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71.
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The study was conducted in 55 patients with cardiac pains. Electrocardiography was used successively prior to, during and following physical exercises, followed by Seldinger selective coronary angiography, and electrocardiography prior to, during and following hyperventilation tests. In 2 of 55 patients the result of the exercise test was interpreted as false-positive, since the coronary angiography demonstrated intact vessels, and during hyperventilation ECG recorded a decreased ST segment. To avoid false-positive results in patients with suspected angina pectoris the physical exercises tests can be considered positive only in cases in which hyperventilation caused no ECG changes typical for angina pectoris. 相似文献
73.
74.
Sizer T. II Kafka J. Duling I. III Gabel C. Mourou G. 《Quantum Electronics, IEEE Journal of》1983,19(4):506-511
In high-gain dye amplifiers, the effective storage time of the gain medium is only a few hundred picoseconds. Therefore, efficient amplification of ultrashort pulses places a stringent requirement on the synchronization between the pump pulse and the pulse to be amplified. We present a technique of short pulse generation using a dye laser synchronously pumped by a frequency-doubled CW mode locked Nd:YAG laser. Pulses as short as 70 fs are produced. The short optical pulses are subsequently amplified with two different synchronous amplification schemes using 100 ps pulses to establish the gain in the dye amplifier stages. Subpicosecond pulses with energies from a few hundred nanojoules at 500 Hz to a few hundred microjoules at 7 Hz can be obtained. 相似文献
75.
76.
II Gitel'zon VP Nefedov VV Mezhevikin VA Samo?lov IuV Kotlovski? 《Canadian Metallurgical Quarterly》1977,84(7):23-24
Hypoxemia (45-minute) influence in vivo on erythropoietic activity of the kidney, liver, spleen, and sternum was studied by normoxemic perfusion of the isolated organs. The erythropoietic activity proved to increase after 6-hour perfusion of the liver; this confirmed the participation of this organ in the extrarenal secretion of the erythropoietic factor. 相似文献
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Allen-Gil SM Ford J Lasorsa BK Monetti M Vlasova T Landers DH 《The Science of the total environment》2003,301(1-3):119-138
The Taimyr Peninsula is directly north of the world's largest heavy metal smelting complex (Norilsk, Russia). Despite this proximity, there has been little research to examine the extent of contamination of the Taimyr Peninsula. We analyzed heavy metal concentrations in lichen (Cetraria cucullata), moss (Hylocomium splendens), soils, lake sediment, freshwater fish (Salvelinus alpinus, Lota lota and Coregonus spp.) and collared lemming (Dicrostonyx torquatus) from 13 sites between 30 and 300 km from Norilsk. Element concentrations were low in both C. cucullata and H. splendens, although concentrations of Al, Fe, Cu, Ni and Pb were significantly higher than those in Arctic Alaska, probably due to natural differences in the geochemical environments. Inorganic surface soils had significantly higher concentrations of Cd, Zn, Pb and Mg than inorganic soils at depth, although a lake sediment core from the eastern Taimyr Peninsula indicated no recent enrichment by atmospherically transported elements. Tissue concentrations of heavy metals in fish and lemming were not elevated relative to other Arctic sites. Our results show that the impact of the Norilsk smelting complex is primarily localized rather than regional, and does not extend northward beyond 100 km. 相似文献
79.
M. Ristich G. Brankovich T. Srechkovich M. Vlasova M. Kakazei M. L. Domingez-Patiño G. F. Domingez-Patiño I. I. Timofeeva L. P. Isaeva 《Inorganic Materials》2003,39(9):988-995
The phase formation in the CdO-rich part (10 wt % Bi2O3) of the CdO–Bi2O3 system was studied by x-ray diffraction, IR spectroscopy, electron microscopy, and other techniques. The results indicate that the grinding of the starting powder mixtures in a planetary mill leads to an inhomogeneous Bi2O3 distribution and a high defect density in the CdO and Bi2O3 particles. Sintering in the range 910–990 K gives rise to the formation of the h phase, whose content depends strongly on the mixture composition and sintering conditions. At sintering temperatures above its melting point, the h phase acts as a binder of CdO grains. 相似文献
80.
Josh A. Pihl Jennifer A. Lewis Todd J. Toops James E. Parks II 《Topics in Catalysis》2013,56(1-8):89-93
The primary technical barrier to deployment of fuel saving lean gasoline engines is NOx emissions control. We conducted automated flow reactor experiments on a commercial LNT catalyst to identify opportunities and challenges associated with the higher temperatures and higher NOx concentrations expected in lean gasoline applications. Overall NOx conversion was quite high at low to moderate temperatures, but dropped off at high temperatures. The decrease in NOx conversion with temperature was worse for higher inlet NOx concentrations. As expected from equilibrium considerations, the catalyst stored more NOx under higher gas phase NOx concentrations, but that NOx was rapidly released during the rich phase and slipped out of the catalyst before it could be converted to N2 by incoming reductant. This rich phase NOx release was the primary factor limiting performance of the catalyst at high temperatures, and resulted in significant spikes of NOx that would likely exceed any not-to-exceed regulated emissions levels. N2O production was also significant, and increased with NOx concentration. The catalyst made very little NH3 at high temperatures. NH3 yield was significant at the lowest operating temperature studied, but it decreased with increasing NOx concentration. 相似文献