Spectrofluorimetric Determination of Dopamine Using Chlorosulfonylthenoyltrifluoroacetone–Europium Probe

A new spectrofluorimetric method was developed for the determination of trace amounts of dopamine (DA). Using chlorosulfonylthenoyltrifluoroacetone (CTTA)–europium ion (Eu³⁺) as a fluorescent probe, in a buffer solution at pH = 10.0, DA can remarkably enhance the fluorescence intensity of the CTTA-Eu³⁺ complex at λ = 612 nm; the enhanced fluorescence intensity of Eu³⁺ is proportional to the concentration of DA. Optimum conditions for the determination of DA were also investigated. The linear range and detection limit for the determination of DA were 5.0 × 10⁻⁸∼1.6 × 10⁻⁵ mol/l and 3.2 × 10⁻⁸ mol/l. This method is simple, practical and relatively free of interference from coexisting substances, and can be applied to assess DA in injection and human serum samples with good precision and accuracy.     

A Batch Chemiluminescence Determination of Enoxacin Using a Tris-(1,10-phenanthroline)ruthenium(II)–Cerium(IV) System

A batch type chemiluminescence (CL) determination of enoxacin is described. In this work, it was observed that enoxacin could enhance the chemiluminescence (CL) emission Ru(phen)₃ ²⁺–Ce(IV) system and this enhancement effect was dependent on the concentration of enoxacin, based on which, CL system was established for the determination of enoxacin. Under the optimum experimental conditions, the linear range and detection limit are 0.6406–64.06 μg/ml and 0.0210 μg/ml, respectively. The R.S.D. is 1.75%. (n=10). The proposed method has been applied to detect the content of enoxacin in pharmaceutical formulation and human serum with satisfactory results. The possible mechanism of the CL reaction was discussed.     

Study of Evaporation of Laser-Heated Iron–Carbon Nanoparticles Using Analysis of Thermal Radiation

Technical Physics - Evaporation of iron nanoparticles in carbon shells under pulsed laser irradiation is analyzed. Iron–carbon nanoparticles are synthesized in a shock tube reactor with the...     

Synthesis and Characterization of a Biologically Active Lanthanum(III)–Catechin Complex and DNA Binding Spectroscopic Studies

A lanthanum(III) complex of catechin has been synthesized and characterized by elemental analysis, molar conductance, UV-Vis spectra, infrared spectra, thermal analysis, and ¹H NMR. The complex behaves as a nonelectrolyte in methanol solvent. The spectral and thermal properties of the complex are examined. A thermogravimetric (TGA) study showed the hydrated nature of the complex. ¹H NMR spectra of the lanthanum and the catechin (CT) ligands measured in CD₃OD-d₄ also show metal ligand coordination. The lanthanum–catechin complex shows bright luminescence in methanol solution. The interaction of the complex with calf thymus DNA has been investigated by absorption and emission spectroscopic measurements. Experimental spectral results suggest CT–DNA binding with catechin complex via an intercalative mode.     

Spectroscopic analysis of a laser-induced NaCl–water plasma. The influence of self-absorption

A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have been constructed for concentrations ranging up to 1.5%.     

Excitation and Detection of a Nonlinear Resonance of Oscillations of a Spring–Mass System Using Electromagnetic Induction

Technical Physics - Nonlinear oscillations and resonances of a spring–mass system are experimentally and theoretically studied. A unified method for excitation, dissipation, and detection of...     

Determination of Optimal Control Strength of Delayed Feedback Control Using Time Series

We study controlling chaos using tlme-delayed feedback control based on chaotic time series without prior knowl-edge of dynamical systems, and determine the optimal control parameters for stabilizing unstable periodic orbitswith maximal stability.     

Determination of the Kardar–Parisi–Zhang equation from experimental data with a small number of configurations

We introduce an inverse method to determine the parameters of the Kardar–Parisi–Zhang equation corresponding to an evolving interface which requires a small number of configurations as input data. Our approach presents advantages for applications in real world scenarios since it does not require small time intervals between fronts. The method is applied to a restricted solid-on-solid model and a stochastic cellular automata model for fire front propagation.     

Determination of the vapor–liquid transition of square-well particles using a novel generalized-canonical-ensemble-based method

The square-well(SW) potential is one of the simplest pair potential models and its phase behavior has been clearly revealed, therefore it has become a benchmark for checking new theories or numerical methods. We introduce the generalized canonical ensemble(GCE) into the isobaric replica exchange Monte Carlo(REMC) algorithm to form a novel isobaric GCE-REMC method, and apply it to the study of vapor–liquid transition of SW particles. It is validated that this method can reproduce the vapor–liquid diagram of SW particles by comparing the estimated vapor–liquid binodals and the critical point with those from the literature. The notable advantage of this method is that the unstable vapor–liquid coexisting states,which cannot be detected using conventional sampling techniques, are accessed with a high sampling efficiency. Besides,the isobaric GCE-REMC method can visit all the possible states, including stable, metastable or unstable states during the phase transition over a wide pressure range, providing an effective pathway to understand complex phase transitions during the nucleation or crystallization process in physical or biological systems.     

Iron-57 Mössbauer Spectroscopic Studies of the High Temperature Properties of Metal-Doped Iron Oxides

⁵⁷Fe Mössbauer spectra recorded in situ in vacuo from chromium- and gallium-doped Fe₃O₄ at elevated temperatures show the dopant ions to depress the Curie temperature of Fe₃O₄ by ca. 70 K. Spectra recorded from aluminium-doped -Fe₂O₃ show the onset of conversion to aluminium-doped -Fe₂O₃ to begin at ca. 750 K, which is ca. 100 K above the conversion temperature for undoped -Fe₂O₃. The variation in magnetic hyperfine fields at temperatures exceeding ca. 750 K is similar to that recorded from -Fe₂O₃ when doped with zinc or magnesium. At temperatures exceeding 900 K the zinc doped -Fe₂O₃ partially converts to spinel-related ZnFe₂O₄.     

Procedures of Separation and Pre‐concentration for Molybdenum Determination Using Atomic Spectrometry—a Review

Abstract

The literature concerning the improvement of atomic and ionic procedures for molybdenum determination through separation and pre‐concentration were updated. Analytical procedures based on flame atomic absorption spectrometry (AAAS), electrothermal or graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma optical emission spectrometry (ICP‐OES), and inductively coupled plasma mass spectrometry were reviewed taking into consideration the preliminary steps, which can enhance the selectivity and sensitivity based on co‐precipitation, solvent extraction, and solid‐phase extraction. Both in‐batch and on‐line procedures were considered.     

Determination of Thermal Diffusivity of a Manganite Thin Film

Thermal diffusivity has been investigated in a manganite thin film La0.6Sr0.4MnO3 by means of transient grating （TG） technique at room temperature. A new method, which is generalized to two-layered samples of the thin film deposited on a semi-infinite substrate, is established to fit the TG signals. The thermal diffusivity of the Lao.6Sro.4MnO3 thin film with a thickness of 200nm on an MgO （100） substrate is determined to be 0.92mm^2/s, which is slightly smaller than that of the single crystal sample （1 mm^2/s）.     

Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH3: Evidence for a Weak C–H–N Hydrogen Bond

ABSTRACT

The hydrogen-bonded bromocyclohexane–ammonia complex has been isolated and characterized for the first time in argon matrices at 16 K. Coordination of the proton adjacent to the Br substituent on the cyclohexane ring to the amino nitrogen was evidenced by distinct blue shifts of bending modes involving the H-C₁–Br unit. In particular, C–C₁–Br, H–C₁–Br, and C–C₁–H bending modes produced blue shifts ranging from 2.8 to 12.2 cm^?1. Density Functional Theory (DFT) calculations at the B3LYP/6–31 + G(d, p) level yield an essentially linear Br–C₁–H–NH₃ hydrogen bond with a C-H–N distance of 2.412 Å and a hydrogen bond energy of 2.95 kcal/mol.     

Mössbauer Spectroscopic Study of Iron Containing Hydrotalcite Catalysts for the Reduction of Aromatic Nitro Compounds

Carbonated layered double magnesium hydroxides containing Fe with hydrotalcite structure which are active and selective catalysts for the reduction of aromatic nitro compounds by hydrazine hydrate have been prepared and characterized by X-ray diffraction and Mössbauer spectroscopy. Using these techniques we have shown that when the Fe/(Fe + Mg) ratio was greater than 0.2, which corresponds to the natural phase composition, ferrihydrite Fe₅HO₈?4H₂O was formed. This last phase, characterized at room temperature by a superparamagnetic doublet, leads after activation under nitrogen at 723 K to small particles of ferric oxide. An in-situ study of the activated catalysts allowed us to show that only iron cations present in this phase could undergo an oxido-reduction under the conditions of catalysis and that the catalytic properties must be related to this last phase.     

Determination of temperature and concentration of a vapor–gas mixture in a wake of water droplets moving through combustion products

Characteristic temperatures and concentrations of a vapor–gas mixture in a wake of water droplets moving through combustion products (initial temperature 1170 K) were determined using the Ansys Fluent mathematical modeling package. We investigated two variants of motion: motion of two droplets (with sizes from 1 mm to 3 mm), consecutive and parallel, and motion of five staggered droplets. The influence of the relative position of droplets and also of distances between them (varied from 0.01 mm to 5 mm) on temperatures and concentrations of water vapor was established. The distances determine the relation between the evaporation areas and the total volume occupied by a droplet aggregate in the gas medium. The results of modeling for conditions that take into account vaporization on the droplet surface at average constant values of evaporation rate and also with consideration of the change in the latter, depending on the droplet temperature field, are compared. We determined conditions under which the modeling results are comparable for the assumption of a constant vaporization rate and with regard to the dependence of the latter on temperature. The earlier hypothesis on formation of a buffer vapor layer (“thermal protection”) around a droplet, which decreases the thermal flow from the external gas medium, was validated.     

Ablation of GaN Using a Femtosecond Laser

We study the pulsed laser ablation of wurtzite gallium nitride(GaN) films grown on sapphire,using the femtosecond laser beam at a central wavelength of 800nm as the source for the high-speed ablation of GaN films.By measuring the backscattered Raman spectrum of ablated samples,the dependence of the ablation depth on laser fluence with one pulse was obtained.The threwshold laser fluence for the ablation of GaN films was determined to be about 0.25J/cm^2,Laser ablation depth increases with the increasing laser fluence until the amount of removed material is not further increased.The ablated surface was investigated by an optical surface interference profile meter.     

Complex Anti-Self-Dual Connections on a Product of Calabi–Yau Surfaces and Triholomorphic Curves

We study the adiabatic limit of a sequence of Ω-anti-self-dual connections on unitary bundles over a product of two compact Calabi–Yau surfaces M×N by scaling metrics to shrink N to a point. We show that after fixing gauge transformations, a subsequence of the N-components of these connections converges to a triholomorphic curve from M away from a Cayley cycle in M×N to the moduli space of instantons on M×N modulo gauge equivalence in the Hausdorff topology, and converges on the blow-up locus to a family, which is parameterized by the Cayley cycle, of triholomorphic curves from C ² to . Received: 22 May 1998 / Accepted: 26 August 1998     

Determination of the Heat of Adsorption and Desorption of a Volatile Organic Compound Under Dynamic Conditions Using Fourier‐Transform Infrared Spectroscopy

Quantitative Fourier‐transform infrared spectroscopic analysis was used for the determination of adsorption capacity of a model volatile organic compound (VOC) under dynamic conditions. The analytical method used also offers the possibility of distinguishing between reversible and irreversible adsorption as well as further detection of adsorbed VOC transformation. The obtained adsorbed amounts have been used for the determination of the heat of adsorption and the activation energy of desorption using, respectively, isosteric and temperature programmed desorption methods. The approach has been applied to explore the potential use of local clay as an adsorbent material for VOC pollutants.     

Spectroscopic and calorimetric studies of phospholipid–polyamine molecular interactions

The effect of polyamines (putrescine, spermine and spermidine) on the physical properties of liposomes of phospholipids with different amount of charge on the bilayer was studied. The measured effect depends both on the charge of the lipid and on the charge of the polyamine, which under physiological conditions can be considered as a polycation. No interaction was observed with a neutral phospholipid for all the polyamines considered. With charged phospholipids, polyamines modify the surface charge and, as a consequence, the inner structure of the core of the bilayer also changes. The polyamine with the highest positive charge and the phospholipid with the highest content of negative groups showed the strongest interaction.     

Excited-State Dynamics of a Novel Bisimide-C60 Complex

The excited-state dynamics of a bisimide derivative (ZI) and a novel Z1-C60 complex (PSF) has been investigated by means of steady state optical spectroscopies and femtosecond time-resolved absorption spectroscopies. The lifetime of the singlet excited state of Z1 shortens drastically from 2.4 ns to 1.7ps upon going from Z1 to PSF, a significant kinetics change is in coincidence with the complete fluorescence quench caused by the C^60 attachment.Highly efficient Zl-to-C60 excitation energy transfer which is governed by the mechanism of Z1-C60 electron exchange has been verified for the PSF complex.