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Selected Abstracts

Effect of humic material on the bacterioplankton community composition in boreal lakes and mesocosms

Kaisa Haukka
Summary The bacterioplankton community composition in two Finnish forest lakes with different content of humic substances was studied by denaturing gradient gel electrophoresis (DGGE) and sequencing of the major bands. The same dominant bacterial phylotypes were detected in the bacterioplankton communities of clear-water Lake Ahvenlammi and humic Lake Sammalisto. For 4 years, in every water layer, Actinobacteria was the dominant and Verrucomicrobia the second most common phylum. In the hypolimnion, other dominant phyla were also found. We set up a mesocosm experiment to assess the effect of a sudden load of allochthonous humus extract to the bacterioplankton community composition. Changes in the bacterial communities were followed in four control and four humus extract-added mesocosms for 50 days. In the humic mesocosms the phylotypes of allochthonous Proteobacteria arriving with the humus extract were initially prevalent but disappeared during the first weeks. After this the Actinobacteria -dominated communities resembled the bacterioplankton communities of the control mesocosms and Lake Ahvenlammi. Towards the end of the experiment the community patterns in all the mesocosms started to change slightly because of erratic occurrence of new proteobacterial phylotypes. Thus the effects of a sudden load of allochthonous humic material and bacteria to the bacterioplankton community composition were transient. [source]

Anti-oxidant activity of added tea catechins on lipid oxidation of raw minced red meat, poultry and fish muscle

Shuze Tang
The comparative anti-oxidative effects of added tea catechins (TC) and ,-tocopherol to raw minced red meat (beef and pork), poultry (chicken, duck and ostrich) and fish (whiting and mackerel) muscle on susceptibility to lipid oxidation were investigated during 10 days of refrigerated (4 °C) display. Fresh meats, poultry and fish, purchased from a local market, were trimmed to remove bones, skin and surface fat and minced through a 4 mm plate. The minced muscle of each species was treated with either the addition of 300 mg TC kg,1 minced muscle (TC300) or 300 mg ,-tocopherol kg,1 minced muscle (VE300). Minced muscle without any additives served as control (C). Oxidative stability (TBARS) was measured at 3-day intervals. Total lipids, fatty acid composition, total iron and haem iron from minced muscle for each species were also analysed. The susceptibility of untreated minced muscle to lipid oxidation was in the decreasing order: mackerel > beef > duck > ostrich > pork , chicken > whiting. This may be because of the different content of total fat, iron and fatty acid composition between species. The TC300 significantly (P < 0.05) reduced lipid oxidation compared with controls for all seven species as shown by lower TBARS values. The anti-oxidant potential of TC was two to fourfold greater than that of ,-tocopherol at the same concentration and this potential was species dependent. The VE300 showed limited capacity in inhibiting lipid oxidation for pork, chicken, duck and whiting. The results obtained show that TCs are powerful natural antioxidants when used in minced muscle food. [source]

Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols.


Abstract Two series of poly(ether urethane)s and one series of poly(ester urethane)s were synthesized, containing, respectively, poly(oxytetramethylene) diol (PTMO) of Mn = 1000 and 2000 and poly(,-caprolactone) diol of Mn = 2000 as soft segments. In each series the same hard segment, i.e., 4,4,-(ethane-1,2-diyl)bis(benzenethiohexanol)/hexane-1,6-diyl diisocyanate, with different content (, 14,72 wt %) was used. The polymers were prepared by a one-step melt polymerization in the presence of dibutyltin dilaurate as a catalyst, at the molar ratio of NCO/OH = 1 (in the case of the polymers from PTMO of Mn = 1000 also at 1.05). For all polymers structures (by FTIR and X-ray diffraction analysis) and physicochemical, thermal (by differential scanning calorimetry and thermogravimetric analysis), and tensile properties as well as Shore A/D hardness were determined. The resulting polymers were thermoplastic materials with partially crystalline structures (except the polymer with the highest content of PTMO of Mn = 2000). It was found that the poly(ether urethane)s showed lower crystallinity, glass-transition temperature (Tg), and hardness as well as better thermal stability than the poly(ester urethane)s. Poly(ether urethane)s also exhibited higher tensile strength (up to 23.5 MPa vs. 20.3 MPa) and elongation at break (up to , 1950% vs. 1200%) in comparison with the corresponding poly(ester urethane)s. Among the poly(ether urethane)s an increase in soft-segment length was accompanied by an increase in thermal stability, tensile strength, and elongation at break, as well as a decrease in Tg, crystallinity, and hardness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

In vitro evaluation of porous poly(L -lactic acid) scaffold reinforced by chitin fibers

Xiaoming Li
Abstract In this study, the previously reported porous three-dimensional poly(L -lactic acid) (PLLA) scaffolds reinforced by the chitin fibers (PLLA/CF) with and without the link were evaluated in vitro. Firstly, pH value of the phosphate buffered saline lixiviums of the PLLA/CF with different content of the chitin fibers was measured to get an appropriate content of the chitin fibers in the PLLA/CF. Then, the cell functions (attachment, proliferation, alkaline phosphatase per unit cell, total protein per unit cell, and osteonectin, osteopontin, and osteocalcin gene expression) of human osteoblast-like cells (SaOS2) cultured on the PLLA/CF with the link, PLLA/CF without the link and PLLA scaffold were compared. The results showed that the link treatment did not significantly influence the pH value of the lixiviums of the scaffolds, 30% volume content might be an appropriate content of the chitin fibers in PLLA/CF scaffold to keep the pH value of the lixiviums of the scaffolds between 7.0 and 7.2 during the lixiviation time of 16 weeks, the PLLA/CF scaffold was significantly better for the attachment, proliferation, differentiation, and mineralization of the osteoblast than PLLA, the link treatment did not significantly influence these cells activities, which further suggested that PLLA/CF with the link treatment might be an appropriate scaffold for tissue engineering. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source]

Effects of Phosphates and Salt in Ground Raw and Cooked Farmed Cod (Gadus morhua) Muscle Studied by the Water Holding Capacity (WHC), and Supported by 31P-NMR Measurements

S.O. Johnsen
ABSTRACT:, A model system consisting of ground farmed cod muscle (80%, w/w) and added brine (20%, w/w) with different content and combinations of salt (0% and 3% in brine) and phosphorus compounds (mono-, di-, tri- and hexametaphosphates; 0% and 3% in brine) was used to simulate industrial brining of muscle foods. Individual phosphorus component concentrations and breakdown as function of time (0, 23 h) were analyzed using 31P-NMR spectroscopy. The effects of salt and phosphate on water holding capacity (WHC) were measured at similar sampling times, and interrelations between phosphorous components determined by NMR and WHC were established. Addition of salt led to a significant increase (+18%) in WHC, and the combined effect of salt and phosphates was even more pronounced (+29%). The positive effect of triphosphate and salt on WHC was also seen after cooking (+36% in raw and +41% in cooked cod muscle, relative to control), although NMR analysis showed a rapid breakdown of di- and triphosphates. [source]

Silicification in sorghum (Sorghum bicolor) cultivars with different drought tolerance

Alexander Lux
Sorghum belongs to a group of economically important, silicon accumulating plants. X-ray microanalysis coupled with environmental scanning electron microscopy (ESEM) of fresh root endodermal and leaf epidermal samples confirms histological and cultivar specificity of silicification. In sorghum roots, silicon is accumulated mostly in endodermal cells. Specialized silica aggregates are formed predominantly in a single row in the form of wall outgrowths on the inner tangential endodermal walls. The density of silica aggregates per square mm of inner tangential endodermal cell wall is around 2700 and there is no significant difference in the cultivars with different content of silicon in roots. In the leaf epidermis, silicon deposits were present in the outer walls of all cells, with the highest concentration in specialized idioblasts termed ,silica cells'. These cells are dumb-bell shaped in sorghum. In both the root endodermis and leaf epidermis, silicification was higher in a drought tolerant cultivar Gadambalia compared with drought sensitive cultivar Tabat. Silicon content per dry mass was higher in leaves than in roots in both cultivars. The values for cv. Gadambalia in roots and leaves are 3.5 and 4.1% Si, respectively, and for cv. Tabat 2.2 and 3.3%. However, based on X-ray microanalysis the amount of Si deposited in endodermal cell walls in drought tolerant cultivar (unlike the drought susceptible cultivar) is higher than that deposited in the leaf epidermis. The high root endodermal silicification might be related to a higher drought resistance. [source]

Theory of Mind and Relational Complexity

Glenda Andrews
Cognitive complexity and control theory and relational complexity theory attribute developmental changes in theory of mind (TOM) to complexity. In 3 studies, 3-, 4-, and 5-year-olds performed TOM tasks (false belief, appearance,reality), less complex connections (Level 1 perspective-taking) tasks, and transformations tasks (understanding the effects of location changes and colored filters) with content similar to TOM. There were also predictor tasks at binary-relational and ternary-relational complexity levels, with different content. Consistent with complexity theories: (a) connections and transformations were easier and mastered earlier than TOM; (b) predictor tasks accounted for more than 80% of age-related variance in TOM; and (c) ternary-relational items accounted for TOM variance, before and after controlling for age and binary-relational items. Prediction did not require hierarchically structured predictor tasks. [source]

When Are Tutorial Dialogues More Effective Than Reading?

Kurt VanLehn
It is often assumed that engaging in a one-on-one dialogue with a tutor is more effective than listening to a lecture or reading a text. Although earlier experiments have not always supported this hypothesis, this may be due in part to allowing the tutors to cover different content than the noninteractive instruction. In 7 experiments, we tested the interaction hypothesis under the constraint that (a) all students covered the same content during instruction, (b) the task domain was qualitative physics, (c) the instruction was in natural language as opposed to mathematical or other formal languages, and (d) the instruction conformed with a widely observed pattern in human tutoring: Graesser, Person, and Magliano's 5-step frame. In the experiments, we compared 2 kinds of human tutoring (spoken and computer mediated) with 2 kinds of natural-language-based computer tutoring (Why2-Atlas and Why2-AutoTutor) and 3 control conditions that involved studying texts. The results depended on whether the students' preparation matched the content of the instruction. When novices (students who had not taken college physics) studied content that was written for intermediates (students who had taken college physics), then tutorial dialogue was reliably more beneficial than less interactive instruction, with large effect sizes. When novices studied material written for novices or intermediates studied material written for intermediates, then tutorial dialogue was not reliably more effective than the text-based control conditions. [source]

A Web page that provides map-based interfaces for VRML/X3D content

Yoshihiro Miyake
Abstract The electronic map is very useful for navigation in the VRML/X3D virtual environments. So far various map-based interfaces have been developed. But they are lacking for generality because they have been separately developed for individual VRML/X3D contents, and users must use different interfaces for different contents. Therefore, we have developed a Web page that provides a common map-based interface for VRML/X3D contents on the Web. Users access VRML/X3D contents via the Web page. The Web page automatically generates a simplified map by analyzing the scene graph of downloaded contents, and embeds the mechanism to link the virtual world and the map. An avatar is automatically created and added to the map, and both a user and its avatar are bidirectionally linked together. In the simplified map, obstructive objects are removed and the other objects are replaced by base boxes. This paper proposes the architecture of the Web page and the method to generate simplified maps. Finally, an experimental system is developed in order to show the improvement of frame rates by simplifying the map. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(2): 28,37, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10017 [source]

Graphite Oxides Obtained from Porous Graphite: The Role of Surface Chemistry and Texture in Ammonia Retention at Ambient Conditions

Mykola Seredych
Abstract Graphite oxides (GO) synthesized using Brodie and Hummers methods are tested for ammonia adsorption at ambient conditions with different contents of water in the system. Surface characterization before and after exposure to ammonia is performed using XRD, FTIR spectroscopy, potentiometric titration, thermal analysis, adsorption of nitrogen, and XPS. Oxidation of the same porous graphite using two methods results in materials with different textural and chemical features. On GO obtained using the Brodie method mainly epoxy and carboxylic groups are present whereas on the GO obtained using the Hummers method chemisorbed oxygen is also found. The contribution of the carboxylic groups in the latter material is greater. It also contains sulfur either in sulfones or as residual sulfuric acid. Ammonia is adsorbed either via reaction with surface groups or dissolution in water. The former is responsible for strong adsorption. The evidence of the catalytic effect of the carbon surface on activation of oxygen leading to surface oxidation is also observed. [source]

FTIR study of the CO adsorption over Pt/MFI catalysts: Ab initio interpretation

N. S. Nesterenko
Abstract The state and dispersion of Pt supported on MFI catalysts with different contents have been studied using Fourier transform infrared (FTIR) spectroscopy. Experimentally predicted Pt-containing complexes were simulated by density functional theory (DFT) for CO frequency shift estimation and determination of the relative intensities. According to DFT calculation and experimental data, a new interpretation was proposed. A new approach for estimation of the Pt dispersion based on IR spectra of adsorbed CO has been developed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]


ABSTRACT Electrical conductivity (EC) of cornstarch,water mixtures in the range 10:90 to 70:30 (w/w) was studied as a function of temperature. An external resistive heating system equipped with an electronic device capable of monitoring EC in real time was used and EC of the mixtures was measured while heated at a rate of 5C/min. Results showed that EC went through four different temperature-dependent stages (A, B, C and D). Stage B (41C to 64C) showed a lower EC increasing rate when compared with that of Stage A (from 25C to 41C), probably as a result of starch granule swelling. In Stage C (64C to 78C), EC behavior was found to be dependent on water content. When water content was more than 50%, the value for EC increased. On the other side, EC decreased when water content was less than 50%. Stage C was related to starch gelatinization, according to differential scanning calorimetry results obtained in this study. In Stage D (78C to 92C), a steady increase in EC was observed, probably as a result of the total solubilization of starch in water. It was concluded that Stage C in EC graphs corresponded to cornstarch gelatinization, so it might be possible to use EC monitoring as an alternative technique to measure cornstarch thermal characteristics with different contents of water. PRACTICAL APPLICATIONS Electrical conductivity can be used as an adequate technique to monitor gelatinization, granule swelling and phase change of starch as a function of temperature in corn starch,water mixtures with a wide range of water contents. With this technique, it is also possible to calculate important thermal parameters, such as the beginning and end of the gelatinization and the energy activation for the heating process of cornstarch. This can lead to a better design and control of important industrial corn processes such as alkaline cooking. [source]


ABSTRACT The study analyzed the effectiveness of two types of electronic nose systems to detect adulteration of extra virgin olive oil (EVOO) with rapeseed and sunflower oils. Tested methods included volatile analysis with the electronic nose based on MOS sensors (HS-E nose) and by direct coupling of SPME to MS (SPME-MS). Volatile compounds were analyzed also by SPME-GC/MS. Samples of EVOO were mixed with different proportions, ranging from 5 to 50% (v/v), of seed oils and fingerprints of volatile profiles of all samples were generated. In order to obtain as much chemical information as possible and to find a volatile marker to detect adulterations of EVOO with seed oils, principal component analysis (PCA) and partial least squares (PLS) analyses were applied to the data. The application of PCA and PLS analyses to the data from two electronic noses and SMPE-GC/MS were sufficient to differentiate the adulterated samples from pure EVOO. Excellent results were obtained in the prediction of the percentage of adulteration by PLS analysis. SPME-GC-MS analysis with subsequent PCA yielded good results; however, it was time-consuming. The two electronic noses, with subsequent PCA treatment of data, offering the advantages of rapidity and reliability, enabled detection of olive oil adulteration with different contents of seed oils. PRACTICAL APPLICATIONS Virgin olive oil is highly appreciated by consumers due to its nutritional benefits. Thus, its adulteration with low-grade olive oils or cheaper vegetable oils could potentially be very profitable for sellers or raw material suppliers and may yield large economic profits. In this way, authentication of virgin olive oils has become an interesting subject from both commercial and health perspectives. It has been proved that the two proposed types of electronic nose systems facilitate reliable detection of rapeseed and sunflower oils in extra virgin olive oil. Both MOS and MS electronic noses are faster than the conventional SMPE-GC/MS analysis. These well-correlated methodologies, offering the advantages of rapidity and reliability, opened up a new way of detecting adulteration of virgin olive oils. [source]

Theoretical studies on structural and electrical properties of PES/SPEEK blend nanofiltration membrane

AICHE JOURNAL, Issue 8 2009
A. F. Ismail
Abstract Polyethersulfone (PES) nanofiltration membranes were prepared using a simple dry-jet wet spinning technique with different contents of sulfonated poly(ether ether ketone) (SPEEK) ranging from 0 to 4 wt %. The structural parameters (rp and Ak/,x) and electrostatic properties (, and X) of the blend membranes were deduced by employing the combination of irreversible thermodynamic model, steric hindrance pore (SHP) model, and Teorell-Meyer-Sievers (TMS) model. The modeling results obtained have been analyzed and discussed. The mean pore radius and pore size distribution of the blends were also determined based on the theoretical models. The results showed that pore radius increased with increasing the concentration of SPEEK from 0 to 2 wt % but decreased with a further increase in SPEEK content. The water flux, however, showed a systematically increase with increasing SPEEK content. The SPEEK also showed significant effect on membrane electrical properties. Both effective charge density and ratio of effective charge density to electrolyte solution increased with increasing concentration of SPEEK in the dope solution, reaching a value of ,21.02 and ,2.29, respectively. The pore radius which was determined by using different transport models has also been analyzed and discussed. It is found that the addition of SPEEK into dope solution is one of the paramount parameters in developing the negatively charged nanofiltration membrane with enhanced water flux while retaining the pore radius in the nanometer range. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Condensed tannins in humid tropical fodder crops and their in vitro biological activity: Part 1,

Juan López
Abstract A descriptive study was conducted in order to determine the tannin profiles of tropical fodder crops. The following types of condensed tannins (CT) were determined (expressed as g kg,1 of dry matter): free (FCT), bound to protein (CTP), bound to fibre (CTF) and total (TCT). High FCT levels were found in Desmodium ovalifolium (228.4), Flemigia macrophylla (181.9), Guazuma ulmyfolia (129.7) and Leucaena leucocephala (129.5). The highest concentrations of CTP were detected in Gliricidia sepium (61.0), F macrophylla (23.3), and G ulmyfolia (21.1). CTF levels were the highest in G ulmyfolia (55.1), F macrophylla (46.7) and G sepium (41.5). Analyzed samples cultivated in vertisol and fluvisol soils showed different contents of tannins. It has been reported that plants with more than 60 g kg,1 FCT are less palatable and digestible than forages with lower concentrations of this chemical class, although there is more protein to bypass the rumen and higher nitrogen retention. Graminaceous plants showed higher concentrations of FCT and TCT concentrations were generally lower than legumes and other forage crops. Copyright © 2004 Society of Chemical Industry [source]

Effect of metallised carbon content of collector strip on the wear of contact wire,collector strip pair in railway systems

B. Pizzigoni
Abstract Among the topics related to the interaction between the contact wire of the overhead line and the collector strip, the wear that takes place at the contact interface, depending on both electrical and mechanical quantities, represents an important aspect of maintenance costs, affecting the mean lifetime of collectors, in terms of travelled kilometers (in terms of tenth of thousands), and contact line duration, in terms of years (between 15 and 40). Due to its importance in the global maintenance of both rolling stock and infrastructure, this topic deserved the attention of several regulations in the last decade. In order to investigate the effects of electro-mechanical wear on both contact wire and contact strip, a new test equipment has been designed and installed at Politecnico di Milano. A series of tests have been performed, involving different kinds of collector strip materials and contact conditions, tested at varying speeds and current intensities. This investigation concerned different collector strip configurations intended for 3kV D.C. lines. The combination of different contents of copper and metallised carbon in the collector has been found to influence the wear rate of both collector strip and contact wire. Differences in wear up to four times for the former and up to six times for the latter have been found depending on the composition of the collector. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A Kinetic Study on the Thermal Degradation of Multi-Walled Carbon Nanotubes-Reinforced Poly(propylene) Composites

Min-Kang Seo
Abstract Summary: The influence of the multi-walled carbon nanotubes (MWNTs) content on the thermal degradation behavior of MWNTs-reinforced poly(propylene) (PP) composites was investigated by using non-isothermal thermogravimetric analysis (TGA). Kinetic parameters of degradation were evaluated by using the Flynn-Wall-Ozawa iso-conversional method and the pseudo first-order method. As a result, compared with pristine PP, MWNTs-PP nanocomposites have lower peak temperatures of degradation, narrower degradation temperature ranges and a higher amount of residual weight at the end of the degradation, which is likely to be a result of specific interactions between complimentary functional groups. The values of the reaction order of MWNTs-PP nanocomposites determined by the Kissinger method are close to 1 in the non-isothermal degradation process. There is a good correlation between the Ea in region II and the peak temperature of degradation for the composites. Activation energies for degradation of different contents of MWNTs-filled PP nanocomposites as a function of conversion. [source]

A Recipe for Concept Similarity

MIND & LANGUAGE, Issue 1 2007
When this is so, it is comparatively easy for me to understand what you say when you deploy your concept, for us to disagree, agree, and so on. But what if your concept and mine do not have exactly the same content? This question has occupied a number of philosophers, including Paul Churchland, Jerry Fodor, and Ernie Lepore. This paper develops a novel and rigorous measure of concept similarity, Proportion, such that concepts with different contents but sufficiently high Proportion scores will also conduce to understanding, agreement, and disagreement. [source]

Temperature dependence of magnetic microstructure in Fe76Mo8Cu1B15 nanocrystalline alloy

M. Miglierini
Abstract Fe76Mo8Cu1B15 nanocrystalline alloy featuring close-to-room Curie temperature of 310 K proves to be suitable for model case studies of complexity of magnetic interactions. Annealed samples with different contents of nanocrystallites are characterized by 57Fe transmission Mössbauer spectrometry performed in a wide temperature range (77,673 K). The validity of the temperature dependences of hyperfine parameters is discussed for all structural components including amorphous residual phase, bcc Fe nanocrystals and interface regions located in between the former two. Cautions which must be considered in deriving information about their relative contents are pointed out, because of the presence of static and dynamic effects at high temperatures due to non-interacting and weakly interacting single domain ferromagnetic grains dispersed into a paramagnetic amorphous matrix. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Protochlorophyllide-independent import of two NADPH:Pchlide oxidoreductase proteins (PORA and PORB) from barley into isolated plastids

Clas Dahlin
The enzyme catalysing the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide), NADPH:Pchlide oxidoreductase (POR; EC, is a nuclear-encoded protein that is post-translationally imported to the plastid. In barley and Arabidopsis thaliana, the reduction of Pchlide is controlled by two different PORs, PORA and PORB. To characterise the possible Pchlide dependency for the import reaction, radiolabelled precursor proteins of barley PORA and PORB (pPORA and pPORB, respectively) were used for in vitro assays with isolated plastids of barley and pea with different contents of Pchlide. To obtain plastids with different endogenous levels of Pchlide, several methods were used. Barley plants were grown in darkness or in greenhouse conditions for 6 days. Alternatively, greenhouse-grown pea plants were incubated for 4 days in darkness before plastid isolation, or chloroplasts isolated from greenhouse-grown plants were incubated with , -aminolevulinic acid (ALA), an early precursor in the Chl biosynthesis resulting in elevated Pchlide contents in the plastids. Both barley pPORA and pPORB were effectively imported into barley and pea chloroplasts isolated from the differentially treated plants, including those isolated from greenhouse-grown plants. The absence or presence of Pchlide did not significantly affect the import capacity of barley pPORA or pPORB. Assays performed on stroma-enriched fractions from chloroplasts and etioplasts of barley indicated that no post-import degradation of the proteins occurred in the stroma, irrespective of whether the incubation was performed in darkness or in light. [source]

Effect of celery (Apium graveolens) extracts on some biochemical parameters of oxidative Stress in mice treated with carbon tetrachloride

Mira Popovi
Abstract Extracts of celery leaves and roots in ether, chloroform, ethyl acetate, n -butanol and water were evaporated to dryness and dissolved in 50% ethanol to make 10% (w[sol ]v) solutions. The potential protective action of the extracts was assessed by the corresponding in vitro and in vivo tests. In the in vitro experiments crude methanol extracts were tested as potential scavengers of free OH, and DPPH, radicals, as well as inhibitors of liposomal peroxidation (LPx). Analogous experiments were also carried out with the extracts of celery root, for comparison. The results obtained show that both the extracts of root and leaves are good scavengers of OH, and DPPH, radicals and reduce LPx intensity in liposomes, which points to their protective (antioxidant) activity. In vivo experiments were concerned with antioxidant systems (activities of GSHPx, GSHR, Px, CAT, XOD, GSH content and intensity of LPx) in liver homogenate and blood of mice after their treatment with extracts of celery leaves, or in combination with CCl4. On the basis of the results obtained it can be concluded that the examined extracts showed a certain protective effect. Of all the extracts the n -butanol extract showed the highest protective effect. Combined treatments with CCl4 and extracts showed both positive and negative synergism , inducing or suppressing the impact of CCl4 alone. The differences observed in the action of particular extracts are probably due to the different contents of flavonoids and some other antioxidant compounds. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Effect of montmorillonite on properties of styrene,butadiene,styrene copolymer modified bitumen

Jianying Yu
Clay/styrene,butadiene,styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na-MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na-MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na-MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high-temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289,1295, 2007. © 2007 Society of Plastics Engineers [source]

Less-ordered lamellar structure of intercalated poly(L -lactide)/organo-modified montmorillonite hybrids

Pham Hoai Nam
Hybrids of poly(L -lactide)/organophilic clay (PLACHs) have been prepared via a melt-compounding process using poly(L -lactide) (PLLA) and different contents of surface-treated montmorillonite modified with dimethyl dioctadecyl ammonium-salt. The crystalline structures of PLLA and dispersion states of clay particles in those PLACHs were investigated by use of wide-angle X-ray diffraction, small-angle X-ray scattering, transmission electron microscopy (both cross section and replication modes), and polarized optical microscopy. Those structures are viewed from the conformational changes of PLLA chains in the space of a few nanometer widths between silicate galleries to crystalline lamellae of several nanometer thicknesses, and spherulitic textures more than micrometer sizes. After annealing treatments at 115°C for 1 hr, the PLACHs formed coarse-grained spherulitic textures with 40 ,m diameter composed of less-ordered and fragmented lamellae, caused by the reduced mobility of the PLLA chain due to the dispersed clay particles in the PLLA matrix and the intercalation of the PLLA chains in the silicate galleries. The formation of the interfibril structure accompanied by the fragmented lamellae among the dispersed clay particles was examined. POLYM. ENG. SCI., 46:703,711, 2006. © 2006 Society of Plastics Engineers [source]

Synthesis and chiroptical properties of liquid crystalline copolymers containing azobenzene chromophores

Zhi Zheng
Abstract A series of new liquid crystalline copolymers, poly[((S)-2-methyl-1-butyl methacrylate)- co -(6-(4-(4-cyanophenylazo)phenoxy)hexyl methacrylate)], with different contents of chiral units of 17, 36, 54 and 78 mol% were synthesized. The structures and properties of the copolymers were characterized and evaluated using infrared, 1H NMR and UV spectroscopy, differential scanning calorimetry, gel permeation chromatography and circular dichroism (CD). The CD results suggested that absorptions of azobenzene chromophores were observed in films of copolymer containing 17, 36 or 54 mol% chiral units, but not in the film of copolymer containing 78 mol% chiral units. Also, CD values of the copolymeric films decreased with increasing chiral content. After irradiation with linear polarized light at 442 nm, CD values were changed in all the copolymeric films, and the CD values increased with decreasing chiral content in a nonlinear way, while the photoinduced change of chirality of the copolymers increased in a linear way with decreasing chiral content. The results are discussed in terms of interactions between structures and chiroptical properties. Copyright © 2007 Society of Chemical Industry [source]

Solid-state linear viscoelastic properties of intercalated poly(L -lactide)/organo-modified montmorillonite hybrids

Pham Hoai Nam
Abstract Hybrids of poly(L -lactide)/organophilic clay (PLACHs) have been prepared by a melt-compounding process using poly(L -lactide) (PLLA) and different contents of surface-treated montmorillonite modified with a dimethyl dioctadecyl ammonium salt. The dispersion structures of clay particles in PLACHs were investigated using wide-angle X-ray diffraction and transmission electron microscopy. The solid-state linear viscoelastic properties for these PLACHs were examined as functions of temperature and frequency. The incorporation of organo-modified silicate into PLLA matrix enhanced significantly both storage moduli (E,) and loss moduli (E,). The strong enhancement observed in dynamic moduli of PLACHs could be attributed to uniformly dispersed state of the clay particles with high aspect ratio (= length/thickness of clay) and the intercalation of the PLLA chains between silicate layers. Copyright © 2006 Society of Chemical Industry [source]

Matrix-assisted laser desorption/ionisation mass spectrometry in the study of polycondensation of Ti(OBun)4 in the presence of Si(OEt)4

Roberta Seraglia
The hydrolysis-polycondensation behaviour of alcoholic solutions containing Si(OEt)4 and Ti(OBun)4, in different molar ratios (Si/Ti,=,10,0.2), was analysed by laser desorption/ionisation (LDI) and matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry. The solutions were prepared using operating conditions usually employed in the sol-gel synthesis of SiO2 -TiO2 materials. In accord with the well-known procedures for controlling the different chemical reactivities of the alkoxides, the pre-hydrolysis of the slower reacting silicon ethoxide and the chelation by acetylacetone of the faster reacting titanium butoxide were performed before mass spectrometric analysis. While LDI-MS did not provide evidence for the presence of mixed Si-Ti species in samples obtained from these reactions, MALDI-MS of samples diluted with chloroform and using 2,5-dihydroxybenzoic acid (DHB) as matrix led to detection of various oligomers with different contents of Si and Ti atoms. The results suggest that the formation of Si-Ti mixed oligomers seems to be the favoured process, especially for solutions in which one of the two components is diluted. Copyright © 2003 John Wiley & Sons, Ltd. [source]