Spectra Of Ab Research Articles

Indazole-derived synthetic cannabinoids: Absolute configuration determination and structure characterization by circular dichroism and DFT calculations

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

Сольватохромные эффекты в спектрах поглощения и люминесценции и стабильность квантового выхода эмиссии углеродных наночастиц (часть I)

The features of the solvatochromic effects of absorption (Ab) and photoluminescence (PL) spectra, as well as the quantum yield of emission (QYE) of carbon nanoparticles (CNPs) synthesized by various methods from a mixture of citric acid and nitrogen-containing precursors, in protic and aprotic solvents have been studied. It has been shown that the parameters of the spectra Ab, PL and the QYE value of particle solutions to a large extent depend on the method, conditions and modes of synthesis, the method of modification and separation of CNPs, the types and composition of precursors, and also the fundamental properties and pH of solvents. In solvents with a dielectric constant of 4.5 – 109.5, the QYE value of particles varies in a wide range from 10.8 to 100.0 %, and the PL band peak shifts from 466.4 to 536.8 nm. The presence of strong solvatochromic effects in the spectra of Ab and PL particles was shown, and the important role of the processes of protonation and deprotonation of surface groups of CNPs was established. The influence of universal and specific interactions on the spectroscopic parameters of CNPs has been investigated, and a significant contribution to the solvatochromic effects of specific interactions has been demonstrated.

On singular spectrum of finite dimensional perturbations (to the Aronszajn-Donoghue-Kac theory)

The main results of the Aronszajn-Donoghue-Kac theory are extended to the case of n-dimensional (in the resolvent sense) perturbations à of an operator A0 = A0* defined on a Hilbert space H. Applying technique of boundary triplets we describe singular continuous and point spectra of extensions AB of a symmetric operator A acting in H in terms of the Weyl function M(·) of the pair {A, A0} and boundary n-dimensional operator B = B*. Assuming that the multiplicity of singular spectrum of A0 is maximal it is established orthogonality of singular parts EsAв and EsAo of the spectral measures EAв and EAo of the operators AB and A0, respectively. It is shown that the multiplicity of singular spectrum of special extensions of direct sums A = A(1) ⊕ A(2) cannot be maximal as distinguished from multiplicity of the absolutely continuous spectrum. In particular, it is obtained a generalization of the Kac theorem on multiplicity of singular spectrum of Schrodinger operator on the line as well as its clarification. The multiplicity of singular spectrum of special extensions of direct sums A = A(1) ⊕ A(2) are investigated. In particular, it is shown that it cannot be maximal as distinguished from multiplicity of the absolutely continuous spectrum. This result generalizes the Kac theorem on multiplicity of singular spectrum of Schrodinger operator on the line and clarifies it.

On Singular Spectrum of Finite-Dimensional Perturbations (toward the Aronszajn–Donoghue–Kac Theory)

The main results of the Aronszajn–Donoghue–Kac theory are extended to the case of n-dimensional (in the resolvent sense) perturbations $$\tilde {A}$$ of an operator $${{A}_{0}} = A_{0}^{ * }$$ defined on a Hilbert space $$\mathfrak{H}$$ . By applying the technique of boundary triplets, the singular continuous and point spectra of extensions AB of a symmetric operator A are described in terms of the Weyl function $$M( \cdot )$$ of the pair {A, A0} and an n-dimensional boundary operator B = B*. Assuming that the multiplicity of the singular spectrum of A0 is maximal, we establish the orthogonality of the singular parts $$E_{{{{A}_{B}}}}^{s}$$ and $$E_{{{{A}_{0}}}}^{s}$$ of the spectral measure $${{E}_{{{{A}_{B}}}}}$$ and $${{E}_{{{{A}_{0}}}}}$$ of the operators AB and A0, respectively. The multiplicity of the singular spectrum of special extensions of direct sums $$A = {{A}^{{(1)}}} \oplus {{A}^{{(2)}}}$$ is investigated. In particular, it is shown that this multiplicity cannot be maximal, as distinguished from the multiplicity of the absolutely continuous spectrum. This result generalizes and refines the Kac theorem on the multiplicity of the singular spectrum of the Schrodinger operator on the line.

HST/STIS ULTRAVIOLET SPECTROSCOPY OF THE COMPONENTS OF THE MASSIVE TRIPLE STARδORI A

The multiple star system of delta Orionis is one of the closest examples of a system containing a luminous O-type, bright giant star (component Aa1). It is often used as a spectral-type standard and has the highest observed X-ray flux of any hot-star binary. The main component Aa1 is orbited by two lower mass stars, faint Aa2 in a 5.7 day eclipsing binary, and Ab, an astrometric companion with an estimated period of 346 years. Generally the flux from all three stars is recorded in ground-based spectroscopy, and the spectral decomposition of the components has proved difficult. Here we present HST/STIS ultraviolet spectroscopy of delta Ori A that provides us with spatially separated spectra of Aa and Ab for the first time. We measured radial velocities for Aa1 and Ab in two observations made near the velocity extrema of Aa1. We show tentative evidence for the detection of the Aa2 component in cross-correlation functions of the observed and model spectra. We discuss the appearance of the UV spectra of Aa1 and Ab with reference to model spectra. Both stars have similar effective temperatures, but Ab is fainter and is a rapid rotator. The results will help in the interpretation of ground-based spectroscopy and in understanding the physical and evolutionary parameters of these massive stars.

Spin algebra andNMRtheory using numerical software

A simple method to execute spin algebra computations is presented. It uses the high‐level numerical program Scilab and its large and convenient set of linear algebra routines. The techniques thus developed are applied to various nuclear magnetic resonance (NMR)‐related simulations. Static spectra of AB and ABC spin systems are computed. Free precession of single or multispin systems are simulated using the density matrix formalism. Magnetization transfer under simple pulse sequences is examined. Matrices representing product operators are displayed and coherence orders are explained. COSY correlation maps for two and three spins are obtained without approximation. The simulation of a DQF‐COSY spectrum, with its eight‐step phase program, is explained. Two simple pulsed field gradient experiments are described. Computation times are under 100 s on a 1.66‐GHz laptop computer. The approach is elementary, requiring only a basic knowledge of spin quantum mechanics. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 114–132, 2015.

Liquid chromatography/mass spectrometry-based structural analysis of soyasaponin Ab metabolites by human fecal microflora

Soyasaponin Ab, a major constituent of soybean by human intestinal microflora, was anaerobically incubated with fecal suspensions from ten individuals for 48 h and its metabolites were measured by LC-MS/MS analysis. Ten metabolites were detected. The spectra of the parental constituent soyasaponin Ab showed a peak at m/z 1435 [M-H](-) ion and those of its nine metabolites showed peaks at m/z 1310.0 [M-3C(2)H(2)O-H](-) ion, m/z 1267.9 [M-4C(2)H(2)O-H](-) ion, m/z 1105.3 [M-Glc-4C(2)H(2)O-H](-) ion, m/z 973.2 [M-Glc-Ara-4C(2)H(2)O-H](-) ion, m/z 943.4 [M-2Glc-4C(2)H(2)O-H](-) ion, m/z 811.1 [M-2Glc-Ara-4C(2)H(2)O-H](-) ion, m/z 781.2 [M-2Glc-Gal-4C(2)H(2)O-H](-) ion, m/z 649.0 [M-2Glc-Gal-Ara-4C(2)H(2)O-H](-) ion, and m/z 458.8 [Soyasapogenol A+H](+) ion. Metabolic activity varied significantly between individuals. The metabolic pathway was classified into two groups: the first group potently produced soyasapogenol A and the second group accumulated soyasapogenol A 3-beta-D-glucuronide.

Influence of the Labeling Group on Ionization and Fragmentation of Carbohydrates in Mass Spectrometry

The ionization and fragmentation behaviors of carbohydrate derivatives prepared by reaction with 2-aminobenzamide (AB), 1-phenyl-3-methyl-5-pyrazolone (PMP), and phenylhydrazine (PHN) were compared under identical mass spectrometric conditions. It has been shown that the intensities of signals in MS spectra depend on the kind of saccharides investigated and reducing end labels used. PMP sialyllactose, when ionized by ESI/MALDI, produced a mixture of [M + H]+, [M + Na]+, [M - H + 2Na]+ ions in the positive mode and [M - H]-, [M + Na - 2H]- ions in the negative mode. The AB and PHN derivatives formed abundant [M + H]+ and [M - H]- ions in ESI, and by matrix-assisted laser desorption/ionization (MALDI) produced abundant [M + Na]+ ions. PMP- and reduced AB-sialyllactose produced only Y-type fragment ions under both MS/MS sources. In the electrospray ionization (ESI)-MS/MS spectrum of PHN-sialyllactose, abundant ions corresponded to B, Z cleavages and in its MALDI-MS/MS spectrum, the abundant ions were consistent with Y glycosidic cleavages with the concurrence of B, C, and cross-ring fragment ions. In the MALDI-MS spectra of oligosaccharides acquired immediately after derivatization, it was possible to detect only PHN derivatives. After purification, spectra of all three types of derivatives showed high signal-to-noise ratios with the most abundant ions observed for AB reduced saccharides. [M + Na]+ ions were the dominant products and their fragmentation patterns were influenced by the type of the labeling and the kind of oligosaccharide considered. In the MALDI-PSD and -MS/MS spectra of AB-derivatized glycans, higher m/z fragment ions corresponded to B and Y cleavages and the loss of bisecting GlcNAc appeared as a weak signal or was not detected at all. Fragmentation patterns observed in the spectra of hybrid/complex PHN and PMP glycans were more comparable-higher m/z fragments corresponded to B and C glycosidic cleavages. For PHN glycans, the abundance of ions resulting from the loss of bisecting GlcNAc depended on the number of residues linked to the 6-positioned mannose. Also, PHN and PMP derivatives produced cross-ring cleavages with abundances higher than observed in the spectra of AB derivatized oligosaccharides. For high-mannose glycans, the most informative cleavages were provided by AB and PHN type of labeling. Here, PMP produced dominant Y-cleavages from the chitobiose while other ions produced weak signals.

Conformational stabilities of dicyclopropyl ketone determined from variable temperature infrared spectra of xenon solutions and ab initio calculationsElectronic supplementary information (ESI) available: Calculated energies, diagonal force constants, symmetry coordinates and calculated asymmetric torsional potential function. See http://www.rsc.org/suppdata/cp/b4/b400142g/

The infrared (3500–40 cm−1) spectra of gaseous and solid dicyclopropyl ketone, (c-C3H5)2CO, along with the Raman (3500–40 cm−1) spectra of the liquid and solid phases have been recorded. Only the major cis–cis (C2v) conformer (CO bond over the two three-membered rings) and minor cis–trans (Cs) form (CO bond eclipsing the hydrogen atom on one of the rings) have been identified in the fluid phases. Variable temperature (−55 to −100 °C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. Utilizing six different combinations of pairs of bands from the C2v and Cs conformers, the average enthalpy difference between these two conformers has been determined to be 530 ± 27 cm−1 (6.34 ± 0.32 kJ/mol), with the C2v form the more stable rotamer. At ambient temperature it is estimated that there is only 13 ± 2% of the Cs conformer present. A complete vibrational assignment is given for the C2v form and several of the fundamentals of the Cs conformer have been identified by utilizing predictions of fundamental frequencies, infrared intensities, and Raman activities from MP2(full)/6-31G(d) ab initio calculations. The structural parameters, dipole moments and conformational stabilities have been obtained from ab initio calculations at the level of restricted Hartree–Fock (RHF), with full electron correlation by the perturbation method to second order (MP2(full)) and hybrid density functional theory (DFT) by the B3LYP method with a variety of basis sets. The predicted conformational stabilities are consistent with the experimental results. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules.

On the Spectrum of the Product of Closed Operators

In this note we study the connection between the spectra of the products AB and BA of unbounded closed operators A and B acting in Banach spaces. Under the condition that the resolvent sets of these products are not empty we show that the spectra of AB and BA coincide away from zero and prove the commutation relation . Further, we prove statements concerning the relationship between the spectra of the operator AB and the block operator matrix .

On the Spectrum of the Product of Closed Operators

In this note we study the connection between the spectra of the products AB and BA of unbounded closed operators A and B acting in Banach spaces. Under the condition that the resolvent sets of these products are not empty we show that the spectra of AB and BA coincide away from zero and prove the commutation relation 𝕀 . Further, we prove statements concerning the relationship between the spectra of the operator AB and the block operator matrix .

Electrospray Mass Spectra of Arsenic Compounds

Positive ion electrospray mass spectra of arsenobetaine, AB, arsenocholine, AK, monomethylarsonic acid, MMA, dimethylarsinic acid, DMA, tetramethylarsonium TMAs, arsenate, AsV, and arsenite, AsIII, have been obtained. When appropriate, negative ion electrospray mass spectra have been performed. In order to clarify fragmentation pathways MS/MS spectra have also been recorded. Positive ion electrospray mass spectra have been found to be more useful for the identification of the organoarsenic compounds AB, AK, MMA, DMA and TMAs, whereas negative ion electrospray mass spectra is more suitable for the identification of the inorganic compounds AsV and AsIII. © 1997 John Wiley & Sons, Ltd.

Spectral consequences of periodic orbit bifurcations of AB 2 stretching vibrational modes

Analysis of the kinetically coupled Morse oscillator model of Thiele and Wilson is used to relate abrupt changes in the qualitative character of the stretching vibrational spectra of AB 2 species to the loss of stability of the symmetric stretching periodic orbit above a certain energy threshold. A new uniform asymptotic solution of the relevant Hill's equation yields novel scaling relations that govern the dependence of the stability parameters on the mass ratio ( m A/ m B) and the reduced energy ( E/ D), scaled with respect to the dissociation energy. Crudely simulated dispersed emission spectra are used to illustrate the quantum mechanical consequences of the theory with particular reference to recent experiments on CS 2.

Fourier transform infrared (FTIR) spectra of soybean saponin Ab and Bb

Fourier transform infrared (FTIR) spectra of soybean saponin Ab and Bb

Semi-empirical and ab-initio calculations of diatomic heteronuclear molecules doped into cubic crystals. Comparison to experimental data

The optical spectra of diatomic molecules Ab, A = Sn, Pb; B = S, Se, Te doped into KCl and KBr are quite different from data of the isolated species. From semi-empirical calculations shifts of electronic bands of the free AB compared to the doped molecules are obtained. The HOMO-LUMO gap is increased when the molecule AB is surrounded by host atoms. A tentative assignment is made for the lowest electronic transitions.Ab-initio methods allow for the calculation of vibrational frequencies of free molecules and the dopants as well. Starting from AB, neighbours on the A-B axis and at least one shell of host atoms is added. The results are used to assign experimental data.

Relaxation studies using saturated bandshapes in high-resolution NMR. I. Symmetric three [formula omitted] systems

Bandshapes of spectra of the types AB 2 and AX 2 have been calculated at various rf field strengths, for relaxation by the intramolecular dipole-dipole and random field mechanisms. In general, different relaxation processes give rise to different bandshapes, and for the symmetric three spin- 1 2 cases studied here the two mechanisms are readily distinguishable if one or the other dominates. Spectra of an AB 2 spin system, for example, show that the behavior of the asymmetric transition is very sensitive to the relaxation processes, with the random field mechanism producing a relatively sharp transition which tends to saturate at low rf amplitude, in contrast to the dipole-dipole mechanism. The programs written for the calculation of these bandshapes are described in some detail, and they may be readily generalized to more complex spin systems and to other relaxation mechanisms in the extreme narrowing limit. These features follow because all required relaxation terms are calculable by the programs when the appropriate relaxation Hamiltonians are put into suitable forms.

Vibrational studies of olivine-type compounds—III. Orthosilicates and germanates A IB IIIX IVO 4

The i.r. and Raman spectra of AB III XO 4 silicates and germanates with an olivine structure are studied and their interpretation is discussed on both theoretical and experimental bases. The investigation of many AB III XO 4 compounds (pure compounds, solid solutions and isotopic species) leads to a detailed and realistic interpretation. This paper shows how the Raman data confirm without doubt the D 2 h 16 space group for these compounds. Lastly, it has been investigated, as for AB II XO 4 isotopic compounds, to what extent the vibrational spectrum is modified by the chemical nature of the A and B cations and in absence of ionization potentials for rare earths cations, a correlation with the values of electronegativity is worked out.

Opacity-Probability Distribution Functions for Carbon Monoxide at Elevated Temperatures

view Abstract Citations (5) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Opacity-Probability Distribution Functions for Carbon Monoxide at Elevated Temperatures Kunde, Virgil G. Abstract Opacity-probability distributions have been computed for 12C160 by the method suggested by Strom and Kurucz The distribution functions have been obtained from computed theoretical spectra of 12C160 at temperatures of 16800, 2016°, 25200, and 33600 K and at turbulent velocities of 0, 2, and 8 km sec'. Spectral intervals of 100 cm' were chosen for the band regions of the fundamental (1000-2400 cm-'), the first overtone (2400-4400 cm-'), and the second overtone (4500-6500 cm'). The contributions of all spectral lines at a given frequency were considered in computing the theoretical spectra of the line ab- sorption coefficient. If only Doppler and turbulent line broadening are considered, the line absorption coefficient of CO is essentially zero over a significant fraction of the spectrum. This is due to the relatively large line separa- tion (4 cm1 for a rigid rotator) and to the rapid decrease of the Doppler wings. Thus the spectra and consequently the opacity-probability distribution functions are characterized by an absorption coefficient which varies through many orders of magnitude A second trend evident in the opacity-probability dis- tribution functions is the closing of the spectral gaps with increasing temperature and/or turbulent velocity Publication: The Astrophysical Journal Pub Date: December 1969 DOI: 10.1086/150275 Bibcode: 1969ApJ...158.1167K full text sources ADS |

Die Analyse «scheinbar einfacher» kernmagnetischer Resonanzspektren

AbstractThe theory of observed spectra that give less than the theoretical number of transitions, i.e. apparently simple spectra, is studied. The general conditions for the existence of such spectra of the type AB … RX … are discussed in terms of effective LARMOR‐frequencies. Explicit experimental conditions for which observed spectra are apparently simple are given for spectra of the type ABX as well as A2B2X.

Proton magnetic resonance in coumarins

The high resolution proton magnetic resonance spectra of AB, ABC and ABCD systems in fourteen coumarins have been studied. Chemical shifts and spin coupling constants for the protons in various positions in the benzo-α-pyrone ring have been obtained. The spectrum of coumarin confirms the ethylenic nature of double bond between carbon atoms in positions 3 and 4. The chemical shifts for the phenyl protons are in conformity with the reactivities of the coumarins at various positions in the ring. A linear relation has been observed between the chemical shift for proton in 8 position in various 6 substituted coumarins and the Hammett’s constants (σ) for substituents in themeta position. The NMR spectra offer a very convenient method for distinguishing between 3 and 4 substituted coumarins on account of the large chemical shift for the protons in positions 3 and 4.