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31.
The bit error rate (BER) analysis of a direct-sequence code-division multiple-access (DS-CDMA) cellular system over a Rayleigh-fading channel often results in complicated expressions even though the Gaussian approximation is applied. A combined probability density function (pdf) approach for the forward link and a mean-method technique for the reverse link are proposed to significantly reduce the computational complexity. The simplified BER expressions are derived and yield accurate results 相似文献
32.
SD Shiian SV Kha?dukov AL Pukhal''ski? AP Toptygina NV Bovin 《Canadian Metallurgical Quarterly》1996,41(2):24-29
The interaction of human peripheral blood leukocytes with alpha 1-acid glycoprotein (AGP), its glycoforms as well as neoglyco-conjugates representing carbohydrate chains of AGP or its fragments was studied by flow cytometry. It was shown that the main target cells for AGP as well as for conjugates of its carbohydrate chains with polyacrylamide (PAA) are monocytes and polymorphonuclear leukocytes but not lymphocytes. The interaction of AGP with monocytes and granulocytes are mediated by its carbohydrate chains: the binding of AGP with cells was inhibited by AGP, AGP oligosaccharides as well as conjugates of oligosaccharides and its fragments with PAA. The data obtained show the existence of monocyte (and granulocyte) receptors which interact with complex type sialooligosaccharides of AGP. 相似文献
33.
34.
The nature of localized deformation that occurs both in metal and polymer samples was examined under uniaxial tension by measuring the complete strain distribution of a deforming specimen at a constant crosshead speed. The development of localized deformation in 6111-T6 aluminium alloy and polycarbonate was recorded along both the longitudinal and lateral directions as the specimen was stretched until it fractured. Determination of the true strain at various points on the tensile specimens was made by using an automated, vision-based image processing method using a CCD camera to measure the deformation of a silk-screened grid on the specimen. This vision-based system produced accurate results, allowing for careful analysis of the entire necking process from initiation to propagation. It has been observed that localized deformation develops principally in the longitudinal direction. The major and minor true strain are uniform for the uniform section specimens, however, these strains peak in the centre of the hourglass specimens in the longitudinal direction for both materials. For both specimen geometries, the major strain is uniform while the minor strain is non-uniform in the lateral direction. The longitudinal true strain to lateral true strain ratio remains at about two for the uniform section specimens, but this ratio increases to between 3 and 5 for the hourglass specimens, due to the constraining effect of the sample geometry. 相似文献
35.
Q Hu M Trevisan Y Xu W Dong SA Berger SD Lyman MD Minden 《Canadian Metallurgical Quarterly》1995,95(6):2530-2538
The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells. 相似文献
36.
RA Malik S Tesfaye SD Thompson A Veves AK Sharma AJ Boulton JD Ward 《Canadian Metallurgical Quarterly》1993,36(5):454-459
Twenty diabetic patients with neuropathy underwent clinical and neurophysiological evaluation together with a detailed morphometric assessment of capillary pathology in endoneurial and epineurial microvascular beds of the sural nerve. Morphological data were compared with ten non-diabetic control subjects. There were no significant differences in control subjects between basement membrane area, endothelial cell area, endothelial cell profile number or luminal area of endoneurial when compared with epineurial capillaries. In contrast, when compared with epineurial capillaries, endoneurial capillaries from diabetic patients demonstrated a significant increase in basement membrane (p < 0.001) and endothelial cell (p < 0.001) area and a significant reduction in luminal area (p < 0.001). There was no significant difference in endothelial cell profile number between endoneurial and epineurial capillaries amongst diabetic patients. Previous studies have demonstrated a good correlation between the degree of microangiopathy and measures of neuropathic severity. In the present study increased endoneurial capillary basement membrane area was significantly related to reduced peroneal nerve conduction velocity (p < 0.001), myelinated fibre density (p < 0.001) and elevated vibration (p < 0.05) and thermal (p < 0.001) perception. Increased endothelial cell area and reduced luminal size were related to a reduced peroneal nerve conduction (p < 0.05, p < 0.01, respectively), reduced myelinated fibre density (p < 0.05, p < 0.01) and elevated thermal perception (p < 0.05, p < 0.001). Epineurial capillary basement membrane, endothelial cell and luminal area failed to relate to measures of neuropathic severity.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
37.
This paper reviews the pathogenesis of Mycobacterium bovis infection in cattle, focusing on aspects relating to the host rather than the organism. A broad concept of pathogenesis has been considered and information is presented on sources and routes of infection, as well as the immune responses and pathology. In addition, data is presented on the excretion of M. bovis from tuberculous cattle. 相似文献
38.
The role of MHC class II in the presentation of Heligmosomoides polygyrus antigens has been investigated, using a number of T cell hybridomas produced in A and E positive and negative mice. By using fixed and irradiated antigen presenting cells (APC), further evidence has emerged, to support earlier data, that there can be differential processing requirements during the presentation of H. polygyrus antigens by A and E molecules. In concordance with these earlier observations, this work provides further evidence than individual T cells can respond to antigen when presented by more than one MHC molecule. Previously, this evidence has been restricted to individual MHC molecules of the same haplotype, but these data show that H. polygyrus produces antigens which can be presented by both syngeneic and allogeneic MHC molecules. These antigens do not appear to be synonymous with the previously described H. polygyrus superantigen, as presentation is restricted to specific MHC haplotypes. It is proposed that H. polygyrus may produce these antigenic molecules as part of its strategy to manipulate the host immune system. 相似文献
39.
40.
Nickel-rich β-NiAl alloys, which are potential materials for high-temperature shape-memory alloys, show a thermoelastic martensitic transformation,
which produces their shape memory effect. However, the transformation to Ni5Al3 phase during heating of NiAl martensite can interrupt the reversible martensitic transformation; consequently, the shape
memory effect in NiAl martensite might not appear after heating. The phase transformation process in binary Ni-(34 to 37)Al
martensite was investigated by differential thermal analysis (DTA) method, and we found that the condition of reversible martensitic
transformation was not the β → Ni5Al3 transformation, but rather the M → Ni5Al3 transformation occurring at 250 °C to 300 °C. Therefore, the transformation temperature of M → Ni5Al3 determined the highest operating temperature for the shape memory effect. For verifying the critical temperature, the phase
transformation process was investigated for eight ternary Ni-33Al-X alloys (X=Cu, Co, Fe, Mn, Cr, Ti, Si, and Nb). Only Ti,
Si, and Nb additions were found to be effective in dropping the M
s temperature, and they facilitated the shape memory effect in Ni-33Al-X alloys. In particular, the addition of Si and Nb raised
the transformation temperature of M → Ni5Al3, a potentially beneficial effect for shape memory at higher temperatures.
This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented
at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint
Committee on Mechanical Behavior of Materials. 相似文献