Phytochemical investigation of the MeOH extract of twigs and leaves of Baeckea frutescens led to the isolation of seven new polymethylated phloroglucinol meroterpenoids(PPMs),named baeckfrutones M-S(1-7).Their structu...Phytochemical investigation of the MeOH extract of twigs and leaves of Baeckea frutescens led to the isolation of seven new polymethylated phloroglucinol meroterpenoids(PPMs),named baeckfrutones M-S(1-7).Their structures and absolute configurations were determined by spectroscopic analyses,chiral-phase HPLC analysis,and electronic circular dichroism(ECD)calculations.PPM 1 is a novel meroterpenoid possessing a 6/6/5/3 tetracyclic skeleton in PPMs,whereas 3 and 4 are the first hydroxytasmanone type phloroglucinol-monoterpene hybrids.(+)-2 and 7 displayed potent antiinflammatory activity with IC50 values of 20.86±0.60 and 36.21±1.18 lL,respectively.展开更多
Drilling and blasting,characterized by their efficiency,ubiquity,and cost-effectiveness,have emerged as predominant techniques in rock excavation;however,they are accompanied by enormous destructive power.Accurately c...Drilling and blasting,characterized by their efficiency,ubiquity,and cost-effectiveness,have emerged as predominant techniques in rock excavation;however,they are accompanied by enormous destructive power.Accurately controlling the blasting energy and achieving the directional fracture of a rock mass have become common problems in the field.A two-dimensional blasting(2D blasting)technique was proposed that utilizes the characteristic that the tensile strength of a rock mass is significantly lower than its compressive strength.After blasting,only a 2D crack surface is generated along the predetermined direction,eliminating the damage to the reserved rock mass caused by conventional blasting.However,the interior of a natural rock mass is a"black box",and the process of crack propagation is difficult to capture,resulting in an unclear 2D blasting mechanism.To this end,a single-hole polymethyl methacrylate(PMMA)test piece was used to conduct a 2D blasting experiment with the help of a high-speed camera to capture the dynamic crack propagation process and the digital image correlation(DIC)method to analyze the evolution law of surface strain on the test piece.On this basis,a three-dimensional(3D)finite element model was established based on the progressive failure theory to simulate the stress,strain,damage,and displacement evolution process of the model under 2D blasting.The simulation results were consistent with the experimental results.The research results reveal the 2D blasting mechanism and provide theoretical support for the application of 2D blasting technology in the field of rock excavation.展开更多
Gel polymer electrolytes(GPEs)effectively combine the advantages of high ionic conductivity and re-duce the risk of leakage associated with liquid.In this study,a chemically cross-linked gel polymer electrolyte was pr...Gel polymer electrolytes(GPEs)effectively combine the advantages of high ionic conductivity and re-duce the risk of leakage associated with liquid.In this study,a chemically cross-linked gel polymer electrolyte was prepared by in-situ polymerization using polymethyl methacrylate(PMMA)as a matrix and neopentyl glycol diacrylate(NPGDA)as cross-linking agent.The cross-linked structure of the GPE was preliminarily investigated,as well as the influence of the degree of cross-linking on its phys-ical properties.The GPE exhibited a superior conductivity of 1.391 mS cm^(-1) at 25℃.Herein,the Li|GPE|LiNi_(0.8) Co_(0.1) Mn_(0.1) O_(2) cell has an excellent capacity retention rate of 80.7%after 150 cycles at 0.5 C in addition to a high discharge specific capacity of 203 mAh g^(-1).The structure of the cathode ma-terial is shielded from the production of byproducts during the charging and discharging of lithium-ion batteries by the cross-linked PMMA GPE.展开更多
Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mec...Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mechanical strength, unique surface characteristics, and improved adherence that is transmitted into the polymer matrix to form a nanocomposite with improved properties. Polymethyl methacrylate is a common carbon source for the synthesis of carbon nanofibres of its high mechanical strength, thermal stability, and low moisture and water absorbing capacity that allows its products to have several applications. In this work, we report the successful electrospinning of carbon nanofibres from Poly methyl methacrylate and functionalizing the resulting carbon nanofibres. The functionalized carbon nanofibres were analyzed to determine their solubility/dispersion in selected organic solvents, then characterized using Fourier transform infra-red spectroscopy, Raman spectroscopy, scanning electron microscopy combined with Energy dispersive spectroscopy and Thermalgravimetric analysis.展开更多
The composite phase change material(PCM) consisting of phase change paraffin(PCP) and polymethyl methacrylate(PMMA) was prepared as a novel type of shape-stabilized PCM for building energy conservation through the met...The composite phase change material(PCM) consisting of phase change paraffin(PCP) and polymethyl methacrylate(PMMA) was prepared as a novel type of shape-stabilized PCM for building energy conservation through the method of bulk polymerization. The chemical structure, morphology, phase change temperature and enthalpy, and mechanical properties of the composite PCM were studied to evaluate the encapsulation effect of PMMA on PCP and determine the optimal composition proportion. FTIR and SEM results revealed that PCP was physically immobilized in the PMMA so that its leakage from the composite was prevented. Based on the thermo-physical and mechanical properties investigations, the optimal mass fraction of PCP in the composite was determined as 70%. The phase change temperature of the composite was close to that of PCP, and its latent heat was equivalent to the calculated value according to the mass fraction of PCP in the composite. For estimating the usability in practical engineering, thermal stability, reliability and temperature regulation performance of the composite were also researched by TG analysis, thermal cycling treatments and heating-cooling test. The results indicated that PCP/PMMA composite PCM behaved good thermal stability depending on the PMMA protection and its latent heat degraded little after 500 thermal cycling. Temperature regulation performance of the composite before and after thermal cycling was both noticeable due to its latent heat absorption and release in the temperature variation processes. The PCP/PMMA phase change plate was fabricated and applied as thermal insulator in miniature concrete box to estimate its temperature regulation effect under the simulated environmental condition. It can be concluded that this kind of PCP/PMMA shape-stabilized PCM with the advantages of no leakage, suitable phase change temperature and enthalpy, good thermal stability and reliability, and effective temperature regulation performance have much potential for thermal energy storage in building energy conservation.展开更多
Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone ce...Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone cement are limited by the high elasticity modulus of PMMA,its low biodegradability,and its limited ability to regenerate bone.To improve PMMA bio activity and biodegradability and to modify its elasticity modulus,we mixed PMMA bone cement with oxidized hyaluronic acid and carboxymethyl chitosan in situ cross-linking hydrogel loaded with bone morphogenetic protein-2(BMP-2)to achieve novel hybrid cement.These fabric ated PMMA-hydrogel hybrid cements exhibited lower setting temperatures,a lower elasticity modulus,and better biodegradability and biocompatibility than that of pure PMMA cement,while retaining acceptable setting times,mechanical strength,and inj ectability.In addition,we detected release of BMP-2 from the PMMA-hydrogel hybrid cements,significantly enhancing in vitro osteogenesis of bone marrow mesenchymal stem cells by up-regulating the gene expression of Runx2,Coll,and OPN.Use of PMMA-hydrogel hybrid cements loaded with BMP-2 on rabbit femoral condyle bone-defect models revealed their biodegradability and enhanced bone formation.Our study demonstrated the favorable mechanical properties,biocompatibility,and biodegradability of fabricated PMMA-hydrogel hybrid cements loaded with BMP-2,as well as their ability to improve osteogenesis,making them a promising material for use in PKP and PVP.展开更多
Effect of interleukin-6 receptor （IL-6R） antibody on polymethyl methacrylate （PMMA） bone cement-mediated expression of osteoprotegerin （OPG） and ：receptor activator of nuclear fac- tor-kappaB ligand （RANKL） i...Effect of interleukin-6 receptor （IL-6R） antibody on polymethyl methacrylate （PMMA） bone cement-mediated expression of osteoprotegerin （OPG） and ：receptor activator of nuclear fac- tor-kappaB ligand （RANKL） in synovial fibroblasts was investigated. Synovial tissue obtained from to- tal knee arthroplasty was digested and cultured. Inverted microscope was employed to observe the synovial cells and immunocytochemistry （SABC method） staining was used to identify synovial fibro- blasts. This experiment was divided into three groups according to different culture media： PMMA group （75μg/mL PMMA bone cement particles）, IL-6R antibody group （10 ng/mL IL-6R antibody＋75 μg/mL PMMA bone cement particles）, and control group （no IL-6R antibody or PMMA bone cement particles）. Influence of IL-6R antibody and PMMA on proliferation of synovial fibroblasts was meas- ured by cell counting kit-8 （CCK-8）. ELISA method was used to measure OPG and RANKL levels in culture solution. Fluorescence quantitative real-time PCR （FQ-PCR） was used to detect the expression of OPG and RANKL mRNA. After three consecutive passages, more than 95% of the primary synovial cells became long spindle fibroblast-like cells. SABC staining results showed that the fibroblast-like cells were negative for anti-CD68 antibody and positive for anti-vimentin antibody, with brown madder stained. CCK-8 test demonstrated that the absorbance （A） value at 450 nm was significantly lower in IL-6R antibody group than in PMMA group and control group （P〈0.01）, but there was no statistically significant difference in A value at 450 nm between the control group and PMMA group （P〉0.05）. Re- suits of ELISA indicated that the expression of OPG was significantly higher in IL-6R antibody group than in PMMA group and control group （P〈0.01）. The expression of RANKL was inhibited （P〈0.05）, and the ratio of OPG/RANKL was significantly increased in IL-6R antibody group as compared with PMMA group and control group. There was no significant difference in the expression of OPG between control group and PMMA group （P〉0.05）, but the expression of RANKL was higher in PMMA group than in control group （P〈0.05）, and there was a significant difference in the ratio of OPG/RANKL be- tween them （P〈0.05）. Results of FQ-PCR revealed the expression of RANKL mRNA was significantly inhibited （P〈0.01） and the expression of OPG mRNA was significantly increased （P〈0.01） in IL-6R an- tibody group as compared with PMMA group and control group. The expression of RANKL mRNA was higher in PMMA group than in control group （P〈0.05）, but the expression of OPG mRNA had no sig- nificant difference between them （P〉0.05）. IL-6R antibody could significantly increase the expression of OPC~ but inhibit the expression of RANKL, which might provide a theoretical basis of molecular bi- ology for the prevention and treatment of aseptic loosening of prosthesis.展开更多
Residual stress induced during manufacturing of injection molded components such as polymethyl methacrylate （PMMA） affects the mechanical and optical properties of these components. These residual stresses can be vi...Residual stress induced during manufacturing of injection molded components such as polymethyl methacrylate （PMMA） affects the mechanical and optical properties of these components. These residual stresses can be visualized and quantified by measuring their birefringence. In this paper, a low birefringence polariscope （LBP） is used to measure the whole-field residual stress distribution of these injection molded specimens. Detailed analytical and experimental study is conducted to quantify the residual stress measurement in these materials. A commercial birefringence measurement system was used to validate the results obtained to our measurement system. This study can help in material diagnosis for quality and manufacturing purpose and be useful for understanding of residual stress in imaging or other anolications.展开更多
Micro-lens （ML） and Micro-lens array （MLA） are important optical components widely used in many fields; Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA; The cy...Micro-lens （ML） and Micro-lens array （MLA） are important optical components widely used in many fields; Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA; The cylinder and spherical MLA of polymethyl methacrylate （PMMA） were successfully obtained by micromolding inSoft-lithography. Some suitable experimental parameters in the process were discussed, and the imaging property of the MLA was also studied simply.展开更多
The biodegradation behavior of Mg,coated by polymethyl methacrylate as well as polymethyl methacrylate(PMMA)−bioactive glass(BG)composite was investigated.Electrophoretic deposition and dip coating techniques were ado...The biodegradation behavior of Mg,coated by polymethyl methacrylate as well as polymethyl methacrylate(PMMA)−bioactive glass(BG)composite was investigated.Electrophoretic deposition and dip coating techniques were adopted to prepare composite coating using a suspension of different percentages of the above two chemical materials.The deposited coatings were characterized using SEM,EDS,FTIR,and water contact angle measurements.Biodegradation behavior study of the coated Mg was performed using linear polarization,impedance spectroscopy,and immersion tests in simulated body fluid.The compact and homogeneous composite coating was developed as evidenced by electron microscopy results.The water contact angle measurement showed a 44°increase in the contact angle of the composite coated Mg compared to the uncoated one.The composite coating was covered by a bone-like hydroxyapatite layer after 336 h,indicating that the coating has an excellent in vitro bioactivity.The electrochemical testing results confirmed a significant reduction,96.9%,in the biodegradation rate of Mg coated with the composite prepared from 45 g/L PMMA+3.5 g/L 45S5 GB suspension compared to that of the uncoated one.Therefore,the composite coated Mg can be proposed as a promising material for biodegradable implant application.展开更多
In order to improve the mechanical properties and thermal conductivity of polymethyl methacrylate(PMMA),multi-walled carbon nanotubes(MWCNTs)were used as reinforcement through in situ polymerization method to prepare ...In order to improve the mechanical properties and thermal conductivity of polymethyl methacrylate(PMMA),multi-walled carbon nanotubes(MWCNTs)were used as reinforcement through in situ polymerization method to prepare PMMA/MWCNTs composites by changing the reaction time,polymerization temperature and the content of MWCNTs.The effects of different reaction conditions on the properties of the composites were studied.The results show that the mechanical properties,thermal/electrical conductivity and thermal stability of the composites are improved compared with the PMMA matrix.The tensile strength of the composites is increased by up to 24%.The bending strength of the composite material increases from20.41 to 68.04 MPa,and the maximum increase is 233%.Meanwhile,when the content of MWCNTs is 3 wt%,the thermal conductivity of the composite is 0.335 W/(m·K),which increases by138%,and the electrical conductivity is 3.94 S/m.The thermal stability of the composite has been significantly enhanced.The modified PMMA will be widely used in medicine,communications,electronics and other fields.展开更多
BACKGROUND In children with osteosarcoma around the knee joint without epiphysis involvement,joint-sparing surgery seems to be an ideal way to retain knee joint function.However,there are two points of debate with reg...BACKGROUND In children with osteosarcoma around the knee joint without epiphysis involvement,joint-sparing surgery seems to be an ideal way to retain knee joint function.However,there are two points of debate with regard to the technique:How to accurately achieve a safe surgical margin,and how to achieve intercalary reconstruction of the massive bone defect following resection of the tumor.CASE SUMMARY We present the case of an 8-year-old girl with osteosarcoma of the distal femur without involvement of the epiphysis.Epiphyseal distraction was applied to separate the epiphysis and metaphysis,and this provided a safe surgical margin.The massive bone defect was reconstructed with a custom-made antibioticloaded polymethyl methacrylate(PMMA)construct combined with a free nonvascularized fibular graft.Six months after surgery,bone union between the autograft and host bone was confirmed in both the proximal and distal femur by computer tomography(CT)examination.Moreover,considerable callus formation was found around the PMMA construct.After 28 mo of follow-up,there was no sign of recurrence or metastasis.The patient could walk without any aid and carry out her daily life activities satisfactorily.CONCLUSION In cases of osteosarcoma without epiphysis involvement,epiphyseal distraction can be easily applied to obtain a safe margin.Hybrid reconstruction with an antibiotic-loaded PMMA construct combined with a free non-vascularized fibular graft has the advantages of being easy to manufacture,less time-consuming to place,and less likely to get infected,while also ensuring bone union.Our case provides an alternative technique for biological reconstruction after joint-sparing surgery in patients with osteosarcoma around the knee without epiphyseal involvement.展开更多
We report on a novel and convenient method of measuring secondary electron spectra for insulators in a secondary electron yield measurement system with a planar grid analyzer configuration and a metal mesh probe. In t...We report on a novel and convenient method of measuring secondary electron spectra for insulators in a secondary electron yield measurement system with a planar grid analyzer configuration and a metal mesh probe. In this measurement, the planar grid is negatively biased to force some emitted secondary electrons to return to the sample surface and to neutralize charges accumulated on the sample during the previous beam irradiation. The surface potential of the sample is then measured by use of a metal mesh probe. The grid bias for neutralization corresponding to the zero surface potential is determined based on the linear relationship between the surface potential and the grid bias. Once the surface potential equals zero, the secondary electron spectra of polymethyl methacrylate（PMMA） are studied experimentally by measuring the -curve and then fitting it to Everhart＇s formula. The measurement results show that the peak energy and the full width at half maximum of the spectra are 4.26 eV and 14.06 eV, respectively.展开更多
BACKGROUND We report a case of Intracardiac,pulmonary,and intravenous cement embolism after cement-augmented pedicle screw instrumentation in treating spondylolisthesis underlying osteoporotic bone,which was successfu...BACKGROUND We report a case of Intracardiac,pulmonary,and intravenous cement embolism after cement-augmented pedicle screw instrumentation in treating spondylolisthesis underlying osteoporotic bone,which was successfully managed by conservative treatment.We describe the treatment and outcome of the patient,hoping to shed light on the management of bone cement embolism.CASE SUMMARY A 67-year-old female suffered from progressive low back pain and numbness in lower extremities for 30 years.She was diagnosed with L4 and L5 spondylolisthesis,spinal stenosis,and osteoporosis.The patient underwent spinal canal decompression,an interbody fusion of L4/5 and L5/S1,cement-augmented pedicle screw instrumentation in L4-L5 segments,and regular pedicle screw in S1 segments.Three days postoperatively,a sudden drop in oxygen saturation occurred.Computerized tomography scan confirmed Intracardiac,pulmonary,and intravenous embolism.The patient was treated conservatively by continuous low-flow oxygen inhalation,anti-coagulation,and antibiotic therapy for 1 mo and continued anticoagulation treatment for 6 mo.The patient showed no further symptoms in a 30-mo follow-up.CONCLUSION Intracardiac,pulmonary cement embolism after cement-augmented pedicle screw instrumentation is extremely rare.Careful clinical and radiographic evaluation is required in multiple sites of bone cement embolism.Conservative treatment may be a primary consideration in scattered emboli without life-threatening conditions,but a clinical decision should be made on an individualized basis.展开更多
Polymethylmethacrylate (PMMA) cltrafines have been prepared applying the meth- od of emulsion dispersion. Their sizes aie determined by size analysis apparatus SA-CP3. Factors affecting particle diameter and its distr...Polymethylmethacrylate (PMMA) cltrafines have been prepared applying the meth- od of emulsion dispersion. Their sizes aie determined by size analysis apparatus SA-CP3. Factors affecting particle diameter and its distribution, which include PMMA conoentration, pH value and water amount, were discussed by a series of comparaison experiments. The influential principle was found, PMMA ultafines having a median diameter of 5.71μm were obtained, the ratio of the particles whose median diameters are under 10μm is 65.%. This method can be applied to the preparation of other oil-soluble polymer ultrafines, it has the advantages of simple, quick and easy to be controlled. It is possible to make it in- dustrialized in the future.展开更多
PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to inv...PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions（GSD） were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd^（3＋） ions at about 1.06 μm due to the ~4F_（3/2）→~4I_（11/2） transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.展开更多
An underground roadway usually contains defects of various types,and when the roadway is subjected to external loading,the locations of those defects influence the roadway by differing degrees.In this study,to study h...An underground roadway usually contains defects of various types,and when the roadway is subjected to external loading,the locations of those defects influence the roadway by differing degrees.In this study,to study how the locations of defects affect crack propagation in a roadway,specimens with tunnel-type voids were made using polymethyl methacrylate,and the stress wave produced by a bullet impacting an incident rod was used as the impact load.Meanwhile,the variations in crack speed,displacement,and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics,and the commercial software ABAQUS was used for numerical simulations.From the experiments and numerical simulations,the crack propagation path was verified and the impact fracture behavior of a semicircular-arch roadway with different defect positions was presented.The results show that when the pre-fabricated crack is on the central axis of the sample,the crack propagation is purely mode I;when the pre-fabricated crack is 5 mm from the central axis,the crack propagation alternates between mode I and a mixture of modes I and II;when the pre-fabricated crack is at the edge of the semicircular-arch roadway,the crack propagation follows the I-II mixed mode.展开更多
Solid-state samples based on modified polymethyl methacrylate （MPMMA） with methanol doped with the dye pyrromethene 650 （PM650） axe prepared. The effects of a volume percentage of methanol on the laser characteris...Solid-state samples based on modified polymethyl methacrylate （MPMMA） with methanol doped with the dye pyrromethene 650 （PM650） axe prepared. The effects of a volume percentage of methanol on the laser characteristics of the sample, including spectra properties, slope efficiency, photostability and tunable properties, are investigated. The broadband dye laser output wavelength is around 655 nm and a highest slope efficiency of 32.23% is achieved. Pumping the samples at a repetition rate of 5 Hz with a pulse energy of as high as 100 mJ （the fluence is 0.26 J/cm2）, the longest lifetime （168000 shots） is obtained in the sample （MMA：methanol=18：2）, and the corresponding normalized photostability reaches 109.19 GJ/mol. When the sample （MMA：methanol=18：2） is placed in a Shoshan-type oscilla- tor, the naxrow-linewidth operation is a continuous tuning range （up to 64 nm）. The results indicate that the laser characteristics of solid-state dyes can be greatly enhanced by using modified PMMA with methanol serving as the solid host.展开更多
Polymethyl methacrylate (PMMA) microspheres with clear surface and diameter close to 1 祄 were synthesized by newly soap-free emulsion polymerization. The results showed that the presence of ethanol and NaCl made the...Polymethyl methacrylate (PMMA) microspheres with clear surface and diameter close to 1 祄 were synthesized by newly soap-free emulsion polymerization. The results showed that the presence of ethanol and NaCl made the increase of diameter and distribution, while the presence of toluene could avoid the problem of the increase of distribution, resulting a harvest of PMMA microspheres with a diameter close to 1 祄.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.31570363 and 31770391)Key Research and Development Plan of Yunnan Province–Special Project of Science and Technology in Yunnan Province(2017IB007)+2 种基金Major Biomedical Project of Yunnan Province(2018ZF005)Innovation Team of the Ministry of Education(No.IRT-17R49)the Foundation of State Key Laboratory of Phytochemistry and Plant Resources in West China(P2017-ZZ04 and P2017-KF06),Kunming Institute of Botany,Chinese Academy of Sciences.
文摘Phytochemical investigation of the MeOH extract of twigs and leaves of Baeckea frutescens led to the isolation of seven new polymethylated phloroglucinol meroterpenoids(PPMs),named baeckfrutones M-S(1-7).Their structures and absolute configurations were determined by spectroscopic analyses,chiral-phase HPLC analysis,and electronic circular dichroism(ECD)calculations.PPM 1 is a novel meroterpenoid possessing a 6/6/5/3 tetracyclic skeleton in PPMs,whereas 3 and 4 are the first hydroxytasmanone type phloroglucinol-monoterpene hybrids.(+)-2 and 7 displayed potent antiinflammatory activity with IC50 values of 20.86±0.60 and 36.21±1.18 lL,respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.52404155 and 52304111)State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining&Technology,Beijing(Grant No.XD2024006).
文摘Drilling and blasting,characterized by their efficiency,ubiquity,and cost-effectiveness,have emerged as predominant techniques in rock excavation;however,they are accompanied by enormous destructive power.Accurately controlling the blasting energy and achieving the directional fracture of a rock mass have become common problems in the field.A two-dimensional blasting(2D blasting)technique was proposed that utilizes the characteristic that the tensile strength of a rock mass is significantly lower than its compressive strength.After blasting,only a 2D crack surface is generated along the predetermined direction,eliminating the damage to the reserved rock mass caused by conventional blasting.However,the interior of a natural rock mass is a"black box",and the process of crack propagation is difficult to capture,resulting in an unclear 2D blasting mechanism.To this end,a single-hole polymethyl methacrylate(PMMA)test piece was used to conduct a 2D blasting experiment with the help of a high-speed camera to capture the dynamic crack propagation process and the digital image correlation(DIC)method to analyze the evolution law of surface strain on the test piece.On this basis,a three-dimensional(3D)finite element model was established based on the progressive failure theory to simulate the stress,strain,damage,and displacement evolution process of the model under 2D blasting.The simulation results were consistent with the experimental results.The research results reveal the 2D blasting mechanism and provide theoretical support for the application of 2D blasting technology in the field of rock excavation.
基金supported by the National Natural Science Foundation of China(No.U22A20420)the Science and Technology Plan Project of Changzhou(No.CJ20235017)In addi-tion,the authors thank Jiangsu Development&Reform Commis-sion for their support.
文摘Gel polymer electrolytes(GPEs)effectively combine the advantages of high ionic conductivity and re-duce the risk of leakage associated with liquid.In this study,a chemically cross-linked gel polymer electrolyte was prepared by in-situ polymerization using polymethyl methacrylate(PMMA)as a matrix and neopentyl glycol diacrylate(NPGDA)as cross-linking agent.The cross-linked structure of the GPE was preliminarily investigated,as well as the influence of the degree of cross-linking on its phys-ical properties.The GPE exhibited a superior conductivity of 1.391 mS cm^(-1) at 25℃.Herein,the Li|GPE|LiNi_(0.8) Co_(0.1) Mn_(0.1) O_(2) cell has an excellent capacity retention rate of 80.7%after 150 cycles at 0.5 C in addition to a high discharge specific capacity of 203 mAh g^(-1).The structure of the cathode ma-terial is shielded from the production of byproducts during the charging and discharging of lithium-ion batteries by the cross-linked PMMA GPE.
文摘Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mechanical strength, unique surface characteristics, and improved adherence that is transmitted into the polymer matrix to form a nanocomposite with improved properties. Polymethyl methacrylate is a common carbon source for the synthesis of carbon nanofibres of its high mechanical strength, thermal stability, and low moisture and water absorbing capacity that allows its products to have several applications. In this work, we report the successful electrospinning of carbon nanofibres from Poly methyl methacrylate and functionalizing the resulting carbon nanofibres. The functionalized carbon nanofibres were analyzed to determine their solubility/dispersion in selected organic solvents, then characterized using Fourier transform infra-red spectroscopy, Raman spectroscopy, scanning electron microscopy combined with Energy dispersive spectroscopy and Thermalgravimetric analysis.
基金Funded by National Natural Science Foundation of China(No.51308275)Natural Science Foundation of Liaoning Province(No.SY2016004)Science Foundation for Young Scientists of Liaoning Educational Committee(No.JQL201915403).
文摘The composite phase change material(PCM) consisting of phase change paraffin(PCP) and polymethyl methacrylate(PMMA) was prepared as a novel type of shape-stabilized PCM for building energy conservation through the method of bulk polymerization. The chemical structure, morphology, phase change temperature and enthalpy, and mechanical properties of the composite PCM were studied to evaluate the encapsulation effect of PMMA on PCP and determine the optimal composition proportion. FTIR and SEM results revealed that PCP was physically immobilized in the PMMA so that its leakage from the composite was prevented. Based on the thermo-physical and mechanical properties investigations, the optimal mass fraction of PCP in the composite was determined as 70%. The phase change temperature of the composite was close to that of PCP, and its latent heat was equivalent to the calculated value according to the mass fraction of PCP in the composite. For estimating the usability in practical engineering, thermal stability, reliability and temperature regulation performance of the composite were also researched by TG analysis, thermal cycling treatments and heating-cooling test. The results indicated that PCP/PMMA composite PCM behaved good thermal stability depending on the PMMA protection and its latent heat degraded little after 500 thermal cycling. Temperature regulation performance of the composite before and after thermal cycling was both noticeable due to its latent heat absorption and release in the temperature variation processes. The PCP/PMMA phase change plate was fabricated and applied as thermal insulator in miniature concrete box to estimate its temperature regulation effect under the simulated environmental condition. It can be concluded that this kind of PCP/PMMA shape-stabilized PCM with the advantages of no leakage, suitable phase change temperature and enthalpy, good thermal stability and reliability, and effective temperature regulation performance have much potential for thermal energy storage in building energy conservation.
基金supported by the National Key R&D Program of China(No.2018YFA0703000)the National Natural Science Foundation of China(Nos.82071564,82072412,and 81772326)+1 种基金the Fundamental Research Program Funding of Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine(No.JYZZ070)Project of Shanghai Science and Technology Commission(No.19XD1434200/18431903700)。
文摘Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone cement are limited by the high elasticity modulus of PMMA,its low biodegradability,and its limited ability to regenerate bone.To improve PMMA bio activity and biodegradability and to modify its elasticity modulus,we mixed PMMA bone cement with oxidized hyaluronic acid and carboxymethyl chitosan in situ cross-linking hydrogel loaded with bone morphogenetic protein-2(BMP-2)to achieve novel hybrid cement.These fabric ated PMMA-hydrogel hybrid cements exhibited lower setting temperatures,a lower elasticity modulus,and better biodegradability and biocompatibility than that of pure PMMA cement,while retaining acceptable setting times,mechanical strength,and inj ectability.In addition,we detected release of BMP-2 from the PMMA-hydrogel hybrid cements,significantly enhancing in vitro osteogenesis of bone marrow mesenchymal stem cells by up-regulating the gene expression of Runx2,Coll,and OPN.Use of PMMA-hydrogel hybrid cements loaded with BMP-2 on rabbit femoral condyle bone-defect models revealed their biodegradability and enhanced bone formation.Our study demonstrated the favorable mechanical properties,biocompatibility,and biodegradability of fabricated PMMA-hydrogel hybrid cements loaded with BMP-2,as well as their ability to improve osteogenesis,making them a promising material for use in PKP and PVP.
基金supported by grants from the Research and Development Projects of Shenzhen of P.R.China(No.JCYJ20130402114702130)the Healthcare and Medical Research Fund of Shenzhen of P.R.China(No.201302064)
文摘Effect of interleukin-6 receptor （IL-6R） antibody on polymethyl methacrylate （PMMA） bone cement-mediated expression of osteoprotegerin （OPG） and ：receptor activator of nuclear fac- tor-kappaB ligand （RANKL） in synovial fibroblasts was investigated. Synovial tissue obtained from to- tal knee arthroplasty was digested and cultured. Inverted microscope was employed to observe the synovial cells and immunocytochemistry （SABC method） staining was used to identify synovial fibro- blasts. This experiment was divided into three groups according to different culture media： PMMA group （75μg/mL PMMA bone cement particles）, IL-6R antibody group （10 ng/mL IL-6R antibody＋75 μg/mL PMMA bone cement particles）, and control group （no IL-6R antibody or PMMA bone cement particles）. Influence of IL-6R antibody and PMMA on proliferation of synovial fibroblasts was meas- ured by cell counting kit-8 （CCK-8）. ELISA method was used to measure OPG and RANKL levels in culture solution. Fluorescence quantitative real-time PCR （FQ-PCR） was used to detect the expression of OPG and RANKL mRNA. After three consecutive passages, more than 95% of the primary synovial cells became long spindle fibroblast-like cells. SABC staining results showed that the fibroblast-like cells were negative for anti-CD68 antibody and positive for anti-vimentin antibody, with brown madder stained. CCK-8 test demonstrated that the absorbance （A） value at 450 nm was significantly lower in IL-6R antibody group than in PMMA group and control group （P〈0.01）, but there was no statistically significant difference in A value at 450 nm between the control group and PMMA group （P〉0.05）. Re- suits of ELISA indicated that the expression of OPG was significantly higher in IL-6R antibody group than in PMMA group and control group （P〈0.01）. The expression of RANKL was inhibited （P〈0.05）, and the ratio of OPG/RANKL was significantly increased in IL-6R antibody group as compared with PMMA group and control group. There was no significant difference in the expression of OPG between control group and PMMA group （P〉0.05）, but the expression of RANKL was higher in PMMA group than in control group （P〈0.05）, and there was a significant difference in the ratio of OPG/RANKL be- tween them （P〈0.05）. Results of FQ-PCR revealed the expression of RANKL mRNA was significantly inhibited （P〈0.01） and the expression of OPG mRNA was significantly increased （P〈0.01） in IL-6R an- tibody group as compared with PMMA group and control group. The expression of RANKL mRNA was higher in PMMA group than in control group （P〈0.05）, but the expression of OPG mRNA had no sig- nificant difference between them （P〉0.05）. IL-6R antibody could significantly increase the expression of OPC~ but inhibit the expression of RANKL, which might provide a theoretical basis of molecular bi- ology for the prevention and treatment of aseptic loosening of prosthesis.
文摘Residual stress induced during manufacturing of injection molded components such as polymethyl methacrylate （PMMA） affects the mechanical and optical properties of these components. These residual stresses can be visualized and quantified by measuring their birefringence. In this paper, a low birefringence polariscope （LBP） is used to measure the whole-field residual stress distribution of these injection molded specimens. Detailed analytical and experimental study is conducted to quantify the residual stress measurement in these materials. A commercial birefringence measurement system was used to validate the results obtained to our measurement system. This study can help in material diagnosis for quality and manufacturing purpose and be useful for understanding of residual stress in imaging or other anolications.
基金Ⅶ. ACKN0WLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20374049） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20040358018）
文摘Micro-lens （ML） and Micro-lens array （MLA） are important optical components widely used in many fields; Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA; The cylinder and spherical MLA of polymethyl methacrylate （PMMA） were successfully obtained by micromolding inSoft-lithography. Some suitable experimental parameters in the process were discussed, and the imaging property of the MLA was also studied simply.
文摘The biodegradation behavior of Mg,coated by polymethyl methacrylate as well as polymethyl methacrylate(PMMA)−bioactive glass(BG)composite was investigated.Electrophoretic deposition and dip coating techniques were adopted to prepare composite coating using a suspension of different percentages of the above two chemical materials.The deposited coatings were characterized using SEM,EDS,FTIR,and water contact angle measurements.Biodegradation behavior study of the coated Mg was performed using linear polarization,impedance spectroscopy,and immersion tests in simulated body fluid.The compact and homogeneous composite coating was developed as evidenced by electron microscopy results.The water contact angle measurement showed a 44°increase in the contact angle of the composite coated Mg compared to the uncoated one.The composite coating was covered by a bone-like hydroxyapatite layer after 336 h,indicating that the coating has an excellent in vitro bioactivity.The electrochemical testing results confirmed a significant reduction,96.9%,in the biodegradation rate of Mg coated with the composite prepared from 45 g/L PMMA+3.5 g/L 45S5 GB suspension compared to that of the uncoated one.Therefore,the composite coated Mg can be proposed as a promising material for biodegradable implant application.
基金Funded by the Science and Technology Research Project of Henan Province(No.222102320419)Natural Scienceof Henan Province(No.232300420312)+1 种基金the Science Foundation of Henan University of Technology(No.2019BS010)the Innovative Funds Plan of Henan University of Technology(No.2020ZKCJ07)。
文摘In order to improve the mechanical properties and thermal conductivity of polymethyl methacrylate(PMMA),multi-walled carbon nanotubes(MWCNTs)were used as reinforcement through in situ polymerization method to prepare PMMA/MWCNTs composites by changing the reaction time,polymerization temperature and the content of MWCNTs.The effects of different reaction conditions on the properties of the composites were studied.The results show that the mechanical properties,thermal/electrical conductivity and thermal stability of the composites are improved compared with the PMMA matrix.The tensile strength of the composites is increased by up to 24%.The bending strength of the composite material increases from20.41 to 68.04 MPa,and the maximum increase is 233%.Meanwhile,when the content of MWCNTs is 3 wt%,the thermal conductivity of the composite is 0.335 W/(m·K),which increases by138%,and the electrical conductivity is 3.94 S/m.The thermal stability of the composite has been significantly enhanced.The modified PMMA will be widely used in medicine,communications,electronics and other fields.
基金Supported by National Natural Science Foundation of China,No.81301671
文摘BACKGROUND In children with osteosarcoma around the knee joint without epiphysis involvement,joint-sparing surgery seems to be an ideal way to retain knee joint function.However,there are two points of debate with regard to the technique:How to accurately achieve a safe surgical margin,and how to achieve intercalary reconstruction of the massive bone defect following resection of the tumor.CASE SUMMARY We present the case of an 8-year-old girl with osteosarcoma of the distal femur without involvement of the epiphysis.Epiphyseal distraction was applied to separate the epiphysis and metaphysis,and this provided a safe surgical margin.The massive bone defect was reconstructed with a custom-made antibioticloaded polymethyl methacrylate(PMMA)construct combined with a free nonvascularized fibular graft.Six months after surgery,bone union between the autograft and host bone was confirmed in both the proximal and distal femur by computer tomography(CT)examination.Moreover,considerable callus formation was found around the PMMA construct.After 28 mo of follow-up,there was no sign of recurrence or metastasis.The patient could walk without any aid and carry out her daily life activities satisfactorily.CONCLUSION In cases of osteosarcoma without epiphysis involvement,epiphyseal distraction can be easily applied to obtain a safe margin.Hybrid reconstruction with an antibiotic-loaded PMMA construct combined with a free non-vascularized fibular graft has the advantages of being easy to manufacture,less time-consuming to place,and less likely to get infected,while also ensuring bone union.Our case provides an alternative technique for biological reconstruction after joint-sparing surgery in patients with osteosarcoma around the knee without epiphyseal involvement.
基金Supported by the National Natural Science Foundation of China under Grant Nos U1537210 and 11375139the National Key Laboratory of Space Microwave Technology China under Grant No 9140C530101130C53013
文摘We report on a novel and convenient method of measuring secondary electron spectra for insulators in a secondary electron yield measurement system with a planar grid analyzer configuration and a metal mesh probe. In this measurement, the planar grid is negatively biased to force some emitted secondary electrons to return to the sample surface and to neutralize charges accumulated on the sample during the previous beam irradiation. The surface potential of the sample is then measured by use of a metal mesh probe. The grid bias for neutralization corresponding to the zero surface potential is determined based on the linear relationship between the surface potential and the grid bias. Once the surface potential equals zero, the secondary electron spectra of polymethyl methacrylate（PMMA） are studied experimentally by measuring the -curve and then fitting it to Everhart＇s formula. The measurement results show that the peak energy and the full width at half maximum of the spectra are 4.26 eV and 14.06 eV, respectively.
基金Fundamental Research Funds for the Central Universities,No.20ykpy94.
文摘BACKGROUND We report a case of Intracardiac,pulmonary,and intravenous cement embolism after cement-augmented pedicle screw instrumentation in treating spondylolisthesis underlying osteoporotic bone,which was successfully managed by conservative treatment.We describe the treatment and outcome of the patient,hoping to shed light on the management of bone cement embolism.CASE SUMMARY A 67-year-old female suffered from progressive low back pain and numbness in lower extremities for 30 years.She was diagnosed with L4 and L5 spondylolisthesis,spinal stenosis,and osteoporosis.The patient underwent spinal canal decompression,an interbody fusion of L4/5 and L5/S1,cement-augmented pedicle screw instrumentation in L4-L5 segments,and regular pedicle screw in S1 segments.Three days postoperatively,a sudden drop in oxygen saturation occurred.Computerized tomography scan confirmed Intracardiac,pulmonary,and intravenous embolism.The patient was treated conservatively by continuous low-flow oxygen inhalation,anti-coagulation,and antibiotic therapy for 1 mo and continued anticoagulation treatment for 6 mo.The patient showed no further symptoms in a 30-mo follow-up.CONCLUSION Intracardiac,pulmonary cement embolism after cement-augmented pedicle screw instrumentation is extremely rare.Careful clinical and radiographic evaluation is required in multiple sites of bone cement embolism.Conservative treatment may be a primary consideration in scattered emboli without life-threatening conditions,but a clinical decision should be made on an individualized basis.
文摘Polymethylmethacrylate (PMMA) cltrafines have been prepared applying the meth- od of emulsion dispersion. Their sizes aie determined by size analysis apparatus SA-CP3. Factors affecting particle diameter and its distribution, which include PMMA conoentration, pH value and water amount, were discussed by a series of comparaison experiments. The influential principle was found, PMMA ultafines having a median diameter of 5.71μm were obtained, the ratio of the particles whose median diameters are under 10μm is 65.%. This method can be applied to the preparation of other oil-soluble polymer ultrafines, it has the advantages of simple, quick and easy to be controlled. It is possible to make it in- dustrialized in the future.
基金Project supported by Istanbul Technical University Scientific Research Projects Department(ITU BAP,project number 39283)
文摘PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions（GSD） were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd^（3＋） ions at about 1.06 μm due to the ~4F_（3/2）→~4I_（11/2） transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.
基金This work was financed by the State Key Development Program for Basic Research of China(2016YFC0600903)the National Natural Science Foundation of China(51774287).
文摘An underground roadway usually contains defects of various types,and when the roadway is subjected to external loading,the locations of those defects influence the roadway by differing degrees.In this study,to study how the locations of defects affect crack propagation in a roadway,specimens with tunnel-type voids were made using polymethyl methacrylate,and the stress wave produced by a bullet impacting an incident rod was used as the impact load.Meanwhile,the variations in crack speed,displacement,and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics,and the commercial software ABAQUS was used for numerical simulations.From the experiments and numerical simulations,the crack propagation path was verified and the impact fracture behavior of a semicircular-arch roadway with different defect positions was presented.The results show that when the pre-fabricated crack is on the central axis of the sample,the crack propagation is purely mode I;when the pre-fabricated crack is 5 mm from the central axis,the crack propagation alternates between mode I and a mixture of modes I and II;when the pre-fabricated crack is at the edge of the semicircular-arch roadway,the crack propagation follows the I-II mixed mode.
基金Project supported by the National Natural Science Foundation of China (Grant No.61008023)the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology,China (Grant No.HIT.NSRIF.2009009)
文摘Solid-state samples based on modified polymethyl methacrylate （MPMMA） with methanol doped with the dye pyrromethene 650 （PM650） axe prepared. The effects of a volume percentage of methanol on the laser characteristics of the sample, including spectra properties, slope efficiency, photostability and tunable properties, are investigated. The broadband dye laser output wavelength is around 655 nm and a highest slope efficiency of 32.23% is achieved. Pumping the samples at a repetition rate of 5 Hz with a pulse energy of as high as 100 mJ （the fluence is 0.26 J/cm2）, the longest lifetime （168000 shots） is obtained in the sample （MMA：methanol=18：2）, and the corresponding normalized photostability reaches 109.19 GJ/mol. When the sample （MMA：methanol=18：2） is placed in a Shoshan-type oscilla- tor, the naxrow-linewidth operation is a continuous tuning range （up to 64 nm）. The results indicate that the laser characteristics of solid-state dyes can be greatly enhanced by using modified PMMA with methanol serving as the solid host.
文摘Polymethyl methacrylate (PMMA) microspheres with clear surface and diameter close to 1 祄 were synthesized by newly soap-free emulsion polymerization. The results showed that the presence of ethanol and NaCl made the increase of diameter and distribution, while the presence of toluene could avoid the problem of the increase of distribution, resulting a harvest of PMMA microspheres with a diameter close to 1 祄.
