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Analysis of stresses at the center of transversely isotropic Brazilian disk

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 618-629页

作者： Ali Aminzadeh Florian amann Institute of Geology of the Czech Academy of Sciences PragueCzech Republic Chair of Engineering Geology RWTH Aachen UniversityAachenGermany

This article presents the stresses at the center of a Brazilian disk(BD)for transversely isotropic rocks.It is shown that the solution of stresses at the center of an anisotropic disk is a function of the disk radius and the magnitude of applied load,as well as the material orientation with respect to the load axis and two dimensionless ratios with specific physical meanings and limitations.These two dimensionless parameters are the ratios of Young’s modulus and apparent shear modulus,although the ratio of apparent shear modulus will be eliminated if the Saint-Venant assumption is considered.Considerable finite element simulations are carried out to find the stresses at the disk center concerning the material orientation and the two dimensionless parameters.Also,an approximate formula obtained from analytical results,previously proposed in the literature for solving the tensile and compressive stresses at the disk center,is re-written and simplified based on these new definitions.The results of the approximate formula fitted to the analytical results are compared to those obtained from numerical solutions,suggesting a good agreement between the numerical and analytical methods.An approximate equation for the shear stress at the disk center is also formulated based on the numerical results.Finally,the influence of the assumptions for simplification of the proposed formula for the tensile,compressive,and shear stresses at the disk center is discussed,and simple and practical equations are proposed as estimations for the stresses at the center of the BD specimen for low to moderate anisotropic rocks.For highly anisotropic rocks,the reference plots can be used for more accuracy.

关键词： Brazilian test Transverse isotropy Rock anisotropy Anisotropic disk Tensile stress Shear stress

The uPA/uPAR system in astrocytic wound healing

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Neural Regeneration Research 2022年第11期17卷 2404-2406页

作者： manuel Yepes Division of Neuropharmacology and Neurologic Diseases Yerkes National Primate Research CenterAtlantaGAUSA Department of Neurology Emory University School of MedicineAtlantaGAUSA Department of Neurology Veterans Affairs Medical CenterAtlantaGAUSA

The repair of injured tissue is a highly complex process that involves cell prolife ration,differentiation,and migration.Cell migration requires the dismantling of intercellular contacts in the injured zone and their subsequent reconstitution in the wounded area.Urokinase-type plasminogen activator(u PA)is a serine proteinase found in multiple cell types including endothelial cells,smooth muscle cells,monocytes,and macrophages.A substantial body of experimental evidence with different cell types outside the central nervous system indicates that the binding of uPA to its receptor(uPAR)on the cell surface prompts cell migration by inducing plasmin-mediated degradation of the extracellular matrix.In contrast,although uPA and uPAR are abundantly found in astrocytes and u PA binding to uPAR triggers astrocytic activation,it is unknown if uPA also plays a role in astrocytic migration.Neuronal cadherin is a member of cell adhesion proteins pivotal for the formation of cell-cell conta cts between astrocytes.More specifically,while the extracellular domain of neuronal cadherin interacts with the extracellular domain of neuronal cadherin in neighboring cells,its intracellular domain binds toβ-catenin,which in turn links the complex to the actin cytos keleton.Glycogen synthase kinase 3βis a serine-threonine kinase that prevents the cytoplasmic accumulation ofβ-catenin by inducing its phosphorylation at Ser33,Ser37,and Ser41,thus activating a sequence of events that lead to its proteasomal degradation.The data discussed in this perspective indicate that astrocytes release u PA following a mechanical injury,and that binding of this u PA to uPAR on the cell membrane induces the detachment ofβ-catenin from the intracellular domain of neuronal cadherin by triggering its extracellular signal-regulated kinase 1/2-mediated phosphorylation at Tyr650.Remarkably,this is followed by the cytoplasmic accumulation ofβ-catenin because uPA-induced extracellular signalregulated kinase 1/2 activation also phosphorylates lipoprotein receptor-r

关键词： astrocytes lipoprotein receptor-related protein 6 plasmin urokinase receptor urokinase-type plasminogen activator Wnt-β-catenin pathway wound healing β-catenin

Tests to measure the quality of spermatozoa at spermiation

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Asian Journal of Andrology 2010年第1期12卷 71-78页

作者： Rupert P. amann Animal Reproduction and Biotechnology Laboratory Colorado State University Ft Collins CO 80526-1683 USA

This commentary is to critique the revised World Health Organization （WHO） semen analysis manual as it pertains to characteristics of a spermatozoon at spermiation. The aims of the revised WHO manual include improving the ＇quality of semen analysis＇ without any restriction to clinical use. Furthermore, the manual states that semen analysis may be useful for （a）＇investigating male fertility status＇ and （b）＇monitoring spermatogenesis during and following male fertility regula- tion.＇ However, if the analysis of ejaculated spermatozoa is intended for the purposes described in （b）, then cells that are abnormal at spermiation must be identified. This paper takes the position that the manual does not identify methods to estimate the quality of spermatozoa at spermiation. Instead, it uses a ＇gold standard＇ of sperm passing through the cervical mucus or arriving near the site of fertilization. Although this standard is appropriate for drawing conclusions regarding the probability that an individual could impregnate his partner, it is not appropriate for studying illness of the testes per se. Herein, the measures of sperm quality presented in the WHO manual are critiqued with respect to the detection of spermatozoa that were abnormal at spermiation vs. those that became abnormal subsequently. Quality assessments based on the percentage of motile or ＇viable＇ spermatozoa are meaningless. Alternative quality attributes defining spermatozoa at spermiation are presented in this paper. In conclusion, assessment of spermatozoal quality at spermiation, on the basis of quality attributes of individual ejaculated spermatozoa, is best achieved through application of （a） a new paradigm for the morphological evaluation of sperm quality and （b） modern analytical techniques to evaluate, in an adequate sample, several appropriate independent attributes in each spermatozoon in order to more accurately identify the proportion of abnormal spermatozoa.

关键词： attributes of spermatozoa purpose of semen examination semen analysis sperm quality spermiation

Load and velocity boundaries of oil-based superlubricity using 1,3-diketone

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Friction 2023年第5期11卷 704-715页

作者： Yuyang YUAN Tobias amann Yuwen XU Yan ZHANG Jingfu CHEN Chenqing YUAN Ke LI School of Transportation and Logistics Engineering Wuhan University of TechnologyWuhan 430063China Reliability Engineering Institute National Engineering Research Center for Water Transport SafetyMOSTWuhan 430063China Fraunhofer Institute for Mechanics of Materials IWM Freiburg 79108Germany

The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry.In this work,the superlubricity region of 1,3-diketone oil EPND(1-(4-ethyl phenyl)nonane-1,3-dione)on steel surfaces was identified by performing a series of ball-on-disk rotation friction tests under various normal loads(3.5–64 N)and sliding velocities(100–600 mm/s).The result shows that beyond certain loads or velocities superlubricity failed to be reached due to the following negative effects:(1)Under low load(≤3.5 N),insufficient running-in could not ensure good asperity level conformity between the upper and lower surfaces;(2)the high load(≥64 N)produced excessive wear and big debris;(3)at low velocity(≤100 mm/s),the weak hydrodynamic effect and the generated debris deteriorated the lubrication performance;(4)at high velocity(≥500 mm/s),oil migration occurred and resulted in oil starvation.In order to expand the load and velocity boundaries of the superlubricity region,an optimized running-in method was proposed to avoid the above negative effects.By initially operating a running-in process under a suitable combination of load and velocity(e.g.16 N and 300 mm/s)and then switching to the target certain higher or lower load/velocity(e.g.100 N),the superlubricity region could break through its original boundaries.The result of this work suggests that oil-based superlubricity of 1,3-diketone is a promising solution to friction reduction under suitable operating conditions especially using a well-designed running-in strategy.

关键词： macroscopic superlubricity 1,3-diketone oil running-in process load and velocity boundaries

The plasminogen activating system in the pathogenesis of Alzheimer’s disease

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Neural Regeneration Research 2021年第10期16卷 1973-1977页

作者： manuel Yepes Department of Neurology Emory University School of MedicineAtlantaGAUSA Department of Neurology Veterans Affairs Medical CenterAtlantaGAUSA Division of Neuropharmacology and Neurologic Diseases Yerkes National Primate Research CenterAtlantaGAUSA

Dementia is a clinical syndrome that affects approximately 47 million people worldwide and is characterized by progressive and irreversible decline of cognitive,behavioral and sesorimotor functions.Alzheimer’s disease(AD)accounts for approximately 60–80%of all cases of dementia,and neuropathologically is characterized by extracellular deposits of insoluble amyloid-β(Aβ)and intracellular aggregates of hyperphosphorylated tau.Significantly,although for a long time it was believed that the extracellular accumulation of Aβwas the culprit of the symptoms observed in these patients,more recent studies have shown that cognitive decline in people suffering this disease is associated with soluble Aβ-induced synaptic dysfunction instead of the formation of insoluble Aβ-containing extracellular plaques.These observations are translationally relevant because soluble Aβ-induced synaptic dysfunction is an early event in AD that precedes neuronal death,and thus is amenable to therapeutic interventions to prevent cognitive decline before the progression to irreversible brain damage.The plasminogen activating(PA)system is an enzymatic cascade that triggers the degradation of fibrin by catalyzing the conversion of plasminogen into plasmin via two serine proteinases:tissue-type plasminogen activator(tPA)and urokinase-type plasminogen activator(uPA).Experimental evidence reported over the last three decades has shown that tPA and uPA play a role in the pathogenesis of AD.However,these studies have focused on the ability of these plasminogen activators to trigger plasmin-induced cleavage of insoluble Aβ-containing extracellular plaques.In contrast,recent evidence indicates that activity-dependent release of uPA from the presynaptic terminal of cerebral cortical neurons protects the synapse from the deleterious effects of soluble Aβvia a mechanism that does not require plasmin generation or the cleavage of Aβfibrils.Below we discuss the role of the PA system in the pathogenesis of AD and the translational relevance of data published t

关键词： Alzheimer’s disease amyloid precursor protein amyloidβ neuroserpin plasmin plasminogen activating system plasminogen activator inhibitor-1 synapse tissue-type plasminogen activator urokinase-type plasminogen activator

The complex Maxwell stress tensor theorem:The imaginary stress tensor and the reactive strength of orbital momentum.A novel scenery underlying electromagnetic optical forces

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Light(Science & Applications) 2022年第11期11卷 2655-2675页

作者： manuel Nieto-Vesperinas Xiaohao Xu Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Cintificas.Campus de CantoblancoMadrid 28049Spain State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi'an 710119China Institute of Nanophotonics Jinan UniversityGuangzhou 511443China

We uncover the existence of a universal phenomenon concerning the electromagnetic optical force exerted by light or other electromagnetic waves on a distribution of charges and currents in general,and of particles in particular.This conveys the appearence of underlying reactive quantities that hinder radiation pressure and currently observed timeaveraged forces.This constitutes a novel paradigm of the mechanical effciency of light on matter,and completes the landscape of the optical,and generally electromagnetic,force in photonics and classical electrodynamics;widening our understanding in the design of both llumination and particles in optical manipulation without the need of increasing the illuminating power,and thus lowering dissipation and heating.We show that this may be accomplished through the minimization of what we establish as the reactive strength of orbital(or canonical)momentum,which plays against the optical force a role analogous to that of the reactive power versus the radiation effciency of an antenna.This long time overlooked quantity,important for current progress of optical manipulation,and that stems from the complex Maxwell theorem of conservation of complex momentum that we put forward,as well as its alternating flow associated to the imaginary part of the complex Maxwell stress tensor,conform the imaginary Lorentz force that we introduce in this work,and that like the reactive strength of orbital momentum,is antagonistic to the well-known time-averaged force;thus making this reactive Lorentz force indirectly observable near wavelengths at which the time-averaged force is lowered.The Minkowski and Abraham momenta are also addressed.

关键词： imaginary tensor orbital

Urokinase-type plasminogen activator is a modulator of synaptic plasticity in the central nervous system:implications for neurorepair in the ischemic brain

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Neural Regeneration Research 2020年第4期15卷 620-624页

作者： manuel Yepes Division of Neuropharmacology and Neurologic Diseases Yerkes National Primate Research Center Department of Neurology Emory University School of Medicine Department of Neurology Veterans Affairs Medical Center

The last two decades have witnessed a rapid decrease in mortality due to acute cerebral ischemia that paradoxically has led to a rapid increase in the number of patients that survive an acute ischemic stroke with various degrees of disability.Unfortunately,the lack of an effective therapeutic strategy to promote neurological recovery among stroke survivors has led to a rapidly growing population of disabled patients.Thus,understanding the mechanisms of neurorepair in the ischemic brain is a priority with wide scientific,social and economic implications.Cerebral ischemia has a harmful effect on synaptic structure associated with the development of functional impairment.In agreement with these observations,experimental evidence indicates that synaptic repair underlies the recovery of neurological function following an ischemic stroke.Furthermore,it has become evident that synaptic plasticity is crucial not only during development and learning,but also for synaptic repair after an ischemic insult.The plasminogen activating system is assembled by a cascade of enzymes and their inhibitors initially thought to be solely involved in the generation of plasmin.However,recent work has shown that in the brain this system has an important function regulating the development of synaptic plasticity via mechanisms that not always require plasmin generation.Urokinase-type plasminogen activator(uPA)is a serine proteinase and one of the plasminogen activators,that upon binding to its receptor(uPAR)not only catalyzes the conversion of plasminogen into plasmin on the cell surface,but also activates cell signaling pathways that promote cell migration,proliferation and survival.The role of uPA is the brain is not fully understood.However,it has been reported while uPA and uPAR are abundantly found in the developing central nervous system,in the mature brain their expression is restricted to a limited group of cells.Remarkably,following an ischemic injury to the mature brain the expression of uPA and uPAR increases to levels comparable

关键词： cerebral ischemia neurorepair plasminogen plasticity stoke synapse urokinase urokinase receptor

Dissecting symbiosis cell by cell

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Molecular Plant 2023年第2期16卷 308-309页

作者： manuel Frank Dugald Reid Department of Molecular Biology and Genetics Aarhus UniversityUniversitetsbyen 818000Aarhus CDenmark Department of Animal Plant and Soil SciencesSchool of AgricultureBiomedicine and EnvironmentLa Trobe UniversityMelbourneVIC 3086Australia

Symbiotic nitrogen fixation in legumes occurs in specialized root organs called nodules.Their development requires coordination across tissues as infection progresses from the epidermis to growing nodules derived from the cortex or pericycle.Moreover,functional nodules include a variety of specialized cells,including those that house the nitrogen-fixing bacteria.This combination of developmental changes across tissues and specialized functions acquired by nodule cells makes dissecting the process difficult using bulk analysis of gene expression,proteins,and metabolites.

关键词： organs cortex specialized

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从计算机科学理论审视意识和通用人工智能

Engineering 2023年第6期25卷 12-16页

作者： Lenore Blum manuel Blum Department of Computer Science School of Computer ScienceCarnegie Mellon UniversityPittsburghPA 15213USA Electrical Engineering and Computer Science Department University of CaliforniaBerkeleyCA 94720USA

1.Introduction We have defined the Conscious Turing Machine(CTM)for the purpose of investigating a theoretical computer science(TCS)approach to consciousness[1].For this,we have hewn to the TCS demand for simplicity and understandability.The CTM is consequently and intentionally a simple machine.It is not a model of the brain,though its design has greatly benefited—and continues to benefit—from neuroscience and psychology.

关键词： computer simplicity Turing