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Showing papers by "Instituto Superior Técnico published in 1998"


Journal ArticleDOI
TL;DR: A new method for separating and recovering the motion and shape of multiple independently moving objects in a sequence of images by introducing a mathematical construct of object shapes, called the shape interaction matrix, which is invariant to both the object motions and the selection of coordinate systems.
Abstract: The structure-from-motion problem has been extensively studied in the field of computer vision. Yet, the bulk of the existing work assumes that the scene contains only a single moving object. The more realistic case where an unknown number of objects move in the scene has received little attention, especially for its theoretical treatment. In this paper we present a new method for separating and recovering the motion and shape of multiple independently moving objects in a sequence of images. The method does not require prior knowledge of the number of objects, nor is dependent on any grouping of features into an object at the image level. For this purpose, we introduce a mathematical construct of object shapes, called the shape interaction matrix, which is invariant to both the object motions and the selection of coordinate systems. This invariant structure is computable solely from the observed trajectories of image features without grouping them into individual objects. Once the matrix is computed, it allows for segmenting features into objects by the process of transforming it into a canonical form, as well as recovering the shape and motion of each object. The theory works under a broad set of projection models (scaled orthography, paraperspective and affine) but they must be linear, so it excludes projective “cameras”.

778 citations


Journal ArticleDOI
TL;DR: In this article, a new methodology for integrated design of guidance and control for unmanned aerial vehicles (AVs) is proposed, which leads to an efficient procedure for the design of controllers for AVs to accurately track reference trajectories defined in an iner- tia! reference frame.
Abstract: . This paper addresses the problem of in- tegrated design of guidance and control systems for au- tonomous vehicles (AVs). In fact, it introduces a new methodology for integrated design of guidance and control for such vehicles. The methodology proposed leads to an efficient procedure for the design of controllers for AVs to accurately track reference trajectories defined in an iner- tia! reference frame. The paper illustrates the application of this procedure on the design of a tracking controller for the Unmanned Air Vehicle Bluebird. The design phase is summarized, and the performance of the resulting con- troller is assessed in simulation using dynamic models of the vehicle and its sensor suite.

321 citations


Journal ArticleDOI
TL;DR: Correlations between the cellular toxicity or the extractive capacities of different solvents and some of their physical properties have been proposed in order to minimize preliminary, solvent-selection experimental work but also to help in the understanding of the molecular mechanisms of toxicity and extraction.

299 citations


Journal ArticleDOI
TL;DR: Anaerobic bioreactors can be used to at least partially treat these effluents and provide a number of significant advantages as discussed by the authors, such as decolourisation of many dyes under the reducing conditions present in an anaerobic reactor.
Abstract: The treatment of textile waste water is commonly carried out using biological (mainly aerobic) and physico-chemical systems. However, anaerobic bioreactors can be used to at least partially treat these effluents and provide a number of significant advantages. The most attractive feature for the treatment of textile effluents is the decolourisation of many dyes under the reducing conditions present in an anaerobic reactor. Laboratory-scale results on this particular topic are here reviewed. A second major advantage of anaerobic processing is its ability to treat wastestreams with high organic loads such as the effluents from the desizing and scouring operations currently employed in the textile manufacturing industry. Reports on successful, full-scale and pilot-scale plants are also reviewed and some limitations are discussed. © 1998 Society of Chemical Industry

280 citations


Journal ArticleDOI
TL;DR: In this article, a 1-parameter family of extremal Kahler metrics of non-constant scalar curvature on convex polytopes is recast using Guillemin's approach.
Abstract: A (symplectic) toric variety X, of real dimension 2n, is completely determined by its moment polytope Δ ⊂ ℝn Recently Guillemin gave an explicit combinatorial way of constructing "toric" Kahler metrics on X, using only data on Δ In this paper, differential geometric properties of these metrics are investigated using Guillemin's construction In particular, a nice combinatorial formula for the scalar curvature R is given, and the Euler–Lagrange condition for such "toric" metrics being extremal (in the sense of Calabi) is proven to be R being an affine function on Δ ⊂ ℝn A construction, due to Calabi, of a 1-parameter family of extremal Kahler metrics of non-constant scalar curvature on is recast very simply and explicitly using Guillemin's approach Finally, we present a curious combinatorial identity for convex polytopes Δ ⊂ ℝn that follows from the well-known relation between the total integral of the scalar curvature of a Kahler metric and the wedge product of the first Chern class of the underlying complex manifold with a suitable power of the Kahler class

248 citations


Journal ArticleDOI
TL;DR: In this paper, a numerical model is developed for the simulation of the 3D deformations of skeletal muscles based on a generalization of the model proposed by Humphrey and Yin for the passive behavior of cardiac muscle.

201 citations


Journal ArticleDOI
TL;DR: In this paper, a kinetic model of low-pressure DC flowing discharges in - mixtures is presented, where the only input parameters are those that can externally be chosen in experiments, such as total gas pressure, radius and length of the discharge tube, discharge current, gas flow rate and initial gas temperature and composition.
Abstract: This work is the first of two companion papers devoted to the kinetic modelling of low-pressure DC flowing discharges in - mixtures. While the present paper is mainly concerned with bulk discharge processes, the second one investigates surface processes involving dissociated N and H atoms, which are essential to understand the discharge properties. The global model combining bulk and surface processes as described in these two papers is self-contained in the sense that the sole input parameters it requires are those that can externally be chosen in experiments, namely: total gas pressure, radius and length of the discharge tube, discharge current, gas flow rate and initial gas temperature and composition (e.g., the relative hydrogen concentration X in the binary mixture at the discharge inlet). For a given set of input parameters, this model enables one to calculate the following bulk plasma properties as a function of the axial coordinate z: concentration of , , NH, , molecules and N, H atoms in the ground electronic state; population in the electronically excited states , (an effective high Rydberg state) and ; concentration of the ions , , , , , and ; vibrational level populations of and molecules; electron density , mean kinetic energy , characteristic energy and drift velocity ; discharge sustaining electric field E; average gas temperature across the tube T and wall temperature . The calculations are compared with data from different experiments in pure and discharges (measurements of electric field as a function of current and pressure) and in - discharges (measurements of relative changes in the electric field and the , concentrations as a function of the percentage). From the comparison to experiment, rate coefficients for associative ionization upon collisions between two excited molecules and deactivation of and by H atoms have been estimated from the model.

196 citations


Journal ArticleDOI
TL;DR: The use of Q-Sepharose columns (1, 10 and 40 ml) for the preparative purification of plasmid pUC18 enabled the isolation of supercoiled plasmids from low-M(r) RNA, cDNA and plasmID variants and anion-exchange HPLC on a Poros QE 20 column was used to quantifyplasmid yield.

195 citations


Journal ArticleDOI
TL;DR: The potential for the efficiency improvement is generally underestimated as mentioned in this paper and most of the energy conversion systems consider efficiency improvement as a separate process and their analysis reflects only the potential improvement of the process but not the potential for efficiency improvement obtained by an exergy analysis of the system.
Abstract: In order to reach the goals indicated by the sustainable energy development the efficiency in the energy conversion use has to meet several criterions [1]. The potential for the efficiency improvement is generally underestimated. Most of the energy conversion systems consider the efficiency improvement as a separate process and their analysis reflects only the potential improvement of the process but not the potential for the efficiency improvement obtained by an exergy analysis of the energy system. Fossil fuel energy resources use is mostly conversion to heat by the combustion processes. Since the combustion process is taking place at temperatures between 900 — 1300°C and over 40% of heat is used a low temperature heat, it is indispensable to take into consideration the thermodynamic assessment of the efficiency in order to bring in line energy conversion processes and energy demand to obtain the optimum fuel utilization.

174 citations


Journal ArticleDOI
TL;DR: In this paper, a series of impact and compression after impact tests were carried out on composite laminates made of carbon fibre reinforced epoxy resin matrix, and four stacking sequences of two different epoxy resins in carbon fibres representative of four different elastic behaviours and with a different number of interfaces were used.

155 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the eigenmass problem given by Witten as a possible approximation for masses in QCD without supersymmetry, and showed that requiring smoothness at the horizon and normalizability gives a well defined eigenvalue problem.
Abstract: In the framework of the conjectured duality relation between large N gauge theory and supergravity the spectra of masses in large N gauge theory can be determined by solving certain eigenvalue problems in supergravity. In this paper we study the eigenmass problem given by Witten as a possible approximation for masses in QCD without supersymmetry. We place a particular emphasis on the treatment of the horizon and related boundary conditions. We construct exact expressions for the analytic expansions of the wave functions both at the horizon and at infinity and show that requiring smoothness at the horizon and normalizability gives a well defined eigenvalue problem. We show, for example, that there are no smooth solutions with a vanishing derivative at the horizon. The mass eigenvalues up to ${m}^{2}=1000$ corresponding to smooth normalizable wave functions are presented. We comment on the relation of our work with the results found in a recent paper by C. Cs\'aki et al., hep-th/9806021, which addresses the same problem.

Journal ArticleDOI
TL;DR: In this article, the vertical motions and wave induced loads on ships with forward speed are studied in the time domain, considering non-linear effects associated with large amolitude motions and hull flare shape.
Abstract: The vertical motions and wave induced loads on ships with forward speed are studied in the time domain, considering non-linear effects associated with large amolitude motions and hull flare shape. The method is based on a strip theory, using singularities distributed on the cross sections which satisfy the linear free surface condition. The solution is obtained in the time domain using convolution to account for the memory effects related to the free surface oscillations. In this way the linear radiation forces are represented in terms of impulse response functions, infinite frequency added masses and radiation restoring coefficients. The diffraction forces associated with incident wave scattering are linear. The hydrostatic and Froude-Krylov forces are evaluated over the instantaneous wetted surface of the hull to account for the large amplitude motions and hull flare. The radiation contribution for wave loads is also obtained in the time domain usine convolution to account for the memory effects related to the free surface oscillations. Results of motions and wave loads for the S175 container ship are presented and analyzed. The results from the present method are compared with linear results.

Journal ArticleDOI
TL;DR: In this article, it was shown that the minimal R-parity breaking model characterized by an effective bilinear violation of R -parity in the superpotential is consistent with minimal N = 1 supergravity unification with radiative breaking of the electroweak symmetry and universal scalar and gaugino masses.

Journal ArticleDOI
01 May 1998
TL;DR: CMM, a meta-learner that seeks to retain most of the accuracy gains of multiple model approaches, while still producing a single comprehensible model, is proposed and evaluated.
Abstract: If it is to qualify as knowledge, a learner's output should be accurate, stable and comprehensible. Learning multiple models can improve significantly on the accuracy and stability of single models, but at the cost of losing their comprehensibility when they possess it, as do, for example, simple decision trees and rule sets. This article proposes and evaluates CMM, a meta-learner that seeks to retain most of the accuracy gains of multiple model approaches, while still producing a single comprehensible model. CMM is based on reapplying the base learner to recover the frontiers implicit in the multiple model ensemble. This is done by giving the base learner a new training set, composed of a large number of examples generated and classified according to the ensemble, plus the original examples. CMM is evaluated using C4.5RULES as the base learner, and bagging as the multiple-model methodology. On 26 benchmark datasets, CMM retains on average 60% of the accuracy gains obtained by bagging relative to a single run of C4.5RULES, while producing a rule set whose complexity is typically a small multiple 2--6 of C4.5RULES's, and also improving stability. Further studies show that accuracy and complexity can be traded off by varying the number of artificial examples generated.

Journal ArticleDOI
TL;DR: It is shown that a selective engagement of the CD94/NKG2‐A inhibitory receptor with a specific monoclonal antibody (mAb) (Z199) was sufficient to induce tyrosine phosphorylation of the NKG 2‐A subunit and SHP‐1 recruitment, constituting a more formal evidence for the receptor‐HLA class I interaction.
Abstract: It has been recently demonstrated that the CD94/NKG2-A killer inhibitory receptor (KIR) specifically recognizes the HLA-E class Ib molecule. Moreover, the apparent CD94-mediated specific recognition of different HLA class Ia allotypes, transfected into the HLA-defective cell line 721.221, indeed depends on their selective ability to concomitantly stabilize the surface expression of endogenous HLA-E molecules, which confer protection against CD94/NKG2-A+ effector cells. In the present study, we show that a selective engagement of the CD94/NKG2-A inhibitory receptor with a specific monoclonal antibody (mAb) (Z199) was sufficient to induce tyrosine phosphorylation of the NKG2-A subunit and SHP-1 recruitment. These early biochemical events, commonly related to negative signaling pathways, were also detected upon the specific interaction of NK cells with an HLA-E+ 721.221 transfectant (.221-AEH), and were prevented by pre-incubation of .221-AEH with an anti-HLA class I mAb. Furthermore, mAb cross-linking of the CD94/NKG2-A receptor, segregated from other NK-associated molecules by transfection into a rat basophilic leukemia cell line (RBL-2H3), promoted tyrosine phosphorylation of NKG2-A and co-precipitation of SHP-1, together with an inhibition of secretory events triggered via Fc epsilonRI. Remarkably, interaction of CD94/NKG2-A+ RBL cells with the HLA-E+ .221-AEH transfectant specifically induced a detectable association of SHP-1 with NKG2-A, constituting a more formal evidence for the receptor-HLA class I interaction.

Proceedings ArticleDOI
31 Aug 1998
TL;DR: In this article, four different methods of determining the compensating current for a shunt active filter that is working under nonsymmetrical conditions were compared. And the synchronous reference frame method had shown the best choice for all situations studied in this paper.
Abstract: Active power filters are used to eliminate current harmonics near nonlinear loads. This paper evaluates four different methods of determining the compensating current for a shunt active filter that is working under nonsymmetrical conditions. The methods compared are the instantaneous reactive power theory, the modified instantaneous reactive power theory, the synchronous reference frame theory and the modified synchronous reference frame theory. The comparison is based on simulation results. In balanced sinusoidal source voltages, the difference between the results obtained by the four methods are of minimum importance. For unbalanced and nonsinusoidal source voltage conditions, the results obtained by the methods referenced are quite different. The synchronous reference frame method had shown the best choice for all situations studied in this paper.

Journal ArticleDOI
TL;DR: Results from research on public perception of floods, flood management and participatory initiatives in Setúbal, Portugal are presented and a number of recommendations for flood hazard management policy making and processes are made.
Abstract: The understanding of how people evaluate and respond to natural hazards in an urban area, and how this knowledge can be integrated in the planning and management process, are becoming very important elements of a comprehensive and participatory approach to flood hazard management. Such an approach demands a clear comprehension of the processes of the risks perception, causal attribution, possible solutions for the problem and patterns of behaviour developed during hazard situations. The willingness of the public to participate in flood management, and the attitudes to previous initiatives also need to be addressed. The provision of structural flood defences can have a major impact on the environment and there has been an expression of concern by many members of the public for the degradation of river corridors. In this context, it is becoming a commonly accepted practice by central or local governments to submit flood management plans to public discussion. Appropriate techniques for interfacing with the public are necessary to support this upsurge of public involvement. This paper presents results from research on public perception of floods, flood management and participatory initiatives in Setubal, Portugal. An extensive interview programme was undertaken with residents and shopkeepers – with and without flood experience, professionals responsible for dealing with flood control problems and local authorities responsible for decision-making on flood management. The paper concludes with a number of recommendations for flood hazard management policy making and processes.

Journal ArticleDOI
TL;DR: Saccharomyces cerevisiae plasma membrane H-ATPase activity was stimulated during octanoic acid-induced latency, reaching maximal values at the early stages of exponential growth, consistent with the role of the physiology and number of viable cells in the inoculum in the duration of latency under acid stress.
Abstract: Saccharomyces cerevisiae plasma membrane H+-ATPase activity was stimulated during octanoic acid-induced latency, reaching maximal values at the early stages of exponential growth. The time-dependent pattern of ATPase activation correlated with the decrease of cytosolic pH (pHi). The cell population used as inoculum exhibited a significant heterogeneity of pHi, and the fall of pHi correlated with the loss of cell viability as determined by plate counts. When exponential growth started, only a fraction of the initial population was still viable, consistent with the role of the physiology and number of viable cells in the inoculum in the duration of latency under acid stress.

Journal ArticleDOI
TL;DR: In this paper, the fundamental processes involved in the hydrothermal synthesis of silicates, using a range of computational techniques, are examined, and ab initio calculations of the structures and energies of silica fragments are reported.
Abstract: We examine the fundamental processes involved in the hydrothermal synthesis of silicates, using a range of computational techniques. We report ab initio calculations of the structures and energies of silica fragments. We estimate hydration energies by using both molecular mechanics methodologies and dielectric screening techniques. Detailed molecular mechanics calculations are reported for the interactions between solvated fragments of zeolitic structures and template molecules, emphasizing the role of the template in modifying fragments so that their structures are closer to those observed in zeolite crystals.

Journal ArticleDOI
TL;DR: In this article, the observed mode splitting is a manifestation of the general nonlinear phenomena due to the combination of resonant waveparticle interaction and collisionlike relaxation of the resonant particles.
Abstract: The measured spectra of fast particle driven Alfv{acute e}n eigenmodes in the JET tokamak plasma are interpreted on the basis of a nonlinear model of near-threshold kinetic instabilities. The observed mode splitting is a manifestation of the general nonlinear phenomena due to the combination of resonant wave-particle interaction and collisionlike relaxation of the resonant particles. The instability growth rate and the effective collision frequency of the resonant particles are determined. {copyright} {ital 1998} {ital The American Physical Society }

Proceedings Article
27 Aug 1998
TL;DR: The balance is strongly against Occam's razor, and a version of the first razor more appropriate to KDD is proposed, and it is argued that continuing to apply the second razor risks causing significant opportunities to be missed.
Abstract: Occam's razor has been the subject of much controversy. This paper argues that this is partly because it has been interpreted in two quite different ways, the first of which (simplicity is a goal in itself) is essentially correct, while the second (simplicity leads to greater accuracy) is not. The paper reviews the large variety of theoretical arguments and empirical evidence for and against the "second razor," and concludes that the balance is strongly against it. In particular, it builds on the case of (Schaffer, 1993) and (Webb, 1996) by considering additional theoretical arguments and recent empirical evidence that the second razor fails in most domains. A version of the first razor more appropriate to KDD is proposed, and we argue that continuing to apply the second razor risks causing significant opportunities to be missed.

Journal ArticleDOI
TL;DR: The cloning and expression of a fungal cutinase from Fusarium solani f.

Journal ArticleDOI
TL;DR: Surface free energy results were found to be greatly dependent on the calculation method and on the number of standard liquids used for contact angle measurements, and it seems that there is not yet a definite solution for the calculation of solid surface free energy.

Journal ArticleDOI
TL;DR: It was demonstrated that, despite the fact that monomeric gp41 fragment incorporates in the membrane model systems studied, the dimeric form does not interact with these vesicles, consistent with a "two steps" model for the gp41 fusion mechanism similar to the one proposed for influenza virus hemagglutinin.
Abstract: Fluorescence spectroscopy (both steady-state and time-resolved) was used to study the fragment 579−601 of gp41 ectodomain (HIV-1), a highly conserved sequence and major epitope, regarding (1) structural information, (2) interaction with membrane model systems, and (3) location in the phospholipid bilayer. The peptide was characterized both in its monomeric (after reduction of the disulfide bond between cysteine residues) and in the dimeric forms. The change of the fluorescence anisotropy between monomer and dimer was rationalized on the basis of energy migration, and a distance between the two tryptophan (Trp) residues of ≈6 A was obtained. Using different fluorescence spectroscopy approaches, it was demonstrated that, despite the fact that monomeric gp41 fragment incorporates in the membrane model systems studied, the dimeric form does not interact with these vesicles. A methodology based on the increase of the mean fluorescence lifetime averaged by the preexponentials was derived, to obtain the partitio...

Journal ArticleDOI
TL;DR: Results based on the use of Intergraph GIS coupled with Idrisi GIS substantially increased the flexibility of using GIS as a tool for flood studies.
Abstract: Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management.

Journal ArticleDOI
TL;DR: In this paper, a series of amorphous Eu3+-doped hybrid organic/inorganic materials prepared by the sol-gel process is presented, where the host matrix of the so-called ureasils is a silica network to which oligopolyoxyethylene chains are grafted by means of urea bonds.

Journal ArticleDOI
TL;DR: In this paper, the effect of supercritical fluid (SCF) addition on polymer viscosity and density was analyzed using a vibrating wire sensor. But the results of the measurements were limited to a commercial linear thermoplastic oligomer [Poly(ethyleneglycol) 400] saturated with CO 2 and at pressures up to 25 MPa.
Abstract: In order to analyse the effect of supercritical fluid (SCF) addition on polymer viscosity we have used, for the first time, a high precision vibrating wire instrument, for the simultaneous measurement of viscosities and densities of a SCF-saturated polymer. For the density measurements, this technique makes use of the buoyancy force exerted by a fluid on a solid sinker, detected by means of a vibrating wire sensor placed inside the measuring cell. The viscosity and density of the fluid are obtained by analysis of the resonance curve of the vibrating-wire, using a rigorous model for describing the hydrodynamic effects of the fluid on the wire motion. Results of the preliminary measurements carried out on a commercial linear thermoplastic oligomer [Poly(ethyleneglycol) 400] saturated with CO 2 are presented, in a range of temperatures from 313 to 348 K (3 isotherms) and at pressures up to 25 MPa. A sharp decrease of the viscosity was observed for all temperatures. The highest viscosity reduction was reached at the lowest temperature.

Journal ArticleDOI
TL;DR: In this paper, the effect of chloride (Cl−) and fly ash on the behavior of the passive film formed on steel in an x-ray photoelectron spectroscopy (XPS) was studied.
Abstract: Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) were used to study the effect of chloride (Cl−) and fly ash on behavior of the passive film formed on steel in ...

Journal ArticleDOI
06 Aug 1998-Langmuir
TL;DR: In this article, the authors investigated the effect of block polyelectrolyte length and temperature on the formation of block copolymers at the air-water interface, and showed that the effects of the length of the PEO chains and the amount of stearic acid on the expansion of the PS38-PEO90 block can be observed.
Abstract: Amphiphilic block copolymers form an important class of materials which have attracted considerable attention because of their outstanding solution properties and a wide range of applications.1,2 These materials are very interesting from the point of view of fundamental research, as they exhibit self-assembling properties in the presence of a selective solvent or surface.3-7 Surface micelles at the air-water interface, of different morphologies depending on the balance between block sizes, have been directly identified by TEM and AFM for block polyelectrolytes8,9 and for nonionic diblock copolymers.10 The present work was mainly motivated by a previous work on monolayers of poly(styrene)-poly(ethylene oxide), PSm-PEOn diblock copolymers, with varying lengths of the PEO block, spread at the air-water interface.11 As for grafted polymers,12-14 a pancake, a quasi-brush state, and a brush state were observed. It was found that compression-expansion cycles of the π-A isotherms superpose in the quasi-brush but not in the brush and pancake regions.11 The hysteresis observed at low surface pressures (pancake region) increases with PEO chain length and decreases with temperature. This was attributed to the irreversible entanglement and hydration of the PEO chains when immersed in the water subphase. The hysteresis at high surface pressuressin the brush regionsexhibited an unusual minimum in the expansion curve. This peculiar shape of the π-A isotherms suggests that the system undergoes a metastable regime during the expansion and finally returns to the equilibrium when the compression and the expansion curves superimpose in the quasi-brush region. The increase of π with the area indicates a overexpanded monolayer due to the high cohesion and local order reached in the brush conformation which is not disrupted in the time scale of the expansion run. This effect tends to disappear with an increase of PEO length and temperature. Both effects difficult the organization of PEO chains and diminish the cohesion. To further clarify this subject, the initial work was extended to study the effect of the concentration of the spreading solution, initial surface concentration of the monolayer, and a number of other experimental variables, namely maximum surface pressure reached on the compression run, rate of the compression-expansion cycles, and number of successive cycles. The present work studies further the influence of the PEO length and shows that the minimum on the π-A isotherms of PS38-PEO90 disappears in the presence of various amounts of stearic acid (SA). Dynamic light scattering measurements show aggregation of the block copolymers PS38-PEO90 and PS38-PEO148 in chloroform solutions, for the same range of concentrations used in the film balance measurements.

Journal ArticleDOI
TL;DR: In this article, the evolution of the corrosion potential is explained based on the electronic behaviour of the inner and outer layers of the film above and below the flatband potential, suggesting that the film breakdown involves the ionization of localized states and/or surface states situated deep in the bandgap.