Engineering Commons^™

The Safety Risks Of Proposed Fuel Economy Legislation, John D. Graham

RISK: Health, Safety & Environment (1990-2002)

Based on, e.g., a comprehensive assessment of what is known of factors influencing automobile safety, previous industry responses to requirements for fuel economy and prior success of regulators in reducing injuries, Professor Graham concludes that pending fuel economy bills are apt to add 1650 fatalities and 8500 serious accidents to the annual highway toll. He also presents several short-term and long-term strategies for simultaneously saving fuel and lives.

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Building Services Engineering

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Microstructure Of Mica Glass-Ceramics And Interface Reactions Between Mica Glass-Ceramics And Bone, W. Holand, W. Gotz, G. Carl, W. Vogel

Cells and Materials

This review paper characterizes glass-ceramics containing mica as main crystal phase. The phase formation reactions in dependence of the chemical composition and the microstructure are shown. Microstructure of mica glass-ceramics has been studied by electron replica and scanning electron microscopic (SEM) techniques.

Mica glass-ceramics have previously been developed in Si02-B20rA120rMgO-F--base glasses. The material is machinable because of the precipitation of micas of fluorophlogopite-type. Also, a machinable glass-ceramic for dental applications was developed based on KMg2_5(Si40 10)F2-micas. We developed mica glass-ceramics in the Si02-Al20rMgO-NaiO-K20-F glass system. Phase formation within these glasses was observed by SEM. A double controlled nucleation and crystallization …

The Effect Of Polymethylmethacrylate Bone Cement Vibration On The Bone-Cement Interface, A. M. C. Thomas, D. J. W. Mcminn, M. Haddaway, I. W. Mccall

Cells and Materials

Low frequency vibration of polymethylmethacrylate (PMMA) bone cement reduces the viscosity of the cement by shear thinning. The effect of this low frequency vibration on the bone-cement interface was studied using microfocal radiography (MFR) and scanning electron microscopy (SEM). Effects were studied in-vitro and in-vivo. In-vitro, samples of Palacos low viscosity PMMA were placed on blocks of Kiel bone and vibrated. MFR and SEM demonstrated an improvement in the appearance of the bone-cement interface. In-vivo, PMMA was injected into the upper tibia of the dog. An assessment of the effect of high and low pressure injection, and the effect of …

Ultrastructural Assessment Of Lesion Development In The Collared Rabbit Carotid Artery Model, J. E. Beesley, A. C. Honey, J. F. Martin

Cells and Materials

Cellular reactions associated with the formation of lesions generated in the carotid artery of rabbits fed either normal or high cholesterol diets by the placement of a flexible, silastic collar around the artery, were studied by electron microscopy.

Endothelial cells remained as a monolayer throughout lesion development. The endothelial cell surface in both experimental and sham operated carotids, 4 hours and 8 hours after the initiation of the experiments, were covered with platelets and leukocytes. Neutrophils were present until 7 days in the arteries from within the collar of animals maintained on a normal diet, but only to 1 day …

The Effect Of Serial Passaging Of Lactobacilli In Liquid Medium On Their Physico-Chemical And Structural Surface Characteristics, Pieter L. Cuperus, Henny C. Van Der Mei, Gregor Reid, Andrew W. Bruce, Antoine E. Khoury, Paul G. Rouxhet, Henk J. Busscher

Cells and Materials

The aim of this study was to examine the effect of serial passaging in liquid medium on physico-chemical and structural surface characteristics of two lactobacillus strains. To this end, starting cultures (p = 1) of urogenital isolate L. acidophilus RC 14 and poultry isolate L. fermentum B54 were serially passaged in liquid medium up to 20 times (p = 20). In both strains, similar physico-chemical and structural changes were observed following serial passaging. According to water contact angle measurements , cells in p = 20 cultures became less hydrophobic. Microelectrophoresis showed that isoelectric points shifted towards the acidic region upon …

The Incorporation Of Glass-Ceramic Implants In Bone After Surface Conditioning Glow-Discharge Treatment, C. M. Muller-Mai, C. Voigt, R. E. Baier, U. M. Gross

Cells and Materials

Glow discharge (GD)-treated and autoclaved glass-ceramics of bone-bonding and non-bonding type were implanted into the femoral diaphysis of rats for 3, 7, 14 and 28 days and were investigated by applying light microscopy and histomorphometry , and scanning and transmission electron microscopy. More bone and chondroid, and faster osteoid development were observed at glow-discharge treated implants even in nonbonding implants when compared to autoclaved controls. Ultrastructural investigations showed a higher leach ing- rate of GD-treated bone-bonding implants during the early days after implantation leading to a higher rugosity, whereas no morphological changes were observed on non-bonding implant surfaces. More extracellular …

Nothing Recedes Like Success - Risk Analysis And The Organizational Amplification Of Risks, William R. Freudenburg

RISK: Health, Safety & Environment (1990-2002)

Professor Freudenburg believes that there is room for improvement in Risk analysis, particularly in drawing on systematic studies of human behavior in the calculation of real, empirical probabilities of failure. The need is argued to be especially acute where technological Risks are associated with low expected probabilities of failure and are managed by human organizations for extended periods of time. This permits complacency to set in.

Reply To Valverde, Paul B. Thompson

RISK: Health, Safety & Environment (1990-2002)

Professor Thompson responds to Valverde's argument, in the last issue, that his approach to Risk puts too much emphasis on the distinction between Risk subjectivism and Risk objectivism. In doing so, he asserts, inter alia, that anchoring Risk judgments in a probabilistic framework does not go far enough in rejecting reigning Risk-analysis notions of "real Risk."

Summary Of Workshop To Review An Omb Report On Regulatory Risk Assessment And Management, John S. Evans, John D. Graham, George M. Gray, Adrienne Hollis

RISK: Health, Safety & Environment (1990-2002)

Summary of the results of an invitational workshop conducted to peer review the 1990 OMB report, CURRENT REGULATORY ISSUES IN Risk ASSESSMENT AND Risk MANAGENMENTIN REGULATORY PROGRAM OF THE UNITED STATES GOVERNMENT, APRIL 1, 1990 - MARCH 31, 1991.

Applications Of Fourier Transform Infrared (Ft-Ir) Microscopy To The Study Of Mineralization In Bone And Cartilage, Adele L. Boskey, Nancy Pleshko, Stephen B. Doty, Richard Mendelsohn

Cells and Materials

Knowledge of the phase, composition, and crystallite size and perfection of the mineral in normal and abnormally calcified tissues provides insight into the mechanism by which this mineral was deposited. These data also can be used to develop rational therapies for pathological conditions characterized by abnormal mineral deposition. As illustrated in this review, coupling of an optical microscope with a Fourier transform infrared (FT-IR) spectrophotometer permits the mapping at 20 μm spatial resolution of changes in mineral characteristics (content, particle size, composition) in the growth plate, in bone biopsies, in mineralizing cell culture systems, and in soft tissue calcifications. Based …

A Model For A Model: Pressure Jackets On Nude Mice With Implants Of Hypertrophic Scars, C. Ward Kischer, Jana Pindur

Cells and Materials

The hypertrophic scar, a consequence of deep surface injury, is peculiar to humankind. Subcutaneous implants of these tissues in nude mice provide a quasi - animal model for experimental use. An efficacious treatment to promote acceleration of maturation of the hypertrophic scar is controlled topical pressure produced by flexible dacron fabric wraps. Implants in the nude mouse provide a model for study of the effects of pressure. Preliminary results indicate that those implants in nude mice, responding favorably to pressure jackets, show changes consistent with those previously obtained in human studies. The collagen matrix shows reduced density and parallel layering …

Quantitative Scanning Electron Microscopy (Sem) To Study The Adhesion And Spreading Of Human Endothelial Cells To Surface-Modified Poly(Carbonate Urethane)S, C. James Kirkpatrick, Tillmann Otterbach, Dirk Anderheiden, Johannes Schiefer, Horst Richter, Hartwig Hartwig Hocker, Christian Mittermayer, Albert Dekker

Cells and Materials

The polymers currently in use as vascular prostheses are, in the native state, poor substrates for endothelial cell (EC) adhesion and growth. This has a negative effect on the success of pre-seeding regimes. One attempt to improve the polymer substrate is to covalently couple reactive molecules to the surface, which can be used as anchorage points for EC or serve as spacer molecule to couple biological signal molecules such as oligopeptides. We have used a digitized image analysis system coupled to a scanning electron microscope to study the adhesion and spreading of human venous EC to unmodified poly(carbonate urethane) (uPCU), …

Comparative Assessment Of The Cytotoxicity Of Various Substrates In Organ Culture And Cell Culture: A Scanning Electron Microscopy Study, J. L. Duval, R. Warocquier-Clerout, M. F. Sigot-Luizard

Cells and Materials

A comparative study of the behavior of chick embryo endothelial cells grown on various substrates was performed in order to establish the reliability and the limitation of both cell and organ culture methods. Following substrates were analyzed to compare these two different culture techniques: bovine serum albumin, pigskin gelatin and albumin + gelatin cross-linked by glutaraldehyde or carbodiimide, fibrin glue and negative control (Thermanox*). Parameters of cell growth and adhesion were calculated and compared with electron microscopic observations of cell morphology and of the extracellular matrix. Both culture methods provided complementary results and led to a similar classification of the …

Scanning Electron Microscopy Of The Bone Interface With Titanium, Titanium Alloy And Hydroxyapatite, R. D. Orr, J. D. De Bruijn, J. E. Davies

Cells and Materials

Screw implants of commercially pure titanium and titanium alloy together with rods of slip-cast dense hydroxyapatite were implanted transfemorally in young adult rats. The femora were harvested after fixation and freeze-fractured in liquid nitrogen to create two tissue fragments of each specimen. The first contained the implant while the second enabled examination of the tissue immediately adjacent to the implant. In all cases, the tissue abutting the implant was a cement line-like layer which separated the implant from the surrounding bone proper. Greater adherence of this interfacial tissue was demonstrated to hydroxyapatite samples compared with the titanium screws, while no …

Microstructural Changes In Retrieved Amalgam Restorations, Grayson W. Marshall Jr., D. D. Mccoy, John H. Kinney, Hugo Letzel, Sally J. Marshall

Cells and Materials

Many blended or dispersed phase high Cu amalgams show excellent clinical performance in long term clinical trials. However, little is known concerning the microstructural changes that occur during clinical use of these systems. This investigation sought to characterize some of the changes that occur in the Ag-Cu particles and their surrounding reaction zones based on a study by backscattered scanning electron microscopy (BSEM), energy dispersive spectroscopy and a new rnicroprobe technique called Colorad which assigns various colors to elements and element combinations and indicates changes in elemental concentration by changes in color value (brightness). Restorations were retrieved from clinical trials …

The Role Of Implant Surface Geometry On Mineralization In Vivo And In Vitro; A Transmission And Scanning Electron Microscopic Study, B. Chehroudi, J. Ratkay, D. M. Brunette

Cells and Materials

The purpose of th.is study was to examine the effect of substratum surface topography on bone formation in vivo and in vitro. Precise control over substratum topography was achieved using micromachining, a technique developed from the fabrication of microelectronic components. In the in vivo studies, titanium-coated epoxy replicas of micromachined surfaces were implanted subcutaneously in the parietal area of rats. After 6 weeks, bone-like tissue was found adjacent to some micromachined surfaces. Detailed observation of this tissue with the transmission electron microscope revealed osteoblast/osteocyte-like cells and a fully or partially mineralized collagenous matrix. Mineralized matrix and collagen bundles were …

Bone Regeneration Materials For The Mandibular And Craniofacial Complex, Jeffrey Hollinger, Anshumali Chaudhari

Cells and Materials

Due to different functional demands and vascularity, the mandibular and craniofacial complex require bone regenerating materials with physical and chemical properties that are different from long bone. However, certain common requirements to both locales must be addressed. Furthermore, reasons why the autograft and allogeneic bank bones are successful in regenerating bone need to be understood if the researcher is to develop satisfactory alternatives. The purpose of this paper is to review some of the requirements needed for bone regenerating materials for mandibular and craniofacial bone repair. In that effort, we have briefly described the autograft and allogeneic bank bones, animal …

Development Of A Rotation Device For Microvascular Endothelial Cell Seeding, G. Pasquinelli, P. Preda, M. Vici, G. N. Martinelli, A. Freyrie, T. Curti, M. D'Addato

Cells and Materials

A rotation device (RD) specifically designed to achieve sterile endothelial cell (EC) seeding of vascular grafts has been developed. The basic characteristics of the RD include: small dimensions, fully autoclavable components, and perfectly sealed graft holders. These features make it possible to maintain sterility during all the steps of EC seeding. This was documented by negativity of all bacteriological assays performed . Moreover, the RD can simultaneously support three vascular grafts with different lengths (20, 40, and 60 cm) and diameters (4-8 mm). EC seeding is performed in the climatized chamber (37 °C; 5 % C02) with constant rotation (0.1 …

The Tissue Responses To Tricalcium Phosphate Ceramics In Bone And Marrow, R. S. Archer, S. Downes, M. V. Kayser, S. Y. Ali

Cells and Materials

Calcium phosphate ceramics are described as "bioactive". Evidence of biological activity associated with calcium phosphate implanted in bone and marrow can be seen as changes in the morphology of the interfaces. In this in vivo model the sequence of progressive bone growth and bone merger with a dense calcium phosphate ceramics were examined by light and transmission electron microscopy. A spectrum of tissue responses to dense tricalcium phosphate ceramics was observed at intervals over a six week period. It is now well established that calcium phosphate ceramics permit bone ingrowth with little or no immunological response; however, a layer of …

Fine Structure Of Remodeling Sites On Iliac Cancellous Bone In Senile Osteoporosis: A Study By Scanning Electron Microscopy Using An Improved Organic Specimen Preparation Method, Toshihiko Takita, Tomonori Naguro, Kichizo Yamamoto

Cells and Materials

We improved on the organic specimen preparation method in order to investigate the details of the functional state of bone in osteoporosis at high magnification level. The usefulness and possibilities of this method are discussed showing fine structural images of remodeling sites. Iliac bones of senile osteoporotic patients obtained by transilial biopsies were studied by scanning electron microscopy (SEM) using the improved preparation method. Excepting the region near the corticoendosteal surface, most of the iliac cancellous bone was composed of thin rod-shaped trabeculae. Remodeling sites on trabeculae appeared as concavities of various sizes and were easily distinguished from inert surfaces. …

Effect Of Surface Treatments On Dentin Bonding Shear Strength, James L. Drummond, D. Racean, J. Van Scoyoc, A. Steinberg

Cells and Materials

The purpose of this study was to determine whether four different treatments on wet or dry teeth, on the buccal and occlusal surfaces, affected the shear bond strength. The surface treatments consisted of a dentin conditioner (pH = 4.0), 10% phosphoric acid (pH = 1.6), 2.5 % nitric acid (pH = 1.0), and 2.5 % citric acid (pH = 1.0). One dentin bonding system and one dental composite was used for all of the specimens. The teeth were mounted in acrylic, ground and etched with the appropriate agent for 15 seconds. The dentin adhesive and composite were applied and the …

Changes In Intracellular Ca2+ And Structure In Platelets Contacting Synthetic Substrates, L. M. Waples, O. E. Olorundare, S. L. Goodman, R. M. Albrecht

Cells and Materials

Platelet structural changes such as spreading and cytoskeletal reorganization that occur upon contact with synthetic surfaces have been well documented . Structural changes such as spreading will vary depending on the substrate involved . Although platelet structural changes following adhesion have been recorded , the cellular mechanisms including changes in intracellular calcium flux underlying these platelet responses are less well understood. In this study, video microscopy was used to image platelet adhesion and spreading while simultaneously imaging intracellular free Ca2+ levels in individual Fura-2 loaded human platelets. This was accomplished using fluorescence video microscopy coupled with video enhanced asymmetric illumination …

Clinical Applications Of Recombinant Gene Technology: Bone And Cartilage Repair, Thomas A. Einhorn

Cells and Materials

Over the past decade, the field of molecular biology has given rise to the development of the applied discipline of molecular medicine. Based on recent developments using recombinant gene technology, genetic mapping analysis and other investigational tools, the physician and surgeon is now ready to begin using those instruments in the diagnosis and treatment of musculoskeletal disease. This article reviews the history of scientific exploration in recombinant gene technology as it applies to bone and cartilage repair. Clinical cases are presented to show how the fruits of scientific knowledge may be brought to bear on some of the more challenging …

Patency Of Small Caliber, Superhydrophobic E-Ptfe Vascular Grafts; A Pilot Study In The Rabbit Carotid Artery, J. M. Schakenraad, I. Stokroos, H. Bartels, H. J. Busscher

Cells and Materials

e-PTFE vascular grafts (Gore, internal diameter 1.5 mm, pore size 30 μm) were luminally treated by ionbeam etching followed by oxygen glow-discharge, to obtain a superhydrophobic luminal surface. Water contact angles of thus modified sheet material were 140-150°, which is significantly higher than on non-treated sheet PTFE (109°). These modified vascular grafts were implanted in the rabbit carotid artery, using an end to end anastomotic technique. After two hours, the grafts were still patent and the wounds were closed. One week after the implantation, the prostheses were still patent. Subsequently, the grafts were harvested and prepared for light microscopy, transmission …

Reactogenicity Of Biomaterials As Studied By Biochemical, Morphological And Ultrastructural Techniques, Leonid I. Slutskii, Natalya A. Sevastjanova, Ivetta L. Ozolanta, Irina V. Kuzmina, Laimdota E. Dombrovska

Cells and Materials

Reactogenicity is a characteristic of biocompatible materials that provokes the reparative and proliferative reaction of connective tissues, a compulsory stage of which is inflammation. Thus, reactogenicity studies should include experiments in vivo. A quantitative assessment of reactogenicity can be obtained by subcutaneous implantation of standard olive-shaped specimens covered by the biomaterial under study followed by biochemical, histological and scanning electron microscopical studies of the capsule developing around the implant. Reactogenicity of surgical threads is evaluated by semiquantitative histological analysis of the wound healing process after suture application. Biomaterial reactogenicity can be modified by changing the structure of the surface and …

Projection Effect Errors In Biomaterials And Bone Research, K. N. Bachus, R. D. Bloebaum

Cells and Materials

Micoradiography and backscattered electron (BSE) imaging are techniques used to investigate the morphologic, histometric, and mineral content changes at the bone/biomaterials interface. Investigators have shown that the superimposition of multiple tissue layers can cause errors with both the morphologic observations and the histometric measurements of bone. The objective of this study was to document errors in the bone mineral content measurements associated with overlapping tissues.

Using a digital image analysis system, microradiographic and BSE images from canine cortical and cancellous bone were captured and analyzed. The results of this study showed that microradiography had more projection effect errors associated with …

Scanning Electron Microscopy Study Of Biofilms On Silicone Voice Prosthesis, T. R. Neu, F. Dijk, G. J. Verkerke, H. C. Van Der Mei, H. J. Busscher

Cells and Materials

Patients after laryngectomy often receive silicone made voice prostheses fot speech rehabilitation. The prosthesis is inserted in a shunt between the trachea and the digestive tract. As the prosthesis is placed in a nonsterile environment it becomes rapidly colonized by microorganisms eventually leading to failure and frequent exchange of the implant. In this study, explanted "Groningen Button" silicone voice prostheses were used to investigate by scanning electron microscopy the biofilm developing on the implant. Two main types of microbial colonization forms could be distinguished. Firstly, macroscopically visible, single colonies dominating on the esophagus side of the prosthesis were found, which …

Apatite - Cholesterol Agglomerates In Human Atherosclerotic Lesions, Sara Sarig, Danielle Hirsch, Reuven Azoury, Teddy A. Weiss, Iony Katz, Howard S. Kruth

Cells and Materials

The purpose of this study was to examine the ultrastructural relationships of cholesterol crystals and apatite deposits in human atherosclerotic lesions. Segments of human aortic atherosclerotic lesions were obtained at autopsy , fixed in glutaraldehyde and dehydrated without using any organic solvents. The aortic segments were coated with carbon and subjected to various scanning electron microscope analyses. These included secondary electron imaging, back scattering of primary electrons, energy dispersive X-ray analysis of selected spots followed by area mapping of calcium and phosphorus , and cathodoluminescence.

The information gathered from scanning of selected areas in the lesions by all the techniques …

Review: Biomaterials For Abdominal Wall Reconstruction, Roger K. J. Simmermacher, Robert P. Bleichrodt, Jeff M. Schakenraad

Cells and Materials

The reconstruction of large abdominal wall defects still is a major surgical problem. Many different techniques have been developed for this purpose, most of which appeared to be unsatisfactory. The lack of sufficient tissue requires the insertion of prosthetic material. Non-absorbable prostheses used to reconstruct abdominal wall defects showed the best results . Polypropylene mesh (PPM) and expanded polytetrafluoroethylene (ePTFE) soft-tissue patch are the most frequently used materials for this purpose . However, PPM induces extensive visceral adhesions and erosion of the skin, whereas ePTFE is insufficiently anchored to the adjacent tissue and therefore both materials are not ideal. As …