Effects of composition and plastifier on the light scattering of polymer glasses and properties of polymeric optical fibers made from styrene-methyl methacrylate copolymers

High optical purity polystyrene (PS), poly(methyl methacrylate) (PMMA) and styrene-methyl methacrylate statistical copolymers (S-MMA) were prepared. Light scattering measured on polymeric glasses depends on the chemical composition of the polymer and on the refractive index of the plastifier added. An isorefractive plastifier reduces considerably the scattering values for the copolymers S-MMA, while having no significant effect on the scattering of PMMA. A plastifier with a refractive index different from that of the polymer raises distinctly the light scattering values in all cases. It has been shown that the isorefractive plastifier has a favourable effect on attenuation loss of polymeric optical fibers (POF) obtained from the copolymer S-MMA 2/1.     

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4–2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu²⁺ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε₃₀₂/Cu > 8 × 10³ M⁻¹ cm⁻¹) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O₂-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O₂-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-Cu^I₂(RS)₂(RSSR) and Cu^I₂(RSSR)₂. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O₂ activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)–thiolates promoted by a growing electronically coupled –[Cu^I₂(RSSR)]_n– polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)–disulfide interaction, which may have a profound impact on biological systems.     

Cytoprotective effect of a bilberry extract against oxidative damage of rat hepatocytes

The effect of a bilberry extract (BE, 25% anthocyanins) against oxidative damage in primary cultures of rat hepatocytes, induced by tert-butyl hydroperoxide and allyl alcohol, was investigated. BE displayed cytoprotective effects at 100 and 500 μg/ml in the MTT viability test. It protected the cells against lactate dehydrogenase leakage and lipoperoxidation products formation. Maximum protection (58%) was noted using 500 μg/ml of BE and intoxication by allyl alcohol. The observed cytoprotective effect is probably due to the antioxidant properties of its constituents, mainly anthocyanins. BE scavenged DPPH (IC₅₀ 3.99 ± 0.14 μg/ml) and enzymatically generated superoxide radical with an activity equivalent to 108 ± 7.2 U of superoxide dismutase per mg of extract. Our results support the use of bilberry and bilberry extracts in functional foods and food supplements designed for the prevention of chronic diseases associated with oxidative stress.     

Temperature fields of the extruded pipe under conditions of co-current cooling

This article examines the temperature fields of the thick wall pipe while cooling it under the process of extrusion. We solved the Fourier–Kirchhoff equation by Fourier method in the form of an infinite row and with the help of Bessel’s functions. The equations were transformed into dimensionless forms and a solution of during heat we got as the function of Biot’s and Fourier’s number, dimensionless inner radius and thermal capacitance ratio of contact phases.     

An in situ Raman spectroelectrochemical study of the controlled doping of single walled carbon nanotubes in a conducting polymer matrix

The interaction of single wall carbon nanotubes (SWCNT) and the conducting polymer poly(3,4-ethylendioxythiophene/polystyrenesulfonate) (PEDOT/PSS) was studied by in situ Raman spectroelectrochemistry. The mixing of SWCNT with PEDOT/PSS caused a partial doping of SWCNT which was indicated by the change of relative intensity of the SWCNT Raman features. We have demonstrated for the first time that in situ Raman spectroelectrochemistry is a method of choice for precise and effective control of doping level of composites of conducting polymers and SWCNT. For electrochemical doping of SWCNT embedded in PEDOT/PSS the bleaching of RBM and TG modes of the SWCNT is delayed as compared to that in pure SWCNT. The delay is of about 0.2 V. This potential difference vanishes at higher potentials. The delayed response to doping is observed for both the SWCNT and the polymer matrix features. In the latter case the response is specific for individual polymer bands. Furthermore, during p-doping most of the polymer bands exhibit a subsequent monotonous bleaching. This contrasts with the behavior of the pristine polymer where the intensity changes are non-monotonous.     

Determination and correlation of axial-mixing parameters in an agitated liquid-liquid extraction column

Dispersion coefficients were measured in a pilot-plant sized agitated liquid-liquid extraction column of the Kuhni type. Available techniques were considered, and the axial mixing in both phases obtained over a broad range of operating conditions, both with and without mass transfer and with two sets of stator plates. Earlier correlations for backmixing in the continuous phase were checked and improved, the final equation being successfully tested on available published data.     

Biosynthesis of Colabomycin E,a New Manumycin‐Family Metabolite,Involves an Unusual Chain‐Length Factor

Colabomycin E is a new member of the manumycin‐type metabolites produced by the strain Streptomyces aureus SOK1/5‐04 and identified by genetic screening from a library of streptomycete strains. The structures of colabomycin E and accompanying congeners were resolved. The entire biosynthetic gene cluster was cloned and expressed in Streptomyces lividans. Bioinformatic analysis and mutagenic studies identified components of the biosynthetic pathway that are involved in the formation of both polyketide chains. Recombinant polyketide synthases (PKSs) assembled from the components of colabomycin E and asukamycin biosynthetic routes catalyzing the biosynthesis of “lower” carbon chains were constructed and expressed in S. aureus SOK1/5‐04 ΔcolC11–14 deletion mutant. Analysis of the metabolites produced by recombinant strains provided evidence that in both biosynthetic pathways the length of the lower carbon chain is controlled by an unusual chain‐length factor supporting biosynthesis either of a triketide in asukamycin or of a tetraketide in colabomycin E. Biological activity assays indicated that colabomycin E significantly inhibited IL‐1β release from THP‐1 cells and might thus potentially act as an anti‐inflammatory agent.     

The control of graphene double-layer formation in copper-catalyzed chemical vapor deposition

The growth of graphene during Cu-catalyzed chemical vapor deposition was studied using ¹²CH₄ and ¹³CH₄ precursor gasses. We suggest that the growth begins by the formation of a multilayer cluster. This seed increases its size but the growth speed of a particular layer depends on its proximity to the copper surface. The layer closest to the substrate grows fastest and thus further limits the growth rate of the upper layers. Nevertheless, the growth of the upper layers continues until the copper surface is completely blocked. It is shown that the upper layers can be removed by modification of the conditions of the growth by hydrogen etching.     

Detection of DNA fragments from wheat in blood of animals

Delivery of foreign DNA is still a very controversial issue, especially in relation to genetically modified organisms. It is not necessary to use genetically modified feed to verify the possible transfer of DNA from food into the body. In this study, we evaluated the possible transfer of DNA from wheat forage (of single component diet) into the blood of three different organisms. DNA isolation kits were used to isolate total DNA from blood and feed. Blood was taken for analysis from rats (after 23 days feeding wheat), broilers (15 days), and carp (34 days). Housekeeping genes were used to verify blood samples (rats: glyceraldehyde-3-phosphate dehydrogenase/GAPDH/, broilers: growth hormone gene/GCH/and carp: small ribosomal subunit/40S/). We used GAPDH and actin to determine whether DNA from wheat was transferred into animal blood. No purple and common wheat DNA fragments were detected in the blood of any animal tested, suggesting no transfer of the tested wheat DNA into the body. Various contents of anthocyanins in the feeding variants had no effect on the transfer of wheat DNA into the blood of animals. Our results correspond to some studies that have not proved transfer DNA from genetically modified feed into the target organism.