Spectrofluorimetric quantification of bilirubin using yttrium–norfloxacin complex as a fluorescence probe in serum samples

A simple and sensitive spectrofluorimetric method was developed to determine trace amounts of bilirubin (BR) using yttrium (Y³⁺)–norfloxacin (NFLX) complex as a fluorescence (FL) probe. NFLX can form a stable binary complex with Y³⁺ and markedly enhances the weak FL signal of the NFLX. The FL intensity of the Y³⁺–NFLX complex decreased significantly in the presence of BR in a buffer solution at pH=7.2. Under optimal conditions, the FL intensity decreased according to the BR concentration and showed a good linear relationship in the range of 0.03–2.3 μg mL^?1 of BR with a correlation coefficient of 0.9988. The limit of detection for the determination of BR was 2.8 ng mL^?1 with a relative standard deviation (RSD) of 1.55% for five replicate determination of 0.05 μg mL^-1 BR. The presented method offers higher sensitivity with simple instrumentation and was applied successfully in detecting BR at low concentrations.     

Effects of partial charge-transfer solute – solvent interactions in absorption spectra of aromatic hydrocarbons in aqueous and alcoholic solutions

A method for study of charge-transfer interactions between solute molecules and solvent based on the comparison of the ratios of spectral shifts of different electronic transitions in solute molecules in chemically inert solvent is proposed. The method is applicable to molecules that do not change their dipole moment on excitation. As an example, a presence of charge transfer interactions in higher electronic states of aromatic hydrocarbons (benzene, phenanthrene, and naphthalene) dissolved in water and alcohols was demonstrated.     

A study of fluorescence properties of citrinin in β-cyclodextrin aqueous solution and different solvents

Citrinin (CIT) is a nephrotoxic mycotoxin initially isolated from filamentous fungus Penicilliu citrinum. It was later isolated from several other species, such as Aspergillus and Monascus. It has a conjugated, planar structure that gives it a natural fluorescence ability, which can be used to develop sensitive methods for detecting CIT in food. In this paper, we used the spectro?uorescence technique to study the effects of pH value, β-cyclodextrin (β-CD) and organic solvents on the CIT fluorescence intensity. The results show that lower pH value, aceitc acid, β-CD and acetonitrile can induce a higher fluorescence intensity of CIT, but methanol or H₂O has a decreasing effect on the fluorescence intensity of CIT. Findings in this study provide a theoretical basis for development of a high sensitivity fluorescence-based trace analysis for CIT detection.     

Study of laser fragmentation process of silver nanoparticles in aqueous media

Laser fragmentation of Ag nanoparticles in Ag hydrosol was studied by simultaneous measurements of the transmitted fluence of the incident laser beam and the time evolution of the surface plasmon extinction (SPE) spectra. The experiments showed that the laser fragmentation in a small volume of hydrosol proceeds during first 20 pulses and then reaches saturation. The value of the transmitted fluence corresponding to saturation increases with incident pulse fluence, but the impact of the first pulse applied to the hydrosols shows an optical limitation. Fluences above 303 mJ/cm² cause the formation of less stable, aggregating nanoparticles, while fluences below 90 mJ/cm² do not provide sufficient energy for efficient fragmentation. The interval of fluences between 90–303 mJ/cm² is optimal for fragmentation, since stable hydrosols constituted by small, non-aggregated nanoparticles are formed.     

Preparation of polymer–rare earth complex using salicylic acid-containing polystyrene and its fluorescence emission property

Salicylic acid (SA) was first bonded onto the side chains of polystyrene (PS), obtaining functional macromolecule SAPS. Using the salicylic acid-containing polystyrene as a macromolecular ligand, a polymer–rare earth complex, SAPS–Eu(III), was prepared. The structure of SAPS–Eu(III) was characterized, and the fluorescence properties of SAPS–Eu(III) were mainly investigated. The experimental results show that the complex SAPS–Eu(III) has fine chemical stability because of the bidentate chelating effect of salicylic acid ligand. More important, the ligand SA on the side chains of PS can strongly sensitize the fluorescence emission of the center ion, Eu³⁺ ion, and it enables the complex SAPS–Eu(III) to produce the apparent “Antenna Effect”. In the diluted solution of the functional macromolecule SAPS, the formed complex SAPS–Eu(III) belongs to an intramolecular complex, or an intrachain complex. For the binary intramolecular complex SAPS–Eu(III), the apparent saturated coordination number of SA of SAPS towards Eu³⁺ ion is equal to 10, and here the binary intrachain complex SAPS–Eu(III) has the strongest fluorescence emission. On this basis, small-molecule 1,10-phenanthroline (Phen) acting as a co-ligand is added and the ternary complex SAPS–Eu(III)–Phen will be formed. As long as a small amount of Phen is added (in the molar ratio 1:1 (n(Phen):n(Eu))), the coordination of the two kinds of ligands, SA of SAPS and Phen, to Eu³⁺ ion will reach complete saturation, and here the fluorescence emission of the ternary complex will be further enhanced via the complementary coordination effect in comparison with that of the binary complex SAPS–Eu(III).     

Diffusion coefficients of sodium dodecylsulfate in aqueous solutions and in aqueous solutions of β-cyclodextrin

Differential diffusion coefficients have been measured of sodium dodecylsulfate (SDS) in aqueous solutions of β-cyclodextrin (β-CD) at 298.15 K over the concentration range 0.001 M to 0.0817 M using a conductimetric cell and an automatic apparatus to follow the diffusion. The cell uses an open ended capillary method, while a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at various recorded times. The β-CD is known to for strong 1:1 complexes with SDS, and the effect of this on the diffusion of this electrolyte was investigated. The presence of β-cyclodextrin can influence the diffusion coefficients of sodium dodecylsulfate both above and below the critical micelle concentration (cmc) of this surfactant. For concentrations of β-cyclodextrin of 0.001 mol dm⁻³ the behaviour of the diffusion of SDS in aqueous solutions is the same in the absence or the presence of β-cyclodextrin. In contrast, when the β-CD concentration is 0.016 mol dm⁻³ we obtain diffusion coefficients higher than those obtained in aqueous solutions. Further, we do not observe the dramatic decrease in diffusion normally found at the cmc of the surfactant. These results are interpreted in terms of the effect of incorporation of dodecylsulfate chains inside the cyclodextrin cavities.     

Asymptotically stable equilibrium and limit cycles in the Rock–Paper–Scissors game in a population of players with complex personalities

We investigate a population of individuals who play the Rock–Paper–Scissors (RPS) game. The players choose strategies not only by optimizing their payoffs, but also taking into account the popularity of the strategies. For the standard RPS game, we find an asymptotically stable polymorphism with coexistence of all strategies. For the general RPS game we find the limit cycles. Their stability depends exclusively on two model parameters: the sum of the entries of the RPS payoff matrix, and a sensitivity parameter which characterizes the personality of the players. Apart from the supercritical Hopf bifurcation, we found the subcritical bifurcation numerically for some intervals of the parameters of the model.     

Nuclear spin–lattice relaxation and complex motion of macromolecules in solution

The NMR spectral densities of a complex motion consisting of a combination of anisotropic overall motion and internal motion have been derived. Two approximations of the equations derived for the cases of slow, J_slow (ω), and fast, J_fast (ω), internal motions are presented. These equations imply that reduction in spectral density of overall motion can be observed if the maxima of internal and overall motions spectral densities versus temperature are well separated, as for fast internal motion. Slow intramolecular motion influences the values of spectral densities of the overall motion if one of the two spins performs a motion, for example a proton in double minimum of the ¹⁵N-H?···?N hydrogen bond. The analysis presented reveals small differences between the temperature dependencies of spectral densities of the isotropic and anisotropic overall motions. The theory is illustrated by the ¹³C protonated carbon spin-lattice relaxation of α-cyclodextrin macromolecule, using the expected motional parameters: D _∥/D _⊥?≈?5 at room temperature and for a fast or slow internal motion.     

Frequency modelling and solution of fluid–structure interaction in complex pipelines

Complex pipelines may have various structural supports and boundary conditions, as well as branches. To analyse the vibrational characteristics of piping systems, frequency modelling and solution methods considering complex constraints are developed here. A fourteen-equation model and Transfer Matrix Method (TMM) are employed to describe Fluid–Structure Interaction (FSI) in liquid-filled pipes. A general solution for the multi-branch pipe is proposed in this paper, offering a methodology to predict frequency responses of the complex piping system. Some branched pipe systems are built for the purpose of validation, indicating good agreement with calculated results.     

Interaction of Airy–Gaussian beams in saturable media

Based on the nonlinear Schr o¨dinger equation, the interactions of the two Airy–Gaussian components in the incidence are analyzed in saturable media, under the circumstances of the same amplitude and different amplitudes, respectively. It is found that the interaction can be both attractive and repulsive depending on the relative phase. The smaller the interval between two Airy–Gaussian components in the incidence is, the stronger the intensity of the interaction. However, with the equal amplitude, the symmetry is shown and the change of quasi-breathers is opposite in the in-phase case and out-of-phase case. As the distribution factor is increased, the phenomena of the quasi-breather and the self-accelerating of the two Airy–Gaussian components are weakened. When the amplitude is not equal, the image does not have symmetry. The obvious phenomenon of the interaction always arises on the side of larger input power in the incidence. The maximum intensity image is also simulated. Many of the characteristics which are contained within other images can also be concluded in this figure.     

Sensitive determination of adenosine disodium triphosphate in soil,milk, and pharmaceutical formulation by enoxacin–europium (III) fluorescence complex in solution

A new spectroflurometric method for the determination of adenosine disodium triphosphate (ATP) is developed. Fluorometric interaction between ATP and enoxacin (ENX)–Eu³⁺ complex was studied using UV–vis and fluorescence spectroscopy. Weak luminescence spectra of Eu³⁺ were enhanced after complexation with ENX at 589 nm and 614 nm upon excitation at 395 nm due to energy transfer from the ligand to the lanthanide ion. It was observed that luminescence spectrum of Eu³⁺ was strongly enhanced further at 614 nm after incorporation of ATP into the ENX–Eu³⁺ complex. Under optimal conditions, the enhancement of luminescence at 614 nm was responded linearly with the concentration of ATP. The linearity was maintained in the range of 1.5×10^?10–1.15×10^?8 M (R=0.9973) with the limit of detection (3σ) of 4.71×10^?11 M. The relative standard deviation (RSD) for 9 repeated measurements of 1×10^?9  M ATP was 1.25%. Successful determinations of ATP in soil, milk, and a pharmaceutical formulation with the proposed method were demonstrated.     

Ultrasonically induced ZnO–biosilica nanocomposite for degradation of a textile dye in aqueous phase

In the present study, a porous clay-like support with unique characteristics was used for the synthesis and immobilization of ZnO nanostructures to be used as sonocatalyst for the sonocatalytic decolorization of methylene blue (MB) dye in the aqueous phase. As a result, the sonocatalytic activity of ZnO–biosilica nanocomposite (77.8%) was higher than that of pure ZnO nanostructures (53.6%). Increasing the initial pH from 3 to 10 led to increasing the color removal from 41.8% to 88.2%, respectively. Increasing the sonocatalyst dosage from 0.5 to 2.5 g/L resulted in increasing the color removal, while further increase up to 3 g/L caused an obvious drop in the color removal. The sonocatalysis of MB dye over ZnO–biosilica nanocomposite was temperature-dependent. The presence of methanol produced the most adverse effect on the sonocatalysis of MB dye. The addition of chloride and carbonate ions had a negligible effect on the sonocatalysis, while the addition of persulfate ion led to increasing the color removal from 77.8% to 99.4% during 90 min. The reusability test exhibited a 15% drop in the color removal (%) within three consecutive experimental runs. A mineralization efficiency of 63.2% was obtained within 4 h.     

Dark periods in the resonance fluorescence of a single Λ system

We use the quantum jump method to study the photon statistics of a single laser-driven atom in the configuration where both lower levels are strongly coupled to the common upper level. Under certain conditions we show that, for almost degenerate lower levels, light and dark periods occur which are similar to those of the well-known Dehmelt V system. Analytic results for their mean lengths and other statistical properties are given. For large separation of the lower levels we prove an interesting bunching property by the photons in the resonance fluorescence near the dark resonance. We propose a realistic system for which these effects may be observed.     

On a generalized Ablowitz–Kaup–Newell–Segur hierarchy in inhomogeneities of media: soliton solutions and wave propagation influenced from coefficient functions and scattering data

In this paper, a generalized Ablowitz–Kaup–Newell–Segur (AKNS) hierarchy in inhomogeneities of media described by variable coefficients is investigated, which includes some important nonlinear evolution equations as special cases, for example, the celebrated Korteweg–de Vries equation modeling waves on shallow water surfaces. To be specific, the known AKNS spectral problem and its time evolution equation are first generalized by embedding a finite number of differentiable and time-dependent functions. Starting from the generalized AKNS spectral problem and its generalized time evolution equation, a generalized AKNS hierarchy with variable coefficients is then derived. Furthermore, based on a systematic analysis on the time dependence of related scattering data of the generalized AKNS spectral problem, exact solutions of the generalized AKNS hierarchy are formulated through the inverse scattering transform method. In the case of reflectionless potentials, the obtained exact solutions are reduced to n-soliton solutions. It is graphically shown that the dynamical evolutions of such soliton solutions are influenced by not only the time-dependent coefficients but also the related scattering data in the process of propagations.     

HF-based clad etching of fibre Bragg grating and its utilization in concentration sensing of laser dye in dye–ethanol solution

This paper presents a fibre Bragg grating (FBG) based sensor to study the concentration of laser dye in dye–ethanol solution. The FBG used in this experiment is indigenously developed using 255 nm UV radiations from copper vapour laser. The cladding of the FBG was partially removed using HF-based etching to make FBG sensitive to changes in the surrounding refractive index. The experimental results on the shift of the Bragg peak wavelength with HF etching and different dye concentration in ethanol are presented. The Bragg wavelength shifted from 1534.670 nm to 1534.225 nm in 30 min and from this point to 1533.97 in the next 2 min. The clad-etched Bragg peak shifted almost linearly from 1534.056 nm to 1534.162 nm as surrounding dye concentration in ethanol changes from 0 mM to 1.5 mM. It was observed that sensitivity depends on the concentration of the solution and found to be 70 pm/mM.     

Vector kink-dark complex solitons in a three-component Bose–Einstein condensate

We investigate kink-dark complex solitons(KDCSs) in a three-component Bose–Einstein condensate(BEC) with repulsive interactions and pair-transition(PT) effects. Soliton profiles critically depend on the phase differences between dark solitons excitation elements. We report a type of kink-dark soliton profile which shows a droplet-bubble-droplet with a density dip, in sharp contrast to previously studied bubble-droplets. The interaction between two KDCSs is further investigated. It demonstrates some striking particle transition behaviours during their collision processes, while soliton profiles survive after the collision. Additionally, we exhibit the state transition dynamics between a kink soliton and a dark soliton. These results suggest that PT effects can induce more abundant complex solitons dynamics in multi-component BEC.     

Dynamics of collinear Laguerre–Gaussian beams in nonlocal nonlinear media

We study the optical fields that are produced by two collinear Laguerre–Gaussian (LG) beams in strongly nonlocal nonlinear media. Various novel kinds of rotating breathers and solitons, such as quadrangle, pentacle, pentagon, etc. can be obtained by combining different mode-index LG beams with the different relative amplitude. The rotating and translating asymmetric breathers and solitons can be obtained when the difference of the azimuthal charge between the two combining LG beams is 1.     

Photoluminescence of terbium-organic complex in aerosol–gel-derived planar waveguides

This work deals with the low-temperature preparation of optically active silica-based materials. Tb³⁺-doped silica monolithic gels were elaborated at 40 °C. Tb³⁺–SSA-doped SiO₂–TiO₂ thin films were deposited by an original sol–gel approach, the aerosol–gel process, and heat-treated at 150 °C. Organic complexation of terbium ions was used to improve the active properties of doped silica gels and thin-film samples. Spectroscopic characterisations are reported for these samples. Photoluminescence increase by a factor two was observed for complexation by sulphosalicylic acid. Received: 16 May 2001 / Revised version: 31 August 2001 / Published online: 23 October 2001