Experimental Bearing Capacity Determination of Bonded Rock Bolts

Import 26/02/2015Diplomová práce se zabývá únosností tmelených horninových svorníků a jejím experimentální stanovením. Tato práce analyzuje a poukazuje na možné způsoby porušení, které vznikají zatížením v těsné blízkosti svorníkové tyče a to především v prstenci tmele na kontaktech svorník – tmel a tmel – hornina. V teoretické části byl navržen způsob měření a stanovení pevnostních a deformačních charakteristik tahem zatížených tmelených svorníků napodobujících zatížení v kořenové délce svorníkové výztuže. V praktické části byly pak navržené postupy uskutečněny sérií laboratorních zkoušek. Výstupem z provedených zkoušek je pracovně-deformační charakteristika tmelené svorníkové výztuže zvoleného testovaného materiálu.The thesis focuses on the bearing capacity of bonded rock bolts and experimental determination of this capacity. Possible ways of failure, which is caused by the load near the rock bolt, especially in the circular ring of the grout and between the rock bolt - the grout and between the grout - the rock, are analysed. The theoretical part includes design of measuring and assessment of strength and deformation characteristics on drawn rock bolts as it simulates the load in the root length of bolt reinforcement. This theory was applied in the laboratory tests and presents the practical part of the thesis. In conclusion, the load - deformation characteristics of bonded rock bolt reinforcement made from chosen material are stated.224 - Katedra geotechniky a podzemního stavitelstvívýborn

Data_Sheet_1_Assessing the individual roles of FII, FV, and FX activity in the thrombin generation process.PDF

Thrombin generation (TG) is known as a physiological approach to assess the hemostatic function. Although it correlates well with thrombosis and bleeding, in the current setup it is not sensitive to the effects of fluctuations in single coagulation factors. We optimized the calibrated automated thrombinography (CAT) method to quantify FII, FV and FX activity within the coagulation system. The CAT assay was fine-tuned for the assessment of FII, FV and FX by diluting the samples in FII-, FV-, or FX-deficient plasma, respectively, and measuring TG. Plasma FII levels correlated linearly with the ETP up to a plasma concentration of 100% FII. FV and FX levels correlated linearly with the peak height up to a plasma level of 2.5% FV and 10% FX, respectively. Sensitized CAT protocols were designed by adding a fixed volume of a pre-diluted patient sample to FII, FV, and FX deficient plasma in TG experiments. This approach makes the TG measurement dependent on the activity of the respective coagulation factor. The ETP or peak height were quantified as readouts for the coagulation factor activity. The intra- and inter-assay variation coefficients varied from 5.0 to 8.6%, and from 3.5 to 5.9%, respectively. Reference values were determined in 120 healthy subjects and the assays were clinically validated in 60 patients undergoing coronary artery bypass grafting (CABG). The sensitized CAT assays revealed that the contribution of FII, FV, and FX to the TG process was reduced after CABG surgery, leading to reduced prothrombin conversion and subsequently, lower TG.</p

Inhibition of thrombin generation in zebrafish by thrombin or FXa inhibition.

<p>Zebrafish were treated with melagatran <b>(A)</b> or rivaroxaban <b>(B)</b> at the indicated doses for 30 min, followed by thrombin generation measurements. <b>(C-D)</b> Results of two independent experiments are expressed as the percentage inhibition compared to a control group of vehicle-treated fish (n = 8). The percentage CV is indicated for all parameters. Statistical differences between treatment and control groups were performed with *Mann-Whitney U-test or ^$1-way ANOVA. (ns = not significant).</p

Prediction of bleeding risk in patients taking vitamin K antagonists using thrombin generation testing

<div><p>Until recently, vitamin K antagonists (VKAs) were the mainstay of oral anticoagulant treatment with bleeding as the most prevalent adverse effect. One to four percent of patients experience major bleeding episodes, while clinically relevant bleeding occurs in up to 20%. At this moment no laboratory assays are available to identify patients at risk for bleeding. With this study we aimed to investigate whether thrombin generation tests might identify a bleeding risk in patients taking VKAs. This prospective cohort study included 129 patients taking VKAs for more than three months. Calibrated automated thrombinography (CAT) was performed in whole blood, platelet rich and platelet poor plasma. Hematocrit, hemoglobin concentrations and the International Normalized Ratio (INR) were defined and coagulation factor levels were measured. Forty clinically relevant bleeding episodes were registered in 26 patients during follow-up. No differences were found in plasma CAT parameters or INR values. Bleeding was not associated with age, sex, hematocrit, hemoglobin levels or coagulation factor levels. In whole blood a significantly lower endogenous thrombin potential (ETP) and peak were found in patients with bleeding (median ETP: 182.5 versus 256.2 nM.min, p = 0.002; peak: 23.9 versus 39.1 nM, p = 0.029). Additionally, the area under the receiver operating curve (AUC ROC) was significantly associated with bleeding (ETP: 0.700, p = 0.002; peak: 0.642, p = 0.029). HAS-BLED scores were also significantly higher in bleeding patients (3 versus 2, p = 0.003), with an AUC ROC 0.682 (p = 0.004). In conclusion, bleeding in patients taking VKAs is associated with a decreased whole blood ETP and peak as well as with an increased HAS-BLED score.</p></div

Inhibition of thrombin generation in zebrafish by inhibition of platelet aggregation.

<p>Zebrafish were treated with 30 μg/g aspirin or vehicle for 30 min <b>(A-B)</b> or were allowed to swim in aspirin-supplemented water (250 mg/ml) for 24 hours <b>(C-D)</b>, followed by thrombin generation measurements. <b>(A,C)</b> Thrombin generation curves are shown. <b>(B,D)</b> Results are expressed as the percentage inhibition compared to a control group of vehicle-treated fish (n = 5). The percentage CV is indicated for all parameters. *Mann-Whitney U-test as compared to controls.</p

Metabolic parameters of the platelet concentrates.

<p>Metabolic parameters of the platelet concentrates.</p

Medians with interquartile ranges of thrombin generation parameters in plasma.

<p>Medians with interquartile ranges of thrombin generation parameters in plasma.</p

Thrombin generation curves and parameters in zebrafish, effect of temperature and comparison with humans.

<p>Thrombin generation was measured in zebrafish at 28°C and 37°C and compared to thrombin generation in humans at 37°C with low (no tissue factor (TF) added) or high (100 pM) TF. <b>(A)</b> Thrombin generation curves are shown (n = 8 or 9 for fish, n = 3 for humans). <b>(B)</b> Mean thrombin generation parameters and their CV are calculated. Statistical differences as compared to the zebrafish group measured at 37°C are indicated (*p<0.05, **p<0.01, ***p<0.0001, 1-way ANOVA). <b>(C-D)</b> Thrombin generation was measured in 6 independent experiments, in a total of 34 zebrafish. <b>(C)</b> Thrombin generation curves are shown. Each color represents an independent experiment. <b>(D)</b> Mean thrombin generation parameters and their CV are calculated, as well as the CV between the means of all 6 experiments (interexp. CV).</p

Scanning electron microscopy (SEM) of blood clots.

<p>Representative image of SEM analysis of blood clots formed during thrombin generation measurements. Sequential enlargements of the fibrin network with entrapped red blood cells are depicted. <b>(A)</b> Zebrafish blood clot. <b>(B)</b> Human blood clot without added tissue factor (TF). <b>(C)</b> Human blood clot with addition of a high dose (100 pM) of TF.</p

Effect of 10-day storage on platelet activation, measured by light transmission aggregometry (LTA).

<p>Aggregometry was measured in response to 10 μmol/L adenosine diphosphate (ADP, panel A), 4 μg/ml collagen (panel B) and 30 μmol/L thrombin receptor-activating peptide (TRAP-14, panel C). Light transmission in platelet concentrates (PCs) compared to autologous platelet poor plasma is expressed as percentage of maximal aggregation. Data are expressed as mean±SD and a dashed line was set on mean day 2—2SD. * = P<0.01, ** = P<0.001 compared to day 2.</p