ANALYSIS AND SIMULATION OF LONG-RANGE CORRELATIONS IN CURVED SPACE

2009 ◽  
Vol 20 (08) ◽  
pp. 1211-1232 ◽  
Author(s):  
ALI REZA MEHRABI ◽  
MUHAMMAD SAHIMI
Keyword(s):  
Long Range ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Amorphous Semiconductors ◽  
Curved Space ◽  
Long Range Correlations ◽  
Planar Surfaces ◽  
Positively Curved ◽  
Industrial Problem

Numerical simulation and analysis of long-range correlations in curved space are studied. The study is motivated by the problem of constructing accurate models of large-scale porous media which usually contain long-range correlations in their various properties (such as their permeability, porosity, and elastic moduli) within and between their strata that are typically curved layers. The problem is, however, relevant to many other important models and phenomena in which extended correlations in curved space play a prominent role. Examples include the nonlinear σ-model in a curved space, models for describing the long-range structural correlations of amorphous semiconductors that consist of polytopes (tilings of positively-curved three-dimensional space), long-range correlations in the extrapolar total zone, and models in which the Universe is created by bubble nucleations and contain long-range correlations in the fluctuations in the curved spacetime. The study is also relevant to the important industrial problem of designing highly curved objects, such as cars and ships, which use composite materials that contain extended correlations in their property values. We study such correlations along two- and three-dimensional curves, as well as curved surfaces. We show that such correlations are well-defined only on developable surfaces, i.e. those that can be flattened to form planar surfaces without any stretching or distortion, and preserve the distance between two points on such surfaces after the stretching. If a given curved surface is not developable, but can be approximated as piecewise developable, one may still define and analyze extended correlations on it. Representative examples are presented and analyzed.

Large- and small-scale vortical motions in a shear layer perturbed by tabs

1999 ◽  
Vol 382 ◽  
pp. 307-329 ◽  
Author(s):  
JUDITH K. FOSS ◽  
K. B. M. Q. ZAMAN
Keyword(s):  
Shear Layer ◽  
Pitch Angle ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Small Scale ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Cross Sectional ◽  
Scale Population

The large- and small-scale vortical motions produced by ‘delta tabs’ in a two-stream shear layer have been studied experimentally. An increase in mixing was observed when the base of the triangular shaped tab was affixed to the trailing edge of the splitter plate and the apex was pitched at some angle with respect to the flow axis. Such an arrangement produced a pair of counter-rotating streamwise vortices. Hot-wire measurements detailed the velocity, time-averaged vorticity (Ωx) and small-scale turbulence features in the three-dimensional space downstream of the tabs. The small-scale structures, whose scale corresponds to that of the peak in the dissipation spectrum, were identified and counted using the peak-valley-counting technique. The optimal pitch angle, θ, for a single tab and the optimal spanwise spacing, S, for a multiple tab array were identified. Since the goal was to increase mixing, the optimal tab configuration was determined from two properties of the flow field: (i) the large-scale motions with the maximum Ωx, and (ii) the largest number of small-scale motions in a given time period. The peak streamwise vorticity magnitude [mid ]Ωx−max[mid ] was found to have a unique relationship with the tab pitch angle. Furthermore, for all cases examined, the overall small-scale population was found to correlate directly with [mid ]Ωx−max[mid ]. Both quantities peaked at θ≈±45°. It is interesting to note that the peak magnitude of the corresponding circulation in the cross-sectional plane occurred for θ≈±90°. For an array of tabs, the two quantities also depended on the tab spacing. An array of contiguous tabs acted as a solid deflector producing the weakest streamwise vortices and the least small-scale population. For the measurement range covered, the optimal spacing was found to be S≈1.5 tab widths.

scholarly journals Improving Hydrologic Modeling Using Cloud-Free MODIS Flood Maps

2019 ◽  
Vol 20 (11) ◽  
pp. 2203-2214 ◽  
Author(s):  
Hoang Tran ◽  
Phu Nguyen ◽  
Mohammed Ombadi ◽  
Kuolin Hsu ◽  
Soroosh Sorooshian ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Skill Score ◽  
Hydrologic Model ◽  
Probability Of Detection ◽  
Landsat 8 ◽  
Inundation Maps ◽  
Flood Maps

Abstract Flood mapping from satellites provides large-scale observations of flood events, but cloud obstruction in satellite optical sensors limits its practical usability. In this study, we implemented the Variational Interpolation (VI) algorithm to remove clouds from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) Snow-Covered Area (SCA) products. The VI algorithm estimated states of cloud-hindered pixels by constructing three-dimensional space–time surfaces based on assumptions of snow persistence. The resulting cloud-free flood maps, while maintaining the temporal resolution of the original MODIS product, showed an improvement of nearly 70% in average probability of detection (POD) (from 0.29 to 0.49) when validated with flood maps derived from Landsat-8 imagery. The second part of this study utilized the cloud-free flood maps for calibration of a hydrologic model to improve simulation of flood inundation maps. The results demonstrated the utility of the cloud-free maps, as simulated inundation maps had average POD, false alarm ratio (FAR), and Hanssen–Kuipers (HK) skill score of 0.87, 0.49, and 0.84, respectively, compared to POD, FAR, and HK of 0.70, 0.61, and 0.67 when original maps were used for calibration.

scholarly journals Phosphatidylinositol-4,5-Bisphosphate-Rich Plasma Membrane Patches Organize Active Zones of Endocytosis and Ruffling in Cultured Adipocytes

2004 ◽  
Vol 24 (20) ◽  
pp. 9102-9123 ◽  
Author(s):  
Shaohui Huang ◽  
Larry Lifshitz ◽  
Varsha Patki-Kamath ◽  
Richard Tuft ◽  
Kevin Fogarty ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Large Scale ◽  
Plasma Membranes ◽  
Fluorescent Protein ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Actin Dynamics ◽  
Ph Domain ◽  
Membrane Ruffling ◽  
Green Fluorescent

ABSTRACT A major regulator of endocytosis and cortical F-actin is thought to be phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] present in plasma membranes. Here we report that in 3T3-L1 adipocytes, clathrin-coated membrane retrieval and dense concentrations of polymerized actin occur in restricted zones of high endocytic activity. Ultrafast-acquisition and superresolution deconvolution microscopy of cultured adipocytes expressing an enhanced green fluorescent protein- or enhanced cyan fluorescent protein (ECFP)-tagged phospholipase Cδ1 (PLCδ1) pleckstrin homology (PH) domain reveals that these zones spatially coincide with large-scale PtdIns(4,5)P2-rich plasma membrane patches (PRMPs). PRMPs exhibit lateral dimensions exceeding several micrometers, are relatively stationary, and display extensive local membrane folding that concentrates PtdIns(4,5)P2 in three-dimensional space. In addition, a higher concentration of PtdIns(4,5)P2 in the membranes of PRMPs than in other regions of the plasma membrane can be detected by quantitative fluorescence microscopy. Vesicular structures containing both clathrin heavy chains and PtdIns(4,5)P2 are revealed immediately beneath PRMPs, as is dense F actin. Blockade of PtdIns(4,5)P2 function in PRMPs by high expression of the ECFP-tagged PLCδ1 PH domain inhibits transferrin endocytosis and reduces the abundance of cortical F-actin. Membrane ruffles induced by the expression of unconventional myosin 1c were also found to localize at PRMPs. These results are consistent with the hypothesis that PRMPs organize active PtdIns(4,5)P2 signaling zones in the adipocyte plasma membrane that in turn control regulators of endocytosis, actin dynamics, and membrane ruffling.

scholarly journals A platform for brain-wide imaging and reconstruction of individual neurons

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Michael N Economo ◽  
Nathan G Clack ◽  
Luke D Lavis ◽  
Charles R Gerfen ◽  
Karel Svoboda ◽  
...  
Keyword(s):  
Long Range ◽  
High Speed ◽  
Large Scale ◽  
Three Dimensional ◽  
Image Data ◽  
Mammalian Brain ◽  
Projection Neurons ◽  
Computational Tools ◽  
Two Photon ◽  
Axonal Arbors

The structure of axonal arbors controls how signals from individual neurons are routed within the mammalian brain. However, the arbors of very few long-range projection neurons have been reconstructed in their entirety, as axons with diameters as small as 100 nm arborize in target regions dispersed over many millimeters of tissue. We introduce a platform for high-resolution, three-dimensional fluorescence imaging of complete tissue volumes that enables the visualization and reconstruction of long-range axonal arbors. This platform relies on a high-speed two-photon microscope integrated with a tissue vibratome and a suite of computational tools for large-scale image data. We demonstrate the power of this approach by reconstructing the axonal arbors of multiple neurons in the motor cortex across a single mouse brain.

Simple examples with features of renormalization for turbulent transport

1994 ◽  
Vol 346 (1679) ◽  
pp. 205-233 ◽  
Keyword(s):  
Long Range ◽  
Large Scale ◽  
Turbulent Transport ◽  
Gaussian White Noise ◽  
Eddy Diffusivity ◽  
Turbulent Velocity ◽  
Effective Equation ◽  
Long Range Correlations ◽  
Velocity Statistics ◽  
Limiting Case

Two simple exactly solvable models for turbulent transport are introduced and discussed here with complete mathematical rigour. These models illustrate several different facets of super-diffusion and renormalization for turbulent transport. The first model involves time dependent velocity fields with suitable long-range correlations and the complete renormalization theory is developed here in detail. In addition rigorous examples are developed by using variants of this model where the effective equation for the ensemble average at large scales and long times is diffusive despite the fact that each realization exhibits catastrophic large-scale instability. The second model introduced previously by the authors involves transport-diffusion in simple shear layers with turbulent velocity statistics. The theories of renormalized eddy diffusivity and higher-order statistics are surveyed here. An extreme limiting case of the theory involving turbulent velocity statistics with long-range spatial correlations but gaussian white noise in time is discussed in detail. Both the renormalized theory of eddy diffusivity and exact explicit equations for second-order correlations related to the pair distance function are developed in complete detail here in this instructive limiting case.

A method for the identification of trees with unusually colored foliage

1996 ◽  
Vol 26 (9) ◽  
pp. 1548-1555 ◽  
Author(s):  
John L. Innes ◽  
Sucharita Ghosh ◽  
Andreas Schwyzer
Keyword(s):  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Crown Condition ◽  
Normal Expectation ◽  
Three Dimensional Space

A method is presented for recognizing trees with unusually colored foliage, based on the use of Munsell plant color charts. Color assessments are made by scoring the crown of each tree for hue, value, and chroma. These values are plotted in three-dimensional space for each species, and a threshold is identified marking the border of an ellipsoid. Trees with foliage outside this ellipsoid are considered as unusual. The method means that assessments of discoloration can cover a range of colors and moves the decision over the color status of a tree from a subjective field decision to a statistically defined decision at the analytical stage. It takes into account that a tree may still be classified as green (previously classed as without discoloration) when its color of green lies outside the normal expectation for the species. The method represents a significant improvement on the discoloration assessments currently being used in large-scale inventories of crown condition in Europe.

scholarly journals The Group Evacuation Behavior Based on Fire Effect in the Complicated Three-Dimensional Space

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Jun Hu ◽  
Huijun Sun ◽  
Ge Gao ◽  
Juan Wei ◽  
Lei You
Keyword(s):  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Target Position ◽  
Velocity Change ◽  
Evacuation Time ◽  
Evacuation Strategy ◽  
Average System ◽  
Evacuation Behavior ◽  
Three Dimensional Space

In order to effectively depict the group evacuation behavior in the complicated three-dimensional space, a novel pedestrian flow model is proposed with three-dimensional cellular automata. In this model the calculation methods of floor field and fire gain are elaborated at first, and the transition gain of target position at the next moment is defined. Then, in consideration of pedestrian intimacy and velocity change, the group evacuation strategy and evolution rules are given. Finally, the experiments were conducted with the simulation platform to study the relationships of evacuation time, pedestrian density, average system velocity, and smoke spreading velocity. The results had shown that large-scale group evacuation should be avoided, and in case of large pedestrian density, the shortest route of evacuation strategy would extend system evacuation time.

scholarly journals Quantifying Evolution of Short and Long-Range Correlations in Chinese Narrative Texts across 2000 Years

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Heng Chen ◽  
Haitao Liu
Keyword(s):  
Long Range ◽  
Word Length ◽  
Large Scale ◽  
Sentence Length ◽  
Small Scale ◽  
Evolutionary Trend ◽  
Narrative Texts ◽  
Long Range Correlations ◽  
Cultural Aspects ◽  
The Social

We investigate how short and long-range word length correlations evolve in Chinese narrative texts. The results show that, for short-range word length correlations, no significant linear evolutionary trend was found. But for long-range correlations, there are two opposite tendencies for two different regimes: the Hurst exponent of small-scale (box size n ranges from 10 to 100) word length correlations decreases over time, and the exponent of large-scale (box size n ranges from 101 to 1000) shows an increasing tendency. The increase of word length is corroborated as an essential regularity of word evolution in written Chinese. Further analyses show that a significant correlation coefficient is obtained between Hurst exponents from the small-scale correlations and mean word length across time. These indicate that word length correlation evolution possesses different self-adaptive mechanisms in terms of different scales of distances between words. We speculate that the increase of word length and sentence length in written Chinese may account for this phenomenon, in terms of both the social-cultural aspects and the self-adapting properties of language structures.

Large-scale dynamics in turbulent mixing and the three-dimensional space–time behaviour of outer fluid interfaces

2002 ◽  
Vol 471 ◽  
pp. 381-408 ◽  
Author(s):  
HARIS J. CATRAKIS ◽  
ROBERTO C. AGUIRRE ◽  
JESUS RUIZ-PLANCARTE ◽  
ROBERT D. THAYNE ◽  
BRENDA A. McDONALD ◽  
...  
Keyword(s):  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Space Time ◽  
Mixing Efficiency ◽  
Fluid Interfaces ◽  
Ambient Fluid ◽  
Wide Range ◽  
Dimensional Space Time ◽  
Three Dimensional Space

Experiments have been conducted to investigate turbulent mixing and the dynamics of outer fluid interfaces, i.e. the interfaces between mixed fluid and pure ambient fluid. A novel six-foot-diameter octagonal-tank flow facility was developed to enable the optical imaging of fluid interfaces above the mixing transition, corresponding to fully developed turbulence. Approximately 10003 whole-field three-dimensional space– time measurements of the concentration field were recorded using laser-induced- fluorescence digital-imaging techniques in turbulent jets at a Reynolds number of Re ∼ 20 000, Schmidt number of Sc ∼ 2000, and downstream distance of ∼ 500 nozzle diameters. Multiple large-scale regions of spatially nearly uniform-concentration fluid are evident in instantaneous visualizations, in agreement with previous findings above the mixing transition. The ensemble-averaged probability density function of concentration is found to exhibit linear dependence over a wide range of concentration thresholds. This can be accounted for in terms of the dynamics of large-scale well- mixed regions. Visualization of the three-dimensional space–time concentration field indicates that molecular mixing of entrained pure ambient fluid is dynamically initiated and accomplished in the vicinity of the unsteady large scales. Examination of the outer interfaces shows that they are dynamically confined primarily near the instantaneous large-scale boundaries of the flow. This behaviour is quantified in terms of the probability density of the location of the outer interfaces relative to the flow centreline and the probability of pure ambient fluid as a function of distance from the centreline. The current measurements show that the dynamics of outer interfaces above the mixing transition is significantly different from the behaviour below the transition, where previous studies have shown that unmixed ambient fluid can extend across a wide range of transverse locations in the flow interior. The present observations of dynamical confinement of the outer interfaces to the unsteady large scales, and considerations of entrainment, suggest that the mechanism responsible for this behaviour must be the coupling of large-scale flow dynamics with the presence of small-scale structures internal to the large-scale structures, above the mixing transition. The dynamics and structure of the outer interfaces across the entire range of space–time scales are quantified in terms of a distribution of generalized level-crossing scales. The outer-interface behaviour determines the mixing efficiency of the flow, i.e. fraction of mixed fluid. The present findings indicate that the large-scale dynamics of the outer interfaces above the mixing transition provides the dominant contribution to the mixing efficiency. This suggests a new way to quantify the mixing efficiency of turbulent flows at high Reynolds numbers.

scholarly journals The zinc finger protein CLAMP promotes long-range chromatin interactions that mediate dosage compensation of the Drosophila male X-chromosome

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
William Jordan ◽  
Erica Larschan
Keyword(s):  
Long Range ◽  
Zinc Finger ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Binding Sites ◽  
Zinc Finger Protein ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Active Chromatin ◽  
Finger Protein

Abstract Background Drosophila dosage compensation is an important model system for defining how active chromatin domains are formed. The male-specific lethal dosage compensation complex (MSLc) increases transcript levels of genes along the length of the single male X-chromosome to equalize with that expressed from the two female X-chromosomes. The strongest binding sites for MSLc cluster together in three-dimensional space largely independent of MSLc because clustering occurs in both sexes. CLAMP, a non-sex specific, ubiquitous zinc finger protein, binds synergistically with MSLc to enrich the occupancy of both factors on the male X-chromosome. Results Here, we demonstrate that CLAMP promotes the observed three-dimensional clustering of MSLc binding sites. Moreover, the X-enriched CLAMP protein more strongly promotes longer-range three-dimensional interactions on the X-chromosome than autosomes. Genome-wide, CLAMP promotes three-dimensional interactions between active chromatin regions together with other insulator proteins. Conclusion Overall, we define how long-range interactions which are modulated by a locally enriched ubiquitous transcription factor promote hyper-activation of the X-chromosome to mediate dosage compensation.

Sign in / Sign up

Export Citation Format

Share Document