Applications of coralline hydroxyapatite with bioabsorbable containment and reinforcement as bone graft substitute : An experimental study

The aim of the present experimental study was to find out if the applications of coralline hydroxyapatite (HA) can be improved by using bioabsorbable containment or binding substance with particulate HA in mandibular contour augmentation and by using bioabsorbable fibre-reinforced HA blocks in filling bone defects and in anterior lumbar interbody fusion. The use of a separate curved polyglycolide (PGA) containment alone or together with a fast resorbing polyglycolide/polylactide (PGA/PLA) binding substance were compared to the conventional non-contained method in ridge augmentation in sheep. The contained methods decreased HA migration, but the augmentations did not differ significantly. The use of the containment caused a risk for wound dehiscence and infection. Histologically there was a rapid connective tissue ingrowth into the HA graft and it was more abundant with the PGA containment compared to the non-contained augmentation and even additionally rich when the HA particles were bound with PGA/PLA copolymer. However, the bone ingrowth was best in the non-contained augmentation exceeding 10-12 % of the total graft area at 24 weeks. Negligible or no bone ingrowth was seen in the cases where the polymer composite was added to the HA particles and, related to that, foreign-body type cells were seen at the interface between the HA and host bone. The PGA and poly-dl/l-lactide (PDLLA) fibre-reinforced coralline HA blocks were studied in the metaphyseal and in the diaphyseal defects in rabbits. A rapid bone ingrowth was seen inside the both types of implants. Both PGA and PDLLA fibres induced an inflammatory fibrous reaction around themselves but it did not hinder the bone ingrowth. The bone ingrowth pattern was directed according to the loading conditions so that the load-carrying cortical ends of the implants as well as the implants sited in the diaphyseal defects were the most ossified. The fibre-reinforced coralline HA implants were further studied as stand-alone grafts in the lumbar anterior interbody implantation in pigs. The strength of the HA implants proved not to be adequate, the implants fractured in six weeks and the disc space was gradually lost similarly to that of the discectomized spaces. Histologically, small quantities of bone ingrowth was seen in some of the PGA and PDLLA reinforced coralline implants while no bone formation was identified in any of the PDLLA reinforced synthetic porous HA implants. While fragmented, the inner structure of the implants was lost, the bone ingrowth was minimal, and the disc was replaced by the fibrous connective tissue. When evaluated radiologically the grade of ossification was assessed as better than histologically, and, when related to the histologic findings, CT was more dependable than the plain films to show ossification of the implanted disc space. Local kyphosis was a frequent finding along with anterior bone bridging and ligament ossification as a consequence of instability of the implanted segment.

Experimental study on shrinkage behaviour and prediction of shrinkage magnitudes of residual soils

The present study examines the shrinkage behaviour of residually derived black cotton (BC) soil and red soil compacted specimens that were subjected to air-drying from the swollen state. The soil specimens were compacted at varying dry density and moisture contents to simulate varied field conditions. The void ratio and moisture content of the swollen specimens were monitored during the drying process and relationship between them is analyzed. Shrinkage is represented as reduction in void ratio with decrease in water content of soil specimens. It is found to occur in three distinct stages. Total shrinkage magnitude depends on the type of clay mineral present. Variation in compaction conditions effect marginally total shrinkage magnitudes of BC soil specimens but have relatively more effect on red soil specimens. A linear relation is obtained between total shrinkage magnitude and volumetric water content of soil specimens in swollen state and can be used to predict the shrinkage magnitude of soils.

Experimental study on behaviour of concrete filled double skin tube columns under lateral impact loading

This paper presents an experimental investigation on the lateral impact response of axially loaded concrete filled double skin tube (CFDST) columns. A total of four test series are being conducted at Queensland University of Technology using a novel horizontal impact-testing rig. The test results reported in this paper are from the first test series, where the columns are pinned at both ends and impacted at mid-span. In the next three series, effects of support conditions, impact location and repeated impact will be treated. The main objectives of the current paper are to describe the innovative testing procedure and provide some insight into the lateral impact behavior and failure of simply supported axially pre-loaded CFDST columns. The results include time histories of impact forces, reaction forces, axial force and global lateral deflection. Based on the test data, the failure mode, peak impact force, peak reaction forces, maximum deflection and residual deflection, with and without axial load, are analyzed and discussed. The findings of this study will serve as a benchmark reference for future analysis and design of CFDST columns.

An Experimental Study of Home Gateway Characteristics

Many residential and small business users connect to the Internet via home gateways, such as DSL and cable modems. The characteristics of these devices heavily influence the quality and performance of the Internet service that these users receive. Anecdotal evidence suggests that an extremely diverse set of behaviors exists in the deployed base, forcing application developers to design for the lowest common denominator. This paper experimentally analyzes some characteristics of a substantial number of different home gateways: binding timeouts, queuing delays, throughput, protocol support and others.

Effectiveness of a Differential Temperature Controller on a Solar Water Heating System: An Experimental Study

A differential temperature controller is incorporated in a solar water heating system to study the influence of its set points on system performance. The effectiveness of the controller set points DeltaT ON and DeltaT OFF on the pump cycling and energy collection has been studied experimentally and the results are presented in this paper.

An Experimental Study to Show the Effect of Thermal Stress on Thermal Contact Conductance at Sub-megapascal Contact Pressures

Experimental studies are presented to show the effect of thermal stresses on thermal contact conductance (TCC) at low contact pressures. It is observed that in a closed contact assembly, contact pressure acting on the interface changes with the changing temperature of contact members. This change in contact pressure consequently causes variations in the TCC of the junction. A relationship between temperature change and the corresponding magnitude of developed thermal stress in a contact assembly is determined experimentally. Inclusion of a term called temperature dependent load correction factor is suggested in the theoretical model for TCC to make it capable of predicting TCC values more accurately in contact assemblies that experience large temperature fluctuations. [DOI: 10.1115/1.4001615]

Role of external electron donor in methylene blue sensitized dichromated gelatin holograms:an experimental study

An experimental study to ascertain the role of external electron donor in methylene blue sensitized dichromated gelatin (MBDCG) holograms has been carried out. The required volume holographic transmission gratings in MBDCG have been recorded using 633-nm light from a He-Ne laser. Three well-known electron donors, namely, N, N-dimethylformamide (DMF); ethylenediaminetetraacetic acid (EDTA); triethanolamine (TEA), were used in this study. The variation of diffraction efficiency (η) as a function of light exposure (E) and concentration (C) of the electron donor under consideration was chosen as the figure of merit for judging the role of external electron donor in MBDCG holograms. A self-consistent analysis of the experimental results was carried out by recalling the various known facts about the photochemistry and the hologram formation in DSDCG and also DCG. The important findings and conclusions are as follows: (i) Each η vs E graph is a bell-shaped curve and its peak height is influenced in a characteristic manner by the external electron donor used. (ii) High diffraction efficiency/recording speed can be achieved in pure MBDCG holograms. (iii) The diffraction efficiency/recording speed achieved in electron donor sensitized MBDCG holograms did not show any significant improvement at all over that observed in pure MBDCG holograms. (iv) In electron donor sensitized MBDCG holograms, the electron donor used, depending on its type and concentration, appears to promote the process of cross-linking of gelatin molecules in a manner to either retain or deteriorate the refractive-index modulation achieved using pure MBDCG.