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101.
Versatile intermediates for the synthesis of C-glycosides and oxygen heterocycles are readily available through titanium mediated methylenation of aldonolactones.Aldonolactones may be alkylated using the titanium carbene complex 2. The resulting enol ethers are of value as potential substrates for glycosidase enzymes. A high yield two step process for alkylation of these enol ethers was described. The products and procedures are relevant to the synthesis of mycotoxins, including citreoviridin and aurovertin B. 相似文献
102.
Kim HJ Kim H Alhakimi G Jeong EJ Thavarajah N Studnicki L Koprianiuk A Lough AJ Suh J Chin J 《Journal of the American Chemical Society》2005,127(47):16370-16371
Crystal structure and activation entropy data indicate that H-bond directed diaza-Cope rearrangement of chiral diimines takes place with a high degree of preorganization. CD spectroscopy and HPLC data show that there is inversion of stereochemistry for the reaction with excellent enantioselectivity. 相似文献
103.
Sec13p has been known as an endoplasmic reticulum-Golgi transport protein. Recently, it has also been shown to be required for the formation of septation in the fission yeast Schizosaccharomyces pombe. In the present study, we focused on the role of a human homolog of Saccharomyces cerevisiae SEC13, Sec13 protein during mitosis in U2OS cells. We found that the expression of Sec13 was constant throughout the cell cycle, and localized to the kinetochores at metaphase during mitosis. By using green fluorescent protein technology, we observed that Sec13 is required for evasion of mitotic arrest in response to spindle damage, leading to G1-like phase and apoptotic cell death. In addition, cells expressing exogenous Sec13 showed giant nuclei compared to endogenous ones in the absence of nocodazole. These results demonstrate that Sec13 is involved in the regulation of the metaphase/anaphase transition and may be functionally associated with mitotic machinery to maintain genomic stability during mitosis. 相似文献
104.
105.
Marten Van Dijk Dwaine Clarke Blaise Gassend G. Edward Suh Srinivas Devadas 《Designs, Codes and Cryptography》2006,39(2):253-273
We present protocols for speeding up fixed-base variable-exponent exponentiation and variable-base fixed-exponent exponentiation
using an untrusted computational resource. In the fixed-base protocols, the exponent may be blinded. In the variable-base
protocols, the base may be blinded. The protocols are described for exponentiation in a cyclic group. We describe how to extend
them to exponentiation modulo an integer where the modulus is the product of primes with single multiplicity. The protocols
provide a speedup of
over the square-and-multiply algorithm, where k is the bitlength of the exponent.
One application of the protocols is to speed up exponentiation-based verification in discrete log-based signature and credential
schemes. The protocols also allow signature verifiers to dynamically choose, for each message, the amount of work it would
like to perform to verify the signature. This results in a work-security tradeoff. We introduce a fifth protocol to perform
variable-base variable- exponent exponentiation, which also has this feature.
Our model allows the trusted resource to perform computations in its idle time. The protocols facilitate the offloading of
work to the offline stage, such that the work the trusted resource performs when it has to do an exponentiation is smaller.
Our protocols are unconditionally secure. 相似文献
106.
Young Jin Suh 《Monatshefte für Mathematik》2006,147(4):337-355
In this paper we give a characterization of real hypersurfaces of type B, that is, a tube over a totally real totally geodesic
in complex two-plane Grassmannians
with the shape operator A satisfying Aφ + φA = kφ, k is non-zero constant, for the structure tensor φ. 相似文献
107.
The gas-phase growth and optical characteristics of 1-dimensional ZnO nanostructure have been investigated. The ZnO nanowires (NWs) were grown vertically on Au coated silicon substrates by vapor-liquid-solid (VLS) growth mechanism using chemical vapor deposition (CVD). The ZnO NWs were grown in the crystal direction of [0 0 0 1]. The ZnO NWs exhibit the uniform size of less than 100 nm in diameter and up to 5 μm in length. Photoluminescence (PL) spectrum of ZnO NWs shows the strong band-edge emission at ∼380 nm (∼3.27 eV) without significant deep-level defect emission. The exciton lifetime of ZnO NWs was measured to be approximately 150 ± 10 ps. 相似文献
108.
Purpose
The purpose of the study was to validate the diagnostic performance of high-resolution isovolumetric magnetic resonance arthrography (MRA) for intrinsic ligament and triangular fibrocartilage complex (TFCC) tears of the wrist as compared to conventional MR imaging (MRI).Materials and methods
Forty-eight patients with traumatic TFCC tears at arthroscopy were enrolled. All patients had underwent proton-density- and T2-weighted MRI before arthrography and three-dimensional T1 high-resolution isovolumetric examination (3D-THRIVE) MRA on a 3-T MR. We assessed the presence of scapholunate interosseous ligament (SLIL)/lunotriquetral interosseous ligament (LTIL) or TFCC tears using the arthroscopy as a gold standard.Results
Arthroscopy revealed 37 TFCC central tears, 15 TFCC peripheral tears, 20 SLIL tears and 13 LTIL tears. Sensitivities of MRI and MRA were 70.3% and 94.6% for detection of TFCC central tears, 60.0% and 93.3% for detection of TFCC peripheral tears, 65.0% and 85.0% for SLIL tears, and 61.5% and 84.6% for LTIL tears. The specificity of the MRI was 100% for the detection of ligaments and TFCC tears. The specificities of the MRA for detection of TFCC central tears, TFCC peripheral tears, SLIL tears and LTIL tears were 100%, 97%, 96.4% and 100%, respectively.Conclusion
Isovolumetric 3D-THRIVE wrist MRA provided better results for depiction of intrinsic ligament and TFCC tears than wrist MRI. 相似文献109.
110.
In this paper we consider a new notion of ${\mathfrak{D}^{\bot}}$ -parallel shape operator for real hypersurfaces in complex two-plane Grassmannians ${G_2(\mathbb{C}^{m+2})}$ and give a non-existence theorem for a Hopf hypersurface in ${G_2(\mathbb{C}^{m+2})}$ with ${\mathfrak{D}^{\bot}}$ -parallel shape operator. 相似文献