Poly Methyl Methacrylate Research Articles

A Mixture Fraction Approach to Predict Polymer Burning

A mixture fraction approach was applied to predict the combustion behavior of polymeric materials. In comparison to the combustion of gaseous mixtures, the presence of solid fuels complicates the description of the combustion. Accurate predictions of burning characteristics can only be achieved through the proper resolution of heat and mass transfer between the gas-phase flame and the solid fuel. We focused on a model case of flame spread over a solid fuel surface. Polymethyl methacrylate (PMMA) was selected as a polymeric material. An approach was proposed to account for heat loss from the gas phase to the solid material through calculations of counterflow diffusion flames with the flame positioned closely to the fuel supply. A combination of these solutions was applied to restore temperature and species mass fractions from tabulated chemistry. An analysis of the numerical results from previous studies on flame spread over PMMA, based on one-step combustion reaction and calculating the chemical source term at each time step, demonstrated a monotonic distribution of the mixture fraction in the flame region between the fuel and oxidizer streams. The shape of the flame tip was satisfactorily resolved using the proposed approach that employs a skeletal chemical mechanism for gas-phase combustion consisting of 29 species and 33 reactions. However, the heat flux from the flame to the solid fuel was overpredicted, resulting in higher flame spread rates compared to experimental data and previous calculations. Preliminary results show a promising opportunity for the mixture fraction approach to describe the combustion behavior of polymers. An analysis showed that oversimplifying the heat transfer process in the flame tip area is a main source of prediction inaccuracies. Multidimensional heat transfer has to be properly incorporated into a tabulated chemistry approach. Several potential directions for future work have been outlined.

A sulfobetaine containing-polymethylmethacrylate surface coating as an excellent antifouling agent against Chlorella sp

Biofouling represents one of the major issues in Photobioreactors (PBRs) for microalgae cultivation. At this aim, a series of zwitterionic-containing polymethylmethacrylate (PMMA) co-ter-polymers, differing in the molar percentage of sulfobetaine (SBMA)- and 2-hydroxyethylmethacrylate (HEMA) components were designed as antifouling (AF) potential coatings for inner PMMA surface of photobioreactors (PBRs). Among these, the sample named PSBM, P(HEMA-co-MMA-co-SBMA), showing the best film capabilities on PMMA slides, was selected, characterized and its AF activity investigated. High transparent and thin PSBM films, as confirmed by AFM and optical transparency investigations, were obtained by a simple drop-casting procedure using a basic isopropylalcohol/water mixture. AFM images of raw PSBM and PSBM films clearly indicate that a conformational change occurred upon treatment with electrolytes. PSBM was further characterized by ATR-FTIR Spectroscopy, Dynamic Light Scattering, X-Ray Photoelectron Spectroscopy, Thermogravimetric analysis, Differential Scanning Calorimetry and Static Water Contact Angle (WCA) investigations. Consistent with hydrophilic behavior, the PSBM surface provided a WCA of 60.9 ± 0.8° which, interestingly, decreased to 27.7 ± 1.2° after immersion in electrolyte culture media. PSBM films displayed a high satisfactory AF behavior in that a rare or no cell adhesion was observed when placed for 7 days in a suspension of the green microalga Chlorella sp. For comparison, the experiments were carried out with untreated and rough PMMA surfaces.

Mechanism of shear-enhanced rotating-disk microfiltration for separation of microbe/protein bio-suspension

Shear-enhanced dynamic filtration is a promising approach for separating fermented biological products. In this study, we aimed to investigate the separation of bovine serum albumin (BSA) and polymethyl methacrylate (PMMA) particles in a binary suspension using rotating-disk microfiltration. Type-R and Type-RB rotating-disk configurations were designed and compared using experimental data and simulated results. The effects of operating conditions, including rotational speed and filtration pressure, on filtration flux, resistance, and protein rejection, were analyzed. Because the filter membrane rejected all the PMMA particles, the primary source of filtration resistance in the PMMA/BSA suspension was the fouling cake. Although BSA rejection increased with higher filtration pressure, it decreased as the rotational speed increased. Computational fluid dynamics simulations were used to model the flow velocity and shear stress distributions within the rotating-disk dynamic microfiltration system. The results showed that Type-RB achieved a 55 % increase in flux compared to Type-R, owing to a significant reduction in cake resistance by approximately 46 %. A proportional relationship between the mean cake mass and the ratio of qs/τw under varying operating conditions was established using a force balance model. These findings suggest that elevated shear stress significantly enhances filtration performance, with Type-RB demonstrating superior effectiveness for bio-suspension separation.

Thin and Flexible PANI/PMMA/CNF Forest Films Produced via a Two-Step Floating Catalyst Chemical Vapor Deposition

In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a carbon source solution with camphor and ACN. The vapors of the catalytic solution inserted in the reaction chamber through external boiling result in a floating catalyst CVD approach that produces vertically aligned CNFs in a consistent manner. CNFs are grown in a conventional CVD horizontal reactor at 850 °C under atmospheric pressure and characterized by Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Coating the MWCNTs with polymethyl methacrylate (PMMA) while still on the Si substrate retains the structure and results in a flexible, conductive thin film suitable for flexible electrodes. The film is 62 μm thick and stable in aqueous solutions, capable of withstanding further processing, such as electropolymerization with polyaniline, to be used for energy storage applications.

Understanding the influence of configurations and intermolecular interaction on thermomechanical and dynamics properties of polymer–clay nanocomposites via molecular dynamics simulations

AbstractPolymer‐clay nanocomposites (PCNs) have emerged as highly versatile structural materials that possess exceptional thermomechanical and dynamic properties, all the while retaining their inherent attributes of being lightweight and optically clear. The fabrication of nanocomposites involves the incorporation of carefully calibrated quantities of clay nanofillers into polymer matrixes. Current research expands upon existing coarse‐grained (CG) models of nanoclay and poly (methyl methacrylate) (PMMA) and utilize molecular dynamics simulations to methodically explore the thermomechanical characteristics of PCNs. Specifically, the effects of exfoliated and stacked configurations of nanoclays, as well as variations in intermolecular interactions between the nanoclay and polymer constituents were tested. Tensile and shear simulations, as well as interfacial behaviors, are conducted. The intermolecular interaction could have significant influences on Shear Modulus and Young's Modulus, and those influences have their characteristics due to different configurations and different force directions, such as in most cases, exfoliated structures exhibit higher mechanical modulus compared with stacked configurations at varying interaction strengths. Additionally, in the in‐plane direction, they demonstrate stronger resistance effects compared with the out‐of‐plane direction. The interaction between PMMA and nanoclay slows down the global dynamics of PMMA, with a stronger effect observed for higher interaction strength. The impact of nanoclay on the segmental dynamics of PMMA decreases as we move away from the nanoclay layers toward the pure PMMA matrix. These findings provide molecular insights into the arrangement of components in PCNs during deformation and highlight the significance of nanoclay and the interface in determining their mechanical and dynamic properties.Highlights Variation patterns of mechanical modulus with interactions and configurations. The property difference in mechanical modulus due to configurations. Positive correlation between polymer Tg and intermolecular interaction. Global and local confinement effects on molecular stiffness during tension. Dynamical heterogeneity behavior on different interactions and temperatures.

Shear Bond Strength Comparison Between Heat Cure Acrylic Resin and Other Types of Acrylic Denture Bases

Objective: The study purpose was to examine the shear bonding strength of heat cure acrylic resin to thermoplastic resin and three-dimensional printed resin materials. Methods: A total of 30 acrylic specimens were fabricated in this study. Each specimen had a basal and top parts. The basal part was rectangular in shape. We had three different groups: 10 specimens of a basal part made of heat cured polymethylmethacrylate, 10 specimens of a basal part made of thermoplastic, and 10 specimens of three dimensionally printed resin. The top part of which is attached to the basal one was formed into a cylindrical shape made of heat cure poly methyl methacrylate in all three groups. Results: Significant differences were found between the heat cured polymethylmethacrylate and the other two groups (P<.001). Heat cured polymethylmethacrylate showed the highest bond strength (75 MPa), and thermoplastic resins showed the lowest (37 MPa). No significant difference in the shear bond strength was noticed between three dimensionally printed and thermoplastic acrylic. Conclusion: This study revealed that the shear bond strength of heat cured acrylic denture base to the relining/repairing from the same material was significantly higher than three dimensionally printed and thermoplastic resins with HC relining/repairing material.

Aliphatic-acid coating and nano chitosan nucleator synergistically regulate the performance of PMMA “bone-Locking” foam dressing used for emergency fixation of clavicle fracture

Clavicle emergency fixation can prevent fractured end from piercing heart and lung organs, which is crucial for wounded life. Clavicle with complex structure, great individual differences, and adjacent to important organs, which places high-requirements on performance of fixation materials. Developing advanced clavicle fixation material is a prominent hot-topic in the field of emergency-engineering. We prepared a Polymethyl-methacrylate (PMMA) “bone-Locking” foam dressing via novel polymer foaming process. Innovatively used aliphatic-acid and bio-polar macromolecule nanoparticles to adjust structure in non-traditional self-curing polymer melts to achieve high-performance. Stearic acid coating was prepared on the surface of foaming agent can delay nucleation period, increasing the initial Polymer-Bubble interface viscosity and effectively retard nuclei growth and escape. Nano-chitosan was compounded synchronously to induce in-situ nucleation and construct polar hydrogen bonds between chains, improve the crystallinity of PMMA matrix, reduce the relaxation ability of PMMA molecular chains and increase the interface viscosity again to inhibit nuclei growth and escape, realizing spontaneous coordination between viscosity and the bubble holes formation process. Obtained high-performance foam with uniform and regular bubble holes structure eventually. More, Dynamic Dual-Variable Field Bubble-Growth Dynamics was proposed, revealing the Bubble-Growth behavior synergistic driven by Viscosity and Temperature theoretically, providing reference for improving theory in polymer foaming field. Prepared foam dressing can be directly and softly coated on clavicle and spontaneously conform to the contour of clavicle with remarkable precision, then quickly (3.5 min) curing into a lightweight (0.57 g/cm3), high-strength (40.5 MPa), breathable (224.73 mm/s) “Armor”, showing great application value in wound emergency engineering. The developed foaming method and theory provide technical and theoretical value for polymer foaming system. The foam dressing provides a promising new scheme for fixing various wound sites and ensuring the life safety of the wounded at the emergency scene.

Survival and Success of 3D-Printed Versus Milled Immediate Provisional Full-Arch Restorations: ARetrospective Analysis.

To evaluate and compare the survival rates of 3D-printed and chairside milled resin polymethylmethacrylate (PMMA) immediate temporary provisional full-arch implant restorations using prosthetic survival as the primary outcome. Records of 335 routine patients receiving 443 temporary six-implant retained maxillary or mandibular prosthetic restorations between January 2019 and January 2022 at a private clinic (Dr Sobczak Clinical Centre, Radosc, Poland) were considered for this retrospective analysis. The analysis compared prosthetic and implant failure rates between printed and milled restorations as primary and secondary outcomes, respectively. Patient-related and treatment-related characteristics between groups were compared using the Chi-square test and Mann-Whitney U-test, respectively. Group-specific cumulative prosthetic survival was qualitatively and quantitively compared using Kaplan-Meier, generalized linear mixed models and univariate cox proportional hazard analyses. Prosthetic survival was set into context to implant survival using Chi-square tests. A multivariable cox proportional hazards model with frailty was used to identify confounding factors affecting prosthetic survival. Prosthetic failure rates of milled and printed temporary restorations were 13.01% and 11.25% over the average follow-up period of 307.7 ± 115.5 days, respectively. The corresponding 180-day cumulative prosthetic survival rates were 92.4% and 93%. Hazard ratios for the prosthetic failure of milled and printed restorations did not show a statistical difference (p = 0.794). Implant failure rates in restorations that experienced prosthetic failure (17.31%) were higher compared to restorations without failures (5.63%), with a 3.2 times significantly higher odds of failure for a prosthesis experiencing implant loss (p = 0.003). Gender, presence of teeth at treatment baseline, smoking, and bone augmentation were identified as confounding factors impacting prosthetic survival. Chairside 3D-printed restorations may represent an equivalent treatment modality to established chairside milled restorations for immediate full-arch therapy. Provisional prosthetic survival may impact implant survival and treatment success.

Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) Monolith with Dual Porosity for Size Exclusion Chromatography.

The use of polymeric monoliths as stationary phases for liquid chromatography has been limited, despite their ability to enhance the convection flow of the mobile phase with respect to particulate-based columns. This is due to a poor balance between the volume of flow through pores and the number of active sites within polymeric monoliths. In this paper, we present the obtainment of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (P(GMA-co-EDMA)) monoliths with dual pore size distributions (with pore sizes of 60 and 550 nm). Hierarchical pore size distributions were achieved by performing the monolith synthesis by reversible addition-fragmentation chain transfer (RAFT) polymerization as well as using ternary porogen mixtures (containing PEG, dodecanol, and dioxane). While the controlled polymerization mechanism promoted mesopores in the monolith, ternary porogen mixtures allowed the formation of macropores. The monoliths obtained were used as stationary phases for size exclusion chromatography (SEC) for the separation of poly(methyl methacrylate) standards with molar masses between 2.50 × 103 and 3.06 × 106 g/mol, allowing selectivities that were comparable with commercially available SEC columns packed with porous particles. We believe the approach presented in this work could be the first step toward the obtainment of stationary phases for SEC with enhanced accessibility of exclusion pores. Monolithic columns with accessible porous structures can be beneficial for size-based separations of ultrahigh molar mass analytes with low diffusion coefficients.

Silver Nanoparticles (AgNPs) Incorporation into Polymethyl Methacrylate (PMMA) for Dental Appliance Fabrication: A Systematic Review and Meta-Analysis of Mechanical Properties

Silver Nanoparticles (AgNPs) Incorporation into Polymethyl Methacrylate (PMMA) for Dental Appliance Fabrication: A Systematic Review and Meta-Analysis of Mechanical Properties

Excitonic-Vibrational Interaction at 2D Material/Organic Molecule Interfaces Studied by Time-Resolved Sum Frequency Generation

The hybrid heterostructures formed between two-dimensional (2D) materials and organic molecules have gained great interest for their potential applications in advanced photonic and optoelectronic devices, such as solar cells and biosensors. Characterizing the interfacial structure and dynamic properties at the molecular level is essential for realizing such applications. Here, we report a time-resolved sum-frequency generation (TR-SFG) approach to investigate the hybrid structure of polymethyl methacrylate (PMMA) molecules and 2D transition metal dichalcogenides (TMDCs). By utilizing both infrared and visible light, TR-SFG can provide surface-specific information about both molecular vibrations and electronic transitions simultaneously. Our setup employed a Bragg grating for generating both a narrowband probe and an ultrafast pump pulse, along with a synchronized beam chopper and Galvo mirror combination for real-time spectral normalization, which can be readily incorporated into standard SFG setups. Applying this technique to the TMDC/PMMA interfaces yielded structural information regarding PMMA side chains and dynamic responses of both PMMA vibrational modes and TMDC excitonic transitions. We further observed a prominent enhancement effect of the PMMA vibrational SF amplitude for about 10 times upon the resonance with TMDC excitonic transition. These findings lay a foundation for further investigation into interactions at the 2D material/organic molecule interfaces.

Preparation and Characterization of Red, Green, Blue (RGB) and White Luminescent Inorganic/Organic Polymers Through In Situ Polymerization.

YVO4:Eu3+/PMMA, LaPO4:Ce3+,Tb3+/PMMA and CaWO4/PMMA nanocomposites were prepared by in situ polymerization method with hydrophobic YVO4:Eu3+, LaPO4:Ce3+,Tb3+ and CaWO4 nanoparticles as the filler and poly (methyl methacrylate) (PMMA) as the host material. All the nanoparticles and composites have been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), the thermogravimetric analysis (TGA), photoluminescence excitation, and emission spectra and luminescence decays. YVO4:Eu3+/PMMA, LaPO4:Ce3+,Tb3+/PMMA, CaWO4/PMMA nanocomposites exhibit strong red, green and blue photoluminescence upon 254nm UV excitation, respectively. The yellow and white LED nanocomposites with CIE coordinates of (0.411, 0.498) and (0.334, 0.359) were obtained by triply integrating the red, green and blue nanoparticles into PMMA. Thanks to the abundant luminescent colors from RGB to yellow and white in these polymer composites under UV excitation, they can be potentially used in various optoelectronic fields.

Synthesis of novel colored substrate-free pearlescent pigments of vanadium phosphates with large-size layered platelet morphology

Novel colored substrate-free pearlescent pigments based on vanadium phosphates, VOPO4·2H2O (VOP) and H0.6(VO)3(PO4)3(H2O)3·4H2O (HVP), with layered structures, were synthesized using solution process and hydrothermal synthesis. XRD and SAED analyses confirmed the single crystallinity of VOP and HVP. Hydrogen peroxide (H2O2) was crucial for producing larger plate-like crystal grains of VOP and contributing to the phase formation of HVP. FE-SEM analysis revealed that VOP and HVP consist of layered plate-like particles (platelets) with smooth surfaces, achieving small thicknesses and high aspect ratios (diameter to thickness). Notably, this study is the first to report particle diameters of 221 µm for VOP and 220 µm for HVP and to propose VOP and HVP as potential substrate-free pearlescent pigments. The optical properties are characterized by optical reflectance spectra and CIE L∗a∗b∗ coordinates, while the pearlescent effect was also evaluated. Under an optical microscope, all samples exhibited striking iridescent colors, visible even in different regions within the same particle. Furthermore, 1 wt% of the green HVP pearlescent pigments were successfully dispersed in the poly(methyl methacrylate) (PMMA) matrix, indicating a good suitability for PMMA colorization.

Physical Aging of Poly(methyl methacrylate) Brushes and Spin-Coated Films.

While there is significant attention aimed at understanding how one-dimensional confinement and chain confirmations can impact the glass transition temperature (Tg) of polymer films, there remains a limited focus on similar effects on sub-Tg processes, notably, structural relaxation. Using spectroscopic ellipsometry, we investigated the combined influence of confinement and molecular packing on Tg and physical aging, i.e., the property changes that accompany structural relaxation, at select film thicknesses and aging temperatures (Ta). We used poly(methyl methacrylate) (PMMA) films in the brush and spin-coated morphologies as model systems. We found that whether a PMMA film exhibited a decrease or increase in physical aging rate with confinement was dependent on the morphology. Notably, PMMA brushes exhibited higher physical aging rates compared to similarly thick spin-coated films at all values of Ta. These intriguing findings reveal the strong effects of confinement and molecular packing on the structural relaxation of polymer films. Results from this study have the potential to aid in the design of thin-film materials with controllable long-term glassy-state properties.

Kaolinite-based Janus nanosheets as effective compatibilizer of PLA/PBAT blend

To address the increasing global plastic pollution while the reducing oil supply, the biodegradable and bio-derived poly(lactic acid) (PLA) has been developed and considered to be the most promising substitute of petroleum-based plastics. However, the severe brittleness of PLA has become the obstacle of its broad application. Blending modification with poly(butylene-adipate-co-terephthalate) (PBAT) has been proved to be an potentially feasible strategy to toughen PLA, but conflicted by the poor compatibility between PLA and PBAT. To tackle the problem, a comb-type clay-based Janus nanosheet of poly(methyl methacrylate- kaolinite- poly(butylene-adipate-co-terephthalate) (PMMA-Kaol-PBAT) was prepared by selectively grafting PMMA and PBAT separately on either sides of kaolinite Janus nanosheets (JNS). PBAT was functionalized with quaternary amine via aminolysis before being cation-exchanged onto the siloxane tetrahedral surface (STS) side of kaolinite nanosheets, while PMMA chains were grafted onto the aluminoxyl octahedral surface (AOS) side after a beforehand surface modification with the silane coupling agent KH-570. Introduced in the PLA/PBAT blend system, the PMMA-Kaol-PBAT was found to enrich at the interface, enhancing the phase compatibility with the phase separation and aggregation inhibited during the film coating and annealing process.

Investigation of the mechanical properties of lavender-reinforced heat-activated polymethyl methacrylate denture base resin

Statement of problemThe antimicrobial efficacy of lavender has been well evidenced. However, investigations into its impact on the mechanical properties of denture resins are lacking. PurposeThe purpose of this in vitro study was to evaluate the flexural strength, impact strength, surface characteristics, roughness, elastic modulus, and yield strength of lavender-reinforced, heat-activated polymethyl methacrylate denture base resin. Material and methodsA total of 200 specimens were categorized into 5 groups based on 0, 0.5, 1.0, 1.5, and 2.0 wt% of dry lavender extract incorporated into heat-activated polymethyl methacrylate denture base resin powder. Unmodified resin served as the control group. Flexural strength, elastic moduli, and yield strength were determined with a universal testing machine, impact strength with an Izod impact tester, surface characteristics with scanning electron microscopy, and roughness with a profilometer. The data were statistically analyzed with 1-way ANOVA followed by Tukey post hoc tests for pairwise comparison within the groups (α=.05). ResultsCompared with the control group, all the mechanical properties significantly improved with the addition of lavender (P<.001). The highest flexural, yield, and impact strengths and elastic modulus values were in the 2% group. Elevated surface roughness in 0.5, 1.0 and 1.5 wt% and a decline in roughness at 2 wt% were noted when compared with the control group. ConclusionsThe addition of lavender enhanced the flexural strength, yield strength, impact strength, elastic moduli, and decreased surface roughness when added at 2 wt%.

Poly (Methyl Methacrylate)/Polyaniline (PMMA/PAni) Electrospun Membranes for Use in Chemical Sensors

Poly (Methyl Methacrylate)/Polyaniline (<scp>PMMA</scp>/<scp>PAni</scp>) Electrospun Membranes for Use in Chemical Sensors

Dip‐Pen Nanolithography‐Based Fabrication of Meta‐Chemical Surface for Heavy Metal Detection: Role of Poly‐Methyl Methacrylate in Sensor Sensitivity

A meta‐chemical surface is being patterned via dip‐pen nanolithography (DPN) for novel electrochemical heavy metal sensors. The unique feature of DPN allows a precise transfer of desired ink onto various surfaces. Two kinds of sensors are being developed, which differ by the ligand in the poly‐methyl methacrylate (PMMA)‐based ink: 1,8‐diaminonaphthalene (DAN) and D‐penicillamine (D‐PA). The nanosize, the surface‐to‐volume ratio (18.6 and 23.1 μm−1 for DAN‐ and D‐PA‐based ink, respectively), and the binding strength between the ligand and the cation (2.21 and −21.37 kcal mol−1 for DAN‐ and D‐PA‐based ink, respectively) are found to be the source of their high sensitivity, with limit of detection values of 0.40 and 0.30 ppb for DAN and D‐PA, respectively. According to the DFT calculations, the binding reactions in the presence of PMMA are more exergonic; this indicates that PMMA added to the ink for the patterning process improves the binding between the metals and the ligands. This enhanced binding between the metals and the ligands is a crucial and innovative function of the PMMA that can enhance sensor performance.

Comparison of three sacral screw internal fixation techniques in the treatment of L4-S1 lumbar degenerative disease with osteoporosis: a retrospective observational study.

Patients with L4-S1 lumbar degenerative disease (LDD) with osteoporosis are prone to sacral-screw loosening during spinal internal fixation. We aimed to compare the clinical efficacy and imaging results of sacral bicortical, tricortical, and polymethylmethacrylate (PMMA)-augmented pedicle-screw fixation in the treatment of L4-S1 LDD with osteoporosis. This is a retrospective study, 72 patients were enrolled and divided into three groups according to the S1-screw fixation method: PMMA-augmented pedicle-screw fixation (Group A, n = 26), bicortical fixation (Group B, n = 22), and tricortical fixation (Group C, n = 24). The visual analog scale (VAS) and Oswestry disability index (ODI) were recorded preoperatively and at the last follow-up, and the postoperative complications, screw-loosening rate, and fusion rate were compared between the three groups. Upon the last follow-up, the VAS and ODI scores of the three groups were significantly improved compared with those recorded preoperatively. The VAS and ODI scores of Group A were significantly smaller than those of Groups B and C (P < 0.05), with no significant difference between Groups B and C. Moreover, the screw-loosening rate of Group A was significantly lower than that of Groups B and C (P < 0.05), with no significant difference between Groups B and C. No significant difference was noted in postoperative complications, bone-cement leakage rates, and intervertebral fusion rates among the three groups. Furthermore, we found that osteoporosis and change of lumbar lordosis(LL) value were independent risk factors for sacral-screw loosening in patients with L4-S1 LDD with osteoporosis. When patients with L4-S1 LDD with osteoporosis undergo lumbosacral fusion and fixation, the use of S1 pedicle screws with PMMA augmentation has better stability and less screw loosening. Furthermore, we recommend this surgery for patients with osteoporosis, and the LL should be increased as much as possible during the operation to restore the matching of lumbar and pelvic parameters.

Preparation and characterization of temperature-induced ultrasensitive SERS large-scale vertical Au nanosphere dimers

Plasmonic dimers have a very wide range of applications as a unique platform for studying the fundamental effects of plasmonics. Most dimer structures are prepared by chemical methods and direct-writing methods, such as coupling agents and lithography. These methods are often complex and expensive. Here, we prepared Au nanospheres (AuNSs) by layer-by-layer (LBL) deposition, used polymethyl methacrylate (PMMA) as a spacer layer, and then annealed the deposited AuNSs to orient the assembly and integrate them together. In this paper, suitable PMMA spin coating conditions and optimal annealing temperatures were explored, and large-scale AuNSs-PMMA-AuNSs(NSs-P-NSs) composed of vertical Au nanosphere dimers were prepared successfully. The detection limits of this substrate can reach 4 × 10−12 M/L and 4 × 10−10 M/L for Rhodamine 6 G (R6G) and Crystal Violet (CV), respectively, demonstrating excellent Raman activity. In addition, the sensitivity of detecting aspartame (APM) is 0.015625 g/L. This method is not only simple to operate but also allows the preparation of a large-scale uniform substrate with excellent detection capabilities.