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991.
992.
P M Colletti H T Dang M W Deseran R M Kerr W D Boswell P W Ralls 《Magnetic resonance imaging》1991,9(3):349-355
Bone scintigraphy (RN) and magnetic resonance imaging (MR) were prospectively and retrospectively correlated in 64 patients with suspected spinal metastatic disease and possible spinal cord compression. Images were retrospectively interpreted and compared with the prospective official RN and MR reports to help decide relative prospective lesion conspicuity. Spinal lesions were confirmed by radiography, computed tomography, myelography or MR and RN follow-up in 56 patients (88%). Prospectively, MR detected 11 lesions not reported on RN while RN detected two lesions not reported on MR. Retrospective review of RN detected six lesions previously not reported. Retrospectively MR showed all lesions. Those lesions seen only in retrospect by RN were rather subtle and would be difficult to detect prospectively. In general, lesions not well seen on RN had relatively more bone marrow abnormality and less cortical bone involvement. In some cases, MR imaging shows spinal marrow lesions not well seen on planar RN. 相似文献
993.
994.
We consider the estimation of the unknown mean of a homogeneous random field from observations on a system of homothetically expanding regions. We examine the asymptotic behavior of the variance of the arithmetic-mean estimator. The arithmetic-mean estimator is shown to be asymptotically efficient in the class of linear estimators.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 66, pp. 106–111, 1988. 相似文献
995.
T. Andreev Y. Hori X. Biquard E. Monroy D. Jalabert A. Farchi M. Tanaka O. Oda Le Si Dang B. Daudin 《Superlattices and Microstructures》2004,36(4-6):707
We have studied the structural and optical properties of GaN quantum dots (QDs) doped with Tm and Eu. It has been found that the morphology of the dots was affected by the presence of the rare earth atoms. Differences in incorporation have also been pointed out, Eu being located inside the QDs while Tm is more likely to be found at the interface between GaN QDs and AlN matrix. Intense and sharp Eu- and Tm-related transition lines are observed in the photoluminescence and cathodoluminescence spectra of doped QDs, with no thermal quenching between 20 and 300 K. They exhibit a saturation effect with increasing excitation power, independently of the temperature. It is tentatively proposed that some transition lines in GaN:Tm QDs could be induced by the presence of the internal electric field. 相似文献
996.
This paper investigates Hilbert polynomials of bigraded algebras which are generated by elements of bidegrees $(1,0), (d_1,1),\ldots,(d_r,1)$, where $d_1,\ldots,d_r$ are non-negative integers. The obtained results can be applied to study Rees algebras of homogeneous ideals and their diagonal subalgebras.
Mathematics Subject Classification (1991):13D40, 13H15.The authors are partially supported by the National Basic Research Program of\break Vietnam. 相似文献
997.
Molecular dynamic simulations with polarizable potentials were performed to systematically investigate the distribution of NaCl, NaBr, NaI, and SrCl(2) at the air/liquid methanol interface. The density profiles indicated that there is no substantial enhancement of anions at the interface for the NaX systems, in contrast to what was observed at the air/aqueous interface. The surfactant-like shape of the larger more polarizable halide anions, which is part of the reason they are driven to air/aqueous interfaces, was compensated by the surfactant nature of methanol itself. These halide anions had on average an induced dipole of moderate magnitude in bulk methanol. As a consequence, methanol hydroxy groups donated hydrogen bonds to anions where the negatively charged side of the anion induced dipole pointed, and methyl groups interacted with anions where the positively charged side of the anion-induced dipole pointed. Furthermore, salts were found to disrupt the surface structure of methanol. For the neat air/liquid methanol interface, there is relative enhancement of methyl groups at the outer edge of the air/liquid methanol interface in comparison with hydroxy groups, but with the addition of NaX this enhancement was reduced somewhat. Finally, with the additional of salts to methanol, the computed surface potentials decreased, which is in contrast to what is observed in corresponding aqueous systems, where the surface potential increases with the addition of salts. Both of these trends have been indirectly observed with experiments. The surface potential trends were found to be due to the greater propensity of anions for the air/water interface that is not present at the air/liquid methanol interface. 相似文献
998.
Quang DT Wu JS Luyen ND Duong T Dan ND Bao NC Quy PT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):753-756
A new rhodamine-derived Schiff base (RS) was synthesized and its sensing property to metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg2+ ions to the aqueous solution of RS gave a visual color change as well as significantly fluorescent enhancement, while other ions including Pb2+, Cd2+, Cr3+, Zn2+, Cu2+, Fe2+, Co3+, Ni2+, Ca2+, Mg2+, K+ and Na+ ions did not induce any distinct color/spectral changes, which constituted a Hg2+-selective fluorescent OFF-ON chemosensor. The Hg2+-induced ring-opening of spirolactam of rhodamine in RS resulted in the dual chromo- and fluorogenic observation. 相似文献
999.
Bai Y Hu XF Dang DB Bi FL Niu JY 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):70-73
A new inorganic–organic hybrid compound [O2NBzQL]4[Cd(SCN)4(NCS)2] (O2NBzQL = 1-(4′-NO2-benzyl)quinolinium cation) has been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Cd(II) atom has an distorted octahedral environment with an N4S2 donor set. In solid state there are three types of face-to-face π–π interactions between adjacent cations and multiform C–H?S and C–H?N hydrogen bonds between [O2NBzQL]+ cations and cadmium thiocyanate anions. The luminescent properties of the title compound were both investigated in H2O solution and in solid state at room temperature, respectively. 相似文献
1000.