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排序方式: 共有672条查询结果,搜索用时 31 毫秒
31.
Olga Yuryevna Ridzel Henryk Kalbe Vytautas Astašauskas Pavel Kuksa Alessandra Bellissimo Wolfgang S. M. Werner 《Surface and interface analysis : SIA》2022,54(5):487-500
Reflection electron energy loss spectroscopy (REELS) spectra were measured for seven insulating organic compounds (DNA, Irganox 1010, Kapton, polyethylene [PE], poly(methyl methacrylate) [PMMA], polystyrene [PS] and polytetrafluoroethylene [PTFE]). Optical constants and energy band gaps were extracted from the measured REELS spectra after elimination of multiple electron scattering via a deconvolution and fitting the normalised single scattering energy loss spectra to Drude and Drude–Lindhard model dielectric functions, constrained by the Kramers–Kronig sum and f-sum rules. Satisfactory agreement is found for those optical constants for which literature data exists. For PTFE, the observed features in the optical data correspond to its electronic structure. 相似文献
32.
Seven-day-old sprouts of fenugreek (Trigonella foenum-graecum L.), lentil (Lens culinaris L.), and alfalfa (Medicago sativa L.) were studied. The legume seeds and then sprouts were soaked each day for 30 min during 6 days with water (control) or mixture of Fe-EDTA and sodium silicate (Optysil), or sodium silicate (Na-Sil) alone. Germination and sprout growing was carried out at temperature 20 ± 2 °C in 16/8 h (day/night) conditions. Phenolic compounds (free, ester, and glycosides) content were determined by HPLC-ESI-MS/MS using a multiple reaction monitoring of selected ions. Flavonoids and phenolic acids were released from their esters after acid hydrolysis and from glycosides by alkaline hydrolysis. The presence and high content of (−)-epicatechin (EC) in fenugreek sprouts was demonstrated for the first time. Applied elicitors decreased the level of free EC in fenugreek and alfalfa sprouts but enhanced the content of its esters. Besides, elicitors decreased the content of quercetin glycosides in lentil and fenugreek sprouts but increased the content of quercetin and apigenin glycosides in alfalfa sprouts. The applied elicitors decreased the glycoside levels of most phenolic acids in lentil and p-hydroxybenzoic acid in fenugreek, while they increased the content of this acid in alfalfa. The mixture of iron chelate and sodium silicate had less effect on changes in flavonoid and phenolic acid content in legume sprouts than silicate alone. In general, the used elicitors increased the content of total phenolic compounds in fenugreek and alfalfa sprouts and decreased the content in lentil sprouts. Among the evaluated elicitors, Optysil seems to be worth recommending due to the presence of iron chelate, which can be used to enrich sprouts with this element. 相似文献
33.
Mechanism of Back Electron Transfer in an Intermolecular Photoinduced Electron Transfer Reaction: Solvent as a Charge Mediator 下载免费PDF全文
Sudhakar Narra Dr. Yoshifumi Nishimura Prof. Dr. Henryk A. Witek Prof. Dr. Shinsuke Shigeto 《Chemphyschem》2014,15(14):2945-2950
Back electron transfer (BET) is one of the important processes that govern the decay of generated ion pairs in intermolecular photoinduced electron transfer reactions. Unfortunately, a detailed mechanism of BET reactions remains largely unknown in spite of their importance for the development of molecular photovoltaic structures. Here, we examine the BET reaction of pyrene (Py) and 1,4‐dicyanobenzene (DCB) in acetonitrile (ACN) by using time‐resolved near‐ and mid‐IR spectroscopy. The Py dimer radical cation (Py2.+) and DCB radical anion (DCB.?) generated after photoexcitation of Py show asynchronous decay kinetics. To account for this observation, we propose a reaction mechanism that involves electron transfer from DCB.? to the solvent and charge recombination between the resulting ACN dimer anion and Py2.+. The unique role of ACN as a charge mediator revealed herein could have implications for strategies that retard charge recombination in dye‐sensitized solar cells. 相似文献
34.
Maciej Jan Rybicki Anna Klimek-Turek Tadeusz Henryk Dzido 《Molecules (Basel, Switzerland)》2020,25(24)
Coccidiostats are drugs used against coccidiosis, a common disease among breeding animals. Their widespread application leads to the appearance of their residues in food, which is potentially harmful for human health and life. The European Union has established limits of concentrations of these drugs in premixtures and food. Nowadays, there are many methods for monitoring coccidiostats’ presence in market products, but their frequent weakness is sample preparation. Solvent Front Position Extraction is a planar chromatography-based sample preparation method that allows for effective assay of samples with coccidiostats when coupled with LC-MS/MS. The purpose of this research was to find common conditions for the effective isolation of eight coccidiostats from biological sample components with both lower and higher retention than the substances of interest. The acquired results were used for effective isolation of monensin and salinomycin from the premixture samples and allowed for their quantitative determination. The application of a semi-automatic device for the development of chromatograms positively impacted the results, confirming the effectiveness of the method for determining coccidiostats in biological samples. 相似文献
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36.
The interaction of atomic antihydrogen with helium has been studied within the Born-Oppenheimer approximation. The linear combination of explicitly correlated Gaussian functions was used as the ansatz for the wave function of light particles. The potential energy curve with the minimum at 3.63 bohr and the barrier at 2.42 bohr has been obtained. 相似文献
37.
Jan Halkiewicz Henryk Lamparczyk Aleksander Radecki 《Fresenius' Journal of Analytical Chemistry》1985,320(6):577-580
Summary Fifteen Dialkyldithiocarbamate complexes each of copper(II) and Ni(II) have been prepared and the retention times of these complexes have been measured on the non-polar OV-101 phase and the polar NGA and OV-225 phases. The relationship has been studied between the retention characteristics of the complexes and their structure. The lenght of the alkyl substituent, regarded as a steric hindrance, turned out to affect the retention of the complexes on the non-polar phases.
Verhalten von Kupfer(II)- und Nickel(II)-dialkyldithiocarbamaten auf polaren und unpolaren stationären Phasen
Zusammenfassung Je 15 Dialkyldithiocarbamatkomplexe von Kupfer(II) und Nickel(II) wurden dargestellt und ihre Retentionszeiten auf der unpolaren Phase OV-101 sowie den polaren Phasen NGA und OV-225 gemessen. Die Beziehung zwischen der Retentionscharakteristik der Komplexe und ihrer Struktur wurde untersucht. Es zeigte sich, daß die Länge des Alkylsubstituenten (als sterische Hinderung) die Retention auf der unpolaren Phase beeinträchtigt.相似文献
38.
We have explored the opportunities for enhanced ratiometric pH sensing using the well-known carboxy seminaphthofluorescein (SNAFL-2) and silver island films (SiFs). Our results show that the metallic surfaces can provide up to a 40-fold increase in probe fluorescence intensity as compared to nonmetallic surfaces with the same probe coverage. However, while the S/N is significantly better for pH sensing, the emission wavelength ratiometric values are similar to that obtained in solution, due to the fact that the emission of both the acidic and basic forms of the probe are enhanced to similar extents. To the best of our knowledge this is the first report of enhanced ratiometric fluorescence sensing on metallic surfaces. 相似文献
39.
Shutao Chen Yunan Cui Henryk Hudzik 《Proceedings of the American Mathematical Society》2004,132(2):473-480
Criteria in order that an Orlicz space equipped with the Orlicz norm contains a linearly isometric copy (or an order linearly isometric copy) of (or ) are given.
40.
Henryk Michalewski 《Proceedings of the American Mathematical Society》2003,131(11):3601-3606
For a coanalytic-complete or -complete subspace of a Polish space we prove that there exists a continuous bijection of onto the Hilbert cube . This extends results of Pytkeev. As an application of our main theorem we give an answer to some questions of Arkhangelskii and Christensen.
Under the assumption of Projective Determinacy we also give some generalizations of these results to higher projective classes.