An Enhanced Temperature Control Approach to Simulate Profile Extrusion.

Thermoplastic extrusion, a widely used method for processing thermoplastic materials, requires precise temperature control to ensure product quality. However, existing computer-aided engineering tools often oversimplify the temperature distribution calculations, leading to additional discrepancies between simulations and the actual processes. This study introduces a novel multi-region modeling approach to address this issue. By employing realistic temperature control conditions, the methodology overcomes the limitations of current numerical modeling tools. The key contributions include the development of a transient, incompressible, non-isothermal solver integrated into the OpenFOAM computational library and the implementation of a specialized boundary condition that emulates Proportional-Integral-Derivative (PID) control using real-time thermocouple measurements. The findings highlight temperature deviations at the flow channel walls and total pressure drop while demonstrating a smaller impact on velocity and flow uniformity at the outlet under steady-state conditions. This research substantially advances the understanding of thermal dynamics in extrusion processes, offering crucial insights for enhancing temperature control and laying the groundwork for more effective and precise operational strategies.

Computational Framework to Model the Selective Laser Sintering Process.

Selective laser sintering (SLS) is one of the most well-regarded additive manufacturing (AM) sub-processes, whose popularity has been increasing among numerous critical and demanding industries due to its capabilities, mainly manufacturing parts with highly complex geometries and desirable mechanical properties, with potential to replace other, more expensive, conventional processes. However, due to its various underlying multi-physics phenomena, the intrinsic complexity of the SLS process often hampers its industrial implementation. Such limitation has motivated academic interest in obtaining better insights into the process to optimize it and attain the required standards. In that regard, the usual experimental optimization methods are time-consuming and expensive and can fail to provide the optimal configurations, leading researchers to resort to computational modeling to better understand the process. The main objective of the present work is to develop a computational model capable of simulating the SLS process for polymeric applications, within an open-source framework, at a particle-length scale to assess the main process parameters' impact. Following previous developments, virgin and used polymer granules with different viscosities are implemented to better represent the actual process feedstock. The results obtained agree with the available experimental data, leading to a powerful tool to study, in greater detail, the SLS process and its physical parameters and material properties, contributing to its optimization.

Trapeziectomy and Suture-Button Suspensionplasty for Basilar Thumb Arthritis: Is It Enough to Prevent First Ray Subsidence?

Introduction Trapeziectomy and suture-button suspensionplasty (SBS) are a novel option to treat end-stage trapeziometacarpal (TMC) osteoarthritis. Our purpose is to evaluate our outcomes with this technique and in this setting, with a minimum of 18 months of follow-up. Materials and Methods Twenty-eight patients were included, operated between 2016 and 2018. We recorded demographic data, preoperative Eaton stage, follow-up and operative times. The patients completed the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire and tip pinch, key pinch, and grip strength were measured. First metacarpal subsidence was calculated, and postoperative complications were documented. Results The average follow-up was 34 months. The mean QuickDASH was 32 at the final follow-up. The average strength results were 20 kg for grip, 3.6 kg for tip pinch, and 4.2 kg for key pinch. The rate of first ray subsidence was 10.7%. We encountered three complications: a hardware intolerance, a second metacarpal fracture, and a suture rupture. There was one reoperation to remove an implant. Conclusion Trapeziectomy and SBS functional results are similar to other techniques, with less subsidence of the first ray and allowing for early mobilization and fast recovery. This procedure is a safe and promising option in the treatment of TMC osteoarthritis, with good medium-term outcomes.

Bilateral hip heterotopic ossification with sciatic nerve compression on a paediatric patient-An individualized surgical approach: A case report.

BACKGROUND: Neurogenic heterotopic ossification is an acquired serious complication described in patients with central nervous system disorders and defined by bone formation in non-osseous tissue. CASE SUMMARY: We present an unusual case of a 13-yr-old boy presenting with hip pain and severe gait impairment 5 mo after the diagnosis of hemiplegia following a spontaneous intracerebral haemorrhage. Computed tomography revealed bilateral heterotopic ossification of both the paretic and the non-paretic limbs, with entrapment of the sciatic nerve. The choice of surgical or nonsurgical management of such patients depends on the timing of diagnosis, the symptoms, and the extent of maturation of the ossified lesions. Surgical resection remains the only treatment with proven, evidence-based effectiveness. The choice of surgical approach largely depends on the location of the ossified lesions. CONCLUSION: We believe the plane of dissection presented is a satisfactory option for resection of a posteromedial mass and sciatic nerve release.

Anterior Slope Correction-Flexion Osteotomy in Traumatic Genu Recurvatum.

A decreased posterior tibial slope has been associated with an increased risk of posterior cruciate ligament failure, anterior knee pain, and premature knee osteoarthritis. Trauma is a common cause of osseous genu recurvatum. Surgical management is recommended to correct the tibial slope and prevent knee pain and osteoarthritis progression. This article discusses our preferred treatment using a proximal tibial opening-wedge osteotomy for surgical management of genu recurvatum secondary to significant anterior tibial slope.

Is bilateral hallux valgus chevron osteotomy a safe procedure for ambulatory surgery?

INTRODUCTION: Several osteotomies of the first metatarsal have been described for treatment of hallux valgus but chevron osteotomy is one of the most common and well-established procedure for treating this deformity. Although there is a trend towards considering bilateral surgery there is lack of publications addressing bilateral treatment in ambulatory units. The aim of this study is to analyze results of bilateral and unilateral distal chevron osteotomies associated with lateral soft tissue release as ambulatory procedures. MATERIALS AND METHODS: A retrospective review was made about the patients treated at our ambulatory unit over a period of five years. Initially, general information as patient's satisfaction's rate and return to normal activity's time and evaluation of standardized follow-up charts and records made by the surgeon were recorded. Secondly, the hallux metatarsophalangeal interphalangeal scale developed by the American Orthopedic Foot & Ankle Society was used. RESULTS: A total of 194 patients with 230 feet operated were included in this study. We found 29 patients that didn't meet the inclusion criteria and were excluded. The unilateral group was composed by 139 feet and the bilateral group by 52 feet. The improvement between preoperative and discharge clinical and radiographic results was significant independently in both groups. A total of 14% of complications were found in our study, 19% in the unilateral group and 12% at the bilateral group. None of them required revision surgery. CONCLUSION: Bilateral distal chevron osteotomies, associated with lateral soft tissue release, are safe and effective ambulatory procedures. It was found a satisfactory deformity correction in moderate HV. Both patients that underwent unilateral and bilateral procedures had similar clinical and radiological outcomes with no increase in complications or return to normal activity time. With this study it was demonstrated that bilateral chevron osteotomies can be performed as ambulatory procedures.

Myocardial oedema: pathophysiological basis and implications for the failing heart.

Myocardial fluid homeostasis relies on a complex interplay between microvascular filtration, interstitial hydration, cardiomyocyte water uptake and lymphatic removal. Dysregulation of one or more of these mechanisms may result in myocardial oedema. Interstitial and intracellular fluid accumulation disrupts myocardial architecture, intercellular communication, and metabolic pathways, decreasing contractility and increasing myocardial stiffness. The widespread use of cardiac magnetic resonance enabled the identification of myocardial oedema as a clinically relevant imaging finding with prognostic implications in several types of heart failure. Furthermore, growing experimental evidence has contributed to a better understanding of the physical and molecular interactions in the microvascular barrier, myocardial interstitium and lymphatics and how they might be disrupted in heart failure. In this review, we summarize current knowledge on the factors controlling myocardial water balance in the healthy and failing heart and pinpoint the new potential therapeutic avenues.

Trapeziectomy with suture-button suspensionplasty versus ligament reconstruction and tendon interposition: a randomized controlled trial.

The purpose of the present study was to compare the results of patients operated with trapeziectomy and ligament reconstruction and tendon interposition (LRTI) using flexor carpi radialis tendon versus trapeziectomy followed by suspension of the first metacarpal to the second metacarpal using a Mini TightRope® suture button (suture button suspension: SBS). A single-center prospective randomized controlled trial was performed, comparing 37 patients with SBS and 39 with LRTI. All surgeries were performed by the same fellowship-trained hand surgeon. Patients were assessed by an independent observer at 40 months' follow-up. Pre- and postoperative strength, trapezial space ratio (TSR), range of motion, QuickDASH and visual analogue pain score were recorded. Both procedures improved functional parameters of pain, key strength, tip strength and grip strength while maintaining range of motion, without significant differences. In the SBS group, TSR decreased by 17%, compared to 28% in the LRTI group. The mean operative time was shorter in SBS (63 vs 91 minutes; p < 0.0001), as was immobilization time (2 vs 6 weeks; p < 0.0001), and patients resumed normal activity sooner (10 vs 12 week; p = 0.0138) and required less physical therapy (19.3 vs 13.1 weeks; p < 0.0001). We believe that our results are related to the hypothesis suggested by biomechanical studies that revealed better initial load bearing profile and maintenance of trapezial space following serial loading in cadaver models.

Assessing the Compressive and Impact Behavior of Plastic Safety Toe Caps through Computational Modelling.

Toe caps are one of the most important components in safety footwear, but have a significant contribution to the weight of the shoe. Efforts have been made to replace steel toe caps by polymeric ones, since they are lighter, insulated and insensitive to magnetic fields. Nevertheless, polymeric solutions require larger volumes, which has a negative impact on the shoe's aesthetics. Therefore, safety footwear manufacturers are pursuing the development of an easy, low-cost and reliable solution to optimize this component. In this work, a solid mechanics toolbox built in the open-source computational library, OpenFOAM®, was used to simulate two laboratory standard tests (15 kN compression and 200 J impact tests). To model the polymeric material behavior, a neo-Hookean hyper-elasto-plastic material law with J2 plastic criteria was employed. A commercially available plastic toe cap was characterized, and the collected data was used for assessment purposes. Close agreements, between experimental and simulated values, were achieved for both tests, with an approximate error of 5.4% and 6.8% for the displacement value in compression and impact test simulations, respectively. The results clearly demonstrate that the employed open-source finite volume computational models offer reliable results and can support the design of toe caps for the R&D footwear industry.

Pinckney fracture: do not underestimate trauma of the distal phalanx of the hallux.

Toe injuries are common in the emergency department and most of them are treated conservatively. In some circumstances, these injuries can present as a physeal fracture with concomitant soft-tissue injury affecting the nail bed and resulting in a hidden open fracture. To adequately treat these patients, a high index of suspicion is needed to diagnose and treat the open fractures and to prevent complications such as infection, osteomyelitis, malunion and premature physeal arrest.We report a case of a patient that was admitted to the hospital with a Salter-Harris type I fracture of the distal phalanx of the hallux. After confirming the diagnosis, antibiotic treatment was started and the fracture was reduced and fixed.The literature on this entity is sparse and most of the management protocols are based on its hand equivalent-the Seymour fracture, emphasising the low threshold for treating these lesions as an open fracture.

Towards Customized Footwear with Improved Comfort.

A methodology enabling the customization of shoes for comfort improvement is proposed and assessed. For this aim, 3D printed graded density inserts were placed in one of the critical plantar pressure zones of conventional insoles, the heel. A semi-automated routine was developed to design the 3D inserts ready for printing, which comprises three main stages: (i) the definition of the number of areas with different mesh density, (ii) the generation of 2D components with continuous graded mesh density, and (iii) the generation of a 3D component having the same 2D base mesh. The adequacy of the mesh densities used in the inserts was previously assessed through compression tests, using uniform mesh density samples. Slippers with different pairs of inserts embedded in their insoles were mechanically characterized, and their comfort was qualitatively assessed by a panel of users. All users found a particular pair, or a set, of prototype slippers more comfortable than the original ones, taken as reference, but their preferences were not consensual. This emphasizes the need for shoe customization, and the usefulness of the proposed methodology to achieve such a goal.

Validation of the Ottawa ankle rules: Strategies for increasing specificity.

INTRODUCTION: The majority of patients with ankle injuries undergo radiological examinations of the foot, ankle or both. The objective of this study was in the first place to validate the Ottawa Ankle Rules (OARs) for the population of our centre. Secondly, an attempt was made to identify parameters that contribute to improve the specificity of the method, with a view to reduce the need for patients to be exposed to radiation as well as optimizing the expenses of the Emergency Ward (EW). MATERIALS AND METHODS: This was a prospective study conducted during a 9-month period. The study population included 148 patients, in 54 (36%) of the patients a fracture was present on the exams performed. Patients were submitted to a sequential protocol in the EW with a form completion, evaluation of OARs, application of the Visual Analog Pain Scale (VAS) and radiographic exams. RESULTS: We found a sensitivity of OARs in ankle injuries of 100%, specificity of 26% and in midfoot injuries of 100% and 62% respectively. All patients with fractures had a VAS of 5 or more points in any of the tested sites. With the VAS criterium, we found a significant increase of global specificity (38% vs 15%), as well as when applied only to the ankle (26% to 47%) or to midfoot trauma (62% to 67%). In both, there would have been a 100% reduction of CT scans. Patients with a fracture or with fractures who required surgical treatment had a mean VAS significantly higher than patients with no fracture or fractures submitted to conservative treatment respectively. Although there was a lower percentage of fractures in the group of injuries in Work Accidents (31% vs 37% Sports Activity and 38% Leisure Activity), there was a statistically significant increase in the sum of average VAS in Accidents at Work vs Leisure Activities and vs Sports Activities. CONCLUSION: We seek to confirm the usefulness of OARs for our population and we investigated strategies to further reduce the need for unnecessary radiographs. The introduction of parameters for grading pain and adapting to the context of the accident seem promising.

Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time.

This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters, thereby creating a series of converging/diverging flows. Numerical simulation of the flow assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. A strong quasi-linear relationship between the evolution of dispersion measured experimentally and the computational data was obtained. Theory was used to interpret experimental data, and the results obtained confirmed the hypotheses previously put forward by various authors that the dispersion of solid agglomerates requires not only sufficiently high hydrodynamic stresses, but also that these act during sufficient time. Based on these considerations, it was estimated that the cohesive strength of the GnP agglomerates is in the range of 5-50 kPa.

In-service characterization of a polymer wick-based quasi-dry electrode for rapid pasteless electroencephalography.

A novel quasi-dry electrode prototype, based on a polymer wick structure filled with a specially designed hydrating solution is proposed for electroencephalography (EEG) applications. The new electrode does not require the use of a conventional electrolyte paste to achieve a wet, low-impedance scalp contact. When compared to standard commercial Ag/AgCl sensors, the proposed wick electrodes exhibit similar electrochemical noise and potential drift values. Lower impedances are observed when tested in human volunteers due to more effective electrode/skin contact. Furthermore, the electrodes exhibit an excellent autonomy, displaying an average interfacial impedance of 37±11 kΩ cm2 for 7 h of skin contact. After performing bipolar EEG trials in human volunteers, no substantial differences are evident in terms of shape, amplitude and spectral characteristics between signals of wick and commercial wet electrodes. Thus, the wick electrodes can be considered suitable to be used for rapid EEG applications (electrodes can be prepared without the presence of the patient) without the traditional electrolyte paste. The main advantages of these novel electrodes over the Ag/AgCl system are their low and stable impedance (obtained without conventional paste), long autonomy, comfort, lack of dirtying or damaging of the hair and because only a minimal cleaning procedure is required after the exam.

Recurrence Plots: a New Tool for Quantification of Cardiac Autonomic Nervous System Recovery after Transplant.

OBJECTIVE: To evaluate a possible evolutionary post-heart transplant return of autonomic function using quantitative and qualitative information from recurrence plots. METHODS: Using electrocardiography, 102 RR tachograms of 45 patients (64.4% male) who underwent heart transplantation and that were available in the database were analyzed at different follow-up periods. The RR tachograms were collected from patients in the supine position for about 20 minutes. A time series with 1000 RR intervals was analyzed, a recurrence plot was created, and the following quantitative variables were evaluated: percentage of determinism, percentage of recurrence, average diagonal length, Shannon entropy, and sample entropy, as well as the visual qualitative aspect. RESULTS: Quantitative and qualitative signs of heart rate variability recovery were observed after transplantation. CONCLUSION: There is evidence that autonomic innervation of the heart begins to happen gradually after transplantation. Quantitative and qualitative analyses of recurrence can be useful tools for monitoring cardiac transplant patients and detecting the gradual return of heart rate variability.

Recurrence plots: a new tool for quantification of cardiac autonomic nervous system recovery after transplant

Abstract Objective: To evaluate a possible evolutionary post-heart transplant return of autonomic function using quantitative and qualitative information from recurrence plots. Methods: Using electrocardiography, 102 RR tachograms of 45 patients (64.4% male) who underwent heart transplantation and that were available in the database were analyzed at different follow-up periods. The RR tachograms were collected from patients in the supine position for about 20 minutes. A time series with 1000 RR intervals was analyzed, a recurrence plot was created, and the following quantitative variables were evaluated: percentage of determinism, percentage of recurrence, average diagonal length, Shannon entropy, and sample entropy, as well as the visual qualitative aspect. Results: Quantitative and qualitative signs of heart rate variability recovery were observed after transplantation. Conclusion: There is evidence that autonomic innervation of the heart begins to happen gradually after transplantation. Quantitative and qualitative analyses of recurrence can be useful tools for monitoring cardiac transplant patients and detecting the gradual return of heart rate variability.

Hollow Polypropylene Yarns as a Biomimetic Brain Phantom for the Validation of High-Definition Fiber Tractography Imaging.

Current brain imaging methods largely fail to provide detailed information about the location and severity of axonal injuries and do not anticipate recovery of the patients with traumatic brain injury. High-definition fiber tractography appears as a novel imaging modality based on water motion in the brain that allows for direct visualization and quantification of the degree of axons damage, thus predicting the functional deficits due to traumatic axonal injury and loss of cortical projections. This neuroimaging modality still faces major challenges because it lacks a "gold standard" for the technique validation and respective quality control. The present work aims to study the potential of hollow polypropylene yarns to mimic human white matter axons and construct a brain phantom for the calibration and validation of brain diffusion techniques based on magnetic resonance imaging, including high-definition fiber tractography imaging. Hollow multifilament polypropylene yarns were produced by melt-spinning process and characterized in terms of their physicochemical properties. Scanning electronic microscopy images of the filaments cross section has shown an inner diameter of approximately 12 µm, confirming their appropriateness to mimic the brain axons. The chemical purity of polypropylene yarns as well as the interaction between the water and the filament surface, important properties for predicting water behavior and diffusion inside the yarns, were also evaluated. Restricted and hindered water diffusion was confirmed by fluorescence microscopy. Finally, the yarns were magnetic resonance imaging scanned and analyzed using high-definition fiber tractography, revealing an excellent choice of these hollow polypropylene structures for simulation of the white matter brain axons and their suitability for constructing an accurate brain phantom.

Assessing a novel polymer-wick based electrode for EEG neurophysiological research.

BACKGROUND: The EEG technique has decades of valid applications in clinical and experimental neurophysiology. EEG equipment and data analysis methods have been characterized by remarkable developments, but the skin-to-electrode signal transfer remains a challenge for EEG recording. NEW METHOD: A novel quasi-dry system - the polymer wick-based electrode - was developed to overcome the limitations of conventional dry and wet silver/silver-chloride (Ag/AgCl) electrodes for EEG recording. RESULTS: Nine participants completed an auditory oddball protocol with simultaneous EEG acquisition using both the conventional Ag/AgCl and the wick electrodes. Wick system successfully recorded the expected P300 modulation. COMPARISON WITH EXISTING METHOD(S): Standard ERP analysis, residual random noise analysis, and single-trial analysis of the P300 wave were performed in order to compare signal acquired by both electrodes. It was found that the novel wick electrode performed similarly to the conventional Ag/AgCl electrodes. CONCLUSIONS: The developed wick electrode appears to be a reliable alternative for EEG research, representing a promising halfway alternative between wet and dry electrodes.

Development of polymer wicks for the fabrication of bio-medical sensors.

Polymer based wicking structures were fabricated by sintering powders of polycarbonate (PC), ultra-high molecular weight polyethylene and polyamide 12, aiming at selecting a suitable material for an innovative electroencephalography (EEG) bio-electrode. Preliminary experiments showed that PC based wicks displayed the best mechanical properties, therefore more detailed studies were carried out with PC to evaluate the influence of powder granulometry and processing parameters (pressure, temperature and time) on the mechanical properties, porosity, mean pore radius and permeability of the wicks. It was concluded that the mechanical properties are significantly enhanced by increasing the processing time and pressure, although at the expense of a significant decrease of porosity and mean pore diameter (and thus permeability), particularly for the highest applied pressures (74kPa). However, a good compromise between porosity/permeability and mechanical properties could be obtained by sintering PC powders of particle sizes below 500µm at 165°C for 5min, upon an applied pressure of 56kPa. Moreover, PC proved to be chemically stable in contact with an EEG common used disinfectant. Thus, wicking structures with appropriate properties for the fabrication of reusable bio-electrodes could be fabricated from the sintering of PC powders.

Study on fibrous materials for brain phantoms.

Generally, current clinical imaging methods do not provide highly detailed information about location of axonal injury, severity of injury or expected recovery of patients with traumatic brain injury (TBI). High-Definition Fiber Tractography (HDFT) is a novel imaging modality that allows visualizing and quantifying, directly, the degree of axons damage, predicting functional deficits due to traumatic axonal injury and loss of cortical projections. This imaging modality is based on diffusion technology. Being a novel modality, validation and quality control are essential. Thus this study aims at the development of a brain phantom to mimic the human brain in order to fill some gaps that currently exist in this area. This paper is focused on this novel imaging approach, the role of brain phantoms on its validation and the quality control, as well as, on the materials used in their construction. Furthermore, some important characteristics of fibrous materials for brain phantom are also discussed.