scholarly journals All-in-one rheology of multicellular aggregates

2021 ◽  
Author(s):  
Gaëtan Mary ◽  
François Mazuel ◽  
Vincent Nier ◽  
Florian Fage ◽  
Irène Nagle ◽  
...  
Keyword(s):  
Magnetic Measurements ◽  
High Stress ◽  
Tissue Mechanics ◽  
Parallel Plates ◽  
F9 Cells ◽  
Multicellular Aggregates ◽  
Wide Range ◽  
External Stresses ◽  
Oscillatory Response ◽  
Magnetic Techniques

Abstract Tissues are generally subjected to external stresses, a potential stimulus for their differentiation or remodelling. While single-cell rheology has been extensively studied, mechanical tissue behavior under external stress is still poorly known because of a lack of adapted set-ups. Herein we introduce magnetic techniques designed both to form aggregates of controlled size, shape and content (magnetic molding) and to deform them under controlled applied stresses over a wide range of timescales and amplitudes (magnetic rheometer). We explore the rheology of multicellular aggregates (F9 cells) using both standard assays (creep and oscillatory response) and an innovative broad spectrum solicitation coupled with inference analysis. We find that multicellular aggregates exhibit a power-law response with non-linearities leading to tissue stiffening at high stress. Comparing magnetic measurements on aggregates to isolated F9 cells characterization by parallel-plates rheometry, we reveal the role of cell-cell adhesions in tissue mechanics. Thanks to its versatility, the magnetic rheometer thus stands as an essential tool to investigate model tissue rheology.

Turbulent Heat Transfer Between a Series of Parallel Plates With Surface-Mounted Discrete Heat Sources

1994 ◽  
Vol 116 (3) ◽  
pp. 577-587 ◽  
Author(s):  
S. H. Kim ◽  
N. K. Anand
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Electronic Equipment ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Computational Domain ◽  
Heat Sources ◽  
Parallel Plates ◽  
Wide Range ◽  
Independent Parameters

Two-dimensional turbulent heat transfer between a series of parallel plates with surface mounted discrete block heat sources was studied numerically. The computational domain was subjected to periodic conditions in the streamwise direction and repeated conditions in the cross-stream direction (Double Cyclic). The second source term was included in the energy equation to facilitate the correct prediction of a periodically fully developed temperature field. These channels resemble cooling passages in electronic equipment. The k–ε model was used for turbulent closure and calculations were made for a wide range of independent parameters (Re, Ks/Kf, s/w, d/w, and h/w). The governing equations were solved by using a finite volume technique. The numerical procedure and implementation of the k–ε model was validated by comparing numerical predictions with published experimental data (Wirtz and Chen, 1991; Sparrow et al., 1982) for a single channel with several surface mounted blocks. Computations were performed for a wide range of Reynolds numbers (5 × 104–4 × 105) and geometric parameters and for Pr = 0.7. Substrate conduction was found to reduce the block temperature by redistributing the heat flux and to reduce the overall thermal resistance of the module. It was also found that the increase in the Reynolds number decreased the thermal resistance. The study showed that the substrate conduction can be an important parameter in the design and analysis of cooling channels of electronic equipment. Finally, correlations for the friction factor (f) and average thermal resistance (R) in terms of independent parameters were developed.

scholarly journals Welcome to the Ziggurat Journal of Materials Technology - a New Open Access Journal

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Jürgen Bast
Keyword(s):  
Urban Areas ◽  
Technological Progress ◽  
High Stress ◽  
Scientific Work ◽  
Open Access Journal ◽  
Human Society ◽  
New Materials ◽  
Wide Range ◽  
Global Population

Dear readers, authors and colleagues, Technological progress plays an essential role in the development of human society. The increasing global population and its mobility, the expansion of urban areas, climate protection and the conservation of fossil resources present challenges that can only be overcome by the improvement of existing resources and the development of new components, materials and production processes. Conventional materials have quickly reached their limit as new mechanisms are developed. These fields of application require the supply of new materials working in aggressive environments at extreme temperatures and high stress. These new materials are also expected to automatically alert us when critical loads are reached to avoid accidents caused by failures. This is the first issue of the Ziggurat Journal of Materials Technology, and we hope that you are satisfied with the content. The title of the journal primarily suggests materials technology; however, we strive to present a broad range of topics, including questions about the interaction between design, material, manufacturing and energy. The efficient interaction between these parameters results in components that are optimally designed and economically feasible. The idea for this journal resulted from the editors' realisation of the large knowledge potential that is being developed at colleges and universities around the world by scholars and PhD students. These clients must have the opportunity to publish their work and get in touch with other scientists. We want to reach out to young researchers and encourage them to present their work to a wide range of readers. Furthermore, a scientific career today requires evidence of publications that withstand the corresponding assessments of specialist colleagues and meet the criteria of good scientific work. In this context, the submitted articles will be subjected to a strict review. The principal objective is not to criticise work but rather to provide advice on how to improve the quality of the work presented. With this in mind, we would like to invite you to submit articles and use this journal as a reference for your ongoing scientific work.

scholarly journals Optogenetic relaxation of actomyosin contractility uncovers mechanistic roles of cortical tension during cytokinesis

2021 ◽  
Author(s):  
Kei Yamamoto ◽  
Haruko Miura ◽  
Motohiko Ishida ◽  
Satoshi Sawai ◽  
Yohei Kondo ◽  
...  
Keyword(s):  
Traction Force ◽  
Tissue Mechanics ◽  
Light Illumination ◽  
Type I ◽  
Contractile Ring ◽  
Cortical Tension ◽  
Regulatory Light Chains ◽  
Actomyosin Contractility ◽  
Nonmuscle Myosin Ii ◽  
Wide Range

Actomyosin contractility generated cooperatively by nonmuscle myosin II and actin filaments plays essential roles in a wide range of biological processes, such as cell motility, cytokinesis, and tissue morphogenesis. However, it is still unknown how actomyosin contractility generates force and maintains cellular morphology. Here, we demonstrate an optogenetic method to induce relaxation of actomyosin contractility. The system, named OptoMYPT, combines a catalytic subunit of the type I phosphatase-binding domain of MYPT1 with an optogenetic dimerizer, so that it allows light-dependent recruitment of endogenous PP1c to the plasma membrane. Blue-light illumination was sufficient to induce dephosphorylation of myosin regulatory light chains and decrease in traction force at the subcellular level. The OptoMYPT system was further employed to understand the mechanics of actomyosin-based cortical tension and contractile ring tension during cytokinesis. We found that the relaxation of cortical tension at both poles by OptoMYPT accelerated the furrow ingression rate, revealing that the cortical tension substantially antagonizes constriction of the cleavage furrow. Based on these results, the OptoMYPT system will provide new opportunities to understand cellular and tissue mechanics.

scholarly journals Stress and Sexual Dysfunction among Call Center Employees

2014 ◽  
Vol 1 (3) ◽  
Author(s):  
Dr. V.D. Kasture
Keyword(s):  
Sexual Dysfunction ◽  
Call Center ◽  
Call Centers ◽  
High Stress ◽  
Work Load ◽  
International Studies ◽  
Positive Thinking ◽  
Wide Range ◽  
Female Employees ◽  
Call Center Employees

The call center community often defines itself as an industry, with numerous national and international call centers. But there has some dispute among researchers as to whether it is appropriate to refer such thing as the ‘call center industry’. Bain and Taylor (1999) argue that it is more appropriate to use the term ‘sector’ as call centers are found across a wide range of industries and may be similar primarily in terms of their core technologies. Belt, Richardson and Websler (2000) agreed that call centers are not an ‘industry’ as the term generally defined, but rather represent certain ways of delivering various services using the telephone and computer technologies across traditional industry boundaries. This research results revealed that female employees from international call centers show high stress score and high sexual dysfunction than domestic call center employees, which means the female employees from international call center differed significantly (t=5.26, p=<0.01) than domestic call center female employees. Results obtained from t test showed that female employees from domestic and international call center differed significantly with one another on stress scores and sexual dysfunction. The reason is that international call center employees have more work stress as compare to that with domestic one. This due to heavy work load, not enough time for social interaction and completion of work within a given period of time. The work culture is more strict and systematic as compared to domestic one. International studies in the past have linked stress t sexual dysfunction and infertility among women. The overall results of the present study suggest the need for stress management programs for reducing the stress and developing positive thinking among young female employees working in call centers.

Flexible Flapping Dynamics of Parallel Elastic Plates in a Uniform Flow: Application to Energy Harvesting Devices

2014 ◽  
Author(s):  
Pardha S. Gurugubelli ◽  
Rajeev K. Jaiman ◽  
Boo Cheong Khoo
Keyword(s):  
Coupled System ◽  
Uniform Flow ◽  
Net Energy ◽  
Elastic Plates ◽  
Parallel Plates ◽  
Mass Ratio ◽  
Bending Rigidity ◽  
Fluid Structure ◽  
Flapping Motion ◽  
Wide Range

A new high-order finite element Coupled Field with Explicit Interface (CFEI) code has been developed for simulating flapping motion of a thin flexible body in a uniform flow with strong add-mass effects. In the first part, we study the flapping dynamics of a single cantilevered plate for wide range of mass ratios and maintaining relatively low bending rigidity through our direct fluid-structure simulations. As a function of mass-ratio, the flapping dynamics reveals three distinct regimes: (i) fixed-point stable; (ii) limit-cycle flapping; and (iii) chaotic flapping. The changes associated with regime transition with increasing mass ratio are analyzed by vortex wake patterns and tip-displacement responses. Dependencies of stability predicted by the theoretical analysis are confirmed by the nonlinear fluid-structure simulations. In the second part, two parallel cantilevered plates will be investigated as a function of spacing between the parallel plates to assess the flapping motion and the net energy transfer. The flow-induced vibrations of this kind of coupled system have a potential to extract energy from the surrounding fluid flow for generation of electric power.

Laboratory Modules for Reinforcement of Concepts Taught in Undergraduate Tissue Mechanics Course

2008 ◽  
Author(s):  
Ozan Akkus ◽  
Allison Sieving
Keyword(s):  
Undergraduate Curriculum ◽  
Tissue Mechanics ◽  
Stress And Strain ◽  
Engineering Curriculum ◽  
Connective Tissues ◽  
Strength Of Materials ◽  
Musculoskeletal Tissues ◽  
State Of Stress ◽  
Wide Range ◽  
Holistic Understanding

Tissue mechanics is one of the key courses of the Biomechanics subtrack of the undergraduate curriculum. The aims of the course include: 1) To understand the concepts of stress, strain, viscoelasticity and how these concepts apply to musculoskeletal tissues. 2) The ability to infer the state of stress and strain at a given point in a biological structure under torsional, axial, bending and other types of loads. 3) To understand the anatomy of musculoskeletal tissues. Accomplishment of these aims requires a holistic understanding of statics, strength of materials and microanatomy of connective tissues. Conveying this wide range of topics in one class is a major challenge and most textbooks on this subject lack depth either in engineering or in physiology. The purpose of this abstract is to describe the benefits of the integration of theory with experimental practice for bridging the difficult topics of statics, strength of materials and tissue anatomy within the framework of undergraduate biomedical engineering curriculum.

Squeeze Film Damping Models Compared With Tests on Microsystems

2006 ◽  
Author(s):  
Hartono (Anton) Sumali ◽  
David S. Epp
Keyword(s):  
Experimental Data ◽  
Damping Ratio ◽  
Laser Doppler Vibrometer ◽  
Squeeze Film ◽  
Parallel Plates ◽  
Squeeze Film Damping ◽  
Wide Range ◽  
Oscillation Frequencies ◽  
Oscillating Plate ◽  
The Continuum

This paper compares three models for computing forces caused by gas film squeezed between parallel plates. The models are used to calculate damping forces on an oscillating plate at different oscillation frequencies. The damping forces are then used to calculate nondimensional damping ratios. The damping ratios are used in making comparisons among the models and with experimental data. The experiment used an oscillating MEMS plate suspended by folded springs. The substrate (base) was shaken with a piezoelectric transducer. The plate vibrated as a result, especially at the resonant frequency. The velocities of the suspended plate and of the substrate were measured with a laser Doppler vibrometer and a microscope. Experimental modal analysis gave the damping ratio. To achieve a wide range of squeeze numbers, the experiment was repeated under several different pressures. The measurement was also repeated on an array of plates. Experimental data indicate that, for atmospheric and higher pressures, squeeze-film damping forces can be modeled accurately with a very simple model. For lower pressures in the continuum regime, a more complete model by Veijola (2004) predicts the damping ratio very well.

Synthesis of Fe2O3/CNTs for the Fast Removal of Tetracycline from Aqueous Solutions

2014 ◽  
Vol 915-916 ◽  
pp. 933-941 ◽  
Author(s):  
Zhong Jie Zhang ◽  
Chang Yu Lu ◽  
Wei Huang ◽  
Wei Sheng Guan ◽  
Yue Xin Peng
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Magnetic Measurements ◽  
Ferrite Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Range ◽  
Fast Removal ◽  
Scanning Electron

The effective remove to tetracycline still remains a big challenge for scientists. In this work, we used a new method for preparing functional magnetic CNTS with ferrite nanoparticles. A wide range of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurements were applied to characterize the obtained Fe2O3/CNTs. Moreover, we have also studied the properties of adsorbent to tetracycline. In addition, we have found that the Fe2O3/CNTs are better reusable adsorbent than other traditional adsorbents by magnetic separation recycling method.

scholarly journals Fabrication of Micron Scale Magnetic Nickel Features by Selective Area Organometallic Chemical Vapor Deposition

1997 ◽  
Vol 475 ◽  
Author(s):  
D. Welipitiya ◽  
C. N. Borca ◽  
P. A. Dowben ◽  
I. Gobulukoglu ◽  
Hong Jiang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Magnetic Measurements ◽  
Chemical Vapor ◽  
Gradient Force ◽  
Selective Area ◽  
Wide Range ◽  
Radiation Induced ◽  
Organometallic Chemical Vapor Deposition

AbstractWe demonstrate that it is possible to deposit a wide range of magnetic features, using photoassisted and electron radiation induced selective area organometallic chemical vapor deposition. Large arrays of identical micron to nano scale Ni features were deposited by these methods. Their magnetic properties were studied by alternating gradient force magnetometry as well as magnetic force microscopy. Our morphological and magnetic measurements show that the structures are spatially well defined, and the magnetic properties are related to the structural shapes of the features.

scholarly journals Magnetic poly(ε-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates for advanced bone tissue engineering

2013 ◽  
Vol 10 (80) ◽  
pp. 20120833 ◽  
Author(s):  
A. Gloria ◽  
T. Russo ◽  
U. D'Amora ◽  
S. Zeppetelli ◽  
T. D'Alessandro ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Laser Scanning ◽  
Magnetic Measurements ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Hyperthermia Treatment ◽  
Wide Range ◽  
Iron Doped

In biomedicine, magnetic nanoparticles provide some attractive possibilities because they possess peculiar physical properties that permit their use in a wide range of applications. The concept of magnetic guidance basically spans from drug delivery and hyperthermia treatment of tumours, to tissue engineering, such as magneto-mechanical stimulation/activation of cell constructs and mechanosensitive ion channels, magnetic cell-seeding procedures, and controlled cell proliferation and differentiation. Accordingly, the aim of this study was to develop fully biodegradable and magnetic nanocomposite substrates for bone tissue engineering by embedding iron-doped hydroxyapatite (FeHA) nanoparticles in a poly(ε-caprolactone) (PCL) matrix. X-ray diffraction analyses enabled the demonstration that the phase composition and crystallinity of the magnetic FeHA were not affected by the process used to develop the nanocomposite substrates. The mechanical characterization performed through small punch tests has evidenced that inclusion of 10 per cent by weight of FeHA would represent an effective reinforcement. The inclusion of nanoparticles also improves the hydrophilicity of the substrates as evidenced by the lower values of water contact angle in comparison with those of neat PCL. The results from magnetic measurements confirmed the superparamagnetic character of the nanocomposite substrates, indicated by a very low coercive field, a saturation magnetization strictly proportional to the FeHA content and a strong history dependence in temperature sweeps. Regarding the biological performances, confocal laser scanning microscopy and AlamarBlue assay have provided qualitative and quantitative information on human mesenchymal stem cell adhesion and viability/proliferation, respectively, whereas the obtained ALP/DNA values have shown the ability of the nanocomposite substrates to support osteogenic differentiation.

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