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251.
Zhao Kai Sun Zhanxue Du Chaochao Zhou Yipeng Li Guangrong Lui Jinhui Xu Lingling 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(6):2631-2644
Journal of Radioanalytical and Nuclear Chemistry - Due to high content of carbonate and sulfide in ore, precipitation of calcium compounds is blocking the in-situ leaching system at Mengqiguer... 相似文献
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254.
Julio Gutierrez Rodney Eisenberg Gabrielle Herrensmith Thomas Tobin Tonglei Li Sihui Long 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(12):o593-o595
Details of the structures of two conformational polymorphs of the title compound, C12H17N2OS+·Cl−, are reported. In form (I) (space group P), the two N—H groups of the cation are in a trans conformation, while in form (II) (space group P21/c), they are in a cis arrangement. This results in different packing and hydrogen‐bond arrangements in the two forms, both of which have extended chains lying along the a direction. In form (I), these chains are composed of centrosymmetric R42(18) (N—H...Cl and O—H...Cl) hydrogen‐bonded rings and R22(18) (N—H...O) hydrogen‐bonded rings. In form (II), the chains are formed by centrosymmetric R42(18) (N—H...Cl and O—H...Cl) hydrogen‐bonded rings and by R42(12) (N—H...Cl) hydrogen‐bonded rings. 相似文献
255.
In this paper we develop a reduction method for multiple time scale stochastic reaction networks. When the transition-rate
matrix between different states of the species is available, we obtain systems of reduced equations, whose solutions can successively
approximate, to any degree of accuracy, the exact probability that the reaction system be in any particular state. For the
case when the transition-rate matrix is not available, one needs to rely on the chemical master equation. For this case, we
obtain a corresponding reduced master equation with first-order accuracy. We illustrate the accuracy and efficiency of both
approaches by simulating several motivating examples and comparing the results of our simulations with the results obtained
by the exact method. Our examples include both linear and nonlinear reaction networks as well as a three time scale stochastic
reaction-diffusion model arising from gene expression. 相似文献
256.
A highly efficient one-pot, three-component microwave-assisted procedure has been developed for the preparation of 1-(para-substituted-aryl)-4-(2-acetoxyethyl)piperazines and 1-(para-substituted-aryl)-4-(2-acetoxyethyl)piperidines. Microwave-accelerated heating of electron-deficient aryl halides and potassium acetate with either 1,4-diazabicyclo[2.2.2]octane (DABCO) or quinuclidine at 180 °C for 120 min provided the title products in good yields and with general substrate scope. Similarly, subjection of potassium pthalimide instead of potassium acetate to the same conditions provided good yields of 1-arylpiperazines and 1-arylpiperidines containing a 2-phthalimidoethyl substituent at the C-4 position. 相似文献
257.
Blumenkrantz G Li X Han ET Newitt DC Crane JC Link TM Majumdar S 《Magnetic resonance imaging》2006,24(8):1001-1007
PURPOSE: Recent studies have proposed that magnetic resonance (MR) T1rho relaxation time is associated with loss of macromolecules. The depletion of macromolecules in the matrix of the intervertebral disc may be an initiating factor in degenerative disc disease. The purpose of this study was to test the feasibility of quantifying T1rho relaxation time in phantoms and intervertebral discs of healthy volunteers using in vivo MR imaging at 3 T. MATERIALS AND METHODS: A multislice T1rho spiral sequence was used to quantify T1rho relaxation time in phantoms with different agarose concentrations and in the intervertebral discs of 11 healthy volunteers (mean age=31.3 years; age range=23-60 years; gender: 5 females, 6 males). RESULTS: The phantom studies demonstrated the feasibility of using spiral imaging at 3 T. The in vivo results indicate that the median T1rho value of the nucleus (116.6+/-21.4 ms) is significantly greater (P<0.05) than that of the annulus (84.1+/-11.7 ms). The correlations between the age of the volunteers and T1rho relaxation time in the nucleus (r2=-0.82; P=0.0001) and the annulus (r2=-0.37; P=0.04) were significant. A trend of decreasing T1rho values from L3-4 to L4-5 to L5-S1 was evident. CONCLUSION: The results of this study suggest that in vivo T1rho quantification is feasible and may potentially be a clinical tool in identifying early degenerative changes in the intervertebral disc. 相似文献
258.
Lioudmila Tchvialeva Igor Markhvida Haishan Zeng David I. McLean Harvey Lui Tim K. Lee 《Optics and Lasers in Engineering》2010,48(7-8):774-778
Quantification of surface roughness greater than a micron is desirable for many industrial and biomedical applications. Polychromatic speckle contrast has been shown theoretically to be able to detect such roughness range using an appropriate light source with a Gaussian spectral shape. In this paper, we extend the theory to arbitrary spectral profile by formulating speckle contrast as a function of spectral profile, surface roughness, and the geometry of speckle formation. Under a far-field set-up, the formulation can be simplified and a calibration curve for contrast and roughness can be calculated. We demonstrated the technique using a blue diode laser with a set of 20 metal surface roughness standards in the range 1–73 μm, and found that the method worked well with both Gaussian and non-Gaussian surfaces. 相似文献
259.
Surface parameterization is widely used in computer graphics and geometry processing. It simplifies challenging tasks such as surface registrations, morphing, remeshing and texture mapping. In this paper, we present an efficient algorithm for computing the disk conformal parameterization of simply-connected open surfaces. A double covering technique is used to turn a simply-connected open surface into a genus-0 closed surface, and then a fast algorithm for parameterization of genus-0 closed surfaces can be applied. The symmetry of the double covered surface preserves the efficiency of the computation. A planar parameterization can then be obtained with the aid of a Möbius transformation and the stereographic projection. After that, a normalization step is applied to guarantee the circular boundary. Finally, we achieve a bijective disk conformal parameterization by a composition of quasi-conformal mappings. Experimental results demonstrate a significant improvement in the computational time by over 60%. At the same time, our proposed method retains comparable accuracy, bijectivity and robustness when compared with the state-of-the-art approaches. Applications to texture mapping are presented for illustrating the effectiveness of our proposed algorithm. 相似文献
260.
Graeme L. Blackman Ronald D. Brown Roger F.C. Brown Frank W. Eastwood Gabrielle L. McMullen 《Journal of Molecular Spectroscopy》1977,68(3):488-491
The microwave spectrum of methylene ketene has been observed from 8 to 35 GHz and assigned. Rotational constants and centrifugal distortion constants have been determined for CH2CCO, CHDCCO, and CD2CCO. The dipole moment was found to be μa = 2.14 ± 0.06 D (7.07 ± 0.2 × 10?30 Cm). We were unable to detect propynal among the pyrolysis products of acrylic anhydride. This pyrolysis proved to be the most convenient route for generating methylene ketene for the present investigation. 相似文献