@article{DelgrandeSchaubTompitsetal.2004,
  author    = {Delgrande, James Patrick and Schaub, Torsten and Tompits, Hans and Woltran, Stefan},
  title     = {On Computing belief change operations using quantifield boolean formulas},
  issn      = {0955-792X},
  year      = {2004},
  abstract  = {In this paper, we show how an approach to belief revision and belief contraction can be axiomatized by means of quantified Boolean formulas. Specifically, we consider the approach of belief change scenarios, a general framework that has been introduced for expressing different forms of belief change. The essential idea is that for a belief change scenario (K, R, C), the set of formulas K, representing the knowledge base, is modified so that the sets of formulas R and C are respectively true in, and consistent with the result. By restricting the form of a belief change scenario, one obtains specific belief change operators including belief revision, contraction, update, and merging. For both the general approach and for specific operators, we give a quantified Boolean formula such that satisfying truth assignments to the free variables correspond to belief change extensions in the original approach. Hence, we reduce the problem of determining the results of a belief change operation to that of satisfiability. This approach has several benefits. First, it furnishes an axiomatic specification of belief change with respect to belief change scenarios. This then leads to further insight into the belief change framework. Second, this axiomatization allows us to identify strict complexity bounds for the considered reasoning tasks. Third, we have implemented these different forms of belief change by means of existing solvers for quantified Boolean formulas. As well, it appears that this approach may be straightforwardly applied to other specific approaches to belief change},
  language  = {en}
}
@article{FloeterNicolasSchaubetal.2004,
  author    = {Fl{\"o}ter, Andr{\´e} and Nicolas, Jacques and Schaub, Torsten and Selbig, Joachim},
  title     = {Threshold extraction in metabolite concentration data},
  year      = {2004},
  abstract  = {Motivation: Continued development of analytical techniques based on gas chromatography and mass spectrometry now facilitates the generation of larger sets of metabolite concentration data. An important step towards the understanding of metabolite dynamics is the recognition of stable states where metabolite concentrations exhibit a simple behaviour. Such states can be characterized through the identification of significant thresholds in the concentrations. But general techniques for finding discretization thresholds in continuous data prove to be practically insufficient for detecting states due to the weak conditional dependences in concentration data. Results: We introduce a method of recognizing states in the framework of decision tree induction. It is based upon a global analysis of decision forests where stability and quality are evaluated. It leads to the detection of thresholds that are both comprehensible and robust. Applied to metabolite concentration data, this method has led to the discovery of hidden states in the corresponding variables. Some of these reflect known properties of the biological experiments, and others point to putative new states},
  language  = {en}
}
@article{SarsakovSchaubTompitsetal.2004,
  author    = {Sarsakov, Vladimir and Schaub, Torsten and Tompits, Hans and Woltran, Stefan},
  title     = {A compiler for nested logic programming},
  isbn      = {3-540- 20721-x},
  year      = {2004},
  language  = {en}
}
@article{OskinovaFeldmeierHamann2004,
  author    = {Oskinova, Lidia M. and Feldmeier, Achim and Hamann, Wolf-Rainer},
  title     = {X-ray emission lines from inhomogeneous stellar winds},
  issn      = {0004-6361},
  year      = {2004},
  abstract  = {It is commonly adopted that X-rays from O stars are produced deep inside the stellar wind, and transported outwards through the bulk of the expanding matter which attenuates the radiation and affects the shape of emission line profiles. The ability of the X-ray observatories Chandra and XMM-Newton to resolve these lines spectroscopically provided a stringent test for the theory of the X-ray production. It turned out that none of the existing models was able to fit the observations consistently. The possible caveat of these models was the underlying assumption of a smooth stellar wind. Motivated by the evidence that the stellar winds are in fact structured, we present a 2-D numerical model of a stochastic, inhomogeneous wind. Small parcels of hot, X-ray emitting gas are permeated by cool, absorbing wind material which is compressed into thin shell fragments. Wind fragmentation alters the radiative transfer drastically, compared to homogeneous models of the same mass-loss rate. X-rays produced deep inside the wind, which would be totally absorbed in a homogeneous flow, can effectively escape from a fragmented wind. The wind absorption becomes wavelength independent if the individual fragments are optically thick. The X-ray line profiles are flat-topped in the blue part and decline steeply in the red part for the winds with a short acceleration zone. For the winds where the acceleration extends over significant distances, the lines can appear nearly symmetric and only slightly blueshifted, in contrast to the skewed, triangular line profiles typically obtained from homogeneous wind models of high optical depth. We show that profiles from a fragmented wind model can reproduce the observed line profiles from zeta Orionis. The present numerical modeling confirms the results from a previous study, where we derived analytical formulae from a statistical treatment},
  language  = {en}
}
@article{BrownBarrettOskinovaetal.2004,
  author    = {Brown, John C. and Barrett, R. K. and Oskinova, Lidia M. and Owocki, S. P. and Hamann, Wolf-Rainer and de Jong, J. A. and Kaper, L. and Henrichs, H. F.},
  title     = {Inference of hot star density stream properties from data on rotationally recurrent DACs},
  issn      = {0004-6361},
  year      = {2004},
  abstract  = {The information content of data on rotationally periodic recurrent discrete absorption components (DACs) in hot star wind emission lines is discussed. The data comprise optical depths tau(w,phi) as a function of dimensionless Doppler velocity w=(Deltalambda/lambda(0))(c/v(infinity)) and of time expressed in terms of stellar rotation angle phi. This is used to study the spatial distributions of density, radial and rotational velocities, and ionisation structures of the corotating wind streams to which recurrent DACs are conventionally attributed. The simplifying assumptions made to reduce the degrees of freedom in such structure distribution functions to match those in the DAC data are discussed and the problem then posed in terms of a bivariate relationship between tau(w, phi) and the radial velocity v(r)(r), transverse rotation rate Omega(r) and density rho(r, phi) structures of the streams. The discussion applies to cases where: the streams are equatorial; the system is seen edge on; the ionisation structure is approximated as uniform; the radial and transverse velocities are taken to be functions only of radial distance but the stream density is allowed to vary with azimuth. The last kinematic assumption essentially ignores the dynamical feedback of density on velocity and the relationship of this to fully dynamical models is discussed. The case of narrow streams is first considered, noting the result of Hamann et al. (2001) that the apparent acceleration of a narrow stream DAC is higher than the acceleration of the matter itself, so that the apparent slow acceleration of DACs cannot be attributed to the slowness of stellar rotation. Thus DACs either involve matter which accelerates slower than the general wind flow, or they are formed by structures which are not advected with the matter flow but propagate upstream (such as Abbott waves). It is then shown how, in the kinematic model approximation, the radial speed of the absorbing matter can be found by inversion of the apparent acceleration of the narrow DAC, for a given rotation law. The case of broad streams is more complex but also more informative. The observed tau(w,phi) is governed not only by v(r)(r) and Omega(r) of the absorbing stream matter but also by the density profile across the stream, determined by the azimuthal (phi(0)) distribution function F- 0(phi(0)) of mass loss rate around the stellar equator. When F-0(phi(0)) is fairly wide in phi(0), the acceleration of the DAC peak tau(w, phi) in w is generally slow compared with that of a narrow stream DAC and the information on v(r)(r), Omega(r) and F-0(phi(0)) is convoluted in the data tau(w, phi). We show that it is possible, in this kinematic model, to recover by inversion, complete information on all three distribution functions v(r)(r), Omega(r) and F- 0(phi(0)) from data on tau(w, phi) of sufficiently high precision and resolution since v(r)(r) and Omega(r) occur in combination rather than independently in the equations. This is demonstrated for simulated data, including noise effects, and is discussed in relation to real data and to fully hydrodynamic models},
  language  = {en}
}
@phdthesis{Laubrock2004,
  author    = {Laubrock, Jochen},
  title     = {Proportional slowing in old adults is modulated by episodic memory demands : an investigation of age-related slowing using compatible and arbitrary stimulus-response mappings},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001782},
  school      = {Universit{\"a}t Potsdam},
  year      = {2004},
  abstract  = {Das dominante Datenmuster im Bereich des kognitiven Alterns ist der Alters-x-Komplexit{\"a}tseffekt. Die vorliegende Studie untersucht, ob das Muster statt durch einen {\"u}blicherweise postulierten unspezifischen durch einen spezifischen Mechanismus erkl{\"a}rt werden kann: die mit dem Alter abnehmende Reliabilit{\"a}t episodischer Akkumulatoren. In sechs Reaktionszeit-Experimenten wurden junge und {\"a}ltere Erwachsene verglichen, dabei wurden fr{\"u}he kognitive (Stroop-Bedingung) und episodische Schwierigkeit (Reiz-Reaktions-Zuordnung) orthogonal manipuliert. Die vorhergesagte Dreifachinteraktion der beiden Faktoren mit dem Alter zeigte sich {\"u}ber die Experimente hinweg relativ konsistent. Eine modifizierte Brinley-Analyse ergibt deutlich unterschiedliche Steigungen der Regressionsgeraden im Alt-Jung-Raum f{\"u}r niedrige und hohe episodische Schwierigkeit. Als methodischer Beitrag wird im Anhang ein zur modifizierten Brinley-Analyse passendes Regressionsmodell entwickelt, das aus einigen einfachen Verarbeitungsannahmen folgt. Es wird gezeigt, dass in einer klassischen Brinley Metaanalyse die Steigung neben der theoretisch interessierenden Varianz von theoretisch uninteressanter Zwischen-Experiment-Varianz beeinflusst wird.},
  language  = {en}
}
@article{Oberauer2004,
  author    = {Oberauer, Klaus},
  title     = {Simultaneous execution of two cognitive operations : Evidence from a continuous updating paradigm},
  year      = {2004},
  language  = {en}
}
@article{EgbeKietzkeCarbonnieretal.2004,
  author    = {Egbe, D. A. M. and Kietzke, Thomas and Carbonnier, B. and Muhlbacher, D. and Horhold, H. H. and Neher, Dieter and Pakula, T.},
  title     = {Synthesis, characterization, and photophysical, electrochemical, electroluminescent, and photovoltaic properties of yne-containing CN-PPVs},
  year      = {2004},
  abstract  = {Alkoxy-substituted CN-containing phenylene-vinylene-alt-phenylene-ethynylene hybrid polymers (CN-PPV-PPE), 3a, 3b, and 7a, were obtained from luminophoric dialdehydes 1 by step growth polymerization via Knoevenagel reaction as high molecular-weight materials. Corresponding CN-free polymers 3c and 7b and an ethynylene-free polymer 5 with similar side chains were synthesized for the purpose of comparison. The chemical structures of the polymers were confirmed by IR, H-1 and C-13 NMR, and elemental analysis. Thermal characterization was conducted by means of thermogravimetric analysis and differential scanning calorimetry. Morphology was investigated by means of optical microscopy and small-angle light scattering. The final morphologies are determined by the molecular characteristics (side chains volume fraction, backbone stiffness) of the studied polymers. All the CN-containing polymers 3b, 5, and 7a exhibit higher fluorescence quantum yield in solid state (50 to 60\%), but lower quantum yields (12-40\%) in dilute chloroform solution, in total contrast to CN-free polymers 3c, 3d, and 7b. Identical optical, E-g(opt), and electrochemical band gap energies, E- g(ec), were obtained for 3b, 3c and 3d with intrinsic self-assembly ability, whereas a discrepancy, DeltaE(g), was observed in the cases of the fully substituted polymers 5, 7a, and 7b, whose values are dependent on the level of backbone stiffness and length of the side groups combined with the presence or absence of CN units. The incorporation of CN units in 3b and 7a lowers their respective LUMO level by 220 and 350 meV compared to their corresponding CN-free counterparts 3c and 7b, suggesting an improvement of the electron-accepting strength. Polymers 3b and 7a are efficient electron acceptors suitable for photovoltaic application. The experiments indicate that 3b is a better electron acceptor when used together with M3EH-PPV, but transport properties seem to be better for 7a. With 3b, high external quantum efficiencies of up to 23\%, an open circuit voltage of up to 1.52 V, and a white light energy efficiency of 0.65\% could be realized in bilayer solar cell devices. LED-devices of configuration ITO/PEDOT:PSS/polymer/Ca/Al from 3b, 3c, 7a, and 7b showed low turn-on voltages between 2 and 2.5 V. The CN-free polymers 3c and 7b exhibit far better EL parameters than their corresponding CN containing counterparts 3b and 7a},
  language  = {en}
}
@article{KietzkeNeherKumkeetal.2004,
  author    = {Kietzke, Thomas and Neher, Dieter and Kumke, Michael Uwe and Montenegro, Rivelino V. D. and Landfester, Katharina and Scherf, Ullrich},
  title     = {A nanoparticle approach to control the phase separation in polyfluorene photovoltaic devices},
  year      = {2004},
  abstract  = {Polymer solar cell devices with nanostructured blend layers have been fabricated using single- and dual- component polymer nanospheres. Starting from an electron-donating and an electron-accepting polyfluorene derivative, PFB and F8BT, dissolved in suitable organic solvents, dispersions of solid particles with mean diameters of ca. 50 nm, containing either the pure polymer components or a mixture of PFB and F8BT in each particle, were prepared with the miniemulsion process. Photovoltaic devices based on these particles have been studied with respect to the correlation between external quantum efficiency and layer composition. It is shown that the properties of devices containing a blend of single-component PFB and F8BT particles differ significantly from those of solar cells based on blend particles, even for the same layer composition. Various factors determining the quantum efficiency in both kinds of devices are identified and discussed, taking into account the spectroscopic properties of the particles. An external quantum efficiency of ca. 4\% is measured for a device made from polymer blend nanoparticles containing PFB:F8BT at a weight ratio of 1:2 in each individual nanosphere. This is among the highest values reported so far for photovoltaic cells using this material combination},
  language  = {en}
}
@article{BagnichBasslerNeher2004,
  author    = {Bagnich, Sergey A. and Bassler, H. and Neher, Dieter},
  title     = {Sensitized phosphorescence of benzil-doped ladder-type methyl-poly(para-phenylene)},
  issn      = {0021-9606},
  year      = {2004},
  abstract  = {The delayed luminescence and phosphorescence of ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with benzil at a concentration of 20\% by weight has been measured. The introduction of benzil leads to a dramatic reduction of the polymer singlet emission. At the same time, a new band with maximum at 611 nm appears, corresponding to the phosphorescence of MeLPPP. The phosphorescence decay on the short time scale is close to an exponential law with a time decay of 15 ms. This indicates that benzil can efficiently sensitize the phosphorescence of the polymer. In addition, a broad and featureless emission is observed in the delayed luminescence spectra of benzil-doped MeLPPP, which is attributed to an exciplex formed between the polymer host and the dopant. We further observe that the delayed fluorescence is enhanced by the addition of benzil. It is concluded that the delayed fluorescence of benzil-doped MeLPPP is mainly due to the annihilation of triplet excitons on the polymer. Finally, efficient triplet-triplet energy transfer from the benzil-doped polymer to the red-emitting phosphorescent dye Pt(II)octaethylporphyrin is established. (C) 2004 American Institute of Physics},
  language  = {en}
}
@article{KulikovskyNeherMecheretal.2004,
  author    = {Kulikovsky, Lazar and Neher, Dieter and Mecher, E. and Meerholz, Klaus and Horhold, H. H. and Ostroverkhova, O.},
  title     = {Photocurrent dynamics in a poly(phenylene vinylene)-based photorefractive composite},
  issn      = {1098-0121},
  year      = {2004},
  abstract  = {All parameters describing the charge carrier dynamics in a poly(phenylene vinylene)-based photorefractive (PR) composite relevant to PR grating dynamics were determined using photoconductivity studies under various illumination conditions. In particular, the values of the coefficients for trap filling and recombination of charges with ionized sensitizer molecules could be extracted independently. It is concluded that the PR growth time without preillumination is mostly determined by the competition between deep trap filling and recombination with ionized sensitizer molecules. Further, the pronounced increase in PR speed upon homogeneous preillumination (gating) as reported recently is quantitatively explained by deep trap filling},
  language  = {en}
}
@article{BommerAbrahamsonStrasseretal.2004,
  author    = {Bommer, Julian J. and Abrahamson, Norman A. and Strasser, F. O. and Pecker, Alain and Bard, Pierre-Yves and Bungum, Hilmar and Cotton, Fabrice and F{\"a}h, Donat and Sabetta, F. and Scherbaum, Frank and Studer, Jost},
  title     = {The challenge of defining upper bounds on earthquake ground motions},
  issn      = {0895-0695},
  year      = {2004},
  language  = {en}
}
@article{ZentelBehlNeheretal.2004,
  author    = {Zentel, Rudolf and Behl, Marc and Neher, Dieter and Zen, Achmad and Lucht, Sylvia},
  title     = {Nanostructured polytriarylamines : orientation layers for polyfluorene},
  issn      = {0065-7727},
  year      = {2004},
  language  = {en}
}
@article{ScherbaumCottonSmit2004,
  author    = {Scherbaum, Frank and Cotton, Fabrice and Smit, P.},
  title     = {On the use of response spectral-reference data for the selection and ranking of ground-motion models for seismic-hazard analysis in regions of moderate seismicity : the case of rock motion},
  issn      = {0037-1106},
  year      = {2004},
  abstract  = {The use of ground-motion-prediction equations to estimate ground shaking has become a very popular approach for seismic-hazard assessment, especially in the framework of a logic-tree approach. Owing to the large number of existing published ground-motion models, however, the selection and ranking of appropriate models for a particular target area often pose serious practical problems. Here we show how observed around-motion records can help to guide this process in a systematic and comprehensible way. A key element in this context is a new, likelihood based, goodness-of-fit measure that has the property not only to quantify the model fit but also to measure in some degree how well the underlying statistical model assumptions are met. By design, this measure naturally scales between 0 and 1, with a value of 0.5 for a situation in which the model perfectly matches the sample distribution both in terms of mean and standard deviation. We have used it in combination with other goodness-of-fit measures to derive a simple classification scheme to quantify how well a candidate ground-rnotion-prediction equation models a particular set of observed-response spectra. This scheme is demonstrated to perform well in recognizing a number of popular ground-motion models from their rock-site- recording, subsets. This indicates its potential for aiding the assignment of logic-tree weights in a consistent and reproducible way. We have applied our scheme to the border region of France, Germany, and Switzerland where the M-w 4.8 St. Die earthquake of 22 February 2003 in eastern France recently provided a small set of observed-response spectra. These records are best modeled by the ground-motion-prediction equation of Berge-Thierry et al. (2003), which is based on the analysis of predominantly European data. The fact that the Swiss model of Bay et al. (2003) is not able to model the observed records in an acceptable way may indicate general problems arising from the use of weak-motion data for strong-motion prediction},
  language  = {en}
}
@article{ScherbaumSchmedesCotton2004,
  author    = {Scherbaum, Frank and Schmedes, J. and Cotton, Fabrice},
  title     = {On the conversion of source-to-site distance measures for extended earthquake source models},
  issn      = {0037-1106},
  year      = {2004},
  abstract  = {One of the major challenges in engineering seismology is the reliable prediction of site-specific ground motion for particular earthquakes, observed at specific distances. For larger events, a special problem arises, at short distances, with the source-to-site distance measure, because distance metrics based on a point-source model are no longer appropriate. As a consequence, different attenuation relations differ in the distance metric that they use. In addition to being a source of confusion, this causes problems to quantitatively compare or combine different ground- motion models; for example, in the context of Probabilistic Seismic Hazard Assessment, in cases where ground-motion models with different distance metrics occupy neighboring branches of a logic tree. In such a situation, very crude assumptions about source sizes and orientations often have to be used to be able to derive an estimate of the particular metric required. Even if this solves the problem of providing a number to put into the attenuation relation, a serious problem remains. When converting distance measures, the corresponding uncertainties map onto the estimated ground motions according to the laws of error propagation. To make matters worse, conversion of distance metrics can cause the uncertainties of the adapted ground-motion model to become magnitude and distance dependent, even if they are not in the original relation. To be able to treat this problem quantitatively, the variability increase caused by the distance metric conversion has to be quantified. For this purpose, we have used well established scaling laws to determine explicit distance conversion relations using regression analysis on simulated data. We demonstrate that, for all practical purposes, most popular distance metrics can be related to the Joyner-Boore distance using models based on gamma distributions to express the shape of some "residual function." The functional forms are magnitude and distance dependent and are expressed as polynomials. We compare the performance of these relations with manually derived individual distance estimates for the Landers, the Imperial Valley, and the Chi-Chi earthquakes},
  language  = {en}
}
@article{StillerKarageorgievGeueetal.2004,
  author    = {Stiller, Burkhard and Karageorgiev, Peter and Geue, Thomas and Morawetz, Knut and Saphiannikova, Marina and Mechau, Norman and Neher, Dieter},
  title     = {Optically induced mass transport studied by scanning near-field optical- and atomic force microscopy},
  issn      = {0204-3467},
  year      = {2004},
  abstract  = {Some functionalised thin organic films show a very unusual property, namely the light induced material transport. This effect enables to generate three-dimensional structures on surfaces of azobenzene containing films only caused by special optical excitation. The physical mechanisms underlying this phenomenon have not yet been fully understood, and in addition, the dimensions of structures created in that way are macroscopic because of the optical techniques and the wavelength of the used light. In order to gain deeper insight into the physical fundamentals of this phenomenon and to open possibilities for applications it is necessary to create and study structures not only in a macroscopic but also in nanometer range. We first report about experiments to generate optically induced nano structures even down to 100 nm size. The optical stimulation was therefore made by a Scanning Near-field Optical Microscope (SNOM). Secondly, physical conditions inside optically generated surface relief gratings were studied by measuring mechanical properties with high lateral resolution via pulse force mode and force distance curves of an AFM},
  language  = {en}
}
@article{YangNeher2004,
  author    = {Yang, X. H. and Neher, Dieter},
  title     = {Polymer electrophosphorescence devices with high power conversion efficiencies},
  issn      = {0003-6951},
  year      = {2004},
  abstract  = {We demonstrate efficient single-layer polymer phosphorescent light-emitting devices based on a green-emitting iridium complex and a polymer host co-doped with electron-transporting and hole-transporting molecules. These devices can be operated at relatively low voltages, resulting in a power conversion efficiency of up to 24 lm/W at luminous efficiencies exceeding 30 cd/A. The overall performances of these devices suggest that efficient electrophosphorescent devices with acceptable operating voltages can be achieved in very simple device structures fabricated by spin coating. (C) 2004 American Institute of Physics},
  language  = {en}
}
@article{YangNeherHerteletal.2004,
  author    = {Yang, X. H. and Neher, Dieter and Hertel, D. and Daubler, T. K.},
  title     = {Highly efficient single-layer polymer electrophosphorescent devices},
  issn      = {0935-9648},
  year      = {2004},
  abstract  = {A commercially available Ir complex has been employed for the preparation of highly efficient (see Figure) single-layer phosphorescent polymer light,emitting diodes by use of appropriate thermal treatment and proper adjustment of the layer composition. These devices exhibit essentially no dependence of the driving field on the concentration of the Ir complex, suggesting that the build-up of space-charge in the layer is insignificant},
  language  = {en}
}
@article{HeydenreichKochKovacsetal.2004,
  author    = {Heydenreich, Matthias and Koch, Andreas and Kovacs, J. and Toth, G. and Kleinpeter, Erich},
  title     = {Electronic influences on (3)J(C,H) coupling constants via -S-, -S(O)- and -SO2--: their determination, calculation and comparison of detection methods},
  issn      = {0749-1581},
  year      = {2004},
  abstract  = {(3)J(C,H) coupling constants via a sulfur atom in two series of compounds, both including a sulfide, a sulfoxide and a sulfone, were detected experimentally and calculated by quantum mechanical methods. In the first series (1-3) the coupling between a hydrogen, bonded to an Sp(3) carbon, and an Sp(2) carbon is treated; the second series (4- 6) deals with the coupling between a hydrogen, bonded to an Sp3 carbon, and an Sp3 carbon. Different pulse sequences (broadband HMBC, SelJres, 1D HSQMBC, J-HMBC-2, selective J-resolved long-range experiment and IMPEACH-MBC) proved to be useful in determining the long-range (3)J(C,H) coupling constants. However, the dynamic behaviour of two of the compounds (4 and 6) led to weighted averages of the two coupling constants expected (concerning equatorial and axial positions of the corresponding hydrogens). DFT calculations proved to be useful to calculate not only the (3)J(C,H) coupling constants but also the different contributions of FC, PSO, DSO and SD terms; the calculation of the Fermi contact term (FC) was found to be sufficient for the correct estimation of (3)J(C,H) coupling constants. Copyright (C) 2004 John Wiley Sons, Ltd},
  language  = {en}
}
@article{HeydenreichWolfWolleretal.2004,
  author    = {Heydenreich, Matthias and Wolf, G. and Woller, Jochen and Kleinpeter, Erich},
  title     = {Restricted rotation of the amino group and ring inversion in highly substituted anilines. A dynamic NMR and computational study},
  issn      = {0040-4020},
  year      = {2004},
  abstract  = {The reaction of cyclic ylidene malononitriles with acetylene (di)carboxylic acid esters led to the production of nine bicyclic systems incorporating highly substituted (5/6) anilines. The free energy of activation (DeltaG(\#)) for the restricted rotation about the aniline-NH2 bond was experimentally measured in each case and a correlation was evident between the increase in steric strain in the ground state, the electron withdrawing capabilities of the ring substituents, and a reduction in the rotational barrier. For four of the compounds, the slow ring interconversion (chairreversible arrowchair) for the annelated saturated seven-membered ring that formed part of the bicyclic system was also evident. In these four compounds, both dynamic processes were also studied theoretically using ab initio methods whilst the ring interconversion was additionally studied using molecular dynamic simulations. The interconversion between the two stable chair forms was deemed to occur via a conformation series consisting of chairreversible arrowboatreversible arrowtwist-boatreversible arrowboatreversible arrowchair. (C) 2004 Elsevier Ltd. All rights reserved},
  language  = {en}
}