Modeling of conductivity in composites with random resistor networks

Composite polymeric electrolytes (CPE) are well known systems in which an improvement in electrical conductivity of the polymer is achieved by the addition of a non-conductive additive (ceramic powders and immiscible polymers). A new class of conductivity models based on the application of the multi-value random resistor networks to the studies of CPE was developed by the authors. The first stage of the simulation is based on the virtual composite sample generation and its transformation into a form of the three-dimensional resistor network. The sample generation can take into account variable material parameters such as average grain diameter, shell thickness as well as their statistical distribution and different dependencies of local shell conductivity on the distance from the grain surface. The second stage of the algorithm is the use of the modified iteration procedure based on Kirkpatrick approach leading to the direct current resistivity of the virtual sample. The presented results were obtained for the matrix size 100 unit × 100 unit × 100 unit (with assumption 1 unit = 1 μm). The dependency of conductivity on the grain filler concentration was studied for varying grain sizes, changing shell thickness as well as for different statistical distributions of these parameters. The obtained results of simulation are in general agreement with the experimental data.     

A Photoexcited Porphyrin System as a Biomimetic Catalyst for D-limonene Biotransformation

A photoexcited porphyrin system has been found to be an efficient catalyst for D-limonene biotransformation. The catalyst showed high selectivity in hydroxylation of D-limonene. The best catalyst for limonene biotransformation was 5,10,15,20-Tetraphenylporphyrin (H₂TPP), which gave the highest accumulation of carvone and an unknown product with a verbenone-like mass spectrum. The highest conversion yield of these products was favoured at 1:2 molar ratio of H₂TPP to limonene. Some factors affecting the biotransformation yield were also investigated. Maximal yield of carvone was obtained in the medium containing 90% of the substrate, within the period of 18–36 h. Mechanism involved in limonene biotransformation catalysed by H₂TPP is also discussed.     

Studies on the usefulness of Cucurbita maxima for the production of ready-to-eat dried vegetable snacks with a high carotenoid content

Recent research indicates a beneficial influence of a diet rich in β-carotene on human health. For that reason, experiments were undertaken to process winter squash with a high carotenoid content into ready-to-eat dried snacks. Sensory quality and dietary value of chips and crispy cubes made from different cultivars were investigated.The suitability of winter squash for drying purposes depended mainly on the dry matter content in the raw material. Although all the investigated cultivars can be used for producing chips, obtaining high quality porous cubes requires at least 15% of dry matter. ‘Justynka F1’ emerged as the most suitable cultivar for processing; both chips and cubes produced from its fruits were characterized by a high sensory quality and contained significant amounts of beta-carotene (225- 253 μg g-1). Also, the cultivar ‘Amazonka’ could be considered for the production of chips as it allowed us to obtain a product with a high beta-carotene content (200 μg g-1) and good sensory properties. The dried ready-to-eat crispy vegetable snacks made from the new cultivars of winter squash could be exploited as a novel attractive product with the attractive taste and colour to serve as a valuable source of carotenoids in human diet.     

Effect of Thermal Treatment on the Photocatalytic Activity in Visible Light of TiO<Subscript>2</Subscript>-W Flame Spray Synthesised Nanopowders

Effect of W doping as well as a thermal treatment on the structural and photocatalytic properties of TiO₂ produced by flame spray synthesis (FSS) were the subject of investigation. Structural properties were studied by means of X-ray diffraction (XRD), BET adsorption isotherm and transmission electron microscopy (TEM). The surface condition was investigated by X-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC) and differential thermal and thermogravimetric analysis (DTA-TGA). The photocatalytic properties were studied by optical measurements and photodecomposition of methylene blue under visible irradiation. It was found that the photoactivity in the visible region was enhanced significantly by the W-doping as well as by additional thermal treatment of those nanopowders. The obtained TiO₂-W nanopowders exhibited higher performance under visible light than P25.     

Bimetallic Au–Cu, Ag–Cu/CrAl3O6 Catalysts for Methanol Synthesis

The influence of silver and gold addition on the activity and physicochemical properties of supported Cu/CrAl₃O₆ catalysts was the aim of this work. The reduction of CrAl₃O₆ support shows only one reduction stage attributed to Cr (VI) species reduction originating from previously oxidized binary oxide. Supported copper catalysts reduce in one or two stages depending on copper concentration representing the reduction of copper oxide—CuO, copper oxide chemically combined with Cr(III) oxide as copper chromite—CuCr₂O₄ and Cr(VI) species originating from surface chromate ions CrO₄ ^2?. Additionally, the introduction of silver into supported copper catalysts Cu/CrAl₃O₆ can led to the appearance of silver chromate phase. XRD investigations of support CrAl₃O₆ alone, supported copper and gold and silver promoted copper supported catalysts calcined at 400, 700 and 900 °C indicated the presence of highly amorphous alumina γ-Al₂O₃ like structure network in which some of cationic locations of aluminum were occupied by chromium atoms and small quantities of α-Cr₂O₃ phase. Additionally, for copper, silver–copper, and gold–copper supported catalysts the following oxide phases were distinguished: monometallic oxides CuO, Ag₂O, binary oxides CuAl₂O₄, Ag₂CrO₄, CuCr₂O₄ and even ternary oxide CuAlCrO₄. In the case of gold promoted copper supported catalysts metallic gold phase was detected. Activity tests carried out for these catalysts show that the most active was 20 wt.% Cu/CrAl₃O₆ catalyst. Promotion of copper catalysts by silver improves the activity in methanol synthesis, what can be assigned to silver chromate formation. The analogical gold chromate like formation was not confirmed.     

Sialic Acid—Modified Nanoparticles—New Approaches in the Glioma Management—Perspective Review

The cell surface is covered by a dense and complex network of glycans attached to the membrane proteins and lipids. In gliomas, the aberrant sialylation, as the final stage of glycosylation, is an important regulatory mechanism of malignant cell behavior and correlates with worse prognosis. Better understanding of the role of sialylation in cellular and molecular processes opens a new way in the development of therapeutic tools for human brain tumors. According to the recent clinical observation, the cellular heterogeneity, activity of brain cancer stem cells (BCSCs), immune evasion, and function of the blood–brain barrier (BBB) are attractive targets for new therapeutic strategies. In this review, we summarize the importance of sialic acid-modified nanoparticles in brain tumor progression.     

UVB Radiation and Selected Tryptophan-Derived AhR Ligands—Potential Biological Interactions in Melanoma Cells

Excessive UV exposure is considered the major environmental factor in melanoma progression. Human skin is constantly exposed to selected tryptophan-derived aryl hydrocarbon receptor (AhR) ligands, including kynurenine (KYN) and kynurenic acid (KYNA), as they are endogenously produced and present in various tissues and body fluids. Importantly, recent studies confirmed the biological activity of KYN and KYNA toward melanoma cells in vitro. Thus, in this study, the potential biological interactions between UVB and tryptophan metabolites KYN and KYNA were studied in melanoma A375, SK-MEL-3, and RPMI-7951 cells. It was shown that UVB enhanced the antiproliferative activity of KYN and KYNA in melanoma cells. Importantly, selected tryptophan-derived AhR ligands did not affect the invasiveness of A375 and RPMI-7951 cells; however, the stimulatory effect was observed in SK-MEL-3 cells exposed to UVB. Thus, the effect of tryptophan metabolites on metabolic activity, cell cycle regulation, and cell death in SK-MEL-3 cells exposed to UVB was assessed. In conclusion, taking into account that both UVB radiation and tryptophan-derived AhR ligands may have a crucial effect on skin cancer formation and progression, these results may have a significant impact, revealing the potential biological interactions in melanoma cells in vitro.     

Comparison of antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from humans and chicken carcasses in Poland

Campylobacter-associated gastroenteritis remains an important cause of morbidity worldwide, and some evidence suggests that poultry is an important source of this foodborne infection in humans. This study was conducted to analyze the prevalence and genetic background of resistance of 149 Campylobacter jejuni and 54 Campylobacter coli strains isolated from broiler chicken carcasses and from stool samples of infected children in Poland from 2003 through 2005. Nearly all isolates were susceptible to macrolides and aminoglycosides. The highest resistance in both human and chicken strains was observed for ciprofloxacin (more than 40%), followed by ampicillin (13 to 21%), and tetracycline (8 to 29%). Resistance to ampicillin and tetracycline rose significantly between 2003 and 2005. Slight differences in resistance between human and chicken isolates indicate that although chicken meat is not the only source of Campylobacter infection in our population, it can be involved in the transmission of drug-resistant Campylobacter strains to humans.     

The application of macroalga Pithophora varia Wille enriched with microelements by biosorption as biological feed supplement for livestock

BACKGROUND: The paper discusses biosorption of microelements by a freshwater macroalga Pithophora varia Wille to produce biological feed supplement for livestock. The biomass was enriched with microelements recommended by feeding standards in a single and a multi‐metal system. RESULTS: The equilibrium of biosorption was described by using a Langmuir model and the following values of the maximum biosorption capacity in the single‐metal system were obtained: Zn(II), 61.1 mg g^?1; Co(II), 52.3 mg g^?1; Cu(II), 55.7 mg g^?1; and Mn(II), 38.3 mg g^?1. The average value of maximum biosorption capacity expressed in molar units for all the cations was equal 1.7 ± 0.2 meq g^?1, suggesting chemical rather than physical biosorption. It was also found that the mechanism of biosorption was due to cation exchange of alkali and alkaline earth metals with microelements. The biomass was also enriched with microelements in multi‐metal system. The total metal ion binding capacity in the multi‐metal system was two‐fold lower than in the single‐metal system and was 0.90 meq g^?1 in the preparation for laying hens and 0.95 meq g^?1 in the supplement for swine. CONCLUSION: Finally, the level of supplementation of livestock feed (with enriched single‐ and multi‐metal system macroalga), to cover 25% of total requirements for microelements, according to feeding standards, was provided. Copyright © 2008 Society of Chemical Industry     

A survey on the incidence of Prototheca mastitis in dairy herds in Lublin province,Poland

Prototheca mastitis has recently become an emerging disease; although its incidence is increasing steadily, its epidemiology remains largely understudied. The aim of this work was to investigate the prevalence of Prototheca spp. in dairy cows and their environment in Lublin province, covering most of southeastern Poland. Between December 2015 and July 2016, a total of 172 milking cows from 10 dairy farms were inspected for mastitis using clinical examination and the California Mastitis Test (CMT). Quarter milk samples (QMS, n = 179) and body site swabs (n = 151) from CMT-positive cows were collected for microbiological culture. In addition, we evaluated QMS and body site swabs from 23 healthy cows, along with 91 environmental samples. Of 100 CMT-positive cows, 71 had at least one QMS positive for microbial growth. In 8 (11.3%) of these cows, originating from 7 dairy farms, Prototheca spp. were cultured. The average somatic cell count of the Prototheca-containing milk was 4.02 × 10⁶ cells/mL compared with 0.13 × 10⁶ cells/mL of the Prototheca-free milk (collected from control animals). No significant differences were observed between mastitis and control cows with respect to counts of total white blood cells, lymphocytes, neutrophils, and eosinophils. Half of the cows with Prototheca spp. in their milk did not yield the algae from other anatomical sites. Eight cows were negative for the presence of Prototheca spp. in their milk but positive for the algae in swabs from anatomical sites. Among the environmental sources that were positive for Prototheca growth were watering troughs, manure, feed, and mud. All (45) Prototheca isolates recovered in this study were subjected to species- and genotype-level molecular identification. All QMS and most of the animal swabs (90%) yielded Prototheca zopfii genotype (gen.) 2. Of the animal samples, P. zopfii gen. 1 and Prototheca blaschkeae were isolated only from feces and rectum. Environmental samples grew either P. zopfii gen. 2 (67%) or P. zopfii gen. 1 (33%). This study demonstrates that P. zopfii gen. 2 is the third most common pathogen of mastitis in cattle in southeast Poland, with an overall incidence of 4.6%. Finding Prototheca spp., including P. zopfii gen. 1 and 2 and P. blaschkeae, in stool and rectal swabs from healthy animals may suggest their role as nonpathogenic microflora of bovine gut.