Search Results (360)

This paper investigates the dual effects of slope variation and flame interaction on counter-directional flame propagation through numerical simulations of polymethylmethacrylate (PMMA) plates. Critical flame propagation parameters, including flame morphology, flame spread speed, mass loss rate, and radiative heat flux density, were analyzed using the Fire Dynamics Simulator (FDS v6.7.5) software. By comparing counter-directional flames and unilateral flames under varying slope conditions, we evaluated how flame interactions influence flame spread speed and mass loss rate, as well as the role of the view factor in radiative heat flux distribution. Numerical results revealed that the counter-directional fire propagation process on slopes could be divided into four distinct stages based on variations in flame spread rate and mass loss rate. Moreover, we propose a novel method to quantify flame interaction intensity on slopes using flame spread time. These findings enhance the mechanistic understanding of slope-dependent counter-directional flame propagation. Full article

Objective: Trauma is a leading cause of enophthalmos, typically resulting from an increase in the volume of the bony orbit. The general consensus is that post-traumatic primary deformity repair should aim to restore the premorbid volume, shape, and cosmesis of the orbitozygomatic complex (OZC). This study aims to utilise novel three-dimensional (3D) printed patient-specific moulds to intraoperatively fabricate enophthalmos wedges and onlays using polymethylmethacrylate (PMMA) bone cement to reconstruct the OZC. Methods: A total of seven patients underwent digital surgical planning using Freeform software to virtually correct orbitozygomatic complex deformities guided by a design algorithm. Three-dimensionally printed nylon patient-specific moulds were used intraoperatively to fabricate enophthalmos wedges and/or onlays using an industry-standard PMMA bone cement. Clinical examination and application of the proposed design algorithm determined that enophthalmos wedges were indicated for four patients, with one also requiring an onlay; and periorbital onlays were required for the three remaining patients. Results: Hertel exophthalmometry at a mean follow-up of 19.1 months demonstrated good outcomes in the correction of post-traumatic enophthalmos and hypoglobus and with patients reporting good subjective cosmetic results. Patients 5 and 7 had follow-up three-dimensional computed tomography (3D-CT) to confirm correct placement. Conclusion: The use of patient-specific PMMA wedges and onlays, fabricated intraoperatively with the aid of 3D-printed moulds, offers a reliable and effective approach for correcting post-traumatic enophthalmos and hypoglobus. This method allows for the restoration of orbital volume and anatomical contours, addressing both functional and aesthetic concerns. Our results demonstrate that this technique yields favourable outcomes. Full article

Nanoplastics (NPs) pose a significant environmental threat due to their small sizes, widespread distribution, and bioavailability, enabling interactions with marine organisms from pelagic to benthic species. In this study, the effects of 10 days of exposure to waterborne poly(methyl)methacrylate (PMMA) NPs were evaluated in the crab Carcinus maenas by assessing behavioral and biochemical endpoints (in gills, hepatopancreas, muscle, and hemolymph). Behavioral assessments using an open field test revealed that exposure to PMMA NPs resulted in an increase in distance walked (from 73.662 ± 17.137 cm in control to 248.560 ± 25.462 cm in the highest PMMA NPs concentration) and in random movement patterns. Muscle acetylcholinesterase (AChE) activity decreased from 10.83 ± 0.73 to 6.75 ± 0.45 nmol/min/mg of protein with PMMA NPs concentration increase, which, combined with behavioral responses, suggests neurological incapacities. In the gills and hepatopancreas, defense and detoxification mechanisms were activated, with a significant increase in superoxide dismutase (SOD) activity (at 20 µg/L in gills and 80 µg/L in hepatopancreas) and glutathione S-transferases (GSTs) activity (all PMMA NPs concentrations in gills and 20 and 320 µg/L in hepatopancreas). Despite these activations, oxidative damage was observed, with a significant increase in protein carbonylation (PC) levels (20, 80, and 320 µg/L in gills and 5, 20, and 80 µg/L in hepatopancreas) and lipid peroxidation (LPO) (80 and 320 µg/L in gills and 80 µg/L in hepatopancreas). Effects on hemolymph followed a pattern similar to those reported for gills and hepatopancreas. An increase in SOD hemolymph activity was observed in organisms exposed to 5 and 80 µg/L, and GSTs activity increased in crabs exposed to 80 µg/L. Oxidative damage in hemolymph was only detected through LPO at 5 and 320 µg/L. Overall, this study showed that PMMA NPs induce biochemical alterations and damage in different tissues of C. maenas and affect its behavior with potential impacts at a population level. Full article

To promote environmental sustainability, this research investigated the potential of utilizing recycled polymethylmethacrylate (PMMA) as raw material in material extrusion (MEX) additive manufacturing (AM). To enhance its mechanical response, carbon black (CB) was employed as the filler in nanocomposite formation. Filament extrusion of the mixture at different concentrations produced printable feedstocks for MEX AM. Rheological analysis (viscosity and material flow rate) showed that the CB introduction to the matrix was beneficial for consistent layer deposition, while differential scanning calorimetry and thermogravimetric analyses verified the thermal stability of the nanocomposites during processing. Mechanical properties were optimized, with increases in modulus (27.8% and 25.8%, respectively, in tensile and bending loadings) and tensile strength at optimal CB loadings. Dynamic mechanical analysis revealed the viscoelastic response of the nanocomposites. Raman and energy dispersive spectroscopy provided element-related insights. Surface morphology and parts structure were observed employing scanning electron microscopy and micro-computed tomography, respectively, revealing a positive impact on the AM parts due to the CB presence in the nanocomposites. The 4 wt.% in CB content nanocomposite was the optimum one. This research pioneers the development of new sustainable nanocomposite filaments and highlights the potential of next-generation MEX-based AM. Full article

Background: Cement leakage remains a significant challenge in percutaneous vertebroplasty (PVP). Leakage can lead to serious complications, including spinal cord compression, pulmonary embolism, and nerve root irritation. While several techniques have been proposed to minimize leakage, an effective and simple solution is still needed. This study investigates the impact of pre-washing vertebral bodies with cold saline before cement injection as a potential method to reduce leakage. Methods: A retrospective analysis was conducted on patients who underwent PVP for osteoporotic vertebral compression fractures. Patients were divided into three groups: (1) conventional PVP, (2) PVP with room-temperature saline pre-injection, and (3) PVP with cold saline (4 °C) pre-injection. Cement leakage was assessed using intraoperative fluoroscopy and postoperative computed tomography (CT), categorized into paravertebral, intervertebral, retrograde, spinal canal, and distant venous leakage. Statistical analysis was performed to compare leakage rates among the groups. Results: A total of 262 patients with 461 treated vertebrae were analyzed. Cold saline pre-treatment significantly reduced cement leakage rates compared to conventional PVP and room-temperature saline pre-injection (p < 0.05). CT imaging detected significantly more cement extravasation than fluoroscopy (p < 0.01). The incidence of spinal canal and intervertebral leakage was lowest in the cold saline group, suggesting improved cement containment and distribution. Conclusions: Pre-washing vertebral bodies with cold saline before cement injection in PVP significantly reduces cement leakage, particularly in the spinal canal and intervertebral spaces. This simple and cost-effective approach may enhance surgical safety and improve patient outcomes. Full article

The antifouling performance of a zwitterionic sulfobetaine-hydroxyethyl-containing polymethylmethacrylate ter-co-polymer (PSBM) is evaluated against three photosynthetic strains, namely Chlorella sp., Nannochloropsis sp., and Arthrospira maxima. PSBM-coated polymethylmethacrylate (PMMA) surfaces displayed a significantly reduced propensity for biofilm formation compared to rough and untreated controls, leaving clean surfaces after 7 days of exposure. A tribological approach was adopted to estimate the long-term durability of the PSBM coating. Repeated cycles of exposure to Chlorella sp., Nannochloropsis sp., and A. maxima biomass subject the coating to stress and continuous biofilm challenges. After several cycles, the PSBM coating maintains a higher antifouling efficacy than the untreated PMMA surface, suggesting stability and high potential in photobioreactor applications. Full article

Microfluidic technology is an emerging interdisciplinary field that uses micropipes to handle or manipulate tiny fluids in chemistry, fluid physics, and biomedical engineering. As one of the rapid prototyping methods, the three-dimensional (3D) printing technique, which is rapid and cost-effective and has integrated molding characteristics, has become an important manufacturing technology for microfluidic chips. Polymethyl-methacrylate (PMMA), as an exceptional thermoplastic material, has found widespread application in the field of microfluidics. This paper presents a comprehensive process study on the fabrication of fused deposition modeling (FDM) 3D-printed PMMA microfluidic chips (chips), encompassing finite element numerical analysis studies, orthogonal process parameter optimization experiments, and the application of 3D-printed integrated microfluidic reactors in the reaction between copper ions and ammonium hydroxide. In this work, a thermal stress finite element model shows that the printing platform temperature was a significant printing parameter to prevent warping and delamination in the 3D printing process. A single printing molding technique is employed to fabricate microfluidic chips with square cross-sectional dimensions reduced to 200 μm, and the microchannels exhibited no clogging or leakage. The orthogonal experimental method of 3D-printed PMMA microchannels was carried out, and the optimized printing parameter resulted in a reduction in the microchannel profile to Ra 1.077 μm. Finally, a set of chemical reaction experiments of copper ions and ammonium hydroxide are performed in a 3D-printed microreactor. Furthermore, a color data graph of copper hydroxide is obtained. This study provides a cheap and high-quality research method for future research in water quality detection and chemical engineering. Full article

Introduction: Chronic osteomyelitis is a persistent infection of the bone that poses significant challenges, particularly when associated with pathological fractures and extensive bone defects. This case report highlights the application of Masquelet’s induced membrane technique (MIMT) in managing a complex distal femur defect in a 50-year-old male with a long-standing history of chronic osteomyelitis. The patient presented with a non-union fracture, severe osseous destruction, and infection, requiring a multidisciplinary approach. Case report: The first stage involved radical debridement of necrotic tissue and stabilization with a titanium plate and an antibiotic-impregnated polymethylmethacrylate spacer to induce a bioactive membrane. The second stage, performed 30 days later, after infection resolution, entailed removing the spacer, harvesting an autologous iliac crest bone graft, and filling the defect within the preserved membrane. Postoperative care included a tailored antibiotic regimen and gradual weight-bearing, leading to favorable clinical and radiological outcomes. Conclusions: This case demonstrates the utility of MIMT in reconstructing extensive bone defects while addressing infection. The technique provides a reliable and effective alternative to amputation, offering high success rates and functional restoration in complex cases. Full article

This study determined the influence of surface treatment and protracted ageing on the shear bond strength (SBS) of orthodontic brackets bonded to CADCAM (milled) and 3D-printed polymethylmethacrylate (PMMA) provisional crowns (PCs). Eighty disc-shaped specimens [forty milled (CopraTemp WhitePeaks) [group (Gp) M] and forty printed (Asiga DentaTooth) (Gp P)] were divided into eight subgroups (Gp) based on surface treatment [no treatment (control) (Gp MC and Gp PC), coarse diamond (Gp MCD and Gp PCD), fine diamond (Gp MFD, and GP PFD) and sandblast (Gp MSB and Gp PSB)]. Orthodontic brackets were bonded (Assure Plus, Transbond XT), thermocycled (2200 cycles), and tested for SBS and failure (Adhesive Remnant Index) (ARI). Statistical tests included analysis of variance (ANOVA); Kruskal–Wallis (ARI ranks); and post hoc (Tukey, Dunn, and Bonferroni) for determining group differences at predetermined probability p-values less than 0.05. SBS was significantly increased in Gp MSB (15.51 Mpa) and Gp PSB (14.11 Mpa), while the coarse diamond subgroups yielded the lowest mean SBS values [Gp MCD (11.28 Mpa) and Gp PCD (11.62 Mpa)]. The SBS of subgroups MFD, MSB, PCD, and PSB showed significant differences from those of their respective controls (Gp MC and Gp PC). Low ARI scores were observed in Gp MC (0.40) and Gp MSB (0.80), while higher scores were observed in Gp PCD (2.10). Both milled and printed PCs fulfil the clinical criteria of the minimum SBS for orthodontic brackets for long-term use. However, milled PC has better SBS and low ARI scores, which make it more clinically feasible for orthodontic treatments. Full article

Although microcellular foams are potential thermal insulators, their low density and small pore size allow infrared radiation to pass through, increasing the effective thermal conductivity. To address this drawback, graphene nanoplatelets (GnPs) have previously been added to polymethylmethacrylate (PMMA) samples as infrared blockers, enhancing insulation by reducing the radiative component of heat transfer. In this work, the effect of the content of GnPs is studied. Cellular PMMA samples with GnP contents ranging from 0.5 to 10 weight total percentage (wt. %) and pore sizes between 2 and 5 microns were tested. Thermal conductivity measurements showed that GnP additions from 0.5 to 5 wt. % significantly decrease the radiative term, achieving a 33% reduction compared to pure PMMA and reaching thermal conductivity values of 38 mW m⁻¹ K⁻¹. Moreover, the structural factor is diminished up to 45% in comparison to pure microcellular PMMA, which, in samples with contents of GnPs such as 1 wt. %, results in a reduction in the conductivity of the solid phase. This approach demonstrates that incorporating small contents of GnPs effectively enhances the thermal performance of microcellular foams, a strategy that could be applied to other polymers to achieve better thermal insulation properties. Full article

Background/Objectives: The long-term success of dental implants can be influenced by the material properties of abutments and their interaction with peri-implant tissues. This study investigates the impact of three abutment materials—titanium (Ti), zirconium oxide (Zr), and polymethylmethacrylate (PMMA)—on the inflammatory response in peri-implant sulcular fluid (PISF), using active-matrix metalloproteinase-8 (aMMP-8) as a biomarker. Methods: In this prospective, randomized clinical trial, 30 patients were assigned to Ti, Zr, or PMMA abutment groups. PISF samples were collected at predefined intervals over 12 months and analyzed for aMMP-8 levels using enzyme-linked immunosorbent assays (ELISA). Clinical parameters (probing depth, bleeding on probing, and plaque index) and radiographic assessments of bone resorption were also evaluated. Results: Two weeks after implant uncovering, baseline aMMP-8 levels varied significantly among materials, with Zr demonstrating the highest levels. Over time (2, 3, 6 and 12 months after implant uncovering), aMMP-8 levels decreased across all groups, with no significant differences observed at 12 months. Radiographic assessments indicated no statistically significant differences in bone resorption, with clinical parameters remaining comparable across all groups. Conclusions: Initial inflammatory responses to abutment materials may vary; however, all tested materials—Ti, Zr, and PMMA—showed long-term biocompatibility and supported healthy peri-implant tissue integration. These findings indicate that selecting any of the tested abutment materials does not significantly affect long-term peri-implant health. Full article

Electrochromic devices (ECDs) are devices that change their optical properties in response to a low applied voltage. These devices typically consist of an electrochromic layer, a transparent conducting substrate, and an electrolyte. The advancement in solid-state ECDs has been driven by the need for improved durability, optical performance, and energy efficiency. In this study, we investigate varying the temperature to the casting solution for polymethylmethacrylate (PMMA)-based electrolytes for solid-state ECDs with a structure of glass/ITO/WO₃/PMMA electrolyte/ITO/glass. The electrochromic layer, composed of WO₃, was deposited using the sol-gel method, while the electrolyte, comprising lithium perchlorate (LiClO₄) in propylene carbonate (PC) with PMMA, was prepared via solution casting. Various electrolyte samples were heated at different temperatures of 25, 40, 60, 80, and 100 °C to analyze the impact on the devices’ performance. Our findings indicate that the devices with electrolytes at 25 °C exhibited superior anodic and cathodic diffusion. An increase in heating temperature corresponded with an increase in switching time. Notably, the sample heated at higher temperatures (60, 80, and 100 °C) demonstrated exceptional cycle stability. Nevertheless, samples with higher temperatures displayed a decrease in optical modulation. Additionally, the 100 °C sample exhibited the highest coloration efficiency compared to other samples at lower temperatures. This research highlights the potential of varying the temperature of solution casting on PMMA-based electrolytes in optimizing the performance of solid-state ECDs, particularly regarding coloration efficiency and durability. Full article

This study aimed to evaluate the antimicrobial effectiveness of different disinfection protocols for dentures by combining methods, varying intervention sequences, sodium hypochlorite (NaOCl) concentrations (0.1% and 0.25%), and post-exposure to intraoral temperature. The heat-polymerized poly(methylmethacrylate) (PMMA) was divided into groups (n = 15): control (C, distilled water immersion), B (brushing), I0.1% and I0.25% (isolated NaOCl immersion), B + I0.1% and B + I0.25% (brushing followed by immersion), I + B0.1% and I + B0.25% (immersion followed by brushing), and B + I0.1% + T and B + I0.25% + T (brushing, NaOCl immersion, and overnight exposure to 35 °C ± 2 °C). The post-disinfection exposure to intraoral temperature simulated the denture use during sleeping time. Quantitative evaluation was performed by colony-forming unit (CFU/mL) counting of C. albicans and qualitative analysis by scanning electron microscopy (SEM) images. Data were processed by one-way ANOVA with Tukey’s post-hoc test to compare different protocols at the same concentration and among groups (α ≤ 0.05). Applying 0.25% NaOCl in associated protocols, the intervention sequence was no different (B + I and I + B) and caused the lowest C. albicans counts. The 0.1% NaOCl lost part of its action when the immersion method started the protocols. B + I0.25%, I0.25% + B, and B + I0.1% had similar antimicrobial efficacy, but the intraoral temperature (B + I + T) reduced the efficacy of these protocols, regardless of NaOCl concentration. Residual biofilm recolonization was also detected in SEM images. In conclusion, all the combinations between mechanical and chemical methods using 0.25% NaOCl were the most effective against C. albicans. The antimicrobial efficacy of NaOCl at 0.1% changes depending on the intervention sequence. The intraoral temperature influenced the C. albicans recolonization after the disinfection protocols. Full article

With increasing energy demands and depleting oil accessibility in reservoirs, the investigation of more effective enhanced oil recovery (EOR) methods for deep and tight reservoirs is imminent. This study investigates a novel hybrid EOR method, a synergistic approach of nonionic surfactant flooding with intermediate CO₂-based oil swelling. This study is focused on the efficiency of surfactant flooding and low-pressure oil swelling in oil recovery. We conducted a fluorescence-based microscopic analysis in a microchannel to explore the effect of sodium dodecyl sulfate (SDS) surfactant on CO₂ diffusion in Texas crude oil. Based on the change in emission intensity of oil, the results revealed that SDS enhanced CO₂ diffusion at low pressure in oil, primarily due to SDS aggregation and reduced interfacial tension at the CO₂ gas–oil interface. To validate the feasibility of our proposed EOR method, we adopted a ‘reservoir-on-a-chip’ approach, incorporating flooding tests in a polymethylmethacrylate (PMMA)-based micromodel. We estimated the cumulative oil recovery by comparing the results of two-stage surfactant flooding with intermediate CO₂ swelling at different pressures. This novel hybrid approach test consisted of a three-stage sequence: an initial flooding stage, followed by intermediate CO₂ swelling, and a second flooding stage. The results revealed an increase in cumulative oil recovery by nearly 10% upon a 2% (w/v) solution of SDS and water flooding compared to just water flooding. The results showed the visual phenomenon of oil imbibition during the surfactant flooding process. This innovative approach holds immense potential for future EOR processes, characterized by its unique combination of surfactant flooding and CO₂ swelling, yielding higher oil recovery. Full article

Ethanol (EtOH) gas detection has garnered considerable attention owing to its wide range of applications in industries such as food, pharmaceuticals, medical diagnostics, and fuel management. The development of highly sensitive EtOH-gas sensors has become a focus of research. This study proposes an optical interferometric surface stress sensor for detecting EtOH gas. The sensor incorporates a 100 nm-thick freestanding membrane of Parylene C and gas-sensitive polymethylmethacrylate (PMMA) fabricated within a microcavity on a Si substrate. The results showed that reducing the thickness of the freestanding Parylene C membrane is essential for achieving higher sensitivity. Previously, a 100-nm-thick membrane transfer onto microcavities was achieved using a surfactant-assisted release technique. However, polymerization inhibition caused by the surfactant presented challenges in forming ultrathin membranes of several tens of nanometers. In this study, we employed a surfactant-free release technique using a hydrophilic natural oxide layer to successfully form a 14-nm-thick freestanding Parylene C membrane. In contrast, the optimum thickness of the gas-adsorbed PMMA membrane was approximately 295 nm. Moreover, we demonstrated that this thinner membrane improved EtOH gas detection sensitivity by a factor of eight compared with our previously reported sensor. Thus, this study advances the field of nanoscale materials and sensor technology. Full article