1
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Lu Y, Egedeuzu CS, Taylor PG, Wong LS. Development of Improved Spectrophotometric Assays for Biocatalytic Silyl Ether Hydrolysis. Biomolecules 2024; 14:492. [PMID: 38672508 PMCID: PMC11048244 DOI: 10.3390/biom14040492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/11/2024] [Accepted: 04/16/2024] [Indexed: 04/28/2024] Open
Abstract
Reported herein is the development of assays for the spectrophotometric quantification of biocatalytic silicon-oxygen bond hydrolysis. Central to these assays are a series of chromogenic substrates that release highly absorbing phenoxy anions upon cleavage of the sessile bond. These substrates were tested with silicatein, an enzyme from a marine sponge that is known to catalyse the hydrolysis and condensation of silyl ethers. It was found that, of the substrates tested, tert-butyldimethyl(2-methyl-4-nitrophenoxy)silane provided the best assay performance, as evidenced by the highest ratio of enzyme catalysed reaction rate compared with the background (uncatalysed) reaction. These substrates were also found to be suitable for detailed enzyme kinetics measurements, as demonstrated by their use to determine the Michaelis-Menten kinetic parameters for silicatein.
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Affiliation(s)
- Yuqing Lu
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, UK; (Y.L.); (C.S.E.)
- Department of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - Chisom S. Egedeuzu
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, UK; (Y.L.); (C.S.E.)
- Department of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - Peter G. Taylor
- School of Life Health and Chemical Sciences, Open University, Milton Keynes MK7 6AA, UK;
| | - Lu Shin Wong
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, UK; (Y.L.); (C.S.E.)
- Department of Chemistry, University of Manchester, Manchester M13 9PL, UK
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2
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Alahakoon P, McCaw JM, Taylor PG. Improving estimates of waning immunity rates in stochastic SIRS models with a hierarchical framework. Infect Dis Model 2023; 8:1127-1137. [PMID: 37886740 PMCID: PMC10597760 DOI: 10.1016/j.idm.2023.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 08/19/2023] [Accepted: 10/05/2023] [Indexed: 10/28/2023] Open
Abstract
As most disease causing pathogens require transmission from an infectious individual to a susceptible individual, continued persistence of the pathogen within the population requires the replenishment of susceptibles through births, immigration, or waning immunity. Consider the introduction of an unknown infectious disease into a fully susceptible population where it is not known how long immunity is conferred once an individual recovers from infection. If, initially, the prevalence of disease increases (that is, the infection takes off), the number of infectives will usually decrease to a low level after the first major outbreak. During this post-outbreak period, the disease dynamics may be influenced by stochastic effects and there is a non-zero probability that the epidemic will die out. Die out in this period following the first major outbreak is known as an epidemic fade-out. If the disease does not die out, the susceptible population may be replenished by the waning of immunity, and a second wave may start. In this study, we investigate if the rate of waning immunity (and other epidemiological parameters) can be reliably estimated from multiple outbreak data, in which some outbreaks display epidemic fade-out and others do not. We generated synthetic outbreak data from independent simulations of stochastic SIRS models in multiple communities. Some outbreaks faded-out and some did not. We conducted Bayesian parameter estimation under two alternative approaches: independently on each outbreak and under a hierarchical framework. When conducting independent estimation, the waning immunity rate was poorly estimated and biased towards zero when an epidemic fade-out was observed. However, under a hierarchical approach, we obtained more accurate and precise posterior estimates for the rate of waning immunity and other epidemiological parameters. The greatest improvement in estimates was obtained for those communities in which epidemic fade-out was observed. Our findings demonstrate the feasibility and value of adopting a Bayesian hierarchical approach for parameter inference for stochastic epidemic models.
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Affiliation(s)
- Punya Alahakoon
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
- School of Population Health, University of New South Wales, Sydney, Australia
- Kirby Institute, University of New South Wales, Sydney, Australia
| | - James M. McCaw
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Peter G. Taylor
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
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3
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Mehra S, McCaw JM, Taylor PG. Superinfection and the hypnozoite reservoir for Plasmodium vivax: a general framework. J Math Biol 2023; 88:7. [PMID: 38040981 PMCID: PMC10692056 DOI: 10.1007/s00285-023-02014-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 10/03/2023] [Accepted: 10/11/2023] [Indexed: 12/03/2023]
Abstract
A characteristic of malaria in all its forms is the potential for superinfection (that is, multiple concurrent blood-stage infections). An additional characteristic of Plasmodium vivax malaria is a reservoir of latent parasites (hypnozoites) within the host liver, which activate to cause (blood-stage) relapses. Here, we present a model of hypnozoite accrual and superinfection for P. vivax. To couple host and vector dynamics for a homogeneously-mixing population, we construct a density-dependent Markov population process with countably many types, for which disease extinction is shown to occur almost surely. We also establish a functional law of large numbers, taking the form of an infinite-dimensional system of ordinary differential equations that can also be recovered by coupling expected host and vector dynamics (i.e. a hybrid approximation) or through a standard compartment modelling approach. Recognising that the subset of these equations that model the infection status of the human hosts has precisely the same form as the Kolmogorov forward equations for a Markovian network of infinite server queues with an inhomogeneous batch arrival process, we use physical insight into the evolution of the latter process to write down a time-dependent multivariate generating function for the solution. We use this characterisation to collapse the infinite-compartment model into a single integrodifferential equation (IDE) governing the intensity of mosquito-to-human transmission. Through a steady state analysis, we recover a threshold phenomenon for this IDE in terms of a parameter [Formula: see text] expressible in terms of the primitives of the model, with the disease-free equilibrium shown to be uniformly asymptotically stable if [Formula: see text] and an endemic equilibrium solution emerging if [Formula: see text]. Our work provides a theoretical basis to explore the epidemiology of P. vivax, and introduces a strategy for constructing tractable population-level models of malarial superinfection that can be generalised to allow for greater biological realism in a number of directions.
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Affiliation(s)
- Somya Mehra
- School of Mathematics and Statistics, The University of Melbourne, Parkville, Australia.
| | - James M McCaw
- School of Mathematics and Statistics, The University of Melbourne, Parkville, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Australia
| | - Peter G Taylor
- School of Mathematics and Statistics, The University of Melbourne, Parkville, Australia
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4
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Alahakoon P, Taylor PG, McCaw JM. How effective were Australian Quarantine Stations in mitigating transmission aboard ships during the influenza pandemic of 1918-19? PLoS Comput Biol 2023; 19:e1011656. [PMID: 38011267 PMCID: PMC10703403 DOI: 10.1371/journal.pcbi.1011656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 12/07/2023] [Accepted: 11/03/2023] [Indexed: 11/29/2023] Open
Abstract
The influenza pandemic of 1918-19 was the most devastating pandemic of the 20th century. It killed an estimated 50-100 million people worldwide. In late 1918, when the severity of the disease was apparent, the Australian Quarantine Service was established. Vessels returning from overseas and inter-state were intercepted, and people were examined for signs of illness and quarantined. Some of these vessels carried the infection throughout their voyage and cases were prevalent by the time the ship arrived at a Quarantine Station. We study four outbreaks that took place on board the Medic, Boonah, Devon, and Manuka in late 1918. These ships had returned from overseas and some of them were carrying troops that served in the First World War. By analysing these outbreaks under a stochastic Bayesian hierarchical modeling framework, we estimate the transmission rates among crew and passengers aboard these ships. Furthermore, we ask whether the removal of infectious, convalescent, and healthy individuals after arriving at a Quarantine Station in Australia was an effective public health response.
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Affiliation(s)
- Punya Alahakoon
- School of Mathematics and Statistics,The University of Melbourne, Melbourne, Australia
- School of Population Health, University of New South Wales, Sydney, Australia
- Kirby Institute, University of New South Wales, Sydney, Australia
| | - Peter G. Taylor
- School of Mathematics and Statistics,The University of Melbourne, Melbourne, Australia
| | - James M. McCaw
- School of Mathematics and Statistics,The University of Melbourne, Melbourne, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
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Asanjarani A, Shausan A, Chew K, Graham T, Henderson SG, Jansen HM, Short KR, Taylor PG, Vuorinen A, Yadav Y, Ziedins I, Nazarathy Y. Emulation of epidemics via Bluetooth-based virtual safe virus spread: Experimental setup, software, and data. PLOS Digit Health 2022; 1:e0000142. [PMID: 36812628 PMCID: PMC9931351 DOI: 10.1371/journal.pdig.0000142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 10/10/2022] [Indexed: 12/03/2022]
Abstract
We describe an experimental setup and a currently running experiment for evaluating how physical interactions over time and between individuals affect the spread of epidemics. Our experiment involves the voluntary use of the Safe Blues Android app by participants at The University of Auckland (UoA) City Campus in New Zealand. The app spreads multiple virtual safe virus strands via Bluetooth depending on the physical proximity of the subjects. The evolution of the virtual epidemics is recorded as they spread through the population. The data is presented as a real-time (and historical) dashboard. A simulation model is applied to calibrate strand parameters. Participants' locations are not recorded, but participants are rewarded based on the duration of participation within a geofenced area, and aggregate participation numbers serve as part of the data. The 2021 experimental data is available as an open-source anonymized dataset, and once the experiment is complete, the remaining data will be made available. This paper outlines the experimental setup, software, subject-recruitment practices, ethical considerations, and dataset description. The paper also highlights current experimental results in view of the lockdown that started in New Zealand at 23:59 on August 17, 2021. The experiment was initially planned in the New Zealand environment, expected to be free of COVID and lockdowns after 2020. However, a COVID Delta strain lockdown shuffled the cards and the experiment is currently extended into 2022.
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Affiliation(s)
- Azam Asanjarani
- Department of Statistics, The University of Auckland, Auckland, New Zealand
- * E-mail:
| | - Aminath Shausan
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
| | - Keng Chew
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Thomas Graham
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
| | - Shane G. Henderson
- School of Operations Research and Information Engineering, Cornell University, Ithaca, New York, United States of America
| | - Hermanus M. Jansen
- Department of Engineering, University College Roosevelt, Middelburg, the Netherlands
| | - Kirsty R. Short
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Peter G. Taylor
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Victoria, Australia
| | - Aapeli Vuorinen
- Department of Industrial Engineering and Operations Research, Columbia University, New York, United States of America
| | - Yuvraj Yadav
- Mechanical Engineering Department, Indian Institute of Technology Delhi, New Delhi, Delhi, India
| | - Ilze Ziedins
- Department of Statistics, The University of Auckland, Auckland, New Zealand
| | - Yoni Nazarathy
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
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6
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Pollett PK, Tafakori L, Taylor PG. A Model for Cell Proliferation in a Developing Organism. J Math Biol 2022; 84:63. [PMID: 35752652 PMCID: PMC9233659 DOI: 10.1007/s00285-022-01769-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/24/2022] [Accepted: 05/27/2022] [Indexed: 11/26/2022]
Abstract
In mathematical biology, there is a great deal of interest in producing continuum models by scaling discrete agent-based models governed by local stochastic rules. We discuss a particular example of this approach: a model for the proliferation of neural crest cells that can help us understand the development of Hirschprung's disease, a potentially-fatal condition in which the enteric nervous system of a new-born child does not extend all the way through the intestine and colon. Our starting point is a discrete-state, continuous-time Markov chain model proposed by Hywood et al. (2013a) for the location of the neural crest cells that make up the enteric nervous system. Hywood et al. (2013a) scaled their model to derive an approximate second order partial differential equation describing how the limiting expected number of neural crest cells evolve in space and time. In contrast, we exploit the relationship between the above-mentioned Markov chain model and the well-known Yule-Furry process to derive the exact form of the scaled version of the process. Furthermore, we provide expressions for other features of the domain agent occupancy process, such as the variance of the marginal occupancy at a particular site, the distribution of the number of agents that are yet to reach a given site and a stochastic description of the process itself.
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Affiliation(s)
- Philip K Pollett
- School of Mathematics and Physics, University of Queensland, Brisbane, Australia
| | - Laleh Tafakori
- Department of Mathematical Sciences, RMIT University, Melbourne, Australia.
| | - Peter G Taylor
- School of Mathematics and Statistics, University of Melbourne, Melbourne, Australia
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7
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Alahakoon P, McCaw JM, Taylor PG. Estimation of the probability of epidemic fade-out from multiple outbreak data. Epidemics 2022; 38:100539. [DOI: 10.1016/j.epidem.2022.100539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 10/13/2021] [Accepted: 01/05/2022] [Indexed: 11/03/2022] Open
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8
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Dandekar R, Henderson SG, Jansen HM, McDonald J, Moka S, Nazarathy Y, Rackauckas C, Taylor PG, Vuorinen A. Safe Blues: The case for virtual safe virus spread in the long-term fight against epidemics. Patterns (N Y) 2021; 2:100220. [PMID: 33748797 PMCID: PMC7961183 DOI: 10.1016/j.patter.2021.100220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Viral spread is a complicated function of biological properties, the environment, preventative measures such as sanitation and masks, and the rate at which individuals come within physical proximity. It is these last two elements that governments can control through social-distancing directives. However, infection measurements are almost always delayed, making real-time estimation nearly impossible. Safe Blues is one way of addressing the problem caused by this time lag via online measurements combined with machine learning methods that exploit the relationship between counts of multiple forms of the Safe Blues strands and the progress of the actual epidemic. The Safe Blues protocols and techniques have been developed together with an experimental minimal viable product, presented as an app on Android devices with a server backend. Following initial exploration via simulation experiments, we are now preparing for a university-wide experiment of Safe Blues.
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Affiliation(s)
- Raj Dandekar
- Department of Computational Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - Shane G. Henderson
- School of Operations Research and Information Engineering, Cornell University, Rhodes Hall, Ithaca, NY 14853, USA
| | - Hermanus M. Jansen
- Department of Applied Mathematics, Delft University of Technology, Mekelweg 4, 2628CD Delft, The Netherlands
| | - Joshua McDonald
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Sarat Moka
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yoni Nazarathy
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Christopher Rackauckas
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - Peter G. Taylor
- School of Mathematics and Statistics, the University of Melbourne, Melbourne, VIC 3010, Australia
| | - Aapeli Vuorinen
- Department of Industrial Engineering and Operations Research, Columbia University, New York, NY 10027, USA
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9
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Fu J, Moran B, Taylor PG, Xing C. Resource competition in virtual network embedding. STOCH MODELS 2020. [DOI: 10.1080/15326349.2020.1858875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Jing Fu
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - Bill Moran
- Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, Australia
| | - Peter G. Taylor
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
| | - Chenchen Xing
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
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10
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Bruce JI, O’Connell PJ, Taylor PG, Smith DP, Adkin RC, Pearson VK. Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents. Molecules 2020; 25:molecules25184253. [PMID: 32947960 PMCID: PMC7570700 DOI: 10.3390/molecules25184253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/11/2020] [Accepted: 09/11/2020] [Indexed: 11/30/2022] Open
Abstract
The relaxivity of MRI contrast agents can be increased by increasing the size of the contrast agent and by increasing concentration of the bound gadolinium. Large multi-site ligands able to coordinate several metal centres show increased relaxivity as a result. In this paper, an “aza-type Michael” reaction is used to prepare cyclen derivatives that can be attached to organosilicon frameworks via hydrosilylation reactions. A range of organosilicon frameworks were tested including silsesquioxane cages and dimethylsilylbenzene derivatives. Michael donors with strong electron withdrawing groups could be used to alkylate cyclen on three amine centres in a single step. Hydrosilylation successfully attached these to mono-, di-, and tri-dimethylsilyl-substituted benzene derivatives. The europium and gadolinium complexes were formed and studied using luminescence spectroscopy and relaxometry. This showed the complexes to contain two bound water moles per lanthanide centre and T1 relaxation time measurements demonstrated an increase in relaxivity had been achieved, in particular for the trisubstituted scaffold 1,3,5-tris((pentane-sDO3A)dimethylsilyl)benzene-Gd3. This showed a marked increase in the relaxivity (13.1 r1p/mM−1s−1).
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Affiliation(s)
- James I. Bruce
- School of Life Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (P.J.O.); (P.G.T.); (D.P.T.S.)
- Correspondence:
| | - Patrick J. O’Connell
- School of Life Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (P.J.O.); (P.G.T.); (D.P.T.S.)
| | - Peter G. Taylor
- School of Life Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (P.J.O.); (P.G.T.); (D.P.T.S.)
| | - David P.T. Smith
- School of Life Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (P.J.O.); (P.G.T.); (D.P.T.S.)
| | - Roy C. Adkin
- School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (R.C.A.); (V.K.P.)
| | - Victoria K. Pearson
- School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; (R.C.A.); (V.K.P.)
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11
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Mehra S, McCaw JM, Flegg MB, Taylor PG, Flegg JA. An Activation-Clearance Model for Plasmodium vivax Malaria. Bull Math Biol 2020; 82:32. [DOI: 10.1007/s11538-020-00706-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 01/27/2020] [Indexed: 11/24/2022]
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12
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Heeley E, El Aziz Y, Ellingford C, Jetybayeva A, Wan C, Crabb E, Taylor PG, Bassindale A. Self-assembly of fluoride-encapsulated polyhedral oligomeric silsesquioxane (POSS) nanocrystals. CrystEngComm 2019. [DOI: 10.1039/c8ce01750f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The self-assembly and crystal packing of a unique series of nanocrystalline fluoride ion-encapsulated polyhedral oligomeric silsesquioxane (F-POSS) compounds, with substituted electron-withdrawing group (EWG) perfluorinated alkyl chain arms of varying lengths, were investigated.
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Affiliation(s)
- Ellen Heeley
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
| | - Youssef El Aziz
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
| | - Christopher Ellingford
- International Institute of Nanocomposites Manufacturing (IINM)
- WMG
- University of Warwick
- UK
| | - Albina Jetybayeva
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
| | - Chaoying Wan
- International Institute of Nanocomposites Manufacturing (IINM)
- WMG
- University of Warwick
- UK
| | - Eleanor Crabb
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
| | - Peter G. Taylor
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
| | - Alan Bassindale
- Faculty of Science, Technology, Engineering and Mathematics
- Open University
- Milton Keynes
- UK
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13
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Negrebetsky VV, Kramarova EP, Shipov AG, Baukov YI, Korlyukov AA, Arkhipov DE, Bassindale AR, Taylor PG, Bylikin SY. Synthesis, structures and stereodynamic behavior of pentacoordinate (O→Si)-Chelate Difluoro(methyl)silylmethyl derivatives of amides and imides. J Organomet Chem 2018. [DOI: 10.1016/j.jorganchem.2018.07.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Bourebrab MA, Oben DT, Durand GG, Taylor PG, Bruce JI, Bassindale AR, Taylor A. Influence of the initial chemical conditions on the rational design of silica particles. J Solgel Sci Technol 2018; 88:430-441. [PMID: 30956401 PMCID: PMC6413825 DOI: 10.1007/s10971-018-4821-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 09/14/2018] [Indexed: 05/14/2023]
Abstract
The influence of the water content in the initial composition on the size of silica particles produced using the Stöber process is well known. We have shown that there are three morphological regimes defined by compositional boundaries. At low water levels (below stoichiometric ratio of water:tetraethoxysilane), very high surface area and aggregated structures are formed; at high water content (>40 wt%) similar structures are also seen. Between these two boundary conditions, discrete particles are formed whose size are dictated by the water content. Within the compositional regime that enables the classical Stöber silica, the structural evolution shows a more rapid attainment of final particle size than the rate of formation of silica supporting the monomer addition hypothesis. The clearer understanding of the role of the initial composition on the output of this synthesis method will be of considerable use for the establishment of reliable reproducible silica production for future industrial adoption.
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Affiliation(s)
- Marion A. Bourebrab
- National Structural Integrity Research Centre, Granta Park, Great Abington, Cambridge, CB21 6AL UK
- School of Engineering, The University of Edinburgh, Edinburgh, EH9 3FB UK
| | - Delphine T Oben
- Chemistry Department, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
| | - Géraldine G. Durand
- TWI Ltd., Great Abington, Granta Park, Cambridge, CB21 6AL UK
- Advanced Resins and Coatings Technologies Innovation Centre, School of Engineering, London South Bank University, 103 Borough Road, London, SE1 0AA UK
| | - Peter G. Taylor
- Chemistry Department, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
| | - James I. Bruce
- Chemistry Department, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
| | - Alan R. Bassindale
- Chemistry Department, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
| | - Alan Taylor
- TWI Ltd., Great Abington, Granta Park, Cambridge, CB21 6AL UK
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15
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El Aziz Y, Mehrban N, Taylor PG, Birchall MA, Bowen J, Bassindale AR, Pitak MB, Coles SJ. Facile synthesis of novel hybrid POSS biomolecules via “Click” reactions. RSC Adv 2017. [DOI: 10.1039/c7ra07915j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A novel alkyne-terminated cubic-octameric POSS was synthesised in high yield and click chemistry has been used to attach bio-oligomers.
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Affiliation(s)
- Youssef El Aziz
- The Open University
- Faculty of Science, Technology, Engineering & Mathematics
- Milton Keynes
- UK
| | - Nazia Mehrban
- University College London
- Ear Institute
- Brain Sciences
- London WC1X 8EE
- UK
| | - Peter G. Taylor
- The Open University
- Faculty of Science, Technology, Engineering & Mathematics
- Milton Keynes
- UK
| | | | - James Bowen
- The Open University
- Faculty of Science, Technology, Engineering & Mathematics
- Milton Keynes
- UK
| | - Alan R. Bassindale
- The Open University
- Faculty of Science, Technology, Engineering & Mathematics
- Milton Keynes
- UK
| | - Mateusz B. Pitak
- UK National Crystallography Service
- Chemistry
- University of Southampton
- Southampton
- UK
| | - Simon J. Coles
- UK National Crystallography Service
- Chemistry
- University of Southampton
- Southampton
- UK
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17
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El Aziz Y, Taylor PG, Bassindale AR, Coles SJ, Pitak MB. Synthesis and Structures of Novel Molecular Ionic Compounds Based on Encapsulation of Anions and Cations. Organometallics 2016. [DOI: 10.1021/acs.organomet.6b00565] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Youssef El Aziz
- Department of Life, Health & Chemical Science, Faculty of Science, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
| | - Peter G. Taylor
- Department of Life, Health & Chemical Science, Faculty of Science, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
| | - Alan R. Bassindale
- Department of Life, Health & Chemical Science, Faculty of Science, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
| | - Simon J. Coles
- U.K.
National Crystallography Service, Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
| | - Mateusz B. Pitak
- U.K.
National Crystallography Service, Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
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18
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Villamizar JE, Angarita AY, Blanco FE, Taylor PG, Salazar FJ. Synthesis of Novel Podocarpa-8,11,13-Triene-7- and 13-Nitriles and Evaluation of their Anti-Inflammatory and Cytotoxic Activity. Journal of Chemical Research 2016. [DOI: 10.3184/174751916x14682323381549] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A series of novel podocarpa-8,11,13-triene-7- and 13-nitriles were prepared from the naturally occurring labdane diterpenoid (+)-manool, using podocarp-8(14)-en-13-one and 13-methoxypodocarpa-8,11,13-trien-7-one as key intermediates and TMSCN and acetonitrile as source of the nitrile. The synthesised compounds were screened for cytotoxicity against mouse macrophage cell line (RAW 264.7), human colon adenocarcinoma cell lines (HT-29) and human prostate adenocarcinoma cell lines (PC3) and for anti-inflammatory, as measured by the inhibition of nitric oxide (NO) production by RAW cells. 7-Oxopodocarpa-8,11,13-triene-13-nitrile exhibited significant inhibition of NO production (IC50 = 6 μM) and was not cytotoxic.
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Affiliation(s)
- José E. Villamizar
- Centro de Química, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
- Departamento de Química Medicinal, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
| | - Ana Y. Angarita
- Centro de Química, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
| | - Frank E. Blanco
- Centro de Medicina Experimental, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
| | - Peter G. Taylor
- Centro de Medicina Experimental, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
| | - Franklin J. Salazar
- Centro de Química, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela
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19
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Abstract
We prove the conjecture formulated in Litvak and Ejov (2009), namely, that the trace of the fundamental matrix of a singularly perturbed Markov chain that corresponds to a stochastic policy feasible for a given graph is minimised at policies corresponding to Hamiltonian cycles.
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20
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Miyazawa M, Taylor PG. A Geometric Product-Form Distribution for a Queueing Network by Non-Standard Batch Arrivals and Batch Transfers. ADV APPL PROBAB 2016. [DOI: 10.2307/1428015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We introduce a batch service discipline, called assemble-transfer batch service, for continuous-time open queueing networks with batch movements. Under this service discipline a requested number of customers is simultaneously served at a node, and transferred to another node as, possibly, a batch of different size, if there are sufficient customers there; the node is emptied otherwise. We assume a Markovian setting for the arrival process, service times and routing, where batch sizes are generally distributed.Under the assumption that extra batches arrive while nodes are empty, and under a stability condition, it is shown that the stationary distribution of the queue length has a geometric product form over the nodes if and only if certain conditions are satisfied for the extra arrivals. This gives a new class of queueing networks which have tractable stationary distributions, and simultaneously shows that the product form provides a stochastic upper bound for the stationary distribution of the corresponding queueing network without the extra arrivals.
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21
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Abstract
We consider the class of level-independent quasi-birth-and-death (QBD) processes that have countably many phases and generator matrices with tridiagonal blocks that are themselves tridiagonal and phase independent. We derive simple conditions for possible decay rates of the stationary distribution of the ‘level’ process. It may be possible to obtain decay rates satisfying these conditions by varying only the transition structure at level 0. Our results generalize those of Kroese, Scheinhardt, and Taylor, who studied in detail a particular example, the tandem Jackson network, from the class of QBD processes studied here. The conditions derived here are applied to three practical examples.
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22
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Nikolin AA, Kramarova EP, Shipov AG, Baukov YI, Negrebetsky VV, Arkhipov DE, Korlyukov AA, Lagunin AA, Bylikin SY, Bassindale AR, Taylor PG. N,N-Bis-(dimethylfluorosilylmethyl)amides of N-organosulfonylproline and sarcosine: synthesis, structure, stereodynamic behaviour and in silico studies. RSC Adv 2016. [DOI: 10.1039/c6ra14450k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
(O→Si)-Chelate difluorides R3R2NCH(R1)C(O)N(CH2SiMe2F)2, were synthesized by silylmethylation of amides R3R2NCH(R1)C(O)NH2, subsequent hydrolysis of unstable dichlorides into 2,6-disilamorpholines and the reaction of the latter compounds with BF3·Et2O.
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Affiliation(s)
- Alexey A. Nikolin
- Department of Chemistry
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
| | - Eugenia P. Kramarova
- Department of Chemistry
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
| | - Alexander G. Shipov
- Department of Chemistry
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
| | - Yuri I. Baukov
- Department of Chemistry
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
| | - Vadim V. Negrebetsky
- Department of Chemistry
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
| | - Dmitry E. Arkhipov
- A. N. Nesmeyanov's Institute of Organoelement Compounds
- 119991 Moscow
- Russian Federation
| | | | - Alexey A. Lagunin
- Department of Bioinformatics
- N.I. Pirogov Russian National Research Medical University
- Moscow 117997
- Russian Federation
- Institute of Biomedical Chemistry
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23
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Heeley EL, Hughes DJ, El Aziz Y, Taylor PG, Bassindale AR. Morphology and crystallization kinetics of polyethylene/long alkyl-chain substituted Polyhedral Oligomeric Silsesquioxanes (POSS) nanocomposite blends: A SAXS/WAXS study. Eur Polym J 2014. [DOI: 10.1016/j.eurpolymj.2013.11.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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24
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Shipov AG, Kramarova EP, Fang H, Arkhipov DE, Nikolin AA, Bylikin SY, Negrebetsky VV, Korlyukov AA, Voronina NA, Bassindale AR, Taylor PG, Baukov YI. 1-Organosulfonyl-2-sila-5-piperazinones: Synthesis, molecular and crystal structure, and chemical transformations into 2-aminoacid derivatives. J Organomet Chem 2013. [DOI: 10.1016/j.jorganchem.2013.05.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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25
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Frascione N, Codina-Barrios A, Bassindale AR, Taylor PG. Enhancing in vitro selection techniques to assist the discovery, understanding and use of inorganic binding peptides. Dalton Trans 2013; 42:10337-46. [PMID: 23740479 DOI: 10.1039/c3dt50541c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reflecting the increasing interest in combinatorial approaches, peptide phage display has seen an unprecedented expansion in a wide range of research areas. Its application to the discovery and analysis of metal binding peptides has opened up new research directions and largely contributed to the nanotechnology field. The rationale behind the need to identify such peptides varies depending on the final aim of the research and its application. Therefore, the possibility to modify the selection technique according to the different requirements would allow for a more systematic approach to be adopted and would ultimately provide substantial benefits. Although the standard panning method can be virtually applied to any target, its use for the identification of metal binding peptides does not provide the characteristics and the flexibility required for an efficient and tailored selection. Here we report on the development of a new panning method that can contribute to a faster, versatile and more informative analysis. Through the use of rolling-circle amplification, polymerase reaction and wild type phage, we have converted the standard selection technique into a more dynamic process in which adjustments can be evaluated and made consistently with the need of the experiment. The successfulness of the improved method is demonstrated in a number of panning experiments with different inorganic targets. The modifications applied to each selection are described and comparisons between the results obtained are made in order to extensively assess and evaluate the impact of the new process. The importance of tailoring the screening method to the specific objectives of a study is also considered. New binder sequences for the materials included in the investigation are identified; their sequences and distinctive characteristics are reported and their ability to act as templates for the nucleation of inorganic material is demonstrated and discussed.
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Affiliation(s)
- Nunzianda Frascione
- Department of Life, Health and Chemical Sciences, Open University, Venables Building, Walton Hall, Milton Keynes, UK.
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26
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Heeley EL, Hughes DJ, El Aziz Y, Taylor PG, Bassindale AR. Linear Long Alkyl Chain Substituted POSS Cages: The Effect of Alkyl Chain Length on the Self-Assembled Packing Morphology. Macromolecules 2013. [DOI: 10.1021/ma400635e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ellen L. Heeley
- Department of Physical Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | | | - Youssef El Aziz
- Department of Physical Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | - Peter G. Taylor
- Department of Physical Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | - Alan R. Bassindale
- Department of Physical Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
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27
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Sohail M, Bassindale AR, Taylor PG, Korlyukov AA, Arkhipov DE, Male L, Coles SJ, Hursthouse MB, Harrington RW, Clegg W. Correction to Synthesis and Hydrolysis–Condensation Study of Water-Soluble Self-Assembled Pentacoordinate Polysilylamides. Organometallics 2013. [DOI: 10.1021/om400319e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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28
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Abstract
Pethidine (meperidine) is a unique member of the opioid family. In addition to its analgesic activity, it also has significant local anaesthetic activity. This property enables it to be used as the sole agent for spinal anaesthesia. We describe the successful use of intrathecal pethidine 1 mg/kg for an elective lower segment caesarean section in a patient presumed to be allergic to amide local anaesthetics. There were no significant adverse effects in either the mother or the newborn.
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Affiliation(s)
- R M Vassiliadis
- Department of Anaesthesia, Gosford District Hospital, Gosford, New South Wales, Australia.
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29
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Sohail M, Bassindale AR, Taylor PG, Korlyukov AA, Arkhipov DE, Male L, Coles SJ, Hursthouse MB. Synthesis and Hydrolysis–Condensation Study of Water-Soluble Self-Assembled Pentacoordinate Polysilylamides. Organometallics 2013. [DOI: 10.1021/om301137b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Muhammad Sohail
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | - Alan R. Bassindale
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | - Peter G. Taylor
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA,
U.K
| | - Alexander A. Korlyukov
- A.N. Nesmeyanov Institute
of Organoelement Compounds (INEOS), Russian Academy of Sciences, 28 Vavilov Street, B-334, Moscow 119991, Russia
| | - Dmitry E. Arkhipov
- A.N. Nesmeyanov Institute
of Organoelement Compounds (INEOS), Russian Academy of Sciences, 28 Vavilov Street, B-334, Moscow 119991, Russia
| | - Louise Male
- EPSRC National Crystallography
Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ U.K
| | - Simon J. Coles
- EPSRC National Crystallography
Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ U.K
| | - Michael B. Hursthouse
- EPSRC National Crystallography
Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ U.K
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30
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Panisch R, Bassindale AR, Korlyukov AA, Pitak MB, Coles SJ, Taylor PG. Selective Derivatization and Characterization of Bifunctional “Janus-Type” Cyclotetrasiloxanes. Organometallics 2013. [DOI: 10.1021/om301158w] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robin Panisch
- The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | | | - Alexander A. Korlyukov
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova Street, 119991, Moscow, Russia
| | - Mateusz B. Pitak
- UK National Crystallography Service,
School of Chemistry, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, U.K
| | - Simon J. Coles
- UK National Crystallography Service,
School of Chemistry, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, U.K
| | - Peter G. Taylor
- The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K
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31
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El Aziz Y, Bassindale AR, Taylor PG, Stephenson RA, Hursthouse MB, Harrington RW, Clegg W. X-ray Crystal Structures, Packing Behavior, and Thermal Stability Studies of a Homologous Series of n-Alkyl-Substituted Polyhedral Oligomeric Silsesquioxanes. Macromolecules 2013. [DOI: 10.1021/ma302229v] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Youssef El Aziz
- Department of Life, Health and
Chemical Sciences, Open University, Venables
Building, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | - Alan R. Bassindale
- Department of Life, Health and
Chemical Sciences, Open University, Venables
Building, Walton Hall, Milton Keynes, MK7 6AA, U.K
- Key Lab Organosilicon
Chemistry
and Material Technology, Minister of Education, Hangzhou Normal University, Hangzhou, 310012, Zhejiang, Peoples
R China
| | - Peter G. Taylor
- Department of Life, Health and
Chemical Sciences, Open University, Venables
Building, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | - Richard A. Stephenson
- EPSRC National Crystallography
Service, University of Southampton, Highfield,
Southampton, SO17 1BJ, U.K
| | - Michael B. Hursthouse
- EPSRC National Crystallography
Service, University of Southampton, Highfield,
Southampton, SO17 1BJ, U.K
| | - Ross W. Harrington
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU,
U.K
| | - William Clegg
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU,
U.K
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32
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Heeley EL, Hughes DJ, El Aziz Y, Williamson I, Taylor PG, Bassindale AR. Properties and self-assembled packing morphology of long alkyl-chained substituted polyhedral oligomeric silsesquioxanes (POSS) cages. Phys Chem Chem Phys 2013; 15:5518-29. [DOI: 10.1039/c3cp44356f] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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El Aziz Y, Bassindale AR, Taylor PG, Horton PN, Stephenson RA, Hursthouse MB. Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion. Organometallics 2012. [DOI: 10.1021/om300277g] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Youssef El Aziz
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, U.K
| | - Alan R. Bassindale
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, U.K
| | - Peter G. Taylor
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, U.K
| | - Peter N. Horton
- EPSRC National Crystallography Service, University of Southampton, Highfield,
Southampton SO17 1BJ, U.K
| | - Richard A. Stephenson
- EPSRC National Crystallography Service, University of Southampton, Highfield,
Southampton SO17 1BJ, U.K
| | - Michael B. Hursthouse
- EPSRC National Crystallography Service, University of Southampton, Highfield,
Southampton SO17 1BJ, U.K
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34
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Nikolin AA, Kramarova EP, Shipov AG, Baukov YI, Negrebetsky VV, Korlyukov AA, Arkhipov DE, Bowden A, Bylikin SY, Bassindale AR, Taylor PG. Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline. Organometallics 2012. [DOI: 10.1021/om3002697] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexei A. Nikolin
- Department of General
and Bioorganic Chemistry, N. I. Pirogov Russian National Investigated Medical University, Ostrovityanov
Street 1, Moscow 117997, Russian Federation
| | - Evgeniya P. Kramarova
- Department of General
and Bioorganic Chemistry, N. I. Pirogov Russian National Investigated Medical University, Ostrovityanov
Street 1, Moscow 117997, Russian Federation
| | - Aleksander G. Shipov
- Department of General
and Bioorganic Chemistry, N. I. Pirogov Russian National Investigated Medical University, Ostrovityanov
Street 1, Moscow 117997, Russian Federation
| | - Yuri I. Baukov
- Department of General
and Bioorganic Chemistry, N. I. Pirogov Russian National Investigated Medical University, Ostrovityanov
Street 1, Moscow 117997, Russian Federation
| | - Vadim V. Negrebetsky
- Department of General
and Bioorganic Chemistry, N. I. Pirogov Russian National Investigated Medical University, Ostrovityanov
Street 1, Moscow 117997, Russian Federation
| | - Alexander A. Korlyukov
- A. N. Nesmeyanov’s
Institute of Organoelement Compounds, RAS, Vavilova Street 28, 119991 Moscow, Russian Federation
| | - Dmitry E. Arkhipov
- A. N. Nesmeyanov’s
Institute of Organoelement Compounds, RAS, Vavilova Street 28, 119991 Moscow, Russian Federation
| | - Allen Bowden
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, United Kingdom
| | - Sergey Yu. Bylikin
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, United Kingdom
| | - Alan R. Bassindale
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, United Kingdom
| | - Peter G. Taylor
- Department of Chemistry, Open University, Walton Hall, Milton
Keynes MK7 6AA, United Kingdom
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35
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36
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Taylor PG, Bassindale AR, El Aziz Y, Pourny M, Stevenson R, Hursthouse MB, Coles SJ. Further studies of fluoride ion entrapment in octasilsesquioxane cages; X-ray crystal structure studies and factors that affect their formation. Dalton Trans 2012; 41:2048-59. [DOI: 10.1039/c1dt11340b] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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37
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Kalashnikova NA, Bylikin SY, Korlyukov AA, Shipov AG, Baukov YI, Taylor PG, Bassindale AR. Cationic complexes of silicon and germanium with (O,S)-chelate ligands. Dalton Trans 2012; 41:12681-2. [DOI: 10.1039/c2dt31554h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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39
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Abstract
Recently, there has been considerable interest in the calculation of decay rates for models that can be viewed as quasi-birth-and-death (QBD) processes with infinitely many phases. In this paper we make a contribution to this endeavour by considering some classes of models in which the transition function is not homogeneous in the phase direction. We characterize the range of decay rates that are compatible with the dynamics of the process away from the boundary. In many cases, these rates can be attained by changing the transition structure of the QBD process at level 0. Our approach, which relies on the use of orthogonal polynomials, is an extension of that in Motyer and Taylor (2006) for the case where the generator has homogeneous blocks.
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40
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Dyne AM, Taylor PG, Boulton-Lewis GM. Information processing and the learning context: an analysis from recent perspectives in cognitive psychology. British Journal of Educational Psychology 2011. [DOI: 10.1111/j.2044-8279.1994.tb01109.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Muhammad S, Bassindale AR, Taylor PG, Male L, Coles SJ, Hursthouse MB. Study of Binuclear Silicon Complexes of Diketopiperazine at SN2 Reaction Profile. Organometallics 2011. [DOI: 10.1021/om1009318] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sohail Muhammad
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | - Alan R. Bassindale
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | - Peter G. Taylor
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K
| | - Louise Male
- EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ, U.K
| | - Simon J. Coles
- EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ, U.K
| | - Michael B. Hursthouse
- EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Southampton, SO17 1BJ, U.K
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42
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Abstract
Significant problems in health care, such as access block and long waiting lists for elective surgery, have led to calls for keeping hospital occupancy at no more than 85%. It is elementary queueing theory that a finite-capacity system with variable demand cannot sustain both full utilisation and full availability. However, the statement that there is a single level of ideal or safe occupancy suitable for all situations is a simplistic interpretation and application of the underlying science. We argue that specific study and action are necessary to understand and deal with the problems of long waiting lists and access block in any given health care facility.
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Affiliation(s)
- Christopher A Bain
- health-mic Special Interest Group, Health Informatics Society of Australia, Melbourne, VIC, Australia.
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43
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Bassindale AR, Sohail M, Taylor PG, Korlyukov AA, Arkhipov DE. Four independent structures of a pentacoordinate silicon species at different points on the Berry pseudorotation pathway. Chem Commun (Camb) 2010; 46:3274-6. [PMID: 20442884 DOI: 10.1039/c000803f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Alan R Bassindale
- Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
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Abbate V, Bassindale AR, Brandstadt KF, Lawson R, Taylor PG. Enzyme mediated silicon–oxygen bond formation; the use of Rhizopus oryzae lipase, lysozyme and phytase under mild conditions. Dalton Trans 2010; 39:9361-8. [DOI: 10.1039/c0dt00151a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bassindale AR, Parker DJ, Taylor PG, Turtle R. A Kinetic and Mechanistic Study of Nucleophilic Substitution at a Pentacoordinated Silicon Atom. Z Anorg Allg Chem 2009. [DOI: 10.1002/zaac.200900127] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Bassindale AR, Taylor PG, Abbate V, Brandstadt KF. Simple and mild preparation of silica-enzyme composites from silicic acid solution. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b916412j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Taylor PG, Dupuy Loo OA, Bonilla JA, Murillo R. Anticancer activities of two sesquiterpene lactones, millerenolide and thieleanin isolated from Viguiera sylvatica and Decachaeta thieleana. Fitoterapia 2008; 79:428-32. [PMID: 18534779 DOI: 10.1016/j.fitote.2007.07.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Accepted: 07/26/2007] [Indexed: 02/06/2023]
Abstract
The present study was carried out in order to examine the anticancer properties of two sesquiterpene lactones, millerenolide and thieleanin, isolated from Viguiera sylvatica and Decachaeta thieleana, against cell lines in vitro, and on the growth B16/BL6 melanoma tumors in C57BL/6 mice. Millerenolide and thieleanin showed a similar pattern of cytotoxicity with the greatest effect on viability being evident with A549 human lung cancer cells (IC(50) - 40 and 32 microM respectively), and with the 3T3/HER2 cell line which are 3T3 mouse fibroblasts transfected with the HER2 oncogene (IC(50) - 16 and 28 microM respectively). The parent 3T3 cells and the B16/BL6 mouse melanoma cells were less sensitive to these compounds, with thieleanin showing an IC(50) with B16/BL6 greater than the highest dose tested (203 microM). Treatment with millerenolide (8 mg/kg, i.p. on days 0, 2 and 4 post-inoculation) significantly inhibited the growth of subcutaneous B16/BL6 tumors in C57BL/6 mice, (50% inhibition at day 25, P=0.015), as well as retarding the appearance of detectable tumor (millerenolide - day 15.2+/-0.4 vs control - day 12.8+/-0.5, mean+/-SEM, P=0.011). In contrast, treatment with thieleanin (8 mg/kg every other day up to the day of kill) neither retarded the appearance of the tumor nor its growth.
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Affiliation(s)
- Peter G Taylor
- Laboratorio de Patología Celular y Molecular, Centro de Medicina Experimental, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 21827, Caracas 1020-A, Venezuela.
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Negrebetsky VV, Taylor PG, Kramarova EP, Shipov AG, Pogozhikh SA, Ovchinnikov YE, Korlyukov AA, Bowden A, Bassindale AR, Baukov YI. Synthesis, structure and dynamic stereochemistry of (O→Si)-chelate N-(trifluorosilylmethyl)-[N-(S)-(1-phenylethyl)]acetamide and 1-(trifluorosilylmethyl)-2-oxoperhydroazepine: Retention of the O→Si coordination in the adduct with KF and 18-crown-6. J Organomet Chem 2008. [DOI: 10.1016/j.jorganchem.2008.01.033] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Bassindale AR, Codina-Barrios A, Frascione N, Taylor PG. The use of silsesquioxane cages and phage display technology to probesilicone–protein interactions. NEW J CHEM 2008. [DOI: 10.1039/b710984a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bassindale AR, Liu Z, Taylor PG, Horton PN, Hursthouse MB. A simple route to novel D spherosilicones; the first crystallographic structures of D6 and D8 cages. Chem Commun (Camb) 2008:5625-7. [DOI: 10.1039/b808456d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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