Cast titanium as implant material

The tissue response in rats to implants made of machined and cast titanium was evaluated after 1 and 12 weeks. The implants consisted of a circular plate portion, located in the abdominal wall, and a cylindrical rod portion protruding into the peritoneal cavity. The chemical and topographical surface properties of the two types of implants differed considerably. The implants with surrounding tissue were processed en bloc for light and electron microscopy. The bulk metal was removed by an electrochemical procedure which permitted the sectioning and evaluation of the intact implant-tissue interface. The general distribution of macrophages and fibroblasts was the same around the plate portion of both types of implants. Macrophages constituted the predominating cell type with the highest concentration in the innermost cell zone closest to the implant. The number of macrophages per section area was significantly higher around machined implants. Multinuclear giant cells, always located at the implant surface, were more frequent around cast implants. The majority of the intraperitoneal rod portions were partially (1 week) or completely (12 weeks) covered by tissue; partial or complete overgrowth of tissue was rare for machined rod portions. Imaging electron energy loss spectroscopy demonstrated the presence of titanium in macrophages in the peripheral part of the tissue capsule around cast, but not machined implants. We conclude that the tissue responses to the two types of titanium implants differed considerably in the two biological environments (soft tissue in abdominal wall; peritoneal cavity) examined and that the response in one environment does not predict the response in the other. We also believe that improvements have to be made in the casting procedure in order to reduce surface roughness and contamination before cast implants can be used in clinical applications.     

Challenging Controversies: A Prospective Analysis of the Influence of New Technologies on the Safety of Offshore Drilling Operations

Integrated operations (IO) is an operating mode in the offshore oil and gas industry that is expected to lead to safer, faster and better operations. This article presents an analysis of the anticipated impacts of increased instrumentation on the safety of drilling operations. The instrumentation is related to the change process of IO, and is exemplified by a group of IO tools for interpretation, diagnosis and automation. An important finding in the study is the identification of a set of controversies that reflect characteristic challenges of drilling operations. These controversies involve the quantity and accessibility of information, the issue of centralized and decentralized control, the relation between standardized and unique interpretation of data, and the heterogeneous nature of engineering work. It is argued that the impact of the IO tools on safety will depend on how these controversies are taken into account when the tools are adopted. It is also argued that the cognitive control of the operations is distributed across a range of human and nonhuman actors and that the impact of the IO tools thus depends on how they are adapted to the system of distributed cognition rather than on the properties of the tools themselves.     

Numerical modeling of the hydraulic blade pitch actuator in a spar‐type floating wind turbine considering fault conditions and their effects on global dynamic responses

This paper deals with numerical modeling of the hydraulic blade pitch actuator and its effect on the dynamic responses of a floating spar‐type wind turbine under valve fault conditions. A spar‐type floating wind turbine concept is modeled and simulated using an aero‐hydro‐servo‐elastic simulation tool (Simo‐Riflex [SR]). Because the blade pitch system has the highest failure rate, a numerical model of the hydraulic blade pitch actuator with/without valve faults is developed and linked to SR to study the effects of faults on global responses of the spar‐type floating wind turbine for different faults, fault magnitudes, and environmental conditions. The consequence of valve faults in the pitch actuator is that the blade cannot be pitched to the desired angle, so there may be a delay in the response due to excessive friction and the wrong voltage, or slit lock may cause runaway blade pitch. A short circuit may cause the blade to get stuck at a particular pitch angle. These faults contribute to rotor imbalance, which result in different effects on the turbine structure and the platform motions. The proposed method for combining global and hydraulic actuator models is demonstrated in case studies with stochastic wind and wave conditions and different types of valve faults.     

Corneal endothelial cell measurements in megalocornea

A pedigree of megalocornea manifested many of the characteristic features as well as some less common features of the disorder. Endothelial specular microscopy of affected patients disclosed normal endothelial cell densities and morphologic characteristics and increased total endothelial cell populations, suggesting a process of total corneal hyperplasia. In contrast, unpublished data indicate diminished densities in congenital glaucoma, a finding more consistent with corneal distention. We conclude that specular microscopy may be of value in differentiating the two disorders, although larger series are necessary for confirmation.     

Some aspects of contralateral compression in carotid angiography

The effect of compression of the noninjected carotid artery at carotid angiography was studied; compression above the bifurcation was compared to compression below the bifurcation. The timing of the compression in relation to the contrast injection was varied. In 12 patients an increased contrast dose was used. Retrograde contrast filling of the noninjected carotid was better when compression was applied below the biturcation. With increased contrast dose and prolonged injection time, visualization of the noninjected carotid artery was further improved, as was contrast filling of the noninjected hemisphere.     

Response productivity: A methodological problem in content analysis studies in psychotherapy.

Contends that most content analysts of psychotherapy materials have failed to consider the possibility that the frequency of units coded to the categories of the content analysis system might be correlated with the total number of units produced. The existence of such relationships may confound interpretation of the association between content analysis variables and other external variables. When investigators have attempted to control for response productivity, they have usually divided the frequency of units in each category by the total number of units. This procedure does not control for response productivity and is often uninterpretable. The issues involved are discussed and demonstrated, and appropriate techniques of controlling for productivity are described. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exponential error bounds for random codes in the arbitrarily varying channel

Random codes for the arbitrarily varying channel are investigated. The code ensemble is restricted to increase only exponentially with codeword length; a quantity called key rate is used as a measure of the rate of increase. The reliability function for such codes is related to the reliability function for codes with unlimited key rate. Explicit results are obtained in some examples of practical interest.     

The mineral phase quantification of vermiculite and interstratified clay minerals-containing ores by X-ray diffraction and Rietveld method after K cation exchange

Hydrothermal transformations and weathering are important mineralizing processes in carbonatite-related ores. But the transformation products of mafic minerals, such as the clay minerals, vermiculite and interstratified phases, preclude the use of X-ray diffraction, particularly the Rietveld method, for mineral phase quantification. After treatment with KCl, vermiculite and interstratified phases (all peaks roughly at 1.2, 1.4-1.5 and 2.4 nm) are converted to a phlogopite-like structure with d(0 0 1) = 1.0 nm, which can successfully be refined. The method was tested using three carbonatite-derived ores, with a total phlogopite-like phase content ranging from 1.2 to 32.3 wt.%. Comparison of the chemical analyses with the calculated chemical composition, based on the phase quantification and the mineral composition is in good agreement for major elements, such as Si, Fe and Al. For P results were also very good, but Ti and Nb are generally underestimated, and Ba is overestimated. Minerals with lower contents, as pyrochlore, approach the diffraction detection limit. Problems to accurately determine mineral composition for some of the phases also impacts on the reconciliation. The chemical composition of the pyrochlore group minerals changed, but not to an extent to constrain the usefulness of the technique. Cation exchange successfully extended the amenability of the Rietveld method for phase quantification.