Realistic time-reversal invariant topological insulators with neutral atoms

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states. We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and drive the development of topological quantum computing.     

In vitro antibiofilm activity of the freshwater bryozoan Hyalinella punctata: a case study of Pseudomonas aeruginosa PAO1

The antibiofilm and possible antiquorum sensing effects against the strain Pseudomonas aeruginosa PAO1 of five crude extracts of the freshwater bryozoan Hyalinella punctata (Hancock, 1850) were evaluated in vitro for the first time. H. punctata ethyl acetate extract (HpEtAc) exhibited the highest antibiofilm activity reducing the biofilm formation of P. aeruginosa PAO1 in the range of 80.63–88.13%. While all tested extracts reduced the twitching motility of the aforementioned bacterial strain, HpEtAc showed to be the most effective. Finally, at a concentration of 0.5 MIC, the same extract mostly inhibited the production of pyocyanin by P. aeruginosa PAO1 (71.53%). In comparison both with the positive controls used (streptomycin and ampicillin, 67.13 and 69.77%, respectively), HpEtAc was found to inhibit pyocyanin in a higher extent. An extensive chemical characterisation of this particular extract may result in isolation and identification of novel lead compounds targeting P. aeruginosa, an opportunistic human pathogen.     

Preparation of cellulosic fibers with biological activity by immobilization of trypsin on periodate oxidized viscose fibers

In this study, a biologically active fibrous material was designed by immobilizing trypsin on viscose fibers. The viscose yarn was first oxidized with sodium periodate to produce aldehyde groups and then employed as a support for subsequent immobilization of trypsin through bovine serum albumin. The oxidation by sodium periodate caused changes in the chemical and physical properties of the modified yarn samples, which were evaluated by determining the aldehyde group content, fineness and tensile strength of yarn. The viscose fibers oxidized under the most severe conditions (0.4 % NaIO₄, 360 min) exhibited the maximum amount of introduced aldehyde groups (1.284 mmol/g), but also the highest decrease in tensile strength. The trypsin activity was assayed with N-α-benzoyl-DL-arginine p-nitroanilide hydrochloride, whereas the amount of bound trypsin was determined by Bradford method. Trypsin immobilized on oxidized viscose yarn retained 97.3 and 83.8 % of the initial activity over 60 days of storage at 4 and 25 °C, respectively, and remained firmly attached to the carrier. The potential application of obtained bioactive fibers is in the treatment of wounds.     

Development of a novel RP‐HPLC method for the efficient separation of aripiprazole and its nine impurities

The development of an RP‐HPLC method for the separation of aripiprazole and its nine impurities was performed with the use of partial least squares regression, response surface plot methodology, and chromatographic response function. The HPLC retention times and computed molecular parameters of the aripiprazole and its nine impurities were further used for the quantitative structure–retention relationship (QSRR) study. The QSRR model, R²: 0.899, Q²: 0.832, root mean square error of estimation: 4.761, root mean square error of prediction: 6.614, was developed. Very good agreement between the predicted and observed retention times (t_R) for three additional aripiprazole impurities (TC1–TC3) indicated the high prediction potential of the QSRR model for t_R evaluation of other aripiprazole impurities and metabolites. The developed HPLC method is the first reported method for the efficient separation of aripiprazole and its nine impurities, which could be used for the analysis of an additional three aripiprazole impurities (TC1–TC3).     

Nanostructured lipid carriers for triamcinolone acetonide delivery to the posterior segment of the eye

Triamcinolone acetonide (TA) is a corticosteroid drug currently administered by intravitreal injection for a broad spectrum of inflammatory, edematous and angiogenic ocular diseases. To increase the drug's bioavailability by ocular instillation, TA was encapsulated in nanostructured lipid carriers (NLC), previously optimized by our group using a factorial design approach. In the present paper, nanometric (∼200 nm), unimodal and negatively charged NLC loaded with the fluorescent lipid marker Nile red (NR-NLC) and drug (TA-NLC) were produced by high pressure homogenization. Based on the selected formulations, in vivo tests were carried out by eye-drop instillation of NR-NLC in mice, revealing the systems’ ability of delivering lipophilic actives to the posterior segment of the eye via the corneal and non-corneal pathways. Short and long-term stability of TA-NLC was assessed by high performance stability analysis using the Turbiscan^®. The results showed a backscattering of less than 1.5% and during a period of 6 months, anticipated the low tendency of these particles for aggregation during shelf life when stored at room temperature.     

Quantitative Structure-Retention Relationship Modeling of the Retention Behavior of Guanidine and Imidazoline Derivatives in Reversed-Phase Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The quantitative structure-retention relationship (QSRR) study has been performed in order to investigate the retention behavior of...     

Conductometric studies on the stability of copper complexes with different oligosaccharides

Bioactive copper complexes with pullulan or dextran oligosaccharides are the subject of intensive research mainly because of their possible application in veterinary and human medicine. The thermal stability and stability under oxidative conditions of the Cu(II) complexes with reduced low-molar pullulan or dextran were investigated in this paper, using a conductometric method. The influence of ligand constitutions on the stability of the complexes was examined on the basis of ligand property. Forced degradation studies were performed on bulk sample of complexes by using heat (25, 40 and 60°C) and an oxidation agent (0.1, 0.5, 1.0 and 10.0% v/v hydrogen peroxide). It can be concluded, according to the results obtained (by examining conductivity during the forced degradation studies), that Cu(II) complexes show a large pharmaceutical stability for both tests.      

Luminescence thermometry using Gd<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript>

In this paper we study the possibility of using the synthesized nanopowder samples of Gd₂Zr₂O₇:Eu³⁺ for temperature measurements by analyzing the temperature effects on its photoluminescence. The nanopowder was prepared by solution combustion synthesis method. The photoluminescence spectra used for analysis of Gd₂Zr₂O₇:Eu³⁺ nano phosphor optical emission temperature dependence were acquired using continuous laser diode excitation at 405 nm. The temperature dependencies of line emission intensities of transitions from ⁵D₀ and ⁵D₁ energy levels to the ground state were analyzed. Based on this analysis we use the two lines intensity ratio method for temperature sensing. Our results show that the synthesized material can be efficiently used as thermographic phosphor up to 650 K.     

Symmetry,phonons and rigid-layers modes in commensurate double wall carbon nanotubes

For translationally periodic double-wall carbon nanotubes stable configurations and full symmetry groups are determined. Using this, the phonon dispersions and eigenvectors are calculated and assigned by the complete set of conserved quantum numbers. In particular, the modes corresponding to the relative coaxial motions of the rigid layers are studied in the context of low inter-wall interaction.Received: 19 June 2003, Published online: 9 September 2003PACS: 63.22.+m Phonons or vibrational states in low-dimensional structures and nanoscale materials - 61.46.+w Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals - 78.30.Na Fullerenes and related materials     

A study of resonance production in the reaction K+p → K0pπ+ from 3 to 16 GeV/c

The reactions $\text{K}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^{\mathrm{1+}}\text{(890)}\text{p}$, $\text{K}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^{\mathrm{1+}}\text{(1420)}\text{p}$ and K⁺p → K⁰Δ⁺⁺ have been systematically studied for eleven incident momenta between 3.0 and 16.0 GeV/c. Cross sections, differential cross sections and density matrix elements are presented. For K¹(890) production the contributions from natural and unnatural parity exchanges have also been separated into I = 0 and I = 1 components. Effective trajectories have been extracted in the case of natural parity exchange, and also for Δ⁺⁺ production.