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Objective To obtain the distribution of stress concentration on the microporous structure of 3D-printed materials through a mapping algorithm with low calculation cost, so as to provide a new method of finite element calculation of 3D-printed materials for the prediction of fatigue life and the optimization of structural design. Methods Node coordinates and stress values within the influential region of the single pore were extracted to calculate the stress concentration coefficients of different nodes. The nearest node to each node on the ideal model was determined by distance, and the corresponding coefficient was multiplied by its stress value. When the nearest nodes of several nodes were the same, the average of these coefficients was assigned. For the pores close to the edge, an edge coefficient must be multiplied to reduce the error. Results An error of less than 8% between the mapping result and the calculation result was achieved for the case in which the pores were not near the edge, but for the case in which the pores were close to each other near the edge, the error was less than 15%. Conclusions The mapping algorithm can effectively characterize the stress concentration of the microporous structure of 3D-printed materials, and determine the stress distribution with low cost. This novel algorithm provides the finite element result for the optimization design and fatigue analysis of implants in clinical applications.
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Objective: To detect the optimal fusing temperature, the fusing time and the best filler ratio of α-Si3N4 and SP1SiO2, and to clarify their influence in the properities of dental resin composites. Methods: The α-Si3N4 crystalline were mixed with SP1SiO2 particle at the ratio of5:l (Wt%), and then were sintered under 500°C, 650°C, 800°C, 950°C and 1 100°C at a rise rate of 250 · h-1 and maintained for 10 min, 30 min and 3 h, respectively (used as α-Si3N4-SP1SiO2 groups). SP1SiO2 particle, α-Si3N4 crystalline, mixed and non-fused α-Si3N4 and SP1SiO2 (mixed) groups were set up, and two commercially available resin composites were selected and used as control groups. And they were fully mixed with the resin matrix in 60% (Wt%) after the treatment of cyclohexane solution to make the samples. The flexural strength of specimen was tested and the morphology of section under SEM was analyzed. Then α-Si3N4 was mixed with SP1SiO2 in a ratio of 2; 1. It was fused under the optimal fusing conditions. After the treatment of cyclohexane solution, it was mixed and polymerized with the resin matrix in the proportions of 20%, 40%, 60%, 70% and 75% (Wt%), and two kinds of commercially available resin composites were selected and used as control groups. The flexural strength of specimens was tested and the morphology of section under SEM was analyzed. Results: The maximum flexural strength value in α-Si3N1-SP1SiO2 groups was at 800°C and 30 min (P>0. 05); the flexural strength value was significantly higher than those in SP1SiO2 group, α-Si3N1 crystalline group, mixed group and two control groups (P<0. 05), and the morphology of section SEM was consistent with the mechanical properties. The flexural strengths of resin composites were increased gradually with the increasing of filler ratios of α-Si3N4 and SP1SiO2 fusion from 20% to 60% (P<0. 05); the flexural strength values of resin composites with the proportion of 60%-70% were not increased significantly, the flexural strength values of resin composites with the proportion of 70%-75% were decreased, and the flexural strength values of the resin composites with the proportion of 60% and 70% were significantly higher than those of resin composites with the proportions of 20%, 40%, 75% and control groups; the morphology of section under SEM was consistent with the mechanical properties. Conclusion: The optimum fusing condition for α-Si3N4 and SP1SiO2 is 800°C for 30 min, and the best filler ratio of α-Si3N4 and SP1SiO2 is 70%.
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Objective When bacterial cellulose (BC) is used as a scaffold material in tissue engineering,the nano-structure of BC may not provide enough space for animal cell growth and differentiation which would not achieve a perfect application in tissue engineering.In order to solve this problem,a novel green approach is developed in this research to produce bacterial nanocellulose materials with micropores ranging 50-800 μm.Methods Several ratios of hydrogen peroxide to sodium chlorite were used to react instantly to produce a large number of bubbles in BC hydrogels,which formed micropores with diameters ranging 50-800 μm.Optical microscopy and scanning electron microscope were used to evaluate microporous BC hydrogels and verify the existence of micropores.Results The size of pores could be regulated along with the changes in the amount of reactants used in the experiment.Fourier transform infrared spectroscopy verified that no cellulose was oxidized.Water content of the microporous BC hydrogels was similar to that of the original BC hydrogels.The Young's modulus of microporous BC hydrogels was 26.1 kPa,which was lower than that of the original BC hydrogels (69.9 kPa).Thiazoyl blue tetrazolium bromide (MTT) test displayed a higher viability on the microporous BC hydrogels compared to the growth on the unmodified BC substrates.Conclusions This study provides a convenient and promising way to prepare microporous materials,which may not be limited to only BC material,but could be used in other hydrogels.The proposed approach is suitable for extensive industrialization.
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Objective To investigate the clinical effect of using leukocyte filter to prevent nonhemolytic febrile transfusion reactions(NHFTR) in hematologic patients who were trarisfused erythrocyte suspension. Methods Select 720 inpatients need erythrocyte transfusion and have transfusion records. The patients were randomly divided into investigation group and control group. We made a routine examination and recorded the patients' body temperature, heart rate, blood pressure, respiration rate and transfusion adverse reaction before and after erythrocyte suspeusion transfusion. Results Before blood transfusion, the body temperature of patients between two groups were normal, but after blood transfusion, there were 35 patients with NHFTR in the control group, while only 5 cases in the investigation group which used leucocyte filter, the difference between two groups is significant( P＜0.01 ). The change of the patients' body temperature were compared between two groups before and after transfusion, the changes in the control group was significantly higher than the investigation group( P＜0.01 ). Compared the changes of serum total bilirubin level in all patients before and after transfusion,there was no difference in both groups. The incidence of NHFTR increased with increasing of the transfusion times, but compared with the investigation group,the incidence of the control group was higher significantly(P＜0.01 ). Conclusion Leukocyte filter can prevent the occurring of NHFTR efficiently, enhance the quality of transfusion,guarantee the blood transfusion safety.
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El catalizador de FCC está constituido por partículas de composición compleja donde el componente activo es una zeolita Y. En este trabajo se presentan los resultados texturales y estructurales de una zeolita USY comercial lixiviada, de una serie de catalizadores con 7, 15, 25, 35 y 45% de material activo y los de estos materiales desactivados hidrotérmicamente. Las muestras se caracterizaron por fluorescencia de rayos X (FRX), difracción de rayos X (DRX), resonancia magnética nuclear de silicio (29Si RMN) y fisiadsorción de nitrógeno a 77 K. A partir de estos resultados se hallaron correlaciones entre el volumen de microporo y el contenido de zeolita y entre el grado de cristalinidad y el porcentaje de zeolita. Además, se encontró que un tratamiento con sólo 20% de vapor de agua a 1033 K durante 16 horas destruye los grupos estructurales Si(2Al) y Si(3Al) como reflejo de la dealuminización drástica que sufre el material.
FCC catalyst is made up of particles of complex composition where the main active component is a Y zeolite. This work presents the textural and structural results of a commercial USY zeolite which had been previously prepared from a set of catalysts with 7, 15, 25, 35 y 45% of active material and of the hydrothermally deactivated materials zeolite. The samples have been characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), 29Si NMR spectroscopy and nitrogen adsorption at 77K. From these results was found correlations between micropore volume and zeolite content and degree crystallinity and %zeolite. Also, it was found that an hydrothermal treatment at 1033 K with only 20% steam during 16 hours destroys the structural groups Si(2Al) and Si(3Al) as a reflection of the strongly dealumination of the zeolite component of the catalyst.
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OBJECTIVE: The purpose of this study was to evaluate the physicochemical properties and cytocompatibility of microporous, spherical biphasic calcium phosphate(BCP) ceramics with a 60/40 hydroxyapatite/beta-tricalcium phosphate weight ratio for application as a bone graft substitute. MATERIALS AND METHODS: Microporous, spherical BCP granules(MGSB) were prepared and their basic characteristics were compared with commercially available BCP(MBCP; Biomatlante, France) and deproteinized bovine bone mineral(Bio-Oss; Geistlich-Pharma, Switzerland, BBP; Oscotec, Korea). Their physicochemical properties were evaluated by scanning electron microscopy, X-ray diffractometry, Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectrometer, and Brunauer-Emmett-Teller method. Cell viability and proliferation of MC3T3-E1 cells on different graft materials were evaluated. RESULTS: MGSB granules showed a chemical composition and crystallinity similar with those in MBCP, they showed surface structure characteristic of three dimensionally, well-interconnected micropores. The results of MTT assay showed increases in cell viablity with increasing incubation times. At 4d of incubation, MGSB, MBCP and BBP showed similar values in optical density, but Bio-Oss exhibited significantly lower optical density compared to other bone substitutes(p < 0.05). MGSB showed significantly greater cell number compared to other bone substitutes at 3, 5, and 7d of incubation(p < 0.05), which were similar with those in polystyrene culture plates. CONCLUSION: These results indicated the suitable physicochemical properties of MGSB granules for application as an effective bone graft substitute, which provided compatible environment for osteoblast cell growth. However, further detailed studies are needed to confirm its biological effects on bone formation in vivo.