Comparisons of Estimation Procedures for Nonlinear Multilevel Models

We introduce General Multilevel Models and discuss the estimation procedures that may be used to fit multilevel models. We apply the proposed procedures to three-level binary data generated in a simulation study. We compare the procedures by two criteria, Bias and efficiency. We find that the estimates of the fixed effects and variance components are substantially and significantly biased using Longford's Approximation and Goldstein's Generalized Least Squares approaches by two software packages VARCL and ML3. These estimates are not significantly biased and are very close to real values when we use Markov Chain Monte Carlo (MCMC) using Gibbs sampling or Nonparametric Maximum Likelihood (NPML) approach. The Gaussian Quadrature (GQ) approach, even with small number of mass points results in consistent estimates but computationally problematic. We conclude that the MCMC and the NPML approaches are the recommended procedures to fit multilevel models.

Characterisation and application of bio-inspired hybrid composite sensors for detecting barely visible damage under out-of-plane loadings

Traditional inspection methods often fall short in detecting defects or damage in fibre-reinforced polymer (FRP) composite structures, which can compromise their performance and safety over time. A prime example is barely visible impact damage (BVID) caused by out-of-plane loadings such as indentation and low-velocity impact that can considerably reduce the residual strength. Therefore, developing advanced visual inspection techniques is essential for early detection of defects, enabling proactive maintenance and extending the lifespan of composite structures. This study explores the viability of using novel bio-inspired hybrid composite sensors for detecting BVID in laminated FRP composite structures. Drawing inspiration from the colour-changing mechanisms found in nature, hybrid composite sensors composed of thin-ply glass and carbon layers are designed and attached to the surface of laminated FRP composites exposed to transverse loading. A comprehensive experimental characterisation, including quasi-static indentation and low-velocity impact tests alongside non-destructive evaluations such as ultrasonic C-scan and visual inspection, is conducted to assess the sensors’ efficacy in detecting BVID. Moreover, a comparison between the two transverse loading types, static indentation and low-velocity impact, is presented. The results suggest that integrating sensors into composite structures has a minimal effect on mechanical properties such as structural stiffness and energy absorption, while substantially improving damage visibility. Additionally, the influence of fibre orientation of the sensing layer on sensor performance is evaluated, and correlations between internal and surface damage are demonstrated

Emergence of a new focus of anthroponotic cutaneous leishmaniasis due to Leishmania tropica in rural communities of Bam district after the earthquake, Iran

objectives To describe a new emerging focus of anthroponotic cutaneous leishmaniasis (ACL) due to Leishmania tropica in rural areas of Dehbakry county, south-eastern Iran, after the earthquake of 2003. methods House-to-house survey of 3884 inhabitants for active leishmaniasis lesions or scars. The diagnosis was confirmed by smears, cultures and identification of the parasite by polymerase chain reaction (PCR). results All age groups were affected, although patients £10 years of age showed the highest rate of infection (P = 0.0001). The overall prevalence rate was 5.3%; 6.3% in females and 4.3% in males. Of 204 cases, 1.8% had active sores and 3.5% had scars, with a significant difference between the sexes (P = 0.005). 47% of the lesions were on the face and 77.9% had one lesion. The incidence rose gradually 2004–2005, but grew exponentially 2006–2008. Electrophoresis of PCR products indicated that L. tropica was the causative agent. conclusions The current emergence was unexpected in this rural locality, where no previous history of CL was recorded. According to our knowledge this is the first report of a gradually establishing new ACL focus in rural communities after the 2003 earthquake

Comparisons of Estimation Procedures for Nonlinear Multilevel Models

We introduce General Multilevel Models and discuss the estimation procedures that may be used to fit multilevel models. We apply the proposed procedures to three-level binary data generated in a simulation study. We compare the procedures by two criteria, Bias and efficiency. We find that the estimates of the fixed effects and variance components are substantially and significantly biased using Longford's Approximation and Goldstein's Generalized Least Squares approaches by two software packages VARCL and ML3. These estimates are not significantly biased and are very close to real values when we use Markov Chain Monte Carlo (MCMC) using Gibbs sampling or Nonparametric Maximum Likelihood (NPML) approach. The Gaussian Quadrature (GQ) approach, even with small number of mass points results in consistent estimates but computationally problematic. We conclude that the MCMC and the NPML approaches are the recommended procedures to fit multilevel models

4D-printed shape memory polymer: Modeling and fabrication

Additive manufacturing (AM), as one of the most powerful manufacturing methods, is fabricating a three-dimensional (3D) structure using computer-aided design (CAD) data by adding material layer by layer. In contrast to traditional manufacturing processes that start from raw block material and remove waste materials, the AM process can demonstrate better aspects such as freedom of design, reduced postprocessing, and waste reduction. With emerging smart materials such as shape memory polymers, the 3D printing technology has upgraded to a technology that is called four-dimensional (4D) printing, in which the fourth dimension expresses time. In this technology, by using active materials, the printed structure can reshape its configuration and also change its mechanical properties in the presence of external stimuli such as temperature, magnetic field, and/or electric field. The fabrication and modeling of 4D-printed structures are considered due to their extensive applications in various areas such as biomedical and robotic. In this chapter, initially based on thermomechanical properties of smart materials, the constitutive modeling is presented for the shape memory feature. Subsequently, the fabrication of 4D-printed elements based on the FDM process is described, and a simple finite element method (FEM) is introduced to predict their self-morphing features. Finally, the fabricated self-morphing and adaptive structures are presented and the proposed model is calibrated based on them. Following model calibration, some smart structures such as grippers, adaptive dynamic structures, and smart composites are presented as case studies, and their behavior under external stimuli is investigated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen

Physical Activity in the Elderly with Fall Experience Over the Past Year: Results from Amirkola Health and Ageing Project

Background and purpose: Nowadays, immobility is known to be the fourth risk factor for mortality. The aim of the present study was to investigate the relationship between fall experience over the previous year and levels of physical activity in the elderly. Materials and Methods: The study was performed with 1616 participants of 60≤ years. The relationship between physical activities in the elderly with age, sex, educational level, body mass index, comorbidities, and fall experience over the previous year was evaluated. Physical activity in the elderly was evaluated using the physical activity scale for the elderly. Results: In the multiple regression model, the age (β: -1.6, 95% CI:  -2.0- -1.1), sex, female (β: 11.0, 95% CI: 4.3-17.6), and comorbidities (β: -6.8, 95% CI: -13.5 - -0.1) had a significant relationship with the physical activity score. On the contrary, there was no significant difference between the score of physical activity and both groups with and without the experience of fall over the previous year (β: 0.09, 95% CI: -8.0 - 8.2). Conclusion: Increasing age with comorbidity resulted in a decrease in the average physical activity score in the studied elderly population. However, the experience of fall had no relationship with it. Providing the conditions alongside the training required to carry out physical activities, especially in the elderly people with the disease, was suggested

Capture-recapture method for assessing publication bias

<p style="line-height: 200%; margin: 0cm 0cm 0pt;"><span style="font-size: small;"><span style="font-family: Times New Roman;"><strong><span style="color: black;">Background</span></strong><span style="color: black;">: Publication bias is an important factor that may result in selection bias and lead to overestimation of the intervention effect. Capture recapture method is considered as a potentially useful procedure for investigating and estimating publication bias. </span></span></span></p><p style="line-height: 200%; margin: 0cm 0cm 0pt;"><span style="font-size: small;"><span style="font-family: Times New Roman;"><strong><span style="color: black;">Methods</span></strong><span style="color: black;">: We conducted a systematic </span><span style="color: black; mso-ansi-language: EN;" lang="EN">review to estimate t</span><span style="color: black;">he duration of protection provided by hepatitis B vaccine by measuring the anamnestic immune response to booster doses of vaccine</span><span style="color: black; mso-ansi-language: EN;" lang="EN"> and retrieved studies from three separate sources, including a) electronic databases, b) reference lists of the studies, and c) conference databases as well as contact with experts and manufacturers. Capture recapture and some conventional methods such as funnel plot, Begg test, Egger test, and trim and fill method were employed for assessing publication bias. </span></span></span></p><p style="line-height: 200%; margin: 0cm 0cm 0pt;"><span style="font-size: small;"><span style="font-family: Times New Roman;"><strong><span style="color: black; mso-ansi-language: EN;" lang="EN">Results</span></strong><span style="color: black; mso-ansi-language: EN;" lang="EN">: </span><span style="color: black;">Based on c</span>apture recapture method, completeness of the overall search results<span style="color: black;"> was 87.2% [95% CI: 84.6% to 89.0%] and </span>log-linear model suggested 5 [95% CI: 4.2 to 6.2] missing studies. The funnel <span style="color: black;">plot was asymmetric but Begg and Egger tests results were not statistically significant and trill and fill approach made no change in pooled effect. </span></span></span></p><p style="line-height: 200%; margin: 0cm 0cm 0pt;"><span style="font-size: small;"><span style="font-family: Times New Roman;"><strong><span style="color: black;">Conclusions</span></strong><span style="color: black;">: Capture recapture method may be a useful practical approach for estimating the number of missing studies which are not usually detected by search strategy, although assumptions of this method may limit its general application in systematic reviews. In addition, capture recapture method may be considered as an alternative approach for estimating the extent of publication bias based on overlapping information rather than mirror image of extreme values on funnel plot.</span></span></span></p&gt