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151.
152.
V. Meyer S.N. Bagayev P.E.G. Baird P. Bakule M.G. Boshier A. Breitrück S.L. Cornish S. Dychkov G.H. Eaton A. Grossmann D. Hübl V.W. Hughes K. Jungmann I.C. Lane Yi Wei Liu D. Lucas Y. Matyugin J. Merkel G. zu Putlitz I. Reinhard P.G.H. Sandars R. Santra P. Schmidt C.A. Scott W.T. Toner M. Towrie K. Träger L. Willmann V. Yakhontov 《Hyperfine Interactions》2000,127(1-4):197-200
The 1s–2s energy interval in the muonium (μ+e−) atom has been measured by Doppler free two photon laser spectroscopy. A value of 2455528941.0(9.8) MHz has been obtained
in good agreement with quantum electrodynamics (QED). The muon-electron mass ratio can be extracted and is found to be 206.76838(17).
The measurement may also be interpreted as a determination of the muon-electron charge ratio as -1- 1.1(2.1)· 10−9. Corresponding measurements in deuterium using the same experimental setup confirmed the validity of the applied analysis
procedure.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
153.
Dual probing of redox species,NAD(P)H and HOCl,with a benzo[a]phenoxazine based far red-emitting dye
Mithun Santra Sourav Sarkar Yong Woong Jun Ye Jin Reo Kyo Han Ahn 《Tetrahedron letters》2018,59(33):3210-3213
We report a benzo[a]phenoxazine-based far red-emitting probe which selectively senses reduced nicotinamide adenine dinucleotide (NADH) and its phosphate ester NADPH, the most indispensable coenzymes found in all living cells, with “turn-off” fluorescence response at 650?nm. The original probe can be regenerated quantitatively through oxidation using hypochlorous acid, a reactive oxygen species, which was accompanied by restored fluorescence at 650?nm. This probe was also applied for fluorescence imaging of NADH in HeLa cells. 相似文献
154.
155.
Brett W. Boote Himashi P. Andaraarachchi Bryan A. Rosales Rafael Blome-Fernández Feng Zhu Malinda D. Reichert Kalyan Santra Jingzhe Li Jacob W. Petrich Javier Vela Emily A. Smith 《Chemphyschem》2019,20(20):2647-2656
Lead halide perovskites possess unique characteristics that are well-suited for optoelectronic and energy capture devices, however, concerns about their long-term stability remain. Limited stability is often linked to the methylammonium cation, and all-inorganic CsPbX3 (X=Cl, Br, I) perovskite nanocrystals have been reported with improved stability. In this work, the photostability and thermal stability properties of CsPbX3 (X=Cl, Br, I) nanocrystals were investigated by means of electron microscopy, X-ray diffraction, thermogravimetric analysis coupled with FTIR (TGA-FTIR), ensemble and single particle spectral characterization. CsPbBr3 was found to be stable under 1-sun illumination for 16 h in ambient conditions, although single crystal luminescence analysis after illumination using a solar simulator indicates that the luminescence states are changing over time. CsPbBr3 was also stable to heating to 250 °C. Large CsPbI3 crystals (34±5 nm) were shown to be the least stable composition under the same conditions as both XRD reflections and Raman bands diminish under irradiation; and with heating the γ (black) phase reverts to the non-luminescent δ phase. Smaller CsPbI3 nanocrystals (14±2 nm) purified by a different washing strategy exhibited improved photostability with no evidence of crystal growth but were still thermally unstable. Both CsPbCl3 and CsPbBr3 show crystal growth under irradiation or heat, likely with a preferential orientation based on XRD patterns. TGA-FTIR revealed nanocrystal mass loss was only from liberation and subsequent degradation of surface ligands. Encapsulation or other protective strategies should be employed for long-term stability of these materials under conditions of high irradiance or temperature. 相似文献
156.
Kalyan Santra Emily A. Smith Xueyu Song Jacob W. Petrich 《Photochemistry and photobiology》2019,95(3):773-779
The measurement of fluorescence lifetimes, especially in small sample volumes, presents the dual challenge of probing a small number of fluorophores and fitting the concomitant sparse data set to the appropriate excited‐state decay function. A common method of analysis, such as the maximum likelihood (ML) technique, assumes a uniform probability distribution of the parameters describing the fluorescence decay function. An improvement is thus suggested by implementing a suitable nonuniform distribution, as is provided by a Bayesian framework, where the distribution of parameters is obtained from both their prior knowledge and the evidence‐based likelihood of an event for a given set of parameters. We have also considered the Dirichlet prior distribution, whose mathematical form enables analytical solutions of the fitting parameters to be rapidly obtained. If Gaussian and exponential prior distributions are judiciously chosen, they reproduce the experimental target lifetime to within 20% with as few as 20 total photon counts for the data set, as does the Dirichlet prior distribution. But because of the analytical solutions afforded by the Dirichlet prior distribution, it is proposed to employ a Dirichlet prior to search parameter space rapidly to provide, if necessary, appropriate parameters for subsequent employment of a Gaussian or exponential prior distribution. 相似文献
157.
Rana Chatterjee Anindita Mukherjee Sougata Santra Grigory V. Zyryanov Oleg N. Chupakhin Adinath Majee 《Mendeleev Communications》2021,31(1):123-124
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158.
H. W. Wilschut U. Dammalapati D. J. van der Hoek K. Jungmann W. Kruithof C. J. G. Onderwater B. Santra P. D. Shidling L. Willmann 《Pramana》2010,75(1):163-170
One of the greatest successes of the Standard Model of particle physics is the explanation of time-reversal violation (TRV)
in heavy mesons. It also implies that TRV is immeasurably small in normal nuclear matter. However, unifying models beyond
the Standard Model predict TRV to be within reach of measurement in nuclei and atoms, thus opening an important window to
search for new physics. We will discuss two complementary experiments sensitive to TRV: Correlations in the β-decay of 21Na and the search for an electric dipole moment (EDM) in radium. 相似文献
159.
Two structurally close tetrasaccharides corresponding to the O-antigens of Escherichia coli O127 and Salmonella enterica O13 have been synthesized using a ‘unichemo’ approach and minimum number of reaction steps. The yields of all glycosylation steps were excellent with a high stereochemical outcome. A common synthetic strategy has been adopted for the simultaneous synthesis of two tetrasaccharides. 相似文献
160.
Dr. Shlomy Arava Dr. Sourav K. Santra Dr. Gulab K. Pathe Raja Kapanaiah Prof. Dr. Alex M. Szpilman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(35):15283-15287
Herein we report on the umpolung of Morita–Baylis–Hillman type intermediates and application to the α-functionalization of enone C−H bonds. This reaction gives direct access to α-chloro-enones, 1,2-diketones and α-tosyloxy-enones. The latter are important intermediates for cross-coupling reaction and, to the best of our knowledge, cannot be made in a single step from enones in any other way. The proposed mechanism is supported by spectroscopic studies. The key initial step involves conjugate attack of an amine (DABCO or pyridine), likely assisted by hypervalent iodine acting as a Lewis acid leading to formation of an electrophilic β-ammonium-enolonium species. Nucleophilic attack by acetate, tosylate, or chloride anion is followed by base induced elimination of the ammonium species to give the noted products. Hydrolysis of α-acetoxy-enones lead to formation of 1,2-diketones. The α-tosyl-enones participate in Negishi coupling reactions under standard conditions. 相似文献