Studies of a weak polyampholyte at the air-buffer interface: The effect of varying pH and ionic strength

We have carried out experiments to probe the static and dynamic interfacial properties of $\beta$--casein monolayers spread at the air-buffer interface, and analysed these results in the context of models of weak polyampholytes. Measurements have been made systematically over a wide range of ionic strength and pH. In the semi-dilute regime of surface concentration a scaling exponent, which can be linked to the degree of chain swelling, is found. This shows that at pH close to the isoelectric point, the protein is compact. At pH away from the isoelectric pH the protein is extended. The transition between compact and extended states is continuous. As a function of increasing ionic strength, we observe swelling of the protein at the isoelectric pH but contraction of the protein at pH values away from it. These behaviours are typical of a those predicted theoretically for a weak polyampholyte. Dilational moduli measurements, made as a function of surface concentration exhibit maxima that are linked to the collapse of hydrophilic regions of the protein into the subphase. Based on this data we present a configuration map of the protein configuration in the monolayer. These findings are supported by strain (surface pressure) relaxation measurements and surface quasi-elastic light scattering (SQELS) measurements which suggest the existence of loops and tails in the subphase at higher surface concentrations.Comment: Submitted to J. Chem. Phy

Maximal small extensions of o-minimal structures

A proper elementary extension of a model is called small if it realizes no new types over any finite set in the base model. We answer a question of Marker, and show that it is possible to have an o-minimal structure with a maximal small extension. Our construction yields such a structure for any cardinality. We show that in some cases, notably when the base structure is countable, the maximal small extension has maximal possible cardinality.Comment: 6 pages. To appear in Mathematical Logic Quarterl

Happy 70th birthday, Professor Sarkyt E. Kudaibergenov

Article featuring research career and main achievements of Prof Sarkyt E. Kudaibergenov to celebrate his 70th Anniversar

Properties of Langmuir-Blodgett Films Based on Organosoluble Polyelectrolyte-Surfactant Complex and Oxazine Dye

Preparation procedure of organosoluble stoichiometric polycomplex based on cationic polyelectrolyte and anionic surfactant has been described. It was shown the formation of mixed monolayers consisting of polyelectrolyte-surfactant complex and dye molecules at the water-air interface. Assembling conditions of fluorescent nanosized solid Langmuir-Blodgett films based on polycomplex and dye Nile Red were defined and the spectral-luminescent properties of obtained films were studied. Absorption and fluorescence spectra of mixed Langmuir-Blodgett films revealed that electrostatic interaction between polycomplex and dye molecules is responsible for formation of dimers. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3500

On low-frequency vibrations of a composite string with contrast properties for energy scavenging fabric devices

Free vibrations of a two-component string with high-contrast material parameters are considered at different boundary conditions to illustrate the very low-frequency energy harvesting capability of fabric devices. It is revealed that, only for the case of mixed boundary conditions, low-frequency (locally) almost rigid-body vibrations are admissible, provided that material parameter ratios lie in some well defined interval. A low-frequency perturbation procedure is carried out to determine the eigenfrequencies as well as the eigenforms. The analysis is extended to a piecewise inhomogeneous string and to a string supported on an elastic foundation. It is shown that both situations may still admit low-frequency vibrations, under certain restrictions on the material properties. This is particularly remarkable given that the situation of elastic support normally possesses two nonzero cutoff frequencies. The results may be especially relevant for energy scavenging fabric devices, where very low-frequency (< 10 Hz) mechanical vibrations of textile fibers are harvested through friction

Preparation, Characterization and Catalytic Activity of Gold Nanoparticles Stabilized by Hydrophilic Polymers

Optical properties, structure, size and morphology of colloidal gold nanoparticles (AuNPs) stabilized by a series of hydrophilic polymers possessing nonionic, anionic, cationic and amphoteric nature were characterized by visible spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electron microscopy (SEM), transmission electron microscopy (TEM). The polymer-protected AuNPs were prepared by “one-pot” synthetic protocol. The kinetics of formation of AuNPs was determined. The influence of the molecular weight (Mw) of polymers and concentration of AuNPs on the size of AuNPs was shown. The catalytic activity of polymer-protected AuNPs with respect to hydrogenation of 4-nitrophenol was studied. High conversion degree of 4-nitrophenol to 4-aminophenol was evaluated by visible spectroscopy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3503

Near-resonant regimes of the moving load on a pre-stressed incompressible elastic half-space

The article is concerned with the analysis of the problem for a concentrated line load moving at a constant speed along the surface of a pre-stressed, incompressible, isotropic elastic half-space, within the framework of the plane-strain assumption. The focus is on the near-critical regimes, when the speed of the load is close to that of the surface wave. Both steady-state and transient regimes are considered. Implementation of the hyperbolic-elliptic asymptotic formulation for the surface wave field allows explicit approximate solution for displacement components expressed in terms of the elementary functions, highlighting the resonant nature of the surface wave. Numerical illustrations of the solutions are presented for several material models

Mucoadhesive Properties of Gellan and Its Modified Derivatives

This review is devoted to recent achievements in the development of macromolecular therapeutic systems with the participation of a polysaccharide, gellan, that possesses conformational and sol–gel transitions. The main attention is paid to the mucoadhesive properties of gellan and its derivatives. Various applications of gellan in biotechnology, bioengineering, and nanomedicine are briefly considered.Peer reviewe

Layer-by-Layer Thin Films and Coatings Containing Metal Nanoparticles in Catalysis

The layer-by-layer (LbL) technique is one of the most promising ways of fabricating multilayer thin films and coatings with precisely controlled composition, thickness, and architecture on a nanometer scale. This chapter considers the multilayer thin films and coatings containing metal nanoparticles. The main attention was paid to LbL films containing metal nanoparticles assembled by convenient methods based on the different intermolecular interactions, such as hydrogen bonding, charge transfer interaction, molecular recognition, coordination interactions, as driving force for the multilayer buildup. Much attention has paid to the LbL films containing metal nanocomposites for multifunctional catalytic applications, in particular, photocatalysis, thermal catalysis, and electrocatalysis. The preparation protocol of LbL-assembled multilayer thin films containing metal nanoparticles (such as Au, Ag, Pd, Pt), metal oxides (Fe3O4), and sulfides (CdS) that are supported on the various surfaces of nanotubes of TiO2, Al2O3 membranes, graphene nanosheets, graphene oxide and further applications as catalysts with respect to photocatalytic, electrocatalytic performances is discussed. The systematization and analysis of literature data on synthesis, characterization, and application of multilayer thin films and coatings containing metal nanoparticles on the diverse supports may open new directions and perspectives in this unique and exciting subject