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DEM investigation of strength and critical state behaviours of granular materials under true triaxial loadings

Particuology 2024年第2期85卷 198-212页

作者： Minyi Zhu Guobin Gong Jun Xia Stephen wilkinson Department of Civil Engineering Xi'an Jiaotong-Liverpool UniversityChina Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Engineering and Information Sciences University of Wollongong in DubaiUnited Arab Emirates

This paper investigates the strength and critical state(CS)behaviours of granular materials via DEM simulations of true triaxial drained tests under three different loading modes including constant b(in-termediate stress ratio)tests with constantσ'1(major principal stress),constant p(mean pressure)and constantσ'3(minor principal stress)*** this end,a series of samples are generated with the same particle size distribution,and with the confining stresses ranging from 100 kPa to 900 *** CS is achieved for all *** the macroscopic behaviours and the microscopic behaviours are examined and compared considering different loading modes,confining stresses and intermediate stress ratios(b).The critical state lines(CSLs)are found to be unique and independent of the loading modes,but dependent on the b *** CSLs with b=0 and b=1 form the two boundaries of CSLs respectively beyond which CSLs under all other b tests cannot go *** different strength criteria are examined and compared in terms of both peak and CS *** Mohr-Coulomb strength criterion is found to be only suitable for axisymmetric loading *** Lade-Duncan criterion is only suitable for describing peak strengths,which is dependent on the loading modes and confining *** Satake criterion and Matsuoka-nakai criterion are the more appropriate strength criteria for describing CS failures,indicating that the CS values of both the Satake parameter and the Matsuoka-nakai parameter describe an inherent property that characterizes the CS failure for a given type of *** CS mechanical coordination number is fitted by a curved line for a given b value,which is unique regardless of the loading *** peak and CS values of both major and minor principal fabric tensors decrease with increasing b values,while they increase with increasing b values for the intermediate principal fabric tensor.

关键词： Discrete element method Intermediate stress ratio Dilation Critical state Failure criterion

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骨转移所致骨相关事件的处理

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英国医学杂志中文版 2009年第2期12卷 101-105页

作者： anna n wilkinson Raymond Viola Michael D Brundage 梅齐(译) 于世英(校) Department of Oneology Ottawa Hospital Cancer Centre 503 Smyth Road Ottawa ON Canada KIH 1C4 Palliative Care Medicine Program Department of Medicine Queen' s University 34 Barrie Street Kingston ON Canada K7L 3J7 Division of Cancer Cave and Epidemiology Queen's Cancer Beseareh Institute Kingston ON Cansda KTL 3N6 武汉华中科技大学同济医学院附属同济医院肿瘤中心

疼痛是姑息治疗中需控制的最常见症状，而超过一半的癌症转移患者罹患骨转移相关的疼痛。约80％的骨转移来源于乳腺癌、肺癌和前列腺癌。转移性乳腺癌和前列腺癌患者生存时间较长，因而控制骨痛对他们尤为重要。因为初级保健医生与患者... 详细信息

疼痛是姑息治疗中需控制的最常见症状，而超过一半的癌症转移患者罹患骨转移相关的疼痛。约80％的骨转移来源于乳腺癌、肺癌和前列腺癌。转移性乳腺癌和前列腺癌患者生存时间较长，因而控制骨痛对他们尤为重要。因为初级保健医生与患者及家属长期密切的联系，他们是实施姑息治疗适合的人选，并能使各方都满意。

关键词：骨转移相关事件前列腺癌患者转移性乳腺癌初级保健医生姑息治疗常见症状癌症转移

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Deterministic epidemic models overestimate the basic reproduction number of observed outbreaks

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Infectious Disease Modelling 2024年第3期9卷 680-688页

作者： Wajid Ali Christopher E.Overton Robert R.wilkinson Kieran J.Sharkey Department of Mathematical Sciences University of LiverpoolPeach StreetLiverpoolL697ZXEnglandUnited Kingdom Department of Applied Mathematics Liverpool John Moores UniversityByrom StreetLiverpoolL35UXEnglandUnited Kingdom

The basic reproduction number,R_(0),is a well-known quantifier of epidemic ***,a class of existing methods for estimating R_(0)from incidence data early in the epidemic can lead to an over-estimation of this *** particular,when fitting deterministic models to estimate the rate of spread,we do not account for the stochastic nature of epidemics and that,given the same system,some outbreaks may lead to epidemics and some may ***,an observed epidemic that we wish to control is a major *** amounts to implicit selection for major outbreaks which leads to the over-estimation *** formally characterised the split between major and minor outbreaks by using Otsu's method which provides us with a working *** show that by conditioning a‘deterministic’model on major outbreaks,we can more reliably estimate the basic reproduction number from an observed epidemic trajectory.

关键词： Estimating R_(0) Simple birth-death process Major outbreak Conditioned epidemic Stochastic fade-out

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no evidence of contagious yawning in the red-footed tortoise Geochelone carbonaria

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Current Zoology 2011年第4期57卷 477-484页

作者： anna wilkinson natalie SEBAnZ Isabella MAnDL Ludwig HUBER Department of Cognitive Biology University of Vienna Althanstrasse 14 Vienna 1090 Austria Department of Biological Sciences University of Lincoln Lincoln LN2 2LG UK Donders Institute for Brain Cognition and Behavior Centre for Cognition Radboud University Nijmegen P.O. Box 9104 6500 HE Nijmegen The Netherlands

Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli： the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions： observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions： real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes [Current Zoology 57 （4）： 477-484, 2011].

关键词： Reptile Contagious yawn Empathy nonconscious mimicry Fixed action pattern

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Perception of artificial conspecifics by bearded dragons(Pogona vitticeps)

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Integrative Zoology 2019年第2期14卷 214-222页

作者： anna FROHnWIESER Thomas W.PIKE John C.MURRAY anna wilkinson School of Life Sciences University of LincolnLincolnUK School of Computer Science University of LincolnLincolnUK Wildlife Research Center Kyoto UniversityKyotoJapan

Artificial animals are increasingly used as conspecific stimuli in animal behavior ***,researchers often have an incomplete understanding of how the species under study perceives conspecifics,and,hence,which features are needed for a stimulus to be perceived *** investigate the features that bearded dragons(Pogona vitticeps)attend to,we measured their lateralized eye use when assessing a successive range of *** ranged through several stages of realism in artificial conspecifics,to see how features such as color,the presence of eyes,body shape and motion influence *** found differences in lateralized eye use depending on the sex of the observing bearded dragon and the artificial conspecific,as well as the artificial conspecific’s ***,this approach can inform the design of robotic animals that elicit biologically-meaningful responses in live animals.

关键词： bearded dragons conspecifics lateralized eye use perception

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Prostaglandin E1 administration post liver transplantation and renal outcomes:A retrospective single center experience

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World Journal of Transplantation 2024年第4期14卷 101-109页

作者： Vinay Jahagirdar Mohamed Ahmed Ifrah Fatima Hassam Ali Laura Alba John H Helzberg Lee S Cummings Matthew wilkinson Jameson Forster Alisa Likhitsup Department of Internal Medicine Saint Luke’s Health System of Kansas City and the University of Missouri-Kansas CityKansas CityMO 64111United States Department of Gastroenterology and Hepatology East Carolina University Brody School of MedicineGreenvilleNC 27834United States Division of Internal Medicine Department of Gastroenterology and HepatologySaint Luke’s Health System of Kansas City and University of Missouri-Kansas CityKansas CityMO 64111United States Department of Surgery University of Missouri-Kansas City and Transplant SurgerySaint Luke’s Hospital of Kansas CityKansas CityMO 64111United States Department of Gastroenterology and Hepatology University of MichiganAnn ArborMI 48109United States

BACKGROUnD Prostaglandin E1(PGE1),or alprostadil,is a potent vasodilator that improves hepatic blood flow and reduces ischemia-reperfusion injury post-liver transplantation(LT).However,the benefits of PGE1 on renal function after LT have not yet been well *** To assess the impact of PGE1 administration on renal function in patients who underwent liver or liver-kidney *** This retrospective study included all patients who underwent liver or liverkidney transplant at our institution from January,2011 to December,*** were classified based on whether they received ***1 was administered post-LT to those with transaminases>1000 U/L in the immediate postoperative ***,post-LT treatments and/or complications,renal function,and survival were *** logistic regression analysis was performed,and a two-tailed P valuensidered statistically *** A total of 145 patients underwent LT,with 44(30%)receiving *** patient characteristics were comparable,except the PGE1 group had significantly higher aspartate aminotransferase(AST)(1961.9 U/L±1862.3 U/L vs 878 U/L±741.4 U/L,P=0.000),alanine aminotransferase(1070.6 U/L±895 U/L vs 547.7 U/L±410 U/L,P=0.000),international normalized ratio on post-LT day 1(2±0.74 vs 1.8±0.4,P=0.03),a longer intensive care unit stay(8.1 days±11.8 days vs 3.8 days±4.6 days,P=0.003),more vasopressor use(55.53 hours±111 hours vs 16.33 hours±26.3 hours,P=0.002),and higher immediate postoperative complications(18.6%vs 4.9%,P=0.04).The PGE1 group also had a significantly higher 90-day readmission rate(29.6%vs 13.1%,P=0.02)and lower 1-year liver graft survival(87.5%vs 98.9%,P=0.005).However,30-day readmission(31.6%vs 27.4%,P=0.64),LT complications(hepatic artery thrombosis,biliary complications,rejection of liver graft,cardiomyopathy),1-year patient survival(96.9%vs 97.8%,P=0.77),overall liver graft survival,and overall patient survival were similar between t

关键词： Liver transplantation Alprostadil Protective agents Transplant Prostaglandin E1

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DEM simulations of critical state behaviour of granular materials under various drained triaxial stress path tests

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Particuology 2023年第10期81卷 98-108页

作者： Shiva Prashanth Kumar Kodicherla Guobin Gong Stephen wilkinson Department of Civil Mining and Process EngineeringNamibia University of Science and TechnologyWindhoekNamibia Department of Civil Engineering Xi’an Jiaotong-Liverpool UniversitySuzhouChina Faculty of Engineering and Information Sciences University of WollongongDubai CampusDubaiUnited Arab Emirates

The present study investigates the critical state behaviour of granular assemblies composed of clumped particles under four different drained axisymmetric triaxial stress paths,using the discrete element method(DEM).A series of numerical samples were prepared at initial states with different density indexes(1D)and different initial confining pressures(ρ′0).These samples were sheared to large strains,at which constant stresses and volumes were maintained to reach the critical *** evolution of stress ratio under the same loading mode(for the same intermediate principal stress ratio,b)is shown to yield an almost identical behaviour independent of stress paths,whereas the stress-strain response depends on the stress *** different axisymmetric stress paths all share the same unique friction angle at critical state,indicating the Mohr-Coulomb failure criterion is the appropriate critical state strength criterion,which is at least true for the axisymmetric stress conditions.A unique coordination number(Cn)is achieved at the critical state for a given po,which is independent of the stress *** critical state Cn is found to increase with the increase in po,which could be attributed to the decrease in the critical state void ratio(ec)as mean effective stress(ρ′0)***,a unique linear functional relationship is found between the critical state values of cn and ec,and a unique polynomial functional relationship is found between the critical state values of Cn andρ′.These functional relationships indicate no dependency on the stress paths or loading modes,thus characterizing unique features at critical states at both macroscopic and microscopic levels for a given type of granular material.

关键词： Discrete element method Critical state Drained behaviour Triaxial stress paths

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Shock fragmentation model for gravitational collapse

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Research in Astronomy and Astrophysics 2011年第5期11卷 545-562页

作者： Michael wilkinson Bernhard Mehlig Michael A.Morgan Department of Mathematics and Statistics The Open UniversityWalton HallMilton KeynesMK7 6AAEngland Department of Physics Gteborg UniversityGothenburg 41296Sweden Department of Physics Seattle UniversitySeattleWA 98122USA

A cloud of gas collapsing under gravity will fragment. We present a new theory for this process, in which layers of shocked gas fragment due to their gravitational instability. Our model explains why angular momentum does not inhibit the collapse process. The theory predicts that the fragmentation process produces objects which are significantly smaller than most stars, implying that accretion onto the fragments plays an essential role in determining the initial masses of stars. This prediction is also consistent with the hypothesis that planets can be produced by gravitational collapse.

关键词： gravitation -instabilities - shock waves -ISM: dust- stars: forma-tion -planetary systems

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Autophagy in cancer biology and therapy

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Frontiers in Biology 2014年第1期9卷 35-50页

作者： noor GAMMOH Simon wilkinson Edinburgh Cancer Research UK Centre MRC Institute of Genetics and Molecular Medicine University of Edinburgh Crewe Road SouthUnited Kingdom EH4 2XR

The role of macroautophagy （hereafter autophagy） in cancer biology and response to clinical intervention is complex. It is clear that autophagy is dysregulated in a wide variety of tumor settings, both during tumor initiation and progression, and in response to therapy. However, the pleiotropic mechanistic roles of autophagy in controlling cell behavior make it difficult to predict in a given tumor setting what the role of autophagy, and, by extension, the therapeutic outcome of targeting autophagy, might be. In this review we summarize the evidence in the literature supporting pro- and anti-tumorigenic and -therapeutic roles of autophagy in cancer. This overview encompasses roles of autophagy in nutrient management, cell death, cell senescence, regulation of proteotoxic stress and cellular homeostasis, regulation of tumor-host interactions and participation in changes in metabolism. We also try to understand, where possible, the mechanistic bases of these roles for autophagy. We specifically expand on the emerging role of genetically- engineered mouse models of cancer in shedding light on these issues in vivo. We also consider how any or all of the above functions of autophagy proteins might be targetable by extant or future classes of pharmacologic agents. We conclude by briefly exploring non-canonical roles for subsets of the key autophagy proteins in cellular processes, and how these might impact upon cancer.

关键词： autophagy cancer inflammation metabolism apoptosis homeostasis

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Active earth pressure acting on retaining wall considering anisotropic seepage effect

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Journal of Mountain Science 2017年第6期14卷 1202-1211页

作者： HU Zheng YAnG Zhong-xuan Stephen Philip wilkinson Department of Civil Engineering Zhejiang University Hangzhou 310058 China Department of Civil Engineering University ofWolverhampton Wulfruna Street WV1 1LY U.K.

This paper presents a general solution for active earth pressure acting on a vertical retaining wall with a drainage system along the soil-structure interface. The backfill has a horizontal surface and is composed of cohesionless and fully saturated sand with anisotropic permeability along the vertical and horizontal directions. The extremely unfavourable seepage flow on the back of the retaining wall due to heavy rainfall or other causes will dramatically increase the active earth pressure acting on the retaining walls, increasing the probability of instability. In this paper, an analytical solution to the Laplace differential governing equation is presented for seepage problems considering anisotropic permeability based on Fourier series expansion method. A good correlation is observed between this and the seepage forces along a planar surface generated via finite element analysis. The active earth pressure is calculated using Coulomb's earth pressure theory based on the calculated pore water pressures. The obtained solutions can be degenerated into Coulomb's formula when no seepage exists in the backfill. A parametric study on the influence of the degree of anisotropy in seepage flow on the distribution of active earth pressure behind the wall is conducted by varying ratios of permeability coefficients in the vertical and horizontal directions,showing that anisotropic seepage flow has a prominent impact on active earth pressure distribution. Other factors such as effective internal friction angle of soils and soil/wall friction conditions are also considered.

关键词： Active earth pressure Seepage Anisotropic permeability Retaining wall Fourier series expansion Cohesionless soils

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