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A computational model of ureteral peristalsis and an investigation into ureteral reflux
G. Hosseini,C. Ji,D. Xu,M. A. Rezaienia,E. Avital,A. Munjiza,J. J. R. Williams,J. S. A. Green 대한의용생체공학회 2018 Biomedical Engineering Letters (BMEL) Vol.8 No.1
The aim of this study is to create a computationalmodel of the human ureteral system that accuratelyreplicates the peristaltic movement of the ureter for avariety of physiological and pathological functions. Theobjectives of this research are met using our in-house fluidstructuraldynamics code (CgLes–Y code). A realisticperistaltic motion of the ureter is modelled using a novelpiecewise linear force model. The urodynamic responsesare investigated under two conditions of a healthy and adepressed contraction force. A ureteral pressure during thecontraction shows a very good agreement with correspondingclinical data. The results also show a dependencyof the wall shear stresses on the contraction velocity and itconfirms the presence of a high shear stress at the proximalpart of the ureter. Additionally, it is shown that an inefficientlumen contraction can increase the possibility of acontinuous reflux during the propagation of peristalsis.
Diversification and enrichment of clinical biomaterials inspired by Darwinian evolution
Green, D.W.,Watson, G.S.,Watson, J.A.,Lee, D.J.,Lee, J.M.,Jung, H.S. Elsevier BV 2016 ACTA BIOMATERIALIA Vol.42 No.-
Regenerative medicine and biomaterials design are driven by biomimicry. There is the essential requirement to emulate human cell, tissue, organ and physiological complexity to ensure long-lasting clinical success. Biomimicry projects for biomaterials innovation can be re-invigorated with evolutionary insights and perspectives, since Darwinian evolution is the original dynamic process for biological organisation and complexity. Many existing human inspired regenerative biomaterials (defined as a nature generated, nature derived and nature mimicking structure, produced within a biological system, which can deputise for, or replace human tissues for which it closely matches) are without important elements of biological complexity such as, hierarchy and autonomous actions. It is possible to engineer these essential elements into clinical biomaterials via bioinspired implementation of concepts, processes and mechanisms played out during Darwinian evolution; mechanisms such as, directed, computational, accelerated evolutions and artificial selection contrived in the laboratory. These dynamos for innovation can be used during biomaterials fabrication, but also to choose optimal designs in the regeneration process. Further evolutionary information can help at the design stage; gleaned from the historical evolution of material adaptations compared across phylogenies to changes in their environment and habitats. Taken together, harnessing evolutionary mechanisms and evolutionary pathways, leading to ideal adaptations, will eventually provide a new class of Darwinian and evolutionary biomaterials. This will provide bioengineers with a more diversified and more efficient innovation tool for biomaterial design, synthesis and function than currently achieved with synthetic materials chemistry programmes and rational based materials design approach, which require reasoned logic. It will also inject further creativity, diversity and richness into the biomedical technologies that we make. All of which are based on biological principles. Such evolution-inspired biomaterials have the potential to generate innovative solutions, which match with existing bioengineering problems, in vital areas of clinical materials translation that include tissue engineering, gene delivery, drug delivery, immunity modulation, and scar-less wound healing. Statement of Significance: Evolution by natural selection is a powerful generator of innovations in molecular, materials and structures. Man has influenced evolution for thousands of years, to create new breeds of farm animals and crop plants, but now molecular and materials can be molded in the same way. Biological molecules and simple structures can be evolved, literally in the laboratory. Furthermore, they are re-designed via lessons learnt from evolutionary history. Through a 3-step process to (1) create variants in material building blocks, (2) screen the variants with beneficial traits/properties and (3) select and support their self-assembly into usable materials, improvements in design and performance can emerge. By introducing biological molecules and small organisms into this process, it is possible to make increasingly diversified, sophisticated and clinically relevant materials for multiple roles in biomedicine.
Local Structure of Fe Impurity Atoms in ZnO: Bulk versus Surface
McLeod, J. A.,Boukhvalov, D. W.,Zatsepin, D. A.,Green, R. J.,Leedahl, B.,Cui, L.,Kurmaev, E. Z.,Zhidkov, I. S.,Finkelstein, L. D.,Gavrilov, N. V.,Cholakh, S. O.,Moewes, A. American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.10
<P>By studying Fe-doped ZnO pellets and thin films with various X-ray spectroscopic techniques, and complementing this with density functional theory calculations, we find that Fe-doping in bulk ZnO induces isovalent (and isostructural) cation substitution (Fe<SUP>2+</SUP> → Zn<SUP>2+</SUP>). In contrast to this, Fe-doping near the surface produces both isovalent and heterovalent substitution (Fe<SUP>3+</SUP> → Zn<SUP>2+</SUP>). The calculations performed herein suggest that the most likely defect structure is the single or double substitution of Zn with Fe, although, if additional oxygen is available, then Fe substitution with interstitial oxygen is even more energetically favorable. Furthermore, it is found that ferromagnetic states are energetically unfavorable, and ferromagnetic ordering is likely to be realized only through the formation of a secondary phase (i.e., ZnFe<SUB>2</SUB>O<SUB>4</SUB>), or codoping with Cu.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-10/jp411219z/production/images/medium/jp-2013-11219z_0010.gif'></P>
The SAMI Galaxy Survey: observing the environmental quenching of star formation in GAMA groups
Schaefer, A L,Croom, S M,Scott, N,Brough, S,Allen, J T,Bekki, K,Bland-Hawthorn, J,Bloom, J V,Bryant, J J,Cortese, L,Davies, L J M,Federrath, C,Fogarty, L M R,Green, A W,Groves, B,Hopkins, A M,Konstant Oxford University Press 2019 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.483 No.3
Structural defects induced by Fe-ion implantation in TiO<sub>2</sub>
Leedahl, B.,Zatsepin, D. A.,Boukhvalov, D. W.,Green, R. J.,McLeod, J. A.,Kim, S. S.,Kurmaev, E. Z.,Zhidkov, I. S.,Gavrilov, N. V.,Cholakh, S. O.,Moewes, A. American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.5
X-ray photoelectron spectroscopy and resonant x-ray emission spectroscopy measurements of pellet and thin film forms of TiO2 with implanted Fe ions are presented and discussed. The findings indicate that Fe-implantation in a TiO2 pellet sample induces heterovalent cation substitution (Fe2+ -> Ti4+) beneath the surface region. But in thin film samples, the clustering of Fe atoms is primarily detected. In addition to this, significant amounts of secondary phases of Fe3+ are detected on the surface of all doped samples due to oxygen exposure. These experimental findings are compared with density functional theory calculations of formation energies for different configurations of structural defects in the implanted TiO2:Fe system. According to our calculations, the clustering of Fe-atoms in TiO2:Fe thin films can be attributed to the formation of combined substitutional and interstitial defects. Further, the differences due to Fe doping in pellet and thin film samples can ultimately be attributed to different surface to volume ratios. (C) 2014 AIP Publishing LLC.
M.K. Bae,S.N. Yi,A.M. Green,D.H. Shin,J.H. Na,N.L. Kang,R.A. Taylor,박승환 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.3
We have studied the microscopic surface morphology of AlN which was revealed by using an atomic force microscopy (AFM). AlN was sputtered on Si (111) and Si (100) substrates for 30 and 60 minutes. AlN was observed to crystallize as cubic-AlN at an annealing temperature of 900 C and an annealing time of 60 minutes. We present a model to explain this cubic AlN bonding configuration. GaN was grown on AlN/Si(111) and AlN/Si(100) substrates by using a hydride vapor phase epitaxy technique. A terrace with saw-tooth-shaped formations was observed on the GaN surface and could be explained in terms of the lattice mismatch and the gas diusion rate.