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The understanding of fracture has tended to follow great public disasters (e.g. over 200 US ships suffered due to catastrophic failure during WW II, later several jet air-craft damaged, destroying some bridges and buildings, etc). Rock fracture mechanics dates back to early 60-s and its application to rock blast problems, collapses deep gold mines in South Africa, earthquake disasters, etc. Pure shear mode (Mode I) or mixed tension and shear mode (Mode I and II) fracturing are the most important in rock mechanics and geophysics. The goal of this paper is to summarize the existing fracture criteria and the observed crack growth firstly from single flaws, secondly from multiply (two) flaws. Analysing the fracture propagations different types of coalescence can be determined and classified. Using these modelling and analysing the observed patterns, for example we could forecast the new failures after the earthquakes or calculating the stability of rock slopes, etc.
The Poisson’s rate value of the rock mass is one of the most important rock mechanical and rock engineering parameter. This value is used for calculating the deformation of the tunnels or displacement on rock foundations, among the others. Unfortunately, measuring this value is very difficult and time consuming in rock masses. The goal of this paper is to present a simple method for estimating the Poisson’s rate value for rock masses if it is known for the intact rock. Using the well-known equations for determining the earth pressure at rest, the relationship between the internal friction angle and the Poisson’s rate value can be determined. Due to the relationship between the internal friction angle and the rock mass classification (namely GSI) are also determined, from these connections the Poisson’s rate value and the GSI can be calculated. A linear equation was found: decreasing the quality of the rock mass, the Poisson’s rate is increasing. The presented calculation is also good, if the Poisson’s rate of the intact rock is not determinable. In this paper it was assumed that the Poisson’s rate value is a material constant. Note, that theoretically it is not true, however for rock mechanical calculations the changing this value is never investigated.
It was 100 years ago, that Theodore von Kármán (born as Tódor Kármán) designed and carried out the first triaxial tests. The goal of this short historical paper to tribute this occasion.
Skin autofluorescence (SAF) measurement is a simple, noninvasive method to assess tissue advanced glycation end products (AGE). In patients with end-stage renal disease and in those on hemodialysis AGE production is increased. Less is known about those treated with peritoneal dialysis (PD). In this study we tested if SAF is influenced by clinical and treatment characteristics in PD patients.This cross-sectional study included 198 PD patients (of those, 128 were on traditional glucose-based solutions and 70 patients were partially switched to icodextrin-based PD). SAF measurements were done with a specific AGE Reader device. The impact of patients’ age, gender, current diabetes, duration of PD, cumulative glucose exposure, body mass index, smoking habits and use of icodextrin on SAF values were tested with multiple regression analysis.Our analysis revealed that patients’ age, current diabetes and icodextrin use significantly increase patients’ SAF values (p = 0.015, 0.012, 0.005, respectively). AGE exposure of PD patients with diabetes and on icodextrin solution is increased. Further investigation is required whether this finding is due to the icodextrin itself or for a still unspecified clinical characteristic of PD population treated with icodextrin.
Mitochondrial functions have a major impact on T-cell functionality. In this study we characterized whether mitochondrial function in the neonatal T-cells differs from that in the adult T-cells during short T-cell activation. Methods: We used fow cytometry methods to test mitochondrial mass and to monitor mitochondrial Ca2+ levels, mitochondrial potential and superoxide generation in parallel with cytoplasmic Ca2+ levels during phythohaemagglutinine-induced activation of CD4+ and CD8+ T-cells of 12 term neonates and 11 healthy adults. Results: Baseline mitochondrial mass of CD4+ and CD8+ cells was lower in the neonate than in the adult. In comparison with the adult, neonatal resting CD4+ T-cells had lower cytoplasmic Ca2+ levels and this was associated with normal activation induced Ca2+-response. During short-term activation cytoplasmic Ca2+-response was lower in neonatal than in adult CD8+ T-cells. Mitochondrial Ca2+ uptake was increased in CD4+ neonatal T cells while it decreased in CD8+ T-cells. Mitochondrial depolarization was increased in CD4+ and decreased in CD8+ neonatal T-cells compared to adults. Superoxide generation was higher and equal in neonatal CD4+ and CD8+ cells, respectively, compared to the adult ones. Conclusion: Our data suggest that neonatal T-cells exhibit marked differences in mitochondrial function and superoxide generation compared to adult T-cells.
Systemic lupus erythematosus (SLE) is a multisystemic inflammatory autoimmune disorder. Thrombotic events occur at a higher incidence among SLE patients. The investigation of thrombin generation (TG) with calibrated automated thrombogram (CAT) test as a global hemostasis assay is applicable for the overall functional assessment of the hemostasis. The aim of this study was to characterize the hemostatic alterations observed in SLE by CAT assay. In this study, CAT parameters and basic coagulation parameters of SLE patients (n = 22) and healthy control subjects (n = 34) were compared. CAT area under the curve (i.e., endogenous thrombin potential) was lower than normal in SLE (807 vs. 1,159 nM*min, respectively), whereas other CAT parameters (peak, lag time, time to peak, and velocity index) and the basic coagulation tests were within the normal range. The presence of anti-phospholipid antibodies and the applied therapy was not associated with hemostasis parameters in SLE. We concluded that the reported high risk of thrombosis is not related to TG potential.
Asthmatic inflammation during pregnancy poses a risk for maternal and fetal morbidities. Circulating T cell immune phenotype is known to correlate with airway inflammation (detectable by fractional concentration of nitric oxide present in exhaled breath (FENO)) in non-pregnant allergic asthmatics. The aim of this study was to assess the relationship of peripheral T cell phenotype to FENO and clinical variables of asthma during pregnancy.We examined 22 pregnant women with allergic asthma in the 2nd/3rd trimester. The prevalence of Th1, Th2, regulatory T (Treg) and natural killer (NK) cell subsets was identified with flow cytometry using cell-specific markers. FENO, Asthma Control Test (ACT) total score and lung function were evaluated.Peripheral blood Th1, Th2, Treg, and NK cell prevalence were not significantly correlated to airway inflammation assessed by FENO in asthmatic pregnant women (all cells p > 0.05; study power > 75%). However, an inverse correlation was detected between Th2 cell prevalence and ACT total scores (p = 0.03) in asthmatic pregnancy.Blunted relationship between T cell profile and airway inflammation may be the result of pregnancy induced immune tolerance in asthmatic pregnancy. On the other hand, increased Th2 response impairs disease control that supports direct relationship between symptoms and cellular mechanisms of asthma during pregnancy.
