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211.
Three-component condensation of 5-(2-furyl)-1,3-cyclohexanedione with 2-naphthylamine and aromatic or heteroaromatic aldehydes afforded 12-aryl(hetaryl)-9-(2-furyl)-7,8,9,10,11,12-hexahydrobenzo[a]-acridin-11-ones possessing two asymmetric carbon atoms (C9 and C12). The products were found to be formed as mixtures of diastereoisomers. 相似文献
212.
A microscopic theory is developed to study the liquid-vapor interfacial properties of simple fluids with ab initio treatment of the inhomogeneous two-body correlation functions, without any interpolation. It consists of the inhomogeneous Ornstein-Zernike equation coupled with the Duh-Henderson-Verlet closure and the Lovett-Mou-Buff-Wertheim equation. For the liquid-vapor interface of the Lennard-Jones fluid, we obtained the density profile and the surface tension, as well as their critical behaviour. In particular, we identified non-classical critical exponents. The theory accurately predicts the phase diagram and the interfacial properties in a very good agreement with simulations. We also showed that the method leads to true capillary-wave asymptotics in the macroscopic limit. 相似文献
213.
Atindra Sapkota Michael Krachler Christian Scholz Andriy K. Cheburkin William Shotyk 《Analytica chimica acta》2005,540(2):247-256
A simple, robust and reliable analytical procedure for the determination of Al, Ca, Fe, K, Li, Mg, Mn, Na, Sr, Ti, and Zn in peat and plant materials by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed. A microwave heated high pressure autoclave was used to digest powdered sample aliquots (approximately 200 mg) with different acid mixtures including nitric acid (HNO3), tetrafluoroboric acid (HBF4) and hydrogen peroxide (H2O2). The optimized acid mixture for digestion of plant and peat samples consisted of 3 mL HNO3 and 0.1 mL HBF4, in addition to H2O2 which was sub-boiled into the PTFE digestion tubes during heating of the autoclave. Using HNO3 alone, recoveries of Al and Ti were too low by 40 and 160%, respectively, because HNO3 could not fully liberate the analytes of interest from the silicate fraction of the plant and peat matrix. However, for all other elements (such as Mn, Sr, and Zn), the use of HBF4 was less critical. The accuracy of the analytical procedure developed was evaluated with peat and plant reference materials of different origin and composition. The ICP-OES instrument was optimized using solutions of plant reference materials considering RF power, nebulizer pressure, auxiliary gas flow and rinse time. Scandium was used as an online internal standard (IS) as it provided accurate results and showed less than 3% drift in sensitivity over time which was lower compared to other potential IS such as Rh (20%) and In (6%). The combination of most sensitive and less sensitive wavelengths allowed to obtain low detection limits and highest possible dynamic range. The achieved procedure detection limits ranged from 0.05 μg g−1 (Li) to 15 μg g−1 (Ca) and allowed a precise quantification of all elements. Comparative X-ray fluorescence spectrometric measurements of solid peat and plant samples generally agreed well with results obtained by digestion/ICP-OES. To overcome interferences caused by Na, K, and Li, a solution of 10 μg g−1 CsCl2 was successfully used as an ionization buffer. The good agreement between the found and certified concentrations in plant and peat reference materials indicates that the developed analytical procedure is well suited for further studies on the fate of major elements in plant and peat matrices. 相似文献
214.
Electron-poor SrAuxIn4−x (0.5?x?1.2) and SrAuxSn4−x (1.3?x?2.2) phases with the BaAl4-type structure
Andriy V. Tkachuk 《Journal of solid state chemistry》2007,180(8):2298-2304
Solid solutions SrAuxIn4−x (0.5?x?1.2) and SrAuxSn4−x (1.3?x?2.2) have been prepared at 700 °C and their structures characterized by powder and single-crystal X-ray diffraction. They adopt the tetragonal BaAl4-type structure (space group I4/mmm, Z=2; SrAu1.1(1)In2.9(1), a=4.5841(2) Å, c=12.3725(5) Å; SrAu1.4(1)Sn2.6(1), a=4.6447(7) Å, c=11.403(2) Å), with Au atoms preferentially substituting into the apical over basal sites within the anionic network. The phase width inherent in these solid solutions implies that the BaAl4-type structure can be stabilized over a range of valence electron counts (vec), 13.0-11.6 for SrAuxIn4−x and 14.1-11.4 for SrAuxSn4−x. They represent new examples of electron-poor BaAl4-type compounds, which generally have a vec of 14. Band structure calculations confirm that substitution of Au, with its smaller size and fewer number of valence electrons, for In or Sn atoms enables the BaAl4-type structure to be stabilized in the parent binaries SrIn4 and SrSn4, which adopt different structure types. 相似文献
215.
M. Sc. Hanna Pieper Dr. Serghei Chercheja Dr. Siegfried Eigler M. Sc. Christian E. Halbig Dr. Milos R. Filipovic Prof. Dr. Andriy Mokhir 《Angewandte Chemie (International ed. in English)》2016,55(1):405-407
Potential biomedicinal applications of graphene oxide (GO), for example, as a carrier of biomolecules or a reagent for photothermal therapy and biosensing, are limited by its cytotoxicity and mutagenicity. It is believed that these properties are at least partially caused by GO‐induced oxidative stress in cells. However, it is not known which chemical fragments of GO are responsible for this unfavorable effect. We generated four GOs containing variable redox‐active groups on the surface, including Mn2+, C‐centered radicals, and endoperoxides (EPs). A comparison of the abilities of these materials to generate reactive oxygen species in human cervical cancer cells revealed that EPs play a crucial role in GO‐induced oxidative stress. These data could be applied to the rational design of biocompatible nontoxic GOs for biomedical applications. 相似文献
216.
Tikhomirov G Yamazaki T Kovalenko A Fenniri H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):4447-4450
Supramolecular synthesis emerged recently as a new formalism to devise complex architectures held through noncovalent forces. Much of the research endeavor has been devoted to the use of H-bonds as the alphabet for chemical information encoding, and the structures expressed have spanned the range of dimensions and shapes, from discrete to infinite networks. Here we describe the synthesis and characterization of a GwedgeC base bearing two C12 alkyl chains, which undergoes a solvent-controlled multistep hierarchical self-assembly process into lamellar prolate nanospheroids. These assemblies were characterized by AFM, SEM, TEM, XRD, and SAXS, and a mechanism for their formation is proposed. 相似文献
217.
Smith D Wang T Pysanenko A Spanel P 《Rapid communications in mass spectrometry : RCM》2008,22(6):783-789
A study has been carried out, involving three healthy volunteers, of the ammonia levels in breath exhaled via the mouth and via the nose and in the static oral cavity using on-line, selected ion flow tube mass spectrometry (SIFT-MS), obviating the problems associated with sample collection of ammonia. The unequivocal conclusion drawn is that the ammonia appearing in the mouth-exhaled breath of the three volunteers is largely generated in the oral cavity and that the ammonia originating at the alveolar interface in the lungs is typically at levels less than about 100 parts-per-billion, which is a small fraction of the total breath ammonia. This leads to the recommendation that exhaled breath analyses should focus on nose-exhaled breath if the objective is to use breath analysis to investigate systemic, metabolic disease. 相似文献
218.
Vyacheslav O. Khavrus Nataliia V. Lemesh Svitlana V. Gordijchuk Andriy I. Tripolsky Tetyana S. Ivashchenko Mykola M. Biliy Peter E. Strizhak 《Reaction Kinetics and Catalysis Letters》2008,93(2):295-303
A simple method for producing unsupported nickel catalyst that can be used to synthesize multi-wall carbon nanotubes (MWNT)
has been developed. The yield of purified MWNTs is about 1.8 gmwnt/(gcat×h). 相似文献
219.
In this Letter, we show that upper limits on the neutrino mass translate into upper limits on the class of neutrino-matter interactions that can generate loop corrections to the neutrino mass matrix. We apply our results to mu and pi decays and derive model-independent limits on six of the ten parameters used to parametrize contributions to mu decay that do not belong to the standard model. These upper limits provide improved constraints on the five Michel parameters, rho, xi', xi", alpha, alpha', that exceed Particle Data Group constraints by at least one order of magnitude. For pi(0) --> nunu we find, for the branching ratio, B(pi(0) --> nunu) < 10(-10). 相似文献
220.
Zhen Liu Guozhu Li Tong Cui Andriy Borodin Chantal Kuhl Frank Endres 《Journal of Solid State Electrochemistry》2018,22(1):91-101
The integration of a battery-type electrode and of a capacitor-type electrode in a single device by proper design is an effective strategy in developing energy storage devices with high energy and power densities. Herein, we present a battery-supercapacitor hybrid device using metallic zinc as anode, a biodegradable ionic liquid (IL) as electrolyte, and graphite as cathode. The recently developed choline acetate ([Ch]OAc) biodegradable IL-based electrolyte enables reversible deposition/stripping of Zn(II). Spongy-like Zn with a high surface area is obtained, which allows fast charge/discharge at high rates. The adsorption/desorption of ions on the surface of the graphite cathode and intercalation/deintercalation of anions into/from the graphite layers occur at the graphite cathode. Raman spectra and X-ray photoelectron reveal the intercalation of IL into and the adsorption of IL on the graphite. Highly reversible adsorption/desorption of ions on the surface of the graphite electrodes in the [Ch]OAc-based electrolyte was demonstrated by a symmetric cell. The Zn/graphite hybrid device delivers an energy density of 53 Wh kg?1 at a power density of ~ 145 W kg?1 and 42 Wh kg?1 at ~ 400 W kg?1. The hybrid device also exhibits a long cycle life with ~ 86% specific capacitance retained after 1000 cycles at a current density of 0.5 A g?1. The combination of well-available zinc, inexpensive graphite, and a biodegradable IL electrolyte in a cell could open new avenues for sustainable energy applications. 相似文献