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排序方式: 共有438条查询结果,搜索用时 15 毫秒
101.
The fiber characteristics (i.e., the fiber type, morphology, and dimension) and polymer melt flow index (MFI) significantly affected mechanical properties of sugarcane fiber/HDPE composites. The length and diameter of sugarcane fibers followed a lognormal distribution before and after compounding. The long fibers had a significant reduction in the dimension and aspect ratio during compounding. However, the short fibers had close values in these two properties before and after compounding. For the resultant sugarcane fiber/polymer composites, the HDPE resins with a low MFI value presented high tensile and impact strengths. Because of high sugar content, the pure rind fiber had a poor performance as filler in the HDPE resins with respect to the raw bagasse fiber and alkali‐extracted bagasse fiber. On the other hand, the aspect ratio was proportional to the mechanical performance of the fibers in the HDPE resins. As a result, the fibers with a large aspect ratio and low sucrose content improved the strength properties of the resultant composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5607–5619, 2006 相似文献
102.
Effects of working parameters on surface finish in ball-burnishing of hardened steels 总被引:4,自引:1,他引:4
Burnishing is a chipless finishing method, which employs a rolling tool, pressed against the workpiece, in order to achieve plastic deformation of the surface layer. Recent developments made possible burnishing of heat-treated steel components up to 65 HRC. Features of burnishing include a good roughness (comparable to grinding), as well as improvement of mechanical characteristics of the surface (fatigue strength, corrosion resistance, and bearing ratio), due to implementation of compressive stresses into the surface layer. This paper will present influences of certain burnishing parameters upon roughness, for a hardened steel component (64 HRC). 相似文献
103.
Mihaela Baibarac Ioan BaltogSerge Lefrant Pedro Gomez-Romero 《Materials Science and Engineering: B》2011,176(2):110-120
Polydiphenylamine/single walled carbon nanotube (PDPA/SWNT) composites were synthesized electrochemically aiming at their application as active electrode materials for rechargeable lithium batteries. The electrochemical polymerization of diphenylamine (DPA) on a SWNT film immersed in a 1 M HCl solution was studied by cyclic voltammetry. Comparing cyclic voltammograms recorded on a blank Pt electrode with those obtained for a SWNT film deposited on Pt electrode one observes in the latter case a decrease of the DPA reduction potential. To elucidate electrochemical polymerization mechanism, photoluminescence studies on DPA/SWNT and PDPA/SWNT systems were carried out. Additional information concerning the functionalization process of SWNT with PDPA was obtained by Raman and IR spectroscopy. Using the PDPA/SWNT composite as active material for the positive electrode of a rechargeable lithium cell (LiPF6 electrolyte), the charge-discharge tests show a specific discharge capacity of ca. 245 mA h g−1, much higher than the 35 mA h g−1 for pure PDPA. 相似文献
104.
Adina Maria Dobos Iuliana Stoica Niculae Olaru Liliana Olaru Emil Ghiocel Ioanid Silvia Ioan 《应用聚合物科学杂志》2012,125(4):2521-2528
The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
105.
Elif Sahin Pinar Camurlu Levent Toppare Viorela M Mercore Ioan Cianga Yusuf Yagci 《Polymer International》2005,54(12):1599-1605
Thiophene functionalized polystyrene samples (TFPS) were synthesized by atom transfer radical polymerization (ATRP) of styrene, followed by Suzuki coupling with 3‐thiophene (Th) boronic acid. Conducting graft polymer of TFPS with thiophene was achieved at 1.5 V in tetrabutylammonium tetrafluoroborate/dichloromethane (TBAFB/DM) by electrochemical methods. Spectroelectrochemical analysis of the resulting copolymers [P(TFPS‐co‐Th)] reflected electronic transitions at 449, 721 and 880 nm, revealing π ? π* transition, polaron and bipolaron band formation, respectively. We also successfully established the utilization of dual type complementary colored polymer electrochromic devices using P(TFPS‐co‐Th)/poly(3,4‐ethylenedioxythiophene (PEDOT) in sandwich configuration. The switching ability, stability and optical memory of the electrochromic device were investigated by UV–visible spectrophotometry and cyclic voltammetry. Device switches between brown and blue color with a switching time of 1.3 s were prepared with optical contrast (%ΔT) of 25 %. Copyright © 2005 Society of Chemical Industry 相似文献
106.
Diffusion and sorption data of methanol and toluene in the ternary system methanol-toluene-poly(vinylacetate) (pvac) were measured by means of a magnetic suspension balance (MSB). Ternary diffusion coefficients were determined from sorption kinetics with a method of Crank [1975. The Mathematics of Diffusion, second ed. Claredon Press, Oxford] classically used for binary polymer solvent systems. Assumptions and limitations for this method are discussed. Sorption data of methanol and toluene in the ternary system were correlated with a modified Flory-Huggins theory taking four instead of three interaction parameters into account and compared with predictions of UNIFAC-FV. All four binary Flory-Huggins interaction parameters were correlated as a function of concentration, determined from binary polymer-solvent sorption measurements and from solvent-solvent equilibrium data. The modified Flory-Huggins approach for ternary systems predicts the two limiting cases for the binary polymer-solvent as well the two solvent-solvent equilibria. Diffusion coefficients determined from sorption kinetics measurements were correlated with free-volume theory predictions of Vrentas et al. [1984. Self diffusion in polymer-solvent-solvent systems. Journal of Polymer Science, Polymer Physics Edition, 22, 459-469] and compared with a few available literature data from Surana et al. [1998. Diffusion and equilibrium measurements in ternary polymer-solvent-solvent systems using inverse gas chromatography. Industrial and Engineering Chemistry Research, 37, 3203-3207]. Cross diffusion terms are not taken into account. Diffusion and sorption data, determined with this gravimetric method, were used in model simulations with modified Flory-Huggins and free-volume theory to predict drying curves of ternary methanol-toluene-pvac solutions. The results were compared with previously published experimental results performed by means of Inverse-Micro-Raman-Spectroscopy (IMRS) from Schabel [2004. Trocknung von Polymerfilmen - Messung von Konzentrationsprofilen mit der Inversen-Mikro-Raman-Spektroskopie. Ph.D. Thesis, Universität Karlsruhe (TH), Germany]. 相似文献
107.
Natalia Simionescu Miruna Nemecz Anca-Roxana Petrovici Ioan Sebastian Nechifor Razvan-Cristian Buga Marius Gabriel Dabija Lucian Eva Adriana Georgescu 《International journal of molecular sciences》2022,23(15)
Glioblastoma (GB) is the most aggressive and recurrent form of brain cancer in adults. We hypothesized that the identification of biomarkers such as certain microRNAs (miRNAs) and the circulating microvesicles (MVs) that transport them could be key to establishing GB progression, recurrence and therapeutic response. For this purpose, circulating MVs were isolated from the plasma of GB patients (before and after surgery) and of healthy subjects and characterized by flow cytometry. OpenArray profiling and the individual quantification of selected miRNAs in plasma and MVs was performed, followed by target genes’ prediction and in silico survival analysis. It was found that MVs’ parameters (number, EGFRvIII and EpCAM) decreased after the surgical resection of GB tumors, but the inter-patient variability was high. The expression of miR-106b-5p, miR-486-3p, miR-766-3p and miR-30d-5p in GB patients’ MVs was restored to control-like levels after surgery: miR-106b-5p, miR-486-3p and miR-766-3p were upregulated, while miR-30d-5p levels were downregulated after surgical resection. MiR-625-5p was only identified in MVs isolated from GB patients before surgery and was not detected in plasma. Target prediction and pathway analysis showed that the selected miRNAs regulate genes involved in cancer pathways, including glioma. In conclusion, miR-625-5p shows potential as a biomarker for GB regression or recurrence, but further in-depth studies are needed. 相似文献
108.
Alexandra Gertrud Paltinean Ioan Petean George Arghir Dana Florina Muntean Liviu-Dorel Bobos 《Particulate Science and Technology》2013,31(5):580-585
ABSTRACTUrban street dust (SD) represents a natural source of mineral floating particles (FP) in the atmosphere. The FP particles have usually a wide range of sizes. These particles were monitored and collected by automatic stations in Cluj-Napoca, Romania. The SD and FP samples were investigated by XRD and SEM-EDX analysis. The obtained results prove that both, SD and FP, have a similar composition, namely quartz, clay particles (e.g., muscovite, and kaolinite), calcite, and trace of lepidocrocite. Nanostructural features and fine micro-scaled particles are observed. Quartz and clay nanoparticles were found in SD samples as well as in FP samples. The AFM investigation reveals a nano-size range for quartz particles between 80–90 nm, and 40–60 nm diameter for clay particles. Similar values were obtained by TEM microscopy. The high resolution microscopy results were confirmed by the values obtained by Scherrer formula applied to the XRD patterns. Composition and dimensional similarities found for the nanoparticles in SD and FP samples prove that mineral nanofractions in atmosphere were induced by the urban environmental interactions with the SD. Results provide valuable information on the size, shape, and composition of nanoparticles induced in atmosphere by winds and by environmental interactions with the SD. This work contributes to the evaluation of the air pollution and simultaneously it offers a basis for an improved life quality for Cluj-Napoca population. 相似文献
109.
110.
Georgiana Anca Nagy Maria Adriana Neag Radu Drasovean Doinita Crisan Romeo Ioan Chira 《International journal of molecular sciences》2022,23(18)
Neuroendocrine tumors (NEN) are a type of heterogenous, slow-growing tumors, that only in about half of the cases can be found in the gastrointestinal tract. Half of these is in the small intestine. The ampullary NENs are rare, accounting for less than 1% of gastroenteropancreatic NENs. Gastrointestinal stromal tumors (GIST) are a more common type of tumors of the gastrointestinal tract that consist of pacemaker cells. The occurrence of both tumors simultaneously is rare, but in patients with neurofibromatosis type 1, the co-existence of NEN and GIST is more often. Here we report a case of simultaneous occurrence of a well-differentiated NEN and a GIST in a patient without neurofibromatosis. Also, we provide a short review of the current knowledge and treatment strategies regarding these tumors. 相似文献