Polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties

ABSTRACT The usage of natural fibers on the composites development has grown rapidly in the recent years due to the fibers plentiful availability, renewable source, low density and biodegradability. However, there are some drawbacks, for instance, the fiber dispersion on a polyolefin matrix. In this work, the influence of processing speed on the mechanical and dynamic mechanical properties of polystyrene (PS) filled with cellulose fiber composites was investigated. The composites were processed on a twin-screw co-rotating extruder, using screw speeds of 200 rpm, 400 rpm and 600 rpm. The dynamic mechanical properties and the mechanical properties were investigated as a function of fiber content. The composites processed on a screw speed of 400 rpm had presented an increase on flexural and impact strength, compared to the composites processed at 200 rpm. The flexural and storage modulus had increased when increasing the fiber content, as well as increasing the processing speed. The greater fiber dispersion obtained at a screw speed of 400 rpm hinders the agglomeration arrangement and distributes the fibers more equally on the matrix. The increase on processing speed probably generates a fiber size reduction, increasing the fiber superficial area and generating a greater contact with the matrix as well. Therefore, the efforts transference of matrix to fibers is improved, originating an increase on the evaluated properties

Dissolution mechanisms of boro-silicate glass fibres in saline solution with added dissolved

Experiments of dissolution of a soluble boro-silica glass were performed at 37°C in a saline solution without and with 50, 75 and 100 ppm of added silica. After reaction silica concentration was measured by AAS and colorimetry and fibers were investigated by SEM-EDS and XPS. The results give informations on the dissolution velocity of the glass and the factors controlling the formation rate of the gel layer and its composition. The dissolution velocity measured at the unaltered glass-gel interface is not significantly decreased by the silica concentration in solution whatever its origin (leaching of the glass fibres or initial addition). Accordingly, gel formation is controlled by the chemical reactions rate at, or near, the boundary of the unaltered core. The composition and the stucture of the gel layer are depending on the silica concentration in solution above a threshold of about 50 ppm. The framework of the gel appears to play the more important role in the dissolution velocity of the glass

DroPNet: a web portal for integrated analysis of Drosophila protein-protein interaction networks

International audienceDroPNet (Drosophila Protein Network) is a Drosophila-dedicated web portal for generating and analyzing protein–protein interaction (PPI) networks. This platform integrates users’ experimental data provided as one or two lists of genes with PPI data from Drosophila and other species. These experimental data can, for example, come from RNAi screens, for which this approach is known to be valuable. DroPNet, therefore, provides an essential basis for further biological analysis by linking functional and physical interactions and reinforcing the relevance of each. DroPNet focuses on the search of PPIs between genes of the entry list, and includes the possibility of searching for intermediate genes for which the corresponding protein indirectly links two entry data. It also offers multiple functions for editing the networks obtained, providing users with interactive possibilities to progressively improve and refine the results. This approach gives a global view of the studied process and makes it possible to highlight specific interactions that have so far been understudied. DroPNet is freely available at http://dropnet.isima.fr

Occurrence of Phosphenes in Patients Undergoing Proton Beam Therapy for Ocular Tumor

cited By 0International audiencePurpose: Phosphenes are frequently reported by patients irradiated in the head and neck area. The aim of the present study was to characterize and investigate potential mechanisms of proton beam therapy (PBT)–induced phosphenes in a large population of patients undergoing PBT for ocular tumors. Design: Prospective cohort study. Methods: Consecutive patients who underwent PBT in a single center were included. Immediately after the first session, all patients completed a questionnaire collecting information about the presence of phosphenes as well as their color, shape, and duration. Patient, tumor and treatment characteristics (dose volume histograms) were also collected. Results: Among the 474 patients included, 62.8% reported phosphenes during the first session of PBT. Reported colors were mainly blue-violet (70.5%) and white (14.1%). The prevalence of phosphenes was higher in younger patients (P =.003); other patient or ocular characteristics were not associated with the occurrence of phosphenes. Irradiation of the macula (P <.001) and/or optic disc (P <.001) were significantly associated with the presence of phosphenes, whereas blue-violet color was only associated with young age and irradiation of macular area (P =.04). Pupillary constriction was reported for 57.1% of patients with phosphenes vs 18.5% of patients without (P <.001). Blue-violet phosphenes (P <.001) and irradiation of macula (P =.001) were statistically associated with pupillary constriction. Conclusions: The present study reported a high rate of phosphenes in patients irradiated by PBT for ocular tumor. Their blue-violet color and their association with a pupillary constriction probably indicates the stimulation of S-cones and retinal ganglion cells that reflects the activation of the afferent visual pathway. © 2018 Elsevier Inc