Flow induced crystallization of polyolefins

Polymers are a widespread class of materials that provide an often advantageous combination of properties. Easy processability and high versatility combined with low costs make polymers the materials for an increasing number of high-tech and commodity applications. Semi-crystalline polyolefins are an important class of polymers, produced in more than 150 million metric tons per year. They are used to make a wide range of products ranging from fibers with superior mechanical properties to flexible packaging and molded parts. The properties of these materials are related to the whole history of the material, from chemistry/catalysis in the reactor and, in particular, to the processing conditions. Nowadays, there is a growing interest in added value to these products by achieving outstanding properties such as high stiffness (up to ~150 GPa) for fibers and clarity for injection molded parts. This demands more thorough studies on the process-properties relation that is not yet fully understood. The main objective of this thesis is to enhance the nucleating efficiency of the polymer by inducing oriented structures possessing good epitaxial matching. The goal is achieved by developing the oriented structures in polymer melt either by (a) making use of fillers that self assemble into nano sized fibrils and orient under flow or (b) by the addition of identical higher molar mass molecules possessing considerably higher relaxation times compared to the base (matrix) polymer. In the first part of the thesis, the crystallization of isotactic polypropylene (iPP) in the presence of 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) is discussed. DMDBS is a small organic compound with a high melting temperature (~250 °C) used as a nucleating agent and so-called clarifier for iPP. The nucleating efficiency of this compound, in the low concentration regime (less than 1 wt%), is very high and leads to very small iPP crystallites that confer clarity to the material. DMDBS can crystallize within the molten polymer matrix forming a percolated network of nano-fibrils whose surface hosts a large number of tailored nucleation sites. Because of the epitaxial relation between iPP and DMDBS, iPP lamellae grow always radially on DMDBS fibrils, i.e. with the crystalline c-axis parallel to the fibril axis, the so the so-called shish-kebab morphology (rather similar to the well-known food product). Therefore, the orientation of DMDBS fibrils templates the orientation of iPP lamellae. Randomly oriented DMDBS fibrils lead to randomly oriented iPP lamellae and aligned DMDBS fibrils lead to aligned iPP lamellae. A long lasting alignment of DMDBS fibrils can be obtained deforming their network even above the melting point of the polymer. Nearly 0.5 wt% of oriented DMDBS fibrils can template very oriented (fiber-like) polymer morphologies. In the second part of this thesis, the flow induced crystallization of high density polyethylene (HDPE) with a bimodal molecular weight distribution is discussed. This material is an intimate blend of low and high molecular weight polymer chains (LMW and HMW) synthesized with a new chemistry route as described in the thesis of N. Kukalyekar (Ph.D. thesis Eindhoven University of Technology, December 2007). Just above the equilibrium melting temperature (T141.2) of the polymer, the mutually entangled HMW chains can be stretched with shear and, due to the restricted number of molecular conformations, nucleate into needle-like crystals. By choosing appropriate flow conditions, a suspension of shishes (extended chain crystals) can be formed while the nucleation of kebabs (folded chain crystals) is suppressed because of a too high temperature. With perfect epitaxy matching and a good state of dispersion, shishes are the ideal substrate for the nucleation of HDPE lamellae. On cooling after the application of shear at 142 °, HDPE lamellae nucleate using shishes as a heterogeneous substrate and, therefore, with the crystalline c-axis parallel to the shish direction. Similarly to the case of iPP-DMDBS blends, it is observed that nearly 0.5 wt% of pre-aligned shishes can template very oriented (fiber-like) morphologies

P02-178 HIV/Aids and mental illness dual diagnosis: Exploring healthcare professionals' perspective

Aims:A growing body of scientific literature emphasizes a strong linkage between HIV/Aids and serious mental illness. In the Italian context, specialized services for combined management of dual diagnosis are increasingly requested, and healthcare professionals (HPWs) have to face up the difficulty emerging by this new situation. To bridge these gaps, the present study aimed at studying the representations of dual diagnosis, analyzing HPWs' experiences from their own perspectives, in order to understand their difficulty and create future good practices in healthcare services.Method:A quali-quantitative study was conducted with a multidisciplinary sample of professionals (N=91), drawn by HIV/Aids and Mental Health sites. Due to the exploratory nature of the research, data were collected from semi-structured interviews: HPWs were asked about their work experiences with HIV/Aids and Mental Illness. The interviews were fully audio-taped and verbatim transcribed. A computer-aided lexical correspondence analysis was conducted by a dedicated text-analysis software.Results:Data analysis showed out two main factorial dimensions: the first regarding the representation of the "Management of dual diagnosis within Health Services", and the second one referring to the "categorization of HIV/Aids-Mental Illness co-morbidity". Furthermore, four different Representational Conceptions were highlighted, corresponding to as many different ways HPWs use to represent/depict the aims of Health Service in relation to HIV/Aids-Mental Illness co-morbidity.Conclusion:This study reveals that socio-cultural meanings of dual diagnosis are not fixed; rather, they are ongoing co-constructed within the activities carried out by the HPWs involved in their specific health contexts in the exercise of their profession

Carba-D,L-allal- and -D,L-galactal-derived vinyl N-nosyl aziridines as useful tools for the synthesis of 4-deoxy-4-(N-nosylamino)-2,3-unsaturated-5a-carbasugars

The novel carba-D,L-allal- and carba-D,L-galactal-derived vinyl N-nosyl aziridines were prepared and the regio- and stereoselective behavior in opening reactions with O- and N-nucleophiles examined. The carbaglycosylating ability of the novel aziridines, as deduced by the amount of 1,4-addition products (1,4-regioselectivity) obtained in the acid-catalyzed methanolysis taken as a model reaction, is similar or superior to that observed with the corresponding carba-D,L-allal- and -D,L-galactal-derived vinyl epoxides, respectively. In all 1,2- and 1,4-addition products obtained, a –(N-nosylamino) group is regio- and stereoselectively introduced at the C(4) carbon of a 1,2- or 2,3-unsaturated carbasugar, susceptible to further elaborations toward aminocyclitol derivatives. The stereoselective synthesis of the corresponding, enantiomerically pure carba-D,L-allal- and -D,L-galactal-derived vinyl N-acetyl aziridines is also described

Phase Ib Trial of Nab-Paclitaxel Plus Gemcitabine, Capecitabine, and Cisplatin (Paxg Regimen) in Patients with Stage III Pancreatic Adenocarcinoma

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The perioperative period of liver transplantation from unconventional extended criteria donors: data from two high-volume centres

Background: As literature largely focuses on long-term outcomes, this study aimed at elucidating the perioperative outcomes of liver transplant patients receiving a graft from two groups of unconventional expanded criteria donors: brain dead aged > 80 years and cardiac dead.Methods: Data of 247 cirrhotic patients transplanted at two high volume liver transplant centers were analysed. Confounders were balanced using a stabilized inverse probability therapy weighting and a propensity score for each patient on the original population was generated. The score was created using a multivariate logistic regression model considering a Comprehensive Complication Index & GE; 42 (no versus yes) as the dependent variable and 11 possible clinically relevant confounders as covariate.Results: Forty-four patients received the graft from a cardiac-dead donor and 203 from a brain-dead donor aged > 80 years. Intraoperatively, cardiac-dead donors liver transplant cases required more fresh frozen plasma units (P < 0.0001) with similar reduced need of fibrinogen to old brain-dead donors cases. The incidence of reperfusion syndrome was similar (P = 0.80). In the Intensive Care Unit, both the groups presented a comparable low need for blood transfusions, renal replacement therapy and inotropes. Cardiac-dead donors liver transplantations required more time to tracheal extubation (P < 0.0001) and scored higher Comprehensive Complication Index (P < 0.0001) however the incidence of a severe complication status (Comprehensive Complication Index & GE; 42) was similar (P = 0.52). ICU stay (P = 0.97), total hospital stay (P = 0.57), in hospital (P = 1.00) and 6 months (P = 1.00) death were similar.Conclusion: Selected octogenarian and cardiac-dead donors can be used safely for liver transplantation

A crack closure system for cementitious composite materials using knotted shape memory polymer (k-SMP) fibres

YesFormation of cracks represents one of the major causes of concrete deterioration, which can lead to durability and safety issues. In this work, a novel crack closure system is developed, using polyethylene terephthalate (PET) polymer fibres embedded in a mortar mix. The PET polymer has shape memory properties and shrinks upon thermal activation, if free to do so, or otherwise exerts shrinkage restraint forces. A single knot was manufactured at each end of the PET fibres to provide mechanical anchorage into the mortar matrix. Mortar samples with embedded knotted fibres were pre-cracked and subsequently placed in an oven to thermally activate the polymers and induce the shrinkage mechanism into the fibres. Crack closure was measured in the range 45–100%, depending on the geometry, dimension and distribution of the fibres, and the size of the initial crack.This work is supported by UKRI-EPSRC (Grant No. EP/P02081X/1, Resilient Materials 4 Life, RM4L)

CDKN2A Determines Mesothelioma Cell Fate to EZH2 Inhibition

Malignant pleural mesothelioma is an aggressive cancer, heterogeneous in its presentation and behaviour. Despite an increasing knowledge about molecular markers and their diagnostic and prognostic value, they are not used as much as they might be for treatment allocation. It has been recently reported that mesothelioma cells that lack BAP1 (BRCA1 Associated Protein) are sensitive to inhibition of the EZH2 (Enhancer of Zeste Homolog 2) histone methyltransferase. Since we observed strong H3K27me3 (histone H3 lysine 27 trimetylation) immunoreactivity in BAP1 wild-type mesothelioma biopsies, we decided to characterize in vitro the response/resistance of BAP1 wild-type mesothelioma cells to the EZH2 selective inhibitor, EPZ-6438. Here we demonstrate that BAP1 wild-type mesothelioma cells were rendered sensitive to EPZ-6438 upon SIRT1 (Sirtuin 1) silencing/inhibition or when cultured as multicellular spheroids, in which SIRT1 expression was lower compared to cells grown in monolayers. Notably, treatment of spheroids with EPZ-6438 abolished H3K27me3 and induced the expression of CDKN2A (Cyclin-Dependent Kinase Inhibitor 2A), causing cell growth arrest. EPZ-6438 treatment also resulted in a rapid and sustained induction of the genes encoding HIF2α (Hypoxia Inducible Factor 2α), TG2 (Transglutaminase 2) and IL-6 (Interleukin 6). Loss of CDKN2 is a common event in mesothelioma. CDKN2A silencing in combination with EPZ-6438 treatment induced apoptotic death in mesothelioma spheroids. In a CDKN2A wild-type setting apoptosis was induced by combining EPZ-6438 with 1-155, a TG2 selective and irreversible inhibitor. In conclusion, our data suggests that the expression of CDKN2A predicts cell fate in response to EZH2 inhibition and could potentially stratify tumors likely to undergo apoptosis