Calculation of the probabilities for transitions into the continuous spectrum by using the L2 basis: A new method of solving the wave-function renormalization problem

A new method is presented for calculating the normalization factor for continuous spectrum functions in the L₂ basis. One variant of this method is applicable to operators given in the form of a tridiagonal matrix and does not require explicit calculation of the roots of the characteristic equation. The other variant of the method can be used in the general case, where after the basis is introduced, its length is gradually increased.     

Near Infrared Spectral Similarity Combined with Variable Selection Method in the Quality Control of Flos Lonicerae: A Preliminary Study

This paper indicates the possibility to use near infrared (NIR) spectral similarity as a rapid method to estimate the quality of Flos Lonicerae. Variable selection together with modelling techniques is utilized to select representative variables that are used to calculate the similarity. NIR is used to build calibration models to predict the bacteriostatic activity of Flos Lonicerae. For the determination of the bacteriostatic activity, the in vitro experiment is used. Models are built for the Gram‐positive bacteria and also for the Gram‐negative bacteria. A genetic algorithm combined with partial least squares regression (GA‐PLS) is used to perform the calibration. The results of GA‐PLS models are compared to interval partial least squares (iPLS) models, full‐spectrum PLS and full‐spectrum principal component regression (PCR) models. Then, the variables in the two GA‐PLS models are combined and then used to calculate the NIR spectral similarity of samples. The similarity based on the characteristic variables and full spectrum is used for evaluating the fingerprints of Flos Lonicerae, respectively. The results show that the combination of variable selection method, modelling techniques and similarity analysis might be a powerful tool for quality control of traditional Chinese medicine (TCM).     

On the assessment of melanin in human skin in vivo

Abstract— A method for estimating the amount of pigment in normal human skin in uivo is presented. This method is based on remittance spectroscopy. The spectrum of normal skin is compared to amelanotic skin and the logarithm of the ratio is fitted with a straight line in the range 620-720 nm. The parameters obtained are strongly correlated for all the volunteers in this study. therefore each spectrum determines one parameter for each individual. When similar analysis was performed on DOPA-melanin we obtained the same strong correlation among different concentrations. We are thus able to determine a relation between the coefficient obtained from the remittance spectrum from normal skin and an equivalent concentration of DOPA-melanin in aqueous solution. We can thus estimate. to a first approximation, the total melanin mass in human skin non-invasively, and can determine a parameter that is uniquely correlated to the amount of melanin pigment in the skin.     

A Spectroscopic Study of the Hemiammine Dicobalt (II) Species

Infrared spectrum of amyl amine forming cobalt complex in benzene solution is described. The D, value and transitions between d orbitals are identified. Since few transition metal salts are soluble in inert solvent, this paper introduces a special method of making cobalt-2-ethyl-hexanoate which is soluble in benzene.     

Interpretation of soft X-ray emission spectra in terms of relativistic electric dipole transition probabilities

The emission process for eigenstates of a model Dirac Hamiltonian of “muffintin” type is described in terms of relativistic electric dipole (E1) transitions with the assumption that the final state is a localized core eigenstate of the system. The proposed method is applied to theL-emission spectrum of V in VC and to theL- andM-emission spectrum of Nb in NbC. Resulting theoretical spectra are compared with experimental data.     

Novel determination of the total phenolic content in crude plant extracts by the use of H NMR of the –OH spectral region

A novel method for the determination of the total phenolic content using ¹H NMR spectroscopy in the –OH spectral region is presented. The use of DMSO-d₆, which is an aprotic and strongly hydrogen bonding solvent, allows the “appearance” of the relative sharp resonances of phenolic hydroxyl protons in the region of 8–14 ppm. The determination of the total phenolic –OH content requires three steps: (i) a 1D ¹H NMR spectrum is obtained in DMSO-d₆; (ii) a subsequent 1D ¹H NMR spectrum is recorded with irradiation of the residual water signal which results in the elimination or reduction of the phenolic –OH groups, due to proton exchange; and (iii) 1D ¹H NMR spectra are recorded with the addition of a progressively increased amount of salt, NaHCO₃, which results in extensive linebroadening of the COOH resonances thus allowing the discrimination of the phenolic from the carboxylic acid signals. Integration, with respect to the internal standard TSP-d₄, of the signal resonances between 14 and 8 ppm in spectrum (i) which are either eliminated or reduced in intensity in steps (ii) and (iii) allows the quantitation of the total phenolic content. The method was applied to model compounds, a mixture of them and several extracts of natural products. The results of the proposed ¹H NMR method were compared to the Folin-Ciocalteu (FC) reagent method. Additionally, since ¹H NMR refers to the total phenolic hydroxyl protons, a reaction factor, A_e, is proposed that corresponds to the hydroxyl reactivity. The ¹H NMR method is rapid and accurate bearing the inherent advantages of the NMR spectroscopy and can be applied directly in complex extracts. Furthermore, it can be applied in a wide range of matrixes from crude plant extracts and food products to biological samples.     

Theory of the excitation spectrum of nondiagonal disordered systems

The spectrum of a two-component solid solution with a nondiagonal disorder is studied in the framework of the average T matrix method. For a one-dimensional system in the nearest-neighbor approximation the criteria for the system parameters are given such that at an in-band resonance, one or two “impurity bands” may be realized, and the corresponding model calculation is performed. In the single-site approximation an expression of the self-energy part of a nondiagonal disordered system Green's function is found taking into account multiple occupancy corrections. The possibility of using it to describe a disordered system excitation spectrum and the calculation of state density moments are discussed.     

Determination of the isotope distribution in partially deuterated compounds by NMR difference spectroscopy

The position and the isotope distribution within labelled compounds can be determined by NMR by analysing the difference spectrum, and its integral, of the labelled and the corresponding parent compound. The method is applied to m-terphenyl and it 4–4″-dideutero derivative.     

In situ Detection of Amide A Bands of Proteins in Water by Raman Ratio Spectrum

The amide A band of protein is sensitive to the hydrogen bands of amide groups of proteins. However, it is hard to distinguish the amide A band of aqueous protein in situ directly, since it overlaps with O-H stretching vibration of water. In this work, we presented a new analytical method of Raman ratio spectrum, which can extract the amide A band of proteins in water. To obtain the Raman ratio spectrum, the Raman spectrum of aqueous protein was divided by that of pure water. A mathematical simulation was employed to examine whether Raman ratio spectrum is effective. Two kinds of protein, lysozyme and α-chymotrypsin were employed. The amide A bands of them in water were extracted from Raman ratio spectra. Additionally, the process of thermal denaturation of lysozyme was detected from Raman ratio spectrum. These results demonstrated the Raman ratio spectra could be employed to study the amide A modes of proteins in water.     

Electronic structure and bonding of the pentasulfur hexanitride (S5N6) molecule

An ab initio version of the Hartree–Fock–Slater method is applied to obtain molecular orbitals and eigenvalues for S₅N₆. The electronic structure, bonding, stability, and electronic spectrum are discussed.     

Effect of Li and Na impurities on the electronic and magnetic properties of beryllium oxide

The ab initio pseudopotential method (VASP package) within the gradient approximation (GGA) for the exchange-correlation potential is used to study the effect of Li and Na substitution for Be atoms on the electronic and magnetic properties of wurtzite-like beryllium monoxide BeO with an impurity concentration of 0.028. When Li impurity is introduced into BeO, the system is found to remain nonmagnetic. At the same time, the BeO:Na system adopts magnetic moments (~0.8 fu_B per cell) through the spin polarization of the 2p-state of oxygen atoms surrounding the impurity center. After lithium incorporation into BeO, the spectrum of BeO:Li becomes metal-like, while the introduction of sodium results in the magnetic semimetal type of the BeO:Na spectrum     

RESOLUTION OF THE FLUORESCENCE EXCITATION SPECTRUM OF INDOLE INTO THE 1La AND 1Lb EXCITATION BANDS*

Abstract— The fluorescence excitation spectrum and the excitation polarization spectrum of indole in propylene glycol were measured at — 58°C, after selecting by optical filters the emission originating from the ¹L_a electronic level. From the analysis of these spectra, the excitation spectrum was resolved into the ¹L_a and ¹L_a excitation bands. A similar resolution of the excitation spectrum of tryptophan is given. This method can also be applied to the resolution of the emission spectrum in cases of dual emission.     

Effect of solution environment on the absorption maxima of Schiff bases of retinal

Abstract— –Preliminary examination of the effect of solution environment on the electronic absorption spectrum of N-retinylidene-n-butylamine(I) is reported. It is established that small amounts of CO₂ dissolved in certain solvents cause the formation of the conjugate acid of I. This reaction is shown to be dependent on temperature and the concentration of CO₂. The pK_b of I in aqueous buffer was measured spectrophotometrically and found to be 8.71. Salts of I were prepared in a number of ways and their spectra were determined in selected solvents. The Λ_max varies with method of preparation, and only one method gives reproducible results. The Λ_mnx is a function of the solvent in which the spectrum is determined. It was also found that the absorption maximum in wavenumbers is proportional to the negative logarithm of acid concentration.     

Study on the spectrum‐effect relationship of the xanthine oxidase inhibitory activity of Ligustrum lucidum

To evaluate the xanthine oxidase inhibitory activity of the chemical constituents of Ligustrum lucidum in vitro, the spectrum‐effect relationship was investigated. The high‐performance liquid chromatography fingerprint was established by ultraviolet spectrophotometry, and the xanthine oxidase inhibitory activity was tested in vitro by a high‐throughput screening method. Cluster analysis, principal component analysis, gray correlation analysis, and partial least squares regression were used to explore the spectrum‐effect relationships. Sixty batches of Ligustrum lucidum were collected from 16 provinces for testing. The results revealed differences among the batches of medicinal materials, and the similarity score was between 0.635 and 0.968. Thirty‐three characteristic peaks (1–33) were calibrated by fingerprint evaluation software for traditional Chinese medicine. The spectrum‐effect relationship study further revealed that the contents of peaks 1, 2, 4, 5, 6, 7, 14, 17, 25, 28, 31, and 33, which are potentially critical ingredients for quality control of Ligustrum lucidum fruit, were highly correlated with the inhibition of xanthine oxidase activity.     

Quantitative Analysis of Clove Oil by NMR Spectrometry

A procedure utilizing NMR spectrometry in the quantitative analysis of clove oil is described. The ¹H-NMR spectrum is determined with acetophenone as internal standard, the ¹³C-NMR spectrum is determined with chloroform as internal standard and 0.1M Cr(acac)₃ as relaxation reagent. The contents of eugenol are compared to the results obtained from G.C. (90.8%, s.d. 0.7%) and from chemical method (89.6% s.d. 1.2%). The result obtained from ¹H-NMR method is 90.4% (s.d. 0.3%) and from ¹³C-NMR method is 90.5% (s.d. 0.7%). The time required for the ¹H-NMR method is about 20mins and for the ¹³C-NMR method is about 2-3hours. Apparently the ¹H-NMR method proves to be more simple, rapid and accurate.     

Comparative analysis of the vibrational structure of the absorption spectra of acrolein in the excited (<Emphasis Type="Italic">S</Emphasis><Subscript>1</Subscript>) electronic state

The assignments of absorption bands of the vibrational structure of the UV spectrum are compared with the assignments of bands obtained by the CRDS method in a supersonic jet from the time of laser radiation damping for the trans isomer of acrolein in the excited (S ₁) electronic state. The ν_00trans = 25861 cm⁻¹ values and fundamental frequencies, including torsional vibration frequency, obtained by the two methods were found to coincide in the excited electronic state (S ₁) for this isomer. The assignments of several absorption bands of the vibrational structure of the spectrum obtained by the CRDS method were changed. Changes in the assignment of (0-v′) transition bands of the torsional vibration of the trans isomer in the Deslandres table from the ν_00trans trans origin allowed the table to be extended to high quantum numbers v′. The torsional vibration frequencies up to v′ = 5 were found to be close to the frequencies found by analyzing the vibrational structure of the UV spectrum and calculated quantum-mechanically. The coincidence of the barrier to internal rotation (the cis-trans transition) in the one-dimensional model with that calculated quantum-mechanically using the two-dimensional model corresponds to a planar structure of the acrolein molecule in the excited (S ₁) electronic state.     

An analytical solution for the kinetics of AB(1k,1ϕ) systems and its application to a spirobenzopyran

A new, rapid method is described which determines the absolute values of all the unknown parameters of an AB(1k,1?) reactive system from experimental information about the change of absorbance with time at any given wavelength. The mathematical algorithm is given for the case where the spectrum of the isomer B is not experimentally accessible and overlaps the spectrum of A. An example of its application to a photochromic spiropyran derivative is given. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 539–545, 2007     

Parametric method in the theory of vibronic spectra of complex molecules. Excited state structure and fluorescence spectrum of stilbene

The parameters of the adiabatic model of the stilbene molecule in the excited state and the vibrational structure of the fluorescence spectrum are calculated by the parametric method of the theory of vibronic spectra of complex molecules. The first and second orders of theory are used. The molecular models are constructed by the fragment method. Satisfactory agreement with experiment is obtained. The parameters of molecular fragments are shown to be highly transferable. The model and the spectrum max be refined in the second order of theory using only one additional parameter for CCC angles (optimal values were obtained). The parametric method under discussion makes it possible to predict variations of structural parameters due to excitation and to calculate the vibrational structure of the electronic spectra of complex molecules, including characteristic variations of the spectra in series of related molecules (stilbene-di-phenylpolyenes). This method surpasses all previous procedures (in particular, the correlation method) in completeness and accuracy of results. Translated fromZhurnal Strukturnoi Khinii, Vol. 41, No. 2, pp. 369–378, March–April, 2000.     

A new mass spectrometric method for determining the degree of labeling with heavy isotopes: The study of deuterated toluenes

A new method of general applicability for determining the percentage deuterium labeling in organic compounds is described. It uses the heights of ‘metastable peaks’ in the mass spectrum to determine the relative amounts of deuterated and undeuterated species. The method is illustrated by describing the analysis of mixtures of toluene-o-d₁ and toluene, of toluene α-d₁ and toluene, and of toluene-2,6-d₂, toluene-o-d₁ and toluene.     

Résolution de spectres RPE par régression non linéaire. Application à des radicaux anions dérivés de thiazoles substitués

A non-linear regression method for the resolution of EPR spectra is described. The theoretical model is fitted with the experimental spectrum and the error on each parameter is calculated. The method is applied to the radical anions of 2-nitro-4-methyl thiazole, 4-p-nitro-phenyl-thiazole and 5-p-nitro-phenyl-thiazole.