Untersuchung über die agglomeration von polymerisatlatices

Different polymer latices are often incompatible, even when the emulsifying agent is the same in each. If one polymer has a proportion of hydrophilic groups (type ?A”? latex) and the other does not (type ?S”? latex), a mixture of the two latices may coagulate within seconds of mixing. Quite small proportions of type ?A”? will cause agglomeration of the particles of a type ?S”? latex. If 1% of a latex prepared from ethyl acrylate and acrylic acid (95:5) is added to a poly(butylacrylate) latex, D?_w, = 800 Å, and the pH is adjusted to 8–9, the resulting latex is characterized by D?_n, = 6300 Å, D?_w, = 7300 Å; addition of any given type ?S”? latex increases the average particle size still more. The mechanisms involved were studied by observing changes in particle size distribution, by the use of polymerizable dyes as markers, and by electron microscopy. The results of these investigations are : The latices are protected only in some respect by the emulsifier. The protective ionic doublelayer formed by the emulsifier around a type ?S”? particle repels other particles, but not type ?A”? particles. If a collision occours between particles of type ?A”? und type ?S”? they stick together; this process is repeated as often as a type ?S”? particle hits the surface of ?A”?. All the type ?S”? particles of the associate combine to one big particle in such a way that the ?A”? particle stays at the surface and remains active for further agglomeration.     

Covalent binding of a selective agonist irreversibly activates guinea pig coronary artery A2 adenosine receptors

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that persisted unchanged when agonist administration continued for up to 165 min, but promptly faded when the agent was withdrawn.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.     

Features of the transformation of Hg by heterogeneous photocatalysis over TiO2

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 Hg^II 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.     

Spatial contiguity, not cue-to-consequence, is the issue in taste-potentiated noise-illness associations: Comment on Holder, Bermudez-Rattoni, and Garcia (1988).

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)     

Design of a solar plant for processing honey

This paper presents the concept and design of a honey processing plant for a rural area in Central Argentina. This requires a heating process with a maximum temperature of 70°C for which solar energy is highly suitable. Flat plate collectors are connected to horizontal storage and processing tanks to achieve a passive system without auxiliary energy requirements. The simple operation of the low cost plant allows the processing of a high quality product with unskilled labour. The general characteristics of the plant are presented together with details and dimensions of the components in addition to a cost-benefit analysis. Technical features of this solar energy application and the social and economic benefits are considered in the conclusions.     

Application of Ross' equation for prediction of water activity in intermediate moisture food systems containing a non-solute solid

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.     

Transverse vibrations of a beam elastically restrained at one end and with a mass and spring at the other subjected to an axial force

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.