It is important to segment mass region accurately in a computer-aided diagnosis (CADx) scheme for evaluating the likelihood of malignancy of the mass on ultrasonographic breast image. The purpose of this study was to ...It is important to segment mass region accurately in a computer-aided diagnosis (CADx) scheme for evaluating the likelihood of malignancy of the mass on ultrasonographic breast image. The purpose of this study was to develop a novel level set method for segmentation of breast mass on ultrasonographic image. Our database consisted of 151 ultrasonographic images with 70 malignant and 81 benign breast masses. In a novel level set method, an energy function was defined with region-based, edge-based, and regularizing terms. The region-based term analyzed global information, whereas the edge-based term analyzed local information. The regularizing term also controlled the length of the boundary curve. The region of breast mass was segmented so that the energy based on those terms was minimized. With our proposed method, true positive (TP) ratio, false positive (FP) ratio, jaccard similarity (JS), and Dice similarity coefficient (DSC) were 92.2%, 9.1%, 84.2%, and 91.3%, respectively. These results tended to be substantially higher than those with two conventional segmentation methods. Our proposed method based on the novel level set method was shown to segment mass region accurately on ultrasonographic breast image.展开更多
Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector induct...Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for their U-Th systematics. Their uranium contents are mostly lower than 3μg/g, and the δ+{234}U(T) values are within the range of 150±5. X-ray diffraction analysis showed that the corals are all composed of aragonite. This demonstrates that the corals determined have maintained a close system for 7000 years and their skeletons bear much information about the primitive tropical marine environment. The highly precise age sequence of the corals determined has revealed that there occurred three phases of high sea level in the South China Sea waters, which are dated at 6799-6307 a B.P., 4472-4285 a B.P. and 1279-1012 a B.P., respectively. The three phases lasted 492 a, 187 a and 267 a, respectively. These three phases of high sea level are corresponding to the warm environments that had appeared in China during the Megathermal Period and the Medieval Warm Period in the past ten thousand years.展开更多
The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples rema...The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples remains challenging. Cr(VI) analyses with multipoint calibration and speciated isotope dilution (SID) adapted from U.S. EPA method 6800 were used to measure lower-level Cr(VI) on an ion chromatograph coupled with a tandem mass spectrometer (IC-MS/MS). Lake sediment samples were collected from various locations in Northern Ontario and Cr(VI) was extracted using both alkaline digestion and ethylene diaminetetraacetic acid (EDTA) extraction. Certified reference materials were extracted and analyzed by IC-MS/MS and UV-VIS detection. The SID-MS approach allowed for the quantification of Cr(VI) in samples with concentration levels below 0.5 μg.g-1 wet weight.展开更多
格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提...格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提供的近20年的月时变重力场数据,以及EuropeanRemote Sensing(ERS-2)、Envisat和CryoSat-2等卫星测高数据,本文对比分析了2002年4月-2020年12月格陵兰冰盖质量变化特征。研究结果表明:(1)卫星重力点质量模型与卫星测高产品估计的质量变化趋势空间分布较为一致,均表明格陵兰冰盖边缘低海拔区域质量亏损严重而内部高原存在质量累积。(2) 2002-2020年格陵兰质量损失对全球平均海平面变化贡献为0.73±0.01mm·a^(-1)。(3)格陵兰冰盖西南部和西北部对海平面变化的贡献占格陵兰总贡献量的43.69%,为主要的海平面上升贡献区。(4)格陵兰冰盖流域尺度的分析表明,Goddard Space Flight Center(GSFC)点质量模型与卫星测高估计的结果更为一致。展开更多
目的建立不同剂量双酚S(Bisphenol S,BPS)暴露动物实验模型,分析大鼠尿液中BPS内暴露水平的动态变化。方法通过灌胃给药建立对照组、1μg/kg低剂量组、100μg/kg中剂量组和10 mg/kg高剂量组Sprague Dawley(SD)大鼠暴露模型,使用超高效...目的建立不同剂量双酚S(Bisphenol S,BPS)暴露动物实验模型,分析大鼠尿液中BPS内暴露水平的动态变化。方法通过灌胃给药建立对照组、1μg/kg低剂量组、100μg/kg中剂量组和10 mg/kg高剂量组Sprague Dawley(SD)大鼠暴露模型,使用超高效液相色谱-串联质谱法(Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry,UPLC-MS/MS)内标法检测大鼠在连续6周暴露不同剂量BPS后其尿样中BPS含量的变化。结果目标物BPS在0.2~100μg/L的范围内呈良好线性关系,r^(2)≥0.998,方法检出限为0.01μg/L,定量限为0.03μg/L。对大鼠尿液的检测结果表明,随着暴露时间的增加,BPS在各剂量组大鼠体内的生物累积效应明显,尿液中BPS的内暴露水平在给药的6周中持续升高,且从给药后的第一周开始,尿液BPS含量的组间差异均有统计学意义(P<0.05)。结论本研究成功建立了不同剂量BPS暴露的SD大鼠动物实验模型,准确测定了大鼠连续6周尿液中双酚S的内暴露水平,为BPS毒理学剂量-效应关系研究提供参考。展开更多
文摘It is important to segment mass region accurately in a computer-aided diagnosis (CADx) scheme for evaluating the likelihood of malignancy of the mass on ultrasonographic breast image. The purpose of this study was to develop a novel level set method for segmentation of breast mass on ultrasonographic image. Our database consisted of 151 ultrasonographic images with 70 malignant and 81 benign breast masses. In a novel level set method, an energy function was defined with region-based, edge-based, and regularizing terms. The region-based term analyzed global information, whereas the edge-based term analyzed local information. The regularizing term also controlled the length of the boundary curve. The region of breast mass was segmented so that the energy based on those terms was minimized. With our proposed method, true positive (TP) ratio, false positive (FP) ratio, jaccard similarity (JS), and Dice similarity coefficient (DSC) were 92.2%, 9.1%, 84.2%, and 91.3%, respectively. These results tended to be substantially higher than those with two conventional segmentation methods. Our proposed method based on the novel level set method was shown to segment mass region accurately on ultrasonographic breast image.
文摘Coral samples collected from the waters off the Leizhou Peninsula, the Hainan Island and the Yongxing Island of the Xisha Islands were analyzed by thermal ionization mass spectrometry (TIMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for their U-Th systematics. Their uranium contents are mostly lower than 3μg/g, and the δ+{234}U(T) values are within the range of 150±5. X-ray diffraction analysis showed that the corals are all composed of aragonite. This demonstrates that the corals determined have maintained a close system for 7000 years and their skeletons bear much information about the primitive tropical marine environment. The highly precise age sequence of the corals determined has revealed that there occurred three phases of high sea level in the South China Sea waters, which are dated at 6799-6307 a B.P., 4472-4285 a B.P. and 1279-1012 a B.P., respectively. The three phases lasted 492 a, 187 a and 267 a, respectively. These three phases of high sea level are corresponding to the warm environments that had appeared in China during the Megathermal Period and the Medieval Warm Period in the past ten thousand years.
文摘The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples remains challenging. Cr(VI) analyses with multipoint calibration and speciated isotope dilution (SID) adapted from U.S. EPA method 6800 were used to measure lower-level Cr(VI) on an ion chromatograph coupled with a tandem mass spectrometer (IC-MS/MS). Lake sediment samples were collected from various locations in Northern Ontario and Cr(VI) was extracted using both alkaline digestion and ethylene diaminetetraacetic acid (EDTA) extraction. Certified reference materials were extracted and analyzed by IC-MS/MS and UV-VIS detection. The SID-MS approach allowed for the quantification of Cr(VI) in samples with concentration levels below 0.5 μg.g-1 wet weight.
文摘格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提供的近20年的月时变重力场数据,以及EuropeanRemote Sensing(ERS-2)、Envisat和CryoSat-2等卫星测高数据,本文对比分析了2002年4月-2020年12月格陵兰冰盖质量变化特征。研究结果表明:(1)卫星重力点质量模型与卫星测高产品估计的质量变化趋势空间分布较为一致,均表明格陵兰冰盖边缘低海拔区域质量亏损严重而内部高原存在质量累积。(2) 2002-2020年格陵兰质量损失对全球平均海平面变化贡献为0.73±0.01mm·a^(-1)。(3)格陵兰冰盖西南部和西北部对海平面变化的贡献占格陵兰总贡献量的43.69%,为主要的海平面上升贡献区。(4)格陵兰冰盖流域尺度的分析表明,Goddard Space Flight Center(GSFC)点质量模型与卫星测高估计的结果更为一致。
文摘目的建立不同剂量双酚S(Bisphenol S,BPS)暴露动物实验模型,分析大鼠尿液中BPS内暴露水平的动态变化。方法通过灌胃给药建立对照组、1μg/kg低剂量组、100μg/kg中剂量组和10 mg/kg高剂量组Sprague Dawley(SD)大鼠暴露模型,使用超高效液相色谱-串联质谱法(Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry,UPLC-MS/MS)内标法检测大鼠在连续6周暴露不同剂量BPS后其尿样中BPS含量的变化。结果目标物BPS在0.2~100μg/L的范围内呈良好线性关系,r^(2)≥0.998,方法检出限为0.01μg/L,定量限为0.03μg/L。对大鼠尿液的检测结果表明,随着暴露时间的增加,BPS在各剂量组大鼠体内的生物累积效应明显,尿液中BPS的内暴露水平在给药的6周中持续升高,且从给药后的第一周开始,尿液BPS含量的组间差异均有统计学意义(P<0.05)。结论本研究成功建立了不同剂量BPS暴露的SD大鼠动物实验模型,准确测定了大鼠连续6周尿液中双酚S的内暴露水平,为BPS毒理学剂量-效应关系研究提供参考。
