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

Chitosan/Poly(2-ethyl-2-oxazoline) films with ciprofloxacin for application in vaginal drug delivery

Chitosan (CHI) and chitosan/poly(2-ethyl-2-oxazoline) (CHI/POZ)-based films were prepared by casting from aqueous solutions of polymer blends with different compositions. Ciprofloxacin was used as a model drug in these formulations. The weight, thickness, folding endurance and transparency of blend films were measured and characterised. All films had a uniform thickness (0.06 ± 0.01 mm) and exhibited sufficient flexibility. The surface pHs of films ranged from 3.76 ± 0.49 to 4.14 ± 0.32, which is within the pH range suitable for vaginal applications. The cumulative release of the drug from the films in experiments in vitro was found to be 42 ± 2% and 56 ± 1% for pure CHI and CHI/POZ (40:60) films, respectively. Drug-free chitosan/poly(2-ethyl-2-oxazoline) films showed weak antimicrobial activity against Escherichia coli. Drug-loaded CHI and CHI/POZ films showed good antimicrobial properties against both Gram-positive Staphylococcus aureus and Gram-negative bacteria Escherichia coli. Mucoadhesive properties of these films with respect to freshly excised sheep vaginal mucosa were evaluated using a tensile method. It was established that all films were mucoadhesive, but an increase in POZ content in the blend resulted in a gradual reduction of their ability to stick to vaginal mucosa. These films could potentially find applications in vaginal drug delivery

Catalytic Properties of Gel-Immobilized Gold Nanoparticles in Decomposition Of Hydrogen Peroxide

This paper reports the study of hydrogen peroxide decomposition catalyzed by polymer-protected gold nanoparticles (AuNPs) immobilized within polyacrylamide hydrogel. The stabilization of AuNPs was achieved using hydrophilic polymers. Embedding of AuNPs stabilized with various polymers into polyacrylamide hydrogels was carried out using three ways: “in situ” polymerization, sorption and boronhydride methods. Size, shape and morphology of AuNPs were characterized by various physicochemical methods

Synthesis and characterization of novel thermo- and salt-sensitive amphoteric terpolymers based on acrylamide derivatives

A novel linear amphoteric terpolymers based on neutral monomer - N-isopropylacrylamide (NIPAM), anionic monomer - 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), and cationic monomer - (3-acrylamidopropyl) trimethylammonium chloride (APTAC) were synthesized by free-radical polymerization in aqueous solution and characterized by methods of H-1 NMR and FTIR spectroscopy, TGA, GPC, Dynamic light scattering (DLS) and zeta-potential. The thermal and salt sensitivity of amphoteric ternary polymers of various compositions, particularly, [NIPAM]:[AMPS]:[APTAC] = 90:2.5:7.5; 90:5:5; 90:7.5:2.5 mol.% were studied in aqueous and aqueous-salt solutions in the temperature range from 25 to 60 degrees C and at the NaCl ionic strength. interval from 10(-3) to 1M. It was found that due to hydrophobic/hydrophilic balance, the temperature dependent conformational and phase change of macromolecular chains becomes sensitive to salt addition and allows the fine-tuning of the phase transition. In aqueous and aqueous-salt solutions, the average hydrodynamic size of amphoteric terpolymers is varied from 8 to 300 nm exhibiting bimodal distribution at room temperature. The number average (M-n) and weight average (M-w) molecular weights, polydispersity index (PDI), and zeta-potentials of amphoteric terpolymers in aqueous solutions were determined.Peer reviewe

Analysis of the influence of motivation on career management using the two-factor theory of Herzberg

The motivation theories play an important role in forming the human resource management system. Especially in modern organizations, Herzberg’s two-factor theory of motivation can be used to study and create a motivation system. Purpose: This article analyzes the relationship between the descriptive characteristics of respondents and hygienic / motivating factors, as well as the influence of these factors on career management of university staff and lecturers. The theoretical significance of the study lies in the fact that the analysis of the relationship between university staff and lecturers and the motivational processes of career management contributes to the HRM theory, to the development of mechanisms and trends in HR development.The practical significance of the study lies in the development of specific recommendations on motivation in order to improve the efficiency of managing the careers of university staff and lecturers.Methodology: To assess the respondent’s own opinion during data collection, it was used a method of questionnaire, compiled using a 5-point Likert scale. The survey results were coded and used in the SPSS Statistics program. Factor analysis, one-way ANOVA-test analysis and regression analysis were carried out. The value of the research: As a result of the study within the framework of the two-factor theory, it was found that both factors are important for the career development of staff and lecturers. In addition, the analysis of the relationship between motivation and personnel career management contributes to the research of scientists in this field and theories of human resource development.The practical value of the study: The motivating factors must be given more importance in order to achieve a positive result in career management. It is necessary to increase motivation and support the desire of personnel for development through the formation of fair and effective motivation practice

Synthesis and Characterization of Carboxymethylated Cornstarch

The aim of this study is preparation and characterization of carboxymethylated cornstarch (CMCS) for potential application as water based drilling fluids. The cornstarch was modified by sodium monochloroacetate. The structure of cornstarch and CMCS was established by H-1 NMR and FTIR spectroscopy. The degree of carboxymethylation of cornstarch determined by H-1 NMR spectroscopy was equal to 80%. The viscosity-average molecular weights (M-eta) of pristine cornstarch and CMCS calculated from Mark-Kuhn-Houwink equation [eta]=K-eta.M-a are equal to 2.15.10 (3) g.mol(-1) and 2.75.10(5 )g.mol(-1) respectively. The temperature dependent viscosity of CMCS was measured in water by Ubbelohde viscometer, while the rheological properties of CMCS in dependence of polymer concentration and ionic strength of the solution were evaluated by rheoviscometer. The thermal characteristics of samples were determined by differential scanning calorimeter (DSC) and thermogravimetric (TGA) and differential thermal analyzer (DTA). The morphological properties of cornstarch and CMCS were studied by scanning electron microscopy (SEM). The structural-mechanical, filtration and filter cake forming properties of drilling fluids and fluid loss indicators of CMCS were found.Peer reviewe

Polymer protected gold nanoparticles: synthesis, characterization and application in catalysis

This review discusses the stabilization of gold nanoparticles (AuNPs) by nonionic, anionic, cationic and amphoteric polymers. The protocols used for synthesis of AuNPs in aqueous and organic solvents are described. Size, shape and morphology of AuNPs are characterized by various physicochemical methods. Application aspects of polymer-protected AuNPs in catalysis are outlined

The use of Lewis acid AlCl3 as a promoter in the Pd-complex catalytic system of the cyclohexene hydroethoxycarbonylation reaction

This paper presents the results of detailed studies of the possibility of using Lewis acid AlCl3 as a promoter of the catalytic three-component system PdCl2(PPh3)2–PPh3–AlCl3 in the hydroethoxycarbonylation reaction of cyclohexene at low carbon monoxide pressures (2.5 MPa). As a result a high catalytic activity of the three-component system was established and the reaction proceeds regioselectively with the formation of ethyl ether of cyclohexanecarboxylic acid. The optimal conditions of the process have been elaborated (molar ratio of the starting reagents [Cyclohexene]:[Ethanol] = 1:1; molar ratio of the components of the catalytic system = = [PdCl2(PPh3)2]:[PPh3]:[AlCl3] = 1:6:9; carbon monoxide pressure PCO = 2.5 MPa; process temperature T = 120 °C and reaction time τ = 5 h) at which the target product yield reaches 80.7 %. To identify the obtained ethyl ester of cyclohexane carboxylic acid gas chromatographic analysis and mass- and IR- spectra were carried out. Based on the data obtained, a possible mechanism of the reaction route of cyclohexene carbonylation with carbon monoxide and ethanol in the presence of the three-component system PdCl2(PPh3)2–PPh3–AlCl3 is proposed and discussed

Synthesis of fluorescently-labelled poly(2-ethyl-2-oxazoline)-protected gold nanoparticles

Gold nanoparticles (GNPs) protected by poly(2-ethyl-2-oxazoline) (POZ) of different molecular weights (Mw = 5, 50, 200 and 500 kDa) were synthesised and characterised by dynamic light scattering, nanoparticle tracking analysis, zeta potential measurement and transmission electron microscopy. It was established that the use of POZ with 50 kDa resulted in formation of GNPs with low polydispersity while POZ with greater molecular weights led to formation of more polydisperse GNPs. Fluorescent labelling of these nanoparticles was achieved through their reaction with polyethyleneglycol dithiol (8-12 kDa) as a linker molecule with subsequent reaction with 6-(iodoacetamido) fluorescein. The fluorescent nature of obtained GNPs was confirmed by the appearance of the fluorescence peak at 510 nm that is typical for fluorescein molecules and glowing of the aqueous solution under the UV irradiaton. The fluorescently-labelled GNPs are promising tool in biomedical application to monitor the biological systems using fluorescent microscopy