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Arthur, Charles. « Fractured state ». Index on Censorship 24, no 4 (juillet 1995) : 13–14. http://dx.doi.org/10.1177/030642209502400404.
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Petersen, German. « Elites and Turnovers in Authoritarian Enclaves : Evidence from Mexico ». Latin American Politics and Society 60, no 2 (17 avril 2018) : 23–40. http://dx.doi.org/10.1017/lap.2018.4.
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AbstractThe year 2010 saw five gubernatorial elections in Mexico in which the PAN and the left built electoral alliances. These alliances were made in states with authoritarian features, where the PRI had never lost the governor’s office. In Oaxaca, Puebla, and Sinaloa the PRI lost, while in Durango and Hidalgo it did not. Why did the electoral outcome differ in similar cases? This article argues that the outcome of each election, turnover or no turnover, depended on the behavior of the elites, both authoritarian and opposition. The PRI lost when the authoritarian elite fractured while the opposition was unified, including the groups that had defected from the established elite.
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Pandey, Dr Aditiya Prakash. « Policies, Programs and Achievements of Ghulam Nabi Azad - led Coalition in Jammu & ; Kashmir ». International Journal for Research in Applied Science and Engineering Technology 9, no 8 (31 août 2021) : 1215–23. http://dx.doi.org/10.22214/ijraset.2021.37587.
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Abstract: The coalition government in Jammu and Kashmir during 2002 to 2008 helped build some kind of confidence in the electoral institutions and processes. Breaking the hegemony of the single dominant party also brought an alternative to the PDPCongress coalition power. PDP- Congress formed a coalition government after 2002 Assembly elections as no political party had won majority and it resulted in a fractured mandate. The coalition was significant in the sense that PDP had recently emerged as regional force, and it was its first game in elections as well as coalition politics. The coalition began very well on a good note. The coalition incorporated their election manifestoes with the basic issues which the people were facing. The PDP promised a corruption- free government, unconditional dialogue with militants, providing a healing touch and like. The present paper analyses the performance of PDP- Congress coalition led by Ghulam Nabi Azad. Keywords: Coalition, Jammu and Kashmir, Ghulam Nabi Azad, PDP-Congress.
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Pal, Michael. « The Fractured Right to Vote : Democracy, Discretion, and Designing Electoral Districts ». McGill Law Journal 61, no 2 (10 août 2016) : 231–74. http://dx.doi.org/10.7202/1037248ar.
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Electoral boundary commissions and Parliament have recently transformed Canada’s federal electoral map. The 2015 federal election was contested on a new map of 338 ridings, after 30 seats were added to the House of Commons by the Fair Representation Act and commissions set the boundaries of each district. The introduction of independent, non-partisan commissions in 1964 to draw the maps has achieved great success in eliminating the previously entrenched practice of gerrymandering. The extensive discretion granted to commissions to set boundaries, however, generates a new series of potential problems that can undermine the fairness of the electoral map. This article takes the new map as an opportune time to analyze the Canadian experience with electoral boundary commissions and, particularly, their exercise of discretionary authority. It demonstrates that the ten provincial commissions have adopted divergent approaches to their common task of establishing electoral boundaries. The commissions are at times in direct conflict with one another on the meaning and scope of fundamental principles of redistricting, such as representation by population, community of interest, and minority representation. These conflicting approaches have gone beyond reasonable disagreements over the specific content of the relevant legislative and constitutional principles. The exercise of the discretion held by the commissions in these competing ways has frustrated the principle of the political equality of all citizens. This article argues that the discretion granted to Canadian electoral boundary commissions should be restructured in order to better achieve a common realization of the right to vote.
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Kaewtathip, Kaewta, Varaporn Tanrattanakul et Thipthida Kaewtathip. « Preparation and Characterization of Thermoplastic Starch/Wheat Gluten Composites ». Key Engineering Materials 531-532 (décembre 2012) : 321–24. http://dx.doi.org/10.4028/www.scientific.net/kem.531-532.321.
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Thermoplastic starch (TPS) and TPS/wheat gluten composites were prepared using compression molding. The wheat gluten contents ranged from 0 wt% to 20 wt%. The morphology of the fractured surfaces, thermal decomposition temperatures and mechanical properties of the TPS and TPS/wheat gluten composites were investigated using scanning election microscopy (SEM), thermal gravimetric analysis (TGA) and tensile testing, respectively. The maximum tensile strength of TPS/wheat gluten composites (1.1 MPa) was obtained when 10 wt% of wheat gluten was used. The crosslinking between wheat gluten protein chains caused an increase in the tensile strength of the TPS/wheat gluten composites. The temperature at the maximum weight loss of the TPS/wheat gluten composites was higher than for TPS. Moreover, wheat gluten decreased the water absorption.
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Peou, Sorpong. « Interparty and Intraparty Factionalism in Cambodian Politics ». Journal of Current Southeast Asian Affairs 39, no 1 (avril 2020) : 17–38. http://dx.doi.org/10.1177/1868103420906023.
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Cambodia’s hegemonic party system that emerged after the violent removal of First Prime Minister Norodom Ranariddh early in July 1997 has now given way to a one-party state, which still remains prone to tension and instability. The party system has become less factionalised and can be characterised as moving from high to medium factionalism. This development resulted from the growing domination of the Cambodian People’s Party (CPP) and the weakening of the opposition parties, such as National United Front for an Independent, Netural, Peaceful and Cooperative Cambodia, which splintered and become almost irrelevant in Cambodian politics. The Cambodian National Rescue Party (CNRP) emerged as the main opposition party after the 2013 election but was then banned from competing in the 2018 election. Although the CNRP remains united by its anti-CPP position, it is still fractured along political lines between two former opposition parties – the Sam Rainsy Party and the Human Rights Party. Historical institutionalism sheds some new light on the variation of political developments among political parties and within them, but does not supplant the fact that party leaders are rational to the extent that they select strategies in pursuit of their interests defined as power or security under specific institutional constraints or the lack thereof.
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Singh, Archana, Ankita Singh, Rajul Vivek, T. P. Chaturvedi, Pankaj Chauhan et Shruti Gupta. « SEM Analysis and Management of Fracture Dental Implant ». Case Reports in Dentistry 2013 (2013) : 1–4. http://dx.doi.org/10.1155/2013/270385.
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Implant fracture is one of the important biomechanical complications which can present with a considerable problem to the patient as well as the dental surgeon. The aim of this case report is to describe the management of a case of fractured endosseous dental implant in premolar region and microscopic evaluation of the fractured implant segment using scanning electron microscopy. In most of such cases, complete removal of the fractured implant has been a preferred treatment option. In the present case, fractured implant segment was successfully removed and rehabilitated immediately with larger diameter implant. It was found that retrieved fracture segment had a diameter of 3.3 mm, and SEM analysis shows fatigue fractures which may be the result of excessive overloading and use of small diameter implant which enhances fatigue failure.
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Sbordone, Ludovico, Tonino Traini, Sergio Caputi, Antonio Scarano, Claudia Bortolaia et Adriano Piattelli. « Scanning Electron Microscopy Fractography Analysis of Fractured Hollow Implants ». Journal of Oral Implantology 36, no 2 (1 avril 2010) : 105–11. http://dx.doi.org/10.1563/aaid-joi-d-10-90000.
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Abstract Fracture of the implant is one of the possible complications affecting dental implants; it is a rare event but of great clinical relevance. The aim of the present study was to perform a scanning electron microscopy (SEM) fractography evaluation of 7 International Team for oral Implantology (ITI) hollow implants removed because of fracture. The most common clinical risk factors, such as malocclusion, bruxism, and cantilevers on the prosthesis, were absent. Seven fractured ITI hollow implants were retrieved from 5 patients and were analyzed with the use of SEM. SEM analysis showed typical signs of a cleavage-type fracture. Fractures could be due to an association of multiple factors such as fatigue, inner defects, material electrochemical problems, and tensocorrosion.
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Rainey, Mark Justin, et Steve Hanson. « The double return of Friedrich Engels : Towards a dialectics of the trace ». Human Geography 14, no 2 (7 mai 2021) : 264–74. http://dx.doi.org/10.1177/19427786211014680.
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Two sculptures of Friedrich Engels have recently been installed in Greater Manchester, the city where the social philosopher spent most of his working life and was the focus of his proto-ethnographic account of the early industrial city. The first sculpture is a fibreglass ‘fabricated ruin’ set within a newly rebuilt section of the University of Salford campus. The second is a former Soviet monument that was transported from eastern Ukraine to Tony Wilson Place, a new arts, business and entertainment space in central Manchester. While the appropriation of the city’s radical figures and movements is very much part of Manchester’s narrative of post-industrial regeneration, the ‘homecoming’ of Engels in the decade following the 2008 financial crash and amid the unfolding Brexit crisis raises certain methodological concerns for us. Engels is a figure who has returned and can be returned to. Here, his ‘double return’ can be read in very particular ways. In this paper, we bring Engels back to Manchester as a figure who will immediately re-signify against the contemporary political, economic and cultural landscape. In doing so, we advocate a dialectics of geographical traces that can grasp the social contradictions and fractures of the present in a way that works both within and beyond the writing and practice of Engels. As we move on from the 2019 UK General Election in which the Conservative party formed a substantial majority government into the fractured British landscapes of 2021 and beyond, this practice becomes increasingly necessary.
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Wanna, John. « A MOST PECULIAR IMPLOSION—THE AUSTRALIAN FEDERAL ELECTION SEPTEMBER 2013 : A CASE OF A FRACTURED GOVERNMENT THAT INFLICTED DEFEAT UPON ITSELF ». Representation 50, no 2 (3 avril 2014) : 271–81. http://dx.doi.org/10.1080/00344893.2014.934506.
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Barbosa, Jussara da Silva, Elisa Diniz de Lima, João Baptista Costa Agra de Melo, André Ulisses Dantas Batista, João Paulo Silva Neto, Herrison Félix Valeriano Silva, Thauany Vasconcelos Soares da Silva, Matheus Gonçalves de Assunção, Ana Maira Pereira Baggio et José Renato Cavalcanti Queiroz. « Fractographic analysis of two fractured removable partial denture metal frameworks ». Research, Society and Development 10, no 10 (4 août 2021) : e08101018370. http://dx.doi.org/10.33448/rsd-v10i10.18370.
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This study aimed to analyze two cases of fracture of the metal framework of Co-Cr-based removable partial dentures, using fractography to identify a true cause of these failures. The first case concerned the coupling between the smaller and larger connectors; the patient brought his fractured removable partial dentures to the clinic. The second case referred to a larger connector; structure of the patient fractured during the test. For failure analysis, images of two fractured metal frameworks were taken by scanning electron microscopy to identify the origin of the fracture and to determine the mechanisms involved in the process. Subsequently, energy dispersive X-ray spectroscopy was used for elemental chemical mapping of the fracture interface. The fractography indicated material fatigue as a possible cause in the first case and an error in the casting process in the second. The energy dispersive X-ray spectroscopy test, performed in the specimen of case B, showed predominant and characteristic peaks for Co and Cr, with a higher concentration of chromium. The fractures identified were associated with inclusions and with material fatigue and a number important characteristics were evidenced by the technique.
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Tribst, João Paulo Mendes, Arie Werner et Erik J. Blom. « Failed Dental Implant : When Titanium Fractures ». Diagnostics 13, no 12 (20 juin 2023) : 2123. http://dx.doi.org/10.3390/diagnostics13122123.
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Despite the widespread use of titanium implants in orthopedic and dental surgeries, concerns have recently emerged regarding potential deformations and fractures after osseointegration. In a recent clinical case, a titanium implant fractured after successful osseointegration. This fracture occurred despite the absence of any significant trauma or excessive external force applied to the area. The fracture was attributed to a combination of factors, including abutment design flaws, material fatigue, and biomechanical stress imposed on the implant during functional loading. This raises concerns about the long-term durability and reliability of titanium implants, particularly in high-stress areas such as the posterior region or weight-bearing bones. An image was made with scanning electron microscopy showing the fracture region near the prosthetic platform and highlighting the knowledge that despite their ductility, titanium implants can fracture.
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Tseronis, D., I. F. Sideris, C. Medrea et Ionel Chicinaş. « Microscopic Examination of the Fracture Surfaces of an H 13 Hot Extrusion Die due to Failure at the Initial Usage Stage ». Key Engineering Materials 367 (février 2008) : 177–84. http://dx.doi.org/10.4028/www.scientific.net/kem.367.177.
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This paper studies the fracture surfaces of an aluminium hot extrusion die that broke down during operation. The die was constructed, from H13 steel and was intended for the production of 60,000 Kg of aluminium profile. The male part fractured during operation after the production of 500 Kg profile. Initially, the machine and thermal treatments that were applied for construction of the die were collected and studied. The die was carefully inspected visually with a stereoscope. The fracture surfaces, some cracks, and the structure that was not affected by the failure, were investigated by optical microscopy. The thickness, quality and homogeneity of the nitrated layers were inspected. Additional information concerning the fracture was obtained by examining a primary crack using a scanning electron microscope and chemical analysis of the material was made using EDX attachment. The paper reports on some interesting observations relating to the fractured component, the type of the fractures, and the quality of the heat treatments, and presents some of the probable causes that led to the premature failure of the die.
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Marat-Mendes, Rosa, et Manuel de Freitas. « Fractographic Observation of Various Loading Modes of Fibre Reinforced Laminates ». Materials Science Forum 730-732 (novembre 2012) : 337–42. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.337.
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One of the major disadvantages of laminated composites is their tendency to delaminate. Unidirectional glass/epoxy laminates have been tested under static conditions by the use of fracture mechanics. Mode I, mode II, mixed mode I-II, mode III and mixed mode II-III tests were performed. Double cantilever beam (DCB), end-notched flexure (ENF), mixed-mode bending (MMB) and edge crack torsion (ECT) specimens were used. Scanning electron microscopy technique was used to identify distinguishing fractographic features and to establish the differences between the various modes of fracture after specimens testing. The propagated orientation of the delamination could be specified from the patterns of fracture surface. Scanning electron micrographs of fractured surfaces showed that the most predominant fractographic features in mode I and mode II are the large amount of fibre pull-out and the cusps markings respectively. In the MMB specimen the fracture surfaces are characterized by fibre breakage under shearing with fractures localized in the resin with cusps having an orientation of 90º (mode II) and also fractures localized in the resin and along the resin/fibre interface (mode I). Mode III characterization concluded that some limited mixed mode II-III seems to be present for ECT specimen on delamination initiation and growth, but a large majority of mode III delamination is present.
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Osenbrück, Karsten, Eva Blendinger, Carsten Leven, Hermann Rügner, Michael Finkel, Natalia Jakus, Hartmut Schulz et Peter Grathwohl. « Nitrate reduction potential of a fractured Middle Triassic carbonate aquifer in Southwest Germany ». Hydrogeology Journal 30, no 1 (7 décembre 2021) : 163–80. http://dx.doi.org/10.1007/s10040-021-02418-9.
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AbstractNitrate reduction constitutes an important natural mechanism to mitigate the widespread and persistent nitrate contamination of groundwater resources. In fractured aquifers, however, the abundance and accessibility of electron donors and their spatial correlation with groundwater flow paths are often poorly understood. In this study, the nitrate reduction potential of a fractured carbonate aquifer in the Upper Muschelkalk of SW Germany was investigated, where denitrification is due to the oxidation of ferrous iron and reduced sulfur. Petrographical analyses of rock samples revealed concentrations of syn-sedimentary and diagenetically formed pyrite ranging from 1 to 4 wt.% with only small differences between different facies types. Additional ferrous iron is available in saddle dolomites (up to 2.6 wt.%), which probably were formed by tectonically induced percolation of low-temperature hydrothermal fluids. Borehole logging at groundwater wells (flowmeter, video, gamma) indicates that most groundwater flow occurs along karstified bedding planes partly located within dolomites of the shoal and backshoal facies. The high porosity (15–30%) of these facies facilitates molecular diffusive exchange of solutes between flow paths in the fractures and the reactive minerals in the pore matrix. The high-porosity facies together with hydraulically active fractures featuring pyrite or saddle dolomite precipitates constitute the zones of highest nitrate reduction potential within the aquifer. Model-based estimates of electron acceptor/donor balances indicate that the nitrate reduction potential protecting water supply wells increases with increasing porosity of the rock matrix and decreases with increasing hydraulic conductivity (or effective fracture aperture) and spacing of the fracture network.
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Kantor, Matvey Matveevich, Konstantin Grigorievich Vorkachev, Vyacheslav Aleksandrovich Bozhenov et Konstantin Aleksandrovich Solntsev. « The Role of Splitting Phenomenon under Fracture of Low-Carbon Microalloyed X80 Pipeline Steels during Multiple Charpy Impact Tests ». Applied Mechanics 3, no 3 (24 juin 2022) : 740–56. http://dx.doi.org/10.3390/applmech3030044.
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The ambiguity of the splitting effect on X80 low-carbon microalloyed pipeline steels’ tendency towards brittle fracture prompted an experimental study of impact toughness scattering based on multiple Charpy impact tests in a temperature range from 20 °C to −100 °C. A fractographic analysis of a large number of fractured samples was carried out. The relationships between impact toughness, deformability and splitting characteristics were studied. A number of common features of three X80 low-carbon microalloyed pipeline steel fractures were revealed. It was experimentally established that the reason for the scattering of the impact toughness values during completely ductile fracture of specimens, as well as during fracture accompanied by the splitting formation, is the local inhomogeneity of plastic properties. The higher the susceptibility to the formation of splits for a particular steel, the lower the impact toughness. Using the electron backscatter diffraction (EBSD) technique, an uneven distribution of local plasticity in the plastic zone of impact-fractured specimens was established. A comparative analysis of specimens with equal impact toughness values at different test temperatures makes it possible to identify the mechanism of negative splitting influence compensation by the increased plasticity of certain specimen.
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Rana, Muhammad H., Sharaz Shaik, Mohammad S. Hameed, Samar Al-Saleh, Eman M. AlHamdan, Abdullah Alshahrani, Abdulaziz Alqahtani, Ahmed Heji Albaqawi, Fahim Vohra et Tariq Abduljabbar. « Influence of Dental Glass Fibers and Orthopedic Mesh on the Failure Loads of Polymethyl Methacrylate Denture Base Resin ». Polymers 13, no 16 (20 août 2021) : 2793. http://dx.doi.org/10.3390/polym13162793.
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The aim of the present study was to evaluate the fracture loads of polymethyl methacrylate (PMMA) complete denture bases reinforced with glass-fiber mesh and orthopedic casting tape (OCT) in comparison to conventional PMMA dentures under artificial aging. Dental fiberglass framework (Group 1) and OCT (Group 2 and 3) reinforced PMMA acrylic dentures were fabricated on the edentulous ridge. Ten PMMA dentures without reinforcement (Group 4) were included as controls. All specimens were placed in a chewing simulator chamber, and fatigue load was applied. To assess the fracture loads, static loads with a universal testing machine were applied. Fractured specimens in each group were evaluated under a scanning electron microscope. The data were statistically analyzed employing analysis of variance and Tukey post-hoc test. The association of denture weight and thickness on fracture load was assessed using Pearson and Spearman correlations. Dental fiberglass (Group 1) displayed the highest fracture load (692.33 ± 751.41 N), and Group 4 (control) exhibited the lowest fracture loads (281.41 ± 302.51 N). Dentures reinforced with fiberglass mesh framework exhibited intact fractures. In contrast, Group 2 and 3 specimens using OCT demonstrated ditching fractures. It was observed that the thickness and weight of all the reinforced specimens influenced the load required to fracture the dentures (p < 0.001). Denture specimens strengthened with OCT (Groups 2 and 3) exhibited failure loads lower than dental fiberglass (Group 1) specimens but higher than unreinforced controls.
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Kraus, Moritz, Carl Neuerburg, Nicole Thomasser, Ulla Cordula Stumpf, Matthias Blaschke, Werner Plötz, Maximilian Michael Saller, Wolfgang Böcker et Alexander Martin Keppler. « Reduced Awareness for Osteoporosis in Hip Fracture Patients Compared to Elderly Patients Undergoing Elective Hip Replacement ». Medicina 58, no 11 (31 octobre 2022) : 1564. http://dx.doi.org/10.3390/medicina58111564.
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Background: Osteoporotic fractures are associated with a loss of quality of life, but only few patients receive an appropriate therapy. Therefore, the present study aims to investigate the awareness of musculoskeletal patients to participate in osteoporosis assessment and to evaluate whether there are significant differences between acute care patients treated for major fractures of the hip compared to elective patients treated for hip joint replacement.; Methods: From May 2015 to December 2016 patients who were undergoing surgical treatment for proximal femur fracture or total hip replacement due to osteoarthritis and were at risk for an underlying osteoporosis (female > 60 and male > 70 years) were included in the study and asked to complete a questionnaire assessing the awareness for an underlying osteoporosis. ASA Score, FRAX Score, and demographic information have also been examined. Results: In total 268 patients (female = 194 (72.0%)/male = 74 (28%)), mean age 77.7 years (±7.7) undergoing hip surgery were included. Of these, 118 were treated for fracture-related etiology and 150 underwent total hip arthroplasty in an elective care setting. Patients were interviewed about their need for osteoporosis examination during hospitalization. Overall, 76 of 150 patients receiving elective care (50.7%) considered that an examination was necessary, whereas in proximal femur fracture patients the awareness was lower, and the disease osteoporosis was assessed as threatening by significantly fewer newly fractured patients. By comparison, patients undergoing trauma surgery had a considerably greater risk of developing another osteoporotic fracture than patients undergoing elective surgery determined by the FRAX® Score (p ≤ 0.001).; Conclusions: The patients’ motivation to endure additional osteoporosis diagnostic testing is notoriously low and needs to be increased. Patients who underwent acute care surgery for a fragility proximal femur fracture, although acutely affected by the potential consequences of underlying osteoporosis, showed lower awareness than the elective comparison population that was also on average 6.1 years younger. Although elective patients were younger and at a lower risk, they seemed to be much more willing to undergo further osteoporosis assessment. In order to better identify and care for patients at risk, interventions such as effective screening, early initiation of osteoporosis therapy in the inpatient setting and a fracture liaison service are important measures.
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Sippola, M., et K. Frühmann. « In situ Longitudinal Tensile Tests of Pine Wood in an Environmental Scanning Electron Microscope ». Holzforschung 56, no 6 (5 novembre 2002) : 669–75. http://dx.doi.org/10.1515/hf.2002.101.
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Summary To study wood fracture on its cellular level, small tensile specimens of pine (Pinus sylvestris [L.]) were fractured in situ in tension inside the chamber of an ESEM (Environmental Scanning Electron Microscope). Fractured surfaces of macroscopic tensile test specimens were also studied with an ESEM. The same kind of fracture phenomena were observed in both small and large specimens. The in situ tests proved to be reproducible and the results revealed typical fracture propagation0 directions and order in softwood under longitudinal tension. The gradual change of material properties of wood in the radial direction was found to strongly influence the fracture process.
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Martinez, A. M. B., et W. De Souza. « A quick-frozen, freeze-fracture and deep-etched study of the cuticle of adult forms of Strongyloides venezuelensis (Nematoda) ». Parasitology 111, no 4 (novembre 1995) : 523–29. http://dx.doi.org/10.1017/s0031182000066038.
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SUMMARYThe cuticle of adult forms of Strongyloides venezuelensis was studied by routine transmission electron microscopy, conventional freeze-fracture and also using quick-freeze and deep-etch techniques. In routine thin sections the cuticle of S. venezuelensis comprises 7 layers: epicuticle, outer cortical, inner corticcal, external medial, internal medial, fibrous and basal. Observation of replicas of specimens fractured across the thickness of the body wall, revealed at the epicuticle an ordered array of particles accompanying the cuticular annulations. At the level of the cortical and medial layers we observed few scattered particles embedded in an amorphous matrix without a particular arrangement. The fibrous layer was represented by several parallel lines of ordered particles of similar size. In tangentially fractured specimens, the epicuticle cleaves readily exposing 2 faces, one exhibiting intramembranous particles without any particular arrangement, immersed in a smooth matrix (P face), and the other showing depressions and very few particles (E face). In replicas of fractures submitted to etching, we observed at the level of the cortical, medial fibrous and basal layers an interconnecting fibrous and globous structure which was organized in a different direction at the fibrous layer. The association of freeze-fracture to deep-etch technique revealed the internal structural organization of the cuticle layers showing details that were not seen before using conventional freeze–fracture technique.
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Kan, Frederick W. K. « Applications of freeze-fracture cytochemistry as applied to the study of tissues and cells ». Proceedings, annual meeting, Electron Microscopy Society of America 45 (août 1987) : 1006–9. http://dx.doi.org/10.1017/s0424820100129280.
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The applications of freeze-fracture cytochemistry to the study of tissues and cells are described. Two approaches will be presented: label-fracture and fracture-label. In both techniques, colloidal gold probe is used as the marker system. The use of cytochemistry in combination with freeze-fracture for the study of distribution of receptor sites, antigens and glyco- conjugates on freeze-fractured plasma membranes as well as on fractured intracellular organelles is illustrated respectively by the two models described below. A variant of the fracture-label technique, Backscattered Electron Imaging of labeled tissues following freeze-fracture cytochemistry, is also introduced as a novel method for the 3-dimensional visualization of the in situ distribution of receptor sites on freeze-fractured membranes.1.Molecular demarcation of surface domains in boar spermatozoa as visualized by label-fracture cytochemistry.The label-fracture technique has been previously described. In brief, boar sperm cells are fixed, labeled and impregnated with glycerol.
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Beckett, A., et R. Porter. « The use of complementary fractures and low-temperature scanning electron microscopy to study hyphal – host cell surface adhesion between Uromyces viciae-fabae and Vicia faba ». Canadian Journal of Botany 66, no 4 (1 avril 1988) : 645–52. http://dx.doi.org/10.1139/b88-091.
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A modified specimen stub, for use with the EMscope SP2000 Sputter Cryo Preparation Unit, that will facilitate the production of complementary fracture faces is described. The application of complementary fractures for studying hypha–host surface adhesion within freeze-fractured leaves is reported for the first time. Freeze fracturing results in the rupture of either the hyphal wall or the host cell wall or both, at the edge of, or just beyond, the adhesive matrix pad that binds the two together. The implication that the adhesive is stronger than either of the two individual apposed walls is discussed in relation to the mechanics of bonding and to the process of penetration of the host cell by the fungus.
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Coble, D. W., et E. O. Kairinen. « A freeze fracture technique for examining human hair medulla with Scanning and Transmission Electron Microscopy ». Proceedings, annual meeting, Electron Microscopy Society of America 45 (août 1987) : 868–69. http://dx.doi.org/10.1017/s0424820100128626.
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Examination of hair medulla by transmission electron microscopy (TEM) is difficult because of the keratinous composition of hair and because of sectioning problems that result from insufficient infiltration and nonmiscibility of hair with embedding resins, even those of low viscosity. Although longitudinally cutting or tearing fibers will expose the medulla for embedment or direct viewing, considerable disruption occurs in its structure. Less disruption results from the use of freeze fracture techniques for either transmission or scanning electron microscopy (SEM).Freshly plucked human scalp and beard hairs were submersed in liquid nitrogen for a minimum of three minutes, held at proximal and distal ends with Dumont #10 tweezers, and slowly bent to an arc until the specimens broke at the apex. Customarily, clean bevelled fractures occurred along the tips of the arcs and exposed not only the medulla but also the cortex and cuticle. The fractured specimens were then removed from liquid nitrogen.
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Siddiqui, Rafiq Ahmed, Saeed Ali Al- Araimi et Ahmet Turgutlu. « Influence of Aging Conditions on Fatigue Fracture Behaviour of 6063 Aluminum Alloy ». Sultan Qaboos University Journal for Science [SQUJS] 6, no 1 (1 décembre 2001) : 53. http://dx.doi.org/10.24200/squjs.vol6iss1pp53-60.
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Aluminum - Magnesium - Silicon (Al-Mg-Si) 6063 alloy was heat-treated using under aged, peak aged and overage temperatures. The numbers of cycles required to cause the fatigue fracture, at constant stress, was considered as criteria for the fatigue resistance. Moreover, the fractured surface of the alloy at different aging conditions was evaluated by optical microscopy and the Scanning Electron Microscopy (SEM). The SEM micrographs confirmed the cleavage surfaces with well-defined fatigue striations. It has been observed that the various aging time and temperature of the 6063 Al-alloy, produces different modes of fractures. The most suitable age hardening time and temperature was found to be between 4 to 5 hours and to occur at 460 K. The increase in fatigue fracture property of the alloy due to aging could be attributed to a vacancy assisted diffusion mechanism or due to pinning of dislocations movement by the precipitates produced during aging. However, the decrease in the fatigue resistance, for the over aged alloys, might be due to the coalescence of precipitates into larger grains.
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JOYCE, T. J. « Analysis of the Mechanism of Fracture of Silicone Metacarpophalangeal Prostheses ». Journal of Hand Surgery (European Volume) 34, no 1 (20 octobre 2008) : 18–24. http://dx.doi.org/10.1177/1753193408093808.
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Eleven fractured Sutter metacarpophalangeal prostheses were obtained from the hands of three patients. All of the implants had fractured at the junction of the distal stem and the hinge. After visual examination, the fracture faces were prepared and viewed using a scanning electron microscope. These images indicated that fracture was initiated by abrasion on the dorsal aspect of the distal stem of the prostheses, close to the hinge. Crack propagation was shown to be due to a fatigue process. Once a crack started, its direction of travel could be followed, using topographical features common to engineering fracture analyses. Propagation was from radial to ulnar and from dorsal to palmar.
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Papahadjopoulos-Sternberg, B. « The Power of Freeze-Fracture Technique in Electron Microscopy ». Microscopy and Microanalysis 7, S2 (août 2001) : 1212–13. http://dx.doi.org/10.1017/s143192760003213x.
Texte intégralRésumé :
In the early 1960s, concerns about artifacts in preparing biological material for electron microscopy led to a new technique whereby samples are rapidly frozen, fractured under high vacuum, the fractured surfaces shadowed and replicated with a thin metal-carbon coat, and the cleaned replica examined in a transmission electron microscope. Pioneered by Moor and Muhlethaler subcellular structures are revealed with extraordinary three-dimensional clarity at near-molecular resolution. Furthermore, it was observed and proven at model systems as well as biological membranes that lipid bilayers split along their hydrophobic interior during freeze-fracture procedure. Therefore, freeze-fracture electron microscopy (FFEM) has the unique advantage of accessing the hydrophobic interior of biological (FIG.l, 5 and 6) as well as artificial bilayers (FIG. 2, 4, 5, and 6). Here it permits study of pattern generated by intrinsic proteins as well as lipids (FIG. 1 and 2).
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An, Qi, Chunyang Hong et Haitao Wen. « Fracture Patterns of Rocks Observed under Cryogenic Conditions Using Cryo-Scanning Electron Microscopy ». Processes 11, no 7 (7 juillet 2023) : 2038. http://dx.doi.org/10.3390/pr11072038.
Texte intégralRésumé :
Cryogenic fracturing, which uses liquid nitrogen (LN2) as a fracturing fluid, is a waterless fracturing method. However, previous attempts to investigate the fracture morphology of rocks after LN2 quenching have been mainly based on standard scanning electron microscopy (SEM) analysis at room temperature. This can be problematic since thermally-induced fractures created by temperature difference tend to close as a sample warms and thermal stress relaxes. To address this issue, we established a novel approach employing Cryo-scanning electron microscopy (Cryo-SEM) to investigate the fracture patterns induced by liquid nitrogen quenching under cryogenic conditions. This method can achieve in-situ visualization of fractures and pores with a nano-scale resolution at −190 °C. X-ray computed tomography (CT) is also employed to illustrate the fracture distribution inside samples. Cryo-SEM and standard SEM are compared, and statistical assessments are conducted to quantify fracture aperture size and closure scale. The results demonstrate that Cryo-SEM can more accurately preserve native fracture morphology and provide a more accurate means of evaluating fracture scales generated during LN2 quenching, particularly at higher temperature differences between rock and liquid nitrogen. Distinct fracture patterns and fracture width are observed for various rock types (i.e., coal, sandstone, shale, granite) by using these methods. More prominently, the maximum fracture width of coal, sandstone, shale and granite were 89.17 µm, 1.29 µm, 0.028 µm and 2.12 µm when the temperature difference between LN2 and rock samples were 296 °C. LN2 is shown to exhibit superior fracturing efficiency on coal and granite, characterized by complex fracture networks with branched fractures. This research contributes to our understanding of liquid nitrogen fracturing mechanisms and may offer effective approaches for unconventional reservoirs stimulation.
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Tian, Wen Tong, Xia Cao et Yi Li. « Microstructure and Properties of 7A04 Alloy Prepared by Thixo-Forging ». Advanced Materials Research 426 (janvier 2012) : 97–100. http://dx.doi.org/10.4028/www.scientific.net/amr.426.97.
Texte intégralRésumé :
The effect of thixo-forging process on morphologies of particles that affect fracture mode of 7A04 alloy was studied. Microstructure and fracture surfaces of thixo-forged samples were investigated by image analyzing technique and scanning electron microscopy. The analyses of the ruptured surface were conducted with specimens taken in-situ from ruptured surfaces of thixo-forged parts. It is suggested that samples fractured in an area with higher liquid fraction have superior mechanical properties, especially elongation, and consequently a failure type of inter-crystalline cracking could be the main fracture mechanism. On the contrary, samples fractured in an area with lower liquid fraction have inferior mechanical properties and the principal resistance force is created by the contacting solid particles, a failure type of trans-crystalline rupture could be the main fracture mechanism.
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Tatami, Junichi, Tomoko Ohbuchi, Katsutoshi Komeya et Takeshi Meguro. « Nanofractography of Alumina by Scanning Probe Microscopy ». Key Engineering Materials 290 (juillet 2005) : 70–77. http://dx.doi.org/10.4028/www.scientific.net/kem.290.70.
Texte intégralRésumé :
Observation of fracture surfaces in ceramics is useful for improving their mechanical properties. In this study, fracture surfaces of polycrystalline alumina were observed using scanning-probe microscopy (SPM) on a nanoscale, also called “nano-fractography.” The average grain size of polycrystalline alumina specimen used in this study was 4.5µm, and the fracture toughness was 3.0MPa･m-1/2. The fracture mode was found to be a mixture of intergranular and transgranular fractures. The fracture surface of intergranular fractures consisted of smooth and rough areas composed of very small steps, whose detection was impossible using scanning electron microscopy. Cleavage and non-cleavage fractures were observed in transgranular fracture grains. The fracture surface of single-crystalline alumina, which is the typical model of the transgranular fracture, was also observed by SPM. The cleavage plane of alumina macroscopically exhibited a very smooth, glass-like surface. However, sub-nano meter steps can be observed on the cleavage fracture surface and appear to be formed by plastic deformation during crack propagation because the size of the step nears that of the Burgers vector.
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Chen, Le. « Failure Analysis of Oil Pipe Fracture in Steam Turbine Oil Supply System of Power Plant ». Journal of Physics : Conference Series 2390, no 1 (1 décembre 2022) : 012063. http://dx.doi.org/10.1088/1742-6596/2390/1/012063.
Texte intégralRésumé :
Abstract Oil pipe fracture of the steam turbine oil supply system of a thermal power plant is carried out by macro inspection, spectral analysis, metallographic analysis, hardness analysis, and scanning electron microscope analysis. The results show that the fractured tubing is a fatigue fracture, and the source of the crack is the fatigue crack formed by the stress concentration of the weld, which eventually leads to the fracture and leakage at the place.
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Niño-Barrera, Javier, José Sánchez-Alemán, Luis Gamboa-Martinez et Carlos Cortes-Rodriguez. « Resistance to fracture due to cyclic fatigue of stainless steel manual files and its association to surface roughness ». Acta Odontológica Latinoamericana 34, no 1 (avril 2021) : 18–26. http://dx.doi.org/10.54589/aol.34/1/018.
Texte intégralRésumé :
The aim of this study was to evaluate the possible association between the roughness of 5 brands of stainless steel endodontic files and their resistance to fracture due to cyclic fatigue. The study included five different brands of stainless steel endodontic files: SybroEndo Triple-Flex Files (Kerr, Glendora, USA), Ready Steel K-Flexofile (Dentsply Sirona, Ballaigues, Switzerland), Mani Flexile Files (Mani, Tochigi- Ken, Japan), FKG K-Files (FKG, La Chaux-de-Fonds, Switzerland) and Zipperer Flexicut Files (VDW, Munich, Germany). Twelve files per brand (total 60 files) were evaluated. File surface roughness over an area (Sa) was quantified using a focus variation microscope. Then the files were subject to a cyclical fatigue test to determine the number cycles to fracture due to fatigue and length of fractured fragment. Finally, fractographic analysis was performed using a scanning electron microscope. The electropolished Ready Steel K-Flexofile® files had the highest roughness according to Sa parameters, though they also had the highest resistance to fracture due to cyclic fatigue and the longest fractured fragment. Moderate positive correlation was found between fractured fragment length and roughness. The fractured surface showed characteristics of ductile fracture with cracks and plastic deformation. The electropolished stainless steel Ready Steel K-Flexofile® files were the most resistant to fracture due to cyclic fatigue even though they had highest surface roughness.
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Khairul, H. Kamarudin, Ahmad Zaidi Ahmad Mujahid, Abdullah Shohaimi, Shah Md Fuad, Thanakodi Suresh, Husain Firdaus, Jamil Hariz, Wan Mat Wan Ali et Othman Mohd Zaid. « Visual Inspection on Failure Surface of Constant Force Spring (CFS) Fitted in a Counterweight Balancing Mechanism ». Materials Science Forum 819 (juin 2015) : 461–66. http://dx.doi.org/10.4028/www.scientific.net/msf.819.461.
Texte intégralRésumé :
A failure characteristic of a fractured constant force spring (CFS) or flat spiral spring fitted in a counterweight balancing mechanism is investigated via series of visual experimentation. Macroscopic examination reveals several beach marks that shows direction of fatigue crack propagation has indicated that the CFS fracture had initiated and propagated due to fatigue from an inner surface origin. Macro cracks resulted from stress concentration were also visible on grain boundaries. The crack was initiated at the center of the CFS which later propagated in the direction perpendicular to the applied cyclic load and finally fractured when it can no longer sustain the applied cyclic load. Inspection via Scanning Electron Microscopy (SEM) has indicatedsign of fatigue striations perpendicular to the fracture propagation which is a characteristic of fatigue failure mechanism. Examination of the fractured surface also pointed porosities that reflects points of crack initiation. Multiple crack initiation points identified shows that the fracture was a result of high stress or high stress concentration.
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Nishi, Yoshitake, Takashi Toriyama, Kazuya Oguri, Akira Tonegawa et Kazuo Takayama. « High fracture resistance of carbon fiber treated by electron beam irradiation ». Journal of Materials Research 16, no 6 (juin 2001) : 1632–35. http://dx.doi.org/10.1557/jmr.2001.0226.
Texte intégralRésumé :
A crack reduction by electron beam (EB) irradiation treatment for carbon fiber, used without the traditional method of accompanying heat, was developed to modify the mechanical properties at lower temperature. The EB treatment improved the resistance to fracture. Namely, the maximum ratio of fractured samples (maxRf) and the minimum bending strain on fracture (minεf) were defined as simple indicators of fracture resistance and became smaller by the EB treatment. Furthermore, a critical density of dangling bonds for a fracture was suggested and determined for carbon fiber treated by EB irradiation. The EB irradiation to reduce cracking and the determination of the critical density of dangling bonds are new concepts that can be broadly applied in the fields of aerospace and rapid-transit production engineering.
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Феррари, Марко, Marco Ferrari, Зиад Саламех, Ziad Salameh, Хани Ф. Оунси, Hani F. Ounsi, Мустафа Н. Абушелиб et al. « EFFECT OF DIFFERENT ONLAY SYSTEMS ON FRACTURE RESISTANCE AND FAILURE PATTERN OF ENDODONTICALLY TREATED MANDIBULAR MOLARS RESTORED WITH AND WITHOUT GLASS FIBER POSTS ». Actual problems in dentistry 11, no 1 (25 février 2015) : 31–37. http://dx.doi.org/10.18481/2077-7566-2015-0-1-31-37.
Texte intégralRésumé :
<p><strong>Purpose: </strong>To investigate the relationship between post and core build-up materials on the fracture resistance of endodontically treated teeth restored with different onlay restorations. Methods: 60 mandibular molars were endodontically treated and divided into three experimental groups that received one of the following onlay restorations: gold onlays, glass ceramic onlays, or resin composite onlays. Half of the specimens in each group received a fiber post (n = 10). Two controls groups (n = 10) were included: one group composed of sound mandibular molars, and the second group was composed of endodontically treated unrestored molars. Fracture tests were carried out by applying axial load using a universal loading machine until fracture. All fractured specimens were fractographically examined using a scanning electron microscope. Data were analyzed using two-way ANOVA and Tukey multiple comparison tests (α = 0.05). Results: Statistical analysis showed that restoration of endodontically treated teeth with gold onlays improved fracture resistance when compared to glass ceramic or resin composite onlays. The presence of a fiber post significantly improved (P< 0.045) fracture resistance of gold onlays from 2271 to 2874N while it did not influence the performance of the other two groups. Fractographic analyses revealed that the presence of fiber post resulted in more restorable fractures due to better stress distribution of the applied load. All onlay systems resulted in significant improvement of the fracture resistance compared to unrestored teeth (711N) but neither of them resulted in restoring the fracture resistance to match that of sound teeth (3212 N). (Am J Dent 2010;23:81-86).</p>
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Zhang, Yunzhao, Lianbo Zeng, Wenya Lyu, Dongsheng Sun, Shuangquan Chen, Cong Guan, Lei Tang, Jinxiong Shi et Junhui Zhang. « Natural fractures in tight gas sandstones : a case study of the Upper Triassic Xujiahe Formation in Xinchang gas field, Western Sichuan Basin, China ». Geological Magazine 158, no 9 (18 mars 2021) : 1543–60. http://dx.doi.org/10.1017/s001675682100008x.
Texte intégralRésumé :
AbstractThe Upper Triassic Xujiahe Formation is a typical tight gas reservoir in which natural fractures determine the migration, accumulation and production capacity of tight gas. In this study, we focused on the influences of natural fractures on the tight gas migration and production. We clarified characteristics and attributes (i.e. dips, apertures, filling degree and cross-cutting relationships) of the fractures based on image logging interpretations and core descriptions. Previous studies of electron spin resonance, carbon and oxygen isotopes, homogenization temperature of fluid inclusions analysis and basin simulation were considered. This study also analysed the fracture sequences, source of fracture fillings, diagenetic sequences and tight gas enrichment stages. We obtained insight into the relationship between fracture evolution and hydrocarbon charging, particularly the effect of the apertures and intensity of natural fractures on tight gas production. We reveal that the bedding fractures are short horizontal migration channels of tight gas. The tectonic fractures with middle, high and nearly vertical angles are beneficial to tight gas vertical migration. The apertures of fractures are controlled by the direction of maximum principal stress and fracture angle. The initial gas production of the vertical wells presents a positive correlation with the fracture abundance, and the intensity and aperture of fractures are the fundamental factors that determine the tight gas production. With these findings, this study is expected to guide the future exploration and development of tight gas with similar geological backgrounds.
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Liu, Shengxin, Zongxiu Wang et Linyan Zhang. « Experimental study on the cracking process of layered shale using X-ray microCT ». Energy Exploration & ; Exploitation 36, no 2 (8 novembre 2017) : 297–313. http://dx.doi.org/10.1177/0144598717736855.
Texte intégralRésumé :
The cracking process in Longmaxi formation shale was experimentally studied during uniaxial compressive loading. Both the evolution of the three-dimensional fracture network and the micromechanics of failure in the layered shale were examined as a function of the inclination angle of the bedding plane. To visualize the cracking process, the test devices presented here used an industrial X-ray CT scanner that enabled scanning during the uniaxial compressive loading. Scanning electron microscopy and environmental scanning electron microscopy imaging techniques were used to observe the microscopic characteristics of fractured surfaces of failed specimens. The combination of these observations clearly illustrated the micromechanics of the failure process in the anisotropic shale. The experimental results suggest that the cracking process could be divided into two stages under uniaxial loading, and the microstructures and bedding planes of the shale played an important role in the cracking process of layered shale. In the first stage of deformation, the cracking mainly occurred as smaller microcracks (such as intergranular, microcracks), and the propagation of the newly formed microcracks was controlled by the bedding plane of the shale specimen. The microscopic imaging study showed that the microscopic damage was mainly dominated by microtensile fractures under uniaxial compression. In the second stage, with the increase in loading, the extensive development and coalescence of the microcracks led to the formation of complex fracture networks. The complexity of the fracture networks was related to the microstructure of the sample. The coalescence of the microcracks could be divided into three levels in the spatial scale, and the coalescence patterns included both tensile and shear patterns.
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Hu, Lin, Jian Can Yang, Wen Guan Zhu et Jie Cao. « Effect of Pulse Current on the Plastic Deformation Behavior of Tungsten ». Materials Science Forum 817 (avril 2015) : 392–98. http://dx.doi.org/10.4028/www.scientific.net/msf.817.392.
Texte intégralRésumé :
The influence of the current density and frequency on the mechanical behavior of the W-CeO2 rod was studied during tension tests in which electric current was applied to the deformation workpiece. A larger decrease in material flow stress and great improvement in the formability were observed in electrically assisted tests compared to the normal tests. The scanning electron microscopy observation showed that the fracture mechanism of tungsten material changed from brittle fracture to ductile fracture, and the second phase fractured, which even became spheroidizing shape.
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Evstifeeva, V. V., V. N. Litovchenko, V. V. Mishakin et R. A. Vorobyev. « Evaluation of crack resistance of 38KhN3MFA-Sh structural steel by fracture properties and elastic wave velocities ». Voprosy Materialovedeniya, no 2(98) (11 août 2019) : 123–35. http://dx.doi.org/10.22349/1994-6716-2019-98-2-123-135.
Texte intégralRésumé :
The results of the study on the effects of tempering temperature on 38KhN3MFA-Sh steel static strength and crack resistance are given. The fractured surface texture has been studied after various heat treatment modes using electron-fractography analysis. Relationships between the fracture properties and the critical stress intensity factor have been established. The effect of tempering temperature on the velocities of ultrasonic bulk waves has been investigated. A linear relationship has been found between the velocity of elastic waves and the critical stress intensity factor of 38KhN3MFA-Sh steel. The dependence discovered allows us to estimate the changes in crack resistance of steel using a non-destructive test method with variations in tempering temperature. The method of electron fractography has been used to analyze specimen fractures having a crack in structural high-quality 38KhN3MFA-Sh steel. Investigations of the fractured surface texture subjected to various heat treatment modes have shown that the microrelief is represented by flattened cone-shape pits. An increase in tempering temperature is accompanied by an increase in the diameter of flattened cone pits on the fractured surface. A quadratic dependence has been established between the crack resistance parameter and the diameter of the pits. It is shown that the contribution of ferrite matrix structural condition to crack resistance value is much more significant than the contribution of isolated carbides. The velocities of elastic waves in steel have been measured; their values increase with the growth of tempering temperature. The characteristics of strength and crack resistance of structural steel exposed to hightemperature tempering have been predicted based on the values of transverse wave velocities. Deviation of the predicted values of crack resistance K1С and ultimate strength σb from the experimental values does not exceed 5.4% and 12.6%, respectively.
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Khan, AM, M. Rafferty et JS Daurka. « Hemiarthroplasty compared with total hip arthroplasty in fractured neck of femur : a shift in national practice ? » Annals of The Royal College of Surgeons of England 101, no 2 (février 2019) : 86–92. http://dx.doi.org/10.1308/rcsann.2018.0123.
Texte intégralRésumé :
Introduction The aim of this study was to determine the trends in national practice regarding total hip arthroplasty compared with hemiarthroplasty in fractured neck of femur between 2010 and 2016. Materials and methods A retrospective review was conducted of NHS Digital data (England) between 2010 and 2016. ‘Emergency’ neck of femur fracture admissions, hemiarthroplasties and total hip arthroplasties were included. Elective total hip arthroplasties, revisions and prostheses relocations were excluded. Annual percentages for each operation were calculated. Trends were tabulated and displayed graphically for analysis. Results The total number of emergency neck of femur diagnoses was 257,789. Total hip arthroplasty was performed in 2217, 2737, 3305, 3686, 3670 and 3825 patients and hemiarthroplasty was performed in 21,335, 21,744, 21,115, 21,798, 21,804 and 22,163 patients for each year between 2011 and 2016, respectively. The rate of change for total hip arthroplasty slowed from 24.54% increase/year (2011–2013) to 5.24% increase/year (2013–2016). Uncemented arthroplasties decreased over the same time period. Discussion Increasing numbers of total hip arthroplasties are conducted for hip fractures; however, this trend has slowed since 2013. Possible explanations include all eligible fractures being treated with total hip arthroplasty, trauma surgeon preference for hemiarthroplasty due to lower surgical specialism or publication of individual surgeon data (National Joint Registry) which may lead to surgeons favouring hemiarthroplasties which have a lower complication rate compared to elective total hip arthroplasties.
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Mergulhão, VA, LS de Mendonça, MS de Albuquerque et R. Braz. « Fracture Resistance of Endodontically Treated Maxillary Premolars Restored With Different Methods ». Operative Dentistry 44, no 1 (1 janvier 2019) : E1—E11. http://dx.doi.org/10.2341/17-262-l.
Texte intégralRésumé :
SUMMARY Purpose: The purpose of this in vitro study was to evaluate the resistance and patterns of fracture of endodontically treated maxillary premolars (ETPs) restored with different methods. Methods and Materials: Mesio-occluso-distal cavities were prepared in 50 extracted caries-free human maxillary premolars after endodontic treatment. The teeth were divided into five groups (n=10), according to the restorative method. G1: intact teeth (control group); G2: conventional composite resin; G3: conventional composite resin with a horizontal glass fiber post inserted between buccal and palatal walls; G4: bulk-fill flowable and bulk-fill restorative composites; and G5: ceramic inlay. For direct restorations, Filtek Z350 XT, Filtek Bulk Fill Flowable Restorative, and Filtek Bulk Fill Posterior Restorative were used. Indirect restorations were fabricated from a pressable lithium disilicate glass-ceramic (IPS e-max Press) and adhesively cemented (RelyX Ultimate). All specimens were subjected to thermocycling (5°C to 55°C/5000 cycles) and additionally submitted to cyclic loading 50,000 times in an Electro-Mechanical Fatigue Machine. Next, the specimens were subjected to a compressive load at a crosshead speed of 1 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern using a stereomicroscope, and then representative specimens were carbon coated to allow for the studying of the fracture surface under scanning electron microscopy. One-way analysis of variance (ANOVA) was used to compare fracture resistance of the groups. The results of fracture patterns were submitted to the Fisher exact test (α=0.05). Results: All specimens survived fatigue. Mean (standard deviation) failure loads (N) for groups were as follows: G1: 949.6 (331.5); G2: 999.6 (352.5); G3: 934.5 (233.6); G4: 771.0 (147.4); and G5: 856.7 (237.5). The lowest fracture resistance was recorded for G4, and the highest ones were recorded for G2, followed by that of G1 and G3. One-way ANOVA did not reveal significant differences between groups (p>0.05). The highest repairable fracture rates were observed in G1 (100%) and G3 (80%). Conclusions: ETPs restored with conventional composite resin with or without horizontal fiber post, bulk-fill composite, and ceramic inlay showed fracture resistance similar to that of sound teeth. Conventional composite resin restorations exhibited the highest prevalence of unrepairable fractures, and the insertion of a horizontal fiber post decreased this prevalence. Intact teeth showed 100% of repairable fractures. It is difficult to extrapolate the results directly to a clinical situation due to the limitations of this study.
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Carlson, Bayard C., William A. Robinson, Nathan R. Wanderman, Arjun S. Sebastian, Ahmad Nassr, Brett A. Freedman et Paul A. Anderson. « A Review and Clinical Perspective of the Impact of Osteoporosis on the Spine ». Geriatric Orthopaedic Surgery & ; Rehabilitation 10 (1 janvier 2019) : 215145931986159. http://dx.doi.org/10.1177/2151459319861591.
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Introduction: Osteopenia and osteoporosis are common conditions in the United States. The health consequences of low bone density can be dire, from poor surgical outcomes to increased mortality rates following a fracture. Significance: This article highlights the impact low bone density has on spine health in terms of vertebral fragility fractures and its adverse effects on elective spine surgery. It also reviews the clinical importance of bone health assessment and optimization. Results: Vertebral fractures are the most common fragility fractures with significant consequences related to patient morbidity and mortality. Additionally, a vertebral fracture is the best predictor of a subsequent fracture. These fractures constitute sentinel events in osteoporosis that require further evaluation and treatment of the patient’s underlying bone disease. In addition to fractures, osteopenia and osteoporosis have deleterious effects on elective spine surgery from screw pullout to fusion rates. Adequate evaluation and treatment of a patient’s underlying bone disease in these situations have been shown to improve patient outcomes. Conclusion: With an increased understanding of the prevalence of low bone mass and its consequences as well an understanding of how to identify these patients and appropriately intervene, spine surgeons can effectively decrease the rates of adverse health outcomes related to low bone mass.
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Tian, Lin, Wenlian Liu, Jiaming Zhang et Haiyan Gao. « Cataclastic Characteristics and Formation Mechanism of Dolomite Rock Mass in Yunnan, China ». Applied Sciences 13, no 12 (9 juin 2023) : 6970. http://dx.doi.org/10.3390/app13126970.
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The dolomite rock mass on the slope of the Yanhe domestic waste incineration power plant was used as the research object. The macro- and micro-structural characteristics of intact rock blocks and rock discontinuities were analyzed qualitatively and quantitatively using in-hole television, wave velocity testing, three-dimensional laser scanning techniques, photogrammetry, image processing techniques, and scanning electron microscopy (SEM). The study shows that the degree of fracturing generally decreases with depth over the exposed borehole depth range, and the rock masses are generally very fractured. The wave velocity of dolomite generally increases with the depth of the borehole, and the integrity of the dolomite is either broken or extremely broken. The excavation profile reveals six sets of discontinuities and joints that are straight, smooth, interconnected, and largely unfilled. The angles of the structural bodies of different grain sizes are sharp, with roundness being angular and sharp-angled. The smaller the blocks, the more complex the surface morphology. SEM observations show that the ultramicroscopic fractures are not flat and smooth, and the fractures are folded. Fracturing mainly occurs along intercrystalline and crystal interfaces. These fracture features suggest that the fracturing of dolomite is mainly related to the original sedimentary construction and tectonism.
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Sutliff, J. A. « Facet crystallography by electron diffraction in the SEM ». Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 août 1993) : 774–75. http://dx.doi.org/10.1017/s0424820100149702.
Texte intégralRésumé :
The study of fracture in engineering materials often involves an analysis of the crystallography of the fracture surface. In particular, the question is often asked, "What, if any, low index plane corresponds to the plane of a particular fracture surface facet?" To determine the crystallographic plane of a surface facet, it is necessary to determine the orientation of the grain and the orientation of the facet plane relative to the grain. For example, if a euhedral crystal of known orientation is fractured, an optical reflection goniometer can be used to measure the angles between a facet and known crystal faces in order to deduce the direction of the facet normal. Laue x-ray diffraction patterns taken from well aligned facets can also be analyzed to determine the orientation of the crystal normal to the facet. In many engineering materials, the facets are small, usually as a result of a small grain size in the material, and it becomes impractical to use these techniques.
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Zhou, Yu Mei, Feng Lin Zhang, Peng Cheng Li, Kun Bai et Shang Hua Wu. « A Study on Ultra-Hard AlMgB14 Modified by TiB2 and Ni3Al ». Materials Science Forum 848 (mars 2016) : 607–12. http://dx.doi.org/10.4028/www.scientific.net/msf.848.607.
Texte intégralRésumé :
AlMgB14 is a very hard and brittle material which need be modified for utilizing as cutting tool materials. In present study, TiB2 and Ni3Al were used to strengthen and toughen AlMgB14 material. The microstructure of the AlMgB14-TiB2-Ni3Al composites was analysized by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and an X-ray diffractometer (XRD). The hardness and fracture toughness of the AlMgB14-TiB2Ni3Al composites were also examined. The results showed that the major phases in AlMgB14-Ni3Al composites were TiB2, AlMgB14, MgAl2O4 , Ni3Al and NiAl. With the increasing of the amount of Ni3Al, more intergranular fractured features can be found in the fractured surface of the composites, the hardness and fracture toughness of the composites were both decreased comparing to the synthesised AlMgB14. The AlMgB14-TiB2-4wt.% Ni3Al composite has a hardness of 28.1 Gpa and a fracture toughness of 3.14 MPa·m1/2.
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Choi, Ju-Hwan, Henzeh Leeghim, Ju-Hun Ahn, Dae-San Choi et Chang-Yull Lee. « Fracture Surface of 3D Printed Honeycomb Structures at Low Temperature Environments ». Journal of Nanoscience and Nanotechnology 20, no 7 (1 juillet 2020) : 4235–38. http://dx.doi.org/10.1166/jnn.2020.17555.
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In this paper, surface characteristics of 3D printed structures fractured at low temperature environments are analyzed. The samples are fabricated by using ABS (acrylonitrile butadiene styrene copolymer) material, and the structures are constructed by the well-known honeycomb models using a FDM-Type 3D printer. To analyze the fracture surface of the samples constructed uniquely by using the 3D printer, the bending loads are applied to the samples at 30, −10 and −50 °C, respectively. The characteristics of the fracture surfaces of the 3D samples are also observed by the FE-SEM (field emission scanning electron microscope) equipment. From this experiment, it is evaluated that the fractured surface of the 3D sample is very rough at 30 °C, while it is smooth at a relatively low temperature. Also, several unique features of the fracture surface of a 3D printed sample structured by honeycomb models are also examined.
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Wang, Hu, Zhiliang He, Yonggui Zhang, Kun Su et Ruyue Wang. « Quantitative identification of microfractures in the marine shale reservoir of the Wufeng-Longmaxi Formation using water immersion tests and image characterization ». Interpretation 6, no 4 (1 novembre 2018) : SN23—SN30. http://dx.doi.org/10.1190/int-2018-0010.1.
Texte intégralRésumé :
Identification of natural microfractures is important for shale reservoir evaluation. In total, 42 selected core samples from the Wufeng-Longmaxi marine shales in the Fuling gas field, southeastern Sichuan Basin, were analyzed using water-immersion testing, computed tomography scanning, and argon-ion polishing scanning electron microscope experiments, along with edge detection and image stitching analysis methods. The results indicate that the immersion experiment is an effective way to identify natural fractures. Three types of natural microfractures correspond to bubble positions with 250 nm resolution scanning electron microscopy: bedding fractures, particle edge fractures, and dissolution fractures. The bedding and dissolution fractures show the same occurrence as the strata, and they are the main bubbling channels. The occurrence of particle edge fractures varies significantly. Microfractures are capable of forming a fracture network, connecting separated storage spaces in the shale reservoir. The best fracture network is formed by bedding and dissolution fractures in 3D space. Furthermore, apportion of the particle edge and dissolution fractures is capable of forming microfracture networks in shale cores increasing the connectivity of pore spaces. The number of bubble points also indicates a positive correlation with shale laminae, which indicates that microfractures are developed mainly within the laminae. The number of shale laminae and the number of microfracture channels can be calculated quantitatively by the number of bubble points. The observations can be used in the drilling site to estimate the physical properties of shale reservoirs quickly and quantitatively.
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Cheng, J., M. Yuan, C. N. J. Wagner et A. J. Ardell. « Fractographic fingerprinting of proton-irradiation-induced disordering and amorphization of intermetallic compounds ». Journal of Materials Research 4, no 3 (juin 1989) : 565–78. http://dx.doi.org/10.1557/jmr.1989.0565.
Texte intégralRésumé :
The intermetallic compounds NiTi, NiTi2, CuZr, CuTi2, and Zr3Al were irradiated by 2 McV protons at various temperatures between –175 °C and –44 °C to a fluence of 1.9 × 1022 H+/m2. Transmission electron microscopy, electron diffraction, and x-ray diffraction were used to evaluate the extents of disordering and amorphization induced by irradiation in the samples. Both phenomena progressed to varying extents in the five compounds, depending on the irradiation temperature and dose. It was observed that the C-A transition began before the degree of long-range order was reduced significantly, and that the amorphous phase nucleated homogeneously throughout the crystalline matrix. A major finding of the current investigation is that the technique of scanning electron fractography provides a useful correlation between the features of the fractured surfaces and the microstructural alterations induced by the proton irradiations. When amorphization is complete the fracture surfaces are either featureless (e.g., NiTi2) or contain branching features resembling river patterns. In some cases (especially in CuZr) these are similar to the markings seen on the surfaces of fractured amorphous ribbons produced by melt-spinning. In general, however, there is not a particularly good correlation between the features on the fracture surfaces of the irradiated and melt-spun ribbons. When the microstructure consists of amorphous regions embedded in a partially disordered crystalline matrix, there is considerable evidence for irradiation-induced ductility. In such cases, exemplified by the results on NiTi and Zr3Al, the fracture surfaces contain dimples, characteristic of ductile fracture, suggesting that disordering promotes ductility.
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Fujimoto, K. « Freeze-fracture replica electron microscopy combined with SDS digestion for cytochemical labeling of integral membrane proteins. Application to the immunogold labeling of intercellular junctional complexes ». Journal of Cell Science 108, no 11 (1 novembre 1995) : 3443–49. http://dx.doi.org/10.1242/jcs.108.11.3443.
Texte intégralRésumé :
We propose a new electron microscopic method, the sodium dodecylsulphate (SDS)-digested freeze-fracture replica labeling technique, to study the two-dimensional distribution of integral membrane proteins in cellular membranes. Unfixed tissue slices were frozen with liquid helium, freeze-fractured, and replicated in a platinum/carbon evaporator. They were digested with 2.5% SDS to solubilize unfractured membranes and cytoplasm. While the detergent dissolved unfractured membranes and cytoplasm, it did not extract fractured membrane halves. After SDS-digestion, the platinum/carbon replicas, along with attached cytoplasmic and exoplasmic membrane halves, were processed for cytochemical labeling, followed by electron microscopic observation. As an initial screening, we applied this technique to the immunogold labeling of intercellular junction proteins: connexins (gap junction proteins), occludin (tight junction protein), desmoglein (desmosome protein), and E-cadherin (adherens junction protein). The immunogold labeling was seen superimposed on the image of a fracture face visualized by platinum/carbon shadowing. The immunoreaction was specific, and only the structures where the proteins were expected were labeled. For instance, anti-occludin immunogold complexes were observed immediately adjacent to the tight junction strands on the protoplasmic and exoplasmic fracture faces. No significant levels of gold label were associated with non-tight-junctional regions of plasma membranes. The procedures of the SDS-digested freeze-fracture replica labeling and its potential significance are discussed.
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Zhang, Zhixiong, Yun Cheng, Zhanping Song et Xueyun Ye. « Anisotropy and Directivity Effects on Uniaxial Compression of Carbonaceous Slate Form Jinman Mine ». Applied Sciences 12, no 19 (29 septembre 2022) : 9811. http://dx.doi.org/10.3390/app12199811.
Texte intégralRésumé :
To determine the anisotropic mechanical characteristics of carbonaceous slate at the Jinman Mine located in Lancang River Gorge, China, uniaxial compression, acoustic emission (AE) monitoring, and scanning electron microscopy (SEM) tests were conducted. The results show that stress loading directions and bedding effects have a significant impact on strain characteristics. The deformation of slate undergoes compaction, elastic, damage accumulation, and failure stages, and there are significant differences in strain paths. The mechanical properties of grey and carbonaceous slate have significant features, and variations of these properties of carbonaceous slate are more than that of grey slate. The discrete degree is significantly related to the direction of stress loading and different types of slate structures. The AE response intensity is related to the loading mode and slate type. A sudden increase in the AE cumulative ring number near peak stress indicates instability and rupture and is a precursor of rock rupture. The failure patterns and fracture characteristics are significantly correlated to the layered structure of the slate. Slates subjected to vertical loading and parallel loading conditions are dominated by shear fracture and tensile fracture, respectively. The peak strains of gray and carbonaceous slate correspond to brittle failure. The SEM tests indicate that slate samples subjected to parallel loading primarily show a tensile failure compared with slate samples subjected to vertical loading, with fractured sections being of lesser roughness, and scattered fractures and sections being smooth without obvious protrusions or cracks.
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KUMAR, SANDEEP, et M. A. HAQUE. « FRACTURE TESTING OF NANOSCALE THIN FILMS INSIDE THE TRANSMISSION ELECTRON MICROSCOPE ». International Journal of Applied Mechanics 02, no 04 (décembre 2010) : 745–58. http://dx.doi.org/10.1142/s1758825110000731.
Texte intégralRésumé :
To visualize the fracture mechanisms in nanoscale thin films while measuring their fracture properties, we developed an experimental setup to carry out the experiments in-situ in the transmission electron microscope. The setup includes a 3 mm × 5 mm micro-electro-mechanical testing chip with actuators and sensors to measure fracture toughness of notched specimens. Fracture experiments were performed on about 125 nm thick free-standing aluminum thin film specimens with average grain size of about 50 nm. The specimens fractured at uniform far field stress of 470 MPa with stress intensity factor of 0.8–1.1 MPa m1/2. Commonly cited deformation mechanisms, such as dislocation-based plasticity and grain boundary sliding processes were not observed even at the notch tip, where the calculated stress considering the concentration factor exceeded 4 GPa. We propose that for grain sizes below 50 nm, dislocation motion confined at grain boundaries and grain rotation emerge to be significant processes in thin film deformation.