Analysis of Mepivacaine in Human Serum by Gas Chromatography After Solid-Phase Extraction

A method using solid-phase extraction (SPE) has been developed for analysis of mepivacaine in human serum. A procedure for isolation of mepivacaine and lidocaine (internal standard) from human serum by use of Chromosorb 104 (acrylonitrile–divinylbenzene polymer) as extraction adsorbent is described in detail. Analysis was performed by gas chromatography on an HP-INNOWax (cross-linked PEG) capillary column, with flame ionization detection, after splitless injection. Relative standard deviations ranged between 3.6 and 4.4 for a serum mepivacaine concentration of 0.5 g mL^–1 and between 4.7 and 5.9 for a concentration of 1 g mL^–1. Recoveries were approximately 95%. The method was applied in a stomatological clinic to healthy volunteers to whom anesthesia with mepivacaine was administered.     

Use of metallic and dielectric films for hollow fibers

The problem of transmission of CO₂ laser radiation through hollow fibers and waveguides was studied theoretically and confirmed experimentally. The transmission of the laser radiation through metal and metal-dielectric tubes was measured and compared with the theoretical data based on a ray model solution. This makes possible the investigation of the transmission of the CO₂ radiation through waveguides when the internal wall is covered with a metal or a metal- dielectric film. It was shown theoretically and proved experimentally that the transmission of the CO₂ radiation is possible even through bent waveguides.     

New Andreev-type states in superconducting nanowires

Superconducting nanowires can exhibit a spatially inhomogeneous pair condensate that leads to the formation of new Andreev-type states. Such states are mainly located beyond the regions where the order parameter is enhanced, and no normal-superconducting contact or external magnetic field is needed for their formation. Our numerical self-consistent solutions of the Bogoliubov-de Gennes equations for cylindrical nanowires, in the clean limit, demonstrate that these new Andreev-type states decrease the ratio of the energy gap to the critical temperature as compared to its bulk value. The low-lying excitations in a clean superconducting nanowire are these new Andreev-type states induced by quantum confinement of the electrons in the transverse direction.     

Chalcogenide infrared As2−xSe3+x glass fibers

Chalcogenide glasses As_2?xSe_3+x have been prepared. A new technique of preparing the raw material and subsequently drawing fibers has been developed in order to avoid the formation of oxygen compounds. The fibers have been drawn by the crucible and rod method from oxygen free raw material inside an Ar atmosphere glove box. The fibers drawn to date have a diameter of 50–500 μm and lengths of several meters. Preliminary attenuation measurements indicate that the attenuation is better than 0.1 dB/cm at 10.6 μm. The attenuation is not affected even when the fiber is bent to a circular radius of 2 cm. By improving the preparation of materials and the drawing technique, we expect to achieve a better transmission.     

An Extension of the Birkhoff Integrability for Multifunctions

A comparison between a set-valued Gould type and simple Birkhoff integrals of bf(X)-valued multifunctions with respect to a non-negative set function is given. Relationships among them and Mc Shane multivalued integrability is given under suitable assumptions.     

A Simple HPLC/DAD Method Validation for the Quantification of Malondialdehyde in Rodent’s Brain

In the present study, a HPLC/DAD method was set up to allow for the determination and quantification of malondialdehyde (MDA) in the brain of rodents (rats). Chromatographic separation was achieved on Supelcosil LC-18 (3 μm) SUPELCO Column 3.3 cm × 4.6 mm and Supelco Column Saver 0.5 μm filter by using a mobile phase acetonitrile (A) and phosphate buffer (20 mM, pH = 6) (B). Isocratic elution was 14% for (A) and 86% for (B). The injection volume (loop mode) was 100 μL with an analysis time of 1.5 min. Flow rate was set at 1 mL/min. The eluted compound was detected at 532 nm by a DAD detector by keeping the column oven at room temperature. The results indicated that the method has good linearity in the range of 0.2–20 μg/g. Both intra- and inter-day precision, expressed as RSD, were ≤15% and the accuracies ranged between ±15%. The lower limit of quantification (LLOQ), stability, and robustness were evaluated and satisfied the validation criteria. The method was successfully applied in a study of chronic toxicology following different treatment regimens with haloperidol and metformin.     

Andreev-type states induced by quantum confinement

The properties of a clean superconductor with nanoscale dimensions are governed by quantum confinement of the electrons. This results in a spatially inhomogeneous superconducting condensate and in the formation of new Andreev-type quasiparticle states. These states are mainly located beyond regions where the superconducting condensate is enhanced. A numerical self-consistent solution of the Bogoliubov-de Gennes equations for a cylindrical metallic nanowire shows that these new Andreev-type states decrease the ratio of the energy gap to the critical temperature. The text was submitted by the authors in English.     

On approximate algorithms for combinatorial linear maximization problems

The worst-case performance of a large class of approximate algorithms for a combinatorial linear maximization problem is examined. As an application the efficacy of heuristics combining enumeration and the greedy algorithm is presented.

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Zusammenfassung Für ein sehr allgemeines kombinatorisches Optimierungsproblem wird eine größere axiomatisch definierte Klasse von approximativen Algorithmen untersucht, deren Güte einheitlich analysiert werden kann. Damit erhält man einerseits einheitliche Güte-Beweise für verschiedene aus der Literatur bekannte Varianten des Greedy-Algorithmus und zum anderen Güte-Beweise für einige neue approximative Algorithmen.

     

Application of the Green's function method to lattice vibrations in thin films

The Green's function method is used to investigate the lattice vibrations in a simple cubic thin film with nearest neighbour interactions. Appropriate Green's functions for the study of the surface waves for (001) and (011) orientations of the surface are determined. For a thin film with two parallel (001) free surfaces the atomic force tensors at the surface are modified in order to satisfy the rotational invariance condition. The surface waves are determined and a detailed discussion is made for the long wave-length limit k_y = 0 and k_x ? 1. For a given k_x there is a critical thickness below which only an antisymmetrical solution can exist. For the (011) orientation only the case of a single free surface is discussed.