This paper demonstrates capabilities of low-field nuclear magnetic resonance (NMR) and microfocus X-ray computed tomography (μCT) in advanced, nondestructive, and quantitative characterization of pore types, producib...This paper demonstrates capabilities of low-field nuclear magnetic resonance (NMR) and microfocus X-ray computed tomography (μCT) in advanced, nondestructive, and quantitative characterization of pore types, producible porosity, pore structure, and spatial disposition of pore-fractures in coals. Results show that the NMR transverse relaxation time (T2) at 0.5–2.5, 20–50, and 】100 ms correspond to pores of 【0.1 μm, 】0.1 μm, and fractures, respectively. A much higher T2 spectrum peak reflects a much better development of pores (or fractures) corresponding to the T2, and vice versa. Three basic components in coals, i.e., the pores (or fractures), coal matrix, and minerals have their distinctive range of CT numbers. Among these, the CT number of pores is commonly less than 600 HU. The producible porosity, which is a determination of permeability, can be calculated by T2 cutoff value (T2C) of coal NMR. The coal pore structure can be efficiently estimated by the newly proposed "T2C based model". Finally, μCT scan was proven capable of modeling and spatial visualization of pores and fractures.展开更多
Objective To investigate the rule of the aquaporin 4 (AQP4) expression in acute ischemic brain edema, and to study the correlation between AQP4 expression and diffusion weighted imaging (DWI) Methods Thirty ...Objective To investigate the rule of the aquaporin 4 (AQP4) expression in acute ischemic brain edema, and to study the correlation between AQP4 expression and diffusion weighted imaging (DWI) Methods Thirty six Wistar rats were divided into 2 groups randomly, control group (n=12) and operation group (n=24) in which right middle cerebral artery of each animal had been occluded unilaterally (MCAO) at interval times of: 15 minutes, 30 minutes, 1 hours, 3 hours, 6 hours and 24 hours, respectively The operation process of the control group was the same as the operation group except for the MCAO All groups were examined using DWI The apparent diffusion coefficient (ADC), relative density (rd) and relative area (rs) of the biggest hyperintensity signal layer on DWI were measured After that the animals were sacrificed and perfused with the mixture solution consisting of TTC The biggest layers of the ischemic cerebral tissues in each rat corresponding to the DWI were stained with TTC and examined with immunochemistry (△S) , in situ hybridization (α) and histology Results There was no significant change in the control group In the operation group, a hyperintensity signal was found in the DWI of the right MAC territory at 15 minutes after MCAO The ADC value decreased quickly within one hour after MCAO, while the AQP4 expression, rd DWI and rs DWI increased rapidly during this stage As time progressed, the ADC value decreased further to (2 1±0 6)×10 4 mm 2/s at 3 hours, and then began to increase slowly till 24 hours But the AQP4 expression (△S and α) and rd as well as the rs continuously increased slowly between 1 hour and 6 hours after MCAO, followed a peak after 6 hours The AQP4 expression (α) showed a positive relationship with the rs DWI, they all presented two peaks and a plateau The corresponding sequential pathologic changes were a gradual increase of intracellular edema (within one hour), then an emergence of vasogenic edema (1-6 hours), and fin展开更多
针对传统的航姿参考系统AHRS(Attitude and Heading Reference System)中姿态角精度不高的问题,设计了一种新型的基于卡尔曼滤波的姿态检测系统。该系统采用了三轴磁传感器、三轴陀螺仪及三轴加速度计,用四元数的方法来描述载体运动的姿...针对传统的航姿参考系统AHRS(Attitude and Heading Reference System)中姿态角精度不高的问题,设计了一种新型的基于卡尔曼滤波的姿态检测系统。该系统采用了三轴磁传感器、三轴陀螺仪及三轴加速度计,用四元数的方法来描述载体运动的姿态,通过陀螺仪测姿态四元数,卡尔曼滤波算法融合加速度计和磁传感器数据,对姿态四元数进行修正,从而提高姿态解算精度。实验数据表明,系统能够较好修正陀螺仪漂移,且三个角度的均方根误差均优于0.25°,具有良好的噪声抑制能力。展开更多
BACKGROUND:The traditional hand-sewn Roux-en-Y choledochojejunostomy is technically complicated,and the incidence of postoperative complications has remained high.A set of novel magnetic compressive anastomats was int...BACKGROUND:The traditional hand-sewn Roux-en-Y choledochojejunostomy is technically complicated,and the incidence of postoperative complications has remained high.A set of novel magnetic compressive anastomats was introduced to facilitate choledochojejunostomy and improve the prognosis of patients.METHODS:After ligating the common bile duct for 7 days,16 dogs were randomly divided into two groups (n=8 per group).Anastomats were used in the study group,and the traditional hand-sewn method was used in the control group for standard Roux-en-Y choledochojejunostomy.We compared the operation time,incidence of complications,gross appearance,and pathological disparity in stoma between the two groups in 1-month and 3-month follow-up examinations.RESULTS:The time spent on constructing the anastomosis for the study group was significantly shortened.Although no anastomotic stenosis occurred in the two groups,the narrowing rate of biliary-enteric anastomosis was much higher in the control group.There was one case of bile leakage in the control group,whereas no bile leakage occurred in the study group.A smoother surface,an improved layer apposition,and a lower local inflammatory response were identified in the anastomosis of the study group.CONCLUSION:The structures of the novel magnetic compressive anastomats are simple,and they are time-saving,safe and efficient for performing Roux-en-Y choledocho- jejunostomy procedures in a canine model of obstructive jaundice.展开更多
Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little...Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little or no rare earth(or heavy rare earth).Nd-Fe-B magnets have been painstakingly and skillfully optimized for a wide range of applications in which high performance is required at reasonable cost.Sm-Co is the material of choice when high-temperature stability is required,and Sm-Fe-N magnets are making their way into some niche applications.The scope for improvement in these basic materials by substitution has been rather thoroughly explored,and the effects of processing techniques on the microstructure and hysteresis are largely understood.A big idea from a generation ago-which held real potential to raise the record energy product significantly-was the oriented exchange-spring hard/soft nanocomposite magnet;however,it has proved very difficult to realize.Nevertheless,the field has evolved,and innovation has flourished in other areas.For example,electrical personal transport has progressed from millions of electric bicycles to the point where cars and trucks with electrical drives are becoming mainstream,and looks ready to bring the dominance of the internal combustion engine to an end.As the limitations of particular permanent magnets become clearer,ingenuity and imagination are being used to design around them,and to exploit the available mix of rare earth resources most efficiently.Huge new markets in robotics beckon,and the opportunities offered by additive manufacturing are just beginning to be explored.New methods of increasing magnet stability at elevated temperature are being developed,and integrated multifunctionality of hard magnets with other useful properties is now envisaged.These themes are elaborated here,with various examples.展开更多
Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an app...Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique to each type of tissue. DWI has been originally used in neuroradiology. More recently, DWI has increasingly been used in addition to conventional unenhanced and enhanced magnetic resonance imaging (MRI) in other parts of the body. The reason for this delay was a number of technical problems inherent to the technique, making DWI very sensitive to artifacts, which had to be overcome. With assessment of ADC values, DWI proved to be helpful in characterization of focal liver lesions. However, DWI should always be used in conjunction to conventional MRI since there is considerable overlap between ADC values of benign and malignant lesions. DWI is useful in the detection of hepatocellular carcinoma in the cirrhotic liver and detection of liver metastases in oncological patients. In addition, DWI is a promising tool in the prediction of tumor responsiveness to chemotherapy and the follow-up of oncological patients after treatment, as DWI may be capable of detecting recurrent disease earlier than conventional imaging.This review focuses on the most common applications of DWI in the liver.展开更多
Imaging studies are a major component in the evaluation of patients for the screening,staging and surveillance of colorectal cancer.This review presents commonly encountered findings in the diagnosis and staging of pa...Imaging studies are a major component in the evaluation of patients for the screening,staging and surveillance of colorectal cancer.This review presents commonly encountered findings in the diagnosis and staging of patients with colorectal cancer using computed tomography(CT)colonography,magnetic resonance imaging(MRI),and positron emission tomography(PET)/CT colonography.CT colonography provides important information for the preoperative assessment of T staging.Wall deformities are associated with muscular or subserosal invasion.Lymph node metastases from colorectal cancer often present with calcifications.CT is superior to detect calcified metastases.Three-dimensional CT to image the vascular anatomy facilitates laparoscopic surgery.T staging of rectal cancer by MRI is an established modality because MRI can diagnose rectal wall laminar structure.N staging in patients with colorectal cancer is still challenging using any imaging modality.MRI is more accurate than CT for the evaluation of liver metastases.PET/CT colonography isvaluable in the evaluation of extra-colonic and hepatic disease.PET/CT colonography is useful for obstructing colorectal cancers that cannot be traversed colonoscopically.PET/CT colonography is able to localize synchronous colon cancers proximal to the obstruction precisely.However,there is no definite evidence to support the routine clinical use of PET/CT colonography.展开更多
Background： Functional magnetic resonance imaging （fMRI） is a novel method for studying the changes of brain networks due to acupuncture treatment. In recent years, more and more studies have focused on the brain f...Background： Functional magnetic resonance imaging （fMRI） is a novel method for studying the changes of brain networks due to acupuncture treatment. In recent years, more and more studies have focused on the brain functional connectivity network of acupuncture stimulation. Objective： To offer an overview of the different influences of acupuncture on the brain functional connec- tivity network from studies using resting-state fMRI. Search strategy： The authors performed a systematic search according to PRISMA guidelines, The database PubMed was searched from January 1, 2006 to December 31, 2016 with restriction to human studies in English language. Inclusion criteria： Electronic searches were conducted in PubMed using the keywords ＂acupuncture＂ and ＂neuroimaging＂ or ＂resting-state fMRI＂ or ＂functional connectivity＂, Data extraction and analysis： Selection of included articles, data extraction and methodological quality assessments were respectively conducted by two review authors. Results： Forty-four resting-state fMRI studies were included in this systematic review according to inclu- sion criteria. Thirteen studies applied manual acupuncture vs. sham, four studies applied electro- acupuncture vs. sham, two studies also compared transcutaneous electrical acupoint stimulation vs. sham, and nine applied sham acupoint as control. Nineteen studies with a total number of 574 healthy subjects selected to perform fMRI only considered healthy adult volunteers. The brain functional connec- tivity of the patients had varying degrees of change. Compared with sham acupuncture, verum acupunc- ture could increase default mode network and sensorimotor network connectivity with pain-, affective- and memory-related brain areas. It has significantly greater connectivity of genuine acupuncture between the periaqueductal gray, anterior cingulate cortex, left posterior cingulate cortex, right anterior insula, limbic/paralimbic and precuneus compared with sham acupuncture. Some research had also shown th展开更多
The New Vacuum Solar Telescope （NVST） is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including me...The New Vacuum Solar Telescope （NVST） is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown.展开更多
Ta/NiO/NiFe/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) between NiO and NiFe reached 120O e. The composition and chemical states at the interface region o...Ta/NiO/NiFe/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) between NiO and NiFe reached 120O e. The composition and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe=Ni+FeO and 3NiO+2Fe=3Ni+Fe2O3. The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products are magnetic defects, and we believe that the Hex and the coercivity (Hc) of NiO/NiFe are affected by these defects. Moreover, the results also show that there is an intermixing layer at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction: 2Ta+5NiO+Ta2O5. This interface reaction has an effect on the exchange coupling as well. The thickness of the intermixing layer as estimated by XPS depth-profiles was about 8-10 nm.展开更多
Nonalcoholic fatty liver disease(NAFLD)is a frequent cause of chronic liver diseases,ranging from simple steatosis to nonalcoholic steatohepatitis(NASH)-related liver cirrhosis.Although liver biopsy is still the gold ...Nonalcoholic fatty liver disease(NAFLD)is a frequent cause of chronic liver diseases,ranging from simple steatosis to nonalcoholic steatohepatitis(NASH)-related liver cirrhosis.Although liver biopsy is still the gold standard for the diagnosis of NAFLD,especially for the diagnosis of NASH,imaging methods have been increasingly accepted as noninvasive alternatives to liver biopsy.Ultrasonography is a well-established and costeffective imaging technique for the diagnosis of hepatic steatosis,especially for screening a large population at risk of NAFLD.Ultrasonography has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis,operator-dependent,and rather qualitative.Computed tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation hazard.However,computed tomography may be effective in specific clinical situations,such as evaluation of donor candidates for hepatic transplantation.Magnetic resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice,especially for longitudinal followup of patients with NAFLD.Ultrasound elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple steatosis.This article will review current imaging methods used to evaluate hepatic steatosis,including the diagnostic accuracy,limitations,and practical applicability of each method.It will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD.展开更多
Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reducti...Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions （i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%）. The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.展开更多
To date the imaging diagnosis of liver lesions is based mainly on the identification of vascular features, which are typical of overt hepatocellular carcinoma(HCC), but the hepatocarcinogenesis is a complex and multis...To date the imaging diagnosis of liver lesions is based mainly on the identification of vascular features, which are typical of overt hepatocellular carcinoma(HCC), but the hepatocarcinogenesis is a complex and multistep event during which, a spectrum of nodules develop within the liver parenchyma, including benign small and large regenerative nodule(RN), low-grade dysplastic nodule(LGDN), high-grade dysplastic nodule(HGDN), early HCC, and well differentiated HCC. These nodules may be characterised not only on the basis of their respective different blood supplies, but also on their different hepatocyte function. Recently, in liver imaging the introduction of hepatobiliary magnetic resonance imaging contrast agent offered the clinicians the possibility to obtain, at once, information not only related to the vascular changes of liver nodules but also information on hepatocyte function. For this reasons this new approach becomes the most relevant diagnostic clue for differentiating low-risk nodules(LGDN-RN) from highrisk nodules(HGDN/early HCC or overt HCC) and consequently new diagnostic algorithms for HCC have been proposed. The use of hepatobiliary contrast agents is constantly increasing and gradually changing the standard of diagnosis of HCC. The main purpose of this review is to underline the added value of Gd-EOB-DTPA in early-stage diagnoses of HCC. We also analyse the guidelines for the diagnosis and management of HCC, the key concepts of HCC development, growth and spread and the imaging appearance of precursor nodules that eventually may transform into overt HCC.展开更多
基金supported by National Major Research Program for Science and Technology of China (Grant Nos. 2008ZX05034-01 and 2008ZX05062-001)National Basic Research Program of China (Grant No. 2009CB219604)+2 种基金National Natural Science Foundation of China (Grant No. 40972107)Petro China Innovation Foundation (Grant No. 2008D-5006-01-04)Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0864)
文摘This paper demonstrates capabilities of low-field nuclear magnetic resonance (NMR) and microfocus X-ray computed tomography (μCT) in advanced, nondestructive, and quantitative characterization of pore types, producible porosity, pore structure, and spatial disposition of pore-fractures in coals. Results show that the NMR transverse relaxation time (T2) at 0.5–2.5, 20–50, and 】100 ms correspond to pores of 【0.1 μm, 】0.1 μm, and fractures, respectively. A much higher T2 spectrum peak reflects a much better development of pores (or fractures) corresponding to the T2, and vice versa. Three basic components in coals, i.e., the pores (or fractures), coal matrix, and minerals have their distinctive range of CT numbers. Among these, the CT number of pores is commonly less than 600 HU. The producible porosity, which is a determination of permeability, can be calculated by T2 cutoff value (T2C) of coal NMR. The coal pore structure can be efficiently estimated by the newly proposed "T2C based model". Finally, μCT scan was proven capable of modeling and spatial visualization of pores and fractures.
基金theNationalNaturalScienceFoundationofChina (No 3 0 0 70 2 47)
文摘Objective To investigate the rule of the aquaporin 4 (AQP4) expression in acute ischemic brain edema, and to study the correlation between AQP4 expression and diffusion weighted imaging (DWI) Methods Thirty six Wistar rats were divided into 2 groups randomly, control group (n=12) and operation group (n=24) in which right middle cerebral artery of each animal had been occluded unilaterally (MCAO) at interval times of: 15 minutes, 30 minutes, 1 hours, 3 hours, 6 hours and 24 hours, respectively The operation process of the control group was the same as the operation group except for the MCAO All groups were examined using DWI The apparent diffusion coefficient (ADC), relative density (rd) and relative area (rs) of the biggest hyperintensity signal layer on DWI were measured After that the animals were sacrificed and perfused with the mixture solution consisting of TTC The biggest layers of the ischemic cerebral tissues in each rat corresponding to the DWI were stained with TTC and examined with immunochemistry (△S) , in situ hybridization (α) and histology Results There was no significant change in the control group In the operation group, a hyperintensity signal was found in the DWI of the right MAC territory at 15 minutes after MCAO The ADC value decreased quickly within one hour after MCAO, while the AQP4 expression, rd DWI and rs DWI increased rapidly during this stage As time progressed, the ADC value decreased further to (2 1±0 6)×10 4 mm 2/s at 3 hours, and then began to increase slowly till 24 hours But the AQP4 expression (△S and α) and rd as well as the rs continuously increased slowly between 1 hour and 6 hours after MCAO, followed a peak after 6 hours The AQP4 expression (α) showed a positive relationship with the rs DWI, they all presented two peaks and a plateau The corresponding sequential pathologic changes were a gradual increase of intracellular edema (within one hour), then an emergence of vasogenic edema (1-6 hours), and fin
文摘针对传统的航姿参考系统AHRS(Attitude and Heading Reference System)中姿态角精度不高的问题,设计了一种新型的基于卡尔曼滤波的姿态检测系统。该系统采用了三轴磁传感器、三轴陀螺仪及三轴加速度计,用四元数的方法来描述载体运动的姿态,通过陀螺仪测姿态四元数,卡尔曼滤波算法融合加速度计和磁传感器数据,对姿态四元数进行修正,从而提高姿态解算精度。实验数据表明,系统能够较好修正陀螺仪漂移,且三个角度的均方根误差均优于0.25°,具有良好的噪声抑制能力。
基金supported by a grant from the National Natural Science Foundation of China (30830099)
文摘BACKGROUND:The traditional hand-sewn Roux-en-Y choledochojejunostomy is technically complicated,and the incidence of postoperative complications has remained high.A set of novel magnetic compressive anastomats was introduced to facilitate choledochojejunostomy and improve the prognosis of patients.METHODS:After ligating the common bile duct for 7 days,16 dogs were randomly divided into two groups (n=8 per group).Anastomats were used in the study group,and the traditional hand-sewn method was used in the control group for standard Roux-en-Y choledochojejunostomy.We compared the operation time,incidence of complications,gross appearance,and pathological disparity in stoma between the two groups in 1-month and 3-month follow-up examinations.RESULTS:The time spent on constructing the anastomosis for the study group was significantly shortened.Although no anastomotic stenosis occurred in the two groups,the narrowing rate of biliary-enteric anastomosis was much higher in the control group.There was one case of bile leakage in the control group,whereas no bile leakage occurred in the study group.A smoother surface,an improved layer apposition,and a lower local inflammatory response were identified in the anastomosis of the study group.CONCLUSION:The structures of the novel magnetic compressive anastomats are simple,and they are time-saving,safe and efficient for performing Roux-en-Y choledocho- jejunostomy procedures in a canine model of obstructive jaundice.
基金supported by Science Foundation Ireland as part of the ZEMS project(16/IA/4534).
文摘Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little or no rare earth(or heavy rare earth).Nd-Fe-B magnets have been painstakingly and skillfully optimized for a wide range of applications in which high performance is required at reasonable cost.Sm-Co is the material of choice when high-temperature stability is required,and Sm-Fe-N magnets are making their way into some niche applications.The scope for improvement in these basic materials by substitution has been rather thoroughly explored,and the effects of processing techniques on the microstructure and hysteresis are largely understood.A big idea from a generation ago-which held real potential to raise the record energy product significantly-was the oriented exchange-spring hard/soft nanocomposite magnet;however,it has proved very difficult to realize.Nevertheless,the field has evolved,and innovation has flourished in other areas.For example,electrical personal transport has progressed from millions of electric bicycles to the point where cars and trucks with electrical drives are becoming mainstream,and looks ready to bring the dominance of the internal combustion engine to an end.As the limitations of particular permanent magnets become clearer,ingenuity and imagination are being used to design around them,and to exploit the available mix of rare earth resources most efficiently.Huge new markets in robotics beckon,and the opportunities offered by additive manufacturing are just beginning to be explored.New methods of increasing magnet stability at elevated temperature are being developed,and integrated multifunctionality of hard magnets with other useful properties is now envisaged.These themes are elaborated here,with various examples.
文摘Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique to each type of tissue. DWI has been originally used in neuroradiology. More recently, DWI has increasingly been used in addition to conventional unenhanced and enhanced magnetic resonance imaging (MRI) in other parts of the body. The reason for this delay was a number of technical problems inherent to the technique, making DWI very sensitive to artifacts, which had to be overcome. With assessment of ADC values, DWI proved to be helpful in characterization of focal liver lesions. However, DWI should always be used in conjunction to conventional MRI since there is considerable overlap between ADC values of benign and malignant lesions. DWI is useful in the detection of hepatocellular carcinoma in the cirrhotic liver and detection of liver metastases in oncological patients. In addition, DWI is a promising tool in the prediction of tumor responsiveness to chemotherapy and the follow-up of oncological patients after treatment, as DWI may be capable of detecting recurrent disease earlier than conventional imaging.This review focuses on the most common applications of DWI in the liver.
文摘Imaging studies are a major component in the evaluation of patients for the screening,staging and surveillance of colorectal cancer.This review presents commonly encountered findings in the diagnosis and staging of patients with colorectal cancer using computed tomography(CT)colonography,magnetic resonance imaging(MRI),and positron emission tomography(PET)/CT colonography.CT colonography provides important information for the preoperative assessment of T staging.Wall deformities are associated with muscular or subserosal invasion.Lymph node metastases from colorectal cancer often present with calcifications.CT is superior to detect calcified metastases.Three-dimensional CT to image the vascular anatomy facilitates laparoscopic surgery.T staging of rectal cancer by MRI is an established modality because MRI can diagnose rectal wall laminar structure.N staging in patients with colorectal cancer is still challenging using any imaging modality.MRI is more accurate than CT for the evaluation of liver metastases.PET/CT colonography isvaluable in the evaluation of extra-colonic and hepatic disease.PET/CT colonography is useful for obstructing colorectal cancers that cannot be traversed colonoscopically.PET/CT colonography is able to localize synchronous colon cancers proximal to the obstruction precisely.However,there is no definite evidence to support the routine clinical use of PET/CT colonography.
基金supported by the National Natural Science Foundation of China(No.81473784)University Science Research Project of Anhui Province of China(No.KJ2017A298)+1 种基金the Key Project of the Youth Elite Support Plan in Universities of Anhui Province of China(No.gxyq ZD2016134)Construction Project of Scientific Research Innovation Platform of Anhui Province of China(No.2015TD033)
文摘Background： Functional magnetic resonance imaging （fMRI） is a novel method for studying the changes of brain networks due to acupuncture treatment. In recent years, more and more studies have focused on the brain functional connectivity network of acupuncture stimulation. Objective： To offer an overview of the different influences of acupuncture on the brain functional connec- tivity network from studies using resting-state fMRI. Search strategy： The authors performed a systematic search according to PRISMA guidelines, The database PubMed was searched from January 1, 2006 to December 31, 2016 with restriction to human studies in English language. Inclusion criteria： Electronic searches were conducted in PubMed using the keywords ＂acupuncture＂ and ＂neuroimaging＂ or ＂resting-state fMRI＂ or ＂functional connectivity＂, Data extraction and analysis： Selection of included articles, data extraction and methodological quality assessments were respectively conducted by two review authors. Results： Forty-four resting-state fMRI studies were included in this systematic review according to inclu- sion criteria. Thirteen studies applied manual acupuncture vs. sham, four studies applied electro- acupuncture vs. sham, two studies also compared transcutaneous electrical acupoint stimulation vs. sham, and nine applied sham acupoint as control. Nineteen studies with a total number of 574 healthy subjects selected to perform fMRI only considered healthy adult volunteers. The brain functional connec- tivity of the patients had varying degrees of change. Compared with sham acupuncture, verum acupunc- ture could increase default mode network and sensorimotor network connectivity with pain-, affective- and memory-related brain areas. It has significantly greater connectivity of genuine acupuncture between the periaqueductal gray, anterior cingulate cortex, left posterior cingulate cortex, right anterior insula, limbic/paralimbic and precuneus compared with sham acupuncture. Some research had also shown th
基金Supported by the National Natural Science Foundation of China
文摘The New Vacuum Solar Telescope （NVST） is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown.
基金supported by the National Natural Science Foundation of China and Beijing under grant No.19890310 and 2012011,respectively
文摘Ta/NiO/NiFe/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) between NiO and NiFe reached 120O e. The composition and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe=Ni+FeO and 3NiO+2Fe=3Ni+Fe2O3. The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products are magnetic defects, and we believe that the Hex and the coercivity (Hc) of NiO/NiFe are affected by these defects. Moreover, the results also show that there is an intermixing layer at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction: 2Ta+5NiO+Ta2O5. This interface reaction has an effect on the exchange coupling as well. The thickness of the intermixing layer as estimated by XPS depth-profiles was about 8-10 nm.
基金Supported by The Basic Science Research Program through the National Research Foundation of South Koreafunded by the Ministry of Education,Science and Technology,No.2012R1A1A1005326
文摘Nonalcoholic fatty liver disease(NAFLD)is a frequent cause of chronic liver diseases,ranging from simple steatosis to nonalcoholic steatohepatitis(NASH)-related liver cirrhosis.Although liver biopsy is still the gold standard for the diagnosis of NAFLD,especially for the diagnosis of NASH,imaging methods have been increasingly accepted as noninvasive alternatives to liver biopsy.Ultrasonography is a well-established and costeffective imaging technique for the diagnosis of hepatic steatosis,especially for screening a large population at risk of NAFLD.Ultrasonography has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis,operator-dependent,and rather qualitative.Computed tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation hazard.However,computed tomography may be effective in specific clinical situations,such as evaluation of donor candidates for hepatic transplantation.Magnetic resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice,especially for longitudinal followup of patients with NAFLD.Ultrasound elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple steatosis.This article will review current imaging methods used to evaluate hepatic steatosis,including the diagnostic accuracy,limitations,and practical applicability of each method.It will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD.
基金supported by the National Natural Science Foundation of China(Nos.51134002 and 51074036)
文摘Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions （i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%）. The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.
文摘To date the imaging diagnosis of liver lesions is based mainly on the identification of vascular features, which are typical of overt hepatocellular carcinoma(HCC), but the hepatocarcinogenesis is a complex and multistep event during which, a spectrum of nodules develop within the liver parenchyma, including benign small and large regenerative nodule(RN), low-grade dysplastic nodule(LGDN), high-grade dysplastic nodule(HGDN), early HCC, and well differentiated HCC. These nodules may be characterised not only on the basis of their respective different blood supplies, but also on their different hepatocyte function. Recently, in liver imaging the introduction of hepatobiliary magnetic resonance imaging contrast agent offered the clinicians the possibility to obtain, at once, information not only related to the vascular changes of liver nodules but also information on hepatocyte function. For this reasons this new approach becomes the most relevant diagnostic clue for differentiating low-risk nodules(LGDN-RN) from highrisk nodules(HGDN/early HCC or overt HCC) and consequently new diagnostic algorithms for HCC have been proposed. The use of hepatobiliary contrast agents is constantly increasing and gradually changing the standard of diagnosis of HCC. The main purpose of this review is to underline the added value of Gd-EOB-DTPA in early-stage diagnoses of HCC. We also analyse the guidelines for the diagnosis and management of HCC, the key concepts of HCC development, growth and spread and the imaging appearance of precursor nodules that eventually may transform into overt HCC.
