Search results for " DEGRADATION"

DUAL APPLICATION OF DIVALENT ION-ANCHORED CATALYST: BIODIESEL SYNTHESIS AND PHOTOCATALYTIC DEGRADATION OF CARBAMAZEPINE

2019

1990

This lecture summarizes some recent results and ideas about interrelations between degradation and mechanical behaviour of polyolefins. Aspects of the heterogeneous nature of oxidative degradation in the solid state, the feedback mechanism in degradation, effects of morphology, particularly orientation, on the degradation process, and the influence of degradation on plasticity and on the ultimate mechanical behaviour are discussed.

Assays of Proteasome-Dependent Cleavage Products

2005

The degradation of misfolded, aged, or no longer needed cytosolic proteins depends largely on the ubiquitin-proteasome system. Proteasomes degrade their substrates into fragments of 3-20 amino acids. Human 20S proteasomes can be purified from human erythrocytes by batch adsorption to DEAE-cellulose, ammonium sulfate precipitation, anion-exchange fast protein liquid chromatography (FPLC), and glycerol density gradient ultracentrifugation. 20S proteasomes purified by this method are suitable for the in vitro digestion of synthetic peptides as well as full-length proteins. The degradation products produced by proteasomes are separated by reversed-phase HPLC using an acetonitrile gradient. The …

Pyrgomorphid grasshoppers of the genus Phymateus contain species-specific decapeptides of the AKH/RPCH family regulating lipid-mobilization during fl…

1996

. Using heterologous and conspecific bioassays, two peptides have been isolated from methanolic extracts of corpora cardiaca from the pyrgomorphid grasshopper Phymateus morbillosus L.The structures of both peptides were elucidated by a combination of Edman degradation, after deblocking the N-terminal pyroglutamic acid residue, and mass spectrometric techniques.One peptide is an octapeptide (pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH2) which also occurs in other insects and is code-named Scg-AKH-II.The second peptide is a novel decapeptide member of the AKH/RPCH family (pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-SerNH2 code-named here Phm-AKH.It is the first example of a different peptide in the same genu…

Degradation Behavior of Nanocomposite Polymer Blends

2014

The usefulness of any material, including nanocomposite polymer blends, depends on its degradability and durability. Thus, this chapter reviews the status of the research on degradation of nanocomposite polymer blends and, in particular, on clay-nanocomposite polymer blends, paying particular attention to both the role of the filler and the role of the blend morphology and composition. The results of recent research indicate that the clay has two opposing effects on the thermal stability of a nanocomposite polymer blend: (1) a promoter effect of the polymer matrix degradation, which decreases the thermal stability, and (2) a barrier effect, which improves the thermal stability. Moreover, th…

Thermodynamically induced shear degradation

1988

The shear degradation of polymers in semiconcentrated solutions is viewed as a function of solvent quality. It is shown that the deterioration of the thermodynamic quality of the solvent leads to a marked flow resistance due to an increasing number of contacts between the chains. This may be probed by viscosimetric measurements as well as by degradation experiments (“thermodynamically induced shear degradation”). For a detailed discussion of this phenomenon the experimental setup for the mechanochemical experiment is outlined first, followed by a survey of the kinetics of chain scission. Finally, experiments mostly obtained on polystyrene in the theta-solvent trans-decalin are discussed. Th…

Influence of soil properties on the aggregation of some Mediterranean soils and the use of aggregate size and stability as land degradation indicators

2001

Abstract Soil aggregation in relation to other soil properties was studied along a climatological transect in the Southeast of Spain. Three sites were selected along this transect ranging from semiarid to subhumid climatological conditions. The aggregate size distribution, the macro and microaggregate stability of the superficial soil horizon and their relations with other soil properties were analysed. Large aggregates (>10, 10–5, 5–2 mm) were present in highest proportions in the most arid of the studied areas. These large aggregates were associated with high values of water-stable microaggregates; however, they did not improve soil structure and are related to high bulk densities and low…

Time-resolved rheology as a tool to monitor the progress of polymer degradation in the melt state – Part II: Thermal and thermo-oxidative degradation…

2015

Abstract Thermal and thermo-oxidative degradation of nanocomposites based on polyamide 11 (PA11) and organo-modified clay (Cloisite® 30B) are studied in the melt state (T = 215 °C) via time-resolved mechanical spectroscopy (TRMS). The goal is assessing the potentiality of rheological analysis for studying polymer degradation in complex systems such as polymer nanocomposites, whose rheological response stems from the combination of the contributions of polymer and nanoparticles. We prove that a thorough analysis grounded on TRMS allows to isolate the effect of degradation of the polymer matrix, whose progress can be hence profitably monitored. Essentially the same degradation mechanisms as i…

Characterization and Reprocessing of Greenhouse Films.

2001

Films for greenhouses are an attractive source of post-consumer plastic materials because they are mainly made of polyethylene and can be easily collected in large amounts in small zones. The types of polymers for this application are, however, increasing and the films contain not only additives and stabilisers, but also fertiliser and pesticide residues. Finally, the extent of photooxidative degradation undergone during the use can strongly influence the recycling operations and the final properties of the secondary material. In this work, a complete characterisation of post-consumer films for greenhouses has been carried out and the properties of the recycled material have been correlated…

Polyethylene glycol/clay nanotubes composites

2012

Nanocomposites of poly(ethylene) glycol (PEG) 20000 filled with clay nanotubes (HNTs) were prepared. The thermal properties obtained from thermogravimetry and differential scanning calorimetry were correlated to the morphology imaged by scanning electron microscopy. Low amounts of HNTs generate compact structure while large amounts of HNTs create craters and voids. The decrease of polymer degradation temperature in the presence of large amount of nanoclay (ca. 80 wt%) is a consequence of the morphology at the mesoscale range. The thermal opposite effect observed in the HNTs low regime (up to ca. 20 wt%) is due to the gas entrapment into the nanoparticles lumen. The quantitative analysis of …