Pulsed-Field Gel Elec rophoresis Pa ern Recogni ion of Bac erial DNA: A Systemic Approach

Pulsed-Field Gel Electrophoresis (PFGE) images contain ‘banding pattern’ information that can be used in bacterial identification.A systemic approach was designed to target the bacterial DNA PFGE pattern recognition problem that requires image processing, feature extraction, data pre-processing, classification and final decision-making. This paper describes the research, development and testing of a complete system to address this identification problem, including Receiver Operating Characteristic Curve (ROC) analysis. Variations due to gel preparation in various laboratories by different technicians are considered. The approach was applied to recognition of E. coli O157:H7 bacteria with excellent results.     

Adhesion of Metallic Bodies Initiated by Physical Contact

Metallic adhesion brought about through the normal compression of two real surfaces is considered. The growth of the real area of contact caused by the impressed load results in die plastic deformation of asperities even before plastic macro-deformation is initiated. The size distribution of the asperities is Gaussian, hence some contact points supporting the load will have experienced heavy deformation while others may have only received weak elastic interactions. The rate of dispersal of the contaminant barrier which inhibits high adhesion strengths has been shown to be a function of the degree of substrate deformation irrespective of the amount or the character of the contaminating layer. The mechanism of metallic adhesion, therefore, is directly dependent on the available energy inputs to the interface, e.g., mechanical, thermal, etc., which can bring about complete dispersal of the interfacial contaminants. At normal compressive loads, when the real area of contact is small compared to the nominal area of contact, the system must be considered a multipoint contact problem with the resistance to fracture of each point contact dependent on the prior history of that point.     

The Manufacture of Resorbable Suture Material from Magnesium

Magnesium alloys present an alternative to medical cases in which polymeric sutures may not be ideal. To date, no efficient and low‐cost manufacturing process for the fabrication of magnesium‐based sutures can be found. To obtain an alternative, the previously characterised magnesium alloys ZEK100 (98% Mg), AX30 (96.2% Mg), AL36 (91% Mg) and MgCa0.8 (99.2% Mg) were cast, extruded into 30 mm diameter bars and extruded into 0.5 mm diameter wires. To determine the mechanical properties of the wires, grain size measurements, tensile tests as well as qualitative bending tests were carried out. The ZEK100 alloy's wires showed the finest microstructure having grains of 1.2 µm in diameter. Coarser microstructures were observed for MgCa0.8, AX30 and AL36. The alloy ZEK100 had the highest tensile stress (367 MPa) also revealing a brittle behaviour due to its fine microstructure. The tensile test, carried out for AX30 as well as AL36, resulted in comparable high fracture strains (10.6%) and tensile stresses (300 MPa). However, MgCa0.8 showed a tensile strength of 315 MPa and a low strain of 1.6%. Within the qualitative bending test wires made of the alloy AL36 were able to form tight knots, which is a key feature for suture applications. The comparison of the magnesium sutures with commercially available polymeric sutures revealed lower strength and elongation for the magnesium alloys. Yet, the wires exhibited mechanical properties that can meet the requirements of a suture material.     

Self-aligned cantilever positioning for on-substrate measurements using DVD pickup head

In this paper, we present a novel approach for measuring the resonant frequency of cantilevers fabricated in polymeric materials. We re-designed the use of a commercial DVD-ROM pickup head and combine it with a glass–polymer substrate in order to obtain a light and portable device to measure the resonant frequency of polymer cantilevers. The use of the Pyrex-SU-8 clamping substrate allows an easy replacement of the cantilever chips and a fast alignment process to the DVD-ROM laser beam. We show measurements of thermal noise for SU-8 and TOPAS cantilevers in air and liquid environment.     

Evaluation of residual strains in epoxy with different nano/micro-fillers using embedded fiber Bragg grating sensor

The influence of SiO₂ nanoparticles and rubber micro-fillers on the mechanical and thermal responses of an epoxy based composite is investigated using classical quantitative thermo-mechanical testing (tensile tests, DMTA, TMA), microstructural analysis (Micro-CT, TEM, SEM microscopy) as well as distributed optical sensing in order to determine different residual strain fields generated during processing. The results show that the tensile modulus of the compounds increases with the addition of SiO₂ and decreases with the rubber content, following estimates of the Hashin–Shtrikman model. The coefficient of thermal expansion appears to be insensitive to the particles’ content in the temperature range investigated. The residual strains generated during processing are influenced by the rubber content that introduces a strong relief, with respect to the one generated by the neat resin, whereas the silica content tends to increase their level.     

Converting the unconverted: The effect of inclination and opportunity to discount health-related fear appeals.

Two experiments indicated that the conventional wisdom for designing fear appeals, higher fear arousal, and a consequences–recommendations ordering, was more persuasive for adherents, or those who were already following the advocated recommendations. Instead, lowering the level of fear arousal and reversing the order of the consequences and recommendations were more effective for persuading the unconverted. The unconverted were more persuaded by the latter message format because it reduced the level of message discounting. Specifically, unconverted participants who received either a low fear appeal or recommendations preceding consequences perceived themselves to be more susceptible, perceived the consequences as more severe, regarded the recommendations as more efficacious, believed they were more able to follow the recommendations, and were less likely to refute the message claims. (PsycINFO Database Record (c) 2010 APA, all rights reserved)