Error Estimates for 1D Asymptotic Models in Coaxial Cables with Non-Homogeneous Cross-Section

This paper is the first contribution towards the rigorous justification of asymptotic 1D models for the time-domain simulation of the propagation of electromagnetic waves in coaxial cables. Our general objective is to derive error estimates between the "exact" solution of the full 3D model and the "approximate" solution of the 1D model known as the Telegraphist's equation.     

Anticlinic-synclinic transitions in superthin free-standing smectic films

Anticlinic-synclinic transition was studied in superthin smectic films using polarized light reflected microscopy. The measurements were made in a compound exhibiting the mC _FI1 ^* subphase in a narrow temperature interval between antiferroelectric C _A ^* and ferroelectric SmC* phases. In films, we observed series of transitions with numbers increasing with increasing film thickness. Surface ordering leads to increasing transition temperatures with decreasing film thickness and to change of orientation of the molecular tilt plane in layers. Succession of transitions results from competition between the surface and the bulk ordering. We found that line string defects may form in a film, their orientation and collective behavior resulting from elastic deformation of molecular ordering.     

Approximate models for wave propagation across thin periodic interfaces

This work deals with the scattering of acoustic waves by a thin ring that contains regularly spaced inhomogeneities. We first explicit and study the asymptotic of the solution with respect to the period and thickness of the inhomogeneities using so-called matched asymptotic expansions. We then build simplified models replacing the thin ring with Approximate Transmission Conditions that are accurate up to third order with respect to the layer width. We pay particular attention to the study of these approximate models and the quantification of their accuracy.     

Cross-phase modulation instability in photonic crystal fibers

We report on the observation of cross-phase modulation instability in a highly nonlinear photonic crystal fiber. In such fibers the presence of higher orders of dispersion results in a complex phase-matching curve. We are able to observe this behavior experimentally and obtain excellent agreement between the measured and predicted shifts.     

On the chaining dynamics of inclusions in SmC* free standing films

A simplified model of an inclusion represented by (+1)-wedge disclination and an accompanying hyperbolic defect ((−1)-wedge disclination) in smectic C* free standing films is used to describe the early stage of the ordering process of inclusions into chains. The elastic interaction between inclusions and their associated hyperbolic defects is used to discuss the dynamics observed experimentally during the inclusion chaining when inclusions are at distances much larger than their radii. This work was also supported by Grant No. 202/02/0840 of the Grant Agency of the Czech Republic and by the research project AV0Z1-010-914.     

Loss of single-molecule-magnet behavior of a Mn12-based compound assembled in a monolayer

Magnetic circular dichroism magnetization measurements on a monolayer of single molecule magnets have been performed and the results are presented. At the measurement temperature (2 K) the hysteresis cycle shows no opening, contrary to what is seen in the bulk with SQUID magnetometry. This result could surprisingly imply that XMCD is unsuited for such measurements given the fact that it excites the core electrons at the origin of the magnetism. This result could also mean that the blocking temperature is greatly decreased or that these molecules loose their hallmark when deposited as adsorbed films, precluding therefore their much sought-after use in magnetic memories.     

Biodegradation study of plasticised corn flour/poly(butylene succinate-co-butylene adipate) blends

Plasticised corn flour/poly(butylene succinate-co-butylene adipate) (PBSA) materials were prepared by extrusion and injection in order to study the impact of PBSA ratio on their physicochemical properties and biodegradability. Scanning electron microscopy observations showed that corn flour and PBSA are incompatible. Three types of morphology have been observed: (i) starch dispersed in a PBSA matrix, (ii) a “co-continuous-like” morphology of starch and PBSA, and (iii) PBSA dispersed in a starch matrix. As expected, the extent of plasticised corn flour starch hydrolysis by amylolytic enzymes decreased when the amount of PBSA increased. Addition of a lipase to hydrolyse PBSA ester bonds enhanced enzymatic hydrolysis of starch by amylolytic enzymes in materials where PBSA formed a continuous phase. This suggests that PBSA formed a barrier restricting the access of amylolytic enzymes to starch. This was consistent with aerobic and anaerobic biodegradation assays, which also showed lower biodegradability of materials containing a majority of PBSA.     

Specific UV photodissociation of tyrosyl-containing peptides in multistage mass spectrometry

UV photodissociation (UVPD) at 262 nm has been carried out on protonated tyrosyl-containing peptides formed by trypsin digestion of apo-transferrin. Under UVPD, the main event is the fragmentation of the C(alpha)-C(beta) bond of the tyrosyl residues leading to a radical ion 107 Da below the precursor ion. The dissociation rate of this specific cleavage appears to be strongly dependent on the peptide sequence and is more prominent on the singly protonated species than on the doubly protonated state. The fragmentation spectra resulting from collisional activation of the protonated even-electron native peptides and of the odd-electron radical species prepared by UVPD are dominated by y-type backbone cleavages. A comparison of their respective y-ion pattern shows complementarities since the combination of both increases the sequence coverage of the peptide sequence. The specific detection of the neutral loss of 107 Da from peptides witnesses the content of at least one tyrosyl residue and, though preliminary, is proposed as a potential new filtering strategy during protein database searching.     

Binding affinity studies of 1,2,3-triazole copper(II) complexes to human serum albumin

Abstract

Two copper(II) complexes with tetradentate 1,4-disubstituted-1,2,3-triazole ligands, [CuL(MeCN)](ClO₄)₂ (1) and [CuL′](ClO₄)₂ (2), have been prepared and characterized by different techniques, including X-ray structure determination, spectroscopic, and electrochemical measurements, as reported elsewhere. Herein, we report the interactions of these complexes, and corresponding free ligands, with human serum albumin (HSA) verifying their relative thermodynamic stability and differences in binding to this protein. Interactions with HSA were verified by CD measurements monitored at 564?nm, up to stoichiometric ratio 2:1 [Complex]:[protein], according to competitive equilibria involving the insertion of copper at the selective N-terminal metal binding site in HSA, and additionally at a secondary nonselective site. Further interactions of these complexes with L-tryptophan residues, and probable supplementary site(s) for the binding, were followed by fluorescence measurements. Analogous experiments with the free L and L′ indicated much weaker interactions. Protein oxidation damage was observed for both complexes, monitored by carbonyl groups formation in the presence of H₂O₂, probably with the participation of reactive oxygen species. Density functional theory calculations exhibit metal-ligand binding interaction energies similar to [Cu(HSA-N_terminal)]⁺, and reinforced the experimental results, showing clearly that such triazole ligands are competitive toward copper(II) in biological medium.     

Numerical simulation of experimental resonance absorption spectra and diffraction of synchrotron radiation in yttrium iron garnet

Extended X-ray absorption fine-structure spectra of yttrium-iron garnet, measured near the absorption edges of iron and yttrium at the Kurchatov synchrotron radiation source are reported. Numerical simulation of the X-ray absorption near-edge structure of these spectra is performed and good agreement with the experimental data is obtained. It is shown theoretically that “forbidden” Bragg reflections can be observed near the absorption edges of iron and yttrium. The indices of these reflections are determined. The energy structure of the “forbidden” reflections 006 and 110 is calculated.