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Ultra-low permeability tight glutenite reservoirs are widely distributed in the Bohai Bay, China. Compared with conventional sandstone reservoirs, the tight glutenite reservoirs are rich in clay minerals, highly developed with dissolved pores and microfractures, and have strong heterogeneity. Invasion of injected fluids into the glutenite reservoirs easily induces formation damage and blocking of pore throats, thereby reducing the flow capacity and the production rates of oil and gas. Cores taken from the glutenite formation in the BZ19-6 block were evaluated for salt sensitivity damage according to the industrial standards and high temperature high back-pressure steady-state method. The types and in-situ characteristics of the sensitive minerals and salt minerals were analyzed using SEM. The experimental results show that the salt sensitivity of the Kongdian glutenite is moderately strong to strong. Since the lower the permeability of the core, the higher the damage to the porosity and permeability of the core by salt precipitation, it is thus recommended that for dense cores with permeability less than 0.1 mD and reservoirs temperature higher than 100 ℃, the high temperature high back pressure steady state evaluation method be used to evaluate the flow sensitivity of the reservoir rocks. The clay minerals in the Kongdian formation are mainly silky/filamentous illite, altered kalinite and mixed illite/montmorillonite which exist in the dissolution pores in the form of comb shell type, dispersed filling and bridging etc., and are the main causes of salt sensitivity of the reservoirs. High temperature accelerates the evaporation of formation water, causing salt precipitation near the wellbore. The precipitated salts are mainly potassium salt and halite which exist on the surfaces of the mineral particles and walls of the pores, and cause the pore throats to be easily clogged. The main mechanisms of dense glutenite formation damage by salt precipitation include static evaporation of formation water which leads to clogging of the dense pore throats, salt crystal migration during dynamic displacement which clogs the pore throats and the weakening of the rock strengths by salt precipitation which leads to particle migration. To minimize reservoir damage by salt sensitivity, KCl-salt saturated polymer sulfonate and zwitterionic polymer drilling fluids are recommended as the drill-in fluids, the filtration rates of the drilling fluids should be reduced, and the crystallization and nucleation of salts in the drilling fluids be inhibited. [ABSTRACT FROM AUTHOR]

The Ca2+-permeable transient receptor potential vanilloid type 4 (TRPV4) channel serves as the sensor of tubular flow, thus being well suited to govern mechanosensitive K+ transport in the distal renal tubule. Here, we directly tested whether the TRPV4 function is significant in affecting K+ balance. We used balance metabolic cage experiments and systemic measurements with different K+ feeding regimens [high (5% K+), regular (0.9% K+), and low (<0.01% K+)] in newly created transgenic mice with selective TRPV4 deletion in the renal tubule (TRPV4fl/fl-Pax8Cre) and their littermate controls (TRPV4fl/fl). Deletion was verified by the absence of TRPV4 protein expression and lack of TRPV4-dependent Ca2+ influx. There were no differences in plasma electrolytes, urinary volume, and K+ levels at baseline. In contrast, plasma K+ levels were significantly elevated in TRPV4fl/fl-Pax8Cre mice on high K+ intake. K+-loaded knockout mice exhibited lower urinary K+ levels than TRPV4fl/fl mice, which was accompanied by higher aldosterone levels by day 7. Moreover, TRPV4fl/fl-Pax8Cre mice had more efficient renal K+ conservation and higher plasma K+ levels in the state of dietary K+ deficiency. H+-K+-ATPase levels were significantly increased in TRPV4fl/fl-Pax8Cre mice on a regular diet and especially on a low-K+ diet, pointing to augmented K+ reabsorption in the collecting duct. Consistently, we found a significantly faster intracellular pH recovery after intracellular acidification, as an index of H+-K+-ATPase activity, in split-opened collecting ducts from TRPV4fl/fl-Pax8Cre mice. In summary, our results demonstrate an indispensable prokaliuretic role of TRPV4 in the renal tubule in controlling K+ balance and urinary K+ excretion during variations in dietary K+ intake. NEW & NOTEWORTHY The mechanoactivated transient receptor potential vanilloid type 4 (TRPV4) channel is expressed in distal tubule segments, where it controls flow-dependent K+ transport. Global TRPV4 deficiency causes impaired adaptation to variations in dietary K+ intake. Here, we demonstrate that renal tubule-specific TRPV4 deletion is sufficient to recapitulate the phenotype by causing antikaliuresis and higher plasma K+ levels in both states of K+ load and deficiency. [ABSTRACT FROM AUTHOR]

Context-sensitive methods of program analysis increase the precision of interprocedural analysis by achieving the effect of call inlining. These methods have been defined using different formalisms and hence appear as algorithms that are very different from each other. Some methods traverse a call graph top-down, whereas some others traverse it bottom-up first and then top-down. Some define contexts explicitly, whereas some do not. Some of them directly compute data flow values, while some first compute summary functions and then use them to compute data flow values. Further, different methods place different kinds of restrictions on the data flow frameworks supported by them. As a consequence, it is difficult to compare the ideas behind these methods in spite of the fact that they solve essentially the same problem. We argue that these incomparable views are similar to those of blind men describing an elephant, called context sensitivity, and make it difficult for a non-expert reader to form a coherent picture of context-sensitive data flow analysis. We bring out this whole-elephant view of context sensitivity in program analysis by proposing a unified model of context sensitivity that provides a clean separation between computation of contexts and computation of data flow values. Our model captures the essence of context sensitivity and defines simple soundness and precision criteria for context-sensitive methods. It facilitates declarative specifications of contextsensitive methods, insightful comparisons between them, and reasoning about their soundness and precision. We demonstrate this by instantiating our model to many known context-sensitive methods. [ABSTRACT FROM AUTHOR]

Bulk motion seriously degrades the image quality of optical coherence tomography angiography (OCTA). Conventional correction methods focus on in‐plane displacement, while the bulk motion component perpendicular to B‐scans also introduces noise. This work first presents an evaluation of this component using a specific scan protocol and an approximate expression derived from peak‐normalized cross‐correlation values, and then quantitatively assesses how interplane bulk motion noise reduce the sensitivity of cross‐sectional angiograms. Finally, we developed a repetitive bulk motion correction method based on the estimated displacements and redundant volume scans. The correction does not require registration and angiogram reconstruction of low flow sensitivity frames, and the results of in vivo mice skin OCTA imaging experiments show that the proposed method can effectively reduce bulk motion noise caused by cardiac and respiratory motion and occasional shaking, and improve OCTA image quality, which has practical significance for clinical OCTA diagnosis and analysis. [ABSTRACT FROM AUTHOR]

Mechanistic water quality models are applied globally for water quality management in rivers and lakes. However, it is unclear how well these models represent the response of lakes to changes in climate and hydrologic conditions. To address this question, we conducted a series of climate and hydrologic sensitivity analyses using a parameterized water quality model, CE‐QUAL‐W2, for the Spokane River and Lake Spokane system. Two experimental tests with climate and flow forcing showed that the model predictions were rather insensitive to climatic‐driven hydrologic changes and a wide range of hydrologic conditions (1st to 99th percentile flows) for two different wastewater treatment plant discharge scenarios. The model realistically represented some aspects of Lake Spokane's observed responses to climatic and hydrologic variability, for example, the water residence time and some water quality trends. However, the model overestimated the reservoir total phosphorus (TPR) concentration by ~37% and the chlorophyll a (Chl a) concentration by ~31% and underestimated the minimum volume‐weighted hypolimnetic dissolved oxygen (DOMIN) concentration by ~26% for a wide range of flows compared to the observed data. In contrast to the model's water quality insensitivity, the modeled temperature was more sensitive to flow than was actually observed in Lake Spokane. This study provides guidance for improving the response of one of the most important mechanistic water quality models to climatic and hydrologic forcing and should help modelers and decision‐makers to develop a rigorous assessment of climate and flow sensitivity to improve the margin of safety when setting total maximum daily load targets. Key Points: We assessed the predicted responses of lake water quality to climatic and hydrologic forcing using the model CE‐QUAL‐W2The model predictions were insensitive to climate‐driven hydrologic changes for a wide range of conditionsTo improve future modeling, we suggest using a much wide range of climatic and hydrologic conditions during model calibration [ABSTRACT FROM AUTHOR]

In this work, we consider a new model for flow in a multiporosity shale gas reservoir constructed within the framework of an upscaling procedure where hydraulic fractures are treated as (n-1) interfaces (n=2,3). Within this framework, the hydrodynamics is governed by a new pressure equation in the shale matrix which is treated as a homogenized porous medium composed of organic matter (kerogen aggregates with nanopores) and inorganic impermeable solid (clay, calcite, quartz) separated from each other by a network of interparticle pores of micrometer size. The solution of the pressure equation is strongly influenced by the constitutive response of the retardation parameter and effective hydraulic conductivity where the former incorporates gas adsorption/desorption in the nanopores of the kerogen. By focusing our analyses on this nonlinear diffusion equation in the domain occupied by the shale matrix, an optimization strategy seated on the adjoint sensitivity method is developed to minimize a cost functional related to gas production and net present value in a single hydraulic fracture. The gradient of the objective functional computed with the adjoint formulation is explored to update the controlled pressure drop aiming to optimize production in a given window of time. The combination of the direct approach and gradient-based optimization using the adjoint formulation leads to the construction of optimal production scenarios under controlled pressure decline in the well. Numerical simulations illustrate the potential of the methodology proposed herein in optimizing gas production. [ABSTRACT FROM AUTHOR]

The need for reliable approaches in numerical simulations stands out as a critical issue for the development and optimization of cardiovascular biomedical devices. This led the US Food and Drug Administration to undertake a programme of validation of computational fluid dynamics methods for transitional and turbulent flows. In the current investigation, large-eddy simulation is used to simulate the flow in the first benchmark medical device, and results are confronted to the existing laboratory experiments. This idealized medical device has the particularity to feature transition to turbulence after a sudden expansion. The effects of numerical parameters and low-level inlet perturbations are investigated. Results indicate a considerable impact of numerical aspects on the prediction of the location of the transition to turbulence. The study also demonstrates that injecting small perturbations at the inflow greatly improves the streamwise velocity estimation in the transition region and substantially contributes to the robustness of the flow statistical data. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Ca 2+ -permeable transient receptor potential vanilloid type 4 (TRPV4) channel serves as the sensor of tubular flow, thus being well suited to govern mechanosensitive K + transport in the distal renal tubule. Here, we directly tested whether the TRPV4 function is significant in affecting K + balance. We used balance metabolic cage experiments and systemic measurements with different K + feeding regimens [high (5% K + ), regular (0.9% K + ), and low (<0.01% K + )] in newly created transgenic mice with selective TRPV4 deletion in the renal tubule (TRPV4 fl/fl -Pax8Cre) and their littermate controls (TRPV4 fl/fl ). Deletion was verified by the absence of TRPV4 protein expression and lack of TRPV4-dependent Ca 2+ influx. There were no differences in plasma electrolytes, urinary volume, and K + levels at baseline. In contrast, plasma K + levels were significantly elevated in TRPV4 fl/fl -Pax8Cre mice on high K + intake. K + -loaded knockout mice exhibited lower urinary K + levels than TRPV4 fl/fl mice, which was accompanied by higher aldosterone levels by day 7 . Moreover, TRPV4 fl/fl -Pax8Cre mice had more efficient renal K + conservation and higher plasma K + levels in the state of dietary K + deficiency. H + -K + -ATPase levels were significantly increased in TRPV4 fl/fl -Pax8Cre mice on a regular diet and especially on a low-K + diet, pointing to augmented K + reabsorption in the collecting duct. Consistently, we found a significantly faster intracellular pH recovery after intracellular acidification, as an index of H + -K + -ATPase activity, in split-opened collecting ducts from TRPV4 fl/fl -Pax8Cre mice. In summary, our results demonstrate an indispensable prokaliuretic role of TRPV4 in the renal tubule in controlling K + balance and urinary K + excretion during variations in dietary K + intake. NEW & NOTEWORTHY The mechanoactivated transient receptor potential vanilloid type 4 (TRPV4) channel is expressed in distal tubule segments, where it controls flow-dependent K + transport. Global TRPV4 deficiency causes impaired adaptation to variations in dietary K + intake. Here, we demonstrate that renal tubule-specific TRPV4 deletion is sufficient to recapitulate the phenotype by causing antikaliuresis and higher plasma K + levels in both states of K + load and deficiency.

Long-standing experimental evidence suggests that epithelial cells in the renal tubule are able to sense osmotic and pressure gradients caused by alterations in ultrafiltrate flow by elevating intracellular Ca2+ concentration. These responses are viewed as critical regulators of a variety of processes ranging from transport of water and solutes to cellular growth and differentiation. A loss in the ability to sense mechanical stimuli has been implicated in numerous pathologies associated with systemic imbalance of electrolytes and to the development of polycystic kidney disease. The molecular mechanisms conferring mechanosensitive properties to epithelial tubular cells involve activation of transient receptor potential (TRP) channels, such as TRPV4, allowing direct Ca2+ influx to increase intracellular Ca2+ concentration. In this review, we critically analyze the current evidence about signaling determinants of TRPV4 activation by luminal flow in the distal nephron and discuss how dysfunction of this mechanism contributes to the progression of polycystic kidney disease. We also review the physiological relevance of TRPV4-based mechanosensitivity in controlling flow-dependent K+ secretion in the distal renal tubule. [ABSTRACT FROM AUTHOR]

This article presents a family of static analyses to determine pointer targets, control flow, and dataflow in combination. The integrated solution to these mutually dependent problems approaches the result from the optimistic side. It is a general strategy for static program analysis and does not need any upfront approximation for one of the problems to overcome the mutual dependencies. A degenerated case yields Andersen's famous pointer analysis; otherwise, the analyses are flow-sensitive and can support direct and indirect strong updates, within the same cubic asymptotic complexity as known for Andersen, albeit with larger constants. Surprisingly, the ideas behind the integrated analysis are intuitive. The strategy we describe naturally evolves from considering the mutual dependencies between the three problems, or from generalizing Andersen's analysis to flow sensitivity. Such a flow-sensitive Andersen analysis not only computes pointer targets with higher precision than the original analysis, but it also creates an interprocedural SSA form at the same time. Our extensive experimental evaluation shows that the integrated solution is practical as it can be applied to reasonably large real-world programs within a few seconds or minutes. This uses some optimizations which together achieve a speedup of more than 100 for several programs. We compare several members of the family of analyses, from flow- and field-insensitive to flow- and field-sensitive with strong updates, both with and without optimizations. This gives some insights into the effects of these dimensions of precision on the results. It also sheds new light on the benefits of flow sensitivity versus the costs associated with it. [ABSTRACT FROM AUTHOR]

The effects of inflow boundary conditions, ambient stratification, and geometry on the behavior of a density-induced current in a stratified reservoir are quantified through numerical experiments with a validated two-dimensional (2D) simulation model. Model results are analyzed to evaluate the sensitivity of reservoir flow variables to changes in the parameters characterizing inflow and ambient water. Quantitative evidence is presented to show that reservoir flow is more sensitive to Froude and Reynolds numbers than to other parameters. A critical value for each parameter is identified, which divides significant and insignificant effects on flow and dilution. [ABSTRACT FROM AUTHOR]

Introduction Because many cardiovascular diseases are related to blood flow features, being able to predict how blood flows would open a window towards better diagnostic and treatment capabilities. Validation of an immersed thick boundary method for simulating fluid-structure interactions of deformable membranes. [Extracted from the article]

Thermal flow sensors in multimaterial fibers that overcome the fundamental trade‐off between sensitivity, pressure drop, measurement range, and temperature rise are demonstrated. Significant performance improvement over existing microelectromechanical systems flow sensors is realized with the use of conductive polymers as hot films and multisegment structures unique to fiber fabrication processes. This unconventional form of flow sensors paves the way toward multifunctional microfluidics feed lines needed in large‐scale multichip integration in microfluidics and opens new possibilities in lab‐on‐fiber technologies. Integrated thermal flow sensors are demonstrated in multimaterial fibers that overcome the fundamental trade‐off between sensitivity, pressure drop, measurement range, and temperature rise. Significant performance improvement over existing MEMs flow sensors is realized with the use of conductive polymers as hot films and multisegment structures unique to fiber fabrication processes. [ABSTRACT FROM AUTHOR]