Experiments employing guinea pig heart Langendorff preparations compared the coronary vasoactivity of a functionalized congener of adenosine, 2-[(2-aminoethyl-aminocarbonylethyl)phenylethylamino]-5'-N-e thyl- carboxamidoadenosine, APEC, with the vasoactivity of the product of the reaction of APEC with 1,4-phenylene-diisothiocyanate, 4-isothiocyanatophenylaminothiocarbonyl-APEC (DITC-APEC). Previous experiments showed that whereas APEC binds reversibly to the A2A adenosine receptor of brain striatum, DITC-APEC binds irreversibly. APEC caused concentration-dependent coronary vasodilation that persisted unchanged when agonist administration continued for up to 165 min, but promptly faded when the agent was withdrawn. The unselective adenosine receptor antagonist 8-(4-sulfophenyl)theophyline (8-SPT) antagonized the vasoactivity of APEC. By contrast, DITC-APEC (0.125-1.0 nM) caused progressive, concentration-independent vasodilation that persisted unchanged for as long as 120 min after the agent was stopped and that was insensitive to antagonism by subsequently applied 8-SPT. However, perfusion of the heart with buffer containing 0.1 mM 8-SPT strongly antagonized the coronary vasodilatory action of DITC-APEC given subsequently. Such observations indicate that the covalent binding of DITC-APEC causes irreversible activation of the guinea pig coronary artery A2A adenosine receptor. Neither APEC nor DITC-APEC appeared to desensitize the coronary adenosine receptor during two or more hours of exposure to either agonist. 相似文献
UV/TiO2 photocatalysis of 0.5 mM mercuric aqueous solutions has been analyzed starting from Hg(NO3)2, Hg(ClO4)2 and HgCl2 at different pH (3, 7 and 11) and in the presence or absence of oxygen. Profiles of HgII concentration with time were characterized by a relatively rapid initial conversion followed by a decrease or an arrest of the rate, the shape of profiles changing with the conditions. Conversions at 60 min and initial quantum efficiencies have been found dependent on the initial conditions and type of mercuric salt. The faster transformation took place at pH 11 for all salts. A good transformation yield is observed also for HgCl2, which behaves differently to the other two salts, at pH 3 under nitrogen and pH 7 (N2 or O2). Inhibition by oxygen was observed in acid and neutral media but not at basic pH. When the conversion was 50% or more, pale or dark gray solids were deposited on the catalyst, identified as mixtures of Hg0, HgO or Hg2Cl2. A unique kinetic scheme could not be defined, which seemed to depend on the nature of the mercury salt, the ambient conditions and the type of deposit. Implications of the application of the technique to real systems are discussed. 相似文献
M. D. Holder et al (see record 1988-28622-001) allege to have failed to corroborate findings from our laboratory (S. R. Ellins et al and Ellins and S. von Kluge; see PA, Vols 73:3082 and 74:24095) that taste-potentiated noise–illness associations can be established under conditions of spatial contiguity. We maintain that Holder et al have provided additional experimental support for our contention that spatial contiguity is an important factor in the taste-potentiation of nongustatory stimuli. In addition, we take issue with their conclusion that the results of our research are incompatible with the conditioning principle of cue-to-consequence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
This work investigates the use of the Ross (1975) equation for the prediction of water activity (a), in aqueous electrolyte or non-electrolyte solutions to which a non-solute (casein) was added. Water activity of the ternary mixtures (casein-water-solute) was in the range of a, = 0.85-0.90 which is of interest for the development of intermediate moisture foods for human consumption. It was found that the use of the Ross equation coupled with a correction for the water strongly bound to casein gives good predictions of a. 相似文献
This paper deals with the exact solution of the title problem. The classical theory of vibrations of beams is used and a tabulation of eigenvalues is presented as a function of some of the governing mechanical parameters.The problem is of basic interest in several areas of engineering, specially to nuclear reactor systems designers since in many instances pumps or other electromechanical arrangements are placed at the end of a clamped beam. 相似文献
In this work various methods concerning the determination of compatibility of polymers are discussed. The conclusion is, that the earlier proposed “kinetical” method, besides the method of phase separation in common solution, is one of the surest methods of compatibility determination for polymers. However, over the latter, the kinetical method offers the advantage of rapidity and the possibility to predict the thermostability, the interactions of functional groups and the formation of solution in the solide state. While the interaction of functional groups may be established also by IR-spectroscopy, the other methods permit no conclusions of this kind. Generally it is very difficult to make statements on the formation of solution in the solid state on the basis of other methods of compatibility investigation. Quite useless, at least for our polymer mixtures, are the measurements of viscosity in concentrated as well as in dilute polymer solutions. 相似文献
Computational models, such as simulations, are central to a wide range of fields in science and industry. Those models take input parameters and produce some output. To fully exploit their utility, relations between parameters and outputs must be understood. These include, for example, which parameter setting produces the best result (optimization) or which ranges of parameter settings produce a wide variety of results (sensitivity). Such tasks are often difficult to achieve for various reasons, for example, the size of the parameter space, and supported with visual analytics. In this paper, we survey visual parameter space exploration (VPSE) systems involving spatial and temporal data. We focus on interactive visualizations and user interfaces. Through thematic analysis of the surveyed papers, we identify common workflow steps and approaches to support them. We also identify topics for future work that will help enable VPSE on a greater variety of computational models. 相似文献
Urban environments, university campuses, and public and private buildings often present architectural barriers that prevent people with disabilities and special needs to move freely and independently. This paper presents a systematic mapping study of the scientific literature proposing devices, and software applications aimed at fostering accessible wayfinding and navigation in indoor and outdoor environments. We selected 111 out of 806 papers published in the period 2009–2020, and we analyzed them according to different dimensions: at first, we surveyed which solutions have been proposed to address the considered problem; then, we analyzed the selected papers according to five dimensions: context of use, target users, hardware/software technologies, type of data sources, and user role in system design and evaluation. Our findings highlight trends and gaps related to these dimensions. The paper finally presents a reflection on challenges and open issues that must be taken into consideration for the design of future accessible places and of related technologies and applications aimed at facilitating wayfinding and navigation.
In this paper a hybrid control scheme is devised in order to regulate traffic conditions in freeway systems. The considered
control actions are ramp metering, i.e. using traffic lights at the on-ramps in order to regulate incoming traffic, and variable
speed limits to be displayed on on-road variable message signs. The proposed scheme is composed of two levels: the lower level
is characterized by different Model Predictive Control regulators, whereas at the higher level the different control actions
are chosen according to a discrete-event dynamics. The overall scheme is then represented with the formalism of discrete-time
discrete-event automata. More in detail, at the lower level, the prediction model used in the Model Predictive Control schemes
is the first-order dynamical model of traffic flow in which we approximate the steady-state speed-density characteristic as
a piecewise constant function. This approximation is motivated by the fact that we need a simpler finite-horizon problem to
be solved on line, that in this case becomes a Mixed-Integer Linear programming problem. Depending on the system operating
conditions, different regulators are determined by means of suitable Model Predictive Control schemes. The higher level of
the control scheme has the function of identifying the present operating conditions and then switching to the suitable control
action. The reported numerical results show the effectiveness of the proposed hybrid control framework. 相似文献