scholarly journals Characterization of Mixing Performance Induced by Double Curved Passive Mixing Structures in Microfluidic Channels

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 556
Author(s):  
Ingrid. H. Oevreeide ◽  
Andreas Zoellner ◽  
Bjørn. T. Stokke
Keyword(s):  
Flow Direction ◽  
Stationary Flow ◽  
Channel Length ◽  
Small Sample ◽  
Confocal Imaging ◽  
Microfluidic Channels ◽  
High Performing ◽  
Passive Micromixer ◽  
Passive Mixing ◽  
Parameter Values

Functionalized sensor surfaces combined with microfluidic channels are becoming increasingly important in realizing efficient biosensing devices applicable to small sample volumes. Relaxing the limitations imposed by laminar flow of the microfluidic channels by passive mixing structures to enhance analyte mass transfer to the sensing area will further improve the performance of these devices. In this paper, we characterize the flow performance in a group of microfluidic flow channels with novel double curved passive mixing structures (DCMS) fabricated in the ceiling. The experimental strategy includes confocal imaging to monitor the stationary flow patterns downstream from the inlet where a fluorophore is included in one of the inlets in a Y-channel microfluidic device. Analyses of the fluorescence pattern projected both along the channel and transverse to the flow direction monitored details in the developing homogenization. The mixing index (MI) as a function of the channel length was found to be well accounted for by a double-exponential equilibration process, where the different parameters of the DCMS were found to affect the extent and length of the initial mixing component. The range of MI for a 1 cm channel length for the DCMS was 0.75–0.98, which is a range of MI comparable to micromixers with herringbone structures. Overall, this indicates that the DCMS is a high performing passive micromixer, but the sensitivity to geometric parameter values calls for the selection of certain values for the most efficient mixing.

scholarly journals Theory and computational study of electrophoretic ion separation and focusing in microfluidic channels

2012 ◽  
Vol 17 (4) ◽  
pp. 431-447 ◽  
Author(s):  
Oleksiy V. Klymenko ◽  
Christian Amatore ◽  
Wen Sun ◽  
Yong-Liang Zhou ◽  
Zhao-Wu Tian ◽  
...  
Keyword(s):  
Computational Study ◽  
Electrical Contact ◽  
Channel Length ◽  
Microfluidic Channels ◽  
Solution Flow ◽  
Ion Separation ◽  
Microfluidic Separation ◽  
2D Simulation ◽  
Ion Focusing ◽  
Ion Conducting

In this work we describe the theory and 2D simulation of ion separation and focusing in a new concept of microfluidic separation device. The principle of the method of ion focusing is classical in the sense that it consists in opposing a hydrodynamic transport ensured by the solution flow to an electrophoretic driving force so that any ionic sample results poised within the microchannel at the point where the two forces equilibrate. The originality of the concept investigated here relies on the fact that thanks to the use of an ion-conducting membrane of variable thickness in electrical contact with the channel the electrophoretic force is varied continuously all along the channel length. Similarly, changing the geometric shape of the membrane allows a facile optimization of the device separation and focusing properties.

O-205 Aneuploidy induces proteotoxic stress and autophagy-mediated apoptosis in human preimplantation embryos

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
M Regin ◽  
E. Couvreu De Deckersberg ◽  
Y Guns ◽  
P Verdyck ◽  
G Verheyen ◽  
...  
Keyword(s):  
Rna Sequencing ◽  
Caspase 3 ◽  
Small Sample ◽  
Confocal Imaging ◽  
Preimplantation Embryos ◽  
Human Embryos ◽  
Dependent Manner ◽  
Sequencing Data ◽  
Proteotoxic Stress ◽  
Human Preimplantation Embryos

Abstract Study question Are aneuploid cells in human preimplantation embryos eliminated by apoptosis due to proteotoxic stress and autophagy-mediated apoptosis? Summary answer Proteotoxic stress, autophagy and apoptosis are differentially activated in aneuploid embryos, showing that aneuploid cells are eliminated by these mechanisms during early human embryogenesis. What is known already Aneuploidies are a common feature of human preimplantation embryos which could explain low success rates after in vitro fertilization (IVF). While most aneuploidies of meiotic origin are detrimental, transfer of euploid-aneuploid mosaic embryos can lead to healthy live-births. Moreover, the proportion of aneuploid cells are lower in blastocysts when compared to cleavage stage embryos. In the mouse, aneuploid cells are eliminated from the epiblast by autophagy-mediated apoptosis in a p53-dependent manner. We propose that in human embryos, aneuploidy causes chronic protein misfolding which leads to autophagy-induced apoptosis. Study design, size, duration Eighty-one blastocysts that were diagnosed by PGT as euploid (n = 49) or uniformly combined abnormal (CA, n = 32), i.e. 2 or more chromosomes were abnormal in every cell, were warmed. Sixty-seven were suitable for trophectoderm (TE) biopsy, 54 biopsies were successfully tubed and sent for RNA-sequencing while the remainder of the embryos was fixed for immunostaining. Thirty-three day-3 embryos were overnight incubated in 0.5µM reversine allowed to develop into blastocysts and treated as the PGT embryos. Participants/materials, setting, methods After TE biopsy, we live-stained the embryos with either Caspase-3/7 or 8 and subsequently fixed them. The biopsies underwent RNA-sequencing using the SMART-seqv4 and the fixed embryos were immunostained for LC3B, p62 (autophagy) and HSP70 (proteotoxic stress). Confocal imaging was performed using a Zeiss LSM800 confocal microscope and the presence of signal was quantified using the Zen Blue 2.0 and Arivis software. Main results and the role of chance Forty-two percent of the embryos in which we induced aneuploidies using reversine developed into blastocysts, which is comparable to untreated embryos. After immunostaining, we observed that CA and reversine-treated (RT) embryos contained less cells than euploid embryos (median number of nuclei: 43.5, 47, 90, respectively). This correlates with a higher expression of apoptotic markers Caspase-3/7 in CA embryos (p = 0.0199) and Caspase-8 in both aneuploid groups (CA: p = 0.0085 and RT: p = 0.0394). Aneuploid embryos showed significantly increased HSP70 levels (median intensity per cell: euploid=165, CA = 313, RT = 400), LC3B (median puncta per cell: euploid=3.07, CA = 10.10, RT = 19.62) and p62 (median puncta per cell: euploid=17.60, CA = 30.53), suggesting increased proteotoxic stress and autophagy. Preliminary analysis of the RNA-sequencing data reveals enrichment for pathways such as the p53-pathway, protein secretion, TNFA signaling via NFkB and apoptosis, supporting the hypothesis of a link between aneuploidy and apoptosis. Limitations, reasons for caution No functional tests e.g. with inhibitors of autophagy were carried out. RNA-sequencing was carried out on a small sample; we will expand this sample in the near future. Wider implications of the findings This study shows for the first time the mechanism by which aneuploid cells are eliminated from the human preimplantation embryo, explaining how mosaic embryos can still lead to a healthy and genetically normal live birth. Trial registration number not applicable

scholarly journals The Numerical Diffusion Effect on the CFD Simulation Accuracy of Velocity and Temperature Field for the Application of Sustainable Architecture Methodology

2020 ◽  
Vol 12 (23) ◽  
pp. 10173
Author(s):  
Vladimíra Michalcová ◽  
Kamila Kotrasová
Keyword(s):  
Temperature Field ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Flow ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Simulation Accuracy ◽  
Numerical Diffusion ◽  
Diffusion Temperature

Numerical simulation of fluid flow and heat or mass transfer phenomenon requires numerical solution of Navier–Stokes and energy-conservation equations, together with the continuity equation. The basic problem of solving general transport equations by the Finite Volume Method (FVM) is the exact calculation of the transport quantity. Numerical or false diffusion is a phenomenon of inserting errors in calculations that threaten the accuracy of the computational solution. The paper compares the physical accuracy of the calculation in the Computational Fluid Dynamics (CFD) code in Ansys Fluent using the offered discretization calculation schemes, methods of solving the gradients of the transport quantity on the cell walls, and the influence of the mesh type. The paper offers possibilities on how to reduce numerical errors. In the calculation area, the sharp boundary of two areas with different temperatures is created in the flow direction. The three-dimensional (3D) stationary flow of the fictitious gas is simulated using FVM so that only advective transfer, in terms of momentum and heat, arises. The subject of the study is to determine the level of numerical diffusion (temperature field scattering) and to evaluate the values of the transport quantity (temperature), which are outside the range of specified boundary conditions at variously set calculation parameters.

scholarly journals A Biocontrol Option to Control a Foodborne Pathogen; Using Campylobacter Bacteriophages to Control Campylobacter in Poultry

Proceedings ◽  
2020 ◽  
Vol 36 (1) ◽  
pp. 162
Author(s):  
Nalini Chinivasagam ◽  
Wiyada Estella ◽  
Samuel Cockerill ◽  
Lance Maddock ◽  
David Mayer ◽  
...  
Keyword(s):  
Broiler Chickens ◽  
Environmental Science ◽  
Management Strategies ◽  
Collaborative Study ◽  
Scale Up ◽  
Foodborne Pathogen ◽  
Small Sample ◽  
High Performing ◽  
The Uk ◽  
On Farm

Campylobacter is a leading cause of foodborne illnesses both in Australia and internationally, and is frequently found in poultry. There is a need for sustainable options to support current farm management strategies that address food-safety. The use of bacteriophages provides a safe biocontrol option. A collaborative study by the Department of Agriculture and Fisheries (QLD), the University of Nottingham (UK) and the Institute of Environmental Science and Research (NZ) is focused on the control of Campylobacter in broiler chickens. Campylobacter bacteriophages were sourced from Queensland poultry farms and following extensive screening, suitable candidates to be used in cocktails were identified. This followed an on-farm proof of concept study on a small sample of chickens, using selected cocktail candidates, to provide an understanding of the hurdles for practical application. The trial demonstrated a 2-log CFU/g reduction of Campylobacter in the caeca of treated birds compared to non-treated (p < 0.05). Another important finding of this study was the absence of bacteriophage resistance, a concern with phage therapy. Work at ESR has addressed approaches to select and adapt bacteriophage cocktails to particular hosts, which included screening against NZ and Australian hosts. This approach enabled the formulation of high performing bacteriophage cocktails for Australian and international markets. Work in the UK is exploring the understanding of the host-bacteriophage relationships to ensure safety to meet regulatory requirements and support potential scale-up options. In summary, the work in progress via international collaborations is aimed at delivering a safe biocontrol option that can meet both commercial and regulatory needs aiming at controlling on-farm Campylobacter.

scholarly journals Mathematical Model for Small Size Time Series Data of Bacterial Secondary Metabolic Pathways

2018 ◽  
Vol 12 ◽  
pp. 117793221877507 ◽  
Author(s):  
Daisuke Tominaga ◽  
Hideo Kawaguchi ◽  
Yoshimi Hori ◽  
Tomohisa Hasunuma ◽  
Chiaki Ogino ◽  
...  
Keyword(s):  
Metabolic Pathways ◽  
Time Series Data ◽  
Reaction Pathway ◽  
Lactate Production ◽  
Reaction Rates ◽  
Small Sample ◽  
Dynamical Analysis ◽  
Series Data ◽  
Sufficient Information ◽  
Parameter Values

Measuring the concentrations of metabolites and estimating the reaction rates of each reaction step consisting of metabolic pathways are significant for an improvement in microorganisms used in maximizing the production of materials. Although the reaction pathway must be identified for such an improvement, doing so is not easy. Numerous reaction steps have been reported; however, the actual reaction steps activated vary or change according to the conditions. Furthermore, to build mathematical models for a dynamical analysis, the reaction mechanisms and parameter values must be known; however, to date, sufficient information has yet to be published for many cases. In addition, experimental observations are expensive. A new mathematical approach that is applicable to small sample data, and that requires no detailed reaction information, is strongly needed. S-system is one such model that can use smaller samples than other ordinary differential equation models. We propose a simplified S-system to apply minimal quantities of samples for a dynamic analysis of the metabolic pathways. We applied the model to the phenyl lactate production pathway of Escherichia coli. The model obtained suggests that actually activated reaction steps and feedback are inhibitions within the pathway.

Wormholing in anisotropic media: Pore orientation effect on large-scale patterns

2020 ◽  
Author(s):  
Roi Roded ◽  
Piotr Szymczak ◽  
Ran Holtzman
Keyword(s):  
Large Scale ◽  
Flow Direction ◽  
Hierarchical Structures ◽  
Anisotropic Media ◽  
Viscous Fingering ◽  
Reactive Flow ◽  
Small Scale ◽  
Microfluidic Channels ◽  
Permeability Evolution ◽  
Scale Invariant

&lt;p&gt;The dissolution of fractured or porous media by reactive flow is often occurring preferentially, forming highly conductive channels, so-called &amp;#8220;wormholes&amp;#8221;. Wormhole formation prevails in subsurface karst where it can form extensive speleological systems, and is also significant for a large range of applications, e.g. well acidizing or CO&lt;sub&gt;2&lt;/sub&gt; geo-sequestration. The underlying mechanism involves positive feedback between reaction and transport&amp;#8212; the flow pathways that focus the reactive flow dissolve preferentially and increase their conductivity, and in turn their flow. An increased pressure ahead of the longer wormholes screens off the shorter ones, which ultimately cease to grow. Over time, the characteristic spacing between active (growing) wormholes increases, while their number declines, which results in a hierarchical scale-invariant distribution of wormhole lengths. Interestingly, a variety of other pattern-forming processes in nature show a similar competitive dynamics and emergent of hierarchical structures, with examples ranging from viscous fingering to crack propagation in brittle solids and side-branches growth in crystallization [1].&lt;/p&gt;&lt;p&gt;The importance of wormholing and its intriguing dynamics motivated intensive research, including on the emergence of reactive-infiltration instabilities [2], as well as on the effects of medium heterogeneity on the wormhole growth. Here, we study wormholing in anisotropic media using a network model of regular geometry&amp;#8212; longitudinal channels (aligned along the main flow direction) and transverse ones, of a different average cross-section. Our simulations show that anisotropy substantially affects wormholing, controlling the characteristic spacing between the wormholes and the overall permeability evolution. In the case of wider transverse channels, wormhole interaction via the pressure field is enhanced, resulting in stronger wormhole competition and hence larger spacing. Conversely, in the extreme case of very narrow transverse channels, spacing becomes minimal and neighboring wormholes tend to merge. Simulations further reveal that narrow transverse channels promote the emergence of thinner and more conical wormholes with several side-branches.&lt;/p&gt;&lt;p&gt;Additionally, we discuss the relation between the wormhole development in an anisotropic medium and viscous fingering phenomena in a network of microfluidic channels [3]. Despite many similarities between these systems we also find important differences&amp;#8212; while the spacing between viscous fingers increases linearly with anisotropy, the corresponding relation for wormholes turns out to be nonlinear. This nonlinearity could be attributed to the effect of anisotropy on wormhole shape and advancement velocity and is of interest for future investigation. Our findings contribute to the understanding of wormholing in geological systems and demonstrate how the small-scale features can fundamentally affect the resulting large-scale morphologies.&lt;/p&gt;&lt;p&gt;[1] Krug, J.,&amp;#160;Adv. Phys.,&amp;#160;46, 139, 1997&lt;/p&gt;&lt;p&gt;[2] Ortoleva, P. et al, Amer. J. Sci., 287, 1008, 1987&lt;/p&gt;&lt;p&gt;[3] Budek, A. et al, Phys. Fluids, 27, 112109, 2015&lt;/p&gt;

scholarly journals Dynamically consistent entrainment laws for depth-averaged avalanche models

2014 ◽  
Vol 759 ◽  
pp. 701-738 ◽  
Author(s):  
Dieter Issler
Keyword(s):  
Stationary Flow ◽  
Analytic Solutions ◽  
Rheological Parameters ◽  
Bottom Surface ◽  
Entrainment Rate ◽  
Stationary Flows ◽  
Start Up ◽  
Flow Variables ◽  
Bed Material ◽  
Parameter Values

AbstractThe bed entrainment rate in a gravity mass flow (GMF) is uniquely determined by the properties of the bed and the flow. In depth-averaging, however, critical information on the flow variables near the bed is lost and empirical assumptions usually are made instead. We study the interplay between bed and flow assuming a perfectly brittle bed, characterized by its shear strength ${\it\tau}_{c}$, and erosion along the bottom surface of the flow; frontal entrainment is neglected here. The brittleness assumption implies that the shear stress at the bed surface cannot exceed ${\it\tau}_{c}$. For quasi-stationary flows in a simplified setting, analytic solutions are found for Bingham and frictional–collisional (FC) fluids. Extending this theory to non-stationary flows requires some assumptions for the velocity profile. For the Bingham fluid, the profile of a ‘proxy’ quasi-stationary eroding flow is used; the rheological parameters are chosen to match the instantaneous velocity and shear-layer depth of the non-stationary flow. For the FC fluid, a two-parameter family of functions that closely match the profiles obtained in depth-resolved numerical simulations is assumed; the boundary conditions determine the instantaneous parameter values and allow computation of the erosion rate. Preliminary tests with the FC erosion formula incorporated in a simple slab model indicate that the non-stationary erosion formula matches the depth-resolved simulations asymptotically, but differs in the start-up phase. The non-stationary erosion formulae are valid only up to a limit velocity (and to a limit flow depth if there is Coulomb friction). This appears to mark the transition to another erosion regime – to be described by a different model – where chunks of bed material are intermittently ripped out and gradually entrained into the flow.

scholarly journals Individual variation in cognitive performance: developmental and evolutionary perspectives

2012 ◽  
Vol 367 (1603) ◽  
pp. 2773-2783 ◽  
Author(s):  
Alex Thornton ◽  
Dieter Lukas
Keyword(s):  
Cognitive Performance ◽  
Individual Variation ◽  
Animal Cognition ◽  
Individual Performance ◽  
Small Sample ◽  
Cognitive Capacity ◽  
Single Individual ◽  
High Performing ◽  
Cognitive Traits ◽  
Meta Analyses

Animal cognition experiments frequently reveal striking individual variation but rarely consider its causes and largely ignore its potential consequences. Studies often focus on a subset of high-performing subjects, sometimes viewing evidence from a single individual as sufficient to demonstrate the cognitive capacity of a species. We argue that the emphasis on demonstrating species-level cognitive capacities detracts from the value of individual variation in understanding cognitive development and evolution. We consider developmental and evolutionary interpretations of individual variation and use meta-analyses of data from published studies to examine predictors of individual performance. We show that reliance on small sample sizes precludes robust conclusions about individual abilities as well as inter- and intraspecific differences. We advocate standardization of experimental protocols and pooling of data between laboratories to improve statistical rigour. Our analyses show that cognitive performance is influenced by age, sex, rearing conditions and previous experience. These effects limit the validity of comparative analyses unless developmental histories are taken into account, and complicate attempts to understand how cognitive traits are expressed and selected under natural conditions. Further understanding of cognitive evolution requires efforts to elucidate the heritability of cognitive traits and establish whether elevated cognitive performance confers fitness advantages in nature.

scholarly journals Curved passive mixing structures: a robust design to obtain efficient mixing and mass transfer in microfluidic channels

2020 ◽  
Vol 31 (1) ◽  
pp. 015006
Author(s):  
Ingrid H Oevreeide ◽  
Andreas Zoellner ◽  
Michal M Mielnik ◽  
Bjørn T Stokke
Keyword(s):  
Mass Transfer ◽  
Robust Design ◽  
Microfluidic Channels ◽  
Passive Mixing

Missing the sociopolitical: examining discourses of writing in a US high-performing, urban middle school

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nadia Behizadeh
Keyword(s):  
Professional Development ◽  
Middle School ◽  
Writing Instruction ◽  
Critical Literacy ◽  
Test Scores ◽  
Small Sample ◽  
Future Research ◽  
Content Type ◽  
High Performing ◽  
Urban Middle School

Purpose This paper aims to examine two teachers’ beliefs and practices on teaching writing at an urban, high-performing middle school to determine: What discourses of writing are being taught in an urban, high-performing US public middle school? What factors prevent or enable particular discourses? Design/methodology/approach Drawing on case study methods, this study uses a single-case design with two seventh-grade teachers at a high-performing urban school as embedded units of analysis. Data collection took place over one semester. Data sources included observations and interviews with the two teachers, an interview with an administrator and multiple instructional artifacts, including unit and lesson plans. Observational data were analyzed using a priori code for writing discourses (Ivanic, 2004) and interview data were analyzed for factors affecting instruction using open, axial and selective coding. Findings Both teachers enacted extended multi-discourse writing instruction integrating skills, creativity, process, genre and social practices discourses supported by their beliefs and experience; colleagues; students’ relatively high test scores; and relative curricular freedom. However, there was minimal evidence of a sociopolitical discourse aligned with critical literacy practices. Limits to the sociopolitical discourse included a lack of a social justice orientation, an influx of low-performing students, a focus on raising test scores, data-focused professional development and district pacing guides. Racism is also considered as an underlying structural factor undermining the sociopolitical discourse. Research limitations/implications Although generalizability is limited because of the small sample size and the unique context of this study, two major implications are the need to layer discourses in writing instruction while centering critical pedagogy and develop teacher beliefs and knowledge. To support these two implications, this study suggests developing university-school partnerships and professional development opportunities that create a community of practice around comprehensive writing instruction. Future research will involve continuing to work with the participants in this study and documenting the effects of providing theory and tools for integrating the sociopolitical discourse into middle school curricula and instruction. Originality/value This study contributes to the field of literacy education’s understanding of internal and external factors limiting the sociopolitical discourse in a high-performing, urban middle school in the USA, an understudied context.

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