Flow-driven Surface Instabilities of Tubular Chitosan Hydrogel

Spatial structures break their symmetry under the influence of shear stress arising from fluid flow. Here, we present surface instabilities appearing on chitosan tubes when an acidic solution of chitosan with various molecular weight is injected into a pool of sodium hydroxide solution. At slow flow rates wrinkle-to-fold transition takes place along the direction of the flow yielding a banded structure. For greater injection rates we observe coexisting modes of wrinkles and folds which are stabilized to periodic wrinkles when the alkaline concentration is increased. The instabilities are characterized by the scaling laws of the pattern wavelength and amplitude with the tube characteristics. Our experimental adaptation of mechanical instabilities provides a new in situ method to create soft biomaterials with the desired surface morphology without the use of any prefabricated templates.     

Complexation of small molecules by open-ended resorcarene hosts

[structure: see text] Sterically hindered tetraaminomethylated resorcarenes form inclusion complexes in CDCl(3) with acetonitrile and acetaldehyde, which are kinetically stable on the NMR time scale at 233 K.     

Spectroscopy of the hyperfine structure of antiprotonic 4He and 3He

The spin magnetic moment $\mu^{\overline{p}}_{s}$ of the antiproton can be determined by comparing the measured transition frequencies in $\overline{p}^4$ He^?+? with three-body QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as $\mu^{\overline{p}}_{s} = -2.7862(83)\mu_{N}$ , slightly better than the previously best measurement. This agrees with $\mu^{p}_{s}$ within 0.24%. In 2009, a new measurement with antiprotonic ³He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on $\overline{p}^3$ He^?+?. We report here on the new experimental setup and the first tests.     

Ra in geothermal and bottled mineral waters of Hungary

Geothermal waters have been used on a large scale for bathing, drinking and medical purposes, while the consumption of bottled mineral waters is increasing. In this work, radon and radium activity concentrations of thermal and bottled mineral waters, originating from different regions of Hungary, were studied by different radioanalytical methods. It was found that the thermal springs, which supply the world famous baths of Budapest along the right riverside of the Danube, have high ²²²Rn and ²²⁶Ra activity concentration: up to about 100 and 1 kBqm⁻³, respectively. The radium content of some investigated geothermal waters found in the NE region of the Great Hungarian Plain is even higher: up to several kBqm⁻³. The ²²⁶Ra content of bottled mineral waters, commercially available in Hungary, was determined by gamma-spectrometric method, applying radiochemical separation. The highest value exceeded 2 kBqm⁻³ in the case of the Apenta mineral water, which is a popular brand in Hungary, as well as in Europe and North America.     

On product of association schemes and Shannon capacity

In this paper we will define the product of two association schemes and using the fact that the strong product of two graphs from two (possibly different) association schemes is in the product of the association schemes, we give a new proof of Schrijver's result on the Shannon capacity of graphs in association schemes. In particular, this will give a new proof of the fact that the Shannon capacity of the pentagon is √5.     

On the models of Coulomb capture of negative particles

Various models of atomic capture of negative mesonic particles are tested against 321 experimental Coulomb-capture ratios, measured on binary systems: gas mixtures, alloys and simple compounds. The comparison has shown that the general agreement between theory and experiment is not satisfactory. We tried to improve on the models by introducing adjustable parameters to be estimated by fitting the experimental data. The predictions of the model proposed by Schneuwly, Pokrovsky and Ponomarev (SPP) are closest to the atomic capture ratios for alloys and compounds while the data measured in gas mixtures are better approximated by the empirical formula of Vasilyev et al. The theoretical formula of Daniel fails in describing the capture in the light elements.     

Relative rate coefficients of⊙OH-radical interactions in nonaqueous medium

For measuring relative rate coefficients of OH-radical reactions in organic media a competitive method has been used. As reference, 2-propanol was applied. For ethylbenzene and 1-phenylethanol the rate coefficients of H-abstraction relative to that of 2-propanol are 1.4 and 2.9, respectively.

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OH. 2-. H 1-, 2-, 1,4 2,9, .

     

Pion study of hydrogen bonds of water in chemical systems

The use of the pion capture method in structural chemistry is demonstrated by experiments performed in Dubna on various hydrogen-bonded chemical systems: pure water and ammonia in solid, liquid, and gaseous phases; aquacompiexes; and solutions of acids and salts. The experimental information, the capture probability of stopped ^– mesons by protons, is related to the electron density near the proton in the molecule.