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Search Results: 1 - 10 of 150035 matches for " WANG Yi-xiang "
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Edge states and phase diagram for graphene under polarized light
Yi-Xiang Wang,Fuxiang Li
Physics , 2015,
Abstract: We investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with up to ten different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the $\pi-$gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, the number and even the chirality of the edge states may change in the $\pi-$gap. The robustness of the edge states to disorder potential are also examined. We close by discussing the feasibility of experimental proposals.
Non-invasive MRI assessment of the articular cartilage in clinical studies and experimental settings
Yi-Xiang J Wang, James F Griffith, Anil T Ahuja
World Journal of Radiology , 2010,
Abstract: Attrition and eventual loss of articular cartilage are important elements in the pathophysiology of osteoarthritis (OA). Preventing the breakdown of cartilage is believed to be critical to preserve the functional integrity of a joint. Chondral injuries are also common in the knee joint, and many patients benefit from cartilage repair. Magnetic resonance imaging (MRI) and advanced digital post-processing techniques have opened possibilities for in vivo analysis of cartilage morphology, structure, and function in healthy and diseased knee joints. Techniques of semi-quantitative scoring of human knee cartilage pathology and quantitative assessment of human cartilage have been developed. Cartilage thickness and volume have been quantified in humans as well as in small animals. MRI detected cartilage loss has been shown to be more sensitive than radiographs detecting joint space narrowing. It is possible to longitudinally study knee cartilage morphology with enough accuracy to follow the disease-caused changes and also evaluate the therapeutic effects of chondro-protective drugs. There are also several MRI methods that may allow evaluation of the glycosaminoglycan matrix or collagen network of articular cartilage, and may be more sensitive for the detection of early changes. The clinical relevance of these methods is being validated. With the development of new therapies for OA and cartilage injury, MR images will play an important role in the diagnosis, staging, and evaluation of the effectiveness of these therapies.
An Analysis of 1256 Cases of Sporadic Ruptured Cerebral Aneurysm in a Single Chinese Institution
Lin Zhao, Lihong Zhang, Xiaolin Zhang, Zhenzhong Li, Linwei Tian, Yi-Xiang J. Wang
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085668
Abstract: Background To review the epidemiology of sporadic ruptured cerebral aneurysm. Methods This is a retrospective study of consecutive 1256 Chinese patients between January 2006 and January 2013, who were admitted to the Second Hospital of Hebei Medical University, China, for spontaneous subarachnoid hemorrhage due to a rupture of cerebral artery aneurysm. In 288 males and 478 females, the size of aneurysms was measured by a neuroradiologist on DSA. In 123 males and 184 females, the size of the ruptured aneurysms was not measured. The remaining patients, with 61 males and 122 females, had multiple aneurysms, and the medical record could not reliably determine the specific aneurysm responsible for the rupture. Results In total there were 784 females and 472 males with a female/male ratio of 1.66. The female/male ratio was down to 0.50 for patients younger than 35 yrs. For both males and females, aneurysm rupture was most common during the age of 50–59 yrs. Ruptured aneurysms were mostly of 2 mm–5 mm in size (47.1%), followed by 5 mm–10 mm (39.7%). Ruptured single cerebral aneurysm occurred in anterior circulation in 95.0% of the cases, with 5.0% occurred in posterior circulation. Ruptured aneurysm most commonly occurred at posterior communicating artery (34.9%) and anterior communicating artery (29.5%). 183 cases (14.6%) had multiple aneurysms. Conclusions With younger patients, there is a male predominance in our series. Ninety percent of patients have ruptured aneurysms less than 10 mm in size.
Organic Nitrate Maintains Bone Marrow Blood Perfusion in Ovariectomized Female Rats: A Dynamic, Contrast-Enhanced Magnetic Resonance Imaging (MRI) Study
Yi-Xiang J. Wang,Chun Hay Ko,James F. Griffith,Min Deng,Hing Lok Wong,Tao Gu,Yu Huang
Pharmaceutics , 2013, DOI: 10.3390/pharmaceutics5010023
Abstract: This study investigated the effects of nitrate on bone mineral density (BMD) and bone marrow perfusion in ovariectomized (OVX) female rats, and also the effects of nitrate on in vitro osteoblastic activity and osteoclastic differentiation of murine monocyte/ macrophage RAW 264.7 cells. Female Sprague–Dawley rats were divided into OVX + nitrate group (isosorbide-5-mononitrate, ISM, 150 mg/kg/ day b.i.d), OVX + vehicle group, and control group. Lumbar spine CT bone densitometry and perfusion MRI were performed on the rats at baseline and week 8 post-OVX. The OVX rats’ BMD decreased by 22.5% ± 5.7% at week 8 ( p < 0.001); while the OVX + ISM rats’ BMD decreased by 13.1% ± 2.7% ( p < 0.001). The BMD loss difference between the two groups of rats was significant ( p = 0.018). The OVX rats’ lumbar vertebral perfusion MRI maximum enhancement ( Emax) decreased by 10.3% ± 5.0% at week 8 ( p < 0.005), while in OVX + ISM rats, the Emax increased by 5.5% ± 6.9% ( p > 0.05). The proliferation of osteoblast-like UMR-106 cells increased significantly with ISM treatment at 0.78 μM to 50 μM. Treatment of UMR-106 cells with ISM also stimulated the BrdU uptake. After the RAW 264.7 cells were co-treated with osteoclastogenesis inducer RANKL and 6.25 μM ~ 100 μM of ISM for 3 days, a trend of dose-dependent increase of osteoclast number was noted.
Time-Efficient Myocardial Contrast Partition Coefficient Measurement from Early Enhancement with Magnetic Resonance Imaging
Shi-Jun Zhang, Yi-Xiang Wang, Jing Yuan, Jiyang Jin, Yuan-Cheng Wang, Di Chang, Dehe Weng, Andreas Greiser, Shenghong Ju
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0093124
Abstract: Objective Our purpose was to validate an early enhancement time point for accurately measuring the myocardial contrast partition coefficient (lambda) using dynamic-equilibrium magnetic resonance imaging. Materials and Methods The pre- and post-contrast longitudinal relaxation rates (reciprocal of T1) of the interventricular septum (R1m) and blood pool (R1b) were obtained from fifteen healthy volunteers and three diabetic patients with hypertension using two optimized T1 mapping sequences (modified Look-Locker inversion recovery) on a 3-Tesla magnetic resonance scanner. Reference lambda values were calculated as the slope of the regression line of R1m versus R1b at dynamic equilibrium (multi-point regression method). The simplified pre-/post-enhancement two-acquisition method (two-point method) was used to calculate lambda by relating the change in R1m and R1b using different protocols according to the acquisition stage of the post-enhancement data point. The agreement with the referential method was tested by calculating Pearson's correlation coefficient and the intra-class correlation coefficient. Results The lambda values measured by the two-point method increased (from 0.479±0.041 to 0.534±0.043) over time from 6 to 45 minutes after contrast and exhibited good correlation with the reference at each time point (r≥0.875, p<0.05). The intra-class correlation coefficient on absolute agreement with the reference lambda was 0.946, 0.929 and 0.922 at the 6th, 7th and 8th minutes and dropped from 0.878 to 0.403 from the 9th minute on. Conclusions The time-efficient two-point method at 6–8 minutes after the Gd-DTPA bolus injection exhibited good agreement with the multi-point regression method and can be applied for accurate lambda measurement in normal myocardium.
Association of Natural Intake of Dietary Plant Sterols with Carotid Intima–Media Thickness and Blood Lipids in Chinese Adults: A Cross-Section Study
Ping Wang, Yu-ming Chen, Li-ping He, Chao-gang Chen, Bo Zhang, Wen-qiong Xue, Yi-xiang Su
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032736
Abstract: Background Many studies showed a moderate cholesterol-lowering effect of plant sterols (PS), but increased circulating PS might be atherogenic. We evaluated the associations between natural dietary intake of PS and carotid intima–media thickness (IMT) and serum lipids. Methodology/Principal Findings This community-based cross-sectional study included 1160 men and 2780 women aged 31–75 years. Dietary intakes were assessed using a food-frequency questionnaire. The IMTs at the common, bifurcation and internal carotid artery segments, and fasting serum total (TC), LDL (LDLc) and HDL (HDLc) cholesterol, and triglycerides (TG) were determined. After adjusting for potential covariates, multivariate analysis showed a dose-dependent inverse association of total PS intake with serum TC, LDLc, non-HDLc in women (P<0.001) and in men (P<0.05). As compared to the lowest quartile of PS intake (<206 mg/d), the multivariate-adjusted means of TC, LDLc and non-HDLc in the highest quartile of PS intake (447 mg/d) decreased by 5.0%, 6.2% and 6.5% in women (P<0.005), and by 6.4%, 7.1% and 6.7% (P>0.05) in men. Although the IMTs tended to be lower with greater intake of dietary PS, only small differences in the left internal IMT between the highest and lowest groups were observed among men (？7.6%) and women (？5.1%) (P<0.05). The multivariate analysis showed no significant mean differences among the PS groups in HDLc, TG and IMTs at other studied sites among men and women (all P>0.05). Conclusions Greater PS consumption from natural diets is associated with lower serum total, LDL, non-HDL cholesterol and with thinner left internal IMT in women and men.
THE SEGMENTED EQUIVALENT CIRCUITS AND RATE EQUATIONS OF A NITROGEN LASER
氮分子激光器的分段等效迴路及速率方程
ZHANG YI-XIANG,WANG TING-YUAN,ZHANG ZHI-GUO,
张绮香,王庭鸢,张治国
物理学报 , 1979,
Abstract: 一、引言 氮分子激光器是一种高功率、毫微秒、脉冲紫外激光器。自1963年Heard首先观察到氮分子第二正带系由C_(π_μ)~3到B_(π_g)~3之间的跃迁产生3371A的激光输出后,围绕着提高激光输出的功率及效率方面进行了一系列的实验和理论工作。1976年Schwab等人根据横向激励氮激光器的腔内瞬时电压测量的结果,提出了放电迴路的等效迴路(集总
A promising diagnostic method: Terahertz pulsed imaging and spectroscopy
Yiwen Sun, Ming Yiu Sy, Yi-Xiang J Wang, Anil T Ahuja, Yuan-Ting Zhang, Emma Pickwell-MacPherson
World Journal of Radiology , 2011,
Abstract: The terahertz band lies between the microwave and infrared regions of the electromagnetic spectrum. This radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecular vibrations in this region have been found in different biological materials. These unique features make terahertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applications such as molecular spectroscopy, tissue characterization and skin imaging are discussed.
Non-Gaussian Analysis of Diffusion Weighted Imaging in Head and Neck at 3T: A Pilot Study in Patients with Nasopharyngeal Carcinoma
Jing Yuan, David Ka Wai Yeung, Greta S. P. Mok, Kunwar S. Bhatia, Yi-Xiang J. Wang, Anil T. Ahuja, Ann D. King
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087024
Abstract: Purpose To technically investigate the non-Gaussian diffusion of head and neck diffusion weighted imaging (DWI) at 3 Tesla and compare advanced non-Gaussian diffusion models, including diffusion kurtosis imaging (DKI), stretched-exponential model (SEM), intravoxel incoherent motion (IVIM) and statistical model in the patients with nasopharyngeal carcinoma (NPC). Materials and Methods After ethics approval was granted, 16 patients with NPC were examined using DWI performed at 3T employing an extended b-value range from 0 to 1500 s/mm2. DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models on primary tumor, metastatic node, spinal cord and muscle. Non-Gaussian parameter maps were generated and compared to apparent diffusion coefficient (ADC) maps in NPC. Results Diffusion in NPC exhibited non-Gaussian behavior at the extended b-value range. Non-Gaussian models achieved significantly better fitting of DWI signal than the mono-exponential model. Non-Gaussian diffusion coefficients were substantially different from mono-exponential ADC both in magnitude and histogram distribution. Conclusion Non-Gaussian diffusivity in head and neck tissues and NPC lesions could be assessed by using non-Gaussian diffusion models. Non-Gaussian DWI analysis may reveal additional tissue properties beyond ADC and holds potentials to be used as a complementary tool for NPC characterization.
Effects of Sod Cultivation in Orchard on Distributions of Soil Aggregates and Soil Organic Carbon of Aggregates
生草栽培对果园土壤团聚体及其有机碳分布的影响
WANG Yi-xiang,WENG Bo-qi,HUANG Yi-bin,WANG Cheng-ji,YE Jing,
王义祥,翁伯琦,黄毅斌,王成己,叶菁
热带亚热带植物学报 , 2012,
Abstract: The effects of sod cultivation in orchard on distribution of organic carbon in soil aggregates were investigated, which located in Yuchi Village, Youxi Xian, Fujian Province. The results showed that compared with downslope and landings clean tillage orchards, the proportion of >0.25 mm water-stable aggregate (R0.25), mean weight diameter (MWD), and geometric mean diameter (GWD) of soil aggregate at 0-20 cm soil layer in sod cultivation orchard increased by 3.78%-5.90%, 16.82%-20.94%, 5.86%-50.31% and 3.81%-13.82%, 13.33%- 19.95%, 7.50%-60.63%, and the fractal dimension decreased by 1.54%-2.35% and 1.09%-9.64%, respectively. The sod cultivation could improve proportion of organic carbon storage in large aggregates (>2 mm) to total organic carbon at 0-20 cm soil layer. Therefore, the sod cultivation was beneficial to improve stability of soil aggregate, and could enhance the protection of organic carbon and carbon sink in soil.
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