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Aim Patients with an increased risk for psychosis (‘at-risk mental state’ (ARMS)) present various neurocognitive deficits. Not least because of differences in identifying the ARMS, results of previous studies are inconsistent. In most studies ARMS-patients are classified by the experience of attenuated psychotic symptoms (APS) and/or brief limited intermittent psychotic symptoms (BLIPS). Few studies additionally assessed cognitive basic symptoms (BS). A comprehensive assessment in the very early stage of the ARMS is missing. Methods In the present study we characterized ARMS-patients for cognitive BS (ARMS-BS), APS and BLIPS (ARMS-A/B) according to the Early Recognition Inventory based on IRAOS (ERIraos). Furthermore, we assessed neurocognitive deficits using the MATRICS consensus cognitive battery for schizophrenia with a primary hypothesis regarding working memory performance. Groups of 38 ARMS-patients and 38 healthy controls were matched for age, gender, education and premorbid verbal intelligence. Results Between-group comparisons revealed significant poorer working memory performance in addition to lower verbal learning and problem solving, slower processing speed and lower global neurocognitive functioning in ARMS-patients as compared to controls. ARMS-BS did not differ from ARMS-A/B. Conclusions These results underscore the presence of cognitive limitations in patients only presenting with cognitive BS. Knowledge of these early cognitive deviations supports the inclusion of early ARMS-stages into a comprehensive concept of the psychosis risk state. Therapeutic interventions already applied at this stage might prevent deterioration of constraints. Longitudinal and interventional studies investigating the interaction of cognitive BS and neurocognitive as well as metacognitive deficits are warranted.

Aim: Patients with an increased risk for psychosis ('at-risk mental state' (ARMS)) present various neurocognitive deficits. Not least because of differences in identifying the ARMS, results of previous studies are inconsistent. In most studies ARMS-patients are classified by the experience of attenuated psychotic symptoms (APS) and/or brief limited intermittent psychotic symptoms (BLIPS). Few studies additionally assessed cognitive basic symptoms (BS). A comprehensive assessment in the very early stage of the ARMS is missing.Methods: In the present study we characterized ARMS‐patients for cognitive BS (ARMS‐BS), APS and BLIPS (ARMS‐A/B) according to the Early Recognition Inventory based on IRAOS (ERIraos). Furthermore, we assessed neurocognitive deficits using the MATRICS consensus cognitive battery for schizophrenia with a primary hypothesis regarding working memory performance. Groups of 38 ARMS‐patients and 38 healthy controls were matched for age, gender, education and premorbid verbal intelligence.Results: Between‐group comparisons revealed significant poorer working memory performance in addition to lower verbal learning and problem solving, slower processing speed and lower global neurocognitive functioning in ARMS‐patients as compared to controls. ARMS‐BS did not differ from ARMS‐A/B.Conclusions: These results underscore the presence of cognitive limitations in patients only presenting with cognitive BS. Knowledge of these early cognitive deviations supports the inclusion of early ARMS‐stages into a comprehensive concept of the psychosis risk state. Therapeutic interventions already applied at this stage might prevent deterioration of constraints. Longitudinal and interventional studies investigating the interaction of cognitive BS and neurocognitive as well as metacognitive deficits are warranted. published

This paper reports on the synthesis of polyester-grafted starch (starch-g-PCL) by in situ ring-opening polymerization (ROP) of e-caprolactone (e-CL) catalyzed by a metal free organic catalyst (imidazole). This reaction has been carried out in bulk, without solvent. The structure of starch-g-PCLwas characterized by IR, NMR, DSC, and SEM. A moisture sorption isotherm of modified starch revealed a more hydrophobic material. A water contact angle measurement also confirmed the hydrophobic character of starch-g-PCL. As expected, this chemical modification reduced the diffusion coefficient of water. The use of an organic catalyst instead of the traditional organometallic catalyst offers an interesting alternative for producing moisture tolerant thermoplastic starch-based materials.

The paper is devoted to the mathematical modelling of an extrusion process. Usually, an extruder has a very complicated geometry. This generates a lot of difficulties for computations of three-dimensional flows. In the present paper, we develop and justify the asymptotic domain decomposition strategy in order to parallelize the computational process and reduce the memory. The error estimates are proved for the Stokes steady-state equation in the two-dimensional and three-dimensional cases. Then, the asymptotic domain decomposition procedure is applied for numerical testing and computations of the non-Newtonian fluid simulating a real process of the polymer extrusion. Copyright © 2007 John Wiley & Sons, Ltd.

A three-dimensional finite element method is applied for analyzing the viscoelastic flow of branched LDPE through 3D planar contraction geometry. For describing the viscoelastic properties of the flowing material, a recently proposed eXtended Pom–Pom model is used. The main purpose of our study is to evaluate the ability of this model to capture some specific 3D effects in the case of converging entry flow of relatively high strain-hardening polyethylene melts. A special attention is paid to the vortex region. Like in our previous study [I. Sirakov, A. Ainser, J. Guillet, Three-dimensional numerical simulation of viscoelastic planar contraction flow, in: Proceedings of the Fourth International ESAFORM Conference, Liege, 23–25 April 2001] (where the Phan-Thien Tanner (PTT) model was used), the calculations predict an open vortex in which the material is involved in a complicated spiral motion, directed from the vertical plane of symmetry to the side wall of the contraction. Quantitative comparisons with experiments are done on the vortex size in the width direction (contraction z-axis).

BackgroundMetamemory describes the monitoring and knowledge about one's memory capabilities. Patients with schizophrenia have been found to be less able in differentiating between correct and false answers (smaller confidence gap) when asked to provide retrospective confidence ratings in previous studies. Furthermore, higher proportions of very-high-confident but false responses have been found in this patient group (high knowledge corruption). Whether and how these biases contribute to the early pathogenesis of psychosis is yet unclear. This study thus aimed at investigating metamemory function in the early course of psychosis.MethodPatients in an at-risk mental state for psychosis (ARMS, n = 34), patients with a first episode of psychosis (FEP, n = 21) and healthy controls (HCs, n = 38) were compared on a verbal recognition task combined with retrospective confidence-level ratings.ResultsFEP patients showed the smallest confidence gap, followed by ARMS patients, followed by HCs. All groups differed significantly from each other. Regarding knowledge corruption, FEP patients differed significantly from HCs, whereas a statistical trend was revealed in comparison of ARMS and FEP groups. Correlations were revealed between metamemory, measures of positive symptoms and working memory performance.ConclusionsThese data underline the presence of a metamemory bias in ARMS patients which is even more pronounced in FEP patients. The bias might represent an early cognitive marker of the beginning psychotic state. Longitudinal studies are needed to unravel whether metacognitive deficits predict the transition to psychosis and to evaluate therapeutic interventions.

The relationship between copolymer composition, molecular weight distribution, and rheological properties of random styrene acrylonitrile copolymers synthesized by radical polymerization in bulk was investigated. From differential scanning calorimetry analysis, glass transition temperature was obtained and increases with the acrylonitrile content. The knowledge of the glass transition is a key factor to compare the different copolymers in an iso-free volume condition for melt rheology. Owing to time temperature superposition, a large frequencies window ranging from the terminal zone until the glassy plateau can be obtained. Thus, the mechanical spectroscopy was used to estimate the rubbery plateau modulus and the Newtonian viscosity.

Nous présentons quelques résultats expérimentaux de l'écoulement dans deux contractions planaires pour deux polymères branchés. Il s'agit du PEbd-Iupac A fondu à 150°C et du PEbd-Atofina fondu à 150°C et 160°C. Un des objectifs de ce travail est de mettre en évidence le caractère tridimensionnel de ce type d'écoulement. Les clichés présentés concernent les franges isochromatiques d'un seul matériau pour un seul taux de déformation dans les deux géométries considérées. La détermination du coefficient des contraintes optiques est effectuée suivant deux approches empiriques. Les résultats de ces méthodes sont comparés à ceux issus de la littérature

The influence of copolymer composition on the rheological properties of random copolymers of styrene with methyl methacrylate (SMMA) obtained by radical polymerization in bulk was investigated. Differential scanning calorimetry (DSC) analysis shows that the glass-transition temperature of the copolymers increases with the methyl methacrylate (MMA) content. The knowledge of the glass transition is used to compare the different copolymers in an iso-free volume condition for melt rheology. Time temperature superposition was used to get a large frequency window ranging from the terminal zone up to the glassy plateau. The mechanical spectroscopy especially, was used to estimate the rubbery plateau modulus and the Newtonian viscosity. It has been possible to estimate the rubbery plateau modulus of SMMA copolymers from the experimental values of the corresponding homopolymers. For this particular system, the molecular weight between entanglement was shown to follow a simple blending law.

The flow of molten polymers in corotating twin screw extruders has been largely studied, but little attention has been paid until now to the melting process. In the present work, we develop an experimental study of melting in twin screw extruders, including pressure and temperature measurements, dead-stop experiments and sampling, observation of cross sections and quantification of solid fraction. The influences of process parameters (screw speed and feed rate), screw profile, pellets size and extruder size are also investigated. An original model of the melting process is proposed, deduced from these observations. This model allows one to calculate the evolution of mean shear rate, pressure gradient, dissipated energy, pellet radius and both solid and liquid temperatures along the screws, for a sequence of right- and left-handed screw elements and blocks of kneading discs. The results of the model are in good agreement with the experiments.

Free radical degradation of polypropylene in the bulk during reactive extrusion has received a lot of interest as an alternative method to produce resins with a wide variety of molecular weight distributions. Accurate design of the resulting products, however, requires a better control of the process, which can be achieved by the use of consistent modeling of the extrusion process. For this purpose, a reasonable constitutive equation describing the rheological behavior of the material during the reactive extrusion operation is necessary. This paper investigates the reliability of the combination of two models describing both chemical and rheological aspects of the process. The first model describes in a simplified manner the kinetics of the free radical degradation and helps to take into account the continuous change of the molecular weight distribution (MWD) of the polymer along the reaction time. On the other hand, various models, from empiricism to more elaborate ones using molecular dynamics, will be presented to relate the MWD to the rheological behavior. Their use, in combination with the previous model describing the kinetics of the degradation, will be shown to give a very accurate depiction of the rheokinetic aspects of the free radical degradation of polypropylene resins in an internal mixer using a peroxide as an initiator.

In the last recent years, electrical techniques like microdielectrometry have presented an attracting and increasing interest for continuous monitoring, in a nondestructive way, of the advancement of the reaction of thermoset resins under cure. We think that the use of electrical analysis for in situ monitoring of chemical reactions can be extended to get information on thermoplastic and the physical phenomena such sa crystallization or study of residence time distribution in processing machines such as extruders.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.