Browsing by Subject "MODEL"

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    A new non-enzymatic method for isolating human intervertebral disc cells preserves the phenotype of nucleus pulposus cells.
    (Cytotechnology, 2014-12) Tang, Xinyan; Richardson, William J; Fitch, Robert D; Brown, Christopher R; Isaacs, Robert E; Chen, Jun
    Cells isolated from intervertebral disc (IVD) tissues of human surgical samples are one of potential sources for the IVD cellular therapy. The purpose of this study was to develop a new non-enzymatic method, "tissue incubation", for isolating human IVD cells. The IVD tissues of annulus fibrosus (AF) and nucleus pulposus (NP) were incubated separately in tissue culture flasks with culture medium. After 7-10 days incubation, cells were able to migrate out of IVD tissues and proliferate in vitro. After 3-4 weeks culture, expanded cells were harvested by trypsinization, and the remaining tissues were transferred to a new flask for another round of incubation. The molecular phenotype of IVD cells from juvenile and adult human samples was evaluated by both flow cytometry analysis and immunocytochemical staining for the expression of protein markers of NP cells (CD24, CD54, CD239, integrin α6 and laminin α5). Flow cytometry confirmed that both AF and NP cells of all ages positively expressed CD54 and integrin α6, with higher expression levels in NP cells than in AF cells for the juvenile group sample. However, CD24 expression was only found in juvenile NP cells, and not in AF or older disc cells. Similar expression patterns for NP markers were also confirmed by immunocytochemistry. In summary, this new non-enzymatic tissue incubation method for cell isolation preserves molecular phenotypic markers of NP cells and may provide a valuable cell source for the study of NP regeneration strategies.
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    Boom and bust carbon-nitrogen dynamics during reforestation
    (Ecological Modelling, 2017-09-24) Parolari, AJ; Mobley, ML; Bacon, AR; Katul, GG; Richter, DDB; Porporato, A
    © 2017 Elsevier B.V. Legacies of historical land use strongly shape contemporary ecosystem dynamics. In old-field secondary forests, tree growth embodies a legacy of soil changes affected by previous cultivation. Three patterns of biomass accumulation during reforestation have been hypothesized previously, including monotonic to steady state, non-monotonic with a single peak then decay to steady state, and multiple oscillations around the steady state. In this paper, the conditions leading to the emergence of these patterns is analyzed. Using observations and models, we demonstrate that divergent reforestation patterns can be explained by contrasting time-scales in ecosystem carbon-nitrogen cycles that are influenced by land use legacies. Model analyses characterize non-monotonic plant-soil trajectories as either single peaks or multiple oscillations during an initial transient phase controlled by soil carbon-nitrogen conditions at the time of planting. Oscillations in plant and soil pools appear in modeled systems with rapid tree growth and low initial soil nitrogen, which stimulate nitrogen competition between trees and decomposers and lead the forest into a state of acute nitrogen deficiency. High initial soil nitrogen dampens oscillations, but enhances the magnitude of the tree biomass peak. These model results are supported by data derived from the long-running Calhoun Long-Term Soil-Ecosystem Experiment from 1957 to 2007. Observed carbon and nitrogen pools reveal distinct tree growth and decay phases, coincident with soil nitrogen depletion and partial re-accumulation. Further, contemporary tree biomass loss decreases with the legacy soil C:N ratio. These results support the idea that non-monotonic reforestation trajectories may result from initial transients in the plant-soil system affected by initial conditions derived from soil changes associated with land-use history.
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    Boom and Bust: The Effect of Entrepreneurial Inertia on Organizational Populations
    (Advances in Strategic Management, 2006) Ruef, M
    Although recent public attention has focused on boom-and-bust cycles in industries and financial markets, organizational theorists have made only limited contributions to our understanding of this issue. In this chapter, I argue that a distinctive strategic insight into the mechanisms generating boom-and-bust cycles arises from a focus on entrepreneurial inertia - the lag time exhibited by organizational founders or investors entering a market niche. While popular perceptions of boom-and-bust cycles emphasize the deleterious effect of hasty entrants or overvaluation, I suggest instead that slow, methodical entries into an organizational population or market may pose far greater threats to niche stability. This proposition is explored analytically, considering the development of U.S. medical schools since the mid-18th century. © 2006 Elsevier Ltd. All rights reserved.
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    Computer aided restoration of handwritten character strokes
    (CAD Computer Aided Design, 2017-08-01) Sober, B; Levin, D
    © 2017 Elsevier Ltd This work suggests a new variational approach to the task of computer aided segmentation and restoration of incomplete characters, residing in a highly noisy document image. We model character strokes as the movement of a pen with a varying radius. Following this model, in order to fit the digital image, a cubic spline representation is being utilized to perform gradient descent steps, while maintaining interpolation at some initial (manually sampled) points. The proposed algorithm was used in the process of restoring approximately 1000 ancient Hebrew characters (dating to ca. 8th–7th century BCE), some of which are presented herein and show that the algorithm yields plausible results when applied on deteriorated documents.
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    Correlates of Parent-Child Physiological Synchrony and Emotional Parenting: Differential Associations in Varying Interactive Contexts
    (Journal of Child and Family Studies, 2019-04-01) Han, ZR; Gao, MM; Yan, J; Hu, X; Zhou, W; Li, X
    © 2019, The Author(s). Objectives: Parent-child synchrony during interaction might possess important features that underlie parenting processes throughout development. However, little is known regarding the association between parent-child physiological synchrony and emotional parenting behaviors during middle childhood. The main goal of the study was to examine whether emotional parenting was positively or negatively associated with parent-child physiological synchrony for school-age children. Methods: Adopting a biopsychosocial perspective, we incorporated the interbeat interval (IBI) and behavioral observation data of 150 parent-child dyads (child M age = 8.77, SD= 1.80) to explore the patterns of moment-to-moment dyadic physiological synchrony and to investigate whether these patterns were associated with two emotional parenting behaviors (psychological control and psychological unavailability). Results: Our findings provided some initial evidence that in low to moderately stressful situations that mimic daily parent-child interaction, parent-child physiological synchrony was indicative of different emotional parenting behaviors in various parent-child interactive situations. Specifically, in the collaborative context (parent-child working together to complete a task), parent-child physiological synchrony was indicative of less psychological unavailability, whereas in the competitive context (parent-child resolving disagreement with each other), parent-child physiological synchrony was indicative of less psychological control. The study implications and future research directions are discussed. Conclusions: Overall, our findings suggested that dyadic physiological synchrony, indexed by parent-child moment-to-moment matching of IBI, was associated with fewer negative emotional parenting behaviors.
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    Homogenization of thermal-hydro-mass transfer processes
    (Discrete and Continuous Dynamical Systems - Series S, 2015-02-01) Xu, S; Yue, X
    In the repository, multi-physics processes are induced due to the long-time heat-emitting from the nuclear waste, which is modeled as a nonlinear system with oscillating coefficients. In this paper we first derive the homogenized system for the thermal-hydro-mass transfer processes by the technique of two-scale convergence, then present some error estimates for the first order expansions.
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    Hydro-geomorphic perturbations on the soil-atmosphere CO2exchange: How (un)certain are our balances?
    (Water Resources Research, 2017-02) Dialynas, Yannis G; Bras, Rafael L; deB. Richter, Daniel
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    Links between physical and chemical weathering inferred from a 65-m-deep borehole through Earth's critical zone.
    (Scientific reports, 2019-03-14) Holbrook, W Steven; Marcon, Virginia; Bacon, Allan R; Brantley, Susan L; Carr, Bradley J; Flinchum, Brady A; Richter, Daniel D; Riebe, Clifford S
    As bedrock weathers to regolith - defined here as weathered rock, saprolite, and soil - porosity grows, guides fluid flow, and liberates nutrients from minerals. Though vital to terrestrial life, the processes that transform bedrock into soil are poorly understood, especially in deep regolith, where direct observations are difficult. A 65-m-deep borehole in the Calhoun Critical Zone Observatory, South Carolina, provides unusual access to a complete weathering profile in an Appalachian granitoid. Co-located geophysical and geochemical datasets in the borehole show a remarkably consistent picture of linked chemical and physical weathering processes, acting over a 38-m-thick regolith divided into three layers: soil; porous, highly weathered saprolite; and weathered, fractured bedrock. The data document that major minerals (plagioclase and biotite) commence to weather at 38 m depth, 20 m below the base of saprolite, in deep, weathered rock where physical, chemical and optical properties abruptly change. The transition from saprolite to weathered bedrock is more gradational, over a depth range of 11-18 m. Chemical weathering increases steadily upward in the weathered bedrock, with intervals of more intense weathering along fractures, documenting the combined influence of time, reactive fluid transport, and the opening of fractures as rock is exhumed and transformed near Earth's surface.
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    Non-stokes drag coefficient in single-particle electrophoresis: New insights on a classical problem
    (Chinese Physics B, 2019-01-01) Liao, MJ; Wei, MT; Xu, SX; Daniel Ou-Yang, H; Sheng, P
    We measured the intrinsic electrophoretic drag coefficient of a single charged particle by optically trapping the particle and applying an AC electric field, and found it to be markedly different from that of the Stokes drag. The drag coefficient, along with the measured electrical force, yield a mobility-zeta potential relation that agrees with the literature. By using the measured mobility as input, numerical calculations based on the Poisson-Nernst-Planck equations, coupled to the Navier-Stokes equation, reveal an intriguing microscopic electroosmotic flow near the particle surface, with a well-defined transition between an inner flow field and an outer flow field in the vicinity of electric double layer's outer boundary. This distinctive interface delineates the surface that gives the correct drag coefficient and the effective electric charge. The consistency between experiments and theoretical predictions provides new insights into the classic electrophoresis problem, and can shed light on new applications of electrophoresis to investigate biological nanoparticles.
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    rbcL phylogeny of the fern genus Trichomanes (Hymenophyllaceae), with special reference to Neotropical taxa
    (International Journal of Plant Sciences, 2003-01-01) Dubuisson, JY; Hennequin, S; Douzery, EJP; Cranfill, RB; Smith, AR; Pryer, KM
    In order to estimate evolutionary relationships within the filmy fern genus Trichomanes (Hymenophyllaceae), we performed a phylogenetic analysis using rbcL nucleotide data from 46 species of Trichomanes belonging to all four of C. V. Morton's subgenera: Achomanes, Didymoglossum, Pachychaetum, and Trichomanes. Outgroups included four species of Hymenophyllum in three different subgenera, plus the monotypic genus Cardiomanes, from New Zealand. We find high resolution and robust support at most nodes, regardless of the phylogenetic optimization criterion used (maximum parsimony or maximum likelihood). Two species belonging to Morton's Asiatic sections Callistopteris and Cephalomanes are in unresolved basal positions within Trichomanes s.l., suggesting that rbcL data alone are inadequate for estimating the earliest cladogenetic events. Out of the four Morton trichomanoid subgenera, only subg. Didymoglossum appears monophyletic. Other noteworthy results include the following: (1) lianescent sect. Lacostea is more closely related to sect. Davalliopsis (traditionally placed in subg. Pachychaetum) than to other members of subg. Achomanes; (2) sections Davalliopsis and Lacostea, together with species of the morphologically different subg. Achomanes, make up a strongly supported Neotropical clade; (3) all hemiepiphytes (but not true lianas) and strictly epiphytic or epipetric species (Morton's subgenera Trichomanes and Didymoglossum) group together in an ecologically definable clade that also includes the terrestrial sect. Nesopteris; and (4) sect. Lacosteopsis (sensu Morton) is polyphyletic and comprises two distantly related clades: large hemiepiphytic climbers and small strictly epiphytic/epipetric taxa. Each of these associations is somewhat unexpected but is supported by cytological, geographical, and/or ecological evidence. We conclude that many morphological characters traditionally used for delimiting groups within Trichomanes are, in part, plesiomorphic or homoplastic. Additionally, we discuss probable multiple origins of Neotropical Trichomanes.
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    Rescuing a Quantum Phase Transition with Quantum Noise.
    (Physical review letters, 2017-02) Zhang, Gu; Novais, E; Baranger, Harold U
    We show that placing a quantum system in contact with an environment can enhance non-Fermi-liquid correlations, rather than destroy quantum effects, as is typical. The system consists of two quantum dots in series with two leads; the highly resistive leads couple charge flow through the dots to the electromagnetic environment, the source of quantum noise. While the charge transport inhibits a quantum phase transition, the quantum noise reduces charge transport and restores the transition. We find a non-Fermi-liquid intermediate fixed point for all strengths of the noise. For strong noise, it is similar to the intermediate fixed point of the two-impurity Kondo model.
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    Social Ontology and the Dynamics of Organizational Forms: Creating Market Actors in the Healthcare Field, 1966-1994
    (Social Forces, 1999) Ruef, M
    Social scientists have evidenced a long-standing interest in the cultural construction of ontologies - symbolic systems of categorization and meaning - but have yet to develop a widely recognized method for the empirical analysis of this process. Analyzing textual data from the area of health services research, this article illustrates a general framework that can be employed to isolate the tacit rules used to structure an ontology and identify changes in those rules over time. Focusing on the process of market reform in U.S. healthcare during the last thirty years, this study finds systematic variation in the dimensions used to differentiate discourse on organizational forms such as hospitals, health maintenance organizations, and nursing homes. Discourse in the sector suggests that the symbolic integration of forms along the dimension of accessibility during the heyday of welfare state policies has given way to symbolic integration along clinical and functional dimensions with the rise of neoliberal ideologies. These segregating and blending processes are discussed as a general response to uncertainty and the desire for ontological security among organizational actors.
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    Soil production and the soil geomorphology legacy of Grove Karl Gilbert
    (Soil Science Society of America Journal, 2020-01-01) Richter, DD; Eppes, MC; Austin, JC; Bacon, AR; Billings, SA; Brecheisen, Z; Ferguson, TA; Markewitz, D; Pachon, J; Schroeder, PA; Wade, AM
    © 2019 The Authors. Soil Science Society of America published by Wiley Periodicals, Inc. on behalf of Soil Science Society of America Geomorphologists are quantifying the rates of an important component of bedrock's weathering in research that needs wide discussion among soil scientists. By using cosmogenic nuclides, geomorphologists estimate landscapes’ physical lowering, which, in a steady landscape, equates to upward transfers of weathered rock into slowly moving hillslope-soil creep. Since the 1990s, these processes have been called “soil production” or “mobile regolith production”. In this paper, we assert the importance of a fully integrated pedological and geomorphological approach not only to soil creep but to soil, regolith, and landscape evolution; we clarify terms to facilitate soil geomorphology collaboration; and we seek a greater understanding of our sciences’ history. We show how the legacy of Grove Karl Gilbert extend across soil geomorphology. We interpret three contrasting soils and regoliths in the USA's Southern Piedmont in the context of a Gilbert-inspired model of weathering and transport, a model of regolith evolution and of nonsteady systems that liberate particles and solutes from bedrock and transport them across the landscape. This exercise leads us to conclude that the Southern Piedmont is a region with soils and regoliths derived directly from weathering bedrock below (a regional paradigm for more than a century) but that the Piedmont also has significant areas in which regoliths are at least partly formed from paleo-colluvia that may be massive in volume and overlie organic-enriched layers, peat, and paleo-saprolite. An explicitly integrated study of soil geomorphology can accelerate our understanding of soil, regoliths, and landscape evolution in all physiographic regions.
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    Stationary state volume fluctuations in a granular medium.
    (Physical review. E, Statistical, nonlinear, and soft matter physics, 2005-03-30) Schröter, Matthias; Goldman, Daniel I; Swinney, Harry L
    A statistical description of static granular material requires ergodic sampling of the phase space spanned by the different configurations of the particles. We periodically fluidize a column of glass beads and find that the sequence of volume fractions phi of postfluidized states is history independent and Gaussian distributed about a stationary state. The standard deviation of phi exhibits, as a function of phi, a minimum corresponding to a maximum in the number of statistically independent regions. Measurements of the fluctuations enable us to determine the compactivity X , a temperaturelike state variable introduced in the statistical theory of Edwards and Oakeshott [Physica A 157, 1080 (1989)].
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    The Formation of Clay-Enriched Horizons by Lessivage
    (Geophysical Research Letters, 2018-08-16) Calabrese, S; Richter, DD; Porporato, A
    ©2018. American Geophysical Union. All Rights Reserved. Soils with argillic horizons comprise more than 25% of the Earth's surface. Although their origin is still debated, lessivage is often invoked to explain them, but the long timescales involved hinder its direct experimental verification. We present a parsimonious model of clay transport, formulated for long timescales over which lessivage is modeled stochastically, complemented by detailed field observations. This probabilistic description allows us to predict the clay profile, the depth of the Bt horizon from the surface, and the mean clay residence time. The results are tested with field measurements at different locations in the Calhoun Critical Zone Observatory. Dimensional analysis unveils two dimensionless parameters governing lessivage dynamics, leading to a classification based on erosion rates and lessivage characteristics. We identify static and eluviated regimes, in which erosion or eluviation prevails, and an illuviated regime, in which the balance between lessivage and erosion brings about the formation of a Bt horizon.
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    The Relationship of Self-Compassion with Perfectionistic Self-Presentation, Perceived Forgiveness, and Perceived Social Support in an Undergraduate Christian Community
    (Journal of Psychology and Theology, 2015-12) Brodar, Kaitlyn E; Crosskey, Laura Barnard; Thompson, Robert J
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    Topographic variability and the influence of soil erosion on the carbon cycle
    (Global Biogeochemical Cycles, 2016-05-01) Dialynas, YG; Bastola, S; Bras, RL; Billings, SA; Markewitz, D; Richter, DDB
    ©2016. American Geophysical Union. All Rights Reserved. Soil erosion, particularly that caused by agriculture, is closely linked to the global carbon (C) cycle. There is a wide range of contrasting global estimates of how erosion alters soil-atmosphere C exchange. This can be partly attributed to limited understanding of how geomorphology, topography, and management practices affect erosion and oxidation of soil organic C (SOC). This work presents a physically based approach that stresses the heterogeneity at fine spatial scales of SOC erosion, SOC burial, and associated soil-atmosphere C fluxes. The Holcombe's Branch watershed, part of the Calhoun Critical Zone Observatory in South Carolina, USA, is the case study used. The site has experienced some of the most serious agricultural soil erosion in North America. We use SOC content measurements from contrasting soil profiles and estimates of SOC oxidation rates at multiple soil depths. The methodology was implemented in the tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially and depth-explicit model of SOC dynamics built within an existing coupled physically based hydro-geomorphic model. According to observations from multiple soil profiles, about 32% of the original SOC content has been eroded in the study area. The results indicate that C erosion and its replacement exhibit significant topographic variation at relatively small scales (tens of meters). The episodic representation of SOC erosion reproduces the history of SOC erosion better than models that use an assumption of constant erosion in space and time. The net atmospheric C exchange at the study site is estimated to range from a maximum source of 14.5 g m−2 yr−1 to a maximum sink of −18.2 g m−2 yr−1. The small-scale complexity of C erosion and burial driven by topography exerts a strong control on the landscape's capacity to serve as a C source or a sink.