The effect of melt viscosity on thermal efficiency for single screw extrusion of HDPE

In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process.

The determination of optimal processing conditions for PLA and PLA/CaCO3 in twin screw extrusion using DoE and multivariate analysis

Biodegradable polymers, such as PLA (Polylactide), come from renewable resources like corn starch and if disposed of correctly, degrade and become harmless to the ecosystem making them attractive alternatives to petroleum based polymers. PLA in particular is used in a variety of applications including medical devices, food packaging and waste disposal packaging. However, the industry faces challenges in melt processing of PLA due to its poor thermal stability which is influenced by processing temperatures and shearing.
Identification and control of suitable processing conditions is extremely challenging, usually relying on trial and error, and often sensitive to batch to batch variations. Off-line assessment in a lab environment can result in high scrap rates, long lead times and lengthy and expensive process development. Scrap rates are typically in the region of 25-30% for medical grade PLA costing between €2000-€5000/kg.
Additives are used to enhance material properties such as mechanical properties and may also have a therapeutic role in the case of bioresorbable medical devices, for example the release of calcium from orthopaedic implants such as fixation screws promotes healing. Additives can also reduce the costs involved as less of the polymer resin is required.
This study investigates the scope for monitoring, modelling and optimising processing conditions for twin screw extrusion of PLA and PLA w/calcium carbonate to achieve desired material properties. A DAQ system has been constructed to gather data from a bespoke measurement die comprising melt temperature; pressure drop along the length of the die; and UV-Vis spectral data which is shown to correlate to filler dispersion. Trials were carried out under a range of processing conditions using a Design of Experiments approach and samples were tested for mechanical properties, degradation rate and the release rate of calcium. Relationships between recorded process data and material characterisation results are explored.

DNA mismatch repair and the DNA damage response to ionizing radiation:making sense of apparently conflicting data

The DNA mismatch repair (MMR) pathway detects and repairs DNA replication errors. While DNA MMR-proficiency is known to play a key role in the sensitivity to a number of DNA damaging agents, its role in the cytotoxicity of ionizing radiation (IR) is less well characterized. Available literature to date is conflicting regarding the influence of MMR status on radiosensitivity, and this has arisen as a subject of controversy in the field. The aim of this paper is to provide the first comprehensive overview of the experimental data linking MMR proteins and the DNA damage response to IR. A PubMed search was conducted using the key words "DNA mismatch repair" and "ionizing radiation". Relevant articles and their references were reviewed for their association between DNA MMR and IR. Recent data suggest that radiation dose and the type of DNA damage induced may dictate the involvement of the MMR system in the cellular response to IR. In particular, the literature supports a role for the MMR system in DNA damage recognition, cell cycle arrest, DNA repair and apoptosis. In this review we discuss our current understanding of the impact of MMR status on the cellular response to radiation in mammalian cells gained from past and present studies and attempt to provide an explanation for how MMR may determine the response to radiation.

Is the Schwabe organ a retained larval eye? Anatomical and behavioural studies of a novel sense organ in adult leptochiton asellus (Mollusca, Polyplacophora) indicate links to larval photoreceptors

The discovery of a sensory organ, the Schwabe organ, was recently reported as a unifying feature of chitons in the order Lepidopleurida. It is a patch of pigmented tissue located on the roof of the pallial cavity, beneath the velum on either side of the mouth. The epithelium is densely innervated and contains two types of potential sensory cells. As the function of the Schwabe organ remains unknown, we have taken a cross-disciplinary approach, using anatomical, histological and behavioural techniques to understand it. In general, the pigmentation that characterises this sensory structure gradually fades after death; however, one particular concentrated pigment dot persists. This dot is positionally homologous to the larval eye in chiton trochophores, found in the same neuroanatomical location, and furthermore the metamorphic migration of the larval eye is ventral in species known to possess Schwabe organs. Here we report the presence of a discrete subsurface epithelial structure in the region of the Schwabe organ in Leptochiton asellus that histologically resembles the chiton larval eye. Behavioural experiments demonstrate that Leptochiton asellus with intact Schwabe organs actively avoid an upwelling light source, while Leptochiton asellus with surgically ablated Schwabe organs and a control species lacking the organ (members of the other extant order, Chitonida) do not (Kruskal-Wallis, H = 24.82, df = 3, p < 0.0001). We propose that the Schwabe organ represents the adult expression of the chiton larval eye, being retained and elaborated in adult lepidopleurans.

Gramsci, austerity common sense and the attacks on the welfare state: The need to understand and resist the imposition of the global neoliberal agenda and the role of the social work profession.

During the last 30 years governments almost everywhere in the world are furthering a global neoliberal agenda by withdrawing the state from the delivery of services, decreasing social spending and lowering corporate taxation etc. This restructuring has led to a massive transfer of wealth from the welfare state and working class people into capital. In order to legitimize this restructuring conservative governments engage in collective blaming towards their denizens. This presentation will examine some of the well circulated phrases that have been used by the dominant elite in some countries during the last year to legitimize the imposition of austerity measures. Phrases such as, ‘We all partied’ used by the Irish finance minister, Brian Lenihan, to explain the Irish crisis and collectively blame all Irish people, ‘We must all share the pain’, deployed by another Irish Minister Gilmore and the UK coalition administration’s sound bite ‘We are all in this together’, legitimize the imposition of austerity measures. Utilizing the Gramscian concept of common sense (Gramsci, 1971), I call these phrases ‘austerity common sense’. They are austerity common sense because they both reflect and legitimate the austerity agenda. By deploying these phrases, the ruling economic and political elite seek to influence the perception of the people and pre-empt any intention of resistance. The dominant theme of these phrases is that there is no alternative and that austerity measures are somehow self-inflicted and, as such, should not be challenged because we are all to blame. The purpose of this presentation is to explore the “austerity common sense” theme from a Gramscian approach, focus on its implications for the social work profession and discuss the ways to resist the imposition of the global neoliberal agenda.

Projective Identification and the Fear of Failing: Making Sense of Practice Educators' Experiences of Failing Social Work Students in Practice Learning Settings

The paper focuses on emotions and processes that may arise for practice educators when working with a struggling or failing student in a practice learning setting.1 The paper firstly documents a previously undertaken thematic review of the literature, which explored why practice educators appeared to find it difficult to fail students in practice learning settings. Secondly, the paper draws on two UK qualitative studies that highlighted the emotional distress experienced by practice educators when working with a marginal or failing student. The paper documents key findings using a case study approach from both studies. We argue that the concept of projective identification offers a plausible and illuminating account of the states of mind experienced by practice educators and in making explicit, unconscious states of mind, our aim is that practice educators will feel confident to make appropriate assessment decisions when required.

Joint inversion of magnetotelluric and seismic data for crustal characterization

Tese de doutoramento, Ciências Geofísicas e da Geoinformação (Geofisíca), Universidade de Lisboa, Faculdade de Ciências, 2014

Joint inversion of geophysical and hydrologic data during water infiltration

Tese de doutoramento, Ciências Geofísicas e da Geoinformação (Geofísica), Universidade de Lisboa, Faculdade de Ciências, 2014

Foodies in the UK: A Sense of Self, Connection and Belonging Beyond the Passion?

The global rise of the Foodie movement has attracted some research attention as well as critique in the food industry trend followers, but little research attention in marketing research. The present study looks at the ‘Foodie’ phenomenon in the UK and aims to extend how the notion has been coined in literature through a qualitative investigation of a sample of self-professed Foodies. The objective is to provide an in-depth understanding of what it means to be a Foodie at the individual and group levels, probing attitudes, motivations and self-awareness. Results indicate that the term Foodie cannot be used as an implicit definition of someone ‘simply interested in food’; the capacity of the Foodie may be dependent on individual involvement and the level of importance along the five emerging themes; these being: Learning and discovery; Pleasure and enjoyment; Inspirational influences; Quality; and Experiencing food as an individual and in connection with others. Findings imply that there might be different levels of Foodies, leading to a start on developing a Foodie Typology. The study poses implications for food marketers and researchers that can assist in more effective segmentation, efficient targeting and tailored positioning, as well as opportunities for future research.