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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.

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.

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.