Optimization of background electrolytes for capillary electrophoresis I. Mathematical and computational model

A mathematical and computational model is introduced for optimization of background electrolyte systems for capillary zone electrophoresis of anions. The model takes into account mono- or di- or trivalent ions and allows also for modeling of highly acidic or alkaline electrolytes, where a presence of hydrogen and hydroxide ions is significant. At maximum, the electrolyte can contain two co-anions and two counter-cations. The mathematical relations of the model are formulated to enable an easy algorithmization and programming in a computer language. The model assesses the composition of the background electrolyte in the analyte zone, which enables prediction of the parameters of the system that are experimentally available, like the transfer ratio, which is a measure of the sensitivity in the indirect photometric detection or the molar conductivity detection response, which expresses the sensitivity of the conductivity detection. Furthermore, the model also enables the evaluation of a tendency of the analyte to undergo electromigration dispersion and allows the optimization of the composition of the background electrolyte to reach a good sensitivity of detection while still having the dispersion properties in the acceptable range. Although the model presented is aimed towards the separation of anions, it can be straightforwardly rearranged to serve for simulation of electromigration of cationic analytes. The suitability of the model is checked by inspecting the behavior of a phosphate buffer for analysis of anions. It is shown that parameters of the phosphate buffer when used at neutral and alkaline pH values possess singularities that indicate a possible occurrence of system peaks. Moreover, if the mobility of any analyte of the sample is close to the mobilities of the system peaks, the indirect detector signals following the background electrolyte properties will be heavily amplified and distorted. When a specific detector sensitive on presence of the analyte were used, the signal would be almost lost due to the excessive dispersion of the peak.     

Proton NMR of isomorphous paramagnetic and diamagnetic monohydrates MeSO4.1 H2O Me = Mn2+, Fe2+, Ni2+ AND Mg2+

Nuclear magnetic resonance of protons of crystallization water in isomorphous paramagnetic and diamagnetic monohydrates MeSO₄. 1 H₂O with Me = Mn²⁺, Fe²⁺, Ni²⁺ and Mg²⁺ is studied in the present paper. Proton NMR spectra in paramagnetic hydrates are asymmetric and their second moments, M₂, depend linearly on the square of the induction of the external magnetic field B₀. NMR spectrum of diamagnetic hydrate MgSO₄. 1 H₂O is symmetric and its shape and the second moment do not change with B₀. The parameters M₂₀ andK which characterize nuclear dipole-dipole interaction of protons and interaction of protons and paramagnetic ions, respectively, are derived from experimentally obtained dependences M₂ vs B ₀ ² and on the other hand, they are calculated by means of crystallographic data for substances studied. Calculations were realized in approximation where two nearest neighbour ions Me²⁺ to each water molecule are considered. The influence of the demagnetizing magnetic field of the sample was neglected.     

Laser deposited YBaCuO thin films

YBa₂Cu₃O_7-x thin films were deposited by laser ablation using KrF excimer laser. In deposition on polycrystalline ZrO₂/(1–102) sapphire substrates influence of deposition conditions on film properties were studied. Zero resistance temperatureT _z of 83 K of epitaxially grown YBaCuO films on poly-ZrO₂/sapphire substrates was reached. Epitaxially grown yttria stabilized zirconia (YSZ) buffer layers were deposited by laser ablation on (1–102) sapphire substrates. On YSZ/sapphire, SrTiO₃ and NdGaO₃ substrates, temperatures T_z between 89–90 K were measured. Results of X-ray diffraction and SEM are also presented.We would like to express our thanks to L. Cibulka, L. and L. Rouek, and J. Stránský for their efficient help during the solution of technological problems connected with the construction of experimental apparatus.     

Channeling measurement of residual damage in silicon

Conclusion The present resulte are in general agreement with those obtained earlier, e.g. in /2/. The complete removal of post-implantation defects in As-implanted Si may be achieved by thermal annealing at temperatures above 700°C and by laser annealing as well. More than 50% of the implanted As atoms enter the host lattice sites during the thermal annealing. By laser annealing, on the other hand, 9056 of the As atoms become substitutional.Some of the samples under study were kindly analysed by Dr. R. Grotzschel in ZfK Rossendorf (GDR). The results obtained in ZfK are in good agreement with the present ones. We thank Dr. J. ervená for her help in processing the measured spectra. The excellent collaboration with the staff of the Van de Graaff accelerator at NPI is also gratefully acknowledged.     

1.6 μm Er:YAP and Er:YAG lasers resonantly pumped by Er:glass laser

1623 nm Er:YAP and 1648 nm Er:YAG lasers resonantly pumped by a solid state Er:glass laser operating at 1535 nm were investigated. Laser generation was reached for Er:YAP and two Er:YAG crystals with different Er ion concentration. The maximal output energies were 20 and 45 mJ for Er:YAP and Er:YAG laser systems, respectively.     

Monochromatic triangles in two-colored plane

We prove that for any partition of the plane into a closed set C and an open set O and for any configuration T of three points, there is a translated and rotated copy of T contained in C or in O.     

Optical emission spectroscopy of nitrogen species and plasma plume induced by laser ablation combined with pulse modulated radio-frequency discharge

Combined laser ablation and pulse modulated radio-frequency (RF) discharge for deposition of CNalpha films was studied by the use of optical emission spectroscopy. Chemically active nitrogen was produced by RF discharge, concentrated between two small electrodes. Influence of RF power, nitrogen pressure, modulation frequency and pulse rate on nitrogen species production was researched. For the same system plasma expansion rate, kinetic energy and concentration of carbon ions emitted by laser from graphite target were determined by Langmuir probes measurement.     

Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces

We study the origin of atomic contrast on Cu(111) and Pt(111) surfaces probed by a non-contact atomic force microscope and scanning tunnelling microscope. First-principles simulations of the interaction between the atoms of the scanning tip and those of the probed surface show a dependence of the resulting contrast on the tip-sample distance and reveal a close relation between contrast changes and relaxation of atomic positions in both the tip and the sample. Contrast reversion around the distance where the short-range attractive atomic force reaches its maximum is predicted for both types of microscopies. We also demonstrate a relation between the maximal attractive force in a F-z atomic force spectroscopy and the chemical identity of the apex atom on the imaging tip.     

Macropolyhedral boron-containing cluster chemistry. Cluster opening and B-frame rearrangement in the reaction of B(16)H(20) with [{(IrCl(2)(eta(5)-C(5)Me(5))}(2)]. Synchrotron X-ray structures of [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(17)Cl] and [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(15)Cl

Products from the reaction of + nido ten-vertex : nido eight-vertex, B(16)H(20) with [{(IrCl(2)(eta(5)-C(5)Me(5))}(2)] and tmnd show unanticipated rearrangement of the starting {B(16)} skeleton, as exhibited by + nido ten-vertex : nido ten-vertex, [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(17)Cl] which has a {B(2)} edge conjunction and by + nido ten-vertex : nido eleven-vertex, [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(15)Cl] which has a {B(3)} face conjunction.