In vitro assessment of bone-implant interface using an acoustic emission transmission test

The aim of this in vitro study was to determine the feasibility of monitoring the primary stability of dental implants using a simple transmission test with acoustic emission. Forty screw-shaped titanium dental implants were installed in the middle of 10 fresh bovine ribs obtained from different animals. The implants were divided into two size groups, 8.5 mm x 3.5 mm and 13 mm x 4.5 mm, and were inserted in either tight- or loose-fitting conditions. For each implant, pulses of acoustic energy were injected at the centre of a customised gold abutment 3 mm in height using a standard pencil lead break source (Hsu-Nielsen source). A total of 30 acoustic emission recordings were made for each implant in which the transmitted energy was measured on the surface of the bone using an acoustic sensor mounted at the middle of the rib. The transmitted acoustic energy for the implants under tight-fitting conditions was significantly higher than for the loose-fitting for both sizes of implant. The acoustic emission energy values for the 13 mm implants were also higher than for the 8.5 mm implants. The results indicate that implants with good primary stability (tight-fitting) had higher acoustic emission energy than implants where primary stability was poor (loose-fitting). The longer and wider implants produced higher acoustic emission energy than shorter and narrower implants. Together, the findings suggest that a simple transmission test, properly calibrated, should be able to assess the quality of the contact between the implant and the bone in the clinical situation.     

A new method for waveform analysis for estimating AE wave arrival times using wavelet decomposition

Here we describe a new method for determination of Acoustic Emission (AE) wave arrival times for source location purposes. In complex structures or structures of small dimension, an AE source can rapidly become distorted by the presence of several modes travelling at different speeds, and through contamination by reflections and mode conversions.Using a simple geometry of carbon-fibre reinforced plastic, the responses acquired from two-sensor and four-sensor arrays have been analysed using a variety of techniques, which are variants on identification of first arrival time and/or the arrival of the maximum intensity of the wave. The methods are compared in terms of the consistency of the velocity which is indicated at different points in the arrays, and a method based on wavelet decomposition, filtering and threshold-crossing is recommended as the most consistent and accurate method of determining arrival time.     

Interfacial phenomena in the sulfur–polytetrafluoroethylene system under hydrothermal conditions

Sulfur occlusion of pyrite particles during oxidative pressure leaching of mineral sulfide concentrates at temperatures below 160 °C has a deleterious effect on pyrite oxidation kinetics. Existing techniques in mitigating sulfur occlusion involve the use of surfactants or operation at temperatures above 160 °C which are a burden to the process economy. This study looks at the suitability of polytetrafluoroethylene (PTFE) to act as a solid sorbent for the liquid sulfur generated during the pressure leach process. The suitability of PTFE as a solid sorbent was determined by comparing interfacial phenomena in the corresponding sulfur–PTFE–leach and sulfur–mineral–leach systems. The work of adhesion in a sulfur–PTFE system was calculated using the interfacial tension and contact angle measured in the relevant sulfur–PTFE system, which is comparable to published values in the pyrite–sulfur system.     

Genital exhibitionism: Courtship disorder or narcissism?

34 male exhibitionists and 20 nonviolent non-sex-offender controls were compared on measures of gender identity and sexual and criminal history. Results indicate that 41% of exhibitionists were transvestitic; gender identity was masculine and not significantly different from controls. Exhibitionists engaged in a variety of other sexually anomalous behaviors (voyeurism, obscene telephone calling, frottage, toucheurism, attempted rape). Frequency of exhibiting was uncorrelated with desire for resulting intercourse with the victim. Nearly all exhibitionists hoped the unsuspecting female would enjoy the experience, and 19 indicated that they would have gone with the complainant, if asked. 20% of exhibitionists had a history of violence-related offenses. Findings support the narcissism hypothesis of exhibitionism, rather than the courtship disorder approach by K. Freund et al (see record 1984-15234-001). (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bacterial diversity on different surfaces in urban freshwater

Microbial loads in freshwater systems have important implications in biogeochemical cycling in urban environments. Immersed surfaces in freshwaters provide surfaces for bacterial attachment and growth. Microorganisms that adhere initially to these surfaces play a critical role in biofilm formation and sustenance. Currently, there is little understanding on the type of organisms that initially adhere to different surfaces in urban canals. In this study, water from an urban stormwater canal was employed to allow bacteria to attach to different surfaces in a flowcell apparatus and understand the differences and changes in bacterial community structure. Bacterial communities were highly diverse on different surfaces as indicated by Jaccard's indices of 0.14-0.56. Bacteria on aluminium were the most diverse and on Plexiglas the least. Bacterial communities were highly dynamic in the early attachment phase and it changed by 59% between 3 and 6 h on aluminium. Specificity of attachment to surfaces was observed for some bacteria. Judicious use of materials in urban aquatic environment would help mitigate microbial load in urban waters.     

Application of phytoplankton community structure for ranking the major riverine catchments influencing the pollution status of a lake basin

The present study demonstrates the application of a multi‐metric Phytoplankton Index of Biotic Integrity (PIBI) approach for ranking of major river catchments in the Kenyan part of Lake Victoria on the basis of their pollution status. The index utilizes water quality and zooplankton data, phytoplankton diversity, abundance and attributes, as well as literature information. The rivers were sampled from 2016 to 2018 during the wet season (March) and dry season (July). The separation power of the Mann–Whitney U test (p < .05) qualified eight discriminant metrics for phytoplankton samples into a scoring system of 1, 3 and 5, based on high, fair and slight deviation from the best site, respectively, in development of the final PIBI. The Kuja and Sondu‐Miriu rivers had the highest PIBI, signifying least pollution influence on the lake. In contrast, the Yala and Nzoia rivers exhibited the lowest PIBI, representing the catchments with a higher pollution influence on the lake. The fair to poor integrity classes for the major river catchments in the region signified a deteriorating lakescape. The present study presents the preliminary results of using phytoplankton metrics for development of the Index of Biotic Integrity (IBI) approach in the region as a decision‐making support tool for the effective management and sustainable use of water resources in the lake basin.     

Cumulative impacts of river engineering,Mississippi and Lower Missouri rivers

The goal of this study was to construct a large, data‐rich model to test hydrological responses to engineering modifications on over 3200 km of the Mississippi and Lower Missouri Rivers. We compiled model explanatory variables from a geospatial database quantifying construction of all bridges, wing dikes, bendway weirs, levees, artificial meander cutoffs, channel constriction and navigational dams over the past 100–150 years. Response variables were derived from 68 rated and un‐rated hydrologic stations in the study area, with responses analysed across a range of discharges from within‐channel flows up to moderate floods. Correlation analysis, multiple linear regression and stepwise regression analyses document strong and consistent responses to construction history, both in individual reach‐scale models and systemwide. Meander cutoffs are associated with degradation and acceleration of flow that has reduced stages across the full discharge range. Navigational dams on the Upper Mississippi River increased low‐flow stages and flood levels to a lesser extent, with little or no post‐dam change. One of the strongest signals was the hydrologic response to wing‐dike construction, which resulted in large back‐water increases in stage upstream of wing dikes and mixed effects downstream, including the overlapping effects of incision and velocity losses. Levees were associated with local flow concentration, overbank storage loss and floodplain conveyance loss depending on reach‐scale conditions. The results presented here (1) quantify incremental and cumulative hydrologic responses to a range of engineering activities and (2) provide an empirical tool for verifying and assessing hydraulic and other models of river‐system change. Copyright © 2009 John Wiley & Sons, Ltd.     

A nonlinear analysis of spatial compliant parallel modules: Multi-beam modules

This paper presents normalized, nonlinear and analytical models of spatial compliant parallel modules—multi-beam modules with a large range of motion. The models address the non-linearity of load-equilibrium equations, applied in the deformed configuration, under small deflection hypothesis. First, spatial nonlinear load-displacement equations of the tip of a beam, conditions of geometry compatibility and load-equilibrium conditions for a spatial three-beam module are derived. The nonlinear and analytical load-displacement equations for the three-beam module are then solved using three methods: approximate analytical method, improved analytical method and numerical method. The nonlinear-analytical solutions, linear solutions and large-deflection FEA solutions are further analyzed and compared. FEA verifies that the accuracy of the proposed nonlinear-analytical model is acceptable. Moreover, a class of multi-beam modules with four or more beams is proposed, and their general nonlinear load-displacement equations are obtained based on the approximate load-displacement equations of the three-beam module. The proposed multi-beam modules and their nonlinear models have potential applications in the compliant mechanism design. Especially, the multi-beam modules can be regarded as building blocks of novel compliant parallel mechanisms.