RESUMO
In this work, the effect of different mixing techniques on thermal and mechanical properties of graphene nanoplatelets (GNPs) and graphene nanofibers (GANFs) loaded epoxy nanocomposites was investigated. Three dispersion methods were employed: a high shear rate (HSR), ultrasonication (US) and the fluidized bed method (FBM). The optical microscopy has revealed that the most suitable dispersion, in terms of homogeneity and cluster size, is achieved by implementing the US and FBM techniques, leading to nanocomposites with the largest increase of glass transition temperature, as supported by the DMA analysis data. The fracture toughness results show a general increase of both the critical stress intensity factor (KIC) and the critical strain energy release rate (GIC), likely due to the homogeneity and the low scale dispersion of the carbonaceous nanostructures. Based on the nanocomposite fracture toughness improvements and also assuming a potential large scale up production of the nanocomposite matrix, a single mixing technique, namely the FBM, was employed to manufacture the carbon fiber reinforced composite (CFRC). This method has resulted in being less time-consuming and is potentially most suitable for the high volume industrial production. The CFRCs were characterized in terms of tensile, flexural and interlaminar fracture toughness properties and the results were analyzed and discussed.
RESUMO
AIM OF THE STUDY: Post-gastrectomy syndromes (PGS) are iatrogenic conditions which may arise from partial gastrectomies, independently from their indications (cancer or ulcer) and the reconstruction technique (Billroth I, Billroth II or Roux-en-Y). They are usually less frequent in patients with a Roux-en-Y reconstruction, but also this technique does not surely prevent SPG. Recently, some new technique have been proposed in order to prevent the PGS. Most of them are based upon a less extensive resection of the viscus, replaced by application of simple stapler mediated interruptions (the so called "uncut" technique). We aimed to verify whether such less invasive technique were also able to exert a therapeutic role for various type of PGS with the same efficiency of the traditional ri-resection techniques, which are known to generally have a major morbidity impact. MATERIAL AND METHODS: Nineteen patients, 12 male and 7 female, aged between 44 and 67 years, have been operated since 1985 up to 2004. All of them had an overt SPG (2 with efferent loop syndrome, 10 with gastro-esophageal biliary reflux, 3 with an afferent loop disease and, finally, 4 with a late dumping disease. The series has been divided into two groups depending on the type of surgical technique we chose for the correction of their SPG: "high surgery" patients (HS), operated with Roux re-resection and TADE, "low surgery" (LS) patients treated with "uncut" techniques and or Braun/GEA anastomosis. Both group were comparatively analyzed for the surgical outcome using an Eckhauser and a Visick scale. RESULTS: Out of the 11 patients of the first group 8 had a Roux ri-resection and 3 a TADE, whereas subjects from the second group underwent in four cases to a Braun/uncut afferent loop closer, which was associated to a GEA in the remnant ones. In both group there was no mortality rate, whereas only one subjects from the HS group had a post-operative complication. Either the Visick and the Eckauser score was better in the LS group. DISCUSSION: Data collected show that SPG, even if represented an heterogeneous group of clinical conditions, can be generally treated following a surgical procedure as conservative as possible. Such conclusion may open further views in the laparoscopic management of SPG.
