426 research outputs found

    Process intensification : spinning disc reactor for the polymerisation of styrene

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    PhD ThesisThis investigation is concerned with the assessment of the performance of a novel spinning disc reactor (SDR) for the polymerisation of chemically initiated freeradical polymerisation of styrene. The application of high acceleration fields such as those created on the surface of the grooved rotating disc to the polymerising system is aimed at intensifying the polymerisation rate and producing a better quality polymer product. As part of the experimental programme, four separate sets of experimental runs were conducted on a 360 mm diameter grooved rotating disc at a fixed temperature of 88-90°C to explore the effects of disc rotational speed and prepolymer feed conversion/viscosity on the extent of monomer conversion and molecular weight properties (M., MW and MWD) of the product from the SDR. The performance data of the SDR was compared with conventional batch polymerisation data. Both the disc rotational speed and prepolymer feed conversion/viscosity variables were found to have a profound influence on the performance of the SDR. A steady increase in conversion, rate of polymerisation and hence time saving in one pass in the SDR were observed with a rise in the prepolymer feed conversion and rotational speed until, for the latter, an optimal speed of rotation which gave the highest rate of polymerisation was reached. The results have been explained in relation to the effect of disc speed and prepolymer feed viscosity on mean film thickness, mean residence time and film surface instabilities. Furthermore, the SDR product is seen to have generally improved characteristics in terms of narrower molecular weight distribution when compared to polymer prepared in the batch at the same conversion. The large enhancement of the rate of styrene polymerisation in the SDR was discussed in terms of a possible improvement in the BPO initiator efficiency f and non-stationary state polymerisation conditions likely to be prevalent on the rotating disc. The general improvement in SDR product quality was ascribed to the combined effects of a reduced diffusion path length and an intense mixing mechanism within the thin film. A separate experimental study exploring the effects of micromixing efficiency on the conversion and molecular weight properties of styrene polymerisation in the batch was also undertaken. The opposing effects of enhanced micromixing in batch and continuous polymerisation systems were contrasted in a theoretical manner. A theoretical case study highlighting the energy efficiency of the SDR was also carried out. Savings in energy of more than 70% was calculated for a semi-batch process using an industrially adapted spinning disc reactor in comparison to a purely batch process. Finally, a two-stage continuous industrial process for free-radical polymerisation has been proposed consisting of an enhanced tubular reactor in the first stage followed by a parallel arrangement of several rotating disc surfaces. Improvements in intrinsic safety and minimised risks of polymer degradation and thermal runaways are the expected potential benefits. Keywords: Process Intensification, Thin Film, Spinning Disc Reactor, Free Radical Polymerisation, Polystyren

    A formative evaluation of the South African Education and Environment Project Bridging Year Programme

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    Includes bibliographical references (leaves 89-94).Many learners from disadvantaged schools struggle to obtain entrance into tertiary institutions. A Bridging Year Programme (BYP) designed by the South African Education and Environment Project (SAEP) seeks to address this problem by offering intensive tuition to post-high school learners who have failed to gain sufficient points for entry into a tertiary institution. The BYP prepares those learners to re-write core National Senior Certificate (NSC) subjects and assists them in applying for entrance into a university or college. A formative evaluation was conducted to assess whether the programme is designed and implemented as intended and whether programme design and delivery takes into account evidence based practices, established in the literature for programmes of this nature. A review of programme records was undertaken, interviews were conducted with the programme manager and programme coordinator, and selfreport questionnaires were administered to course tutors and programme beneficiaries. The results of the evaluation indicate that while the programme has the necessary potential to set high standards of participation for beneficiaries and provide them with personalised attention, and while learners are generally positive about their experience, a number of limitations are evident. These include in particular: the need for better monitoring of learner compliance with their contractual obligation, improved quality assurance with regard to the teaching and learning programme, and tutor preparation and training. Recommendations for improved programme implementation, as well as monitoring of programme standards, learner participation and performance, and tutor quality are provided

    Replication of Marek's Disease Virus Is Dependent on Synthesis of De Novo Fatty Acid and Prostaglandin E2

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    Marek’s disease virus (MDV) causes deadly lymphoma and induces an imbalance of the lipid metabolism in infected chickens. Here, we discovered that MDV activates the fatty acid synthesis (FAS) pathway in primary chicken embryo fibroblasts (CEFs). In addition, MDV-infected cells contained high levels of fatty acids and showed increased numbers of lipid droplets (LDs). Chemical inhibitors of the FAS pathway (TOFA and C75) reduced MDV titers by approximately 30-fold. Addition of the downstream metabolites, including malonyl-coenzyme A and palmitic acid, completely restored the inhibitory effects of the FAS inhibitors. Furthermore, we could demonstrate that MDV infection activates the COX-2/prostaglandin E2 (PGE2) pathway, as evident by increased levels of arachidonic acid, COX-2 expression, and PGE2 synthesis. Inhibition of the COX-2/PGE2 pathway by chemical inhibitors or knockdown of COX2 using short hairpin RNA reduced MDV titers, suggesting that COX-2 promotes virus replication. Exogenous PGE2 completely restored the inhibition of the COX-2/PGE2 pathway in MDV replication. Unexpectedly, exogenous PGE2 also partially rescued the inhibitory effects of FAS inhibitors on MDV replication, suggesting that there is a link between these two pathways in MDV infection. Taken together, our data demonstrate that the FAS and COX-2/PGE2 pathways play an important role in the replication of this deadly pathogen

    Islamic Fundamentalism in the Caribbean (Dialogue #135)

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    Design of dual-band matching network for highly efficient power amplifier

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    In the last decades wireless communications has been growing tremendously and given that the trend will most likely continue at a cumulative pace it is imperative that in the future, the transceivers designed need to operate at a near ideal energy efficiency on new frequency bands demanded by the 5G standard. Since transmitters are the corner stone of any wireless communication systems and that power amplifier (PA) is a high power consuming device within it. It is evident that the design of a highly efficient PA might tackle the significant portion of power loss within RF and microwave systems. The design of PA proposed in this work is aimed at dual band frequencies based on the LTE standards of LTE 42 and LTE 43 having range of 3.4 GHz to 3.6 GHz and 3.6 GHz to 3.8 GHz respectively. The design of a PA begins at characterizing the transistor employed then followed by conjugate matching of the input aimed at the gate. In the design for a highly efficient power amplifier, the design of the OMN plays a pivotal role. This is usually achieved by employing load pull techniques aimed at the drain to find the optimum impedance requirement at desired frequency. Then by employing band-pass filters aimed only to allow the two LTE bands to pass through will cause all the other harmonic frequencies suppression. Having an ideal efficiency of 100% and their simplistic design over other PA classes makes the Class E amplifier a viable choice. Although theoretically Class E amplifier have an ideal efficiency, we expect by achieving 60% to 80% efficiency will be an acceptable target since in practice the efficiency largely depends on the type of transistor being implemented in the PA system

    Drawing On The Earth

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    Social Comment as a Phase in the Development of a More Personal Expression in Oil Painting

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    The purpose of this study is (1) to examine the presence or social comment in painting from a historical point or view, (2) to support its validity as a theme in art, (3) to use this theme in the creation or a number or oil paintings, and (4) to develop through this means a more personal expression in painting

    HOSX: Hospital operations excellence model

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    Hospital performance can be evaluated in four categories: (i) quality of care, (ii) process of care (iii) financial and (iv) operations productivity. Of these, ‘quality of care’ is the most widely reported and studied measure of performance, and focuses primarily on the clinical outcomes of the patient. In contrast, operations productivity and efficiency is the least studied measure, and currently there is limited ability to evaluate how efficiently the hospital has used its resources to deliver healthcare services. Cost containment in the healthcare industry is a challenging problem, and there is a lack of models and methods to benchmark hospital operating costs. Every hospital claims they are unique, and hence comparative assessments across hospitals cannot be made effectively. This research presents a performance framework for hospital operations to be called HOSx: Hospital Operations Excellence Model, used to measure and evaluate the operations productivity of hospitals. A key part of this research is healthcare activity data extracted from Medicare Provider Analysis and Review (MedPAR) database and the Healthcare Provider Cost Reporting Information System (HCRIS), both of which are maintained by the Center for Medicare Services (CMS). A key obstacle to hospital productivity measurement is defining a standard unit of output. Traditionally used units of output are inpatient day, adjusted patient day (APD) and adjusted discharge, which are reasonable estimators of patient volume, but are fundamentally limited in that they assume that all patients are equivalent. This research develops a standardized productivity output measure for a Hospital Unit of Care (HUC), which is defined as the resources required to provide one general medical/surgical inpatient day. The HUC model views patient care as a series of healthcare related activities that are designed to provide the needed quality of care for the specific disease. A healthcare activity is defined as a patient centric activity prescribed by physicians and requiring the direct use of hospital resources. These resources include (i) clinical staff (ii) non-clinical staff (iii) equipment (iv) supplies and (v) facilities plus other indirect resources. The approach followed here is to derive a roll-up equivalency parameter for each of the additional care/services activities that the hospital provides. Six HUC components are proposed: (i) case-mix adjusted inpatient days (ii) discharge disposition (iii) intensive care (iv) nursery (v) outpatient care and (vi) ancillary services. The HUC is compatible with the Medicare Cost Report data format. Model application is demonstrated on a set of 17 honor roll hospitals using data from MedPar 2011. An expanded application on 203 hospitals across multiple U.S. states shows that the HUC is significantly better correlated than the more traditional APD to hospital operating costs. The HUC measure will facilitate the development of an array of models and methods to benchmark hospital operating costs, productivity and efficiency. This research develops two hospital operations metrics. The first is the Hospital Resource Efficiency (HRE), which is defined as operating cost per Hospital Unit of Care, and the second is the Hospital Productivity Index, which benchmarks performance across the reference set of hospitals. Productivity analysis of all 203 hospitals in our database was conducted using these two measures. Specific factors studied include (i) functional areas (ii) patient volume (iii) geographical location. The results provide for the first time a ranking of most productive hospitals in each state – New Jersey, Pennsylvania, Nebraska, South Dakota and Washington as well as an interstate ranking. This research also provides detailed analysis of all outlier hospitals and causes of productivity variance in hospitals. The final output, the Hospital Total Performance Matrix combines clinical performance with productivity to identify the leading U.S. hospitals
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