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Struktura roztworów polimerowo-micelarnych

Malcher Tadeusz

Przemysł Chemiczny

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2020

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T. 99, nr 9

1342--1343

PL

Roztwory polimerowo-micelarne swoje właściwości zmniejszania oporów przepływu zawdzięczają strukturze wewnętrznej. Struktura ta powstaje najczęściej podczas zmieszania roztworu polimerowego z roztworem zawierającym środek powierzchniowo czynny.

EN

Fundamentals and review with 24 refs.

2

Optimality and sensitivity for semilinear bang-bang type optimal control problems

Felgenhauer U.

International Journal of Applied Mathematics and Computer Science

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2004

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Vol. 14, no 4

447-454

EN

In optimal control problems with quadratic terminal cost functionals and systems dynamics linear with respect to control, the solution often has a bang-bang character. Our aim is to investigate structural solution stability when the problem data are subject to perturbations. Throughout the paper, we assume that the problem has a (possibly local) optimum such that the control is piecewise constant and almost everywhere takes extremal values. The points of discontinuity are the switching points. In particular, we will exclude the so-called singular control arcs, see Assumptions 1 and 2, Section 2. It is known from the results by Agrachev et al. (2002) stating that regularity assumptions, together with a certain strict second-order condition for the optimization problem formulated in switching points, are sufficient for strong local optimality of a state-control solution pair. This finite-dimensional problem is analyzed in Section 3 and optimality conditions are formulated (Lemma 2). Using well-known results concerning solution sensitivity for mathematical programs in Rn (Fiacco, 1983) one may further conclude that, under parameter changes in the problem data, the switching points will change Lipschitz continuously. The last section completes these qualitative statements by calculating sensitivity differentials (Theorem 2, Lemma 6). The method requires a simultaneous solution of certain linearized multipoint boundary value problems.

3

Formy występowania oraz właściwości kationów metali w środowisku wodnym

Grzybkowski W.

Chemia i Inżynieria Ekologiczna

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2004

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Vol. 11, nr S2

151-164

PL

Dokonano przeglądu chemicznych, termodynamicznych i kinetycznych właściwości kationów metali w roztworach wodnych. Omówiono współczesne poglądy na strukturę hydratów, wymianę molekuł wody oraz hydrolizę soli. Zwrócono uwagę na kwasowość hydratów. Wskazano istotne związki między stanem koordynacyjnym soli w roztworach wodnych a właściwościami fizykalnymi roztworów. Omówiono formy wystepowania kationów metali w wodzie morskiej.

EN

Chemical, thermodynamic and kinetic properties of metal cations in aqueous solutions are presented and discussed in terms of structural factors controlling physical properties of the systems. Structure of hydrated cations, reaction mechanism of water exchange on the cations, hydrolytic phenomena and acidity of the cations are descibed. Correlations between coordination states of the salts in and bulk properties of the solutions are indicated. Elements of aquatic chemistry are presented.

4

The Study of Conformational Equilibrium of c[Gln-Trp-Phe-Gly-Leu-Met], a NK-2 Tachykinin Antagonist

Brzozowski K., Łęgowska A., Rodziewicz-Motowidło S., Liwo A., Rolka K.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 6

807-814

EN

Conformational studies of NK-2 tachykinin antagonist c[Gln-Trp-Phe-Gly-Leu-Met] were performed using a combination of two-dimensional NMR spectroscopy and theoretical methods. The three dimensional structure of the peptide studied was determined by global conformational search, using the EDMC method with the ECEPP/3 force field and subsequent calculation of statistical weights of the obtained conformations by fitting the theoretical NOESY spectra and vicinal coupling constants 3JNHH_ to the experimental ones. Using this approach, a set of six conformations with statistical weights higher than 3% was obtained. The first two ones with the values of statistical weights over 30% can be considered as dominant ones. The structure of the most populated conformation is stabilized by type IV _-turn around Trp7-Phe8 and a _-turn centered at Trp7. In the second one, two _ turns were found: II and III_ around Met11-Gln6 and Gln6-Trp7, respectively. In both conformations, the aromatic groups of Trp7 and Phe8 are almost perpendicularly oriented to the peptide backbone. The results obtained correlate well with those published for the peptide studied by three other groups. In contrast to the results obtained by other groups, which used interproton distances as constrains, the approach described here enables to determine the conformational equilibrium of the peptide studied.

5

Solution structure of Cu(II) complexes with spermine and nucleosides or nucleotides in ternary systems

Gąsowska A., Łomozik L., Brieger-Jarzębowska R.

Polish Journal of Chemistry

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1999

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vol. 73 nr 6

909-913

EN

The mode of coordination of the complexes formed in the systems Cu/spermine/nucleoside (or nucleotide) was proposed on the basis of the equilibrium and spectral studies. Significant differences were found in the coordination character of nucleosides and nucleotides. In the systems with adenosine or cytidine, mixed-ligand complexes are formed with the N5 type coordination. On the other hand, in the systems with their monophosphates, molecular complexes are formed with metal ions coordinated through monophosphates, molecular complexes are formed with metal ions coordinated through oxygen atoms from the phosphate groups. Spermine, left outside the inner coordination sphere, is involved in non-covalent interactions with nitrogen atoms from the nucleotide bases.