排序方式: 共有55条查询结果,搜索用时 46 毫秒
31.
Jaka Horvat Marija Bešter-Rogač Cveto Klofutar Darja Rudan-Tasic 《Journal of solution chemistry》2008,37(9):1329-1342
The viscosities of aqueous solutions of lithium, sodium, potassium, rubidium and caesium cyclohexylsulfamates were measured
at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity data were analyzed and interpreted in terms of the
Kaminsky equation, η
r=1+Ac
1/2+Bc+Dc
2. The viscosity A-coefficient was calculated from the Falkenhagen-Dole theory. The viscosity B-coefficients are positive and relatively large. Their temperature coefficient ∂
B/∂
T is negative or near zero for lithium and sodium salts whereas for potassium, rubidium and caesium salts it is positive. The
viscosity D-coefficient is positive. This was explained by the size of the ions, structural solute–solute interactions, hydrodynamic
effect, and by higher terms of the long-range Debye-Hückel type of forces. From the viscosity B-coefficients the thermodynamic functions of activation of viscous flow were calculated. The limiting partial molar Gibbs
energy of activation of viscous flow of the solute was divided into contributions due to solvent molecules and the solute
in the transition state. The activation energy of the solvent molecules was calculated using the limiting Gibbs energy of
activation for the conductance of the solute ions. The activation energy of the solvent molecules was then discussed in terms
of the nature of the alkali-metal ions and their influence on the structure of water. The limiting activation entropy and
enthalpy of the solute for activation of viscous flow were interpreted by ion-solvent bond formation or breaking in the transition
state of the solvent. The hydration numbers of the investigated electrolytes were calculated from the specific viscosity of
the solutions. 相似文献
32.
Darja Steiner Petrovi? Miran Pirnat Grega Klan?nik Primo? Mrvar Jo?ef Medved 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1185-1191
The effects of the cooling rate on the solidification and microstructure evolution in the duplex stainless steel SAF 2205 was studied using DSC and light microscopy. A ferritoscope was used to measure the ferrite content. It was revealed that the cooling rate has an influence on the ??-ferrite nucleation temperature and the width of the solidification interval. Moreover, with an increase in cooling rate, the content of ??-ferrite increases, while the quantity of austenite in the ferrite matrix decreases and its morphology changes to acicular. A two-cycle DSC experiment made possible a more accurate interpretation of the collected data. 相似文献
33.
The nanostructure of non-oriented electrical steel sheets 总被引:1,自引:0,他引:1
Darja Steiner Petrovic Bostjan Markoli 《Journal of magnetism and magnetic materials》2010,322(20):3041-1544
Nanostructures of two non-oriented electrical steels were investigated in order to elucidate the influence of nanostructure and its components on magnetic properties. The main difference between the two samples was related to the mean grain size and level of core loss. Surprisingly, the sample with coarser ferrite grains exhibited higher core loss. For this reason (HR)TEM imaging was carried out. Precipitation reactions were monitored using differential scanning calorimetry (DSC). Light microscopy, FE-SEM/EDX and EBSD analyses were also performed to analyse the microstructures and crystallographic textures. The results were compared and related to the magnetic properties. It was shown that besides the microstructural components, the nanostructure and nanoprecipitates also have a crucial impact on the magnetic properties. 相似文献
34.
Saša Zavadlav Darja Mazej Janez Zavašnik Aleksander Rečnik David Dominguez-Víllar Neven Cukrov 《Isotopes in environmental and health studies》2013,49(2):354-371
Secondary carbonate precipitates (dripstones) formed on concrete surfaces in four different environments – Mediterranean and continental open-space and indoor environments (inside a building and in a karstic cave) – were studied. The fabric of dripstones depends upon water supply, pH of mother solution and carbonate-resulting precipitation rate. Very low δ13C (average?28.2‰) and δ18O (average?18.4‰) values showed a strong positive correlation, typical for carbonate precipitated by rapid dissolution of CO2 in a highly alkaline solution and consequent disequilibrium precipitation of CaCO3. The main source of carbon is atmospheric or biogenic CO2 in the poorly ventilated karstic cave, which is reflected in even lower δ13C values. Statistical analysis of δ13C and δ18O values of the four groups of samples showed that the governing factor of isotope fractionation is not the temperature, but rather the precipitation rate. 相似文献
35.
A digestion procedure using H2SO4/HNO3/H2O2 was found to be effective for destruction of human milk samples. In conjunction with a sensitive hydride generation atomic fluorescence spectrometry detection system, it is suitable for determination of selenium in those samples where the available mass of breast milk and the low selenium concentration are limiting factors. Only 1g of milk sample is needed. The procedure is simple, rapid and of low contamination potential since it is performed in the same Teflon tube from weighing to measurement. The digestion of 20 samples is completed in three hours. The detection limit is 0.25±0.04ngg–1 of a measured solution of sample or 2.5ngg–1 of milk. The relative uncertainty is 10% (coverage factor of 2.3, 95% probability). Because of these advantages the method is particularly suitable for epidemiological studies. The mean concentration of selenium in 62 samples of human milk from lactating women residing in the North East of Italy was 12±3ngg–1, which is in the range of reference data. 相似文献
36.
Ivan Kreft Alena Vollmannov Judita Lidikov Janette Musilov Mateja Germ Aleksandra Golob Blanka Vombergar Darja Kocjan A
ko Zlata Luthar 《Molecules (Basel, Switzerland)》2022,27(17)
Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are adapted to growing in harsh conditions of high altitudes. Ultraviolet radiation at high altitudes strongly impacts plant growth and development. Under the influence of ultraviolet radiation, protecting substances are synthesized in plants. The synthesis of UV-B defense metabolites is genetically conditioned, and their quantity depends on the intensity of the ultraviolet radiation to which the plants and plant parts are exposed. These substances include flavonoids, and especially rutin. Other substances with aromatic rings of six carbon atoms have a similar function, including fagopyrin, the metabolite specific for buckwheat. Defensive substances are formed in the leaves and flowers of common and Tartary buckwheat, up to about the same concentration in both species. In comparison, the concentration of rutin in the grain of Tartary buckwheat is much higher than in common buckwheat. Flavonoids also have other functions in plants so that they can protect them from pests and diseases. After crushing the grains, rutin is exposed to contact with the molecules of rutin-degrading enzymes. In an environment with the necessary humidity, rutin is turned into bitter quercetin under the action of rutin-degrading enzymes. This bitterness has a deterrent effect against pests. Moreover, flavonoids have important functions in human nutrition to prevent several chronic diseases, including obesity, cardiovascular diseases, gallstone formation, and hypertension. 相似文献
37.
Arbeiter Jože Vončina Maja Volšak Darja Medved Jožef 《Journal of Thermal Analysis and Calorimetry》2020,142(5):1693-1699
Journal of Thermal Analysis and Calorimetry - Homogenization heat treatment is the first step in the processing of aluminium alloys, which for most alloys is carried out before any deformation... 相似文献
38.
Zavadlav S Mazej D Zavašnik J Rečnik A Dominguez-Víllar D Cukrov N Lojen S 《Isotopes in environmental and health studies》2012,48(2):354-371
Secondary carbonate precipitates (dripstones) formed on concrete surfaces in four different environments--Mediterranean and continental open-space and indoor environments (inside a building and in a karstic cave)--were studied. The fabric of dripstones depends upon water supply, pH of mother solution and carbonate-resulting precipitation rate. Very low δ(13)C (average-28.2‰) and δ(18)O (average-18.4‰) values showed a strong positive correlation, typical for carbonate precipitated by rapid dissolution of CO(2) in a highly alkaline solution and consequent disequilibrium precipitation of CaCO(3). The main source of carbon is atmospheric or biogenic CO(2) in the poorly ventilated karstic cave, which is reflected in even lower δ(13)C values. Statistical analysis of δ(13)C and δ(18)O values of the four groups of samples showed that the governing factor of isotope fractionation is not the temperature, but rather the precipitation rate. 相似文献
39.
Olivier E. Nonga Darja Lavogina Erki Enkvist Katrin Kestav Apirat Chaikuad Sarah E. Dixon-Clarke Alex N. Bullock Sergei Kopanchuk Taavi Ivan Ramesh Ekambaram Kaido Viht Stefan Knapp Asko Uri 《Molecules (Basel, Switzerland)》2021,26(14)
We performed an X-ray crystallographic study of complexes of protein kinase PIM-1 with three inhibitors comprising an adenosine mimetic moiety, a linker, and a peptide-mimetic (d-Arg)6 fragment. Guided by the structural models, simplified chemical structures with a reduced number of polar groups and chiral centers were designed. The developed inhibitors retained low-nanomolar potency and possessed remarkable selectivity toward the PIM kinases. The new inhibitors were derivatized with biotin or fluorescent dye Cy5 and then applied for the detection of PIM kinases in biochemical solutions and in complex biological samples. The sandwich assay utilizing a PIM-2-selective detection antibody featured a low limit of quantification (44 pg of active recombinant PIM-2). Fluorescent probes were efficiently taken up by U2OS cells and showed a high extent of co-localization with PIM-1 fused with a fluorescent protein. Overall, the developed inhibitors and derivatives represent versatile chemical tools for studying PIM function in cellular systems in normal and disease physiology. 相似文献
40.
We have studied the preparation of oriented BaFe(12)O(19) films produced using electrophoretic deposition (EPD). Highly anisotropic, platelike BaFe(12)O(19) particles were synthesized under hydrothermal conditions, and from these particles, stable suspensions were prepared in 1-butanol by the addition of dodecylbenzene sulfonic acid as a surfactant. The interplay of the interaction forces between the suspended particles and the forces acting on the particles during the EPD directed the particles' assembly in the plane of the substrate. The most significant effect on the orientation of the films was the diameter-to-thickness ratio of the particles, which was experimentally confirmed with X-ray analyses, electron microscopy, and magnetic measurements. The abnormal grain growth that accompanied the sintering at 1150 °C further improved the overall orientation of the films, which showed highly anisotropic magnetic behavior with a remanent-to-saturation magnetization ratio exceeding 0.8. 相似文献