Solid-Phase Luminescence Determination of Ciprofloxacin and Norfloxacin in Biological Fluids

A simple, rapid, and sensitive luminescence test method for the determination of ciprofloxacin (CIP) and norfloxacin (NOR) has been described. The method is based on the intramolecular energy transfer from organic acid to terbium (Tb³⁺) ion. Luminescence of terbium (III) complex with CIP (NOR), sorbed on the zeolite has been studied. Under optimized conditions the detection limit is 1 g/mL in urine and human plasma.     

Unusual conformational preferences of 1,3‐dimethyl‐3‐isopropoxy‐3‐silapiperidine

The conformational analysis of the first representative of the Si‐alkoxy substituted six‐membered Si,N‐heterocycles, 1,3‐dimethyl‐3‐isopropoxy‐3‐silapiperidine, was performed by low‐temperature ¹H and ¹³C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Me_axi‐PrO_eq conformer was found to predominate in the conformational equilibrium in the ratio Me_axi‐PrO_eq : Me_eqi‐PrO_ax of ca. 2 : 1 as from the ¹H and ¹³C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation. Copyright © 2012 John Wiley & Sons, Ltd.     

Polarization-controlled switching between diffraction orders in transverse-periodically aligned nematic liquid crystals

Transverse-periodic-oriented nematic liquid crystals (LCs) are a special type of optical axis grating that are capable of very high efficiency diffraction (theoretically, 100%) in thin layers of materials with thickness comparable to the radiation wavelength. In particular, they fully diffract linearly polarized input beam into circularly polarized +1st and -1st diffraction orders. We experimentally demonstrate switching between diffraction orders of such gratings when the polarization of the incident beam changes from right-circular to left-circular and vice versa with the aid of an electrically controlled LC phase retarder. Such a setup in which the diffraction efficiency and direction are controlled externally, without application of an electric field to the transverse-periodic grating, provides additional control opportunities and does not compromise the quality of the grating. The grating used in the experiment was 1.5 microm thick and had a period of 4 microm. The contrast ratio of switching between the +1st and -1st orders was as high as 267:1 for a He-Ne laser beam with a switching time of 6.6 ms.     

Novel Zinc(II) Bis(Dipyrromethenate)-Doped Ethyl Cellulose Sensors for Acetone Vapor Fluorescence Detection

In this paper, we report on the results of spectrofluorimetric study of new fluorescent sensor based on [Zn₂L₂] doped in ethyl cellulose. The sensor optical signal is based on the rapid fluorescence quenching in the presence of acetone vapor. The acetone vapor detection limit in a gas mixture by means of sensor based on [Zn₂L₂] doped in ethyl cellulose is 1.68 ppb. Being highly sensitive to the acetone acetone presence, instant in response and easy to use, the sensor can find an application for the noninvasive diagnostics of diabetes as well as for the monitoring of the content of acetone acetone in the air at industrial and laboratory facilities.

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Selective creation of maximum coherence in multi-level Λ system

We consider the creation of the maximum Raman coherence in the six-level Λ system using optimal control theory. Optimal fields are designed for different initial conditions, resonant, and off-resonant, using the Krotov method including a reference field into the cost functional. Suppression of the population transfer to the intermediate level is achieved via an additional functional constraint which depends on the system dynamics. We demonstrate that the spectrum of the optimised fields has major contribution from the corresponding resonant frequencies independently of the choice of carrier frequency of the initial guess field. We also indicate that the pulse train emerges as a solution of the control problem of coherence optimisation in multi-level quantum systems.     

Synchronous ultrasonic Doppler imaging of magnetic microparticles in biological tissues

We considered applicability of acoustic imaging technology for the detection of magnetic microparticles and nanoparticles inside soft biological tissues. Such particles are widely used for magnetically targeted drug delivery and magnetic hyperthermia. We developed a new method of ultrasonic synchronous tissue Doppler imaging with magnetic modulation for in vitro and in vivo detection and visualization of magnetic ultradisperse objects in soft tissues. Prototype hardware with appropriate software was produced and the method was successfully tested on magnetic microparticles injected into an excised pig liver.     

High‐power HgGa2S4 optical parametric oscillator pumped at 1064 nm and operating at 100 Hz

The defect chalcopyrite crystal HgGa₂S₄ has been employed in a 1064‐nm pumped optical parametric oscillator operating at 100 Hz, to generate ∼5 ns long idler pulses near 4 µm with energies as high as 6.1 mJ and average power of 610 mW. At crystal dimensions comparable to those available for the commercial AgGaS₂ crystal, operation of the 1064‐nm pumped HgGa₂S₄ OPO is characterized by much lower pump threshold and higher conversion efficiency, with the most important consequence that such a device might become practical at pump levels sufficiently lower than the optical damage threshold.     

Self‐assembly of p‐tert‐butyl thiacalix[4]arenes and metal cations into nanoscale three‐dimensional particles

The shape of supramolecular aggregates based on stereoisomers of p‐tert‐butyl thiacalix[4]arenes functionalized with secondary, tertiary amide and hydrazide groups at the lower rim in cone, partial cone and 1,3‐alternate conformations with several metal cations were investigated by atomic force microscopy. The examined p‐tert‐butyl thiacalix[4]arenes form host–guest complexes; dimers, spherics ellipsoids and elongated nanoscale particles depending on the conformation of macrocycles, the nature of the binding centers and the nature of the metal cation. Only associates formed by p‐tert‐butyl thiacalix[4]arenes with morpholide groups at the lower rim in cone conformation with silver cations exhibited a higher antimicrobial activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Small silver clusters at paramagnetic defects of silica surfaces: A density functional embedded-cluster study

We studied the interaction of small Ag_n clusters (n = 1–4) with paramagnetic defect centers of a dehydroxylated silica surface using an all-electron scalar relativistic density functional method. The surface and adsorption complexes on it were modeled with an accurate quantum mechanics/molecular mechanics (QM/MM) scheme of embedding QM clusters in an elastic polarizable environment, described at the molecular mechanics level (MM). We analyzed two types of frequent point defects as sites for trapping and growing of Ag clusters: a silicon atom with a dangling bond (E′ center), ≡ Si?, and a non-bridging oxygen center (NBO), ≡ Si–O?. The Ag clusters interact with these paramagnetic centers forming strong covalent metal-defect bonds. The high adsorption energy allows one to consider the NBO and E′ sites as traps of single Ag atoms and as centers of cluster growth. We also explored the effect of adsorption on observable electronic properties of the silver clusters and of the defects of the silica surface.