Functional studies of synthetic gramicidin hybrid ion channels in CHO cells

The function of a gramicidin hybrid ion channel in living Chinese hamster ovary (CHO) cells was investigated by the patch clamp method. The synthetic ion channel 1 consists of two cyclohexyl ether amino acids that link two mini-gramicidin strands. With 1 at a concentration of 1.0 microM, an increase in the whole-cell membrane conductance was observed after 1.37 min. The conductance showed larger currents when Cs(+) was used as charge carrier than when Na(+) and K(+) were used. In single-channel recordings with Cs(+) as charge carrier, the substance showed comparable single-channel amplitudes in the membrane of living cells and artificial black lipid bilayers. In addition to functioning as a cation channel, compound 1 appeared to be a water channel. Exposure of the CHO cells to an extracellular hypoosmotic solution did not substantially change the cell volume. Extracellular hypoosmotic conditions in the presence of 1 increased the cell size to 146.5 % that of the control. Thus, the synthetic hybrid channel 1 can function as a cation channel with some Cs(+) specificity, and as a water channel in CHO cells.     

Curcumin and Its New Derivatives: Correlation between Cytotoxicity against Breast Cancer Cell Lines,Degradation of PTP1B Phosphatase and ROS Generation

Breast cancer is the most common cancer of women—it affects more than 2 million women worldwide. PTP1B phosphatase can be one of the possible targets for new drugs in breast cancer therapy. In this paper, we present new curcumin derivatives featuring a 4-piperidone ring as PTP1B inhibitors and ROS inducers. We performed cytotoxicity analysis for twelve curcumin derivatives against breast cancer MCF-7 and MDA-MB-231 cell lines and the human keratinocyte HaCaT cell line. Furthermore, because curcumin is a known antioxidant, we assessed antioxidant effects in its derivatives. For the most potent cytotoxic compounds, we determined intracellular ROS and PTP1B phosphatase levels. Moreover, for curcumin and its derivatives, we performed real-time microscopy to observe the photosensitizing effect. Finally, computational analysis was performed for the curcumin derivatives with an inhibitory effect against PTP1B phosphatase to assess the potential binding mode of new inhibitors within the allosteric site of the enzyme. We observed that two tested compounds are better anticancer agents than curcumin. Moreover, we suggest that blocking the -OH group in phenolic compounds causes an increase in the cytotoxicity effect, even at a low concentration. Furthermore, due to this modification, a higher level of ROS is induced, which correlates with a lower level of PTP1B.     

A Median-Unbiased Estimator of the AR(1) Coefficient

A proof is given that the median of the ratios of consecutive observations of a stationary first-order autoregressive process X_t = α X _{t −1} + Y_t with P ( Y_t ≥ 0) = P ( Y_t ≤ 0) = 1/2 and P ( X_t = 0) = 0 is a median-unbiased estimator of α.     

The compression specificity of plant tissue

The aim of this study was to determine the compression characteristics of nonhomogeneous plant materials with a complex morphological structure (beetroots, celery roots, and potato tubers), to compare the analyzed samples with the compression characteristics of reference materials (homogeneous isotropic structural materials: steel coil spring and vulcanized rubber), and to determine the influence of the compression rate on stress in compressed samples. Structural materials and plant materials clearly differed in compression characteristics. Excluding the short initial compression phase, the compression curves for the steel coil spring and vulcanized rubber were straight parallel lines, and the higher the crosshead speed, the higher the lines' location in the diagram. In tests conducted on plant materials, the rate of changes in compression force increased throughout the experiment with an increase in crosshead speed. The greatest variations in compression force resulting from differences in crosshead speed were observed in potato samples. The apparent retardation times determined in the developed rheological model ranged from 0.079 s for the steel coil spring to 6.863 s for potatoes.     

Low Temperature Endotherm in Multiblock Terpoly(ester‐b‐ether‐b‐amide) Thermoplastic Elastomers

The phenomenon of the occurrence of a middle‐temperature thermal effect in crystallizable multiblock thermoplastic elastomers, the so‐called annealing endotherm has not yet been univocally explained, hence, it was subjected to DSC analysis. The formation of this endotherm in response to the time and temperature of conditioning (stabilisation) of the sample has been followed. The investigations have been performed for a specific polymer system, poly(tetramethylene terephthalate)‐block‐poly(oxytetramethylene)‐block‐polylaurolactam‐(PBT‐b‐PTMO‐b‐PA12)‐_n. The specific property of this elastomer is the solubility or a partial solubility of one of the components (PBT block) in the two remaining ones being mutually insoluble. The occurrence of the two different amorphous phases (PBT and PA12) in this elastomer with glass transition temperatures T_g > 20°C is also possible. This specific system permits to observe an interesting phenomenon, since at the points determining the middle‐temperatures of the glass transition temperatures of the elastomer, the two small endotherms are shaping; after proper stabilisation they are approaching each other, and as a result of this process they would form one extreme. This extreme comprises the thermal effect of the dispersion of the mesomorphic aggregates being the intermediate form between the amorphous state and the crystalline state. The mesomorphic aggregates constitute the additional network points of the physical polymer network of the elastomer.     

Kinetic models of quality parameters of spreadable processed Gouda cheese during storage

The aim of the study was to prepare mathematical models based on the Arrhenius equation as predictive tools for the assessment of changes in quality parameters during the storage of spreadable Gouda cheese at temperatures of 8, 20 and 30 °C. The activation energy value and the chemical reaction rate constant enabled the construction of kinetic models, which helped to estimate the direction and rate of changes. Moreover, the activation energy (E_a) of the quality parameters was used to determine the sequence of their vulnerability during storage. The value of activation energy corresponding to temperature changes resulted in the following order of susceptibility of the quality parameters: ΔC?>?ΔE?≈?water activity?>?texture parameters?>?pH?>?colour?>?sensory parameters?>?rheological parameters. The research showed limited applicability of the mathematical models for estimation of quality parameters referring to spreadable processed Gouda cheese.     

Synthesis and photocatalytic performance of TiO<Subscript>2</Subscript> nanospheres–graphene nanocomposite under visible and UV light irradiation

In this article, we present a fast and simple method to produce TiO₂ nanospheres–graphene nanocomposite with high photocatalytic activity under visible and UV light irradiation. TiO₂ nanospheres were adsorbed on graphene in sol–gel process. First, titanium (IV) butoxide underwent hydrolysis in graphene oxide (GO) ethanol solution resulting in TiO₂ nanospheres deposition on GO. Next, the material was calcinated to generate the phase transition of TiO₂ into anatase and reduce GO to graphene. The detailed characterization of the material was performed via transmission electron microscopy, energy dispersive X-rays spectrometer, Fourier-transformed infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Interestingly, the band-gap energy of the prepared photocatalyst was drastically decreased in comparison with the commercial photocatalyst P25 from 3.05 to 2.36 eV. This influenced in the activation of the material under visible light and resulted in high photocatalytic activity in the process of phenol decomposition in visible and UV irradiation.     

Application Tests of New Wetting Compositions for Wildland Firefighting

Extinguishing forest fires is a critical issue for fire brigades; fire can spread throughout vast areas in a relatively short period of time. The studies presented in this paper describe the results of laboratory and field tests of new compositions of wetting agents for extinguishing wildland fires. The studies assessed the ability to penetrate surface fuels using 0.5 and 1% solution of wetting compositions. The penetration of the liquid through the layer of the loose rotting wood with solutions of obtained wetting agents was up to 68 times faster than with water. The absorption of water droplet was even 40 times slower in comparison to wetting agent solutions. Based on laboratory research, compositions that exhibit the best wetting properties were analysed in real conditions in field tests to assess their capacity to penetrate in surface fuels, their ability to make fire barriers and their efficiency in suppressing fires of soil cover and thickets. In tests performed in 4 m² plots, the wetting compositions hold the flames from crossing a thin firebreak for up to three times longer periods than water. The results of the studies confirmed a significant increase in efficiency when new biodegradable wetting agents are employed to extinguish forest fires.     

Deformation of Cotton Weft-Knitted Fabric Subjected to Tensile Loads

The main goal of paper presented is to introduce the SolidWorks environment to model the complex structure of knitted fabric. The geometrical model according to Leaf and Glaskin consists of some paths of unequivocal shape. The problem is described using the physical model and the set of mathematical equations. The structure is next discretized by means of finite element net and used to investigate the biaxial tensile elastic properties of cotton plain knitted fabrics. The obtained theoretical results are verified with a good convergence by means of tensile tests of knitted fabrics.     

Heat Transfer and Pressure Drop Measurements During Boiling in Vertical Tubes with Coiled-Wire Inserts

ABSTRACT

The paper presents thermal and flow analyses of the boiling process of R507, R410 and R407 C refrigerants inside vertical tubes (21 mm) with coiled-wire inserts and various coil diameters (20; 20.5 mm), coil pitches (26; 44 mm) and wire diameters (1.5; 2 mm). The study differs from other publications as regards the conditions under which the experiment was conducted. It focuses on the boiling process in two long vertical tube sections (2 m), paired in an in-line arrangement. The study was conducted within a moderate range of mass flux densities 80–240 kgm^?2s^?1 and at low heat flux densities 5–11 kWm^?2, corresponding to the operating conditions of air coolers. The study examined the influence of vapour quality, mass flux density, geometrical parameters of the inserts and the impact of temperature glide on heat transfer coefficient and flow resistance increases as compared with a plain tube. The obtained increase ratios of heat transfer coefficients amounted to 1.1-1.7 for an azeotropic agent and to 1.1-1.3 for zeotropic agents, with the relative increase in flow resistances amounting to 1.8-4.5. New equations are proposed in the paper for the calculation of heat transfer coefficient and flow resistance values for boiling inside vertical tubes with spiral inserts.