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The directions of the dipole moments in esters RCOOR' in which R and R' are alkyl or aryl groups have been deduced by analysis of experimental values of dipole moments of six compounds containing two polar groups, one or both of which are esters. New determinations of molecular dipole moments are reported for dimethyl truns-1,4-cyclohexanedicarboxylate and for truns-l,4-cyclohexanediol diacetate. The moment of the ester group is directed (in the positive sense) at an angle 73 = 123 f 3" from the R-CO axis in both aromatic and aliphatic esters, formates excepted.

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Besides its high osteoinductive properties, hydroxyapatite (HAp) exhibits a relatively low mechanical strength. In order to improve the mechanical properties and reliability of HAp based composites, the addition of selected polymers is highly recommended. The main objective of this work is to study the microstructural characteristics of HAp/poly-L-lactide (PLLA) composites obtained by cold or hot processing. The composites were prepared from a mixture of a chloroform solution of poly-L-lactide with granulated HAp. After elimination of chloroform by vacuum evaporation, dense compacts were obtained by cold or hot pressing. The pressing pressure ranged from 98.10 to 294.3 MPa for both cold and hot pressing. The hot pressing was performed in the temperature region 293-457 K for a time period of 15-60 min. Depending on the PLLA amount and the pressing procedure it is possible to obtain highly porous or nearly fully dense composites. The scanning electron microscopy examination of fracture as well as of free surfaces revealed that the final porosity and wetting are affected to a great extent by the synthesis conditions and amount of polymer added. An increase in temperature to 457 K for a longer period of time results in fully dense compacts. The formation of a nearly continuous polymer network that leads to the hardening of HAp has also been observed. However, it should be pointed out that some layers of HAp may be free of polymer film since PLLA penetrates more deeply into the porous HAp.

The rheological model is developed to elucidate the mechanism of Ca-alginate microbead deformation in the course of cell growth within. It is a complex process influenced by relaxation of the expanded polymer network inside a bead, and forces generated by cell growth inside the bead and interactions between solvent, network parts and cells as well. The resulting effects are measured experimentally by estimating isotropic volumetric deformations of beads with yeast cells as function of time and cell concentration per bead. The mathematical model of the process is developed based on a modified general Zener model with fractional derivatives. It is particularly suitable for incorporating effects of different nature also during different stages of such complex process development. The results of theoretical analyses using the model developed and comparison with experimental values obtained, indicate a high impact of partial decomposition, i.e. plastic response of polymer network inside a bead due to cell growth, on bead deformation. For comparison, corresponding deformation measurements and modelling were performed on the same network system exposed to swelling in the solvent, but without the cells. In this case elastic forces are dominant, indicating different mechanism of relaxation without the influence of cells, in agreement with previous conclusions.

The uppermost layer of the ocean, the sea surface microlayer (ML), covers more than 70 % of the world's surface. It is a sink for natural and anthropogenic material that determines its chemical composition. This article is aimed at providing novel data on the characterization of organic matter in ML and underlying waters (ULW) in the rarely investigated subarctic, north that organic substances in the films were mainly produced in the subsurface water. There was negligible fractionation of hydrophobic substances to the microlayer and even depletion of fatty acids was found in some ML samples. Fjords' surface waters were found to be very rich in fatty acids in July, up to 188 g/l, with high contributions of polyunsaturated compounds.The enrichment of DOC and SAS concentrations in the ML as compared to the ULW was in the range of 1.2 -2.8, while higher enrichment factors (1.3 -5.1) were determined for copper complexing ligands, indicating increased contribution of hydrophilic, lower molecular weight molecules. The detected characteristics and concentrations of organic substances in the surface microlayer and adjacent subsurface water differ for each month of sampling.Gašparović, Blaženka; Plavšić, Marta; Ćosović, Božena; Saliot, Alain. Organic matter characterization in the sea surface microlayers in the subarctic Norwegian fjords region. // Marine Chemistry.

In this work, the redox processes of copper ions were studied by electrochemical methods in NaCl and NaC10, solutions in the absence or in the presence of nonionic surfactant Triton X-100 (T-X-100). The enhancement of the anodic peak current of copper in the presence of T-X-100 in sodium chloride solutions was observed depending on the concentrations of T-X-100 and copper (11) ions. This is the consequence of destabilization of the otherwise stabile CuCly complex in chloride solutions by the presence of T-X-100. The process involves disproportionation of formed copper (I) species to copper (0) and copper (11).