3,589 research outputs found

    Nanotopography of Polystyrene/Poly(methyl methacrylate) for the Promotion of Patient Specific Von Willebrand Factor Entrapment and Platelet Adhesion in a Whole Blood Microfluidic Assay

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    Platelet function testing is essential for the diagnosis of patients with bleeding disorders. Specifically, there is a need for a whole blood assay that is capable of analysing platelet behaviour in contact with a patient-specific autologous von Willebrand factor (vWF), under physiologically relevant conditions. The creation of surface topography capable of entrapping and uncoiling vWF for the support of subsequent platelet adhesion within the same blood sample offers a potential basis for such an assay. In this study, spin coating of polystyrene/poly (methyl methacrylate) (PS/PMMA) demixed solutions onto glass substrates in air has been used to attain surfaces with well-defined topographical features. The effect of augmenting the PS/PMMA solution with uniform 50 Āµm PS microspheres that can moderate the demixing process on the resultant surface features has also been investigated. The topographical features created here by spin coating under ambient air pressure conditions, rather than in nitrogen, which previous work reports, produces substrate surfaces with the ability to entrap vWF from flowing blood and facilitate platelet adhesion. The direct optical visualisation of fluorescently-labelled platelets indicates that topography resulting from inclusion of PS microspheres in the PS/PMMA spin coating solution increases the total number of platelets that adhere to the substrate surface over the period of the microfluidic assay. However, a detailed analysis of the adhesion rate, mean translocating velocity, mean translocation distance, and fraction of the stably adhered platelets measured during blood flow under arterial equivalent mechanical shear conditions indicates no significant difference for topographies created with or without inclusion of the PS microspheres.Ā </p

    A combined experimental and computational study on the reaction of fluoroarenes with Mgā€“Mg, Mgā€“Zn, Mgā€“Al and Alā€“Zn bonds

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    Through a combined experimental and computational (DFT) approach, the reaction mechanism of the addition of fluoroarenes to Mgā€“Mg bonds has been determined as a concerted S_{N}Ar-like pathway in which one Mg centre acts as a nucleophile and the other an electrophile. The experimentally determined Gibbs activation energy for the addition of Cā‚†Fā‚† to a Mgā€“Mg bond of a molecular complex, Ī”Gā€”_{ā‚‚ā‚‰ā‚ˆK}(experiment) = 21.3 kcal molā»Ā¹ is modelled by DFT with the Ļ‰B97X functional, Ī”Gā€”ā‚‚ā‚‰ā‚ˆ {K}_(DFT) = 25.7 kcal molā»Ā¹. The transition state for Cā€“F activation involves a polarisation of the Mgā€“Mg bond and significant negative charge localisation on the fluoroarene moiety. This transition state is augmented by stabilising closed-shell Mgā‹ÆF_{ortho} interactions that, in combination with the known trends in Cā€“F and Cā€“M bond strengths in fluoroarenes, provide an explanation for the experimentally determined preference for Cā€“F bond activation to occur at sites flanked by ortho-fluorine atoms. The effect of modification of both the ligand coordination sphere and the nature and polarity of the Mā€“M bond (M = Mg, Zn, Al) on Cā€“F activation has been investigated. A series of highly novel Ī²-diketiminate stabilised complexes containing Znā€“Mg, Znā€“Znā€“Zn, Znā€“Al and Mgā€“Al bonds has been prepared, including the first crystallographic characterisation of a Mgā€“Al bond. Reactions of these new Mā€“M containing complexes with perfluoroarenes were conducted and modelled by DFT. Cā€“F bond activation is dictated by the steric accessibility, and not the polarity, of the Mā€“M bond. The more open coordination complexes lead to enhanced Mgā‹ÆF_{ortho} interactions which in turn lower the energy of the transition states for Cā€“F bond activation

    Keeper-animal interactions: differences between the behaviour of zoo animals affect stockmanship

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    Stockmanship is a term used to describe the management of animals with a good stockperson someone who does this in a in a safe, effective, and low-stress manner for both the stock-keeper and animals involved. Although impacts of unfamiliar zoo visitors on animal behaviour have been extensively studied, the impact of stockmanship i.e familiar zoo keepers is a new area of research; which could reveal significant ramifications for zoo animal behaviour and welfare. It is likely that different relationships are formed dependant on the unique keeper-animal dyad (human-animal interaction, HAI). The aims of this study were to (1) investigate if unique keeper-animal dyads were formed in zoos, (2) determine whether keepers differed in their interactions towards animals regarding their attitude, animal knowl- edge and experience and (3) explore what factors affect keeper-animal dyads and ultimately influence animal behaviour and welfare. Eight black rhinoceros (Diceros bicornis), eleven Chapmanā€™s zebra (Equus burchellii), and twelve Sulawesi crested black macaques (Macaca nigra) were studied in 6 zoos across the UK and USA. Subtle cues and commands directed by keepers towards animals were identified. The animals latency to respond and the respective behavioural response (cue-response) was recorded per keeper-animal dyad (n=93). A questionnaire was constructed following a five-point Likert Scale design to record keeper demographic information and assess the job satisfaction of keepers, their attitude towards the animals and their perceived relationship with them. There was a significant difference in the animalsā€™ latency to appropriately respond after cues and commands from different keepers, indicating unique keeper-animal dyads were formed. Stockmanship style was also different between keepers; two main components contributed equally towards this: ā€œattitude towards the animalsā€ and ā€œknowledge and experience of the animalsā€. In this novel study, data demonstrated unique dyads were formed between keepers and zoo animals, which influenced animal behaviour

    The effect of deworming on growth in one-year-old children living in a soil-transmitted helminth-endemic area of Peru: a randomized controlled trial

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    BACKGROUND:Appropriate health and nutrition interventions to prevent long-term adverse effects in children are necessary before two years of age. One such intervention may include population-based deworming, recommended as of 12 months of age by the World Health Organization in soil-transmitted helminth (STH)-endemic areas; however, the benefit of deworming has been understudied in early preschool-age children. METHODOLOGY/PRINCIPAL FINDINGS:A randomized, double-blind, placebo-controlled trial was conducted to determine the effect of deworming (500 mg single-dose crushed mebendazole tablet) on growth in one-year-old children in Iquitos, Peru. Children were enrolled during their routine 12-month growth and development clinic visit and followed up at their 18 and 24-month visits. Children were randomly allocated to: Group 1: deworming at 12 months and placebo at 18 months; Group 2: placebo at 12 months and deworming at 18 months; Group 3: deworming at both 12 and 18 months; or Group 4: placebo at both 12 and 18 months (i.e. control group). The primary outcome was weight gain at the 24-month visit. An intention-to-treat approach was used. A total of 1760 children were enrolled between September 2011 and June 2012. Follow-up of 1563 children (88.8%) was completed by July 2013. STH infection was of low prevalence and predominantly light intensity in the study population. All groups gained between 1.93 and 2.05 kg on average over 12 months; the average difference in weight gain (kg) compared to placebo was: 0.05 (95% CI: -0.05, 0.17) in Group 1; -0.07 (95%CI: -0.17, 0.04) in Group 2; and 0.04 (95%CI: -0.06, 0.14) in Group 3. There was no statistically significant difference in weight gain in any of the deworming intervention groups compared to the control group. CONCLUSIONS:Overall, with one year of follow-up, no effect of deworming on growth could be detected in this population of preschool-age children. Low baseline STH prevalence and intensity and/or access to deworming drugs outside of the trial may have diluted the potential effect of the intervention. Additional research is required to overcome these challenges and to contribute to strengthening the evidence base on deworming. TRIAL REGISTRATION:ClinicalTrials.gov (NCT01314937)

    Interfacial Origin of the Magnetisation Suppression of Thin Film Yttrium Iron Garnet

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    Yttrium iron garnet has a very high Verdet constant, is transparent in the infrared and is an insulating ferrimagnet leading to its use in optical and magneto-optical applications. Its high Q-factor has been exploited to make resonators and filters in microwave devices, but it also has the lowest magnetic damping of any known material. In this article we describe the structural and magnetic properties of single crystal thin-film YIG where the temperature dependence of the magnetisation reveals a decrease in the low temperature region. In order to understand this complex material we bring a large number of structural and magnetic techniques to bear on the same samples. Through a comprehensive analysis we show that at the substrate -YIG interface, an interdiffusion zone of only 4 - 6nm exists. Due to the interdiffusion of Y from the YIG and Gd from the substrate, an addition magnetic layer is formed at the interface whose properties are crucially important in samples with a thickness of YIG less than 200nm

    The Surface Characterisation of Fused Filament Fabricated (FFF) 3D Printed PEEK/Hydroxyapatite Composites

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    Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer which has found increasing application in orthopaedics and has shown a lot of promise for ā€˜made-to-measureā€™ implants via additive manufacturing approaches. However, PEEK is bioinert and needs to undergo surface modification to make it at least osteoconductive to ensure a more rapid, improved, and stable fixation that will last longer in vivo. One approach to solving this issue is to modify PEEK with bioactive agents such as hydroxyapatite (HA). The work reported in this study demonstrates the direct 3D printing of PEEK/HA composites of up to 30 weight percent (wt%) HA using a Fused Filament Fabrication (FFF) approach. The surface characteristics and in vitro properties of the composite materials were investigated. X-ray diffraction revealed the samples to be semi-crystalline in nature, with X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealing HA materials were available in the uppermost surface of all the 3D printed samples. In vitro testing of the samples at 7 days demonstrated that the PEEK/HA composite surfaces supported the adherence and growth of viable U-2 OS osteoblast like cells. These results demonstrate that FFF can deliver bioactive HA on the surface of PEEK bio-composites in a one-step 3D printing process
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