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91.
基于Snake模型的低对比度噪声心脏MRI图像分割 总被引:4,自引:0,他引:4
提出了一种基于Snake模型的低对比度、噪声心脏MRI图像分割算法。Snake模型通过轮廓线的变形得到感兴趣区域(ROI)的边界,但其分割结果依赖于初始轮廓线的位置,且变形曲线容易收敛于局部梯度极大值区域或从弱边界处泄漏,对于深度凹陷的区域也难以分割。通过增加局部面积能量项,扩大了Snake模型寻找边界的范围;在模糊C均值集群分类的基础上,构造模糊能量项,能够较好地处理心脏MRI图像中的弱边界、局部梯度极大值区域、伪影等现象。分割实验证明了改进的模型能够有效地分割低对比度、噪声心脏MRI图像。 相似文献
92.
Qu Chen XiuMing Liu F. Heller Ann M. Hirt Bin Lü XueLian Guo XueGang Mao JiaSheng Chen GuoYong Zhao Hua Feng Hui Guo 《科学通报(英文版)》2012,57(15):1844-1855
The magnetic susceptibility of loess from the Ily Basin,northwestern China shows maximum values in S0 paleosols but minimum values in other paleosols,the mechanism of which has been well debated.In this work,systematic magnetic measurements were made on a representative section from Neleke county.The results show that the loess horizons(L1,L2 and L3) have multi-domain magnetite grains of aeolian origin,S0 is characterized by production of pedogenetic ultrafine-grained ferrimagnetic minerals,and the other paleosols(S1,S2,and S3) are characterized by the formation of nonferrimagnetic minerals associated with waterlogging.The correlation between the low concentration of ferrimagnets,high paramagnetic content,high magnetic coercivity remanence,fine ferrimagnetic grain size and intensified pedogenesis suggest two competing processes of pedogenetic enhancement and pedogenetic depletion in the lower paleosols.Pedogenetic depletion dominates and is responsible for the low susceptibility.Changes in magnetic grain size distribution occur during pedogenetic depletion.The susceptibility variations are of multiple origins in the loess of the Ily Basin.Pedogenetic enhancement,pedogenetic depletion,and allochthonous input of magnetic minerals should all be taken into account to explain the variations of magnetic parameters. 相似文献
93.
Riassunto Si dimostra che l'utero di ratta, sottoposta ad ablazione della ovaie 15 mesi e mezzo prima, risponde nettamente a tre iniezioni sottocutanee quotidiane di 17-estradiolo: si ottennero aumenti di peso del 92, 207 e 231% al di sopra del peso degli uteri di controlli sottoposti ad ovariectomia e trattati con semplice olio di sesamo. Si conclude, percio, che l'utero di ratta esposta a deficienza ormonica ovarica di lunga durata è notevolmente sensibile a trattamento con estrogeni. 相似文献
94.
Chromatin-IgG complexes activate B cells by dual engagement of IgM and Toll-like receptors 总被引:85,自引:0,他引:85
Leadbetter EA Rifkin IR Hohlbaum AM Beaudette BC Shlomchik MJ Marshak-Rothstein A 《Nature》2002,416(6881):603-607
Autoreactive B cells are present in the lymphoid tissues of healthy individuals, but typically remain quiescent. When this homeostasis is perturbed, the formation of self-reactive antibodies can have serious pathological consequences. B cells expressing an antigen receptor specific for self-immunoglobulin-gamma (IgG) make a class of autoantibodies known as rheumatoid factor (RF). Here we show that effective activation of RF+ B cells is mediated by IgG2a-chromatin immune complexes and requires the synergistic engagement of the antigen receptor and a member of the MyD88-dependent Toll-like receptor (TLR) family. Inhibitor studies implicate TLR9. These data establish a critical link between the innate and adaptive immune systems in the development of systemic autoimmune disease and explain the preponderance of autoantibodies reactive with nucleic acid-protein particles. The unique features of this dual-engagement pathway should facilitate the development of therapies that specifically target autoreactive B cells. 相似文献
95.
E. Katchburian Ann M. C. Burgess F. R. Johnson 《Cellular and molecular life sciences : CMLS》1973,29(8):1020-1022
Résumé A l'aide du microscope électronique muni d'un goniomètre, la structure tri-dimensionelle du disque Z de la fibre musculaire striée a été analysée. Les résultats obtenus sont comparés avec un modèle construit en perspex et avec les images conventionnelles du disque Z.
Acknowledgment. We wish to thank Pye Unicam (Philips) an Jeol (U. K.) Ltd. for kindly allowing us to use their electron microscopes. Technical assistance from Messrs.H. Fisher, J. Manston andR. Birchenough is gratefully acknowledged. 相似文献
Acknowledgment. We wish to thank Pye Unicam (Philips) an Jeol (U. K.) Ltd. for kindly allowing us to use their electron microscopes. Technical assistance from Messrs.H. Fisher, J. Manston andR. Birchenough is gratefully acknowledged. 相似文献
96.
Shirley Ann Gilmore 《Cellular and molecular life sciences : CMLS》1979,35(9):1237-1237
Summary X-irradiation temporarily decreases the proliferative activity of neuroglia in immature rat spinal cord. Later, the proliferative activity in these irradiated regions surpasses that noted in control rats. Areas adjacent to the irradiated region have a greater than normal percentage of labelled neuroglia and may also be a source for neuroglia which re-populate the irradiated zone.Acknowledgments. Sincere thanks to Ms Jane Leiting for her assistance in doing the cell counts and to Mr Napoleon Phillips for preparing the autoradiographs. Supported by USPHS grant NS 04761. 相似文献
97.
Nicotinic acetylcholine receptor alpha7 subunit is an essential regulator of inflammation 总被引:90,自引:0,他引:90
Wang H Yu M Ochani M Amella CA Tanovic M Susarla S Li JH Wang H Yang H Ulloa L Al-Abed Y Czura CJ Tracey KJ 《Nature》2003,421(6921):384-388
Excessive inflammation and tumour-necrosis factor (TNF) synthesis cause morbidity and mortality in diverse human diseases including endotoxaemia, sepsis, rheumatoid arthritis and inflammatory bowel disease. Highly conserved, endogenous mechanisms normally regulate the magnitude of innate immune responses and prevent excessive inflammation. The nervous system, through the vagus nerve, can inhibit significantly and rapidly the release of macrophage TNF, and attenuate systemic inflammatory responses. This physiological mechanism, termed the 'cholinergic anti-inflammatory pathway' has major implications in immunology and in therapeutics; however, the identity of the essential macrophage acetylcholine-mediated (cholinergic) receptor that responds to vagus nerve signals was previously unknown. Here we report that the nicotinic acetylcholine receptor alpha7 subunit is required for acetylcholine inhibition of macrophage TNF release. Electrical stimulation of the vagus nerve inhibits TNF synthesis in wild-type mice, but fails to inhibit TNF synthesis in alpha7-deficient mice. Thus, the nicotinic acetylcholine receptor alpha7 subunit is essential for inhibiting cytokine synthesis by the cholinergic anti-inflammatory pathway. 相似文献
98.
This paper sets out some observations arising from on-going research into the use of systemic methods in the planning of complex projects within the National Health Service (NHS) in Staffordshire and Shropshire in the UK. This brief paper sets out the main reasons for the application of systemic approaches, the nature of the methodologies put in place and some of the outcomes and reflections of those involved in the various workshops. Whilst not attempting to be definitive in our conclusions, the authors believe that the results of the application of systemic methods by Health and Care professionals show a range of strengths going forward.Published with the kind permission of Staffordshire and Shropshire Workforce Development Directorate. 相似文献
99.
100.
Cichon S Buervenich S Kirov G Akula N Dimitrova A Green E Schumacher J Klopp N Becker T Ohlraun S Schulze TG Tullius M Gross MM Jones L Krastev S Nikolov I Hamshere M Jones I Czerski PM Leszczynska-Rodziewicz A Kapelski P Bogaert AV Illig T Hauser J Maier W Berrettini W Byerley W Coryell W Gershon ES Kelsoe JR McInnis MG Murphy DL Nurnberger JI Reich T Scheftner W O'Donovan MC Propping P Owen MJ Rietschel M Nöthen MM McMahon FJ Craddock N 《Nature genetics》2004,36(8):783-4; author reply 784-5