Numerical analysis of the impact of flow rate, heart rate, vessel geometry, and degree of stenosis on coronary hemodynamic indices

Background: The stenosis of the coronary arteries is usually caused by atherosclerosis. Hemodynamic significance of patient-specific coronary stenoses and the risk of its progression may be assessed by comparing the hemodynamic effects induced by flow disorders. The present study shows how stenosis degree and variable flow conditions in coronary artery affect the oscillating shear index, residence time index, pressure drop coefficient and fractional flow reserve. We assume that changes in the hemodynamic indices in relation to variable flow conditions and geometries evaluated using the computational fluid dynamics may be an additional factor for a non-invasive assessment of the coronary stenosis detected on multi-slice computed tomography. Methods: The local-parametrised models of basic shapes of the vessels, such as straight section, bend, and bifurcation as well as the global-patient-specific models of left coronary artery were used for numerical simulation of flow in virtually reconstructed stenotic vessels. Calculations were carried out for vessels both without stenosis, and vessels of 10 to 95% stenosis. The flow rate varied within the range of 20 to 1000 ml/min, and heart rate frequency within the range of 30 to 210 cycles/min. The computational fluid dynamics based on the finite elements method verified by the experimental measurements of the velocity profiles was used to analyse blood flow in the coronary arteries. Results: The results confirm our preliminary assumptions. There is significant variation in the coronary hemodynamic indices value caused by disturbed flow through stenosis in relation to variable flow conditions and geometry of vessels. Conclusion: Variations of selected hemodynamic indexes induced by change of flow rate, heart rate and vessel geometry, obtained during a non-invasive study, may assist in evaluating the risk of stenosis progression and in carrying out the assessment of the hemodynamic significance of coronary stenosis. However, for a more accurate assessment of the variability of indices and coronary stenosis severity both local (near the narrowing) and global (in side branches) studies should be used

Cerebral venous and sinus thrombosis diagnosis: preliminary study of clinical picture and D-dimer concentration correlation

Aim of the study. We investigated whether D-dimer (DD) concentration is elevated in cerebral venous and sinus thrombosis (CVST), as has been reported in the literature. Clinical rationale for the study. CVST is a disease with variable clinical presentations and a challenging diagnosis. We looked into whether D-dimer concentration might be an indicator of CVST, and the need for neuroimaging tests correlated with clinical factors. Materials and methods. We included all consecutive patients (mean age 41.6 years) with CVST treated in our neurology department from 2014 to 2018 whose DD levels had been measured. DD concentrations were categorised as normal (≤ 0.5 μg/ml) or elevated ( > 0.5 μg/ml). Appropriate imaging confirmed the diagnosis of CVST. The results were compared to those of a control group consisting of 22 age- and sex-matched patients (mean age 40 years) with a diagnosis of primary headache (tension type or migraine) hospitalised to exclude secondary causes. Results. In 20 patients in the CVST study group, median level of DD was 1.0 + 0.57 μg/ml (range 0.19–2.45 μg/ml), compared to the control group’s mean DD level of 0.50 + 0.45 μg/ml (range 0.15–1.73 μg/ml), with p < 0.005. Higher DD levels were associated with complications of the disease and fatal course (p < 0.005). One female and one male patient died because of CVST with DD levels of (respectively) 2.45 and 1.80 μg/ml — the two highest concentrations in our study group. Conclusions and clinical implications. DD concentration, especially in headache patients, may be a factor to predict CVST and an indicator for further diagnostic procedures with venography. But in clinical practice, low levels of DD cannot be taken to exclude CVST

Modelling of failures in thin-walled metal silos under eccentric discharge

Eccentric discharge of granular solids is widely considered one of the most serious design conditions for thin-walled metal silos, and one which has been the cause of very many silo disasters in the past. Yet the reasons for these consequences have not been very well understood, given the serious difficulties inherent in measuring or modelling flow patterns of granular solids, wall pressures and the associated structural response. To this end, this thesis presents a programme of theoretical and computational analyses which investigate the effects of a very wide range of different discharge flow patterns from silos, including both concentric and eccentric flows. The critical effects of changes of flow channel geometry, silo aspect ratio, changes of plate thickness and geometric and material nonlinearity are explored in detail. The codified procedures and pressure distributions for concentric and eccentric discharge of the EN 1991-4 (2007) European Standard are analysed first on a number of example silos custom-designed according to EN 1993-1-6 (2007) and EN 1993-4-1 (2007), followed by the development and investigation of a more complete mixed flow pressure theory. The computational analyses presented in this thesis are thought to be the first of their kind

Molecular Beam Epitaxy growth of MoTe2_{\tiny{\textrm{2}}} on Hexagonal Boron Nitride

Hexagonal boron nitride has already been proven to serve as a decent substrate for high quality epitaxial growth of several 2D materials, such as graphene, MoSe$_{\tiny{\textrm{2}}}$, MoS$_{\tiny{\textrm{2}}}$ or WSe$_{\tiny{\textrm{2}}}$. Here, we present for the first time the molecular beam epitaxy growth of MoTe$_{\tiny{\textrm{2}}}$ on atomically smooth hexagonal boron nitride (hBN) substrate. Occurrence of MoTe$_{\tiny{\textrm{2}}}$ in various crystalline phases such as distorted octahedral 1T' phase with semimetal properties or hexagonal 2H phase with semiconducting properties opens a possibility of realisation of crystal-phase homostructures with tunable properties. Atomic force microscopy studies of MoTe$_{\tiny{\textrm{2}}}$ grown in a single monolayer regime enable us to determine surface morphology as a function of the growth conditions. The diffusion constant of MoTe$_{\tiny{\textrm{2}}}$ grown on hBN can be altered 5 times by annealing after the growth, reaching about 5 $\cdot$ 10$^{-6}$ cm$^{2}$/s. Raman spectroscopy results suggest a coexistence of both 2H and 1T' MoTe$_{\tiny{\textrm{2}}}$ phases in the studied samples.Comment: 6 pages, 3 figure

Adherence to antihypertensive therapy among heart transplant recipients

INTRODUCTION: Adherence to therapeutic recommendations, concerning in particular drug administration, diet and healthy life style, is essential to obtain optimal medical treatment effects. Elevated blood pressure is an extremely important risk factor for cardiovascular diseases such as coronary artery disease, chronic heart failure and stroke, as well as chronic kidney disease. AIM: The aim of the study was to assess the level of adherence among heart transplant recipients and to explain the reasons for non-adherence phenomenon. MATERIAL AND METHODS: The study was performed on 55 heart allograft recipients: 11 women (20%) and 44 men (80%), all hypertensive. Participation in the study was voluntary and the three-part questionnaire was anonymous to obtain reliable answers. The second part was designed using the Modified Morisky Scale (MMS) consisting of questions assessing motivation and knowledge among patients. The third included questions concerning lifestyle, reasons for non-adherence and methods to improve it. RESULTS: In self-assessment of the adherence to medical recommendations on a scale of 0 to 10 the analyzed population estimated their level of adherence to be on average 8.49 ± 1.33, which is a considerably high result. It was discovered that both the level of motivation (2.20) and knowledge (2.83) are high among heart transplant recipients. Still, the level of knowledge was significantly higher than the motivation (p < 0.005). Correlation analysis revealed that the self-assessed adherence level correlated positively with the level of motivation (r = 0.357; p < 0.007). CONCLUSIONS: Creation of an active attitude of the patient in the process of treatment is a crucial and at the same time often difficult task demanding cooperation of the patient, the patient's close family and the whole therapeutic team

Lead shielding efficiency from the gamma background measurements in the salt cavern of the Polkowice–Sieroszowice copper mine

The studies of lead shielding efficiency from the gamma background measurements were performed in the salt cavern of the copper mine - a site considered for an underground laboratory. Within the energy range of 50–2700 keV, the measured gamma-ray count rates normalized to the mass of the high-purity detectors germanium crystal are 5.93 and 6.32 s−1kg−1 for the used low-background and portable spectrometers, respectively. The gamma-ray flux of 0.124 (2) cm−2s−1 connected with the natural radioisotopes was observed by the portable HPGe, including 0.026 (1) cm−2s−1 contribution of radon decay products, whereas the photon flux at the spectrum continuum was 0.18 (5) cm−2s−1