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111.
Brandon L. Salazar Zoe Y. Marr Jason B. Benedict Luis A. Colón 《Journal of separation science》2023,46(10):2200830
Diarylethene-based photoswitches have become very popular over the last few decades for potential applications in chemistry, materials science, and biotechnology due to their unique physical and chemical properties. We report the isomeric separation of a diarylethene-based photoswitchable compound using high-performance liquid chromatography. The separated isomers were characterized by ultraviolet-visible spectroscopy and mass spectrometry confirmed the isomeric nature of the compounds. The isomers were purified by preparative high-performance liquid chromatography, providing fractionated samples to study the isomers individually. A total amount of 13 mg of an isomer of interest was fractionated from a solution of 0.4 mg/ml of the isomeric mixture. Because the preparative high-performance liquid chromatographic method required large quantities of solvent, we explored the use of supercritical fluid chromatography as an alternative separation mode which, to the best of our knowledge, is the first time this technique is used to separate diarylethene-based photoswitchable compounds. Supercritical fluid chromatography provided faster analysis times while maintaining sufficient baseline resolution for the separated compounds and consuming less organic solvent in the mobile phase compared to high-performance liquid chromatography. It is proposed that the supercritical fluid chromatographic method be upscaled and used in future fractionation of the diarylethene isomeric compounds, becoming a more environmentally benign approach for compound purification. 相似文献
112.
Bachir AI Kolin DL Heinze KG Hebert B Wiseman PW 《The Journal of chemical physics》2008,128(22):225105
Fluctuation-based fluorescence correlation techniques are widely used to study dynamics of fluorophore labeled biomolecules in cells. Semiconductor quantum dots (QDs) have been developed as bright and photostable fluorescent probes for various biological applications. However, the fluorescence intermittency of QDs, commonly referred to as "blinking", is believed to complicate quantitative correlation spectroscopy measurements of transport properties, as it is an additional source of fluctuations that contribute on a wide range of time scales. The QD blinking fluctuations obey power-law distributions so there is no single characteristic fluctuation time for this phenomenon. Consequently, it is highly challenging to separate fluorescence blinking fluctuations from those due to transport dynamics. Here, we quantify the bias introduced by QD blinking in transport measurements made using fluctuation methods. Using computer simulated image time series of diffusing point emitters with set "on" and "off" time emission characteristics, we show that blinking results in a systematic overestimation of the diffusion coefficients measured with correlation analysis when a simple diffusion model is used to fit the time correlation decays. The relative error depends on the inherent blinking power-law statistics, the sampling rate relative to the characteristic diffusion time and blinking times, and the total number of images in the time series. This systematic error can be significant; moreover, it can often go unnoticed in common transport model fits of experimental data. We propose an alternative fitting model that incorporates blinking and improves the accuracy of the recovered diffusion coefficients. We also show how to completely eliminate the bias by applying k-space image correlation spectroscopy, which completely separates the diffusion and blinking dynamics, and allows the simultaneous recovery of accurate diffusion coefficients and QD blinking probability distribution function exponents. 相似文献
113.
J. Philibert Th. P. Nash Jr. St. R. Benedict Clarence E. May H. P. Ross H. Strauss A. Hahn Elisabeth Kootz R. Movy K. L. Gad-Andresen W. Mestrezat M. P. Janet M. Ljungdahl S. Levy-Simpson D. Ch. Carroll J. K. Parnas J. Heller A. Novanowitch A. P. Orr 《Analytical and bioanalytical chemistry》1926,69(9):364-368
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Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi) 下载免费PDF全文
Thomas M. Rookes Dr. Elizabeth P. Wildman Dr. Gábor Balázs Dr. Benedict M. Gardner Dr. Ashley J. Wooles Dr. Matthew Gregson Dr. Floriana Tuna Prof. Dr. Manfred Scheer Prof. Dr. Stephen T. Liddle 《Angewandte Chemie (International ed. in English)》2018,57(5):1332-1336
The synthesis and characterisation is presented of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS=N(CH2CH2NSiMe2But)3, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; TrenTIPS=N(CH2CH2NSiPri3)3, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route. 相似文献
117.
Benedict T. W. Lo Lin Ye Jin Qu Junliang Sun Junlin Zheng Dejing Kong Claire A. Murray Chiu C. Tang Shik Chi Edman Tsang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(20):6085-6088
Microporous H‐ZSM‐5 containing one Brønsted acid site per asymmetric unit is deliberately chosen to host pyridine, methanol, and ammonia as guest molecules. By using new‐generation in situ synchrotron X‐ray powder diffraction combined with Rietveld refinement, the slight but significant alteration in scattering parameters of framework atoms modified by the guest molecules enables the user to elucidate their adsorption geometries and interactions with the Brønsted acid sites in H‐ZSM‐5 in terms of atomic distances and angles within experimental errors. The conclusion, although demonstrated in the H‐ZSM‐5, is expected to be transferable to other zeolites. This approach provides a stepping stone towards the rational engineering of molecular interaction(s) with acid sites in zeolitic catalysis. 相似文献
118.
Marjolein J.W. Harmsen - van Hout P. Jean-Jacques Herings Benedict G.C. Dellaert 《European Journal of Operational Research》2013
We model strategic communication network formation with (i) link specificity: link maintenance lowers specific attention and thus value (negative externality previously ignored for communication) and (ii) value transferability via indirect links for informational but not for social value (positive externality modeled uniformly before). Assuming only social value, the pairwise stable set includes many nonstandard networks under high and particular combinations of complete components under low link specificity. Allowing for social and informational value reduces this set to certain fragmented networks under high and the complete network under low link specificity. These extremes are efficient, whereas intermediate link specificity generates inefficiency. 相似文献
119.
Benedict H. Gross 《Journal of Number Theory》2009,129(6):1468-1478
In this paper, we show that the orbits of some simple group actions parametrize cubic rings and quaternion rings. 相似文献
120.
Titanium production by a direct TiO2 reduction route which is highly energy-efficient and environment-friendly compared to commercial Kroll's process, known as HAMR (Hydrogen Assisted Magnesiothermic Reduction) process has been developed in recent times to meet the growing global demands of low-cost pure Ti. Removal of the Mg compounds after each reduction and de-oxygenation step in the HAMR process by leaching, is essential to ensure good purity and mechanical properties of the final Ti powder. In this study, we investigate the effects of temperature, particle size, and pH on the dissolution kinetics of Mg from Mg-bearing compounds such as MgO and MgCl2 that remain after the HAMR Process. We also report the underlying mechanism and rate-controlling steps of Mg removal using HCl in connection with the HAMR process. The dissolution kinetics followed a logarithmic rate kinetic model for diffusion through a porous medium that is commonly used for battery research. Kinetics of leaching were significantly improved using finer particles with 99.96 wt.% Mg removal and corresponding Ti loss of only 1.8 wt. %. The rate of dissolution exhibited a weak dependence with the pH and did not abide by the rate-controlling steps of dissolution of ionic oxides like MgO proposed by previous kinetic models. 相似文献