The Experts below are selected from a list of 6522 Experts worldwide ranked by ideXlab platform
Franklin D Lowy - One of the best experts on this subject based on the ideXlab platform.
-
role of biofilm in staphylococcus aureus and staphylococcus epidermidis ventricular assist device Driveline infections
The Journal of Thoracic and Cardiovascular Surgery, 2011Co-Authors: Faustino A Toba, Carlos Arrecubieta, Hirokazu Akashi, Franklin D LowyAbstract:Objective Infections, especially those involving Drivelines, are among the most serious complications that follow ventricular assist device implantation. Staphylococci are the most common causes of these infections. Once Driveline infections are established, they can remain localized or progress as an ascending infection to cause metastatic seeding of other tissue sites. Although elaboration of biofilm appears to be critical in prosthetic device infections, its role as a facilitator of staphylococcal infection and migration along the Driveline and other prosthetic devices is unclear. Methods A murine model of Driveline infection was used to investigate staphylococcal migration along the Driveline. A biofilm-producing strain of Staphylococcus epidermidis and a Staphylococcus aureus strain and its intercellular adhesion gene cluster (ica) –negative (biofilm-deficient) isogenic mutant were used in these studies. Bacterial density on the Driveline and the underlying tissue was measured over time. Scanning electron microscopy was used to examine the morphology of S epidermidis biofilm formation as the infection progressed. Results The biofilm-deficient S aureus mutant was less effective at infecting and migrating along the Driveline than the wild-type strain over time. However, the ica mutation had no effect on the ability of the strain to infect underlying tissue. S aureus exhibited more rapid migration than S epidermidis . Scanning electron microscopy revealed the deposition of host matrix on the Dacron material after implantation. This was followed by elaboration of a bacterial biofilm that correlated with more rapid migration along the Driveline. Conclusions Biofilm formation is a critical virulence determinant that facilitates the progression of Drivelines infections.
-
sdrf a staphylococcus epidermidis surface protein contributes to the initiation of ventricular assist device Driveline related infections
PLOS Pathogens, 2009Co-Authors: Carlos Arrecubieta, Faustino A Toba, Manuel Prinz Von Bayern, Hirokazu Akashi, Mario C Deng, Yoshifumi Naka, Franklin D LowyAbstract:Staphylococcus epidermidis remains the predominant pathogen in prosthetic-device infections. Ventricular assist devices, a recently developed form of therapy for end-stage congestive heart failure, have had considerable success. However, infections, most often caused by Staphylococcus epidermidis, have limited their long-term use. The transcutaneous Driveline entry site acts as a potential portal of entry for bacteria, allowing development of either localized or systemic infections. A novel in vitro binding assay using explanted Drivelines obtained from patients undergoing transplantation and a heterologous lactococcal system of surface protein expression were used to identify S. epidermidis surface components involved in the pathogenesis of Driveline infections. Of the four components tested, SdrF, SdrG, PIA, and GehD, SdrF was identified as the primary ligand. SdrF adherence was mediated via its B domain attaching to host collagen deposited on the surface of the Driveline. Antibodies directed against SdrF reduced adherence of S. epidermidis to the Drivelines. SdrF was also found to adhere with high affinity to Dacron, the hydrophobic polymeric outer surface of Drivelines. Solid phase binding assays showed that SdrF was also able to adhere to other hydrophobic artificial materials such as polystyrene. A murine model of infection was developed and used to test the role of SdrF during in vivo Driveline infection. SdrF alone was able to mediate bacterial adherence to implanted Drivelines. Anti-SdrF antibodies reduced S. epidermidis colonization of implanted Drivelines. SdrF appears to play a key role in the initiation of ventricular assist device Driveline infections caused by S. epidermidis. This pluripotential adherence capacity provides a potential pathway to infection with SdrF-positive commensal staphylococci first adhering to the external Dacron-coated Driveline at the transcutaneous entry site, then spreading along the collagen-coated internal portion of the Driveline to establish a localized infection. This capacity may also have relevance for other prosthetic device–related infections.
Hao Ying - One of the best experts on this subject based on the ideXlab platform.
-
active damping wheel torque control system to reduce Driveline oscillations in a power split hybrid electric vehicle
IEEE Transactions on Vehicular Technology, 2009Co-Authors: F U Syed, Ming Lang Kuang, Hao YingAbstract:Power-split hybrid electric vehicles (HEVs) provide a great opportunity to improve fuel economy and emissions. This power-split hybrid system has inherent low damping in Driveline since it uses planetary gear sets to directly connect the engine, the generator, and the motor to the Driveline for improved vehicle efficiency, thus lacking a clutch or a torque converter that provides the conventional vehicles with Driveline damping. When they are subjected to acceleration or disturbances, the low damping in the Driveline may cause torsional vibrations. Since the power-split control system is closed loop in nature, these torsional vibrations can result in sustained Driveline oscillations. These oscillations can be very objectionable to the driver as they affect the vehicle's drivability. In this paper, we present the design of an active damping wheel-torque control system to suppress such oscillations to improve the drivability of a power-split HEV. To the best of our knowledge, this is the first reported use of an active damping wheel-torque control system to suppress the Driveline oscillations in a power-split HEV. Simulations in a power-split HEV environment and experimental tests in the field using a Ford Escape Hybrid demonstrate the effectiveness of the proposed system in suppressing the oscillations. The Driveline disturbances are suppressed to below the perceptible level of wheel torque (<100 Nmiddotm). Additional simulations are performed to validate the system to other key factors that can affect its performance. Even with increased motor/generator disturbances by a factor of 2 and change in Driveline stiffness of plusmn50%, the proposed control system can still effectively suppress Driveline oscillations and thereby improve drivability.
-
Active Damping Wheel-Torque Control System to Reduce Driveline Oscillations in a Power-Split Hybrid Electric Vehicle
IEEE Transactions on Vehicular Technology, 2009Co-Authors: F U Syed, Ming Lang Kuang, Hao YingAbstract:Power-split hybrid electric vehicles (HEVs) provide a great opportunity to improve fuel economy and emissions. This power-split hybrid system has inherent low damping in Driveline since it uses planetary gear sets to directly connect the engine, the generator, and the motor to the Driveline for improved vehicle efficiency, thus lacking a clutch or a torque converter that provides the conventional vehicles with Driveline damping. When they are subjected to acceleration or disturbances, the low damping in the Driveline may cause torsional vibrations. Since the power-split control system is closed loop in nature, these torsional vibrations can result in sustained Driveline oscillations. These oscillations can be very objectionable to the driver as they affect the vehicle's drivability. In this paper, we present the design of an active damping wheel-torque control system to suppress such oscillations to improve the drivability of a power-split HEV. To the best of our knowledge, this is the first reported use of an active damping wheel-torque control system to suppress the Driveline oscillations in a power-split HEV. Simulations in a power-split HEV environment and experimental tests in the field using a Ford Escape Hybrid demonstrate the effectiveness of the proposed system in suppressing the oscillations. The Driveline disturbances are suppressed to below the perceptible level of wheel torque (
F U Syed - One of the best experts on this subject based on the ideXlab platform.
-
active damping wheel torque control system to reduce Driveline oscillations in a power split hybrid electric vehicle
IEEE Transactions on Vehicular Technology, 2009Co-Authors: F U Syed, Ming Lang Kuang, Hao YingAbstract:Power-split hybrid electric vehicles (HEVs) provide a great opportunity to improve fuel economy and emissions. This power-split hybrid system has inherent low damping in Driveline since it uses planetary gear sets to directly connect the engine, the generator, and the motor to the Driveline for improved vehicle efficiency, thus lacking a clutch or a torque converter that provides the conventional vehicles with Driveline damping. When they are subjected to acceleration or disturbances, the low damping in the Driveline may cause torsional vibrations. Since the power-split control system is closed loop in nature, these torsional vibrations can result in sustained Driveline oscillations. These oscillations can be very objectionable to the driver as they affect the vehicle's drivability. In this paper, we present the design of an active damping wheel-torque control system to suppress such oscillations to improve the drivability of a power-split HEV. To the best of our knowledge, this is the first reported use of an active damping wheel-torque control system to suppress the Driveline oscillations in a power-split HEV. Simulations in a power-split HEV environment and experimental tests in the field using a Ford Escape Hybrid demonstrate the effectiveness of the proposed system in suppressing the oscillations. The Driveline disturbances are suppressed to below the perceptible level of wheel torque (<100 Nmiddotm). Additional simulations are performed to validate the system to other key factors that can affect its performance. Even with increased motor/generator disturbances by a factor of 2 and change in Driveline stiffness of plusmn50%, the proposed control system can still effectively suppress Driveline oscillations and thereby improve drivability.
-
Active Damping Wheel-Torque Control System to Reduce Driveline Oscillations in a Power-Split Hybrid Electric Vehicle
IEEE Transactions on Vehicular Technology, 2009Co-Authors: F U Syed, Ming Lang Kuang, Hao YingAbstract:Power-split hybrid electric vehicles (HEVs) provide a great opportunity to improve fuel economy and emissions. This power-split hybrid system has inherent low damping in Driveline since it uses planetary gear sets to directly connect the engine, the generator, and the motor to the Driveline for improved vehicle efficiency, thus lacking a clutch or a torque converter that provides the conventional vehicles with Driveline damping. When they are subjected to acceleration or disturbances, the low damping in the Driveline may cause torsional vibrations. Since the power-split control system is closed loop in nature, these torsional vibrations can result in sustained Driveline oscillations. These oscillations can be very objectionable to the driver as they affect the vehicle's drivability. In this paper, we present the design of an active damping wheel-torque control system to suppress such oscillations to improve the drivability of a power-split HEV. To the best of our knowledge, this is the first reported use of an active damping wheel-torque control system to suppress the Driveline oscillations in a power-split HEV. Simulations in a power-split HEV environment and experimental tests in the field using a Ford Escape Hybrid demonstrate the effectiveness of the proposed system in suppressing the oscillations. The Driveline disturbances are suppressed to below the perceptible level of wheel torque (
Mats Leijon - One of the best experts on this subject based on the ideXlab platform.
-
electrical motor Drivelines in commercial all electric vehicles a review
IEEE Transactions on Vehicular Technology, 2012Co-Authors: J De Santiago, Hans Bernhoff, Boel Ekergard, Sandra Eriksson, S Ferhatovic, Rafael Waters, Mats LeijonAbstract:This paper presents a critical review of the Drivelines in all-electric vehicles (EVs). The motor topologies that are the best candidates to be used in EVs are presented. The advantages and disadvantages of each electric motor type are discussed from a system perspective. A survey of the electric motors used in commercial EVs is presented. The survey shows that car manufacturers are very conservative when it comes to introducing new technologies. Most of the EVs on the market mount a single induction or permanent-magnet (PM) motor with a traditional mechanic Driveline with a differential. This paper illustrates that comparisons between the different motors are difficult by the large number of parameters and the lack of a recommended test scheme. The authors propose that a standardized drive cycle be used to test and compare motors.
Carlos Arrecubieta - One of the best experts on this subject based on the ideXlab platform.
-
role of biofilm in staphylococcus aureus and staphylococcus epidermidis ventricular assist device Driveline infections
The Journal of Thoracic and Cardiovascular Surgery, 2011Co-Authors: Faustino A Toba, Carlos Arrecubieta, Hirokazu Akashi, Franklin D LowyAbstract:Objective Infections, especially those involving Drivelines, are among the most serious complications that follow ventricular assist device implantation. Staphylococci are the most common causes of these infections. Once Driveline infections are established, they can remain localized or progress as an ascending infection to cause metastatic seeding of other tissue sites. Although elaboration of biofilm appears to be critical in prosthetic device infections, its role as a facilitator of staphylococcal infection and migration along the Driveline and other prosthetic devices is unclear. Methods A murine model of Driveline infection was used to investigate staphylococcal migration along the Driveline. A biofilm-producing strain of Staphylococcus epidermidis and a Staphylococcus aureus strain and its intercellular adhesion gene cluster (ica) –negative (biofilm-deficient) isogenic mutant were used in these studies. Bacterial density on the Driveline and the underlying tissue was measured over time. Scanning electron microscopy was used to examine the morphology of S epidermidis biofilm formation as the infection progressed. Results The biofilm-deficient S aureus mutant was less effective at infecting and migrating along the Driveline than the wild-type strain over time. However, the ica mutation had no effect on the ability of the strain to infect underlying tissue. S aureus exhibited more rapid migration than S epidermidis . Scanning electron microscopy revealed the deposition of host matrix on the Dacron material after implantation. This was followed by elaboration of a bacterial biofilm that correlated with more rapid migration along the Driveline. Conclusions Biofilm formation is a critical virulence determinant that facilitates the progression of Drivelines infections.
-
sdrf a staphylococcus epidermidis surface protein contributes to the initiation of ventricular assist device Driveline related infections
PLOS Pathogens, 2009Co-Authors: Carlos Arrecubieta, Faustino A Toba, Manuel Prinz Von Bayern, Hirokazu Akashi, Mario C Deng, Yoshifumi Naka, Franklin D LowyAbstract:Staphylococcus epidermidis remains the predominant pathogen in prosthetic-device infections. Ventricular assist devices, a recently developed form of therapy for end-stage congestive heart failure, have had considerable success. However, infections, most often caused by Staphylococcus epidermidis, have limited their long-term use. The transcutaneous Driveline entry site acts as a potential portal of entry for bacteria, allowing development of either localized or systemic infections. A novel in vitro binding assay using explanted Drivelines obtained from patients undergoing transplantation and a heterologous lactococcal system of surface protein expression were used to identify S. epidermidis surface components involved in the pathogenesis of Driveline infections. Of the four components tested, SdrF, SdrG, PIA, and GehD, SdrF was identified as the primary ligand. SdrF adherence was mediated via its B domain attaching to host collagen deposited on the surface of the Driveline. Antibodies directed against SdrF reduced adherence of S. epidermidis to the Drivelines. SdrF was also found to adhere with high affinity to Dacron, the hydrophobic polymeric outer surface of Drivelines. Solid phase binding assays showed that SdrF was also able to adhere to other hydrophobic artificial materials such as polystyrene. A murine model of infection was developed and used to test the role of SdrF during in vivo Driveline infection. SdrF alone was able to mediate bacterial adherence to implanted Drivelines. Anti-SdrF antibodies reduced S. epidermidis colonization of implanted Drivelines. SdrF appears to play a key role in the initiation of ventricular assist device Driveline infections caused by S. epidermidis. This pluripotential adherence capacity provides a potential pathway to infection with SdrF-positive commensal staphylococci first adhering to the external Dacron-coated Driveline at the transcutaneous entry site, then spreading along the collagen-coated internal portion of the Driveline to establish a localized infection. This capacity may also have relevance for other prosthetic device–related infections.
