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991.
N Ivanovska S Philipov R Istatkova P Georgieva 《Canadian Metallurgical Quarterly》1996,54(2-3):143-151
The antimicrobial and immunological properties of ethanol extracts, non-alkaloid, tertiary alkaloid and quaternary alkaloid fractions, obtained from roots and aerial parts of Isopyrum thalictroides were examined. The non-alkaloid fraction from aerial parts inhibited the growth of seven test microorganisms and was the most effective suppressor of classical pathway (CP) complement activity in normal human serum (NHS) and guinea pig serum (GPS). The alkaloid fractions, containing quaternary alkaloids expressed suppressive effect on mitogen-induced splenocyte proliferation. The in vitro antibody response against sheep red blood cells (anti-SRBC) was inhibited by ethanol extracts and quaternary alkaloid fraction. The intraperitoneal (i.p.) application of ethanol extract and tertiary alkaloid fraction from aerial parts showed that they possess in vivo effect on alternative pathway (AP) complement activity, anti-SRBC response and delayed type hypersensitivity (DTH). 相似文献
992.
Richards-Kortum R. Mahadevan-Jansen A. Ramanujam N. 《Circuits and Devices Magazine, IEEE》1996,12(4):34-40
A novel non-invasive technique for detecting cancer and precancer offers a viable adjunct to biopsies. Here, we summarize the principles of optical spectroscopy and present some of the highlights obtained with the successful application of fluorescence and Raman spectroscopy for cancer and precancer detection 相似文献
993.
The device degradation under ac and dc stress have been discussed and a relationship between the two has been established,. We have shown that the commonly used lifetime criteria of 10% linear current degradation for 10 years for a transistor under dc stress is overly conservative for representing the circuit operating lifetime. Using experimental and simulated data for inverter chains, we proposed that a meaningful equivalent lifetime based on 10% Idl degradation under dc stress is 1 year lifetime (for a 10 year circuit lifetime based on 54b degradation in ring oscillator frequency). We also compared this criteria to actual circuit degradation for microprocessors and a DRAM. For DSP microprocessors with 0.8 μm LDD transistors, the projected lifetime was more than 200 years at 5.5 V, with a corresponding 10% I dr lifetime of 20 years. For 1 Mb DRAMs with 1 pm LDD transistors, the 5% speed degradation lifetime at 5.5 V was more than 100 years, whereas the individual transistors had 10% Idl lifetime of 4 years. These circuit results support the 10% Idl transistor lifetime. We believe these criterion should be very safe and reasonable for digital IC chips currently in the field, as well as those in future design and development 相似文献
994.
Sabate J.A. Jovanovic M.M. Lee F.C. Gean R.T. 《Industrial Electronics, IEEE Transactions on》1995,42(1):63-71
The analysis and design of an LCC resonant inverter for a 20 kHz AC distributed power system are presented. Several resonant converter topologies are assessed to determine their suitability for high efficiency power conversion, under resistive and reactive loads. Two LCC-resonant inverter designs were implemented. One with all switches operating with zero voltage switching (ZVS), and another with two switches operating with ZVS and two switches with zero current switching (ZCS). The experimental results are presented along with a performance comparison of the two versions 相似文献
995.
996.
997.
Dotti D. Lombardi R. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(5):864-869
Correlation functions, calculated on the ultrasonic echoes scattered by blood, provide a rich harvest of information concerning the local speed, which has often been underestimated; in particular, blood flow measurement usually yields only the longitudinal component of the velocity, even if significant information about the speed direction can be extracted. In this paper it is shown how correlation functions, calculated on the dependency of both time and space displacements, allow us to evaluate the angle Θ between ultrasound beam and blood flow; when straight vessels are considered, this single parameter, combined with the longitudinal velocity profile, permits the complete hemodynamic characterization. The underlying theory is developed and preliminary experimental results are presented 相似文献
998.
999.
Lightly p-doped (3×1017 cm-3) GaN grown on GaAs substrates by metal organic molecular beam epitaxy (MOMBE) shows deactivation of the residual acceptors on exposure to a microwave (2.45 GHz) hydrogen plasma at 250°C. Subsequent annealing to 350°C produces further dopant passivation, while higher temperatures (450°C) restore the initial conductivity. These results suggest that hydrogen carrier gases should be avoided during vapour phase growth of III-V nitrides 相似文献
1000.
The feasibility of using a thick ground plane with an aperture coupled microstrip patch antenna while maintaining reasonable antenna performance is demonstrated using moment method and reciprocity analyses in the spectral domain. The thick ground plane, which may serve as a heatsink for active MMIC circuitry, or as a mechanical support for thin substrates, is particularly advantageous in millimetre wave phased array applications. It is found that the effect of ground plane thickness is to reduce the level of coupling from the feed line to the patch 相似文献