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91.
Pobłocka-Olech L van Nederkassel AM Vander Heyden Y Krauze-Baranowska M Glód D Baczek T 《Journal of separation science》2007,30(17):2958-2966
The separation of nine phenol glycosides--salicin, salicortin, 2'-acetylsalicortin, populin, tremulacin, salidroside, triandrin, picein and helicin--by normal phase (NP), reversed phase (RP) HPLC techniques and a coupling of NP and RP monolithic silica columns was studied. Among the above nine compounds only five--salicin, populin, tremulacin, salidroside and triandrin--were resolved in an NP system with a mobile phase comprising hexane/isopropanol/methanol (87:12:1, v/v/v). Optimized separation was performed with two coupled monolithic silica columns of different polarity (bare silica and RP-18). The method was applied to verify the presence of salicylic compounds and other phenolic derivatives in the bark of six species from the genus Salix, namely S. purpurea, S. daphnoides clone 1095, S. alba clone 1100, S. triandra, S. viminalis, and S. herbacea. Gradient elution with a mobile phase composed of acetonitrile and water containing 0.05% of trifluoroacetic acid, with increasing acetonitrile concentration from 3% to 48%, was chosen as optimal. For the selective detection of the salicylic compounds, an evaporative light scattering detector was employed along with a UV detector. The differences in the composition of phenols in the different plant materials were confirmed. Additionally, it must be emphasized that for the first time the presence of 2'-acetylsalicortin was revealed in S. alba clone 1100. Furthermore, an SPE-HPLC method was developed for the rapid analysis of the salicin content, analyzed as free and total fraction, in willow barks. The determined concentrations of total salicin varied from 25.4 mg/g in S. alba clone 1100 to 96.47 mg/g in S. daphnoides clone 1095. 相似文献
92.
Mazurowska L Nowak-Buciak K Mojski M 《Analytical and bioanalytical chemistry》2007,388(5-6):1157-1163
Copper can be found in many cosmetic formulations, mainly as complexes with peptides, hydroxyacids or amino acids. The main
reason that the usage of this element in this context is still increasing is its beneficial biochemical activity, although
the mechanism that enables its complexes to permeate through skin barriers is largely unknown. The ability of copper complexes
with amino acids to penetrate through the stratum corneum and participate in copper ion transport processes is key to their
cosmetic and pharmaceutical activities. The penetration process was studied in vitro in a model system, a Franz diffusion
cell with a liposome membrane, where a liquid crystalline system with physicochemical properties similar to those of the intercellular
cement of stratum corneum was used to model the skin barrier. The influences of various ligands on the model membrane migration
rate of copper ions was studied, and the results highlighted the crucial roles of metal ion complex structure and stability
in this process. 相似文献
93.
We present sufficient conditions for the existence of positive solutions for some second order boundary value problems at resonance. The boundary conditions that we study are quite general, involve a Stieltjes integral and include, as particular cases, multi‐point and integral boundary conditions. Our results are based on a Leggett‐Williams norm‐type theorem due to O'Regan and Zima. We employ a general abstract approach which allows us to improve and complement recent results in the literature. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
94.
Bombalska A Mularczyk-Oliwa M Kwaśny M Włodarski M Kaliszewski M Kopczyński K Szpakowska M Trafny EA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(4):1221-1226
Rapid detection and discrimination of dangerous biological materials such as bacteria and their spores has become a security aim of considerable importance. Various analytical methods, including FTIR spectroscopy combined with statistical analysis have been used to identify vegetative bacteria, bacterial spores and background interferants. The present work discusses the application of FTIR technique performed in reflectance mode using Horizontal Attenuated Total Reflectance accessory (HATR) to the discrimination of biological materials. In comparison with transmission technique the HATR is more rapid and do not require the sample destruction, simultaneously giving similar absorbance bands. HATR-FTIR results combined with statistical analysis PCA and HCA demonstrate that this combination provides novel and accurate microbial identification technique. 相似文献
95.
Jabłoński M 《The journal of physical chemistry. A》2012,116(14):3753-3764
We present high-level ab initio calculations for representative group of molecules possessing the intramolecular interaction of the X···O type (X = F, Cl, Br, and I). Few examples of molecules with intramolecular O···O and F···F interactions are also investigated. We show that, although most often investigated as bonding, all these interactions are nonbonding or repulsive, as indicated by positive values of interaction energies obtained by means of a few estimating methods, by thorough studies of geometrical changes that take place during the X···O contact formation and by the lateral contact of electron density isosurfaces of X and O atoms, which both are characterized by negative values of electrostatic potential. The presented conclusion about the repulsive nature of the intramolecular X···O and similar interactions is in opposition to the proclamation of the quantum theory of atoms in molecules of Bader that the presence of a bond path and a corresponding bond critical point is always to indicate the bonding, thus, stabilizing interaction. 相似文献
96.
Mirosław Szarmach Ewa Wagner-Wysiecka Marina S. Fonari Elżbieta Luboch 《Tetrahedron》2012,68(2):507-515
Novel biscrowns were successfully synthesized from azobenzocrown ethers containing hydroxyl groups in para position relative to the azo group. The synthesized host molecules, differing in the size of the macrocycles, the length of the linker and their potential to act as sodium or potassium ionophores, were characterized and used as ionophores in classic and miniature (screen-printed) ion-selective electrodes. Metal cation complexation for selected macrocycles was carried out with the use of UV–vis spectroscopy in acetonitrile. The structural features of novel complex have been deduced by X-ray crystallography. X-ray analysis indicated the formation of sandwich structures with two sodium cations encapsulated between two macrocyclic molecules of 13C2. 相似文献
97.
Krzysztof Kozak Beata Koz?owskaTadeusz A. Przylibski Jadwiga MazurAnna Adamczyk-Lorenc Kalina Mamont-Cie?laOlga Stawarz Jerzy DordaBarbara K?os Miros?aw JanikEl?bieta Kochowska 《Radiation measurements》2012,47(1):89-95
The paper presents the results of intercalibration measurements of 222Rn concentration in water samples. The aim of the experiments was to evaluate the different measurement methods of radon determination in water samples performed by eleven laboratories in Poland and to test these methods in field work. In the years 2001-2003 three national intercomparison experiments were organized. The results allowed the participating laboratories to improve their measurement methodologies and to achieve better, i.e. more convergent results of determining radon concentration in water samples. The results show that the use of liquid-scintillation technique seems to be the best measurement method. It should be emphasized that comparative experiments are essential for all laboratories and they should be carried out as often as possible, based both on prepared samples with known concentration values of 222Rn and natural water samples, the most commonly used in laboratory practice. 相似文献
98.
Grzegorz Gabor Lech Górniewicz Mirosław Ślosarski 《Set-Valued and Variational Analysis》2009,17(1):1-19
A concept of generalized topological essentiality for a large class of multivalued maps in topological vector Klee admissible
spaces is presented. Some direct applications to differential equations are discussed. Using the inverse systems approach
the coincidence point sets of limit maps are examined. The main motivation as well as main aim of this note is a study of
fixed points of multivalued maps in Fréchet spaces. The approach presented in the paper allows to check not only the nonemptiness
of the fixed point set but also its topological structure.
相似文献
99.
Using the SAPT2 + 3(CCD)δMP2 method in complete basis set (CBS) limit, it is shown that the interactions in the recently studied silane⋯carbene dimers are mainly dispersive in nature. Consequently, slow convergence of dispersion energy also forces slow convergence of the interaction energy. Therefore, obtaining very accurate values requires extrapolation of the correlation part to the CBS limit. The most accurate values obtained at the CCSD(T)/CBS level of theory show that the studied silane⋯carbene dimers are rather weakly bound, with interaction energies ranging from about −1.9 to −1.3 kcal/mol. Comparing to CCSD(T)/CBS, it will be shown that SCS-MP2 and MP2C methods clearly underestimate and methods based on SAPT2+ and having some third-order corrections, as well as the MP2 method, overestimate values of interaction energies. Popular SAPT(DFT) method performs better than SCS-MP2 and MP2C; nevertheless, underestimation is still considerable. The underestimation is slightly quenched if third-order dispersion energy and its exchange counterpart is added to the SAPT(DFT). The closest value of CCSD(T)/CBS has been given by the SAPT2 + (3)(CCD)δMP2 method in quadruple-ζ basis set. © 2019 Wiley Periodicals, Inc. 相似文献
100.
Mariusz Mądrala Mirosław Wąsik Piotr Małoszewski 《Isotopes in environmental and health studies》2017,53(5):466-483
Environmental isotopes and hydrogeological data have been used for the construction of a conceptual model of fresh groundwater flow in the K?odzko Basin, Sudetes, Poland. The model has allowed the verification of a groundwater circulation scheme resulting from the general morphological assumptions and the recharge role to the surrounding mountains. Combined interpretation of the tritium ages and the isotopic altitude effect allowed determining the volume of water-bearing rock Vr and hydrogeological parameters of systems drained by springs and wells. Prior to the final determination of the recharge zone of individual objects, calculations were made for the thickness of the flow zone (h) and the distance from the recharge zone to the drainage point (L). The recharge areas for springs are located within a distance of 1–1.5 km and are characterized by a width of 0.75–1.65 km. The recharge area of wells is located in significantly longer distances of 2.1–12 km but yet definitely lower width. The recharge of groundwater from the Western direction seems to be obvious for all the wells and springs located westward from Nysa K?odzka River. The eastern component of the recharge appeared during the interpretation of the well in D?ugopole.Dedicated to Professor Peter Fritz on the occasion of his 80th birthday 相似文献