The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Babu Joseph - One of the best experts on this subject based on the ideXlab platform.
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flow induced by acoustic streaming on Surface acoustic wave Devices and its application in biofouling removal a computational study and comparisons to experiment
Physical Review E, 2008Co-Authors: Subramanian K R S Sankaranarayanan, Stefan Cular, Venkat R Bhethanabotla, Babu JosephAbstract:All transducers used in biological sensing suffer from fouling resulting from nonspecific binding of protein molecules to the Device Surface. The acoustic-streaming phenomenon, which results from the fluid motion induced by high-intensity sound waves, can be used to remove these nonspecifically bound proteins to allow more accurate determinations and reuse of these Devices. We present a computational and experimental study of the acoustic-streaming phenomenon induced by Surface acoustic waves.A coupled-field fluid-structure interaction (FSI) model of a Surface-acoustic-wave (SAW) Device based on a micrometer-sized piezoelectric substrate $(YZ{\text{-LiNbO}}_{3})$ in contact with a liquid loading was developed to study the Surface-acoustic-wave interaction with fluid loading. The fluid domain was modeled using the Navier-Stokes equation; the arbitrary Lagrangian-Eulerian approach was employed to handle the mesh distortions arising from the motion of the solid substrate. The fluid-solid coupling was established by maintaining stress and displacement continuity at the fluid-structure interface. A transient analysis was carried out by applying a time-varying voltage to the transmitter interdigital transducer (IDT) fingers. Simulation results predict strong coupling of ultrasonic Surface waves on the piezoelectric substrate with the thin liquid layer causing wave mode conversion from Rayleigh to leaky SAWs, which leads to acoustic streaming. The transient solutions generated from the FSI model were utilized to predict trends in acoustic-streaming velocity for varying design parameters such as voltage intensity, Device frequency, fluid viscosity, and density. The induced streaming velocities typically vary from $1\text{ }\ensuremath{\mu}\text{m}/\text{s}$ to 1 cm/s, with the exact values dictated by the Device operating conditions as well as fluid properties. Additionally, the model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the Device Surface and the fluid-induced drag and lift forces prevent their reattachment. The streaming velocity fields computed using the finite-element model in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Predictions of the model are in good agreement with those of simple analytical theories as well as the experimentally observed trends of nonspecific protein removal in typical SAW biosensing operations.
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flow induced by acoustic streaming on Surface acoustic wave Devices and its application in biofouling removal a computational study and comparisons to experiment
Physical Review E, 2008Co-Authors: Subramanian K R S Sankaranarayanan, Stefan Cular, Venkat R Bhethanabotla, Babu JosephAbstract:All transducers used in biological sensing suffer from fouling resulting from nonspecific binding of protein molecules to the Device Surface. The acoustic-streaming phenomenon, which results from the fluid motion induced by high-intensity sound waves, can be used to remove these nonspecifically bound proteins to allow more accurate determinations and reuse of these Devices. We present a computational and experimental study of the acoustic-streaming phenomenon induced by Surface acoustic waves.A coupled-field fluid-structure interaction (FSI) model of a Surface-acoustic-wave (SAW) Device based on a micrometer-sized piezoelectric substrate (YZ-LiNbO3) in contact with a liquid loading was developed to study the Surface-acoustic-wave interaction with fluid loading. The fluid domain was modeled using the Navier-Stokes equation; the arbitrary Lagrangian-Eulerian approach was employed to handle the mesh distortions arising from the motion of the solid substrate. The fluid-solid coupling was established by maintaining stress and displacement continuity at the fluid-structure interface. A transient analysis was carried out by applying a time-varying voltage to the transmitter interdigital transducer (IDT) fingers. Simulation results predict strong coupling of ultrasonic Surface waves on the piezoelectric substrate with the thin liquid layer causing wave mode conversion from Rayleigh to leaky SAWs, which leads to acoustic streaming. The transient solutions generated from the FSI model were utilized to predict trends in acoustic-streaming velocity for varying design parameters such as voltage intensity, Device frequency, fluid viscosity, and density. The induced streaming velocities typically vary from 1 mum/s to 1 cm/s, with the exact values dictated by the Device operating conditions as well as fluid properties. Additionally, the model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the Device Surface and the fluid-induced drag and lift forces prevent their reattachment. The streaming velocity fields computed using the finite-element model in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Predictions of the model are in good agreement with those of simple analytical theories as well as the experimentally observed trends of nonspecific protein removal in typical SAW biosensing operations.
J Zhou - One of the best experts on this subject based on the ideXlab platform.
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characterisation of aluminium nitride films and Surface acoustic wave Devices for microfluidic applications
Sensors and Actuators B-chemical, 2014Co-Authors: J Zhou, M Demiguelramos, L Garciagancedo, E Iborra, J Olivares, Hao Jin, Jikui Luo, A S ElhadyAbstract:Aluminium nitride (AlN) films with different thicknesses (from 2.3 to 4.7 μm) were deposited onto high resistivity silicon substrates using magnetron sputtering. Crystalline and bonding structures of the deposited AlN films were characterised. The AlN films showed a highly c-axis texture. AlN film based Surface acoustic wave (SAW) Devices were fabricated and characterised. The SAW Devices showed Rayleigh wave transmission band with a large side-lobe suppression of ∼15 dB. With the increase in film thickness, both the central band frequency and electromechanical coupling coefficient were increased, and values of temperature coefficient of frequency was increased linearly from −21.3 to −27.4 ppm/K. Microfluidic manipulations including streaming, pumping and jetting have been realised using AlN SAW Devices. The applied RF power boundary between streaming and pumping and that between the pumping and jetting decreased with the increase of film thickness. The measured streaming and pumping velocities as well as Device Surface temperatures increased with the film thickness.
Georg Peters - One of the best experts on this subject based on the ideXlab platform.
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left ventricular assist Device infection is associated with increased mortality but is not a contraindication to transplantation
Circulation, 1997Co-Authors: Mathias Herrmann, M Weyand, Britta Greshake, Christof Von Eiff, Richard A Proctor, H H Scheld, Georg PetersAbstract:Background Left ventricular assist Devices (LVADs) are increasingly used as a bridge to transplantation. Infection is a frequent and major complication associated with the use of these Devices; however, the correlation of infection and outcome has not yet been evaluated in a prospective fashion. Methods and Results Twenty-five patients (24 male, 1 female) with end-stage cardiac failure and resulting organ dysfunction were included. Patients were bridged with the Novacor N100 portable LVAD (median duration of support, 55 days) and were evaluated prospectively by Device Surface cultures on explantation, molecular typing of isolates, and correlation of infection with survival to transplant. Twelve (48%) of 25 patients had LVAD infection as defined by recovery of multiple isolates of identical genotype from the Device Surface. Whereas only 5 (42%) of 12 patients with LVAD infection survived until transplantation, 11 (85%) of 13 patients without infection were successfully transplanted (P<.05). Death of the 7 ...
Subramanian K R S Sankaranarayanan - One of the best experts on this subject based on the ideXlab platform.
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flow induced by acoustic streaming on Surface acoustic wave Devices and its application in biofouling removal a computational study and comparisons to experiment
Physical Review E, 2008Co-Authors: Subramanian K R S Sankaranarayanan, Stefan Cular, Venkat R Bhethanabotla, Babu JosephAbstract:All transducers used in biological sensing suffer from fouling resulting from nonspecific binding of protein molecules to the Device Surface. The acoustic-streaming phenomenon, which results from the fluid motion induced by high-intensity sound waves, can be used to remove these nonspecifically bound proteins to allow more accurate determinations and reuse of these Devices. We present a computational and experimental study of the acoustic-streaming phenomenon induced by Surface acoustic waves.A coupled-field fluid-structure interaction (FSI) model of a Surface-acoustic-wave (SAW) Device based on a micrometer-sized piezoelectric substrate $(YZ{\text{-LiNbO}}_{3})$ in contact with a liquid loading was developed to study the Surface-acoustic-wave interaction with fluid loading. The fluid domain was modeled using the Navier-Stokes equation; the arbitrary Lagrangian-Eulerian approach was employed to handle the mesh distortions arising from the motion of the solid substrate. The fluid-solid coupling was established by maintaining stress and displacement continuity at the fluid-structure interface. A transient analysis was carried out by applying a time-varying voltage to the transmitter interdigital transducer (IDT) fingers. Simulation results predict strong coupling of ultrasonic Surface waves on the piezoelectric substrate with the thin liquid layer causing wave mode conversion from Rayleigh to leaky SAWs, which leads to acoustic streaming. The transient solutions generated from the FSI model were utilized to predict trends in acoustic-streaming velocity for varying design parameters such as voltage intensity, Device frequency, fluid viscosity, and density. The induced streaming velocities typically vary from $1\text{ }\ensuremath{\mu}\text{m}/\text{s}$ to 1 cm/s, with the exact values dictated by the Device operating conditions as well as fluid properties. Additionally, the model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the Device Surface and the fluid-induced drag and lift forces prevent their reattachment. The streaming velocity fields computed using the finite-element model in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Predictions of the model are in good agreement with those of simple analytical theories as well as the experimentally observed trends of nonspecific protein removal in typical SAW biosensing operations.
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flow induced by acoustic streaming on Surface acoustic wave Devices and its application in biofouling removal a computational study and comparisons to experiment
Physical Review E, 2008Co-Authors: Subramanian K R S Sankaranarayanan, Stefan Cular, Venkat R Bhethanabotla, Babu JosephAbstract:All transducers used in biological sensing suffer from fouling resulting from nonspecific binding of protein molecules to the Device Surface. The acoustic-streaming phenomenon, which results from the fluid motion induced by high-intensity sound waves, can be used to remove these nonspecifically bound proteins to allow more accurate determinations and reuse of these Devices. We present a computational and experimental study of the acoustic-streaming phenomenon induced by Surface acoustic waves.A coupled-field fluid-structure interaction (FSI) model of a Surface-acoustic-wave (SAW) Device based on a micrometer-sized piezoelectric substrate (YZ-LiNbO3) in contact with a liquid loading was developed to study the Surface-acoustic-wave interaction with fluid loading. The fluid domain was modeled using the Navier-Stokes equation; the arbitrary Lagrangian-Eulerian approach was employed to handle the mesh distortions arising from the motion of the solid substrate. The fluid-solid coupling was established by maintaining stress and displacement continuity at the fluid-structure interface. A transient analysis was carried out by applying a time-varying voltage to the transmitter interdigital transducer (IDT) fingers. Simulation results predict strong coupling of ultrasonic Surface waves on the piezoelectric substrate with the thin liquid layer causing wave mode conversion from Rayleigh to leaky SAWs, which leads to acoustic streaming. The transient solutions generated from the FSI model were utilized to predict trends in acoustic-streaming velocity for varying design parameters such as voltage intensity, Device frequency, fluid viscosity, and density. The induced streaming velocities typically vary from 1 mum/s to 1 cm/s, with the exact values dictated by the Device operating conditions as well as fluid properties. Additionally, the model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the Device Surface and the fluid-induced drag and lift forces prevent their reattachment. The streaming velocity fields computed using the finite-element model in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Predictions of the model are in good agreement with those of simple analytical theories as well as the experimentally observed trends of nonspecific protein removal in typical SAW biosensing operations.
Ranjit John - One of the best experts on this subject based on the ideXlab platform.
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interactions between the recipient immune system and the left ventricular assist Device Surface immunological and clinical implications
The Annals of Thoracic Surgery, 2003Co-Authors: Silviu Itescu, Ranjit JohnAbstract:The unquestionable clinical success of left ventricular assist Device (LVAD) implantation has, nevertheless, been accompanied by complications arising from interactions between the implanted biomaterial and the host immune system. The aberrant state of monocyte and T-cell activation resulting from these host/Device interactions is accompanied by two parallel processes: (1) selective loss of Th1 cytokine producing CD4 T-cells through activation-induced cell death; and (2) unopposed activation of Th2 cytokine producing CD4 T-cells resulting in B-cell hyperreactivity and dysregulated immunoglobulin synthesis through Th2 cytokines and heightened CD40 ligand-CD40 interactions. The net results of these events is that, on the one hand, the LVAD recipient develops progressive defects in cellular immunity and is at increased risk of serious infection, and, on the other hand, is more likely to develop allosensitization, posing a significant risk to successful transplant outcome. Intravenous immunoglobulin therapy is an effective and safe modality for sensitized LVAD recipients awaiting cardiac transplantation, reducing serum anti-human lymphoicyte antigen (HLA) alloreactivity and shortening the duration to transplantation. The therapeutic and safety profile of intravenous immunoglobulin would appear to be superior to plasmapheresis. Immunosuppression incorporating intravenous cyclophosphamide before and after transplantation is safe and highly effective in sensitized LVAD recipients of cardiac transplantation. When used after transplantation as part of triple immunosuppressive regimens, cyclophosphamide is superior to mycophenolate mofetil in reducing episodes of allograft rejection in these patients. Because these immune dysfunctions appear to be related to the effects of excessive biomaterial-associated T-cell activation, future efforts will need to be directed at either altering the physical properties of the materials interacting with the host circulation or pharmacological intervention aimed more selectively at inhibiting T-cell activation.