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1.
Sebastian Kuntze 《ZDM》2006,38(6):456-463
So-called “bottom-up” strategies for implementation based on mathematics teachers' own developmental activities are considered to be a powerful approach when encouraging teachers to introduce alternative instructional practices. For evaluational research of in-service teacher training programs using “bottom-up” implementation strategies, the way how teachers implement contents of the teacher training is at the centre of interest. As the teachers' active role in the implementation process is necessary, their individual beliefs on the contents of the teacher training and their expectancies might influence the teachers' implementational activities. These beliefs can be considered as components of professional knowledge and pedagogical contents knowledge (Shulman, 1986) in particular. For this reason, the study focuses on the development of beliefs on contents of a teacher training program throughout the training on the one hand and relationships with characteristics of implementation on the other hand. We consider the example of introducing a student-centred learning environment, the so-called topic study method, in the teachers' classrooms. The results indicate that there are interdependencies between beliefs on the teacher training contents and characteristics of implementation. 相似文献
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4.
Wolfgang?Gutleben Verena?Unterholzner Dietmar?Volgger Andreas?ZemannEmail author 《Mikrochimica acta》2004,146(2):111-117
In the course of this investigation, a method for the characterization and differentiation of paper pulps was developed. After hydrolyzation of the papers and the respective raw pulps with trifluoroacetic acid, the hydrolyzates were analyzed with respect to their carbohydrate composition using ion exchange chromatography. The variations in carbohydrate composition mainly arise from the various hemicelluloses of the papers and pulps. The chromatographic results were then further processed using principal component analysis which allows correlating the various papers to different pulp materials. 相似文献
5.
The CD. spectra of carotenoids in the 220-500 nm region may by inspection be classified as (a) essentially Conservative, (b) intermediate, or (c) essentially nonconservative. A conservative spectrum shows in that spectral region a sequence of 5-6 relatively sharp Cotton effects of alternating sign, the rotatory strengths of which roughly add to zero. In a non-conservative spectrum Δ? has the same sign over the whole region and its absolute value is in general somewhat smaller. In general, typical conservative spectra invert upon isomerization of the molecule from all-trans to mono-cis. Non-conservative spectra do not invert. The model of a chiral polyene of the length of the conjugated carotene chromophore reproduces well the main features of the conservative spectra. The theoretical predictions and the experimental data are shown to conform to the C2-rule [43] [44]. The particular nature of the longest-wavelength transition is interpreted. Based on a summary of the chiroptic data on about 50 naturally occurring compounds, the question is discussed of when conservative spectra arise and when not. 相似文献
6.
Colourless single crystals of the caffeine adduct of mercurous perchlorate dihydrate, [Hg2(Caf)2](ClO4)2(H2O)2, were grown from aqueous solutions of mercurous perchlorate and caffeine by isothermal evaporation at ambient temperature. The crystal structure (monoclinic, P21/n, Z = 4, a = 1628.0(2), b = 780.4(1), c = 2229.6(3) pm, β = 99.84(1)°, R1(all data) = 0.0894) contains [trans‐Caf‐Hg‐Hg‐Caf]2+ cations with a Hg‐Hg distance of 250.88(6) pm, Hg‐N (bond) distances of 214.4(6) and 215.1(6) pm and Hg‐Hg‐N angles of 176.9(2) and 165.1(2)°, respectively. These cations are attached via weak Hg‐O contacts to dimers which are further arranged to leave large channels into which one crystal water molecule is included. The second water molecule and the two perchlorate anions are weakly attracted to one Hg atom. 相似文献
7.
Braun T Steffen A Schorlemer V Neumann B Stammler HG 《Dalton transactions (Cambridge, England : 2003)》2005,(20):3331-3336
Treatment of a toluene solution of [PdMe(2)(Cy(2)PCH(2)PCy(2))](1) with pentafluoropyridine in the presence of traces of water affords the generation of the A-frame complexes [(PdMe)(2){mu-kappa(2)(P,P)Cy(2)PCH(2)PCy(2)}(2)(mu-F)][SiMeF(4)]() and [(PdMe)(2){mu-kappa(2)(P,P)Cy(2)PCH(2)PCy(2)}(2)(mu-F)][OC(5)NF(4)](2b). If the reaction is performed in an NMR tube equipped with a PFA inliner, complex 2b is produced, only. Treatment of 1 with pentafluoropyridine in the presence of an excess water yields the pyridyloxy complex [PdMe(OC(5)NF(4))(Cy(2)PCH(2)PCy(2))](3). Compound [(PdMe)(2){mu-kappa(2)(P,P)Cy(2)PCH(2)PCy(2)}(2)(mu-F)][FHF](2c) bearing a bifluoride anion instead of SiMeF(4)(-) or OC(5)NF(4)(-) can be generated by reaction of 1 with substoichiometric amounts of Et(3)N.3HF. The analogous complex [(PdMe)(2){mu-kappa(2)(P,P)Ph(2)PCH(2)PPh(2)}(2)(mu-F)][FHF] (5c) has been synthesized by addition of Ph(2)PCH(2)PPh(2) to a solution of [PdMe(2)(Me(2)NCH(2)CH(2)NMe(2))](4) in THF and subsequent treatment of the reaction mixture with Et(3)N.3HF. The structure of the A-frame complex 5c has been determined by X-ray crystallography. 相似文献
8.
The carborane–siloxane copolymers Dexsil 300, a 34.5% bis(dimethylsilyl)-m-carborane–65.5% dimethylsiloxane copolymer, and Dexsil 400, a 24.9% bis(dimethylsilyl)-m-carborane–50.8% dimethyl, 24.3% methylphenylsiloxane copolymer, were coated on fused silica capillary columns and their gas
chromatographic properties were evaluated. Their selectivity was evaluated using both Rohrschneider–McReynolds constants and
triacylglycerol indices. The bis(dimethylsilyl)-m-carborane unit turned out to be equivalent to two dimethylsiloxy units and one half of a diphenylsiloxy unit. The m-carborane unit was found to cause a 15–25 K shift in the elution temperature between 120 and 360 °C. The working range was
from 20 and 0 °C to 380 °C for Dexsil 300 and Dexsil 400, respectively. The column bleeding levels at 380 °C were below 20
and 15 pA for Dexsil 300 and Dexsil 400, respectively. 相似文献
9.
Zhen G Eggli V Vörös J Zammaretti P Textor M Glockshuber R Kuennemann E 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10464-10473
Understanding the conformation, orientation, and specific activity of proteins bound to surfaces is crucial for the development and optimization of highly specific and sensitive biosensors. In this study, the very efficient enzyme beta-lactamase is used as a model protein. The wild-type form was genetically engineered by site-directed mutagenesis to introduce single cysteine residues on the surface of the enzyme. The cysteine thiol group is subsequently biotinylated with a dithiothreitol (DTT)-cleavable biotinylation reagent. beta-Lactamase is then immobilized site-specifically via the biotin group on neutral avidin-covered surfaces with the aim to control the orientation of the enzyme molecule at the surface and study its effect on enzymatic activity using Nitrocefin as the substrate. The DTT-cleavable spacer allows the release of the specifically bound enzyme from the surface. Immobilization of the enzyme is performed on a monolayer of the polycationic, biotinylated polymer PLL-g-PEG/PEG-biotin assembled on niobium oxide (Nb2O5) surfaces via neutral avidin as the docking site. Two different assembly protocols, the sequential adsorption of avidin and biotinylated beta-lactamase and the immobilization of preformed complexes of beta-lactamase and avidin, are compared in terms of immobilization efficiency. In situ optical waveguide lightmode spectroscopy and colorimetric analysis of enzymatic activity were used to distinguish between specific and unspecific enzyme adsorption, to sense quantitatively the amount of immobilized enzyme, and to determine Michaelis-Menten kinetics. All tested enzyme variants turned out to be active upon immobilization at the polymeric surface. However, the efficiency of immobilized enzymes relative to the soluble enzymes was reduced about sevenfold, mainly because of impaired substrate (Nitrocefin) diffusion or restricted accessibility of the active site. No significant effect of different enzyme orientations could be detected, probably because the enzymes were attached to the surface through long, flexible PEG chain linkers. 相似文献