Now showing items 1-20 of 8641

    • Pluronic F127 thermosensitive injectable smart hydrogels for controlled drug delivery system development

      Shriky, Banah; Kelly, Adrian L.; Isreb, Mohammad; Babenko, Maksims; Mahmoudi, N.; Rogers, S.; Shebanova, O.; Snow, T.; Gough, Timothy D. (2020-04-01)
      Understanding structure-property relationships is critical for the development of new drug delivery systems. This study investigates the properties of Pluronic smart hydrogel formulations for future use as injectable controlled drug carriers. The smart hydrogels promise to enhance patient compliance, decrease side effects and reduce dose and frequency. Pharmaceutically, these systems are attractive due to their unique sol-gel phase transition in the body, biocompatibility, safety and injectability as solutions before transforming into gel matrices at body temperature. We quantify the structural changes of F127 systems under controlled temperature after flow, as experienced during real bodily injection. Empirical formulae combining the coupled thermal and shear dependency are produced to aid future application of these systems. Induced structural transitions measured in-situ by small angle x-ray and neutron scattering reveal mixed oriented structures that can be exploited to tailor the drug release profile.
    • An approximation to the PTT viscoelastic model for Gas Assisted Injection Moulding simulation

      Olley, Peter (2020)
      An approximation to the Phan-Thien Tanner (PTT) constitutive model is developed with the aim of giving low-cost simulation of Gas Assisted Injection Moulding (GAIM) while incorporating important viscoelastic characteristics. It is shown that the developed model gives a response typical of full viscoelastic models in transient and steady state uniaxial and constant shear rate deformations. The model is incorporated into a 3D finite element GAIM simulation which uses the ‘pseudo-concentration’ method to predict residual polymer, and applied to published experimental results for a Boger fluid and a shear-thinning polystyrene melt. It is shown that the simulation gives a very good match to published results for the Boger fluid which show increasing Residual Wall Thickness (RWT) with increasing Deborah number. Against the shear-thinning polymer, the quality of match depends upon which of two ‘plausible’ relaxation times is chosen; qualitatively different results arise from two different means of estimating a single relaxation time. A ‘multi-mode’ approach is developed to avoid this uncertainty. It is shown that the multi-mode approach gives decreasing RWT with increasing Deborah number in agreement with the published experimental results, and avoids the issues that arise from estimating a single relaxation time for a molten polymer.
    • Peace, War and Gender in the Modern Era

      Pankhurst, Donna T. (2019-03-19)
      The practices and conceptions of peace and war have been highly gendered throughout world history. Indeed, the defining of genders has often itself been rooted in ideas and experiences of war and violence, with men as warriors, and women as the embodiment of peace. It is certainly the case that throughout human history the majority of war combatants have been men. By contrast many women have used their gendered identities, as mothers and guardians of life, in their activism in global peace movements, and in peacemaking at very local levels all over the globe. These gendered experiences of women and men have resonance everywhere in the world, but are also stereotypes. As well as being warriors and the bearers of violence, men have also resisted dominant social pressures to fight, and been active in movements to build peace. Women have also cajoled men, and socialised boys, to fight, and shamed those who did not. Thus, whereas a focus on the stereotypes suggests that the differences between women and men are due to their violent or peaceful natures, paying attention to the full range of behaviour of women and men makes it self-evident that these differences cannot be explained by biological differences alone, because they are so varied. Nonetheless, the roles played by women and men that go beyond the simple stereotypes are persistently regarded as transgressive or insignificant in many cultures, making it difficult to keep the broader picture in mind. That is not to say that gender differences are not significant however; gender remains one of the most important lenses through which to understand war and peace.
    • An ontological approach for pathology assessment and diagnosis of tunnels

      Dimitrova, V.; Mehmood, M.O.; Thakker, Dhaval; Sage-Vallier, B.; Valdes, J.; Cohn, A.G. (ELSEVIER, 2020-04)
      Tunnel maintenance requires complex decision making, which involves pathology diagnosis and risk assessment, to ensure full safety while optimising maintenance and repair costs. A Decision Support System (DSS) can play a key role in this process by supporting the decision makers in identifying pathologies based on disorders present in various tunnel portions and contextual factors affecting a tunnel. Another key aspect is to identify which spatial stretches within a tunnel contain pathologies of similar kinds within neighbouring tunnel segments. This paper presents PADTUN, a novel intelligent decision support system that assists with pathology diagnosis and assessment of tunnels with respect to their disorders and diagnosis influencing factors. It utilises semantic web technologies for knowledge capture, representation, and reasoning. The core of PADTUN is a family of ontologies which represent the main concepts and relations associated with pathology assessment, and capture the decision process concerning tunnel maintenance. Tunnel inspection data is linked to these ontologies to take advantage of inference capabilities offered by semantic technologies. In addition, an intelligent mechanism is presented which exploits abstraction and inference capabilities. Thus PADTUN provides the world’s first semantically based intelligent DSS for tunnel maintenance. PADTUN was developed by an interdisciplinary team of tunnel experts and knowledge engineers in real-world settings offered by the NeTTUN EU Project. An evaluation of the PADTUN system is performed using real-world tunnel data and diagnosis tasks. We show how the use of semantic technologies allows addressing the complex issues of tunnel pathology inferencing, aiding in, and matching transportation experts’ expectations of decision support. The methodology is applicable to any linear transport structures, offering intelligent ways to aid with complex decision processes related to diagnosis and maintenance.
    • How reproducible is the acoustical characterization of porous media?

      Pompoli, F.; Bonfiglio, P.; Horoshenkov, K.V.; Khan, Amir; Jaouen, L.; Bécot, F-X.; Sgard, F.; Asdrubali, F.; D'Alessandro, F.; Hübelt, J.; et al. (2017-02)
      There is a considerable number of research publications on the characterization of porous media that is carried out in accordance with ISO 10534-2 (International Standards Organization, Geneva, Switzerland, 2001) and/or ISO 9053 (International Standards Organization, Geneva, Switzerland, 1991). According to the Web of Science(TM) (last accessed 22 September 2016) there were 339 publications in the Journal of the Acoustical Society of America alone which deal with the acoustics of porous media. However, the reproducibility of these characterization procedures is not well understood. This paper deals with the reproducibility of some standard characterization procedures for acoustic porous materials. The paper is an extension of the work published by Horoshenkov, Khan, Bécot, Jaouen, Sgard, Renault, Amirouche, Pompoli, Prodi, Bonfiglio, Pispola, Asdrubali, Hübelt, Atalla, Amédin, Lauriks, and Boeckx [J. Acoust. Soc. Am. 122(1), 345-353 (2007)]. In this paper, independent laboratory measurements were performed on the same material specimens so that the naturally occurring inhomogeneity in materials was controlled. It also presented the reproducibility data for the characteristic impedance, complex wavenumber, and for some related pore structure properties. This work can be helpful to better understand the tolerances of these material characterization procedures so improvements can be developed to reduce experimental errors and improve the reproducibility between laboratories.
    • Negative bubbles and shocks in cryptocurrency markets

      Fry, John; Cheah, E-T. (2016-10)
      In this paper we draw upon the close relationship between statistical physics and mathematical finance to develop a suite of models for financial bubbles and crashes. The derived models allow for a probabilistic and statistical formulation of econophysics models closely linked to mainstream financial models. Applications include monitoring the stability of financial systems and the subsequent policy implications. We emphasise the timeliness of our contribution with an application to the two largest cryptocurrency markets: Bitcoin and Ripple. Results shed new light on emerging debates over the nature of cryptocurrency markets and competition between rival digital currencies.
    • Quantifying the sustainability of Bitcoin and Blockchain

      Fry, John; Serbera, J-P. (2020)
      Purpose: We develop new quantitative methods to estimate the level of speculation and long-term sustainability of Bitcoin and Blockchain. Design/Methodology/Approach: We explore the practical application of speculative bubble models to cryptocurrencies. We then show how the approach can be extended to provide estimated brand values using data from Google Trends. Findings: We confirm previous findings of speculative bubbles in cryptocurrency markets. Relatedly, Google searches for cryptocurrencies seem to be primarily driven by recent price rises. Overall results are sufficient to question the long-term sustainability of Bitcoin with the suggestion that Ethereum, Bitcoin Cash and Ripple may all enjoy technical advantages relative to Bitcoin. Our results also demonstrate that Blockchain has a distinct value and identity beyond cryptocurrencies - providing foundational support for the second generation of academic work on Blockchain. However, a relatively low estimated long-term growth rate suggests that the benefi ts of Blockchain may take a long time to be fully realised. Originality/value: We contribute to an emerging academic literature on Blockchain and to a more established literature exploring the use of Google data within business analytics. Our original contribution is to quantify the business value of Blockchain and related technologies using Google Trends.
    • Sensationalism and speaking to the public: scientific rigour and interdisciplinary collaborations in palaeopathology

      Snoddy, A.M.E.; Beaumont, Julia; Buckley, H.R.; Colombo, A.; Halcrow, S.E.; Kinaston, R.L.; Vlok, M. (Elsevier, 2020-03)
      Objectives: In this brief communication we discuss issues concerning scientific rigour in palaeopathological publications, particularly studies published in clinical or general science journals, that employ skeletal analysis to elucidate the lives and deaths of historical figures or interpret “mysterious” assemblages or burials. We highlight the relationship between poor methodological rigour and lack of interdisciplinary communication, and discuss how this can result in scientifically weak, sensational narratives being presented to the public. Conclusions: Although most high profile publications involving analysis of archaeological human remains are methodologically sound and well interpreted, others have suffered from poor scientific rigour stemming from an apparent lack of awareness of anthropological methods and ethics. When these publications are highlighted by the press, sensationalistic narratives are perpetuated which may reflect poorly on our discipline and give the public unrealistic expectations about our work. Suggestions for future research: We suggest that best practice in high-profile paleopathological research include recruitment of a range of authors and reviewers from clinical sciences, anthropology, and the humanities, consideration of the ethical issues surrounding retrospective diagnosis, and transparency with the press in regards to the limitations inherent in this kind of work.
    • Predicting the location of weld line in microinjection-molded polyethylene via molecular orientation distribution

      Liao, T.; Zhao, X.; Yang, X.; Whiteside, Benjamin R.; Coates, Philip D.; Jiang, Z.; Men, Y. (2019-01)
      The microstructure and molecular orientation distribution over both the length and the thickness of microinjection‐molded linear low‐density polyethylene with a weld line were characterized as a function of processing parameters using small‐angle X‐ray scattering and wide‐angle X‐ray diffraction techniques. The weld line was introduced via recombination of two separated melt streams with an angle of 180° to each other in injection molding. The lamellar structure was found to be related to the mold temperature strongly but the injection velocity and the melt temperature slightly. Furthermore, the distributions of molecular orientation at different molding conditions and different positions in the cross section of molded samples were derived from Hermans equation. The degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with an increase of both mold temperature and melt temperature, which could be explained by the stress relaxation of sheared chains and the reduced melt viscosity, respectively. The level of molecular orientation was found to be lowest in the weld line when varying injection velocity, mold temperature, and melt temperature, thus providing an effective means to identify the position of weld line induced by flow obstacles during injection‐molding process.
    • Organic synthesis by Twin Screw Extrusion (TSE): Continuous, scalable and solvent-free

      Crawford, Deborah E.; Miskimmin, C.K.G.; Albadarin, A.B.; Walker, G.; James, S.L. (2017-01)
      Mechanochemistry provides a method to reduce or eliminate the use of solvents by carrying out reactions through the grinding of neat reagents. Until recently a significant drawback of this form of synthesis has been the limited ability to scale up. However, it has been shown that twin screw extrusion (TSE) may overcome this problem as demonstrated in the continuous synthesis of co-crystals, Metal Organic Frameworks (MOFs) and Deep Eutectic Solvents (DES), in multi kg h−1 quantities. TSE has provided a means to carry out mechanochemical synthesis in a continuous, large scale and efficient fashion, which is adaptable to a manufacturing process. Herein, we highlight the potential of this technique for organic synthesis by reporting four condensation reactions, the Knoevenagel condensation, imine formation, aldol reaction and the Michael addition, to produce analytically pure products, most of which did not require any post synthetic purification or isolation. Each reaction was carried out in the absence of solvents and the water byproduct was conveniently removed as water vapour during the extrusion process due to the elevated temperatures used. Furthermore, the Knoevenagel condensation has been studied in detail to gain insight into the mechanism by which these mechanochemical reactions proceed. The results point to effective wetting of one reactant by another as being critical for these reactions to occur under these reaction conditions.
    • Feedback Kinetics in Mechanochemistry: The Importance of Cohesive States.

      Hutchings, B.P.; Crawford, Deborah E.; Gao, L.; Hu, P.; James, S.L. (2017-11-27)
      Although mechanochemical synthesis is becoming more widely applied and even commercialised, greater basic understanding is needed if the field is to progress on less of a trial‐and‐error basis. We report that a mechanochemical reaction in a ball mill exhibits unusual sigmoidal feedback kinetics that differ dramatically from the simple first‐order kinetics for the same reaction in solution. An induction period is followed by a rapid increase in reaction rate before the rate decreases again as the reaction goes to completion. The origin of these unusual kinetics is found to be a feedback cycle involving both chemical and mechanical factors. During the reaction the physical form of the reaction mixture changes from a powder to a cohesive rubber‐like state, and this results in the observed reaction rate increase. The study reveals that non‐obvious and dynamic rheological changes in the reaction mixture must be appreciated to understand how mechanochemical reactions progress.
    • Synthesis by extrusion: continuous, large-scale preparation of MOFs using little or no solvent

      Crawford, Deborah E.; Casaban, J.; Haydon, R.; Giri, N.; McNally, T.; James, S.L. (2015-03)
      Grinding solid reagents under solvent-free or low-solvent conditions (mechanochemistry) is emerging as a general synthetic technique which is an alternative to conventional solvent-intensive methods. However, it is essential to find ways to scale-up this type of synthesis if its promise of cleaner manufacturing is to be realised. Here, we demonstrate the use of twin screw and single screw extruders for the continuous synthesis of various metal complexes, including Ni(salen), Ni(NCS)2(PPh3)2 as well as the commercially important metal organic frameworks (MOFs) Cu3(BTC)2 (HKUST-1), Zn(2-methylimidazolate)2 (ZIF-8, MAF-4) and Al(fumarate)(OH). Notably, Al(fumarate)(OH) has not previously been synthesised mechanochemically. Quantitative conversions occur to give products at kg h−1 rates which, after activation, exhibit surface areas and pore volumes equivalent to those of materials produced by conventional solvent-based methods. Some reactions can be performed either under completely solvent-free conditions whereas others require the addition of small amounts of solvent (typically 3–4 mol equivalents). Continuous neat melt phase synthesis is also successfully demonstrated by both twin screw and single screw extrusion for ZIF-8. The latter technique provided ZIF-8 at 4 kg h−1. The space time yields (STYs) for these methods of up to 144 × 103 kg per m3 per day are orders of magnitude greater than STYs for other methods of making MOFs. Extrusion methods clearly enable scaling of mechanochemical and melt phase synthesis under solvent-free or low-solvent conditions, and may also be applied in synthesis more generally.
    • A Truly Future-Oriented Legal Framework for Fintech in the EU

      Kapsis, Ilias (2020)
      This article reviews critically the recent EU legislation and proposals for the regulation of financial technology (‘fintech”) and makes recommendations for legal improvements in the proposed frameworks, which will help to accelerate fintech growth, a declared EU goal, in the years to come. The rise of fintech driven by non-bank entities (technology startups, finance, big tech and big retail companies) helps to transform financial services industry, but also threatens the market positions of traditional banks and through them potentially the stability of the financial system. The current EU proposals, as presented in the Commission’s Fintech Action Plan published in 2018 and follow-up measures, outlined a number of steps to support fintech, while ensuring the protection of market stability and consumers and the maintenance of level playing field in the financial services markets. The article argues that, while the Commission’s proposed policy mix contains certain positive measures for fintech, it remains, overall, conservative and favours the incumbents. It also argues that unless the Commission becomes bolder and adopts a more flexible legal framework for fintech (for which the article makes specific recommendations), the latter will not grow at the pace needed to help build a competitive ad-vantage for the EU financial sector. The Commission’s continuing support of the established market landscape dominated by financial conglomerates employing traditional business models risks undermining the ability of the European financial system to adapt to the changing competition landscape created by advancing financial technologies and to fully address stability concerns, which emerged as a result of the financial crisis.
    • Recent developments of reconfigurable antennas for 4G and 5G wireless communications: A survey

      Ojaroudi Parchin, Naser; Basherlou, H.J.; Al-Yasir, Yasir; Abd-Alhameed, Raed A.; Abdulkhaleq, A.M.; Noras, James M. (Avid Science, 2019-12)
      Reconfigurable antennas play important roles in smart and adaptive systems and are the subject of many research studies. They offer several advantages such as multifunctional capabilities, minimized volume requirements, low front-end processing efforts with no need for a filtering element, good isolation, and sufficient out-ofband rejection; these make them well suited for use in wireless applications such as fourth generation (4G) and fifth generation (5G) mobile terminals. With the use of active materials such as microelectromechanical systems (MEMS), varactor or p-i-n (PIN) diodes, an antenna’s characteristics can be changed through altering the current flow on the antenna structure. If an antenna is to be reconfigurable into many different states, it needs to have an adequate number of active elements. However, a large number of high-quality active elements increases cost, and necessitates complex biasing networks and control circuitry. We review some recently proposed reconfigurable antenna designs suitable for use in wireless communications such as cognitiveratio (CR), multiple-input multiple-output (MIMO), ultra-wideband (UWB), and 4G/5G mobile terminals. Several examples of antennas with different reconfigurability functions are analyzed and their performances are compared. Characteristics and fundamental properties of reconfigurable antennas with single and multiple reconfigurability modes are investigated.
    • Limits and possibilities in the geolocation of humans using multiple isotope ratios (H, O, N, C) of hair from east coast cities of the USA

      Reynard, L.M.; Burt, N.; Koon, Hannah E.C; Tuross, N. (2016-07)
      We examined multiple natural abundance isotope ratios of human hair to assess biological variability within and between geographic locations and, further, to determine how well these isotope values predict location of origin. Sampling locations feature differing seasonality and mobile populations as a robust test of the method. Serially-sampled hair from Cambridge, MA, USA, shows lower δ2 H and δ18 O variability over a one-year time course than model-predicted precipitation isotope ratios, but exhibits considerable differences between individuals. Along a ∼13° northsouth transect in the eastern USA (Brookline, MA, 42.3 ° N, College Park, MD, 39.0 ° N, and Gainesville, FL, 29.7 ° N) δ18 O in human hair shows relatively greater differences and tracks changes in drinking water isotope ratios more sensitively than δ2 H. Determining the domicile of humans using isotope ratios of hair can be confounded by differing variability in hair δ18 O and δ2 H between locations, differential incorporation of H and O into this protein and, in some cases, by tap water δ18 O and δ2 H that differ significantly from predicted precipitation values. With these caveats, randomly chosen people in Florida are separated from those in the two more northerly sites on the basis of the natural abundance isotopes of carbon, nitrogen, hydrogen, and oxygen.
    • Basilar portion porosity: A pathological lesion possibly associated with infantile scurvy

      Moore, Joanna; Koon, Hannah E.C. (2017-09)
      Recent analysis of the juvenile (≤12 years) human remains from a 19th century site in Wolverhampton, England revealed a relatively high level of nutritional deficiency diseases within the population. Indeed, 41.7% of the 48 juvenile skeletons analysed exhibited a combination of porous and proliferative bone lesions consistent with the pathological alterations associated with nutritional stress. This paper describes a pathological lesion on the inferior surface of the basilar portion of the occipital bone, not previously reported in association with infantile scurvy, but which was exhibited by 90% (N=9) of the 10 scorbutic individuals identified during this study.
    • A carbon and nitrogen isotopic investigation of a case of probable infantile scurvy (6th- 4th centuries BC, Slovenia)

      Nicholls, Rebecca A.; Buckberry, Jo; Beaumont, Julia; Črešnar, M.; Mason, P.; Koon, Hannah E.C. (2020-04)
      This paper presents a case study of a young infant, from a larger isotopic and osteological investigation of Bronze/Iron Age (14th-4th century BC) skeletal assemblages from Croatia and Slovenia. The osteological analysis of this infant identified pathological lesions including abnormal porosity and new bone formation consistent with malnutrition and phases of recovery. The distribution and appearance of these pathological lesions (i.e. diffuse micro-porosities and plaques of subperiosteal new bone formation on the skull and long bones) led to the conclusion that this infant probably suffered from scurvy (vitamin C deficiency). The diet and nitrogen balance of this individual were investigated by incremental dentine sampling and stable carbon and nitrogen isotope analysis. This sampling method provided a high resolution record of dietary and metabolic changes from pre-birth to around the time of death. The resulting isotope data exhibited unusually high δ13C values for this region and time period (between -11.3‰ and -12.6‰), while δ15N values were observed to be c. 3‰ above that of rib collagen sampled from contemporary adults recovered from the same site. The isotope profiles generated from the incremental dentine analysis show that δ13C and especially δ15N continue to increase until death. The evidence from the skeletal remains and high resolution isotopic data support the hypothesis that this infant suffered from severe malnutrition and an increasingly negative nitrogen balance. The paper discusses some scenarios which could have resulted in these unusual isotope ratios, whilst considering the diagnosis of possible metabolic disease. The paper also addresses the need for context when interpreting isotopic results. The isotope data should not be viewed in isolation, but rather as part of a multidisciplinary approach, considering the multiple causes of isotopic variability.
    • Modelling the Mechanical and Strain Recovery Behaviour of Partially Crystalline PLA

      Sweeney, John; Spencer, Paul E.; Karthik, N.; Coates, Philip D. (MDPI, 2019-08-13)
      This is a study of the modelling and prediction of strain recovery in a polylactide. Strain recovery near the glass transition temperature is the underlying mechanism for the shape memory in an amorphous polymer. The investigation is aimed at modelling such shape memory behaviour. A PLA-based copolymer is subjected to stress-strain, stress relaxation and strain recovery experiments at large strain at 60 °C just below its glass transition temperature. The material is 13% crystalline. Using published data on the mechanical properties of the crystals, finite element modelling was used to determine the effect of the crystal phase on the overall mechanical behaviour of the material, which was found to be significant. The finite element models were also used to relate the stress-strain results to the yield stress of the amorphous phase. This yield stress was found to possess strain rate dependence consistent with an Eyring process. Stress relaxation experiments were also interpreted in terms of the Eyring process, and a two-process Eyring-based model was defined that was capable of modelling strain recovery behaviour. This was essentially a model of the amorphous phase. It was shown to be capable of useful predictions of strain recovery.
    • Observation and analysis on free surface air entrainment and single bubble movement in supercritical open channel flow

      Wei, W.; Xu, W.; Deng, J.; Guo, Yakun (2020)
      There has been little study on the microscopic bubble entrainment and diffusion process on the high-speed self-aerated flows although the problem under investigation is theoretically important and has important engineering application. This study presents an experimental investigation on visual processes of free surface air entrainment and single bubble diffusion in supercritical open channel flows. The typical surface deformation, single air bubble rising and penetration are recorded using a high-speed camera system. Results show that for a single bubble formation process, surface entrapment development and bubble entrainment through a deformation evolution underneath the free surface are the two main features. The shape variation of local surface deformation with time follows an identical power law for different bubble size generations. The entrained bubble size depends on both size scale and shape of entrapped free surface. As the single bubble moves downstream, its longitudinal velocity is approximately the same as that of water flow surrounded it, while its vertical velocity for rising and penetration increases with the increase of the water flow velocity. An empirical-linear relationship for the bubble rising and penetration velocity with water flow velocity is obtained. This study demonstrates that the microscopic bubble movement can improve the self-aeration prediction in the open channel flow and advance the knowledge of our understanding of the macroscopic and microscopic air–water properties in hydraulic engineering.
    • Entrepreneurs' Passion, Home Country's Institutional Voids and Small Firm Internationalization

      Adomako, Samuel; Amankwah-Amoah, J.; Chu, Irene (2020)
      The international entrepreneurship literature has revealed that entrepreneurs’ psychological characteristics drive a firm’s degree of internationalization. However, drivers that relate to entrepreneurs’ passion are not well developed in the international entrepreneurship literature. To fill this gap, this study uses a sample of 233 small firms to examine how entrepreneurs’ passion is related to small firms’ degree of internationalization and it also investigates whether this relationship is affected by levels of the home country’s institutional voids. The results show that passion is positively related to firms’ degree of internationalization and this relationship is positively moderated by levels of institutional voids. Implications for theory and practice are discussed.