Numerical modelling has been widely used in the underground excavation design, where the in situ stress state plays a crucial role in the stability analysis. However, determination of an exact stress state for a specific geological region remains uncertain due to the complicated tectonic nature and measurement limitations. The stability is thus better analysed by considering the in situ stress as a finite spectrum and pinpointing the possible worst-case scenario. The most probable scenarios of in situ stress states in the Rožná mine area were analysed based on the varying trends in principal stress ratio and mean stress values obtained from four different measurement/analysis campaigns. The influence of different in situ stress judgement on the deformation and failure characteristics of the Bukov Underground Research Facility (URF) (Phase II, Czech) were investigated by the finite volume program FLAC3D. Results show that the increased horizontal stress anisotropy and the mean stress level jointly increase the overall deformation and lower the URF stability. Such influences on the roadway horizontal convergence are more considerable than the vertical ones. A mathematical model considering mean stress and horizontal stress ratio was proposed to quantitatively describe the overall stability, especially useful for excavations possessing complicated configuration., Libin Gong, Kamil Soucek, Petr Waclawik, Martin Vavro, Lubomir Stas, Jan Nemcik and Sahendra Ram., and Obsahuje bibliografii
The aim of this study was to analyze the possibilities of various types of stent modeling and to develop some new models. A brief survey of basic properties of stents and a list of basic designs of stents is presented. Two approaches to stent modeling were identified. Structural mechanics is the theoretical background of our analytical model of a spiral stent. The finite element method was also used. The measurement equipment for model evaluation was developed., J. Záhora, A. Bezrouk, J. Hanuš., and Obsahuje bibliografii
The known models of recent vertical movements of the Earth crust surface in the area of Poland were processed in the form of contour line map on the basis of the data of the first and second class geometric state levelling network. Second map done by Wyrzykowski (1985) was based on the results of measurements made in 1871-1882, 1926-1937, 1952-1956 and 1975-1977. The newest results of assignment of recent vertical movements of the Earth surface in the territory of Poland were published by Kowalczyk in 2006. The map of the contemporary vertical movements velocities has been processed using the least squares collocation method on the basis of repeated measurements of state precise levelling, executed mainly in 1974-1982 and 1997-2003. Presently, after about 3 years of satellite observations at about one hundred of permanent GPS stations of the ASG-EUPOS network, a verification of the mentioned models is possible on the basis of independent (satellite) measurements. As the resolution of the stations in Poland is sufficient, the model processed using satellite data was determined for the whole area of Poland and it was confronted with earlier (levelling) models. There are some differences in the analyzed models. A comparison of levelling and satellite mode ls indicates defect of reference distinctly resulting from sea level variability., Bernard Kontny and Janusz Bogusz., and Obsahuje bibliografické odkazy
Atomic nuclei are objects with a complicated internal structure but many aspects of their behavior can be understood in terms of relatively simple models. Since early times in nuclear physics many nuclear models have been developed. Among them, two basic types are of special importance. The shell model which converts the nuclear many-body problem to the independent movement of particles in a potential well, and the collective model which describes low energy excitations as the manifestation of the coherent motion of nucleons. In the article we review, in a nutshell, basic ideas which significantly influenced our understanding of nuclear phenomena., Atómové jadrá sú komplexné objekty so zaujímavými vlastnosťami a bohatou vnútornou štruktúrou, Dôležité informácie o dejoch vnútri jadier sa dozvedáme zo štúdia ich spektier a skúmaním jadrových reakcií. Pochopenie dejov vnútri jadier je nevyhnutnou podmienkou pre ich využitie v jadrovej energetike, medicínskych aplikáciách ale aj pre porozumenie procesom produkcie prvkov vo hviezdach., and František Knapp.
The review aims to summarize current knowledge on the effects of moderate alcohol consumption ( 1 standard drink a day for women; 2 drinks a day for men) on triglyceride concentration in circulation. Current evidence suggests that the relationship between alcohol consumption and triglyceridemia is J -shaped. Triglyceridemia is lowest in subjects who drink 10 -20 g/alcohol a day. Such a J -shaped association is comparable with that described for the relationship between alcohol and cardiovascular risk. On the contrary, alcohol taken with a meal increases and prolongs postprandi al triglyceridemia. Such effects of alcohol consumption may be at least partially explained by the effects of ethanol on lipoprotein lipase (LPL) activity. Long -term moderate alcohol consumption increases LPL activity, which may explain its TG -lowering effect. On the other hand, LPL activity is acutely downregulated by ethanol, which explains increased postprandial triglyceridemia., J. Kovář, K. Zemánková., and Obsahuje bibliografii
Numerous countermeasures have been proposed to minimize microgravity-induced physical deconditioning, but their benefits are limited. The present study aimed to investigate whether personalized aerobic exercise based on artificial gravity (AG) mitigates multisystem physical deconditioning. Fourteen men were assigned to the control group (n=6) and the countermeasure group (CM, n=8). Subjects in the CM group were exposed to AG (2 Gz at foot level) for 30 min twice daily, during which time cycling exercise of 80-95 % anaerobic threshold (AT) intensity was undertaken. Orthostatic tolerance (OT), exercise tests, and blood assays were determined before and after 4 days head-down bed rest (HDBR). Cardiac systolic function was measured every day. After HDBR, OT decreased to 50.9 % and 77.5 % of pre-HDBR values in control and CM groups, respectively. Exercise endurance, maximal oxygen consumption, and AT decreased to 96.5 %, 91.5 % and 91.8 % of pre-HDBR values, respectively, in the control group. Nevertheless, there were slight changes in the CM group. HDBR increased heart rate, sympathetic activity, and the pre-ejection period, but decreased plasma volume, parasympathetic activity and left-ventricular ejection time in the control group, whereas these effects were eliminated in the CM group. Aldosterone had no change in the control group but increased significantly in the CM group. Our study shows that 80-95 % AT aerobic exercise based on 2 Gz of AG preserves OT and exercise endurance, and affects body fluid regulation during short-term HDBR. The underlying mechanisms might involve maintained cardiac systolic function, preserved plasma volume, and improved sympathetic responses to orthostatic stress., X.-T. Li, C.-B. Yang, Y.-S. Zhu, J. Sun, F. Shi, Y.-C. Wang, Y. Gao, J.-D. Zhao, X.-Q. Sun., and Obsahuje bibliografii
Príspevok je pokusom stručne charakterizovat rozsiahly arzenál súčasných astronomických prístrojov a metód s krátkym presahom do blízkej budúcnosti. Podstatným znakom astronomického výskumu je multispektrálnosť s nasadením kozmických observatórií. Vel'ký pozemský optický teleskop už sám o sebe nestačí a k dosiahnutiu perfektného obrazu daného difrakčným limitom je nevyhnutná aktívna a adaptívna optika s následnou rekonštrukciou obrazu založenou na Fourierovej transformácii. Interpretačným nástrojom napomáhajúcim pochopiť a vysvetliť pozorovania sú počítačové numerické simulácie. Vybrané vzorky sú kompromisom poznačeným profesionálnym zameraním autora na fyziku Slnka v najlepšej snahe zachovať ich všeobecnejšiu platnosť., The review attempts to characterize briefly a vast arsenal of contemporary astronomical instruments and methods with an outlook to the near future. Essential features of astronomical research are multispectral observations involving both ground and space observatories. Big ground-based telescope in itself is no longer sufficient. Supporting active and adaptive optics with follow-up post-processing and image reconstruction based on Fourier transform are needed to achieve perfect diffraction-limited image. Numerical simulations are essential tools in interpretation and explanation of observations. Presented samples are influenced by the author's specialization in solar physics but he seeks to maintain their generic validity., Július Koza., and Obsahuje bibliografii
Akutní iktus je častou příčinou mortality a invalidity. Skepse k léčeným možnostem přetrvává jak mezi lékaři, tak mezi laickou veřejností. Nicméně výsledky moderní reperfuzní léčby pacientů postižených akutním iktem se zlepšily – alespoň u těch, kteří se dostaví časně po projevení se symptomu. Tento článek představuje multidisciplinární přístup ke zvládání akutního iktu – spolupráci neurologů, kardiologů a radiologů. Pojednává se o obou strategiích reperfuze: katetrizační trombektomii i trombolýze., Acute ischemic stroke is a frequent cause of death and disability. Therepautic scepticism persists both among doctors and lay people. However, modern reperfusion therapy improved outcomes of acute stroke patients – at least of those presenting early after symptom onset. This review presents multidisciplinary approach to acute stroke – cooperation of neurologists, cardiologists and radiologists. Both reperfusion strategies are discussed: catheter-based thrombectomy and thrombolysis., Petr Widimský, Boris Kožnar, Ivana Štětkářová, and Literatura
Fibrilace síní představuje v moderní populaci stále větší medicínský i socioekonomický problém. Poslední desetiletí zaznamenalo výrazný rozmach nefarmakologické léčby fibrilace síní. Radiofrekvenční katetrová ablace získala v léčbě této arytmie významnou pozici obzvláště tam, kde selhala léčba antiarytmiky, a v určitých případech i jako léčba první volby dle preference pacienta. Neuspokojivá úspěšnost prvního ablačního výkonu, zejména u dlouhodobě perzistující formy fibrilace síní, vedla k rozvoji chirurgických miniinvazivních a především hybridních přístupů v léčbě této arytmie. Autoři v článku shrnují dosavadní literární data o těchto kombinovaných přístupech a uvádějí i vlastní zkušenosti., Atrial fibrillation represents a quickly growing medical and socio‑economic problem in the modern population. We have witnessed an enormous expansion of non‑pharmacological treatment modalities for AF over the last decade. Developments in radiofrequency catheter ablation have given it an important role in AF treatment, especially in cases where antiarrhythmic therapy has failed. In certain groups of patients, based on patient preference, it has even become a first‑line therapy. The early attempts at catheter ablation had unsatisfactory success rates, especially in patients with long‑standing persistent AF. These failures led to the development of minimally invasive surgical and hybrid procedures. The authors of this article summarize the current literature reporting on these new procedures and also discuss their own experiences., and Bulava A., Mokráček A.