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排序方式: 共有134条查询结果,搜索用时 31 毫秒
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32.
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
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Summary. Solubilities of methyl acetate (MeOAc), ethyl acetate (EtOAc), 1-propyl acetate (1-PrOAc), 1-butyl acetate (1-BuOAc), 2-methyl-1-propyl
acetate (iso-BuOAc), 2-butyl acetate (sec-BuOAc), 2-methyl-2-propyl acetate (ter-BuOAc), 1-pentyl acetate (1-PeOAc) and 1-hexyl acetate (1-HeOAc) in water and in aqueous sodium chloride solutions at concentrations ranging up to 1.0 molċdm−3 were determined at 25.0°C by analyzing the saturated aqueous or salt solutions. Solubility ratios of alkyl acetates in pure
water and in aqueous sodium chloride solution were calculated and found to be linearly dependent on the concentration of sodium
chloride. The solubility ratios were also calculated by the approach of the scaled particle theory and according to the theories
of McDevit and Long, Cross, Conway et al., and Aveyard. All these theories, except that of Conway, correctly predict the order of magnitude of the experimental results, but do not discriminate between isomeric butyl acetates.
The theoretical values obtained from the scaled particle and Aveyard theories coincide well with the experimental values, especially for the higher alkyl acetates. The purely electrostatic theory
of Conway et al. not even predicts the salting-out effect for the alkyl acetates investigated.
Received July 12, 1999. Accepted September 23, 1999 相似文献
35.
36.
Jonathan Burns Egor Dolzhenko Nataša Jonoska Tilahun Muche Masahico Saito 《Discrete Applied Mathematics》2013,161(10-11):1378-1394
Genome rearrangement and homological recombination processes have been modeled by Angeleska et al. [A. Angeleska, N. Jonoska, M. Saito, DNA recombinations through assembly graphs, Discrete Appl. Math. 157 (2009) 3020–3037] as 4-regular spacial graphs with rigid vertices, called assembly graphs. These graphs can also be represented by double occurrence words called assembly words. The rearranged DNA segments are modeled by certain types of paths in the assembly graphs called polygonal paths. The minimum number of polygonal paths visiting all vertices in a graph is called an assembly number for the graph.In this paper, we give formulas for counting certain types of assembly graphs and assembly words. Some of these formulas produce sequences not previously reported at the Online Encyclopedia of Integer Sequences (http://oeis.org). We provide a sharp upper bound for the number of polygonal paths in Hamiltonian sets of polygonal paths, and present a family of graphs that achieves this bound. We investigate changes in the assembly numbers as a result of graph compositions. Finally, we introduce a polynomial invariant for assembly graphs and show properties of this invariant. 相似文献
37.
The preparation of BaCeO3 doped by gadolinium, europium, and terbium oxides (BaCe0.8Eu0.1Tb0.1O2.9 and BaCe0.8Gd0.2O2.9) has been performed by solid-state reaction from BaCO3, CeO2, Gd2O3, Eu2O3, Tb4O7. The X-ray measurements have showed that BaCe0.8RE0.2O2.9 (RE = Gd, Eu, Tb) was orthorhombic structure (space group Pnma). The standard formation enthalpies of BaCe0.8Eu0.1Tb0.1O2.9 and BaCe0.8Gd0.2O2.9 have been determined by solution calorimetry combining the solution enthalpies of BaCe0.8Gd0.2O2.9 (BaCe0.8Eu0.1Tb0.1O2.9) and BaCl2 + 0.8CeCl3 + 0.2GdCl3 (BaCl2 + 0.8CeCl3 + 0.1EuCl3 + 0.1TbCl3) mixtures in 1 M HCl with 0.1 M KI at T = 298.15 K and literature data. 相似文献
38.
Nataša Novak Tušar Dr. Alenka Ristić Dr. Gregor Mali Dr. Matjaž Mazaj Dr. Iztok Arčon Prof. Denis Arčon Prof. Venčeslav Kaučič Prof. Nataša Zabukovec Logar Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(19):5783-5793
A two‐step synthesis of a novel mesostructured silicate, KIL‐2, and its manganese‐containing analogue, Mn/KIL‐2, has been developed. KIL‐2 possesses interparticle mesopores with pore dimensions between 5 and 60 nm and a surface area of 448 m2. The mesopores are formed by the aggregation of silica nanoparticles, which creates a network with interparticle voids. The particle size and the pore diameters depend on the temperature of the ageing step (first step) and on the solvothermal treatment in ethanol (second step), respectively. Mn/KIL‐2 contains octahedrally coordinated Mn3+ (80 %) and tetrahedrally coordinated Mn2+ (20 %) ions. Mn3+ ions are present in the extra‐framework MnOx nanoparticles with typical dimensions of 2 nm, which are homogeneously distributed throughout the material. Mn2+ ions occur as isolated manganese framework sites. The material is also able to retain its structure characteristics after the hydrothermal treatment in boiling water. Because of its non‐toxic nature and cost‐effective synthesis, Mn/KIL‐2 thus exhibits properties that are needed for an environment‐friendly catalyst. 相似文献
39.
Nataša Bilić 《Mathematica Slovaca》2010,60(1):83-96
This paper deals with the optimal control of a coefficient in the modification of Navier-Stokes equations. Namely, the motion
of the viscous incompressible fluid for a small gradient of velocity is described by Navier-Stokes equations where the coefficient
of the kinematic viscosity ν is the positive constant (ν
0). For a greater gradient of velocity the coefficient of kinematic viscosity is a positive function of the gradient of velocity,
that is ν (|∇u|). In our case ν (|∇u|) = ν
0 + ν
1
a (|∇u|) where ν
0, ν
1 ∈ ℝ+. The function a is positive and monotone and it is taken as a control variable. The existence of a solution of the optimal control problem
is proved. Further, the approximation of the control problem by the finite-dimensional control problem is performed. The proof
of the existence of a solution of that aproximate problem has been brought into light. Finally, the connection between the
solution of the control problem and the solution of the approximate control problem is established. 相似文献
40.
N. Bebiano H. Nakazato A. Nata J. da Providência 《Annali di Matematica Pura ed Applicata》2010,189(4):539-551
In this article, tracial numerical ranges associated with matrices in an indefinite inner product space are investigated.
The boundary equations of these sets are obtained, and the case of the boundary being a polygon is studied. As an application,
a numerical algorithm for plotting the tracial numerical range of an arbitrary complex matrix is presented. Our approach uses
the elementary idea that the boundary may be traced by computing the supporting lines. 相似文献