scholarly journals Polymerization Kinetics Stability, Volumetric Changes, Apatite Precipitation, Strontium Release and Fatigue of Novel Bone Composites for Vertebroplasty

2018 ◽  
Author(s):  
Piyaphong Panpisut ◽  
Kirsty Main ◽  
Muhammad Adnan Khan ◽  
Mayda Arshad ◽  
Wendy Xia ◽  
...  
Keyword(s):  
Heat Generation ◽  
Glass Fibers ◽  
Monomer Conversion ◽  
Reaction Rates ◽  
Polymerization Kinetics ◽  
Fatigue Properties ◽  
Apatite Formation ◽  
Maximum Reaction ◽  
Urethane Dimethacrylate ◽  
Lower Temperature

AbstractPurposeThe aim was to determine effects of diluent monomer and monocalcium phosphate monohydrate (MCPM) on polymerization kinetics and volumetric stability, apatite precipitation, strontium release and fatigue of novel dual-paste composites for vertebroplasty.Materials and methodsPolypropylene (PPGDMA) or triethylene (TEGDMA) glycol dimethacrylates (25 wt%) diluents were combined with urethane dimethacrylate (70 wt%) and hydroxyethyl methacrylate (5 wt%). 70 wt% filler containing glass particles, glass fibers (20 wt%) and polylysine (5 wt%) was added. Benzoyl peroxide and MCPM (10 or 20 wt%) or N-tolyglycine glycidyl methacrylate and tristrontium phosphate (15 wt%) were included to give initiator or activator pastes. Commercial PMMA (Simplex) and bone composite (Cortoss) were used for comparison.ATR-FTIR was used to determine thermal activated polymerization kinetics of initiator pastes at 50-80 °C. Paste stability, following storage at 4-37 °C, was assessed visually or through mixed paste polymerization kinetics at 25 °C. Polymerization shrinkage and heat generation were calculated from final monomer conversions. Subsequent expansion and surface apatite precipitation in simulated body fluid (SBF) were assessed gravimetrically and via SEM. Strontium release into water was assessed using ICP-MS. Biaxial flexural strength (BFS) and fatigue properties were determined at 37 °C after 4 weeks in SBF.ResultsPolymerization profiles all exhibited an inhibition time before polymerization as predicted by free radical polymerization mechanisms. Initiator paste inhibition times and maximum reaction rates were described well by Arrhenius plots. Plot extrapolation, however, underestimated lower temperature paste stability. Replacement of TEGDMA by PPGDMA, enhanced paste stability, final monomer conversion, water-sorption induced expansion and strontium release but reduced polymerisation shrinkage and heat generation. Increasing MCPM level enhanced volume expansion, surface apatite precipitation and strontium release. Although the experimental composite flexural strengths were lower compared to those of commercially available Simplex, the extrapolated low load fatigue lives of all materials were comparable.ConclusionsIncreased inhibition times at high temperature give longer predicted shelf-life whilst stability of mixed paste inhibition times is important for consistent clinical application. Increased volumetric stability, strontium release and apatite formation should encourage bone integration. Replacing TEGDMA by PPGDMA and increasing MCPM could therefore increase suitability of the above novel bone composites for vertebroplasty. Long fatigue lives of the composites may also ensure long-term durability of the materials.

scholarly journals Urca nuclide production in Type-I X-ray bursts and implications for nuclear physics studies

2020 ◽  
Vol 500 (3) ◽  
pp. 2958-2968
Author(s):  
Grant Merz ◽  
Zach Meisel
Keyword(s):  
Light Curve ◽  
Nuclear Reaction ◽  
Nuclear Physics ◽  
Thermal Structure ◽  
Reaction Rates ◽  
High Mass ◽  
Type I ◽  
Model Calculations ◽  
X Ray ◽  
Lower Temperature

ABSTRACT The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harbouring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code MESA, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass (A ≥ 55) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The ∼0.4–0.6 GK temperature relevant for the nucleosynthesis of these urca nuclides is much lower than the ∼1 GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.

scholarly journals Physico-Mechanical Properties of the Poly(oxymethylene) Composites Reinforced with Glass Fibers under Dynamical Loading

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2064 ◽  
Author(s):  
Stanisław Kuciel ◽  
Patrycja Bazan ◽  
Aneta Liber-Kneć ◽  
Aneta Gądek-Moszczak
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
Fiber Diameter ◽  
Glass Fibers ◽  
Fiber Reinforced Composites ◽  
Dynamic Loads ◽  
Fatigue Properties ◽  
Reinforced Composites ◽  
The Impact ◽  
Microscopy Images

The paper evaluated the possibility of potential reinforcing of poly(oxymethylene) (POM) by glass fiber and the influence of fiberglass addition on mechanical properties under dynamic load. Four types of composites with glass fiber and another four with carbon fiber were produced. The fiber content ranged from 5% to 40% by weight. In the experimental part, the basic mechanical and fatigue properties of POM-based composites were determined. The impact of water absorption was also investigated. The influence of fiber geometry on the mechanical behavior of fiber-reinforced composites of various diameters was determined. To refer to the effects of reinforcement and determine the features of the structure scanning electron microscopy images were taken. The results showed that the addition of up to 10 wt %. fiberglass increases the tensile properties and impact strength more than twice, the ability to absorb energy also increases in relation to neat poly(oxymethylene). Fiber geometry also has a significant impact on the mechanical properties. The study of the mechanical properties at dynamic loads over time suggests that composites filled with a smaller fiber diameter have better fatigue properties.

Bone Formation in Non-Osseous Tissues of Biphasic HA/β-TCP Bioceramics Sintered by Different Ways

2007 ◽  
Vol 336-338 ◽  
pp. 1666-1669 ◽  
Author(s):  
Jun Guo Ran ◽  
Li Gou ◽  
Bao Hui Su ◽  
Fang Hu Wang ◽  
Lu Wei Sun ◽  
...  
Keyword(s):  
Bone Formation ◽  
Body Fluid ◽  
Microwave Plasma ◽  
Microwave Sintering ◽  
Apatite Formation ◽  
Conventional Furnace ◽  
Plasma Sintering ◽  
Higher Temperature ◽  
Healthy Dogs ◽  
Lower Temperature

In order to improve the bioactivity of calcium phosphate bioceramics, biphasic HA/β-TCP (BCP) bioceramics were prepared by the microwave sintering and the microwave plasma sintering. Bone-like apatite formation of the resulting samples was investigated in simulated body fluid (SBF). The samples were also implanted in dorsal muscles of healthy dogs for 1.5and 3 months. All samples after taking out were examined by histological observation. Bone formation in different sintering ways and temperatures was investigated in details. Better osteoinductivity was found in samples sintered by the microwave and microwave plasma instead of the conventional furnace, as well as by lower temperature (1050 oC) instead of higher temperature (1150 oC). It accounts for that the increase in degradability of materials sintered by microwave and microwave plasma or lower temperature leads to the better of bone-like apatite formation and bone formation due to fine grains and lower crystallinity.

scholarly journals Enhanced Degree of Monomer Conversion of Orthodontic Adhesives Using a Glass-Fiber Layer under the Bracket

2009 ◽  
Vol 79 (3) ◽  
pp. 546-550 ◽  
Author(s):  
Makiha Shinya ◽  
Akikazu Shinya ◽  
Lippo V. J. Lassila ◽  
Juha Varrela ◽  
Pekka K. Vallittu
Keyword(s):  
Glass Fiber ◽  
Glass Fibers ◽  
Fiber Reinforcement ◽  
Monomer Conversion ◽  
Fiber Reinforced ◽  
Fiber Layer ◽  
Adhesive Resin ◽  
Orthodontic Adhesives ◽  
Glass Fiber Reinforcement ◽  
Light Curing

Abstract Objective: To test the hypothesis that there is no difference in the degree of conversion (DC%) of orthodontic composites during the light-curing process with or without the use of a glass-fiber reinforcement. Materials and Methods: Two light-curing orthodontic adhesives, Transbond XT (TB) and Beauty Ortho Bond (BO), were used with woven preimpregnated glass fibers. The degree of monomer conversion was determined for both adhesives in three settings (n = 5 per group): in the first group, the adhesive was cured without a bracket (control); in the second group, the bracket was bonded using adhesive without fiber reinforcement; and in the third group, a layer of glass-fiber net was added between the bracket and resin. The adhesive resin was light cured, and the DC% was determined by Fourier transform infrared spectroscopy. Results: A two-way analysis of variance revealed significant differences in the DC% (P < .001) between adhesives and between the fiber-reinforced and nonreinforced groups. When the nonreinforced adhesives were light cured under the brackets, the DC% was significantly lower (TB: 37.0%, SD 3.4; BO: 36.9%, SD 1.9) compared with the control (TB: 54.7%, SD 0.6; BO: 65.9%, SD 0.5). A higher DC% was found when the resin was light cured in the presence of a glass-fiber net (TB: 44.1%, SD 0.3; BO: 55.3%, SD 1.7). Conclusion: The hypothesis is rejected. The degree of monomer conversion of the light-curing adhesive resin under stainless steel bracket can be improved by adding a thin layer of glass-fiber–reinforced composite between the bracket and adhesive resin.

scholarly journals APLICAÇÃO DO MÉTODO DE MONTE CARLO NA ESTIMATIVA DA TAXA DE DEGRADAÇÃO TÉRMICA DO β-CAROTENO

e-xacta ◽  
2018 ◽  
Vol 11 (2) ◽  
pp. 39
Author(s):  
Pedro Prates Valério ◽  
Mariane De Carvalho Sabarense
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Monte Carlo ◽  
Palm Oil ◽  
Reaction Rates ◽  
Industrial Processes ◽  
Reaction Systems ◽  
Chemical Reaction Systems ◽  
Lower Temperature ◽  
Β Carotene

<p><em>A compreensão dos parâmetros de reações químicas é essencial para o desenvolvimento de processos industriais mais eficazes. O presente trabalho apresenta a aplicação do método estocástico de Monte Carlo com Cadeias de Markov, utilizando a abordagem de Metropolis-Hastings, no contexto de simulações cinéticas de sistemas reacionais. Avaliou-se a viabilidade do desenvolvimento de um algoritmo que simule o comportamento da degradação térmica do composto β-caroteno, em matriz oleica vegetal – óleo de palma. Para tanto, os valores de energia de ativação 86,0 kJ.mol<sup>-1</sup> e 109,4 kJ.mol<sup>-1</sup> são considerados como parâmetros, em relação aos quais avaliam-se as temperaturas de reação 170 °C, 190 °C, 210 °C e 230 °C e determinam-se as constantes cinéticas e as taxas da reação. Os resultados foram sintetizados em forma de tabelas e gráficos e então comparados a estudos experimentais prévios encontrados na literatura. A comparação indicou eficiência parcial do algoritmo desenvolvido na determinação dos parâmetros cinéticos supracitados, sendo sua eficácia restrita à menor temperatura analisada.</em></p><p><em> </em></p><p><em>Abstract</em></p><p><em>To understand chemical reactions parameters is vital to the development of more effective industrial processes. This paper presents the application of Monte Carlo with Markov Chains stochastic method, using Metropolis-Hastings approach, in chemical reaction systems kinetic simulations context. The possibility of developing an algorithm to simulate the behaviour of β-carotene compounds in a vegetable oil matrix - Palm oil – during heat treatment was evaluated. Therefore, activation energies of 86,0 kJ.mol<sup>-1</sup> e 109,4 kJ.mol<sup>-1</sup> were established as parameters and reaction temperatures of 170 ºC, 190 °C, 210 °C e 230 °C were analysed to determine corresponding kinetic constants and reaction rates. Results were organised in charts and spreadsheets and compared to previous experimental data found in the literature. The algorithm developed was partially efficient to calculate the reactional parameters analysed, presenting higher efficiency for the lower temperature of simulation. </em></p>

Dynamic Simulation of an Autothermal Methane Reformer

2004 ◽  
Author(s):  
Li Yuan ◽  
Jacob Brouwer ◽  
G. Scott Samuelsen
Keyword(s):  
Catalyst Activity ◽  
Reaction Rates ◽  
Temperature Limit ◽  
Chemical Kinetic ◽  
Dynamic Responses ◽  
Outlet Temperature ◽  
Gas Temperature ◽  
Advantages And Disadvantages ◽  
Oxidation Of Methane ◽  
Lower Temperature

A dynamic autothermal methane reformer model has been developed and tested for the production of a hydrogen- and carbon monoxide-rich syngas. This study looks at potential advantages and disadvantages of an autothermal reformer, both operating in stand-alone mode and in conjunction with a high temperature fuel cell stack. The model uses a conservation of moles as the fundamental continuity relationship, and applies basic energy conservation equations to simulate both the gas and the catalyst bed energies. Chemical kinetic expressions using empirical constants for the Arrhenius rate terms that describe steam reformation of methane and partial oxidation of methane are simultaneously solved to provide an accurate picture of the reaction dynamics. This paper presents dynamic responses of reformer outlet temperature, hydrogen mole fraction, reaction rates and methane conversion to the perturbation of the reformer inlet variables of steam-to-carbon ratio, oxygen-to-carbon ratio and inlet gas temperature. Also explored is the concept of catalyst “light-off,” where there is found to be a lower temperature limit above which catalyst activity is substantially increased.

l-Lactide polymerization studied by 1H NMR with diffusion-ordered spectroscopy (DOSY): a “One NMR Tube Experiment” providing data on monomer conversion, polymer structure, Mn and Mw

2015 ◽  
Vol 6 (24) ◽  
pp. 4353-4357 ◽  
Author(s):  
P. Lewinski ◽  
S. Sosnowski ◽  
S. Kazmierski ◽  
S. Penczek
Keyword(s):  
1H Nmr ◽  
Molar Mass ◽  
Monomer Conversion ◽  
Polymer Structure ◽  
Polymerization Kinetics ◽  
Average Molar Mass ◽  
On Line ◽  
First Time ◽  
Lactide Polymerization

The standard NMR and DOSY techniques allowed for the first time the on-line study of the polymerization kinetics together with the determination of number average molar mass Mn and mass average molar mass Mw.

Experimental Investigation on Fatigue Property of Asphalt Concrete Modified by Diatomite-Glass Fibers

2012 ◽  
Vol 236-237 ◽  
pp. 38-42 ◽  
Author(s):  
Yong Chun Cheng ◽  
Hui Li Ma ◽  
Qing Lin Guo ◽  
Chun Xu ◽  
Peng Zhang
Keyword(s):  
Experimental Investigation ◽  
Glass Fiber ◽  
Asphalt Concrete ◽  
Glass Fibers ◽  
Fatigue Property ◽  
Fatigue Properties ◽  
Pavement Materials ◽  
Modified Asphalt ◽  
Durability Design ◽  
Property Changes

Diatomite and glass fiber are used for modifying asphalt concrete in this paper. Besides, wet and dry processes are adopted to achieve the composite modified asphalt concrete. Meanwhile, experimental investigation has been done on its fatigue properties and dynamic mechanical property, it indicates that diatomite-glass fiber modified asphalt concrete has a better capacity to resist fatigue damage. Compared with matrix asphalt concrete, the modified asphalt concrete has higher fatigue life. Thus, its mechanical parameter of fatigue property changes obviously so as to provide a reference basis for the durability design of pavement materials.

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