Endothelial Progenitor Cells as a Sole Source for Ex Vivo Seeding of Tissue-Engineered Heart Valves

PubMed Central

Mettler, Bret A.; Engelmayr, George C.; Aikawa, Elena; Bischoff, Joyce; Martin, David P.; Exarhopoulos, Alexis; Moses, Marsha A.; Schoen, Frederick J.; Sacks, Michael S.

2010-01-01

Purposes: We investigated whether circulating endothelial progenitor cells (EPCs) can be used as a cell source for the creation of a tissue-engineered heart valve (TEHV). Methods: Trileaflet valved conduits were fabricated using nonwoven polyglycolic acid/poly-4-hydroxybutyrate polymer. Ovine peripheral blood EPCs were dynamically seeded onto a valved conduit and incubated for 7, 14, and 21 days. Results: Before seeding, EPCs were shown to express CD31+, eNOS+, and VE-Cadherin+ but not α-smooth muscle actin. Histological analysis demonstrated relatively homogenous cellular ingrowth throughout the valved conduit. TEHV constructs revealed the presence of endothelial cell (EC) markers and α-smooth muscle actin+ cells comparable with native valves. Protein levels were comparable with native valves and exceeded those in unseeded controls. EPC-TEHV demonstrated a temporal pattern of matrix metalloproteinases-2/9 expression and tissue inhibitors of metalloproteinase activities comparable to that of native valves. Mechanical properties of EPC-TEHV demonstrated significantly greater stiffness than that of the unseeded scaffolds and native valves. Conclusions: Circulating EPC appears to have the potential to provide both interstitial and endothelial functions and could potentially serve as a single-cell source for construction of autologous heart valves. PMID:19698056

Knitting for heart valve tissue engineering

PubMed Central

Ayad, Nadia; Wojciechowska, Dorota; Zielińska, Dorota; Struszczyk, Marcin H.; Latif, Najma; Yacoub, Magdi

Knitting is a versatile technology which offers a large portfolio of products and solutions of interest in heart valve (HV) tissue engineering (TE). One of the main advantages of knitting is its ability to construct complex shapes and structures by precisely assembling the yarns in the desired position. With this in mind, knitting could be employed to construct a HV scaffold that closely resembles the authentic valve. This has the potential to reproduce the anisotropic structure that is characteristic of the heart valve with the yarns, in particular the 3-layered architecture of the leaflets. These yarns can provide oriented growth of cells lengthwise and consequently enable the deposition of extracellular matrix (ECM) proteins in an oriented manner. This technique, therefore, has a potential to provide a functional knitted scaffold, but to achieve that textile engineers need to gain a basic understanding of structural and mechanical aspects of the heart valve and in addition, tissue engineers must acquire the knowledge of tools and capacities that are essential in knitting technology. The aim of this review is to provide a platform to consolidate these two fields as well as to enable an efficient communication and cooperation among these two research areas. PMID:29043276

FLUID MECHANICS OF ARTIFICIAL HEART VALVES

PubMed Central

Dasi, Lakshmi P; Simon, Helene A; Sucosky, Philippe; Yoganathan, Ajit P

2009-01-01

SUMMARY 1. Artificial heart valves have been in use for over five decades to replace diseased heart valves. Since the first heart valve replacement performed with a caged-ball valve, more than 50 valve designs have been developed, differing principally in valve geometry, number of leaflets and material. To date, all artificial heart valves are plagued with complications associated with haemolysis, coagulation for mechanical heart valves and leaflet tearing for tissue-based valve prosthesis. For mechanical heart valves, these complications are believed to be associated with non-physiological blood flow patterns. 2. In the present review, we provide a bird’s-eye view of fluid mechanics for the major artificial heart valve types and highlight how the engineering approach has shaped this rapidly diversifying area of research. 3. Mechanical heart valve designs have evolved significantly, with the most recent designs providing relatively superior haemodynamics with very low aerodynamic resistance. However, high shearing of blood cells and platelets still pose significant design challenges and patients must undergo life-long anticoagulation therapy. Bioprosthetic or tissue valves do not require anticoagulants due to their distinct similarity to the native valve geometry and haemodynamics, but many of these valves fail structurally within the first 10–15 years of implantation. 4. These shortcomings have directed present and future research in three main directions in attempts to design superior artificial valves: (i) engineering living tissue heart valves; (ii) development of advanced computational tools; and (iii) blood experiments to establish the link between flow and blood damage. PMID:19220329

Fluid mechanics of artificial heart valves.

PubMed

Dasi, Lakshmi P; Simon, Helene A; Sucosky, Philippe; Yoganathan, Ajit P

2009-02-01

1. Artificial heart valves have been in use for over five decades to replace diseased heart valves. Since the first heart valve replacement performed with a caged-ball valve, more than 50 valve designs have been developed, differing principally in valve geometry, number of leaflets and material. To date, all artificial heart valves are plagued with complications associated with haemolysis, coagulation for mechanical heart valves and leaflet tearing for tissue-based valve prosthesis. For mechanical heart valves, these complications are believed to be associated with non-physiological blood flow patterns. 2. In the present review, we provide a bird's-eye view of fluid mechanics for the major artificial heart valve types and highlight how the engineering approach has shaped this rapidly diversifying area of research. 3. Mechanical heart valve designs have evolved significantly, with the most recent designs providing relatively superior haemodynamics with very low aerodynamic resistance. However, high shearing of blood cells and platelets still pose significant design challenges and patients must undergo life-long anticoagulation therapy. Bioprosthetic or tissue valves do not require anticoagulants due to their distinct similarity to the native valve geometry and haemodynamics, but many of these valves fail structurally within the first 10-15 years of implantation. 4. These shortcomings have directed present and future research in three main directions in attempts to design superior artificial valves: (i) engineering living tissue heart valves; (ii) development of advanced computational tools; and (iii) blood experiments to establish the link between flow and blood damage.

Mid-term function and remodeling potential of tissue engineered tricuspid valve: Histology and biomechanics.

PubMed

Ropcke, Diana M; Rasmussen, Jonas; Ilkjær, Christine; Skov, Søren N; Tjørnild, Marcell J; Baandrup, Ulrik T; Christian Danielsen, Carl; Hjortdal, Vibeke E; Nielsen, Sten L

2018-04-11

Tricuspid valve reconstruction using a small intestinal submucosal porcine extracellular matrix (ECM) tube graft is hypothesized to be durable for six months and show signs of recellularization and growth potential. The purpose was to histologically and biomechanically test ECM valves before and after six months of implantation in pigs for comparison with native valves. Ten 60 kg pigs were included, which survived tricuspid valve tube graft insertion. Anterior and septal tricuspid leaflets were explanted from all animals surviving more than one month and examined histologically (n = 9). Endothelialization, collagen content, mineralization, neovascularization, burst strength and tensile strength were determined for native valves (n = 5), ECM before implantation (n = 5), and ECM after six months (n = 5). Collagen density was significantly larger in ECM at implantation (baseline) compared to native leaflet tissue (0.3 ± 0.02 mg/mm 3 vs. 0.1 ± 0.03 mg/mm 3 , p < .0001), but collagen density decreased and reached native leaflet collagen content, six months after ECM implantation (native vs. ECM valve at six months: 0.1 ± 0.03 mg/mm 3 vs. 0.2 ± 0.05 mg/mm 3 , p = .8). Histologically, ECM valves showed endothelialization, host cell infiltration and structural collagen organization together with elastin generation after six months, indicating tissue remodeling and -engineering together with gradual development of a close-to-native leaflet structure without foreign body response. ECM tricuspid tube grafts were stronger than native leaflet tissue. Histologically, the acellular ECM tube grafts showed evidence of constructive tissue remodeling with endothelialization and connective tissue organization. These findings support the concept of tissue engineering and recellularization, which are prerequisites for growth. Copyright © 2018 Elsevier Ltd. All rights reserved.

Assessment of Parylene C Thin Films for Heart Valve Tissue Engineering

PubMed Central

Marei, Isra; Chester, Adrian; Carubelli, Ivan; Prodromakis, Themistoklis; Trantidou, Tatiana

2015-01-01

Background: Scaffolds are a key component of tissue-engineered heart valves (TEHVs). Several approaches had been adopted in the design of scaffolds using both natural and synthetic resources. We have investigated the suitability of parylene C (PC), a vapor deposited polymeric material, for the use as a scaffold in TEHV. Aims: To evaluate the adsorption of extracellular matrix components onto plasma-activated PC and study the biocompatibility of PC by measuring cellular adhesion, viability, apoptosis, and phenotypic expression of valve endothelial and interstitial cells. Finally, the mechanical properties of PC were compared with those of native aortic valve cusp tissue. Methods: PC slides were plasma activated and then coated with gelatin, type I collagen, or fibronectin. Porcine pulmonary valve endothelial and interstitial cells were then grown on plasma oxidized PC with different types of coatings and their adhesion was observed after 20 h of incubation. Cell viability was tested using the MTS assay, and apoptosis was estimated using TUNEL staining. The mechanical properties of PC and valve tissue were measured using a Bose Mechanical Tester. Finally, cell-seeded PC films were exposed to pulsatile pressure and aortic shear stress, respectively, to test their durability in a dynamic environment. Results: Our findings show that collagen and fibronectin could bind to plasma oxidized PC. Both valve endothelial and interstitial cells adhered to protein-coated ECM. PC had a profile of mechanical stiffness and ultimate tensile strength that were comparable with or in excess of those seen in porcine aortic valve cusps. Cells were still attached to PC films after 3 days of exposure to up to 50 mmHg pulsatile pressure or aortic levels of shear stress. Conclusion: PC is a promising candidate for use as a scaffold in tissue engineering heart valves. Additional studies are required to determine both the durability and long-term performance of cell-seeded PC when in a similar hemodynamic environment to that of the aortic valve. PMID:26101808

Aortic valve cell seeding into decellularized animal pericardium by perfusion-assisted bioreactor.

PubMed

Amadeo, Francesco; Boschetti, Federica; Polvani, Gianluca; Banfi, Cristina; Pesce, Maurizio; Santoro, Rosaria

2018-04-27

Animal-derived pericardium is the elective tissue employed in manufacturing heart valve prostheses. The preparation of this tissue for biological valve production consists of fixation with aldehydes, which reduces, but not eliminates, the xenoantigens and the donor cellular material. As a consequence, especially in patients below 65-70 years of age, the employment of valve substitutes contaning pericardium is not indicated due to progressive calcification that causes tissue degeneration and recurrence of valve insufficiency. Decellularization with ionic or nonionic detergents has been proposed as an alternative procedure to prepare aldehyde- or xenoantigen-free pericardium for biological valve manufacturing. In the present contribution, we optimized a decellularization procedure that is permissive for seeding and culturing valve competent cells able to colonize and reconstitute a valve-like tissue. A high-efficiency cellularization was achieved by forcing cell penetration inside the pericardium matrix using a perfusion bioreactor. Because the decellularization procedure was found not to alter the collagen composition of the pericardial matrix and cells seeded in the tissue constructs consistently grew and acquired the phenotype of "quiescent" valve interstitial cells, our investigation sets a novel standard in pericardium application for tissue engineering of "living" valve implants. Copyright © 2018 John Wiley & Sons, Ltd.

Multiple-Step Injection Molding for Fibrin-Based Tissue-Engineered Heart Valves

PubMed Central

Weber, Miriam; Gonzalez de Torre, Israel; Moreira, Ricardo; Frese, Julia; Oedekoven, Caroline; Alonso, Matilde; Rodriguez Cabello, Carlos J.

2015-01-01

Heart valves are elaborate and highly heterogeneous structures of the circulatory system. Despite the well accepted relationship between the structural and mechanical anisotropy and the optimal function of the valves, most approaches to create tissue-engineered heart valves (TEHVs) do not try to mimic this complexity and rely on one homogenous combination of cells and materials for the whole construct. The aim of this study was to establish an easy and versatile method to introduce spatial diversity into a heart valve fibrin scaffold. We developed a multiple-step injection molding process that enables the fabrication of TEHVs with heterogeneous composition (cell/scaffold material) of wall and leaflets without the need of gluing or suturing components together, with the leaflets firmly connected to the wall. The integrity of the valves and their functionality was proved by either opening/closing cycles in a bioreactor (proof of principle without cells) or with continuous stimulation over 2 weeks. We demonstrated the potential of the method by the two-step molding of the wall and the leaflets containing different cell lines. Immunohistology after stimulation confirmed tissue formation and demonstrated the localization of the different cell types. Furthermore, we showed the proof of principle fabrication of valves using different materials for wall (fibrin) and leaflets (hybrid gel of fibrin/elastin-like recombinamer) and with layered leaflets. The method is easy to implement, does not require special facilities, and can be reproduced in any tissue-engineering lab. While it has been demonstrated here with fibrin, it can easily be extended to other hydrogels. PMID:25654448

Multiple-Step Injection Molding for Fibrin-Based Tissue-Engineered Heart Valves.

PubMed

Weber, Miriam; Gonzalez de Torre, Israel; Moreira, Ricardo; Frese, Julia; Oedekoven, Caroline; Alonso, Matilde; Rodriguez Cabello, Carlos J; Jockenhoevel, Stefan; Mela, Petra

2015-08-01

Heart valves are elaborate and highly heterogeneous structures of the circulatory system. Despite the well accepted relationship between the structural and mechanical anisotropy and the optimal function of the valves, most approaches to create tissue-engineered heart valves (TEHVs) do not try to mimic this complexity and rely on one homogenous combination of cells and materials for the whole construct. The aim of this study was to establish an easy and versatile method to introduce spatial diversity into a heart valve fibrin scaffold. We developed a multiple-step injection molding process that enables the fabrication of TEHVs with heterogeneous composition (cell/scaffold material) of wall and leaflets without the need of gluing or suturing components together, with the leaflets firmly connected to the wall. The integrity of the valves and their functionality was proved by either opening/closing cycles in a bioreactor (proof of principle without cells) or with continuous stimulation over 2 weeks. We demonstrated the potential of the method by the two-step molding of the wall and the leaflets containing different cell lines. Immunohistology after stimulation confirmed tissue formation and demonstrated the localization of the different cell types. Furthermore, we showed the proof of principle fabrication of valves using different materials for wall (fibrin) and leaflets (hybrid gel of fibrin/elastin-like recombinamer) and with layered leaflets. The method is easy to implement, does not require special facilities, and can be reproduced in any tissue-engineering lab. While it has been demonstrated here with fibrin, it can easily be extended to other hydrogels.

Tissue-Engineered Fibrin-Based Heart Valve with a Tubular Leaflet Design

PubMed Central

Weber, Miriam; Heta, Eriona; Moreira, Ricardo; Gesche, Valentine N.; Schermer, Thomas; Frese, Julia

2014-01-01

The general approach in heart valve tissue engineering is to mimic the shape of the native valve in the attempt to recreate the natural haemodynamics. In this article, we report the fabrication of the first tissue-engineered heart valve (TEHV) based on a tubular leaflet design, where the function of the leaflets of semilunar heart valves is performed by a simple tubular construct sutured along a circumferential line at the root and at three single points at the sinotubular junction. The tubular design is a recent development in pericardial (nonviable) bioprostheses, which has attracted interest because of the simplicity of the construction and the reliability of the implantation technique. Here we push the potential of the concept further from the fabrication and material point of view to realize the tube-in-tube valve: an autologous, living HV with remodelling and growing capability, physiological haemocompatibility, simple to construct and fast to implant. We developed two different fabrication/conditioning procedures and produced fibrin-based constructs embedding cells from the ovine umbilical cord artery according to the two different approaches. Tissue formation was confirmed by histology and immunohistology. The design of the tube-in-tube foresees the possibility of using a textile coscaffold (here demonstrated with a warp-knitted mesh) to achieve enhanced mechanical properties in vision of implantation in the aortic position. The tube-in-tube represents an attractive alternative to the conventional design of TEHVs aiming at reproducing the valvular geometry. PMID:23829551

Engineering tissue constructs to mimic native aortic and pulmonary valve leaflets' structures and mechanics

NASA Astrophysics Data System (ADS)

Masoumi, Nafiseh

There are several disadvantages correlated with current heart valve replacement, including anticoagulation therapy for patients with mechanical valves and the low durability of bioprosthetic valves. The non-viable nature of such devices is a critical drawback especially for pediatric cases due to the inability of the graft to grow in vivo with the patients. A tissue engineered heart valve (TEHV) with remodeling and growth ability, is conceptually appealing to use in the surgical repair and could serve as a permanent replacements when operating for pediatric valvular lesions. It is critical that scaffolds for functional heart valve tissue engineering, be capable of mimicking the native leaflet's structure and mechanical properties at the time of implantation. Meanwhile, the scaffolds should be able to support cellular proliferation and native-like tissue formation as the TEHV remodels toward a scaffold-free state. Our overall hypothesis is that an "ideal" engineered construct, designed based on native leaflet's structure and mechanics, will complement a native heart valve leaflet in providing benchmarks for use in the design of clinically-applicable TEHV. This hypothesis was addressed through several experiments conducted in the present study. To establish a functional biomimetic TEHV, we developed scaffolds capable of matching the anisotropic stiffness of native leaflet while promoting native-like cell and collagen content and supporting the ECM generation. Scaffolds with various polymer contents (e.g., poly (glycerol sebacate) (PGS) and poly (epsilon-caprolactone) (PCL)) and structural designs (e.g., microfabricated and microfibrous scaffolds), were fabricated based on native leaflet's structure and mechanics. It was found that the tri-layered scaffold, designed with assembly of microfabricated PGS and microfibrous PGS/PCL was a functional leaflet capable of promoting tissue formation. Furthermore, to investigate the effect of cyclic stress and flexure individually on the TEHV development, we designed a simple and novel stretch-flexure bioreactor in which samples were subjected to well-defined stimulations with a controlled strain-rate. The stretch and flexure was found to accelerate and increase tissue formation on the microfabricated PGS scaffolds cultivated in the bioreactors.

Micro and nanotechnologies in heart valve tissue engineering.

PubMed

Hasan, Anwarul; Saliba, John; Pezeshgi Modarres, Hassan; Bakhaty, Ahmed; Nasajpour, Amir; Mofrad, Mohammad R K; Sanati-Nezhad, Amir

2016-10-01

Due to the increased morbidity and mortality resulting from heart valve diseases, there is a growing demand for off-the-shelf implantable tissue engineered heart valves (TEHVs). Despite the significant progress in recent years in improving the design and performance of TEHV constructs, viable and functional human implantable TEHV constructs have remained elusive. The recent advances in micro and nanoscale technologies including the microfabrication, nano-microfiber based scaffolds preparation, 3D cell encapsulated hydrogels preparation, microfluidic, micro-bioreactors, nano-microscale biosensors as well as the computational methods and models for simulation of biological tissues have increased the potential for realizing viable, functional and implantable TEHV constructs. In this review, we aim to present an overview of the importance and recent advances in micro and nano-scale technologies for the development of TEHV constructs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Integrating valve-inspired design features into poly(ethylene glycol) hydrogel scaffolds for heart valve tissue engineering.

PubMed

Zhang, Xing; Xu, Bin; Puperi, Daniel S; Yonezawa, Aline L; Wu, Yan; Tseng, Hubert; Cuchiara, Maude L; West, Jennifer L; Grande-Allen, K Jane

2015-03-01

The development of advanced scaffolds that recapitulate the anisotropic mechanical behavior and biological functions of the extracellular matrix in leaflets would be transformative for heart valve tissue engineering. In this study, anisotropic mechanical properties were established in poly(ethylene glycol) (PEG) hydrogels by crosslinking stripes of 3.4 kDa PEG diacrylate (PEGDA) within 20 kDa PEGDA base hydrogels using a photolithographic patterning method. Varying the stripe width and spacing resulted in a tensile elastic modulus parallel to the stripes that was 4.1-6.8 times greater than that in the perpendicular direction, comparable to the degree of anisotropy between the circumferential and radial orientations in native valve leaflets. Biomimetic PEG-peptide hydrogels were prepared by tethering the cell-adhesive peptide RGDS and incorporating the collagenase-degradable peptide PQ (GGGPQG↓IWGQGK) into the polymer network. The specific amounts of RGDS and PEG-PQ within the resulting hydrogels influenced the elongation, de novo extracellular matrix deposition and hydrogel degradation behavior of encapsulated valvular interstitial cells (VICs). In addition, the morphology and activation of VICs grown atop PEG hydrogels could be modulated by controlling the concentration or micro-patterning profile of PEG-RGDS. These results are promising for the fabrication of PEG-based hydrogels using anatomically and biologically inspired scaffold design features for heart valve tissue engineering. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

AN INVERSE MODELING APPROACH FOR STRESS ESTIMATION IN MITRAL VALVE ANTERIOR LEAFLET VALVULOPLASTY FOR IN-VIVO VALVULAR BIOMATERIAL ASSESSMENT

PubMed Central

Lee, Chung-Hao; Amini, Rouzbeh; Gorman, Robert C.; Gorman, Joseph H.; Sacks, Michael S.

2013-01-01

Estimation of regional tissue stresses in the functioning heart valve remains an important goal in our understanding of normal valve function and in developing novel engineered tissue strategies for valvular repair and replacement. Methods to accurately estimate regional tissue stresses are thus needed for this purpose, and in particular to develop accurate, statistically informed means to validate computational models of valve function. Moreover, there exists no currently accepted method to evaluate engineered heart valve tissues and replacement heart valve biomaterials undergoing valvular stresses in blood contact. While we have utilized mitral valve anterior leaflet valvuloplasty as an experimental approach to address this limitation, robust computational techniques to estimate implant stresses are required. In the present study, we developed a novel numerical analysis approach for estimation of the in-vivo stresses of the central region of the mitral valve anterior leaflet (MVAL) delimited by a sonocrystal transducer array. The in-vivo material properties of the MVAL were simulated using an inverse FE modeling approach based on three pseudo-hyperelastic constitutive models: the neo-Hookean, exponential-type isotropic, and full collagen-fiber mapped transversely isotropic models. A series of numerical replications with varying structural configurations were developed by incorporating measured statistical variations in MVAL local preferred fiber directions and fiber splay. These model replications were then used to investigate how known variations in the valve tissue microstructure influence the estimated ROI stresses and its variation at each time point during a cardiac cycle. Simulations were also able to include estimates of the variation in tissue stresses for an individual specimen dataset over the cardiac cycle. Of the three material models, the transversely anisotropic model produced the most accurate results, with ROI averaged stresses at the fully-loaded state of 432.6±46.5 kPa and 241.4±40.5 kPa in the radial and circumferential directions, respectively. We conclude that the present approach can provide robust instantaneous mean and variation estimates of tissue stresses of the central regions of the MVAL. PMID:24275434

Decellularization of human donor aortic and pulmonary valved conduits using low concentration sodium dodecyl sulfate

PubMed Central

Vafaee, Tayyebeh; Thomas, Daniel; Desai, Amisha; Jennings, Louise M.; Berry, Helen; Rooney, Paul; Kearney, John; Fisher, John

2017-01-01

Abstract The clinical use of decellularized cardiac valve allografts is increasing. Long‐term data will be required to determine whether they outperform conventional cryopreserved allografts. Valves decellularized using different processes may show varied long‐term outcomes. It is therefore important to understand the effects of specific decellularization technologies on the characteristics of donor heart valves. Human cryopreserved aortic and pulmonary valved conduits were decellularized using hypotonic buffer, 0.1% (w/v) sodium dodecyl sulfate and nuclease digestion. The decellularized tissues were compared to cellular cryopreserved valve tissues using histology, immunohistochemistry, quantitation of total deoxyribose nucleic acid, collagen and glycosaminoglycan content, in vitro cytotoxicity assays, uniaxial tensile testing and subcutaneous implantation in mice. The decellularized tissues showed no histological evidence of cells or cell remnants and >97% deoxyribose nucleic acid removal in all regions (arterial wall, muscle, leaflet and junction). The decellularized tissues retained collagen IV and von Willebrand factor staining with some loss of fibronectin, laminin and chondroitin sulfate staining. There was an absence of major histocompatibility complex Class I staining in decellularized pulmonary valve tissues, with only residual staining in isolated areas of decellularized aortic valve tissues. The collagen content of the tissues was not decreased following decellularization however the glycosaminoglycan content was reduced. Only moderate changes in the maximum load to failure of the tissues were recorded postdecellularization. The decellularized tissues were noncytotoxic in vitro, and were biocompatible in vivo in a mouse subcutaneous implant model. The decellularization process will now be translated into a good manufacturing practices‐compatible process for donor cryopreserved valves with a view to future clinical use. Copyright © 2016 The Authors Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd. PMID:27943656

Weaving for heart valve tissue engineering.

PubMed

Liberski, Albert; Ayad, Nadia; Wojciechowska, Dorota; Kot, Radoslaw; Vo, Duy M P; Aibibu, Dilibaier; Hoffmann, Gerald; Cherif, Chokri; Grobelny-Mayer, Katharina; Snycerski, Marek; Goldmann, Helmut

2017-11-01

Weaving is a resourceful technology which offers a large selection of solutions that are readily adaptable for tissue engineering (TE) of artificial heart valves (HV). The different ways that the yarns are interlaced in this technique could be used to produce complex architectures, such as the three-layer architecture of the leaflets. Once the assembly is complete, growth of cells in the scaffold would occur in the orientation of the yarn, enabling the deposition of extra cellular matrixes proteins in an oriented manner. Weaving technology is a rapidly evolving field that, first, needs to be understood, and then explored by tissue engineers, so that it could be used to create efficient scaffolds. Similarly, the textile engineers need to gain a basic understanding of key structural and mechanical aspects of the heart valve. The aim of this review is to provide the platform for joining these two fields and to enable cooperative research efforts. Moreover, examples of woven medical products and patents as well as related publication are discussed in this review, nevertheless due to the large, and continuously growing volume of data, only the aspects strictly associated with HVTE lay in the scope of this paper. Copyright © 2017 Elsevier Inc. All rights reserved.

Generation and Assessment of Functional Biomaterial Scaffolds for Applications in Cardiovascular Tissue Engineering and Regenerative Medicine

PubMed Central

Hinderer, Svenja; Brauchle, Eva

2015-01-01

Current clinically applicable tissue and organ replacement therapies are limited in the field of cardiovascular regenerative medicine. The available options do not regenerate damaged tissues and organs, and, in the majority of the cases, show insufficient restoration of tissue function. To date, anticoagulant drug‐free heart valve replacements or growing valves for pediatric patients, hemocompatible and thrombus‐free vascular substitutes that are smaller than 6 mm, and stem cell‐recruiting delivery systems that induce myocardial regeneration are still only visions of researchers and medical professionals worldwide and far from being the standard of clinical treatment. The design of functional off‐the‐shelf biomaterials as well as automatable and up‐scalable biomaterial processing methods are the focus of current research endeavors and of great interest for fields of tissue engineering and regenerative medicine. Here, various approaches that aim to overcome the current limitations are reviewed, focusing on biomaterials design and generation methods for myocardium, heart valves, and blood vessels. Furthermore, novel contact‐ and marker‐free biomaterial and extracellular matrix assessment methods are highlighted. PMID:25778713

Architecture of an in vivo-tissue engineered autologous conduit "Biovalve".

PubMed

Hayashida, Kyoko; Kanda, Keiichi; Oie, Tomonori; Okamoto, Yoshihiro; Ishibashi-Ueda, Hatsue; Onoyama, Masaaki; Tajikawa, Tsutomu; Ohba, Kenkichi; Yaku, Hitoshi; Nakayama, Yasuhide

2008-07-01

As a practical concept of regenerative medicine, we have focused on in vivo tissue engineering utilizing the foreign body reaction. Plastic substrates for valvular leaflet organization, consisting of two pieces assembled with a small aperture were inserted into a microporous polyurethane conduit scaffold. The assembly was placed in the subcutaneous spaces of Japanese white rabbits for 1 month. After the substrates were pulled out from the harvested implant, valve leaflet-shaped membranous tissue was formed inside the tubular scaffold as designed. The valve leaflet was composed of the same collagen-rich tissue, with the absence of any elastic fiber, as that which had ingrown or covered the scaffold. No abnormal collection or infiltration of inflammatory cells in the leaflet and the scaffold could be demonstrated. According to the immunohistochemical staining, the leaflet was comprised of numerous vimentin- or alpha-SMA-positive cells, corresponding to fibroblasts or myofibroblats, but contained no desmin-positive cells. The analysis of the video data of the valve movement showed that, in synchronization with the backward flow in the diastolic phase, the valve closed rapidly and tightly and, in the transition phase of the flow direction, the valve opened smoothly without flapping or hitting the scaffold wall. Using mold designs, consisting of two different plastic substrates and the tubular scaffold, in conjunction with "in body tissue architecture," the complex 3-dimensional autologous conduit-typed Biovalve was developed for the first time. 2007 Wiley Periodicals, Inc.

Biomaterial Characterization of Off-the-Shelf Decellularized Porcine Pericardial Tissue for use in Prosthetic Valvular Applications.

PubMed

Choe, Joshua A; Jana, Soumen; Tefft, Brandon J; Hennessy, Ryan S; Go, Jason; Morse, David; Lerman, Amir; Young, Melissa D

2018-05-10

Fixed pericardial tissue is commonly used for commercially available xenograft valve implants, and has proven durability, but lacks the capability to remodel and grow. Decellularized porcine pericardial tissue has the promise to outperform fixed tissue and remodel, but the decellularization process has been shown to damage the collagen structure and reduce mechanical integrity of the tissue. Therefore, a comparison of uniaxial tensile properties was performed on decellularized, decellularized-sterilized, fixed, and native porcine pericardial tissue, versus native valve leaflet cusps. The results of non-parametric analysis showed statistically significant differences (p<0.05) between the stiffness of 1) decellularized vs. native pericardium, and native cusps as well as fixed tissue respectively; however decellularized tissue showed large increases in elastic properties. Porosity testing of the tissues showed no statistical difference between decellularized or decell-sterilized tissue compared to native cusps (p>0.05). SEM confirmed that valvular endothelial and interstitial cells colonized the decellularized pericardial surface when seeded and grown for 30 days in static culture. Collagen assays and TEM analysis showed limited reductions in collagen with processing; yet, GAG assays showed great reductions in the processed pericardium relative to native cusps. Decellularized pericardium had comparatively lower mechanical properties amongst the groups studied; yet, the stiffness was comparatively similar to the native cusps and demonstrated a lack of cytotoxicity. Suture retention, accelerated wear, and hydrodynamic testing of prototype decellularized and decell-sterilized valves showed positive functionality. Sterilized tissue could mimic valvular mechanical environment in vitro, therefore making it a viable potential candidate for off-the-shelf tissue engineered valvular applications. KEYTERMS Decellularization, Sterilization, Pericardial Tissue, Heart Valves, Tissue Engineering, Biomechanics. This article is protected by copyright. All rights reserved.

Prediction of oxygen distribution in aortic valve leaflet considering diffusion and convection.

PubMed

Wang, Ling; Korossis, Sotirios; Fisher, John; Ingham, Eileen; Jin, Zhongmin

2011-07-01

Oxygen supply and transport is an important consideration in the development of tissue engineered constructs. Previous studies from our group have focused on the effect of tissue thickness on the oxygen diffusion within a three-dimensional aortic valve leaflet model, and highlighted the necessity for additional transport mechanisms such as oxygen convection. The aims of this study were to investigate the effect of interstitial fluid flow within the aortic valve leaflet, induced by the cyclic loading of the leaflet, on oxygen transport. Indentation testing and finite element modelings were employed to derive the biphasic properties of the leaflet tissue. The biphasic properties were subsequently used in the computational modeling of oxygen convection in the leaflet, which was based on the effective interstitial fluid velocity and the tissue deformation. Subsequently, the oxygen profile was predicted within the valve leaflet model by solving the diffusion and convection equation simultaneously utilizing the finite difference method. The compression modulus (E) and hydraulic permeability were determined by adapting a finite element model to the experimental indentation test on valvular tissue, E = 0.05MPa, and k =2.0 mm4/Ns. Finite element model of oxygen convection in valvular tissue incorporating the predicted biphasic properties was developed and the interstitial fluid flow rate was calculated falling in range of 0.025-0.25 mm/s depending on the tissue depth. Oxygen distribution within valvular tissue was predicted using one-dimensional oxygen diffusion model taking into consider the interstitial fluid effect. It was found that convection did enhance the oxygen transport in valvular tissue by up to 68% increase in the minimum oxygen tension within the tissue, depending on the strain level of the tissue as reaction of the magnitude and frequencies of the cardiac loading. The effective interstitial fluid velocity was found to play an important role in enhancing the oxygen transport within the valve leaflet. Such an understanding is important in the development of valvular tissue engineered constructs.

The mechanobiology of mitral valve function, degeneration, and repair

PubMed Central

Richards, Jennifer M.; Farrar, Emily J.; Kornreich, Bruce G.; Moïse, N. Sydney; Butcher, Jonathan T.

2013-01-01

In degenerative valve disease, the highly organized mitral valve leaflet matrix stratification is progressively destroyed and replaced with proteoglycan rich, mechanically inadequate tissue. This is driven by the actions of originally quiescent valve interstitial cells that become active contractile and migratory myofibroblasts. While treatment for myxomatous mitral valve disease in humans ranges from repair to total replacement, therapies in dogs focus on treating the consequences of the resulting mitral regurgitation. The fundamental gap in our understanding is how the resident valve cells respond to altered mechanical signals to drive tissue remodeling. Despite the pathological similarities and high clinical occurrence, surprisingly little mechanistic insight has been gleaned from the dog. This review presents what is known about mitral valve mechanobiology from clinical, in vivo, and in vitro data. There are a number of experimental strategies already available to pursue this significant opportunity, but success requires the collaboration between veterinary clinicians, scientists, and engineers. PMID:22366572

Feasibility of pig and human-derived aortic valve interstitial cells seeding on fixative-free decellularized animal pericardium.

PubMed

Santoro, Rosaria; Consolo, Filippo; Spiccia, Marco; Piola, Marco; Kassem, Samer; Prandi, Francesca; Vinci, Maria Cristina; Forti, Elisa; Polvani, Gianluca; Fiore, Gianfranco Beniamino; Soncini, Monica; Pesce, Maurizio

2016-02-01

Glutaraldehyde-fixed pericardium of animal origin is the elective material for the fabrication of bio-prosthetic valves for surgical replacement of insufficient/stenotic cardiac valves. However, the pericardial tissue employed to this aim undergoes severe calcification due to chronic inflammation resulting from a non-complete immunological compatibility of the animal-derived pericardial tissue resulting from failure to remove animal-derived xeno-antigens. In the mid/long-term, this leads to structural deterioration, mechanical failure, and prosthesis leaflets rupture, with consequent need for re-intervention. In the search for novel procedures to maximize biological compatibility of the pericardial tissue into immunocompetent background, we have recently devised a procedure to decellularize the human pericardium as an alternative to fixation with aldehydes. In the present contribution, we used this procedure to derive sheets of decellularized pig pericardium. The decellularized tissue was first tested for the presence of 1,3 α-galactose (αGal), one of the main xenoantigens involved in prosthetic valve rejection, as well as for mechanical tensile behavior and distensibility, and finally seeded with pig- and human-derived aortic valve interstitial cells. We demonstrate that the decellularization procedure removed the αGAL antigen, maintained the mechanical characteristics of the native pig pericardium, and ensured an efficient surface colonization of the tissue by animal- and human-derived aortic valve interstitial cells. This establishes, for the first time, the feasibility of fixative-free pericardial tissue seeding with valve competent cells for derivation of tissue engineered heart valve leaflets. © 2015 Wiley Periodicals, Inc.

Heart valve scaffold fabrication: Bioinspired control of macro-scale morphology, mechanics and micro-structure.

PubMed

D'Amore, Antonio; Luketich, Samuel K; Raffa, Giuseppe M; Olia, Salim; Menallo, Giorgio; Mazzola, Antonino; D'Accardi, Flavio; Grunberg, Tamir; Gu, Xinzhu; Pilato, Michele; Kameneva, Marina V; Badhwar, Vinay; Wagner, William R

2018-01-01

Valvular heart disease is currently treated with mechanical valves, which benefit from longevity, but are burdened by chronic anticoagulation therapy, or with bioprosthetic valves, which have reduced thromboembolic risk, but limited durability. Tissue engineered heart valves have been proposed to resolve these issues by implanting a scaffold that is replaced by endogenous growth, leaving autologous, functional leaflets that would putatively eliminate the need for anticoagulation and avoid calcification. Despite the diversity in fabrication strategies and encouraging results in large animal models, control over engineered valve structure-function remains at best partial. This study aimed to overcome these limitations by introducing double component deposition (DCD), an electrodeposition technique that employs multi-phase electrodes to dictate valve macro and microstructure and resultant function. Results in this report demonstrate the capacity of the DCD method to simultaneously control scaffold macro-scale morphology, mechanics and microstructure while producing fully assembled stent-less multi-leaflet valves composed of microscopic fibers. DCD engineered valve characterization included: leaflet thickness, biaxial properties, bending properties, and quantitative structural analysis of multi-photon and scanning electron micrographs. Quasi-static ex-vivo valve coaptation testing and dynamic organ level functional assessment in a pressure pulse duplicating device demonstrated appropriate acute valve functionality. Copyright © 2017. Published by Elsevier Ltd.

Generation and Assessment of Functional Biomaterial Scaffolds for Applications in Cardiovascular Tissue Engineering and Regenerative Medicine.

PubMed

Hinderer, Svenja; Brauchle, Eva; Schenke-Layland, Katja

2015-11-18

Current clinically applicable tissue and organ replacement therapies are limited in the field of cardiovascular regenerative medicine. The available options do not regenerate damaged tissues and organs, and, in the majority of the cases, show insufficient restoration of tissue function. To date, anticoagulant drug-free heart valve replacements or growing valves for pediatric patients, hemocompatible and thrombus-free vascular substitutes that are smaller than 6 mm, and stem cell-recruiting delivery systems that induce myocardial regeneration are still only visions of researchers and medical professionals worldwide and far from being the standard of clinical treatment. The design of functional off-the-shelf biomaterials as well as automatable and up-scalable biomaterial processing methods are the focus of current research endeavors and of great interest for fields of tissue engineering and regenerative medicine. Here, various approaches that aim to overcome the current limitations are reviewed, focusing on biomaterials design and generation methods for myocardium, heart valves, and blood vessels. Furthermore, novel contact- and marker-free biomaterial and extracellular matrix assessment methods are highlighted. © 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Clinical Application of Stem Cells in the Cardiovascular System

NASA Astrophysics Data System (ADS)

Stamm, Christof; Klose, Kristin; Choi, Yeong-Hoon

Regenerative medicine encompasses "tissue engineering" - the in vitro fabrication of tissues and/or organs using scaffold material and viable cells - and "cell therapy" - the transplantation or manipulation of cells in diseased tissue in vivo. In the cardiovascular system, tissue engineering strategies are being pursued for the development of viable replacement blood vessels, heart valves, patch material, cardiac pacemakers and contractile myocardium. Anecdotal clinical applications of such vessels, valves and patches have been described, but information on systematic studies of the performance of such implants is not available, yet. Cell therapy for cardiovascular regeneration, however, has been performed in large series of patients, and numerous clinical studies have produced sometimes conflicting results. The purpose of this chapter is to summarize the clinical experience with cell therapy for diseases of the cardiovascular system, and to analyse possible factors that may influence its outcome.

Application of Hydrogels in Heart Valve Tissue Engineering

PubMed Central

Zhang, Xing; Xu, Bin; Puperi, Daniel S.; Wu, Yan; West, Jennifer L.; Grande-Allen, K. Jane

2015-01-01

With an increasing number of patients requiring valve replacement, there is heightened interest in advancing heart valve tissue engineering (HVTE) to provide solutions to the many limitations of current surgical treatments. A variety of materials have been developed as scaffolds for HVTE including natural polymers, synthetic polymers, and decellularized valvular matrices. Among them, biocompatible hydrogels are generating growing interest. Natural hydrogels, such as collagen and fibrin, generally show good bioactivity, but poor mechanical durability. Synthetic hydrogels, on the other hand, have tunable mechanical properties; however, appropriate cell-matrix interactions are difficult to obtain. Moreover, hydrogels can be used as cell carriers when the cellular component is seeded into the polymer meshes or decellularized valve scaffolds. In this review, we discuss current research strategies for HVTE with an emphasis on hydrogel applications. The physicochemical properties and fabrication methods of these hydrogels, as well as their mechanical properties and bioactivities are described. Performance of some hydrogels including in vitro evaluation using bioreactors and in vivo tests in different animal models are also discussed. For future HVTE, it will be compelling to examine how hydrogels can be constructed from composite materials to replicate mechanical properties and mimic biological functions of the native heart valve. PMID:25955010

Intrinsic Cell Stress is Independent of Organization in Engineered Cell Sheets.

PubMed

van Loosdregt, Inge A E W; Dekker, Sylvia; Alford, Patrick W; Oomens, Cees W J; Loerakker, Sandra; Bouten, Carlijn V C

2018-06-01

Understanding cell contractility is of fundamental importance for cardiovascular tissue engineering, due to its major impact on the tissue's mechanical properties as well as the development of permanent dimensional changes, e.g., by contraction or dilatation of the tissue. Previous attempts to quantify contractile cellular stresses mostly used strongly aligned monolayers of cells, which might not represent the actual organization in engineered cardiovascular tissues such as heart valves. In the present study, therefore, we investigated whether differences in organization affect the magnitude of intrinsic stress generated by individual myofibroblasts, a frequently used cell source for in vitro engineered heart valves. Four different monolayer organizations were created via micro-contact printing of fibronectin lines on thin PDMS films, ranging from strongly anisotropic to isotropic. Thin film curvature, cell density, and actin stress fiber distribution were quantified, and subsequently, intrinsic stress and contractility of the monolayers were determined by incorporating these data into sample-specific finite element models. Our data indicate that the intrinsic stress exerted by the monolayers in each group correlates with cell density. Additionally, after normalizing for cell density and accounting for differences in alignment, no consistent differences in intrinsic contractility were found between the different monolayer organizations, suggesting that the intrinsic stress exerted by individual myofibroblasts is independent of the organization. Consequently, this study emphasizes the importance of choosing proper architectural properties for scaffolds in cardiovascular tissue engineering, as these directly affect the stresses in the tissue, which play a crucial role in both the functionality and remodeling of (engineered) cardiovascular tissues.

Translational Applications of Tissue Engineering in Cardiovascular Medicine.

PubMed

Dogan, Arin; Elcin, A Eser; Elcin, Y Murat

2017-03-26

Cardiovascular diseases are the leading cause of global deaths. The current paradigm in medicine seeks novel approaches for the treatment of progressive or end-stage diseases. The organ transplantation option is limited in availability, and unfortunately, a significant number of patients are lost while waiting for donor organs. Animal studies have shown that upon myocardial infarction, it is possible to stop adverse remodeling in its tracks and reverse with tissue engineering methods. Regaining the myocardium function and avoiding further deterioration towards heart failure can benefit millions of people with a significantly lesser burden on healthcare systems worldwide. The advent of induced pluripotent stem cells brings the unique advantage of testing candidate drug molecules on organ-on-chip systems, which mimics human heart in vitro. Biomimetic three-dimensional constructs that contain disease-specific or normal cardiomyocytes derived from human induced pluripotent stem cells are a useful tool for screening drug molecules and studying dosage, mode of action and cardio-toxicity. Tissue engineering approach aims to develop the treatments for heart valve deficiency, ischemic heart disease and a wide range of vascular diseases. Translational research seeks to improve the patient's quality of life, progressing towards developing cures, rather than treatments. To this end, researchers are working on tissue engineered heart valves, blood vessels, cardiac patches, and injectable biomaterials, hence developing new ways for engineering bio-artificial organs or tissue parts that the body will adopt as its own. In this review, we summarize translational methods for cardiovascular tissue engineering and present useful tables on pre-clinical and clinical applications. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Current progress in 3D printing for cardiovascular tissue engineering.

PubMed

Mosadegh, Bobak; Xiong, Guanglei; Dunham, Simon; Min, James K

2015-03-16

3D printing is a technology that allows the fabrication of structures with arbitrary geometries and heterogeneous material properties. The application of this technology to biological structures that match the complexity of native tissue is of great interest to researchers. This mini-review highlights the current progress of 3D printing for fabricating artificial tissues of the cardiovascular system, specifically the myocardium, heart valves, and coronary arteries. In addition, how 3D printed sensors and actuators can play a role in tissue engineering is discussed. To date, all the work with building 3D cardiac tissues have been proof-of-principle demonstrations, and in most cases, yielded products less effective than other traditional tissue engineering strategies. However, this technology is in its infancy and therefore there is much promise that through collaboration between biologists, engineers and material scientists, 3D bioprinting can make a significant impact on the field of cardiovascular tissue engineering.

In vivo evaluation of an in-body, tissue-engineered, completely autologous valved conduit (biovalve type VI) as an aortic valve in a goat model.

PubMed

Takewa, Yoshiaki; Yamanami, Masashi; Kishimoto, Yuichiro; Arakawa, Mamoru; Kanda, Keiichi; Matsui, Yuichi; Oie, Tomonori; Ishibashi-Ueda, Hatsue; Tajikawa, Tsutomu; Ohba, Kenkichi; Yaku, Hitoshi; Taenaka, Yoshiyuki; Tatsumi, Eisuke; Nakayama, Yasuhide

2013-06-01

Using simple, safe, and economical in-body tissue engineering, autologous valved conduits (biovalves) with the sinus of Valsalva and without any artificial support materials were developed in animal recipients' bodies. In this study, the feasibility of the biovalve as an aortic valve was evaluated in a goat model. Biovalves were prepared by 2-month embedding of the molds, assembled using two types of specially designed plastic rods, in the dorsal subcutaneous spaces of goats. One rod had three projections, resembling the protrusions of the sinus of Valsalva. Completely autologous connective tissue biovalves (type VI) with three leaflets in the inner side of the conduit with the sinus of Valsalva were obtained after removing the molds from both terminals of the harvested implants with complete encapsulation. The biovalve leaflets had appropriate strength and elastic characteristics similar to those of native aortic valves; thus, a robust conduit was formed. Tight valvular coaptation and a sufficient open orifice area were observed in vitro. Biovalves (n = 3) were implanted in the specially designed apico-aortic bypass for 2 months as a pilot study. Postoperative echocardiography showed smooth movement of the leaflets with little regurgitation under systemic circulation (2.6 ± 1.1 l/min). α-SMA-positive cells appeared significantly with rich angiogenesis in the conduit and expanded toward the leaflet tip. At the sinus portions, marked elastic fibers were formed. The luminal surface was covered with thin pseudointima without thrombus formation. Completely autologous biovalves with robust and elastic characteristics satisfied the higher requirements of the systemic circulation in goats for 2 months with the potential for valvular tissue regeneration.

How to Make a Heart Valve: From Embryonic Development to Bioengineering of Living Valve Substitutes

PubMed Central

MacGrogan, Donal; Luxán, Guillermo; Driessen-Mol, Anita; Bouten, Carlijn; Baaijens, Frank; de la Pompa, José Luis

2014-01-01

Cardiac valve disease is a significant cause of ill health and death worldwide, and valve replacement remains one of the most common cardiac interventions in high-income economies. Despite major advances in surgical treatment, long-term therapy remains inadequate because none of the current valve substitutes have the potential for remodeling, regeneration, and growth of native structures. Valve development is coordinated by a complex interplay of signaling pathways and environmental cues that cause disease when perturbed. Cardiac valves develop from endocardial cushions that become populated by valve precursor mesenchyme formed by an epithelial–mesenchymal transition (EMT). The mesenchymal precursors, subsequently, undergo directed growth, characterized by cellular compartmentalization and layering of a structured extracellular matrix (ECM). Knowledge gained from research into the development of cardiac valves is driving exploration into valve biomechanics and tissue engineering directed at creating novel valve substitutes endowed with native form and function. PMID:25368013

Prenatally fabricated autologous human living heart valves based on amniotic fluid derived progenitor cells as single cell source.

PubMed

Schmidt, Dörthe; Achermann, Josef; Odermatt, Bernhard; Breymann, Christian; Mol, Anita; Genoni, Michele; Zund, Gregor; Hoerstrup, Simon P

2007-09-11

A novel concept providing prenatally tissue engineered human autologous heart valves based on routinely obtained fetal amniotic fluid progenitors as single cell source is introduced. Fetal human amniotic progenitors were isolated from routinely sampled amniotic fluid and sorted using CD133 magnetic beads. After expansion and differentiation, cell phenotypes of CD133- and CD133+ cells were analyzed by immunohistochemistry and flowcytometry. After characterization, CD133- derived cells were seeded onto heart valve leaflet scaffolds (n=18) fabricated from rapidly biodegradable polymers, conditioned in a pulse duplicator system, and subsequently coated with CD133+ derived cells. After in vitro maturation, opening and closing behavior of leaflets was investigated. Neo-tissues were analyzed by histology, immunohistochemistry, and scanning electron microscopy (SEM). Extracellular matrix (ECM) elements and cell numbers were quantified biochemically. Mechanical properties were assessed by tensile testing. CD133- derived cells demonstrated characteristics of mesenchymal progenitors expressing CD44 and CD105. Differentiated CD133+ cells showed features of functional endothelial cells by eNOS and CD141 expression. Engineered heart valve leaflets demonstrated endothelialized tissue formation with production of ECM elements (GAG 80%, HYP 5%, cell number 100% of native values). SEM showed intact endothelial surfaces. Opening and closing behavior was sufficient under half of systemic conditions. The use of amniotic fluid as single cell source is a promising low-risk approach enabling the prenatal fabrication of heart valves ready to use at birth. These living replacements with the potential of growth, remodeling, and regeneration may realize the early repair of congenital malformations.

Functional Heart Valve Scaffolds Obtained by Complete Decellularization of Porcine Aortic Roots in a Novel Differential Pressure Gradient Perfusion System

PubMed Central

Sierad, Leslie Neil; Shaw, Eliza Laine; Bina, Alexander; Brazile, Bryn; Rierson, Nicholas; Patnaik, Sourav S.; Kennamer, Allison; Odum, Rebekah; Cotoi, Ovidiu; Terezia, Preda; Branzaniuc, Klara; Smallwood, Harrison; Deac, Radu; Egyed, Imre; Pavai, Zoltan; Szanto, Annamaria; Harceaga, Lucian; Suciu, Horatiu; Raicea, Victor; Olah, Peter; Simionescu, Agneta; Liao, Jun; Movileanu, Ionela

2015-01-01

There is a great need for living valve replacements for patients of all ages. Such constructs could be built by tissue engineering, with perspective of the unique structure and biology of the aortic root. The aortic valve root is composed of several different tissues, and careful structural and functional consideration has to be given to each segment and component. Previous work has shown that immersion techniques are inadequate for whole-root decellularization, with the aortic wall segment being particularly resistant to decellularization. The aim of this study was to develop a differential pressure gradient perfusion system capable of being rigorous enough to decellularize the aortic root wall while gentle enough to preserve the integrity of the cusps. Fresh porcine aortic roots have been subjected to various regimens of perfusion decellularization using detergents and enzymes and results compared to immersion decellularized roots. Success criteria for evaluation of each root segment (cusp, muscle, sinus, wall) for decellularization completeness, tissue integrity, and valve functionality were defined using complementary methods of cell analysis (histology with nuclear and matrix stains and DNA analysis), biomechanics (biaxial and bending tests), and physiologic heart valve bioreactor testing (with advanced image analysis of open–close cycles and geometric orifice area measurement). Fully acellular porcine roots treated with the optimized method exhibited preserved macroscopic structures and microscopic matrix components, which translated into conserved anisotropic mechanical properties, including bending and excellent valve functionality when tested in aortic flow and pressure conditions. This study highlighted the importance of (1) adapting decellularization methods to specific target tissues, (2) combining several methods of cell analysis compared to relying solely on histology, (3) developing relevant valve-specific mechanical tests, and (4) in vitro testing of valve functionality. PMID:26467108

Three-dimensional printed trileaflet valve conduits using biological hydrogels and human valve interstitial cells.

PubMed

Duan, B; Kapetanovic, E; Hockaday, L A; Butcher, J T

2014-05-01

Tissue engineering has great potential to provide a functional de novo living valve replacement, capable of integration with host tissue and growth. Among various valve conduit fabrication techniques, three-dimensional (3-D) bioprinting enables deposition of cells and hydrogels into 3-D constructs with anatomical geometry and heterogeneous mechanical properties. Successful translation of this approach, however, is constrained by the dearth of printable and biocompatible hydrogel materials. Furthermore, it is not known how human valve cells respond to these printed environments. In this study, 3-D printable formulations of hybrid hydrogels are developed, based on methacrylated hyaluronic acid (Me-HA) and methacrylated gelatin (Me-Gel), and used to bioprint heart valve conduits containing encapsulated human aortic valvular interstitial cells (HAVIC). Increasing Me-Gel concentration resulted in lower stiffness and higher viscosity, facilitated cell spreading, and better maintained HAVIC fibroblastic phenotype. Bioprinting accuracy was dependent upon the relative concentrations of Me-Gel and Me-HA, but when optimized enabled the fabrication of a trileaflet valve shape accurate to the original design. HAVIC encapsulated within bioprinted heart valves maintained high viability, and remodeled the initial matrix by depositing collagen and glyosaminoglycans. These findings represent the first rational design of bioprinted trileaflet valve hydrogels that regulate encapsulated human VIC behavior. The use of anatomically accurate living valve scaffolds through bioprinting may accelerate understanding of physiological valve cell interactions and progress towards de novo living valve replacements. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Valve replacement in children: a challenge for a whole life.

PubMed

Henaine, Roland; Roubertie, François; Vergnat, Mathieu; Ninet, Jean

2012-10-01

Valvular pathology in infants and children poses numerous challenges to the paediatric cardiac surgeon. Without question, valvular repair is the goal of intervention because restoration of valvular anatomy and physiology using native tissue allows for growth and a potentially better long-term outcome. When reconstruction fails or is not feasible, valve replacement becomes inevitable. Which valve for which position is controversial. Homograft and bioprosthetic valves achieve superior haemodynamic results initially but at the cost of accelerated degeneration. Small patient size and the risk of thromboembolism limit the usefulness of mechanical valves, and somatic outgrowth is an universal problem with all available prostheses. The goal of this article is to address valve replacement options for all four valve positions within the paediatric population. We review current literature and our practice to support our preferences. To summarize, a multitude of opinions and surgical experiences exist. Today, the valve choices that seem without controversy are bioprosthetic replacement of the tricuspid valve and Ross or Ross-Konno procedures when necessary for the aortic valve. On the other hand, bioprostheses may be implanted when annular pulmonary diameter is adequate; if not or in case of right ventricular outflow tract discontinuity, it is better to use a pulmonary homograft with the Ross procedure. Otherwise, a valved conduit. Mitral valve replacement remains the most problematic; the mechanical prosthesis must be placed in the annular position, avoiding oversizing. Future advances with tissue-engineered heart valves for all positions and new anticoagulants may change the landscape for valve replacement in the paediatric population. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Development of a tissue engineered heart valve for pediatrics: a case study in bioengineering ethics.

PubMed

Merryman, W David

2008-03-01

The following hypothetical case study was developed for bioengineering students and is concerned with choosing between two devices used for development of a pediatric tissue engineered heart valve (TEHV). This case is intended to elicit assessment of the devices, possible future outcomes, and ramifications of the decision making. It is framed in light of two predominant ethical theories: utilitarianism and rights of persons. After the case was presented to bioengineering graduate students, they voted on which device should be released. The results revealed that these bioengineering students preferred the more reliable (and substantially more expensive) design, though this choice precludes the majority of the world from having access to this technology. This case is intended to examine and explore where the balance lies between design, cost, and adequate distribution of biomedical devices.

Bioreactor Technology in Cardiovascular Tissue Engineering

NASA Astrophysics Data System (ADS)

Mertsching, H.; Hansmann, J.

Cardiovascular tissue engineering is a fast evolving field of biomedical science and technology to manufacture viable blood vessels, heart valves, myocar-dial substitutes and vascularised complex tissues. In consideration of the specific role of the haemodynamics of human circulation, bioreactors are a fundamental of this field. The development of perfusion bioreactor technology is a consequence of successes in extracorporeal circulation techniques, to provide an in vitro environment mimicking in vivo conditions. The bioreactor system should enable an automatic hydrodynamic regime control. Furthermore, the systematic studies regarding the cellular responses to various mechanical and biochemical cues guarantee the viability, bio-monitoring, testing, storage and transportation of the growing tissue.

3D Bioprinting of Heterogeneous Aortic Valve Conduits with Alginate/Gelatin Hydrogels

PubMed Central

Duan, Bin; Hockaday, Laura A.; Kang, Kevin H.; Butcher, Jonathan T.

2013-01-01

Heart valve disease is a serious and growing public health problem for which prosthetic replacement is most commonly indicated. Current prosthetic devices are inadequate for younger adults and growing children. Tissue engineered living aortic valve conduits have potential for remodeling, regeneration, and growth, but fabricating natural anatomical complexity with cellular heterogeneity remain challenging. In the current study, we implement 3D bioprinting to fabricate living alginate/gelatin hydrogel valve conduits with anatomical architecture and direct incorporation of dual cell types in a regionally constrained manner. Encapsulated aortic root sinus smooth muscle cells (SMC) and aortic valve leaflet interstitial cells (VIC) were viable within alginate/gelatin hydrogel discs over 7 days in culture. Acellular 3D printed hydrogels exhibited reduced modulus, ultimate strength, and peak strain reducing slightly over 7-day culture, while the tensile biomechanics of cell-laden hydrogels were maintained. Aortic valve conduits were successfully bioprinted with direct encapsulation of SMC in the valve root and VIC in the leaflets. Both cell types were viable (81.4±3.4% for SMC and 83.2±4.0% for VIC) within 3D printed tissues. Encapsulated SMC expressed elevated alpha-smooth muscle actin when printed in stiff matrix, while VIC expressed elevated vimentin in soft matrix. These results demonstrate that anatomically complex, heterogeneously encapsulated aortic valve hydrogel conduits can be fabricated with 3D bioprinting. PMID:23015540

Rapid 3D printing of anatomically accurate and mechanically heterogeneous aortic valve hydrogel scaffolds

PubMed Central

Hockaday, L A; Kang, K H; Colangelo, N W; Cheung, P Y C; Duan, B; Malone, E; Wu, J; Girardi, L N; Bonassar, L J; Lipson, H; Chu, C C; Butcher, J T

2013-01-01

The aortic valve exhibits complex three-dimensional (3D) anatomy and heterogeneity essential for long-term efficient biomechanical function. These are, however, challenging to mimic in de novo engineered living tissue valve strategies. We present a novel simultaneous 3D-printing/photocrosslinking technique for rapidly engineering complex, heterogeneous aortic valve scaffolds. Native anatomic and axisymmetric aortic valve geometries (root wall and tri-leaflets) with 12 to 22 mm inner diameters (ID) were 3D printed with poly-ethylene glycol-diacrylate (PEG-DA) hydrogels (700 or 8000 MW) supplemented with alginate. 3D printing geometric accuracy was quantified and compared using Micro-CT. Porcine aortic valve interstitial cells (PAVIC) seeded scaffolds were cultured for up to 21 days. Results showed that blended PEG-DA scaffolds could achieve over 10-fold range in elastic modulus (5.3±0.9 to 74.6±1.5 kPa). 3D printing times for valve conduits with mechanically contrasting hydrogels were optimized to 14 to 45 minutes, increasing linearly with conduit diameter. Larger printed valves had greater shape fidelity (93.3±2.6, 85.1±2.0, and 73.3±5.2% for 22, 17, and 12 mm ID porcine valves; 89.1±4.0, 84.1±5.6, and 66.6±5.2% for simplified valves). PAVIC seeded scaffolds maintained near 100% viability over 21 days. These results demonstrate that 3D hydrogel printing with controlled photocrosslinking can rapidly fabricate anatomical heterogeneous valve conduits that support cell engraftment. PMID:22914604

A human pericardium biopolymeric scaffold for autologous heart valve tissue engineering: cellular and extracellular matrix structure and biomechanical properties in comparison with a normal aortic heart valve.

PubMed

Straka, Frantisek; Schornik, David; Masin, Jaroslav; Filova, Elena; Mirejovsky, Tomas; Burdikova, Zuzana; Svindrych, Zdenek; Chlup, Hynek; Horny, Lukas; Daniel, Matej; Machac, Jiri; Skibová, Jelena; Pirk, Jan; Bacakova, Lucie

2018-04-01

The objective of our study was to compare the cellular and extracellular matrix (ECM) structure and the biomechanical properties of human pericardium (HP) with the normal human aortic heart valve (NAV). HP tissues (from 12 patients) and NAV samples (from 5 patients) were harvested during heart surgery. The main cells in HP were pericardial interstitial cells, which are fibroblast-like cells of mesenchymal origin similar to the valvular interstitial cells in NAV tissue. The ECM of HP had a statistically significantly (p < 0.001) higher collagen I content, a lower collagen III and elastin content, and a similar glycosaminoglycans (GAGs) content, in comparison with the NAV, as measured by ECM integrated density. However, the relative thickness of the main load-bearing structures of the two tissues, the dense part of fibrous HP (49 ± 2%) and the lamina fibrosa of NAV (47 ± 4%), was similar. In both tissues, the secant elastic modulus (Es) was significantly lower in the transversal direction (p < 0.05) than in the longitudinal direction. This proved that both tissues were anisotropic. No statistically significant differences in UTS (ultimate tensile strength) values and in calculated bending stiffness values in the longitudinal or transversal direction were found between HP and NAV. Our study confirms that HP has an advantageous ECM biopolymeric structure and has the biomechanical properties required for a tissue from which an autologous heart valve replacement may be constructed.

Tissue-engineered lymphatic graft for the treatment of lymphedema

PubMed Central

Kanapathy, Muholan; Patel, Nikhil M.; Kalaskar, Deepak M.; Mosahebi, Afshin; Mehrara, Babak J.; Seifalian, Alexander M.

2015-01-01

Background Lymphedema is a chronic debilitating condition and curative treatment is yet to be found. Tissue engineering approach, which combines cellular components, scaffold, and molecular signals hold great potential in the treatment of secondary lymphedema with the advent of lymphatic graft to reconstruct damaged collecting lymphatic vessel. This review highlights the ideal characteristics of lymphatic graft, the limitation and challenges faced, and the approaches in developing tissue-engineered lymphatic graft. Methods Literature on tissue engineering of lymphatic system and lymphatic tissue biology was reviewed. Results The prime challenge in the design and manufacturing of this graft is producing endothelialized conduit with intraluminal valves. Suitable scaffold material is needed to ensure stability and functionality of the construct. Endothelialization of the construct can be enhanced via biofunctionalization and nanotopography, which mimics extracellular matrix. Nanocomposite polymers with improved performance over existing biomaterials are likely to benefit the development of lymphatic graft. Conclusions With the in-depth understanding of tissue engineering, nanotechnology, and improved knowledge on the biology of lymphatic regeneration, the aspiration to develop successful lymphatic graft is well achievable. PMID:25248852

Transcatheter aortic valve implantation using anatomically oriented, marrow stromal cell-based, stented, tissue-engineered heart valves: technical considerations and implications for translational cell-based heart valve concepts.

PubMed

Emmert, Maximilian Y; Weber, Benedikt; Behr, Luc; Sammut, Sebastien; Frauenfelder, Thomas; Wolint, Petra; Scherman, Jacques; Bettex, Dominique; Grünenfelder, Jürg; Falk, Volkmar; Hoerstrup, Simon P

2014-01-01

While transcatheter aortic valve implantation (TAVI) has rapidly evolved for the treatment of aortic valve disease, the currently used bioprostheses are prone to continuous calcific degeneration. Thus, autologous, cell-based, living, tissue-engineered heart valves (TEHVs) with regeneration potential have been suggested to overcome these limitations. We investigate the technical feasibility of combining the concept of TEHV with transapical implantation technology using a state-of-the-art transcatheter delivery system facilitating the exact anatomical position in the systemic circulation. Trileaflet TEHVs fabricated from biodegradable synthetic scaffolds were sewn onto self-expanding Nitinol stents seeded with autologous marrow stromal cells, crimped and transapically delivered into the orthotopic aortic valve position of adult sheep (n = 4) using the JenaValve transapical TAVI System (JenaValve, Munich, Germany). Delivery, positioning and functionality were assessed by angiography and echocardiography before the TEHV underwent post-mortem gross examination. For three-dimensional reconstruction of the stent position of the anatomically oriented system, a computed tomography analysis was performed post-mortem. Anatomically oriented, transapical delivery of marrow stromal cell-based TEHV into the orthotopic aortic valve position was successful in all animals (n = 4), with a duration from cell harvest to TEHV implantation of 101 ± 6 min. Fluoroscopy and echocardiography displayed sufficient positioning, thereby entirely excluding the native leaflets. There were no signs of coronary obstruction. All TEHV tolerated the loading pressure of the systemic circulation and no acute ruptures occurred. Animals displayed intact and mobile leaflets with an adequate functionality. The mean transvalvular gradient was 7.8 ± 0.9 mmHg, and the mean effective orifice area was 1.73 ± 0.02 cm(2). Paravalvular leakage was present in two animals, and central aortic regurgitation due to a single-leaflet prolapse was detected in two, which was primarily related to the leaflet design. No stent dislocation, migration or affection of the mitral valve was observed. For the first time, we demonstrate the technical feasibility of a transapical TEHV delivery into the aortic valve position using a commercially available and clinically applied transapical implantation system that allows for exact anatomical positioning. Our data indicate that the combination of TEHV and a state-of-the-art transapical delivery system is feasible, representing an important step towards translational, transcatheter-based TEHV concepts.

In-body tissue-engineered aortic valve (Biovalve type VII) architecture based on 3D printer molding.

PubMed

Nakayama, Yasuhide; Takewa, Yoshiaki; Sumikura, Hirohito; Yamanami, Masashi; Matsui, Yuichi; Oie, Tomonori; Kishimoto, Yuichiro; Arakawa, Mamoru; Ohmuma, Kentaro; Tajikawa, Tsutomu; Kanda, Keiichi; Tatsumi, Eisuke

2015-01-01

In-body tissue architecture--a novel and practical regeneration medicine technology--can be used to prepare a completely autologous heart valve, based on the shape of a mold. In this study, a three-dimensional (3D) printer was used to produce the molds. A 3D printer can easily reproduce the 3D-shape and size of native heart valves within several processing hours. For a tri-leaflet, valved conduit with a sinus of Valsalva (Biovalve type VII), the mold was assembled using two conduit parts and three sinus parts produced by the 3D printer. Biovalves were generated from completely autologous connective tissue, containing collagen and fibroblasts, within 2 months following the subcutaneous embedding of the molds (success rate, 27/30). In vitro evaluation, using a pulsatile circulation circuit, showed excellent valvular function with a durability of at least 10 days. Interposed between two expanded polytetrafluoroethylene grafts, the Biovalves (N = 3) were implanted in goats through an apico-aortic bypass procedure. Postoperative echocardiography showed smooth movement of the leaflets with minimal regurgitation under systemic circulation. After 1 month of implantation, smooth white leaflets were observed with minimal thrombus formation. Functional, autologous, 3D-shaped heart valves with clinical application potential were formed following in-body embedding of specially designed molds that were created within several hours by 3D printer. © 2014 Wiley Periodicals, Inc.

Engineering Complex Tissues

PubMed Central

MIKOS, ANTONIOS G.; HERRING, SUSAN W.; OCHAREON, PANNEE; ELISSEEFF, JENNIFER; LU, HELEN H.; KANDEL, RITA; SCHOEN, FREDERICK J.; TONER, MEHMET; MOONEY, DAVID; ATALA, ANTHONY; VAN DYKE, MARK E.; KAPLAN, DAVID; VUNJAK-NOVAKOVIC, GORDANA

2010-01-01

This article summarizes the views expressed at the third session of the workshop “Tissue Engineering—The Next Generation,” which was devoted to the engineering of complex tissue structures. Antonios Mikos described the engineering of complex oral and craniofacial tissues as a “guided interplay” between biomaterial scaffolds, growth factors, and local cell populations toward the restoration of the original architecture and function of complex tissues. Susan Herring, reviewing osteogenesis and vasculogenesis, explained that the vascular arrangement precedes and dictates the architecture of the new bone, and proposed that engineering of osseous tissues might benefit from preconstruction of an appropriate vasculature. Jennifer Elisseeff explored the formation of complex tissue structures based on the example of stratified cartilage engineered using stem cells and hydrogels. Helen Lu discussed engineering of tissue interfaces, a problem critical for biological fixation of tendons and ligaments, and the development of a new generation of fixation devices. Rita Kandel discussed the challenges related to the re-creation of the cartilage-bone interface, in the context of tissue engineered joint repair. Frederick Schoen emphasized, in the context of heart valve engineering, the need for including the requirements derived from “adult biology” of tissue remodeling and establishing reliable early predictors of success or failure of tissue engineered implants. Mehmet Toner presented a review of biopreservation techniques and stressed that a new breakthrough in this field may be necessary to meet all the needs of tissue engineering. David Mooney described systems providing temporal and spatial regulation of growth factor availability, which may find utility in virtually all tissue engineering and regeneration applications, including directed in vitro and in vivo vascularization of tissues. Anthony Atala offered a clinician’s perspective for functional tissue regeneration, and discussed new biomaterials that can be used to develop new regenerative technologies. PMID:17518671

Embryological origin of the endocardium and derived valve progenitor cells: from developmental biology to stem cell-based valve repair.

PubMed

Pucéat, Michel

2013-04-01

The cardiac valves are targets of both congenital and acquired diseases. The formation of valves during embryogenesis (i.e., valvulogenesis) originates from endocardial cells lining the myocardium. These cells undergo an endothelial-mesenchymal transition, proliferate and migrate within an extracellular matrix. This leads to the formation of bilateral cardiac cushions in both the atrioventricular canal and the outflow tract. The embryonic origin of both the endocardium and prospective valve cells is still elusive. Endocardial and myocardial lineages are segregated early during embryogenesis and such a cell fate decision can be recapitulated in vitro by embryonic stem cells (ESC). Besides genetically modified mice and ex vivo heart explants, ESCs provide a cellular model to study the early steps of valve development and might constitute a human therapeutic cell source for decellularized tissue-engineered valves. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction. Copyright © 2012 Elsevier B.V. All rights reserved.

State-of-the-Art Review of 3D Bioprinting for Cardiovascular Tissue Engineering.

PubMed

Duan, Bin

2017-01-01

3D bioprinting is a group of rapidly growing techniques that allows building engineered tissue constructs with complex and hierarchical structures, mechanical and biological heterogeneity. It enables implementation of various bioinks through different printing mechanisms and precise deposition of cell and/or biomolecule laden biomaterials in predefined locations. This review briefly summarizes applicable bioink materials and various bioprinting techniques, and presents the recent advances in bioprinting of cardiovascular tissues, with focusing on vascularized constructs, myocardium and heart valve conduits. Current challenges and further perspectives are also discussed to help guide the bioink and bioprinter development, improve bioprinting strategies and direct future organ bioprinting and translational applications.

30. Engine controls and valve gear, looking aft on main ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

30. Engine controls and valve gear, looking aft on main (promenade) deck level. Threaded admission valve lift rods (two at immediate left of chronometer) permit adjustment of valve timing in lower and upper admission valves of cylinder (left rod controls lower valve, right rod upper valve). Valve rods are lifted by jaw-like "wipers" during operation. Exhaust valve lift rods and wipers are located to right of chronometer. Crank at extreme right drives valve wiper shaft when engaged to end of eccentric rod, shown under "Crank Indicator" dial. Pair of handles to immediate left of admission valve rods control condenser water valves; handles to right of exhaust valve rods control feedwater flow to boilers from pumps. Gauges indicate boiler pressure (left) and condenser vacuum (right); "Crank Indicator" on wall aids engineer in keeping engine crank off "dead-center" at stop so that engine may be easily restarted. - Steamboat TICONDEROGA, Shelburne Museum Route 7, Shelburne, Chittenden County, VT

Application of stem cells for cardiovascular grafts tissue engineering.

PubMed

Wu, Kaihong; Liu, Ying Long; Cui, Bin; Han, Zhongchao

2006-06-01

Congenital and acquired heart diseases are leading causes of morbidity and mortality world-wide. Currently, the synthetic materials or bioprosthetic replacement devices for cardiovascular surgery are imperfect and subject patients to one or more ongoing risks including thrombosis, limited durability and need for reoperations due to lack of growth in children and young adults. Suitable replacement grafts should have appropriate characteristics, including resistance to infection, low immunogenicity, good biocompatability and thromboresistance, with appropriate mechanical and physiological properties. Tissue engineering is a new scientific field aiming at fabrication of living, autologous grafts having structure or function properties that can be used to restore, maintain or improve tissue function. The use of autologous stem cells in cardiovascular tissue engineering is quite promising due to their capacity of self-renewal, high proliferation, and differentiation into specialized progeny. Progress has been made in engineering the various components of the cardiovascular system, including myocardial constructs, heart valves, and vascular patches or conduits with autologous stem cells. This paper will review the current achievements in stem cell-based cardiovascular grafts tissue engineering, with an emphasis on its clinical or possible clinical use in cardiovascular surgery.

New Technologies for Surgery of the Congenital Cardiac Defect

PubMed Central

Kalfa, David; Bacha, Emile

2013-01-01

The surgical repair of complex congenital heart defects frequently requires additional tissue in various forms, such as patches, conduits, and valves. These devices often require replacement over a patient’s lifetime because of degeneration, calcification, or lack of growth. The main new technologies in congenital cardiac surgery aim at, on the one hand, avoiding such reoperations and, on the other hand, improving long-term outcomes of devices used to repair or replace diseased structural malformations. These technologies are: 1) new patches: CorMatrix® patches made of decellularized porcine small intestinal submucosa extracellular matrix; 2) new devices: the Melody® valve (for percutaneous pulmonary valve implantation) and tissue-engineered valved conduits (either decellularized scaffolds or polymeric scaffolds); and 3) new emerging fields, such as antenatal corrective cardiac surgery or robotically assisted congenital cardiac surgical procedures. These new technologies for structural malformation surgery are still in their infancy but certainly present great promise for the future. But the translation of these emerging technologies to routine health care and public health policy will also largely depend on economic considerations, value judgments, and political factors. PMID:23908869

The potential of prolonged tissue culture to reduce stress generation and retraction in engineered heart valve tissues.

PubMed

van Vlimmeren, Marijke A A; Driessen-Mol, Anita; Oomens, Cees W J; Baaijens, Frank P T

2013-03-01

In tissue-engineered (TE) heart valves, cell-mediated processes cause tissue compaction during culture and leaflet retraction at time of implantation. We have quantified and correlated stress generation, compaction, retraction, and tissue quality during a prolonged culture period of 8 weeks. Polyglycolic acid/poly-4-hydroxybutyrate strips were seeded with vascular-derived cells and cultured for 4-8 weeks. Compaction in width, generated force, and stress was measured during culture. Retraction in length, generated force, and stress was measured after release of constraints at weeks 4, 6, and 8. Further, the amount of DNA, glycosaminoglycans (GAGs), collagen, and collagen cross-links was assessed. During culture, compaction and force generation increased to, respectively, 63.9% ± 0.8% and 43.7 ± 4.3 mN at week 4, after which they remained stable. Stress generation reached 27.7 ± 3.2 kPa at week 4, after which it decreased to ∼8.5 kPa. At release of constraints, tissue retraction was 44.0% ± 3.7% at week 4 and decreased to 29.2% ± 2.8% and 26.1% ± 2.2% at, respectively, 6 and 8 weeks. Generated force (8-16 mN) was lower at week 6 than at weeks 4 and 8. Generated stress decreased from 11.8 ± 0.9 kPa at week 4 to 1.4 ± 0.3 and 2.4 ± 0.4 kPa at, respectively, weeks 6 and 8. The amount of GAGs increased at weeks 6 and 8 compared to week 4 and correlated to the reduced stress and retraction. In summary, prolonged culture resulted in decreased stress generation and retraction, likely as a result of the increased amount of GAGs. These results demonstrate the potential of prolonged tissue culture in developing functional, nonretracting, TE heart valves.

Angiogenesis and Tissue Engineering Research

DTIC Science & Technology

2010-08-01

grafts were stained with hematoxylin and eosin for general morphology, Masson trichrome stain for collagen organization, and von Geison for elastin...autologous semilunar heart valve. Circulation 111, 2783, 2005. 21. Sodian, R., Hoerstrup, S.P., Sperling , J.S., Daebritz, S., Mar- tin, D.P., Moran, A.M

Design considerations and challenges for mechanical stretch bioreactors in tissue engineering.

PubMed

Lei, Ying; Ferdous, Zannatul

2016-05-01

With the increase in average life expectancy and growing aging population, lack of functional grafts for replacement surgeries has become a severe problem. Engineered tissues are a promising alternative to this problem because they can mimic the physiological function of the native tissues and be cultured on demand. Cyclic stretch is important for developing many engineered tissues such as hearts, heart valves, muscles, and bones. Thus a variety of stretch bioreactors and corresponding scaffolds have been designed and tested to study the underlying mechanism of tissue formation and to optimize the mechanical conditions applied to the engineered tissues. In this review, we look at various designs of stretch bioreactors and common scaffolds and offer insights for future improvements in tissue engineering applications. First, we summarize the requirements and common configuration of stretch bioreactors. Next, we present the features of different actuating and motion transforming systems and their applications. Since most bioreactors must measure detailed distributions of loads and deformations on engineered tissues, techniques with high accuracy, precision, and frequency have been developed. We also cover the key points in designing culture chambers, nutrition exchanging systems, and regimens used for specific tissues. Since scaffolds are essential for providing biophysical microenvironments for residing cells, we discuss materials and technologies used in fabricating scaffolds to mimic anisotropic native tissues, including decellularized tissues, hydrogels, biocompatible polymers, electrospinning, and 3D bioprinting techniques. Finally, we present the potential future directions for improving stretch bioreactors and scaffolds. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:543-553, 2016. © 2016 American Institute of Chemical Engineers.

Double-reed exhaust valve engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Charles L.

An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a double reed outlet valve for controlling the flow of low-pressure working fluid out of the engine. The double reed provides a stronger force resisting closure of the outlet valve than the force tending to open the outlet valve. The double reed valve enables engine operation at relatively higher torque and lower efficiency at low speed, with lower torque, but higher efficiency at high speed.

Harmonic engine

DOEpatents

Bennett, Charles L.; Sewall, Noel; Boroa, Carl

2014-08-19

An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.

Magnesium Presence Prevents Removal of Antigenic Nuclear-Associated Proteins from Bovine Pericardium for Heart Valve Engineering.

PubMed

Dalgliesh, Ailsa J; Liu, Zhi Zhao; Griffiths, Leigh G

2017-07-01

Current heart valve prostheses are associated with significant complications, including aggressive immune response, limited valve life expectancy, and inability to grow in juvenile patients. Animal derived "tissue" valves undergo glutaraldehyde fixation to mask tissue antigenicity; however, chronic immunological responses and associated calcification still commonly occur. A heart valve formed from an unfixed bovine pericardium (BP) extracellular matrix (ECM) scaffold, in which antigenic burden has been eliminated or significantly reduced, has potential to overcome deficiencies of current bioprostheses. Decellularization and antigen removal methods frequently use sequential solutions extrapolated from analytical chemistry approaches to promote solubility and removal of tissue components from resultant ECM scaffolds. However, the extent to which such prefractionation strategies may inhibit removal of antigenic tissue components has not been explored. We hypothesize that presence of magnesium in prefractionation steps causes DNA precipitation and reduces removal of nuclear-associated antigenic proteins. Keeping all variables consistent bar the addition or absence of magnesium (2 mM magnesium chloride hexahydrate), residual BP ECM scaffold antigenicity and removed antigenicity were assessed, along with residual and removed DNA content, ECM morphology, scaffold composition, and recellularization potential. Furthermore, we used proteomic methods to determine the mechanism by which magnesium presence or absence affects scaffold residual antigenicity. This study demonstrates that absence of magnesium from antigen removal solutions enhances solubility and subsequent removal of antigenic nuclear-associated proteins from BP. We therefore conclude that the primary mechanism of action for magnesium removal during antigen removal processes is avoidance of DNA precipitation, facilitating solubilization and removal of nuclear-associated antigenic proteins. Future studies are necessary to further facilitate solubility and removal of nuclear-associated antigenic proteins from xenogeneic ECM scaffolds, in addition to an in vivo assessing of the material.

System and method for controlling hydraulic pressure in electro-hydraulic valve actuation systems

DOEpatents

Brennan, Daniel G; Marriott, Craig D; Cowgill, Joel; Wiles, Matthew A; Patton, Kenneth James

2014-09-23

A control system for an engine includes a first lift control module and a second lift control module. The first lift control module increases lift of M valves of the engine to a predetermined valve lift during a period before disabling or re-enabling N valves of the engine. The second lift control module decreases the lift of the M valves to a desired valve lift during a period after enabling or re-enabling the N valves of the engine, wherein N and M are integers greater than or equal to one.

Modification and performance evaluation of a mono-valve engine

NASA Astrophysics Data System (ADS)

Behrens, Justin W.

A four-stroke engine utilizing one tappet valve for both the intake and exhaust gas exchange processes has been built and evaluated. The engine operates under its own power, but has a reduced power capacity than the conventional 2-valve engine. The reduction in power is traced to higher than expected amounts of exhaust gases flowing back into the intake system. Design changes to the cylinder head will fix the back flow problems, but the future capacity of mono-valve engine technology cannot be estimated. The back flow of exhaust gases increases the exhaust gas recirculation (EGR) rate and deteriorates combustion. Intake pressure data shows the mono-valve engine requires an advanced intake valve closing (IVC) time to prevent back flow of charge air. A single actuation camshaft with advanced IVC was tested in the mono-valve engine, and was found to improve exhaust scavenging at TDC and nearly eliminated all charge air back flow at IVC. The optimum IVC timing is shown to be approximately 30 crank angle degrees after BDC. The mono-valve cylinder head utilizes a rotary valve positioned above the tappet valve. The open spaces inside the rotary valveand between the rotary valve and tappet valve represent a common volume that needs to be reduced in order to reduce the base EGR rate. Multiple rotary valve configurations were tested, and the size of the common volume was found to have no effect on back flow but a direct effect on the EGR rate and engine performance. The position of the rotary valve with respect to crank angle has a direct effect on the scavenging process. Optimum scavenging occurs when the intake port is opened just after TDC.

System and method for controlling engine knock using electro-hydraulic valve actuation

DOEpatents

Brennan, Daniel G

2013-12-10

A control system for an engine includes a knock control module and a valve control module. The knock control module adjusts a period that one or more of an intake valve and an exhaust valve of a cylinder are open based on engine knock corresponding to the cylinder. The valve control module, based on the adjusted period, controls the one or more of the intake valve and the exhaust valve using one or more hydraulic actuators.

Design and CFD analysis of intake port and exhaust port for a 4 valve cylinder head engine

NASA Astrophysics Data System (ADS)

Latheesh, V. M.; Parthasarathy, P.; Baskaran, V.; Karthikeyan, S.

2018-02-01

In cylinder air motion in a compression ignition engine effects mixing of air-fuel, quality of combustion and emission produced. The primary objective is to design and analyze intake and the exhaust port for a four valve cylinder head to meet higher emission norms for a given diesel engine with two valves. In this work, an existing cylinder head designed for two valves was redesigned with 4 valves. The modern trend also confirms this approach. This is being followed in the design and development of new generation engines to meet the stringent environment norms, competition in market and demand for more fuel-efficient engines. The swirl ratio and flow coefficient were measured for different valve lifts using STAR CCM+. CFD results were validated with the two-valve cylinder experimental results. After validation, a comparison between two-valve and four-valve cylinder head was done. The conversion of two valve cylinder head to 4 valves may not support modern high swirl generating port layout and requires a trade-off between many design parameters.

Dedicated EGR engine with dynamic load control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayman, Alan W.; McAlpine, Robert S.; Keating, Edward J.

An internal combustion engine comprises a first engine bank and a second engine bank. A first intake valve is disposed in an intake port of a cylinder of the first engine bank, and is configured for metering the first flow of combustion air by periodically opening and closing according to a first intake valve lift and duration characteristic. A variable valve train control mechanism is configured for affecting the first intake valve lift and duration characteristic. Either a lift or duration of the first intake valve is modulated so as to satisfy an EGR control criterion.

Simultaneously firing two cylinders of an even firing camless engine

DOEpatents

Brennan, Daniel G

2014-03-11

A valve control system includes an engine speed control module that determines an engine speed and a desired engine stop position. A piston position module determines a desired stopping position of a first piston based on the desired engine stop position. A valve control module receives the desired stopping position, commands a set of valves to close at the desired stopping position if the engine speed is less than a predetermined shutdown threshold, and commands the set of valves to reduce the engine speed if the engine speed is greater than the predetermined shutdown threshold.

Amniotic Fluid-Derived Stem Cells for Cardiovascular Tissue Engineering Applications

PubMed Central

Petsche Connell, Jennifer; Camci-Unal, Gulden; Khademhosseini, Ali

2013-01-01

Recent research has demonstrated that a population of stem cells can be isolated from amniotic fluid removed by amniocentesis that are broadly multipotent and nontumorogenic. These amniotic fluid-derived stem cells (AFSC) could potentially provide an autologous cell source for treatment of congenital defects identified during gestation, particularly cardiovascular defects. In this review, the various methods of isolating, sorting, and culturing AFSC are compared, along with techniques for inducing differentiation into cardiac myocytes and endothelial cells. Although research has not demonstrated complete and high-yield cardiac differentiation, AFSC have been shown to effectively differentiate into endothelial cells and can effectively support cardiac tissue. Additionally, several tissue engineering and regenerative therapeutic approaches for the use of these cells in heart patches, injection after myocardial infarction, heart valves, vascularized scaffolds, and blood vessels are summarized. These applications show great promise in the treatment of congenital cardiovascular defects, and further studies of isolation, culture, and differentiation of AFSC will help to develop their use for tissue engineering, regenerative medicine, and cardiovascular therapies. PMID:23350771

Reinforced chitosan-based heart valve scaffold and utility of bone marrow-derived mesenchymal stem cells for cardiovascular tissue engineering

NASA Astrophysics Data System (ADS)

Albanna, Mohammad Zaki

Recent research has demonstrated a strong correlation between the differentiation profile of mesenchymal stem cells (MSCs) and scaffold stiffness. Chitosan is being widely studied for tissue engineering applications due to its biocompatibility and biodegradability. However, its use in load-bearing applications is limited due to moderate to low mechanical properties. In this study, we investigated the effectiveness of a fiber reinforcement method for enhancing the mechanical properties of chitosan scaffolds. Chitosan fibers were fabricated using a solution extrusion and neutralization method and incorporated into porous chitosan scaffolds. The effects of different fiber/scaffold mass ratios, fiber mechanical properties and fiber lengths on scaffold mechanical properties were studied. The results showed that incorporating fibers improved scaffold strength and stiffness in proportion to the fiber/scaffold mass ratio. A fiber-reinforced heart valve leaflet scaffold achieved strength values comparable to the radial values of human pulmonary and aortic valves. Additionally, the effects of shorter fibers (2 mm) were found to be up to 3-fold greater than longer fibers (10 mm). Despite this reduction in fiber mechanical properties caused by heparin crosslinking, the heparin-modified fibers still improved the mechanical properties of the reinforced scaffolds, but to a lesser extent than the unmodified fibers. The results demonstrate that chitosan fiber-reinforcement can be used to generate tissue-matching mechanical properties in porous chitosan scaffolds and that fiber length and mechanical properties are important parameters in defining the degree of mechanical improvement. We further studied various chemical and physical treatments to improve the mechanical properties of chitosan fibers. With combination of chemical and physical treatments, fiber stiffness improved 40fold compared to unmodified fibers. We also isolated ovine bone marrow-derived MSCs and evaluated their utility for cardiovascular tissue engineering applications. Moreover, we evaluated the effect of various glycosaminoglycans (GAGs) on MSCs morphology and proliferation. Lastly, we studied the effect of stiffness of mechanically improved chitosan fibers on MSCs viability, attachment and proliferation. Results showed that MSCs proliferation improved in proportion to fiber stiffness.

Harmonic uniflow engine

DOEpatents

Bennett, Charles L.

2016-03-22

A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.

Effects of bileaflet mechanical heart valve orientation on coronary flow

NASA Astrophysics Data System (ADS)

Haya, Laura; Tavoularis, Stavros

2015-11-01

The aortic sinus is approximately tri-radially symmetric, but bileaflet mechanical heart valves (BMHVs), which are commonly used to replace diseased aortic valves, are bilaterally symmetric. This mismatch in symmetry suggests that the orientation in which a BMHV is implanted within the aortic sinus affects the flow characteristics downstream of it. This study examines the effect of BMHV orientation on the flow in the coronary arteries, which originate in the aortic sinus and supply the heart tissue with blood. Planar particle image velocimetry measurements were made past a BMHV mounted at the inlet of an anatomical aorta model under physiological flow conditions. The complex interactions between the valve jets, the sinus vortex and the flow in the right coronary artery were elucidated for three valve orientations. The coronary flow rate was directly affected by the size, orientation, and time evolution of the vortex in the sinus, all of which were sensitive to the valve's orientation. The total flow through the artery was highest when the valve was oriented with its axis of symmetry intersecting the artery's opening. The findings of this research may assist surgeons in choosing the best orientation for BMHV implantation. The bileaflet valve was donated by St. Jude Medical. Financial support was provided by the Natural Sciences and Engineering Research Council of Canada.

Polysaccharides as cell carriers for tissue engineering: the use of cellulose in vascular wall reconstruction.

PubMed

Bačáková, L; Novotná, K; Pařízek, M

2014-01-01

Polysaccharides are long carbohydrate molecules of monosaccharide units joined together by glycosidic bonds. These biological polymers have emerged as promising materials for tissue engineering due to their biocompatibility, mostly good availability and tailorable properties. This complex group of biomolecules can be classified using several criteria, such as chemical composition (homo- and heteropolysaccharides), structure (linear and branched), function in the organism (structural, storage and secreted polysaccharides), or source (animals, plants, microorganisms). Polysaccharides most widely used in tissue engineering include starch, cellulose, chitosan, pectins, alginate, agar, dextran, pullulan, gellan, xanthan and glycosaminoglycans. Polysaccharides have been applied for engineering and regeneration of practically all tissues, though mostly at the experimental level. Polysaccharides have been tested for engineering of blood vessels, myocardium, heart valves, bone, articular and tracheal cartilage, intervertebral discs, menisci, skin, liver, skeletal muscle, neural tissue, urinary bladder, and also for encapsulation and delivery of pancreatic islets and ovarian follicles. For these purposes, polysaccharides have been applied in various forms, such as injectable hydrogels or porous and fibrous scaffolds, and often in combination with other natural or synthetic polymers or inorganic nanoparticles. The immune response evoked by polysaccharides is usually mild, and can be reduced by purifying the material or by choosing appropriate crosslinking agents.

Flow interactions with cells and tissues: cardiovascular flows and fluid-structure interactions. Sixth International Bio-Fluid Mechanics Symposium and Workshop, March 28-30, 2008, Pasadena, California.

PubMed

Friedman, Morton H; Krams, Rob; Chandran, Krishnan B

2010-03-01

Interactions between flow and biological cells and tissues are intrinsic to the circulatory, respiratory, digestive and genitourinary systems. In the circulatory system, an understanding of the complex interaction between the arterial wall (a living multi-component organ with anisotropic, nonlinear material properties) and blood (a shear-thinning fluid with 45% by volume consisting of red blood cells, platelets, and white blood cells) is vital to our understanding of the physiology of the human circulation and the etiology and development of arterial diseases, and to the design and development of prosthetic implants and tissue-engineered substitutes. Similarly, an understanding of the complex dynamics of flow past native human heart valves and the effect of that flow on the valvular tissue is necessary to elucidate the etiology of valvular diseases and in the design and development of valve replacements. In this paper we address the influence of biomechanical factors on the arterial circulation. The first part presents our current understanding of the impact of blood flow on the arterial wall at the cellular level and the relationship between flow-induced stresses and the etiology of atherosclerosis. The second part describes recent advances in the application of fluid-structure interaction analysis to arterial flows and the dynamics of heart valves.

Platelet-lysate as an autologous alternative for fetal bovine serum in cardiovascular tissue engineering.

PubMed

Riem Vis, Paul W; Bouten, Carlijn V C; Sluijter, Joost P G; Pasterkamp, Gerard; van Herwerden, Lex A; Kluin, Jolanda

2010-04-01

There is an ongoing search for alternative tissue culture sera to engineer autologous tissues, since use of fetal bovine serum (FBS) is limited under Good Tissue Practice guidelines. We compared FBS with human platelet-lysate (PL) in media for in vitro cell culture. A threefold increase in duplication rate was found when human, saphenous vein-derived myofibroblasts were cultured in PL, whereas expression of marker proteins (alpha-smooth muscle actin, vimentin, desmin, and nonmuscle myosin heavy chain) was similar. Heat shock protein 47 mRNA expression was increased in PL cells, and type III collagen fibers were seen on PL-cell monolayers but not on cells cultured in FBS. These results imply a more efficient collagen fiber production. We also found higher levels of proteins involved in tissue repair and collagen remodeling, which could explain increased production of proteases and protease inhibitors by PL cells. Our findings indicate that PL is beneficial due to the increased duplication rate, in addition to the increased matrix production and remodeling. This could lead to production of strong tissue with properly organized collagen fibers, which is important for heart valve tissue engineering.

A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers.

PubMed

Stasiak, Joanna; Brubert, Jacob; Serrani, Marta; Nair, Sukumaran; de Gaetano, Francesco; Costantino, Maria Laura; Moggridge, Geoff D

2014-08-28

It is well known that block copolymers with cylindrical morphology show alignment with shear, resulting in anisotropic mechanical properties. Here we show that well-ordered bi-directional orientation can be achieved in such materials by slow injection moulding. This results in a microstructure, and anisotropic mechanical properties, similar to many natural tissues, making this method attractive for engineering prosthetic fibrous tissues. An application of particular interest to us is prosthetic polymeric heart valve leaflets, mimicking the shape, microstructure and hence performance of the native valve. Anisotropic layers have been observed for cylinder-forming block copolymers centrally injected into thin circular discs. The skin layers exhibit orientation parallel to the flow direction, whilst the core layer shows perpendicularly oriented domains; the balance of skin to core layers can be controlled by processing parameters such as temperature and injection rate. Heart valve leaflets with a similar layered structure have been prepared by injection moulding. Numerical modelling demonstrates that such complex orientation can be explained and predicted by the balance of shear and extensional flow.

Internal combustion engine and method for control

DOEpatents

Brennan, Daniel G

2013-05-21

In one exemplary embodiment of the invention an internal combustion engine includes a piston disposed in a cylinder, a valve configured to control flow of air into the cylinder and an actuator coupled to the valve to control a position of the valve. The internal combustion engine also includes a controller coupled to the actuator, wherein the controller is configured to close the valve when an uncontrolled condition for the internal engine is determined.

The two-stroke poppet valve engine. Part 2: Numerical investigations of intake and exhaust flow behaviour

NASA Astrophysics Data System (ADS)

Kamili Zahidi, M.; Razali Hanipah, M.

2017-10-01

A two-stroke poppet valve engine is developed to overcome the common problems in conventional two-stroke engine designs. However, replacing piston control port with poppet valve will resulted different flow behaviour. This paper presents the model and simulation result of three-dimensional (3D) port flow investigation of a two-stroke poppet valve engine. The objective of the investigation is to conduct a numerical investigation on port flow performance of two-stroke poppet valve engine and compare the results obtained from the experimental investigation. The model is to be used for the future numerical study of the engine. The volume flow rate results have been compared with the results obtained experimentally as presented in first part of this paper. The model has shown good agreement in terms of the flow rate at initial and final valve lifts but reduced by about 50% during half-lift region.

Application of several variable-valve-timing concepts to an LHR engine

NASA Technical Reports Server (NTRS)

Morel, T.; Keribar, R.; Sawlivala, M.; Hakim, N.

1987-01-01

The paper discusses advantages provided by electronically controlled hydraulically activated valves (ECVs) when applied to low heat rejection (LHR) engines. The ECV concept provides additional engine control flexibility by allowing for a variable valve timing as a function of speed and load, or for a given transient condition. The results of a study carried out to assess the benefits that this flexibility can offer to an LHR engine indicated that, when judged on the benefits to BSFC, volumetric efficiency, and peak firing pressure, ECVs would provide only modest benefits in comparison to conventional valve profiles. It is noted, however, that once installed on the engine, the ECVs would permit a whole range of certain more sophisticated variable valve timing strategies not otherwise possible, such as high compression cranking, engine braking, cylinder cutouts, and volumetric efficiency timing with engine speed.

Engine control system having pressure-based timing

DOEpatents

Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL

2011-10-04

A control system for an engine having a first cylinder and a second cylinder is disclosed having a first engine valve movable to regulate a fluid flow of the first cylinder and a first actuator associated with the first engine valve. The control system also has a second engine valve movable to regulate a fluid flow of the second cylinder and a sensor configured to generate a signal indicative of a pressure within the first cylinder. The control system also has a controller that is in communication with the first actuator and the sensor. The controller is configured to compare the pressure within the first cylinder with a desired pressure and selectively regulate the first actuator to adjust a timing of the first engine valve independently of the timing of the second engine valve based on the comparison.

Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple

NASA Technical Reports Server (NTRS)

Sanders, J. C.; Wilsted, H. D.; Mulcahy, B. A.

1943-01-01

A thermocouple was installed in the crown of a sodium-cooled exhaust valve. The valve was then tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 F was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 rpm. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

PubMed Central

Schipke, Kimberly J.; Filip To, S. D.; Warnock, James N.

2011-01-01

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment. PMID:21876532

Design of a cyclic pressure bioreactor for the ex vivo study of aortic heart valves.

PubMed

Schipke, Kimberly J; To, S D Filip; Warnock, James N

2011-08-23

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage(1-3). Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease(4). The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve(5). Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves(6-9). Pulsatile bioreactors have also been developed to study a range of tissues including cartilage(10), bone(11) and bladder(12). The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Experimental study of physical properties of artificial materials for the development of the tissue-engineered valvular heart apparatus in comparison with biological analogs

NASA Astrophysics Data System (ADS)

Chiryatyeva, Aleksandra; Trebushat, Dmitry; Prokhorokhin, Aleksei; Khakhalkin, Vladimir; Andreev, Mark; Novokhreschenov, Aleksei; Kretov, Evgeny

2017-12-01

Cardiovascular diseases are the leading cause of death worldwide. Valvular heart disease often requires valve repair or replacement. Today, surgery uses xenograft—porcine or bovine pericardium. However, bioprosthetic valves do not ensure sufficient durability. We investigated 0.6% glutaraldehyde-treated porcine pericardium to define its properties. Using a tensile test stand, we studied characteristics of the polymeric material—expanded polytetrafluoroethylene (ePTFE)—and compared it to xenopericardium. The artificial material provides a better durability; it has higher elastic modulus and ultimate tensile strength. However, ePTFE samples demonstrated direction anisotropy due to extrusion features. It requires the enhancement of quality of the ePTFE sheet or investigation of other polymeric materials to find the adequate replacement for bioprosthetic heart valves.

Heart valves from polyester fibers: a preliminary 6-month in vivo study.

PubMed

Vaesken, Antoine; Pelle, Anne; Pavon-Djavid, Graciela; Rancic, Jeanne; Chakfe, Nabil; Heim, Frederic

2018-06-27

Transcatheter aortic valve implantation (TAVI) has become a popular alternative technique to surgical valve replacement for critical patients. Biological valve tissue has been used in TAVI procedures for over a decade, with over 150,000 implantations to date. However, with only 6 years of follow up, little is known about the long-term durability of biological tissue. Moreover, the high cost of tissue harvesting and chemical treatment procedures favor the development of alternative synthetic valve leaflet materials. In that context, textile polyester [polyethylene terephthalate (PET)] could be considered as an interesting candidate to replace the biological valve leaflets in TAVI procedures. However, no result is available in the literature about the behavior of textile once in contact with biological tissue in the valve position. The interaction of synthetic textile material with living tissues should be comparable to biological tissue. The purpose of this preliminary work is to compare the in vivo performances of various woven textile PET valves over a 6-month period in order to identify favorable textile construction features. In vivo results indicate that fibrosis as well as calcium deposit can be limited with an appropriate material design.

Space Shuttle Orbital Maneuvering Subsystem (OMS) Engine Propellant Leakage Ball-Valve Shaft Seals

NASA Technical Reports Server (NTRS)

Lueders, Kathy; Buntain, Nick; Fries, Joseph (Technical Monitor)

1999-01-01

Evidence of propellant leakage across ball-valve shaft seals has been noted during the disassembly of five flight engines and one test engine at the NASA Lyndon B. Johnson Space Center, White Sands Test Facility. Based on data collected during the disassembly of these five engines, the consequences of propellant leakage across the ball-valve shaft seals can be divided into four primary areas of concern: Damage to the ball-valve pinion shafts, damage to sleeved bearings inside the ball-valve and actuator assemblies, degradation of the synthetic rubber o-rings used in the actuator assemblies, and corrosion and degradation to the interior of the actuator assemblies. The exact time at which leakage across the ball-valve shaft seals occurs has not been determined, however, the leakage most likely occurs during engine firings when, depending on the specification used, ball-valve cavity pressures range as high as 453 to 550 psia. This potential pressure range for the ball-valve cavities greatly exceeds the acceptance leakage test pressure of 332 psia. Since redesign and replacement of the ball-valve shaft seals is unlikely, the near term solution to prevent damage that occurs from shaft-seal leakage is to implement a routine overhaul and maintenance program for engines in the fleet. Recommended repair, verification, and possible preventative maintenance measures are discussed in the paper.

Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple

NASA Technical Reports Server (NTRS)

Sanders, J C; Wilsted, H D; Mulcahy, B A

1943-01-01

Report presents the results of a thermocouple installed in the crown of a sodium-cooled exhaust valve. The valve was tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 degrees F. was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 r.p.m. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear-spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve.

Hydraulically actuated gas exchange valve assembly and engine using same

DOEpatents

Carroll, Thomas S.; Taylor, Gregory O.

2002-09-03

An engine comprises a housing that defines a hollow piston cavity that is separated from a gas passage by a valve seat. The housing further defines a biasing hydraulic cavity and a control hydraulic cavity. A gas valve member is also included in the engine and is movable relative to the valve seat between an open position at which the hollow piston cavity is open to the gas passage and a closed position in which the hollow piston cavity is blocked from the gas passage. The gas valve member includes a ring mounted on a valve piece and a retainer positioned between the ring and the valve piece. A closing hydraulic surface is included on the gas valve member and is exposed to liquid pressure in the biasing hydraulic cavity.

Engine Valve Actuation For Combustion Enhancement

DOEpatents

Reitz, Rolf Deneys; Rutland, Christopher J.; Jhavar, Rahul

2004-05-18

A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-stroke combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

Engine valve actuation for combustion enhancement

DOEpatents

Reitz, Rolf Deneys [Madison, WI; Rutland, Christopher J [Madison, WI; Jhavar, Rahul [Madison, WI

2008-03-04

A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-strokes combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

Two phase exhaust for internal combustion engine

DOEpatents

Vuk, Carl T [Denver, IA

2011-11-29

An internal combustion engine having a reciprocating multi cylinder internal combustion engine with multiple valves. At least a pair of exhaust valves are provided and each supply a separate power extraction device. The first exhaust valves connect to a power turbine used to provide additional power to the engine either mechanically or electrically. The flow path from these exhaust valves is smaller in area and volume than a second flow path which is used to deliver products of combustion to a turbocharger turbine. The timing of the exhaust valve events is controlled to produce a higher grade of energy to the power turbine and enhance the ability to extract power from the combustion process.

Liquid rocket valve assemblies

NASA Technical Reports Server (NTRS)

1973-01-01

The design and operating characteristics of valve assemblies used in liquid propellant rocket engines are discussed. The subjects considered are as follows: (1) valve selection parameters, (2) major design aspects, (3) design integration of valve subassemblies, and (4) assembly of components and functional tests. Information is provided on engine, stage, and spacecraft checkout procedures.

Two-tank working gas storage system for heat engine

DOEpatents

Hindes, Clyde J.

1987-01-01

A two-tank working gas supply and pump-down system is coupled to a hot gas engine, such as a Stirling engine. The system has a power control valve for admitting the working gas to the engine when increased power is needed, and for releasing the working gas from the engine when engine power is to be decreased. A compressor pumps the working gas that is released from the engine. Two storage vessels or tanks are provided, one for storing the working gas at a modest pressure (i.e., half maximum pressure), and another for storing the working gas at a higher pressure (i.e., about full engine pressure). Solenoid valves are associated with the gas line to each of the storage vessels, and are selectively actuated to couple the vessels one at a time to the compressor during pumpdown to fill the high-pressure vessel with working gas at high pressure and then to fill the low-pressure vessel with the gas at low pressure. When more power is needed, the solenoid valves first supply the low-pressure gas from the low-pressure vessel to the engine and then supply the high-pressure gas from the high-pressure vessel. The solenoid valves each act as a check-valve when unactuated, and as an open valve when actuated.

The Effect of Valve Cooling upon Maximum Permissible Engine Output as Limited by Knock

NASA Technical Reports Server (NTRS)

Munger, Maurice; Wilsted, H D; Mulcahy, B A

1942-01-01

A Wright GR-1820-G200 cylinder was tested over a wide range of fuel-air ratios at maximum permissible power output as limited by knock with three different degrees of valve cooling. The valves used were stock valves (solid inlet valve and hollow sodium-cooled exhaust valve), hollow valves with no coolant, and hollow valves with flowing water as a coolant. Curves showing the variation in maximum permissible values of inlet-air pressure, indicated mean effective pressure, cylinder charge, and indicated specific fuel consumption with change in fuel-air ratio and valve cooling are shown. The use of valves cooled by a stream of water passing through their hollow interiors permitted indicated mean effective pressures 10 percent higher than the mean effective pressures permissible with stock valves when the engine was operated with fuel-air ratios from 0.055 to 0.065. Operation of the engine with lean mixtures with uncooled hollow valves resulted in power output below the output obtained with the stock valves. The data show an increase in maximum permissible indicated mean effective pressure due to cooling the valves, which averages only 2.1 percent with fuel-air ratios from 0.075 to 0.105.

The two-stroke poppet valve engine. Part 1: Intake and exhaust ports flow experimental assessments

NASA Astrophysics Data System (ADS)

Kamili Zahidi, M.; Razali Hanipah, M.; Ramasamy, D.; Noor, M. M.; Kadirgama, K.; Rahman, M. M.

2017-10-01

A two-stroke poppet valve engine is developed to overcome the common problems in conventional two-stroke engine designs. However, replacing piston control port with poppet valve will resulted different flow behaviour. This paper is looking at experimental assessment on a two-stroke poppet valve engine configuration to investigate the port flow performance. The aims are to evaluate the intake and exhaust coefficient of discharge and assess the twostroke capability of the cylinder head. The results has shown comparable coefficient of discharge values as production engine for the intake while the exhaust has higher values which is favourable for the two-stroke cycle operation.

CD133 antibody conjugation to decellularized human heart valves intended for circulating cell capture.

PubMed

Vossler, John D; Min Ju, Young; Williams, J Koudy; Goldstein, Steven; Hamlin, James; Lee, Sang Jin; Yoo, James J; Atala, Anthony

2015-09-03

The long term efficacy of tissue based heart valve grafts may be limited by progressive degeneration characterized by immune mediated inflammation and calcification. To avoid this degeneration, decellularized heart valves with functionalized surfaces capable of rapid in vivo endothelialization have been developed. The aim of this study is to examine the capacity of CD133 antibody-conjugated valve tissue to capture circulating endothelial progenitor cells (EPCs). Decellularized human pulmonary valve tissue was conjugated with CD133 antibody at varying concentrations and exposed to CD133 expressing NTERA-2 cl.D1 (NT2) cells in a microflow chamber. The amount of CD133 antibody conjugated on the valve tissue surface and the number of NT2 cells captured in the presence of shear stress was measured. Both the amount of CD133 antibody conjugated to the valve leaflet surface and the number of adherent NT2 cells increased as the concentration of CD133 antibody present in the surface immobilization procedure increased. The data presented in this study support the hypothesis that the rate of CD133(+) cell adhesion in the presence of shear stress to decellularized heart valve tissue functionalized by CD133 antibody conjugation increases as the quantity of CD133 antibody conjugated to the tissue surface increases.

Monovalve with integrated fuel injector and port control valve, and engine using same

DOEpatents

Milam, David M.

2001-11-06

An engine includes an engine casing that defines a hollow piston cavity separated from an exhaust passage and an intake passage by a valve seat. A gas exchange valve member is positioned adjacent the valve seat and is moveable between an open position and a closed position. The gas exchange valve member also defines an opening that opens into the hollow piston cavity. A needle valve member is positioned in the gas exchange valve member adjacent a nozzle outlet and is moveable between an inject position and a blocked position. A port control valve member, which has a hydraulic surface, is mounted around the gas exchange valve member and moveable between an intake position and an exhaust position. A pilot valve is moveable between a first position at which the port control hydraulic surface is exposed to a source of high pressure fluid, and a second position at which the port control hydraulic surface is exposed to a source of low pressure fluid.

Dynamic control of a homogeneous charge compression ignition engine

DOEpatents

Duffy, Kevin P [Metamora, IL; Mehresh, Parag [Peoria, IL; Schuh, David [Peoria, IL; Kieser, Andrew J [Morton, IL; Hergart, Carl-Anders [Peoria, IL; Hardy, William L [Peoria, IL; Rodman, Anthony [Chillicothe, IL; Liechty, Michael P [Chillicothe, IL

2008-06-03

A homogenous charge compression ignition engine is operated by compressing a charge mixture of air, exhaust and fuel in a combustion chamber to an autoignition condition of the fuel. The engine may facilitate a transition from a first combination of speed and load to a second combination of speed and load by changing the charge mixture and compression ratio. This may be accomplished in a consecutive engine cycle by adjusting both a fuel injector control signal and a variable valve control signal away from a nominal variable valve control signal. Thereafter in one or more subsequent engine cycles, more sluggish adjustments are made to at least one of a geometric compression ratio control signal and an exhaust gas recirculation control signal to allow the variable valve control signal to be readjusted back toward its nominal variable valve control signal setting. By readjusting the variable valve control signal back toward its nominal setting, the engine will be ready for another transition to a new combination of engine speed and load.

Investigation of the effect of different carbon film thickness on the exhaust valve

NASA Astrophysics Data System (ADS)

Karamangil, M. I.; Avci, A.; Bilal, H.

2008-03-01

Valves working under different loads and temperatures are the mostly forced engine elements. In an internal combustion engine, pressures and temperatures affecting on the valves vary with fuel type and the combustion characteristics of the fuel. Consequently, valves are exposed to different dynamic and thermal stress. In this study, stress distributions and temperature profiles on exhaust valve are obtained depending on different carbon film thickness. It is concluded that heat losses and valve temperatures decrease and valve surfaces are exposed to less thermal shocks with increasing carbon film thickness.

Fault Study of Valve Based on Test Analysis and Comparison

NASA Astrophysics Data System (ADS)

Cheng, Li; Yang, Wukui; Liang, Tao; Xu, Yu; Chen, Chao

2017-10-01

The valve of a certain type of small engine often has the fault phenomenon of abnormal vibration noise and can’t close under the specified pressure, which may cause the engine automatic stop because of valve incomplete close leading to fuel leakage during test and startup on the bench. By test study compared to imported valve with the same use function and test condition valve, and put forward the thinking of improving valve structure, compared no-improved valve to improved valve by adopting Fluent field simulation software. As a result, improved valve can restore close pressure of valve, restrain abnormal vibration noise phenomenon, and effectively compensate compression value of spring because of steel ball contacting position downward with valve casing.

Engine control system having speed-based timing

DOEpatents

Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL

2012-02-14

A control system for an engine having a cylinder is disclosed having an engine valve movable to regulate a fluid flow of the cylinder and an actuator associated with the engine valve. The control system also has a controller in communication with the actuator. The controller is configured to receive a signal indicative of engine speed and compare the engine speed signal with a desired engine speed. The controller is also configured to selectively regulate the actuator to adjust a timing of the engine valve to control an amount of air/fuel mixture delivered to the cylinder based on the comparison.

Understanding the requirements of self-expandable stents for heart valve replacement: Radial force, hoop force and equilibrium.

PubMed

Cabrera, María Sol; Oomens, Cees W J; Baaijens, Frank P T

2017-04-01

A proper interpretation of the forces developed during stent crimping and deployment is of paramount importance for a better understanding of the requirements for successful heart valve replacement. The present study combines experimental and computational methods to assess the performance of a nitinol stent for tissue-engineered heart valve implantation. To validate the stent model, the mechanical response to parallel plate compression and radial crimping was evaluated experimentally. Finite element simulations showed good agreement with the experimental findings. The computational models were further used to determine the hoop force on the stent and radial force on a rigid tool during crimping and self-expansion. In addition, stent deployment against ovine and human pulmonary arteries was simulated to determine the hoop force on the stent-artery system and the equilibrium diameter for different degrees of oversizing. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Preliminary engineering study: Quick opening valve MSFC high Reynolds number wind tunnel

NASA Technical Reports Server (NTRS)

1983-01-01

FluiDyne Engineering Corporation has conducted a preliminary engineering study of a quick-opening valve for the MSFC High Reynolds Number Wind Tunnel under NASA Contract NAS8-35056. The subject valve is intended to replace the Mylar diaphragm system as the flow initiation device for the tunnel. Only valves capable of opening within 0.05 sec. and providing a minimum of 11.4 square feet of flow area were considered. Also, the study focused on valves which combined the quick-opening and tight shutoff features in a single unit. A ring sleeve valve concept was chosen for refinement and pricing. Sealing for tight shutoff, ring sleeve closure release and sleeve actuation were considered. The resulting cost estimate includes the valve and requisite modifications to the facility to accommodate the valve as well as the associated design and development work.

Development of a novel passive top-down uniflow scavenged two-stroke GDI engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciccarelli, G.; Reynolds, Steve; Oliver, Phillip

2010-02-15

The design and performance characteristics of a novel top-down uniflow scavenged gasoline direct-injection two-stroke engine are presented. The novelty of the engine lies in the cylinder head that contains multiple check valves that control scavenging airflow into the cylinder from a supercharged air plenum. When the cylinder pressure drops below the intake plenum pressure during the expansion stroke, air flows into the cylinder through the check valves. During compression the cylinder pressure increases to a level above the intake plenum pressure and the check valves close preventing back-flow into the intake plenum. The engine head design provides asymmetrical intake valvemore » timing without the use of poppet valves and the associated valve-train. In combination with an external Roots-type supercharger that supplies the plenum and exhaust ports at the bottom of the cylinder wall, the novel head provides top-down uniflow air scavenging. Motoring tests indicated that the check valves seal and the peak pressure is governed by the compression ratio. The only drawback observed is that valve closing is delayed as the engine speed increases. In order to investigate the valve dynamics, additional tests were performed in an optically-accessible cold flow test rig that enabled the direct measurement of valve opening and closing time under various conditions. (author)« less

The automotive application of discontinuously reinforced TiB-Ti composites

NASA Astrophysics Data System (ADS)

Saito, Takashi

2004-05-01

In 1998, Toyota Motor Corporation adopted intake valves and exhaust valves made of titanium-based alloys for the engine of its Altezza. Both valves were manufactured via a newly developed cost-effective powder metallurgy process. The exhaust valve is made of a newly developed titanium metal-matrix composite (MMC). The valve has achieved sufficient durability and reliability with a manufacturing cost acceptable for the mass-produced automobile engine components.

Valve assembly for internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakeman, R.J.; Shea, S.F.

1989-09-05

This patent describes an improvement in a valve assembly for an internal combustion engine of the type including a valve having a valve stem, a valve guideway for mounting this valve for reciprocal strokes between opened and seated position, and spring means for biasing the valve into the seated position. The improvement comprising a valve spool of greater cross-sectional diameter as compared to the valve stem, and a valve spool guideway within which the valve spool is movable during the strokes of the valve, an upper surface of the valve spool and a portion of the spool guideway collectively establishingmore » a damper chamber which varies in volume during the valve strokes. a feed passage for introducing oil into the damper chamber, and a bleed passage for discharging oil from the damper chamber. The bleed passages each laterally opening into the valve spool guideway.« less

Hydraulic engine valve actuation system including independent feedback control

DOEpatents

Marriott, Craig D

2013-06-04

A hydraulic valve actuation assembly may include a housing, a piston, a supply control valve, a closing control valve, and an opening control valve. The housing may define a first fluid chamber, a second fluid chamber, and a third fluid chamber. The piston may be axially secured to an engine valve and located within the first, second and third fluid chambers. The supply control valve may control a hydraulic fluid supply to the piston. The closing control valve may be located between the supply control valve and the second fluid chamber and may control fluid flow from the second fluid chamber to the supply control valve. The opening control valve may be located between the supply control valve and the second fluid chamber and may control fluid flow from the supply control valve to the second fluid chamber.

The future of heart valve banking and of homografts: perspective from the Deutsches Herzzentrum Berlin.

PubMed

Delmo Walter, E M; de By, T M M H; Meyer, R; Hetzer, R

2012-01-01

Ever since the early days of homograft implantation in 1956, and the introduction into clinical practice by Ross and Barrat Boyes, homograft heart valves have proven to have many advantages. Its disadvantages became evident during long-term follow up. Factors, such as donor and recipient morbidity, tissue banking techniques, and the often complex surgical technique required to implant, are of great influence on the long term results. Because of European Directives, legally binding quality assurance regulations have been introduced in homograft banks. However, still not all processing methods have been scientifically sub-structured on their effects on the final product and its durability. The donor shortage has stimulated researchers and industries to develop and improve mechanical and biological valve substitutes such as the stentless bioprostheses. In general, candidates for homograft valve implantation include patients with: endocarditis, congenital defects and women who wish to become pregnant. For each category of patients different implantation techniques are required. The results of homograft banking and homograft transplantation in the German Heart Institute Berlin are satisfactory. Freedom of re-infection rate after homograft implantation is 91.9% +/- 3.6% after 15 years. Current developments show an increased interest in tissue engineered as well as in de- and re-cellularization of heart valve homografts. The advantages and disadvantages of the several processing techniques have not yet been proven in long term clinical results. For homograft bankers these developments pose as a challenge to join forces and to initiate cooperate projects aimed at scientific and organizational development.

Tissue and Organ 3D Bioprinting.

PubMed

Xia, Zengmin; Jin, Sha; Ye, Kaiming

2018-02-01

Three-dimensional (3D) bioprinting enables the creation of tissue constructs with heterogeneous compositions and complex architectures. It was initially used for preparing scaffolds for bone tissue engineering. It has recently been adopted to create living tissues, such as cartilage, skin, and heart valve. To facilitate vascularization, hollow channels have been created in the hydrogels by 3D bioprinting. This review discusses the state of the art of the technology, along with a broad range of biomaterials used for 3D bioprinting. It provides an update on recent developments in bioprinting and its applications. 3D bioprinting has profound impacts on biomedical research and industry. It offers a new way to industrialize tissue biofabrication. It has great potential for regenerating tissues and organs to overcome the shortage of organ transplantation.

Integrated hydraulic cooler and return rail in camless cylinder head

DOEpatents

Marriott, Craig D [Clawson, MI; Neal, Timothy L [Ortonville, MI; Swain, Jeff L [Flushing, MI; Raimao, Miguel A [Colorado Springs, CO

2011-12-13

An engine assembly may include a cylinder head defining an engine coolant reservoir, a pressurized fluid supply, a valve actuation assembly, and a hydraulic fluid reservoir. The valve actuation assembly may be in fluid communication with the pressurized fluid supply and may include a valve member displaceable by a force applied by the pressurized fluid supply. The hydraulic fluid reservoir may be in fluid communication with the valve actuation assembly and in a heat exchange relation to the engine coolant reservoir.

Rheumatic Heart Disease and Myxomatous Degeneration: Differences and Similarities of Valve Damage Resulting from Autoimmune Reactions and Matrix Disorganization.

PubMed

Martins, Carlo de Oliveira; Demarchi, Lea; Ferreira, Frederico Moraes; Pomerantzeff, Pablo Maria Alberto; Brandao, Carlos; Sampaio, Roney Orismar; Spina, Guilherme Sobreira; Kalil, Jorge; Cunha-Neto, Edecio; Guilherme, Luiza

2017-01-01

Autoimmune inflammatory reactions leading to rheumatic fever (RF) and rheumatic heart disease (RHD) result from untreated Streptococcus pyogenes throat infections in individuals who exhibit genetic susceptibility. Immune effector mechanisms have been described that lead to heart tissue damage culminating in mitral and aortic valve dysfunctions. In myxomatous valve degeneration (MXD), the mitral valve is also damaged due to non-inflammatory mechanisms. Both diseases are characterized by structural valve disarray and a previous proteomic analysis of them has disclosed a distinct profile of matrix/structural proteins differentially expressed. Given their relevance in organizing valve tissue, we quantitatively evaluated the expression of vimentin, collagen VI, lumican, and vitronectin as well as performed immunohistochemical analysis of their distribution in valve tissue lesions of patients in both diseases. We identified abundant expression of two isoforms of vimentin (45 kDa, 42 kDa) with reduced expression of the full-size protein (54 kDa) in RHD valves. We also found increased vitronectin expression, reduced collagen VI expression and similar lumican expression between RHD and MXD valves. Immunohistochemical analysis indicated disrupted patterns of these proteins in myxomatous degeneration valves and disorganized distribution in rheumatic heart disease valves that correlated with clinical manifestations such as valve regurgitation or stenosis. Confocal microscopy analysis revealed a diverse pattern of distribution of collagen VI and lumican into RHD and MXD valves. Altogether, these results demonstrated distinct patterns of altered valve expression and tissue distribution/organization of structural/matrix proteins that play important pathophysiological roles in both valve diseases.

Constitutive modeling of jugular vein-derived venous valve leaflet tissues.

PubMed

Kaul, Nayyan; Huang, Hsiao-Ying Shadow

2017-11-01

Venous valve tissues, though used in vein reconstruction surgeries and bioprosthetic valves with moderate success, have not been extensively studied with respect to their structure. Their inherent anisotropic, non-linear behavior combined with severe diseases which affect veins, such as chronic venous insufficiency, warrant understanding the structure and material behavior of these tissues. Hence, before any bioprosthetic grafts may be used in place of tissues, it is of the utmost importance to understand the mechanical and structural properties of these tissues as this may lead to higher success rates for valve replacement surgeries. The longevity of the bioprosthetics may also increase if the manufactured grafts behave the same as native valves. Building on the scant information about the uniaxial and biaxial mechanical properties of jugular venous valves and wall tissues from previous studies, the current focus of our investigation lies in understanding the material behavior by establishing a phenomenological strain energy-based constitutive relation for the tissues. We used bovine veins to study the behavior of valve leaflet tissue and adjoining wall tissue (from the proximal and distal ends of the veins) under different biaxial testing protocols. We looked at the behavior of numerical partial derivatives of the strain energy to select a suitable functional form for the strain energy for wall and valve tissues. Using this strain energy descriptor, we determined the Cauchy stress and compared it with experimental results under additional sets of displacement-controlled biaxial testing protocols to find material specific model parameters by the Powell's method algorithm. Results show that whereas wall tissue strain energy can be explained using a polynomial non-linear function, the valve tissue, due to higher non-linearities, requires an exponential function. This study may provide useful information for the primary stages of bioprosthetic designs and replacement surgeries and may support future studies investigating structural models. It may also support the study of valvular diseases by providing a way to understand material properties and behavior and to form a continuum model when required for numerical analyses and computational simulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optimal Elastomeric Scaffold Leaflet Shape for Pulmonary Heart Valve Leaflet Replacement

PubMed Central

Fan, Rong; Bayoumi, Ahmed S.; Chen, Peter; Hobson, Christopher M.; Wagner, William R.; Mayer, John E.; Sacks, Michael S.

2012-01-01

Surgical replacement of the pulmonary valve (PV) is a common treatment option for congenital pulmonary valve defects. Engineered tissue approaches to develop novel PV replacements are intrinsically complex, and will require methodical approaches for their development. Single leaflet replacement utilizing an ovine model is an attractive approach in that candidate materials can be evaluated under valve level stresses in blood contact without the confounding effects of a particular valve design. In the present study an approach for optimal leaflet shape design based on finite element (FE) simulation of a mechanically anisotropic, elastomeric scaffold for PV replacement is presented. The scaffold was modeled as an orthotropic hyperelastic material using a generalized Fung-type constitutive model. The optimal shape of the fully loaded PV replacement leaflet was systematically determined by minimizing the difference between the deformed shape obtained from FE simulation and an ex-vivo microCT scan of a native ovine PV leaflet. Effects of material anisotropy, dimensional changes of PV root, and fiber orientation on the resulting leaflet deformation were investigated. In-situ validation demonstrated that the approach could guide the design of the leaflet shape for PV replacement surgery. PMID:23294966

Modulation of Human Valve Interstitial Cell Phenotype and Function Using a Fibroblast Growth Factor 2 Formulation

PubMed Central

Latif, Najma; Quillon, Alfred; Sarathchandra, Padmini; McCormack, Ann; Lozanoski, Alec; Yacoub, Magdi H.; Chester, Adrian H.

2015-01-01

Valve interstitial cells (VICs) are fibroblastic in nature however in culture it is widely accepted that they differentiate into a myofibroblastic phenotype. This study assessed a fibroblast culture media formulation for its ability to maintain the phenotype and function of VICs as in the intact healthy valve. Normal human VICs were cultured separately in standard DMEM and in fibroblast media consisting of FGF2 (10ng/ml), insulin (50ng/ml) and 2% FCS for at least a week. Cell morphology, aspect ratio, size, levels and distribution of protein expression, proliferation, cell cycle, contraction and migration were assessed. Some VICs and some valve endothelial cells expressed FGF2 in valve tissue and this expression was increased in calcified valves. VICs in DMEM exhibited large, spread cells whereas VICs in fibroblast media were smaller, elongated and spindly. Aspect ratio and size were both significantly higher in DMEM (p<0.01). The level of expression of α-SMA was significantly reduced in fibroblast media at day 2 after isolation (p<0.01) and the expression of α-SMA, SM22 and EDA-fibronectin was significantly reduced in fibroblast media at days 7 and 12 post-isolation (p<0.01). Expression of cytoskeletal proteins, bone marker proteins and extracellular matrix proteins was reduced in fibroblast media. Proliferation of VICs in fibroblast media was significantly reduced at weeks 1 (p<0.05) and 2 (p<0.01). Collagen gel contraction was significantly reduced in fibroblast media (p<0.05). VICs were found to have significantly fewer and smaller focal adhesions in fibroblast media (p<0.01) with significantly fewer supermature focal adhesions in fibroblast media (p<0.001). Ultrastructurally, VICs in fibroblast media resembled native VICs from intact valves. VICs in fibroblast media demonstrated a slower migratory ability after wounding at 72 hours (p<0.01). Treatment of human VICs with this fibroblast media formulation has the ability to maintain and to dedifferentiate the VICs back to a fibroblastic phenotype with phenotypic and functional characteristics ascribed to cells in the intact valve. This methodology is fundamental in the study of normal valve biology, pathology and in the field of tissue engineering. PMID:26042674

Thermal and mechanical analysis of major components for the advanced adiabatic diesel engine

NASA Technical Reports Server (NTRS)

1983-01-01

The proposed design for the light duty diesel is an in-line four cylinder spark assisted diesel engine mounted transversely in the front of the vehicle. The engine has a one piece cylinder head, with one intake valve and one exhaust valve per cylinder. A flat topped piston is used with a cylindrical combustion chamber recessed into the cylinder head directly under the exhaust valve. A single ceramic insert is cast into the cylinder head to insulate both the combustion chamber and the exhaust port. A similar ceramic insert is cast into the head to insulate the intake port. A ceramic faceplate is pressed into the combustion face of the head to insulate the face of the head from hot combustion gas. The valve seats are machined directly into the ceramic faceplate for the intake valve and into the ceramic exhaust pot insert for the exhaust valve. Additional ceramic applications in the head are the use of ceramic valve guides and ceramic insulated valves. The ceramic valve guides are press fit into the head and are used for increased wear resistance. The ceramic insulated valves are conventional valves with the valve faces plasma spray coated with ceramic for insulation.

Testing of RPMI-1640 as a Nutrient Medium for Fresh Semilunar Valve Storage.

DTIC Science & Technology

1979-01-01

familiarization with cage life, canine distemper and hepatitis vaccinations, worming for internal parasites, and obtain one normal complete blood count. Atropine...human valves. If these results are similar to this canine study, a more realistic evaluation can be made as to whether the best tissue for heart valve...replacement is from live tissue of human allografts or dead tissue of procine xenografts. I SUMMARY The medium selected to store canine heart valves

Design and Performance Evaluation of an Electro-Hydraulic Camless Engine Valve Actuator for Future Vehicle Applications

PubMed Central

Nam, Kanghyun; Cho, Kwanghyun; Park, Sang-Shin; Choi, Seibum B.

2017-01-01

This paper details the new design and dynamic simulation of an electro-hydraulic camless engine valve actuator (EH-CEVA) and experimental verification with lift position sensors. In general, camless engine technologies have been known for improving fuel efficiency, enhancing power output, and reducing emissions of internal combustion engines. Electro-hydraulic valve actuators are used to eliminate the camshaft of an existing internal combustion engines and used to control the valve timing and valve duration independently. This paper presents novel electro-hydraulic actuator design, dynamic simulations, and analysis based on design specifications required to satisfy the operation performances. An EH-CEVA has initially been designed and modeled by means of a powerful hydraulic simulation software, AMESim, which is useful for the dynamic simulations and analysis of hydraulic systems. Fundamental functions and performances of the EH-CEVA have been validated through comparisons with experimental results obtained in a prototype test bench. PMID:29258270

Design and Performance Evaluation of an Electro-Hydraulic Camless Engine Valve Actuator for Future Vehicle Applications.

PubMed

Nam, Kanghyun; Cho, Kwanghyun; Park, Sang-Shin; Choi, Seibum B

2017-12-18

This paper details the new design and dynamic simulation of an electro-hydraulic camless engine valve actuator (EH-CEVA) and experimental verification with lift position sensors. In general, camless engine technologies have been known for improving fuel efficiency, enhancing power output, and reducing emissions of internal combustion engines. Electro-hydraulic valve actuators are used to eliminate the camshaft of an existing internal combustion engines and used to control the valve timing and valve duration independently. This paper presents novel electro-hydraulic actuator design, dynamic simulations, and analysis based on design specifications required to satisfy the operation performances. An EH-CEVA has initially been designed and modeled by means of a powerful hydraulic simulation software, AMESim, which is useful for the dynamic simulations and analysis of hydraulic systems. Fundamental functions and performances of the EH-CEVA have been validated through comparisons with experimental results obtained in a prototype test bench.

The effectiveness of a double-stem injection valve in controlling combustion in a compression-ignition engine

NASA Technical Reports Server (NTRS)

Spanogle, J A; Whitney, E G

1931-01-01

An investigation was made to determine to what extent the rates of combustion in a compression-ignition engine can be controlled by varying the rates of fuel injection. The tests showed that the double-stem valve operated satisfactorily under all normal injection conditions; the rate of injection has a definite effect on the rate of combustion; the engine performance with the double-stem valve was inferior to that obtained with a single-stem valve; and the control of injection rates permitted by an injection valve of two stages of discharge is not sufficient to effect the desired rates of combustion.

Modulation of the tissue reninangiotensin-aldosterone system in dogs with chronic mild regurgitation through the mitral valve.

PubMed

Fujii, Yoko; Orito, Kensuke; Muto, Makoto; Wakao, Yoshito

2007-10-01

To investigate whether the tissue and plasma renin-angiotensin-aldosterone system (RAAS) is activated in dogs with mild regurgitation through the mitral valve and determine the contribution of chymase and angiotensin-converting enzyme (ACE) to the activation of the RAAS and potential production of angiotensin II during the chronic stage of mild mitral valve regurgitation. 5 Beagles with experimentally induced mild mitral valve regurgitation and 6 clinically normal (control) Beagles. Tissue ACE and chymase-like activities and plasma RAAS were measured and the RAAS evaluated approximately 1,000 days after experimental induction of mitral valve regurgitation in the 5 dogs. Dogs with experimentally induced mitral valve regurgitation did not have clinical signs of the condition, although echocardiography revealed substantial eccentric hyper- trophy. On the basis of these findings, dogs with mitral valve regurgitation were classified as International Small Animal Cardiac Health Council class Ib. Plasma activity of renin and plasma concentrations of angiotensin I, angiotensin II, and aldosterone were not significantly different between dogs with mitral valve regurgitation and clinically normal dogs. Tissue ACE activity was significantly increased and chymase-like activity significantly decreased in dogs with mitral valve regurgitation, compared with values in clinically normal dogs. The tissue RAAS was modulated without changes in the plasma RAAS in dogs with mild mitral valve regurgitation during the chronic stage of the condition. An ACE-dependent pathway may be a major route for production of angiotensin II during this stage of the condition.

Experimental investigations on the fluid-mechanics of an electrospun heart valve by means of particle image velocimetry.

PubMed

Del Gaudio, Costantino; Gasbarroni, Pier Luca; Romano, Giovanni Paolo

2016-12-01

End-stage failing heart valves are currently replaced by mechanical or biological prostheses. Both types positively contribute to restore the physiological function of native valves, but a number of drawbacks limits the expected performances. In order to improve the outcome, tissue engineering can offer an alternative approach to design and fabricate innovative heart valves capable to support the requested function and to promote the formation of a novel, viable and correctly operating physiological structure. This potential result is particularly critical if referred to the aortic valve, being the one mainly exposed to structural and functional degeneration. In this regard, the here proposed study presents the fabrication and in vitro characterization of a bioresorbable electrospun heart valve prosthesis using the particle image velocimetry technique either in physiological and pathological fluid dynamic conditions. The scaffold was designed to reproduce the aortic valve geometry, also mimicking the fibrous structure of the natural extracellular matrix. To evaluate its performances for possible implantation, the flow fields downstream the valve were accurately investigated and compared. The experimental results showed a correct functionality of the device, supported by the formation of vortex structures at the edge of the three cusps, with Reynolds stress values below the threshold for the risk of hemolysis (which can be comprised in the range 400-4000N/m(2) depending on the exposure period), and a good structural resistance to the mechanical loads generated by the driving pressure difference. Copyright © 2016 Elsevier Ltd. All rights reserved.

Anatomic, histopathologic, and echocardiographic features in a dog with an atypical pulmonary valve stenosis with a fibrous band of tissue and a patent ductus arteriosus.

PubMed

Yoon, Hakyoung; Kim, Jaehwan; Nahm, Sang-Soep; Eom, Kidong

2017-07-11

Congenital pulmonary valve stenosis and patent ductus arteriosus are common congenital heart defects in dogs. However, concurrence of atypical pulmonary valve stenosis and patent ductus arteriosus is uncommon. This report describes the anatomic, histopathologic, and echocardiographic features in a dog with concomitant pulmonary valve stenosis and patent ductus arteriosus with atypical pulmonary valve dysplasia that included a fibrous band of tissue. A 1.5-year-old intact female Chihuahua dog weighing 3.3 kg presented with a continuous grade VI cardiac murmur, poor exercise tolerance, and an intermittent cough. Echocardiography indicated pulmonary valve stenosis, a thickened dysplastic valve without annular hypoplasia, and a type IIA patent ductus arteriosus. The pulmonary valve was thick line-shaped in systole and dome-shaped towards the right ventricular outflow tract in diastole. The dog suffered a fatal cardiac arrest during an attempted balloon pulmonary valvuloplasty. Necropsy revealed pulmonary valve dysplasia, commissural fusion, and incomplete opening and closing of the pulmonary valve because of a fibrous band of tissue causing adhesion between the right ventricular outflow tract and the dysplastic intermediate cusp of the valve. A fibrous band of tissue between the right ventricular outflow track and the pulmonary valve should be considered as a cause of pulmonary valve stenosis. Pulmonary valve stenosis and patent ductus arteriosus can have conflicting effects on diastolic and systolic dysfunction, respectively. Therefore, beta-blockers should always be used carefully, particularly in patients with a heart defect where there is concern about left ventricular systolic function.

Ceramic valve development for heavy-duty low heat rejection diesel engines

NASA Technical Reports Server (NTRS)

Weber, K. E.; Micu, C. J.

1989-01-01

Monolithic ceramic valves can be successfully operated in a heavy-duty diesel engine, even under extreme low heat rejection operating conditions. This paper describes the development of a silicon nitride valve from the initial design stage to actual engine testing. Supplier involvement, finite element analysis, and preliminary proof of concept demonstration testing played a significant role in this project's success.

Dynamic behavior of prosthetic aortic tissue valves as viewed by high-speed cinematography.

PubMed

Rainer, W G; Christopher, R A; Sadler, T R; Hilgenberg, A D

1979-09-01

Using a valve testing apparatus of our own design and with a high-speed (600 to 800 frames per second) 16 mm movie camera, films were made of Hancock porcine, Carpentier-Edwards porcine, and Ionescu-Shiley bovine pericardial valves mounted in the aortic position and cycled under physiological conditions at 72 to 100 beats per minute. Fresh and explanted valves were observed using saline or 36.5% glycerol as the pumping solution. When fresh valves were studied using saline solution as the pumpint fluid, the Hancock and Carpentier-Edwards porcine valves showed high-frequency leaflet vibration, which increased in frequency with higher cycling rates. Abnormal leaflet motion was decreased when glycerol was used as the blood analogue. The Ionescu-Shiley bovine pericardial valve did not show abnormal leaflet motion under these conditions. Conclusions drawn from tissue valve testing studies that use excessively high pulsing rates and pressures (accelerated testing) and saline or water as pumping solutions cannot be transposed to predict the fate of tissue valves in a clinical setting.

Are anticoagulant independent mechanical valves within reach-fast prototype fabrication and in vitro testing of innovative bi-leaflet valve models.

PubMed

Scotten, Lawrence N; Siegel, Rolland

2015-08-01

Exploration for causes of prosthetic valve thrombogenicity has frequently focused on forward or post-closure flow detail. In prior laboratory studies, we uncovered high amplitude flow velocities of short duration close to valve closure implying potential for substantial shear stress with subsequent initiation of blood coagulation pathways. This may be relevant to widely accepted clinical disparity between mechanical and tissue valves vis-à-vis thrombogenicity. With a series of prototype bi-leaflet mechanical valves, we attempt reduction of closure related velocities with the objective of identifying a prototype valve with thrombogenic potential similar to our tissue valve control. This iterative design approach may find application in preclinical assessment of valves for anticoagulation independence. Tested valves included: prototype mechanical bi-leaflet BVs (n=56), controls (n=2) and patented early prototype mechanicals (n=2) from other investigators. Pulsatile and quasi-steady flow systems were used for testing. Projected dynamic valve area (PDVA) was measured using previously described novel technology. Flow velocity over the open and closing periods was determined by volumetric flow rate/PDVA. For the closed valve interval, use was made of data obtained from quasi-steady back pressure/flow tests. Performance was ranked by a proposed thrombogenicity potential index (TPI) relative to tissue and mechanical control valves. Optimization of the prototype valve designs lead to a 3-D printed model (BV3D). For the mitral/aortic site, BV3D has lower TPI (1.10/1.47) relative to the control mechanical valve (3.44/3.93) and similar to the control tissue valve (ideal TPI ≤1.0). Using unique technology, rapid prototyping and thrombogenicity ranking, optimization of experimental valves for reduced thrombogenic potential was expedited and simplified. Innovative mechanical valve configurations were identified that merit consideration for further development which may bring the anti-coagulation independent mechanical valve within reach.

Are anticoagulant independent mechanical valves within reach—fast prototype fabrication and in vitro testing of innovative bi-leaflet valve models

PubMed Central

Siegel, Rolland

2015-01-01

Background Exploration for causes of prosthetic valve thrombogenicity has frequently focused on forward or post-closure flow detail. In prior laboratory studies, we uncovered high amplitude flow velocities of short duration close to valve closure implying potential for substantial shear stress with subsequent initiation of blood coagulation pathways. This may be relevant to widely accepted clinical disparity between mechanical and tissue valves vis-à-vis thrombogenicity. With a series of prototype bi-leaflet mechanical valves, we attempt reduction of closure related velocities with the objective of identifying a prototype valve with thrombogenic potential similar to our tissue valve control. This iterative design approach may find application in preclinical assessment of valves for anticoagulation independence. Methods Tested valves included: prototype mechanical bi-leaflet BVs (n=56), controls (n=2) and patented early prototype mechanicals (n=2) from other investigators. Pulsatile and quasi-steady flow systems were used for testing. Projected dynamic valve area (PDVA) was measured using previously described novel technology. Flow velocity over the open and closing periods was determined by volumetric flow rate/PDVA. For the closed valve interval, use was made of data obtained from quasi-steady back pressure/flow tests. Performance was ranked by a proposed thrombogenicity potential index (TPI) relative to tissue and mechanical control valves. Results Optimization of the prototype valve designs lead to a 3-D printed model (BV3D). For the mitral/aortic site, BV3D has lower TPI (1.10/1.47) relative to the control mechanical valve (3.44/3.93) and similar to the control tissue valve (ideal TPI ≤1.0). Conclusions Using unique technology, rapid prototyping and thrombogenicity ranking, optimization of experimental valves for reduced thrombogenic potential was expedited and simplified. Innovative mechanical valve configurations were identified that merit consideration for further development which may bring the anti-coagulation independent mechanical valve within reach. PMID:26417581

Supercritical carbon dioxide-based sterilization of decellularized heart valves.

PubMed

Hennessy, Ryan S; Jana, Soumen; Tefft, Brandon J; Helder, Meghana R; Young, Melissa D; Hennessy, Rebecca R; Stoyles, Nicholas J; Lerman, Amir

2017-02-01

The goal of this research project encompasses finding the most efficient and effective method of decellularized tissue sterilization. Aortic tissue grafts have been utilized to repair damaged or diseased valves. Although, the tissues for grafting are collected aseptically, it does not eradicate the risk of contamination nor disease transfer. Thus, sterilization of grafts is mandatory. Several techniques have been applied to sterilize grafts; however, each technique shows drawbacks. In this study, we compared several sterilization techniques: supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide for impact on the sterility and mechanical integrity of porcine decellularized aortic valves. Valve sterility was characterized by histology, microbe culture, and electron microscopy. Uniaxial tensile testing was conducted on the valve cusps along their circumferential orientation to study these sterilization techniques on their integrity. Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile. The tensile strength of supercritical carbon dioxide treated valves (4.28 ± 0.22 MPa) was higher to those valves treated with electrolyzed water, gamma radiation, ethanol-peracetic acid and hydrogen peroxide (1.02 ± 0.15, 1.25 ± 0.25, 3.53 ± 0.41 and 0.37 ± 0.04 MPa, respectively). Superior sterility and integrity were found in the decellularized porcine aortic valves with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues. Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile using histology, microbe culture and electron microscopy assays. The cusp tensile properties of supercritical carbon dioxide treated valves were higher compared to valves treated with other techniques. Superior sterility and integrity was found in the decellularized valves treated with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues.

Monovalve with integrated fuel injector and port control valve, and engine using same

DOEpatents

Milam, David M.

2002-01-01

Each cylinder of an internal combustion engine includes a combined gas exchange valve and fuel injector with a port control valve. The port control valve operates to open either an intake passage or an exhaust passage. The operation of the combined device is controlled by a pair of electrical actuators. The device is hydraulically actuated.

Simplified pulse reactor for real-time long-term in vitro testing of biological heart valves.

PubMed

Schleicher, Martina; Sammler, Günther; Schmauder, Michael; Fritze, Olaf; Huber, Agnes J; Schenke-Layland, Katja; Ditze, Günter; Stock, Ulrich A

2010-05-01

Long-term function of biological heart valve prostheses (BHV) is limited by structural deterioration leading to failure with associated arterial hypertension. The objective of this work was development of an easy to handle real-time pulse reactor for evaluation of biological and tissue engineered heart valves under different pressures and long-term conditions. The pulse reactor was made of medical grade materials for placement in a 37 degrees C incubator. Heart valves were mounted in a housing disc moving horizontally in culture medium within a cylindrical culture reservoir. The microprocessor-controlled system was driven by pressure resulting in a cardiac-like cycle enabling competent opening and closing of the leaflets with adjustable pulse rates and pressures between 0.25 to 2 Hz and up to 180/80 mmHg, respectively. A custom-made imaging system with an integrated high-speed camera and image processing software allow calculation of effective orifice areas during cardiac cycle. This simple pulse reactor design allows reproducible generation of patient-like pressure conditions and data collection during long-term experiments.

Fault detection and diagnosis of diesel engine valve trains

NASA Astrophysics Data System (ADS)

Flett, Justin; Bone, Gary M.

2016-05-01

This paper presents the development of a fault detection and diagnosis (FDD) system for use with a diesel internal combustion engine (ICE) valve train. A novel feature is generated for each of the valve closing and combustion impacts. Deformed valve spring faults and abnormal valve clearance faults were seeded on a diesel engine instrumented with one accelerometer. Five classification methods were implemented experimentally and compared. The FDD system using the Naïve-Bayes classification method produced the best overall performance, with a lowest detection accuracy (DA) of 99.95% and a lowest classification accuracy (CA) of 99.95% for the spring faults occurring on individual valves. The lowest DA and CA values for multiple faults occurring simultaneously were 99.95% and 92.45%, respectively. The DA and CA results demonstrate the accuracy of our FDD system for diesel ICE valve train fault scenarios not previously addressed in the literature.

Carbon Fiber Reinforced Carbon Composite Valve for an Internal Combustion Engine

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

1999-01-01

A carbon fiber reinforced carbon composite valve for internal combustion engines and the like formed of continuous carbon fibers throughout the valve's stem and head is disclosed. The valve includes braided carbon fiber material over axially aligned unidirectional carbon fibers forming a valve stem; the braided and unidirectional carbon fibers being broomed out at one end of the valve stem forming the shape of the valve head; the valve-shaped structure being densified and rigidized with a matrix of carbon containing discontinuous carbon fibers: and the finished valve being treated to resist oxidation. Also disclosed is a carbon matrix plug containing continuous and discontinuous carbon fibers and forming a net-shape valve head acting as a mandrel over which the unidirectional and braided carbon fibers are formed according to textile processes. Also disclosed are various preform valves and processes for making finished and preform carbon fiber reinforced carbon composite valves.

75 FR 51659 - Airworthiness Directives; Pratt & Whitney Canada Corp. PW617F-E Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-23

... showed that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that engine had... that the Fuel Filter Bypass Valve poppet in the FOHE on that engine had worn through the housing seat... an ASB No. PW600-72-A66021 that introduced a new fuel Filter Bypass Valve Assembly with an improved...

75 FR 27489 - Airworthiness Directives; Pratt & Whitney Canada Corp. PW615F-A Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-17

.... Investigation showed that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that...-A engine Fuel Filter Bypass Valve is very similar to that of PW617F-E, but so far there have been no... Fuel Filter Bypass Valve poppet in the FOHE on that engine had worn through the housing seat, allowing...

Space shuttle main engine definition (phase B). Volume 5: Valves and interconnects. [for space shuttle

NASA Technical Reports Server (NTRS)

Schultz, D. F.

1971-01-01

The steady state thermodynamic cycle balance of the single preburner staged combustion engine, coupled with dynamic transient analyses, dictated in detail the location and requirements for each valve defined in this volume. Valve configuration selections were influenced by overall engine and vehicle system weight and failure mode determinations. Modulating valve actuators are external to the valve and are line replaceable. Development and satisfactory demonstration of a high pressure dynamic shaft seal has made this configuration practical. Pneumatic motor driven actuators that use engine pumped hydrogen gas as the working fluid are used. The helium control system is proposed as a module containing a cluster of solenoid actuated valves. The separable couplings and flanges are designed to assure minimum leakage with minimum coupling weight. The deflection of the seal surface in the flange is defined by finite element analysis that has been confirmed with test data. The seal design proposed has passed preliminary pressure cycling and thermal cycling tests.

[Periodontal microbiota and microorganisms isolated from heart valves in patients undergoing valve replacement surgery in a clinic in Cali, Colombia].

PubMed

Moreno, Sandra; Parra, Beatriz; Botero, Javier E; Moreno, Freddy; Vásquez, Daniel; Fernández, Hugo; Alba, Sandra; Gallego, Sara; Castillo, Gilberto; Contreras, Adolfo

2017-12-01

Periodontitis is an infectious disease that affects the support tissue of the teeth and it is associated with different systemic diseases, including cardiovascular disease. Microbiological studies facilitate the detection of microorganisms from subgingival and cardiovascular samples. To describe the cultivable periodontal microbiota and the presence of microorganisms in heart valves from patients undergoing valve replacement surgery in a clinic in Cali. We analyzed 30 subgingival and valvular tissue samples by means of two-phase culture medium, supplemented blood agar and trypticase soy agar with antibiotics. Conventional PCR was performed on samples of valve tissue. The periodontal pathogens isolated from periodontal pockets were: Fusobacterium nucleatum (50%), Prevotella intermedia/ nigrescens (40%), Campylobacter rectus (40%), Eikenella corrodens (36.7%), Gram negative enteric bacilli (36.7%), Porphyromonas gingivalis (33.3%), and Eubacterium spp. (33.3%). The pathogens isolated from the aortic valve were Propionibacterium acnes (12%), Gram negative enteric bacilli (8%), Bacteroides merdae (4%), and Clostridium bifermentans (4%), and from the mitral valve we isolated P. acnes and Clostridium beijerinckii. Conventional PCR did not return positive results for oral pathogens and bacterial DNA was detected only in two samples. Periodontal microbiota of patients undergoing surgery for heart valve replacement consisted of species of Gram-negative bacteria that have been associated with infections in extraoral tissues. However, there is no evidence of the presence of periodontal pathogens in valve tissue, because even though there were valve and subgingival samples positive for Gram-negative enteric bacilli, it is not possible to maintain they corresponded to the same phylogenetic origin.

Exhaust gas bypass valve control for thermoelectric generator

DOEpatents

Reynolds, Michael G; Yang, Jihui; Meisner, Greogry P.; Stabler, Francis R.; De Bock, Hendrik Pieter Jacobus; Anderson, Todd Alan

2012-09-04

A method of controlling engine exhaust flow through at least one of an exhaust bypass and a thermoelectric device via a bypass valve is provided. The method includes: determining a mass flow of exhaust exiting an engine; determining a desired exhaust pressure based on the mass flow of exhaust; comparing the desired exhaust pressure to a determined exhaust pressure; and determining a bypass valve control value based on the comparing, wherein the bypass valve control value is used to control the bypass valve.

Internal combustion engine with rotary valve assembly having variable intake valve timing

DOEpatents

Hansen, Craig N.; Cross, Paul C.

1995-01-01

An internal combustion engine has rotary valves associated with movable shutters operable to vary the closing of intake air/fuel port sections to obtain peak volumetric efficiency over the entire range of speed of the engine. The shutters are moved automatically by a control mechanism that is responsive to the RPM of the engine. A foot-operated lever associated with the control mechanism is also used to move the shutters between their open and closed positions.

Transcatheter treatment of tricuspid regurgitation by caval valve implantation--experimental evaluation of decellularized tissue valves in central venous position.

PubMed

Lauten, Alexander; Laube, Adrian; Schubert, Harald; Bischoff, Sabine; Nietzsche, Sandor; Horstkötter, Kim; Poudel-Bochmann, Bhawana; Franz, Marcus; Lichtenberg, Artur; Figulla, Hans R; Akhyari, Payam

2015-01-01

Caval valve implantation has been suggested for transcatheter treatment of severe tricuspid regurgitation (TR). Combining the interventional technique with the promising surgical experience with decellularized valves, we sought to evaluate the functional and structural outcome of decellularized pericardial tissue valves (dTVs) in the low-pressure venous circulation in a chronic model of TR. Sixteen pericardial tissue valves were heterotopically implanted in the inferior and superior vena cava in a sheep model (54-98 kg; median 74.5 kg, n = 8) of severe TR. The devices were assembled using self-expanding nitinol stents and bovine pericardia decellularized by a detergent-based protocol (group dTV; n = 8). Glutaraldehyde-fixed pericardial tissue valves served as control (GaTV, n = 8). After 6 months, device function and structural maturation were analyzed using echocardiographic, histologic, immunohistologic, and electron microscopic approaches. After implantation, cardiac output increased significantly from 3.7 ± 1.1 l/min to 4.8 ± 1.1 l/min (P < 0.05) and competent valve function was verified by angiography. At 6 months, angiographic and echocardiographic evaluation revealed moderate to severe regurgitation in all GaTV. In contrast, five of the eight dTVs functioned well with only minor regurgitation. In these animals, autopsy revealed preserved valve structure with tender leaflets without signs of thrombosis or calcification. Conversely, GaTV showed severe degeneration with large calcification areas. Microscopic and histologic analysis confirmed endothelial repopulation in both valve types. However, additional interstitial reseeding was observed in decellularized valves. In the venous circulation in severe TR, decellularized valves show superior functional performance compared to Ga-fixed tissue valves. Macroscopic and microscopic analyses suggest preserved structural integrity and advanced endothelial and interstitial repopulation with evidence of less degradation in dTV. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

A New, Highly Improved Two-Cycle Engine

NASA Technical Reports Server (NTRS)

Wiesen, Bernard

2008-01-01

The figure presents a cross-sectional view of a supercharged, variable-compression, two-cycle, internal-combustion engine that offers significant advantages over prior such engines. The improvements are embodied in a combination of design changes that contribute synergistically to improvements in performance and economy. Although the combination of design changes and the principles underlying them are complex, one of the main effects of the changes on the overall engine design is reduced (relative to prior two-cycle designs) mechanical complexity, which translates directly to reduced manufacturing cost and increased reliability. Other benefits include increases in the efficiency of both scavenging and supercharging. The improvements retain the simplicity and other advantages of two-cycle engines while affording increases in volumetric efficiency and performance across a wide range of operating conditions that, heretofore have been accessible to four-cycle engines but not to conventionally scavenged two-cycle ones, thereby increasing the range of usefulness of the two-cycle engine into all areas now dominated by the four-cycle engine. The design changes and benefits are too numerous to describe here in detail, but it is possible to summarize the major improvements: Reciprocating Shuttle Inlet Valve The entire reciprocating shuttle inlet valve and its operating gear is constructed as a single member. The shuttle valve is actuated in a lost-motion arrangement in which, at the ends of its stroke, projections on the shuttle valve come to rest against abutments at the ends of grooves in a piston skirt. This shuttle-valve design obviates the customary complex valve mechanism, actuated from an engine crankshaft or camshaft, yet it is effective with every type of two-cycle engine, from small high-speed single cylinder model engines, to large low-speed multiple cylinder engines.

Imaging of cardiovascular structures using near-infrared femtosecond multiphoton laser scanning microscopy.

PubMed

Schenke-Layland, Katja; Riemann, Iris; Stock, Ulrich A; König, Karsten

2005-01-01

Multiphoton imaging represents a novel and very promising medical diagnostic technology for the high-resolution analysis of living biological tissues. We performed multiphoton imaging to analyzed structural features of extracellular matrix (ECM) components, e.g., collagen and elastin, of vital pulmonary and aortic heart valves. High-resolution autofluorescence images of collagenous and elastic fibers were demonstrated using multifluorophore, multiphoton excitation at two different wavelengths and optical sectioning, without the requirement of embedding, fixation, or staining. Collagenous structures were selectively imaged by detection of second harmonic generation (SHG). Additionally, routine histology and electron microscopy were integrated to verify the observed results. In comparison with pulmonary tissues, aortic heart valve specimens show very similar matrix formations. The quality of the resulting three-dimensional (3-D) images enabled the differentiation between collagenous and elastic fibers. These experimental results indicate that multiphoton imaging with near-infrared (NIR) femtosecond laser pulses may prove to be a useful tool for the nondestructive monitoring and characterization of cardiovascular structures. Copyright 2005 Society of Photo-Optical Instrumentation Engineers.

Three-dimensional transient numerical simulation for intake process in the engine intake port-valve-cylinder system.

PubMed

Luo, Ma-Ji; Chen, Guo-Hua; Ma, Yuan-Hao

2003-01-01

This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine intake system.

Engine including hydraulically actuated valvetrain and method of valve overlap control

DOEpatents

Cowgill, Joel [White Lake, MI

2012-05-08

An exhaust valve control method may include displacing an exhaust valve in communication with the combustion chamber of an engine to an open position using a hydraulic exhaust valve actuation system and returning the exhaust valve to a closed position using the hydraulic exhaust valve actuation assembly. During closing, the exhaust valve may be displaced for a first duration from the open position to an intermediate closing position at a first velocity by operating the hydraulic exhaust valve actuation assembly in a first mode. The exhaust valve may be displaced for a second duration greater than the first duration from the intermediate closing position to a fully closed position at a second velocity at least eighty percent less than the first velocity by operating the hydraulic exhaust valve actuation assembly in a second mode.

Supercharged two-cycle engines employing novel single element reciprocating shuttle inlet valve mechanisms and with a variable compression ratio

NASA Technical Reports Server (NTRS)

Wiesen, Bernard (Inventor)

2008-01-01

This invention relates to novel reciprocating shuttle inlet valves, effective with every type of two-cycle engine, from small high-speed single cylinder model engines, to large low-speed multiple cylinder engines, employing spark or compression ignition. Also permitting the elimination of out-of-phase piston arrangements to control scavenging and supercharging of opposed-piston engines. The reciprocating shuttle inlet valve (32) and its operating mechanism (34) is constructed as a single and simple uncomplicated member, in combination with the lost-motion abutments, (46) and (48), formed in a piston skirt, obviating the need for any complex mechanisms or auxiliary drives, unaffected by heat, friction, wear or inertial forces. The reciprocating shuttle inlet valve retains the simplicity and advantages of two-cycle engines, while permitting an increase in volumetric efficiency and performance, thereby increasing the range of usefulness of two-cycle engines into many areas that are now dominated by the four-cycle engine.

Heart Valve Biomechanics and Underlying Mechanobiology

PubMed Central

Ayoub, Salma; Ferrari, Giovanni; Gorman, Robert C.; Gorman, Joseph H.; Schoen, Frederick J.; Sacks, Michael S.

2017-01-01

Heart valves control unidirectional blood flow within the heart during the cardiac cycle. They have a remarkable ability to withstand the demanding mechanical environment of the heart, achieving lifetime durability by processes involving the ongoing remodeling of the extracellular matrix. The focus of this review is on heart valve functional physiology, with insights into the link between disease-induced alterations in valve geometry, tissue stress, and the subsequent cell mechanobiological responses and tissue remodeling. We begin with an overview of the fundamentals of heart valve physiology and the characteristics and functions of valve interstitial cells (VICs). We then provide an overview of current experimental and computational approaches that connect VIC mechanobiological response to organ- and tissue-level deformations and improve our understanding of the underlying functional physiology of heart valves. We conclude with a summary of future trends and offer an outlook for the future of heart valve mechanobiology, specifically, multiscale modeling approaches, and the potential directions and possible challenges of research development. PMID:27783858

View forward from bulkhead no. 38 of compartment B126 crew ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View forward from bulkhead no. 38 of compartment B-126 crew space. Note stop valves on bulkhead at right side of photograph; these steam control valves allowed remote activation of the main, auxiliary and safety valves for the port engine in the event that the engine room valves were disabled or unreachable. (044) - USS Olympia, Penn's Landing, 211 South Columbus Boulevard, Philadelphia, Philadelphia County, PA

In Vitro Evaluation of a Novel Hemodynamically Optimized Trileaflet Polymeric Prosthetic Heart Valve

PubMed Central

Claiborne, Thomas E.; Sheriff, Jawaad; Kuetting, Maximilian; Steinseifer, Ulrich; Slepian, Marvin J.; Bluestein, Danny

2013-01-01

Calcific aortic valve disease is the most common and life threatening form of valvular heart disease, characterized by stenosis and regurgitation, which is currently treated at the symptomatic end-stages via open-heart surgical replacement of the diseased valve with, typically, either a xenograft tissue valve or a pyrolytic carbon mechanical heart valve. These options offer the clinician a choice between structural valve deterioration and chronic anticoagulant therapy, respectively, effectively replacing one disease with another. Polymeric prosthetic heart valves (PHV) offer the promise of reducing or eliminating these complications, and they may be better suited for the new transcatheter aortic valve replacement (TAVR) procedure, which currently utilizes tissue valves. New evidence indicates that the latter may incur damage during implantation. Polymer PHVs may also be incorporated into pulsatile circulatory support devices such as total artificial heart and ventricular assist devices that currently employ mechanical PHVs. Development of polymer PHVs, however, has been slow due to the lack of sufficiently durable and biocompatible polymers. We have designed a new trileaflet polymer PHV for surgical implantation employing a novel polymer—xSIBS—that offers superior bio-stability and durability. The design of this polymer PHV was optimized for reduced stresses, improved hemodynamic performance, and reduced thrombogenicity using our device thrombogenicity emulation (DTE) methodology, the results of which have been published separately. Here we present our new design, prototype fabrication methods, hydrodynamics performance testing, and platelet activation measurements performed in the optimized valve prototype and compare it to the performance of a gold standard tissue valve. The hydrodynamic performance of the two valves was comparable in all measures, with a certain advantage to our valve during regurgitation. There was no significant difference between the platelet activation rates of our polymer valve and the tissue valve, indicating that similar to the latter, its recipients may not require anticoagulation. This work proves the feasibility of our optimized polymer PHV design and brings polymeric valves closer to clinical viability. PMID:23445066

40 CFR 1054.230 - How do I select emission families?

Code of Federal Regulations, 2010 CFR

2010-07-01

...). (3) Valve configuration (for example, side-valve vs. overhead valve). (4) Method of air aspiration... configuration) and approximate total displacement. (7) Engine class, as defined in § 1054.801. (8) Method of control for engine operation, other than governing (mechanical or electronic). (9) The numerical level of...

Engine control system having fuel-based adjustment

DOEpatents

Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL

2011-03-15

A control system for an engine having a cylinder is disclosed having an engine valve configured to affect a fluid flow of the cylinder, an actuator configured to move the engine valve, and an in-cylinder sensor configured to generate a signal indicative of a characteristic of fuel entering the cylinder. The control system also has a controller in communication with the actuator and the sensor. The controller is configured to determine the characteristic of the fuel based on the signal and selectively regulate the actuator to adjust a timing of the engine valve based on the characteristic of the fuel.

Protein kinase D2 controls cardiac valve formation in zebrafish by regulating histone deacetylase 5 activity.

PubMed

Just, Steffen; Berger, Ina M; Meder, Benjamin; Backs, Johannes; Keller, Andreas; Marquart, Sabine; Frese, Karen; Patzel, Eva; Rauch, Gerd-Jörg; Katus, Hugo A; Rottbauer, Wolfgang

2011-07-19

The molecular mechanisms that guide heart valve formation are not well understood. However, elucidation of the genetic basis of congenital heart disease is one of the prerequisites for the development of tissue-engineered heart valves. We isolated here a mutation in zebrafish, bungee (bng(jh177)), which selectively perturbs valve formation in the embryonic heart by abrogating endocardial Notch signaling in cardiac cushions. We found by positional cloning that the bng phenotype is caused by a missense mutation (Y849N) in zebrafish protein kinase D2 (pkd2). The bng mutation selectively impairs PKD2 kinase activity and hence Histone deacetylase 5 phosphorylation, nuclear export, and inactivation. As a result, the expression of Histone deacetylase 5 target genes Krüppel-like factor 2a and 4a, transcription factors known to be pivotal for heart valve formation and to act upstream of Notch signaling, is severely downregulated in bungee (bng) mutant embryos. Accordingly, the expression of Notch target genes, such as Hey1, Hey2, and HeyL, is severely decreased in bng mutant embryos. Remarkably, downregulation of Histone deacetylase 5 activity in homozygous bng mutant embryos can rescue the mutant phenotype and reconstitutes notch1b expression in atrioventricular endocardial cells. We demonstrate for the first time that proper heart valve formation critically depends on Protein kinase D2-Histone deacetylase 5-Krüppel-like factor signaling.

Detecting Solenoid Valve Deterioration in In-Use Electronic Diesel Fuel Injection Control Systems

PubMed Central

Tsai, Hsun-Heng; Tseng, Chyuan-Yow

2010-01-01

The diesel engine is the main power source for most agricultural vehicles. The control of diesel engine emissions is an important global issue. Fuel injection control systems directly affect fuel efficiency and emissions of diesel engines. Deterioration faults, such as rack deformation, solenoid valve failure, and rack-travel sensor malfunction, are possibly in the fuel injection module of electronic diesel control (EDC) systems. Among these faults, solenoid valve failure is most likely to occur for in-use diesel engines. According to the previous studies, this failure is a result of the wear of the plunger and sleeve, based on a long period of usage, lubricant degradation, or engine overheating. Due to the difficulty in identifying solenoid valve deterioration, this study focuses on developing a sensor identification algorithm that can clearly classify the usability of the solenoid valve, without disassembling the fuel pump of an EDC system for in-use agricultural vehicles. A diagnostic algorithm is proposed, including a feedback controller, a parameter identifier, a linear variable differential transformer (LVDT) sensor, and a neural network classifier. Experimental results show that the proposed algorithm can accurately identify the usability of solenoid valves. PMID:22163597

Detecting solenoid valve deterioration in in-use electronic diesel fuel injection control systems.

PubMed

Tsai, Hsun-Heng; Tseng, Chyuan-Yow

2010-01-01

The diesel engine is the main power source for most agricultural vehicles. The control of diesel engine emissions is an important global issue. Fuel injection control systems directly affect fuel efficiency and emissions of diesel engines. Deterioration faults, such as rack deformation, solenoid valve failure, and rack-travel sensor malfunction, are possibly in the fuel injection module of electronic diesel control (EDC) systems. Among these faults, solenoid valve failure is most likely to occur for in-use diesel engines. According to the previous studies, this failure is a result of the wear of the plunger and sleeve, based on a long period of usage, lubricant degradation, or engine overheating. Due to the difficulty in identifying solenoid valve deterioration, this study focuses on developing a sensor identification algorithm that can clearly classify the usability of the solenoid valve, without disassembling the fuel pump of an EDC system for in-use agricultural vehicles. A diagnostic algorithm is proposed, including a feedback controller, a parameter identifier, a linear variable differential transformer (LVDT) sensor, and a neural network classifier. Experimental results show that the proposed algorithm can accurately identify the usability of solenoid valves.

Flex Fuel Optimized SI and HCCI Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Guoming; Schock, Harold; Yang, Xiaojian

The central objective of the proposed work is to demonstrate an HCCI (homogeneous charge compression ignition) capable SI (spark ignited) engine that is capable of fast and smooth mode transition between SI and HCCI combustion modes. The model-based control technique was used to develop and validate the proposed control strategy for the fast and smooth combustion mode transition based upon the developed control-oriented engine; and an HCCI capable SI engine was designed and constructed using production ready two-step valve-train with electrical variable valve timing actuating system. Finally, smooth combustion mode transition was demonstrated on a metal engine within eight enginemore » cycles. The Chrysler turbocharged 2.0L I4 direct injection engine was selected as the base engine for the project and the engine was modified to fit the two-step valve with electrical variable valve timing actuating system. To develop the model-based control strategy for stable HCCI combustion and smooth combustion mode transition between SI and HCCI combustion, a control-oriented real-time engine model was developed and implemented into the MSU HIL (hardware-in-the-loop) simulation environment. The developed model was used to study the engine actuating system requirement for the smooth and fast combustion mode transition and to develop the proposed mode transition control strategy. Finally, a single cylinder optical engine was designed and fabricated for studying the HCCI combustion characteristics. Optical engine combustion tests were conducted in both SI and HCCI combustion modes and the test results were used to calibrate the developed control-oriented engine model. Intensive GT-Power simulations were conducted to determine the optimal valve lift (high and low) and the cam phasing range. Delphi was selected to be the supplier for the two-step valve-train and Denso to be the electrical variable valve timing system supplier. A test bench was constructed to develop control strategies for the electrical variable valve timing (VVT) actuating system and satisfactory electrical VVT responses were obtained. Target engine control system was designed and fabricated at MSU for both single-cylinder optical and multi-cylinder metal engines. Finally, the developed control-oriented engine model was successfully implemented into the HIL simulation environment. The Chrysler 2.0L I4 DI engine was modified to fit the two-step vale with electrical variable valve timing actuating system. A used prototype engine was used as the base engine and the cylinder head was modified for the two-step valve with electrical VVT actuating system. Engine validation tests indicated that cylinder #3 has very high blow-by and it cannot be reduced with new pistons and rings. Due to the time constraint, it was decided to convert the four-cylinder engine into a single cylinder engine by blocking both intake and exhaust ports of the unused cylinders. The model-based combustion mode transition control algorithm was developed in the MSU HIL simulation environment and the Simulink based control strategy was implemented into the target engine controller. With both single-cylinder metal engine and control strategy ready, stable HCCI combustion was achived with COV of 2.1% Motoring tests were conducted to validate the actuator transient operations including valve lift, electrical variable valve timing, electronic throttle, multiple spark and injection controls. After the actuator operations were confirmed, 15-cycle smooth combustion mode transition from SI to HCCI combustion was achieved; and fast 8-cycle smooth combustion mode transition followed. With a fast electrical variable valve timing actuator, the number of engine cycles required for mode transition can be reduced down to five. It was also found that the combustion mode transition is sensitive to the charge air and engine coolant temperatures and regulating the corresponding temperatures to the target levels during the combustion mode transition is the key for a smooth combustion mode transition. As a summary, the proposed combustion mode transition strategy using the hybrid combustion mode that starts with the SI combustion and ends with the HCCI combustion was experimentally validated on a metal engine. The proposed model-based control approach made it possible to complete the SI-HCCI combustion mode transition within eight engine cycles utilizing the well controlled hybrid combustion mode. Without intensive control-oriented engine modeling and HIL simulation study of using the hybrid combustion mode during the mode transition, it would be impossible to validate the proposed combustion mode transition strategy in a very short period.« less

STS-55 pad abort: Engine 2011 oxidizer preburner augmented spark igniter check valve leak

NASA Technical Reports Server (NTRS)

1993-01-01

The STS-55 initial launch attempt of Columbia (OV102) was terminated on KSC launch pad A March 22, 1993 at 9:51 AM E.S.T. due to violation of an ME-3 (Engine 2011) Launch Commit Criteria (LCC) limit exceedance. The event description and timeline are summarized. Propellant loading was initiated on 22 March, 1993 at 1:15 AM EST. All SSME chill parameters and launch commit criteria (LCC) were nominal. At engine start plus 1.44 seconds, a Failure Identification (FID) was posted against Engine 2011 for exceeding the 50 psia Oxidizer Preburner (OPB) purge pressure redline. The engine was shut down at 1.50 seconds followed by Engines 2034 and 2030. All shut down sequences were nominal and the mission was safely aborted. The OPB purge pressure redline violation and the abort profile/overlay for all three engines are depicted. SSME Avionics hardware and software performed nominally during the incident. A review of vehicle data table (VDT) data and controller software logic revealed no failure indications other than the single FID 013-414, OPB purge pressure redline exceeded. Software logic was executed according to requirements and there was no anomalous controller software operation. Immediately following the abort, a Rocketdyne/NASA failure investigation team was assembled. The team successfully isolated the failure cause to the oxidizer preburner augmented spark igniter purge check valve not being fully closed due to contamination. The source of the contaminant was traced to a cut segment from a rubber O-ring which was used in a fine clean tool during valve production prior to 1992. The valve was apparently contaminated during its fabrication in 1985. The valve had performed acceptably on four previous flights of the engine, and SSME flight history shows 780 combined check valve flights without failure. The failure of an Engine 3 (SSME No. 2011) check valve to close was sensed by onboard engine instruments even though all other engine operations were normal. This resulted in an engine shutdown and safe sequential shutdown of all three engines prior to ignition of the solid boosters.

Conceptual model for early health technology assessment of current and novel heart valve interventions

PubMed Central

Huygens, Simone A; Rutten-van Mölken, Maureen P M H; Bekkers, Jos A; Bogers, Ad J J C; Bouten, Carlijn V C; Chamuleau, Steven A J; de Jaegere, Peter P T; Kappetein, Arie Pieter; Kluin, Jolanda; van Mieghem, Nicolas M D A; Versteegh, Michel I M; Witsenburg, Maarten; Takkenberg, Johanna J M

2016-01-01

Objective The future promises many technological advances in the field of heart valve interventions, like tissue-engineered heart valves (TEHV). Prior to introduction in clinical practice, it is essential to perform early health technology assessment. We aim to develop a conceptual model (CM) that can be used to investigate the performance and costs requirements for TEHV to become cost-effective. Methods After scoping the decision problem, a workgroup developed the draft CM based on clinical guidelines. This model was compared with existing models for cost-effectiveness of heart valve interventions, identified by systematic literature search. Next, it was discussed with a Delphi panel of cardiothoracic surgeons, cardiologists and a biomedical scientist (n=10). Results The CM starts with the valve implantation. If patients survive the intervention, they can remain alive without complications, die from non-valve-related causes or experience a valve-related event. The events are separated in early and late events. After surviving an event, patients can experience another event or die due to non-valve-related causes. Predictors will include age, gender, NYHA class, left ventricular function and diabetes. Costs and quality adjusted life years are to be attached to health conditions to estimate long-term costs and health outcomes. Conclusions We developed a CM that will serve as foundation of a decision-analytic model that can estimate the potential cost-effectiveness of TEHV in early development stages. This supports developers in deciding about further development of TEHV and identifies promising interventions that may result in faster take-up in clinical practice by clinicians and reimbursement by payers. PMID:27843569

Supercritical carbon dioxide-based sterilization of decellularized heart valves

PubMed Central

Hennessy, Ryan S.; Jana, Soumen; Tefft, Brandon J.; Helder, Meghana R.; Young, Melissa D.; Hennessy, Rebecca R.; Stoyles, Nicholas J.; Lerman, Amir

2017-01-01

Objective The goal of this research project encompasses finding the most efficient and effective method of decellularized tissue sterilization. Background Aortic tissue grafts have been utilized to repair damaged or diseased valves. Although, the tissues for grafting are collected aseptically, it does not eradicate the risk of contamination nor disease transfer. Thus, sterilization of grafts is mandatory. Several techniques have been applied to sterilize grafts; however, each technique shows drawbacks. In this study, we compared several sterilization techniques: supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide for impact on the sterility and mechanical integrity of porcine decellularized aortic valves. Methods Valve sterility was characterized by histology, microbe culture, and electron microscopy. Uniaxial tensile testing was conducted on the valve cusps along their circumferential orientation to study these sterilization techniques on their integrity. Results Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile. The tensile strength of supercritical carbon dioxide treated valves (4.28 ± 0.22 MPa) was higher to those valves treated with electrolyzed water, gamma radiation, ethanol-peracetic acid and hydrogen peroxide (1.02 ± 0.15, 1.25 ± 0.25, 3.53 ± 0.41 and 0.37 ± 0.04 MPa, respectively). Conclusions Superior sterility and integrity were found in the decellularized porcine aortic valves with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues. Summary Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid and supercritical carbon dioxide treated valves were found to be sterile using histology, microbe culture and electron microscopy assays. The cusp tensile properties of supercritical carbon dioxide treated valves were higher compared to valves treated with other techniques. Superior sterility and integrity was found in the decellularized valves treated with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues. PMID:28337488

Initial Experience and Early Results of Mitral Valve Repair with Cardiocel Pericardial Patch.

PubMed

Tomšič, Anton; Bissessar, Daniella D; van Brakel, Thomas J; Marsan, Nina Ajmone; Klautz, Robert J M; Palmen, Meindert

2018-06-07

To assess the performance of a tissue engineering process-treated bovine pericardium patch (CardioCel) in the setting of reconstructive mitral valve surgery. Between 3/2014 and 4/2016, 30 patients (57.2±14.3 years, 27% female) underwent mitral valve leaflet repair with a CardioCel patch. Perioperative mortality was 7% (2 patients, non-graft-related). In 28 remaining patients, pre-discharge echocardiography demonstrated good repaired valve function. At a mean follow-up of 1.7±0.9 years, 3 additional deaths occurred (2 due to infective endocarditis, 1 non-cardiac related). On follow-up echocardiography [follow-up time 1.7±0.8 years, available for 26/28 (93%) hospital survivors], recurrent regurgitation was seen in 2 patients (both infective endocarditis) and 1 underwent reoperation (no infection at the level of patch repair was observed). In the remaining patients, the most recent echocardiogram demonstrated ≤mild regurgitation and stable gradients. The thickness and echodensity of the implanted patch on follow-up echocardiograms were comparable with postoperative echocardiograms. Initial results of the CardioCel patch in mitral valve repair surgery are satisfactory. The resistance to infection and late degeneration will need to be assessed in the future. Copyright © 2018. Published by Elsevier Inc.

40 CFR Appendix Viii to Part 85 - Vehicle and Engine Parameters and Specifications

Code of Federal Regulations, 2010 CFR

2010-07-01

... pressure. 3. Valves (intake and exhaust). a. Head diameter dimension. b. Valve lifter or actuator type and... diameter dimension. b. Valve lifter or actuator type and valve lash dimension. 5. Camshaft timing. a. Valve... dimension. b. Valve lifter or actuator type and valve lash dimension. 5. Camshaft timing. a. Valve opening...

40 CFR Appendix Viii to Part 85 - Vehicle and Engine Parameters and Specifications

Code of Federal Regulations, 2011 CFR

2011-07-01

... pressure. 3. Valves (intake and exhaust). a. Head diameter dimension. b. Valve lifter or actuator type and... diameter dimension. b. Valve lifter or actuator type and valve lash dimension. 5. Camshaft timing. a. Valve... dimension. b. Valve lifter or actuator type and valve lash dimension. 5. Camshaft timing. a. Valve opening...

The Effect of Valve Timing Upon the Performance of a Supercharged Engine at Altitude and an Unsupercharged Engine at Sea Level

NASA Technical Reports Server (NTRS)

Schey, Oscar W; Biermann, Arnold E

1932-01-01

This investigation was conducted to determine the comparative effects of valve timing on the performance of an unsupercharged engine at sea level and a supercharged engine at altitude. The tests were conducted on the NACA universal test engine. The timing of the four valve events was varied over a wide range; the engine speeds were varied between 1,050 and 1,500 r.p.m.; the compression ratios were varied between 4.35:1 and 7.35:1. The conditions of exhaust pressure and carburetor pressure of a supercharged engine were simulated for altitudes between 0 and 18,000 feet. The results show that optimum valve timing for a supercharged engine at an altitude of 18,000 feet differs slightly from that for an unsupercharged engine at sea level. A small increase in power is obtained by using the optimum timing for 18,000 feet for altitudes above 5,000 feet. The timing of the intake opening and exhaust closing becomes more critical as the compression ratio is increased.

Biomaterial-driven in situ cardiovascular tissue engineering-a multi-disciplinary perspective.

PubMed

Wissing, Tamar B; Bonito, Valentina; Bouten, Carlijn V C; Smits, Anthal I P M

2017-01-01

There is a persistent and growing clinical need for readily-available substitutes for heart valves and small-diameter blood vessels. In situ tissue engineering is emerging as a disruptive new technology, providing ready-to-use biodegradable, cell-free constructs which are designed to induce regeneration upon implantation, directly in the functional site. The induced regenerative process hinges around the host response to the implanted biomaterial and the interplay between immune cells, stem/progenitor cell and tissue cells in the microenvironment provided by the scaffold in the hemodynamic environment. Recapitulating the complex tissue microstructure and function of cardiovascular tissues is a highly challenging target. Therein the scaffold plays an instructive role, providing the microenvironment that attracts and harbors host cells, modulating the inflammatory response, and acting as a temporal roadmap for new tissue to be formed. Moreover, the biomechanical loads imposed by the hemodynamic environment play a pivotal role. Here, we provide a multidisciplinary view on in situ cardiovascular tissue engineering using synthetic scaffolds; starting from the state-of-the art, the principles of the biomaterial-driven host response and wound healing and the cellular players involved, toward the impact of the biomechanical, physical, and biochemical microenvironmental cues that are given by the scaffold design. To conclude, we pinpoint and further address the main current challenges for in situ cardiovascular regeneration, namely the achievement of tissue homeostasis, the development of predictive models for long-term performances of the implanted grafts, and the necessity for stratification for successful clinical translation.

Carbon Fiber Reinforced Carbon Composites Rotary Valves for Internal Combustion Engines

NASA Technical Reports Server (NTRS)

Northam, G. Burton (Inventor); Ransone, Philip O. (Inventor); Rivers, H. Kevin (Inventor)

1999-01-01

Carbon fiber reinforced carbon composite rotary, sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or warp-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties, do not present the sealing and lubrication problems that have prevented rotary, sleeve, and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

Compact valve actuation mechanism

NASA Technical Reports Server (NTRS)

Brogdon, James William (Inventor); Gill, David Keith (Inventor)

2000-01-01

A valve actuation device. The device may include a free floating valve bridge movably supported within a cavity in the engine housing. The bridge may be provided with a cavity and an orifice arrangement for pumping gases entrained with lubricating fluid toward the piston stems as the bridge reciprocates back and forth. The device may also include a rocker arm that has a U-shaped cross-sectional shape for receiving at least a portion of the valve bridge, valve stem valve spring and spring retainer therein. The rocker arm may be provided with lubrication passages for directing lubrication to the point wherein it is pivotally affixed to the engine housing.

Determination of oxidation state of iron in normal and pathologically altered human aortic valves

NASA Astrophysics Data System (ADS)

Czapla-Masztafiak, J.; Lis, G. J.; Gajda, M.; Jasek, E.; Czubek, U.; Bolechała, F.; Borca, C.; Kwiatek, W. M.

2015-12-01

In order to investigate changes in chemical state of iron in normal and pathologically altered human aortic valves X-ray absorption spectroscopy was applied. Since Fe is suspected to play detrimental role in aortic valve stenosis pathogenesis the oxidation state of this element has been determined. The experimental material consisted of 10 μm sections of valves excised during routine surgery and from autopsies. The experiment was performed at the MicroXAS beamline of the SLS synchrotron facility in Villigen (Switzerland). The Fe K-edge XANES spectra obtained from tissue samples were carefully analyzed and compared with the spectra of reference compounds containing iron in various chemical structures. The analysis of absorption edge position and shape of the spectra revealed that both chemical forms of iron are presented in valve tissue but Fe3+ is the predominant form. Small shift of the absorption edge toward higher energy in the spectra from stenotic valve samples indicates higher content of the Fe3+ form in pathological tissue. Such a phenomenon suggests the role of Fenton reaction and reactive oxygen species in the etiology of aortic valve stenosis. The comparison of pre-edge regions of XANES spectra for control and stenotic valve tissue confirmed no differences in local symmetry or spin state of iron in analyzed samples.

Characterizing the Collagen Fiber Orientation in Pericardial Leaflets Under Mechanical Loading Conditions

PubMed Central

Alavi, S. Hamed; Ruiz, Victor; Krasieva, Tatiana; Botvinick, Elliot L.; Kheradvar, Arash

2014-01-01

When implanted inside the body, bioprosthetic heart valve leaflets experience a variety of cyclic mechanical stresses such as shear stress due to blood flow when the valve is open, flexural stress due to cyclic opening and closure of the valve, and tensile stress when the valve is closed. These types of stress lead to a variety of failure modes. In either a natural valve leaflet or a processed pericardial tissue leaflet, collagen fibers reinforce the tissue and provide structural integrity such that the very thin leaflet can stand enormous loads related to cyclic pressure changes. The mechanical response of the leaflet tissue greatly depends on collagen fiber concentration, characteristics, and orientation. Thus, understating the microstructure of pericardial tissue and its response to dynamic loading is crucial for the development of more durable heart valve, and computational models to predict heart valves’ behavior. In this work, we have characterized the 3D collagen fiber arrangement of bovine pericardial tissue leaflets in response to a variety of different loading conditions under Second-Harmonic Generation Microscopy. This real-time visualization method assists in better understanding of the effect of cyclic load on collagen fiber orientation in time and space. PMID:23180029

Measurements of droplet velocity and size downstream of the moving valves of a four-valve engine with manifold injection, operated under isothermal steady suction conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Posylkin, M.; Taylor, A.M.K.P.; Whitelaw, J.H.

The four-valve head of a VTEC engine was mounted on an open cylinder and the valves and fuel injection system operated as in the engine with a rotational speed of 1,200 rpm. Local measurements of droplet characteristics were obtained with a phase-Doppler velocimeter and iso-octane injected over 5 ms intervals, corresponding to 36 crank angle degrees, with manifold depression of 20 mbar. The results show that most of the fuel droplets were located close to the liner and on the side of the cylinder adjacent to the exhaust valves. In the plane of the measurement, 10 mm below TDC, themore » liquid flux diminished as the initiation of injection was advanced before opening of the inlet valves. With injection with the inlet valves closed, there were two waves of droplets, one from each of the two valves and separated by 60 deg CA and both with the Sauter mean diameter of about 120 {micro}m. With injection with the inlet valves open, most of the droplets emerged from the main inlet valve and with Sauter mean diameters of about 50 {micro}m, smaller than those of the unconfined spray.« less

Bioprinting technology and its applications.

PubMed

Seol, Young-Joon; Kang, Hyun-Wook; Lee, Sang Jin; Atala, Anthony; Yoo, James J

2014-09-01

Bioprinting technology has emerged as a powerful tool for building tissue and organ structures in the field of tissue engineering. This technology allows precise placement of cells, biomaterials and biomolecules in spatially predefined locations within confined three-dimensional (3D) structures. Various bioprinting technologies have been developed and utilized for applications in life sciences, ranging from studying cellular mechanisms to constructing tissues and organs for implantation, including heart valve, myocardial tissue, trachea and blood vessels. In this article, we introduce the general principles and limitations of the most widely used bioprinting technologies, including jetting- and extrusion-based systems. Application-based research focused on tissue regeneration is presented, as well as the current challenges that hamper clinical utility of bioprinting technology. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Hybrid textile heart valve prosthesis: preliminary in vitro evaluation.

PubMed

Vaesken, Antoine; Pidancier, Christian; Chakfe, Nabil; Heim, Frederic

2016-09-22

Transcatheter aortic valve implantation (TAVI) is nowadays a popular alternative technique to surgical valve replacement for critical patients. Biological valve tissue has been used in these devices for over a decade now with over 100,000 implantations. However, material degradations due to crimping for catheter insertion purpose have been reported, and with only 6-year follow-up, no information is available about the long-term durability of biological tissue. Moreover, expensive biological tissue harvesting and chemical treatment procedures tend to promote the development of synthetic valve leaflet materials. Textile polyester (PET) material is characterized by outstanding folding and strength properties combined with proven biocompatibility and could therefore be considered as a candidate to replace biological valve leaflets in TAVI devices. Nevertheless, the material should be preferentially partly elastic in order to limit water hammer effects at valve closing time and prevent exaggerated stress from occurring into the stent and the valve. The purpose of the present work is to study in vitro the mechanical as well as the hydrodynamic behavior of a hybrid elastic textile valve device combining non-deformable PET yarn and elastic polyurethane (PU) yarn. The hybrid valve properties are compared with those of a non-elastic textile valve. Testing results show improved hydrodynamic properties with the elastic construction. However, under fatigue conditions, the interaction between PU and PET yarns tends to limit the valve durability.

Strength and fatigue of NT551 silicon nitride and NT551 diesel exhaust valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, M.J.; Werezczak, A.A.; Kirkland, T.P.

2000-02-01

The content of this report is excerpted from Mark Andrew's Ph.D. Thesis (Andrews, 1999), which was funded by a DOE/OTT High Temperature Materials Laboratory Graduate Fellowship. It involves the characterization of NT551 and valves fabricated with it. The motivations behind using silicon nitride (Si{sub 3}N{sub 4}) as an exhaust valve for a diesel engine are presented in this section. There are several economic factors that have encouraged the design and implementation of ceramic components for internal combustion (IC) engines. The reasons for selecting the diesel engine valve for this are also presented.

PIV measurements of in-cylinder, large-scale structures in a water-analogue Diesel engine

NASA Astrophysics Data System (ADS)

Kalpakli Vester, A.; Nishio, Y.; Alfredsson, P. H.

2016-11-01

Swirl and tumble are large-scale structures that develop in an engine cylinder during the intake stroke. Their structure and strength depend on the design of the inlet ports and valves, but also on the valve lift history. Engine manufacturers make their design to obtain a specific flow structure that is assumed to give the best engine performance. Despite many efforts, there are still open questions, such as how swirl and tumble depend on the dynamics of the valves/piston as well as how cycle-to-cycle variations should be minimized. In collaboration with Swedish vehicle industry we perform PIV measurements of the flow dynamics during the intake stroke inside a cylinder of a water-analogue engine model having the same geometrical characteristics as a typical truck Diesel engine. Water can be used since during the intake stroke the flow is nearly incompressible. The flow from the valves moves radially outwards, hits the vertical walls of the cylinder, entrains surrounding fluid, moves along the cylinder walls and creates a central backflow, i.e. a tumble motion. Depending on the port and valve design and orientation none, low, or high swirl can be established. For the first time, the effect of the dynamic motion of the piston/valves on the large-scale structures is captured. Supported by the Swedish Energy Agency, Scania CV AB and Volvo GTT, through the FFI program.

Engine control system having fuel-based timing

DOEpatents

Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL

2012-04-03

A control system for an engine having a cylinder is disclosed having an engine valve movable to regulate a fluid flow of the cylinder and an actuator associated with the engine valve. The control system also has a sensor configured to generate a signal indicative of an amount of an air/fuel mixture remaining within the cylinder after completion of a first combustion event and a controller in communication with the actuator and the sensor. The controller may be configured to compare the amount with a desired amount, and to selectively regulate the actuator to adjust a timing of the engine valve associated with a subsequent combustion event based on the comparison.

Organ engineering--combining stem cells, biomaterials, and bioreactors to produce bioengineered organs for transplantation.

PubMed

Murphy, Sean Vincent; Atala, Anthony

2013-03-01

Often the only treatment available for patients suffering from diseased and injured organs is whole organ transplant. However, there is a severe shortage of donor organs for transplantation. The goal of organ engineering is to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Recent progress in stem cell biology, biomaterials, and processes such as organ decellularization and electrospinning has resulted in the generation of bioengineered blood vessels, heart valves, livers, kidneys, bladders, and airways. Future advances that may have a significant impact for the field include safe methods to reprogram a patient's own cells to directly differentiate into functional replacement cell types. The subsequent combination of these cells with natural, synthetic and/or decellularized organ materials to generate functional tissue substitutes is a real possibility. This essay reviews the current progress, developments, and challenges facing researchers in their goal to create replacement tissues and organs for patients. Copyright © 2013 WILEY Periodicals, Inc.

49 CFR 195.116 - Valves.

Code of Federal Regulations, 2010 CFR

2010-10-01

... PIPELINE Design Requirements § 195.116 Valves. Each valve installed in a pipeline system must comply with the following: (a) The valve must be of a sound engineering design. (b) Materials subject to the...

Valves and other mechanical components and equipment: A compilation

NASA Technical Reports Server (NTRS)

1976-01-01

The articles in this Compilation will be of interest to mechanical engineers, users and designers of machinery, and to those engineers and manufacturers specializing in fluid handling systems. Section 1 describes a number of valves and valve systems. Section 2 contains articles on machinery and mechanical devices that may have applications in a number of different areas.

The role of visual and direct force feedback in robotics-assisted mitral valve annuloplasty.

PubMed

Currie, Maria E; Talasaz, Ali; Rayman, Reiza; Chu, Michael W A; Kiaii, Bob; Peters, Terry; Trejos, Ana Luisa; Patel, Rajni

2017-09-01

The objective of this work was to determine the effect of both direct force feedback and visual force feedback on the amount of force applied to mitral valve tissue during ex vivo robotics-assisted mitral valve annuloplasty. A force feedback-enabled master-slave surgical system was developed to provide both visual and direct force feedback during robotics-assisted cardiac surgery. This system measured the amount of force applied by novice and expert surgeons to cardiac tissue during ex vivo mitral valve annuloplasty repair. The addition of visual (2.16 ± 1.67), direct (1.62 ± 0.86), or both visual and direct force feedback (2.15 ± 1.08) resulted in lower mean maximum force applied to mitral valve tissue while suturing compared with no force feedback (3.34 ± 1.93 N; P < 0.05). To achieve better control of interaction forces on cardiac tissue during robotics-assisted mitral valve annuloplasty suturing, force feedback may be required. Copyright © 2016 John Wiley & Sons, Ltd.

Simulations of Instabilities in Complex Valve and Feed Systems

NASA Technical Reports Server (NTRS)

Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy; Cavallo, Peter A.

2006-01-01

CFD analyses are playing an increasingly important role in identifying and characterizing flow induced instabilities in rocket engine test facilities and flight systems. In this paper, we analyze instability mechanisms that range from turbulent pressure fluctuations due to vortex shedding in structurally complex valve systems to flow resonance in plug cavities to large scale pressure fluctuations due to collapse of cavitation induced vapor clouds. Furthermore, we discuss simulations of transient behavior related to valve motion that can serve as guidelines for valve scheduling. Such predictions of valve response to varying flow conditions is of crucial importance to engine operation and testing.

Carbon Fiber Reinforced Carbon Composite Rotary Valve for an Internal Combustion Engine

NASA Technical Reports Server (NTRS)

Northam, G.Burton (Inventor); Ransone, Philip O. (Inventor); Rivers, H. Kevin (Inventor)

2000-01-01

Carbon fiber reinforced carbon composite rotary sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or wrap-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties do not present the sealing and lubrication problems that have prevented rotary sleeve and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

Experimental and Analytical Determination of the Motion of Hydraulically Operated Valve Stems in Oil Engine Injection Systems

NASA Technical Reports Server (NTRS)

Gelalles, A G; Rothrock, A M

1930-01-01

This research on the pressure variations in the injection system of the N.A.C.A. Spray Photography Equipment and on the effects of these variations on the motion of the timing valve stem was undertaken in connection with the study of fuel injection systems for high-speed oil engines. The methods of analysis of the pressure variations and the general equation for the motion of the spring-loaded stem for the timing valve are applicable to a spring-loaded automatic injection valve, and in general to all hydraulically operated valves. A sample calculation for a spring-loaded automatic injection valve is included.

Valve Repair or Replacement

MedlinePlus

... called anticoagulants) for the rest of their lives. Biological valves are made from animal tissue (called a ... for valve replacement (called an autograft). Patients with biological valves usually do not need to take blood- ...

Antimisting Fuel (AMK) Flight Degrader Development and Aircraft Fuel System Investigation

DTIC Science & Technology

1987-02-01

Summary of Test Results 134 CV880 Support of the CID Mission 135 Comparison of the Pump/Degrader and Needle- Valve Degrader 146 Operation on Freshly Blended...Drain Valve 53 AM 33. View of Right Side of Number 3 Engine 54 34. Redundant Shutoff Valve 55 35. Bottom View of Number 3 Engine 55 36. Onboard...Supply and Regulation/Shutoff Valves 78 44. ATMP8O-1 Pump/Degrader Test Module 79 45. Fuel Flow Circuits 80 vii La LIST OF ILLUSTRATIONS (Continued

Fault Diagnosis of Internal Combustion Engine Valve Clearance Using the Impact Commencement Detection Method.

PubMed

Jiang, Zhinong; Mao, Zhiwei; Wang, Zijia; Zhang, Jinjie

2017-12-15

Internal combustion engines (ICEs) are widely used in many important fields. The valve train clearance of an ICE usually exceeds the normal value due to wear or faulty adjustment. This work aims at diagnosing the valve clearance fault based on the vibration signals measured on the engine cylinder heads. The non-stationarity of the ICE operating condition makes it difficult to obtain the nominal baseline, which is always an awkward problem for fault diagnosis. This paper overcomes the problem by inspecting the timing of valve closing impacts, of which the referenced baseline can be obtained by referencing design parameters rather than extraction during healthy conditions. To accurately detect the timing of valve closing impact from vibration signals, we carry out a new method to detect and extract the commencement of the impacts. The results of experiments conducted on a twelve-cylinder ICE test rig show that the approach is capable of extracting the commencement of valve closing impact accurately and using only one feature can give a superior monitoring of valve clearance. With the help of this technique, the valve clearance fault becomes detectable even without the comparison to the baseline, and the changing trend of the clearance could be trackable.

MC-1 Engine Valves, Lessons Learned

NASA Technical Reports Server (NTRS)

Laszar, John

2003-01-01

Many lessons were learned during the development of the valves for the MC-1 engine. The purpose of this report is to focus on a variety of issues related to the engine valves and convey the lessons learned. This paper will not delve into detailed technical analysis of the components. None of the lessons learned are new or surprising, but simply reinforce the importance of addressing the details of the design early, at the component level. The Marshall Space Flight Center (MSFC), Huntsville, Alabama developed the MC-1 engine, a LOX / FW-1, 60,000 pound thrust engine. This engine was developed under the Low Cost Boost Technology office at MSFC and proved to be a very successful project for the MSFC Propulsion team and the various subcontractors working the development of the engine and its components.

Valve actuator for internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uchida, T.

1987-06-16

A valve actuating mechanism is described for an overhead valve and overhead cam type internal combustion engine in which the camshaft is positioned above and between the valve and a cam follower seat member in a cylinder head of the engine. The cam follower seat member is threadedly mounted in the cylinder head and has a semi-spherical recess facing upwardly. A cam follower has an adjustable bolt threadedly received in one end of the cam follower. The adjustable bolt has a spherical fulcrum engaging the semispherical recess of the seat member. The cam follower also has a downwardly facing meansmore » on the other end for engaging the valve and an upwardly facing slipper face for sliding engagement with a cam on the camshaft. The cam is adapted to rotate across the slipper face in the direction of the valve. The slipper face has a surface shape for engaging the cam at the start of valve-lifting movement of the cam follower at a point through which a line tangent to the slipper face is substantially parallel to a line through contact points between the cam follower. The seat member and valve for minimizing the lateral forces are imposed on the cam follower by the cam at the start of the valve-lifting movement.« less

The first fifty consecutive Bentall operations with a prefabricated tissue-valved aortic conduit: a single-center experience.

PubMed

Baraki, Hassina; Al Ahmad, Ammar; Sarikouch, Samir; Koigeldiev, Nurbol; Khaladj, Nawid; Hagl, Christian; Pichlmaier, Maximillian; Haverich, Axel; Shrestha, Malakh

2010-05-01

Composite replacement is the standard treatment for the repair of aortic aneurysm with aortic valve pathology. With improved long-term durability and no requirement for long-term anticoagulation, tissue-valved conduits have become increasingly popular. Herein are reported the results achieved with 50 consecutive 'Bentall' operations, using the first commercially available prefabricated stentless tissue-valved conduit (Vascutek BioValsalva). Between September 2007 and September 2009, a total of 50 patients (10 females, 40 males; mean age 65 +/- 7 years) received a BioValsalva conduit. Concomitant procedures included coronary artery bypass grafting (CABG; n = 15), other valve (n = 5), and aortic arch replacement with circulatory arrest (n = 20; three of these had an additional frozen elephant trunk). Four of the procedures were re-operations. A six-month follow up with echocardiography and clinical examination was completed in 25 patients. The 30-day mortality was 8% (4/50). Three of these patients underwent concomitant procedures. The cardiopulmonary bypass (CPB) and cross-clamp times were 178 +/- 30 min and 106 +/- 7 min, respectively. The triple-layered vascular graft proved to be hemostatic, without suture-line bleeding. Both, the initial and follow up echocardiography showed no valvular insufficiency, with a mean gradient of 13 +/- 5 mmHg. All patients were in NYHA class I-II. The BioValsalva prefabricated tissue-valved conduit showed very good early results. The ischemic time required to construct a 'home-made' stentless tissue-valved conduit was eliminated, thus reducing the cross-clamp time. The conduit also offered the hemodynamic advantages of a stentless valve.

Evaluation of a multiplex real-time PCR assay for detecting pathogens in cardiac valve tissue in patients with endocarditis.

PubMed

Fernández, Angel L; Varela, Eduardo; Martínez, Lucía; Martínez, Amparo; Sierra, Juan; González-Juanatey, José R; Regueiro, Benito

2010-10-01

With a novel real-time multiplex polymerase chain reaction test, the LightCycler SeptiFast® test, 25 bacterial and fungal species can be identified directly in blood. The SeptiFast® test has been used for rapid etiologic diagnosis in infectious endocarditis using blood samples but has not been evaluated directly on cardiac vegetations in patients being treated for infectious endocarditis. We prospectively analyzed 15 samples of heart valve tissue with active infectious endocarditis using the SeptiFast® test and compared the test's sensitivity with that of blood culture, valve tissue culture, and the SeptiFast® test in blood. The sensitivity of the SeptiFast test in heart valve tissue was 100%. The test results confirmed the diagnosis obtained using blood culture in 13 cases and identified the pathogen in 2 cases where blood culture tested negative. The sensitivity of the SeptiFast® test in heart valve tissue was greater than that obtained with conventional culture of vegetations or with the SeptiFast test in blood.

Systems for delivering liquified natural gas to an engine

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; O'Brien, James E.; Siahpush, Ali S.; Brown, Kevin B.

2000-01-01

A fuel delivery system includes a fuel tank configured to receive liquid natural gas. A first conduit extends from a vapor holding portion of the fuel tank to an economizer valve. A second conduit extends from a liquid holding portion of the fuel tank to the economizer valve. Fluid coupled to the economizer valve is a vaporizer which is heated by coolant from the engine and is positioned below the fuel tank. The economizer valve selectively withdraws either liquid natural gas or vaporized natural gas from the fuel tank depending on the pressure within the vapor holding portion of the fuel tank. A delivery conduit extends from the vaporizer to the engine. A return conduit having a check valve formed therein extends from the delivery conduit to the vapor holding portion of the fuel tank for pressurizing the fuel tank.

Options for Heart Valve Replacement

MedlinePlus

... which may include human or animal donor tissue) Ross Procedure — “Borrowing” your healthy valve and moving it ... Considerations for Surgery Medications Valve Repair Valve Replacement - Ross Procedure - Newer Surgery Options - What is TAVR? - Types ...

Decellularized heart valve as a scaffold for in vivo recellularization: deleterious effects of granulocyte colony-stimulating factor.

PubMed

Juthier, Francis; Vincentelli, André; Gaudric, Julien; Corseaux, Delphine; Fouquet, Olivier; Calet, Christine; Le Tourneau, Thierry; Soenen, Valérie; Zawadzki, Christophe; Fabre, Olivier; Susen, Sophie; Prat, Alain; Jude, Brigitte

2006-04-01

Autologous recellularization of decellularized heart valve scaffolds is a promising challenge in the field of tissue-engineered heart valves and could be boosted by bone marrow progenitor cell mobilization. The aim of this study was to examine the spontaneous in vivo recolonization potential of xenogeneic decellularized heart valves in a lamb model and the effects of granulocyte colony-stimulating factor mobilization of bone marrow cells on this process. Decellularized porcine aortic valves were implanted in 12 lambs. Six lambs received granulocyte colony-stimulating factor (10 microg x kg(-1) x d(-1) for 7 days, granulocyte colony-stimulating factor group), and 6 received no granulocyte colony-stimulating factor (control group). Additionally, nondecellularized porcine valves were implanted in 5 lambs (xenograft group). Angiographic and histologic evaluation was performed at 3, 6, 8, and 16 weeks. Few macroscopic modifications of leaflets and the aortic wall were observed in the control group, whereas progressive shrinkage and thickening of the leaflets appeared in the granulocyte colony-stimulating factor and xenograft groups. In the 3 groups progressive ovine cell infiltration (fluorescence in situ hybridization) was observed in the leaflets and in the adventitia and the intima of the aortic wall but not in the media. Neointimal proliferation of alpha-actin-positive cells, inflammatory infiltration, adventitial neovascularization, and calcifications were more important in the xenograft and the granulocyte colony-stimulating factor groups than in the control group. Continuous re-endothelialization appeared only in the control group. Decellularized xenogeneic heart valve scaffolds allowed partial autologous recellularization. Granulocyte colony-stimulating factor led to accelerated heart valve deterioration similar to that observed in nondecellularized xenogeneic cardiac bioprostheses.

75 FR 27491 - Airworthiness Directives; Pratt & Whitney Canada Corp. PW617F-E Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-17

.... Investigation showed that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that... Fuel Filter Bypass Valve poppet in the FOHE on that engine had worn through the housing seat, allowing.... PW600-72-A66021 that introduced a new fuel Filter Bypass Valve Assembly with an improved design poppet...

Diagnostic Importance of Hyphae on Heart Valve Tissue in Histoplasma Endocarditis and Treatment With Isavuconazole.

PubMed

Wiley, Zanthia; Woodworth, Michael H; Jacob, Jesse T; Lockhart, Shawn R; Rouphael, Nadine G; Gullett, Jonathan C; Guarner, Jeannette; Workowski, Kimberly

2017-01-01

A patient who never resided in an endemic area for dimorphic fungi was diagnosed with Histoplasma capsulatum endocarditis. His diagnosis was suggested by yeast and hyphae on cardiac valve tissue pathology. Isavuconazole was an optimal therapeutic option due to renal dysfunction and anticoagulation with warfarin for mechanical valve replacement.

Diagnostic Importance of Hyphae on Heart Valve Tissue in Histoplasma Endocarditis and Treatment With Isavuconazole

PubMed Central

Wiley, Zanthia; Woodworth, Michael H; Jacob, Jesse T; Lockhart, Shawn R; Rouphael, Nadine G; Gullett, Jonathan C; Guarner, Jeannette

2017-01-01

Abstract A patient who never resided in an endemic area for dimorphic fungi was diagnosed with Histoplasma capsulatum endocarditis. His diagnosis was suggested by yeast and hyphae on cardiac valve tissue pathology. Isavuconazole was an optimal therapeutic option due to renal dysfunction and anticoagulation with warfarin for mechanical valve replacement. PMID:29255737

Afebrile Pannus-Induced Blood Culture-Negative Mechanical Valve Endocarditis.

PubMed

Matsukuma, Seiji; Eishi, Kiyoyuki; Tanigawa, Kazuyoshi; Miura, Takashi; Matsumaru, Ichiro; Hisatomi, Kazuki; Tsuneto, Akira

2016-12-01

The diagnosis of prosthetic valve endocarditis may be challenging in patients with an atypical clinical presentation. Virtually all infections associated with mechanical prosthetic valves are localized to the prosthesis-tissue junction at the sewing ring and are accompanied by tissue destruction around the prosthesis. Because the orifice of the mechanical prosthetic valve is made of metal and pyrolytic carbon, which do not enable the adherence of microorganisms, any vegetation originating from the interior of the valve orifice is usually rare. Here we present a rare case of pannus-induced mechanical prosthetic valve endocarditis that was difficult to diagnose. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Electrodynamic actuators for rocket engine valves

NASA Technical Reports Server (NTRS)

Fiet, O.; Doshi, D.

1972-01-01

Actuators, employed in acoustic loudspeakers, operate liquid rocket engine valves by replacing light paper cones with flexible metal diaphragms. Comparative analysis indicates better response time than solenoid actuators, and improved service life and reliability.

Carburetor for internal combustion engines

DOEpatents

Csonka, John J.; Csonka, Albert B.

1978-01-01

A carburetor for internal combustion engines having a housing including a generally discoidal wall and a hub extending axially from the central portion thereof, an air valve having a relatively flat radially extending surface directed toward and concentric with said discoidal wall and with a central conoidal portion having its apex directed toward the interior of said hub portion. The housing wall and the radially extending surface of the valve define an air passage converging radially inwardly to form an annular valving construction and thence diverge into the interior of said hub. The hub includes an annular fuel passage terminating at its upper end in a circumferential series of micro-passages for directing liquid fuel uniformly distributed into said air passage substantially at said valving constriction at right angles to the direction of air flow. The air valve is adjustable axially toward and away from the discoidal wall of the carburetor housing to regulate the volume of air drawn into the engine with which said carburetor is associated. Fuel is delivered under pressure to the fuel metering valve and from there through said micro-passages and controlled cams simultaneously regulate the axial adjustment of said air valve and the rate of delivery of fuel through said micro-passages according to a predetermined ratio pattern. A third jointly controlled cam simultaneously regulates the ignition timing in accordance with various air and fuel supply settings. The air valve, fuel supply and ignition timing settings are all independent of the existing degree of engine vacuum.

Design of Epoxy based Resin Composites for Automotive Applications: A Case Study on IC Engine Valve Guide

NASA Astrophysics Data System (ADS)

Sidhu, J. S.; Lathkar, G. S.; Sharma, S. B.

2018-01-01

The present attempt in this project is to reduce the vibrations, temperature due to friction, noise and weight of I C engine valve guide by replacing conventional metal valve guide with composite valve guide. Composite materials have been used in automotive components because of their properties such as low weight, high specific stiffness, corrosion resistance, ability to produce complex shapes, high specific strength and good impact energy absorption etc. The Internal combustion engine valve guides are the parts that support the valves in the cylinder head, besides this it keeps lubricating oil from getting sucked into the combustion chamber past the intake valve stem, it keeps exhaust gases from getting into the crankcase past the exhaust valve stem and it also keeps the valve face in perfect alignment with the valve seat. A valve guide test rig is indigenously fabricated. Valve guides are manufactured using the developed composite material (Resin ARL-136, Hardener AH-126 and 4 vol% WS2), on a CNC lathe. The performance of the developed composite guide under varied conditions of speeds, that is, fixed change in rpm and modulated changes in rpm is assessed. Noise, temperature and vibrations are measured. The experimental data revealed that contribution of composite guide in respect of acceleration, velocity and displacement components of vibration is not substantial. A substantial reduction in noise levels is seen. As far as temperature rise due to friction is concerned maximum components fail at elevated temperatures, with composite guides the temperature generated due to friction at higher speeds is less, a considerable weight reduction is also observed.

Liquid rocket valve components

NASA Technical Reports Server (NTRS)

1973-01-01

A monograph on valves for use with liquid rocket propellant engines is presented. The configurations of the various types of valves are described and illustrated. Design criteria and recommended practices for the various valves are explained. Tables of data are included to show the chief features of valve components in use on operational vehicles.

46 CFR 56.20-15 - Valves employing resilient material.

Code of Federal Regulations, 2010 CFR

2010-10-01

....20-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-15 Valves employing resilient material. (a) A valve in which the... piping system manifolds; (ii) Isolation valves in cross-connects between two piping systems, at least one...

Advanced diesel engine component development program, tasks 4-14

NASA Astrophysics Data System (ADS)

Kaushal, Tony S.; Weber, Karen E.

1994-11-01

This report summarizes the Advanced Diesel Engine Component Development (ADECD) Program to develop and demonstrate critical technology needed to advance the heavy-duty low heat rejection engine concept. Major development activities reported are the design, analysis, and fabrication of monolithic ceramic components; vapor phase and solid film lubrication; electrohydraulic valve actuation; and high pressure common rail injection. An advanced single cylinder test bed was fabricated as a laboratory tool in studying these advanced technologies. This test bed simulates the reciprocator for a system having no cooling system, turbo compounding, Rankine bottoming cycle, common rail injection, and variable valve actuation to achieve fuel consumption of 160 g/kW-hr (.26 lb/hp-hr). The advanced concepts were successfully integrated into the test engine. All ceramic components met their functional and reliability requirements. The firedeck, cast-in-place ports, valves, valve guides, piston cap, and piston ring were made from silicon nitride. Breakthroughs required to implement a 'ceramic' engine included the fabrication of air-gap cylinder heads, elimination of compression gaskets, machining of ceramic valve seats within the ceramic firedeck, fabrication of cast-in-place ceramic port liners, implementation of vapor phase lubrication, and elimination of the engine coolant system. Silicon nitride valves were successfully developed to meet several production abuse test requirements and incorporated into the test bed with a ceramic valve guide and solid film lubrication. The ADECD cylinder head features ceramic port shields to increase insulation and exhaust energy recovery. The combustion chamber includes a ceramic firedeck and piston cap. The tribological challenge posed by top ring reversal temperatures of 550 C was met through the development of vapor phase lubrication using tricresyl phosphate at the ring-liner interface. A solenoid-controlled, variable valve actuation system that eliminated the conventional camshaft was demonstrated on the test bed. High pressure fuel injection via a common rail system was also developed to reduce particulate emissions.

Advanced diesel engine component development program, tasks 4-14

NASA Technical Reports Server (NTRS)

Kaushal, Tony S.; Weber, Karen E.

1994-01-01

This report summarizes the Advanced Diesel Engine Component Development (ADECD) Program to develop and demonstrate critical technology needed to advance the heavy-duty low heat rejection engine concept. Major development activities reported are the design, analysis, and fabrication of monolithic ceramic components; vapor phase and solid film lubrication; electrohydraulic valve actuation; and high pressure common rail injection. An advanced single cylinder test bed was fabricated as a laboratory tool in studying these advanced technologies. This test bed simulates the reciprocator for a system having no cooling system, turbo compounding, Rankine bottoming cycle, common rail injection, and variable valve actuation to achieve fuel consumption of 160 g/kW-hr (.26 lb/hp-hr). The advanced concepts were successfully integrated into the test engine. All ceramic components met their functional and reliability requirements. The firedeck, cast-in-place ports, valves, valve guides, piston cap, and piston ring were made from silicon nitride. Breakthroughs required to implement a 'ceramic' engine included the fabrication of air-gap cylinder heads, elimination of compression gaskets, machining of ceramic valve seats within the ceramic firedeck, fabrication of cast-in-place ceramic port liners, implementation of vapor phase lubrication, and elimination of the engine coolant system. Silicon nitride valves were successfully developed to meet several production abuse test requirements and incorporated into the test bed with a ceramic valve guide and solid film lubrication. The ADECD cylinder head features ceramic port shields to increase insulation and exhaust energy recovery. The combustion chamber includes a ceramic firedeck and piston cap. The tribological challenge posed by top ring reversal temperatures of 550 C was met through the development of vapor phase lubrication using tricresyl phosphate at the ring-liner interface. A solenoid-controlled, variable valve actuation system that eliminated the conventional camshaft was demonstrated on the test bed. High pressure fuel injection via a common rail system was also developed to reduce particulate emissions.

Slide valve apparatus for internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, B.A.; McMahan, T.O.

This patent describes an internal combustion engine including a combustion cylinder having an opening at one end thereof, a piston mounted within the cylinder for coaxial reciprocable movement, a driven crankshaft, and a connecting rod connecting the crankshaft to the cylinder for linear reciprocable movement of the piston in response to the rotary movement of the crankshaft, a valve apparatus comprising: (a) a valve chamber extending longitudinally across and in fluid communication with the opening in the cylinder, (b) an intake valve plate having a longitudinal axis mounted within the valve chamber for slidable, reciprocable, longitudinal movement, (c) an exhaustmore » valve plate having a longitudinal axis mounted within the valve chamber alongside the intake valve plate for slidable, reciprocable, longitudinal movement and parallel to the longitudinal axis of the intake valve plate, (d) each of the valve plates having a plurality of longitudinally spaced valve ports therein, the valve ports comprising movable intake valve ports in the intake valve plate and movable exhaust valve ports in the exhaust valve plate, (e) the valve chamber comprising a planar wall on the opposite side of the valve plates from the cylinder opening and having a plurality of fixed valve ports therethrough. The fixed valve ports being equal in number and substantially equal in size and spacing as the movable intake and exhaust valve ports, whereby the movable intake valve ports are adapted to register with their corresponding fixed valve ports when the intake valve plate is in its intake operative position for opening fluid communication between the cylinder and the corresponding fixed valve ports.« less

Phase 1 Development Testing of the Advanced Manufacturing Demonstrator Engine

NASA Technical Reports Server (NTRS)

Case, Nicholas L.; Eddleman, David E.; Calvert, Marty R.; Bullard, David B.; Martin, Michael A.; Wall, Thomas R.

2016-01-01

The Additive Manufacturing Development Breadboard Engine (BBE) is a pressure-fed liquid oxygen/pump-fed liquid hydrogen (LOX/LH2) expander cycle engine that was built and operated by NASA at Marshall Space Flight Center's East Test Area. The breadboard engine was conceived as a technology demonstrator for the additive manufacturing technologies for an advanced upper stage prototype engine. The components tested on the breadboard engine included an ablative chamber, injector, main fuel valve, turbine bypass valve, a main oxidizer valve, a mixer and the fuel turbopump. All parts minus the ablative chamber were additively manufactured. The BBE was successfully hot fire tested seven times. Data collected from the test series will be used for follow on demonstration tests with a liquid oxygen turbopump and a regeneratively cooled chamber and nozzle.

Performance of a High-Speed Compression-Ignition Engine Using Multiple Orifice Fuel Injection Nozzles

NASA Technical Reports Server (NTRS)

Spanogle, J A; Foster, H H

1930-01-01

This report presents test results obtained at the Langley Memorial Aeronautical Laboratory of the National Advisory Committee for Aeronautics during an investigation to determine the relative performance of a single-cylinder, high-speed, compression-ignition engine when using fuel injection valve nozzles with different numbers, sizes, and directions of round orifices. A spring-loaded, automatic injection valve was used, centrally located at the top of a vertical disk-type combustion chamber formed between horizontally opposed inlet and exhaust valves of a 5 inch by 7 inch engine.

[Pannus Formation Six-years after Aortic and Mitral Valve Replacement with Tissue Valves;Report of a Case].

PubMed

Nakamura, Makoto; Muraoka, Arata; Aizawa, Kei; Akutsu, Hirohiko; Kurumisawa, Soki; Misawa, Yoshio

2015-07-01

A 77-year-old man presented with exertional dyspnea. He had undergone aortic and mitral valve replacement with tissue valves 6-years earlier. The patient's hemoglobin level was 9.8 g/dl and serum aspartate aminotransferase (70 mU/ml) and lactate dehydrogenase (1,112 mU/ml) were elevated. Echocardiography revealed stenosis of the prosthetic valve in the aortic position with peak flow velocity of 3.8 m/second and massive mitral regurgitation. The patient underwent repeat valve replacement. Pannus formation around both implanted valves was observed. The aortic valve orifice was narrowed by the pannus, and one cusp of the prosthesis in the mitral position was fixed and caused the regurgitation, but they were free from cusp laceration or calcification. The patient's postoperative course was uneventful, and he continues to do well 14 months after surgery.

Influence of the single EGR valve usability on development of the charge directed to individual cylinders of an internal combustion engine

NASA Astrophysics Data System (ADS)

Krakowian, Konrad; Kaźmierczak, Andrzej; Górniak, Aleksander; Wróbel, Radosław

2017-11-01

Exhaust gas recirculation systems (EGR), aside to a catalytic converters, are nowadays widely used in piston internal combustion engines to reduce nitrogen oxides (NOx) in the exhaust gas. They are characterized in that a portion of exhaust gases from the exhaust manifold is recirculated (via a condenser), and directed to a particular valve. The valve, depending on the current engine load and speed, doses the appropriate amount of exhaust gas into the exhaust manifold. Moreover, its location has a significant impact on the diverse formation of nitrogen oxides and fumes smokiness from the individual cylinders of the engine, which is a result of uneven propagation of exhaust gas into the channels of the intake manifold. This article contains the results of numerical characterized charges formed in symmetrical intake manifold with a centrally-placed EGR valve. Simulations were performed for the original intake system derived from the two-liter, turbocharged VW diesel engine.

Fault Diagnosis of Internal Combustion Engine Valve Clearance Using the Impact Commencement Detection Method

PubMed Central

Jiang, Zhinong; Wang, Zijia; Zhang, Jinjie

2017-01-01

Internal combustion engines (ICEs) are widely used in many important fields. The valve train clearance of an ICE usually exceeds the normal value due to wear or faulty adjustment. This work aims at diagnosing the valve clearance fault based on the vibration signals measured on the engine cylinder heads. The non-stationarity of the ICE operating condition makes it difficult to obtain the nominal baseline, which is always an awkward problem for fault diagnosis. This paper overcomes the problem by inspecting the timing of valve closing impacts, of which the referenced baseline can be obtained by referencing design parameters rather than extraction during healthy conditions. To accurately detect the timing of valve closing impact from vibration signals, we carry out a new method to detect and extract the commencement of the impacts. The results of experiments conducted on a twelve-cylinder ICE test rig show that the approach is capable of extracting the commencement of valve closing impact accurately and using only one feature can give a superior monitoring of valve clearance. With the help of this technique, the valve clearance fault becomes detectable even without the comparison to the baseline, and the changing trend of the clearance could be trackable. PMID:29244722

75 FR 51657 - Airworthiness Directives; Pratt & Whitney Canada Corp. (P&WC) PW615F-A Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-23

... showed that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that engine had... a dormant failure that could result in an unsafe condition. The PW615F-A engine Fuel Filter Bypass... that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that engine had worn...

Development and Characterization Testing of an Air Pulsation Valve for a Pulse Detonation Engine Supersonic Parametric Inlet Test Section

NASA Technical Reports Server (NTRS)

Tornabene, Robert

2005-01-01

In pulse detonation engines, the potential exists for gas pulses from the combustor to travel upstream and adversely affect the inlet performance of the engine. In order to determine the effect of these high frequency pulses on the inlet performance, an air pulsation valve was developed to provide air pulses downstream of a supersonic parametric inlet test section. The purpose of this report is to document the design and characterization tests that were performed on a pulsation valve that was tested at the NASA Glenn Research Center 1x1 Supersonic Wind Tunnel (SWT) test facility. The high air flow pulsation valve design philosophy and analyses performed are discussed and characterization test results are presented. The pulsation valve model was devised based on the concept of using a free spinning ball valve driven from a variable speed electric motor to generate air flow pulses at preset frequencies. In order to deliver the proper flow rate, the flow port was contoured to maximize flow rate and minimize pressure drop. To obtain sharp pressure spikes the valve flow port was designed to be as narrow as possible to minimize port dwell time.

Geometry and Mechanics in the Opening of Chiral Seed Pods

NASA Astrophysics Data System (ADS)

Armon, Shahaf; Efrati, Efi; Kupferman, Raz; Sharon, Eran

2011-09-01

We studied the mechanical process of seed pods opening in Bauhinia variegate and found a chirality-creating mechanism, which turns an initially flat pod valve into a helix. We studied configurations of strips cut from pod valve tissue and from composite elastic materials that mimic its structure. The experiments reveal various helical configurations with sharp morphological transitions between them. Using the mathematical framework of “incompatible elasticity,” we modeled the pod as a thin strip with a flat intrinsic metric and a saddle-like intrinsic curvature. Our theoretical analysis quantitatively predicts all observed configurations, thus linking the pod’s microscopic structure and macroscopic conformation. We suggest that this type of incompatible strip is likely to play a role in the self-assembly of chiral macromolecules and could be used for the engineering of synthetic self-shaping devices.

System and method for diagnosing EGR performance using NOx sensor

DOEpatents

Mazur, Christopher John

2003-12-23

A method and system for diagnosing a condition of an EGR valve used in an engine system. The EGR valve controls the portion exhaust gases produced by such engine system and fed back to an intake of such engine system. The engine system includes a NOx sensor for measuring NOx in such exhaust. The method includes: determining a time rate of change in NOx measured by the NOx sensor; comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx; and determining the condition of the EGR valve as a function of such comparison. The method also includes: determining from NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition; and determining the condition of the EGR valve as a function of a statistical analysis of such indications. The method includes determining whether the NOx sensor is faulty and wherein the EGR condition determining includes determining whether the NOx sensor is faulty.

The Technique for CFD-Simulation of Fuel Valve from Pneumatic-Hydraulic System of Liquid-Propellant Rocket Engine

NASA Astrophysics Data System (ADS)

Shabliy, L. S.; Malov, D. V.; Bratchinin, D. S.

2018-01-01

In the article the description of technique for simulation of valves for pneumatic-hydraulic system of liquid-propellant rocket engine (LPRE) is given. Technique is based on approach of computational hydrodynamics (Computational Fluid Dynamics - CFD). The simulation of a differential valve used in closed circuit LPRE supply pipes of fuel components is performed to show technique abilities. A schematic and operation algorithm of this valve type is described in detail. Also assumptions made in the construction of the geometric model of the hydraulic path of the valve are described in detail. The calculation procedure for determining valve hydraulic characteristics is given. Based on these calculations certain hydraulic characteristics of the valve are given. Some ways of usage of the described simulation technique for research the static and dynamic characteristics of the elements of the pneumatic-hydraulic system of LPRE are proposed.

Engineering based assessment for a shape design of a pediatric ePTFE pulmonary conduit valve.

PubMed

Tsuboko, Yusuke; Shiraishi, Yasuyuki; Yamada, Akihiro; Yambe, Tomoyuki; Miura, Hidekazu; Mura, Seitaro; Yamagishi, Masaaki

2016-08-01

The authors examined the hemodynamic characteristics of expanded polytetrafluoroethylene (ePTFE) pulmonary valved conduits quantitatively by our originally developed pediatric pulmonary mechanical circulatory system, in order to suggest the optimal shape design. The system consisted of pneumatically driven right atrium and ventricle model, a pulmonary valve chamber, and elastic pulmonary compliance model with peripheral vascular resistance units, a venous reservoir. We employed two different types of ePTFE valve and evaluated the relationship between the leaflets motion and hemodynamic characteristics by using a high-speed video camera. As a result, we successfully reproduced hemodynamic simulations in our pediatric pulmonary mock system. We confirmed that the presence of bulging sinuses in the pulmonary valved conduit reduced the transvalvular energy loss and increased the valve opening area during systolic period. Our engineering-based in vitro analysis could be useful for proposing a shape design optimization of sophisticated pediatric ePTFE pulmonary valve.

Inlet Flow Valve Engine Analyses

NASA Technical Reports Server (NTRS)

Champagne, G. A.

2004-01-01

Pratt&Whitney, under Task Order 13 of the NASA Large Engine Technology (LET) Contract, conducted a study to determine the operating characteristics, performance and weights of Inlet Flow Valve (IFV) propulsion concepts for a Mach 2.4 High Speed Civil Transport (HSCT).

Kangaroo versus porcine aortic valve tissue--valve geometry morphology, tensile strength and calcification potential.

PubMed

Neethling, W M; Papadimitriou, J M; Swarts, E; Hodge, A J

2000-06-01

Valve related factors and patient related factors are responsible for calcification of valvular bioprostheses. Recent studies showed different donor and recipient species have different influences on the total calcification rate of bioprostheses. This study was performed to evaluate and compare Kangaroo aortic valve leaflets with porcine aortic valve leaflets. Experimental design. Prospective study. Setting. Cardio-thoracic experimental research of a university department. Glutaraldehyde-fixed Kangaroo and porcine valve leaflets were evaluated in vitro according to valve geometry (internal diameter and leaflet thickness), morphology (light and electron microscopy) and tensile strength. In vivo evaluation consisted of implantation in a rat model for 8 weeks, Von Kossa stain for calcium and atomic absorption spectrophotometry for total extractable calcium content. Kangaroo valves indicated a smaller internal valve diameter as well as a thinner valve leaflet (p<0.01, ANOVA) at corresponding body weight, less proteoglycan spicules in the fibrosa, increased elasticity (p<0.05) and low calcification potential (p<0.01, confidence interval 95%). Kangaroo aortic valve leaflets have different valvular qualities compared to porcine valve tissue. Kangaroo valve leaflets are significantly superior to porcine valve leaflets as far as calcification is concerned. These results are encouraging and suggest further in vivo evaluation in a larger animal model before clinical application can be considered.

Split radiator design for heat rejection optimization for a waste heat recovery system

DOEpatents

Ernst, Timothy C.; Nelson, Christopher R.

2016-10-18

A cooling system provides improved heat recovery by providing a split core radiator for both engine cooling and condenser cooling for a Rankine cycle (RC). The cooling system includes a radiator having a first cooling core portion and a second cooling core portion. An engine cooling loop is fluidly connected the second cooling core portion. A condenser of an RC has a cooling loop fluidly connected to the first cooling core portion. A valve is provided between the engine cooling loop and the condenser cooling loop adjustably control the flow of coolant in the condenser cooling loop into the engine cooling loop. The cooling system includes a controller communicatively coupled to the valve and adapted to determine a load requirement for the internal combustion engine and adjust the valve in accordance with the engine load requirement.

Study of the Pressure and Velocity Across the Aortic Valve

NASA Astrophysics Data System (ADS)

Kyung, Seo Young; Chung, Erica Soyun; Lee, Joo Hee; Kyung, Hayoung; Choi, Si Young

Biomechanics of the heart, requiring an extensive understanding of the complexity of the heart, have become the interests of many biomedical engineers in cardiology today. In order to study aortic valve disease, engineers have focused on the data obtained through bio-fluid flow analysis. To further this study, physical and computational analysis on the biomechanical determinants of blood flow in the stenosed aortic valve have been examined. These observations, along with the principles of cardiovascular physiology, confirm that when blood flows through the valve opening, pressure gradient across the valve is produced as a result of stenosis of the aortic valve. The aortic valve gradient is used to interpret the increase and decrease on each side of the defective valve. To compute different pressure gradients across the aortic valve, this paper analyzes Aortic Valve Areas (AVA) using simulations based on the continuity equation and Gorlin equation. The data obtained from such analysis consist of patients in the AS category that display mild Aortic Valve Velocity (AVV) and pressure gradient. Such correlation results in the construction of a dependent relationship between severe AS causing LV systolic dysfunction and the transaortic velocity.

The Use of Large Valve Overlap in Scavenging a Supercharged Spark-ignition Engine Using Fuel Injection

NASA Technical Reports Server (NTRS)

Schey, Oscar W; Young, Alfred W

1932-01-01

This investigation was conducted to determine the effect of more complete scavenging on the full throttle power and the fuel consumption of a four-stroke-cycle engine. The NACA single-cylinder universal test engine equipped with both a fuel-injection system and a carburetor was used. The engine was scavenged by using a large valve overlap and maintaining a pressure in the inlet manifold of 2 inches of mercury above atmospheric. The maximum valve overlap used was 112 degrees. Tests were conducted for a range of compression ratios from 5.5 to 8.5. Except for variable speed tests, all tests were conducted at an engine speed of 1,500 r.p.m. The results of the tests show that the clearance volume of an engine can be scavenged by using a large valve overlap and about 2 to 5 inches of mercury pressure difference between the inlet and exhaust valve. With a fuel-injection system when the clearance volume was scavenged, a b.m.e.p. of over 185 pounds per square inch and a fuel consumption of 9.45 pound per brake horsepower per hour were obtained with a 6.5 compression ratio. An increase of approximately 10 pounds per square inch b.m.e.p. was obtained with a fuel-injection system over that with a carburetor.

Expanding Robust HCCI Operation with Advanced Valve and Fuel Control Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szybist, J. P.; Confer, K.

2012-09-11

Delphi Automotive Systems and ORNL established this CRADA to advance the commercialization potential of the homogeneous charge compression ignition (HCCI) advanced combustion strategy for gasoline engine platforms. HCCI combustion has been shown by others to produce high diesel-like efficiency on a gasoline engine platform while simultaneously producing low NOX and particulate matter emissions. However, the commercialization barriers that face HCCI combustion are significant, with requirements for a more active engine control system, likely with next-cycle closed-loop feedback control, and with advanced valve train technologies to enable negative valve overlap conditions. In the partnership between Delphi and ORNL, each organization broughtmore » a unique and complementary set of skills to the project. Delphi has made a number of breakthroughs with production-intent valve train technologies and controls in recent years to make a part time production-intent HCCI engine plausible. ORNL has extensive knowledge and expertise with HCCI combustion, and also has a versatile research engine with hydraulic valve actuation (HVA) that is useful for guiding production of a cam-based HCCI system. Partnering these knowledge bases and capabilities was essential towards making progress to better understand HCCI combustion and the commercialization barriers that it faces. ORNL and Delphi maintained strong collaboration throughout the project. Meetings were held regularly, with additional reports, presentations, and meetings as necessary to maintain progress. Delphi provided guidance to ORNL regarding operational strategies to investigate on their single-cylinder research engine with HVA and data from their experimental multi-cylinder engine for modeling. ORNL provided single-cylinder engine data and modeling results.« less

Two-step rocket engine bipropellant valve concept

NASA Technical Reports Server (NTRS)

Capps, J. E.; Ferguson, R. E.; Pohl, H. O.

1969-01-01

Initiating combustion of altitude control rocket engines in a precombustion chamber of ductile material reduces high pressure surges generated by hypergolic propellants. Two-step bipropellant valve concepts control initial propellant flow into precombustion chamber and subsequent full flow into main chamber.

Numerical Simulation of Flow in Fluidic Valves in Rotating Detonation Engines

NASA Astrophysics Data System (ADS)

Gopalakrishnan, Nandini

Rotating detonation engines (RDE) have received considerable research attention in recent times for use in propulsion systems. The cycle frequency of operation of an RDE can be as high as 10,000 Hz. Conventional mechanical valves cannot operate at such high frequencies, leading to the need for propellant injectors or valves with no moving parts. A fluidic valve is such a valve and is the focus of this study. The valve consists of an orifice connected to a constant area plenum cavity which operates at constant pressure. The fluidic valve supplies propellants to the detonation tube through the orifice. Hydrogen - oxygen detonation is studied in a tube with fluidic valves. A detailed 19-step chemical reaction mechanism has been used to model detonation and the flow simulated in ANSYS Fluent. This research aims to determine the location of contact surface in the cavity and the time taken for the contact surface to leave the valve after a shock wave has passed through it. This will help us understand if the steady-state flow in the cavity is comprised of detonation products or fresh propellants.

Pulse-width-modulated servo valve for autopilot system

NASA Technical Reports Server (NTRS)

Garner, H. D.

1974-01-01

Valve was developed for autopilot wing-lever system and is to be used in light, single-engine aircraft. Valve is controlled by electronic circuit which feeds pulse-width-modulated correction signals to two solenoids. Valve housing is cast from plastic, making it very economical to fabricate.

46 CFR 52.01-120 - Safety valves and safety relief valves (modifies PG-67 through PG-73).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Safety valves and safety relief valves (modifies PG-67 through PG-73). 52.01-120 Section 52.01-120 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-120 Safety valves and safety relief valves (modifies PG-67 through PG-73). (a)...

46 CFR 52.01-120 - Safety valves and safety relief valves (modifies PG-67 through PG-73).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Safety valves and safety relief valves (modifies PG-67 through PG-73). 52.01-120 Section 52.01-120 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-120 Safety valves and safety relief valves (modifies PG-67 through PG-73). (a)...

46 CFR 52.01-120 - Safety valves and safety relief valves (modifies PG-67 through PG-73).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Safety valves and safety relief valves (modifies PG-67 through PG-73). 52.01-120 Section 52.01-120 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-120 Safety valves and safety relief valves (modifies PG-67 through PG-73). (a)...

46 CFR 52.01-120 - Safety valves and safety relief valves (modifies PG-67 through PG-73).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Safety valves and safety relief valves (modifies PG-67 through PG-73). 52.01-120 Section 52.01-120 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-120 Safety valves and safety relief valves (modifies PG-67 through PG-73). (a)...

46 CFR 52.01-120 - Safety valves and safety relief valves (modifies PG-67 through PG-73).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Safety valves and safety relief valves (modifies PG-67 through PG-73). 52.01-120 Section 52.01-120 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-120 Safety valves and safety relief valves (modifies PG-67 through PG-73). (a)...

Pericardial tissue valves and Gore-Tex conduits as an alternative for right ventricular outflow tract replacement in children.

PubMed

Allen, Bradley S; El-Zein, Chawki; Cuneo, Betina; Cava, Joseph P; Barth, Mary Jane; Ilbawi, Michel N

2002-09-01

There is still no perfect conduit for reconstruction of the right ventricular outflow tract (RVOT) in children. Homografts are not always available in the appropriate size, and degenerate in a few years. This study evaluates the pericardial valve with Gore-Tex conduit as an alternative for RVOT construction. From January 1, 1993, to September 30, 1999, a pericardial tissue valve was inserted in all patients undergoing RVOT reconstruction or pulmonary valve replacement (PVR) who were large enough to accommodate a tissue valve. In patients without a native main pulmonary artery, a new technique was used to construct an RV-PA conduit out of a flat sheet of Gore-Tex, as Dacron frequently leads to stenosis. Data were collected by retrospective review, follow-up echocardiograms, and assessment by a single cardiologist. There were 48 patients, 22 undergoing a PVR alone and 26 a RV-PA valved Gore-Tex conduit. Diagnosis included tetralogy of Fallot (n = 25); truncus arteriosis (n = 9); ventricular septal defect with PA (n = 5); DORV (n = 4); D-TGA with PS (n = 2); and 1 each IAA with sub AS, VSD with PI, and PS s/p Ross procedure. Patient age ranged from 3 to 33 years and 98% were reoperations. The valve sizes ranged from 19 to 33 mm and the median hospital length of stay was 4 days. There were 2 (4.2%) perioperative and 1 (2.1%) late deaths, none related to the valve or Gore-Tex conduit. At a follow-up of 15 to 86 months (mean 43 +/- 16 months), all remaining 45 patients are New York Heart Association class I, all valves are functional, and no patient has required valve or conduit replacement or revision; more importantly, echocardiogram revealed no significant valve or conduit stenosis (mean gradient 16 +/- 8 mm Hg) and no evidence of regurgitation or structural degeneration. A pericardial tissue valve and Gore-Tex conduit provides a reliable alternative for RVOT reconstruction in pediatric patients. It is readily available, molds in the limited retrosternal space, and has outstanding intermediate results with no evidence of failure or deterioration up to 7 years after insertion.

Multi-bottle, no compressor, mean pressure control system for a Stirling engine

DOEpatents

Corey, John A.

1990-01-01

The invention relates to an apparatus for mean pressure control of a Stirling engine without the need for a compressor. The invention includes a multi-tank system in which there is at least one high pressure level tank and one low pressure level tank wherein gas flows through a maximum pressure and supply line from the engine to the high pressure tank when a first valve is opened until the maximum pressure of the engine drops below that of the high pressure tank opening an inlet regulator to permit gas flow from the engine to the low pressure tank. When gas flows toward the engine it flows through the minimum pressure supply line 2 when a second valve is opened from the low pressure tank until the tank reaches the engine's minimum pressure level at which time the outlet regulator opens permitting gas to be supplied from the high pressure tank to the engine. Check valves between the two tanks prevent any backflow of gas from occurring.

Tissue Engineering Applications of Three-Dimensional Bioprinting.

PubMed

Zhang, Xiaoying; Zhang, Yangde

2015-07-01

Recent advances in tissue engineering have adapted the additive manufacturing technology, also known as three-dimensional printing, which is used in several industrial applications, for the fabrication of bioscaffolds and viable tissue and/or organs to overcome the limitations of other in vitro conventional methods. 3D bioprinting technology has gained enormous attention as it enabled 3D printing of a multitude of biocompatible materials, different types of cells and other supporting growth factors into complex functional living tissues in a 3D format. A major advantage of this technology is its ability for simultaneously 3D printing various cell types in defined spatial locations, which makes this technology applicable to regenerative medicine to meet the need for suitable for transplantation suitable organs and tissues. 3D bioprinting is yet to successfully overcome the many challenges related to building 3D structures that closely resemble native organs and tissues, which are complex structures with defined microarchitecture and a variety of cell types in a confined area. An integrated approach with a combination of technologies from the fields of engineering, biomaterials science, cell biology, physics, and medicine is required to address these complexities. Meeting this challenge is being made possible by directing the 3D bioprinting to manufacture biomimetic-shaped 3D structures, using organ/tissue images, obtained from magnetic resonance imaging and computerized tomography, and employing computer-aided design and manufacturing technologies. Applications of 3D bioprinting include the generation of multilayered skin, bone, vascular grafts, heart valves, etc. The current 3D bioprinting technologies need to be improved with respect to the mechanical strength and integrity in the manufactured constructs as the presently used biomaterials are not of optimal viscosity. A better understanding of the tissue/organ microenvironment, which consists of multiple types of cells, is imperative for successful 3D bioprinting.

Engine Cycle Analysis of Air Breathing Microwave Rocket with Reed Valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukunari, Masafumi; Komatsu, Reiji; Yamaguchi, Toshikazu

The Microwave Rocket is a candidate for a low cost launcher system. Pulsed plasma generated by a high power millimeter wave beam drives a blast wave, and a vehicle acquires impulsive thrust by exhausting the blast wave. The thrust generation process of the Microwave Rocket is similar to a pulse detonation engine. In order to enhance the performance of its air refreshment, the air-breathing mechanism using reed valves is under development. Ambient air is taken to the thruster through reed valves. Reed valves are closed while the inside pressure is high enough. After the time when the shock wave exhaustsmore » at the open end, an expansion wave is driven and propagates to the thrust-wall. The reed valve is opened by the negative gauge pressure induced by the expansion wave and its reflection wave. In these processes, the pressure oscillation is important parameter. In this paper, the pressure oscillation in the thruster was calculated by CFD combined with the flux through from reed valves, which is estimated analytically. As a result, the air-breathing performance is evaluated using Partial Filling Rate (PFR), the ratio of thruster length to diameter L/D, and ratio of opening area of reed valves to superficial area {alpha}. An engine cycle and predicted thrust was explained.« less

Kangaroo vs. porcine aortic valves: calcification potential after glutaraldehyde fixation.

PubMed

Narine, K; Chéry, Cyrille C; Goetghebeur, Els; Forsyth, R; Claeys, E; Cornelissen, Maria; Moens, L; Van Nooten, G

2005-01-01

The aim of this study was to evaluate and compare the calcification potential of kangaroo and porcine aortic valves after glutaraldehyde fixation at both low (0.6%) and high (2.0%) concentrations of glutaraldehyde in the rat subcutaneous model. To our knowledge this is the first report comparing the time-related, progressive calcification of these two species in the rat subcutaneous model. Twenty-two Sprague-Dawley rats were each implanted with two aortic valve leaflets (porcine and kangaroo) after fixation in 0.6% glutaraldehyde and two aortic valve leaflets (porcine and kangaroo) after fixation in 2% glutaraldehyde respectively. Animals were sacrificed after 24 h and thereafter weekly for up to 10 weeks after implantation. Calcium content was determined using inductively coupled plasma-mass spectrometry and confirmed histologically. Mean calcium content per milligram of tissue (dry weight) treated with 0.6 and 2% glutaraldehyde was 116.2 and 110.4 microg/mg tissue for kangaroo and 95.0 and 106.8 microg/mg tissue for porcine valves. Calcium content increased significantly over time (8.8 microg/mg tissue per week) and was not significantly different between groups. Regression analysis of calcification over time showed no significant difference in calcification of valves treated with 0.6 or 2% glutaraldehyde within and between the two species. Using the subcutaneous model, we did not detect a difference in calcification potential between kangaroo and porcine aortic valves treated with either high or low concentrations of glutaraldehyde. Copyright 2005 S. Karger AG, Basel.

Application of image converter camera to measure flame propagation in S. I. engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, A.; Ishii, K.; Sasaki, T.

1989-01-01

A combustion flame visualization system, for use as an engine diagnostics tool, was developed in order to evaluate combustion chamber shapes in the development stage of mass-produced spark ignition (S.I.) engines. The system consists of an image converter camera and a computer-aided image processing system. The system is capable of high speed photography (10,000 fps) at low intensity light (1,000 cd/m/sup 2/), and of real-time display of the raw images of combustion flames. By using this system, flame structure estimated from the brightness level on a photograph and direction of flame propagation in a mass-produced 4-valve engine were measured. Itmore » was observed that the difference in the structure and the propagation of the flame in the cases of 4-valve and quasi-2-valve combustion chambers, which has the same in the pressure diagram, were detected. The quasi-2-valve configuration was adopted in order to improve swirl intensity.« less

Conceptual Study of the LB/TS (Large Blast/Thermal Simulator) Instrumentation, Data Acquisition and Facility Controls System.

DTIC Science & Technology

1984-09-12

423, R. Jones ATTN: DAEN-ECE-T ATTN: DAEN-RDL DEPARTMENT OF THE AIR FORCE ATTN: DAEN-RDM. J. Healy ATTN: DAEN-ZCM Air Force Engineering & Services Ctr...31 7 Comparison Chart of Various Femperature Sensors (Prepared by HY-CAL Engineering ) ... ...... 36 8 Temperature Sensor Requirements and...Positions * TRS Valve Positions; LOX, AL, N2 Solenoid and Control . - Valve Positions 1.4 Air Compressor System Control * Valve Positions 0 Pressure

Total ellipse of the heart valve: the impact of eccentric stent distortion on the regional dynamic deformation of pericardial tissue leaflets of a transcatheter aortic valve replacement

PubMed Central

Gunning, Paul S.; Saikrishnan, Neelakantan; Yoganathan, Ajit P.; McNamara, Laoise M.

2015-01-01

Transcatheter aortic valve replacements (TAVRs) are a percutaneous alternative to surgical aortic valve replacements and are used to treat patients with aortic valve stenosis. This minimally invasive procedure relies on expansion of the TAVR stent to radially displace calcified aortic valve leaflets against the aortic root wall. However, these calcium deposits can impede the expansion of the device causing distortion of the valve stent and pericardial tissue leaflets. The objective of this study was to elucidate the impact of eccentric TAVR stent distortion on the dynamic deformation of the tissue leaflets of the prosthesis in vitro. Dual-camera stereophotogrammetry was used to measure the regional variation in strain in a leaflet of a TAVR deployed in nominal circular and eccentric (eccentricity index = 28%) orifices, representative of deployed TAVRs in vivo. It was observed that (i) eccentric stent distortion caused incorrect coaptation of the leaflets at peak diastole resulting in a ‘peel-back’ leaflet geometry that was not present in the circular valve and (ii) adverse bending of the leaflet, arising in the eccentric valve at peak diastole, caused significantly higher commissure strains compared with the circular valve in both normotensive and hypertensive pressure conditions (normotension: eccentric = 13.76 ± 2.04% versus circular = 11.77 ± 1.61%, p = 0.0014, hypertension: eccentric = 15.07 ± 1.13% versus circular = 13.56 ± 0.87%, p = 0.0042). This study reveals that eccentric distortion of a TAVR stent can have a considerable impact on dynamic leaflet deformation, inducing deleterious bending of the leaflet and increasing commissures strains, which might expedite leaflet structural failure compared to leaflets in a circular deployed valve. PMID:26674192

Thermoelectric system

DOEpatents

Reiners, Eric A.; Taher, Mahmoud A.; Fei, Dong; McGilvray, Andrew N.

2007-10-30

In one particular embodiment, an internal combustion engine is provided. The engine comprises a block, a head, a piston, a combustion chamber defined by the block, the piston, and the head, and at least one thermoelectric device positioned between the combustion chamber and the head. In this particular embodiment, the thermoelectric device is in direct contact with the combustion chamber. In another particular embodiment, a cylinder head configured to sit atop a cylinder bank of an internal combustion engine is provided. The cylinder head comprises a cooling channel configured to receive cooling fluid, valve seats configured for receiving intake and exhaust valves, and thermoelectric devices positioned around the valve seats.

OMS engine shutoff valve and actuation system design and evaluation. [for space shuttles

NASA Technical Reports Server (NTRS)

Wichmann, H.

1974-01-01

Shutoff valve and actuation system concepts that are most suitable for the Orbital Maneuvering Systems engine application were determined. Emphasis was placed on the ten year and 100 mission life requirement, propellant and propellant residue compatibility and weight. It was found that poppet or ball valves utilizing electric or electropneumatic actuation were most applicable. Preliminary design layouts of a number of valve and actuation concepts were prepared and analyzed to make the optimum concept selection. Pneumatic actuation systems were required to feature their own pneumatic supply so that for the quad redundant valve, it was necessary to include two pneumatic supply systems, one for each of the series legs of the quad redundant package. The requirement for the pneumatic package placed heavy reliability, weight, and maintenance penalties upon electropneumatic actuation systems. The two valve and actuation systems concepts selected featured electric torque motor operation and a poppet as well as a ball valve concept with a retractable seal.

Actuation and system design and evaluation OMS engine shutoff valve, Volume 1. [space shuttles

NASA Technical Reports Server (NTRS)

Dunn, V. B.

1975-01-01

A technology program was conducted to identify and verify the optimum valve and actuation system concept for the Space Shuttle Orbit Maneuvering System engine. Of major importance to the valve and actuation system selection was the ten-year, 100-mission, 10,000-cycle life requirement, while maintaining high reliability, low leakage, and low weight. Valve and actuation system concepts were comparatively evaluated against past valve failure reports and potential failure modes due to the shuttle mission profile to aid in the selection of the most optimum concept for design, manufacture and verification testing. Two valve concepts were considered during the preliminary design stage; i.e., the moving seat and lifting ball. Two actuation systems were manufactured and tested. Test results demonstrate the viability of a lifting ball concept as well as the applicability of an ac motor actuation system to best meet the requirements of the shuttle mission.

Systems and method for delivering liquified gas to an engine

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; O'Brien, James E.; Siahpush, Ali S.; Brown, Kevin B.

2002-01-01

A liquified gas delivery system for a motorized platform includes a holding tank configured to receive liquified gas. A first conduit extends from a vapor holding portion of the tank to a valve device. A second conduit extends from a liquid holding portion of the tank to the valve device. Fluid coupled to the valve device is a vaporizer which is in communication with an engine. The valve device selectively withdraws either liquified gas or liquified gas vapor from the tank depending on the pressure within the vapor holding portion of the tank. Various configurations of the delivery system can be utilized for pressurizing the tank during operation.

Methods For Delivering Liquified Gas To An Engine

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; O'Brien, James E.; Siahpush, Ali S.; Brown, Kevin B.

2003-09-16

A liquified gas delivery system for a motorized platform includes a holding tank configured to receive liquified gas. A first conduit extends from a vapor holding portion of the tank to a valve device. A second conduit extends from a liquid holding portion of the tank to the valve device. Fluid coupled to the valve device is a vaporizer which is in communication with an engine. The valve device selectively withdraws either liquified gas or liquified gas vapor from the tank depending on the pressure within the vapor holding portion of the tank. Various configurations of the delivery system can be utilized for pressurizing the tank during operation.

Methods For Delivering Liquified Gas To An Engine

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; O'Brien, James E.; Siahpush, Ali S.; Brown, Kevin B.

2005-10-11

A liquified gas delivery system for a motorized platform includes a holding tank configured to receive liquified gas. A first conduit extends from a vapor holding portion of the tank to a valve device. A second conduit extends from a liquid holding portion of the tank to the valve device. Fluid coupled to the valve device is a vaporizer which is in communication with an engine. The valve device selectively withdraws either liquified gas or liquified gas vapor from the tank depending on the pressure within the vapor holding portion of the tank. Various configurations of the delivery system can be utilized for pressurizing the tank during operation.

Systems for delivering liquified gas to an engine

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; O'Brien, James E.; Siahpush, Ali S.; Brown, Kevin B.

2006-05-16

A liquified gas delivery system for a motorized platform includes a holding tank configured to receive liquified gas. A first conduit extends from a vapor holding portion of the tank to a valve device. A second conduit extends from a liquid holding portion of the tank to the valve device. Fluid coupled to the valve device is a vaporizer which is in communication with an engine. The valve device selectively withdraws either liquified gas or liquified gas vapor from the tank depending on the pressure within the vapor holding portion of the tank. Various configurations of the delivery system can be utilized for pressurizing the tank during operation.

46 CFR 64.41 - Stop valve closure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Stop valve closure. 64.41 Section 64.41 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS Standards for an MPT § 64.41 Stop valve closure. A stop valve that operates by a screwed...

33 CFR 183.528 - Fuel stop valves.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Fuel stop valves. 183.528 Section...) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Fuel Systems Equipment Standards § 183.528 Fuel stop valves. (a) Each electrically operated fuel stop valve in a fuel line between the fuel tank and the engine...

Fuel control for gas turbine with continuous pilot flame

DOEpatents

Swick, Robert M.

1983-01-01

An improved fuel control for a gas turbine engine having a continuous pilot flame and a fuel distribution system including a pump drawing fuel from a source and supplying a line to the main fuel nozzle of the engine, the improvement being a control loop between the pump outlet and the pump inlet to bypass fuel, an electronically controlled throttle valve to restrict flow in the control loop when main nozzle demand exists and to permit substantially unrestricted flow without main nozzle demand, a minimum flow valve in the control loop downstream of the throttle valve to maintain a minimum pressure in the loop ahead of the flow valve, a branch tube from the pilot flame nozzle to the control loop between the throttle valve and the minimum flow valve, an orifice in the branch tube, and a feedback tube from the branch tube downstream of the orifice to the minimum flow valve, the minimum flow valve being operative to maintain a substantially constant pressure differential across the orifice to maintain constant fuel flow to the pilot flame nozzle.

A WEAR MODEL FOR DIESEL ENGINE EXHAUST VALVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blau, Peter Julian

2009-11-01

The work summarized here comprises the concluding effort of a multi-year project, funded by the U.S. Department of Energy, Office of Vehicle Technologies. It supports the development of a better understanding of advanced diesel engine designs in which enhanced power density, energy efficiency, and emissions control place increasing demands upon the durability of engine materials. Many kinds of metallic alloys are used in engines depending on the operating stresses, temperatures, and chemical environments. Exhaust valves, for example, are subjected to high temperatures and repetitive surface contacts that place demands on durability and frictional characteristics of the materials. Valves must continuemore » to seal the combustion chamber properly for thousands of hours of cyclic engine operation and under varying operating conditions. It was the focus of this effort to understand the wear processes in the valve-seat area and to develop a model for the surface deformation and wear of that important interface. An annotated bibliography is provided to illustrate efforts to understand valve wear and to investigate the factors of engine operation that affect its severity and physical manifestation. The project for which this modeling effort was the final task, involved construction of a high-temperature repetitive impact test system as well as basic tribology studies of the combined processes of mechanical wear plus oxidation at elevated temperatures. Several publications resulted from this work, and are cited in this report. The materials selected for the experimental work were high-performance alloys based on nickel and cobalt. In some cases, engine-tested exhaust valves were made available for wear analysis and to ensure that the modes of surface damage produced in experiments were simulative of service. New, production-grade exhaust valves were also used to prepare test specimens for experimental work along with the other alloy samples. Wear analysis of valves and seats run for hundreds of hours in heavy-duty diesels provided insights into the kinds of complexity that the contact conditions in engines can produce, and suggested the physical basis for the current approach to modeling. The model presented here involves four terms, two representing the valve response and two for its mating seat material. The model's structure assumes that wear that takes place under a complex combination of plastic deformation, tangential shear, and oxidation. Tribolayers form, are removed, and may reform. Layer formation affects the friction forces in the interface, and in turn, the energy available to do work on the materials to cause wear. To provide friction data for the model at various temperatures, sliding contact experiments were conducted from 22 to 850 C in a pin-on-disk apparatus at ORNL. In order to account for the behavior of different materials and engine designs, parameters in all four terms of the model can be adjusted to account for wear-in and incubation periods before the dominant wear processes evolve to their steady-state rates. For example, the deformation rate is assumed to be maximum during the early stages of operation, and then, due to material work-hardening and the increase in nominal contact area (which reduces the load per unit area), decreases to a lower rate at long times. Conversely, the rate of abrasion increases with time or number of cycles due to the build-up of oxides and tribo-layers between contact surfaces. The competition between deformation and abrasion results in complex, non-linear behavior of material loss per cycle of operation. Furthermore, these factors are affected by valve design features, such as the angle of incline of the valve seat. Several modeling scenarios are presented to demonstrate how the wear profile versus number of cycles changes in response to: (a) different relative abrasion rates of the seat and valve materials, (b) the friction coefficient as a function of temperature, (c) the relative deformation contribution of valve and seat materials, and (d) an interruption in the dominant wear process.« less

Lyme Endocarditis.

PubMed

Paim, Ana C; Baddour, Larry M; Pritt, Bobbi S; Schuetz, Audrey N; Wilson, John W

2018-03-29

We describe a case of Lyme endocarditis which, to our knowledge, is the first reported case confirmed by molecular diagnostics in the United States. Valvular involvement as a manifestation of Lyme carditis is rare 4 . The first case describing a possible association between Lyme disease and cardiac valvular disease in the United States was published in 1993 5 . Since that time, there have been 2 cases of Lyme endocarditis confirmed by Borrelia positive 16S rRNA polymerase chain reaction (PCR) and sequencing from valvular tissue 8,10 and reported from Europe. We present the case of a 68-year-old male with progressive dyspnea had mitral valve perforation with severe mitral valve insufficiency and perforation seen on transesophageal echocardiogram. Subsequently resected valve tissue had sings of acute inflammation without organisms seen. Although blood and valve tissue cultures were negative, 16S rRNA PCR and sequencing demonstrated Borrelia burgdorferi. Lyme endocarditis can be a challenging diagnosis to confirm, given the rarity of cases and the need for molecular tools of resected valve tissue. It should be included among diagnostic possibilities in patients with culture-negative endocarditis who have exposure to ticks in endemic and emerging areas of Lyme disease. Copyright © 2018. Published by Elsevier Inc.

Development and modification of a single overhead camshaft 4-valve 4-stroke 135 cc formula varsity race car engine

NASA Astrophysics Data System (ADS)

Abdullah, M. A.; Tamaldin, N.; Rusnandi, H.; Manoharan, T.; Samsir, M. A.

2013-12-01

The engine that was chosen to be developed and modified is Yamaha LC 135 Single Overhead Camshaft (SOHC) 4-valve 4-stroke 135cc liquid-cooled engine. The engine selection is based on the specification, rule and regulation in UTeM Formula Varsity 2012 (FV 2012). The engine performance is determined by engine operating characteristics. The engine air flow affects the filtration, intake and exhaust systems. The heat from the engine rejected to the surrounding through the active cooling system which has radiator and fan. The selection of the engine is based on weighted decision matrix which consists of reliability, operating and maintenance cost, fuel consumption and weight. The score of the matrix is formulated based on relative weighted factor among the selections. It been compared between Yamaha LC 135 Single Overhead Camshaft (SOHC) 4-valve 4-stroke 135cc liquid-cooled engine, Honda Wave 125 X Air Cooled, 4 Cycle Engine Overhead Camshaft (OHC) and Suzuki Shogun RR 4 stroke air cooled Single Overhead Camshaft (SOHC). The modification is applied to the engine through the simulation and tuning of Capacitor Discharge Ignition (CDI).

Method and apparatus for rapid stopping and starting of a thermoacoustic engine

DOEpatents

Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.

2003-11-11

A thermoacoustic engine-driven system with a hot heat exchanger, a regenerator or stack, and an ambient heat exchanger includes a side branch load for rapid stopping and starting, the side branch load being attached to a location in the thermoacoustic system having a nonzero oscillating pressure and comprising a valve, a flow resistor, and a tank connected in series. The system is rapidly stopped simply by opening the valve and rapidly started by closing the valve.

Assessing Anticalcification Treatments in Bioprosthetic Tissue by Using the New Zealand Rabbit Intramuscular Model

PubMed Central

Wright, Gregory A; Faught, Joelle M; Olin, Jane M

2009-01-01

The objective of this work was to demonstrate that the New Zealand White (NZW) rabbit intramuscular model can be used for detecting calcification in bioprosthetic tissue and to compare the calcification in the rabbit to that of native human valves. The rabbit model was compared with the commonly used Sprague–Dawley rat subcutaneous model. Eighteen rabbits and 18 rats were used to assess calcification in bioprosthetic tissue over time (7, 14, 30, and 90 d). The explanted rabbit and rat tissue discs were measured for calcium by using atomic absorption and Raman spectroscopy. Calcium deposits on the human valve explants were assessed by using Raman spectroscopy. The results showed that the NZW rabbit model is robust for detecting calcification in a shorter duration (14 d), with less infection complications, more space to implant tissue groups (thereby reducing animal use numbers), and a more metabolically and mechanically dynamic environment than the rat subcutaneous model . The human explanted valves and rabbit explanted tissue both showed Raman peaks at 960 cm−1 which is representative of hydroxyapatite. Hydroxyapatite is the final calcium and phosphate species in the calcification of bioprosthetic heart valves and rabbit intramuscular implants. The NZW rabbit intramuscular model is an effective model for assessing calcification in bioprosthetic tissue. PMID:19619417

46 CFR 153.208 - Ballast equipment.

Code of Federal Regulations, 2013 CFR

2013-10-01

... BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Design and Equipment General Vessel... engine room or accommodation space. (b) Piping used only to fill a dedicated ballast tank adjacent to a cargo tank may enter an engine room or accommodation space if the piping has a valve or valving...

46 CFR 153.208 - Ballast equipment.

Code of Federal Regulations, 2011 CFR

2011-10-01

... BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Design and Equipment General Vessel... engine room or accommodation space. (b) Piping used only to fill a dedicated ballast tank adjacent to a cargo tank may enter an engine room or accommodation space if the piping has a valve or valving...

46 CFR 153.208 - Ballast equipment.

Code of Federal Regulations, 2010 CFR

2010-10-01

... BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Design and Equipment General Vessel... engine room or accommodation space. (b) Piping used only to fill a dedicated ballast tank adjacent to a cargo tank may enter an engine room or accommodation space if the piping has a valve or valving...

Engine with pulse-suppressed dedicated exhaust gas recirculation

DOEpatents

Keating, Edward J.; Baker, Rodney E.

2016-06-07

An engine assembly includes an intake assembly, a spark-ignited internal combustion engine, and an exhaust assembly. The intake assembly includes a charge air cooler disposed between an exhaust gas recirculation (EGR) mixer and a backpressure valve. The charge air cooler has both an inlet and an outlet, and the back pressure valve is configured to maintain a minimum pressure difference between the inlet of the charge air cooler and an outlet of the backpressure valve. A dedicated exhaust gas recirculation system is provided in fluid communication with at least one cylinder and with the EGR mixer. The dedicated exhaust gas recirculation system is configured to route all of the exhaust gas from the at least one cylinder to the EGR mixer for recirculation back to the engine.

* A Rat Model for the In Vivo Assessment of Biological and Tissue-Engineered Valvular and Vascular Grafts.

PubMed

Sugimura, Yukiharu; Schmidt, Anna Kathrin; Lichtenberg, Artur; Assmann, Alexander; Akhyari, Payam

2017-12-01

The demand for an improvement of the biocompatibility and durability of vascular and valvular implants requires translational animal models to study the in vivo fate of cardiovascular grafts. In the present article, a review on the development and application of a microsurgical rat model of infrarenal implantation of aortic grafts and aortic valved conduits is provided. By refinement of surgical techniques and inclusion of hemodynamic considerations, a functional model has been created, which provides a modular platform for the in vivo assessment of biological and tissue-engineered grafts. Through optional addition of procalcific diets, disease-inducing agents, and genetic modifications, complex multimorbidity scenarios mimicking the clinical reality in cardiovascular patients can be simulated. Applying this model, crucial aspects of the biocompatibility, biofunctionality and degeneration of vascular and valvular implants in dependency on graft preparation, and modification as well as systemic antidegenerative treatment of the recipient have been and will be addressed.

Two stroke homogenous charge compression ignition engine with pulsed air supplier

DOEpatents

Clarke, John M.

2003-08-05

A two stroke homogenous charge compression ignition engine includes a volume pulsed air supplier, such as a piston driven pump, for efficient scavenging. The usage of a homogenous charge tends to decrease emissions. The use of a volume pulsed air supplier in conjunction with conventional poppet type intake and exhaust valves results in a relatively efficient scavenging mode for the engine. The engine preferably includes features that permit valving event timing, air pulse event timing and injection event timing to be varied relative to engine crankshaft angle. The principle use of the invention lies in improving diesel engines.

Study of normal, fibrous and calcified aortic valve tissue by Raman and reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Rodrigues, Kátia Calligaris; Munin, Egberto; Alves, Leandro P.; Silveira, Fabrício L.; Junior, Landulfo S.; De Lima, Carlos J.; Lázzaro, João C.; De Souza, Genivaldo C.; Piotto, José A. B.; Pacheco, Marcos T. T.; Zângaro, Renato A.

2007-02-01

Several studies have identified the degree of aortic valve calcification as a strong predictor both for the progression and outcome of aortic stenosis. In industrialized countries, aortic valve stenosis is most frequently caused by progressive calcification and degeneration of aortic cusps. However, there are no accurate methods to quantify the extent of aortic valve calcification. To provide a non-invasive alternative to biopsy, a range of optical methods have been investigated, including Raman and reflectance spectroscopy. A Raman spectrum can be used to access the molecular constitution of a particular tissue and classify it. Raman spectroscopy is largely used in the quantification and evaluation of human atherosclerosis, being a powerful technique for performing biochemical analysis without tissue removal. Nevertheless, increased thickness and disorganization of the collagen fibre network and extracellular matrix are known to affect the diffuse spectral reflectance of the tissue. A catheter with the "6 around 1" configuration, the central fiber transmit laser radiation to the sample and the scattered light is collected by the other six surrounding fibers, was used both for Raman and reflectance spectroscopy. A white light (krypton lamp, flashtube Model FX 1160 Perkin Elmer, USA) excitation was used for reflectance measurements. A Ti-sapphire (785nm, Spectra Physics, model 3900S, USA) laser, pumped by an argon laser (Spectra Physics, model Stabilite 2017, USA) was used as the near infrared Raman set up. Several ex-vivo spectra of aortic valve samples were analyzed. The results show a promising way to differentiate normal, fibrous and calcified tissue in aortic valve.

High-performance space shuttle auxiliary propellant valve system

NASA Technical Reports Server (NTRS)

Smith, G. M.

1973-01-01

Several potential valve closures for the space shuttle auxiliary propulsion system (SS/APS) were investigated analytically and experimentally in a modeling program. The most promising of these were analyzed and experimentally evaluated in a full-size functional valve test fixture of novel design. The engineering investigations conducted for both model and scale evaluations of the SS/APS valve closures and functional valve fixture are described. Preliminary designs, laboratory tests, and overall valve test fixture designs are presented, and a final recommended flightweight SS/APS valve design is presented.

Improvement on Main/backup Controller Switching Device of the Nozzle Throat Area Control System for a Turbofan Aero Engine

NASA Astrophysics Data System (ADS)

Li, Jie; Duan, Minghu; Yan, Maode; Li, Gang; Li, Xiaohui

2014-06-01

A full authority digital electronic controller (FADEC) equipped with a full authority hydro-mechanical backup controller (FAHMBC) is adopted as the nozzle throat area control system (NTACS) of a turbofan aero engine. In order to ensure the switching reliability of the main/backup controller, the nozzle throat area control switching valve was improved from three-way convex desktop slide valve to six-way convex desktop slide valve. Simulation results show that, if malfunctions of FAEDC occur and abnormal signals are outputted from FADEC, NTACS will be seriously influenced by the main/backup controller switching in several working states, while NTACS will not be influenced by using the improved nozzle throat area control switching valve, thus the controller switching process will become safer and smoother and the working reliability of this turbofan aero engine is improved by the controller switching device improvement.

Working Characteristics of Variable Intake Valve in Compressed Air Engine

PubMed Central

Yu, Qihui; Shi, Yan; Cai, Maolin

2014-01-01

A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine. PMID:25379536

Working characteristics of variable intake valve in compressed air engine.

PubMed

Yu, Qihui; Shi, Yan; Cai, Maolin

2014-01-01

A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine.

Assessment of the effect of gaseous fuel delivery mode on thermal efficiency and fuel losses during the valve overlap period in a dual-fuel compression ignition engine

NASA Astrophysics Data System (ADS)

Skrzek, T.

2016-09-01

The paper describes the effect of dual fuelling of single cylinder AVL test CI engine with the use of two ways of gas delivery to the engine manifold. The engine was fuelled diesel oil and propane. For all the tests, gas consumption was maintained at the same level. In the first mode the gas was delivered by injector located under inlet valve. In the second method, there was used a mixer fitted to the intake manifold. The paper compares the results of thermal efficiency and emissions of propane in the exhaust for both fuelling modes. Research clearly show how important it is to synchronize the injector opening time of the intake stroke. This is especially important for supercharged engines in which there is a valve overlap.

Engine restart aid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedewa, Andrew

A system is disclosed comprising an engine having coolant passages defined therethrough, a first coolant pump, and a first radiator. The system additionally comprises a second coolant pump, a second radiator, and a liquid-to-air heat exchanger configured to condition the temperature of intake air to the engine. The system further includes a coolant valve means. For a first configuration of the coolant valve means the first coolant pump is configured to urge coolant through the coolant passages in the engine and through the first radiator, and the second coolant pump is configured to urge coolant through the liquid-to-air heat exchangermore » and through the second radiator. For a second configuration of the coolant valve means the second coolant pump is configured to urge coolant through the coolant passages in the engine and through the liquid-to-air heat exchanger. A method for controlling the system is also disclosed.« less

Variable Valve Actuation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeffrey Gutterman; A. J. Lasley

2008-08-31

Many approaches exist to enable advanced mode, low temperature combustion systems for diesel engines - such as premixed charge compression ignition (PCCI), Homogeneous Charge Compression Ignition (HCCI) or other HCCI-like combustion modes. The fuel properties and the quantity, distribution and temperature profile of air, fuel and residual fraction in the cylinder can have a marked effect on the heat release rate and combustion phasing. Figure 1 shows that a systems approach is required for HCCI-like combustion. While the exact requirements remain unclear (and will vary depending on fuel, engine size and application), some form of substantially variable valve actuation ismore » a likely element in such a system. Variable valve actuation, for both intake and exhaust valve events, is a potent tool for controlling the parameters that are critical to HCCI-like combustion and expanding its operational range. Additionally, VVA can be used to optimize the combustion process as well as exhaust temperatures and impact the after treatment system requirements and its associated cost. Delphi Corporation has major manufacturing and product development and applied R&D expertise in the valve train area. Historical R&D experience includes the development of fully variable electro-hydraulic valve train on research engines as well as several generations of mechanical VVA for gasoline systems. This experience has enabled us to evaluate various implementations and determine the strengths and weaknesses of each. While a fully variable electro-hydraulic valve train system might be the 'ideal' solution technically for maximum flexibility in the timing and control of the valve events, its complexity, associated costs, and high power consumption make its implementation on low cost high volume applications unlikely. Conversely, a simple mechanical system might be a low cost solution but not deliver the flexibility required for HCCI operation. After modeling more than 200 variations of the mechanism it was determined that the single cam design did not have enough flexibility to satisfy three critical OEM requirements simultaneously, (maximum valve lift variation, intake valve opening timing and valve closing duration), and a new approach would be necessary. After numerous internal design reviews including several with the OEM a dual cam design was developed that had the flexibility to meet all motion requirements. The second cam added complexity to the mechanism however the cost was offset by the deletion of the electric motor required in the previous design. New patent applications including detailed drawings and potential valve motion profiles were generated and alternate two cam designs were proposed and evaluated for function, cost, reliability and durability. Hardware was designed and built and testing of sample hardware was successfully completed on an engine test stand. The mechanism developed during the course of this investigation can be applied by Original Equipment Manufacturers, (OEM), to their advanced diesel engines with the ultimate goal of reducing emissions and improving fuel economy. The objectives are: (1) Develop an optimal, cost effective, variable valve actuation (VVA) system for advanced low temperature diesel combustion processes. (2) Design and model alternative mechanical approaches and down-select for optimum design. (3) Build and demonstrate a mechanism capable of application on running engines.« less

Flow diverter value and flow diversion method

NASA Technical Reports Server (NTRS)

Arline, S. B.; Carlson, R. L. (Inventor)

1964-01-01

A flow diverter valve applicable to any fluid flow system requiring rapid bleed or bypass is disclosed. Examples of application of the flow diverter valve to a liquid rocket and a turbojet aircraft engine are given. Features of the valve include: (1) an independent fluid source is used to activate the flow diverter valve toward its closed position during its initial stage of travel; (2) the flow diverter port area and size is unlimited and the valve travel is unlimited; and (3) the valve housing is fabricated such that the valve can be a one step valve, a two step valve, or include as many steps as are found desirable.

46 CFR 53.05-5 - Discharge capacities and valve markings.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Discharge capacities and valve markings. 53.05-5 Section 53.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-5 Discharge capacities and valve markings. The discharge capacities and valve markings must...

46 CFR 53.05-5 - Discharge capacities and valve markings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Discharge capacities and valve markings. 53.05-5 Section 53.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-5 Discharge capacities and valve markings. The discharge capacities and valve markings must...

46 CFR 53.05-5 - Discharge capacities and valve markings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Discharge capacities and valve markings. 53.05-5 Section 53.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-5 Discharge capacities and valve markings. The discharge capacities and valve markings must...

46 CFR 53.05-5 - Discharge capacities and valve markings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Discharge capacities and valve markings. 53.05-5 Section 53.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-5 Discharge capacities and valve markings. The discharge capacities and valve markings must...

46 CFR 53.05-5 - Discharge capacities and valve markings.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Discharge capacities and valve markings. 53.05-5 Section 53.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-5 Discharge capacities and valve markings. The discharge capacities and valve markings must...

Air flow through poppet valves

NASA Technical Reports Server (NTRS)

Lewis, G W; Nutting, E M

1920-01-01

Report discusses the comparative continuous flow characteristics of single and double poppet valves. The experimental data presented affords a direct comparison of valves, single and in pairs of different sizes, tested in a cylinder designed in accordance with current practice in aviation engines.

High-resolution subject-specific mitral valve imaging and modeling: experimental and computational methods.

PubMed

Toma, Milan; Bloodworth, Charles H; Einstein, Daniel R; Pierce, Eric L; Cochran, Richard P; Yoganathan, Ajit P; Kunzelman, Karyn S

2016-12-01

The diversity of mitral valve (MV) geometries and multitude of surgical options for correction of MV diseases necessitates the use of computational modeling. Numerical simulations of the MV would allow surgeons and engineers to evaluate repairs, devices, procedures, and concepts before performing them and before moving on to more costly testing modalities. Constructing, tuning, and validating these models rely upon extensive in vitro characterization of valve structure, function, and response to change due to diseases. Micro-computed tomography ([Formula: see text]CT) allows for unmatched spatial resolution for soft tissue imaging. However, it is still technically challenging to obtain an accurate geometry of the diastolic MV. We discuss here the development of a novel technique for treating MV specimens with glutaraldehyde fixative in order to minimize geometric distortions in preparation for [Formula: see text]CT scanning. The technique provides a resulting MV geometry which is significantly more detailed in chordal structure, accurate in leaflet shape, and closer to its physiological diastolic geometry. In this paper, computational fluid-structure interaction (FSI) simulations are used to show the importance of more detailed subject-specific MV geometry with 3D chordal structure to simulate a proper closure validated against [Formula: see text]CT images of the closed valve. Two computational models, before and after use of the aforementioned technique, are used to simulate closure of the MV.

AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT VIII. ENGINE COMPONENTS--PART I.

ERIC Educational Resources Information Center

Human Engineering Inst., Cleveland, OH.

THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE CONSTRUCTION AND MAINTENANCE OF DIESEL ENGINE CYLINDER HEADS AND CYLINDER ASSEMBLIES. TOPICS ARE CYLINDER ASSEMBLY (LINERS), CYLINDER HEADS, VALVES AND VALVE MECHANISMS, AND PISTON AND PISTON RINGS. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL BRANCH PROGRAMED TRAINING…

Unsteady Analyses of Valve Systems in Rocket Engine Testing Environments

NASA Technical Reports Server (NTRS)

Shipman, Jeremy; Hosangadi, Ashvin; Ahuja, Vineet

2004-01-01

This paper discusses simulation technology used to support the testing of rocket propulsion systems by performing high fidelity analyses of feed system components. A generalized multi-element framework has been used to perform simulations of control valve systems. This framework provides the flexibility to resolve the structural and functional complexities typically associated with valve-based high pressure feed systems that are difficult to deal with using traditional Computational Fluid Dynamics (CFD) methods. In order to validate this framework for control valve systems, results are presented for simulations of a cryogenic control valve at various plug settings and compared to both experimental data and simulation results obtained at NASA Stennis Space Center. A detailed unsteady analysis has also been performed for a pressure regulator type control valve used to support rocket engine and component testing at Stennis Space Center. The transient simulation captures the onset of a modal instability that has been observed in the operation of the valve. A discussion of the flow physics responsible for the instability and a prediction of the dominant modes associated with the fluctuations is presented.

Increasing the Air Charge and Scavenging the Clearance Volume of a Compression-Ignition Engine

NASA Technical Reports Server (NTRS)

Spanogle, J A; Hicks, C W; Foster, H H

1934-01-01

The object of the investigation presented in this report was to determine the effects of increasing the air charge and scavenging the clearance volume of a 4-stroke-cycle compression-ignition engine having a vertical-disk form combustion chamber. Boosting the inlet-air pressure with normal valve timing increased the indicated engine power in proportion to the additional air inducted and resulted in smoother engine operation with less combustion shock. Scavenging the clearance volume by using a valve overlap of 145 degrees and an inlet-air boost pressure of approximately 2 1/2 inches of mercury produced a net increase in performance for clear exhaust operation of 33 percent over that obtained with normal valve timing and the same boost pressure. The improved combustion characteristics result in lower specific fuel consumption, and a clearer exhaust.

Amyloidosis, Inflammation, and Oxidative Stress in the Heart of an Alkaptonuric Patient

PubMed Central

Ghezzi, Lorenzo; Giorgetti, Giovanna; Viti, Cecilia; Geminiani, Michela; Soldani, Patrizia; Lupetti, Pietro; Benvenuti, Chiara; Perfetto, Federico; Spreafico, Adriano; Santucci, Annalisa

2014-01-01

Background. Alkaptonuria, a rare autosomal recessive metabolic disorder caused by deficiency in homogentisate 1,2-dioxygenase activity, leads to accumulation of oxidised homogentisic acid in cartilage and collagenous structures present in all organs and tissues, especially joints and heart, causing a pigmentation called ochronosis. A secondary amyloidosis is associated with AKU. Here we report a study of an aortic valve from an AKU patient. Results. Congo Red birefringence, Th-T fluorescence, and biochemical assays demonstrated the presence of SAA-amyloid deposits in AKU stenotic aortic valve. Light and electron microscopy assessed the colocalization of ochronotic pigment and SAA-amyloid, the presence of calcified areas in the valve. Immunofluorescence detected lipid peroxidation of the tissue and lymphocyte/macrophage infiltration causing inflammation. High SAA plasma levels and proinflammatory cytokines levels comparable to those from rheumatoid arthritis patients were found in AKU patient. Conclusions. SAA-amyloidosis was present in the aortic valve from an AKU patient and colocalized with ochronotic pigment as well as with tissue calcification, lipid oxidation, macrophages infiltration, cell death, and tissue degeneration. A local HGD expression in human cardiac tissue has also been ascertained suggesting a consequent local production of ochronotic pigment in AKU heart. PMID:24876668

Main Oxidizer Valve Design

NASA Technical Reports Server (NTRS)

Addona, Brad; Eddleman, David

2015-01-01

A developmental Main Oxidizer Valve (MOV) was designed by NASA-MSFC using additive manufacturing processes. The MOV is a pneumatically actuated poppet valve to control the flow of liquid oxygen to an engine's injector. A compression spring is used to return the valve to the closed state when pneumatic pressure is removed from the valve. The valve internal parts are cylindrical in shape, which lends itself to traditional lathe and milling operations. However, the valve body represents a complicated shape and contains the majority of the mass of the valve. Additive manufacturing techniques were used to produce a part that optimized mass and allowed for design features not practical with traditional machining processes.

Investigation of a rotary valving system with variable valve timing for internal combustion engines

NASA Astrophysics Data System (ADS)

Cross, Paul C.; Hansen, Craig N.

1994-11-01

The objective of the program was to provide a functional demonstration of the Hansen Rotary Valving System with Variable Valve Timing (HRVS/VVT), capable of throttleless inlet charge control, as an alternative to conventional poppet-valves for use in spark ignited internal combustion engines. The goal of this new technology is to secure benefits in fuel economy, broadened torque band, vibration reduction, and overhaul accessibility. Additionally, use of the variable valve timing capability to vary the effective compression ratio is expected to improve multifuel tolerance and efficiency. Efforts directed at the design of HRVS components proved to be far more extensive than had been anticipated, ultimately requiring that proof-trial design/development work be performed. Although both time and funds were exhausted before optical or ion-probe types of in-cylinder investigation could be undertaken, a great deal of laboratory data was acquired during the course of the design/development work. This laboratory data is the basis for the information presented in this final report.

Histopathological and Immunohistochemical Evaluation of Pannus Tissue in Patients with Prosthetic Valve Dysfunction.

PubMed

Karakoyun, Süleyman; Ozan Gürsoy, Mustafa; Yesin, Mahmut; Kalçık, Macit; Astarcıoğlu, Mehmet Ali; Gündüz, Sabahattin; Emrah Oğuz, Ali; Çoban Kökten, Şermin; Nimet Karadayı, Ayşe; Tuncer, Altuğ; Köksal, Cengiz; Gökdeniz, Tayyar; Özkan, Mehmet

2016-01-01

Prosthetic valve dysfunction due to pannus formation is a rare but serious complication. Currently, limited data are available concerning the pathogenesis and immunohistochemical properties of pannus. The study aim was to investigate the morphological, histopathological and immunohistochemical characteristics of pannus formation in patients with prosthetic valve dysfunction. A total of 35 patients (10 males, 25 females; mean age 44 ± 16 years) who had undergone re-do valve surgery due to prosthetic valve obstruction was enrolled in the study. Immunohistochemical studies were aimed at evaluating the expression of alphasmooth muscle actin (α-SMA) and desmin in myofibroblasts and smooth muscle cells; epithelial membrane antigen (EMA) in epithelial cells; and CD34, Factor VIII and vascular endothelial growth factor (VEGF) in endothelial cells. Matrix metalloproteinases (MMPs) -2 and -9, and transforming growth factor-beta (TGF-β) were used to demonstrate cytokine release from macrophages, leukocytes, fibroblasts and myofibroblasts. Pannus appeared as a tough and thick tissue hyperplasia which began from outside the suture ring in the periannular region and extended to the inflow and outflow surfaces of the prosthetic valves. Histopathological analysis showed the pannus tissue to consist of chronic inflammatory cells (lymphocytes, plasma cells, macrophages and foreign body giant cells), spindle cells such as myofibroblasts, capillary blood vessels and endothelial cells laying down the lumens. Calcification was present in the pannus tissue of 19 explanted prostheses. Immunohistochemical studies revealed positive α-SMA expression in all patients, whereas 60.5% of patients were positive for desmin, 50% for EMA, 42.1% for VEGF, 39.5% for TBF-β, 42.1% for MMP-2, 86.8% for CD34, and 97.4% for Factor VIII. MMP-9 was negative in all patients. Pannus tissue appears to be formed as the result of a neointimal response in periannular regions of prosthetic valves that consist of periannular tissue migration, myofibroblast and extracellular matrix proliferation with vascular components. It is a chronic active process in which mediators such as TGF-β, VEGF and MMP-2 play roles in both matrix formation and degradation.

A thin film nitinol heart valve.

PubMed

Stepan, Lenka L; Levi, Daniel S; Carman, Gregory P

2005-11-01

In order to create a less thrombogenic heart valve with improved longevity, a prosthetic heart valve was developed using thin film nitinol (NiTi). A "butterfly" valve was constructed using a single, elliptical piece of thin film NiTi and a scaffold made from Teflon tubing and NiTi wire. Flow tests and pressure readings across the valve were performed in vitro in a pulsatile flow loop. Bio-corrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material's in vivo biocompatibility, thin film nitinol was implanted in pigs using stents covered with thin film NiTi. Flow rates and pressure tracings across the valve were comparable to those through a commercially available 19 mm Perimount Edwards tissue valve. No signs of corrosion were present on thin film nitinol samples after immersion in Hank's solution for one month. Finally, organ and tissue samples explanted from four pigs at 2, 3, 4, and 6 weeks after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation. Although long term testing is still necessary, thin film NiTi may be very well suited for use in artificial heart valves.

[Pannus Formation Two Years after Bioprosthetic Aortic Valve Implantation;Report of a Case].

PubMed

Ono, Kimiyo; Kuroda, Hiroaki

2015-08-01

We report a case of early deterioration of the bioprosthetic aortic valve 23 months postoperatively. A 77-year-old man who had undergone aortic valve replacement with a 23-mm Epic valve( St. Jude Medical [SJM])presented to us after a syncopal episode. Echocardiography revealed severe aortic stenosis, and redo aortic valve replacement with a 21-mm SJM mechanical valve was performed. All 3 cusps of the tissue valve were thickened by fibrous pannus overgrowth. Neither calcification nor invasion of inflammatory cells was observed. The cause of pannus formation at such an early stage after implantation remains unknown.

TGF-β mediates early angiogenesis and latent fibrosis in an Emilin1-deficient mouse model of aortic valve disease

PubMed Central

Munjal, Charu; Opoka, Amy M.; Osinska, Hanna; James, Jeanne F.; Bressan, Giorgio M.; Hinton, Robert B.

2014-01-01

Aortic valve disease (AVD) is characterized by elastic fiber fragmentation (EFF), fibrosis and aberrant angiogenesis. Emilin1 is an elastin-binding glycoprotein that regulates elastogenesis and inhibits TGF-β signaling, but the role of Emilin1 in valve tissue is unknown. We tested the hypothesis that Emilin1 deficiency results in AVD, mediated by non-canonical (MAPK/phosphorylated Erk1 and Erk2) TGF-β dysregulation. Using histology, immunohistochemistry, electron microscopy, quantitative gene expression analysis, immunoblotting and echocardiography, we examined the effects of Emilin1 deficiency (Emilin1−/−) in mouse aortic valve tissue. Emilin1 deficiency results in early postnatal cell-matrix defects in aortic valve tissue, including EFF, that progress to latent AVD and premature death. The Emilin1−/− aortic valve displays early aberrant provisional angiogenesis and late neovascularization. In addition, Emilin1−/− aortic valves are characterized by early valve interstitial cell activation and proliferation and late myofibroblast-like cell activation and fibrosis. Interestingly, canonical TGF-β signaling (phosphorylated Smad2 and Smad3) is upregulated constitutively from birth to senescence, whereas non-canonical TGF-β signaling (phosphorylated Erk1 and Erk2) progressively increases over time. Emilin1 deficiency recapitulates human fibrotic AVD, and advanced disease is mediated by non-canonical (MAPK/phosphorylated Erk1 and Erk2) TGF-β activation. The early manifestation of EFF and aberrant angiogenesis suggests that these processes are crucial intermediate factors involved in disease progression and therefore might provide new therapeutic targets for human AVD. PMID:25056700

klf2a couples mechanotransduction and zebrafish valve morphogenesis through fibronectin synthesis

PubMed Central

Steed, Emily; Faggianelli, Nathalie; Roth, Stéphane; Ramspacher, Caroline; Concordet, Jean-Paul; Vermot, Julien

2016-01-01

The heartbeat and blood flow signal to endocardial cell progenitors through mechanosensitive proteins that modulate the genetic program controlling heart valve morphogenesis. To date, the mechanism by which mechanical forces coordinate tissue morphogenesis is poorly understood. Here we use high-resolution imaging to uncover the coordinated cell behaviours leading to heart valve formation. We find that heart valves originate from progenitors located in the ventricle and atrium that generate the valve leaflets through a coordinated set of endocardial tissue movements. Gene profiling analyses and live imaging reveal that this reorganization is dependent on extracellular matrix proteins, in particular on the expression of fibronectin1b. We show that blood flow and klf2a, a major endocardial flow-responsive gene, control these cell behaviours and fibronectin1b synthesis. Our results uncover a unique multicellular layering process leading to leaflet formation and demonstrate that endocardial mechanotransduction and valve morphogenesis are coupled via cellular rearrangements mediated by fibronectin synthesis. PMID:27221222

Back-pressure Effect on Shock-Train Location in a Scramjet Engine Isolator

DTIC Science & Technology

2010-03-01

valves .......................................................................................... 57 Side project: making an actuator stand...21 Figure 8. Main manual shut off valve ...................................................................................22 Figure 9 . A small...characteristic about this wind tunnel. With Mach 1.8 nozzle, prior to test runs, the upstream regulator pressure valve (Figure 9 ) was set at

Design and development of a direct injection system for cryogenic engines

NASA Astrophysics Data System (ADS)

Mutumba, Angela; Cheeseman, Kevin; Clarke, Henry; Wen, Dongsheng

2018-04-01

The cryogenic engine has received increasing attention due to its promising potential as a zero-emission engine. In this study, a new robust liquid nitrogen injection system was commissioned and set up to perform high-pressure injections into an open vessel. The system is used for quasi-steady flow tests used for the characterisation of the direct injection process for cryogenic engines. An electro-hydraulic valve actuator provides intricate control of the valve lift, with a minimum cycle time of 3 ms and a frequency of up to 20 Hz. With additional sub-cooling, liquid phase injections from 14 to 94 bar were achieved. Results showed an increase in the injected mass with the increase in pressure, and decrease in temperature. The injected mass was also observed to increases linearly with the valve lift. Better control of the injection process, minimises the number of variables, providing more comparable and repeatable sets of data. Implications of the results on the engine performance were also discussed.

Sequential hydrophile and lipophile solubilization as an efficient method for decellularization of porcine aortic valve leaflets: Structure, mechanical property and biocompatibility study.

PubMed

Qiao, Wei-Hua; Liu, Peng; Hu, Dan; Al Shirbini, Mahmoud; Zhou, Xian-Ming; Dong, Nian-Guo

2018-02-01

Antigenicity of xenogeneic tissues is the major obstacle to increased use of these materials in clinical medicine. Residual xenoantigens in decellularized tissue elicit the immune response after implantation, causing graft failure. With this in mind, the potential use is proposed of three protein solubilization-based protocols for porcine aortic valve leaflets decellularization. It was demonstrated that hydrophile solubilization alone achieved incomplete decellularization; lipophile solubilization alone (LSA) completely removed all cells and two most critical xenoantigens - galactose-α(1,3)-galactose (α-Gal) and major histocompatibility complex I (MHC I) - but caused severe alterations of the structure and mechanical properties; sequential hydrophile and lipophile solubilization (SHLS) resulted in a complete removal of cells, α-Gal and MHC I, and good preservation of the structure and mechanical properties. In contrast, a previously reported method using Triton X-100, sodium deoxycholate and IGEPAL CA-630 resulted in a complete removal of all cells and MHC I, but with remaining α-Gal epitope. LSA- and SHLS-treated leaflets showed significantly reduced leucocyte activation (polymorphonuclear elastase) upon interaction with human blood in vitro. When implanted subdermally in rats for 6 weeks, LSA- or SHLS-treated leaflets were presented with more biocompatible implants and all four decellularized leaflets were highly resistant to calcification. These findings illustrate that the SHLS protocol could be considered as a promising decellularization method for the decellularization of xenogeneic tissues in tissue engineering and regenerative medicine. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Mazda's new V-6 gasoline engine and its innovative induction system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatamura, K.; Morishita, K.; Asanomi, K.

1987-01-01

Mazda succeeded in the development of a new V-type 6-cylinder engine series comprising 2-liter JF naturally aspirated and turbocharged units and also a 3-liter JE naturally aspirated unit. This engine is 60-degree-banked and has 18 valves: two intake valves and one exhaust valve per cylinder. Various techniques, such as High Rigidity Cylinder Block and HLA, are adopted to upgrade quietness and smoothness. The Dynamic Charge Effects system, a combination of inertia and resonance charge effects, is modeled on the principle of two-degree-of-freedom system. The application of this principle helped develop the Induction system that is compatible with the three enginemore » types. The turbocharger adopted on the JF engine is of a twin scroll type to considerably improve power response quality and increase torque at low speed. Triple Port Induction Control System is used to help improve fuel economy and running performance.« less

Advances in cardiovascular fluid mechanics: bench to bedside.

PubMed

Dasi, Lakshmi P; Sucosky, Philippe; de Zelicourt, Diane; Sundareswaran, Kartik; Jimenez, Jorge; Yoganathan, Ajit P

2009-04-01

This paper presents recent advances in cardiovascular fluid mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the fluid mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex fluid mechanics associated with the cardiovascular system and have led to new translational technologies.

Selective propensity of bovine jugular vein material to bacterial adhesions: An in-vitro study.

PubMed

Jalal, Zakaria; Galmiche, Louise; Lebeaux, David; Villemain, Olivier; Brugada, Georgia; Patel, Mehul; Ghigo, Jean-Marc; Beloin, Christophe; Boudjemline, Younes

2015-11-01

Percutaneous pulmonary valve implantation (PPVI) using Melody valve made of bovine jugular vein is safe and effective. However, infective endocarditis has been reported for unclear reasons. We sought to assess the impact of valvular substrates on selective bacterial adhesion. Three valved stents (Melody valve, homemade stents with bovine and porcine pericardium) were tested in-vitro for bacterial adhesion using Staphylococcus aureus and Streptococcus sanguinis strains. Bacterial adhesion was higher on bovine jugular venous wall for S. aureus and on Melody valvular leaflets for S. sanguinis in control groups and significantly increased in traumatized Melody valvular leaflets with both bacteria (traumatized vs non traumatized: p=0.05). Bacterial adhesion was lower on bovine pericardial leaflets. Selective adhesion of S. aureus and S. sanguinis pathogenic strains to Melody valve tissue was noted on healthy tissue and increased after implantation procedural steps. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Description of the NACA Universal Test Engine and Some Test Results

NASA Technical Reports Server (NTRS)

Ware, Marsden

1927-01-01

This report describes the 5-inch bore by 7-inch stroke single cylinder test engine used at the Langley Field Laboratory of the National Advisory Committee for Aeronautics in laboratory research on internal-combustion engine problems and presents some results of tests made therewith. The engine is arranged for variation over wide ranges, of the compression ratio and lift and timing of both inlet and exhaust valves while the engine is in operation. Provision is also made for the connection of a number of auxiliaries. These features tend to make the engine universal in character, and especially suited for the study of certain problems involving change in compression ratio, valve timing, and lift.

Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

1993-01-01

In order to reduce heat transfer between a hot gas heat source and a metallic engine component, a thermal insulating layer of material is placed between them. This thermal barrier coating is applied by plasma spray processing the thin films. The coating has been successfully employed in aerospace applications for many years. Lewis Research Center, a leader in the development engine components coating technology, has assisted Caterpillar, Inc. in applying ceramic thermal barrier coatings on engines. Because these large engines use heavy fuels containing vanadium, engine valve life is sharply decreased. The barrier coating controls temperatures, extends valve life and reduces operating cost. Additional applications are currently under development.

A Theoretical and Experimental Analysis of Post-Compression Water Injection in a Rolls-Royce M250 Gas Turbine Engine

DTIC Science & Technology

2015-05-18

Figure 14: Pump and motor mounting assembly Solenoid valves Water Heater Ball Valves Spray nozzles Compressor Discharge Scroll Pump ...configuration schematic ........................................................................ 31 Figure 14: Pump and motor mounting assembly...Tubes (1 each side) Compressor Discharge Scroll 11 compared to the same engine cycle without the gas generator turbine stage. A temperature

Fluid valve with wide temperature range

NASA Technical Reports Server (NTRS)

Kast, Howard Berdolt (Inventor)

1976-01-01

A fluid valve suitable for either metering or pressure regulating fluids at various temperatures is provided for a fuel system as may be utilized in an aircraft gas turbine engine. The valve includes a ceramic or carbon pad which cooperates with a window in a valve plate to provide a variable area orifice which remains operational during large and sometimes rapid variations in temperature incurred from the use of different fuels.

Integrated control and health management. Orbit transfer rocket engine technology program

NASA Technical Reports Server (NTRS)

Holzmann, Wilfried A.; Hayden, Warren R.

1988-01-01

To insure controllability of the baseline design for a 7500 pound thrust, 10:1 throttleable, dual expanded cycle, Hydrogen-Oxygen, orbit transfer rocket engine, an Integrated Controls and Health Monitoring concept was developed. This included: (1) Dynamic engine simulations using a TUTSIM derived computer code; (2) analysis of various control methods; (3) Failure Modes Analysis to identify critical sensors; (4) Survey of applicable sensors technology; and, (5) Study of Health Monitoring philosophies. The engine design was found to be controllable over the full throttling range by using 13 valves, including an oxygen turbine bypass valve to control mixture ratio, and a hydrogen turbine bypass valve, used in conjunction with the oxygen bypass to control thrust. Classic feedback control methods are proposed along with specific requirements for valves, sensors, and the controller. Expanding on the control system, a Health Monitoring system is proposed including suggested computing methods and the following recommended sensors: (1) Fiber optic and silicon bearing deflectometers; (2) Capacitive shaft displacement sensors; and (3) Hot spot thermocouple arrays. Further work is needed to refine and verify the dynamic simulations and control algorithms, to advance sensor capabilities, and to develop the Health Monitoring computational methods.

Collagen organization in canine myxomatous mitral valve disease: an x-ray diffraction study.

PubMed

Hadian, Mojtaba; Corcoran, Brendan M; Han, Richard I; Grossmann, J Günter; Bradshaw, Jeremy P

2007-10-01

Collagen fibrils, a major component of mitral valve leaflets, play an important role in defining shape and providing mechanical strength and flexibility. Histopathological studies show that collagen fibrils undergo dramatic changes in the course of myxomatous mitral valve disease in both dogs and humans. However, little is known about the detailed organization of collagen in this disease. This study was designed to analyze and compare collagen fibril organization in healthy and lesional areas of myxomatous mitral valves of dogs, using synchrotron small-angle x-ray diffraction. The orientation, density, and alignment of collagen fibrils were mapped across six different valves. The findings reveal a preferred collagen alignment in the main body of the leaflets between two commissures. Qualitative and quantitative analysis of the data showed significant differences between affected and lesion-free areas in terms of collagen content, fibril alignment, and total tissue volume. Regression analysis of the amount of collagen compared to the total tissue content at each point revealed a significant relationship between these two parameters in lesion-free but not in affected areas. This is the first time this technique has been used to map collagen fibrils in cardiac tissue; the findings have important applications to human cardiology.

Control apparatus for hot gas engine

DOEpatents

Stotts, Robert E.

1986-01-01

A mean pressure power control system for a hot gas (Stirling) engine utilizing a plurality of supply tanks for storing a working gas at different pressures. During pump down operations gas is bled from the engine by a compressor having a plurality of independent pumping volumes. In one embodiment of the invention, a bypass control valve system allows one or more of the compressor volumes to be connected to the storage tanks. By selectively sequencing the bypass valves, a capacity range can be developed over the compressor that allows for lower engine idle pressures and more rapid pump down rates.

Method and apparatus for controlling the solenoid current of a solenoid valve which controls the amount of suction of air in an internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiuchi, T.; Yasuoka, A.

1988-05-24

A method of controlling the solenoid current of a solenoid valve which controls suction air in an internal combustion engine, is described comprising the steps of: calculating a solenoid current control value as a function of engine operating conditions; detecting an engine coolant temperature corresponding to the solenoid temperature; determining a temperature correction value in accordance with the solenoid temperature; and calculating a driving signal for controlling the operation of the solenoid as a function of the solenoid current control value and the temperature correction value.

46 CFR 162.018-5 - Blow-down adjustment and popping tolerance.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-5 Blow-down adjustment and popping tolerance. (a) Safety relief valves shall be so.... Safety relief valves shall be designed to open sharply and reach full lift and capacity at the maximum...

46 CFR 58.16-15 - Valves and safety relief devices.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Valves and safety relief devices. 58.16-15 Section 58.16-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND... and safety relief devices. (a) Each cylinder shall have a manually operated screw-down shutoff valve...

46 CFR 162.018-5 - Blow-down adjustment and popping tolerance.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-5 Blow-down adjustment and popping tolerance. (a) Safety relief valves shall be so.... Safety relief valves shall be designed to open sharply and reach full lift and capacity at the maximum...

46 CFR 58.16-15 - Valves and safety relief devices.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Valves and safety relief devices. 58.16-15 Section 58.16-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND... and safety relief devices. (a) Each cylinder shall have a manually operated screw-down shutoff valve...

46 CFR 162.018-5 - Blow-down adjustment and popping tolerance.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-5 Blow-down adjustment and popping tolerance. (a) Safety relief valves shall be so.... Safety relief valves shall be designed to open sharply and reach full lift and capacity at the maximum...

46 CFR 162.018-5 - Blow-down adjustment and popping tolerance.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-5 Blow-down adjustment and popping tolerance. (a) Safety relief valves shall be so.... Safety relief valves shall be designed to open sharply and reach full lift and capacity at the maximum...

46 CFR 162.018-5 - Blow-down adjustment and popping tolerance.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-5 Blow-down adjustment and popping tolerance. (a) Safety relief valves shall be so.... Safety relief valves shall be designed to open sharply and reach full lift and capacity at the maximum...

46 CFR 58.16-15 - Valves and safety relief devices.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Valves and safety relief devices. 58.16-15 Section 58.16-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND... and safety relief devices. (a) Each cylinder shall have a manually operated screw-down shutoff valve...

46 CFR 58.16-15 - Valves and safety relief devices.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Valves and safety relief devices. 58.16-15 Section 58.16-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND... and safety relief devices. (a) Each cylinder shall have a manually operated screw-down shutoff valve...

78 FR 70198 - Airworthiness Directives; Rolls-Royce Deutschland Ltd & Co KG Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-25

.... This AD requires a one-time inspection of the high-pressure (HP) air bleed valve operating mechanism... discovered that the High Pressure (HP) air bleed valve operating mechanism is exposed to excessive... excessive deterioration of the high- pressure (HP) air bleed valve operating mechanism which is influencing...

46 CFR 58.16-15 - Valves and safety relief devices.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Valves and safety relief devices. 58.16-15 Section 58.16-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Liquefied Petroleum Gases for Cooking and Heating § 58.16-15 Valves...

On-chip self-assembly of cell embedded microstructures to vascular-like microtubes.

PubMed

Yue, Tao; Nakajima, Masahiro; Takeuchi, Masaru; Hu, Chengzhi; Huang, Qiang; Fukuda, Toshio

2014-03-21

Currently, research on the construction of vascular-like tubular structures is a hot area of tissue engineering, since it has potential applications in the building of artificial blood vessels. In this paper, we report a fluidic self-assembly method using cell embedded microstructures to construct vascular-like microtubes. A novel 4-layer microfluidic device was fabricated using polydimethylsiloxane (PDMS), which contains fabrication, self-assembly and extraction areas inside one channel. Cell embedded microstructures were directly fabricated using poly(ethylene glycol) diacrylate (PEGDA) in the fabrication area, namely on-chip fabrication. Self-assembly of the fabricated microstructures was performed in the assembly area which has a micro well. Assembled tubular structures (microtubes) were extracted outside the channel into culture dishes using a normally closed (NC) micro valve in the extraction area. The self-assembly mechanism was experimentally demonstrated. The performance of the NC micro valve and embedded cell concentration were both evaluated. Fibroblast (NIH/3T3) embedded vascular-like microtubes were constructed inside this reusable microfluidic device.

Effect of Maximum Cruise-power Operation at Ultra-lean Mixture and Increased Spark Advance on the Mechanical Condition of Cylinder Components

NASA Technical Reports Server (NTRS)

Harris, Herbert B.; Duffy, Robert T.; Erwin, Robert D., Jr.

1945-01-01

A continuous 50-hour test was conducted to determine the effect of maximum cruise-power operation at ultra-lean fuel-air mixture and increased spark advance on the mechanical conditions of cylinder components. The test was conducted on a nine-cylinder air-cooled radial engine at the following conditions:brake horsepower, 750; engine speed, 1900 rpm; brake mean effective pressure, 172 pounds per square inch; fuel-air ratio, 0.052; spark advance, 30 deg B.T.C.; and maximum rear-spark-plug-bushing temperature, 400 F. In addition to the data on corrosion and wear, data are presented and briefly discussed on the effect of engine operation at the conditions of this test on economy, knock, preignition, and mixture distribution. Cylinder, piston, and piston-ring wear was small and all cylinder component were in good condition at the conclusion of the 50-hour test except that all exhaust-valve guides were bellmouthed beyond the Army's specified limit and one exhaust-valve face was lightly burned. It is improbable that the light burning in one spot of the valve face would have progressed further because the burn was filled with a hard deposit so that the valve face formed an unbroken seal and the mating seat showed no evidence of burning. The bellmouthing of the exhaust-valve guides is believed to have been a result of the heavy carbon and lead-oxide deposits, which were present on the head end of the guided length of the exhaust-valve stem. Engine operational the conditions of this test was shown to result In a fuel saving of 16.8 percent on a cooled-power basis as compared with operation at the conditions recommended for this engine by the Army Air Forces for the same power.

46 CFR 162.018-2 - Scope.

Code of Federal Regulations, 2011 CFR

2011-10-01

... APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-2 Scope. (a) This specification covers requirements for the design, construction and testing of safety relief valves intended for...

46 CFR 162.018-2 - Scope.

Code of Federal Regulations, 2014 CFR

2014-10-01

... APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-2 Scope. (a) This specification covers requirements for the design, construction and testing of safety relief valves intended for...

46 CFR 162.018-2 - Scope.

Code of Federal Regulations, 2012 CFR

2012-10-01

... APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-2 Scope. (a) This specification covers requirements for the design, construction and testing of safety relief valves intended for...

46 CFR 162.018-2 - Scope.

Code of Federal Regulations, 2010 CFR

2010-10-01

... APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-2 Scope. (a) This specification covers requirements for the design, construction and testing of safety relief valves intended for...

46 CFR 162.018-2 - Scope.

Code of Federal Regulations, 2013 CFR

2013-10-01

... APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-2 Scope. (a) This specification covers requirements for the design, construction and testing of safety relief valves intended for...

Fibrous composite material for textile heart valve design: in vitro assessment.

PubMed

Amri, Amna; Laroche, Gaetan; Chakfe, Nabil; Heim, Frederic

2018-04-17

With over 150,000 implantations performed over the world, transcatheter aortic valve replacement (TAVR) has become a surgical technique, which largely competes with open surgery valve replacement for an increasing number of patients. The success of the procedure favors the research toward synthetic valve leaflet materials as an alternative to biological tissues, whose durability remains unknown. In particular, fibrous constructions have recently proven to be durable in vivo over a 6-month period of time in animal sheep models. Exaggerated fibrotic tissue formation remains, however, a critical issue to be addressed. This work investigates the design of a composite fibrous construction combining a woven polyethylene terephthalate (PET) layer and a non-woven PET mat, which are expected to provide, respectively, strength and appropriate topography toward limited fibrotic tissue ingrowth. For this purpose, a specific equipment has been developed to produce non-woven PET mats made from fibers with small diameter. These mats were assembled with woven PET substrates using various assembling techniques in order to obtain hybrid fibrous constructions. The physical and mechanical properties of the obtained materials were assessed and valve samples were manufactured to be tested in vitro for hydrodynamic performances. The results show that the composite fibrous construction is characterized by properties suitable for the valve leaflet function, but the durability of the assembling is however limited under accelerated cyclic loading.

Mixed mode fuel injector with individually moveable needle valve members

DOEpatents

Stewart, Chris; Chockley, Scott A.; Ibrahim, Daniel R.; Lawrence, Keith; Tomaseki, Jay; Azam, Junru H.; Tian, Steven Ye; Shafer, Scott F.

2004-08-03

A fuel injector includes a homogenous charge nozzle outlet set and a conventional nozzle outlet set controlled respectively, by first and second needle valve members. One of the needle valve members moves to an open position while the other needle valve member remains stationary for a homogeneous charge injection event. The former needle valve member stays stationary while the other needle valve member moves to an open position for a conventional injection event. One of the needle valve members is at least partially positioned in the other needle valve member. Thus, the injector can perform homogeneous charge injection events, conventional injection events, or even a mixed mode having both types of injection events in a single engine cycle.

Method of Manufacturing Carbon Fiber Reinforced Carbon Composite Valves

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

1998-01-01

A method for forming a carbon composite valve for internal combustion engines is discussed. The process includes the steps of braiding carbon fiber into a rope thereby forming a cylindrically shaped valve stem portion and continuing to braid said fiber while introducing into the braiding carbon fiber rope a carbon matrix plug having an outer surface in a net shape of a valve head thereby forming a valve head portion. The said carbon matrix plug acting as a mandrel over which said carbon fiber rope is braided, said carbon fiber rope and carbon matrix plug forming a valve head portion suitable for mating with a valve seat; cutting said braided carbon valve stem portion at one end to form a valve tip and cutting said braided carbon fiber after said valve head portion to form a valve face and thus provide a composite valve preform; and densifying said preform by embedding the braided carbon in a matrix of carbon to convert said valve stem portion to a valve stem and said valve head portion to a valve head thereby providing said composite valve.

ILIDS measurements of the evaporation of fuel droplets during the intake and compression strokes in a firing lean burn engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skippon, S.M.; Tagaki, Y.

1996-09-01

The evaporation of fuel droplets is an important factor in determining the quality of mixture preparation in lean-burn engines, particularly when using open-valve injection timing, which results in large in-cylinder droplet populations. Interferometric Laser Imaging for Droplet Sizing (ILIDS) has been used to measure the in-cylinder droplet size distribution and fuel volume in the droplet phase as a function of crank angle for a typical full boiling range gasoline and three single component fuels with different boiling points: iso-pentane, iso-octane, and xylene, representing the volatilities of the light end, mid-range and heavy ends of a typical gasoline. The measurements weremore » made under firing conditions, with both open and closed valve injection timing, and at two different coolant temperatures, representing simulated cold start and fully warmed up conditions. A specially built single cylinder research engine was used, equipped with a transparent sapphire cylinder to provide all-round sidewall optical access to the cylinder interior. The engine had a four-valve leanburn head, swirl control valve and air-assisted injector. The experimental arrangements for ILIDS in a firing engine, and the optical access engine itself, are discussed in detail. The results showed significant differences in the rates of evaporation of the three fuel components: iso-pentane evaporated fully very early in the induction stroke, iso-octane droplets persisted longer, and xylene droplets persisted to the end of the compression stroke.« less

Bistable (latching) solenoid actuated propellant isolation valve

NASA Technical Reports Server (NTRS)

Wichmann, H.; Deboi, H. H.

1979-01-01

The design, fabrication, assembly and test of a development configuration bistable (latching) solenoid actuated propellant isolation valve suitable for the control hydrazine and liquid fluorine to an 800 pound thrust rocket engine is described. The valve features a balanced poppet, utilizing metal bellows, a hard poppet/seat interface and a flexure support system for the internal moving components. This support system eliminates sliding surfaces, thereby rendering the valve free of self generated particles.

Echocardiographic versus histologic findings in Marfan syndrome.

PubMed

Gu, Xiaoyan; He, Yihua; Li, Zhian; Han, Jiancheng; Chen, Jian; Nixon, J V Ian

2015-02-01

This retrospective study attempted to establish the prevalence of multiple-valve involvement in Marfan syndrome and to compare echocardiographic with histopathologic findings in Marfan patients undergoing valvular or aortic surgery. We reviewed echocardiograms of 73 Marfan patients who underwent cardiovascular surgery from January 2004 through October 2009. Tissue histology was available for comparison in 29 patients. Among the 73 patients, 66 underwent aortic valve replacement or the Bentall procedure. Histologic findings were available in 29 patients, all of whom had myxomatous degeneration. Of 63 patients with moderate or severe aortic regurgitation as determined by echocardiography, 4 had thickened aortic valves. The echocardiographic findings in 18 patients with mitral involvement included mitral prolapse in 15. Of 11 patients with moderate or severe mitral regurgitation as determined by echocardiography, 4 underwent mitral valve repair and 7 mitral valve replacement. Histologic findings among mitral valve replacement patients showed thickened valve tissue and myxomatous degeneration. Tricuspid involvement was seen echocardiographically in 8 patients, all of whom had tricuspid prolapse. Two patients had severe tricuspid regurgitation, and both underwent repair. Both mitral and tricuspid involvement were seen echocardiographically in 7 patients. Among the 73 patients undergoing cardiac surgery for Marfan syndrome, 66 had moderate or severe aortic regurgitation, although their valves manifested few histologic changes. Eighteen patients had mitral involvement (moderate or severe mitral regurgitation, prolapse, or both), and 8 had tricuspid involvement. Mitral valves were most frequently found to have histologic changes, but the tricuspid valve was invariably involved.

Use of bovine pericardial tissue for aortic valve and aortic root replacement: long-term results.

PubMed

Vrandecic, M; Gontijo Filho, B; Fantini, F; Barbosa, J; Martins, I; de Oliveira, O C; Martins, C; Max, R; Drumond, L; Oliveira, C; Ferrufino, A; Alcocer, E; Silva, J A; Vrandecic, E

1998-03-01

The study aimed to determine the clinical performance of bovine pericardial aldehyde-treated products alone or in combination with aortic leaflets of porcine origin. These included a composite porcine stentless aortic valve attached to a scalloped pericardial tube (BSAV), and valved and non-valved bovine pericardial conduits for use in left-sided heart lesions (BPG). For BSAV grafts, between January 1990 and August 1996, 163 patients (119 males) had their aortic valves replaced by SJM Biocor BASV. Mean age was 37.9 +/- 17.6 years (range: 1 to 76 years). Rheumatic heart disease sequelae (n = 72) and replacement of a prosthetic heart valve (n = 46) were predominant. Preoperative NYHA functional class showed 90 patients (55.2%) in class III and 50 (30.7%) in class IV. BPVC and NVPC grafts were used in 166 patients: acute aortic dissection was the main indication in 52 (31.3%) and chronic in 36 (21/7%). The ascending aorta was involved in 141 patients (84.9%); grafts were seldom used at other sites. In most patients the graft implanted was either a non-valved (n = 79) or a valved (n = 75) pericardial conduit. Twelve patients had a localized lesion and required a patch repair. For BASV grafts, the non-valve-related hospital mortality rate was 4.9%. There were 14.7% non-fatal complications with full recovery of all patients. Mean follow up in 141 patients was 3.0 +/- 1.4 years (range: 1 month to 7.2 years); 14 patients were lost to follow up. Late, non-conduit-related, mortality occurred in seven patients (4.9%). Eight patients underwent reoperation. The current clinical follow up of 127 patients has shown 118 (92.9%) with competent valves and nine (7.0%) with mild stable aortic insufficiency. For BPVC and NVPC grafts, hospital mortality rate was 16.9%, death being related to poor preoperative clinical condition. Postoperative follow up was accomplished in 125 patients; reoperation was necessary in seven patients. Histology showed good tissue preservation up to five years; echocardiography revealed satisfactory findings. No valved conduit had to be reoperated for valve or pericardial tissue wear. Clinical results of left-sided heterologous pericardial grafts have shown excellent performance over time. The BASV (over seven years) and BPVC and NVPC (eight years) have demonstrated superior results as aortic valves alone or in combination with a pericardial conduit.

Additively Manufactured Main Fuel Valve Housing

NASA Technical Reports Server (NTRS)

Eddleman, David; Richard, Jim

2015-01-01

Selective Laser Melting (SLM) was utilized to fabricate a liquid hydrogen valve housing typical of those found in rocket engines and main propulsion systems. The SLM process allowed for a valve geometry that would be difficult, if not impossible to fabricate by traditional means. Several valve bodies were built by different SLM suppliers and assembled with valve internals. The assemblies were then tested with liquid nitrogen and operated as desired. One unit was also burst tested and sectioned for materials analysis. The design, test results, and planned testing are presented herein.

A linear acoustic model for intake wave dynamics in IC engines

NASA Astrophysics Data System (ADS)

Harrison, M. F.; Stanev, P. T.

2004-01-01

In this paper, a linear acoustic model is described that has proven useful in obtaining a better understanding of the nature of acoustic wave dynamics in the intake system of an internal combustion (IC) engine. The model described has been developed alongside a set of measurements made on a Ricardo E6 single cylinder research engine. The simplified linear acoustic model reported here produces a calculation of the pressure time-history in the port of an IC engine that agrees fairly well with measured data obtained on the engine fitted with a simple intake system. The model has proved useful in identifying the role of pipe resonance in the intake process and has led to the development of a simple hypothesis to explain the structure of the intake pressure time history: the early stages of the intake process are governed by the instantaneous values of the piston velocity and the open area under the valve. Thereafter, resonant wave action dominates the process. The depth of the early depression caused by the moving piston governs the intensity of the wave action that follows. A pressure ratio across the valve that is favourable to inflow is maintained and maximized when the open period of the valve is such to allow at least, but no more than, one complete oscillation of the pressure at its resonant frequency to occur while the valve is open.

Development of a completely autologous valved conduit with the sinus of Valsalva using in-body tissue architecture technology: a pilot study in pulmonary valve replacement in a beagle model.

PubMed

Yamanami, Masashi; Yahata, Yuki; Uechi, Masami; Fujiwara, Megumi; Ishibashi-Ueda, Hatsue; Kanda, Keiichi; Watanabe, Taiji; Tajikawa, Tsutomu; Ohba, Kenkichi; Yaku, Hitoshi; Nakayama, Yasuhide

2010-09-14

We developed autologous prosthetic implants by simple and safe in-body tissue architecture technology. We present the first report on the development of autologous valved conduit with the sinus of Valsalva (BIOVALVE) by using this unique technology and its subsequent implantation in the pulmonary valves in a beagle model. A mold of BIOVALVE organization was assembled using 2 types of specially designed silicone rods with a small aperture in a trileaflet shape between them. The concave rods had 3 projections that resembled the protrusions of the sinus of Valsalva. The molds were placed in the dorsal subcutaneous spaces of beagle dogs for 4 weeks. The molds were covered with autologous connective tissues. BIOVALVEs with 3 leaflets in the inner side of the conduit with the sinus of Valsalva were obtained after removing the molds. These valves had adequate burst strength, similar to that of native valves. Tight valvular coaptation and sufficient open orifice area were observed in vitro. These BIOVALVEs were implanted to the main pulmonary arteries as allogenic conduit valves (n=3). Postoperative echocardiography demonstrated smooth movement of the leaflets with trivial regurgitation. Histological examination of specimens obtained at 84 days showed that the surface of the leaflet was covered by endothelial cells and neointima, including an elastin fiber network, and was formed at the anastomosis sides on the luminal surface of the conduit. We developed the first completely autologous BIOVALVE and successfully implanted these BIOVALVEs in a beagle model in a pilot study.

Air intake side secondary air supply system for an internal combustion engine with a duty ratio control operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawanabe, T.; Asakura, M.; Shina, T.

1987-09-01

An air intake side secondary air supply system is described for an internal combustion engine having an air intake passage with a carburetor and an exhaust passage, comprising: an air intake side secondary air supply passage communicating with the air intake passage on the downstream side of the carburetor; an open/close valve disposed in the air intake side secondary air supply passage; an oxygen concentration sensor disposed in the exhaust passage; and detection and control means for detecting whether an air-fuel ratio of mixture to be supplied to the engine is leaner or richer with respect to a target air-fuelmore » ratio through a level of an output signal of the oxygen concentration sensor and for periodically actuating the open/close valve, the detection and control means decreasing a valve open period of the open/close valve within each cyclic period by a first predetermined amount when a detected air-fuel ratio of mixture is leaner than the target air-fuel ratio and increasing the valve open period by a second predetermined amount when the detected air-fuel ratio of mixture is richer than the target air-fuel ratio. The second predetermined amount is different from the first predetermined amount.« less

Molecular structure of human aortic valve by μSR- FTIR microscopy

NASA Astrophysics Data System (ADS)

Borkowska, Anna M.; Nowakowski, Michał; Lis, Grzegorz J.; Wehbe, Katia; Cinque, Gianfelice; Kwiatek, Wojciech M.

2017-11-01

Aortic valve is a part of the heart most frequently affected by pathological processes in humans what constitute a very serious health problem. Therefore, studies of morphology and molecular microstructure of the AV are needed. μSR- FTIR spectroscopy and microscopy represent unique tools to study chemical composition of the tissue and to identify spectroscopic markers characteristic for structural and functional features. Normal AV reveals a multi-layered structure and the compositional and structural changes within particular layers may trigger degenerative processes within the valve. Thus, deep insight into the structure of the valve to understand pathological processes occurring in AV is needed. In order to identify differences between three layers of human AV, tissue sections of macroscopically normal AV were studied using μSR- FTIR spectroscopy in combination with histological and histochemical stainings. Tissue sections deposited onto CaF2 substrates were mapped and representative set of IR spectra collected from fibrosa, spongiosa and ventricularis were analysed by Principal Component Analysis (PCA) in the spectral range between 1850-1000 cm-1 and 3050-2750 cm-1. PCA revealed a layered molecular structure of the valve and it was possible to identify IR bands associated to different tissue parts. Spongiosa layer was well differentiated from other two layers mainly based on IR bands characteristic for the distribution of glycosaminoglycans (GAGs) in the tissue - like 1170 cm-1 (υas(C-O-S)) and 1380 cm-1 (acetyl amino group). Additionally, it was distinguished from fibrosa and ventricularis based on 1085 cm-1 and 1240 cm-1 bands characteristic for GAGs and for carbohydrates- ν(C-O) and ν(C-O-C) respectively and nucleic acids -νsym(PO2-) and νasym(PO2-) respectively, which were less specific for this layer. The use of μSR- FTIR spectroscopy demonstrated co-localization of GAGs and lipids in spongiosa layer what may indicate their contribution in the very early phase of aortic valve calcific degeneration.

76 FR 36231 - American Society of Mechanical Engineers (ASME) Codes and New and Revised ASME Code Cases

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-21

... exceed the test facility limits and reduces the number of functional tests for specific valve designs... addresses reducing the number of functional tests for specific valve designs. The NRC has identified no... the required test pressure for the new Class 1 incompressible-fluid, pressure-relief valve designs...

46 CFR 52.20-17 - Opening between boiler and safety valve (modifies PFT-44).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Opening between boiler and safety valve (modifies PFT-44). 52.20-17 Section 52.20-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Requirements for Firetube Boilers § 52.20-17 Opening between boiler and safety valve...

46 CFR 52.20-17 - Opening between boiler and safety valve (modifies PFT-44).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Opening between boiler and safety valve (modifies PFT-44). 52.20-17 Section 52.20-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Requirements for Firetube Boilers § 52.20-17 Opening between boiler and safety valve...

46 CFR 52.20-17 - Opening between boiler and safety valve (modifies PFT-44).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Opening between boiler and safety valve (modifies PFT-44). 52.20-17 Section 52.20-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Requirements for Firetube Boilers § 52.20-17 Opening between boiler and safety valve...

46 CFR 52.20-17 - Opening between boiler and safety valve (modifies PFT-44).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Opening between boiler and safety valve (modifies PFT-44). 52.20-17 Section 52.20-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Requirements for Firetube Boilers § 52.20-17 Opening between boiler and safety valve...

46 CFR 52.20-17 - Opening between boiler and safety valve (modifies PFT-44).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Opening between boiler and safety valve (modifies PFT-44). 52.20-17 Section 52.20-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Requirements for Firetube Boilers § 52.20-17 Opening between boiler and safety valve...

3D printed mitral valve models: affordable simulation for robotic mitral valve repair.

PubMed

Premyodhin, Ned; Mandair, Divneet; Ferng, Alice S; Leach, Timothy S; Palsma, Ryan P; Albanna, Mohammad Z; Khalpey, Zain I

2018-01-01

3D printed mitral valve (MV) models that capture the suture response of real tissue may be utilized as surgical training tools. Leveraging clinical imaging modalities, 3D computerized modelling and 3D printing technology to produce affordable models complements currently available virtual simulators and paves the way for patient- and pathology-specific preoperative rehearsal. We used polyvinyl alcohol, a dissolvable thermoplastic, to 3D print moulds that were casted with liquid platinum-cure silicone yielding flexible, low-cost MV models capable of simulating valvular tissue. Silicone-moulded MV models were fabricated for 2 morphologies: the normal MV and the P2 flail. The moulded valves were plication and suture tested in a laparoscopic trainer box with a da Vinci Si robotic surgical system. One cardiothoracic surgery fellow and 1 attending surgeon qualitatively evaluated the ability of the valves to recapitulate tissue feel through surveys utilizing the 5-point Likert-type scale to grade impressions of the valves. Valves produced with the moulding and casting method maintained anatomical dimensions within 3% of directly 3D printed acrylonitrile butadiene styrene controls for both morphologies. Likert-type scale mean scores corresponded with a realistic material response to sutures (5.0/5), tensile strength that is similar to real MV tissue (5.0/5) and anatomical appearance resembling real MVs (5.0/5), indicating that evaluators 'agreed' that these aspects of the model were appropriate for training. Evaluators 'somewhat agreed' that the overall model durability was appropriate for training (4.0/5) due to the mounting design. Qualitative differences in repair quality were notable between fellow and attending surgeon. 3D computer-aided design, 3D printing and fabrication techniques can be applied to fabricate affordable, high-quality educational models for technical training that are capable of differentiating proficiency levels among users. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Combustion mode switching with a turbocharged/supercharged engine

DOEpatents

Mond, Alan; Jiang, Li

2015-09-22

A method for switching between low- and high-dilution combustion modes in an internal combustion engine having an intake passage with an exhaust-driven turbocharger, a crankshaft-driven positive displacement supercharger downstream of the turbocharger and having variable boost controllable with a supercharger bypass valve, and a throttle valve downstream of the supercharger. The current combustion mode and mass air flow are determined. A switch to the target combustion mode is commanded when an operating condition falls within a range of predetermined operating conditions. A target mass air flow to achieve a target air-fuel ratio corresponding to the current operating condition and the target combustion mode is determined. The degree of opening of the supercharger bypass valve and the throttle valve are controlled to achieve the target mass air flow. The amount of residual exhaust gas is manipulated.

Ethics in biomedical engineering.

PubMed

Morsy, Ahmed; Flexman, Jennifer

2008-01-01

This session focuses on a number of aspects of the subject of Ethics in Biomedical Engineering. The session starts by providing a case study of a company that manufactures artificial heart valves where the valves were failing at an unexpected rate. The case study focuses on Biomedical Engineers working at the company and how their education and training did not prepare them to deal properly with such situation. The second part of the session highlights the need to learn about various ethics rules and policies regulating research involving human or animal subjects.

Installation for the catalytic afterburning of exhaust gases in the exhaust gas system of an internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lange, K.

1974-12-06

An installation is described for the catalytic afterburning of exhaust gases in an internal combustion engine. The system includes a line by-passing the installation for the catalytic afterburning, in which is arranged a throttle valve actuated in dependence on the temperature of the installation. The throttle valve also can be actuated independently of the temperature of the installation, but in dependence of the oil pressure which continues to exist for a short period of time after turning off the engine.

Design type air engine Di Pietro

NASA Astrophysics Data System (ADS)

Zwierzchowski, Jaroslaw

The article presents a pneumatic engine constructed by Angelo Di Pietro. 3D solid models of pneumatic engine components were presented therein. A directional valve is a key element of the control system. The valve functions as a camshaft distributing air to particular engine chambers. The construction designed by Angelo Di Pietro is modern and innovative. A pneumatic engine requires low pressure to start rotary movement. With the use of CFD software, the fields of velocity vectors' distribution were determined. Moreover, the author determined the distribution of pressure values in engine inlet and outlet channels. CFD model studies on engine operation were conducted for chosen stages of operating cycles. On the basis of simulation tests that were conducted, the values of flow rates for the engine were determined. The distribution of pressure values made it possible to evaluate the torque value on the rotating shaft.

Bacterial adherence to graft tissues in static and flow conditions.

PubMed

Veloso, Tiago Rafael; Claes, Jorien; Van Kerckhoven, Soetkin; Ditkowski, Bartosz; Hurtado-Aguilar, Luis G; Jockenhoevel, Stefan; Mela, Petra; Jashari, Ramadan; Gewillig, Marc; Hoylaerts, Marc F; Meyns, Bart; Heying, Ruth

2018-01-01

Various conduits and stent-mounted valves are used as pulmonary valve graft tissues for right ventricular outflow tract reconstruction with good hemodynamic results. Valve replacement carries an increased risk of infective endocarditis (IE). Recent observations have increased awareness of the risk of IE after transcatheter implantation of a stent-mounted bovine jugular vein valve. This study focused on the susceptibility of graft tissue surfaces to bacterial adherence as a potential risk factor for subsequent IE. Adhesion of Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus sanguinis to bovine pericardium (BP) patch, bovine jugular vein (BJV), and cryopreserved homograft (CH) tissues was quantified under static and shear stress conditions. Microscopic analysis and histology were performed to evaluate bacterial adhesion to matrix components. In general, similar bacteria numbers were recovered from CH and BJV tissue surfaces for all strains, especially in flow conditions. Static bacterial adhesion to the CH wall was lower for S sanguinis adhesion (P < .05 vs BP patch). Adhesion to the BJV wall, CH wall, and leaflet was decreased for S epidermidis in static conditions (P < .05 vs BP patch). Bacterial adhesion under shear stress indicated similar bacterial adhesion to all tissues, except for lower adhesion to the BJV wall after S sanguinis incubation. Microscopic analysis showed the importance of matrix component exposure for bacterial adherence to CH. Our data provide evidence that the surface composition of BJV and CH tissues themselves, bacterial surface proteins, and shear forces per se are not the prime determinants of bacterial adherence. Copyright © 2017 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

The Further Development of Heat-Resistant Materials for Aircraft Engines

NASA Technical Reports Server (NTRS)

Bollenrath, Franz

1946-01-01

The present report deals with the problems involved in the greater utilization and development of aircraft engine materials, and specifically; piston materials, cylinder heads, exhaust valves, and exhaust gas turbine blading. The blades of the exhaust gas turbine are likely to be the highest stressed components of modern power plants from a thermal-mechanical and chemical standpoint, even though the requirements on exhaust valves of engines with gasoline injection are in general no less stringent. For the fire plate in Diesel engines the specifications for mechanical strength and design are not so stringent, and the question of heat resistance, which under these circumstances is easier obtainable, predominates.

Multiple volume compressor for hot gas engine

DOEpatents

Stotts, Robert E.

1986-01-01

A multiple volume compressor for use in a hot gas (Stirling) engine having a plurality of different volume chambers arranged to pump down the engine when decreased power is called for and return the working gas to a storage tank or reservoir. A valve actuated bypass loop is placed over each chamber which can be opened to return gas discharged from the chamber back to the inlet thereto. By selectively actuating the bypass valves, a number of different compressor capacities can be attained without changing compressor speed whereby the capacity of the compressor can be matched to the power available from the engine which is used to drive the compressor.

Dynamic Mechanical Analysis (DMA) to Help Characterize Vespel SP-211 Polyimide Material for Use as a 750 F Valve Seal on the Ares I Upper Stage J-2X Engine

NASA Technical Reports Server (NTRS)

Wingard, Doug

2013-01-01

DuPont (TM) Vespel (R) SP-211 polyimide was selected as the top candidate seal material for use in the Oxidizer Turbine Bypass Valve (OTBV) on NASA's Ares I Upper Stage J-2X engine. In the OTBV, the seal material would get exposed to temperatures up to 750degF for approx 10 minutes at a time. Although the J-2X engine is not reusable, the valve material could be exposed to multiple temperature cycles up to 750 F during engine operation. The Constellation Program that included the Ares I rocket was eventually cancelled, but the J-2X engine was chosen for continued use for development of NASA's Space Launch System (SLS). The SLS is a heavy-lift launch vehicle that will have capability of taking astronauts and hardware to the Moon, Mars and asteroids. Dynamic mechanical analysis (DMA) was one of several test techniques used to characterize Vespel SP-211 to help prove its worthiness for use on the OTBV of the J-2X engine.

Dynamic Mechanical Analysis (DMA) to Help Characterize Vespel SP-211 Polyimide Material for Use as a 750 F Valve Seal on the Ares I Upper Stage J-2X Engine

NASA Technical Reports Server (NTRS)

Wingard, Doug

2013-01-01

DuPont(tm) Vespel(R) SP-211 polyimide was selected as the top candidate seal material for use in the Oxidizer Turbine Bypass Valve (OTBV) on NASA's Ares I Upper Stage J-2X engine. In the OTBV, the seal material would get exposed to temperatures up to 750degF for approx 10 minutes at a time. Although the J-2X engine is not reusable, the valve material could be exposed to multiple temperature cycles up to 750degF during engine operation. The Constellation Program that included the Ares I rocket was eventually cancelled, but the J-2X engine was chosen for continued use for development of NASA's Space Launch System (SLS). The SLS is a heavy-lift launch vehicle that will have capability of taking astronauts and hardware to the Moon, Mars and asteroids. Dynamic mechanical analysis (DMA) was one of several test techniques used to characterize Vespel SP-211 to help prove its worthiness for use on the OTBV of the J-2X engine.

Acoustic Emission Sensing for Maritime Diesel Engine Performance and Health

DTIC Science & Technology

2016-05-01

diesel internal combustion engine operating condition and health. A commercial-off- the-shelf AE monitoring system and a purpose-built data acquisition...subjected to external events such as a combustion event, fluid flow or the opening and closing of valves. This document reports on the monitoring and...conjunction with injection- combustion processes and valve events. AE from misfire as the result of a fuel injector malfunction was readily detectable

Tissue Doppler imaging and echo-Doppler findings associated with a mitral valve stenosis with an immobile posterior valve leaflet in a bull terrier.

PubMed

Tidholm, A; Nicolle, A P; Carlos, C; Gouni, V; Caruso, J L; Pouchelon, J L; Chetboul, V

2004-04-01

A mitral valve stenosis was diagnosed in a 2-year-old female Bull Terrier by use of two-dimensional (2-D) and M-mode echocardiography, colour-flow imaging and spectral Doppler examinations. Tissue Doppler Imaging was also performed to assess the segmental radial myocardial motion. The mitral valve stenosis was characterized by a decreased mitral orifice area/left ventricle area ratio (0.14), an increased early diastolic flow velocity (E wave = 1.9 m/s), a prolonged pressure half-time (106 ms) and a decreased E-F slope (4.5 cm/s) on pulsed-wave Doppler examination. This mitral stenosis was associated with an immobile posterior leaflet, as seen on 2-D and M-mode echocardiography. Immobility of the posterior mitral leaflet is considered to be a rare finding in humans and, to our knowledge, has not been precisely documented in dogs with mitral valve stenosis.

Q Fever: Statistics and Epidemiology

MedlinePlus

... severe with complications requiring hospitalization that may include endocarditis (infection of the heart tissue), encephalitis (inflammation of ... people with a history of heart valve defects, endocarditis, or heart valve implants may increase the risk ...

A novel culture device for the evaluation of three-dimensional extracellular matrix materials.

PubMed

Akhyari, Payam; Ziegler, Heiko; Gwanmesia, Patricia; Barth, Mareike; Schilp, Soeren; Huelsmann, Joern; Hoffmann, Stefanie; Bosch, Julia; Kögler, Gesine; Lichtenberg, Artur

2014-09-01

Cell-matrix interactions in a three-dimensional (3D) extracellular matrix (ECM) are of fundamental importance in living tissue, and their in vitro reconstruction in bioartificial structures represents a core target of contemporary tissue engineering concepts. For a detailed analysis of cell-matrix interaction under highly controlled conditions, we developed a novel ECM evaluation culture device (EECD) that allows for a precisely defined surface-seeding of 3D ECM scaffolds, irrespective of their natural geometry. The effectiveness of EECD was evaluated in the context of heart valve tissue engineering. Detergent decellularized pulmonary cusps were mounted in EECD and seeded with endothelial cells (ECs) to study EC adhesion, morphology and function on a 3D ECM after 3, 24, 48 and 96 h. Standard EC monolayers served as controls. Exclusive top-surface-seeding of 3D ECM by viable ECs was demonstrated by laser scanning microscopy (LSM), resulting in a confluent re-endothelialization of the ECM after 96 h. Cell viability and protein expression, as demonstrated by MTS assay and western blot analysis (endothelial nitric oxide synthase, von Willebrand factor), were preserved at maintained levels over time. In conclusion, EECD proves as a highly effective system for a controlled repopulation and in vitro analysis of cell-ECM interactions in 3D ECM. Copyright © 2012 John Wiley & Sons, Ltd.

Analysis of IR spectra of mineralized deposits on human cardiac valves

NASA Astrophysics Data System (ADS)

Ivanov-Omskii, V. I.; Yastrebov, S. G.; Gulyaev, N. I.

2017-05-01

IR spectroscopy in the range of vibration of hydroxy groups has been used to analyze the binding energy of mineralized deposits to cardiac valves of patients of varied gender and age. A tendency was revealed toward a gender-independent rise in the binding energy of mineralized deposits to valve tissues with increasing age of patients. The analysis enables making recommendations concerning the early diagnostics of valve calcination, monitoring of its development, and therapy of calcinoses.

Mechanics of cryopreserved aortic and pulmonary homografts.

PubMed

Vesely, I; Casarotto, D C; Gerosa, G

2000-01-01

The surgical placement of pulmonary valve grafts into the aortic position (the Ross procedure) has been performed for three decades. Cryopreserved pulmonary valves have had mixed clinical results, however. The objectives of this study were to compare the mechanics of cryopreserved human aortic and pulmonary valve cusps and roots to determine if the pulmonary root can withstand the greater pressures of the aortic position. Six aortic and six pulmonary valve roots were obtained from the Oxford Valve Bank. They were harvested during cardiac transplantation from hearts explanted for dilated cardiomyopathy (mean patient age 68 years). The whole roots were initially stored frozen at -186 degrees C, then shipped packed on dry ice. After complete thawing, the roots were pressurized whole; test strips were then cut from the valve cusps, roots and sinuses and tested for stress/strain, stress relaxation, and ultimate failure strength. The pulmonary roots were more distensible (30% versus 20% strain to lock-up) and less compliant when loaded to aortic pressures. The pulmonary valve cusp and root tissue also showed greater extensibility and greater stiffness (lower compliance) when subjected to the same loads. We conclude that mechanical differences between aortic and pulmonary valve tissues are minimal. The pulmonary root should withstand the forces imposed on it when placed in the aortic position. However, if implanted whole, the pulmonary root will distend about 30% more than the aortic root when subjected to aortic pressures. These geometric changes may affect valve function in the long term and should be appreciated when implanting a pulmonary valve graft.

Biomedical Impact in Implantable Devices-The Transcatheter Aortic Valve as an example

NASA Astrophysics Data System (ADS)

Anastasiou, Alexandros; Saatsakis, George

2015-09-01

Objective: To update of the scientific community about the biomedical engineering involvement in the implantable devices chain. Moreover the transcatheter Aortic Valve (TAV) replacement, in the field of cardiac surgery, will be analyzed as an example of contemporary implantable technology. Methods: A detailed literature review regarding biomedical engineers participating in the implantable medical product chain, starting from the design of the product till the final implantation technique. Results: The scientific role of biomedical engineers has clearly been established. Certain parts of the product chain are implemented almost exclusively by experienced biomedical engineers such as the transcatheter aortic valve device. The successful professional should have a multidisciplinary knowledge, including medicine, in order to pursue the challenges for such intuitive technology. This clearly indicates that biomedical engineers are among the most appropriate scientists to accomplish such tasks. Conclusions: The biomedical engineering involvement in medical implantable devices has been widely accepted by the scientific community, worldwide. Its important contribution, starting from the design and extended to the development, clinical trials, scientific support, education of other scientists (surgeons, cardiologists, technicians etc.), and even to sales, makes biomedical engineers a valuable player in the scientific arena. Notably, the sector of implantable devices is constantly raising, as emerging technologies continuously set up new targets.

Use of a Valved-Conduit for Exclusion of the Infected Portion in the Prosthetic Pulmonary Valve Endocarditis

PubMed Central

Jung, Joonho; Lee, Cheol Joo; Lim, Sang-Hyun; Choi, Ho; Park, Soo-Jin

2013-01-01

A 51-year-old male was admitted to the hospital with complaints of fever and hemoptysis. After evaluation of the fever focus, he was diagnosed with pulmonary valve infective endocarditis. Thus pulmonary valve replacement and antibiotics therapy were performed and discharged. He was brought to the emergency unit presenting with a high fever (>39℃) and general weakness 6 months after the initial operation. The echocardiography revealed prosthetic pulmonary valve endocarditis. Therefore, redo-pulmonary valve replacement using valved conduit was performed in the Rastelli fashion because of the risk of pulmonary arterial wall injury and recurrent endocarditis from the remnant inflammatory tissue. We report here on the successful surgical treatment of prosthetic pulmonary valve endocarditis with an alternative surgical method. PMID:23772409

Modeling and control of fuel distribution in a dual-fuel internal combustion engine leveraging late intake valve closings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kassa, Mateos; Hall, Carrie; Ickes, Andrew

Advanced internal combustion engines, although generally more efficient than conventional combustion engines, often encounter limitations in multi-cylinder applications due to variations in the combustion process encountered across cylinders and between cycles. This study leverages experimental data from an inline 6-cylinder heavy-duty dual fuel engine equipped with exhaust gas recirculation (EGR), a variable geometry turbocharger, and a fully-flexible variable intake valve actuation system to study cylinder-to-cylinder variations in power production and the underlying uneven fuel distribution that causes these variations. The engine is operated with late intake valve closure timings in a dual-fuel combustion mode in which a high reactivity fuelmore » is directly injected into the cylinders and a low reactivity fuel is port injected into the cylinders. Both dual fuel implementation and late intake valve closing (IVC) timings have been shown to improve thermal efficiency. However, experimental data from this study reveal that when late IVC timings are used on a multi-cylinder dual fuel engine a significant variation in IMEP across cylinders results and as such, leads to efficiency losses. The difference in IMEP between the different cylinders ranges from 9% at an IVC of 570°ATDC to 38% at an IVC of 610°ATDC and indicates an increasingly uneven fuel distribution. These experimental observations along with engine simulation models developed using GT-Power have been used to better understand the distribution of the port injected fuel across cylinders under various operating conditions on such dual fuel engines. This study revealed that the fuel distribution across cylinders in this dual fuel application is significantly affected by changes in the effective compression ratio as determined by the intake valve close timing as well as the design of the intake system (specifically the length of the intake runners). Late intake valve closures allow a portion of the trapped air and port injected fuel to flow back out of the cylinders into the intake manifold. The fuel that is pushed back in the intake manifold is then unevenly redistributed across the cylinders largely due to the dominating direction of the flow in the intake manifold. The effects of IVC as well as the impact of intake runner length on fuel distribution were quantitatively analyzed and a model was developed that can be used to accurately predict the fuel distribution of the port injected fuel at different operating conditions with an average estimation error of 1.5% in cylinder-specific fuel flow.« less

46 CFR 58.30-15 - Pipe, tubing, valves, fittings, pumps, and motors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Pipe, tubing, valves, fittings, pumps, and motors. 58.30-15 Section 58.30-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Fluid Power and Control Systems § 58.30-15 Pipe, tubing, valves, fittings, pumps, and motors. ...

Turbo-generator control with variable valve actuation

DOEpatents

Vuk, Carl T [Denver, IA

2011-02-22

An internal combustion engine incorporating a turbo-generator and one or more variably activated exhaust valves. The exhaust valves are adapted to variably release exhaust gases from a combustion cylinder during a combustion cycle to an exhaust system. The turbo-generator is adapted to receive exhaust gases from the exhaust system and rotationally harness energy therefrom to produce electrical power. A controller is adapted to command the exhaust valve to variably open in response to a desired output for the turbo-generator.

Systematic Engine Uprate Technology Development and Deployment for Pipeline Compressor Engines through Increased Torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dennis Schmitt; Daniel Olsen

2005-09-30

Three methods were utilized to analyze key components of slow-speed, large-bore, natural gas integral engines. These three methods included the application of computational fluid dynamics (CFD), dynamic modal analysis using finite element analysis (FEA), and a stress analysis method also using FEA. The CFD analysis focuses primarily on the fuel mixing in the combustion chamber of a TLA engine. Results indicate a significant increase in the homogeneity of the air and fuel using high-pressure fuel injection (HPFI) instead of standard low-pressure mechanical gas admission valve (MGAV). A modal analysis of three engine crankshafts (TLA-6, HBA-6, and GMV-10) is developed andmore » presented. Results indicate that each crankshaft has a natural frequency and corresponding speed that is well away from the typical engine operating speed. A frame stress analysis method is also developed and presented. Two different crankcases are examined. A TLA-6 crankcase is modeled and a stress analysis is performed. The method of dynamic load determination, model setup, and the results from the stress analysis are discussed. Preliminary results indicate a 10%-15% maximum increase in frame stress due to a 20% increase in HP. However, the high stress regions were localized. A new hydraulically actuated mechanical fuel valve is also developed and presented. This valve provides equivalent high-energy (supersonic) fuel injection comparable to a HPFI system, at 1/5th of the natural gas fuel pressure. This valve was developed in cooperation with the Dresser-Rand Corporation.« less

Coal slurry fuel supply and purge system

DOEpatents

McDowell, Robert E.; Basic, Steven L.; Smith, Russel M.

1994-01-01

A coal slurry fuel supply and purge system for a locomotive engines is disclosed which includes a slurry recirculation path, a stand-by path for circulating slurry during idle or states of the engine when slurry fuel in not required by the engine, and an engine header fluid path connected to the stand-by path, for supplying and purging slurry fuel to and from fuel injectors. A controller controls the actuation of valves to facilitate supply and purge of slurry to and from the fuel injectors. A method for supplying and purging coal slurry in a compression ignition engine is disclosed which includes controlling fluid flow devices and valves in a plurality of fluid paths to facilitate continuous slurry recirculation and supply and purge of or slurry based on the operating state of the engine.

Plasma and tissue oxidative stress index in patients with rheumatic and degenerative heart valve disease.

PubMed

Rabus, Murat; Demirbağ, Recep; Sezen, Yusuf; Konukoğlu, Oğuz; Yildiz, Ali; Erel, Ozcan; Zeybek, Rahmi; Yakut, Cevat

2008-12-01

We investigated whether patients with rheumatic and degenerative heart valve disease (HVD) differed with regard to plasma and tissue oxidative stress index (OSI). The study included 56 patients who underwent valve replacement due to rheumatic (n=32; 15 males; mean age 47+/-10 years) and degenerative (n=24; 13 males; mean age 55+/-12 years) HVD. Plasma and tissue total oxidative status (TOS) and total antioxidative capacity (TAC) levels were measured and OSI was calculated. Patients with degenerative HVD had significantly higher age, increased interventricular septum thickness, and higher frequency of aortic stenosis, whereas the incidence of mitral stenosis was higher in patients with rheumatic HVD (p<0.05). Plasma oxidative characteristics did not differ between the two HVD groups (p>0.05). Tissue TAC was significantly lower in patients with rheumatic HVD (p=0.027), whereas tissue TOS and OSI were similar between the two HVD groups (p>0.05). In bivariate analysis, plasma OSI did not show any correlation with clinical, laboratory, and echocardiographic variables (p>0.05). Our data show that plasma and tissue OSI levels are similar in patients with rheumatic and degenerative HVD.

Influence of pre-injection control parameters on main-injection fuel quantity for an electronically controlled double-valve fuel injection system of diesel engine

NASA Astrophysics Data System (ADS)

Song, Enzhe; Fan, Liyun; Chen, Chao; Dong, Quan; Ma, Xiuzhen; Bai, Yun

2013-09-01

A simulation model of an electronically controlled two solenoid valve fuel injection system for a diesel engine is established in the AMESim environment. The accuracy of the model is validated through comparison with experimental data. The influence of pre-injection control parameters on main-injection quantity under different control modes is analyzed. In the spill control valve mode, main-injection fuel quantity decreases gradually and then reaches a stable level because of the increase in multi-injection dwell time. In the needle control valve mode, main-injection fuel quantity increases with rising multi-injection dwell time; this effect becomes more obvious at high-speed revolutions and large main-injection pulse widths. Pre-injection pulse width has no obvious influence on main-injection quantity under the two control modes; the variation in main-injection quantity is in the range of 1 mm3.

High speed variable delivery helical screw compressor/expander automotive air conditioning and waste heat energy recovery system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gagnon, J.A.; Schaefer, D.D.; Shaw, D.N.

1980-09-02

A compact, helical screw compressor/expander unit is described that is mounted in a vehicle and connected to the vehicle engine driven drive shaft has inlet and outlet ports and a capacity control slide valve and a pressure matching or volume ratio slide valve, respectively, for said ports. A refrigerant loop includes the compressor, a condenser mounted in the path of air flow over the engine and an evaporator mounted in a fresh air/cab return air flow duct for the occupant. Heat pipes thermally connect the cab air flow duct to the engine exhaust system which also bears the vapor boiler.more » Selectively operated damper valves control the fresh air/cab return air for passage selectively over the evaporator coil and the heat pipes as well as the exhaust gas flow over opposite ends of the heat pipes and the vapor boiler.« less

Engine having a variable valve actuation system

DOEpatents

Hefler, Gregory W [Chillicothe, IL

2004-10-12

An engine has a cylinder head having a first surface and a second surface spaced from the first surface. A valve is moveably connected to the cylinder head. A rocker arm is connected to the valve, and a rocker shaft having a first location spaced a maximum distance from the cylinder head is connected to the rocker arm. A support member has and an actuator fluid passage network. The actuator fluid passage network defines a volume. The support member is connected to the cylinder head and is positioned such that a majority of the volume of the actuator fluid passage network is between the first location of the rocker shaft and the second surface of the cylinder head.

Engine having a variable valve actuation system

DOEpatents

Hefler, Gregory W.

2005-10-12

An engine has a cylinder head having a first surface and a second surface spaced from the first surface. A valve is moveably connected to the cylinder head. A rocker arm is connected to the valve, and a rocker shaft having a first location spaced a maximum distance from the cylinder head is connected to the rocker arm. A support member has and an actuator fluid passage network. The actuator fluid passage network defines a volume. The support member is connected to the cylinder head and is positioned such that a majority of the volume of the actuator fluid passage network is between the first location of the rocker shaft and the second surface of the cylinder head.

System and method for conditioning intake air to an internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sellnau, Mark C.

A system for conditioning the intake air to an internal combustion engine includes a means to boost the pressure of the intake air to the engine and a liquid cooled charge air cooler disposed between the output of the boost means and the charge air intake of the engine. Valves in the coolant system can be actuated so as to define a first configuration in which engine cooling is performed by coolant circulating in a first coolant loop at one temperature, and charge air cooling is performed by coolant flowing in a second coolant loop at a lower temperature. Themore » valves can be actuated so as to define a second configuration in which coolant that has flowed through the engine can be routed through the charge air cooler. The temperature of intake air to the engine can be controlled over a wide range of engine operation.« less

Computational Modeling of Liquid and Gaseous Control Valves

NASA Technical Reports Server (NTRS)

Daines, Russell; Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy; Moore, Arden; Sulyma, Peter

2005-01-01

In this paper computational modeling efforts undertaken at NASA Stennis Space Center in support of rocket engine component testing are discussed. Such analyses include structurally complex cryogenic liquid valves and gas valves operating at high pressures and flow rates. Basic modeling and initial successes are documented, and other issues that make valve modeling at SSC somewhat unique are also addressed. These include transient behavior, valve stall, and the determination of flow patterns in LOX valves. Hexahedral structured grids are used for valves that can be simplifies through the use of axisymmetric approximation. Hybrid unstructured methodology is used for structurally complex valves that have disparate length scales and complex flow paths that include strong swirl, local recirculation zones/secondary flow effects. Hexahedral (structured), unstructured, and hybrid meshes are compared for accuracy and computational efficiency. Accuracy is determined using verification and validation techniques.

Mitral valve replacement with the Hancock stabilized glutaraldehyde valve. Clinical and laboratory evaluation.

PubMed

Buch, W S; Pipkin, R D; Hancock, W D; Fogarty, T J

1975-11-01

From March 1971 through April 1975, one hundred twenty patients underwent mitral valve replacement with a Hancock "stabilized glutaraldehyde process" porcine aortic xenograft. A simultaneous canine experimental series was also carried out. In the clinical series, the early mortality was 8.3%. Actuarial analyses of all patients predicts survival at two years of 81.0% and at four years of 70.0%. The predicted survival for patients without coronary disease or prior prosthetic valve replacement is 87.5% at two years and 77.5% at four years. There were four thromboembolic episodes, a rate of 2.4% per patient-year. None were fatal. No valve failure were noted. Histologic examination and shrink temperature analysis of recovered valves show excellent tissue preservation at 40 months. The data indicate that the Hancock valve is durable, enjoys a low incidence of thromboembolism, and may be the valve of choice for mitral valve replacement.

A Description and Test Results of a Spark-Ignition and a Compression-Ignition 2-Stroke-Cycle Engine

NASA Technical Reports Server (NTRS)

Spanogle, J A; Whitney, E G

1935-01-01

This report presents performance results of air cooled and water-cooled engines. The results obtained were sufficiently promising to warrant further investigation with fuel injection and spark ignition, with the same arrangement of inlet ports and exhaust valves at the bottom of the cylinder and the exhaust gases discharged through two poppet valves in the cylinder head. The displacement of the engine was 118 cubic inches. Optimum performance was obtained with the inlet air directed into the cylinder at an angle of 20 degrees to the radial.

On discharge from poppet valves: effects of pressure and system dynamics

NASA Astrophysics Data System (ADS)

Winroth, P. M.; Ford, C. L.; Alfredsson, P. H.

2018-02-01

Simplified flow models are commonly used to design and optimize internal combustion engine systems. The exhaust valves and ports are modelled as straight pipe flows with a corresponding discharge coefficient. The discharge coefficient is usually determined from steady-flow experiments at low pressure ratios and at fixed valve lifts. The inherent assumptions are that the flow through the valve is insensitive to the pressure ratio and may be considered as quasi-steady. The present study challenges these two assumptions through experiments at varying pressure ratios and by comparing measurements of the discharge coefficient obtained under steady and dynamic conditions. Steady flow experiments were performed in a flow bench, whereas the dynamic measurements were performed on a pressurized, 2 l, fixed volume cylinder with one or two moving valves. In the latter experiments an initial pressure (in the range 300-500 kPa) was established whereafter the valve(s) was opened with a lift profile corresponding to different equivalent engine speeds (in the range 800-1350 rpm). The experiments were only concerned with the blowdown phase, i.e. the initial part of the exhaustion process since no piston was simulated. The results show that the process is neither pressure-ratio independent nor quasi-steady. A measure of the "steadiness" has been defined, relating the relative change in the open flow area of the valve to the relative change of flow conditions in the cylinder, a measure that indicates if the process can be regarded as quasi-steady or not.

Aortic valve ochronosis: a rare manifestation of alkaptonuria

PubMed Central

Steger, Christina Maria

2011-01-01

Alkaptonuric ochronosis is a heritable disorder of tyrosine metabolism, with various systemic abnormalities related to pigment deposition and degeneration of collagen and other tissues, including the heart and aorta. A 65-year-old woman with alkaptonuric ochronosis and a history of four joint replacements required aortic valve replacement for severe aortic stenosis. Operative findings included ochronosis of a partly calcified aortic valve and the aortic intima. The aortic valve was removed at surgery and histologically investigated. Light microscopic examination of the aortic valve revealed intracellular and extracellular deposits of ochronotic pigment and a chronic inflammatory infiltrate. Beside the case representation, the disease history, aetiology, pathogenesis, clinical presentation and treatment of aortic valve ochronosis are reviewed. PMID:22689837

Aortic valve ochronosis: a rare manifestation of alkaptonuria.

PubMed

Steger, Christina Maria

2011-07-28

Alkaptonuric ochronosis is a heritable disorder of tyrosine metabolism, with various systemic abnormalities related to pigment deposition and degeneration of collagen and other tissues, including the heart and aorta. A 65-year-old woman with alkaptonuric ochronosis and a history of four joint replacements required aortic valve replacement for severe aortic stenosis. Operative findings included ochronosis of a partly calcified aortic valve and the aortic intima. The aortic valve was removed at surgery and histologically investigated. Light microscopic examination of the aortic valve revealed intracellular and extracellular deposits of ochronotic pigment and a chronic inflammatory infiltrate. Beside the case representation, the disease history, aetiology, pathogenesis, clinical presentation and treatment of aortic valve ochronosis are reviewed.

46 CFR 52.01-105 - Piping, valves and fittings (modifies PG-58 and PG-59).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Piping, valves and fittings (modifies PG-58 and PG-59). 52.01-105 Section 52.01-105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-105 Piping, valves and fittings (modifies PG-58 and PG-59). (a) Boiler external piping within...

46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Safety valve requirements for steam boilers (modifies HG-400 and HG-401). 53.05-1 Section 53.05-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety valve requirements for steam boilers (modifies HG...

46 CFR 53.05-2 - Relief valve requirements for hot water boilers (modifies HG-400.2).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Relief valve requirements for hot water boilers (modifies HG-400.2). 53.05-2 Section 53.05-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-2 Relief valve requirements for hot water boilers (modifies HG...

46 CFR 52.01-105 - Piping, valves and fittings (modifies PG-58 and PG-59).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Piping, valves and fittings (modifies PG-58 and PG-59). 52.01-105 Section 52.01-105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-105 Piping, valves and fittings (modifies PG-58 and PG-59). (a) Boiler external piping within...

46 CFR 53.05-2 - Relief valve requirements for hot water boilers (modifies HG-400.2).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Relief valve requirements for hot water boilers (modifies HG-400.2). 53.05-2 Section 53.05-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-2 Relief valve requirements for hot water boilers (modifies HG...

46 CFR 53.05-2 - Relief valve requirements for hot water boilers (modifies HG-400.2).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Relief valve requirements for hot water boilers (modifies HG-400.2). 53.05-2 Section 53.05-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-2 Relief valve requirements for hot water boilers (modifies HG...

46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Safety valve requirements for steam boilers (modifies HG-400 and HG-401). 53.05-1 Section 53.05-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety valve requirements for steam boilers (modifies HG...

46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Safety valve requirements for steam boilers (modifies HG-400 and HG-401). 53.05-1 Section 53.05-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety valve requirements for steam boilers (modifies HG...

46 CFR 52.01-105 - Piping, valves and fittings (modifies PG-58 and PG-59).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Piping, valves and fittings (modifies PG-58 and PG-59). 52.01-105 Section 52.01-105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-105 Piping, valves and fittings (modifies PG-58 and PG-59). (a) Boiler external piping within...

46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Safety valve requirements for steam boilers (modifies HG-400 and HG-401). 53.05-1 Section 53.05-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety valve requirements for steam boilers (modifies HG...

46 CFR 53.05-2 - Relief valve requirements for hot water boilers (modifies HG-400.2).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Relief valve requirements for hot water boilers (modifies HG-400.2). 53.05-2 Section 53.05-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-2 Relief valve requirements for hot water boilers (modifies HG...

46 CFR 53.05-2 - Relief valve requirements for hot water boilers (modifies HG-400.2).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Relief valve requirements for hot water boilers (modifies HG-400.2). 53.05-2 Section 53.05-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-2 Relief valve requirements for hot water boilers (modifies HG...

System for detecting operating errors in a variable valve timing engine using pressure sensors

DOEpatents

Wiles, Matthew A.; Marriot, Craig D

2013-07-02

A method and control module includes a pressure sensor data comparison module that compares measured pressure volume signal segments to ideal pressure volume segments. A valve actuation hardware remedy module performs a hardware remedy in response to comparing the measured pressure volume signal segments to the ideal pressure volume segments when a valve actuation hardware failure is detected.

21. VIEW TO NORTHWEST, ENGINE/PUMP HOUSE EXTENSION, HIGH PRESSURE PISTON ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

21. VIEW TO NORTHWEST, ENGINE/PUMP HOUSE EXTENSION, HIGH PRESSURE PISTON OF STEAM ENGINE NO. 4; CONTROL PANEL MOUNTED ON THE ENGINE; FLOOR VALVES CONTROL THE STEAM. - Deer Island Pumping Station, Boston, Suffolk County, MA

Selection of Reference Genes for Quantitative Real Time PCR (qPCR) Assays in Tissue from Human Ascending Aorta

PubMed Central

Rueda-Martínez, Carmen; Lamas, Oscar; Mataró, María José; Robledo-Carmona, Juan; Sánchez-Espín, Gemma; Jiménez-Navarro, Manuel; Such-Martínez, Miguel; Fernández, Borja

2014-01-01

Dilatation of the ascending aorta (AAD) is a prevalent aortopathy that occurs frequently associated with bicuspid aortic valve (BAV), the most common human congenital cardiac malformation. The molecular mechanisms leading to AAD associated with BAV are still poorly understood. The search for differentially expressed genes in diseased tissue by quantitative real-time PCR (qPCR) is an invaluable tool to fill this gap. However, studies dedicated to identify reference genes necessary for normalization of mRNA expression in aortic tissue are scarce. In this report, we evaluate the qPCR expression of six candidate reference genes in tissue from the ascending aorta of 52 patients with a variety of clinical and demographic characteristics, normal and dilated aortas, and different morphologies of the aortic valve (normal aorta and normal valve n = 30; dilated aorta and normal valve n = 10; normal aorta and BAV n = 4; dilated aorta and BAV n = 8). The expression stability of the candidate reference genes was determined with three statistical algorithms, GeNorm, NormFinder and Bestkeeper. The expression analyses showed that the most stable genes for the three algorithms employed were CDKN1β, POLR2A and CASC3, independently of the structure of the aorta and the valve morphology. In conclusion, we propose the use of these three genes as reference genes for mRNA expression analysis in human ascending aorta. However, we suggest searching for specific reference genes when conducting qPCR experiments with new cohort of samples. PMID:24841551

Experimental Investigation of a Multi-Cycle Single-Tube Pulse Detonation Rocket Engine with a Coaxial Rotary Valve

NASA Astrophysics Data System (ADS)

Matsuoka, Ken; Esumi, Motoki; Ikeguchi, Ken Bryan; Kasahara, Jiro; Matsuo, Akiko; Funaki, Ikkoh

We developed a novel coaxial rotary valve for a multi-tube PDE. Since this single valve can supply three different gases (fuel, oxidizer and purge gas) into a combustor, the unification of the valve systems for three different gases is possible by using our newly designed valve. A PDRE system can be simple and lightweight by using this valve, and thus its thrust-weight ratio can be increased. We proposed the design of a multi-tube rotary-valved PDRE system by this rotary valve. Moreover, in preparation for a multi-tube rotary-valved PDRE, we carried out the multi-cycle operation experiment by the single-tube rotary-valved PDRE system. The combustion wave velocity was measured to confirm the operation of the PDRE system. Deflagration-to-detonation transition (DDT) was confirmed and DDT distance decreased under the condition of high operation frequency. In addition, a maximum operation frequency was 159 Hz.

Pulmonary valve autotransplantation (the Ross operation).

PubMed

Ross, D

1988-09-01

In 1967, homografts had been in place five years and the early nonviable and natant freeze-dried valves were showing irrefutable signs of degeneration and calcification. For this reason, in 1967, we moved to reserving both viability and tissue integrity by cryopreservation. To overcome the problems of procurement, the next logical step was to transfer the patient's own pulmonic valve to the aortic area. In the past twenty years, 249 operations have been performed. Of the 249 patients, there have been 16 operative deaths (6.5%), but no operative deaths in the past ten years. There have been no details related to primary tissue failure in the aortic area. There have been 36 reoperations (14.4%).

Computerized microfluidic cell culture using elastomeric channels and Braille displays.

PubMed

Gu, Wei; Zhu, Xiaoyue; Futai, Nobuyuki; Cho, Brenda S; Takayama, Shuichi

2004-11-09

Computer-controlled microfluidics would advance many types of cellular assays and microscale tissue engineering studies wherever spatiotemporal changes in fluidics need to be defined. However, this goal has been elusive because of the limited availability of integrated, programmable pumps and valves. This paper demonstrates how a refreshable Braille display, with its grid of 320 vertically moving pins, can power integrated pumps and valves through localized deformations of channel networks within elastic silicone rubber. The resulting computerized fluidic control is able to switch among: (i) rapid and efficient mixing between streams, (ii) multiple laminar flows with minimal mixing between streams, and (iii) segmented plug-flow of immiscible fluids within the same channel architecture. The same control method is used to precisely seed cells, compartmentalize them into distinct subpopulations through channel reconfiguration, and culture each cell subpopulation for up to 3 weeks under perfusion. These reliable microscale cell cultures showed gradients of cellular behavior from C2C12 myoblasts along channel lengths, as well as differences in cell density of undifferentiated myoblasts and differentiation patterns, both programmable through different flow rates of serum-containing media. This technology will allow future microscale tissue or cell studies to be more accessible, especially for high-throughput, complex, and long-term experiments. The microfluidic actuation method described is versatile and computer programmable, yet simple, well packaged, and portable enough for personal use.

Computerized microfluidic cell culture using elastomeric channels and Braille displays

PubMed Central

Gu, Wei; Zhu, Xiaoyue; Futai, Nobuyuki; Cho, Brenda S.; Takayama, Shuichi

2004-01-01

Computer-controlled microfluidics would advance many types of cellular assays and microscale tissue engineering studies wherever spatiotemporal changes in fluidics need to be defined. However, this goal has been elusive because of the limited availability of integrated, programmable pumps and valves. This paper demonstrates how a refreshable Braille display, with its grid of 320 vertically moving pins, can power integrated pumps and valves through localized deformations of channel networks within elastic silicone rubber. The resulting computerized fluidic control is able to switch among: (i) rapid and efficient mixing between streams, (ii) multiple laminar flows with minimal mixing between streams, and (iii) segmented plug-flow of immiscible fluids within the same channel architecture. The same control method is used to precisely seed cells, compartmentalize them into distinct subpopulations through channel reconfiguration, and culture each cell subpopulation for up to 3 weeks under perfusion. These reliable microscale cell cultures showed gradients of cellular behavior from C2C12 myoblasts along channel lengths, as well as differences in cell density of undifferentiated myoblasts and differentiation patterns, both programmable through different flow rates of serum-containing media. This technology will allow future microscale tissue or cell studies to be more accessible, especially for high-throughput, complex, and long-term experiments. The microfluidic actuation method described is versatile and computer programmable, yet simple, well packaged, and portable enough for personal use. PMID:15514025

Fuel supply device for supplying fuel to an engine combustor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindsay, M.H.; Kerr, W.B.

1990-05-29

This patent describes a variable flow rate fuel supply device for supplying fuel to an engine combustor. It comprises: fuel metering means having a fuel valve means for controlling the flow rate of fuel to the combustor; piston means for dividing a first cooling fluid chamber from a second cooling fluid chamber; coupling means for coupling the piston means to the fuel valve means; and cooling fluid supply means in communication with the first and second cooling fluid chamber for producing a first pressure differential across the piston means for actuating the fuel valve means in a first direction, andmore » for producing a second pressure differential across the piston means for actuating the valve means in a second direction opposite the first direction, to control the flow rate of the fuel through the fuel metering means and into the engine combustor; and means for positioning the fuel metering means within the second cooling air chamber enabling the cooling air supply means to both cool the fuel metering means and control the fuel supply rate of fuel supplied by the fuel metering means to the combustor.« less

Some Notes on Gasoline-Engine Development

NASA Technical Reports Server (NTRS)

Ricardo, H R

1927-01-01

Experiments were carried out using a special engine with small glass windows and a stroboscope to record various aspects of engine performance. Valve position, supercharging, and torque recoil were all investigated with this experimental apparatus.

Diesel engine catalytic combustor system. [aircraft engines

NASA Technical Reports Server (NTRS)

Ream, L. W. (Inventor)

1984-01-01

A low compression turbocharged diesel engine is provided in which the turbocharger can be operated independently of the engine to power auxiliary equipment. Fuel and air are burned in a catalytic combustor to drive the turbine wheel of turbine section which is initially caused to rotate by starter motor. By opening a flapper value, compressed air from the blower section is directed to catalytic combustor when it is heated and expanded, serving to drive the turbine wheel and also to heat the catalytic element. To start, engine valve is closed, combustion is terminated in catalytic combustor, and the valve is then opened to utilize air from the blower for the air driven motor. When the engine starts, the constituents in its exhaust gas react in the catalytic element and the heat generated provides additional energy for the turbine section.

The relative performance obtained with several methods of control of an overcompressed engine using gasoline

NASA Technical Reports Server (NTRS)

Gardiner, Arthur W; Whedon, William E

1928-01-01

This report presents some results obtained during an investigation to determine the relative characteristics for several methods of control of an overcompressed engine using gasoline and operating under sea-level conditions. For this work, a special single cylinder test engine, 5-inch bore by 7-inch stroke, and designed for ready adjustment of compression ratio, valve timing and valve lift while running, was used. This engine has been fully described in NACA-TR-250. Tests were made at an engine speed of 1,400 R. P. M. for compression ratios ranging from 4.0 to 7.6. The air-fuel ratios were on the rich side of the chemically correct mixture and were approximately those giving maximum power. When using plain domestic gasoline, detonation was controlled to a constant, predetermined amount (audible), such as would be permissible for continuous operation, by (a) throttling the carburetor, (b) maintaining full throttle but greatly retarding the ignition, and (c) varying the timing of the inlet valve to reduce the effective compression ratio. From the results of the tests, it may be concluded that method (b) gives the best all-round performance and, being easily employed in service, appears to be the most practicable method for controlling an overcompressed engine using gasoline at low altitudes.

High Temperature Solid Lubricant Materials for Heavy Duty and Advanced Heat Engines

NASA Technical Reports Server (NTRS)

Dellacorte, C.; Wood, J. C.

1994-01-01

Advanced engine designs incorporate higher mechanical and thermal loading to achieve efficiency improvements. This approach often leads to higher operating temperatures of critical sliding elements (e.g. piston ring/cylinder wall contacts and valve guides) which compromise the use of conventional and even advanced synthetic liquid lubricants. For these applications solid lubricants must be considered. Several novel solid lubricant composites and coatings designated PS/PM200 have been employed to dry and marginally oil lubricated contacts in advanced heat engines. These applications include cylinder kits of heavy duty diesels, and high temperature Stirling engines, sidewall seals of rotary engines, and various exhaust valve and exhaust component applications. This paper describes the tribological and thermophysical properties of these tribomaterials and reviews the results of applying them to engine applications. Other potential tribological materials and applications are also discussed with particular emphasis on heavy duty and advanced heat engines.

Pulsatile perfusion bioreactor for cardiac tissue engineering.

PubMed

Brown, Melissa A; Iyer, Rohin K; Radisic, Milica

2008-01-01

Cardiovascular disease is the number one cause of mortality in North America. Cardiac tissue engineering aims to engineer a contractile patch of physiological thickness to use in surgical repair of diseased heart tissue. We previously reported that perfusion of engineered cardiac constructs resulted in improved tissue assembly. Because heart tissues respond to mechanical stimuli in vitro and experience rhythmic mechanical forces during contraction in vivo, we hypothesized that provision of pulsatile interstitial medium flow to an engineered cardiac patch would result in enhanced tissue assembly by way of mechanical conditioning and improved mass transport. Thus, we constructed a novel perfusion bioreactor capable of providing pulsatile fluid flow at physiologically relevant shear stresses and flow rates. Pulsatile perfusion (PP) was achieved by incorporation of a normally closed solenoid pinch valve into the perfusion loop and was carried out at a frequency of 1 Hz and a flow rate of 1.50 mL/min (PP) or 0.32 mL/min (PP-LF). Nonpulsatile flow at 1.50 mL/min (NP) or 0.32 mL/min (NP-LF) served as controls. Static controls were cultivated in well plates. The main experimental groups were seeded with cells enriched for cardiomyocytes by one preplating step (64% cardiac Troponin I+, 34% prolyl-4-hydroxylase+), whereas pure cardiac fibroblasts and cells enriched for cardiomyocytes by two preplating steps (81% cardiac Troponin I+, 16% prolyl-4-hydroxylase+) served as controls. Cultivation under pulsatile flow had beneficial effects on contractile properties. Specifically, the excitation threshold was significantly lower in the PP condition (pulsatile perfusion at 1.50 mL/min) than in the Static control, and the contraction amplitude was the highest; whereas high maximum capture rate was observed for the PP-LF conditions (pulsatile perfusion at 0.32 mL/min). The enhanced hypertrophy index observed for the PP-LF group was consistent with the highest cellular length and diameter in this group. Within the same cultivation groups (Static, NP-LF, PP-LF, PP, and NP) there were no significant differences in the diameter between fibroblasts and cardiomyocytes, although cardiomyocytes were significantly more elongated than fibroblasts under PP-LF conditions. Cultivation of control cell populations resulted in noncontractile constructs when cardiac fibroblasts were used (as expected) and no overall improvement in functional properties when two steps of preplating were used to enrich for cardiomyocytes in comparison with only one step of preplating.

Heart valve bioprosthesis durability: a challenge to the new generation of porcine valves.

PubMed

Valente, M; Minarini, M; Maizza, A F; Bortolotti, U; Thiene, G

1992-01-01

Long-term experience with first generation porcine valve xenografts enabled identification of the major limitations to their durability: (1) prosthetic-ventricular mismatch due to the high profile of the stent in patients with mitral stenosis and a small left ventricle; (2) high-pressure fixation with loss of natural collagen crimping in the fibrosa, and wash-out of proteoglycans in the spongiosa; (3) xenograft tissue autolysis, due to the long interval between animal slaughter and aortic valve removal fixation; (4) muscle shelf in the right coronary cusp, which created a gradient and could undergo accelerated calcification and/or spontaneous perforation with time; (5) a flexible polypropylene stent, which could creep or even fracture with consequent inward bending of the stent; (6) progressive time-related dystrophic calcification; (7) host fibrous tissue ingrowth. An awareness of these limitations stimulated technical modifications, which frequently brought about distinct improvements: (1) the reduction of the stent profile eliminated the problem of mismatch, but resulted in a higher tendency towards cusp prolapse and earlier commissural tearing; (2) natural collagen waviness, proteoglycans and cusp extensibility were preserved by employing low or even zero pressure during the fixation process; (3) earlier valve fixation enabled preservation of cell integrity; (4) a new orifice for small valves was designed by replacing the right muscular cusp, thus achieving less gradient and avoiding muscle-shelf-related complications; (5) polypropylene was replaced by Delrin as stent material; (6) calcium-retarding agents like T6 and toluidine blue were applied during commercial processing and storage in order to mitigate tissue mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)

Three decades of the history of donation and transplantation in Uruguay.

PubMed

Alvarez, I; Bengochea, M; Mizraji, R; Toledo, R; Saldías, M C; Carretto, E; Pérez, H; Castro, A; García, C

2009-10-01

The aim of this study was to analyze the evolution of the legal framework, health system of donation, and transplantation of cells, tissues, and organs, measured based on processes and rates from 1978 to 2008 in Uruguay. We analyzed 3 decades (1978-1988/1989-1998/1999-2008) by the following evaluation: the legislation, donation and transplantation system, procurement, registration of pre-state of voluntary donations, actual donations and transplantation rates of solid organs (kidneys, heart, liver, and pancreas), and rates of donation and transplantation of tissues (corneal and laminar [skin, amniotic membrane, and fascialata]), of cardiovascular elements (valves and vases), and of ostearticular tissues (bones and tendons). Uruguay has maintained continuous governmental politics in donation and transplantation. In the last decade the elaboration of a strategic plan by promoting Laws and Decrees of Encephalic Death, Presumed Donation and Security of Cells and Tissues, as well as the creation of the Unit Procurement, the registration of nonrelated donors for hematopoietic stem cells, and the re-engineering of tissue banking, has shown a significant increase in deceased donation and cadaveric transplantation, reaching the first highest overall donor rate in Latin America with 24/pmp multiorgan donors.

11. DETAIL OF UNITEDTOD TWINTANDEM STEAM ENGINE, SHOWING HIGHPRESSURE CYLINDER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

11. DETAIL OF UNITED-TOD TWIN-TANDEM STEAM ENGINE, SHOWING HIGH-PRESSURE CYLINDER AND VALVE, AND LUBRICATING EQUIPMENT FOR ENGINE. - Republic Iron & Steel Company, Youngstown Works, Blooming Mill & Blooming Mill Engines, North of Poland Avenue, Youngstown, Mahoning County, OH

The processes in spring-loaded injection valves of solid injection oil engines

NASA Technical Reports Server (NTRS)

Lutz, O

1934-01-01

On the premise of a rectangular velocity wave arriving at the valve, the equation of motion of a spring-loaded valve stem is developed and analyzed. It is found that the stem oscillates, the oscillation frequency being consistently above the natural frequency of the nozzle stem alone, and whose amplitudes would increase in the absence of damping. The results are evaluated and verified on an example. The pressure in the valve and the spray volume are analyzed and several pertinent questions are discussed on the basis of the results.

Fluid mechanics of heart valves.

PubMed

Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S

2004-01-01

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szybist, James P; Edwards, Kevin Dean; Foster, Matthew

2013-01-01

While the potential emissions and efficiency benefits of homogeneous charge compression ignition (HCCI) combustion are well known, realizing the potentials on a production intent engine presents numerous challenges. In this study we focus on characterizing the authority of the available engine controls as the high load limit of HCCI combustion is approached. The experimental work is performed on a boosted single-cylinder research engine equipped with direct injection (DI) fueling, cooled external exhaust gas recirculation (EGR), and a hydraulic valve actuation (HVA) valve train to enable the negative valve overlap (NVO) breathing strategy. Valve lift and duration are held constant whilemore » phasing is varied in an effort to make the results as relevant as possible to production intent cam-based variable valve actuation (VVA) systems on multi-cylinder engines. Results presented include engine loads from 350 to 650 kPa IMEPnet and manifold pressure from 98 to 190 kPaa at 2000 rpm. It is found that in order to increase engine load to 650 kPa IMEPnet, it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. Both NVO duration and fuel injection timing are effective means of controlling combustion phasing, with NVO duration being a coarse control and fuel injection timing being a fine control. NOX emissions are low throughout the study, with emissions below 0.1 g/kW-h at all boosted HCCI conditions, while good combustion efficiency is maintained (>96.5%). Net indicated thermal efficiency increases with load up to 600 kPa IMEPnet, where a peak efficiency of 41% is achieved. Results of independent parametric investigations are presented on the effect of external EGR, intake effect of manifold pressure, and the effect of NVO duration. It is found that increasing EGR at a constant manifold pressure and increasing manifold pressure at a constant EGR rate both have the effect of retarding combustion phasing. It is also found that combustion phasing becomes increasingly sensitive to NVO duration as engine load increases. Finally, comparisons are made between three commonly used noise metrics (AVL noise meter, ringing intensity (RI), and maximum pressure rise rate (MPRR)). It is found that compared to the AVL noise meter, RI significantly underestimates combustion noise under boosted conditions.« less

Knowledge Gained from Practical Experience in the Designing of Aircraft Engines

NASA Technical Reports Server (NTRS)

Kurtz, Oskar

1933-01-01

The present report examines a few important points of engine design such as: in-line water cooled engines, air-cooled in-line engines, and air-cooled radial engines. Subassemblies are also discussed like cylinder types, blower driving gears, pistons, valves, bearings, and crankshafts.

The Ross operation: the autologous pulmonary valve in the aortic position.

PubMed

Gonzalez-Lavin, L; Robles, A; Graf, D

1988-03-01

Aortic valve replacement (AVR) with a pulmonary valve autograft (PVA) was first reported by Donald N. Ross (DNR) in 1967. The expectation of this procedure was to avoid degenerative changes seen in other biological tissue valves such as calcification, attenuation, and rupture of the leaflets. Recent reports by the original investigator's group have confirmed the lack of degenerative changes in PVA. To corroborate their conclusions, the fate of 12 patients undergoing AVR with PVA by one of us (LGL) has been ascertained. From March 1969 to June 1971, 12 patients underwent AVR with PVA. The right ventricular outflow tract (RVOT) was reconstructed with an aortic homograft valved conduit. The mean age was 42.7 years (range 21 to 52 years). The mean follow-up for 11 hospital survivors is 12.4 years. Three PVA have been replaced; one following infective endocarditis at 13 years, and two at 15 and 73 months due to technical malalignment. There was no evidence of PVA degeneration during histological examination of these explanted PVAs. Six patients are alive and retain the original PVA at 12 years (55%). This analysis corroborates the conclusions of the DNR report and strongly suggests an immunological mechanism in the process of calcification of other biological tissue valves. The Ross operation is advocated for AVR in young patients as valve durability is of paramount importance especially in this group.

A high-frequency servosystem for fuel control in hypersonic engines

NASA Technical Reports Server (NTRS)

Simon, Donald L.

1991-01-01

A hydrogen fuel-flow valve with an electrohydraulic servosystem is described. An analysis of the servosystem is presented along with a discussion of the limitations imposed on system performance by nonlinearities. The response of the valve to swept-frequency inputs is experimentally determined and compared with analytical results obtained from a computer model. The valve is found to perform favorably for frequencies up to 200 Hz.

Determination of YAV-8B Reaction Control System bleed flow usage

NASA Technical Reports Server (NTRS)

Borchers, Paul F.; Moralez, Ernesto, III; Merrick, Vernon K.; Stortz, Michael W.; Eames, David J. H.

1992-01-01

Using a calibrated Rolls-Royce Pegasus engine, total Reaction Control System (RCS) bleed flow rates have been measured on a YAV-8B Harrier during typical short takeoff, transition, hover and vertical landing maneuvers. Using existing aircraft instrumentation and pressure taps located in the RCS ducts, bleed flow rates at each RCS valve were also measured directly during flight and ground tests. These data were compared with the calibrated engine data and with the RCS part of a YAV-8B mathematical model used in piloted simulation at NASA Ames Research Center. Areas of disagreement were small, being confined to the estimation of closed RCS valve leakages and the modeling of the RCS butterfly valve pressure losses.

Prognostication of valvular aortic stenosis using tissue Doppler echocardiography: underappreciated importance of late diastolic mitral annular velocity.

PubMed

Poh, Kian-Keong; Chan, Mark Yan-Yee; Yang, Hong; Yong, Quek-Wei; Chan, Yiong-Huak; Ling, Lieng H

2008-05-01

Intact left atrial booster pump function helps maintain cardiac compensation in patients with aortic valve stenosis (AS). Because late diastolic mitral annular (A') velocity reflects left atrial systolic function, we hypothesized that A' velocity correlates with plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) level and clinical outcome in AS. We prospectively enrolled 53 consecutive patients (median age 74 years) with variable degrees of AS, in sinus rhythm, and left ventricular ejection fraction greater than 50%. Indices of valvular stenosis, left ventricular diastolic dysfunction, and mitral annular motion were correlated with plasma NT-proBNP and a composite clinical end point comprising cardiac death and symptom-driven aortic valve replacement. Tissue Doppler echocardiographic parameters, including early diastolic (E') velocity and A' velocity and ratio of early diastolic transmitral (E) to E' velocity (E/E') at the annular septum correlated better with NT-proBNP levels than body surface area-indexed aortic valve area. Eighteen patients had the composite end point, which was univariately predicted by body surface area-indexed aortic valve area, NT-proBNP, and all tissue Doppler echocardiographic indices. This outcome was most strongly predicted by the combination of septal A' velocity and E/E' ratio in bivariate Cox modeling. Septal annular A' velocity less than 9.6 cm/s was associated with significantly reduced event-free survival (Kaplan Meier log rank = 27.3, P < .0001) and predicted the end point with a sensitivity, specificity, and accuracy of 94%, 80%, and 85%, respectively. In patients with AS and normal ejection fraction, annular tissue Doppler echocardiographic indices may better reflect the physiologic consequences of afterload burden on the left ventricle than body surface area-indexed aortic valve area. Lower A' velocity is a predictor of cardiac death and need for valve surgery, suggesting an important role for compensatory left atrial booster pump function.

Diagnostic for two-mode variable valve activation device

DOEpatents

Fedewa, Andrew M

2014-01-07

A method is provided for diagnosing a multi-mode valve train device which selectively provides high lift and low lift to a combustion valve of an internal combustion engine having a camshaft phaser actuated by an electric motor. The method includes applying a variable electric current to the electric motor to achieve a desired camshaft phaser operational mode and commanding the multi-mode valve train device to a desired valve train device operational mode selected from a high lift mode and a low lift mode. The method also includes monitoring the variable electric current and calculating a first characteristic of the parameter. The method also includes comparing the calculated first characteristic against a predetermined value of the first characteristic measured when the multi-mode valve train device is known to be in the desired valve train device operational mode.

Measurement and reconstruction of the leaflet geometry for a pericardial artificial heart valve.

PubMed

Jiang, Hongjun; Campbell, Gord; Xi, Fengfeng

2005-03-01

This paper describes the measurement and reconstruction of the leaflet geometry for a pericardial heart valve. Tasks involved include mapping the leaflet geometries by laser digitizing and reconstructing the 3D freeform leaflet surface based on a laser scanned profile. The challenge is to design a prosthetic valve that maximizes the benefits offered to the recipient as compared to the normally operating naturally-occurring valve. This research was prompted by the fact that artificial heart valve bioprostheses do not provide long life durability comparable to the natural heart valve, together with the anticipated benefits associated with defining the valve geometries, especially the leaflet geometries for the bioprosthetic and human valves, in order to create a replicate valve fabricated from synthetic materials. Our method applies the concept of reverse engineering in order to reconstruct the freeform surface geometry. A Brown & Shape coordinate measuring machine (CMM) equipped with a HyMARC laser-digitizing system was used to measure the leaflet profiles of a Baxter Carpentier-Edwards pericardial heart valve. The computer software, Polyworks was used to pre-process the raw data obtained from the scanning, which included merging images, eliminating duplicate points, and adding interpolated points. Three methods, creating a mesh model from cloud points, creating a freeform surface from cloud points, and generating a freeform surface by B-splines are presented in this paper to reconstruct the freeform leaflet surface. The mesh model created using Polyworks can be used for rapid prototyping and visualization. To fit a freeform surface to cloud points is straightforward but the rendering of a smooth surface is usually unpredictable. A surface fitted by a group of B-splines fitted to cloud points was found to be much smoother. This method offers the possibility of manually adjusting the surface curvature, locally. However, the process is complex and requires additional manipulation. Finally, this paper presents a reverse engineered design for the pericardial heart valve which contains three identical leaflets with reconstructed geometry.

Simulation of long-term fatigue damage in bioprosthetic heart valves: effects of leaflet and stent elastic properties

PubMed Central

Martin, Caitlin

2014-01-01

One of the major failure modes of bioprosthetic heart valves (BHVs) is noncalcific structural deterioration due to fatigue of the tissue leaflets; yet, the mechanisms of fatigue are not well understood. BHV durability is primarily assessed based on visual inspection of the leaflets following accelerated wear testing. In this study, we developed a computational framework to simulate BHV leaflet fatigue, which is both efficient and quantitative, making it an attractive alternative to traditional accelerated wear testing. We utilize a phenomenological soft tissue fatigue damage model developed previously to describe the stress softening and permanent set of the glutaraldehyde-treated bovine pericardium leaflets in BHVs subjected to cyclic loading. A parametric study was conducted to determine the effects of altered leaflet and stent elastic properties on the fatigue of the leaflets. The simulation results show that heterogeneity of the leaflet elastic properties, poor leaflet coaptation, and little stent-tip deflection may accelerate leaflet fatigue, which agrees with clinical findings. Therefore, the developed framework may be an invaluable tool for evaluating leaflet durability in new tissue valve designs, including traditional BHVs as well as new transcatheter valves. PMID:24092257

Polymeric trileaflet prosthetic heart valves: evolution and path to clinical reality

PubMed Central

Claiborne, Thomas E; Slepian, Marvin J; Hossainy, Syed; Bluestein, Danny

2013-01-01

Present prosthetic heart valves, while hemodynamically effective, remain limited by progressive structural deterioration of tissue valves or the burden of chronic anticoagulation for mechanical valves. An idealized valve prosthesis would eliminate these limitations. Polymeric heart valves (PHVs), fabricated from advanced polymeric materials, offer the potential of durability and hemocompatibility. Unfortunately, the clinical realization of PHVs to date has been hampered by findings of in vivo calcification, degradation and thrombosis. Here, the authors review the evolution of PHVs, evaluate the state of the art of this technology and propose a pathway towards clinical reality. In particular, the authors discuss the development of a novel aortic PHV that may be deployed via transcatheter implantation, as well as its optimization via device thrombogenicity emulation. PMID:23249154

Prosthetic aortic valve endocarditis complicated with annular abscess, sub-aortic obstruction and valve dehiscence.

PubMed

Hassoulas, Joannis; Patrianakos, Alexandros P; Parthenakis, Fragiskos I; Vardas, Panos E

2009-01-01

We present a 76-year-old woman with infective endocarditis of a prosthetic aortic valve. The course of her illness started with an ischaemic stroke and she was admitted with prolonged fever and an episode of loss of consciousness. Echocardiography revealed acute aortic regurgitation and dehiscence of the prosthetic valve with excessive "rocking motion", aortic abscesses and left ventricular outflow obstruction caused by a semilunar shelf of tissue probably due to endocarditis vegetations. She underwent an urgent surgical procedure that confirmed the echocardiographic findings. Our case report reinforces the value of early diagnosis in the presence of a high clinical suspicion of prosthetic valve endocarditis. An extended workup, including transoesophageal echocardiography, in such a patient with a mechanical valve is mandatory.

WOOV (Water On/Off Valve) 3

NASA Image and Video Library

2011-10-14

ISS029-E-027343 (14 Oct. 2011) --- In the International Space Station’s Columbus laboratory, Japan Aerospace Exploration Agency astronaut Satoshi Furukawa, Expedition 29 flight engineer, works on Water On/Off Valves (WOOV), performing inspection, cleaning, disinfection and encapsulation on WOOV 3, 4 and 5.

WOOV (Water On/Off Valve) 3

NASA Image and Video Library

2011-10-14

ISS029-E-027341 (14 Oct. 2011) --- In the International Space Station’s Columbus laboratory, Japan Aerospace Exploration Agency astronaut Satoshi Furukawa, Expedition 29 flight engineer, works on Water On/Off Valves (WOOV), performing inspection, cleaning, disinfection and encapsulation on WOOV 3, 4 and 5.

Reed Valve Regulates Welding Back-Purge Pressure

NASA Technical Reports Server (NTRS)

Coby, J. Ben, Jr.; Weeks, Jack L.

1991-01-01

Simple modification yields welds of better quality. Reed valve halves fluctuations in pressure in back-purge chamber attached to workpiece undergoing keyhole plasma arc welding. Identical to one used in fuel system of two-cycle gasoline engine. Backbead smoother, and weld penetrates more uniformly.

46 CFR 162.017-2 - Type.

Code of Federal Regulations, 2013 CFR

2013-10-01

... APPROVAL ENGINEERING EQUIPMENT General Provisions; Valves, Pressure-Vacuum Relief, for Tank Vessels § 162.017-2 Type. This specification covers the design and construction of pressure-vacuum relief valves intended for use in venting systems on all tank vessels transporting inflammable or combustible liquids...

46 CFR 162.017-2 - Type.

Code of Federal Regulations, 2014 CFR

2014-10-01

... APPROVAL ENGINEERING EQUIPMENT General Provisions; Valves, Pressure-Vacuum Relief, for Tank Vessels § 162.017-2 Type. This specification covers the design and construction of pressure-vacuum relief valves intended for use in venting systems on all tank vessels transporting inflammable or combustible liquids...

46 CFR 162.017-2 - Type.

Code of Federal Regulations, 2012 CFR

2012-10-01

... APPROVAL ENGINEERING EQUIPMENT General Provisions; Valves, Pressure-Vacuum Relief, for Tank Vessels § 162.017-2 Type. This specification covers the design and construction of pressure-vacuum relief valves intended for use in venting systems on all tank vessels transporting inflammable or combustible liquids...

High speed exhaust gas recirculation valve

DOEpatents

Fensom, Rod; Kidder, David J.

2005-01-18

In order to minimize pollutants such as Nox, internal combustion engines typically include an exhaust gas recirculation (EGR) valve that can be used to redirect a portion of exhaust gases to an intake conduit, such as an intake manifold, so that the redirected exhaust gases will be recycled. It is desirable to have an EGR valve with fast-acting capabilities, and it is also desirable to have the EGR valve take up as little space as possible. An exhaust gas recirculation valve is provided that includes an exhaust passage tube, a valve element pivotally mounted within the exhaust passage tube, a linear actuator; and a gear train. The gear train includes a rack gear operatively connected to the linear actuator, and at least one rotatable gear meshing with the rack gear and operatively connected to the valve element to cause rotation of the valve element upon actuation of the linear actuator. The apparatus provides a highly compact package having a high-speed valve actuation capability.

Automated Decellularization of Intact, Human-Sized Lungs for Tissue Engineering

PubMed Central

Price, Andrew P.; Godin, Lindsay M.; Domek, Alex; Cotter, Trevor; D'Cunha, Jonathan; Taylor, Doris A.

2015-01-01

We developed an automated system that can be used to decellularize whole human-sized organs and have shown lung as an example. Lungs from 20 to 30 kg pigs were excised en bloc with the trachea and decellularized with our established protocol of deionized water, detergents, sodium chloride, and porcine pancreatic DNase. A software program was written to control a valve manifold assembly that we built for selection and timing of decellularization fluid perfusion through the airway and the vasculature. This system was interfaced with a prototypic bioreactor chamber that was connected to another program, from a commercial source, which controlled the volume and flow pressure of fluids. Lung matrix that was decellularized by the automated method was compared to a manual method previously used by us and others. Automation resulted in more consistent acellular matrix preparations as demonstrated by measuring levels of DNA, hydroxyproline (collagen), elastin, laminin, and glycosaminoglycans. It also proved highly beneficial in saving time as the decellularization procedure was reduced from days down to just 24 h. Developing a rapid, controllable, automated system for production of reproducible matrices in a closed system is a major step forward in whole-organ tissue engineering. PMID:24826875

Minimally invasive mitral valve repair in osteogenesis imperfecta.

PubMed

Tagliasacchi, Isabella; Martinelli, Luigi; Bardaro, Leopoldo; Chierchia, Sergio

2017-10-01

Osteogenesis imperfecta is a disorder of the connective tissue that affects several structures including heart valves. However, cardiac surgery is associated with high mortality and morbidity rates. In a 48-year-old man with osteogenesis imperfecta and mitral valve prolapse, we performed the first successful mitral valve repair by right anterior mini-thoracotomy. At the 1-year follow-up, he was asymptomatic and echocardiography confirmed the initial success. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

A hybrid disturbance rejection control solution for variable valve timing system of gasoline engines.

PubMed

Xie, Hui; Song, Kang; He, Yu

2014-07-01

A novel solution for electro-hydraulic variable valve timing (VVT) system of gasoline engines is proposed, based on the concept of active disturbance rejection control (ADRC). Disturbances, such as oil pressure and engine speed variations, are all estimated and mitigated in real-time. A feed-forward controller was added to enhance the performance of the system based on a simple and static first principle model, forming a hybrid disturbance rejection control (HDRC) strategy. HDRC was validated by experimentation and compared with an existing manually tuned proportional-integral (PI) controller. The results show that HDRC provided a faster response and better tolerance of engine speed and oil pressure variations. © 2013 ISA Published by ISA All rights reserved.

46 CFR 90.20-1 - Marine engineering details.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Marine engineering details. 90.20-1 Section 90.20-1... PROVISIONS General Marine Engineering Requirements § 90.20-1 Marine engineering details. (a) All marine engineering details such as piping, valves, fittings, boilers, pressure vessels, etc., and their appurtenances...

46 CFR 90.20-1 - Marine engineering details.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Marine engineering details. 90.20-1 Section 90.20-1... PROVISIONS General Marine Engineering Requirements § 90.20-1 Marine engineering details. (a) All marine engineering details such as piping, valves, fittings, boilers, pressure vessels, etc., and their appurtenances...

46 CFR 90.20-1 - Marine engineering details.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Marine engineering details. 90.20-1 Section 90.20-1... PROVISIONS General Marine Engineering Requirements § 90.20-1 Marine engineering details. (a) All marine engineering details such as piping, valves, fittings, boilers, pressure vessels, etc., and their appurtenances...

46 CFR 90.20-1 - Marine engineering details.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Marine engineering details. 90.20-1 Section 90.20-1... PROVISIONS General Marine Engineering Requirements § 90.20-1 Marine engineering details. (a) All marine engineering details such as piping, valves, fittings, boilers, pressure vessels, etc., and their appurtenances...

46 CFR 90.20-1 - Marine engineering details.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Marine engineering details. 90.20-1 Section 90.20-1... PROVISIONS General Marine Engineering Requirements § 90.20-1 Marine engineering details. (a) All marine engineering details such as piping, valves, fittings, boilers, pressure vessels, etc., and their appurtenances...

On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

PubMed Central

Lee, Chung-Hao; Zhang, Will; Liao, Jun; Carruthers, Christopher A.; Sacks, Jacob I.; Sacks, Michael S.

2015-01-01

In this study, we evaluated the hypothesis that the constituent fibers follow an affine deformation kinematic model for planar collagenous tissues. Results from two experimental datasets were utilized, taken at two scales (nanometer and micrometer), using mitral valve anterior leaflet (MVAL) tissues as the representative tissue. We simulated MVAL collagen fiber network as an ensemble of undulated fibers under a generalized two-dimensional deformation state, by representing the collagen fibrils based on a planar sinusoidally shaped geometric model. The proposed approach accounted for collagen fibril amplitude, crimp period, and rotation with applied macroscopic tissue-level deformation. When compared to the small angle x-ray scattering measurements, the model fit the data well, with an r2 = 0.976. This important finding suggests that, at the homogenized tissue-level scale of ∼1 mm, the collagen fiber network in the MVAL deforms according to an affine kinematics model. Moreover, with respect to understanding its function, affine kinematics suggests that the constituent fibers are largely noninteracting and deform in accordance with the bulk tissue. It also suggests that the collagen fibrils are tightly bounded and deform as a single fiber-level unit. This greatly simplifies the modeling efforts at the tissue and organ levels, because affine kinematics allows a straightforward connection between the macroscopic and local fiber strains. It also suggests that the collagen and elastin fiber networks act independently of each other, with the collagen and elastin forming long fiber networks that allow for free rotations. Such freedom of rotation can greatly facilitate the observed high degree of mechanical anisotropy in the MVAL and other heart valves, which is essential to heart valve function. These apparently novel findings support modeling efforts directed toward improving our fundamental understanding of tissue biomechanics in healthy and diseased conditions. PMID:25902446

Variable cooling circuit for thermoelectric generator and engine and method of control

DOEpatents

Prior, Gregory P

2012-10-30

An apparatus is provided that includes an engine, an exhaust system, and a thermoelectric generator (TEG) operatively connected to the exhaust system and configured to allow exhaust gas flow therethrough. A first radiator is operatively connected to the engine. An openable and closable engine valve is configured to open to permit coolant to circulate through the engine and the first radiator when coolant temperature is greater than a predetermined minimum coolant temperature. A first and a second valve are controllable to route cooling fluid from the TEG to the engine through coolant passages under a first set of operating conditions to establish a first cooling circuit, and from the TEG to a second radiator through at least some other coolant passages under a second set of operating conditions to establish a second cooling circuit. A method of controlling a cooling circuit is also provided.

CorMatrix valved conduit in a porcine model: long-term remodelling and biomechanical characterization.

PubMed

Mosala Nezhad, Zahra; Poncelet, Alain; de Kerchove, Laurent; Fervaille, Caroline; Banse, Xavier; Bollen, Xavier; Dehoux, Jean-Paul; El Khoury, Gebrine; Gianello, Pierre

2017-01-01

Porcine small intestinal submucosa extracellular matrix (CorMatrix; CorMatrix Cardiovascular, Rosewell, GA) is a relatively novel tissue substitute used in cardiovascular applications. We investigated the biological reaction and remodelling of CorMatrix as a tri-leaflet valved conduit in a pig model. We hypothesized that CorMatrix maintains a durable architecture as a valved conduit and remodels to resemble surrounding tissues. We fashioned the valved conduit using a 7 × 10 cm 4-ply CorMatrix sheet and placed it in the thoracic aorta of seven landrace pigs for 3, 4, 5 and 6 months. Biodegradation, replacement by native tissue, strength and durability were examined by histology, immunohistochemistry and mechanical testing. Four pigs, one per time frame, completed the study. The conduit lost its original architecture as a tri-leaflet valve due to cusp immobility, subsequent attachment to the wall segment and consequent maintenance of a thick arterial wall-like structure. Scaffold resorption was incomplete, with disorganized inconsistent spatial and temporal degradation even at 6 months. Fibrosis, scarring and calcification started at 4 months and chronic inflammation persisted. The partially remodelled scaffold did not resemble the aortic wall, suggesting impaired remodelling. Mechanical testing showed progressive weakening of the tissues over time, which were liable to breakage. CorMatrix is biodegradable; however, it failed to remodel in a structured and anatomical fashion in an arterial environment. Progressive mechanical and remodelling failure in this scenario might be explained by the complexity of the conduit design and the host's chronic inflammatory response, leading to early fibrosis and calcification. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Biodegradable materials for surgical management of infective endocarditis: new solution or a dead end street?

PubMed

Myers, Patrick O; Cikirikcioglu, Mustafa; Kalangos, Afksendiyos

2014-08-03

One third of patients with infective endocarditis will require operative intervention. Given the superiority of valve repair over valve replacement in many indications other than endocarditis, there has been increasing interest and an increasing number of reports of excellent results of valve repair in acute infective endocarditis. The theoretically ideal material for valve repair in this setting is non-permanent, "vanishing" material, not at risk of seeding or colonization. The goal of this contribution is to review currently available data on biodegradable materials for valve repair in infective endocarditis. Rigorous electronic and manual literature searches were conducted to identify reports of biodegradable materials for valve repair in infective endocarditis. Articles were identified in electronic database searches of Medline, Embase and the Cochrane Library, using a predetermined search strategy. 49 manuscripts were included in the review. Prosthetic materials needed for valve repair can be summarized into annuloplasty rings to remodel the mitral or tricuspid annulus, and patch materials to replace resected valvar tissue. The commercially available biodegradable annuloplasty ring has shown interesting clinical results in a single-center experience; however further data is required for validation and longer follow-up. Unmodified extra-cellular matrix patches, such as small intestinal submucosa, have had promising initial experimental and clinical results in non-infected valve repair, although in valve repair for endocarditis has been reported in only one patient, and concerns have been raised regarding their mechanical stability in an infected field. These evolving biodegradable devices offer the potential for valve repair with degradable materials replaced with autologous tissue, which could further improve the results of valve repair for infective endocarditis. This is an evolving field with promising experimental or initial clinical results, however long-term outcomes are lacking and further data is necessary to validate this theoretically interesting approach to infective endocarditis.

Biodegradable materials for surgical management of infective endocarditis: new solution or a dead end street?

PubMed Central

2014-01-01

Background One third of patients with infective endocarditis will require operative intervention. Given the superiority of valve repair over valve replacement in many indications other than endocarditis, there has been increasing interest and an increasing number of reports of excellent results of valve repair in acute infective endocarditis. The theoretically ideal material for valve repair in this setting is non-permanent, “vanishing” material, not at risk of seeding or colonization. The goal of this contribution is to review currently available data on biodegradable materials for valve repair in infective endocarditis. Discussion Rigorous electronic and manual literature searches were conducted to identify reports of biodegradable materials for valve repair in infective endocarditis. Articles were identified in electronic database searches of Medline, Embase and the Cochrane Library, using a predetermined search strategy. 49 manuscripts were included in the review. Prosthetic materials needed for valve repair can be summarized into annuloplasty rings to remodel the mitral or tricuspid annulus, and patch materials to replace resected valvar tissue. The commercially available biodegradable annuloplasty ring has shown interesting clinical results in a single-center experience; however further data is required for validation and longer follow-up. Unmodified extra-cellular matrix patches, such as small intestinal submucosa, have had promising initial experimental and clinical results in non-infected valve repair, although in valve repair for endocarditis has been reported in only one patient, and concerns have been raised regarding their mechanical stability in an infected field. Summary These evolving biodegradable devices offer the potential for valve repair with degradable materials replaced with autologous tissue, which could further improve the results of valve repair for infective endocarditis. This is an evolving field with promising experimental or initial clinical results, however long-term outcomes are lacking and further data is necessary to validate this theoretically interesting approach to infective endocarditis. PMID:25087015

Mechanism of valvular regurgitation.

PubMed

Khoo, Nee S; Smallhorn, Jeffery F

2011-10-01

Despite improvements in surgical techniques, valvular regurgitation results in major morbidity in children with heart disease. Functional anatomy, mechanisms of valve closure and adaptation to changing hemodynamic stress in normal mitral and tricuspid valves are complex and only partially understood. As well, pathology of atrioventricular valve regurgitation is further complicated by congenital valve abnormalities involving leaflet tissue, supporting chordal apparatus and displaced papillary muscles. This review provides a current understanding of the mechanisms that result in atrioventricular valve failure. Mitral valve leaflets have contractile elements, in addition to atrial muscle modulation of leaflet tension. When placed under mechanical tethering stress, the mitral valve adapts by leaflet expansion, which increases coaptation surface reserve and chordal thickening. Both pediatric and adult studies are increasingly reporting on the importance of subvalvar apparatus function in maintaining valve competency. The maintenance of efficient valve function is accomplished by a complex series of events involving atrial and annular contraction, annular deformation, active leaflet tension, chordal transmission of papillary muscle contractions and ventricular contraction.

41. #1 ARRESTING GEAR ENGINE AFT LOOKING FORWARD PORT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

41. #1 ARRESTING GEAR ENGINE - AFT LOOKING FORWARD PORT TO STARBOARD SHOWING ARRESTING GEAR ENGINE ACCUMULATOR, AIR FLASK, CONTROL VALVE, WITH CONTROL RAM, SHEAVES AND WIRES UNDERNEATH ENGINE STAND. - U.S.S. HORNET, Puget Sound Naval Shipyard, Sinclair Inlet, Bremerton, Kitsap County, WA

A mathematical model for the determination of forming tissue moduli in needled-nonwoven scaffolds.

PubMed

Soares, João S; Zhang, Will; Sacks, Michael S

2017-03-15

Formation of engineering tissues (ET) remains an important scientific area of investigation for both clinical translational and mechanobiological studies. Needled-nonwoven (NNW) scaffolds represent one of the most ubiquitous biomaterials based on their well-documented capacity to sustain tissue formation and the unique property of substantial construct stiffness amplification, the latter allowing for very sensitive determination of forming tissue modulus. Yet, their use in more fundamental studies is hampered by the lack of: (1) substantial understanding of the mechanics of the NNW scaffold itself under finite deformations and means to model the complex mechanical interactions between scaffold fibers, cells, and de novo tissue; and (2) rational models with reliable predictive capabilities describing their evolving mechanical properties and their response to mechanical stimulation. Our objective is to quantify the mechanical properties of the forming ET phase in constructs that utilize NNW scaffolds. We present herein a novel mathematical model to quantify their stiffness based on explicit considerations of the modulation of NNW scaffold fiber-fiber interactions and effective fiber stiffness by surrounding de novo ECM. Specifically, fibers in NNW scaffolds are effectively stiffer than if acting alone due to extensive fiber-fiber cross-over points that impart changes in fiber geometry, particularly crimp wavelength and amplitude. Fiber-fiber interactions in NNW scaffolds also play significant role in the bulk anisotropy of the material, mainly due to fiber buckling and large translational out-of-plane displacements occurring to fibers undergoing contraction. To calibrate the model parameters, we mechanically tested impregnated NNW scaffolds with polyacrylamide (PAM) gels with a wide range of moduli with values chosen to mimic the effects of surrounding tissues on the scaffold fiber network. Results indicated a high degree of model fidelity over a wide range of planar strains. Lastly, we illustrated the impact of our modeling approach quantifying the stiffness of engineered ECM after in vitro incubation and early stages of in vivo implantation obtained in a concurrent study of engineered tissue pulmonary valves in an ovine model. Regenerative medicine has the potential to fully restore diseased tissues or entire organs with engineered tissues. Needled-nonwoven scaffolds can be employed to serve as the support for their growth. However, there is a lack of understanding of the mechanics of these materials and their interactions with the forming tissues. We developed a mathematical model for these scaffold-tissue composites to quantify the mechanical properties of the forming tissues. Firstly, these measurements are pivotal to achieve functional requirements for tissue engineering implants; however, the theoretical development yielded critical insight into particular mechanisms and behaviors of these scaffolds that were not possible to conjecture without the insight given by modeling, let alone describe or foresee a priori. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

WOOV (Water On/Off Valve) 3 before encapsulation

NASA Image and Video Library

2011-10-14

ISS029-E-027334 (14 Oct. 2011) --- In the International Space Station’s Columbus laboratory, Japan Aerospace Exploration Agency astronaut Satoshi Furukawa, Expedition 29 flight engineer, works on Water On/Off Valves (WOOV), performing inspection, cleaning, disinfection and encapsulation on WOOV 3, 4 and 5.

46 CFR 56.50-20 - Pressure relief piping.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... authorized by the Marine Safety Center. (b) Discharge lines (reproduces 122.6.2(d)). Discharge lines from pressure-relieving safety devices shall be designed to facilitate drainage. (c) Stop valves. Stop valves...

46 CFR 56.50-20 - Pressure relief piping.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... authorized by the Marine Safety Center. (b) Discharge lines (reproduces 122.6.2(d)). Discharge lines from pressure-relieving safety devices shall be designed to facilitate drainage. (c) Stop valves. Stop valves...

Engineering Design Handbook. Military Vehicle

DTIC Science & Technology

1998-05-01

C0NNECTIN6 NOD HEARINGS. CAMSHAFT BEARINGS. AND VALVE THAIH PRESSURE REGULATOR VALVE SB PSI sc OIL PAH SCAVENGE PUMP INLET SCREEN Figure 1-6...to 40 percent, hogbacks, ditches, racks, embankments, random log obstacles, brush, tree stumps, dust, and mud. Most vehicles have requirements for

Spin valves with spin-engineered domain-biasing scheme

NASA Astrophysics Data System (ADS)

Lu, Z. Q.; Pan, G.

2003-06-01

Synthetic spin-filter spin valves with spin-engineered biasing scheme "sub/Ta/NiFe/IrMn/NiFe/NOL/Cu1/CoFe/Cu2/CoFe/Ru/CoFe/IrMn/Ta" were developed. In the structure, the orthogonal magnetic configuration for biasing and pinning field was obtained by one-step magnetic annealing process by means of spin flop, which eliminated the need for two antiferromagnetic materials with distinctively different blocking temperatures and two-step magnetic annealing as in conventional exchange biasing scheme. The longitudinal domain biasing of spin valves was achieved by using interlayer coupling field through Cu1 spacer. By adjusting the thickness of the Cu1 layer, the interlayer coupling biasing field can provide domain stabilization and was sufficiently strong to constrain the magnetization in coherent rotation. This can prevent Barkhausen noises associated with magnetization reversal. We report here a proof of concept study of such a domain-biasing scheme, which has its important technological applications in nanoscale spin valve and magnetic tunneling junction read heads and other spintronic devices.

Acoustic Detection of Faults and Degradation in a High-Bypass Turbofan Engine during VIPR Phase III Testing

NASA Technical Reports Server (NTRS)

Boyle, Devin K.

2017-01-01

The Vehicle Integrated Propulsion Research (VIPR) Phase III project was executed at Edwards Air Force Base, California, by the National Aeronautics and Space Administration and several industry, academic, and government partners in the summer of 2015. One of the research objectives was to use external radial acoustic microphone arrays to detect changes in the noise characteristics produced by the research engine during volcanic ash ingestion and seeded fault insertion scenarios involving bleed air valves. Preliminary results indicate the successful acoustic detection of suspected degradation as a result of cumulative exposure to volcanic ash. This detection is shown through progressive changes, particularly in the high-frequency content, as a function of exposure to greater cumulative quantities of ash. Additionally, detection of the simulated failure of the 14th stage stability bleed valve and, to a lesser extent, the station 2.5 stability bleed valve, to their fully-open fail-safe positions was achieved by means of spectral comparisons between nominal (normal valve operation) and seeded fault scenarios.

[Status of aortic valve reconstruction and Ross operation in aortic valve diseases].

PubMed

Sievers, Hans H

2002-08-01

At first glance the aortic valve is a relative simple valve mechanism connecting the left ventricle and the ascending aorta. Detailed analysis of the different components of the aortic valve including the leaflets and sinuses revealed a complex motion of each part leading to a perfect durable valve mechanism at rest and during exercise. Theoretically, the reconstruction or imitation of these structures in patients with aortic valve disease should lead to optimal results. Prerequisite is the exact knowledge of the important functional characteristics of the aortic valve. The dynamic behavior of the aortic root closely harmonizing with the leaflets not only warrants stress minimizing and valve durability, but also optimizes coronary flow, left ventricular function and aortic impedance. The newly discovered contractile capacity of the leaflets and the root components are important for tuning the dynamics. Isolated reconstruction of the aortic valve such as decalcification, commissurotomy, plication of ring or leaflets of a tricuspid aortic valve and cusp extension are seldom indicated in contrast to the reconstruction of the bicuspid insufficient valve. Proper indication and skilled techniques lead to excellent hemodynamic and clinical intermediate-term result up to 7 years after reconstruction. Latest follow-up revealed a mean aortic insufficiency of 0.7, maximal pressure gradient of 11.4 +/- 8.5 mm Hg with zero hospital or late mortality, reoperation or thromboembolic events in 22 patients. The reconstructive techniques for aortic root aneurysm and/or type A dissection according to David or Yacoub have become routine procedures in the last 10 years. The hemodynamic and clinical results are excellent with low reoperation rate and very low risk of thromboembolism. Generally, a maximal diameter of the root of 5 cm is indicative for performing the operation. In patients with Marfan's syndrome the reconstruction should be advanced even with smaller diameters especially if these are progressive and combined with aortic insufficiency. ROSS-OPERATION: The Ross-Operation includes the replacement of the diseased aortic valve with the pulmonary autograft and reconstruction of the right ventricular outflow tract using a homograft. The hemodynamic results are excellent regarding the autograft and also the clinical results with very low thromboembolic risk and acceptable reoperation rate. This method is especially indicated for active young patients, women, who desire children, athletes and patients in general, who like to avoid long-term anticoagulation. In some cases the homograft may develop a dysfunction predominantly a pulmonary stenosis requiring reoperation. In the author's series of 245 Ross-operations in 12 years the homograft had to be replaced in 4 cases without letality. Innovative, decellularized homografts with the potential to repopulate with autologeous cells show promising results after 1 year of clinical implantation without signs of antibody development. Probably these tissue-engineered modification may improve the homograft results. The reconstructive techniques of the aortic valve and the Ross-operation have a certain risk of reoperation that must be weighed against the advantages of very low hospital and late valve related death, excellent hemodynamics, very low risk of macro- and microembolism as well as bleeding, lack of long-term anticoagulation and unrestricted life-style.

Materials-Enabled High-Efficiency (MEHE) Heavy-Duty Diesel Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kass, M.; Veliz, M.

2011-09-30

The purpose of this Cooperative Research and Development Agreement (CRADA) between UTBattelle, Inc. and Caterpillar, Inc. was to improve diesel engine efficiency by incorporating advanced materials to enable higher combustion pressures and temperatures necessary for improved combustion. The project scope also included novel materials for use in advanced components and designs associated with waste-heat recovery and other concepts for improved thermal efficiency. Caterpillar initially provided ORNL with a 2004 Tier 2 C15 ACERT diesel engine (designed for on-highway use) and two 600 hp motoring dynamometers. The first year of the CRADA effort was focused on establishing a heavy-duty experimental enginemore » research cell. First year activities included procuring, installing and commissioning the cell infrastructure. Infrastructure components consisted of intake air handling system, water tower, exhaust handling system, and cell air conditioning. Other necessary infrastructure items included the fuel delivery system and bottled gas handling to support the analytical instrumentation. The second year of the CRADA focused on commissioning the dynamometer system to enable engine experimentation. In addition to the requirements associated with the dynamometer controller, the electrical system needed a power factor correction system to maintain continuity with the electrical grid. During the second year the engine was instrumented and baseline operated to confirm performance and commission the dynamometer. The engine performance was mapped and modeled according to requirements provided by Caterpillar. This activity was further supported by a Work-for-Others project from Caterpillar to evaluate a proprietary modeling system. A second Work-for-Others activity was performed to evaluate a novel turbocharger design. This project was highly successful and may lead to new turbocharger designs for Caterpillar heavy-duty diesel engines. During the third (and final) year of the CRADA, a novel valve material was evaluated to assess high temperature performance and durability. A series of prototype valves, composed of a unique nickel-alloy was placed in the engine head. The engine was aggressively operated using a transient test cycle for 200 hours. The valve recession was periodically measured to determine valve performance. Upon completion of the test the valves were removed and returned to Caterpillar for additional assessment. Industrial in-kind support was available throughout the project period. Review of the status and research results were carried out on a regular basis (meetings and telecons) which included direction for future work activities. A significant portion of the industrial support was in the form of information exchange and technical consultation.« less

Research on digital system design of nuclear power valve

NASA Astrophysics Data System (ADS)

Zhang, Xiaolong; Li, Yuan; Wang, Tao; Dai, Ye

2018-04-01

With the progress of China's nuclear power industry, nuclear power plant valve products is in a period of rapid development, high performance, low cost, short cycle of design requirements for nuclear power valve is proposed, so there is an urgent need for advanced digital design method and integrated design platform to provide technical support. Especially in the background of the nuclear power plant leakage in Japan, it is more practical to improve the design capability and product performance of the nuclear power valve. The finite element numerical analysis is a common and effective method for the development of nuclear power valves. Nuclear power valve has high safety, complexity of valve chamber and nonlinearity of seal joint surface. Therefore, it is urgent to establish accurate prediction models for earthquake prediction and seal failure to meet engineering accuracy and calculation conditions. In this paper, a general method of finite element modeling for nuclear power valve assembly and key components is presented, aiming at revealing the characteristics and rules of finite element modeling of nuclear power valves, and putting forward aprecision control strategy for finite element models for nuclear power valve characteristics analysis.

The Influence of Directed Air Flow on Combustion in Spark-Ignition Engine

NASA Technical Reports Server (NTRS)

Rothrock, A M; Spencer, R C

1939-01-01

The air movement within the cylinder of the NACA combustion apparatus was regulated by using shrouded inlet valves and by fairing the inlet passage. Rates of combustion were determined at different inlet-air velocities with the engine speed maintained constant and at different engine speeds with the inlet-air velocity maintained approximately constant. The rate of combustion increased when the engine speed was doubled without changing the inlet-air velocity; the observed increase was about the same as the increase in the rate of combustion obtained by doubling the inlet-air velocity without changing the engine speed. Certain types of directed air movement gave great improvement in the reproducibility of the explosions from cycle to cycle, provided that other variables were controlled. Directing the inlet air past the injection valve during injection increased the rate of burning.

Bioprosthetic Valve Fracture to Facilitate Transcatheter Valve-in-Valve Implantation.

PubMed

Allen, Keith B; Chhatriwalla, Adnan K; Cohen, David J; Saxon, John T; Aggarwal, Sanjeev; Hart, Anthony; Baron, Suzanne; Davis, J Russell; Pak, Alex F; Dvir, Danny; Borkon, A Michael

2017-11-01

Valve-in-valve transcatheter aortic valve replacement is less effective in small surgical bioprostheses. We evaluated the feasibility of bioprosthetic valve fracture with a high-pressure balloon to facilitate valve-in-valve transcatheter aortic valve replacement. In vitro bench testing on aortic tissue valves was performed on 19-mm and 21-mm Mitroflow (Sorin, Milan, Italy), Magna and Magna Ease (Edwards Lifesciences, Irvine, CA), Trifecta and Biocor Epic (St. Jude Medical, Minneapolis, MN), and Hancock II and Mosaic (Medtronic, Minneapolis, MN). High-pressure balloons Tru Dilation, Atlas Gold, and Dorado (C.R. Bard, Murray Hill, NJ) were used to determine which valves could be fractured and at what pressure fracture occurred. Mitroflow, Magna, Magna Ease, Mosaic, and Biocor Epic surgical valves were successfully fractured using high-pressures balloon 1 mm larger than the labeled valve size whereas Trifecta and Hancock II surgical valves could not be fractured. Only the internal valve frame was fractured, and the sewing cuff was never disrupted. Manufacturer's rated burst pressures for balloons were exceeded, with fracture pressures ranging from 8 to 24 atmospheres depending on the surgical valve. Testing further demonstrated that fracture facilitated the expansion of previously constrained, underexpanded transcatheter valves (both balloon and self-expanding) to the manufacturer's recommended size. Bench testing demonstrates that the frame of most, but not all, bioprosthetic surgical aortic valves can be fractured using high-pressure balloons. The safety of bioprosthetic valve fracture to optimize valve-in-valve transcatheter aortic valve replacement in small surgical valves requires further clinical investigation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Transgenic zebrafish reveal tissue-specific differences in estrogen signaling in response to environmental water samples.

PubMed

Gorelick, Daniel A; Iwanowicz, Luke R; Hung, Alice L; Blazer, Vicki S; Halpern, Marnie E

2014-04-01

Environmental endocrine disruptors (EEDs) are exogenous chemicals that mimic endogenous hormones such as estrogens. Previous studies using a zebrafish transgenic reporter demonstrated that the EEDs bisphenol A and genistein preferentially activate estrogen receptors (ERs) in the larval heart compared with the liver. However, it was not known whether the transgenic zebrafish reporter was sensitive enough to detect estrogens from environmental samples, whether environmental estrogens would exhibit tissue-specific effects similar to those of BPA and genistein, or why some compounds preferentially target receptors in the heart. We tested surface water samples using a transgenic zebrafish reporter with tandem estrogen response elements driving green fluorescent protein expression (5xERE:GFP). Reporter activation was colocalized with tissue-specific expression of ER genes by RNA in situ hybridization. We observed selective patterns of ER activation in transgenic fish exposed to river water samples from the Mid-Atlantic United States, with several samples preferentially activating receptors in embryonic and larval heart valves. We discovered that tissue specificity in ER activation was due to differences in the expression of ER subtypes. ERα was expressed in developing heart valves but not in the liver, whereas ERβ2 had the opposite profile. Accordingly, subtype-specific ER agonists activated the reporter in either the heart valves or the liver. The use of 5xERE:GFP transgenic zebrafish revealed an unexpected tissue-specific difference in the response to environmentally relevant estrogenic compounds. Exposure to estrogenic EEDs in utero was associated with adverse health effects, with the potentially unanticipated consequence of targeting developing heart valves.

Transgenic zebrafish reveal tissue-specific differences in estrogen signaling in response to environmental water samples

USGS Publications Warehouse

Gorelick, Daniel A.; Iwanowicz, Luke R.; Hung, Alice L.; Blazer, Vicki; Halpern, Marnie E.

2014-01-01

Background: Environmental endocrine disruptors (EED) are exogenous chemicals that mimic endogenous hormones, such as estrogens. Previous studies using a zebrafish transgenic reporter demonstrated that the EEDs bisphenol A and genistein preferentially activate estrogen receptors (ER) in the larval heart compared to the liver. However, it was not known whether the transgenic zebrafish reporter was sensitive enough to detect estrogens from environmental samples, whether environmental estrogens would exhibit similar tissue-specific effects as BPA and genistein or why some compounds preferentially target receptors in the heart. Methods: We tested surface water samples using a transgenic zebrafish reporter with tandem estrogen response elements driving green fluorescent protein expression (5xERE:GFP). Reporter activation was colocalized with tissue-specific expression of estrogen receptor genes by RNA in situ hybridization. Results: Selective patterns of ER activation were observed in transgenic fish exposed to river water samples from the Mid-Atlantic United States, with several samples preferentially activating receptors in embryonic and larval heart valves. We discovered that tissue-specificity in ER activation is due to differences in the expression of estrogen receptor subtypes. ERα is expressed in developing heart valves but not in the liver, whereas ERβ2 has the opposite profile. Accordingly, subtype-specific ER agonists activate the reporter in either the heart valves or the liver. Conclusion: The use of 5xERE:GFP transgenic zebrafish has revealed an unexpected tissue-specific difference in the response to environmentally relevant estrogenic compounds. Exposure to estrogenic EEDs in utero is associated with adverse health effects, with the potentially unanticipated consequence of targeting developing heart valves.

KSC-2009-1875

NASA Image and Video Library

2009-02-25

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a technician holds one of space shuttle Discovery's gaseous hydrogen flow control valves after its removal. Two of the three valves being removed will undergo detailed inspection. Part of the main propulsion system, the valves channel gaseous hydrogen from the main engines to the external tank. NASA and contractor teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight. Approximately 4,000 images of each valve removed will be reviewed for evidence of cracks. Valves that have flown fewer times will be installed in Discovery. NASA's Space Shuttle Program has established a plan that could support shuttle Discovery's launch to the International Space Station, tentatively targeted for March 12. An exact target launch date will be determined as work on the valves progresses. Photo credit: NASA/Dimitri Gerondidakis

KSC-2009-1876

NASA Image and Video Library

2009-02-25

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a technician holds one of space shuttle Discovery's gaseous hydrogen flow control valves after its removal. Two of the three valves being removed will undergo detailed inspection. Part of the main propulsion system, the valves channel gaseous hydrogen from the main engines to the external tank. NASA and contractor teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight. Approximately 4,000 images of each valve removed will be reviewed for evidence of cracks. Valves that have flown fewer times will be installed in Discovery. NASA's Space Shuttle Program has established a plan that could support shuttle Discovery's launch to the International Space Station, tentatively targeted for March 12. An exact target launch date will be determined as work on the valves progresses. Photo credit: NASA/Dimitri Gerondidakis

KSC-2009-1874

NASA Image and Video Library

2009-02-25

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a technician bags one of space shuttle Discovery's gaseous hydrogen flow control valves after its removal. Two of the three valves being removed will undergo detailed inspection. Part of the main propulsion system, the valves channel gaseous hydrogen from the main engines to the external tank. NASA and contractor teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight. Approximately 4,000 images of each valve removed will be reviewed for evidence of cracks. Valves that have flown fewer times will be installed in Discovery. NASA's Space Shuttle Program has established a plan that could support shuttle Discovery's launch to the International Space Station, tentatively targeted for March 12. An exact target launch date will be determined as work on the valves progresses. Photo credit: NASA/Dimitri Gerondidakis

46 CFR 162.018-1 - Applicable specifications, and referenced material.

Code of Federal Regulations, 2012 CFR

2012-10-01

...) The ASME Code may be obtained from the American Society of Mechanical Engineers, United Engineering..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied... (Procedures Applicable to the Public) and Subpart 50.15 of Subchapter F (Marine Engineering) of this chapter...

46 CFR 162.018-1 - Applicable specifications, and referenced material.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) The ASME Code may be obtained from the American Society of Mechanical Engineers, United Engineering..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied... (Procedures Applicable to the Public) and Subpart 50.15 of Subchapter F (Marine Engineering) of this chapter...

46 CFR 162.018-1 - Applicable specifications, and referenced material.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) The ASME Code may be obtained from the American Society of Mechanical Engineers, United Engineering..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied... (Procedures Applicable to the Public) and Subpart 50.15 of Subchapter F (Marine Engineering) of this chapter...

46 CFR 162.018-1 - Applicable specifications, and referenced material.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) The ASME Code may be obtained from the American Society of Mechanical Engineers, United Engineering..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied... (Procedures Applicable to the Public) and Subpart 50.15 of Subchapter F (Marine Engineering) of this chapter...

46 CFR 162.018-1 - Applicable specifications, and referenced material.

Code of Federal Regulations, 2011 CFR

2011-10-01

...) The ASME Code may be obtained from the American Society of Mechanical Engineers, United Engineering..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied... (Procedures Applicable to the Public) and Subpart 50.15 of Subchapter F (Marine Engineering) of this chapter...

46 CFR 162.017-2 - Type.

Code of Federal Regulations, 2011 CFR

2011-10-01

... APPROVAL ENGINEERING EQUIPMENT Valves, Pressure-Vacuum Relief, for Tank Vessels § 162.017-2 Type. This specification covers the design and construction of pressure-vacuum relief valves intended for use in venting systems on all tank vessels transporting inflammable or combustible liquids. [56 FR 35827, July 29, 1991] ...

46 CFR 162.017-2 - Type.

Code of Federal Regulations, 2010 CFR

2010-10-01

... APPROVAL ENGINEERING EQUIPMENT Valves, Pressure-Vacuum Relief, for Tank Vessels § 162.017-2 Type. This specification covers the design and construction of pressure-vacuum relief valves intended for use in venting systems on all tank vessels transporting inflammable or combustible liquids. [56 FR 35827, July 29, 1991] ...

Glutaraldehyde exposures among workers making bioprosthetic heart valves.

PubMed

Sutton, Patrice M; Quint, Julia; Prudhomme, Janice; Flattery, Jennifer; Materna, Barbara; Harrison, Robert

2007-05-01

Exposure to glutaraldehyde is a recognized cause of work-related asthma. An investigation was undertaken to describe exposure to glutaraldehyde among workers making bioprosthetic heart valves and to make recommendations for prevention. At the two largest heart valve manufacturing facilities in California, the work process was observed; employer representatives and glutaraldehyde-exposed workers were interviewed; and employer written records, including company-generated industrial hygiene data, were analyzed. Approximately 600 female workers had continuous airborne exposure to glutaraldehyde over the course of every work shift and the routine potential for skin and eye contact with glutaraldehyde while making heart valves. Employee short-term (15-min) glutaraldehyde exposures were all well below the current regulatory ceiling level (0.20 ppm). Overall, approximately 40% of the glutaraldehyde-related job tasks involved exposures above the American Conference of Industrial Hygienists threshold limit value ceiling of 0.05 ppm; the majority (71.4% and 83.3%, depending on the company) involved exposures greater than 0.015 ppm. At one company, two cases of physician-diagnosed asthma were recorded by the employer in the previous 5-year period; these reports met the surveillance case definition for new-onset, work-related asthma associated with a known asthma inducer. Factors that contributed to worker exposure included large exposed surface areas of glutaraldehyde under agitation; working with glutaraldehyde-treated tissue in proximity to workers' breathing zones; manual pouring and disposal of glutaraldehyde solutions without local exhaust ventilation, eye protection, and waste neutralization; and prolonged use of latex gloves. Workers making bioprosthetic heart valves are at risk for occupationally acquired asthma. Employers should implement additional engineering controls to minimize workers' exposures to at least below a level of 0.015 ppm, an appropriate glove to prevent workers' skin exposure to glutaraldehyde, consistent and universal use of eye protection, and a medical surveillance program for glutaraldehyde-exposed workers.

Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation.

PubMed

Sturla, Francesco; Redaelli, Alberto; Puppini, Giovanni; Onorati, Francesco; Faggian, Giuseppe; Votta, Emiliano

2015-06-01

Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edge-to-edge repair technique treats mitral regurgitation by suturing the leaflets together and creating a double-orifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip(®) device. Edge-to-edge features and evolution have stimulated debate and multidisciplinary research by both clinicians and engineers. After providing an overview of representative studies in the field, here we propose a novel computational approach to the most recent percutaneous evolution of the edge-to-edge technique. Image-based structural finite element models of three mitral valves affected by posterior prolapse were derived from cine-cardiac magnetic resonance imaging. The models accounted for the patient-specific 3D geometry of the valve, including leaflet compound curvature pattern, patient-specific motion of annulus and papillary muscles, and hyperelastic and anisotropic mechanical properties of tissues. The biomechanics of the three valves throughout the entire cardiac cycle was simulated before and after Mitraclip(®) implantation, assessing the biomechanical impact of the procedure. For all three simulated MVs, Mitraclip(®) implantation significantly improved systolic leaflets coaptation, without inducing major alterations in systolic peak stresses. Diastolic orifice area was decreased, by up to 58.9%, and leaflets diastolic stresses became comparable, although lower, to systolic ones. Despite established knowledge on the edge-to-edge surgical repair, latest technological advances make its percutanoues implementation a challenging field of research. The modeling approach herein proposed may be expanded to analyze clinical scenarios that are currently critical for Mitraclip(®) implantation, helping the search for possible solutions.

Breast Cancer Tissue Bioreactor for Direct Interrogation and Observation of Response to Antitumor Therapies

DTIC Science & Technology

2012-07-01

regulate microfluidic flow rates within the TTB, including flow channel height variation and incorporation of valves (see Figure 2 and Supplemental...cartridge. As an alternative to individual channel TURN valve -adjusted flow regulators, we investigated use of pre-fabricated microfluidic flow resistance...Small Parts, Inc. and B) Microfluidic manifolds with built-in TURN valves . Supplemental Figure S3. Simplified 2D and 3D diffusional model

Fluid Dynamic Characterization of a Polymeric Heart Valve Prototype (Poli-Valve) tested under Continuous and Pulsatile Flow Conditions

PubMed Central

De Gaetano, Francesco; Serrani, Marta; Bagnoli, Paola; Brubert, Jacob; Stasiak, Joanna; Moggridge, Geoff D.; Costantino, Maria Laura

2016-01-01

Introduction Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy, the latter display better fluid dynamic behaviour but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the haemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of two groups of newly developed supra-annular tri-leaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. Methods Two types of Poli-Valves made of SBC differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. An ad - hoc designed pulse duplicator allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to assess the valve’s behaviour. Results Both types Poli-Valves met the minimum requirements in terms of regurgitation and EOA as specified by ISO 5840 Standard. Results were compared with five mechanical heart valves (MHVs) and five tissue heart valves (THVs), currently available on the market. Conclusion Based on these results, polymeric heart valves based on styrenic block copolymers, as Poli-Valves are, can be considered as promising alternative for heart valve replacement in near future. PMID:26689146

Fluid dynamic characterization of a polymeric heart valve prototype (Poli-Valve) tested under continuous and pulsatile flow conditions.

PubMed

De Gaetano, Francesco; Serrani, Marta; Bagnoli, Paola; Brubert, Jacob; Stasiak, Joanna; Moggridge, Geoff D; Costantino, Maria Laura

2015-11-01

Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy; the latter display better fluid dynamic behavior but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the hemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of 2 groups of newly developed supra-annular, trileaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. 2 types of Poli-Valves made of SBC and differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. A pulse duplicator designed ad hoc allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to assess the behavior of the valve. Both types of Poli-Valves met the minimum requirements in terms of regurgitation and EOA as specified by the ISO 5840 Standard. Results were compared with 5 mechanical heart valves (MHVs) and 5 tissue heart valves (THVs), currently available on the market. Based on these results, PHVs based on styrenic block copolymers, as are Poli-Valves, can be considered a promising alternative for heart valve replacement in the near future.

Active tissue stiffness modulation controls valve interstitial cell phenotype and osteogenic potential in 3D culture.

PubMed

Duan, Bin; Yin, Ziying; Hockaday Kang, Laura; Magin, Richard L; Butcher, Jonathan T

2016-05-01

Calcific aortic valve disease (CAVD) progression is a highly dynamic process whereby normally fibroblastic valve interstitial cells (VIC) undergo osteogenic differentiation, maladaptive extracellular matrix (ECM) composition, structural remodeling, and tissue matrix stiffening. However, how VIC with different phenotypes dynamically affect matrix properties and how the altered matrix further affects VIC phenotypes in response to physiological and pathological conditions have not yet been determined. In this study, we develop 3D hydrogels with tunable matrix stiffness to investigate the dynamic interplay between VIC phenotypes and matrix biomechanics. We find that VIC populated within hydrogels with valve leaflet like stiffness differentiate towards myofibroblasts in osteogenic media, but surprisingly undergo osteogenic differentiation when cultured within lower initial stiffness hydrogels. VIC differentiation progressively stiffens the hydrogel microenvironment, which further upregulates both early and late osteogenic markers. These findings identify a dynamic positive feedback loop that governs acceleration of VIC calcification. Temporal stiffening of pathologically lower stiffness matrix back to normal level, or blocking the mechanosensitive RhoA/ROCK signaling pathway, delays the osteogenic differentiation process. Therefore, direct ECM biomechanical modulation can affect VIC phenotypes towards and against osteogenic differentiation in 3D culture. These findings highlight the importance of the homeostatic maintenance of matrix stiffness to restrict pathological VIC differentiation. We implement 3D hydrogels with tunable matrix stiffness to investigate the dynamic interaction between valve interstitial cells (VIC, major cell population in heart valve) and matrix biomechanics. This work focuses on how human VIC responses to changing 3D culture environments. Our findings identify a dynamic positive feedback loop that governs acceleration of VIC calcification, which is the hallmark of calcific aortic valve disease. Temporal stiffening of pathologically lower stiffness matrix back to normal level, or blocking the mechanosensitive signaling pathway, delays VIC osteogenic differentiation. Our findings provide an improved understanding of VIC-matrix interactions to aid in interpretation of VIC calcification studies in vitro and suggest that ECM disruption resulting in local tissue stiffness decreases may promote calcific aortic valve disease. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Multi-Element Unstructured Analyses of Complex Valve Systems

NASA Technical Reports Server (NTRS)

Sulyma, Peter (Technical Monitor); Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy

2004-01-01

The safe and reliable operation of high pressure test stands for rocket engine and component testing places an increased emphasis on the performance of control valves and flow metering devices. In this paper, we will present a series of high fidelity computational analyses of systems ranging from cryogenic control valves and pressure regulator systems to cavitating venturis that are used to support rocket engine and component testing at NASA Stennis Space Center. A generalized multi-element framework with sub-models for grid adaption, grid movement and multi-phase flow dynamics has been used to carry out the simulations. Such a framework provides the flexibility of resolving the structural and functional complexities that are typically associated with valve-based high pressure feed systems and have been difficult to deal with traditional CFD methods. Our simulations revealed a rich variety of flow phenomena such as secondary flow patterns, hydrodynamic instabilities, fluctuating vapor pockets etc. In the paper, we will discuss performance losses related to cryogenic control valves, and provide insight into the physics of the dominant multi-phase fluid transport phenomena that are responsible for the choking like behavior in cryogenic control elements. Additionally, we will provide detailed analyses of the modal instability that is observed in the operation of the dome pressure regulator valve. Such instabilities are usually not localized and manifest themselves as a system wide phenomena leading to an undesirable chatter at high flow conditions.

The effect of lymphatic valve morphology on fluid transport

NASA Astrophysics Data System (ADS)

Alexeev, Alexander; Ballard, Matthew; Nepiyushchikh, Zhanna; Dixon, Brandon

2016-11-01

The lymphatic vasculature is present in nearly all invertebrate tissue, and is essential in the transport of fluid and particles such as immune cells, antigens, proteins and lipids from the tissue to lymph nodes and to the venous circulation. Lymphatic vessels are made of up a series of contractile units that work together in harmony as "micro hearts" to pump fluid against a pressure gradient. Lymphatic valves are critical to this functionality, as they open and close with the oscillating pressure gradients from contractions, thus allowing flow in only one direction and leading to a net pumping effect. We use a hybrid lattice-Boltzmann lattice spring model which captures fluid-solid interactions through two-way coupling between a viscous fluid and lymphatic valves in a section of a lymphatic vessel to study the dynamics of lymphatic valves and their effect on fluid transport. Further, we investigate the effect of variations in valve geometry and material properties on fluid pumping. This work helps to increase our understanding of the mechanisms of lymphatic fluid transport, which has implications in a variety of pathologies, including cancer metastasis, autoimmunity, atherosclerosis and obesity. Support from NSF CMMI 1635133 is gratefully acknowledged.

30 CFR 36.23 - Engine intake system.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Engine intake system. 36.23 Section 36.23... EQUIPMENT Construction and Design Requirements § 36.23 Engine intake system. (a) Construction. The intake... operator's compartment, to shut off the air supply to the engine. This valve shall be constructed to permit...

30 CFR 36.23 - Engine intake system.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Engine intake system. 36.23 Section 36.23... EQUIPMENT Construction and Design Requirements § 36.23 Engine intake system. (a) Construction. The intake... operator's compartment, to shut off the air supply to the engine. This valve shall be constructed to permit...

28. Main engine air pump located to port side of ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

28. Main engine air pump located to port side of main engine cylinder beside engine bed. Dynamo lies aft of air pump (at right), pipe at extreme left of image carries lake water to condenser valves. - Steamboat TICONDEROGA, Shelburne Museum Route 7, Shelburne, Chittenden County, VT

46 CFR 56.20-7 - Ends.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Ends. 56.20-7 Section 56.20-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-7 Ends. (a) Valves may be used with flanged, threaded, butt welding, socket welding or other ends...

46 CFR 162.018-6 - Marking.

Code of Federal Regulations, 2013 CFR

2013-10-01

...: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-6 Marking. (a) Each safety relief valve shall be plainly marked by the manufacturer with the required data...-* *”. * * Number to be assigned by the Commanding Officer, USCG Marine Safety Center. (b) [Reserved] [CGFR 68-82...

46 CFR 162.018-6 - Marking.

Code of Federal Regulations, 2012 CFR

2012-10-01

...: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-6 Marking. (a) Each safety relief valve shall be plainly marked by the manufacturer with the required data...-* *”. * * Number to be assigned by the Commanding Officer, USCG Marine Safety Center. (b) [Reserved] [CGFR 68-82...

46 CFR 162.018-6 - Marking.

Code of Federal Regulations, 2014 CFR

2014-10-01

...: SPECIFICATIONS AND APPROVAL ENGINEERING EQUIPMENT Safety Relief Valves, Liquefied Compressed Gas § 162.018-6 Marking. (a) Each safety relief valve shall be plainly marked by the manufacturer with the required data...-* *”. * * Number to be assigned by the Commanding Officer, USCG Marine Safety Center. (b) [Reserved] [CGFR 68-82...

46 CFR 56.20-7 - Ends.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Ends. 56.20-7 Section 56.20-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-7 Ends. (a) Valves may be used with flanged, threaded, butt welding, socket welding or other ends...

46 CFR 56.20-7 - Ends.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Ends. 56.20-7 Section 56.20-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-7 Ends. (a) Valves may be used with flanged, threaded, butt welding, socket welding or other ends...

46 CFR 56.20-7 - Ends.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Ends. 56.20-7 Section 56.20-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-7 Ends. (a) Valves may be used with flanged, threaded, butt welding, socket welding or other ends...

46 CFR 56.20-7 - Ends.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Ends. 56.20-7 Section 56.20-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Valves § 56.20-7 Ends. (a) Valves may be used with flanged, threaded, butt welding, socket welding or other ends...

46 CFR 56.20-20 - Valve bypasses.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Valve bypasses. 56.20-20 Section 56.20-20 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES..., and of a material of the same nominal chemical composition and physical properties as that used for...

46 CFR 56.20-20 - Valve bypasses.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Valve bypasses. 56.20-20 Section 56.20-20 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES..., and of a material of the same nominal chemical composition and physical properties as that used for...

46 CFR 56.20-20 - Valve bypasses.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Valve bypasses. 56.20-20 Section 56.20-20 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES..., and of a material of the same nominal chemical composition and physical properties as that used for...

46 CFR 56.20-20 - Valve bypasses.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Valve bypasses. 56.20-20 Section 56.20-20 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES..., and of a material of the same nominal chemical composition and physical properties as that used for...

46 CFR 56.20-20 - Valve bypasses.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Valve bypasses. 56.20-20 Section 56.20-20 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES..., and of a material of the same nominal chemical composition and physical properties as that used for...

MFCVs (Manual Flow Control Valves) in the Lab

NASA Image and Video Library

2009-07-07

ISS020-E-017705 (7 July 2009) --- NASA astronaut Michael Barratt, Expedition 20 flight engineer, works at a rotated rack in the Destiny laboratory of the International Space Station during in-flight maintenance (IFM) to adjust the periodic flow rate of manual flow control valves for coolant loops.

MFCVs (Manual Flow Control Valves) in the Lab

NASA Image and Video Library

2009-07-07

ISS020-E-017710 (7 July 2009) --- NASA astronaut Michael Barratt, Expedition 20 flight engineer, works at a rotated rack in the Destiny laboratory of the International Space Station during in-flight maintenance (IFM) to adjust the periodic flow rate of manual flow control valves for coolant loops.

PBF (PER620) interior, first basement. Detail of valves and other ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PBF (PER-620) interior, first basement. Detail of valves and other penetrations along wall. Bricks are made of high density shielding materials. Date: March 2004. INEEL negative no. HD-41-4-2 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

Single-use thermoplastic microfluidic burst valves enabling on-chip reagent storage

PubMed Central

Rahmanian, Omid D.

2014-01-01

A simple and reliable method for fabricating single-use normally closed burst valves in thermoplastic microfluidic devices is presented, using a process flow that is readily integrated into established workflows for the fabrication of thermoplastic microfluidics. An experimental study of valve performance reveals the relationships between valve geometry and burst pressure. The technology is demonstrated in a device employing multiple valves engineered to actuate at different inlet pressures that can be generated using integrated screw pumps. On-chip storage and reconstitution of fluorescein salt sealed within defined reagent chambers are demonstrated. By taking advantage of the low gas and water permeability of cyclic olefin copolymer, the robust burst valves allow on-chip hermetic storage of reagents, making the technology well suited for the development of integrated and disposable assays for use at the point of care. PMID:25972774

KSC-2009-1873

NASA Image and Video Library

2009-02-25

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, technicians have removed space shuttle Discovery's three gaseous hydrogen flow control valves, two of which will undergo detailed inspection. Part of the main propulsion system, the valves channel gaseous hydrogen from the main engines to the external tank. NASA and contractor teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight. Approximately 4,000 images of each valve removed will be reviewed for evidence of cracks. Valves that have flown fewer times will be installed in Discovery. NASA's Space Shuttle Program has established a plan that could support shuttle Discovery's launch to the International Space Station, tentatively targeted for March 12. An exact target launch date will be determined as work on the valves progresses. Photo credit: NASA/Dimitri Gerondidakis

Valve leakage inspection, testing, and maintenance process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aikin, J.A.; Reinwald, J.W.

1989-01-01

Atomic Energy of Canada Limited-Research Company (AECL-RC), Chalk River, has more than 50 person-years dedicated toward the leak-free valve. In the early 1970s, the Chalk River Nuclear Laboratories (CRNL) developed valve stem live-loading and recently completed the packing tests for the Electric Power Research Institute (EPRI)-funded Valve Packing Improvement Study. Current safety concerns with asbestos-based valve packings and the difficulty in removing newer graphite packings prompted CRNL to investigate methods to improve valve repacking procedures. The present practice of valve packing replacement is very labor-intensive, requiring use of hand tools such as corkscrew devices and special packing picks. Use ofmore » water jets to cut or fragment the packing for withdrawal from the stuffing box does improve the process, but removal of the lantern or junk rings is still difficult. To address these problems, AECL-RC has developed a unique valve maintenance process designed to reduce person-rem exposures, the risk of scoring the stem or stuffing box, and maintenance costs and to improve the engineering quality of valve repair.« less

Analysis of the STS-126 Flow Control Valve Structural-Acoustic Coupling Failure

NASA Technical Reports Server (NTRS)

Jones, Trevor M.; Larko, Jeffrey M.; McNelis, Mark E.

2010-01-01

During the Space Transportation System mission STS-126, one of the main engine's flow control valves incurred an unexpected failure. A section of the valve broke off during liftoff. It is theorized that an acoustic mode of the flowing fuel, coupled with a structural mode of the valve, causing a high cycle fatigue failure. This report documents the analysis efforts conducted in an attempt to verify this theory. Hand calculations, computational fluid dynamics, and finite element methods are all implemented and analyses are performed using steady-state methods in addition to transient analysis methods. The conclusion of the analyses is that there is a critical acoustic mode that aligns with a structural mode of the valve

Variable camshaft timing system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butterfield, R.P.; Smith, F.R.

1989-09-05

This patent describes an improvement in a variable camshaft timing system for an internal combustion engine having intake and exhaust valves and a camshaft for each of the intake and exhaust valves, an intake sprocket and an exhaust sprocket keyed to their respective camshaft, only one of the camshafts being directly driven by an engine crankshaft, and a timing chain engaging both sprockets. The improvement comprising a single bracket carrying at least one idler sprocket engaging the timing chain, the bracket being mounted for movement to alter the timing relationship between the intake and exhaust sprockets.

PROCESS WATER BUILDING, TRA605, INTERIOR. FIRST FLOOR. CAMERA IS IN ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PROCESS WATER BUILDING, TRA-605, INTERIOR. FIRST FLOOR. CAMERA IS IN SOUTHEAST CORNER AND FACES NORTHWEST. CONTROL ROOM AT RIGHT. CRANE MONORAIL IS OVER FLOOR HATCHES AND FLOOR OPENINGS. SIX VALVE HANDWHEELS ALONG FAR WALL IN LEFT CENTER VIEW. SEAL TANK IS ON OTHER SIDE OF WALL; PROCESS WATER PIPES ARE BELOW VALVE WHEELS. NOTE CURBS AROUND FLOOR OPENINGS. INL NEGATIVE NO. HD46-26-3. Mike Crane, Photographer, 2/2005 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

MALDI-Imaging Mass Spectrometry: a step forward in the anatomopathological characterization of stenotic aortic valve tissue.

PubMed

Mourino-Alvarez, Laura; Iloro, Ibon; de la Cuesta, Fernando; Azkargorta, Mikel; Sastre-Oliva, Tamara; Escobes, Iraide; Lopez-Almodovar, Luis F; Sanchez, Pedro L; Urreta, Harkaitz; Fernandez-Aviles, Francisco; Pinto, Angel; Padial, Luis R; Akerström, Finn; Elortza, Felix; Barderas, Maria G

2016-06-03

Aortic stenosis (AS) is the most common form of valve disease. Once symptoms develop, there is an inexorable deterioration with a poor prognosis; currently there are no therapies capable of modifying disease progression, and aortic valve replacement is the only available treatment. Our goal is to study the progression of calcification by matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) and get new insights at molecular level that could help in the understanding of this disease. In this work, we analyzed consecutive slices from aortic valve tissue by MALDI-IMS, to establish the spatial distribution of proteins and peptides directly from the surface of the histological sections. The analysis showed different structures corresponding to regions observed in conventional histology, including large calcification areas and zones rich in collagen and elastic fibers. Peptide extraction from the tissue, followed by liquid chromatography mass spectrometry analysis, provided the identification of collagen VI α-3 and NDRG2 proteins which correlated with the masses obtained by MALDI-IMS and were confirmed by immunohistochemistry. These results highlighted the molecular mechanism implied in AS using MALDI-IMS, a novel technique never used before in this pathology. In addition, we can define specific regions proving a complementary resolution of the molecular histology.

Variable valve timing in a homogenous charge compression ignition engine

DOEpatents

Lawrence, Keith E.; Faletti, James J.; Funke, Steven J.; Maloney, Ronald P.

2004-08-03

The present invention relates generally to the field of homogenous charge compression ignition engines, in which fuel is injected when the cylinder piston is relatively close to the bottom dead center position for its compression stroke. The fuel mixes with air in the cylinder during the compression stroke to create a relatively lean homogeneous mixture that preferably ignites when the piston is relatively close to the top dead center position. However, if the ignition event occurs either earlier or later than desired, lowered performance, engine misfire, or even engine damage, can result. The present invention utilizes internal exhaust gas recirculation and/or compression ratio control to control the timing of ignition events and combustion duration in homogeneous charge compression ignition engines. Thus, at least one electro-hydraulic assist actuator is provided that is capable of mechanically engaging at least one cam actuated intake and/or exhaust valve.