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- 저자 : Katula (검색결과 3 건)
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Experimental study on standard and innovative bolted end-plate beam-to-beam joints under bending
Levente Katula,László Dunai 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.6
The paper presents the details and results of an experimental study on bolted end-plate joints of industrial type steel building frames. The investigated joints are commonly used in Lindab-Astron industrial buildings and are optimized for manufacturing, erection and durability. The aim of the research was to provide an experimental background for the design model development by studying load-bearing capacity of joints, bolt force distribution, and end-plate deformations. Because of the special joint details, (i.e., joints with four bolts in one bolt-row and HammerHead arrangements), the Eurocode 3 standardized component model had to be improved and extended. The experimental programme included six different end-plate and bolt arrangements and covered sixteen specimens. The steel grade of test specimens was S355, the bolt diameter M20, whereas the bolt grade was 8.8 and 10.9 for the two series. The end-plate thickness varied between 12 mm and 24 mm. The specimens were investigated under pure bending conditions using a four-point-bending test arrangement. In all tests the typical displacements and the bolt force distribution were measured. The end-plate plastic deformations were measured after the tests by an automatic measuring device. The measured data were presented and evaluated by the moment-bolt-row force and momentdistance from centre of compression diagrams and by the deformed end-plate surfaces. From the results the typical failure modes and the joint behaviour were specified and presented. Furthermore the influence of the end-plate thickness and the pretension of the bolts on the behaviour of bolted joints were analysed.
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Karen S. Katula,Johnette A. McCain,Anthony T. Radewicz 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2
The ability of various dietary compounds to modulate the activity of the transcription factor nuclear factor .B(NF-.B) was examined using a cell-based reporter system. NF-.B is central to the response of cells to stress and has beenlinked to cancer. HCT 116 (human colon carcinoma) and HepG2 (human liver carcinoma) cell lines were stably transfectedwith a NF-.B luciferase reporter vector. The reporter cell lines were preincubated with different concentrations (050 .M)of ascorbic acid, epigallocatechin gallate, genistein, quercetin, naringenin, and resveratrol for varying periods of times (112hours), after which the NF-.B inducer tumor necrosis factor-. (TNF-.) was added (48 ng/mL) for 4 hours. Compound alone,without TNF-., did not alter luciferase activity. Levels of TNF-.-induced luciferase (NF-.B) activity varied depending oncompound type and concentration, whereas preincubation time and cell type contributed less. Significant changes in luciferase(NF-.B) activity were detected for some of the compounds at more physiological concentrations (110 .M). Our data sug-gest that dietary modulation of NF-.B activity involves distinct mechanisms, depending on compound type and concentra-tion. More generally, this approach can be utilized for analyzing dietary compounds for effects on specific cellular factorsover a range of concentrations and incubation times, in combination, and in different cell types.
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Effects of Various Polyphenolics on Hydrogen Peroxide-Induced p53 Activity in NIH3T3 Cells
Thomas A. Radewicz II,Juanita L. Edwards,Karen S. Katula 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.1
A cell-based assay system was developed to evaluate the potential antioxidant and pro-oxidant effects of various dietary polyphenolic compounds based on the induction of p53 activity by hydrogen peroxide. A p53-luciferase reporter vector was stably transfected into NIH3T3 cells. Individual clones were isolated, and one clone (number 33) was selected that showed the highest induction levels with different generators of free radicals. Clone 33 was preincubated for 1 hour with 0, 0.1, 1.0, 10, 50, and 100μM genistein, resveratrol, naringenin, quercetin, epicatechin gallate, and epigallocatechin-3-gallate and then treated with 40μM hydrogen peroxide or left untreated for 4 hours. Cell lysates were prepared and assayed for luciferase activity. Results show that the effects on p53 activity by the different polyphenolics varied depending on the compound and concentration. Quercetin and genistein reduced p53 activity at 1.0μM, whereas the other four compounds did not attenuate p53 activity. With the exception of naringenin, the other compounds increased p53 at the higher (50μM or 100μM) amounts, without added hydrogen peroxide, suggesting that these compounds can act as pro-oxidants or possibly stimulate p53 activity by another mechanism.
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