Resistance Gradient Research Articles

Controlled Patterning of Complex Resistance Gradients in Conducting Polymers with Bipolar Electrochemistry

AbstractConducting polymers have gained considerable attention for the possible design of localized electroactive patterns for microelectronics. In this work, the authors take advantage of the properties of polypyrrole, in synergy with a wireless polarization, triggered by bipolar electrochemistry, to produce localized resistance gradient patterns. The physicochemical modification is caused by the reduction and overoxidation of polypyrrole, which produces highly resistive regions at different positions along the conducting substrate at predefined locations. Due to the outstanding flexibility of polypyrrole, U‐, S‐, and E‐shaped bipolar electrodes can be formed for prove‐of‐concept experiments, and electrochemically modified in order to generate well‐defined resistance gradients. Energy‐dispersive X‐ray spectroscopy analysis of the samples confirms the localized physicochemical modifications. This approach presents as main advantages the wireless nature of bipolar electrochemistry and the possible fine‐tuning of the spatial distribution of the electrochemical modification, in comparison with more conventional patterning methods.

Three-dimensional anisotropic inversion and electrostratigraphic imaging of marine magnetotelluric data to understand the control of crustal deformations by pre-existing lithospheric structures in the Mexican Ridges Fold belt, Southwestern Gulf of Mexico

SUMMARY3-D imaging of the lithosphere in the Mexican Ridges fold belt is important for understanding how the crustal deformations in this basin relate to deep tectonic processes and structures inherited from extinct Jurassic seafloor spreading. Here, we use broad-band (0.0001–0.4642 Hz) marine magnetotelluric data from the basin to reconstruct the 3-D anisotropic resistivities of the lithosphere and their spatial gradients. The resistivity gradients maxima enabled independent definition of important geological boundaries (seen on collocated seismic reflection data) and estimation of crustal thickness. We found anomalous layered zones of low resistivity and high electrical anisotropy at 5–8 km depth (coinciding with the regional detachment zone in Eocene shales in 3-D seismic data) and in the upper mantle which we interpret as indicating intense deformation and/or recent magmatic influence. We also found a banded crystalline basement structure across the fossil spreading centre comprising WSW–ENE trending, 6–10 km wide, electrically resistive subvertical sheets with conductive and anisotropic borders, which merge into a basal resistive stock-like body at 15–20 km depth. These are cut or bounded by later NNW trending major faults. These WSW and NNW structural trends correlate with the previously interpreted transform and normal faults that formed during the Late Jurassic opening of the Gulf of Mexico only if rotated clockwise by 25–30°. Surprisingly, the rugged thrust-related seabed is offset at the projected positions of the steep resistive-conductive basement sheets (which also have spatially coincident high magnetic intensity and seismicity) enabling us to infer they represent magmatic intrusions facilitated by pre-existing faults. Their conductive borders spatially coincide with possibly fluid-filled vertical fracture-sets in the overlying sediments seen in seismic data which we interpret as hydrothermal fluid pathways. We infer that a magmatic body recently intruded our study area, its ascent controlled by pre-existing basement structures, and influenced the deformation of the Neogene sequences and the seafloor topography.

Estimating resistance surfaces using gradient forest and allelic frequencies.

Understanding landscape connectivity has become a global priority for mitigating the impact of landscape fragmentation on biodiversity. Connectivity methods that use link-based methods traditionally rely on relating pairwise genetic distance between individuals or demes to their landscape distance (e.g., geographic distance, cost distance). In this study, we present an alternative to conventional statistical approaches to refine cost surfaces by adapting the gradient forest approach to produce a resistance surface. Used in community ecology, gradient forest is an extension of random forest, and has been implemented in genomic studies to model species genetic offset under future climatic scenarios. By design, this adapted method, resGF, has the ability to handle multiple environmental predicators and is not subjected to traditional assumptions of linear models such as independence, normality and linearity. Using genetic simulations, resistance Gradient Forest (resGF) performance was compared to other published methods (maximum likelihood population effects model, random forest-based least-cost transect analysis and species distribution model). In univariate scenarios, resGF was able to distinguish the true surface contributing to genetic diversity among competing surfaces better than the compared methods. In multivariate scenarios, the gradient forest approach performed similarly to the other random forest-based approach using least-cost transect analysis but outperformed MLPE-based methods. Additionally, two worked examples are provided using two previously published data sets. This machine learning algorithm has the potential to improve our understanding of landscape connectivity and inform long-term biodiversity conservation strategies.

Riverine antibacterial resistance gradient determined by environmental factors.

Polluted waterbodies such as rivers provide a pathway or reservoir for bacterial resistance. We studied water quality and bacterial antibacterial resistance along the subtropical Qishan River in Taiwan as a case study of environmental resistance spread in a pristine rural area. Human settlement densities increased generally from pristine mountain sites to the more polluted lowlands. Accordingly, as a working hypothesis, we expected the antibacterial resistance level to increase downstream. We collected sediment samples from 8 stations along the Qishan river and where the Qishan river reaches the Kaoping river. The samples were processed in the lab for bacteriological and physicochemical analysis. Antibacterial resistance was tested with common antibacterial. A comparison was made among the sites where isolates began to occur at the upstream (sites 1-6) with the downstream, including site 7 (Qishan town), site 8 (wastewater treatment plant), and site 9 (Kaoping river). The results of multivariate analysis for bacteriological and physicochemical parameters showed increasing water pollution levels downstream of the Qishan river. Bacterial isolates including Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter sp., Acinetobacter sp., Staphylococcus spp., and Bacillus spp. were analyzed and tested in the study. Their percentage of occurrence varied at each site. The resistance level was determined from the growth inhibition zone diameter (disk diffusion) and the minimum inhibitory concentration (micro-dilution). The results indicated that antibacterial resistance was related to certain environmental factors. Besides, the usage pattern of different classes of antibacterial in different sections could alter trends of their resistance. Bacteria were found with increased resistance to antibacterial used in agriculture through the downstream sites. The WWTP discharging wastewater was demonstrated to be a hotspot of resistance in aquatic environments. In conclusion, bacterial resistance against antibacterial from the Qishan river has become a potential public health threat. This study could assist authorities by providing a reference for risk assessment and management of water quality in Kaohsiung city and southern Taiwan.

Core endophytic mycobiome in Ulmus minor and its relation to Dutch elm disease resistance.

The core microbiota of plants exerts key effects on plant performance and resilience to stress. The aim of this study was to identify the core endophytic mycobiome in U. minor stems and disentangle associations between its composition and the resistance to Dutch elm disease (DED). We also defined its spatial variation within the tree and among distant tree populations. Stem samples were taken i) from different heights of the crown of a 168-year-old elm tree, ii) from adult elm trees growing in a common garden and representing a gradient of resistance to DED, and iii) from trees growing in two distant natural populations, one of them with varying degrees of vitality. Endophyte composition was profiled by high throughput sequencing of the first internal transcribed spacer region (ITS1) of the ribosomal DNA. Three families of yeasts (Buckleyzymaceae, Trichomeriaceae and Bulleraceae) were associated to DED-resistant hosts. A small proportion (10%) of endophytic OTUs was almost ubiquitous throughout the crown while tree colonization by most fungal taxa followed stochastic patterns. A clear distinction in endophyte composition was found between geographical locations. By combining all surveys, we found evidence of a U. minor core mycobiome, pervasive within the tree and ubiquitous across locations, genotypes and health status.

Functional thresholds alter the relationship of plant resistance and recovery to drought.

The ecological consequences of future droughts are difficult to predict due to a limited understanding of the nonlinear responses of plants to increasing drought intensity, which can change abruptly when critical thresholds of drought intensity are crossed. Drought responses are composed of resistance and postdrought recovery. Although it is well established that higher drought intensity increases the impact and, thus, reduces plant resistance, less is known about how drought intensity affects recovery and how resistance and recovery are related. In this study, we tested the hypothesis that resistance, recovery, and their relationship change abruptly upon crossing critical thresholds of drought intensity. We exposed mesocosms of two monospecific stands of the common grassland species Dactylis glomerata and Plantago lanceolata to a large gradient of drought intensity and quantified the resistance and recovery of multiple measures of plant productivity, including gross-primary productivity, vegetative height, Normalized Difference Vegetation Index, and aboveground biomass production. Drought intensity had nonlinear and contrasting effects on plant productivity during drought and recovery, which differed between the two species. Increasing drought intensity decreased the resistance of plant productivity and caused rapid compensatory growth during postdrought recovery, the degree of which was highly dependent on drought intensity. Across multiple response parameters two thresholds of drought intensity emerged, upon which we observed abrupt changes in plant resistance and recovery, as well as their relationship. We conclude that across gradients of drought intensity resistance and recovery are tightly coupled and that both the magnitude and the direction of drought effects on resistance and recovery can change abruptly upon specific thresholds of stress intensity. These findings highlight the urgent need to account for nonlinear responses of resistance and recovery to drought intensity as critical drivers of productivity in a changing climate.

Noninvasive Monitoring of Subsurface Soil Conditions to Evaluate the Efficacy of Mole Drain in Heavy Clay Soils

Soil degradation and low productivity are among the major agricultural problems facing farmers of the newly reclaimed agricultural area in the Nile Delta region, Egypt. High content of clay and silt characterizes the soil texture of all farms in the area, while farmers still rely on the traditional mole drainage (MD) system to reduce the salinity of the farm soil. We present a comparison of innovative geo-resistivity methods to evaluate mole drains and the salinity affected clay soils. Geoelectrical surveys were conducted on three newly reclaimed farms to image the subsurface soil drainage conditions and to evaluate the efficiency of using the traditional MD systems in these heavy clay environments. The surveys included measuring the natural spontaneous potential (SP), apparent resistivity gradient (RG), and electrical resistivity tomography (ERT). Integrating the results of the three methods reduced the ambiguous interpretation of the inverted ERT models and allowed us to determine the subsurface soil structure. The inverted ERT models were suitable for locating the buried MDs and delineating the upper surface of the undisturbed clay beds. The proximity of these layers to the topsoil reduces the role played by MDs in draining the soil in the first farm and prevents the growth of deep-rooted plants in the second farm. Time-lapse ERT measurements on the third farm revealed a defect in its drainage network where the slope of the clay beds opposes the main direction of the MDs. That has completely obstructed the drainage system of the farm and caused waterlogging. The presented geo-resistivity methods show that integrated models can be used to improve the assessment of in situ sub-surface drainage in clay-rich soils.

Dependence of resistivity gradient guiding of laser-driven relativistic electron beams on laser intensity and duration

A laser-driven relativistic electron beam (REB) has a large beam divergence. For the efficient heating of material by REB, for example, core heating in fast ignition, beam guiding from its generation point to the heating material to be heated by suppressing spatial divergence in a perpendicular direction to keep its intensity sufficiently high is indispensable. We evaluated the dependences of the REB guiding performance in the resistivity gradient guiding scheme [A. P. L. Robinson and M. Sherlock, “Magnetic collimation of fast electrons produced by ultraintense laser irradiation by structuring the target composition,” Phys. Plasmas 14, 083105 (2007)] on laser intensity and duration, from the present petawatt laser parameters to the fast ignition-relevant laser parameters, in terms of the temperature dependence of resistivity and energy deposition of the REB. The REB transport simulations in solid materials show that for a fast ignition-relevant laser condition, a nickel cylinder works as a guiding material; an REB transport efficiency of 40% is obtained for a 100-μm propagation. The simulation results show that the resistive gradient guiding scheme is one of possible candidates for improving core heating efficiency.

The Improvement of the Wear Resistance of T15 Laser Clad Coating by the Uniformity of Microstructure

The uniformity of microstructure and wear properties exist in the T15 coating for the laser cladding on 42CrMo steel. It can be improved by a post-heat treatment process. Temperature ranges from 1100 to 1240 °C were applied on the cladding layer to investigate the effect of the heat treatment on the wear resistance and hardness gradient. The post-heat treatment can efficiently improve the inhomogeneity of microstructure. The lower wear rate is obtained after the quenching process at 1100 °C, and the wear rate is increased though the tempering process. The carbides at the grain boundary are decomposed and integrated into the matrix during the high temperature quenching process. The carbides are precipitated and dispersed in the grain during the tempering process. The content of martensite and alloy carbide is significantly increased through the heat treatment process. The microhardness of the cladding layer is 910 HV after quenching and 750 HV after tempering. The wear mechanism of the cladding layer is mainly abrasive wear and fatigue wear. The crack and falling off from cladding layers are significantly reduced for the quenching–tempering process.

Modelling Investigation of the Impact of Several Process Parameters on the Growth of the Viscous Layer during the Electropolishing

Electrochemical polishing (EP) is of great interest because it is able to deal with small parts exhibiting high complex shapes and/or material hard to be polished. Electropolishing is an electrolytic process based on the anodic dissolution of the workpiece under constant current or potential. Previous work done on stainless steel 316L shows the ability of the process to obtain smooth and bright surfaces [1]. The mechanisms describing EP are not yet fully understood, but several mechanisms can be taken into account for its description and prediction. Jacquet’s theory is based on the influence of an electric resistance gradient [2]. Elmore will then complete it with the gradient of concentration in metal cation [3,4]. Diard and al proposed the role of so called “acceptor” species [5]. While Hoar and Mowat’s work are based on the formation of an oxide layer on the surface [6]. All theories have in common the establishment of a viscous layer (solid or liquid) that governs the process. On this basis, it is possible to propose a numerical approach for the simulation of the viscous layer formation during electropolishing of stainless steel 316L and Inconel parts. The objective is to demonstrate the impact of various process parameters (electrochemical parameters, electrolyte nature and concentration as well as hydrodynamic conditions) on the growth and the stability of this layer.The figure illustrate the simulation of the viscous layer growth during the electropolishing of a plate at the bottom taking into account the circulation of the electrolyte from the left to the right.[1] C. Rotty, A. Mandroyan, M-L Doche, J-Y Hihn, Surface & Coatings Technology vol.307 p125–135 (2016).[2] JACQUET, P.A., Electrolytic method for obtaining bright copper surfaces, Nature 135 (1935) 1076.[3] ELMORE, W.C., Electrolytic Polishing, J. Appl. Phys. 10 (1939) 724–727, http://dx.doi.org/10.1063/1.1707257.[4] ELMORE, W.C., Electrolytic Polishing II, J. Appl. Phys. 11 (1940) 797–799, http://dx.doi.org/10.1063/1.1712738.[5] DIARD, J.P., LANDAUD, P., LE CANUT, J.-M., LE GORREC, B., Interprétation cinétique du palier de polissage électrochimique des métaux, 6ème forum sur les impédances électrochimiques, Montrouge, 1992.[6] HOAR, T.P., MOWAT, J.A.S., Mechanism of electropolishing, Nature 165 (1950) 64–65. Figure 1

Pulmonary Vascular Reverse Remodeling After Left Ventricular Assist Device Implantation in Patients With Pulmonary Hypertension.

Prevalence of combined pre- and post-capillary (Cpc) pulmonary hypertension (PH) in patients with PH due to left heart disease (PH-LHD) and the long-term impact of left ventricular assist device (LVAD) implantation in patients with Cpc-PH are not fully elucidated. Eighty-nine patients with PH-LHD who underwent LVAD implantation were retrospectively analyzed. Patients were divided into two groups according to their preoperative pulmonary vascular resistance (PVR) and diastolic pressure gradient (DPG) values (Cpc-PH group, PVR >3 wood units [WU], or DPG ≥7 mmHg; isolated postcapillary [Ipc]-PH group, PVR ≤3 WU, and DPG <7 mmHg). There were 50 patients with Cpc-PH (PVR >3 WU [group A, n = 41]; PVR >3 WU and DPG ≥7 mmHg [group B, n = 8]; DPG ≥7 mmHg [group C, n = 1]), and 39 patients with Ipc-PH. Despite a successful LVAD implantation in all participants, 13 and two patients remained in groups A and B, respectively, early after LVAD implantation, whereas two patients each remained in groups A and B 1 year postoperatively. Values of PVR and DPG in the Cpc-PH group returned to normal levels by 3 years postoperatively. Over 50% of patients with PH-LHD had Cpc-PH, and PVR and DPG normalized in all participants within 3 years after LVAD implantation.

Research on the Armature–Rail Dynamic Contact Characteristics of the Series Enhanced Electromagnetic Rail Launcher

To study the dynamic contact characteristics of the armature–rail of the series-enhanced electromagnetic rail launcher, the electrical connection of the launcher is divided into an armature circuit, an arc suppression circuit, and a vice rail circuit to construct an effective electrical model that considers the actual motion of the armature. The mathematical relationship model of the armature–rail contact resistance and outlet voltage, rail current, armature speed–displacement, and device parameters (inductance gradient, resistance gradient, mutual inductance gradient) and other physical quantities is obtained, and the change curve of the contact resistance of the armature–rail is measured through experiments and finite element/boundary element simulation calculations. The results show that the contact state of the armature–rail can be divided into three stages by the change curve, which is consistent with the rail damage state obtained by the actual measurement. The work done in this article can provide an effective reference for predicting the rail damage and armature thermal load design of the series-enhanced electromagnetic rail launcher.

High prevalence of occult left ventricular diastolic dysfunction detected by exercise stress test in systemic sclerosis

Despite the poor prognosis of systemic sclerosis (SSc) due to the co-occurrence of left ventricular diastolic dysfunction (LVDD), presence of occult LVDD has not been sufficiently investigated. This retrospective study aimed to reveal the prevalence and determinants of occult LVDD in patients with SSc by exercise stress test. Forty-five SSc patients (age, 63 ± 13 years; men/women, 6/39) with normal pulmonary artery pressure and pulmonary artery wedge pressure (PAWP) at rest underwent a symptom-limited exercise test with right heart catheterization using a supine cycle ergometer; haemodynamic parameters at rest, leg raise and during exercise were evaluated. Occult LVDD defined PAWP ≥ 25 mmHg during exercise was seen in 13 patients (29%). Higher PAWP, lower pulmonary vascular resistance and diastolic pulmonary pressure gradient, larger left atrium at rest, and higher PAWP during leg raise (15 ± 4 vs 10 ± 4 mmHg in non-LVDD group, p < 0.001) were observed in the occult LVDD group. The area under the ROC curve for PAWP after leg raise was largest at 0.83 (95% CI: 0.70–0.95, p = 0.001). About one-third (29%) of SSc patients with normal haemodynamics at rest showed occult LVDD. A higher PAWP after leg raise could be useful for detecting occult LVDD.

Soil Resistivity, its Impact on Optimum Depth of Electrodes in Earthing System– Case Study University of Port Harcourt Residential Staff Quarters

A well-designed earthing system plays a vital role in any Electrical Facility. Soil resistivity measurement is an important parameter when designing earthing system. However, it is a known fact that the resistance of an earth electrode which is a component of earthing system is heavily influenced by the resistivity of the soil in which it is driven to. A knowledge of the soil resistivity at the intended site, and how this varies with parameters such as moisture content, temperature and depth, provides a valuable insight into how the desired earth resistance value can be achieved and maintained over the life of the installation with the minimum cost and effort. One of the main objectives of earthing electrical systems is to establish a common reference potential for the power supply system, building structure, plant steelwork, electrical conduits, cable ladders and trays and the instrumentation system. To achieve this objective, a suitable low resistance connection to earth is desirable. In this research paper, soil resistivity was investigated in three different residential staff quarters of University of Port Harcourt Choba, Abuja and Delta Campuses during the wet and dry season of 2022 using the relevant IEEE standards and International best practices for determining Electrical substation and residential buildings earthing system designs. To determine the optimum depth of grounding electrodes that will have the acceptable values of earth resistance and resistivity for earthing system designs, the Wenner four pin method of measuring soil resistivity was employed. The findings of this research paper show the optimum depth the grounding electrodes will get to in order to obtain the best earth resistance and resistivity values that is suitable for substation and residential earthing system designs. The outcome of this study is also useful for purposes of estimating the number of grounding electrodes, ground resistance and potential gradients including step and touch voltages of substation grounding installations around the three locations of study in university of Port Harcourt residential staff quarters.

Measurement Method for the Simultaneous DeterMination of Thermal Resistance and Temperature Gradients in the DeterMination of Thermal Properties of Textile Material Layers.

The thermal properties of most clothing products are still not designed according to engineering science due to the lack of simple and acceptable measuring equipment and methods; the type of thermal insulation material, the number of layers of clothing and their thickness are thus chosen empirically. The novelty of this study was the development of a new measuring device and method for simultaneous measurements in the determination of the thermal resistance in one or more textile material layers, such as in multilayer composite clothing. Temperature gradients of textile material layers are presented, as well as the theoretical principles of operation and practical results. Four materials for the production of protective jackets were selected, from which different combinations of composite clothing were constructed and the thermal parameters were measured with a new method and a new device, both individually for the built-in materials and for the composites. Subsequently, five test jackets with the same arrangement of textile material layers as the previously tested composites were produced, and measurements of important thermal parameters were recorded with a thermal mannequin. The determined temperature gradients and measurement results are presented, and based on these it was determined that the total thermal resistance was not equal to the algebraic sum of the resistances of the individual textile material layers in the horizontal position; it was, however, higher, increasing from 30% to 94% due to small air layers caused by crimping and protruding fibres of yarn in the textile fabrics. The same textile material layers built into clothing in the vertical position allowed the formation of significantly wider air layers that increased the thermal resistance by between 2.5 and 9 times.

Influence of reservoir lithology on porous flow resistance of gas-bearing tight oil reservoirs and production forecast

The release of dissolved gas during the development of gas-bearing tight oil reservoirs has a great influence on the effect of development. In this article, the high-pressure mercury intrusion experiment was carried out in cores from different regions and lithologies of the Ordos Basin and the Sichuan Basin. The objectives are to study the microscopic characteristics of the porous throat structure of these reservoirs and to analyze the porous flow resistance laws of different lithology by conducting a resistance gradient test experiment. A mathematical model is established and the oil production index is corrected according to the experiment results to predict the oil production. The experimental results show that for tight reservoirs in the same area and lithology, the lower the permeability under the same back pressure, the greater the resistance gradient. And for sandstone reservoirs in different areas, the resistance gradients have little difference and the changes in the resistance coefficients are similar. However, limestone under the same conditions supports a much higher resistance gradient than sandstone reservoirs. Furthermore, the experimental results are consistent with the theoretical analysis indicating that the PVT (pressure–volume-temperature) characteristics in the nanoscale pores are different from those measured in the high-temperature, high-pressure sampler. Only when the pressure is less than a certain value of the bubble point pressure, the dissolved gas will begin to separate and generate resistance. This pressure is lower than the bubble point pressure measured in the high-temperature and pressure sampler. The calculation results show that the heterogeneity of limestone reservoirs and the mismatch of fluid storage and flow space will make the resistance, generated by the separation of dissolved gas, have a greater impact on oil production.

Growth and mineralization of osteoblasts from mesenchymal stem cells on microporous membranes: Epithelial-like growth with transmembrane resistance and pH gradient

Osteoblasts in vivo form an epithelial-like layer with tight junctions between cells. Bone formation involves mineral transport into the matrix and acid transport to balance pH levels. To study the importance of the pH gradient in vitro, we used Transwell inserts composed of polyethylene terephthalate (PET) membranes with 0.4 μm pores at a density of (2 ± 0.4) x 106 pores per cm2. Mesenchymal stem cells (MSCs) prepared from murine bone marrow were used to investigate alternative conditions whereby osteoblast differentiation would better emulate in vivo bone development. MSCs were characterized by flow cytometry with more than 90% CD44 and 75% Sca-1 labeling. Mineralization was validated with paracellular alkaline phosphatase activity, collagen birefringence, and mineral deposition confirming MSCs identity. We demonstrate that MSCs cultured and differentiated on PET inserts form an epithelial-like layer while mineralizing. Measurement of the transepithelial resistance was ∼1400 Ω•cm2 at three weeks of differentiation. The pH value of the media above and under the cells were measured while cells were in proliferation and differentiation. In mineralizing cells, a difference of 0.145 pH unit was observed between the medium above and under the cells indicating a transepithelial gradient. A significant difference in pH units was observed between the medium above and below the cells in proliferation compared to differentiation. Data on pH below membranes were confirmed by pH-dependent SNARF1 fluorescence. Control cells in proliferative medium did not form an epithelial-like layer, displayed low transepithelial resistance, and there was no significant pH gradient. By transmission electron microscopy, membrane attached osteoblasts in vitro had abundant mitochondria consistent with active transport that occurs in vivo by surface osteoblasts. In keeping with osteoblastic differentiation, scanning electron microscopy identified deposition of extracellular collagen surrounded by hydroxyapatite. This in vitro model is a major advancement in modeling bone in vivo for understanding of osteoblast bone matrix production.

Sinuous bar fingers of digitate shallow‐water deltas: Insights into their formative processes and deposits from integrating morphological and sedimentological studies with mathematical modelling

AbstractThis paper helps to address the growing need to resolve the severe loss of deltaic lands by providing a new understanding for shallow‐water digitate delta growth. The integration of satellite image analysis of modern deltas, field studies of the Ganjiang Delta in the Poyang Lake and ‘Delft3D’ simulations further results in improved facies models for shallow‐water digitate deltas. These analyses show that shallow‐water digitate delta bar fingers are sinuous in contrast to the straight deep‐water digitate delta bar fingers. These differences are assigned to the effect of water depth on outflow hydraulics, where friction‐dominated shallow‐water delta effluents promote mouth bar deposition that then divert flow around the mouth bar, resulting in the formation of sinuous bar fingers. These effects are further strengthened by the meandering of the shallow‐water jet that increases lateral sediment transport, and by the higher flow resistance and lower gradient of the shallow‐water outflows. Our data and analyses further show differences in the morphology and deposits of the shallow‐water sinuous bar fingers, where some bar fingers develop sinuous and others meandering (with point bars) distributary channels. Lateral channel migration and point bar formation (meandering) occur as a secondary process that does not change the shape or width of the bar fingers themselves, and is suggested to be a function of slight initial differences in channel sinuosity. These differences in distributary channel morphology have a strong effect on bar finger facies distribution. Sediment cohesion is another important control on bar finger bending processes, because high cohesion promotes formation of enclosed bays, where their bank strength exceeds the centrifugal force of water flow. Lower sediment cohesion results in sinuous bar fingers without formation of enclosed bays. This work provides insights into natural and artificial shallow‐water digitate delta growth and provides new quantitative facies models for shallow‐water digitate deltas.

Clinical significance of pulmonary hypertension in patients with constrictive pericarditis

ObjectivesWe investigated haemodynamics and clinical outcomes according to type of pulmonary hypertension (PH) in patients with constrictive pericarditis (CP).BackgroundAs the prevalence of CP with concomitant myocardial disease (mixed CP) grows,...

Coronary Circulatory Indexes Before and After Percutaneous Coronary Intervention in a Porcine Tandem Stenoses Model.

BackgroundIn tandem stenoses, nonhyperemic pressure ratio pullback is the preferred method to fractional flow reserve (FFR), based on the assumption of stable resting coronary flow. This study aimed to evaluate temporal changes of coronary circulatory indexes in tandem stenoses before and after angioplasty for proximal stenosis.Methods and ResultsCoronary tandem stenoses were created by porcine restenosis model with 2 bare metal stents in the left anterior descending artery. Four weeks later, changes in distal coronary pressure (Pd), averaged peak velocity, microvascular resistance, transstenotic pressure gradient across distal stenosis, resting Pd/aortic pressure, and FFR were measured before and 1, 5, 10, 15, and 20 minutes after balloon angioplasty for proximal stenosis. After angioplasty, there were significant changes in both resting and hyperemic Pd, averaged peak velocity, microvascular resistance, and transstenotic pressure gradient across distal stenosis (all P values <0.01). After initial acute changes, hyperemic averaged peak velocity and microvascular resistance did not show significant difference from the baseline values (P=0.712 and 0.972, respectively). Conversely, resting averaged peak velocity remained increased (10.1±0.7 to 17.8±0.7; P<0.001) and resting microvascular resistance decreased (6.0±0.1 to 2.2±0.7; P<0.001). Transstenotic pressure gradient across distal stenosis was significantly increased in both resting (13.1±7.6 to 25.3±4.2; P=0.040) and hyperemic conditions (11.0±3.0 to 27.4±3.3 mm Hg; P<0.001). Actual post–percutaneous coronary intervention Pd/aortic pressure and FFR were significantly lower than predicted values (Pd/aortic pressure, 0.68±0.22 versus 0.85±0.14; P<0.001; FFR, 0.63±0.08 versus 0.81±0.08; P<0.001).ConclusionsAfter angioplasty for proximal stenosis, transstenotic pressure gradient across distal stenosis showed similar changes between resting and hyperemic conditions. Both actual post–percutaneous coronary intervention resting Pd/aortic pressure and FFR were significantly lower than predicted values.