HIGH STRAIN RATE BEHAVIOUR OF AN AZ31 + 0.5 Ca MAGNESIUM ALLOY

<em>The paper reports behaviour of magnesium alloy AZ31 (nominal composition 3 % Al - 1 % Zn – balance Mg) with an addition of 0.5 wt. % Ca at high strain rates. Samples were prepared by the squeeze cast technology. Dynamic compression Hopkinson tests were performed at room temperature with impact velocities ranging from 11.2 to 21.9 m.s^-1. A rapid increase of the flow stress and the strain rate sensitivity was observed at high strain rates. Transmission electron microscopy showed extremely high dislocation density and mechanical twins of two types. Adiabatic shear banding is discussed as the reason for the observed behaviour at high strain rates.</em><span> </span

W-Cr solid solution: Comparison of alloying in SPS and by ball milling

Tungsten alloys currently represent prospective candidates to replace tungsten in the first wall applications in future fusion facilities. They are anticipated to suppress unfavorable mechanical properties of commercially pure tungsten and/or to gain advantages such as ability of self-passivation under accidental conditions. The self-passivating alloys are designed to minimize possible consequences related mainly to a LOCA (Loss of Coolant Accident) event with simultaneous air ingress into the reactor vessel. Please click Additional Files below to see the full abstract

The influence of different formulations and process parameters during the preparation of drug-loaded PLGA microspheres evaluated by multivariate data analysis

The main objective of this study was to evaluate the influence of the formulation and process parameters on PLGA microparticles containing a practically insoluble model drug (ibuprofen) prepared by the o/w solvent evaporation method. Multivariate data analysis was used. The effects of altered stirring speed of a mechanical stirrer (600, 1000 rpm), emulsifier concentrations (PVA concentration 0.1 %, 1 %) and solvent selection (dichlormethane, ethyl acetate) on microparticles characteristics (encapsulation efficiency, drug loading, burst effect) were observed. It was found that with increased stirring speed, the PVA concentration or the use of ethyl acetate had a significantly negative effect on encapsulation efficiency. In addition, ethyl acetate had an adverse effect on the burst effect, while the increased stirring speed had the opposite effect. Drug load was not affected by any individual variable, but rather by the interactions of evaluated variables

Silver Nanoparticles Stabilised by Cationic Gemini Surfactants with Variable Spacer Length

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition

Silver Nanoparticles Stabilized with Phosphorus-Containing Heterocyclic Surfactants: Synthesis, Physico-Chemical Properties, and Biological Activity Determination

Phosphorus-containing heterocyclic cationic surfactants alkyldimethylphenylphospholium bromides with the alkyl chain length 14 to 18 carbon atoms were used for the stabilization of silver nanodispersions. Zeta potential of silver nanodispersions ranges from +35 to +70 mV, which indicates the formation of stable silver nanoparticles (AgNPs). Long-chain heptadecyl and octadecyl homologs of the surfactants series provided the most intensive stabilizing effect to AgNPs, resulting in high positive zeta potential values and smaller diameter of AgNPs in the range 50-60 nm. A comparison with non-heterocyclic alkyltrimethylphosphonium surfactants of the same alkyl chain length showed better stability and more positive zeta potential values for silver nanodispersions stabilized with heterocyclic phospholium surfactants. Investigations of biological activity of phospholium-capped AgNPs are represented by the studies of antimicrobial activity and cytotoxicity. While cytotoxicity results revealed an increased level of HepG2 cell growth inhibition as compared with the cytotoxicity level of silver-free surfactant solutions, no enhanced antimicrobial action of phospholium-capped AgNPs against microbial pathogens was observed. The comparison of cytotoxicity of AgNPs stabilized with various non-heterocyclic ammonium and phosphonium surfactants shows that AgNPs capped with heterocyclic alkyldimethylphenylphospholium and non-heterocyclic triphenyl-substituted phosphonium surfactants have the highest cytotoxicity among silver nanodispersions stabilized by the series of ammonium and phosphonium surfactants

Demotivation of medical staff in the selected health facility in Slovakia

The biggest challenges for today’s businesses and facilities in ministries (health, education, defence, police, etc.) are to constantly increase their effectiveness. The quality and efficiency of each business are above all quality employees. They should be as satisfied and motivated as possible to their work performance. This requires careful and funded leadership by properly prepared and carefully considered managers. Providing excellent employee work performance is beneficial to the enterprise/organization and workers themselves. Nowadays, when employees are an integral part of a knowledge-based business/organization, there is a progress that cannot be achieved without development of the workforce. Although educated people work in the healthcare facility under investigation, it is not always possible to achieve a synergy effect based on excellent work performance and successful system management of the given healthcare facility. Managerial readiness and knowledge of factors affecting employee satisfaction and motivation enables them to prepare an appropriate incentive program that can influence the behaviour of individuals or workgroups towards to develop and effectively use the potential of employees, their responsible and quality work, considering their personal goals, and also the interest in the entire facility. Motivation/demotivation of healthcare personnel are frequently discussed issue in relation to healthcare policy making and overall health performance. The quality of health care and the performance of healthcare providers depend not only on the level of education, but also on the willingness and motivation of healthcare professionals. Even in a relatively stable environment, it is necessary to examine what contributes to the motivation of individual workers and what their behavioural patterns are. While motivation is generally paid great attention, in the healthcare system, research is mainly carried out on its performance and relatively few studies relate only to the field of motivation of healthcare professionals. The authors’ ambition is to present research on this topic and to introduce some measures that could contribute to improving the motivation systém of healthcare personnel in Slovakia. In a sense, we have tried to briefly compare the similarity of the system of healthcare motivation in Slovakia to systems in selected, mainly developed countries