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21.
It is proved that every variety satisfying the Congruence Intersection Property (CIP) is Abelian. In addition, a CM Abelian
variety has the CIP if and only if it has a constant term operation. Finally, a CM variety is Abelian if and only if it has
the weak CIP.
Received October 8, 1998; accepted in final form January 5, 1999. 相似文献
22.
Andreja Lesac Ute Baumeister Irena Dokli Zdenko Hameršak Trpimir Ivšić Darko Kontrec 《Liquid crystals》2018,45(7):1101-1110
Herein we report a comprehensive study on novel carbonyl- and ethenyl-linked symmetric dimers that combine synthesis, mesomorphic properties and molecular modelling. The study has been focused on the impact of geometry imposed by the linkage group on the incidence of the twist-bend nematic (NTB) phase. Comparison of the mesomorphic properties of these two series complemented with computational studies of conformational space around the linkage group points molecular curvature and intramolecular torsion plays important role in the appearance of the NTB phase and can be regarded as the basic structural requirements for design of new twist-bend nematogen materials. 相似文献
23.
In acidic aqueous solutions UO(2)(2+) serves as a photocatalyst (lambda(irr) >/= 425 nm) for the oxidation of benzene by H(2)O(2). Under conditions where 50% of the excited state UO(2)(2+) is quenched by H(2)O(2) (k = 5.4 x 10(6) M(-)(1) s(-)(1)) and 50% by benzene (k = 2.9 x 10(8) M(-)(1) s(-)(1)), the quantum yield for the formation of phenol is 0.70. The yield does not change when benzene is replaced by benzene-d(6), but decreases by a factor of approximately 4 upon the change of solvent from H(2)O to D(2)O. Photocatalytic oxidation of toluene by UO(2)(2+)/H(2)O(2) produces PhCHO, PhCH(2)OH, and a mixture of cresols with a total quantum yield of 0.28 under conditions where 50% of UO(2)(2+) is quenched by H(2)O(2). The quenching of UO(2)(2+) by benzene and substituted benzenes takes place with k > 10(8) M(-)(1) s(-)(1). The system UO(2)(2+)/t-BuOOH/C(6)H(6)/hnu does not result in the oxidation of benzene, but instead yields methane and ethane. 相似文献
24.
Nataša Lilek Andreja Kandolf Borovšak Jasna Bertoncelj Katarina Vogel Mikuš Marijan Nečemer 《X射线光谱测定》2022,51(3):186-197
Bee pollen contains proteins, amino acids, carbohydrates, fats, fatty acids, vitamins, polyphenols, and mineral nutrients that make it useful as a good nutritional supplement in the human diet. It has the richest elemental composition among bee products which is not uniform and consequently varies greatly depending on botanical and geographical origin. In polyfloral and selected monofloral bee pollen samples: sweet chestnut, maple, dandelion, rapeseed, flowering ash, buckwheat, common ivy, and plantain, the concentrations of P, S, Cl, K, Ca, Mn, Fe, Zn, Br, Rb, and Sr were determined. A non-destructive energy dispersive X-ray fluorescence spectrometry was used for elemental fingerprinting. The most abundant elements in Slovenian bee pollen are K, P, S, Ca, and Cl followed by Fe, Mn, Zn, Rb, Br, and Sr. Several statistically significant differences in the content of analysed elements were found between studied groups according to the botanical and geographical origin which can be related to soil and plant elemental composition and plant metabolism. The obtained data extend our previous chemical profiling of Slovenian bee pollen and contribute to a more precise evaluation of some essential mineral nutrients in bee pollen to cover recommended dietary allowances in human nutrition. Additionally, this work contributes to a better understanding of mineral nutrient requirements in honey bee nutrition and of the environmental and agricultural impact of this product. 相似文献
25.
Krajcar Bronić Ines Sironić Andreja Barešić Jadranka Lovrenčić Mikelić Ivanka Borković Damir 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3289-3294
Journal of Radioanalytical and Nuclear Chemistry - Determination of fraction of biogenic component in liquid fuels by a direct radiocarbon measurement in liquid scintillation counter (direct-LSC... 相似文献
26.
Eszter K. Horváth Branimir ?e?elja Andreja Tepav?evi? 《Central European Journal of Mathematics》2013,11(2):296-307
We deal with rectangular m×n boards of square cells, using the cut technics of the height function. We investigate combinatorial properties of this function, and in particular we give lower and upper bounds for the number of essentially different cuts. This number turns out to be the cardinality of the height function’s range, in case the height function has maximally many rectangular islands. 相似文献
27.
Ján Derco Andreja Žgajnar Gotvajn Jana Zagorc-Končan Beáta Almásiová Angelika Kassai 《Chemical Papers》2010,64(2):237-245
Kinetics and efficiency of Fenton’s and ozonation processes for the pretreatment of two landfill leachates (fresh and mature)
resulting from municipal waste disposal were studied. Both samples presented high organic load, high toxicity and low biodegradability.
These were the reasons why oxidative treatment was proposed. Fresh and mature leachate showed different behaviors in the oxidation
experiments. The final extents of removal were attained in comparable time intervals in both oxidation systems. Maximal removal
of organics by the Fenton’s oxidation reached more than 50 % according to COD. Zero or first order kinetics were found the
best to describe the organic components (in terms of COD and DOC) removal by the Fenton’s oxidation for both landfill leachates.
Higher reaction rate values of the Fenton’s oxidation were achieved with fresh leachate samples. The efficiency of initial
organics removal with ozone was about 70 % for mature leachate, while in case of the fresh one only 41 % of COD were removed.
The best fits of COD and DOC experimental data from oxidation of fresh and mature leachates were obtained by a combined kinetic
model. No significant improvement of the biodegradability of landfill leachates was achieved using these treatment procedures.
Regarding toxicity, ozonation showed to be more effective than the Fenton’s oxidation. Advanced oxidation experiments confirmed
that the Fenton’s oxidation and ozonation are comparable oxidative treatment techniques for the reduction of organic pollution
in the investigated municipal landfill leachates. However, neither of them is effective enough to be used as a pretreatment
method followed by biological treatment. 相似文献
28.
The aqueous iron(IV) ion, Fe(IV)(aq)O(2+), generated from O(3) and Fe(aq)(2+), reacts rapidly with various oxygen atom acceptors (sulfoxides, a water-soluble triarylphosphine, and a thiolatocobalt complex). In each case, Fe(IV)(aq)O(2+) is reduced to Fe(aq)(2+), and the substrate is oxidized to a product expected for oxygen atom transfer. Competition methods were used to determine the kinetics of these reactions, some of which have rate constants in excess of 10(7) M(-1) s(-1). Oxidation of dimethyl sulfoxide (DMSO) has k = 1.26 x 10(5) M(-1) s(-1) and shows no deuterium kinetic isotope effect, k(DMSO-d(6)) = 1.23 x 10(5) M(-1) s(-1). The Fe(IV)(aq)O(2+)/sulfoxide reaction is the product-forming step in a very efficient Fe(aq)(2+)-catalyzed oxidation of sulfoxides by ozone. This catalytic cycle, combined with labeling experiments in H(2)(18)O, was used to determine the rate constant for the oxo-group exchange between Fe(IV)(aq)O(2+) and solvent water under acidic conditions, k(exch) = 1.4 x 10(3) s(-1). 相似文献
29.
Jania Križan Milić Irena Petrinić Andreja Goršek Marjana Simonič 《Central European Journal of Chemistry》2014,12(2):242-249
In this study, a Taguchi experimental design methodology was used to determine the importance of process parameters influencing the ultrafiltration (UF) of oil-in-water emulsions. Four parameters including pH (5–11), oil concentration (φ) (0.5–3% (v/v)), temperature (T) (25–45°C) and trans-membrane pressure (TMP) (1–5 bar) were studied at three levels. The highest flux was used as optimization criterion. In order to reduce the number of experiments, a Taguchi method was applied. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the optimization criterion. Filtration experiments were performed in a cross-flow operation at a total recycle condition in a laboratory-scale plant. The ceramic UF membrane with a pore size of 50 nm was employed in a tubular module with an active area of 0,418 m2. We used water-soluble cutting oil mixed with water as a model oil-in-water emulsion. During the experiment, the drop size and zeta potential distributions were evaluated. The optimum conditions for UF providing the highest flux were found at TMP = 5 bar, pH = 7, and φ = 0.5 v/v%. The pH of emulsion had the highest impact on COD retention. The results of this study could be used as a guideline for operating UF systems with ceramic membranes at optimal conditions. 相似文献
30.