36 resultados para Resins, Synthetic


Relevância:

20.00% 20.00%

Publicador:

Resumo:

One of the less desirable aftermaths of the so-called "Media Wars" - the intellectual debate over the role of cultural studies in the study of journalism - was reinforcement for some of the notion of fortress journalism: a Windschuttlian purist version of the Empire. This paper uses the alleged confrontation between the forces of that Empire (that is, proponents of pure journalism) and the forces of the Dark (that is, critics from a cultural studies tradition) as a means of examining the teaching of journalism in universities. The paper questions how the discipline of journalism should interface with others within the academy and asks what notion of journalism underpins our pedagogy and our epistemology. It is argued that it is time to discard an outdated craft model with its associations of authenticity and replace it with a model of synthetic professionalism.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Juvenile Cherax destructor (commonly called the yabby) (mean weight 48.3 mg) were cultured intensively (stocking density 360/m2) under controlled conditions for 48 days. The animals were provided with a combination of food (high protein pellets and/or natural feed organisms attached to a conditioned synthetic substrate) and refuge. Fastest growth and highest yield was recorded when both pellets and the conditioned synthetic material were provided. Although the yabbies sheltered in the synthetic substrate, it did not increase survival. Juvenile yabbies (< 200 mg) were able to graze on small organisms attached to the synthetic material but this ability appeared to decline as the yabbies grew to a larger size. The use of artificial substrates in the intensive nursery phase production of juvenile freshwater crayfish is discussed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Heat generation in fabrics coated with the conductive polymer polypyrrole was investigated. The PET fabrics were coated by chemical synthesis using four different oxidizing agent–dopant combinations. The samples from the four different dopant systems all show an increase in temperature when a fixed voltage is applied to the fabric. The antraquinone-2-sulfonic acid (AQSA) sodium salt doped polypyrrole coating was the most effective in heat generation whereas the sodium perchlorate dopant system was the least effective. The power density per unit area achieved in polypyrrole coated polyester–Lycra® fabric with 0.027 mol/l of AQSA acting as dopant was 430 W/m2. The power density per unit area achieved for the sodium perchlorate system, using the same synthesis conditions, was 55 W/m2.


Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Several sets of model-based estimates (synthetic estimates) of the prevalence of risk factors for coronary heart disease for small areas in England have been developed. These have been used in policy documents to indicate which areas are in need of intervention. In general, these models have not been subjected to validity assessment. This paper describes a validity assessment of 16 sets of synthetic estimates, by comparison of the models with national, regional and local survey-based estimates, and local mortality rate estimates. Model-based estimates of the prevalence of smoking, low fruit and vegetable consumption, obesity, hypertension and raised cholesterol are found to be valid.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The oxidation of substituted phenols with phenyliodonium diacetate in methanol was found to afford 2,4-cyclohexadienones, 2,5-cyclohexadienones or mixtures of isomers depending on the substrate being oxidized. A reaction mechanism was proposed for this oxidation which involved an intermediate aryloxenium ion. A strong correlation was observed between the experimentally determined product ratios and the results predicted by calculation of the LUMO coefficients of the proposed intermediates, Annulation of these cyclohexadienones with the anion derived from cyanophthalide afforded substituted anthraquinones in high yields. The chemistry relating to the annulation of Michael acceptors with phthalide anions was comprehensively reviewed. A mild selective method for the oxidation of hydroquinones to quinones using dibenzoyl peroxide and base is presented. A general synthetic approach to C-glycosylanthraquinones was presented, based on the annulation of a C-glycosylcyclohexadienone with the anion derived from cyanophthalide, A suitable precursor to a C-glycosylcyclohexadienone, 2-(2’,3’,4’,6’-tetra-0-acetyl-|3-D-glucopyranosyl)benzyloxybenzene, was prepared via the reaction of benzoylbromoglucose with 2-benzyloxyphenylmagnesium bromide, A group of molecules were prepared by a Marschalk reaction between /ewcoquinizarin and aldehydo-sugsrs. These compounds are potential bioreductive alkylating agents in which molecular simplicity can be achieved without overly sacrificing DNA binding ability.

Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to investigate correlations between the molecular changes and postcuring reaction on the surface of a diglycidyl ether of bisphenol A and diglycidylether of bisphenol F based epoxy resin cured with two different amine-based hardeners. The aim of this work was to present a proof of concept that ToF-SIMS has the ability to provide information regarding the reaction steps, path, and mechanism for organic reactions in general and for epoxy resin curing and postcuring reactions in particular. Contact-angle measurements were taken for the cured and postcured epoxy resins to correlate changes in the surface energy with the molecular structure of the surface. Principal components analysis (PCA) of the ToFSIMS positive spectra explained the variance in the molecular information, which was related to the resin curing and postcuring reactions with different hardeners and to the surface energy values. The first principal component captured information related to the chemical phenomena of the curing reaction path, branching, and network density based on changes in the relative ion density of the aliphatic hydrocarbon and the C7H7O+ positive ions. The second principal component captured information related to the difference in the surface energy, which was correlated to the difference in the relative intensity of the CxHyNz+ ions of the samples. PCA of the negative spectra provided insight into the extent of consumption of the hardener molecules in the curing and postcuring reactions of both systems based on the relative ion intensity of the nitrogen-containing negative ions and showed molecular correlations with the sample surface energy.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The invention relates to a modified ultra-fine natural fibre powder for use in a melt forming process for the preparation of a semi-synthetic material, the powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particles during said melt forming process. The invention also relates to a semi-synthetic material including a modified ultra-fine natural fibre powder and a synthetic polymer component.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The invention relates to a modified ultra-fine natural fibre powder for use in a melt forming process for the preparation of a semi-synthetic material, the powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particles during said melt forming process. The invention also relates to a semi-synthetic material including a modified ultra-fine natural fibre powder and a synthetic polymer component.