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91.
Quantum Zeno and anti-Zeno paradoxes 总被引:1,自引:0,他引:1
Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox).
We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure
change of state: an anti-Zeno paradox. 相似文献
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Anke M. Leufkens Thomas C. Kwee Maurice A.A.J. van den Bosch Willem P.Th.M. Mali Taro Takahara Peter D. Siersema 《Magnetic resonance imaging》2013
The purpose of this study was to determine the feasibility of diffusion-weighted magnetic resonance imaging (DWI) for detecting colorectal polyps. DWI (high b-value of 1000 s/mm2) was prospectively performed in 26 symptomatic patients who were scheduled to undergo colonoscopy. DWI and colonoscopic findings were interpreted in a blinded manner. The sensitivity and positive predictive value (PPV) of DWI for the detection of clinically relevant polyps (≥ 6 mm) and colorectal cancer (CRC) were calculated on a per-lesion basis, using colonoscopy results as the standard of reference. Sensitivity, specificity, PPV and negative predictive value (NPV) on a per-patient basis were also calculated. Sensitivity and PPV on a per-lesion basis were 80.0% [95% confidence interval (CI): 49.0%–94.3%] and 72.7% (95% CI: 43.4%–90.3%) for polyps ≥ 6 mm and CRC. Sensitivity, specificity, PPV and NPV on a per-patient basis were 85.7% (95% CI: 48.7%–97.4%), 84.2% (95% CI: 62.4%–94.5%), 66.7% (95% CI: 35.4%–87.9%) and 94.1% (95% CI: 73.0%–99.0%) for polyps ≥ 6mm and CRC. In conclusion, DWI cannot yet be recommended in a clinical setting in which DWI is performed first and subsequent colonoscopy is only performed in patients with positive findings at DWI. Further (technical) developments are required to increase its diagnostic yield. 相似文献
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Stable Crystalline Forms of Na Polysulfides: Experiment versus Ab Initio Computational Prediction
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Prof. Gregor Mali Dr. Manu U. M. Patel Dr. Matjaž Mazaj Dr. Robert Dominko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3355-3360
For the design of light‐metal–sulfur batteries and for the understanding of their performance, knowledge on the stable crystalline polysulfides is very important. We confronted experimental and ab initio crystal structure prediction studies on the stability of Na polysulfides. The selected evolutionary‐based structure‐prediction algorithm was able to quickly and correctly predict the thermodynamically stable crystalline forms of Na polysulfides with small unit cells. For Na polysulfides with large unit cells, the algorithm correctly proposed short unbranched polysulfide chains to be energetically favorite structural motifs, but could not find proper three‐dimensional structures in the limited number of generations. Experimentally, the polysulfides were studied by X‐ray diffraction and 23Na solid‐state NMR spectroscopy. Complemented by calculations of the isotropic chemical shifts and quadrupolar coupling constants, NMR spectroscopy proved to be an excellent tool for the examination of Na polysulfides, because it allowed easy distinction and quantification of components in the samples. 相似文献
97.
Navnath B. Khomane Rayala Naveen Kumar Prakash R. Mali Prashishkumar K. Shirsat H.M. Meshram 《Tetrahedron letters》2017,58(50):4687-4690
Formal synthesis of 14-membered unsymmetrical bis-macrolactone, (?)-colletodiol was accomplished from homopropargylic alcohol derivative. Building of the two different hydroxy acid fragments from the same intermediate of homoallylic alcohol was particularly advantageous. A Sharpless asymmetric dihydroxylation, homologation of carbon chain, a Pinnick oxidation, and a macrolactonization to assemble the 14-membered macrodiolide were the additional salient features of this convergent synthesis. 相似文献
98.
The fusion splicing of double-clad (DC) specialty fibers based on active alignment is crucial to the investigation of high-power monolithic fiber lasers. Given the wave-guiding characteristic of DC fiber, a light stripper is introduced in an active alignment experiment. We propose a novel method for stripping light that is convenient, highly effcient, and low cost. This method is also effective for low-numerical-aperture beams that escape from the fiber core. A splice loss as low as 0.05 dB is achieved. 相似文献
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A fully stereoselective preparation of the advanced intermediate 24 for the synthesis of (+)-lactacystin from known 1,2:5,6-di-O-isopropylidene-α-d-gulofuranose (2), as the source of chirality, has been achieved. The C-5 methyl group was introduced via a Wittig olefination followed by Pd/C-mediated hydrogenation of the conformationally restricted alkene 11 in a highly stereoselective manner. The stereogenic tetrasubstituted carbon centre at C-3, with an amino group, was installed stereoselectively via an Overman rearrangement, which was efficiently controlled by a saccharide environment. 相似文献