The Experts below are selected from a list of 972 Experts worldwide ranked by ideXlab platform
Schifino-wittmann, Maria Teresa - One of the best experts on this subject based on the ideXlab platform.
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Determinação da quantidade de DNA nuclear em plantas
2010Co-Authors: Schifino-wittmann, Maria TeresaAbstract:O valor C de DNA é um caráter de significado biológico fundamental e o conhecimento da quantidade de DNA nuclear de um grupo de organismos pode ser útil em vários campos da ciência. Do ponto de vista prático, a determinação da quantidade de DNA nuclear, que é mais comumente realizada por microdensitometria de Feulgen e citometria de fluxo, pode substituir a contagem de cromossomos, especialmente quando se trabalha com um número muito grande de indivíduos. A microdensitometria por Feulgen baseia-se na ligação específica do DNA a esse corante, havendo uma proporcionalidade entre a quantidade de DNA existente e a quantidade de corante que o núcleo incorporou. A citometria de fluxo envolve a análise das propriedades óticas de partículas em fluxo. Em plantas, basicamente consiste no isolamento dos núcleos, coloração destes com um fluorocromo e leitura da fluorescência emitida As grandes vantagens desta técnica, em relação à microdensitometria de Feulgen, são a relativa facilidade e a rapidez da preparação das amostras, o grande número de núcleos que podem ser analisados, a necessidade de pequenas quantidades de tecido e a possibilidade de detecção de pequenas diferenças na quantidade de DNA. Relatos de resultados conflitantes entre determinações de diferentes autores mostram a necessidade de uma criteriosa padronização das técnicas, para que problemas metodológicos não venham a ser interpretados como eventuais diferenças reais na quantidade de DNA.The DNA C value is an important biological characteristic and the knowledge of DNA content may be applied to several branches of science. Nuclear DNA content determinations, normally performed by Feulgen Microdensitometry and flow cytometry, may replace chromosome counts especially when a high number of individuals are being analysed. Feulgen Microdensitometry is based on the affinity of this dye and the DNA: the amount of DNA is proportional to the amount of dye taken by the nucleus. Flow cytometry is based on the optical properties of particles on a flow. In plants the technique basically consists in the isolation of nuclei, staining with a fluorochrome and measurement of the emitted fluorescence. The advantages of this technique, when compared to Feulgen densitometry, are the relative easiness and speed of sample preparation, the possibility to analyse a high number of nuclei, the need of small tissue amounts and the detection of small differences in DNA contents. Conflicting results from different authors show the need of a rigid technical standardization so that methodological errors are not misinterpreted with eventual real differences in DNA contents
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Nuclear DNA content determination in plants
Universidade Federal de Santa Maria, 2001Co-Authors: Schifino-wittmann, Maria TeresaAbstract:O valor C de DNA é um caráter de significado biológico fundamental e o conhecimento da quantidade de DNA nuclear de um grupo de organismos pode ser útil em vários campos da ciência. Do ponto de vista prático, a determinação da quantidade de DNA nuclear, que é mais comumente realizada por microdensitometria de Feulgen e citometria de fluxo, pode substituir a contagem de cromossomos, especialmente quando se trabalha com um número muito grande de indivíduos. A microdensitometria por Feulgen baseia-se na ligação específica do DNA a esse corante, havendo uma proporcionalidade entre a quantidade de DNA existente e a quantidade de corante que o núcleo incorporou. A citometria de fluxo envolve a análise das propriedades óticas de partículas em fluxo. Em plantas, basicamente consiste no isolamento dos núcleos, coloração destes com um fluorocromo e leitura da fluorescência emitida. As grandes vantagens desta técnica, em relação à microdensitometria de Feulgen, são a relativa facilidade e a rapidez da preparação das amostras, o grande número de núcleos que podem ser analisados, a necessidade de pequenas quantidades de tecido e a possibilidade de detecção de pequenas diferenças na quantidade de DNA. Relatos de resultados conflitantes entre determinações de diferentes autores mostram a necessidade de uma criteriosa padronização das técnicas, para que problemas metodológicos não venham a ser interpretados como eventuais diferenças reais na quantidade de DNA.The DNA C value is an important biological characteristic and the knowledge of DNA content may be applied to several branches of science. Nuclear DNA content determinations, normally performed by Feulgen Microdensitometry and flow cytometry, may replace chromosome counts especially when a high number of individuals are being analysed. Feulgen Microdensitometry is based on the affinity of this dye and the DNA: the amount of DNA is proportional to the amount of dye taken by the nucleus. Flow cytometry is based on the optical properties of particles on a flow. In plants the technique basically consists in the isolation of nuclei, staining with a fluorochrome and measurement of the emitted fluorescence. The advantages of this technique, when compared to Feulgen densitometry, are the relative easiness and speed of sample preparation, the possibility to analyse a high number of nuclei, the need of small tissue amounts and the detection of small differences in DNA contents. Conflicting results from different authors show the need of a rigid technical standardization so that methodological errors are not misinterpreted with eventual real differences in DNA contents
Yu Hua Tong - One of the best experts on this subject based on the ideXlab platform.
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retinal arteriolar morphometry based on full width at half maximum analysis of spectral domain optical coherence tomography images
PLOS ONE, 2015Co-Authors: Yu Hua Tong, Tie Pei Zhu, Ze Lin Zhao, Hai Jing Zhan, Fang Zheng Jiang, Heng Li LianAbstract:Objectives In this study, we develop a Microdensitometry method using full width at half maximum (FWHM) analysis of the retinal vascular structure in a spectral-domain optical coherence tomography (SD-OCT) image and present the application of this method in the morphometry of arteriolar changes during hypertension. Methods Two raters using manual and FWHM methods measured retinal vessel outer and lumen diameters in SD-OCT images. Inter-rater reproducibility was measured using coefficients of variation (CV), intraclass correlation coefficient and a Bland-Altman plot. OCT images from forty-three eyes of 43 hypertensive patients and 40 eyes of 40 controls were analyzed using an FWHM approach; wall thickness, wall cross-sectional area (WCSA) and wall to lumen ratio (WLR) were subsequently calculated. Results Mean difference in inter-rater agreement ranged from -2.713 to 2.658 μm when using a manual method, and ranged from -0.008 to 0.131 μm when using a FWHM approach. The inter-rater CVs were significantly less for the FWHM approach versus the manual method (P < 0.05). Compared with controls, the wall thickness, WCSA and WLR of retinal arterioles were increased in the hypertensive patients, particular in diabetic hypertensive patients. Conclusions The Microdensitometry method using a FWHM algorithm markedly improved inter-rater reproducibility of arteriolar morphometric analysis, and SD-OCT may represent a promising noninvasive method for in vivo arteriolar morphometry.
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Measurement of the retinal vessel outer and lumen diameters in an optical coherence tomography (OCT) image using the Microdensitometry method.
2015Co-Authors: Yu Hua Tong, Tie Pei Zhu, Ze Lin Zhao, Hai Jing Zhan, Fang Zheng Jiang, Heng Li LianAbstract:(Top left) A line scan was performed across the vessel in zone B, and the line was aligned manually as perpendicular as possible to the running direction of the vessel. (Top right) The cross-sectional structure of the retinal arteriole (red arrow) and venule (blue arrow) could be identified in the OCT image. (Bottom left) The line selection vertically crossed the middle of the upper and lower vessel walls to produce an intensity profile. (Bottom right) The boundary points (arrow heads) were estimated at half maximum intensity for each side of the two parabolas in the profile. The distance between the boundary points was calculated for the vessel outer and lumen diameters.
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Spectral-Domain Optical Coherence Tomography
2015Co-Authors: Yu Hua Tong, Tie Pei Zhu, Ze Lin Zhao, Hai Jing Zhan, Fang Zheng Jiang, Li LianAbstract:Objectives In this study, we develop a Microdensitometry method using full width at half maximum (FWHM) analysis of the retinal vascular structure in a spectral-domain optical coherence tomography (SD-OCT) image and present the application of this method in the morphome-try of arteriolar changes during hypertension. Methods Two raters using manual and FWHMmethods measured retinal vessel outer and lumen diameters in SD-OCT images. Inter-rater reproducibility was measured using coefficients of variation (CV), intraclass correlation coefficient and a Bland-Altman plot. OCT images from forty-three eyes of 43 hypertensive patients and 40 eyes of 40 controls were analyzed using an FWHM approach; wall thickness, wall cross-sectional area (WCSA) and wall to lumen ratio (WLR) were subsequently calculated. Results Mean difference in inter-rater agreement ranged from-2.713 to 2.658 μmwhen using a manual method, and ranged from-0.008 to 0.131 μmwhen using a FWHM approach. The inter-rater CVs were significantly less for the FWHM approach versus the manual method (P < 0.05). Compared with controls, the wall thickness, WCSA andWLR of retinal arterioles were increased in the hypertensive patients, particular in diabetic hypertensive patients
Heng Li Lian - One of the best experts on this subject based on the ideXlab platform.
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retinal arteriolar morphometry based on full width at half maximum analysis of spectral domain optical coherence tomography images
PLOS ONE, 2015Co-Authors: Yu Hua Tong, Tie Pei Zhu, Ze Lin Zhao, Hai Jing Zhan, Fang Zheng Jiang, Heng Li LianAbstract:Objectives In this study, we develop a Microdensitometry method using full width at half maximum (FWHM) analysis of the retinal vascular structure in a spectral-domain optical coherence tomography (SD-OCT) image and present the application of this method in the morphometry of arteriolar changes during hypertension. Methods Two raters using manual and FWHM methods measured retinal vessel outer and lumen diameters in SD-OCT images. Inter-rater reproducibility was measured using coefficients of variation (CV), intraclass correlation coefficient and a Bland-Altman plot. OCT images from forty-three eyes of 43 hypertensive patients and 40 eyes of 40 controls were analyzed using an FWHM approach; wall thickness, wall cross-sectional area (WCSA) and wall to lumen ratio (WLR) were subsequently calculated. Results Mean difference in inter-rater agreement ranged from -2.713 to 2.658 μm when using a manual method, and ranged from -0.008 to 0.131 μm when using a FWHM approach. The inter-rater CVs were significantly less for the FWHM approach versus the manual method (P < 0.05). Compared with controls, the wall thickness, WCSA and WLR of retinal arterioles were increased in the hypertensive patients, particular in diabetic hypertensive patients. Conclusions The Microdensitometry method using a FWHM algorithm markedly improved inter-rater reproducibility of arteriolar morphometric analysis, and SD-OCT may represent a promising noninvasive method for in vivo arteriolar morphometry.
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Measurement of the retinal vessel outer and lumen diameters in an optical coherence tomography (OCT) image using the Microdensitometry method.
2015Co-Authors: Yu Hua Tong, Tie Pei Zhu, Ze Lin Zhao, Hai Jing Zhan, Fang Zheng Jiang, Heng Li LianAbstract:(Top left) A line scan was performed across the vessel in zone B, and the line was aligned manually as perpendicular as possible to the running direction of the vessel. (Top right) The cross-sectional structure of the retinal arteriole (red arrow) and venule (blue arrow) could be identified in the OCT image. (Bottom left) The line selection vertically crossed the middle of the upper and lower vessel walls to produce an intensity profile. (Bottom right) The boundary points (arrow heads) were estimated at half maximum intensity for each side of the two parabolas in the profile. The distance between the boundary points was calculated for the vessel outer and lumen diameters.
F. Pichelin - One of the best experts on this subject based on the ideXlab platform.
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Enhancing the exterior performance of wood joined by linear and rotational welding
Journal of Adhesion Science and Technology, 2011Co-Authors: Antonio Pizzi, H. R. Mansouri, Jean-michel Leban, L. Delmotte, F. PichelinAbstract:Application of rosin, a wood derived, non-toxic, natural, inexpensive and easily and abundantly available natural material, to the wood faces to be joined by either linear vibration welding or rotational dowel welding has shown to greatly enhance the water resistance of welded wood joints. The method of application has been shown to have a marked effect on the results, with the application and drying of a diluted rosin solution to the wood surfaces before welding yielding the best results. The considerable improvement in water resistance does not still allow classification of the joints as fully exterior grade. However, dowel welding can now be used for protected exterior joints due to a combination of rosin waterproofing and joint geometry. Welded dowel joints holding together for longer than 455 days immersion in water indicate this to be the case. Rosin-treated linear vibration joints held together well in excess of 30 days but retained a measurable strength, in the best case, only up to 18 days water immersion. The wood anatomy and chemical reasons for the effect of rosin were determined by X-ray Microdensitometry and CP-MAS (13)C-NMR analysis.
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Temperature and density distribution in mechanical vibration wood welding
Wood Science and Technology, 2006Co-Authors: C. Ganne-chedeville, Jean-michel Leban, M. Properzi, F. Pichelin, Antonio PizziAbstract:Nondestructive evaluation of wood joints welded by linear vibration welding was performed with an infrared (IR) thermography technique, which allowed the maximal and average peak temperature profile/distribution to be measured. The density profile/distribution at the joint interface was measured by X-ray Microdensitometry. The results show that the width of the welded zone also varies as a function of the maximum temperature reached during welding and that the maximum temperature reached at the ends of the specimens is lower than that obtained in the central part of the specimens
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x ray Microdensitometry analysis of vibration welded wood
Journal of Adhesion Science and Technology, 2004Co-Authors: Jean-michel Leban, A. Pizzi, M. Properzi, Stefanie Wieland, M Zanetti, F. PichelinAbstract:X-ray Microdensitometry tests on vibration-welded hardwoods (beech and oak) and a softwood (spruce) showed that adhesion of wood surfaces by vibration welding was accompanied by a considerable increase in the density of the wood at the bonded interface. This is due to the loss of the intercellular structure of the wood at the interface and considerable decrease of empty spaces in its cellular structure. The sharper and more regular is the increase in density at the interface the better is the mechanical performance of the joint. This was ascribed to the marked difference in wood density between earlywood and latewood. This intra-ring wood heterogeneity is a limiting factor for reaching high local compression rates during the welding process. In the case of spruce wood it causes cells collapse and, consequently, poorer bonding. Absolute and relative density maps of well-bonded, poorly-bonded and unbonded joints are reported. X-ray Microdensitometry proved to be a valuable technique to determine the extent ...
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X-ray Microdensitometry analysis of vibration-welded wood
Journal of Adhesion Science and Technology, 2004Co-Authors: Jean-michel Leban, M. Properzi, Antonio Pizzi, Stefanie Wieland, M Zanetti, F. PichelinAbstract:X-ray Microdensitometry tests on vibration-welded hardwoods (beech and oak) and a softwood (spruce) showed that adhesion of wood surfaces by vibration welding was accompanied by a considerable increase in the density of the wood at the bonded interface. This is due to the loss of the intercellular structure of the wood at the interface and considerable decrease of empty spaces in its cellular structure. The sharper and more regular is the increase in density at the interface the better is the mechanical performance of the joint. This was ascribed to the marked difference in wood density between earlywood and latewood. This intra-ring wood heterogeneity is a limiting factor for reaching high local compression rates during the welding process. In the case of spruce wood it causes cells collapse and, consequently, poorer bonding. Absolute and relative density maps of well-bonded, poorly-bonded and unbonded joints are reported. X-ray Microdensitometry proved to be a valuable technique to determine the extent of wood welding
Jean-michel Leban - One of the best experts on this subject based on the ideXlab platform.
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Enhancing the exterior performance of wood joined by linear and rotational welding
Journal of Adhesion Science and Technology, 2011Co-Authors: Antonio Pizzi, H. R. Mansouri, Jean-michel Leban, L. Delmotte, F. PichelinAbstract:Application of rosin, a wood derived, non-toxic, natural, inexpensive and easily and abundantly available natural material, to the wood faces to be joined by either linear vibration welding or rotational dowel welding has shown to greatly enhance the water resistance of welded wood joints. The method of application has been shown to have a marked effect on the results, with the application and drying of a diluted rosin solution to the wood surfaces before welding yielding the best results. The considerable improvement in water resistance does not still allow classification of the joints as fully exterior grade. However, dowel welding can now be used for protected exterior joints due to a combination of rosin waterproofing and joint geometry. Welded dowel joints holding together for longer than 455 days immersion in water indicate this to be the case. Rosin-treated linear vibration joints held together well in excess of 30 days but retained a measurable strength, in the best case, only up to 18 days water immersion. The wood anatomy and chemical reasons for the effect of rosin were determined by X-ray Microdensitometry and CP-MAS (13)C-NMR analysis.
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improved water resistance of uf adhesives for plywood by small pmdi additions
European Journal of Wood and Wood Products, 2006Co-Authors: H. R. Mansouri, A. Pizzi, Jean-michel LebanAbstract:Addition of small amounts of isocyanate (pMDI), between 10% and 15% by weight, to UF resins for plywood considerably improve the UF glue line water resistance. Analysis of the plywood by X-ray Microdensitometry indicate that on both sides of the glue lines there is a local density increase which reflects either some adhesive diffusion in the wood layers immediately in contact with the glue line, or some extent of wood densification as a result of the gluing process, or both.
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Temperature and density distribution in mechanical vibration wood welding
Wood Science and Technology, 2006Co-Authors: C. Ganne-chedeville, Jean-michel Leban, M. Properzi, F. Pichelin, Antonio PizziAbstract:Nondestructive evaluation of wood joints welded by linear vibration welding was performed with an infrared (IR) thermography technique, which allowed the maximal and average peak temperature profile/distribution to be measured. The density profile/distribution at the joint interface was measured by X-ray Microdensitometry. The results show that the width of the welded zone also varies as a function of the maximum temperature reached during welding and that the maximum temperature reached at the ends of the specimens is lower than that obtained in the central part of the specimens
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wood joints by through dowel rotation welding microstructure 13c nmr and water resistance
Journal of Adhesion Science and Technology, 2006Co-Authors: A. Pizzi, H. R. Mansouri, Jean-michel Leban, A Despres, Severinne RigoletAbstract:Two-block wood joints were obtained by insertion and welding without adhesives of dowels by high-speed rotation. Their strengths were better than that obtained by poly(vinyl acetate) (PVAc) gluing. X-ray-Microdensitometry analysis showed that a complete welding of the dowel to the substrate occurred and that a perfectly tight joint was formed. Isolation of the flow material allowed CP-MAS 13C-NMR analysis of its composition with possibly low interference from the constituents from the substrate. The flow material appeared to be composed of hemicelluloses, apparently xylans, and lignin. Scanning electron microscopy coupled with the NMR analysis results showed that microfibrils of cellulose, in both amorphous and crystalline states, torn from the wood surface during welding, as well as very small proportions possibly of recrystallized xylans and furanic compounds formed by heat transformation of the carbohydrates, were present. The geometry of the dowel joint allowed the joint to maintain up to 88% of its i...
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x ray Microdensitometry analysis of vibration welded wood
Journal of Adhesion Science and Technology, 2004Co-Authors: Jean-michel Leban, A. Pizzi, M. Properzi, Stefanie Wieland, M Zanetti, F. PichelinAbstract:X-ray Microdensitometry tests on vibration-welded hardwoods (beech and oak) and a softwood (spruce) showed that adhesion of wood surfaces by vibration welding was accompanied by a considerable increase in the density of the wood at the bonded interface. This is due to the loss of the intercellular structure of the wood at the interface and considerable decrease of empty spaces in its cellular structure. The sharper and more regular is the increase in density at the interface the better is the mechanical performance of the joint. This was ascribed to the marked difference in wood density between earlywood and latewood. This intra-ring wood heterogeneity is a limiting factor for reaching high local compression rates during the welding process. In the case of spruce wood it causes cells collapse and, consequently, poorer bonding. Absolute and relative density maps of well-bonded, poorly-bonded and unbonded joints are reported. X-ray Microdensitometry proved to be a valuable technique to determine the extent ...