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Sample records for continuous aortic flow

  1. Is a Bioprosthetic Valve in the Aortic Position Desirable with a Continuous Flow LVAD?

    PubMed

    Doi, Atsuo; Marasco, Silvana F; McGiffin, David C

    2015-05-01

    Commissural fusion of the native aortic valve in a patient with a continuous flow left ventricular assist device (LVAD) is a known phenomenon. This may result in aortic insufficiency (AI) leading to symptomatic heart failure. In patients with AI at the time of LVAD implantation, repairing, or replacing the aortic valve is advisable. We describe a patient who had a severe dilated cardiomyopathy and moderate AI who underwent implantation of an LVAD and aortic valve replacement with a bioprosthesis that subsequently developed commissural fusion which was found at the time of heart transplantation. This case highlights the conundrum of the management of AI in patients requiring LVAD support.

  2. VASCULAR INFLAMMATION AND ABNORMAL AORTIC HISTOMORPHOMETRY IN PATIENTS FOLLOWING PULSATILE AND CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICE PLACEMENT

    PubMed Central

    Lee, Mike; Akashi, Hirokazu; Kato, Tomoko S.; Takayama, Hiroo; Wu, Christina; Xu, Katherine; Collado, Elias; Weber, Matthew P.; Kennel, Peter J.; Brunjes, Danielle L; Ji, Ruiping; Naka, Yoshifumi; George, Isaac; Mancini, Donna; Farr, Maryjane; Schulze, P. Christian

    2017-01-01

    Objective Left ventricular assist devices are increasingly used in patients with advanced heart failure as both destination therapy and bridge-to-transplantation. We aimed to analyze histomorphometric, structural and inflammatory changes following pulsatile and continuous flow left ventricular assist device placement. Method Clinical and echocardiographic data were collected from medical records. Aortic wall diameter, cellularity and inflammation were assessed by immunohistochemistry on aortic tissue collected at left ventricular assist device placement and at explantation during heart transplantation. Expression of adhesion molecules was quantified by western blot. Results Decellularization of the aortic tunica media was observed in patients receiving continuous flow support. Both device types showed an increased inflammatory response following left ventricular assist device placement with variable T cell and macrophage accumulations and increased expression of vascular E-selectin, ICAM and VCAM in the aortic wall. Conclusion Left ventricular assist device implantation is associated with distinct vascular derangements with development of vascular inflammation. These changes are pronounced in patients on continuous flow left ventricular assist and associated with aortic media decellularization. These findings help to explain the progressive aortic root dilation and vascular dysfunction in patients following continuous flow device placement. PMID:26899764

  3. 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

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

    PubMed

    Moore, Brandon L; Dasi, Lakshmi Prasad

    2015-09-01

    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.

  5. Flow in an Aortic Coarctation

    NASA Astrophysics Data System (ADS)

    Loma, Luis; Miller, Paul; Hertzberg, Jean

    2009-11-01

    Coarctation of the aorta is a congenital cardiovascular defect that causes a constriction in the descending thoracic aorta. To gain a better understanding of the cause of post-surgical problems, a rigid glass and a compliant in vitro model of the aortic arch and descending aorta with a coarctation were constructed. Near-physiologic compliance was obtained using a silicone elastomer. Stereoscopic PIV was used to obtain 3D velocity maps. Results show a high speed turbulent jet formed at the exit of the coarctation. Flow in the rigid model was significantly different from in the compliant model. In the rigid model, the jet was symmetric, creating a toroidal recirculation area. In the compliant model, the jet was directed towards the medial wall, inducing flow reversal only at the lateral wall. Peak velocities and turbulence intensities were higher in the rigid model, however shear rate values in the compliant model were significantly above both the rigid model and normal in vivo values at the medial wall. In both models the reattachment region fluctuated, creating oscillatory shear.

  6. 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.

  7. Effects of aortic irregularities on blood flow.

    PubMed

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

    2016-04-01

    Anatomic aortic anomalies are seen in many medical conditions and are known to cause disturbances in blood flow. Turner syndrome (TS) is a genetic disorder occurring only in females where cardiovascular anomalies, particularly of the aorta, are frequently encountered. In this study, numerical simulations are applied to investigate the flow characteristics in four TS patient- related aortic arches (a normal geometry, dilatation, coarctation and elongation of the transverse aorta). The Quemada viscosity model was applied to account for the non-Newtonian behavior of blood. The blood is treated as a mixture consisting of water and red blood cells (RBC) where the RBCs are modeled as a convected scalar. The results show clear geometry effects where the flow structures and RBC distribution are significantly different between the aortas. Transitional flow is observed as a jet is formed due to a constriction in the descending aorta for the coarctation case. RBC dilution is found to vary between the aortas, influencing the WSS. Moreover, the local variations in RBC volume fraction may induce large viscosity variations, stressing the importance of accounting for the non-Newtonian effects.

  8. 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.

  9. Chaotic flow in an aortic aneurysm

    NASA Astrophysics Data System (ADS)

    Parashar, Abhinav; Singh, Rahul; Panigrahi, P. K.; Muralidhar, K.

    2013-06-01

    Oscillatory flow in straight and deformed geometries is seen in various biomedical applications. The nature of flow plays a significant role in the pathogenesis of an abdominal aortic aneurysm. The present study examines the onset of chaotic flow inside a bulged tube under oscillating flow conditions. An experimental facility is set up for generating the oscillatory flow field inside the model. A fusiform shaped model is hollowed out in a rectangular silicone model. A mixture of water and glycerin is used as the working liquid. Two-camera imaging system placed at right angles is used for three-component velocity measurement of a spherical particle inside the model. Images recorded as a time sequence are analyzed by a particle tracking algorithm. The particle trajectories in space and instantaneous velocities within the bulge have been obtained from experiments as well as numerical simulation. The frequency of oscillation considered is 1.2 Hz and the peak Reynolds numbers are in the range of 650-1200 (experiments) and 1000-3500 (simulation). The dimensionless frequency defined by the Womersely number is in the range of 10-12. Velocity signals obtained from the experiment have been analyzed to study chaotic behavior of fluid flow. Chaos is quantified in terms of the largest Lyapunov exponent, positive values being a signature of chaos. The Lyapunov exponent increases with Reynolds number and is significantly higher in the bulged geometry compared to that of the straight tube. The signature of chaotic flow is also seen in power spectra and Poincaré plots.

  10. Myocardial blood flow during induced aortic hypertension in dogs

    SciTech Connect

    Thai, B.N.; Levesque, M.J.; Nerem, R.M.

    1986-03-01

    Myocardial blood flow was measured in anesthetized dogs during control conditions and under conditions where the aortic pressure was increased due to aortic constriction or during infusion. Blood flow was measured using the radioactive microsphere technique. Radioactive microspheres (15 m Ce-141, Sr-85, and Sc-46) were injected under control, aortic constriction and arterenol infusion in four dogs and under control conditions in two others. All microsphere injections were performed under stabilized conditions. It was found that coronary blood flow rose by 80% during aortic constriction and by 158% during arterenol infusion (P < 0.05). This increase in blood flow was not uniform throughout the heart, and higher increases were observed in the middle and apex regions of the left ventricle. Furthermore, under hypertension the increase in blood flow in LAD (left anterior descending) perfused territories was slightly higher than that in CFX (left circumflex) perfused territories.

  11. Effects of increasing flow rate on aortic stenotic indices: evidence from percutaneous transvenous balloon dilatation of the mitral valve in patients with combined aortic and mitral stenosis.

    PubMed Central

    Lee, T. M.; Su, S. F.; Chen, M. F.; Liau, C. S.; Lee, Y. T.

    1996-01-01

    OBJECTIVES: To investigate the effects of transvalvar flow rate on aortic valve resistance and valve area after percutaneous transvenous balloon dilatation of the mitral valve in a homogeneous group of patients with rheumatic heart disease. DESIGN: Retrospective analysis of 12 patients with combined aortic and mitral stenosis who had undergone balloon dilatation of the mitral valve over a period of 9 years. SETTING: Tertiary referral centre. PATIENTS: Twelve (8 women, 4 men; mean (SD) age 37 (9) of 227 consecutive patients with critical mitral stenosis undergoing transvenous balloon dilation of the mitral valve in the centre also had aortic stenosis, defined as a transaortic pressure gradient of more than 25 mm Hg measured at a catheterisation study before valvuloplasty. INTERVENTIONS: Echocardiographic variables (mitral valve area measured by the pressure half-time method and planimetry, and the aortic valve area derived from the continuity equation) and haemodynamic measurements (cardiac output, left ventricular mean systolic pressure, aortic mean pressure, transaortic valve pressure gradient, mitral valve and aortic valve areas derived from the Gorlin formula, and aortic valve resistance) were assessed before and after transvenous balloon dilatation of the mitral valve. Follow up catheterisation to measure haemodynamic variables was performed one week after mitral valvuloplasty. RESULTS: Mean transaortic flow rate increased 33% after mitral valvuloplasty (from 198 (68) to 254 (41) ml/s, P = 0.002). Aortic valve areas derived from the Gorlin formula were significantly increased from 0.57 (0.12) to 0.73 (0.14) cm2 (P = 0.006) after mitral valvuloplasty. However, aortic valve area and valve resistance derived from the continuity equation were independent of the increase in flow rate after mitral valvuloplasty (from 1.29 (0.35) to 1.30 (0.29) cm2 and from 317 (65) to 259 (75) dyn.s.cm-5, both P = NS). CONCLUSION: The Gorlin-derived aortic valve area tends to be flow

  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.

  13. 4D Flow MRI in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity

    PubMed Central

    Lorenz, R.; Bock, J.; Barker, A. J.; von Knobelsdorff-Brenkenhoff, F.; Wallis, W.; Korvink, J. G.; Bissell, M. M.; Schulz-Menger, J.; Markl, M.

    2013-01-01

    Purpose Changes in aortic geometry or presence of aortic valve disease can result in substantially altered aortic hemodynamics. Dilatation of the ascending aorta or aortic valve abnormalities can result in an increase in helical flow. Methods 4D flow MRI was used to test the feasibility of quantitative helicity analysis using equidistantly distributed 2D planes along the entire aorta. The evaluation of the method included three parts: 1) the quantification of helicity in 12 healthy subjects, 2) an evaluation of observer variability and test-retest reliability, and 3) the quantification of helical flow in 16 patients with congenitally altered bicuspid aortic valves. Results Helicity quantification in healthy subjects revealed consistent directions of flow rotation along the entire aorta with high clockwise helicity in the aortic arch and an opposite rotation sense in the ascending and descending aorta. The results demonstrated good scan-rescan and inter- and intra-observer agreement of the helicity parameters. Helicity quantification in patients revealed a significant increase of absolute peak relative helicity during systole and a considerably greater heterogeneous distribution of mean helicity in the aorta. Conclusion The method has the potential to serve as a reference distribution for comparisons of helical flow between healthy subjects and patients or between different patient groups. PMID:23716466

  14. 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

  15. 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

  16. 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

  17. Obstetric analgesia and fetal aortic blood flow during labour.

    PubMed

    Lindblad, A; Bernow, J; Marsál, K

    1987-04-01

    Fetal aortic blood flow was studied in 50 women during labour, using a method combining real-time ultrasonography and a pulsed Doppler technique. Eleven women had no analgesia, 24 women received 75-100 mg pethidine intramuscularly, 12 epidural analgesia with 0.25% bupivacaine and three paracervical block with 0.125% bupivacaine. Fetal aortic blood flow increased during labour from 200 to 245 ml/min/kg in the group without analgesia (P less than 0.05) and from 211 to 236 ml/min/kg in the group with epidural analgesia (P less than 0.05) but decreased insignificantly from 216 to 204 ml/min/kg after pethidine. After paracervical block the aortic blood flow fell in two out of three fetuses. Not only is epidural analgesia the most effective means of pain relief during labour, it is also the type of obstetric analgesia that interferes least with the physiological response to labour in terms of its effect on the fetal blood flow.

  18. 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.

  19. Continuous information flow fluctuations

    NASA Astrophysics Data System (ADS)

    Rosinberg, Martin Luc; Horowitz, Jordan M.

    2016-10-01

    Information plays a pivotal role in the thermodynamics of nonequilibrium processes with feedback. However, much remains to be learned about the nature of information fluctuations in small-scale devices and their relation with fluctuations in other thermodynamics quantities, like heat and work. Here we derive a series of fluctuation theorems for information flow and partial entropy production in a Brownian particle model of feedback cooling and extend them to arbitrary driven diffusion processes. We then analyze the long-time behavior of the feedback-cooling model in detail. Our results provide insights into the structure and origin of large deviations of information and thermodynamic quantities in autonomous Maxwell's demons.

  20. 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.

  1. 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.

  2. Complications of Continuous-Flow Mechanical Circulatory Support Devices

    PubMed Central

    Patel, Harsh; Madanieh, Raef; Kosmas, Constantine E; Vatti, Satya K; Vittorio, Timothy J

    2015-01-01

    Left ventricular assist devices (LVADs), more importantly the continuous-flow subclass, have revolutionized the medical field by improving New York Heart Association (NYHA) functional class status, quality of life, and survival rates in patients with advanced systolic heart failure. From the first pulsatile device to modern day continuous-flow devices, LVADs have continued to improve, but they are still associated with several complications. These complications include infection, bleeding, thrombosis, hemolysis, aortic valvular dysfunction, right heart failure, and ventricular arrhythmias. In this article, we aim to review these complications to understand the most appropriate approach for their prevention and to discuss the available therapeutic modalities. PMID:26052234

  3. Does altered aortic flow in marfan syndrome relate to aortic root dilatation?

    PubMed Central

    Wang, Hung‐Hsuan; Chiu, Hsin‐Hui; Tseng, Wen‐Yih Isaac

    2016-01-01

    Purpose To examine possible hemodynamic alterations in adolescent to adult Marfan syndrome (MFS) patients with aortic root dilatation. Materials and Methods Four‐dimensional flow MRI was performed in 20 MFS patients and 12 age‐matched normal subjects with a 3T system. The cross‐sectional areas of 10 planes along the aorta were segmented for calculating the axial and circumferential wall shear stress (WSSaxial, WSScirc), oscillatory shear index (OSIaxial, OSIcirc), and the nonroundness (NR), presenting the asymmetry of segmental WSS. Pearson's correlation analysis was performed to present the correlations between the quantified indices and the body surface area (BSA), aortic root diameter (ARD), and Z score of the ARD. P < 0.05 indicated statistical significance. Results Patients exhibited lower WSSaxial in the aortic root and the WSScirc in the arch (P < 0.05–0.001). MFS patients exhibited higher OSIaxial and OSIcirc in the sinotubular junction and arch, but lower OSIcirc in the descending aorta (all P < 0.05). The NR values were lower in patients (P < 0.05). The WSSaxial or WSScirc exhibited moderate to strong correlations with BSA, ARD, or Z score (R2 = 0.50–0.72) in MFS patients. Conclusion The significant differences in the quantified indices, which were associated with BSA, ARD, or Z score, in MFS were opposite to previous reports for younger MFS patients, indicating that altered flows in MFS patients may depend on the disease progress. The possible time dependency of hemodynamic alterations in MFS patients strongly suggests that longitudinal follow‐up of 4D Flow is needed to comprehend disease progress. J. Magn. Reson. Imaging 2016;44:500–508. PMID:26854646

  4. Influence of Beta-Blocker Therapy on Aortic Blood Flow in Patients with Bicuspid Aortic Valve

    PubMed Central

    Allen, Bradley D.; Markl, Michael; Barker, Alex J.; van Ooij, Pim; Carr, James C.; Malaisrie, S Chris; McCarthy, Patrick; Bonow, Robert O.; Kansal, Preeti

    2016-01-01

    Purpose In patients with bicuspid aortic valve (BAV), beta-blockers (BB) are assumed to slow ascending aorta (AAo) dilation by reducing wall shear stress (WSS) on the aneurysmal segment. The aim of this study was to assess differences in AAo peak velocity and WSS in BAV patients with and without BB therapy. Methods BAV patients receiving BB (BB+, n=30, age:47±11 years) or not on BB (BB−, n=30, age:46±13 years) and healthy controls (n=15, age:43±11 years) underwent 4D flow MRI for the assessment of in-vivo aortic 3D blood flow. Peak systolic velocities and 3D WSS were calculated at the anterior and posterior walls of the AAo. Results Both patient groups had higher maximum and mean WSS relative to the control group (p=0.001 to p=0.04). WSS was not reduced in the BB+ group compared to BB− patients in the anterior AAo (maximum: 1.49±0.47N/m2 vs. 1.38±0.49N/m2, p=0.99, mean: 0.76±0.2N/m2 vs. 0.74±0.18N/m2, p=1.00) or posterior AAo (maximum: 1.45±0.42N/m2 vs. 1.39±0.58N/m2, p=1.00; mean: 0.65±0.16N/m2 vs. 0.63±0.16N/m2, p=1.00). AAo peak velocity was elevated in patients compared to controls (p<0.01) but similar for BB+ and BB− groups (p=0.42). Linear models identified significant relationships between aortic stenosis severity and increased maximum WSS (β=0.186, p=0.007) and between diameter at the sinus of Valsalva and reduced mean WSS (β=−0.151, p=0.045). Conclusions Peak velocity and systolic WSS were similar for BAV patients irrespective of BB therapy. Further prospective studies are needed to investigate the impact of dosage and duration of BB therapy on aortic hemodynamics and development of aortopathy. PMID:26817758

  5. Influence of beta-blocker therapy on aortic blood flow in patients with bicuspid aortic valve.

    PubMed

    Allen, Bradley D; Markl, Michael; Barker, Alex J; van Ooij, Pim; Carr, James C; Malaisrie, S Chris; McCarthy, Patrick; Bonow, Robert O; Kansal, Preeti

    2016-04-01

    In patients with bicuspid aortic valve (BAV), beta-blockers (BB) are assumed to slow ascending aorta (AAo) dilation by reducing wall shear stress (WSS) on the aneurysmal segment. The aim of this study was to assess differences in AAo peak velocity and WSS in BAV patients with and without BB therapy. BAV patients receiving BB (BB+, n = 30, age: 47 ± 11 years) or not on BB (BB-, n = 30, age: 46 ± 13 years) and healthy controls (n = 15, age: 43 ± 11 years) underwent 4D flow MRI for the assessment of in vivo aortic 3D blood flow. Peak systolic velocities and 3D WSS were calculated at the anterior and posterior walls of the AAo. Both patient groups had higher maximum and mean WSS relative to the control group (p = 0.001 to p = 0.04). WSS was not reduced in the BB+ group compared to BB- patients in the anterior AAo (maximum: 1.49 ± 0.47 vs. 1.38 ± 0.49 N/m(2), p = 0.99, mean: 0.76 ± 0.2 vs. 0.74 ± 0.18 N/m(2), p = 1.00) or posterior AAo (maximum: 1.45 ± 0.42 vs. 1.39 ± 0.58 N/m(2), p = 1.00; mean: 0.65 ± 0.16 vs. 0.63 ± 0.16 N/m(2), p = 1.00). AAo peak velocity was elevated in patients compared to controls (p < 0.01) but similar for BB+ and BB- groups (p = 0.42). Linear models identified significant relationships between aortic stenosis severity and increased maximum WSS (β = 0.186, p = 0.007) and between diameter at the sinus of Valsalva and reduced mean WSS (β = -0.151, p = 0.045). Peak velocity and systolic WSS were similar for BAV patients irrespective of BB therapy. Further prospective studies are needed to investigate the impact of dosage and duration of BB therapy on aortic hemodynamics and development of aortopathy.

  6. Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

    PubMed Central

    von Knobelsdorff-Brenkenhoff, Florian; Karunaharamoorthy, Achudhan; Trauzeddel, Ralf Felix; Barker, Alex J; Blaszczyk, Edyta; Markl, Michael; Schulz-Menger, Jeanette

    2016-01-01

    Background Aortic stenosis (AS) leads to variable stress for the left ventricle (LV) and consequently a broad range of LV remodeling. Study aim was to describe blood flow patterns in the ascending aorta of AS patients and determine their association with remodeling. Methods and Results Thirty-seven patients with AS (14 mild, 8 moderate, 15 severe; age 63±13 years) and 37 healthy controls (age 60±10 years) underwent 4D-flow MRI. Helical and vortical flow formations and flow eccentricity were assessed in the ascending aorta. Normalized flow displacement from the vessel center and peak systolic wall shear stress (WSSpeak) in the ascending aorta were quantified. LV remodeling was assessed based on LV mass index (LVMI-I) and the ratio of LV mass to enddiastolic volume (relative wall mass; RWM). Marked helical and vortical flow formation and eccentricity were more prevalent in patients with AS than in healthy subjects, and AS patients exhibited an asymmetric and elevated distribution of WSSpeak. In AS, aortic orifice area was strongly negatively associated with vortical flow formation (p=0.0274), eccentricity (p=0.0070) and flow displacement (p=0.0021). Bicuspid aortic valve was associated with more intense helical (p=0.0098) and vortical flow formation (p=0.0536), higher flow displacement (p=0.11) and higher WSSpeak (p=0.0926). LVM-I and RWM were significantly associated with aortic orifice area (p=0.0611, p=0.0058) and flow displacement (p=0.0058, p=0.0283). Conclusions In this pilot study, AS leads to abnormal blood flow pattern and WSSpeak in the ascending aorta. In addition to aortic orifice area, normalized flow displacement was significantly associated with LV remodeling. PMID:26917824

  7. Flow dynamics of stenotic aortic valves assessed by signal processing of Doppler spectrograms.

    PubMed

    Bermejo, J; Antoranz, J C; García-Fernández, M A; Moreno, M M; Delcán, J L

    2000-03-01

    Clinical assessment of aortic stenosis (AS) is sometimes challenging, because all hemodynamic indexes of severity are modified by flow rate. However, the mechanisms underlying flow dependence remain controversial. Analysis of instantaneous flow dynamics has provided crucial information in a number of cardiovascular disorders and may add new insight into this phenomenon. This study was designed to analyze in vivo the effects of flow interventions on instantaneous valvular dynamics of stenotic valves. For this purpose, a custom algorithm for signal processing of Doppler spectrograms was developed and validated against a control population. Digital Doppler recordings at the aortic valve and left ventricular outflow tract were obtained in 15 patients with AS, at baseline and during low-dose dobutamine infusion; 10 normal subjects were studied as controls. Spectrograms were processed by signal averaging, time alignment, modal-velocity enhancement, envelope tracing, and numerical interpolation. Instantaneous relative aortic valve area (rAVA) was obtained by the continuity equation and plotted against normalized ejection time. Curves were classified as either type A (rapid, early-systolic opening) or type B (slow, end-systolic opening). Curves from controls closely matched prior knowledge of normal valve dynamics, but curves from patients were clearly different: all controls except 2 (80%) had type A, whereas all patients except 3 (80%) had a type B pattern (p = 0.03). Dobutamine infusion in patients increased and slightly anticipated peak rAVA by accelerating valve opening. Despite similar values of area and pressure difference, type B dynamics were associated with lower blood pressure (p = 0.01) and worse long-term outcome (>3 years) than type A flow dynamics (p = 0.02). Signal processing of Doppler spectrograms allows a comprehensive assessment of aortic flow dynamics. Differences in timing of valve aperture and in maximal leaflet excursion account for flow

  8. The effect of flow recirculation on abdominal aortic aneurysm

    NASA Astrophysics Data System (ADS)

    Taib, Ishkrizat; Amirnordin, Shahrin Hisham; Madon, Rais Hanizam; Mustafa, Norrizal; Osman, Kahar

    2012-06-01

    The presences of flow recirculation at the abdominal aortic aneurysm (AAA) region yield the unpredictable failure of aneurismal wall. The failure of the aneurismal wall is closely related to the hemodynamic factor. Hemodynamic factor such as pressure and velocity distribution play a significance role of aneurysm growth and rupture. By using the computational approach, the influence of hemodynamic factor is investigated using computational fluid dynamic (CFD) method on the virtual AAA model. The virtual 3D AAAs model was reconstructed from Spiral Computed Tomography scan (CT-scan). The blood flow is assumed as being transient, laminar and Newtonian within a rigid section of the vessel. The blood flow also driven by an imposed of pressure gradient in the form of physiological waveform. The pulsating blood flow is also considered in this simulation. The results on pressure distribution and velocity profile are analyzed to interpret the behaviour of flow recirculation. The results show the forming of vortices is seen at the aneurysm bulge. This vortices is form at the aneurysm region then destroyed rapidly by flow recirculation. Flow recirculation is point out much higher at distal end of aneurysm closed to iliac bifurcation. This phenomenon is managed to increase the possibility of aneurysm growth and rupture.

  9. 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.

  10. Abnormal distribution of pulmonary blood flow in aortic valve disease

    PubMed Central

    Goodenday, Lucy S.; Simon, George; Craig, Hazel; Dalby, Lola

    1970-01-01

    Wasted ventilatory volume (VD) and its ratio to tidal volume (VD/VT) were measured at rest and during exertion in 17 patients with aortic valve disease. We considered VD/VT to indicate abnormal ventilation: perfusion relations if it did not decrease on exertion, or if the exercising value was greater than 40 per cent. Plain chest radiographs were independently examined for evidence of diversion of pulmonary blood to the upper lobes. There was significant agreement (p<0·05) between radiographic and pulmonary function estimations of abnormality. This suggests that the raised pulmonary venous pressure associated with left ventricular failure creates an abnormal pattern of blood flow through the lung, which is responsible for causing inadequate perfusion with respect to ventilation. Images PMID:5420086

  11. Aortic stiffness determines diastolic blood flow reversal in the descending thoracic aorta: potential implication for retrograde embolic stroke in hypertension.

    PubMed

    Hashimoto, Junichiro; Ito, Sadayoshi

    2013-09-01

    Aortic stiffening often precedes cardiovascular diseases, including stroke, but the underlying pathophysiological mechanisms remain obscure. We hypothesized that such abnormalities could be attributable to altered central blood flow dynamics. In 296 patients with uncomplicated hypertension, Doppler velocity pulse waveforms were recorded at the proximal descending aorta and carotid artery to calculate the reverse/forward flow ratio and diastolic/systolic flow index, respectively. Tonometric waveforms were recorded on the radial artery to estimate aortic pressure and characteristic impedance (Z0) and to determine carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities. In all subjects, the aortic flow waveform was bidirectional, comprising systolic forward and diastolic reverse flows. The aortic reverse/forward flow ratio (35 ± 10%) was positively associated with parameters of aortic stiffness (including pulse wave velocity, Z0, and aortic/peripheral pulse wave velocity ratio), independent of age, body mass index, aortic diameter, and aortic pressure. The carotid flow waveform was unidirectional and bimodal with systolic and diastolic maximal peaks. There was a positive relationship between the carotid diastolic/systolic flow index (28 ± 9%) and aortic reverse/forward flow ratio, which remained significant after adjustment for aortic stiffness and other related parameters. The Bland-Altman plots showed a close time correspondence between aortic reverse and carotid diastolic flow peaks. In conclusion, aortic stiffness determines the extent of flow reversal from the descending aorta to the aortic arch, which contributes to the diastolic antegrade flow into the carotid artery. This hemodynamic relationship constitutes a potential mechanism linking increased aortic stiffness, altered flow dynamics, and increased stroke risk in hypertension.

  12. Continuous flow dielectrophoretic particle concentrator

    SciTech Connect

    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.

  13. Thermodynamics with Continuous Information Flow

    NASA Astrophysics Data System (ADS)

    Horowitz, Jordan M.; Esposito, Massimiliano

    2014-07-01

    We provide a unified thermodynamic formalism describing information transfers in autonomous as well as nonautonomous systems described by stochastic thermodynamics. We demonstrate how information is continuously generated in an auxiliary system and then transferred to a relevant system that can utilize it to fuel otherwise impossible processes. Indeed, while the joint system satisfies the second law, the entropy balance for the relevant system is modified by an information term related to the mutual information rate between the two systems. We show that many important results previously derived for nonautonomous Maxwell demons can be recovered from our formalism and use a cycle decomposition to analyze the continuous information flow in autonomous systems operating at a steady state. A model system is used to illustrate our findings.

  14. 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.

  15. 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.

  16. 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.

  17. Direct numerical simulation of a 2D-stented aortic heart valve at physiological flow rates.

    PubMed

    Dimakopoulos, Y; Bogaerds, A C B; Anderson, P D; Hulsen, M A; Baaijens, F P T

    2012-01-01

    We study the nonlinear interaction of an aortic heart valve, composed of hyperelastic corrugated leaflets of finite density attached to a stented vessel under physiological flow conditions. In our numerical simulations, we use a 2D idealised representation of this arrangement. Blood flow is caused by a time-varying pressure gradient that mimics that of the aortic valve and corresponds to a peak Reynolds number equal to 4050. Here, we fully account for the shear-thinning behaviour of the blood and large deformations and contact between the leaflets by solving the momentum and mass balances for blood and leaflets. The mixed finite element/Galerkin method along with linear discontinuous Lagrange multipliers for coupling the fluid and elastic domains is adopted. Moreover, a series of challenging numerical issues such as the finite length of the computational domain and the conditions that should be imposed on its inflow/outflow boundaries, the accurate time integration of the parabolic and hyperbolic momentum equations, the contact between the leaflets and the non-conforming mesh refinement in part of the domain are successfully resolved. Calculations for the velocity and the shear stress fields of the blood reveal that boundary layers appear on both sides of a leaflet. The one along the ventricular side transfers blood with high momentum from the core region of the vessel to the annulus or the sinusoidal expansion, causing the continuous development of flow instabilities. At peak systole, vortices are convected in the flow direction along the annulus of the vessel, whereas during the closure stage of the valve, an extremely large vortex develops in each half of the flow domain.

  18. Assessment of baroreflex sensitivity by continuous noninvasive monitoring of peripheral and central aortic pressure.

    PubMed

    Kouchaki, Zahra; Butlin, Mark; Qasem, Ahmed; Avolio, Alberto P

    2014-01-01

    Noninvasive assessment of baroreceptor sensitivity (BRS) facilitates clinical investigation of autonomic function. The spontaneous sequence method estimates BRS using the continuous measurement of arterial pressure in the finger. Since the baroreceptors are centrally located (aortic arch, carotid arteries), this study assessed the use of a continuous aortic pressure signal derived from the peripheral pressure pulse to compute the BRS from changes in systolic pressure (SBP) and pulse interval (PI). BRS computed from central aortic (cBRS) and peripheral pressure (pBRS) was calculated in 12 healthy subjects (25-62 years, 7 females). The difference between pBRS and cBRS was calculated for four levels of pulse lags between changes in SBP and PI. For each lag and for the pooled data for all lags, cBRS was significantly correlated with pBRS (r(2)=0.82). The within subject difference ranged from -41.2% to 59.2%. This difference was not related to age, gender of hemodynamic parameters (systolic or diastolic pressure, heart rate, aortic pulse wave velocity). However 18.2% of the variance was due to the difference in the number of spontaneous pulse sequences used to determine values of cBRS and pBRS. The differences between pBRS and cBRS are in the range of values of BRS as those found, in other studies, to discriminate between patient groups with different levels of autonomic function. Findings of this study suggest that, given the heart rate dependent amplification of the arterial pressure pulse between the central aorta and the peripheral limbs, BRS determined from central aortic pressure derived from the peripheral pulse may provide an improved method for noninvasive assessment of baroreceptor function.

  19. Flow structure in continuous flow electrophoresis chambers

    NASA Technical Reports Server (NTRS)

    Deiber, J. A.; Saville, D. A.

    1982-01-01

    There are at least two ways that hydrodynamic processes can limit continiuous flow electrophoresis. One arises from the sensitivity of the flow to small temerature gradients, especially at low flow rates and power levels. This sensitivity can be suppressed, at least in principle, by providing a carefully tailored, stabilizing temperature gradient in the cooling system that surrounds the flow channel. At higher power levels another limitation arises due to a restructuring of the main flow. This restructuring is caused by buoyancy, which is in turn affected by the electro-osmotic crossflow. Approximate solutions to appropriate partial differential equations have been computed by finite difference methods. One set of results is described here to illustrate the strong coupling between the structure of the main (axial) flow and the electro-osmotic flow.

  20. Impairment of flow-mediated dilation correlates with aortic dilation in patients with Marfan syndrome.

    PubMed

    Takata, Munenori; Amiya, Eisuke; Watanabe, Masafumi; Omori, Kazuko; Imai, Yasushi; Fujita, Daishi; Nishimura, Hiroshi; Kato, Masayoshi; Morota, Tetsuro; Nawata, Kan; Ozeki, Atsuko; Watanabe, Aya; Kawarasaki, Shuichi; Hosoya, Yumiko; Nakao, Tomoko; Maemura, Koji; Nagai, Ryozo; Hirata, Yasunobu; Komuro, Issei

    2014-07-01

    Marfan syndrome is an inherited disorder characterized by genetic abnormality of microfibrillar connective tissue proteins. Endothelial dysfunction is thought to cause aortic dilation in subjects with a bicuspid aortic valve; however, the role of endothelial dysfunction and endothelial damaging factors has not been elucidated in Marfan syndrome. Flow-mediated dilation, a noninvasive measurement of endothelial function, was evaluated in 39 patients with Marfan syndrome. Aortic diameter was measured at the aortic annulus, aortic root at the sinus of Valsalva, sinotubular junction and ascending aorta by echocardiography, and adjusted for body surface area (BSA). The mean value of flow-mediated dilation was 6.5 ± 2.4 %. Flow-mediated dilation had a negative correlation with the diameter of the ascending thoracic aorta (AscAd)/BSA (R = -0.39, p = 0.020) and multivariate analysis revealed that flow-mediated dilation was an independent factor predicting AscAd/BSA, whereas other segments of the aorta had no association. Furthermore, Brinkman index had a somewhat greater influence on flow-mediated dilation (R = -0.42, p = 0.008). Although subjects who smoked tended to have a larger AscAd compared with non-smokers (AscA/BSA: 17.3 ± 1.8 versus 15.2 ± 3.0 mm/m(2), p = 0.013), there was no significant change in flow-mediated dilation, suggesting that smoking might affect aortic dilation via an independent pathway. Common atherogenic risks, such as impairment of flow-mediated dilation and smoking status, affected aortic dilation in subjects with Marfan syndrome.

  1. 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

  2. Paradoxical low flow aortic valve stenosis: incidence, evaluation, and clinical significance.

    PubMed

    Clavel, Marie-Annick; Pibarot, Philippe; Dumesnil, Jean G

    2014-01-01

    Paradoxical low-flow (PLF) aortic stenosis is defined by a stroke volume index <35 ml/m(2) despite the presence of preserved LV ejection fraction (≥ 50 %). This entity is typically characterized by pronounced LV concentric remodeling with small LV cavity, impaired LV filling, increased arterial load, and reduced LV longitudinal shortening. Patients with PLF also have a worse prognosis compared to patients with normal flow. Because of the low flow state, these patients often have a low gradient despite the presence of severe stenosis, thus leading to discordant AS grading (i.e., aortic valve area < 1.0 cm(2) but mean gradient < 40 mmHg) and thus uncertainty about the indication of aortic valve replacement. Stress echocardiography and aortic valve calcium score by computed tomography may be helpful to differentiate true from pseudo severe stenosis and thereby guide therapeutic management in these patients. Aortic valve replacement improves outcomes in patients with PLF low gradient AS having evidence of severe stenosis. Transcatheter aortic valve replacement may provide an interesting alternative to surgery in these patients.

  3. 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

  4. 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

  5. Predicting flow in aortic dissection: comparison of computational model with PC-MRI velocity measurements.

    PubMed

    Cheng, Z; Juli, C; Wood, N B; Gibbs, R G J; Xu, X Y

    2014-09-01

    Aortic dissection is a life-threatening process in which the weakened wall develops a tear, causing separation of wall layers. The dissected layers separate the original true aortic lumen and a newly created false lumen. If untreated, the condition can be fatal. Flow rate in the false lumen is a key feature for false lumen patency, which has been regarded as one of the most important predictors of adverse early and later outcomes. Detailed flow analysis in the dissected aorta may assist vascular surgeons in making treatment decisions, but computational models to simulate flow in aortic dissections often involve several assumptions. The purpose of this study is to assess the computational models adopted in previous studies by comparison with in vivo velocity data obtained by means of phase-contrast magnetic resonance imaging (PC-MRI). Aortic dissection geometry was reconstructed from computed tomography (CT) images, while PC-MRI velocity data were used to define inflow conditions and to provide distal velocity components for comparison with the simulation results. The computational fluid dynamics (CFD) simulation incorporated a laminar-turbulent transition model, which is necessary for adequate flow simulation in aortic conditions. Velocity contours from PC-MRI and CFD in the two lumens at the distal plane were compared at four representative time points in the pulse cycle. The computational model successfully captured the complex regions of flow reversal and recirculation qualitatively, although quantitative differences exist. With a rigid wall assumption and exclusion of arch branches, the CFD model over-predicted the false lumen flow rate by 25% at peak systole. Nevertheless, an overall good agreement was achieved, confirming the physiological relevance and validity of the computational model for type B aortic dissection with a relatively stiff dissection flap.

  6. Simulations of blood flow in patient-specific aortic dissections with a deformable wall model

    NASA Astrophysics Data System (ADS)

    Baeumler, Kathrin; Vedula, Vijay; Sailer Karmann, Anna; Marsden, Alison; Fleischmann, Dominik

    2016-11-01

    Aortic dissection is a life-threatening condition in which blood penetrates into the vessel wall, creating a second flow channel, often requiring emergency surgical repair. Up to 50% of patients who survive the acute event face late complications like aortic dilatation and eventual rupture. Prediction of late complications, however, remains challenging. We therefore aim to perform accurate and reliable patient-specific simulations of blood flow in aortic dissections, validated by 4D-Flow MRI. Among other factors, this is a computational challenge due to the compliance of the vessel walls and the large degree of membrane deformation between the two flow channels. We construct an anatomic patient-specific model from CT data including both flow channels and the membrane between them. We then run fluid structure interaction simulations using an arbitrary Lagrangian-Eulerian (ALE) formulation within a multiscale variational framework, employing stabilized finite element methods. We compare hemodynamics between a rigid and a deformable wall model and examine membrane dynamics and pressure differences between the two flow channels. The study focuses on the computational and modeling challenges emphasizing the importance of employing a deformable wall model for aortic dissections.

  7. 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.

  8. 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.

  9. Acute increase in reversal blood flow during counterpulsation is associated with vasoconstriction and changes in the aortic mechanics.

    PubMed

    Bia, Daniel; Zócalo, Yanina; Armentano, Ricardo; de Forteza, Eduardo; Cabrera-Fischer, Edmundo

    2007-01-01

    While the effects of increases in forward blood flow on the arterial diameter and elasticity are known, the effects of reversal flow on the arterial properties remain to be characterized. The intra-aortic balloon pumping (IABP), the device most frequently used in circulatory support, acts generating changes in aortic flow (i.e. increasing reversal flow). Recently, in vitro studies showed that flow reversion reduces the endothelial release of relaxing factors. Hence, vascular smooth muscle (VSM) dependent changes in the aortic properties would be expected during IABP. The aim was to analyze the changes in flow during IABP and to characterize the potential effects of reversal blood flow on the aortic biomechanics. Pressure, flow and diameter were measured in sheep, before and during IABP circulatory support. Potential effects of IABP-dependent high reversal flow conditions on viscous and elastic aortic modulus were analyzed, using isobaric analysis. Flow and pressure waveforms were analyzed in the time domain, and the contribution of oscillatory forward and backward waves to the IABP-dependent changes in flow patterns were evaluated. We found that IABP changed mainly diastolic blood flow, with an increase in the reversal flow, secondary to an increase in the oscillatory backward wave amplitude. The acute increase in reversal flow during IABP was associated with vasoconstriction and changes in the aortic mechanics, possibly due to VSM activation.

  10. 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.

  11. 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

  12. 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

    2015-06-10

    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.

  13. Continuous Flow Microfluidic Bioparticle Concentrator

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  14. 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.

  15. Electrohydrodynamic effects in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, P. H.; Snyder, R. S.; Roberts, G. O.; Baygents, J. C.

    1991-01-01

    We demonstrate experimentally and theoretically the importance of electrohydrodynamic (EHD) flows in continuous-flow electrophoresis (CFE) separations. These flows are associated with variations in the conductivity or dielectric constant, and are quadratic in the field strength. They appear to be the main cause of extraneous and undesired flows in CFE which have degraded separation performance and have until now not been explained. We discuss the importance of EHD flows relative to other effects. We also describe possible techniques for reducing the associated degradation of CFE separations.

  16. The Relationship Between Pulsatile Flow Impingement and Intraluminal Thrombus Deposition in Abdominal Aortic Aneurysms.

    PubMed

    Lozowy, Richard J; Kuhn, David C S; Ducas, Annie A; Boyd, April J

    2017-03-01

    Direct numerical simulations were performed on four patient-specific abdominal aortic aneurysm (AAA) geometries and the resulting pulsatile blood flow dynamics were compared to aneurysm shape and correlated with intraluminal thrombus (ILT) deposition. For three of the cases, turbulent vortex structures impinged/sheared along the anterior wall and along the posterior wall a zone of recirculating blood formed. Within the impingement region the AAA wall was devoid of ILT and remote to this region there was an accumulation of ILT. The high wall shear stress (WSS) caused by the impact of vortexes is thought to prevent the attachment of ILT. WSS from impingement is comparable to peak-systolic WSS in a normal-sized aorta and therefore may not damage the wall. Expansion occurred to a greater extent in the direction of jet impingement and the wall-normal force from the continuous impact of vortexes may contribute to expansion. It was shown that the impingement region has low oscillatory shear index (OSI) and recirculation zones can have either low or high OSI. No correlation could be identified between OSI and ILT deposition since different flow dynamics can have similar OSI values.

  17. 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.

  18. 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

  19. Aortic angiography

    MedlinePlus

    ... to: Abdominal aortic aneurysm Aortic dissection Aortic regurgitation Aortic stenosis Congenital (present from birth) problems Double aortic arch ... Aortic aneurysm repair - endovascular Aortic dissection Aortic insufficiency Aortic stenosis Magnetic resonance ... Patient Instructions Abdominal ...

  20. Characterization of neonatal aortic cannula jet flow regimes for improved cardiopulmonary bypass.

    PubMed

    Menon, Prahlad G; Teslovich, Nikola; Chen, Chia-Yuan; Undar, Akif; Pekkan, Kerem

    2013-01-18

    During pediatric and neonatal cardiopulmonary bypass (CPB), tiny aortic outflow cannulae (2-3 mm inner diameter), with micro-scale blood-wetting features transport relatively large blood volumes (0.3 to 1.0 L/min) resulting in high blood flow velocities (2 to 5 m/s). These severe flow conditions are likely to complement platelet activation, release pro-inflammatory cytokines, and further result in vascular and blood damage. Hemodynamically efficient aortic outflow cannulae are required to provide high blood volume flow rates at low exit force. In addition, optimal aortic insertion strategies are necessary in order to alleviate hemolytic risk, post-surgical neurological complications and developmental defects, by improving cerebral perfusion in the young patient. The methodology and results presented in this study serve as a baseline for design of superior aortic outflow cannulae. In this study, direct numerical simulation (DNS) computational fluid dynamics (CFD) was employed to delineate baseline hemodynamic performance of jet wakes emanating from microCT scanned state-of-the-art pediatric cannula tips in a cuboidal test rig operating at physiologically relevant laminar and turbulent Reynolds numbers (Re: 650-2150 , steady inflow). Qualitative and quantitative validation of CFD simulated device-specific jet wakes was established using time-resolved flow visualization and particle image velocimetry (PIV). For the standard end-hole cannula tip design, blood damage indices were further numerically assessed in a subject-specific cross-clamped neonatal aorta model for different cannula insertion configurations. Based on these results, a novel diffuser type cannula tip is proposed for improved jet flow-control, decreased blood damage and exit force and increased permissible flow rates. This study also suggests that surgically relevant cannula orientation parameters such as outflow angle and insertion depth may be important for improved hemodynamic performance. The jet

  1. 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.

  2. Device specific analysis of neonatal aortic outflow cannula jet flows for improved cardiopulmonary bypass hemodynamics

    NASA Astrophysics Data System (ADS)

    Menon, Prahlad; Sotiropoulos, Fotis; Undar, Akif; Pekkan, Kerem

    2011-11-01

    Hemodynamically efficient aortic outflow cannulae can provide high blood volume flow rates at low exit force during extracorporeal circulation in pediatric or neonatal cardiopulmonary bypass repairs. Furthermore, optimal hemolytic aortic insertion configurations can significantly reduce risk of post-surgical neurological complications and developmental defects in the young patient. The methodology and results presented in this study serve as a baseline for design of superior aortic outflow cannulae based on a novel paradigm of characterizing jet-flows at different flow regimes. In-silico evaluations of multiple cannula tips were used to delineate baseline hemodynamic performance of the popular pediatric cannula tips in an experimental cuboidal test-rig, using PIV. High resolution CFD jet-flow simulations performed for various cannula tips in the cuboidal test-rig as well as in-vivo insertion configurations have suggested the existence of optimal surgically relevant characteristics such as cannula outflow angle and insertion depth for improved hemodynamic performance during surgery. Improved cannula tips were designed with internal flow-control features for decreased blood damage and increased permissible flow rates.

  3. Flow and thermal effects in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Saville, D. A.; Rhodes, P. H.; Snyder, R. S.

    1979-01-01

    In continuous flow electrophoresis the axial flow structure changes from a fully developed rectilinear form to one characterized by meandering as power levels are increased. The origin of this meandering is postulated to lie in a hydrodynamic instability driven by axial (and possibly lateral) temperature gradients. Experiments done at MSFC show agreement with the theory.

  4. A comparison of two forms of the continuity equation in the Trifecta bovine pericardial aortic valve

    PubMed Central

    Parkin, Denise; Roxburgh, James; Bapat, Vinayak; Young, Christopher

    2016-01-01

    Abstract Aim To compare the classical and simplified form of the continuity equation in small Trifecta valves. Methods This is a retrospective analysis of post-operative echocardiograms performed for clinical reasons after implantation of Trifecta bioprosthetic valves. Results There were 60 patients aged 74 (range 38–89) years. For the valves of size 19, 21 and 23mm, the mean gradient was 11.3, 10.7 and 9.7mmHg, respectively. The effective orifice areas by the classical form of the continuity equation were 1.4, 1.7 and 1.9cm2, respectively. There was a good correlation between the two forms of the continuity equation, but they were significantly different using a t-test (P<0.00001). Results using the classical form were a mean 0.11 (s.d. 0.18)cm2 larger than those using the simple formula. Conclusion Haemodynamic function of the Trifecta valve in the small aortic root is good. There are significant differences between the classical and simplified forms of the continuity equation. PMID:27249811

  5. 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

  6. A clean air continuous flow propulsion facility

    NASA Technical Reports Server (NTRS)

    Krauss, R. H.; Mcdaniel, J. C., Jr.

    1992-01-01

    Consideration is given to a contaminant-free, high enthalpy, continuous flow facility designed to obtain detailed code validation measurements of high speed combustion. The facility encompasses uncontaminated air temperature control to within 5 K, fuel temperature control to 2 K, a ceramic flow straightener, drying of inlet air, and steady state continuous operation. The air heating method provides potential for independent control of contaminant level by injection, mixing, and heating upstream. Particular attention is given to extension of current capability of 1250 K total air temperature, which simulates Scramjet enthalpy at Mach 5.

  7. Pulsatile flows and wall-shear stresses in models simulating normal and stenosed aortic arches

    NASA Astrophysics Data System (ADS)

    Huang, Rong Fung; Yang, Ten-Fang; Lan, Y.-K.

    2010-03-01

    Pulsatile aqueous glycerol solution flows in the models simulating normal and stenosed human aortic arches are measured by means of particle image velocimetry. Three transparent models were used: normal, 25% stenosed, and 50% stenosed aortic arches. The Womersley parameter, Dean number, and time-averaged Reynolds number are 17.31, 725, and 1,081, respectively. The Reynolds numbers based on the peak velocities of the normal, 25% stenosed, and 50% stenosed aortic arches are 2,484, 3,456, and 3,931, respectively. The study presents the temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall-shear stress during the systolic and diastolic phases. It is found that the flow pattern evolving in the central plane of normal and stenosed aortic arches exhibits (1) a separation bubble around the inner arch, (2) a recirculation vortex around the outer arch wall upstream of the junction of the brachiocephalic artery, (3) an accelerated main stream around the outer arch wall near the junctions of the left carotid and the left subclavian arteries, and (4) the vortices around the entrances of the three main branches. The study identifies and discusses the reasons for the flow physics’ contribution to the formation of these features. The oscillating wall-shear stress distributions are closely related to the featured flow structures. On the outer wall of normal and slightly stenosed aortas, large wall-shear stresses appear in the regions upstream of the junction of the brachiocephalic artery as well as the corner near the junctions of the left carotid artery and the left subclavian artery. On the inner wall, the largest wall-shear stress appears in the region where the boundary layer separates.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Fluid-structure interaction analysis of the flow through a stenotic aortic valve

    NASA Astrophysics Data System (ADS)

    Maleki, Hoda; Labrosse, Michel R.; Durand, Louis-Gilles; Kadem, Lyes

    2009-11-01

    In Europe and North America, aortic stenosis (AS) is the most frequent valvular heart disease and cardiovascular disease after systemic hypertension and coronary artery disease. Understanding blood flow through an aortic stenosis and developing new accurate non-invasive diagnostic parameters is, therefore, of primarily importance. However, simulating such flows is highly challenging. In this study, we considered the interaction between blood flow and the valve leaflets and compared the results obtained in healthy valves with stenotic ones. One effective method to model the interaction between the fluid and the structure is to use Arbitrary Lagrangian-Eulerian (ALE) approach. Our two-dimensional model includes appropriate nonlinear and anisotropic materials. It is loaded during the systolic phase by applying pressure curves to the fluid domain at the inflow. For modeling the calcified stenotic valve, calcium will be added on the aortic side of valve leaflets. Such simulations allow us to determine the effective orifice area of the valve, one of the main parameters used clinically to evaluate the severity of an AS, and to correlate it with changes in the structure of the leaflets.

  16. Analysis of flow patterns in a patient-specific aortic dissection model.

    PubMed

    Cheng, Z; Tan, F P P; Riga, C V; Bicknell, C D; Hamady, M S; Gibbs, R G J; Wood, N B; Xu, X Y

    2010-05-01

    Aortic dissection is the most common acute catastrophic event affecting the thoracic aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent aneurysmal dilatation of the thoracic aorta. This study aimed at gaining more detailed knowledge of the flow phenomena associated with this condition. Morphological features and flow patterns in a dissected aortic segment of a presurgery type B dissection patient were analyzed based on computed tomography images acquired from the patient. Computational simulations of blood flow in the patient-specific model were performed by employing a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport turbulence model implemented in ANSYS CFX 11. Our results show that the dissected aorta is dominated by locally highly disturbed, and possibly turbulent, flow with strong recirculation. A significant proportion (about 80%) of the aortic flow enters the false lumen, which may further increase the dilatation of the aorta. High values of wall shear stress have been found around the tear on the true lumen wall, perhaps increasing the likelihood of expanding the tear. Turbulence intensity in the tear region reaches a maximum of 70% at midsystolic deceleration phase. Incorporating the non-Newtonian behavior of blood into the same transitional flow model has yielded a slightly lower peak wall shear stress and higher maximum turbulence intensity without causing discernible changes to the distribution patterns. Comparisons between the laminar and turbulent flow simulations show a qualitatively similar distribution of wall shear stress but a significantly higher magnitude with the transitional turbulence model.

  17. 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.

  18. Sensitivity Optimization in Continuous-Flow FTNMR

    NASA Astrophysics Data System (ADS)

    Sudmeier, James L.; Günther, Ulrich L.; Albert, Klaus; Bachovchin, William W.

    Equations simulating the steady-state magnetization of liquids in continuous-flow FTNMR are derived using a classical vector model, assuming plug flow. These equations are applied to calculation of ( S/ N) t, the relative signal/noise per unit time of any nucleus undergoing any degree of Overhauser enhancement either in the detection cell or upstream, or both, and to optimization of experimental conditions, including pulse repetition time Trep, pulse angle β, and flow rate. Ideal parameters include a pulse angle of 90° and a Trepvalue equal to sample residence time in the NMR detection cell. Optimal flow rates are directly proportional to the premagnetization volume (the portion of sample equilibrated with the magnetic field prior to detection) and inversely proportional to spin-lattice relaxation times T1. Optimal premagnetization times are smaller than previously assumed, varying from about 1.1 to 1.9 T1values. ( S/ N) tfor static FTNMR is discussed in some detail, and a new graphical method is presented for its optimization. Flow advantage, the ( S/ N) tof optimized flow FTNMR experiments compared to that of static FTNMR in a given detection cell, is proportional to the square root of the ratio of premagnetization to detection cell volumes, and virtually independent of[formula]where[formula]is the apparent transverse-relaxation time. The theory is applied to examples from recent literature, including dynamic electron-nuclear polarization, and the literature is critically reviewed. The analysis shows that claims by previous authors of recycled flow FTNMR by itself leading to increased ( S/ N) tfor slowly relaxing resonances are misleading, owing to underdetermination of ( S/ N) tin static measurements and failure to account for greater sample sizes required in flow experiments. For monitoring and control of chemical processes, the theory presented here enables the first rational basis for the design of a flow FTNMR apparatus and for the selection of acquisition

  19. 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.

  20. Unsteady and three-dimensional simulation of blood flow in the human aortic arch.

    PubMed

    Shahcheraghi, N; Dwyer, H A; Cheer, A Y; Barakat, A I; Rutaganira, T

    2002-08-01

    A three-dimensional and pulsatile blood flow in a human aortic arch and its three major branches has been studied numerically for a peak Reynolds number of 2500 and a frequency (or Womersley) parameter of 10. The simulation geometry was derived from the three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo using CAT scan imaging on a human aorta. The numerical simulations were obtained using a projection method, and a finite-volume formulation of the Navier-Stokes equations was used on a system of overset grids. Our results demonstrate that the primary flow velocity is skewed towards the inner aortic wall in the ascending aorta, but this skewness shifts to the outer wall in the descending thoracic aorta. Within the arch branches, the flow velocities were skewed to the distal walls with flow reversal along the proximal walls. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, wall shear stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. Within the branches, the shear stresses were considerably higher along the distal walls than along the proximal walls. Wall pressure was low along the inner aortic wall and high around the branches and along the outer wall in the ascending thoracic aorta. Comparison of our numerical results with the localization of early atherosclerotic lesions broadly suggests preferential development of these lesions in regions of extrema (either maxima or minima) in wall shear stress and pressure.

  1. 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.

  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. [Measurement of fractional flow reserve in patients with severe aortic stenosis: A valid test?

    PubMed

    Kikoïne, J; Lebon, M; Gouffran, G; Millischer, D; Cattan, S; Nallet, O

    2016-11-01

    A 54-year-old woman was hospitalized for an acute pulmonary oedema revealing a severe aortic stenosis (AS) associated with an aortic aneurysm and a left ventricular hypertrophy (LVH). The coronary angiography found an equivocal left main lesion. Fractional flow reserve (FFR) showed hemodynamic significance (FFR=0.78) and optical coherence tomography confirmed this result with a minimal lumen area of 4.9mm(2). FFR-guided percutaneous intervention is reported to improve outcome in patients with stable coronary disease. However, only few data are available in cases of AS. In this condition, secondary LVH is associated with microcirculatory dysfunction, which interferes with optimal hyperemia. An elevated right atrial pressure could also modify FFR measurement. This risk of underestimation of a coronary lesion in patients with severe AS has to be taken into consideration in clinical practice.

  4. 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.

  5. 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.

  6. In vitro flow investigations in the aortic arch during cardiopulmonary bypass with stereo-PIV.

    PubMed

    Büsen, Martin; Kaufmann, Tim A S; Neidlin, Michael; Steinseifer, Ulrich; Sonntag, Simon J

    2015-07-16

    The cardiopulmonary bypass is related to complications like stroke or hypoxia. The cannula jet is suspected to be one reason for these complications, due to the sandblast effect on the vessel wall. Several in silico and in vitro studies investigated the underlying mechanisms, but the applied experimental flow measurement techniques were not able to address the highly three-dimensional flow character with a satisfying resolution. In this work in vitro flow measurements in a cannulated and a non-cannulated aortic silicone model are presented. Stereo particle image velocimetry measurements in multiple planes were carried out. By assembling the data of the different measurement planes, quasi 3D velocity fields with a resolution of~1.5×1.5×2.5 mm(3) were obtained. The resulting velocity fields have been compared regarding magnitude, streamlines and vorticity. The presented method shows to be a suitable in vitro technique to measure and address the three-dimensional aortic CPB cannula flow with a high temporal and spatial resolution.

  7. Endothelial adaptations in aortic stenosis. Correlation with flow parameters.

    PubMed Central

    Zand, T.; Nunnari, J. J.; Hoffman, A. H.; Savilonis, B. J.; MacWilliams, B.; Majno, G.; Joris, I.

    1988-01-01

    A 69 +/- 5% stenosis was produced in the rat aorta, with the purpose of correlating endothelial changes with local flow patterns and with levels of shear stress; the hydrodynamic data were obtained from a scaled-up model of the stenosed aorta. In the throat of the stenosis, where shear stress values were 15-25 times normal, the endothelium was stripped off within 1 hour. It regenerated at half the rate of controls but modulated into a cell type that could withstand the increased shear stress. Adaptations included changes in cell orientation, number, length, width, thickness, stress fibers, and anchoring structures, as well as changes in the length, argyrophilia, and permeability of the junctions. Areas of either elongated or "polygonal" cells consistently developed at the same sites in relation to the stenosis, but the hydrodynamic data showed that they did not always correspond (as had been anticipated) to high and low shear, respectively. It is concluded that endothelial cell shape in the living artery must be determined by some other factor(s) in addition to shear stress. Images Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:3189514

  8. Continuous microwave flow synthesis of mesoporous hydroxyapatite.

    PubMed

    Akram, Muhammad; Alshemary, Ammar Z; Goh, Yi-Fan; Wan Ibrahim, Wan Aini; Lintang, Hendrik O; Hussain, Rafaqat

    2015-11-01

    We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Aortic valve orifice equation independent of valvular flow intervals: application to aortic valve area computation in aortic stenosis and comparison with the Gorlin formula.

    PubMed

    Seitz, W; Oppenheimer, L; McIlroy, M; Nelson, D; Operschall, J

    1986-12-01

    An orifice equation is derived relating the effective aortic valve area, A, the average aortic valve pressure gradient, dP, the stroke volume, SV, and the heart frequency, FH, through considerations of momentum conservation across the aortic valve. This leads to a formula consistent with Newton's second law of motion. The form of the new equation is A = (7.5 X 10(-5)) SV FH2/Pd, where A, VS, FH and Pd are expressed in cm2, ml, s-1 and mmHg, respectively. Aortic valve areas computed with the new orifice equation are found to correlate with those computed by the Gorlin formula in conditions of resting haemodynamic states at a level of r = 0.86, SE = 0.25 cm2, N = 120. The results suggest that the new formula may be considered as an independent orifice equation having a similar domain of validity as the Gorlin formula. The new equation offers the possibility of deriving additional useful haemodynamic relationships through combination with established cardiological formulas and applying it in a noninvasive Doppler ultrasonic or echocardiographic context.

  15. Continuous flow peritoneal dialysis: clinical applications.

    PubMed

    Diaz-Buxo, José A

    2002-01-01

    Continuous flow peritoneal dialysis (CFPD) can be considered a special form of hemodialysis, during which peritoneal effluent, rather than blood, is being dialyzed using standard hemodialysis technology. Preliminary clinical data have identified poor mixing of the dialysis solution, streaming and recirculation as a significant limitation in achieving maximal solute removal and ultrafiltration. Better catheter designs remain a research priority in this field. Although the clinical experience is limited to short-lasting experiments with CFPD, the preliminary data strongly support the superiority of CFPD as the most effective peritoneal dialysis modality in removing small solutes and providing high ultrafiltration rates. The levels of clearance attained are similar to quotidian hemodialysis. In addition, it is expected that the current methodology will provide a new standard of solution biocompatibility.

  16. Diazo compounds in continuous-flow technology.

    PubMed

    Müller, Simon T R; Wirth, Thomas

    2015-01-01

    Diazo compounds are very versatile reagents in organic chemistry and meet the challenge of selective assembly of structurally complex molecules. Their leaving group is dinitrogen; therefore, they are very clean and atom-efficient reagents. However, diazo compounds are potentially explosive and extremely difficult to handle on an industrial scale. In this review, it is discussed how continuous flow technology can help to make these powerful reagents accessible on large scale. Microstructured devices can improve heat transfer greatly and help with the handling of dangerous reagents safely. The in situ formation and subsequent consumption of diazo compounds are discussed along with advances in handling diazomethane and ethyl diazoacetate. The potential large-scale applications of a given methodology is emphasized.

  17. Role of Transesophageal Echocardiography in the Diagnosis of Paradoxical Low Flow, Low Gradient Severe Aortic Stenosis

    PubMed Central

    Abudiab, Muaz M.; Pandit, Anil

    2017-01-01

    Background and Objectives Prior studies indicate that up to 35% of cases of severe aortic stenosis (AS) have paradoxical low flow, low gradient despite preserved left ventricular ejection fraction (LVEF). However, error in left ventricular outflow tract (LVOT) diameter may lead to misclassification. Herein, we determined whether measurement of LVOT diameter by transesophageal echocardiography (TEE) results in reclassification of cases to non-severe AS. Subjects and Methods Patients with severe AS with aortic valve area (AVA) <1 cm2 by transthoracic echocardiography (TTE) within 6 months were studied. Paradoxical low flow, low gradient was defined as mean Doppler gradient (MG) <40 mm Hg and stroke volume index (SVI) ≤35 mL/m2. Preserved LVEF was defined as ≥0.50. Results Among 108 patients, 12 (15%) had paradoxical low flow, low gradient severe AS despite preserved LVEF based on TTE measurement. When LVOT diameter by TEE in 2D was used, only 5 (6.3%) patients had low flow, low gradient severe AS (p<0.001). Coefficients of variability for intraobserver and interobserver measurement of LVOT were <10%. However, the limits of agreement between TTE and TEE measurement of LVOT ranged from 0.43 cm (95% confidence interval [CI]: 0.36 to 0.5) to -0.31 cm (95% CI: -0.38 to -0.23). Conclusion TEE measured LVOT diameter may result in reclassification to moderate AS in some patients due to low prevalence of true paradoxical low flow, low gradient (PLFLG) severe AS. PMID:28154595

  18. A novel counterpulse drive mode of continuous-flow left ventricular assist devices can minimize intracircuit backward flow during pump weaning.

    PubMed

    Ando, Masahiko; Nishimura, Takashi; Takewa, Yoshiaki; Ogawa, Daisuke; Yamazaki, Kenji; Kashiwa, Koichi; Kyo, Shunei; Ono, Minoru; Taenaka, Yoshiyuki; Tatsumi, Eisuke

    2011-03-01

    Recent developments in adjunct therapeutic options for end-stage heart failure have enabled us to remove implanted left ventricular assist devices (LVADs) from more patients than before. However, a safe and proper protocol for pump-off trials is yet to be established, because diastolic backward flow in a pump circuit turns up when it is driven at low-flow conditions. We have developed a novel drive mode of centrifugal pumps that can change its rotational speed in synchronization with the cardiac cycle of the native heart. The purpose of this study was to test-drive this novel system of a centrifugal pump in a mock circulation and to evaluate the effect of the counterpulse mode, which increases pump speed just in diastole, on the amount of this nonphysiological intracircuit retrograde flow. A rotary pump (EVAHEART, Sun Medical Technology Research Corporation) was connected to the mock circulation by left ventricular uptake and ascending aortic return. We drove it in the following four conditions: (A) continuous mode at 1500 rpm, (B) counterpulse mode (systolic 1500 rpm, diastolic 2500 rpm), (C) continuous mode at 2000 rpm, and (D) counterpulse mode (systolic 2000 rpm, diastolic 2500 rpm). Data concerning the rotation speed, pump flow, left ventricular pressure, aortic pressure, and pressure head (i.e., aortic pressure-left ventricular pressure) in each condition were collected. After data collection, we analyzed pump flow, and calculated its forward and backward flow. Counterpulse mode decreased the amounts of pump backward flow compared with the continuous mode [mean backward flow, -4, -1, -0.5, 0 l/min, in (A), (B), (C), and (D) conditions, respectively]. The actual amounts of mean backward flow can be different from those in clinical situations; however, this novel drive mode for rotary pumps can relatively decrease pump backward flow during pump weaning and can be beneficial for safe and proper pump-off trials. Further investigations in in vivo settings are

  19. MRI-based aortic blood flow model in 3D ballistocardiography.

    PubMed

    Lejeune, L; Prisk, G K; Nonclercq, A; Migeotte, P-F

    2015-01-01

    Ballistocardiography (BCG) is a non-invasive technique which measures the acceleration of a body induced by cardiovascular activity, namely the force exerted by the beating heart. A one dimensional aortic flow model based on the transmission lines theory is developped and applied to the simulation of three dimensional BCG. A four-element Windkessel model is used to generate the pressure-wave. Using transverse MRI slices of a human subject, a reconstruction of the aorta allows the extraction of parameters used to relate the local change in mass of the 1D flow model to 3D acceleration BCG. Simulated BCG curves are then compared qualitatively with the ensemble average curves of the same subject recorded in sustained microgravity. Confirming previous studies, the main features of the y-axis are well simulated. The simulated z-axis, never attempted before, shows important similarities. The simulated x-axis is less faithful and suggests the presence of reflections.

  20. On the flow through the normal fetal aortic arc at late gestation

    NASA Astrophysics Data System (ADS)

    Pekkan, Kerem; Nourparvar, Paymon; Yerneni, Srinivasu; Dasi, Lakshmi; de Zelicourt, Diane; Fogel, Mark; Yoganathan, Ajit

    2006-11-01

    During the fetal stage, the aortic arc is a complex junction of great vessels (right and left ventricular outflow tracks (RVOT, LVOT), pulmonary arteries (PA), ductus, head-neck vessels, decending aorta (Dao)) delicately distributing the oxygenated blood flow to the lungs and the body -preferential to the brain. Experimental and computational studies are performed in idealized models of the fetal aorta to understand and visualize the unsteady hemodynamics. Unsteady in vitro flow, generated by two peristaltic pumps (RVOT and LVOT) is visualized with two colored dyes and a red laser in a rigid glass model with physiological diameters. Helical flow patterns at the PA's and ductal shunting to the Dao are visualized. Computational fluid dynamics of the same geometry is modeled using the commercial code Fidap with porous boundary conditions representing systemic and pulmonary resistances (˜400000 tetrahedral elements). Combined (RVOT+LVOT) average flow rates ranging from 1.9 to 2.1-L/min for 34 to 38-weeks gestation were simulated with the Reynolds and Womersly numbers (Dao) of 500 and 8. Computational results are compared qualitatively with the flow visualizations at this target flow condition. Understanding fetal hemodynamics is critical for congenital heart defects, tissue engineering, fetal cardiac MRI and surgeries.

  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. Continuous-flow electrophoretic separator for biologicals

    NASA Technical Reports Server (NTRS)

    Mccreight, L. R.; Griffin, R. N.; Locker, R. J.

    1976-01-01

    In the near absence of gravity, a continuous-flow type of electrophoretic separator can be operated with a much thicker separation chamber than is possible under 1 g conditions. This should permit either better resolution or shorter separation time per unit of sample. An apparatus to perform experiments on sounding rockets is under development and will be described. The electrophoresis cell is 5 mm thick by 5 cm wide with 10 cm long electrodes. It is supplied with buffer, sample, and coolant at about 4 C through the use of a passive refrigerant system. UV sample detection and provision for recovery and cold storage of up to 50 sample fractions are now being added to the basic unit. A wide range of operating conditions are electronically programmable into the unit, even up to a short time before flight, and a further range of some parameters can be achieved by exchanging power supplies and by changing gears in the motor drive units of the pump. The preliminary results of some separation studies on various biological products using a commercially available electrophoretic separator are also presented.

  3. Transcatheter aortic valve replacement

    MedlinePlus

    ... fully will restrict blood flow. This is called aortic stenosis. If there is also a leak, it is ... TAVR is used for people with severe aortic stenosis who aren't ... valve . In adults, aortic stenosis usually occurs due to calcium ...

  4. Flow of a blood analogue fluid in a compliant abdominal aortic aneurysm model: experimental modelling.

    PubMed

    Deplano, Valérie; Knapp, Yannick; Bailly, Lucie; Bertrand, Eric

    2014-04-11

    The aim of this work is to develop a unique in vitro set-up in order to analyse the influence of the shear thinning fluid-properties on the flow dynamics within the bulge of an abdominal aortic aneurysm (AAA). From an experimental point of view, the goals are to elaborate an analogue shear thinning fluid mimicking the macroscopic blood behaviour, to characterise its rheology at low shear rates and to propose an experimental device able to manage such an analogue fluid without altering its feature while reproducing physiological flow rate and pressure, through compliant AAA. Once these experimental prerequisites achieved, the results obtained in the present work show that the flow dynamics is highly dependent on the fluid rheology. The main results point out that the propagation of the vortex ring, generated in the AAA bulge, is slower for shear thinning fluids inducing a smaller travelled distance by the vortex ring so that it never impacts the anterior wall in the distal region, in opposition to Newtonian fluids. Moreover, scalar shear rate values are globally lower for shear thinning fluids inducing higher maximum stress values than those for the Newtonian fluids. Consequently, this work highlights that a Newtonian fluid model is finally inadequate to obtain a reliable prediction of the flow dynamics within AAA.

  5. Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System.

    PubMed

    Bozkurt, Selim; van de Vosse, Frans N; Rutten, Marcel C M

    Continuous-flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which reduces pulsatility in the arteries and may lead to complications such as functional changes in the vascular system, gastrointestinal bleeding, or both. The purpose of this study is to increase the arterial pulse pressure and pulsatility by controlling the CF-LVAD flow rate. A MicroMed DeBakey pump was used as the CF-LVAD. A model simulating the flow rate through the aortic valve was used as a reference model to drive the pump. A mock circulation containing two synchronized servomotor-operated piston pumps acting as left and right ventricles was used as a circulatory system. Proportional-integral control was used as the control method. First, the CF-LVAD was operated at a constant speed. With pulsatile-speed CF-LVAD assistance, the pump was driven such that the same mean pump output was generated. Continuous and pulsatile-speed CF-LVAD assistance provided the same mean arterial pressure and flow rate, while the index of pulsatility increased significantly for both arterial pressure and pump flow rate signals under pulsatile speed pump support. This study shows the possibility of improving the pulsatility of CF-LVAD support by regulating pump speed over a cardiac cycle without reducing the overall level of support.

  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.

  7. Late presentation of double aortic arch in school-age children presumed to have asthma: the benefits of spirometry and examination of the flow-volume curve.

    PubMed

    Uchida, Derek A

    2009-10-01

    Children with double aortic arch most often present in infancy. This report presents 3 patients in whom the diagnosis of double aortic arch was not revealed until later in childhood. They were all given a misdiagnosis of asthma, but abnormalities detected on the flow-volume curve led to the true diagnosis.

  8. Morphotype-Dependent Flow Characteristics in Bicuspid Aortic Valve Ascending Aortas: A Benchtop Particle Image Velocimetry Study

    PubMed Central

    McNally, Andrew; Madan, Ashish; Sucosky, Philippe

    2017-01-01

    The bicuspid aortic valve (BAV) is a major risk factor for secondary aortopathy such as aortic dilation. The heterogeneous BAV morphotypes [left-right-coronary cusp fusion (LR), right-non-coronary cusp fusion (RN), and left-non-coronary cusp fusion (LN)] are associated with different dilation patterns, suggesting a role for hemodynamics in BAV aortopathogenesis. However, assessment of this theory is still hampered by the limited knowledge of the hemodynamic abnormalities generated by the distinct BAV morphotypes. The objective of this study was to compare experimentally the hemodynamics of a normal (i.e., non-dilated) ascending aorta (AA) subjected to tricuspid aortic valve (TAV), LR-BAV, RN-BAV, and NL-BAV flow. Tissue BAVs reconstructed from porcine TAVs were subjected to physiologic pulsatile flow conditions in a left-heart simulator featuring a realistic aortic root and compliant aorta. Phase-locked particle image velocimetry experiments were carried out to characterize the flow in the aortic root and in the tubular AA in terms of jet skewness and displacement, as well as mean velocity, viscous shear stress and Reynolds shear stress fields. While all three BAVs generated skewed and asymmetrical orifice jets (up to 1.7- and 4.0-fold increase in flow angle and displacement, respectively, relative to the TAV at the sinotubular junction), the RN-BAV jet was out of the plane of observation. The LR- and NL-BAV exhibited a 71% increase in peak-systolic orifice jet velocity relative to the TAV, suggesting an inherent degree of stenosis in BAVs. While these two BAV morphotypes subjected the convexity of the aortic wall to viscous shear stress overloads (1.7-fold increase in maximum peak-systolic viscous shear stress relative to the TAV-AA), the affected sites were morphotype-dependent (LR-BAV: proximal AA, NL-BAV: distal AA). Lastly, the LR- and NL-BAV generated high degrees of turbulence in the AA (up to 2.3-fold increase in peak-systolic Reynolds shear stress relative

  9. Morphotype-Dependent Flow Characteristics in Bicuspid Aortic Valve Ascending Aortas: A Benchtop Particle Image Velocimetry Study.

    PubMed

    McNally, Andrew; Madan, Ashish; Sucosky, Philippe

    2017-01-01

    The bicuspid aortic valve (BAV) is a major risk factor for secondary aortopathy such as aortic dilation. The heterogeneous BAV morphotypes [left-right-coronary cusp fusion (LR), right-non-coronary cusp fusion (RN), and left-non-coronary cusp fusion (LN)] are associated with different dilation patterns, suggesting a role for hemodynamics in BAV aortopathogenesis. However, assessment of this theory is still hampered by the limited knowledge of the hemodynamic abnormalities generated by the distinct BAV morphotypes. The objective of this study was to compare experimentally the hemodynamics of a normal (i.e., non-dilated) ascending aorta (AA) subjected to tricuspid aortic valve (TAV), LR-BAV, RN-BAV, and NL-BAV flow. Tissue BAVs reconstructed from porcine TAVs were subjected to physiologic pulsatile flow conditions in a left-heart simulator featuring a realistic aortic root and compliant aorta. Phase-locked particle image velocimetry experiments were carried out to characterize the flow in the aortic root and in the tubular AA in terms of jet skewness and displacement, as well as mean velocity, viscous shear stress and Reynolds shear stress fields. While all three BAVs generated skewed and asymmetrical orifice jets (up to 1.7- and 4.0-fold increase in flow angle and displacement, respectively, relative to the TAV at the sinotubular junction), the RN-BAV jet was out of the plane of observation. The LR- and NL-BAV exhibited a 71% increase in peak-systolic orifice jet velocity relative to the TAV, suggesting an inherent degree of stenosis in BAVs. While these two BAV morphotypes subjected the convexity of the aortic wall to viscous shear stress overloads (1.7-fold increase in maximum peak-systolic viscous shear stress relative to the TAV-AA), the affected sites were morphotype-dependent (LR-BAV: proximal AA, NL-BAV: distal AA). Lastly, the LR- and NL-BAV generated high degrees of turbulence in the AA (up to 2.3-fold increase in peak-systolic Reynolds shear stress relative

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

    PubMed

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

    2014-02-01

    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. MRI 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 were 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.

  12. Adaptive Flow Simulation of Turbulence in Subject-Specific Abdominal Aortic Aneurysm on Massively Parallel Computers

    NASA Astrophysics Data System (ADS)

    Sahni, Onkar; Jansen, Kenneth; Shephard, Mark; Taylor, Charles

    2007-11-01

    Flow within the healthy human vascular system is typically laminar but diseased conditions can alter the geometry sufficiently to produce transitional/turbulent flows in regions focal (and immediately downstream) of the diseased section. The mean unsteadiness (pulsatile or respiratory cycle) further complicates the situation making traditional turbulence simulation techniques (e.g., Reynolds-averaged Navier-Stokes simulations (RANSS)) suspect. At the other extreme, direct numerical simulation (DNS) while fully appropriate can lead to large computational expense, particularly when the simulations must be done quickly since they are intended to affect the outcome of a medical treatment (e.g., virtual surgical planning). To produce simulations in a clinically relevant time frame requires; 1) adaptive meshing technique that closely matches the desired local mesh resolution in all three directions to the highly anisotropic physical length scales in the flow, 2) efficient solution algorithms, and 3) excellent scaling on massively parallel computers. In this presentation we will demonstrate results for a subject-specific simulation of an abdominal aortic aneurysm using stabilized finite element method on anisotropically adapted meshes consisting of O(10^8) elements over O(10^4) processors.

  13. Vortex and energy characteristics of flow in the left ventricle following progressive severities of aortic valve regurgitation

    NASA Astrophysics Data System (ADS)

    di Labbio, Giuseppe; Kadem, Lyes

    2016-11-01

    During the heart's filling phase, a notorious vortex is known to develop in the left ventricle (LV). Improper development and poor energetic behavior of this vortex can be correlated with cardiac disease. In particular, during aortic valve regurgitation (leakage of blood through the aortic valve during LV filling), this vortex is forced to interact with a jet emanating from a regurgitant orifice in the valve. The ensuing flow in the left ventricle subject to this disease has yet to be fully characterized and may lead to new indices for evaluation of its severity. As such, this experimental work investigates flow in a model LV subject to aortic regurgitation on a novel double-activation left heart duplicator for six progressive grades of regurgitation (beginning from the healthy case). Double-activation (independent activation of the atrium and ventricle) is critical to the simulation of this pathology. Regurgitation is induced by restricting the closure of the aortic valve to a centralized orifice. The velocity fields for each case are acquired using 2D time-resolved particle image velocimetry. Viscous energy dissipation and vortex formation time are investigated and found to significantly increase as the pathology progresses, while a histogram of vorticity tends toward a shifted and depressed Gaussian distribution. Proper orthogonal decomposition reveals significant disruption of the dominant energetic coherent structures.

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

    PubMed

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

    2016-01-07

    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.

  15. Numerical study of purely viscous non-Newtonian flow in an abdominal aortic aneurysm.

    PubMed

    Marrero, Victor L; Tichy, John A; Sahni, Onkar; Jansen, Kenneth E

    2014-10-01

    It is well known that blood has non-Newtonian properties, but it is generally accepted that blood behaves as a Newtonian fluid at shear rates above 100 s-1. However, in transient conditions, there are times and locations where the shear rate is well below 100 s-1, and it is reasonable to infer that non-Newtonian effects could become important. In this study, purely viscous non-Newtonian (generalized Newtonian) properties of blood are incorporated into the simulation-based framework for cardiovascular surgery planning developed by Taylor et al. (1999, "Predictive Medicine: Computational Techniques in Therapeutic Decision Making," Comput. Aided Surg., 4, pp. 231-247; 1998, "Finite Element Modeling of Blood Flow in Arteries," Comput. Methods Appl. Mech. Eng., 158, pp. 155-196). Equations describing blood flow are solved in a patient-based abdominal aortic aneurysm model under steady and physiological flow conditions. Direct numerical simulation (DNS) is used, and the complex flow is found to be constantly transitioning between laminar and turbulent in both the spatial and temporal sense. It is found for the case simulated that using the non-Newtonian viscosity modifies the solution in subtle ways that yield a mesh-independent solution with fewer degrees of freedom than the Newtonian counterpart. It appears that in regions of separated flow, the lower shear rate produces higher viscosity with the non-Newtonian model, which reduces the associated resolution needs. When considering the real case of pulsatile flow, high shear layers lead to greater unsteadiness in the Newtonian case relative to the non-Newtonian case. This, in turn, results in a tendency for the non-Newtonian model to need fewer computational resources even though it has to perform additional calculations for the viscosity. It is also shown that both viscosity models predict comparable wall shear stress distribution. This work suggests that the use of a non-Newtonian viscosity models may be attractive

  16. Relation between symptoms and profiles of coronary artery blood flow velocities in patients with aortic valve stenosis: a study using transoesophageal Doppler echocardiography.

    PubMed Central

    Omran, H.; Fehske, W.; Rabahieh, R.; Hagendorff, A.; Lüderitz, B.

    1996-01-01

    OBJECTIVE: To analyse profiles of coronary artery flow velocity at rest in patients with aortic stenosis and to determine whether changes of the coronary artery flow velocities are related to symptoms in patients with aortic stenosis. DESIGN: A prospective study investigating the significance of aortic valve area, pressure gradient across the aortic valve, systolic left ventricular wall stress index, ejection fraction, and left ventricular mass index in the coronary flow velocity profile of aortic stenosis; and comparing flow velocity profiles between symptomatic and asymptomatic patients with aortic stenosis using transoesophageal Doppler echocardiography to obtain coronary artery flow velocities of the left anterior descending coronary artery. SETTING: Tertiary referral cardiac centre. PATIENTS: Fifty eight patients with aortic stenosis and 15 controls with normal coronary arteries. RESULTS: Adequate recordings of the profile of coronary artery flow velocities were obtained in 46 patients (79%). Left ventricular wall stress was the only significant haemodynamic variable for determining peak systolic velocity (r = -0.83, F = 88.5, P < 0.001). The pressure gradient across the aortic valve was the only contributor for explaining peak diastolic velocity (r = 0.56, F = 20.9, P < 0.001). Controls and asymptomatic patients with aortic stenosis (n = 12) did not differ for peak systolic velocity [32.8 (SEM 9.7) v 27.0 (8.7) cm/s, NS] and peak diastolic velocity [58.3 (18.7) v 61.9 (13.5) cm/s, NS]. In contrast, patients with angina (n = 12) or syncope (n = 8) had lower peak systolic velocities and higher peak diastolic velocities than asymptomatic patients (P < 0.01). Peak systolic and diastolic velocities were -7.7 (22.5) cm/s and 81.7 (17.6) cm/s for patients with angina, and -19.5 (22.3) cm/s and 94.0 (20.9) cm/s for patients with syncope. Asymptomatic patients and patients with dyspnoea (n = 14) did not differ. CONCLUSIONS: Increased pressure gradient across the

  17. 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.

  18. A continuous method for gene flow.

    PubMed

    Palczewski, Michal; Beerli, Peter

    2013-07-01

    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.

  19. Energy-Efficient, Continuous-Flow Ash Lockhopper

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Pressure balance in control gas prevents loss of reactor gas. Energy efficiency of continuous-flow ash lockhopper increased by preventing hot gases from flowing out of reactor vessel through ash-hopper outlet and carrying away heat energy. Stopping loss of reactor gases also important for reasons other than energy efficiency; desired reaction product toxic or contained to prevent pollution. In improved continuous-flow ash lockhopper, pressure-driven loss of hot gas from reactor vessel through ash-hopper outlet prevented by using control gas in fluidic flow-control device to equalize pressure in reactor vessel. Also enables reactor to attain highest possible product yield with continuous processing while permitting controllable, continuous flow of ash.

  20. 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.

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

    PubMed

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

    2016-05-06

    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.

  2. Assessment of low-flow, low-gradient aortic stenosis: multimodality imaging is the key to success.

    PubMed

    Clavel, Marie-Annick; Pibarot, Philippe

    2014-09-01

    In patients with aortic stenosis (AS), a low-flow state may occur with reduced LV ejection fraction (LVEF) (i.e., classic low flow) or with preserved LVEF (i.e., paradoxical low flow) and it is often associated with low gradient because the gradient is highly flow-dependent. Low-flow, low-gradient (LF-LG) AS is a frequent clinical entity generally associated with worse outcomes. A multimodality imaging approach, including comprehensive resting echocardiography, dobutamine stress echocardiography (DSE), and multidetector computed tomography (MDCT), is the key to successful management of patients with LF-LG AS, who represent a highly challenging subset from both a diagnostic and a therapeutic standpoint. DSE and quantification of aortic valve calcification by MDCT provide important information that is crucial to differentiate true-severe from pseudo-severe AS and therefore select the most appropriate therapy (i.e., AVR vs. medical). The assessment of LV flow reserve by DSE is useful to stratify the operative risk and guide decision making between surgical and transcatheter AVR. Other imaging biomarkers, such as the global LV longitudinal strain measured during DSE or the amount of myocardial fibrosis assessed by cardiac magnetic resonance imaging, may provide incremental information for risk stratification and therapeutic management in LF-LG AS, but additional studies are needed to validate and refine these emerging biomarkers further.

  3. CFD and PTV steady flow investigation in an anatomically accurate abdominal aortic aneurysm.

    PubMed

    Boutsianis, Evangelos; Guala, Michele; Olgac, Ufuk; Wildermuth, Simon; Hoyer, Klaus; Ventikos, Yiannis; Poulikakos, Dimos

    2009-01-01

    There is considerable interest in computational and experimental flow investigations within abdominal aortic aneurysms (AAAs). This task stipulates advanced grid generation techniques and cross-validation because of the anatomical complexity. The purpose of this study is to examine the feasibility of velocity measurements by particle tracking velocimetry (PTV) in realistic AAA models. Computed tomography and rapid prototyping were combined to digitize and construct a silicone replica of a patient-specific AAA. Three-dimensional velocity measurements were acquired using PTV under steady averaged resting boundary conditions. Computational fluid dynamics (CFD) simulations were subsequently carried out with identical boundary conditions. The computational grid was created by splitting the luminal volume into manifold and nonmanifold subsections. They were filled with tetrahedral and hexahedral elements, respectively. Grid independency was tested on three successively refined meshes. Velocity differences of about 1% in all three directions existed mainly within the AAA sack. Pressure revealed similar variations, with the sparser mesh predicting larger values. PTV velocity measurements were taken along the abdominal aorta and showed good agreement with the numerical data. The results within the aneurysm neck and sack showed average velocity variations of about 5% of the mean inlet velocity. The corresponding average differences increased for all velocity components downstream the iliac bifurcation to as much as 15%. The two domains differed slightly due to flow-induced forces acting on the silicone model. Velocity quantification through narrow branches was problematic due to decreased signal to noise ratio at the larger local velocities. Computational wall pressure and shear fields are also presented. The agreement between CFD simulations and the PTV experimental data was confirmed by three-dimensional velocity comparisons at several locations within the investigated AAA

  4. 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

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

    PubMed

    Liu, Hongpeng; Yang, Zhen; Hu, Jian; Luo, Yan; Zhu, Lingqin; Yang, Huifang; Li, Guanghua

    2015-07-01

    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

  6. Preliminary results by flow-sensitive magnetic resonance imaging after Tiron David I procedure with an anatomically shaped ascending aortic graft.

    PubMed

    Frydrychowicz, Alex; Berger, Alexander; Stalder, Aurélien F; Markl, Michael

    2009-08-01

    We present preliminary data of the vascular hemodynamics in a novel, anatomically shaped ascending aortic graft in comparison to non-operated individuals by use of 3D magnetic resonance (MR) flow measurements. We examined a 72-year-old male patient after Tiron David I valve sparing aortic root reconstruction and replacement of the ascending aorta (AAo) with an anatomically curved prosthesis. Results from flow-sensitive MR at 3T were compared to 12 age-matched individuals with comparable diameters of the AAo. For 3D flow visualization, streamlines and time-resolved particle traces were applied. A visual analysis of hemodynamic properties including blood flow helicity, vorticity and retrograde flow was performed. In contrast to reported highly disturbed flow of straight aortic grafts in the literature, the patient analysis revealed smooth blood flow through the graft which gave rise to a right-handed helical flow in the reconstructed aorta. In comparison to non-operated volunteers, blood flow helicity was more pronounced. Flow jets or vortices were not encountered. While physiological retrograde flow was seen in the volunteers, it was absent in the patient which may be explained by the altered aortic compliance and thus reduced Windkessel effect. This promising finding will have to prove its validity in further comparative studies.

  7. 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.

  8. Turbulence significantly increases pressure and fluid shear stress in an aortic aneurysm model under resting and exercise flow conditions.

    PubMed

    Khanafer, Khalil M; Bull, Joseph L; Upchurch, Gilbert R; Berguer, Ramon

    2007-01-01

    The numerical models of abdominal aortic aneurysm (AAA) in use do not take into account the non-Newtonian behavior of blood and the development of local turbulence. This study examines the influence of pulsatile, turbulent, non-Newtonian flow on fluid shear stresses and pressure changes under rest and exercise conditions. We numerically analyzed pulsatile turbulent flow, using simulated physiological rest and exercise waveforms, in axisymmetric-rigid aortic aneurysm models (AAMs). Discretization of governing equations was achieved using a finite element scheme. Maximum turbulence-induced shear stress was found at the distal end of an AAM. In large AAMs (dilated to undilated diameter ratio = 3.33) at peak systolic flow velocity, fluid shear stress during exercise is 70.4% higher than at rest. Our study provides a numerical, noninvasive method for obtaining detailed data on the forces generated by pulsatile turbulent flow in AAAs that are difficult to study in humans and in physical models. Our data suggest that increased flow turbulence results in increased shear stress in aneurysms. While pressure readings are fairly uniform along the length of an aneurysm, the kinetic energy generated by turbulence impacting on the wall of the distal half of the aneurysm increases fluid and wall shear stress at this site. If the increased fluid shear stress results in further dilation and hence further turbulence, wall stress may be a mechanism for aneurysmal growth and eventual rupture.

  9. Continuous Morse-Smale flows with three equilibrium positions

    NASA Astrophysics Data System (ADS)

    Zhuzhoma, E. V.; Medvedev, V. S.

    2016-05-01

    Continuous Morse-Smale flows on closed manifolds whose nonwandering set consists of three equilibrium positions are considered. Necessary and sufficient conditions for topological equivalence of such flows are obtained and the topological structure of the underlying manifolds is described. Bibliography: 36 titles.

  10. Electrohydrodynamics and other hydrodynamic phenomena in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Saville, D. A.

    1982-01-01

    The process known as continuous flow electrophoresis employs an electric field to separate the constituents of particulate samples suspended in a liquid. Complications arise because the electric field generates temperature gradients due to Joule heating and derives an electrohydrodynamic crossflow. Several aspects of the flow are discussed including entrance effects, hydrodynamic stability and a flow restructuring due to the combined effects of buoyancy and the crossflow.

  11. 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.

  12. Verification of a computational cardiovascular system model comparing the hemodynamics of a continuous flow to a synchronous valveless pulsatile flow left ventricular assist device.

    PubMed

    Gohean, Jeffrey R; George, Mitchell J; Pate, Thomas D; Kurusz, Mark; Longoria, Raul G; Smalling, Richard W

    2013-01-01

    The purpose of this investigation is to use a computational model to compare a synchronized valveless pulsatile left ventricular assist device with continuous flow left ventricular assist devices at the same level of device flow, and to verify the model with in vivo porcine data. A dynamic system model of the human cardiovascular system was developed to simulate the support of a healthy or failing native heart from a continuous flow left ventricular assist device or a synchronous pulsatile valveless dual-piston positive displacement pump. These results were compared with measurements made during in vivo porcine experiments. Results from the simulation model and from the in vivo counterpart show that the pulsatile pump provides higher cardiac output, left ventricular unloading, cardiac pulsatility, and aortic valve flow as compared with the continuous flow model at the same level of support. The dynamic system model developed for this investigation can effectively simulate human cardiovascular support by a synchronous pulsatile or continuous flow ventricular assist device.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. Effect of intra-aortic balloon pump on coronary blood flow during different balloon cycles support: A computer study.

    PubMed

    Aye, Thin Pa Pa; Htet, Zwe Lin; Singhavilai, Thamvarit; Naiyanetr, Phornphop

    2015-01-01

    Intra-aortic balloon pump (IABP) has been used in clinical treatment as a mechanical circulatory support device for patients with heart failure. A computer model is used to study the effect on coronary blood flow (CBF) with different balloon cycles under both normal and pathological conditions. The model of cardiovascular and IABP is developed by using MATLAB SIMULINK. The effect on coronary blood flow has been studied under both normal and pathological conditions using different balloon cycles (balloon off; 1:4; 1:2; 1:1). A pathological heart is implemented by reducing the left ventricular contractility. The result of this study shows that the rate of balloon cycles is related to the level of coronary blood flow.

  19. 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.

  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, 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.

  2. 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.

  3. Application of Digital Ultrasound Speckle Image Velocimetry(DUSIV) for Quantitative Flow Measurements in Aortic Vessel- an In Vitro Study

    NASA Astrophysics Data System (ADS)

    Zarandi, Mehrdad; Dabiri, Dana; Gharib, Morteza

    2001-11-01

    A new method is developed to use speckle signals for obtaining quantitative information about the flow field and its related properties such as wall shear stress. Speckle imaging allows for mapping flows at normal angles to the probe where Doppler technique render little information. Our custom developed method of Digital Ultrasound Speckle Image Velocimetry is used to measure the flow field and wall shear stress in a model of aortic vessel. The method has great potential for other applications such as flow in curved vessels, branching vessels, heart chambers and through valves for quantitative blood flow measurements. It also allows us to correct for the errors in ultrasound measurements caused by the angle of interrogation , or signal attenuation with distance from the ultrasound probe. Speckle velocimetry also allows calibration of the results obtained from the conventional Doppler shift based ultrasound methods and should therefore contribute to more accurate quantitative measurements of blood flow by ultrasound. Providing quantitative information with much higher resolution than Color Doppler measurements and applicability to optically inaccessible flows are the other advantages of this method.

  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. Continuous-flow synthesis of vitamin D3.

    PubMed

    Fuse, Shinichiro; Tanabe, Nobutake; Yoshida, Masahito; Yoshida, Hayato; Doi, Takayuki; Takahashi, Takashi

    2010-12-14

    A highly efficient, two-stage, continuous-flow synthesis of vitamin D(3) from provitamin D(3) was achieved. The developed method afforded the desired product in high yield (HPLC-UV: 60%, isolated: 32%) and required neither intermediate purification nor high-dilution conditions.

  6. Separation of rat pituitary secretory granules by continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Hayes, Daniel; Exton, Carrie; Salada, Thomas; Shellenberger, Kathy; Waddle, Jenny; Hymer, W. C.

    1990-01-01

    The separation of growth hormone-containing cytoplasmic secretory granules from the rat pituitary gland by continuous flow electrophoresis is described. The results are consistent with the hypothesis that granule subpopulations can be separated due to differences in surface charge; these, in turn, may be related to the oligomeric state of the hormone.

  7. Coupled chemo(enzymatic) reactions in continuous flow.

    PubMed

    Yuryev, Ruslan; Strompen, Simon; Liese, Andreas

    2011-01-01

    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.

  8. 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.

  9. False Lumen Flow Patterns and their Relation with Morphological and Biomechanical Characteristics of Chronic Aortic Dissections. Computational Model Compared with Magnetic Resonance Imaging Measurements

    PubMed Central

    Segers, Patrick; Pineda, Victor; Cuellar, Hug; García-Dorado, David; Evangelista, Arturo

    2017-01-01

    Aortic wall stiffness, tear size and location and the presence of abdominal side branches arising from the false lumen (FL) are key properties potentially involved in FL enlargement in chronic aortic dissections (ADs). We hypothesize that temporal variations on FL flow patterns, as measured in a cross-section by phase-contrast magnetic resonance imaging (PC-MRI), could be used to infer integrated information on these features. In 33 patients with chronic descending AD, instantaneous flow profiles were quantified in the FL at diaphragm level by PC-MRI. We used a lumped-parameter model to assess the changes in flow profiles induced by wall stiffness, tear size/location, and the presence of abdominal side branches arising from the FL. Four characteristic FL flow patterns were identified in 31/33 patients (94%) based on the direction of flow in systole and diastole: BA = systolic biphasic flow and primarily diastolic antegrade flow (n = 6); BR = systolic biphasic flow and primarily diastolic retrograde flow (n = 14); MA = systolic monophasic flow and primarily diastolic antegrade flow (n = 9); MR = systolic monophasic flow and primarily diastolic retrograde flow (n = 2). In the computational model, the temporal variation of flow directions within the FL was highly dependent on the position of assessment along the aorta. FL flow patterns (especially at the level of the diaphragm) showed their characteristic patterns due to variations in the cumulative size and the spatial distribution of the communicating tears, and the incidence of visceral side branches originating from the FL. Changes in wall stiffness did not change the temporal variation of the flows whereas it importantly determined intraluminal pressures. FL flow patterns implicitly codify morphological information on key determinants of aortic expansion in ADs. This data might be taken into consideration in the imaging protocol to define the predictive value of FL flows. PMID:28125720

  10. 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/.

  11. [The assessment of mechanical heart valves stenosis in adults after aortic valve replacement: the advantage of full-flow design of mechanical valve].

    PubMed

    Bokeria, L A; Bokeria, O L; Fadeev, A A; Makhachev, O A; Kosareva, T I; Averina, I I

    2013-01-01

    The analysis of transprosthetic hemodynamics in adults after aortic valve replacement in the Bakoulev Center for Cardiovascular Surgery in 2007-2010 demonstrated the hemodynamic advantage of the concept of new full-flow mechanical aortic valve prosthesis "CorBeat". Having the same size of internal orifice and tissue annulus diameters, the values of transprosthetic parameters (peak and mean gradients, blood flow velocities) through "CorBeat" were close to physiological values of transvalvular native aortic parameters and had a tendency to be not dependent on the size of prosthesis (p = 0.63). In the article for the first time a morphometric database of geometric values of internal orifice area of normal native aortic valves in adults was used taking into account both the gender and the body surface area's of a patient. There was also used the standardized prosthesis size Z-score which represents the number of SDs by which the internal prosthesis area differs from the mean normal native aortic valve area for the patient's body surface area. The article emphasizes the need of the personal selection of the size and the type of prosthesis for any patient as well as the need for new design development of prosthetic heart valves.

  12. 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

  13. Selective Pinacol-Coupling Reaction using a Continuous Flow System.

    PubMed

    Sotto, Nicolas; Cazorla, Clément; Villette, Carole; Billamboz, Muriel; Len, Christophe

    2016-11-18

    The first continuous flow pinacol coupling reaction of carbonyl compounds was successfully achieved within only 2 min during a single pass through a cartridge filled with zinc(0). The optimized method allowed the efficient production of gram-scale value-added compounds with high productivity. The developed methodology is efficient for aromatic or α,β-unsaturated aldehydes but gives moderate results for more stable acetophenone derivatives. Moreover, the flow method displayed better results in terms of yield and selectivity in comparison to the corresponding batch methodology.

  14. 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 (Cs2CO3 or K3PO4) 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.

  15. 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.

  16. 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.

  17. Continuous heatable Langmuir probe for flowing afterglow measurements

    NASA Astrophysics Data System (ADS)

    Laubé, Sylvain; Mostefaoui, Toufik; Rowe, Bertrand

    2000-02-01

    A heatable Langmuir probe consisting of a continuous dc-heating-current loop of tungsten wire is presented. This technique is efficient to keep the probe surface clean for flowing afterglow measurements. In our experimental conditions, the perturbations on the electron density determination can be considered as very small. The measurement of the well-known rate for the dissociative recombination of O2+ shows that the gas surrounding the probe is not heated for estimated probe temperature up to 700 K.

  18. Giant Volume Change of Active Gels under Continuous Flow

    DTIC Science & Technology

    2014-04-21

    communication17 of BZ droplets and chemical self-organiza- tion,18 the properties and potential of self-oscillating gels in a microfluidic system have yet to be...active gels driven by the Belousov−Zhabotinsky reaction. These results demon- strate that microfluidics offers a useful and facile experimental...soft materials and microfluidic systems. ■ INTRODUCTION This paper reports the use of a continuous reactant flow in a microfluidic system to achieve

  19. 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.

  20. Fluoride removal by a continuous flow electrocoagulation reactor.

    PubMed

    Emamjomeh, Mohammad M; Sivakumar, Muttucumaru

    2009-02-01

    Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. Electrocoagulation (EC) is an electrochemical technique, in which a variety of unwanted dissolved particles and suspended matter can be effectively removed from an aqueous solution by electrolysis. Continuous flow experiments with monopolar aluminium electrodes for fluoride removal were undertaken to investigate the effects of the different parameters such as: current density (12.5-50A/m(2)), flow rate (150-400 mL/min), initial pH (4-8), and initial fluoride concentration (5-25mg/L). The highest treatment efficiency was obtained for the largest current and the removal efficiency was found to be dependent on the current density, the flow rate and the initial fluoride concentration when the final pH ranged between 6 and 8. The composition of the sludge produced was analysed using the X-ray diffraction (XRD) spectrum. The strong presence of the aluminium hydroxide [Al(OH)(3)] in the above pH range, which maximizes the formation of aluminium fluoride hydroxide complex [Al(n)F(m)(OH)(3n-m)], is the main reason for defluoridation by electrocoagulation. The results obtained showed that the continuous flow electrocoagulation technology is an effective process for defluoridation of potable water supplies and could also be utilized for the defluoridation of industrial wastewater.

  1. 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.

  2. 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

  3. Experimental and computational studies on the flow fields in aortic aneurysms associated with deployment of AAA stent-grafts

    NASA Astrophysics Data System (ADS)

    Zhang, Xiwen; Yao, Zhaohui; Zhang, Yan; Xu, Shangdong

    2007-10-01

    Pulsatile flow fields in rigid abdominal aortic aneurysm (AAA) models were investigated numerically, and the simulation results are found in good agreement with particle image velocimetry (PIV) measurements. There are one or more vortexes in the AAA bulge, and a fairly high wall shear stress exists at the distal end, and thus the AAA is in danger of rupture. Medical treatment consists of inserting a vascular stent-graft in the AAA, which would decrease the blood impact to the inner walls and reduce wall shear stress so that the rupture could be prevented. A new computational model, based on porous medium model, was developed and results are documented. Therapeutic effect of the stent-graft was verified numerically with the new model.

  4. Abnormal distribution of pulmonary blood flow in aortic valve disease. Relation between pulmonary function and chest radiograph.

    PubMed

    Goodenday, L S; Simon, G; Craig, H; Dalby, L

    1970-05-01

    Wasted ventilatory volume (V(D)) and its ratio to tidal volume (V(D)/V(T)) were measured at rest and during exertion in 17 patients with aortic valve disease. We considered V(D)/V(T) to indicate abnormal ventilation: perfusion relations if it did not decrease on exertion, or if the exercising value was greater than 40 per cent. Plain chest radiographs were independently examined for evidence of diversion of pulmonary blood to the upper lobes. There was significant agreement (p<0.05) between radiographic and pulmonary function estimations of abnormality. This suggests that the raised pulmonary venous pressure associated with left ventricular failure creates an abnormal pattern of blood flow through the lung, which is responsible for causing inadequate perfusion with respect to ventilation.

  5. Non-Newtonian Study of Blood Flow in an Abdominal Aortic Aneurysm with a Stabilized Finite Element Method

    NASA Astrophysics Data System (ADS)

    Marrero, Victor; Sahni, Onkar; Jansen, Kenneth; Tichy, John; Taylor, Charles

    2008-11-01

    In recent years the methods of computational fluid dynamics (CFD) have been applied to the human cardiovascular system to better understand the relationship between arterial blood flow and the disease process, for example in an abdominal aortic aneurysm (AAA). Obviously, the technical challenges associated with such modeling are formidable. Among the many problems to be addressed, in this paper we add yet another complication -- the known non-Newtonian nature of blood. In this preliminary study, we used a patient-based AAA model with rigid walls. The pulsatile nature of the flow and the RCR outflow boundary condition are considered. We use the Carreau-Yasuda model to describe the non-Newtonian viscosity variation. Preliminary results for 200K, 2M, and 8M elements mesh are presented for the Newtonian and non-Newtonian cases. The broad fundamental issue we wish to eventually resolve is whether or not non-Newtonian effects in blood flow are sufficiently strong in unhealthy vessels that they must be addressed in meaningful simulations. Interesting differences during the flow cycle shed light on the problem, but further research is needed.

  6. Innovative Method for Greatly Reducing Flow Resistance and Obtaining Well-Ordered Continuous Flow

    NASA Astrophysics Data System (ADS)

    Lin, Weiyi

    2009-11-01

    In this paper, firstly, the experiment on the flow resistance of the aerated pipe flow is introduced. And some experimental research on comparison between different volumes of air entrained is presented. Secondly, the characteristics of Gravity Pipe Flow under the action of Torricelli's Vacuum, shortly called as GPFUTV are dissertated, including creative and functional design, fundamental principle, etc. Under GPFUTV condition the water flow in the tube is full-pipe and continuous, colorless and non-aerated, high-speed and non-rotational as distinguished from laminar flow. Thirdly, an appeal in relation to the experimental research, the applied studies and basic theory research is given. For instance, the well-known Reynolds' experiment under GPFUTV condition, the potential for GPFUTV to be developed for deep seawater suction technology, seawater intake pipe of OTEC and lifting technology for deep ocean mining in Fe-Mn concretions, flow stability and flow resistance under GPFUTV condition, etc.

  7. Noninvasive 4D pressure difference mapping derived from 4D flow MRI in patients with repaired aortic coarctation: comparison with young healthy volunteers.

    PubMed

    Rengier, Fabian; Delles, Michael; Eichhorn, Joachim; Azad, Yoo-Jin; von Tengg-Kobligk, Hendrik; Ley-Zaporozhan, Julia; Dillmann, Rüdiger; Kauczor, Hans-Ulrich; Unterhinninghofen, Roland; Ley, Sebastian

    2015-04-01

    To assess spatial and temporal pressure characteristics in patients with repaired aortic coarctation compared to young healthy volunteers using time-resolved velocity-encoded three-dimensional phase-contrast magnetic resonance imaging (4D flow MRI) and derived 4D pressure difference maps. After in vitro validation against invasive catheterization as gold standard, 4D flow MRI of the thoracic aorta was performed at 1.5T in 13 consecutive patients after aortic coarctation repair without recoarctation and 13 healthy volunteers. Using in-house developed processing software, 4D pressure difference maps were computed based on the Navier-Stokes equation. Pressure difference amplitudes, maximum slope of pressure amplitudes and spatial pressure range at mid systole were retrospectively measured by three readers, and twice by one reader to assess inter- and intraobserver agreement. In vitro, pressure differences derived from 4D flow MRI showed excellent agreement to invasive catheter measurements. In vivo, pressure difference amplitudes, maximum slope of pressure difference amplitudes and spatial pressure range at mid systole were significantly increased in patients compared to volunteers in the aortic arch, the proximal descending and the distal descending thoracic aorta (p < 0.05). Greatest differences occurred in the proximal descending aorta with values of the three parameters for patients versus volunteers being 19.7 ± 7.5 versus 10.0 ± 2.0 (p < 0.001), 10.9 ± 10.4 versus 1.9 ± 0.4 (p = 0.002), and 8.7 ± 6.3 versus 1.6 ± 0.9 (p < 0.001). Inter- and intraobserver agreements were excellent (p < 0.001). Noninvasive 4D pressure difference mapping derived from 4D flow MRI enables detection of altered intraluminal aortic pressures and showed significant spatial and temporal changes in patients with repaired aortic coarctation.

  8. 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

  9. Analytical solutions for flow fields near continuous wall reactive barriers

    NASA Astrophysics Data System (ADS)

    Klammler, Harald; Hatfield, Kirk

    2008-05-01

    Permeable reactive barriers (PRBs) are widely applied for in-situ remediation of contaminant plumes transported by groundwater. Besides the goal of a sufficient contaminant remediation inside the reactive cell (residence time) the width of plume intercepted by a PRB is of critical concern. A 2-dimensional analytical approach is applied to determine the flow fields towards rectangular PRBs of the continuous wall (CW) configuration with and without impermeable side walls (but yet no funnel). The approach is based on the conformal mapping technique and assumes a homogeneous aquifer with a uniform ambient flow field. The hydraulic conductivity of the reactive material is furthermore assumed to exceed the conductivity of the aquifer by at least one order of magnitude as to neglect the hydraulic gradient across the reactor. The flow fields are analyzed regarding the widths and shapes of the respective capture zones as functions of the dimensions (aspect ratio) of the reactive cell and the ambient groundwater flow direction. Presented are an improved characterization of the advantages of impermeable side walls, a convenient approach to improved hydraulic design (including basic cost-optimization) and new concepts for monitoring CW PRBs. Water level data from a CW PRB at the Seneca Army Depot site, NY, are used for field demonstration.

  10. Continuous flow magnetic cell fractionation based on antigen expression level.

    PubMed

    Schneider, Thomas; Moore, Lee R; Jing, Ying; Haam, Seungjoo; Williams, P Stephen; Fleischman, Aaron J; Roy, Shuvo; Chalmers, Jeffrey J; Zborowski, Maciej

    2006-07-31

    Cell separation is important in medical and biological research and plays an increasingly important role in clinical therapy and diagnostics, such as rare cancer cell detection in blood. The immunomagnetic labeling of cells with antibodies conjugated to magnetic nanospheres gives rise to a proportional relationship between the number of magnetic nanospheres attached to the cell and the cell surface marker number. This enables the potential fractionation of cell populations by magnetophoretic mobility (MM). We exploit this feature with our apparatus, the Dipole Magnet Flow Fractionator (DMFF), which consists of an isodynamic magnetic field, an orthogonally-oriented thin ribbon of cell suspension in continuous sheath flow, and ten outlet flows. From a sample containing a 1:1 mixture of immunomagnetically labeled (label+) and unlabeled (label-) cells, we achieved an increase in enrichment of the label+ cell fraction with increasing outlet numbers in the direction of the magnetic field gradient (up to 10-fold). The total recovery of the ten outlet fractions was 90.0+/-7.7%. The mean MM of label+ cells increased with increasing outlet number by up to a factor of 2.3. The postulated proportionality between the number of attached magnetic beads and the number of cell surface markers was validated by comparison of MM measured by cell tracking velocimetry (CTV) with cell florescence intensity measured by flow cytometry.

  11. Electrohydrodynamic distortion of sample streams in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1989-01-01

    Continuous flow electrophoresis experiments were carried out, using an electrolyte and a sample both made of aqueous solutions of phosphate buffer (with polystyrene latex added for visibility), to investigate causes of the sample spreading in this procedure. It is shown theoretically that an electric field perpendicular to a circular filament of conducting fluid surrounded by a fluid of different conductivity produces an electrohydrodynamic flow, which distorts the filament into an ellipse. Experimental results were found to be fully consistent with theretical predictions. It was found that the rate of distortion of the sample stream into a ribbon was proportional to the square of the applied voltage gradient. Furthermore, the orientation of the ribbon depends on the ratios of dielectric constant and electrical conductivity between the buffer and the sample.

  12. 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.

  13. Synthesis of nanomaterials by continuous-flow microfluidics: a review.

    PubMed

    Makgwane, Peter Ramashadi; Ray, Suprakas Sinha

    2014-02-01

    The development of controlled synthesis protocols of nanostructured materials with tailored particle size and shape has been a significant research area in nanoscience and nanotechnology. Much innovative research efforts had been focused on finding suitable chemical reagents and synthetic methodologies that offer opportunities to produce the desired structure-function controlled nanomaterials. On the other hand, the reactor equipment for the synthesis of these tailored nanomaterials is of prime importance not only at laboratory-scale but also with view of up-scaling the synthetic processes into large-scale productions. Whilst the sequential three-stage scale-up from the conventional process (i.e., lab-scale/pilot-scale/large-scale) using multi-purpose batch reactor is masked with complications, on the other hand, the interface of nanomaterials synthesis processes and continuous-flow microfluidic chemistry has demonstrated relatively superior process performance over conventional technologies. Consequently, the uses of continuous-flow microfluidics systems have recently attracted much research attention as versatile tools for the synthesis of various structured nanomaterials. In this review, we highlight and analyze the key achievements to date of adopting microfluidics technologies for the controlled synthesis of nanomaterials with well-defined structural properties desirable for the intended applications. We devote the significant emphasis on demonstrating the improved potential characteristics features of continuous-flow microfluidics as a capable technology to provide efficient synthesis processes for the production of various nanosized scale structured materials with precise control of the involved chemistry. Moreover, we discuss the novel process window opportunities of hyphenated microfluidics nanoparticles synthesis with the in-situ or in-line structure characterization during synthesis under real-time reaction conditions which provide interesting insights

  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. 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.

  16. Prilezhaev dihydroxylation of olefins in a continuous flow process.

    PubMed

    van den Broek, Bas A M W; Becker, René; Kössl, Florian; Delville, Mariëlle M E; Nieuwland, Pieter J; Koch, Kaspar; Rutjes, Floris P J T

    2012-02-13

    Epoxidation of both terminal and non-terminal olefins with peroxy acids is a well-established and powerful tool in a wide variety of chemical processes. In an additional step, the epoxide can be readily converted into the corresponding trans-diol. Batch-wise scale-up, however, is often troublesome because of the thermal instability and explosive character of the peroxy acids involved. This article describes the design and semi-automated optimization of a continuous flow process and subsequent scale-up to preparative production volumes in an intrinsically safe manner.

  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. 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.

  19. Characterization of renal parenchymal perfusion during experimental infrarenal aortic clamping and declamping with enhanced thermodiffusion electrodes.

    PubMed

    Kraus, T; Mehrabi, A; Angelescu, M; Golling, M; Allenberg, J R; Klar, E

    2001-07-01

    Despite multiple previous experimental and clinical investigations, it has not been fully clarified until now whether infrarenal aortic cross-clamping (IRAC) induces a significant disturbance of renal parenchymal perfusion. Most renal cortical flow data collected thus far have been heterogenous because of inherent limitations of available measurement technology. The enhanced thermal diffusion (TD) electrode is a newly developed and previously validated prototype device that allows continuous quantification of parenchymal kidney perfusion after local probe implantation. We monitored renal perfusion during experimental IRAC with TD for the first time, thereby also evaluating the potential applicability of the method in clinical aortic surgery. IRAC (20 min) followed by sudden declamping was performed in pigs under general anesthesia (n = 14). Renal cortical blood flow (RCBF) was continuously quantified by TD, total aortic flow (TABF) and renal artery flow (RABF) were measured by ultrasonic flow probes, and parameters of systemic circulation were determined by Swan-Ganz catheter. Our results showed that kidney perfusion can be continuously quantified using TD electrodes during experimental aortic surgery in a porcine model. IRAC does not lead to a significant impairment of RCBF in young pigs as measured by TD. Renal perfusion appears to be predominantly pressure driven. Consequently, abrubt aortic declamping can bring about prolonged renal ischemia. Transfer of the TD method to RCBF monitoring during clinical aortic surgery appears to be feasible and should be investigated in selected cases.

  20. Direct and Continuous Numerical Simulations of Bubbly Flows

    NASA Astrophysics Data System (ADS)

    Lu, Tianshi; Samulyak, Roman; Glimm, James

    2003-11-01

    We have studied numerically the propagation of linear and nonlinear waves in bubbly flows using direct and continuous approaches. The direct method represents a mixture of gas bubbles in a liquid as a system of one phase domains separated by free interfaces. FronTier, a front tracking hydro code was used for numerical simulations. It is capable of tracking simultaneously a large number of interfaces and resolving their topological changes (the breakup and merger of bubbles) in two- and three-dimensional spaces. The continuous method describes a bubbly fluid as a homogeneous system or pseudofluid that obeys an equation of state of single-component flow. Homogeneous equation of state models based on the Rayleigh-Plesset equation have been developed for the FronTier code. We have compared results of our numerical simulations with theoretical predictions and experimental data on the propagation of shocks and linear sound waves in bubbly fluids. The two methods can be applied to estimate the efficiency of gas bubble mitigation in reducing the cavitation erosion of the container of the Spallation Neutron Source liquid mercury target.

  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.

  2. 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.

  3. Continuous-flow automation and hemolysis index: a crucial combination.

    PubMed

    Lippi, Giuseppe; Plebani, Mario

    2013-04-01

    A paradigm shift has occurred in the role and organization of laboratory diagnostics over the past decades, wherein consolidation or networking of small laboratories into larger factories and point-of-care testing have simultaneously evolved and now seem to favorably coexist. There is now evidence, however, that the growing implementation of continuous-flow automation, especially in closed systems, has not eased the identification of hemolyzed specimens since the integration of preanalytical and analytical workstations would hide them from visual scrutiny, with an inherent risk that unreliable test results may be released to the stakeholders. Along with other technical breakthroughs, the new generation of laboratory instrumentation is increasingly equipped with systems that can systematically and automatically be tested for a broad series of interferences, the so-called serum indices, which also include the hemolysis index. The routine implementation of these technical tools in clinical laboratories equipped with continuous-flow automation carries several advantages and some drawbacks that are discussed in this article.

  4. 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

  5. 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

  6. Aortic Arch Interruption and Persistent Fifth Aortic Arch in Phace Syndrome: Prenatal Diagnosis and Postnatal Course.

    PubMed

    Chiappa, Enrico; Greco, Antonella; Fainardi, Valentina; Passantino, Silvia; Serranti, Daniele; Favilli, Silvia

    2015-09-01

    PHACE is a rare congenital neurocutaneous syndrome where posterior fossa malformations, hemangiomas, cerebrovascular anomalies, aortic arch anomalies, cardiac defects, and eye abnormalities are variably associated. We describe the prenatal detection and the postnatal course of a child with PHACE syndrome with a unique type of aortic arch anomaly consisting of proximal interruption of the aortic arch and persistence of the fifth aortic arch. The fifth aortic arch represented in this case a vital systemic-to-systemic connection between the ascending aorta and the transverse portion of the aortic arch allowing adequate forward flow through the aortic arch without surgical treatment.

  7. PDBD with continuous liquids flows in a discharge reactor

    NASA Astrophysics Data System (ADS)

    Rodríguez-Méndez, B. G.; Gutiérrez-León, D. G.; Belman-Flores, J. M.; López-Callejas, R.; Valencia-Alvarado, R.; Muñoz-Castro, A. E.; Mercado-Cabrera, A.; Peña-Eguiluz, R.; de la Piedad-Beneitez, A.

    2015-03-01

    This paper presents the design, construction and testing of a cylindrical pulsed dielectric barrier discharge (PDBD) reactor aimed to microbiological elimination of Escherichia coli ATCC 8739 bacteria. In the reactor, water flowed continuously and to countercurrent an oxygen gas was injected. The water pumping was carried out with a peristaltic pump type, stainless steel and aluminum constructed, and water was recirculated through norprene tubing. The considered parameters in order to promote energetic efficiency were: the residence time of the water contaminated with bacteria, flow rate of the liquid, shape and material used to build electrodes and dielectric, pressure, and gas injection flow rate. The pulsed power supply parameters are featured by 25-30 kV high voltage, 500 Hz frequency and 30 μs width. The outcome elimination of E. coli bacteria at 103, 104 and 106 CFU/mL concentrations reached an efficiency over 0.5 log-order in absence of oxygen; while >2 log-orders when oxygen gas was injected during the process.

  8. Clinical implications of physiological flow adjustment in continuous-flow left ventricular assist devices.

    PubMed

    Tchantchaleishvili, Vakhtang; Luc, Jessica G Y; Cohan, Caitlin M; Phan, Kevin; Hübbert, Laila; Day, Steven W; Massey, H Todd

    2016-11-15

    There is increasing evidence for successful management of end-stage heart failure with continuous-flow left ventricular assist device (CF-LVAD) technology. However, passive flow adjustment at fixed CF-LVAD speed is susceptible to flow balancing issues as well as adverse hemodynamic effects relating to the diminished arterial pulse pressure and flow. With current therapy, flow cannot be adjusted with changes in venous return, which can vary significantly with volume status. This limits the performance and safety of CF-LVAD. Active flow adjustment strategies have been proposed to improve the synchrony between the pump and the native cardiovascular system, mimicking the Frank-Starling mechanism of the heart. These flow adjustment strategies include modulation by CF-LVAD pump speed by synchrony and maintenance of constant flow or constant pressure head, or a combination of these variables. However, none of these adjustment strategies have evolved sufficiently to gain widespread attention. Herein we review the current challenges and future directions of CF-LVAD therapy and sensor technology focusing on the development of a physiologic, long-term active flow adjustment strategy for CF-LVADs.

  9. Continuous-Flow Detector for Rapid Pathogen Identification

    SciTech Connect

    Barrett, Louise M.; Skulan, Andrew J.; Singh, Anup K.; Cummings, Eric B.; Fiechtner, Gregory J.

    2006-09-01

    This report describes the continued development of a low-power, portable detector for the rapid identification of pathogens such as B. anthracis and smallpox. Based on our successful demonstration of the continuous filter/concentrator inlet, we believe strongly that the inlet section will enable differentiation between viable and non-viable populations, between types of cells, and between pathogens and background contamination. Selective, continuous focusing of particles in a microstream enables highly selective and sensitive identification using fluorescently labeled antibodies and other receptors such as peptides, aptamers, or small ligands to minimize false positives. Processes such as mixing and lysing will also benefit from the highly localized particle streams. The concentrator is based on faceted prisms to contract microfluidic flows while maintaining uniform flowfields. The resulting interfaces, capable of high throughput, serve as high-, low-, and band-pass filters to direct selected bioparticles to a rapid, affinity-based detection system. The proposed device is superior to existing array-based detectors as antibody-pathogen binding can be accomplished in seconds rather than tens of minutes or even hours. The system is being designed to interface with aerosol collectors under development by the National Laboratories or commercial systems. The focused stream is designed to be interrogated using diode lasers to differentiate pathogens by light scattering. Identification of particles is done using fluorescently labeled antibodies to tag the particles, followed by multiplexed laser-induced fluorescence (LIF) detection (achieved by labeling each antibody with a different dye).

  10. The Impact of Direct Cardiac Output Determination On Using A Widely Available Direct Continuous Oxygen Consumption Measuring Device On The Hemodynamic Assessment of Aortic Valve

    PubMed Central

    Fanari, Zaher; Grove, Matthew; Rajamanickam, Anitha; Hammami, Sumaya; Walls, Cassie; Kolm, Paul; Saltzberg, Mitchell; Weintraub, William S.; Doorey, Andrew J.

    2016-01-01

    Background Accurate assessment of cardiac output (CO) is essential for the hemodynamic assessment of aortic valve area (AVA). Estimation of oxygen consumption (VO2) and Thermodilution (TD) is employed in many cardiac catheterization laboratories (CCL) given the historically cumbersome nature of direct continuous VO2 measurement, the “gold standard” for this technique. A portable facemask device simplifies the direct continuous measurement of VO2, allowing for relatively rapid and continuous assessment of CO and AVA. Methods and Materials Seventeen consecutive patients undergoing right heart catheterization had simultaneous determination of CO by both direct continuous and assumed VO2 and TD. Assessments were only made when a plateau of VO2 had occurred. All measurements of direct continuous and assumed VO2, as well as, TD CO were obtained in triplicate. Results Direct continuous VO2 CO and assumed VO2 CO correlated poorly (R= 0.57; ICC =0.59). Direct continuous VO2 CO and TD CO also correlated poorly (R= 0.51; ICC=0.60). Similarly AVA derived from direct continuous VO2 correlated poorly with those of assumed VO2 (R= 0.68; ICC=0.55) and TD (R=0.66, ICC=0.60). Repeated direct continuous VO2 CO and AVA measurements were extremely correlated and reproducible [(R=0.93; ICC=0.96) and (R=0.99; ICC>0.99) respectively], suggesting that this was the most reliable measurement of CO. Conclusions CO calculated from direct continuous VO2 measurement varies substantially from both assumed VO2 and TD based CO, which are widely used in most CCL. These differences may significantly impact the CO and AVA measurements. Furthermore, continuous, rather than average, measurement of VO2 appears to give highly reproducible results. PMID:27904163

  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. Drops transformed from a continuous flow on a superhydrophobic incline

    NASA Astrophysics Data System (ADS)

    Katariya, Mayur; Ng, Tuck Wah

    2013-08-01

    Biochemical analysis with discrete drops on superhydrophobic surfaces will benefit from low loss, low contamination and open access features, but is challenged by the ability to generate them. A simple approach for delivering the drops from a continuous flow through an inclined superhydrophobic surface here showed the rear pinning contact line to be strongly influential in retention, providing potential for volume control, yet without any lossy daughter droplet formation. At a high flowrate regime prior to jetting, the liquid body was found to develop a grown out section that was able to flip up and down to be airborne, depending on the gravitational effect. While the section was airborne, the drop was able to increase its volume without the action of the three-phase mechanics dictating detachment.

  13. On-chip diamagnetic repulsion in continuous flow.

    PubMed

    Tarn, Mark D; Hirota, Noriyuki; Iles, Alexander; Pamme, Nicole

    2009-02-01

    We explore the potential of a microfluidic continuous flow particle separation system based on the repulsion of diamagnetic materials from a high magnetic field. Diamagnetic polystyrene particles in paramagnetic manganese (II) chloride solution were pumped into a microfluidic chamber and their deflection behaviour in a high magnetic field applied by a superconducting magnet was investigated. Two particle sizes (5 and 10 μm) were examined in two concentrations of MnCl2 (6 and 10%). The larger particles were repelled to a greater extent than the smaller ones, and the effect was greatly enhanced when the particles were suspended in a higher concentration of MnCl2. These findings indicate that the system could be viable for the separation of materials of differing size and/or diamagnetic susceptibility, and as such could be suitable for the separation and sorting of small biological species for subsequent studies.

  14. Thermohydraulic modelling of a transfer line for continuous flow cryostats

    NASA Astrophysics Data System (ADS)

    Dittmar, N.; Weisemann, A.; Haberstroh, Ch; Hesse, U.; Krzyzowski, M.

    2017-02-01

    Continuous flow cryostats have to be steadily supplied with the cryogenic cooling agent, e.g. liquid helium (LHe) via a transfer line. The overall setup has to be characterised by a low consumption of the cryogen, determined not only by the cryostat design, but also by the transfer line design. In order to improve the transfer line’s performance, i.e. reducing the evaporation losses a thermohydraulic model has been developed to evaluate different transfer line designs. The presented model is validated by experimental data achieved with a transfer line equipped with built-in pressure sensors. This transfer line has been designed in order to examine the related frictional pressure drop. The developed model allows to examine the impact of the hydraulic and the insulation design on the resulting evaporation losses.

  15. New Continuous-Flow Total Artificial Heart and Vascular Permeability

    PubMed Central

    Feng, Jun; Cohn, William E.; Parnis, Steven M.; Sodha, Neel R.; Clements, Richard T.; Sellke, Nicholas; Frazier, O. Howard; Sellke, Frank W.

    2015-01-01

    Background We tested the short-term effects of completely non-pulsatile versus pulsatile circulation after ventricular excision and replacement with total implantable pumps in an animal model on peripheral vascular permeability. Methods Ten calves underwent cardiac replacement with two HeartMate III continuous-flow rotary pumps. In five calves, the pump speed was rapidly modulated to impart a low-frequency pulse pressure in the physiologic range (10–25 mmHg) at a rate of 40 pulses per minute (PP). The remaining 5 calves were supported with a pulseless systemic circulation and no modulation of pump speed (NP). Skeletal muscle biopsies were obtained before cardiac replacement (baseline) and on postoperative days (POD) 1, 7 and 14. Skeletal muscle tissue water content was measured and morphological alterations of skeletal muscle were assessed. VE-cadherin, phospho-VE-cadherin and CD31 were analyzed by immuno-histochemistry. Results There were no significant changes in tissue water content and skeletal muscle morphology within group or between groups at baseline, POD 1, 7 and 14, respectively. There were no significant alterations in the expression/distribution of VE-cadherin, phospho-VE cadherin and CD31 in skeletal muscle vasculature at baseline, POD 1, 7 and 14 within each group or between the two groups, respectively. Although continuous-flow total artificial heart (CFTAH) with or without a pulse pressure caused slight increase in tissue water content and histological damage scores at POD 7 and 14, it failed to reach statistical significance. Conclusions There was no significant adherens-junction protein degradation and phosphorylation in calf skeletal muscle microvasculature after CFTAH implantation, suggesting that short term of CFTAH with or without pulse pressure did not cause peripheral endothelial injury and did not increase the peripheral microvascular permeability. PMID:26188957

  16. 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.

  17. Continuous flow analysis of labile iron in ice-cores.

    PubMed

    Hiscock, William T; Fischer, Hubertus; Bigler, Matthias; Gfeller, Gideon; Leuenberger, Daiana; Mini, Olivia

    2013-05-07

    The important active and passive role of mineral dust aerosol in the climate and the global carbon cycle over the last glacial/interglacial cycles has been recognized. However, little data on the most important aeolian dust-derived biological micronutrient, iron (Fe), has so far been available from ice-cores from Greenland or Antarctica. Furthermore, Fe deposition reconstructions derived from the palaeoproxies particulate dust and calcium differ significantly from the Fe flux data available. The ability to measure high temporal resolution Fe data in polar ice-cores is crucial for the study of the timing and magnitude of relationships between geochemical events and biological responses in the open ocean. This work adapts an existing flow injection analysis (FIA) methodology for low-level trace Fe determinations with an existing glaciochemical analysis system, continuous flow analysis (CFA) of ice-cores. Fe-induced oxidation of N,N'-dimethyl-p-pheylenediamine (DPD) is used to quantify the biologically more important and easily leachable Fe fraction released in a controlled digestion step at pH ~1.0. The developed method was successfully applied to the determination of labile Fe in ice-core samples collected from the Antarctic Byrd ice-core and the Greenland Ice-Core Project (GRIP) ice-core.

  18. Prototype continuous flow ventricular assist device supported on magnetic bearings.

    PubMed

    Allaire, P E; Kim, H C; Maslen, E H; Olsen, D B; Bearnson, G B

    1996-06-01

    This article describes a prototype continuous flow pump (CFVAD2) fully supported in magnetic bearings. The pump performance was measured in a simulated adult human circulation system. The pump delivered 6 L/min of flow at 100 mm Hg of differential pressure head operating at 2,400 rpm in water. The pump is totally supported in 4 magnetic bearings: 2 radial and 2 thrust. Magnetic bearings offer the advantages of no required lubrication and large operating clearances. The geometry and other properties of the bearings are described. Bearing parameters such as load capacity and current gains are discussed. Bearing coil currents were measured during operation in air and water. The rotor was operated in various orientations to determine the actuator current gains. These values were then used to estimate the radial and thrust forces acting on the rotor in both air and water. Much lower levels of force were found than were expected, allowing for a very significant reduction in the size of the next prototype. Hemolysis levels were measured in the prototype pump and found not to indicate damage to the blood cells.

  19. 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.

  20. Shear-scaling-based approach for irreversible energy loss estimation in stenotic aortic flow - An in vitro study.

    PubMed

    Gülan, Utku; Binter, Christian; Kozerke, Sebastian; Holzner, Markus

    2017-03-12

    Today, the functional and risk assessment of stenosed arteries is mostly based on ultrasound Doppler blood flow velocity measurements or catheter pressure measurements, which rely on several assumptions. Alternatively, blood velocity including turbulent kinetic energy (TKE) may be measured using MRI. The aim of the present study is to validate a TKE-based approach that relies on the fact that turbulence production is dominated by the flow's shear to determine the total irreversible energy loss from MRI scans. Three-dimensional particle tracking velocimetry (3D-PTV) and phase-contrast magnetic resonance imaging (PC-MRI) simulations were performed in an anatomically accurate, compliant, silicon aortic phantom. We found that measuring only the laminar viscous losses does not reflect the true losses of stenotic flows since the contribution of the turbulent losses to the total loss become more dominant for more severe stenosis types (for example, the laminar loss is 0.0094±0.0015W and the turbulent loss is 0.0361±0.0015W for the Remax=13,800 case, where Remax is the Reynolds number based on the velocity in the vena-contracta). We show that the commonly used simplified and modified Bernoulli's approaches overestimate the total loss, while the new TKE-based method proposed here, referred to as "shear scaling" approach, results in a good agreement between 3D-PTV and simulated PC-MRI (mean error is around 10%). In addition, we validated the shear scaling approach on a geometry with post-stenotic dilatation using numerical data by Casas et al. (2016). The shear scaling-based method may hence be an interesting alternative for irreversible energy loss estimation to replace traditional approaches for clinical use. We expect that our results will evoke further research, in particular patient studies for clinical implementation of the new method.

  1. Experimental unsteady flow study in a patient-specific abdominal aortic aneurysm model

    NASA Astrophysics Data System (ADS)

    Stamatopoulos, Ch.; Mathioulakis, D. S.; Papaharilaou, Y.; Katsamouris, A.

    2011-06-01

    The velocity field in a patient-specific abdominal aneurysm model including the aorto-iliac bifurcation was measured by 2D PIV. Phase-averaged velocities obtained in 14 planes reveal details of the flow evolution during a cycle. The aneurysm expanding asymmetrically toward the anterior side of the aorta causes the generation of a vortex at its entrance, covering the entire aneurysm bulge progressively before flow peak. The fluid entering the aneurysm impinges on the left side of its distal end, following the axis of the upstream aorta segment, causing an increased flow rate in the left (compared to the right) common iliac artery. High shear stresses appear at the aneurysm inlet and outlet as well as along the posterior wall, varying proportionally to the flow rate. At the same regions, elevated flow disturbances are observed, being intensified at flow peak and during the deceleration phase. Low shear stresses are present in the recirculation region, being two orders of magnitude smaller than the previous ones. At flow peak and during the deceleration phase, a clockwise swirling motion (viewed from the inlet) is present in the aneurysm due to the out of plane curvature of the aorta.

  2. 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.

  3. [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.

  4. Aortic Valve Disease

    MedlinePlus

    ... Ventricle Normal Heart Select Disease To Learn More Aortic Stenosis Aortic Insufficiency Aorta The aorta is the main ... the rest of your body. Aortic Valve In aortic stenosis, the aortic valve becomes narrowed and does not ...

  5. 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.

  6. 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.

  7. Stress echocardiography to assess stenosis severity and predict outcome in patients with paradoxical low-flow, low-gradient aortic stenosis and preserved LVEF.

    PubMed

    Clavel, Marie-Annick; Ennezat, Pierre Vladimir; Maréchaux, Sylvestre; Dumesnil, Jean G; Capoulade, Romain; Hachicha, Zeineb; Mathieu, Patrick; Bellouin, Annaïk; Bergeron, Sébastien; Meimoun, Patrick; Arsenault, Marie; Le Tourneau, Thierry; Pasquet, Agnès; Couture, Christian; Pibarot, Philippe

    2013-02-01

    The objective of this study was to examine the value of stress-echocardiography in patients with paradoxical low-flow, low-gradient (PLFLG) aortic stenosis (AS). The projected aortic valve area (AVAProj) at a normal flow rate was calculated in 55 patients with PLFLG AS. In the subset of patients (n = 13) who underwent an aortic valve replacement within 3 months after stress echocardiography, AVA(Proj) correlated better with the valve weight compared to traditional resting and stress echocardiographic parameters of AS severity (AVA(Proj): r = -0.78 vs. other parameters: r = 0.46 to 0.56). In the whole group (N = 55), 18 (33%) patients had an AVA(Proj) >1.0 cm(2), being consistent with the presence of pseudo severe AS. The AVA(Proj) was also superior to traditional parameters of stenosis severity for predicting outcomes (hazard ratio: 1.32/0.1 cm(2) decrease in AVA(Proj)). In patients with PLFLG AS, the measurement of AVA(proj) derived from stress echocardiography is helpful to determine the actual severity of the stenosis and predict risk of adverse events.

  8. Development of a patient-specific simulation tool to analyse aortic dissections: assessment of mixed patient-specific flow and pressure boundary conditions.

    PubMed

    Alimohammadi, Mona; Agu, Obiekezie; Balabani, Stavroula; Díaz-Zuccarini, Vanessa

    2014-03-01

    Aortic dissection has high morbidity and mortality rates and guidelines regarding surgical intervention are not clearly defined. The treatment of aortic dissection varies with each patient and detailed knowledge of haemodynamic and mechanical forces would be advantageous in the process of choosing a course of treatment. In this study, a patient-specific dissected aorta geometry is constructed from computed tomography scans. Dynamic boundary conditions are implemented by coupling a three element Windkessel model to the 3D domain at each outlet, in order to capture the essential behaviour of the downstream vasculature. The Windkessel model parameters are defined based on clinical data. The predicted minimum and maximum pressures are close to those measured invasively. Malperfusion is indicated and complex flow patterns are observed. Pressure, flow and wall shear stress distributions are analysed. The methodology presented here provides insight into the haemodynamics in a patient-specific dissected aorta and represents a development towards the use of CFD simulations as a diagnostic tool for aortic dissection.

  9. Role of the left aortic arch and blood flows in embryonic American alligator (Alligator mississippiensis).

    PubMed

    Eme, John; Crossley, Dane A; Hicks, James W

    2011-04-01

    All embryonic and fetal amniotes possess a ductus(i) arteriosus(i) that allows blood to bypass the pulmonary circulation and the non-functional lungs. The central hemodynamic of embryonic reptiles are unique, given the additional systemic aorta that allows pulmonary circulatory bypass, the left aorta (LAo). The LAo exits in the right ventricle or 'pulmonary side' of reptilian hearts in both embryos and adults, but its functional significance in ovo is unknown. This study investigated the role of the LAo in embryonic American alligators by surgically occluding the LAo and measuring oxygen consumption and, in addition, measured hemodynamic responses to hypoxia in embryonic alligators. We measured systemic cardiac output and primary chorioallantoic membrane (CAM) artery blood flow for normoxic and hypoxic-incubated (10% O(2)) American alligator embryos (Alligator mississippiensis). Chronic blood flow (1-124 h) in the primary CAM artery for hypoxic-incubated embryos (92 ± 26 ml min(-1) kg(-1)) was elevated when compared with normoxic-incubated embryos (29 ± 14 ml min(-1) kg(-1), N = 6; P = 0.039). For hypoxic-incubated embryos, acute LAo blood flow (49.6 ± 24.4 ml min(-1) kg(-1)) was equivalent to the combined flow of the three systemic great vessels that arise from the left ventricle, the right aorta, common carotid and subclavian arteries (43.6 ± 21.5 ml min(-1) kg(-1), N = 5). Similarly, for normoxic-incubated embryos, LAo blood flow (27.3 ± 6.6 ml min(-1) kg(-1)) did not statistically differ from the other three vessels (18.4 ± 4.9 ml min(-1) kg(-1), N = 5). This study contains the first direct test of LAo function and the first measurements of blood flow in an embryonic reptile. These data support the hypotheses that embryonic alligators utilize the LAo to divert a significant amount of right ventricular blood into the systemic circulation, and that CAM blood flow increases following chronic hypoxic conditions. However, surgical occlusion of the LAo did not

  10. Continuous flowing membraneless microbial fuel cells with separated electrode chambers.

    PubMed

    Du, Fangzhou; Xie, Beizhen; Dong, Wenbo; Jia, Boyang; Dong, Kun; Liu, Hong

    2011-10-01

    Microbial fuel cell (MFC) is an emerging technology in the energy and environment field. Its application is limited due to its high cost caused by the utilization of membranes and noble metal catalysts. In this paper, a membraneless MFC, with separated electrode chambers, was designed. The two separated chambers are connected via a channel and the continuous electrolyte flow from anode to cathode drives proton transfer. The proton mass transfer coefficiency in this MFC is 0.9086 cm/s, which is higher than reported MFCs with membranes, such as J-cloth and glass fiber. The maximum output voltage is 160.7 mV, with 1000 Ω resistor. Its peak power density is 24.33 mW/m³. SCOD removal efficiency can reach 90.45% via this MFC. If the connection between the two electrode chambers is blocked, the performance of MFC will decrease severely. All the above results prove the feasibility and advantages of this special MFC model.

  11. 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.

  12. Randomized Trial of the Effect of Magnesium Sulfate Continuous Infusion on IL-6 and CRP Serum Levels Following Abdominal Aortic Aneurysm Surgery

    PubMed Central

    Mojtahedzadeh, Mojtaba; chelkeba, Legese; Ranjvar- Shahrivar, Mona; Najafi, Atabak; Moini, Majid; Najmeddin, Farhad; Sadeghi, Kourosh; Barkhordari, Khosro; Gheymati, Azin; Ahmadi, Arezoo

    2016-01-01

    Abdominal aortic aneurysm (AAA) is widely considered as the disease of elderly white men. Inflammation is one of the most well-known mechanisms involved in the pathogenesis of AAA. Magnesium is one of the most important minerals in the body with established anti-inflammatory effects. In this study, we aimed to investigate the impact of Mg loading following AAA surgery on two inflammation markers, IL-6 and CRP, as well as patientʼs outcome. This study was conducted as a randomized clinical trial on 18 patients (divided into two groups) after surgical correction of Acute Aortic Aneurysm (AAA). All the patients admitted in ICU ward of Sina Hospital. In intervention group, 10 g of MgSO4 has been infused through 12 h. The control group has not received the intervention. IL-6 and CRP were measured and compared at times 0, 12, 24 and 36 h. The patients were monitored for 36 h. After intervention, the differences of heart rate and APACHE II score were not statistically significant between intervention and control groups (P = 0.097 and P = 0.472, respectively). IL-6 levels decreased consistently in both groups after inclusion in the study. However, IL-6 level was significantly less in intervention group early after the end of MgSO4 infusion comparing with control group (P = 0.01). Likewise, the CRP level decreased significantly after inclusion in the study (P = 0.005). However, these changes were not significant between intervention and control groups (P = 0.297). According to the results of this study, continuous infusion of MgSO4 after AAA surgery may provide IL-6 suppression. PMID:28243294

  13. 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.

  14. Continuous-flow solar UVB disinfection reactor for drinking water.

    PubMed

    Mbonimpa, Eric Gentil; Vadheim, Bryan; Blatchley, Ernest R

    2012-05-01

    Access to safe, reliable sources of drinking water is a long-standing problem among people in developing countries. Sustainable solutions to these problems often involve point-of-use or community-scale water treatment systems that rely on locally-available resources and expertise. This philosophy was used in the development of a continuous-flow, solar UVB disinfection system. Numerical modeling of solar UVB spectral irradiance was used to define temporal variations in spectral irradiance at several geographically-distinct locations. The results of these simulations indicated that a solar UVB system would benefit from incorporation of a device to amplify ambient UVB fluence rate. A compound parabolic collector (CPC) was selected for this purpose. Design of the CPC was based on numerical simulations that accounted for the shape of the collector and reflectance. Based on these simulations, a prototype CPC was constructed using materials that would be available and inexpensive in many developing countries. A UVB-transparent pipe was positioned in the focal area of the CPC; water was pumped through the pipe to allow exposure of waterborne microbes to germicidal solar UVB radiation. The system was demonstrated to be effective for inactivation of Escherichia coli, and DNA-weighted UV dose was shown to govern reactor performance. The design of the reactor is expected to scale linearly, and improvements in process performance (relative to results from the prototype) can be expected by use of larger CPC geometry, inclusion of better reflective materials, and application in areas with greater ambient solar UV spectral irradiance than the location of the prototype tests. The system is expected to have application for water treatment among communities in (developing) countries in near-equatorial and tropical locations. It may also have application for disaster relief or military field operations, as well as in water treatment in areas of developed countries that receive

  15. Sample stream distortion modeled in continuous-flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, P. H.

    1979-01-01

    Buoyancy-induced disturbances in an electrophoresis-type chamber were investigated. Five tracer streams (latex) were used to visualize the flows while a nine-thermistor array sensed the temperature field. The internal heating to the chamber was provided by a 400 Hz electrical field. Cooling to the chamber was provided on the front and back faces and, in addition, on both chamber side walls. Disturbances to the symmetric base flow in the chamber occurred in the broad plane of the chamber and resulted from the formation of lateral and axial temperature gradients. The effect of these gradients was to retard or increase local flow velocities at different positions in the chamber cross section, which resulted in lateral secondary flows being induced in the broad plane of the chamber. As the adverse temperature gradients increased in magnitude, the critical Rayleigh number was approached and reverse (separated) flow became apparent, which, subsequently, led to the onset of time variant secondary flows.

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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.

  2. Continuous flow in open microfluidics using controlled evaporation.

    PubMed

    Zimmermann, Martin; Bentley, Steven; Schmid, Heinz; Hunziker, Patrick; Delamarche, Emmanuel

    2005-12-01

    This paper presents a method for programming the flow rate of liquids inside open microfluidic networks (MFNs). A MFN comprises a number of independent flow paths, each of which starts with an open filling port, has a sealed microchannel in which assays can be performed, and an open capillary pump (CP). The MFN is placed over Peltier elements and its flow paths initially fill owing to capillary forces when liquids are added to the filling ports. A cooling Peltier element underneath the filling ports dynamically prevents evaporation in all filling ports using the ambient temperature and relative humidity as inputs. Another Peltier element underneath the CPs heats the pumps thereby inducing evaporation in the CPs and setting the flow rate in the microchannels. This method achieves flow rates in the microchannels ranging from approximately 1.2 nL s(-1) to approximately 30 pL s(-1), and is able to keep 90% of a 0.6 microL solution placed in an open filling port for 60 min. This simple and efficient method should be applicable to numerous assays or chemical reactions that require small and precise flow of liquids and reagents inside microfluidics.

  3. [Congenital aortic stenosis].

    PubMed

    Yamaguchi, M

    2001-08-01

    Recent advances in and controversies concerning the management of children with congenital valvular aortic stenosis are discussed. In neonates with critical aortic stenosis, improved survival has recently been reported after surgical open valvotomy and balloon valvuloplasty, although it is difficult at this point to compare the results of the two procedures and determine their differential indications. Good results have also been achieved after extended aortic valvuloplasty for recurrent aortic stenosis and/or insufficiency, but the length of follow-up in these patients is still short. The technique first reported in 1991 for bilateral enlargement fo a small annulus permits the insertion of an aortic valve 3-4 sizes larger than the native annulus. It entails no risk of distorting the mitral valve, damaging the conduction system or important branches of the coronary arteries, or resulting in left ventricular dysfunction. The Ross procedure is now widely applied in the West, with reports of early mortality rates of less than 5% and event-free survival rates of 80-90% during follow-up of 4-8 years. Longer follow-up and continued careful evaluation are required to resolve the issue of possible dilatation and subsequent neoaortic valve dysfunction and pulmonary stenosis due to allograft degeneration after pulmonary autograft root replacement in children.

  4. 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.

  5. Aortic Aneurysm

    MedlinePlus

    ... these occur in the part of the aorta running through the chest Abdominal aortic aneurysms (AAA) - these occur in the part of the aorta running through the abdomen Most aneurysms are found during ...

  6. 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.

  7. Aortic Valve Stenosis

    MedlinePlus

    ... By Mayo Clinic Staff Aortic valve stenosis — or aortic stenosis — occurs when the heart's aortic valve narrows. This ... pressure may prevent or slow the development of aortic stenosis. Ask your doctor if you need to lower ...

  8. Aquaporin-1 shifts the critical transmural pressure to compress the aortic intima and change transmural flow: theory and implications.

    PubMed

    Joshi, Shripad; Jan, Kung-Ming; Rumschitzki, David S

    2015-12-01

    Transmural-pressure (ΔP)-driven plasma advection carries macromolecules into the vessel wall, the earliest prelesion atherosclerotic event. The wall's hydraulic conductivity, LP, the water flux-to-ΔP ratio, is high at low pressures, rapidly decreases, and remains flat to high pressures (Baldwin AL, Wilson LM. Am J Physiol Heart Circ Physiol 264: H26-H32, 1993; Nguyen T, Toussaint, Xue JD, Raval Y, Cancel CB, Russell LM, Shou S, Sedes Y, Sun O, Yakobov Y, Tarbell JM, Jan KM, Rumschitzki DS. Am J Physiol Heart Circ Physiol 308: H1051-H1064, 2015; Tedgui A, Lever MJ. Am J Physiol Heart Circ Physiol. 247: H784-H791, 1984. Shou Y, Jan KM, Rumschitzki DS. Am J Physiol Heart Circ Physiol 291: H2758-H2771, 2006) due to pressure-induced subendothelial intima (SI) compression that causes endothelial cells to partially block internal elastic laminar fenestrae. Nguyen et al. showed that rat and bovine aortic endothelial cells express the membrane protein aquaporin-1 (AQP1) and transmural water transport is both transcellular and paracellular. They found that LP lowering by AQP1 blocking was perplexingly ΔP dependent. We hypothesize that AQP1 blocking lowers average SI pressure; therefore, a lower ΔP achieves the critical force/area on the endothelium to partially block fenestrae. To test this hypothesis, we improve the approximate model of Huang et al. (Huang Y, Rumschitzki D, Chien S, Weinbaum SS. Am J Physiol Heart Circ Physiol 272: H2023-H2039, 1997) and extend it by including transcellular AQP1 water flow. Results confirm the observation by Nguyen et al.: wall LP and water transport decrease with AQP1 disabling. The model predicts 1) low-pressure LP experiments correctly; 2) AQP1s contribute 30-40% to both the phenomenological endothelial + SI and intrinsic endothelial LP; 3) the force on the endothelium for partial SI decompression with functioning AQP1s at 60 mmHg equals that on the endothelium at ∼43 mmHg with inactive AQP1s; and 4) increasing endothelial AQP1

  9. Four-dimensional visualization of thoracic blood flow by magnetic resonance imaging in a patient following correction of transposition of the great arteries (d-TGA) and uncorrected aortic coarctation.

    PubMed

    Ley-Zaporozhan, J; Unterhinninghofen, R; Rengier, F; Markl, M; Eichhorn, J; von Tengg-Kobligk, H; Ley, S

    2009-10-01

    Recent advances in flow-sensitive magnetic resonance imaging (MRI) and data analysis allow for comprehensive noninvasive three-dimensional (3D) visualization of complex blood flow. Electrocardiogram (ECG)-gated three-directional (3dir) flow measurements were employed to assess and visualize time-resolved 3D blood flow in the pulmonary arteries (PA) and thoracic aorta. We present findings in a juvenile patient with surgically corrected transposition of the great arteries (d-TGA) and aortic coarctation. For the first time, the complex flow patterns in the PA following d-TGA were visualized. Morphologically, a slight asymmetry of the PA was found, with considerable impact on vascular hemodynamics, resulting in diastolic retrograde flow in the larger vessel and diastolic filling of the smaller PA. Additionally, increased flow to the supraaortic vessels was found due to aortic coarctation.

  10. Design of a continuous flow centrifugal pediatric ventricular assist device.

    PubMed

    Throckmorton, A L; Wood, H G; Day, S W; Song, X; Click, P C; Allaire, P E; Olsen, D B

    2003-11-01

    Thousands of pediatric patients suffering from cardiomyopathy or single ventricular physiologies secondary to debilitating heart defects may benefit from long-term mechanical circulatory support due to the limited number of donor hearts available. This article presents the initial design of a fully implantable centrifugal pediatric ventricular assist device (PVAD) for 2 to 12 year olds. Conventional pump design equations, including a nondimensional scaling approach, enabled performance estimations of smaller scale versions (25 mm and 35 mm impeller diameters) of our adult support VAD. Based on this estimated performance, a computational model of the PVAD with a 35 mm impeller diameter was generated. Employing computational fluid dynamics (CFD) software, the flow paths through the PVAD and overall performance were analyzed for steady state flow conditions. The numerical simulations involved flow rates of 2 to 5 LPM for rotational speeds of 2750 to 3250 RPM and incorporated a k-epsilon fluid turbulence model with a logarithmic wall function to characterize near-wall flow conditions. The CFD results indicated best efficiency points ranging from 25% to 28%, which correlate well with typical values of blood pumps. The results further demonstrated that the pump could deliver 2 to 5 LPM at 70 to 95 mmHg for desired physiologic conditions in resting 2 to 12 year olds. Scalar stress levels remained below 300 Pa, thereby signifying potentially low levels of hemolysis. Several flow regions in the pump exhibited signs of vortices, retrograde flow, and stagnation points, which require optimization and further study. This CFD model represents a reasonable starting point for future model enhancements, leading to prototype manufacturing and experimental validation.

  11. 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

  12. Prosthesis-preserving aortic root repair after aortic valve replacement.

    PubMed

    Hamamoto, Masaki; Kobayashi, Taira; Kodama, Hiroshi

    2015-07-01

    We describe a new technique of prosthesis-preserving aortic root replacement for patients who have previously undergone aortic valve replacement. With preservation of the mechanical prosthesis, we implant a Gelweave Valsalva graft using double suture lines. The first suture line is made between the sewing cuff of the mechanical valve and the graft, with mattress sutures of 2/0 braided polyester with pledgets. After the first sutures are tied, the second suture line is created between the graft collar and the aortic root remnant with continuous 4/0 polypropylene sutures.

  13. Influence of catheter and arterial diameter on flow distal to an intra-aortic balloon insertion site: a theoretic examination and in vitro assessment.

    PubMed

    Ohley, W J; Antonelli, L; Leschinsky, B

    1998-01-01

    Percutaneous placement of an intra-aortic balloon (IAB) through a femoral artery of a patient is associated with a risk of reduction of blood flow distal to the balloon insertion site. If this reduction is severe, it ultimately causes limb ischemia and necessitates IAB removal. Although clinicians intuitively know that larger catheters cause higher flow restrictions, very few studies have examined this situation quantitatively. The authors theoretically analyzed the insertion site geometry in relationship to the catheter diameter and other factors effecting distal flow. To verify the findings, in vitro flow tests were conducted with various IAB catheters currently available on the market, as well as their respective sheaths and hemostasis plugs. This was done using a blood analog solution in an array of polyvinyl chloride tubing sizes. Diameters of the vessel and catheter have a profound and nonlinear effect on the distal flow. For example, a 12.2 Fr catheter in a 0.187 in. vessel only allows 19.9% of normal flow, whereas a 6.1 Fr catheter in the same size vessel allows a 92.0% flow. As the catheter diameter increases, the physical resistance suddenly grows, which causes a significant drop in distal flow. These results are accurately predicted by a mathematical model that gives flow percentage results to within 15% of those measured experimentally. In general, vessels larger than 5 mm in diameter do not exhibit substantial flow reduction for most IABs with and without sheaths. In smaller vessels, however, this reduction may be significant. Sheathless insertion is extremely effective in improving distal blood flow in such a situation. Hemostasis plugs restrict the distal flow similar to respective sheaths, thus diminishing the benefits of sheathless insertion.

  14. Hypertensive Emergency in Aortic Dissection and Thoracic Aortic Aneurysm—A Review of Management

    PubMed Central

    Gupta, Prateek K.; Gupta, Himani; Khoynezhad, Ali

    2009-01-01

    Over the last few decades, treatment for aortic dissection and thoracic aortic aneurysms has evolved significantly with improvement in outcomes. Treatment paradigms include medical, endovascular and surgical options. As aortic dissection presents as a hypertensive emergency, diligent control of BP is of utmost importance in order to reduce the progression of dissection with possible aortic branch malperfusion. Treatment should begin on arrival to the emergency department and continues in the intensive care unit, endovascular suite or the operating room. Novel antihypertensive medications with improved pharmacological profile and improved surgical techniques, have improved the prognosis of patients with aortic aneurysm and/or aortic dissection. Nevertheless, morbidity and mortality remain high and hypertensive emergency poses a significant challenge in aortic dissection and thoracic aortic aneurysms. PMID:27713224

  15. Effect of the load size on the efficiency of microwave heating under stop flow and continuous flow conditions.

    PubMed

    Patil, Narendra G; Rebrov, Evgeny V; Eränen, Kari; Benaskar, Faysal; Meuldijk, Jan; Mikkola, Jyri-Pekka; Hessel, Volker; Hulshof, Lumbertus A; Murzin, Dmitry Yu; Schouten, Jaap C

    2012-01-01

    A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4-29 mm on the heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However, microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load Length decreasing the heating efficiency as compared to stop-flow conditions.

  16. 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...

  17. 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.

  18. Numerical study of thermal driven buoyancy flow effect on solidification process of continuous slab caster

    NASA Astrophysics Data System (ADS)

    JAMBHULKAR, ROHIT Y.; SINGH, V.; MISHRA, P.; KRISHNAMURTHY, R.

    2016-09-01

    The main aim of the present research is to study the role of thermal driven buoyancy flow in solidification process of continues slab caster. A 3-D fluid flow, heat transfer and solidification model was developed. The result from the model combined with nondimensional number to study the effect of thermal driven buoyancy flow on fluid flow and temperature distribution. For mushy region Kozeny-Carman is applicable. Observations show the relative strength between thermal driven buoyancy flow and forced flow and steel flow through mushy region. It is observed that buoyancy force in mould and sub mould region depend on the characteristic flow velocity, temperature difference and porosity of mushy zone. The most effect zone of thermal driven buoyancy flow is mushy zone and centre of mould where inertial flow is inferior. The convection flow creates by thermal buoyancy cause appearance of local turbulence.

  19. Initial experience of EVAHEART explantation after continuous-flow LVAD off test with percutaneous occlusion balloon.

    PubMed

    Kashiyama, Noriyuki; Toda, Koichi; Miyagawa, Shigeru; Nishi, Hiroyuki; Yoshikawa, Yasushi; Fukushima, Satsuki; Yoshioka, Daisuke; Saito, Tetsuya; Sawa, Yoshiki

    2014-12-01

    In contrast to a pulsatile-flow left ventricular assist device (LVAD), an LVAD off test for evaluation of cardiac recovery with a continuous-flow device is difficult because of intra-circuit backflow from the outflow graft when a device is stopped. We report a case of reliable evaluation of cardiac recovery using balloon occlusion of the outflow graft, followed by successful removal of a continuous-flow EVAHEART LVAD using a minimally invasive approach.

  20. ``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.

  1. Compartmental models for continuous flow reactors derived from CFD simulations.

    PubMed

    Gresch, Markus; Brügger, Raphael; Meyer, Alain; Gujer, Willi

    2009-04-01

    Reactor modeling is of major interest in environmental technology. In this context, new contaminants with higher degradation requirements increase the importance of reactor hydraulics. CFD (Computational Fluid Dynamics) may meet this challenge but is expensive for everyday use. In this paper, we provide research and practice with a methodology designed to automatically reduce the complexity of such a high-dimensional flow model to a compartmental model. The derivation is based on the concentration field of a reacting species which is included in the steady state CFD simulation. While still capturing the most important flow features, the compartmental model is fast, easy to use, and open for process modeling with yet unknown compounds. The inherent overestimation of diffusion by compartmental models has been corrected by locally adjusting turbulent fluxes. We successfully applied the methodology to the ozonation process and experimentally verified it with tracer experiments. The loss of information was quantified as a deviation from CFD performance prediction for different reactions. With increasing discretisation of the compartmental model, these deviations diminish. General advice on the necessary discretisation is given.

  2. Continuous flow two-dimensional acoustic orientation of nonspherical cells.

    PubMed

    Jakobsson, Ola; Antfolk, Maria; Laurell, Thomas

    2014-06-17

    Flow cytometry is a frequently used method when it comes to cell sorting and analysis. Nonspherical cells, such as red blood cells or sperm cells, however, pose a challenge as they reduce the precision of light scatter measurements which interfere with the analysis of these and other cell populations in the same sample. Here, we present a microfluidic chip for acoustophoresis utilizing ultrasonic standing waves to focus and orient red blood cells in two dimensions in the channel center. The cells can be oriented to show either their flat or up-ended side toward the optical axis and the observer. In an acoustic standing wave field the cells will be rotated until the direction of the smallest dimension is parallel with the direction where the acoustic energy is strongest. While keeping the cells focused in the channel center utilizing acoustic resonances in two dimensions, the orientation can be controlled by increasing the acoustic energy in either the horizontal or vertical resonance mode. It was shown that 87.8 ± 3.8% of the red blood cells could be horizontally oriented while 98.7 ± 0.3% could be vertically oriented. The ability to control the orientation of nonspherical cells with high accuracy is a beneficial feature and potential contribution to the rapidly growing field of flow and image cytometry.

  3. 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.

  4. [Aortic dissection].

    PubMed

    Ogino, Hitoshi

    2011-07-01

    Acute aortic dissection suddenly occurrs and results in a variety of catastrophic sequelae including cardiac tamponade, rupture, and organ malperfusion. In acute stage (< 2 weeks), according to the classifications on the region of aortic dissection, the condition of the false channel and the onset, appropriate medical, surgical, or endovascular treatments including endovascular aneurysm repair followed by the rapid and accurate diagnosis of aortic dissection using computed tomography and ultrasound should be performed without delay. In the chronic stage (> 2 weeks), the behavior of the chronic dissection or residual distal dissection after the initial treatment should be followed-up carefully with best medical treatment at the regular intervals. If necessary, appropriate surgical and endovascular treatment should be carried out in the proper timing before rupture.

  5. 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.

  6. Computational fluid dynamics-based study of possibility of generating pulsatile blood flow via a continuous-flow VAD.

    PubMed

    Nammakie, Erfan; Niroomand-Oscuii, Hanieh; Koochaki, Mojtaba; Ghalichi, Farzan

    2017-01-01

    Until recent years, it was almost beyond remedy to save the life of end-stage heart failure patients without considering a heart transplant. This is while the need for healthy organs has always far exceeded donations. However, the evolution of VAD technology has certainly changed the management of these patients. Today, blood pumps are designed either pulsatile flow or continuous flow, each of which has its own concerns and limitations. For instance, pulsatile pumps are mostly voluminous and hardly can be used for children. On the other hand, the flow generated by continuous-flow pumps is in contrast with pulsatile flow of the natural heart. In this project, having used computational fluid dynamics, we studied the possibility of generating pulsatile blood flow via a continuous-flow blood pump by adjusting the rotational speed of the pump with two distinct patterns (sinusoidal and trapezoidal), both of which have been proposed and set based on physiological needs and blood flow waveform of the natural heart. An important feature of this study is setting the outlet pressure of the pump similar to the physiological conditions of a patient with heart failure, and since these axial pumps are sensitive to outlet pressures, more secure and reliable results of their performance are achieved. Our results show a slight superiority of a sinusoidal pattern compared to a trapezoidal one with the potential to achieve an adequate pulsatile flow by precisely controlling the rotational speed.

  7. 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.

  8. Bicuspid Aortic Valve

    DTIC Science & Technology

    2006-08-01

    severe aortic stenosis . Figure 1F. Oblique axial cine bright blood imaging through the valve plane of the aorta, demonstrates the aortic valve to...the ascending aorta. This moderate to large jet is consistent with moderate to severe aortic stenosis . No diastolic jet to suggest aortic ...conditions. Functional impairment of the aortic valve—namely aortic stenosis and aortic regurgitation—is the most common complication (in up to 68-85% of

  9. Continuous flow, explosives vapor generator and sensor chamber

    NASA Astrophysics Data System (ADS)

    Collins, Greg E.; Giordano, Braden C.; Sivaprakasam, Vasanthi; Ananth, Ramagopal; Hammond, Mark; Merritt, Charles D.; Tucker, John E.; Malito, Michael; Eversole, Jay D.; Rose-Pehrsson, Susan

    2014-05-01

    A novel liquid injection vapor generator (LIVG) is demonstrated that is amenable to low vapor pressure explosives, 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine. The LIVG operates in a continuous manner, providing a constant and stable vapor output over a period of days and whose concentration can be extended over as much as three orders of magnitude. In addition, a large test atmosphere chamber attached to the LIVG is described, which enables the generation of a stable test atmosphere with controllable humidity and temperature. The size of the chamber allows for the complete insertion of testing instruments or arrays of materials into a uniform test atmosphere, and various electrical feedthroughs, insertion ports, and sealed doors permit simple and effective access to the sample chamber and its vapor.

  10. Lead making for improved continuous-flow manufacturing systems

    NASA Astrophysics Data System (ADS)

    Heintzman, P.

    The importance of the latest in connector technology, chip carriers, surface mounted devices, and high density interconnects not withstanding, the foreseeable future of most durable goods includes designs in which discrete wires play a significant role. As long as user operated electro-mechanical controls exist for widely spaced functional components such as motors, relays, and safety switches, discrete wiring harnesses will continue to be a major concern of original equipment manufacturers. Economy and productivity must be maintained in spite of competitive pressures which demand expanded product lines and carefully controlled component inventories, manufacturing schedules, and deliveries. This paper explores some of the options available to answer these needs as they relate to discrete wiring and harnessing. Not only is available manufacturing hardware analyzed in terms of production capabilities but also in-house and vendor supply source alternatives are considered.

  11. Applications of Continuous-Flow Photochemistry in Organic Synthesis, Material Science, and Water Treatment.

    PubMed

    Cambié, Dario; Bottecchia, Cecilia; Straathof, Natan J W; Hessel, Volker; Noël, Timothy

    2016-09-14

    Continuous-flow photochemistry in microreactors receives a lot of attention from researchers in academia and industry as this technology provides reduced reaction times, higher selectivities, straightforward scalability, and the possibility to safely use hazardous intermediates and gaseous reactants. In this review, an up-to-date overview is given of photochemical transformations in continuous-flow reactors, including applications in organic synthesis, material science, and water treatment. In addition, the advantages of continuous-flow photochemistry are pointed out and a thorough comparison with batch processing is presented.

  12. Continuous-flow synthesis of highly functionalized imidazo-oxadiazoles facilitated by microfluidic extraction

    PubMed Central

    Herath, Ananda

    2017-01-01

    A versatile continuous-flow synthesis of highly functionalized 1,2,4-oxadiazoles starting from carboxylic acids is reported. This process was applied to the multistep synthesis of imidazo[1,2-a]pyridin-2-yl-1,2,4-oxadiazoles, using a three reactor, multistep continuous-flow system without isolation of intermediates. This continuous-flow method was successfully combined with a single-step liquid–liquid microextraction unit to remove high boiling point polar solvents and impurities and provides the target compounds in high purity with excellent overall yields. PMID:28326132

  13. Developing a miniaturized continuous flow electrochemical cell for biosensor applications

    NASA Astrophysics Data System (ADS)

    Ilie, M.; Ovreiu, E.; Dejana, R.; Foglietti, V.; Nardi, L.; Masci, A.; Lanza, B.; Della Seta, L.; Montereali, M.-R.; Vastarella, W.; Pilloton, R.

    2009-01-01

    The development of a miniaturized electrochemical cell for biosensor application regards both the structuring of an array of electrodes in a fluidic chamber and their connections to the control & processing unit The sensitivity of the chrono-amperometric measurement performed with the cell is increased by: (a) integrating the reference electrode on the same chip with the counter- and working- electrodes, (b) designing a specific pattern of the gold electrodes and (c) serially distributing them along the pipeline reservoir. Borosilicate glass is used as substrate for the electrodes, allowing, due to its transparency, an accurate and easy pad to pad alignment of the up-side-down chip versus a PCB soldered on a standard DIL 40 socket. This alignment is necessary to accomplish the elastomer-based-solderless electric contact, between chip and PCB. The solderless contact significantly improves both reliability and signal processing accuracy. The reservoir and its cover are micromachined out of silicone rubber respectively photosensitive glass in order to easy disassemble the fluidic chamber without any damage. Both thickness and elasticity of the photosensitive glass rend the device less brittle. A plug-in -plug-flow device with improved characteristics has been obtained with a modular structure that allows further extension of the number of electrodes.

  14. 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.

  15. Ruptured abdominal aortic aneurysm.

    PubMed

    Sachs, T; Schermerhorn, M

    2010-06-01

    Ruptured abdominal aortic aneurysm (AAA) continues to be one of the most lethal vascular pathologies we encounter. Its management demands prompt and efficient evaluation and repair. Open repair has traditionally been the mainstay of treatment. However, the introduction of endovascular techniques has altered the treatment algorithm for ruptured AAA in most major medical centers. We present recent literature and techniques for ruptured AAA and its surgical management.

  16. 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...

  17. 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...

  18. Continuous gas/liquid–liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination

    PubMed Central

    Breen, Jessica R; Yufit, Dmitrii S; Howard, Judith A K; Fray, Jonathan; Patel, Bhairavi

    2011-01-01

    Summary 4-Fluoropyrazole systems may be prepared by a single, sequential telescoped two-step continuous gas/liquid–liquid/liquid flow process from diketone, fluorine gas and hydrazine starting materials. PMID:21915207

  19. 76 FR 9984 - Airworthiness Directives; B/E Aerospace, Continuous Flow Passenger Oxygen Mask Assembly, Part...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-23

    ..., Continuous Flow Passenger Oxygen Mask Assembly, Part Numbers 174006-(), 174080-(), 174085-(), 174095... manufacturer and part number of the oxygen mask assemblies installed, an inspection to determine the manufacturing date and modification status if certain oxygen mask assemblies are installed, and...

  20. 76 FR 41669 - Airworthiness Directives; B/E Aerospace, Continuous Flow Passenger Oxygen Mask Assembly, Part...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-15

    ..., Continuous Flow Passenger Oxygen Mask Assembly, Part Numbers 174006-( ), 174080-( ), 174085-( ), 174095... oxygen mask assemblies installed, an inspection to determine the manufacturing date and modification status if certain oxygen mask assemblies are installed, and corrective action for certain oxygen...

  1. Continuous-flow ATP amplification system for increasing the sensitivity of quantitative bioluminescence assay.

    PubMed

    Satoh, Tetsuya; Shinoda, Yasuharu; Alexandrov, Maxym; Kuroda, Akio; Murakami, Yuji

    2008-08-01

    We constructed a novel ATP amplification reactor using a continuous-flow system, and this allowed us to increase the sensitivity of a quantitative bioluminescence assay by controlling the number of ATP amplification cycles. We previously developed a bioluminescence assay coupled with ATP amplification using a batch system. However, it was difficult to control the number of amplification cycles. In this study, ATP amplification was performed using a continuous-flow system, and significant linear correlations between amplified luminescence and initial ATP concentration were observed. When performing four cycles of continuous-flow ATP amplification, the gradient of amplification was 1.87(N). Whereas the lower quantifiable level was 500 pM without amplification, values as low as 50 pM ATP could be measured after amplification. The sensitivity thus increased 10-fold, with further improvements expected with additional amplification cycles. The continuous-flow system thus effectively increased the sensitivity of the quantitative bioluminescence assay.

  2. Fluid dynamic characterization of operating conditions for continuous flow blood pumps.

    PubMed

    Wu, Z J; Antaki, J F; Burgreen, G W; Butler, K C; Thomas, D C; Griffith, B P

    1999-01-01

    As continuous flow pumps become more prominent as long-term ventricular assist devices, the wide range of conditions under which they must be operated has become evident. Designed to operate at a single, best-efficiency, operating point, continuous flow pumps are required to perform at off-design conditions quite frequently. The present study investigated the internal fluid dynamics within two representative rotary fluid pumps to characterize the quality of the flow field over a full range of operating conditions. A Nimbus/UoP axial flow blood pump and a small centrifugal pump were used as the study models. Full field visualization of flow features in the two pumps was conducted using a laser based fluorescent particle imaging technique. Experiments were performed under steady flow conditions. Flow patterns at inlet and outlet sections were visualized over a series of operating points. Flow features specific to each pump design were observed to exist under all operating conditions. At off-design conditions, an annular region of reverse flow was commonly observed within the inlet of the axial pump, while a small annulus of backflow in the inlet duct and a strong disturbed flow at the outlet tongue were observed for the centrifugal pump. These observations were correlated to a critical nondimensional flow coefficient. The creation of a "map" of flow behavior provides an additional, important criterion for determining favorable operating speed for rotary blood pumps. Many unfavorable flow features may be avoided by maintaining the flow coefficient above a characteristic critical coefficient for a particular pump, whereas the intrinsic deleterious flow features can only be minimized by design improvement. Broadening the operating range by raising the band between the critical flow coefficient and the designed flow coefficient, is also a worthy goal for design improvement.

  3. Thrombolysis for suspected intrapump thrombosis in patients with continuous flow centrifugal left ventricular assist device.

    PubMed

    Muthiah, Kavitha; Robson, Desiree; Macdonald, Peter S; Keogh, Anne M; Kotlyar, Eugene; Granger, Emily; Dhital, Kumud; Spratt, Phillip; Jansz, Paul; Hayward, Christopher S

    2013-03-01

    The current recommended anticoagulation regimen during continuous flow centrifugal left ventricular device support is a combination of antiplatelet therapy as well as oral anticoagulation. Despite this, pump thrombosis occurs in rare situations. We report the risk factors and nonsurgical management and outcomes of five patients implanted with continuous flow centrifugal left ventricular assist devices who displayed clinical, hemodynamic, and laboratory features of intrapump thrombosis. This information may support the use of intravenous thrombolytics for suspected pump thrombus in these newer generation devices.

  4. Renewable Wood Pulp Paper Reactor with Hierarchical Micro/Nanopores for Efficient Continuous-Flow Nanocatalysis.

    PubMed

    Koga, Hirotaka; Namba, Naoko; Takahashi, Tsukasa; Nogi, Masaya; Nishina, Yuta

    2017-04-10

    Continuous-flow nanocatalysis by metal nanoparticle (NP) catalyst-anchored flow reactors has recently provided an excellent platform for effective chemical manufacturing. However, there has been limited progress in porous structure design and recycling systems for metal NP-anchored flow reactors to create more efficient and sustainable catalytic processes. Here, we renovated traditional paper as an efficient, recyclable, and renewable flow reactor by tailoring the ultra-structures of wood pulp. The 'paper reactor' offers hierarchically interconnected micro/nanoscale pores for efficient access of reactants to catalysts. In continuous-flow catalytic reduction of 4-nitrophenol, a gold NP-anchored paper reactor with the tailored micro/nanopores provided higher reaction efficiency than state-of-the-art flow reactors. Successful recycling and renewing of the paper reactors were also demonstrated. Our strategy offers potential for highly efficient and truly sustainable chemical manufacturing.

  5. 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... flow class; minimum requirements. (a) Respirators tested under this section shall be approved only...

  6. Evaluation of Intravascular Hemolysis With Erythrocyte Creatine in Patients With Aortic Stenosis.

    PubMed

    Sugiura, Tetsuro; Okumiya, Toshika; Kubo, Toru; Takeuchi, Hiroaki; Matsumura, Yoshihisa

    2016-07-27

    Chronic intravascular hemolysis has been identified in patients with cardiac valve prostheses, but only a few case reports have evaluated intravascular hemolysis in patients with native valvular heart disease. To detect intravascular hemolysis in patients with aortic stenosis, erythrocyte creatine was evaluated with hemodynamic indices obtained by echocardiography.Erythrocyte creatine, a marker of erythrocyte age, was assayed in 30 patients with aortic stenosis and 10 aged matched healthy volunteers. Peak flow velocity of the aortic valve was determined by continuous-wave Doppler echocardiography. Twenty of 30 patients with aortic stenosis had high erythrocyte creatine levels (> 1.8 µmol/g Hb) and erythrocyte creatine was significantly higher as compared with control subjects (1.98 ± 0.49 versus 1.52 ± 0.19 µmol/g Hb, P = 0.007). Peak transvalvular pressure gradient ranged from 46 to 142 mmHg and peak flow velocity ranged from 3.40 to 5.95 m/second. Patients with aortic stenosis had a significantly lower erythrocyte count (387 ± 40 versus 436 ± 42 × 10(4) µL, P = 0.002) and hemoglobin (119 ± 11 versus 135 ± 11 g/L, P < 0.001) as compared with control subjects. Erythrocyte creatine had a fair correlation with peak flow velocity (r = 0.55, P = 0.002).In conclusion, intravascular hemolysis due to destruction of erythrocytes was detected in patients with moderate to severe aortic stenosis and the severity of intravascular hemolysis was related to valvular flow velocity of the aortic valve.

  7. Continuous flow chemistry: a discovery tool for new chemical reactivity patterns.

    PubMed

    Hartwig, Jan; Metternich, Jan B; Nikbin, Nikzad; Kirschning, Andreas; Ley, Steven V

    2014-06-14

    Continuous flow chemistry as a process intensification tool is well known. However, its ability to enable chemists to perform reactions which are not possible in batch is less well studied or understood. Here we present an example, where a new reactivity pattern and extended reaction scope has been achieved by transferring a reaction from batch mode to flow. This new reactivity can be explained by suppressing back mixing and precise control of temperature in a flow reactor set up.

  8. 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

  9. Flow structure in submarine meandering channels, a continuous discussion on secondary flow

    NASA Astrophysics Data System (ADS)

    Abad, J. D.; Parker, G.; Sequeiros, O.; Spinewine, B.; Garcia, M. H.; Pirmez, C.

    2011-12-01

    The understanding of the flow structure in deep-sea turbidity currents is important for the formation of submarine meandering channels. Similarly to the case of subaerial channels, several types of secondary flows include turbulence-, curvature- and bed morphodynamic-driven flow structures that modulate sediment transport and channel bed morphodynamics. This study focuses on [1] a review of long-time research effort (Abad et al., 2011) that tackles the description of the secondary flow associated with a subaqueous bottom current (saline) in a high-curvature meandering channel and [2] ongoing numerical simulations of similar settings as the experiments to describe the entire flow structure. In the case of subaerial channels, the classical Rozovskiian paradigm is often invoked which indicates that the near-bottom secondary flow in a bend is directed inward. It has recently been suggested based on experimental and theoretical considerations, however, that this pattern is reversed (near-bottom secondary flow is directed outward) in the case of submarine meandering channels. Experimental results presented here, on the other hand, indicate near-bottom secondary flows that have the same direction as observed in a river (normal secondary flow). The implication is an apparent contradiction between experimental results. This study combines theory, experiments, reconstructions of field flows and ongoing simulations to resolve this apparent contradiction based on the flow densimetric Froude number. Three ranges of densimetric Froude number are found, such that a) in an upper regime, secondary flow is reversed, b) in a middle regime, it is normal and c) in a lower regime, it is reversed. These results are applied to field scale channel-forming turbidity currents in the Amazon submarine canyon-fan system (Amazon Channel) and the Monterey canyon and a saline underflow in the Black Sea flowing from the Bosphorus. Our analysis indicates that secondary flow should be normal

  10. Thoracic aortic aneurysm

    MedlinePlus

    ... common cause of a thoracic aortic aneurysm is hardening of the arteries . This condition is more common ... aortic aneurysm repair - open Aortic aneurysm repair - endovascular Hardening of the arteries High blood pressure Marfan syndrome ...

  11. Aortic Valve Regurgitation

    MedlinePlus

    ... valve. Also, a narrowing of the aortic valve (aortic stenosis) can be associated with leaking. High blood pressure (hypertension). High blood pressure may stretch the root of the aorta where the aortic valve sits. The valve flaps ( ...

  12. Taming hazardous chemistry in flow: the continuous processing of diazo and diazonium compounds.

    PubMed

    Deadman, Benjamin J; Collins, Stuart G; Maguire, Anita R

    2015-02-02

    The synthetic utilities of the diazo and diazonium groups are matched only by their reputation for explosive decomposition. Continuous processing technology offers new opportunities to make and use these versatile intermediates at a range of scales with improved safety over traditional batch processes. In this minireview, the state of the art in the continuous flow processing of reactive diazo and diazonium species is discussed.

  13. Is Continuous Flow Superior to Pulsatile Flow in Single Ventricle Mechanical Support? Results from a Large Animal Pilot Study.

    PubMed

    Fujii, Yasuhiro; Ferro, Giuseppe; Kagawa, Hiroshi; Centola, Luca; Zhu, Liqun; Ferrier, William T; Talken, Linda; Riemer, R Kirk; Maeda, Katsuhide; Nasirov, Teimour; Hodges, Bill; Amirriazi, Saleh; Lee, Eric; Sheff, Donald; May, Judith; May, Robert; Reinhartz, Olaf

    2015-01-01

    Durable mechanical support in situations of physiologic single ventricle has been met with little success so far, particularly in small children. We created an animal model to investigate whether pulsatile or continuous flow would be superior. Three 1 month old sheep (10-16 kg) were instrumented. Via sternotomy and with cardiopulmonary bypass, a large ventricular septal defect and atrial septal defect were created. The left ventricle was cannulated using a Berlin Heart inflow cannula. This was connected sequentially to a continuous flow device (Thoratec HeartMate X, Pleasanton, CA) and to a pulsatile device (Berlin Heart Excor, The Woodlands, TX). Outflow was via a Y-graft to both aorta and pulmonary artery, striving for equal flow to both. Atrial filling pressures were controlled with volume infusions over a wide range. Under comparable loading conditions, significantly higher maximum flow was obtained by HeartMate X than by Excor (4.95 ± 1.27 L/min [range, 3.84-6.34 L/min] for HeartMate X vs. 1.80 ± 0.85 L/min [range, 1.01-2.7 L/min] for Excor; p < 0.05). Judging from this limited animal study, in single ventricle scenarios, continuous flow devices may achieve higher pump flows than pulsatile devices when provided with similar filling pressures. Their clinical use should be investigated. More extensive experimental studies are needed.

  14. Aortic Stenosis.

    PubMed

    Bakaeen, Faisal G; Rosengart, Todd K; Carabello, Blase A

    2017-01-03

    This issue provides a clinical overview of aortic stenosis, focusing on screening, diagnosis, treatment, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

  15. 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.

  16. Ductal stent implantation in tetralogy of fallot with aortic arch abnormality.

    PubMed

    Tola, Hasan Tahsin; Ergul, Yakup; Saygi, Murat; Ozyilmaz, Isa; Guzeltas, Alper; Odemis, Ender

    2015-06-01

    Stenting of patent ductus arteriosus is an alternative to palliative cardiac surgery in newborns with duct-dependent or decreased pulmonary circulation; however, the use of this technique in patients with an aortic arch abnormality presents a challenge. Tetralogy of Fallot is a congenital heart defect that is frequently associated with anomalies of the aortic arch and its branches. The association is even more common in patients with chromosome 22q11 deletion. We present the case of an 18-day-old male infant who had cyanosis and a heart murmur. After an initial echocardiographic evaluation, the patient was diagnosed with tetralogy of Fallot and right-sided aortic arch. The pulmonary annulus and the main pulmonary artery and its branches were slightly hypoplastic; the ductus arteriosus was small. Conventional and computed tomographic angiograms revealed a double aortic arch and an aberrant left subclavian artery. The right aortic arch branched into the subclavian arteries and continued into the descending aorta, whereas the left aortic arch branched into the common carotid arteries and ended with the patent ductus arteriosus. After evaluation of the ductal anatomy, we implanted a 3.5 × 15-mm coronary stent in the duct. Follow-up injections showed augmented pulmonary flow and an increase in oxygen saturation from 65% to 94%. The patient was also found to have chromosome 22q11 deletion.

  17. Continuous-Flow Total Artificial Heart Supports Long-Term Survival of a Calf

    PubMed Central

    Frazier, O. H.; Cohn, William E.; Tuzun, Egemen; Winkler, Jo Anna; Gregoric, Igor D.

    2009-01-01

    The development and clinical use of continuous-flow left ventricular assist devices (LVADs) stimulated our interest in developing a total heart replacement with continuous-flow rotary blood pumps. We constructed a continuous-flow total artificial heart (CFTAH) from 2 HeartMate II axial-flow LVADs and used this CFTAH to replace the native heart of a calf. The purpose of this experiment was to study the effects of total continuous flow on physiologic parameters at rest and during exercise after the animal recovered from surgery. We monitored pulmonary and systemic pump performance, and we assessed arterial blood gases, hemodynamic and biochemical variables, and neurohormone levels during the 7 weeks of CFTAH support. At day 36 after CFTAH implantation, the calf was exercised on a treadmill at increasing speeds for 40 minutes; total oxygen consumption, pump flow, blood pressure, and respiratory rate were monitored. Baseline hematologic levels were altered postoperatively but returned to normal by 2 weeks. We saw no signs of hemolysis or thrombosis during CFTAH support. The calf had a normal physiologic response to treadmill exercise. The animal gained weight and appeared to function normally during the study. The CFTAH operated within design specifications throughout the study. Homeostasis, end-organ and vasomotor function, and the ability to exercise are not adversely affected by 7 weeks of totally pulseless circulation in a calf. PMID:20069083

  18. Continuous-flow total artificial heart supports long-term survival of a calf.

    PubMed

    Frazier, O H; Cohn, William E; Tuzun, Egemen; Winkler, Jo Anna; Gregoric, Igor D

    2009-01-01

    The development and clinical use of continuous-flow left ventricular assist devices (LVADs) stimulated our interest in developing a total heart replacement with continuous-flow rotary blood pumps. We constructed a continuous-flow total artificial heart (CFTAH) from 2 HeartMate II axial-flow LVADs and used this CFTAH to replace the native heart of a calf. The purpose of this experiment was to study the effects of total continuous flow on physiologic parameters at rest and during exercise after the animal recovered from surgery. We monitored pulmonary and systemic pump performance, and we assessed arterial blood gases, hemodynamic and biochemical variables, and neurohormone levels during the 7 weeks of CFTAH support. At day 36 after CFTAH implantation, the calf was exercised on a treadmill at increasing speeds for 40 minutes; total oxygen consumption, pump flow, blood pressure, and respiratory rate were monitored. Baseline hematologic levels were altered postoperatively but returned to normal by 2 weeks. We saw no signs of hemolysis or thrombosis during CFTAH support. The calf had a normal physiologic response to treadmill exercise. The animal gained weight and appeared to function normally during the study. The CFTAH operated within design specifications throughout the study. Homeostasis, end-organ and vasomotor function, and the ability to exercise are not adversely affected by 7 weeks of totally pulseless circulation in a calf.

  19. High-throughput continuous flow synthesis of nickel nanoparticles for the catalytic hydrodeoxygenation of guaiacol

    SciTech Connect

    Roberts, Emily J.; Habas, Susan E.; Wang, Lu; Ruddy, Daniel A.; White, Erick A.; Baddour, Frederick G.; Griffin, Michael B.; Schaidle, Joshua A.; Malmstadt, Noah; Brutchey, Richard L.

    2016-11-07

    The translation of batch chemistries to high-throughput continuous flow methods dresses scaling, automation, and reproducibility concerns associated with the implementation of colloidally prepared nanoparticle (NP) catalysts for industrial catalytic processes. Nickel NPs were synthesized by the high-temperature amine reduction of a Ni2+ precursor using a continuous millifluidic (mF) flow method, achieving yields greater than 60%. The resulting Ni NP catalysts were compared against catalysts prepared in a batch reaction under conditions analogous to the continuous flow conditions with respect to total reaction volume, time, and temperature and by traditional incipient wetness (IW) impregnation for the hydrodeoxygenation (HDO) of guaiacol under ex situ catalytic fast pyrolysis conditions. Compared to the IW method, the colloidally prepared NPs displayed increased morphological control and narrowed size distributions, and the NPs prepared by both methods showed similar size, shape, and crystallinity. The Ni NP catalyst synthesized by the continuous flow method exhibited similar H-adsorption site densities, site-time yields, and selectivities towards deoxygenated products as compared to the analogous batch reaction, and outperformed the IW catalyst with respect to higher selectivity to lower oxygen content products and a 6.9-fold slower deactivation rate. These results demonstrate the utility of synthesizing colloidal Ni NP catalysts using continuous flow methods while maintaining the catalytic properties displayed by the batch equivalent. Finally, this methodology can be extended to other catalytically relevant base metals for the high-throughput synthesis of metal NPs for the catalytic production of biofuels.

  20. Numeric simulation of heat transfer and electrokinetic flow in an electroosmosis-based continuous flow PCR chip.

    PubMed

    Gui, Lin; Ren, Carolyn L

    2006-09-01

    Precise design and operational control of the polymerase chain reaction process is key to the performance of on-chip DNA analysis. This research is dedicated to understanding the fluid flow and heat transfer mechanisms occurring in continuous flow PCR chips from the engineering point of view. In this work, a 3-dimensional model was developed to simulate the electrical potential field, the flow field, and the temperature field in an electroosmosis-based continuous flow PCR chip. On the basis of the simultaneous solution to this model, the effects of the channel/chip size, the chip material, and the applied voltage difference on the temperature distribution and control are discussed in detail. The importance of each heat transfer mechanism for different situations is also discussed. It was found that if a larger chip thickness or a material with a lower heat conductivity was used, the temperature in the microfluidic PCR chip would decrease dramatically. The effects of the applied electrical field strength and flow velocity on the temperature distribution, however, are negligible for microchannels with a small cross-sectional area. With bigger channels, the flow direction will affect the temperature distribution in the channel because heat convection will dominate heat transfer.

  1. 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.

  2. Micromachined pre-focused M×N flow switches for continuous multi-sample injection

    NASA Astrophysics Data System (ADS)

    Lee, Gwo-Bin; Hwei, Bao-Herng; Huang, Guan-Ruey

    2001-11-01

    In this paper we present a novel microfluidic chip capable of continuous multi-sample switching and injection for bio-analytical applications. The innovative device integrates two important microfluidic phenomena, including hydrodynamic focusing and valveless flow switching inside multi-ported microchannels. The multiple samples can be pre-focused to narrow streams and can then be continuously injected into desired outlet ports. In this study, a theoretical model based on the `flow-rate-ratio' method is first proposed to predict the performance of the microfluidic device. Then, a simple but reliable one-mask micromachining process is developed to fabricate the pre-focused M×N flow switch on a quartz substrate. The multi-sample switching and injection is then verified experimentally with the use of microscopic visualization of water sheath flows and dye-containing sample flows. The experimental data indicate that the multi-sample flows can be hydrodynamically pre-focused and then guided into the desired outlet ports precisely based on relative sheath and sample flow rates. The data predicted by the proposed theoretical model are highly consistent with the experimental results. It is also noted that the `pre-focusing' function added prior to multi-sample flow switching is crucial for precise sample injection. The novel microfluidic chip has great potential for high-throughput chemical analysis, cell fusion, fraction collection, fast sample mixing and many other applications in the field of micro-total-analysis systems.

  3. An improved continuous flow analysis system for high-resolution field measurements on ice cores.

    PubMed

    Kaufmann, Patrik R; Federer, Urs; Hutterli, Manuel A; Bigler, Matthias; Schüpbach, Simon; Ruth, Urs; Schmitt, Jochen; Stocker, Thomas F

    2008-11-01

    Continuous flow analysis (CFA) is a well-established method to obtain information about impurity contents in ice cores as indicators of past changes in the climate system. A section of an ice core is continuously melted on a melter head supplying a sample water flow which is analyzed online. This provides high depth and time resolution of the ice core records and very efficient sample decontamination as only the inner part of the ice sample is analyzed. Here we present an improved CFA system which has been totally redesigned in view of a significantly enhanced overall efficiency and flexibility, signal quality, compactness, and ease of use. These are critical requirements especially for operations of CFA during field campaigns, e.g., in Antarctica or Greenland. Furthermore, a novel deviceto measure the total air content in the ice was developed. Subsequently, the air bubbles are now extracted continuously from the sample water flow for subsequent gas measurements.

  4. 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.

  5. 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

  6. 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.

  7. Unique, clean-air, continuous-flow, high-stagnation-temperature facility for supersonic combustion research

    NASA Technical Reports Server (NTRS)

    Krauss, R. H.; Mcdaniel, J. C., Jr.; Scott, J. E., Jr.; Whitehurst, R. B., III; Segal, C.

    1988-01-01

    Accurate, spatially-resolved measurements can be conducted of a model supersonic combustor in a clean air/continuous flow supersonic combustion facility whose long run times will allow not only the point-by-point mapping of flow field variables with laser diagnostics but facilitate the simulation of steady-state combustor conditions. The facility will provide a Mach 2 freestream with static pressures in the 1 to 1/6 atm range, and stagnation temperatures of up to 2000 K.

  8. Continuous Flow 1H and 13C NMR Spectroscopy in Microfluidic Stripline NMR Chips

    PubMed Central

    2017-01-01

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline’s favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional 1H, 13C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds. PMID:28194934

  9. Continuous Flow (1)H and (13)C NMR Spectroscopy in Microfluidic Stripline NMR Chips.

    PubMed

    Oosthoek-de Vries, Anna Jo; Bart, Jacob; Tiggelaar, Roald M; Janssen, Johannes W G; van Bentum, P Jan M; Gardeniers, Han J G E; Kentgens, Arno P M

    2017-02-21

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline's favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional (1)H, (13)C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds.

  10. 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.

  11. Diels–Alder reactions of myrcene using intensified continuous-flow reactors

    PubMed Central

    Álvarez-Diéguez, Miguel Á; Kohl, Thomas M; Tsanaktsidis, John

    2017-01-01

    This work describes the Diels–Alder reaction of the naturally occurring substituted butadiene, myrcene, with a range of different naturally occurring and synthetic dienophiles. The synthesis of the Diels–Alder adduct from myrcene and acrylic acid, containing surfactant properties, was scaled-up in a plate-type continuous-flow reactor with a volume of 105 mL to a throughput of 2.79 kg of the final product per day. This continuous-flow approach provides a facile alternative scale-up route to conventional batch processing, and it helps to intensify the synthesis protocol by applying higher reaction temperatures and shorter reaction times. PMID:28228853

  12. Toward efficient asymmetric carbon-carbon bond formation: continuous flow with chiral heterogeneous catalysts.

    PubMed

    Tsubogo, Tetsu; Yamashita, Yasuhiro; Kobayashi, Shū

    2012-10-22

    A chiral Ca catalyst based on CaCl(2) with a chiral ligand was developed and applied to the asymmetric 1,4-addition of 1,3-dicarbonyl compounds to nitroalkenes as a model system. To address product inhibition issues, the Ca catalyst was applied to continuous flow with a chiral heterogeneous catalyst. The continuous flow system using a newly synthesized, polymer-supported Pybox was successfully employed, and the TON was improved 25-fold compared with those of the previous Ca(OR)(2) catalysts.

  13. Experimental fluid dynamics of transventricular apical aortic cannulation.

    PubMed

    Fukuda, Ikuo; Yanaoka, Hideki; Inamura, Takao; Minakawa, Masahito; Daitoku, Kazuyuki; Suzuki, Yasuyuki

    2010-03-01

    To clarify the flow pattern from a transventricular apical aortic cannula, hydrodynamic analysis of transventricular apical aortic cannulation (apical cannulation) was performed using particle-image velocimetry in a glass aortic model. Simulated apical cannulation using a 7-mm Sarns Soft-Flow cannula and the newly developed 7-mm apical aortic cannula was compared with standard aortic cannulation. The flow-velocity, streamline, and distribution of magnitude of the strain rate tensor (function of shear stress) were analyzed. Streamline analysis revealed a steady and organized flow profile in apical cannulation as compared with that in standard aortic cannulation. The magnitude of the strain rate tensor decreased within a few centimeters from the exit of the apical cannula.

  14. 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.

  15. 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.

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

    SciTech Connect

    Resnik, Kevin P.; Pennline, Henry W.

    2013-03-01

    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.

  17. 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.

  18. Continuous Processing of Active Pharmaceutical Ingredients Suspensions via Dynamic Cross-Flow Filtration.

    PubMed

    Gursch, Johannes; Hohl, Roland; Toschkoff, Gregor; Dujmovic, Diana; Brozio, Jörg; Krumme, Markus; Rasenack, Norbert; Khinast, Johannes

    2015-10-01

    Over the last years, continuous manufacturing has created significant interest in the pharmaceutical industry. Continuous filtration at low flow rates and high solid loadings poses, however, a significant challenge. A commercially available, continuously operating, dynamic cross-flow filtration device (CFF) is tested and characterized. It is shown that the CFF is a highly suitable technology for continuous filtration. For all tested model active pharmaceutical ingredients, a material-specific strictly linear relationship between feed and permeate rate is identified. Moreover, for each tested substance, a constant concentration factor is reached. A one-parameter model based on a linear equation is suitable to fully describe the CFF filtration performance. This rather unexpected finding and the concentration polarization layer buildup is analyzed and a basic model to describe the observed filtration behavior is developed.

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

    DOE PAGES

    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

  20. Generation and Synthetic Application of Trifluoromethyl Diazomethane Utilizing Continuous Flow Technologies.

    PubMed

    Pieber, Bartholomäus; Kappe, C Oliver

    2016-03-04

    A continuous process for the synthesis and inline separation of anhydrous trifluoromethyl diazomethane in a single continuous flow process is presented. The diazo building block is generated from the corresponding amine and NaNO2 under acidic, aqueous conditions and subsequently diffuses through a gas-permeable membrane into an organic stream. To avoid storage and transportation of the hazardous compound, a representative downstream process in a packed-bed reactor yielding highly functionalized building blocks was developed.

  1. Parallel-plate Flow Chamber and Continuous Flow Circuit to Evaluate Endothelial Progenitor Cells under Laminar Flow Shear Stress

    PubMed Central

    Lane, Whitney O.; Jantzen, Alexandra E.; Carlon, Tim A.; Jamiolkowski, Ryan M.; Grenet, Justin E.; Ley, Melissa M.; Haseltine, Justin M.; Galinat, Lauren J.; Lin, Fu-Hsiung; Allen, Jason D.; Truskey, George A.; Achneck, Hardean E.

    2012-01-01

    The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses1. Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs2,3. This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts. The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (> 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy5. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12)6. PMID:22297325

  2. Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress.

    PubMed

    Lane, Whitney O; Jantzen, Alexandra E; Carlon, Tim A; Jamiolkowski, Ryan M; Grenet, Justin E; Ley, Melissa M; Haseltine, Justin M; Galinat, Lauren J; Lin, Fu-Hsiung; Allen, Jason D; Truskey, George A; Achneck, Hardean E

    2012-01-17

    The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses. Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs. This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts. The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (> 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12).

  3. Micromachined pre-focused 1×N flow switches for continuous sample injection

    NASA Astrophysics Data System (ADS)

    Lee, Gwo-Bin; Hung, Chen-I.; Ke, Bin-Jo; Huang, Guan-Ruey; Hwei, Bao-Herng

    2001-09-01

    In this paper, we present an investigation of a microfluidic chip capable of continuous sample switching and injection for bio-analytical applications. The novel device integrates two important microfluidic phenomena, including hydrodynamic focusing and valveless flow switching inside multi-ported microchannels. In this study, a simple theoretical model based on the `flow-rate-ratio' method is first proposed to predict the performance of the device. Based on these data, a pre-focused 1×N flow switch is designed and fabricated using micromachining techniques. A novel micromachining technique is demonstrated which combines quartz template fabrication and replication of microstructures on polymethylmethacrylate (PMMA) substrates for mass production of microfluidic devices. Three-dimensional templates with an inverse image of microfluidic channels are fabricated on quartz substrates and then used to imprint microstructures onto PMMA substrates using hot embossing methods. Finally, the flow switching is verified experimentally with the use of microscopic visualization of water sheath flows and a dye-containing sample flow. The experimental data indicate that the sample flow could be hydrodynamically pre-focused to a narrow stream and then guided into a desired outlet port based on relative sheath and sample flow rates. It also shows that the added `pre-focusing' function prior to the flow switching is crucial for precise sample injection. The microfluidic chip could be applied in the fields of bio/chemical analysis.

  4. Computational analysis of an aortic valve jet

    NASA Astrophysics Data System (ADS)

    Shadden, Shawn C.; Astorino, Matteo; Gerbeau, Jean-Frédéric

    2009-11-01

    In this work we employ a coupled FSI scheme using an immersed boundary method to simulate flow through a realistic deformable, 3D aortic valve model. This data was used to compute Lagrangian coherent structures, which revealed flow separation from the valve leaflets during systole, and correspondingly, the boundary between the jet of ejected fluid and the regions of separated, recirculating flow. Advantages of computing LCS in multi-dimensional FSI models of the aortic valve are twofold. For one, the quality and effectiveness of existing clinical indices used to measure aortic jet size can be tested by taking advantage of the accurate measure of the jet area derived from LCS. Secondly, as an ultimate goal, a reliable computational framework for the assessment of the aortic valve stenosis could be developed.

  5. Aortic Stiffness, Cerebrovascular Dysfunction, and Memory

    PubMed Central

    Cooper, Leroy L.; Mitchell, Gary F.

    2016-01-01

    Background Aortic stiffness is associated with cardiovascular and cerebrovascular events and cognitive decline. This mini-review focuses on relations of aortic stiffness with microvascular dysfunction and discusses the contribution of abnormal pulsatile hemodynamics to cerebrovascular damage and cognitive decline. We also provide a rationale for considering aortic stiffness as a putative and important contributor to memory impairment in older individuals. Summary Aging is associated with stiffening of the aorta but not the muscular arteries, which reduces wave reflection and increases the transmission of pulsatility into the periphery. Aortic stiffening thereby impairs a protective mechanism that shields the peripheral microcirculation from excessive pulsatility within downstream target organs. Beyond midlife, aortic stiffness increases rapidly and exposes the cerebral microcirculation to abnormal pulsatile mechanical forces that are associated with microvascular damage and remodeling in the brain. Aortic stiffening and high-flow pulsatility are associated with alterations in the microvasculature of the brain; however, a mechanistic link between aortic stiffness and memory has not been established. We showed that in a community-based sample of older individuals, cerebrovascular resistance and white matter hyperintensities - markers of cerebrovascular remodeling and damage - mediated the relation between higher aortic stiffness and lower performance on memory function tests. These data suggest that microvascular and white matter damage associated with excessive aortic stiffness contribute to impaired memory function with advancing age. Key Messages Increasing evidence suggests that vascular etiologies - including aortic stiffness and microvascular damage - contribute to memory impairment and the pathogenesis of dementia, including Alzheimer's disease. Interventions that reduce aortic stiffness may delay memory decline among older individuals. PMID:27752478

  6. 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 ...

  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.

  8. 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…

  9. 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…

  10. 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...

  11. 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...

  12. 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.

  13. Continuous scaling 3d micro flow printing for improved spot morphology in protein microarrays - biomed 2013.

    PubMed

    Romanov, Valentin; Gale, Bruce; Eckman, Josh; Miles, Adam; Brooks, Benjamin

    2013-01-01

    The protein microarray platform while innovative still poses a number of challenges which can only be met through creative and sophisticated system design. Pin printing while allowing for flexibility as to the type of medium printed does not offer the kind of spot reproducibility that a very sensitive application may require. The Continuous Flow Microspotter (CFM) was designed to not only allow for flexibility and reproducibility but to also achieve solution stability through flow scaling. This study uses the emerging CFM for printing protein and antibodies three dimensionally for general protein microarray applications. Consistent spot morphology, a continual and persistent problem in traditional pin printed microarrays, was compared under variable printed flow rates. The final assessment was performed using a rudimentary shear model. Force effects discussion and statistical data was used to demonstrate the versatility of the system.

  14. 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.

  15. 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.

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

    PubMed

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

    2016-09-06

    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.

  17. 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 ...

  18. [Acute aortic syndromes and sleep apnea].

    PubMed

    Baguet, Jean-Philippe

    2016-10-01

    Obstructive sleep apnea (OSA) is a common disease, often present in "cardiovascular or metabolic patients". OSA favours the occurrence of arterial lesions, all the more if severe. There is a strong relationship between OSA and acute aortic syndromes (AAS). This relationship is in part explained by aortic dilatation linked to OSA. The presence of repeated episodes of sudden variation of transmural pressure applied on aortic wall seems to play a major role in this dilatation. All OSA patients should have a search of aortic dilatation by ultrasound (at a thoracic and abdominal level). Also, screening of OSA should be systematically performed in patients with aortic disease. The effect of continuous positive airway pressure in apneic patients with AAS has not been studied.

  19. Predicting Right Ventricular Failure in the Modern, Continuous Flow Left Ventricular Assist Device Era

    PubMed Central

    Atluri, Pavan; Goldstone, Andrew B.; Fairman, Alex S.; MacArthur, John W.; Shudo, Yasuhiro; Cohen, Jeffrey E.; Acker, Alexandra L.; Hiesinger, William; Howard, Jessica L.; Acker, Michael A.; Woo, Y. Joseph

    2014-01-01

    Background In the era of destination continuous flow left ventricular assist devices (LVAD), the decision of whether a patient will tolerate isolated LVAD support or will need biventricular support (BIVAD) can be challenging. Incorrect decision making with delayed right ventricular (RV) assist device implantation results in increased morbidity and mortality. Continuous flow LVADs have been shown to decrease pulmonary hyper-tension and improve RV function. We undertook this study to determine predictors in the continuous flow LVAD era that identify patients who are candidates for isolated LVAD therapy as opposed to biventricular support. Methods We reviewed demographic, hemodynamic, laboratory, and echocardiographic variables for 218 patients who underwent VAD implant from 2003 through 2011 (LVAD = 167, BIVAD = 51), during the era of continuous flow LVADs. Results Fifty preoperative risk factors were compared between patients who were successfully managed with an LVAD and those who required a BIVAD. Seventeen variables demonstrated statistical significance by univariate analysis. Multivariable logistic regression analysis identified central venous pressure >15 mmHg (OR 2.0, “C”), severe RV dysfunction (OR 3.7, “R”), preoperative intubation (OR 4.3, “I”), severe tricuspid regurgitation (OR 4.1, “T”), heart rate >100 (OR 2.0, Tachycardia - “T”) -CRITT as the major criteria predictive of the need for biventricular support. Utilizing these data, a highly sensitive and easy to use risk score for determining RV failure was generated that outperformed other established risk stratification tools. Conclusions We present a preoperative risk calculator to determine suitability of a patient for isolated LVAD support in the current continuous flow ventricular assist device era. PMID:23791165

  20. Analysis and Application of Silicon Nano-Particles Produced via Continuous Flow Non-Thermal Plasmas

    NASA Astrophysics Data System (ADS)

    Lopez, Thomas David

    Continuous flow non-thermal plasma reactors are being investigated for their ability to efficiently produce high quality nanoparticles. While many nanomaterials can be produced via continuous flow non-thermal plasma reactors, silicon is of particular interest, due to its abundance and relevance in many energy related fields. Significant gaps still exist in the understanding of the kinetics responsible for particle growth, structural evolution, and surface termination of continuous flow non-thermal plasma reactor produced particles. Particle interaction with plasma radicals results in the heating of the particles, which in turn affects the kinetics of particle growth, structural evolution, and surface termination during synthesis and processing. We have investigated the details of plasma-nanoparticle interaction by using in-flight and in-situ characterization techniques. For the first time, we have measured the temperature of a free-standing particle immersed in a non-equilibrium processing plasma. In parallel, we have utilized continuous flow non-thermal plasma reactor-produced nanoparticles to create bulk nanostructured materials. The ability to tune size, structure, and surface termination of the continuous flow non-thermal plasma reactor produced nanoparticles allows for significant control of the precursor powders used in the densification processes. Hot pressing processes allow for the production of samples with bulk-like densities while limiting grain growth, allowing for the creation of nanostructured bulk systems. Nanostructured bulk silicon represents an ideal system to study the role of nano-structuring on transport of charge carriers and phonons in bulk materials. Initial results show that small particle and narrow particle size distributions allows for the creation of bulk nanostructured silicon with high ZT values. This system has shown to be relevant for direct conversion of heat into electrical power, but is also a model for the optimization of

  1. High-throughput continuous flow synthesis of nickel nanoparticles for the catalytic hydrodeoxygenation of guaiacol

    DOE PAGES

    Roberts, Emily J.; Habas, Susan E.; Wang, Lu; ...

    2016-11-07

    The translation of batch chemistries to high-throughput continuous flow methods dresses scaling, automation, and reproducibility concerns associated with the implementation of colloidally prepared nanoparticle (NP) catalysts for industrial catalytic processes. Nickel NPs were synthesized by the high-temperature amine reduction of a Ni2+ precursor using a continuous millifluidic (mF) flow method, achieving yields greater than 60%. The resulting Ni NP catalysts were compared against catalysts prepared in a batch reaction under conditions analogous to the continuous flow conditions with respect to total reaction volume, time, and temperature and by traditional incipient wetness (IW) impregnation for the hydrodeoxygenation (HDO) of guaiacol undermore » ex situ catalytic fast pyrolysis conditions. Compared to the IW method, the colloidally prepared NPs displayed increased morphological control and narrowed size distributions, and the NPs prepared by both methods showed similar size, shape, and crystallinity. The Ni NP catalyst synthesized by the continuous flow method exhibited similar H-adsorption site densities, site-time yields, and selectivities towards deoxygenated products as compared to the analogous batch reaction, and outperformed the IW catalyst with respect to higher selectivity to lower oxygen content products and a 6.9-fold slower deactivation rate. These results demonstrate the utility of synthesizing colloidal Ni NP catalysts using continuous flow methods while maintaining the catalytic properties displayed by the batch equivalent. Finally, this methodology can be extended to other catalytically relevant base metals for the high-throughput synthesis of metal NPs for the catalytic production of biofuels.« less

  2. Transient Asymmetric Flow and Bubble Transport Inside a Slab Continuous-Casting Mold

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Li, Baokuan; Jiang, Maofa

    2014-04-01

    A one third scale water model experiment was conducted to observe the asymmetric flow and vortexing flow inside a slab continuous-casting mold. Dye-injection experiment was used to show the evolution of the transient flow pattern in the liquid pool without and with gas injection. The spread of the dye was not symmetric about the central plane. The flow pattern inside the mold was not stationary. The black sesames were injected into water to visualize the vortexing flow pattern on the top surface. The changes of shape and location of single vortex and two vortices with time had been observed during experiments. Plant ultrasonic testing (UT) of slabs was used to analyze the slab defects distribution, which indicated that the defects are intermittent and asymmetric. A mathematical model has been developed to analyze the time-dependent flow using the realistic geometries, which includes the submerged entry nozzle (SEN), actual mold, and part of the secondary cooling zone. The transient turbulent flow of molten steel inside the mold has been simulated using the large eddy simulation computational approach. Simulation results agree acceptably well with the water model experimentally observed and plant UT results. The oscillating motions of jet and the turbulence naturally promote the asymmetric flow even without the effects of slide gate nozzle or the existence of clogs inside the SEN. The periodic behavior of transient fluid flow in the mold is identified and characterized. The vortexing flow is resulted from asymmetric flow in the liquid pool. The vortices are located at the low-velocity side adjacent to the SEN, and the positions and sizes are different. Finally, the model is applied to investigate the influence of bubble size and casting speed on the time-dependent bubble distribution and removal fraction from the top surface inside the mold.

  3. 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.

  4. The use of a continuous flow-reactor employing a mixed hydrogen-liquid flow stream for the efficient reduction of imines to amines.

    PubMed

    Saaby, Steen; Knudsen, Kristian Rahbek; Ladlow, Mark; Ley, Steven V

    2005-06-21

    Imines have been reduced to amines in high yield, and with excellent chemoselectivity, by catalytic hydrogenation in a continuous flow-reactor, utilising an electrochemically-generated hydrogen source to produce a mixed hydrogen-liquid flow stream.

  5. Effect of pulsatile and continuous flow on yes-associated protein.

    PubMed

    Chitragari, Gautham; Shalaby, Sherif Y; Sumpio, Brandon J; Sumpio, Bauer E

    2014-09-01

    Yes-associated protein (YAP) is a mechanosignaling protein that relays mechanical information to the nucleus by changing its level of phosphorylation. We hypothesize that different flow patterns show differential effect on phosphorylated YAP (pYAP) (S127) and total YAP and could be responsible for flow dependent localization of atherosclerosis. Confluent human umbilical vein endothelial cells (HUVECs) seeded on fibronectin-coated glass slides were exposed to continuous forward flow (CFF) and pulsatile forward flow (PFF) using a parallel plate flow chamber system for 30 minutes. Cell lysates were prepared and immunoblotted to detect the levels of phosphorylated YAP and total YAP. HUVECs exposed to both PFF and CFF showed a mild decrease in the levels of both pYAP (S127) and total YAP. While the levels of pYAP (S127) decreased to 87.85 and 85.21% of static control with PFF and CFF, respectively, the levels of total YAP significantly decreased to 91.31 and 92.27% of static control. No significant difference was seen between CFF and PFF on their effect on pYAP (S127), but both conditions resulted in a significant decrease in total YAP at 30 minutes. The results of this experiment show that the possible effect of different types of flow on YAP is not induced before 30 minutes. Experiments exposing endothelial cells to various types of flow for longer duration of time could help to elucidate the role of YAP in the pathogenesis of atherosclerosis.

  6. 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

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

    PubMed

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

    2015-03-01

    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.

  8. Experimental investigation and analysis of continuous flow through trace gas preconcentrator

    NASA Astrophysics Data System (ADS)

    Kim, Jihyun

    2013-11-01

    It was proposed by Muntz et al. in 2004 to study a micro/mesoscale continuous flow through trace gas preconcentrator, which could avoid the time fidelity problem. The preconcentrator for rarefied trace gas analysis, which is one part of a gas detector or analyzer, has been built and consists of a main flow channel, pumping chambers, and separation membranes that are located upper and lower surface of the main flow channel. The preconcentration is not from stop, adsorption, and release, but is caused by the gradually decreasing cross section of the main flow channel until release through the detection unit such as gas chromatography, mass spectrometry, or optical diagnostics. This has the possibility of achieving concentration increase of various gases in a carrier gas by using relatively simple micro/macroscale mass diffusion separation stages, and is suitable for improving the time accuracy of analytical systems. A series of experiments were conducted in an attempt to validate the available numerical data, such as the concentration and gas flow speed of the newly continuous preconcentration technology. This study involved experimental investigations to obtain a base-line comparison of the existing numerical predictions provided by the prototype preconcentrator.

  9. Continuous cell sorting in a flow based on single cell resonance Raman spectra.

    PubMed

    McIlvenna, David; Huang, Wei E; Davison, Paul; Glidle, Andrew; Cooper, Jon; Yin, Huabing

    2016-04-21

    Single cell Raman spectroscopy measures a spectral fingerprint of the biochemistry of cells, and provides a powerful method for label-free detection of living cells without the involvement of a chemical labelling strategy. However, as the intrinsic Raman signals of cells are inherently weak, there is a significant challenge in discriminating and isolating cells in a flowing stream. Here we report an integrated Raman-microfluidic system for continuous sorting of a stream of cyanobacteria, Synechocystis sp. PCC6803. These carotenoid-containing microorganisms provide an elegant model system enabling us to determine the sorting accuracy using the subtly different resonance Raman spectra of microorganism cultured in a (12)C or (13)C carbon source. Central to the implementation of continuous flow sorting is the use of "pressure dividers" that eliminate fluctuations in flow in the detection region. This has enabled us to stabilise the flow profile sufficiently to allow automated operation with synchronisation of Raman acquisition, real-time classification and sorting at flow rates of ca. <100 μm s(-1), without the need to "trap" the cells. We demonstrate the flexibility of this approach in sorting mixed cell populations with the ability to achieve 96.3% purity of the selected cells at a speed of 0.5 Hz.

  10. Computer-controlled apparatus for automated development of continuous flow methods

    PubMed Central

    Wentzell, Peter D.; Hatton, Michael J.; Shiundu, Paul M.; Ree, Ronald M.; Betteridge, D.; Sly, Timothy J.

    1989-01-01

    An automated apparatus to assist in the development of analytical continuous flow methods is described. The system is capable of controlling and monitoring a variety of pumps, valves, and detectors through an IBM PC-AT compatible computer. System components consist of two types of peristaltic pumps (including a multiple pump unit), syringe pumps, electrically and pneumatically actuated valves, and an assortment of spectrophotometric and electrochemical detectors. Details of the interface circuitry are given where appropriate. To demonstrate the utility of the system, an automatically generated response surface is presented for the flow injection determination of iron(II) by its reaction with 1,10-phenanthroline. PMID:18924682

  11. Controlling of immiscible liquids fluid in a capillary reactor - from continuous to segmented flow

    NASA Astrophysics Data System (ADS)

    Matyushkin, L. B.; Mbwahnche, R. C.; Ryzhov, O. A.

    2016-11-01

    Experimental variation of the droplets form in the flow of immiscible fluids in a capillary with the inner diameter of 0,9 mm is presented. The possibility of the transition from continuous to segmented flow by varying the velocity of precursors and carrier liquids is demonstrated. It is shown that the rate of variation of one precursor in respect to other makes it possible to vary the ratio of mixing components. Simulation results for Ψ-shaped mixer in COMSOL Multiphysics software are also presented.

  12. C1-Continuous relative permeability and hybrid upwind discretization of three phase flow in porous media

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Efendiev, Y.

    2016-10-01

    Three-phase flow in a reservoir model has been a major challenge in simulation studies due to slowly convergent iterations in Newton solution of nonlinear transport equations. In this paper, we examine the numerical characteristics of three-phase flow and propose a consistent, "C1-continuous discretization" (to be clarified later) of transport equations that ensures a convergent solution in finite difference approximation. First, we examine three-phase relative permeabilities that are critical in solving nonlinear transport equations. Three-phase relative permeabilities are difficult to measure in the laboratory, and they are often correlated with two-phase relative permeabilities (e.g., oil-gas and water-oil systems). Numerical convergence of non-linear transport equations entails that three-phase relative permeability correlations are a monotonically increasing function of the phase saturation and the consistency conditions of phase transitions are satisfied. The Modified Stone's Method II and the Linear Interpolation Method for three-phase relative permeability are closely examined for their mathematical properties. We show that the Linear Interpolation Method yields C1-continuous three-phase relative permeabilities for smooth solutions if the two phase relative permeabilities are monotonic and continuously differentiable. In the second part of the paper, we extend a Hybrid-Upwinding (HU) method of two-phase flow (Lee, Efendiev and Tchelepi, ADWR 82 (2015) 27-38) to three phase flow. In the HU method, the phase flux is divided into two parts based on the driving forces (in general, it can be divided into several parts): viscous and buoyancy. The viscous-driven and buoyancy-driven fluxes are upwinded differently. Specifically, the viscous flux, which is always co-current, is upwinded based on the direction of the total velocity. The pure buoyancy-induced flux is shown to be only dependent on saturation distributions and counter-current. In three-phase flow, the

  13. 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.

  14. Continuous-flow automation of the Lactobacillus casei serum folate assay.

    PubMed Central

    Tennant, G B

    1977-01-01

    A method is described for the continuous-flow automation of the serum folate assay using Lactobacillus casei. The total incubation period is approximately four hours. The growth response of the organism to folate is estimated by measuring the rate of reduction of 2,3,5-triphenyl tetrazolium chloride (TTC). A simple continuous culture apparatus is used to grow the inoculum. Supplementation of the assay medium is necessary to obtain parallel results. A statistical assessment shows a favourable comparison with the whole-serum tube assay using a chloramphenicol resistant strain of L. casei. The method is less sensitive to inhibitory substances than the tube assay. PMID:415069

  15. Effects of the Transient Blood Flow-Wall Interaction on the Wall Stress Distribution in Abdominal Aortic Aneurysm (AAA)

    NASA Astrophysics Data System (ADS)

    Tang, Rubing; Geindreau, Christian; Lasheras, Juan

    2006-11-01

    Our static finite element analysis (FEA) of both idealized and real clinical models has shown that the maximum diameter and asymmetry have substantial influence on the AAA wall stress distribution. The thrombus inside the AAA was also found to reduce the magnitude of the wall stresses. To achieve a better understanding of the wall stress distribution in real AAAs, a dynamic FEA was also performed. We considered models, both symmetric and non-symmetric, in which the aorta is assumed isotropic with nonlinear material properties. For the limiting case of rigid walls, the evolution of the flow pattern and the wall shear stresses due to fluid flow at different stages of cardiac cycle predicted by our simulations are compared with experimental results obtained in in-vitro models. A good agreement is found between both results. Finally, we have extended the analysis to the physiologically correct case of deformable walls and characterized the transient effects on the wall stresses.

  16. 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.

  17. 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.

  18. Convenient and Simple Esterification in Continuous-Flow Systems using g-DMAP.

    PubMed

    Okuno, Yoshinori; Isomura, Shigeki; Sugamata, Anna; Tamahori, Kaoru; Fukuhara, Ami; Kashiwagi, Miyu; Kitagawa, Yuuichi; Kasai, Emiri; Takeda, Kazuyoshi

    2015-11-01

    The utility and applicability of polyethylene-g-polyacrylic acid-immobilized dimethylaminopyridine (g-DMAP) as a catalyst in a continuous-flow system were investigated for decarboxylative esterification. High catalytic activity toward acylation was provided by g-DMAP containing a flexible grafted-polymer structure. During decarboxylation, carboxylic acids and alcohols were converted cleanly using di-tert-butyl dicarbonate (Boc2O) as a coupling reagent, which reduced by-products. In addition, the use of Boc2O resulted in the formation of tert-butyl esters. These esterifications dramatically reduced the reaction time under continuous-flow conditions, with a residence time of approximately 2 min. This highly efficient esterification procedure will provide more practical industrial applications.

  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. 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.

  1. 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

  2. A catalytic reactor for the organocatalyzed enantioselective continuous flow alkylation of aldehydes.

    PubMed

    Porta, Riccardo; Benaglia, Maurizio; Puglisi, Alessandra; Mandoli, Alessandro; Gualandi, Andrea; Cozzi, Pier Giorgio

    2014-12-01

    The use of immobilized metal-free catalysts offers the unique possibility to develop sustainable processes in flow mode. The challenging intermolecular organocatalyzed enantioselective alkylation of aldehydes was performed for the first time under continuous flow conditions. By using a packed-bed reactor filled with readily available supported enantiopure imidazolidinone, different aldehydes were treated with three distinct cationic electrophiles. In the organocatalyzed α-alkylation of aldehydes with 1,3-benzodithiolylium tetrafluoroborate, excellent enantioselectivities, in some cases even better than those obtained in the flask process (up to 95% ee at 25 °C), and high productivity (more than 3800 h(-1) ) were obtained, which thus shows that a catalytic reactor may continuously produce enantiomerically enriched compounds. Treatment of the alkylated products with Raney-nickel furnished enantiomerically enriched α-methyl derivatives, key intermediates for active pharmaceutical ingredients and natural products.

  3. Stable aerobic granules for continuous-flow reactors: Precipitating calcium and iron salts in granular interiors.

    PubMed

    Juang, Yu-Chuan; Sunil S, Adav; Lee, Duu-Jong; Tay, Joo-Hwa

    2010-11-01

    Aerobic sludge granules are compact, strong microbial aggregates that have excellent settling ability and capability to efficiently treat high-strength and toxic wastewaters. The aerobic granules cultivated with low ammonium and phosphates lost structural stability within 3 days in continuous-flow reactors. Conversely, stable aerobic granules were cultivated in substrate with high levels of ammonium salts that could stably exist for 216 days in continuous-flow reactors with or without submerged membrane. The scanning electron microscopy, energy dispersive spectroscopy microanalysis and the confocal laser scanning microscopy imaging detected large amounts of calcium and iron precipitates in granule interiors. The Visual MINTEQ version 2.61 calculation showed that the phosphates and hydroxides were the main species in the precipitate.

  4. Abdominal Aortic Aneurysm (AAA)

    MedlinePlus

    ... Professions Site Index A-Z Abdominal Aortic Aneurysm (AAA) Abdominal aortic aneurysm (AAA) occurs when atherosclerosis or plaque buildup causes the ... weak and bulge outward like a balloon. An AAA develops slowly over time and has few noticeable ...

  5. Abdominal aortic aneurysm

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000162.htm Abdominal aortic aneurysm To use the sharing features on this page, ... blood to the abdomen, pelvis, and legs. An abdominal aortic aneurysm occurs when an area of the aorta becomes ...

  6. Synthesis of palladium nanoparticles using a continuous flow polymeric micro reactor.

    PubMed

    Song, Yujun; Kumar, Challa S S R; Hormes, Josef

    2004-09-01

    A continuous flow polymeric micro reactor, fabricated using a negative photo resist SU-8 on a 10 x 10 cm PEEK (polyetheretherketone) substrate by standard UV lithography, was utilized to synthesize palladium nanoparticles. The nanoparticles were characterized by Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Diffraction. The Pd nanoparticles synthesized in the micro reactor were found to have a narrower size distribution when compared with those obtained by the conventional batch process.

  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.

  8. 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

  9. 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.

  10. 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.

  11. Method and apparatus for improved melt flow during continuous strip casting

    DOEpatents

    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.

  12. Method and apparatus for improved melt flow during continuous strip casting

    DOEpatents

    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.

  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. 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.

  15. 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.

  16. Continuous flow synthesis of ZSM-5 zeolite on the order of seconds

    NASA Astrophysics Data System (ADS)

    Liu, Zhendong; Okabe, Kotatsu; Anand, Chokkalingam; Yonezawa, Yasuo; Zhu, Jie; Yamada, Hiroki; Endo, Akira; Yanaba, Yutaka; Yoshikawa, Takeshi; Ohara, Koji; Okubo, Tatsuya; Wakihara, Toru

    2016-12-01

    The hydrothermal synthesis of zeolites carried out in batch reactors takes a time so long (typically, on the order of days) that the crystallization of zeolites has long been believed to be very slow in nature. We herein present a synthetic process for ZSM-5, an industrially important zeolite, on the order of seconds in a continuous flow reactor using pressurized hot water as a heating medium. Direct mixing of a well-tuned precursor (90 °C) with the pressurized water preheated to extremely high temperature (370 °C) in the millimeter-sized continuous flow reactor resulted in immediate heating to high temperatures (240–300 °C); consequently, the crystallization of ZSM-5 in a seed-free system proceeded to completion within tens of or even several seconds. These results indicate that the crystallization of zeolites can complete in a period on the order of seconds. The subtle design combining a continuous flow reactor with pressurized hot water can greatly facilitate the mass production of zeolites in the future.

  17. Pulse Oximeter Derived Blood Pressure Measurement in Patients With a Continuous Flow Left Ventricular Assist Device.

    PubMed

    Hellman, Yaron; Malik, Adnan S; Lane, Kathleen A; Shen, Changyu; Wang, I-Wen; Wozniak, Thomas C; Hashmi, Zubair A; Munson, Sarah D; Pickrell, Jeanette; Caccamo, Marco A; Gradus-Pizlo, Irmina; Hadi, Azam

    2016-10-26

    Currently, blood pressure (BP) measurement is obtained noninvasively in patients with continuous flow left ventricular assist device (LVAD) by placing a Doppler probe over the brachial or radial artery with inflation and deflation of a manual BP cuff. We hypothesized that replacing the Doppler probe with a finger-based pulse oximeter can yield BP measurements similar to the Doppler derived mean arterial pressure (MAP). We conducted a prospective study consisting of patients with contemporary continuous flow LVADs. In a small pilot phase I inpatient study, we compared direct arterial line measurements with an automated blood pressure (ABP) cuff, Doppler and pulse oximeter derived MAP. Our main phase II study included LVAD outpatients with a comparison between Doppler, ABP, and pulse oximeter derived MAP. A total of five phase I and 36 phase II patients were recruited during February-June 2014. In phase I, the average MAP measured by pulse oximeter was closer to arterial line MAP rather than Doppler (P = 0.06) or ABP (P < 0.01). In phase II, pulse oximeter MAP (96.6 mm Hg) was significantly closer to Doppler MAP (96.5 mm Hg) when compared to ABP (82.1 mm Hg) (P = 0.0001). Pulse oximeter derived blood pressure measurement may be as reliable as Doppler in patients with continuous flow LVADs.

  18. Rapid detection of genetically modified organisms on a continuous-flow polymerase chain reaction microfluidics.

    PubMed

    Li, Yuyuan; Xing, Da; Zhang, Chunsun

    2009-02-01

    The ability to perform DNA amplification on a microfluidic device is very appealing. In this study, a compact continuous-flow polymerase chain reaction (PCR) microfluidics was developed for rapid analysis of genetically modified organisms (GMOs) in genetically modified soybeans. The device consists of three pieces of copper and a transparent polytetrafluoroethylene capillary tube embedded in the spiral channel fabricated on the copper. On this device, the P35S and Tnos sequences were successfully amplified within 9min, and the limit of detection of the DNA sample was estimated to be 0.005 ng microl(-1). Furthermore, a duplex continuous-flow PCR was also reported for the detection of the P35S and Tnos sequences in GMOs simultaneously. This method was coupled with the intercalating dye SYBR Green I and the melting curve analysis of the amplified products. Using this method, temperature differences were identified by the specific melting temperature values of two sequences, and the limit of detection of the DNA sample was assessed to be 0.01 ng microl(-1). Therefore, our results demonstrated that the continuous-flow PCR assay could discriminate the GMOs in a cost-saving and less time-consuming way.

  19. 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

  20. Continuous flow synthesis of ZSM-5 zeolite on the order of seconds

    PubMed Central

    Liu, Zhendong; Okabe, Kotatsu; Anand, Chokkalingam; Yonezawa, Yasuo; Zhu, Jie; Yamada, Hiroki; Endo, Akira; Yanaba, Yutaka; Yoshikawa, Takeshi; Ohara, Koji; Okubo, Tatsuya; Wakihara, Toru

    2016-01-01

    The hydrothermal synthesis of zeolites carried out in batch reactors takes a time so long (typically, on the order of days) that the crystallization of zeolites has long been believed to be very slow in nature. We herein present a synthetic process for ZSM-5, an industrially important zeolite, on the order of seconds in a continuous flow reactor using pressurized hot water as a heating medium. Direct mixing of a well-tuned precursor (90 °C) with the pressurized water preheated to extremely high temperature (370 °C) in the millimeter-sized continuous flow reactor resulted in immediate heating to high temperatures (240–300 °C); consequently, the crystallization of ZSM-5 in a seed-free system proceeded to completion within tens of or even several seconds. These results indicate that the crystallization of zeolites can complete in a period on the order of seconds. The subtle design combining a continuous flow reactor with pressurized hot water can greatly facilitate the mass production of zeolites in the future. PMID:27911823

  1. HeartMate® II continuous-flow left ventricular assist system.

    PubMed

    Sheikh, Farooq H; Russell, Stuart D

    2011-01-01

    Left ventricular assist devices (LVADs) have emerged as a beneficial therapeutic strategy proven to improve the morbidity and mortality of patients with advanced heart failure. Continuous-flow rotary LVADs have been developed in the hopes of delivering circulatory support in a more durable manner with fewer device-related complications. The HeartMate(®) II continuous-flow left ventricular assist system (LVAS; Thoratec Corporation, Pleasanton, CA, USA) has become the standard of care for heart failure patients who require long-term mechanical circulatory support. The efficacy of the HeartMate II has been demonstrated in patients where temporary support with an LVAD is needed until a suitable donor organ can be found for transplant (termed 'bridge to transplantation'), as well as for terminally-ill heart failure patients who are not candidates for transplant ('destination therapy'). When directly compared with a pulsatile LVAD, the implantation of a HeartMate II LVAS resulted in an overall improvement in survival with a reduction in the number of device-related complications and adverse events. The purpose of this article is threefold: to describe the history of the development of continuous-flow LVADs; to describe the technology of the HeartMate II; and, finally, to review the clinical outcomes in patients who have been implanted with the device.

  2. Colo-colonic anastomosis in a continuous-flow left ventricular assist device patient.

    PubMed

    Knaus, William J; Olson, Craig H

    2015-03-12

    Noncardiac operations are being increasingly performed on patients with left ventricular assist devices (LVADs). However, little is known on the impact of continuous-flow LVADs on the vascular supply of the colon for anastomoses. In this case, a 67-year-old male supported on an LVAD underwent four successful noncardiac operations including two intestinal anastomoses; left colon and small bowel anastomosis. To the best of our knowledge, no existing literature has reported successful colonic anastomosis on a continuous-flow LVAD. This case illustrates the plausibility of performing colonic anastomoses with appropriately selected patients supported on an LVAD. A 67-year-old male with congestive heart failure underwent LVAD placement for decompensated heart failure while awaiting orthotopic transplantation. During his recovery, he developed a stage IV sacral decubitus ulcer which required a sigmoid loop colostomy placement and a rotational flap. Subsequent stoma closure with partial sigmoid colectomy and stapled anastomosis was performed, and healed without evidence of anastomotic leak. This case illustrates the potential for colonic anastomoses for patients on continuous-flow LVAD support. Although oxygenation is known to be an important aspect of healing, this patient's outcome suggests that intestinal anastomoses can be performed on the induced pulseless environment of an LVAD. Further studies will be needed to further elucidate the success of longer segment resections and appropriate surgical candidates.

  3. [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.

  4. 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.

  5. Factors influencing arsenic and nitrate removal from drinking water in a continuous flow electrocoagulation (EC) process.

    PubMed

    Kumar, N Sanjeev; Goel, Sudha

    2010-01-15

    An experimental study was conducted under continuous flow conditions to evaluate some of the factors influencing contaminant removal by electrocoagulation (EC). A bench-scale simulation of drinking water treatment was done by adding a filtration column after a rectangular EC reactor. Contaminant removal efficiency was determined for voltages ranging from 10 to 25 V and a comparative study was done with distilled water and tap water for two contaminants: nitrate and arsenic(V). Maximum removal efficiency was 84% for nitrate at 25 V and 75% for arsenic(V) at 20 V. No significant difference in contaminant removal was observed in tap water versus distilled water. Increase in initial As(V) concentration from 1 ppm to 2 ppm resulted in a 10% increase in removal efficiency. Turbidity in the EC reactor effluent was 52 NTU and had to be filtered to achieve acceptable levels of final turbidity (5 NTU) at steady-state. The flow regime in the continuous flow reactor was also evaluated in a tracer study to determine whether it is a plug flow reactor (PFR) or constantly stirred tank reactor (CSTR) and the results show that this reactor was close to an ideal CSTR, i.e., it was fairly well-mixed.

  6. 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.

  7. Effect of a Magnetic Field on Turbulent Flow in Continuous Casting Mold

    NASA Astrophysics Data System (ADS)

    Singh, Ramnik; Vanka, Pratap; Thomas, Brian G.

    2012-11-01

    Electromagnetic Braking (EMBr) fields are applied to control the turbulent mold flow for defect reduction in continuous steel casting. The effect of EMBr depends on the path of induced electric current which is modified by presence of the highly conducting solidifying shell. The mold geometry is complex involving flow in a high-aspect ratio closed channel with bifurcated jet impinging obliquely on the side walls. The extremely transient nature and the anisotropic behavior of turbulence under the EMBr field make numerical studies challenging. We use large eddy simulations to study effects of EMBr with electrically insulating and conducting boundary conditions. Magnetohydrodynamic equations are solved using a fractional step method with second order spatial and temporal accuracy. The electric potential method is used as magnetic Reynolds number is low for liquid metal flows. The solver was first validated with measurements from scaled GaInSn model and simulations were then performed to study real casters at industrial conditions. Time averaged and transient behaviors of the flow were studied by collecting distributions of mean velocities, turbulent fluctuations and vorticity. The simulations reveal that the electrical boundary conditions have a major effect on the flow structure. National Science Foundation Grant CMMI 11-30882.

  8. 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

  9. 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).

  10. 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.

  11. 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

  12. Three-dimensional visualization of axial velocity profiles downstream of six different mechanical aortic valve prostheses, measured with a hot-film anemometer in a steady state flow model.

    PubMed

    Hasenkam, J M; Westphal, D; Reul, H; Gormsen, J; Giersiepen, M; Stodkilde-Jorgensen, H; Paulsen, P K

    1987-01-01

    Hot-film anemometry was used for in vitro steady-state measurements downstream of six mechanical aortic valve prostheses at flow rates 10, 20 and 30 l.min-1. Three-dimensional visualizations of velocity profiles at two downstream levels were made with the valves rotated 0 and 60 degrees in relation to the sinuses of valsalvae. The velocity fields downstream of the disc valves were generally skew with increasing velocity gradients and laminar shear stresses with increasing flow rates. Furthermore, increased skewness of the velocity profiles was noticed when the major orifices of the disc valves were towards the commissure than when approaching a sinus of valsalvae. The velocity profiles downstream of the ball valve were generally flat but with considerably more disturbed flow, consistent with the findings in turbulent flow.

  13. Heparin-Induced-Thrombocytopenia Causing Massive Aortic Thrombosis after Ascending Aortic Replacement for Type A Acute Aortic Dissection

    PubMed Central

    Imoto, Kiyotaka; Uchida, Keiji; Isoda, Susumu; Karube, Norihisa; Yasuda, Shota; Masuda, Munetaka

    2016-01-01

    A 77-year-old woman underwent emergency ascending aortic replacement for type A acute aortic dissection. Fifteen days after the operation, she had motor and sensory disturbances in the lower limbs. Computed tomography revealed multiple aortic thrombi and disrupted blood flow in the right external iliac and left common iliac arteries. She underwent an emergency thrombectomy for acute limb ischemia. Because heparin- induced-thrombocytopenia (HIT) was suspected to have caused the multiple aortic thrombi, we postoperatively changed the anticoagulant therapy from heparin to argatroban. Seventeen days after the first operation, gastrointestinal bleeding developed, and the patient died of mesenteric ischemia caused by HIT. Arterial embolization caused by HIT after cardiovascular surgery is a rare, but fatal event. To avoid fatal complications, early diagnosis and early treatment are essential. Use of a scoring system would probably facilitate early diagnosis. PMID:26780951

  14. Titer plate formatted continuous flow thermal reactors for high throughput applications: fabrication and testing

    NASA Astrophysics Data System (ADS)

    Sang-Won Park, Daniel; Chen, Pin-Chuan; You, Byoung Hee; Kim, Namwon; Park, Taehyun; Lee, Tae Yoon; Datta, Proyag; Desta, Yohannes; Soper, Steven A.; Nikitopoulos, Dimitris E.; Murphy, Michael C.

    2010-05-01

    A high throughput, multi-well (96) polymerase chain reaction (PCR) platform, based on a continuous flow (CF) mode of operation, was developed. Each CFPCR device was confined to a footprint of 8 × 8 mm2, matching the footprint of a well on a standard micro-titer plate. While several CFPCR devices have been demonstrated, this is the first example of a high-throughput multi-well continuous flow thermal reactor configuration. Verification of the feasibility of the multi-well CFPCR device was carried out at each stage of development from manufacturing to demonstrating sample amplification. The multi-well CFPCR devices were fabricated by micro-replication in polymers, polycarbonate to accommodate the peak temperatures during thermal cycling in this case, using double-sided hot embossing. One side of the substrate contained the thermal reactors and the opposite side was patterned with structures to enhance thermal isolation of the closely packed constant temperature zones. A 99 bp target from a λ-DNA template was successfully amplified in a prototype multi-well CFPCR device with a total reaction time as low as ~5 min at a flow velocity of 3 mm s-1 (15.3 s cycle-1) and a relatively low amplification efficiency compared to a bench-top thermal cycler for a 20-cycle device; reducing the flow velocity to 1 mm s-1 (46.2 s cycle-1) gave a seven-fold improvement in amplification efficiency. Amplification efficiencies increased at all flow velocities for 25-cycle devices with the same configuration.

  15. 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.

  16. Aortobronchial Fistula after Thoracic Endovascular Aortic Repair (TEVAR) for Descending Thoracic Aortic Aneurysm.

    PubMed

    Melvan, John Nicholas; DeLaRosa, Jacob; Vasquez, Julio C

    2017-03-07

    Continued enlargement of the aneurysm sac after thoracic endovascular aortic repair (TEVAR) is a known risk after endovascular treatment of thoracic aortic aneurysms. For this reason, periodic outpatient follow-up is required to identify situations that require repair. Here, we describe an aortobronchial fistula (ABF) in a patient lost to follow-up, that presented 3 years after an elective TEVAR done for a primary, descending thoracic aortic aneurysm. Our patient arrived in extremis and suffered massive hemoptysis leading to her demise. Computed tomography (CT) angiogram near the time of her death demonstrated a bleeding ABF immediately distal to her previous TEVAR repair. Aortic aneurysmal disease remains life threatening even after repair. Improved endovascular techniques and devices have resulted in decreased need for reintervention. However, this case demonstrates the risk of thoracic aortic disease progression and highlights the importance of establishing consistent, long-term follow-up after TEVAR.

  17. Repair for acquired aortic valve disease.

    PubMed

    Antunes, M J

    1996-10-01

    The favorable results of mitral valvuloplasty when compared with valve replacement have renewed the interest of many surgeons in aortic valve repair. However, these efforts have, for the most part, been unsuccessful. Also, the results of aortic valve replacement are usually better than those of mitral valve replacement. Yet, some patients appear to derive benefit from a conservative aortic valve procedure. The best examples are mild or moderate aortic valve disease associated with mitral valve or coronary artery disease, which constitute the primary indication for operation, where "prophylactic" aortic valve replacement does not appear justifiable. Other possible indications for aortic valvuloplasty includes patient's lack of compliance or contraindication to anticoagulation in young patients. Senile aortic stenosis, in very old patients with a small annulus, preserved leaflet morphology and nonsignificant commissural fusion should be considered for repair. However, since the procedure is not easily reproducible and the results not uniformly predictable, it cannot be recommended for generalized use. Nonetheless, experienced surgeons should be encouraged to continue these efforts.

  18. 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

  19. Surgical management of a hypoplastic distal aortic arch and coarctation of aorta in a patient with Klippel-Feil syndrome, ascending aortic aneurysm and bicuspid aortic valve.

    PubMed

    Sabol, Frantisek; Kolesar, Adrián; Toporcer, Tomás; Bajmoczi, Milan

    2014-10-01

    Klippel-Feil syndrome has been associated with cardiovascular malformations, but only 3 cases have been reported to be associated with aortic coarctation and surgical management is not defined. A 51-year old woman with Klippel-Feil syndrome associated with an aneurysm of the ascending aorta, hypoplastic aortic arch and aortic coarctation at the level of the left subclavian artery presented with shortness of breath 2 years after diagnosis. Imaging identified interim development of a 7.2-cm aneurysm at the level of the aortic coarctation. She underwent surgical repair with a Dacron interposition graft under hypothermic circulatory arrest. She continues to do well 18 months following repair.

  20. Mobile magnetic particles as solid-supports for rapid surface-based bioanalysis in continuous flow.

    PubMed

    Peyman, Sally A; Iles, Alexander; Pamme, Nicole

    2009-11-07

    An extremely versatile microfluidic device is demonstrated in which multi-step (bio)chemical procedures can be performed in continuous flow. The system operates by generating several co-laminar flow streams, which contain reagents for specific (bio)reactions across a rectangular reaction chamber. Functionalized magnetic microparticles are employed as mobile solid-supports and are pulled from one side of the reaction chamber to the other by use of an external magnetic field. As the particles traverse the co-laminar reagent streams, binding and washing steps are performed on their surface in one operation in continuous flow. The applicability of the platform was first demonstrated by performing a proof-of-principle binding assay between streptavidin coated magnetic particles and biotin in free solution with a limit of detection of 20 ng mL(-1) of free biotin. The system was then applied to a mouse IgG sandwich immunoassay as a first example of a process involving two binding steps and two washing steps, all performed within 60 s, a fraction of the time required for conventional testing.

  1. Continuous-flow gas-lift installation design utilizing production-pressure-operated valve performance

    SciTech Connect

    Winkler, H.W.

    1995-12-31

    The variable-gradient design-line method is a widely accepted procedure for spacing gas-lift valves (GLVs) in a continuous-flow gas-lift (GL) installation. Injection-pressure-operated (IPO) and production-pressure-operated (PPO) GLVs can be used in a variable gradient designed installation. The primary purpose of GLVs is to unload a well to the desired depth of gas injection. If the installation design is based on a constant surface injection-gas pressure (p{sub io}), the GLVs must be opened by an increase in the flowing-production pressure at valve depth (p{sub pfD}) rather than an increase in injection-gas pressure at valve depth (p{sub ioD}). PPO, also called fluid-operated, valves are opened and closed by changes in p{sub pfD}. This paper outlines in detail the calculations for a variable-gradient continuous-flow installation design procedure based on a constant p{sub io} for spacing the unloading PPO valves. The valve spacing and port size selection includes performance characteristics of PPO GLVs. A simplified method for calculating the injection daily volumetric gas rate (q{sub gsc}) throughput of an unbalanced bellows type of PPO valve on the basis of a change in p{sub pfD} and the valve bellows-assembly load rate (B{sub lr}) is given in the Appendix.

  2. 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.

  3. Titer-plate formatted continuous flow thermal reactors: Design and performance of a nanoliter reactor.

    PubMed

    Chen, Pin-Chuan; Park, Daniel S; You, Byoung-Hee; Kim, Namwon; Park, Taehyun; Soper, Steven A; Nikitopoulos, Dimitris E; Murphy, Michael C

    2010-08-06

    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

  4. 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

  5. Pressure fields by flow-sensitive, 4D, velocity-encoded CMR in patients with aortic coarctation.

    PubMed

    Riesenkampff, Eugénie; Fernandes, Joao Filipe; Meier, Sebastian; Goubergrits, Leonid; Kropf, Siegfried; Schubert, Stephan; Berger, Felix; Hennemuth, Anja; Henneumuth, Anja; Kuehne, Titus

    2014-09-01

    This study compared pressure fields by 4-dimensional (4D), velocity-encoded cine (VEC) cardiac magnetic resonance imaging (CMR) with pressures measured by the clinical gold standard catheterization. Thirteen patients (n = 7 male, n = 6 female) with coarctation were studied. The 4D-VEC-CMR pressure fields were computed by solving the Pressure-Poisson equation. The agreement between catheterization and CMR-based methods was determined at 5 different measurement sites along the aorta. For all sites, the correlation coefficients between measures varied between 0.86 and 0.97 (p < 0.001). The Bland-Altman test showed good agreement between peak systolic pressure gradients across the coarctation. The nonsignificant (p > 0.2) bias was +2.3 mm Hg (± 6.4 mm Hg, 2 SDs) for calibration with dynamic pressures and +1.5 mm Hg (± 4.6 mm Hg, 2 SDs) for calibration with static pressure. In a clinical setting of coarctation, pressure fields can be accurately computed from 4D-VEC-CMR-derived flows. In patients with coarctation, this noninvasive technique might evolve to an alternative to invasive catheterization.

  6. Continuous Flow Processing of ZIF-8 Membranes on Polymeric Porous Hollow Fiber Supports for CO2 Capture.

    PubMed

    Marti, Anne M; Wickramanayake, Wasala; Dahe, Ganpat; Sekizkardes, Ali; Bank, Tracy L; Hopkinson, David P; Venna, Surendar R

    2017-02-22

    We have utilized an environmentally friendly synthesis approach for the accelerated growth of a selective inorganic membrane on a polymeric hollow fiber support for postcombustion carbon capture. Specifically, continuous defect-free ZIF-8 thin films were grown and anchored using continuous flow synthesis on the outer surface of porous supports using water as solvent. These membranes demonstrated CO2 permeance of 22 GPU and the highest reported CO2/N2 selectivity of 52 for a continuous flow synthesized ZIF-8 membrane.

  7. Solar disinfection for the post-treatment of greywater by means of a continuous flow reactor.

    PubMed

    Pansonato, Natália; Afonso, Marcos V G; Salles, Carlos A; Boncz, Marc A; Paulo, Paula L

    2011-01-01

    SODIS (solar disinfection) is a low-cost alternative for water decontamination. The method is based on the exposure of water, contained in PET bottles, to direct sunlight, and mainly its UV-A and infrared components. The present research studied SODIS as a low cost alternative for the inactivation of Escherichia coli (E. coli) in treated greywater, aiming at its reuse for more noble applications. Experiments were performed in (i) batch mode (2 L PET-bottles), testing the effect of turbidity on system efficiency and, (ii) in a continuous pilot-scale reactor prototype (51 L, using interconnected 2 L-PET bottles), testing hydraulic retention times (HRT) of 18 and 24 h. Samples were exposed to an average solar radiation intensity of 518 W/m2. The results obtained indicate that the SODIS system has potential for total coliforms and E. coli inactivation in the pre-treated greywater, reaching 2.1 log units E. coli inactivation in batch experiments for low turbidity samples (21 NTU), and > 2 log units inactivation of total coliforms (and E. coli, when present) for the 24 h HRT-continuous prototype. The continuous flow prototype needs more testing and structural improvements to cope with the difficulties posed by algae growth, as they complicate maintaining conditions of constant flow and make frequent maintenance inevitable.

  8. Microfluidic chip integrating high throughput continuous-flow PCR and DNA hybridization for bacteria analysis.

    PubMed

    Jiang, Xiran; Shao, Ning; Jing, Wenwen; Tao, Shengce; Liu, Sixiu; Sui, Guodong

    2014-05-01

    Rapid identification of clinical pathogens is the initial and essential step for antimicrobial therapy. Herein, we successfully developed a microfluidic device which combines high-throughput continuous-flow PCR and DNA hybridization for the detection of various bacterial pathogens. Universal primers were designed based on the conserved regions of bacterial 16S ribosomal DNA (16S rDNA), and specific probes were designed from a variable region of 16S rDNA within the amplicon sequences. In the chip operation, after the continuous flow PCR was achieved in the first microfluidic chip, the product was directly introduced into a hybridization chip integrated with microarray containing the immobilized DNA probes. The target-probe hybridization was completed within 1h at 55 °C, and fluorescence signals were obtained as the readout. The presented device is simple, versatile and with less sample consumption compared with traditional instruments. It can perform high-throughput bacteria detections continuously in a single assay, which makes it a promising platform for clinical bacteria identifications.

  9. Ventilatory modes and mechanics of the hedgehog skate (Leucoraja erinacea): testing the continuous flow model.

    PubMed

    Summers, A P; Ferry-Graham, L A

    2001-05-01

    The movement of water across the gills of non-ram-ventilating fishes involves the action of two pumps: a pressure pump that pushes water across the gills from the oropharyngeal to the parabranchial cavity, and a suction pump that draws water across the gills from the oropharyngeal into the parabranchial cavity. Together, the two are thought to keep water flowing continuously anteroposteriorly through the head of the respiring animal. However, there is evidence that the pressure and suction pumps do not always work in perfect phase in elasmobranch fishes, leading to periods of higher pressure in the parabranchial than in the oropharyngeal cavity. We investigated the existence and consequence of such pressure reversals in the hedgehog skate Leucoraja erinacea using pressure transducers, sonomicrometry and flow visualization including internal visualization using endoscopy. We noted four patterns of respiration in the experimental skates distinguished by the flow pattern at the three openings into the respiratory system: (1) in through the spiracle only, (2) in through the mouth + spiracle, (3) in through the mouth only, and (4) the mouth held open throughout the respiratory cycle. The first two were by far the dominant modes recorded from experimental animals. We determined that pressure reversals exist in the hedgehog skate, and that the gill bars adducted during such pressure reversals. Direct observation confirmed that these pressure reversals do correspond to pulsatile flow across the gills. During mouth+spiracle ventilation the flow completely reversed direction, flowing from the parabranchial chambers back across the gills and into the oropharyngeal cavity. Finally, we addressed the utility of sonomicrometry as a technique for determining kinematics in aquatic animals. Despite some problems involving errors inherent to the system design, we found the technique useful for complementing such techniques as pressure measurements and endoscopy.

  10. 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

  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. 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.

  13. Limitations of respiratory muscle and vastus lateralis blood flow during continuous exercise.

    PubMed

    Henderson, William R; Guenette, Jordan A; Dominelli, Paolo B; Griesdale, Donald E G; Querido, Jordan S; Boushel, Robert; Sheel, A William

    2012-05-31

    Measurement of regional blood flow to the respiratory muscles has traditionally been invasive. The blood flow index (BFI), a minimally invasive method using indocyanine green dye (ICG) and near infrared spectroscopy, allows assessment of within subject changes in regional blood flow. This study assessed regional BFI to the vastus lateralis muscle (QBFI) and the superficial respiratory muscles in the seventh intercostal space (RMBFI). Eight healthy subjects cycled continuously at incrementally more difficulty stages to exhaustion. In our subjects, QBFI declined between 83% and 100% of maximal exertion (p=0.002) and no statistically significant changes in RMBFI were seen despite steadily increasing ventilatory workloads. Post hoc pairwise comparisons demonstrated that QBFI at 83% work (0.015μmoless(-1)±0.005) was significantly higher than at maximum work output (0.011μmoless(-1)±0.004, p=0.007). There were no other significant differences of QBFI between maximum work output and different levels of work. The current study suggests that respiratory and locomotor muscle blood flow during sub-maximal and maximal exertion is unable to match increasing workloads.

  14. Coupled turbulent flow, heat, and solute transport in continuous casting processes

    NASA Astrophysics Data System (ADS)

    Aboutalebi, M. Reza; Hasan, M.; Guthrie, R. I. L.

    1995-08-01

    A fully coupled fluid flow, heat, and solute transport model was developed to analyze turbulent flow, solidification, and evolution of macrosegregation in a continuous billet caster. Transport equations of total mass, momentum, energy, and species for a binary iron-carbon alloy system were solved using a continuum model, wherein the equations are valid for the solid, liquid, and mushy zones in the casting. A modified version of the low-Reynolds number k-ɛ model was adopted to incorporate turbulence effects on transport processes in the system. A control-volume-based finite-difference procedure was employed to solve the conservation equations associated with appropriate boundary conditions. Because of high nonlinearity in the system of equations, a number of techniques were used to accelerate the convergence process. The effects of the parameters such as casting speed, steel grade, nozzle configuration on flow pattern, solidification profile, and carbon segregation were investigated. From the computed flow pattern, the trajectory of inclusion particles, as well as the density distribution of the particles, was calculated. Some of the computed results were compared with available experimental measurements, and reasonable agreements were obtained.

  15. A scalable procedure for light-induced benzylic brominations in continuous flow.

    PubMed

    Cantillo, David; de Frutos, Oscar; Rincon, Juan A; Mateos, Carlos; Kappe, C Oliver

    2014-01-03

    A continuous-flow protocol for the bromination of benzylic compounds with N-bromosuccinimide (NBS) is presented. The radical reactions were activated with a readily available household compact fluorescent lamp (CFL) using a simple flow reactor design based on transparent fluorinated ethylene polymer (FEP) tubing. All of the reactions were carried out using acetonitrile as the solvent, thus avoiding hazardous chlorinated solvents such as CCl4. For each substrate, only 1.05 equiv of NBS was necessary to fully transform the benzylic starting material into the corresponding bromide. The general character of the procedure was demonstrated by brominating a diverse set of 19 substrates containing different functional groups. Good to excellent isolated yields were obtained in all cases. The novel flow protocol can be readily scaled to multigram quantities by operating the reactor for longer time periods (throughput 30 mmol h(-1)), which is not easily possible in batch photochemical reactors. The bromination protocol can also be performed with equal efficiency in a larger flow reactor utilizing a more powerful lamp. For the bromination of phenylacetone as a model, a productivity of 180 mmol h(-1) for the desired bromide was achieved.

  16. High-throughput continuous flow femtosecond laser-assisted cell optoporation and transfection.

    PubMed

    Breunig, Hans Georg; Uchugonova, Aisada; Batista, Ana; König, Karsten

    2014-12-01

    We present a femtosecond-laser based nanoprocessing system for transient optical cell membrane poration to allow the introduction of foreign molecules into the interior of a cell with very high throughput. In the setup, cells flow through a micro-flow tube for spatial confinement and are simultaneously targeted by fs laser radiation. Beam-shaping generates a focal geometry along a line which is scanned across the micro-flow cell to increase the number of reachable cells. Successful cell membrane poration was observed indirectly by cell transfection even with cell-light interaction times in the millisecond range. The system was characterized by experiments with Chinese hamster ovary cells regarding cell viability, the uptake of extrinsic molecules and cell transfection efficiency. The continuous flow of cells enables a tremendous increase of cell throughput compared to previous nonflow approaches by treating millions of cells, although with only limited efficiency. The setup opens the possibility to realize a completely automated high-throughput laser-assisted cell-poration system which could be integrated in lab-on-a-chip devices.

  17. Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.

    PubMed

    Collins, David J; Khoo, Bee Luan; Ma, Zhichao; Winkler, Andreas; Weser, Robert; Schmidt, Hagen; Han, Jongyoon; Ai, Ye

    2017-04-10

    Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 μm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 μm from a mixed suspension with 1 μm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells.

  18. Modification of turbulent transport with continuous variation of flow shear in the large plasma device.

    PubMed

    Schaffner, D A; Carter, T A; Rossi, G D; Guice, D S; Maggs, J E; Vincena, S; Friedman, B

    2012-09-28

    Continuous control over azimuthal flow and shear in the edge of the Large Plasma Device (LAPD) has been achieved using a biasable limiter which has allowed a careful study of the effect of flow shear on pressure-gradient-driven turbulence and transport in the LAPD. The LAPD rotates spontaneously in the ion diamagnetic direction; positive limiter bias first reduces, then minimizes (producing a near-zero shear state), and finally reverses the flow into the electron diamagnetic direction. Degradation of particle confinement is observed in the minimum shearing state and a reduction in the turbulent particle flux is observed with increasing shearing in both flow directions. Near-complete suppression of the turbulent particle flux is observed for shearing rates comparable to the turbulent autocorrelation rate measured in the minimum shear state. Turbulent flux suppression is dominated by amplitude reduction in low-frequency (<10 kHz) density fluctuations. An increase in fluctuations for the highest shearing states is observed with the emergence of a coherent mode which does not lead to net particle transport. The variations of density fluctuations are fit well with power laws and compare favorably to simple models of shear suppression of transport.

  19. Robust Extraction Interface for Coupling Droplet-Based and Continuous Flow Microfluidics

    SciTech Connect

    Sun, Xuefei; Tang, Keqi; Smith, Richard D.; Kelly, Ryan T.

    2012-03-07

    Reliable and highly efficient extraction of droplets from oil to aqueous phase is key for downstream coupling with chemical separations and nonoptical detection methods such as amperometry and mass spectrometry. This paper presents an improved interface providing robust extraction for droplet-based poly(dimethylsiloxane) (PDMS) microfluidic devices. The extraction interface consists of an array of cylindrical posts with narrow apertures in between. The aqueous flow channel into which droplets coalesced was simply and selectively modified to be hydrophilic, while the continuous oil phase flow channel that contained encapsulated aqueous droplets retained a hydrophobic surface. The different surfaces on both sides of the extraction region form a highly stable liquid interface between the two immiscible phases, allowing rapid droplet transfer to the aqueous stream. Entire droplets could be completely extracted within broad ranges of aqueous and oil flow rates (0 - 1 and 0.1 - 1 uL/min, respectively). After extraction, the droplet contents could be transported electrophoretically or by pressure-driven flow to a monolithically integrated emitter for nano-electrospray ionization mass spectrometry (nanoESI-MS) analysis. This interface should be amenable to the separation and identification of droplet contents and on-line monitoring of in-droplet reactions.

  20. 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.

  1. 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.

  2. A continuous-flow system for high-precision kinetics using small volumes.

    PubMed

    Zhou, Xianzhi; Medhekar, Rohit; Toney, Michael D

    2003-08-01

    A generally applicable continuous-flow kinetic analysis system that gives data of a precision high enough to measure small kinetic isotope effects for enzymatic and nonenzymatic reactions is described. It employs commercially available components that are readily assembled into an apparatus that is easy to use. It operates under laminar flow conditions, which requires that the time between the initiation of the reaction in the mixer and the observation be long enough that molecular diffusion can effect a symmetrization of the concentration profile that results from a thin plug of reagents introduced at the mixer. The analysis of a second-order irreversible reaction under pseudo-first-order conditions is presented. The Yersinia pestis protein tyrosine phosphatase catalyzed hydrolysis of p-nitrophenyl phosphate is characterized with the system, and a proton inventory on kcat is presented.

  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. 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.

  5. Bacterial communities in batch and continuous-flow wetlands treating the herbicide S-metolachlor.

    PubMed

    Elsayed, O F; Maillard, E; Vuilleumier, S; Imfeld, G

    2014-11-15

    Knowledge of wetland bacterial communities in the context of pesticide contamination and hydrological regime is scarce. We investigated the bacterial composition in constructed wetlands receiving Mercantor Gold(®) contaminated water (960 g L(-1) of the herbicide S-metolachlor, >80% of the S-enantiomer) operated under continuous-flow or batch modes to evaluate the impact of the hydraulic regime. In the continuous-flow wetland, S-metolachlor mass removal was >40%, whereas in the batch wetland, almost complete removal of S-metolachlor (93-97%) was observed. Detection of ethanesulfonic and oxanilic acid degradation products further indicated S-metolachlor biodegradation in the two wetlands. The dominant bacterial populations were characterised by terminal restriction fragment length polymorphism (T-RFLP) and 454 pyrosequencing. The bacterial profiles evolved during the first 35 days of the experiment, starting from a composition similar to that of inlet water, with the use of nitrate and to a lesser extent sulphate and manganese as terminal electron acceptors for microbial metabolism. Proteobacteria were the most abundant phylum, with Beta-, Alpha- and Gammaproteobacteria representing 26%, 19% and 17% respectively of total bacterial abundance. Bacterial composition in wetland water changed gradually over time in continuous-flow wetland and more abruptly in the batch wetland. Differences in overall bacterial water structure in the two systems were modest but significant (p=0.008), and S-metolachlor, nitrate, and total inorganic carbon concentrations correlated with changes in the bacterial profiles. Together, the results highlight that bacterial composition profiles and their dynamics may be used as bioindicators of herbicide exposure and hydraulic disturbances in wetland systems.

  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.

  8. Selected low-flow frequency statistics for continuous-record streamgage locations in Maryland, 2010

    USGS Publications Warehouse

    Doheny, Edward J.; Banks, William S.L.

    2010-01-01

    According to a 2008 report by the Governor's Advisory Committee on the Management and Protection of the State's Water Resources, Maryland's population grew by 35 percent between 1970 and 2000, and is expected to increase by an additional 27 percent between 2000 and 2030. Because domestic water demand generally increases in proportion to population growth, Maryland will be facing increased pressure on water resources over the next 20 years. Water-resources decisions should be based on sound, comprehensive, long-term data and low-flow frequency statistics from all available streamgage locations with unregulated streamflow and adequate record lengths. To provide the Maryland Department of the Environment with tools for making future water-resources decisions, the U.S. Geological Survey initiated a study in October 2009 to compute low-flow frequency statistics for selected streamgage locations in Maryland with 10 or more years of continuous streamflow records. This report presents low-flow frequency statistics for 114 continuous-record streamgage locations in Maryland. The computed statistics presented for each streamgage location include the mean 7-, 14-, and 30-consecutive day minimum daily low-flow dischages for recurrence intervals of 2, 10, and 20 years, and are based on approved streamflow records that include a minimum of 10 complete climatic years of record as of June 2010. Descriptive information for each of these streamgage locations, including the station number, station name, latitude, longitude, county, physiographic province, and drainage area, also is presented. The statistics are planned for incorporation into StreamStats, which is a U.S. Geological Survey Web application for obtaining stream information, and is being used by water-resource managers and decision makers in Maryland to address water-supply planning and management, water-use appropriation and permitting, wastewater and industrial discharge permitting, and setting minimum required

  9. 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.

  10. Low-gradient aortic stenosis.

    PubMed

    Clavel, Marie-Annick; Magne, Julien; Pibarot, Philippe

    2016-09-07

    An important proportion of patients with aortic stenosis (AS) have a 'low-gradient' AS, i.e. a small aortic valve area (AVA <1.0 cm(2)) consistent with severe AS but a low mean transvalvular gradient (<40 mmHg) consistent with non-severe AS. The management of this subset of patients is particularly challenging because the AVA-gradient discrepancy raises uncertainty about the actual stenosis severity and thus about the indication for aortic valve replacement (AVR) if the patient has symptoms and/or left ventricular (LV) systolic dysfunction. The most frequent cause of low-gradient (LG) AS is the presence of a low LV outflow state, which may occur with reduced left ventricular ejection fraction (LVEF), i.e. classical low-flow, low-gradient (LF-LG), or preserved LVEF, i.e. paradoxical LF-LG. Furthermore, a substantial proportion of patients with AS may have a normal-flow, low-gradient (NF-LG) AS: i.e. a small AVA-low-gradient combination but with a normal flow. One of the most important clinical challenges in these three categories of patients with LG AS (classical LF-LG, paradoxical LF-LG, and NF-LG) is to differentiate a true-severe AS that generally benefits from AVR vs. a pseudo-severe AS that should be managed conservatively. A low-dose dobutamine stress echocardiography may be used for this purpose in patients with classical LF-LG AS, whereas aortic valve calcium scoring by multi-detector computed tomography is the preferred modality in those with paradoxical LF-LG or NF-LG AS. Although patients with LF-LG severe AS have worse outcomes than those with high-gradient AS following AVR, they nonetheless display an important survival benefit with this intervention. Some studies suggest that transcatheter AVR may be superior to surgical AVR in patients with LF-LG AS.

  11. Planimetry of aortic valve area using multiplane transoesophageal echocardiography is not a reliable method for assessing severity of aortic stenosis.

    PubMed Central

    Bernard, Y.; Meneveau, N.; Vuillemenot, A.; Magnin, D.; Anguenot, T.; Schiele, F.; Bassand, J. P.

    1997-01-01

    OBJECTIVE: To assess the reliability of aortic valve area planimetry by multiplane transoesophageal echocardiography (TOE) in aortic stenosis. DESIGN: Study of the diagnostic value of aortic valve area planimetry using multiplane TOE, compared with catheterisation and the continuity equation, both being considered as criterion standards. SETTING: University hospital. PATIENTS: 49 consecutive patients (29 male, 20 female, aged 44 to 82 years, average 66.6 (SD 8.5)), referred for haemodynamic evaluation of an aortic stenosis, were enrolled in a prospective study. From this sample, 37 patients were eligible for the final analysis. METHODS: Transthoracic and multiplane transoesophageal echocardiograms were performed within 24 hours before catheterisation. At transthoracic echo, aortic valve area was calculated by the continuity equation. At TOE, the image of the aortic valve opening was obtained with a 30-65 degrees rotation of the transducer. Numerical dynamic images were stored on optical discs for off-line analysis and were reviewed by two blinded observers. Catheterisation was performed in all cases and aortic valve area was calculated by the Gorlin formula. RESULTS: Feasibility of the method was 92% (48/52). The agreement between aortic valve area measured at TOE (mean 0.88 (SD 0.35) cm2) and at catheterisation (0.79 (0.24) cm2) was very poor. The same discrepancies were found between TOE and the continuity equation (0.72 (0.26) cm2). TOE planimetry overestimated aortic valve area determined by the two other methods. Predictive positive and negative values of planimetry to detect aortic valve area < 0.75 cm2 were 62% (10/16) and 43% (9/21) respectively. CONCLUSIONS: Planimetry of aortic valve area by TOE is difficult and less accurate than the continuity equation for assessing the severity of aortic stenosis. Images PMID:9290405

  12. Lab on a chip for continuous-flow magnetic cell separation.

    PubMed

    Hejazian, Majid; Li, Weihua; Nguyen, Nam-Trung

    2015-02-21

    Separation of cells is a key application area of lab-on-a-chip (LOC) devices. Among the various methods, magnetic separation of cells utilizing microfluidic devices offers the merits of biocompatibility, efficiency, and simplicity. This review discusses the fundamental physics involved in using magnetic force to separate particles, and identifies the optimisation parameters and corresponding methods for increasing the magnetic force. The paper then elaborates the design considerations of LOC devices for continuous-flow magnetic cell separation. Examples from the recently published literature illustrate these state-of-the-art techniques.

  13. Real-time segmentation in 4D ultrasound with continuous max-flow

    NASA Astrophysics Data System (ADS)

    Rajchl, M.; Yuan, J.; Peters, T. M.

    2012-02-01

    We present a novel continuous Max-Flow based method to segment the inner left ventricular wall from 3D trans-esophageal echocardiography image sequences, which minimizes an energy functional encoding two Fisher-Tippett distributions and a geometrical constraint in form of a Euclidean distance map in a numerically efficient and accurate way. After initialization the method is fully automatic and is able to perform at up to 10Hz making it available for image-guided interventions. Results are shown on 4D TEE data sets from 18 patients with pathological cardiac conditions and the speed of the algorithm is assessed under a variety of conditions.

  14. Trauma in patients with continuous-flow left ventricular assist devices.

    PubMed

    Sarsam, Sinan H; Meyers, Deborah E; Civitello, Andrew B; Agunanne, Enoch E; Odegaard, Peggy; Cohn, William E; Frazier, O H

    2013-11-01

    Trauma-related failure of a continuous-flow left ventricular assist device (LVAD) has not previously been reported. We present 4 cases in which LVAD complications were likely caused by external trauma and led to failure of a HeartMate II device. In 1 case, the onset of symptoms was delayed and the patient did not seek medical attention until months after the traumatic event. All 4 patients required surgical intervention, and 1 patient died of respiratory complications several months postoperatively. In conclusion, a history of external trauma should be considered as a possible etiologic factor when LVAD-supported patients in previously stable condition present with device malfunction.

  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. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Aortic Valve Calcification is Mediated by a Differential Response of Aortic Valve Interstitial Cells to Inflammation

    PubMed Central

    Venardos, Neil; Nadlonek, Nicole A.; Zhan, Qiong; Weyant, Michael J.; Reece, T. Brett; Meng, Xianzhong; Fullerton, David A.

    2014-01-01

    Background While calcific aortic stenosis is common, calcification of the other three heart valves is not. The aortic valve interstitial cell (VIC) has been implicated in the pathogenesis of aortic stenosis. Pro-inflammatory stimulation of aortic VICs induces an osteogenic and inflammatory phenotypic change. We hypothesized that the VICs of the other heart valves do not undergo these changes. Using isolated human VICs from normal aortic, mitral, pulmonary and tricuspid valves, our purpose was to compare the osteogenic response to pro-inflammatory stimulation via TLR-4. Materials And Methods Aortic, pulmonic, mitral, and tricuspid (n=4 for each valve type) VICs were isolated from hearts valves explanted from patients undergoing cardiac transplantation. Cells were cultured and grown to confluence in passage 2-6 before treatment with LPS (100-200ng/mL) for 24 or 48 hours. Cells were characterized by immunofluorescent staining. TLR-4 expression was analyzed (immunoblotting, flow cytometry). BMP-2 and intercellular adhesion molecule-1 (ICAM-1) production were determined (immunoblotting). Monocyte chemoattractant protein-1 (MCP-1) levels were determined by ELISA. Statistics were by Mann-Whitney U test. Results TLR-4 stimulation induced BMP-2 production only in aortic VICs (p<0.05). ICAM-1 production and MCP-1 secretion increased in a similar fashion among TLR4-stimulated VICs from all four valves. Conclusions Pro-inflammatory stimulation induces an osteogenic phenotype in aortic VICs but not mitral, pulmonic, or tricuspid VICs. We conclude that this differential osteogenic response of aortic VICs contributes to the pathogenesis of calcific aortic stenosis. PMID:24746950

  3. Supravalvular aortic stenosis in adult with anomalies of aortic arch vessels and aortic regurgitation

    PubMed Central

    Valente, Acrisio Sales; Alencar, Polyanna; Santos, Alana Neiva; Lobo, Roberto Augusto de Mesquita; de Mesquita, Fernando Antônio; Guimarães, Aloyra Guedis

    2013-01-01

    The supravalvular aortic stenosis is a rare congenital heart defect being very uncommon in adults. We present a case of supravalvular aortic stenosis in adult associated with anomalies of the aortic arch vessels and aortic regurgitation, which was submitted to aortic valve replacement and arterioplasty of the ascending aorta with a good postoperative course. PMID:24598962

  4. Temperature-Controlled Continuous Cold Flow Device after Total Knee Arthroplasty: A Randomized Controlled Trial Study.

    PubMed

    Ruffilli, Alberto; Castagnini, Francesco; Traina, Francesco; Corneti, Isabella; Fenga, Domenico; Giannini, Sandro; Faldini, Cesare

    2016-11-30

    Total knee arthroplasty (TKA) is a widely accepted and successful procedure for end-stage arthritis. Nevertheless, fast-track may be compromised by many factors, such as pain, edema, and blood loss. Cryotherapy has been advocated as a safe and effective strategy to improve the postoperative results, acting on pain, edema, and blood loss. This study is a prospective randomized controlled study, involving 50 patients after primary TKA. A power analysis was performed preoperatively. Twenty-four patients were addressed to a postoperative treatment with a continuous cold flow device (Hilotherm, Hilotherm GmbH, Germany). Twenty-six patients represented the control group, treated with crushed ice packs. All the patients shared the same analgesic strategy and the same rehabilitation protocol. Pain, analgesic consumption, active knee range of motion, drain output, transfusion requirement, and total blood loss were evaluated at different follow-ups (postoperative first, third, and seventh days). The two groups were homogenous for preoperative and intraoperative features. The groups showed no statistically significant differences in all the evaluated parameters. A modest reduction of knee volume was evident after 7 days from surgery (trend). No differences in blood loss were noticed. Continuous cold flow device in the acute postoperative setting after TKA did not show superiority in reducing edema, pain, and blood loss, compared with traditional icing regimen. Thus, due to the costs, it should be reserved to selected cases.

  5. Continuous-flow DNP polarizer for MRI applications at 1.5 T

    PubMed Central

    Denysenkov, V.; Terekhov, M.; Maeder, R.; Fischer, S.; Zangos, S.; Vogl, T.; Prisner, T. F.

    2017-01-01

    Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1.5 ml/min, which should be high enough for DNP MR angiography applications in small animals like mice and rats. The hyperpolarized liquid cooled to physiological temperature can be routed by a mechanical switch to a quartz capillary for injection into the blood vessels of the target object. This new approach allows hyperpolarization of protons without the need of an additional magnet and avoids the losses arising from the transfer of the hyperpolarized solution between magnets. The signal-to-noise improvement of this method is demonstrated on two- and three-dimensional phantoms of blood vessels. PMID:28290535

  6. 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

    2016-01-01

    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.

  7. Stable aerobic granules in continuous-flow bioreactor with self-forming dynamic membrane.

    PubMed

    Liu, Hongbo; Li, Yajie; Yang, Changzhu; Pu, Wenhong; He, Liu; Bo, Fu

    2012-10-01

    A novel continuous-flow bioreactor with aerobic granular sludge and self-forming dynamic membrane (CGSFDMBR) was developed for efficient wastewater treatment. Under continuous-flow operation, aerobic granular sludge was successfully cultivated and characterized with small particle size of about 0.1-1.0mm, low settling velocity of about 15-25 m/h, loose structure and high water content of about 96-98%. To maintain the stability of aerobic granular sludge, strategies based on the differences of settling velocity and particle-size between granular and flocculent sludge were implemented. Moreover, in CGSFDMBR, membrane fouling was greatly relieved. Dynamic membrane was just cleaned once in more than 45 days' operation. CGSFDMBR presented good performance in treating septic tank wastewater, obtaining average COD, NH(4)(+)-N, TN and TP removal rates of 83.3%, 73.3%, 67.3% and 60%, respectively, which was more efficient than conventional bioreactors since that carbon, nitrogen and phosphorus were simultaneously removed in a single aerobic reactor.

  8. Continuous-flow high pressure hydrogenation reactor for optimization and high-throughput synthesis.

    PubMed

    Jones, Richard V; Godorhazy, Lajos; Varga, Norbert; Szalay, Daniel; Urge, Laszlo; Darvas, Ferenc

    2006-01-01

    This paper reports on a novel continuous-flow hydrogenation reactor and its integration with a liquid handler to generate a fully automated high-throughput hydrogenation system for library synthesis. The reactor, named the H-Cube, combines endogenous hydrogen generation from the electrolysis of water with a continuous flow-through system. The system makes significant advances over current batch hydrogenation reactors in terms of safety, reaction validation efficiency, and rates of reaction. The hydrogenation process is described along with a detailed description of the device's main parts. The reduction of a series of functional groups, varying in difficulty up to 70 degrees C and 70 bar are also described. The paper concludes with the integration of the device into an automated liquid handler followed by the reduction of a nitro compound in a high throughput manner. The system is fully automated and can conduct 5 reactions in the time it takes to perform and workup one reaction manually on a standard batch reactor.

  9. Continuous-flow DNP polarizer for MRI applications at 1.5 T.

    PubMed

    Denysenkov, V; Terekhov, M; Maeder, R; Fischer, S; Zangos, S; Vogl, T; Prisner, T F

    2017-03-14

    Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1.5 ml/min, which should be high enough for DNP MR angiography applications in small animals like mice and rats. The hyperpolarized liquid cooled to physiological temperature can be routed by a mechanical switch to a quartz capillary for injection into the blood vessels of the target object. This new approach allows hyperpolarization of protons without the need of an additional magnet and avoids the losses arising from the transfer of the hyperpolarized solution between magnets. The signal-to-noise improvement of this method is demonstrated on two- and three-dimensional phantoms of blood vessels.

  10. 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.

  11. Continuous-flow DNP polarizer for MRI applications at 1.5 T

    NASA Astrophysics Data System (ADS)

    Denysenkov, V.; Terekhov, M.; Maeder, R.; Fischer, S.; Zangos, S.; Vogl, T.; Prisner, T. F.

    2017-03-01

    Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1.5 ml/min, which should be high enough for DNP MR angiography applications in small animals like mice and rats. The hyperpolarized liquid cooled to physiological temperature can be routed by a mechanical switch to a quartz capillary for injection into the blood vessels of the target object. This new approach allows hyperpolarization of protons without the need of an additional magnet and avoids the losses arising from the transfer of the hyperpolarized solution between magnets. The signal-to-noise improvement of this method is demonstrated on two- and three-dimensional phantoms of blood vessels.

  12. 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.

  13. Restricted pollen flow of Dieffenbachia seguine populations in fragmented and continuous tropical forest.

    PubMed

    Cuartas-Hernández, S; Núñez-Farfán, J; Smouse, P E

    2010-08-01

    Habitat fragmentation can change the ecological context of populations, rupturing genetic connectivity among them, changing genetic structure, and increasing the loss of genetic diversity. We analyzed mating system and pollen structure in two population fragments and two continuous forest populations of Dieffenbachia seguine (Araceae), an insect-pollinated understory herb in the tropical rain forest of Los Tuxtlas, México, using nine allozyme loci. Mating system analysis indicated almost complete outcrossing but some inbreeding among the adults. Pollen structure analysis indicated highly restricted pollen flow, both within and among populations. We showed that the effective pollination neighborhood was small in all populations, and slightly (though not significantly) smaller in fragments, partially as a consequence of an increase in density of reproductive individuals in those fragments. Using assignment analysis, we showed that all populations were strongly structured, suggesting that pollen and seed flow across the Los Tuxtlas landscape has been spatially restricted, though sufficient to maintain connectedness. Forest fragmentation at Los Tuxtlas has (so far) had limited impact on pollen dynamics, despite the changing ecological context, with reduced pollinator abundance being partially offset by increased flowering density in fragments. Continued outcrossing and limited pollen immigration, coupled with more extensive seed migration, should maintain genetic connectedness in D. seguine, if fragmentation is not further exacerbated by additional deforestation.

  14. Continued development of the Nimbus/University of Pittsburgh (UOP) axial flow left ventricular assist system.

    PubMed

    Thomas, D C; Butler, K C; Taylor, L P; Le Blanc, P; Griffith, B P; Kormos, R L; Borovetz, H S; Litwak, P; Kameneva, M V; Choi, S; Burgreen, G W; Wagner, W R; Wu, Z; Antaki, J F

    1997-01-01

    Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system.

  15. 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

  16. Continuous-flow C. elegans fluorescence expression analysis with real-time image processing through microfluidics.

    PubMed

    Yan, Yuanjun; Boey, Daryl; Ng, Li Theng; Gruber, Jan; Bettiol, Andrew; Thakor, Nitish V; Chen, Chia-Hung

    2016-03-15

    The nematode Caenorhabditis elegans has become an essential model organism in neuroscience research because of its stereotyped anatomy, relevance to human biology, and capacity for genetic manipulation. To solve the intrinsic challenges associated with performing manual operations on C. elegans, many automated chip designs based on immobilization-imaging-release approaches have been proposed. These designs are prone to limitations such as the exertion of physical stress on the worms and limited throughput. In this work, a continuous-flow, high-throughput, automated C. elegans analyzer based on droplet encapsulation and real-time image processing was developed to analyze fluorescence expression in worms. To demonstrate its capabilities, two strains of C. elegans nematodes with different levels of expression of green fluorescent protein (GFP) were first mixed in a buffer solution. The worms were encapsulated in water-in-oil droplets to restrict random locomotion. The droplets were closely packed in a two-layer polydimethylsiloxane (PDMS) platform and were flowed through a narrow straight channel, in which a region of interest (ROI) was defined and continuously recorded by a frame acquisition device. Based on the number of pixels counted in the selected color range, our custom software analyzed GFP expression to differentiate between two strains with nearly 100% accuracy and a throughput of 0.5 seconds/worm.

  17. Continuous-flow submicroliter-scale PCR chip for DNA amplification

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Chen, Shaochen

    2001-09-01

    Polymerase chain reaction (PCR) is a well-described method for selective identical replication of DNA molecules. In recent years, many micromachined PCR chips have been reported. These miniaturized PCR chips have great advantages such as a significant reduction in reagent costs and vastly reduced reaction time over the conventional PCR devices. In this paper a micro analysis system that will allow submicro-liter scale, continuous-flow PCR to be conducted in a glass chip has been presented. This glass chip is achieved through thermally bonding two pyrex 7740 glass wafers. One pyrex wafer is etched to form a 20-cycle microchannel of 80 micron wide and 30 micron deep. The other pyrex wafer with microheaters is thermally bonded to the microchannel wafer to produce a closed continuous microchannel for PCR. The total length of the microchannel is 0.5 m. The size of this device is 56 mm 'e 24 mm 'e 1 mm. Three reaction temperatures are controlled by three PID controllers. This PCR chip has a significant reagent reduction with a volume of less than 1 micro-liter. With 1 micro-liter reagent, we get total reaction time of 0.5 min to 3 min depending on various flow rates. This analysis chip is fabricated using standard micromachining techniques. The advantages of this chip include small quantities of reagent needed, high throughput, rapid thermal cycling, and batch micro-fabrication resulting in a significant cost reduction.

  18. Simulation of flow in a continuous galvanizing bath: Part I. Thermal effects of ingot addition

    NASA Astrophysics Data System (ADS)

    Ajersch, F.; Ilinca, F.; Hétu, J.-F.

    2004-02-01

    A numerical analysis has been developed to simulate the velocity and temperature fields in an industrial galvanizing bath for the continuous coating of steel strip. Operating variables such as ingot addition, line speed, and inductor mixing were evaluated in order to determine their effect on the velocity and temperature distribution in the bath. The simulations were carried out using high-performance computational fluid-dynamics software developed at the Industrial Materials Institute of the National Research Council Canada (IMI-NRC) in solving the incompressible Navier-Stokes equations for steady-state and transient turbulent flow using the k-ɛ model. Cases with and without temperature-dependent density conditions were considered. It was found that the strip velocity does not alter the global flow pattern but modifies the velocities in the snout, near the strip, and near the sink and guide rolls. At a low inductor capacity, the effect of induced mixing is small but is considerably increased at the maximum inductor capacities used during ingot-melting periods. When considering the thermal effects, the flow is affected by variations in density especially near the inductors and the ingot, while little effect is observed near the sheet-and-roller region. Thermal effects are also amplified when the inductor operates at high capacity during ingot melting. The simulations allow visualization of regions of varying velocity and temperature fields and clearly illustrate the mixed and stagnant zones for different operating conditions.

  19. 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

  20. 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.

  1. Separation of magnetic beads in a hybrid continuous flow microfluidic device

    NASA Astrophysics Data System (ADS)

    Samanta, Abhishek; Ganguly, Ranjan; Datta, Amitava; Modak, Nipu

    2017-04-01

    Magnetic separation of biological entities in microfluidic environment is a key task for a large number of bio-analytical protocols. In magnetophoretic separation, biochemically functionalized magnetic beads are allowed to bind selectively to target analytes, which are then separated from the background stream using a suitably imposed magnetic field. Here we present a numerical study, characterizing the performance of a magnetophoretic hybrid microfluidic device having two inlets and three outlets for immunomagnetic isolation of three different species from a continuous flow. The hybrid device works on the principle of split-flow thin (SPLITT) fractionation and field flow fractionation (FFF) mechanisms. Transport of the magnetic particles in the microchannel has been predicted following an Eulerian-Lagrangian model and using an in-house numerical code. Influence of the salient geometrical parameters on the performance of the separator is studied by characterizing the particle trajectories and their capture and separation indices. Finally, optimum channel geometry is identified that yields the maximum capture efficiency and separation index.

  2. 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.

  3. 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.

  4. 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

  5. Aortic valve surgery - minimally invasive

    MedlinePlus

    ... of the heart is reduced. This is called aortic stenosis. The aortic valve can be replaced using: Minimally ... RN, Wang A. Percutaneous heart valve replacement for aortic stenosis: state of the evidence. Ann Intern Med . 2010; ...

  6. Quantitative Assessment of Mass Flow Boundaries in Continuous Twin-screw Granulation.

    PubMed

    Schmidt, Adrian; de Waard, Hans; Moll, Klaus-Peter; Krumme, Markus; Kleinebudde, Peter

    2016-01-01

    In pharmaceutical manufacturing, there is an increasing interest in continuous manufacturing. As an example for fast continuous processes in general of considerable complexity, this study was focussed on improving the understanding of twin-screw wet granulation. The impact of the liquid-to-solid (L/S) mass flow ratio on product quality (granules) as well as on downstream process operations (tableting) was investigated in detail. Initially two methods were used to define L/S ratio boundaries for the granulation regime in twin-screw wet granulation. It was shown that the first method, which is based on measuring the wet granule mass flow variation, can be used to define the upper L/S ratio boundary of the granulation regime. The second method, based on measuring the granule size distribution, can be used to define the lower L/S ratio boundary of the regime. Using these methods, the granulation regime for different formulations could be established. This information was then used to show that the formulation could be optimised such that the process is more robust (i.e. wider L/S ratio boundaries for the granulation regime). Also it could be used to optimise the formulation considering further downstream processing such as drying (using as little water as possible to reduce drying efforts) or tableting (obtain granules with optimised tableting properties). Preferably, the process should be performed close to the lower L/S ratio boundary of the granulation regime. In summary, these tools enabled the quantitative establishment of granulation regime boundaries in a twin-screw wet granulation process and can be used to optimise formulation and to create a robust process. Analogies to other continuous processes in completely different applications can be conceived.

  7. Quantification of abdominal aortic deformation after EVAR

    NASA Astrophysics Data System (ADS)

    Demirci, Stefanie; Manstad-Hulaas, Frode; Navab, Nassir

    2009-02-01

    Quantification of abdominal aortic deformation is an important requirement for the evaluation of endovascular stenting procedures and the further refinement of stent graft design. During endovascular aortic repair (EVAR) treatment, the aortic shape is subject to severe deformation that is imposed by medical instruments such as guide wires, catheters, and, the stent graft. This deformation can affect the flow characteristics and morphology of the aorta which have been shown to be elicitors for stent graft failures and be reason for reappearance of aneurysms. We present a method for quantifying the deformation of an aneurysmatic aorta imposed by an inserted stent graft device. The outline of the procedure includes initial rigid alignment of the two abdominal scans, segmentation of abdominal vessel trees, and automatic reduction of their centerline structures to one specified region of interest around the aorta. This is accomplished by preprocessing and remodeling of the pre- and postoperative aortic shapes before performing a non-rigid registration. We further narrow the resulting displacement fields to only include local non-rigid deformation and therefore, eliminate all remaining global rigid transformations. Finally, deformations for specified locations can be calculated from the resulting displacement fields. In order to evaluate our method, experiments for the extraction of aortic deformation fields are conducted on 15 patient datasets from endovascular aortic repair (EVAR) treatment. A visual assessment of the registration results and evaluation of the usage of deformation quantification were performed by two vascular surgeons and one interventional radiologist who are all experts in EVAR procedures.

  8. Flow Data for Solute Transport Modeling from Tracer Experiments in a Stream Not Continuously Gaining Water

    NASA Astrophysics Data System (ADS)

    Bencala, K. E.; Kimball, B. A.; Gooseff, M. N.

    2007-12-01

    In-stream tracer experiments are a well-established method for determining flow data to be incorporated in solute transport modeling. For a gaining stream, this method is implemented to provide spatial flow data at scales of minutes and tens of meters without physical disturbance to the flow of water, the streambed, or biota. Of importance for solute transport modeling, solute inflow loading along the stream can be estimated with this spatial data. The tracer information can also be interpreted to characterize hyporheic exchange time-scales for a stream with hyporheic exchange flowpaths (HEFs) that are short relative to the distance over which the stream gains water. The interpretation of tracer data becomes uncertain for a stream that is not gaining water continuously over intended study reach. We demonstrate, with straight-forward mass-balances, uncertainties for solute loading which arise in the analysis of streams locally losing water while predominantly gaining water (and solutes) over a larger scale. With field data from Mineral Creek (Silverton, Colorado) we illustrate the further uncertainty distinguishing HEFs from (locally) losing segments of the stream. Comparison of bromide tracer with ambient sulfate concentrations suggests that subsurface inflows and outflows, concurrent with likely HEFs, occur in a hydrogeochemical setting of multiple, dispersed and mixed, sources of water along a 64 m sub-reach of the predominately gaining, but locally losing, stream. To compute stream-reach mass-balances (the simplest of water quality models) there is a need to quantitatively define the character and source of contaminants entering streams from ground-water pathways, as well as the potential for changes in water chemistry and contaminant concentrations along flow paths crossing the sediment-water interface. Identification of inflow solute mass requires quantifying water gain, loss, and hyporheic exchange in addition to concentration.

  9. Fluid Flow-Related Transport Phenomena in Steel Slab Continuous Casting Strands under Electromagnetic Brake

    NASA Astrophysics Data System (ADS)

    Wang, Yufeng; Zhang, Lifeng

    2011-12-01

    In the current study, a three-dimensinal (3D) numerical model is built to investigate the effect of a local-type electromagnetic brake (EMBr) on the fluid flow, heat transfer, and inclusion motion in slab continuous casting strands. The results indicate that the magnetic force affects the jet characteristics, including jet angle, turbulent kinetic energy, and its dissipation rate. To reduce the top surface velocity and stabilize the top surface, the magnetic flux intensity should be larger than a critical value. With a 0.39 T magnetic flux intensity, the top surface velocity and its fluctuation can be well controlled, and less slag is entrained. The motion of argon bubbles is also studied. More bubbles, especially >2.0-mm bubbles, escape from the top surface between the mold submerged entry nozzle (SEN) and 1/4 width for the case with a 0.39 T EMBr. This may push the top slag away and create an open "eye" on the top slag. Small bubbles (≤1 mm) tend to escape from one side of wide face no matter with or without EMBr, which is induced by the swirl flow from the SEN outport. EMBr has a little effect on the overall removal fraction of inclusions; however, it affects the local distribution of inclusion in the slab. With EMBr, more inclusions accumulate the region just below the surface, thus a worse subsurface quality, whereas the inner quality of the slab is better than that without EMBr. For heat transfer in the mold, the heat flux on the narrow face and the area of possible break-out zones can be reduced by using EMBr. Prevention of bias flow and/or asymmetrical flow in mold by EMBr is also concluded.

  10. 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.

  11. Aortic Disease in the Young: Genetic Aneurysm Syndromes, Connective Tissue Disorders, and Familial Aortic Aneurysms and Dissections

    PubMed Central

    Cury, Marcelo; Zeidan, Fernanda; Lobato, Armando C.

    2013-01-01

    There are many genetic syndromes associated with the aortic aneurysmal disease which include Marfan syndrome (MFS), Ehlers-Danlos syndrome (EDS), Loeys-Dietz syndrome (LDS), familial thoracic aortic aneurysms and dissections (TAAD), bicuspid aortic valve disease (BAV), and autosomal dominant polycystic kidney disease (ADPKD). In the absence of familial history and other clinical findings, the proportion of thoracic and abdominal aortic aneurysms and dissections resulting from a genetic predisposition is still unknown. In this study, we propose the review of the current genetic knowledge in the aortic disease, observing, in the results that the causative genes and molecular pathways involved in the pathophysiology of aortic aneurysm disease remain undiscovered and continue to be an area of intensive research. PMID:23401778

  12. Selected low-flow frequency statistics for continuous-record streamgages in Georgia, 2013

    USGS Publications Warehouse

    Gotvald, Anthony J.

    2016-04-13

    This report presents the annual and monthly minimum 1- and 7-day average streamflows with the 10-year recurrence interval (1Q10 and 7Q10) for 197 continuous-record streamgages in Georgia. Streamgages used in the study included active and discontinued stations having a minimum of 10 complete climatic years of record as of September 30, 2013. The 1Q10 and 7Q10 flow statistics were computed for 85 streamgages on unregulated streams with minimal diversions upstream, 43 streamgages on regulated streams, and 69 streamgages known, or considered, to be affected by varying degrees of diversions upstream. Descriptive information for each of these streamgages, including the U.S. Geological Survey (USGS) station number, station name, latitude, longitude, county, drainage area, and period of record analyzed also is presented.Kendall’s tau nonparametric test was used to determine the statistical significance of trends in annual and monthly minimum 1-day and 7-day average flows for the 197 streamgages. Significant negative trends in the minimum annual 1-day and 7-day average streamflow were indicated for 77 of the 197 streamgages. Many of these significant negative trends are due to the period of record ending during one of the recent droughts in Georgia, particularly those streamgages with record through the 2013 water year. Long-term unregulated streamgages with 70 or more years of record indicate significant negative trends in the annual minimum 7-day average flow for central and southern Georgia. Watersheds for some of these streamgages have experienced minimal human impact, thus indicating that the significant negative trends observed in flows at the long-term streamgages may be influenced by changing climatological conditions. A Kendall-tau trend analysis of the annual air temperature and precipitation totals for Georgia indicated no significant trends. A comprehensive analysis of causes of the trends in annual and monthly minimum 1-day and 7-day average flows in central

  13. 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... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. The resistance to air flowing from the...

  14. 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

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Airflow resistance test; Type C supplied-air... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. The resistance to air flowing from the...

  15. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Airflow resistance test; Type C supplied-air... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. The resistance to air flowing from the...

  16. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Airflow resistance test; Type C supplied-air... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. The resistance to air flowing from the...

  17. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Airflow resistance test; Type C supplied-air... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. The resistance to air flowing from the...

  18. 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.

  19. 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.

  20. Continuous Flow Metathesis for Direct Valorization of Food Waste: An Example of Cocoa Butter Triglyceride.

    PubMed

    Schotten, Christiane; Plaza, Dorota; Manzini, Simone; Nolan, Steven P; Ley, Steven V; Browne, Duncan L; Lapkin, Alexei

    2015-07-06

    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.

  1. Assessing optimal fermentation type for bio-hydrogen production in continuous-flow acidogenic reactors.

    PubMed

    Ren, N Q; Chua, H; Chan, S Y; Tsang, Y F; Wang, Y J; Sin, N

    2007-07-01

    In this study, the optimal fermentation type and the operating conditions of anaerobic process in continuous-flow acidogenic reactors was investigated for the maximization of bio-hydrogen production using mixed cultures. Butyric acid type fermentation occurred at pH>6, propionic acid type fermentation occurred at pH about 5.5 with E(h) (redox potential) >-278mV, and ethanol-type fermentation occurred at pH<4.5. The representative strains of these fermentations were Clostridium sp., Propionibacterium sp. and Bacteriodes sp., respectively. Ethanol fermentation was optimal type by comparing the operating stabilities and hydrogen production capacities between the fermentation types, which remained stable when the organic loading rate (OLR) reached the highest OLR at 86.1kgCOD/m(3)d. The maximum hydrogen production reached up to 14.99L/d.

  2. 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

  3. 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

  4. Parallel continuous flow: a parallel suffix tree construction tool for whole genomes.

    PubMed

    Comin, Matteo; Farreras, Montse

    2014-04-01

    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.

  5. [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.

  6. Continuous flow determination of carbon dioxide in water by membrane separation-chemiluminescent detection

    SciTech Connect

    Aoki, T.; Ito, K.; Munemori, M.

    1988-10-01

    Carbon dioxide has been found to enhance the chemiluminescence of a luminol system. A determination method for carbon dioxide in water was developed by applying this reaction to a continuous flow membrane-separation system. Concentrations of carbon dioxide as low as 0.04 ..mu..g C/mL were determined. Membrane-separation effectively eliminated interferences from Co(II), Cr(III), Fe(III), and other ions which also enhance chemiluminescence. The relative standard deviation for this method was 2.8% (n=5) for 4.0 ..mu..g C/mL and the time required for the analysis of one sample was 3.0 min.

  7. Continuous flow left ventricular assist devices: shared care goals of monitoring and treating patients.

    PubMed

    Estep, Jerry D; Trachtenberg, Barry H; Loza, Laurie P; Bruckner, Brian A

    2015-01-01

    Continuous-flow left ventricular assist devices (CF-LVADs) have been clinically adopted as a long-term standard of care therapy option for patients with end-stage heart failure. For many patients, shared care between the care providers at the implanting center and care providers in the community in which the patient resides is a clinical necessity. The aims of this review are to (1) provide a rationale for the outpatient follow-up exam and surveillance testing used at our center to monitor patients supported by the HeartMate II(®) CF-LVAD (Thoratec Corporation, Pleasanton, CA) and (2) provide the protocol/algorithms we use for blood pressure, driveline exit site, LVAD alarm history, surveillance blood work, and echocardiography monitoring in this patient population. In addition, we define our partnership outpatient follow-up protocol and the "shared care" specific responsibilities we use with referring health care providers to best manage many of our patients.

  8. Green Route for Silver Nanoparticles Synthesis by Raphanus Sativus Extract in a Continuous Flow Tubular Microreactor

    NASA Astrophysics Data System (ADS)

    Jolhe, P. D.; Bhanvase, B. A.; Patil, V. S.; Sonawane, S. H.

    The present work deals with the investigation of the greener route for the production of silver nanoparticles using Raphanus sativus (R. sativus) bioextract in a continuous flow tubular microreactor. The parameters affecting the particle size and distribution were investigated. From the results obtained it can be inferred that the ascorbic acid (reducing agent) present in the R. sativus bioextract is responsible for the reduction of silver ions. At optimum condition, the particle size distribution of nanoparticles is found between 18nm and 39nm. The absorbance value was found to be decreased with an increase in the diameter of the microreactor. It indicates that a number of nuclei are formed in the micrometer sized (diameter) reactor because of the better solute transfer rate leading to the formation of large number of silver nanoparticles. The study of antibacterial activity of green synthesized silver nanoparticles shows effective inhibitory activity against waterborne pathogens, Shegella and Listeria bacteria.

  9. Optimization of high-resolution continuous flow analysis for transient climate signals in ice cores.

    PubMed

    Bigler, Matthias; Svensson, Anders; Kettner, Ernesto; Vallelonga, Paul; Nielsen, Maibritt E; Steffensen, Jørgen Peder

    2011-05-15

    Over the past two decades, continuous flow analysis (CFA) systems have been refined and widely used to measure aerosol constituents in polar and alpine ice cores in very high-depth resolution. Here we present a newly designed system consisting of sodium, ammonium, dust particles, and electrolytic meltwater conductivity detection modules. The system is optimized for high-resolution determination of transient signals in thin layers of deep polar ice cores. Based on standard measurements and by comparing sections of early Holocene and glacial ice from Greenland, we find that the new system features a depth resolution in the ice of a few millimeters which is considerably better than other CFA systems. Thus, the new system can resolve ice strata down to 10 mm thickness and has the potential of identifying annual layers in both Greenland and Antarctic ice cores throughout the last glacial cycle.

  10. Continuous-flow analysis of dissolved inorganic carbon content in seawater.

    PubMed

    Stoll, M H; Bakker, K; Nobbe, G H; Haese, R R

    2001-09-01

    A rapid, continuous-flow determination of total inorganic carbon (TIC) in seawater samples is presented. The method runs on an autoanalyzer Traacs 800 spectrophotometric system and is calibrated versus certified reference materials readily available. A typical analysis speed of 45 samples/h can be reached with an accuracy of 2-3 microM and a precision of approximately 2.5 microM. The analysis requires only a small amount of sample and is thus ideally suited for pore water samples and samples taken from cultures where sample volume is at a premium. The speed of the analysis makes mapping of oceanic surface water characteristics possible. Potential interference of sulfide in anoxic (e.g., pore water) samples can be masked by the addition of a hydrogen peroxide step. Although the latter is a strong oxidative reagent, no significant effect on TIC concentration due to oxidation of (labile) organic matter could be found.

  11. Continuous Drip Flow System to Develop Biofilm of E. faecalis under Anaerobic Conditions

    PubMed Central

    Gonzalez, Ana Maria; Corpus, Erika; Silva-Herzog, Daniel; Aragon-Piña, Antonio; Cohenca, Nestor

    2014-01-01

    Purpose. To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. Methods. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic conditions. The inoculum was replaced every 24 hours with a fresh growth medium for up to 10 days to feed the system. Gram staining was done every 24 hours to control the microorganism purity. Biofilms developed under the system were evaluated under the scanning electron microscope (SEM). Results. SEM micrographs demonstrated mushroom-shaped structures, corresponding to a mature E. faecalis biofilm. In the mature biofilm bacterial cells are totally encased in a polymeric extracellular matrix. Conclusions. The proposed in vitro system model provides an additional useful tool to study the biofilm concept in endodontic microbiology, allowing for a better understanding of persistent root canal infections. PMID:25371913

  12. Development of Safe and Scalable Continuous-Flow Methods for Palladium-Catalyzed Aerobic Oxidation Reactions†

    PubMed Central

    Ye, Xuan; Diao, Tianning

    2010-01-01

    Summary 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% O2 in N2) 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

  13. 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

  14. A multi-electrode continuous flow microbial fuel cell with separator electrode assembly design.

    PubMed

    Ahn, Yongtae; Logan, Bruce E

    2012-03-01

    Scaling up microbial fuel cells (MFCs) requires the development of compact reactors with multiple electrodes. A scalable single chamber MFC (130 mL), with multiple graphite fiber brush anodes and a single air-cathode cathode chamber (27 m2/m3), was designed with a separator electrode assembly (SEA) to minimize electrode spacing. The maximum voltage produced in fed-batch operation was 0.65 V (1,000 Ω) with a textile separator, compared to only 0.18 V with a glass fiber separator due to short-circuiting by anode bristles through this separator with the cathode. The maximum power density was 975 mW/m2, with an overall chemical oxygen demand (COD) removal of >90% and a maximum coulombic efficiency (CE) of 53% (50 Ω resistor). When the reactor was switched to continuous flow operation at a hydraulic retention time (HRT) of 8 h, the cell voltage was 0.21 ± 0.04 V, with a very high CE = 85%. Voltage was reduced to 0.13 ± 0.03 V at a longer HRT = 16 h due to a lower average COD concentration, and the CE (80%) decreased slightly with increased oxygen intrusion into the reactor per amount of COD removed. Total internal resistance was 33 Ω, with a solution resistance of 2 Ω. These results show that the SEA type MFC can produce stable power and a high CE, making it useful for future continuous flow treatment using actual wastewaters.

  15. [Continuous dry fermentation of pig manure using up plug-flow type anaerobic reactor].

    PubMed

    Chen, Chuang; Deng, Liang-Wei; Xin, Xin; Zheng, Dan; Liu, Yi; Kong, Chui-Xue

    2012-03-01

    To solve the problems of ammonia inhibition and discharging difficulty in continuous dry fermentation of pig manure, under the experimental conditions of temperature of (25 +/- 2) degrees C and organic loading rate (TS) of 4.44 g x (L x d) (-1), a lab-scale up plug-flow type anaerobic reactor (UPAR) was setup to investigate biogas production, ammonia inhibition, effluent liquidity, and the feasibility of continuous dry fermentation of pig manure using up plug-flow type anaerobic reactor. The experiment was operated for 160 days using the pig manure with four different TS mass fractions (20%, 25%, 30%, 35%) as feeding. Results showed that the feeding TS mass fraction exerted a significant influence on the dry fermentation of pig manure; the stable volumetric biogas production rates of four different feeding TS mass fractions were 2.40, 1.73, 0.89, and 0.62 L x (L x d)(-1), respectively; the biogas producing efficiencies of the reactors with feeding TS mass fractions of 20%, 25% and 30% were obviously superior to that with feeding TS of 35%. With feeding TS mass fraction increased from 20% to 35%, obvious inhibition to biogas producing occurred when concentration of ammonia nitrogen reached more than 2 300 mg x L(-1). When the feeding TS mass fraction was 35%, the concentration of ammonia nitrogen could accumulate to 3 800 mg x L(-1) but biogas production rate decreased 74.1% of that with feeding TS of 20%. Additionally, while the feeding TS mass fraction was 35%, the effluent TS mass fraction achieved 17.1%, and the velocity of effluent was less than 0.002 m x s(-1) the effluent of UPAR could not be smoothly discharged.

  16. Acoustofluidics 11: Affinity specific extraction and sample decomplexing using continuous flow acoustophoresis.

    PubMed

    Augustsson, Per; Laurell, Thomas

    2012-04-24

    Acoustic standing wave technology combined with ligand complexed microbeads offers a means for affinity specific selection of target analytes from complex samples. When realized in a microfluidic format we can capitalize on laminar flow and acoustic forces that can drive cells or microbeads across fluid interfaces. Given this, we have the ability to perform carrier fluid (suspending medium) exchange operations in continuous flow in microfluidic chips based solely on acoustofluidic properties. A key issue here is to ensure that a minimum of the original carrier fluid follows the cells/particles across the fluid interface. Simple processing protocols can be achieved that may outperform macroscale magnetic bead-based sample extraction or centrifugation steps, which can also be straightforwardly integrated with downstream analytical instrumentation. This tutorial outlines some basic fluidic configurations for acoustophoresis based sample decomplexing and details the different system parameters that will impact the outcome of an acoustophoresis based affinity extraction experiment or a cell medium exchange step. Examples are given of both targeted extraction of microbes and selective elusion of molecular species.

  17. Locally conservative groundwater flow in the continuous Galerkin method using 3-D prismatic patches

    NASA Astrophysics Data System (ADS)

    Wu, Qiang; Zhao, Yingwang; Lin, Yu-Feng F.; Xu, Hua

    2016-11-01

    A new procedure has been developed to improve the velocity field computed by the continuous Galerkin finite element method (CG). It enables extending the postprocessing algorithm proposed by Cordes and Kinzelbach (1992) to three-dimensional (3-D) models by using prismatic patches for saturated groundwater flow. This approach leverages a dual mesh to preserve local mass conservation and provides interpolated velocities based on consistent fluxes. To develop this 3-D approach, a triangular conservative patch is introduced by computing not only advection fluxes, but also vertical infiltrations, storage changes, and other sink or source terms. This triangular patch is then used to develop a prismatic patch, which consists of subprisms in two layers. By dividing a single two-layer patch into two separate one-layer patches, two dimensional (2-D) algorithms can be applied to compute velocities. As a consequence, each subelement is able to preserve local mass conservation. A hypothetical 3-D model is used to evaluate the precision of streamlines and flow rates generated by this approach and the FEFLOW simulation program.

  18. Single Cell Analysis of Leukocyte Protease Activity Using Integrated Continuous-Flow Microfluidics.

    PubMed

    Jing, Tengyang; Lai, Zhangxing; Wu, Lidan; Han, Jongyoon; Lim, Chwee Teck; Chen, Chia-Hung

    2016-12-06

    Leukocytes are the essential cells of the immune system that protect the human body against bacteria, viruses, and other foreign invaders. Secretory products of individual leukocytes, such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase (ADAMs), are critical for regulating the inflammatory response and mediating host defense. Conventional single cell analytical methods, such as flow cytometry for cellular surface biomarker studies, are insufficient for performing functional assays of the protease activity of individual leukocytes. Here, an integrated continuous-flow microfluidic assay is developed to effectively detect secretory protease activity of individual viable leukocytes. Leukocytes in blood are first washed on-chip with defined buffer to remove background activity, followed by encapsulating individual leukocytes with protease sensors in water-in-oil droplets and incubating for 1 h to measure protease secretion. With this design, single leukocyte protease profiles under naive and phorbol 12-myristate 13-acetate (PMA)-stimulated conditions are reliably measured. It is found that PMA treatment not only elevates the average protease activity level but also reduces the cellular heterogeneity in protease secretion, which is important in understanding immune capability and the disease condition of individual patients.

  19. Continuous flow analysis of total organic carbon in polar ice cores.

    PubMed

    Federer, Urs; Kaufmann, Patrik R; Hutterli, Manuel A; Schüpbach, Simon; Stocker, Thomas F

    2008-11-01

    Ice cores are a widely used archive to reconstruct past changes of the climate system. This is done by measuring the concentration of substances in the ice and in the air of bubbles enclosed in ice. Some species pertaining to the carbon cycle (e.g., CO2, CH4) are routinely measured. However, information about the organic fraction of the impurities in polar ice is still very limited. Therefore, we developed a new method to determine the content of total organic carbon (TOC) in ice cores using a continuous flow analysis (CFA) system. The method is based on photochemical oxidation of TOC and the electrolytic quantification of the CO2 produced during oxidation. The TOC instrument features a limit of detection of 2 ppbC and a response time of 60 s at a sample flow rate of 0.7 mL/min and a linear measurement range of 2-4000 ppbC. First measurements on the ice core from Talos Dome, Antarctica, reveal TOC concentrations varying between 80 and 360 ppbC in the 20 m section presented.

  20. 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.

  1. Sensitivity of protein array deposition using continuous flow printing for fluorescent microarray applications - biomed 2013.

    PubMed

    Romanov, Valentin; Miles, Adam; Gale, Bruce; Eckman, Josh; Brooks, Benjamin

    2013-01-01

    The promise of antibody and protein microarrays to revolutionize disease diagnostics has failed to live up to the hype primarily due to the problems associated with the printing of the antibodies and/or proteins onto the detection surface. The current standard in printing proteins is pin printing. An alternative to the pin printer is the continuous-flow microspotter (CFM), a protein printer that uses microfluidic flow to print down the proteins. The advantages of the CFM include consistent spot morphology, spot-to-spot uniformity and enhanced surface concentration. Further, the CFM is effective at capturing proteins and antibodies from either dilute or complex (e.g. blood or tissue) samples. In this study, the sensitivity of CFM printing Cy3 and Cy5 fluorescently labeled proteins was determined. Values were obtained at low concentrations tens of ng/mL with low coefficients of variation. Thus, the CFM can effectively print and quantify proteins and antibodies from low concentration and complex buffered samples.

  2. 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)

  3. Continuous wave laser absorption techniques for gasdynamic measurements in supersonic flows

    NASA Technical Reports Server (NTRS)

    Davidson, David F.; Chang, Albert Y.; Dirosa, Michael D.; Hanson, Ronald K.

    1991-01-01

    Line-of-sight measurements of velocity, temperature, pressure, density, and mass flux were performed in a transient shock tube flow using three laser absorption schemes. All methods employed an intracavity-doubled ring dye laser tuned to an OH transition at 306 nm. In the first scheme, the gas was labeled by 193.3-nm excimer photolysis of H2O, and the passage of the generated OH was detected downstream. In the second method, the laser was tuned at a rate of 3 kHz over the R1(7) and R1(11) line pair, and absorption was simultaneously monitored at 90 and 60 deg with respect to the flow. Velocity was determined from the Doppler shift of the profiles and the temperature from the intensity ratio of the lines. Pressure was determined from both the magnitude of absorption and the collisional broadening. In the third method, the laser wavelength was fixed at a single frequency, and a continuous measurement of velocity and pressure was obtained using the signals from the two beam paths. All methods gave results which compare favorably to calculated values.

  4. 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.

  5. Rapid Catalyst Screening by a Continuous-Flow Microreactor Interfaced with Ultra High Pressure Liquid Chromatography

    PubMed Central

    Fang, Hui; Xiao, Qing; Wu, Fanghui; Floreancig, Paul E.; Weber, Stephen G.

    2010-01-01

    A high-throughput screening system for homogeneous catalyst discovery has been developed by integrating a continuous-flow capillary-based microreactor with ultra-high pressure liquid chromatography (UHPLC) for fast online analysis. Reactions are conducted in distinct and stable zones in a flow stream that allows for time and temperature regulation. UHPLC detection at high temperature allows high throughput online determination of substrate, product, and byproduct concentrations. We evaluated the efficacies of a series of soluble acid catalysts for an intramolecular Friedel-Crafts addition into an acyliminium ion intermediate within one day and with minimal material investment. The effects of catalyst loading, reaction time, and reaction temperature were also screened. This system exhibited high reproducibility for high-throughput catalyst screening and allowed several acid catalysts for the reaction to be identified. Major side products from the reactions were determined through off-line mass spectrometric detection. Er(OTf)3, the catalyst that showed optimal efficiency in the screening, was shown to be effective at promoting the cyclization reaction on a preparative scale. PMID:20666502

  6. Combination of constant-flow and continuous positive-pressure ventilation in canine pulmonary edema.

    PubMed

    Sznajder, J I; Becker, C J; Crawford, G P; Wood, L D

    1989-08-01

    Constant-flow ventilation (CFV) maintains alveolar ventilation without tidal excursion in dogs with normal lungs, but this ventilatory mode requires high CFV and bronchoscopic guidance for effective subcarinal placement of two inflow catheters. We designed a circuit that combines CFV with continuous positive-pressure ventilation (CPPV; CFV-CPPV), which negates the need for bronchoscopic positioning of CFV cannula, and tested this system in seven dogs having oleic acid-induced pulmonary edema. Addition of positive end-expiratory pressure (PEEP, 10 cmH2O) reduced venous admixture from 44 +/- 17 to 10.4 +/- 5.4% and kept arterial CO2 tension (PaCO2) normal. With the innovative CFV-CPPV circuit at the same PEEP and respiratory rate (RR), we were able to reduce tidal volume (VT) from 437 +/- 28 to 184 +/- 18 ml (P less than 0.001) and elastic end-inspiratory pressures (PEI) from 25.6 +/- 4.6 to 17.7 +/- 2.8 cmH2O (P less than 0.001) without adverse effects on cardiac output or pulmonary exchange of O2 or CO2; indeed, PaCO2 remained at 35 +/- 4 Torr even though CFV was delivered above the carina and at lower (1.6 l.kg-1.min-1) flows than usually required to maintain eucapnia during CFV alone. At the same PEEP and RR, reduction of VT in the CPPV mode without CFV resulted in CO2 retention (PaCO2 59 +/- 8 Torr). We conclude that CFV-CPPV allows CFV to effectively mix alveolar and dead spaces by a small bulk flow bypassing the zone of increased resistance to gas mixing, thereby allowing reduction of the CFV rate, VT, and PEI for adequate gas exchange.

  7. 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

  8. Continuous Purification of Colloidal Quantum Dots in Large-Scale Using Porous Electrodes in Flow Channel

    NASA Astrophysics Data System (ADS)

    Lim, Hosub; Woo, Ju Young; Lee, Doh C.; Lee, Jinkee; Jeong, Sohee; Kim, Duckjong

    2017-02-01

    Colloidal quantum dots (QDs) afford huge potential in numerous applications owing to their excellent optical and electronic properties. After the synthesis of QDs, separating QDs from unreacted impurities in large scale is one of the biggest issues to achieve scalable and high performance optoelectronic applications. Thus far, however, continuous purification method, which is essential for mass production, has rarely been reported. In this study, we developed a new continuous purification process that is suitable to the mass production of high-quality QDs. As-synthesized QDs are driven by electrophoresis in a flow channel and captured by porous electrodes and finally separated from the unreacted impurities. Nuclear magnetic resonance and ultraviolet/visible/near-infrared absorption spectroscopic data clearly showed that the impurities were efficiently removed from QDs with the purification yield, defined as the ratio of the mass of purified QDs to that of QDs in the crude solution, up to 87%. Also, we could successfully predict the purification yield depending on purification conditions with a simple theoretical model. The proposed large-scale purification process could be an important cornerstone for the mass production and industrial use of high-quality QDs.

  9. Continuous Purification of Colloidal Quantum Dots in Large-Scale Using Porous Electrodes in Flow Channel

    PubMed Central

    Lim, Hosub; Woo, Ju Young; Lee, Doh C.; Lee, Jinkee; Jeong, Sohee; Kim, Duckjong

    2017-01-01

    Colloidal quantum dots (QDs) afford huge potential in numerous applications owing to their excellent optical and electronic properties. After the synthesis of QDs, separating QDs from unreacted impurities in large scale is one of the biggest issues to achieve scalable and high performance optoelectronic applications. Thus far, however, continuous purification method, which is essential for mass production, has rarely been reported. In this study, we developed a new continuous purification process that is suitable to the mass production of high-quality QDs. As-synthesized QDs are driven by electrophoresis in a flow channel and captured by porous electrodes and finally separated from the unreacted impurities. Nuclear magnetic resonance and ultraviolet/visible/near-infrared absorption spectroscopic data clearly showed that the impurities were efficiently removed from QDs with the purification yield, defined as the ratio of the mass of purified QDs to that of QDs in the crude solution, up to 87%. Also, we could successfully predict the purification yield depending on purification conditions with a simple theoretical model. The proposed large-scale purification process could be an important cornerstone for the mass production and industrial use of high-quality QDs. PMID:28240242

  10. Continuous Purification of Colloidal Quantum Dots in Large-Scale Using Porous Electrodes in Flow Channel.

    PubMed

    Lim, Hosub; Woo, Ju Young; Lee, Doh C; Lee, Jinkee; Jeong, Sohee; Kim, Duckjong

    2017-02-27

    Colloidal quantum dots (QDs) afford huge potential in numerous applications owing to their excellent optical and electronic properties. After the synthesis of QDs, separating QDs from unreacted impurities in large scale is one of the biggest issues to achieve scalable and high performance optoelectronic applications. Thus far, however, continuous purification method, which is essential for mass production, has rarely been reported. In this study, we developed a new continuous purification process that is suitable to the mass production of high-quality QDs. As-synthesized QDs are driven by electrophoresis in a flow channel and captured by porous electrodes and finally separated from the unreacted impurities. Nuclear magnetic resonance and ultraviolet/visible/near-infrared absorption spectroscopic data clearly showed that the impurities were efficiently removed from QDs with the purification yield, defined as the ratio of the mass of purified QDs to that of QDs in the crude solution, up to 87%. Also, we could successfully predict the purification yield depending on purification conditions with a simple theoretical model. The proposed large-scale purification process could be an important cornerstone for the mass production and industrial use of high-quality QDs.

  11. Mechanical Circulatory Support for the Failing Heart: Continuous-Flow Left Ventricular Assist Devices

    PubMed Central

    Englert, Joseph A. R.; Davis, Jennifer A.; Krim, Selim R.

    2016-01-01

    Background: Heart transplantation remains the definitive therapy for patients with advanced heart failure; however, owing to limited donor organ availability and long wait times, continuous-flow left ventricular assist devices (LVADs) have become standard therapy. Methods: This review summarizes the history, progression, function, and basic management of LVADs. Additionally, we provide some clinical pearls and important caveats for managing this unique patient population. Results: Currently, the most common LVADs being implanted in the United States are second- and third-generation devices, the HeartMate II (Thoratec Corp., St. Jude Medical) and the HeartWare HVAD (HeartWare International, Inc.). A newer third-generation pump, the HeartMate III (Thoratec Corp., St. Jude Medical), is designed to create an artificial pulse and is currently under investigation in the United States. Conclusion: LVAD use is promising, will continue to grow, and has become standard therapy for advanced heart failure as a bridge to recovery, as destination therapy, and as a bridge to transplantation. PMID:27660575

  12. 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.

  13. 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.

  14. Characterization of extended channel bioreactors for continuous-flow protein production

    DOE PAGES

    Timm, Andrea C.; Shankles, Peter G.; Foster, Carmen M.; ...

    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

  15. Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

    NASA Astrophysics Data System (ADS)

    Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

    2017-03-01

    The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

  16. 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.

  17. A microfluidic device providing continuous-flow polymerase chain reaction heating and cooling

    NASA Astrophysics Data System (ADS)

    Harandi, A.; Farquhar, T.

    2014-11-01

    The objective of this study is to describe a new type of microfluidic device that could be used to manipulate fluid temperature in many microfluidic applications. The key component is a composite material containing a thermally conductive phase placed in a purposeful manner to manipulate heat flow into and out of an embedded microchannel. In actual use, the device is able to vary temperature along a defined flow path with remarkable precision. As a demonstration of capability, a functional prototype was designed and fabricated using four layers of patterned copper laminated between alternating layers of polyimide and acrylic. The key fabrication steps included laser micromachining, acid etching, microchannel formation, and hot lamination. In order to achieve the desired temperature variations along the microchannel, an outer optimization loop and an inner finite element analysis loop were used to iteratively obtain a near-optimal copper pattern. With a minor loss of generality, admissible forms were restricted to comb-like patterns. For a given temperature profile, the pattern was found by refining a starting guess based on a deterministic rubric. Thermal response was measured using fine thermocouples placed at critical locations along the microchannel wall. At most of these points, the agreement between measured and predicted temperatures was within 1 °C, and temperature gradients as high as ±45 °C mm-1 (equivalent to ±90 °C s-1 at 2 μl min-1 flow rate) were obtained within the range of 59-91 °C. The particular profile chosen for case study makes it possible to perform five cycles of continuous-flow polymerase chain reaction (PCR) in less than 15 s, i.e. it entails five successive cycles of cooling from 91 to 59 °C, rapid reheating from 59 to 73 °C, slow reheating from 73 to 76 °C, and a final reheating from 73 to 91 °C, using a resistively heated source at 100 °C at and a thermoelectrically cooled sink at 5 °C.

  18. Endovascular Management of Chronic Type B Dissecting Aortic Aneurysm Utilizing Aortic and Renal Stents

    SciTech Connect

    Taylor, J. D. Dunckley, M.; Thompson, M.; Morgan, R. A.

    2008-07-15

    Over the last 10 years endovascular stent-graft placement has been increasingly used to treat complicated acute Type B thoracic aortic dissections. While studies have demonstrated the use of additional aortic stent-grafts to treat continued false lumen perfusion and case reports have detailed the use of renal artery stents to treat renal ischemia related to aortic dissection, to our knowledge the adjuvant use of renal artery stents to reduce false lumen perfusion has not been reported. We present the case of a 72-year-old male who had previously undergone endovascular repair of a complicated Type B thoracic aortic dissection and presented with an expanding false lumen in the peridiaphragmatic aorta despite coverage of the entire thoracic aorta. This was treated by closure of a right renal fenestration using a renal stent.

  19. Subcoronary versus supracoronary aortic stenosis. an experimental evaluation

    PubMed Central

    2011-01-01

    Background Valvular aortic stenosis is the most common cause of left ventricular hypertrophy due to gradually increasing pressure work. As the stenosis develop the left ventricular hypertrophy may lead to congestive heart failure, increased risk of perioperative complications and also increased risk of sudden death. A functional porcine model imitating the pathophysiological nature of valvular aortic stenosis is very much sought after in order to study the geometrical and pathophysiological changes of the left ventricle, timing of surgery and also pharmacological therapy in this patient group. Earlier we developed a porcine model for aortic stenosis based on supracoronary aortic banding, this model may not completely imitate the pathophysiological changes that occurs when valvular aortic stenosis is present including the coronary blood flow. It would therefore be desirable to optimize this model according to the localization of the stenosis. Methods In 20 kg pigs subcoronary (n = 8), supracoronary aortic banding (n = 8) or sham operation (n = 4) was preformed via a left lateral thoracotomy. The primary endpoint was left ventricular wall thickness; secondary endpoints were heart/body weight ratio and the systolic/diastolic blood flow ratio in the left anterior descending coronary. Statistical evaluation by oneway anova and unpaired t-test. Results Sub- and supracoronary banding induce an equal degree of left ventricular hypertrophy compared with the control group. The coronary blood flow ratio was slightly but not significantly higher in the supracoronary group (ratio = 0.45) compared with the two other groups (subcoronary ratio = 0.36, control ratio = 0.34). Conclusions A human pathophysiologically compatible porcine model for valvular aortic stenosis was developed by performing subcoronary aortic banding. Sub- and supracoronary aortic banding induce an equal degree of left ventricular hypertrophy. This model may be valid for experimental investigations of aortic

  20. 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