Biomedical Engineering and Bioengineering Commons^™

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 …

Evaluation Of Bacterial Glycocalyx Preservation And Staining By Ruthenium Red, Ruthenium Red-Lysine And Alcian Blue For Several Methanotroph And Staphylococcal Species, Theresa A. Fassel, James E. Van Over, Christopher C. Hauser, Lorie E. Buchholz, Charles E. Edmiston, James R. Sanger, Charles C. Remsen

Cells and Materials

The cationic reagents, ruthenium red (RR), alcian blue (AB) and ruthenium red -lysine were compared for ultrastructural preservation and staining of the bacterial glycocalyx. En bloc RR, AB and RR-lysine procedures, and a glutaraldehyde/OsO4 fixation withou t cationic reagent, were evaluated by transmission electron microscopy (TEM) for several methanotroph and staphylococcal species. The glutaraldehyde/OsO4 fixation was totally ineffective in preserving or staining the glycocalyx material in all species studied. The RR procedure was more effective than the glutaraldehyde/OsO4 fixation but was generally less so than the RR-lysine procedure. By the RR-lysine procedure, extensive layers that were often filamentous or fibrous …

Performance Of Chemigation Backflow Prevention Assemblies, H. M. Munir, Dean E. Eisenhauer, John E. Gilley

Department of Agricultural and Biological Systems Engineering: Faculty Publications

When chemicals are applied using irrigation systems, there is potential for contamination of the water source by backflow if the irrigation system shuts off while unattended. This study was conducted to determine the operating and performance characteristics of new, i.e., unused, chemigation backflow prevention assemblies (CBPAs). Four manufacturer's models were tested in the laboratory. However, two of CBPAs have been modified since the testing was completed. In general, the CBPAs do not meet the standards established for municipal water suppliers and many industries. The backpressures required for the two current models to seal were 0.0 and 6.7 kPa (1.0 psi). …

Sediment Delivery On Rill And Interrill Areas, John E. Gilley, D. C. Kincaid, W. J. Elliot, J. M. Laflen

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Equations which relate sediment delivery to a power function of flow rate and slope gradient were evaluated in this study. The data used to parameterize the calculations were obtained from sites where crop residues had been removed, and moldboard plowing and disking had occurred. Measurements of sediment delivery resulting from simulated rainfall were obtained from preformed rills and interrill areas. The equations provided reliable sediment delivery estimates for selected soils located throughout the United States. To use the sediment delivery equations, soil-related parameter values must he identified. Multiple regression analyses were performed to relate parameter values used in the equations …

Management Of Feedlot Runoff Control Systems, Elbert C. Dickey, Gerald R. Bodman

Department of Agricultural and Biological Systems Engineering: Faculty Publications

During recent years, most open feedlot operators have found it desirable and, in some cases, necessary to install runoff control facilities. Even though the primary purpose of feedlot runoff control systems is the prevention of water pollution, many producers have found that good management of these systems also offers limited economic benefits in the form of fertilizer nutrients and supplemental irrigation water. Well managed runoff control systems also reduce weeds, odors, insects and muddy areas at or near feedlot edges. The runoff control system that has proved most satisfactory for all areas of the country is one consisting of clean …

Darcy-Weisbach Roughness Coefficients For Gravel And Cobble Surfaces, John E. Gilley, Eugene R. Kottwitz, Gary A. Wieman

Department of Agricultural and Biological Systems Engineering: Presentations and White Papers

A laboratory study is conducted to measure Darcy-Weisbach roughness coefficients for selected gravel and cobble materials. Varying rates of flow are introduced into a flume in which a given size class of gravel or cobble material is securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to develop regression equations for relating roughness coefficients to surface cover and Reynolds number. Accurate prediction of roughness coefficients for gravel and cobble surfaces will improve our ability to understand and properly model upland flow hydraulics.

Cultivators For Conservation Tillage, Robert Grisso, Paul J. Jasa, Elbert C. Dickey

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Cultivation, a proven weed control methods, should be used primarily to control weeds, rebuild ridges, or aerate poorly drained or crusted soils. Cultivating just to stir the soil usually dries the soil and can result in lower yields during drier cropping conditions. For example, cultivating during warm and windy conditions can result in ¼ to ¾ inches of soil moisture loss.

The main difference between a conservation tillage cultivator and a conventional cultivator is the ability to handle residue and penetrate the soil. By definition, conservation tillage should leave at least 30 percent of the soil surface covered with crop …

Definitions Of Tillage Systems For Corn, J. C. Siemens, Elbert C. Dickey, E. D. Threadgill

Department of Agricultural and Biological Systems Engineering: Faculty Publications

If "tillage" is defined as the mechanical manipulation of soil, it follows, then, that a "tillage system" would be the sequence of soil-manipulation operations performed in producing a crop. Today, however, such a definition is recognized as inadequate. We know, for instance, that the management of non-harvested plant tissue (i.e., residue) affects both crop production and soil erosion, and that field operations in which the soil is not tilled have a marked influence on soil condition.

Therefore, in this publication, a tillage system is the sequence of all operations involved in producing the crop, including soil manipulation, harvesting, chopping or …

A Conservation Tillage Educational Program, Elbert C. Dickey, Paul J. Jasa, David P. Shelton

Department of Agricultural and Biological Systems Engineering: Faculty Publications

An educational program was conducted to enhance the adoption of conservation tillage practices in targeted areas to reduce soil erosion and on-farm fuel use. Traditional extension methods such as meetings, field days, demonstrations, and plots were used extensively. In addition, the following nontraditional educational methods were used to achieve project objectives: targeting high priority areas, local program guidance committees, surveys to evaluate perceptions and use of conservation tillage, employment of extension assistants to work in the target areas, use of a rainfall simulator to demonstrate the effectiveness of residue cover in reducing erosion, and small group or "coffee shop" meetings …

Area Conservation Tillage Meetings-A Successful Educational Program, Elbert C. Dickey, Paul J. Jasa, David P. Shelton, Robert Grisso, Keith Glewen

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Interest in conservation tillage began to increase in the early 1980s, and farmers wanted information on how to adopt and manage various tillage and planting systems. Area conservation tillage meetings were developed by the University of Nebraska Cooperative Extension to provide the needed information on a regional basis. Local extension agents and Soil Conservation Service personnel helped extension specialists determine program content. The multidisciplinary meetings included farmer presentations and allowed space and time for commercial exhibits. About 80% of respondents to meeting evaluations indicated they planned to change their tillage practices as a result of the information presented.

Roughness Coefficients For Selected Residue Materials, John E. Gilley, Eugene R. Kottwitz, Gary A. Wieman

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Analysis of surface runoff on upland areas requires identification of roughness coefficients. A laboratory study is conducted to measure Darcy-Weisbach and Manning roughness coefficients for corn, cotton, peanut, pine needles, sorghum, soybeans, sunflower, and wheat residue. Varying rates of flow are introduced into a flume in which selected amounts of residue are securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to derive regression equations for relating roughness coefficients to Reynolds number and either percent residue cover or residue rate. Separate equations are developed for Reynolds number values from 500 …

Hydraulic Roughness Coefficients As Affected By Random Roughness, John E. Gilley, S. C. Finkner

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Random roughness parameters are used to characterize surface microrelief. In this study, random roughness was determined following six selected tillage operations. Random roughness measurements agreed closely with values reported in the literature.

Surface runoff on upland areas is analyzed using hydraulic roughness coefficients. Darcy-Weisbach and Manning hydraulic roughness coefficients were identified in this investigation on each soil surface where random roughness values were determined. Hydraulic roughness coefficients were obtained from measurements of discharge rat巳and flow velocity.

The experimental data were used to derive regression relationships which related Darcy-Weisbach and Manning hydraulic roughness coefficients to random roughness and Reynolds number. Random …

Peripheral Nerve Bridges For Central Nervous System Regeneration, Silvio Varon, Theo Hagg, H. Lee Vahlsing, Marston Manthorpe

Cells and Materials

A neuronotrophic hypothesis for the adult central nervous system (CNS) has been increasingly supported by in vivo studies of Nerve Growth Factor (NGF) impacts on adult rat CNS cholinergic neurons. We have extended these investigations to NGF effects on cholinergic axonal regeneration in an adult rat septo-hippocampal model. A fimbriafornix lesion deprives the dorsal hippocampal formation (HF) of its cholinergic afferents and provides a cavity into which sciatic nerve segments can be implanted to serve as regeneration bridges from septum to HF. Septa! cholinergic fibers enter and course through fresh cell-containing nerve bridges to attain a maximal number by the …

Primary Bone Formation In Porous Hydroxyapatite Ceramic: A Light And Scanning Electron Microscopic Study, M. Okumura, H. Ohgushi, S. Tamai, E. C. Shors

Cells and Materials

Porous hydroxyapatite ceramics combined with rat marrow cells were implanted subcutaneously in the back of syngeneic Fischer rats . Fluorochrome-labeling (calcein, tetracycline) was performed post-operatively and the ceramics were harvested 4 weeks after implantation. Undecalcified thin sections of the implants were observed under light microscopy or fluoromicroscopy and the corresponding areas were also analyzed in a scanning electron microscope connected to an electron probe microanalyzer (SEM-EPMA). Many pore areas of the ceramics showed bone and osteoid formation together with active osteoblasts. The bone formation began directly on the surface of the ceramic and proceeded in a centripetal direction towards the …

Deposition And Resorption Of Calcified Matrix In Vitro By Rat Marrow Cells, J. E. Davies, R. Chernecky, B. Lowenberg, A. Shiga

Cells and Materials

Rat bone marrow derived cells were cultured using a-Minimal Essential Medium supplemented with antibiotics, ascorbic acid and !3-glycerphosphate in the presence of 10-8M dexamethasone, on polystyrene and hydrophilic fluorocarbon substrata for periods of 2 - 4 weeks. During this time, a large yield of bone nodules was achieved and the elaborated tissue was examined by both scanning and transmission electron microscopy. The matrix produced by the cells contacting the underlying substratum was an afibrillar, globular, calcified material which formed a layer approximately 0.5μm thick. The calcium and phosphorus content of this material was confirmed by energy dispersive X-ray dot mapping …

Analysis Of Protein Adsorption On Retrieved Human Vascular Grafts Using Immunogold Labelling With Silver Enhancement, N. P. Ziats, N. S. Topham, D. A. Pankowsky, J. M. Anderson

Cells and Materials

The adsorption of proteins on biomedical materials such as vascular grafts is important in modulating thrombosis, one eventual cause of vascular graft failure. We have identified proteins expressed on the surfaces of retrieved vascular grafts to determine if certain proteins were present at the end stage of vascular failure. Scanning electron microscopic analysis of protein adsorption on the surfaces of retrieved vascular prostheses was determined using antibodies to human blood proteins fibrinogen, fibronectin, Hageman factor (factor XII) and factor VIII/von Willebrand Factor. The detection of these proteins on the blood contacting surface was evaluated by immunogold labelling with protein A-gold …

Scanning Electron Microscopic Evaluation Of The Fractured Surfaces Of Canine Calculi From Substrata With Different Surface Free Energy, H. M. W. Uyen, W. L. Jongebloed, H. J. Busscher

Cells and Materials

The strength of adhesion between dental calculus and enamel or dentin surfaces determines the ease with which the calculus can be removed by brushing or professional dental treatment. In this study, we examined the adhesion of canine calculi formed on substrata with different surface free energies (sfe) and roughness by means of scanning electron microscopy. In 4 beagle dogs fenestrated crowns were made on the upper fourth premolars. Subsequently, facings of glass (sfe = 120 mJ. m-2), bovine enamel (sfe = 85 mJ.m-2), bovine dentin (sfe = 92 mJ.m-2), polymethyl-methacrylate (PMMA, sfe = 56 mJ.m-2) and polytetrafluorethylene (PTFE, sfe = …

Polylysine Stimulation Of Ectopic Cartilage Formation, Rocky S. Tuan, Dina M. Turchi, David S. Kreitzer

Cells and Materials

Cartilage development, or chondrogenesis, is a process which involves the condensation of prechondrogenic mesenchymal cells, followed by the expression of the cartilage phenotype characterized by the biosynthesis of cartilage-specific, extracellular matrix components. We have previously shown that the cationic biopolymer, polylysine (PL), is able to stimulate chondrogenesis by embryonic limb bud mesenchymal cells in vitro. In this study, we have evaluated the chondrogenesis-stimulating activity of PL in vivo using an experimental system consisting of chick embryonic muscle explants, which were grafted onto the chorioallantoic membrane of chick embryos maintained in long-term shell-less culture. The muscle grafts were treated with PL …

A Versatile, Low Toxicity Glycol Methacrylate Embedding Medium For Use In Biological Research, And For Recovered Biomaterials Prostheses, Peter O. Gerrits, Bernhard Eppinger, Harry Van Goor, Richard W. Horobin

Cells and Materials

Methods for preparing standardized glycol methacrylate (GMA) based embedding media for use in light microscopy in a rational, precise and reproducible manner are described. The application of these procedures resulted in a versatile, low toxicity GMA embedding medium.

GMA embedding medium and resin blocks were tested utilizing a variety of physico-chemical techniques, namely: gas chromatography, determination of the maximum temperature reached during polymerization, the time taken to reach the maximum temperature, hardness testing, determination of the glass transition temperature, and measurement of the dimensional changes following section stretching and mounting at various temperatures. Data obtained from these techniques enabled a …

Fracture Toughness And Fractography Of Dental Ceramics, H. J. Mueller

Cells and Materials

Chevron-notch short-rod fracture toughness (KIv) and scanning electron microscopy analyses of leucite-, tetrasilicic fluormica-, and alumina- reinforced dental ceramics and control materials were investigated. Short-rod fracture toughness is a measure of the bulk resistance to crack propagation but not of the surface resistance to crack initiation. Results indicated significant differences in KIv among the following six groups (from lowest to highest (a) Dicor and Optec, (b) Optec, Excelco's Incisal, Macor and Excelco's Gingival, (c) Excelco's Brush-O-Paque, (d) Vitadur-N core, (e) Coming's 9606 glass-ceramic, and (t) Vita Hi Ceram. Good agreement occurred with published data for Macor and 9606. Comparisons of …

Composite Filler Characterization By Scanning Electron Microscopy, Image Analysis And Thermogravimetry, J. Vaidyanathan, T. K. Vaidyanathan

Cells and Materials

The morphological and compositional characterization of the filler particles in selected dental composites has been accomplished by a combination of backscattered electron imaging, digital imaging , energy dispersive X-ray analysis and thermogravimetry. Backscattered electron images provide excellent composition contrast between the filler and the matrix in this analysis . Qualitative energy dispersive spectroscopy was used to classify the filler composition in the composites studied. The digital imaging technique of feature analysis was utilized to quantitatively characterize the particle morphological parameters and their distributions. Several parameters were determined of which the particle area, breadth, height and Waddel diameter are emphasized. Particle …

Adhesion Of Staphylococci To Breast Prosthesis Biomaterials: An Electron Microscopic Evaluation, T. A. Fassel, J. E. Van Over, C. C. Hauser, C. E. Edmiston, J. R. Sanger

Cells and Materials

Gram-positive coagulase-negative staphylococci have been implicated in breast prosthesis infection. Staphylococcus au re us, Staphylococcus epidermidis, and Staphylococcus hominis strains were examined for adhesion and proliferation morphology to polyurethane foam and smooth silicone rubber prosthetic biomaterials. Ruthenium red, alcian blue and ruthenium red-lysine in en bloc procedures were applied to optimally visualize the polysaccharide slime. Ruthenium red processing resulted in observation of additional outer material close to the cell wall, more than seen in the absence of cationic reagent. Alcian blue preserved fibrous or netlike strands or meshworks of material. Ruthenium red-lysine preserved considerable amounts of slime covering the cocci …

The Articular Cartilage Of The Rabbit Knee: A Scanning Electron Microscopy Study, Daniel Levanon, Haim Stein

Cells and Materials

The surface morphology of eight sectors in the rabbit knee articular cartilage was studied using scanning electron microscopy. Cartilage surfaces showed wide variation in the shape, dimensions , and density of gaps and acellular processes. Patellas and load-bearing condyles revealed a relatively higher density of processes than did load-free condyles. Surface processes and gaps were abundant. They might represent a condensation product(s) of hyaluronic acid/protein complex that accrues during cycles of loading/weight bearing.

Preservation Of The Cell-Biomaterial Interface At The Ultrastructural Level, J. M. Schakenraad, J. A. Oosterbaan, E. H. Blaauw

Cells and Materials

Studying the tissue-biomaterial interface at the ultrastructural level is not without problems. Dissolution of the biomaterial in one of the dehydration or embedding media causes holes and shatter during sectioning or dislodgement of the biomaterial. The fine tuning of the hardness of both biomaterial and embedding medium, as well as the introduction of butyl-2,3- epoxypropylether as an intermediate between the dehydration series and the Epon resin , improving the impregnation , will solve many of the problems mentioned. With this improved technique good results were obtained with materials ranging from teflon, poly(Lactic acid) and polyurethanes to tissue culture polystyrene. No …

Adhesion And Spreading Of Human Fibroblasts On Superhydrophobic Fep-Teflon, H. J. Busscher, I. Stokroos, J. G. Golverdingen, J. M. Shakenraad

Cells and Materials

Adhesion and spreading of human fibroblasts was studied on hydrophobized and hydrophilized FEPTeflon, and compared with adhesion and spreading on untreated FEP-Teflon and Tissue culture polystyrene (TCPS). Superhydrophobic FEP-Teflon was prepared by ion etching followed by oxygen glow-discharge. Hydrophilic PEP-Teflon was prepared by ion etching only. Water contact angles of the modified surfaces were 140- 1500 and 5-10° for the hydrophobic and the hydrophilic variant, respectively. (Untreated FEP-Teflon: 109°). Spreading of human skin fibroblasts significantly increased on hydrophilic FEP-Teflon (257 μm2 per cell), whereas a significant decrease was observed on superhydrophobic FEP-Teflon (158 μm2 per cell), as compared to untreated …

Surface Modification Of Polymers To Permit Endothelial Cell Growth, C. James Kirkpatrick, Detlef Mueller-Schulte, Marc Roye, Guenter Hollweg, Claudia Gossen, Horst Richter, Christian Mittermayer

Cells and Materials

The interaction between endothelial cells (EC) and polymers has become relevant to medicine as a result of attempts to improve the biocompatibility of vascular prostheses. In man, endothelialization is minimal, so that vascular surgeons have attempted to pre-seed vascular grafts with autologous EC. The poor results of EC seeding of commonly used materials for vascular grafts, such as expanded polytetrafluoroethylene (ePTFE) or woven polyester (Dacron) has led to attempts to modify the surface of these and other polymers. Three principal modification techniques have been employed : 1. adsorption of bioactive molecules from applied solutions. Examples are fibronectin, collagen types I …

Dusts Produced During Cutting Of Modern Splinting Bandages, R. Wytch, D. W. Gregory, R. Clayton, D. Wardlaw

Cells and Materials

Previous work carried out by the authors (Wytch et al ., 1988a) has shown that airborne dust generated during removal of orthopaedic casts with a power saw could represent a respiratory hazard. Further work has been carried out on all types of splinting bandage currently available in the United Kingdom to assess the potential dust hazard when sawing these materials. It has been shown that although plaster of Paris bandage produces significant concentrations of airborne dust, most of the polyurethane-impregnated fabric bandages generate extremely low levels of dust and in the case of the non-glass fabrics, the level is insignificant. …

A Simple Method For Ultrastructural Evaluation Of Fragile Collagenous Biomaterials, Arthur J. Wasserman, Yasushi P. Kato, Frederick H. Silver

Cells and Materials

No abstract provided.

Peripheral Nerve Regeneration Within Tubular Prosthesis: Effects Of Laminin And Collagen Matrices On Cellular Ingrowth, Ivar J. Kljavin, Roger D. Madison

Cells and Materials

Bridging a severed peripheral nerve with a tubular conduit, "entubulation repair" , allows manipulation of the microenvironment encountered by regenerating axons. In the present study, we placed the ends of severed mouse sciatic nerves into nonpermeable Tygon tubes to bridge a 4 mm nerve gap. The tube lumen was filled with either a collagen or laminin matrix. The matrices formed a stable 3-D structure connecting both proximal and distal stumps, and provided a scaffolding for the regenerating axons and their supporting cells. We examined with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy, the initial events of …

Ultrastructural Study Of Bone Formation On Synthetic Hydroxyapatite In Osteoblast Cultures, J. M. Sautier, J. R. Nefussi, N. Forest

Cells and Materials

Collagenase isolated rat calvaria cells forming a mineralized matrix in vitro were cultured in the presence of synthetic hydroxyapatite. Interactions between bone cells and hydroxyapatite biomaterial were followed by transmission electron microscopy. The appearance of a granular, collagen free, electron-dense layer at the periphery of the material was noted initially. Progressively, an amorphous, granular material formed and extended between the hydroxyapatite aggregates. Osteoblastic cells then synthesized an osteoid matrix which mineralized on the first formed granular collagen free layer, following a classical pattern of calcification . Demineralization of ultrathin sections confirmed the presence of this interface between the material and …