A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filte...A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.展开更多
Rare earth barium copper oxide(REBCO)is the most researched and commercialized second-generation high-temperature superconducting material.Due to the anisotropic structure,strong deformation sensitivity,and central fi...Rare earth barium copper oxide(REBCO)is the most researched and commercialized second-generation high-temperature superconducting material.Due to the anisotropic structure,strong deformation sensitivity,and central field errors caused by screening current effects,it is still a challenge for commercialization applications.In this study,the transversely isotropic constitutive relationship is selected as the mechanical model based on the structural characteristics of REBCO tapes,and suitable microelements are selected to equate the elastic constants using their average stress-strain relationships.Then,a two-dimensional axisymmetric model for coils wound by single-layer tapes is constructed to analyze the dependence of the electric-magnetic-force distribution in the tape on the strain.Finally,the anisotropic approximation of the homogenized bulk method is used to equate large-turn high-field coils,and the electric-magnetic-force distribution characteristics of the coils with/without screening effects and mechanical strain conditions are investigated,respectively.The results reveal that the mechanical strain has a weakening effect on the electromagnetic field distribution of superconducting tapes,but causes a significant enhancement in the force field distribution.In the presence of 0.5% mechanical strain,the maximum weakening of the peak value of the current density and the critical current density inside the high-field coil can reach about 8% and 13%,respectively,with a nearly 5 times increase in the peak stress.The screening current makes the current field distribution inside the coil improve by about 10 times.The screening current induced magnetic field can reach up to 0.8 T,making the relative error of the high-field coil center up to 7.8%.展开更多
The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick supercon...The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick superconducting Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure with an onset transition temperature of~9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO_(3) substrate during thin-film deposition and post chemical reduction for the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) heterostructure. It was found that the critical current density of the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure is relatively small, ~4×10^(3) A·cm^(-2). Although the surface steps of SrTiO_(3) substrates lead to an anisotropy for in-plane resistivity, the superconducting transition temperatures are almost the same. The out-of-plane magnetotransport measurements yield an upper critical field of~11.4 T and an estimated in-plane Ginzburg–Landau coherence length of~5.4 nm. High-field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO_(3) substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.展开更多
Background: Tolosa Hunt Syndrome is an inflammatory condition of unknown etiology of the cavernous sinus and superior orbital fissure. Because of the difficulty in establishing histological evidence, his diagnosis is ...Background: Tolosa Hunt Syndrome is an inflammatory condition of unknown etiology of the cavernous sinus and superior orbital fissure. Because of the difficulty in establishing histological evidence, his diagnosis is based on a set of arguments established by the International Headache Society. MRI allows indirect visualization of the granuloma and plays a key role in diagnosis and follow-up. Aim: To illustrate High-field MRI contribution in Tolosa-Hunt Syndrome (THS). Cases Presentation: Two patients, a 25-year-old female and a 40-year-old male were recruited in this retrospective case report study at the Radiology service of Fann University Hospital (Dakar Senegal). The first patient has been suffering from a right retro-orbital pain and diplopia for 2 months and the second from a painful oculomotor nerve palsy for 3 months. Blood tests, lumbar puncture, thyroid hormone levels and an infectious screen were done. Screening for converting enzymes, and serum antibodies were also done. They underwent a high field MRI (Siemens 1.5T) with T1, T2, FLAIR, T2*, diffusion B1000, TOF polygon, CISS 3D and T1 gadolinium sequences in the 3 planes space. No significant abnormality was detected in blood tests or CSF analysis. Screening for converting enzymes and serum antibodies screen were also negative. For each patient, MRI examinations showed a non tumoral thickening of the right cavernous sinus, suggesting a granulomatous involvement. Tolosa Hunt Syndrome was evoked firstly. They were put on corticotherapy at high doses with a spectacular regression of symptoms. The Criteria of the International Headache Society of THS were met in both patients. Conclusion: High-field MRI is a significant diagnostic tool in the assessment of painful ophthalmoplegia. It allows a direct visualization of the granuloma of the cavernous sinus and assesses its course throughout the disease.展开更多
To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in ...To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in the large helicM device （LHD）. 77 GHz electron cyclotron （EC） wave beams injected from an existing EC-wave injection system toward the new mirror are reflected on the mirror so that the beams are injected to plasmas from HFS. Evident increases in the electron temperature at the plasma core region and the plasma stored energy were observed by the HFS beam injection to the plasmas with the line-average electron density of 7.5~ 1019 m-3, which is slightly higher than the plasma cut-off density of 77 GHz EC-waves, 7.35~ 1019 m-3. The heating efficiency evaluated from the changes in the time derivative of the plasma stored energy reached ,,~70%. Although so far it is not clear which is the main cause of the heating effect, the mode-converted EBW or the X-mode wave itself injected from the HFS, an effective heating of high-density plasma over the plasma cut-off of EC-wave was successfully demonstrated.展开更多
A near-resonant, red-detuning laser-assisted Stark deceleration scheme is proposed to slow CaF in its high-fieldseeking rovibronic ground state. The assisting Gaussian laser beam can confine CaF molecules transversely...A near-resonant, red-detuning laser-assisted Stark deceleration scheme is proposed to slow CaF in its high-fieldseeking rovibronic ground state. The assisting Gaussian laser beam can confine CaF molecules transversely owing to the optical Stark effect. Simulations suggest that the present scheme is superior to previous Stark decelerators. Under typical experimental conditions, when the assisting laser frequency is red-detuned to the molecular transition(λ～606.3 nm) by5.0 GHz and the laser power is about 5.6 W, the proposed decelerator can achieve a total number at the order of 10~4 CaF molecules with a number density at the order of 10~8 cm^(-3). The equivalent temperature of the obtained cold CaF molecules is 2.3 mK. Additionally, the desired assisting laser power can be as low as about 1.2 W if keeping the red-detuning value to be 1.0 GHz, which further suggests its experimental feasibility.展开更多
Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Her...Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field(90–180V) anodization method to grow highly ordered TiO_2 NTAs on Si substrate,and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO_2 NTAs. The current density–time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO_2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields(40–60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.展开更多
A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient ...A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient is observed in the stress sequence,beyond which the HEMT device starts to recover from degradation induced by early lower voltage stress.While the performance degradation featuring the drain current slump stems from electron trapping in the surface or bulk states during low-to-medium bias stress,the recovery is attributed to high field induced electron detrapping.The carrier detrapping mechanism could be helpful for lessening the trapping-related performance degradation of a GaN-based HEMT.展开更多
Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriche...Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.展开更多
This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current li...This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current limitations are highlighted.Based on the first promising studies,potential clinical applications at 7 Tesla are suggested.Other aims are to stimulate awareness of the potential of ultra-high field magnetic resonance and to stimulate active participation in much needed basic or clinical research at 7 Tesla or higher.展开更多
目的磁共振化学交换饱和转移(chemical exchange saturation transfer,CEST)技术是一种可以无创测量生物体组织代谢物的分子影像新方法,它利用代谢物上不稳定基团与水分子的化学交换过程,实施微弱代谢信号的探测和成像。高场强对代谢物...目的磁共振化学交换饱和转移(chemical exchange saturation transfer,CEST)技术是一种可以无创测量生物体组织代谢物的分子影像新方法,它利用代谢物上不稳定基团与水分子的化学交换过程,实施微弱代谢信号的探测和成像。高场强对代谢物有着更强的分辨能力,但同时也面临BO、B1不均匀的挑战。本研究在脑肿瘤病人采集了酰胺质子转移成像(amide proton transfer imaging CEST,APT-CEST)和谷氨酸质子转移成像(glutamate CEST,Glu-CEST)图像,探究高场强(5T)磁共振下不同组织CEST技术的可重复性。方法招募14例脑肿瘤患者,对所有患者分别进行两次APT-CEST和Glu-CEST成像,每位患者均勾画2处感兴趣区(region of interest,ROI),分别在肿瘤区域和对侧正常脑组织。评估两次扫描两个ROI磁化转移率的平均值,计算病灶和对侧健康组织ROI两次扫描间均值之差在所有受试者中中的标准差(the standard deviation across all participants of the within-participant difference between two scans,SDdiff)和组内相关系数(interclass correlation coefficient,ICC)。结果(1)在5T磁共振上,两类CEST成像都表现出较好的重复性;(2)相较于正常组织,肿瘤组织在5T磁共振上CEST成像的可重复性更好,表现为更低的SDdiff以及更高的ICC。结论CEST在5T场强下有着较好的可重复性,尤其是在脑肿瘤组织中。这为CEST技术应用于脑肿瘤的影像学研究提供了可靠的基础。展开更多
复杂地形风电机组建设时易形成高边坡地形,可能严重影响机组的发电量和疲劳寿命。以重庆市某复杂山地风电场为例,基于CDRFG(Consistent Discretizing Random Flow Generation)方法生成大气边界层湍流入口,采用大涡模拟技术重现高边坡复...复杂地形风电机组建设时易形成高边坡地形,可能严重影响机组的发电量和疲劳寿命。以重庆市某复杂山地风电场为例,基于CDRFG(Consistent Discretizing Random Flow Generation)方法生成大气边界层湍流入口,采用大涡模拟技术重现高边坡复杂地形的湍流风场分布,并根据激光测风雷达和测风塔实测数据验证大涡模拟结果的准确性;对比分析了风机平台开挖导致的3种不同高边坡地形下,风机机位湍流风场的差异性,提出了风机平台开挖影响评估指标,深入分析了高边坡地形对风电机组发电效益和安全运行的影响。研究为复杂地形风机平台建设提供了科学保障。展开更多
文摘A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.
文摘Rare earth barium copper oxide(REBCO)is the most researched and commercialized second-generation high-temperature superconducting material.Due to the anisotropic structure,strong deformation sensitivity,and central field errors caused by screening current effects,it is still a challenge for commercialization applications.In this study,the transversely isotropic constitutive relationship is selected as the mechanical model based on the structural characteristics of REBCO tapes,and suitable microelements are selected to equate the elastic constants using their average stress-strain relationships.Then,a two-dimensional axisymmetric model for coils wound by single-layer tapes is constructed to analyze the dependence of the electric-magnetic-force distribution in the tape on the strain.Finally,the anisotropic approximation of the homogenized bulk method is used to equate large-turn high-field coils,and the electric-magnetic-force distribution characteristics of the coils with/without screening effects and mechanical strain conditions are investigated,respectively.The results reveal that the mechanical strain has a weakening effect on the electromagnetic field distribution of superconducting tapes,but causes a significant enhancement in the force field distribution.In the presence of 0.5% mechanical strain,the maximum weakening of the peak value of the current density and the critical current density inside the high-field coil can reach about 8% and 13%,respectively,with a nearly 5 times increase in the peak stress.The screening current makes the current field distribution inside the coil improve by about 10 times.The screening current induced magnetic field can reach up to 0.8 T,making the relative error of the high-field coil center up to 7.8%.
基金financially supported by the National Natural Science Foundation of China(Nos.51822101,51861135104 and 51771009)。
文摘The emerging Ni-based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14-nm-thick superconducting Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure with an onset transition temperature of~9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO_(3) substrate during thin-film deposition and post chemical reduction for the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) heterostructure. It was found that the critical current density of the Nd_(0.8)Sr_(0.2)NiO_(2)/SrTiO_(3) thin-film heterostructure is relatively small, ~4×10^(3) A·cm^(-2). Although the surface steps of SrTiO_(3) substrates lead to an anisotropy for in-plane resistivity, the superconducting transition temperatures are almost the same. The out-of-plane magnetotransport measurements yield an upper critical field of~11.4 T and an estimated in-plane Ginzburg–Landau coherence length of~5.4 nm. High-field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO_(3) substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.
文摘Background: Tolosa Hunt Syndrome is an inflammatory condition of unknown etiology of the cavernous sinus and superior orbital fissure. Because of the difficulty in establishing histological evidence, his diagnosis is based on a set of arguments established by the International Headache Society. MRI allows indirect visualization of the granuloma and plays a key role in diagnosis and follow-up. Aim: To illustrate High-field MRI contribution in Tolosa-Hunt Syndrome (THS). Cases Presentation: Two patients, a 25-year-old female and a 40-year-old male were recruited in this retrospective case report study at the Radiology service of Fann University Hospital (Dakar Senegal). The first patient has been suffering from a right retro-orbital pain and diplopia for 2 months and the second from a painful oculomotor nerve palsy for 3 months. Blood tests, lumbar puncture, thyroid hormone levels and an infectious screen were done. Screening for converting enzymes, and serum antibodies were also done. They underwent a high field MRI (Siemens 1.5T) with T1, T2, FLAIR, T2*, diffusion B1000, TOF polygon, CISS 3D and T1 gadolinium sequences in the 3 planes space. No significant abnormality was detected in blood tests or CSF analysis. Screening for converting enzymes and serum antibodies screen were also negative. For each patient, MRI examinations showed a non tumoral thickening of the right cavernous sinus, suggesting a granulomatous involvement. Tolosa Hunt Syndrome was evoked firstly. They were put on corticotherapy at high doses with a spectacular regression of symptoms. The Criteria of the International Headache Society of THS were met in both patients. Conclusion: High-field MRI is a significant diagnostic tool in the assessment of painful ophthalmoplegia. It allows a direct visualization of the granuloma of the cavernous sinus and assesses its course throughout the disease.
基金supported by KAKENHI (Grant-in-Aid for Scientific Research(C), 21560862) of Japan
文摘To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in the large helicM device （LHD）. 77 GHz electron cyclotron （EC） wave beams injected from an existing EC-wave injection system toward the new mirror are reflected on the mirror so that the beams are injected to plasmas from HFS. Evident increases in the electron temperature at the plasma core region and the plasma stored energy were observed by the HFS beam injection to the plasmas with the line-average electron density of 7.5~ 1019 m-3, which is slightly higher than the plasma cut-off density of 77 GHz EC-waves, 7.35~ 1019 m-3. The heating efficiency evaluated from the changes in the time derivative of the plasma stored energy reached ,,~70%. Although so far it is not clear which is the main cause of the heating effect, the mode-converted EBW or the X-mode wave itself injected from the HFS, an effective heating of high-density plasma over the plasma cut-off of EC-wave was successfully demonstrated.
基金Project supported by the National Natural Science Foundation of China(Grant No.11604164)
文摘A near-resonant, red-detuning laser-assisted Stark deceleration scheme is proposed to slow CaF in its high-fieldseeking rovibronic ground state. The assisting Gaussian laser beam can confine CaF molecules transversely owing to the optical Stark effect. Simulations suggest that the present scheme is superior to previous Stark decelerators. Under typical experimental conditions, when the assisting laser frequency is red-detuned to the molecular transition(λ～606.3 nm) by5.0 GHz and the laser power is about 5.6 W, the proposed decelerator can achieve a total number at the order of 10~4 CaF molecules with a number density at the order of 10~8 cm^(-3). The equivalent temperature of the obtained cold CaF molecules is 2.3 mK. Additionally, the desired assisting laser power can be as low as about 1.2 W if keeping the red-detuning value to be 1.0 GHz, which further suggests its experimental feasibility.
基金supported by National 863 Program 2011AA050518the Natural Science Foundation of China(Grant Nos.11174197,11574203,and 61234005)
文摘Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field(90–180V) anodization method to grow highly ordered TiO_2 NTAs on Si substrate,and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO_2 NTAs. The current density–time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO_2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields(40–60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.
文摘A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient is observed in the stress sequence,beyond which the HEMT device starts to recover from degradation induced by early lower voltage stress.While the performance degradation featuring the drain current slump stems from electron trapping in the surface or bulk states during low-to-medium bias stress,the recovery is attributed to high field induced electron detrapping.The carrier detrapping mechanism could be helpful for lessening the trapping-related performance degradation of a GaN-based HEMT.
文摘Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.
文摘This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current limitations are highlighted.Based on the first promising studies,potential clinical applications at 7 Tesla are suggested.Other aims are to stimulate awareness of the potential of ultra-high field magnetic resonance and to stimulate active participation in much needed basic or clinical research at 7 Tesla or higher.
文摘目的磁共振化学交换饱和转移(chemical exchange saturation transfer,CEST)技术是一种可以无创测量生物体组织代谢物的分子影像新方法,它利用代谢物上不稳定基团与水分子的化学交换过程,实施微弱代谢信号的探测和成像。高场强对代谢物有着更强的分辨能力,但同时也面临BO、B1不均匀的挑战。本研究在脑肿瘤病人采集了酰胺质子转移成像(amide proton transfer imaging CEST,APT-CEST)和谷氨酸质子转移成像(glutamate CEST,Glu-CEST)图像,探究高场强(5T)磁共振下不同组织CEST技术的可重复性。方法招募14例脑肿瘤患者,对所有患者分别进行两次APT-CEST和Glu-CEST成像,每位患者均勾画2处感兴趣区(region of interest,ROI),分别在肿瘤区域和对侧正常脑组织。评估两次扫描两个ROI磁化转移率的平均值,计算病灶和对侧健康组织ROI两次扫描间均值之差在所有受试者中中的标准差(the standard deviation across all participants of the within-participant difference between two scans,SDdiff)和组内相关系数(interclass correlation coefficient,ICC)。结果(1)在5T磁共振上,两类CEST成像都表现出较好的重复性;(2)相较于正常组织,肿瘤组织在5T磁共振上CEST成像的可重复性更好,表现为更低的SDdiff以及更高的ICC。结论CEST在5T场强下有着较好的可重复性,尤其是在脑肿瘤组织中。这为CEST技术应用于脑肿瘤的影像学研究提供了可靠的基础。
文摘复杂地形风电机组建设时易形成高边坡地形,可能严重影响机组的发电量和疲劳寿命。以重庆市某复杂山地风电场为例,基于CDRFG(Consistent Discretizing Random Flow Generation)方法生成大气边界层湍流入口,采用大涡模拟技术重现高边坡复杂地形的湍流风场分布,并根据激光测风雷达和测风塔实测数据验证大涡模拟结果的准确性;对比分析了风机平台开挖导致的3种不同高边坡地形下,风机机位湍流风场的差异性,提出了风机平台开挖影响评估指标,深入分析了高边坡地形对风电机组发电效益和安全运行的影响。研究为复杂地形风机平台建设提供了科学保障。
