Search results for "Spectroscopy"
showing 10 items of 10293 documents
Use of response factorial design for process optimization of basic dye adsorption onto activated carbon derived from Persea species
2017
Abstract Full factorial design is a powerful and efficient mathematical approach widely applied in the optimization of response. The important parameters which affect the removal efficiency of methylene blue such temperature, initial pH of the solution, concentration and adsorbent dosage were optimized. They coded as A, B, C and D, consecutively, and were investigated at two levels (+ 1 and − 1). A linear mathematical model representing the influence of the different variables and their interactions was obtained. Main effect, Normal probability plot of residuals, analysis of variance (ANOVA), surface plots, and contour plots were used to study the effects and interaction effects between ope…
Vibrational spectral studies of methyl 3-(4-methoxyphenyl)prop-2-enoate, a new organic non-linear optic crystal
2005
Single crystals of methyl 3-(4-methoxyphenyl)prop-2-enoate were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. Ab initio quantum computations were also performed at the HF/6–311G (d,p) level to derive the equilibrium geometry, vibrational wavenumbers and intensities and first hyperpolarizability. The large NLO efficiency predicted for the first time in this new class of compounds was confirmed by powder efficiency experiments. Hartree–Fock calculations reveal that the endocyclic angle at the junction of the propeonate group and the phenyl ring is decreased from 120° by 2.5…
Energy landscapes of ligand-receptor couples probed by dynamic force spectroscopy.
2013
Playing a dominant role in many biochemical processes are the dynamic properties of molecular linkages; examples include cell adhesion, enzyme-catalyzed reactions, and molecular recognition by antibodies. Dynamic force spectroscopy, namely separating molecular bonds under external force ramps has rapidly become a powerful tool to study the rugged energy landscape of noncovalent ligand-receptor bonds. The picture shows a surface and tip-bound pair being pulled apart and the derived potential energy diagram.
Evidence for a surface self-cleaning sputtering mechanism in fast atom bombardment mass spectrometry
1985
Evidence for a surface self-cleaning sputtering mechanism in fast atom bombardment mass spectrometry involving significant sputtering from the bulk of the glycerol matrix has been obtained from (a) the time dependence of sample ion abundances and chemical noise for bioorganic compounds, (b) determinations of the sputtering volume in glycerol solution, and (c) studies of in situ chemical and biochemical reactions. The relevance of these results for optimal sample/matrix preparation in analytical applications is pointed out.
<title>Time-resolved fluorescence study of interaction of the monoclonal anticoproporphyrin antibodies and (Pt-)coproporphyrin</title>
1995
Mechanisms of ligand binding by monoclonal anti-coproporphyrin antibodies are studied by steady-state and time-resolved fluorescence spectroscopy by use of a picosecond laser system. The antibodies quench the coproporphyrin (CP) fluorescence, but the CP fluorescence spectra show a strong shift of maxima at high concentrations of antibodies (Ab) or their Fab fragment. This can be explained by a special type of Ab or Fab dimerization. Fluorescence decays of CP are measured at different concentrations of Ab and different pH values. The following deconvolution procedure based on the non-linear least squares method reveals a two- exponential character of the fluorescence decay. Data obtained by …
Development of a dielectric spectroscopy technique for the determination of apple (Granny Smith) maturity
2010
Abstract Dielectric measurements of apple were done during its maturity in order to find relations with apple physiological compounds (sugar content, malic acid). An Agilent 85070E open-ended coaxial probe connected to an Agilent E8362B vector network analyzer were used in these experiments. All determinations were made at 30 °C from 500 MHz to 20 GHz. These assays were performed in order to consider the potential use of dielectric spectroscopy for determining the state of fruit maturity. Good correlations among apples Thiault Index with a new defined Dielectric Maturity Index were found. The Dielectric Maturity Index was related to loss factor at two punctual frequencies (0.5 GHz and dipol…
Electrical impedance spectroscopy of ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate (ECOENG™ 110)
2011
Abstract Ionic liquid “ECOENG™ 110”, a promising electrolyte for electrochemical devices, was investigated by impedance spectroscopy. Metallic electrodes (Pt, Cu, Ag, and Mo) as well as carbon were used for the electrochemical characterization. The dependences of the real and imaginary impedance, polarization resistance and electrochemical capacity of the double layer on the electrode potential were investigated using electrical equivalent circuits of R1(QR2) and R1[Q(R2W)] types.
Collisional line broadening and line shifting in N2-CO2 mixture studied by inverse Raman spectroscopy
1990
Abstract Collisional effects in the Raman Q-branch of N 2 perturbed by CO 2 have been studied by high-resolution stimulated Raman spectroscopy. The Raman spectra recorded in the 0.3–1.0 atm and 295–1000 K pressure and temperature ranges are fitted with a theoretical profile taking into account line broadening, frequency shift and line mixing due to rotational energy transfers. The data at low density are used as basic data for the modeling of rotationally inelastic rates through sets of adjustable parameters. We have used in this study the two main models developed in the last decade and known as modified exponential gap (MEG) and energy corrected sudden (ECS) laws. Experimental spectra rec…
Fourier-transform spectroscopy of (4)1Σ+→A 1Σ+−b 3Π,A 1Σ+−b 3Π →X1Σ+, and (1)3Δ1→bΠ0±3 transitions in KCs and deperturbation treatment ofA 1Σ+andb 3Π…
2013
High resolution Fourier-transform spectroscopy data of term values in the spin-orbit (SO) coupled first excited A 1Σ+ and b 3Π states in KCs were obtained from (4)1Σ+ → A 1Σ+ − b 3Π, A 1Σ+ − b 3Π → X1Σ+, and (1)3Δ1→bΠ0±3 spectra of laser-induced fluorescence (LIF). About 3000 new rovibronic term values of the A 1Σ+ and b3ΠΩ states were obtained with an uncertainty about 0.01 cm−1 and added to the previously obtained 3439 term values in Kruzins et al. [Phys. Rev. A 81, 042509 (2010)] and 30 term values of the b3Π0+ state levels below the A 1Σ+ state in Tamanis et al. [Phys. Rev. A 82, 032506 (2010)]. The data field was extended considerably, going down to vibrational level vb = 0 and up in e…
Experimental and theoretical study of line mixing in methane spectra. III. The Q branch of the Raman ν1 band
2000
The shape of the ν1 Raman Q branch of CH4 perturbed by Ar and He at room temperature has been studied. Stimulated Raman spectroscopy (SRS) experiments have been made in the 2915–2918 cm−1 spectral region for total pressures from 0.4 to 70 atm and mixtures of ≈5% CH4 with He and Ar. Analysis of the spectra demonstrates that the shape of the Q branch is significantly influenced by line mixing and much narrower than what is predicted by the addition of individual line profiles. For the first time, a model is proposed for the calculation and analysis of the effects of collisions on the considered spectra. In this approach, the rotational part of the relaxation matrix is constructed, with no adj…