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Direct visualization of lead sulfide nanoparticle growth is demonstrated by selectively decomposing a chemical precursor from a multicomponent solution using in situ liquid transmission electron microscopy. We demonstrate reproduc...
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Direct visualization of lead sulfide nanoparticle growth is demonstrated by selectively decomposing a chemical precursor from a multicomponent solution using in situ liquid transmission electron microscopy. We demonstrate reproducible control over growth mechanisms that dictate the final morphology of nanostructures while observing growth in real-time with subnanometer spatial resolution. Furthermore, while an intense electron beam can initiate nanoparticle growth, it is also shown that a laser can trigger the reaction independently of the imaging electrons.
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The transmission electron microscopy in-situ straining technique is employed to measure the breaking angles of strengthening precipitates in aluminium alloy 6056-T6 as they are sheared by dislocations. The experimental determinati...
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The transmission electron microscopy in-situ straining technique is employed to measure the breaking angles of strengthening precipitates in aluminium alloy 6056-T6 as they are sheared by dislocations. The experimental determination of the character of bowed dislocation segments when dislocations are pinned on precipitates allows us to calculate the corresponding line tensions. From this, the maximum forces F-m that precipitates can sustain before being sheared by dislocations are deduced. It is suggested that F-m may be regarded as a quantitative parameter which includes the effects of the various strengthening mechanisms operative in precipitation-hardened alloys. An attempt is made to relate the maximum force calculated from in-situ straining data to the macroscopic yield strength of the material.
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Orientation maps similar to electron backscatter diffraction maps can be obtained in a transmission electron microscope. A method of such mapping by automatic indexing of electron diffraction patterns has been proposed recently. T...
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Orientation maps similar to electron backscatter diffraction maps can be obtained in a transmission electron microscope. A method of such mapping by automatic indexing of electron diffraction patterns has been proposed recently. The procedure is relatively simple and fast but it does not avoid the 180 degrees ambiguity. Using tests on simulated patterns, it is shown that under current practice automatic indexing may give a considerable fraction of erroneous solutions. Optimization of measurement conditions leading to a reduction of that fraction is considered.
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The presented article characterized microstructural aspects of thermal barrier coatings (TBCs) analysis using methods of electron microscopy such as electron backscatter diffraction (EBSD), transmission/scanning electron microscop...
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The presented article characterized microstructural aspects of thermal barrier coatings (TBCs) analysis using methods of electron microscopy such as electron backscatter diffraction (EBSD), transmission/scanning electron microscopy (S/TEM), and TEM. The analyzed TBC system is based on gadolinium zirconate deposited by air plasma spraying method, and additionally, it was subjected to an oxidation test for 500 hr at a temperature of 1,100 degrees C. Moreover, the morphological characterization of feedstock powder was showed. EBSD analysis revealed the inhomogeneity of feedstock materials in the form of complex phase composition. In the case of deposited coating, this method was used to characterize the crystallite size of zirconate coating and phase composition of thermally grown oxide zone. S/TEM and TEM analysis showed morphological details of this zone but not revealed such phase as perovskite oxide of GdAlO3 type.
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Rapid strides realized in the field of ordered mesoporous silica(OMS)with a well-defined pore shape and nanometric sizes,provide new gateways for the preparation of nanostructured materials having controlled shape and size with a ...
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Rapid strides realized in the field of ordered mesoporous silica(OMS)with a well-defined pore shape and nanometric sizes,provide new gateways for the preparation of nanostructured materials having controlled shape and size with a very narrow distribution.The focus of the current review is on the synthesis of nanostructures templated by OMS either in bulk or in thin film form.The importance of electron microscopy as an indispensable technique in the structural characterization of OMS templated nanostructures,including cryo-TEM,electron tomography and HR-SEM,is highlighted in this review.
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Transanal endoscopic microsurgery (TEM) allows the local excision of rectal tumors and achieves lower morbidity and mortality rates than total mesorectal excision. TEM can treat lesions up to 18 to 20?cm from the anal verge, obtai...
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Transanal endoscopic microsurgery (TEM) allows the local excision of rectal tumors and achieves lower morbidity and mortality rates than total mesorectal excision. TEM can treat lesions up to 18 to 20?cm from the anal verge, obtaining good oncological results in T1 stage cancers and preserving sphincter function. TEM is technically demanding. Large lesions (>5?cm), those with high risk of perforation into the peritoneal cavity, those in the upper rectum or the rectosigmoid junction, and those in the anal canal are specially challenging. Primary suture after peritoneal perforation during TEM is safe and it does not necessarily require the creation of a protective stoma. We recommend closing the wall defect in all cases to avoid the risk of inadvertent perforation. It is important to identify these complex lesions promptly to transfer them to reference centers. This article summarizes complex procedures in TEM.
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We studied Pt?Co bimetallic nanoparticles during oxidation in O_2 and reduction in H2 atmospheres using an aberration corrected environmental transmission electron microscope. During oxidation Co migrates to the nanoparticle surfa...
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We studied Pt?Co bimetallic nanoparticles during oxidation in O_2 and reduction in H2 atmospheres using an aberration corrected environmental transmission electron microscope. During oxidation Co migrates to the nanoparticle surface forming a strained epitaxial CoO film. It subsequently forms islands via strain relaxation. The atomic restructuring is captured as a function of time. During reduction cobalt migrates back to the bulk, leaving a monolayer of platinum on the surface
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Abstract Insight into the nucleation, growth and phase transformations of calcium sulphate could improve the performance of construction materials, reduce scaling in industrial processes and aid understanding of its formation in t...
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Abstract Insight into the nucleation, growth and phase transformations of calcium sulphate could improve the performance of construction materials, reduce scaling in industrial processes and aid understanding of its formation in the natural environment. Recent studies have suggested that the calcium sulphate pseudo polymorph, gypsum (CaSO4·2H2O) can form in aqueous solution via a bassanite (CaSO4·0.5H2O) intermediate. Some in situ experimental work has also suggested that the transformation of bassanite to gypsum can occur through an oriented assembly mechanism. In this work, we have exploited liquid cell transmission electron microscopy (LCTEM) to study the transformation of bassanite to gypsum in an undersaturated aqueous solution of calcium sulphate. This was benchmarked against cryogenic TEM (cryo‐TEM) studies to validate internally the data obtained from the two microscopy techniques. When coupled with Raman spectroscopy, the real‐time data generated by LCTEM, and structural data obtained from cryo‐TEM show that bassanite can transform to gypsum via more than one pathway, the predominant one being dissolution/reprecipitation. Comparisons between LCTEM and cryo‐TEM also show that the transformation is slower within the confined region of the liquid cell as compared to a bulk solution. This work highlights the important role of a correlated microscopy approach for the study of dynamic processes such as crystallisation from solution if we are to extract true mechanistic understanding.
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Graphene oxide (GO) and reduced GO (rGO) are the only variants of graphene that can be manufactured at the kilogram scale, and yet the widely accepted model for their structure has largely relied on indirect evidence. Notably, exi...
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Graphene oxide (GO) and reduced GO (rGO) are the only variants of graphene that can be manufactured at the kilogram scale, and yet the widely accepted model for their structure has largely relied on indirect evidence. Notably, existing high-resolution transmission electron microscopy (HRTEM) studies of graphene oxide report long-range order of sp(2) lattice with isolated defect clusters. Here, we present HRTEM evidence of a different structural form of GO, where nanocrystalline regions of sp(2) lattice are surrounded by regions of disorder. The presence of contaminants that adsorb to the surface of the material at room temperature normally prevents direct observation of the intrinsic atomic structure of this defective GO. To overcome this, we use an in situ heating holder within an aberration-corrected TEM (AC-TEM) to study the atomic structure of this nanocrystalline graphene oxide from room temperature to 700 degrees C. As the temperature increases to above 500 degrees C, the adsorbates detach from the GO and the underlying atomic structure is imaged to be small 2-4 nm crystalline domains within a polycrystalline GO film. By combining spectroscopic evidence with the AC-TEM data, we support the dynamic interpretation of the structural evolution of graphene oxide.
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The introduction of the National Danish screening programme for colorectal cancer will result in the detection of more early rectal cancers (ERC), which may be considered for local excision. For the low risk ≤T1 cancer, the oncol...
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The introduction of the National Danish screening programme for colorectal cancer will result in the detection of more early rectal cancers (ERC), which may be considered for local excision. For the low risk ≤T1 cancer, the oncological outcome at local excision in smaller patient series has shown similar results to conventional surgery, but with a significantly lower rate of serious complications, morbidity and mortality. The challenge is correct preoperative staging, and a meticulous systematic histopathological staging of the excised specimen to distinguish the low risk from high-risk cases, where rescue surgery may be considered. The establishment of a regional or national clinical database is necessary to improve the local treatment of ERC.
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