Transport properties of hot-pressed bulk carbon nanotubes compacted by spark plasma sintering

Electrical and thermal transport properties of the carbon nanotube bulk material compacted by spark plasma sintering have been investigated. The electrical conductivity of the as-prepared sample shows a lnT dependence from 4 to 50 K, after which the conductivity begins to increase approximately linearly with temperature. A magnetic field applied perpendicularly to the sample increases the electrical conductivity in the range of 0-8T at all testing temperatures, indicating that the sample possesses the two-dimensional weak localization at lower temperatures (?50 K), while behaviors like a semimetal at higher temperatures (?50 K). This material acts like a uniform compact consisting of randomly distributed two dimensional graphene layers. For the same material, the thermal conductivity is found to decrease almost linearly with decreasing temperature, similar to that of a single multi-walled carbon nanotube. Magnetic fields applied perpendicularly to the sample cause the thermal conductivity to decrease significantly, but the influence of the magnetic fields becomes weak when temperature increases.

Inositol polyphosphate-mediated iron transport in Pseudomonas aeruginosa

It has previously been shown that myo-inositol hexakisphosphate (myo- InsP6) mediates iron transport into Pseudomonas aeruginosa and overcomes iron-dependent growth inhibition. In this study, the iron transport properties of myo-inositol trisphosphate and tetrakisphosphate regio-isomers were studied. Pseudomonas aeruginosa accumulated iron (III) at similar rates whether complexed with myo-Ins(1,2,3)P3 or myo-InsP6. Iron accumulation from other compounds, notably D/L myo-Ins(1,2,4,5)P4 and another inositol trisphosphate regio-isomer, D-myo-Ins(1,4,5)P3, was dramatically increased. Iron transport profiles from myo-InsP6 into mutants lacking the outer membrane porins oprF, oprD and oprP were similar to the wild-type, indicating that these porins are not involved in the transport process. The rates of reduction of iron (III) to iron (II) complexed to any of the compounds by a Ps. aeruginosa cell lysate were similar, suggesting that a reductive mechanism is not the rate-determining step.

Experiments to assess the transport of fibrous insulation debris

Loss of coolant accidents (LOCA) in the primary cooling circuit of a nuclear reactor may result in damage to insulation materials that are located near to the leak. The insulation materials released may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fibre agglomerates (MWFA) maybe transported to the containment sump strainers mounted at the inlet of the emergency cooling pumps, where the insulation fibres may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fibre cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Thus, knowledge of transport characteristics of the damaged insulation materials in various scenarios is required to help plan for the long-term operability of nuclear reactors, which undergo LOCA. An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a LOCA. The study entails the generation of fibre agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion of the containment internals by the coolant has on the strainer pressure drop. The focus of this presentation is on the experiments performed that characterize the horizontal transport of MWFA, whereas the corresponding CFD simulations are described in an accompanying contribution (see abstract of Cartland Glover et al.). The experiments were performed a racetrack type channel that provided a near uniform horizontal flow. The channel is 0.1 wide by 1.2 m high with a straight length of 5 m and two bends of 0.5 m. The measurement techniques include particle imaging (both wide-angle and macro lens), concurrent particle image velocimetry, ultravelocimetry, laser detection sensors to sense the presence of absence of MWFA and pertinent measurements of the MWFA concentration and quiescent settling characteristics. The transport of the MWFA was observed at velocities of 0.1 and 0.25 m s-1 to verify numerical model behaviour in and just beyond expected velocities in the containment sump of a nuclear reactor.

Verification and validation of numerical models of the transport of insulation debris

Damage to insulation materials located near to a primary circuit coolant leak may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fiber agglomerates (MWFA) maybe transported to the containment sump strainers, where they may block or penetrate the strainers. Though the impact of MWFA on the pressure drop across the strainers is minimal, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion and erosion of the containment internals by the coolant has on the strainer pressure drop. The focus of this paper is on the verification and validation of numerical models that can predict the transport of MWFA. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Note that the relative viscosity is only significant at high concentrations. Three single effect experiments were used to provide validation data on the transport of the fiber agglomerates under conditions of sedimentation in quiescent fluid, sedimentation in a horizontal flow and suspension in a horizontal flow. The experiments were performed in a rectangular column for the quiescent fluid and a racetrack type channel that provided a near uniform horizontal flow. The numerical models of sedimentation in the column and the racetrack channel found that the sedimentation characteristics are consistent with the experiments. For channel suspension, the heavier fibers tend to accumulate at the channel base even at high velocities, while lighter phases are more likely to be transported around the channel.

Numerical models used for the modelling of the transport of fibrous insulation debris

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA. An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop. The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Only one of the single effect experimental scenarios is described here that are used in validation of the numerical models. The scenario examines the suspension and horizontal transport of the fiber agglomerates in a racetrack type channel. The corresponding experiments will be described in an accompanying presentation (see abstract of Seeliger et al.).

Sump simulations

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA. An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop. The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations in the containment sump. Two dispersed phases were conditions to determine the influence of entrained air from a jet on the transport of fibre agglomerates through the sump. The strainer model of A. Grahn was implemented to observe the impact that the accumulation of the fibres have on the pressure drop across the strainers. The geometry considered is similar to the containment sump configurations found in Nuclear Power Plants.

Simulations of agglomerate sedimentation and suspension

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA. An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop. The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Application of such a model to sedimentation in a quiescent column and a horizontal flow are examined. The scenario also presents the suspension and horizontal transport of a single fiber agglomerate phase in a racetrack type channel.

Modified hydrogel matrices in fibre optic sensors

Common problems encountered in clinical sensing are those of non-biocompatibility, and slow response time of the device. The latter, also applying to chemical sensors, is possibly due to a lack of understanding of polymer support or membrane properties and hence failure to optimise membranes chosen for specific sensor applications. Hydrogels can be described as polymers which swell in water. In addition to this, the presence of water in the polymer matrix offers some control of biocompatibility. They thus provide a medium through which rapid transport of a sensed species to an incorporated reagent could occur. This work considers the feasibility of such a system, leading to the design and construction of an optical sensor test bed. The development of suitable membrane systems and of suitable coating techniques in order to apply them to the fibre optics is described. Initial results obtained from hydrogel coatings implied that the refractive index change in the polymer matrix, due to a change in water content with pH is the major factor contributing to the sensor response. However the presence of the colourimetric reagent was also altering the output signal obtained. An analysis of factors contributing to the overall response, such as colour change and membrane composition were made on both the test bed, via optical response, and on whole membranes via measurement of water content change. The investigation of coatings with low equilibrium water contents, of less than 10% was carried out and in fact a clearer signal response from the test bed was noted. Again these membranes were suprisingly responding via refractive index change, with the reagent playing a primary role in obtaining a sensible or non-random response, although not in a colourimetric fashion. A photographic study of these coatings revealed some clues as to the physical nature of these coatings and hence partially explained this phenomenon. A study of the transport properties of the most successful membrane, on a coated wire electrode and also on the fibre optic test bed, in a series of test environments, indicated that the reagent was possibly acting as an ion exchanger and hence having a major influence on transport and therefore sensor characteristics.

Synthetic polymers for ophthalmic applications

The contact lens represents a well-established important class of biomaterials. This thesis brings together the literature, mostly Japanese and American patents, concerned with an important group of polymers, `rigid gas permeable contact lens materials'. A comparison is made of similarities in the underlying chemical themes, centring on the use of variants of highly branched siloxy compounds with polymerizable methacrylate groups. There is a need for standard techniques to assess laboratory behaviour in relation to in vitro performance. A major part of the present work is dedicated to the establishment of such standardised techniques. It is apparent that property design requirements in this field (i.e. oxygen permeability, surface and mechanical properties) are to some extent conflicting. In principle, the structural approaches used to obtain high oxygen permeability lead to surface properties that are less than ideal in terms of compatibility with tears. PMMA is known to have uniquely good (but not perfect) surface properties in this respect; it has been used as a starting point in attempting to design new materials that possess a more acceptable compromise of transport and surface properties for ocular use. Initial examination of the oxygen permeabilities of relatively simple alkyl methacrylates, show that butyl methacrylate which has a permeability some fifty times greater than PMMA, represents an interesting and hitherto unexplored group of materials for ophthalmic applications. Consideration was similarly given to surface modification techniques that would produce materials having the ability to sustain coherent tear film in the eye without markedly impairing oxygen transport properties. Particular attention is paid to the use of oxygen plasma techniques in this respect. In conclusion, similar design considerations were applied to an extended wear hydrogel lens material in an attempt to overcome mechanical stability deficiencies which manifest themselves lq`in vivo' but not `in vitro'. A relatively simple structure modification, involving steric shielding of the amide substituent group, proved to be an effective solution to the problem.

Hydrogels containing linear and cyclic polyethers

Hydrogels are a unique class of polymer which swell, but do not dissolve in, water. A range of 2-hydroxyethyl methacrylate based copolymer hydrogels containing both cyclic and linear polyethers have been synthesised and are described in this thesis. Initially, cyclic polyethers were occluded within the polymer matrix and the transport properties investigated. The results indicated that the presence of an ionophore can be used to modulate ion transport and that ion transport is described by a dual-sorption mechanism. However, these studies were limited due to ionophore loss during hydration. Hence, the synthesis of a range of acrylate based crown ether monomers was considered. A pure sample of 4-acryolylaminobenzo-15-crown-5 was obtained and a terpolymer containing this monomer was prepared. Transport studies illustrated that the presence of a `bound' ionophore modulates ion transport in a similar way to the occluded systems. The transport properties of a series of terpolymers containing linear polyethers were then investigated. The results indicated that the dual-sorption mechanism is observed for these systems with group II metal cations while the transport of group I metal cations, with the exception of sodium, is enhanced. Finally, the equilibrium water contents (EWC) surface and mechanical properties of these terpolymers containing linear polyethers were examined. Although subtle variations in EWC are observed as the structure of the polyether side chain varies, generally EWC is enhanced due to the hydrophilicity of the polyether side chain. The macroscopic surface properties were investigated using a sessile drop technique and FTIR spectroscopy. At a molecular level surface properties were probed using an in vitro ocular spoilation model and preliminary cell adhesion studies. The results indicate that the polyethylene oxide side chains are expressed at the polymer surface thus reducing the adhesion of biological species.

The percutaneous absorption of ionisable compounds

The effects of ionisation on transdermal drug delivery using excised human epidermis (HS) and silastic rubber (SR) as model permeation barriers were investigated in vitro using Franz-type absorption cells. Suspensions and solutions of salicylic acid (SA), the model ionogenic permeant, were used as donors and the variables studied were vehicle pH and trans-membrane pH-gradients. For solutions, the pH effect was related to the level of ionisation of the drug and the degree of saturation of the solution. With suspensions, the observed permeation rate was unaffected by pH. The penetration profiles through HS and SR were similar, although the overall flux through HS was about 70% of that observed through SR. Pretreatment of the membranes with various enhancer regimens, including oleic acid, Azone and N, N-dimethylamides in propylene glycol (PG) and isopropyl myristate (IPM) promoted the penetration of SA. SR was not a suitable model for enhancer pretreatment using IPM as a vehicle as the membrane was significantly disrupted by this vehicle. The results from comparable experiments with and without a trans-membrane pH-gradient did not have a significant effect upon flux or flux enhancement after pretreatment with the above enhancers. A theoretical model for the extraction coefficients of weak acids was derived using the partition coefficients of the ionised and unionised species, pH and pKa. This model was shown to account for the variation in overall partition of salicylic acid dependent upon pH and pKa. This model was shown to account for the variation in overall partition of salicylic acid dependent upon pH and pKa. The distribution of this solute between aqueous and oily phases, with and without added enhancer, was measured as a function of pH. The extraction coefficients determined were consistent with the model and showed that the behaviour of the system can be explained without referral to ion-pair mechanisms. Phosphonoacetate is an effective antiviral agent. However, as it is charged at physiological pH, its permeation across cell membranes is limited. To assess the improvement of the transport properties of this molecule, mono-, di- and tri-ester prodrugs were examined. These were assessed for stability and subsequent breakdown with respect to pH by HPLC. In vitro percutaneous absorption was observed using the triester, but not the ionic mono- or di-esters. The triester absorption could be potentiated using a range of enhancers with oleic acid being the most effective. Cyclodextrins (CD) have a role as absorption enhancers for peptide compounds across nasal epithelium. One potential mode of action is that CDs include these compounds, protect them from enzymic attack and thereby increase their residence time in the nasal epithelium. This study investigated the potential of CDs to protect ester prodrugs from enzymatic breakdown and prevent production of poorly transportable ionic species. Using a range of CD to ester molar ratios (10:1 to 2500:1) a small, but measurable, protection for the model esters (parabens) against esterase attack was observed. Possible mechanisms for this phenomenon are that CDs include the ester, making it unavailable for hydrolysis, the CDs may also affect the esterase in some way preventing access for the ester into the active site.

Prodrugs of antiviral phosphonates

Phosphonoformate and phosphonoacetate are effective antiviral agents, however they are charged at physiological pH and as such penetration into cells and diffusion across the blood-brain bamer is limited. In an attempt to increase the lipophilicity and improve the transport properties of these molecules, prodrugs were synthesised and their stabilities and reconversion to the parent compound subsequently investigated by the techniques of 31P nuclear magnetic resonance spectroscopy and high performance liquid Chromatography. A series of 4-substituted dibenzyl (methoxycarbonyl)phosphonates were prepared and found to be hydrolytically unstable giving predominantly the diesters, benzyl (methoxycarbonyl)phosphonates. This instability arose from the electron-withdrawing effect of the carbonyl group promoting nucleophilic attack at phosphorus. It was possible to influence the mechanism and, to some extent, the rate of hydrolysis of the phosphonoformate triesters to the diesters by varying the electronic nature of the substituent in the 4-position of the aromatic ring. Strongly electron-withdrawing groups increased the sensitivity of phosphorus to nucleophilic attack, thus promoting P-O .bond cleavage and rapid hydrolysis. Conversely, weakly electron-withdrawing substituents encouraged C-O bond fission, presumably through resonance stabilisation of the benzyl carbonium ion. The loss of the protecting group on phosphorus was in competition with nucleophilic attack at the carbonyl group, resulting in P-C bond cleavage with dibenzyl phosphite formation. The high instability and P-C bond fission make triesters unsuitable prodrug forms of phosphonoformate. A range of chemically stable triesters of phosphonoacetate were synthesised and their bioactivation investigated. Di(benzoyloxymethyl) (methoxycarbonylmethyl)phosphonates degraded to the relevant benzoyloxymethyl (methoxycarbonylmethyl)phosphonate in the presence of esterase. The enzymatic activation was restricted to the removal of only one protecting group from phosphorus, most likely due to the close proximity of the benzoyloxy ester function to the anionic charge on the diester. However, in similar systems di(4-alkanoyloxybenzyl) (methoxycarbonylmethyl)phosphonates degraded in the presence of esterase with the loss of both protecting groups on phosphorus to give the monoester, (methoxycarbonylmethyl)phosphonate, via the intermediary of the unstable 4-hydroxy benzyl esters. The methoxycarbonyl function remained intact. The rate of enzymatic hydrolysis and subsequent removal of the protecting groups on phosphorus was dependent on the nature of the alkanoyl group and was most rapid for the 4-nbutanoyloxybenzyl and 4-iso-butanoyloxybenzyl esters of phosphonoacetate. This provides a strategy for the design of a prodrug with sufficient stability in plasma to reach the central nervous system in high concentration, wherein rapid metabolism to the active drug by brain-associated enzymes occurs.

Delivery of phosphonoformate prodrugs

AIDS dementia complex is a common neurological syndrome thought to result from the invasion of the CNS by HIV. Phosphonoformate has anti-HIV activity but due to its charged nature is excluded from the CNS by the blood-brain barrier. Lipophilic triesters of phosphonoformate designed to improve transport properties are unsuitable prodrugs due to their rapid and complicated hydrolysis, involving competitive P-O and P-C bond cleavage. Diesters, though hydrolytically stable, are considered too polar to passively diffuse into the CNS. Hydrophilic drugs mimicking endogenous nutrients are known to be actively transported across the blood-brain barrier. In this thesis the possibility that diesters of phosphonoformate may be actively transported is investigated. Triesters of phosphonoformate with labile aryl carboxyl esterrs were synthesised and their hydrolysis followed by 31P NMR spectroscopy. The triesters were found to undergo rapid hydrolysis via P-C bond cleavage to the phosphite. Phosphonoformate diesters designed to be analogues of actively transported -keto acids have been synthesised and fully characterised. Tyrosine-phosphonoformate and lipid-phosphonoformate conjugates have also been synthesised and characterised. An in vitro model of the blood-brain barrier utilising confluent monolayers of porcine brain microvessel endothelial cells grown on a permeable support has been established. The presence of enzyme and antigen markers specific to the blood-brain barrier has been demonstrated for the endothelial cells and the diffusional properties of the model investigated with hydrophilic and lipophilic compounds. Active transport systems for -keto acids and large amino acids have been identified in the endothelial cell monolayers using 14C-pyruvate and 3H-L-tyrosine respectively. Temperature and concentration dependence of the two systems have been demonstrated and transport constants calculated. Competition with 14C-pyruvate transport was shown with other monocarboxylic acids including the anti-epileptic drug valproate. Stereospecificity was shown in that L-lactate inhibited pyruvate transport while D-lactate did not. Sodium methyl methoxycarbonylphosphonate, a phosphonoformate diester was shown not to compete for 14C-pyruvate transport indicating that this compound has no affinity for the carrier. Competition with 3H-L-tyrosine transport was shown with other large amino acids, including the anti-Parkinsonian agent L-dopa. Stereospecificity was shown using L- and D-tyrosine and L- and D-dopa. The tyrosine-phosphonoformate conjugate, which was stable under the experimental conditions, was shown to compete with 3H-Ltyrosine transport indicating that it may be actively transported at the blood-brain barrier. Thirty two triesters, diesters and monoesters of phosphonoformate, showed no activity in an anti-HIV screen above that attributable to hydrolysis to the parent compound.

Microstructural analysis of surface and interface zones in concrete

Several of OPC paste and concrete specimens, with different mix proportions, were cast against CPF and impermeable formwork (IF) and the profiles of pore structure, microhardness and scratch hardness of the cover zone were established. The chloride ingress and the depth of carbonation of the surface zone of concrete cast against CPF and IF were investigated. The main mechanisms controlling the ECR processes and the factors affecting such treatment were critically reviewed. Subsequently, as a means of restoring passivation of steel embedded in carbonated concrete, such HCP specimens were subjected to ECR. The influence of ECR on the chemistry of the pore solution and the microstructure of the surface and the steel/cement past interface zones were also studied. The main findings of this investigation were as follows: (a) The thickness of the microstructure gradient of cover concrete is significantly decreased with increasing period of water curing but is relatively unaffected by curing temperature, w/e ratio and the use of cement replacement materials. (b) The scratch hardness technique was shown to be potentially useful for characterising the microstructure and microhardness gradients of the surface zone. (c) A relationship between the microstructure gradient and mass transport properties of the surface zone was established. (d) The use of CPF resulted in a significant reduction in porosity of both the cement paste matrix and the aggregate/cement paste transition zone, and a marked improvement in the resistance of the surface zone to carbonation and the ingress of chloride ions. (e) The ECR treatment resulted in a marked densification of the pore structure and in changes to the pore solution chemistry and the cement phases of near-surface and steel/cement paste transition zones. This effect was more pronounced with current density, period of treatment and particularly with the use of sodium phosphate as an electrolyte.

Effect of electron-phonon coupling on transmission through Luttinger liquid hybridized with resonant level

We show that electron-phonon coupling strongly affects transport properties of the Luttinger liquid hybridized with a resonant level. Namely, this coupling significantly modifies the effective energy-dependent width of the resonant level in two different geometries, corresponding to the resonant or antiresonant transmission in the Fermi gas. This leads to a rich phase diagram for a metal-insulator transition induced by the hybridization with the resonant level.