Showing papers by "Simón Bolívar University published in 2001"

Molecular-Based Equations of State for Associating Fluids: A Review of SAFT and Related Approaches

Abstract: We present a review of recent advances in the statistical associating fluid theory (SAFT). In contrast to the “chemical theory”, in which nonideality is explained in terms of chemical reactions between the species, SAFT and similar approaches relate nonideality to the intermolecular forces involved. Such physical theories can be tested against molecular simulations, and improvements to the theory can be made where needed. We describe the original SAFT approach and more recent modifications to it. Emphasis is placed on pointing out that SAFT is a general method and not a unique equation of state. Applications to a wide variety of fluids and mixtures are reviewed, including aqueous mixtures and electrolytes, liquid−liquid immiscible systems, amphiphilic systems, liquid crystals, polymers, petroleum fluids, and high-pressure phase equilibria.

Interfacial Tension of Alkane + Water Systems†

Abstract: Interfacial tension was measured for hexane + water, heptane + water, octane + water, nonane + water, decane + water, undecane + water, and dodecane + water, using the emergent drop experimental technique with a numerical method based on a fourth degree spline interpolation of the drop profile. The experimental equipment used to generate the drop consists of a cell with a stainless steel body and two Pyrex windows. The inner cell was previously filled with water. A surgical needle (at the bottom of the cell) was used to introduce the organic phase into the cell (forming the emergent drop). Water was used to keep the temperature constant inside the cell (between 10 °C and 60 °C). The cell was illuminated from the back using a fiber optic lamp and a diffuser. A video camera (with a 60 mm microlens and an extension ring) was located at the front window. The emergent drop image was captured and sent to the video recording system. The cell and the optical components were placed on an optical table with vibrati...

Mechanical behavior of acrylonitrile butadiene styrene (ABS) fused deposition materials. Experimental investigation

Abstract: An experimental study of the mechanical behavior of fused‐deposition (FD) ABS plastic materials is described. Elastic moduli and strength values are determined for the ABS monofilament feedstock and various unidirectional FD‐ABS materials. The results show a reduction of 11 to 37 per cent in modulus and 22 to 57 per cent in strength for FD‐ABS materials relative to the ABS monofilament. These reductions occur due to the presence of voids and a loss of molecular orientation during the FD extrusion process. The results can be used to benchmark computational models for stiffness and strength as a function of the processing parameters for use in computationally optimizing the mechanical performance of FD‐ABS materials in functional applications.

Dynamic models for spatiotemporal data

Abstract: We propose a model for non-stationary spatiotemporal data. To account for spatial variability, we model the mean function at each time period as a locally weighted mixture of linear regressions. To incorporate temporal variation, we allow the regression coefficients to change through time. The model is cast in a Gaussian state space framework, which allows us to include temporal components such as trends, seasonal effects and autoregressions, and permits a fast implementation and full probabilistic inference for the parameters, interpolations and forecasts. To illustrate the model, we apply it to two large environmental data sets: tropical rainfall levels and Atlantic Ocean temperatures.

GPS estimate of relative motion between the Caribbean and South American plates, and geologic implications for Trinidad and Venezuela

Abstract: Global Positioning System (GPS) data from eight sites on the Caribbean plate and five sites on the South American plate were inverted to derive an angular velocity vector describing present-day relative plate motion. Both the Caribbean and South American velocity data fit rigid-plate models to within ±1–2 mm/yr, the GPS velocity uncertainty. The Caribbean plate moves approximately due east relative to South America at a rate of ∼20 mm/yr along most of the plate boundary, significantly faster than the NUVEL-1A model prediction, but with similar azimuth. Pure wrenching is concentrated along the approximately east-striking, seismic, El Pilar fault in Venezuela. In contrast, transpression occurs along the 068°-trending Central Range (Warm Springs) fault in Trinidad, which is aseismic, possibly locked, and oblique to local plate motion.

New procedure for the extraction of basic a-Si:H TFT model parameters in the linear and saturation regions

Abstract: A new procedure is proposed to extract basic parameters for the AIM-Spice amorphous thin film transistor model in the above-threshold region. Our method avoids non-linear optimization, which is mainly the method utilized up to now, when using a program extractor included in AIM-Spice. The present extraction procedure is based on the integration of the experimental data current. The integration method as in known is convenient to decrease the effects of experimental noise. The method is applied to the linear and saturation regions for the above-threshold regime and allows the extraction of all the above-threshold parameters. The accuracy of the simulated curves using the parameters extracted with the new procedure is verified with measured and calculated data using the expressions contained in the model.

Real-time ECG transmission via Internet for nonclinical applications

Abstract: Telemedicine is having a great impact on the monitoring of patients located in remote non-clinical environments, such as homes, elderly communities, gymnasiums, schools, remote military bases, ships, and the like. A number of applications, ranging from data collection to chronic patient surveillance, and even to the control of therapeutic procedures, are being implemented in many parts of the world. As part of this growing trend, this paper discusses the problems in electrocardiogram (ECG) real-time data acquisition, transmission and visualization over the Internet. ECG signals are transmitted in real time from a patient in a remote non-clinical environment to a specialist in a hospital or clinic using the current capabilities and availability of the Internet. A prototype system is described that is composed of (1) a portable data acquisition and pre-processing module connected to the computer at the remote site via its RS-232 port, (2) a Java-based client-server platform, and (3) software modules to handle communication protocols between the data acquisition module and the patient's personal computer, and to handle client-server communication. The purpose of the system is the provision of extended monitoring for patients under drug therapy after infarction, data collection in some particular cases, remote consultation and low-cost ECG monitoring for the elderly.

Velocity field across the Southern Caribbean Plate Boundary and estimates of Caribbean/South‐American Plate Motion using GPS Geodesy 1994–2000

Abstract: Global Positioning System (GPS) observations between 1994 and 2000 at twenty-two sites in the Lesser Antilles and northern South-America indicate that the Caribbean plate, along its southern boundary, slips at a rate of 20.5±2 mm/a with an azimuth of N 84°±2°E at 65°W, relative to the South-American plate. East of 68° W, 80% of the dextral slip is contained within a 80-km wide shear zone centered on the El Pilar-San Sebastian fault system. West of 68° W the plate boundary broadens to more than 300 km with dextral shear shared between the northeast trending Bocono fault (9–11 mm/a) in western Venezuelan, and an offshore system near the northern coast.

Closed‐form formulas for Kirchhoff index

Abstract: We find closed-form expressions for the resistance, or Kirchhoff index, of certain connected graphs using Foster's theorems, random walks, and the superposition principle. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 135–140, 2001

Sequential approximate optimization using variable fidelity response surface approximations

Abstract: The dimensionality and complexity of typical multidisciplinary systems hinders the use of formal optimization techniques in application to this class of problems. The use of approximations to represent the system design metrics and constraints has become vital for achieving good performance in many multidisciplinary design optimization (MDO) algorithms. This paper reports recent research efforts on the use of variable fidelity response surface approximations (RSA) to drive the convergence of MDO problems using a trust region model management algorithm. The present study focuses on a comparative study of different response sampling strategies based on design of experiment (DOE) approaches within the disciplines to generate the zero order data to build the RSAs. Two MDO test problems that have complex coupling between disciplines are used to benchmark the performance of each sampling strategy. The results show that these types of variable fidelity RSAs can be effectively managed by the trust region model management strategy to drive convergence of MDO problems. It is observed that the efficiency of the optimization algorithm depends on the sampling strategy used. A comparison of the DOE approaches with those obtained using a optimization based sampling strategy (i.e. concurrent subspace optimization --- CSSO) shows the DOE methodologies to be competitive with the CSSO based sampling methodology in some cases. However, the CSSO based sampling strategy was found to be, in general, more efficient in driving the optimization.

Resistance distance in graphs and random walks

Abstract: We study the resistance distance on connected undirected graphs, linking this concept to the fruitful area of random walks on graphs. We provide two short proofs of a general lower bound for the resistance, or Kirchhoff index, of graphs on N vertices, as well as an upper bound and a general formula to compute it exactly, whose complexity is that of inverting an N×N matrix. We argue that the formulas for the resistance in the case of the Platonic solids can be generalized to all distance-transitive graphs. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 29–33, 2001

The Kronecker Product of Schur Functions Indexed by Two-Row Shapes or Hook Shapes

Abstract: The Kronecker product of two Schur functions i>sμ and i>sν, denoted by i>sμ a i>sν, is the Frobenius characteristic of the tensor product of the irreducible representations of the symmetric group corresponding to the partitions μ and ν The coefficient of i>sλ in this product is denoted by γλμν, and corresponds to the multiplicity of the irreducible character χλ in χμχν We use Sergeev's Formula for a Schur function of a difference of two alphabets and the comultiplication expansion for i>sλ[i>XY] to find closed formulas for the Kronecker coefficients γλμν when λ is an arbitrary shape and μ and ν are hook shapes or two-row shapes Remmel (JB Remmel, i>J Algebra 120 (1989), 100–118; i>Discrete Math 99 (1992), 265–287) and Remmel and Whitehead (JB Remmel and T Whitehead, i>Bull Belg Math Soc Simon Stiven 1 (1994), 649–683) derived some closed formulas for the Kronecker product of Schur functions indexed by two-row shapes or hook shapes using a different approach We believe that the approach of this paper is more natural The formulas obtained are simpler and reflect the symmetry of the Kronecker product

Effects of filler treatments on the mechanical and morphological behavior of PP+wood flour and PP+sisal fiber

Abstract: Composites were prepared from waste wood flour, sisal fiber and polypropylene (PP) The surface of the filler was modified to enhance the chemical affinity between hydrophilic cellulosic and hydrophobic polymer The treatments studied were: a) The addition of a coupling agent; b) chemical treatment with NaOH; and c) the addition of functionalized polypropylene (Polybond 3150 and 3200) After treatment, mixtures of PP with 40% and 20% of the filler, wood flour and sisal fiber respectively, were extruded and injection molded In the case of wood flour, a mixture of two particle sizes (mesh 20 and 40, 50% each) was used, and in the case of sisal, 10 mm long fibers were selected Results showed that, regardless of the treatment to which the filler was previously submitted, Young’s modulus was always higher for mixtures prepared with wood flour, with values varying between 2839 and 3150 MPa Whereas for mixtures with sisal fiber, the modulus’ values varied between 1704 and 2220 MPa Values of breaking strength, elongation at break and impact strength for PP mixtures with treated sisal fiber were always higher than those for mixtures of PP with wood flour Based on these results, we can conclude that sisal fiber is an organic filler which, due to its mechanical and morphological characteristics, has a reinforcing effect higher than that of wood flour

Interleukin-6 (IL-6) in seminal plasma of infertile men, and lipid peroxidation of their sperm.

Abstract: Concentrations of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in seminal fluid, as well as levels of sperm lipid membrane peroxidation, were investigated in fertile and infertile men. Semen samples, obtained by masturbation from 37 infertile and 14 fertile men, were examined for the presence of TNF-alpha and IL-6. The level of lipid peroxidation of the sperm membrane was measured by determining malondialdehyde (MDA) formation. The correlation between the IL-6 and the TNF-alpha concentrations in seminal plasma with the levels of lipid peroxidation of the sperm membranes was statistically evaluated. The IL-6 concentration in seminal plasma of infertile men was significantly higher than that of fertile men (p < .05). Similarly, the level of membrane lipid peroxidation was higher for the semen of infertile men than that of fertile men (p < .001). A significant positive correlation was found between IL-6 levels in seminal plasma and membrane sperm lipid peroxidation (p < .002), but not between this parameter and TNF-alpha levels in seminal plasma. These findings suggest a possible association between IL-6 seminal plasma levels and lipid peroxidation of sperm membrane. Stimulation of reactive species production by human sperm and leucocytes, induced by the high levels of IL-6, could explain these results.

Atrial activity enhancement by Wiener filtering using an artificial neural network

Abstract: Describes a novel technique for the cancellation of the ventricular activity for applications such as P-wave or atrial fibrillation detection. The procedure was thoroughly tested and compared with a previously published method, using quantitative measures of performance. The novel approach estimates, by means of a dynamic time delay neural network (TDNN), a time-varying, nonlinear transfer function between two ECG leads. Best results were obtained using an Elman TDNN with 9 input samples and 20 neurons, employing a sigmoidal tangencial activation in the hidden layer and one linear neuron in the output stage. The method does not require a previous stage of QRS detection. The technique was quantitatively evaluated using the MIT-BIH arrhythmia database and compared with an adaptive cancellation scheme proposed in the literature. Results show the advantages of the proposed approach, and its robustness during noisy episodes and QRS morphology variations.

Optimal Computation of Distance Relays Second Zone Timing in a Mixed Protection Scheme with Directional Overcurrent Relays

Abstract: This paper describes a technique to determine the optimal time setting for the second zone of distance relays when used in a mixed protection scheme with directional overcurrent relays. The technique consists of including the second zone operation time as a new variable in the original problem statement of optimal computation of directional overcurrent relays settings. It is shown that the influence of distance relays and directional overcurrent relays must be considered when the settings of these relays are computed. Numerical results obtained with the proposed method for a realistic power system are presented.

Thermal characterization of polycarbonate/polycaprolactone blends

Abstract: In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(∈-caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass-transition temperature (T g ) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the T g was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T o m ) by the Hoffman-Weeks extrapolation method. A T o m depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60-70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed.

Friction and wear behavior of several hard materials

Abstract: Sliding friction, abrasion and erosion tests were performed on several materials: cemented carbides, partially stabilized zirconia (Mg–PSZ), electroless Ni–P coatings and SAE 4140 steel as reference material. Sliding friction test was carried out in a pin-on-disk system. A micro-abrasion test was performed using the ball cratering methods. The erosion test consisted an air stream carrying abrasive particles of SiC, impinging flat samples. Sizes of wear scars were determined by optical microscopy and laser profilometry. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were employed to observe morphological and chemical features of worn surfaces. The sliding pin-on-disk results of Ni–P coating showed smooth variation of the friction coefficient (mean values of 0.16–0.21), as well as the lowest wear rate compare with the other evaluate materials. Experimental results of the micro-abrasion test showed linear behavior between wear volume and sliding distance for all the evaluate materials. Cemented carbides showed the lowest wear rates followed by SAE 4140 steel, Mg–PSZ and Ni–P coating, respectively. Erosion test values ranked evaluated materials from lower to higher eroded volume as follows: SAE 4140 Steel, Ni–P coating, cemented carbides and Mg–PSZ ceramic.

First Dioxomolybdenum(VI) Complexes Containing Chiral Oxazoline Ligands: Synthesis, Characterization and Catalytic Activity

Abstract: The cis-[MoO2(N,O)2] complexes containing chiral oxazoline ligands (N,O) [1: N,O = A, (4′R)-2-(4′-ethyl-3′,4′-dihydroxazol-2′-yl)phenolato; 2: N,O = B, (4′S)-2-(4′-isopropyl-3′,4′-dihydroxazol-2′-yl)phenolato] were synthesised and characterised, both in solution and in the solid state. These pseudo-octahedral neutral complexes were obtained as mixtures of diastereomers due to the chirality of the ligand and at the metal centre (Δ or Λ). Theoretical DFT calculations corroborate the isomer distribution. For complex 1, the two major diastereomers, Δ-N-cis-1 and Λ-N-trans-1, crystallised independently and the molecular structures were determined by single-crystal X-ray diffraction. NMR experiments at 800 MHz for 2 allowed the determination of the isomeric composition in solution. The product distribution depends on the coordinating nature of the solvent. Complexes 1 and 2 catalyse the oxidation of triphenylphosphane and styrene.

Toward a Systemic Notion of Information: Practical Consequences

Abstract: Introduction The meaning of "information systems" has been growing in diversity and complexity. Several authors have pointed out this fact, described the phenomena and tried to bring some order to the perceived chaos in the field. Cohen (1997, 1999, 2000), for example, after describing the attacks on the Information Systems (IS) field, for "its lack of tradition and focus" and the "misunderstandings of the nature of Information Systems," examines "the limitations of existing frameworks for defining IS" and reconceptualizes Information Systems and tries "to demonstrate that it has evolved to be part on an emerging discipline of fields, Informing Science" (Cohen, 2000). Our objective in this paper is to participate in the process of conceptualization and re-conceptualization required in the area of Information Systems and in Cohen's proposed Informing Science. We will try to do that making a first step in the description of a systemic notion of information, by identifying, first, the meaning of information. We are using the word "meaning" in its pragmatic sense, i.e. in the sense Peirce formulated when he pointed out that "in order to ascertain the meaning of an intellectual conception one should consider what practical consequences might conceivably result by necessity from the truth of that conception; and the sum of these consequences will constitute the entire meaning of the conception." (Peirce, 5.9.) When Peirce talks about "consequences," he is referring to the relation (consequentia) between the pair of antecedent and consequent, not just about the consequent (consequens). So, accordingly, we will try to analyze the antecedents, by means of Ackoff's approach to conceptual definitions (1962), then we will try to relate them to the respective consequents. In this way the meaning we will looking for the term "information" will be both its conceptual definition, as well as its respective practical consequences in the field of Information Systems and Informing Sciences. This will provide the input for establishing the direction of a systemic meaning of the notion of information. The term "information" has been widely and increasingly used, but not always with a clear idea about its meaning. As Dretske (1981) and Lewis (1991) pointed out, few books concerning information actually define it clearly. And Mingers (1997) adds, "Information systems could not exist without information and yet there is no secure agreement over what information actually is" (p. 73). The word "information" is one of the most used, and very abused, words. Different scientific disciplines and engineering fields provide diverse meanings to the word, which is becoming the umbrella of divergent, and sometimes dissimilar and incoherent homonyms. When concepts are not clear, the use of homonyms might be intellectually and pragmatically dangerous. We will try, here, to make an initial step, attempting first a conceptual definition. We are using "conceptual definition" with the meaning Ackoff (1962) described for it, and with the role he ascribed to it as a first step both in scientific inquiry and in systems analysis and synthesis. We will also follow the method suggested by Ackoff, but with the space restrictions of this paper. We can find, in the last years, a growing number of research studies directed to establish the meaning of "information." Some of these research studies will be cited below. In spite of the plurality of the approaches followed, we did not find studies oriented by Peirce's definition of "meaning" as applied to the concept "information", let alone studies where the defining process has the objective of finding practical consequences in the area of information systems development. We have no knowledge, either, of any kind of efforts made for the elaboration of a systemic notion of information. In our opinion, these two lacking aspects in the literature are very important, both from the intellectual and scientific perspective, as well as from the pragmatic one. …

Responses of Ribulose-1,5-Bisphosphate Carboxylase, Protein Content, and Stomatal Conductance to Water Deficit in Maize, Tomato, and Bean

Abstract: We compared responses of maize, tomato, and bean plants to water stress. Maize reached a severe water deficit (leaf water potential −1.90 MPa) in a longer period of time as compared with tomato and bean plants. Maize stomatal conductance (gs) decreased at mild water deficit. gs of tomato and bean decreased gradually and did not reach values as low as in maize. The protein content was maintained in maize and decreased at low water potential (ψw); in tomato it fluctuated and also decreased at low ψw; in bean it gradually decreased. Ribulose-1,5-bisphosphate carboxylase/oxygenase activity remained high at mild and moderate stress in maize and tomato plants; in bean it remained high only at mild stress.

Sex pheromone of tomato fruit borer, Neoleucinodes elegantalis

Abstract: Five candidate pheromone components were identified by analyzing pheromone gland extracts by gas chromatography (GC), coupled GC-electroantennographic detection (EAD), and coupled GC-mass spectrometry (MS): (E)-11-hexadecenol(E11–16 : OH), (Z)-11-hexadecenol (Z11–16 : OH),(E)-11-hexadecenal, (E)-11-hexadecenyl acetate, and (Z)-3,(Z)-6,(Z)-9-tricosatriene (Z3,Z6,Z9–23 : Hy). In electroantennogram (EAG) recordings, synthetic E11–16 : OH elicited stronger antennal responses at low doses than other candidate pheromone components. Field tests demonstrated that synthetic E11–16 : OH as a trap bait was effective in attracting males, whereas addition of Z11–16 : OH inhibited the males' response. Z3,Z6,Z9–23 : Hy strongly enhanced attractiveness of E11–16 : OH, but was not attractive by itself. A pheromone blend with synergistic behavioral activity of an alcohol (E11–16 : OH) and hydrocarbon (Z3,Z6,Z9–23 : Hy) component is most unusual in the Lepidoptera. The synthetic two-component pheromone is approximately 60 times more attractive than the female-produced blend and might facilitate the control of this pest.

Compactified D=11 supermembranes and symplectic noncommutative gauge theories

Abstract: It is shown that a double compactified D=11 supermembrane with nontrivial wrapping may be formulated as a symplectic noncommutative gauge theory on the world volume The symplectic noncommutative structure is intrinsically obtained from the symplectic two-form on the world volume defined by the minimal configuration of its Hamiltonian The gauge transformations on the symplectic fibration are generated by the area preserving diffeomorphisms on the world volume Geometrically, this gauge theory corresponds to a symplectic fibration over a compact Riemann surface with a symplectic connection

Multichannel electroencephalographic analyses via dynamic regression models with time‐varying lag–lead structure

Abstract: Summary. Multiple time series of scalp electrical potential activity are generated routinely in electroencephalographic (EEG) studies. Such recordings provide important non-invasive data about brain function in human neuropsychiatric disorders. Analyses of EEG traces aim to isolate characteristics of their spatiotemporal dynamics that may be useful in diagnosis, or may improve the understanding of the underlying neurophysiology or may improve treatment through identifying predictors and indicators of clinical outcomes. We discuss the development and application of nonstationary time series models for multiple EEG series generated from individual subjects in a clinical neuropsychiatric setting. The subjects are depressed patients experiencing generalized tonic-clonic seizures elicited by electroconvulsive therapy (ECT) as antidepressant treatment. Two varieties of models-dynamic latent factor models and dynamic regression models-are introduced and studied. We discuss model motivation and form, and aspects of statistical analysis including parameter identifiability, posterior inference and implementation of these models via Markov chain Monte Carlo techniques. In an application to the analysis of a typical set of 19 EEG series recorded during an ECT seizure at different locations over a patient's scalp, these models reveal time-varying features across the series that are strongly related to the placement of the electrodes. We illustrate various model outputs, the exploration of such time-varying spatial structure and its relevance in the ECT study, and in basic EEG research in general.

Identification of gas-producing components in different varieties of Phaseolus vulgaris by in vitro fermentation

Abstract: Phaseolus vulgaris consumption has been limited as part of the occidental diet owing to flatulence production. Raffinose, stachyose and verbascose have been shown to be the main components responsible for flatulence; however, it is thought that soluble fibre could also be involved in this phenomenon. The aim of the present study was to identify the main components of beans influencing flatus. Ten varieties of P vulgaris originating from South America were first analysed for their main nutrient and carbohydrate fractions. Three of the varieties were then fractionated to extract soluble and insoluble fibres. Various combinations of α-galactosides and soluble and insoluble fibre fractions, in similar proportions to those contained in cooked grains, were used as substrates for in vitro fermentation studies using human faecal inoculum to determine the fermentative capacity of each of the three fractions. Considering the white varieties, total gas production and acidification of the medium were correlated with fermented organic matter from soluble fibre (R2 = 1)) and with α-galactosides (R2 = 0.75). On the other hand, tannins present in pigmented varieties did not seem to interfere significantly in fermentation of soluble fibre. The total production of gas per gram of mixed fractions of soluble fibre and α-galactosides in proportions found in cooked grains was lower than that expected from each substrate separately. It can be concluded that soluble fibre and α-galactosides are good substrates for endogenous colonic flora subjected to in vitro fermentation studies and are thus responsible for flatulence induced by legume consumption. © 2001 Society of Chemical Industry