Use of UV photography to identify aflatoxin-producing strains ofAspergillus flavus andA. parasiticus

UV photography in glucose, yeast extract (GY) agar medium was tested as a simple and rapid method for the distinction of afiatoxin-positive from aflatoxin-negative strains ofAspergillus flavus andA. parasiticus. In the UV photographs aflatoxin-producing moulds were identified as grey or black colonies, whereas aflatoxin-non-producing moulds appeared as white colonies. Of the afiatoxin-positive strains detected by the UV photographic method, 10% was confirmed by extraction of the GY agar medium and mould mycelium in chloroform, extracts which were analysed subsequently using thinlayer chromatography. Confirmation of aflatoxigenic strains was achieved by biosynthesis on liquid medium yeast extract sucrose (YES) broth.     

An Analysis of Intermetallic Bonding between a Ring Carrier and an Aluminum Piston Alloy

This paper presents the results of an analysis of the formation of an intermetallic bond between a ring carrier and an aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) to increase the wear resistance of the first ring groove and is applied in highly loaded diesel engines. The most important thing is that the Ni-Resist (ferrous) must be bonded with a non-ferrous piston material during the casting of the piston. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that if the proper conditions are met, then the preparation of the ring carrier can be made successfully, as can the formation of the metal connection between the two materials of different qualities.     

Study of Eye Drops Dispensing and Dose Variability by Using Plastic Dropper Tips

ABSTRACT

The application of eye drops from flexible dropper bottles fitted with different types of dropper tips is associated with the high variability of eye drop weights. The aim of this report was to investigate the simultaneous effect of three factors influencing the mean weight of drops dispensing from two plastic dropper tips. Using a designed experiment (Box-Behnken), the effect of the concentration of benzalkonium chloride solutions (BAC) in the range of 0–0.02%, the dispensing angle from 90° to 30° from horizontal, and the residual volume of liquid in the dropper bottle from 4 to 10 mL on the mean drop weights were examined. The significant effect of the increase in BAC concentration resulted in a linear decrease in drop weights for both of the dropper tips investigated. The significant effect of the dispensing angle was influenced by the dropper tip design. For the dropper tip A, the effect of the dropper tip tilt was described by the quadratic equation with a minimum, which corresponded to the dispensing angle equal to that of 48° from horizontal. Below this angle, the increase in drop weights occurred due to the drop formation from the wetted external surface of the tip orifice. The linear decrease in drop weights in response to the decrease in dispensing angle was detected for the dropper tip B. The regression equations and the contour line plots obtained allowed the drop weights to be estimated for the actual combinations of both the BAC concentration and the dispensing angle. The effect of the residual volume was found to be non-significant. Based on the formula of Tate's law, the direct proportion between surface tension of a solution and the radius of the effective perimeter of a dropper tip can be used to estimate the theoretical maximal weight of drops at the dispensing angle of 90°. Using the stalagmometric values of surface tension of the BAC solutions, the maximal drop weights were estimated for both of the dropper tips investigated. A comparison between the theoretical and the experimentally measured drop weights enabled the dropper tips behavior to be discussed by using Harkins and Brown correction factor F. The F-value of 0.74 noted for the dropper tip A differed from that of stalagmometer F-value (0.61) indicating a deviation from the simple drop formation process in answer to more complicated design of the dropper tip A. On the other hand, the F-value of 0.6 observed for the dropper tip B demonstrated the better consistency with stalagmometry. As a result, the dropper tip B with the linear decrease of drop weights in response to the increased concentration of BAC and the decreased dispensing angle without the adverse external drop formation could be recommended in real drop dispensing.     

Grafting of gold nanoparticles and nanorods on plasma-treated polymers by thiols

Grafting of gold nanoparticles and nanorods on the surface of polymers, modified by plasma discharge, is studied with the aim to create structures with potential applications in electronics or tissue engineering. Surfaces of polyethyleneterephthalate and polytetrafluoroethylene were modified by plasma discharge and subsequently, grafted with 2-mercaptoethanol, 4,4′-biphenyldithiol, and cysteamine. The thiols are expected to be fixed via one of –OH, –SH or –NH₂ groups to reactive places on the polymer surface created by the plasma treatment. “Free” –SH groups are allowed to interact (graft) with gold nanoparticles and nanorods. Gold nano-objects were characterized before grafting by transmission electron microscopy and UV–Vis spectroscopy. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electrokinetic analysis (zeta potential determination) were used for the characterization of polymer surface at different modification phases. It was proved by FTIR and XPS measurements that the thiols were chemically bonded on the surface of the plasma-treated polymers, and they mediate subsequent grafting of the gold nano-objects. On the surfaces, modified polymers were indicated some objects by AFM, size of which was dramatically larger in comparison with that of original nanoparticles and nanorods. This result and the other results of UV–Vis spectroscopy indicate an aggregation of deposited gold nano-objects.     

Schimmelpilze in Lebensmitteln der Tschechoslowakei

Zusammenfassung Es wurde die Mykoflora von 13 527 g sensorisch unveränderten Lebensmitteln (Pulver) und von 22017 verschiedetien Proben sensorisch unveränderter, an der Oberfläche sterilisierter Körner und Nüsse untersucht.Aus den Proben wurden 147 027 Kolonien von 44 Schimmelpilzgattungen isoliert und identifiziert.Am häufigsten waren Kolonien vonPenicillium sp.,Aspergillus sp. undCladosporium sp. vertreten, weniger oft oder ganz seltenRhizopus sp.,Mucor sp.,Absidia sp.,Alternaria sp.,Circinella sp.,Trichoderma sp.,Botrytis sp.,Paecilomyces sp.,Geotrichum sp.,Syncephalastrum sp.,Scopulariopsis sp.,Phoma sp.,Aureobasidium sp.,Fusarium sp.,Thamnidium sp.,Cunninghamella sp.,Stemphylium sp.,Torula sp.,Trichothecium sp.,Verticillium sp.,Cephalosporium sp.,Mortierella sp.,Neurospora sp.,Ostracoderma sp.,Arthrinium sp.,Monodyctis sp.,Papularia sp.,Acremonium sp.,Chaetomium sp.,Chrysosporium sp.,Beauveria sp.,Cephaliophora sp.,Dactylosporium sp.,Drechslera sp.,Gliomastix sp.,Helminthosporium sp.,Humicola sp.,Monilia sp.,Sepedonium sp.,Ulocladium sp. andWallemia sp.

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Molds in foods of the Czechoslovak Socialistic Republik

Summary The mycoflora of 13.527 g of food powders which were normal upon sensory evaluation as well of 22.017 pieces of surface sterilized grains and nuts was examined in the Czechoslovak Socialist Republic. 147.027 colonies of 44 genera of molds were isolated and identified from samples.Colonies ofPenicillium sp.,Aspergillus sp., andCladosporium sp. occured most often, less often or quite infrequentlyRhizopus sp.,Mucor sp.,Absidia sp.,Alternaria sp.,Circinella sp.,Trichoderma sp.,Botrytis sp.,Paecilomyces sp.,Geotrichum sp.,Syncephalastrum sp.,Scopulariopsis sp.,Phoma sp.,Aureobasidium sp.,Fusarium sp.,Thamnidium sp.,Cunninghamella sp.,Stemphylium sp.,Torula sp.,Trichothecium sp.,Verticillium sp.,Cephalosporium sp.,Mortierella sp.,Neurospora sp.,Ostracoderma sp.,Arthrinium sp.,Monodyctis sp.,Papularia sp.,Acremonium sp.,Chaetomium sp.,Chrysosporium sp.,Beauveria sp.,Cephaliophora sp.,Dactylosporium sp.,Drechslera sp.,Gliomastix sp.,Helminthosporium sp.,Humicola sp.,Moniliasp.,Sepedonium sp.,Ulocladium sp., andWallemia sp.

     

Reaktive Polymere. II. Die Herstellung von Metallchelaten vernetzter Polymerer

The reaction of bivalent ions (Cu, Co, Zn, Ni) with ethylene diamine bounded to homogeneous crosslinked terpolymer glycidyl methacrylate-styrene-divinylbenzene or macroporous copolymer glycidyl methacrylate-ethyleneglycole dimethacrylate has been studied. The capacity of polymer sorbent, exchange ability and the kinetic of the reaction has been studied.     

The effect of composition of a polymeric coating on the biofilm formation of bacteria and filamentous fungi

Functionality of polymeric coating, especially in terms of anti-corrosive properties and stability, can be negatively influenced by formation of either bacterial or fungal biofilm on its surface. Herein, the epoxy-ester resin based polymeric coating was filled with pigments (natural silicon dioxide diatomite, natural wollastonite, tungstate and molybdate). Pigments was modified by conducting polymers (polyaniline phosphate, polypyrrole phosphate, poly(p-phenylenediamine) phosphate and ZnFe₂O₄). Impact of modified pigments on the surface energy and formation of biofilm were tested. The use of various biofilm forming species of both the bacteria and fungi filled a knowledge gap about their behavior on polymeric coatings.     

Smart Solution of Traffic Congestion through Bike Sharing System in a Small City

Bike sharing system as mode of public transport is very popular in the world. This smart solution can be described as answer to an increasingly frequent traffic congestion and parking problems in many cities all around the world. This issue is beginning to relate to some cities in Slovakia as well. Bicycles address traffic congestion as they form a valid substitution for cars on short trips, contribute to the use of public transport by providing effective last-mile connectivity and simply take up less space on the road. As the system of shared bicycles works from 2016, it is relatively new in Slovakia. This is a reason why this system still has some problems and deficiencies that need to be optimized. Presented paper focused on the city of Nitra, which is currently struggling with the issue of traffic congestion. The main aim of paper is to point out the opportunities and constraints arising from the concept of shared bicycles in the conditions of city of Nitra. Our proposals and recommendations are based on the opinions of the citizens of Nitra obtained from conducted marketing survey(625 respondents – citizens of Nitra). The results of the survey have brought important insights into improving the strategy of shared bicycles, focusing on attractiveness for citizens, and ultimately, urban transport solutions.

     

Fabrication of buried microfluidic channels with observation windows using femtosecond laser photoablation and parylene-C coating

We developed an advanced method for fabricating microfluidic structures comprising channels and inputs/outputs buried within a silicon wafer based on single level lithography. We etched trenches into a silicon substrate, covered these trenches with parylene-C, and selectively opened their bottoms using femtosecond laser photoablation, forming channels and inputs/outputs by isotropic etching of silicon by xenon difluoride vapors. We subsequently sealed the channels with a second parylene-C layer. Unlike in previously published works, this entire process is conducted at ambient temperature to allow for integration with complementary metal oxide semiconductor devices for smart readout electronics. We also demonstrated a method of chip cryo-cleaving with parylene presence that allows for monitoring of the process development. We also created an observation window for in situ visualization inside the opaque silicon substrate by forming a hole in the parylene layer at the silicon backside and with local silicon removal by xenon difluoride vapor etching. We verified the microfluidic chip performance by forming a segmented flow of a fluorescein solution in an oil stream. This proposed technique provides opportunities for forming simple microfluidic systems with buried channels at ambient temperature.     

Behaviour of Titanium Dioxide Particles in Artificial Body Fluids and Human Blood Plasma

The growing application of materials containing TiO₂ particles has led to an increased risk of human exposure, while a gap in knowledge about the possible adverse effects of TiO₂ still exists. In this work, TiO₂ particles of rutile, anatase, and their commercial mixture were exposed to various environments, including simulated gastric fluids and human blood plasma (both representing in vivo conditions), and media used in in vitro experiments. Simulated body fluids of different compositions, ionic strengths, and pH were used, and the impact of the absence or presence of chosen enzymes was investigated. The physicochemical properties and agglomeration of TiO₂ in these media were determined. The time dependent agglomeration of TiO₂ related to the type of TiO₂, and mainly to the type and composition of the environment that was observed. The presence of enzymes either prevented or promoted TiO₂ agglomeration. TiO₂ was also observed to exhibit concentration-dependent cytotoxicity. This knowledge about TiO₂ behavior in all the abovementioned environments is critical when TiO₂ safety is considered, especially with respect to the significant impact of the presence of proteins and size-related cytotoxicity.