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Discovering plasticity models without stress data

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npj Computational Materials 2022年第1期8卷 857-866页

作者： moritz Flaschel Siddhant Kumar Laura De Lorenzis Department of Mechanical and Process engineering ETH Zürich8092ZürichSwitzerland Department of Materials Science and engineering Delft University of Technology2628 CDDelftThe Netherlands

We propose an approach for data-driven automated discovery of material laws,which we call eUCLID(efficient Unsupervised Constitutive Law Identification and Discovery),and we apply it here to the discovery of plasticity models,including arbitrarily shaped yield surfaces and isotropic and/or kinematic hardening *** approach is unsupervised,i.e.,it requires no stress data but only full-field displacement and global force data;it delivers interpretable models,i.e.,models that are embodied by parsimonious mathematical expressions discovered through sparse regression of a potentially large catalog of candidate functions;it is one-shot,i.e.,discovery only needs one *** material model library is constructed by expanding the yield function with a Fourier series,whereas isotropic and kinematic hardening is introduced by assuming a yield function dependency on internal history variables that evolve with the plastic *** selecting the most relevant Fourier modes and identifying the hardening behavior,eUCLID employs physics knowledge,i.e.,the optimization problem that governs the discovery enforces the equilibrium constraints in the bulk and at the loaded boundary of the *** promoting regularization is deployed to generate a set of solutions out of which a solution with low cost and high parsimony is automatically *** virtual experiments,we demonstrate the ability of eUCLID to accurately discover several plastic yield surfaces and hardening mechanisms of different complexity.

关键词： stress plasticity selecting

Two new hyperspectral indices for comparing vegetation chlorophyll content

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Geo-Spatial Information Science 2014年第1期17卷 17-25页

作者： amy e.FRAZIeR Le WANG Jin CHeN Department of Geography University at Buffalo-The State University of New YorkBuffaloNYUSA College of Resource environment and Tourism Capital Normal UniversityBeijingChina State Key Laboratory for earth Surface Processes and Resource ecology Beijing Normal UniversityBeijingChina Department of Geography Oklahoma State UniversityStillwaterOKUSA

The red edge region of a hyperspectral vegetation reflectance curve provides important information regarding the biochemical and biophysical parameters of plants such as stress,senescence,and chlorophyll ***,shifts of the red edge position(ReP)to longer or shorter wavelengths have also been correlated with other factors such as water content,nitrogen,and *** other factors can confuse the effect of chlorophyll on *** objective of this study is to define two new hyperspectral curve indices,the red valley width(RVW)and the chlorophyll absorption region(CAR)that are designed to provide less-sensitive characterizations of the chlorophyll content of vegetation in order to allow better comparisons among spatially or temporally distant populations of *** RVW and the CAR are both located in the visible near-infrared portion of the light spectrum and are derived from multiple hyperspectral curve features that have been found to be correlated with chlorophyll content,thus making them less sensitive to other biophysical and biochemical factors that can affect the ReP *** robustness of the two new features is tested using the Leaf Optical Properties experiment database,and the findings are used to compare two populations of saltcedar(Tamarix spp.)from a native habitat in China and an invasive habitat in the *** is a highly invasive plant species in the USA but does not pose the same ecological and economic threats in its native habitat throughout *** findings are interpreted in the context of the environmental characteristics of each region.

关键词： remote sensing spectral comparison non-native exotic species

Gradients in predation risk in a tropical river system

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Current Zoology 2018年第2期64卷 213-221页

作者： amy e. DeACON Faith A. M. JONeS Anne e. MAGURRAN Department of Life Sciences The University of the West Indies St Augustine Trinidad and Tobago School of Biology University of St Andrews Fife KY16 9TH Scotland UK

The importance of predation risk as a key driver of evolutionary change is exemplified by the Northern Range in Trinidad, where research on guppies living in multiple parallel streams has pro- vided invaluable insights into the process of evolution by natural selection. Although Trinidadian guppies are now a textbook example of evolution in action, studies have generally categorized predation as a dichotomous variable, representing high or low risk. Yet, ecologists appreciate that community structure and the attendant predation risk vary substantially over space and time. Here, we use data from a longitudinal study of fish assemblages at 16 different sites in the Northern Range to quantify temporal and spatial variation in predation risk. Specifically we ask： 1） Is there evidence for a gradient in predation risk？ 2） Does the ranking of sites （by risk） change with the defi- nition of the predator community （in terms of species composition and abundance currency）, and 3） Are site rankings consistent over time？ We find compelling evidence that sites lie along a contin- uum of risk. However, site rankings along this gradient depend on how predation is quantified in terms of the species considered to be predators and the abundance currency is used. Nonetheless, for a given categorization and currency, rankings are relatively consistent over time. Our study sug- gests that consideration of predation gradients will lead to a more nuanced understanding of the role of predation risk in behavioral and evolutionary ecology. It also emphasizes the need to justify and report the definition of predation risk being used.

关键词： abundance currency gradients Poecilia reticulata predation risk Trinidad Trinidadian guppy.

Lipid reserves and immune defense in healthy and diseased migrating monarchs Danaus plexippus

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Current Zoology 2013年第3期59卷 393-402页

作者： Dara A. SATTeRFIeLD amy e. WRIGHT Sonia ALTIZeR Odum School of ecology University of Georgia Athens GA 30602 USA

Recent studies suggest that the energetic demands of long-distance migration might lower the pool of resources available for costly immune defenses. Moreover, migration could amplify the costs of parasitism if animals suffering from para- site-induced damage or depleted energy reserves are less able to migrate long distances. We investigated relationships between long-distance migration, infection, and immunity in wild fall-migrating monarch butterflies Danaus plexippus. Monarchs migrate annually from eastern North America to central Mexico, accumulating lipids essential for migration and winter survival as they travel southward. Monarchs are commonly infected by the debilitating protozoan parasite Ophryocystis elektroscirrha （Oe）. We collected data on lipid reserves, parasite loads, and two immune measures （hemocyte concentration and phenoloxidase activity） from wild monarchs migrating through north GA （USA） to ask whether （1） parasite infection negatively affects lipid reserves, and （2） greater investment in lipid reserves is associated with lower immune measures. Results showed that monarchs sampled later in the fall migration had lower but not significantly different immune measures and significantly higher lipid reserves than those sampled earlier. Lipid measures correlated negatively but only nearly significantly with one measure of immune defense （phenoloxidase activity） in both healthy and infected monarchs, but did not depend on monarch infection status or parasite load. These results provide weak support for a trade-off between energy reserves and immune defense in migrants, and suggest that previously-demonstrated costs of Oe infection for monarch migration are not caused by depleted lipid reserves .

关键词： Butterfly Hemocytes Migration Neogregarine Infection energy reserves

Spatial heterogeneity of flesh-cell osmotic potential in sweet cherry affects partitioning of absorbed water

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Horticulture Research 2020年第1期7卷 2104-2113页

作者： eckhard Grimm Daniel Pflugfelder Jan Hahn moritz Jonathan Schmidt Hendrik Dieckmann moritz Knoche Institut für Gartenbauliche Produktionssysteme Leibniz Universität HannoverAbteilung ObstbauHerrenhäuser Straße 2D-30419 HannoverGermany Forschungszentrum Jülich IBG-2:PflanzenwissenschaftenWilhelm-Johnen-StraßeD-52428 JülichGermany Laser Zentrum Hannover e.V. Hollerithallee 8D-30419 HannoverGermany

A fleshy fruit is commonly assumed to resemble a thin-walled pressure vessel containing a homogenous carbohydrate *** sweet cherry(Prunus avium L.)as a model system,we investigate how local differences in cell water potential affect H2O and D2O(heavy water)*** partitioning of H2O and D2O was mapped nondestructively using magnetic resonance imaging(MRI).The change in size of mesocarp cells due to water movement was monitored by optical coherence tomography(OCT,non-destructive).Osmotic potential was mapped using microosmometry(destructive).Virtual sections through the fruit revealed that the H2O distribution followed a net pattern in the outer mesocarp and a radial pattern in the inner *** patterns align with the disposition of the vascular bundles.D2O uptake through the skin paralleled the acropetal gradient in cell osmotic potential gradient(from less negative to more negative).Cells in the vicinity of a vascular bundle were of more negative osmotic potential than cells more distant from a vascular *** revealed net H2O uptake was the result of some cells loosing volume and other cells increasing volume.H2O and D2O partitioning following uptake is non-uniform and related to the spatial heterogeneity in the osmotic potential of mesocarp cells.

关键词： potential Spatial bundle

SNL fibroblast feeder layers support derivation and maintenance of human induced pluripotent stem cells

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Journal of Genetics and Genomics 2010年第4期37卷 241-248页

作者： Chuanying Pan amy Hicks Xuan Guan Hong Chen Colin e. Bishop College of Animal Science and Technology Shaanxi Key Laboratory of Molecular BiologyJbr Agriculture Northwest A & F University Yangling 712100 China Wake Forest University Institute for Regenerative Medicine Wake Forest University Winston-Salem NC 2 7101 USA

Induced pluripotent stem （iPS） cells can be derived from human somatic cells by cellular reprograrnming. This technology provides a potential source of non-controversial therapeutic ceils for tissue repair, drug discovery, and opportunities for studying the molecular basis of human disease. Normally, mouse embryonic fibroblasts （MeFs） are used as feeder layers in the initial derivation of iPS lines. The pur- pose of this study was to determine whether SNL fibrohlasts can be used to support the growth of human iPS cells reprogrammed from somatic cells using lentiviral expressed reprogramming factors. In our study, iPS cells expressed common pluripotency markers, dis- played human embryonic stem cells （heSCs） morphology and unmethylated promoters of NANOG and OCT4. These data demonstrate that SNL feeder cells can support the derivation and maintenance of human iPS cells.

关键词： induced pluripotent stem cells derivation maintenance SNL feeder cells

primiReference: a reference for analysis of primary-microRNA expression in single-nucleus sequencing data

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Journal of Genetics and Genomics 2023年第2期50卷 108-121页

作者： amy e.elias Thomas A.Nuñez Bianca Kun Jill A.Kreiling Roche WilmingtonMA 01887USA. Department of Molecular Biology Cell Biology and BiochemistryBrown UniversityProvidenceRI02903USA Public Health Genetics University of PittsburghPittsburghPA 15260USA

Single-nucleus RNA-sequencing technology has revolutionized understanding of nuanced changes in gene expression between cell types within ***,our understanding of regulatory RNAs,such as microRNAs(miRNAs),is limited through both single-cell and single-nucleus techniques due to the short length of miRNAs in the cytoplasm and the incomplete reference of longer primary miRNA(pri-miRNA)transcripts in the *** build a custom reference to align and count pri-miRNA sequences in singlenucleus *** young and aged subventricular zone(SVZ)nuclei,we show differential expression of pri-miRNAs targeting genes involved in neural stem cells(NSC)differentiation in the aged ***,using wild-type and 5XFAD mouse model cortex nuclei,to validate the use of primiReference,we find cell-type-specific expression of pri-miRNAs known to be involved in Alzheimer’s disease(AD).pri-miRNAs likely contribute to NSC dysregulation with age and AD *** is paramount in capturing a global profile of gene expression and regulation in single-nucleus data and can provide key insights into cell-type-specific expression of pri-miRNAs,paving the way for future studies of regulation and pathway *** looking at pri-miRNA abundance and transcriptional differences,regulation of gene expression by miRNAs in disease and aging can be further explored.

关键词： Primary-microRNA Aging Subventricular zone Alzheimer’s disease Single-nucleus RNA-Seq microRNA Transcriptomics

Natural regeneration responses to thinning and burning treatments in ponderosa pine forests and implications for restoration

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Journal of Forestry Research 2022年第3期33卷 741-753页

作者： Tzeidle N.Wasserman amy e.M.Waltz John Paul Roccaforte Judith D.Springer Joseph e.Crouse ecological Restoration Institute Northern Arizona UniversityP.O.Box 15017FlagstaffAZ86011-5017USA

Understanding naturally occurring pine regeneration dynamics in response to thinning and burning treatments is necessary not only to measure the longevity of the restoration or fuels treatment,but also to assess how well regeneration meets forest sustainability guidelines and whether natural regeneration is sufficient for maintaining a sustainable forest structure and composition.A synthesis review was carried out on the effects of mechanical thinning and prescribed burn treatments on natural pine regeneration response in frequent-fire ponderosa pine forests across the western United *** focus was on site-specific variability in pine regeneration dynamics,temporal trends in regeneration presence and abundance,and response to treatment as described in the current literature using 29 studies that met our evidence-based review *** showed that the effects of thinning and burning treatments on regeneration depended on time since *** thinning,prescribed burning,and thinning plus burn treatments all increased seedling density,but there was high variability among sites and *** were mixed results in the short-term(ears)with both increasing and decreasing regeneration,and a general increase in regeneration 11−20 years *** long-term studies(>20 years)concluded that stands can return to pre-treatment densities in terms of total trees per hectare and forest floor duff levels when there are no maintenance treatments *** studies showed the average ponderosa pine seedling presence,survival and growth found in today’s forests to be at a high density;this combined with missed fire cycles could contribute to future fire risk and reduce the efficacy of maintaining fuel reduction goals.

关键词： Regeneration Ponderosa pine Frequent-fire Treatments Thinning Burning

Method for rapid on-site identification of VOCs

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Journal of environmental Sciences 2009年第7期21卷 1005-1008页

作者： Justin D Fair William F Bailey Robert A Felty amy e Gifford Benjamin Shultes Leslie H Volles Department of Chemistry University of Connecticut Storrs Connecticut 06269-3060 USA. INFICON Inc. 2 Technology Place East Syracuse New York 13057 USA

Rapid on-site identification of volatile organic compounds （VOCs） in ambient air is an important first step in remediation efforts. This study describes modification of a commercially available, portable GC/MS system and development of an analysis protocol for rapid （〈 3 min） sampling and identification of VOCs typically found at contaminated sites at the low ppbv level.

关键词： field analysis gas chromatograph mass spectrometer toxic industrial chemicals thermal desorption