Recent advances in amino acid analysis by capillary electrophoresis

This paper describes a number of articles that have been published on amino acid analysis using CE during the period from June 2003 to May 2005. This review article follows the previous ones of Smith (Electrophoresis 1999, 20, 3078-3083), Prata et al. (Electrophoresis 2001, 22, 4129-4138), and Poinsot et al. (Electrophoresis 2003, 24, 4047-4062). Several new developments in amino acid analysis with CE are reported concerning UV detection, LIF, MS, and NMR. In addition, we describe articles concerning clinical and pharmaceutical studies, neuroclinical applications, and agricultural and food analysis.     

Comparative theoretical analysis of continuous wave laser cutting of metals at 1 and 10 μm wavelength

We present a derivation and, based on it, an extension of a model originally proposed by V.G. Niziev to describe continuous wave laser cutting of metals. Starting from a local energy balance and by incorporating heat removal through heat conduction to the bulk material, we find a differential equation for the cutting profile. This equation is solved numerically and yields, besides the cutting profiles, the maximum cutting speed, the absorptivity profiles, and other relevant quantities. Our main goal is to demonstrate the model’s capability to explain some of the experimentally observed differences between laser cutting at around 1 and 10 μm wavelengths. To compare our numerical results to experimental observations, we perform simulations for exactly the same material and laser beam parameters as those used in a recent comparative experimental study. Generally, we find good agreement between theoretical and experimental results and show that the main differences between laser cutting with 1- and 10-μm beams arise from the different absorptivity profiles and absorbed intensities. Especially the latter suggests that the energy transfer, and thus the laser cutting process, is more efficient in the case of laser cutting with 1-μm beams.     

Pulse shaper assisted short laser pulse characterization

We demonstrate that a pulse shaper is able to simultaneously act as an optical waveform generator and a short pulse characterization device when combined with an appropriate nonlinear element. We present autocorrelation measurements and their frequency resolved counterparts. We show that control over the carrier envelope phase allows continuous tuning between an intensity-like and an interferometric autocorrelation. By changing the transfer function other measurement techniques, for example STRUT, are easily realized without any modification of the optical setup. PACS 42.65.Re; 42.30.Lr; 42.30.Rx     

New lasers based on c-cut vanadat crystals

Spectroscopic and lasing properties of c-cut Nd-doped Nd:Gd_0.7Y_0.3VO₄, Nd:YVO₄, and Nd:GdVO₄ crystals were investigated. Spectral tuning from 1062 to 1067 nm was demonstrated. CW, Q-switching and mode-locking regimes for two-color laser operations were realized. A novel THz source based on Q-switch two-color diode-pumped solid state c-cut Nd:GdVO₄ laser with Filter Lio as selective element and the GaSe nonlinear optical crystals as convertor was demonstrated. Terahertz radiation with wavelength 436 mm (0.56 THz) was detected. One picosecond laser pulses in mode-locking diode pumped c-cut vanadat lasers with a Kerr-lens and PbS-doped glasses as saturable absorbers are observed.     

Optically Controlled Electron Transfer in a ReI Complex

Ultrafast optical control of intramolecular charge flow was demonstrated, which paves the way for photocurrent modulation and switching with a highly wavelength-selective ON/OFF ratio. The system that was explored is a fac-[Re(CO)₃(TTF-DPPZ)Cl] complex, where TTF-DPPZ=4’,5’-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2’,3’-c]phenazine. DFT calculations and AC-Stark spectroscopy confirmed the presence of two distinct optically active charge-transfer processes, namely a metal-to-ligand charge transfer (MLCT) and an intra-ligand charge transfer (ILCT). Ultrafast transient absorption measurements showed that the ILCT state decays in the ps regime. Upon excitation to the MLCT state, only a long-lived ³MLCT state was observed after 80 ps. Remarkably, however, the bleaching of the ILCT absorption band remained as a result of the effective inhibition of the HOMO–LUMO transition.     

Electric quadrupole interaction of the 75 keV state of100Rh in a beryllium matrix

The quadrupole interaction frequencyv _q =eQV _zz /h = 8.92(9) MHz was observed for the 75 keV state of¹⁰⁰Rh in a polycrystalline beryllium matrix by use of the e^?-γ time differential perturbed angular correlation technique. The measured spin rotation pattern is hardly disturbed in spite of the fact that the source was produced by an isotope separator implantation of¹⁰⁰Pd into a beryllium foil without any after-treatment.     

Contribution a l'etude des composes fluores ternaires du vanadium + II

Very few vanadium (+ II) fluorides are known and some difficulty is experienced in preparing them. In accordance with previous results, only three ternary fluorides, NaVF₃, KVF₃ and RbVF₃, may be prepared in the systems MF-VF₂, where M is an alkali element. Whatever MF/VF₂ ratio a partial or a total disproportionation of vanadium + II accurs. The structures of NaVF₃, KVF₃, and RbVF₃ have been defined. The ternary compounds of MVF₃ formulation have been compared with those of other 3d elements.     

Near-field investigation of induced transparency in similarly oriented double split-ring resonators

We present near-field measurements of an induced transparency behavior using a double split-ring resonator geometry. Mapping the out-of-plane electric field component directly reveals that the induced transparency is linked to an asymmetric mode profile with the subunits oscillating in antiphase. The measurements are compared to complementary numerical simulations, and excellent agreement is found.