Masking misfit in confirmatory factor analysis by increasing unique variances: A cautionary note on the usefulness of cutoff values of fit indices.

Fit indices are widely used in order to test the model fit for structural equation models. In a highly influential study, Hu and Bentler (1999) showed that certain cutoff values for these indices could be derived, which, over time, has led to the reification of these suggested thresholds as “golden rules” for establishing the fit or other aspects of structural equation models. The current study shows how differences in unique variances influence the value of the global chi-square model test and the most commonly used fit indices: Root-mean-square error of approximation, standardized root-mean-square residual, and the comparative fit index. Using data simulation, the authors illustrate how the value of the chi-square test, the root-mean-square error of approximation, and the standardized root-mean-square residual are decreased when unique variances are increased although model misspecification is present. For a broader understanding of the phenomenon, the authors used different sample sizes, number of observed variables per factor, and types of misspecification. A theoretical explanation is provided, and implications for the application of structural equation modeling are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Modular Palladium Bipyrazoles for the Isomerization of Allylbenzenes – Mechanistic Considerations and Insights into Catalyst Design and Activity,Role of Solvent,and Additive Effects

The catalytic activity of novel bidentate N,N‐chelated palladium complexes derived from electron excessive, backbone fused 3,3′‐bipyrazoles in the selective isomerization of terminal arylpropenoids and 1‐alkenes is described. The catalysts are easily modified by appropriate wing tip substitution, while maintaining the same bulky, rigid unreactive aliphatic backbone. Eleven novel palladium complexes with different electronic and steric properties were investigated. Their performance in the palladium(II)‐catalyzed isomerization of a series of substituted allylbenzenes was evaluated in terms of electronic as well as steric effects. Besides the clear finding of a general trend towards higher catalyst activity with more electron‐donating properties of the coordinated N,N‐bidentate ligands, we found that the catalytic process strongly depends on the choice of solvents and additives. Extensive solvent screening revealed that reactions run best in a 2:1 toluene‐methanol mixture, with the alcohol employed being a crucial factor in terms of electronic and steric factors. A reaction mechanism involving a hydride addition–elimination mechanism starting with a palladium hydride species generated in situ in alcoholic solutions, as corroborated by experiments using deuterium labeled allylbenzene, seems to be most likely. The proposed mechanism is also supported by the observed reaction rate orders of κ_obs[cat.]≈1 (0.94), κ_obs [substrate]=0.20→1.0 (t→∞) and κ_obs [methanol]=−0.51 for the isomerization of allylbenzene. Furthermore, the influence of acid and base, as well as the role of the halide coordinated to the catalyst, are discussed. The system catalyzes the isomerization of allylbenzenes very efficiently yielding high E:Z selectivities under very mild conditions (room temperature) and at low catalyst loadings of 1 mol% palladium even in unpurified solvents. The integrity and stability of the catalyst system were confirmed by multiple addition reaction cycles, successive filtration and isolation experiments, and the lack of palladium black formation.     

Controlled radical polymerization of N,N-dimethylaminoethyl methacrylate using triazolinyl as counter radical

Summary The role of the triazolinyl radical as additive for controlled radical polymerisation is investigated for N,N-dimethylaminoethyl methacrylate (DMAEMA) as polar monomer. A linear increase of the molecular weight with conversion and first-order kinetics are observed proving the controlled behaviour of the polymerization. The end-functionalisation of the obtained polymers was proven by both GPC und UV-spectroscopy. Furthermore, various amphiphilic block copolymers were obtained by chain extension with styrene, methyl methacrylate and ethyl methacrylate. In all cases monomodal GPC curves were obtained indicating an almost quantitative reinitiation.     

Carborane Analogues of Fenoprofen Exhibit Improved Antitumor Activity

Fenoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) against rheumatoid arthritis, degenerative joint disease, ankylosing spondylitis and gout. Like other NSAIDs, fenoprofen inhibits the synthesis of prostaglandins by blocking both cyclooxygenase (COX) isoforms, COX-1 the “house-keeping” enzyme and COX-2 the induced isoform from pathological stimuli. Unselective inhibition of both COX isoforms results in many side effects, but off-target effects have also been reported. The steric modifications of the drugs could afford the desired COX-2 selectivity. Furthermore, NSAIDs have shown promising cytotoxic properties. The structural modification of fenoprofen using bulky dicarba-closo-dodecaborane(12) (carborane) clusters and the biological evaluation of the carborane analogues for COX inhibition and antitumor potential showed that the carborane analogues exhibit stronger antitumor potential compared to their respective aryl-based compounds.     

Technische und wirtschaftliche Prüfung eines zweiten Tagaufschlusses der Reviere V & VI (VII) des Bergbaues Breitenau

As a master thesis the possibilities of an additional access to the lower regions of the magnesite mine of Breitenau, Styria, Austria, were evaluated. After identifying and determining all the required parameters, the various types of openings to access a mineral deposit and their combinations were prepared and their advantages and disadvantages as well as the applicability examined. Transport systems for the respective variants of access were developed and economic considerations about construction costs and running costs were made. Furthermore, changes in safety and mine winding were assessed. The aim of this work was to identify the best type of opening in terms of investment, running costs and safety.     

Thermodynamic real gas analysis of a tank filling process

A zero-dimensional thermodynamic real gas simulation model for a tank filling process with hydrogen is presented in this paper. Ideal gas and real gas simulations are compared and the entropy balance of the filling process is formulated. Calculated results are validated for a type I tank (steel vessel) with measurements.