We complement the recently introduced classes of lower and upper semilinear copulas by two new classes, called vertical and horizontal semilinear copulas, and characterize the corresponding class of diagonals. The new copulas are in essence asymmetric, with maximum asymmetry given by 1/16. The only symmetric members turn out to be also lower and upper semilinear copulas, namely convex sums of Π and M.
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The gob side entry retaining with high water material is often used in coal mines. To study the stress evolution characteristics of surrounding rock and asymmetric support control technology of gob side entry retaining with high water material, the evolution law of stress and deformation of surrounding rock in gob side entry retaining during working face mining is studied by theoretical analysis, numerical simulation and field measurement. According to the stress variation of overlying strata during the mining process of the working face, the mechanical models before and after the basic roof fracture were established respectively. The stress and deformation of the filling body and the roof on the side of the filling body are larger, and the stress and deformation of the solid coal and the roof on the side of solid coal are smaller. The maximum stress is at 3 m away from the roadway. The first weighting step distance is 40 m and the periodic weighting step distance is 30 m. Based on the stress and deformation characteristics of the roadway surrounding, the roadway surrounding support is divided into filling bodyside, solid coal side, and middle part of roadway roof. The asymmetric support technology of "filling body+ double row hydraulic prop+ I-beam+ high-strength pretension anchor cable+ high-strength bolt" is proposed. The field engineering practice shows that the surrounding rock control effect of asymmetric support technology with high water material is good., Qiyuan Shan, Yongli Liu, Tao Li and Zhupeng Jin., and Obsahuje bibliografii
Hemispheric EEG slow-potential asymmetry (SPA) during a one-dimensional horizontal tracking task was recorded over Oi, O2, C3 and C4 electrode positions. The time instants of tracking error occurrences (CXJT events) and their corrections (IN events) were used as synchronization events in selected EEG epochs. The central values (medians) of amplitudes in the averaged 500 ms EEG epochs were used for SPA description. Significant negative correlations between medians calculated for the time epochs prior to and after the events were found indicating a specific influence of these events on SPA. Prior IN events the left hemisphere (represented by Oi and C3 positions only) was more negative than the right one, while it was significantly more positive after the same type of events. An opposite relationship was suggested for OUT events.
Stenóza cervikálního kanálu může vést ke kompresi krční míchy a představuje nejvýznamnější mechanický faktor v patofyziologii cervikální spondylogenní myelopatie. Míšní tkáň je však vůči kompresi poměrně odolná a k rozvoji manifestní myelopatie dochází až při vyšším stupni komprese a v kombinaci s dalšími patofyziologickými faktory, zejm. dynamickým faktorem a zevním traumatem. Asymptomatická spondylogenní komprese krční míchy (ASCCC) je velmi častým nálezem zvláště v populaci vyššího věku nad 50 let. Objektivizace a kvantifikace cervikální stenózy a komprese krční míchy jsou však nejednotné a nejsou jasně stanoveny prediktory progrese do manifestní myelopatie a s tím související indikace případné preventivní chirurgické dekomprese. Přehled obsahuje nejčastěji používané metody stanovení cervikální stenózy a cervikální míšní komprese pomocí zobrazovacích metod. Nativní radiogram a výpočetní tomografie mají význam v objektivizaci cervikální stenózy, zatímco dominantní metodou objektivizace míšní komprese je magnetická rezonance (MR). Z parametrů, které nejvíce korelují s klinickou manifestací komprese, jsou uváděny příčná plocha míchy v místě komprese a přítomnost intenzitních změn míšního signálu. Z novějších zobrazovacích modalit je nejcitlivější MR zobrazení tenzorů difúze. Z prognostických faktorů rozvoje manifestní myelopatie u ASCCC jsou obecně akceptovány přítomnost manifestní radikulopatie a abnormita motorických a senzomotorických evokovaných potenciálů. Význam zobrazovacích metod v predikci rozvoje manifestní myelopatie a benefit provedení preventivní dekomprese ve skupině nemocných s asymptomatickou kompresí a vyšším rizikem rozvoje manifestní myelopatie bude nutné ověřit dalšími studiemi., Cervical spinal stenosis may lead to cervical cord compression and represents the most important mechanical factor in pathophysiology of cervical spondylotic myelopathy. Medullar tissue is, however, rather resistant to compression and development of symptomatic myelopathy occurs only when higher degree stenosis is present and in combination with other pathophysiological factors, mainly dynamic compression and trauma. Asymptomatic spondylotic cervical cord compression (ASCCC) is a quite frequent finding in older population above the age of fifty. However, reliability of the methods used to verify and quantify cervical stenosis and cervical cord compression is low and clear predictors of development of symptomatic myelopathy and related indication of potential preventive surgical decompression in ASCCC have not been determined yet. The overview discusses the most frequently used methods to establish cervical spinal stenosis and cervical cord compression using imaging methods. Radiogram and especially computed tomography are important for verification of cervical spinal stenosis, while magnetic resonance imaging (MRI) is a preferable method to detect cervical cord compression. The cross‑sectional spinal cord area and T2 MRI spinal cord hyperintensity are among the parameters considered to be the most closely correlated with clinical manifestation of spinal cord compression. Among newly introduced imaging modalities, MRI diffusion tensor imaging seems to be the most promising one. The presence of symptomatic radiculopathy and abnormality of motor and somatosensory evoked potentials are among generally accepted predictors of symptomatic myelopathy. The importance of imaging methods as predictors of symptomatic myelopathy development as well as benefits of preventive surgical decompression in ASCCC individuals with high risk of developing symptomatic myelopathy is to be established in future studies. Key words: cervical spinal stenosis – cervical spondylotic myelopathy – asymptomatic spondylotic cervical cord compression – magnetic resonance imaging – diffusion tensor imaging –computed tomography The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE “uniform requirements” for biomedical papers., and I. Kovalová, J. Bednařík, M. Keřkovský, B. Adamová, Z. Kadaňka
Kyselina močová je u človeka biologicky aktívny koncový produkt metabolizmu purínov. Zvýšené koncentrácie kyseliny močovej sprevádzajú metabolický syndróm a jeho komponenty už u detí a mladistvých. K hyperurikémii prispieva konzumácia nápojov prisládzaných fruktózou, nakoľko je jediným sacharidom, pri ktorého metabolizme vzniká kyselina močová. Súčasné vedomosti neumožňujú odlíšiť, či je hyperurikémia kauzálnou príčinou komponentov metabolického syndrómu, alebo len sprievodným znakom naznačujúcim zvýšené riziko vzniku kardiovaskulárnych ochorení. V súčasnosti neexistuje konsenzus či a ako liečiť asymptomatickú hyperurikémiu u detí a mladistvých. Zaujať zásadný postoj k týmto otázkam umožnia len výsledky randomizovaných kontrolovaných prospektívnych štúdií, ktoré poskytnú dôkazy o prospešných účinkoch tejto liečby na prevalenciu metabolického syndrómu a incidenciu kardiovaskulárnych chorôb., In humans, uric acid represents a biologically active end-product of purine nucleotides. Several studies in children and adolescents documented an association between hyperuricaemia and the components metabolic syndrome. High intake of fructose-sweetened beverages might increase uricaemia, since fructose is the only saccharide which metabolism results in the formation of uric acid. Current knowledge does not allow distinguishing whether hyperuricaemia is causally related to the components of metabolic syndrome, or rather represents a marker of an enhanced risk, and poor outcome. No guidelines exist whether or not to treat asymptomatic hyperuricaemia in the adolescents. Randomized controlled prospective clinical studies are needed to elucidate whether uric acid-lowering management would beneficially affect the prevalence of metabolic syndrome, and the incidence of cardiovascular disease., and Ivana Koborová, Radana Gurecká, Anna Hlavatá, Katarína Šebeková
In this paper we prove two results. The first is an extension of the result of G. D. Jones [4]: (A) Every nontrivial solution for \[ \left\rbrace \begin{array}{ll}(-1)^n u^{(2n)} + f(t,u) = 0,\hspace{5.0pt}\text{in} \hspace{5.0pt}(\alpha , \infty ), u^{(i)}(\xi ) = 0, \quad i = 0,1,\dots , n-1, \hspace{5.0pt} \text{and} \hspace{5.0pt}\xi \in (\alpha , \infty ), \end{array}\right.\] must be unbounded, provided $f(t,z)z\ge 0$, in $E \times \mathbb R$ and for every bounded subset $I$, $f(t,z)$ is bounded in $E \times I$. (B) Every bounded solution for $(-1)^n u^{(2n)} + f(t,u) = 0$, in $\mathbb R$, must be constant, provided $f(t,z)z\ge 0$ in $\mathbb R \times \mathbb R$ and for every bounded subset $I$, $f(t,z)$ is bounded in $\mathbb R \times I$.
The nonlinear difference equation (E) xn+1 − xn = anϕn(xσ(n) ) + bn, where (an), (bn) are real sequences, ϕn : −→ , (σ(n)) is a sequence of integers and lim n−→∞ σ(n) = ∞, is investigated. Sufficient conditions for the existence of solutions of this equation asymptotically equivalent to the solutions of the equation yn+1 − yn = bn are given. Sufficient conditions under which for every real constant there exists a solution of equation (E) convergent to this constant are also obtained.
Asymptotic behavior of solutions of an area-preserving crystalline curvature flow equation is investigated. In this equation, the area enclosed by the solution polygon is preserved, while its total interfacial crystalline energy keeps on decreasing. In the case where the initial polygon is essentially admissible and convex, if the maximal existence time is finite, then vanishing edges are essentially admissible edges. This is a contrast to the case where the initial polygon is admissible and convex: a solution polygon converges to the boundary of the Wulff shape without vanishing edges as time tends to infinity.