Assignment Of Modes Research Articles

Experimental and theoretical spectroscopic analysis, hydrogen bonding, reduced density gradient and antibacterial activity study on 2-Phenyl quinoline alkaloid

The main objective of the study was based on combined experimental and quantum chemical computation methodology performed on spectroscopic analysis, structural activity study in order to find the antibacterial activity of 2-phenyl quinoline (2PQ) alkaloid. Solvent effect of 2PQ with water complexes (2PQ·nH2O, n = 1,2,3…7) was performed at the B3LYP/6-311G(d,p) level to investigate the different types of hydrogen bonding interactions in compound 2PQ. The optimized structural parameters of the title compound were computationally obtained at DFT/B3LYP level of theory. The interaction energies of 2PQ·H2O complexes were calculated with the basis set superposition error (BSSE) correction. The fundamental modes of vibration were examined by experimental FT-IR and FT-Raman techniques. The assignments of vibrational modes were carried out by using normal co-ordinate analysis (NCA). Stability of the molecule, intra and intermolecular hydrogen bonding and hyperconjugative interaction of 2PQ and its water complexes were also analyzed by using NBO analysis. Non-covalent interactions of 2PQ and its water complexes were studied by reduced density gradient (RDG) analysis. The UV–visible spectrum of the molecule in ethanol and water solvent were recorded and compared with calculated data. Molecular docking studies were performed to predict binding site of 2PQ with its target protein. The antibacterial activity of 2-phenyl quinoline alkaloid were tested against standard strain of the bacteria Escherichia coli and Staphylococus aureus.

Exploring the Vibrational Side of Spin-Phonon Coupling in Single-Molecule Magnets via 161 Dy Nuclear Resonance Vibrational Spectroscopy.

Synchrotron‐based nuclear resonance vibrational spectroscopy (NRVS) using the Mössbauer isotope 161Dy has been employed for the first time to study the vibrational properties of a single‐molecule magnet (SMM) incorporating DyIII, namely [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O ⋅2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the DyIII ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that 161Dy NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs.

Association between sexual dysfunction and avulsion of the levator ani muscle after instrumental vaginal delivery.

The effects of levator ani muscle (LAM) avulsion after instrumental delivery on the sexual function of patients are currently unknown. Therefore, the objective of our study was to use a validated questionnaire, namely, the Female Sexual Function Index (FSFI), to compare the sexual function in patients with and without LAM avulsion after instrumental vaginal delivery. This was a prospective observational study of 112 primiparous women after instrumental (vacuum or forceps) vaginal delivery. The obstetric and general characteristics of the population were studied. At 6 months postpartum, the contraceptive method used and the occurrence of LAM avulsion (using four-dimensional transperineal ultrasound) were determined, and the FSFI was administered. A total of 100 patients (62 without avulsion and 38 with avulsion) completed the study. Thirty-eight (38%) were diagnosed with avulsion (42.1% after Kielland forceps delivery, 57.9% after Malmström vacuum delivery; P = .837). Women with LAM avulsion had significantly lower scores for desire (2.9 ± 1.2 vs 3.4 ± 1.1; P = .049), arousal (2.8 ± 1.7 vs 3.6 ± 1.4; P = .014), lubrication (2.3 ± 1.4 vs 3.0 ± 1.2; P = .011), orgasm (2.6 ± 1.6 vs 3.3 ± 1.2; P = .006) and satisfaction (3.1 ± 1.8 vs 3.9 ± 1.5; P = .051) than did women without LAM avulsion. The overall FSFI score was lower in patients with avulsion (16.7 ± 8.9 vs 20.7 ± 6.9, P = .033). These results were obtained after controlling for confounders (delivery mode, induced labor, birthweight, perineal tears, avulsion degree, contraceptive method and group assignment for the parent study) in the multivariate analysis (F = 4.974, P = .001). Patients with LAM avulsion present a higher degree of sexual dysfunction compared wiith patients without avulsion at 6 months after instrumental vaginal delivery.

A Branch and Bound Algorithm for a Multi-Mode Project Scheduling Problem With a Single Non-Renewable Resource

In this paper, a project scheduling problem with multi-modes and a single non-renewable resource is considered. The resource is released in pre-specified times at pre-specified quantities. An activity can be executed at different modes where a mode is defined by a processing time and a resource requirement amount. The objective is to minimize the project completion time. A branch and bound algorithm that enumerates the partial solutions based on the mode assignment decisions is presented. The results of the experiments have revealed that the branch and bound algorithm can solve problem instances with up to 100 activities in reasonable times.

Structural, Spectroscopic (FT-IR, Raman, NMR and UV-Vis.) and Theoretical Investigations of Cyclopentolate

In this study, the structural and spectroscopic characterizations (FT-IR, Laser-Raman, 1H and 13C NMR and UV-vis spectra) of cyclopentolate were performed using experimental and theoretical methods. Four conformational structures and optimized molecular geometries of the molecule were examined. The vibrational wavenumbers, proton and carbon-13 NMR chemical shifts, UV-Vis. parameters were theoretically obtained for the most stable form of the molecule and the HOMO-LUMO analyses were performed with DFT/B3LYP method at aug-cc-pVDZ basis set. The weak intra-molecular hydrogen bond interaction in O45-H46…N23 group was determined. The 1H and 13C NMR chemical shifts were experimentally and theoretically investigated. The assignments of theoretical vibrational modes were obtained using VEDA 4 software in terms of potential energy distribution (PED). The theoretically and experimentally obtained data were found to be consistent with each other.

Vibrational Dynamics of Crystalline 4-Phenylbenzaldehyde from INS Spectra and Periodic DFT Calculations.

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, thus validating their assignment and correcting previous reports based on single molecule calculations. The calculations allow the unambiguous assignment of the phenyl torsional mode at ca. 118–128 cm−1, from which a phenyl torsional barrier of ca. 4000 cm−1 is derived, and the identification of the collective mode involving the antitranslational motion of CH···O bonded pairs, a hallmark vibrational mode of systems where C-H···O contacts are an important feature.

IR and Raman spectra with Gaussian-09 molecular analysis of some other parameters and vibrational spectra of 5-fluoro-uracil

Recorded IR and Raman spectra of 5-fluoro-uracil have been analyzed with the carried out theoretical computation by Gaussian-09 [DFT/B3LYP/6-311 ++G**] and GAR2PED software. In the assignment of fundamental modes, the GAR2PED software has been used to calculate the PEDs. HOMO–LUMO energy gap study supports the possibility of charge transfer in biomolecule. Electrostatic potential plotting with iso-surface plot and the mappings of electron density with molecular electrostatic potential have been made for the concept of charge distribution in molecules as the sites of nucleophilic reactions and electrophilic effect. The DFT calculations have been employed to yield the atomic polarizability tensor charges, Mulliken atomic charges, molecular structure and thermodynamic functional properties of the biomolecule. The assignment has been made in the two species for the normal mode of the fluoro group substituent on pyrimidine ring.

Paper: In-situ high-pressure Raman scattering and ab-initio studies in Cu2Sb up to 45 GPa

The influence of pressure on the optical properties of nanostructured tetragonal Cu2Sb has been investigated jointly by experimental Raman spectroscopy (RS) and theoretical first-principles calculation based on density functional theory (DFT) varying pressure from zero (ambient condition) to 45 GPa. The DFT determined pressure dependence of the Raman active modes and the mode-Grüneisen parameters for each Raman mode are found to be in excellent agreement with those experimentally determined. Comparison of the pressure evolution of the experimental Raman data with those of DFT has allowed us to make the proper assignment of optical phonon modes.

Determination of Hg2+ in water based on acriflavine functionalized AgNPs by SERS

We conducted a related study on the determination of Hg2+ in water by surface-enhanced Raman scattering (SERS). It is based on acriflavine as a signal probe with the assistance of aggregation agent MgSO4 for the SERS investigation. Moreover, the density functional theory (DFT) calculations of acriflavine were performed for interpreting the assignments of the vibrational normal modes. The interaction of acriflavine with AgNPs was inhibited because the citrate reduced Hg2+ to Hg and formed Ag amalgam on the AgNPs surface. The formation of Ag-Hg alloys reduced the SERS intensity of acriflavine. This sensing system displayed excellent sensitivity and a detection limit as low as 1.4 mol L − 1. The relationship between the SERS intensity and Hg2+ concentration was found in the range of 0.1–8.0 × 10−7 mol L − 1. This method for detecting Hg2+ is inexpensive, facile and sensitive.

Group Vibrational Mode Assignments as a Broadly Applicable Tool for Characterizing Ionomer Membrane Structure as a Function of Degree of Hydration

Infrared spectra of Nafion, Aquivion, and the 3 M membrane were acquired during total dehydration of fully hydrated samples. Fully hydrated exchange sites are in a sulfonate form with a C3V local s...

Raman spectra and phonon structures of BaGa4Se7 crystal

BaGa4Se7 is a promising nonlinear optical crystal at infrared frequencies and shows interesting terahertz phonon-polaritons and high nonlinear coefficients for terahertz generation. Phonons are the key players in infrared absorptions and the photon-phonon resonance phenomena at terahertz frequencies. Here, we study the phonon structures of BaGa4Se7 crystal, with polarized Raman spectroscopy and theoretical calculations for phonon dispersion curves, density of states and vibration modes. An interesting phonon gap separates the modes with still or vibrating Ba atoms. We also determine the nine strongest Raman peaks’ vibration modes and Raman tensors. Our Raman mode assignments and phonon calculations show consistencies in phonon energies, phonon types, and vibration directions. Above knowledge provides a new case example for phonon gaps, offers a complete picture of the phonon structures of BaGa4Se7, and helps us understand phonon gaps, monoclinic crystals, and its phenomena at infrared and terahertz frequency ranges.

Mid-IR Dirac-cone dispersion relation materialized in SOI photonic crystal slabs.

We materialized the isotropic Dirac-cone dispersion relation in the mid-infrared range by fabricating photonic crystal slabs of the C4v symmetry in SOI (silicon-on-insulator) wafers by electron beam lithography. The dispersion relation was examined by the angle-resolved reflection spectra with our home-made high-resolution apparatus, which showed a good agreement with the dispersion relation and the reflection spectra calculated by the finite element method. The reflection spectra also agreed with the selection rules derived from the spatial symmetry of the Dirac-cone modes, which proved to be a powerful tool for the mode assignment.

Polarized Raman spectra of hematite and assignment of external modes

AbstractNotwithstanding the significant practical importance of hematite, α‐Fe2O3, the complete assignment and understanding of the Raman spectrum acquired on this crystalline solid are uncertain. Above all, only one of the two external Eg phonons arising from the Γ point has been resolved and hence assigned. It is well known that the Eg mode at 294 cm−1 has been attributed to one of the two external phonons arising from the Γ point. To this end, we have undertaken studies to examine the polarized Raman scattering on a pure single crystal to gain a better understanding and assignment of phonons arising from the Γ point in the Raman spectrum of hematite. Here, we resolve and assign the previously unidentified external Eg phonon at 245 cm−1 and, additionally, confirm that the band at 294 cm−1 is an external Eg phonon, in the first‐order Raman spectrum of hematite. Further, our polarized Raman spectra display interesting polarization behavior of the 2LO mode at 1320 cm−1, where this band is only Raman active in ei||es polarization configurations.

Определение энергетической структуры и спектроскопических параметров колебательного состояния (v-=SUB=-5-=/SUB=-=v-=SUB=-12-=/SUB=-=1) молекулы C-=SUB=-2-=/SUB=-D-=SUB=-4-=/SUB=-

Ro-vibrational structure of v5+v12 band of C2D4 molecule was recorded by using the Bruker IFS 125HR Fourier spectrometer with a resolution of 0.0025 cm-1 in the first time. As the first step, the assignment of transitions has been made and then obtained results were used as initial experimental data to solve the inverse spectroscopic problem. A set of 12 spectroscopic parameters of the investigated vibrational state was determined for the first time with drms = 0.0013 cm-1.

Whispering gallery mode emission from dye-doped polymer fiber cross-sections fabricated by near-field electrospinning.

Whispering gallery mode (WGM) resonators demonstrate great potential for photonic and sensing applications. Yet, these devices are often disadvantaged by costly materials or complex fabrication approaches, in addition to lack of manufacturing scalability. Near-field electrospinning (NFES), a recently emerged facile fiber fabrication method, offers a solution. Here, WGM resonances are reported in Rhodamine 6G-doped poly(vinyl) alcohol (PVA) microfibers via NFES. Diameters are tuned over a range of more than 10 μm by varying substrate stage speed. Fibers display uniform distribution of dye, smooth surfaces, and circular cross-sections, all critical for supporting WGMs. High quality (Q) resonances are confirmed within fiber cross-sections through polarization experiments, free-spectral range analysis, and Mie-theory-derived mode assignment. In addition to WGMs, groups of associated spiral or conical modes are observed due to taper-induced weak optical confinement along the fiber axis. Crosslinked, dye-doped PVA fibers are utilized to sense the ethanol concentration in ethanol-water mixtures and actuation mechanisms are evaluated by comparison to theoretical spectra. The demonstration of high-Q resonances within NFES polymer microfibers is a critical step toward simple, cost effective, high-volume fabrication of WGM resonators for optoelectronics and biomedical devices.

Single molecule magnet behaviour in a square planar S = 1/2 Co(ii) complex and spin-state assignment of multiple relaxation modes.

We report the first example of field-induced single molecule magnet (SMM) behaviour in a square-planar S = 1/2 Co(ii) pincer complex [(PNNNP)CoBr]Br (2). The related five-coordinate complexes [(PCNCP)CoBr2] (1) and [(PONOP)CoBr2] (3) also exhibit SMM properties. Partial spin crossover displayed by 3 allows for assignment of distinct relaxation modes to each spin state.

Modeling the hardness of the titanium alloy subjected to laser processing

The article considers the influence of the radiation power W, the longitudinal feed Spr of the laser beam and the distance L from the protective glass of the laser focusing head to the workpiece on the hardness Hv of the titanium alloy TiTaN. A multi-factor model is established that relates the surface layer hardness to the input factors of laser processing and allows you to quickly assign a laser treatment mode and to control it in order to improve the quality of the processed layer. The power W has the greatest effect on the hardness of the surface layer. With increasing W, the hardness increases. Increasing the feed Spr leads to a decrease in the Hv parameter. The effect of the distance L is similar to the radiation power, but the degree of influence of L is more than half as small as W. The developed method of operational assignment of the laser processing mode allows to reduce the auxiliary time for performing the technological operation. The research results are relevant for manufacturing enterprises that implement laser processing processes, as well as for design organizations that develop modern laser equipment.

Channel-resolved molecular Auger spectroscopy

SynopsisMolecular Auger spectra typically consist of many overlapping lines that are hard or impossible to resolve experimentally even with highest-resolution electron spectroscopy techniques. Since molecular Auger energies depend on non-adibatatic dynamics, they can also be difficult to calculate precisely, such that the assignment of molecular Auger transitions is often ambiguous. Here we show that by measuring Auger-electron multi-ion coincidences, we can disentangle the spectra into the contributions from specific ionic final states, which helps significantly with their interpretation and assignment.

Structure, stability, infrared spectra, and bonding of OHm(H2O)7 (m = 0, ±1) clusters: ab initio study combining the particle swarm optimization algorithm.

The various structural candidates of anionic, neutral, and cationic water clusters OHm(H2O)7 (m = 0, ±1) have been globally predicted by combining the particle swarm optimization method and quantum chemical calculations. Geometry optimization and vibrational analysis for the optimal structures were performed with the MP2/aug-cc-pVDZ method, and the energy profile was further refined at the CCSD(T)/CBS level. Special attention was paid to the relationships between configurations and energies, particularly the first solvation shell coordination number of OH- and OH. For OH-(H2O)7, OH(H2O)7, and OH+(H2O)7 clusters, the most stable species at room temperature are predicted to be the tetra-solvated multi-ring structure A6, the tri-solvated hemibond cage structure N1, and the single five-membered ring structure C2, respectively. The temperature effects on the stability of these three systems were also explored via Gibbs free energies. Furthermore, for the OH-(H2O)7 clusters, the assignments of vibrational transitions in the OH stretching region are in good agreement with the studies of small hydroxide ion-water clusters, and the IR spectra of two isomers (tetra-solvated multi-ring A6 and penta-solvated cage A3) may match future experimental observation well. By topological analysis and reduced density gradient analysis, the structural characteristics and bonding strengths of the studied clusters were investigated. This work indicates the excellent performance of the PSO search algorithm and CALYPSO on water clusters, and may further provide extensive insights into the chemical behavior such as the transport mechanism of OH- ions and OH radicals in the aqueous phase.

On the SN2 reactions modified in vibrational strong coupling experiments: reaction mechanisms and vibrational mode assignments.

Recent experiments have reported modified chemical reactivity under vibrational strong coupling (VSC) in microfluidic Fabry-Pérot cavities. In particular, the reaction rate of nucleophilic substitution reactions at silicon centers (SN2@Si) has been altered when a vibrational mode of the reactant was coupled to a confined light mode in the strong coupling regime. In this situation, hybrid light-matter states known as polaritons are formed and seem to be responsible for the modified chemical kinetics. These results are very encouraging for future applications of polaritonic chemistry to catalyze chemical reactions, with the ability to manipulate chemical phenomena without any external excitation of the system. Still, there is no theory capable of explaining the mechanism behind these results. In this work we address two points that are crucial for the interpretation of these experiments. Firstly, by means of electronic structure calculations we report the reaction mechanism in normal conditions of the two recently modified SN2@Si reactions, obtaining in both cases a triple-well PES where the rate-determining step is due to the Si-C and Si-O bond cleavage. Secondly, we characterize in detail the normal modes of vibration of the reactants. In the VSC experiments, reaction rates were modified only when specific vibrations of the reactants were coupled to a cavity mode. We find that these vibrations are highly mixed among the different fragments of the reactants leading to a completely new assignment of the IR peaks coupled to cavity modes in the original experimental works. Our results are fundamental for the interpretation of the VSC experiments given that in the absence of a theory explaining these results, the current phenomenological understanding relies on the assignment of the character of the vibrational IR peaks.