• Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

      Carvalho, M. Fernanda N. N.; Ferreira, M. Joao; Knittel, Ana S. O.; Oliveira, Maria da C.; Pessoa, Joao C.; Herrmann, Rudolf; Wagner, Gabriele; Universidade de Lisboa; University of Augsburg; University of Chester (Beilstein-Institut, 2016-04-18)
      A camphor-derived sulfonimine with a conjugated carbonyl group, oxoimine 1 (O2SNC10H13O), reacts with amino acids (glycine, L-alanine, L-phenylalanine, L-leucine) to form a compound O2SNC10H13NC10H14NSO2 (2) which was characterized by spectroscopic means (MS and NMR) and supported by DFT calculations. The product, a single diastereoisomer, contains two oxoimine units connected by a –N= bridge, and thus has a structural analogy to the colored product Ruhemann´s purple obtained by the ninhydrin reaction with amino acids. A plausible reaction mechanism that involves zwitterions, a Strecker degradation of an intermediate imine and water-catalyzed tautomerizations was developed by means of DFT calculations on potential transition states.
    • Structural speciation in chemical reactivity profiling of binary-ternary systems of Ni(II) with iminodialcohol and aromatic chelators

      Salifoglou, Athanasios; Papadopoulos, Theodoros; Reimann, M. K.; Pöttgen, R.; Salifoglou, A.; Matsia, S.; Kaoulla, A.; Menelaou, M.; Hatzidimitriou, A.; Aristotle University of Thessaloniki; University of Chester; Universität Münster; Cyprus University of Technology (Elsevier, 2021-11-10)
      The importance of structural speciation in the control of chemical reactivity in Ni(II) binary-ternary systems, involving (O,O,N)-containing substrates (1,1’-iminodi-2-propanol), and aromatic chelators (2,2’-bipyridine, 1,10-phenanthroline), prompted the systematic synthesis of new crystalline materials characterized by elemental analysis, FT-IR, UV-Visible, Luminescence, TGA, magnetic susceptibility, and X-ray crystallography. The structures contain mononuclear octahedral assemblies, the lattice architecture of which exemplifies reaction conditions under which conformational variants and solvent-associated lattice-imposed complexes are assembled. Transformations between complex species denote their association with reactivity pathways, suggesting alternate synthetic methodologies for their isolation. Theoretical work (Hirshfeld, Electrostatic Potential, DFT) signifies the impact of crystal structure on energy profiles of the generated species. The arisen physicochemical profiles of all compounds portray a well-configured interwoven network of pathways, projecting strong connection between structural speciation and Ni(II) reactivity patterns in organic-solvent media. The collective results provide well-defined parameterized profiles, poised to influence the synthesis of new Ni(II)-iminodialcohol materials with specified structural-magneto-optical properties.
    • Structure and dielectric properties of double A-site doped bismuth sodium titanate relaxor ferroelectrics for high power energy storage applications

      Yang, Bin; Zhang, Hangfeng; Fortes, Dominic; Yan, Haixue; Abrahams, Isaac; University of Chester; Queen Mary University of London; Rutherford Appleton Laboratory
      The structural and dielectric properties of barium/strontium substituted Bi0.5Na0.5TiO3 were examined in compositions of general formula (Ba0.4Sr0.6TiO3)x(Bi0.5Na0.5TiO3)1-x. An average classic cubic perovskite structure is maintained from x = 0.5 to 1.0. The temperature dependence of dielectric properties of studied compositions shows relaxor-ferroelectric behaviour attributed to the existence of polar nano-regions. Ferroelectric measurements under variable temperature demonstrated two transitions from normal ferroelectric to relaxor-ferroelectric and relaxor-ferroelectric to paraelectric, at the dipole freezing temperature, Tf, and temperature of maximum permittivity, Tm, respectively. The obtained value of Tf coincides with the onset of linear thermal expansion of the cubic unit cell parameter obtained from high resolution powder neutron diffraction data. Careful analysis of the neutron diffraction data revealed no significant change in the average cubic structure from -263 to 150 C. However, changes in the Gaussian variance component of the neutron peak shape, reveal three distinct regions with transitions at about -100 and 100 C corresponding to the beginning and end of the dielectric dispersion seen in the permittivity and loss spectra. This variation in the Gaussian variance parameter is attributed to the activity of the polar nano-regions. The composition (Ba0.4Sr0.6)0.5(Bi0.5Na0.5)0.5TiO3 was found to exhibit the maximum recoverable energy storage density, with a value of 1.618 J cm-3 and 76.9% storage efficiency at a field of 17 kV mm-1.
    • Studies of black diamond as an antibacterial surface for gram negative bacteria: the interplay between chemical and mechanical bactericidal activity

      Dunseath, Olivia; Smith, E. J. W.; Al-Jeda, T.; Smith, J. A.; King, Sophie; May, Paul W.; Nobbs, Angela H.; Hazell, Gavin; Welch, Colin C.; Su, Bo; et al. (Nature, 2019-06-19)
      ‘Black silicon’ (bSi) samples with surfaces covered in nanoneedles of length ~5 μm were fabricated using a plasma etching process and then coated with a conformal uniform layer of diamond using hot filament chemical vapour deposition to produce ‘black diamond’ (bD) nanostructures. The diamond needles were then chemically terminated with H, O, NH2 or F using plasma treatment, and the hydrophilicity of the resulting surfaces were assessed using water droplet contact-angle measurements, and scaled in the order O > H ≈NH2 >F, with the F-terminated surface being superhydrophobic. The effectiveness of these differently terminated bD needles in killing the Gram-negative bacterium E. coli was semiquantified by Live/Dead staining and fluorescence microscopy, and visualised by environmental scanning electron microscopy. The total number of adhered bacteria was consistent for all the nanostructured bD surfaces at around 50% of the value for the flat diamond control. This, combined with a chemical bactericidal effect of 20–30%, shows that the nanostructured bD surfaces supported significantly fewer viable E. coli than flat surfaces. Moreover, the bD surfaces were particularly effective at preventing the establishment of bacterial aggregates – a precursor to biofilm formation. The percentage of dead bacteria also decreased as a function of hydrophilicity. These results are consistent with a predominantly mechanical mechanism for bacteria death based on the stretching and disruption of the cell membrane, combined with an additional effect from the chemical nature of the surface.
    • Studies of black silicon and black diamond as materials for antibacterial surfaces

      Hazell, Gavin; May, Paul W.; Taylor, Paul W.; Nobbs, Angela H.; Su, Bo; University of Bristol; Oxford Instruments Plasma Technology (Royal Society of Chemistry, 2018-03-27)
      ‘Black silicon’ (bSi) samples with surfaces covered in nanoneedles of varying length, areal density and sharpness, have been fabricated using a plasma etching process. These nanostructures were then coated with a conformal uniform layer of diamond using hot filament chemical vapour deposition to produce ‘black diamond’ (bD) surfaces. The effectiveness of these bSi and bD surfaces in killing Gram-negative (E. coli) and Gram-positive (S. gordonii) bacteria was investigated by culturing the bacteria on the surfaces for a set time and then measuring the live-to-dead ratio. All the nanostructured surfaces killed E. coli at a significantly higher rate than the respective flat Si or diamond control samples. The length of the needles was found to be less important than their separation, i.e. areal density. This is consistent with a model for mechanical bacteria death based on the stretching and disruption of the cell membrane, enhanced by the cells motility on the surfaces. In contrast, S. gordonii were unaffected by the nanostructured surfaces, possibly due to their smaller size, thicker cell membrane and/or their lack of motility.
    • Superfast solution of linear convolutional Volterra equations using QTT approximation

      Roberts, Jason A.; Savostyanov, Dmitry V.; Tyrtyshnikov, Eugene E.; University of Chester ; Russian Academy of Sciences / University of Chester ; Russian Academy of Sciences / Lomonosov Moscow State University (Elsevier, 2014-04)
      This article address a linear fractional differential equation and develop effective solution methods using algorithms for the inversion of triangular Toeplitz matrices and the recently proposed QTT format. The inverses of such matrices can be computed by the divide and conquer and modified Bini’s algorithms, for which we present the versions with the QTT approximation. We also present an efficient formula for the shift of vectors given in QTT format, which is used in the divide and conquer algorithm. As a result, we reduce the complexity of inversion from the fast Fourier level O(nlogn) to the speed of superfast Fourier transform, i.e., O(log^2n). The results of the paper are illustrated by numerical examples.
    • Surface adjustment strategy for a large radio telescope with adjustable dual reflectors

      Lian, Peiyuan; Wang, Congsi; Xue, Song; Xu, Qian; Shi, Yu; Jia, Yu; Xiang, Binbin; Wang, Yan; Yan, Yuefei; Xidian University; University of Chester; Chinese Academy of Sciences (IET, 2019-08-15)
      With the development of large-aperture and high-frequency radio telescopes, a surface adjustment procedure for the compensation of surface deformations has become of great importance. In this study, an innovative surface adjustment strategy is proposed to achieve an automated adjustment for the large radio telescope with adjustable dual reflectors. In the proposed strategy, a high-precision and long-distance measurement instrument is adopted and installed on the back of the sub-reflector to measure the distances and elevation angles of the target points on the main reflector. Here, two surface adjustment purposes are discussed. The first purpose is to ensure that the main reflector and sub-reflector are always positioned at their ideal locations during operation. The second purpose is to adjust the main reflector to the location of the best fitting reflector, and the sub-reflector to the focus of the best fitting reflector. Next, the calculation procedures for the adjustments of the main reflector and the sub-reflector are discussed in detail, and corresponding simulations are carried out to verify the proposed method. The results show that the proposed strategy is effective. This study can provide helpful guidance for the design of automated surface adjustments for large telescopes.
    • Surface glazing of concrete using lasers for protection and decommissioning

      Lawrence, Jonathan; Waugh, David G.; Shukla, Pratik; University of Chester (2015-01)
    • Surface passivation effect by fluorine plasma treatment on ZnO for efficiency and lifetime improvement of inverted polymer solar cells

      Polydorou, Ermioni; Zeniou, Angelos; Tsikritzis, Dimitris; Soultati, Anastasia; Sakellis, Ilias; Gardelis, Spyros; Papadopoulos, Theodoros A.; Briscoe, Joe; Palilis, Leonidas C.; Kennou, Stella; et al. (Royal Society of Chemistry, 2016-06-24)
      Zinc oxide (ZnO) is an important material for polymer solar cells (PSCs) where the characteristics of the interface can dominate both the efficiency and lifetime of the device. In this work we study the effect of fluorine (SF6) plasma surface treatment of ZnO films on the performance of PSCs with an inverted structure. The interaction between fluorine species present in the SF6 plasma and the ZnO surface is also investigated in detail. We provide fundamental insights into the passivation effect of fluorine by analyzing our experimental results and theoretical calculations and we propose a mechanism according to which a fluorine atom substitutes an oxygen atom or occupies an oxygen vacancy site eliminating an electron trap while it may also attract hydrogen atoms thus favoring hydrogen doping. These multiple fluorine roles can reduce both the recombination losses and the electron extraction barrier at the ZnO/fullerene interface improving the selectivity of the cathode contact. Therefore, the fabricated devices using the fluorine plasma treated ZnO show high efficiency and stable characteristics, irrespective of the donor : acceptor combinations in the photoactive blend. Inverted polymer solar cells, consisting of the P3HT:PC71BM blend, exhibited increased lifetime and high power conversion efficiency (PCE) of 4.6%, while the ones with the PCDTBT:PC71BM blend exhibited a PCE of 6.9%. Our champion devices with the PTB7:PC71BM blends reached a high PCE of 8.0% and simultaneously showed exceptional environmental stability when using the fluorine passivated ZnO cathode interlayers.
    • Surface treatments to modulate bioadhesion: A critical review

      Waugh, David G.; Toccaceli, Christina; Gillett, Alice R.; Ng, Chi-Ho; Hodgson, Simon D.; Lawrence, Jonathan; University of Chester (Scrivener Publishing, 2016-03-01)
      On account of the recent increase in importance of biological and microbiological adhesion in industries such as healthcare and food manufacturing many researchers are now turning to the study of materials, wettability and adhesion to develop the technology within these industries further. This is highly significant as the stem cell industry alone, for example, is currently worth £3.5 million in the United Kingdom (UK) alone. This paper reviews the current state-of-the-art techniques used for surface treatment with regards to modulating biological adhesion including laser surface treatment, plasma treatment, micro/nano printing and lithography, specifically highlighting areas of interest for further consideration by the scientific community. What is more, this review discusses the advantages and disadvantages of the current techniques enabling the assessment of the most attractive means for modulating biological adhesion, taking in to account cost effectiveness, complexity of equipment and capabilities for processing and analysis.
    • Surfactant-exfoliated 2D hexagonal boron nitride (2D-hBN): role of surfactant upon the electrochemical reduction of oxygen and capacitance applications

      Khan, Aamar F.; Down, Michael P.; Smith, Graham C.; Foster, Christopher W.; Banks, Craig E.; University of Chester; Manchester Metropolitan University (Royal Society of Chemistry, 2017-02-02)
      Surfactant-exfoliated 2D hexagonal boron nitride (2D-hBN) nanosheets are fabricated using the surfactant sodium cholate in aqueous media and are explored towards the electrochemical reduction of oxygen (oxygen reduction reaction) within acidic media for the first time. Large quantifiable voltammetric signatures are observed at significantly reduced potentials compared to traditional graphitic-based electrodes indicating 2D-hBN's possible electrocatalytic activity towards the oxygen reduction reaction, therefore having the potential as a useful electrode platform within fuel cell technology. We also demonstrate, for the first time, that surfactant-exfoliated 2D-hBN is an effective electrochemical supercapacitor material with a specific capacitance value of up to 1745 F g-1. A full analysis of the electrochemical properties of 2D-hBN is performed, including the application of a novel capacitive circuit applied to galvanostatic charge/discharge analysis, which provides an unambiguous analysis of the capacitance of the 2D-hBN. Furthermore, a diverse range of methods are introduced and utilised to calculate the specific capacitance, a substantially overlooked and misinterpreted parameter within the literature allowing standardisation in the academic literature to be achieved. In both examples, we demonstrate through control experiments in the form of surfactant modified graphite electrodes, sodium cholate is the major contributing factor to the aforementioned electrocatalytic and capacitive behaviour, which has yet to be reported.
    • Surfactants at the design limit

      Hazell, Gavin; Czajka, Adam; Eastoe, Julian; University of Chester, University of Bristol (American Chemical Society, 2015-08-04)
      This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, γcmc. Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence γcmc. By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter ϕcmc represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that ϕcmc is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.
    • Swarm Communication by Evolutionary Algorithms

      Vaughan, Neil; University of Chester (IEEE, 2018-05-27)
      This research has applied evolutionary algorithms to evolve swarm communication. Controllers were evolved for colonies of artificial simulated ants during a food foriaging task which communicate using pheromone. Neuroevolution enables both weights and the topology of the artificial neural networks to be optimized for food foriaging. The developed model results in evolution of ants which communicate using pheromone trails. The ants successfully collect and return food to the nest. The controller has evolved to adjust the strength of pheromone which provides a signal to guide the direction of other ants in the colony by hill climbing strategy. A single ANN controller for ant direction successfully evolved which exhibits many separate skills including food search, pheromone following, food collection and retrieval to the nest.
    • Synergistic carbon metabolism in a fast growing mixotrophic freshwater microalgal species Micractinium inermum

      Smith, Richard T.; Bangert, Krys; Wilkinson, Stephen J.; Gilmour, D. James; University of Sheffield ; University of Sheffield ; University of Sheffield/University of Chester ; University of Sheffield (Elsevier, 2015-05-11)
      In recent years microalgae have attracted significant interest as a potential source of sustainable biofuel. Mixotrophic microalgae are able to simultaneously photosynthesise while assimilating and metabolising organic carbon. By combining autotrophic and heterotrophic metabolic pathways biomass productivity can be significantly increased. In this study, acetate-fed mixotrophic Micractinium inermum cultures were found to have a specific growth rate 1.74 times the sum of autotrophic and heterotrophic growth. It was hypothesised that gas exchange between the two metabolic pathways within mixotrophic cultures may have prevented growth limitation and enhanced growth. To determine the extent of synergistic gas exchange and its influence on metabolic activity, dissolved inorganic carbon (DIC), dissolved oxygen (DO) and photosynthesis and respiration rates were measured under different trophic conditions. A 32.7 fold and 2.4 fold increase in DIC and DO concentrations, relative to autotrophic and heterotrophic cultures respectively, were coupled with significant increases in rates of photosynthesis and respiration. These data strongly support the hypothesis of mixotrophic gas exchange within M. inermum cultures. In addition to enhanced growth, this phenomenon may provide reductions in aeration and oxygen stripping costs related to microalgae production.
    • Synthesis and Characterisation of a New Anion Exchangeable Layered Hydroxyiodide

      Southworth, Faye Y.; Wilson, Claire; Coles, Simon J.; Fogg, Andrew M.; University of Liverpool; University of Southampton (Royal Society of Chemistry, 2014-03-04)
      Lu4O(OH)9I·3H2O is a new member of the anion exchangeable lanthanide hydroxyanion family of materials which has been synthesised hydrothermally. Its structure comprises positively charged [Lu4O(OH)9(H2O)3]+ layers with exchangeable charge balancing iodide anions located in the interlayer gallery. It has been found to undergo facile anion exchange reactions with dicarboxylate anions such as succinate and terephthalate at room temperature but reacts less readily with disulfonate anions such as 1,5- and 2,6-naphthalenedisulfonate under the same conditions. At reaction temperatures above 200 °C the cationic inorganic framework Lu3O(OH)6I·2H2O forms instead of the layered phase.
    • Synthesis of Alkynyl-substituted Camphor Derivatives and their Use in the Preparation of Paclitaxel-related Compounds.

      Carvalho, M. Fernanda N. N.; Herrmann, Rudolf; Wagner, Gabriele; Universidade de Lisboa, University of Augsburg, University of Chester (Beilstein, 2017-06-26)
      Compounds containing two alkyne groups in close vicinity at the rigid skeleton of camphorsulfonamide show unique reactivities when treated with electrophiles or catalytic amounts of platinum(II), the product structures depending not only on the reagents but also on the substituents attached to the triple bonds. Cycloisomerisations with perfect atom economy lead to polycyclic heterocycles that resemble to some extent the AB ring system of paclitaxel. Herein, we present practical synthetic methods for the selective synthesis of precursor dialkynes bearing different substituents (alkyl, aryl) at the triple bonds, based on ketals or an imine as protecting groups. We show for isomeric dialkynes that the reaction cascade induced by Pt(II) includes ring annulation, sulfur reduction and ring enlargement. One isomeric dialkyne additionally allows for the isolation of a pentacyclic compound lacking the ring enlargement step, which we have proposed as a potential intermediate in the catalytic cycle.
    • Synthesis, characterisation and in-vitro cytotoxicity of mixed ligand Pt(II) oxadiazoline complexes with hexamethylenetetramine and 7-nitro-1,3,5-triazaadamantane.

      Sieste, Stefanie; Lifincev, Irina; Stein, Nina; Wagner, Gabriele; University of Ulm (Germany); University of Chester (UK) (Royal Society of Chemistry, 2017-08-21)
      Trans-platinum(II) oxadiazoline complexes with 7-nitro-1,3,5-triazaadamantane (NO2-TAA) or hexamethylenetetramine (hmta) ligands have been synthesised from trans-[PtCl2(PhCN)2] via cycloaddition of nitrones to one of the coordinated nitriles, followed by exchange of the other nitrile by NO2-TAA or hmta. Stoichiometric control allows for the selective synthesis of mono- and dinuclear complexes where 7-NO2TAA and hmta act as mono- and bidentate ligands, respectively. Precursors and the target complexes trans-[PtCl2(hmta)(oxadiazoline)], trans-[PtCl2(NO2-TAA)(oxadiazoline)] and trans-[{PtCl2(oxadiazoline)}2(hmta)] were characterised by elemental analysis, IR and multinuclear (1H, 13C, 195Pt) NMR spectroscopy. DFT (B3LYP/6-31G*/LANL08) and AIM calculations suggest a stronger bonding of hmta with the [PtCl2(oxadiazoline)] fragment, in agreement with the experimentally observed reactivity in the ligand exchange (hmta > 7-NO2TAA). Replacement of the nitrile by hmta is predicted more exothermic than that with 7-NO2-TAA, although the activation barriers are similar. Protonation of the non-coordinated N atoms is anticipated to weaken the Pt-N bond and lower the activation barrier for ligand exchange. This effect might help activate these compounds in a slightly acidic environment such as some tumour tissues. Ten of the new compounds were tested for their in vitro cytotoxicity in the human cancer cell lines HeLa and A549. Some of the mononuclear complexes are more potent than cisplatin, and their activity is still high in A549 where cisplatin shows little effect. The dinuclear complexes are inactive, presumably due to their lipophilicity and reduced solubility in water.
    • Systems Based Mechanisms of Aging

      Proctor, Carole; Morgan, Amy; Mc Auley, Mark; Newcastle University; University of Chester
      The last number of decades have witnessed an unrelenting global rise in the number of older people. This demographic shift is laudable; however, many older people are burdened by poor health. The main reason so many older people have their healthspan compromised is due to the complex biology which underpins ageing and the diseases which are associated with this intriguing phenomenon. Fortunately, however, in recent years there has been a paradigm shift within biological research which has seen the emergence of systems biology. In contrast to a reductionist approach which was commonplace in biological research for many years, systems biology seeks to understand biological systems in an integrated manner. Investigating ageing and age related disease in this way is becoming increasingly effective. In this article we discuss the methods which underpin systems and provide examples of their application to biogerontology research.
    • Systems biology and Nutrition

      Mc Auley, Mark
      Systems biology has established itself as a paradigm which has been adopted in order to integrate a wealth of omics data which has been generated in the last few decades. Nutrition research has gradually embraced the systems biology approach, and this holistic way of investigating biological systems is beginning to pay dividends for our understanding of diet and its relationship with health. This chapter presents an overview of the key strands of systems biology; these include, genomics, transcriptomics, proteomics, metabolomics, bioinformatics and computational modelling. I discuss how these techniques are being used to gain new insights into nutrition research. Moreover, I reveal how computational modelling is being used to unravel how ageing effects cholesterol and folate metabolism. The chapter concludes by providing an insight into how systems biology will be applied to nutrition research in the future.
    • Systems biology and synthetic biology: A new epoch for toxicology research

      Mc Auley, Mark T.; Choi, Hyunok; Mooney, Kathleen M.; Paul, Emily; Miller, Veronica M.; University of Chester ; SUNY Albany ; Edge Hill University ; New York State Department of Health ; New York State Department of Health (Hindawi Publishing Corporation, 2015-01-26)
      Systems biology and synthetic biology are emerging disciplines which are becoming increasingly utilised in several areas of bioscience. Toxicology is beginning to benefit from systems biology and we suggest in the future that is will also benefit from synthetic biology. Thus, a new era is on the horizon. This review illustrates how a suite of innovative techniques and tools can be applied to understanding complex health and toxicology issues. We review limitations confronted by the traditional computational approaches to toxicology and epidemiology research, using polycyclic aromatic hydrocarbons (PAHs) and their effects on adverse birth outcomes as an illustrative example. We introduce how systems toxicology (and their subdisciplines, genomic, proteomic, and metabolomic toxicology) will help to overcome such limitations. In particular, we discuss the advantages and disadvantages of mathematical frameworks that computationally represent biological systems. Finally, we discuss the nascent discipline of synthetic biology and highlight relevant toxicological centred applications of this technique, including improvements in personalised medicine. We conclude this review by presenting a number of opportunities and challenges that could shape the future of these rapidly evolving disciplines.