On the classification of all self-dual additive codes over GF(4) of length up to 12

We consider additive codes over GF(4) that are self-dual with respect to the Hermitian trace inner product. Such codes have a well-known interpretation as quantum codes and correspond to isotropic systems. It has also been shown that these codes can be represented as graphs, and that two codes are equivalent if and only if the corresponding graphs are equivalent with respect to local complementation and graph isomorphism. We use these facts to classify all codes of length up to 12, where previously only all codes of length up to 9 were known. We also classify all extremal Type II codes of length 14. Finally, we find that the smallest Type I and Type II codes with trivial automorphism group have length 9 and 12, respectively.     

Oxidative addition transition states of Pd(0) complexes in polar solvent—a DFT study involving implicit and explicit solvation

Previous reports in the literature have suggested that concerted transition states for oxidative addition would not exist in solution. By contrast, this report describes the successful location of transition states for the oxidative addition of monoligated Pd(P^tBu₃), bisligated Pd(P^tBu₃)(MeCN), and anionic Pd(P^tBu₃)F^? complexes to C–Cl and C–OTf of an aryl chloro triflate in polar solvent (MeCN). Optimizations were done with implicit solvation and a combined implicit/explicit solvation approach in which six acetonitrile molecules were additionally involved in the optimization. The geometries obtained from optimizations employing an implicit solvation model are structurally largely analogous to those found using a combination of implicit and explicit solvation.     

3D ultrasound reconstruction algorithms from analog and digital data

Freehand 3D ultrasound is increasingly being introduced in the clinic for diagnostics and image-assisted interventions. Various algorithms exist for combining 2D images of regular ultrasound probes to 3D volumes, being either voxel-, pixel- or function-based. Previously, the most commonly used input to 3D ultrasound reconstruction has been digitized analog video. However, recent scanners that offer access to digital image frames exist, either as processed or unprocessed data. To our knowledge, no comparison has been performed to determine which data source gives the best reconstruction quality. In the present study we compared both reconstruction algorithms and data sources using novel comparison methods for detecting potential differences in image quality of the reconstructed volumes. The ultrasound scanner used in this study was the Sonix RP from Ultrasonix Medical Corp (Richmond, Canada), a scanner that allow third party access to unprocessed and processed digital data. The ultrasound probe used was the L14-5/38 linear probe. The assessment is based on a number of image criteria: detectability of wire targets, spatial resolution, detectability of small barely visible structures, subjective tissue image quality, and volume geometry. In addition we have also performed the more “traditional” comparison of reconstructed volumes by removing a percentage of the input data. By using these evaluation methods and data from the specific scanner, the results showed that the processed video performed better than the digital scan-line data, digital video being better than analog video. Furthermore, the results showed that the choice of video source was more important than the choice of tested reconstruction algorithms.     

1H,13C and 19F NMR data of N‐substituted 6‐(4‐methoxyphenyl)‐7H‐pyrrolo[2,3‐d]pyrimidin‐4‐amines in DMSO‐d6

Chemical shift assignment of seven N‐substituted 6‐(4‐methoxyphenyl)‐7H‐pyrrolo[2, 3‐d]pyrimidin‐4‐amines, six of which are fluorinated, have been performed based on ¹H, ¹³C, ¹⁹F, and 2D COSY, HMBC and HSQC experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

Response probability density functions of strongly non-linear systems by the path integration method

The paper discusses challenges in numerical analysis and numerical/analytical results for strongly non-linear systems—systems with “signum”-type non-linearities. Such non-linearities are implemented for instantaneous variations of the systems’ parameters, to reduce their mean energy response when subjected to random excitations. Numerical results for displacement and velocity response probability density functions (PDFs), energy response PDFs and various order moments are obtained by the path integration technique. Attention is also given to evaluation of mean upcrossing rate, related to the system's half period, via Rice's formula informally applied to discontinuous response PDFs.     

Comparison of quantum mechanical and experimental gas-phase basicities of amines and alcohols

A comparison was made between the experimental and B3LYP relative gas-phase basicities and proton affinities of a series of 9 amine, 3 alcohol, and 3 alkanolamine molecules. While agreement is good for most of the species studied, it is poor for the alkanolamines and 1,2-ethanediol. A series of calculations were undertaken at the B3LYP and MP2 levels using various basis sets to see if the uncertainties in the calculations can account for the discrepancies. The results suggest that this is unlikely and that the theoretical values are likely to be reasonably accurate. Calculations are also presented for the dimer formation energies of alkanolamine molecules, diamine molecules, and 1,2-ethanediol. These calculations suggest that all of these species can form proton-bound dimers. The alkanolamines and 1,2-ethanediol also appear to have relatively high formation energies for neutral dimers.     

Two-photon absorption of [2.2]paracyclophane derivatives in solution: a theoretical investigation

The two-photon absorption of a class of [2.2]paracyclophane derivatives has been studied using quadratic response and density functional theories. For the molecules investigated, several effects influencing the two-photon absorption spectra have been investigated, such as side-chain elongation, hydrogen bonding, the use of ionic species, and solvent effects, the latter described by the polarizable continuum model. The calculations have been carried out using a recent parallel implementation of the polarizable continuum model in the DALTON code. Special attention is given to those aspects that could explain the large solvent effect on the two-photon absorption cross sections observed experimentally for this class of compounds.     

Molecular dynamics study of ethanolamine as a pure liquid and in aqueous solution

Molecular dynamics simulations have been carried out for ethanolamine as a pure liquid and in aqueous solution at 298 and 333 K. The ethanolamine force field has been parametrized to reproduce intramolecular energies from quantum mechanical calculations and experimentally determined properties of the liquid. The results are presented for conformer distributions, density, enthalpy of vaporization, self-diffusion constant, dielectric constant, and radial distribution functions. The results strongly suggest that the main (O-C-C-N) dihedral tends to stay in its gauche conformers in solution and that the ethanolamine molecules populate conformers with a significant degree of intramolecular hydrogen bonding. This result is also supported by results from a continuum solvation model. Simulation of a 10 mol % aqueous ethanolamine system suggests that ethanolamine is preferentially solvated to by water molecules. The results suggest that ethanolamine dimer formation in aqueous solution is very limited. Simulations were also carried out for CO2 in an aqueous ethanolamine system. The results suggest that CO2 has a comparable level of attraction to ethanolamine and water. The degree of interaction between CO2 and the amine and alcohol functionalities in ethanolamine also appear to be of comparable strength.     

Chiral derivatives of Butenafine and Terbinafine: synthesis and antifungal activity

Two series of allylamines/benzylamines have been synthesised and evaluated for their antifungal activity towards Cryptococcus neoformans. All compounds are chiral derivatives of Butenafine and Terbinafine, having additional substituents at the carbon connected to the central nitrogen atom. In both series, the antifungal activity was strongly dependent on both the steric bulk and the electronic nature of the substituents. Compared to the parent compounds (Butenafine and Terbinafine), the activity was maintained when the hydrogen was replaced with a methyl group. Lower activity was observed for ethyl, whereas introduction of -CH₂F, -CHF₂, -CF₃ or -CN substituents removed all antifungal activity. Testing of (R)- and (S)-N-(4-tert-butylbenzyl)-N-methyl-1-(naphthalen-1-yl)ethanamine against C. neoformans, Cryptococcus diffluens and Trichosporon cutaneum revealed that most of the activity resides in the (R)-enantiomer. The (R)-enantiomer performed as well as, or better (lower MIC values) than Butenafine against each test strain, suggesting that antimycotics based on this compound might be an improvement of existing Butenafine-based formulations.     

Microwave assisted fluorination: an improved method for side chain fluorination of substituted 1-arylethanones

A two-step, one-pot microwave (MW) assisted fluorination of 1-arylethanones to their corresponding 1-aryl-2-fluoroethanones has been developed. The first step utilises Selectfluor™ as a fluorinating agent in methanol forming 1-aryl-2-fluoroethanones and their corresponding dimethyl acetals. In the second step, water is added and Selectfluor™ acts as a Lewis acid in the hydrolytic cleavage of the dimethyl acetals. Compared to the thermal synthesis, the MW assisted method leads to a reduction in reaction time both in the fluorination and for the dimethyl acetal cleavage. Moreover, the one-pot procedure reduces reagent and solvent consumption. The method is best suited for the preparation of 1-aryl-2-fluoroethanones containing substituents that deactivates electrophilic aromatic substitution, however highly electron deficient ketones such as 1-(3,5-dinitrophenyl)ethanone reacts more slowly. Reactions using electron rich aromatic ketones had a low regioselectivity, and also produced fluoroaromatic products.