Physicochemical Investigations of Hydrogels Containing Gold Nanoparticles Designed for Biomedical Use

Currently, many investigations are being performed to develop dressing materials with a positive effect on the wound healingprocess. In general, innovative dressings should ensure wound exudate absorption, constitute an external barrier limiting thepossibility of wound contamination and, importantly, also provide therapeutic properties. This work is focused on obtainingmaterials with potential use as dressings for treatment of difficult-to-heal wounds. The synthesis methodology of acrylic hydrogelsmodified with selected modifiers, i.e. arabic gum, nanogold, bee pollen and chamomile extract, was developed. Next, thesorption properties of the materials were determined as well as their behavior during the incubation in fluids imitating theenvironment of the human body. Additionally, the impact of such an incubation on their structure was evaluated by FT-IR spectroscopy.It was proved that the modifiers affected the sorption properties of hydrogels, i.e. samples with additives showed evenapprox. 2.5-fold lower swelling ability. In turn, incubation of hydrogels in simulated body fluids did not cause any rapid changesin pH, which may indicate the biocompatibility of the tested materials with the tested fluids. Thus, it may be concluded that thedeveloped materials show great application potential for biomedical purposes and may be subjected to more advanced studiessuch as cytotoxicity assessments towards selected cell lines.

Thermal Insulation Of The Foundation Walls Of Buildings And Calculation Of Its Thickness

If the surface temperature of any building material drops sharply without changing the humidity and the surface temperature is lower than the dew point temperature, dew-like water droplets are formed on the surface of this material. This condition is called condensing humidity condition. Condensation moisture formed on the surfaces of building materials and external barriers is slowly absorbed into the body of building materials over time, increasing the relative humidity of this structure. Condensation moisture can be observed when the temperature of the surfaces of external barrier structures drops sharply. This condition can be observed everywhere where the basement is connected to the outer walls of the basement. The article deals with the issue of thermal insulation and calculation of basement walls of modern energy-efficient buildings, which are widely used in the country and abroad.

Exceptionally preserved ‘skin’ in an Early Cretaceous fish from Colombia

Studies of soft tissue, cells and original biomolecular constituents preserved in fossil vertebrates have increased greatly in recent years. Here we report preservation of ‘skin’ with chemical and molecular characterization from a three-dimensionally preserved caudal portion of an aspidorhynchid Cretaceous fish from the equatorial Barremian of Colombia, increasing the number of localities for which exceptional preservation is known. We applied several analytical techniques including SEM-EDS, FTIR and ToF-SIMS to characterize the micromorphology and molecular and elemental composition of this fossil. Here, we show that the fossilized ‘skin’ exhibits similarities with those from extant fish, including the wrinkles after suffering compression stress and flexibility, as well as architectural and tissue aspects of the two main layers (epidermis and dermis). This similarity extends also to the molecular level, with the demonstrated preservation of potential residues of original proteins not consistent with a bacterial source. Our results show a potential preservation mechanism where scales may have acted as an external barrier and together with an internal phosphate layer resulting from the degradation of the dermis itself creating an encapsulated environment for the integument.

Reverse logistics in the Czech Republic: Barriers to development

The article presents empirical survey results concerning two objectives. The first objective was to describe barriers of reverse logistics (RL) development in Czech companies. The other one was to research whether there are different views of these barriers between company experts and top managers. The analyses are based on data obtained through a questionnaire survey of 102 representatives of companies operating in the Czech Republic. The study applied basic statistical methods used in quantitative research.Based on answer frequencies of respondents, the main internal barrier of RL development is its little importance in comparison with other activities, followed by the lack of systematic management, and unskilled workforce. On the other hand, customers are regarded as the most significant external barrier due to their careless handling with products and packaging as well as their pressure on the sale price. The obtained data also speak volumes about the differences in the view of the RL importance (in the second part of the article). Employees whose work is directly connected with reverse flows report the insignificance of RL as a barrier less frequently than top managers, who quoted this opinion in 50% cases.

A Protein Kinase from Colletotrichum trifolii Is Induced by Plant Cutin and Is Required for Appressorium Formation

When certain phytopathogenic fungi contact plant surfaces, specialized infection structures (appressoria) are produced that facilitate penetration of the plant external barrier; the cuticle. Recognition of this hydrophobic host surface must be sensed by the fungus, initiating the appropriate signaling pathway or pathways for pathogenic development. Using polymerase chain reaction and primers designed from mammalian protein kinase C sequences (PKC), we have isolated, cloned, and characterized a protein kinase from Colletotrichum trifolii, causal agent of alfalfa anthracnose. Though sequence analysis indicated conserved sequences in mammalian PKC genes, we were unable to induce activity of the fungal protein using known activators of PKC. Instead, we show that the C. trifolii gene, designated LIPK (lipidinduced protein kinase) is induced specifically by purified plant cutin or long-chain fatty acids which are monomeric constituents of cutin. PKC inhibitors prevented appressorium formation and, to a lesser extent, spore germination. Overexpression of LIPK resulted in multiple, abnormally shaped appressoria. Gene replacement of lipk yielded strains which were unable to develop appressoria and were unable to infect intact host plant tissue. However, these mutants were able to colonize host tissue following artificial wounding, resulting in typical anthracnose lesions. Taken together, these data indicate a central role in triggering infection structure formation for this protein kinase, which is induced specifically by components of the plant cuticle. Thus, the fungus is able to sense and use host surface chemistry to induce a protein kinase-mediated pathway that is required for pathogenic development.

Pricing Multi-Asset Options with an External Barrier

An external barrier of an option contract is a stochastic variable which determines whether the option is knocked in or out when the value of the variable is above or below some predetermined level, but itself is not the price of an asset which underlies the option. In this paper, we present analytic formulation for the valuation of European options on one or multiple assets with single external barrier, where the barrier level can be exponential. As the domain of the problem becomes semi-infinite due to the presence of the external barrier, we employ the method of images to find the Green function of the governing differential equation. An efficient and accurate fractional step finite difference scheme is proposed for the numerical valuation of these barrier options.