Filler cement: The effect of the secondary component on the hydration of Portland cement: Part 2: Fine hydraulic binders

In Part 1 of this paper, it was shown that enhanced hydration was achieved by blending a fine non-hydraulic filler into an ordinary Portland cement. This enhancement was considered to be a particle size effect and associated with the presence of fine particles of filler which provided the additional nucleation sites. The filler, rutile, had a variable cement equivalence and reached a maximum value of 0.9kg/kg after hydration had proceeded for three days. In this second part, the same Portland cement was blended seperately with latent hydraulic binders (two pulverized fuel ashes and a ground granulated blastfurnace slag, a Lurgi slag and a volatilized silica). The apparent overall reactivity of these binders was seen to have two components, the first being the particle size effect with its influence on the hydration of the Portland cement and the second the inherent hydraulicity of the secondary material.     

Characterization of the aramid: Epoxy and carbon: Epoxy interphases

The matrix/reinforcement interphase in aramid fiber/epoxy and carbon fiber/epoxy composites were modeled by coating an internal reflection spectroscopy (IRS) element with a thin layer of an aramid or of carbonized poly(acrylonitrile) (PAN). The coated element was then used as a substrate on which the curing of an epoxy resin took place. Infrared (IR) spectroscopy was used to demonstrate that the simulated reinforcement surfaces modified the crosslinking chemistry in the first 200–400 nm of epoxy matrix adjacent to the surfaces, producing an interphase of matrix material with properties different from those of the bulk of the epoxy matrix. This hypothesis was confirmed by the fabrication and testing of a series of unidirectional aramid fiber/epoxy and carbon fiber/epoxy composites.     

Models for the formation of poly(butylene terephthalate): Kinetics of the titanium tetrabutylate-catalysed reactions: 2

In order to investigate the mechanism of catalysis of titanium tetrabutoxide on the polycondensation of poly(butylene terephthalate), this reaction has been studied with the aid of model molecules. The catalytic and retarding effects of benzoic acid have also been taken into account. Appropriate kinetic equations are derived and discussed and the results compared with experimental data obtained at different temperatures and molar ratios of reactants.     

Anaerobic degradation: the effect of the combined treatment of substrates on the refractory fraction

The anaerobic digestion of landfill leachates mixed with domestic sewage was studied using a batch reactor at laboratory scale. Batch assays were carried out with different proportions of leachate in the feed: 100, 70, 50 and 30% by volume, with and without adjustment of pH, in order to determine the percentage of acidification and methanization, COD removal, anaerobic biodegradability and biomass growth yield. The main effect of the mixing with sewage was a synergistic improvement of the anaerobic treatment of leachates, but in different ways; the greatest improvement in COD removal was obtained when the proportion of leachate in the feed was 70%, but the highest degree of anaerobic biodegradability was obtained with 30% of leachate in the feed. The kinetics of these assays was studied and the experimental data were fitted to a modification of the equation of Chen and Hashimoto. A new concept of ‘non‐biodegradable fraction’ is proposed. © 2002 Society of Chemical Industry     

Dynamics of Particle-Shock Interactions: Part II: Effect of the Basset Term

Small particles and droplets encounter normal shocks in a variety of applications. The particle-shock interaction subjects the particles to large unsteady drag forces behind the shock front. In the present paper, an analysis has been made of the relative importance of the Basset history integral in the equation of motion for particle displacement and velocity behind a normal shock wave. The effect of the Basset integral has been related to gas stagnation conditions upstream of the shock and the local gas Mach number. In the present theoretical study it has been demonstrated that particle velocity and displacement relative to the gas behind the shock is unaffected by the inclusion of the Basset term until the latter stages of particle relaxation. The effect of the Basset history integral, that results from diffusion of vorticity from the decelerating particle, has been shown to decrease the particle drag or increase the displacement of the particle behind the shock. The effect is magnified with increasing stagnation pressures and particle diameters but with decreasing gas stagnation temperatures.     

Chrome dyeing: the role of soluble proteins

A significant factor preventing the achievement of zero chromium in the effluent from the after‐chrome dyeing process is the presence of soluble proteins in the dyebath. These proteins can react with the dichromate anion and thus interfere with its reaction with the wool fibre and dye molecules. This understanding may lead to the development of very low chromium in effluent dyeing methods that ensure the viability of chrome dyeing.     

Application of the Conant-Finkelstein Reaction to the Modification of PVC: Iodinated PVC

The Conant-Finkelstein reaction was applied to PVC with the aiming of replacing the chlorine atoms with iodine ones. The effect of reaction temperature with regard to the characteristics of the modified PVC was significant. Formation of a gel and degraded polymeric materials was observed when working at temperatures higher than 60 °C. The degraded polymer formed at 70 °C was insoluble and gave rise to a polyacetylene-like chain with a melting point of 60 °C. However, the reaction on PVC at lower temperatures resulted in soluble polymers which were easily amenable to spectral characterization. The molecular weights of the iodine-modified PVCs were temperature-dependent. At 40, 45, 50 and 60 °C, molecular weights lower than that of the initial PVC were measured; however, at 35, 30 and 25 °C, a gain of about 9% in molecular weight was seen. Substitution and elimination reactions occurred to different extents depending mostly on temperature. Optimal substitution was obtained at 50 °C for a reaction time of 20 h.     

RO systems: the importance of pre-treatment

The ability or reverse osmosis (RO) to produce a continuous and dependable water product has seen its use within the water treatment industry grow. However, incorrectly designed pre-treatments to this technology can reduce the expected benefits. Simon Gare, Ecolochem International Inc, UK, explores both physical and chemical pre-treatment methods routinely used with RO systems, and discusses some of the factors that are important when choosing the right pre-treatment.     

Governing the use of water: the institutional context

The use of water presents an inherent problem for governing, and this paper brings a political science perspective to bear on institutional questions which arise in relation to recycling. Here, “institution” is not to be equated with “government organization”: the paper draws on institutional organizational analysis and social construction analysis to show that the governing of water use should be seen not as a technical response to an unambiguous need, but as the outcome of a continuing and complex process of institutionalization. It briefly outlines the “traditional” institutionalization of water use in Australia, and the way in which this has been challenged by rhetorics of managerial control, goal specificity, market forces, and public accessibility, all of which underlie the recent National Water Initiative. In this context, recycling has to be seen not simply as a technical alternative to present practice, but as a challenge to the existing institutionalization of water use, particularly in respect of the place of water users in governing of water use.     

Molecular Electronics: Beyond the Limits of Conventional Electronics

Abstract

Future technologies in information science will reiy on structures with decreasing size and on systems with increasing complexity. The physical and technological limits of semiconductor nanostructures point to the use of molecules and atoms in information science. In particular, organic molecules are very attractive because they can be engineered with very large complexity, and their electronic and optical properties can be controlled technologically. Already today many fundamental functions and devices relevant to information technology can be realized with systems of organic molecules: Switchable molecules lead to the development of memories with large capacity, transmission of information is possible through “molecular wires”, and the flow of information can be interrupted by “switching molecules”. Together with other logical elements this opens the possibility to develop future systems in information technology. However, this requires suitable supramolecular arrangements for complex interconnections of logical elements and memory molecules, as well as a suitable electrical or optical periphery.     

Modelling of a dynamic multiphase flash: the positive flash: Application to the calculation of ternary diagrams

A general and polyvalent model for the dynamic simulation of a vapor, liquid, liquid–liquid, vapor–liquid or vapor–liquid–liquid stage is proposed. This model is based on the τ-method introduced as a minimization problem by [Comput. Chem. Eng. 22 (7/8) (1998) 897] for steady-state simulation. They suggested modifying the mole fraction summation such that the same set of governing equations becomes valid for all phase regions. Thanks to judicious additional switch equations, the τ-formulation is extended to dynamic simulation and the minimization problem is transformed into a set of differential algebraic equations (DAE). Validation of the model consists in testing its capacity to overcome phase number changes and to be able to solve several problems with the same set of equations: calculation of heterogeneous residue curves, azeotropic points and distillation boundaries in ternary diagrams.     

Electrodeposition of copper: the nucleation mechanisms

The nucleation mechanisms of copper during electrodeposition of thin films from sulfate solutions were studied by utilizing the electrochemical techniques (cyclic voltammetry and chronoamperometry) and atomic force microscopy (AFM). Near atomically smooth glassy carbon was used as the deposition substrate (electrode). The copper nucleation mechanisms were examined as a function of solution pH, copper concentration, deposition potential, temperature, and background electrolyte. It was found that with pH and copper concentration increase, the nuclei size increased, while the nuclei population density decreased. An increase of deposition potential produced smaller nuclei and higher nuclei population density. Temperature affected the morphology of deposited copper. The presence of background electrolyte also influenced the morphology and population density of copper nuclei. The nucleation mechanisms were examined by fitting the experimental data (chronoamperometry) into the Scharifker-Hills nucleation models. It was found that at pH 1, in the absence of background electrolyte, copper nucleation was instantaneous. At pH 2 and 3, the mechanism was inconclusive. In the presence of background electrolyte, the mechanism at pH 1 and 2 was mixed, while at pH 3, the mechanism was progressive nucleation.     

Characterising the time-dependant behaviour on the single fibre level of SHCC: Part 1: Mechanism of fibre pull-out creep

SHCC (Strain Hardening Cement-based Composite) has been designed and optimised to overcome the main weaknesses of ordinary concrete, which is its brittleness. SHCC shows a high tensile ductility and can resist the full load at a tensile strain of more than 4%. An in depth investigation into the time-dependant behaviour is still lacking for SHCC. This paper is the first part of a two paper series about the time-dependant behaviour on the single fibre level. In this paper, the tensile creep behaviour of SHCC is studied to distinguish mechanisms of creep. Tensile creep and shrinkage test results are reported for dumbbell type SHCC specimens. The specimens are pre-cracked to simulate in-service conditions, with subsequent sustained load at various levels, here chosen as 30%, 50%, 70% and 80% of the ultimate resistance. To distinguish the sources of significant creep deformation under these sustained loads, single fibre pull-out tests are performed under sustained load. It is shown that the time-dependent fibre pull-out is a significant source of time-dependent deformation, along with the formation of new cracks in SHCC under sustained load.     

Adipocyte-Derived Extracellular Vesicles: State of the Art

White adipose tissue (WAT) is involved in long-term energy storage and represents 10–15% of total body weight in healthy humans. WAT secretes many peptides (adipokines), hormones and steroids involved in its homeostatic role, especially in carbohydrate–lipid metabolism regulation. Recently, adipocyte-derived extracellular vesicles (AdEVs) have been highlighted as important actors of intercellular communication that participate in metabolic responses to control energy flux and immune response. In this review, we focus on the role of AdEVs in the cross-talks between the different cellular types composing WAT with regard to their contribution to WAT homeostasis and metabolic complications development. We also discuss the AdEV cargoes (proteins, lipids, RNAs) which may explain AdEV’s biological effects and demonstrate that, in terms of proteins, AdEV has a very specific signature. Finally, we list and suggest potential therapeutic strategies to modulate AdEV release and composition in order to reduce their deleterious effects during the development of metabolic complications associated with obesity.     

Evolution of the activated sludge process: the first 50 years

The paper presents a critical overview of the first 50 years in the evolution of the activated sludge process. Recognition of the role of aeration and microbial activity in the purification of sewage in the early studies established the basis for the accidental discovery of the process, which was immediately adapted into practice. The problems encountered during operation started a period of empirical expansion with many process modifications. As scientific support lagged behind practice, efforts were then directed towards exploring and understanding the fundamentals of the system related to substrate removal mechanisms, microbiology, process kinetics and stoichiometry, nitrogen transformations and, then, translating accumulated information into design. Extensive research generated remarkable findings which should be regarded as major milestones for future progress in many areas such as fractionation of substrate and biomass, particle size distribution, and substrate storage. A rational foundation of the activated sludge process for the removal of organic carbon could then be established based on mass balance. This approach also defined essential parameters that could relate microbial reactions involved with plant design and operation. Scientific ideas and discoveries have also enabled conceptual development of many emerging technologies such as the sequencing batch reactor, enhanced biological phosphorus removal, the oxic‐settling anaerobic process, and the super‐fast membrane bioreactor. © 2014 Society of Chemical Industry     

Fluorinated carbon blacks: influence of the morphology of the starting material on the fluorination mechanism

The effect of fluorination, using CF₄ r.f. plasmas, has been studied on three different types of carbon blacks: a thermal black, a furnace black and a high electrical conducting black. The influences of the morphology and structure of the three blacks on the fluorination mechanism have been investigated. In particular, the ratio Type I/Type II structures (i.e., surface (CF) and border groups of graphitic domains with sp²C/polyalicyclic perfluorinated structures with sp³C), has been correlated to the microstructural organisation. The transformation into Type II structures is more easily achieved in highly accessible XE2 blacks, whereas in materials with lower crystallinity (MT), the presence of numerous defects leads preferentially to surface (CF_x) perfluorinated groups.     

Ball-milling: the behavior of graphite as a function of the dispersal media

The ball-milling in liquid media leads to well organized, thin and highly anisometric graphite (HAG) crystals. The presence in the milling container of a liquid, which acts as a lubricant and decreases the violence of the shocks, is relevant. Two liquids are used: n-dodecane and water. With dodecane, inert towards graphite and the metal of the milling tools, the powder consists of pure graphite whereas with water, the graphite particles are covered with nanocrystallites (15 nm) of a magnetic compound: the maghemite (γ Fe₂O₃). The electrochemical properties of those powders are interesting. The highly anisometric graphite leads to an irreversible capacity around half of that for the initial graphite powder, in contradiction with previous results claiming that higher the surface area, the higher the irreversible capacity. In fact, milling in the presence of dodecane provokes essentially a cleavage, which increases the global area, but does not drastically change the number of edge carbon atoms, responsible for the increase of the large irreversible capacity. The graphite–maghemite composites present a high capacity, partly reversible by oxidation–reduction between iron and wustite (FeO). This reaction is made possible by the nanometric size of the particles, and therefore their high reactivity.     

Opinion: On the Way towards the New Paradigm of Atherosclerosis

Atherosclerosis is a multicausal disease characterized by the formation of cholesterol-containing plaque in the pronounced intima nearest to the heart’s elastic-type arteries that have high levels of blood circulation. Plaques are formed due to arterial pressure-induced damage to the endothelium in areas of turbulent blood flow. It is found in the majority of the Western population, including young people. This denies the monogenic mechanism of atherogenesis. In 1988, Orekhov et al. and Kawai et al. discovered that the presence of atherogenic (modified, including oxidized ones) LDLs is necessary for atherogenesis. On the basis of our discovery, suggesting that the overloading of enterocytes with lipids could lead to the formation of modified LDLs, we proposed a new hypothesis explaining the main factors of atherogenesis. Indeed, when endothelial cells are damaged and then pass through the G2 phase of their cell cycle they secrete proteins into their basement membrane. This leads to thickening of the basement membrane and increases its affinity to LDL especially for modified ones. When the enterocyte transcytosis pathway is overloaded with fat, very large chylomicrons are formed, which have few sialic acids, circulate in the blood for a long time, undergo oxidation, and can induce the production of autoantibodies. It is the sialic acids that shield the short forks of the polysaccharide chains to which autoantibodies are produced. Here, these data are evaluated from the point of view of our new model.     

The fluorescence of dihydroxyphenylalanine: the effects of protonation-deprotonation

The fluorescence excitation and emission spectra and quantum yields of 3,4-dihydroxyphenylalanine (DOPA), its methyl ester (DOPAM) and the N -acetylated derivative (DOPANA) in aqueous solution at pH values ranging from 3.0 to 10.0 have been determined and the excitation spectra related to their absorption spectra. The fluorescence quantum yield of the phenolic form of DOPA is 0.09. However, the fluorescence yield is substantially reduced for the conjugate base forms, i.e. deprotonation of the amine group and the phenolic hydroxyl group. The fluorescence spectra are dominated by the phenolic forms of DOPA, DOPAM and DOPANA from pH 3.0 to 10.0 with excitation and emission spectral maxima at 280 and 315 nm respectively. The excitation maxima for all the compounds correspond to the absorption maxima of their phenolic forms. The phenolate anions of DOPA and DOPAM exhibit weak fluorescence with emission maxima at 325 and 330 nm respectively.     

Controlling the tacticity in the polymerization of N-isopropylacrylamide: A computational study

In this study, the effect of alcohols as solvents on the kinetics and the tacticity of poly(N-Isopropylacrylamide) (PNIPAM) is investigated with a combined static and molecular dynamics set of computational tools. Classical molecular dynamics calculations have been carried out to determine the location of the solvent molecules in the proximity of the monomer and the dimer. A combined implicit/explicit solvent model was used for the evaluation of the kinetics of the dimeric polymer chains. Rate constants are calculated with the B3LYP/6-311 + G(d,p)//B3LYP/6-31 + G(d), BMK/6-311 + G(d,p)//B3LYP/6-31 + G(d), and MPWB1K/6-311 + G(d,p)//B3LYP/6-31 + G(d) methodologies via the standard transition state theory. We show that due to the proximity of the -NH and carbonyl groups on the syndiotactic propagating dimeric and trimeric chains, the alcohol can stabilize the corresponding transition states by forming a bridge between these functionalities and accelerate this path more than its isotactic counterpart. In agreement with experiment, the increase in the syndiotactic PNIPAM and the acceleration of the reaction in the presence of t-BuOH is predicted with all the DFT functionals utilized in this study.