Selective localization of organoclay and effects on the morphology and mechanical properties of LDPE/PA11 blends with distributed and co-continuous morphology

A study was made on the effect of small amounts of organically modified clay on the morphology and mechanical properties of blends of low-density polyethylene and polyamide 11 at different compositions. The influence of the filler on the blend morphology was investigated using wide angle X-ray diffractometry, scanning and transmission electron microscopy and selective extraction experiments. The filler was found to locate predominantly in the more hydrophilic polyamide phase. Although such uneven distribution does not have a significant effect on the onset of phase co-continuity of the polymer components, it brings about a drastic refinement of the microstructure for the blends both with droplets/matrix and co-continuous morphologies. In addition to the expected reinforcing action of the filler, the resulting fine microstructure plays an important role in enhancing the mechanical properties of the blends. This is essentially because of a good quality of stress transfer across the interface between the constituents, which also seems to benefit for a good interfacial adhesion promoted by the filler. Our results provide the experimental evidence for the capabilities of nanoparticles added to multiphase polymer systems to act selectively as a reinforcing agent for specific domains of the material and as a medium able to assist the refinement of the polymer phases during mixing.

Caking behaviour of spray-dried milk powders:using scanning probe microscopy to study nanoscale surface properties and material composition

Spray drying is widely used to manufacture many powdered products, with the drying process parameters having significant influence over the final powder's surface properties and propensity for unwanted caking. In most cases caking experiments are performed on bulk powders, but especially in multi-component powders, it is often difficult to interpret these results, where interaction effects between particles can be complex. Here the technique of scanning probe microscopy is used to characterize the nanoscale properties of spray dried model milk powders in order to investigate the surface properties of the powders.

Mechanical properties and the evolution of matrix molecules in PTFE upon irradiation with MeV alpha particles

The morphology, chemical composition, and mechanical properties in the surface region of α-irradiated polytetrafluoroethylene (PTFE) have been examined and compared to unirradiated specimens. Samples were irradiated with 5.5 MeV 4He2+ ions from a tandem accelerator to doses between 1 × 106 and 5 × 1010 Rad. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), using a 20 keV C60+ source, was employed to probe chemical changes as a function of a dose. Chemical images and high resolution spectra were collected and analyzed to reveal the effects of a particle radiation on the chemical structure. Residual gas analysis (RGA) was utilized to monitor the evolution of volatile species during vacuum irradiation of the samples. Scanning electron microscopy (SEM) was used to observe the morphological variation of samples with increasing a particle dose, and nanoindentation was engaged to determine the hardness and elastic modulus as a function of a dose. The data show that PTFE nominally retains its innate chemical structure and morphology at a doses <109 Rad. At α doses ≥109 Rad the polymer matrix experiences increased chemical degradation and morphological roughening which are accompanied by increased hardness and declining elasticity. At  α doses >1010 Rad the polymer matrix suffers severe chemical degradation and material loss. Chemical degradation is observed in ToF-SIMS by detection of ions that are indicative of fragmentation, unsaturation, and functionalization of molecules in the PTFE matrix. The mass spectra also expose the subtle trends of crosslinking within the α-irradiated polymer matrix. ToF-SIMS images support the assertion that chemical degradation is the result of a particle irradiation and show morphological roughening of the sample with increased a dose. High resolution SEM images more clearly illustrate the morphological roughening and the mass loss that accompanies high doses of a particles. RGA confirms the supposition that the outcome of chemical degradation in the PTFE matrix with continuing irradiation is evolution of volatile species resulting in morphological roughening and mass loss. Finally, we reveal and discuss relationships between chemical structure and mechanical properties such as hardness and elastic modulus.

Characterization and effects on cAMP accumulation of adrenomedullin and calcitonin gene-related peptide (CGRP) receptors in dissociated rat spinal cord cell culture

1 Adrenomedullin (AM) and calcitonin gene-related peptide (CGRP) have structural similarities, interact with each others receptors (calcitonin receptor-like receptor (CLR)/receptor-activity-modifying proteins (RAMPs)) and show overlapping biological activities. AM and CGRP receptors are chiefly coupled to cAMP production. In this study, a method of primary dissociated cell culture was used to investigate the presence of AM and CGRP receptors and their effects on cAMP production in embryonic spinal cord cells. 2 Both neuronal and non-neuronal CLR immunopositive cells were present in our model. 3 High affinity, specific [ 125I]-AM binding sites (K(d) 79±9 pM and B(max) 571±34 fmol mg -1 protein) were more abundant than specific [ 125I]-CGRP binding sites (K(d) 12±0.7 pM and B(max) 32±2 fmol mg -1 protein) in embryonic spinal cord cells. 4 Specific [ 125I]-AM binding was competed by related molecules with a ligand selectivity profile of rAM>hAM(22-52)>rCGRPα>CGRP(8-37) ≫[r-(r*,s*)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl] carbonyl]pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1, 4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-piperidinecarboxamide (BIBN4096BS). 5 Specific [ 125I]-CGRP binding was competed by rCGRPα>rAM≥ CGRP(8-37)≥BIBN4096BS>hAM(22-52). 6 Cellular levels of cAMP were increased by AM (pEC"5"0 10.2±0.2) and less potently by rCGRPα (pEC"5"0 8.9±0.4). rCGRPα-induced cAMP accumulation was effectively inhibited by CGRP(8-37) (pA"2 7.63±0.44) and hAM(22-52) (pA"2 6.18±0.21) while AM-stimulation of cAMP levels was inhibited by CGRP(8-37) (pA"2 7.41±0.15) and AM(22-52) (pA"2 7.26±0.18). BIBN4096BS only antagonized the effects of CGRP (pA"2 8.40±0.30) on cAMP accumulation. 7 These pharmacological profiles suggest that effects of CGRP are mediated by the CGRP"1 (CLR/RAMP1) receptor in our model while those of AM are related to the activation of the AM"1 (CLR/RAMP2) receptor subtype. © 2006 Nature Publishing Group All rights reserved.

Degradable poly(ethylene glycol)-based hydrogels:synthesis, physico-chemical properties and in vitro characterization

Designing degradable hydrogels is complicated by the structural and temporal complexities of the gel and evolving tissue. A major challenge is to create scaffolds with sufficient mechanical properties to restore initial function while simultaneously controlling temporal changes in the gel structure to facilitate tissue formation. Poly(ethylene glycol) was used in this work, to form biodegradable poly(ethylene glycol)-based hydrogels with hydrolyzable poly-l-lactide segments in the backbone. Non-degradable poly(ethylene glycol) was also introduced in the formulation to obtain control of the degradation profile that encompasses cell growth and new tissue formation. The dependence on polymer composition was observed by higher degradation profiles and decreased mechanical properties as the content of degradable segments was increased in the formulation. Based on in vitro tests, no toxicity of extracts or biomaterial in direct contact with human adipose tissue stem cells was observed, and the ultraviolet light treatment did not affect the proliferation capacity of the cells.

Effectiveness and effects of attempts to regulate the UK petrol industry

This paper evaluates the impact that investigation and regulation of the UK petrol industry has had on the profitability of the companies. Using a gross margin for petrol, we estimate a series of variable parameter autoregressive processes. The results demonstrate that the 1979 Monopolies and Mergers Commission investigation into the industry, caused a long term decline in profit margins in the industry, despite the fact that no recommendations or undertakings were made. This cannot however be said for subsequent investigations.

Hypercoiling and hydrophobically associating polymers : interfacial synthesis, surface properties and pharmaceutical applications

The objective of the work described was to identify and synthesize a range of biodegradable hypercoiling or hydrophobically associating polymers to mimic natural apoproteins, such as those found in lung surfactant or plasma apolipoproteins. Stirred interfacial polymerization was used to synthesize potentially biodegradable aromatic polyamides (Mw of 12,000-26,000) based on L-Iysine, L-Iysine ethyl ester, L-ornithine and DL-diaminopropionic acid, by reaction with isophthaloyl chloride. A similar technique was used to synthesize aliphatic polyamides based on L-Iysine ethyl ester and either adipoyl chloride or glutaryl chloride resulting in the synthesis of poly(lysine ethyl ester adipamide) [PLETESA] or poly(lysine ethyl ester glutaramide) (Mw of 126,000 and 26,000, respectively). PLETESA was found to be soluble in both polar and non-polar solvents and the hydrophobic/hydrophilic balance could be modified by partial saponification (66-75%) of the ethyl ester side chains. Surface or interfacial tension/pH profiles were used to assess the conformation of both the poly(isophthalamides) and partially saponified PLETESA in aqueous solution. The results demonstrated that a loss of charge from the polymer was accompanied by an initial fall in surface activity, followed by a rise in activity, and ultimately, by polymer precipitation. These observations were explained by a collapse of the polymer chains into non-surface active intramolecular coils, followed by a transition to an amphipathic conformation, and finally to a collapsed hydrophobe. 2-Dimensional NMR analysis of polymer conformation in polar and non-polar solvents revealed intramolecular associations between the hydrophobic groups within partially saponified PLETESA. Unsaponified PLETESA appeared to form a coiled structure in polar solvents where the ethyl ester side chains were contained within the polymer coil. The implications of the secondary structure of PLETESA and potential biomedical applications are discussed.

Acanthamoebal surface properties and the modulation of phagocytosis

The surface nature of Acanthamoeba trophozoites and cysts was investigated with respect to cell surface charge, hydrophobicity and surface carbohydrate composition. Particulate microelectrophoresis revealed a marked negative charge for both morphological forms, though less for cyst surfaces. Hydrophobicity was determined by adhesion to n-hexadecane and indicated a relatively low hydrophobic nature of both forms, though less so for cysts. Surface carbohydrate composition was studied by the use of fluorescent lectins and flow cytometry, using a ligand-receptor approach for further in depth analysis of binding of particular lectins. These studies showed trophozoite and cyst surfaces to be rich in N-acetylglucosamine, N-acteylneuraminic acid, mannose and glucose, with the addition of N-acetylgalactosamine on cysts. The importance of such surface properties was investigated with respect to phagocytosis of polystyrene latex microspheres, of different surface types and size. Investigations into the optimum conditions of uptake of beads indicated a preference for a medium devoid of nutrients, such as saline, though temperature was not a factor. An amoebal predilection for beads of lower charge and greater hydrophobicity was demonstrated. Furthermore, a preference for the largest bead size used (2.0 m) was observed. The influence of either Con A or mannose or glucose on bead association was apparently limited. The fate of foreign DNA ingested by Acanthamoeba appeared to indicate that such DNA was destroyed, as it could not be detected following extraction procedures and PCR amplification.

The response to and effects of microcomputers in the education sector:the introduction of an innovation in local authority secondary schools

The study addresses the introduction of an innovation of new technology into a bureaucratic profession. The organisational setting is that of local authority secondary schools at a time at which microcomputers were being introduced in both the organisational core (for teaching) and its periphery (school administration). The research studies innovation-adopting organisations within their sectoral context; key actors influencing the innovation are identified at the levels of central government, local government and schools.A review of the literature on new technology and innovation (including educational innovation), and on schools as organisations in a changing environment leads to the development of the conceptual framework of the study using a resource dependency model within a cycle of the acquisition, allocation and utilisation of financial, physical and intangible resources. The research methodology is longitudinal and draws from both positivist and interpretive traditions. lt includes an initial census of the two hundred secondary schools in four local education authorities, a final survey of the same population, and four case studies, using both interview methods and documentation. Two modes of innovation are discerned. In respect of administrative use a rationalising, controlling mode is identified, with local education authorities developing standardised computer-assisted administrative systems for use in schools. In respect of curricular use, in contrast, teachers have been able to maintain an indeterminate occupational knowledge base, derived from an ideology of professionalism in respect of the classroom use of the technology. The mode of innovation in respect of curricular use has been one of learning and enabling. The resourcing policies of central and local government agencies affect the extent of use of the technology for teaching purposes, but the way in which it is used is determined within individual schools, where staff with relevant technical expertise significantly affect the course of the innovation.

Properties and performance of polymer modified cements and mortars

Polymer modified cements and mortars have become popular for use as patch repair materials. General evidence suggests that these materials offer considerable improvements compared to traditional mortars although the mechanisms for this are not fully understood. This work elucidates the factors which govern some properties and performance of different polymer systems. In view of the wide range of commercial systems available, investigations concentrated on the use of three of the most commonly available groups of polymers. These were: (1) Styrene Butadiene Rubber (SBR), (2) Acrylics and, (3) Ethylene Vinyl Acetates (EVA). The later two were in the form of both emulsions and redispersible powders. Experiments concentrated on: (1) Rheological behaviour of polymer modified cement pastes; (2) Workability of polymer modified mortars; (3) Influence of curing conditions on the pore size distribution and diffusion of chloride ions; (4) Bond strength of polymer modified cement and mortar patches; and (5) Microscopic examination and semi-quantitative analyses of the bulk and interfacial microstructures. The following main conclusions were reached: (1) The addition of polymer emulsions have a considerable influence on the workability of fresh cement pastes, the extent of this depending on the type of system used. (2) The rheological parameters of fresh polymer modified mortars can be established using a two-point workability test which may be used when comparing the properties of different systems at constant workability. (3) Curing conditions affect the properties of polymer modified systems and a wet/dry curing regime was essential for good adhesion of these materials to mortar substrates. (4) In contrast, the wet/dry curing regime resulted in a curing affected zone at the surface of patch materials. This can result in a much coarser pore structure and enhanced diffusion of e.g. chloride ions. (5) The microstructure of polymer modified systems was very different compared with the unmodified cement/mortar and varied depending on curing conditions.

The mechanical properties and formability of dual-phase steel

In recent years dual phase steels comprising of 5-20% martensite in a ferrite matrix have come into the limelight of high strength cold formable steels because of their potential for vehicle weight saving. They show the following features: no yield point; relatively low initial flow stress; high initial workhardening rate; well sustained work hardening. As a consequence of these characteristics, dual phase steels exhibit a better combination of strength and elongation than other HSLA steels. In this thesis, a broad view of the factors which influence their properties is presented. Mechanical properties and forming ability of a commercially available dual phase steel and an AL-Si killed steel processed to dual phase form are investigated to ascertain the effect of their microstructure on their properties. It is found that the yield phenomena are masked by the transformation induced stresses present during processing and so yield point could be recovered under suitable ageing treatment; that apart from giving the above properties dual phasing gives rise to very low strain-rate sensitivity and a low R value ~ 1; that the mechanical response under rolling conditions is not different from those under tension; that there is a danger of damage to tooling during forming operations of these steels if fracture should precede instability as a result of grain size dependent strength found for these steels. It is also found that very little deformation of the martensite islands took place during deformation except at high strains. The work-hardening and the strength levels can be controlled by either decreasing the grain size or increasing the martensite volume fraction, but it is found that increasing martensite has a detrimental effect on ductility and the ductility and fracture strength can be controlled better by refining the grain size. A remarkable effect found in the dual phase steel tested is that the compressive strength is higher than the tensile strength. The reason for this observation is not yet clear but it is suggested that it might be due to the introduction of emissary type dislocations into the ferrite lattice as a result of twins formed in the martensite during transformation from austenite. The twins are envisaged to be {111} <112> in character.

Study of the deposition, properties and applications of electroless deposits containing particles

The deposition efficiencies of a number of electroless nickel and cobalt plating solutions were studied and in the case of nickel compared with a commercial plating solution Nifoss 80. At the optimum plating conditions (92ºC and pH 4.5) Nifoss 80 produced nickel layers most efficiently, the alkaline cobalt solution operated most efficiently at 90ºC and pH 9. The methods of producing compostte layers containing 2-3 µm carbide particles and chromium powder is described. Nickel and cobalt layers containing approximately 27% carbide particles, or 40% (Ni) and 30% (Co) chromium particles by volume were obtained. This value is independent of the particle concentration in the plating solution within the range (20~200 g/l). Hardness of the nickel. as deposited was 515 Hv, this was increased to a maximum of 1155 Hv by heat treatment at 200ºC for 5 hours in vacuum. Incorporation. of .chromium carbide particles resulted in a maximum hardness of 1225 Hv after heating at 500ºC for 5 hours in vacuum and chromium particles resulted in a maximum hardness of 16S0 Hv after heat treatment at 400ºC for 2 hours in vacuum. Similarly the hardness of cobalt as deposited was 600 Hv, this was increased to a maximum of 1300 Hv after heat treatment at 400ºC for 1 hour. Incorporation of chromium carbide particles resulted jn a maximum hardness of 1405 Hv after heating at 400ºC for 5 hours in vacuum and chromium particles resulted in a maximum hardness of 1440 Hv after. heat treating for 2 hours at 400ºC in vacuum. The structure of the deposits was studied by optical and scanning electron microscopy. The wear rate and coefficient of friction was determined by a pin and disc method. Wear rate and coefficient of friction decreased with increase in hardness. The wear resistance of the materials was also determined using a simulated forging test. Dies made of standard die steel were coated and the wear rates of the layers as deposited and after heat treatment were compared with those of uncoated tools. The wear resistance generally increased with hardness, it was 50-75% more than the uncoated die steel. Acetic acid salt spray test and outdoor exposure for six months was used to study the corrosion behaviour of the deposits and potentiodynamic curves plotted to find their corrosion potential. Nickel deposit exhibited less staining than carbide composite deposits and nickel-chromium deposits had the most noble corrosion potential.

Oxidized phospholipids:their properties and interactions with proteins

Lipids are a highly diverse class of biomolecules, with an average eukaryotic cell estimated as containing at least 100,000 different species. The significance of this diversity is still poorly understood, yet it has become clear that lipids have critical regulatory as well as structural roles, varying from signaling (e.g. phosphatidylinositols, prostaglandins, platelet activating factor, ceramide) to the control of permeability properties of skin, for instance. An unprecedented discovery from recent efforts in lipidomics, aimed at the elucidation of the functional roles of lipids in cells, was the key role for lipid oxidation in cell behavior and pathology. More specifically, oxidized phospholipids (oxPL) have been shown to increase significantly in apoptosis as well as in inflammation and to be involved in several pathological conditions, such as atherosclerosis, cancer, inflammation, Alzheimer's and Parkinson's disease, as well as type 2 diabetes, with the detailed mechanisms remaining to be established. However, a coherent overall view of the causalities and mechanisms has been lacking, mainly because of insufficient understanding of the cellular as well as molecular level mechanisms. This Special Issue represents a focused, integrated interdisciplinary approach summarizing very recent leading edge developments in this emerging field with emphasis on lipid–protein interactions. The data now becoming available are paving the way to the development of improved diagnostics, therapies and preventive measures to combat the above diseases.