Search

Copyright of Revista Colombiana de Ciencias Químico-Farmacéuticas is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A systematic study of Brown's characteristic curves of the two center Lennard–Jones plus point quadrupole (2CLJQ) fluid was carried out using molecular simulation and molecular-based equation of state (EOS) modeling. The model parameters (elongation and quadrupole moment) were varied systematically covering the range relevant for real fluid models. In total, 36 model fluids were studied. The independent predictions from the EOS and the computer experiments are found to be in very good agreement. Based on these results, the influence of the quadrupole moment on the fluid behavior at extreme conditions is elucidated. The quadrupole interactions are found to have a surprisingly minor influence on the extreme state fluid behavior. In particular, for the Amagat curve, the quadrupole moment is found to have an almost negligible influence in a wide temperature range. The results also provide new insights into the applicability of the corresponding states principle, which is compared to other molecular property features. Interestingly, for a wide range of quadrupole moments, the fluid behavior at extreme conditions is conform with the corresponding states principle—opposite to the influence of other molecular features. This is attributed to the symmetry of the quadrupole interactions. Moreover, an empirical correlation for the characteristic curves was developed as a global function of the model parameters and tested on real substance models. Additionally, the applicability of Batschinski's linearity law for the Zeno curve was assessed using the results for the 2CLJQ fluid. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the potential of the decorated boron nitride nanocage (BNNc) with transition metals for capturing carbon monoxide (CO) as a toxic gas in the air. Design/methodology/approach: BNNc was modeled in the presence of doping atoms of titanium (Ti), vanadium (V), chromium (Cr), cobalt (Co), copper (Cu) and zinc (Zn) which can increase the gas sensing ability of BNNc. In this research, the calculations have been accomplished by CAM–B3LYP–D3/EPR–3, LANL2DZ level of theory. The trapping of CO molecules by (Ti, V, Cr, Co, Cu, Zn)–BNNc has been successfully incorporated because of binding formation consisting of C → Ti, C → V, C → Cr, C → Co, C → Cu, C → Zn. Findings: Nuclear quadrupole resonance data has indicated that Cu-doped or Co-doped on pristine BNNc has high fluctuations between Bader charge versus electric potential, which can be appropriate options with the highest tendency for electron accepting in the gas adsorption process. Furthermore, nuclear magnetic resonance spectroscopy has explored that the yield of electron accepting for doping atoms on the (Ti, V, Cr, Co, Cu, Zn)–BNNc in CO molecules adsorption can be ordered as follows: Cu > Co >> Cr > Zn ˜ V> Ti that exhibits the strength of the covalent bond between Ti, V, Cr, Co, Cu, Zn and CO. In fact, the adsorption of CO gas molecules can introduce spin polarization on the (Ti, V, Cr, Co, Cu, Zn)–BNNc which specifies that these surfaces may be used as magnetic-scavenging surface as a gas detector. Gibbs free energy based on IR spectroscopy for adsorption of CO molecules adsorption on the (Ti, V, Cr, Co, Cu, Zn)–BNNc have exhibited that for a given number of carbon donor sites in CO, the stabilities of complexes owing to doping atoms of Ti, V, Cr, Co, Cu, Zn can be considered as: CO →Cu–BNNc >> CO → Co–BNNc > CO → Cr–BNNc > CO → V–BNNc > CO → Zn–BNNc > CO → Ti–BNNc. Originality/value: This study by using materials modeling approaches and decorating of nanomaterials with transition metals is supposed to introduce new efficient nanosensors in applications for selective sensing of carbon monoxide. [ABSTRACT FROM AUTHOR]

Noise and Radio-frequency interference or RFI causes a significant restriction on the Free induction Decay or FID signal detection of the Nuclear Quadrupole Resonance procedure. Therefore, using this method in non-isolated environments such as industry and ports requires extraordinary measures. For this purpose, noise reduction algorithms and increasing signal-to-noise-and-interference ratio or SNIR have been used. In this research, sodium nitrite has been used as a sample and algorithms have been tested in a non-isolated environment. The resonant frequencies for the 150 g of test sample were measured at 303 K at about 1 MHz and 3.4 MHz. The main novelty in this study was, (1) using two types of antennas in the receiver to improve adaptive noise and interference cancellation, (2) using a separate helical antenna in the transmitter to eliminate the duplexer, (3) estimating the noise before sending the pulse to calculate the weighting factors and reduce the noise by adaptive noise cancellation, (3) reject the interference by blanking algorithm, (4) pulse integration in the frequency domain to increase the SNR, and (5) increasing the detection speed by new pulse integration technique. By interference rejection and noise cancellation, the SNIR is improved to 9.24 dB at 1 MHz and to 7.28 dB at 3.4 MHz, and by pulse integration 44.8 dB FID signal amplification is achieved, and the FID signals are detected at 1.057 MHz and 3.402 MHz at room temperature.

We consider the longitudinal quadrupole relaxation rate enhancement (QRE) of a 1H nucleus due to the time fluctuations of the local dipolar magnetic field created by a close quadrupole 14N nucleus, the electric-field gradient (EFG) Hamiltonian of which changes with time because of vibrations/distortions of its chemical environment. The QRE is analytically expressed as a linear combination of the cosine Fourier transforms of the three quantum time auto-correlation functions GAA(t) of the 14N spin components along the principal axes A = X, Y, and Z of the mean (time-averaged) EFG Hamiltonian. Denoting the three transition frequencies between the energy levels of this mean Hamiltonian by νA, the functions GAA(t) oscillate at frequencies νA + sA/(2π) with mono-exponential decays of relaxation times τA, where the frequency dynamic shifts sA and the relaxation times τA are closed expressions of the magnitude of the fluctuations of the instantaneous EFG Hamiltonian about its mean and of the characteristic fluctuation time. Thus, the theoretical QRE is the sum of three Lorentzian peaks centered at νA + sA/(2π) with full widths at half maxima 1/(πτA). The predicted peak widths are nearly equal. The predicted dynamic shifts of the peaks are much smaller than their widths and amazingly keep proportional to the transition frequencies νA for reasonably fast EFG fluctuations. The theory is further improved by correcting the transition frequencies by the 14N Zeeman effects of second order. It is successfully applied to reinterpret the QRE pattern measured by Broche, Ashcroft, and Lurie [Magn. Reson. Med. 68, 358 (2012)] in normal cartilage. [ABSTRACT FROM AUTHOR]

We present experimental and theoretical investigations of magnetic noise originating from radio-frequency (RF) conductive shields of flat geometry in the inductance-dominated impedance regime below 300 kHz. The measurement is based on a Q -factor determination of a coil that provides a sufficient sensitivity, placed at the position where the shield magnetic noise is measured. The theory is based on calculations of magnetic field and inductance of one or a few flat rings that emulate a conductive shield. The theoretical model is found to be in close agreement with experimental data. It can be used to predict the magnetic noise of a conductive shield with different thicknesses, conductivities, and temperatures at different distances for a wide range of frequencies. Although the model can be generalized for a more arbitrary shield geometry, in its presented form, it can be applied to the magnetic noise predictions when the shield surface curvature is not large. One important conclusion is that the RF conductive shield can generate the magnetic noise much lower than femtotesla, and, thus, it can be used in many precision experiments targeting minute high-frequency magnetic signals, such as detection of magnetic resonance imaging and nuclear quadrupole resonance signals and search for axion dark matter. [ABSTRACT FROM AUTHOR]

We present a five-dimensional intermolecular potential energy surface (PES) of the NH3–N2 complex, bound state calculations, and new microwave (MW) measurements that provide information on the structure of this complex and a critical test of the potential. Ab initio calculations were carried out using the explicitly correlated coupled cluster [CCSD(T)-F12a] approach with the augmented correlation-consistent aug-cc-pVTZ basis set. The global minimum of the PES corresponds to a configuration in which the angle between the NH3 symmetry axis and the intermolecular axis is 58.7° with the N atom of the NH3 unit closest to the N2 unit, which is nearly parallel to the NH3 symmetry axis. The intermolecular distance is 7.01 a0, and the binding energy De is 250.6 cm–1. The bound rovibrational levels of the four nuclear spin isomers of the complex, which are formed when ortho/para (o/p)-NH3 combines with (o/p)-N2, were calculated on this intermolecular potential surface. The computed dissociation energies D0 are 144.91 cm−1, 146.50 cm−1, 152.29 cm−1, and 154.64 cm−1 for (o)-NH3–(o)-N2, (o)-NH3–(p)-N2, (p)-NH3–(o)-N2, and (p)-NH3–(p)-N2, respectively. Guided by these calculations, the pure rotational transitions of the NH3–N2 van der Waals complex were observed in the frequency range of 13–27 GHz using the chirped-pulse Fourier-transform MW technique. A complicated hyperfine structure due to three quadrupole 14N nuclei was partly resolved and examined for all four nuclear spin isomers of the complex. Newly obtained data definitively established the K values (the projection of the angular momentum J on the intermolecular axis) for the lowest states of the different NH3–N2 nuclear spin isomers. [ABSTRACT FROM AUTHOR]

Nuclear magnetic quadrupole moments (MQMs), such as intrinsic electric dipole moments of elementary particles, violate both parity and time-reversal symmetry and, therefore, probe physics beyond the standard model. We report on accurate relativistic coupled cluster calculations of the nuclear MQM interaction constants in BaF, YbF, BaOH, and YbOH. We elaborate on estimates of the uncertainty of our results. The implications of experiments searching for nonzero nuclear MQMs are discussed. [ABSTRACT FROM AUTHOR]

The nuclear electric quadrupole moment (NQM) of ruthenium was reevaluated by means of the molecular method. Therefore, four-component relativistic electronic structure calculations of the electric field gradient at the Ru nucleus in ruthenium monocarbide, which were done with the coupled cluster methodology and carefully augmented large basis sets, were combined with the respective nuclear quadrupole coupling constant from experiments. This provided a recommended NQM value of (425 ± 13) mbarn for 101Ru. [ABSTRACT FROM AUTHOR]

The quantized bulk quadrupole moment has so far revealed a non-trivial boundary state with lower-dimensional topological edge states and in-gap zero-dimensional corner modes. In contrast to photonic implementations, state-of-the-art strategies for topological thermal metamaterials struggle to achieve such higher-order hierarchical features. This is due to the absence of quantized bulk quadrupole moments in thermal diffusion fundamentally prohibiting possible band topology expansions. Here, we report a recipe for generating quantized bulk quadrupole moments in fluid heat transport and observe the quadrupole topological phases in non-Hermitian thermal systems. Our experiments show that both the real- and imaginary-valued bands exhibit the hierarchical features of bulk, gapped edge and in-gap corner states—in stark contrast to the higher-order states observed only on real-valued bands in classical wave fields. Our findings open up unique possibilities for diffusive metamaterial engineering and establish a playground for multipolar topological physics. Topological transport in thermal diffusion is governed by physical principles that are distinct from those encountered in solid-state or photonic topological systems. Here, the authors demonstrate an experimental strategy for engineering topological thermal phases with bulk, edge and corner modes. [ABSTRACT FROM AUTHOR]

Clarifying the interplay between charge-density waves (CDWs) and superconductivity is important in the kagome metal CsV3Sb5, and pressure (P) can play a crucial role. Here, we present 121/123Sb nuclear quadrupole resonance (NQR) measurements under hydrostatic pressures up to 2.43 GPa in CsV3Sb5 single crystals. We demonstrate that the CDW gradually changes from a commensurate modulation with a star-of-David (SoD) pattern to an incommensurate one with a superimposed SoD and Tri-hexagonal (TrH) pattern stacking along the c-axis. Moreover, the linewidth δν of 121/123Sb-NQR spectra increases with cooling down to TCDW, indicating the appearance of a short-range CDW order due to CDW fluctuations pinned by quenched disorders. The δν shows a Curie–Weiss temperature dependence and tends to diverge at Pc ~ 1.9 GPa, suggesting that a CDW quantum critical point (QCP) exists at Pc where Tc shows the maximum. For P > Pc, spin fluctuations are enhanced when the CDW is suppressed. Our results suggest that the maximal Tc at Pc ~ 1.9 GPa is related to the CDW QCP, and the presence of spin fluctuations prevents the Tc from a rapid decrease otherwise, after the CDW is completely suppressed. [ABSTRACT FROM AUTHOR]

The sulfur electric‐field‐gradient tensor for a disulfide bond in 33S2‐labeled L‐cystine has been investigated by 33S nuclear quadrupole resonance (NQR). 33S2‐labeled L‐cystine is synthesized by introduction of disulfide ions prepared from elemental 33S‐sulfur into an amino acid derivative, the side chain of which is iodinated. In its NQR spectrum, sharp single peaks are observed at between 24.63 and 24.90 MHz in the temperature range from 80 to 298 K. The two‐dimensional nutation echo 33S NQR experiment is carried out at 160 K, and the quadrupole coupling constant, CQ, and the asymmetric parameter, ηQ, are obtained to be 46.9(9) MHz and 0.6(1), respectively. The calculated 33S electric‐field‐gradient tensor components with respect to the molecular frame is briefly discussed. [ABSTRACT FROM AUTHOR]

Favipiravir (6-fluoro-3-hydroxypyrazine-2-carboxamide, FPV), an active pharmaceutical component of the drug discovered and registered in March 2014 in Japan under the name Avigan, with an indication for pandemic influenza, has been studied. The study of this compound was prompted by the idea that effective processes of recognition and binding of FPV to the nucleic acid are affected predominantly by the propensity to form intra- and intermolecular interactions. Three nuclear quadrupole resonance experimental techniques, namely 1H-14N cross-relaxation, multiple frequency sweeps, and two-frequency irradiation, followed by solid-state computational modelling (density functional theory supplemented by the quantum theory of atoms in molecules, 3D Hirshfeld Surfaces, and reduced density gradient) approaches were applied. The complete NQR spectrum consisting of nine lines indicating the presence of three chemically inequivalent nitrogen sites in the FPV molecule was detected, and the assignment of lines to particular sites was performed. The description of the nearest vicinity of all three nitrogen atoms was used to characterize the nature of the intermolecular interactions from the perspective of the local single atoms and to draw some conclusions on the nature of the interactions required for effective recognition and binding. The propensity to form the electrostatic N−H···O, N−H···N, and C−H···O intermolecular hydrogen bonds competitive with two intramolecular hydrogen bonds, strong O−H···O and very weak N−H···N, closing the 5-member ring and stiffening the structure, as well as π···π and F···F dispersive interactions, were analysed in detail. The hypothesis regarding the similarity of the interaction pattern in the solid and the RNA template was verified. It was discovered that the -NH2 group in the crystal participates in intermolecular hydrogen bonds N–H···N and N–H···O, in the precatalytic state only in N–H···O, while in the active state in N–H···N and N–H···O hydrogen bonds, which is of importance to link FVP to the RNA template. Our study elucidates the binding modes of FVP (in crystal, precatalytic, and active forms) in detail and should guide the design of more potent analogues targeting SARS-CoV-2. Strong direct binding of FVP-RTP to both the active site and cofactor discovered by us suggests a possible alternative, allosteric mechanism of FVP action, which may explain the scattering of the results of clinical trials or the synergistic effect observed in combined treatment against SARS-CoV-2. [ABSTRACT FROM AUTHOR]

The international postal network is one of the most widely used methods for correspondence throughout the world. Most postal traffic across the globe consists of legitimate interpersonal, business-consumer, and business-business communications. However, the global postal system is also utilized for criminal activity. In particular, it is often utilized to ship and distribute contraband, including illegal psychoactive drugs such as fentanyl and heroin, to consumers. Existing technological solutions are capable of identifying synthetic opioids and other illegal drugs within packages, but are accompanied by several disadvantages that make them unsuitable for large-scale authentication of international mail traffic. This paper presents a novel method for non-invasive authentication of mail packages that overcomes these challenges. The approach uses nuclear quadrupole resonance (NQR) spectroscopy to detect and quantify the presence of known active pharmaceutical ingredients (APIs) within the package. It has been experimentally demonstrated using a bench top prototype. Test results from a variety of package types demonstrate the effectiveness of the proposed authentication approach. [ABSTRACT FROM AUTHOR]

Context: In this research, CO2 and NO2 adsorption on doped nanographene (NG) sheets with transition metals (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, have been applied for scavenging of these toxic gases as the environmental pollutants. The values of changes of atomic charge density have illustrated a more significant charge transfer for Ni-doped C-NG through CO2 adsorption and a more remarkable charge transfer for Co-doped C-NG through NO2 adsorption. The data of NMR spectroscopy has depicted several fluctuations around the graph of Zn-doped on the nanographene surface. The thermodynamic results from IR spectroscopy have indicated that Δ G ads , NO 2 → TM @ C - NG o values are almost similar for doped metal transitions of Mn, Co, and Cu on the C-NG nanosheet, while Δ G ads , CO 2 → TM @ C - NG o has the largest gap of Gibbs free energy adsorption with dipole moment. Methods: The Langmuir adsorption model with a three-layered ONIOM using CAM-B3LYP functional accompanying LANL2DZ, EPR-III and 6-31 + G (d,p) basis sets due to Gaussian 16 revision C.01 program on the complexes of CO2 → (Fe, Ni, Zn) and NO2 → (Mn, Co, Cu) doped on the C-NG has been accomplished. Then, NMR and IR spectroscopy, nuclear quadrupole resonance, and natural bond orbital analysis have been accomplished for evaluating chemical shielding tensors, thermodynamic properties, electric potential, and occupancy fluctuation through bond orbitals, respectively. In addition, frontier orbitals of LUMO, HOMO, and also a series of chemical reactivity parameters have been calculated. Finally, time-dependent-DFT method due to UV-VIS spectrums has been accomplished to discern the low-lying excited states of CO2 and NO2 adsorption on the (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, doped C-NG sheet. [ABSTRACT FROM AUTHOR]

Nuclear quadrupole resonances for 14N and 17O nuclei are exquisitely sensitive to interactions with surrounding atoms. As a result, nitrogen and oxygen solid‐state nuclear magnetic resonance (ssNMR) provides a powerful tool for investigating structure and dynamics in complex systems. First‐principles calculations are increasingly used to facilitate spectral assignment and to evaluate and adjust crystal structures. Recent work combining the strengths of planewave density functional theory (DFT) calculations with a single molecule correction obtained using a higher level of theory has proven successful in improving the accuracy of predicted chemical shielding (CS) tensors and 17O quadrupolar coupling constants (Cq). Here we extend this work by examining the accuracy of predicted 14N and 17O electric field gradient (EFG) tensor components obtained using alternative planewave‐corrections involving cluster and two‐body fragment‐based calculations. We benchmark the accuracy of CS and EFG tensor predictions for both nitrogen and oxygen using planewave, two‐body fragment, and enhanced planewave‐corrected techniques. Combining planewave and two‐body fragment calculations reduces the error in predicted 17O Cq values by 35% relative to traditional planewave calculations. These enhanced planewave‐correction methods improve the accuracy of 17O and 14N EFG tensor components by 15% relative to planewave DFT but yield minimal improvement relative to a simple molecular correction. However, in structural environments involving either high symmetry or strong intermolecular interactions, enhanced planewave‐corrected methods provide a distinct advantage. [ABSTRACT FROM AUTHOR]

Here, we investigate in detail the impact of the size of the methylammonium iodide (MAI) reactants in the mechanochemical powder synthesis of the halide perovskite methylammonium lead iodide (MAPbI3). Morphology and structural characterizations by scanning electron microscopy and X‐ray diffraction reveal that with increasing MAI reactant size, the particle size of the perovskite powder increases, while its defect density decreases, as suggested by nuclear quadrupole resonance spectroscopy and photoluminescence investigations. The reason for this behavior seems to be associated to the sensitive influence of the MAI size on the time durations of MAPbI3 synthesis and delayed MAPbI3 crushing stage during ball milling. Thus, our results emphasize the high importance the reactant properties have on the mechanochemical synthesis of halide perovskites and will contribute to enhance the reproducibility and control of the fabrication of halide perovskites in powder form. [ABSTRACT FROM AUTHOR]

The nuclear quadrupole moment of aluminum (27Al) has been re-evaluated by determining the electric field gradients at this nucleus for AlF and AlCl using the coupled cluster method with single, double, and perturbative triple excitations [CCSD(T)]/aug-cc-pwCVXZ (X = T and Q) accounting for both vibrational averaging and core–core/core–valence electron correlation and then comparing to the experimentally measured nuclear quadrupole coupling constants (NQCCs). The new recommended value is Q(27Al) = 148.2 ± 0.5 mb, which can be compared to the previous value of 146.6 ± 1 mb. Using the new value of the nuclear quadrupole moment, the accuracy is assessed for several computational approaches [i.e., Hartree–Fock, Møller–Plesset perturbation theory to the second order, quadratic configuration interaction with single and double excitations, CCSD, CCSD(T), and density functional theory (DFT) with the B3LYP, PBE0, and M06-2X functionals] and basis sets (the aug-cc-pVXZ and aug-cc-pwCVXZ families) for determining the nuclear quadruple coupling constants for AlCN, AlNC, AlSH, AlOH, and AlCCH, where experimental measurements are available. From the results at equilibrium geometries of the polyatomic molecules, it has been determined that (i) the CCSD(T)/aug-cc-pwCVXZ approach is needed to obtain results within 4% of the experimental measurements, (ii) typical DFT values are only within 10%–15% of the experimental measurements, and (iii) the aug-cc-pVXZ family of basis sets is not recommended for computing the electric field gradients at aluminum. The present results also suggest that the NQCC for AlOH should be remeasured. Using the recommended CCSD(T)/aug-cc-pwCVXZ approach, the equilibrium geometries and corresponding NQCCs for AlCH3 and AlCCCN were determined, and the NQCCs are in excellent agreement with previously reported experimental values. [ABSTRACT FROM AUTHOR]

1H spin-lattice nuclear magnetic resonance relaxation experiments have been performed for triphenylbismuth dichloride (C18H15BiCl2) and phenylbismuth dichloride (C6H5BiCl2) in powder. The frequency range of 20–128 MHz has been covered. Due to 1H-209Bi dipole-dipole interactions, a rich set of pronounced Quadrupole Relaxation Enhancement (QRE) peaks (quadrupole peaks) has been observed. The QRE patterns for both compounds have been explained in terms of single- and double-quantum transitions of the participating nuclei. The analysis has revealed a complex, quantum-mechanical mechanism of the QRE effects. The mechanism goes far beyond the simple explanation of the existence of three quadrupole peaks for 14N reported in literature. The analysis has been supported by nuclear quadrupole resonance results that independently provided the 209Bi quadrupole parameters (amplitude of the quadrupole coupling constant and asymmetry parameter). [ABSTRACT FROM AUTHOR]

Properties of gas-phase thorium nitride, ThN, have been experimentally determined from a combined optical and microwave spectroscopic study. An intense band near 555 nm has been assigned as the [18.0]1.5–X2Σ+ (0,0) transition and recorded at high resolution in the presence of static electric and magnetic fields. The observed optical Stark shifts were analyzed to determine permanent electric dipole moments, μ → e l for the [18.0]1.5 and X2Σ+ states of 4.38 ± 0.02D and 5.11 ± 0.09D, respectively. Zeeman shifts were used to determine the magnetic g-factors. The pure rotational spectrum was recorded using a separated field optical pump/probe microwave repopulation scheme and analyzed to determine the bond length and 14N magnetic hyperfine and nuclear electric quadrupole parameters. A molecular orbital correlation diagram and ligand field electronic structure models are used to provide a qualitative interpretation of the electronic state ordering, magneto- and electro-static properties, and hyperfine interactions. Electronic structure calculations for the X2Σ+ state were performed, and results were compared with observations. Observed trends in μ → e l for the ThX (X = N, S, O, F, and Cl) series are discussed. [ABSTRACT FROM AUTHOR]

THE PURPOSE. Study the possibility of using a laboratory nuclear magnetic resonance console as a device for detecting counterfeit medicines. The problem of detecting counterfeit and counterfeit medicines is now very acute. Consider the potential of applying the nuclear quadrupole resonance radiospectroscopy method to determine the authenticity and quality of medicines by non-destructive means.ACTUALITY. The nuclear magnetic resonance method is included in the list of physico-chemical methods used in pharmacopia. The spectroscopy of nuclear quadrupole resonance, being similar in physical principles, has its advantages and advantages, which in general will strengthen the control of the authenticity and quality of medicines.METHODS. The theory of nuclear quadrupole resonance and features that allow to investigate medicinal preparations is resulted. The structural design of this hardware and software complex based on the Apollo Redstone nuclear quadrupole resonance spectrometer is described, its nodes are described, characteristics and parameters are given, a special attention is paid to the development of the sensor for the hardwarethe software complex and its coordination system with the spectrometer. Detailed description of its radio technical characteristics.RESULTS. The article shows the results of using the hardware software complex - measurements of spectra of nuclear quadrupole resonance for the drug paracetamol developed by various manufacturers, both Russia and foreign pharmaceutical companies. The possibility of measuring spectral characteristics directly in the package is shown. The necessary multi-pulse series of pulses, used in the measurement of spectral characteristics, are given. The possibility of receiving signals of spin echo with a good signal/noise ratio is shown, as well as the possibility of distinguishing different manufacturers' spectra of paracetamol according to the form of the release.CONCLUSION. The article shows a principal possibility of creation on the basis of this method of compact and portable devices for non-destructive identification of medicinal preparations.

The results of studying the parameters of the nuclear quadrupole resonance spectra I127 of mixed layered semiconductors Pb1-xCoxI2 (0.0 ≤ x ≤ 0.1) were carried out. A change in the frequency and integrated intensity of the I127 NQR spectrum lines with a change in the Co+2 content was recorded. The possibility of the formation of nanocluster structures associated with the ferromagnetic influence of Co+2 ions is discussed. A deviation from the exponentiality of the spin-spin quadrupole relaxation time T2 is established, which indicates the heterogeneity of the distribution of nanocluster structures over the crystal volume. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We discuss the mixing of the simple and complex configurations of the giant dipole resonance for describing the double -decay width of the state of an even–even spherical nucleus. Using the model based on the Skyrme energy density functional, the large configuration space is taken into account. We make a prediction for the branching ratio of the competitive -decay relative to its single -decay for the case of the Sn region of the nuclear chart. [ABSTRACT FROM AUTHOR]

This paper presents the conceptual stages of the simulation and development of a modified transceiver antenna for a high-power pulsed nuclear quadrupole resonance (NQR) detector of explosives containing the 14N isotope. At a frequency of 4.645 MHz, better characteristics are obtained using a nine-turn coil shaped as half of a Fermat spiral with an outer radius of 75 mm. Using a COMSOL Multiphysics numerical parametric simulation and a materials browser, it was possible to calculate a physical system with parameters as close to reality as possible. According to the results of the experimental studies of the radio frequency (RF) energy, the proposed antenna features an increase in the working area compared to a similar antenna, the topology of the conductive coil of which has the form of an Archimedean spiral. The resulting diagrams of the distribution of the magnetic induction also indicate that the topology of the electromagnetic (EM) field does not depend on the orientation of the sample under study relative to the axis of the radial symmetry observed in square–rectangular planar antennas. [ABSTRACT FROM AUTHOR]

The railgun is a promising weapon, but suffers from poor contact and harsh magnetic field environment. We used the moment of inertia to measure the deformation resistance of the rail, studied the contact characteristics of the railgun by contact force, and compared the performances of different structures of the rail. The magnetic field environment in the bore and the thrust on the armature of different structure railguns were studied by FEM-BEM simulation, and the final structure of the hyperbolic augmented quadrupole railgun was determined. The new structure of the railgun possesses better deformation resistance and contact characteristics, and can provide an electromagnetic shielding area and greater thrust. The test results show that the proposed railgun exhibits less rail damage and less armature ablation after launch. [ABSTRACT FROM AUTHOR]

Localized surface plasmons (LSPs) have a wide range of applications in enhancing the performance of optoelectronic devices. For those applications, LSPs are often located on the surfaces or interfaces between dielectric mediums. Hence, it is necessary to investigate interaction between LSPs and interface. In this paper, we investigate the far-field and near-field LSP behaviors of silver nanocube arrays on a dielectric substrate. Finite-difference time-domain simulation results demonstrate that, when light is incident normally from the vacuum, a much deeper dip between the two peaks corresponding to bonding and anti-bonding modes of the LSPs generated in the metal nanocubes on dielectric mediums, comparing to the case that incident light is from the substrate. The charge distribution diagram shows that these behaviors can be described as a dipole-like mode and a quadrupole-like mode. A model based on the Fano interferences using modified Fresnel equations is employed to explain the physical mechanism of these behaviors. It reveals that this phenomenon is caused by the phase difference between the superimposed dipolar modes generated on the upper and lower interfaces of nanocube. A simplified mathematical model has been built to illustrate that symmetric dips can arise from the Fano interference between two discrete states and one continuum state. [ABSTRACT FROM AUTHOR]

A 1958 paper by Silver & Bray introduced the use of nuclear magnetic resonance (NMR) spectra for 11B to study structure and bonding in glasses. The NMR spectra clearly distinguished between 3-coordinated and 4-coordinated borons on the basis of the larger 11B quadrupole interactions for the BO3 configuration (2⋅4-2⋅9 MHz) and the smaller values for the BO4 (less than 0·90 MHz). Quantitative measurements of the area under the narrow resonance (BO4) and broad response (BO3) allowed the fraction, N4, of 4-coordinated borons to be established. It was soon found that the "borate anomaly" in binary alkali borate glasses was not, as previously thought, due to the destruction of BO4 with added alkali oxide above 15-20 mol%. Advances in experiment and theory then permitted clear distinctions between the NMR spectra for symmetric and asymmetric BO3 units (e.g. a BO3 with all bridging or all non-bridging oxygens (NBO) and one with 1 or 2 NBO.) The NMR data for many binary and ternary borate glass systems are consistent with the Krogh-Moe model in which the glasses consist of mixtures of structural groupings from the crystalline compounds of the glassforming oxides. More recent uses of zero-field NMR, or pure nuclear quadrupole resonance (NQR) spectroscopy, have yielded major improvement in the resolution of the 11B responses from the various boron--oxygen bonding configurations. (As an example: the NQR spectra clearly display responses from two boron sites in vitreous B2O3.) Extension of the NQR studies to the 10B isotope has yielded improvements by two or three significant figures in the parameters of the quadrupole interaction. These developments have greatly increased the ability to identify with high accuracy and relative certainty the type and amount of each boron site in a solid, and should allow clear identification of the structural groupings in glasses. The high accuracy in the quadrupolar parameters, and their sensitivity to minor changes in charge distribution and structure, make these parameters sensitive tools for comparison with calculated values and for monitoring compositional variations, radiation damage, stress, thermal histories, and other aspects of boron-containing solids. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Coulomb crystals in linear ion trap with a nonlinear dissipative force induced by optical radiation. We discuss a relation between 2D and 3D ion crystals formation and the crystalline units' initial conditions. A phase diagram of the Coulomb crystal configurations is constructed. We introduce a cross size and surface area metrics to define a Coulomb crystals dimension sensitivity to the initial conditions and show the hysteresis-like-type phase transition between 2D and 3D configurations. [ABSTRACT FROM AUTHOR]

There are basically two ways to determine precision values for nuclear quadrupole moments (Q): measurements for stable or reasonably long-lived (mostly ground) states by atomic and molecular spectroscopy and measurements for much shorter-lived excited states using nuclear condensed-matter techniques like Mössbauer or perturbed-angular distribution and correlation (PAC) spectroscopy. In all cases, the direct experimental result is the product of the electric-field gradient (EFG) at the nuclear site with Q. The EFG for atomic and simple molecular systems can now mostly be calculated by theory with good accuracy, while the present status of density functional calculations of solid-state systems used for short-lived excited states limits the accuracy, generally to a 10%–20% level. Thus, the EFG of at least one matrix where data for exited states exist must be calibrated by measuring a ground state with known Q using magnetic or quadrupole resonance. This procedure is obviously not applicable to elements having no stable isotope with I > 1/2. For Cd, the problem has now been overcome using a concept proposed in Berkeley half a century ago, measuring isolated free Cd (and Hg) molecules with PAC. A similar project for Pb ongoing at ISOLDE/CERN is sketched, as well as a related one for Sn. [ABSTRACT FROM AUTHOR]

In this paper, we have applied a simple interacting boson model (IBM) to Cadmium (Cd) isotopic chain to obtain the quadrupole transition rates and effective deformation. To this aim, we use the U(5) and O(6) dynamical symmetry limits of this model to classify the considered states. Also, the energy spectra of some levels are determined which their experimental counterparts are available. The results describe the regular states with high accuracy but suggest notable deviation in the prediction of intruder energy levels. Also, our results show the advantages of this formalism in the description of quadrupole transition rates and indicate a significant relationship between the values of effective quadrupole deformations and effective boson charge. Also, for the 1 1 4 Cd, 1 1 2 Cd and 1 1 0 Cd isotopes, we have the largest variation of the quadrupole shape constants which are located in the region of shape coexistence. The study of the ratios of different energy levels indicates that there is a close relationship between ground and excited-state quantum phase transitions (ESQPTs). [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) spectroscopy of bulk quantum materials have provided insight into phenomena, such as quantum phase criticality, magnetism, and superconductivity. With the emergence of nanoscale 2D materials with magnetic phenomena, inductively detected NMR and NQR spectroscopy are not sensitive enough to detect the smaller number of spins in nanomaterials. The nitrogen-vacancy (NV) center in diamond has shown promise in bringing the analytic power of NMR and NQR spectroscopy to the nanoscale. However, due to depth-dependent formation efficiency of the defect centers, noise from surface spins, band bending effects, and the depth dependence of the nuclear magnetic field, there is ambiguity regarding the ideal NV depth for surface NMR of statistically polarized spins. In this work, we prepared a range of shallow NV ensemble layer depths and determined the ideal NV depth by performing NMR spectroscopy on statistically polarized 19F in Fomblin oil on the diamond surface. We found that the measurement time needed to achieve a signal-to-noise ratio of 3 using XY8-N noise spectroscopy has a minimum at an NV ensemble depth of 5.5 ± 1.5 nm for ensembles activated from 100 ppm nitrogen concentration. To demonstrate the sensing capabilities of NV ensembles, we perform NQR spectroscopy on the 11B of hexagonal boron nitride flakes. We compare our best diamond to previous work with a single NV and find that this ensemble provides a shorter measurement time with excitation diameters as small as 4 μm. This analysis provides ideal conditions for further experiments involving NMR/NQR spectroscopy of 2D materials with magnetic properties. [ABSTRACT FROM AUTHOR]

In the current study, 92Nb and 92Mo isotopes have been determined for calculating energy levels and electric quadrupole transition probabilities. Two interactions that have been applied in this study are surface delta and modified surface delta interactions. The calculations have been achieved by using appropriate effective charges for proton and neutron as well as parameter length of harmonic potential. Computed results have been compared with the experimental values. After this comparison, energy and the transition probability values have a good agreement with the experimental values, also there are values of the total angular momentum and parity are determined and confirmed for some of the experimental energies, undetermined and unconfirmed experimentally. Theoretically, new values of quadrupole electric transition probabilities have been explored which have not been known in the experimental data. [ABSTRACT FROM AUTHOR]

Using emission Mössbauer spectroscopy data for the 67Zn isotope and nuclear quadrupole resonance data for the 17O isotope, as well as calculations of the lattice electric field gradient, the effective charges of all atoms in superconducting copper metal oxide YBa2Cu3O7 and La2 – xSrxCuO4 crystal lattices were determined. The effective charges of metal atoms and most oxygen atoms correspond to their standard oxidation states (Y3+, La3+, Ba2+, Sr2+, Cu2+ and O2−). However, the atoms of chain oxygen (in YBa2Cu3O7) and planar oxygen (in YBa2Cu3O7 and La2 – xSrxCuO4) show a reduced charge, which is explained by the localisation of holes in the corresponding sublattices.

14N nuclear quadrupole resonance (NQR) lineshapes mostly contain information of low interest, although in nanocrystals they may display some unexpected behaviour. In this work, we present an ab initio computational study of the 14N NQR lineshapes in urea nanocrystals as a function of the nanocrystal size and geometry, focusing on the surface induced broadening of the lineshapes. The lineshapes were obtained through a calculation of the electric field gradient for each nitrogen site in the nanocrystal separately, taking into account the individual crystal field by embedding the molecule of interest in a suitable lattice of point multipoles representing other urea molecules in the nanocrystal. The small influence of distant molecules is found with a series expansion, using the incrystal Sternheimer shieldings which we also calculated ab initio. We have considered nanocrystals with two geometries: a sphere and a cube, with characteristic sizes between 5 and 100 nm. Our calculations suggest that there is a dramatic difference between the linewidths for the two geometries. For spheres, we find a steep drop in linewidths at ~10 nm; at 5 nm the linewidth is ~11 kHz, whereas for sizes above 20 nm the linewidth is practically negligible (<100 Hz). For cubes, on the other hand, we find a steady 1/size decrease, from 12 kHz at 10 nm to 1.2 kHz at 100 nm. This analysis is important for 14N NQR spectroscopy of crystalline pharmaceuticals, where nanoparticles are increasingly more often embedded in some sort of matrix. Although this is only a theoretical analysis, we believe that this work can serve as a guidance for the forthcoming experimental analysis. [ABSTRACT FROM AUTHOR]

AV3Sb5 (A = K, Rb, Cs) is a novel kagome superconductor coexisting with the charge density wave (CDW) order. Identifying the structure of the CDW order is crucial for understanding the exotic normal state and superconductivity in this system. Here, we report 51V nuclear magnetic resonance (NMR) and 121/123Sb nuclear quadrupole resonance (NQR) studies on kagome-metal CsV3Sb5. Below the CDW transition temperature TCDW ~ 98 K, an abrupt change of spectra was observed, indicating that the transition is of the first order. By further analyzing the spectra, we find that the CDW order is commensurate. And most remarkably, the obtained experimental results suggest that the charge modulation of the CDW order is of star-of-David pattern and accompanied by an additional charge modulation in bulk below T* ~ 40 K. Our results revealing the unconventional CDW order provide new insights into AV3Sb5. [ABSTRACT FROM AUTHOR]

The solubilization of sodium diclofenac (Na-DFC) in a glycerol monooleate-based emulsion triggers series of structural changes. Incorporation of Na-DFC, leads to formation of a reverse hexagonal mesophase between 2 and 5 wt% Na-DFC. Between 6 and 9 wt% Na-DFC, the hexagonal symmetry gradually transitions to a disordered lamellar mesophase. These structural shifts impact the system's storage modulus, structuring enthalpy, and structural diffusivity. Despite these transitions, the driving force for Na-DFC release remains consistent, leading to hypothesize that the interfacial structure remains unchanged during Na-DFC release. The nano-structural modifications imposed by the Na-DFC load and release were assessed by small-angle X-ray diffraction (SAXD), spin-probe electron paramagnetic resonance (EPR), and nuclear quadrupole resonance (NQR). The selective solubilization of Na-DFC was demonstrated by SAXD peak fittings, revealing an increase of hexagonally oriented rods at the expense of non-oriented micelles, rather than gradual micellar elongation. Computation of the EPR spectra also showcased the selective solubilization of Na-DFC at an enhanced free energy interface (γ), evidenced by step-wise variations in polarity, microviscosity, and order parameters. Additionally, NQR analysis highlighted a higher anisotropy for sodium compared to deuterium, linking the selective solubilization of Na-DFC to heterogeneous structural transformations. These findings underscore the heterogeneous nature of solubilization-release processes, driven by locally increased micellar free energy. Consequently, the loaded Na-DFC interfaces maintain a constant γ, ensuring a consistent release driving force despite the structural transitions affecting the matrix. The ability to selectively solubilize guest molecules may herald a new era in the utilization of selective molecular interfacial loading., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Control over the stacking patterns in 2D molecular assemblies is demonstrated using chemical modification. A target system is a hydrogen‐bonded cocrystal (2:1) composed of 2‐pyrrolidone (Py) and chloranilic acid (CA) (PyCA). X‐ray crystallography showed that weak intersheet interactions give rise to a variety of metastable overlapping patterns comprised of the 2D assemblies mainly formed via hydrogen bonds, affording reversible and irreversible structural phase transitions. We prepared cocrystals of Py and anilic acids bearing different halogens, in which 2D assemblies isostructural with those observed in PyCA exhibit various overlapping patterns. The order of stability for each overlapping pattern estimated using calculations of the intermolecular interactions did not completely coincide with those indicated by our experimental results, which can be explained by considering the entropic effect: the molecular motion of Py as detected using nuclear quadrupole resonance spectroscopy. [ABSTRACT FROM AUTHOR]

This paper presents the conceptual stages of the simulation and development of a modified transceiver antenna for a high-power pulsed nuclear quadrupole resonance (NQR) detector of explosives containing the 14N isotope. At a frequency of 4.645 MHz, better characteristics are obtained using a nine-turn coil shaped as half of a Fermat spiral with an outer radius of 75 mm. Using a COMSOL Multiphysics numerical parametric simulation and a materials browser, it was possible to calculate a physical system with parameters as close to reality as possible. According to the results of the experimental studies of the radio frequency (RF) energy, the proposed antenna features an increase in the working area compared to a similar antenna, the topology of the conductive coil of which has the form of an Archimedean spiral. The resulting diagrams of the distribution of the magnetic induction also indicate that the topology of the electromagnetic (EM) field does not depend on the orientation of the sample under study relative to the axis of the radial symmetry observed in square–rectangular planar antennas.

A thorough characterization of the γ, β, and glass phases of deuterated 1,1,2,2 tetrachloroethane (C2D2Cl4) via nuclear quadrupole resonance and Molecular Dynamic Simulations (MDSs) is reported. The presence of molecular reorientations was experimentally observed in the glass phase and in the β phase. In the β phase, and from MDS, these reorientations are attributed to two possible movements, i.e., a 180? reorientation around the C2 molecular symmetry axis and a reorientation of the molecule between two non-equivalent positions. In the glass phase, the spin-lattice relaxation time T¹ is of the order of 16 times lower than in the crystalline phase and varies as T-1 below 100 K in good agreement with the strong quadrupolar relaxation observed in amorphous materials and in the glassy state of molecular organic systems. The activation energy of molecular reorientations in the glass phase (19 kJ/mol) is comparable to that observed in the glassy crystal of a "molecular cousin" compound, Freon 112 (C2F2Cl4), for the secondary β-relaxation. Moreover, the on-site orientational motion of tetrachloroethane molecules offers a new indirect evidence of the prominent role of such orientational disorder in glassy dynamics. [ABSTRACT FROM AUTHOR]

This paper describes the features of choosing the sweep method and mode in the study of broadband multiplet nuclear quadrupole resonance (NQR) spectra using a marginal oscillator sensor with increased conversion linearity. In particular, the work of the improved sensor in the frequency sweep mode is considered when using: bipolar frequency modulation with synchronous second harmonic detection; Zeeman modulation with synchronous first harmonic detection, provided that the modulation depth is much greater than the line width; Zeeman modulation with synchronous second harmonic detection. Much attention is paid to experimental studies of the NQR spectra and the orientation dependence of the relative integral intensity of their resonance lines for three multiplet groups in the frequency range 20.4-20.7 MHz of the 3/2 ↔ 5/2 115In quadrupole junction in a semiconductor layered InSe compound grown by the Bridgeman method. It is established that to obtain the optimal signal amplitude, the shape of the modulating field must be square-rectangular. The performed NQR studies in InSe confirm the complexity of the problem of polymorphism in layered crystals, which requires further research using various experimental techniques. [ABSTRACT FROM AUTHOR]

We report 121/123Sb nuclear quadrupole resonance (NQR) and 51V nuclear magnetic resonance (NMR) measurements on kagome metal CsV3Sb5 with Tc = 2.5 K. Both 51V NMR spectra and 121/123Sb NQR spectra split after a charge density wave (CDW) transition, which demonstrates a commensurate CDW state. The coexistence of the high temperature phase and the CDW phase between 91 K and 94 K manifests that it is a first-order phase transition. At low temperature, electric-field-gradient fluctuations diminish and magnetic fluctuations become dominant. Superconductivity emerges in the charge order state. Knight shift decreases and 1/T1T shows a Hebel–Slichter coherence peak just below Tc, indicating that CsV3Sb5 is an s-wave superconductor. [ABSTRACT FROM AUTHOR]

Rotational spectra of the weakly bound H2O--N2O complex and its HOD--N2O isotopologue in a supersonic jet are reported. Rotational constants of the singly substituted deuterium in water and each singly substituted nitrogen-15 are presented. Combinations of isotopic data and high level ab initio calculations place the water in a similar position to those of the isoelectronic H2O--CO2 complex, with a slight tilt of the OH towards the NNO axis. The deuterium nuclear quadrupole coupling constant places the deuterium on the O--H axis quasi-parallel to the NNO axis. [ABSTRACT FROM AUTHOR]