The Effects of Surface Curvature on Cartilage Behaviour in Indentation Test: A Finite Element Study

Computational modelling of the behaviour of articular cartilage is important in order to improve the understanding of disease processes such as arthritis, and the suitability of biomaterials in surgical treatment. In previous computational studies, the cartilage surface of axisymmetric models was assumed to be flat in order to evaluate the cartilage behaviour. This assumption was inappropriate since the synovial joint possessed curvature geometrical shape and may contribute to inaccurate results. Therefore, this study aims to examine the effects of the cartilage surface curvature to the cartilage behavior in indentation test using finite element analysis. Axisymmetric biphasic poroelastic finite element models of flat and various cartilage surface radii, including both concave and convex shapes of the curve, were generated to simulate creep indentation test in order to investigate possible effect to the contact stress and pore pressure of the cartilage. Based on the results, the smaller cartilage surface of 10 mm radius produced higher difference of the cartilage behaviour where it generated 39% difference in pore pressure and 6% difference in contact stress, compared to the flat cartilage. This could indicate that the cartilage curvature does affect the cartilage behavior in indentation test particularly the pore pressure of cartilage

Association between hazard ratios of surrogate time-to-event endpoints and overall survival in advanced/metastatic cancers

Objectives: Surrogate endpoints can support early access to novel therapies. In trial-level endpoint validation studies, the association between treatment effect e.g., the hazard ratio (HR) on both the surrogate and hard endpoint can be estimated. We aimed to review studies reporting an association between HRs of surrogate time-to-event endpoints and overall survival (OS) in advanced/metastatic cancers. Methods: A systematic review was conducted using Medline and Embase. We included full reports assessing the association between HRs of surrogate time-to-event endpoints and OS in advanced/metastatic cancer indications. The following information was extracted: study characteristics, association measure, use of weighted analyses, logarithmic transformation of HRs, use of multivariate analysis, evaluation of crossover impact, use of IQWiG framework, estimating surrogate threshold effect (STE), and reported results and/or regression equations. Results: Forty-five studies were included. Retrieved studies were conducted in 16 different cancer indications. Different methods were used to assess associations, including Spearman's/Pearson’s correlation coefficient and linear regression analysis. Weighted analyses, logarithmic transformation of HRs and multivariate analysis were implemented in 35, 26 and 10 studies, respectively. Few studies assessed the crossover impact on the association (8 studies) and implemented IQWiG framework and STE assessment (11 studies and 3 studies, respectively). Detailed results are extracted, summarized and will be presented. Conclusions: There is inconsistency in conducting/reporting of trial-level endpoint validation studies in advanced/metastatic cancers. Future studies would benefit from building a structured data analysis checklist. Also, trial-level surrogacy was not assessed in all advanced/metastatic cancers and the strength of association varied across indications. The generalizability of results from one indication to another is limited

Design guidance and structural integrity of bonded connections in GRE pipes

Extensive research, involving a large programme of both experimental and numerical analyses, has been undertaken into the structural integrity of adhesively bonded GRE composite taper/taper pipe joints, initial studies investigated the short-term static performance under various modes of loading and these were followed by studies of long-term creep performance. A significant element of the research was a study of the effect that defects in the adhesive bond have on the overall performance of the bonded joint-pipe system. The numerical analyses were correlated with the experimental data for validation of the computer simulations and failure predictions. The results of the research demonstrate the substantial defect tolerance of the bonded composite components. From the results it is possible to present guidelines for residual strength, deflection and the effects of defect size, as a function of pipe diameter, temperature and time. Such guidelines may be used at the initial design stage or to inform inspection and repair strategies

Augmenting Password Strength Meter Design Using the Elaboration Likelihood Model: Evidence from Randomized Experiments

Password-based authentication is the most commonly used method for gaining access to secured systems. Unfortunately, empirical evidence highlights the fact that most passwords are significantly weak, and encouraging users to create stronger passwords is a significant challenge. In this research, we propose a theoretically augmented password strength meter design that is guided by the elaboration likelihood model of persuasion (ELM). We evaluate our design by leveraging three independent and complementary methods: a survey-based experiment using students to evaluate the saliency of our conceptual design (proof of concept), a controlled laboratory experiment conducted on Amazon Mechanical Turk to test the effectiveness of the proposed design (proof of value), and a randomized field experiment conducted in collaboration with an online forum in Asia to establish proof of use. In each study, we observe the changes in users’ behavior in response to our proposed password strength meter. We find that the ELM-augmented password strength meter is significantly effective at addressing the challenges of password-based authentication. Users exposed to this strength meter are more likely to change their passwords, leading to a new password that is significantly stronger. Our findings suggest that the proposed design of augmented password strength meters is an effective method for promoting secure password behavior among end users.12 month embargo; published online: 23 March 2022This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

High sensitivity flat SiO2 fibres for medical dosimetry

We describe investigation of a novel undoped flat fibre fabricated for medical radiation dosimetry. Using high energy X-ray beams generated at a potential of 6 MV, comparison has been made of the TL yield of silica flat fibres, TLD-100 chips and Ge-doped silica fibres. The flat fibres provide competitive TL yield to that of TLD-100 chips, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. The dose enhancement factor (DEF) of (0.0150±0.0003) nm-1 Pt is comparable to that obtained using gold, agreeing at the 1% level with the value expected on the basis of photoelectron generation. Finally, X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface oxidation state of the fibre medium. The charge state of Si2p was found to lie on 103.86 eV of binding energy and the atomic percentage obtained from the XPS analysis is 22.41%