The Impact of Surface Charge on the Mechanical Behavior of High-Porosity Chalk

Abstract Background After the golden age of antibiotic discovery, bacterial infections still represent a major challenge for public health worldwide. The biofilm mode of growth is mostly responsible for chronic infections that current therapeutics fail to cure and it is well-established that novel strategies must be investigated. Particulate drug delivery systems are considered as a promising strategy to face issues related to antibiotic treatments in a biofilm context. Particularly, poly-lactic acid (PLA) nanoparticles present a great interest due to their ability to migrate into biofilms thanks to their submicronic size. However, questions still remain unresolved about their mode of action in biofilms depending on their surface properties. In the current study, we have investigated the impact of their surface charge, firstly on their behavior within a bacterial biofilm, and secondly on the antibiotic delivery and the treatment efficacy. Results Rifampicin-loaded PLA nanoparticles were synthetized by nanoprecipitation and characterized. A high and superficial loading of rifampicin, confirmed by an in silico simulation, enabled to deliver effective antibiotic doses with a two-phase release, appropriate for biofilm-associated treatments. These nanoparticles were functionalized with poly-l-lysine, a cationic peptide, by surface coating inducing charge reversal without altering the other physicochemical properties of these particles. Positively charged nanoparticles were able to interact stronger than negative ones with Staphylococcus aureus, under planktonic and biofilm modes of growth, leading to a slowed particle migration in the biofilm thickness and to an improved retention of these cationic particles in biofilms. While rifampicin was totally ineffective in biofilms after washing, the increased retention capacity of poly-l-lysine-coated rifampicin-loaded PLA nanoparticles has been associated with a better antibiotic efficacy than uncoated negatively charged ones. Conclusions Correlating the carrier retention capacity in biofilms with the treatment efficacy, positively charged rifampicin-loaded PLA nanoparticles are therefore proposed as an adapted and promising approach to improve antibiotic delivery in S. aureus biofilms.

Download Full-text

The effect of the outlet angle β2 on the thermomechanical behavior of a centrifugal compressor blade

Journal of the Mechanical Behavior of Materials ◽

10.1515/jmbm-2020-0001 ◽

2020 ◽

Vol 29 (1) ◽

pp. 1-8

Author(s):

Ahmed Allali ◽

Sadia Belbachir ◽

Ahmed Alami ◽

Belhadj Boucham ◽

Abdelkader Lousdad

Keyword(s):

Mechanical Behavior ◽

Centrifugal Compressor ◽

Three Dimensional ◽

Complex Form ◽

Compressor Blade ◽

Stress Fields ◽

The Finite Element Method ◽

Mechanical Fatigue ◽

Outlet Angle ◽

The Impact

AbstractThe objective of this work lies in the three-dimensional study of the thermo mechanical behavior of a blade of a centrifugal compressor. Numerical modeling is performed on the computational code "ABAQUS" based on the finite element method. The aim is to study the impact of the change of types of blades, which are defined as a function of wheel output angle β2, on the stress fields and displacements coupled with the variation of the temperature.This coupling defines in a realistic way the thermo mechanical behavior of the blade where one can note the important concentrations of stresses and displacements in the different zones of its complex form as well as the effects at the edges. It will then be possible to prevent damage and cracks in the blades of the centrifugal compressor leading to its failure which can be caused by the thermal or mechanical fatigue of the material with which the wheel is manufactured.

Download Full-text

Airflow Characteristics According to the Change in the Height and Porous Rate of Building Roofs for Efficient Installation of Small Wind Power Generators

Sustainability ◽

10.3390/su13105688 ◽

2021 ◽

Vol 13 (10) ◽

pp. 5688

Author(s):

Jangyoul You ◽

Kipyo You ◽

Minwoo Park ◽

Changhee Lee

Keyword(s):

Wind Speed ◽

Wind Power ◽

Turbulence Intensity ◽

Flow Characteristics ◽

High Porosity ◽

Power Generators ◽

Speed Reduction ◽

Reduction Effect ◽

Wind Power Generators ◽

The Impact

In this paper, the air flow characteristics and the impact of wind power generators were analyzed according to the porosity and height of the parapet installed in the rooftop layer. The wind speed at the top was decreasing as the parapet was installed. However, the wind speed reduction effect was decreasing as the porosity rate increased. In addition, the increase in porosity significantly reduced turbulence intensity and reduced it by up to 40% compared to no railing. In the case of parapets with sufficient porosity, the effect of reducing turbulence intensity was also increased as the height increased. Therefore, it was confirmed that sufficient parapet height and high porosity reduce the effect of reducing wind speed by parapets and significantly reducing the turbulence intensity, which can provide homogeneous wind speed during installation of wind power generators.

Download Full-text

Numerical analysis of the mechanical behavior of the impact-damaged RC beams strengthened with CFRP

Composite Structures ◽

10.1016/j.compstruct.2021.114353 ◽

2021 ◽

pp. 114353

Author(s):

Liu Jin ◽

Yuchang Lan ◽

Renbo Zhang ◽

Xiuli Du

Keyword(s):

Numerical Analysis ◽

Mechanical Behavior ◽

Rc Beams ◽

The Impact

Download Full-text

Modeling the Large Deformation and Microstructure Evolution of Nonwoven Polymer Fiber Networks

Journal of Applied Mechanics ◽

10.1115/1.4041677 ◽

2018 ◽

Vol 86 (1) ◽

Cited By ~ 6

Author(s):

Mang Zhang ◽

Yuli Chen ◽

Fu-pen Chiang ◽

Pelagia Irene Gouma ◽

Lifeng Wang

Keyword(s):

Mechanical Properties ◽

Aspect Ratio ◽

Mechanical Behavior ◽

Large Deformation ◽

Biological Tissues ◽

High Porosity ◽

Polymer Fiber ◽

Fiber Networks ◽

Fiber Aspect Ratio ◽

Network Microstructure

The electrospinning process enables the fabrication of randomly distributed nonwoven polymer fiber networks with high surface area and high porosity, making them ideal candidates for multifunctional materials. The mechanics of nonwoven networks has been well established for elastic deformations. However, the mechanical properties of the polymer fibrous networks with large deformation are largely unexplored, while understanding their elastic and plastic mechanical properties at different fiber volume fractions, fiber aspect ratio, and constituent material properties is essential in the design of various polymer fibrous networks. In this paper, a representative volume element (RVE) based finite element model with long fibers is developed to emulate the randomly distributed nonwoven fibrous network microstructure, enabling us to systematically investigate the mechanics and large deformation behavior of random nonwoven networks. The results show that the network volume fraction, the fiber aspect ratio, and the fiber curliness have significant influences on the effective stiffness, effective yield strength, and the postyield behavior of the resulting fiber mats under both tension and shear loads. This study reveals the relation between the macroscopic mechanical behavior and the local randomly distributed network microstructure deformation mechanism of the nonwoven fiber network. The model presented here can also be applied to capture the mechanical behavior of other complex nonwoven network systems, like carbon nanotube networks, biological tissues, and artificial engineering networks.

Download Full-text

Comparison of Mechanical Behavior and Acoustic Emission Characteristics of Three Thermally-Damaged Rocks

Energies ◽

10.3390/en11092350 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2350 ◽

Cited By ~ 11

Author(s):

Jun Peng ◽

Sheng-Qi Yang

Keyword(s):

Mechanical Properties ◽

Acoustic Emission ◽

Mechanical Behavior ◽

Thermal Damage ◽

Strain Curve ◽

Treatment Temperature ◽

P Wave ◽

High Temperature Treatment ◽

High Porosity ◽

Compression Tests

High temperature treatment has a significant influence on the mechanical behavior and the associated microcracking characteristic of rocks. A good understanding of the thermal damage effects on rock behavior is helpful for design and stability evaluation of engineering structures in the geothermal field. This paper studies the mechanical behavior and the acoustic emission (AE) characteristic of three typical rocks (i.e., sedimentary, metamorphic, and igneous), with an emphasis on how the difference in rock type (i.e., porosity and mineralogical composition) affects the rock behavior in response to thermal damage. Compression tests are carried out on rock specimens which are thermally damaged and AE monitoring is conducted during the compression tests. The mechanical properties including P-wave velocity, compressive strength, and Young’s modulus for the three rocks are found to generally show a decreasing trend as the temperature applied to the rock increases. However, these mechanical properties for quartz sandstone first increase to a certain extent and then decrease as the treatment temperature increases, which is mainly attributed to the high porosity of quartz sandstone. The results obtained from stress–strain curve, failure mode, and AE characteristic also show that the failure of quartz-rich rock (i.e., quartz sandstone and granite) is more brittle when compared with that of calcite-rich rock (i.e., marble). However, the ductility is enhanced to some extent as the treatment temperature increases for all the three examined rocks. Due to high brittleness of quartz sandstone and granite, more AE activities can be detected during loading and the recorded AE activities mostly accumulate when the stress approaches the peak strength, which is quite different from the results of marble.

Download Full-text

Investigation on Mechanical Properties of Fibreglass Reinforced Flexible Pipes Under Torsion

Volume 7B: Ocean Engineering ◽

10.1115/omae2018-77354 ◽

2018 ◽

Cited By ~ 2

Author(s):

Pan Fang ◽

Yuxin Xu ◽

Shuai Yuan ◽

Yong Bai ◽

Peng Cheng

Keyword(s):

Mechanical Behavior ◽

Torsion Angle ◽

Experimental Studies ◽

Three Dimensional ◽

Load Condition ◽

Element Model ◽

Flexible Pipe ◽

Torsional Load ◽

Flexible Pipes ◽

The Impact

Fibreglass reinforced flexible pipe (FRFP) is regarded as a great alternative to many bonded flexible pipes in the field of oil or gas transportation in shallow water. This paper describes an analysis of the mechanical behavior of FRFP under torsion. The mechanical behavior of FRFP subjected to pure torsion was investigated by experimental, analytical and numerical methods. Firstly, this paper presents experimental studies of three 10-layer FRFP subjected to torsional load. Torque-torsion angle relations were recorded during this test. Then, a theoretical model based on three-dimensional (3D) anisotropic elasticity theory was proposed to study the mechanical behavior of FRFP. In addition, a finite element model (FEM) including reinforced layers and PE layers was used to simulate the torsional load condition in ABAQUS. Torque-torsion angle relations obtained from these three methods agree well with each other, which illustrates the accuracy and reliability of the analytical model and FEM. The impact of fibreglass winding angle, thickness of reinforced layers and radius-thickness ratio were also studied. Conclusions obtained from this research may be of great practicality to manufacturing engineers.

Download Full-text

Effects of Co-Culture of Graphene Oxide Scaffolds with Different Concentrations and Umbilical Mesenchymal Stem Cells on the Proliferation and Differentiation of Stem Cells

10.21203/rs.3.rs-164379/v1 ◽

2021 ◽

Author(s):

Aifeng Liu ◽

Jixin Chen ◽

Shuwei Gong ◽

Qiang Wei ◽

Ye Yuan

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Graphene Oxide ◽

Stem Cell ◽

Mesenchymal Stem Cell ◽

Umbilical Cord ◽

High Porosity ◽

Proliferation And Differentiation ◽

Scaffold Materials ◽

The Impact

Abstract The main role of the scaffold materials is to enable cells to survive in the scaffold binding as while as to further promote their proliferation and differentiation ability. For mesenchymal stem cell, the scaffold could provide an environment for them to maintain their phenotype, and synthesize all necessary molecules and proteins. Generally, scaffold materials for stem cell need to possess basic characteristics such as high porosity, large surface area, surface rigidity and biodegradability. Thus, the two-dimensional graphene oxide (GO) with oxygen-containing functional groups may be suitable scaffold materials for mesenchymal stem cell culture.MethodsIn this study, the effect of GO on the value-added differentiation activity of mesenchymal stem cell was systematically investigated. ResultsIt was found that low concentration of GO and sufficient concentration of umbilical cord mesenchymal stem cells are suitable for the second Co-culture. Furthermore, the addition of hyaluronic acid will make this culture more evenly distributed. ConclusionsThe adsorption of GO on umbilical cord mesenchymal stem cells can also make the two closely linked, which avoids the impact of animal joint activities on cells.

Download Full-text

Mechanical Behavior of Heat Activated Film Adhesives

10.1115/ipack2021-69719 ◽

2021 ◽

Author(s):

Prabhat Janamanchi ◽

Abhijit Dasgupta ◽

Narendra Singh

Keyword(s):

Mechanical Behavior ◽

Thermal Exposure ◽

Melting Transition ◽

Preliminary Evaluation ◽

Curing Conditions ◽

Structural Applications ◽

History Of ◽

Favorable Conditions ◽

The Impact ◽

Curing Age

Abstract Heat activated film (HAF) adhesives enable the bonding of materials that are difficult to bond with conventional adhesives where one of the substrates is flexible. Although they are traditionally found in the context of industrial and structural applications, they are increasingly finding use in in electronic products. This paper provides a preliminary evaluation of the mechanical behavior of HAFs. Two commercial polyurethane HAF formulations (designated as HAF-II and HAF-III, for the purpose of this paper) were evaluated to assess the dependence of the mechanical properties on phase transitions and on the thermal exposure history of the material. Both factors were found to play a significant role in determining the overall usability of the materials. The melting transition occurs under 50°C for both materials, after which their stiffness drops significantly. Among the two, HAF-III is preferable as it undergoes a delayed melting transition, effectively extending the usable operating temperature range. As with any adhesive, there are several other factors that can influence the performance of adhesives such as post-curing age, storage, and curing conditions to name a few. The impact of these factors on the material’s strength is also discussed in brief and a recommendation for favorable conditions is provided.

Download Full-text

Impact of Mine Panel Size on Hydraulic Permeability of Weakly Cemented Strata

Sustainability ◽

10.3390/su12062396 ◽

2020 ◽

Vol 12 (6) ◽

pp. 2396

Author(s):

Gangwei Fan ◽

Shizhong Zhang ◽

Bobo Cao ◽

Dongsheng Zhang ◽

Chengguo Zhang

Keyword(s):

Coal Mine ◽

Design Method ◽

Maximum Flow ◽

Mining Operation ◽

Hydraulic Permeability ◽

Optimal Size ◽

High Porosity ◽

Panel Size ◽

The Impact ◽

Overlying Strata

The effect of underground coal mining on groundwater, ranging from minimal to severe depending on the mined-out panel size, is primarily associated with the change in ground hydraulic permeability. This paper presents a novel panel design method, taking consideration of reducing water loss during the mining operation, which is based on evaluating and ranking the impact of panel size on the hydraulic permeability of weakly cemented strata. The permeability test results of weakly cemented rock samples collected in the Yili No.4 Coal Mine in Xinjiang, China strongly indicates that, in contrast to common rock, their post-peak permeability during the total stress–strain process is lower than the initial permeability due to high porosity and the presence of clay minerals. A numerical modeling based on strain–permeability functions reveals that the post-mining permeability distribution in the weakly cemented overlying strata could be subdivided into three zones: the permeability reduction zone, the permeability restoring zone, and the permeability high-increment zone. The impact significance of different size factors on the post-mining permeability of overlying strata can be ranked in decreasing order as follows: mining height, panel width, and panel length, the quantification of which was based on the variance analysis of such indices as maximum pore pressure and maximum flow velocity. Based on the above findings, the optimal size of panel 21103 in the Yili No.4 Coal Mine was determined and validated by water level field observations.

Download Full-text