42 resultados para radical recycling


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The antioxidant property of myo-inositol hexakisphosphate is important in the prevention of hydroxyl radical formation which may allow it to act as a 'safe' carrier of iron within the cell. Here, the hypothesis that the recently discovered natural product, myo-inositol 1,2,3-trisphosphate represents the simplest structure to mimic phytate's antioxidant activity has been tested. The first synthesis of myo-inositol 1,2,3-trisphosphate has been completed, along with its X-ray structure determination and that of key synthetic intermediates. Iron binding studies of myo-inositol 1,2,3-trisphosphate demonstrated that phosphate groups with the equatorial-axial-equatorial conformation are required for complete inhibition of hydroxyl radical formation. myo-Inositol monophosphatase is a key enzyme in recycling myo-inositol from its monophosphates in the brain and its inhibition is implicated in lithium's antimanic properties. Current synthetic strategies require inositol compounds to be protected (often with more than one group), resolved, phosphorylated and deprotected to produce the desired optically active myo-inositol phosphates. Here, the synthesis of myo-inositol 3-phosphate has been achieved in only 4 steps from myo-inositol. The stereoselective addition of the chiral phosphorylating agent (2R,4S,5R)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidin-2-one to a protected inositol intermediate allowed separation of diastereoisomers and easy deprotection to myo-inositol 3-phosphate. This strategy also allows the possible introduction of labels of oxygen and sulphur to give a thiophosphate of known stereochemistry at phosphorus which would be useful for the analysis of the stereochemical course of phosphate hydrolysis catalysed by inositol monophosphatase.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The effect of substituents on the value of the oxidation potential of quinones is reviewed and attempts to prepare substituted diphenoquinones with high oxidation potentials are reported. Attempts to characterise the mechanism of addition and substitution in diphenoquinones by identifying the products of the Thiele acetylation of diphenoquinone are reported. The reaction proved most efficient when the incoming acetylinium ion is directed by substituents in the diphenoquinone. A 1,8-addition to diphenoquinone is reported and characterised by isolating the products of the reaction between acetyl chloride and diphenoquinone, with perchloric acid as catalyst. The alternating linewidth effects observed in e.s.r.spectra are discussed and applied to account for such effects observed in the e.s.r.spectra of diphenosemiquinone anion and cation radicals. The spectra are analysed and the intramolecular processes producing these effects are discussed. A dianion diradical where intramolecular rotation about the 1 - 1' bond is restricted is produced by the oxidation of 2,2' ,4,4' -tetra hydroxybiphenyl. Previous studies of diphenosemiquinone anions are reviewed and alkylated diphenosemiquinone anion are produced by the reduction of the parent quinone with potassium hydroxide solution, the resulting radical being stabilised by the presence of pyridine. A qualitative interpretation of the solvent-ion effect in alkylated diphenosemiquinone anions is given. Diphanosemiquinone cation radicals are reviewed and previous studies are re-examined.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The techno-economic implications of recycling the components of mixed plastics waste have been studied in a two-part investigation: (a) An economic survey of the prospects for plastics recycling, the plastics waste arisings from retailing, building, automotive, light engineering and chemical industries have been surveyed by mans of questionnaires and interviews. This was partially successful and indicated that very considerable quantities of relatively clean plastics packaging was available in major department chains and household stores. The possibility of devising collection systems for such sources, which do not lead to any extra cost, have been suggested. However, the household collection of plastics waste has been found to be uneconomic due to high cost of collection, transportation and lack of markets for the end products. (b) In a technical study of blends of PE/PP and PE/PS which are found in admixture in waste plastics, it has been shown that they exhibit poor mechanical properties due to incompatibility. Consequently reprocessing of such unsegregated blends results in products of little technological value. The inclusion of some commercial block and graft copolymers which behave as solid phase dispersants (SPES) increase the toughness of the blends (e.g. EPDM in PE/PP blend and SBS in PE/PS blend). Also, EPDM is found to be very effective for improving the toughness of single component polypropylene. However, the improved Technical properties of such blends have been accompanied by a fast rate of photo-oxidation and loss of toughness due to the presence of unsaturation in SPD's. The change in mechanical properties occurring during oven ageing and ultra-violet light accelerated weathering of these binary and ternary blends was followed by a viscoelastonetric technique (Rheovibron) over 9,, wide range of temperatures, impact resistance at room temperature (20-41'G) and changes in functional groups (i.e. carbonyl and trans-1,4-polybutadiene). Also the heat and light stability of single and mixed plastics to which thiol antioxidants were bound to SPE1 segment have been studied and compared with conventional antioxidants. The long-term performance of the mixed plastics containing SPE1 have been improved significantly by the use of conventional and bound antioxidants. It is concluded that an estimated amount of 30000 tonnes/year of plastics waste is available from department chains and household stores which can be converted to useful end products. This justifies pilot-experiments in collaboration with supermarkets, recyclers and converters by use of low cost SPD's and additives designed to make the materials more compatible.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The field of free radical biology and medicine continues to move at a tremendous pace, with a constant flow of ground-breaking discoveries. The following collection of papers in this issue of Biochemical Society Transactions highlights several key areas of topical interest, including the crucial role of validated measurements of radicals and reactive oxygen species in underpinning nearly all research in the field, the important advances being made as a result of the overlap of free radical research with the reinvigorated field of lipidomics (driven in part by innovations in MS-based analysis), the acceleration of new insights into the role of oxidative protein modifications (particularly to cysteine residues) in modulating cell signalling, and the effects of free radicals on the functions of mitochondria, extracellular matrix and the immune system. In the present article, we provide a brief overview of these research areas, but, throughout this discussion, it must be remembered that it is the availability of reliable analytical methodologies that will be a key factor in facilitating continuing developments in this exciting research area.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Starting from a number of general tenets about radical political parties, this article examines the Front National (FN) in relation to its core policy issue of immigration. To what extent has FN immigration policy been defined from the outset by its radicalism? Has that radicalism been constant or variable over time? And how far can a reciprocal influence be detected between the FN and the center Right in immigration policy formulation? Focusing on election campaigns, manifestos, and key moments in the FN's evolution, the article assesses how the party has tailored its radicalism to contextual factors and tactical considerations. It reveals an FN less bound to a fixed policy and more ready to seek accommodation (with circumstance, public opinion, or the center Right) than is generally acknowledged. Conversely, it also assesses how the FN's mobilization of strong support on the immigration issue has had radicalizing effects on the center Right. The article concludes by considering whether the change of leadership in January 2011 might confine the FN to the radical Right or see it adopt a more center-oriented course.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

How motorsport companies harness network diversity for discontinuous innovation.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The motorsport industry is a significant part of the UK economy. According to industry estimates approximately 4,500 companies are involved in the UK Motorsport and Performance Engineering Industry and its wide-ranging support activities. The industry has an annual turnover of £6.0 billion, and contributes £3.6 billion worth of exports. The Motorsport Industry Association estimates that the support side of the sector alone "involving events management, public relations, marketing, sponsorship and a host of other support functions" accounts for approximately £1.7 billion of the yearly industry total. And in terms of employment, UK Motorsport supports 38,500 full and part-time jobs, including 25,000 engineers.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cost efficiency has been a dominant perspective in the traditional IT literature. However, in complex technology and business environment, the widely recognized cost efficient assumption of information technology has been increasingly challenged. Drawing from a case study of wireless network implementation situated in a politically sensitive workplace, this paper provided practice insights for IT managers in today’s networked economy. More specifically, stories experienced in the case study illustrated that despite well-calculated cost efficiency of wireless network infrastructure, the radical implementation process in the case organization encountered enormous challenges and opposition due to the fact that administrators failed to consider various stakeholders’ positions and interests. Eventually, the implementation objectives and outcome were considerably undermined. Implications from this empirical case research reemphasized the significance of understanding political forces situated in any business environment where different stakeholders hold conflicting interests. Lessons learned from the case story further encouraged IT managers and policy makers to better strategize emerging information technology in general and wireless networks in particular as the whole global society and business environment are increasingly facing an emerging wireless world.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper analyzes a case study of wireless network implementation in a politically sensitive environment and seeks to gain practical insights for IT managers in today’s networked economy. The case evolved around an urgent decision to implement wireless networks that were a radical replacement for the existing wired network infrastructure. Although the wireless network infrastructure was well calculated as being considerably cost-efficient, inexperienced administrators and IT department failed to consult various involved stakeholders. Consequently, unintended results of wireless network implementation entangled with the cost efficiency of technology outcome and in turn undermined the objectives and achievement of the initial project plan. Drawing from social perspectives, this case study challenges traditionally dominant perspectives of technology efficiency and summarizes several lessons that could help IT managers and policy makers to better strategize ICT in general, and wireless networks in particular.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Data Envelopment Analysis (DEA) is recognized as a modern approach to the assessment of performance of a set of homogeneous Decision Making Units (DMUs) that use similar sources to produce similar outputs. While DEA commonly is used with precise data, recently several approaches are introduced for evaluating DMUs with uncertain data. In the existing approaches many information on uncertainties are lost. For example in the defuzzification, the a-level and fuzzy ranking approaches are not considered. In the tolerance approach the inequality or equality signs are fuzzified but the fuzzy coefficients (inputs and outputs) are not treated directly. The purpose of this paper is to develop a new model to evaluate DMUs under uncertainty using Fuzzy DEA and to include a-level to the model under fuzzy environment. An example is given to illustrate this method in details.