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121.
122.
ZDM – Mathematics Education - While the number of studies of flipped classrooms has increased, they have primarily addressed the efficacy of using such an approach on student outcomes, often... 相似文献
123.
Reviewing the literature solubility isotherms in the ternary systems K2SO4–MSO4–H2O (M = Co, Ni, Cu, Zn) revealed a lack at ambient temperatures. The solid–liquid phase equilibria have been determined in the systems K2SO4–MSO4–H2O (M = Co, Ni, Cu) at T = 313 K. With increasing bivalent metal sulfate concentration, the solubility of potassium sulfate rises until the two-salt point is reached. Reciprocally, the solubility of the bivalent metal sulfate hydrates (CoSO4·7H2O, α-NiSO4·6H2O, CuSO4·5H2O) increases with rising potassium sulfate concentration. In all three systems the double salts of Tutton's type K2SO4·MSO4·6H2O (M = Co, Ni, Cu) are formed. 相似文献
124.
Margit Voigt 《Discrete Mathematics》2009,309(15):4926-4930
Let G=G(V,E) be a simple graph, L a list assignment with |L(v)|=Δ(G)∀v∈V and W⊆V an independent subset of the vertex set. Define to be the minimum distance between two vertices of W. In this paper it is shown that if G is 2-connected with Δ(G)=3 and G is not K4 then every precoloring of W is extendable to a proper list coloring of G provided that d(W)≥6. An example shows that the bound is sharp. This result completes the investigation of precoloring extensions for graphs with |L(v)|=Δ(G) for all v∈V where the precolored set W is an independent set. 相似文献
125.
A risk assessment of chemicals is to be performed on the basis of the model EUSES, developed by the Commission of the European Union. The model package E4CHEM (Exposure Estimation for Potentially Ecotoxic Environmental Chemicals), developed in 1984-1992, is presented and applied in this paper as a model which allows a model-supported evaluation of chemicals. E4CHEM consequently does not have the wide applicability and technical comfort of the more recently developed model EUSES. The simulation models of E4CHEM characterize the chemical behavior in the environment by many aspects. Hence, there is a need to condense all of these aspects to get a clear impression of what will be the fate of the chemicals. Starting with the already published concept of exposure maps, we will discuss how partial orders may be helpful in establishing generalized structure-fate relationships. The software WHASSE is applied. 相似文献
126.
The solubility of the binary system (LiNO3 + H2O) from T = 273.15 K to T = 333.15 K and solubility isotherms of the ternary system (LiCl + LiNO3 + H2O) were elaborately measured at T = 273.15 K and T = 323.15 K. These solubility data, as well as water activities in the binary systems from the literature, were treated by an empirically modified BET model. The isotherms of the ternary system (LiCl + LiNO3 + H2O) were reproduced and a complete phase diagram of the ternary system in the temperature range from 273.15 K to 323.15 K predicted. It is shown that the solubility data for the binary system (LiNO3 + H2O) measured in this work are slightly different from the literature data. Simulated results showed that the saturated salt solution of (2.8LiCl + LiNO3) is in equilibrium with the stable solid phase LiNO3(s) over the temperature range from 283.15 K to 323.15 K, other than the solid phases LiNO3 · 3H2O(s) and LiClH2O(s) as reported by Iyoki et al. [S. Iwasaki, Y. Kuriyama. T. Uemura, J. Chem. Eng. Data 38 (1993) 396–398]. 相似文献
127.
Voigt K Gasteiger J Bruggemann R 《Journal of chemical information and computer sciences》2000,40(1):44-49
In a constantly expanding world of chemical and environmental information sources, the need for their evaluation gains more and more importance. This paper presents a comparative evaluation of datasources of online databases and databases on CD-ROM (called CD-ROMs in this paper) in the field of environmental chemicals. The approach is based on research results gained in the years 1996/1997. The authors are aware that changes in the database industry may lead to different results. Before the actual evaluation process can be carried out, two major procedures are necessary, namely, the selection of sets of datasources and the definition of evaluation criteria. In order to perform the difficult task of an evaluation based on several criteria, a general order relation has to be introduced. Methods of partially ordered set theory are applied, and the results are visualized by the technique of Hasse diagrams. On the basis of these evaluation results, the datasources are grouped and then evaluated. It will be shown that there are groups of datasources with quite specific property profiles, and only two groups turn out to be relatively better than the others. 相似文献
128.
Dieter Leupold Bernd Voigt Michael Pfeiffer Michael Bandilla Hugo Scheer 《Photochemistry and photobiology》1993,57(1):24-28
Nonlinear polarization spectroscopy in the frequency domain allows rate constant determinations of fast electronic energy and phase relaxations together with characterization of the type of line broadening. Application of this method to the B850 component of the isolated B800–850antenna ofRhodobacter sphaeroides at room temperature shows that B850 is inhomogeneously broadened, with homogeneous widths between 30 and 200 cm?1, depending on the spectral position of the subforms. The corresponding phase relaxation times are clearly in the subpicosecond range. There is also indication of an up-to-now unspecified1–5 ps energy relaxation channel per subunit. 相似文献
129.
Two Representatives of the α-LiFeO2 Type: LiInO2 and α-LiYbO2 Single crystals of LiInO2 (well ground mixtures of ‘In2O’: KO2: Li2O = 1:1.8:1, Ag-tube, 22d, 520°C); and α-LiYbO2 (Yb2O3:Li2O = 1:1.1, Ni-tube, 30d, 1150°C) were prepared for the first time from mixtures of the binary oxides. The determination of the structure confirmed the α-LiFeO2 type. Both oxides crystallize in the space group I 41/amd (Z = 4); LiInO2: a = 431.2(1) pm c = 934.2(2) pm; c/a = 2.167; 123 Io(hkl), R = 3.6%, Rw = 2.9%. α-LiYbO2:a = 438.7(1) pm c = 1006.7(2) pm; c/a = 2.295, 130 Io(hkl), R = 4.4%, Rw = 3.6%. The Madelung part of lattice energy, MAPLE and characteristics of this kind of structure are discussed. 相似文献
130.
Morten Gotthold Vinum Laura Voigt Steen H. Hansen Colby Bell Kensha Marie Clark Ren Wugt Larsen Kasper S. Pedersen 《Chemical science》2020,11(31):8267
The quest for simple ligands that enable multi-electron metal–ligand redox chemistry is driven by a desire to replace noble metals in catalysis and to discover novel chemical reactivity. The vast majority of simple ligand systems display electrochemical potentials impractical for catalytic cycles, illustrating the importance of creating new strategies towards energetically aligned ligand frontier and transition metal d orbitals. We herein demonstrate the ability to chemically control the redox-activity of the ubiquitous acetylacetonate (acac) ligand. By employing the ligand field of high-spin Cr(ii) as a switch, we were able to chemically tailor the occurrence of metal–ligand redox events via simple coordination or decoordination of the labile auxiliary ligands. The mechanism of ligand field actuation can be viewed as a destabilization of the dz2 orbital relative to the π* LUMO of acac, which proffers a generalizable strategy to synthetically engineer redox-activity with seemingly redox-inactive ligands.Tailoring the chemical surroundings of chromium(ii) allows reversible electron-transfer to the ubiquitous, purportedly redox-inactive acetylacetonate. 相似文献