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排序方式: 共有1446条查询结果,搜索用时 15 毫秒
931.
932.
Nowicka K Bujacz A Paluch P Sobczuk A Jeziorna A Ciesielski W Bujacz GD Jurczak J Potrzebowski MJ 《Physical chemistry chemical physics : PCCP》2011,13(14):6423-6433
In this work we present solid state data for five host-guest complexes formed by N-(4,19-dioxo-2,8,15,21-tetraoxa-5,18-diazatricyclohexacosa-1(25),9(14),10,12,22(26),23-hexaen-26-yl)-benzamide (1) belonging to the group of benzodiazacoronands, achiral compounds for which chiral crystals were found (J. Kalisiak and J. Jurczak, Cryst. Growth Des., 2006, 6, 20). The X-ray structure was resolved for four of them. It was found that 1 crystallizes in P2(1)/c, P1 and P2(1)/n achiral space groups. Differentiation of molecular packing and the presence of guest molecules within the crystal lattice were analyzed with solid state NMR. An attempt was made to correlate changes in (13)C δ(ii) and (15)N δ(ii) chemical shift tensor values, obtained from analysis of spinning sidebands of 1D and 2D (2D PASS) NMR spectra, with changes in the strength of hydrogen bonding. Quantum mechanical DFT GIAO calculations of NMR shielding parameters carried out on structures with coordinates taken from XRD were employed for signals assignment and verification of structural constraints. 相似文献
933.
Lewandowska H Kalinowska M Brzóska K Wójciuk K Wójciuk G Kruszewski M 《Dalton transactions (Cambridge, England : 2003)》2011,40(33):8273-8289
Nitrosyl complexes of iron are formed in living species in the presence of nitric oxide. They are considered a form in which NO can be stored and stabilized within a living cell. Upon entering a topic in bioinorganic chemistry the researcher faces a wide spectrum of issues concerning synthetic methods, the structure and chemical properties of the complex on the one hand, and its biological implications on the other. The aim of this review is to present the newest knowledge on nitrosyl iron complexes, summarizing the issues that are important for understanding the nature of nitrosyl iron complexes, their possible interactions, behavior in vitro and in vivo, handling of the preparations etc. in response to the growing interest in these compounds. Herein we focus mostly on the dinitrosyl iron complexes (DNICs) due to their prevailing occurrence in NO-treated biological samples. This article reviews recent knowledge on the structure, chemical properties and biological action of DNICs and some mononitrosyls of heme proteins. Synthetic methods are also briefly reviewed. 相似文献
934.
The distribution of distillation temperatures of liquid and semi-fluid products, including petroleum fractions and products,
is an important process and practical parameter. It provides information on properties of crude oil and content of particular
fractions, classified on the basis of their boiling points, as well as the optimum conditions of atmospheric or vacuum distillation.
At present, the distribution of distillation temperatures is often investigated by simulated distillation (SIMDIS) using capillary
gas chromatography (CGC) with a short capillary column with polydimethylsiloxane as the stationary phase. This paper presents
the results of investigations on the possibility of replacing currently used CGC columns for SIMDIS with a deactivated fused
silica capillary tube without any stationary phase. The SIMDIS technique making use of such an empty fused silica column allows
a considerable lowering of elution temperature of the analytes, which results in a decrease of the final oven temperature
while ensuring a complete separation of the mixture. This eliminates the possibility of decomposition of less thermally stable
mixture components and bleeding of the stationary phase which would result in an increase of the detector signal. It also
improves the stability of the baseline, which is especially important in the determination of the end point of elution, which
is the basis for finding the final temperature of distillation. This is the key parameter for the safety process of hydrocracking,
where an excessively high final temperature of distillation of a batch can result in serious damage to an expensive catalyst
bed. This paper compares the distribution of distillation temperatures of the fraction from vacuum distillation of petroleum
obtained using SIMDIS with that obtained by the proposed procedure. A good agreement between the two procedures was observed.
In addition, typical values of elution temperatures of n-paraffin standards obtained by the two procedures were compared. Finally, the agreement between boiling points of polar compounds
determined from their retention times and actual boiling points was investigated. 相似文献
935.
Grzegorz??ukaszewicz José?Real James?C.?RobinsonEmail author 《Journal of Dynamics and Differential Equations》2011,23(2):225-250
Inspired by a theory due to Foias and coworkers (see, for example, Foias et al. Navier–Stokes equations and turbulence, Cambridge University Press, Cambridge, 2001) and recent work of Wang (Disc Cont Dyn Sys 23:521–540, 2009), we show that the generalised Banach limit can be used to construct invariant measures for continuous dynamical systems
on metric spaces that have compact attracting sets, taking limits evaluated along individual trajectories. We also show that
if the space is a reflexive separable Banach space, or if the dynamical system has a compact absorbing set, then rather than
taking limits evaluated along individual trajectories, we can take an ensemble of initial conditions: the generalised Banach
limit can be used to construct an invariant measure based on an arbitrary initial probability measure, and any invariant measure
can be obtained in this way. We thus propose an alternative to the classical Krylov–Bogoliubov construction, which we show
is also applicable in this situation. 相似文献
936.
Optical Frequency Comb-Based Cavity-Enhanced Fourier-Transform Spectroscopy: Application to Collisional Line-Shape Study
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Akiko Nishiyama Grzegorz Kowzan Dominik Charczun Ryszard S. Trawiński Piotr Mas?owski 《化学物理学报(中文版)》2020,33(1):23-30
Direct-comb spectroscopy techniques uses optical frequency combs (OFCs) as spectroscopic light source. They deliver high sensitivity, high frequency resolution and precision in a broad spectral range. Due to these features, the field has burgeoned in recent years. In this work we constructed an OFC-based cavity-enhanced Fourier-transform spectrometer in the near-infrared region and used it for a line-shape study of rovibrational transitions of CO perturbed by Ar. The highly sensitive measurements spanned the wavenumber range from 6270 cm\begin{document}$^{-1}$\end{document} to 6410 cm\begin{document}$^{-1}$\end{document} , which covered both P and R branch of the second overtone band of CO. The spectrometer delivers high-resolution surpassing the Fourier-transform resolution limit determined by interferogram length, successfully removing ringing and broadening effects caused by instrumental line shape function. The instrumental-line-shape-free method and high signal-to-noise ratio in the measurement allowed us to observe collisional effects beyond those described by the Voigt profile. We retrieved collisional line-shape parameters by fitting the speed-dependent Voigt profile and found good agreement with the values given by precise cavity ring-down spectroscopy measurements that used a continuous-wave laser referenced to a stabilized OFC. The results demonstrate that OFC-based cavity-enhanced Fourier-transform spectroscopy is a strong tool for accurate line-shape studies that will be crucial for future spectral databases. 相似文献
937.
Magorzata Starowicz Ewa Lelujka Ewa Ciska Grzegorz Lamparski Tomasz Sawicki Magorzata Wronkowska 《Molecules (Basel, Switzerland)》2020,25(23)
Aroma plays an important role in designing innovative functional foods. This study aimed to study the influence of incorporating herbs from the Lamiaceae family (sage, mint, rosemary, oregano, thyme) on aroma compound formation and sensory properties in oat-buckwheat products. DPPH, FRAP and PCL have been used to describe possible antioxidant activity changes and reduce power of cookies after Lamiaceae Lindl. addition. The volatiles analysis by HS-SPME-GC/MS, has shown that Lamiaceae addition significantly influences the volatiles composition (29 molecules) with a predominance of molecules with a positive sensorial impression. Cookies elaborated with herbs were characterized by a greater share of monoterpenes (e.g., limonene, eucalyptol), in the volatile profile than in control cookies. These compounds’ occurrence was closely correlated with the appearance of herbal odor and taste among sensory attributes in cookies with herbs addition. In contrast, a decrease of negative oil aroma and the bitter aftertaste was noted by a sensory panel. Moreover, in cookies of mint and rosemary, hexanal share decreased about 13 and 9.7-times, respectively. Considering all presented experiments, rosemary addition was the most effective in forming a positive aroma profile with high sensory acceptance and increased functional properties. 相似文献
938.
Sylwia Siebielec Grzegorz Siebielec Piotr Sugier Magorzata Wo
niak Jarosaw Grzdziel Anna Gazka Tomasz Stuczyski 《Molecules (Basel, Switzerland)》2020,25(23)
The aim was to assess plant driven changes in the activity and diversity of microorganisms in the top layer of the zinc and lead smelter waste piles. The study sites comprised two types (flotation waste—FW and slag waste—SW) of smelter waste deposits in Piekary Slaskie, Poland. Cadmium, zinc, lead, and arsenic contents in these technosols were extremely high. The root zone of 8 spontaneous plant species (FW—Thymus serpyllum, Silene vulgaris, Solidago virgaurea, Echium vulgare, and Rumex acetosa; and SW—Verbascum thapsus; Solidago gigantea, Eupatorium cannabinum) and barren areas of each waste deposit were sampled. We observed a significant difference in microbial characteristics attributed to different plant species. The enzymatic activity was mostly driven by plant-microbial interactions and it was significantly greater in soil affected by plants than in bulk soil. Furthermore, as it was revealed by BIOLOG Ecoplate analysis, microorganisms inhabiting barren areas of the waste piles rely on significantly different sources of carbon than those found in the zone affected by spontaneous plants. Among phyla, Actinobacteriota were the most abundant, contributing to at least 25% of the total abundance. Bacteria belonging to Blastococcus genera were the most abundant with the substantial contribution of Nocardioides and Pseudonocardia, especially in the root zone. The contribution of unclassified bacteria was high—up to 38% of the total abundance. This demonstrates the unique character of bacterial communities in the smelter waste. 相似文献
939.
Guć Maria Reszke Edward Cegłowski Michał Schroeder Grzegorz 《Plasma Chemistry and Plasma Processing》2020,40(1):235-260
Plasma Chemistry and Plasma Processing - The application of an independent source of ions working with mass spectrometers and permitting generation of ions at atmospheric pressure from samples of... 相似文献
940.
Grzegorz Greczynski Lars Hultman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5034-5038
X-ray photoelectron spectroscopy (XPS) is an indispensable technique in modern materials science for the determination of chemical bonding as evidenced by more than 10 000 XPS papers published annually. A literature survey reveals that in the vast majority of cases an incorrect referencing of the binding energy scale is used, neglecting warnings that have been formulated from the early days of the technique. Consequences for the data reliability are disastrous and decades of XPS work require revisiting. The purpose of this Viewpoint is to highlight the existing problems, review the criticism and suggest ways forward. 相似文献