The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides...The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides such as^(60)Fe.In this work,we stepped up the development of an accelerator mass spectrometry(AMS)method for detecting^(60)Fe using the HI-13tandem accelerator at the China Institute of Atomic Energy(CIAE).Since interferences could not be sufficiently removed solely with the existing magnetic systems of the tandem accelerator and the following Q3D magnetic spectrograph,a Wien filter with a maximum voltage of±60 kV and a maximum magnetic field of 0.3 T was installed after the accelerator magnetic systems to lower the detection background for the low abundance nuclide^(60)Fe.A 1μm thick Si_(3)N_(4) foil was installed in front of the Q3D as an energy degrader.For particle detection,a multi-anode gas ionization chamber was mounted at the center of the focal plane of the spectrograph.Finally,an^(60)Fe sample with an abundance of 1.125×10^(-10)was used to test the new AMS system.These results indicate that^(60)Fe can be clearly distinguished from the isobar^(60)Ni.The sensitivity was assessed to be better than 4.3×10^(-14)based on blank sample measurements lasting 5.8 h,and the sensitivity could,in principle,be expected to be approximately 2.5×10^(-15)when the data were accumulated for 100 h,which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.展开更多
Background： The clinical behavior and management of poorly differentiated thyroid carcinoma （PDTC） are very different from papillary thyroid carcinoma （PTC）. By comparing the clinical and ultrasonographic feature...Background： The clinical behavior and management of poorly differentiated thyroid carcinoma （PDTC） are very different from papillary thyroid carcinoma （PTC）. By comparing the clinical and ultrasonographic features between the two tumors, we proposed to provide more possibilities for recognizing PDTC before treatment. Methods： The data of 13 PDTCs and 39 ageand gender-matched PTCs in Peking Union Medical College Hospital between December 2003 and September 2013 were retrospectively reviewed. The clinical and ultrasonic features between the two groups were compared. Results： The frequencies of family history of carcinoma, complication with other thyroid lesions, lymph node metastases, recurrent laryngeal nerve injuries, and distant metastases were higher in PDTCs （30.8%, 61.6%, 69.2%, 23.1%, and 46.2%, respectively） than those in PTCs （2.6%, 23.1%, 25.6%, 2.6%, and 2.6%, respectively） （P 〈 0.05）. The mortality rate of PDTCs was greatly higher than PTCs （P 〈 0.01）. Conventional ultrasound showed that the size of PDTCs was larger than that of PTCs （3.1±1.9 cm vs. 1.7± 1.0 cm）. Clear margins and rich and/or irregular blood flow were found in 92.3% of PDTCs, which differed substantially from PTCs （51.7% and 53.8%, respectively） （P 〈 0.05）. Conclusions： PDTC is more aggressive and its mortality rate is higher than PTCs. Accordingly, more attention should be given to suspicious thyroid cancer nodules that show large size, regular shape, and rich blood flow signals on ultrasound to exclude the possibility of PDTCs.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12125509,12222514,11961141003,and 12005304)National Key Research and Development Project(No.2022YFA1602301)+1 种基金CAST Young Talent Support Planthe CNNC Science Fund for Talented Young Scholars Continuous support for basic scientific research projects。
文摘The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides such as^(60)Fe.In this work,we stepped up the development of an accelerator mass spectrometry(AMS)method for detecting^(60)Fe using the HI-13tandem accelerator at the China Institute of Atomic Energy(CIAE).Since interferences could not be sufficiently removed solely with the existing magnetic systems of the tandem accelerator and the following Q3D magnetic spectrograph,a Wien filter with a maximum voltage of±60 kV and a maximum magnetic field of 0.3 T was installed after the accelerator magnetic systems to lower the detection background for the low abundance nuclide^(60)Fe.A 1μm thick Si_(3)N_(4) foil was installed in front of the Q3D as an energy degrader.For particle detection,a multi-anode gas ionization chamber was mounted at the center of the focal plane of the spectrograph.Finally,an^(60)Fe sample with an abundance of 1.125×10^(-10)was used to test the new AMS system.These results indicate that^(60)Fe can be clearly distinguished from the isobar^(60)Ni.The sensitivity was assessed to be better than 4.3×10^(-14)based on blank sample measurements lasting 5.8 h,and the sensitivity could,in principle,be expected to be approximately 2.5×10^(-15)when the data were accumulated for 100 h,which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.
文摘Background： The clinical behavior and management of poorly differentiated thyroid carcinoma （PDTC） are very different from papillary thyroid carcinoma （PTC）. By comparing the clinical and ultrasonographic features between the two tumors, we proposed to provide more possibilities for recognizing PDTC before treatment. Methods： The data of 13 PDTCs and 39 ageand gender-matched PTCs in Peking Union Medical College Hospital between December 2003 and September 2013 were retrospectively reviewed. The clinical and ultrasonic features between the two groups were compared. Results： The frequencies of family history of carcinoma, complication with other thyroid lesions, lymph node metastases, recurrent laryngeal nerve injuries, and distant metastases were higher in PDTCs （30.8%, 61.6%, 69.2%, 23.1%, and 46.2%, respectively） than those in PTCs （2.6%, 23.1%, 25.6%, 2.6%, and 2.6%, respectively） （P 〈 0.05）. The mortality rate of PDTCs was greatly higher than PTCs （P 〈 0.01）. Conventional ultrasound showed that the size of PDTCs was larger than that of PTCs （3.1±1.9 cm vs. 1.7± 1.0 cm）. Clear margins and rich and/or irregular blood flow were found in 92.3% of PDTCs, which differed substantially from PTCs （51.7% and 53.8%, respectively） （P 〈 0.05）. Conclusions： PDTC is more aggressive and its mortality rate is higher than PTCs. Accordingly, more attention should be given to suspicious thyroid cancer nodules that show large size, regular shape, and rich blood flow signals on ultrasound to exclude the possibility of PDTCs.
