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51.
52.
目的:研究熔附温度和熔附时间对多微孔纳米二氧化硅粒子(SP1 SiO2)表面结构及形态的影响。方法:将SP1SiO2以250℃/h的升温速度分别升至500、650、800、950、1100℃,并分别保持10、30min和3h制作试样,进行表面结构及形态测试。结果:随烧结温度的增高和时间的延长,SP1 SiO2颗粒表面的Si-OH键特征峰值逐渐减弱,条件为950℃、10min和30min,650℃、3h时完全消失;随着熔附温度的升高和熔附时间的延长颗粒增大、粒度分布变窄。结论:熔附温度和熔附时间影响SP1 SiO2颗粒表面的Si-OH含量和颗粒大小、粒度分布。 相似文献
53.
Objective
Millimeter-scale (“miniature”) specimens enable in-situ evaluation of mechanical properties of engineering materials at reduced cost. Here three such specimens for measuring fracture toughness (KC) are developed and implemented to new dental materials. The latter include concurrent methacrylate-based and new ether-based resin composites designed to reduce polymerization stress and enhance service life in restored teeth.Methods
Fracture toughness of four experimental and one commercial dental resin composites are evaluated using three-point bending (3PB), wedge double-cantilever-beam (WDCD) and edge chipping miniature test specimens. The values of KC were compared with those obtained following ISO standard method ISO6872: 2014. The stress intensity factor (K) for the 3PB and WDCB specimens was determined using linear fracture mechanics analyses made in conjunction with the Finite Element technique, with due consideration given to the finite width of pre-crack.Results
Analytic expressions for predicting KC were developed for all three miniature specimens. The width of pre-crack, generally neglected for conventional specimens, significantly affect K. Measured KC conclusively agree with those of commercial or well-studied materials as obtained using conventional specimens, with error bounded by 5–10 percent.Significance
The edge chipping test was successfully applied for the first time to non-brittle materials like dental resin composites. The miniature specimens developed will expedite the evaluation of fracture toughness of dental resin composites by saving materials and provide needed in-situ assessment capability. The chipping test which requires no introduction of initial crack and involves no use of elastic constants is especially suitable to functionally graded materials and in-situ study of restored teeth. The WDCB specimen enables stable crack growth, a useful trait in fatigue studies. 相似文献54.
55.
Amelogenin and enamelin are structural proteins in the enamel matrix of developing teeth. The temporal and spatial patterns of enamelin expression in developing mouse molars have not been characterized, while controversy remains with respect to amelogenin expression by odontoblasts and cementoblasts. Here we report the results of in situ hybridization analyses of amelogenin and enamelin expression in mouse molars from postnatal days 1, 2, 3, 7, 9, 14, and 21. Amelogenin and enamelin mRNA in maxillary first molars was first observed in pre-ameloblasts on the cusp slopes at day 2. The onsets of amelogenin and enamelin expression were approximately synchronous with the initial accumulation of predentin matrix. Both proteins were expressed by ameloblasts throughout the secretory, transition, and early maturation stages. Enamelin expression terminated in maturation stage ameloblasts on day 9, while amelogenin expression is still detected in maturation stage ameloblasts on day 14. No amelogenin expression was observed in day 21 mouse molars. Amelogenin and enamelin RNA messages were restricted to ameloblasts. No expression was observed in pulp, bone, or along the developing root. We conclude that amelogenin and enamelin are enamel-specific and do not directly participate in the formation of dentin or cementum in developing mouse molars. 相似文献
56.
57.
目的探讨术中x-线定位在经神经内镜下甲介型蝶窦垂体瘤手术的应用。方法回顾性分析6例甲介型蝶窦垂体瘤病人的临床资料,均采用神经内镜下垂体瘤切除结合术中X-线定位方法。结果术中X-线定位准确4例;2例发生纵向偏差,均纠正。肿瘤全切除5例,次全切除1例。术后激素水平正常,视力视野改善。出现暂时性尿崩1例,治疗后痊愈。无脑脊液鼻漏、垂体功能低下、蝶窦炎发生,无死亡病例。6例病人随访3年,均无复发。结论神经内镜技术结合术中X-线定位是一种治疗甲介型蝶窦垂体瘤的安全、有效方法。 相似文献
58.
Background/Aims
We tried to investigate the expression characteristics of KAI1, a suppressor of wide-spectrum tumor metastasis, and vascular endothelial growth factor (VEGF), the most common angiogenesis factor, and then to analyze their diagnostic value for hepatocellular carcinoma (HCC).Methods
The protein and mRNA expression levels of KAI1 or VEGF in HCC tissues and in self-controlled para-carcinoma tissues were analyzed by Western blot and real-time polymerase chain reaction, respectively. Serum levels of KAI1 and VEGF in the patients with HCC, benign liver disease or in healthy controls were quantitatively detected by enzyme-linked immunosorbent assay.Results
The expression level of KAI1 was downregulated, while the expression level of VEGF was upregulated in the tissues or serum of the patients with HCC. The expression level of serum KAI1 in HCC patients was correlated with TNM staging, intrahepatic metastasis, lymph node or peritoneal metastasis, and portal vein thrombus. In addition to the factors that were correlated with KAI1 expression, VEGF expression was also closely related to the α-fetoprotein level of the patients. The area under the receiver operating characteristic curve for the diagnosis of HCC was 0.907 for KAI1 and 0.779 for VEGF. The sensitivity of serum KAI1 levels in the diagnosis of HCC was 86.96%; the accuracy was 83.06%, while the sensitivity, the accuracy and the negative predictive value were improved to 91.86%, 84.68%, and 78.79% according to the combined detection of KAI1 and VEGF, respectively.Conclusions
A combined detection of KAI1 and VEGF may greatly improve the efficiency of diagnosis and form a reliable panel of diagnostic markers for HCC. 相似文献59.
Yohannes G Asfaw Francis J Sun 《Journal of the American Association for Laboratory Animal Science》2010,49(5):644-646
Husbandry staff noticed a research-naïve, young-adult, female finch tossing its head back intermittently. A second finch exhibiting similar signs was reported a few days later. Postmortem necropsy and histopathology with hematoxylin and eosin and acid-fast staining on the first finch revealed the presence of acid-fast organisms in several organs. After presumptive diagnosis of mycobacteriosis, all remaining finches housed in the same room as the first underwent necropsy and histology. Three additional finches were positive for Mycobacterium-like acid-fast organisms. Incidental findings of megabacteriosis were noted histopathologically on 2 other finches.Abbreviation: MAC, Mycobacterium avium complexMycobacteriosis has a worldwide distribution and is found often in free-living birds, poultry, and wild birds. Several natural cases of mycobacteriosis have occurred in pet birds, including canaries (Spinus cucullatus), Eurasian goldfinches (Carduelis carduelis), and Zebra finches (Taeniopygia guttata).6 Reports regarding cases of mycobacteriosis in the laboratory animal research setting are scarce. The most common agents of avian mycobacteriosis are Mycobacterium avium intracellulare, one of the group of bacteria known as Mycobacterium avium complex (MAC), and Mycobacterium genavense, a known cause of mycobacteriosis in birds and mammals.1,5,9-11 In addition, immunocompromised humans can be infected with MAC.3,6,10 Mycobacteria are saprophytic, aerobic, and common in soil and the environment. These organisms can be transmitted by ingestion of soil or cage litter contaminated by fecal matter from infected birds.1,2 The most common clinical signs in affected birds are depression, lethargy, and feather erection or fluffing, as are typical for most sick birds.9,11 Neurologic signs, if they occur, can include imbalance and the inability to walk or fly normally.9 相似文献
60.
C. A. Simpson D. Foer G. S. Lee J. Bihuniak B. Sun R. Sullivan J. Belsky K. L. Insogna 《Osteoporosis international》2014,25(10):2383-2388