1522 research outputs found
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Supercritical Fluid Technology Assisted Incorporation of Antimicrobials into Medical Devices
No full textCatheter-associated infections (CAIs) are a serious concern worldwide. In the United States alone, about 80,000 catheter line-associated bloodstream infections (CLABSIs) are recorded each year with increased mortality rates for seriously ill patients. Current means used for incorporating antimicrobials include coating, impregnation, engineered surface topography and hot-melt extrusion (HME). However, the major problems associated with these methods are leaching, uncontrolled drug delivery and degradation of thermosensitive drugs. The aim of this research work was to produce antimicrobial loaded thermoplastic polyurethanes for delivering a proven solution to the current unmet need of eliminating the occurrence of biofilm formation. The incorporation of selected antimicrobial agents in polyurethanes was approached in two different fashions.
Firstly, the use of sub-critical carbon dioxide (sbCO2) to assist the single HME process, which successfully lowered melt process temperature of Quadrathane polyurethane from 190 to 175 °C. Unfortunately, it was higher than the melting temperature of chlorhexidine diacetate (CHX-A) at which CHX lost its antimicrobial properties. Graphene oxide (GO), was also selected to incorporate into Quadrathane polyurethane by using the single step HME processing with the assistance of sbCO2. The results demonstrated that the incorporation of GO into Quadrathane polyurethane resulted in a change in mechanical, thermal, and rheological properties of the composites. The incorporation of GO also imparted more strength to the Quadrathane matrix.
Another medical grade polyurethane, Pellethane polyurethane, was chosen to be extruded using a two-step HME processing approach with pressurized CO2 at the subcritical point. The results showed that under both conditions, pressurised CO2 could change the rheological properties of the Pellethane in the barrel of the extruder. The melt viscosity decreased to 36.36 percent and 40.04 percent at 600 and 1000 psi, respectively. The process temperature of Pellethane polyurethane was reduced from 185 °C to 160 °C. The processing window temperature was raised by 25 °C and may be extended for other polymers. Crystallinity and thermal decomposition kinetics and behaviour of the Pellethane polyurethane extrudates were also investigated. The activation energy (Ea) values of the polyurethane treated with pressurised CO2 at 600 and 1000 psi were 155 and 150 kJ·mol-1 , respectively. Both were higher than that of untreated samples which was 135 kJ·mol-1. The greater Ea values for thermal decomposition provided higher thermal stability of the Pellethane polyurethane. A second technique proposed to incorporate the antimicrobials into Quadrathane polyurethane using sbCO2 assisted impregnation technique. CHX-A was impregnated into Quadrathane polyurethane by using sbCO2 at 400 and 600 psi and methanol as a co-solvent. The highest CHX-A uptake was1.23 mg (0.13%) for the Quadrathane sample treated at 600 psi, 5 wt%, the distribution of CHX-A in the matrix was not homogeneous which decreases from the outer part to the inner part of the matrix.
Gram-positive bacteria, S. aureus were chosen for antimicrobial performance test. At the experimental time points, the CHX-A impregnated Quadrathane samples outperformed the negative control. Log 10 value increased from 0.00 to 2.83 for the samples treated at 400 and 600 psi. Unfortunately, the GO composite samples at all scenarios for both sbCO2 assisted impregnation and HME did not perform any efficacy against S. aureus. The elution study demonstrates that CHX was not eluted from the Quadrathane matrix because a very small amount of CHX-A was found in the Quadrathane matrix
Circulating Angiogenic and Senescent T Cells in Ageing and Frailty
No full textAgeing and frailty represent an increasing challenge for societies worldwide, with a growing emphasis on identifying their underlying pathophysiologies and prospects for intervention. Although not part of frailty based on some definitions employed, there is an important cardiovascular dimension to frailty. T lymphocyte subsets have been implicated both positively and negatively in vascular health and age-related vascular disease. There is evidence a circulating T cell subset exists (CD31+ angiogenic T cells) which may play a role in vascular maintenance and repair. On the other hand, there also exists a population of T cells that display pro-inflammatory function (CD28NULL senescent T cells). Ageing, an established cardiovascular risk factor has been linked with decreasing numbers of circulating CD31+ T cells and increases in CD28NULL T cells. Using flow cytometry, we have examined the effects of ageing and frailty on these cells and their discrete subsets. We have also isolated CD31+ and CD31- T cells from young adults, investigated their cytokine secretion profile and T cell differentiation state. Our key findings include (1) a progressive decrease in CD31+ T cells with ageing and a paradoxical increase in age-matched frail older adults, (2) increased CD28NULL T cells in frail older adults, which is particularly prominent in the CD8+ T cell pool (3) higher secretion of angiogenic and pro-inflammatory cytokines from CD31+ than CD31- T cells (4) CD31+ T cells exist across the T cell differentiation spectrum with considerable proportions present in the senescent T cell pool. Overall, our findings indicate that CD31+ T cells have more complex functional and phenotypic characteristics than previously described, and these characteristics should be considered in future studies investigating these cells in disease states. We have identified CD8+CD28NULL T cells as a frailty associated biomarker that may be used to track immune changes in intervention studies concerning frail populations
PRINTING OF DISSOLVING MICRONEEDLE ARRAYS USING AEROSOL JET PRINTING TECHNOLOGY FOR TRANSDERMAL DELIVERY
Full text linkMicroneedles have been extensively studied for the transdermal delivery of drugs over the last number of decades. They are an attractive means for drug delivery as they are painless and can facilitate the delivery of drugs which would not ordinarily penetrate the skin. In recent times, additive manufacturing techniques such as stereolithography have been used to fabricate microneedles. However, research to date is limited to solid, hollow and coated microneedles 1, 2 . Stereolithography methods do not lend themselves well to dissolving microneedle fabrication. The traditional method of fabricating dissolving microneedles by micro-moulding techniques has its drawbacks such as variability in the administered dose, non reproducibility, needle breakage upon removing from moulds and long curing times. Aerosol Jet Printing is an additive manufacturing technique which may overcome these issues due to its high reproducibility and precision. Structures are formed as the instrument creates an aerosol mist and deposits the ink dropwise in a controlled manner onto a substrate, thus building up layers to form a microneedle array. The instrument gives freedom of design, in terms of needle shape and spacing, allows for increased drug loading capacity as no backing layer is present and can print formulations with a wide range of viscosities. Here we report the manufacture of the first dissolving microneedle array fabricated by Aerosol Jet Printing. The formulation is a mixture containing PVP, trehalose, glycerol and water. The formulation characteristics include a measured viscosity of 3.82 ± 0.22 cP and surface tension of 63.76 ± 0.25 mN/m. The formulation was deposited onto a double sided polished silicon wafer via ultrasonic atomisation. The printed microneedle array consisted of 64 needles which was made up of 75 layers of the deposited formulation. Print times for a full array is less than 150 min. The fabricated needles are printed at temperatures below 50° C, therefore, the technique is suitable for many thermolabile active ingredients. The potential for the fabricated microneedle arrays to penetrate porcine skin is currently being evaluated. Future work will focus on the inclusion of therapeutic peptide molecules into the microneedle array and the study of the release properties from the array using Franz diffusion cells
Creating a transdisciplinary landscape biography of Kilrossanty parish, Comeragh Mountains, Ireland, using GIS mapping
Full text linkLandscape biographies have gained in popularity in recent years as a holistic assessment tool to enable local government planning and also to promote a community’s sense of place and identity. The approach however, has yet to be applied to the Republic of Ireland’s unique historic and cultural landscape. This thesis aims to address this omission by exploring how previous biographical approaches can be adapted and applied to Ireland, by using the region of Kilrossanty parish, situated in County Waterford in the south east of the island, as a case study. The new methodology intends to complement the current governmental approach to landscape assessment in Ireland which focuses solely on Landscape Character Assessments. The thesis argues that the complexities of the Irish historical background require a more layered approach for which a biography is more appropriate. By conducting transdisciplinary fieldwork, an Irish landscape biographical model has been produced focusing upon the landscape’s structural transformations and identification of its authors who have been categories to better reflect the societal and political strata of this formerly colonised country
Deep Learning for Autonomic SLA Management of NFV Resources towards Next Generation Networks
Full text linkRecent advancements in the domain of Network Function Virtualization (NFV), and the
rollout of next-generation networks have led to a new era of applications delivered via a
paradigm of flexible and softwarized communication networks. This has opened the market
to a wider movement towards virtualized applications and services in key verticals such
as automated vehicles, smart grid, virtual reality (VR), Internet of Things (IoT), industry
4.0, telecommunications, etc. This has necessitated the requirement for the upkeep of
latency-critical application architectures in future networks and communications. While
Cloud service providers recognize the evolving mission-critical requirements in latency
sensitive verticals, there is a wide gap to bridge the Quality of Service (QoS) constraints
for the end-user experience. Most latency-critical services are over-provisioned on all
fronts to offer reliability, which is inefficient towards scalability in the long run.
The research presented in this work aims to address the challenges behind effectively
managing the trade-off between efficiency and reliability when considering latency critical
applications based in a high-availability network slice in next-generation softwarized
networks. In the course of research done in this work, we design and develop algorithms
to address the complexity towards meeting QoS demands in serving upcoming verticals
through the softwarised network architecture, and develop deep learning based frameworks
for proactive SLA management in the use-case of a latency-critical NFV application. We
utilize data from a real-world deployment to configure and draft a realistic set of Service
Level Objectives (SLOs) for a voice based NFV application, and leverage various machine
learning based methodologies to proactively identify and predict multiple categories of
SLO breaches associated with an application state. With this, we aim to gain granular
SLA and SLO violation insights, enabling us to study and mitigate their impact and inform
precision in drafting proactive scaling policies in future
Enantioselective Synthesis of Biologically Relevant Molecules Using Catalysis in Continuous Flow
Full text linkThe overarching aim of this work was to engineer and develop a continuous flow process for the synthesis of 3-substituted-3-hydroxyoxindoles which are core moieties of biological importance. The first part of this work involved transferring the L-leucinol catalysed aldol reaction of isatin with acetone from batch to continuous flow for the first time. An initial batch solvent screening revealed neat acetone as the media best suited in flow. Solvents with Kamlet-Taft basicity (β)>0.6 and proticity (α) ≈ 0 had a higher solubility of isatin but poor reaction performance while solvents with β<0.2 and α< 0.6 performed excellently in the reaction albeit with poor isatin solubility. Addition of 10 equivalents of water improved the neat reaction to afford 94% yield in 93% ee at 20°C after 48 h.
Having identified an ideal solvent in the batch screening, a PTFE tubing reactor was fabricated, and the identified optimal batch conditions transferred to flow and optimised. Complete conversions were obtained in 12 h residence time at 40°C without a loss in enantioselectivity. Other variants of isatin were also tested in batch and flow and in all cases, the reaction proceeded excellently with the flow reaction outperforming that in batch. Some isatin derivatives required a 4-fold dilution to achieve a solubility transferable to continuous flow, however, excellent yields and enantioselectivities were obtained in most cases.
A second part of the substrate scope studies sought to examine the diastereoselective and regioselective potentials of the L-leucinol catalysed reactions of isatin with enolisable ketones for the first time. Reactions with symmetrical ketones, unsymmetrical ketones and cyclic ketones were carried out in batch and interestingly, high enantioselectivity and diastereoselectivity was observed with symmetrical ketones and cyclic ketones. Reactions with unsymmetrical ketones also proceeded smoothly but afforded two regioisomers indicating leucinol is a non-regioselective organocatalyst.
Another major part of this work involved the use of aerosol jet printing and stereolithography (SLA) 3D printing for rapid prototyping of moulds which would be utilised for soft lithography fabrication of microfluidic devices. Moulds with the desired channels size (300 μm width and height) were printed using the SLA 3D printer, silanised and successfully used to fabricate PDMS based microfluidic devices. While reactions through our PDMS device were not successful, the proof of concept was demonstrated and could be extended to other replica moulding techniques which utilise polymers with better solvent and chemical resistant properties
A bibliometric analysis of the literature on the market orientation of higher education institutions
Full text linkPurpose The purpose of this paper is to provide a bibliometric analysis of the research on market orientation (MO) as it relates to higher education institutions (HEI). Methodology The Scopus database was used to identify 170 relevant publications over a thirty-year period. The Scopus database functionality and VOSviewer software were subsequently used to address the research purpose. Findings Identifies the journal that has published the maximum number of papers on market orientation as it relates to higher education; the years which have the maximum number of papers published; the most cited papers, authors and journals; the most prolific authors and the most prolific higher education institutions and countries; the authors which have co-authored the maximum, with other authors; the countries’ authors which have co-authored the maximum with the authors of other countries; the most frequently appearing keywords and which citations, journals, authors have been co-cited to the greatest degree. Research Implications This study contributes to the existing literature on MO in HE. A comprehensive and reliable picture of the research area is provided using bibliometric techniques. The results can help in guiding authors interested in conducting future research on this topic
Aspects of low fertiliser nitrogen input seasonal pasture-based milk production
Full text linkSynthetic fertiliser nitrogen (N) is a significant contributor to the environmental footprints of dairy products from pasture-based systems. Biological N fixation (BNF) in association with white clover can reduce dependency on fertiliser N and consequently lower environmental footprints. This thesis investigated aspects of white clover management strategies in seasonal pasture-based dairy production. One experiment quantified the supply of background N in Irish permanent grasslands. Another investigated the productivity of white clover-based grassland for milk production based on several systems-scale studies. A third experiment examined the effect of fertiliser N input to grass-clover swards and calving date on the productivity of pasture-based dairy production. Mean background N was 141 kg ha-1 across Irish grasslands and varied both temporally and spatially during the growing season. The background N was influenced by soil physical and chemical properties along with meteorological factors. Dairy production based on low-input clover-based grassland receiving fertiliser N input of approximately 97 kg N ha-1 was similar to N-fertilised grass-only receiving 244 kg N ha-1 in several systems-scale studies. Mean annual and seasonal pasture production per ha and milk production per cow was similar between these two grassland systems. Sward white clover and BNF decreased with increasing annual N fertilisation. A mean calving date in mid-February is recommended for zero-fertiliser N input white clover-based systems. A later than typical calving date (in mid-April) resulted in inefficient use of pasture for milk production in a zero-fertiliser N white clover-based system. Extending lactation into the following winter resulted in lower concentrations of milk constituents and affected processing characteristics of late lactation milk. Nevertheless, maximising overwintering of stolon and root dry matter mass by tight winter grazing increased white clover productivity and persistence in grassland. There is considerable potential for milk production on clover-based swards receiving low or no input of fertiliser N
Mitigating the Effects of Precarity: Brazilian Migrant Workers and Place-Making in Rural Ireland
Full text linkThis research aimed to investigate the everyday lived experiences of Brazilian migrant
workers with precarity in rural Ireland. The study sought to understand how different
factors contributed to shaping their overall experience as migrants. The research had one
main objective, to examine the social conditions of precarity affecting Brazilian migrant
workers, and to analyse how they mitigate the challenges of living precarious lives. The
qualitative study incorporated participant observation and semi-structured interviews
with 21 participants carried out over a period of 18 months of intermittent fieldwork.
Fieldwork took place predominantly in the small rural town of Gort as well as the towns
of Roscommon, Ennis, and Waterford city. The study relied on an adaptation of
Abdelmalek Sayad’s double absence theory (2004), incorporating place and placemaking
theory (Agnew 2005; Tuan 1977; Relph 1976; Gieryn 2000) to the former as a
means to expand its explanatory power. Place theory was employed in the study to grasp
the Brazilian migrant workers’ response to precarity.
The study demonstrated that the State, its immigration policies, and the status which they
produce create and compound vulnerabilities amongst the Brazilian migrant population
in rural Ireland. It also illustrated the costs experienced by Brazilian migrant workers as
a result of living in precarity. Through an analysis of findings centred on work, the costs
of migrant precarity, community, and home, this doctoral thesis has made an original
contribution to knowledge in the field of migration studies, by providing an in-depth
understanding of the social conditions prevailing among Brazilian migrant workers living
in precarity in rural Ireland and the strategies employed by them to mitigate the negative
effects of migration and precarity
Part-Time Learners Perceptions of Success During ERT
Full text linkThe Faculty of Lifelong Learning at South East Technological University’s Carlow campus, is one of the largest providers of part-time learning in the Irish Higher Education sector. A large majority of our lifelong learners, 88%, are adult learners over the age of 23, therefore the perspectives of our part-time learners offer us valuable insights into adult learner experiences in the Irish Higher Education sector. The outbreak of COVID-19 saw us pivot our provision to an emergency remote teaching (ERT) model in the first wave of the pandemic. The faculty undertook an extensive study of its learners in 2021 to examine the impacts of ERT on learners, and this article takes a qualitative approach to the findings of this study, looking specifically at learners’ comments about success, and the barriers to success which ERT posed. Our study provided an opportunity to learn about our learners’ conceptions of student identity, and how they interpret success as part-time learners