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We prove that the category of -manifolds has all finite products. Further, we show that a -manifold (resp., a -morphism) can be reconstructed from its algebra of global -functions (resp., from its algebra morphism between global -function algebras). These results are of importance in the study of Lie groups. The investigation is all the more challenging, since the completed tensor product of the structure sheafs of two -manifolds is not a sheaf. We rely on a number of results on (pre)sheaves of topological algebras, which we establish in the appendix. 相似文献
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The automated Risø TL/OSL Reader Model DA-20, often used in dating and retrospective dosimetry, was examined for possible applications in thermoluminescent dosimetry related to radiation protection. The investigations revealed that performance of the DA-20 is comparable with that of the Harshaw 3500 manual reader, which was used as a reference instrument. All studied parameters, like stability, reproducibility, low-dose measuring capabilities, were at the same level or only somewhat inferior to those of Harshaw 3500. In particular, using the highly-sensitive LiF:Mg,Cu,P dosimeters, it is possible to measure doses at the microgray level.The DA-20 reader possesses built-in alpha and beta sources, which cause an increased radiation background. At positions just under the closed sources the dose-rate rises to about 50 μGy/h. When the 90Sr/90Y source is open a quite high dose-rate of 100 mGy/h was measured at the position adjacent to the one being irradiated. Additionally the TLD response to the background radiation significantly depends on the TLD type (atomic number), as the radiation leaking through shielding is composed of low-energy photons. The dose-rate under the closed 241Am source was over 10 times higher, when measured with CaF2 dosimeters, than with LiF.In spite of these problems, the DA-20 reader due to its good stability, reproducibility and sensitivity, combined with such obvious benefits as a 48-dosimeter carousel, temperatures up to 700 °C and full automatics of measurements control, encourages the opinion that the DA-20 Risø reader can be successfully used in practical dosimetric measurements. 相似文献
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Purpose
The purpose of the study was to validate diffusion-weighted imaging (DWI) in the assessment of hypervascular hepatocellular carcinoma (HCC) compared with superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) in the cirrhotic liver.Material and Methods
Forty-six consecutive patients with 106 hypervascular focal lesions in the cirrhotic liver who underwent DWI using three b factors and gadopentetate dimeglumine-enhanced dynamic MRI followed by SPIO-enhanced MRI were enrolled. Two independent radiologists evaluated two separated image sets (SPIO set, dynamic MRI and SPIO-enhanced T2*-weighted images; DWI set, DWI and dynamic MRI) and assigned confidence levels for diagnosis of HCC using a five-point scale for each lesion. Area under the receiver operating characteristic curve (Az) was calculated for each image set.Results
The Az value of the DWI set was larger than the SPIO set by both readers (reader 1, 0.936 vs. 0.900, P=.050; reader 2, 0.938 vs. 0.905, P=.110). For the sensitivity (reader 1, 93.1% vs. 86.2%, P=.146; reader 2, 95.4% vs. 88.5%, P=.070) and specificity (reader 1, 89.5% vs. 73.7%, P=.250; reader 2, 79.0% vs. 73.7%, P=1.000) of HCC diagnosis, DWI sets were superior to SPIO sets without statistically significant differences.Conclusion
For assessment of hypervascular HCC, DWI in combination with dynamic MRI provides comparable or slightly better information compared with the combination of dynamic and SPIO-enhanced MRI. 相似文献13.
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The Watson version of the molecular vibration-rotation hamiltonian is expanded in terms of the scalar invariants of the inverse of the moment of inertia tensor using the generalized Lucas polynomials. The resultant expansion consists of the matrices Î, , 2 with coefficients depending on the normal coordinates. This is in contrast to the usual expansion as a power series in the matrix . 相似文献