Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were direc...Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/h.We find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat treatment.Profile of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/h.The critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification theory.Dark and light contrast areas in macrostructure are directly related to elemental segregation.Dark contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast areas.We conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification conditions.Based on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.展开更多
Background:Stargardt disease 1(STGD1;MIM 248200)is a monogenic form of autosomal recessive genetic disease caused by mutation in ABCA4.This gene has a major role in hydrolyzing N-retinylidene-phosphatidylethanolamine ...Background:Stargardt disease 1(STGD1;MIM 248200)is a monogenic form of autosomal recessive genetic disease caused by mutation in ABCA4.This gene has a major role in hydrolyzing N-retinylidene-phosphatidylethanolamine to all-trans-retinal and phosphatidylethanolamine.The purpose of this study is to identify the frequency of putative disease-causing mutations associated with Stargardt disease in a South Indian population.Methods:A total of 28 clinically diagnosed Stargardt-like phenotype patients were recruited from south India.Ophthalmic examination of all patients was carefully carried out by a retina specialist based on the stages of fundus imaging and ERG grouping.Genetic analysis of ABCA4 was performed for all patients using Sanger sequencing and clinical exome sequencing.Results:This study identified disease-causing mutations in ABCA4 in 75%(21/28)of patients,7%(2/28)exhibited benign variants and 18%(5/28)were negative for the disease-causing mutation.Conclusion:This is the first study describing the genetic association of ABCA4 disease-causing mutation in South Indian Stargardt 1 patients(STGD1).Our findings highlighted the presence of two novel missense mutations and an(in/del,single base pair deletion&splice variant)in ABCA4.However,genetic heterogeneity in ABCA4 mutants requires a larger sample size to establish a true correlation with clinical phenotype.展开更多
Stargardt disease(also known as juvenile macular degeneration or Stargardt macular degeneration)is an inherited disorder of the retina,which can occur in the eyes of children and young adults.It is the most prevalent ...Stargardt disease(also known as juvenile macular degeneration or Stargardt macular degeneration)is an inherited disorder of the retina,which can occur in the eyes of children and young adults.It is the most prevalent form of juvenile-onset macular dystrophy,causing progressive(and often severe)vision loss.Images with Stargardt disease are characterized by the appearance of flecks in early and intermediate stages,and the appearance of atrophy,due to cells wasting away and dying,in the advanced stage.The primary measure of late-stage Stargardt disease is the appearance of atrophy.Fundus autofluorescence is a widely available two-dimensional imaging technique,which can aid in the diagnosis of the disease.Spectral-domain optical coherence tomography,in contrast,provides three-dimensional visualization of the retinal microstructure,thereby allowing the status of the individual retinal layers.Stargardt disease may cause various levels of disruption to the photoreceptor segments as well as other outer retinal layers.In recent years,there has been an exponential growth in the number of applications utilizing artificial intelligence for help with processing such diseases,heavily fueled by the amazing successes in image recognition using deep learning.This review regarding artificial intelligence deep learning approaches for the Stargardt atrophy screening and segmentation on fundus autofluorescence images is first provided,followed by a review of the automated retinal layer segmentation with atrophic-appearing lesions and fleck features using artificial intelligence deep learning construct.The paper concludes with a perspective about using artificial intelligence to potentially find early risk factors or biomarkers that can aid in the prediction of Stargardt disease progression.展开更多
以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6...以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6a）和叶面积指数的变化。结果表明，杏树冠层内部平均PAR的垂直分布具有随着向下累计叶面积指数的增加而递减的趋势，在冠层中上部，透光率较高，PAR递减很明显，冠层下部则维持较低水平，变化不大，在相同的天气和时间条件下不同树龄冠层内PAR同一相对高度的透光率有随树龄增加而递减的趋势，但在不同时刻不同天气条件下，即使同一棵树相同高度同一方位冠层内也具有不同的消光系数，影响杏树冠内光分布的因素是多样的，它们之间存在着复杂的关系；2～6年生杏树冠层中部的全天平均透光率分别为49．5％、30．0％、27．5％、13．4％和7．8％，冠层下部的平均透光率分别为29．1％、12．1％、10．9％、6．4％和5．9％；杏树冠层叶面积指数LAI（kaf Area Index）与透光率呈极显著指数相关关系，其表达式为Y=131．39e^-0．8963X（R^2=0．907^＊＊）；试验结果也可为果树冠层内PAR三维空间分布的模拟研究及冠层结构的优化提供试验方法和理论验证上的参考。展开更多
文摘Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/h.We find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat treatment.Profile of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/h.The critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification theory.Dark and light contrast areas in macrostructure are directly related to elemental segregation.Dark contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast areas.We conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification conditions.Based on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.
基金This work was funded by the Aravind Eye Care System-Madurai,India.
文摘Background:Stargardt disease 1(STGD1;MIM 248200)is a monogenic form of autosomal recessive genetic disease caused by mutation in ABCA4.This gene has a major role in hydrolyzing N-retinylidene-phosphatidylethanolamine to all-trans-retinal and phosphatidylethanolamine.The purpose of this study is to identify the frequency of putative disease-causing mutations associated with Stargardt disease in a South Indian population.Methods:A total of 28 clinically diagnosed Stargardt-like phenotype patients were recruited from south India.Ophthalmic examination of all patients was carefully carried out by a retina specialist based on the stages of fundus imaging and ERG grouping.Genetic analysis of ABCA4 was performed for all patients using Sanger sequencing and clinical exome sequencing.Results:This study identified disease-causing mutations in ABCA4 in 75%(21/28)of patients,7%(2/28)exhibited benign variants and 18%(5/28)were negative for the disease-causing mutation.Conclusion:This is the first study describing the genetic association of ABCA4 disease-causing mutation in South Indian Stargardt 1 patients(STGD1).Our findings highlighted the presence of two novel missense mutations and an(in/del,single base pair deletion&splice variant)in ABCA4.However,genetic heterogeneity in ABCA4 mutants requires a larger sample size to establish a true correlation with clinical phenotype.
基金supported by the National Eye Institute of the National Institutes of Health under Award Number R21EY029839 (to ZJH)
文摘Stargardt disease(also known as juvenile macular degeneration or Stargardt macular degeneration)is an inherited disorder of the retina,which can occur in the eyes of children and young adults.It is the most prevalent form of juvenile-onset macular dystrophy,causing progressive(and often severe)vision loss.Images with Stargardt disease are characterized by the appearance of flecks in early and intermediate stages,and the appearance of atrophy,due to cells wasting away and dying,in the advanced stage.The primary measure of late-stage Stargardt disease is the appearance of atrophy.Fundus autofluorescence is a widely available two-dimensional imaging technique,which can aid in the diagnosis of the disease.Spectral-domain optical coherence tomography,in contrast,provides three-dimensional visualization of the retinal microstructure,thereby allowing the status of the individual retinal layers.Stargardt disease may cause various levels of disruption to the photoreceptor segments as well as other outer retinal layers.In recent years,there has been an exponential growth in the number of applications utilizing artificial intelligence for help with processing such diseases,heavily fueled by the amazing successes in image recognition using deep learning.This review regarding artificial intelligence deep learning approaches for the Stargardt atrophy screening and segmentation on fundus autofluorescence images is first provided,followed by a review of the automated retinal layer segmentation with atrophic-appearing lesions and fleck features using artificial intelligence deep learning construct.The paper concludes with a perspective about using artificial intelligence to potentially find early risk factors or biomarkers that can aid in the prediction of Stargardt disease progression.
文摘以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6a）和叶面积指数的变化。结果表明，杏树冠层内部平均PAR的垂直分布具有随着向下累计叶面积指数的增加而递减的趋势，在冠层中上部，透光率较高，PAR递减很明显，冠层下部则维持较低水平，变化不大，在相同的天气和时间条件下不同树龄冠层内PAR同一相对高度的透光率有随树龄增加而递减的趋势，但在不同时刻不同天气条件下，即使同一棵树相同高度同一方位冠层内也具有不同的消光系数，影响杏树冠内光分布的因素是多样的，它们之间存在着复杂的关系；2～6年生杏树冠层中部的全天平均透光率分别为49．5％、30．0％、27．5％、13．4％和7．8％，冠层下部的平均透光率分别为29．1％、12．1％、10．9％、6．4％和5．9％；杏树冠层叶面积指数LAI（kaf Area Index）与透光率呈极显著指数相关关系，其表达式为Y=131．39e^-0．8963X（R^2=0．907^＊＊）；试验结果也可为果树冠层内PAR三维空间分布的模拟研究及冠层结构的优化提供试验方法和理论验证上的参考。
