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Abstract: To be able to predict the throughput of a single-screw extruder or the metering time of an injection moulding machine for a given screw geometry, set of processing conditions and polymeric material is important both for practical and designing purposes. The model is based on viewing the entire screw simply as a pump, conveying a solid and a molten fraction. The evolution of the solid fraction is the essence of the plastication process, but under a particular hypothesis on solid bed acceleration, its influence on the throughput is nil. This allows getting a good estimate on the throughput and pressure development along the screw. Calculations are compared to a large set of experiments available from the literature. Consistent agreement with these published results is obtained, both for throughput and pressure along the screw. The effect of the plasticating process on the throughput is non-existent if the plastication length is short, and more visible if the plastication length takes a good part of the screw length (for instance, at higher screw rotation frequency). This diminishes the throughput value and widens the pressure peak. The model also shows that the screw geometry is the most important parameter, followed by polymer rheology and processing conditions. Melting properties and length seem to intervene to a lesser extent. Finally, the model is used for screw design, highlighting the influence of the compression zone on throughput. [Copyright &y& Elsevier]

Introduction L’anesthésie intraveineuse est une stratégie anesthésique connue pour réduire l’incidence des nausées et vomissements postopératoires (NVPO). L’objectif de cette étude est de déterminer l’incidence des NVPO et d’évaluer l’impact d’une bithérapie préventive dans le cadre de la chirurgie de l’obésité lors de l’utilisation d’un système d’asservissement de l’anesthésie intraveineuse à partir de l’index bispectral. Matériel et méthodes Après accord du comité de protection des personnes, nous avons mené une étude contrôlée randomisée monocentrique en double insu, comparant l’association peropératoire dexaméthasone (4 mg)/ondansetron (4 mg) (DO) versus placebo (CTL) pour la prévention des NVPO. Les patients majeurs à haut risque de NVPO (Apfel ≥ 2) durant une chirurgie laparoscopique de gastroplastie verticale calibrée avec résection gastrique ont été inclus après recueil écrit de leur consentement. L’anesthésie totale intraveineuse a consisté en l’administration automatisée de propofol et de rémifentanil guidée par le BIS [1] . Le critère de jugement principal a été l’incidence des nausées sévères (≥ 4/10 par échelle verbale simple) et des vomissements durant les 24 premières heures postopératoires. L’analyse a également porté sur la nécessité d’administrer un traitement de secours durant cette période. Résultats Sur 123 patients inclus, 117 ont été analysables. Les caractéristiques des patients et de l’anesthésie sont résumées dans le tableau ci-dessous ( Tableau 1 ). Dix-neuf pour cent des patients dans le groupe DO et 20 % dans le groupe CTL ont présenté le critère de jugement principal ( p = 1). Quarante-trois pour cent des patients dans le groupe DO et 54 % des patients dans le groupe CTL ont nécessité l’administration d’un traitement antiémétique de secours ( p = 0,31). Discussion La prévention n’a pas réduit l’incidence des NVPO dans ce contexte anesthésique. Dans cette étude sans groupe utilisant des halogénés, cette incidence est faible. L’étude de l’effet d’une augmentation des doses des traitements de prévention des NVPO est à envisager dans cette population de patients obèses. [ABSTRACT FROM AUTHOR]

Crop-livestock integration is a theoretical ideal for sustainable agriculture. However, the number of European crop-livestock farms has decreased due to multiple factors (e.g. agricultural policies and work constraints). Crop-livestock integration beyond the farm level (e.g. through grain-manure exchanges) is a relevant option to address these limiting factors. However, this integration within farmer groups is challenging because it requires collective redesign to address organizational issues. We developed a participatory approach that includes the serious game Dynamix to support the co-design of scenarios of crop-livestock integration among farms. The approach consists of six steps: (1) initial group meeting to define the problem; (2) farmer interviews to identify motivations and collect technical and economic farm data; (3) scenario co-design meeting using the serious game Dynamix, including a spatially explicit board game and a simulation model; (4) multicriteria evaluation of these scenarios at the individual farm and group levels using the simulation model included in Dynamix; (5) group meeting to discuss the results; and (6) monitoring of selected scenario implementation. We applied this methodology with two groups of farmers in southwestern France. In the two groups, crop farmers wanted to diversify their cropping systems and use manure to improve soil quality. Livestock farmers were interested in local and non-GMO feed for their animals. The scenario they selected included i) inserting cereal-legume mixtures into crop rotations on crop farms to be sold to livestock farms and ii) transferring manure from livestock farms to crop farms. In this scenario, the predicted overall gross margin increased more for livestock farmers (median = 29.90 €/ha) than for crop farmers (median = 6.60 €/ha). Nitrogen balance management was improved: crop farmers decreased their use of mineral fertilizer by 2.8–17.4 kg/ha/year; livestock farmers decreased their feed inputs improving local feed self-sufficiency. However, farmers' workload and management complexity increased, with 22–54 h of additional work per farmer per year. Compared to other scenarios, trade-offs between individual farm and group benefits resulted in greater local autonomy in inputs but lower autonomy in decision-making. In the two groups, discussions improved trust, which is a key ingredient for transitioning to integration beyond the farm level. Our study is the first to use a standardized participatory approach based on a serious game to support the complex issue of crop-livestock integration beyond the farm level. Applying the approach to a case-study revealed its strong potential. It can easily be scaled-out to other agricultural contexts. [Display omitted] • The approach co-designs crop-livestock integration among farms, as a relevant option for limiting inputs and pollution. • The serious game Dynamix allows a spatially explicit redesign at individual farm and group level. • Scenarios include an explicit design of the logistics of integration and multicriteria evaluation at farm and group level. • The scenario selected reduces logistical, legal and trust barriers involved in integration among farms. • The serious game was applied to a case-study but can easily be scaled-out to other agricultural contexts. [ABSTRACT FROM AUTHOR]

Background: Nitrous oxide (N2O) offers both hypnotic and analgesic characteristics. We therefore tested the hypothesis that N2O administration decreases the amount of propofol and remifentanil given by a closed-loop automated controller to maintain a similar bispectral index (BIS).Methods: In a randomized multicentre double-blind study, patients undergoing elective surgery were randomly assigned to breathe 60% inspired N2O (N2O group) or 40% oxygen (AIR group). Anaesthesia depth was evaluated by the proportion of time where BIS was within the range of 40-60 (BIS40-60). The primary outcomes were propofol and remifentanil consumption, with reductions of 20% in either being considered clinically important.Results: A total of 302 patients were randomized to the N2O group and 299 to the AIR group. At similar BIS40-60 [79 (67-86)% vs 76 (65-85)%], N2O slightly decreased propofol consumption [4.5 (3.7-5.5) vs 4.8 (4.0-5.9) mg kg(-1) h(-1), P=0.032], but not remifentanil consumption [0.17 (0.12-0.23) vs 0.18 (0.14-0.24) µg kg(-1) min(-1)]. For the subgroups of men, at similar BIS40-60 [80 (72-88)% vs 80 (70-87)%], propofol [4.2 (3.4-5.3) vs 4.4 (3.6-5.4) mg kg(-1) h(-1)] and remifentanil [0.19 (0.13-0.25) vs 0.18 (0.15-0.23) µg kg(-1) min(-1)] consumptions were similar in the N2O vs AIR group, respectively. For the subgroups of women, at similar BIS40-60 [76 (64-84)% vs 72 (62-82)%], propofol [4.7 (4.0-5.8) vs 5.3 (4.5-6.6) mg kg(-1) h(-1), P=0.004] and remifentanil [0.18 (0.13-0.25) vs 0.20 (0.15-0.27) µg kg(-1) min(-1), P=0.029] consumptions decreased with the co-administration of N2O.Conclusions: With automated drug administration titrated to comparable BIS, N2O only slightly reduced propofol consumption and did not reduce remifentanil consumption. There was a minor gender dependence, but not by a clinically important amount. Clinical trial registration This study was registered at ClinicalTrials.gov, number NCT00547209. [ABSTRACT FROM AUTHOR]

Abstract: The elaboration of composites with natural fibers and polymeric matrices has to face two major difficulties: natural fibers present a hydrophilic character (absorption of water and possible deterioration of the properties) and thermal sensitivity (the fibers can be degraded during composite elaboration and/or in certain applications). In addition, common polymers are generally hydrophobic, which induces poor compatibility at the polymer/fiber interface. It has been demonstrated that the quality of the interface between the natural fibers and the polymeric matrix is a key issue which should be controlled in order to improve the mechanical properties, the durability and the recyclability of such composites. In this purpose, our approach is to develop a new method of fibers/polymer coupling consisting in a unique operation of reactive compounding, based on an original chemistry of organosilanes in the polymer melt. Our objective is to enhance the fibers/polymer interface by using two functionalized organosilanes simultaneously. The method is then to graft covalently one of these functions on the polymer chains and the other one onto hemp surface. In parallel, formation of Si–O–Si network between the two grafted organosilanes occurs during reactive extrusion. The achievement of this grafting of hemp fibers and thermoplastic matrix during a single compounding operation constitutes a new route for the elaboration of bio-based composites. Mechanical properties (tensile and impact) and thermal behavior of these new composites were compared to those of fibers/polymer composites without coupling agent or with a single classical one (Vinyltrimethoxysilane). Results showed that the presence of two organosilane coupling agents enhances considerably the tensile strength (+40%) of the newly developed composite. Their thermal decomposition, as shown by TGA, was shifted to higher temperatures and their water uptake at room temperature was decreased. Morphological characterizations by SEM suggest better adhesion at the interface, which can explain the properties enhancement. [Copyright &y& Elsevier]

Abstract: The microstructure and properties of plastic parts made by laser sintering are known to be affected by a number of process and material parameters, whose influences are not totally elucidated yet. This study addresses the influence of the energy supplied to the powder on the microstructure and on the physical properties of sintered parts. Two different polyamide 12 powders were used. The energy density, which is derived from the laser characteristics, was shown to have a great impact on the residual porosity and on the amount of nascent particles in parts. The study of the pore size and of the porosity distribution was carried out by X-ray tomography. It is shown that the particles size distribution and the crystallisation temperature are the key parameters in the porosity formation. Finally, the influence of the microstructure and crystalline features on the mechanical properties of sintered parts is discussed. [Copyright &y& Elsevier]

This work investigates the capacity of a particular class of flows, namely drag and pressure driven flows, to propagate and distorts a transient sinusoidal temperature disturbance occurring at the inlet of the metering zone of a polymer processing screw channel. The integral transform method is applied to the forced convection heat transfer problem in a parallel plate channel with a general drag and pressure driven flow velocity profile for a Newtonian fluid, with the pressure gradient as an adjustable flow parameter. We follow closely the procedure outlined by Cotta and Özişik in their seminal paper [5]. We found that the knowledge of the lowest eigenvalue in the solution is sufficient to characterise the dampening efficiency of an inlet temperature fluctuation by the flow and that a higher level of positive pressure difference is indeed improving the thermal homogeneity in the flow. Moreover, we found that for any given flow, the higher frequency disturbances are dispersed more efficiently than the lower frequency disturbances. [ABSTRACT FROM AUTHOR]