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In radiation dosimetry, achieving electronic equilibrium is vital for accurate dose measurements in radioprotection. This study investigates the effect of Poly Methyl Methacrylate (PMMA) layers, known by its chemical formula C 5 H 8 O 2 and a density of 1.19 g/cm³ (PNNL, 2011), on electronic equilibrium for the calibration of radiation protection instruments, focusing on photon beams of varying energies. Using DOSIMEX 2.0 simulation software, we modeled the influence of PMMA thickness on calibration factors across different X-ray and gamma-ray beam energies. Experimental validation with Cs-137 and Co-60 sources confirmed the reliability of the simulation. Our results highlight that while PMMA layers have a minimal impact on calibration for higher-energy beams, their role becomes significant for energies below 40 keV. For X-ray beams (From 30 to 140 kV), the results show minimal calibration factor deviation (<1.6%), whereas radionuclide beams exhibit more significant variations (4.1%), necessitating customized calibration approaches. This study underscores the importance of adhering to ISO 4037-3 standards in radioprotection, particularly in low-energy scenarios, to ensure the precision of calibration procedures and optimize radiation protection practices. Furthermore, based on the results obtained, the absence of PMMA does not have a dramatic effect on the calibration of X-ray radiation instruments, whereas for gamma-ray beams, it has a significant impact. • First study to verify the impact of not considering this effect: PMMA layers on electronic equilibrium during radioprotection instrument calibration. • Shows minimal calibration factor deviation (<1.6%) for X-ray beams but significant variations (4.1%) for radionuclide beams, requiring customized calibration approaches. • Stresses the importance of adhering to international standards, like those set by the IAEA and ISO, in radiation dosimetry. • Highlights the importance of adding a 3 mm PMMA layer for calibration, especially for energies below 40 keV and with Co-60 sources. [ABSTRACT FROM AUTHOR]

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• The low concentrations of photocatalytic nanoparticles, such as emodin (≤0.5 %), curcumin (≤0.5 %), curcumin nisin (≤5 %), and ulva lactuca (≤1 %), could be incorporated into orthodontic acrylic resins without compromising flexural strength. • The addition of zinc oxide (≤2 %) and titanium dioxide (≤3 %) to acrylic resins improved flexural strength. • Titanium dioxide was found to be the most prevalent photocatalytic nanoparticle. Orthodontic acrylic resins containing antimicrobial photocatalytic nanoparticles aims to reduce oral lesions including denture stomatitis and white spot lesions but they should not imperil its mechanical properties. This systematic review was done to evaluate the effect of various photocatalytic nanoparticles on the flexural strength (FS) of acrylic resins. We systematically searched the PubMed/Medline, Cochrane Library, and Scopus databases from January 2018 to October 2023. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the quality of the studies was evaluated using the QUIN tool, which is specifically designed to assess the risk of bias in vitro studies. Following screening of 1016 initial records, 23 studies were deemed eligible for inclusion. The addition of photocatalytic nanoparticles, such as emodin (Emo), curcumin (Cur), Cur nisin (CurNis), zeolite/zinc oxide (Zeo/ZnO), and Ulva lactuca (U. lactuca), to acrylic resins resulted in a reduction in FS, with the extent of reduction dependent on the nanoparticle concentration. Specifically, the addition of Emo (≥0.5 %), Cur (≥0.5 %), CurNis (≥5 %), Zeo/ZnO (≥2), and U. lactuca (≥1 %) to acrylic resins significantly decreased FS. Conversely, the inclusion of ZnO and titanium dioxide (TiO 2) in acrylic resins improved FS, but higher concentrations (≥5 % for TiO 2) had a limited positive effect. Our study supports the use of low concentrations of photocatalytic nanoparticles, such as ZnO (≤2 %), TiO 2 (≤3 %), Emo (≤0.5 %), Cur (≤0.5 %), CurNis (≤5 %), and U. lactuca (≤1 %), in orthodontic acrylic resins without compromising FS. [ABSTRACT FROM AUTHOR]

Bioactive scaffolds with polymer and nanostructured bioactive glass-based composites are promising materials for regenerative applications in consequence of close mimics of natural bone composition. Poly methyl methacrylate (PMMA) is a highly preferred thermoplastic polymer for orthopedic applications as it has good biocompatibility. Different kinds of bioactive, biodegradable as well as biocompatible biomaterial composites such as Bioglass (BG), Hydroxyapatite (Hap), and Tricalcium phosphate (TCP) can be integrated with PMMA, so as to augment the bioactivity, porosity as well as regeneration of hard tissues in human body. Among the bioactive glass, 60S BG (Bioactive glass with 60 percentage of Silica without Sodium ions) is better materials among aforementioned systems owning to mechanical stability as well as controlled bioactive material. In this work, the fabrication of PMMA-CaP (calcium phosphate)-based scaffolds were carried out by Thermal Induced Phase Separation method (TIPS). X-ray diffractogram analysis (XRD) is used to examine the physiochemical properties of the scaffolds that evidently reveal the presence of calcium phosphate besides calcium phosphate silicate phases. The Field Emission Scanning Electron Microscopy (FESEM) studies obviously exhibited the microstructure of the scaffolds as well as their interconnected porous morphology. The PMMA/60S BG/TCP (C50) scaffold has the maximum pore size, measuring 77 ± 23 μm, while the average pore size ranges from 50 ± 20 to 80 ± 23 μm. By performing a liquid displacement method, the C50 scaffold is found to have the largest porosity of 50%, high hydrophilicity of 118.16°, and a compression test reveals the scaffolds to have a maximum compressive strength of 0.16 MPa. The emergence of bone-like apatite on the scaffold surface after 1st and 21st days of SBF immersion is further supported by in vitro bioactivity studies. Cytocompatibility and hemocompatibility analyses undoubtedly confirmed the biocompatibility behavior of PMMA-based bioactive scaffolds. Nano-CT investigation demonstrates that PMMA-CaP scaffolds provide more or less alike morphologies of composites that resemble the natural bone. Therefore, this combination of scaffolds could be considered as potential biomaterials for bone regeneration application. This detailed study promisingly demonstrates the eminence of the unique scaffolds in the direction of regenerative medicines. [ABSTRACT FROM AUTHOR]

Eu(DBM) 3 and Eu(DBM) 3 Phen were introduced into poly methyl methacrylate (PMMA) in comparative, and the differential luminescence behaviors were revealed under ultraviolet (UV) radiation. The comparison of excitation behavior between Eu(DBM) 3 and Eu(DBM) 3 Phen doped PMMAs indicates that the introduction of Phen ligand largely enhances the excitation intensity of europium in the entire UV region. The total quantum yield of Eu(DBM) 3 Phen doped PMMA was derived to be (9.34 ± 0.14)%, and it is about 8 times higher than that of the Eu(DBM) 3 doped PMMA under 373 nm UVA light emitting diode (UVA-LED) excitation, which confirms the effective utilization of UVA radiation by introducing Phen ligand. Similar results on absolute spectral parameters of the bi-ligand under the excitation of 308 nm UVB light emitting diode (UVB-LED) further support the availability for photon conversion. The brilliant red fluorescence of Eu(DBM) 3 Phen doped PMMA under direct sunlight demonstrates the contribution of Phen to modify the solar spectrum and enhance the UV radiation conversion efficiency, which make the Eu(DBM) 3 Phen doped PMMA an attractive UV radiation conversion layer for solar cell. [ABSTRACT FROM AUTHOR]

Abstract: In this work the feasibility of friction spot welding of thermoplastics was investigated on poly (methyl methacrylate) plates. Preliminary results have shown that the weld strength is comparable to other available welding techniques, while joining times are equal or shorter. Light optical microscopy and Vickers microhardness measurements showed the presence of a heat affected zone and a thin, consolidated stir zone, where physical–chemical transformations related to thermo-mechanical processing led to changes in local mechanical strength. The work has demonstrated for the first time that the welding of thermoplastic materials by friction spot welding is feasible. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, polymeric materials such as polycarbonate (PC) and poly methyl methacrylate (PMMA) are replacing silicon as major substrates in microfluidic system fabrication due to the outstanding features like low cost and good chemical resistance. In this study, chemical mechanical polishing (CMP) of PC and PMMA substrates was investigated. First, four types of slurry were tested. Then, the slurry producing relatively high material removal rate (MRR) and low surface roughness was chosen, and experiments were designed and carried out to investigate the effects of key process parameters. The experimental results show impacts of key CMP process parameters on MRR and surface finish of PC and PMMA substrates. An increase in head load or table speed would cause an increase in surface roughness heights and MRR. The surface quality of the polymers after CMP appeared to be acceptable for most of microelectromechanical system applications as the process conditions were restrained within the process window. [Copyright &y& Elsevier]

Energy transfer of Rh 6G:Rh B dye–mixtures in a poly methyl methacrylate (PMMA) matrix was studied by investigating the emission spectral characteristics under argon ion laser excitation. The fluorescence behaviour of the acceptor dye (Rh B) was investigated for various concentration of the donor (Rh 6G) and excitation powers. The energy transfer rate constants (kf), transfer probability (Pda) and the transfer efficiency (η) have been evaluated and their concentration dependence on donor molecules was studied. The observed decrement in the emission peak wavelength of the acceptor dye with donor concentration is attributed to the formation of complexes in the dye–mixture and also to the result of cross-relaxation taking place in the donor dye system. The blue shift in the emission wavelength of the acceptor was also investigated for various donor concentrations. A significant enhancement of fluorescence intensity of the acceptor (Rh B) of the order of 226% and a transfer efficiency of 90% were observed in the present dye–mixture system as compared with pure Rh B, both in PMMA matrices. Further the experimental results revealed the non-radiative type energy transfer for the dye system in the PMMA matrix. [Copyright &y& Elsevier]