow recirculation pattern in the aneurysm sac diminishes while the average velocity magnitude in the aneurysm sac was reduced in the range of 39% to 53%. FRSG intervention protects the aneurysm against the impacts of high velocity concentrated flow and decreases wall shear stress by more than 50%. The simulation results highlighted that FRSG may effectively treat aneurysm with high aortic neck angulations via the mechanism of promoting thrombus formation and subsequently led to the resorption of the aneurysm. PMID:27247612

  12. Dependence of aortic arch morphogenesis on intracardiac blood flow in the left atrial ligated chick embryo.

    PubMed

    Hu, Norman; Christensen, Douglas A; Agrawal, Amit K; Beaumont, Charity; Clark, Edward B; Hawkins, John A

    2009-05-01

    Partial left atrial ligation before cardiac septation redistributes intracardiac blood flow and produces left ventricular hypoplasia in the chick. We hypothesized that redistributed intracardiac blood flow adversely alters aortic arch development. We ligated the left atrial appendage with a 10-0 nylon suture at stage 21 chick embryos, then reincubated up to stage 34. Sham embryos had a suture tied adjacent to the atrial wall, and normal controls were unoperated. We measured simultaneous atrioventricular (AV) and dorsal aortic (DAo) blood velocities from stage 24 embryos with an ultrasound pulsed-Doppler flow meter; and the left and right third and fourth aortic arch blood flow with a laser-Doppler flow meter. Ventricular and atrial cross-sectional areas were measured from sequential video fields for planimetry. Intracardiac flow patterns were imaged on video by injecting India ink into the vitelline vein. In separate embryos, radiopaque microfil was injected into the cardiovascular system for micro-CT scanning. We analyzed the morphologic characteristics of the heart at stage 34. Active AV and DAo stroke volume (mm(3)), right third and fourth aortic arch blood flow (mm(3)/s) were all decreased in ligated embryos (P < 0.05) when compared with normal and sham embryos. Ventricular end-diastolic volume versus normal and sham embryos decreased by 45% and 46%, respectively (P < 0.05). India ink injection revealed altered right aortic arch flow patterns in the ligated embryos compared with normal embryos. micro-CT imaging confirmed altered arch morphogenesis. Alterations in intracardiac blood flow disrupt both early cardiac morphogenesis and aortic arch selection. PMID:19322826

  13. Assessment of left ventricular function by indices derived from aortic flow velocity.

    PubMed Central

    Kolettis, M; Jenkins, B S; Webb-Peploe, M M

    1976-01-01

    The velocity and acceleration of aortic blood flow were measured by means of a catheter velocity probe in 40 patients during routine diagnostic cardiac catheterization. Ten different variables were derived from the aortic velocity measurements, and their ability to discriminate between good and bad left ventricular (LV) function was tested. By means of eight conventional indices of LV function derived from pressure, mean flow, and quantitative cineangiography, the patients were divided into 3 groups: group 1, good LV function; group 2, moderate LV function; group 3, poor LV function. Aortic peak velocity and maximal acceleration correlated well with stroke volume and were thus indices of LV pump function. Aortic peak velocity also showed a significant correlation with LV stroke work. Both aortic peak velocity and maximal acceleration failed to discriminate between the three groups of patients, and correlated poorly with conventional indices of LV function. The mean values of stroke volume differed significantly between groups 1 and 2, and between groups 1 and 3, and also correlated better with the conventional functional indices. The best discrimination between normal and abnormal LV function was provided by dividing stroke volume by maximal acceleration, but stroke volume divided by peak velocity discriminated better than stroke volume alone. Stroke volume divided by maximal acceleration also gave more significant individual correlations with the conventional functional indices than did any other variable derived from aortic velocity. PMID:1252292

  14. Noninvasive calculation of the aortic blood pressure waveform from the flow velocity waveform: a proof of concept.

    PubMed

    Vennin, Samuel; Mayer, Alexia; Li, Ye; Fok, Henry; Clapp, Brian; Alastruey, Jordi; Chowienczyk, Phil

    2015-09-01

    Estimation of aortic and left ventricular (LV) pressure usually requires measurements that are difficult to acquire during the imaging required to obtain concurrent LV dimensions essential for determination of LV mechanical properties. We describe a novel method for deriving aortic pressure from the aortic flow velocity. The target pressure waveform is divided into an early systolic upstroke, determined by the water hammer equation, and a diastolic decay equal to that in the peripheral arterial tree, interposed by a late systolic portion described by a second-order polynomial constrained by conditions of continuity and conservation of mean arterial pressure. Pulse wave velocity (PWV, which can be obtained through imaging), mean arterial pressure, diastolic pressure, and diastolic decay are required inputs for the algorithm. The algorithm was tested using 1) pressure data derived theoretically from prespecified flow waveforms and properties of the arterial tree using a single-tube 1-D model of the arterial tree, and 2) experimental data acquired from a pressure/Doppler flow velocity transducer placed in the ascending aorta in 18 patients (mean ± SD: age 63 ± 11 yr, aortic BP 136 ± 23/73 ± 13 mmHg) at the time of cardiac catheterization. For experimental data, PWV was calculated from measured pressures/flows, and mean and diastolic pressures and diastolic decay were taken from measured pressure (i.e., were assumed to be known). Pressure reconstructed from measured flow agreed well with theoretical pressure: mean ± SD root mean square (RMS) error 0.7 ± 0.1 mmHg. Similarly, for experimental data, pressure reconstructed from measured flow agreed well with measured pressure (mean RMS error 2.4 ± 1.0 mmHg). First systolic shoulder and systolic peak pressures were also accurately rendered (mean ± SD difference 1.4 ± 2.0 mmHg for peak systolic pressure). This is the first noninvasive derivation of aortic pressure based on fluid dynamics (flow and wave speed) in the

  15. Aortic Relative Pressure Components Derived from Four-Dimensional Flow Cardiovascular Magnetic Resonance

    PubMed Central

    Lamata, Pablo; Pitcher, Alex; Krittian, Sebastian; Nordsletten, David; Bissell, Malenka M; Cassar, Thomas; Barker, Alex J; Markl, Michael; Neubauer, Stefan; Smith, Nicolas P

    2014-01-01

    Purpose To describe the assessment of the spatiotemporal distribution of relative aortic pressure quantifying the magnitude of its three major components. Methods Nine healthy volunteers and three patients with aortic disease (bicuspid aortic valve, dissection, and Marfan syndrome) underwent 4D-flow CMR. Spatiotemporal pressure maps were computed from the CMR flow fields solving the pressure Poisson equation. The individual components of pressure were separated into time-varying inertial (“transient”), spatially varying inertial (“convective”), and viscous components. Results Relative aortic pressure is primarily caused by transient effects followed by the convective and small viscous contributions (64.5, 13.6, and 0.3 mmHg/m, respectively, in healthy subjects), although regional analysis revealed prevalent convective effects in specific contexts, e.g., Sinus of Valsalva and aortic arch at instants of peak velocity. Patients showed differences in peak transient values and duration, and localized abrupt convective changes explained by abnormalities in aortic geometry, including the presence of an aneurysm, a pseudo-coarctation, the inlet of a dissection, or by complex flow patterns. Conclusion The evaluation of the three components of relative pressure enables the quantification of mechanistic information for understanding and stratifying aortic disease, with potential future implications for guiding therapy. Magn Reson Med 72:1162–1169, 2014. © 2013 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:24243444

  16. Flow dynamics in anatomical models of abdominal aortic aneurysms: computational analysis of pulsatile flow.

    PubMed

    Finol, Ender A; Amon, Cristina H

    2003-01-01

    Blood flow in human arteries is dominated by time-dependent transport phenomena. In particular, in the abdominal segment of the aorta under a patient's average resting conditions, blood exhibits laminar flow patterns that are influenced by secondary flows induced by adjacent branches and in irregular vessel geometries. The flow dynamics becomes more complex when there is a pathological condition that causes changes in the normal structural composition of the vessel wall, for example, in the presence of an aneurysm. An aneurysm is an irreversible dilation of a blood vessel accompanied by weakening of the vessel wall. This work examines the importance of hemodynamics in the characterization of pulsatile blood flow patterns in individual Abdominal Aortic Aneurysm (AAA) models. These patient-specific computational models have been developed for the numerical simulation of the momentum transport equations utilizing the Finite Element Method (FEM) for the spatial and temporal discretization. We characterize pulsatile flow dynamics in AAAs for average resting conditions by means of identifying regions of disturbed flow and quantifying the disturbance by evaluating wall pressure and wall shear stresses at the aneurysm wall. PMID:14515766

  17. Continuous-Flow Centrifugal Separator

    NASA Technical Reports Server (NTRS)

    Waldron, Robert D.

    1988-01-01

    Apparatus combines principles of centrifugal and cyclone separators to control movement of solid or liquid particles suspended in flowing gas. Spinning disk contains radial channels, width varys as function of distance from center. Gas flows from outer ring around disk toward center. Particles in gas collected at periphery, center or both.

  18. Uncertainty Quantification applied to flow simulations in thoracic aortic aneurysms

    NASA Astrophysics Data System (ADS)

    Boccadifuoco, Alessandro; Mariotti, Alessandro; Celi, Simona; Martini, Nicola; Salvetti, Maria Vittoria

    2015-11-01

    The thoracic aortic aneurysm is a progressive dilatation of the thoracic aorta causing a weakness in the aortic wall, which may eventually cause life-threatening events. Clinical decisions on treatment strategies are currently based on empiric criteria, like the aortic diameter value or its growth rate. Numerical simulations can give the quantification of important indexes which are impossible to be obtained through in-vivo measurements and can provide supplementary information. Hemodynamic simulations are carried out by using the open-source tool SimVascular and considering patient-specific geometries. One of the main issues in these simulations is the choice of suitable boundary conditions, modeling the organs and vessels not included in the computational domain. The current practice is to use outflow conditions based on resistance and capacitance, whose values are tuned to obtain a physiological behavior of the patient pressure. However it is not known a priori how this choice affects the results of the simulation. The impact of the uncertainties in these outflow parameters is investigated here by using the generalized Polynomial Chaos approach. This analysis also permits to calibrate the outflow-boundary parameters when patient-specific in-vivo data are available.

  19. Aortic pressure reduction redistributes transmural blood flow in dog left ventricle

    SciTech Connect

    Smolich, J.J.; Weissberg, P.L.; Broughton, A.; Korner, P.I. )

    1988-02-01

    The authors studied the effect of graded aortic blood pressure reduction on left ventricular (LV) blood flow in anesthetized, autonomically blocked, open-chest dogs at constant heart rate and mean left atrial pressure. Aortic diastolic pressure (ADP) was lowered from rest to 90, 75, and 60 mmHg with an arteriovenous fistula. Global and regional LV blood flow was measured with radioactive microspheres. Mean LV blood flow fell stepwise from 145 ml {center dot} min{sup {minus}1} {center dot} 100 g{sup {minus}1} at rest to 116 ml {center dot} min{sup {minus}1} {center dot} 100 g{sup {minus}1} at ADP of 60 mmHg, whereas the endocardial-to-epicardial flow ratio decreased from 1.20 to 084. The transmural redistribution of LV blood flow was not accompanied by increases in LV oxygen extraction, depression of LV contractility, LV dilatation or LV electrical dysfunction and also occurred in the presence of considerable coronary vasodilator flow reserve. Electrical evidence of subendocardial ischemia appeared at ADP of 32 mmHg and an endocardial-to-epicardial flow ratio of 0.41 in a subgroup of animals. They conclude that the redistribution of LV flow during moderate aortic pressure reduction was an appropriate physiological adjustment to uneven transmural alterations in regional LV wall stress and that it preceded a more pronounced redistribution evident with myocardial ischemia.

  20. Wearable system for non-invasive and continuous monitoring central aortic pressure curve and augmentation index.

    PubMed

    Krivoshei, Andrei; Lamp, Jürgen; Min, Mart; Uuetoa, Tiina; Uuetoa, Hasso; Annus, Paul

    2013-01-01

    The paper presents a non-invasive method and system for a long-term and continuous monitoring of the central aortic pressure (CAP) waveform and the augmentation index (AI). The CAP curve is estimated from the measured radial electrical bio-impedance (EBI) using spectral domain transfer functions (TF), which are established on the basis of data analysis during clinical experiments. Experiments were carried out on 3 volunteers by now. During the experiment, a 0.5 mg sublingual nitroglycerin tablet was administrated to each volunteer. Both, the reconstructed CAP curve and the AI have very good correlation with the results obtained by the SphygmoCor system. But, in opposite to the traditional tonometry based CAP curve and AI estimation methods, the proposed one is more convenient to use and allows continuous and long-term personalized monitoring of the CAP curve and of the AI. PMID:23739366

  1. Estimation of global aortic pulse wave velocity by flow-sensitive 4D MRI.

    PubMed

    Markl, Michael; Wallis, Wolf; Brendecke, Stefanie; Simon, Jan; Frydrychowicz, Alex; Harloff, Andreas

    2010-06-01

    The aim of this study was to determine the value of flow-sensitive four-dimensional MRI for the assessment of pulse wave velocity as a measure of vessel compliance in the thoracic aorta. Findings in 12 young healthy volunteers were compared with those in 25 stroke patients with aortic atherosclerosis and an age-matched normal control group (n = 9). Results from pulse wave velocity calculations incorporated velocity data from the entire aorta and were compared to those of standard methods based on flow waveforms at only two specific anatomic landmarks. Global aortic pulse wave velocity was higher in patients with atherosclerosis (7.03 +/- 0.24 m/sec) compared to age-matched controls (6.40 +/- 0.32 m/sec). Both were significantly (P < 0.001) increased compared to younger volunteers (4.39 +/- 0.32 m/sec). Global aortic pulse wave velocity in young volunteers was in good agreement with previously reported MRI studies and catheter measurements. Estimation of measurement inaccuracies and error propagation analysis demonstrated only minor uncertainties in measured flow waveforms and moderate relative errors below 16% for aortic compliance in all 46 subjects. These results demonstrate the feasibility of pulse wave velocity calculation based on four-dimensional MRI data by exploiting its full volumetric coverage, which may also be an advantage over standard two-dimensional techniques in the often-distorted route of the aorta in patients with atherosclerosis. PMID:20512861

  2. Combustion synthesis continuous flow reactor

    DOEpatents

    Maupin, Gary D.; Chick, Lawrence A.; Kurosky, Randal P.

    1998-01-01

    The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor.

  3. Combustion synthesis continuous flow reactor

    DOEpatents

    Maupin, G.D.; Chick, L.A.; Kurosky, R.P.

    1998-01-06

    The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor. 10 figs.

  4. Classification of Aortic Stenosis by Flow and Gradient Patterns Provides Insights into the Pathophysiology of Disease.

    PubMed

    Bhattacharyya, Sanjeev; Mittal, Tarun; Abayalingam, Mayavan; Kabir, Tito; Dalby, Miles; Cleland, John G; Baltabaeva, Aigul; Rahman Haley, Shelley

    2016-08-01

    Different patterns of flow and valve gradients can lead to diagnostic uncertainty about the severity of aortic stenosis (AS). Consecutive patients with severe AS (valve area <1 cm(2)) underwent echocardiography and computed tomography. Patients were classified into 4 groups (high-gradient/normal flow [HGNF], high-gradient/low flow [HGLF], low-gradient/normal flow [LGNF], and low-gradient/low flow [LGLF]). Low flow was defined as stroke volume index <35 mL/m(2) and low gradient as a mean aortic gradient <40 mm Hg. Aortic valve calcification (AVC) was calculated using the Agatston score. Of 181 patients, 56, 30, 46, and 49 had HGNF, HGLF, LGNF and LGLF with median AVC of 2048, 2015, 1366, and 1178 AU/m(2) (P < .0001) and valvuloarterial impedance of 4.5, 6.4, 4.2, and 5.9, respectively (P < .0001). Among those with LGLF, AVC was lower in patients with preserved compared to reduced left ventricular ejection fraction (1018 vs 2550 AU/m(2); P < .0001), but valvuloarterial impedance was similar (P = .33). The LGLF AS with preserved ejection fraction is associated with lower AVC and may identify patients with less severe AS in association with an adaptive ventricular response to high afterload. PMID:26475710

  5. A High Performance Pulsatile Pump for Aortic Flow Experiments in 3-Dimensional Models.

    PubMed

    Chaudhury, Rafeed A; Atlasman, Victor; Pathangey, Girish; Pracht, Nicholas; Adrian, Ronald J; Frakes, David H

    2016-06-01

    Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies, as well as for planning their surgical repair. In vitro experiments are required to validate the simulations against real world data, and the experiments require a pulsatile flow pump system that can provide physiologic flow conditions characteristic of the aorta. We designed a newly capable piston-based pulsatile flow pump system that can generate high volume flow rates (850 mL/s), replicate physiologic waveforms, and pump high viscosity fluids against large impedances. The system is also compatible with a broad range of fluid types, and is operable in magnetic resonance imaging environments. Performance of the system was validated using image processing-based analysis of piston motion as well as particle image velocimetry. The new system represents a more capable pumping solution for aortic flow experiments than other available designs, and can be manufactured at a relatively low cost. PMID:26983961

  6. The effects of thoracic aortic cross-clamping and declamping on visceral organ blood flow.

    PubMed Central

    Oyama, M; McNamara, J J; Suehiro, G T; Suehiro, A; Sue-Ako, K

    1983-01-01

    Blood flow was measured using radioactive microspheres in 11 macaque monkeys 1) before hemorrhage shock, 2) after onset of shock, 3) after aortic cross-clamping and resuscitation, and 4) after release of the cross-clamp and stabilization. Hemodynamic parameters (cardiac output, arterial, right atrial and left atrial pressure) and blood gases were also monitored. Total abdominal organ flow fell with hemorrhage and fell further with aortic clamping. Reinfusion of shed volume did not restore abdominal organ flow (4.7% baselines) but increased LAP and cardiac output to the upper body. Release of the cross-clamp produced profound acidosis that was treated effectively with NcHCO3. After stabilization of blood, flow to kidney remained low (49% baseline) although intestinal flow was increased threefold (320% of baseline). It is clear that thoracic aortic cross-clamping in shock further compromises already reduced visceral blood flow and may contribute to the problem of ischemic multiple organ failure after resuscitation from hemorrhagic shock. PMID:6830352

  7. Continuous Flow Microfluidic Bioparticle Concentrator

    PubMed Central

    Martel, Joseph M.; Smith, Kyle C.; Dlamini, Mcolisi; Pletcher, Kendall; Yang, Jennifer; Karabacak, Murat; Haber, Daniel A.; Kapur, Ravi; Toner, Mehmet

    2015-01-01

    Innovative microfluidic technology has enabled massively parallelized and extremely efficient biological and clinical assays. Many biological applications developed and executed with traditional bulk processing techniques have been translated and streamlined through microfluidic processing with the notable exception of sample volume reduction or centrifugation, one of the most widely utilized processes in the biological sciences. We utilize the high-speed phenomenon known as inertial focusing combined with hydraulic resistance controlled multiplexed micro-siphoning allowing for the continuous concentration of suspended cells into pre-determined volumes up to more than 400 times smaller than the input with a yield routinely above 95% at a throughput of 240 ml/hour. Highlighted applications are presented for how the technology can be successfully used for live animal imaging studies, in a system to increase the efficient use of small clinical samples, and finally, as a means of macro-to-micro interfacing allowing large samples to be directly coupled to a variety of powerful microfluidic technologies. PMID:26061253

  8. Continuous Flow Microfluidic Bioparticle Concentrator.

    PubMed

    Martel, Joseph M; Smith, Kyle C; Dlamini, Mcolisi; Pletcher, Kendall; Yang, Jennifer; Karabacak, Murat; Haber, Daniel A; Kapur, Ravi; Toner, Mehmet

    2015-01-01

    Innovative microfluidic technology has enabled massively parallelized and extremely efficient biological and clinical assays. Many biological applications developed and executed with traditional bulk processing techniques have been translated and streamlined through microfluidic processing with the notable exception of sample volume reduction or centrifugation, one of the most widely utilized processes in the biological sciences. We utilize the high-speed phenomenon known as inertial focusing combined with hydraulic resistance controlled multiplexed micro-siphoning allowing for the continuous concentration of suspended cells into pre-determined volumes up to more than 400 times smaller than the input with a yield routinely above 95% at a throughput of 240 ml/hour. Highlighted applications are presented for how the technology can be successfully used for live animal imaging studies, in a system to increase the efficient use of small clinical samples, and finally, as a means of macro-to-micro interfacing allowing large samples to be directly coupled to a variety of powerful microfluidic technologies. PMID:26061253

  9. Continuous flow measurements using fixed ultrasonic meters

    USGS Publications Warehouse

    Oltmann, Rick

    1993-01-01

    USGS has or soon will be installing four continuous flow-monitoring stations in the delta that will use ultrasonic velocity meters (DVM). Funding for the stations has been provided by USGS, DWR, USBR, and Contra Costa Water District.

  10. Preservation Of Native Aortic Valve Flow And Full Hemodynamic Support With The TORVAD™ Using A Computational Model Of The Cardiovascular System

    PubMed Central

    Gohean, Jeffrey R.; George, Mitchell J.; Chang, Kay-Won; Larson, Erik R.; Pate, Thomas D.; Kurusz, Mark; Longoria, Raul G.; Smalling, Richard W.

    2014-01-01

    This paper describes the stroke volume selection and operational design for the TORVAD™, a synchronous, positive-displacement ventricular assist device (VAD). A lumped parameter model was used to simulate hemodynamics with the TORVAD™ compared to those under continuous flow VAD support. Results from the simulation demonstrated that a TORVAD™ with a 30 mL stroke volume ejecting with an early diastolic counterpulse provides comparable systemic support to the HeartMate II® (HMII) (cardiac output 5.7 L/min up from 3.1 L/min in simulated heart failure). By taking advantage of synchronous pulsatility, the TORVAD™ delivers full hemodynamic support with nearly half the VAD flow rate (2.7 L/min compared to 5.3 L/min for the HMII) by allowing the left ventricle to eject during systole, thus preserving native aortic valve flow (3.0 L/min compared to 0.4 L/min for the HMII, down from 3.1 L/min at baseline). The TORVAD™ also preserves pulse pressure (26.7 mmHg compared to 12.8 mmHg for the HMII, down from 29.1 mmHg at baseline). Preservation of aortic valve flow with synchronous pulsatile support could reduce the high incidence of aortic insufficiency and valve cusp fusion reported in patients supported with continuous flow VADs. PMID:25485562

  11. Instrument continuously measures density of flowing fluids

    NASA Technical Reports Server (NTRS)

    Jacobs, R. B.; Macinko, J.; Miller, C. E.

    1967-01-01

    Electromechanical densitometer continuously measures the densities of either single-phase or two-phase flowing cryogenic fluids. Measurement is made on actual flow. The instrument operates on the principle that the mass of any vibrating system is a primary factor in determining the dynamic characteristics of the system.

  12. Increasing Sensitivity In Continuous-Flow Electrophoresis

    NASA Technical Reports Server (NTRS)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Sensitivity of continuous-flow electrophoresis (CFE) chamber increased by introducing lateral gradients in concentration of buffer solution and thickness of chamber. Such gradients, with resulting enhanced separation, achieved in CFE chamber with wedge-shaped cross section and collateral flow. Enables improved separations of homogeneous components of mixtures of variety of biologically important substances.

  13. Continuous flow nitration in miniaturized devices

    PubMed Central

    2014-01-01

    Summary This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

  14. Transcatheter valve implantation can alter fluid flow fields in aortic sinuses and ascending aorta

    NASA Astrophysics Data System (ADS)

    Saikrishnan, Neelakantan; Yoganathan, Ajit

    2012-11-01

    Transcatheter aortic valves (TAVs) are valve replacements used to treat aortic stenosis. Currently, these have been used in elderly patients at high-risk for open-heart procedures. Since these devices are implanted under fluoroscopic guidance, the implantation position of the valve can vary with respect to the native aortic valve annulus. The current study characterizes the altered hemodynamics in the aortic sinus and ascending aorta under different implantation (high and low) and cardiac output (2.5 and 5.0 L/min) conditions. Two commonly used TAV designs are studied using 2-D Particle Image Velocimetry (PIV). 200 phase locked images are obtained at every 25ms in the cardiac cycle, and the resulting vector fields are ensemble averaged. High implantation of the TAV with respect to the annulus causes weaker sinus washout and weaker sinus vortex formation. Additionally, the longer TAV leaflets can also result in a weaker sinus vortex. The level of turbulent fluctuations in the ascending aorta did not appear to be affected by axial positioning of the valve, but varied with cardiac output. The results of this study indicates that TAV positioning is important to be considered clinically, since this can affect coronary perfusion and potential flow stagnation near the valve.

  15. Descending aortic flow reversal in obstructed total anomalous pulmonary venous connection.

    PubMed

    Nair, Anupama K; Radhakrishnan, Sitaraman; Iyer, Krishna S

    2016-06-01

    In this study, we present the case of a neonate with obstructed infracardiac total anomalous pulmonary venous connection with severe pulmonary hypertension and a patent ductus arteriosus with right-to-left shunting. The patient had an unusual finding of pandiastolic flow reversal in the upper descending thoracic aorta. He underwent emergency surgical re-routing of the pulmonary veins to the left atrium, and postoperative echocardiography showed disappearance of the descending aortic flow reversal. We hypothesise that in severely obstructed total anomalous pulmonary venous connection the left ventricular output may be extremely low, resulting in flow reversal in the descending aorta. PMID:27055647

  16. Aquaporin-1 facilitates pressure-driven water flow across the aortic endothelium

    PubMed Central

    Nguyen, Tieuvi; Toussaint, Jimmy; Xue, Yan; Raval, Chirag; Cancel, Limary; Russell, Stewart; Shou, Yixin; Sedes, Omer; Sun, Yu; Yakobov, Roman; Tarbell, John M.; Jan, Kung-ming

    2015-01-01

    Aquaporin-1, a ubiquitous water channel membrane protein, is a major contributor to cell membrane osmotic water permeability. Arteries are the physiological system where hydrostatic dominates osmotic pressure differences. In the present study, we show that the walls of large conduit arteries constitute the first example where hydrostatic pressure drives aquaporin-1-mediated transcellular/transendothelial flow. We studied cultured aortic endothelial cell monolayers and excised whole aortas of male Sprague-Dawley rats with intact and inhibited aquaporin-1 activity and with normal and knocked down aquaporin-1 expression. We subjected these systems to transmural hydrostatic pressure differences at zero osmotic pressure differences. Impaired aquaporin-1 endothelia consistently showed reduced engineering flow metrics (transendothelial water flux and hydraulic conductivity). In vitro experiments with tracers that only cross the endothelium paracellularly showed that changes in junctional transport cannot explain these reductions. Percent reductions in whole aortic wall hydraulic conductivity with either chemical blocking or knockdown of aquaporin-1 differed at low and high transmural pressures. This observation highlights how aquaporin-1 expression likely directly influences aortic wall mechanics by changing the critical transmural pressure at which its sparse subendothelial intima compresses. Such compression increases transwall flow resistance. Our endothelial and historic erythrocyte membrane aquaporin density estimates were consistent. In conclusion, aquaporin-1 significantly contributes to hydrostatic pressure-driven water transport across aortic endothelial monolayers, both in culture and in whole rat aortas. This transport, and parallel junctional flow, can dilute solutes that entered the wall paracellularly or through endothelial monolayer disruptions. Lower atherogenic precursor solute concentrations may slow their intimal entrainment kinetics. PMID:25659484

  17. Aquaporin-1 facilitates pressure-driven water flow across the aortic endothelium.

    PubMed

    Nguyen, Tieuvi; Toussaint, Jimmy; Xue, Yan; Raval, Chirag; Cancel, Limary; Russell, Stewart; Shou, Yixin; Sedes, Omer; Sun, Yu; Yakobov, Roman; Tarbell, John M; Jan, Kung-ming; Rumschitzki, David S

    2015-05-01

    Aquaporin-1, a ubiquitous water channel membrane protein, is a major contributor to cell membrane osmotic water permeability. Arteries are the physiological system where hydrostatic dominates osmotic pressure differences. In the present study, we show that the walls of large conduit arteries constitute the first example where hydrostatic pressure drives aquaporin-1-mediated transcellular/transendothelial flow. We studied cultured aortic endothelial cell monolayers and excised whole aortas of male Sprague-Dawley rats with intact and inhibited aquaporin-1 activity and with normal and knocked down aquaporin-1 expression. We subjected these systems to transmural hydrostatic pressure differences at zero osmotic pressure differences. Impaired aquaporin-1 endothelia consistently showed reduced engineering flow metrics (transendothelial water flux and hydraulic conductivity). In vitro experiments with tracers that only cross the endothelium paracellularly showed that changes in junctional transport cannot explain these reductions. Percent reductions in whole aortic wall hydraulic conductivity with either chemical blocking or knockdown of aquaporin-1 differed at low and high transmural pressures. This observation highlights how aquaporin-1 expression likely directly influences aortic wall mechanics by changing the critical transmural pressure at which its sparse subendothelial intima compresses. Such compression increases transwall flow resistance. Our endothelial and historic erythrocyte membrane aquaporin density estimates were consistent. In conclusion, aquaporin-1 significantly contributes to hydrostatic pressure-driven water transport across aortic endothelial monolayers, both in culture and in whole rat aortas. This transport, and parallel junctional flow, can dilute solutes that entered the wall paracellularly or through endothelial monolayer disruptions. Lower atherogenic precursor solute concentrations may slow their intimal entrainment kinetics. PMID:25659484

  18. Magnetic particle capture for biomagnetic fluid flow in stenosed aortic bifurcation considering particle-fluid coupling

    NASA Astrophysics Data System (ADS)

    Bose, Sayan; Banerjee, Moloy

    2015-07-01

    Magnetic nanoparticles drug carriers continue to attract considerable interest for drug targeting in the treatment of cancer and other pathological conditions. Guiding magnetic iron oxide nanoparticles with the help of an external magnetic field to its target is the basic principle behind the Magnetic Drug Targeting (MDT). It is essential to couple the ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) principles when magnetic fields are applied to blood as a biomagnetic fluid. The present study is devoted to study on MDT technique by particle tracking in the presence of a non uniform magnetic field in a stenosed aortic bifurcation. The present numerical model of biomagnetic fluid dynamics (BFD) takes into accounts both magnetization and electrical conductivity of blood. The blood flow in the bifurcation is considered to be incompressible and Newtonian. An Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ANSYS FLUENT two way particle-fluid coupling. An implantable infinitely long cylindrical current carrying conductor is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Results concerning the velocity and temperature field indicate that the presence of the magnetic field influences the flow field considerably and the disturbances increase as the magnetic field strength increases. The insert position is also varied to observe the variation in flow as well as temperature field. Parametric investigation is conducted and the influence of the particle size (dp), flow Reynolds number (Re) and external magnetic field strength (B0) on the "capture efficiency" (CE) is reported. The difference in CE is also studied for different particle loading condition. According to the results, the magnetic field increased the particle concentration in the target region

  19. Comparison of tricuspid and bicuspid aortic valve hemodynamics under steady flow conditions

    NASA Astrophysics Data System (ADS)

    Seaman, Clara; Ward, James; Sucosky, Philippe

    2011-11-01

    The bicuspid aortic valve (BAV), a congenital valvular defect consisting of two leaflets instead of three, is associated with a high prevalence of calcific aortic valve disease (CAVD). CAVD also develops in the normal tricuspid aortic valve (TAV) but its progression in the BAV is more severe and rapid. Although hemodynamic abnormalities are increasingly considered potential pathogenic contributor, the native BAV hemodynamics remain largely unknown. Therefore, this study aims at comparing experimentally the hemodynamic environments in TAV and BAV anatomies. Particle-image velocimetry was used to characterize the flow downstream of a native TAV and a model BAV mounted in a left-heart simulator and subjected to three steady flow rates characterizing different phases of the cardiac cycle. While the TAV developed a jet aligned along the valve axis, the BAV was shown to develop a skewed systolic jet with skewness decreasing with increasing flow rate. Measurement of the transvalvular pressure revealed a valvular resistance up to 50% larger in the BAV than in the TAV. The increase in velocity between the TAV and BAV leads to an increase in shear stress downstream of the valve. This study reveals strong hemodynamic abnormalities in the BAV, which may contribute to CAVD pathogenesis.

  20. Age and gender related differences in aortic blood flow

    NASA Astrophysics Data System (ADS)

    Enevoldsen, Marie Sand; Pedersen, Mads Møller; Hemmsen, Martin Christian; Lönn, Lars; Henneberg, Kaj-Åge; Jensen, Jørgen Arendt

    2012-03-01

    The abdominal aorta (AA) is predisposed to development of abdominal aneurysms (AAA), a focal dilatation with fatal consequences if left untreated. The blood flow patterns is thought to play an important role in the development of AAA. The purpose of this work is to investigate the blood flow patterns within a group of healthy volunteers (six females, eight males) aged 23 to 76 years to identify changes and differences related to age and gender. The healthy volunteers were categorized by gender (male/female) and age (below/above 35 years). Subject-specific flow and geometry data were acquired using the research interface on a Profocus ultrasound scanner (B-K Medical, Herlev, Denmark; segmentation of 3D magnetic resonance angiography (Magnetom Trio, Siemens Healthcare, Erlangen, Germany). The largest average diameter was among the elderly males (19.7 (+/- 1.33) mm) and smallest among the young females (12.4 (+/- 0.605) mm). The highest peak systolic velocity was in the young female group (1.02 (+/- 0.336) m/s) and lowest in the elderly male group (0.836 (+/- 0.127) m/s). A geometrical change with age was observed as the AA becomes more bended with age. This also affects the blood flow velocity patterns, which are markedly different from young to elderly. Thus, changes in blood flow patterns in the AA related to age and gender are observed. Further investigations are needed to determine the relation between changes in blood flow patterns and AAA development.

  1. A Novel Intra-aortic Device Designed for Coronary Blood Flow Amplification in Unrevascularizable Patients.

    PubMed

    Nussinovitch, Udi; Shtenberg, Giorgi; Roguin, Ariel; Feld, Yair

    2016-08-01

    Patients with unrevascularizable coronary artery disease represent a substantial number of all patients with coronary disease. However, their therapeutic options are limited; they endure recurrent hospitalizations, a poor quality of life and prognosis. We aim to investigate a novel alternative approach to the treatment of this common medical condition by using a specialized intra-aortic device with coiling properties capable of enhancing diastolic coronary flow. Both a mathematical analysis and in vitro study presented in the current study have yielded enhanced coronary diastolic blood flow and energetic advantages. We suggest that this original approach might be implicated in severely symptomatic unrevascularizable patients. PMID:27260505

  2. Numerical simulation of the non-Newtonian blood flow through a mechanical aortic valve. Non-Newtonian blood flow in the aortic root

    NASA Astrophysics Data System (ADS)

    De Vita, F.; de Tullio, M. D.; Verzicco, R.

    2016-04-01

    This work focuses on the comparison between Newtonian and non-Newtonian blood flows through a bileaflet mechanical heart valve in the aortic root. The blood, in fact, is a concentrated suspension of cells, mainly red blood cells, in a Newtonian matrix, the plasma, and consequently its overall behavior is that of a non-Newtonian fluid owing to the action of the cells' membrane on the fluid part. The common practice, however, assumes the blood in large vessels as a Newtonian fluid since the shear rate is generally high and the effective viscosity becomes independent of the former. In this paper, we show that this is not always the case even in the aorta, the largest artery of the systemic circulation, owing to the pulsatile and transitional nature of the flow. Unexpectedly, for most of the pulsating cycle and in a large part of the fluid volume, the shear rate is smaller than the threshold level for the blood to display a constant effective viscosity and its shear thinning character might affect the system dynamics. A direct inspection of the various flow features has shown that the valve dynamics, the transvalvular pressure drop and the large-scale features of the flow are very similar for the Newtonian and non-Newtonian fluid models. On the other hand, the mechanical damage of the red blood cells (hemolysis), induced by the altered stress values in the flow, is larger for the non-Newtonian fluid model than for the Newtonian one.

  3. Changes in mesenteric, renal, and aortic flows with +Gx acceleration

    NASA Technical Reports Server (NTRS)

    Stone, H. L.; Erickson, H. H.; Sandler, H.

    1974-01-01

    Previous studies in man and dogs have indicated that the splanchnic bed might contribute to the maintenance of arterial pressure during +Gx acceleration. Eight mongrel dogs were chronically instrumented with Doppler flow probes around the superior mesenteric (SMA) and renal arteries (RA) as well as the terminal aorta (TA). A solid-state pressure transducer was placed in the aorta distal to the flow probe. Using alpha-chloralose anesthesia following a 2-4 week recovery period, the animals were subjected to 120 sec at levels of 5, 10 and 15 +Gx acceleration on a 7.6-m radius centrifuge. The results indicate that both an active component and a mechanical component contribute to the maintenance of arterial pressure during +Gx acceleration.

  4. Feasibility of patient specific aortic blood flow CFD simulation.

    PubMed

    Svensson, Johan; Gårdhagen, Roland; Heiberg, Einar; Ebbers, Tino; Loyd, Dan; Länne, Toste; Karlsson, Matts

    2006-01-01

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data. PMID:17354898

  5. Continuous-Flow Gas-Phase Bioreactors

    NASA Technical Reports Server (NTRS)

    Wise, Donald L.; Trantolo, Debra J.

    1994-01-01

    Continuous-flow gas-phase bioreactors proposed for biochemical, food-processing, and related industries. Reactor contains one or more selected enzymes dehydrated or otherwise immobilized on solid carrier. Selected reactant gases fed into reactor, wherein chemical reactions catalyzed by enzyme(s) yield product biochemicals. Concept based on discovery that enzymes not necessarily placed in traditional aqueous environments to function as biocatalysts.

  6. Moving wall, continuous flow electronphoresis apparatus

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H. (Inventor); Snyder, Robert S. (Inventor)

    1988-01-01

    This invention relates generally to electrophoresis devices and more particularly to a moving wall, continuous flow device in which an electrophoresis chamber is angularly positionable with respect to the direction of moving belt walls. A frame with an electrophoresis chamber is rotatably supported between two synchronously driven belt walls. This allows the chamber to be angularly positionable with respect to the direction of belt travel, which compensates for electroosmotic flow within the electrophoresis chamber. Injection of a buffer solution via an opening and a homogenous sample stream via another opening is performed at the end of a chamber, and collection of buffer and the fractionated species particles is done by a conventional collection array at an opposite end of the chamber. Belts are driven at a rate which exactly matches the flow of buffer and sample through the chamber, which entrains the buffer to behave as a rigid electrophoretic medium, eliminating flow distortions (Poiseuille effect). Additionally, belt material for each belt is stored at one end of the device and is taken up by drive wheels at an opposite end. The novelty of this invention particularly lies in the electrophoresis chamber being angularly positionable between two moving belt walls in order to compensate for electroosmotic flow. Additionally, new belt material is continuously exposed within the chamber, minimizing flow distortion due to contamination of the belt material by the sample.

  7. Fluid flow releases fibroblast growth factor-2 from human aortic smooth muscle cells

    NASA Technical Reports Server (NTRS)

    Rhoads, D. N.; Eskin, S. G.; McIntire, L. V.

    2000-01-01

    This study tested the hypothesis that fluid shear stress regulates the release of fibroblast growth factor (FGF)-2 from human aortic smooth muscle cells. FGF-2 is a potent mitogen that is involved in the response to vascular injury and is expressed in a wide variety of cell types. FGF-2 is found in the cytoplasm of cells and outside cells, where it associates with extracellular proteoglycans. To test the hypothesis that shear stress regulates FGF-2 release, cells were exposed to flow, and FGF-2 amounts were measured from the conditioned medium, pericellular fraction (extracted by heparin treatment), and cell lysate. Results from the present study show that after 15 minutes of shear stress at 25 dyne/cm(2) in a parallel-plate flow system, a small but significant fraction (17%) of the total FGF-2 was released from human aortic smooth muscle cells. FGF-2 levels in the circulating medium increased 10-fold over medium from static controls (P<0.01). A 50% increase in FGF-2 content versus control (P<0.01) was found in the pericellular fraction (extracted by heparin treatment). Furthermore, a significant decrease in FGF-2 was detected in the cell lysate, indicating that FGF-2 was released from inside the cell. Cell permeability studies with fluorescent dextran were performed to examine whether transient membrane disruption caused FGF-2 release. Flow cytometry detected a 50% increase in mean fluorescence of cells exposed to 25 dyne/cm(2) versus control cells. This indicates that the observed FGF-2 release from human aortic smooth muscle cells is likely due to transient membrane disruption on initiation of flow.

  8. Mathematical Models of Continuous Flow Electrophoresis

    NASA Technical Reports Server (NTRS)

    Saville, D. A.; Snyder, R. S.

    1985-01-01

    Development of high resolution continuous flow electrophoresis devices ultimately requires comprehensive understanding of the ways various phenomena and processes facilitate or hinder separation. A comprehensive model of the actual three dimensional flow, temperature and electric fields was developed to provide guidance in the design of electrophoresis chambers for specific tasks and means of interpreting test data on a given chamber. Part of the process of model development includes experimental and theoretical studies of hydrodynamic stability. This is necessary to understand the origin of mixing flows observed with wide gap gravitational effects. To insure that the model accurately reflects the flow field and particle motion requires extensive experimental work. Another part of the investigation is concerned with the behavior of concentrated sample suspensions with regard to sample stream stability particle-particle interactions which might affect separation in an electric field, especially at high field strengths. Mathematical models will be developed and tested to establish the roles of the various interactions.

  9. Dynamic damping of the aortic pressure trace during hyperemia: the impact on fractional flow reserve measurement.

    PubMed

    Lockie, Tim; Rolandi, M Cristina; Piek, Jan J

    2013-10-01

    We report on two cases that illustrate an important caveat in the measurement of fractional flow reserve (FFR) in coronary arteries. To obtain accurate FFR measurements, two fundamental requirements must be fulfilled. One is to minimize microvascular resistance; the other is that there is no damping of the proximal aortic pressure trace. A problem with either of these requirements can be a source of serious error in the measurement of FFR. In each case we present here, despite a good aortic pressure trace at the start of the procedure, there is dynamic damping of the pressure trace during hyperemia, secondary to axial migration of the guiding catheter into the left main stem (LMS). In both cases, a normal aortic pressure trace (Pa) is present at baseline. After intracoronary adenosine injection, there was a fall in both mean Pa and distal coronary pressure (Pd) concomitant with damping of Pa, evidenced by loss of the dicrotic notch and ventricularization of the pressure trace. The resultant FFR value is underestimated. As hyperemia wears off, both pressure traces return to normal with good articulation of the dicrotic notch. When the procedure was repeated taking care to ensure that the guide did not move into the LMS during hyperemia, the Pa trace remained stable following intracoronary adenosine, while mean Pd decreased as before. In both cases, hemodynamically significant lesions were demonstrated that had been masked by the artifactual drop in Pa during the first attempt. PMID:24088431

  10. The fluid mechanics of continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Saville, D. A.

    1990-01-01

    The overall objective is to establish theoretically and confirm experimentally the ultimate capabilities of continuous flow electrophoresis chambers operating in an environment essentially free of particle sedimentation and buoyancy. The efforts are devoted to: (1) studying the effects of particle concentration on sample conductivity and dielectric constant. The dielectric constant and conductivity were identified as playing crucial roles in the behavior of the sample and on the resolving power and throughput of continuous flow devices; and (2) improving the extant mathematical models to predict flow fields and particle trajectories in continuous flow electrophoresis. A dielectric spectrometer was designed and built to measure the complex dielectric constant of a colloidal dispersion as a function of frequency between 500 Hz and 200 kHz. The real part of the signal can be related to the sample's conductivity and the imaginary part to its dielectric constant. Measurements of the dielectric constants of several different dispersions disclosed that the dielectric constants of dilute systems of the sort encountered in particle electrophoresis are much larger than would be expected based on the extant theory. Experiments were carried out to show that, in many cases, this behavior is due to the presence of a filamentary structure of small hairs on the particle surface. A technique for producing electrokinetically ideal synthetic latex particles by heat treating was developed. Given the ubiquitous nature of hairy surfaces with both cells and synthetic particles, it was deemed necessary to develop a theory to explain their behavior. A theory for electrophoretic mobility of hairy particles was developed. Finally, the extant computer programs for predicting the structure of electro-osmotically driven flows were extended to encompass flow channels with variable wall mobilities.

  11. Aortic angiography

    MedlinePlus

    ... with the aorta or its branches, including: Aortic aneurysm Aortic dissection Congenital (present from birth) problems AV ... Abnormal results may be due to: Abdominal aortic aneurysm Aortic dissection Aortic regurgitation Aortic stenosis Congenital (present ...

  12. Continuous flow nanoparticle concentration using alternating current-electroosmotic flow.

    PubMed

    Hoettges, Kai F; McDonnell, Martin B; Hughes, Michael P

    2014-02-01

    Achieving real-time detection of environmental pathogens such as viruses and bacterial spores requires detectors with both rapid action and a suitable detection threshold. However, most biosensors have detection limits of an order of magnitude or more above the potential infection threshold, limiting their usefulness. This can be improved through the use of automated sample preparation techniques such as preconcentration. In this paper, we describe the use of AC electroosmosis to concentrate nanoparticles from a continuous flow. Electrodes at an optimized angle across a flow cell, and energized by a 1 kHz signal, were used to push nanoparticles to one side of a flow cell, and to extract the resulting stream with a high particle concentration from that side of the flow cell. A simple model of the behavior of particles in the flow cell has been developed, which shows good agreement with experimental results. The method indicates potential for higher concentration factors through cascading devices. PMID:24166772

  13. Nitric oxide production by cultured human aortic smooth muscle cells: stimulation by fluid flow

    NASA Technical Reports Server (NTRS)

    Papadaki, M.; Tilton, R. G.; Eskin, S. G.; McIntire, L. V.

    1998-01-01

    This study demonstrated that exposure of cultured human aortic smooth muscle cells (SMC) to fluid flow resulted in nitric oxide (NO) production, monitored by nitrite and guanosine 3',5'-cyclic monophosphate production. A rapid burst in nitrite production rate was followed by a more gradual increase throughout the period of flow exposure. Neither the initial burst nor the prolonged nitrite production was dependent on the level of shear stress in the range of 1.1-25 dyn/cm2. Repeated exposure to shear stress after a 30-min static period restimulated nitrite production similar to the initial burst. Ca(2+)-calmodulin antagonists blocked the initial burst in nitrite release. An inhibitor of nitric oxide synthase (NOS) blocked nitrite production, indicating that changes in nitrite reflect NO production. Treatment with dexamethasone or cycloheximide had no effect on nitrite production. Monoclonal antibodies directed against the inducible and endothelial NOS isoforms showed no immunoreactivity on Western blots, whereas monoclonal antibodies directed against the neuronal NOS gave specific products. These findings suggest that human aortic SMC express a constitutive neuronal NOS isoform, the enzymatic activity of which is modulated by flow.

  14. Energy efficient continuous flow ash lockhopper

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr. (Inventor); Suitor, Jerry W. (Inventor); Dubis, David (Inventor)

    1989-01-01

    The invention relates to an energy efficient continuous flow ash lockhopper, or other lockhopper for reactor product or byproduct. The invention includes an ash hopper at the outlet of a high temperature, high pressure reactor vessel containing heated high pressure gas, a fluidics control chamber having an input port connected to the ash hopper's output port and an output port connected to the input port of a pressure letdown means, and a control fluid supply for regulating the pressure in the control chamber to be equal to or greater than the internal gas pressure of the reactor vessel, whereby the reactor gas is contained while ash is permitted to continuously flow from the ash hopper's output port, impelled by gravity. The main novelty resides in the use of a control chamber to so control pressure under the lockhopper that gases will not exit from the reactor vessel, and to also regulate the ash flow rate. There is also novelty in the design of the ash lockhopper shown in two figures. The novelty there is the use of annular passages of progressively greater diameter, and rotating the center parts on a shaft, with the center part of each slightly offset from adjacent ones to better assure ash flow through the opening.

  15. Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions.

    PubMed

    Andersson, Magnus; Lantz, Jonas; Ebbers, Tino; Karlsson, Matts

    2015-09-01

    Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies. PMID:26577361

  16. [Aortic valve surgery in a patient with cold agglutinin disease; effectiveness of continuous retrograde cardioplegia].

    PubMed

    Miyaki, Yasuko; Takagi, Nobuyuki; Hasegawa, Takeo; Yasuda, Naomi; Nakajima, Tomohiro; Tachibana, Kazutoshi; Higami, Tetsuya

    2013-03-01

    A 76-year-old female was hospitalized because of congestive heart failure and anemia. A thorough examination led to a diagnosis of severe aortic stenosis and cold agglutinin disease. The critical temperature for hemagglutination was 27 °C, which caused particular problems with regard to the myocardial protection temperature during surgery. Aortic valve replacement was performed safely by increasing the normal myocardial protection temperature from 15 °C to 32 °C and using 3 times the normal volume of cardioplagic fluid. As a result of strict perioperative thermal management, the operation was completed without any complications. PMID:23445641

  17. [Antegrade flow in the aorta ascendens despite aortic atresia: 2 case reports with retrograde coronary perfusion through coronary fistulas and sinusoids].

    PubMed

    Jux, C; Kaulitz, R; von Wasielewski, R; Peuster, M; Fink, C; Paul, T; Hausdorf, G

    2000-06-01

    In aortic atresia, coronary perfusion normally occurs through retrograde blood flow in the ascending aorta. We report on two patients with antegrade flow in the ascending aorta despite aortic atresia. In one patient with hypoplastic left heart syndrome (aortic atresia, severe mitral stenosis), an intact interatrial septum/premature closure of the foramen ovale was found. While no other way of left atrial or ventricular decompression was found, echocardiography, angiography and the post-mortem examination showed left ventricular to coronary sinusoids as the sole pathway for systemic oxygenation. In a second patient with complex congenital heart disease, including aortic atresia, antegrade flow in the ascending aorta was through a left coronary fistula with shunt flow originating from the pulmonary trunk. This report describes systemic perfusion depending on retrograde coronary flow due to coronary-cameral (sinusoids) and coronary arterio-venous fistulas leading to the phenomenon of antegrade blood flow in the ascending aorta despite aortic atresia. PMID:10929434

  18. Relationship of cerebral blood flow to aortic-to-pulmonary collateral/shunt flow in single ventricles

    PubMed Central

    Fogel, Mark A; Li, Christine; Wilson, Felice; Pawlowski, Tom; Nicolson, Susan C; Montenegro, Lisa M; Berenstein, Laura Diaz; Spray, Thomas L; Gaynor, J William; Fuller, Stephanie; Keller, Marc S; Harris, Matthew A; Whitehead, Kevin K; Clancy, Robert; Elci, Okan; Bethel, Jim; Vossough, Arastoo; Licht, Daniel J

    2016-01-01

    Objective Patients with single ventricle can develop aortic-to-pulmonary collaterals (APCs). Along with systemic-to-pulmonary artery shunts, these structures represent a direct pathway from systemic to pulmonary circulations, and may limit cerebral blood flow (CBF). This study investigated the relationship between CBF and APC flow on room air and in hypercarbia, which increases CBF in patients with single ventricle. Methods 106 consecutive patients with single ventricle underwent 118 cardiac magnetic resonance (CMR) scans in this cross-sectional study; 34 prior to bidirectional Glenn (BDG) (0.50±0.30 years old), 50 prior to Fontan (3.19±1.03 years old) and 34 3–9 months after Fontan (3.98±1.39 years old). Velocity mapping measured flows in the aorta, cavae and jugular veins. Analysis of variance (ANOVA) and multiple linear regression were used. Significance was p<0.05. Results A strong inverse correlation was noted between CBF and APC/shunt both on room air and with hypercarbia whether CBF was indexed to aortic flow or body surface area, independent of age, cardiopulmonary bypass time, Po2 and Pco2 (R=−0.67–−0.70 for all patients on room air, p<0.01 and R=−0.49–−0.90 in hypercarbia, p<0.01). Correlations were not different between surgical stages. CBF was lower, and APCs/shunt flow was higher prior to BDG than in other stages. Conclusions There is a strong inverse relationship between CBF and APC/shunt flow in patients with single ventricle throughout surgical reconstruction on room air and in hypercarbia independent of other factors. We speculate that APC/shunt flow may have a negative impact on cerebral development and neurodevelopmental outcome. Interventions on APC may modify CBF, holding out the prospect for improving neurodevelopmental trajectory. Trial Registration Number NCT02135081. PMID:26048877

  19. [Evaluation of tissue perfusion by simultaneous monitoring of aortic flow rate and capnography].

    PubMed

    Brunel, D; Muchada, R

    1991-10-26

    Ten patients under general anaesthesia were subjected to non-invasive haemodynamic monitoring, together with arterial gasometry and capnography. When enflurane was administered for maintenance anaesthesia, a 33 percent fall in aortic flow rate was observed (P less than 0.01), together with prolongation of the pre-ejection period and left ventricular pre-ejection/ejection ratio, an increase of central venous pressure and total vascular systemic resistances. The end-expiratory CO2 (Pet CO2) was reduced by 13 percent (P less than 0.05). There was no significant variation in arteriolo-alveolar CO2 difference (P(a-A)CO2). Under dobutamine (mean dose: 3.4 +/- 0.5 micrograms/kg/min), the haemodynamic parameters returned to their initial values. Pet CO2 rose above its initial level (+ 12 percent; P less than 0.05), but P(a-A)CO2 was not significantly modified. The variations of Pet CO2 were parallel with those of aortic flow rate. It is concluded that the changes in Pet CO2 observed during haemodynamic modifications could be used as markers for qualitative evaluation of tissue perfusion. PMID:1836570

  20. Enhancement of aortic blood flow with a linear anionic macropolymer of extraordinary molecular length.

    PubMed

    Polimeni, P I; Ottenbreit, B; Coleman, P

    1985-07-01

    The addition of small amounts of high mol. wt polymers to a fluid moving through a pipe typically increases fluid viscosity and thereby diminishes the rate of flow. Under appropriate conditions of flow, however, the addition of linear polymers of high mol. wt--of the order of 10(5) to 10(7) daltons--may cause the flow to increase as much as 3-fold and occasionally more without altering the driving pressure. This effect, generally known to hydrodynamicists under the rubric 'Toms phenomenon' or as 'polymer drag reduction', generally occurs at high (greater than 1000) Reynolds numbers. However, flow also increases at much lower Reynolds numbers under certain conditions, including oscillatory, pulsatile, and helicoidal flows and flow through a column of sand. The Toms phenomenon has been repeatedly observed in various types of flow with both aqueous and organic solvents in combination with a wide variety of polymer additives. A marked fall in the pressure gradients of constant blood flows through pipes has also been observed upon the addition of polyacrylamide, poly(ethylene oxide), deoxyribonucleic acid, or a polysaccharide extracted from okra. It is the consensus among students of fluid mechanics that linear macromolecules suppress flow disturbances by stabilizing or laminizing the dynamic fluid structure when rod- or thread-like particles align themselves parallel to the axis of flow. Mostardi et al. demonstrated with hot film anemometry that aortic flow instabilities downstream from a temporary partial occlusion are dampened after infusion of a polymer drag-reducing agent, Separan AP-30 (Dow Chemical Co.).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:4020886

  1. Flow topology in patient-specific abdominal aortic aneurysms during rest and exercise

    NASA Astrophysics Data System (ADS)

    Arzani, Amirhossein; Shadden, Shawn

    2012-11-01

    Abdominal aortic aneurysm (AAA) is a permanent, localized widening of the abdominal aorta. Flow in AAA is dominated by recirculation, transitional turbulence and low wall shear stress. Image-based CFD has recently enabled high resolution flow data in patient-specific AAA. This study aims to characterize transport in different AAAs, and understand flow topology changes from rest to exercise, which has been a hypothesized therapy due to potential acute changes in flow. Velocity data in 6 patients with different AAA morphology were obtained using image-based CFD under rest and exercise conditions. Finite-time Lyapunov exponent (FTLE) fields were computed from integration of the velocity data to identify dominant Lagrangian coherent structures. The flow topology was compared between rest and exercise conditions. For all patients, the systolic inflow jet resulted in coherent vortex formation. The evolution of this vortex varied greatly between patients and was a major determinant of transport inside the AAA during diastole. During exercise, previously observed stagnant regions were either replaced with undisturbed flow, regions of uniform high mixing, or persisted relatively unchanged. A mix norm measure provided a quantitative assessment of mixing. This work was supported by the National Institutes of Health, grant number 5R21HL108272.

  2. Flow Through Surface Mounted Continuous Slits

    NASA Astrophysics Data System (ADS)

    Tariq, A.; Ali, M. A.; Gad-El-Hak, M.

    2014-11-01

    Ribs are used inside certain gas-turbine blades as passive devices to enhance heat transfer. Slits in those ribs are utilized to control the primary shear layer. The role of secondary flow through a continuous slit behind a surface mounted rib is investigated herein in a rectangular duct using hotwire anemometry and particle image velocimetry. Changing the open-area-ratio and the slit's location within the rib dominate the observed shear layer. The behavior of discrete Fourier modes of the velocity fluctuations generated by different configurations is explored. Two distinct flow mechanisms are observed in the rib's wake. Both mechanisms are explained on the basis of large-scale spectral peak in the shear layer. The results show the successful impact of changing the open-area-ratio by manipulating the small-scale vortices at the leeward corner of the rib, which is suspected to be the potential cause of surface ``hot spots'' in a variety of engineering devices with heat transfer. Eventually, the size and location of the slit are seen to be an additional parameter that can be used to control the fluid flow structures behind rib turbulators.

  3. Hybrid Amyloid Membranes for Continuous Flow Catalysis.

    PubMed

    Bolisetty, Sreenath; Arcari, Mario; Adamcik, Jozef; Mezzenga, Raffaele

    2015-12-29

    Amyloid fibrils are promising nanomaterials for technological applications such as biosensors, tissue engineering, drug delivery, and optoelectronics. Here we show that amyloid-metal nanoparticle hybrids can be used both as efficient active materials for wet catalysis and as membranes for continuous flow catalysis applications. Initially, amyloid fibrils generated in vitro from the nontoxic β-lactoglobulin protein act as templates for the synthesis of gold and palladium metal nanoparticles from salt precursors. The resulting hybrids possess catalytic features as demonstrated by evaluating their activity in a model catalytic reaction in water, e.g., the reduction of 4-nitrophenol into 4-aminophenol, with the rate constant of the reduction increasing with the concentration of amyloid-nanoparticle hybrids. Importantly, the same nanoparticles adsorbed onto fibrils surface show improved catalytic efficiency compared to the same unattached particles, pointing at the important role played by the amyloid fibril templates. Then, filter membranes are prepared from the metal nanoparticle-decorated amyloid fibrils by vacuum filtration. The resulting membranes serve as efficient flow catalysis active materials, with a complete catalytic conversion achieved within a single flow passage of a feeding solution through the membrane. PMID:26673736

  4. Decentralized, continuous-flow gas anchor

    SciTech Connect

    Podio, A.L.; McCoy, J.N.; Woods, M.D.

    1995-12-31

    A novel gas separator design has been developed and successfully tested in several beam pumped wells which were subject to severe gas interference. This paper presents a detailed description of various designs to cover various ranges of fluid production for the most common sizes of completions (4-1/2 to 7 inch casing) and rates from 120 to 825 barrels of liquid per day. The new design is based on two innovations: decentralization of the gas separator in the casing, insures that a minimum amount of gas enters the separator; and the presence of two ports located on the narrow side of the annulus and placed a significant distance apart allow continuous flow of fluids into and out of the separator during both the upstroke and downstroke of the pump. These innovations have resulted in a gas separator efficiency much greater than that of conventional designs.

  5. Application of a novel particle tracking algorithm in the flow visualization of an artificial abdominal aortic aneurysm.

    PubMed

    Zhang, Yang; Wang, Yuan; He, Wenbo; Yang, Bin

    2014-01-01

    A novel Particle Tracking Velocimetry (PTV) algorithm based on Voronoi Diagram (VD) is proposed and briefed as VD-PTV. The robustness of VD-PTV for pulsatile flow is verified through a test that includes a widely used artificial flow and a classic reference algorithm. The proposed algorithm is then applied to visualize the flow in an artificial abdominal aortic aneurysm included in a pulsatile circulation system that simulates the aortic blood flow in human body. Results show that, large particles tend to gather at the upstream boundary because of the backflow eddies that follow the pulsation. This qualitative description, together with VD-PTV, has laid a foundation for future works that demand high-level quantification. PMID:25226961

  6. Blood flow dynamic improvement with aneurysm repair detected by a patient-specific model of multiple aortic aneurysms.

    PubMed

    Sughimoto, Koichi; Takahara, Yoshiharu; Mogi, Kenji; Yamazaki, Kenji; Tsubota, Ken'ichi; Liang, Fuyou; Liu, Hao

    2014-05-01

    Aortic aneurysms may cause the turbulence of blood flow and result in the energy loss of the blood flow, while grafting of the dilated aorta may ameliorate these hemodynamic disturbances, contributing to the alleviation of the energy efficiency of blood flow delivery. However, evaluating of the energy efficiency of blood flow in an aortic aneurysm has been technically difficult to estimate and not comprehensively understood yet. We devised a multiscale computational biomechanical model, introducing novel flow indices, to investigate a single male patient with multiple aortic aneurysms. Preoperative levels of wall shear stress and oscillatory shear index (OSI) were elevated but declined after staged grafting procedures: OSI decreased from 0.280 to 0.257 (first operation) and 0.221 (second operation). Graftings may strategically counter the loss of efficient blood delivery to improve hemodynamics of the aorta. The energy efficiency of blood flow also improved postoperatively. Novel indices of pulsatile pressure index (PPI) and pulsatile energy loss index (PELI) were evaluated to characterize and quantify energy loss of pulsatile blood flow. Mean PPI decreased from 0.445 to 0.423 (first operation) and 0.359 (second operation), respectively; while the preoperative PELI of 0.986 dropped to 0.820 and 0.831. Graftings contributed not only to ameliorate wall shear stress or oscillatory shear index but also to improve efficient blood flow. This patient-specific modeling will help in analyzing the mechanism of aortic aneurysm formation and may play an important role in quantifying the energy efficiency or loss in blood delivery. PMID:23852404

  7. Effect of exercise on patient specific abdominal aortic aneurysm flow topology and mixing

    PubMed Central

    Arzani, Amirhossein; Les, Andrea S.; Dalman, Ronald L.; Shadden, Shawn C.

    2014-01-01

    SUMMARY Computational fluid dynamics modeling was used to investigate changes in blood transport topology between rest and exercise conditions in five patient-specific abdominal aortic aneurysm models. Magnetic resonance imaging was used to provide the vascular anatomy and necessary boundary conditions for simulating blood velocity and pressure fields inside each model. Finite-time Lyapunov exponent fields, and associated Lagrangian coherent structures, were computed from blood velocity data, and used to compare features of the transport topology between rest and exercise both mechanistically and qualitatively. A mix-norm and mix-variance measure based on fresh blood distribution throughout the aneurysm over time were implemented to quantitatively compare mixing between rest and exercise. Exercise conditions resulted in higher and more uniform mixing, and reduced the overall residence time in all aneurysms. Separated regions of recirculating flow were commonly observed in rest, and these regions were either reduced or removed by attached and unidirectional flow during exercise, or replaced with regional chaotic and transiently turbulent mixing, or persisted and even extended during exercise. The main factor that dictated the change in flow topology from rest to exercise was the behavior of the jet of blood penetrating into the aneurysm during systole. PMID:24493404

  8. Initial hydrodynamic study on a new intraaortic axial flow pump: Dynamic aortic valve.

    PubMed

    Li, G; Zhao, H; Hu, S; Zhu, X; Wu, Q; Ren, B; Ma, W

    2001-04-01

    Rotary blood pumps have been researched as implantable ventricular assist devices for years. To further reduce the complex of implanted axial pumps, the authors proposed a new concept of intraaortic axial pump, termed previously as "dynamic aortic valve (DAV)". Instead of being driven by an intraaortic micro-electric motor, it was powered by a magnetic field from outside of body. To ensure the perfusion of coronary artery, the axial flow pump is to be implanted in the position of aortic valve. It could serve as either a blood pump or a mechanical valve depending on the power input. This research tested the feasibility of the new concept in model study. A column, made from permanent magnet, is jointed to an impeller in a concentric way to form a "rotor-impeller". Supported by a hanging shaft cantilevered in the center of a rigid cage, the rotor-impeller can be turned by the magnetic field in the surrounding space. In the present prototype, the rotor is 8 mm in diameter and 15 mm in length, the impeller has 3 vanes with an outer diameter of 18 mm. The supporting cage is 22 mm in outer diameter and 20 mm in length. When tested, the DAV prototype is inserted into the tube of a mock circuit. The alternative magnetic field is produced by a rotating magnet placed side by side with the rotor-impeller at a distance of 30 mm. Once the alternative magnetic field is presented in the surrounding space, the DAV starts to turn, leading to a pressure difference and liquid flow in the tube. The flow rate or pressure difference is proportioned to rotary speed. At the maximal output of hydraulic power, the flow rate reached 5 L/min against an afterload of 100 mmHg. The maximal pressure difference generated by DAV at a rotation rate of 12600 r/min was 147 mmHg. The preliminary results demonstrated the feasibility of "DAV", further research on this concept is justifiable. PMID:18726438

  9. Effect of Different Rotational Directions of BJUT-II VAD on Aortic Swirling Flow Characteristics: A Primary Computational Fluid Dynamics Study.

    PubMed

    Zhang, Qi; Gao, Bin; Chang, Yu

    2016-01-01

    BACKGROUND The BJUT-II VAD is a novel left ventricular assist device (LVAD), which is thought to have significant effects on the characteristics of aortic swirling flow. However, the precise mechanism of the rotational direction of BJTU-II VAD in the aortic swirling flow is unclear. MATERIAL AND METHODS A patient-specific aortic geometric model was reconstructed based on the CT data. Three pump's output flow profiles with varied rotational direction, termed "counterclockwise", "flat profile", and "clockwise", were used as the boundary conditions. The helicity density, area-weighted average of helicity density (Ha), localized normalized helicity (LNH), wall shear stress (WSS), and WSS spatial gradient (WSSG) were calculated to evaluate the swirling flow characteristics in the aorta. RESULTS The results demonstrated that the swirling flow characteristics in the aorta and 3 branches are directly affected by the output blood flow of BJUT-II VAD. In the aortic arch, the helicity density, supported by the clockwise case, achieved the highest value. In the 3 branches, the flat profile case achieved the highest helicity density, whereas the maximum WSS and WSSG generated by clockwise case were lower than in other cases. CONCLUSIONS The outflow of the BJUT-II VAD has significant effects on the aortic hemodynamics and swirling flow characteristics. The helical blood profiles can enhance the strength of aortic swirling flow, and reduce the areas of low WSS and WSSG regions. The clockwise case may have a benefit for preventing development of atherosclerosis in the aorta. PMID:27440399

  10. Continuous Precipitation of Ceria Nanoparticles from a Continuous Flow Micromixer

    SciTech Connect

    Tseng, Chih Heng; Paul, Brian; Chang, Chih-hung; Engelhard, Mark H.

    2013-01-01

    Cerium oxide nanoparticles were continuously precipitated from a solution of cerium(III) nitrate and ammonium hydroxide using a micro-scale T-mixer. Findings show that the method of mixing is important in the ceria precipitation process. In batch mixing and deposition, disintegration and agglomeration dominates the deposited film. In T-mixing and deposition, more uniform nanorod particles are attainable. In addition, it was found that the micromixing approach reduced the exposure of the Ce(OH)3 precipates to oxygen, yielding hydroxide precipates in place of CeO2 precipitates. Advantages of the micro-scale T-mixing approach include shorter mixing times, better control of nanoparticle shape and less agglomeration.

  11. New echocardiographic windows for quantitative determination of aortic regurgitation volume using color Doppler flow convergence and vena contracta

    NASA Technical Reports Server (NTRS)

    Shiota, T.; Jones, M.; Agler, D. A.; McDonald, R. W.; Marcella, C. P.; Qin, J. X.; Zetts, A. D.; Greenberg, N. L.; Cardon, L. A.; Sun, J. P.; Sahn, D. J.; Thomas, J. D.

    1999-01-01

    Color Doppler images of aortic regurgitation (AR) flow acceleration, flow convergence (FC), and the vena contracta (VC) have been reported to be useful for evaluating severity of AR. However, clinical application of these methods has been limited because of the difficulty in clearly imaging the FC and VC. This study aimed to explore new windows for imaging the FC and VC to evaluate AR volumes in patients and to validate this in animals with chronic AR. Forty patients with AR and 17 hemodynamic states in 4 sheep with strictly quantified AR volumes were evaluated. A Toshiba SSH 380A with a 3.75-MHz transducer was used to image the FC and VC. After routine echo Doppler imaging, patients were repositioned in the right lateral decubitus position, and the FC and VC were imaged from high right parasternal windows. In only 15 of the 40 patients was it possible to image clearly and measure accurately the FC and VC from conventional (left decubitus) apical or parasternal views. In contrast, 31 of 40 patients had clearly imaged FC regions and VCs using the new windows. In patients, AR volumes derived from the FC and VC methods combined with continuous velocity agreed well with each other (r = 0.97, mean difference = -7.9 ml +/- 9.9 ml/beat). In chronic animal model studies, AR volumes derived from both the VC and the FC agreed well with the electromagnetically derived AR volumes (r = 0.92, mean difference = -1.3 +/- 4.0 ml/beat). By imaging from high right parasternal windows in the right decubitus position, complementary use of the FC and VC methods can provide clinically valuable information about AR volumes.

  12. Improvement of thoracic aortic vasoreactivity by continuous and intermittent exercise in high-fat diet-induced obese rats

    PubMed Central

    LIU, HONGPENG; YANG, ZHEN; HU, JIAN; LUO, YAN; ZHU, LINGQIN; YANG, HUIFANG; LI, GUANGHUA

    2015-01-01

    The aim of the present study was to explore the effects of continuous and intermittent exercise on the thoracic aortic vasoreactivity and free radical metabolism in rats fed with a high-fat diet (HD). Sprague-Dawley (SD) rats were randomly divided into four groups (n=8, each group): Conventional diet (CD), HD, HD with continuous exercise (HCE) and HD with intermittent exercise (HIE). HCE rats swam once/day for 90 min; HIE rats performed swimming exercises 3 times/day, 30 min each time with an interval of 4 h. In these two groups, the exercise was conducted 5 days a week for 8 weeks. Rats in the CD and HD groups were fed without swimming training. At the end of the exercise, all the rats were sacrificed and the blood, thoracic aorta and myocardium were collected immediately. The thoracic aortic vasoreactivity, the plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), superoxide dismutase (SOD), malondialdehyde (MDA) and vascular endothelial nitric oxide synthase (eNOS) gene expression were measured. Compared to the control group, in the HD group the enhanced contractile response of the thoracic aortic rings to noradrenaline (NA) was observed (P<0.01). The levels of TC and LDL (P<0.01) were also increased in serum while the HDL level was reduced without statistical significance. In addition, the MDA content was upregulated in the myocardium, but the SOD level decreased (P<0.01). Furthermore, the expression of vascular eNOS mRNA was reduced (P<0.01). However, following the exercise the contraction of the thoracic aorta vascular rings to NA was reduced in the HCE and HIE groups (P<0.01), and the decreased contractile response was more evident in the HIE group compared to the HCE group (P<0.01). Additionally, in the HCE group the level of TG (P<0.01) was decreased, while the HDL (P<0.01) level was increased. Although the reduction of the TC and LDL level was also observed there was no significant difference

  13. Evaluation of Aortic Stenosis Severity using 4D Flow Jet Shear Layer Detection for the Measurement of Valve Effective Orifice Area

    PubMed Central

    Garcia, Julio; Markl, Michael; Schnell, Susanne; Allen, Bradley; Entezari, Pegah; Mahadevia, Riti; Malaisrie, S Chris; Pibarot, Philippe; Carr, James; Barker, Alex J

    2014-01-01

    Aims The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method. Methods and Results An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOAJSLD-2D and EOAJSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOACE) with the 2D PC-MRI velocity field and compared to the EOAJSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA=0.78 cm2) and experimental measurement (EOAJSLD-4D=0.78±0.01 cm2) for peak velocities ranging from 0.9 to 3.7 m/s. In-vivo results showed good correlation and agreement between EOAJSLD-2D and EOACE (r=0.91, p<0.001; bias: −0.01±0.38cm2; agreement limits: 0.75 to −0.77cm2), and between EOAJSLD-4D and EOACE (r=0.95, p<0.001; bias: −0.09±0.26cm2; limits: 0.43 to −0.62cm2). Conclusion This study demonstrates the feasibility of measuring EOAJSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOACE measurement variability. PMID:24865143

  14. A three-layer model for buckling of a human aortic segment under specific flow-pressure conditions.

    PubMed

    Amabili, M; Karazis, K; Mongrain, R; Païdoussis, M P; Cartier, R

    2012-05-01

    Human aortas are subjected to large mechanical stresses because of blood flow pressurization and through contact with the surrounding tissue. It is essential that the aorta does not lose stability by buckling with deformation of the cross-section (shell-like buckling) (i) for its proper functioning to ensure blood flow and (ii) to avoid high stresses in the aortic wall. A numerical bifurcation analysis employs a refined reduced-order model to investigate the stability of a straight aorta segment conveying blood flow. The structural model assumes a nonlinear cylindrical orthotropic laminated composite shell composed of three layers representing the tunica intima, media and adventitia. Residual stresses because of pressurization are evaluated and included in the model. The fluid is formulated using a hybrid model that contains the unsteady effects obtained from linear potential flow theory and the steady viscous effects obtained from the time-averaged Navier-Stokes equations. The aortic segment loses stability by divergence with deformation of the cross-section at a critical flow velocity for a given static pressure, exhibiting a strong subcritical behaviour with partial or total collapse of the inner wall. Preliminary results suggest directions for further study in relation to the appearance and growth of dissection in the aorta. PMID:25099454

  15. Liquid phase oxidation chemistry in continuous-flow microreactors.

    PubMed

    Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy

    2016-01-01

    Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described. PMID:26203551

  16. Distant downstream steady-state flow studies of a mechanical heart valve: PIV study of secondary flow in a model aortic arch

    NASA Astrophysics Data System (ADS)

    Fix, Brandon R.; Popma, Christopher J.; Bulusu, Kartik V.; Plesniak, Michael W.

    2013-11-01

    Each year, hundreds of thousands of aortic and mitral heart valves are replaced with prosthetic valves. In efforts to develop a valve that does not require lifelong anticoagulation therapy, previous experimental research has been devoted to analyzing the hemodynamics of various heart valve designs, limited to the flow up to only 2 diameters downstream of the valve. Two-component, two-dimensional (2C-2D) particle image velocimetry (PIV) was used in this study to examine secondary flow velocity fields in a curved tube modeling an aorta at five locations (0-, 45-, 90-, 135-, 180-degrees). A bileaflet valve, opened to 30-, 45-, and 59-degrees, and one (no-valve) baseline condition were examined under three steady flow inflows (Re = 218, 429, 634). In particular, variations in the two-dimensional turbulent shear stresses at each cross sectional plane were analyzed. The results suggest that bileaflet valves in the aortic model produce significant turbulence and vorticity up to 5.5 downstream diameters, i.e. up to the 90-degrees location. Expanding this research towards aortic heart valve hemodynamics highlights a need for additional studies extending beyond the typical few diameters downstream to fully characterize valvular function. Supported by the NSF Grant No. CBET- 0828903 and GW Center for Biomimetics and Bioinspired Engineering.

  17. A Continuous Method for Gene Flow

    PubMed Central

    Palczewski, Michal; Beerli, Peter

    2013-01-01

    Most modern population genetics inference methods are based on the coalescence framework. Methods that allow estimating parameters of structured populations commonly insert migration events into the genealogies. For these methods the calculation of the coalescence probability density of a genealogy requires a product over all time periods between events. Data sets that contain populations with high rates of gene flow among them require an enormous number of calculations. A new method, transition probability-structured coalescence (TPSC), replaces the discrete migration events with probability statements. Because the speed of calculation is independent of the amount of gene flow, this method allows calculating the coalescence densities efficiently. The current implementation of TPSC uses an approximation simplifying the interaction among lineages. Simulations and coverage comparisons of TPSC vs. MIGRATE show that TPSC allows estimation of high migration rates more precisely, but because of the approximation the estimation of low migration rates is biased. The implementation of TPSC into programs that calculate quantities on phylogenetic tree structures is straightforward, so the TPSC approach will facilitate more general inferences in many computer programs. PMID:23666937

  18. The Impact of Cardiac Motion on Aortic Valve Flow Used in Computational Simulations of the Thoracic Aorta.

    PubMed

    Wendell, David C; Samyn, Margaret M; Cava, Joseph R; Krolikowski, Mary M; LaDisa, John F

    2016-09-01

    Advancements in image-based computational modeling are producing increasingly more realistic representations of vasculature and hemodynamics, but so far have not compensated for cardiac motion when imposing inflow boundary conditions. The effect of cardiac motion on aortic flow is important when assessing sequelae in this region including coarctation of the aorta (CoA) or regurgitant fraction. The objective of this investigation was to develop a method to assess and correct for the influence of cardiac motion on blood flow measurements through the aortic valve (AoV) and to determine its impact on patient-specific local hemodynamics quantified by computational fluid dynamics (CFD). A motion-compensated inflow waveform was imposed into the CFD model of a patient with repaired CoA that accounted for the distance traveled by the basal plane during the cardiac cycle. Time-averaged wall shear stress (TAWSS) and turbulent kinetic energy (TKE) values were compared with CFD results of the same patient using the original waveform. Cardiac motion resulted in underestimation of flow during systole and overestimation during diastole. Influences of inflow waveforms on TAWSS were greatest along the outer wall of the ascending aorta (AscAo) (∼30 dyn/cm2). Differences in TAWSS were more pronounced than those from the model creation or mesh dependence aspects of CFD. TKE was slightly higher for the motion-compensated waveform throughout the aortic arch. These results suggest that accounting for cardiac motion when quantifying blood flow through the AoV can lead to different conclusions for hemodynamic indices, which may be important if these results are ultimately used to predict patient outcomes. PMID:27367143

  19. Early diagnosis and surgical intervention of acute aortic dissection by transesophageal color flow mapping.

    PubMed

    Adachi, H; Kyo, S; Takamoto, S; Kimura, S; Yokote, Y; Omoto, R

    1990-11-01

    To determine whether transesophageal color Doppler echocardiography (TEE) is useful for the early diagnosis and surgical intervention in acute aortic dissection, 57 serial patients with acute aortic dissection were examined. These patients were evaluated by TEE with either the single-plane probe (39 patients) or the biplanar probe (18 patients) just after admission. The intimal flap was detected in all patients, and there were 18 patients with type A dissection and 39 patients with type B dissection. The entry was visualized in 83% of type A dissection cases and in 90% of type B dissection cases. In two of 18 patients examined with the biplanar probe technique, the entry was detected in the longitudinal view only. Emergency operations were performed in 18 patients with type A dissection and in 10 patients with ruptured type B dissection. Twenty-nine of 39 patients with type B dissection were treated conservatively. The operative mortality rate of patients with type A dissection was 22%, and that of patients with ruptured type B dissection was 60%. The major advantage of TEE is its ease of application at the bedside or in the operating room, which allows immediate and accurate diagnosis of acute aortic dissection for emergency surgical intervention. Biplanar TEE provides additional acoustic windows, ease of spatial orientation, and more accurate visualization of entry. TEE is a useful and powerful diagnostic tool for acute aortic dissection, and by using this method, one may achieve a more rapid and aggressive surgical approach for patients with acute aortic dissection. PMID:2225402

  20. Simulation of the three-dimensional hinge flow fields of a bileaflet mechanical heart valve under aortic conditions.

    PubMed

    Simon, Hélène A; Ge, Liang; Borazjani, Iman; Sotiropoulos, Fotis; Yoganathan, Ajit P

    2010-03-01

    Thromboembolic complications of bileaflet mechanical heart valves (BMHV) are believed to be due to detrimental stresses imposed on blood elements by the hinge flows. Characterization of these flows is thus crucial to identify the underlying causes for complications. In this study, we conduct three-dimensional pulsatile flow simulations through the hinge of a BMHV under aortic conditions. Hinge and leaflet geometries are reconstructed from the Micro-Computed Tomography scans of a BMHV. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Physiologic flow boundary conditions and leaflet motion are extracted from the Fluid-Structure Interaction simulations of the bulk of the flow through a BMHV. Calculations reveal the presence, throughout the cardiac cycle, of flow patterns known to be detrimental to blood elements. Flow fields are characterized by: (1) complex systolic flows, with rotating structures and slow reverse flow pattern, and (2) two strong diastolic leakage jets accompanied by fast reverse flow at the hinge bottom. Elevated shear stresses, up to 1920 dyn/cm2 during systole and 6115 dyn/cm2 during diastole, are reported. This study underscores the need to conduct three-dimensional simulations throughout the cardiac cycle to fully characterize the complexity and thromboembolic potential of the hinge flows. PMID:19960368

  1. Transient Aortic Occlusion Augments Collateral Blood Flow and Reduces Mortality During Severe Ischemia due to Proximal Middle Cerebral Artery Occlusion.

    PubMed

    Ramakrishnan, Gomathi; Dong, Bin; Todd, Kathryn G; Shuaib, Ashfaq; Winship, Ian R

    2016-04-01

    Cerebral collateral circulation provides alternative vascular routes for blood to reach ischemic tissues during stroke. Collateral therapeutics attempt to augment flow through these collateral channels to reduce ischemia and brain damage during acute ischemic stroke. Transient aortic occlusion (TAO) has pre-clinical data suggesting that it can augment collateral blood flow and clinical data suggesting a benefit for patients with moderate cortical strokes. By diverting blood from the periphery towards the cerebral circulation, TAO has the potential to augment primary collateral flow at the circle of Willis and thereby improve outcome even during large, hemispheric strokes. Using proximal middle and anterior cerebral artery occlusion in rats, we demonstrate that TAO reduces mortality and improves collateral blood flow in severely ischemic animals. As such, TAO may be an effective therapy to reduce early mortality during severe ischemia associated with proximal occlusions. PMID:26706246

  2. Closed continuous-flow centrifuge rotor

    DOEpatents

    Breillatt, Jr., Julian P.; Remenyik, Carl J.; Sartory, Walter K.; Thacker, Louis H.; Penland, William Z.

    1976-01-01

    A blood separation centrifuge rotor having a generally parabolic core disposed concentrically and spaced apart within a housing having a similarly shaped cavity. Blood is introduced through a central inlet and into a central passageway enlarged downwardly to decrease the velocity of the entrant blood. Septa are disposed inside the central passageway to induce rotation of the entrant blood. A separation chamber is defined between the core and the housing wherein the whole blood is separated into red cell, white cell, and plasma zones. The zones are separated by annular splitter blades disposed within the separation chamber. The separated components are continuously removed through conduits communicating through a face seal to the outside of the rotor.

  3. Aortic insufficiency

    MedlinePlus

    ... Heart valve - aortic regurgitation; Valvular disease - aortic regurgitation; AI - aortic insufficiency ... BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: ...

  4. Aortic Aneurysm

    MedlinePlus

    ... chest and abdomen. There are two types of aortic aneurysm: Thoracic aortic aneurysms - these occur in the part of the aorta running through the chest Abdominal aortic aneurysms - these occur in the part of the aorta ...

  5. Aortic Aneurysm

    MedlinePlus

    ... chest and abdomen. There are two types of aortic aneurysm: Thoracic aortic aneurysms (TAA) - these occur in the part of the aorta running through the chest Abdominal aortic aneurysms (AAA) - these occur in the part of the ...

  6. Aortic insufficiency

    MedlinePlus

    Aortic valve prolapse; Aortic regurgitation ... Any condition that prevents the aortic valve from closing completely can cause this problem. When the valve doesn't close all the way, a small amount of blood comes ...

  7. Effect of Different Rotational Directions of BJUT-II VAD on Aortic Swirling Flow Characteristics: A Primary Computational Fluid Dynamics Study

    PubMed Central

    Zhang, Qi; Gao, Bin; Chang, Yu

    2016-01-01

    Background The BJUT-II VAD is a novel left ventricular assist device (LVAD), which is thought to have significant effects on the characteristics of aortic swirling flow. However, the precise mechanism of the rotational direction of BJTU-II VAD in the aortic swirling flow is unclear. Material/Methods A patient-specific aortic geometric model was reconstructed based on the CT data. Three pump’s output flow profiles with varied rotational direction, termed “counterclockwise”, “flat profile”, and “clockwise”, were used as the boundary conditions. The helicity density, area-weighted average of helicity density (Ha), localized normalized helicity (LNH), wall shear stress (WSS), and WSS spatial gradient (WSSG) were calculated to evaluate the swirling flow characteristics in the aorta. Results The results demonstrated that the swirling flow characteristics in the aorta and 3 branches are directly affected by the output blood flow of BJUT-II VAD. In the aortic arch, the helicity density, supported by the clockwise case, achieved the highest value. In the 3 branches, the flat profile case achieved the highest helicity density, whereas the maximum WSS and WSSG generated by clockwise case were lower than in other cases. Conclusions The outflow of the BJUT-II VAD has significant effects on the aortic hemodynamics and swirling flow characteristics. The helical blood profiles can enhance the strength of aortic swirling flow, and reduce the areas of low WSS and WSSG regions. The clockwise case may have a benefit for preventing development of atherosclerosis in the aorta. PMID:27440399

  8. Difluorocarbene Addition to Alkenes and Alkynes in Continuous Flow.

    PubMed

    Rullière, Pauline; Cyr, Patrick; Charette, André B

    2016-05-01

    The first in-flow difluorocarbene generation and addition to alkenes and alkynes is reported. The application of continuous flow technology allowed for the controlled generation of difluorocarbene from TMSCF3 and a catalytic quantity of NaI. The in situ generated electrophilic carbene reacts smoothly with a broad range of alkenes and alkynes, allowing the synthesis of the corresponding difluorocyclopropanes and difluorocyclopropenes. The reaction is complete within a 10 min residence time at high reaction concentrations. With a production flow rate of 1 mmol/min, continuous flow chemistry enables scale up of this process in a green, atom-economic, and safe manner. PMID:27119573

  9. Renal flow studies after abdominal aortic aneurysmectomy and axillo-bifemoral bypass graft: case report

    SciTech Connect

    LaManna, M.M.; Yussen, P.S.

    1988-03-01

    Vascular disorders affecting the kidneys are either acquired or congenital. Included in this category are common multiplicity of renal arteries, the rare arteriovenous malformation, stresses due to fibromuscular disease or atherosclerosis including abdominal aortic aneurysms, arterial thrombosis, venous thrombosis, and infarction. In contrast to the group of cystic and neoplastic kidneys where scintigraphic or pathologic are not diagnostic, scintigraphic or pathologic anatomy in vascular disease is often diagnostic by nuclear medicine techniques. The authors present an interesting case of evaluation of acute renal failure in a patient abdominal aortic aneurysmectomy and axillo-bifemoral bypass graft.

  10. Continuous subsonic-sonic flows in a general nozzle

    NASA Astrophysics Data System (ADS)

    Wang, Chunpeng

    2015-10-01

    This paper concerns continuous subsonic-sonic potential flows in a two dimensional finite nozzle with a general upper wall and a straight lower wall. We give a class of nozzles where continuous subsonic-sonic flows may exist. Consider a continuous subsonic-sonic flow in such a nozzle after rescaling the upper wall in a small scale. It is shown that for a given inlet and a fixed point at the upper wall, there exists uniquely a continuous subsonic-sonic flow whose velocity vector is along the normal direction at the inlet and the sonic curve, which satisfies the slip conditions on the nozzle walls and whose sonic curve intersects the upper wall at the fixed point. Furthermore, the sonic curve of this flow is a free boundary, where the flow is singular in the sense that the speed is only C 1 / 2 Hölder continuous and the acceleration blows up at the sonic state. As the scale tends to zero, the precise convergent rate of the continuous subsonic-sonic flow converging to the sonic state is also determined.

  11. THE CONTINUOUS FLOW ANALYZER AUTOMATION SYSTEM. PART I - FUNCTIONAL SPECIFICATIONS

    EPA Science Inventory

    This document contains the project definition, the functional requirements, and the functional design for a proposed computer automation system for the continuous flow analyzer. The proposed system will accomplish real-time data acquisition, calibration, baseline correction, calc...

  12. [Noninvasive hemodynamic monitoring via the integration of data obtained by ECG, aortic flow by Doppler esophageal probe and by finger plethysmography].

    PubMed

    Muchada, R; Rinaldi, A; Vernier, F; Fady, J F; Lavandier, B; Cathignol, D

    1990-05-01

    The aims of this work are to describe the general and technical characteristics of a new device for the noninvasive monitoring of patients in intensive care and during general anaesthesia, and the results concerning the reliability of this method. An ultrasonic esophageal probe and an echo-Doppler device have been used to obtain continuous data of the aortic diameter and of blood velocity. Aortic output is calculated automatically. This method, together with other non-invasive monitoring techniques (blood pressure, heart rate, rhythm and cardiac conduction), gives on the one hand the data of aortic output, systemic peripheral resistance and stroke volume; on the other, through a computerized elaboration, the systolic time intervals (PEP pre-ejection period, LVET left ventricular ejection time, QS2 electromechanical systole, PEP/LVET ratio of PEP to LVET). The validation of STI data, has been obtained through 125 comparative measurements for each of the three parameters. The data obtained through the aortic velocity waveform in descending aorta (pulsed Doppler) have been compared with those obtained through the aortic pressure waveform (intra aortic catheter). The correlation was: PEP 0.92, LVET 0.95, QS2 0.93. The clinical application of this method supplies data concerning cardiac load, after-load and indirectly cardiac pre-load. This non-invasive procedure gives us a continuous measurement of hemo-dynamic situation, which allows the physician to plan and evaluate the therapeutical efficacy. Finally new pathologic events may be opportunely faced. PMID:2247249

  13. Brachial artery diameter has a predictive value in the improvement of flow-mediated dilation after aortic valve replacement for aortic stenosis.

    PubMed

    Takata, Munenori; Amiya, Eisuke; Watanabe, Masafumi; Ozeki, Atsuko; Watanabe, Aya; Kawarasaki, Shuichi; Nakao, Tomoko; Hosoya, Yumiko; Uno, Kansei; Saito, Aya; Murasawa, Takahide; Ono, Minoru; Nagai, Ryozo; Komuro, Issei

    2015-03-01

    Aortic stenosis (AS) is the most common valvular disease and aortic valve replacement (AVR) is one of its most effective interventions. AS affects not only the left ventricle, but also vascular function beyond the stenotic valve, which can lead to various types of vascular dysfunction. However, research evaluating the effect of AS on aortic vascular function is limited. In this study, we investigated clinical meaning to evaluate endothelial function in subjects with AS. From April 2011 to April 2012, 20 consecutive adult patients with degenerative AS (mean age, 74.7 ± 7.4 years; range 50-83 years) who underwent AVR at our institution were included in the study. We measured flow-mediated dilation (FMD) to evaluate the effect of AS on endothelial function. The difference between brachial artery diameter (BAD) before (4.0 ± 0.7 mm) and after AVR (3.9 ± 0.6 mm) was not significant (p = 0.043), but FMD significantly improved after AVR (from 3.1 ± 1.8 to 6.0 ± 2.7 %, p < 0.0001). We also analyzed FMD × BAD index, endogenous vasodilatory capability independent of BAD, resulting that it also significantly increased after AVR (12.3 ± 7.0-22.5 ± 9.3, p < 0.0001). We divided patients into two groups by pre- to post-AVR change in FMD (ΔFMD); large-ΔFMD group [ΔFMD >3.0 % (median value)] and small-ΔFMD group (ΔFMD <3.0 %). There were no significant changes in age, blood pressure, heart rate, B-type natriuretic peptide, or echocardiographic parameters in either group. In contrast, BAD was significantly larger in the small ΔFMD group (4.3 ± 0.7 mm) than in the large ΔFMD group (3.7 ± 0.7 mm) (p = 0.030). In addition, cardio-thoracic ratio was significantly greater in the small ΔFMD group (58.4 ± 7.1 %) than in the large ΔFMD group (53.7 ± 4.6 %) (p = 0.048). Receiver operating characteristic curve analysis of BAD to differentiate large and small ΔFMD demonstrated an area under the curve of 0.750 (p = 0.059) and that optimal cutoff for BAD was 4.28 mm (70

  14. Pressurized tundish for controlling a continuous flow of molten metal

    DOEpatents

    Lewis, T.W.; Hamill, P.E. Jr.; Ozgu, M.R.; Padfield, R.C.; Rego, D.N.; Brita, G.P.

    1990-07-24

    A pressurized tundish for controlling a continuous flow of molten metal is characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate. 1 fig.

  15. High-bandwidth continuous-flow arc furnace

    DOEpatents

    Hardt, David E.; Lee, Steven G.

    1996-01-01

    A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics.

  16. High-bandwidth continuous-flow arc furnace

    DOEpatents

    Hardt, D.E.; Lee, S.G.

    1996-08-06

    A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics. 4 figs.

  17. The fluid mechanics of continuous flow electrophoresis in perspective

    NASA Technical Reports Server (NTRS)

    Saville, D. A.

    1980-01-01

    Buoyancy alters the flow in continuous flow electrophoresis chambers through the mechanism of hydrodynamic instability and, when the instability is supressed by careful cooling of the chamber boundaries, by restructuring the axial flow. The expanded roles of buoyancy follow upon adapting the size of the chamber and the electric field so as to fractionate certain sorts of cell populations. Scale-up problems, hydrodynamic stability and the altered flow fields are discussed to show how phenomena overlooked in the design and operations of narrow-gap devices take on an overwhelming importance in wide-gap chambers

  18. Sorting and Manipulation of Magnetic Droplets in Continuous Flow

    NASA Astrophysics Data System (ADS)

    Al-Hetlani, Entesar; Hatt, Oliver J.; Vojtíšek, Martin; Tarn, Mark D.; Iles, Alexander; Pamme, Nicole

    2010-12-01

    We report the rapid on-chip generation and subsequent manipulation of magnetic droplets in continuous flow. Magnetic droplets were formed using aqueous-based ferrofluid as the dispersed phase and fluorocarbon oil as the continuous phase. Droplet manipulation was demonstrated with simple permanent magnets using two microfluidic platforms: (i) flow focusing droplet generation followed by their splitting into daughter droplets containing different amounts of magnetic nanoparticles, and (ii) droplet generation at a T-junction and their downstream deflection across a chamber for sorting based on the applied magnetic field and magnetite loading of the droplet. Both systems show great potential for performing a wide range of high throughput continuous flow processes including sample dilution, cell sorting and screening, and microparticle fabrication.

  19. Controlled synthesis of poly(3-hexylthiophene) in continuous flow

    PubMed Central

    Seyler, Helga; Subbiah, Jegadesan; Jones, David John; Holmes, Andrew Bruce

    2013-01-01

    Summary There is an increasing demand for organic semiconducting materials with the emergence of organic electronic devices. In particular, large-area devices such as organic thin-film photovoltaics will require significant quantities of materials for device optimization, lifetime testing and commercialization. Sourcing large quantities of materials required for the optimization of large area devices is costly and often impossible to achieve. Continuous-flow synthesis enables straight-forward scale-up of materials compared to conventional batch reactions. In this study, poly(3-hexylthiophene), P3HT, was synthesized in a bench-top continuous-flow reactor. Precise control of the molecular weight was demonstrated for the first time in flow for conjugated polymers by accurate addition of catalyst to the monomer solution. The P3HT samples synthesized in flow showed comparable performance to commercial P3HT samples in bulk heterojunction solar cell devices. PMID:23946848

  20. Pressurized tundish for controlling a continuous flow of molten metal

    DOEpatents

    Lewis, Thomas W.; Hamill, Jr., Paul E.; Ozgu, Mustafa R.; Padfield, Ralph C.; Rego, Donovan N.; Brita, Guido P.

    1990-01-01

    A pressurized tundish for controlling a continous flow of molten metal characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate.

  1. Continuous-flow free acid monitoring method and system

    DOEpatents

    Strain, J.E.; Ross, H.H.

    1980-01-11

    A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

  2. Continuous-flow free acid monitoring method and system

    DOEpatents

    Strain, James E.; Ross, Harley H.

    1981-01-01

    A free acid monitoring method and apparatus is provided for continuously measuring the excess acid present in a process stream. The disclosed monitoring system and method is based on the relationship of the partial pressure ratio of water and acid in equilibrium with an acid solution at constant temperature. A portion of the process stream is pumped into and flows through the monitor under the influence of gravity and back to the process stream. A continuous flowing sample is vaporized at a constant temperature and the vapor is subsequently condensed. Conductivity measurements of the condensate produces a nonlinear response function from which the free acid molarity of the sample process stream is determined.

  3. Effect of coarctation of the aorta and bicuspid aortic valve on flow dynamics and turbulence in the aorta using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Keshavarz-Motamed, Zahra; Garcia, Julio; Gaillard, Emmanuel; Maftoon, Nima; Di Labbio, Giuseppe; Cloutier, Guy; Kadem, Lyes

    2014-03-01

    Blood flow in the aorta has been of particular interest from both fluid dynamics and physiology perspectives. Coarctation of the aorta (COA) is a congenital heart disease corresponding to a severe narrowing in the aortic arch. Up to 85 % of patients with COA have a pathological aortic valve, leading to a narrowing at the valve level. The aim of the present work was to advance the state of understanding of flow through a COA to investigate how narrowing in the aorta (COA) affects the characteristics of the velocity field and, in particular, turbulence development. For this purpose, particle image velocimetry measurements were conducted at physiological flow and pressure conditions, with three different aorta configurations: (1) normal case: normal aorta + normal aortic valve; (2) isolated COA: COA (with 75 % reduction in aortic cross-sectional area) + normal aortic valve and (3) complex COA: COA (with 75 % reduction in aortic cross-sectional area) + pathological aortic valve. Viscous shear stress (VSS), representing the physical shear stress, Reynolds shear stress (RSS), representing the turbulent shear stress, and turbulent kinetic energy (TKE), representing the intensity of fluctuations in the fluid flow environment, were calculated for all cases. Results show that, compared with a healthy aorta, the instantaneous velocity streamlines and vortices were deeply changed in the presence of the COA. The normal aorta did not display any regions of elevated VSS, RSS and TKE at any moment of the cardiac cycle. The magnitudes of these parameters were elevated for both isolated COA and complex COA, with their maximum values mainly being located inside the eccentric jet downstream of the COA. However, the presence of a pathologic aortic valve, in complex COA, amplifies VSS (e.g., average absolute peak value in the entire aorta for a total flow of 5 L/min: complex COA: = 36 N/m2; isolated COA = 19 N/m2), RSS (e.g., average peak value in the entire aorta for a total flow of 5

  4. Mathematical models of continuous flow electrophoresis: Electrophoresis technology

    NASA Technical Reports Server (NTRS)

    Saville, Dudley A.

    1986-01-01

    Two aspects of continuous flow electrophoresis were studied: (1) the structure of the flow field in continuous flow devices; and (2) the electrokinetic properties of suspended particles relevant to electrophoretic separations. Mathematical models were developed to describe flow structure and stability, with particular emphasis on effects due to buoyancy. To describe the fractionation of an arbitrary particulate sample by continuous flow electrophoresis, a general mathematical model was constructed. In this model, chamber dimensions, field strength, buffer composition, and other design variables can be altered at will to study their effects on resolution and throughput. All these mathematical models were implemented on a digital computer and the codes are available for general use. Experimental and theoretical work with particulate samples probed how particle mobility is related to buffer composition. It was found that ions on the surface of small particles are mobile, contrary to the widely accepted view. This influences particle mobility and suspension conductivity. A novel technique was used to measure the mobility of particles in concentrated suspensions.

  5. HIGH TEMPERATURE CONTINUOUS FLOW CURING OF SWEET ONIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was undertaken to investigate the feasibility of heat treating sweet onions under controlled commercial conditions. Three batches, approximately 2.5 tons each, were passed through a single pass continuous flow drier. Air temperatures of 43 and 46 C were used to cure sweet onions for 17 and...

  6. THE CONTINUOUS FLOW ANALYZER AUTOMATION SYSTEM. PART III -- PROGRAM DOCUMENTATION

    EPA Science Inventory

    This report contains complete documentation for the 21 programs and eight data files of the EPA Continuous Flow Analyzer Automation System. This system can receive lists of samples from the Sample File Control System and return the measured concentrations to that system. It is ca...

  7. Shape complexes in continuous max-flow segmentation

    NASA Astrophysics Data System (ADS)

    Baxter, John S. H.; Yuan, Jing; Drangova, Maria; Peters, Terry M.; Inoue, Jiro

    2016-03-01

    Optimization-based segmentation approaches deriving from discrete graph-cuts and continuous max-flow have become increasingly nuanced, allowing for topological and geometric constraints on the resulting segmentation while retaining global optimality. However, these two considerations, topological and geometric, have yet to be combined in a unified manner. This paper presents the concept of shape complexes, which combine geodesic star convexity with extendable continuous max-flow solvers. These shape complexes allow more complicated shapes to be created through the use of multiple labels and super-labels, with geodesic star convexity governed by a topological ordering. These problems can be optimized using extendable continuous max-flow solvers. Previous work required computationally expensive co-ordinate system warping which are ill-defined and ambiguous in the general case. These shape complexes are validated in a set of synthetic images as well as atrial wall segmentation from contrast-enhanced CT. Shape complexes represent a new, extendable tool alongside other continuous max-flow methods that may be suitable for a wide range of medical image segmentation problems.

  8. Coupled chemo(enzymatic) reactions in continuous flow

    PubMed Central

    Yuryev, Ruslan; Strompen, Simon

    2011-01-01

    Summary This review highlights the state of the art in the field of coupled chemo(enzymatic) reactions in continuous flow. Three different approaches to such reaction systems are presented herein and discussed in view of their advantages and disadvantages as well as trends for their future development. PMID:22238518

  9. Aortic Input Impedance during Nitroprusside Infusion

    PubMed Central

    Pepine, Carl J.; Nichols, W. W.; Curry, R. C.; Conti, C. Richard

    1979-01-01

    Beneficial effects of nitroprusside infusion in heart failure are purportedly a result of decreased afterload through “impedance” reduction. To study the effect of nitroprusside on vascular factors that determine the total load opposing left ventricular ejection, the total aortic input impedance spectrum was examined in 12 patients with heart failure (cardiac index <2.0 liters/min per m2 and left ventricular end diastolic pressure >20 mm Hg). This input impedance spectrum expresses both mean flow (resistance) and pulsatile flow (compliance and wave reflections) components of vascular load. Aortic root blood flow velocity and pressure were recorded continuously with a catheter-tip electromagnetic velocity probe in addition to left ventricular pressure. Small doses of nitroprusside (9-19 μg/min) altered the total aortic input impedance spectrum as significant (P < 0.05) reductions in both mean and pulsatile components were observed within 60-90 s. With these acute changes in vascular load, left ventricular end diastolic pressure declined (44%) and stroke volume increased (20%, both P < 0.05). Larger nitroprusside doses (20-38 μg/min) caused additional alteration in the aortic input impedance spectrum with further reduction in left ventricular end diastolic pressure and increase in stroke volume but no additional changes in the impedance spectrum or stroke volume occurred with 39-77 μg/min. Improved ventricular function persisted when aortic pressure was restored to control values with simultaneous phenylephrine infusion in three patients. These data indicate that nitroprusside acutely alters both the mean and pulsatile components of vascular load to effect improvement in ventricular function in patients with heart failure. The evidence presented suggests that it may be possible to reduce vascular load and improve ventricular function independent of aortic pressure reduction. PMID:457874

  10. Regional blood flow during continuous low-dose endotoxin infusion

    SciTech Connect

    Fish, R.E.; Lang, C.H.; Spitzer, J.A.

    1986-01-01

    Escherichia coli endotoxin (ET) was administered to adult rats by continuous IV infusion from a subcutaneously implanted osmotic pump (Alzet). Cardiac output and regional blood flow were determined by the radiolabeled microsphere method after 6 and 30 hr of ET or saline infusion. Cardiac output (CO) of ET rats was not different from time-matched controls, whereas arterial pressure was 13% lower after 30 hr of infusion. After both 6 and 30 hr of ET, pancreatic blood flow and percentage of cardiac output were lower than in controls. Estimated portal venous flow was decreased at each time point, and an increased hepatic arterial flow (significant after 30 hr) resulted in an unchanged total hepatic blood flow. Blood flow to most other tissues, including epididymal fat, muscle, kidneys, adrenals, and gastrointestinal tract, was similar between treatments. Maintenance of blood flow to metabolically important tissues indicates that the previously reported alterations in in vitro cellular metabolism are not due to tissue hypoperfusion. Earlier observations of in vitro myocardial dysfunction, coexistent with the significant impairment in pancreatic flow, raise the possibility that release of a myocardial depressant factor occurs not only in profound shock but also under less severe conditions of sepsis and endotoxemia.

  11. From continuous flow analysis to programmable Flow Injection techniques. A history and tutorial of emerging methodologies.

    PubMed

    Ruzicka, Jaromir Jarda

    2016-09-01

    Automation of reagent based assays, also known as Flow Analysis, is based on sample processing, in which a sample flows towards and through a detector for monitoring of its components. The Achilles heel of this methodology is that the majority of FA techniques use constant continuous forward flow to transport the sample - an approach which continually consumes reagents and generates chemical waste. Therefore the purpose of this report is to highlight recent developments of flow programming that not only save reagents, but also lead by means of advanced sample processing to selective and sensitive assays based on stop flow measurement. Flow programming combined with a novel approach to data harvesting yields a novel approach to single standard calibration, and avoids interference caused by refractive index. Finally, flow programming is useful for sample preparation, such as rapid, extensive sample dilution. The principles are illustrated by selected references to an available online tutorial http://www.flowinjectiontutorial,com/. PMID:27343609

  12. Stacking in a continuous sample flow interface in capillary electrophoresis.

    PubMed

    Gstoettenmayr, Daniel; Quirino, Joselito; Ivory, Cornelius F; Breadmore, Michael

    2015-08-21

    Using a tee connector in a commercial capillary electrophoresis instrument, the effect of field amplified sample injection from both flowing and static sample volumes was investigated. It is shown that under identical conditions (40min electrokinetic injection at 5kV from a sample volume of 295μL) the limit of detection using the continuous sample flow interface is 4 times lower than from a static vial. The relationship between different flow rates and injection voltages on the injected sample amount was also investigated using a 2D axisymmetric simulation (COMSOL 4.3b) and verified experimentally, confirming conditions under which there is near-quantitative injection of the sample target ions. Using electrokinetic injection at 30kV and a flow rate of 558nL/s the same enhancement from an even smaller volume of 184μL could be achieved in 5.5min than could be achieved from 295μL and a 40min injection. This sensitivity enhancement factor corresponded to four orders of magnitude improvement compared to a hydrodynamic injection. This is the first report showing that a continuous sample flow interface combined with stacking methods under conditions approaching quantitative injection from the entire sample volume has the potential to be more sensitive than a static system. PMID:26189205

  13. Visualization periodic flows in a continuously stratified fluid.

    NASA Astrophysics Data System (ADS)

    Bardakov, R.; Vasiliev, A.

    2012-04-01

    To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken

  14. Rapid protein immobilization for thin film continuous flow biocatalysis.

    PubMed

    Britton, Joshua; Raston, Colin L; Weiss, Gregory A

    2016-08-01

    A versatile enzyme immobilization strategy for thin film continuous flow processing is reported. Here, non-covalent and glutaraldehyde bioconjugation are used to immobilize enzymes on the surfaces of borosilicate reactors. This approach requires only ng of protein per reactor tube, with the stock protein solution readily recycled to sequentially coat >10 reactors. Confining reagents to thin films during immobilization reduced the amount of protein, piranha-cleaning solution, and other reagents by ∼96%. Through this technique, there was no loss of catalytic activity over 10 h processing. The results reported here combines the benefits of thin film flow processing with the mild conditions of biocatalysis. PMID:27461146

  15. Immersed boundary-finite element model of fluid-structure interaction in the aortic root

    NASA Astrophysics Data System (ADS)

    Flamini, Vittoria; DeAnda, Abe; Griffith, Boyce E.

    2016-04-01

    It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe a fluid-structure interaction model of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employs a version of Peskin's immersed boundary (IB) method with a finite element description of the structural elasticity. As in earlier work, we use a fiber-based model of the valve leaflets, but this study extends earlier IB models of the aortic root by employing an incompressible hyperelastic model of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backward displacement method that determines the unloaded configuration of the root model. Our model yields realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations indicate that although the detailed leaflet and root kinematics show some grid sensitivity, our IB model of the aortic root nonetheless produces essentially grid-converged flow rates and pressures at practical grid spacings for the high Reynolds number flows of the aortic root. These results thereby clarify minimum grid resolutions required by such models when used as stand-alone models of the aortic valve as well as when used to provide models of the outflow valves in models of left-ventricular fluid dynamics.

  16. Compartmentalized Droplets for Continuous Flow Liquid-Liquid Interface Catalysis.

    PubMed

    Zhang, Ming; Wei, Lijuan; Chen, Huan; Du, Zhiping; Binks, Bernard P; Yang, Hengquan

    2016-08-17

    To address the limitations of batch organic-aqueous biphasic catalysis, we develop a conceptually novel method termed Flow Pickering Emulsion, or FPE, to process biphasic reactions in a continuous flow fashion. This method involves the compartmentalization of bulk water into micron-sized droplets based on a water-in-oil Pickering emulsion, which are packed into a column reactor. The compartmentalized water droplets can confine water-soluble catalysts, thus "immobilizing" the catalyst in the column reactor, while the interstices between the droplets allow the organic (oil) phase to flow. Key fundamental principles underpinning this method such as the oil phase flow behavior, the stability of compartmentalized droplets and the confinement capability of these droplets toward water-soluble catalysts are experimentally and theoretically investigated. As a proof of this concept, case studies including a sulfuric acid-catalyzed addition reaction, a heteropolyacid-catalyzed ring opening reaction and an enzyme-catalyzed chiral reaction demonstrate the generality and versatility of the FPE method. Impressively, in addition to the excellent durability, the developed FPE reactions exhibit up to 10-fold reaction efficiency enhancement in comparison to the existing batch reactions, indicating a unique flow interface catalysis effect. This study opens up a new avenue to allow conventional biphasic catalysis reactions to access more sustainable and efficient flow chemistry using an innovative liquid-liquid interface protocol. PMID:27429173

  17. Continuous-flow sheathless diamagnetic particle separation in ferrofluids

    NASA Astrophysics Data System (ADS)

    Zhou, Yilong; Song, Le; Yu, Liandong; Xuan, Xiangchun

    2016-08-01

    Separating particles from a complex mixture is often necessary in many chemical and biomedical applications. This work presents a continuous-flow sheathless diamagnetic particle separation in ferrofluids through U-shaped microchannels. Due to the action of a size-dependent magnetic force, diamagnetic particles are focused into a single stream in the inlet branch of the U-turn and then continuously separated into two streams in its outlet branch. A 3D numerical model is developed to predict and understand the diamagnetic particle transport during this separation process. The numerical predictions are found to agree well with the experimental observations in a systematic study of the effects of multiple parameters including ferrofluid flow rate, concentration and magnet-channel distance. Additional numerical studies of the geometric effects of the U-turn reveal that increasing the outlet-branch width of the U-turn can significantly enhance the diamagnetic particle separation in ferrofluids.

  18. Continuous-Flow N-Heterocyclic Carbene Generation and Organocatalysis.

    PubMed

    Di Marco, Lorenzo; Hans, Morgan; Delaude, Lionel; Monbaliu, Jean-Christophe M

    2016-03-18

    Two methods were assessed for the generation of common N-heterocyclic carbenes (NHCs) from stable imidazol(in)ium precursors using convenient and straightforward continuous-flow setups with either a heterogeneous inorganic base (Cs2 CO3 or K3 PO4 ) or a homogeneous organic base (KN(SiMe3 )2 ). In-line quenching with carbon disulfide revealed that the homogeneous strategy was most efficient for the preparation of a small library of NHCs. The generation of free nucleophilic carbenes was next telescoped with two benchmark NHC-catalyzed reactions; namely, the transesterification of vinyl acetate with benzyl alcohol and the amidation of N-Boc-glycine methyl ester with ethanolamine. Both organocatalytic transformations proceeded with total conversion and excellent yields were achieved after extraction, showcasing the first examples of continuous-flow organocatalysis with NHCs. PMID:26880372

  19. Anaerobic dehalogenation of TCE in continuous flow systems

    SciTech Connect

    Singhal, N. |; Jaffe, P.; Maier, W.

    1995-12-31

    This study focuses on the effect of various factors on trichloroethene (TCE) degradation in batch and continuous flow systems, develops mathematical models to describe the dehalogenation of TCE, and provides results of simulations conducted using these models to determine the conditions necessary for maximizing the degradation of TCE. Batch parameters were shown to underpredict substrate and TCE degradation in continuous flow systems. The active biomass concentration had the most significant effect on TCE degradation. TCE degradation may be enhanced in the field by changing the substrate injection pattern to result in a more uniform distribution of the substrate. Gas production under anaerobic conditions needs to be included in any model describing TCE degradation in the field; ignoring this effect can result in gross overpredictions of TCE degradation by the model.

  20. Continuous-flow Electrokinetic Particle Separation in a Bifurcating Microchannel

    NASA Astrophysics Data System (ADS)

    Li, Di; Lu, Xinyu; Xuan, Xiangchun

    Separating particles from a heterogeneous mixture is important and necessary in many engineering and biomedical applications. Electrokinetic flow-based continuous particle separation has so far been realized primarily by the use of particle dielectrophoresis induced in constricted and/or curved microchannels. We demonstrate in this talk that particles can be continuously separated by size when passing through a bifurcating microchannel. This sheathless label-free separation relies on the wall-induced electrical lift force that acts to focus particles to the center of the main-branch and deflect them to size-dependent flow paths in the two side-branches. We also develop a numerical model to predict and understand this separation.

  1. Comparison of continuous-flow and pulsatile-flow left ventricular assist devices: is there an advantage to pulsatility?

    PubMed Central

    Cheng, Allen; Williamitis, Christine A.

    2014-01-01

    Background Continuous-flow left ventricular assist devices (CFVAD) are currently the most widely used type of mechanical circulatory support as bridge-to-transplant and destination therapy for end-stage congestive heart failure (HF). Compared to the first generation pulsatile-flow left ventricular assist devices (PFVADs), CFVADs have demonstrated improved reliability and durability. However, CFVADs have also been associated with certain complications thought to be linked with decreased arterial pulsatility. Previous studies comparing CFVADs and PFVADs have presented conflicting results. It is important to understand the outcome differences between CFVAD and PFVAD in order to further advance the current VAD technology. Methods In this review, we compared the outcomes of CFVADs and PFVADs and examined the need for arterial pulsatility for the future generation of mechanical circulatory support. Results CVADs offer advantages of smaller size, increased reliability and durability, and subsequent improvements in survival. However, with the increasing duration of long-term support, it appears that CFVADs may have specific complications and a lower rate of left ventricular recovery associated with diminished pulsatility, increased pressure gradients on the aortic valve and decreased compliance in smaller arterial vessels. PFVAD support or pulsatility control algorithms in CFVADs could be beneficial and potentially necessary for long term support. Conclusions Given the relative advantages and disadvantages of CFVADs and PFVADs, the ultimate solution may lie in incorporating pulsatility into current and emerging CFVADs whilst retaining their existing benefits. Future studies examining physiologic responses, end-organ function and LV remodeling at varying degrees of pulsatility and device support levels are needed. PMID:25512897

  2. Method and apparatus for continuous flow injection extraction analysis

    DOEpatents

    Hartenstein, Steven D.; Siemer, Darryl D.

    1992-01-01

    A method and apparatus for a continuous flow injection batch extraction aysis system is disclosed employing extraction of a component of a first liquid into a second liquid which is a solvent for a component of the first liquid, and is immiscible with the first liquid, and for separating the first liquid from the second liquid subsequent to extraction of the component of the first liquid.

  3. Flow lasers. [fluid mechanics of high power continuous output operations

    NASA Technical Reports Server (NTRS)

    Christiansen, W. H.; Russell, D. A.; Hertzberg, A.

    1975-01-01

    The present work reviews the fluid-mechanical aspects of high-power continuous-wave (CW) lasers. The flow characteristics of these devices appear as classical fluid-mechanical phenomena recast in a complicated interactive environment. The fundamentals of high-power lasers are reviewed, followed by a discussion of the N2-CO2 gas dynamic laser. Next, the HF/DF supersonic diffusion laser is described, and finally the CO electrical-discharge laser is discussed.

  4. Estimation of the minimum pump speed to prevent regurgitation in the continuous flow left ventricular assist device: left ventricular drainage versus left atrial drainage.

    PubMed

    Tayama, E; Ohashi, Y; Niimi, Y; Takami, Y; Ohtsuka, G; Benkowski, R; Glueck, J A; Nosé, Y

    1997-12-01

    Due to the fact that centrifugal and axial pumps do not require valves, there is a possibility of back flow when the pump speed is low. To estimate the minimum required pump speed to prevent this regurgitation, an in vitro simulation test was conducted. A pulsatile pump simulated the natural heart while a centrifugal pump simulated the continuous flow left ventricular assist device (LVAD). The LVAD flow was attained from the left atrial (LA) drainage or left ventricular (LV) drainage. The minimum or regurgitate flow was observed in the systolic phase with LA drainage and in the diastolic phase with LV drainage. LV drainage always provided higher flow than LA drainage at the same pump speed. These differences are due to the various total pressure heads of the LVAD. To prevent the regurgitation, the LVAD should maintain a certain pump speed which can create positive flow against the aortic systolic pressure with LA drainage and against the aortic diastolic pressure with LV drainage. These required pump speeds can be identified by the LVAD flow-pressure curve. PMID:9423981

  5. Apparatus for irradiating a continuously flowing stream of fluid

    DOEpatents

    Speir, Leslie G.; Adams, Edwin L.

    1984-01-01

    An apparatus for irradiating a continuously flowing stream of fluid is diosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4.pi. radiation geometry. The irradiation source, for example a .sup.252 CF neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

  6. Changes in luminal flow rate modulate basal and bradykinin-stimulated cell [Ca2+] in aortic endothelium.

    PubMed

    Oliver, J A; Chase, H S

    1992-04-01

    Hemodynamic forces influence many endothelial cell functions. The coupling between hemodynamic forces and cell function could be mediated by mechano-sensitive ion channels present in the plasma membrane of endothelial cells. Because one of these channels is permeable to Ca2+, we tested whether hemodynamic forces influence endothelial cell Ca2+ ([Ca2+]i). Bovine aortic endothelial cells were grown inside cylindrical glass tubes, loaded with fura-2, and perfused at different pressures and flow rates on the stage of a fluorescence microscope. Decreasing flow from 110 to 2 ml.min-1 raised [Ca2+]i from 57 +/- 11 to 186 +/- 29 nM (mean +/- SEM, p less than 0.01) by increasing the entry of extracellular Ca2+ into the cytoplasm. Increasing flow from 2 to 110 ml.min-1 transiently decreased [Ca2+]i from 62 +/- 3 to 33 +/- 5 nM (p less than 0.01) apparently due to reduced Ca2+ entry and concomitant extrusion by the plasma membrane Ca(2+)-ATPase. The rise in [Ca2+]i induced by bradykinin was magnified during a decrease in flow; in control cells, 10(-7) M bradykinin increased [Ca2+]i by 162 +/- 26 nM, whereas [Ca2+]i increased 350 +/- 67 nM (p less than 0.05) in cells previously exposed to 110 ml.min-1. These observations suggest that flow-induced changes in [Ca2+]i might be a signal-transduction mechanism for endothelial functions responsive to hemodynamic forces and may also modulate the magnitude of hormonally mediated increases in [Ca2+]i. PMID:1313820

  7. Patterned Periodic Nanofilter Array for Continuous-Flow Bimolecular Separation

    NASA Astrophysics Data System (ADS)

    Fu, Jianping; Han, Jongyoon

    2006-03-01

    We present an experimental study on sieving process of small biomolecules (i.e., proteins and small DNAs) in one- and two-dimensional periodic arrays of nanofilter. The nanofilters served as artificial sieves with precise pore size characterization and showed exceptional size selectivity and separation efficiency from the periodicity of the environment. A kinetic model is developed to explain the electrophoretic drift of charged molecules across periodically modulated free energy landscapes. Further experimental evidence shows the crossover from Ogston-like sieving to entropic trapping mechanism depending on nanofilter thickness and on electric field strength. We also demonstrate continuous-flow biomolecule separation with a device containing of two-dimensional periodic nanofilter arrays. The interaction between migrating molecules and the two-dimensional physical landscapes cause molecules of different sizes to follow radically different paths leading to separation. Continuous-flow fractionations of small DNA molecules (50bp-766bp) as well as SDS-protein complexes (11kDa-200kDa) were achieved in about 5 minutes with a resolution of 10%. By virtue of its gel-free and continuous-flow operation, this device suggests himself a key component to an integrated biomolecule sample preparation and analysis microsystem.

  8. Control of continuous polyhydroxybutyrate synthesis using calorimetry and flow cytometry.

    PubMed

    Maskow, Thomas; Müller, Susann; Lösche, Andreas; Harms, Hauke; Kemp, Richard

    2006-02-20

    The substrate-carbon flow can be controlled in continuous bioreactor cultures by the medium composition, for example, by the C/N ratio. The carbon distribution is optimal when a maximum fraction flows into the desired product and the residual is just sufficient to compensate for the dilution of the microbial catalyst. Undershooting of the latter condition is reflected immediately by changes in the Gibbs energy dissipation and cellular states. Two calorimetric measurement principles were applied to optimize the continuous synthesis of polyhydroxybutyrate (PHB) by Variovorax paradoxus DSM4065 during growth with constantly increasing supply rates of fructose or toxic phenol. Firstly, the changed slope of the heat production rate in a complete heat balanced bioreactor (CHB) indicated optimum carbon channeling into PHB. The extent of the alteration depended directly on the toxic properties of the substrate. Secondly, a flow through calorimeter was connected with the bioreactor as a "measurement loop." The optimum substrate carbon distribution was indicated by a sudden change in the heat production rate independent of substrate toxicity. The sudden change was explained mathematically and exploited for the long-term control of phenol conversion into PHB. LASER flow cytometry measurements distinguished between subpopulations with completely different PHB-content. Populations grown on fructose preserved a constant ratio of two subpopulations with double and quadruple sets of DNA. Cells grown on phenol comprised a third subpopulation with a single DNA set. Rising phenol concentrations caused this subpopulation to increase. It may thus be considered as an indicator of chemostress. PMID:16245347

  9. Intra-aortic balloon pumping reduces the increased arterial load caused by acute cardiac depression, modifying central and peripheral load determinants in a time- and flow-related way.

    PubMed

    Bia, Daniel; Cabrera-Fischer, Edmundo I; Zócalo, Yanina; Armentano, Ricardo L

    2012-09-01

    The mechanisms that explain intra-aortic balloon pumping (IABP) effects are not completely understood, and attributing them only to pressure-associated changes in cardiac function would be an oversimplification. Since IABP modifies the aortic and systemic blood-flow pattern, flow-related effects could be expected. To characterize effects of acute heart failure (AHF) on the arterial biomechanics; IABP effects on the arterial biomechanics during AHF, and their potential time-dependence; the association between hemodynamics and biomechanical changes during AHF and IABP. Sheep (n = 6) aortic pressure, flow, and diameter were measured: (1) before (Basal) and (2) 1-3 (HF(1-3)) and 28-30 (HF(28-30)) min after starting halothane to induce AHF; and (3) at specific times (1-3, 14-15 and 28-30 min) during IABP assistance. Calculus: aortic characteristic impedance (Z(c)), beta stiffness (β), incremental (E(INC)) and pressure-strain elastic modulus (E(P)); total arterial compliance (C(G)), total systemic vascular resistance and wave propagation parameters. (1) AHF resulted in an acute increase in aortic and systemic stiffness (HF(28-30) % changes with respect to Basal conditions: β +217%, E (P) +143%, E(INC) +101%, Z(c) +52%, C(G) -13%), associated with the reduction in the aortic blood flow; (2) during AHF IABP resulted in acute beneficial changes aortic and systemic biomechanics (% changes in IABP(1-3) with respect HF(28-30): β -62%, E(P) -68%, E (INC) -66%, Z(c) -38%, C(G) 66%), and in wave propagation parameters, (3) IABP-related changes were time-dependent and associated with changes in aortic blood flow. Aortic and systemic biomechanical and impedance properties are detrimentally modified during AHF, being the changes rapidly reverted during IABP. IABP-related beneficial changes in arterial biomechanics were time-dependent and associated with IABP capability to increase blood flow. PMID:22068608

  10. [Safe and Effective Analgesia with Bilateral Continuous TAP Block for a Patient with Marfan Syndrome after Open Abdominal Aortic Aneurysm Repair].

    PubMed

    Katakura, Yumi; Sakurai, Asako; Endo, Masaru; Hamada, Takako; Nomoto, Mayuko; Yamada, Hiroshi; Takeda, Koji

    2016-06-01

    A patient with Marfan syndrome underwent emergency open abdominal aortic aneurysm repair. She was referred to our department for postoperative analgesia. Taking the risk of possible dural ectasia into consideration, we avoided epidural block. Alternatively, we performed bilateral continuous transversus abdominis plane (TAP) block with sufficient analgesia. Lumbosacral dural ectasia is frequently observed in patients with Marfan syndrome. A few reports described that their fragile dura may contribute to an increased risk of dural puncture and postdural puncture headache (PDPH). Thus, in planning neuraxial block for a patient with Marfan syndrome, the possible consequences of lumbosacral dural ectasia should be considered. A case we herein present shows bilateral continuous TAP block could be a safe and effective alternative to epidural block. PMID:27483660

  11. [Stent Grafting for Aortic Dissection].

    PubMed

    Uchida, Naomichi

    2016-07-01

    The purpose of stent graft for aortic dissection is to terminate antegrade blood flow into the false lumen through primary entry. Early intervention for primary entry makes excellent aortic remodeling and emergent stent grafting for complicated acute type B aortic dissection is supported as a class I. On the other hand stent grafting for chronic aortic dissection is controversial. Early stent grafting is considered with in 6 months after on-set if the diameter of the descending aorta is more than 40 mm. Additional interventions for residual false lumen on the downstream aorta are still required. Stent graft for re-entry, candy-plug technique, and double stenting, other effective re-interventions were reported. Best treatment on the basis of each anatomical and physical characteristics should be selected in each institution. Frozen elephant trunk is alternative procedure for aortic dissection without the need to take account of proximal anatomical limitation and effective for acute type A aortic dissection. PMID:27440026

  12. Visualization and finite element analysis of pulsatile flow in models of the abdominal aortic aneurysm.

    PubMed

    Fukushima, T; Matsuzawa, T; Homma, T

    1989-01-01

    Pulsatile flows in glass models simulating fusiform and lateral saccular aneurysms were investigated by a flow visualization method. When resting fluid starts to flow, the initial fluid motion is practically irrotational. After a short period of time, the flow began to separate from the proximal wall of the aneurysm. Then the separation bubble or vortex grew rapidly in size and filled the whole area of the aneurysm circumferentially. During this period of time, the center of the vortex moved from the proximal end to the distal point of the aneurysm. The transient reversal flow, for instance, which may occur at the end of the ejection period, passed between the wall of the aneurysm and the centrally located vortex. When the rate and pulsatile frequency of flow were high, the vortex broke down into highly disturbed flow (or turbulence) at the distal portion of the aneurysm. The same effect was observed when the length of the aneurysm was increased. A reduction in pulsatile amplitude made the flow pattern close to that in steady flow. A finite element analysis was made to obtain velocity and pressure fields in pulsatile flow through a tube with an axisymmetric expansion. Calculations were performed with the pulsatile flows used in the visualization experiment in order to study the effects of change in the pulsatile wave form by keeping the time-mean Reynolds number and Womersley's parameter unchanged. Calculated instantaneous patterns of velocity field and stream lines agreed well with the experimental results. The appearance and disappearance of the vortex in the dilated portion and its development resulted in complex distributions of pressure and shear fields. Locally minimum and maximum values of wall shear stress occurred at points just upstream and downstream of the distal end of the expansion when the flow rate reached its peak. PMID:2605323

  13. Some aspects of continuous flow electrophoresis in microgravity

    NASA Astrophysics Data System (ADS)

    Biscans, B.; Hennequin, J. C.; Bertrand, J.

    Zone electrophoresis is a highly efficient method of separating biological products. It is based on the differences of mobilities of ionized particles in an electric field. During the separation complications arise due to electro-osmosis or thermal convection generated by Joule heating. This paper analyses the hydrodynamical running of a continuous flow zone electrophoresis cell and shows the influence of specific parameters on the separation. The modelling of the flow structure of the buffer solution is developed. The equations and the corresponding boundary conditions are solved by finite difference method. The model established provides knowledge of the hydrodynamical perturbations generated by electro-osmosis and thermal free convection. The case of microgravity is considered.

  14. Comparison of continuous and discontinuous discretizations for the Stokes flow

    NASA Astrophysics Data System (ADS)

    Lehmann, Ragnar; Kaus, Boris J. P.; Lukáčová-Medvid'ová, Maria

    2013-04-01

    Finite element methods (FEM) of various types are widely used to solve incompressible flow problems in general and Stokes flow in particular. We present first results of a study comparing two numerical methods: the continuous Galerkin and the discontinuous Galerkin (DG) method. For this purpose a Matlab code was developed employing 2D Stokes flow in a model setup with known analytical solution. [2] Nonlinearities of, e.g., the viscosity can lead to discontinuities in the velocity-pressure solution. Hence, using continuous approximations may result in avoidable inaccuracies. In contrast to the FEM, the DG method allows for discontinuities of velocity and pressure across interior mesh edges. This increases the number of degrees of freedom by a constant factor depending on the chosen element. A parameter is introduced to penalize the jumps in the velocity. The DG method provides the capability to locally adapt the polynomial degree of the shape functions. Moreover, it only needs communication between directly adjacent mesh cells, which makes it highly flexible and easy to parallelize. The velocity and pressure errors of the methods are measured in the L1-norm [1]. Orders of convergence are determined and compared. [1] Duretz, T., May, D.A., Garya, T.V. and Tackley, P.J., 2011. Discretization errors and free surface stabilization in the finite difference and marker-in-cell method for applied geodynamics: A numerical Study, Geochem. Geophys. Geosyst., 12, Q07004, doi:10.1029/2011GC003567. [2] Zhong, S., 1996. Analytic solution for Stokes' flow with lateral variations in viscosity, Geophys. J. Int., 124, 18-128, doi:10.1111/j.1365-246X.1996.tb06349.x.

  15. The effect of small temperature gradients on flow in a continuous flow electrophoresis chamber

    NASA Technical Reports Server (NTRS)

    Rhodes, P. H.; Snyder, R. S.

    1982-01-01

    Continuous flow electrophoresis employs an electric field to separate biological cells suspended in a flowing liquid buffer solution. Good separations based on differences in electrophoretic mobility are obtained only when a unidirectional flow is maintained. The desired flow has a parabolic structure in the narrow dimension of the chamber and is uniform acros the width, except near the edges where the no-slip condition prevails. However, because of buoyancy, very small laterall or axial temperature gradients deform the flow significantly. The results of experiments conducted with a specially instrumented chamber show the origin and structure of the buoyancy-driven perturbations. It is found that very small temperature gradients can disturb the flow significantly, as was predicted by earlier theoretical work.

  16. Method and apparatus for chemically altering fluids in continuous flow

    DOEpatents

    Heath, W.O.; Virden, J.W. Jr.; Richardson, R.L.; Bergsman, T.M.

    1993-10-19

    The present invention relates to a continuous flow fluid reactor for chemically altering fluids. The reactor operates on standard frequency (50 to 60 Hz) electricity. The fluid reactor contains particles that are energized by the electricity to form a corona throughout the volume of the reactor and subsequently a non-equilibrium plasma that interacts with the fluid. Particles may form a fixed bed or a fluid bed. Electricity may be provided through electrodes or through an inductive coil. Fluids include gases containing exhaust products and organic fuels requiring oxidation. 4 figures.

  17. Method and apparatus for chemically altering fluids in continuous flow

    DOEpatents

    Heath, William O.; Virden, Jr., Judson W.; Richardson, R. L.; Bergsman, Theresa M.

    1993-01-01

    The present invention relates to a continuous flow fluid reactor for chemically altering fluids. The reactor operates on standard frequency (50 to 60 Hz) electricity. The fluid reactor contains particles that are energized by the electricity to form a corona throughout the volume of the reactor and subsequently a non-equilibrium plasma that interacts with the fluid. Particles may form a fixed bed or a fluid bed. Electricity may be provided through electrodes or through an inductive coil. Fluids include gases containing exhaust products and organic fuels requiring oxidation.

  18. Continuous-flow thermolysis for the preparation of vinylglycine derivatives.

    PubMed

    Lamborelle, Nicolas; Simon, Justine F; Luxen, André; Monbaliu, Jean-Christophe M

    2015-12-28

    Syn sulfoxide elimination was carried out under continuous-flow conditions in a mesofluidic thermolysis reactor. The design of the reactor enabled accurate control of reaction time and conditions, affording a convenient scale-independent procedure for the production of N,C-protected vinylglycine derivatives. Thermolysis at 270 °C under 1000 psi of pressure in superheated toluene enabled typical daily outputs ranging from 11 to 46 g per day with excellent selectivities and ee (>97%). The various competitive reaction pathways were studied and rationalized according to a computational study. PMID:26552900

  19. Graphene-based battery electrodes having continuous flow paths

    DOEpatents

    Zhang, Jiguang; Xiao, Jie; Liu, Jun; Xu, Wu; Li, Xiaolin; Wang, Deyu

    2014-05-24

    Some batteries can exhibit greatly improved performance by utilizing electrodes having randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the electrode. The network of channels can provide a diffusion pathway for the liquid electrolyte and/or for reactant gases. Metal-air batteries can benefit from such electrodes. In particular Li-air batteries show extremely high capacities, wherein the network of channels allow oxygen to diffuse through the electrode and mesopores in the electrode can store discharge products.

  20. A Simple Chaotic Flow with a Continuously Adjustable Attractor Dimension

    NASA Astrophysics Data System (ADS)

    Munmuangsaen, Buncha; Sprott, Julien Clinton; Thio, Wesley Joo-Chen; Buscarino, Arturo; Fortuna, Luigi

    This paper describes two simple three-dimensional autonomous chaotic flows whose attractor dimensions can be adjusted continuously from 2.0 to 3.0 by a single control parameter. Such a parameter provides a means to explore the route through limit cycles, period-doubling, dissipative chaos, and eventually conservative chaos. With an absolute-value nonlinearity and certain choices of parameters, the systems have a vast and smooth continual transition path from dissipative chaos to conservative chaos. One system is analyzed in detail by means of the largest Lyapunov exponent, Kaplan-Yorke dimension, bifurcations, coexisting attractors and eigenvalues of the Jacobian matrix. An electronic version of the system has been constructed and shown to perform in accordance with expectations.

  1. A continuous-flow process for the synthesis of artemisinin.

    PubMed

    Kopetzki, Daniel; Lévesque, François; Seeberger, Peter H

    2013-04-22

    Isolation of the most effective antimalarial drug, artemisinin, from the plant sweet wormwood, does not yield sufficient quantities to provide the more than 300 million treatments needed each year. The high prices for the drug are a consequence of the unreliable and often insufficient supply of artemisinin. Large quantities of ineffective fake drugs find a market in Africa. Semisynthesis of artemisinin from inactive biological precursors, either dihydroartemisinic acid (DHAA) or artemisinic acid, offers a potentially attractive route to increase artemisinin production. Conversion of the plant waste product, DHAA, into artemisinin requires use of photochemically generated singlet oxygen at large scale. We met this challenge by developing a one-pot photochemical continuous-flow process for the semisynthesis of artemisinin from DHAA that yields 65 % product. Careful optimization resulted in a process characterized by short residence times. A method to extract DHAA from the mother liquor accumulated during commercial artemisinin extractions, a material that is currently discarded as waste, is also reported. The synthetic continuous-flow process described here is an effective means to supplement the limited availability of artemisinin and ensure increased supplies of the drug for those in need. PMID:23520059

  2. Continuous-Flow Bioseparation Using Microfabricated Anisotropic Nanofluidic Sieving Structures

    PubMed Central

    Fu, Jianping; Mao, Pan; Han, Jongyoon

    2010-01-01

    The anisotropic nanofluidic filter (nanofilter) array (ANA) is a unique molecular sieving structure for separating biomolecules. Here we describe fabrication of planar and vertical ANA chips and how to perform continuous-flow bioseparation using them. This protocol is most useful for bioengineers that are interested in developing automated multistep chip-based bioanalysis systems and assumes prior cleanroom microfabrication knowledge. The ANA consists of a two-dimensional periodic nanofilter array, and the designed structural anisotropy of the ANA causes different sized- or charged-biomolecules to follow distinct trajectories under applied electric fields, leading to efficient continuous-flow separation. Using microfluidic channels surrounding the ANA, the fractionated biomolecule streams are collected and routed to different fluid channels or reservoirs for convenient sample recovery and downstream bioanalysis. The ANA is physically robust and can be reused repeatedly. Compared to conventional gel-based separation techniques, the ANA offers the potential for faster separation, higher throughput, and more convenient sample recovery. PMID:19876028

  3. Continuous flow system for controlling phases separation near λ transition

    SciTech Connect

    Chorowski, M.; Poliński, J.; Kempiński, W.; Trybuła, Z.; Łoś, Sz.; Chołast, K.; Kociemba, A.

    2014-01-29

    As demands on 3He are increasing and conventional 3He production through tritium decay is decreasing, alternative 3He production methods are becoming economically viable. One such possibility is to use entropy filters for extraction of the 3He isotope from natural gas. According to the phase diagram of the 3He, its solidification is impossible by only lowering of the temperature. Hence during the cooling process at stable pressure we can reach λ-point and pass to the special phase - He II. The total density of HeII is a sum of the two phases: normal the superfluid ones. It is possible to separate these two phases with an entropy filter - the barrier for the classically-behaving normal phase. This barrier can also be used to separate the two main isotopes of He: 4He and 3He, because at temperatures close to the 4He-λ-point the 3He isotope is part of the normal phase. The paper presents continuous flow schemes of different separation methods of 3He from helium commodity coming from natural gas cryogenic processing. An overall thermodynamic efficiency of the 3He/4He separation process is presented. A simplified model of continuous flow HeI -HeII recuperative heat exchanger is given. Ceramic and carbon porous plugs have been tested in entropy filter applications.

  4. Continuous flow aerobic granular sludge reactor for dairy wastewater treatment.

    PubMed

    Bumbac, C; Ionescu, I A; Tiron, O; Badescu, V R

    2015-01-01

    The focus of this study was to assess the treatment performance and granule progression over time within a continuous flow reactor. A continuous flow airlift reactor was seeded with aerobic granules from a laboratory scale sequencing batch reactor (SBR) and fed with dairy wastewater. Stereomicroscopic investigations showed that the granules maintained their integrity during the experimental period. Laser diffraction investigation showed proof of new granules formation with 100-500 μm diameter after only 2 weeks of operation. The treatment performances were satisfactory and more or less similar to the ones obtained from the SBR. Thus, removal efficiencies of 81-93% and 85-94% were observed for chemical oxygen demand and biological oxygen demand, respectively. The N-NH(+)(4) was nitrified with removal efficiencies of 83-99% while the nitrate produced was simultaneously denitrified - highest nitrate concentration determined in the effluent was 4.2 mg/L. The removal efficiency of total nitrogen was between 52 and 80% depending on influent nitrogen load (39.3-76.2 mg/L). Phosphate removal efficiencies ranged between 65 and above 99% depending on the influent phosphate concentration, which varied between 11.2 and 28.3 mg/L. PMID:25714645

  5. Hydrothermal Processing of Macroalgal Feedstocks in Continuous-Flow Reactors

    SciTech Connect

    Elliott, Douglas C.; Hart, Todd R.; Neuenschwander, Gary G.; Rotness, Leslie J.; Roesijadi, Guri; Zacher, Alan H.; Magnuson, Jon K.

    2014-02-03

    Wet macroalgal slurries have been converted into a biocrude by hydrothermal liquefaction (HTL) in a bench-scale continuous-flow reactor system. Carbon conversion to a gravity-separable oil product of 58.8% was accomplished at relatively low temperature (350 °C) in a pressurized (subcritical liquid water) environment (20 MPa) when using feedstock slurries with a 21.7% concentration of dry solids. As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent, and biomass trace mineral components were removed by processing steps so that they did not cause processing difficulties. In addition, catalytic hydrothermal gasification (CHG) was effectively applied for HTL byproduct water cleanup and fuel gas production from water-soluble organics. Conversion of 99.2% of the carbon left in the aqueous phase was demonstrated. Finally, as a result, high conversion of macroalgae to liquid and gas fuel products was found with low levels of residual organic contamination in byproduct water. Both process steps were accomplished in continuous-flow reactor systems such that design data for process scale-up was generated.

  6. High Resolution Continuous Flow Analysis System for Polar Ice Cores

    NASA Astrophysics Data System (ADS)

    Dallmayr, Remi; Azuma, Kumiko; Yamada, Hironobu; Kjær, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

    2014-05-01

    In the last decades, Continuous Flow Analysis (CFA) technology for ice core analyses has been developed to reconstruct the past changes of the climate system 1), 2). Compared with traditional analyses of discrete samples, a CFA system offers much faster and higher depth resolution analyses. It also generates a decontaminated sample stream without time-consuming sample processing procedure by using the inner area of an ice-core sample.. The CFA system that we have been developing is currently able to continuously measure stable water isotopes 3) and electrolytic conductivity, as well as to collect discrete samples for the both inner and outer areas with variable depth resolutions. Chemistry analyses4) and methane-gas analysis 5) are planned to be added using the continuous water stream system 5). In order to optimize the resolution of the current system with minimal sample volumes necessary for different analyses, our CFA system typically melts an ice core at 1.6 cm/min. Instead of using a wire position encoder with typical 1mm positioning resolution 6), we decided to use a high-accuracy CCD Laser displacement sensor (LKG-G505, Keyence). At the 1.6 cm/min melt rate, the positioning resolution was increased to 0.27mm. Also, the mixing volume that occurs in our open split debubbler is regulated using its weight. The overflow pumping rate is smoothly PID controlled to maintain the weight as low as possible, while keeping a safety buffer of water to avoid air bubbles downstream. To evaluate the system's depth-resolution, we will present the preliminary data of electrolytic conductivity obtained by melting 12 bags of the North Greenland Eemian Ice Drilling (NEEM) ice core. The samples correspond to different climate intervals (Greenland Stadial 21, 22, Greenland Stadial 5, Greenland Interstadial 5, Greenland Interstadial 7, Greenland Stadial 8). We will present results for the Greenland Stadial -8, whose depths and ages are between 1723.7 and 1724.8 meters, and 35.520 to

  7. A custom-made scalloped stentgraft to preserve left subclavian artery flow in descending thoracic aortic disease with a short neck.

    PubMed

    Van Der Weijde, Emma; Bakker, Olaf J; Heijmen, Robin H

    2016-05-01

    In thoracic stentgrafting, a short proximal landing zone may necessitate intentional occlusion of the left subclavian artery, which may lead to brain, spinal cord, and left arm malperfusion. A scalloped stentgraft is designed for adequate proximal sealing and preserving the left subclavian artery flow. We performed a systematic review, describe the required pre-operative planning and details of the perioperative technique used and report our own experience. In literature, only 29 patients were reported so far using a proximal scalloped stentgraft. Results show a high technical success rate and low complication rate. These results are comparable to the results from our own institution. From these first small series the scalloped thoracic endovascular aortic repair appears to be a safe and relatively simple solution for thoracic aortic disease involving the left subclavian artery. PMID:27018248

  8. Numerical analysis of blood flow in the clearance regions of a continuous flow artificial heart pump.

    PubMed

    Anderson, J; Wood, H G; Allaire, P E; Olsen, D B

    2000-06-01

    The CFVAD3 is the third prototype of a continuous flow ventricular assist device being developed for implantation in humans. The pump consists of a fully shrouded 4-blade impeller supported by magnetic bearings. On either side of this suspended rotating impeller is a small clearance region through which the blood flows. The spacing and geometry of these clearance regions are very important to the successful operation of this blood pump. Computational fluid dynamics (CFD) solutions for this flow were obtained using TascFlow, a software package available from AEA Technology, U.K. Flow in these clearance regions was studied parametrically by varying the size of the clearance, the blood flow rate into the pump, and the rotational speed of the pump. The numerical solutions yield the direction and magnitude of the flow and the dynamic pressure. Experimentally measured pump flow rates are compared to the numerical study. The results of the study provide guidance for improving pump efficiency. It is determined that current clearances can be significantly reduced to improve pump efficiency without negative impacts. PMID:10886072

  9. Protein separation by continuous-flow electrophoresis in microgravity.

    PubMed

    Clifton, M J; Roux-de Balmann, H; Sanchez, V

    1996-07-01

    During the IML-2 space shuttle mission, the RAMSES instrument was operated in the Spacelab module. This continuous-flow electrophoresis device performs separation and purification of protein solutions on a preparative scale. Samples containing artificial mixtures of pure proteins were used to test the capabilities of the device, and useful separations were obtained for proteins having a mobility difference of only 3 x 10(-9) m2 V-1 s-1. Operating conditions that cannot be applied on earth were explored for two different sample concentrations, one of which is too high to allow treatment on earth. It agrees well with a previously published numerical model in that the main cause of loss in resolution in this process is the electrohydrodynamic spreading of the protein filaments. PMID:11539848

  10. Synthesis of phytochelatins by the continuous flow solid phase procedure.

    PubMed

    Chen, Z; Hemmasi, B

    1993-11-01

    A nona- and an undecapeptide corresponding to phytochelatins with the general structure H-[gamma-Glu-Cys]n-Gly-OH were each synthesized by the continuous flow solid phase method using two different methodologies. Fmoc-amino acid derivatives were used as precursors, and two different H2N-POE-PS supports were employed. Different procedures were used to remove Acm protecting groups from Cys residues. In a second synthesis, Acm groups were removed before cleavage of the peptides from the polymer supports. The partially protected peptides of the first synthesis were purified by preparative HPLC. The purity and identity of all the synthesized peptides were verified by analytical HPLC and IS-MS and in some cases by amino acid analysis. PMID:8292265

  11. Continuous flow ink etching for direct micropattern of silicon dioxide

    NASA Astrophysics Data System (ADS)

    Xing, Jiyao; Rong, Weibin; Wang, Lefeng; Sun, Lining

    2016-07-01

    A continuous flow ink etching (CFIE) method is presented to directly create micropatterns on a 60 nm thick silicon dioxide (SiO2) layer. This technique employs a micropipette filled with potassium bifluoride (KHF2) aqueous solution to localize SiO2 dissolution in the vicinity of the micropipette tip. Both dot and line features with well-defined edges were fabricated and used as hardmasks for silicon etching. The linear density of etchant ink deposited on the SiO2 can be used to regulate the depth, width and 2D morphology of the line pattern. The characterization of CFIE including the resolution (about 4 μm), reproducibility and capability to form complex structures are reported. This technique provides a simple and flexible alternative to generate the SiO2 hardmask for silicon microstructure fabrication.

  12. A Continuation and Bifurcation Technique for Navier-Stokes Flows

    NASA Astrophysics Data System (ADS)

    Sanchez, J.; Marques, F.; Lopez, J. M.

    2002-07-01

    An efficient numerical bifurcation and continuation method for the Navier-Stokes equations in cylindrical geometries is presented and applied to a nontrivial fluid dynamics problem, the flow in a cylindrical container driven by differential rotation. The large systems that result from discretizing the Navier-Stokes equations, especially in regimes where inertia is important, necessitate the use of iterative solvers which in turn need preconditioners. We use incomplete lower-upper decomposition (ILU) as an effective preconditioner for such systems and show the significant gain in efficiency when an incomplete LU of the full Jacobian is used instead of using only the Stokes operator. The computational cost, in terms of CPU time, grows with the size of the system (i.e., spatial resolution) according to a power law with exponent around 1.7, which is very modest compared to direct methods, indicating the appropriateness of the schemes for large nonlinear partial differential equation problems.

  13. Thermal and flow measurements of continuous cryogenic spray cooling.

    PubMed

    Hsieh, Shou-Shing; Tsai, Huang-Hsiu

    2006-07-01

    The performance of single sprays for high heat flux cooling using R-134a was studied. The heat flux and heat transfer coefficient at the surface of a sprayed jet based on measurements of steady-state temperature gradients on a thin copper plate during continuous spraying. Meanwhile, the spray droplets flow characteristics was also quantified through laser doppler velocimetry (LDV) measurements to obtain the local velocity distributions. The effects of mass flow rate and average droplet velocity, and spray exit-to-target distance on the surface heat flux including the corresponding critical heat flux (CHF) were explored through three different nozzle diameters of 0.2, 0.3, and 0.4 mm. Finally, the effective use of the fluid being delivered based on the cooling efficiency and cooling effectiveness was also examined. The relationship between CHF and nozzle performance in terms of cooling efficiency and cooling effectiveness was found. The heat transfer removal rate can reach up to 140 W/cm(2) for the present nozzle size of d (j)=0.2 and 0.3 mm, which may enhance the current cryogen spray cooling (CSC) technique that assists laser therapy of dermatoses. PMID:16598481

  14. Smart catheter flow sensor for real-time continuous regional cerebral blood flow monitoring

    NASA Astrophysics Data System (ADS)

    Li, Chunyan; Wu, Pei-Ming; Hartings, Jed A.; Wu, Zhizhen; Ahn, Chong H.; LeDoux, David; Shutter, Lori A.; Narayan, Raj K.

    2011-12-01

    We present a smart catheter flow sensor for real-time, continuous, and quantitative measurement of regional cerebral blood flow using in situ temperature and thermal conductivity compensation. The flow sensor operates in a constant-temperature mode and employs a periodic heating and cooling technique. This approach ensures zero drift and provides highly reliable data with microelectromechanical system-based thin film sensors. The developed flow sensor has a sensitivity of 0.973 mV/ml/100 g/min in the range from 0 to 160 ml/100 g/min with a linear correlation coefficient of R2 = 0.9953. It achieves a resolution of 0.25 ml/100 g/min and an accuracy better than 5 ml/100 g/min.

  15. Cr(VI) reduction in continuous-flow coculture bioreactor

    SciTech Connect

    Wang, Y.T.; Chirwa, E.M.; Shen, H.

    2000-04-01

    A continuous-flow coculture bioreactor with a phenol-degrading organism, Pseudomonas putida DMP-1, and a Cr(VI)-reducing species, Escherichia coli ATCC 33456, was developed for simultaneous removal of phenol and Cr(VI). Phenol was the sole energy and carbon source added to the coculture along with a basal medium and hexavalent chromium. The coculture bioreactor was operated under three liquid detention times (0.20, 0.31, and 0.52 days) with phenol and Cr(VI) loadings ranging from 2,500 to 8,200 mg/L/day and 4.5-33.2 mg/L/day, respectively. After 279 days of continuous operation, eight quasi-steady-state operation conditions were obtained with near complete removal of phenol and Cr(VI). Elevated levels of Cr(VI) and phenol were observed in the effluent under a high influent Cr(VI) concentration (16 mg/L) or a short liquid detention time (0.20 days). The system recovered from Cr(VI) toxicity after influent Cr(VI) level was reduced. Chromium mass balance analysis revealed that nearly all of the influent Cr(VI) was reduced to Cr(III) in the coculture bioreactor through biological activity. Spectra of UV-Vis and mass spectrometers suggested that phenol metabolites produced by P. putida were utilized by E. coli.

  16. Computational flow study of the continuous flow ventricular assist device, prototype number 3 blood pump.

    PubMed

    Anderson, J B; Wood, H G; Allaire, P E; Bearnson, G; Khanwilkar, P

    2000-05-01

    A computational fluid dynamics study of blood flow in the continuous flow ventricular assist device, Prototype No. 3 (CFVAD3), which consists of a 4 blade shrouded impeller fully supported in magnetic bearings, was performed. This study focused on the regions within the pump where return flow occurs to the pump inlet, and where potentially damaging shear stresses and flow stagnation might occur: the impeller blade passages and the narrow gap clearance regions between the impeller-rotor and pump housing. Two separate geometry models define the spacing between the pump housing and the impeller's hub and shroud, and a third geometry model defines the pump's impeller and curved blades. The flow fields in these regions were calculated for various operating conditions of the pump. Pump performance curves were calculated, which compare well with experimentally obtained data. For all pump operating conditions, the flow rates within the gap regions were predicted to be toward the inlet of the pump, thus recirculating a portion of the impeller flow. Two smaller gap clearance regions were numerically examined to reduce the recirculation and to improve pump efficiency. The computational and geometry models will be used in future studies of a smaller pump to determine increased pump efficiency and the risk of hemolysis due to shear stress, and to insure the washing of blood through the clearance regions to prevent thrombosis. PMID:10848679

  17. Continuous-Flow System Produces Medical-Grade Water

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Dahl, Roger W.; Wheeler, Richard R.

    2009-01-01

    A continuous-flow system utilizes microwave heating to sterilize water and to thermally inactivate endotoxins produced in the sterilization process. The system is designed for use in converting potable water to medical-grade water. Systems like this one could be used for efficient, small-scale production of medical- grade water in laboratories, clinics, and hospitals. This system could be adapted to use in selective sterilization of connections in ultra-pure-water-producing equipment and other equipment into which intrusion by microorganisms cannot be tolerated. Lightweight, port - able systems based on the design of this system could be rapidly deployed to remote locations (e.g., military field hospitals) or in response to emergencies in which the normal infrastructure for providing medical-grade water is disrupted. Larger systems based on the design of this system could be useful for industrial production of medical-grade water. The basic microwave-heating principle of this system is the same as that of a microwave oven: An item to be heated, made of a lossy dielectric material (in this case, flowing water) is irradiated with microwaves in a multimode microwave cavity. The heating is rapid and efficient because it results from absorption of microwave power throughout the volume of the lossy dielectric material. In this system, a copper tube having a length of 49.5 cm and a diameter of 2.25 cm serves as both the microwave cavity and the sterilization chamber. Microwave power is fed via a coaxial cable to an antenna mounted inside the tube at mid-length (see figure). Efficient power transfer occurs due to the shift in wavelength associated with the high permittivity of water combined with the strong coupling of 2.45-GHz microwaves with rotational-vibrational transitions of the dipolar water molecule.

  18. Environmental optimization of continuous flow ozonation for urban wastewater reclamation.

    PubMed

    Rodríguez, Antonio; Muñoz, Iván; Perdigón-Melón, José A; Carbajo, José B; Martínez, María J; Fernández-Alba, Amadeo R; García-Calvo, Eloy; Rosal, Roberto

    2012-10-15

    Wastewater samples from the secondary clarifier of two treatment plants were spiked in the microgram-to-tens-of-microgram per liter range with diuron (herbicide), ibuprofen and diclofenac (anti-inflammatory drugs), sulfamethoxazole and erythromycin (antibiotics), bezafibrate and gemfibrozil (lipid regulators), atenolol (β-blocker), carbamazepine (anti-epileptic), hydrochlorothiazide (diuretic), caffeine (stimulant) and N-acetyl-4-amino-antipiryne, a metabolite of the antipyretic drug dypirone. They were subsequently ozonated in continuous flow using 1.2L lab-scale bubble columns. The concentration of all spiking compounds was monitored in the outlet stream. The effects of varying ozone input, expressed as energy per unit volume, and water flow rate, and of using single or double column were studied in relation to the efficiency of ozone usage and the ratio of pollutant depletion. The ozone dosage required to treat both wastewaters with pollutant depletion of >90% was in the 5.5-8.5 mg/L range with ozone efficiencies greater than 80% depending on the type of wastewater and the operating conditions. This represented 100-200 mol of ozone transferred per mole of pollutant removed. Direct and indirect environmental impacts of ozonation were assessed according to Life Cycle Assessment, a technique that helped identify the most effective treatments in terms of potential toxicity reduction, as well as of toxicity reduction per unit mass of greenhouse-gas emissions, which were used as an indicator of environmental efficiency. A trade-off between environmental effectiveness (toxicity reduction) and greenhouse-gas emissions was observed since maximizing toxicity removal led to higher greenhouse-gas emissions, due to the latter's relatively high ozone requirements. Also, there is an environmental trade-off between effectiveness and efficiency. Our results indicate that an efficient use of ozone was not compatible with a full pollutant removal. PMID:22922131

  19. Lava flows during the continuing eruption of Mt. Etna, Italy

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The current eruption of Mt. Etna started on July 17, and has continued to the present. This ASTER image was acquired on Sunday, July 29 and shows advancing lava flows on the southern flank of Mt. Etna above the town of Nicolosi, which is potentially threatened if the eruption increases in magnitude. Also visible are glowing summit craters above the main lava flows, and a small fissure eruption. The bright puffy clouds were formed from water vapor released during the eruption. The image covers an area of 24 x 30 km.

    The image is centered at 37.7 degrees north latitude, 15 degrees east longitude.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils

  20. Aortic Aneurysm Statistics

    MedlinePlus

    ... Blood Pressure Salt Cholesterol Million Hearts® WISEWOMAN Aortic Aneurysm Fact Sheet Recommend on Facebook Tweet Share Compartir ... cause of most deaths from aortic aneurysms. Aortic Aneurysm in the United States Aortic aneurysms were the ...

  1. Abdominal Aortic Aneurysm (AAA)

    MedlinePlus

    ... Resources Professions Site Index A-Z Abdominal Aortic Aneurysm (AAA) Abdominal aortic aneurysm (AAA) occurs when atherosclerosis ... aortic aneurysm treated? What is an abdominal aortic aneurysm? The aorta, the largest artery in the body, ...

  2. Flow-Induced Damage to Blood Cells in Aortic Valve Stenosis.

    PubMed

    Vahidkhah, Koohyar; Cordasco, Dan; Abbasi, Mostafa; Ge, Liang; Tseng, Elaine; Bagchi, Prosenjit; Azadani, Ali N

    2016-09-01

    Valvular hemolysis and thrombosis are common complications associated with stenotic heart valves. This study aims to determine the extent to which hemodynamics induce such traumatic events. The viscous shear stress downstream of a severely calcified bioprosthetic valve was evaluated via in vitro 2D particle image velocimetry measurements. The blood cell membrane response to the measured stresses was then quantified using 3D immersed-boundary computational simulations. The shear stress level at the boundary layer of the jet flow formed downstream of the valve orifice was observed to reach a maximum of 1000-1700 dyn/cm(2), which was beyond the threshold values reported for platelet activation (100-1000 dyn/cm(2)) and within the range of thresholds reported for red blood cell (RBC) damage (1000-2000 dyn/cm(2)). Computational simulations demonstrated that the resultant tensions at the RBC membrane surface were unlikely to cause instant rupture, but likely to lead to membrane plastic failure. The resultant tensions at the platelet surface were also calculated and the potential damage was discussed. It was concluded that although shear-induced thrombotic trauma is very likely in stenotic heart valves, instant hemolysis is unlikely and the shear-induced damage to RBCs is mostly subhemolytic. PMID:27048168

  3. Aortic stenting.

    PubMed

    Droc, Ionel; Calinescu, Francisca Blanca; Droc, Gabriela; Blaj, Catalin; Dammrau, Rolf

    2015-01-01

    The approach to aortic pathology is nowadays more and more endovascular at both thoracic and abdominal levels. Thoracic stenting has gained worldwide acceptance as first intention to treat pathologies of the descending thoracic aorta. Indications have been extended to aortic arch aneurysms and also to diseases of the ascending aorta. The current devices in use for thoracic endovascular repair (TEVAR) are Medtronic Valiant, Gore TAG, Cook Tx2 and Jotec. The choice of the endograft depends on the thoracic aortic pathology and the anatomical suitability. The technological evolution of the abdominal aortic endografts was very rapid, arriving now at the fourth generation. We report the results of 55 elective cases of endovascular abdominal aortic repair (EVAR) performed in two vascular surgical centers in Romania and Germany. The prostheses used were 16 E-vita Abdominal XT, 12 Excluder, eight Talent, seven PowerLink, three Endurant and nine custom-made, fenestrated or branched from Jotec. The mean follow-up was 18 months with CT-scan, duplex ultrasound and contrast-enhanced ultrasound. The mortality was 2%. EVAR tends to become the gold standard for abdominal aortic aneurysm repair. Technological development of the devices with lowest profile introduction systems will permit to extend the anatomical indications to new frontiers. PMID:26200430

  4. Aortic dissection.

    PubMed

    Nienaber, Christoph A; Clough, Rachel E; Sakalihasan, Natzi; Suzuki, Toru; Gibbs, Richard; Mussa, Firas; Jenkins, Michael T; Thompson, Matt M; Evangelista, Arturo; Yeh, James S M; Cheshire, Nicholas; Rosendahl, Ulrich; Pepper, John

    2016-01-01

    Aortic dissection is a life-threatening condition caused by a tear in the intimal layer of the aorta or bleeding within the aortic wall, resulting in the separation (dissection) of the layers of the aortic wall. Aortic dissection is most common in those 65-75 years of age, with an incidence of 35 cases per 100,000 people per year in this population. Other risk factors include hypertension, dyslipidaemia and genetic disorders that involve the connective tissue, such as Marfan syndrome. Swift diagnostic confirmation and adequate treatment are crucial in managing affected patients. Contemporary management is multidisciplinary and includes serial non-invasive imaging, biomarker testing and genetic risk profiling for aortopathy. The choice of approach for repairing or replacing the damaged region of the aorta depends on the severity and the location of the dissection and the risks of complication from surgery. Open surgical repair is most commonly used for dissections involving the ascending aorta and the aortic arch, whereas minimally invasive endovascular intervention is appropriate for descending aorta dissections that are complicated by rupture, malperfusion, ongoing pain, hypotension or imaging features of high risk. Recent advances in the understanding of the underlying pathophysiology of aortic dissection have led to more patients being considered at substantial risk of complications and, therefore, in need of endovascular intervention rather than only medical or surgical intervention. PMID:27440162

  5. Continuous Flow Cryostat for X-Ray Fluorescence

    SciTech Connect

    Weng, T.-C.; Linden, Peter J. E. M. van der; Glatzel, Pieter; Lapras, Christophe; Krzyzowski, Michael

    2010-06-23

    A continuous Helium flow cryostat was designed and built by Cryovac GMbH to specifications given by ESRF beamline ID26. The beamline has constructed a high energy resolution X-ray emission spectrometer using multiple spherically bent analyser crystals, together with the sample and detector on a vertical Rowland circle. The double shrouded cryostat has a low profile designed to fit into the spectrometer setup, the lowest detector position allows for a Bragg angle of 85 degrees with a 1 meter diameter Rowland circle. The cryostat has a temperature range of 5 to 300 Kelvin on the sample holder which is cooled by static Helium exchange gas. The cryostat has triple windows for beam entrance, transmission and fluorescence; the latter offers an opening angle of 80 degrees horizontally and 50 degrees vertically. The cryostat can be configured to work in two different operation modes: translation or rotation. The translation mode offers a displacement of 50 mm to accommodate multiple samples on the sample holder. The rotation mode is used for polarisation studies on single crystals.We show recent results obtained on Chromium containing molecular complexes; data collection was done at a temperature of 10 Kelvin to avoid radiation damage.

  6. Hydrothermal upgrading of algae paste in a continuous flow reactor.

    PubMed

    Patel, Bhavish; Hellgardt, Klaus

    2015-09-01

    This investigation demonstrates the utility of a novel laboratory scale continuous plug flow reactor for fast Hydrothermal Liquefaction (HTL) of microalgae in a quartz lined chamber. Reactions were carried out between 300 and 380 °C and residence times of 0.5-4 min. Cyclohexane was used as a co-solvent to enhance extraction and prevent char formation. Highest biocrude yield of 38 wt.% was achieved at 380 °C and 30 s as well as Water Soluble Fraction containing up to 60 wt.% matter recovered. Analysis of the biocrude showed that the extent of deoxygenation and denitrogenation after HTL varied and is dependent on the reaction conditions, Fourier Transform Infrared Spectroscopy analysis showed that biocrude contains similar functional moieties with only a small difference observed at different reaction conditions. Conversely, the Simulated Distillation and Size Exclusion Chromatography data showed that harsher conditions produced marginally better biocrude with improved boiling point profile and lower molecular weight compounds, respectively which was confirmed using Gas Chromatography-Mass Spectrometry. PMID:25908412

  7. Microfluidic Continuous Flow Digital Loop-Mediated Isothermal Amplification (LAMP)

    PubMed Central

    Rane, Tushar D.; Chen, Liben; Zec, Helena C.; Wang, Tza-Huei

    2015-01-01

    Digital nucleic acid detection is rapidly becoming a popular technique for ultra-sensitive and quantitative detection of nucleic acid molecules in a wide range of biomedical studies. Digital polymerase chain reaction (PCR) remains the most popular way of conducting digital nucleic acid detection. However, due to the need for thermocycling, digital PCR is difficult to implement in a streamlined manner on a single microfluidic device, leading to complex fragmented workflows and multiple separate devices and instruments. Loop-mediated isothermal amplification (LAMP) is an excellent isothermal alternative to PCR with potentially better specificity than PCR through the use of multiple primer sets for a nucleic acid target. Here we report a microfluidic droplet device implementing all the steps required for digital nucleic acid detection including droplet generation, incubation and in-line detection for digital LAMP. As compared to microchamber or droplet array-based digital assays, continuous flow operation of this device eliminates the constraints on the number of total reactions by the footprint of the device and the analysis throughput by the time for lengthy incubation and transfers of materials between instruments. PMID:25431886

  8. Simulation of Dilated Heart Failure with Continuous Flow Circulatory Support

    PubMed Central

    Wang, Yajuan; Loghmanpour, Natasha; Vandenberghe, Stijn; Ferreira, Antonio; Keller, Bradley; Gorcsan, John; Antaki, James

    2014-01-01

    Lumped parameter models have been employed for decades to simulate important hemodynamic couplings between a left ventricular assist device (LVAD) and the native circulation. However, these studies seldom consider the pathological descending limb of the Frank-Starling response of the overloaded ventricle. This study introduces a dilated heart failure model featuring a unimodal end systolic pressure-volume relationship (ESPVR) to address this critical shortcoming. The resulting hemodynamic response to mechanical circulatory support are illustrated through numerical simulations of a rotodynamic, continuous flow ventricular assist device (cfVAD) coupled to systemic and pulmonary circulations with baroreflex control. The model further incorporated septal interaction to capture the influence of left ventricular (LV) unloading on right ventricular function. Four heart failure conditions were simulated (LV and bi-ventricular failure with/without pulmonary hypertension) in addition to normal baseline. Several metrics of LV function, including cardiac output and stroke work, exhibited a unimodal response whereby initial unloading improved function, and further unloading depleted preload reserve thereby reducing ventricular output. The concept of extremal loading was introduced to reflect the loading condition in which the intrinsic LV stroke work is maximized. Simulation of bi-ventricular failure with pulmonary hypertension revealed inadequacy of LV support alone. These simulations motivate the implementation of an extremum tracking feedback controller to potentially optimize ventricular recovery. PMID:24465511

  9. Full dimensional computer simulations to study pulsatile blood flow in vessels, aortic arch and bifurcated veins: Investigation of blood viscosity and turbulent effects.

    PubMed

    Sultanov, Renat A; Guster, Dennis

    2009-01-01

    We report computational results of blood flow through a model of the human aortic arch and a vessel of actual diameter and length. A realistic pulsatile flow is used in all simulations. Calculations for bifurcation type vessels are also carried out and presented. Different mathematical methods for numerical solution of the fluid dynamics equations have been considered. The non-Newtonian behaviour of the human blood is investigated together with turbulence effects. A detailed time-dependent mathematical convergence test has been carried out. The results of computer simulations of the blood flow in vessels of three different geometries are presented: for pressure, strain rate and velocity component distributions we found significant disagreements between our results obtained with realistic non-Newtonian treatment of human blood and the widely used method in the literature: a simple Newtonian approximation. A significant increase of the strain rate and, as a result, the wall shear stress distribution, is found in the region of the aortic arch. Turbulent effects are found to be important, particularly in the case of bifurcation vessels. PMID:19964834

  10. A Mock Circulatory System to Assess the Performance of Continuous-Flow Left Ventricular Assist Devices (LVADs): Does Axial Flow Unload Better Than Centrifugal LVAD?

    PubMed Central

    2014-01-01

    Hemodynamic performances comparisons between different types of left ventricular assist devices (LVADs) remain difficult in a clinical context. The aim of this study was to create an experimental model to assess and compare two types of LVAD under hemodynamic conditions that simulated physical effort and pulmonary hypertension. An experimental mock circulatory system was created to simulate the systemic and pulmonary circulations and consisted of pulsatile left and right cardiac simulators (cardiowest pump), air/water tanks to model compliances, and tubes to model the venous and arterial resistances. Two types of continuous-flow ventricular assist devices were connected to this pulsated model: an axial flow pump, Heartmate II (HTM II), and a centrifugal pump, VentrAssist (VTA). The hemodynamic conditions at rest and during exercise were replicated. Mean aortic pressures were not significantly different at rest and during effort but mean flow under maximum pump speed was higher with HTM II (13 L vs. 10 L, p = 0.02). Left atrial pressure was lower at rest and during effort for the HTM II (11 mm Hg vs. 3 mm Hg, p = 0.02 and 9 mm Hg vs. 2 mm Hg, p = 0.008) than with the VTA, but with greater risk of left-ventricle suck-down for the axial flow. Power consumption for a similar flow was lower with the VTA during rest (4.7 W vs. 6.9 W, p = 0.002) and during effort (4.3 W vs. 6.6 W, p = 0.008). In case of high pulmonary vascular resistance with preserved right ventricular function, lower right ventricular pressure was obtained with HTM II (21 mm Hg vs. 28 mm Hg, p = 0.03). Observed results are in favor of a better discharge of the left and right cavities with the HTM II compared to the VTA yet with a higher risk of left cavity collapse occurrence. PMID:24577368

  11. A mock circulatory system to assess the performance of continuous-flow left ventricular assist devices (LVADs): does axial flow unload better than centrifugal LVAD?

    PubMed

    Sénage, Thomas; Février, Dorothée; Michel, Magali; Pichot, Emmanuel; Duveau, Daniel; Tsui, Steven; Trochu, Jean Noel; Roussel, Jean Christian

    2014-01-01

    Hemodynamic performances comparisons between different types of left ventricular assist devices (LVADs) remain difficult in a clinical context. The aim of this study was to create an experimental model to assess and compare two types of LVAD under hemodynamic conditions that simulated physical effort and pulmonary hypertension. An experimental mock circulatory system was created to simulate the systemic and pulmonary circulations and consisted of pulsatile left and right cardiac simulators (cardiowest pump), air/water tanks to model compliances, and tubes to model the venous and arterial resistances. Two types of continuous-flow ventricular assist devices were connected to this pulsated model: an axial flow pump, Heartmate II (HTM II), and a centrifugal pump, VentrAssist (VTA). The hemodynamic conditions at rest and during exercise were replicated. Mean aortic pressures were not significantly different at rest and during effort but mean flow under maximum pump speed was higher with HTM II (13 L vs. 10 L, p = 0.02). Left atrial pressure was lower at rest and during effort for the HTM II (11 mm Hg vs. 3 mm Hg, p = 0.02 and 9 mm Hg vs. 2 mm Hg, p = 0.008) than with the VTA, but with greater risk of left-ventricle suck-down for the axial flow. Power consumption for a similar flow was lower with the VTA during rest (4.7 W vs. 6.9 W, p = 0.002) and during effort (4.3 W vs. 6.6 W, p = 0.008). In case of high pulmonary vascular resistance with preserved right ventricular function, lower right ventricular pressure was obtained with HTM II (21 mm Hg vs. 28 mm Hg, p = 0.03). Observed results are in favor of a better discharge of the left and right cavities with the HTM II compared to the VTA yet with a higher risk of left cavity collapse occurrence. PMID:24577368

  12. Implementation of the Continuous AutoTransfusion System (C.A.T.S) in open abdominal aortic aneurysm repair: an observational comparative cohort study.

    PubMed

    Tawfick, Wael A; O'Connor, Martina; Hynes, Niamh; Sultan, Sherif

    2008-01-01

    The use of the Continuous AutoTransfusion System (C.A.T.S; Fresenius Hemotechnology, Bad Homburg v.d.H., Germany), which conserves allogenic blood, is reported in 187 patients having abdominal aortic aneurysm repair during a 9-year period. Patients were allocated to C.A.T.S if a Haemovigilance technician was available. A mean of 685 mL of retrieved blood was reinfused in 101 patients receiving C.A.T.S; 61% required 2 U or less. All control patients required 3 U or more of allogenic blood. Allogenic transfusion in C.A.T.S patients decreased significantly (P < .0001). Mean intensive care unit stay was significantly reduced in C.A.T.S patients (P = .042). Mean postoperative hospital stay was 18 days for C.A.T.S group and 25 days in control patients (P = .014). The respective 30-day mortality was 12% versus 19% (P = .199). The C.A.T.S markedly reduced the amount of blood transfused, was associated with reduced intensive care unit and postoperative hospital stay, and was cost-effective. PMID:18238865

  13. ``Smart'' baroreception along the aortic arch, with reference to essential hypertension

    NASA Astrophysics Data System (ADS)

    Kember, G. C.; Zamir, M.; Armour, J. A.

    2004-11-01

    Beat-to-beat regulation of heart rate is dependent upon sensing of local stretching or local “disortion” by aortic baroreceptors. Distortions of the aortic wall are due mainly to left ventricular output and to reflected waves arising from the arterial tree. Distortions are generally believed to be useful in cardiac control since stretch receptors or aortic baroreceptors embedded in the adventitia of the aortic wall, transduce the distortions to cardiovascular neural reflex pathways responsible for beat-to-beat regulation of heart rate. Aortic neuroanatomy studies have also found a continuous strip of mechanosensory neurites spread along the aortic inner arch. Although their purpose is now unknown, such a combined sensing capacity would allow measurement of the space and time dependence of inner arch wall distortions due, among other things, to traveling waves associated with pulsatile flow in an elastic tube. We call this sensing capability-“smart baroreception.” In this paper we use an arterial tree model to show that the cumulative effects of wave reflections, from many sites far downstream, have a surprisingly pronounced effect on the pressure distribution in the root segment of the tree. By this mechanism global hemodynamics can be focused by wave reflections back to the aortic arch, where they can rapidly impact cardiac control via smart baroreception. Such sensing is likely important to maintain efficient heart function. However, alterations in the arterial tree due to aging and other natural processes can lead in such a system to altered cardiac control and essential hypertension.

  14. 21 CFR 862.2150 - Continuous flow sequential multiple chemistry analyzer for clinical use.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Continuous flow sequential multiple chemistry..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2150 Continuous flow sequential multiple...

  15. 21 CFR 862.2150 - Continuous flow sequential multiple chemistry analyzer for clinical use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Continuous flow sequential multiple chemistry..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2150 Continuous flow sequential multiple...

  16. 21 CFR 862.2150 - Continuous flow sequential multiple chemistry analyzer for clinical use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Continuous flow sequential multiple chemistry..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2150 Continuous flow sequential multiple...

  17. 21 CFR 862.2150 - Continuous flow sequential multiple chemistry analyzer for clinical use.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Continuous flow sequential multiple chemistry..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2150 Continuous flow sequential multiple...

  18. 21 CFR 862.2150 - Continuous flow sequential multiple chemistry analyzer for clinical use.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Continuous flow sequential multiple chemistry..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2150 Continuous flow sequential multiple...

  19. Continuous flow measurements using ultrasonic velocity meters - an update

    USGS Publications Warehouse

    Oltmann, Rick

    1995-01-01

    An article in the summer 1993 Newsletter described USGS work to continously monitor tidal flows in the delta using ultrasonic velocity meters.  This article updates progress since 1993, including new installations, results of data analysis, damage during this year's high flows, and the status of each site.

  20. Comparing contact and immersion freezing from continuous flow diffusion chambers

    NASA Astrophysics Data System (ADS)

    Nagare, Baban; Marcolli, Claudia; Welti, André; Stetzer, Olaf; Lohmann, Ulrike

    2016-07-01

    due to the position of the INP on the droplet, and we discriminate it from collisional contact freezing, which assumes an enhancement due to the collision of the particle with the droplet. For best comparison with contact freezing results, immersion freezing experiments of the same INPs were performed with the continuous flow diffusion chamber Immersion Mode Cooling chAmber-Zurich Ice Nucleation Chamber (IMCA-ZINC) for a 3 s residence time. In IMCA-ZINC, each INP is activated into a droplet in IMCA and provides its surface for ice nucleation in the ZINC chamber. The comparison of contact and immersion freezing results did not confirm a general enhancement of freezing efficiency for contact compared with immersion freezing experiments. For AgI particles the onset of heterogeneous freezing in CLINCH was even shifted to lower temperatures compared with IMCA-ZINC. For ATD, freezing efficiencies for contact and immersion freezing experiments were similar. For kaolinite particles, contact freezing became detectable at higher temperatures than immersion freezing. Using contact angle information between water and the INP, it is discussed how the position of the INP in or on the droplets may influence its ice nucleation activity.

  1. Flow characteristics of continuous-flow left ventricular assist devices in a novel open-loop system.

    PubMed

    Stanfield, J Ryan; Selzman, Craig H; Pardyjak, Eric R; Bamberg, Stacy

    2012-01-01

    Fluid-pumping technology is a mature engineering subject area with a well-documented knowledge base. However, the pump design optimization techniques accepted in industry are geared toward steady-state constant-flow conditions. In contrast, the implantation of a continuous-flow pump to aid the output of the human left ventricle subjects the device to perpetual variation. This study measures pressure-flow performance characteristics for both axial- and centrifugal continuous-flow rotary blood pumps across a wide range of pressure differential values under uniform conditions by means of a novel open-loop flow system. The axial-flow devices show lower hydraulic efficiency. All pumps yield best efficiency point at a head to flow coefficient ratio of approximately 1.7. The open-loop flow system accounts for the dynamic changes associated with human heart physiology and allows for more precise characterization of existing heart pumps and those in development. PMID:22990285

  2. Contemporary Management of Type B Aortic Dissection in the Endovascular Era.

    PubMed

    Bannazadeh, Mohsen; Tadros, Rami O; McKinsey, James; Chander, Rajiv; Marin, Michael L; Faries, Peter L

    2016-04-01

    Aortic dissection (AD) is one of the most common catastrophic pathologies affecting the aorta. Anatomic classification is based on the origin of entry tear and its extension. Type A dissections originate in the ascending aorta, whereas the entry tear in Type B dissections starts distal to the left subclavian artery. The patients with aortic dissection who manifest complications such as rupture, malperfusion, aneurysmal degeneration, and intractable pain are classified as complicated AD. Risk factors for developing aortic dissection include age, male gender, and aortic wall structural abnormalities. The most common presenting symptom of acute aortic dissection is pain. Malperfusion occurs as a result of end-organ ischemia due to involvement of aortic branches from the dissecting process. This can happen in various locations causing mesenteric ischemia (mesenteric vessels), stroke (aortic arch vessels), renal failure (renal arteries), spinal ischemia, and limb ischemia (iliac or subclavian arteries). Aneurysmal degeneration is the most common complication of patients with chronic Type B dissection who are managed with medical therapy. Management of Type B aortic dissection (TBAD) remains controversial. Many groups recommend conservative therapy for newly diagnosed TBAD and reserve surgical management for patients who develop complications such as rupture, malperfusion, aneurysmal dilatation, and refractory pain. The mainstay of medical therapy includes antihypertensive medication to reduced ΔP/ ΔT by lowering blood pressure and heart rate. With the continued success of thoracic endovascular aortic repair (TEVAR), this procedure has been extended to treat TBAD in selected patients. The outcomes of TEVAR are promising, with early mortality rates from 10% to 20%. With promising results from these series, some groups recommend early TEVAR in uncomplicated TBAD to prevent future adverse events. The goals of endovascular treatment of TBAD are to cover the entry tear

  3. Continuous Flow of Nitroso Diels-Alder Reaction

    PubMed Central

    2015-01-01

    Our flow reaction systems have provided quantitative yields of nitroso Diels-Alder products with no byproducts in cases of cyclic dienes without temperature and pressure controls. Additionally, the reaction times were significantly shortened by using homogeneous catalyst (CuCl) or heterogeneous reagent (MnO2) in comparison with batch reaction. PMID:26138229

  4. Cerebral Blood Flow Autoregulation Is Preserved After Continuous Flow Left Ventricular Assist Device Implantation

    PubMed Central

    Ono, Masahiro; Joshi, Brijen; Brady, Kenneth; Easley, R. Blaine; Kibler, Kathy; Conte, John; Shah, Ashish; Russell, Stuart D.; Hogue, Charles W.

    2012-01-01

    Objective To compare cerebral blood flow (CBF) autoregulation in patients undergoing continuous flow left ventricular assist device (LVAD) implantation with that in patients undergoing coronary artery bypass graft (CABG) surgery. Design Prospective, observational, controlled study. Setting Academic medical center. Participants Fifteen patients undergoing LVAD insertion and 10 patients undergoing CABG surgery. Measurements and Main Results Cerebral autoregulation was monitored with transcranial Doppler and near-infrared spectroscopy (NIRS). A continuous, Pearson's correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity, and between MAP and NIRS data rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Mx and COx approach zero when autoregulation is intact (no correlation between CBF and MAP), but approach 1 when autoregulation is impaired. Mx was lower during and immediately after cardiopulmonary bypass (CPB) in the LVAD group than it was in the CABG surgery patients, indicating better preserved autoregulation. Based on COx monitoring, autoregulation tended to be better preserved in the LVAD group than in the CABG group immediately after surgery (p=0.0906). On postoperative day 1, COx was lower in LVAD patients than in CABG surgery patients, again indicating preserved CBF autoregulation (p=0.0410). Based on COx monitoring, 3 (30%) of the CABG patients had abnormal autoregulation (COx ≥ 0.3) on the first postoperative day but none of the LVAD patients had this abnormality (p=0.037). Conclusion These data suggest that CBF autoregulation is preserved during and immediately after surgery in patients undergoing LVAD insertion. PMID:23122299

  5. Acute Aortic Syndromes and Thoracic Aortic Aneurysm

    PubMed Central

    Ramanath, Vijay S.; Oh, Jae K.; Sundt, Thoralf M.; Eagle, Kim A.

    2009-01-01

    Acute and chronic aortic diseases have been diagnosed and studied by physicians for centuries. Both the diagnosis and treatment of aortic diseases have been steadily improving over time, largely because of increased physician awareness and improvements in diagnostic modalities. This comprehensive review discusses the pathophysiology and risk factors, classification schemes, epidemiology, clinical presentations, diagnostic modalities, management options, and outcomes of various aortic conditions, including acute aortic dissection (and its variants intramural hematoma and penetrating aortic ulcers) and thoracic aortic aneurysms. Literature searches of the PubMed database were conducted using the following keywords: aortic dissection, intramural hematoma, aortic ulcer, and thoracic aortic aneurysm. Retrospective and prospective studies performed within the past 20 years were included in the review; however, most data are from the past 15 years. PMID:19411444

  6. Aortic Valve Disease

    MedlinePlus

    ... Disease Tricuspid Valve Disease Cardiac Rhythm Disturbances Thoracic Aortic Aneurysm Pediatric and Congenital Heart Disease Heart abnormalities that ... Disease Tricuspid Valve Disease Cardiac Rhythm Disturbances Thoracic Aortic Aneurysm Aortic Valve Disease Overview The human heart has ...

  7. Thoracic aortic aneurysm

    MedlinePlus

    Aortic aneurysm - thoracic; Syphilitic aneurysm; Aneurysm - thoracic aortic ... The most common cause of a thoracic aortic aneurysm is hardening of the ... with high cholesterol, long-term high blood pressure, or who ...

  8. Illegal gene flow from transgenic creeping bentgrass: the saga continues.

    PubMed

    Snow, Allison A

    2012-10-01

    Ecologists have paid close attention to environmental effects that fitness-enhancing transgenes might have following crop-to-wild gene flow (e.g. Snow et al. 2003). For some crops, gene flow also can lead to legal problems,especially when government agencies have not approved transgenic events for unrestricted environmental release.Creeping bentgrass (Agrostis stolonifera), a common turf grass used in golf courses, is the focus of both areas of concern. In 2002, prior to expected deregulation (still pending), The Scotts Company planted creeping bentgrass with transgenic resistance to the herbicide glyphosate,also known as RoundUp, on 162 ha in a designated control area in central Oregon (Fig. 1).Despite efforts to restrict gene flow, wind-dispersed pollen carried transgenes to florets of local A. stolonifera and A. gigantea as far as 14 km away, and to sentinel plants placed as far as 21 km away (Watrud et al. 2004).Then, in August 2003, a strong wind event moved transgenic seeds from wind rows of cut bentgrass into nearby areas. The company’s efforts to kill all transgenic survivors in the area failed: feral glyphosate-resistant populations of A. stolonifera were found by Reichman et al.(2006), and 62% of 585 bentgrass plants had the telltale CP4 EPSPS transgene in 2006 (Zapiola et al. 2008; Fig. 2).Now, in this issue, the story gets even more interesting as Zapiola & Mallory-Smith (2012) describe a transgenic,intergeneric hybrid produced on a feral, transgenic creeping bentgrass plant that received pollen from Polypogon monspeliensis (rabbitfoot grass). Their finding raises a host of new questions about the prevalence and fitness of intergeneric hybrids, as well as how to evaluate the full extent of gene flow from transgenic crops. PMID:23009646

  9. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous flow microwave sterilization is an emerging technology which has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temp...

  10. EFFECT OF CHEMICALS ON SOIL NITRIFYING POPULATIONS USING A CONTINUOUS-FLOW CULTURE TECHNIQUE

    EPA Science Inventory

    This study examines the effects of Roundup [N-(phosphonomethyl)glycine] and N-Serve[2-chloro-6-(trichloromethyl)pyridine] on nitrifying organisms in static batch, perfusion soil columns, and a new continuous-flow soil column system. he continuous-flow method is new to nitrificati...

  11. PROCESS INTENSIFICATION: MICROWAVE INITIATED REACTIONS USING A CONTINUOUS FLOW REACTOR

    EPA Science Inventory

    The concept of process intensification has been used to develop a continuous narrow channel reactor at Clarkson capable of carrying out reactions under isothermal conditions whilst being exposed to microwave (MW) irradiation thereby providing information on the true effect of mi...

  12. The Effects of Positioning of Transcatheter Aortic Valve on Fluid Dynamics of the Aortic Root

    PubMed Central

    Su, Jimmy L; Kheradvar, Arash

    2015-01-01

    Transcatheter aortic valve implantation is a novel treatment for severe aortic valve stenosis. Due to the recent use of this technology and the procedural variability, there is very little data that quantifies the hemodynamic consequences of variations in valve placement. Changes in aortic wall stresses and fluid retention in the sinuses of Valsalva can have a significant effect on the clinical response a patient has to the procedure. By comprehensively characterizing complex flow in the sinuses of Valsalva using Digital Particle Image Velocimetry and an advanced heart flow simulator, various positions of a deployed transcatheter valve with respect to a bioprosthetic aortic valve (valve-in-valve) were tested in vitro. Displacements of the transcatheter valve were axial and directed below the simulated native valve annulus. It was determined that for both blood residence time and aortic Reynolds stresses, it is optimal to have the annulus of the transcatheter valve deployed as close to the aortic valve annulus as possible. PMID:25010918

  13. Continuous flow isoelectric focusing for purification of proteins.

    PubMed

    Soulet, N; Roux-de Balmann, H; Sanchez, V

    1998-06-01

    To estimate the feasibility of isoelectric focusing in a continuous mode, the conditions for obtaining stable and linear pH gradients were first investigated, using a mixture of carrier ampholytes. Then the operating parameters allowing the isoelectric focusing of bovine serum albumin as model protein were determined. A theoretical approach was used to find conditions minimizing the electrohydrodynamic effect, mainly responsible for protein dispersion, for the separation of bovine serum albumin and alpha-lactalbumin from bovine milk. PMID:9694268

  14. Macrosegregation Improvement by Swirling Flow Nozzle for Bloom Continuous Castings

    NASA Astrophysics Data System (ADS)

    Sun, Haibo; Zhang, Jiaquan

    2014-06-01

    Based on mathematical model coupling electromagnetism, fluid flow, heat transfer, and solute transport, the metallurgical performances of conventional straight nozzle, swirling flow nozzle (SFN), and M-EMS have been evaluated and compared. The soundness improvement of bloom castings has been investigated by casting tests of adopting the newly designed SFN. As compared to the normal nozzle, center porosity has been eliminated along with the popular center radial crack, and a better chemical homogeneity was obtained by employing the SFN accordingly, where the maximum segregation degree of C and S at the strand cross section is decreased from 1.28 to 1.02 and from 1.32 to 1.06, respectively. Combined with the results of numerical simulation, the positive effect obtained can be attributed to the remarkable superheat dissipation under the implementation of SFN, where, compared with the normal nozzle, the melt superheat degree at the mold exit is reduced by 15.5 K, 9.8 K, and 17.3 K (15.5 °C, 9.8 °C, and 17.3 °C) under the other three casting measures of SFN, normal nozzle with M-EMS, and SFN with M-EMS, respectively.

  15. Continuous and Discontinuous Dynamic Unbinding Transitions in Drawn Film Flow

    NASA Astrophysics Data System (ADS)

    Galvagno, M.; Tseluiko, D.; Lopez, H.; Thiele, U.

    2014-04-01

    When a plate is withdrawn from a liquid bath a coating layer is deposited whose thickness and homogeneity depend on the velocity and the wetting properties of the plate. Using a long-wave mesoscopic hydrodynamic description that incorporates wettability via a Derjaguin (disjoining) pressure we identify four qualitatively different dynamic transitions between microscopic and macroscopic coatings that are out-of-equilibrium equivalents of known equilibrium unbinding transitions. Namely, these are continuous and discontinuous dynamic wetting and emptying transitions. Several of their features have no equivalent at equilibrium.

  16. Electroosmotic flow and Joule heating in preparative continuous annular electrochromatography.

    PubMed

    Laskowski, René; Bart, Hans-Jörg

    2015-09-01

    An openFOAM "computational fluid dynamic" simulation model was developed for the description of local interaction of hydrodynamics and Joule heating in annular electrochromatography. A local decline of electrical conductivity of the background eluent is caused by an electrokinetic migration of ions resulting in higher Joule heat generation. The model equations consider the Navier-Stokes equation for incompressible fluids, the energy equation for stationary temperature fields, and the mass transfer equation for the electrokinetic flow. The simulations were embedded in commercial ANSYS Fluent software and in open-source environment openFOAM. The annular gap (1 mm width) contained an inorganic C8 reverse-phase monolith as stationary phase prepared by an in situ sol-gel process. The process temperature generated by Joule heating was determined by thermal camera system. The local hydrodynamics in the prototype was detected by a gravimetric contact-free measurement method and experimental and simulated values matched quite well. PMID:25997390

  17. Kinetic model of continuous-wave flow chemical lasers

    NASA Astrophysics Data System (ADS)

    Gao, Z.; X., E.

    1982-02-01

    A kinetic approach to modeling the gain in a chemical wave continuous laser when the lasing frequency is coincident with the center of the line shape is presented. Governing equations are defined for the relaxing behavior of an initially nonequilibrium distribution toward the local equilibrium Boltzmann-Maxwellian distribution. A new gain is introduced which is related to the thermal motion of the molecules and cold-reaction and premixed CW models are discussed. Coincidence of the lasing frequency with the line shape is demonstrated to result in a radiative intensity within the homogeneous broadening limit. The rate model predictions are compared with those of the kinetic model. It is found that when the broadening parameter is less than 0.2 the kinetic model more accurately describes the behavior of the CW chemical laser.

  18. Scalability of Continuous Flow Production of Metal-Organic Frameworks.

    PubMed

    Rubio-Martinez, Marta; Hadley, Trevor D; Batten, Michael P; Constanti-Carey, Keri; Barton, Tim; Marley, Dylan; Mönch, Andreas; Lim, Kok-Seng; Hill, Matthew R

    2016-05-10

    Achieving the large-scale production of metal-organic frameworks (MOFs) is crucial for their utilization in applied settings. For many MOFs, quality suffers from large-scale, batch reaction systems. We have developed continuous processes for their production which showed promise owing to their versatility and the high quality of the products. Here, we report the successful upscaling of this concept by more than two orders of magnitude to deliver unprecedented production rates and space-time-yields (STYs) while maintaining the product quality. Encouragingly, no change in the reaction parameters, obtained at small scale, was required. The production of aluminium fumarate was achieved at an STY of 97 159 kg m(-3)  day(-1) and a rate of 5.6 kg h(-1) . PMID:27075923

  19. Deterministic sequential isolation of floating cancer cells under continuous flow.

    PubMed

    Tran, Quang D; Kong, Tian Fook; Hu, Dinglong; Marcos; Lam, Raymond H W

    2016-08-01

    Isolation of rare cells, such as circulating tumor cells, has been challenging because of their low abundance and limited timeframes of expressions of relevant cell characteristics. In this work, we devise a novel hydrodynamic mechanism to sequentially trap and isolate floating cells in biosamples. We develop a microfluidic device for the sequential isolation of floating cancer cells through a series of microsieves to obtain up to 100% trapping yield and >95% sequential isolation efficiency. We optimize the trappers' dimensions and locations through both computational and experimental analyses using microbeads and cells. Furthermore, we investigated the functional range of flow rates for effective sequential cell isolation by taking the cell deformability into account. We verify the cell isolation ability using the human breast cancer cell line MDA-MB-231 with perfect agreement with the microbead results. The viability of the isolated cells can be maintained for direct identification of any cell characteristics within the device. We further demonstrate that this device can be applied to isolate the largest particles from a sample containing multiple sizes of particles, revealing its possible applicability in isolation of circulating tumor cells in cancer patients' blood. Our study provides a promising sequential cell isolation strategy with high potential for rapid detection and analysis of general floating cells, including circulating tumor cells and other rare cell types. PMID:27387093

  20. Assembly-gas flow control panel - continuous yarn coater; continuous yarn coater (Engineering Materials)

    SciTech Connect

    Not Available

    1982-08-10

    A problem addressed by this invention was how to obtain very long lengths of refractory metal-coated multifilamentary yarns having a uniform coating on the filaments which make up each yard, the coating being uniform throughout the length of the yarn such that the coated yarns are suitable for being woven and are suitable for a variety of other uses. The solution is a continuous process which employs a chemical vapor deposition reaction at relatively low temperature and pressure and a separation of the gaseous reaction products from the coated yarn prior to allowing the coated yarn to cool. Reference US Patent 4,343,836. (MCG)

  1. Continuous flow Sonogashira C-C coupling using a heterogeneous palladium-copper dual reactor.

    PubMed

    Tan, Li-Min; Sem, Zhi-Yu; Chong, Wei-Yuan; Liu, Xiaoqian; Hendra; Kwan, Wei Lek; Lee, Chi-Lik Ken

    2013-01-01

    We report the development of a heterogeneous catalyst system on continuous flow chemistry. A palladium (Pd) coated tubular reactor was placed in line with copper (Cu) tubing using a continuous flow platform, and a Sonogashira C-C coupling reaction was used to evaluate the performance. The reactions were favorably carried out in the Cu reactor, catalyzed by the traces of leached Pd from the Pd reactor. The leached Pd and Cu were trapped with a metal scavaging resin at the back-end of the continuous flow system, affording a genuine approach toward green chemistry. PMID:23248977

  2. Remote semi-continuous flow rate logging seepage meter

    NASA Technical Reports Server (NTRS)

    Reay, William G.; Walthall, Harry G.

    1991-01-01

    The movement of groundwater and its associated solutes from upland regions was implicated in the degradation of receiving surface water bodies. Current efforts to directly measure this influx of water incorporate manually operated seepage meters which are hindered by severe limitations. A prototype seepage meter was developed by NASA Langley Research Center and Virginia Polytechnic Institute and State University that will allow for the semi-continuous collection and data logging of seepage flux across the sediment water interface. The meter is designed to operate at depths to 40 meters, and alleviate or minimize all disadvantages associated with traditional methods while remaining cost effective. The unit was designed to operate independently for time periods on the order of weeks with adjustable sample sequences depending upon hydrologic conditions. When used in conjunction with commercially available pressure transducers, this seepage meter allows for correlations to be made between groundwater discharge and tidal/sea state conditions in coastal areas. Field data from the Chesapeake Bay and Florida Bay systems are presented.

  3. X-rays from protostellar jets: emission from continuous flows

    NASA Astrophysics Data System (ADS)

    Bonito, R.; Orlando, S.; Peres, G.; Favata, F.; Rosner, R.

    2007-02-01

    Context: Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. Aims: We performed an extensive exploration of the parameter space for the main parameters influencing the jet/ambient medium interaction. Aims include: 1) to constrain the jet/ambient medium interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predictions to be compared with optical and X-ray observations of protostellar jets; 3) to get insight into the protostellar jet's physical conditions. Methods: We performed a set of two-dimensional hydrodynamic numerical simulations, in cylindrical coordinates, modeling supersonic jets ramming into a uniform ambient medium. The model takes into account the most relevant physical effects, namely thermal conduction and radiative losses. Results: Our model explains the observed X-ray emission from protostellar jets in a natural way. In particular, we find that a protostellar jet that is less dense than the ambient medium well reproduces the observations of the nearest Herbig-Haro object, HH 154, and allows us to make detailed predictions of a possible X-ray source proper motion (v_sh ≈500 km s-1) detectable with Chandra. Furthermore, our results suggest that the simulated protostellar jets which best reproduce the X-rays observations cannot drive molecular outflows.

  4. Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams (Final Report)

    EPA Science Inventory

    This final report is a technical "best practices" document describing sensor deployment for and collection of continuous temperature and flow data at ungaged sites in wadeable streams. This document addresses questions related to equipment needs; configuration, placement, and ins...

  5. A cubic triangular element with local continuity - An application in potential flow

    NASA Astrophysics Data System (ADS)

    Wu, E.-R.

    1981-08-01

    A triangular element is developed using a complete third-degree polynomial as the interpolation function. The nodal variables include the function and its first-order derivatives. A local continuity condition, which implements the conservation of the normal gradients of the interpolation function along the three boundaries of the element, is provided as a remedy for the nonconformity of the first-order derivatives in conventional elements with zeroth order continuity. The element is applied to potential flow problems. Numerical results for the flow over a cylinder and the flow through a draft tube elbow of a hydraulic turbine confirm the validity and the accuracy of this new cubic element. A comparison of this element with a triangular element with zeroth order continuity is made by checking their differences from an analytical solution for the flow over the cylinder. This element appears to be more accurate than the element with zeroth order continuity.

  6. Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams (External Review Draft)

    EPA Science Inventory

    This external review draft report is a technical "best practices" document describing sensor deployment for and data collection of continuous temperature and flow at ungaged sites in wadeable streams. This document addresses questions related to equipment needs; configuration, pl...

  7. Aortic valve decalcification revisited.

    PubMed

    Marty, A T; Mufti, S; Murabit, I

    1989-11-01

    A 75-year-old woman with a small calcified aortic root, severe aortic stenosis and triple vessel coronary artery disease developed angina at rest. Aortic valve decalcification and quadruple aorto-coronary bypass were done as her aortic root was too small and calcified to do anything else. Postoperative clinical and hemodynamic results have been excellent. Literature review supports application of this therapy in selected patients with trileaflet senescent aortic stenosis. PMID:2614067

  8. Fetal cardiac circulation in isolated aortic atresia assessed with ultrasound.

    PubMed

    Sayit, Aslı Tanrıvermiş; Ipek, Ali; Kurt, Aydın; Aghdasi, Bayan G; Arslan, Halil; Gümüş, Mehmet

    2012-01-01

    Congenital heart diseases are common, with an incidence of more than 8 in 1000 live births. Aortic atresia is a rare diagnosis and its prognosis is very poor. In this article, we present a case of isolated aortic atresia, a very rare cardiovascular anomaly, and its fetal ultrasound findings which include blood flow at foramen ovale from left to right, right deviation of the interventricular septum, dysfunction of the mitral valve and cardiomegaly. Aortic stenosis should be considered in the differential diagnosis of aortic atresia. However, in the case of severe aortic stenosis and/or accompanying ventricular septal defect, differential diagnosis may not be done. PMID:24592058

  9. Preoperative Prediction of Aortic Insufficiency During Ventricular Assist Device Treatment.

    PubMed

    Imamura, Teruhiko; Kinugawa, Koichiro

    2016-01-01

    Survival rate in patients with stage D heart failure has improved significantly owing to the development of continuous flow left ventricular assist devices (LVAD), but aortic insufficiency (AI) still remains one of the major unsolved complications that impairs patient quality of life. There are no established treatments for AI, and preoperative prediction and prevention of AI is needed. The opening of a native aortic valve (AV) is a sufficient condition for prevention of AI, and improvement of LV ejection fraction due to LV reverse remodeling (LVRR) is essential to open a native AV. Preoperative insufficient β-blocker treatment and pulsatile flow LVAD usage are keys for LVRR, opening of an AV, and prevention of AI. The second mechanism that leads to AI is remodeling of the aortic root and degeneration of a native AV, which results from reduced pulse pressure during LVAD support. Centrifugal or pulsatile flow LVAD usage has an advantage in terms of preserving pulsatility, and may prevent AI compared with an axial pump. There is less probability of avoiding AI with sufficient β-blocker treatment, and these patients may be good candidates for concomitant surgical intervention to a native AV at the time of LVAD implantation. PMID:26742702

  10. Balloon aortic valvuloplasty as a treatment option in the era of transcatheter aortic valve implantation.

    PubMed

    Costopoulos, Charis; Sutaria, Nilesh; Ariff, Ben; Fertleman, Michael; Malik, Iqbal; Mikhail, Ghada W

    2015-05-01

    Aortic valve stenosis is the commonest encountered valvular pathology and a frequent cause of morbidity and mortality in cases of severe stenosis. Definitive treatment has traditionally been offered in the form of surgical aortic valve replacement in patients with an acceptable surgical risk and more recently with the less invasive transcatheter aortic valve implantation (TAVI) in those where surgery is not a viable option. Prior to the introduction of TAVI, inoperable patients were treated medically and where appropriate with balloon aortic valvuloplasty, a procedure which although effective only provided short-term relief and was associated with high complication rates especially during its infancy. Here we discuss whether balloon aortic valvuloplasty continues to have a role in contemporary clinical practice in an era where significant advances have been achieved in the fields of surgical aortic valve replacement, TAVI and postoperative care. PMID:25865236

  11. GROWTH MEASUREMENTS OF TERRESTRIAL MICROBIAL SPECIES BY A CONTINUOUS-FLOW TECHNIQUE (JOURNAL VERSION)

    EPA Science Inventory

    A continuous nutrient flow system has been developed to measure microbial activity in soil with various concentrations of added substrate. The system consists of a thin soil layer through which substrate was added continuously over periods up to 4.5 days. Substrate utilization wa...

  12. Continuous flow total artificial heart: modeling and feedback control in a mock circulatory system.

    PubMed

    Khalil, Hassan A; Kerr, Daniel T; Franchek, Matthew A; Metcalfe, Ralph W; Benkowski, Robert J; Cohn, William E; Tuzun, Egemen; Radovancevic, Branislav; Frazier, O H; Kadipasaoglu, Kamuran A

    2008-01-01

    We developed a mock circulatory loop and used mathematical modeling to test the in vitro performance of a physiologic flow control system for a total artificial heart (TAH). The TAH was constructed from two continuous flow pumps. The objective of the control system was to maintain loop flow constant in response to changes in outflow resistance of either pump. Baseline outflow resistances of the right (pulmonary vascular resistance) and the left (systemic vascular resistance) pumps were set at 2 and 18 Wood units, respectively. The corresponding circuit flow was 4 L/min. The control system consisted of two digital integral controllers, each regulating the voltage, hence, the rotational speed of one of the pumps. The in vitro performance of the flow control system was validated by increasing systemic and pulmonary vascular resistances in the mock loop by 4 and 8 Wood units (simulating systemic and pulmonary hypertension conditions), respectively. For these simulated hypertensive states, the flow controllers regulated circuit flow back to 4 L/min within seconds by automatically adjusting the rotational speed of either or both pumps. We conclude that this multivariable feedback mechanism may constitute an adequate supplement to the inherent pressure sensitivity of rotary blood pumps for the automatic flow control and left-right flow balance of a dual continuous flow pump TAH system. PMID:18496274

  13. Effect of continuous regional vasoactive agent infusion on liver metastasis blood flow.

    PubMed Central

    Dworkin, M. J.; Carnochan, P.; Allen-Mersh, T. G.

    1997-01-01

    Regionally administered vasopressors might increase tumour chemotherapy uptake by differentially constricting normal and tumour blood vessels, leading to a selective increase in blood flow to the tumour. In this study, we compared the effects of the vasopressors angiotensin II, vasopressin and endothelin I and the vasodilator calcitonin gene-related peptide (CGRP) by continuously measuring liver parenchymal and tumour blood flow during a 30-min regional vasoactive infusion in a rat HSN liver metastasis model. Vasopressin and angiotensin II produced a vasoconstriction that decreased despite continued infusion, while endothelin I infusion led to prolonged vasoconstriction with a more gradual onset. CGRP infusion resulted in increased vessel conductance but a reduction in blood flow due to systemic hypotension. The tumour to normal flow ratio (TNR) was transiently increased during infusion of all pressors, but only endothelin I produced sufficient change to result in a rise in average TNR throughout pressor infusion. Continuous liver and tumour blood flow measurement throughout vasoactive infusion demonstrated that the extent and the duration of blood flow change varied with the agents assessed. No vasoactive agent increased tumour blood flow, but endothelin I had the most suitable vasoactive properties for enhancing tumour uptake of continuously infused chemotherapy. PMID:9365170

  14. Studies with sample conductivity, insertion rates, and particle deflection in a continuous flow electrophoresis system

    NASA Technical Reports Server (NTRS)

    Williams, G., Jr.

    1982-01-01

    The continuous flow electrophoresis system makes electrophoresis possible in a free-flowing film of aqueous electrolyte medium. The sample continuously enters the electrolyte at the top of the chamber and is subjected to the action of a lateral dc field. This divides the sample into fractions since each component has a distinctive electrophoretic mobility. Tests were made using monodisperse polystyrene latex microspheres to determine optimum sample conductivity, insertion rates and optimum electric field applications as baseline data for future STS flight experiments. Optimum sample flow rates for the selected samples were determined to be approximately 26 micro-liters/min. Experiments with samples in deionized water yielded best results and voltages in the 20 V/cm to 30 V/cm range were optimum. Deflections of formaldehyde fixed turkey and bovine erythrocytes were determined using the continuous flow electrophoresis system. The effects of particle interactions on sample resolution and migration in the chamber was also evaluated.

  15. Synthesis of Nitro-Containing Compounds through Multistep Continuous Flow with Heterogeneous Catalysts.

    PubMed

    Ishitani, Haruro; Saito, Yuki; Tsubogo, Tetsu; Kobayashi, Shū

    2016-03-18

    Synthesis of β-nitrostyrene derivatives and their following reactions through two-step continuous-flow protocols with heterogeneous catalysts are described. In the first step to provide β-nitrostyrenes from aromatic aldehydes and nitromethane, readily available amino-functionalized silica gel was employed as a catalyst and gave the products continuously for at least 100 h with high selectivity. In the second step, reactions of β-nitrostyrenes, solid bases, immobilized bases, solid acids, and chiral supported metals and nonmetals were used as catalysts, and seven kinds of nitro-containing organic compounds could be effectively synthesized through the two-step continuous-flow systems. PMID:26926210

  16. Simulation for the development of the continuous groundwater flow measurement technology

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kaoru; Kumagai, Koki; Fujima, Ritsuko; Chikahisa, Hiroshi

    The flow of groundwater varies with time due to rainfall, atmospheric pressure change, tidal change, melting of snow during seasonal change, underground construction works etc. Therefore, to increase the precision of assessing in-situ groundwater flow characteristics, it is important to measure continuously the direction and velocity of the flow, in addition to obtaining accurate data for the afore mentioned environmental changes. The first part of this paper describes the development of a new device for measuring the direction and velocity of groundwater flow. The device was composed of a unique floating sensor with a hinge end at the bottom, which enabled continuous measurement of groundwater flow based on image data processing technique. In the second part, discussion is focused on clarifying the optimum cross-section shape and the behavior of the float sensor in saltwater and freshwater using numerical analysis.

  17. Significance and function of different spinal collateral compartments following thoracic aortic surgery: immediate versus long-term flow compensation.

    PubMed

    Meffert, Philipp; Bischoff, Moritz S; Brenner, Robert; Siepe, Matthias; Beyersdorf, Friedhelm; Kari, Fabian A

    2014-05-01

    Iatrogenic paraplegia has been accompanying cardiovascular surgery since its beginning. As a result, surgeons have been developing many theories about the exact mechanisms of this devastating complication. Thus, the impact of single arteries that contribute to the spinal perfusion is one of the most discussed subjects in modern surgery. The subsequent decision of reattachment or the permanent disconnection of these intercostal arteries divides the surgical community. On the one hand, the anatomical or vascular approach pleads for the immediate reimplantation to reconstruct the anatomical situation. On the other hand, the decision of the permanent disconnection aims at avoiding stealing phenomenon away from the spinal vascular network. This spinal collateral network can be described as consisting of three components-the intraspinal and two paraspinal compartments-that feed the nutrient arteries of the spinal cord. The exact functional impact of the different compartments of the collateral network remains poorly understood. In this review, the function of the intraspinal compartment in the context of collateral network principle as an immediate emergency backup system is described. The exact structure and architectural principles of the intraspinal compartment are described. The critical parameters with regard to the risk of postoperative spinal cord ischaemia are the number of anterior radiculomedullary arteries (ARMAs) and the distance between them in relation to the longitudinal extent of aortic disease. The paraspinal network as a sleeping reserve is proposed as the long-term backup system. This sleeping reserve has to be activated by arteriogenic stimuli. These are presented briefly, and prior findings regarding arteriogenesis are discussed in the light of the collateral network concept. Finally, the role of preoperative visualization of the ARMAs in order to evaluate the risk of postoperative paraplegia is emphasized. PMID:24078102

  18. Hydrodynamic evaluation of a new dispersive aortic cannula (Stealthflow).

    PubMed

    Goto, Takeshi; Inamura, Takao; Shirota, Minori; Fukuda, Wakako; Fukuda, Ikuo; Daitoku, Kazuyuki; Minakawa, Masahito; Ito, Kazuo

    2016-06-01

    The aim of this study was to evaluate flow from a new dispersive aortic cannula (Stealthflow) in the aortic arch using flow visualization methods. Particle image velocimetry was used to analyze flow dynamics in the mock aortic model. Flow patterns, velocity distribution, and streamlines with different shape cannulas were evaluated in a glass aortic arch model. We compared flow parameters in two different dispersive type cannulas: the Stealthflow and the Soft-flow cannula. A large vortex and regurgitant flow were observed in the aortic arch with both cannulas. With the Stealthflow cannula, a high-velocity area with a maximum velocity of 0.68 m/s appeared on the ostium of the cannula in the longitudinal plane. With the Soft-flow cannula, 'multiple jet streams, each with a velocity less than 0.60 m/s, were observed at the cannula outlet. Regurgitant flow from the cannula to the brachiocephalic artery and to the ascending aorta on the greater curvature was specific to the Soft-flow cannula. The degree of regurgitation on the same site was lower with the Stealthflow cannula than with the Soft-flow cannula. The Stealthflow cannula has similar flow properties to those of the Soft-flow cannula according to glass aortic model analysis. It generates gentle flow in the aortic arch and slow flow around the ostia of the aortic arch vessels. The Stealthflow cannula is as effective as the Soft-flow cannula. Care must be taken when the patient has thick atheromatous plaque or frail atheroma on the lesser curvature of the aortic arch. PMID:26526561

  19. Mathematical modeling of aortic valve dynamics during systole.

    PubMed

    Aboelkassem, Yasser; Savic, Dragana; Campbell, Stuart G

    2015-01-21

    We have derived a mathematical model describing aortic valve dynamics and blood flow during systole. The model presents a realistic coupling between aortic valve dynamics, sinus vortex local pressure, and variations in the systemic vascular resistance. The coupling is introduced by using Hill׳s classical semi-spherical vortex model and an aortic pressure-area compliance constitutive relationship. The effects of introducing aortic sinus eddy vortices and variable systemic vascular resistance on overall valve opening-closing dynamics, left ventricular pressure, aortic pressure, blood flow rate, and aortic orifice area are examined. In addition, the strength of the sinus vortex is coupled explicitly to the valve opening angle, and implicitly to the aortic orifice area in order to predict how vortex strength varies during the four descriptive phases of aortic valve motion (fast-opening, fully-opening, slow-closing, and fast-closing). Our results compare favorably with experimental observations and the model reproduces well-known phenomena corresponding to aortic valve function such as the dicrotic notch and retrograde flow at end systole. By invoking a more complete set of physical phenomena, this new model will enable representation of pathophysiological conditions such as aortic valve stenosis or insufficiency, making it possible to predict their integrated effects on cardiac load and systemic hemodynamics. PMID:25451522

  20. Aortic valve replacement in rheumatoid aortic incompetence.

    PubMed Central

    Devlin, A B; Goldstraw, P; Caves, P K

    1978-01-01

    Rheumatoid aortic valve disease is uncommon. and there are few reports of valve replacement in this condition. Aortic valve replacement and partial pericardiectomy was performed in a patient with acute rheumatoid aortitis and aortic incompetence. Previous reports suggest that any patient with rheumatoid arthritis who develops cardiac symptoms should be carefully assessed for surgically treatable involvement of the pericardium or heart valves. Images PMID:725829

  1. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions.

    PubMed

    Kumar, P; Coronel, P; Simunovic, J; Truong, V D; Sandeep, K P

    2007-05-01

    Continuous flow microwave sterilization is an emerging technology that has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temperature range of 20 to 130 degrees C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso. Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso, which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system. PMID:17995769

  2. Open aortic surgery after thoracic endovascular aortic repair.

    PubMed

    Coselli, Joseph S; Spiliotopoulos, Konstantinos; Preventza, Ourania; de la Cruz, Kim I; Amarasekara, Hiruni; Green, Susan Y

    2016-08-01

    In the last decade, thoracic endovascular aortic aneurysm repair (TEVAR) has emerged as an appealing alternative to the traditional open aortic aneurysm repair. This is largely due to generally improved early outcomes associated with TEVAR, including lower perioperative mortality and morbidity. However, it is relatively common for patients who undergo TEVAR to need a secondary intervention. In select circumstances, these secondary interventions are performed as an open procedure. Although it is difficult to assess the rate of open repairs after TEVAR, the rates in large series of TEVAR cases (>300) have ranged from 0.4 to 7.9 %. Major complications of TEVAR that typically necessitates open distal aortic repair (i.e., repair of the descending thoracic or thoracoabdominal aorta) include endoleak (especially type I), aortic fistula, endograft infection, device collapse or migration, and continued expansion of the aneurysm sac. Conversion to open repair of the distal aorta may be either elective (as for many endoleaks) or emergent (as for rupture, retrograde complicated dissection, malperfusion, and endograft infection). In addition, in select patients (e.g., those with a chronic aortic dissection), unrepaired sections of the aorta may progressively dilate, resulting in the need for multiple distal aortic repairs. Open repairs after TEVAR can be broadly classified as full extraction, partial extraction, or full salvage of the stent-graft. Although full and partial stent-graft extraction imply failure of TEVAR, such failure is generally absent in cases where the stent-graft can be fully salvaged. We review the literature regarding open repair after TEVAR and highlight operative strategies. PMID:27314956

  3. Continuous subsonic-sonic flows in convergent nozzles with straight solid walls

    NASA Astrophysics Data System (ADS)

    Nie, Yuanyuan; Wang, Chunpeng

    2016-01-01

    This paper concerns continuous subsonic-sonic potential flows in a two-dimensional convergent nozzle with straight solid walls. It is shown that for the given inlet, which is a perturbation of an arc centered at the vertex of the nozzle, and the given incoming flow angle which is a perturbation of the angle of the inner normal of the inlet, and the given incoming mass flux belonging to an open interval depending only on the adiabatic exponent and the length of the arc, there is a unique continuous subsonic-sonic flow from the given inlet with the given incoming flow angle and the given incoming mass flux. Furthermore, the sonic curve of this flow is a free boundary, where the flow is singular in the sense that the speed is only Hölder continuous and the acceleration blows up at the sonic state. The perturbation problem is solved in the potential plane, where the flow is governed by a degenerate elliptic problem with two free boundaries, on one of which the equation is degenerate and on the other of which the boundary condition is nonlocal.

  4. Highly accurate thermal flow microsensor for continuous and quantitative measurement of cerebral blood flow.

    PubMed

    Li, Chunyan; Wu, Pei-ming; Wu, Zhizhen; Limnuson, Kanokwan; Mehan, Neal; Mozayan, Cameron; Golanov, Eugene V; Ahn, Chong H; Hartings, Jed A; Narayan, Raj K

    2015-10-01

    Cerebral blood flow (CBF) plays a critical role in the exchange of nutrients and metabolites at the capillary level and is tightly regulated to meet the metabolic demands of the brain. After major brain injuries, CBF normally decreases and supporting the injured brain with adequate CBF is a mainstay of therapy after traumatic brain injury. Quantitative and localized measurement of CBF is therefore critically important for evaluation of treatment efficacy and also for understanding of cerebral pathophysiology. We present here an improved thermal flow microsensor and its operation which provides higher accuracy compared to existing devices. The flow microsensor consists of three components, two stacked-up thin film resistive elements serving as composite heater/temperature sensor and one remote resistive element for environmental temperature compensation. It operates in constant-temperature mode (~2 °C above the medium temperature) providing 20 ms temporal resolution. Compared to previous thermal flow microsensor based on self-heating and self-sensing design, the sensor presented provides at least two-fold improvement in accuracy in the range from 0 to 200 ml/100 g/min. This is mainly achieved by using the stacked-up structure, where the heating and sensing are separated to improve the temperature measurement accuracy by minimization of errors introduced by self-heating. PMID:26256480

  5. Abdominal aortic aneurysm

    MedlinePlus

    ... to the abdomen, pelvis, and legs. An abdominal aortic aneurysm occurs when an area of the aorta becomes ... blood pressure Male gender Genetic factors An abdominal aortic aneurysm is most often seen in males over age ...

  6. Aortic aneurysm repair - endovascular

    MedlinePlus

    ... Endovascular aneurysm repair - aorta; AAA repair - endovascular; Repair - aortic aneurysm - endovascular ... leaking or bleeding. You may have an abdominal aortic aneurysm that is not causing any symptoms or problems. ...

  7. Aortic aneurysm repair - endovascular

    MedlinePlus

    EVAR; Endovascular aneurysm repair - aorta; AAA repair - endovascular; Repair - aortic aneurysm - endovascular ... leaking or bleeding. You may have an abdominal aortic aneurysm that is not causing any symptoms or problems. ...

  8. Flow angle dependent photoacoustic Doppler power spectra under intensity-modulated continuous wave laser excitation

    NASA Astrophysics Data System (ADS)

    Tong, Yu; Zhao, Hongcai; Fang, Hui; Zhao, Youquan; Yuan, Xiaocong

    2016-02-01

    Photoacoustic Doppler (PAD) power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.

  9. Continuation in a parameter - Experience with viscous and free surface flows

    NASA Technical Reports Server (NTRS)

    Kheshgi, H. S.; Basaran, O. A.; Benner, R. E.; Kistler, S. F.; Scriven, L. E.

    1983-01-01

    The results of modifications in continuation methods applied to obtain solutions to the Navier-Stokes systems of equations for incompressible, two-dimensional, steady flows are reported. It is shown that parameter continuation permits prediction of accurate, initial estimates for iterative processing of nonlinear finite difference and finite element equations of motions. The new parameter steps are derived from values of the preceding parameter steps. The accuracy of the estimates is ensured with appropriate choices of the step size. The continuation predictor/iterative corrector is demonstrated to trace the branches of parameter space along which steady flow states are found, and techniques are available for tracing multiply branching paths. The techniques are applied to solving the Navier-Stokes equations for flow through a rotating square channel, the formation of a falling liquid curtain, and gyrostatic equilibria of rotating cylindrical drops.

  10. Polystyrene latex separations by continuous flow electrophoresis on the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Snyder, R. S.; Rhodes, P. H.; Miller, T. Y.; Micale, F. J.; Mann, R. V.

    1986-01-01

    The seventh mission of the Space Shuttle carried two NASA experiments in the McDonnell Douglas Astronautics Corporation continuous flow electrophoresis system. The objectives were to test the operation of continuous flow electrophoresis in a reduced gravity environment using stable particles with established electrokinetic properties and specifically to evaluate the influence of the electrical properties of the sample constituents on the resolution of the continuous flow electrophoretic device. Polystrene latex microspheres dispersed in a solution with three times the electrical conductivity of the curtain buffer separated with a significantly larger band spread compared to the second experiment under matched conductivity conditions. It is proposed that the sample of higher electrical conductivity distorted the electric field near the sample stream so that the polystyrene latex particles migrated toward the chamber walls where electroosmosis retarded and spread the sample.

  11. The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

    PubMed Central

    2015-01-01

    Summary The implementation of continuous flow processing as a key enabling technology has transformed the way we conduct chemistry and has expanded our synthetic capabilities. As a result many new preparative routes have been designed towards commercially relevant drug compounds achieving more efficient and reproducible manufacture. This review article aims to illustrate the holistic systems approach and diverse applications of flow chemistry to the preparation of pharmaceutically active molecules, demonstrating the value of this strategy towards every aspect ranging from synthesis, in-line analysis and purification to final formulation and tableting. Although this review will primarily concentrate on large scale continuous processing, additional selected syntheses using micro or meso-scaled flow reactors will be exemplified for key transformations and process control. It is hoped that the reader will gain an appreciation of the innovative technology and transformational nature that flow chemistry can leverage to an overall process. PMID:26425178

  12. Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity

    NASA Technical Reports Server (NTRS)

    Smolka, A. J. K.; Mcguire, J. K.

    1978-01-01

    The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

  13. Discrepancies between cardiovascular magnetic resonance and Doppler echocardiography in the measurement of transvalvular gradient in aortic stenosis: the effect of flow vorticity

    PubMed Central

    2013-01-01

    Background Valve effective orifice area EOA and transvalvular mean pressure gradient (MPG) are the most frequently used parameters to assess aortic stenosis (AS) severity. However, MPG measured by cardiovascular magnetic resonance (CMR) may differ from the one measured by transthoracic Doppler-echocardiography (TTE). The objectives of this study were: 1) to identify the factors responsible for the MPG measurement discrepancies by CMR versus TTE in AS patients; 2) to investigate the effect of flow vorticity on AS severity assessment by CMR; and 3) to evaluate two models reconciling MPG discrepancies between CMR/TTE measurements. Methods Eight healthy subjects and 60 patients with AS underwent TTE and CMR. Strouhal number (St), energy loss (EL), and vorticity were computed from CMR. Two correction models were evaluated: 1) based on the Gorlin equation (MPGCMR-Gorlin); 2) based on a multivariate regression model (MPGCMR-Predicted). Results MPGCMR underestimated MPGTTE (bias = −6.5 mmHg, limits of agreement from −18.3 to 5.2 mmHg). On multivariate regression analysis, St (p = 0.002), EL (p = 0.001), and mean systolic vorticity (p < 0.001) were independently associated with larger MPG discrepancies between CMR and TTE. MPGCMR-Gorlin and MPGTTE correlation and agreement were r = 0.7; bias = −2.8 mmHg, limits of agreement from −18.4 to 12.9 mmHg. MPGCMR-Predicted model showed better correlation and agreement with MPGTTE (r = 0.82; bias = 0.5 mmHg, limits of agreement from −9.1 to 10.2 mmHg) than measured MPGCMR and MPGCMR-Gorlin. Conclusion Flow vorticity is one of the main factors responsible for MPG discrepancies between CMR and TTE. PMID:24053194

  14. Abdominal Aortic Aneurysms: Treatments

    MedlinePlus

    ... information Membership Directory (SIR login) Interventional Radiology Abdominal Aortic Aneurysms Interventional Radiologists Treat Abdominal Aneurysms Nonsurgically Interventional radiologists ...

  15. Continuous-flow organic synthesis: a tool for the modern medicinal chemist.

    PubMed

    Wiles, Charlotte; Watts, Paul

    2009-12-01

    Medicinal chemists are under increasing pressure, not only to identify lead compounds and optimize them into clinical candidates, but also to produce materials in sufficient quantities for subsequent investigation. With this in mind, continuous-flow methodology presents an opportunity to reduce the time taken to, first, identify the compound and, second, scale the process for evaluation and, where necessary, production. It is therefore the aim of this review to provide the reader with an insight into the advantages associated with the use of continuous-flow chemistry through the use of strategically selected literature examples. PMID:21425981

  16. A new apparatus for continuous countercurrent flow of solids and liquids

    NASA Astrophysics Data System (ADS)

    Haas, P. A.

    A contactor was developed to provide true countercurrent, continuous flow of gel spheres and liquid in a moving bed. To provide smooth and controlled movement of solids, the key features consisted of a common cross section for the moving bed and a small fluidized bed, a jet to give a slurry at the bottom of the moving bed, and a controlled flow of part of this slurry to the fluidized bed. A completely continuous pilot plant for preparation of nuclear fuel by a gel-sphere process was operated with three of these moving-bed fluidized-bed contactors. Different control procedures and good countercurrent washing results were demonstrated.

  17. An efficient continuous flow process for the synthesis of a non-conventional mixture of fructooligosaccharides.

    PubMed

    Zambelli, Paolo; Tamborini, Lucia; Cazzamalli, Samuele; Pinto, Andrea; Arioli, Stefania; Balzaretti, Silvia; Plou, Francisco J; Fernandez-Arrojo, Lucia; Molinari, Francesco; Conti, Paola; Romano, Diego

    2016-01-01

    A sustainable and scalable process for the production of a new mixture of fructooligosaccharides (FOS) was developed using a continuous-flow approach based on an immobilized whole cells-packed bed reactor. The technological transfer from a classical batch system to an innovative flow environment allowed a significant improvement of the productivity. Moreover, the stability of this production system was ascertained by up to 7 days of continuous working. These results suggest the suitability of the proposed method for a large-scale production of the desired FOS mixture, in view of a foreseeable use as a novel prebiotic preparation. PMID:26213017

  18. Large-Scale mRNA Transfection of Dendritic Cells by Electroporation in Continuous Flow Systems.

    PubMed

    Selmeczi, David; Hansen, Thomas Steen; Met, Özcan; Svane, Inge Marie; Larsen, Niels B

    2016-01-01

    Electroporation is well established for transient mRNA transfection of many mammalian cells, including immune cells such as dendritic cells used in cancer immunotherapy. Therapeutic application requires methods to efficiently electroporate and transfect millions of immune cells in a fast process with high cell survival. Continuous flow of suspended dendritic cells through a channel incorporating spatially separated microporous meshes with a synchronized electrical pulsing sequence can yield dendritic cell transfection rates of >75 % with survival rates of >90 %. This chapter describes the instrumentation and methods needed for the efficient transfection by electroporation of millions of dendritic cells in one continuous flow process. PMID:27236798

  19. Continuous-flow stereoselective organocatalyzed Diels-Alder reactions in a chiral catalytic "homemade" HPLC column.

    PubMed

    Chiroli, Valerio; Benaglia, Maurizio; Cozzi, Franco; Puglisi, Alessandra; Annunziata, Rita; Celentano, Giuseppe

    2013-07-19

    Continuous-flow organocatalyzed Diels-Alder reactions have been performed with excellent enantioselectivity for the first time in a chiral "homemade" HPLC column, packed with silica on which a MacMillan catalyst has been supported by a straightforward immobilization procedure. The versatility of the system was also proven by running with the same column continuous-flow stereoselective reactions with three different substrates, showing that the catalytic reactor may efficiently work in continuo for more than 150 h; the regeneration of the HPLC column was also demonstrated, allowing to further extend the activity of the reactor to more than 300 operating hours. PMID:23808663

  20. Multistep continuous-flow synthesis of (R)- and (S)-rolipram using heterogeneous catalysts

    NASA Astrophysics Data System (ADS)

    Tsubogo, Tetsu; Oyamada, Hidekazu; Kobayashi, Shū

    2015-04-01

    Chemical manufacturing is conducted using either batch systems or continuous-flow systems. Flow systems have several advantages over batch systems, particularly in terms of productivity, heat and mixing efficiency, safety, and reproducibility. However, for over half a century, pharmaceutical manufacturing has used batch systems because the synthesis of complex molecules such as drugs has been difficult to achieve with continuous-flow systems. Here we describe the continuous-flow synthesis of drugs using only columns packed with heterogeneous catalysts. Commercially available starting materials were successively passed through four columns containing achiral and chiral heterogeneous catalysts to produce (R)-rolipram, an anti-inflammatory drug and one of the family of γ-aminobutyric acid (GABA) derivatives. In addition, simply by replacing a column packed with a chiral heterogeneous catalyst with another column packed with the opposing enantiomer, we obtained antipole (S)-rolipram. Similarly, we also synthesized (R)-phenibut, another drug belonging to the GABA family. These flow systems are simple and stable with no leaching of metal catalysts. Our results demonstrate that multistep (eight steps in this case) chemical transformations for drug synthesis can proceed smoothly under flow conditions using only heterogeneous catalysts, without the isolation of any intermediates and without the separation of any catalysts, co-products, by-products, and excess reagents. We anticipate that such syntheses will be useful in pharmaceutical manufacturing.

  1. Multistep continuous-flow synthesis of (R)- and (S)-rolipram using heterogeneous catalysts.

    PubMed

    Tsubogo, Tetsu; Oyamada, Hidekazu; Kobayashi, Shū

    2015-04-16

    Chemical manufacturing is conducted using either batch systems or continuous-flow systems. Flow systems have several advantages over batch systems, particularly in terms of productivity, heat and mixing efficiency, safety, and reproducibility. However, for over half a century, pharmaceutical manufacturing has used batch systems because the synthesis of complex molecules such as drugs has been difficult to achieve with continuous-flow systems. Here we describe the continuous-flow synthesis of drugs using only columns packed with heterogeneous catalysts. Commercially available starting materials were successively passed through four columns containing achiral and chiral heterogeneous catalysts to produce (R)-rolipram, an anti-inflammatory drug and one of the family of γ-aminobutyric acid (GABA) derivatives. In addition, simply by replacing a column packed with a chiral heterogeneous catalyst with another column packed with the opposing enantiomer, we obtained antipole (S)-rolipram. Similarly, we also synthesized (R)-phenibut, another drug belonging to the GABA family. These flow systems are simple and stable with no leaching of metal catalysts. Our results demonstrate that multistep (eight steps in this case) chemical transformations for drug synthesis can proceed smoothly under flow conditions using only heterogeneous catalysts, without the isolation of any intermediates and without the separation of any catalysts, co-products, by-products, and excess reagents. We anticipate that such syntheses will be useful in pharmaceutical manufacturing. PMID:25877201

  2. Study of an ammonia-based wet scrubbing process in a continuous flow system

    SciTech Connect

    Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan

    2013-01-01

    A continuous gas and liquid flow, regenerative scrubbing process for CO{sub 2} capture was demonstrated at the bench-scale level. An aqueous ammonia-based solution captures CO{sub 2} from simulated flue gas in an absorber and releases a nearly pure stream of CO{sub 2} in the regenerator. After the regeneration, the solution of ammonium compounds is recycled to the absorber. The design of a continuous flow unit was based on earlier exploratory results from a semi-batch reactor, where a CO{sub 2} and N{sub 2} simulated flue gas mixture flowed through a well-mixed batch of ammonia-based solution. During the semi-batch tests, the solution was cycled between absorption and regeneration steps to measure the carrying capacity of the solution at various initial ammonia concentrations and temperatures. Consequentially, a series of tests were conducted on the continuous unit to observe the effect of various parameters on CO{sub 2} removal efficiency and regenerator effectiveness within the flow system. The parameters that were studied included absorber temperature, regenerator temperature, initial NH{sub 3} concentration, simulated flue gas flow rate, liquid solvent inventory in the flow system, and height of the packed-bed absorber. From this testing and subsequent testing, ammonia losses from both the absorption and regeneration steps were quantified, and attempts were made to maintain steady state during operations. Implications of experimental results with respect to process design are discussed.

  3. The synthesis of cadmium sulfide nanoplatelets using a novel continuous flow sonochemical reactor

    DOE PAGESBeta

    Palanisamy, Barath; Paul, Brian; Chang, Chih -hung

    2015-01-21

    A continuous flow sonochemical reactor was developed capable of producing metastable cadmium sulfide (CdS) nanoplatelets with thicknesses at or below 10 nm. The continuous flow sonochemical reactor included the passive in-line micromixing of reagents prior to sonochemical reaction. Synthesis results were compared with those from reactors involving batch conventional heating and batch ultrasound-induced heating. The continuous sonochemical synthesis was found to result in high aspect ratio hexagonal platelets of CdS possessing cubic crystal structures with thicknesses well below 10 nm. The unique shape and crystal structure of the nanoplatelets are suggestive of high localized temperatures within the sonochemical process. Asmore » a result, the particle size uniformity and product throughput are much higher for the continuous sonochemical process in comparison to the batch sonochemical process and conventional synthesis processes.« less

  4. The synthesis of cadmium sulfide nanoplatelets using a novel continuous flow sonochemical reactor

    SciTech Connect

    Palanisamy, Barath; Paul, Brian; Chang, Chih -hung

    2015-01-21

    A continuous flow sonochemical reactor was developed capable of producing metastable cadmium sulfide (CdS) nanoplatelets with thicknesses at or below 10 nm. The continuous flow sonochemical reactor included the passive in-line micromixing of reagents prior to sonochemical reaction. Synthesis results were compared with those from reactors involving batch conventional heating and batch ultrasound-induced heating. The continuous sonochemical synthesis was found to result in high aspect ratio hexagonal platelets of CdS possessing cubic crystal structures with thicknesses well below 10 nm. The unique shape and crystal structure of the nanoplatelets are suggestive of high localized temperatures within the sonochemical process. As a result, the particle size uniformity and product throughput are much higher for the continuous sonochemical process in comparison to the batch sonochemical process and conventional synthesis processes.

  5. Programmed Speed Reduction Enables Aortic Valve Opening and Increased Pulsatility in the LVAD-Assisted Heart.

    PubMed

    Tolpen, Sam; Janmaat, Jochem; Reider, Claudine; Kallel, Faouzi; Farrar, David; May-Newman, Karen

    2015-01-01

    Aortic valve opening (AVO) during left ventricular assist device (LVAD) support aids in preventing valve fusion, incompetence, and thrombosis. The programmed low speed algorithm (PLSA) allows AVO intermittently by reducing continuous motor speed during a dwell time. AVO and hemodynamics in the LVAD-assisted heart were measured using a HeartMate II (Thoratec Corporation, Pleasanton, CA) LVAD with a PLSA controller in a mock circulatory loop. Left ventricle and aortic pressures, LVAD, and total aortic flow were measured during pre-LVAD, non-PLSA and PLSA combinations of cardiac function, and LVAD speed. The low cardiac setting corresponded to a pre-LVAD cardiac output of 2.8 L/min, stroke volume of 40 ml, and ejection fraction of 22%; the medium setting produced values of 3.5 L/min, 50 ml, and 28%, respectively. Results show that the PLSA controller set at 10 krpm, dropping to 7 krpm for dwell time of 6 s, adequately produced AVO for all tested cardiac functions with only minimal changes in cardiac output. However, AVO frequency was independent of opening area and systolic duration, which both decreased with increasing LVAD support. Furthermore, aortic pulsatility index quadrupled in the aortic root and doubled in the distal aorta during PLSA conditions, providing evidence that AVO and blood mixing are enabled by PLSA control at the appropriate speed. PMID:25961849

  6. Transcatheter aortic valve implantation

    PubMed Central

    Oliemy, Ahmed

    2014-01-01

    Transcatheter aortic valve implantation was developed to offer a therapeutic solution to patients with severe symptomatic aortic stenosis who are not candidates for conventional aortic valve replacement. The improvement in transcatheter aortic valve implantation outcomes is still of concern in the areas of stroke, vascular injury, heart block, paravalvular regurgitation and valve durability. Concomitantly, the progress, both technical and in terms of material advances of transcatheter valve systems, as well as in patient selection, renders transcatheter aortic valve implantation an increasingly viable treatment for more and more patients with structural heart disease. PMID:25374670

  7. Axial and centrifugal continuous-flow rotary pumps: a translation from pump mechanics to clinical practice.

    PubMed

    Moazami, Nader; Fukamachi, Kiyotaka; Kobayashi, Mariko; Smedira, Nicholas G; Hoercher, Katherine J; Massiello, Alex; Lee, Sangjin; Horvath, David J; Starling, Randall C

    2013-01-01

    The recent success of continuous-flow circulatory support devices has led to the growing acceptance of these devices as a viable therapeutic option for end-stage heart failure patients who are not responsive to current pharmacologic and electrophysiologic therapies. This article defines and clarifies the major classification of these pumps as axial or centrifugal continuous-flow devices by discussing the difference in their inherent mechanics and describing how these features translate clinically to pump selection and patient management issues. Axial vs centrifugal pump and bearing design, theory of operation, hydrodynamic performance, and current vs flow relationships are discussed. A review of axial vs centrifugal physiology, pre-load and after-load sensitivity, flow pulsatility, and issues related to automatic physiologic control and suction prevention algorithms is offered. Reliability and biocompatibility of the two types of pumps are reviewed from the perspectives of mechanical wear, implant life, hemolysis, and pump deposition. Finally, a glimpse into the future of continuous-flow technologies is presented. PMID:23260699

  8. [Continuous-flow determination of delta-aminolevulinic acid in urine (author's transl)].

    PubMed

    Balduyck-Aouadi, M; Mizon-Capron, C; Mizon, J; Boniface, M

    1981-01-01

    The automatic determination of urinary ALA using a continuous flow methodology, is described. The amplification of the measured signal, with an adjusted range expander, allows to reduce the sample volume and to decrease drastically the effects of interfering substances. The results are compared with the reference method of Davis and Andelman [11]. PMID:7212399

  9. Effects Of Nutrient Source And Supply On Crude Oil Biodegradation In Continuous-Flow Beach Microcosms

    EPA Science Inventory

    Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or the exten...

  10. Catalytic Macrocyclization Strategies Using Continuous Flow: Formal Total Synthesis of Ivorenolide A.

    PubMed

    de Léséleuc, Mylène; Godin, Éric; Parisien-Collette, Shawn; Lévesque, Alexandre; Collins, Shawn K

    2016-08-01

    A formal total synthesis of ivorenolide A has been accomplished employing a Z-selective olefin cross metathesis and a macrocyclic Glaser-Hay coupling as key steps. The macrocyclization protocol employed a phase separation/continuous flow manifold whose advantages include catalysis, fast reaction times, high concentrations, and facile scale-up. PMID:27404899

  11. Studying Fast Reactions: Construction and Use of a Low-Cost Continuous-Flow Instrument

    ERIC Educational Resources Information Center

    Bisson, Patrick J.; Whitten, James E.

    2006-01-01

    The construction and use of a low-cost continuous-flow instrument for measuring the kinetics of fast reaction which include the use of an light emitting diode light source, a photodiode-on-a-chip detector, and a position sensor is demonstrated. The instrument is suitable for the physical chemistry laboratory and could be used to study the kinetics…

  12. Series DNA Amplification Using the Continuous-Flow Polymerase Chain Reaction Chip

    NASA Astrophysics Data System (ADS)

    Joung, Seung-Ryong; Kang, Chi Jung; Kim, Yong-Sang

    2008-02-01

    We proposed a continuous-flow polymerase chain reaction (PCR) chip that can be used for series DNA amplification. The continuous-flow PCR chip has several advantages such as fast thermal cycling, series of amplifications, cost-effective fabrication, portability, and fluorescence detection. The continuous-flow PCR chip is composed of two parts namely poly(dimethylsiloxane) (PDMS) microchannel for sample injection and indium-tin-oxide (ITO) heater/glass chip for thermal cycling. The fabricated microchannel width and depth are 250 and 200 µm, respectively. Also, the total working length of the PDMS microchannel is 1340 mm which is equivalent for 20 cycles of amplification. A 2:2:3 microchannel length ratio for three different temperature zones namely denaturation, annealing, and extension was assigned, respectively. Upon the operation of the fabricated continuous-flow PCR chip, the amplification of plasmid DNA pKS-GFP with 720 base pairs and PG-noswsi with 300 base pairs were found successfully with a total reaction time of 15 min.

  13. Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Initial test runs were conducted using a 5 kW microwave unit to measure dielectr...

  14. Methylation of 2-Naphthol Using Dimethyl Carbonate under Continuous-Flow Gas-Phase Conditions

    ERIC Educational Resources Information Center

    Tundo, Pietro; Rosamilia, Anthony E.; Arico, Fabio

    2010-01-01

    This experiment investigates the methylation of 2-naphthol with dimethyl carbonate. The volatility of the substrates, products, and co-products allows the reaction to be performed using a continuous-flow gas-phase setup at ambient pressure. The reaction uses catalytic quantities of base, achieves high conversion, produces little waste, and…

  15. Continuous flow hydrogenation of nitroarenes, azides and alkenes using maghemite-Pd nanocomposites

    EPA Science Inventory

    Maghemite-supported ultra-fine Pd (1-2 nm) nanoparticles, prepared by a simple co-precipitation method, find application in the catalytic continuous flow hydrogenation of nitroarenes, azides, and alkenes wherein they play an important role in reduction of various functional group...

  16. Enrichment of Denitrifying Methane-Oxidizing Microorganisms Using Up-Flow Continuous Reactors and Batch Cultures

    PubMed Central

    Hatamoto, Masashi; Kimura, Masafumi; Sato, Takafumi; Koizumi, Masato; Takahashi, Masanobu; Kawakami, Shuji; Araki, Nobuo; Yamaguchi, Takashi

    2014-01-01

    Denitrifying anaerobic methane oxidizing (DAMO) microorganisms were enriched from paddy field soils using continuous-flow and batch cultures fed with nitrate or nitrite as a sole electron acceptor. After several months of cultivation, the continuous-flow cultures using nitrite showed remarkable simultaneous methane oxidation and nitrite reduction and DAMO bacteria belonging to phylum NC10 were enriched. A maximum volumetric nitrite consumption rate of 70.4±3.4 mg-N·L−1·day−1 was achieved with very short hydraulic retention time of 2.1 hour. In the culture, about 68% of total microbial cells were bacteria and no archaeal cells were detected by fluorescence in situ hybridization. In the nitrate-fed continuous-flow cultures, 58% of total microbial cells were bacteria while archaeal cells accounted for 7% of total cell numbers. Phylogenetic analysis of pmoA gene sequence showed that enriched DAMO bacteria in the continuous-flow cultivation had over 98% sequence similarity to DAMO bacteria in the inoculum. In contrast, for batch culture, the enriched pmoA gene sequences had 89–91% sequence similarity to DAMO bacteria in the inoculum. These results indicate that electron acceptor and cultivation method strongly affect the microbial community structures of DAMO consortia. PMID:25545013

  17. ESTIMATION OF PHYTOPLANKTON DECOMPOSITION RATES USING TWO-STAGE CONTINUOUS FLOW STUDIES

    EPA Science Inventory

    A two-stage continuous flow (TSCF) system was used to quantify phytoplankton decomposition rates and to characterize the decay process as a function of phytoplankton species, phytoplankton physiological state, and the presence and character of a decomposer community. A TSCF syste...

  18. EFFECTS OF GLYPHOSATE AND NITRAPYRIN ON SELECTED BACTERIAL POPULATIONS IN CONTINUOUS-FLOW CULTURE

    EPA Science Inventory

    This study examines the effects of Roundup [N-(phosphonomethyl)glycine] and N-Serve [2-chloro-6-(trichloromethyl)pyridine] on the culture of soil organisms in a continuous-flow column system. n this study, nitrifying and various heterotrophic bacterial populations were enumerated...

  19. 42 CFR 84.148 - Type C supplied-air respirator, continuous flow class; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Type C supplied-air respirator, continuous flow class; minimum requirements. 84.148 Section 84.148 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

  20. Cardiovascular devices; reclassification of intra-aortic balloon and control systems for acute coronary syndrome, cardiac and non-cardiac surgery, or complications of heart failure; effective date of requirement for premarket approval for intra-aortic balloon and control systems for septic shock or pulsatile flow generation. Final order.

    PubMed

    2013-12-30

    The Food and Drug Administration (FDA) is issuing a final order to reclassify intra-aortic balloon and control system (IABP) devices when indicated for acute coronary syndrome, cardiac and non-cardiac surgery, or complications of heart failure, a preamendments class III device, into class II (special controls), and to require the filing of a premarket approval application (PMA) or a notice of completion of a product development protocol (PDP) for IABPs when indicated for septic shock or pulsatile flow generation. PMID:24383147

  1. Flow Effects on the Controlled Growth of Nanostructured Networks at Microcapillary Walls for Applications in Continuous Flow Reactions.

    PubMed

    Wang, Gang; Yuan, Cansheng; Fu, Boyi; He, Luye; Reichmanis, Elsa; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang

    2015-09-30

    Low-cost microfluidic devices are desirable for many chemical processes; however, access to robust, inert, and appropriately structured materials for the inner channel wall is severely limited. Here, the shear force within confined microchannels was tuned through control of reactant solution fluid-flow and shown to dramatically impact nano- through microstructure growth. Combined use of experimental results and simulations allowed controlled growth of 3D networked Zn(OH)F nanostructures with uniform pore distributions and large fluid contact areas on inner microchannel walls. These attributes facilitated subsequent preparation of uniformly distributed Pd and PdPt networks with high structural and chemical stability using a facile, in situ conversion method. The advantageous properties of the microchannel based catalytic system were demonstrated using microwave-assisted continuous-flow coupling as a representative reaction. High conversion rates and good recyclability were obtained. Controlling materials nanostructure via fluid-flow-enhanced growth affords a general strategy to optimize the structure of an inner microchannel wall for desired attributes. The approach provides a promising pathway toward versatile, high-performance, and low-cost microfluidic devices for continuous-flow chemical processes. PMID:26352859

  2. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. 84.155 Section... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type... shall not exceed 25 mm. (1 inch) of water-column height when the air flow into the...

  3. Switchgrass (Panicum virgatum) fermentation by Clostridium thermocellum and Clostridium saccharoperbutylacetonicum sequential culture in a continuous flow reactor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study was conducted to evaluate fermentation by Clostridium thermocellum and C. saccharoperbutylacetonicum in a continuous-flow, high-solids reactor. Liquid medium was continuously flowed through switchgrass (2 mm particle size) at one of three flow rates: 83.33 mL h-1 (2 L d-1), 41.66 mL h-1(1 ...

  4. Continuous production of Cu2ZnSnS4 nanocrystals in a flow reactor.

    PubMed

    Shavel, Alexey; Cadavid, Doris; Ibáñez, Maria; Carrete, Alex; Cabot, Andreu

    2012-01-25

    A procedure for the continuous production of Cu(2)ZnSnS(4) (CZTS) nanoparticles with controlled composition is presented. CZTS nanoparticles were prepared through the reaction of the metals' amino complexes with elemental sulfur in a continuous-flow reactor at moderate temperatures (300-330 °C). High-resolution transmission electron microscopy and X-ray diffraction analysis showed the nanocrystals to have a crystallographic structure compatible with that of the kesterite. Chemical characterization of the materials showed the presence of the four elements in each individual nanocrystal. Composition control was achieved by adjusting the solution flow rate through the reactor and the proper choice of the nominal precursor concentration within the flowing solution. Single-particle analysis revealed a composition distribution within each sample, which was optimized at the highest synthesis temperatures used. PMID:22211575

  5. Continuous flow electrophoresis system experiments on shuttle flights STS-6 and STS-7

    NASA Technical Reports Server (NTRS)

    Snyder, Robert S.; Rhodes, Percy H.; Miller, Teresa Y.

    1988-01-01

    The development of a space continuous flow electrophoresis system (CFES) is discussed. The objectives of the experiment were: (1) to use a model sample material at a high concentration to evaluate the continuous flow electrophoresis process in the McDonnell Douglass CFES instrument and compare its separation resolution and sample throughput with related devices on Earth, and (2) to expand the basic knowledge of the limitations imposed by fluid flows and particle concentration effects on the electrophoresis process by careful design and evaluation of the space experiment. Hemoglobin and polysaccharide were selected as samples of concentration effects. The results from space show a large band spread of the high concentration of the single species of hemoglobin that was principally due to the mismatch of electrical conductivity between the sample and buffer.

  6. Highly Efficient Photocatalysts and Continuous-Flow Photocatalytic Reactors for Degradation of Organic Pollutants in Wastewater.

    PubMed

    Chang, Sujie; Yang, Xiaoqiu; Sang, Yuanhua; Liu, Hong

    2016-09-01

    One of the most important applications for photocatalysis is engineered water treatment that photodegrades organic pollutants in wastewater at low cost. To overcome the low efficiency of batch degradation methods, continuous-flow photocatalytic reactors have been proposed and have become the most promising method for mass water treatment. However, most commercial semiconductor photocatalysts are granular nanoparticles with low activity and a narrow active light wavelength band; this creates difficulties for direct use in continuous-flow photocatalytic reactors. Therefore, a high-performance photodegradation photocatalyst with proper morphology or structure is key for continuous photocatalytic degradation. Moreover, a well-designed photocatalytic device is another important component for continuous-flow photocatalysis and determines the efficiency of photocatalysis in practical water treatment. This review describes the basic design principles and synthesis of photocatalysts with excellent performance and special morphologies suitable for a filtering photocatalysis process. Certain promising continuous photodegradation reactors are also categorized and summarized. Additionally, selected scientific and technical problems that must be urgently solved are suggested. PMID:27389817

  7. Continuous flow electrocoagulation in the treatment of wastewater from dairy industries.

    PubMed

    Benazzi, Toni L; Di Luccio, Marco; Dallago, Rogério M; Steffens, Juliana; Mores, Rúbia; Do Nascimento, Mariele S; Krebs, Jociane; Ceni, Gustavo

    2016-01-01

    Dairy industry wastewater contains high levels of organic matter, consisting mainly of fat, protein and products of their partial microbial decomposition. In the present study, the use of continuous electrocoagulation is proposed for the primary treatment of dairy wastewater. The electrochemical treatment was carried out in a continuous flow cell with aluminum electrodes. The influence of the voltage, the distance between the electrodes and the hydraulic residence time (HRT) on the process performance was assessed, by measuring the removal of color, turbidity, total organic carbon (TOC) and chemical oxygen demand (COD). The optimum voltage, distance between the electrodes and HRT were 10 V, 1 cm and 90 min, respectively, yielding a current density of 13.3 A.m(-2). Under these conditions, removal of color, turbidity, TOC and COD were 94%, 93%, 65% and 69%, respectively, after a steady state was reached in the continuous flow reactor. PMID:27003084

  8. Continuous measurement of enzymatic kinetics in droplet flow for point-of-care monitoring.

    PubMed

    Hassan, Sammer-Ul; Nightingale, Adrian M; Niu, Xize

    2016-05-23

    Droplet microfluidics is ideally suited to continuous biochemical analysis, requiring low sample volumes and offering high temporal resolution. Many biochemical assays are based on enzymatic reactions, the kinetics of which can be obtained by probing droplets at multiple points over time. Here we present a miniaturised multi-detector flow cell to analyse enzyme kinetics in droplets, with an example application of continuous glucose measurement. Reaction rates and Michaelis-Menten kinetics can be quantified for each individual droplet and unknown glucose concentrations can be accurately determined (errors <5%). Droplets can be probed continuously giving short sample-to-result time (∼30 s) measurement. In contrast to previous reports of multipoint droplet measurement (all of which used bulky microscope-based setups) the flow cell presented here has a small footprint and uses low-powered, low-cost components, making it ideally suited for use in field-deployable devices. PMID:27007645

  9. On-demand continuous-flow production of pharmaceuticals in a compact, reconfigurable system.

    PubMed

    Adamo, Andrea; Beingessner, Rachel L; Behnam, Mohsen; Chen, Jie; Jamison, Timothy F; Jensen, Klavs F; Monbaliu, Jean-Christophe M; Myerson, Allan S; Revalor, Eve M; Snead, David R; Stelzer, Torsten; Weeranoppanant, Nopphon; Wong, Shin Yee; Zhang, Ping

    2016-04-01

    Pharmaceutical manufacturing typically uses batch processing at multiple locations. Disadvantages of this approach include long production times and the potential for supply chain disruptions. As a preliminary demonstration of an alternative approach, we report here the continuous-flow synthesis and formulation of active pharmaceutical ingredients in a compact, reconfigurable manufacturing platform. Continuous end-to-end synthesis in the refrigerator-sized [1.0 meter (width) × 0.7 meter (length) × 1.8 meter (height)] system produces sufficient quantities per day to supply hundreds to thousands of oral or topical liquid doses of diphenhydramine hydrochloride, lidocaine hydrochloride, diazepam, and fluoxetine hydrochloride that meet U.S. Pharmacopeia standards. Underlying this flexible plug-and-play approach are substantial enabling advances in continuous-flow synthesis, complex multistep sequence telescoping, reaction engineering equipment, and real-time formulation. PMID:27034366

  10. Endovascular repair of thoracic aortic aneurysms.

    PubMed

    Cartes-Zumelzu, F; Lammer, J; Kretschmer, G; Hoelzenbein, T; Grabenwöger, M; Thurnher, S

    2000-03-01

    The standard technique for the treatment of descending thoracic aortic aneurysms is elective open surgical repair with graft interposition. This standard approach, although steadily improving, is associated with high morbidity and substantial mortality rates and implies a major surgical procedure with lateral thoracotomy, use of cardiopulmonary bypass, long operation times and a variety of peri- and postoperative complications. This and the success of the first endoluminal treatment of abdominal aortic aneurysms by Parodi et al. prompted the attention to be thrown on the treatment of descending thoracic aortic aneurysms with endoluminal stent-grafts in many large centres. The aim of this new minimally invasive technique is to exclude the aneurysm from blood flow and in consequence to avoid pressure stress on the aneurysmatic aortic wall, by avoiding a large open operation with significant perioperative morbidity. The potentially beneficial effect of this new treatment approach was evaluated in the course of this study. PMID:10875224

  11. Respiratory variation in aortic flow peak velocity and inferior vena cava distensibility as indices of fluid responsiveness in anaesthetised and mechanically ventilated children

    PubMed Central

    Achar, Shreepathi Krishna; Sagar, Maddani Shanmukhappa; Shetty, Ranjan; Kini, Gurudas; Samanth, Jyothi; Nayak, Chaitra; Madhu, Vidya; Shetty, Thara

    2016-01-01

    Background and Aims: Dynamic parameters such as the respiratory variation in aortic flow peak velocity (ΔVpeak) and inferior vena cava distensibility index (dIVC) are accurate indices of fluid responsiveness in adults. Little is known about their utility in children. We studied the ability of these indices to predict fluid responsiveness in anaesthetised and mechanically ventilated children. Methods: This prospective study was conducted in 42 children aged between one to 14 years scheduled for elective surgery under general endotracheal anaesthesia. Mechanical ventilation was initiated with a tidal volume of 10 ml/kg. ΔVpeak, dIVC and stroke volume index (SVI) were measured before and after volume expansion (VE) with 10 ml/kg of crystalloid using transthoracic echocardiography. Patients were considered to be responders (R) and non-responders (NR) when SVI increased to either ≥15% or <15% after VE. ΔVpeak and dIVC were analysed between R and NR. Results: The best cut-off value for ΔVpeak as defined by the receiver operator characteristics (ROC) curve analysis was 12.2%, for which sensitivity, specificity, positive predictive value and negative predictive value were 100%, 94%, 96% and 100%, respectively, the area under the curve was 0.975. The best cut-off value for dIVC as defined by the ROC curve analysis was 23.5%, for which sensitivity, specificity, positive predictive value and negative predictive value were 91%, 89%, 91% and 89%, respectively, the area under the curve was 0.95. Conclusion: ΔVpeak and dIVC are reliable indices of fluid responsiveness in children. PMID:27013751

  12. An efficient and more sustainable one-step continuous-flow multicomponent synthesis approach to chromene derivatives

    EPA Science Inventory

    A simple and rapid one-step continuous-flow synthesis route has been developed for the preparation of chromene derivatives from the reaction of aromatic aldehydes, α-cyanomethylene compounds and naphthols. In this contribution, a one-step continuous-flow protocol in a continuous ...

  13. Enhanced photo-H₂ production by unsaturated flow condition in continuous culture.

    PubMed

    Guo, Cheng-Long; Cao, Hong-Xia; Guo, Fei-Qiang; Huang, Cong-Liang; Wang, Huan-Guang; Rao, Zhong-Hao

    2015-02-01

    A biofilm photobioreactor under unsaturated flow condition (BFPBR-U) is proposed using a polished optical fiber as the internal light source for photo-H2 production in continuous culture. The main chamber was filled with spherical glass beads to create the reaction bed and the cells were immobilized to form a biofilm under unsaturated flow condition obtained by pumping substrate solution over a packing bed at a rate to create a thin fluid film and injecting the argon to maintain the gas phase space. The effects of operational conditions, including flow rate and influent substrate concentration, on the photo-H2 production performance were investigated. The unsaturated flow conditions eliminated the inhibition caused by high organic loading rate and enhanced light transmission efficiency, leading to an improvement in the photo-H2 production performance. PMID:25257592

  14. Optimization of flow control devices in a single-strand slab continuous casting tundish

    NASA Astrophysics Data System (ADS)

    Ding, Ning; Bao, Yan-Ping; Sun, Qi-Song; Wang, Li-Feng

    2011-06-01

    The optimization of flow control devices in a single-slab continuous casting tundish was carried out by physical modeling, and the optimized scheme was presented. With the optimal tundish configuration, the minimum residence time of liquid steel was increased by 1.4 times, the peak concentration time was increased by 97%, and the dead volume fraction was decreased by 72%. A mathematical model for molten steel in the tundish was established by using the fluid dynamics package Fluent. The velocity field, concentration field, and the residence time distribution (RTD) curves of molten steel flow before and after optimization were obtained. Experimental results showed that the reasonable configuration with flow control devices can improve the fluid flow characteristics in the tundish. The results of industrial application show that the nonmetallic inclusion area ratio in casting slabs is decreased by 32% with the optimal tundish configuration.

  15. Feature identification for image-guided transcatheter aortic valve implantation

    NASA Astrophysics Data System (ADS)

    Lang, Pencilla; Rajchl, Martin; McLeod, A. Jonathan; Chu, Michael W.; Peters, Terry M.

    2012-02-01

    Transcatheter aortic valve implantation (TAVI) is a less invasive alternative to open-heart surgery, and is critically dependent on imaging for accurate placement of the new valve. Augmented image-guidance for TAVI can be provided by registering together intra-operative transesophageal echo (TEE) ultrasound and a model derived from pre-operative CT. Automatic contour delineation on TEE images of the aortic root is required for real-time registration. This study develops an algorithm to automatically extract contours on simultaneous cross-plane short-axis and long-axis (XPlane) TEE views, and register these features to a 3D pre-operative model. A continuous max-flow approach is used to segment the aortic root, followed by analysis of curvature to select appropriate contours for use in registration. Results demonstrate a mean contour boundary distance error of 1.3 and 2.8mm for the short and long-axis views respectively, and a mean target registration error of 5.9mm. Real-time image guidance has the potential to increase accuracy and reduce complications in TAVI.

  16. Long-term continuous-flow left ventricular assist devices (LVAD) as bridge to heart transplantation

    PubMed Central

    Pozzi, Matteo; Giraud, Raphaël; Tozzi, Piergiorgio; Bendjelid, Karim; Robin, Jacques; Meyer, Philippe; Obadia, Jean François

    2015-01-01

    Heart transplantation (HTx) is the treatment of choice for end-stage heart failure but the limited availability of heart’s donors still represents a major issue. So long-term mechanical circulatory support (MCS) has been proposed as an alternative treatment option to assist patients scheduled on HTx waiting list bridging them for a variable time period to cardiac transplantation—the so-called bridge-to-transplantation (BTT) strategy. Nowadays approximately 90% of patients being considered for MCS receive a left ventricular assist device (LVAD). In fact, LVAD experienced several improvements in the last decade and the predominance of continuous-flow over pulsatile-flow technology has been evident since 2008. The aim of the present report is to give an overview of continuous-flow LVAD utilization in the specific setting of the BTT strategy taking into consideration the most representative articles of the scientific literature and focusing the attention on the evolution, clinical outcomes, relevant implications on the HTx strategy and future perspectives of the continuous-flow LVAD technology. PMID:25922736

  17. Understanding the pathogenesis of abdominal aortic aneurysms

    PubMed Central

    Kuivaniemi, Helena; Ryer, Evan J.; Elmore, James R.; Tromp, Gerard

    2016-01-01

    Summary An aortic aneurysm is a dilatation in which the aortic diameter is ≥ 3.0 cm. If left untreated, the aortic wall continues to weaken and becomes unable to withstand the forces of the luminal blood pressure resulting in progressive dilatation and rupture, a catastrophic event associated with a mortality of 50 – 80%. Smoking and positive family history are important risk factors for the development of abdominal aortic aneurysms (AAA). Several genetic risk factors have also been identified. On the histological level, visible hallmarks of AAA pathogenesis include inflammation, smooth muscle cell apoptosis, extracellular matrix degradation, and oxidative stress. We expect that large genetic, genomic, epigenetic, proteomic and metabolomic studies will be undertaken by international consortia to identify additional risk factors and biomarkers, and to enhance our understanding of the pathobiology of AAA. Collaboration between different research groups will be important in overcoming the challenges to develop pharmacological treatments for AAA. PMID:26308600

  18. Tracheo-Bronchial Obstruction and Esophageal Perforation after TEVAR for Thoracic Aortic Rupture

    PubMed Central

    Fukui, Daisuke; Tanaka, Haruki; Komatsu, Kazunori; Ohtsu, Yoshinori; Terasaki, Takamitsu; Wada, Yuko; Takano, Tamaki; Koike, Shoichiro; Amano, Jun

    2014-01-01

    A 67-year-old man was referred to our hospital for an ascending aortic aneurysm, thoracoabdominal aortic aneurysm and aortic regurgitation. Graft repair of the thoracic aortic arch and aortic valve replacement was given priority and completed, however he developed descending aortic rupture before the second scheduled surgery, and endovascular stent grafting was performed. He subsequently developed tracheobronchial obstruction and esophageal perforation. The patient underwent urgent esophagectomy and enterostomy with continuity later reestablished. However, he died of sepsis 5 months after surgery. Despite the less invasive nature of endovascular treatment, esophageal perforation can nevertheless occur and postoperative vigilance is well warranted. PMID:25593630

  19. Gene transcript amplification from cell lysates in continuous-flow microfluidic devices.

    PubMed

    Gonzalez, Asensio; Ciobanu, Doina; Sayers, Michael; Sirr, Noel; Dalton, Tara; Davies, Mark

    2007-10-01

    Continuous-flow analysis, where samples circulate encapsulated in a carrier fluid is an attractive alternative to batch processing for high-throughput devices that use the polymerase chain reaction (PCR). Challenges of continuous-flow prototypes include the hydrodynamic and biological incompatibility of the carrier fluid, microchannel fouling, sample carryover and the integration of a nucleic acid extraction and reverse transcription step. We tested two homemade, continuous-flow thermocycler microdevices for amplification of reverse-transcribed messages from cell lysates without nucleic acid extraction. Amplification yield and specificity were assessed with state-of-the-art, real-time quantitative equipment. Carryover contamination between consecutive samples was absent. Amplification specificity and interference by genomic DNA were optimized by primer design. Robust detection of the low-copy transcript CLIC5 from 18 cells per microliter is demonstrated in cultured lymphoblasts. The results prove the concept that the development of micro-total analysis systems (micro-TAS) for continuous gene expression directly from cell suspensions is viable with current technology. PMID:17492382

  20. Continuous flow real-time PCR device using multi-channel fluorescence excitation and detection.

    PubMed

    Hatch, Andrew C; Ray, Tathagata; Lintecum, Kelly; Youngbull, Cody

    2014-02-01

    High throughput automation is greatly enhanced using techniques that employ conveyor belt strategies with un-interrupted streams of flow. We have developed a 'conveyor belt' analog for high throughput real-time quantitative Polymerase Chain Reaction (qPCR) using droplet emulsion technology. We developed a low power, portable device that employs LED and fiber optic fluorescence excitation in conjunction with a continuous flow thermal cycler to achieve multi-channel fluorescence detection for real-time fluorescence measurements. Continuously streaming fluid plugs or droplets pass through tubing wrapped around a two-temperature zone thermal block with each wrap of tubing fluorescently coupled to a 64-channel multi-anode PMT. This work demonstrates real-time qPCR of 0.1-10 μL droplets or fluid plugs over a range of 7 orders of magnitude concentration from 1 × 10(1) to 1 × 10(7). The real-time qPCR analysis allows dynamic range quantification as high as 1 × 10(7) copies per 10 μL reaction, with PCR efficiencies within the range of 90-110% based on serial dilution assays and a limit of detection of 10 copies per rxn. The combined functionality of continuous flow, low power thermal cycling, high throughput sample processing, and real-time qPCR improves the rates at which biological or environmental samples can be continuously sampled and analyzed. PMID:24297040

  1. Aortic Valve Sparing in Different Aortic Valve and Aortic Root Conditions.

    PubMed

    David, Tirone E

    2016-08-01

    The development of aortic valve-sparing operations (reimplantation of the aortic valve and remodeling of the aortic root) expanded the surgical armamentarium for treating patients with aortic root dilation caused by a variety of disorders. Young adults with aortic root aneurysms associated with genetic syndromes are ideal candidates for reimplantation of the aortic valve, and the long-term results have been excellent. Incompetent bicuspid aortic valves with dilated aortic annuli are also satisfactorily treated with the same type of operation. Older patients with ascending aortic aneurysm and aortic insufficiency secondary to dilated sinotubular junction and a normal aortic annulus can be treated with remodeling of the aortic root or with reimplantation of the aortic valve. The first procedure is simpler, and both procedures are likely equally effective. As with any heart valve-preserving procedure, patient selection and surgical expertise are keys to successful and durable repairs. PMID:27491910

  2. Segregation behavior of magnetic ions in continuous flowing solution under gradient magnetic field

    NASA Astrophysics Data System (ADS)

    Bing, Ji; Ping, Wu; Han, Ren; Shiping, Zhang; Abdul, Rehman; Li, Wang

    2016-07-01

    The research of magnetic separation starts from magnetic solid particles to nanoparticles, and in the research progress, particles become smaller gradually with the development of application of magnetic separation technology. Nevertheless, little experimental study of magnetic separation of molecules and ions under continuous flowing conditions has been reported. In this work, we designed a magnetic device and a “layered” flow channel to study the magnetic separation at the ionic level in continuous flowing solution. A segregation model was built to discuss the segregation behavior as well as the factors that may affect the separation. The magnetic force was proved to be the driving force which plays an indispensable role leading to the segregation and separation. The flow velocity has an effect on the segregation behavior of magnetic ions, which determines the separation result. On the other hand, the optimum flow velocity which makes maximum separation is related to the initial concentration of solution. Project supported by the National Natural Science Foundation of China (Grant No. 51276016).

  3. Transesophageal echocardiography: first-line imaging for aortic diseases

    NASA Technical Reports Server (NTRS)

    Yalcin, F.; Thomas, J. D.; Homa, D.; Flachskampf, F. A.

    2000-01-01

    Transesophageal echocardiography (TEE) is now commonly used to evaluate the thoracic aorta, because it is widely available and provides high-resolution images and flow information by Doppler. This article reviews the essential features on TEE of acute and chronic aortic diseases, such as aortic dissection, aneurysm, and atherosclerosis, and discusses its strengths, weaknesses, and indications.

  4. Continuous field-flow separation of particle populations in a dielectrophoretic chip with three dimensional electrodes

    NASA Astrophysics Data System (ADS)

    Iliescu, Ciprian; Tresset, Guillaume; Xu, Guolin

    2007-06-01

    This letter presents a dielectrophoretic (DEP) separation method of particles under continuous flow. The method consists of flowing two particle populations through a microfluidic channel, in which the vertical walls are the electrodes of the DEP device. The irregular shape of the electrodes generates both electric field and fluid velocity gradients. As a result, the particles that exhibit negative DEP can be trapped in the fluidic dead zones, while the particles that experience positive DEP are concentrated in the regions with high velocity and collected at the outlet. The device was tested with dead and living yeast cells.

  5. Measurements of continuous mix evolution in a high energy density shear flow

    SciTech Connect

    Loomis, E. Doss, F.; Flippo, K.; Fincke, J.

    2014-04-15

    We report on the novel integration of streaked radiography into a counter-flowing High Energy Density (HED) shear environment that continually measures a growing mix layer of Al separating two low-density CH foams. Measurements of the mix width allow us to validate compressible turbulence models and with streaked imaging, make this possible with a minimal number of experiments on large laser facilities. In this paper, we describe how the HED counter-flowing shear layer is created and diagnosed with streaked radiography. We then compare the streaked data to previous two-dimensional, single frame radiography and radiation hydrodynamic simulations of the experiment with inline compressible turbulent mix models.

  6. Improvement of the accuracy of continuous hematocrit measurement under various blood flow conditions

    NASA Astrophysics Data System (ADS)

    Kim, Myounggon; Yang, Sung

    2014-04-01

    We propose an accurate method for continuous hematocrit (HCT) measurement of flowing blood under varying plasma conditions of electrical conductivity, osmolality, and flow rate. Two parameters, namely the hematocrit estimation parameter (HEP) and normalized difference, are proposed to reduce the HCT measurement error. HEP was demonstrated in a previous work. The results of multiple linear regression analysis showed that the two parameters were strongly correlated with the reference HCT measured by microcentrifugation. The measurement error was less than 9% despite significant simultaneous variations in the plasma properties and shear rate.

  7. Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons.

    PubMed

    Svensson, L G; Von Ritter, C M; Groeneveld, H T; Rickards, E S; Hunter, S J; Robinson, M F; Hinder, R A

    1986-07-01

    There is a high incidence of paraplegia associated with thoracic aortic cross-clamping, even when cardiopulmonary bypass or shunts are used. In 56 adult baboons, spinal cord blood flow (SCBF), vascular anatomy, and paraplegia rates were evaluated. Tissue blood flow was measured by radioactive microspheres. Various procedures were used to increase SCBF and to prevent ischemia-reperfusion injury. It was found that the rate of paraplegia was inversely correlated with neural tissue ischemia (SCBF) and directly correlated with reperfusion hyperemia. Two methods completely prevented paraplegia. These two methods were a thoracic shunt with occlusion of the infrarenal aorta or cerebrospinal fluid drainage plus intrathecal papaverine injection, both of which were associated with an increased SCBF. Furthermore, papaverine dilated the anterior spinal artery (ASA) (p = 0.007) and increased the blood flow through the lower ASA. Whereas procedures utilizing a calcium channel blocker (flunarizine), allopurinol, superoxide dismutase (SOD), laminectomy alone, and a thoracoabdominal shunt not perfusing the arteria radicularis magna (ARM) all failed to prevent paraplegia, allopurinol (p = 0.026) and SOD (p = 0.004) did prevent gastric stress lesions, indicating that their failure to prevent paraplegia was not due to a lack of activity. Of great clinical interest is that, if a shunt is used and the ARM is perfused, infrarenal aortic cross-clamping increases SCBF, thus preventing paraplegia. Intrathecal application of papaverine proved to be even more effective in increasing SCBF and also completely prevented paraplegia. As this is a safer procedure than the insertion of shunts, this is the method of choice for the prevention of paraplegia associated with thoracic aortic cross-clamping. The preliminary trial using intrathecal papaverine in human beings has thus far shown no adverse side effects from the drug, and no paraplegia has occurred. PMID:3729582

  8. Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons.

    PubMed Central

    Svensson, L G; Von Ritter, C M; Groeneveld, H T; Rickards, E S; Hunter, S J; Robinson, M F; Hinder, R A

    1986-01-01

    There is a high incidence of paraplegia associated with thoracic aortic cross-clamping, even when cardiopulmonary bypass or shunts are used. In 56 adult baboons, spinal cord blood flow (SCBF), vascular anatomy, and paraplegia rates were evaluated. Tissue blood flow was measured by radioactive microspheres. Various procedures were used to increase SCBF and to prevent ischemia-reperfusion injury. It was found that the rate of paraplegia was inversely correlated with neural tissue ischemia (SCBF) and directly correlated with reperfusion hyperemia. Two methods completely prevented paraplegia. These two methods were a thoracic shunt with occlusion of the infrarenal aorta or cerebrospinal fluid drainage plus intrathecal papaverine injection, both of which were associated with an increased SCBF. Furthermore, papaverine dilated the anterior spinal artery (ASA) (p = 0.007) and increased the blood flow through the lower ASA. Whereas procedures utilizing a calcium channel blocker (flunarizine), allopurinol, superoxide dismutase (SOD), laminectomy alone, and a thoracoabdominal shunt not perfusing the arteria radicularis magna (ARM) all failed to prevent paraplegia, allopurinol (p = 0.026) and SOD (p = 0.004) did prevent gastric stress lesions, indicating that their failure to prevent paraplegia was not due to a lack of activity. Of great clinical interest is that, if a shunt is used and the ARM is perfused, infrarenal aortic cross-clamping increases SCBF, thus preventing paraplegia. Intrathecal application of papaverine proved to be even more effective in increasing SCBF and also completely prevented paraplegia. As this is a safer procedure than the insertion of shunts, this is the method of choice for the prevention of paraplegia associated with thoracic aortic cross-clamping. The preliminary trial using intrathecal papaverine in human beings has thus far shown no adverse side effects from the drug, and no paraplegia has occurred. PMID:3729582

  9. Modeling and Measurements of Multiphase Flow and Bubble Entrapment in Steel Continuous Casting

    NASA Astrophysics Data System (ADS)

    Jin, Kai; Thomas, Brian G.; Ruan, Xiaoming

    2016-02-01

    In steel continuous casting, argon gas is usually injected to prevent clogging, but the bubbles also affect the flow pattern, and may become entrapped to form defects in the final product. To investigate this behavior, plant measurements were conducted, and a computational model was applied to simulate turbulent flow of the molten steel and the transport and capture of argon gas bubbles into the solidifying shell in a continuous slab caster. First, the flow field was solved with an Eulerian k- ɛ model of the steel, which was two-way coupled with a Lagrangian model of the large bubbles using a discrete random walk method to simulate their turbulent dispersion. The flow predicted on the top surface agreed well with nailboard measurements and indicated strong cross flow caused by biased flow of Ar gas due to the slide-gate orientation. Then, the trajectories and capture of over two million bubbles (25 μm to 5 mm diameter range) were simulated using two different capture criteria (simple and advanced). Results with the advanced capture criterion agreed well with measurements of the number, locations, and sizes of captured bubbles, especially for larger bubbles. The relative capture fraction of 0.3 pct was close to the measured 0.4 pct for 1 mm bubbles and occurred mainly near the top surface. About 85 pct of smaller bubbles were captured, mostly deeper down in the caster. Due to the biased flow, more bubbles were captured on the inner radius, especially near the nozzle. On the outer radius, more bubbles were captured near to narrow face. The model presented here is an efficient tool to study the capture of bubbles and inclusion particles in solidification processes.

  10. The microwave-to-flow paradigm: translating high-temperature batch microwave chemistry to scalable continuous-flow processes.

    PubMed

    Glasnov, Toma N; Kappe, C Oliver

    2011-10-17

    The popularity of dedicated microwave reactors in many academic and industrial laboratories has produced a plethora of synthetic protocols that are based on this enabling technology. In the majority of examples, transformations that require several hours when performed using conventional heating under reflux conditions reach completion in a few minutes or even seconds in sealed-vessel, autoclave-type, microwave reactors. However, one severe drawback of microwave chemistry is the difficulty in scaling this technology to a production-scale level. This Concept article demonstrates that this limitation can be overcome by translating batch microwave chemistry to scalable continuous-flow processes. For this purpose, conventionally heated micro- or mesofluidic flow devices fitted with a back-pressure regulator are employed, in which the high temperatures and pressures attainable in a sealed-vessel microwave chemistry batch experiment can be mimicked. PMID:21932289

  11. MARS--multiple automated robotic synthesizer for continuous flow of peptides.

    PubMed

    Krchnák, V; Cabel, D; Lebl, M

    1996-01-01

    We have designed and constructed a multiple automated robotic synthesizer, the MARS. Its novel timing procedure for handling multiple synthetic tasks eliminates unnecessary respite time by keeping the robotic arm in continuous operation. Polypropylene syringes equipped at the bottom with polypropylene frits serve as physically independent reaction vessels. All operations are performed by the robotic arm, which is equipped with a specially designed gripper to hold a syringe and to aspirate and dispense liquid. Typically, the MARS synthesizes concurrently 5 to 15 peptides of different length, and once one peptide is finished it automatically starts the synthesis of the next peptide in the queue, assuring a continuous flow of peptides. PMID:8727483

  12. Progress on the Design and Development of the Continuous-Flow Total Artificial Heart

    PubMed Central

    Kobayashi, Mariko; Horvath, David J.; Mielke, Nicole; Shiose, Akira; Kuban, Barry; Goodin, Mark; Fukamachi, Kiyotaka; Golding, Leonard A. R.

    2013-01-01

    Cleveland Clinic’s continuous-flow total artificial heart has one motor and one rotating assembly supported by a hydrodynamic bearing. The right hydraulic output is self regulated by passive axial movement of the rotating assembly to balance itself with the left output. The purpose of this article is to present progress in four areas of development: the automatic speed control system, self-regulation to balance right/left inlet pressures and flows, hemolysis testing using calf blood, and coupled electromagnetics (EMAG) and computational fluid dynamics (CFD) analysis. The relationships between functions of motor power and speed, systemic flow, and systemic vascular resistance (SVR) were used for the sensorless speed control algorithm and demonstrated close correlations. Based on those empirical relationships, systemic flow and SVR were calculated in the system module and showed good correlation with measured pump flow and SVR. The automatic system adjusted the pump’s speed to obtain the target flow in response to the calculated SVR. Atrial pressure difference (left minus right atrial pressure) was maintained within ± 10 mm Hg for a wide range of SVR/PVR (systemic/pulmonary vascular resistance) ratios, demonstrating a wide margin of self-regulation under fixed-speed mode and 25% sinusoidally modulated speed mode. Hemolysis test results indicated acceptable values (normalized index of hemolysis <.01 mg/dL). The coupled EMAG/CFD model was validated for use in further device development. PMID:22747979

  13. Contactless inductive flow tomography: basic principles and first applications in the experimental modelling of continuous casting

    NASA Astrophysics Data System (ADS)

    Stefani, F.; Eckert, S.; Ratajczak, M.; Timmel, K.; Wondrak, T.

    2016-07-01

    Contactless inductive flow tomography (CIFT) aims at reconstructing the flow structure of a liquid metal from the magnetic fields measured at various positions outside the fluid body which are induced by the flow under the influence of one or multiple applied magnetic fields. We recap the basic mathematical principles of CIFT and the results of an experiment in which the propeller-driven three-dimensional flow in a cylindrical had been reconstructed. We also summarize the recent activities to utilize CIFT in various problems connected with the experimental simulation of the continuous casting process. These include flow reconstructions in single-phase and two-phase flow problems in the Mini-LIMMCAST model of slab-casting, studies of the specific effects of an electromagnetic stirrer attached to the Submerged Entry Nozzle (SEN), as well as first successful applications of CIFT on the background of a strong electromagnetic brake field. We conclude by discussing some remaining obstacles for the deployment of CIFT in a real caster.

  14. Simulation of transient fluid flow in mold region during steel continuous casting

    NASA Astrophysics Data System (ADS)

    Liu, R.; Thomas, B. G.; Sengupta, J.

    2012-07-01

    A system of models has been developed to study transient flow during continuous casting and applied to simulate an event of multiple stopper-rod movements. It includes four sub-models to incorporate different aspects in this transient event. A three-dimensional (3-D) porous-flow model of the nozzle wall calculates the rate argon gas flow into the liquid steel, and the initial mean bubble size is estimated. Transient CFD models simulate multiphase flow of steel and gas bubbles in the Submerged Entry Nozzle (SEN) and mold and have been validated with experimental data from both nail dipping and Sub-meniscus Velocity Control (SVC) measurements. To obtain the transient inlet boundary conditions for the simulation, two semi-empirical models, a stopper-rod-position based model and a metal-level-based model, predict the liquid steel flow rate through the SEN based on recorded plant data. Finally the model system was applied to study the effects of stopper rod movements on SEN/mold flow patterns. Meniscus level fluctuations were calculated using a simple pressure method and compared well with plant measurements. Insights were gained from the simulation results to explain the cause of meniscus level fluctuations and the formation of sliver defects during stopper rod movements.

  15. Electrospun Nanofibrous Sheets for Selective Cell Capturing in Continuous Flow in Microchannels.

    PubMed

    Son, Young Ju; Kang, Jihyun; Kim, Hye Sung; Yoo, Hyuk Sang

    2016-03-14

    Electrospun nanofibrous meshes were surface-modified for selective capturing of specific cells from a continuous flow in PDMS microchannels. We electrospun nanofibrous mats composed of poly(ε-carprolactone) (PCL) and amine-functionalized block copolymers composed of PCL and poly(ethylenimine) (PEI). A mixture of biotinylated PEG and blunt PEG was chemically tethered to the nanofibrous mats via the surface-exposed amines on the mat. The degree of biotinylation was fluorescently and quantitatively assayed for confirming the surface-biotinylation levels for avidin-specific binding. The incorporation level of avidin gradually increased when the blend ratio of biotinylated PEG on the mat increased, confirming the manipulated surfaces with various degree of biotinylation. Biotinylated cells were incubated with avidin-coated biotinylated mats and the specific binding of biotinylated cells was monitored in a microfluidic channel with a continuous flow of culture medium, which suggests efficient and selective capturing of the biotinylated cells on the nanofibrous mat. PMID:26812501

  16. Study of aerobic granular sludge stability in a continuous-flow membrane bioreactor.

    PubMed

    Corsino, S F; Campo, R; Di Bella, G; Torregrossa, M; Viviani, G

    2016-01-01

    A granular continuous-flow membrane bioreactor with a novel hydrodynamic configuration was developed to evaluate the stability of aerobic granular sludge (AGS). Under continuous-flow operation (Period I), AGS rapidly lost their structural integrity resulting in loose and fluffy microbial aggregates in which filamentous bacteria were dominant. The intermittent feeding (Period II) allowed obtaining the succession of feast and famine conditions that favored the increase in AGS stability. Although no further breakage occurred, the formation of new granules was very limited, owing to the absence of the hydraulic selection pressure. These results noted the necessity to ensure, on the one hand the succession of feast/famine conditions, and on the other, the hydraulic selection pressure that allows flocculent sludge washout. This preliminary study shows that the proposed configuration could meet the first aspect; in contrast, biomass selection needs to be improved. PMID:26526094

  17. Strategic Application of Residence-Time Control in Continuous-Flow Reactors

    PubMed Central

    Mándity, István M; Ötvös, Sándor B; Fülöp, Ferenc

    2015-01-01

    As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals. Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity. This review furnishes a brief insight into flow reactions in which high chemo- and/or stereoselectivity can be attained by strategic residence-time control and illustrates the importance of the residence time as a crucial parameter in sustainable method development. Such a fine reaction control cannot be performed in conventional batch reaction set-ups. PMID:26246983

  18. Continuous-flow technology—a tool for the safe manufacturing of active pharmaceutical ingredients.

    PubMed

    Gutmann, Bernhard; Cantillo, David; Kappe, C Oliver

    2015-06-01

    In the past few years, continuous-flow reactors with channel dimensions in the micro- or millimeter region have found widespread application in organic synthesis. The characteristic properties of these reactors are their exceptionally fast heat and mass transfer. In microstructured devices of this type, virtually instantaneous mixing can be achieved for all but the fastest reactions. Similarly, the accumulation of heat, formation of hot spots, and dangers of thermal runaways can be prevented. As a result of the small reactor volumes, the overall safety of the process is significantly improved, even when harsh reaction conditions are used. Thus, microreactor technology offers a unique way to perform ultrafast, exothermic reactions, and allows the execution of reactions which proceed via highly unstable or even explosive intermediates. This Review discusses recent literature examples of continuous-flow organic synthesis where hazardous reactions or extreme process windows have been employed, with a focus on applications of relevance to the preparation of pharmaceuticals. PMID:25989203

  19. Evaluation of the Separability of Monodisperse Polystyrene Latex Microspheres in a Continuous Flow Electrophoresis System

    NASA Technical Reports Server (NTRS)

    Williams, G., Jr.

    1983-01-01

    The continuous flow electrophoresis system makes electrophoresis possible in a free flowing film of aqueous electrolyte medium. The sample is introduced at one end of the chamber and is subjected to a lateral dc field. This process separates the sample into fractions since each component has a distinctive electrophoric mobility. Evaluations were made of sample conductivity and buffer conductivity as they affect sample band spread and separation using the Continuous Particle Electrophoresis (CPE) system. Samples were prepared from mixtures of 5 percent and 1 percent polystyrene latex (PSL) microspheres which were .4, .56 and .7 microns in diameter. These were prepared in electrolyte media 1x and 3x the conductivity of the curtain buffer, approximately 150 and 450 micro mhos/cm. Samples with matched conductivities produced greater resolution and less band spread than those with 3x the conductivity of the curtain buffer.

  20. Calcium accumulation characterization in the aerobic granules cultivated in a continuous-flow airlift bioreactor.

    PubMed

    Zhou, Dandan; Liu, Mengyuan; Gao, Linlin; Shao, Chunyan; Yu, Jie

    2013-06-01

    Limited work has been done on the accumulation characterization of Ca(2+) in aerobic granules that are cultivated in a continuous-flow bioreactor. In this work, the contribution of Ca(2+) to the biogranulation in a continuous flow airlift fluidized bed (CAFB) reactor has been studied. The spatial distribution and form of calcium in the granules were investigated by scanning electron microscopy-mapping, energy dispersive X-ray and X-ray diffraction (XRD). Calcium was located throughout the Ca-rich granules, rather than accumulating in the center of the granules of the sequencing batch reactor. Furthermore, CaCO3 was detected as the main crystalline mineral form of the calcium. Calcium augmentation of the inflow promoted the accumulation of magnesium in the granules in the CAFB. The magnesium was presented as Ca7Mg2P6O24 according to XRD analyses. PMID:23436127

  1. Acute aortic syndrome

    PubMed Central

    2016-01-01

    Acute aortic syndrome (AAS) is a term used to describe a constellation of life-threatening aortic diseases that have similar presentation, but appear to have distinct demographic, clinical, pathological and survival characteristics. Many believe that the three major entities that comprise AAS: aortic dissection (AD), intramural hematoma (IMH) and penetrating aortic ulcer (PAU), make up a spectrum of aortic disease in which one entity may evolve into or coexist with another. Much of the confusion in accurately classifying an AAS is that they present with similar symptoms: typically acute onset of severe chest or back pain, and may have similar radiographic features, since the disease entities all involve injury or disruption of the medial layer of the aortic wall. The accurate diagnosis of an AAS is often made at operation. This manuscript will attempt to clarify the similarities and differences between AD, IMH and PAU of the ascending aorta and describe the challenges in distinguishing them from one another. PMID:27386405

  2. Acute aortic syndrome.

    PubMed

    Corvera, Joel S

    2016-05-01

    Acute aortic syndrome (AAS) is a term used to describe a constellation of life-threatening aortic diseases that have similar presentation, but appear to have distinct demographic, clinical, pathological and survival characteristics. Many believe that the three major entities that comprise AAS: aortic dissection (AD), intramural hematoma (IMH) and penetrating aortic ulcer (PAU), make up a spectrum of aortic disease in which one entity may evolve into or coexist with another. Much of the confusion in accurately classifying an AAS is that they present with similar symptoms: typically acute onset of severe chest or back pain, and may have similar radiographic features, since the disease entities all involve injury or disruption of the medial layer of the aortic wall. The accurate diagnosis of an AAS is often made at operation. This manuscript will attempt to clarify the similarities and differences between AD, IMH and PAU of the ascending aorta and describe the challenges in distinguishing them from one another. PMID:27386405

  3. Experimental and numerical modelling of the fluid flow in the continuous casting of steel

    NASA Astrophysics Data System (ADS)

    Timmel, K.; Miao, X.; Wondrak, T.; Stefani, F.; Lucas, D.; Eckert, S.; Gerbeth, G.

    2013-03-01

    This article gives an overview of recent research activities with respect to the mold flow in the continuous casting of steel in presence of DC magnetic fields. The magnetic fields appear to be an attractive tool for controlling the melt flow in a contactless way. Various kinds of magnetic systems are already in operation in industrial steel casting, but the actual impact on the melt flow has not been sufficiently verified by experimental studies. The rapid development of innovative diagnostic techniques in low-melting liquid metals over the last two decades enables new possibilities for systematic flow measurements in liquid metal model experiments. A new research program was initiated at HZDR comprising three experimental facilities providing a LIquid Metal Model for continuous CASTing of steel (LIMMCAST). The facilities operate in a temperature range from room temperature up to 400∘C using the low-melting alloys GaInSn and SnBi, respectively. The experimental program is focused on quantitative flow measurements in the mold, the submerged entry nozzle and the tundish. Local potential probes, Ultrasonic Doppler Velocimetry (UDV) and Contactless Inductive Flow Tomography (CIFT) are employed to measure the melt flow. The behavior of two-phase flows in case of argon injection is investigated by means of the Mutual Inductance Tomography (MIT) and X-ray radioscopy. The experimental results provide a substantial data basis for the validation of related numerical simulations. Numerical calculations were performed with the software package ANSYS-CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of MHD turbulence was taken into account by specific modifications of the turbulence model. First results of the LIMMCAST program reveal important findings such as the peculiar, unexpected phenomenon that the application of a DC magnetic field may excite non-steady, non-isotropic large-scale flow oscillations in the mold. Another important result of our

  4. Validation of a continuous penile blood-flow measurement by pulse-volume-plethysmography.

    PubMed

    Lavoisier, P; Barbe, R; Gally, M

    2002-04-01

    Today, in the assessment of cavernous artery blood-flow, the most commonly used technique is Doppler ultrasound velocimetry (continuous, pulsed, color-coded or power), which is often considered as the gold standard. Plethysmographic techniques and radioactive tracers have been widely used for the assessment of global penis flow variations but are not adequate for continuous blood-flow measurement. A new pulse-volume plethysmographic (PVP) device using a water-filled penile cuff was employed to assess continuous blood-flow measurement in the penis. Simultaneously Doppler velocity was recorded and served as a gold standard. A penile water-cuff is connected through a pressure tube to a three-way tap. The pulse-volume changes in the penile water-cuff are measured by means of a latex membrane placed over one of the three-way taps. The displacements of the latex are recorded by a photoplethysmograph. The third tap is connected to a 5 l perfusion bag placed 30 cm above the penis so as to maintain constant pressure in the whole device whatever the penis volume. Twenty-four volunteers were tested. The Doppler velocity signal and pulse volume of cavernous arteries were measured simultaneously after PGE1 intra-cavernous injection. Blood-flow variations were induced by increasing penis artery compression with a second penile water-cuff used as a tourniquet fitted onto the penis root, and the pressure of which could be modified by a water-filled syringe. The amplitude of the plethysmographic pulse-volume signal and the area under the Doppler velocity signal were correlated. The inter-patient (n=24) correlation ranged from 0.455 to 0.904, with a mean correlation of 0.704 and P<0.0001. PVP measurement by a water-filled cuff was validated by ultrasound velocimetry. This new continuous, non-invasive and easy-to-use technique enables physiological and physiopathological flow-measurement during sleep, under visual sexual stimulation (VSS), or following artificial erection

  5. Eight-year experience with a continuous-flow total artificial heart in calves.

    PubMed

    Cohn, William E; Handy, Kelly M; Parnis, Steven M; Conger, Jeffrey L; Winkler, Jo Anna; Frazier, O H

    2014-01-01

    Over the last 8 years, we have developed and evaluated a continuous-flow total artificial heart (CFTAH) comprising two rotary blood pumps. To understand the physiologic effects of nonpulsatile circulation, we evaluated the CFTAH in 65 calves for 90 days or less. We describe our experience with 29 calves that survived for 7 days or more. The calves received dual axial-flow (n = 24) or centrifugal-flow (n = 5) pumps. Several iterations of customized atrial cuffs were developed to facilitate an adequate anatomical fit. Pressures (arterial pressure [AoP], pulmonary artery pressure [PAP], left atrial pressure [LAP], and right atrial pressure [RAP]) and pump parameters were continuously monitored. Hematologic and biochemistry values were analyzed. After each case, a necropsy was performed. The calves survived for 7-92 days (mean, 24 days). Pressures were 94 ± 14 (AoP), 25 ± 8 (PAP), 14 ± 6 (RAP), and 16 ± 6 (LAP) mm Hg. Pump flow was maintained at 9.1 ± 1.7 L/minute (right) and 9.4 ± 1.9 L/minute (left). Hematologic and biochemistry values remained acceptable. Eight animals underwent treadmill evaluations, in which oxygen consumption (VO2) was comparable with physiologic total-body VO2. In the two animals that survived to 90 days, the end-organs appeared unremarkable at autopsy, and the CFTAH circuits were free of thrombus. Our results show that a CFTAH can maintain a large animal physiologically and hemodynamically for up to 90 days with continuous flow. PMID:24281122

  6. 78 FR 65306 - Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-31

    ...EPA is announcing a 30-day public comment period for the draft document titled, ``Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams'' (EPA/600/R-13/170). The EPA also is announcing that either ERG or Versar, EPA contractors for external scientific peer review, will select an independent group of experts to conduct a letter peer review of the draft document.......

  7. Domestic wastewater treatment using multi-electrode continuous flow MFCs with a separator electrode assembly design.

    PubMed

    Ahn, Yongtae; Logan, Bruce E

    2013-01-01

    Treatment of domestic wastewater using microbial fuel cells (MFCs) will require reactors with multiple electrodes, but this presents unique challenges under continuous flow conditions due to large changes in the chemical oxygen demand (COD) concentration within the reactor. Domestic wastewater treatment was examined using a single-chamber MFC (130 mL) with multiple graphite fiber brush anodes wired together and a single air cathode (cathode specific area of 27 m(2)/m(3)). In fed-batch operation, where the COD concentration was spatially uniform in the reactor but changed over time, the maximum current density was 148 ± 8 mA/m(2) (1,000 Ω), the maximum power density was 120 mW/m(2), and the overall COD removal was >90 %. However, in continuous flow operation (8 h hydraulic retention time, HRT), there was a 57 % change in the COD concentration across the reactor (influent versus effluent) and the current density was only 20 ± 13 mA/m(2). Two approaches were used to increase performance under continuous flow conditions. First, the anodes were separately wired to the cathode, which increased the current density to 55 ± 15 mA/m(2). Second, two MFCs were hydraulically connected in series (each with half the original HRT) to avoid large changes in COD among the anodes in the same reactor. The second approach improved current density to 73 ± 13 mA/m(2). These results show that current generation from wastewaters in MFCs with multiple anodes, under continuous flow conditions, can be improved using multiple reactors in series, as this minimizes changes in COD in each reactor. PMID:23053104

  8. Automated formation of multicomponent-encapuslating vesosomes using continuous flow microcentrifugation

    PubMed Central

    Jang, Huisoo; Hu, Peichi C.; Jung, Sungho; Kim, Won Young; Kim, Sun Min; Malmstadt, Noah; Jeon, Tae-Joon

    2014-01-01

    Vesosomes – hierarchical assemblies consisting of membrane-bound vesicles of various scales – are potentially powerful models of cellular compartmentalization. Current methods of vesosome fabrication are labor intensive, and offer little control over the size and uniformity of the final product. In this article, we report the development of an automated vesosome formation platform using a microfluidic device and a continuous flow microcentrifuge. In the microfluidic device, water-in-oil droplets containing nanoscale vesicles in the water phase were formed using T-junction geometry, in which a lipid monolayer is formed at the oil/water interface. These water-in-oil droplets were then immediately transferred to the continuous flow microcentrifuge. When a water-in-oil droplet passed through a second lipid monolayer formed in the continuous flow microcentrifuge, a bilayer-encapsulated vesosome was created, which contained all of the contents of the aqueous phase encapsulated within the vesosome. Encapsulation of nanoscale liposomes within the outer vesosome membrane was confirmed by fluorescence microscopy. Laser diffraction analysis showed that the vesosomes we fabricated were uniform (coefficient of variation of 0.029). The yield of the continuous flow microcentrifuge is high, with over 60% of impinging water droplets being converted to vesosomes. Our system provides a fully automatable route for the generation of vesosomes that are able to encapsulate any desired content. The method employed in this work is simple and can be readily applied to a variety of systems, providing a facile platform for fabricating multicomponent carriers and model cells. PMID:23894035

  9. Flow Intermittency, Dispersion, and Correlated Continuous Time Random Walks in Porous Media

    SciTech Connect

    de Anna, Pietro; Le Borgne, Tanguy; Dentz, Marco; Tartakovsky, Alexandre M.; Bolster, Diogo; Davy, Philippe

    2013-05-01

    We study the intermittency of fluid velocities in porous media and its relation to anomalous dispersion. Lagrangian velocities measured at equidistant points along streamlines are shown to form a spatial Markov process. As a consequence of this remarkable property, the dispersion of fluid particles can be described by a continuous time random walk with correlated temporal increments. This new dynamical picture of intermittency provides a direct link between the microscale flow, its intermittent properties, and non-Fickian dispersion.

  10. Comparison of heavy metal toxicity in continuous flow and batch reactors

    NASA Astrophysics Data System (ADS)

    Sengor, S. S.; Gikas, P.; Moberly, J. G.; Peyton, B. M.; Ginn, T. R.

    2009-12-01

    The presence of heavy metals may significantly affect microbial growth. In many cases, small amounts of particular heavy metals may stimulate microbial growth; however, larger quantities may result in microbial growth reduction. Environmental parameters, such as growth pattern may alter the critical heavy metal concentration, above which microbial growth stimulation turns to growth inhibition. Thus, it is important to quantify the effects of heavy metals on microbial activity for understanding natural or manmade biological reactors, either in situ or ex situ. Here we compare the toxicity of Zn and Cu on Arthrobacter sp., a heavy metal tolerant microorganism, under continuous flow versus batch reactor operations. Batch and continuous growth tests of Arthrobacter sp. were carried out at various individual and combined concentrations of Zn and Cu. Biomass concentration (OD) was measured for both the batch and continuous reactors, whereas ATP, oxygen uptake rates and substrate concentrations were additionally measured for the continuous system. Results indicated that Cu was more toxic than Zn under all conditions for both systems. In batch reactors, all tested Zn concentrations up to 150 uM showed a stimulatory effect on microbial growth. However, in the case of mixed Zn and Cu exposures, the presence of Zn either eliminated (at the 50 uM level both Zn and Cu) or reduced by ~25% (at the 100 and 150 uM levels both Zn and Cu) the Cu-induced inhibition. In the continuous system, only one test involved combined Cu (40uM) and Zn (125uM) and this test showed similar results to the 40uM Cu continuous test, i.e., no reduction in inhibition. The specific ATP concentration, i.e., ATP/OD, results for the continuous reactor showed an apparent recovery for both Cu-treated populations, although neither the OD nor glucose data showed any recovery. This may reflect that the individual microorganisms that survived after the addition of heavy metals, kept maintaining the usual ATP

  11. Numerical modeling of continuous flow microwave heating: a critical comparison of COMSOL and ANSYS.

    PubMed

    Salvi, D; Boldor, Dorin; Ortego, J; Aita, G M; Sabliov, C M

    2010-01-01

    Numerical models were developed to simulate temperature profiles in Newtonian fluids during continuous flow microwave heating by one way coupling electromagnetism, fluid flow, and heat transport in ANSYS 8.0 and COMSOL Multiphysics v3.4. Comparison of the results from the COMSOL model with the results from a pre-developed and validated ANSYS model ensured accuracy of the COMSOL model. Prediction of power Loss by both models was in close agreement (5-13% variation) and the predicted temperature profiles were similar. COMSOL provided a flexible model setup whereas ANSYS required coupling incompatible elements to transfer load between electromagnetic, fluid flow, and heat transport modules. Overall, both software packages provided the ability to solve multiphysics phenomena accurately. PMID:21721467

  12. Changes of a continuous character caused by gene flow. A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Sznajd-Weron, Katarzyna; Pȩkalski, Andrzej

    We introduce a model of a large, sexual, population in which partners for reproduction are chosen randomly, without any bias. This large population is composed of two groups of local populations living in different environments and being in contact. We propose a dynamic equation describing, like the existing one for the allele frequency, the temporal changes of a continuous character due to gene flow, i.e. the transfer of the allels resulting from migration of individuals between the populations, and natural selection. We show that the gene flow can be described by the linear term in the proposed equation and the natural selection by the nonlinear term. Additional killing rule introduces a random factor into our model. We discuss the role of both factors (gene flow and selection) on the structure of the population, i.e. spatial distribution of the considered character and the resulting from it existence of hybrid zones. We use the standard Monte Carlo simulations.

  13. Simulation of fluid flow induced by opposing ac magnetic fields in a continuous casting mold

    SciTech Connect

    Chang, F.C.; Hull, J.R.; Beitelman, L.

    1995-07-01

    A numerical simulation was performed for a novel electromagnetic stirring system employing two rotating magnetic fields. The system controls stirring flow in the meniscus region of a continuous casting mold independently from the stirring induced within the remaining volume of the mold by a main electromagnetic stirrer (M-EMS). This control is achieved by applying to the meniscus region an auxiliary electromagnetic field whose direction of rotation is opposite to that of the main magnetic field produced by the M-EMS. The model computes values and spatial distributions of electromagnetic parameters and fluid flow in the stirred pools of mercury in cylindrical and square geometries. Also predicted are the relationships between electromagnetics and fluid flows pertinent to a dynamic equilibrium of the opposing stirring swirls in the meniscus region. Results of the numerical simulation compared well with measurements obtained from experiments with mercury pools.

  14. Continuous flow electrophoretic separation of proteins and cells from mammalian tissues

    NASA Technical Reports Server (NTRS)

    Hymer, W. C.; Barlow, Grant H.; Blaisdell, Steven J.; Cleveland, Carolyn; Farrington, Mary Ann; Feldmeier, Mary; Hatfield, J. Michael; Lanham, J. Wayne; Grindeland, Richard; Snyder, Robert S.

    1987-01-01

    This paper describes an apparatus for continuous flow electrophoresis (CFE), designed to separate macromolecules and cells at conditions of microgravity. In this CFE, buffer flows upward in a 120-cm long flow chamber, which is 16-cm wide x 3.0-mm thick in the microgravity version (and 6-cm wide x 1.5-mm thick in the unit-gravity laboratory version). Ovalbumin and rat serum albumin were separated in space (flight STS-4) with the same resolution of the two proteins achieved at 25 percent total w/v concentration that was obtained in the laboratory at 0.2 percent w/v concentration. Rat anterior pituitary cells, cultured human embryonic kidney cells, and canine Langerhans cells were separated into subpopulations (flight STS-8) more effectively than in unit gravity, with comparable resolution having been achieved at 100 times the concentration possible on earth.

  15. Method and apparatus for improved melt flow during continuous strip casting

    SciTech Connect

    Follstaedt, D.W.; King, E.L.; Schneider, K.C.

    1991-11-12

    The continuous casting of metal strip using the melt overflow process is improved by controlling the weir conditions in the nozzle to provide a more uniform flow of molten metal across the width of the nozzle and reducing the tendency for freezing of metal along the interface with refractory surfaces. A weir design having a sloped rear wall and tapered sidewalls and critical gap controls beneath the weir has resulted in the drastic reduction in edge tearing and a significant improvement in strip uniformity. The floor of the container vessel is preferably sloped and the gap between the nozzle and the rotating substrate is critically controlled. The resulting flow patterns observed with the improved casting process have reduced thermal gradients in the bath, contained surface slag and eliminated undesirable solidification near the discharge area by increasing the flow rates at those points. 8 figures.

  16. Method and apparatus for improved melt flow during continuous strip casting

    SciTech Connect

    Follstaedt, Donald W.; King, Edward L.; Schneider, Ken C.

    1991-11-12

    The continuous casting of metal strip using the melt overflow process is improved by controlling the weir conditions in the nozzle to provide a more uniform flow of molten metal across the width of the nozzle and reducing the tendency for freezing of metal along the interface with refractory surfaces. A weir design having a sloped rear wall and tapered sidewalls and critical gap controls beneath the weir has resulted in the drastic reduction in edge tearing and a significant improvement in strip uniformity. The floor of the container vessel is preferably sloped and the gap between the nozzle and the rotating substrate is critically controlled. The resulting flow patterns observed with the improved casting process have reduced thermal gradients in the bath, contained surface slag and eliminated undesirable solidification near the discharge area by increasing the flow rates at those points.

  17. Apparatus for irradiating a continuously flowing stream of fluid. [For neutron activation analysis

    DOEpatents

    Speir, L.G.; Adams, E.L.

    1982-05-13

    An apparatus for irradiating a continuously flowing stream of fluid is disclosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4..pi.. radiation geometry. The irradiation source, for example a /sup 252/Cf neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

  18. A combined kinetic and thermodynamic approach for the interpretation of continuous-flow heterogeneous catalytic processes.

    PubMed

    Bortolini, Olga; Cavazzini, Alberto; Giovannini, Pier Paolo; Greco, Roberto; Marchetti, Nicola; Massi, Alessandro; Pasti, Luisa

    2013-06-10

    The heterogeneous proline-catalyzed aldol reaction was investigated under continuous-flow conditions by means of a packed-bed microreactor. Reaction-progress kinetic analysis (RPKA) was used in combination with nonlinear chromatography for the interpretation, under synthetically relevant conditions, of important mechanistic aspects of the heterogeneous catalytic process at a molecular level. The information gathered by RPKA and nonlinear chromatography proved to be highly complementary and allowed for the assessment of optimal operating variables. In particular, the determination of the rate-determining step was pivotal for optimizing the feed composition. On the other hand, the competitive product inhibition was responsible for the unexpected decrease in the reaction yield following an apparently obvious variation in the feed composition. The study was facilitated by a suitable 2D instrumental arrangement for simultaneous flow reaction and online flow-injection analysis. PMID:23589216

  19. Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow.

    PubMed

    Webb, R Chad; Ma, Yinji; Krishnan, Siddharth; Li, Yuhang; Yoon, Stephen; Guo, Xiaogang; Feng, Xue; Shi, Yan; Seidel, Miles; Cho, Nam Heon; Kurniawan, Jonas; Ahad, James; Sheth, Niral; Kim, Joseph; Taylor, James G; Darlington, Tom; Chang, Ken; Huang, Weizhong; Ayers, Joshua; Gruebele, Alexander; Pielak, Rafal M; Slepian, Marvin J; Huang, Yonggang; Gorbach, Alexander M; Rogers, John A

    2015-10-01

    Continuous monitoring of variations in blood flow is vital in assessing the status of microvascular and macrovascular beds for a wide range of clinical and research scenarios. Although a variety of techniques exist, most require complete immobilization of the subject, thereby limiting their utility to hospital or clinical settings. Those that can be rendered in wearable formats suffer from limited accuracy, motion artifacts, and other shortcomings that follow from an inability to achieve intimate, noninvasive mechanical linkage of sensors with the surface of the skin. We introduce an ultrathin, soft, skin-conforming sensor technology that offers advanced capabilities in continuous and precise blood flow mapping. Systematic work establishes a set of experimental procedures and theoretical models for quantitative measurements and guidelines in design and operation. Experimental studies on human subjects, including validation with measurements performed using state-of-the-art clinical techniques, demonstrate sensitive and accurate assessment of both macrovascular and microvascular flow under a range of physiological conditions. Refined operational modes eliminate long-term drifts and reduce power consumption, thereby providing steps toward the use of this technology for continuous monitoring during daily activities. PMID:26601309

  20. Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow

    PubMed Central

    Webb, R. Chad; Ma, Yinji; Krishnan, Siddharth; Li, Yuhang; Yoon, Stephen; Guo, Xiaogang; Feng, Xue; Shi, Yan; Seidel, Miles; Cho, Nam Heon; Kurniawan, Jonas; Ahad, James; Sheth, Niral; Kim, Joseph; Taylor VI, James G.; Darlington, Tom; Chang, Ken; Huang, Weizhong; Ayers, Joshua; Gruebele, Alexander; Pielak, Rafal M.; Slepian, Marvin J.; Huang, Yonggang; Gorbach, Alexander M.; Rogers, John A.

    2015-01-01

    Continuous monitoring of variations in blood flow is vital in assessing the status of microvascular and macrovascular beds for a wide range of clinical and research scenarios. Although a variety of techniques exist, most require complete immobilization of the subject, thereby limiting their utility to hospital or clinical settings. Those that can be rendered in wearable formats suffer from limited accuracy, motion artifacts, and other shortcomings that follow from an inability to achieve intimate, noninvasive mechanical linkage of sensors with the surface of the skin. We introduce an ultrathin, soft, skin-conforming sensor technology that offers advanced capabilities in continuous and precise blood flow mapping. Systematic work establishes a set of experimental procedures and theoretical models for quantitative measurements and guidelines in design and operation. Experimental studies on human subjects, including validation with measurements performed using state-of-the-art clinical techniques, demonstrate sensitive and accurate assessment of both macrovascular and microvascular flow under a range of physiological conditions. Refined operational modes eliminate long-term drifts and reduce power consumption, thereby providing steps toward the use of this technology for continuous monitoring during daily activities. PMID:26601309

  1. [Quick Start-up and Sustaining of Shortcut Nitrification in Continuous Flow Reactor].

    PubMed

    Wu, Peng; Zhang Shi-ying; Song, Yin-ling; Xu, Yue-zhong; Shen, Yao-liang

    2016-04-15

    How to achieve fast and stable startup of shortcut nitrification has a very important practical value for treatment of low C/N ratio wastewater. Thus, the quick start-up and sustaining of shortcut nitrification were investigated in continuous flow reactor targeting at the current situation of urban wastewater treatment plant using a continuous flow process. The results showed that quick start-up of shortcut nitrification could be successfully achieved in a continuous flow reactor after 60 days' operation with intermittent aeration and controlling of three stages of stop/aeration time (15 min/45 min, 45 min/45 min and 30 min/30 min). The nitrification rates could reach 90% or 95% respectively, while influent ammonia concentrations were 50 or 100 mg · L⁻¹ with stop/aeration time of 30 min/30 min. In addition, intermittent aeration could inhibit the activity of nitrite oxidizing bacteria (NOB), while short hydraulic retention time (HRT) may wash out NOB. And a combined use of both measures was beneficial to sustain shortcut nitrification. PMID:27548971

  2. In-airway molecular flow sensing: A new technology for continuous, noninvasive monitoring of oxygen consumption in critical care

    PubMed Central

    Ciaffoni, Luca; O’Neill, David P.; Couper, John H.; Ritchie, Grant A. D.; Hancock, Gus; Robbins, Peter A.

    2016-01-01

    There are no satisfactory methods for monitoring oxygen consumption in critical care. To address this, we adapted laser absorption spectroscopy to provide measurements of O2, CO2, and water vapor within the airway every 10 ms. The analyzer is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. The precision is illustrated by integrating the balance gas (N2 plus Ar) flow and showing that this exchange was near zero. Measured O2 consumption changed by <5% between air and O2 breathing. Clinical capability was illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible. PMID:27532048

  3. In-airway molecular flow sensing: A new technology for continuous, noninvasive monitoring of oxygen consumption in critical care.

    PubMed

    Ciaffoni, Luca; O'Neill, David P; Couper, John H; Ritchie, Grant A D; Hancock, Gus; Robbins, Peter A

    2016-08-01

    There are no satisfactory methods for monitoring oxygen consumption in critical care. To address this, we adapted laser absorption spectroscopy to provide measurements of O2, CO2, and water vapor within the airway every 10 ms. The analyzer is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. The precision is illustrated by integrating the balance gas (N2 plus Ar) flow and showing that this exchange was near zero. Measured O2 consumption changed by <5% between air and O2 breathing. Clinical capability was illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible. PMID:27532048

  4. 21 CFR 870.3535 - Intra-aortic balloon and control system

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Intra-aortic balloon and control system 870.3535... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3535 Intra-aortic balloon and control system (a) Identification. A intra-aortic balloon and control system is a device...

  5. 21 CFR 870.3535 - Intra-aortic balloon and control system

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intra-aortic balloon and control system 870.3535... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3535 Intra-aortic balloon and control system (a) Identification. A intra-aortic balloon and control system is a device...

  6. 21 CFR 870.3535 - Intra-aortic balloon and control system

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Intra-aortic balloon and control system 870.3535... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3535 Intra-aortic balloon and control system (a) Identification. A intra-aortic balloon and control system is a device...

  7. 21 CFR 870.3535 - Intra-aortic balloon and control system

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Intra-aortic balloon and control system 870.3535... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3535 Intra-aortic balloon and control system (a) Identification. A intra-aortic balloon and control system is a device...

  8. Effect of Stopper-Rod Misalignment on Fluid Flow in Continuous Casting of Steel

    NASA Astrophysics Data System (ADS)

    Chaudhary, R.; Lee, Go-Gi; Thomas, B. G.; Cho, Seong-Mook; Kim, Seon-Hyo; Kwon, Oh-Duck

    2011-04-01

    Misalignment of metal-delivery systems can cause asymmetric fluid flow in the mold region of continuous casters, leading to abnormal surface turbulence, insufficient superheat transport to the meniscus, slag entrainment, inclusion entrapment, and other quality problems. This work investigates the effect of stopper-rod misalignment on nozzle and mold flow velocities in a conventional continuous casting process using both a water model and a computational model. Three stopper-rod configurations are studied (aligned, front misaligned by 2 mm, and left misaligned by 2 mm). The 3-D steady k- ɛ finite-volume model matched well with impeller probe measurements of both velocity and its fluctuations. Negligible asymmetry was found near the narrow faces. Asymmetry close to submerged entry nozzle is the main cause of vortex formation observed in all cases. The left-misaligned stopper-rod produces a shallower jet with a higher flow rate from the right port, leading to higher surface velocities on the right surface. This produced substantially more large vortices on the left side. The asymmetry produced by the nozzle length bore diameter ratio of ~21 in this work is consistent with the theoretical critical entrance length of ~24 for turbulent pipe flow.

  9. A simple microfluidic device for the deformability assessment of blood cells in a continuous flow.

    PubMed

    Rodrigues, Raquel O; Pinho, Diana; Faustino, Vera; Lima, Rui

    2015-12-01

    Blood flow presents several interesting phenomena in microcirculation that can be used to develop microfluidic devices capable to promote blood cells separation and analysis in continuous flow. In the last decade there have been numerous microfluidic studies focused on the deformation of red blood cells (RBCs) flowing through geometries mimicking microvessels. In contrast, studies focusing on the deformation of white blood cells (WBCs) are scarce despite this phenomenon often happens in the microcirculation. In this work, we present a novel integrative microfluidic device able to perform continuous separation of a desired amount of blood cells, without clogging or jamming, and at the same time, capable to assess the deformation index (DI) of both WBCs and RBCs. To determine the DI of both WBCs and RBCs, a hyperbolic converging microchannel was used, as well as a suitable image analysis technique to measure the DIs of these blood cells along the regions of interest. The results show that the WBCs have a much lower deformability than RBCs when subjected to the same in vitro flow conditions, which is directly related to their cytoskeleton and nucleus contents. The proposed strategy can be easily transformed into a simple and inexpensive diagnostic microfluidic system to simultaneously separate and assess blood cells deformability. PMID:26482154

  10. Removal of natural organic matter and arsenic from water by electrocoagulation/flotation continuous flow reactor.

    PubMed

    Mohora, Emilijan; Rončević, Srdjan; Dalmacija, Božo; Agbaba, Jasmina; Watson, Malcolm; Karlović, Elvira; Dalmacija, Milena

    2012-10-15

    The performance of the laboratory scale electrocoagulation/flotation (ECF) reactor in removing high concentrations of natural organic matter (NOM) and arsenic from groundwater was analyzed in this study. An ECF reactor with bipolar plate aluminum electrodes was operated in the horizontal continuous flow mode. Electrochemical and flow variables were optimized to examine ECF reactor contaminants removal efficiency. The optimum conditions for the process were identified as groundwater initial pH 5, flow rate=4.3 l/h, inter electrode distance=2.8 cm, current density=5.78 mA/cm(2), A/V ratio=0.248 cm(-1). The NOM removal according to UV(254) absorbance and dissolved organic matter (DOC) reached highest values of 77% and 71% respectively, relative to the raw groundwater. Arsenic removal was 85% (6.2 μg As/l) relative to raw groundwater, satisfying the drinking water standards. The specific reactor electrical energy consumption was 17.5 kWh/kg Al. The specific aluminum electrode consumption was 66 g Al/m(3). According to the obtained results, ECF in horizontal continuous flow mode is an energy efficient process to remove NOM and arsenic from groundwater. PMID:22902131

  11. Simultaneous detection of E. coli K12 and S. aureus Using a Continuous Flow Multijunction Biosensor.

    PubMed

    Lee, Inae; Jun, Soojin

    2016-06-01

    Rapid detection and identification of potentially harmful bacteria is ideal for food manufacturers to prevent foodborne illness outbreaks. Continuous monitoring method of foodborne pathogens levels and trends in food gives real-time results. Therefore, the objectives of this study were to fabricate and characterize the continuous flow multijunction biosensor for simultaneous detection of Escherichia coli K12 and Staphylococcus aureus. Junction biosensors were fabricated using gold plated tungsten wires coated with polyethylenimine and single walled carbon nanotubes. Each junction was functionalized with streptavidin and biotinylated antibodies specific to E. coli K12 and S. aureus. Then, single or 2 biosensors for each targeted analyte were connected to tubing, perpendicular to the flow direction. Pure serial diluted samples of E. coli K12 and S. aureus and microbial cocktail samples were continuously pumped at a 0.0167 mL/s into the detection zone. Changes in the electric current by biorecognition reactions between antibody and antigens were calculated. The developed junction sensor coupled with the fluidic channel showed the enhancement of the electric signal responses for detection of E. coli K12, compared to the stationary sensor. A linear regression was observed for both the E. coli and S. aureus functionalized array sensors in the detection range of 10(2) to 10(5) CFU/mL. Multiplexed detection of bacteria at the sensing levels as low as 10(2) CFU/mL for E. coli K12 and S. aureus was achieved within 2 min. Therefore, the continuous flow multijunction biosensor shows potential for rapid and continuous multiplexed detection of foodborne pathogens. PMID:27096467

  12. Manufacture and properties of continuous grain flow crankshafts for locomotive and power generation diesel engines

    SciTech Connect

    Antos, D.J.; Nisbett, E.G.

    1997-12-31

    The bulk of the large crankshaft production volume is associated with the medium speed diesel engine market. These engines have seen intense development to obtain higher power outputs without change in the physical size of the crankshaft and at the same time there has been continuing pressure to reduce costs. Fatigue and bearing normal wear are the major technical hurdles that threaten the crankshaft life, and measures for dealing with these issues are described. Continuous grain flow (CGF) crankshafts are responsible for the continued integrity of these enhanced power output engines and the production of these crankshafts is described. Comparisons are made with the older slab forging crankshaft production method. The demand for the medium speed diesel engine and its natural gas derivative is strong and supports an aggressive engine building industry serving locomotive, marine and power generation markets. This demand in turn relies on practical national standards that serve the needs of the engine builder, material supplier and the end user.

  13. Study of continuously mixed crosslinked fracturing fluids with a recirculating flow-loop viscometer

    SciTech Connect

    Harris, P.C.; Harms, W.M.; Norman, L.R. )

    1989-11-01

    Continuously mixed gel fracturing fluids were successfully prepared with polymer slurries of guar, derivatized guar, and derivatized cellulose. The authors describe the rheological behavior of the continuously mixed fluids measured on a recirculating flow-loop viscometer over a temperature range of 80 to 300{sup 0}F (27 to 149{sup 0}C). Rapid and complete base-gel hydration required proper pH control and high mixing energy. Oil-based polymer slurries allowed rapid hydration rates sufficient to achieve performance from a crosslinked fluid prepared during a completely continuous operation. Water-based polymer slurries required a short holding period for complete hydration. Delayed-crosslink-gel viscosity was influenced by shear rate and the degree of base-gel hydration. Chemical factors influencing viscosity development included base-gel concentration, crosslinking-agent concentration, fluid pH, and ionic strength. Hydration time and pH requirements may differ for specific polymer/crosslinker pairs.

  14. A Continuous-Flow Polymerase Chain Reaction Microchip With Regional Velocity Control

    PubMed Central

    Li, Shifeng; Fozdar, David Y.; Ali, Mehnaaz F.; Li, Hao; Shao, Dongbing; Vykoukal, Daynene M.; Vykoukal, Jody; Floriano, Pierre N.; Olsen, Michael; McDevitt, John T.; Gascoyne, Peter R.C.; Chen, Shaochen

    2009-01-01

    This paper presents a continuous-flow polymerase chain reaction (PCR) microchip with a serpentine microchannel of varying width for “regional velocity control.” Varying the channel width by incorporating expanding and contracting conduits made it possible to control DNA sample velocities for the optimization of the exposure times of the sample to each temperature phase while minimizing the transitional periods during temperature transitions. A finite element analysis (FEA) and semi-analytical heat transfer model was used to determine the distances between the three heating assemblies that are responsible for creating the denaturation (96 °C), hybridization (60 °C), and extension (72 °C) temperature zones within the microchip. Predictions from the thermal FEA and semi-analytical model were compared with temperature measurements obtained from an infrared (IR) camera. Flow-field FEAs were also performed to predict the velocity distributions in the regions of the expanding and contracting conduits to study the effects of the microchannel geometry on flow recirculation and bubble nucleation. The flow fields were empirically studied using micro particle image velocimetry (μ-PIV) to validate the flow-field FEA’s and to determine experimental velocities in each of the regions of different width. Successful amplification of a 90 base pair (bp) bacillus anthracis DNA fragment was achieved. PMID:19829760

  15. Avalanche to Continuous flow transition in wet and cohesive granular media

    NASA Astrophysics Data System (ADS)

    Orpe, Ashish; Basu, Saprativ; Doshi, Pankaj

    2013-11-01

    We have studied the flow of wet and cohesive granular media in a partially filled, horizontally rotating cylinder. Very small, amount of viscous liquid is added to dry granular particles and the mixture is rotated in the cylinder at various rotational speeds to determine the angle of repose in the avalanching regime, the continuous regime and at the transition rotational speed separating the two regimes. Every experimental run is carried out afresh at a pre-defined rotational speed using liquids with different free surface tension and added in different amounts. Increasing the liquid surface tension increases the angle of repose as well as shifts the transition rotational speed to increasingly higher values. Similar qualitative behaviour is also observed on increasing the amount liquid added. A linear dependence is observed when the transition angle of repose for all cases is plotted against the corresponding transition rotational speed. The entire flow regime is modeled using momentum and mass balance equations for the flowing layer of particles. The total stress in the flowing mass of particles is assumed to be a linear combination of frictional, collisional and capillary force contributions. The model equations are able to reproduce most of the observed flow behavior. Department of Science and Technology, India, (Grant No. SR/S3/CE/037/2009).

  16. Effect of an Electromagnetic Brake on the Turbulent Melt Flow in a Continuous-Casting Mold

    NASA Astrophysics Data System (ADS)

    Miao, Xincheng; Timmel, Klaus; Lucas, Dirk; Ren, Zhongmin; Eckert, Sven; Gerbeth, Gunter

    2012-08-01

    This article presents numerical and experimental investigations with respect to the fluid flow in the continuous-casting process under the influence of an external direct current (DC) magnetic field. Numerical calculations were performed by means of the software package CFX (Ansys, Inc., Canonsburg, PA) with an implemented Reynolds-averaged Navier-Stokes (RANS)-SST turbulence model. The nonisotropic nature of the magnetohydrodynamic (MHD) turbulence was taken into account by specific modifications of the turbulence model. The numerical results were validated by flow measurements carried out in a small-scale mockup using the eutectic alloy GaInSn. The jet flow discharging from the submerged entry nozzle was exposed to a level magnetic field spanning across the entire wide side of the mold. The comparison between our numerical calculations and the experimental results displays a good agreement; in particular, we reconstructed the peculiar phenomenon of an excitation of nonsteady, nonisotropic, large-scale flow perturbations caused by the application of the DC magnetic field. Another important result of our study is the feature that the electrical boundary conditions, namely the wall conductivity ratio, have a serious influence on the mold flow while it is exposed to an external magnetic field.

  17. Overcoming issues associated with the scale-up of a continuous flow microwave system for aseptic processing of vegetable purees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous flow microwave heating is a promising alternative to conventional heating for aseptic processing of low-acid vegetable purees. However, non-uniform temperature distribution and control of processing parameters are the major hurdles in the implementation of continuous flow microwave heatin...

  18. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. 84.155 Section... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and...

  19. Onset of entrainment and degree of dispersion in dual continuous horizontal oil-water flows

    SciTech Connect

    Al-Wahaibi, Talal; Angeli, Panagiota

    2009-04-15

    The transition from stratified to dual continuous oil-water flow (where each phase retains its continuity but there is dispersion of one phase into the other) as well as the dispersed phase fractions in the layers of the dual continuous pattern, were studied experimentally. Transition to this pattern from stratified flow occurs when drops of one phase appear into the other (onset of entrainment). The studies were carried out in a 38 mm ID horizontal stainless steel test section using two different inlet geometries, a T- and a Y-junction. The patterns were visualized through a transparent acrylic section located at 7 m from the inlet using a high speed video camera. Phase distribution measurements in a pipe cross section were obtained just before the acrylic section with a local impedance probe and the results were used to calculate the volume fraction of each phase entrained into the other. The onset of entrainment was found to occur at lower superficial water velocities as the oil superficial velocities increased. However, the inlet geometry did not affect significantly the transition line. During dual continuous flow, the dispersion of one phase into the opposite was found to extend further away from the interface with increasing water superficial velocity for a certain oil superficial velocity. An increase in the superficial water velocity increased the entrained fraction of water in oil (E{sub w/o}) but there was no trend with the oil velocity. Similarly, an increase in the superficial oil velocity increased the fraction of oil drops in water (E{sub o/w}) but the water velocity had no clear effect. The entrainment fractions were affected by the inlet geometry, with the T-inlet resulting in higher entrainment than the Y-inlet, perhaps because of the increased mixing induced by the T-inlet. The difference between the two inlets increased as the oil and water velocities increased. (author)

  20. Methods used to compute low-flow frequency characteristics for continuous-record streamflow stations in Minnesota, 2006

    USGS Publications Warehouse

    Winterstein, Thomas A.; Arntson, Allan D.; Mitton, Gregory B.

    2007-01-01

    The 1-, 7-, and 30-day low-flow series were determined for 120 continuous-record streamflow stations in Minnesota having at least 20 years of continuous record. The 2-, 5-, 10-, 50-, and 100-year statistics were determined for each series by fitting a log Pearson type III distribution to the data. The methods used to determine the low-flow statistics and to construct the plots of the low-flow frequency curves are described. The low-flow series and the low-flow statistics are presented in tables and graphs.

  1. Continuous-flow water sampler for real-time isotopic water measurements

    NASA Astrophysics Data System (ADS)

    Carter, J.; Dennis, K.

    2013-12-01

    Measuring the stable isotopes of liquid water (δ18O and δD) is a tool familiar to many Earth scientists, but most current techniques require discrete sampling. For example, isotope ratio mass spectrometry requires the collection of aliquots of water that are then converted to CO2, CO or H2 for analysis. Similarly, laser-based techniques, such as Cavity Ring-Down Spectroscopy (CRDS) convert discrete samples (typically < 2μL) of liquid water to water vapor using a flash vaporization process. By requiring the use of discrete samples fine-scale spatial and temporal studies of changes in δ18O and δD are limited. Here we present a continuous-flow water sampler that will enable scientists to probe isotopic changes in real-time, with applications including, but not limited to, quantification of the 'amount effect' (Dansgaard, 1964) during an individual precipitation event or storm track, real-time mixing of water in river systems, and shipboard continuous water measurements (Munksgaard et al., 2012). Due to the inherent ability of CRDS to measure a continuous flow of water vapor it is an ideal candidate for interfacing with a continuous water sampling system. Here we present results from the first commercially available continuous-flow water sampler, developed by engineers at Picarro. This peripheral device is compatible with Picarro CRDS isotopic water analyzers, allowing real-time, continuous isotopic measurements of liquid water. The new device, which expands upon the design of Munskgaard et al. (2011), utilizes expanded polytetrafluoroethylene (ePTFE) membrane technology to continuously generate gas-phase water, while liquid water is pumped through the system. The water vapor subsequently travels to the CRDS analyzer where the isotopic ratios are measured and recorded. The generation of water vapor using membrane technology is sensitive to environmental conditions, which if not actively control, lead to sustainable experimental noise and drift. Consequently, our

  2. Biomechanical factors in the biology of aortic wall and aortic valve diseases

    PubMed Central

    Bäck, Magnus; Gasser, T. Christian; Michel, Jean-Baptiste; Caligiuri, Giuseppina

    2013-01-01

    The biomechanical factors that result from the haemodynamic load on the cardiovascular system are a common denominator of several vascular pathologies. Thickening and calcification of the aortic valve will lead to reduced opening and the development of left ventricular outflow obstruction, referred to as aortic valve stenosis. The most common pathology of the aorta is the formation of an aneurysm, morphologically defined as a progressive dilatation of a vessel segment by more than 50% of its normal diameter. The aortic valve is exposed to both haemodynamic forces and structural leaflet deformation as it opens and closes with each heartbeat to assure unidirectional flow from the left ventricle to the aorta. The arterial pressure is translated into tension-dominated mechanical wall stress in the aorta. In addition, stress and strain are related through the aortic stiffness. Furthermore, blood flow over the valvular and vascular endothelial layer induces wall shear stress. Several pathophysiological processes of aortic valve stenosis and aortic aneurysms, such as macromolecule transport, gene expression alterations, cell death pathways, calcification, inflammation, and neoangiogenesis directly depend on biomechanical factors. PMID:23459103

  3. Continuous flow electrophoresis system experiments on shuttle flights STS-6 and STS-7

    NASA Technical Reports Server (NTRS)

    Snyder, Robert S.; Rhodes, Percy H.; Miller, Teresa Y.

    1987-01-01

    A space continuous flow electrophoresis system (CFES) was developed that would incorporate specific modifications to laboratory instruments to take advantage of weightlessness. The specific objectives were to use a model sample material at a high concentration to evaluate the continuous flow electrophoresis process in the CFES instrument and compare its separation resolution and sample throughput with related devices on Earth and to expand the basic knowledge of the limitations imposed by fluid flows and particle concentration effects on the electrophoresis process by careful design and evaluation of the space experiment. Hemoglobin and polysaccharide were selected as primary samples. The results from space show a large band spread of the high concentration of the single species of hemoglobin that was due to the mismatch of electrical conductivity between the sample and the buffer. On STS-7 the major objective was to evaluate the influence of the electrical properties of the sample constituents on the resolution of the CFES. As expected, the polystyrene latex microspheres dispersed in a solution with 3 times the electrical conductivity of the curtain buffer separated with a larger band spread than in the 2nd experiment.

  4. A simple automated continuous-flow-equilibration method for measuring carbon monoxide in seawater.

    PubMed

    Xie, H; Zafiriou, O C; Wang, W; Taylor, C D

    2001-04-01

    A simple, robust, low-maintenance method using air-segmented continuous-flow equilibration was developed and automated to measure carbon monoxide (CO) in natural waters precisely and accurately. Finely regulated flows of CO-free air and of seawater or standard water were pumped into a glass coil, forming discrete gas/liquid segments. The partially CO-equilibrated gas effluent was injected into a Trace Analytical reduction analyzer for CO detection. A semiempirical mass-balance model was established for predicting and optimizing the performance of the CO extractor. The optimized gas and water flow rates were approximately 1.2 and approximately 14 mL min(-1), respectively, giving a response time of less than 15 min and a CO-extraction yield of approximately 80%. The analytical blank, precision, and accuracy were, respectively, 0.02 nM, +/-2.5% (at the approximately 1 nM level), and better than 5%. Two extractors can be interfaced to one detector at 4-6 samples per hour for each extractor. Coupled with a continuous surface-water sampler, the system was successfully applied to monitoring the diurnal variation of CO concentration in Sargasso Sea surface waters. PMID:11348089

  5. Low volume ultrasonic resonator for liquid characterization under continuous flow conditions

    NASA Astrophysics Data System (ADS)

    Aparicio, C.; Elvira, L.; Durán, C.; Montero, F.; Resa, P.

    2014-11-01

    A new ultrasonic resonator called MICRUS for measuring and characterizing liquid samples in continuous flow is presented. High accuracy and thermal stability are obtained by handling small liquid volumes passing through a heat exchanger before reaching the ultrasonic measurement chamber. The core measuring element consists of a resonant quartz flow-cell with LiNbO3 piezoelectric discs attached face-to-face. The resonator is operated using pulsed excitation to provide rapid measurements. The software is implemented in LabView, giving a friendly and fully-automated interface well-suited for process monitoring. Different measurements for checking instrument performance (temperature stability, solute detection, measurement repeatability) are performed and a ±0.024 m s-1 uncertainty is obtained. Application examples requiring liquid measurement under continuous flow conditions are also presented. When monitoring processes taking place in containers and conduits with uncontrolled thermal conditions, results show that measurement stability can be kept under 0.1 m s-1 even when the sample temperature changes by more than 2 °C due to environmental variations.

  6. Titer-plate formatted continuous flow thermal reactors: Design and performance of a nanoliter reactor

    PubMed Central

    Chen, Pin-Chuan; Park, Daniel S.; You, Byoung-Hee; Kim, Namwon; Park, Taehyun; Soper, Steven A.; Nikitopoulos, Dimitris E.; Murphy, Michael C.

    2010-01-01

    Arrays of continuous flow thermal reactors were designed, configured, and fabricated in a 96-device (12 × 8) titer-plate format with overall dimensions of 120 mm × 96 mm, with each reactor confined to a 8 mm × 8 mm footprint. To demonstrate the potential, individual 20-cycle (740 nL) and 25-cycle (990 nL) reactors were used to perform the continuous flow polymerase chain reaction (CFPCR) for amplification of DNA fragments of different lengths. Since thermal isolation of the required temperature zones was essential for optimal biochemical reactions, three finite element models, executed with ANSYS (v. 11.0, Canonsburg, PA), were used to characterize the thermal performance and guide system design: (1) a single device to determine the dimensions of the thermal management structures; (2) a single CFPCR device within an 8 mm × 8 mm area to evaluate the integrity of the thermostatic zones; and (3) a single, straight microchannel representing a single loop of the spiral CFPCR device, accounting for all of the heat transfer modes, to determine whether the PCR cocktail was exposed to the proper temperature cycling. In prior work on larger footprint devices, simple grooves between temperature zones provided sufficient thermal resistance between zones. For the small footprint reactor array, 0.4 mm wide and 1.2 mm high fins were necessary within the groove to cool the PCR cocktail efficiently, with a temperature gradient of 15.8°C/mm, as it flowed from the denaturation zone to the renaturation zone. With temperature tolerance bands of ±2°C defined about the nominal temperatures, more than 72.5% of the microchannel length was located within the desired temperature bands. The residence time of the PCR cocktail in each temperature zone decreased and the transition times between zones increased at higher PCR cocktail flow velocities, leading to less time for the amplification reactions. Experiments demonstrated the performance of the CFPCR devices as a function of flow

  7. Differential aspects of the disease and treatment of Thoracic Acute Aortic Dissection (TAAD)-the European experience.

    PubMed

    Pepper, John

    2016-07-01

    The management of patients with acute aortic dissection continues to be a challenge. It is an uncommon but lethal condition which continues to be under-diagnosed and under-treated. In this review, the term acute aortic syndrome is preferred in order to embrace the closely related pathologies of intramural hematoma (IMH) and penetrating aortic ulcer (PAU). PMID:27563549

  8. Differential aspects of the disease and treatment of Thoracic Acute Aortic Dissection (TAAD)—the European experience

    PubMed Central

    2016-01-01

    The management of patients with acute aortic dissection continues to be a challenge. It is an uncommon but lethal condition which continues to be under-diagnosed and under-treated. In this review, the term acute aortic syndrome is preferred in order to embrace the closely related pathologies of intramural hematoma (IMH) and penetrating aortic ulcer (PAU). PMID:27563549

  9. Comparison of different Methods to model Transient Turbulent Magnetohydrodynamic Flow in Continuous Casting Molds

    NASA Astrophysics Data System (ADS)

    Kratzsch, C.; Asad, A.; Schwarze, R.

    2016-07-01

    Modeling of the processes in the continuous casting mold engaged many scientists once the computer-technology was able to accomplish that task. Despite that, CFD modeling of the fluid flow is still challenging. The methods allow deeper and deeper inside views into transient flow processes. Mostly two kinds of methods are applied for this purpose. URANS simulations are used for a coarse overview of the transient behavior on scales determined by the big rollers inside the mold. Besides, LES were done to study the processes on smaller scales. Unfortunately, the effort to set up a LES is orders of magnitude higher in time and space compared to URANS. Often, the flow determining processes take place in small areas inside the flow domain. Hence, scale resolving methods (SRS) came up, which resolve the turbulence in some amount in these regions, whereas they go back to URANS in the regions of less importance. It becomes more complex when dealing with magnetic fields in terms of EMBr devices. The impact of electro magnetically forces changes the flow structure remarkably. Many important effects occur, e.g. MHD turbulence, which are attributable to processes on large turbulent scales. To understand the underlying phenomena in detail, SRS allows a good inside view by resolving these processes partially. This study compares two of these methods, namely the Scale Adaptive Simulation (SAS) and the Delayed Detached Eddy Simulation (DDES), with respect to rendition of the results known from experiments and URANS simulation. The results show, that the SAS as well as the DDES are able to deliver good results with higher mesh resolutions in important regions in the flow domain

  10. On-line monitoring of continuous flow chemical synthesis using a portable, small footprint mass spectrometer.

    PubMed

    Bristow, Tony W T; Ray, Andrew D; O'Kearney-McMullan, Anne; Lim, Louise; McCullough, Bryan; Zammataro, Alessio

    2014-10-01

    For on-line monitoring of chemical reactions (batch or continuous flow), mass spectrometry (MS) can provide data to (1) determine the fate of starting materials and reagents, (2) confirm the presence of the desired product, (3) identify intermediates and impurities, (4) determine steady state conditions and point of completion, and (5) speed up process optimization. Recent developments in small footprint atmospheric pressure ionization portable mass spectrometers further enable this coupling, as the mass spectrometer can be easily positioned with the reaction system to be studied. A major issue for this combination is the transfer of a sample that is representative of the reaction and also compatible with the mass spectrometer. This is particularly challenging as high concentrations of reagents and products can be encountered in organic synthesis. The application of a portable mass spectrometer for on-line characterization of flow chemical synthesis has been evaluated by coupling a Microsaic 4000 MiD to the Future Chemistry Flow Start EVO chemistry system. Specifically, the Hofmann rearrangement has been studied using the on-line mass spectrometry approach. Sample transfer from the flow reactor is achieved using a mass rate attenuator (MRA) and a sampling make-up flow from a high pressure pump. This enables the appropriate sample dilution, transfer, and preparation for electrospray ionization. The capability of this approach to provide process understanding is described using an industrial pharmaceutical process that is currently under development. The effect of a number of key experimental parameters, such as the composition of the sampling make-up flow and the dilution factor on the mass spectrometry data, is also discussed. PMID:25106707

  11. On-line Monitoring of Continuous Flow Chemical Synthesis Using a Portable, Small Footprint Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Bristow, Tony W. T.; Ray, Andrew D.; O'Kearney-McMullan, Anne; Lim, Louise; McCullough, Bryan; Zammataro, Alessio

    2014-10-01

    For on-line monitoring of chemical reactions (batch or continuous flow), mass spectrometry (MS) can provide data to (1) determine the fate of starting materials and reagents, (2) confirm the presence of the desired product, (3) identify intermediates and impurities, (4) determine steady state conditions and point of completion, and (5) speed up process optimization. Recent developments in small footprint atmospheric pressure ionization portable mass spectrometers further enable this coupling, as the mass spectrometer can be easily positioned with the reaction system to be studied. A major issue for this combination is the transfer of a sample that is representative of the reaction and also compatible with the mass spectrometer. This is particularly challenging as high concentrations of reagents and products can be encountered in organic synthesis. The application of a portable mass spectrometer for on-line characterization of flow chemical synthesis has been evaluated by coupling a Microsaic 4000 MiD to the Future Chemistry Flow Start EVO chemistry system. Specifically, the Hofmann rearrangement has been studied using the on-line mass spectrometry approach. Sample transfer from the flow reactor is achieved using a mass rate attenuator (MRA) and a sampling make-up flow from a high pressure pump. This enables the appropriate sample dilution, transfer, and preparation for electrospray ionization. The capability of this approach to provide process understanding is described using an industrial pharmaceutical process that is currently under development. The effect of a number of key experimental parameters, such as the composition of the sampling make-up flow and the dilution factor on the mass spectrometry data, is also discussed.

  12. Juxtarenal aortic occlusion.

    PubMed Central

    Tapper, S S; Jenkins, J M; Edwards, W H; Mulherin, J L; Martin, R S; Edwards, W H

    1992-01-01

    The authors' experience with 113 aortic occlusions in 103 patients during a 26-year period (1965 to 1991) is reviewed. The authors found three distinct patterns of presentation: group I (n = 26) presented with acute aortic occlusion, group II (n = 66) presented with chronic aortic occlusion, and group III (n = 21) presented with complete occlusion of an aortic graft. Perioperative mortality rates were 31%, 9%, and 4.7% for each respective group and achieved statistical significance when comparing group I with group II (p = 0.009) and group I with group III (p = 0.015). Group I presented with profound metabolic insults due to acute ischemia and fared poorly. Group II presented with chronic claudication and did well long-term. Group III presented with acute ischemia but did well because of established collateral circulation. The treatment and expected outcome of aortic occlusion depends on the cause. PMID:1616381

  13. Methodological inaccuracies in clinical aortic valve severity assessment: insights from computational fluid dynamic modeling of CT-derived aortic valve anatomy

    NASA Astrophysics Data System (ADS)

    Traeger, Brad; Srivatsa, Sanjay S.; Beussman, Kevin M.; Wang, Yechun; Suzen, Yildirim B.; Rybicki, Frank J.; Mazur, Wojciech; Miszalski-Jamka, Tomasz

    2016-04-01

    Aortic stenosis is the most common valvular heart disease. Assessing the contribution of the valve as a portion to total ventricular load is essential for the aging population. A CT scan for one patient was used to create one in vivo tricuspid aortic valve geometry and assessed with computational fluid dynamics (CFD). CFD simulated the pressure, velocity, and flow rate, which were used to assess the Gorlin formula and continuity equation, current clinical diagnostic standards. The results demonstrate an underestimation of the anatomic orifice area (AOA) by Gorlin formula and overestimation of AOA by the continuity equation, using peak velocities, as would be measured clinically by Doppler echocardiography. As a result, we suggest that the Gorlin formula is unable to achieve the intended estimation of AOA and largely underestimates AOA at the critical low-flow states present in heart failure. The disparity in the use of echocardiography with the continuity equation is due to the variation in velocity profile between the outflow tract and the valve orifice. Comparison of time-averaged orifice areas by Gorlin and continuity with instantaneous orifice areas by planimetry can mask the errors of these methods, which is a result of the assumption that the blood flow is inviscid.

  14. Large Eddy Simulation of Transient Flow, Solidification, and Particle Transport Processes in Continuous-Casting Mold

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Li, Linmin; Li, Baokuan; Jiang, Maofa

    2014-07-01

    The current study developed a coupled computational model to simulate the transient fluid flow, solidification, and particle transport processes in a slab continuous-casting mold. Transient flow of molten steel in the mold is calculated using the large eddy simulation. An enthalpy-porosity approach is used for the analysis of solidification processes. The transport of bubble and non-metallic inclusion inside the liquid pool is calculated using the Lagrangian approach based on the transient flow field. A criterion of particle entrapment in the solidified shell is developed using the user-defined functions of FLUENT software (ANSYS, Inc., Canonsburg, PA). The predicted results of this model are compared with the measurements of the ultrasonic testing of the rolled steel plates and the water model experiments. The transient asymmetrical flow pattern inside the liquid pool exhibits quite satisfactory agreement with the corresponding measurements. The predicted complex instantaneous velocity field is composed of various small recirculation zones and multiple vortices. The transport of particles inside the liquid pool and the entrapment of particles in the solidified shell are not symmetric. The Magnus force can reduce the entrapment ratio of particles in the solidified shell, especially for smaller particles, but the effect is not obvious. The Marangoni force can play an important role in controlling the motion of particles, which increases the entrapment ratio of particles in the solidified shell obviously.

  15. ET-AAS determination of aluminium in dialysis concentrates after continuous flow solvent extraction.

    PubMed

    Komárek, J; Cervenka, R; Růzicka, T; Kubán, V

    2007-11-01

    Conditions of a continuous flow extraction (CFE) of aluminium acetylacetonate in acetylacetone and aluminium 8-hydroxyquinolinate into methylisobutylketone (lengths of reaction and extraction coils, flow rates of aqueous and organic phases and their flow rate ratio, pH of aqueous phase, lengths of coils for transport of aqueous and organic phases and effect of salts) were studied. The analytical signal of the aluminium chelates present in the organic phase was measured at 309.3 nm using atomic absorption spectrometry with electrothermal atomization (ET-AAS) at the flow rate ratio F aq/F org=3 for aqueous and organic phases. The five points calibration curves were linear (R2 0.9973 and 0.9987) up to 21 microgl(-1) Al with the limits of detection of 0.3 microgl(-1) and the recovery 100+/-2% and precision of 3% at 2-10-fold dilution of the dialysis concentrates. The acetylacetonate method was applied to the determination of aluminium in real dialysis concentrates. Aluminium in concentrations 5-6 microgl(-1) (R.S.D.s 5-10% in real samples) were found and the results were in the very good agreement with those obtained by an ET-AAS using preconcentration of Al(III) on a Spheron-Salicyl chelating sorbent (absolute and relative differences were under 0.4 microgl(-1) and 8.2%, respectively). PMID:17897803

  16. Large Eddy Simulations of Double-Ruler Electromagnetic Field Effect on Transient Flow During Continuous Casting

    NASA Astrophysics Data System (ADS)

    Singh, Ramnik; Thomas, Brian G.; Vanka, Surya P.

    2014-06-01

    Transient flow during nominally steady conditions is responsible for many intermittent defects during the continuous casting of steel. The double-ruler electromagnetic field configuration, or "FC-Mold EMBr," is popular in commercial slab casting as it provides independent control of the applied static field near the jet and free surface regions of the mold. In the current study, transient flow in a typical commercial caster is simulated in the absence and in the presence of a double-ruler magnetic field, with rulers of equal strengths. Large eddy simulations with the in-house code CU-FLOW resolve the important transient behavior, using grids of over five million cells with a fast parallel solver. In the absence of a magnetic field, a double-roll pattern is observed, with transient unbalanced behavior, high surface velocities (~0.5 m/s), surface vortex formation, and very large surface-level fluctuations (~±12 mm). Applying the magnetic field suppresses the unbalanced behavior, producing a more complex mold flow pattern, but with much lower surface velocities (~0.1 m/s), and a flat surface level with small level fluctuations (<±1 mm). Nail board measurements taken at this commercial caster, in the absence of the field, matched reasonably well with the calculated results, both quantitatively and qualitatively.

  17. Conservative Management of Chronic Aortic Dissection with Underlying Aortic Aneurysm

    PubMed Central

    Yusuf Beebeejaun, Mohammad; Malec, Aleksandra; Gupta, Ravi

    2013-01-01

    Aortic dissection is one of the most common aortic emergencies affecting around 2000 Americans each year. It usually presents in the acute state but in a small percentage of patients aortic dissections go unnoticed and these patients survive without any adequate therapy. With recent advances in medical care and diagnostic technologies, aortic dissection can be successfully managed through surgical or medical options, consequently increasing the related survival rate. However, little is known about the optimal long-term management of patients suffering from chronic aortic dissection. The purpose of the present report is to review aortic dissection, namely its pathology and the current diagnostic tools available, and to discuss the management options for chronic aortic dissection. We report a patient in which chronic aortic dissection presented with recurring episodes of vomiting and also discuss the management plan of our patient who had a chronic aortic dissection as well as an underlying aortic aneurysm. PMID:24179638

  18. Fluid dynamics of aortic root dilation in Marfan syndrome.

    PubMed

    Querzoli, Giorgio; Fortini, Stefania; Espa, Stefania; Costantini, Martina; Sorgini, Francesca

    2014-09-22

    Aortic root dilation and propensity to dissection are typical manifestations of the Marfan Syndrome (MS), a genetic defect leading to the degeneration of the elastic fibres. Dilation affects the structure of the flow and, in turn, altered flow may play a role in vessel dilation, generation of aneurysms, and dissection. The aim of the present work is the investigation in-vitro of the fluid dynamic modifications occurring as a consequence of the morphological changes typically induced in the aortic root by MS. A mock-loop reproducing the left ventricle outflow tract and the aortic root was used to measure time resolved velocity maps on a longitudinal symmetry plane of the aortic root. Two dilated model aortas, designed to resemble morphological characteristics typically observed in MS patients, have been compared to a reference, healthy geometry. The aortic model was designed to quantitatively reproduce the change of aortic distensibility caused by MS. Results demonstrate that vorticity released from the valve leaflets, and possibly accumulating in the root, plays a fundamental role in redirecting the systolic jet issued from the aortic valve. The altered systolic flow also determines a different residual flow during the diastole. PMID:25001203

  19. Continuous-flow stirred-tank reactor 20-L demonstration test: Final report

    SciTech Connect

    Lee, D.D.; Collins, J.L.

    2000-02-01

    One of the proposed methods of removing the cesium, strontium, and transuranics from the radioactive waste storage tanks at Savannah River is the small-tank tetraphenylborate (TPB) precipitation process. A two-reactor-in-series (15-L working volume each) continuous-flow stirred-tank reactor (CSTR) system was designed, constructed, and installed in a hot cell to test the Savannah River process. The system also includes two cross-flow filtration systems to concentrate and wash the slurry produced in the process, which contains the bulk of radioactivity from the supernatant processed through the system. Installation, operational readiness reviews, and system preparation and testing were completed. The first test using the filtration systems, two CSTRs, and the slurry concentration system was conducted over a 61-h period with design removal of Cs, Sr, and U achieved. With the successful completion of Test 1a, the following tests, 1b and 1c, were not required.

  20. Experimental study of submillimeter droplets dynamics and breakup in continuous supersonic flow terminated by shock wave

    NASA Astrophysics Data System (ADS)

    Gobyzov, Oleg; Lozhkin, Yuriy; Ryabov, Mikhail; Markovich, Dmitriy

    2016-03-01

    The present paper reports an application of optical methods, namely PIV, background-oriented-schlieren (BOS) and high-magnification imaging with background illumination to study of dynamics and breakup of 10-100 μm size droplets in continuous supersonic flow terminated by a normal shock wave. Flow diagnostics was performed by means of BOS and PIV. Shadow photography allowed to specify velocity ranges for different droplet sizes and to visualize droplets dynamics and breakup modes. Features of the experimental setup and certain details of implemented measurement system are considered. Results of velocity measurements and droplets behavior, including deformation and breakup, are presented and analysis of experimental conditions and dimensionless parameters affecting the droplets behavior is performed. Distinctive features of deformation and breakup processes of submillimeter scale droplets are revealed.

  1. A review on continuous-flow microfluidic PCR in droplets: Advances, challenges and future.

    PubMed

    Zhang, Yonghao; Jiang, Hui-Rong

    2016-03-31

    Significant advances have been made in developing microfluidic polymerase chain reaction (PCR) devices in the last two decades. More recently, microfluidic microdroplet technology has been exploited to perform PCR in droplets because of its unique features. For example, it can prevent crossover contamination and PCR inhibition, is suitable for single-cell and single-molecule analyses, and has the potential for system integration and automation. This review will therefore focus on recent developments on droplet-based continuous-flow microfluidic PCR, and the major research challenges. This paper will also discuss a new way of on-chip flow control and a rational design simulation tool, which are required to underpin fully integrated and automated droplet-based microfluidic systems. We will conclude with a scientific speculation of future autonomous scientific discoveries enabled by microfluidic microdroplet technologies. PMID:26965323

  2. Accelerated gas-liquid visible light photoredox catalysis with continuous-flow photochemical microreactors.

    PubMed

    Straathof, Natan J W; Su, Yuanhai; Hessel, Volker; Noël, Timothy

    2016-01-01

    In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime. PMID:26633128

  3. Measurements of natural ice nuclei with a continuous flow diffusion chamber

    NASA Technical Reports Server (NTRS)

    Rogers, D. C.

    1983-01-01

    A description is given of a continuous flow diffusion chamber technique for measuring the atmospheric concentrations of natural C-F nuclei. It is noted that the same device can also measure deposition nuclei; these two modes can thus be separated and compared. The laminar flow characteristics allow the temperature and supersaturation to be calculated with a high degree of precision and confidence. The method avoids the problems of a supporting substrate and of concentrating the sample into a small volume (as for membrane filters). The present measurements of natural ice nucleus concentrations at +1 percent water supersaturation are found to be comparable to research aircraft measurements of ice crystal concentrations in winter cap clouds over Elk Mountain, Wyoming (Vali et al., 1982).

  4. An experimental study of pulsed micro-flows pertinent to continuous subcutaneous insulin infusion therapy

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Demuren, Ayodeji; Gyuricsko, Eric; Hu, Hui

    2011-07-01

    An experimental study was conducted to investigate the unsteady micro-flow driven by an insulin pump commonly used in continuous subcutaneous insulin infusion (CSII) therapy. A microscopic particle image velocimetry (PIV) system was used to characterize the transient behavior of the micro-flow upon the pulsed excitation of the insulin pump in order to elucidate the underlying physics for a better understanding of the microphysical process associated with the insulin delivery in CSII therapy. The effects of air bubbles entrained inside the micro-sized CSII tubing system on the insulin delivery process were also assessed based on the micro-PIV measurements. While most solutions to insulin occlusion-related problems are currently based on clinical trials, the findings derived from the present study can be used to provide a better guidance for the troubleshooting of insulin occlusion in CSII therapy.

  5. Continuous Crystallization of Proteins in a Tubular Plug-Flow Crystallizer

    PubMed Central

    2015-01-01

    Protein crystals have many important applications in many fields, including pharmaceutics. Being more stable than other formulations, and having a high degree of purity and bioavailability, they are especially promising in the area of drug delivery. In this contribution, the development of a continuously operated tubular crystallizer for the production of protein crystals has been described. Using the model enzyme lysozyme, we successfully generated product particles ranging between 15 and 40 μm in size. At the reactor inlet, a protein solution was mixed with a crystallization agent solution to create high supersaturations required for nucleation. Along the tube, supersaturation was controlled using water baths that divided the crystallizer into a nucleation zone and a growth zone. Low flow rates minimized the effect of shear forces that may impede crystal growth. Simultaneously, a slug flow was implemented to ensure crystal transport through the reactor and to reduce the residence time distribution. PMID:25774098

  6. First continuous flow analysis results from the Greenland ReCAP project

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid

    2016-04-01

    The new Renland ice core was drilled in summer 2015 in Greenland and measured by means of Continuous flow analysis during the last 3 months of 2015. The Renland ice core was obtained as part of the ReCAP project, extending 584.11 meters to the bottom of the Renland ice cap located in east Greenland. The unique position on a mountain saddle above 2000 meters altitude, but close to the coast, ensures that the Renland ice core offers high accumulation, but also reaches far back in time. Preliminary results show that the record holds ice from the past warm interglacial period, the Eemian. The record was analyzed for multiple elements including the forest fire tracers NH4+ and black carbon, insoluble dust particles by means of Abakus laser particle counter and the dust ion Ca2+, sea salt Na and acidity useful for finding volcanic layers to date the core. Further H2O2, and the nutrients Fe and dissolved reactive phosphorus was analyzed as well as the temperature indicator δ18O all by means of continuous flow analysis (CFA). The core was melted at a rate of 3 cm/min providing a temporal resolution for most components determined sufficient to resolve annual layers through the Holocene. The glacial section is strongly thinned, but nonetheless due to the high resolution of the measurements all DO events could be identified. Below the glacial section another ˜20 meters of warm Eemian ice have been analysed. Here we present the first chemistry results as obtained by continuous flow analysis (CFA).

  7. Experimental study on the disinfection efficiencies of a continuous-flow ultrasound/ultraviolet baffled reactor.

    PubMed

    Zhou, Xiaoqin; Guo, Hao; Li, Zifu; Zhao, Junyuan; Yun, Yupan

    2015-11-01

    A self-designed continuous-flow ultrasound/ultraviolet (US/UV) baffled reactor was tested in this work, and the disinfection efficiency of secondary effluent from a wastewater treatment plant (WWTP) was investigated in terms of the different locations of ultrasonic transducers inside the reactor under similar input power densities and specific energy consumptions. Results demonstrated that the two-stage simultaneous US/UV irradiation in both chambers 2 and 3 at a flow rate of 1200 L/h performed excellent disinfection efficiency. It achieved an average feacal coliforms concentration of 201±78 colony forming unit (CFU)/L in the effluent and an average of (4.24±0.26) log10 reduction. Thereafter, 8 days of continuous operation was performed under such a condition. A total of 31 samples were taken, and all the samples were analyzed in triplicate for feacal coliforms analysis. Experimental results showed that feacal coliforms concentrations remained at about 347±174 CFU/L under the selected optimum disinfection condition, even if the influent concentrations fluctuated from 3.97×10(5) to 3.57×10(6) CFU/L. This finding implied that all effluents of continuous-flow-baffled-reactor with simultaneous US/UV disinfection could meet the requirements of the discharge standard of pollutants for municipal WWTP (GB 18918-2002) Class 1-A (1000 CFU/L) with a specific energy consumption of 0.219 kWh/m(3). Therefore, the US/UV disinfection process has great potential for practical applications. PMID:26186823

  8. In vitro characterization of a magnetically suspended continuous flow ventricular assist device.

    PubMed

    Kim, H C; Bearnson, G B; Khanwilkar, P S; Olsen, D B; Maslen, E H; Allaire, P E

    1995-01-01

    A magnetically suspended continuous flow ventricular assist device using magnetic bearings was developed aiming at an implantable ventricular assist device. The main advantage of this device includes no mechanical wear and minimal chance of blood trauma such, as thrombosis and hemolysis, because there is no mechanical contact between the stationary and rotating parts. The total system consists of two subsystems: the centrifugal pump and the magnetic bearing. The centrifugal pump is comprised of a 4 vane logarithmic spiral radial flow impeller and a brushless DC motor with slotless stator, driven by the back emf commutation scheme. Two radial and one thrust magnetic bearing that dynamically controls the position of the rotor in a radial and axial direction, respectively, contains magnetic coils, the rotor's position sensors, and feedback electronic control system. The magnetic bearing system was able to successfully suspend a 365.5g rotating part in space and sustain it for up to 5000 rpm of rotation. Average force-current square factor of the magnetic bearing was measured as 0.48 and 0.44 (kg-f/Amp2) for radial and thrust bearing, respectively. The integrated system demonstrated adequate performance in mock circulation tests by providing a 6 L/min flow rate against 100 mmHg differential pressure at 2300 rpm. Based on these in vitro performance test results, long-term clinical application of the magnetically suspended continuous flow ventricular assist device is very promising after system optimization with a hybrid system using both active (electromagnet) and passive (permanent magnets) magnet bearings. PMID:8573825

  9. Continuous flow room temperature reductive aqueous homo-coupling of aryl halides using supported Pd catalysts

    PubMed Central

    Feiz, Afsaneh; Bazgir, Ayoob; Balu, Alina M.; Luque, Rafael

    2016-01-01

    A convenient and environmentally friendly protocol for the preparation of biaryls at room temperature under continuous flow conditions is reported. A simple reductive homo-coupling Ullmann-type reaction was performed in an H-Cube mini using commercially available supported Pd catalysts under mild reaction conditions, with quantitative conversion to target products. Commercial Pd catalysts were found to be highly stable under the investigated reaction conditions, with a minimum Pd leaching into solution after several reaction runs (ca. 20 h on stream). PMID:27600989

  10. Boundary-layer flow of a micropolar fluid on a continuous moving or fixed surface

    NASA Astrophysics Data System (ADS)

    Ishak, A.; Nazar, R.; Pop, I.

    2006-05-01

    The present paper deals with the analysis of boundary-layer flow of a micropolar fluid on a fixed or continuous moving plane surface. Both parallel and reverse moving surfaces to the free stream are considered. The resulting system of nonlinear ordinary differential equations is solved numerically using the Keller-box method. Numerical results are obtained for skin friction coefficient, local Nusselt number, velocity, angular velocity, and temperature profiles. The results indicate that the effect of the material parameter on skin friction and heat transfer depends on the velocity ratio of the plate and the fluid.

  11. Continuous flow room temperature reductive aqueous homo-coupling of aryl halides using supported Pd catalysts.

    PubMed

    Feiz, Afsaneh; Bazgir, Ayoob; Balu, Alina M; Luque, Rafael

    2016-01-01

    A convenient and environmentally friendly protocol for the preparation of biaryls at room temperature under continuous flow conditions is reported. A simple reductive homo-coupling Ullmann-type reaction was performed in an H-Cube mini using commercially available supported Pd catalysts under mild reaction conditions, with quantitative conversion to target products. Commercial Pd catalysts were found to be highly stable under the investigated reaction conditions, with a minimum Pd leaching into solution after several reaction runs (ca. 20 h on stream). PMID:27600989

  12. Rapid identification of Yersinia pestis and Brucella melitensis by chip-based continuous flow PCR

    NASA Astrophysics Data System (ADS)

    Dietzsch, Michael; Hlawatsch, Nadine; Melzer, Falk; Tomaso, Herbert; Gärtner, Claudia; Neubauer, Heinrich

    2012-06-01

    To combat the threat of biological agents like Yersinia pestis and Brucella melitensis in bioterroristic scenarios requires fast, easy-to-use and safe identification systems. In this study we describe a system for rapid amplification of specific genetic markers for the identification of Yersinia pestis and Brucella melitensis. Using chip based PCR and continuous flow technology we were able to amplify the targets simultaneously with a 2-step reaction profile within 20 minutes. The subsequent analysis of amplified fragments by standard gel electrophoresis requires another 45 minutes. We were able to detect both pathogens within 75 minutes being much faster than most other nucleic acid amplification technologies.

  13. Versatile, High Quality and Scalable Continuous Flow Production of Metal-Organic Frameworks

    PubMed Central

    Rubio-Martinez, Marta; Batten, Michael P.; Polyzos, Anastasios; Carey, Keri-Constanti; Mardel, James I.; Lim, Kok-Seng; Hill, Matthew R.

    2014-01-01

    Further deployment of Metal-Organic Frameworks in applied settings requires their ready preparation at scale. Expansion of typical batch processes can lead to unsuccessful or low quality synthesis for some systems. Here we report how continuous flow chemistry can be adapted as a versatile route to a range of MOFs, by emulating conditions of lab-scale batch synthesis. This delivers ready synthesis of three different MOFs, with surface areas that closely match theoretical maxima, with production rates of 60 g/h at extremely high space-time yields. PMID:24962145

  14. Hydromagnetic flow and heat transfer past a continuously moving porous boundary

    SciTech Connect

    Chandran, P.; Sacheti, N.C.; Singh, A.K.

    1996-10-01

    The effect of magnetic field on the flow and heat transfer past a continuously moving porous plate in a stationary fluid has been analyzed. The governing boundary layer equations have been reduced to a set of nonlinear ordinary differential equations using similarity transformations. The resulting boundary value problem has been solved numerically. The effects of magnetic and suction (or injection) parameters on the velocity and temperature profiles as well as on the skin friction and heat transfer coefficients have been studied. It has been observed that the effect of magnetic field is to increase the wall skin friction while the reverse occurs in the case of Nusselt number.

  15. Periodicity and chaos from switched flow systems - Contrasting examples of discretely controlled continuous systems

    NASA Technical Reports Server (NTRS)

    Chase, Christopher; Serrano, Joseph; Ramadge, Peter J.

    1993-01-01

    We analyze two examples of the discrete control of a continuous variable system. These examples exhibit what may be regarded as the two extremes of complexity of the closed-loop behavior: one is eventually periodic, the other is chaotic. Our examples are derived from sampled deterministic flow models. These are of interest in their own right but have also been used as models for certain aspects of manufacturing systems. In each case, we give a precise characterization of the closed-loop behavior.

  16. From discovery to production: Scale-out of continuous flow meso reactors

    PubMed Central

    Parracho, Ana I R

    2009-01-01

    Summary A continuous flow parallel reactor system has been developed to provide a rapid and seamless transition from the discovery phase and production phase of chemical synthesis, particularly in low volume-high value pharmaceuticals production. Using a single fixed bed catalytic meso reactor, reactions can be screened on a small discovery scale over short time scales. The intensified process produces sufficient material for a full analysis. By replication of the single reactor in parallel, the same chemistry can be achieved on a larger scale, on a small footprint and without the mass and heat transport limitations of reactor scale-out in batch. PMID:19590741

  17. Matrix metalloproteinase inhibitor, doxycycline and progression of calcific aortic valve disease in hyperlipidemic mice.

    PubMed

    Jung, Jae-Joon; Razavian, Mahmoud; Kim, Hye-Yeong; Ye, Yunpeng; Golestani, Reza; Toczek, Jakub; Zhang, Jiasheng; Sadeghi, Mehran M

    2016-01-01

    Calcific aortic valve disease (CAVD) is the most common cause of aortic stenosis. Currently, there is no non-invasive medical therapy for CAVD. Matrix metalloproteinases (MMPs) are upregulated in CAVD and play a role in its pathogenesis. Here, we evaluated the effect of doxycycline, a nonselective MMP inhibitor on CAVD progression in the mouse. Apolipoprotein (apo)E(-/-) mice (n = 20) were fed a Western diet (WD) to induce CAVD. After 3 months, half of the animals was treated with doxycycline, while the others continued WD alone. After 6 months, we evaluated the effect of doxycycline on CAVD progression by echocardiography, MMP-targeted micro single photon emission computed tomography (SPECT)/computed tomography (CT), and tissue analysis. Despite therapeutic blood levels, doxycycline had no significant effect on MMP activation, aortic valve leaflet separation or flow velocity. This lack of effect on in vivo images was confirmed on tissue analysis which showed a similar level of aortic valve gelatinase activity, and inflammation between the two groups of animals. In conclusion, doxycycline (100 mg/kg/day) had no effect on CAVD progression in apoE(-/-) mice with early disease. Studies with more potent and specific inhibitors are needed to establish any potential role of MMP inhibition in CAVD development and progression. PMID:27619752

  18. Preliminary Computational Hemodynamics Study of Double Aortic Aneurysms under Multistage Surgical Procedures: An Idealised Model Study

    PubMed Central

    Otsuki, Yosuke; Bui Minh, Nhat; Ohtake, Hiroshi; Watanabe, Go; Matsuzawa, Teruo

    2013-01-01

    Double aortic aneurysm (DAA) falls under the category of multiple aortic aneurysms. Repair is generally done through staged surgery due to low invasiveness. In this approach, one aneurysm is cured per operation. Therefore, two operations are required for DAA. However, post-first-surgery rupture cases have been reported. Although the problems involved with managing staged surgery have been discussed for more than 30 years, investigation from a hemodynamic perspective has not been attempted. Hence, this is the first computational fluid dynamics approach to the DAA problem. Three idealized geometries were prepared: presurgery, thoracic aortic aneurysm (TAA) cured, and abdominal aortic aneurysm (AAA) cured. By applying identical boundary conditions for flow rate and pressure, the Navier-Stokes equation and continuity equations were solved under the Newtonian fluid assumption. Average pressure in TAA was increased by AAA repair. On the other hand, average pressure in AAA was decreased after TAA repair. Average wall shear stress was decreased at the peak in post-first-surgery models. However, the wave profile of TAA average wall shear stress was changed in the late systole phase after AAA repair. Since the average wall shear stress in the post-first-surgery models decreased and pressure at TAA after AAA repair increased, the TAA might be treated first to prevent rupture. PMID:24348172

  19. Cerebral blood flow with the continuous infusion of oxygen-15-labeled water

    SciTech Connect

    Jones, S.C.; Greenberg, J.H.; Dann, R.; Robinson, G.D. Jr.; Kushner, M.; Alavi, A.; Reivich, M.

    1985-12-01

    This work describes the determination of CBF in eight normal human subjects with positron emission tomographic (PET) imaging using the continuous intravenous infusion of H2(15)O. A whole-brain CBF model is described that permits the comparison of the CBF values determined using PET with those obtained using other methods. This model includes a correction for whole-brain recovery coefficient, a correction for the underestimation of flow due to the nonlinearity of the CBF model when considering tissue that includes both gray and white matter, the use of in vitro-determined brain-blood partition coefficients for gray and white matter, and a variation of the equilibrium model that permits the arterial concentration to vary. CBF values using this method compare well with values determined previously. Regional determinations using a brain overlay atlas are presented. Radiation dosimetry for the continuous infusion of H2(15)O is also included.

  20. Nitrification and denitrifying phosphorus removal in an upright continuous flow reactor.

    PubMed

    Reza, Maryam; Alvarez Cuenca, Manuel

    2016-01-01

    Simultaneous nitrification and denitrifying phosphorus removal was achieved in a single-sludge continuous flow bioreactor. The upright bioreactor was aligned with a biomass fermenter (BF) and operated continuously for over 350 days. This study revealed that unknown bacteria of the Saprospiraceae class may have been responsible for the successful nutrient removal in this bioreactor. The successive anoxic-aerobic stages of the bioreactor with upright alignment along with a 60 L BF created a unique ecosystem for the growth of nitrifier, denitrifiers, phosphorus accumulating organisms and denitrifying phosphorus accumulating organisms. Furthermore, total nitrogen to chemical oxygen demand (COD) ratio and total phosphorus to COD ratio of 0.6 and 0.034, respectively, confirmed the comparative advantages of this advanced nutrient removal process relative to both sequencing batch reactors and activated sludge processes. The process yielded 95% nitrogen removal and over 90% phosphorus removal efficiencies. PMID:27148710

  1. Critical Transitions in Early Embryonic Aortic Arch Patterning and Hemodynamics

    PubMed Central

    Kowalski, William J.; Dur, Onur; Wang, Yajuan; Patrick, Michael J.; Tinney, Joseph P.; Keller, Bradley B.; Pekkan, Kerem

    2013-01-01

    Transformation from the bilaterally symmetric embryonic aortic arches to the mature great vessels is a complex morphogenetic process, requiring both vasculogenic and angiogenic mechanisms. Early aortic arch development occurs simultaneously with rapid changes in pulsatile blood flow, ventricular function, and downstream impedance in both invertebrate and vertebrate species. These dynamic biomechanical environmental landscapes provide critical epigenetic cues for vascular growth and remodeling. In our previous work, we examined hemodynamic loading and aortic arch growth in the chick embryo at Hamburger-Hamilton stages 18 and 24. We provided the first quantitative correlation between wall shear stress (WSS) and aortic arch diameter in the developing embryo, and observed that these two stages contained different aortic arch patterns with no inter-embryo variation. In the present study, we investigate these biomechanical events in the intermediate stage 21 to determine insights into this critical transition. We performed fluorescent dye microinjections to identify aortic arch patterns and measured diameters using both injection recordings and high-resolution optical coherence tomography. Flow and WSS were quantified with 3D computational fluid dynamics (CFD). Dye injections revealed that the transition in aortic arch pattern is not a uniform process and multiple configurations were documented at stage 21. CFD analysis showed that WSS is substantially elevated compared to both the previous (stage 18) and subsequent (stage 24) developmental time-points. These results demonstrate that acute increases in WSS are followed by a period of vascular remodeling to restore normative hemodynamic loading. Fluctuations in blood flow are one possible mechanism that impacts the timing of events such as aortic arch regression and generation, leading to the variable configurations at stage 21. Aortic arch variations noted during normal rapid vascular remodeling at stage 21 identify a

  2. Acute Biventricular Interaction in Pediatric Patients Implanted with Continuous Flow and Pulsatile Flow LVAD: A Simulation Study.

    PubMed

    Di Molfetta, Arianna; Ferrari, Gianfranco; Iacobelli, Roberta; Fresiello, Libera; Pilati, Mara; Toscano, Alessandra; Filippelli, Sergio; Morelli, Stefano; Amodeo, Antonio

    2016-01-01

    Left ventricular assist devices (LVADs) are used to bridge pediatric patients till transplantation. However, the LVADs effects on right ventricular (RV) function are controversial. This work aims at studying the ventricular interdependency in the presence of continuous (c-) and pulsatile (p-) flow LVAD in pediatric patients using a lumped parameter model including the representation of the septum. Five pediatric patients' data were used to simulate patients' baseline. The effects on LV and RV functions, energetics, preloads and afterloads of different c-LVAD speeds, p-LVAD rate, p-LVAD systole duration, p-LVAD filling and ejection pressures were simulated. c-LVAD and p-LVAD unload the LV decreasing the LV external work and improving the LV ventriculo-arterial coupling and these effects are more evident increasing the c-LVAD speed and the p-LVAD rate. Continuous-LVAD and p-LVAD decrease the RV afterload, increase the RV ejection fraction and improve the RV ventriculo-arterial coupling. The changes in RV function are inversely proportional to the degree of the interventricular septum leftward shift that increased by increasing the LVAD contribution. The study of the interventricular interaction could lead to the development of a dedicated algorithm to optimize LVAD setting in pediatric population. PMID:27258223

  3. Total Aortic Arch Replacement: Superior Ventriculo-Arterial Coupling with Decellularized Allografts Compared with Conventional Prostheses

    PubMed Central

    Schmack, Bastian; Korkmaz, Sevil; Li, Shiliang; Chaimow, Nicole; Pätzold, Ines; Becher, Peter Moritz; Hartyánszky, István; Soós, Pál; Merkely, Gergő; Németh, Balázs Tamás; Istók, Roland; Veres, Gábor; Merkely, Béla; Terytze, Konstantin; Karck, Matthias; Szabó, Gábor

    2014-01-01

    Background To date, no experimental or clinical study provides detailed analysis of vascular impedance changes after total aortic arch replacement. This study investigated ventriculoarterial coupling and vascular impedance after replacement of the aortic arch with conventional prostheses vs. decellularized allografts. Methods After preparing decellularized aortic arch allografts, their mechanical, histological and biochemical properties were evaluated and compared to native aortic arches and conventional prostheses in vitro. In open-chest dogs, total aortic arch replacement was performed with conventional prostheses and compared to decellularized allografts (n = 5/group). Aortic flow and pressure were recorded continuously, left ventricular pressure-volume relations were measured by using a pressure-conductance catheter. From the hemodynamic variables end-systolic elastance (Ees), arterial elastance (Ea) and ventriculoarterial coupling were calculated. Characteristic impedance (Z) was assessed by Fourier analysis. Results While Ees did not differ between the groups and over time (4.1±1.19 vs. 4.58±1.39 mmHg/mL and 3.21±0.97 vs. 3.96±1.16 mmHg/mL), Ea showed a higher increase in the prosthesis group (4.01±0.67 vs. 6.18±0.20 mmHg/mL, P<0.05) in comparison to decellularized allografts (5.03±0.35 vs. 5.99±1.09 mmHg/mL). This led to impaired ventriculoarterial coupling in the prosthesis group, while it remained unchanged in the allograft group (62.5±50.9 vs. 3.9±23.4%). Z showed a strong increasing tendency in the prosthesis group and it was markedly higher after replacement when compared to decellularized allografts (44.6±8.3dyn·sec·cm−5 vs. 32.4±2.0dyn·sec·cm−5, P<0.05). Conclusions Total aortic arch replacement leads to contractility-afterload mismatch by means of increased impedance and invert ventriculoarterial coupling ratio after implantation of conventional prostheses. Implantation of decellularized allografts preserves vascular impedance

  4. Dynamic cross-flow filtration: enhanced continuous small-scale solid-liquid separation.

    PubMed

    Gursch, Johannes; Hohl, Roland; Dujmovic, Diana; Brozio, Jörg; Krumme, Markus; Rasenack, Norbert; Khinast, Johannes

    2016-06-01

    In a previous study, a small-scale dynamic filtration device (SFD) was analyzed and the basic mechanisms governing the filtration process were characterized. The present work aims at improving the device's performance in terms of actual production. Various operation modes were tested in order to increase permeate flow and concentration factors (CF), while maintaining a fully continuous production mode. Both, a vacuum-enhanced and a pulsating operation mode, proved to be superior to the currently implemented open-operation mode. For example, for lactose, an increase of the CF could be achieved from 1.7 in open mode to 7.6 in pulsating operation mode. The investigated operation strategy enables process control systems to rapidly react to fluctuating feeds that may occur due to changes in upstream manufacturing steps. As a result, not only filtration performance in terms of permeate rate but also process flexibility can be significantly increased. Overall, vacuum-enhanced operation was shown to be most promising for integration into an industrial environment. The option to elevate achievable concentration factors, ease of flow monitoring as well as the ability to react to changes in the feed conditions allow for effective and efficient continuous small-scale filtration. PMID:26489453

  5. Process Development for Hydrothermal Liquefaction of Algae Feedstocks in a Continuous-Flow Reactor

    SciTech Connect

    Elliott, Douglas C.; Hart, Todd R.; Schmidt, Andrew J.; Neuenschwander, Gary G.; Rotness, Leslie J.; Olarte, Mariefel V.; Zacher, Alan H.; Albrecht, Karl O.; Hallen, Richard T.; Holladay, Johnathan E.

    2013-10-01

    Wet algae slurries can be converted into an upgradeable biocrude by hydrothermal liquefaction (HTL). High levels of carbon conversion to gravity-separable biocrude product were accomplished at relatively low temperature (350 °C) in a continuous-flow, pressurized (sub-critical liquid water) environment (20 MPa). As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent and biomass trace components were removed by processing steps so that they did not cause process difficulties. High conversions were obtained even with high slurry concentrations of up to 35 wt% of dry solids. Catalytic hydrotreating was effectively applied for hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization of the biocrude to form liquid hydrocarbon fuel. Catalytic hydrothermal gasification was effectively applied for HTL byproduct water cleanup and fuel gas production from water soluble organics, allowing the water to be considered for recycle of nutrients to the algae growth ponds. As a result, high conversion of algae to liquid hydrocarbon and gas products was found with low levels of organic contamination in the byproduct water. All three process steps were accomplished in bench-scale, continuous-flow reactor systems such that design data for process scale-up was generated.

  6. Partial nitrification using aerobic granules in continuous-flow reactor: rapid startup.

    PubMed

    Wan, Chunli; Sun, Supu; Lee, Duu-Jong; Liu, Xiang; Wang, Li; Yang, Xue; Pan, Xiangliang

    2013-08-01

    This study applied a novel strategy to rapid startup of partial nitrification in continuous-flow reactor using aerobic granules. Mature aerobic granules were first cultivated in a sequencing batch reactor at high chemical oxygen demand in 16 days. The strains including the Pseudoxanthomonas mexicana strain were enriched in cultivated granules to enhance their structural stability. Then the cultivated granules were incubated in a continuous-flow reactor with influent chemical oxygen deamnad being stepped decreased from 1,500 ± 100 (0-19 days) to 750 ± 50 (20-30 days), and then to 350 ± 50 mg l(-1) (31-50 days); while in the final stage 350 mg l(-1) bicarbonate was also supplied. Using this strategy the ammonia-oxidizing bacterium, Nitrosomonas europaea, was enriched in the incubated granules to achieve partial nitrification efficiency of 85-90% since 36 days and onwards. The partial nitrification granules were successfully harvested after 52 days, a period much shorter than those reported in literature. PMID:23751489

  7. Gastrointestinal bleeding in a patient with a continuous-flow biventricular assist device

    PubMed Central

    Mirasol, Raymond V; Tholany, Jason J; Reddy, Hasini; Fyfe-Kirschner, Billie S; Cheng, Christina L; Moubarak, Issam F; Nosher, John L

    2016-01-01

    The association between continuous-flow left ventricular assist devices (CF-LVADs) and gastrointestinal (GI) bleeding from angiodysplasia is well recognized. However, the association between continuous-flow biventricular assist devices (CF-BIVADs) and bleeding angiodysplasia is less understood. We report a case of GI bleeding from a patient with a CF-BIVAD. The location of GI bleeding was identified by nuclear red blood cell bleeding scan. The vascular malformation leading to the bleed was identified and localized on angiography and then by pathology. The intensity of bleeding, reflected by number of units of packed red blood cells needed for normalization of hemoglobin, as well as the time to onset of bleeding after transplantation, are similar to that seen in the literature for CF-LVADs and pulsatile BIVADs. While angiography only detected a dilated late draining vein, pathology demonstrated the presence of both arterial and venous dilation in the submucosa, vascular abnormalities characteristic of a late arteriovenous malformation. PMID:27158430

  8. Continuous-flow reactor-based synthesis of carbohydrate and dihydrolipoic acid-capped quantum dots.

    PubMed

    Laurino, Paola; Kikkeri, Raghavendra; Seeberger, Peter H

    2011-08-01

    A detailed protocol for the large-scale synthesis of carbohydrate and dihydrolipoic acid (DHLA)-coated CdSe/ZnS and CdTe/ZnS nanoparticles using continuous flow reactors is described here. Three continuous flow microreaction systems, operating at three different temperatures, are used for the synthesis of mannose-, galactose- or DHLA-functionalized quantum dots (QDs). In the first step of synthesis, the CdSe and CdTe nanoparticles are prepared. The size and spectral properties of the CdSe core of the nanoparticles are controlled by adjustment of the residence time and the temperature. As a second step, the zinc sulfide capping under homogenous conditions is carried out at a substantially lower temperature than is required for nanoparticle growth in batch processes. Finally, the trioctylphosphine/oleic acid ligand is effectively replaced with either carbohydrate PEG-thiol moieties or DHLA at 60 °C. This new protocol allows the synthesis of biologically active fluorescent QDs in 4 d. PMID:21799489

  9. A disposable, continuous-flow polymerase chain reaction device: design, fabrication and evaluation.

    PubMed

    Ragsdale, Victoria; Li, Huizhong; Sant, Himanshu; Ameel, Tim; Gale, Bruce K

    2016-08-01

    Polymerase Chain Reaction (PCR) is used to amplify a specific segment of DNA through a thermal cycling protocol. The PCR industry is shifting its focus away from macro-scale systems and towards micro-scale devices because: micro-scale sample sizes require less blood from patients, total reaction times are on the order of minutes opposed to hours, and there are cost advantages as many microfluidic devices are manufactured from inexpensive polymers. Some of the fastest PCR devices use continuous flow, but they have all been built of silicon or glass to allow sufficient heat transfer. This article presents a disposable polycarbonate (PC) device that is capable of achieving real-time, continuous flow PCR in a completely disposable polymer device in less than 13 minutes by thermally cycling the sample through an established temperature gradient in a serpentine channel. The desired temperature gradient was determined through simulations and validated by experiments which showed that PCR was achieved. Practical demonstration included amplification of foot-and-mouth disease virus (FMDV) derived cDNA. PMID:27393216

  10. Gastrointestinal bleeding in a patient with a continuous-flow biventricular assist device.

    PubMed

    Mirasol, Raymond V; Tholany, Jason J; Reddy, Hasini; Fyfe-Kirschner, Billie S; Cheng, Christina L; Moubarak, Issam F; Nosher, John L

    2016-04-28

    The association between continuous-flow left ventricular assist devices (CF-LVADs) and gastrointestinal (GI) bleeding from angiodysplasia is well recognized. However, the association between continuous-flow biventricular assist devices (CF-BIVADs) and bleeding angiodysplasia is less understood. We report a case of GI bleeding from a patient with a CF-BIVAD. The location of GI bleeding was identified by nuclear red blood cell bleeding scan. The vascular malformation leading to the bleed was identified and localized on angiography and then by pathology. The intensity of bleeding, reflected by number of units of packed red blood cells needed for normalization of hemoglobin, as well as the time to onset of bleeding after transplantation, are similar to that seen in the literature for CF-LVADs and pulsatile BIVADs. While angiography only detected a dilated late draining vein, pathology demonstrated the presence of both arterial and venous dilation in the submucosa, vascular abnormalities characteristic of a late arteriovenous malformation. PMID:27158430

  11. Sutureless aortic valve replacement

    PubMed Central

    Phan, Kevin

    2015-01-01

    The increasing incidence of aortic stenosis and greater co-morbidities and risk profiles of the contemporary patient population has driven the development of minimally invasive aortic valve surgery and percutaneous transcatheter aortic valve implantation (TAVI) techniques to reduce surgical trauma. Recent technological developments have led to an alternative minimally invasive option which avoids the placement and tying of sutures, known as “sutureless” or rapid deployment aortic valves. Potential advantages for sutureless aortic prostheses include reducing cross-clamp and cardiopulmonary bypass (CPB) duration, facilitating minimally invasive surgery and complex cardiac interventions, whilst maintaining satisfactory hemodynamic outcomes and low paravalvular leak rates. However, given its recent developments, the majority of evidence regarding sutureless aortic valve replacement (SU-AVR) is limited to observational studies and there is a paucity of adequately-powered randomized studies. Recently, the International Valvular Surgery Study Group (IVSSG) has formulated to conduct the Sutureless Projects, set to be the largest international collaborative group to investigate this technology. This keynote lecture will overview the use, the potential advantages, the caveats, and current evidence of sutureless and rapid deployment aortic valve replacement (AVR). PMID:25870807

  12. Multiphysics numerical modeling of the continuous flow microwave-assisted transesterification process.

    PubMed

    Muley, Pranjali D; Boldor, Dorin

    2012-01-01

    Use of advanced microwave technology for biodiesel production from vegetable oil is a relatively new technology. Microwave dielectric heating increases the process efficiency and reduces reaction time. Microwave heating depends on various factors such as material properties (dielectric and thermo-physical), frequency of operation and system design. Although lab scale results are promising, it is important to study these parameters and optimize the process before scaling up. Numerical modeling approach can be applied for predicting heating and temperature profiles including at larger scale. The process can be studied for optimization without actually performing the experiments, reducing the amount of experimental work required. A basic numerical model of continuous electromagnetic heating of biodiesel precursors was developed. A finite element model was built using COMSOL Multiphysics 4.2 software by coupling the electromagnetic problem with the fluid flow and heat transfer problem. Chemical reaction was not taken into account. Material dielectric properties were obtained experimentally, while the thermal properties were obtained from the literature (all the properties were temperature dependent). The model was tested for the two different power levels 4000 W and 4700 W at a constant flow rate of 840ml/min. The electric field, electromagnetic power density flow and temperature profiles were studied. Resulting temperature profiles were validated by comparing to the temperatures obtained at specific locations from the experiment. The results obtained were in good agreement with the experimental data. PMID:24432470

  13. Practical Strategies for Stable Operation of HFF-QCM in Continuous Air Flow

    PubMed Central

    Wessels, Alexander; Klöckner, Bernhard; Siering, Carsten; Waldvogel, Siegfried R.

    2013-01-01

    Currently there are a few fields of application using quartz crystal microbalances (QCM). Because of environmental conditions and insufficient resolution of the microbalance, chemical sensing of volatile organic compounds in an open system was as yet not possible. In this study we present strategies on how to use 195 MHz fundamental quartz resonators for a mobile sensor platform to detect airborne analytes. Commonly the use of devices with a resonant frequency of about 10 MHz is standard. By increasing the frequency to 195 MHz the frequency shift increases by a factor of almost 400. Unfortunately, such kinds of quartz crystals tend to exhibit some challenges to obtain a reasonable signal-to-noise ratio. It was possible to reduce the noise in frequency in a continuous air flow of 7.5 m/s to 0.4 Hz [i.e., σ(τ) = 2 × 10−9] by elucidating the major source of noise. The air flow in the vicinity of the quartz was analyzed to reduce turbulences. Furthermore, we found a dependency between the acceleration sensitivity and mechanical stress induced by an internal thermal gradient. By reducing this gradient, we achieved reduction of the sensitivity to acceleration by more than one decade. Hence, the resulting sensor is more robust to environmental conditions such as temperature, acceleration and air flow. PMID:24021970

  14. Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

    NASA Astrophysics Data System (ADS)

    Zheng, Lin; Zheng, Song; Zhai, Qinglan

    2016-02-01

    In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn-Hilliard equation which is solved in the frame work of LBE. The scalar convection-diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results.

  15. Submillisecond mixing in a continuous-flow, microfluidic mixer utilizing mid-infrared hyperspectral imaging detection

    PubMed Central

    Kise, Drew P.; Magana, Donny; Reddish, Michael J.

    2014-01-01

    We report a continuous-flow, microfluidic mixer utilizing mid-infrared hyperspectral imaging detection, with an experimentally determined, submillisecond mixing time. The simple and robust mixer design has the microfluidic channels cut through a polymer spacer that is sandwiched between two IR transparent windows. The mixer hydrodynamically focuses the sample stream with two side flow channels, squeezing it into a thin jet and initiating mixing through diffusion and advection. The detection system generates a mid-infrared hyperspectral absorbance image of the microfluidic sample stream. Calibration of the hyperspectral image yields the mid-IR absorbance spectrum of the sample versus time. A mixing time of 269 μs was measured for a pD jump from 3.2 to above 4.5 in a D2O sample solution of adenosine monophosphate (AMP), which acts as an infrared pD indicator. The mixer was further characterized by comparing experimental results with a simulation of the mixing of an H2O sample stream with a D2O sheath flow, showing good agreement between the two. The IR microfluidic mixer eliminates the need for fluorescence labeling of proteins with bulky, interfering dyes, because it uses the intrinsic IR absorbance of the molecules of interest, and the structural specificity of IR spectroscopy to follow specific chemical changes such as the protonation state of AMP. PMID:24302515

  16. Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel

    PubMed Central

    Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

    2014-01-01

    Refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, RI contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving parts approach that provides three-dimensional refractive index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate RI maps of the samples from the measured spectra. Using this method, we demonstrate label-free 3-D imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass and density of these cells from the measured 3-D refractive index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, promises as a quantitative tool for stain-free characterization of large number of cells. PMID:25419536

  17. Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel

    NASA Astrophysics Data System (ADS)

    Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

    2014-02-01

    The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

  18. Abdominal aortic aneurysm.

    PubMed

    Keisler, Brian; Carter, Chuck

    2015-04-15

    Abdominal aortic aneurysm refers to abdominal aortic dilation of 3.0 cm or greater. The main risk factors are age older than 65 years, male sex, and smoking history. Other risk factors include a family history of abdominal aortic aneurysm, coronary artery disease, hypertension, peripheral artery disease, and previous myocardial infarction. Diagnosis may be made by physical examination, an incidental finding on imaging, or ultrasonography. The U.S. Preventive Services Task Force released updated recommendations for abdominal aortic aneurysm screening in 2014. Men 65 to 75 years of age with a history of smoking should undergo one-time screening with ultrasonography based on evidence that screening will improve abdominal aortic aneurysm-related mortality in this population. Men in this age group without a history of smoking may benefit if they have other risk factors (e.g., family history of abdominal aortic aneurysm, other vascular aneurysms, coronary artery disease). There is inconclusive evidence to recommend screening for abdominal aortic aneurysm in women 65 to 75 years of age with a smoking history. Women without a smoking history should not undergo screening because the harms likely outweigh the benefits. Persons who have a stable abdominal aortic aneurysm should undergo regular surveillance or operative intervention depending on aneurysm size. Surgical intervention by open or endovascular repair is the primary option and is typically reserved for aneurysms 5.5 cm in diameter or greater. There are limited options for medical treatment beyond risk factor modification. Ruptured abdominal aortic aneurysm is a medical emergency presenting with hypotension, shooting abdominal or back pain, and a pulsatile abdominal mass. It is associated with high prehospitalization mortality. Emergent surgical intervention is indicated for a rupture but has a high operative mortality rate. PMID:25884861

  19. Haemodynamics in the mouse aortic arch computed from MRI-derived velocities at the aortic root.

    PubMed

    Van Doormaal, Mark A; Kazakidi, Asimina; Wylezinska, Marzena; Hunt, Anthony; Tremoleda, Jordi L; Protti, Andrea; Bohraus, Yvette; Gsell, Willy; Weinberg, Peter D; Ethier, C Ross

    2012-11-01

    Mice are widely used to investigate atherogenesis, which is known to be influenced by stresses related to blood flow. However, numerical characterization of the haemodynamic environment in the commonly studied aortic arch has hitherto been based on idealizations of inflow into the aorta. Our purpose in this work was to numerically characterize the haemodynamic environment in the mouse aortic arch using measured inflow velocities, and to relate the resulting shear stress patterns to known locations of high- and low-lesion prevalence. Blood flow velocities were measured in the aortic root of C57/BL6 mice using phase-contrast MRI. Arterial geometries were obtained by micro-CT of corrosion casts. These data were used to compute blood flow and wall shear stress (WSS) patterns in the arch. WSS profiles computed using realistic and idealized aortic root velocities differed significantly. An unexpected finding was that average WSS in the high-lesion-probability region on the inner wall was actually higher than the WSS in the low-probability region on the outer wall. Future studies of mouse aortic arch haemodynamics should avoid the use of idealized inflow velocity profiles. Lesion formation does not seem to uniquely associate with low or oscillating WSS in this segment, suggesting that other factors may also play a role in lesion localization. PMID:22764131

  20. Bubble-free on-chip continuous-flow polymerase chain reaction: concept and application.

    PubMed

    Wu, Wenming; Kang, Kyung-Tae; Lee, Nae Yoon

    2011-06-01

    Bubble formation inside a microscale channel is a significant problem in general microfluidic experiments. The problem becomes especially crucial when performing a polymerase chain reaction (PCR) on a chip which is subject to repetitive temperature changes. In this paper, we propose a bubble-free sample injection scheme applicable for continuous-flow PCR inside a glass/PDMS hybrid microfluidic chip, and attempt to provide a theoretical basis concerning bubble formation and elimination. Highly viscous paraffin oil plugs are employed in both the anterior and posterior ends of a sample plug, completely encapsulating the sample and eliminating possible nucleation sites for bubbles. In this way, internal channel pressure is increased, and vaporization of the sample is prevented, suppressing bubble formation. Use of an oil plug in the posterior end of the sample plug aids in maintaining a stable flow of a sample at a constant rate inside a heated microchannel throughout the entire reaction, as compared to using an air plug. By adopting the proposed sample injection scheme, we demonstrate various practical applications. On-chip continuous-flow PCR is performed employing genomic DNA extracted from a clinical single hair root sample, and its D1S80 locus is successfully amplified. Also, chip reusability is assessed using a plasmid vector. A single chip is used up to 10 times repeatedly without being destroyed, maintaining almost equal intensities of the resulting amplicons after each run, ensuring the reliability and reproducibility of the proposed sample injection scheme. In addition, the use of a commercially-available and highly cost-effective hot plate as a potential candidate for the heating source is investigated. PMID:21461443

  1. Modeling on Fluid Flow and Inclusion Motion in Centrifugal Continuous Casting Strands

    NASA Astrophysics Data System (ADS)

    Wang, Qiangqiang; Zhang, Lifeng; Sridhar, Seetharaman

    2016-05-01

    During the centrifugal continuous casting process, unreasonable casting parameters can cause violent level fluctuation, serious gas entrainment, and formation of frozen shell pieces at the meniscus. Thus, in the current study, a three-dimensional multiphase turbulent model was established to study the transport phenomena during centrifugal continuous casting process. The effects of nozzle position, casting and rotational speed on the flow pattern, centrifugal force acting on the molten steel, level fluctuation, gas entrainment, shear stress on mold wall, and motion of inclusions during centrifugal continuous casting process were investigated. Volume of Fluid model was used to simulate the molten steel-air two-phase. The level fluctuation and the gas entrainment during casting were calculated by user-developed subroutines. The trajectory of inclusions in the rotating system was calculated using the Lagrangian approach. The results show that during centrifugal continuous casting, a large amount of gas was entrained into the molten steel, and broken into bubbles of various sizes. The greater the distance to the mold wall, the smaller the centrifugal force. Rotation speed had the most important influence on the centrifugal force distribution at the side region. Angular moving angle of the nozzle with 8° and keeping the rotation speed with 60 revolutions per minute can somehow stabilize the level fluctuation. The increase of angular angle of nozzle from 8 to 18 deg and rotation speed from 40 to 80 revolutions per minute favored to decrease the total volume of entrained bubbles, while the increase of distance of nozzle moving left and casting speed had reverse effects. The trajectories of inclusions in the mold were irregular, and then rotated along the strand length. After penetrating a certain distance, the inclusions gradually moved to the center of billet and gathered there. More work, such as the heat transfer, the solidification, and the inclusions entrapment

  2. Modeling on Fluid Flow and Inclusion Motion in Centrifugal Continuous Casting Strands

    NASA Astrophysics Data System (ADS)

    Wang, Qiangqiang; Zhang, Lifeng; Sridhar, Seetharaman

    2016-08-01

    During the centrifugal continuous casting process, unreasonable casting parameters can cause violent level fluctuation, serious gas entrainment, and formation of frozen shell pieces at the meniscus. Thus, in the current study, a three-dimensional multiphase turbulent model was established to study the transport phenomena during centrifugal continuous casting process. The effects of nozzle position, casting and rotational speed on the flow pattern, centrifugal force acting on the molten steel, level fluctuation, gas entrainment, shear stress on mold wall, and motion of inclusions during centrifugal continuous casting process were investigated. Volume of Fluid model was used to simulate the molten steel-air two-phase. The level fluctuation and the gas entrainment during casting were calculated by user-developed subroutines. The trajectory of inclusions in the rotating system was calculated using the Lagrangian approach. The results show that during centrifugal continuous casting, a large amount of gas was entrained into the molten steel, and broken into bubbles of various sizes. The greater the distance to the mold wall, the smaller the centrifugal force. Rotation speed had the most important influence on the centrifugal force distribution at the side region. Angular moving angle of the nozzle with 8° and keeping the rotation speed with 60 revolutions per minute can somehow stabilize the level fluctuation. The increase of angular angle of nozzle from 8 to 18 deg and rotation speed from 40 to 80 revolutions per minute favored to decrease the total volume of entrained bubbles, while the increase of distance of nozzle moving left and casting speed had reverse effects. The trajectories of inclusions in the mold were irregular, and then rotated along the strand length. After penetrating a certain distance, the inclusions gradually moved to the center of billet and gathered there. More work, such as the heat transfer, the solidification, and the inclusions entrapment

  3. Acute Aortic Dissection Extending Into the Lung.

    PubMed

    Makdisi, George; Said, Sameh M; Schaff, Hartzell V

    2015-07-01

    The radiologic manifestations of ruptured acute aortic dissection, Stanford type A aortic dissection, DeBakey type 1 can present in different radiographic scenarios with devastating outcomes. Here, we present a rare case of a 70-year-old man who presented to the emergency department with chest pain radiating to the back. A chest computed tomography scan showed a Stanford type A, DeBakey type 1, acute aortic dissection ruptured into the aortopulmonary window and stenosing the pulmonary trunk, both main pulmonary arteries, and dissecting the bronchovascular sheaths and flow into the pulmonary interstitium, causing pulmonary interstitial hemorrhage. The patient underwent emergent ascending aorta replacement with hemiarch replacement with circulatory arrest. The postoperative course was unremarkable. PMID:26140779

  4. Feasibility of utilizing bio-indicators for testing microbial inactivation in sweetpotato purees processed with a continuous flow microwave system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous flow microwave heating has potential in aseptic processing of various food products, including the purees from sweetpotatoes and other vegetables. Establishing the feasibility of a new processing technology for achieving commercial sterility requires evaluating microbial inactivation. Thi...

  5. Method 349.0 Determination of Ammonia in Estuarine and Coastal Waters by Gas Segmented Continuous Flow Colorimetric Analysis

    EPA Science Inventory

    This method provides a procedure for the determination of ammonia in estuarine and coastal waters. The method is based upon the indophenol reaction,1-5 here adapted to automated gas-segmented continuous flow analysis.

  6. Apicoaortic conduit and cerebral perfusion in mixed aortic valve disease: a computational analysis

    PubMed Central

    Fragomeni, Gionata; Rossi, Michele; Condemi, Francesca; Mazzitelli, Rosario; Serraino, Giuseppe Filiberto; Renzulli, Attilio

    2013-01-01

    OBJECTIVES The revival of the apicoaortic conduit has attracted new interest in this alternative treatment for severe aortic stenosis unsuitable for conventional valve replacement. However, doubts still exist about the perfusion of the epiaortic vessels after apicoaortic conduit implantation, especially when severe aortic stenosis is associated with aortic valve insufficiency. The aim of the study was to evaluate the perfusion of the epiaortic vessels (innominate artery, left carodit artery and left subclavian artery) in cases of mixed aortic valve disease before and after apicoaortic conduit implantation. METHODS Starting from the data of a real patient with severe aortic stenosis and mild aortic insufficiency who underwent apicoaortic conduit implantation, we created a computational model where severe aortic valve stenosis was associated with different grades of aortic insufficiency (mild, medium and moderate). RESULTS A total of six combinations were analysed. In all simulations, the more severe the concomitant aortic insufficiency, the more the flow through the epiaortic vessels was diminished. After apicoaortic conduit implantation, there was an absolute augmentation of the median output in each epiaortic vessel compared with the same combination of mixed aortic valve disease before implantation. Interestingly, retrograde flow from the conduit in the descending aorta was minimal and did not contribute to the improved output of the epiaortic vessels. CONCLUSIONS The computational analysis suggested a protective effect, rather than steal phenomenon, of the apicoaortic conduit towards the cerebral perfusion, even in cases of mixed aortic valve disease. PMID:23962852

  7. Advances in Transcatheter Aortic Valve Replacement

    PubMed Central

    Kleiman, Neal S.; Reardon, Michael J.

    2016-01-01

    Transcatheter aortic valve replacement (TAVR) is becoming widely used for the treatment of symptomatic severe aortic stenosis in patients with high surgical risk. Data from The PARTNER Trial (Placement of AoRtic TraNscathetER Valves) and the Medtronic CoreValve® U.S. Pivotal Investigational Device Exemption trial indicate that survival for extreme-risk patients is superior to best medical therapy and equivalent or superior to surgical aortic valve replacement (SAVR), although long-term durability remains unknown. Paravalvular leak remains higher in TAVR than SAVR, as does permanent pacemaker implantation in self-expanding valves. New-generation valves are addressing these issues, especially for paravalvular leak. There is strong evidence that TAVR is appropriate for both extreme-risk and high-risk patients with symptomatic severe aortic stenosis, and the continued development of new valves are making implantation more reliable. This review discusses the studies supporting the use of TAVR and explores current advances in the field. PMID:27127560

  8. [Abdominal aortic aneurysm and renovascular disease].

    PubMed

    Riambau, Vicente; Guerrero, Francisco; Montañá, Xavier; Gilabert, Rosa

    2007-06-01

    Recent technological advances in the diagnosis and therapy of abdominal aortic aneurysm and renovascular disease are continuing to bring about changes in the way patients suffering from these conditions are treated. The prevalence of both these conditions is increasing. This is due to greater life-expectancy in patients with arteriosclerosis, a pathogenetic factor underlying both conditions. The application of diagnostic imaging techniques to non-vascular conditions has led to the early diagnosis of abdominal aortic aneurysm. Clinical suspicion of reno-vascular disease can be confirmed easily using high-resolution diagnostic imaging modalities such as CT angiography and magnetic resonance angiography. Endovascular intervention is successfully replacing conventional surgical repair techniques, with the result that it may be possible to improve outcome in both conditions using effective and minimally invasive approaches. Future technological developments will enable these endovascular techniques to be applied in the large majority of patients with abdominal aortic aneurysm or renovascular disease. PMID:17580053

  9. Aortic valve surgery - open

    MedlinePlus

    ... choose to have your aortic valve surgery at a center that does many of these procedures. ... DA, Harken AH. Acquired heart disease: valvular. In: Townsend CM, ... Textbook of Cardiovascular Medicine . 10th ed. Philadelphia, PA: ...

  10. Double aortic arch

    MedlinePlus

    ... double aortic arch may press on the windpipe (trachea) and esophagus, leading to trouble breathing and swallowing. ... to relieve pressure on the esophagus and windpipe (trachea). The surgeon ties off the smaller branch and ...

  11. [Acute aortic syndrome].

    PubMed

    Nienaber, Christoph A

    2016-06-01

    Acute aortic syndrome is the common denominator for acute events to the aortic wall and encompasses dissection of the aorta, intramural hematoma, formation of aortic ulcers and trauma to the aorta with an annual incidence of up to 35 cases/100.000 between 65 and 75 years of age. Both, inflammation and/or microtrauma at the level of the aortic media layer, and a genetic disposition are promoting elements of AAS, while the extent and anatomic involvement of the ascending aorta call for either surgical resection/repair in the proximal part of the aorta, or an endovascular solution for pathologies in the distal aorta; in all cases of dissection (regardless of location) reconstruction/realignment has been proven to portend better long-term outcomes (in addition to medical management of blood pressure). PMID:27254622

  12. Abdominal aortic aneurysm

    MedlinePlus

    ... main blood vessel that supplies blood to the abdomen, pelvis, and legs. An abdominal aortic aneurysm occurs ... dissection). Symptoms of rupture include: Pain in the abdomen or back. The pain may be severe, sudden, ...

  13. Continuous flow electrophoresis: The effect of sample concentration on throughput and resolution in an upward flowing system

    NASA Technical Reports Server (NTRS)

    Jandebeur, T. S.

    1980-01-01

    The effect of sample concentration on throughput and resolution in a modified continuous particle electrophoresis (CPE) system with flow in an upward direction is investigated. Maximum resolution is achieved at concentrations ranging from 2 x 10 to the 8th power cells/ml to 8 x 10 to the 8th power cells/ml. The widest peak separation is at 2 x 10 to the 8th power cells/ml; however, the sharpest peaks and least overlap between cell populations is at 8 x 10 to the 8th power cells/ml. Apparently as a result of improved electrophoresis cell performance due to coasting the chamber with bovine serum albumin, changing the electrode membranes and rinse, and lowering buffer temperatures, sedimentation effects attending to higher concentrations are diminished. Throughput as measured by recovery of fixed cells is diminished at the concentrations judged most likely to yield satisfactory resolution. The tradeoff appears to be improved recovery/throughput at the expense of resolution.

  14. Clarification of Reconstituted Frozen Orange Juice Concentrate by Continuous Flow Centrifugation for Limonin Glucoside Solid Phase Extraction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The clarification of reconstituted frozen orange juice concentrate by continuous-flow centrifugation in preparation to being applied to a solid phase extraction column for the isolation of limonin glucoside has been evaluated. Clarification experiments spanning over three different flow rates (325,...

  15. Abdominal aortic aneurysm.

    PubMed

    Setacci, Francesco; Galzerano, Giuseppe; De Donato, Gianmarco; Benevento, Domenico; Guerrieri, Massimiliano W; Ruzzi, Umberto; Borrelli, Maria P; Setacci, Carlo

    2016-02-01

    Endovascular repair of abdominal aortic aneurysms has become a milestone in the treatment of patients with abdominal aortic aneurysm. Technological improvement allows treatment in more and more complex cases. This review summarizes all grafts available on the market. A complete review of most important trial on this topic is provided to the best of our knowledge, and technical tips and tricks for standard cases are also included. PMID:26771730

  16. An efficient continuous flow approach to furnish furan-based biaryls.

    PubMed

    Trinh, Trieu N; Hizartzidis, Lacey; Lin, Andrew J S; Harman, David G; McCluskey, Adam; Gordon, Christopher P

    2014-12-21

    Suzuki cross-couplings of 5-formyl-2-furanylboronic acid with activated or neutral aryl bromides were performed under continuous flow conditions in the presence of (Bu)4N(+)F(-) and the immobilised t-butyl based palladium catalyst CatCart™ FC1032™. Deactivated aryl bromides and activated aryl chlorides were cross-coupled with 5-formyl-2-furanylboronic in the presence of (Bu)4N(+)OAc(-) using the bis-triphenylphosphine CatCart™ PdCl2(PPh3)2-DVB. Initial evidence indicates the latter method may serve as a universal approach to conduct Suzuki cross-couplings with the protocol successfully employed in the synthesis of the current gold standard Hedgehog pathway inhibitor LDE225. PMID:25333944

  17. Development of Safe and Scalable Continuous-Flow Methods for Palladium-Catalyzed Aerobic Oxidation Reactions.

    PubMed

    Ye, Xuan; Johnson, Martin D; Diao, Tianning; Yates, Matthew H; Stahl, Shannon S

    2010-01-01

    The synthetic scope and utility of Pd-catalyzed aerobic oxidation reactions has advanced significantly over the past decade, and these reactions have potential to address important green-chemistry challenges in the pharmaceutical industry. This potential has been unrealized, however, because safety concerns and process constraints hinder large-scale applications of this chemistry. These limitations are addressed by the development of a continuous-flow tube reactor, which has been demonstrated on several scales in the aerobic oxidation of alcohols. Use of a dilute oxygen gas source (8% O(2) in N(2)) ensures that the oxygen/organic mixture never enters the explosive regime, and efficient gas-liquid mixing in the reactor minimizes decomposition of the homogeneous catalyst into inactive Pd metal. These results provide the basis for large-scale implementation of palladium-catalyzed (and other) aerobic oxidation reactions for pharmaceutical synthesis. PMID:20694169

  18. Harnessing the Versatility of Continuous-Flow Processes: Selective and Efficient Reactions.

    PubMed

    Mándity, István M; Ötvös, Sándor B; Szőlősi, György; Fülöp, Ferenc

    2016-06-01

    There is a great need for effective transformations and a broad range of novel chemical entities. Continuous-flow (CF) approaches are of considerable current interest: highly efficient and selective reactions can be performed in CF reactors. The reaction setup of CF reactors offers a wide variety of possible points where versatility can be introduced. This article presents a number of selective and highly efficient gas-liquid-solid and liquid-solid reactions involving a range of reagents and immobilized catalysts. Enantioselective transformations through catalytic hydrogenation and organocatalytic reactions are included, and isotopically labelled compounds and pharmaceutically relevant 1,2,3-triazoles are synthesized in CF reactors. Importantly, the catalyst bed can be changed to a solid-phase peptide synthesis resin, with which peptide synthesis can be performed with the utilization of only 1.5 equivalents of the amino acid. PMID:26997251

  19. Parallel Continuous Flow: A Parallel Suffix Tree Construction Tool for Whole Genomes

    PubMed Central

    Farreras, Montse

    2014-01-01

    Abstract The construction of suffix trees for very long sequences is essential for many applications, and it plays a central role in the bioinformatic domain. With the advent of modern sequencing technologies, biological sequence databases have grown dramatically. Also the methodologies required to analyze these data have become more complex everyday, requiring fast queries to multiple genomes. In this article, we present parallel continuous flow (PCF), a parallel suffix tree construction method that is suitable for very long genomes. We tested our method for the suffix tree construction of the entire human genome, about 3GB. We showed that PCF can scale gracefully as the size of the input genome grows. Our method can work with an efficiency of 90% with 36 processors and 55% with 172 processors. We can index the human genome in 7 minutes using 172 processes. PMID:24597675

  20. A patterned anisotropic nanofluidic sieving structure for continuous-flow separation of DNA and proteins

    PubMed Central

    Fu, Jianping; Schoch, Reto B.; Stevens, Anna L.; Tannenbaum, Steven R.; Han, Jongyoon

    2008-01-01

    Microfabricated regular sieving structures hold great promise as an alternative to gels to improve biomolecule separation speed and resolution. In contrast to disordered gel porous networks, these regular structures also provide well-defined environments ideal for study of molecular dynamics in confining spaces. However, previous regular sieving structures have been limited for separation of long DNA molecules, and separation of smaller, physiologically-relevant macromolecules, such as proteins, still remains as a challenge. Here we report a microfabricated anisotropic sieving structure consisting of a two-dimensional periodic nanofluidic filter array (Anisotropic Nanofilter Array: ANA). The designed structural anisotropy in the ANA causes different-sized or -charged biomolecules to follow distinct trajectories, leading to efficient separation. Continuous-flow size-based separation of DNA and proteins as well as electrostatic separation of proteins were achieved, thus demonstrating the potential of the ANA as a generic molecular sieving structure for an integrated biomolecule sample preparation and analysis system. PMID:18654231

  1. Continuous Flow Metathesis for Direct Valorization of Food Waste: An Example of Cocoa Butter Triglyceride

    PubMed Central

    2015-01-01

    The direct chemical conversion of cocoa butter triglycerides, a material available as a postmanufacture waste stream from the food industry, to 1-decene by way of ethenolysis is reported. The conversion of the raw waste material was made possible by use of 1 mol % of the [RuCl2(iBu-phoban)2(3-phenylindenyl)] catalyst. The process has been investigated in both batch and flow conditions, where the latter approach employs a Teflon AF-2400 tube-in-tube gas–liquid membrane contactor to deliver ethylene to the reaction system. These preliminary studies culminate in a continuous processing system, which maintained a constant output over a 150 min period tested. PMID:26322250

  2. Semi-automated continuous-flow enzyme immunoassay for antiepileptic drugs in serum.

    PubMed

    Hayashi, S; Kurooka, S; Arisue, K; Kohda, K; Hayashi, C

    1983-10-01

    We have developed a semi-automated method for measuring five kinds of antiepileptic drugs in serum by successfully adapting commercial competitive-binding enzyme immunoassay kits (MARKIT; Dainippon) for use with a continuous-flow analyzer (Technicon AutoAnalyzer II equipped with a dialyzer). The free enzyme-labeled drug is automatically separated by a microfilter from the competitive immunoreaction mixture between labeled and unlabeled drug for anti-drug immunoglobulin coupled to bacterial cell walls. The concentrations of the antiepileptic drugs in serum samples can be determined by automated measurement of enzyme activity of the enzyme-labeled drugs. Results of the semi-automated method correlated well with those obtained by manual enzyme immunoassay, gas-liquid chromatography, and "high-pressure" liquid chromatography. The correlation coefficients were all greater than 0.95, showing the practicality of this method for therapeutic monitoring of antiepileptic drugs. PMID:6352086

  3. [Unsegmented continuous-flow sample processing and electrochemical detection of gaseous species

    SciTech Connect

    Mottola, H.A.

    1991-01-01

    Goals were a continuous-flow, unsegmented, all-gas carrier and/or a segmented liquid/gas interface system for sample introduction and transport to detection/determination point; a regenerable electrode probe base on redox reactions of Fe(II) and Fe(III) complexes with 1, 10-phenanthroline and related ligands; and amperometric/coulometric current measurements providing analyte signals. Gases to be detected included NO[sub x] and SO[sub 2]. This report is divided into 3 parts: preparation of new ligands of 1,10-phenanthroline family; glassy carbon surfaces coated with polymeric films prepared from monomeric units of tris[5-amino-1,10-phenanthroline]iron(II); and sulfite oxidase/hexacyanoferrate modified C paste electrode.

  4. Time Resolved Particle Image Velocimetry Techniques with Continuous Wave Laser and their Application to Transient Flows

    NASA Astrophysics Data System (ADS)

    Esposito, Chiara

    The demand to increase the temporal resolution of Stereo-Particle Image Velocimetry systems used in the measurement of highly unsteady flow fields is limited by the low repetition rate of the pulse lasers and cameras. The availability of high-frame-rate digital cameras and CW lasers opens new possibilities in the development of continuous PIV systems with increased temporal resolution. Time-Resolved Particle Image Velocimetry (TR-PIV) with continuous wave (CW) laser sheet technique and a high frame-rate camera is introduced here to be used in gas flows at low to moderate Reynolds numbers. This experimental technique can measure velocity of the flow in a planar field with good spatial and temporal resolution. Additional modifications led to the development of a Split view TR-PIV system capable of resolving three-component velocity fields. The optical setup consists of a single high-frame-rate camera which can accommodate two simultaneous stereo view images of the deforming fluid on its CMOS chip obtained by using four different planar mirrors, appropriately positioned. This approach offers several advantages over traditional systems with two different cameras. First, it provides identical system parameters for the two views which minimize their differences and thus facilitating robust stereo matching. Second, it reduces calibration time since only one camera is used and third its cost is substantially lower than the cost of a system with two cameras. The TR-PIV with the CW laser technique has been evaluated in canonical turbulent boundary layer flows and the results were compared to data from the vast literature. Particular attention has been given to the performance of the system components, such as the high speed cameras, and the CW lasers. The techniques were also investigated in terms of the duration of exposure of PIV images. The effect of the duration of exposure was proven to be particularly important, and it has a negative effect for the case with higher

  5. Continuous flow peptide synthesis on aminopolyoxyethylene-polystyrene graft copolymer using Fmoc-strategy.

    PubMed

    Hellstern, H; Hemmasi, B

    1988-04-01

    An insoluble graft copolymer consisting of the covalently bound polyoxyethylene to cross-linked polystyrene (HO-POE-PS) was prepared by anionic polymerization of ethylene oxide on the resin. The copolymer was then converted to the corresponding amino-polymer (H2N-POE-PS) and the latter was employed as the solid carrier for peptide synthesis. Although HO-POE-PS has successfully been employed as a carrier for peptide synthesis by the standard shaking procedure using t-butoxycarbonyl-amino acids, now we deemed it of interest to test its suitability for the continuous flow synthesis. Thus, the C-terminal octapeptide of the porcine insulin B chain (B23-30) was prepared by this procedure using a photolabile anchoring group and fluoren-9-ylmethoxycarbonyl-amino acids. All the reactions were carried out in a continuous flow manner in a steel column under pressure using a high-performance liquid chromatography (HPLC) system. At the end of the synthesis, a sample of the protected peptide was cleaved from the support by photolysis. For the cleavage of another sample, an aqueous solution of sodium carbonate was employed. The protected peptide was purified on silica gel and Sephadex-LH 20. All the protecting groups of a sample of the octapeptide were removed with piperidine/dimethylformamide and trifluoroacetic acid and the deblocked peptide was purified by ion-exchange chromatography. The free peptide was shown to be homogeneous by thin-layer chromatography, HPLC, and electrophoresis. The identify of the free octapeptide was confirmed by amino-acid analysis, 13C-nuclear magnetic resonance measurement and field-desorption mass spectrometry. The peptide was also shown to be free of racemization. PMID:3041990

  6. Readmissions After Continuous Flow Left Ventricular Assist Device Implantation: Differences Observed Between Two Contemporary Device Types.

    PubMed

    Haglund, Nicholas A; Davis, Mary E; Tricarico, Nicole M; Keebler, Mary E; Maltais, Simon

    2015-01-01

    Readmissions after continuous flow left ventricular assist devices implantation are common. We compared the frequency and etiology of readmissions between two continuous flow left ventricular assist devices 6 months after implant. We retrospectively assessed readmissions in 81 patients who received a bridge to transplant HeartMate-II (HM-II) n = 35, 43% or HeartWare (HW) n = 46, 57%, from 2009 to 2014. Readmissions were divided into cardiac, infection, gastrointestinal bleeding, stroke, pump thrombosis, and miscellaneous profiles. Age, gender, creatinine, INTERMACS profiles were comparable between groups (p > 0.05). Sixty-one patients accounted for 141 readmissions. At 6 months, the overall readmission rate was higher among HM-II versus HW recipients (2.3 ± 1.7 vs. 1.4 ± 1.3; p = 0.024). Multiple readmissions (≥2) occurred more frequently in HM-II recipients (HM-II 23, 66% vs. HW 20, 44%; p = 0.047) which accounted for 87% of overall readmission frequency. Cardiac profile was the most common reason for readmission (HM-II = 15, HW = 17; p = 0.95). Readmission for arrhythmia (HM-II = 10, HW = 3; p = 0.021) and overall infection rate (0.49 ± 0.70 vs. 0.17 ± 0.68; p = 0.001) were more common among HM-II recipients; however, other readmission profiles were comparable between devices (p > 0.05). Readmission frequency, multiple readmissions, and clinical profile characteristics were different between HM-II and HW recipients. PMID:25806614

  7. Startup and oxygen concentration effects in a continuous granular mixed flow autotrophic nitrogen removal reactor.

    PubMed

    Varas, Rodrigo; Guzmán-Fierro, Víctor; Giustinianovich, Elisa; Behar, Jack; Fernández, Katherina; Roeckel, Marlene

    2015-08-01

    The startup and performance of the completely autotrophic nitrogen removal over nitrite (CANON) process was tested in a continuously fed granular bubble column reactor (BCR) with two different aeration strategies: controlling the oxygen volumetric flow and oxygen concentration. During the startup with the control of oxygen volumetric flow, the air volume was adjusted to 60mL/h and the CANON reactor had volumetric N loadings ranging from 7.35 to 100.90mgN/Ld with 36-71% total nitrogen removal and high instability. In the second stage, the reactor was operated at oxygen concentrations of 0.6, 0.4 and 0.2mg/L. The best condition was 0.2 mgO2/L with a total nitrogen removal of 75.36% with a CANON reactor activity of 0.1149gN/gVVSd and high stability. The feasibility and effectiveness of CANON processes with oxygen control was demonstrated, showing an alternative design tool for efficiently removing nitrogen species. PMID:25965951

  8. Site-specific protein modification using immobilized sortase in batch and continuous-flow systems

    PubMed Central

    Witte, Martin D.; Wu, Tongfei; Guimaraes, Carla P.; Theile, Christopher S.; Blom, Annet E.M.; Ingram, Jessica R.; Li, Zeyang; Kundrat, Lenka; Goldberg, Shalom D.; Ploegh, Hidde L.

    2016-01-01

    Transpeptidation catalyzed by sortase A allows the preparation of proteins that are site-specifically and homogeneously modified with a wide variety of functional groups, such as fluorophores, PEG moieties, lipids, glycans, bioorthogonal reactive groups and affinity handles. This protocol describes immobilization of sortase A on a solid support (sepharose beads). Immobilization of sortase A simplifies downstream purification of a protein of interest after labeling of its N- or C- terminus. Small batch and larger scale continuous flow reactions require only a limited amount of enzyme. The immobilized enzyme can be reused for multiple cycles of protein modification reactions. The described protocol also works with a Ca2+-independent variant of sortase A with increased catalytic activity. This heptamutant variant of sortase A (7M) was generated by combining previously published mutations and this immobilized enzyme can used for the modification of calcium-senstive substrates or in instances where low temperatures are needed. Preparation of immobilized sortase A takes 1–2 days. Batch reactions take 3–12 hours and flow reactions proceed at 0.5 mL per hour, depending on the geometry of the reactor used. PMID:25719269

  9. Low-cost, real-time, continuous flow PCR system for pathogen detection.

    PubMed

    Fernández-Carballo, B Leticia; McGuiness, Ian; McBeth, Christine; Kalashnikov, Maxim; Borrós, Salvador; Sharon, Andre; Sauer-Budge, Alexis F

    2016-04-01

    In this paper, we present a portable and low cost point-of-care (POC) PCR system for quantitative detection of pathogens. Our system is based on continuous flow PCR which maintains fixed temperatures zones and pushes the PCR solution between two heated areas allowing for faster heat transfer and as a result, a faster PCR. The PCR system is built around a 46.0 mm × 30.9 mm × 0.4 mm disposable thermoplastic chip. In order to make the single-use chip economically viable, it was manufactured by hot embossing and was designed to be compatible with roll-to-roll embossing for large scale production. The prototype instrumentation surrounding the chip includes two heaters, thermal sensors, and an optical system. The optical system allows for pathogen detection via real time fluorescence measurements. FAM probes were used as fluorescent reporters of the amplicons generated during the PCR. To demonstrate the function of the chip, two infectious bacteria targets were selected: Chlamydia trachomatis and Escherichia coli O157:H7. For both bacteria, the limit of detection of the system was determined, PCR efficiencies were calculated, and different flow velocities were tested. We have demonstrated successful detection for these two bacterial pathogens highlighting the versatility and broad utility of our portable, low-cost, and rapid PCR diagnostic device. PMID:26995085

  10. Numerical study of steady turbulent flow through bifurcated nozzles in continuous casting

    SciTech Connect

    Najjar, F.M.; Thomas, B.G.; Hershey, D.E.

    1995-08-01

    Bifurcated nozzles are used in continuous casting of molten steel, where they influence the quality of the cast steel slabs. The present study performs two-dimensional (2-D) and three-dimensional (3-D) simulations of steady turbulent (K-{epsilon}) flow in bifurcated nozzles, using a finite-element (FIDAP) model, which has been verified previously with water model experiments. The effects of nozzle design and casting process operating variables on the jet characteristics exiting the nozzle are investigated. The nozzle design parameters studied include the shape, angle, height, width, and thickness of the ports and the bottom geometry. The process operating practices include inlet velocity profile and angle as well as port curvature caused by erosion or inclusion buildup. Results show that the jet angle is controlled mainly by the port angle but is steeper with larger port area and thinner walls. The degree of swirl is increased by larger or rounder ports. The effective port area, where there is no recirculation, is increased by smaller or curved ports. Flow asymmetry is more severe with skewed or angled inlet conditions or unequal port sizes. Turbulence levels in the jet are higher with higher casting speed and small ports.

  11. A simple toxicity apparatus for continuous flow with small volumes: demonstration with mysids and naphthalene

    SciTech Connect

    Smith, R.L.; Hargreaves, B.R.

    1983-04-01

    To determine the toxicity of naphthalene to the mysid crustacean Neomysis americana a small continuous-flow toxicant exposure system was built using design features of Mariotte bottle chemostats. Chemostats maintain cultures at constant cell concentrations by providing constant nutrient inputs. Such cultures remain well-mixed and have minimal cell contact with the container. The same characteristics are useful for exposing small invertebrates to volatile toxicants. The Mariotte bottles in the exposure system were modified by addition of air inlet restrictors. This modification provided stable flow at low pressure heads. The apparatus provided good water quality and physical environment for 10 mysids per chamber, and a more constant concentration of naphthalene than did static chambers replenished daily. Preliminary 96 h toxicity tests with N. americana were performed at 15/sup 0/C and 25/sup 0/C at concentrations of 900 and 1800 ..mu..g l/sup -1/ naphthalene in artificial seawater, for comparison with similar tests performed under static conditions. (JMT)

  12. High Flow Nasal Cannula as a Method for Rapid Weaning From Nasal Continuous Positive Airway Pressure

    PubMed Central

    Badiee, Zohreh; Eshghi, Alireza; Mohammadizadeh, Majid

    2015-01-01

    Background: To compare two methods of weaning premature infants from nasal continuous positive airway pressure (NCPAP). Methods: Between March and November 2012, 88 preterm infants who were stable on NCPAP of 5 cmH2O with FIO2 <30% for a minimum of 6 h were randomly allocated to one of two groups. The high flow nasal cannula (HFNC) group received HFNC with flow of 2 L/min and FIO2 = 0.3 and then stepwise reduction of FIO2 and then flow. The non-HFNC group was maintained on NCPAP of 5 cmH2O and gradual reduction of oxygen until they were on FIO2 = 0.21 for 6 h, and we had weaned them directly from NCPAP (with pressure of 5 cmH2O) to room air. Results: No significant differences were found between 2 study groups with regards to gestational age, birth weight, Apgar score at 1 and 5 min after birth, patent ductus arteriosus and use of xanthines. The mean duration of oxygen therapy after randomization was significantly lower in HFNC group compared to non-HFNC group (20.6 ± 16.8 h vs. 49.6 ± 25.3 h, P < 0.001). Also, the mean length of hospital stay was significantly lower in HFNC group compared to non-HFNC group (11.3 ± 7.8 days vs. 14.8 ± 8.6 days, P = 0.04). The rate of successful weaning was not statistically different between two groups. Conclusions: Weaning from NCPAP to HFNC could decrease the duration of oxygen therapy and length of hospitalization in preterm infants. PMID:25949783

  13. Continuous-Flow Electrokinetic-Assisted Plasmapheresis by Using Three-Dimensional Microelectrodes Featuring Sidewall Undercuts.

    PubMed

    Xing, Xiaoxing; He, Minghao; Qiu, Huihe; Yobas, Levent

    2016-05-17

    We present a novel plasmapheresis device designed for a fully integrated point-of-care blood analysis microsystem. In the device, fluidic microchannels exhibit a characteristic cross-sectional profile arising from distinct three-dimensional (3D) microelectrodes featuring sidewall undercuts readily integrated through a single-mask process. The structure leverages mainly electrothermal convective rolls that efficiently manifest themselves in physiological fluids and yet have received inadequate attention for the application of plasmapheresis due to concerns over Joule heating. Using this device, we show that such convective rolls not only lead to plasma extraction at a high yield and purity but also deliver plasma at an acceptable quality with no evidence of hemolytic stress or protein denaturation. Specifically, plasma from 1.5 μL of whole blood diluted to 4% hematocrit in a high-conductivity buffer (1.5 S/m) is extracted in a continuous flow at a fraction of 70% by using a peak voltage of ±10 Vp applied at 650 kHz; the extracted plasma is nearly 99% pure, as shown by a rigorous assessment using flow cytometry. The plasmas obtained using this device and using conventional centrifugation and sedimentation are of comparable quality as revealed by absorbance and circular dichroism spectra despite thermal gradients; however, these gradients effectively drive electrothermal bulk flows, as assessed using the microparticle image velocity technique. The device achieves high target molecule recovery efficiency, delivering about 97% of the proteins detected in the plasma obtained using sedimentation. The utility of the extracted plasma is further validated based on the detection of prostate-specific antigen at clinically relevant levels. PMID:27094711

  14. Continuous monitoring of a large active earth flow using an integrated GPS - automatic total station approach

    NASA Astrophysics Data System (ADS)

    Corsini, A.

    2009-04-01

    Landslide monitoring has evolved as a crucial tool in civil protection to mitigate and prevent disasters. The research presents an approach to continuous monitoring of a large-scale active earth flow using a system that integrates surface measurements obtained by a GPS and an automatic total station. With the data obtained from the system the landslide can be monitored in near-real-time and surface displacements can be directly utilized to provide early warning of slope movements and to study the behavior of the landslide, e.g. to predict timing and mechanisms of future failure. The Valoria landslide located in the northern Apennines of Italy was reactivated in 2001, 2005 and 2007 damaging roads and endangering houses. A monitoring system was installed in 2007-2008 in the frame of a civil protection plan aimed at risk mitigation. The system consists of an automatic total station measuring about 40 prisms located in the landslide to a maximum distance of 1.800 km; one double-frequency GPS receiver connects in streaming by wireless communication with 4 single-frequency GPS in side the flow. Until December 2007 the monitoring network was operated with periodic static surveying followed by the data post-processing. From September 2007 until March 2008 the landslide deformation was evaluated by periodic surveys with the total station and the GPS system. This first measure showed that the displacements were influenced by the rainfall events and by the snow melting. The total displacements measured vary from centimeter scale in the crown zone, where retrogressive movements were in progress, to over 50 m in the flow track zone. Starting in March 2008 data acquisition by the total station system and GPS were automated in order to allow continuous and near-real-time data processing. The displacement data collected in one and a half year of continuous operation show different acceleration and deceleration phases as a result of the pore water pressure distribution inside the

  15. Development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous flow left ventricular assist devices: The Columbia Ramp Study

    PubMed Central

    Uriel, Nir; Morrison, Kerry A; Garan, Arthur R; Kato, Tomoko; Yuzefpolskaya, Melana; Latif, Farhana; Restaino, Susan W; Mancini, Donna M; Flannery, Margaret; Takayama, Hiroo; John, Ranjit; Colombo, Paolo C; Naka, Yoshifumi; Jorde, Ulrich P

    2012-01-01

    Objective Develop a novel approach of optimizing continuous flow left ventricular assist device (CF-LVAD) function and diagnosing device malfunctions. Background In CF-LVAD patients, the dynamic interaction of device speed, left and right ventricular decompression, and valve function can be assessed during an echocardiography-monitored speed ramp-test. Methods We devised a unique ramp-test protocol to be routinely done at the time of discharge for speed optimization and/or if device malfunction was suspected. The patient’s left ventricular end diastolic dimension (LVEDD), frequency of aortic valve (AV) opening, valvular insufficiency, blood pressure, and CF-LVAD parameters were recorded at increments of 400 rpm from 8,000 rpm to 12,000 rpm. The results of the speed designations were plotted, and linear function slopes for LVEDD, PI, and power were calculated. Results Fifty-two ramp-tests from 39 patients were prospectively collected and analyzed. Twenty-eight ramp-tests were performed for speed optimization, and speed was changed in 17 (61%) with a mean absolute value adjustment of 424±211 rpm. Seventeen patients had ramp-tests performed for suspected device thrombosis and 10 tests were suspicious for device thrombosis; these patients were then treated with intensified anticoagulation and/or device exchange/emergent transplant. Device thrombosis was confirmed in 8/10 cases at the time of emergent device exchange or transplant. All patients with device thrombosis, but none of the remaining patients, had a LVEDD slope > −0.16. Conclusion Ramp-tests facilitated optimal speed changes and device malfunction detection, and may be used to monitor the effects of therapeutic interventions and need for surgical intervention in CF-LVAD patients. PMID:23040584

  16. A stroboscopic technique for using CCD cameras in flow visualization systems for continuous viewing and stop action photography

    NASA Technical Reports Server (NTRS)

    Franke, John M.; Rhodes, David B.; Jones, Stephen B.; Dismond, Harriet R.

    1992-01-01

    A technique for synchronizing a pulse light source to charge coupled device cameras is presented. The technique permits the use of pulse light sources for continuous as well as stop action flow visualization. The technique has eliminated the need to provide separate lighting systems at facilities requiring continuous and stop action viewing or photography.

  17. A continuous-flow biodiesel production process using a rotating packed bed.

    PubMed

    Chen, Yi-Hung; Huang, Yu-Hang; Lin, Rong-Hsien; Shang, Neng-Chou

    2010-01-01

    The continuous-flow transesterification of soybean oil with methanol using a rotating packed bed (RPB) for the production of fatty acid methyl esters (biodiesel) is presented herein. The RPB, which provides high centrifugal force and has an adjustable rotational speed, is employed as a novel transesterification reactor. In this study, biodiesel is synthesized via the methanolysis of soybean oil using potassium hydroxide as the catalyst. The following variables were investigated for their effects on transesterification efficiency: the methanol-oil molar ratio, the estimated hydraulic retention time, the rotational speed of the packed-bed rotator, the reaction temperature, and the catalyst dosage. The yield of the fatty acid methyl esters (Y(FAME)) in the RPB system depends significantly on the experimental conditions, which influence the residence time distribution, the transesterification reaction rate, and the micromixing intensity. Due to its excellent micromixing characteristics, the RPB system shows satisfactory transesterification efficiency. The values of Y(FAME), productivity of FAMEs (P(FAME)), and P(FAME) per unit reactor volume (P(FAME)/V(R)) in the RPB are used to evaluate the performance for biodiesel production and allow for further comparison with other continuous transesterification reactors. Consequently, a RPB is considered a practical transesterification reactor with high transesterification efficiency. PMID:19751970

  18. Enhanced aerobic granulation, stabilization, and nitrification in a continuous-flow bioreactor by inoculating biofilms.

    PubMed

    Yang, Yang; Zhou, Dandan; Xu, Zhengxue; Li, Aijun; Gao, Hang; Hou, Dianxun

    2014-06-01

    In this study, the possibility of using backwashed biofilm as seed in an aerobic granular sludge continuous-flow airlift fluidized bed (CAFB) reactor was investigated. After the addition of the inoculated backwashed biofilm, the start-up period of this reactor fed with municipal wastewater was reduced to 25 days, and aerobic granulation and stabilization were enhanced. At steady state, the chemical oxygen demand (COD) removal efficiency and nitrification efficiency were as high as 80-90 and 60 %, respectively. The CAFB was operated continuously and totally for 90 days, and its performance was much more stable when compared with system inoculated with activated sludge. Microbial distribution analyzed by fluorescence in situ hybridization (FISH) showed that the nitrite-oxidizing bacteria (NOB) and ammonium-oxidizing bacteria (AOB) were compatible with heterotrophic bacteria and distributed evenly throughout the granules. Such unique population distribution might be attributed to the low COD level and abundant dissolved oxygen in the entire granule as simulated by the mathematic models. Moreover, scanning electron microscopy revealed broad holes in the granules, which might promote the mass transfer of the nutrients from the surface to the center and enable simultaneous COD removal and nitrification. In conclusion, backwashed biofilm is an alternative seed of the conventional flocculent activated sludge in the aerobic granular sludge system to enhance carbonaceous oxidization and nitrification. PMID:24643735

  19. Continuous-flow wood chip reactor for biodegradation of 2,4-DCP

    SciTech Connect

    Yum, K.J.; Peirce, J.J.

    1998-02-01

    Chlorinated phenols are by-products of chlorine bleaching in numerous industries including pulp and paper mills and can be emitted from a variety of incineration processes. This research investigates the ability and efficiency of continuous-flow wood chip reactors seeded with a white-rot fungus to degrade 2,4-dichlorophenol (2,4-DCP) using wood chips as a carbon source. When 2,4-DCP was the only substrate (nonglucose treatment conditions), the wood chip reactor system had a high degradation efficiency and operated continuously without excessive fungal biomass buildup on the wood chips. In the presence of added glucose, a clogging problem and an effluent contamination problem of fungal cells are found during the reactor operating period. In addition, 2,4-DCP is degraded effectively both under low-nitrogen as well as high-nitrogen treatment conditions. The 2,4-DCP is degraded to a greater extent with small-size wood chips and hardwood chips as a carbon source. The results of this research demonstrate a potential application of wood chip reactor systems for the treatment of contaminated water while expanding the use of wasted forest products.

  20. Continuous flow hydroformylation using supported ionic liquid phase catalysts with carbon dioxide as a carrier.

    PubMed

    Hintermair, Ulrich; Gong, Zenxing; Serbanovic, Ana; Muldoon, Mark J; Santini, Catherine C; Cole-Hamilton, David J

    2010-09-28

    A supported ionic liquid phase (SILP) catalyst prepared from [PrMIM][Ph(2)P(3-C(6)H(4)SO(3))] (PrMIM = 1-propyl-3-methylimidazolium), [Rh(CO)(2)(acac)] (acacH = 2,4-pentanedione) [OctMIM]NTf(2) (OctMIM = 1-n-octyl-3-methylimidazolium, Tf = CF(3)SO(2)) and microporous silica has been used for the continuous flow hydroformylation of 1-octene in the presence of compressed CO(2). Statistical experimental design was used to show that the reaction rate is neither much affected by the film thickness (IL loading) nor by the syngas:substrate ratio. However, a factor-dependent interaction between the syngas:substrate ratio and film thickness on the reaction rate was revealed. Increasing the substrate flow led to increased reaction rates but lower overall yields. One of the most important parameters proved to be the phase behaviour of the mobile phase, which was studied by varying the reaction pressure. At low CO(2) pressures or when N(2) was used instead of CO(2) rates were low because of poor gas diffusion to the catalytic sites in the SILP. Furthermore, leaching of IL and Rh was high because the substrate is liquid and the IL had been designed to dissolve in it. As the CO(2) pressure was increased, the reaction rate increased and the IL and Rh leaching were reduced, because an expanded liquid phase developed. Due to its lower viscosity the expanded liquid allows better transport of gases to the catalyst and is a poorer solvent for the IL and the catalyst because of its reduced polarity. Above 100 bar (close to the transition to a single phase at 106 bar), the rate of reaction dropped again with increasing pressure because the flowing phase becomes a better and better solvent for the alkene, reducing its partitioning into the IL film. Under optimised conditions, the catalyst was shown to be stable over at least 40 h of continuous catalysis with a steady state turnover frequency (TOF, mol product (mol Rh)(-1)) of 500 h(-1) at low Rh leaching (0.2 ppm). The selectivity of the

  1. Design and testing of a unique randomized gravity, continuous flow bioreactor

    NASA Technical Reports Server (NTRS)

    Lassiter, Carroll B.

    1993-01-01

    high concentrations of oxygen into the culture medium. The system described allows for continuous, on line sampling for production of product without disturbing fluid and particle dynamics in the reaction chamber. It provides for the introduction of substrate, or control substances after cell adaptation to simulated microgravity has been accomplished. The reactor system provides for the nondisruptive, continuous flow replacement of nutrient and removal of product. On line monitoring and control of growth conditions such as pH and nutrient status are provided. A rotating distribution valve allows cessation of growth chamber rotation, thereby preserving the simulated microgravity conditions over longer periods of time.

  2. Characterization of extended channel bioreactors for continuous-flow protein production

    DOE PAGESBeta

    Timm, Andrea C.; Shankles, Peter G.; Foster, Carmen M.; Doktycz, Mitchel John; Retterer, Scott T.

    2015-10-02

    these reactions continuously and in line with downstream purification modules. Here, the authors demonstrate the capability to produce protein over time with continuous-flow reactions and examine basic design features and operation specifications fundamental to continuous microfluidic protein synthesis.« less

  3. Characterization of extended channel bioreactors for continuous-flow protein production

    SciTech Connect

    Timm, Andrea C.; Shankles, Peter G.; Foster, Carmen M.; Doktycz, Mitchel John; Retterer, Scott T.

    2015-10-02

    reactions continuously and in line with downstream purification modules. Here, the authors demonstrate the capability to produce protein over time with continuous-flow reactions and examine basic design features and operation specifications fundamental to continuous microfluidic protein synthesis.

  4. Left main coronary artery occlusion after percutaneous aortic valve implantation.

    PubMed

    Bartorelli, Antonio L; Andreini, Daniele; Sisillo, Erminio; Tamborini, Gloria; Fusari, Melissa; Biglioli, Paolo

    2010-03-01

    Left main coronary artery occlusion occurred immediately after transfemoral aortic valve implantation in an 87-year-old woman, which resulted in ventricular fibrillation and hemodynamic collapse. This life-threatening complication was promptly diagnosed with transesophageal echocardiography, which showed the disappearance of diastolic left main coronary artery jet flow and was confirmed with aortic root angiography. After prompt defibrillation, hemodynamic support was obtained with intra-aortic balloon pump and inotropic drugs. Functional recovery and survival were achieved with coronary stenting. This report highlights the importance of an integrated team approach of highly skilled specialists for these novel interventions. PMID:20172163

  5. Experimental and theoretical investigation of the stability of stepwise pH gradients in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Kuhn, Reinhard; Wagner, Horst; Mosher, Richard A.; Thormann, Wolfgang

    1987-01-01

    Isoelectric focusing in the continuous flow mode can be more quickly and economically performed by admitting a stepwise pH gradient composed of simple buffers instead of uniform mixtures of synthetic carrier ampholytes. The time-consuming formation of the pH gradient by the electric field is thereby omitted. The stability of a three-step system with arginine - morpholinoethanesulfonic acid/glycylglycine - aspartic acid is analyzed theoretically by one-dimensional computer simulation as well as experimentally at various flow rates in a continuous flow apparatus. Excellent agreement between experimental and theoretical data was obtained. This metastable configuration was found to be suitable for focusing of proteins under continuous flow conditions. The influence of various combinations of electrolytes and membranes between electrophoresis chamber and electrode compartments is also discussed.

  6. Surgical Aortic Valvuloplasty Versus Balloon Aortic Valve Dilatation in Children.

    PubMed

    Donald, Julia S; Konstantinov, Igor E

    2016-09-01

    Balloon aortic valve dilatation (BAD : is assumed to provide the same outcomes as surgical aortic valvuloplasty (SAV). However, the development of precise modern surgical valvuloplasty techniques may result in better long-term durability of the aortic valve repair. This review of the recent literature suggests that current SAV provides a safe and durable repair. Furthermore, primary SAV appears to have greater freedom from reintervention and aortic valve replacement when compared to BAD. PMID:27587493

  7. Aortic regurgitation after transcatheter aortic valve replacement.

    PubMed

    Werner, Nikos; Sinning, Jan-Malte

    2014-01-01

    Paravalvular aortic regurgitation (AR) negatively affects prognosis following transcatheter aortic valve replacement (TAVR). As transcatheter heart valves (THV) are anchored using a certain degree of oversizing at the level of the aortic annulus, incomplete stent frame expansion because of heavily annular calcifications, suboptimal placement of the prosthesis, and/or annulus-prosthesis size-mismatch can contribute to paravalvular AR with subsequent increased mortality risk. Echocardiography is essential to differentiate between transvalvular and paravalvular AR and to further elucidate the etiology of AR during the procedure. However, because echocardiographic quantification of AR in TAVR patients remains challenging, especially in the implantation situation, a multimodal approach to the evaluation of AR with use of hemodynamic measurements and imaging modalities is useful to precisely quantify the severity of AR immediately after valve deployment. "Next-generation" THVs are already on the market and first results show that paravalvular AR related to design modifications (eg, paravalvular space-fillers, full repositionability) are rarely seen in these valve types.  PMID:24632758

  8. Aerobic biodegradability of methyldiethanolamine (MDEA) used in natural gas sweetening plants in batch tests and continuous flow experiments.

    PubMed

    Fürhacker, M; Pressl, A; Allabashi, R

    2003-09-01

    Mixtures of different amines including tertiary amines (methyldiethanolamine, MDEA) are commonly used for the removal of CO2 from gas mixtures or in gas sweetening processes for the extraction of CO2 and H2S. The absorber solutions used can be released into the industrial waste water due to continuous substitution of degraded MDEA, periodically cleaning processes or an accidental spill. In this study, the aerobic biodegradability of MDEA was investigated in a standardised batch test and a continuous flow experiment (40 l/d). The results of the batch test indicated that the MDEA-solution was non-biodegradable during the test period of 28 days, whereas the continuous flow experiments showed biodegradation of more than 96% based on TOC-measurements. This was probably due to the adaptation of the microorganisms to this particular waste water contamination during continuous flow experiment. PMID:12871741

  9. Aortic aneurysm repair - endovascular- discharge

    MedlinePlus

    ... page: //medlineplus.gov/ency/patientinstructions/000236.htm Aortic aneurysm repair - endovascular - discharge To use the sharing features ... enable JavaScript. AAA repair - endovascular - discharge; Repair - aortic aneurysm - endovascular - discharge; EVAR - discharge; Endovascular aneurysm repair - discharge ...

  10. Screening for Abdominal Aortic Aneurysm

    MedlinePlus

    Understanding Task Force Recommendations Screening for Abdominal Aortic Aneurysm The U.S. Preventive Services Task Force (Task Force) ... final recommendation statement on Screening for Abdominal Aortic Aneurysm. This final recommendation statement applies to adults ages ...

  11. Visualization of Liquid Metal Two-phase Flows in a Physical Model of the Continuous Casting Process of Steel

    NASA Astrophysics Data System (ADS)

    Timmel, Klaus; Shevchenko, Natalia; Röder, Michael; Anderhuber, Marc; Gardin, Pascal; Eckert, Sven; Gerbeth, Gunter

    2015-04-01

    We present an experimental study concerned with investigations of the two-phase flow in a mock-up of the continuous casting process of steel. A specific experimental facility was designed and constructed at HZDR for visualizing liquid metal two-phase flows in the mold and the submerged entry nozzle (SEN) by means of X-ray radioscopy. This setup operates with the low melting, eutectic alloy GaInSn as model liquid. The argon gas is injected through the tip of the stopper rod into the liquid metal flow. The system operates continuously under isothermal conditions. First results will be presented here revealing complex flow structures in the SEN widely differing from a homogeneously dispersed bubbly flow. The patterns are mainly dominated by large bubbles and large-area detachments of the liquid metal flow from the inner nozzle wall. Various flow regimes can be distinguished depending on the ratio between the liquid and the gas flow rate. Smaller gas bubbles are produced by strong shear flows near the nozzle ports. The small bubbles are entrained by the submerged jet and mainly entrapped by the lower circulation roll in the mold. Larger bubbles develop by coalescence and ascend toward the free surface.

  12. Large-Scale, Continuous-Flow Production of Stressed Biomass (Desulfovibrio vulgaris Hildenborough)

    SciTech Connect

    Geller, Jil T.; Borglin, Sharon E.; Fortney, Julian L.; Lam, Bonita R.; Hazen, Terry C.; Biggin, Mark D.

    2010-05-01

    The Protein Complex Analysis Project (PCAP, http://pcap.lbl.gov/), focuses on high-throughput analysis of microbial protein complexes in the anaerobic, sulfate-reducing organism, DesulfovibriovulgarisHildenborough(DvH).Interest in DvHas a model organism for bioremediation of contaminated groundwater sites arises from its ability to reduce heavy metals. D. vulgarishas been isolated from contaminated groundwater of sites in the DOE complex. To understand the effect of environmental changes on the organism, midlog-phase cultures are exposed to nitrate and salt stresses (at the minimum inhibitory concentration, which reduces growth rates by 50percent), and compared to controls of cultures at midlogand stationary phases. Large volumes of culture of consistent quality (up to 100 liters) are needed because of the relatively low cell density of DvHcultures (one order of magnitude lower than E. coli, for example) and PCAP's challenge to characterize low-abundance membrane proteins. Cultures are grown in continuous flow stirred tank reactors (CFSTRs) to produce consistent cell densities. Stressor is added to the outflow from the CFSTR, and the mixture is pumped through a plug flow reactor (PFR), to provide a stress exposure time of 2 hours. Effluent is chilled and held in large carboys until it is centrifuged. A variety of analyses -- including metabolites, total proteins, cell density and phospholipidfatty-acids -- track culture consistency within a production run, and differences due to stress exposure and growth phase for the different conditions used. With our system we are able to produce the requisite 100 L of culture for a given condition within a week.

  13. Hypertension: An Unstudied Potential Risk Factor for Adverse Outcomes during Continuous Flow Ventricular Assist Device Support

    PubMed Central

    Wasson, Lauren T.; Yuzefpolskaya, Melana; Wakabayashi, Michiyori; Takayama, Hiroo; Naka, Yoshifumi; Uriel, Nir; Jorde, Ulrich P.; Demmer, Ryan T.; Colombo, Paolo C.

    2014-01-01

    In end-stage heart failure, left ventricular assist devices (LVADs) represent an exciting new frontier in which post-device-implantation survival approaches that of heart transplant. However, expansion of this technology is still limited by complications that impact morbidity and mortality. Thus, it is essential to identify and optimize modifiable predictors of poor outcomes. One such predictor may be hypertension (HTN). Not only may chronic HTN as a traditional cardiovascular risk factor be present during long-term LVAD support, but HTN may also contribute to device malfunction or device-associated complications. Although current guidelines identify blood pressure (BP) control as important to outpatient continuous flow (CF) LVAD management, there is no evidence base to support these guidelines. Indeed, our comprehensive literature search did not identify any studies that evaluated post-device-implantation HTN as a potential predictor of adverse CF-LVAD outcomes. Hypertension among CF-LVAD patients is likely a relatively unstudied factor because of difficulties using standard non-invasive techniques to measure BP in the setting of reduced pulsatile flow. Fortunately, recent research has elucidated the meaning of Doppler BP measurements and validated a slow-deflation cuff system for BP measurements in the setting of CF-LVAD support. Therefore, CF-LVAD researchers and clinicians may i) consider potential mechanisms relating HTN to poor outcomes, ii) realize that HTN management is a stated goal despite scarce evidence, and iii) utilize the new reliable and valid methods for outpatient BP measurement that make research and management possible. It is critical and now feasible that research on HTN in the CF-LVAD patient population move forward. PMID:25283767

  14. Gas exchange and intrapulmonary distribution of ventilation during continuous-flow ventilation

    SciTech Connect

    Vettermann, J.; Brusasco, V.; Rehder, K.

    1988-05-01

    In 12 anesthetized paralyzed dogs, pulmonary gas exchange and intrapulmonary inspired gas distribution were compared between continuous-flow ventilation (CFV) and conventional mechanical ventilation (CMV). Nine dogs were studied while they were lying supine, and three dogs were studied while they were lying prone. A single-lumen catheter for tracheal insufflation and a double-lumen catheter for bilateral endobronchial insufflation (inspired O2 fraction = 0.4; inspired minute ventilation = 1.7 +/- 0.3 (SD) 1.kg-1.min-1) were evaluated. Intrapulmonary gas distribution was assessed from regional 133Xe clearances. In dogs lying supine, CO2 elimination was more efficient with endobronchial insufflation than with tracheal insufflation, but the alveolar-arterial O2 partial pressure difference was larger during CFV than during CMV, regardless of the type of insufflation. By contrast, endobronchial insufflation maintained both arterial PCO2 and alveolar-arterial O2 partial pressure difference at significantly lower levels in dogs lying prone than in dogs lying supine. In dogs lying supine, the dependent lung was preferentially ventilated during CMV but not during CFV. In dogs lying prone, gas distribution was uniform with both modes of ventilation. The alveolar-arterial O2 partial pressure difference during CFV in dogs lying supine was negatively correlated with the reduced ventilation of the dependent lung, which suggests that increased ventilation-perfusion mismatching was responsible for the increase in alveolar-arterial O2 partial pressure difference. The more efficient oxygenation during CFV in dogs lying prone suggests a more efficient matching of ventilation to perfusion, presumably because the distribution of blood flow is also nearly uniform.

  15. Hypertension: an unstudied potential risk factor for adverse outcomes during continuous flow ventricular assist device support.

    PubMed

    Wasson, Lauren T; Yuzefpolskaya, Melana; Wakabayashi, Michiyori; Takayama, Hiroo; Naka, Yoshifumi; Uriel, Nir; Jorde, Ulrich P; Demmer, Ryan T; Colombo, Paolo C

    2015-05-01

    In end-stage heart failure, left ventricular assist devices (LVADs) represent an exciting new frontier in which post-device implantation survival approaches that of heart transplant. However, expansion of this technology is still limited by complications that impact morbidity and mortality. Thus, it is essential to identify and optimize modifiable predictors of poor outcomes. One such predictor may be hypertension (HTN). Not only may chronic HTN as a traditional cardiovascular risk factor be present during long-term LVAD support, but HTN may also contribute to device malfunction or device-associated complications. Although current guidelines identify blood pressure (BP) control as important to outpatient continuous flow (CF) LVAD management, there is no evidence base to support these guidelines. Indeed, our comprehensive literature search did not identify any studies that evaluated post-device implantation HTN as a potential predictor of adverse CF-LVAD outcomes. HTN among CF-LVAD patients is likely a relatively unstudied factor because of difficulties using standard noninvasive techniques to measure BP in the setting of reduced pulsatile flow. Fortunately, recent research has elucidated the meaning of Doppler BP measurements and validated a slow-cuff deflation system for BP measurements in the setting of CF-LVAD support. Therefore, CF-LVAD researchers and clinicians may (1) consider potential mechanisms relating HTN to poor outcomes, (2) realize that HTN management is a stated goal despite scarce evidence, and (3) utilize the new reliable and valid methods for outpatient BP measurement that make research and management possible. It is critical and now feasible that research on HTN in the CF-LVAD patient population move forward. PMID:25283767

  16. Cultivation of methanogenic community from subseafloor sediments using a continuous-flow bioreactor

    PubMed Central

    Imachi, Hiroyuki; Aoi, Ken; Tasumi, Eiji; Saito, Yumi; Yamanaka, Yuko; Saito, Yayoi; Yamaguchi, Takashi; Tomaru, Hitoshi; Takeuchi, Rika; Morono, Yuki; Inagaki, Fumio; Takai, Ken

    2011-01-01

    Microbial methanogenesis in subseafloor sediments is a key process in the carbon cycle on the Earth. However, the cultivation-dependent evidences have been poorly demonstrated. Here we report the cultivation of a methanogenic microbial consortium from subseafloor sediments using a continuous-flow-type bioreactor with polyurethane sponges as microbial habitats, called down-flow hanging sponge (DHS) reactor. We anaerobically incubated methane-rich core sediments collected from off Shimokita Peninsula, Japan, for 826 days in the reactor at 10 °C. Synthetic seawater supplemented with glucose, yeast extract, acetate and propionate as potential energy sources was provided into the reactor. After 289 days of operation, microbiological methane production became evident. Fluorescence in situ hybridization analysis revealed the presence of metabolically active microbial cells with various morphologies in the reactor. DNA- and RNA-based phylogenetic analyses targeting 16S rRNA indicated the successful growth of phylogenetically diverse microbial components during cultivation in the reactor. Most of the phylotypes in the reactor, once it made methane, were more closely related to culture sequences than to the subsurface environmental sequence. Potentially methanogenic phylotypes related to the genera Methanobacterium, Methanococcoides and Methanosarcina were predominantly detected concomitantly with methane production, while uncultured archaeal phylotypes were also detected. Using the methanogenic community enrichment as subsequent inocula, traditional batch-type cultivations led to the successful isolation of several anaerobic microbes including those methanogens. Our results substantiate that the DHS bioreactor is a useful system for the enrichment of numerous fastidious microbes from subseafloor sediments and will enable the physiological and ecological characterization of pure cultures of previously uncultivated subseafloor microbial life. PMID:21654849

  17. Durability of continuous-flow left ventricular assist devices: a systematic review

    PubMed Central

    Xie, Ashleigh; Phan, Kevin

    2014-01-01

    Background Left ventricular assist devices (LVADs) are becoming an increasingly viable alternative therapy for heart failure, either as a bridge to heart transplantation (BTT) or destination therapy (DT). The latter has become increasingly popular in recent years, in the face of a donor organ shortage and a rise in elderly patients ineligible for heart transplants. For these patients in particular, device durability is a key contributor to survival, morbidity, and quality of life. This systematic review aimed to assess the long-term durability of current continuous-flow LVADs. Methods Six electronic databases were searched from their dates of inception to August 2014 for original studies reporting on patients receiving continuous-flow LVADs. LVAD failure was defined as device malfunction necessitating exchange or explantation, or causing patient mortality. Pooled averages were calculated for outcomes and rates of device failure were reconstructed from digitized graph curves using the software, WebPlotDigitizer v3.3. Results Twelve retrospective observational studies with a total of 5,471 patients were included for analysis. The mean duration of LVAD support was 504.7 (range, 303-568) days, and the overall weighted incidence of device failure was 3.9% (range, 1-11.3%). On average, pump thrombosis was the most common cause of device failure (50.5%), followed by lead or cable damage (21.7%), mechanical pump failure (11.6%), device-related infection (11.1%), and surgical complications from implantation (2.5%). Long-term device failure rates at 2-, 6-, 12-, 18- and 24-months post-implantation were 0.5%, 1.8%, 2.9%, 4.5% and 6.5%, respectively. Conclusions With the expected rise in LVAD usage for end-stage heart failure, particularly as a DT, the steady minority of patients experiencing device failure is likely to increase. Further investigation is required into the incidence and mechanism of major causes of failure, as well as design improvements that may address these

  18. Aneurysms: thoracic aortic aneurysms.

    PubMed

    Chun, Kevin C; Lee, Eugene S

    2015-04-01

    Thoracic aortic aneurysms (TAAs) have many possible etiologies, including congenital heart defects (eg, bicuspid aortic valves, coarctation of the aorta), inherited connective tissue disorders (eg, Marfan, Ehlers-Danlos, Loeys-Dietz syndromes), and degenerative conditions (eg, medial necrosis, atherosclerosis of the aortic wall). Symptoms of rupture include a severe tearing pain in the chest, back, or neck, sometimes associated with cardiovascular collapse. Before rupture, TAAs may exert pressure on other thoracic structures, leading to a variety of symptoms. However, most TAAs are asymptomatic and are found incidentally during imaging for other conditions. Diagnosis is confirmed with computed tomography scan or echocardiography. Asymptomatic TAAs should be monitored with imaging at specified intervals and patients referred for repair if the TAAs are enlarging rapidly (greater than 0.5 cm in diameter over 6 months for heritable etiologies; greater than 0.5 cm over 1 year for degenerative etiologies) or reach a critical aortic diameter threshold for elective surgery (5.5 cm for TAAs due to degenerative etiologies, 5.0 cm when associated with inherited syndromes). Open surgery is used most often to treat asymptomatic TAAs in the ascending aorta and aortic arch. Asymptomatic TAAs in the descending aorta often are treated medically with aggressive blood pressure control, though recent data suggest that endovascular procedures may result in better long-term survival rates. PMID:25860136

  19. [Thoracoabdominal aortic aneurysm].

    PubMed

    Kalder, J; Kotelis, D; Jacobs, M J

    2016-09-01

    Thoracoabdominal aortic aneurysms (TAAA) are rare events with an incidence of 5.9 cases per 100,000 persons per year. In Germany approximately 940 TAAA procedures are performed annually. The cause of TAAA is mostly degenerative but they can also occur on the basis of an aortic dissection or connective tissue disease (e. g. Marfan's syndrome). Patients often have severe comorbidities and suffer from hypertension, coronary heart disease or chronic obstructive pulmonary disease, mostly as a result of smoking. Operative treatment is indicated when the maximum aortic diameter has reached 6 cm (> 5 cm in patients with connective tissue disease) or the aortic diameter rapidly increases (> 5 mm/year). Treatment options are open surgical aortic repair with extracorporeal circulation, endovascular repair with branched/fenestrated endografts and parallel grafts (chimneys) or a combination of open and endovascular procedures (hybrid procedures). Mortality rates after both open and endovascular procedures are approximately 8 % depending on the extent of the repair. Furthermore, there are relevant risks of complications, such as paraplegia (up to 20 %) and the necessity for dialysis. In recent years several approaches to minimize these risks have been proposed. Besides cardiopulmonary risk evaluation, clinical assessment of patients by the physician with respect to the patient-specific anatomy influences the allocation of patients to one treatment option or another. Surgery of TAAA should ideally be performed in high-volume centers in order to achieve better results. PMID:27558261

  20. Continuous monitoring of water flow and solute transport using vadose zone monitoring technology

    NASA Astrophysics Data System (ADS)

    Dahan, O.

    2009-04-01

    Groundwater contamination is usually attributed to pollution events that initiate on land surface. These may be related to various sources such as industrial, urban or agricultural, and may appear as point or non point sources, through a single accidental event or a continuous pollution process. In all cases, groundwater pollution is a consequence of pollutant transport processes that take place in the vadose zone above the water table. Attempts to control pollution events and prevent groundwater contamination usually involve groundwater monitoring programs. This, however, can not provide any protection against contamination since pollution identification in groundwater is clear evidence that the groundwater is already polluted and contaminants have already traversed the entire vadose zone. Accordingly, an efficient monitoring program that aims at providing information that may prevent groundwater pollution has to include vadose-zone monitoring systems. Such system should provide real-time information on the hydrological and chemical properties of the percolating water and serve as an early warning system capable of detecting pollution events in their early stages before arrival of contaminants to groundwater. Recently, a vadose-zone monitoring system (VMS) was developed to allow continuous monitoring of the hydrological and chemical properties of percolating water in the deep vadose zone. The VMS includes flexible time-domain reflectometry (FTDR) probes for continuous tracking of water content profiles, and vadose-zone sampling ports (VSPs) for frequent sampling of the deep vadose pore water at multiple depths. The monitoring probes and sampling ports are installed through uncased slanted boreholes using a flexible sleeve that allows attachment of the monitoring devices to the borehole walls while achieving good contact between the sensors and the undisturbed sediment column. The system has been successfully implemented in several studies on water flow and

  1. Primary Infrarenal Aortic Stenting With or Without Iliac Stenting for Isolated and Aortoiliac Stenoses: Single-Centre Experience With Long-Term Follow-Up

    SciTech Connect

    Tapping, C. R.; Ahmed, M.; Scott, P. M.; Lakshminarayan, R.; Robinson, G. J.; Ettles, D. F.; Shrivastava, V.

    2013-02-15

    The purpose of this study was to evaluate the technical success, complications, long-term clinical outcome, and patency after primary infrarenal aortic stenting for aortic and aortoiliac stenosis. Between January 1999 and January 2006, 22 consecutive patients underwent endovascular treatment because of infrarenal aortic stenosis with and without common iliac stenosis (10 men; mean age 64 {+-} 14 years). Eleven (11 of 22) patients had an isolated aortic stenosis, whereas 11 of 22 had aortic stenosis that extended into the common iliac arteries (CIAs). Thirteen patients were Rutherford classification type 3, and 9 patients were type 4. Statistical analysis included paired Student t test and Kaplan-Meier life table analysis; p < 0.05 was considered significant. Technical and initial clinical success was achieved in all patients. There were three (14 %) procedure-related complications, which included two access-point pseudoaneurysms and one non-flow-limiting left external iliac dissection. Patients were followed-up for a mean period of 88 months (range 60-132). Mean preprocedure ankle brachial pressure indexes (ABPI) were 0.60 {+-} -0.15 (right) and 0.61 {+-} -0.16 (left). After the procedure they were 0.86 {+-} -0.07 (right) and 0.90 {+-} -0.09 (left). The increase in ABPI was significant (p < 0.05), and this continued throughout follow-up. Four (18 %) patients had recurrence of symptoms during follow-up. These occurred at 36, 48, 48, and 50 months after the original procedure. All four patients were successfully treated with repeat angioplasty procedures. There was a significant difference in primary patency between isolated aortic stenosis (100 %) and aortoiliac stenosis (60 %) (p = 0.031). Cumulative follow-up was 1920 months yielding a reintervention rate of 0.025/events/year. Primary stenting of infrarenal stenosis is safe and successful with a low reintervention rate. It should be considered as first-line treatment for patients with infrarenal aortic stenotic

  2. A Microfluidic Device for Continuous-Flow Magnetically Controlled Capture and Isolation of Microparticles.

    PubMed

    Zhou, Yao; Wang, Yi; Lin, Qiao

    2010-08-01

    This paper presents a novel microfluidic device that exploits magnetic manipulation for integrated capture and isolation of microparticles in continuous flow. The device, which was fabricated from poly(dimethylsiloxane) (PDMS) by soft-lithography techniques, consists of an incubator and a separator integrated on a single chip. The incubator is based on a novel scheme termed target acquisition by repetitive traversal (TART), in which surface-functionalized magnetic beads repetitively traverse a sample to seek out and capture target particles. This is accomplished by a judicious combination of a serpentine microchannel geometry and a time-invariant magnetic field. Subsequently, in the separator, the captured target particles are isolated from nontarget particles via magnetically driven fractionation in the same magnetic field. Due to the TART incubation scheme that uses a corner-free serpentine channel, the device has no dead volume and allows minimization of undesired particle or magnetic-bead retention. Single-chip integration of the TART incubator with the magnetic-fractionation separator further allows automated continuous isolation and retrieval of specific microparticles in an integrated manner that is free of manual off-chip sample incubation, as often required by alternative approaches. Experiments are conducted to characterize the individual incubation and separation components, as well as the integrated device. The device is found to allow 90% of target particles in a sample to be captured and isolated and 99% of nontarget particles to be eliminated. With this high separation efficiency, along with excellent reliability and flexibility, the device is well suited to sorting, purification, enrichment, and detection of micro/nanoparticles and cells in lab-on-a-chip systems. PMID:24511214

  3. Integrated continuous flow polymerase chain reaction and micro-capillary electrophoresis system with bioaffinity preconcentration.

    PubMed

    Njoroge, Samuel K; Witek, Magorzata A; Battle, Katrina N; Immethun, Vicki E; Hupert, Mateusz L; Soper, Steven A

    2011-11-01

    An integrated and modular DNA analysis system is reported that consists of two modules: (i) A continuous flow polymerase chain reaction (CFPCR) module fabricated in a high T(g) (150°C) polycarbonate substrate in which selected gene fragments were amplified using biotin and fluorescently labeled primers accomplished by continuously shuttling small packets of PCR reagents and template through isothermal zones as opposed to heating and cooling large thermal masses typically performed in batch-type thermal reactors. (ii) μCE (micro-capillary electrophoresis) module fabricated in poly(methylmethacrylate) (PMMA), which utilized a bioaffinity selection and purification bed (2.9  μL) to preconcentrate and purify the PCR products generated from the CFPCR module prior to electrophoretic sorting. Biotin-labeled CFPCR products were hydrostatically pumped through the streptavidin-modified bed, where they were extracted onto the surface of micropillars. The affinity bed was also fabricated in PMMA and was populated with an array of microposts (50  μm width; 100  μm height) yielding a total surface area of ∼117  mm(2). This solid-phase extraction (SPE) process demonstrated high selectivity for biotinylated amplicons and utilized the strong streptavidin/biotin interaction (K(d) = 10(-15)  M) to generate high recoveries. The SPE selected CFPCR products were thermally denatured and single-stranded DNA released for injection into a 7-cm-long μCE channel for size-based separations and fluorescence detection. The utility of the system was demonstrated using Alu DNA typing for gender and ethnicity determinations as a model. Compared with the traditional cross-T injection procedure typically used for μCE, the affinity pre-concentration and injection procedure generated signal enhancements of 17- to 40-fold, critical for CFPCR thermal cyclers due to Taylor dispersion associated with their operation. PMID:22038569

  4. Comparison of Reductive Dechlorination of Chlorinated Ethylene in Batch and Continuous-Flow Reactor

    NASA Astrophysics Data System (ADS)

    Park, S.; Jonghwan, L.; Hong, U.; Kim, N.; Ahn, H.; Lee, S.; Kim, Y.

    2010-12-01

    A 1.28 L-Batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloriethene (TCE) were operated for 120 days and 72 days, respectively, to study the effect of formate as electron donor on reductive dechlorination of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 μmol TCE was completely degraded in presence of 20% hydrogen gas (H2) in less than 8 days by Evanite culture (300 mg-soluble protein) with ability to completely degrade tetrachloroethene (PCE) and TCE to ETH under anaerobic conditions. To determine the effect of formate as electron donor instead of H2, about 3 or 11 mmol of formate injected into batch-reactor every 15 days was enough to support H2 for dechlorination of c-DCE to VC and ETH. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 μmol/L) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at HRT 18 days for 13 days, but TCE was completed degraded at HRT 36 days without accumulation during left of experiment period, getting H2 from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after CFSTR operation, it reached steady-state without accumulation in presence of excessive formate. However, since c-DCE in CFSTR was not completely dechlorinated, we will determine the transcriptional level of enzyme involved in reductive dechlorination of TCE, c-DCE, and VC in our future work.

  5. Spatiotemporal complexity of the aortic sinus vortex

    NASA Astrophysics Data System (ADS)

    Moore, Brandon; Dasi, Lakshmi Prasad

    2014-07-01

    The aortic sinus vortex is a classical flow structure of significant importance to aortic valve dynamics and the initiation and progression of calcific aortic valve disease. We characterize the spatiotemporal characteristics of aortic sinus vortex dynamics in relation to the viscosity of blood analog solution as well as heart rate. High-resolution time-resolved (2 kHz) particle image velocimetry was conducted to capture 2D particle streak videos and 2D instantaneous velocity and streamlines along the sinus midplane using a physiological but rigid aorta model fitted with a porcine bioprosthetic heart valve. Blood analog fluids used include a water-glycerin mixture and saline to elucidate the sensitivity of vortex dynamics to viscosity. Experiments were conducted to record 10 heart beats for each combination of blood analog and heart rate condition. Results show that the topological characteristics of the velocity field vary in timescales as revealed using time bin-averaged vectors and corresponding instantaneous streamlines. There exist small timescale vortices and a large timescale main vortex. A key flow structure observed is the counter vortex at the upstream end of the sinus adjacent to the base (lower half) of the leaflet. The spatiotemporal complexity of vortex dynamics is shown to be profoundly influenced by strong leaflet flutter during systole with a peak frequency of 200 Hz and peak amplitude of 4 mm observed in the saline case. While fluid viscosity influences the length and timescales as well as the introduction of leaflet flutter, heart rate influences the formation of counter vortex at the upstream end of the sinus. Higher heart rates are shown to reduce the strength of the counter vortex that can greatly influence the directionality and strength of shear stresses along the base of the leaflet. This study demonstrates the impact of heart rate and blood analog viscosity on aortic sinus hemodynamics.

  6. Opening of Aortic Valve During Exercise Is Key to Preventing Development of Aortic Insufficiency During Ventricular Assist Device Treatment.

    PubMed

    Imamura, Teruhiko; Kinugawa, Koichiro; Nitta, Daisuke; Hatano, Masaru; Ono, Minoru

    2015-01-01

    Although we previously demonstrated that opening of the native aortic valve (AV) at rest prevents development of aortic insufficiency (AI) during continuous-flow (CF) left ventricular assist device (LVAD) support, the clinical impact of native AV opening during exercise remained unknown. We enrolled 37 patients with a closed native AV at rest 3 months after CF LVAD implantation and followed them from 2006 to 2014. Seven patients (19%) who achieved opening of the native AV during cardiopulmonary exercise testing at 3 months (opening AV group) had higher exercise tolerability and improved left ventricular contractility during exercise compared with those with a closed native AV (closed AV group) (p < 0.05 for all). The opening group experienced no AI at 6 months and had a higher readmission-free rate because of cardiovascular events compared with the closed group during the 2 years study period (100% vs. 56%, p = 0.005). Among those with a closed AV, use of the centrifugal pump was a significant predictor of AI-free status (p < 0.05; odds ratio, 5.400). In conclusion, opening of the native AV during exercise and centrifugal pump use were key to preventing the development of AI. Aggressive cardiac rehabilitation may have a prophylactic impact on development of AI during CF LVAD treatment. PMID:25955152

  7. Continuous high-energy low-flow-rate enteral support: a panoramic review of 1000 cases.

    PubMed

    Levy, E; Huguet, C; Parc, R; Ollivier, J M; Goldberg, J; Loygue, J

    1985-01-01

    One thousand intensive care digestive surgical cases are reviewed concerning continuous low-flow-rate enteral support (CLFRES), using Nutripompe: 607 males and 393 females, average age 51 years. The average duration of CLFRES is 21.5 days +/- 13, range 4 to 180 days. CLFRES was used postoperatively in 76 per cent, preoperatively in 10 per cent, and pre- and postoperatively in 14 per cent of cases, respectively. The enteral support route was 63 per cent nasogastric, 20 per cent gastrostomy and 17 per cent jejunostomy. Five hundred and ten patients required extensive digestive surgery with temporary exclusions. More than 100 patients with either temporary enterostomies or enterocutaneous fistulas have had continuous reinstillation of digestive chyme (CRDC) associated with their intensive care unit treatment management. CRDC in the lower end of an enterostomy has shown a specific retrograde inhibitory effect on the upper digestive secretions, particularly on the intestinal secretions during pathologies associated with one or several interruptions of the continuity of the gastrointestinal tract. This technique and its physiological implications were discussed. The principal pathologies in this important study group are: severe digestive fistulas, 24 per cent; acute diffuse peritonitis, 18 per cent; acute enterocolitis, 14 per cent; digestive tumours, 35 per cent; and acute necrotizing haemorrhagic pancreatitis, 9 per cent. A comparative analysis of nutritional energy nitrogen requirement was presented in view of the cancer, the septic, and the non-cancer non-septic patient groups. Enteral support nutritional solutions were primarily mixed non-degraded food, 70 per cent, and semi-elemental diets, 30 per cent. Certain pathology groups required variations in protein and lipid percentage. An up-to-date evaluation of nutritive formulas based on small peptides in normal and small bowel postoperative patients was discussed. Four CLFRES administration programmes were discussed

  8. Continuously Infusing Hyperpolarized 129Xe into Flowing Aqueous Solutions Using Hydrophobic Gas Exchange Membranes

    PubMed Central

    Cleveland, Zackary I.; Möller, Harald E.; Hedlund, Laurence W.; Driehuys, Bastiaan

    2009-01-01

    Hyperpolarized (HP) 129Xe yields high signal intensities in magnetic resonance (MR) and, through its large chemical shift range of ∼300 ppm, provides detailed information about the local chemical environment. To exploit these properties in aqueous solutions and living tissues requires the development of methods for efficiently dissolving HP 129Xe over an extended time period. To this end, we have used commercially available gas exchange modules to continuously infuse concentrated HP 129Xe into flowing liquids, including rat whole blood, for periods as long as one hour, and have demonstrated the feasibility of dissolved-phase MR imaging with sub-millimeter resolution within minutes. These modules, which exchange gases using hydrophobic microporous polymer membranes, are compatible with a variety of liquids and are suitable for infusing HP 129Xe into the bloodstream in vivo. Additionally, we have developed a detailed mathematical model of the infused HP 129Xe signal dynamics that should be useful in designing improved infusion systems that yield even higher dissolved HP 129Xe signal intensities. PMID:19702286

  9. Human Fitting Studies of Cleveland Clinic Continuous-Flow Total Artificial Heart

    PubMed Central

    Karimov, Jamshid H.; Steffen, Robert J.; Byram, Nicole; Sunagawa, Gengo; Horvath, David; Cruz, Vincent; Golding, Leonard A.R.; Fukamachi, Kiyotaka; Moazami, Nader

    2015-01-01

    Implantation of mechanical circulatory support devices is challenging, especially in patients with a small chest cavity. We evaluated how well the Cleveland Clinic continuous-flow total artificial heart (CFTAH) fit the anatomy of patients about to receive a heart transplant. A mock pump model of the CFTAH was rapid-prototyped using biocompatible materials. The model was brought to the operative table, and the direction, length, and angulation of the inflow/outflow ports and outflow conduits were evaluated after the recipient's ventricles had been resected. Thoracic cavity measurements were based on preoperative computed tomographic data. The CFTAH fit well in all five patients (height, 170 ± 9 cm; weight, 75 ± 24 kg). Body surface area was 1.9 ± 0.3 m2 (range, 1.6-2.1 m2). The required inflow and outflow port orientation of both the left and right housings appeared consistent with the current version of the CFTAH implanted in calves. The left outflow conduit remained straight, but the right outflow direction necessitated a 73 ± 22 degree angulation to prevent potential kinking when crossing over the connected left outflow. These data support the fact that our design achieves the proper anatomical relationship of the CFTAH to a patient's native vessels. PMID:25806613

  10. Bioprocessing in Microgravity: Applications of Continuous Flow Electrophoresis to Rat Anterior Pituitary Particles

    NASA Technical Reports Server (NTRS)

    Hymer, W. C.; Salada, T.; Cenci, R.; Krishnan, K.; Seaman, G. V. F.; Snyder, R.; Matsumiya, H.; Nagaoka, S.

    1996-01-01

    In this report we describe the results of a continuous flow electrophoresis (CFE) experiment done on STS-65 in which we tested the idea that intracellular growth hormone (GH) particles contained in a cell lysate prepared from cultured rat anterior pituitary cells in microgravity might have different electrophoretic mobilities from those in a synchronous ground control cell lysate. Collectively, the results suggested that CFE processing in microgravity was better than on earth; more samples could be processed at a time (6 x) and more variant forms of GH molecules could be resolved as well. We had also hoped to carry out a pituitary cell CFE experiment, but failure of the hardware required that the actual cell electrophoresis trials be done on earth shortly after Shuttle landing. Data from these experiments showed that space-flown cells possessed a higher electrophoretic mobility than ground control cells, thereby offering evidence for the idea that exposure of cultured cells to microgravity can change their net surface charge-density especially when the cells are fed. Collectively, the results from this pituitary cell experiment document the advantage of using coupled cell culture and CFE techniques in the microgravity environment.

  11. Stopped-flow DNA polymerase assay by continuous monitoring of dNTP incorporation by fluorescence.

    PubMed

    Montgomery, Jesse L; Rejali, Nick; Wittwer, Carl T

    2013-10-15

    DNA polymerase activity was measured by a stopped-flow assay that monitors polymerase extension using an intercalating dye. Double-stranded DNA formation during extension of a hairpin substrate was monitored at 75°C for 2 min. Rates were determined in nucleotides per second per molecule of polymerase (nt/s) and were linear with time and polymerase concentration from 1 to 50 nM. The concentrations of 15 available polymerases were quantified and their extension rates determined in 50 mM Tris, pH 8.3, 0.5 mg/ml BSA, 2 mM MgCl₂, and 200 μM each dNTP as well as their commercially recommended buffers. Native Taq polymerases had similar extension rates of 10-45 nt/s. Three alternative polymerases showed faster speeds, including KOD (76 nt/s), Klentaq I (101 nt/s), and KAPA2G (155 nt/s). Fusion polymerases including Herculase II and Phusion were relatively slow (3-13 nt/s). The pH optimum for Klentaq extension was between 8.5 and 8.7 with no effect of Tris concentration. Activity was directly correlated to the MgCl2 concentration and inversely correlated to the KCl concentration. This continuous assay is relevant to PCR and provides accurate measurement of polymerase activity using a defined template without the need of radiolabeled substrates. PMID:23872003

  12. Catheter ablation for ventricular tachyarrhythmias in patients supported by continuous-flow left ventricular assist devices.

    PubMed

    Garan, Arthur R; Iyer, Vivek; Whang, William; Mody, Kanika P; Yuzefpolskaya, Melana; Colombo, Paolo C; Te-Frey, Rosie; Takayama, Hiroo; Naka, Yoshifumi; Garan, Hasan; Jorde, Ulrich P; Uriel, Nir

    2014-01-01

    Ventricular arrhythmias (VAs) are common after implantation of a left ventricular assist device (LVAD) and in a subset of patients may be refractory to medication. Morbidity from VA in this population includes right ventricular failure (RVF). We sought to evaluate the efficacy of catheter ablation for VA in patients with LVAD. A retrospective analysis of patients supported by continuous-flow LVAD referred for catheter ablation of ventricular tachycardia (VT) between 2008 and the present was performed. Seven patients were referred for VT ablation an average of 236 ± 292 days after LVAD implantation. Three patients (42.9%) developed RVF in the setting of intractable arrhythmias. A transfemoral approach was used for six patients (85.7%) and an epicardial for one patient (14.3%). The clinical VT was inducible and successfully ablated in six patients (85.7%). The location of these arrhythmias was apical in three cases (42.9%). A total of 13 VTs were ablated in seven patients. Although the majority had reduction in VA frequency, recurrent VAs were observed in six patients (85.7%). One patient (14.3%) experienced a bleeding complication after the procedure. For patients with a high VA burden after LVAD implantation, VT ablation is safe and feasible, but VA frequently recurs. PMID:24614361

  13. Surgical Considerations and Challenges for Bilateral Continuous-Flow Durable Device Implantation.

    PubMed

    Maltais, Simon; Womack, Sara; Davis, Mary E; Danter, Matthew R; Kushwaha, Sudhir S; Stulak, John M; Haglund, Nicholas

    2016-01-01

    The concept of biventricular support with durable centrifugal pumps is evolving, and the surgical strategy and best practice guidelines for implantation of right-sided devices are still unknown. We present optimal strategy for bilateral HeartWare continuous-flow ventricular assist device (HVAD) implantation in a series of four patients. Patients were implanted with the HVAD pumps simultaneously or sequentially. This report offers a perspective on surgical considerations such as right ventricular positioning, implications related to potential risks of obstruction from the tricuspid apparatus, the role if any of downsizing the outflow anastomosis, and considerations for speed adjustments. In this series, one patient died on support and three patients experienced pump thrombosis requiring device revision. All other patients survived until orthotopic heart transplantation, although one of these patients died from perioperative complications, 2 days posttransplantation. Surgical management of patients with medically refractory biventricular heart failure remains challenging and associated with a high incidence of pump thrombosis. Best practice guidelines from experts' consensus are still needed to address this challenging population. PMID:26479465

  14. Segmentation of bone structures in 3D CT images based on continuous max-flow optimization

    NASA Astrophysics Data System (ADS)

    Pérez-Carrasco, J. A.; Acha-Piñero, B.; Serrano, C.

    2015-03-01

    In this paper an algorithm to carry out the automatic segmentation of bone structures in 3D CT images has been implemented. Automatic segmentation of bone structures is of special interest for radiologists and surgeons to analyze bone diseases or to plan some surgical interventions. This task is very complicated as bones usually present intensities overlapping with those of surrounding tissues. This overlapping is mainly due to the composition of bones and to the presence of some diseases such as Osteoarthritis, Osteoporosis, etc. Moreover, segmentation of bone structures is a very time-consuming task due to the 3D essence of the bones. Usually, this segmentation is implemented manually or with algorithms using simple techniques such as thresholding and thus providing bad results. In this paper gray information and 3D statistical information have been combined to be used as input to a continuous max-flow algorithm. Twenty CT images have been tested and different coefficients have been computed to assess the performance of our implementation. Dice and Sensitivity values above 0.91 and 0.97 respectively were obtained. A comparison with Level Sets and thresholding techniques has been carried out and our results outperformed them in terms of accuracy.

  15. Continuous-flow combined process of nitritation and ANAMMOX for treatment of landfill leachate.

    PubMed

    Wang, Zhong; Peng, Yongzhen; Miao, Lei; Cao, Tianhao; Zhang, Fangzhai; Wang, Shuying; Han, Jinhao

    2016-08-01

    Due to the difficulty in removing nitrogen from landfill leachate, a combined continuous-flow process of nitritation and anammox was applied to process mature leachate. The transformation rate of ammonia and nitrite accumulation ratio in A/O reactor were kept above 95% and 92% respectively through associated inhibition of free ammonia (FA) and free nitrous acid (FNA) to NOB. The total nitrogen volumetric load of anammox in an UASB reactor was brought up from 0.5kg/(m(3)·d) to 1.2kg/(m(3)·d) by gradually increasing influent substrate concentration and reducing hydraulic retention time (HRT). The results show that COD from mature leachate did not bring obvious inhibition effects to anammox. Under concentrations of influent ammonia and COD which were respectively 1330mg/L and 2250mg/L, the removal efficiencies of TN and COD reached 94% and 62% respectively. In the quantitative PCR reactions, the proportions occupied by AOB, NOB and anammox in A/O were 11.39%, 1.76% and 0.05% respectively; and proportions of those in UASB were 0.35%, 4.01% and 7.78% respectively. PMID:27176671

  16. Non-aerosol detection of explosives with a continuous flow immunosensor.

    PubMed

    Shriver-Lake, Lisa C; Charles, Paul T; Kusterbeck, Anne W

    2003-10-01

    Contamination of groundwater, soil, and the marine environment by explosives is a global issue. Identification, characterization and remediation are all required for a site recognized as contaminated with 2,4,6-trinitrotoluene (TNT) or hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). For each step, a method to accurately measure the contaminant level is needed. This paper reviews some of the current methods with emphasis on a single biosensor developed in our laboratory. Current regulatory methods require samples to be sent off-site to a certified laboratory resulting in time delays up to a month. A continuous flow biosensor for detection of explosives has been developed and tested for the rapid field screening of environmental samples. The detection system is based on a displacement immunoassay in which monoclonal antibodies to (TNT) and RDX are immobilized on solid substrates, allowed to bind fluorescently labeled antigens, and then exposed to explosives in aqueous samples. Explosive compounds present in the sample displace proportional amounts of the fluorescent label, which can then be measured to determine the original TNT or RDX concentration. The system can accurately detect ppb to ppt levels of explosives in groundwater or seawater samples and in extracts of contaminated soil. The biosensor has applications in environmental monitoring at remediation sites or in the location of underwater unexploded ordnance. PMID:12920500

  17. Micropatterned fluid lipid bilayer arrays created using a continuous flow microspotter.

    PubMed

    Smith, Kathryn A; Gale, Bruce K; Conboy, John C

    2008-11-01

    We have developed a new method for creating micropatterned lipid bilayer arrays (MLBAs) using a 3D microfluidic system. An array of fluid lipid membranes was patterned onto a glass substrate using a Continuous Flow Microspotter. Fluorescence microscopy experiments were used to verify the formation of a bilayer structure on the glass substrate. Fluorescence recovery after photobleaching experiments demonstrated the bilayers' fluidity was maintained while being individually corralled on the substrate. The reproducibility of bilayer formation within an array was demonstrated by the linear response of membrane fluorescence versus mol % rhodamine functionalized lipids incorporated into the vesicles prior to fusion to the surface. The highly customizable nature of the MLBAs was demonstrated utilizing three different fluorescently labeled lipids to generate a multiple component lipid array. Finally, the cholera toxin B/ganglioside GM 1, antidinitrophenyl (DNP) antibody/DNP, and NeutrAvidin/biotin protein-ligand systems were used to model multiple protein-ligand binding on the MLBAs. The multicomponent patterned bilayers were functionalized with GM 1, DNP, and biotin lipids, and binding curves was generated by recording surface fluorescence versus increasing concentration of membrane bound ligands. PMID:18841940

  18. Micropatterned Fluid Lipid Bilayer Arrays Created Using a Continuous Flow Microspotter

    PubMed Central

    Smith, Kathryn A.; Gale, Bruce K.; Conboy, John C.

    2010-01-01

    We have developed a new method for creating micropatterned lipid bilayer arrays (MLBAs) using a 3D microfluidic system. An array of fluid lipid membranes was patterned onto a glass substrate using a Continuous Flow Microspotter™ (CFM). Fluorescence microscopy experiments were used to verify the formation of a bilayer structure on the glass substrate. Fluorescence recovery after photobleaching (FRAP) experiments demonstrated the bilayers fluidity was maintained while being individually corralled on the substrate. The reproducibility of bilayer formation within an array was demonstrated by the linear response of membrane fluorescence versus mol % rhodamine functionalized lipids incorporated into the vesicles prior to fusion to the surface. The highly customizable nature of the MLBAs was demonstrated utilizing three different fluorescently labeled lipids to generate a multiple component lipid array. Finally, the cholera toxin B (CTB)/ganglioside GM1, anti-dinitrophenyl (DNP) antibody/DNP and NeutrAvidin/biotin protein-ligand systems were used to model multiple protein-ligand binding on the MLBAs. The multi-component patterned bilayers were functionalized with GM1, DNP and biotin lipids and binding curves was generated by recording surface fluorescence versus increasing concentration of membrane bound ligands. PMID:18841940

  19. Sirolimus formulation with improved pharmacokinetic properties produced by a continuous flow method.

    PubMed

    Solymosi, Tamás; Angi, Réka; Basa-Dénes, Orsolya; Ránky, Soma; Ötvös, Zsolt; Glavinas, Hristos; Filipcsei, Genovéva; Heltovics, Gábor

    2015-08-01

    The oral bioavailability of Sirolimus is limited by poor dissolution of the compound in the gastrointestinal tract resulting in a low bioavailability and large inter-individual differences in blood levels. Several different formulation approaches were applied to overcome these disadvantageous pharmacokinetic properties including the marketed oral solution and a tablet form containing wet milled nanocrystals. These approaches deliver improved pharmacokinetics, yet, they share the characteristics of complex production method and composition. We have developed a nanostructured Sirolimus formulation prepared by the controlled continuous flow precipitation of the compound from its solution in the presence of stabilizers. We have shown that contrary to the batch production the process could be easily intensified and scaled up; apparently the uniformity of the precipitation is heavily dependent on the production parameters, most likely the mixing of the solvent and antisolvent. We compared the physicochemical and pharmacokinetic properties of the nanostructured formula with the marketed nanoformula. We found that our method produces particles in the size range of less than 100nm. The solid form redispersed instantaneously in water and in biorelevant media. Both the solid form and the redispersed colloid solution showed excellent stability even in accelerated test conditions. The oral administration of the nanostructured formula resulted in faster absorption, higher exposure and higher trough concentrations when compared to the marked form. These advantageous properties could allow the development of solid oral Sirolimus formulae with lower strength and gel based topical delivery systems. PMID:26003815

  20. Temperature measurements with two different IR sensors in a continuous-flow microwave heated system.

    PubMed

    Rydfjord, Jonas; Svensson, Fredrik; Fagrell, Magnus; Sävmarker, Jonas; Thulin, Måns; Larhed, Mats

    2013-01-01

    In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field will influence most traditional methods of temperature measurement. Thus, we used a microwave transparent fiber optic probe, capable of measuring the temperature inside the reactor, and investigated two different IR sensors as non-contact alternatives to the internal probe. IR sensor 1 measures the temperature on the outside of the reactor whilst IR sensor 2 is designed to measure the temperature of the fluid through the borosilicate glass that constitutes the reactor wall. We have also, in addition to the characterization of the before mentioned IR sensors, developed statistical models to correlate the IR sensor reading to a correct value of the inner temperature (as determined by the internal fiber optic probe), thereby providing a non-contact, indirect, temperature assessment of the heated solvent. The accuracy achieved with these models lie well within the range desired for most synthetic chemistry applications. PMID:24204419