The Experts below are selected from a list of 47754 Experts worldwide ranked by ideXlab platform
A M Donald - One of the best experts on this subject based on the ideXlab platform.
-
2003 Use of Environmental Scanning electron microscopy to image the spore adhesive of the marine alga Enteromorpha in its natural hydrated state
2020Co-Authors: James A. Callow, Maureen E. Callow, M P Osborne, F Baker, A M DonaldAbstract:Abstract The Environmental Scanning electron microscope (ESEM) has been used to image the adhesive secreted by zoospores of the marine alga Enteromorpha as they settle on a surface, under natural, hydrated conditions. Results reveal a featureless, swollen gel-like adhesive pad, in contrast to the fibrillar character of the adhesive when imaged by standard SEM. At high spore densities the adhesive is confluent. Dynamic hydration/dehydration events were followed by changing the water vapour pressure in the sample chamber. Rapid hydration and swelling were observed indicating a very hygroscopic material. Adhesive footprints were detected when surfaces from which spores had been removed by water jetting were examined.
-
application of Environmental Scanning electron microscopy to determine biological surface structure
Journal of Microscopy, 2009Co-Authors: S E Kirk, Jeremy N Skepper, A M DonaldAbstract:Summary The use of Environmental Scanning electron microscopy in biology is growing as more becomes understood about the advantages and limitations of the technique. These are discussed and we include new evidence about the effect of Environmental Scanning electron microscopy imaging on the viability of mammalian cells. We show that although specimen preparation for high-vacuum Scanning electron microscopy introduces some artefacts, there are also challenges in the use of Environmental Scanning electron microscopy, particularly at higher resolutions. This suggests the two technologies are best used in combination. We have used human monocyte-derived macrophages as a test sample, imaging their complicated and delicate membrane ruffles and protrusions. We have also explored the possibility of using Environmental Scanning electron microscopy for dynamic experiments, finding that mammalian cells cannot be imaged and kept alive in the Environmental Scanning electron microscopy. The dehydration step in which the cell surface is exposed causes irreversible damage, probably via loss of membrane integrity during liquid removal in the specimen chamber. Therefore, mammalian cells should be imaged after fixation where possible to protect against damage as a result of chamber conditions.
-
an Environmental Scanning electron microscopy examination of the film formation mechanism of novel acrylic latex
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Kalin I Dragnevski, A M DonaldAbstract:We have employed Environmental Scanning electron microscopy (ESEM) to study the film formation mechanisms of two acrylic latex compositions, here defined as standard (carboxymethyl cellulose stabilised) and novel (stabilised with a novel polysaccharide derived from agricultural waste). The ESEM analysis revealed that the microstructure of the standard system consists of individual particles and upon evaporation a continuous film is formed, which is consistent with the current models. However, in the case of the novel system the microstructure consists of individual particles and clusters and during evaporation a discontinuous film is formed with voids present within its structure. Based on the experimental evidence we propose a modification to the film formation mechanism for the novel latex system.
-
use of the Environmental Scanning electron microscope for the observation of the swelling behaviour of cellulosic fibres
Scanning, 2006Co-Authors: L M Jenkins, A M DonaldAbstract:We have developed a method for observing transverse swelling of cellulosic fibres in the Environmental Scanning electron microscope (ESEM). The presence of liquid water in the ESEM specimen chamber allows the observation of in situ hydration without the need for coating, freezing, or drying of the sample. For reproducibility of the hydration and dehydration process, specialised mounting techniques are required and control of the conditions for condensation and evaporation of liquid water is necessary. The sensitivity of these cellulosic materials to the electron beam was investigated, showing that some damage mechanisms are enhanced by the continual presence of water vapour in the chamber. A discussion is presented of the effect of various experimental parameters on the extent and time of onset of the damage, and we outline steps to maximise the amount of useful experimental time for these fibres.
-
use of Environmental Scanning electron microscopy to image the spore adhesive of the marine alga enteromorpha in its natural hydrated state
Colloids and Surfaces B: Biointerfaces, 2003Co-Authors: James A. Callow, Maureen E. Callow, M P Osborne, F Baker, A M DonaldAbstract:The Environmental Scanning electron microscope (ESEM) has been used to image the adhesive secreted by zoospores of the marine alga Enteromorpha as they settle on a surface, under natural, hydrated conditions. Results reveal a featureless, swollen gel-like adhesive pad, in contrast to the fibrillar character of the adhesive when imaged by standard SEM. At high spore densities the adhesive is confluent. Dynamic hydration/dehydration events were followed by changing the water vapour pressure in the sample chamber. Rapid hydration and swelling were observed indicating a very hygroscopic material. Adhesive footprints were detected when surfaces from which spores had been removed by water jetting were examined.
Afrooz Barnoush - One of the best experts on this subject based on the ideXlab platform.
-
In situ micromechanical testing in Environmental Scanning electron microscope: A new insight into hydrogen-assisted cracking
Acta Materialia, 2018Co-Authors: Bjørn Rune Sørås Rogne, Nousha Kheradmand, Yun Deng, Afrooz BarnoushAbstract:The susceptibility of Fe–26Al–0.5Cr (at.%) intermetallic alloy to hydrogen assisted cracking was evaluated by micromechanical fracture mechanics specimens. The notched micro-beams were loaded in situ in an Environmental Scanning electron microscope under two conditions: one with low pressure to avoid any hydrogen effect and the other with water vapour to promote hydrogen uptake and hydrogen assisted cracking. Fractographic and electron backscatter diffraction analysis carried out on the fracture surfaces of the ruptured beams revealed the mechanisms of the crack propagation. Under both conditions, the failure was cleavage-like, accommodated with plastic deformation. The results show the influence of hydrogen-induced embrittlement on the initiation of the fracture and the plasticity of the crack tip during the propagation of the crack, where the latter becomes localised and uniform over the fracture surface. From the observations, a three stage crack propagation process is proposed. Also, the fracture toughness of the samples was evaluated by linear elastic fracture mechanics and the validity of the results are discussed.
-
hydrogen enhanced cracking revealed by in situ micro cantilever bending test inside Environmental Scanning electron microscope
Philosophical Transactions of the Royal Society A, 2017Co-Authors: Yun Deng, Tarlan Hajilou, Afrooz BarnoushAbstract:To evaluate the hydrogen (H)-induced embrittlement in iron aluminium intermetallics, especially the one with stoichiometric composition of 50 at.% Al, a novel in situ micro-cantilever bending test was applied within an Environmental Scanning electron microscope (ESEM), which provides both a full process monitoring and a clean, in situ H-charging condition. Two sets of cantilevers were analysed in this work: one set of un-notched cantilevers, and the other set with focused ion beam-milled notch laying on two crystallographic planes: (010) and (110). The cantilevers were tested under two Environmental conditions: vacuum (approximately 5 × 10 −4 Pa) and ESEM (450 Pa water vapour). Crack initiation at stress-concentrated locations and propagation to cause catastrophic failure were observed when cantilevers were tested in the presence of H; while no cracking occurred when tested in vacuum. Both the bending strength for un-notched beams and the fracture toughness for notched beams were reduced under H exposure. The hydrogen embrittlement (HE) susceptibility was found to be orientation dependent: the (010) crystallographic plane was more fragile to HE than the (110) plane. This article is part of the themed issue ‘The challenges of hydrogen and metals’.
-
in situ micro cantilever bending test in Environmental Scanning electron microscope real time observation of hydrogen enhanced cracking
Scripta Materialia, 2017Co-Authors: Yun Deng, Nousha Kheradmand, Tarlan Hajilou, Afrooz BarnoushAbstract:Abstract A novel approach of in-situ micro-cantilever bending tests is introduced, integrating nanoindentation and Environmental Scanning electron microscopy (ESEM) to elucidate hydrogen embrittlement (HE) in FeAl. Bending tests were performed in vacuum (~ 5 × 10− 4 Pa) and in ESEM with water vapor (180 Pa, 450 Pa) conditions, which introduce H in-situ into the cantilevers during the test. Micro-scale In-situ SEM testing provides a full control of all the parameters involved in HE as well as avoids the proximity effect from the free surface, which is always criticized in nano-scale in-situ TEM experiments. Both hydrogen induced cracking and hydrogen reduced flow stress were observed.
Yun Deng - One of the best experts on this subject based on the ideXlab platform.
-
In situ micromechanical testing in Environmental Scanning electron microscope: A new insight into hydrogen-assisted cracking
Acta Materialia, 2018Co-Authors: Bjørn Rune Sørås Rogne, Nousha Kheradmand, Yun Deng, Afrooz BarnoushAbstract:The susceptibility of Fe–26Al–0.5Cr (at.%) intermetallic alloy to hydrogen assisted cracking was evaluated by micromechanical fracture mechanics specimens. The notched micro-beams were loaded in situ in an Environmental Scanning electron microscope under two conditions: one with low pressure to avoid any hydrogen effect and the other with water vapour to promote hydrogen uptake and hydrogen assisted cracking. Fractographic and electron backscatter diffraction analysis carried out on the fracture surfaces of the ruptured beams revealed the mechanisms of the crack propagation. Under both conditions, the failure was cleavage-like, accommodated with plastic deformation. The results show the influence of hydrogen-induced embrittlement on the initiation of the fracture and the plasticity of the crack tip during the propagation of the crack, where the latter becomes localised and uniform over the fracture surface. From the observations, a three stage crack propagation process is proposed. Also, the fracture toughness of the samples was evaluated by linear elastic fracture mechanics and the validity of the results are discussed.
-
hydrogen enhanced cracking revealed by in situ micro cantilever bending test inside Environmental Scanning electron microscope
Philosophical Transactions of the Royal Society A, 2017Co-Authors: Yun Deng, Tarlan Hajilou, Afrooz BarnoushAbstract:To evaluate the hydrogen (H)-induced embrittlement in iron aluminium intermetallics, especially the one with stoichiometric composition of 50 at.% Al, a novel in situ micro-cantilever bending test was applied within an Environmental Scanning electron microscope (ESEM), which provides both a full process monitoring and a clean, in situ H-charging condition. Two sets of cantilevers were analysed in this work: one set of un-notched cantilevers, and the other set with focused ion beam-milled notch laying on two crystallographic planes: (010) and (110). The cantilevers were tested under two Environmental conditions: vacuum (approximately 5 × 10 −4 Pa) and ESEM (450 Pa water vapour). Crack initiation at stress-concentrated locations and propagation to cause catastrophic failure were observed when cantilevers were tested in the presence of H; while no cracking occurred when tested in vacuum. Both the bending strength for un-notched beams and the fracture toughness for notched beams were reduced under H exposure. The hydrogen embrittlement (HE) susceptibility was found to be orientation dependent: the (010) crystallographic plane was more fragile to HE than the (110) plane. This article is part of the themed issue ‘The challenges of hydrogen and metals’.
-
in situ micro cantilever bending test in Environmental Scanning electron microscope real time observation of hydrogen enhanced cracking
Scripta Materialia, 2017Co-Authors: Yun Deng, Nousha Kheradmand, Tarlan Hajilou, Afrooz BarnoushAbstract:Abstract A novel approach of in-situ micro-cantilever bending tests is introduced, integrating nanoindentation and Environmental Scanning electron microscopy (ESEM) to elucidate hydrogen embrittlement (HE) in FeAl. Bending tests were performed in vacuum (~ 5 × 10− 4 Pa) and in ESEM with water vapor (180 Pa, 450 Pa) conditions, which introduce H in-situ into the cantilevers during the test. Micro-scale In-situ SEM testing provides a full control of all the parameters involved in HE as well as avoids the proximity effect from the free surface, which is always criticized in nano-scale in-situ TEM experiments. Both hydrogen induced cracking and hydrogen reduced flow stress were observed.
Augusto Shoji Kato - One of the best experts on this subject based on the ideXlab platform.
-
comparative analysis of dentinal erosion after passive ultrasonic irrigation versus irrigation with reciprocating activation an Environmental Scanning electron study
Journal of Endodontics, 2017Co-Authors: Ana Paula Simezo, Rodrigo Sanches Cunha, Carlos Eduardo Da Silveira Bueno, Rina Andrea Pelegrine, Alexandre Sigrist De Martin, Daniel Guimaraes Pedro Rocha, Augusto Shoji KatoAbstract:Abstract Introduction The aim of this study was to assess ex vivo the erosive effects of passive ultrasonic irrigation versus irrigation with reciprocating activation on the dentinal surface of the root canal at 3 predetermined levels using Environmental Scanning electron microscopy. Methods Ten roots of mandibular premolars were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland). The specimens were embedded in flasks cleaved longitudinally, and indentations were made 3.0, 6.0, and 9.0 mm from the apex. The specimens in the control group ( n = 10) were cleaned in an ultrasonic bath containing 2.5% sodium hypochlorite and 17% EDTA and then dried. Then, Environmental Scanning electron microscopic images were obtained at magnification × 800. The specimens were then reassembled in their flasks, and the NaOCl and EDTA solutions were activated according to the conditions established for the experimental groups (ie, the passive ultrasonic irrigation group [ n = 5] and the EasyClean (Easy Equipamentos Odontologicos, Belo Horizonte, MG, Brazil) group, irrigation with reciprocating activation with the EasyClean instrument [ n = 5]). The specimens of both experimental groups were analyzed in the same manner as in the control group. Analysis of the dentinal surface topography was conducted using the 3D Roughness Reconstruction program (Phenom-World BV, Eindhoven, the Netherlands) as a means for assessing erosion. The data were evaluated by means of the Kruskal-Wallis, Student-Newman-Keuls, and Mann-Whitney tests. Results In the EasyClean group, the degree of dentinal erosion at 3.0 mm was significantly higher than at 9.0 mm. In the other comparisons, there was no statistically significant difference ( P Conclusions The final irrigation techniques tested were equivalent in relation to the degree of erosion caused to the dentinal surface.
-
investigation of the efficacy of passive ultrasonic irrigation versus irrigation with reciprocating activation an Environmental Scanning electron microscopic study
Journal of Endodontics, 2016Co-Authors: Augusto Shoji Kato, Rodrigo Sanches Cunha, Carlos Eduardo Da Silveira Bueno, Rina Andrea Pelegrine, Carlos Eduardo Fontana, Alexandre Sigrist De MartinAbstract:Abstract Introduction The objective of this ex vivo study was to compare the efficacy of passive ultrasonic irrigation (PUI) versus a new activation system using reciprocating motion (EasyClean [EC]; Easy Equipamentos Odontologicos, Belo Horizonte, Brazil) to remove debris from the root canal walls at 6 predetermined apical levels using Environmental Scanning electron microscopy. Methods Mesiobuccal root canals of 10 mandibular molars were prepared with a 30/.05 final instrument. The specimens were embedded in flasks containing heavy body silicone, cleaved longitudinally, and 6 round indentations were made into the apical region of the buccal half at 1-mm intervals. The same specimens were used to prepare a blank control group (no debris), a negative control group (completely covered by debris), and 2 experimental groups: PUI and irrigation with reciprocating activation. Standardized images of the indentations were obtained under Environmental Scanning electron microscopy and assessed by 2 examiners. The amount of debris was then classified using a 4-category scoring system. The kappa test was applied to determine interexaminer agreement, whereas the Kruskal-Wallis, Dunn, and Friedman tests were used to compare scores. Results The EC group had results statistically similar to those of the blank control group for all 6 root levels examined. The PUI group had results statistically similar to those of the negative control group for the 3 most apical levels and similar to those of the blank control group for the 3 most cervical levels. Conclusions Activating the irrigant with a reciprocating system (EC) promoted more effective debris removal from the more apical regions of the root canal when compared with PUI.
Alexandre Sigrist De Martin - One of the best experts on this subject based on the ideXlab platform.
-
comparative analysis of dentinal erosion after passive ultrasonic irrigation versus irrigation with reciprocating activation an Environmental Scanning electron study
Journal of Endodontics, 2017Co-Authors: Ana Paula Simezo, Rodrigo Sanches Cunha, Carlos Eduardo Da Silveira Bueno, Rina Andrea Pelegrine, Alexandre Sigrist De Martin, Daniel Guimaraes Pedro Rocha, Augusto Shoji KatoAbstract:Abstract Introduction The aim of this study was to assess ex vivo the erosive effects of passive ultrasonic irrigation versus irrigation with reciprocating activation on the dentinal surface of the root canal at 3 predetermined levels using Environmental Scanning electron microscopy. Methods Ten roots of mandibular premolars were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland). The specimens were embedded in flasks cleaved longitudinally, and indentations were made 3.0, 6.0, and 9.0 mm from the apex. The specimens in the control group ( n = 10) were cleaned in an ultrasonic bath containing 2.5% sodium hypochlorite and 17% EDTA and then dried. Then, Environmental Scanning electron microscopic images were obtained at magnification × 800. The specimens were then reassembled in their flasks, and the NaOCl and EDTA solutions were activated according to the conditions established for the experimental groups (ie, the passive ultrasonic irrigation group [ n = 5] and the EasyClean (Easy Equipamentos Odontologicos, Belo Horizonte, MG, Brazil) group, irrigation with reciprocating activation with the EasyClean instrument [ n = 5]). The specimens of both experimental groups were analyzed in the same manner as in the control group. Analysis of the dentinal surface topography was conducted using the 3D Roughness Reconstruction program (Phenom-World BV, Eindhoven, the Netherlands) as a means for assessing erosion. The data were evaluated by means of the Kruskal-Wallis, Student-Newman-Keuls, and Mann-Whitney tests. Results In the EasyClean group, the degree of dentinal erosion at 3.0 mm was significantly higher than at 9.0 mm. In the other comparisons, there was no statistically significant difference ( P Conclusions The final irrigation techniques tested were equivalent in relation to the degree of erosion caused to the dentinal surface.
-
investigation of the efficacy of passive ultrasonic irrigation versus irrigation with reciprocating activation an Environmental Scanning electron microscopic study
Journal of Endodontics, 2016Co-Authors: Augusto Shoji Kato, Rodrigo Sanches Cunha, Carlos Eduardo Da Silveira Bueno, Rina Andrea Pelegrine, Carlos Eduardo Fontana, Alexandre Sigrist De MartinAbstract:Abstract Introduction The objective of this ex vivo study was to compare the efficacy of passive ultrasonic irrigation (PUI) versus a new activation system using reciprocating motion (EasyClean [EC]; Easy Equipamentos Odontologicos, Belo Horizonte, Brazil) to remove debris from the root canal walls at 6 predetermined apical levels using Environmental Scanning electron microscopy. Methods Mesiobuccal root canals of 10 mandibular molars were prepared with a 30/.05 final instrument. The specimens were embedded in flasks containing heavy body silicone, cleaved longitudinally, and 6 round indentations were made into the apical region of the buccal half at 1-mm intervals. The same specimens were used to prepare a blank control group (no debris), a negative control group (completely covered by debris), and 2 experimental groups: PUI and irrigation with reciprocating activation. Standardized images of the indentations were obtained under Environmental Scanning electron microscopy and assessed by 2 examiners. The amount of debris was then classified using a 4-category scoring system. The kappa test was applied to determine interexaminer agreement, whereas the Kruskal-Wallis, Dunn, and Friedman tests were used to compare scores. Results The EC group had results statistically similar to those of the blank control group for all 6 root levels examined. The PUI group had results statistically similar to those of the negative control group for the 3 most apical levels and similar to those of the blank control group for the 3 most cervical levels. Conclusions Activating the irrigant with a reciprocating system (EC) promoted more effective debris removal from the more apical regions of the root canal when compared with PUI.
