scholarly journals Mechanical Properties of Weathered Feldspar Sandstone after Experiencing Dry-Wet Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Wen-bo An ◽  
Laigui Wang ◽  
He Chen
Keyword(s):  
Mechanical Properties ◽  
Salt Crystallization ◽  
Salt Rock ◽  
Rock Interaction ◽  
Maximum Variation ◽  
Group A ◽  
Yungang Grottoes ◽  
Group B ◽  
Water Swelling ◽  
Water Rock Interaction

Weathering is one of the important geological hazards to many stone cultural relics carved on feldspar sandstone (such as the Datong Yungang Grottoes). To study the mechanical properties of the weathered Yungang Grottoes, feldspar sandstone was subjected to comparative dry-wet cycle tests with water-rock interaction (Group A) and salt-rock interaction (Group B). The variation patterns of the macroscopic physical and mechanical parameters as well as the micro/mesoscopic structures of the two groups of feldspar sandstone with the number of dry-wet cycles were measured. The results showed that for the Group A and Group B sandstones, as the number of dry-wet cycles increased the saturated water absorption and the longitudinal wave velocity increased, with the maximum variation rates reaching 28.02%, 36.98%, 16.20%, and 33.27%. The peak strength and elastic modulus gradually decreased, with the maximum variation rate reaching 48.53%, 73.44%, 26.61%, and 72.39%. The surface height deviation increased by as much as 1.06 μm and 3.34 μm. The mechanism of weathering for the water-rock interaction included three effects, namely, the hydrolysis of the K-Na feldspar, the water swelling of the clay minerals such as kaolinite, and the dissolution of the soluble minerals. The mechanism of weathering for the salt-rock interaction included salt crystallization in the pores or fissures and chemical reactions between the minerals (such as feldspar and calcite) and sulfate, in addition to the above three effects. Therefore, the crystallization stress of the salt exerted the most notable effect on the deterioration of the feldspar sandstone. The results are expected to provide a reference for the stability evaluation and protection of the rock mass of the Grottoes.

A Study of Mechanical Properties of Human Femoral Heads Using Nanoindentation

2010 ◽  
Vol 126-128 ◽  
pp. 957-962 ◽  
Author(s):  
Chih Ling Lin ◽  
Han Huang ◽  
Bronwen W. Cribb ◽  
Anthony Russell
Keyword(s):  
Mechanical Properties ◽  
Replacement Surgery ◽  
Hip Replacement Surgery ◽  
Reduced Modulus ◽  
Significant Difference ◽  
Femoral Heads ◽  
Group A ◽  
Trabecular Bones ◽  
Male Patients ◽  
Group B

Human bone fracture associated with osteoporosis was hypothesized to be related to the alteration of mechanical properties in bones. In this work, cortical and trabecular bones from human femoral heads were studied. Bone samples of eight female and four male patients, with ages varying from 37 to 93 years, were collected from total hip replacement surgery. Reduced modulus (Er) and hardness (H) of osteons, interstitial lamellae and trabeculae were characterized by nanoindentation. The results showed both the reduced modulus and hardness of the interstitial lamellae were significant higher than those of osteons and trabeculae. Though there was no significant difference in microstructures in the Group A (age < 60 years) and B (age > 60 years), the Group B bones demonstrated to be stiffer.

scholarly journals Effect of Dry-Wet Cycling on the Mechanical Properties of Rocks: A Laboratory-Scale Experimental Study

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 199 ◽  
Author(s):  
Xiaojie Yang ◽  
Jiamin Wang ◽  
Dinggui Hou ◽  
Chun Zhu ◽  
Manchao He
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Open Pit ◽  
Rock Surface ◽  
Periodic Action ◽  
Rock Interaction ◽  
The Impact ◽  
Water Rock Interaction

Taking Nanfen open-pit iron mine in Liaoning Province as the engineering background, this study analyzes the effect of water-rock circulation on the mechanical properties of rock through a combination of macro-mechanical experiments and microstructure tests in the laboratory. Uniaxial compression experiments and acoustic wave tests are used to determine the degradation law of the mechanical properties of chlorite under the periodic action of water. The experimental results show that dry-wet cycles have a continuous and gradual effect on the rock sampled: Its uniaxial compressive strength, elastic modulus, and acoustic velocity all decrease gradually with an increase in the number of cycles. After 15 wet-dry cycles, the uniaxial compressive strength and elastic modulus of the rock decreased by 34.21% and 44.63%, respectively. Electron microscope scans of the rock indicate that the particle size, characteristics, and pore distribution at the rock surface had changed significantly after water-rock interaction. Finally, a drainage system and sliding force monitoring devices have been arranged at the mine site that can effectively reduce the impact of water-rock interaction on the stability of the mine. This combination of macro-experiments and micro-analysis allowed the weakening effect of dry-wet cycles on slope rock to be studied quantitatively, providing a theoretical reference for stability evaluation in geotechnical engineering.

scholarly journals Donor/Recipient Delta Age: A Possible Risk for Arterial Stenosis in Renal Transplantation

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Giovanni Pallotti ◽  
Gabriele Donati ◽  
Irene Capelli ◽  
Olga Baraldi ◽  
Giorgia Comai ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Retrospective Study ◽  
Renal Transplantation ◽  
Arterial Wall ◽  
Turbulent Fluxes ◽  
Arterial Stenosis ◽  
Age Difference ◽  
Wall Properties ◽  
Group A ◽  
Group B

Different arterial wall properties can significantly increase the risk of blood turbulent fluxes leading to complications such as atherosclerosis. Since the mechanical properties of arterial vessels are influenced by age, we investigated, in a retrospective study, the effects on renal artery stenosis of an age difference >15 years between donor and recipient in a cohort of 164 patients undergoing renal transplantation between 1981 and 1991. The age difference between donor and recipient was ≤15 years in 87 patients (53.0%) (Group A) and >15 years in 77 patients (47.0%) (Group B,p=ns). None of the Group A patients developed an anastomotic arterial stenosis, whereas 8/77 Group B patients (10.4%) had an anastomotic arterial stenosis (p<0.001). This study shows that an age difference >15 years is significantly linked to the risk of developing arterial stenosis after renal transplantation. Indeed, different wall properties can significantly increase the risk of generation of blood turbulent fluxes and involve, in the arterial vessels, the development of complications such as atherosclerosis.

Biomechanical changes of freezer-storaged and decellularized pig tracheal scaffoldings

2021 ◽  
pp. 088532822098566
Author(s):  
Jinping Wang ◽  
Haixiang Zhang ◽  
Yangmeng Feng ◽  
Yang Sun ◽  
Ruina Ma ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Testing Machine ◽  
Biomechanical Properties ◽  
Universal Testing ◽  
Significant Difference ◽  
Group A ◽  
Biomechanical Changes ◽  
Group B ◽  
Group D

Background As an excellent xenotransplant, the pig trachea can be decellularized and cryopreserved to reduce its immunogenicity. However, few reports are found on the changes of its mechanical properties after cryopreservation and decellularization. Objective To evaluate the structure and biomechanical properties in pig tracheal scaffolds resulting from decellularized and cryopreserved. Material and methods Twenty-five pig tracheal segments were separated into five groups: untreated (group A), only decellularized (group B), only cryopreserved (group C), decellularized after cryopreserved (group D) and cryopreserved after decellularized (group E). Tracheal segments were subjected to uniaxial tension or compression using a universal testing machine to determine structural biomechanical changes. Results It showed that there was no statistically significant difference in the tensile strength of the trachea in each group. The compressive strength of group B, C and D were same as the group A ( P > 0.05), while the group E was lower than that of the group A ( P < 0.05). Conclusions and significance: The histological examination of the decellularization after cryopreservation shows that the removal of epithelial cells and submucosal cells is more thorough, and the biomechanical structure of the trachea is better preserved. This proved to be a new method to prepare xenotransplantation of trachea graft.

scholarly journals Evaluating the Mechanical Properties, and Calcium and Fluoride Release of Glass-Ionomer Cement Modified with Chicken Eggshell Powder

2018 ◽  
Vol 6 (3) ◽  
pp. 40
Author(s):  
Gehan Allam ◽  
Ola Abd El-Geleel
Keyword(s):  
Mechanical Properties ◽  
Calcium Release ◽  
Glass Ionomer Cement ◽  
Fluoride Release ◽  
Glass Ionomer ◽  
Ion Release ◽  
Chicken Eggshell ◽  
Group A ◽  
Group B ◽  
Ionomer Cement

The aim of this study was to test the effect of adding chicken eggshell powder (CESP) to conventional glass-ionomer cement (GIC) on its mechanical properties, and fluoride and calcium release. CESP was added with proportions of 3% and 5% by weight to the powder component of conventional glass-ionomer cement. The specimens were categorized into group A: GIC without CESP; group B: GIC with 3% wt. CESP; and group C: GIC with 5% wt. CESP; there were 12 specimens in each group. Groups B and C showed higher compressive strength values compared to group A. However, microhardness scores were higher in group C compared to groups A and B. As for ion-release results, group B displayed the highest values of fluoride release followed by group C at both 7 and 30 days. Group C showed the highest amount of calcium release followed by both groups B and C at 7 days, while at 30 days, groups A and B showed higher calcium release compared to group C. The mechanical properties of conventional glass-ionomer restorative material were enhanced by the addition of CESP. Moreover, fluoride and calcium release were not compromised by adding CESP.

scholarly journals The Number of Platelets in Patient’s Blood Influences the Mechanical and Morphological Properties of PRP-Clot and Lysophosphatidic Acid Quantity in PRP

2019 ◽  
Vol 21 (1) ◽  
pp. 139 ◽  
Author(s):  
Michela Bosetti ◽  
Paolo Boffano ◽  
Alice Marchetti ◽  
Massimiliano Leigheb ◽  
Mattia Colli ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Regeneration ◽  
Lysophosphatidic Acid ◽  
Platelet Rich Plasma ◽  
Active Role ◽  
Morphological Properties ◽  
Before And After ◽  
Platelet Concentration ◽  
Group A ◽  
Group B

The objectives of this study were to compare platelet-rich plasma (PRP) from patients with different concentrations of platelets and to assess the influence of these PRP preparations on human osteoblast (hOB) activity. In the literature, growth factors released by activated platelets have been considered responsible for the active role of PRP on bone regeneration but no specific role has been attributed to lysophosphatidic acid (LPA) as a possible effector of biological responses. In this study, patients were grouped into either group A (poor in platelets) or group B (rich in platelets). Clots from PRP fraction 2 (F2-clots), obtained with CaCl2 activation of PRP from the two groups, were compared macroscopically and microscopically and for their mechanical properties before testing their activity on the proliferation and migration of hOB. LPA was quantified before and after PRP fractioning and activation. The fibrin network of F2-clots from patients with a lower platelet concentration had an organized structure with large and distinct fibers while F2-clots from patients in group B revealed a similar structure to those in group A but with a slight increase in density. ELISA results showed a significantly higher plasma level of LPA in patients with a higher platelet concentration (group B) in comparison to those in group A (p < 0.05). This different concentration was evidenced in PRP but not in the clots. Depending on the number of platelets in patient’s blood, a PRP-clot with higher or lower mechanical properties can be obtained. The higher level of LPA in PRP from patients richer in platelets should be considered as responsible for the higher hOB activity in bone regeneration.

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