scholarly journals Adhesion Percolation Determines Global Deformation Behavior in Biomimetic Emulsions

2021 ◽  
Vol 9 ◽  
Author(s):  
Lorraine Montel ◽  
Iaroslava Golovkova ◽  
Silvia Grigolon ◽  
Elie Wandersman ◽  
Alexis M. Prevost ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Transmembrane Proteins ◽  
Viscoelastic Behavior ◽  
Threshold Value ◽  
Point Of View ◽  
Local Order ◽  
Biological Processes ◽  
Adhesion Forces ◽  
Adhesive Properties ◽  
Global Deformation

Characterizing the mechanical properties of tissues is key for the understanding of fundamental biological processes such as morphogenesis or tumor progression. In particular, the intercellular adhesion forces, mediated by transmembrane proteins like cadherins, are expected to control the topology and viscoelastic behavior of tissues under mechanical stress. In order to understand the influence of adhesion in tissues, we use biomimetic emulsions in which droplets mimic cells and adhere to each other through specific bonds. Here, we tune both the binding energy of the adhesive inter-droplets contacts as well as the fraction of contacts that are adhesive, thereby defining a so-called adhesiveness. Our experimental results show that adhesion prevents the emergence of local order in emulsions even at high packing fractions by preventing energetically costly droplet rearrangements. By studying the deformation of droplets within packings with different average adhesiveness values, we reveal the existence of a threshold value of adhesiveness above which all droplets in a packing are deformed as adhesive ones irrespective of their local adhesive properties. We show that this critical adhesiveness coincides with the threshold for percolation of adhesive structures throughout the tissue. From a biological point of view, this indicates that only a fraction of adhesive cells would be sufficient to tune the global mechanical properties of a tissue, which would be critical during processes such as morphogenesis.

scholarly journals Adhesive Behavior of Propolis on Different Substrates

2021 ◽  
Vol 7 ◽  
Author(s):  
Leonie Saccardi ◽  
Jonas Schiebl ◽  
Katharina Weber ◽  
Oliver Schwarz ◽  
Stanislav Gorb ◽  
...  
Keyword(s):  
Viscoelastic Behavior ◽  
Point Of View ◽  
Organic Substances ◽  
Compression Tests ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Adhesive Properties ◽  
Wide Range ◽  
Medicinal Properties ◽  
Main Components

Propolis is a sticky substance used by bees to seal their hive and protect the colony against pathogens. Its main components are plant resins, beeswax, essential oils, pollen, and other organic substances. The chemical and medicinal properties of propolis have been extensively studied, but little is known about its physical and especially adhesive properties. To gain a better understanding of propolis and its potential for adhesive applications, we performed several experiments, including adhesion tests with propolis in different conditions and on various substrates, differential scanning calorimetry analysis, and compression tests. Propolis shows clear viscoelastic behavior and temperature-dependent mechanical properties. Our results demonstrate that propolis adheres well to a wide range of substrates from glass to PTFE, but also enables stronger adhesion at higher temperatures and longer contact times. Even underwater, in wet conditions, quite a substantial adhesion was measured. The data are interpreted from a biomechanical point of view, and the significance of the obtained results for bee biology is discussed.

scholarly journals A family of pathogen-induced cysteine-rich transmembrane proteins is involved in plant disease resistance

Planta ◽  
2021 ◽  
Vol 253 (5) ◽  
Author(s):  
Marciel Pereira Mendes ◽  
Richard Hickman ◽  
Marcel C. Van Verk ◽  
Nicole M. Nieuwendijk ◽  
Anja Reinstädler ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Plasma Membrane ◽  
Disease Resistance ◽  
Plant Disease Resistance ◽  
Transmembrane Proteins ◽  
Series Data ◽  
Immune Gene ◽  
Biological Processes ◽  
Hypocotyl Growth ◽  
Enhanced Resistance

Abstract Main conclusion Overexpression of pathogen-induced cysteine-rich transmembrane proteins (PCMs) in Arabidopsis thaliana enhances resistance against biotrophic pathogens and stimulates hypocotyl growth, suggesting a potential role for PCMs in connecting both biological processes. Abstract Plants possess a sophisticated immune system to protect themselves against pathogen attack. The defense hormone salicylic acid (SA) is an important player in the plant immune gene regulatory network. Using RNA-seq time series data of Arabidopsis thaliana leaves treated with SA, we identified a largely uncharacterized SA-responsive gene family of eight members that are all activated in response to various pathogens or their immune elicitors and encode small proteins with cysteine-rich transmembrane domains. Based on their nucleotide similarity and chromosomal position, the designated Pathogen-induced Cysteine-rich transMembrane protein (PCM) genes were subdivided into three subgroups consisting of PCM1-3 (subgroup I), PCM4-6 (subgroup II), and PCM7-8 (subgroup III). Of the PCM genes, only PCM4 (also known as PCC1) has previously been implicated in plant immunity. Transient expression assays in Nicotiana benthamiana indicated that most PCM proteins localize to the plasma membrane. Ectopic overexpression of the PCMs in Arabidopsis thaliana resulted in all eight cases in enhanced resistance against the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis Noco2. Additionally, overexpression of PCM subgroup I genes conferred enhanced resistance to the hemi-biotrophic bacterial pathogen Pseudomonas syringae pv. tomato DC3000. The PCM-overexpression lines were found to be also affected in the expression of genes related to light signaling and development, and accordingly, PCM-overexpressing seedlings displayed elongated hypocotyl growth. These results point to a function of PCMs in both disease resistance and photomorphogenesis, connecting both biological processes, possibly via effects on membrane structure or activity of interacting proteins at the plasma membrane.

Rheology of hydrocarbon gels

1950 ◽  
Vol 200 (1061) ◽  
pp. 183-188 ◽  
Keyword(s):  
Mechanical Properties ◽  
Experimental Measurement ◽  
Theoretical Basis ◽  
Continuous Media ◽  
Point Of View ◽  
Coarse Grained ◽  
Testing Instrument ◽  
Fine Grained ◽  
Mineral Oils ◽  
Space And Time

Hydrocarbon gels contain a number of materials, such as rubber, greases, saponified mineral oils, etc., of great interest for various engineering purposes. Specific requirements in mechanical properties have been met by producing gels in appropriately chosen patterns of constituent components of visible, colloidal, molecular and atomic sizes, ranging from coarse-grained aggregates, represented by sponges, foams, emulsions, etc.; to fine-grained and apparently homogeneous ones, represented by optically clear compounds. The engineer who has to deal with the whole range of such materials will adopt a macroscopic point of view, based on an apparent continuity of all the material structures and of the distributions in space and time of the displacements and forces occurring under mechanical actions. It has been possible to determine these distributions in the framework of a comprehensive scheme in which the fundamental principles of the mechanics of continuous media provide the theoretical basis, and a testing instrument of new design, termed Rheogoniometer, the means of experimental measurement (Weissenberg 1931, 1934, 1946, 1947, 1948).

A Nanoindentation Method for Hydrated Compliant Materials

2011 ◽  
Author(s):  
Donna M. Ebenstein
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Adhesion Forces ◽  
Surface Detection ◽  
Heterogeneous Samples ◽  
Mineralized Tissues ◽  
Fluid Interactions

Nanoindentation is becoming an increasingly popular tool in the biomaterials field due to its ability to measure local mechanical properties in small, irregularly-shaped or heterogeneous samples.1 Although this technique was readily adapted to the study of mineralized tissues, the application of nanoindentation to compliant, hydrated biomaterials such as soft tissues and hydrogels has led to many challenges.1 Three key concerns associated with nanoindentation of compliant, hydrated materials are inaccurate surface detection, errors due to adhesion forces, and fluid interactions with the tip.1–4

Mechanical Properties of Epoxy Adhesive Under Thermal Aging and Their Chemical Degradation Behavior

2021 ◽  
Vol 21 (8) ◽  
pp. 4444-4449
Author(s):  
Bongjin Chung ◽  
Shin Sungchul ◽  
Jaeho Shim ◽  
Seongwoo Ryu
Keyword(s):  
Mechanical Properties ◽  
Thermal Aging ◽  
Photoelectron Spectroscopy ◽  
Thermal Exposure ◽  
Chain Scission ◽  
Epoxy Adhesive ◽  
Chemical Degradation ◽  
Adhesive Properties ◽  
Noticeable Reduction

Epoxy adhesive was analyzed under long term thermal aging and mechanical properties and chemical degradation were observed by X-ray photoelectron spectroscopy (XPS). Long term thermal exposure of epoxy causes a noticeable reduction in adhesive properties. We developed a predictive model of temperature and time dependent aging. The temperature dependent aging behavior of epoxy adhesive shows good agreement with conventional Arrhenius equations. Using XPS analysis, we also discovered a correlation between chemical degradation and the adhesive properties. Decay of C–C bonding ratio induced chain-scission of epoxy adhesive; increase of total numbers of C–O and C═O induced oxidation of epoxy adhesive during thermal exposure.

scholarly journals Copper Containing Glass-Based Bone Adhesives for Orthopaedic Applications: Glass Characterization and Advanced Mechanical Evaluation

2020 ◽  
Author(s):  
Sahar. Mokhtari ◽  
Anthony.W. Wren
Keyword(s):  
Mechanical Properties ◽  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Viscoelastic Behavior ◽  
Polymer Chains ◽  
Nano Particles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compression Data

AbstractThis study addresses issues with currently used bone adhesives, by producing novel glass based skeletal adhesives through modification of the base glass composition to include copper (Cu) and by characterizing each glass with respect to structural changes. Bioactive glasses have found applications in fields such as orthopedics and dentistry, where they have been utilized for the restoration of bone and teeth. The present work outlines the formation of flexible organic-inorganic polyacrylic acid (PAA) – glass hybrids, commercial forms are known as glass ionomer cements (GICs). Initial stages of this research will involve characterization of the Cu-glasses, significant to evaluate the properties of the resulting adhesives. Scanning electron microscopy (SEM) of annealed Cu glasses indicates the presence of partial crystallization in the glass. The structural analysis of the glass using Raman suggests the formation of CuO nanocrystals on the surface. X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS) further confirmed the formation of crystalline CuO phases on the surface of the annealed Cu-glass. The setting reaction was studied using Fourier transform infrared spectroscopy (ATR-FTIR). The mechanical properties of the Cu containing adhesives exhibited gel viscoelastic behavior and enhanced mechanical properties when compared to the control composition. Compression data indicated the Cu glass adhesives were efficient at energy dissipation due to the reversible interactions between CuO nano particles and PAA polymer chains.

Mechanical Properties of Fired-Clay Brick Masonry Models in Moist and Dry Conditions

2014 ◽  
Vol 624 ◽  
pp. 307-312 ◽  
Author(s):  
Cristina Gentilini ◽  
Elisa Franzoni ◽  
Gabriela Graziani ◽  
Simone Bandini
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Point Of View ◽  
Shear Behaviour ◽  
Masonry Buildings ◽  
Masonry Structures ◽  
Clay Brick ◽  
Clay Bricks ◽  
Dry Conditions ◽  
Rising Damp

Rising damp is one of the main issues affecting masonry buildings. However, its consequences on the mechanical performance of masonry structures are not so largely explored. In this paper, the compressive and shear behaviour of masonry triplets, manufactured with solid fired-clay bricks and cement-based mortar, is investigated in dry and moist conditions. The results are interpreted on the basis of the features of the single materials, from both a mechanical and microstructural point of view.

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