Bonded, Thin-Lift, Non-Reinforced Portland Cement Concrete Resurfacing, MLR-77-2, 1977

A research project involving 2, 3, 4, and 5 in. (5.1, 7.6, 10.2, and 12.7 cm) of bonded portland cement concrete (PCC) overlay on a 1.3 mile (2.1 km) PCC pavement was conducted in Clayton County, Iowa, during September 1977, centering on the following objectives: (1) Determine the mixing and proportioning procedures required in using a conventional, central mix proportioning plant to produce a dense PCC mixture using standard mixes with super water reducing admixtures; (2) Determine the economics, longevity and maintenance performance of a bonded, thin-lift, non-reinforced PCC resurfacing course using conventional procedures, equipment and concrete paving mixtures both with and without super water reducing admixtures; and (3) Determine if an adequate bond between the existing pavement and an overlay of thin-lift, dense, non-reinforced PCC can be obtained with only special surface cleaning and no surface removal or grinding. The conclusions are as follows: (1) Normal mixing equipment and proportioning procedures could be used using a conventional central-mix proportioning plant. This was successful when used with super water reducing admixtures. Only minor changes need be made in procedures and timing. (2) The time has been too short since the completion of the project to determine how the new pavement will perform, however, initially it appears that the method is economical and no reason is seen at this time why the life of the pavement should not be comparable to an all new pavement. (3) The initial test results show that bond strength, regardless of which method of cleaning is used, scarifying, sand blasting or water blasting, far exceed what is considered the minimum bond strength of 200 psi (1379 kPa) except where the paint stripes were intentionally left, thus showing that the paint must be removed. (4) It appears that either cement and water grout or sand, cement and water grout may be used and still obtain the required bond.

Retaining Wall - Modular Unit Reinforced Earth Tensar Geogrid Reinforcement, HR-549, 1998

This research, initiated in October 1992, was located at the intersection of Blairs Ferry Road and Lindale Drive in the City of Marion. The wall is located on the southeast corner of the intersection. Reinforced retaining wall construction started with a five inch base of roadstone with one inch of sand for leveling purposes. One and one-half to two feet of one inch clean stone was placed behind the blocks. A four inch perforated plastic pipe was placed approximately nine inches from the bottom of the one inch clean stone. The Tenswal, tensar geogrid was placed at every third layer. Openings in the Tenswal are hooked over plastic dowels in the blocks. The tenswal reaches from the face of the wall back 5' to 8'. The cost for constructing this wall was $124,400. The wall has performed well for the past five years. The wall improves the aesthetics of a high traffic volume intersection of an urban area. Many positive comments have been received by the city regarding its appearance. The City of Marion has been pleased with the wall and has used this type of wall on subsequent projects.

Bonded, Thin-Lift, Non-Reinforced Portland Cement Concrete Resurfacing, HR-191, 1980

A Research Project involving two, three, four and five inches of bonded Portland Cement Concrete Overlay on a 1.3 mile Portland Cement Concrete pavement was conducted in Clayton County, Iowa, during September, 1977, centering on the following objectives: 1. Determine the mixing and proportioning procedures required in using a conventional, central mix proportioning plant to produce a dense Portland Cement Concrete mixture using standard mixes with super-water reducing admixtures; 2. Determine the economics, longevity and maintenance performance of a bonded, thin-lift, non-reinforced Portland Cement Concrete resurfacing course using conventional procedures, equipment and concrete paving mixtures both with and without super-water reducing admixtures; 3. Determine if an adequate bond between the existing pavement and an overlay of thin-lift, dense, non-reinforced Portland Cement Concrete can be obtained with only special surface cleaning and no surface removal or grinding.

Reinforced Earth and Stone Columns for Weak Subsoil Conditions, HR-510, 1980

Reinforced Earth is a French development that has been used in the United States for approximately ten years. Virbro-Replacement, more commonly referred to as stone columns, is an outgrowth of deep densification of cohesionless soils originally developed in Germany. Reinforced Earth has applicability when wall height is greater than about twelve feet and deep seated foundation failure is not a concern. Stone columns are applicable when soft, cohesive subsoil conditions are encountered and bearing capacity and shearing resistance must be increased. The conditions in Sioux City on Wesley Way can be summarized as: (1) restricted right of way, (2) fill height in excess of 25 feet creating unstable conditions, (3) adjacent structures that could not be removed. After analyzing alternatives, it was decided that Reinforced Earth walls constructed on top of stone columns were the most practical approach.

Detection of Steel Corrosion in Bridge Decks and Reinforced Concrete Pavement, HR-156, 1977

The Iowa Department of Transportation initiated this research to evaluate the reliability, benefit and application of the corrosion detection device. Through field testing prior to repair projects and inspection at the time of repair, the device was shown to be reliable. With the reliability established, twelve additional devices were purchased so that this evaluation procedure could be used routinely on all repair projects. The corrosion detection device was established as a means for determining concrete removal for repair. Removal of the concrete down to the top reinforcing steel is required for all areas exhibiting electrical potentials greater than 0.45 Volt. It was determined that the corrosion detection device was not applicable to membrane testing. The corrosion detection device has been used to evaluate corrosion of reinforcing steel in continuously reinforced concrete pavement.

A Ten Year Performance Summary of Fibrous PC Concrete Overlay Research in Greene County, Iowa, HR-165, 1984

The Greene County, Iowa, overlay project, completed in October, 1973, was evaluated in October, 1978, after five years of service and most recently in October, 1983, after ten years of service. The 33 fibrous concrete sections, four CRCP sections, two mesh reinforced and two plain concrete sections with doweled reinforcement were rated relative to each other on a scale of 0 to 100. The rating was conducted by original members of the Project Planning Committee, Iowa DOT, Iowa County, Federal Highway Administration, University of Illinois and industry representatives. In all, there were 23 and 24 representatives who rated the project in 1978 and 1983 respectively. The 23 or 24 values were then averaged to provide a final rating number for each section or variable. All experimental overlay sections had performed quite well in the period from five through 10 years, experiencing only limited additional deterioration. Based upon this relatively good performance through 10 years, the sections will be maintained for further research with another evaluation at 15 years. The 4" thick nonfibrous mesh reinforced continuous reinforced concrete pavement overlay sections provided the best performance in this research project. Another nonfibrous 5" thick bar reinforced overlay section performed almost as well. The best performance of a fibrous reinforced concrete section was obtained with 160 pounds of fiber per cubic yard.

The geometric structure of the brain fiber pathways.

The structure of the brain as a product of morphogenesis is difficult to reconcile with the observed complexity of cerebral connectivity. We therefore analyzed relationships of adjacency and crossing between cerebral fiber pathways in four nonhuman primate species and in humans by using diffusion magnetic resonance imaging. The cerebral fiber pathways formed a rectilinear three-dimensional grid continuous with the three principal axes of development. Cortico-cortical pathways formed parallel sheets of interwoven paths in the longitudinal and medio-lateral axes, in which major pathways were local condensations. Cross-species homology was strong and showed emergence of complex gyral connectivity by continuous elaboration of this grid structure. This architecture naturally supports functional spatio-temporal coherence, developmental path-finding, and incremental rewiring with correlated adaptation of structure and function in cerebral plasticity and evolution.

Brittle to ductile transition in a fiber bundle with strong heterogeneity

We analyze the failure process of a two-component system with widely different fracture strength in the framework of a fiber bundle model with localized load sharing. A fraction 0≤α≤1 of the bundle is strong and it is represented by unbreakable fibers, while fibers of the weak component have randomly distributed failure strength. Computer simulations revealed that there exists a critical composition αc which separates two qualitatively different behaviors: Below the critical point, the failure of the bundle is brittle, characterized by an abrupt damage growth within the breakable part of the system. Above αc, however, the macroscopic response becomes ductile, providing stability during the entire breaking process. The transition occurs at an astonishingly low fraction of strong fibers which can have importance for applications. We show that in the ductile phase, the size distribution of breaking bursts has a power law functional form with an exponent μ=2 followed by an exponential cutoff. In the brittle phase, the power law also prevails but with a higher exponent μ=92. The transition between the two phases shows analogies to continuous phase transitions. Analyzing the microstructure of the damage, it was found that at the beginning of the fracture process cracks nucleate randomly, while later on growth and coalescence of cracks dominate, which give rise to power law distributed crack sizes.

Development of Craniofacial Bone Defect Reconstruction Implant Based on Fibre-Reinforced Composite with Photopolymerisable Resin Systems. Experimental studies in vitro and in vivo.

Reconstruction of defects in the craniomaxillofacial (CMF) area has mainly been based on bone grafts or metallic fixing plates and screws. Particularly in the case of large calvarial and/or craniofacial defects caused by trauma, tumours or congenital malformations, there is a need for reliable reconstruction biomaterials, because bone grafts or metallic fixing systems do not completely fulfill the criteria for the best possible reconstruction methods in these complicated cases. In this series of studies, the usability of fibre-reinforced composite (FRC) was studied as a biostable, nonmetallic alternative material for reconstructing artificially created bone defects in frontal and calvarial areas of rabbits. The experimental part of this work describes the different stages of the product development process from the first in vitro tests with resin-impregnated fibrereinforced composites to the in vivo animal studies, in which this FRC was tested as an implant material for reconstructing different size bone defects in rabbit frontal and calvarial areas. In the first in vitro study, the FRC was polymerised in contact with bone or blood in the laboratory. The polymerised FRC samples were then incubated in water, which was analysed for residual monomer content by using high performance liquid chromatography (HPLC). It was found that this in vitro polymerisation in contact with bone and blood did not markedly increase the residual monomer leaching from the FRC. In the second in vitro study, different adhesive systems were tested in fixing the implant to bone surface. This was done to find an alternative implant fixing system to screws and pins. On the basis of this study, it was found that the surface of the calvarial bone needed both mechanical and chemical treatments before the resinimpregnated FRC could be properly fixed onto it. In three animal studies performed with rabbit frontal bone defects and critical size calvarial bone defect models, biological responses to the FRC implants were evaluated. On the basis of theseevaluations, it can be concluded that the FRC, based on E-glass (electrical glass) fibres forming a porous fibre veil enables the ingrowth of connective tissues to the inner structures of the material, as well as the bone formation and mineralization inside the fibre veil. Bone formation could be enhanced by using bioactive glass granules fixed to the FRC implants. FRC-implanted bone defects healed partly; no total healing of defects was achieved. Biological responses during the follow-up time, at a maximum of 12 weeks, to resin-impregnated composite implant seemed to depend on the polymerization time of the resin matrix of the FRC. Both of the studied resin systems used in the FRC were photopolymerised and the heat-induced postpolymerisation was used additionally.

Fiber Laser Cutting of Mild Steel

Fiber laser for materials processing have undergone a rapid development in the pastseveral years. As fiber laser provides a combination of high beam quality and awavelength that is easily absorbed by metal surfaces, the named future laser isexpected to challenge the CO2 and Nd:YAG lasers in the area of metal cutting. This thesis studied the performance of fiber laser cutting mild steel. In the literature review part, it introduced the laser cutting principle and the principle of fiber laser including the newest development of fiber laser cuttingtechnology. Because the fiber laser cutting mild steel is a very young technology, a preliminary test was made in order to investigate effect of the cutting parameters on cut quality. Then the formal fiber laser cutting experiment was madeby using 3 mm thickness S355 steel with oxygen as assistant gas. The experimentwas focused on the cut quality with maximum cutting speed and minimum oxygen gas pressure. And the cut quality is mainly decided by the kerf width, perpendicularity tolerance, surface roughness and striation patterns. After analysis the cutting result, several conclusions were made. Although the best result got in the experiment is not perfect as predicted, the whole result of the test can be accepted. Compared with CO2 laser, a higher cutting speed was achieved by fiber laser with very low oxygen gas pressure. A further improvement about the cutting quality might be possible by proper selection of process parameters. And in order to investigate the cutting performance more clearly, a future study about cutting different thickness mild steel and different shape was recommended.

Development of a hepatocyte hollow fiber bioreactor for the study of contrast agents by magnetic resonance imaging

Thanks to the continuous progress made in recent years, medical imaging has become an important tool in the diagnosis of various pathologies. In particular, magnetic resonance imaging (MRI) permits to obtain images with a remarkably high resolution without the use of ionizing radiation and is consequently widely applied for a broad range of conditions in all parts of the body. Contrast agents are used in MRI to improve tissue discrimination. Different categories of contrast agents are clinically available, the most widely used being gadolinium chelates. One can distinguish between extracellular gadolinium chelates such as Gd-DTPA, and hepatobiliary gadolinium chelates such as Gd-BOPTA. The latter are able to enter hepatocytes from where they are partially excreted into the bile to an extent dependent on the contrast agent and animal species. Due to this property, hepatobiliary contrast agents are particularly interesting for the MRI of the liver. Actually, a change in signal intensity can result from a change in transport functions signaling the presence of impaired hepatocytes, e.g. in the case of focal (like cancer) or diffuse (like cirrhosis) liver diseases. Although the excretion mechanism into the bile is well known, the uptake mechanisms of hepatobiliary contrast agents into hepatocytes are still not completely understood and several hypotheses have been proposed. As a good knowledge of these transport mechanisms is required to allow an efficient diagnosis by MRI of the functional state of the liver, more fundamental research is needed and an efficient MRI compatible in vitro model would be an asset. So far, most data concerning these transport mechanisms have been obtained by MRI with in vivo models or by a method of detection other than MRI with cellular or sub-cellular models. Actually, no in vitro model is currently available for the study and quantification of contrast agents by MRI notably because high cellular densities are needed to allow detection, and no metallic devices can be used inside the magnet room, which is incompatible with most tissue or cell cultures that require controlled temperature and oxygenation. The aim of this thesis is thus to develop an MRI compatible in vitro cellular model to study the transport of hepatobiliary contrast agents, in particular Gd-BOPTA, into hepatocytes directly by MRI. A better understanding of this transport and especially of its modification in case of hepatic disorder could permit in a second step to extrapolate this knowledge to humans and to use the kinetics of hepatobiliary contrast agents as a tool for the diagnosis of hepatic diseases.

The effect of oxygen delignification on fiber properties in kraft pulp production - a review

Fiber damages comprise fiber deformations, characterized as fiber curl, kink, dislocations and strength losses as well as some yet unidentified factors. This recently discovered phenomenon is especially evident in mill scale kraftpulps. Laboratory produced pulps tend to have less damages and superior strength properties compared to those produced in pulp mills. Generally fiber damages pose a problem in the production of reinforcement pulp because they tend to decrease the ability of fibers to transmit load. Previous studies on fiber damage have shown that most of the fiber damages occur during brown stock processing starting from cooking and discharging. This literature review gives an overall picture on fiber damages occurring during softwood kraft pulp production with an emphasis on the oxygen delignification stage. In addition the oxygen delignification stage itself is described in more detailed extent in order to understand the mechanisms behind the delignification and fiber damaging effect. The literature available on this subject is unfortunately quite contradictory and implicates a lotof different terms. Only a few studies have been published which help to understand the nature of fiber damages. For that reason the knowledge presented in this work is not only based on previous studies but also on research scientist and mill staff interviews.

Fibre-reinforced composites as root canal posts

Fibre-reinforced composite (FRC) root canal posts are suggested to have biomechanical benefits over traditional metallic posts, but they lack good adhesion to resin composites. The aim of this series of studies was to evaluate the adhesion of individually formed fibre-reinforced composite material to composite resin and dentin, as well as some mechanical properties. Flexural properties were evaluated and compared between individually formed FRC post material and different prefabricated posts. The depth of polymerization of the individually formed FRC post material was evaluated with IR spectrophotometry and microhardness measurements, and compared to that of resin without fibres. Bonding properties of the individually formed FRC post to resin cements and dentin were tested using Pull-out- and Push-out-force tests, evaluated with scanning electron microscopy, and compared to those of prefabricated FRC and metal posts. Load-bearing capacity and microstrain were evaluated and failure mode assessment was made on incisors restored with individually formed FRC posts of different structures and prefabricated posts. The results of these studies show that the individually polymerized and formed FRC post material had higher flexural properties compared to the commercial prefabricated FRC posts. The individually polymerized FRC material showed almost the same degree of conversion after light polymerization as monomer resin without fibres. Moreover, it was found that the individually formed FRC post material with a semiinterpenetrating polymer network (IPN) polymer matrix bonded better to composite resin luting cement, than did the prefabricated posts with a cross-linked polymer matrix. Furthermore, it was found that, contrary to the other posts, there were no adhesive failures between the individually formed FRC posts and composite resin luting cement. This suggests better interfacial adhesion of cements to these posts. Although no differences in load-bearing capacity or microstrain could be seen, the incisors restored with individually formed FRC posts with a hollow structure showed more favourable failures compared to other prefabricated posts. These studies suggest that it is possible to use individually formed FRC material with semi-IPN polymer matrix as root canal post material. They also indicate that there are benefits especially regarding the bonding properties to composite resin and dentin with this material compared to prefabricated FRC post material with a cross-linked matrix. Furthermore, clinically more repairable failures were found with this material compared to those of prefabricated posts.

Caloric restriction induces energy-sparing alterations in skeletal muscle contraction, fiber composition and local thyroid hormone metabolism that persist during catch-up fat upon refeeding.

Weight regain after caloric restriction results in accelerated fat storage in adipose tissue. This catch-up fat phenomenon is postulated to result partly from suppressed skeletal muscle thermogenesis, but the underlying mechanisms are elusive. We investigated whether the reduced rate of skeletal muscle contraction-relaxation cycle that occurs after caloric restriction persists during weight recovery and could contribute to catch-up fat. Using a rat model of semistarvation-refeeding, in which fat recovery is driven by suppressed thermogenesis, we show that contraction and relaxation of leg muscles are slower after both semistarvation and refeeding. These effects are associated with (i) higher expression of muscle deiodinase type 3 (DIO3), which inactivates tri-iodothyronine (T3), and lower expression of T3-activating enzyme, deiodinase type 2 (DIO2), (ii) slower net formation of T3 from its T4 precursor in muscles, and (iii) accumulation of slow fibers at the expense of fast fibers. These semistarvation-induced changes persisted during recovery and correlated with impaired expression of transcription factors involved in slow-twitch muscle development. We conclude that diminished muscle thermogenesis following caloric restriction results from reduced muscle T3 levels, alteration in muscle-specific transcription factors, and fast-to-slow fiber shift causing slower contractility. These energy-sparing effects persist during weight recovery and contribute to catch-up fat.