1221. Experimental and numerical investigation of restrained shrinkage of concreteLucija Hanžič, Jurij Karlovšek, Tomaž Hozjan, Sabina Huč, Zhongyu Xu, Igor Planinc, Johnny Ching Ming Ho, 2020, published scientific conference contribution Abstract: To promote the understanding of shrinkage related behaviour of concrete used for tunnel linings the experimental and theoretical investigation including numerical and analytical approach was performed on ring-shaped specimens. Overall one analytical (an.) and two numerical models, namely (i) and (ii) were also developed. Models (an.) and (i) considered the restraining steel ring to be rigid, thus not exhibiting any deformation. Numerical model (ii) considered the steel ring to be deformable. The experimental set-up consisted of a large concrete ring with an inner diameter of 120 cm, an outer diameter of 160cm and 20 cm in height. The restraining steel ring was 5.5 cm thick. Two concrete rings were made, namely R1 with a low compressive strength of ~26MPa and the other, R2, with medium compressive strength of ~40 MPa. The strain was measured in the hoop direction on the inner circumference of the steel ring and on the outer circumference of the concrete ring. Concrete rings were subjected to circumferential drying. Numerical model (ii) predicted critical time to the formation of the first crack to be between 13 and 14 days. The experimentally determined critical time is found to be 11 to 13 days with cracks gradually opening over several days. This was indicated by changes in measured concrete and steel strain. Modelled concrete strain just before cracking was between -20 and -30 % 10-6 m m-1 however, measured concrete strain was ~150 % 10-6 m m-1. Modelled steel strain was between -30 and -40 % 10-6 m m-1 while measured steel strain was between -10 and 20 % 10-6 m m-1. These discrepancies, in particular the positive steel strain obtained in experiments, require further investigation and improvements of the experimental set-up.
Keywords: concrete, tunnel lining, restrained shrinkage, Reissner beam theory, modelling
Published in DiRROS: 19.01.2024; Views: 338; Downloads: 134
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1222. The role of thyroid radiation carcinogenesis in ratsKatarina Koritnik, Andrej Cör, 1998, original scientific article Abstract: The aimof this study was to test the hypothesis on the protective role of thyroxin administration before and during irradiation on the occurrence of thyroid carcinoma in rats. Application of thyroxin before and during irradiation was expected to decrease production of thyrotropin by the hypophyseal feedback mechanism, caused by radiation damage of thyroid tissue. Stabilizing the thyroid cells in this way during irradiation would thus make them less radiosensitive. In the experiment, we first divided 81 three to fourweek old Wistar strain rats of both sexes into two groups, i.e. thyroxin (T4) and water (H2O). The T4 rats were injected 1% thyroxin solution (0.01 mg/100 g body weight) twice a day for 15 days, while the H2O rats received saline in the same way. After ten days, the two main groups were divided each into two subgroups. The rats from both irradiated subgroups (T4/X and (H2O/X) recieved 10 Gy to the neck area. They were iradiated with a telecobalt machinefor five consecutive days with one direct field. During a two years follow - up, all moribund animals were sacrificed and their thyroid glands taken. The rest of the thyroid glands were taken at the end of the experiment.All glands were pathohistologically analysed. Besides, all suspicious and enlarged extrathyroid organs and tissues were examined and the occurrence of tumors was noted. Pathohistological examination revealed the occurrence of 8 thyroid carcinomas and 7 adenomas in the H2O/X group, and 3 adenomas in the T4/X group. In the iradiated group of rats without thyroxin, significantly (P = 0.01) more thyroid carcinomas occurred than in the irradiated group without thyroxin.
Published in DiRROS: 19.01.2024; Views: 256; Downloads: 60
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1223. Micronuclei in cytokinesis-blocked lymphocytes as an index of occupational exposure to antineoplastic drugsVera Garaj-Vrhovec, Nevenka Kopjar, 1998, original scientific article Abstract: In order to investigate possible DNA damiging effects of antineoplastic drugs,the micronucleus assay combined with Giemsa, DAPI and silver staining was performed. Blood samples were taken from nurses working without adequate protection in oncological department on preparing and administration of different antineoplastic drugs. Lymphocytes were cultivated in vitro at 37 degrees C. To prevent cytokinesis, at 44th cytochalasine-B at a final concentration of 3 micro g/ml was added. The results obtained indicate statistically significant increases in the total number of micronuclei in the exposed subjects compontrols. DAPI staining has revealed signal-positive and signal-negative miuclei while silver staiing has revealed Ag-NOR+ and Ag-NOR- micronuclei. Compred to controls, the number of signal-positive exposed subjects were increased, indicating a greater susceptibility of particular chromosomes to damage caused by antineopalstic agents.
Published in DiRROS: 19.01.2024; Views: 193; Downloads: 46
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1224. p53 - the paradigm of tumor-suppresor genes?Barbara Jezeršek Novaković, Srdjan Novaković, 1998, review article Abstract: p53 is a tumor-suppressor gene the alterations of which are among the most frequent genetic changes detected in human neoplasms. Its product - p53 protein is a component of several biochemical pathways that are central to carcinogenesis: DNA transcription, genomic stability, DNA repair, cell cycle control, and apoptosis. The analysis of the spectrum of p53 mutations and insight into the p53 mediated biochemical pathways of programmed cell death and cell cycle arrest, provide clues to understanding of molecular pathogenesis of cancer of mechanisms related to p53 mediated tumor suppression. The purpose of the resent article is to summarise the most important facts concerning p53 since understanding of the above listed processes might provide the potential molecular targets for the development ofa rational cancer treatment.
Published in DiRROS: 19.01.2024; Views: 238; Downloads: 73
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1227. Plasma membrane fluidity alterations in cancerous tissuesMarjeta Šentjurc, Mihael Sok, Gregor Serša, 1998, original scientific article Abstract: Plasma membrane is a heterogeneous structure with several coexisting domains having different fluidity characteristics. It plays an important role in the control of cell growth, differentiation and transformation. Fluidity of the whole plasma membrane reflects the ordering and dynamics of phospholipid acyl chains in specific membrane domains, as well as the fraction of each domain inthe membrane. Changes in the membrane fluidity affect processes on the membrane such as transport, enzyme activities and expression of the redeptors.In this paper we present results of our recent electron paramagneticresonance (EPR) studies of plasma membrane fluidity characteristics, which take into account heterogeneous nature of the plasma membrane, By the computer simulation of the EPR spectra line-shapes, the number of coexisting domains in the plasma membrane, their relative portion inthe membrane as well as the ordering and dynamics of each domain be determined. Therefore, we could distinguish the contribution of the relative portion of each domain from the contribution of fulidity alterations in the domain to the entire fluidity changes in the membrane. Two examples will be discussed: membrane fluidity characteristics of excised lung tumor tissues andinfluence of microtubule depolymerizing agent vinblastine on membrane fluidity of vinblastine sensitive and resistant HeLa cells.
Published in DiRROS: 19.01.2024; Views: 261; Downloads: 62
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1228. Image cytometry analysis of normal buccal mucosa smears: influence of smoking and sex-related differencesJaka Lavrenčak, Margareta Strojan Fležar, Mario Žganec, Marija Us-Krašovec, 1998, original scientific article Abstract: To get more information about the influence of smoking on chromatin pattern ofnormal buccal mucosa cells and to assess sex-related differences in nuclear features, quantitative analysis of normal buccal mucosa smears was performed. In this study, buccal smears were collected from 78 healthy subjects. Image cytometry analysis was performed on Feulgen-thionin stained smears. probability distributions of 78 nuclear features were calculated for both, cell-by-cell and slide-by-slide classifications. Seven nuclear features showeddiscriminative ability between smokers and non-smokers; most of them were nuclear texture features. Statistical analysis of nuclear features in groups of females and males hoswed that only two nuclear features were different. It is concluded that smoking should be considered in image cytometry analysis of lesions in oral cavity.
Published in DiRROS: 19.01.2024; Views: 239; Downloads: 79
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1229. Longitudinal study of malignancy associated changes in progressive cervical dysplasiaMargareta Strojan Fležar, Jaka Lavrenčak, Mario Žganec, Marija Us-Krašovec, 1998, original scientific article Abstract: Eight of 29 patients with progressive CIN were followed for 2 to 10 years. Their consecutive Pap smears were destained and stained according to Feulgen thionin method. Cyto-Savant/TM high resolution image cytometer (Oncometrics Technol. Corp., Vancouver, Canaderage values of muclear texture features and their probability distributions for consecutive Pap smears from each patient were calculated. Three out of 5 discriminant MAC, highDNAamount, highDNAcomp and highDNAarea, were to increase as a function of time in 5 out of 8 patients. A preliminary analysis which was performed on non-standardized archival material demonstrated a monotonous increase of discrete texture features as a function of time in patients with progressive CIN.
Published in DiRROS: 19.01.2024; Views: 257; Downloads: 72
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1230. Flexible polymer connections for clt structuresBoris Azinović, Andreja Pondelak, Jaka Gašper Pečnik, Václav Sebera, 2020, published scientific conference contribution Abstract: This paper explores the possibility of using flexible polymer adhesives to dissipate energy in CLT buildings during earthquakes. In the first series of tests, pull-off tests of various polyurethane (PUR) adhesives were performed. The connection was tested in pull-pull configuration using monotonic, tension-only loading. The tests have shown that the adhesive can resist large deformations already in tension loading and with small thicknesses of the bond-line. Based on the pull-off test results, one adhesive has been selected for further testing. Monotonic lap-shear tests were performed with the selected adhesive and thick bond-line (3 mm and 6 mm). The results show, that the standard method for lap-shear testing (EN 205) needs to be adapted for thick glue-line. It was found that the strength of 3 mm glue-line is higher than 6mm one, which is in agreement with adhesion theory. The flexible PUR adhesives could potentially be used in CLT structures for anchoring the CLT wall with “flexible” glued-in rods or as a “flexible” vertical shear connection between the CLT walls. Such systems have a potential to dissipate energy in seismic areas.
Keywords: CLT connections, flexible adhesive, polyurethane, energy dissipation, pull-off, lap-shear
Published in DiRROS: 19.01.2024; Views: 296; Downloads: 140
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