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Knowledge of oxygen diffusion in garnet is crucial for a correct interpretation of oxygen isotope signatures in natural samples. A series of experiments was undertaken to determine the diffusivity of oxygen in garnet, which remains poorly constrained. The first suite included high-pressure (HP), nominally dry experiments performed in piston-cylinder apparatus at: (1) T = 1050-1600 degrees C and P = 1.5 GPa and (2) T = 1500 degrees C and P = 2.5 GPa using yttrium aluminum garnet (YAG; Y3Al5O12) cubes. Second, HP H2O-saturated experiments were conducted at T = 900 degrees C and P = 1.0-1.5 GPa, wherein YAG crystals were packed into a YAG + Corundum powder, along with O-18-enriched H2O. Third, 1 atm experiments with YAG cubes were performed in a gas-mixing furnace at T = 1500-1600 degrees C under Ar flux. Finally, an experiment at T = 900 degrees C and P = 1.0 GPa was done using a pyrope cube embedded into pyrope powder and O-18-enriched H2O. Experiments using grossular were not successful., Profiles of O-18/(O-18+O-16) in the experimental charges were analyzed with three different secondary ion mass spectrometers (SIMS): sensitive high-resolution ion microprobe (SHRIMP II and SI), CAMECA IMS-1280, and NanoSIMS. Considering only the measured length of O-18 diffusion profiles, similar results were obtained for YAG and pyrope annealed at 900 degrees C, suggesting limited effects of chemical composition on oxygen diffusivity. However, in both garnet types, several profiles deviate from the error function geometry, suggesting that the behavior of O in garnet cannot be fully described as simple concentration-independent diffusion, certainly in YAG and likely in natural pyrope as well. The experimental results are better described by invoking O diffusion via two distinct pathways with an inter-site reaction allowing O to move between these pathways. Modeling this process yields two diffusion coefficients (D values) for O, one of which is approximately two orders of magnitude higher than the other. Taken together, Arrhenius relationships are, logDm(2)s(-1) = -7.2(+/- 1.3)+(-321(+/- 32)kJ mol(-1))/2.303RT), for the slow pathway, and, logDm(2)s(-1) = -5.4(+/- 0.7)+(-312(+/- 20)kJ mol(-1)/2.303RT), for the fast pathway. We interpret the two pathways as representing diffusion following vacancy and interstitial mechanisms, respectively. Regardless, our new data suggest that the slow mechanism is prevalent in garnet with natural compositions, and thus is likely to control the retentivity of oxygen isotopic signatures in natural samples., The diffusivity of oxygen is similar to Fe-Mn diffusivity in garnet at 1000-1100 degrees C and Ca diffusivity at 850 degrees C. However, the activation energy for 0 diffusion is larger, leading to lower diffusivities at P-T conditions characterizing crustal metamorphism. Therefore, original O isotopic signatures can be retained in garnets showing major element zoning partially re-equilibrated by diffusion, with the uncertainty caveat of extrapolating the experimental data to lower temperature conditions.

Comments to K.M. Pervaiz Fathima, Ren\'e de Borst, Implications of single or multiple pressure degrees of freedom at fracture in fluid saturated porous media, Engineering Fracture Mechanics, 213 (2019), 1-20.

This paper puts forward a perspective or opinion that we can demonstrate Darcy’s law is valid at any scale where fluid can be modelled/analyzed as a continuum. Darcy’s law describes the flow of a fluid through a porous medium by a linear relationship between the flow rate and the pore pressure gradient through the permeability tensor. We show that such a linear relationship can be established at any scale, so long as the permeability tensor is expressed as a function of adequate parameters that describe the pore space geometry, fluid properties and physical phenomena. Analytical models at pore scale provide essential information on the key variables that permeability depends on under different flow regimes. Upscaling techniques based on the Lippman-Schwinger equation, pore network models orEshelby’s homogenization theory make it possible to predict fluid flow beyond the pore scale. One of the key challenges to validate these techniques is to characterize microstructure and measure transport properties at multiple scales. Recent developments in imaging, multi-scale modeling and advanced computing offer new possibilities to address some of these challenges.

Centrifuge experiments on olivine, chromite, and plagioclase aggregates saturated in basaltic liquid show evidence of viscous compaction by grain-boundary diffusion-controlled creep. The experiments confirm that the exponential dependence of shear viscosity on melt fraction, observed at low porosities in earlier shear deformation experiments, extends to sedimentary porosities. The compaction profiles are inconsistent with the porosity-dependence commonly ascribed to viscosity in macroscopic compaction models, which underestimate the effect of matrix disaggregation and consequently overestimate the viscosities of crystal mushes by 1–2 orders of magnitude. The time to halve the porosity of natural olivine igneous sediments by compaction is estimated from the centrifuge experiments to be O(103)y. Half-times for plagioclase and chromite layers are O(104–105)y, suggesting that such layers compact on magmatic time scales only if they are loaded by additional sedimentation. At conditions relevant to melt flow in asthenospheric settings and trans-crustal magmatic systems, the bulk and shear viscosities inferred for olivine and plagioclase are O(1017)Pa s, 4 orders of magnitude less than inferred from earlier experimental studies of the diffusion creep rheology. The reduced viscosities imply time- and length-scales for compaction processes that are substantially shorter than previously anticipated. Our analysis serendipitously reveals that the oft-neglected solidity term of the Carman-Kozeny porosity-permeability relation is essential to prevent non-physical behavior in models of cumulate compaction., Journal of Geophysical Research: Solid Earth, 127 (9), ISSN:2169-9313, ISSN:0148-0227, ISSN:2169-9356

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If we assume the biochemical signals to be one side of the coin, the other side comprises biophysical cues. There is a growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. In this review, we provide an overview of the current state of the art in design and development of such materials and devices, with a focus on their design principles, and highlight challenges and perspectives for future research directions. This article is protected by copyright. All rights reserved.

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If we assume the biochemical signals to be one side of the coin, the other side comprises biophysical cues. There is a growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. In this review, we provide an overview of the current state of the art in design and development of such materials and devices, with a focus on their design principles, and highlight challenges and perspectives for future research directions. This article is protected by copyright. All rights reserved.

Studies on the involvement of intrusive magmatism in hydrocarbon generation within sedimentary basins have gained momentum owing to increasing appraisal of the role that such processes may play in controlling global carbon cycle perturbations, and the exploration potential of the volcanic sedimentary basins. Nevertheless, for many areas the causal link between the intrusions and surrounding hydrocarbon systems remains disputed, encouraging a search for methods that could aid in identifying different hydrocarbon sources. Here, we have performed a multi-proxy geochemical study of the middle Cretaceous methane-seep deposits of the Basque-Cantabrian Basin, an early-stage, peri-cratonic rift marking the Mesozoic opening of the Bay of Biscay. Infilled by a thick sedimentary succession intruded by shallow-level igneous bodies, the basin shares analogies with modern young, sedimented rifts that sustain hydrocarbon seepage. We have applied a novel approach that uses the Nd isotope composition of the seep deposits to constrain the relationship between hydrocarbon seepage and igneous activity, and to explore the general potential of Nd isotopes to trace magmatic-influenced fluids in volcanic sedimentary basins. The Nd isotope data have been combined with rare earth element analyses and carbon and oxygen isotope measurements, providing broad insight into the former composition of the seeping fluids. For three out of four investigated seeps, the Nd isotope ratios observed in authigenic seep carbonates include signatures markedly more radiogenic than that reconstructed for background seawater-derived pore waters. The level of this Nd-143-enrichment varies both between and within individual deposits, reflecting spatial and temporal differences in fluid composition typical of seep-related environments. The radiogenic Nd isotope signals provide evidence of subseafloor interactions between the seeping fluids and mafic igneous materials, supporting the model of an igneous control on the mid-Cretaceous methane expulsion in the Basque-Cantabrian Basin. The thermogenic origin of the methane is in accord with the moderately negative delta C-13 values and paragenetic successions observed in the studied seep carbonates. For a single deposit, its relatively unradiogenic Nd isotope composition can be attributed to the smallest size and shallowest emplacement depth of the underlying intrusion, likely resulting in a short-lived character and limited hydrocarbon-generation potential of the associated contact metamorphism. The study demonstrates that Nd isotope analyses of seep carbonates offer a tool in disentangling methane fluxes from different organic matter alteration pathways for the numerous, both fossil and modern sedimented rifts for which the involvement of various methane sources remains insufficiently understood. This work was supported by the National Science Centre, Poland (grant No. 2016/23/D/ST10/00444; to MJ) , and the Eusko Jaurlaritza (Ikerketa Taldeak IT930-16) and the Spanish State Research Agency (project PID2019-105670GB-I00/AEI/10.13039/501100011033; both to LMA)

An overview of previous researches related to the problem of flow around a bluff-body, using experimental and numerical methods, is presented in the paper. Experimental investigation was performed by a laser doppler anemometer, measuring velocity components of the water flow around a smooth sphere, and a sphere with dimples in square channels. Measurement results in subcritical velocity flow field, velocity fluctuation components, lift, drag and pressure coefficients, and 2-D Reynolds stress at quasi-stationary flow are conducted using 1-D laser doppler anemometer probe. The obtained experimental results are compared with numerical simulations, which are performed using the ANSYS-CFX software. For the numerical simulations of quasi-steady-state flow, k-? turbulent model was used, while for numerical simulation of unsteady fluid-flow and for the comparison of results related to the eddy structures, vortex shedding and Reynolds stresses, detached eddy simulation were used. Since the obtained results of experimental and numerical investigation of flow around smooth sphere and sphere with dimples showed good agreement, the considered flow problem was expanded by introducing the influence of a transverse magnetic field with a slight modification of the electrical conductivity of the working fluid. The other physical properties of the fluid remained the same, which also corresponds to realistically possible physical conditions. Numerical simulations were performed for three different values of Hartmann number and very small values of Reynolds magnetic number (inductionless approximation). Comparisons and analyzes of the results were made for the cases containing a magnetic field and those with an absence of a magnetic field.

Mixing is a basic but challenging step to achieve in high throughput microfluidic applications such as organic synthesis or production of particles. A common approach to improve micromixer performance is to devise a single component that enhances mixing through optimal convection, and then sequence multiple such units back-to-back to enhance overall mixing at the end of the sequence. However, the mixing units are often optimized only for the initial non-mixed fluid composition, which is no longer the input condition for each subsequent unit. Thus, there is no guarantee that simply repeating a single mixing unit will achieve optimally mixed fluid flow at the end of the sequence. In this work, we analyzed sequences of 20 cylindrical obstacles, or pillars, to optimize the mixing in the inertial regime (where mixing is more difficult due to higher Peclet number) by managing their interdependent convection operations on the composition of the fluid. Exploiting a software for microfluidic design optimization called FlowSculpt, we predicted and optimized the interfacial stretching of two co-flowing fluids, neglecting diffusive effects. We were able to quickly design three different optimal pillar sequences through a space of 3220 possible combinations of pillars. As proof of concept, we tested the new passive mixer designs using confocal microscopy and full 3D CFD simulations for high Peclet numbers (Pe ≈ O(105–6)), observing fluid flow shape and mixing index at several cross-sections, reaching mixing efficiencies around 80%. Furthermore, we investigated the effect of the inter-pillar spacing on the most optimal design, quantifying the tradeoff between mixing performance and hydraulic resistance. These micromixer designs and the framework for the design in inertial regimes can be used for various applications, such as lipid nanoparticle fabrication which has been of great importance in vaccine scale up during the pandemic.

International audience; Osteocytes are the most frequent bone cells connected with each other through cell processes within tiny tubular-shaped canaliculi. The so-called osteocyte lacunar-canalicular network (LCN) plays a crucial role in bone remodeling and mineral homeostasis. Given the critical nature of these functions, it is herein hypothesized that the LCN must be structurally “overengineered” to provide network resilience. This hypothesis is tested by characterizing canalicular networks in human bone at the fundamental “building-block” level of LCN formed by two adjacent osteocytes. As the hierarchical micro- and macroscale structure of bone is influenced by anatomical location, subjected loads, and growth rate, three distinct tissue types are studied. These include femur, jaw, and heterotopic ossification (HO), a rapidly forming mineralized tissue found in soft tissue compartments following severe trauma. It is found that the LCNs at the fundamental level are composed of hundreds of canalicular segments but of only few separated groups of linked canaliculi (canalicular clusters), resulting in a strongly pronounced interconnectivity. Fluid permeability simulations on intact and artificially altered LCN suggest that the function of the LCN is not only to optimize rapid and efficient access to bone mineral, but also to maintain high permeability when inevitable local interruption of canaliculi occurs.

Numerical solutions of acoustic wave scattering are often used to describe sound propagation through complex geometries. For cases with flow, various forms of the convected equation have been used. A better alternative that includes vortex-sound interaction is instead to use the linearized and harmonic forms of the unsteady fluid flow governing equations. In this paper, a formulation of the linearized equations that include rotational effects, in an acoustic computation using a rotating frame of reference in a stationary geometry, is presented. We demonstrate that rotational effects can be important, e.g., when computing the transmission loss through high-speed compressors. The implementation of the proposed addition to the existing schemes is both simple and numerically inexpensive. The results are expected to have an impact on the research and development related to noise control of high-performance turbo-machinery, e.g., used in automotive or aviation applications at operating conditions that can be represented by steady background flows.

One of the widely used type of biosensors are paper-based lateral flow systems. They are used to detect a wide variety of biomolecules like microorganisms, proteins, chemicals, oligonucleotides among many others. In this research, a setup was created using dual magnet sets in which the flow of cell sample on two kinds of different sample paper was explored. There were two factors which affected the movement of the sample the most, the magnetic field and the wetting. Images were obtained using a cell phone along and/or a bright field optical microscope and then analyzed using image processing. Images were also taken using scanning electron microscope. The effects of the wetting and the magnetic field were tested and studied. It was found that at least 90% of the cells were able to reach the edge of the paper. Although the cells were not able to maintain their shape on the paper due to the unideal conditions of the paper for cells but still this kind of paper-based lateral flow assay setup can be used for cells to see their behavior when they were labelled and exposed to a magnetic field. This research shows support that this technique can be used for separating cells as well as detecting different cells. Yaygın olarak kullanılan biyosensör tiplerinden biri kağıt tabanlı yanal akış sistemleridir. Bu sistemler mikroorganizmalar, proteinler, kimyasallar, oligonükleotitler ve diğerleri gibi çok çeşitli biyomolekülleri tespit etmek için kullanılırlar. Bu araştırmada, hücre numunesinin akışının iki çeşit farklı numune kağıdı üzerinde araştırıldığı ikili mıknatıs setleri kullanılarak bir düzenek oluşturulmuştur. Numunenin hareketini en çok etkileyen iki faktör manyetik alan ve ıslanmadır. Bu çalışmada ki görüntüler bir cep telefonu ve/veya parlak alan optik mikroskobu kullanılarak elde edilmiş ve ardından görüntü işleme kullanılarak analiz edilmiştir. Ayrıca bazı örnekler taramalı elektron mikroskobu kullanılarak görüntülenmiştir. Bu çalışmada ıslanmanın ve manyetik alanın etkileri test edilmiş ve incelenmiştir. Hücrelerin en az %90'ının kağıdın kenarına ulaşabildiği gözlenmiştir. Kağıdın hücreler için ideal olmayan koşulları nedeniyle hücreler kağıt üzerinde şekillerini uzun süre koruyamasa da, bu tür kağıt tabanlı yanal akış sistemleri önemli avantajları nedeniyle, hücresel uyuglamlar için potansiyel barındırmaktadır ve hücreleri algılamak için kullanılabilir. Bu çalışma, manyetik alanın ve kağıt temelli platformların hücreleri ayırmak ve farklı hücreleri tespit etmek için kullanılabileceğini göstermektedir. 1. INTRODUCTION .................................................................................................... 1 1.1 BIOSENSORS ............................................................................................................. 1 1.2 MAGNETOPHORESIS ................................................................................................. 2 1.3 LATERAL FLOW BIOSENSORS ................................................................................... 3 1.4 MICRO/NANO MAGNETIC PARTICLES ...................................................................... 4 1.5 ANTIBODIES ............................................................................................................. 6 1.5 FORCES .................................................................................................................... 7 1.6 FLUID FLOW ON PAPER ............................................................................................ 8 2. MATERIALS AND METHODS ........................................................................... 10 2.1 MAGNETIC PLATFORM ........................................................................................... 10 2.2 MAGNETIC FORCE .................................................................................................. 11 2.3 WETTING ............................................................................................................... 12 2.4 PAPER-BASED MAGNETOPHORESIS ........................................................................ 12 2.4.1 Cell Preparation ............................................................................................ 12 2.4.2 Paper Preparation ......................................................................................... 14 2.4.3 Paper-Based Experiment ............................................................................... 15 2.4.5 BSA Wetting ................................................................................................... 16 2.4.7 Imaging .......................................................................................................... 17 2.4.8 Magnetic Field Cell Experiments .................................................................. 17 2.5 IMAGE PROCESSING ............................................................................................... 17 2.6 COMSOL SIMULATION ......................................................................................... 19 3. RESULTS ................................................................................................................ 24 3.1 MAGNETIC FORCE AND WETTING .......................................................................... 24 3.2 PAPER-BASED MAGNETOPHORESIS ........................................................................ 31 4. DISCUSSION AND CONCLUSION .................................................................... 38 4.1 DISCUSSION ........................................................................................................... 38 4.2 SOCIETAL IMPACT AND CONTRIBUTION TO GLOBAL SUSTAINABILITY .................. 40 4.3 CONCLUSION AND FUTURE PROSPECTS .................................................................. 40

Solid particulate additives are sometimes used to promote the uniform growth of multiple hydraulic fractures in horizontal oil and gas wells. The principle is that solid particulates block, accumulate, and form larger porous plugging zones preferentially at entrances of fracture taking in the most fluid volume. These porous zones create fluid flow resistance or additional pressure loss; thereby, inhibiting the growth of these dominant fractures and diverting fluid to suppressed fractures. While this technology is promising, governing design parameters and ramifications of placing solids diverters inside the fracture remain unclear. This paper models the propagation of multi-fractures with diverter pressure losses induced by the porous plugging zones. The resulting non-linear hydraulic fracturing problem is solved numerically with an Implicit Level Set Algorithm (ILSA) for each time step and the mechanisms of diversion are illustrated by comparing and contrasting cases with and without particle diverter. In both cases, during the fluid ramp-up period (pumping rate gradually increases from 0 to fracturing rate (QT)), the injection can be equally distributed among fractures before the stress interference affects the fluid allocation (Phase I). Then, stress interference starts to partition more fluid into outer fractures and suppress the growth of the middle fracture (Phase II). Once the perforation friction loss is sufficient to counteract the stress interaction, injection begins to shift to the middle fracture, but still gives a significantly nonuniform fracture growth (Phase III). At this point, solid diverter particles are introduced, leading to three additional phases of growth. Phase IV introduces solid diverters to the treatment at a reduced pumping rate. Particles bridge, accumulate and create porous plugging zones at the flow entrance. A higher pressure drop in outer fractures diverts injection fluids to the middle fracture. Phase V resumes the treatment rate to QT without diverter. The increased pump rate in turn increases the pressure drop in outer fractures and diverts more fluids to the middle fracture. This results in a rapid extension velocity for the middle fracture, enabling it to have the chance to catch up with the longer outer fractures (in Phase VI). This process is controlled by the interplay among stress interference, perforation friction loss, and diverting pressure drop. These simulations demonstrate that a model-based optimization could improve the effectiveness of the diverter technology and promote a uniform multi-fracture growth.

Dating of fracture-filling calcite with U-Pb geochronology is becoming a rapidly adopted technique for determining the absolute timing of brittle deformation in the upper crust. Slickenfibre calcite is a desirable target, as it precipitates between individual fault slip displacement events, and provides additional kinematic information. Here we present a case study of slickenfibres formed on the Ockov thrust in the Lower Palaezoic Prague Basin, Bohemian Massif, utilising a combination of petrographic and in situ methods. We demonstrate that slickenfibre external textures can be preserved, whilst internally primary textures are removed by fluid infiltration and recrystallization, leading to variable U and Pb mobilisation. One slickenfibre yielded a date of ca. 250 Ma, which we interpret as recording fault slip along the Ockov thrust. Another cross-cutting slickenfibre yielded more scattered U-Pb data, with an imprecise apparent age around ca. 95 Ma. This slickenfibre is recrystallised, destroying the primary textures, and exhibits element mobility. The meaning of this younger apparent age is therefore questionable; whereas it likely reflects Cretaceous U and Pb mobility assisted by fluid-flow along the fault plane, it may not reflect a period of fault slip. Our results demonstrate that slickenfibre-based U-Pb dates do not unequivocally relate to fault motion, and that petrographic and elemental analyses are important requirements for interpreting calcite U-Pb data.

WOS: 000509489100003, The present paper deals with the introduction of Backlund transformations by extended Harry-Dym flow and with the aid of the extended version of the Riccati mapping method is obtained new solutions. Then, we give the Backlund transformation of the Schrodinger flow and obtain its the Bonnet surface. In finally, results obtained with the mathematical model are evaluated by applying to mathematica.

Heterogeneous fracture aperture distribution, dictated by surface roughness, mechanical rock and fracture properties, and effective stress, limits the predictive capabilities of many reservoir‐scale models that commonly assume smooth fracture walls. Numerous experimental studies have probed key hydromechanical responses in single fractures; however, many are constrained by difficulties associated with sample preparation and quantitative roughness characterisation. Here, we systematically examine the effect of roughness on fluid flow properties by 3D printing seven self‐affine fractures, each with controlled roughness distributions akin to those observed in nature. Photogrammetric microscopy was employed to validate the 3D topology of each printed fracture surface, enabling quantification using traditional roughness metrics, namely the Joint Roughness Coefficient (JRC). Core‐flooding experiments performed on each fracture across eight incremental confining pressure increases (11 to 25 bar), shows smoother fractures (JRC < 5.5) exhibit minor permeability variation, whilst rougher fractures (JRC > 7) show as much as a 219% permeability increase. Micro‐computed tomography imaging of the roughest fracture under varying effective stresses (5 to 13.8 bar), coupled with inspection into the degree of similarity between fracture closure behaviour in 3D‐printed and natural rock fractures, highlight the capabilities of 3D‐printed materials to act as useful analogues to natural rocks. Comparison of experimental data to existing empirical aperture‐permeability models demonstrates that fracture contact area is a better permeability predictor than roughness when the mechanical aperture is below ∼20 μm. Such findings are relevant for models incorporating the effects of heterogeneous aperture structures and applied stress to predict fracture flow in the deep subsurface.

Geological modelling is widely used to predict resource potential in subsurface reservoirs. However, modelling is often slow, requires use of mathematical methods that are unfamiliar to many geoscientists, and is implemented in expert software. We demonstrate here an alternative approach using sketch-based interface and modelling, which allows rapid creation of complex three-dimensional (3D) models from 2D sketches. Sketches, either on vertical cross-sections or in map-view, are converted to 3D surfaces that outline geological interpretations. We propose a suite of geological operators that handle interactions between the surfaces to form a geologically realistic 3D model. These operators deliver the flexibility to sketch a geological model in any order and provide an intuitive framework for geoscientists to rapidly create 3D models. Two case studies are presented, demonstrating scenarios in which different approaches to model sketching are used depending on the geological setting and available data. These case studies show the strengths of sketching with geological operators. Sketched 3D models can be queried visually or quantitatively to provide insights into heterogeneity distribution, facies connectivity or dynamic model behaviour; this information cannot be obtained by sketching in 2D or on paper. Supplementary material: Rapid Reservoir Modelling prototype (executable and source code) is available at: https://bitbucket.org/rapidreservoirmodelling/rrm. Supplementary screen recordings for the different case studies showing sketch-based modelling in action are available at https://doi.org/10.6084/m9.figshare.c.5084141 and supplementary figure S1-S4 are available at https://doi.org/10.6084/m9.figshare.c.5303043

Alignment of arterial endothelial cells with the mean wall shear stress (WSS) vector is the prototypical example of their responsiveness to flow. However, evidence for this behaviour rests on experiments where many WSS metrics had the same orientation or where they were incompletely characterised. In the present study, we tested the phenomenon more rigorously. Aortic endothelial cells were cultured in cylindrical wells on the platform of an orbital shaker. In this system, orientation would differ depending on the WSS metric to which the cells aligned. Variation in flow features and hence in possible orientations was further enhanced by altering the viscosity of the medium. Orientation of endothelial nuclei was compared to WSS characteristics obtained by computational fluid dynamics. At low mean WSS magnitudes, endothelial cells aligned with the modal WSS vector whilst at high mean WSS magnitudes they aligned so as to minimise the shear acting across their long axis (“transverse WSS”). Their failure to align with the mean WSS vector implies that other aspects of endothelial behaviour attributed to this metric require re-examination. The evolution of a mechanism for minimising transverse WSS is consistent with it having detrimental effects on the cells and with its putative role in atherogenesis.

Tectonic faults typically break in a single rupture mode within the range of styles from slow slip to dynamic earthquake failure. However, in increasingly well‐documented instances, the same fault segment fails in both slow and fast modes within a short period, as in the sequences that culminated in the 2011 Mw = 9.0 Tohoku‐Oki, Japan, and 2014 Mw = 8.2 Iquique, Chile, earthquakes. Why slow slip alternates with dynamic rupture in certain regions but not in others is not well understood. Here, we integrate laboratory experiments and numerical simulations to investigate the physical conditions leading to cycles where the two rupture styles alternate. We show that a bifurcation takes place near the stability transition with sequences encompassing various rupture modes under constant loading rate. The range of frictional instabilities and slip cycles identified in this study represents important end‐members to understand the interaction of slow and fast slip on the same fault segment. Ministry of Education (MOE) Published version This work is funded by the Earth Observatory of Singapore and by the Singapore Ministry of Education and also the 2017 Stephen Riady Funding from the Earth Observatory of Singapore (M4430260.B50.500000).

This paper provides an overview of the Curiosity rover's exploration at Vera Rubin ridge and summarizes the science results. Vera Rubin ridge (VRR) is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mt. Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray‐colored patches concentrated towards the upper elevations of VRR, and these gray patches also contain small, dark Fe‐rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric‐related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars’ rock record.

This paper presents image velocimetry measurements on turbulent flows adjacent to a permeable bed made of randomly packed glass particles. For measuring flow velocities inside the bed, the refractive index of the glass particles was matched with that of the fluid. By continuously scanning in the transverse direction, we measured the streamwise and vertical velocity components within a three-dimensional domain (3D2C-PIV), including first- and second-order turbulent statistics. We established how the scanning travel speed is associated with the laser sheet thickness and the space-time velocity fluctuations for collecting reliable measurements. The methodology was applied to free-surface flows over a sloping bed under low relative submergence and supercritical conditions. Space- and time-averaged profiles were obtained in a representative elementary volume as defined by thedouble-averagingprocedure (Nikora et al. in J Hydraulic Eng.127(2):123–133, 2001). A turbulent boundary layer over the rough bed was observed when experiments were run at intermediate Reynolds numbers Re =$$O(1000)$$O(1000). Apart from measuring subsurface velocities, this method shed light on the part played by the rough bed in the overall flow dynamics: the roughness layer was a buffer region within which porosity varied sharply and turbulent stress was rapidly dampened.Graphic abstract

Reservoir models typically contain hundreds-of-thousands to millions of grid cells in which petrophysical properties such as porosity and permeability vary on a cell-to-cell basis. However, although the petrophysical properties of rocks do vary on a point-to-point basis, this variability is not equivalent to the cell-to-cell variations in models. We investigate the impact of removing cell-to-cell variability on predictions of fluid flow in reservoir models. We remove cell-to-cell variability from models containing hundreds of thousands of unique porosity and permeability values to yield models containing just a few tens of unique porosity and permeability values grouped into a few internally homogeneous domains. The flow behavior of the original model is used as a reference. We find that the impact of cell-to-cell variability on predicted flow is small. Cell-to-cell variability is not necessary to capture flow in reservoir models; rather, it is the spatially correlated variability in petrophysical properties that is important. Reservoir modelling effort should focus on capturing correlated geologic domains in the most realistic and computationally efficient manner.

Large volumes of hydrocarbons reside in volcanically influenced sedimentary basins. Despite having a good conceptual understanding of how magmatism impacts the petroleum systems of such basins, we still lack detailed case studies documenting precisely how intrusive magmatism influences, for example, trap development and reservoir quality. Here we combine 3D seismic reflection, borehole, petrographical and palaeothermometric data to document the geology of borehole 5/22-1, NE Irish Rockall Basin, offshore western Ireland. This borehole (Errigal) tested a four-way dip closure that formed to accommodate emplacement of a Paleocene–Eocene igneous sill-complex during continental break-up in the North Atlantic. Two water-bearing turbidite-sandstone-bearing intervals occur in the Upper Paleocene; the lowermost contains thin (c. 5 m), quartzose-feldspathic sandstones of good reservoir quality, whereas the upper is dominated by poor-quality volcaniclastic sandstones. Palaeothermometric data provide evidence of anomalously high temperatures in the Paleocene–Eocene succession, suggesting the poor reservoir quality within the target interval is likely to reflect sill-induced heating, fluid flow, and related diagenesis. The poor reservoir quality is also probably the result of the primary composition of the reservoir, which is dominated by volcanic grains and related clays derived from an igneous-rock-dominated, sediment source area. Errigal appeared to fail due to a lack of hydrocarbon charge: that is, the low bulk permeability of the heavily intruded Cretaceous mudstone succession may have impeded the vertical migration of sub-Cretaceous-sourced hydrocarbons into supra-Cretaceous reservoirs. Break-up-related magmatism did, however, drive the formation of a large structural closure, with data from Errigal at least proving high-quality, Upper Paleocene deep-water reservoirs. Future exploration targets in the NE Irish Rockall Basin include: (i) stratigraphically trapped Paleocene–Eocene deep-water sandstones that onlap the flanks of intrusion-induced forced folds; (ii) structurally trapped, intra-Cretaceous, deep-water sandstones incorporated within intrusion-induced forced folds; and (iii) more conventional, Mesozoic fault-block traps underlying the heavily intruded Cretaceous succession (e.g. Dooish). Similar plays may exist on other continental margins influenced by break-up magmatism. Supplementary material: Borehole-related reports, and litho- and composite logs are available at https://doi.org/10.6084/m9.figshare.c.4803267

This thesis describes a computational model for an initial/pre-collecting lymphatic network and a study on valvogenesis (formation of valves in the lymphatics during embryonic development). The computational model was applied to rat mesenteric lymphatic networks (19- and 163-segment) with sparse secondary valves. The network was simulated with these secondary valves being operational and non-operational. Sensitivity of parameters like the vessel stiffness, interstitial resistance, and the availability of primary valves, on the cycle-mean outflow-rate from the 19-segment network was considered. Results for the study on valvogenesis, simulations done on the 2D images of embryonic skin lymphatic network suggest that fluid shear stress does not localize the expression of Prox1 (a transcription factor responsible for valve formation).

International audience; Because cracks control the global mechanical and transport properties of crystalline rocks, it is of a crucial importance to suitably determine their aperture distribution, which evolves through alteration processes and rock weathering. Due to the high variability of crack networks in rocks, a multiscale approach is needed. The 14C‐PMMA (polymethylmethacrylate) method was developed to determine crack apertures using a set of artificial crack samples with different controlled apertures and tilt angles and also using Monte Carlo simulations. The experiments and simulations show the same result: the estimation of apparent aperture wA was successful regardless of tilt angle, even if the estimates are less accurate for low tilt angles (

In this study, delta winglet-type vortex generators, widely used in conventional macro channels and proven to be effective, are used in microchannels to increase their heat transfer capacities. The effects of vortex generators on heat transfer and pressure loss characteristics are studied numerically for different angles of attack, vortex generator arrangement type, the transverse and longitudinal distance between vortex generators, vortex generator length and height, and different Reynolds numbers. The thermal and hydraulic characteristics are presented as the Nusselt number, the friction factor, and the performance evaluation criteria number (PEC) that takes into account the heat transfer enhancement and the corresponding increase in pressure loss. The variation of Nu/Nu0, f/f0, and PEC are found to be in the range of 1.03–1.87, 1.04–1.8, and 0.92–1.62, respectively. A multi-objective optimization study are performed with the response surface methodology analysis to see how different parameters affect heat transfer and pressure loss and to determine the most optimum design. Besides, local sensitivity analysis study is carried out through the RSM, and water inlet velocity for heat transfer enhancement is found to be the most effective parameter. Among the geometric parameters, vortex generator height is determined as the most effective factor. Finally, practical Nusselt number and friction factor correlations taking many parameters into account are proposed to be able to compare the results of other researchers, and for engineers designing microchannel cooling systems.

Summary: Chirality is a property of asymmetry between an object and its mirror image. Most biomolecules and many cell types are chiral. In the left-right organizer (LRO), cilia-driven flows transfer such chirality to the body scale. However, the existence of cellular chirality within tissues remains unknown. Here, we investigate this question in Kupffer’s vesicle (KV), the zebrafish LRO. Quantitative live imaging reveals that cilia populating the KV display asymmetric orientation between the right and left sides, resulting in a chiral structure, which is different from the chiral cilia rotation. This KV chirality establishment is dynamic and depends on planar cell polarity. While its impact on left-right (LR) symmetry breaking remains unclear, we show that this asymmetry does not depend on the LR signaling pathway or flow. This work identifies a different type of tissue asymmetry and sheds light on chirality genesis in developing tissues. : During left-right axis specification, motile cilia are required for breaking the axis of symmetry. In this context, Ferreira et al. show that cilia orientation is chiral, defining an alternative type of asymmetry in the embryo. Keywords: Danio rerio, trilobite/Vangl2, lrdr1, Dnaaf1/Lrrc50, spaw, nodal, tissue asymmetry, PKD2/PC2/TRPP2/polycistin-2, blebbistatin, Rock2B