Deeply penetrating waves in lossy media

The incidence of an inhomogeneous plane wave on the interface between two lossy media is analyzed. The analytical expressions of the incidence angle of the phase vector, for which the transmitted wave has the phase or the attenuation vector parallel to the interface, are obtained. The transmitted wave with the attenuation vector parallel to the interface is physically interpreted, finding a wave in a lossy medium without attenuation away from the interface. The same effect appears at the interface between a lossless medium and a lossy one.     

The role of communication and imitation in limit order markets

In this paper we develop an order driver market model with heterogeneous traders that imitate each other on different network structures. We assess how imitations among otherway noise traders, can give rise to well known stylized facts such as fat tails and volatility clustering. We examine the impact of communication and imitation on the statistical properties of prices and order flows when changing the networks’ structure, and show that the imitation of a given, fixed agent, called “guru", can generate clustering of volatility in the model. We also find a positive correlation between volatility and bid-ask spread, and between fat-tailed fluctuations in asset prices and gap sizes in the order book.     

Facile and purification free synthesis of peptides utilizing ROMPgel- and ROMPsphere-supported coupling reagents

5-Norbornene-2-carboxaldehyde and norbornadiene were respectively converted into norbornene derivatives functionalized with fluoroformamidinium hexafluorophosphate and 2-bromo-N-methylpyridinium tetrafluoroborate residues. Both these norbornene monomers were ring opening metathesis polymerized or graft copolymerized onto polystyrene cores to produce ROMPgel and ROMPsphere peptide-coupling reagents. These were used to prepare hindered amides, dipeptides and tripeptides with minimal purification in parallel arrays.     

Quantum chemistry-based interpretations on the lowest triplet state of luminescent lanthanides complexes. Part 1. Relation between the triplet state energy of hydroxamate complexes and their luminescence properties

In this paper, we evaluate the potential use of theoretical calculations to obtain an energy scale of the lowest ligand-centred triplet excited state in luminescent terbium(III) complexes. In these complexes, non-radiative deactivation of the terbium emitting state via a back-energy transfer process (T1<--Tb(5D4)) is a common quenching process. Consequently the prediction of the energy gap between these two excited states should be useful for programming highly luminescent Tb(III) systems. We report on a strategy based upon experimental and theoretical investigations of the excited state properties of a series of four simple aromatic hydroxamate ligands coordinated to Tb(III) and Gd(III) ions. By using previously reported crystallographic data, the structural and energies properties of these systems were investigated in the ground and first excited triplet states at the density functional theory (DFT) level of calculations. Our theoretical results are consistent with a triplet excited state T1 which is localised on one ligand only and whose the energy level is independent of the lanthanide ion nature (Tb(III), Gd(III)). A good agreement between the calculated adiabatic transition energies and experimental data derived from emission spectra is obtained when a corrective term is considered. These satisfactory results are an indication that this type of modelling can lead to discriminate in terms of the position of the lowest ligand triplet energy level the best antenna among a family of chromophoric compounds. In addition this theoretical approach has provided indications that the difference between the adiabatic transition energies of all the investigated complexes can be mainly explained by metal-ligand electrostatic interactions. The influence of the number of antennae on the quantum yield and the luminescence lifetime is discussed.     

Synthesis of new chiral PNAs bearing a dipeptide-mimic monomer with two lysine-derived stereogenic centres

The synthesis of new chiral PNA analogues based on lysine is reported. In particular, l- and/or d-lysine-based PNA submonomers bearing two lysine side chains exactly spaced as in the dipeptide Lys-Lys were synthesized and incorporated in the middle of decameric PNA strands, obtaining four diastereomeric (LD, DL, LL and DD) lysine-based chiral PNAs. The hybridization with their complementary antiparallel DNA strand was studied by melting temperature determination and compared with the analogue achiral PNA and chiral PNAs bearing one residue with either of the two lysine enantiomers. The binding abilities were shown to be strongly dependent on the configuration of the stereogenic centres.     

Gas chromatography/mass spectrometry determination of amphetamine-related drugs and ephedrines in plasma, urine and hair samples after derivatization with 2,2,2-trichloroethyl chloroformate

A new analytical approach, based on derivatization with 2,2,2-trichloroethyl chloroformate and gas chromatography/mass spectrometry (GC/MS), was investigated for qualitative and quantitative analyses of a large range of amphetamine-related drugs and ephedrines in plasma, urine and hair samples. Sample preparation involved alkaline extraction of analytes from biological samples using Extrelut columns, after addition of the internal standard 3,4-methylenedioxypropylamphetamine (MDPA), and subsequent derivatization to produce 2,2,2-trichloroethylcarbamates. GC/MS analyses, in splitless mode using a slightly polar 30-m capillary column, were performed with quadrupole or ion trap instruments. MS acquisition modes were electron ionization (EI) in full-scan or selected ion monitoring (SIM) modes (quadrupole), and full-scan MS or MS/MS modes with chemical ionization (CI) conditions (ion trap). EI spectra of 2,2,2-trichloroethylcarbamates showed variably abundant molecular ions as well as abundant diagnostic fragment ions, both characterized by ion clusters reflecting the isotope distribution of three chlorine atoms in the derivatized molecules. CI spectra showed abundant protonated molecules. Quantitative studies using EI SIM conditions gave recoveries in the range 74-89%, linear response over ranges of 10-2000 ng/mL (plasma and urine) and 0.20-20 ng/mg (hair), with corresponding limits of detection in the ranges 2-5 ng/mL and 0.1-0.2 ng/mg. Potential applications (following full method validation) include clinical and forensic toxicology, as well as doping control.     

1-Aminopyrazolin-5-ones. Synthesis and reactivity

A synthesis of 1-aminopyrazolin-5-ones (I) by chloramine attack on the 2-benzylpyrazolones (IVd-e) has been accomplished. Nucleophilic substitution reactions of aminopyrazolones (I) are investigated; with 1,4-diketones, N,N'-pyrrolylpyrazolones (XVIIa-c) are obtained. Chlorination of acetylaminopyrazolones (VII) led to the corresponding 1-amino-5-chloropyrazoles (XXI) via the isolable pyrazolo[3,2-b]oxadiazoles (XIX).     

Rearrangements of 5-isoxazolylhydrazines: 1-amino- and 4-aminopyrazolin-5-ones

5-Isoxazolylhydrazines rearranged to 1-aminopyrazolin-5-ones on heating. Under the same conditions, 5-(3-methyl-4-phenylisoxazolyl)hydrazine also gave 3-methyl-4-amino-4-phenylpyra-zolin-5-one. The structures of aminopyrazolones were assigned on the basis of spectroscopic properties and chemical behavior.