scholarly journals Viscoelastic microfluidics: progress and challanges

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Jian Zhou ◽  
Ian Papautsky
Keyword(s):  
Driving Forces ◽  
Three Dimensional ◽  
Clinical Diagnostics ◽  
Viscoelastic Flows ◽  
Migration Behavior ◽  
Microfluidic Platforms ◽  
Fluid Physics ◽  
Fluid Elasticity ◽  
Migration Dynamics ◽  
Fluid Rheology

AbstractThe manipulation of cells and particles suspended in viscoelastic fluids in microchannels has drawn increasing attention, in part due to the ability for single-stream three-dimensional focusing in simple channel geometries. Improvement in the understanding of non-Newtonian effects on particle dynamics has led to expanding exploration of focusing and sorting particles and cells using viscoelastic microfluidics. Multiple factors, such as the driving forces arising from fluid elasticity and inertia, the effect of fluid rheology, the physical properties of particles and cells, and channel geometry, actively interact and compete together to govern the intricate migration behavior of particles and cells in microchannels. Here, we review the viscoelastic fluid physics and the hydrodynamic forces in such flows and identify three pairs of competing forces/effects that collectively govern viscoelastic migration. We discuss migration dynamics, focusing positions, numerical simulations, and recent progress in viscoelastic microfluidic applications as well as the remaining challenges. Finally, we hope that an improved understanding of viscoelastic flows in microfluidics can lead to increased sophistication of microfluidic platforms in clinical diagnostics and biomedical research.

Adult Acquired Flatfoot

2020 ◽  
Vol 62 (1) ◽  
pp. 55-59
Author(s):  
Krzysztof Mataczyński ◽  
Mateusz Pelc ◽  
Halina Romualda Zięba ◽  
Zuzana Hudakova
Keyword(s):  
Soft Tissues ◽  
Three Dimensional ◽  
Clinical Diagnostics ◽  
Clinical Image ◽  
Tibialis Posterior ◽  
Dynamic Force ◽  
Posterior Tibial ◽  
Flat Feet ◽  
Foot Arch ◽  
Motion Range

Acquired adult flatfoot is a three-dimensional deformation, which consists of hindfoot valgus, collapse of the longitudinal arch of the foot and adduction of the forefoot. The aim of the work is to present problems related to etiology, biomechanics, clinical diagnostics and treatment principles of acquired flatfoot. The most common cause in adults is the dysfunction of the tibialis posterior muscle, leading to the lack of blocking of the transverse tarsal joint during heel elevation. Loading the unblocked joints consequently leads to ligament failure. The clinical image is dominated by pain in the foot and tibiotarsal joint. The physical examination of the flat feet consists of: inspection, palpation, motion range assessment and dynamic force assessment. The comparable attention should be paid to the height of the foot arch, the occurrence of “too many toes” sign, evaluate the heel- rise test and correction of the flatfoot, exclude Achilles tendon contracture. The diagnosis also uses imaging tests. In elastic deformations with symptoms of posterior tibial tendonitis, non-steroidal anti-inflammatory drugs, short-term immobilization, orthotics stabilizing the medial arch of the foot are used. In rehabilitation, active exercises of the shin muscles and the feet, especially the eccentric exercises of the posterior tibial muscle, are intentional. The physiotherapy and balneotherapy treatments, in particular hydrotherapy, electrotherapy and laser therapy, are used as a support. In advanced lesions, surgical treatment may be necessary, including plastic surgery of soft tissues, tendons, as well as osteotomy procedures.

scholarly journals Prospects of Nanostructure-Based Solar Cells for Manufacturing Future Generations of Photovoltaic Modules

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
N. Gupta ◽  
G. F. Alapatt ◽  
R. Podila ◽  
R. Singh ◽  
K. F. Poole
Keyword(s):  
Solar Cells ◽  
Heat Dissipation ◽  
Driving Forces ◽  
Three Dimensional ◽  
Solar Spectrum ◽  
Future Generation ◽  
Theoretical Work ◽  
Future Generations ◽  
Pv Modules ◽  
Quantum Phenomena

We present a comprehensive review on prospects for one-, two-, or three-dimensional nanostructure-based solar cells for manufacturing the future generation of photovoltaic (PV) modules. Reducing heat dissipation and utilizing the unabsorbed part of the solar spectrum are the key driving forces for the development of nanostructure-based solar cells. Unrealistic assumptions involved in theoretical work and the tendency of stretching observed experimental results are the primary reasons why quantum phenomena-based nanostructures solar cells are unlikely to play a significant role in the manufacturing of future generations of PV modules. Similar to the invention of phase shift masks (to beat the conventional diffraction limit of optical lithography) clever design concepts need to be invented to take advantage of quantum-based nanostructures. Silicon-based PV manufacturing will continue to provide sustained growth of the PV industry.

The Coupling Effect of Driving Forces to the Anti-Gravity Flow in the Spiral Micro-Channel

2011 ◽  
Author(s):  
Yan Li ◽  
Shuchao Zhang ◽  
Ning Mei
Keyword(s):  
Driving Force ◽  
Driving Forces ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Horizontal Tube ◽  
Gravity Flow ◽  
Micro Channel ◽  
Reciprocal Relations ◽  
Coupling Relationship ◽  
Onsager Reciprocal Relations

In this paper, the anti-gravity flow in the spiral micro-channel on the surface of horizontal tube was visualized by the three-dimensional ultra-microscope system. The coupling relationship between the driving force and the flow was studied by Onsager reciprocal relations. The results show that the formation of the anti-gravity flow in the spiral micro-channel on the surface of horizontal tube is impacted by the combining effect of several factors, such as the capillary pressure, wettability, temperature, and bubbles.

Mechanical evaluation of theories of neurulation using computer simulations

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 1013-1023 ◽  
Author(s):  
D. A. Clausi ◽  
G. W. Brodland
Keyword(s):  
Computer Simulations ◽  
Driving Forces ◽  
Shape Change ◽  
Three Dimensional ◽  
Dorsal Surface ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Amphibian Embryo ◽  
Axial Elongation ◽  
Shape Changes

Current theories about the forces that drive neurulation shape changes are evaluated using computer simulations. Custom, three-dimensional, finite element-based computer software is used. The software draws on current engineering concepts and makes it possible to construct a ‘virtual’ embryo with any user-specified mechanical properties. To test a specific hypothesis about the forces that drive neurulation, the whole virtual embryo or any selected part of it is ascribed with the force generators specified in the hypothesis. The shape changes that are produced by these forces are then observed and compared with experimental data. The simulations demonstrate that, when uniform, isotropic circumferential microfilament bundle (CMB) constriction and cephalocaudal (axial) elongation act together on a circular virtual neural plate, it becomes keyhole shaped. When these forces act on a spherical (amphibian) embryo, dorsal surface flattening occurs. Simulations of transverse sections further show that CMB constriction, acting with or without axial elongation, can produce numerous salient transverse features of neurulation. These features include the sequential formation of distinct neural ridges, narrowing and thickening of the neural plate, skewing just medial to the ridges, ‘hinge’ formation and neural tube closure. No region-specific ‘programs’ or non-mechanical cell-cell communications are used. The increase in complexity results entirely from mechanical interactions. The transverse simulations show how changes to the driving forces would affect the patterns of shape change produced. Hypotheses regarding force generation by microtubules, intercellular adhesions and forces extrinsic to the neural plate are also evaluated. The simulations show that these force-generating mechanisms do not, by themselves, produce shape changes that are consistent with normal development. The simulations support the concept of cooperation of forces and suggest that neurulation is robust because redundant force generating mechanisms exist.

scholarly journals Integration of digital maxillary dental casts with 3D facial images in orthodontic patients:

2019 ◽  
Vol 90 (3) ◽  
pp. 397-404 ◽  
Author(s):  
Zhuoxing Xiao ◽  
Zijin Liu ◽  
Yan Gu
Keyword(s):  
Intraclass Correlation ◽  
Three Dimensional ◽  
Correlation Coefficients ◽  
Reference Standards ◽  
Clinical Diagnostics ◽  
Step Method ◽  
Intraclass Correlation Coefficients ◽  
Orthodontic Patients ◽  
Facial Images ◽  
Dental Casts

ABSTRACT Objective To evaluate three-dimensional (3D) accuracy and reliability of nonradiographic dentofacial images integrated with a two-step method. Methods 3D facial images, cone-beam computed tomography (CBCT) images and digital maxillary dental casts were obtained from 20 pre-orthodontic subjects. Digital dental casts were integrated into 3D facial images using a two-step method based on the anterior tooth area. 3D coordinate values of five dental landmarks were identified in both dentofacial images and CBCT images. The accuracy of the integration method was assessed with paired t-tests between dentofacial images and CBCT-based reference standards. Intraclass correlation coefficients (ICCs) were assessed for the reliability of dentofacial images and CBCT-based images. Analysis of variance and Kruskal-Wallis tests evaluated the accuracy of the method in different dimensions. Results There was no statistical difference between dentofacial images and CBCT reference standards in both translational and rotational dimensions (P > .05). Translational mean absolute errors for full dentitions were within 0.42 mm and ICCs were over 0.998 in x, y, and z directions. Rotational mean absolute errors for full dentitions were within 0.92° and ICCs over 0.734 in pitch, yaw, and roll orientations. Integration errors were significantly greater in the first molar, z-translation, and pitch rotation (P < .05). Conclusions Integrating 3D dentofacial images with the two-step method is precise and acceptable for clinical diagnostics and scientific purposes. Errors were greater in the molar region, z-translation, and pitch rotation.

scholarly journals A 3D Printed Jet Mixer for Centrifugal Microfluidic Platforms

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 695 ◽  
Author(s):  
Yunxia Wang ◽  
Yong Zhang ◽  
Zheng Qiao ◽  
Wanjun Wang
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
Mixing Efficiency ◽  
Medical Applications ◽  
Microfluidic Platforms ◽  
Mixing Performance ◽  
Wide Range ◽  
3D Printed ◽  
Miscible Liquids ◽  
Biological And Medical Applications

Homogeneous mixing of microscopic volume fluids at low Reynolds number is of great significance for a wide range of chemical, biological, and medical applications. An efficient jet mixer with arrays of micronozzles was designed and fabricated using additive manufacturing (three-dimensional (3D) printing) technology for applications in centrifugal microfluidic platforms. The contact surface of miscible liquids was enhanced significantly by impinging plumes from two opposite arrays of micronozzles to improve mixing performance. The mixing efficiency was evaluated and compared with the commonly used Y-shaped micromixer. Effective mixing in the jet mixer was achieved within a very short timescale (3s). This 3D printed jet mixer has great potential to be implemented in applications by being incorporated into multifarious 3D printing devices in microfluidic platforms.

Journey to Shanghai: The Effects of Rural-to-urban Migration and Social Class on Perceptions of Home

2020 ◽  
pp. 0972558X2097523
Author(s):  
Arianna Ponzini
Keyword(s):  
Qualitative Data ◽  
Driving Forces ◽  
Upward Mobility ◽  
Urban Migration ◽  
Migration Dynamics ◽  
Primary Reference ◽  
Social Advancement ◽  
Rural To Urban Migration ◽  
The Village ◽  
The City

The present article centers on the home, the perceptions of which are challenged, and modified by rural-to-urban migration dynamics and outcomes. The core research interest hereby presented pertains to the effects of migration and social advancement on individuals’ perceptions of home: whereas some identify their original rural home as their “home,” others manage to achieve a “shift” of the home after migration, by relocating their “home” from their original home in the village to their created home in the city. These two opposite perceptions about where the home of primary reference is located are not coincidental. Rather, the article presents a pattern that connects home shifting to upward mobility and social advancement: in fact, the shift in the location of the home owes to three major driving forces that are key in social mobility processes: career development, locus, and networks. The findings of this research, reached through the analysis of empirical qualitative data, provide practical insights to post-migratory class formation as well as upward mobility dynamics.

Three-Dimensional High-Resolution Optical/X-Ray Stereoscopic Tracking Velocimetry

2004 ◽  
Author(s):  
David J. Lee ◽  
Soyoung S. Cha ◽  
Narayanan Ramachandran
Keyword(s):  
Three Dimensional ◽  
Initial Step ◽  
Industrial Applications ◽  
Materials Processing ◽  
Current Status ◽  
Motion Velocity ◽  
Processing Efficiency ◽  
X Ray ◽  
Fluid Physics ◽  
Component Velocity

Measurement of three-dimensional (3-D) three-component velocity fields is of great importance in a variety of research and industrial applications for understanding materials processing, fluid physics, and strain/displacement measurements. The 3-D experiments in these fields most likely inhibit the use of conventional techniques, which are based only on planar and optically-transparent-field observation. Here, we briefly review the current status of 3-D diagnostics for motion/velocity detection, for both optical and x-ray systems. As an initial step for providing 3-D capabilities, we have developed stereoscopic tracking velocimetry (STV) to measure 3-D flow/deformation through optical observation. The STV is advantageous in system simplicity, for continually observing 3-D phenomena in near real-time. In an effort to enhance the data processing through automation and to avoid the confusion in tracking numerous markers or particles, artificial neural networks are employed to incorporate human intelligence. Our initial optical investigations have proven the STV to be a very viable candidate for reliably measuring 3-D flow motions. With previous activities are focused on improving the processing efficiency, overall accuracy, and automation based on the optical system, the current efforts is directed to the concurrent expansion to the x-ray system for broader experimental applications.

scholarly journals DETERMINISTIC CHAOS VERSUS STOCHASTIC OSCILLATION IN A PREY-PREDATOR-TOP PREDATOR MODEL

2011 ◽  
Vol 16 (3) ◽  
pp. 343-364 ◽  
Author(s):  
Ranjit Kumar Upadhyay ◽  
Malay Banerjee ◽  
Rana Parshad ◽  
Sharada Nandan Raw
Keyword(s):  
Deterministic Model ◽  
Driving Forces ◽  
Equilibrium Points ◽  
Chaotic Oscillation ◽  
Three Dimensional ◽  
Deterministic Chaos ◽  
Model System ◽  
Dynamical Analysis ◽  
Interior Equilibrium ◽  
Predator Model

The main objective of the present paper is to consider the dynamical analysis of a three dimensional prey-predator model within deterministic environment and the influence of environmental driving forces on the dynamics of the model system. For the deterministic model we have obtained the local asymptotic stability criteria of various equilibrium points and derived the condition for the existence of small amplitude periodic solution bifurcating from interior equilibrium point through Hopf bifurcation. We have obtained the parametric domain within which the model system exhibit chaotic oscillation and determined the route to chaos. Finally, we have shown that chaotic oscillation disappears in presence of environmental driving forces which actually affect the deterministic growth rates. These driving forces are unable to drive the system from a regime of deterministic chaos towards a stochastically stable situation. The stochastic stability results are discussed in terms of the stability of first and second order moments. Exhaustive numerical simulations are carried out to validate the analytical findings.

Mixing of a viscoelastic fluid in a time-periodic flow

1993 ◽  
Vol 256 ◽  
pp. 243-268 ◽  
Author(s):  
T. C. Niederkorn ◽  
J. M. Ottino
Keyword(s):  
Viscoelastic Fluid ◽  
Three Dimensional ◽  
Deborah Number ◽  
Weissenberg Number ◽  
Periodic Flow ◽  
Dimensionless Numbers ◽  
Fluid Elasticity ◽  
Exponential Stretching ◽  
The Impact ◽  
Time Periodic

We present an experimental and computational investigation of mixing of a viscoelastic fluid in two-dimensional time-periodic flows generated in an eccentric cylindrical geometry. The objective of the study is to investigate the impact of fluid elasticity on the morphological structures produced by the advection of passive tracers in chaotic flows. The relevant dimensionless numbers that quantify the rheological differences with respect to the Newtonian fluid are the Deborah number (De), defined as the ratio of the fluid timescale to the flow timescale, and the Weissenberg number (We), defined as the product of the fluid timescale and the mean shear rate. The effects of elasticity are investigated in the limit of slow flows, De ≈ 0 and We < 0.1. The experimental window of We is limited to Newtonian behaviour on the low end and the transition to three-dimensional flow on the high end; experiments show that this window is small, 0.02 < We < 0.1. Typical values of the Reynolds number and the Strouhal number are O(0.001) and O(0.1), respectively.Results from experiments with a constant-viscosity elastic fluid and computations using the upper-convected Maxwell constitutive equation are presented. Even though the streamlines for the elastic flow are nearly indistinguishable from the Newtonian flow, small deviations in the velocity field produce large effects on chaotically advected patterns. Elasticity affects both the asymptotic coverage of a dyed passive tracer and the rate at which the tracer is stretched. In all cases the tracer undergoes exponential stretching, but on a longer timescale as the elasticity increases. According to flow conditions, elasticity might increase or decrease the degree of regularity; however, island symmetry does not seem to be affected. Similar phenomena are observed in both the experiments and computations; therefore, an analysis of the chaotic dynamics of the periodic flow using numerical techniques is possible.

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