Procedure for human saphenous veins ex vivo perfusion and external reinforcement.

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex vivo perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex vivo conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. I, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Characterization of slope failures is complicated, because the factors affecting slope stability can be difficult to discern and measure, particularly soil shear strength parameters. While in the past extensive research has been conducted on slope stability investigations and analysis, this research consists of field investigations addressing both the characterization and reinforcement of such slope failures. The current research focuses on applying an infrequently-used testing technique comprised of the Borehole Shear Test (BST). This in-situ test rapidly provides effective (i.e., drained) shear strength parameter values of soil. Using the BST device, fifteen Iowa slopes (fourteen failures and one proposed slope) were investigated and documented. Particular attention was paid to highly weathered shale and glacial till soil deposits, which have both been associated with slope failures in the southern Iowa drift region. Conventional laboratory tests including direct shear tests, triaxial compression tests, and ring shear tests were also performed on undisturbed and reconstituted soil samples to supplement BST results. The shear strength measurements were incorporated into complete evaluations of slope stability using both limit equilibrium and probabilistic analyses. The research methods and findings of these investigations are summarized in Volume 1 of this report. Research details of the independent characterization and reinforcement investigations are provided in Volumes 2 and 3, respectively. Combined, the field investigations offer guidance on identifying the factors that affect slope stability at a particular location and also on designing slope reinforcement using pile elements for cases where remedial measures are necessary. The research findings are expected to benefit civil and geotechnical engineers of government transportation agencies, consultants, and contractors dealing with slope stability, slope remediation, and geotechnical testing in Iowa.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. II, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. While in the past extensive research has been conducted on slope stability investigations and analysis, this current research study consists of field investigations addressing both the characterization and reinforcement of such slope failures. While Volume I summarizes the research methods and findings of this study, Volume II provides procedural details for incorporating an infrequently-used testing technique, borehole shear tests, into practice. Fifteen slopes along Iowa highways were investigated, including thirteen slides (failed slopes), one unfailed slope, and one proposed embankment slope (the Sugar Creek Project). The slopes are mainly comprised of either clay shale or glacial till, and are generally gentle and of small scale, with slope angle ranging from 11 deg to 23 deg and height ranging from 6 to 23 m. Extensive field investigations and laboratory tests were performed for each slope. Field investigations included survey of slope geometry, borehole drilling, soil sampling, in-situ Borehole Shear Testing (BST) and ground water table measurement. Laboratory investigations mainly comprised of ring shear tests, soil basic property tests (grain size analysis and Atterberg limits test), mineralogy analyses, soil classifications, and natural water contents and density measurements on the representative soil samples from each slope. Extensive direct shear tests and a few triaxial compression tests and unconfined compression tests were also performed on undisturbed soil samples for the Sugar Creek Project. Based on the results of field and lab investigations, slope stability analysis was performed on each of the slopes to determine the possible factors resulting in the slope failures or to evaluate the potential slope instabilities using limit equilibrium methods. Deterministic slope analyses were performed for all the slopes. Probabilistic slope analysis and sensitivity study were also performed for the slope of the Sugar Creek Project. Results indicate that while the in-situ test rapidly provides effective shear strength parameters of soils, some training may be required for effective and appropriate use of the BST. Also, it is primarily intended to test cohesive soils and can produce erroneous results in gravelly soils. Additionally, the quality of boreholes affects test results, and disturbance to borehole walls should be minimized before test performance. A final limitation of widespread borehole shear testing may be its limited availability, as only about four to six test devices are currently being used in Iowa. Based on the data gathered in the field testing, reinforcement investigations are continued in Volume III.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. III, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Volume I of this current study summarizes research methods and findings, while Volume II provides procedural details for incorporating into practice an infrequently-used testing technique–borehole shear tests. Volume III of this study of field investigation of fifteen slopes in Iowa demonstrates through further experimental testing how lateral forces develop along stabilizing piles to resist slope movements. Results establish the feasibility of an alternative stabilization approach utilizing small-diameter pile elements. Also, a step-by-step procedure that can be used by both state and county transportation agencies to design slope reinforcement using slender piles is documented. Initial evidence of the efficiency and cost-effectiveness of stabilizing nuisance slope failures with grouted micropiles is presented. Employment of the remediation alternative is deemed more appropriate for stabilizing shallow slope failures. Overall, work accomplished in this research study included completing a comprehensive literature review on the state of the knowledge of slope stability and slope stabilization, the preparation and performance of fourteen full-scale pile load tests, the analysis of load test results, and the documentation of a design methodology for implementing the technology into current practices of slope stabilization. Recommendations for further research include monitoring pilot studies of slope reinforcement with grouted micropiles, supplementary experimental studies, and advanced numerical studies.

Thermoset Composite Concrete Reinforcement, HR-325, Part 1, 1992

The feasibility of substituting fibercomposite (FC) (thermoset) pavement dowels for steel pavement dowels was investigated in this research project. Load transfer capacity, flexural capacity, and material properties were examined. The objectives of Part 1 of this final report included the shear behavior and strength deformations of FC dowel bars without aging. Part 2 will contain the aging effects. This model included the effects of modulus of elasticity for the pavement dowel and concrete, dowel diameter, subgrade stiffness, and concrete compressive strength. An experimental investigation was carried out to establish the modulus of dowel support which is an important parameter for the analysis of dowels. The experimental investigation included measured deflections, observed behavioral characteristics, and failure mode observations. An extensive study was performed on various shear testing procedures. A modified Iosipescu shear method was selected for the test procedure. Also, a special test frame was designed and fabricated for this procedure. The experimental values of modulus of support for shear and FC dowels were used for arriving at the critical stresses and deflections for the theoretical model developed. Different theoretical methods based on analyses suggested by Timoshenko, Friberg, Bradbury, and Westergaard were studied and a comprehensive theoretical model was developed. The fibercomposite dowels were found to provide strengths and behavioral characteristics that appear promising as a potential substitute for steel dowels.

Mediastinal reinforcement after induction therapy and pneumonectomy: comparison of intercostal muscle versus diaphragm flaps.

OBJECTIVE: Prospective non-randomised comparison of full-thickness pedicled diaphragm flap with intercostal muscle flap in terms of morbidity and efficiency for bronchial stump coverage after induction therapy followed by pneumonectomy for non-small cell lung cancer (NSCLC). METHODS: Between 1996 and 1998, a consecutive series of 26 patients underwent pneumonectomy following induction therapy. Half of the patients underwent mediastinal reinforcement by use of a pedicled intercostal muscle flap (IF) and half of the patients by use of a pedicled full-thickness diaphragm muscle flap (DF). Patients in both groups were matched according to age, gender, side of pneumonectomy and stage of NSCLC. Postoperative morbidity and mortality were recorded. Six months follow-up including physical examination and pulmonary function testing was performed to examine the incidence of bronchial stump fistulae, gastro-esophageal disorders or chest wall complaints. RESULTS: There was no 30-day mortality in both groups. Complications were observed in one of 13 patients after IF and five of 13 after DF including pneumonia in two (one IF and one DF), visceral herniations in three (DF) and bronchopleural fistula in one patient (DF). There were no symptoms of gastro-esophageal reflux disease (GERD). Postoperative pulmonary function testing revealed no significant differences between the two groups. CONCLUSIONS: Pedicled intercostal and diaphragmatic muscle flaps are both valuable and effective tools for prophylactic mediastinal reinforcement following induction therapy and pneumonectomy. In our series of patients, IF seemed to be associated with a smaller operation-related morbidity than DF, although the difference was not significant. Pedicled full-thickness diaphragmatic flaps may be indicated after induction therapy and extended pneumonectomy with pericardial resection in order to cover the stump and close the pericardial defect since they do not adversely influence pulmonary function.

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.

Speciation genetics: reinforcement by shades and hues.

Mating with a member of another species can seriously reduce an organism's fitness, so mechanisms ought to evolve to prevent it where hybridizing species meet. This old idea of 'reinforcement' has found new support in an elegant pair of studies of the ecological genetics of flower colour in an annual herb.

Thermoset Composite Concrete Reinforcement, HR-325, Part 2, 1992

This is the second part of the final report submitted to the Iowa Department of Transportation. Part 1 contained a comparison of unaged fiber composite and steel dowels and derivation of the appropriate theoretical model for analyzing the results. Part 2 of this final report covers the theoretical and experimental models for accelerated aging of fiber composite reinforcing bars and dowels cast in a concrete environment. Part 2 contains results from testing of unaged and aged fiber composite dowels and steel dowels, in addition to unaged and aged fiber composite reinforcing bars. Additional tests have been performed on unaged dowels (both steel and fibercomposite) to verify results from Part 1 and to keep the testing program consistent. Slight modifications have been made to the dowel specimens presented in Part 1. These modifications are noted in the Section 3.4 of this report. The flexural modulus of elasticity for the FC dowel bar given in Part 1 of the final report (Table 3. 2) was for the incorrect structural shape (non-circular cross section). The value is corrected and given in Part 2 of the final report (Table 3.4 for the.modulus of elasticity supplied by the manufacturer, and Tables 3. 5 and 3. 6 for experimentally determined modulus of elasticities) • The value in Part 1 was not used for any analysis of the FC dowel bars.

Demonstration and Field Evaluation of Alternative Portland Cement Concrete Pavement Reinforcement Materials, HR-1069, 2003

Transverse joints are placed in portland cement concrete pavements to control the development of random cracking due to stresses induced by moisture and thermal gradients and restrained slab movement. These joints are strengthened through the use of load transfer devices, typically dowel bars, designed to transfer load across the joint from one pavement slab to the next. Epoxy coated steel bars are the materials of choice at the present time, but have experienced some difficulties with resistance to corrosion from deicing salts. The research project investigated the use of alternative materials, dowel size and spacing to determine the benefits and limitations of each material. In this project two types of fiber composite materials, stainless steel solid dowels and epoxy coated dowels were tested for five years in side by side installation in a portion of U.S. 65 near Des Moines, Iowa, between 1997 and 2002. The work was directed at analyzing the load transfer characteristics of 8-in. vs. 12-in. spacing of the dowels and the alternative dowel materials, fiber composite (1.5- and 1.88-in. diameter) and stainless steel (1.5-in. diameter), compared to typical 1.5-in. diameter epoxy-coated steel dowels placed on 12-in. spacing. Data were collected biannually within each series of joints and variables in terms of load transfer in each lane (outer wheel path), visual distress, joint openings, and faulting in each wheel path. After five years of performance the following observations were made from the data collected. Each of the dowel materials is performing equally in terms of load transfer, joint movement and faulting. Stainless steel dowels are providing load transfer performance equal to or greater than epoxy-coated steel dowels at the end of five years. Fiber reinforced polymer (FRP) dowels of the sizes and materials tested should be spaced no greater than 8 in. apart to achieve comparable performance to epoxy coated dowels. No evidence of deterioration due to road salts was identified on any of the products tested. The relatively high cost of stainless steel solid and FRP dowels was a limitation at the time of this study conclusion. Work is continuing with the subject materials in laboratory studies to determine the proper shape, spacing, chemical composition and testing specification to make the FRP and stainless (clad or solid) dowels a viable alternative joint load transfer material for long lasting portland cement concrete pavements.

Performance of Reinforcement Fabric Used Under Asphaltic Concrete Overlays, MLR-83-03, 1983

The 1982 cost of a two-inch asphaltic concrete overlay, with fabric, was an average of 85% of the cost of a three-inch overlay (see attached calculations). A structural number can be assigned to the extra inch of overlay, whereas it is doubtful that any number can be assigned to the fabric. The observations made on the projects in this report leave little reason to be optimistic on the use of fabrics under asphalt overlays. This is especially true of the Floyd, Dallas and Clarke county projects. A great amount of fabric is being used nationwide for this purpose, probably more from sales promotion than from actual documented performance. Full scale field testing is continuing each time a project is let utilizing fabric reinforcement under asphaltic concrete overlays. It has already become apparent that the use of fabrics in AC overlays is not always cost effective.

Evaluation of Corrosion Resistance of Different Steel Reinforcement Types, 2006

The corrosion of steel reinforcement in an aging highway infrastructure is a major problem currently facing the transportation engineering community. In the United States alone, maintenance and replacement costs for deficient bridges are measured in billions of dollars. The application of corrosion-resistant steel reinforcement as an alternative reinforcement to existing mild steel reinforced concrete bridge decks has potential to mitigate corrosion problems, due to the fundamental properties associated with the materials. To investigate corrosion prevention through the use of corrosion-resistant alloys, the performance of corrosion resistance of MMFX microcomposite steel reinforcement, a high-strength, high-chromium steel reinforcement, was evaluated. The study consisted of both field and laboratory components conducted at the Iowa State University Bridge Engineering Center to determine whether MMFX reinforcement provides superior corrosion resistance to epoxy-coated mild steel reinforcement in bridge decks. Because definitive field evidence of the corrosion resistance of MMFX reinforcement may require several years of monitoring, strict attention was given to investigating reinforcement under accelerated conditions in the laboratory, based on typical ASTM and Rapid Macrocell accelerated corrosion tests. After 40 weeks of laboratory testing, the ASTM ACT corrosion potentials indicate that corrosion had not initiated for either MMFX or the as-delivered epoxy-coated reinforcement. Conversely, uncoated mild steel specimens underwent corrosion within the fifth week, while epoxy-coated reinforcement specimens with induced holidays underwent corrosion between 15 and 30 weeks. Within the fifth week of testing, the Rapid Macrocell ACT produced corrosion risk potentials that indicate active corrosion for all reinforcement types tested. While the limited results from the 40 weeks of laboratory testing may not constitute a prediction of life expectancy and life-cycle cost, a procedure is presented herein to determine life expectancy and associated life-cycle costs.

Demonstration and Field Evaluation of Alternative Portland Cement Concrete Pavement Reinforcement Materials, Construction Report, HR-1069, 1998

The function of dowel bars is the transfer of a load across the transverse joint from one pavement slab to the adjoining slab. In the past, these transfer mechanisms have been made of steel. However, pavement damage such as loss of bonding, deterioration, hollowing, cracking and spalling start to occur when the dowels begin to corrode. A significant amount of research has been done to evaluate alternative types of materials for use in the reinforcement of concrete pavements. Initial findings have indicated that stainless steel and fiber composite materials possess properties, such as flexural strength and corrosion resistance, that are equivalent to the Department of Transportation specifications for standard steel, 1 1/2 inch diameter dowel bars. Several factors affect the load transfer of dowels; these include diameter, alignment, grouting, bonding, spacing, corrosion resistance, joint spacing, slab thickness and dowel embedment length. This research is directed at the analysis of load transfer based on material type and dowel spacing. Specifically, this research is directed at analyzing the load transfer characteristics of: (a) 8-inch verses 12-inch spacing, and (b) alternative dowel material compared to epoxy coated steel dowels, will also be analyzed. This report documents the installation of the test sections, placed in 1997. Dowel material type and location are identified. Construction observations and limitations with each dowel material are shown.

Reinforcement learning utilizes proxemics: an avatar learns to manipulate the position of people in immersive virtual reality

A reinforcement learning (RL) method was used to train a virtual character to move participants to a specified location. The virtual environment depicted an alleyway displayed through a wide field-of-view head-tracked stereo head-mounted display. Based on proxemics theory, we predicted that when the character approached within a personal or intimate distance to the participants, they would be inclined to move backwards out of the way. We carried out a between-groups experiment with 30 female participants, with 10 assigned arbitrarily to each of the following three groups: In the Intimate condition the character could approach within 0.38m and in the Social condition no nearer than 1.2m. In the Random condition the actions of the virtual character were chosen randomly from among the same set as in the RL method, and the virtual character could approach within 0.38m. The experiment continued in each case until the participant either reached the target or 7 minutes had elapsed. The distributions of the times taken to reach the target showed significant differences between the three groups, with 9 out of 10 in the Intimate condition reaching the target significantly faster than the 6 out of 10 who reached the target in the Social condition. Only 1 out of 10 in the Random condition reached the target. The experiment is an example of applied presence theory: we rely on the many findings that people tend to respond realistically in immersive virtual environments, and use this to get people to achieve a task of which they had been unaware. This method opens up the door for many such applications where the virtual environment adapts to the responses of the human participants with the aim of achieving particular goals.

Gambling against neglect: unconscious spatial biases induced by reward reinforcement in healthy people and brain-damaged patients.

Orienting attention in space recruits fronto-parietal networks whose damage results in unilateral spatial neglect. However, attention orienting may also be governed by emotional and motivational factors; but it remains unknown whether these factors act through a modulation of the fronto-parietal attentional systems or distinct neural pathways. Here we asked whether attentional orienting is affected by learning about the reward value of targets in a visual search task, in a spatially specific manner, and whether these effects are preserved in right-brain damaged patients with left spatial neglect. We found that associating rewards with left-sided (but not right-sided) targets during search led to progressive exploration biases towards left space, in both healthy people and neglect patients. Such spatially specific biases occurred even without any conscious awareness of the asymmetric reward contingencies. These results show that reward-induced modulations of space representation are preserved despite a dysfunction of fronto-parietal networks associated with neglect, and therefore suggest that they may arise through spared subcortical networks directly acting on sensory processing and/or oculomotor circuits. These effects could be usefully exploited for potentiating rehabilitation strategies in neglect patients.