Functionalization of silicon surfaces with Si-C linked beta-cyclodextrin monolayers

Vinyl-terminated heptapodyl beta-cyclodextrins react with hydrogenated silicon surfaces to generate covalently-bound molecular recognition devices.     

Some predictions on ‘microscopic Hubble constant’ for the energies available at FAIR - GSI

The goal of this paper is to present some estimations of so-called 'microscopic Hubble constant' in the nucleus-nucleus collisions at the energies available at FAIR GSI, in the frame of CBM experiment. The analysis, based on the experimental data obtained in the previous nucleus-nucleus collisions at RHIC, indicated values of this constant of about 10²³s⁻¹ and ratios between the Hubble constant and 'microscopic Hubble constant' with the same magnitude as the ratio between the intensities of both interactions types involved. The UrQMD v 2.3 simulation code is used to generate events for Au-Au collisions at the energies of 5 GeV/u, 10 GeV/u, 15 GeV/u and 20 GeV/u and the Buda-Lund model is used for evaluation.     

Modelling of sorbic acid diffusion through bacterial cellulose-based antimicrobial films

Antimicrobial packaging protects the product from the external environment and microbial contamination, conferring numerous advantages on human health. Interest in biopolymers as packaging materials has considerably increased recently. Bacterial cellulose is an interesting biomaterial produced as nanofibrils by Acetobacter xylinium and is a promising candidate due to its remarkable properties. New composite materials with antimicrobial properties were developed in this work, containing poly(vinyl alcohol) (PVA) as polymer matrix and ground bacterial cellulose (BC) as reinforcing fibres. Sorbic acid was used as an antimicrobial agent because it is a preservative recognised in the food industry. The materials obtained were studied using Fourier-transformed infrared spectroscopy (FTIR). The swelling rate of the composites was also measured. Release experiments of sorbic acid from the composite films into water were performed and the mass transfer phenomena were investigated using Fick’s law of diffusion. The antimicrobial effect was tested against Escherichia coli K12-MG1655. The results obtained indicated that the new biocomposite films could be promising antimicrobial food packaging materials.     

The Effect of UV-Irradiation on Poly(vinyl alcohol) Composites with Bacterial Cellulose

The development of biodegradable packaging materials, especially from renewable resources is a constant preoccupation of nowadays, because of the environmental problems caused by synthetic polymers. The combination of cellulose with other polymeric materials could be an ecologic alternative and a way to use renewable resources for food packaging. Bacterial cellulose which is produced by microbial fermentation is also a promising material which can be used not only in biomedical application, but also as food packaging material. In this research different composite films between poly(vinyl alcohol)-bacterial cellulose (PVA-BC) were obtained by casting method. The obtained films were UV irradiated for different periods of times from 1 to 10 hours, using a mercury lamp, Philips TUV-30, emitting light mainly at 254 nm. Changes in FT-IR spectra before and after UV irradiation and the modification of transparency and of the swelling characteristics of the films were observed. As it was expected the composites materials are sensitive at UV exposure.     

Improvement in Radiation Stability of EPDM by Efficient Antioxidants

This paper analyses the stabilization effect induced by the presence of several compounds with antioxidant features (oleanolic acid, quercetin, capsaicin, metallic selenium and rosemary extract). The investigation are carried out for different additive concentrations (0, 0.25, 0.50 and 1% w/w), as well as for pairs of metallic selenium with the other four compounds. For antirad contribution to the delaying of radiochemical oxidation, modified and pristine EPDM samples were irradiated in GAMMATOR machinery provided with ¹³⁷Cs source. While dose rate is 0.4 kGy.h⁻¹, the total doses were 0, 10, 20 and 30 kGy, which are specific for radiosterilization. The results are obtained by application of two complementary techniques: isothermal chemiluminescence (180 °C) and FT-IR spectroscopy. From chemiluminescence determinations oxidation induction times and rate of oxidation were calculated as the main kinetic characteristics depicting the progress in the oxidative degradation of polymer substrate. FT-IR spectroscopy allows us to evaluate the evolution of hydroxyl and carbonyl accumulations.     

Silicone composites containing stabilized silver clusters or nanoparticles

Silver nanoparticles are of high importance due to their electrical, magnetic, and optical properties, as well as catalytic and biocidal activity that are superior to the bulk silver and other metals. To prepare certain devices, generally, silver is incorporated into a matrix either as preformed or in situ‐generated particles. Silver nanoparticles were generated in situ into a silicone matrix formed by cohydrolysis of the mixture of silanes, each of them having a certain role: dimethyldiethoxysilane (DMDES) as a precursor for highly flexible polydimethylsiloxane, methyltriethoxysilane (MTES) as a cross‐linker highly compatible with polydimethylsiloxane, and 3‐aminopropyltriethoxysilane as a stabilizer, since it can readily complex to silver atoms through its amine functionality. Dimethylformamide (DMF) was used as a solvent for the silver nitrate and reducing agent. The samples were investigated both in sol state and as aged coating films deposited on glass substrate. The complexation of the silver and the matrix formation were emphasized by FTIR. The size of the formed silicone particles encapsulating silver was estimated by dynamic light scattering (DLS) (about 100 nm) in sol and by AFM in film (about 90 nm). The formation of the clusters or nanoparticles depending on the ratio between the reducing and complexing agents was evidenced by UV–Vis absorption spectra. Thus, it would create conditions to stop and isolate clusters at the desired size by precise control of the experimental conditions. The composites could be used alone as antibacterial‐coating materials but also, porous silica having incorporated silver clusters with potential applicability in catalysis may result after their calcination. Copyright © 2010 John Wiley & Sons, Ltd.     

Process Intensification of Emulsion Polymerization in the Continuous Taylor Reactor

Summary: Process intensification is investigated by the emulsion polymerization of styrene in the continuous Taylor reactor. The result is an increase in space time yield up to a factor 200 in comparison to a semi-batch polymerization process. This is obtained by a fast emulsion polymerization with a mean residence time, which is reduced to 60 seconds. The article presented the results of the process and the economical aspects of the Taylor reactor plant.     

GD3- and O-acetylated GD3-gangliosides in the GM2 synthase-deficient mouse brain and their immunohistochemical localization

Gangliosides in the brain of the knockout mouse deficient in the activity of β1,4 N-acetylgalactosaminyl transferase (β1,4 GalNAc-T)(GM2 synthase) consisted of nearly exclusively of GM3- and GD3-gangliosides as expected from the known substrate specificity of the enzyme and in confirmation of the initial reports from two laboratories that generated the mutant mouse experimentally. The total molar amount of gangliosides was approximately 30% higher in the mutant mouse brain than that in the wild-type brain. However, contrary to the initial reports, one-fourth of total GD3-ganglioside was O-acetylated. It reacted positively with an anti-O-acetylated GD3 monoclonal antibody and disappeared with a corresponding increase in GD3-ganglioside after mild alkaline treatment. The absence of O-acetylated GD3 in the initial reports can be explained by the saponification step included in their analytical procedures. Although quantitatively much less and identification tentative, we also detected GT3 and O-acetylated GT3. Anti-GD3 and anti-O-acetylated GD3 monoclonal antibodies gave positive reactions in the brain of mutant mouse as expected from the analytical results. Either antibody barely stained wild-type brain except for immunoreactivity of GD3 in the cerebellar Purkinje cells. The distributions of GD3 and O-acetylated GD3 in the brain of mutant mouse were similar but differential localization was noted in the cerebellar Purkinje cells and cerebral cortex.     

A catalytic activity model based on the structural defects of catalysts II. Alumina catalyst characterisation by radioluminescence method

The characterisation by radiothermoluminescence /RTL/ method of alumina TA 600 catalyst used for 1-butene isomerisation in cis- and trans-2-butene is described. The glow curve, the RTL parameters and the catalyst-reactant radiative coupling evidenced by RTL method are presented. Using the correlation between catalytic activity and RTL data a catalytic activity model is suggested. On the basis of such a model the importance of the structural defects of the catalyst and/or support for the catalytic activity is explained.