scholarly journals Red noise in steady-state multiphase flow

2021 ◽  
Author(s):  
Catherine Spurin ◽  
Gaetano Garfi ◽  
Maja Rücker ◽  
Tom Bultreys ◽  
Samuel Krevor ◽  
...  
Keyword(s):  
Steady State ◽  
Multiphase Flow ◽  
Pore Space ◽  
Spatial Scales ◽  
Pressure Fluctuations ◽  
Subsurface Flow ◽  
Porous Rock ◽  
Wide Range ◽  
Temporal And Spatial ◽  
Continuous Range

Understanding the interaction between competing fluids in the pore space of rocks is key for predicting subsurface flow and trapping, such as with CO2 in a saline aquifer. These processes occur over a large span of timescales (from seconds to thousands of years), and length scales (from microns to kilometres). Understanding the link between these temporal and spatial scales will enable us to interpolate between observations made at different resolutions. In this work we explore the temporal scales present during macroscopically steady-state multiphase flow in a porous rock using differential pressure measurements. We observe a cascade of timescales in the pressure differential i.e. a continuous range of frequencies, with lower frequencies having greater amplitudes. We demonstrate a scaling of the spectral density with frequency of S ∼ 1/f^2, or red noise, to describe the dynamics. This scaling is independent of the flow rate of the fluids or the fraction of the flow taken by water. This red, or Brownian, noise indicates a stochastic process where pressure fluctuations are seen throughout the pore space, resulting in intermittent filling of pores over a wide range of time-scales, from seconds to minutes in these experiments. This observation will aid future modelling of subsurface flow as it suggests self-organised critically of the system with no characteristic time or length scale.

scholarly journals The Application of Complexity Analysis in Brain Blood-Oxygen Signal

2021 ◽  
Vol 11 (11) ◽  
pp. 1415
Author(s):  
Xiaoyang Xin ◽  
Shuyang Long ◽  
Mengdan Sun ◽  
Xiaoqing Gao
Keyword(s):  
Complexity Analysis ◽  
Spatial Scales ◽  
Blood Oxygen ◽  
Complexity Measures ◽  
Future Directions ◽  
Brain Physiology ◽  
Wide Range ◽  
Signal Complexity ◽  
Temporal And Spatial ◽  
The Brain

One of the daunting features of the brain is its physiology complexity, which arises from the interaction of numerous neuronal circuits that operate over a wide range of temporal and spatial scales, enabling the brain to adapt to the constantly changing environment and to perform various cognitive functions. As a reflection of the complexity of brain physiology, the complexity of brain blood-oxygen signal has been frequently studied in recent years. This paper reviews previous literature regarding the following three aspects: (1) whether the complexity of the brain blood-oxygen signal can serve as a reliable biomarker for distinguishing different patient populations; (2) which is the best algorithm for complexity measure? And (3) how to select the optimal parameters for complexity measures. We then discuss future directions for blood-oxygen signal complexity analysis, including improving complexity measurement based on the characteristics of both spatial patterns of brain blood-oxygen signal and latency of complexity itself. In conclusion, the current review helps to better understand complexity analysis in brain blood-oxygen signal analysis and provide useful information for future studies.

Biogeomorphological research frontiers: from ant mounds to Mars

2020 ◽  
Author(s):  
Heather Viles
Keyword(s):  
High Risk ◽  
Spatial Scales ◽  
The Past ◽  
Scientific Controversies ◽  
Wide Range ◽  
Geomorphological Processes ◽  
Temporal And Spatial ◽  
Ecological Dimension ◽  
Research Frontiers ◽  
Ant Mounds

<p>Biogeomorphology is a vibrant area of scientific research which focuses on the two-way interrelationships between ecological and geomorphological processes across a wide range of temporal and spatial scales. Whilst ecological influences on geomorphology were often perceived in the past as a rather niche topic, most geomorphologists now  consider the ecological dimension as being crucial to the evolution and behaviour of geomorphological systems. However, there is still much to be done to explore the intersections between ecology and geomorphology. It is now timely to investigate what frontier research in biogeomorphology might look like over the coming years. This paper explores some characteristics of frontier research (addressing scientific controversies, focusing on hard-to-answer questions, employing atypical methods and concepts, being paradigm-challenging, and having a high risk of failure) in the context of tomorrow’s biogeomorphology. As examples, the paper addresses current progress in research on the geomorphological contributions of ants on Earth, and microbial biosignatures on Mars.</p>

ON REYNOLDS' DILATANCY AND SHEAR BAND EVOLUTION: A NEW PERSPECTIVE

2013 ◽  
Vol 23 (09) ◽  
pp. 1330034 ◽  
Author(s):  
DAVID M. WALKER ◽  
KEVIN VO ◽  
ANTOINETTE TORDESILLAS
Keyword(s):  
Shear Band ◽  
Granular Material ◽  
Pore Space ◽  
Spatial Scales ◽  
Shear Bands ◽  
Force Chains ◽  
Weight Functions ◽  
Wide Range ◽  
Pore Evolution ◽  
Interstitial Material

Dense granular media exhibit rich phenomenology when subject to imposed stresses and strains. This is a result of the many degrees of freedom present in an assembly of grains and the nonlinear interactions between the grains. Their complex behavior include the self-organization of load-bearing columnar structures known as force chains across a wide range of spatial scales. Behavior akin to phase transitions from a strong solid-like to a weak liquid-like response can also be observed with shear bands, i.e. regions where force chains collectively buckle, being the signature microstructure in this transition from the stable to the failure regime. An inherent aspect of shear bands and dense granular failure is the phenomenon of dilatancy, i.e. expansion in volume, when the material is subjected to a combined compression and shear. To understand the origins of dilatancy, it is useful to consider the granular material as a mixture of two components: grains and the interstitial material filling the voids or pores between the grains. The grains within a dense granular material respond to applied loads by rearranging to create local zones which contract and dilate. Extant studies of this mechanical response are typically focused on the solid skeleton, in particular, the topology of the network representing the physical contacts between grains. Here, we propose an alternative perspective which is to consider network representations of the evolving anisotropic pore space. We demonstrate how to construct pore space networks that express the local size of voids about a grain through network edge weights. We investigate sectors of the loading history when a percolating giant component of the pore space network exists. By defining two weight functions for edge properties, we: (i) discover via a recurrence plot-based analysis a temporal time scale for jamming–unjamming (contractant-dilatant) dynamics in shear bands; and show that (ii) the formation of a persistent shear band in response to the deformation places grains in a configuration predisposed to the efficient transport of interstitial material as evidenced by the location of percolating shortest path routes through the most dilatant sites. A proper understanding of the micromechanics of pore evolution with respect to shear bands and dilatancy is key to a range of applications such as modeling ground water flow, dewatering systems, carbon capture and sequestration.

Analytical Study of Effects of Flow Rate, Capillarity, and Gravity on CO2/Brine Multiphase-Flow System in Horizontal Corefloods

SPE Journal ◽  
2013 ◽  
Vol 18 (04) ◽  
pp. 708-720 ◽  
Author(s):  
Chia-Wei Kuo ◽  
Sally M. Benson
Keyword(s):  
Steady State ◽  
Multiphase Flow ◽  
Flow Rate ◽  
Flow System ◽  
Rock Properties ◽  
Displacement Efficiency ◽  
Dimensionless Numbers ◽  
Two Phase ◽  
The Core ◽  
Wide Range

Summary This paper presents an approximate semianalytical solution for predicting the average steady-state saturation during multiphase coreflood experiments across a wide range of capillary and gravity numbers. Recently, the influences of flow rate, gravity, and subcore heterogeneity on brine displacement efficiency have been studied with the 3D simulator TOUGH2 (Kuo et al. 2010). These studies have demonstrated that the average saturation depends on the capillary and gravity numbers in a predictable way. The purpose of this paper is to provide a simple and approximate semianalytical solution for predicting the average saturation (during two-phase coreflood experiments across a wide range of flow rates) for different average rock properties and fluid pairs. A 2D analysis of the governing equations for the multiphase-flow system at steady state is used to develop the approximate semianalytical solution. We have developed a new criterion to identify the viscous-dominated regime at the core scale. Variations of interfacial tension (IFT), core permeability, and length of the core and the effects of buoyancy, capillary, and viscous forces are all accounted for in the semianalytical solutions. We also have shown that three dimensionless numbers (NB, Ngv, Rl) and two critical gravity numbers (Ngv,c1, Ngv,c2) are required to properly capture the balance of viscous, gravity, and capillary forces. There is good agreement between the average saturations calculated from the 3D simulations and the analytical model. This new model can be used to design and interpret multiphase-flow coreflood experiments, gain better understanding of multiphase-flow displacement efficiency across a wide range of conditions and for different fluid pairs, and perhaps even provide a tool for studying the influence of subgrid-scale multiphase-flow phenomena on reservoir-scale simulations.

Development and Application of a Storage Model for River Flow Forecasting

1983 ◽  
Vol 14 (3) ◽  
pp. 139-154 ◽  
Author(s):  
Takeshi Hata ◽  
Malcolm G. Anderson
Keyword(s):  
River Flow ◽  
Spatial Scales ◽  
Forecasting Model ◽  
Data Input ◽  
Storage Model ◽  
Topographic Data ◽  
River Flow Forecasting ◽  
Wide Range ◽  
Temporal And Spatial

A lumped sequential river flow forecasting model is outlined. It is shown to be flexible in both temporal and spatial scales, thereby allowing simulations to be undertaken for a wide range of practical purposes. In addition, the required data input is very low, and is restricted to topographic data for only small segments of the entire catchment. The model is successfully applied to the River Avon in England and the River Kako in Japan.

Temporal and Spatial Variations of Atmospheric CO2 Growth reproduced by Ground-Based Remote Sensing and CO2 Inverse Modelling

2020 ◽  
Author(s):  
Lev Labzovskii ◽  
Samuel Takele Kenea ◽  
Jinwon Kim ◽  
Young-Hwa Byun ◽  
Tae-Young Goo ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Spatial Scales ◽  
Central Africa ◽  
Global Scale ◽  
Spatial Variations ◽  
Temporal And Spatial Variations ◽  
Spatial Coverage ◽  
Wide Range ◽  
Temporal And Spatial

<p>Atmospheric CO<sub>2</sub> growth rate is the primary driver of the global warming and a valuable indicator of the interannual changes in carbon cycle. We broaden the knowledge about temporal and spatial variations of annual CO<sub>2</sub> growth (AGR) by using CO<sub>2</sub> observations from the Total Column Observing Network (TCCON), CO<sub>2</sub> simulations from Carbon Tracker (CT) and Copernicus Atmospheric Monitoring System (CAMS) models together with the global-scale AGR references from Global Carbon Budget (GCB) and satellite data (SAT) for 2004-2019 years. TCCON and the CO<sub>2</sub> models reveal temporal AGR variations (AGR<sub>TCCON</sub> = 1.71 – 3.35 ppm, AGR<sub>CT</sub> = 1.59 – 3.30 ppm, AGR<sub>CAMS</sub> = 1.66 – 3.13 ppm) of the similar magnitude to the global-scale CO<sub>2</sub> growth references (AGR<sub>GCB</sub> = 1.59 – 3.23 ppm, AGR<sub>SAT</sub> = 1.55 – 2.92 ppm). However, TCCON estimates of global AGR agree well with the referenced AGR growth only during the 2010s since the network has considerably improved its spatial coverage after 2009. Moreover, TCCON-based AGRs reasonably agree (r = 0.67) with strength of El Nino Southern Oscillations (ENSO) in the 2010s. The highest atmospheric CO<sub>2</sub> growth (2015-2016) driven by the very strong El-Nino event is accurately reproduced by TCCON that provided AGR of 2015-2016 years (3.29 ± 0.98 ppm) in very close agreement to the SAT reference (3.23 ± 0.50 ppm). We validate CAMS and CT simulations of AGR versus the newly-acquired TCCON-based AGR (as the point-location reference) for an every single TCCON site and low agreement (r < 0.50) is evidenced only at 3 out of 20 stations. This minor caveat has not affected the accuracy of simulated global AGR since it exhibits high agreement with SAT, GCB (r = 0.74 – 0.78) and TCCON (r > 0.65) references at global scales. Moreover, the correlation of AGR simulations across all grid cells (3 x 2 degree) between CAMS and CT is nearly perfect (r = 0.95) for the modeling period (2004-2016). Similarly, land-wise AGR intercomparison between CAMS and CT yields in perfect correlation (r ≧ 0.90) for 15 out of 20 MODIS land classes where the least vegetated areas exhibit the highest agreement. From spatial perspective, the highest AGR estimates (> 20% from the median value) are observed in the regions with intense combustion (East Asia) or with frequent biomass burning (Amazon, Central Africa). The slight disagreement of AGR spatial variability simulated by CT and CAMS is likely driven by the latter two regions of SH where drier conditions during El-Nino events allegedly increase the probability for divergence between the models. In overall, the current estimates of global AGR are consistent across a wide range of the data sources and strengthening of CO<sub>2</sub> observational infrastructure should further improve the accuracy of AGR estimates on global and fine spatial scales.</p>

Spectroscopic Studies of Asparaginyl-tRNA Synthetase from Entamoeba histolytica

2019 ◽  
Vol 26 (6) ◽  
pp. 435-448
Author(s):  
Priyanka Biswas ◽  
Dillip K. Sahu ◽  
Kalyanasis Sahu ◽  
Rajat Banerjee
Keyword(s):  
Circular Dichroism ◽  
Steady State ◽  
Entamoeba Histolytica ◽  
Protein Concentration ◽  
Trna Synthetase ◽  
Solvent Exposure ◽  
Steady State Fluorescence ◽  
State Process ◽  
Wide Range ◽  
Circular Dichroïsm

Background: Aminoacyl-tRNA synthetases play an important role in catalyzing the first step in protein synthesis by attaching the appropriate amino acid to its cognate tRNA which then transported to the growing polypeptide chain. Asparaginyl-tRNA Synthetase (AsnRS) from Brugia malayi, Leishmania major, Thermus thermophilus, Trypanosoma brucei have been shown to play an important role in survival and pathogenesis. Entamoeba histolytica (Ehis) is an anaerobic eukaryotic pathogen that infects the large intestines of humans. It is a major cause of dysentery and has the potential to cause life-threatening abscesses in the liver and other organs making it the second leading cause of parasitic death after malaria. Ehis-AsnRS has not been studied in detail, except the crystal structure determined at 3 Å resolution showing that it is primarily α-helical and dimeric. It is a homodimer, with each 52 kDa monomer consisting of 451 amino acids. It has a relatively short N-terminal as compared to its human and yeast counterparts. Objective: Our study focusses to understand certain structural characteristics of Ehis-AsnRS using biophysical tools to decipher the thermodynamics of unfolding and its binding properties. Methods: Ehis-AsnRS was cloned and expressed in E. coli BL21DE3 cells. Protein purification was performed using Ni-NTA affinity chromatography, following which the protein was used for biophysical studies. Various techniques such as steady-state fluorescence, quenching, circular dichroism, differential scanning fluorimetry, isothermal calorimetry and fluorescence lifetime studies were employed for the conformational characterization of Ehis-AsnRS. Protein concentration for far-UV and near-UV circular dichroism experiments was 8 µM and 20 µM respectively, while 4 µM protein was used for the rest of the experiments. Results: The present study revealed that Ehis-AsnRS undergoes unfolding when subjected to increasing concentration of GdnHCl and the process is reversible. With increasing temperature, it retains its structural compactness up to 45ºC before it unfolds. Steady-state fluorescence, circular dichroism and hydrophobic dye binding experiments cumulatively suggest that Ehis-AsnRS undergoes a two-state transition during unfolding. Shifting of the transition mid-point with increasing protein concentration further illustrate that dissociation and unfolding processes are coupled indicating the absence of any detectable folded monomer. Conclusion: This article indicates that GdnHCl induced denaturation of Ehis-AsnRS is a two – state process and does not involve any intermediate; unfolding occurs directly from native dimer to unfolded monomer. The solvent exposure of the tryptophan residues is biphasic, indicating selective quenching. Ehis-AsnRS also exhibits a structural as well as functional stability over a wide range of pH.

Larval Feeding: Mechanisms, Rates, and Performance in Nature

2018 ◽  
Keyword(s):  
Marine Invertebrates ◽  
Spatial Scales ◽  
Size Spectrum ◽  
Larval Feeding ◽  
Natural Habitats ◽  
Feeding Mechanism ◽  
Temporal And Spatial ◽  
And Performance ◽  
Bioenergetics Models ◽  
Many Particles

Larvae of many marine invertebrates must capture and ingest particulate food in order to develop to metamorphosis. These larvae use only a few physical processes to capture particles, but implement these processes using diverse morphologies and behaviors. Detailed understanding of larval feeding mechanism permits investigators to make predictions about feeding performance, including the size spectrum of particles larvae can capture and the rates at which they can capture them. In nature, larvae are immersed in complex mixtures of edible particles of varying size, density, flavor, and nutritional quality, as well as many particles that are too large to ingest. Concentrations of all of these components vary on fine temporal and spatial scales. Mechanistic models linking larval feeding mechanism to performance can be combined with data on food availability in nature and integrated into broader bioenergetics models to yield increased understanding of the biology of larvae in complex natural habitats.

Humans and the Environment

2013 ◽  
Keyword(s):  
Spatial Scales ◽  
Empirical Studies ◽  
Human Action ◽  
Cultural Practice ◽  
Environmental Archaeology ◽  
Archaeological Data ◽  
Temporal And Spatial ◽  
Global And Local ◽  
The Relationship ◽  
The Way

The environment has always been a central concept for archaeologists and, although it has been conceived in many ways, its role in archaeological explanation has fluctuated from a mere backdrop to human action, to a primary factor in the understanding of society and social change. Archaeology also has a unique position as its base of interest places it temporally between geological and ethnographic timescales, spatially between global and local dimensions, and epistemologically between empirical studies of environmental change and more heuristic studies of cultural practice. Drawing on data from across the globe at a variety of temporal and spatial scales, this volume resituates the way in which archaeologists use and apply the concept of the environment. Each chapter critically explores the potential for archaeological data and practice to contribute to modern environmental issues, including problems of climate change and environmental degradation. Overall the volume covers four basic themes: archaeological approaches to the way in which both scientists and locals conceive of the relationship between humans and their environment, applied environmental archaeology, the archaeology of disaster, and new interdisciplinary directions.The volume will be of interest to students and established archaeologists, as well as practitioners from a range of applied disciplines.

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