Electrochemistry of carbazolylalkyl substituted polysiloxanes

Carbazolylalkyl-substituted polysiloxanes undergo anodic oxidation to give insoluble electrode supported cross-linked films containing dicarbazolyl groups. The electrochemistry of the immobilized dicarbazolyls can be addressed and the electrochemical switching between the coloured (oxidized) and colourless (reduced) states forms the basis of an electrochromic display. Cyclic voltammetry suggests a model in which virtually all of the pendant carbazole groups are converted into dicarbazolyls. The model is consistent with observation of a range of polymers, and analogous oligomers, and contrasts with earlier reports on the same type of material.     

Mechanical and Thermal Pretreatments of Crushed Tomatoes: Effects on Consistency and In Vitro Accessibility of Lycopene

ABSTRACT:  The effects of mechanical and thermal treatments on the consistency and  in vitro  lycopene accessibility of crushed tomatoes were evaluated. Different crushing intensities and a subsequent heat treatment carried out as a heat shock (95 °C for 8 min) or a boiling step (100 °C for 20 min) were examined. Additional homogenization was compared with milder crushing regarding the effect on lycopene content and  in vitro  accessibility. Textural properties, polygalacturonase and pectinmethylesterase activity, pectin degree of methoxylation, lycopene content, and  in vitro  lycopene accessibility were evaluated. Microstructure was studied using both light and transmission electron microscopy. Crushing and subsequent heating affected the pectin degree of methoxylation and the consistency of the crushed tomatoes. The mechanical and thermal treatments did not affect the lycopene content to any great extent; however,  in vitro  accessibility seemed to improve with extensive crushing followed by heating. Crushing or homogenization in itself was not enough to increase  in vitro  lycopene accessibility.     

Some properties of the polygalacturonase from four Zimbabwean wild fruits (Uapaca kirkiana, Zizphus mauritiana, Tamarindus indica and Berchemia discolor fruits)

Polygalacturonase was extracted from ripe Uapaca kirkiana, Zizphus mauritiana, Tamarindus indica and Berchemia discolor fruits of Zimbabwe. Protein concentrations and activities of the enzymes in the extracts were determined in the four fruit extracts. The protein concentrations in the enzyme extracts ranged from 0.82 ± 0.17 to 1.97 ± 0.13 mg/ml and enzyme activities from 1.99 ± 0.13 to 6.64 ± 0.38 mmol min⁻¹ mg⁻¹ in the four fruit extracts. Optimum pH of the enzyme ranged from 4.5 to 5 and optimum temperature from 25 to 37 °C. The enzyme extracts reduced the viscosity of 1% pectin solutions in an experiment which was done together with assay for reducing sugars to prove the activities of the enzyme extracts in the four wild fruits. The K_m and V_max ranged from 0.115 to 0.252 mg/ml and 0.0057 to 0.0119 mmol reducing groups/min/mg protein, respectively, in the four polygalacturonase extracts. Calcium chloride and sodium chloride activated the PG from all sources to a greater extend than magnesium chloride and barium chloride. PG from the other three fruits had very little effect on the polysaccharide from U. kirkiana.     

Ultrafast nonlinear optical properties of bundles of carbon nanotubes

The optical properties of bundled nanotubes were examined for high-bit-rate telecommunication applications. The diameters of the nanotubes in the bundles were determined to be from 0.6783 to 1.5147 nm, and their chiralities were also determined using resonant vibration modes. Their crystallographic quality was examined using atomic-scale resolution microscopy. Then, we highlight this vicinity performing calculations to determine the intertube equilibrium distance. These simulations integrate van der Waals interactions between nanotubes. Ultrafast and efficient nonlinear absorption properties of bundled nanotube films produced using a simple process were demonstrated and compared with semiconducting quantum-wells.     

Rheology and microstructure of carrot and tomato emulsions as a result of high-pressure homogenization conditions

High-pressure homogenization, as a way to further mechanically disrupt plant cells and cell walls compared to conventional blending, has been applied to thermally treated and comminuted carrot and tomato material in the presence of 5% olive oil. Mixes of both vegetables in a 1:1 ratio were also included. Both the effect of homogenization pressure and the effect of multiple process cycles were studied. The different microstructures generated were linked to different rheological properties analyzed by oscillatory and steady state measurements. The results showed that while carrot tissue requires a high shear input to be disrupted into cells and cell fragments, tomato cells were broken across the cell walls already at moderate shear input, and the nature of the tomato particles changed to amorphous aggregates, probably composed of cell contents and cell wall polymers. All the plant stabilized emulsions generated were stable against creaming under centrifugation. While for tomato a low-pressure multiple cycle and a high-pressure single-cycle process led to comparable microstructures and rheological properties, carrot showed different rheological properties after these treatments linked to differences in particle morphology. Mixes of carrot and tomato showed similar rheological properties after homogenizing in a single or in a split-stream process. Practical Application: Following consumers' demand, the food industry has shown a growing interest in manufacturing products free of gums and stabilizers, which are often perceived as artificial. By tailored processing, fresh plant material could be used to structure food products in a more natural way while increasing their nutritional quality.     

Marine phospholipids as dietary carriers of long‐chain polyunsaturated fatty acids

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are polyunsaturated fatty acids (PUFA) of the n‐3 series. Fish oil is a classical source of n‐3 PUFA, where they occur in the form of triacylglycerols (TAG). However, new sources of n‐3 PUFA esterified in phospholipids (PL) are emerging. We prepared liposomes from a natural marine lipid extract and examined their behaviour under conditions mimicking that of the gastrointestinal tract. This physicochemical approach proved that liposomes could be used as an effective oral PUFA delivery system. In vivo studies in rats were performed to examine the metabolic fate of EPA (20:5 n‐3) and DHA (22:6 n‐3) delivered either in PL from liposomes or in TAG from oil. Liposome ingestion increased PUFA bioavailability in lymph compared with fish oil. The proportion of n‐3 PUFA esterified in the sn‐2 position of chylomicron TAG depended on the dietary lipid source. Complex time‐course profiles were observed for plasma lipids with liposome supplementation over a 2‐week period, suggesting time‐dependent regulations. Taken together, the type of PUFA, EPA or DHA, as well as its intramolecular distribution in chylomicron TAG seemed to influence the metabolic fate of the fatty acids and their physiological activities.     

Few electron limit of n-type metal oxide semiconductor single electron transistors

We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.     

Efficient block size selection in H.264 video coding standard

Selecting an efficient variable block size mode in H.264 video coding standard for better compression performance is considered. The proposed scheme is based on a 3D recursive search algorithm and takes into account the motion vector cost and previous frame information. The best mode for the current macroblock is obtained by analysing the modes for a maximum of four macroblocks in the current and previous frames. An improvement in the encoding time with negligible impact on subjective and quantitative performance has been achieved.