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Steven M Kurtz - One of the best experts on this subject based on the ideXlab platform.

  • biomechanical modeling of acetabular component polyethylene stresses fracture risk and wear rate following press fit implantation
    2009
    Co-Authors: Steve Rundell, Imants Liepins, Ryan J Laurent, David C Markel, Steven M Kurtz
    Abstract:

    Press-fit implantation may result in acetabular component deformation between the ischial-ilial columns (“pinching”). The biomechanical and clinical consequences of liner pinching due to press-fit implantation have not been well studied. We compared the effects of pinching on the polyethylene fracture risk, potential wear rate, and stresses for two different thickness liners using computational methods. Line-to-line (“no pinch”) reaming and 2 mm underreaming press fit (“pinch”) conditions were examined for Trident cups with X3™ polyethylene liner wall thicknesses of 5.9 mm (36E) and 3.8 mm (40E). Press-fit cup deformations were measured from a foam Block Configuration. A hybrid material model, calibrated to experimentally determined stress–strain behavior of sequentially annealed polyethylene, was applied to the computational model. Molecular chain stretch did not exceed the fracture threshold in any cases. Nominal shell pinch of 0.28 mm was estimated to increase the volumetric wear rate by 70% for both cups and peak contact stresses by 140 and 170% for the 5.9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1467–1472, 2009

  • biomechanical modeling of acetabular component polyethylene stresses fracture risk and wear rate following press fit implantation
    2009
    Co-Authors: Steve Rundell, Imants Liepins, Ryan J Laurent, David C Markel, Steven M Kurtz, Kevin L Ong
    Abstract:

    Press-fit implantation may result in acetabular component deformation between the ischial-ilial columns (“pinching”). The biomechanical and clinical consequences of liner pinching due to press-fit implantation have not been well studied. We compared the effects of pinching on the polyethylene fracture risk, potential wear rate, and stresses for two different thickness liners using computational methods. Line-to-line (“no pinch”) reaming and 2 mm underreaming press fit (“pinch”) conditions were examined for Trident cups with X3™ polyethylene liner wall thicknesses of 5.9 mm (36E) and 3.8 mm (40E). Press-fit cup deformations were measured from a foam Block Configuration. A hybrid material model, calibrated to experimentally determined stress–strain behavior of sequentially annealed polyethylene, was applied to the computational model. Molecular chain stretch did not exceed the fracture threshold in any cases. Nominal shell pinch of 0.28 mm was estimated to increase the volumetric wear rate by 70% for both cups and peak contact stresses by 140 and 170% for the 5.9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1467–1472, 2009

Koenig, William J. - One of the best experts on this subject based on the ideXlab platform.

  • Orion Heat Shield Manufacturing Producibility Improvements for the EM-1 Flight Test Program
    2019
    Co-Authors: Harris, Richard F., Stewart, Michael C., Koenig, William J.
    Abstract:

    This paper describes how the Orion program is incorporating improvements in the heat shield design and manufacturing processes reducing programmatic risk and ensuring crew safety in support of NASAs Exploration Missions. The Orion program successfully completed the EFT-1 flight test in 2014 and is currently developing the EM-1 spacecraft to meet the test objectives of an orbital mission to the moon and return to earth in 2019. Lessons learned from the EFT-1 manufacturing and flight test experience are being incorporated into a wide variety of vehicle systems and manufacturing processes to reduce risk to the Orion missions and flight crew. A critical contributor to crew safety is the heat shield that protects the crew capsule during re-entry through the earths atmosphere for return from deep space. The first flight test vehicle, EFT-1, was manufactured and tested in the Neil Armstrong Operations and Checkout (O&C) facility at KSC to demonstrate early risk reduction including the functionality of the Thermal Protection Systems (TPS) for capsule safe return to earth. The approach for the EFT-1 heat shield utilized a low risk approach using Apollo heritage design and manufacturing processes using an Avcoat TPS ablator with a honeycomb substrate to provide a one piece heat shield to meet the mission re-entry heating environments. The manufacturing processes used honeycomb cell injection guns which were redeveloped from the Apollo Lunar Program processes to build the EFT-1 heat shield. The completed heat shield was transported across the country by aircraft to the O&C at KSC for installation onto the capsule. The EFT-1 heat shield successfully performed its mission and experienced ~80% of the re-entry velocity (50% heating rate) for a lunar return for an Exploration Mission. The second flight test vehicle is the EM-1 mission which will have additional flight systems installed to fly to the moon and return. Heat shield design and producibility improvements have been incorporated in the EM-1 vehicle to meet deep space mission and programmatic requirements. The design continues to use the Avcoat material, but in a Block Configuration to enable improvements in the application processes as well as additional improvements in the carrier structure design and manufacturing operations. Incorporating flight test results and producibility improvements from EFT-1 for the heat shield system design and processes have improved the thermal protection capability, improved the producibility, and cost for EM-1 flight test

  • Orion Heat Shield Manufacturing Producibility Improvements for the EM-1 Flight Test Program
    2018
    Co-Authors: Harris, Richard F., Stewart Michael, Koenig, William J.
    Abstract:

    This paper describes how the ORION program is incorporating improvements in the heat shield design and manufacturing processes reducing programmatic risk and ensuring crew safety in support of NASA's Exploration missions. The approach for the EFT-1 heat shield utilized a low risk Apollo heritage design and manufacturing process using an Avcoat TPS ablator with a honeycomb substrate to provide a one piece heat shield to meet the mission re-entry heating environments. The EM-1 mission will have additional flight systems installed to fly to the moon and return to Earth. Heat shield design and producibility improvements have been incorporated in the EM-1 vehicle to meet deep space mission requirements. The design continues to use the Avcoat material, but in a Block Configuration to enable improvements in consistant and repeatable application processes using tile bonding experience developed on the Space Shuttle Transportation System Program

  • Thermal Protection Systems Technology Transfer from Apollo and Space Shuttle to the Orion Program
    2018
    Co-Authors: Stewart Michael, Harris, Richard F., Koenig, William J.
    Abstract:

    This paper describes how the Orion program is utilizing the Thermal Protection System (TPS) experience from the Apollo and Space Shuttle programs to reduce program risk and improve affordability to meet NASA's future manned exploration missions. The Orion program successfully completed the Exploration Flight Test (EFT-1) mission in 2014 and is currently assembling, integrating, and testing the next spacecraft for the Exploration Mission (EM-1) to meet the flight test objectives of an unmanned orbital mission to the moon and return to earth in 2019. The Orion spacecraft production operations are located in the Neil Armstrong Operations and Checkout (O&C) facility at the Kennedy Space Center (KSC) providing an affordable and seamless delivery approach of vehicles directly to the launch site eliminating spacecraft transportation and additional checkout testing. Innovative vehicle design, manufacturing and test operations approaches are maturing and evolving with each Orion vehicle build to support the challenging NASA exploration mission requirements beyond Low Earth Orbit (LEO) while reducing program cost and schedule impacts. An example of Orion's evolution is the incorporation of an improved heat shield design, assembly and testing approach to meet the higher re-entry velocities for a lunar return for the EM-1 mission. The EFT- 1 heat shield was based on the Apollo heat shield manufacturing processes and was assembled at a supplier location and then transported to KSC for final integration. The EM-1 heat shield is now manufactured, assembled, tested, and installed into the spacecraft at the O&C facility reducing program cost and production schedules. The transition of the Space Shuttle TPS capabilities has enabled Orion to provide a human rated capsule design using proven materials and processes established over years of orbiter re-entry missions. The Orion Crew Module (CM) TPS Configuration is derived from the Apollo CM approach utilizing improved materials and processes developed from the Space Shuttle program. The Orion EFT-1 heat shield utilized the Avcoat ablative material from Apollo which was injected into a honeycomb substrate and has been updated for EM-1 incorporating a Block Configuration bonded to a composite shell structure. This approach utilizes the proven Avcoat material for the heat shield ablator and is utilizing derived bonding and inspection methods and techniques from the Space Shuttle tile experience. The Orion back shell TPS Configuration is based on Space Shuttle tile designs using proven tile materials and coatings. The Orion forward bay cover utilizes the high temperature tiles similar to the back shell tiles and low temperature blankets derived from the Space Shuttle program reducing weight impacts. Space Shuttle Multi-Layer Insulation (MLI) is installed in the Orion capsule to control the interior temperature environment providing a light weight design. These TPS design approaches have performed successfully on the Orion first flight test on EFT-1 and are incorporated in the Configuration for the next flight test for EM-1. Completion of these two flight tests will certify the TPS for the Orion program for human rated exploration missions and has reduced the development cost to the Orion program. In addition to transitioning the Space Shuttle TPS design Configurations to Orion, the supporting manufacturing infrastructure, manufacturing processes, and inspection methods are also incorporated into the Orion assembly operations at KSC. This has avoided significant startup schedule and costs impacts of new capabilities and development of support operations necessary to fabricate, install, inspect, and validate the TPS installations for the Orion spacecraft. The Thermal Protection System Facility (TPSF) which supported the Space Shuttle program provides the heat shield Avcoat Blocks and the back shell AETB-8 tiles for Orion program. Extending the existing Space Shuttle TPS operations at KSC provides onsite support to the Orion spacecraft assembly operations. A significant benefit to the Orion program is the transition of the Space Shuttle technician work force at KSC. This highly skilled workforce was able to transition to the Orion program and immediately support the TPS installation operations. They brought with them the human rated manufacturing and assembly operations culture that was critical to the Space Shuttle success avoiding the retraining cost and schedule impacts of a new workforce to Orion. The technician skills certification program from the Space Shuttle was found to be compatible with the Lockheed Martin technician certification programs enabling a seamless training process utilizing process similarity avoiding the cost of retraining the work force to Orion standards. The existing workforce is certificated for multiple processes enabling reassignment of technicians to other tasks in the Orion AI&P operations reducing the overall touch labor manpower requirements. Additional benefits of using the Space Shuttle workforce is the incorporation of the lessons learned from Space Shuttle processes to improve the Orion TPS processes. This has resulted in a continuous evolution of TPS processes to improve the producibility and reduce the program cost for the TPS for the Orion program. Transitioning the Apollo and Space Shuttle TPS designs, processes, and technician workforce has been instrumental in enabling Orion to successfully meet the program challenges for NASA's exploration missions of the future

Steve Rundell - One of the best experts on this subject based on the ideXlab platform.

  • biomechanical modeling of acetabular component polyethylene stresses fracture risk and wear rate following press fit implantation
    2009
    Co-Authors: Steve Rundell, Imants Liepins, Ryan J Laurent, David C Markel, Steven M Kurtz
    Abstract:

    Press-fit implantation may result in acetabular component deformation between the ischial-ilial columns (“pinching”). The biomechanical and clinical consequences of liner pinching due to press-fit implantation have not been well studied. We compared the effects of pinching on the polyethylene fracture risk, potential wear rate, and stresses for two different thickness liners using computational methods. Line-to-line (“no pinch”) reaming and 2 mm underreaming press fit (“pinch”) conditions were examined for Trident cups with X3™ polyethylene liner wall thicknesses of 5.9 mm (36E) and 3.8 mm (40E). Press-fit cup deformations were measured from a foam Block Configuration. A hybrid material model, calibrated to experimentally determined stress–strain behavior of sequentially annealed polyethylene, was applied to the computational model. Molecular chain stretch did not exceed the fracture threshold in any cases. Nominal shell pinch of 0.28 mm was estimated to increase the volumetric wear rate by 70% for both cups and peak contact stresses by 140 and 170% for the 5.9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1467–1472, 2009

  • biomechanical modeling of acetabular component polyethylene stresses fracture risk and wear rate following press fit implantation
    2009
    Co-Authors: Steve Rundell, Imants Liepins, Ryan J Laurent, David C Markel, Steven M Kurtz, Kevin L Ong
    Abstract:

    Press-fit implantation may result in acetabular component deformation between the ischial-ilial columns (“pinching”). The biomechanical and clinical consequences of liner pinching due to press-fit implantation have not been well studied. We compared the effects of pinching on the polyethylene fracture risk, potential wear rate, and stresses for two different thickness liners using computational methods. Line-to-line (“no pinch”) reaming and 2 mm underreaming press fit (“pinch”) conditions were examined for Trident cups with X3™ polyethylene liner wall thicknesses of 5.9 mm (36E) and 3.8 mm (40E). Press-fit cup deformations were measured from a foam Block Configuration. A hybrid material model, calibrated to experimentally determined stress–strain behavior of sequentially annealed polyethylene, was applied to the computational model. Molecular chain stretch did not exceed the fracture threshold in any cases. Nominal shell pinch of 0.28 mm was estimated to increase the volumetric wear rate by 70% for both cups and peak contact stresses by 140 and 170% for the 5.9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1467–1472, 2009

Masayasu Hiraoka - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of bundle branch reentrant ventricular tachycardia with a right bundle branch Block Configuration feasibility of atrial pacing
    2009
    Co-Authors: Yuka Mizusawa, Akiko Uedatatsumoto, Harumizu Sakurada, Mitsuhiro Nishizaki, Seiji Fukamizu, Masayasu Hiraoka
    Abstract:

    Aims We assessed the inducibility of bundle branch reentrant ventricular tachycardia (BBR-VT) with a right bundle branch Block (RBBB) Configuration in patients with BBR-VT. Methods and results Eight consecutive patients (5 men, 45 ± 18 years old) with inducible BBR-VT were included. We evaluated the clinical and electrophysiological characteristics in these patients to explore the inducible factors of BBR-VT with an RBBB Configuration. Six of eight patients had inducible BBR-VT with an RBBB Configuration, including four patients with a clinical VT with the same QRS morphology. All patients exhibited an LBBB or RBBB type intraventricular conduction disturbance during sinus rhythm. The mean HV interval at baseline was 79 ± 18 ms. The reproducibility of the BBR-VT with an RBBB pattern was achieved by incremental atrial pacing during an isoproterenol infusion in 4/6 patients (67%) and by programmed ventricular stimulation in the other two. After a right bundle ablation, the BBR-VT was no longer inducible in any of the cases. Conclusion Our results indicate that it is not rare to induce BBR-VT with an RBBB Configuration. For the induction of an RBBB type BBR-VT, incremental atrial pacing may play a significant role in addition to ventricular pacing.

  • bidirectional ventricular tachycardia caused by a reentrant mechanism with left bundle branch Block Configuration on electrocardiography
    2008
    Co-Authors: Akiko Uedatatsumoto, Harumizu Sakurada, Mitsuhiro Nishizaki, Hidetaka Okazaki, Kota Komiyama, Yuka Mizusawa, Tamotsu Tejima, Masayasu Hiraoka
    Abstract:

    Reentrant bidirectional ventricular tachycardia (VT) with left bundle branch Block (LBBB) Configuration was diagnosed in a 54-year-old woman who showed 2 types of VT: QRS morphologies of LBBB with inferior axis and LBBB with superior axis. The development of VT with a superior axis was preceded by VT with inferior axis and/or both Configurations of VT in alternate beats exhibiting bidirectional VT. The electrophysiological study demonstrated reproducible induction of both types of VT by programmed ventricular stimulation and both types of VT were entrained. Using conventional pace mapping and electro-anatomical mapping methods, radiofrequency energy applications at the 2 exit sites of the reentry path successfully terminated both types of VT and the patient was free from VT attacks for more than 15 months. (Circ J 2008; 72: 1373 - 1377)

Akihiko Nogami - One of the best experts on this subject based on the ideXlab platform.

  • fascicular ventricular tachycardia originating from papillary muscles purkinje network involvement in the reentrant circuit
    2017
    Co-Authors: Yuki Komatsu, Takashi Kaneshiro, Akihiko Nogami, Kenji Kurosaki, I Morishima, Keita Masuda, Tomoya Ozawa, Yuichi Hanaki, Yasutoshi Shinoda, Ahmed Karim Talib
    Abstract:

    Background— Verapamil-sensitive fascicular ventricular tachycardia (FVT) has been demonstrated to be a reentrant mechanism using the Purkinje network as a part of its reentrant circuit. Although the papillary muscles (PMs) are implicated in arrhythmogenic structure, reentrant FVT originating from the PMs has not been well defined. Methods and Results— We studied 13 patients in whom FVT was successfully eliminated by ablation at the posterior PMs (n=8; PPM-FVT) and anterior PMs (n=5; APM-FVT). Although intravenous administration of verapamil (5 mg) terminated ventricular tachycardia (VT) in 6 patients, VT was only slowed in the remaining 7 patients. PPM-FVT exhibited right bundle branch Block and superior right axis (extreme right axis) or horizontal axis deviation. APM-FVT exhibited right bundle branch Block Configuration and right axis deviation with deep S wave in leads I, V5, and V6. VT was reproducibly induced by programmed atrial or ventricular stimulation. His-ventricular interval during VT was shorter than that during sinus rhythm. Ablation at the left posterior or anterior fascicular regions often changed the QRS morphology but did not completely eliminate it. Mid-diastolic Purkinje potentials were recorded during VT around the PMs, where ablation successfully eliminated the tachycardia. All patients have been free from recurrent VT after ablation. Conclusions— Reentrant circuit of verapamil-sensitive FVT can involve the Purkinje network lying around the PMs. PM-FVT is a distinct entity that is characterized by distinctive electrocardiographic characteristics and less sensitivity to verapamil administration compared with common type FVT. Ablation targeting the mid-diastolic Purkinje potentials around the PMs during tachycardia can be effective in suppressing this arrhythmia.

  • verapamil sensitive upper septal idiopathic left ventricular tachycardia prevalence mechanism and electrophysiological characteristics
    2015
    Co-Authors: Ahmed Karim Talib, Akihiko Nogami, Suguru Nishiuchi, Shinya Kowase, Kenji Kurosaki, Yumie Matsui, Satoshi Kawada, Atsuyuki Watanabe, Masatsugu Nozoe, Kikuya Uno
    Abstract:

    Abstract Objectives This study sought to demonstrate the prevalence, mechanism, and electrocardiographic and electrophysiological characteristics of upper septal idiopathic left fascicular ventricular tachycardia (US-ILVT). Background ILVT is classified into left anterior and posterior types with no clear data about US-ILVT. Methods Among 193 ILVT patients, we identified 12 patients (6.2%; age 41 ± 22 years, 7 men) with US-ILVT. Results Of 12 patients with US-ILVT, 6 patients (50%) had previous history of radiofrequency catheter ablation for common ILVT. Sustained VT (cycle length: 349 ± 53 ms) was seen in all patients with a QRS interval slightly wider (104 ± 18 ms) than that during sinus rhythm (90 ± 19 ms). The VT exhibited an identical QRS Configuration as sinus rhythm in 6 (50%) and incomplete right bundle branch Block Configuration in another 6. His-ventricular interval during VT was always shorter than that during sinus rhythm (27 ± 5 ms vs. 47 ± 10 ms). Purkinje potentials were activated in a reverse direction to that of common ILVT; namely, the diastolic potential (P1) was activated retrogradely but the pre-systolic potential (P2) was activated antegradely. At the left upper-middle ventricular septum, P1 potential was recorded during VT, preceding the QRS by 54 ± 20 ms. Radiofrequency catheter ablation at that site eliminated the VT with no recurrence during a 58 ± 35 months of follow-up. Conclusions US-ILVT is an identifiable VT that shares common criteria with ILVT and has a narrow QRS interval. Some US-ILVT cases appeared after common ILVT ablation. It is a reverse type of common ILVT (orthodromic form) with baseline morphological abnormalities that might provide a potential substrate for such VT.

  • successful catheter ablation of bidirectional ventricular premature contractions triggering ventricular fibrillation in catecholaminergic polymorphic ventricular tachycardia with ryr2 mutation
    2012
    Co-Authors: Takashi Kaneshiro, Yoshihisa Naruse, Akihiko Nogami, Hiroshi Tada, Kentaro Yoshida, Yukio Sekiguchi, Nobuyuki Murakoshi, Yoshiaki Kato, Hitoshi Horigome, Mihoko Kawamura
    Abstract:

    The subject of this report is a 38-year-old woman who often experienced syncope since childhood. Syncope occurred >10 times a year and was associated with convulsion during exercise and emotionally exciting situations. The patient's 13-year-old daughter had also experienced frequent episodes of syncope and developed ventricular fibrillation (VF) during treadmill exercise testing that was successfully defibrillated with electric shock. Witnessing this situation, the patient also lost consciousness, with documented VF that was converted to sinus rhythm by cardiopulmonary resuscitation without electric defibrillation. Both the patient and her daughter were admitted to our hospital. We performed echocardiography, coronary angiography, and cardiac CT, the results of which revealed no structural heart disease. Resting 12-lead ECG did not indicate any abnormalities, including long-QT syndrome or Brugada syndrome. A signal-averaged ECG revealed no late potentials. Treadmill exercise testing easily induced bigeminal ventricular premature contractions (VPCs) with a right bundle branch Block Configuration and inferior axis (Figure 1A), and the exercise was terminated because of intolerable symptoms. Catecholamine stress test was started with administration of continuous intravenous infusion of epinephrine in a stepwise manner from 0.025 μg/kg per minute.1 During epinephrine infusion at a rate of 0.1 μg/kg per minute, multifocal VPCs (VPC #1, right bundle branch Block Configuration and superior axis; VPC #2, right bundle branch Block Configuration and inferior axis [the same VPC Configuration as that induced during the treadmill exercise testing]; and VPC #3, left bundle branch Block Configuration and inferior axis) appeared, and VPC #1 following VPC #2 subsequently induced VF (Figure 1B). Figure 1. A , Twelve-lead ECG recording during treadmill exercise testing. Bigeminal ventricular premature contractions (VPCs) appeared during the second stage of the Bruce protocol. VPC morphology …