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排序方式: 共有466条查询结果,搜索用时 31 毫秒
41.
Agata Roguska Andrzej KudelskiMarcin Pisarek Magdalena OparaMaria Janik-Czachor 《Applied Surface Science》2011,257(19):8182-8189
Tubular arrays of TiO2 nanotubes (ranging in diameter from 40 to 110 nm) on a Ti substrate were used as a support for Ag, Au or Cu deposits obtained by the sputter deposition technique, where the amount of metal varied from 0.01 to 0.2 mg/cm2. Those composite supports were intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured at different cathodic potentials ranging from −0.2 down to −1.2 V after the pyridine had been adsorbed on the metal-covered TiO2 nanotube/Ti substrates. In addition, SERS spectra on a bulk standard activated Ag, Au and Cu substrates were also measured. The SERS activity of the composite samples was strongly dependent on the amount of metal deposit, e.g. at and above 0.06 mg Ag/cm2, the intensity of SERS signal was even higher than that for the Ag reference substrate. The high activity of these composites is mainly a result of their specific morphology. The high SERS sensitivity on the surface morphology of the substrate made it possible to monitor very small temporal changes in the Ag metal clusters. This rearrangement was not detectable with microscopic (SEM) or microanalytical (AES) methods. The SERS activity of Au or Cu clusters was distinctly lower than those of Ag. The spectral differences exhibited by the three kinds of composites as compared to the reference metal samples are discussed. 相似文献
42.
The complex product of (non-empty) subalgebras of a given algebra from a variety \(\mathcal{V}\) is again a subalgebra if and only if the variety \(\mathcal{V}\) has the so-called generalized entropic property. This paper is devoted to algebras with a neutral element or with a semigroup operation. We investigate relationships between the generalized entropic property and the commutativity of the fundamental operations of the algebra. In particular, we characterize the algebras with a neutral element that have the generalized entropic property. Furthermore, we show that, similarly as for n-monoids and n-groups, for inverse semigroups, the generalized entropic property is equivalent to commutativity. 相似文献
43.
Phenanthriporphyrin: An Antiaromatic Aceneporphyrinoid as a Ligand for a Hypervalent Organophosphorus(V) Moiety 下载免费PDF全文
Dr. Bartosz Szyszko Dr. Agata Białońska Dr. Ludmiła Szterenberg Prof. Dr. Lechosław Latos‐Grażyński 《Angewandte Chemie (International ed. in English)》2015,54(16):4932-4936
The incorporation of a phenanthrene moiety into a porphyrin framework results in the formation of a hybrid macrocycle—phenanthriporphyrin—merging the structural features of polycyclic aromatic hydrocarbons and porphyrins. An antiaromatic aceneporphyrinoid, adopting the trianionic {CCNN} core, is suitable for the incorporation of a phosphorus(V) center to form a hypervalent organophosphorus(V) derivative. 相似文献
44.
45.
Agata Krakowska Witold Reczyński Włodzimierz Opoka Waldemar Turski 《International journal of environmental analytical chemistry》2015,95(9):855-866
Honey is a sweet product made by bees using nectar from flowers. Concentrations of Ca, K, Mg, Fe, Zn, Mn, Cu, Pb and Cd were determined in 13 honey samples from the selected regions around the world. Levels of Ca, Mg, Cu, Fe, Zn and Mn were measured using flame atomic absorption spectrometry (FAAS). Potassium concentration was determined via flame photometry. Concentrations of Cd and Pb were determined using the electrothermal technique (ETAAS). It was estimated that the examined samples of honey from Greece, Turkey, Spain, Poland, Mexico, Argentina and Italy were of good quality in terms of metal concentrations (compliant with the norms referring to food products – WHO, Fifty-third Report of the joint FAO/WHO Expert Committee on Food Additives; Technical Report Series 776, Geneva), although the analysed samples were not free of heavy metals. The concentrations of the elements in the honey samples ranged from 2.38 to 9.31 μg · g?1 for Zn, from 3.86 to 35.10 μg · g?1 for Fe, from 0.19 to 21.64 μg · g?1 for Mn, from 49.53 to 1006.90 μg · g?1 for Ca, from 388.25 to 4761.50 μg · g?1 for K and from 0.20 to 1.53 μg · g?1 for Cu and regarding heavy metals from 0.11 to 2.78 μg · g?1 for Pb and from 0.02 to 0.44 μg · g?1 for Cd. According to these results it was found that the concentrations of heavy metals in the honey samples (except for alfalfa honey and eucalyptus honey from Italy) were under the acceptable limits for foods set out by the FAO/WHO. It was confirmed that the application of chemometric tools supports the extraction of significant information from analytical data, even though the availability of samples is not fully sufficient (this problem is often encountered in environmental analyses). 相似文献
46.
Alina Sionkowska Sławomir Skrzyński Krzysztof Śmiechowski Agata Kołodziejczak 《先进技术聚合物》2017,28(1):4-9
This review reports recent advances in the versatile application of collagen. Collagen materials have attracted great attention because they exhibit properties required in cosmetic preparations, in the biomedical field, and in the tanning industry leading to leather production. Herein, the structure and application of collagen are discussed in general, and detailed examples are also drawn from scientific literature and practical work. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
47.
Agata Górska Karolina Szulc Ewa Ostrowska-Ligęza Joanna Bryś Magdalena Wirkowska-Wojdyła 《Journal of Thermal Analysis and Calorimetry》2017,128(1):177-183
Epoxy-based nanocomposites containing different concentrations (0–3%) of surface-modified graphene nanosheets (GNS) with 3-aminopropyltriethoxysilane were prepared and their thermal and mechanical properties including dynamic mechanical analysis, tensile strength, hardness, and abrasion tests were evaluated in order to have a database for thermo-mechanical properties of epoxy nanocomposites. The main aim of this study was to understand the optimum percentage of GNS which would perform the best reinforcing influence on mechanical and physical performance of an epoxy nanocomposite. The results explain how applying the analysis of variance (ANOVA) method as a useful tool in optimization of GNS concentration in preparation of high-performance epoxy-based nanocomposites. 相似文献
48.
Agata Smoktunowicz 《Israel Journal of Mathematics》2017,219(2):555-608
A well-known theorem by S. A. Amitsur shows that the Jacobson radical of the polynomial ring R[x] equals I[x] for some nil ideal I of R. In this paper, however, we show that this is not the case for differential polynomial rings, by proving that there is a ring R which is not nil and a derivation D on R such that the differential polynomial ring R[x;D] is Jacobson radical. We also show that, on the other hand, the Amitsur theorem holds for a differential polynomial ring R[x;D], provided that D is a locally nilpotent derivation and R is an algebra over a field of characteristic p > 0. The main idea of the proof introduces a new way of embedding differential polynomial rings into bigger rings, which we name platinum rings, plus a key part of the proof involves the solution of matrix theory-based problems. 相似文献
49.
PMB ethers of alcohols are obtained in good yields and under mild conditions using the 4-methoxybenzyl N-allyl thiocarbamate and N-bromosuccinimide (NBS)/TfOH as the catalyst. The present method is very fast, simple, and efficient. 相似文献
50.
Maślanka A Krzek J Stolarczyk M Walczak M Głogowska A 《Journal of AOAC International》2011,94(6):1791-1799
Stability of clonazepam, diazepam, haloperidol, and doxepin was determined in acidic solutions. In addition, determination of the kinetic and thermodynamic properties of this stability was carried out. Reaction rate constants (k), half-life times (t(0.1) and t(0.5)), and activation energy (Ea) were estimated for the drugs, which differed in polarity expressed with log P values. It was observed that estimated Ea values increased from 42.13 to 125.03 kJ/mol with an increase of lipophilicity (log P) beginning from the most hydrophilic drug (clonazepam, 2.70 log P) to the most lipophilic drug (doxepin, 4.10 log P). All degradation products were studied using an HPLC/electrospray ionization-MS technique in the positive ionization mode. 相似文献