Effects of Seawater on Mechanical Performance of Composite Sandwich Structures: A Machine Learning Framework.

Sandwich structures made with fibre-reinforced plastics are commonly used in maritime vessels thanks to their high strength-to-weight ratios, corrosion resistance, and buoyancy. Understanding their mechanical performance after moisture uptake and the implications of moisture uptake for their structural integrity and safety within out-of-plane loading regimes is vital for material optimisation. The use of modern methods such as acoustic emission (AE) and machine learning (ML) could provide effective techniques for the assessment of mechanical behaviour and structural health monitoring. In this study, the AE features obtained from quasi-static indentation tests on sandwich structures made from E-glass fibre face sheets with polyvinyl chloride foam cores were employed. Time- and frequency-domain features were then used to capture the relevant information and patterns within the AE data. A k-means++ algorithm was utilized for clustering analysis, providing insights into the principal damage modes of the studied structures. Three ensemble learning algorithms were employed to develop a damage-prediction model for samples exposed and unexposed to seawater and were loaded with indenters of different geometries. The developed models effectively identified all damage modes for the various indenter geometries under different loading conditions with accuracy scores between 86.4 and 95.9%. This illustrates the significant potential of ML for the prediction of damage evolution in composite structures for marine applications.

Damage Assessment of Glass-Fibre-Reinforced Plastic Structures under Quasi-Static Indentation with Acoustic Emission.

The use of fibre-reinforced plastics (FRPs) in various industrial applications continues to increase thanks to their good strength-to-weight ratio and impact resistance, as well as the high strength that provides engineers with advanced options for the design of modern structures subjected to a variety of out-of-plane impacts. An assessment of the damage morphology under such conditions using non-destructive techniques could provide useful data for material design and optimisation. This study investigated the damage mechanism and energy-absorption characteristics of E-glass laminates and sandwich structures with GFRP face sheets with PVC cores under quasi-static indentation with conical, square, and hemispherical indenters. An acoustic emission (AE) technique, coupled with a k-means++ pattern-recognition algorithm, was employed to identify the dominant microscopic and macroscopic damage mechanisms. Additionally, a post-mortem damage assessment was performed with X-ray micro computed tomography and scanning electron microscopy to validate the identified clusters. It was found that the specific energy absorption after impact with the square and hemispherical indenters of the GFRP sandwich and the plain laminate differed significantly, by 19.29% and 43.33%, respectively, while a minimal difference of 3.5% was recorded for the conical indenter. Additionally, the results obtained with the clustering technique applied to the acoustic emission signals detected the main damaged modes, such as matrix cracking, fibre/matrix debonding, delamination, the debonding of face sheets/core, and core failure. The results therefore could provide a methodology for the optimisation and prediction of damage for the health monitoring of composites.

Assessing Crimp of Fibres in Random Networks with 3D Imaging.

The analysis of fibrous structures using micro-computer tomography (µCT) is becoming more important as it provides an opportunity to characterise the mechanical properties and performance of materials. This study is the first attempt to provide computations of fibre crimp for various random fibrous networks (RFNs) based on µCT data. A parametric algorithm was developed to compute fibre crimp in fibres in a virtual domain. It was successfully tested for six different X-ray µCT models of nonwoven fabrics. Computations showed that nonwoven fabrics with crimped fibres exhibited higher crimp levels than those with non-crimped fibres, as expected. However, with the increased fabric density of the non-crimped nonwovens, fibres tended to be more crimped. Additionally, the projected fibre crimp was computed for all three major 2D planes, and the obtained results were statistically analysed. Initially, the algorithm was tested for a small-size, nonwoven model containing only four fibres. The fraction of nearly straight fibres was computed for both crimped and non-crimped fabrics. The mean value of the fibre crimp demonstrated that fibre segments between intersections were almost straight. However, it was observed that there were no perfectly straight fibres in the analysed RFNs. This study is applicable to approach employing a finite-element analysis (FEA) and computational fluid dynamics (CFD) to model/analyse RFNs.

Algorithm to determine orientation distribution function from microscopic images of fibrous networks: Validation with X-ray microtomography.

Quantitative analysis of fibre orientation in a random fibrous network (RFN) is important to understand their microstructure, properties and performance. 2D fibre orientation distribution presents an in-plane fibre orientation without any information on fibre orientation in thickness direction. This research introduces a fully parametric algorithm for computing 3D fibre orientation as thickness is important for high-density or thick fibrous networks. The algorithm is tested for 3 major classes of nonwoven fabrics called low- (L), medium- (M) and high-density (H) ones. H fabric density is 6-8 times larger than the L fabric density. M fabric density (traditional intermediate fabric density) is 3-4 times larger than the L fabric density. Voxel models of experimental nonwoven webs were generated by an X-ray micro-CT (µCT) system and evaluated with the algorithm. Statistical results showed that a fraction of fibres orientated along the thickness direction increases as fibre density grows. To validate the accuracy of findings, deterministic voxelated virtual fibrous structures, created using mathematical functions were used. This novel algorithm is able to produce a 3D orientation distribution function (ODF) for any RFN including, models of nonwovens produced with various manufacturing parameters, experimentally verified and validated with X-ray µCT. Also, it can compute 2D ODFs of various types of RFNs to evaluate 2D behaviour of fibrous structures. The obtained results are useful for applications in many fields including finite element analysis, computational fluid dynamics, additive manufacturing, etc.

Endothelial Dysfunction and Ischemia-Modified Albumin Levels in Males with Diabetic and Nondiabetic Erectile Dysfunction.

In this study, we aimed to determine endothelial dysfunction and ischemia-modified albumin (IMA) levels in patients diagnosed with erectile dysfunction (ED) and to examine the relationship between these and diabetes disease. 86 male patients (46 patients with diabetes, age: 51.5 ± 9.2 and 40 patients with nondiabetes (control group), age: 54.78 ± 12.2) were included in the study. IMA, a new indicator of tissue ischemia and oxidative stress, was checked. Superoxide dismutase (SOD) activity, another oxidative stress indicator, was examined. Endothelin-1 (ET-1), one of the parameters of endothelial dysfunction, was measured. Additionally, endothelial function was evaluated with flow-mediated vasodilatation (FMD). Student's t-test was used for statistical evaluation. p values less than 0.05 were considered statistically significant. SOD activity was significantly lower in the diabetic group than in the control group, and ET-1 was significantly higher (p < 0.001). IMA was found to be significantly higher in the diabetic group than the control group (p < 0.001). FMD was significantly lower in diabetic group compared to the control group (p < 0.002). According to our findings, the co-occurrence of erectile dysfunction and diabetes demonstrates a complex condition that includes endothelial dysfunction, oxidative stress, and tissue ischemia. When the correlation of indicators, which are markers, was examined, the severity of the co-occurrence of diabetes and erectile dysfunction was again demonstrated.

A Rare Complication of Amplatz Sheath: Amplatz Sheath Rupture During Percutaneous Nephrolithotomy.

Introduction: Amplatz sheaths are hollow tubes that serve as the portal for the insertion of the nephroscope during percutaneous nephrolithotomy (PCNL). Breakage of this tube during the procedure is rare, but when it does occur it should be recognized and addressed promptly. Case Presentation: A 46-year-old Caucasian male patient was scheduled for PCNL. The Amplatz sheath was inserted in the usual manner over a balloon dilator and nephroscopy was performed. Profuse bleeding was encountered early. Upon meticulous endoscopic navigation, the broken Amplatz tube was recognized and replaced. This allowed us to identify and remove the fragment of the Amplatz tube, followed by stone fragmentation and removal. Conclusion: Our experience highlights the importance of recognizing this rare complication of a broken Amplatz sheath that should be managed promptly and effectively through endoscopic means without the need to abort the planned PCNL.

Anisotropic cytocompatible electrospun scaffold for tendon tissue engineering elicits limited inflammatory response in vitro.

Tendon tears are a relevant concern for today's national health systems because of their social impact and high recurrence rate. The current gold standard for fixing tendon tears is surgical repair; however, this strategy is not able to fully re-establish tendon integrity and functionality. Tissue engineering approaches aim at promoting tissue regeneration by delivering the opportune signals to the injured site combining biomaterials, cells and biochemical cues. Electrospinning is currently one of the most versatile polymer processing techniques that allows manufacturing of nano- and micro-fibres substrates. Such fibrous morphology is deemed to be an ideal substrate to convey topographical cues to cells. Here we evaluated the potential of polycaprolactone processed by means of electrospinning technology for tendon tissue engineering. Fibrous free-of-defects substrate with random and aligned fibres were successfully fabricated. Rat tenocytes were used to assess the cytocompatibility of the substrates for application as tendon tissue engineered devices. Tenocytes were able to proliferate and adapt to the substrates topography acquiring an elongated morphology, which is the precondition for oriented collagen deposition, when seeded on aligned fibres. Real time Polymerase Chain Reaction (Rt-PCR) also revealed the overall maintenance of tenocyte phenotype over 7 days culture. To verify suitability for in vivo implantation, the level of inflammatory cytokine genes expressed by THP-1 cells cultured in presence of electrospun polycaprolactone substrates was evaluated. Inflammatory response was limited. The novel preliminary in vitro work presented herein showing tenocytes compatibility and limited inflammatory cytokines synthesis suggests that electrospun polycaprolactone may be taken into consideration as substrate for tendon healing applications.

Diagnostic Value of Plasma Pentraxin3- Level For Diagnosis of Erectile Dysfunction.

PURPOSE: Erectile dysfunction (ED) is a sexual dysfunction described as the inability to develop or maintain an erection of the penis adequate for sexual intercourse, and its prevalence increases with age. Seen as a common sexual disorder worldwide, organic causes are the underlying reason for 80 percent of ED cases, with the most characteristic pathology responsible for organic ED being atherosclerosis. This study investigates the diagnostic value of plasma PTX-3 levels in arterial ED. MATERIALS AND METHODS: This study included a total of 45 patients who were admitted to the urology and cardiologyoutpatient clinics of the Medical Faculty of Canakkale Onsekiz Mart University (COMU) and consented to participate in this study. Patients were categorized into three equal groups in number: (1) patients with ED diagnosed with coronary artery disease (CAD) (15 patients in total); (2) patients with ED not having coronary artery disease or any other equivalent diseases (diabetes mellitus, hypertension and hyperlipidemia) (15 patients in total);and (3) ordinary patients with no ED (15 patients in total). An interview was conducted at the andrology polyclinic with each patient in order to ascertain detailed information on their medical and sexual history and on demographic characteristics. All patients were also administered the International Index of Erectile Function (IIEF) questionnaire. RESULT: The findings from this study investigating the diagnostic value of plasma PTX-3 levels in ED were statistically significant for two comparisons: the differences between the peripheral blood and cavernous blood values of the patient groups (group 1 and 2) and the control group (group 3), and the differences between the peripheral blood and cavernous blood values of group 2 (patients with ED who do not have CAD) and the control group (group 3). CONCLUSION: As PTX-3 is more specific than the formerly recognized biochemical markers in endothelial dysfunction, it can be used in the diagnosis of vascular originated ED.

Efficacy of Duloxetine in the Early Management of Urinary Continence after Radical Prostatectomy.

AIM: To evaluate the efficacy of early duloxetine therapy in stress urinary incontinence occurring after radical prostatectomy (RP). MATERIAL AND METHOD: Patients that had RP were randomly divided into 2 groups following the removal of the urinary catheter. Group A patients (n = 28) had pelvic floor exercise and duloxetine therapy. Group B patients (n = 30) had only pelvic floor exercise. The incontinence status of the patients and number of pads were recorded and 1-hour pad test and Turkish validation of International Consultation on Incontinence Questionnaire-Short Form test were applied to the patients at the follow-up. RESULTS: When the dry state of the patients was evaluated, 5, 17, 3, and 2 of 28 Group A patients stated that they were completely dry in the 3rd, 6th, 9th and 12th month respectively and pad use was stopped. There was no continence in 30 Group B in the first 3 months. Twelve, 6, and 8 patients stated that they were completely dry in the 6th, 9th and 12th month, respectively. But 3 of 4 patients in whom dryness could not be provided were using a mean of 7.6 pads in the first day and a mean of 1.3 pads after 1 year. When pad use of the patients was evaluated, the mean monthly number of pad use was determined to be 6.2 (4-8) in the initial evaluation, 2.7 (0-5) in the in 3rd month, 2 (0-3) in the 6th month and 1.6 (0-2) pad/d in the 9th month in the group taking medicine. The mean monthly number of pads used was determined to be 5.8 (4-8) in the initial evaluation, 4.3 (3-8) in the 3rd month, 3 (0-6) in the 6th month and 1.6 (0-6) pad/d in the 9th month in the group not taking medicine. CONCLUSION: According to the results, early duloxetine therapy in stress urinary incontinence that occurred after RP provided early continence.

Penetration of cutting tool into cortical bone: experimental and numerical investigation of anisotropic mechanical behaviour.

An anisotropic mechanical behaviour of cortical bone and its intrinsic hierarchical microstructure act as protective mechanisms to prevent catastrophic failure due to natural loading conditions; however, they increase the extent of complexity of a penetration process in the case of orthopaedic surgery. Experimental results available in literature provide only limited information about processes in the vicinity of a tool-bone interaction zone. Also, available numerical models the bone-cutting process do not account for material anisotropy or the effect of damage mechanisms. In this study, both experimental and numerical studies were conducted to address these issues and to elucidate the effect of anisotropic mechanical behaviour of cortical bone tissue on penetration of a sharp cutting tool. First, a set of tool-penetration experiments was performed in directions parallel and perpendicular to bone axis. Also, these experiments included bone samples cut from four different cortices to evaluate the effect of spatial variability and material anisotropy on the penetration processes. Distinct deformation and damage mechanisms linked to different microstructure orientations were captured using a micro-lens high-speed camera. Then, a novel hybrid FE model employing a smoothed-particle-hydrodynamic domain embedded into a continuum FE one was developed based on the experimental configuration to characterise the anisotropic deformation and damage behaviour of cortical bone under a penetration process. The results of our study revealed a clear anisotropic material behaviour of the studied cortical bone tissue and the influence of the underlying microstructure. The proposed FE model reflected adequately the experimental results and demonstrated the need for the use of the anisotropic and damage material model to analyse cutting of the cortical-bone tissue.