Changes In Local Properties Research Articles

A hierarchical streamline-assisted history matching approach with global and local parameter updates

The effective strategies for traditional manual history matching commonly follow a structured approach with a sequence of adjustments from global to regional parameters followed by local changes in model properties, associated with matching for pressure (reservoir energy), flood front progression, and individual well performance. In contrast, many of the automatic history matching methods utilize parameter sensitivities or gradients to directly update the fine-scale reservoir properties, potentially combining elements at all of these scales. In this paper we present a hierarchical streamline-assisted history matching approach that emulates the traditional structured procedures. First, a probabilistic approach is used to understand the uncertainty in the large-scale static and dynamic parameters, and to calibrate these global parameters. In this global calibration, the intent is to develop multiple models that all match the field performance. This global calibration is followed by a streamline sensitivity-based deterministic model calibration for local permeability changes in which each of the distinct models created in the global match are history matched in additional detail.In the probabilistic global calibration, design of experiments and response surface methodologies with evolutionary algorithms are used to calibrate the global parameters. Typical parameters are regional pore volume multipliers, regional vertical and areal transmissibility multipliers, fault transmissibilities and aquifer strength. Key global parameters are first identified via a sensitivity analysis and an initial ensemble of models that span these parameters is created. The cases studied in this sensitivity analysis are used to construct a proxy model using experimental design and response surface analysis. An improved genetic algorithm with heat-bath sampling is used to generate an updated ensemble of models conditioned to static MDT pressures and total liquid rates at the wells, corresponding to a traditional pressure history match. Next, each ensemble member is updated using water-cut, GOR and flowing BHP via sensitivity-based local permeability calibration. We utilize streamline-derived analytic sensitivities to determine the spatial distribution and magnitude of these local changes.The proposed approach was tested by a 3D synthetic case and a field application. Our hierarchical approach appears to be stable in the sense that the local changes for permeability (inner loop) do not invalidate the pressure history match (outer loop). This is not entirely unexpected since the local permeability changes are regularized by a norm constraint that minimizes deviations from the globally updated model. Nonetheless, this is a very useful property in that it allows us to powerfully combine history matching procedures on global and local scales.

Effects of polar cortical cytoskeleton and unbalanced cortical surface tension on intercellular bridge thinning during cytokinesis

To probe the contributions of polar cortical cytoskeleton and the surface tension of daughter cells to intercellular bridge thinning dynamics during cytokinesis, we applied cytochalasin D (CD) or colchicine (COLC) in a highly localized manner to polar regions of dividing normal rat kidney (NRK) cells. We observed cellular morphological changes and analyzed the intercellular bridge thinning trajectories of dividing cells with different polar cortical characteristics. Global blebbistatin (BS) application was used to obtain cells losing active contractile force groups. Our results show that locally released CD or colchicine at the polar region caused inhibition of cytokinesis before ingression. Similar treatment at phases after ingression allowed completion of cytokinesis but dramatically influenced the trajectories of intercellular bridge thinning. Disturbing single polar cortical actin induced transformation of the intercellular bridge thinning process, and polar cortical tension controlled deformation time of intercellular bridges. Our study provides a feasible framework to induce and analyze the effects of local changes in mechanical properties of cellular components on single cellular cytokinesis.

Numerical sensitivity modeling for the detection of skin tumors by using tetrapolar probe

The measurement of electrical impedance of skin using surface electrodes permits the assessment of changes in local properties of the skin and can be used in the detection of tumors. The sensitivity of this technique depends mainly on the geometry of the probe and the size of the tumor. In this article, the impedance method was used to estimate the sensitivity of a tetrapolar probe in detecting small regions of increased conductivity in a stratified model of human skin. The impedance method was used to model the potential distribution using fasorial analysis to solve the node equations of the equivalent circuit. Interpolation was applied to reduce discretization error. The skin was modeled as a three-layer structure with different conductivity and permittivity obtained from the literature. A tumor was modeled as a small volume with admittivity four times higher than the normal tissue. Sensitivity calculation was made as a function of electrode diameter and separation, tumor size, and excitation frequency. The simulations indicated that by inserting a one square millimeter tumor in the epidermis, the load impedance to the current source varies about 1% while the transfer impedance varied 8%. The sensitivity also increases nonlinearly with increasing tumor area and thickness. Additionally, it was found that the sensitivity of the transfer impedance has a maximum value when the electrodes are separated by 1.8 mm. The results show that transfer impedance measurements of the skin may detect small skin tumors with a reasonable sensitivity by using an appropriate tetrapolar probe.

Solute effects on supercritical fluid

Supercritical carbon dioxide has been widely used as solvent, although its solubility is much lower than that of typical organic solvents in liquid state in general. Entrainer effects are known and utilised, in which adding low-weight molecules, such as alcohols (e.g. methanol and ethanol) and hydrocarbons (e.g. pentane and hexane), increases the solubility and the chemical reactivity. In this study, we investigated the change of local fluid structure and thermodynamic properties with molecular dynamics simulations, focusing on the entrainer effect. A monatomic fluid mixture model based on the Lennard-Jones model potential was adopted for simplicity; the parameters of which roughly correspond to those of carbon dioxide (solvent) and ethanol (solute). A series of simulations were performed in the vicinity of the gas–liquid critical point (CP). The radial distribution function and the coordination number reveal the enhancement of the solvent local density. The solvent chemical potential was evaluated with the Widom's particle insertion method. The chemical potential change by adding solutes is smallest in magnitude at the CP, qualitatively agreeing with recent experimental analysis and interpretation with a small-angle neutron scattering method.

Brain Morphological Signatures for Chronic Pain

Chronic pain can be understood not only as an altered functional state, but also as a consequence of neuronal plasticity. Here we use in vivo structural MRI to compare global, local, and architectural changes in gray matter properties in patients suffering from chronic back pain (CBP), complex regional pain syndrome (CRPS) and knee osteoarthritis (OA), relative to healthy controls. We find that different chronic pain types exhibit unique anatomical ‘brain signatures’. Only the CBP group showed altered whole-brain gray matter volume, while regional gray matter density was distinct for each group. Voxel-wise comparison of gray matter density showed that the impact on the extent of chronicity of pain was localized to a common set of regions across all conditions. When gray matter density was examined for large regions approximating Brodmann areas, it exhibited unique large-scale distributed networks for each group. We derived a barcode, summarized by a single index of within-subject co-variation of gray matter density, which enabled classification of individual brains to their conditions with high accuracy. This index also enabled calculating time constants and asymptotic amplitudes for an exponential increase in brain re-organization with pain chronicity, and showed that brain reorganization with pain chronicity was 6 times slower and twice as large in CBP in comparison to CRPS. The results show an exuberance of brain anatomical reorganization peculiar to each condition and as such reflecting the unique maladaptive physiology of different types of chronic pain.

The role of vascular calcification in inducing fatigue and fracture of coronary stents

Traditional approaches for in-vitro pulsatile and fatigue testing of endovascular stents do not take into consideration the pathologies of the stented vessel and their associated biomechanical effects. One important pathology is calcification, which may be capable of inducing changes in the vessel wall leading to inhomogeneous distribution of stresses combined with wall motion during the cardiac cycle. These local property changes in the region adjacent to stents could directly influence in-vivo stent performance. Seven cases containing a total of 18 stents were obtained from autopsy. Radiographs were evaluated and vessels were sectioned for histology and stent topographical analysis. Stents were retrieved by chemical removal of surrounding tissue and surfaces were evaluated using 3D digital optical and scanning electron microscopy for biomechanical abrasion and fracture features. Pathologic complications such as restenosis and thrombus formation were assessed from histological sections. Direct evidence of fracture was found in 6 of the 7 cases (in 12 out of 18 stents; 9 drug eluting and 3 bare metal). The degree of stent alterations was variable, where separation of segments due to fracture occurred mostly in drug-eluting stents. All fracture surfaces were representative of a high cycle fatigue mechanism. These fractures occurred in complex lesions involving the presence of diffuse calcification alone, or in combination with vessel angulations and multiple overlapping stents. Morphologic analysis of tissue at or near some fracture sites showed evidence of thrombus formation and/or neointimal tissue growth.

Nanoscale structural and mechanical effects of beta-amyloid (1–42) on polymer cushioned membranes: A combined study by neutron reflectometry and AFM Force Spectroscopy

The interaction of beta-amyloid peptides with lipid membranes is widely studied as trigger agents in Alzheimer's disease. Their mechanism of action at the molecular level is unknown and their interaction with the neural membrane is crucial to elucidate the onset of the disease. In this study we have investigated the interaction of water soluble forms of beta-amyloid Aβ(1–42) with lipid bilayers supported by polymer cushion. A reproducible protocol for the preparation of a supported phospholipid membrane with composition mimicking the neural membrane and in physiological condition (PBS buffer, pH=7.4) was refined by neutron reflectivity. The change in structure and local mechanical properties of the membrane in the presence of Aβ(1–42) was investigated by neutron reflectivity and Atomic Force Microscopy (AFM) Force Spectroscopy. Neutron reflectivity evidenced that Aβ(1–42) interacts strongly with the supported membrane, causing a change in the scattering length density profile of the lipid bilayer, and penetrates into the membrane. Concomitantly, the local mechanical properties of the bilayer are deeply modified by the interaction with the peptide as seen by AFM Force Spectroscopy. These results may be of great importance for the onset of the Alzheimer's disease, since a simultaneous change in the structural and mechanical properties of the lipid matrix could influence all membrane based signal cascades.

Pulmonary vascular stiffness: measurement, modeling, and implications in normal and hypertensive pulmonary circulations.

This article introduces the concept of pulmonary vascular stiffness, discusses its increasingly recognized importance as a diagnostic marker in the evaluation of pulmonary vascular disease, and describes methods to measure and model it clinically, experimentally, and computationally. It begins with a description of systems-level methods to evaluate pulmonary vascular compliance and recent clinical efforts in applying such techniques to better predict patient outcomes in pulmonary arterial hypertension. It then progresses from the systems-level to the local level, discusses proposed methods by which upstream pulmonary vessels increase in stiffness, introduces concepts around vascular mechanics, and concludes by describing recent work incorporating advanced numerical methods to more thoroughly evaluate changes in local mechanical properties of pulmonary arteries.

대퇴골 골 간단 부 골절치료용 복합재료 고정판의 국부적 거동 예측을 위한 기초 연구

본 논문은 복잡한 형상으로 드레이핑 성행된 직물 복합재료 구조의 국부적 물성 변화 및 재료거동 예측을 위한 방법을 제시하였다. 제안된 방법을 적용하기 위해 대퇴골 골 간단 부 골절치료용 고정판을 대상으로 선정하였다. 드레이핑 공정 종 발생하는 재료의 거시적/미시적 변형에 의한 국부적 재료물성 변화를 다양한 실험을 통해 검증하고, 그 결과를 복잡한 형상을 가지는 고정판의 정적/피로 거동 예측에 활용하였다. 본 논문은 복잡한 형상을 가지는 복합재료 구조물의 설계 및 성능평가에 유용한 정보와 해석방법을 제시할 것으로 기대된다. This paper presents an estimating method for local property changes and failure prediction of composite materials experiencing large shear deformation during draping process. The bone plate for the metaphyseal femur fracture was chosen to apply the presented method because it has complex geometry. The local property changes due to macro-/microscopic deformations of fabric composites during draping process were evaluated by various tests and the result was applied to predict static/fatigue behaviors of the bone plate. This paper was expected to present useful information on the design of composite structures with complex geometry and their performance evaluation.

Mathematical Modelling and Feature Extraction for Probing Crucial Changes Associated with Alzheimers Disease

Transverse relaxation time T2 and magnetization transfer ratio MTR are examples of two magnetic resonance imaging parameters that allow for a sensitive characterization of microscopic tissue properties in the brain. Classically, the mean values of these parameters are assessed in a region-of-interest and compared groupwise. In contrast to this, modern voxel-based methods test for localized changes in imaging parameters on a per-voxel basis, by registering the image to an average brain template or atlas. An intermediary method is distributional analysis, where the distribution of an imaging parameter over an anatomical region, identified from a brain atlas, is the main object of interest. This distribution captures local variation and changes in tissue properties and can ideally be described by a parametric mixture model. It can directly be compared across subjects by a distance measure and classification of subjects can be based on features extracted from these distributions of imaging parameters. This approach reduces the high dimensionality of the data and, consequently, the impact of noise and avoids the problem of collinearity. In this article the applicability of these and related methods of feature extraction and discrimination is reviewed in the context of Alzheimers disease. Keywords: Discriminant analysis, histogram analysis, magnetic resonance imaging, magnetization transfer ratio, relaxometry, tissue characterization, NFT, Cerebrosinal fluid CSF

Structures and property distributions in the three oceans surrounding Canada in 2007: A basis for a long‐term ocean climate monitoring strategy

The panarctic region is tightly connected to subarctic regions by through‐flowing Atlantic and Pacific water masses and, as such, local changes in ice cover, ocean properties and ecosystem dynamics cannot be fully understood separately from large‐scale oceanographic structures and advective processes. The Canadian International Polar Year (IPY) project Canada's Three Oceans (C3O) and the related Joint Ocean Ice Study (JOIS) have collected oceanographic data along a transit extending around northern North America to establish an initial, large‐scale baseline against which present and future changes can be gauged. Special focus was given to the shelf and the basin regions of the Canada Basin and the Canadian Arctic Archipelago. We use the first results from physical and geochemical data obtained during the summer of 2007 to discuss linkages between the Arctic and Subarctic domains and trace the cascade of key processes that affect contemporary ocean structure. A review of the literature, combined with these observations, is used to identify early signs of ongoing change throughout the three oceans surrounding northern North America including ocean warming and freshening, sea‐ice melting, increased hypoxia, reduced pH and altered biogeography.

Mechanical properties of cellularly responsive hydrogels and their experimental determination.

Hydrogels are increasingly employed as multidimensional cell culture platforms often with a necessity that they respond to or control the cellular environment. Specifically, synthetic hydrogels, such as poly(ethylene glycol) (PEG)-based gels, are frequently utilized for probing the microenvironment's influence on cell function, as the gel properties can be precisely controlled in space and time. Synthetically tunable parameters, such as monomer structure and concentration, facilitate initial gel property control, while incorporation of responsive degradable units enables cell- and/or user-directed degradation. Such responsive gel systems are complex with dynamic changes occurring over multiple time-scales, and cells encapsulated in these synthetic hydrogels often experience and dictate local property changes profoundly different from those in the bulk material. Consequently, advances in bulk and local measurement techniques are needed to monitor property evolution quantatively and understand its effect on cell function. Here, recent progress in cell-responsive PEG hydrogel synthesis and mechanical property characterization is reviewed.

AFM characterization of model nuclear fuel oxide multilayer structures modified by heavy ion beam irradiation

This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO 2 layers. HfO 2 served as a surrogate fissile material for UO 2 while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO 2 layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au 3+ ions at a range of fluences from 5 × 10 13 to 3.74 × 10 16 ions/cm 2. Separate single layer constituent films and the substrate were also irradiated at 5 × 10 15 and 8 × 10 14 and 2 × 10 16, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences.

Maturation of stretch‐induced contractile activity and its muscarinic regulation in isolated whole bladder strips from rat

Besides the establishment of neural reflex pathways, developmental changes in local bladder properties probably also contribute to the onset of mature voiding reflexes. Here we explored the behavior of stretch-induced contractile activity (SIC) and its muscarinic regulation in neonatal and adult rat bladders. SIC was studied in bladder strips from D0, D7, D28 rat pups and adult rats (15 weeks). The responses to a non-selective [Carbachol (CA), 10(-8.5)-10(-6) M] and an M(2)-selective muscarinic agonist [arecaidine but-2-ynyl ester tosylate (ABET), 10(-9.5)-10(-7) M] were studied. The expression of M(2) and M(3) mRNA was investigated using quantitative PCR in whole bladders. The response of SIC to KCl (50 mM) and to the non-adrenergic non-cholinergic (NANC) drugs Substance P (1 microM) and alpha,beta-Methyleneadenosine 5'-triphosphate lithium salt (MATP) (1 microM) were also studied. We found evidence for an enhanced response to the muscarinic agonists CA and ABET in neonatal bladders. This might be due to the onset of a direct contractile role for M(2), given the moderate M(2)-properties of ABET and the absence of ABET-effects on adult bladder strips. Further data showed an increased expression of both M(2) and M(3) at the mRNA level and a changed response of SIC to NANC drugs in neonatal bladder. This study reveals a changed response of SIC to muscarinic and NANC drugs in neonatal rat bladder together with changes at the muscarinic mRNA level, which might all contribute to a better insight in the role of SIC in the onset of mature voiding.

Fabrication of Advanced Functional Devices Combining Soft Chemistry with X-ray Lithography in One Step.

Deep X-ray lithography combined with sol-gel techniques offers facile fabrication of controlled patterned films. Using sol-gel, different functional properties can be induced; deep X-ray lithography alters the functionality in the exposed regions. Miniaturized devices based on local property changes are easily fabricated: this technique requires no resist, enabling direct patterning of films in a one-step lithographic process.

Changes of local and systemic hemorheological properties in intestinal ischemia‐reperfusion injury in the rat model

The aim of this study was to investigate intestinal ischemia-reperfusion and its local and systemic hemorheological relations in the rat. Ten anaesthetized female CD outbred rats were equally divided into 2 experimental groups. (1) Ischemia-reperfusion (I/R): the superior mesenterial artery was clipped for 30 minutes. After removing the clip, 60 minutes of the reperfusion was observed before extermination. Blood samples were taken from the caudal caval vein and from the portal vein before ischemia, 1 minute before and after clip removal, and at the 15th, 30th, and 60th minutes of the reperfusion. (2) Sham operation: median laparotomy and blood sampling were done according to the timing as in I/R group. Hematological parameters, red blood cell aggregation, and deformability were determined. Leukocyte count and mean volume of erythrocytes increased slightly but continuously in portal venous samples during the reperfusion period. Red blood cell aggregation values were higher in portal blood by the end of ischemia, and then became elevated further comparing to the caval venous blood. Both in caval and portal venous samples of I/R group red blood cell deformability significantly worsened during the experimental period compared to its base and Sham group. In portal blood red blood cell deformability was impaired more than in caval vein samples. Histology showed denuded villi, dilated capillaries, and the inflammatory cells were increased after a 30 minutes ischemia. In conclusion, intestinal ischemia-reperfusion causes changes in erythrocyte deformability and aggregation, showing local versus systemic differences in venous blood during the first hour of reperfusion.

Solvation in protein (un)folding of melittin tetramer–monomer transition

Protein structural integrity and flexibility are intimately tied to solvation. Here, we examine the effect that changes in bulk and local solvent properties have on protein structure and stability. We observe the change in solvation of an unfolding of the protein model, melittin, in the presence of a denaturant, trifluoroethanol. The peptide system displays a well defined transition in that the tetramer unfolds without disrupting the secondary or tertiary structure. In the absence of local structural perturbation, we are able to reveal exclusively the role of solvation dynamics in protein structure stabilization and the (un)folding pathway. A sudden retardation in solvent dynamics, which is coupled to the change in protein structure, is observed at a critical trifluoroethanol concentration. The large amplitude conformational changes are regulated by the local solvent hydrophobicity and bulk solvent viscosity.

Topographical, chemical, thermal and electrostatic properties of latex films

Scanning probe microscopy (SPM) was used for studying the changes in topographical, chemical, thermal and electrostatic properties of a styrene-butadiene latex coating as a function of annealing time. Changes in local surface properties obtained with SPM were correlated with changes in surface chemistry measured by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and contact angle measurements. The studied copolymer film goes through chemically and topographically meta-stable transition states during thermal annealing, reaching a steady state only after a significant annealing time (21 h). The differences in surface chemistry of the meta-stable states appeared as characteristic thermal and electrostatic properties of the latex coating. The results on film formation and drying are discussed in light of existing literature and theories. In this transition stage, the surface concentrations of polymeric components show unstable behavior, accordingly shifting the thermal transitions. Furthermore, the drying of the surface and desorption of surfactants is affecting the surface charge balance, changing from negative to positive. This was attributed to the change of balance of ionic components on the surface.

Structured Approach for Probabilistic Assisted History Matching Using Evolutionary Algorithms: Tengiz Field

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 116212, "A Structured Approach for Probabilistic Assisted History Matching Using Evolutionary Algorithms: Tengiz Field Applications," by H. Cheng, SPE, and K. Dehghani, SPE, Chevron Energy Technology Company, and T. Billiter, Tengizchevroil Kazakhstan, prepared for the 2008 SPE Annual Technical Conference and Exhibition, Denver, Colorado, 21-24 September. The paper has not been peer reviewed. Model calibration, or history matching, commonly has been conducted on a single deterministic model with a trial-and-error approach. Advances have been made in experimental design for use of numerical models in probabilistic forecasting. By use of evolutionary algorithms, a structured (staged) assisted history-matching method can be applied by considering probabilistic ranges of relevant input parameters and tailored objective functions for each stage of the process. A workflow was designed so that the ranges of selected parameters used to attain the best solutions at each stage could be carried over to the next stage to continue the history-match process. Introduction Numerical models are used to predict a range of ultimate recoveries and to appraise different development scenarios for oil and gas assets. The validity of reservoir models for performance prediction in brownfield assets is determined by their calibration against the historical production data. History Match. Model calibration has been conducted by changing regional and local reservoir properties to reconcile the model with observed production data. In manual history matching, a structured approach is used widely in which the sequence of scales of adjustments has been from global to flow units (regional), followed by local changes in model properties. In a geologically based automatic history matching, integrating production data typically requires minimization of a predefined data misfit and penalty terms to match the observed and calculated production response. There are two general methods to assist history matching by derivative-free (or direct search) technologies. In one, optimization of the objective function relies mainly on proxies. In this approach, experimental design is used to generate a response surface to guide the history-matching process. The second method uses genetic algorithm (GA) and evolution strategy. In this application, proxies and evolutionary algorithms were used together to accelerate the history-match process. Workflow Issues. Probabilistic history matching by use of proxies from experimental design and evolutionary algorithms, combined with parallel computing, brought about new tools for achieving a range of possibilities for acceptable history-match solutions. The structured-approach workflow of manual history matching has not been applied in probabilistic history-matching techniques. The assisted-history-matching process using experimental design and stochastic methods can be conducted by adjusting all the parameters at the same time regardless of considering any hierarchy in scale.

Keratoconus prediction using a finite element model of the cornea with local biomechanical properties

The ability to predict and understand which biomechanical properties of the cornea are responsible for the stability or progression of keratoconus may be an important clinical and surgical tool for the eye-care professional. We have developed a finite element model of the cornea, that tries to predict keratoconus-like behavior and its evolution based on material properties of the corneal tissue. Corneal material properties were modeled using bibliographic data and corneal topography was based on literature values from a schematic eye model. Commercial software was used to simulate mechanical and surface properties when the cornea was subject to different local parameters, such as elasticity. The simulation has shown that, depending on the corneal initial surface shape, changes in local material properties and also different intraocular pressures values induce a localized protuberance and increase in curvature when compared to the remaining portion of the cornea. This technique provides a quantitative and accurate approach to the problem of understanding the biomechanical nature of keratoconus. The implemented model has shown that changes in local material properties of the cornea and intraocular pressure are intrinsically related to keratoconus pathology and its shape/curvature.