scholarly journals Hierarchical Structure of the Cocos nucifera (Coconut) Endocarp: Functional Morphology and its Influence on Fracture Toughness

Molecules ◽  
2020 ◽  
Vol 25 (1) ◽  
pp. 223 ◽  
Author(s):  
Stefanie Schmier ◽  
Naoe Hosoda ◽  
Thomas Speck
Keyword(s):  
Fracture Toughness ◽  
Functional Morphology ◽  
Role Models ◽  
Imaging Techniques ◽  
Cocos Nucifera ◽  
Hierarchical Level ◽  
Special Focus ◽  
Toughening Mechanisms ◽  
Hierarchical Levels ◽  
Organ Level

In recent years, the biomimetic potential of lignified or partially lignified fruit pericarps has moved into focus. For the transfer of functional principles into biomimetic applications, a profound understanding of the structural composition of the role models is important. The aim of this study was to qualitatively analyze and visualize the functional morphology of the coconut endocarp on several hierarchical levels, and to use these findings for a more precise evaluation of the toughening mechanisms in the endocarp. Eight hierarchical levels of the ripe coconut fruit were identified using different imaging techniques, including light and scanning electron microscopy as well as micro-computer-tomography. These range from the organ level of the fruit (H0) to the molecular composition (H7) of the endocarp components. A special focus was laid on the hierarchical levels of the endocarp (H3–H6). This investigation confirmed that all hierarchical levels influence the crack development in different ways and thus contribute to the pronounced fracture toughness of the coconut endocarp. By providing relevant morphological parameters at each hierarchical level with the associated toughening mechanisms, this lays the basis for transferring those properties into biomimetic technical applications.

Analyzing the Russian tool-making industry within the sustainable development concept

2020 ◽  
Vol 16 (4) ◽  
pp. 662-677 ◽  
Author(s):  
T.N. Ryzhikova ◽  
V.G. Borovskii
Keyword(s):  
Sustainable Development ◽  
Hierarchical Level ◽  
Economic Systems ◽  
Resource Use Efficiency ◽  
The Sustainable Development ◽  
Case Methods ◽  
Hierarchical Levels ◽  
Use Efficiency ◽  
Intensive Development

Subject. The article explores the economic component of sustainable development through the classification of industries from the perspective of assigning the output goods to fixed or current assets, using different types of resources and assessing their condition. It considers factors of production affecting the achievement of the result and determining the development of economic systems at the meso- and micro-hierarchical level. Objectives. The aim is to assess the function of economic systems of different hierarchical levels on the tool-making facilities case. Methods. We apply an approach using general and special methods of comparative and statistical analysis, synthesis and analogies. Results. The paper analyzes the development of the Russian tool-making industry on the basis of resource-oriented approach to assess the functioning of economic systems at various levels. We review interrelations between resource use efficiency, types of sustainable development of economic systems at various hierarchical levels and strategic security of the country. Conclusions. Any development can be considered sustainable, if there is an increment in the intensive development of economic systems at all three levels.

scholarly journals In Vivo Imaging of Biodegradable Implants and Related Tissue Biomarkers

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2348
Author(s):  
Leon Riehakainen ◽  
Chiara Cavallini ◽  
Paolo Armanetti ◽  
Daniele Panetta ◽  
Davide Caramella ◽  
...  
Keyword(s):  
Imaging Modality ◽  
Imaging Techniques ◽  
Special Focus ◽  
Tissue Remodelling ◽  
Biodegradable Implant ◽  
Advantages And Disadvantages ◽  
Non Invasive ◽  
Positron Emission ◽  
Longitudinal Imaging

Non-invasive longitudinal imaging of osseointegration of bone implants is essential to ensure a comprehensive, physical and biochemical understanding of the processes related to a successful implant integration and its long-term clinical outcome. This study critically reviews the present imaging techniques that may play a role to assess the initial stability, bone quality and quantity, associated tissue remodelling dependent on implanted material, implantation site (surrounding tissues and placement depth), and biomarkers that may be targeted. An updated list of biodegradable implant materials that have been reported in the literature, from metal, polymer and ceramic categories, is provided with reference to the use of specific imaging modalities (computed tomography, positron emission tomography, ultrasound, photoacoustic and magnetic resonance imaging) suitable for longitudinal and non-invasive imaging in humans. The advantages and disadvantages of the single imaging modality are discussed with a special focus on preclinical imaging for biodegradable implant research. Indeed, the investigation of a new implant commonly requires histological examination, which is invasive and does not allow longitudinal studies, thus requiring a large number of animals for preclinical testing. For this reason, an update of the multimodal and multi-parametric imaging capabilities will be here presented with a specific focus on modern biomaterial research.

Alternative Family Structures: A Career Advantage?

1997 ◽  
Vol 81 (3) ◽  
pp. 812-814 ◽  
Author(s):  
Ronald J. Burke
Keyword(s):  
Professional Services ◽  
Hierarchical Level ◽  
Family Structures ◽  
Men And Women ◽  
Hierarchical Levels ◽  
Professional Services Firm

This research examined the presence of homemakers among spouses of men and women at four hierarchical levels within a single large professional services firm. Men at the most senior level were significantly more likely to have spouses as homemakers than were men at lower levels and women at any hierarchical level. Men were generally more likely than women to have spouses as homemakers, thus family structures may create potential career disadvantages for women.

scholarly journals Cracking and Toughening Mechanisms in Nanoscale Metallic Multilayer Films: A Brief Review

2018 ◽  
Vol 8 (10) ◽  
pp. 1821 ◽  
Author(s):  
Qing Zhou ◽  
Yue Ren ◽  
Yin Du ◽  
Dongpeng Hua ◽  
Weichao Han
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Plastic Instability ◽  
Multilayer Films ◽  
Fracture Mechanisms ◽  
Toughening Mechanisms ◽  
Individual Layer ◽  
Practical Applications ◽  
Mechanical Responses ◽  
The Individual

Nanoscale metallic multilayer films (NMMFs) have captured scientific interests on their mechanical responses. Compared with the properties of monolithic films, multilayers possess unique high strength as the individual layer thickness reduces to the nanoscale, which is benefited from the plentiful hetero-interfaces. However, NMMFs always exhibit a low fracture toughness and ductility, which seriously hinders their practical applications. While there have been reviews on the strengthening and deformation mechanisms of microlaminate, rapid developments in nanotechnology have brought an urgent requirement for an overview focused on the cracking and toughening mechanisms in nanoscale metallic multilayers. This article provides an extensive review on the structure, standard methodology and fracture mechanisms of NMMFs. A number of issues about the crack-related properties of NMMFs have been displayed, such as fracture toughness, wear resistance, adhesion energy, and plastic instability. Taken together, it is hoped that this review will achieve the following two purposes: (1) introducing the size-dependent cracking and toughness performance in NMMFs; and (2) offer a better understanding of the role interfaces displayed in toughening mechanisms. Finally, we list a few questions we concerned, which may shed light on further development.

scholarly journals Fracture Toughness Analysis of Epoxy-Recycled Rubber-Based Composite Reinforced with Graphene Nanoplatelets for Structural Applications in Automotive and Aeronautics

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 448 ◽  
Author(s):  
Alaeddin Burak Irez ◽  
Emin Bayraktar ◽  
Ibrahim Miskioglu
Keyword(s):  
Fracture Toughness ◽  
Building Materials ◽  
Bending Strength ◽  
Mechanical Test ◽  
Graphene Nanoplatelets ◽  
Test Results ◽  
Toughening Mechanisms ◽  
Structural Applications ◽  
Recycled Rubber ◽  
Cost Efficient

This study proposes a new design of lightweight and cost-efficient composite materials for the aeronautic industry utilizing recycled fresh scrap rubber, epoxy resin, and graphene nanoplatelets (GnPs). After manufacturing the composites, their bending strength and fracture characteristics were investigated by three-point bending (3PB) tests. Halpin–Tsai homogenization adapted to composites containing GnPs was used to estimate the moduli of the composites, and satisfactory agreement with the 3PB test results was observed. In addition, 3PB tests were simulated by finite element method incorporating the Halpin–Tsai homogenization, and the resulting stress–strain curves were compared with the experimental results. Mechanical test results showed that the reinforcement with GnPs generally increased the modulus of elasticity as well as the fracture toughness of these novel composites. Toughening mechanisms were evaluated by SEM fractography. The typical toughening mechanisms observed were crack deflection and cavity formation. Considering the advantageous effects of GnPs on these novel composites and cost efficiency gained by the use of recycled rubber, these composites have the potential to be used to manufacture various components in the automotive and aeronautic industries as well as smart building materials in civil engineering applications.

Al2O3/ZrO2 (Y2O3) PREPARED BY COMBUSTION SYNTHESIS UNDER HIGH GRAVITY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1148-1153 ◽  
Author(s):  
LONG ZHANG ◽  
ZHONGMIN ZHAO ◽  
YIGANG SONG ◽  
WEIGUO WANG ◽  
HONGBO LIU
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Combustion Synthesis ◽  
High Fracture Toughness ◽  
High Gravity ◽  
Transformation Toughening ◽  
Composite Ceramics ◽  
Directionally Solidified ◽  
High Fracture ◽  
Toughening Mechanisms

By introducing ZrO 2 (4 Y ) powder into the thermit, Al 2 O 3/ ZrO 2 (4 Y ) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al 2 O 3/33% ZrO 2 (4 Y ) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t - ZrO 2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t - ZrO 2 grains; meanwhile, Al 2 O 3/45% ZrO 2 (4 Y ) were comprised of spherically-shaped micron-meter t - ZrO 2 grains. Similar to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the increase in hardness and flexural strength of Al 2 O 3/33% ZrO 2 (4 Y ) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al 2 O 3/45% ZrO 2 (4 Y ) was considered to be a result of the fine spherically-shaped t - ZrO 2 grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.

scholarly journals Osteochondritis Dissecans: Etiology, Pathology, and Imaging with a Special Focus on the Knee Joint

Cartilage ◽  
2017 ◽  
Vol 9 (4) ◽  
pp. 346-362 ◽  
Author(s):  
Juergen Bruns ◽  
Mathias Werner ◽  
Christian Habermann
Keyword(s):  
Osteochondritis Dissecans ◽  
Clinical Symptoms ◽  
Imaging Techniques ◽  
Long Term Results ◽  
Special Focus ◽  
Low Grade ◽  
Aseptic Necrosis ◽  
Growth Plates ◽  
Open Growth Plates ◽  
Number Of Publications

This article is a review of the current understanding of the etiology, pathogenesis, and how to diagnose and treat knee osteochondritis dissecans (OCD) followed by an analysis of and outcomes of the treatments available. OCD is seen in children and adolescents with open growth plates (juvenile OCD) and adults with closed growth plates (adult OCD). The etiology of OCD lesions remains unclear and is characterized by an aseptic necrosis in the subchondral bone area. Mechanical factors seem to play an important role. Clinical symptoms are unspecific. Thus, imaging techniques are most important. Regarding treatment, a tremendous number of publications exist. Spontaneous healing is expected unless there is an unstable fragment, and treatment involves rest and different degrees of immobilization until healing. Patients with open physes and low-grade lesions have good results with conservative therapy. When surgery is necessary, the procedure depends on the stage and on the state of the cartilage. With intact cartilage, retrograde procedures are favorable. When the cartilage is damaged, several techniques can be used. While techniques such as drilling and microfracturing produce reparative cartilage, other techniques reconstruct the defect with additional osteochondral grafts or cell-based procedures such as chondrocyte transplantation. There is a tendency toward better results when using procedures that reconstruct the bone and the cartilage and there is also a trend toward better long-term results when comorbidities are treated. Severe grades of osteoarthrosis are rare.

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