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The technique of embedding components inside printed circuit boards (PCBs) is described, using different filling masses. To investigate the possibility of placing the components inside the printed circuit board, a residual circuit breaker with an overload protection (RCBO) system was adapted. Four types of fillings (two epoxy and two silicone) were used in the tests, which were carried out showing the full functionality of the systems embedded in the PCB, regardless of the applied sealing compound. A certain disadvantage was the shrinkage of the applied masses, which was visible in some cases in the occurrence of gaps in the flooding spaces. However, it should be emphasized that the tests were preliminary and that the adjustment of the filling shrinkage will be optimized in subsequent tests.

The paper presents the first record of a Chara connivens (Characeae) stand from Fuerteventura (Canary Islands, Spain). The species was previously recorded only on Tenerife and Lanzarote, mostly in marine and artificial habitats. Physicochemical parameters of water and morphological features of the thalli and plant community were analyzed. General habitat requirements of C. connivens populations located in Europe, North Africa, and South-West Asia were reviewed. The newly described stand was located in a natural rock crevice that was part of a riverbed in El Barranco de las Peñitas (Penitas Canyon). This habitat was unshaded and filled with brackish water. C. connivens co-occurred with Cladophora glomerata and Ruppia maritima. Our report on the presence of C. connivens in the Spanish territory of the Atlantic Ocean is the first in almost 40 years. The distribution of C. connivens and its plant associations on the Canary Archipelago are poorly explored, which is why this topic requires further research.

The majority of parts used in the electrical apparatus are made of polymer materials; however, pure polymers do not provide the antibacterial functionality. Therefore, in order to add such property to them it is necessary to use antibacterial additives. The study concerned intercalation of triclosan (TCS) as biocide into montmorillonite (MMT) interlayer spaces was performed in order to increase TCS resistance to high-temperature treatment, which is necessary during polymer composite processing. The obtained MMT + TCS hybrids were tested for structural and antibacterial properties. The degree of biocide intercalation was assessed using X-ray diffractometry, by analyzing changes in MMT interlayer distance, and thermal analysis was performed to assess the effect of the intercalation process on the thermal stability of TCS. Antibacterial tests against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) were also carried out on the obtained MMT + TCS powders in order to confirm the bactericidal properties of TCS released from the clay after the intercalation process. As a final proof of concept, the hybrid powder, namely MMT with incorporated TCS, was incorporated into polycarbonate matrix and antibacterial activity of modified polymer samples was tested. The obtained results have proven that montmorillonite–triclosan hybrid is an effective antibacterial additive with enhanced thermal stability which can be applied for protection of plastic parts used in electrical devices.

Epoxy resin composites filled with ceramic particles are commonly applied in electrification devices as an electrical insulation. In order to maintain proper functionality of such apparatuses it is crucial to optimize a broad range of properties, such as thermal, mechanical and dielectric parameters. In an earlier paper, a novel core-shell filler was developed in order to enhance the thermal conductivity in the epoxy composite used as electrical insulation. The new filler was made of a standard material, which was covered by a thin layer of high thermally conductive shell, namely, alumina coated by aluminum nitride. It was previously shown that the epoxy resin filled with the core-shell Al2O3@AlN particles showed a significant increase in thermal conductivity with a 63% relative increase. In this paper, a set of complementary measurements was performed and analyzed, namely, rheology, tensile strength, dynamic mechanical analysis, and dilatometry. Moreover, the dielectric permittivity and strength, and electrical resistivity were investigated in order to check if the electrical insulation properties were maintained. The obtained results were compared with the epoxy composite filled with the standard filler. The rheological behavior of the core-shell filled system showed that the processability will not be hindered. The mechanical properties of the composite based on core-shell filler are better than those of the reference system. The coefficient of linear thermal expansion is lower for epoxy filled with core-shell filler, which can lead to better adhesion to internal parts in the electrification devices. The dielectric strength was enhanced by 16% for the core-shell filled epoxy. The investigation clearly demonstrates that the epoxy composite filled with the core-shell particles is an appropriate material for application as electrical insulation with enhanced thermal conductivity.

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.

Metallic glasses are metallic materials, which exhibit an amorphous structure. These are mostly three or more component alloys, and some of them are magnetic metals. Materials of this kind are characterized by high electrical resistivity and at the same time exhibit very good magnetic properties (e.g. low-magnetization loss). The above mentioned properties are very useful in electrical engineering industry and this material is more and more popular as a substance for high-efficiency electrical devices production. This industry area is still evolving, and thus even higher efficiency of apparatus based on amorphous material is expected. A raw material must be carefully investigated and characterized before the main production process is started. Presented work contains results of complementary examination of amorphous metal Metglas 2605. Studies involve two ways to obtain clean and oxidized surface with high reactivity, namely degreasing followed by annealing process and plasma treatment. The amorphous metal parameters were examined by means of several techniques: surface free energy (SFE) measurements by sessile drop method, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and both ex situ and in situ Raman spectroscopy. Additionally, influence of plasma parameters on wetting properties were optimized in systematic way with Design of Experiments (DOE) method. A wide range of used methods allow to fully investigate the amorphous metal material during preliminary preparation of surface. Obtained results provide information about appropriate parameters that should be applied in order to obtain highly reactive surface with functional oxide layer on it.

Over recent decades, wide-ranging research has been focused on algae due to their potential applications, e.g., for biomass, extract and “third”-generation biofuel production. In particular, microalgae, which are very fast-growing organisms with low nutrient requirements, are ideal research objects. This review focuses on one of the most significant microalgae genus, i.e., Dunaliella, which includes D. salina and D. tertiolecta. The valuable components of these unicellular eukaryotes include glycerol, carotenoids (such as zeaxanthin and β-carotene) and many others, which mainly accumulate when these microalgae are affected by stress conditions (i.e., hypersaline and oxidative stress). The rapid growth of these microalgae in artificial/natural systems certainly has to be based not only on nutrient uptake and photosynthesis rates but also on efficient nucleotide metabolism. Nucleoside diphosphate kinases (NDPKs), which are considered conserved housekeeping proteins responsible for nucleotide turnover, could play an important role in this context, together with proper mitochondrial and chloroplast function. A more detailed understanding of the biochemical nature of Dunaliella spp. will help optimize the massive cultivation of these microorganisms. Ultimately, it will facilitate the greater use of coastal waters to multiply Dunaliella biomass production significantly. This strategy will save freshwater resources, e.g., in obtaining land plant oils to make biofuels. Greater access to different algal bioactive compounds may support the treatment of various diseases, such as asthma, eye diseases, cancer, and viral infections.

Salinity is one of the main determinants of species diversity in macroalgae. This study analyzes the occurrence of 16 species of the genus Ulva (Ulvaceae, Chlorophyta) in the salinity gradient. Ulva populations originated mainly from shores and estuaries with a minor number occurring in ocean lagoons, coastal lakes, canals and rivers. Ulva species were found in waters where salinity ranged from

The efficient management of heat is a key issue when considering the performance of electrical devices. To reduce the probability of their failure an effective heat dissipation should be ensured. The thermal conductivity of pure epoxy is low and can be improved through the addition of fillers. Graphene has been considered as an adequate filler, due to its excellent thermal conductivity. However, graphene-based composites also show a high electrical conductivity, which limits their application as an electrical insulation considerably. The presented work shows that it is possible to enhance thermal conductivity through the incorporation of a new class of hybrid filler, namely a masterbatch of graphene nanoplatelets (GNPs) and a standard filler like silica. This unique structural design combines the advantages of both, GNPs and silica powder, resulting in composites that not only show high thermal conductivity, but also preserve electrical insulation functionality. A modified processing method leads to the improvement of thermal conductivity. GNPs-silica hybrid epoxy composites with only 2 wt% of GNPs reached 1.54 W/mK, whereas the volume resistivity remained at the level of 1015 Ω cm. The unique scientific aspect, namely temperature dependence of thermal conductivity, was studied. The presented novel hybrid composites show great potential in applications requiring electrical insulation with enhanced thermal conductivity in high voltage devices. POLYM. COMPOS., 39:E1682–E1691, 2018.

Ulva species are characterised by the capacity to achieve rapid biomass increase, which results in the formation of “green tides”, particularly in nutrient-rich seawaters. Over the last decade, formation of large-scale Ulva mats has been increasingly observed in freshwater systems in Central Europe. Mass development of Ulva in freshwater ecosystems presents a growing burden in spite of its economic benefits. This study explores the formation dynamics of Ulva flexuosa mats with respect to habitat conditions, using the examples of a number of water systems located in Poland. Elevated water temperature, pH and high concentration of sulphates are among the most important factors affecting biometric parameters of Ulva blooms. An evident disparity was observed between lotic water ecosystems and lentic water ecosystems, which differed in terms of chemical characteristics of the habitat and mat structure properties. In flowing water, U. flexuosa displays a definitely higher potential for blooms. On the other hand, mass occurrence of U. flexuosa in freshwaters is caused by the inflow of fecund waters, especially following intense precipitation in summertime, as well as by periodic increases in salinity, pH and sulphate levels. The study suggests that potential U. flexuosa blooms in landlocked ecosystems may be controlled by means of reducing the inflow of particularly sulphate-rich waters. This research was partially supported by the project S/P – B/028: “Interrelation among abiotic and biotic factors in aquatic ecosystems: environmental and experimental research”.

In this work, a novel core–shell material has been manufactured in order to enhance the thermal conductivity of epoxy-based composites. The polymer derived ceramics technique has been used to produce fillers whose core is composed of a standard material – silica, and whose outer layer consists of a boron nitride or silicon nitride shell. The synthesized filler was characterized by infrared spectroscopy, X-ray diffraction, and scanning electron microscopy coupled with an energy dispersive spectroscopy analysis. The successful formation of core–shell structure was proven. Composite samples based on an epoxy resin filled with 31 vol% of synthetized core–shell filler have been investigated in order to determine the effective thermal conductivity of the modified system. The resulting core–shell composite samples exhibited improvements in thermal conductivity of almost 30% in relation to standard systems, making them a promising material for heat management applications. Additionally, the temperature dependence of the thermal conductivity was investigated over a broad temperature range indicating that the thermal behavior of the composite with incorporated core–shell filler is stable. This stability is a crucial factor when considering the potential of using this technology in applications such as electronics and power systems. Copyright © 2017 John Wiley & Sons, Ltd.

In this paper, measurement results of the arc erosion limitation in low voltage (LV) switches are presented. The reduction of the arc erosion in the analyzed electromechanical switches was achieved through an application of the hybrid switching in the tested alternative current circuit during interruption of the inductive current. The presented method is based on a commutation of the current during its interruption into a semiconductor branch that is connected in parallel to the operated switch. Thus, this approach is able to limit the electric arc energy efficiently, and as a consequence the arc erosion of the electrical contacts is also significantly reduced. For this reason, the application of the hybrid switching has a positive influence on a lifespan and a reliability of the operated switch. In order to evaluate the influence of the hybrid switching application on an effectiveness of the limitation of the arc erosion in the analyzed LV switches, 50 000 current interruptions were conducted in the tested circuit by each of four analyzed switches. Researches were performed for two standalone switches during a standard current interruption, as well as, for two switches with applied the hybrid switching system. In order to compare the arc erosion of the contact surfaces in both considered cases, scanning electron microscope method coupled with energy dispersion spectroscopy was applied. Moreover, photos of the electric contact surfaces are presented. Additionally, frames registered by high-speed camera during current interruption are presented for both considered approaches.

The evaluation of a possible application of functional shrinkable materials in thermally conductive electrical insulation elements was investigated. The effectiveness of an electron beam and gamma radiation on the crosslinking of a selected high density polyethylene grade was analyzed, both qualitatively and quantitatively. The crosslinked polymer composites filled with ceramic particles were successfully fabricated and tested. On the basis of the performed investigation, it was concluded that the selected filler, namely a boron nitride powder, is suitable for the preparation of the crosslinked polymer composites with enhanced thermal conductivity. The shape memory effect was fully observed in the crosslinked samples with a recovery factor reaching nearly 99%. There was no significant influence of the crosslinking, stretching, and recovery of the polymer composite during shape memory phenomenon on the value of thermal conductivity. The proposed boron nitride filled polyethylene composite subjected to crosslinking is a promising candidate for fabrication of thermally shrinkable material with enhanced heat dissipation functionality for application as electrically insulating components.

This work proposes the use of a biomaterial sodium alginate for microencapsulating stonewort oospores. The microencapsulation method has been adopted and optimized to improve research work carried out on the oospores. A detailed protocol for the production of microcapsules with stonewort oospores has been presented, with particular attention paid to the critical stages and factors interfering with the efficient production process. The advantages and disadvantages of this method have also been indicated. Microcapsules with oospores can be successfully used in various laboratory (observation of the germination phases) and field experiments (reintroduction of rare species of stonewort). Alginate microcapsule may consist of water taken directly from the habitat of the stonewort, a medium, as well as specific additives (antibiotics or fungicides). The hardness of the encasement is regulated by the concentration of the sodium alginate. The optimum alginate concentration for oospores is between 2 and 3%. Encasements produced with less than 2% sodium alginate concentration do not form circular microcapsules during gelation. On the other hand, concentration >3% may limit the oospores' ability to germinate (higher density of the microcapsule). In such a dense environment, the germinating primary cells may encounter difficulties in outgrowing the microcapsule. It has been shown that alginate encasement creates an effective protective layer for the oospores inside it. The oospore is protected from mechanical damage as well as from direct exposure to the external environment; especially from pathogens and other microorganisms that can inhibit its germination and limit the growth of the protonemal and primary rhizoidal cell. The main application of oospore microencapsulation using sodium alginate is facilitating further mechanical manipulations of oospores, which by nature are very small structures (max. length 1 mm), while a microcapsule with an oospore embedded inside it can have a diameter from 3 to 5 mm (as required).

An appropriate filler is a key component required to achieve an useful composite with expected properties. Not only sophisticated types of filler, like graphene are popular, but also more common ones, like silica flour or fly ash because of their low costs. Besides production costs, adequate size and possibility of functionalization of particles surface to create stable bonds with a matrix are essential in filler selection. To create an useful filler for epoxy resin based composites with use of a waste material, namely fly ash, two-step procedure was proposed. In the first part, raw material was sieved and five different ranges of the filler size were obtained. After mechanical tests with fracture toughness, tensile strength and Young Modulus, as well thermal conductivity, the best size of the fly ash was chosen for further modification. During the second step, filler was modified with coupling agent [3-(2-aminoethylamino)propyl]trimethoxysilane in order to enhance the coupling between particular components of composite. Presence of the silane layer was confirmed with infrared spectroscopy and scanning electron microscopy measurements, whilst prepared epoxy composite filled with silanized fly ash was examined similarly as previous composites. Obtained results have proved the significant influence of size of a filler and bonding to the matrix on mechanical and thermal properties of fly ash-epoxy resin composite. Proposed simple method of fly ash modification is an environmentally friendly way for utilization of the fly ash. Moreover, it creates an alternative material applicable in electrical devices as functional composite.

Epoxy resins are materials commonly used for insulations and encapsulations due to their easy processing process and mechanical strength. For their applications in power industry and electronics the effective heat dissipation is essential, thus their thermal conductivity is one of the most important properties. Introduction of appropriate dielectric powders, preferably in an ordered way, can increase the thermal conductivity of the polymer while keeping its good electrical insulation properties. In this work we used strontium ferrite as a filler to study the evolution of the filler particles distribution in the fluid before curing. Magnetic ferrite particles were dispersed in liquid epoxy resin and formation of chain-like or more complex structures under applied external magnetic field was observed and investigated. Computer simulations made show that with increasing magnetic field these structures are characterized by longer chains, higher speed of particles displacement and stronger structural anisotropy. However, for highly-filled systems, stronger inter-particle interactions make the alignment process less effective. The effective thermal conductivity simulated with FEM methods increases with increasing filler content and the percolation threshold in aligned systems is achieved at lower filler concentrations than for reference isotropic samples. The results are compared with the experimental data and a good qualitative agreement is obtained.

SUMMARY Cosmopolitan species of the genus Ulva (Ulvaceae; Chlorophyta) that populate the littoral zone of marine habitats constitute a staple diet for a variety of organisms, particularly snails, shellfish, polychaetes, and birds. Occurrence of Ulva species (e.g., U. flexuosa and U . prolifera) has also been observed in freshwater inland ecosystems that have no contact with saline water. However, the influence of the development of macroalgal mats of Ulva on indigenous organisms in limnic ecosystems has not been established. This study investigates the trophic relationships between Ulva flexuosa and one species of snail from freshwater habitats in central Europe. During the summer, the great pond snail (Lymnaea stagnalis) consumed Ulva as a source of nutrition even when other algae and plants were available. Lymnaea stagnalis consumed an average of 100 mg of Ulva thalli per day. This level of biomass exceeded the consumption of an alternative food source, the shoots of Elodea canadensis. Ulva thalli are more actively consumed by great pond snails than Elodea shoots, and this is expressed in terms of the differences of biomass consumption. It was also observed that the interior of the monostromatic tubular thalli of Ulva flexuosa serves as a protective shelter for juvenile great pond snails.

The insulation material of electronic devices should offers high thermal conductivity whilst retaining suitable mechanical properties. Epoxy resin is an example of a material that is commonly used by industry for electronic insulation, despite the fact that neither the thermal conductivity nor the mechanical properties are particularly satisfying. These properties can be enhanced by incorporating filler, with silica flour representing the most popular filler. An economically appealing solution is to replace silica flour with fly ash as filler material, however it must be remembered that compatibility of fly ash and epoxy resin is not ideal. In order to improve the coupling between these two materials, fly ash particles covered with [3-(2-Aminoethylamino)propyl]trimethoxysilane were obtained with six different conditions of the silanization process, where the amount of silane, the temperature and the time of the reaction were changed. The presence of the silane layer was confirmed via Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis and Scanning Electron Microscopy. The mechanical properties, including tensile strength, Young Modulus and fracture toughness, as well as the thermal conductivity of the final samples were investigated. In the case of composites with silanized fillers, all of the mechanical properties were improved, and an enhancement of thermal conductivity was observed for several composites. Moreover, the differences in coupling between the silanized fly ash and the untreated fly ash, and the epoxy matrix were precisely recorded by means of SEM. The presented studies confirm that an effective silanization process can significantly improve the properties of composites, while also verifying the usefulness of waste material. The results highlight that fly ash may be utilized to create a more economically affordable insulation material.

Research on the diversity of thalli and mats built by freshwater Ulva flexuosa, as well as the impact of abiotic factors on the development and distribution of Ulva mats, was conducted from May to August 2013. The study describes the dynamics of “green tides” formation by U. flexuosa. The study assessed abiotic factors that may influence the colonization and the growth of Ulva populations in freshwater systems. The results are of major importance to the trade and industry sectors. In total, eleven environmental parameters were included in the analysis. The most important environmental parameters characterizing the Ulva sites are sodium chloride levels and conductivity. High values of pH inhibited the development of Ulva, leading to a lower percentage of mature thalli in the mats. The water depth was positively correlated with an increase in the density of thalli in the mats and the average thallus length. Significant differences were identified between the concentrations of nitrates under and outside the Ulva mats. Concentrations of nitrate under the Ulva thalli were always lower.

Mass occurrence of green algae of the genus Ulva in the form of algal blooms (known as “green tides”) is often associated with high concentrations of biogens in the water. Therefore, Ulva species are most often used in monitoring seawater trophy and far less frequently freshwater trophy. In Europe, the biomonitoring of river ecosystems is based on aquatic plants. According to the River Macrophyte Index (RMI), river populations of Ulva macroalgae (only tubular Enteromorpha-like Ulva) are considered good indicators for eutrophic waters. This paper analyses the legitimacy of using U. pilifera as a trophy indicator in the case of ponds. It has been noted that freshwater populations of U. pilifera are much more common in lakes, dammed reservoirs, or ponds than in rivers. In this study, analysed populations of U. pilifera originated from 14 ponds located in central Poland. Data analysis relied on the Carlson Trophic State Index (CTSI), which was compared with other known trophic indices. According to CTSI values, U. pilifera was most common in eutrophic ponds, where the mean concentrations of ammonium nitrogen, nitrates, total phosphorus, and chlorophyll a reached 581, 241, 212, and 20 µg·L−1, respectively. The results indicate that U. pilifera can be considered a bioindicator for eutrophic waters (50–70 of CTSI). It would therefore be appropriate to introduce U. pilifera as part of biomonitoring conducted in small bodies of water. Major arguments in favour of practical application of U. pilifera are: (i) it is a large macroalga, the thalli of which can reach a length of > 1.0 m, (ii) it is an easy-to-identify species; even by non-experts (it is characterized by a distinctive tubular shape of the thallus), and (iii) it occurs in bulk in conditions of eutrophy, creating an easily observable bloom.

Over the last few decades, amorphous steel has been gaining more and more interest as a key material for modern electrical transformers. Amorphous steel has already excellent electromagnetic properties, however, the efficiency of the transformer core can be further enhanced by the mechanical strengthening achieved by using a specially designed bonding material. Such an advanced material must combine numerous functionalities. Good surface adhesion is one of the most crucial characteristics of the binder. The presented work contains the results of research on synthesized double-layered binder based on the tetraethyl orthosilicate and 1,2-bis(triethoxysilyl)ethane and its binding properties to an amorphous metal substrate. The binder layers were deposited on an amorphous metal Metglas 2605 HB1M ribbon by dip coating method. A range of methods was used to examine the quality of the layers, its structure,thermal expansion coefficient and the forces causing delamination. The obtained results clearly evidence the studied hybrid layer made of tetraethyl orthosilicate and 1,2-bis(triethoxysilyl)ethane as a suitable, good quality binder for mechanical strengthening of electrical devices made of amorphous metal ribbon.

This research presents an overview of the properties of highly structured, low density polyethylene-graphene nanoplatelets (LDPE-GnP). The influence of nanofiller content, size and processing conditions on the material properties have been investigated. Therefore, rheological and thermal nanocomposite properties were investigated. So-called dry-coating method has been used in order to prepare masterbatches which were thereafter extruded by means of single screw extruder resulting in a strong anisotropy in the extruded samples. Graphene nanoplatelets were oriented in the extrusion direction for all shear rates and flow histories investigated, as confirmed by scanning electron microscopy. The rheological percolation was determined via nonlinear parameters to be around 11wt%. Thermal conductivity measurements revealed strong anisotropy with in-plane conductivity increasing with GnP content.

Results of a theoretical and experimental investigation of THz detection of randomly-oriented metal particles smaller than 1 mm embedded in pressboard are reported and critically compared with X-ray scanner results. A theoretical description based on Gaussian beam theory and a transfer function approach enabled simulation of signals transmitted around and reflected from real particles and was able to predict signal detectability. Simulated signals and detection limits were compared with experimental transmission and reflection time domain spectroscopy (TDS) raster scanning data. Simulated and measured pulse amplitude and shape were in agreement. Reflection mode was superior to transmission mode in terms of both particle visibility and hit ratio. Imaging of particles was also possible in “reflection in transmission” mode, which can be used to complement classical transmission mode. X-ray images did not detect the smallest particles sufficiently and, therefore, could not be used as reference data for comparison with THz data. The results demonstrate that TDS reflection scanning is able to determine the position of small metal particles and the technique could be possibly used for quality control of pressboard insulation.

The macroalgae representing the cosmopolitan Ulva flexuosa Wulfen species have been found in inland water ecosystems of Europe since the mid-1800s. The presence of the Ulva genus in waters of inland salt marshes was explained by high salinity of water in such systems. However, Ulva flexuosa thalli were found in lakes and rivers having no supply from strongly mineralized sources, either of natural or anthropogenic origin. The study focused only on populations of Ulva flexuosa subsp. pilifera (Kűtz.) M.J. Wynne and Ulva flexuosa subsp. paradoxa (C. Agardh) M.J. Wynne occurring in inland ecosystems isolated from seawater. The differentiation of inland U. flexuosa subsp. pilifera and subspecies paradoxa was assessed by using classical morphological data and molecular techniques. We found that only two subspecies of Ulva flexuosa Wulfen occur in inland water ecosystems of Poland. On the basis of the analysis combining morphological features with the ITS region and rbcL gene sequences, a small degree of differentiation of the two inland taxa was demonstrated. These two subspecies have high differentiation of the habitat niches. U. flexuosa subsp. paradoxa settled in habitats featuring high salinity levels, and the second subspecies pilifera occurred only in fresh waters.

Filled epoxy composites are broadly used in electronic and power devices as an electrical insulation. It is of importance to achieve efficient heat dissipation in such devices due to fact that thermal properties have a strong influence on their proper operation. For this reason, the modification of standard filler materials, such as silica or alumina, can give a promising solution. In this work, a novel core–shell material has been proposed and manufactured by means of a carbothermal reduction and nitridation process. The obtained fillers are made of a standard material which is covered by the high thermally conductive shell. The synthesized fillers were characterized by means of X-ray diffraction, and scanning electron microscopy coupled with elemental analysis. The composite samples based on epoxy resin filled with the manufactured core–shell fillers have been investigated in order to determine their effective thermal conductivity. The obtained composite samples exhibited a significant improvement in the thermal conductivity, represented by a 63 % relative increase. The obtained results show the potential for the novel core–shell fillers to be applied for the electrical insulation with the enhanced thermal conductivity.

The aim of the presented work is to show the influence of the various polymer matrices and the different amounts of the cellulose filler on the composites properties. Samples based on polypropylene, polystyrene, polyoxymethylene, acrylonitrile butadiene styrene, polyester resin, and polylactic acid with different contents of cellulose fibers were prepared by injection molding process. The mechanical and dielectric properties of these composites were studied in order to check whether investigated wood polymer composites fulfill requirements for their application in electrical devices. For all tested composites, a linear increase of modulus with cellulose content was observed. Addition of cellulose to the tested polymers significantly reduces strain at break. In the case of polypropylene and polyoxymethylene composites, the tensile strength increases with the content of the filler. For other materials, there is an inverse relationship, namely the addition of cellulose decreases the tensile strength. The electrical strength decrease was observed with increased cellulose content for the majority of the investigated composites. Polar groups incorporated by cellulose fibers have led to dielectric constant increase. Furthermore, aging of composites in mineral oil and evaluation of water uptake for wood–plastic samples were performed. Wood polymer composites have changed significantly after aging. The water diffusion coefficients were determined, and the significant influence of the amount of cellulose on the water absorption was shown. Copyright © 2015 John Wiley & Sons, Ltd.

Metal migration effects occurring at the conductor/cross-linked polyethylene (XLPE) interface are presented in the paper. The phenomenon was studied under various electrical stresses: direct current, pulse-width modulated and sinusoidal. The comparison of aging effects on specimens subjected to the stimuli was presented. The electrical stress results in partial discharges, both around the electrode in the form of surface discharges and directly at the micro air gap interface between conductor and polymeric material. In order to isolate the impact of interface discharges, the surface effects were suppressed, eliminated and compared with results containing both forms of discharges. The electrical and thermal migration mechanism was investigated in the paper and assessment was performed by means of time to breakdown and both micro morphological and elemental analysis. Migration of the conductor atoms, where metallic particles are transferred to the insulating medium, was observed. Primarily, attention was afforded to the migration of copper and aluminum electrode atoms in two zones; one zone being the direct contact area at the interface and the second zone incorporating the area surrounding the electrode which is enhanced by surface discharges. A novel aspect relates to the investigation of the metal migration depth profile and the concentration intensity at different voltage stresses. The transport phenomena were analyzed with respect to both electrical and thermal mechanisms.

This paper investigates the influence of magnetic field-assisted filler alignment technology on the morphology and the thermal conductivity of magnetite-filled epoxy composites. A magnetic field was applied during the solidification of the composite in order to change the position of the filler and its distribution in the polymer matrix. It is shown that the applied procedure leads to the filler being oriented along the direction of the magnetic field, and as a result, the thermal conductivity is improved by up to 120 % compared to a composite with randomly oriented filler obtained without the assistance of a magnetic field. This positive effect is caused by the appearance of conductive paths at a much lower content of the filler when the composite solidification is assisted by a magnetic field, relative to an equivalent isotropic sample. These morphological changes were confirmed by microscopic and X-ray microtomography imaging. The temperature dependences of thermal conductivity were also investigated over a broad temperature range for a magnetite-filled epoxy composite sample and compared to the bulk magnetite reference, showing that thermal behaviour of the magnetite-filled composite is stable, which is a promising result when considering the future application of the technology.

This contribution reports on properties of low-density polyethylene-based composites filled with different amounts of graphene nanoplatelets. The studied samples were prepared in the form of films by means of the precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement of graphene flakes and results in a strong anisotropy of composites morphology. The performed tests of gas permeability reveal a drastic decrease of this property with increasing filler content. A clear correlation is found between permeability and free volume fraction in the material, the latter evaluated by means of positron annihilation spectroscopy. A strong anisotropy of the thermal conductivity is also achieved and the thermal conductivity along the extrusion direction for samples filled with 7.5 wt % of GnP (graphene nanoplatelets) reached 2.2 W/m·K. At the same time, when measured through a plane, a slight decrease of thermal conductivity is found. The use of GnP filler leads also to improvements of mechanical properties. The increase of Young’s modulus and tensile strength are reached as the composites become more brittle.

The time domain spectroscopy (TDS) setup in a reflection configuration was exploited for non-destructive measurements of four samples with a 10-mm (approx.) leaf-shaped air void at the interface between the plastic and metal structures. We identified and measured the material parameters of the samples required for precise determination of the voids’ thicknesses in the range of 125–500 μm. For high resolution measurements we selected the reflection TDS setup with a short focal length and developed a method for the accurate calculation of the incidence angle. We used a deconvolution-based method for thickness monitoring of voids and discussed its limitations. The two-dimensional thickness, amplitude and binary maps were exploited for imaging of the void areas. We also showed that the multiplication of the deconvolved and binarised maps can provide relevant information about the real thickness of the layer and the presence of the void in the single image. The correlation coefficient between the real and TDS measured shapes of the leaf in the range 0.8–0.9 suggests a good perspective for this technique in industrial applications.

Getting to know the response of different groups of aquatic organisms tested in altered thermal environments to environmental conditions makes it possible to understand processes of adaptation and limitation factors such as temperature and light. Field sites were located in three thermally abnormal lakes (cooling system of power plants), in eastern part of Wielkopolska region (western Poland): Pątnowskie, Wąsosko-Mikorzyńskie and Licheńskie. Water temperatures of these lakes do not fall below 10°C throughout the year, and the surface water temperature in spring is about 20˚C. In this study, we investigated the species structure of the spring phytoplankton community in a temperature gradient and analyzed diversity of periphyton collected from alien species (Vallisneria spiralis) and stones. 94 taxa belonging to 56 genera of algae (including phytoplankton and periphyton) were determined. The highest number of algae species were observed among Chlorophyta (49), Bacillariophyceae (34) and Cyanobacteria (6). In spite of important differences in temperature in the investigated lakes, taxonomic composition of phytoplankton was comparable. Thermophilic species: Glochidinium penardiforme and Cylindrospermopsis raciborskii were found in the species structure (blooms were not observed). The obtained data also showed that the biotic surface of Vallisneria spiralis was a better substrate for Bacillariophyceae colonization than stones. The examination in the spring season of these thermally altered lakes, indicated the taxonomic composition of phytoplankton typical for eutrophic reservoirs (not heated). There was no replacement of any phytoplankton groups which are characteristic for spring conditions, even if there were changes in the competition dynamics.

The results of thermal conductivity study of epoxy–matrix composites filled with different type of powders are reported. Boron nitride and aluminum nitride micro-powders with different size distribution and surface modification were used. A representative set of samples has been prepared with different contents of the fillers. The microstructure was investigated by SEM observations. Thermal conductivity measurements have been performed at room temperature and for selected samples it was also measured as a function of temperature from 300 K down to liquid helium temperatures. The most spectacular enhancement of the thermal conductivity was obtained for composites filled with hybrid fillers of boron nitride–silica and aluminum nitride–silica. In the case of sample with 31 vol.% of boron nitride–silica hybrid filler it amounts to 114% and for the sample with 45 vol.% of hybrid filler by 65% as compared with the reference composite with silica filler. However, in the case of small aluminum nitride grains application, large interfacial areas were introduced, promoting creation of thermal resistance barriers and causing phonon scattering more effective. As a result, no thermal conductivity improvement was obtained. Different characters of temperature dependencies are observed for hybrid filler composites which allowed identifying the component filler of the dominant contribution to the thermal conductivity in each case. The data show a good agreement with predictions of Agari-Uno model, indicating the importance of conductive paths forming effect already at low filler contents. Copyright © 2014 John Wiley & Sons, Ltd.

Species of Ulva (Ulvaceae, Chlorophyta) are relatively common macroalgae in most coastal areas. In this paper, we examine Ulva in inland aquatic ecosystems to determine relationships between the chemical parameters of the water and the Ulva taxa present. Two groups of samples of freshwater Ulva were selected from: (i) habitats with high salinity levels, and (ii) habitats with fresh or slightly saline waters. We showed that these two groups of Ulva, which occupy distinct habitats, represent two separate taxa. The first group represents Ulva flexuosa subsp. pilifera (Kutzing) M.J. Wynne, which is very common and regularly encountered in fresh waters, but is equally well represented in slightly saline waters. The second is U. flexuosa subsp. paradoxa (C. Agardh) M.J. Wynne, which is less common, preferring mainly salt-wedge saline waters. We did not find both Ulva flexuosa subspecies together at any of the research sites.There were significant morphological differences between the Ulva flexuosa subspecies. U...

Hybrid organic/inorganic nanocomposite solar cells are a potential candidate as an alternative to photovoltaic (PV) devices based on semiconducting inorganic or organic nanomaterials. In a recent study, carried on ITO/PVK:n-TiO2/Al structures, we have observed a performance degradation due to bipolar charge recombination and space-charge formation. Then, a simulation of I–V characteristics of photovoltaic (PV) diodes for different organic nanomaterials suggested replacing poly (N-vinylcarbazole) (PVK) by poly (3-hexylthiophene-2,5-diyl) P3HT. In this work, we have studied the current–voltage characteristics of ITO/PEDOT:PSS/P3HT:SiNW/Al solar cell under white illumination with different volume ratios (10%, 20%, 50%) of SiNW. The results have shown a maximum FF for 20% silicon nanowire (SiNW) volume ratio corresponding on the one hand to the morphology exhibiting the lowest RMS and on the other hand the maximum quenching of PL spectra. A degradation of the PV properties is induced at higher composition by the formation of larger of SiNW aggregates. Procedures have been developed to extract the different parameters from I–V characteristics under illumination in the basis of an equivalent circuit. The variation of the photogenerated current with SiNW volume ratios confirms that the PV response is optimum for 20 vol% SiNW.

We analyze nonlinear magneto-optical rotation (NMOR) in rubidium vapor subjected to continuously-scanned magnetic field. By varying magnetic-field sweep rate, a transition from traditionally-observed dispersive-like NMOR signals (low sweep rate) to oscillating signals (higher sweep rates) is demonstrated. The transient oscillatory behavior is studied versus light and magnetic-field parameters, revealing a strong dependence of the signals on magnetic-sweep rate and light intensity. The experimental results are supported with density-matrix calculations, which enable quantitative analysis of the effect. Fitting of the signals simulated versus different parameters with a theoretically-motivated curve reveals presence of oscillatory and static components in the signals. The components depend differently on the system parameters, which suggests their distinct nature. The investigations provide insight into dynamics of ground-state coherence generation and enable application of NMOR in detection of transient spin couplings., Comment: 9 pages, 7 figures, Submitted to Physical Review A

The possibility of using freshwater Ulva (Chlorophyta) as a bioaccumulator of metals (Co, Cr, Cu, Mn and Zn) in lake and river water was examined weekly in the summer of 2010 in three types of samples: the water, the sediment and the thalli of Ulva. Samples of freshwater Ulva were collected from two aqueous ecosystems lie 250 km away from the basin of the Baltic Sea and 53 km from each other. A flow lake located in the centre of the big city was the first water reservoir (10 sites) and second, the suburban river (6 sites). The mean metal concentrations in the Ulva tissue from the river and the lake decreased in the following order: Mn>Zn>Cr>Cu>Co and Mn>Cr>Zn> Cu>Co, respectively. Moreover, a negative and statistically significant correlation between Mn concentrations in the Ulva thalli and the river water was observed. Additionally, numerous correlations were noted between the different concentrations of metals within the Ulva thalli, in the water and in the sediment. The great concentrations of Mn and Zn and the smallest of Co were found in thalli of Ulva, irrespective of the type of the ecosystem from which samples of algal thalli originated. Freshwater Ulva populations examined in this study were clearly characterized a dozen or so times by the higher Mn and Cr accumulation than taxa from that genera coming from sea ecosystems. The calculated bioconcentration factor (BCF) confirm the high potential for freshwater Ulva to be a bioaccumulator of trace metals in freshwater ecosystems. This project was supported by funds from the Polish Ministry of Science and Higher Education; grant number N N304 013 437. The field research was funded partially by the project GDWB-07/2011. Andrzej Rybak has received a PhD fellowship from the Adam Mickiewicz University Foundation.

A novel investigation into the behavior of the interface between an insulating material and a conductor subjected to sinusoidal stimulus is presented. Both copper and aluminum wires are used in the windings of electrical machines and also as power cable conductors. During in-service operation, partial discharges (PD) may be initiated in the insulation systems. The paper presents experimental results showing the interaction of different kinds of conductors and dielectric materials on the mechanism of partial discharges in the insulation system. The dedicated test setup is designed to perform experiments with various electrodes, with special focus on copper. Two kinds of specially prepared insulation samples were tested, ethylene propylene rubber (EPR), cross-linked polyethylene (XLPE). These insulating materials were subjected to a sinusoidal stimulus at predefined time intervals and were exposed to PD action. The paper comprises the results of PD measurements and microstructural observations performed by means of scanning electron microscope (SEM) coupled with energy dispersive analysis (EDS). The morphological and elemental analysis reveals the interaction of conductor on polymeric material degradation. Two zones were distinguished, migration and erosion. The migration of atoms of electrode material into the dielectric substrate due to PD activity was observed.

The paper includes results of the first study on the accumulation of selected metals in freshwater populations of Ulva taxa at 16 sites in Poland. The thalli examined contained very high concentrations of Ca and Mg, owing to well-developed surface incrustations of carbonate. Among the heavy metals investigated, the most significant concentration in the thalli was Ni, whereas the lowest was Pb. The median concentrations of Ni and Cd in the freshwater Ulva thalli were significantly higher than those reported in the available literature for marine taxa of the same genus. Several statistically significant correlations were found when the concentrations of different metals in the thalli and the water were analysed.

We analyzed the ability of freshwater taxa of the genus Ulva (Ulvaceae, Chlorophyta) to serve as bioindicators of metal in lakes and rivers. Changes in heavy metal (Ni, Cd and Pb) and alkaline earth metal (Ca and Mg) concentrations in freshwater Ulva thalli were investigated during the period from June to August 2010. The study was conducted in two ecosystems in Western Poland, the Malta lake (10 sites) and the Nielba river (six sites). Three components were collected for each sample, including water, sediment and Ulva thalli. The average concentrations of metals in the water sample and in the macroalgae decreased in the following order: Ca > Mg > Ni > Pb > Cd. The sediment revealed a slightly altered order: Ca > Mg > Pb > Ni > Cd. Ca and Mg were found at the highest concentrations in thalli due to the presence of carbonate on its surface. Among the examined heavy metals in thalli, Ni was in the highest concentration, and Cd found in the lowest concentration. There were statistically significant correlations between the levels of metals in macroalgae, water and sediment. Freshwater populations of Ulva exhibited a greater efficiency to bioaccumulate nickel as compared to species derived from marine ecosystems.

An epoxy-anhydride formulation used for the coating of electrical devices was modified with a commercially available hyperbranched poly(ester-amide), Hybrane™ S2200, in order to improve the thermal degradability of the resulting thermoset and thus facilitate the recovery of substrate materials after use of the component. The curing kinetics of the unmodified and modified formulations were studied in detail with differential scanning calorimetry, Fourier transform infrared spectroscopy and rheology. The results suggest that S2200 gets incorporated into the network structure and the curing kinetics are accelerated by the presence of hydroxyl groups from S2200. Copyright © 2012 Society of Chemical Industry

Photoactive hybrid films based on n type silicon nanowires [SiNWs] dispersed in poly(3-hexylthiophene) [P3HT], a p type conjugated polymer known for its good ordering properties, have a main interest for the production of photovoltaic films at a limited cost. Silicon nanowires synthesized at high yield by the oxide assisted growth technique have been dispersed in tetrahydrofuran: THF, and mixed with a P3HT solution in THF to form a blend of the inorganic-organic components in the appropriate proportions. The blend of SiNWs and P3HT have been deposited by spin coating on PEDOT-PSS/ITO substrates leading to the production of 100 nm thick SiNWs/P3HT thin layers of controlled compositions. The quenching of the P3HT fluorescence has shown the effective dissociation of the photogenerated pairs for an optimum composition of 6 SiNWs vol. % in the blend, which is in accordance with the low percolation threshold expected from the high aspect ratio of the nanowires. Current/voltage experiments under illumination have however led to collected photocurrents remaining limited to some 10 μA/cm2 whereas an interesting open circuit voltage of 0.65 V was obtained. It has been possible from surface potential decay experiments to assign the main limiting process to the low electron transport along nanowires of diameter smaller than 10 nm, whereas easy hole transport in the P3HT thickness was obtained. The high densities of silicon surface states acting as electron traps can simultaneously account for efficient charge pair dissociation and low photocurrents in nanosized structures.

The electrical properties (dielectric characteristics and conductivity) measured on DC and AC and thermomechanical properties of polyvinylchloride-multiwalled carbon nanotube (PVC/MWNT) nanocomposites were investigated. The segregated PVC/MWCNT composites were formed by the hot compacting method. Measurement of DC and AC conductivity shows a presence of ultralow percolation threshold with value of φ c = 0.045 vol.%. Temperature dependence of conductivity demonstrates a transition from the ionic conductivity in pure PVC and in filled PVC below percolation threshold to the electron type of the charge transport along the MWNT phase in the composites above percolation threshold. Frequency dependence of the dielectric parameters e′, e″ demonstrates percolation behavior of the studied systems. The thermomechanical analysis indicates the formation of a rigid network of filler in the volume of the polymer matrix, which restricts the transition of polymer into the plastic state.

The paper presents an updated version of the phycological key which includes additional morphological features, so as to facilitate identification of taxa (subspecies and variants) from the Ulva flexuosa complex, spanning populations from ecosystems with varying degrees of salinity. Data were collected in several locations in central and western regions of Poland. Only two subspecies were observed in inland water ecosystems: U. flexuosa subsp. pilifera , and subsp. paradoxa. Another taxon— U. flexuosa subsp. flexuosa, inhabits only brackish waters of costal lakes and estuaries. Two further taxa, namely U. flexuosa var. linziformis and subsp. biflagellata are found only in marine ecosystems and do not tend to settle in freshwater habitats.

The influence of the structure and the temperature on the Conductive Polymer Composites (CPC) properties has been studied. The investigated CPC are based on homo- and heterogeneous polymer blends of high density polyethylene, polybutylene terephthalate and poly(m-xylene adipamide), filled with dispersed silver nanoparticles (Ag). It is shown that by the appropriate use of the immiscible polymers blends the percolation threshold can be decreased twice, what significantly reduces costs and keeps better mechanical properties. Additionally, it was found that depending on the choice of CPC structure the commutation temperature from a conducting state to an insulating state can be observed between 45 and 180 °C. The observed high intensity of Positive Temperature Coefficient (PTC) effect, i.e. a sharp (narrow temperature range) and strong (10 orders of magnitude) resistivity increase, makes such composites promising for current limiting devices and temperature sensors.

X-ray diffraction investigations show, that in the vacuum evaporated layers of 2,9-di(pent-3yl)-anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10-tetrone (PTCDI) the PTCDI molecules may have edge-on or face-on arrangement. For the samples with different molecular arrangement the dependences of the photogeneration quantum yield on electric field were determined by using the photoinduced surface potential decay technique. The obtained results were analysed using the Onsager's model of photogeneration. The clear influence of the molecular order on the photogeneration efficiency has been found.

Photogeneration quantum yield in layers of discotic liquid crystals (DLC, hole transport material), perylene derivative (electron transport material) and of their mixtures were determined by using surface potential decay technique. While in pure DLC only very weak photogeneration in the visible range was detected, and in pure perylene derivative only negative mobile charge carriers were photogenerated, in the mixtures a synergetic effect of photogeneration of both positive and negative mobile charge carriers was observed. This is because the excitons photogenerated at perylene derivative dissociate into electron–hole pairs, and then electrons are transported via perylene derivative while the holes are transferred onto the DLC molecules. The obtained results were correlated with performance of the photovoltaic devices with active layer made of the mixtures of the DLC and perylene derivative and of their blends with photoconducting polymer. It was found, that the power conversion efficiency of the device is dependent on the film morphology.