Influence of two-step process and of different stoichiometric ratios on morphologies generated in castor oil epoxy resins

Phase separation during polymerization was studied in a model system consisting of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA), variable amounts of ethylenediamine (EDA) and the mass of castor oil (CO) necessary to obtain a mass fraction equal to 0-15 in a final system where the stoichiometric ratio of amine to epoxy equivalents, r, was equal to 1. A two-step polymerization process was performed by curing first a system with r = 0-5, during variable times before phase separation, and then carrying the system to r = 1. Thermodynamic analysis of samples with different r values led to a linear relationship between the Flory-Huggins interaction parameter and r. The concentration (P) and average size (D?) of dispersed-phase particles followed opposite trends, i.e. P increased while D? decreased, when either r was increased or the time of curing in the first step of a two-step process was decreased. This was explained by assuming that the competition between nucleation and growth was determined by the viscosity at the cloud point, η_cp. Low values of η_cp favoured growth over nucleation and led to fewer but larger particles.     

Determining the core of journals of a research centre: The example of researchers from the Department of Rural Economy and Sociology of the Institut National de la Recherche Agronomique,France

This paper analyses the determination of visibility of journals in which researchers of INRA (National Institute for Agricultural Research) publish. The corpus is comprised of 671 articles published over a period of four years in 258 journals. The advantage of the method applied for determining the visibility of journals is that it combines two approaches: a) bibliometric indicators (coverage by the ISI-publications and by two specific French databases) and b) experts' opinions (10 economists and sociologists). The main results are: a) There is a convergence between the opinion of the experts and «visibility» in the databases, b) The impact factor confirms the main opinions of the experts. The first journals ranked by the experts and JCR Social Sciences are the same but represent only 40 per cent of the total journals analysed. The other journals were revealed by the experts and French databases.«Whoever seeks to pass a balanced but lucid judgement on the general trends of the activity carried out by the profession to which he belongs, is liable to say either banalities or to hurt his colleagues»The notion which we retain of core is that which is successively and conjointly validated by the experts and by the major databases representative of the field.This study was financed by the Department of Rural Economy and Sociology of INRA.     

MRI of intramedullary sarcoidosis: follow-up of a case

Significative enhancement of free radical formation (FRO) in vivo is an important feature of hypertensive disorders of pregnancy (HDP), namely preeclampsia (PIH). The latest investigations about the pathology of HDP, showed the contribution of placental circulation to the development and evolution of such disease. The placental bed can be a potential source of FRO or activation of cells that can produce FRO. Glutathione, is an important molecule for cellular protection against damage, is a cofactor of many enzymes, in particular, for the glutathione peroxidase of the placental tissue; this enzyme in the placenta bed prevent the production of thromboxan and lipoperoxides; the latter are potentially damaging to the endothelium cells and can cause vasoconstriction, the most important feature of PIH. The activity of that enzyme is deficient in PIH. We studied, by fluorometric assay, the concentrations of the two states of glutathione in placental homogenates (PLH) from pregnant women without pathology (PWN) and from pregnant women with PIH (PWPIH). The data showed significant low concentrations in the PLH of the two states of glutathione in the PWN against high concentrations of this molecule in the PLH from PWPIH. This feature can result from a deficient user of the glutathione by the cellular mechanism for prevention against oxidative factors. In addition, our study shows a biochemical marker that is suggestive that the placental bed is a potential source of FRO production in PIH.     

The covariation of common psychosomatic symptoms among children from socio-economically differing residential areas. An epidemiological study

Psychosomatic symptoms among children are believed to be commonplace. In this investigation by questionnaire, 47% of 1333 schoolchildren reported one or several symptoms, such as recurrent abdominal pain, headache, chest pains, loss of appetite and disturbances in bowel function. Coexistence of such symptoms was considerable and if a child had one of these, the probability that it would have one or more other symptoms was significantly increased. This correlation may strengthen both the suspicion that these symptoms are often psychosomatic and the idea that they have common CNS origin. There were appreciable differences in the frequency of the symptoms, between children at the more socially stable schools and schools with social problems. In the latter, the frequencies of symptoms differed between Swedish and immigrant children, which was not the case in the more socially stable schools.     

Production and properties of micro‐porous glas bubble zinc and aluminium composites

Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.     

From information to probability: An axiomatic approach—Inference is information processing

We define the very rich language of composed conditionals on a three‐valued logic and use this language as the communication tool between man and machine. Communication takes place for three reasons: knowledge acquisition, query, and response. Learning, thinking, and answering questions are of a pure information theoretical nature. The pivot of this knowledge processing concept is the amount of information (bit) we receive if a conditional becomes true. We follow an axiomatic approach to information theory rather than the classical probabilistic approach of Shannon; information comes first, and then comes probability. In the light of this philosophy, query and response experience new interpretations. Both, acquisition and response are realized by maximizing entropy and minimizing relative entropy, respectively. The iterative solution of these mathematical optimization problems gives new insights into the adaptation of prior knowledge to new information. Our expert system shell SPIRIT supports this kind of knowledge processing, which will be established by suitable examples. © 2003 Wiley Periodicals, Inc.     

Prediction of fire classification for wood based products. A multivariate statistical approach based on the cone calorimeter

Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd.