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排序方式: 共有846条查询结果,搜索用时 15 毫秒
841.
The mortality from coronary heart disease (CHD) in Norway increased rapidly during 1951-70, the highest mortality rates as well as the most rapid increases being found in Northern Norway. Several surveys of CHD were then planned, one of them is reported here. All men, 20-49 years of age, living in the municipality of Troms?o, Troms county, were called up for examination. In total, 6595 men, 74.4% of those invited, were examined. Cholesterol, triglyceride and Hb values, BP, body weight and height, the percentage of smokers, and cigarette consumption have been tabulated according to area, age, work schedule, health condition, physical activity and ethnic background. The results suggest that the relatively high mortality from CHD in Northern Norway is associated with high serum cholesterol concentrations as well as a relatively high prevalence of smoking. During the screening there were indications of changes in dietary habits in the municipality, presumably as a result of accompanying publicity. 相似文献
842.
DJ Sass RA Van Dyke EH Wood SA Johnson P Didisheim 《Canadian Metallurgical Quarterly》1976,40(5):745-751
Lethal gas embolism always occurs after FC 80 liquid fluorocarbon is injected intravenously (0.1 ml/kg body mass) in dogs breathing room air but not in dogs breathing oxygenated FC 80 liquid fluorocarbon. Gas embolism is not prevented in dogs that have been injected intravenously with FC 80 when they are exposed to 2 ATA (atmospheres absolute) 20% 02-80% N2, 9 ATA 5% O2-95% He, or 1 ATA 100%, O2. In dogs that die of FC 80-induced gas embolism, free gas in the right atrium contains approximately 0.5 g FC 80/liter, and Po2 and Pco2 in the gas are in equilibrium with their corresponding tensions in right atrial blood. These observations are consistent with the hypothesis that PFC 80 in alveolar gas does not equilibrate with PFC 80 (55 mmHg) in blood. The total gas tension in pulmonary capillary blood containing FC 80 and its vapor thus exceeds the total tension of alveolar gases (atmospheric pressure). Bubbles of O2, CO2, N2, FC 80, and water vapor form in the regions of the pulmonary capillary bed where the total tension of gases dissolved in blood exceeds the absolute blood pressure. 相似文献
843.
844.
AG Engel M Tsujihata EH Lambert JM Lindstrom VA Lennon 《Canadian Metallurgical Quarterly》1976,35(5):569-587
Neuromuscular junction ultrastructure in rat forelimb digit extensor muscle was sequentially and quantitatively investigated in experimental autoimmune myasthenia gravis (EAMG). Experimental animals were immunized with highly purified eel electroplax acetylcholine receptor protein plus complete Freund's adjuvant and B pertussis vaccine; control animals received only adjuvant and vaccine. During the first 7 days (latent period) after immunization end-plate structure and neuromuscular transmission remained normal in the experimental group. Between day 7 and 11 (acute phase) mononuclear cells infiltrated those regions of muscle where the end-plates were located and there was intense degeneration of the postsynaptic regions with splitting away of abnormal junctional folds from the underlying muscle fibers. Macrophages entered the gaps thus formed and removed the degenerating folds by phagocytosis. The nerve terminals were displaced from their usual location but maintained their structural integrity. Neuromuscular transmission was blocked in many muscle fibers. Miniature end-plate potentias (MEPPs), detectable in only a few fibers, were of abnormally low amplitude. After day 11 (chronic phase) the nerve terminals returned to the highly simplified postsynaptic folds became reconstituted and again degenerated. Immature junctions with poorly differentiated postsynaptic regions and nerve sprouts near end-plates were also observed. In two animals relapsing during the chronic phase degeneration of the postsynaptic folds was more intense than in the other chronic-phase animals. The posysynaptic membrane length and length per unit area and the MEPP amplitudes were significantly decreased in all chronic phase animals and the decreases were greater in the relapsing than in the non-lapsing animals. Minor morphometric alterations were also observed in the nerve terminals. These might have been secondary to the postsynaptic changes. The postsynaptic region is the primary target of the autoimmune reaction in EAMG. The ultrastructural, morphometric and electrophysiological abnormalities of the end-plate in chronic EAMG resemble those which have been observed in human myasthenia gravis. 相似文献
845.
Siyuan Dai Jiawei Zhang Qiong Ma Salinporn Kittiwatanakul Alex McLeod Xinzhong Chen Stephanie Gilbert Corder Kenji Watanabe Takashi Taniguchi Jiwei Lu Qing Dai Pablo Jarillo‐Herrero Mengkun Liu D. N. Basov 《Advanced materials (Deerfield Beach, Fla.)》2019,31(18)
Unlike conventional plasmonic media, polaritonic van der Waals (vdW) materials hold promise for active control of light–matter interactions. The dispersion relations of elementary excitations such as phonons and plasmons can be tuned in layered vdW systems via stacking using functional substrates. In this work, infrared nanoimaging and nanospectroscopy of hyperbolic phonon polaritons are demonstrated in a novel vdW heterostructure combining hexagonal boron nitride (hBN) and vanadium dioxide (VO2). It is observed that the insulator‐to‐metal transition in VO2 has a profound impact on the polaritons in the proximal hBN layer. In effect, the real‐space propagation of hyperbolic polaritons and their spectroscopic resonances can be actively controlled by temperature. This tunability originates from the effective change in local dielectric properties of the VO2 sublayer in the course of the temperature‐tuned insulator‐to‐metal phase transition. The high susceptibility of polaritons to electronic phase transitions opens new possibilities for applications of vdW materials in combination with strongly correlated quantum materials. 相似文献
846.
The retinex theory of color vision 总被引:8,自引:0,他引:8
EH Land 《Canadian Metallurgical Quarterly》1977,237(6):108-128