The ambient/personal dose equivalent per fluence for D2O moderated 252Cf neutron source was determined by measurement. An appropriate subtraction of the scattered neutrons is required for the ...accurate measurement of direct neutrons. A cubic shadow object was used for the subtraction of the scattered neutrons from the surroundings. The scattered neutrons to be subtracted vary with the position of the shadow object due to the large volume of the source. Using the Monte Carlo code MCNP-4C, the optimum positions of the shadow object were surveyed for subtracting the scattered neutrons. The energy spectra of direct neutrons were measured in the optimum position. The dosimetric parameters for the D2O moderated 252Cf neutron source were reasonable, taking into account the uncertainties of the parameters.
Bridge infrastructure maintenance and assurance of adequate safety is of paramount importance in transportation engineering and maintenance management industry. Corrosion causes strength ...deterioration, leading to impairment of its operation and progressive weakening of the structure. Since the actual corroded surfaces are different from each other, only experimental approach is not enough to estimate the remaining strength of corroded members. However, in modern practices, numerical simulation is being used to replace the time-consuming and expensive experimental work and to comprehend on the lack of knowledge on mechanical behavior, stress distribution, ultimate behavior, and so on. This paper presents the nonlinear FEM analyses results of many corroded steel plates and compares them with their respective tensile coupon tests. Further, the feasibility of establishing an accurate analytical methodology to predict the residual strength capacities of a corroded steel member with lesser number of measuring points is also discussed.
Sevoflurane previously has been reported to undergo extensive degradation in the presence of soda lime. To more completely characterize the extent and significnce of this reaction, we studied ...degradation of sevoflurane with and without soda lime, as well as the toxicity and mutagenicity of the degradation products. Two degradation products detected were CF2 = C(CF3)OCH2F (compound A) and CH3OCF2CH(CF3)OCH2F (compound B). During circulation of 1%, 2%, and 3% sevoflurance in a closed anesthesia circuit for 8 h, peak concentrations of compound A were 13.3 +/- 0.27, 30.2 +/- 0.10, and 42.1 +/- 1.07 ppm at 2 h, respectively. The concentrations of compound B did not exceed 2 ppm. The temperature of the soda lime was 43.3 +/- 2.8 degrees C at 1 h and increased gradually to 47.9 +/- 1.5 degrees C after 8 h. In closed flasks with soda lime, the magnitude of the decrease in sevoflurance concentrations (3%) and of the increase in compound A concentrations was temperature dependent. The peak concentrations of compound A at 23 degrees C, 37 degrees C, and 54 degrees C were 32.8 +/- 6.8 at 2 h, 46.6 +/- 1.0 at 0.5 h, and 78.5 +/- 2.3 ppm at 0.5 h, respectively. The LC50 (50% lethal concentration) of compound A in Wistar rats was 1,090 ppm in males and 1,050 ppm in females exposed for 1 h. The LC50 was 420 ppm in males and 400 ppm in females exposed for 3 h. The chronic toxicity of compound A in Wistar rats was studied by exposing rats 24 times, for 3 h each, to initial concentrations of 30, 60, or 120 ppm in a ventilated chamber. At all concentrations, there were no apparent effects other than a loss of body weight in females (120 ppm) on the final day (P < 0.01). Compound A did not induce mutation on the reverse (Ames) test at less than 2,500 micrograms/dish (culture medium 2.7 ml) with activation by S-9 mixture, and below 1,250 micrograms/dish (culture medium 2.7 ml) without activation, in four strains of S. typhimurium and in 1 strain of E. coli. Exposure of fibroblasts to 7,500 ppm of compound A for 1 h, compound A did not induce structural change. In a study of acute toxicity of compound B, there was no toxicity in Wistar rats after 3 h of exposure at 2,400 ppm. The reverse (Ames) test for compound B was negative at 625-1,250 micrograms/dish.
Objective. The purpose of this study was to investigate the effect of the applied load in a rolling-ball device on the surface contact fatigue of two dental filling materials: a microfilled composite ...(FA) and a glass ionomer (GFII).
Methods. Disk specimens 10 mm diameter by 1.5 mm thick were set into cavities cut in plates of PMMA. After setting, the specimens were ground and polished using wet-carborundum paper followed by 1 μm alumina and then stored for 24 h in water at 23 °C. The surface fatigue test was carried out using loads ranging from 100 to 500
gf through a ruby ball 2 mm diameter using a rolling-ball device. The ball was set to rotate at 720 rpm and a surface profile was determined on impressions recorded at regular intervals. Fatigue life was defined as the number of cycles to produce a track 5 μm deep and was determined by interpolation. Data were statistically analyzed by ANOVA and t-tests at a significance level of 0.05.
Results. At loads ranging from 200 to 500
gf the fatigue life was 0.7–10.6×10
5 cycles for FA, and 0.7–4.8×10
3 cycles for GFII. For both materials the fatigue life was reduced significantly by increasing the test load (
p<0.05). The surface contact fatigue life for FA was at least 100 times greater than that for GFII at all loads.
Significance. The rolling ball device was confirmed as a simple and meaningful device for the study of surface contact fatigue. A microfilled composite is very much more resistant to contact fatigue than a glass ionomer.
Aim
Clear cell chondrosarcoma (CCC) is a rare malignant cartilaginous neoplasm of bone. CCC is characterized by clear cells (CCC cells), osteoclasts and osteoblasts. Many important questions ...concerning the varied histological features of CCC, and the interactions between CCC cells and coexisting osteoclasts and osteoblasts have not been fully investigated and remain controversial. The aim of this study is to clarify and explain the varied histological features and the possible interaction between tumour cells (CCC cells) and stromal cells such as osteoclasts and osteoblasts.
Methods and results
Four cases of CCC were histologically and immunohistochemically studied in order to elucidate the biological nature and histological characteristics. A comparative study with chondroblastoma and grade I conventional chondrosarcoma (CC) was also performed. S100 protein and type II collagen were expressed in CCC cells, chondroblastoma cells and CC cells. CD68 and matrix metalloproteinase‐9 were expressed in coexisting histiocytes and osteoclasts. Parathyroid hormone‐like protein (PTH‐LP) was expressed in histiocytes, osteoclasts, osteoblasts, chondroblastoma cells and CCC cells. Platelet‐derived growth factor (PDGF) and its receptor (PDGF‐R) were observed in osteoblasts, chondroblastoma cells and CCC cells. However, PTH‐LP, PDGF and PDGF‐R were not expressed in CC cells. PCNA (proliferating‐cell nuclear antigen) was expressed more intensely in CCC than in chondroblastoma.
Conclusion
These observations suggest that CCC cells trigger the varied histological changes in association with several cytokines. The difference of PCNA expression between CCC and chondroblastoma seemed to be related to the biological difference between the two tumours.
The effect of carbon dioxide (CO(2)) pneumoperitoneum on the liberation of cancer cells from the primary tumor is not clear. This study investigated the influence of laparotomy versus CO(2) ...pneumoperitoneum on the progression of colon cancer with serosal invasion in a mouse model.
Pieces of human colon adenocarcinoma (HT29) tumor were implanted in the cecal wall of 45 BALB/c nude mice. Each mouse underwent one of three procedures: laparotomy, CO(2) pneumoperitoneum, or anesthesia (control). Three weeks later, the size and weight of cecal tumors, the number of nodules, and the tumor volume score of peritoneal dissemination were examined. Another 45 mice were treated in the same way. The cecal tumor was resected on days 1, 3, or 5 after treatment. Total RNA was isolated from the resected tumors. The expression of E-cadherin and beta-1 integrin messenger RNA (mRNA) was examined by semiquantitative real-time reverse transcriptase-polymerase chain reaction assay.
Significantly more nodules of peritoneal dissemination were found in the laparotomy group than in the control group (p < 0.05). The tumor volume score of peritoneal dissemination in the laparotomy group was significantly higher than in the other two groups (p < 0.05). The expression of E-cadherin mRNA at day 5 in the laparotomy group was significantly less than in the other two groups (p < 0.05). There were no differences in beta-1 integrin among three groups.
Peritoneal dissemination was more extensive after laparotomy than after CO(2) pneumoperitoneum in a mouse model of cecal cancer with serosal invasion. Decreased expression of E-cadherin mRNA in tumors after laparotomy, but not after CO(2) pneumoperitoneum, may be associated with the increase in peritoneal dissemination.
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