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29972. Time course of isolated rat fundus response to muscarinic agonists: a measure of intrinsic efficacy
- Creator:
- Jankovic, S. M., Kouvelas, D., and Mirtsou-Fidani, V.
- Type:
- article, model:article, and TEXT
- Subject:
- choline esters, rat, gastric fundus, dose-response relationship, and contraction
- Language:
- English
- Description:
- The establishment of a dose-response relationship and its quantification is the usual procedure for analysing drug action on an isolated organ. However, the time course of the effect seems to be an inherent characteristic of the agonist which produces it. In our study, we have analyzed the time-response curves of four cholinergic agonists (acetylcholine, methacholine, carbachol and bethanechol) which produce tonic contractions of the isolated rat gastric fundus. The order of affinity of agonists to muscarinic receptors on the rat fundus were carbachol > bethanechol > methacholine > acetylcholine (Ka values: 46 ±12, 84±21, 380±110 and 730±120 nM, respectively). The effective concentrations which produced 60 % of the maximal response (EC5Q) were used for establishing the time-response curves. The time-response curves were also recorded after partial alkylation of muscarinic receptors with phenoxybenzamine, after exposure of the isolated rat fundus to physostigmine and after addition of supramaximal concentrations of the agonists. The experimental time-response curve for acetylcholine was on the extreme left, followed by curves for methacholine, bethanechol and carbachol, respectively. Phenoxybenzamine and supramaximal doses of the agonists did not change the order of response development in time, but supramaximal doses shifted all curves to the left and phenoxybenzamine shifted all time-response curves to the right. Only physostigmine shifted the time-response curve for methacholine to the right. The results of our study suggest that the response rate of the isolated rat gastric fundus to cholinergic agonists depends on the intrinsic activity of these agents, but not on their affinity for muscarinic receptors.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29973. Time course of leukocyte response and free radical release in an early reperfusion injury of the superior mesenteric artery
- Creator:
- Hamar, J., Rácz, I., Milan Číž, Antonín Lojek, Pállinger, É., and Fűrész, J.
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, lymfocyty, lymphocytes, rat, polymorphonuclear leukocytes, chemiluminescence, 14, and 612
- Language:
- English
- Description:
- The sequence of changes in circulating immune cells and in free radical production was studied during the small intestine reperfusion. Rat small intestine ischemia/reperfusion was induced by a 45 min superior mesenteric artery occlusion followed by a 4-hour reperfusion. Samples of peripheral blood were collected every 20 min during reperfusion. While the number of polymorphonuclear leukocytes increased significantly both in the sham-operated controls and the experimental group (about 400 % at the end of reperfusion), a decrease in lymphocyte counts to 60 % was observed in the experimental group only. Although there were no changes in the counts of total T lymphocytes, a significant reduction in B cell counts was observed. Flow-cytometrical measurements showed no changes in the Tc subpopulation, while the Th subpopulation increased in the experimental group only. Free radical generation in blood (luminometric measurements) increased gradually and reached an eight-fold level by the end of reperfusion in both groups. Thus, it has been shown that the increase in free radical production is mainly due to the increased number of polymorphonuclear leukocytes mobilized already at the initial stages of reperfusion. The reduction in B lymphocyte population is probably due to homing mechanisms., J. Hamar, I. Rácz, M. Číž, A. Lojek, É. Pállinger, J. Fűrész., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29974. Time of concentration of surface flow in complex hillslopes
- Creator:
- Sabzevari, Touraj, Saghafian, Bahram, Talebi, Ali, and Ardakanian, Reza
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- complex hillslopes, time of concentration, and surface flow
- Language:
- Slovak
- Description:
- Time of concentration (TC) of surface flow in watersheds depends on the coupled response of hillslopes and stream networks. The important point in this background is to study the effects of the geometry and the shape of complex hillslopes on the time of concentration considering the degree of flow convergence (convergent, parallel or divergent) as well as the profile curvature (concave, straight or convex). In this research, the shape factor of complex hillslopes as introduced by Agnese et al. (2007) is generalized and linked to the TC. A new model for calculating TC of complex hillslopes is presented, which depends on the plan shape, the type and degree of profile curvature, the Manning roughness coefficient, the flow regime, the length, the average slope, and the excess rainfall intensity. The presented model was compared to that proposed by Singh and Agiralioglu (1981a,b) and Agiralioglu (1985). Moreover, the results of laboratory experiments on the travel time of surface flow of complex hillslopes were used to calibrate the model. The results showed that TC for convergent hillslopes is nearly double those of parallel and divergent ones. TC in convex hillslopes was very close to that in straight and concave hillslopes. While the effect of convergence on TC is considerable, the curvature effect confirmed insignificant. Finally, in convergent hillslopes, TC increases with the degree of convergence, but in divergent hillslopes, it decreases as degree of divergence increases.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29975. Time sensitivity and acceptance of testimony
- Creator:
- Alsamaani, Nader
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- acceptance of testimony, time sensitivity, reductionism, and non-reductionism
- Language:
- Slovak
- Description:
- Time sensitivity seems to affect our intuitive evaluation of the reasonable risk of fallibility in testimonies. All things being equal, we tend to be less demanding in accepting time sensitive testimonies as opposed to time insensitive testimonies. This paper considers this intuitive response to testimonies as a strategy of acceptance. It argues that the intuitive strategy, which takes time sensitivity into account, is epistemically superior to two adjacent strategies that do not: the undemanding strategy adopted by non-reductionists and the cautious strategy adopted by reductionists. The paper demonstrates that in adopting the intuitive strategy of acceptance, one is likely to form more true beliefs and fewer false beliefs. Also, in following the intuitive strategy, the listener will be fulfilling his epistemic duties more efficiently.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29976. Time series analysis of hydrologic data for water resources planning and management: a review
- Creator:
- Machiwal, Deepesh and Jha, Madan K.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- time series analysis techniques, review, climatologic time series, hydrologic time series, water resources planning and management, techniky analýzy časových radov, prehľad, časové rady v hydrológii, časové rady v klimatológii, vodohospodárske plánovanie, and riadenie vodného hospodárstva
- Language:
- Slovak
- Description:
- The main intent of this paper is to present a review on the application of time series analysis techniques in hydrology and climatology. An overview of various statistical tests for detecting and estimating the hydrologic time series characteristics (i.e., homogeneity, stationarity, trend, periodicity, and persistence) is presented, together with their merits and demerits followed by comprehensive reviews of past studies (both basic and applied), and future research directions. The present review revealed that the climatologic time series of precipitation, air temperature, evapotranspiration and climatic change, and the hydrologic time series of streamflow and surface water quality have received a great deal of attention worldwide. Although the application areas of time series analysis techniques are expanding with growing concerns about climate change and global warming, their application is still very limited in groundwater hydrology as well as for non-traditional hydrologic time series. It is also apparent from this review that the detection of trend and stationarity by parametric and/or nonparametric tests has been a major focus in the past. Multiple comparison tests lack appreciation by the researchers for testing homogeneity in the hydrologic and climatologic time series. Furthermore, most studies have ignored the importance of testing periodicity and persistence in the time series, which are equally important properties of hydrologic and climatologic time series. Based on the comprehensive review, future research needs for time series studies in hydrology and climatology are discussed. and Príspevok prináša prehľad aplikácií techník analýzy časových radov v hydrológii a klimatológii. Uvádza prehľad rôznych štatistických testov na zistenie charakteristík týchto radov (napr. homogenity, stacionarity, trendov, periodicity a perzistencie), spolu s ich prednosťami a nedostatkami. Ďalej je uvedený tiež celkový prehľad uskutočnených štúdií (základných aj aplikovaných) a smery výskumu pre budúcnosť. Súčasný prehľad naznačuje celosvetové sústredenie pozornosti na časové súbory klimatologických dát zrážok, teploty vzduchu, evapotranspirácie a zmien klímy, a tiež hydrologických dát prietokov a kvality povrchových vôd. Aj keď so zvýšením záujmu o zmenu klímy a globálne otepľovanie sa oblasti použitia techník analýzy časových radov rozširujú, ich aplikácie v oblasti hydrológie podzemných vôd a ďalších nie celkom tradičných hydrologických údajov sú veľmi obmedzené. Tento prehľad tiež uvádza, že v minulosti sa vyskytli snahy o sústredenie úsilia na postihnutie trendov a stacionarity radov použitím parametrických a/alebo neparametrických testov. Mnohí výskumníci dostatočne neoceňujú viacnásobné porovnávacie testy (multiple comparison tests) homogenity hydrologických a klimatických časových radov. Okrem toho vo väčšine štúdií sú zanedbané dôležité testy periodicity a perzistencie hydrologických radov. Tieto sú ich rovnako dôležité charakteristiky. Na základe všeobecného prehľadu príspevok tiež pojednáva o potrebe ďalšieho výskumu časových radov v hydrológii a klimatológii.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29977. Time transfer using optical fiber links
- Creator:
- Kuna, Alexander and Smotlacha, Vladimír
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- time, frequency, time transfer, optical fiber, optical network, čas, frekvence, časový transfer, optické vlákno, and optická síť
- Language:
- Czech
- Description:
- This paper describes our experience with time transfer using optical fibers and fully optical networks. We developed a technique and instrumentation for the comparison of distant time scales. These were first verified using a 740km optical loop within the Czech NREN backbone network and later a long term two-way optical time transfer between Czech and Austrian national time and frequency laboratories where the maintaining of their national time and frequency standards was evaluated. The optical link utilizes either dedicated optical fibers or Dense Wavelength Division Multiplex (DWDM) channels in all-optical production telecommunication networks. Results from the optical transfer, i.e. clock comparison and link delay including diurnal and seasonal effects are shown and also compared with a traditional time transfer using signals from the satellite navigation systems. and Článek popisuje naše dlouhodobé zkušenosti s časovým transferem prostřednictvím optických vláken a plně optických sítí. Pro porovnávání časových stupnic na velkou vzdálenost jsme proto vytvořili techniku a vyvinuli potřebné přístrojové vybavení, které jsme nejprve ověřili pomocí optické smyčky v délce 744 km v rámci páteřní sítě CESNET a posléze také využili pro dvoucestný optický transfer mezi českou a rakouskou národní laboratoří, které jsou zodpovědné za vytváření národních časových stupnic v České republice a Rakousku. Optickou trasu tvoří temná vlákna nebo vyhrazené kanály ve vlnovém multiplexu DWDM. Článek uvádí dosažené výsledky časového transferu, včetně měření zpoždění signálu na trase, a tyto jsou rovněž srovnány s obecně používaným časovým transferem prostřednictvím satelitních navigačních systémů.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29978. Time-course of photosynthetic induction in four tropical woody species grown in contrasting irradiance habitats
- Creator:
- Portes, M. T., Alves, T. H., and Souza, G. M.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Bauhinia, Esenbeckia, Guazuma, Hymenaea, intercellular CO2 concentration, plant eco-physiology, respiration rate, stomatal conductance, sunfleck utilization, and tropical forest succession
- Language:
- Multiple languages
- Description:
- We investigated the photosynthetic induction time-course in species of different ecological groups grown in contrasting forest irradiance environments, gap and understorey, exposed to different darkness times in order to verify the plant capacity to exploit irradiance heterogeneity. Photosynthetic induction was studied in leaves of Bauhinia forficata and Guazuma ulmifolia (early succession species, ES), and Esenbeckia leiocarpa and Hymenaea courbaril (late succession species, LS). T50 and T90 (time estimates to attain 50 and 90 % of maximum net photosynthetic rate, respectively) varied according to the time of previous exposure to darkness and growth irradiance. In both darkness times of 10 and 30 min, T50 was lower in the LS-than ES-species. These results, jointly with significant higher induction state of the leaves after 10 min of darkness, suggest that the LS-species has a higher potential to sunfleck utilization compared to ES-species, both grown in the understorey. After 10 and 30 min of darkness the differences between ecological groups were not clearly detected in the gap for T50 and T90, indicating that eco-physiological characteristics of each ecological group did not influence the induction time of the species evaluated herein. Thus the capacity to show phenotypic plasticity is not exclusive to an ecological group, but it is rather a more intrinsic feature related to the differential capacity of individuals. and M. T. Portes, T. H. Alves, G. M. Souza.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29979. Time-course of tissue factor plasma level in patients with acute coronary syndrome
- Creator:
- Josef Bis, Jan Vojáček, Jan Dušek, Miroslav Pecka, Vladimír Palička, Josef Šťásek, and Jan Malý
- Format:
- bez média and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, akutní koronární syndromy, arteriální trombóza, physiology, acute coronary syndromes, coronary artery disease, tissue factor, 14, and 612
- Language:
- English
- Description:
- Enhanced expression of tissue factor (TF) may result in thrombosis contributing to acute clinical consequences of coronary artery disease. Several studies demonstrated elevated plasma levels of TF in patients with acute coronary syndrome (ACS). The aim of our study was to compare the concentrations of TF in coronary sinus (CS), proximal part of the left coronary artery (LCA) and peripheral vein (PV) of patients with ACS and stable coronary artery disease (SCAD). Time course of the TF plasma levels in PV was followed on day 1 and day 7 after index event of ACS presentation and was compared to day 0 values. No heparin was given prior to the blood sampling. Twenty-nine patients in the ACS group (age 63.6±10.8 years, 20 males, 9 females) and 24 patients with SCAD (age 62.3±8.1 years, 21 males, 3 females) were examined. TF plasma level was significantly higher in patients with ACS than in those with SCAD (239.0±99.3 ng/ml vs. 164.3±114.2 ng/ml; p=0.016). There was no difference in TF plasma levels in PV, CS and LCA (239.0± 99.3 ng/ml vs. 253.7±131.5 ng/ml vs. 250.6±116.4 ng/ml, respectively). TF plasma levels tended to decrease only non-significantly on the day 7 (224.4± 109.8 ng/ml). Significant linear correlation between TF and high sensitivity CRP (hs-CRP) levels on day 0 was found. In conclusion, TF plasma levels are elevated in patients with ACS not only locally in CS but also in systematic circulation. Our data support the relationship between TF production and proinflammatory mediators., J. Bis ... [et al.]., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29980. Time-dependent analysis of composite steel-concrete beams using integral equation of Volterra, according EUROCODE-4
- Creator:
- Partov, Doncho and Kantchev, Vesselin
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- composite steel-concrete section, Volterra integral equations, rheology, and EUROCODE-4
- Language:
- English
- Description:
- The paper present analysis of the stress changes due to creep in statically determinate composite steel-concrete beam. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. and elastic law for the steel part and an integral-type creep law of Boltzmann-Volterra for the concrete part. For determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time t, Volterra integral equations of the second kind have been derived, on the basis of the theory of the viscoelastic body of Arutyunian-Trost-Bazant. Numerical method, which makes use of linear approximation of the singular kernal function in the integral equations is presented. Example with the model proposed is investigated. The creep functions is suggested by the 'CEB-FIP' models code 1990. The elastic modulus of concrete Ec(t) is assumed to be constant in time t. and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public