Series Of NO Research Articles

Discovery of NO Donor-Aurovertin Hybrids as Dual Ferroptosis and Apoptosis Inducers for Treating Triple Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a highly lethal malignancy, and its clinical management encounters severe challenges due to its high metastatic propensity and the absence of effective therapeutic targets. To improve druggability of aurovertin B (AVB), a natural polyketide with a significant antiproliferative effect on TNBC, a series of NO donor/AVB hybrids were synthesized and tested for bioactivities. Among them, compound 4d significantly inhibited the proliferation and metastasis of TNBC in vitro and in vivo with better safety than that of AVB. The structure-activity relationship analysis suggested that the types of NO donor and the linkers had considerable effects on the activities. Mechanistic investigations unveiled that 4d induced apoptosis and ferroptosis by the reduction of mitochondrial membrane potential and the down-regulation of GPX4, respectively. The antimetastatic effect of 4d was associated with the upregulation of DUSP1. Overall, these compelling results underscore the tremendous potential of 4d for treating TNBC.

Air pollution during COVID-19 pandemic: Exploration in the Bulgarian city of Stara Zagora using interrupted time series ARMA model

The COVID-19 global pandemic has likely affected air quality due to extreme changes in human behavior. The aim of this paper is to explore the consequence of the COVID-19 pandemic on the air quality improvement in the Bulgarian city of Stara Zagora using Interrupted Time Series ARMA Model. After adjusting by meteorology and Sunday effect, the results confirm positive and significant effect immediately after the announcement of COVID-19 pandemic in Bulgaria and negative and significant trend in the levels for PM[Formula: see text] and O3. For the remaining CO and NO series of data, the estimate of the time series slope, i.e. the expected change in the concentration associated with a time unit increase is positive and significant. The temporal dynamics for each time series are reported by the ARMA coefficients: an ARMA(2,3) structure is estimated for O3 and NO, and an ARMA(1,1) is the best choice for CO while AR(5) for PM[Formula: see text]. Understanding how air pollution is affected during COVID-19 pandemic will contribute to future air quality management policies and human health.

2005–2018 trends in ozone peak concentrations and spatial contributions in the Guadalquivir Valley, southern Spain

We assessed 2005─2018 data series of NO, NO2, and O3 surface measurements, meteorological data and remote sensing of tropospheric NO2 by OMI-NASA in the Guadalquivir Valley (GV, Andalucía). The GV is one of the Spanish atmospheric basins with the most exceedances of the EU's hourly O3 information threshold (180 μg O3 m−3). We aimed to deepen understanding of the phenomenology of O3 episodes in the GV, quantify local and regional contributions from long-range transported O3, and identify key episodes and atmospheric parameters to validate modeling tools for the assessment of O3 abatement policies with acceptable uncertainty levels.A significant proportion of acute O3 episodes (defined as episodes of 1–7 consecutive days, when very high hourly O3 concentrations are recorded) in the GV is caused by long-range transported contributions in addition to the regional accumulation of pollution which is, in most cases, driven by the vertical recirculation of air masses, as described in several basins of the Iberian Peninsula. In these episodes, high O3 arises from the fumigation of high reserve recirculated strata as the boundary layer grows, sea-breeze transport of O3 and precursors, local formation, and long-range transport. The most acute episodes are recorded close to Sevilla, probably because of the mix of precursors from the urban areas and the petrochemical industry of Huelva.We quantified the average O3 contributions to O3 concentrations in Sevilla during these episodes as 53% background levels before the episode (defined as the concentration measured at the coastal remote sites at the beginning of the pollution episode, when the Atlantic air masses transport background O3 from synoptic air mass transport), 22% accumulation throughout the episode, and 25% of daily local and regional contribution to the average 8h-daily maxima (157 μg O3 m−3). Thus, a maximum decreasing potential of 74 μg O3 m−3 (47%) of the average 8h-daily maxima can be expected when applying abatement measures to reduce O3 precursors in the day before the start of an episode and until the end of the episode. Our results demonstrate that it is crucial to meteorologically forecast the occurrence of such recirculation and accumulation processes in the GV basin.

Computational study of the equilibrium geometry and anharmonic vibrational spectra of PbX2 ··· NO and PbX2 ··· ON (X = F, Cl, Br, I) complexes

Equilibrium geometry parameters of the open shell PbX2 ··· NO and PbX2 ··· ON (X = F, Cl, Br, I) complexes have been computed by second-order Z-averaged perturbation theory (ZAPT2) with Stevens–Basch–Krauss–Jasien–Cundari (SBKJC) scalar-relativistic effective core potentials (RECP) and basis sets on all atoms. Equilibrium geometries of both PbX2 ··· NO and PbX2 ··· ON bonding isomers conform to Cs symmetry structure with end-on ligand coordination, and are characterized by Pb-N bond length within 266.6–271.7 pm range, Pb–O distance of 267.8–275.8 pm, Pb–N–O angle within 109.2–120.7° range, and Pb–O–N angle of 117.1–127.8°. Anharmonic vibrational spectra of the PbX2 ··· NO and PbX2 ··· ON complexes have been calculated by direct correlation-corrected vibrational self-consistent field (CC-VSCF) method enhanced with second-order perturbative correction using potential energy surfaces (PESs) determined at ZAPT2/SBKJC+(d) level in curvilinear (internal) coordinates. Fundamental ν(Pb–N) stretching mode has been computed at 232.8 to 209.0 cm−1 within PbX2 ··· NO series. whereas ν(Pb–O) stretching mode fundamental evaluation in PbX2 ··· ON series afforded wavenumbers within 183.2–150.7 cm−1 range. Blue shift of the ν(N=O) stretching mode wavenumber upon PbX2 ··· NO complex formation, computed in anharmonic approximation, 15.8–14.6 cm−1, correctly reproduces the effect observed in the low-temperature Ar matrix spectra of PbX2 ··· NO compounds. Influence of complex formation on the νs(Pb–X) and νas(Pb–X) fundamentals of PbX2 halides has also been discussed. Two-dimensional mapping of the (Qi , Qj ) mode-mode coupling potential has been used to rationalize the origin of mode coupling related anharmonic corrections.

A methodology to urban air quality assessment during large time periods of winter using computational fluid dynamic models

The representativeness of point measurements in urban areas is limited due to the strong heterogeneity of the atmospheric flows in cities. To get information on air quality in the gaps between measurement points, and have a 3D field of pollutant concentration, Computational Fluid Dynamic (CFD) models can be used. However, unsteady simulations during time periods of the order of months, often required for regulatory purposes, are not possible for computational reasons. The main objective of this study is to develop a methodology to evaluate the air quality in a real urban area during large time periods by means of steady CFD simulations. One steady simulation for each inlet wind direction was performed and factors like the number of cars inside each street, the length of streets and the wind speed and direction were taken into account to compute the pollutant concentration. This approach is only valid in winter time when the pollutant concentrations are less affected by atmospheric chemistry. A model based on the steady-state Reynolds-Averaged Navier–Stokes equations (RANS) and standard k-ɛ turbulence model was used to simulate a set of 16 different inlet wind directions over a real urban area (downtown Pamplona, Spain). The temporal series of NO x and PM 10 and the spatial differences in pollutant concentration of NO 2 and BTEX obtained were in agreement with experimental data. Inside urban canopy, an important influence of urban boundary layer dynamics on the pollutant concentration patterns was observed. Large concentration differences between different zones of the same square were found. This showed that concentration levels measured by an automatic monitoring station depend on its location in the street or square, and a modelling methodology like this is useful to complement the experimental information. On the other hand, this methodology can also be applied to evaluate abatement strategies by redistributing traffic emissions.

Theoretical Study of the X2NO Systems (X = F, Cl, Br, I): Effects of Halogen Substitution on Structural and Spectroscopic Properties.

Structural and spectroscopic properties of the X2 NO series of radicals, with X = F, Cl, Br, I, have been computed by the coupled cluster ansatz in conjunction with hierarchical series of basis sets, accounting for, in most cases, core correlation effects and extrapolation to the complete basis set limit. Namely, equilibrium structures, vibrational frequencies, and hyperfine coupling constants have been considered. Methods rooted into the density functional theory have been used to estimate anharmonic and, in conjunction with the polarizable continuum model, environmental effects. The remarkable agreement with the available experimental data, limited to the lighter member of the series, confirms the reliability of our computational approach and suggests that the data for heavier species represent reliable benchmarks for future experimental data and/or cheaper computational methods devised for larger systems.

Observation of the nighttime nitrate radical in Hefei, China

Observation of nighttime nitrate radical (NO 3) was performed by using long path differential optical absorption spectroscopy (LP-DOAS), on the outskirts of Hefei, China. The time series of NO 3 and supporting parameters were simultaneously measured for a week (31 May–7 June 2006). The results indicated that the average concentration of NO 3 was 15.6 pptv with an average lifetimes of 96 s, whereas, NO 3 production rates varied from 8 × 10 5/(cm 3·s) to 2.98 × 10 7/(cm 3·s). Furthermore, the calculated N 2O 5concentration averaged at 380 pptv. Analysis of data indicated that direct sinks were probably dominating the NO 3 loss process during this campaign. The results were compared with other campaigns in the boundary layer.

Dissociation mechanisms and dynamics of core-excited (N 2O) n clusters

Dissociation of nitrous oxide clusters (N 2O) n , induced by core level excitation near the nitrogen K-edge was studied by time-of-flight (TOF) fragment mass spectroscopy. Besides the cluster ions (N 2O) n + with n ≦ 26, we identified another series of NO(N 2O) m + with m = 0–12 as well as O 2 + and N 3 + products characteristic of ion-molecule reactions within the clusters. Photoelectron–photoion–photoion-coincidence (PEPIPICO) technique was applied to study dissociation mechanisms and dynamics of core-excited (N 2O) n clusters. Charge separation mechanisms of the doubly charged (N 2O) n 2+ clusters by N t(1s → π*) excitation were interpreted in terms of kinetic energy release (KER) and charge separation distance (CSD).

원료의 계열성분 변화에 따른 NiCuZn Ferrite 물성연구

The electromagnetic properties and microstructures of the basic composition of (Ni0.2/Cu0.1/Zn0.2/)0.5/ (FeO)0.5/ were invested by changing of SO, Cl and NO series. We were prepared by coprecipitation method and sintered at temperatures 950, 1150, l350, respectively. When sintering at temperature 950, Cl and NO series became perfection sintering. On the other hand, SO series showed perfection sintering at temperature 1150. According to particle size analysis result, higher magnetic permeability and magnetization value were observed by Cl series than SO or NO series.

Simulation of NOx and ultrafine particles in a street canyon in Stockholm, Sweden

Abstract A computational fluid dynamic (CFD) model has been used to assess the concentrations of NO x and particle number in a street canyon in Stockholm with a high traffic volume. Comparisons of a simulated 11-week long time series of NO x with measurements (both sides of the street, urban background excluded) show good agreement, especially if emissions are distributed to be three times higher along the side of the street where the traffic is uphill, as compared to the downhill side. The simulation of number concentrations of inert particles indicates a similar asymmetry in emissions. A month-long measurement of particle size distribution (7–450 nm) at street level indicates that the ratio of nucleation size mode particle (7–20 nm) to total particle number (7–450 nm) is decreasing for increased particle surface area. Given the strong dominance of the locally generated particles over the urban background, this is interpreted as a local change in the size distribution. The results of a monodisperse aerosol dynamic model, coupled to the CFD model that simulates also the turbulence generated by vehicle movements, show that coagulation and deposition may reduce total particle inside the canyon with approximately 30% during low wind speeds. Most of the removal occurs shortly after emission, before the particles reach the leeward curb-side. Losses between the leeward curb-side and other locations in the street, e.g. roof levels, is estimated to be smaller, less than 10%. Coagulation is the dominating removal process under low wind speed conditions and deposition for higher wind speeds, the summed removal being smaller for high wind velocities. Deposition is enhanced over the road surface due to the velocities generated by vehicle movements. Although coagulation and deposition removal is most effective on the smallest ultrafine particles, this effect is not sufficient to explain the observed change in size distribution. It is suggested that also the formation of particles in the exhaust plumes is influenced by a larger particle surface area in the ambient air.

Extension of the molecular quantum defect orbital methodology to the calculation of intensities and lifetimes for vibronic transitions within electronic Rydberg series of NO

AbstractExpressions relating explicitly the radiative lifetimes of vibronic states to the electronic transition moment and the absorption oscillator strengths for spin‐allowed transitions have been developed for the first time within the molecular quantum defect orbital (MQDO) methodology. Application to the intensities of the γ(A2Σ+ ← X2Π), ε(D2Σ+ ← X2Π), and (D2Σ+ ← A2Σ+) bands of NO, which are known to be of relevance in atmospheric studies, has been made. The MQDO results are in excellent accord with the measurements available in the literature. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

FTIR analysis of storage behavior and sulfur tolerance in barium-based NOx storage and reduction (NSR) catalysts

A series of NOx storage and reduction (NSR) catalysts containing platinum, BaO, and iron supported on γ-Al2O3 has been studied using FTIR spectroscopy. CO adsorption studies at room temperature have shown that the BaO phase can chemisorb large quantities of CO, and that platinum sites can become encapsulated by BaO, following a reducing pretreatment. Exposure of the catalysts to fuel-lean and fuel-rich conditions has revealed that the species that participates in the storage is a surface nitrite complex (prevalent below 350°C), which is converted to a surface monodentate nitrate species above 350°C. Both of these species have also been identified at room temperature and are bonded to the surface through BaO lattice oxygen atoms. A mechanism has been proposed to describe the storage and reduction process in which NO reacts directly with the BaO surface to form nitrite and monodentate nitrate. The role of platinum is to adsorb O2 under lean conditions and reducing gases (H2 or hydrocarbons) under rich conditions. Once adsorbed, the oxygen and reducing agents spill over onto nearby BaO sites and react with the adsorbed NO. The oxidation of NO to NO2 on platinum does not appear in this work to be a critical step, in contrast to previous studies. Sulfur tolerance studies using SO2 have confirmed the previous observation that promotion with iron increases the durability of NSR catalysts. However, FTIR results show that the improvement is caused by the formation of a previously unobserved bulk nitrate species and not to a decrease in the sulfate decomposition temperature.

Optical Emission Analysis of 15N: Pressure Effects and Identification of NO and Gaydon—Herman N2 Bands in the Discharge

The optical emission method, an alternative to mass spectrometry for 15N analysis, is based on measuring ratios of the intensities of the 14N2(28), 14N 15N (29), and 15N2 (30) lines of the 2→0 band of the C(3πu)→B(3πg) N2 transition near 298 nm. However, properties of the discharge are not well understood, and interferences that affect the analysis have never been explicitly identified. An efficient low-energy radio-frequency source and home-built spectrometer were used to obtain spectra over a wide range and with multiple scans. Weak extraneous bands were identified as the overlapping β andγ series of NO, not CO or OH as previously thought. Bands identified as the third positive system of CO were only observed under conditions far removed from normal practice. As tube pressure was increased from 0.3 to 1.8 kPa, the N2 intensity decreased relative to that of NO peaks. The 29/28 intensity ratio also varied with pressure, although not in a completely consistent way. A weak band underlying the 14N15N transition was identified as part of the Gaydon–Herman singlet series of N2; this interference rather than peaks from other species, may be the single factor most limiting analytical performance. Implications for the analytical method are discussed.

A non-adiabatic calculation of NO Rydberg states above several ionisation thresholds

An ab initio study of the ns, np, nd, nf and ng Rydberg series of NO above a number of ionisation thresholds is presented. Calculations of the eigenphase sum of electron scattering by NO +, using a non-adiabatic R -matrix method, are used to obtain vibrationally resolved positions and widths of NO autoionizing states. The complex quantum defects of the resonances are used to identify the Rydberg series, and these are separated according to the vibrational state of the target. Comparisons are made with experimental studies of this system.

Size dependence of radiative association rates

Large but regular changes in the rates of formation of gas-phase complexes by radiative association occur as the number of degrees of freedom of the complex changes. In interpreting measurements of such rates for purposes like bonding energy comparisons, it is important to have a confident and predictively useful understanding of these size effects; the present work was carried out to provide useful sets of comparative data for two homologous series of ketone complexes, and to match the observations with our present theoretical understanding. Improved measurements were made in the ion cyclotron resonance ion trap for the series of NO +/ketone complexes from acetone to pentanone. Also, the series of complexes of protonated ketones with their parent ketones was extended upward from the well-studied acetone case, by new measurements for the butanone, pentanone and hexanone molecules. For both series, the systematic dependence of the association rate on the number of degrees of freedom of the complex was considered in the context of the semiquantitative generic theoretical approach termed the ‘standard hydrocarbon’ approach. For both series, the standard hydrocarbon predictions were in excellent agreement with the relative values observed for the different sized members of the series. The model also gave reasonable predictions for the absolute rates of the NO +/ketone series, but was much too low for the protonated ketone/ketone series. The latter discrepancy is due in large part to emission rates from the protonated ketone/ketone complexes being exceptionally high relative to typical hydrocarbon systems. The results are encouraging to the use of the standard hydrocarbon approach for comparisons and predictions of radiative association for series of related molecules, while also reinforcing the warning against expecting better than order-of-magnitude predictions of absolute rates from this approach.

Theoretical study of cyclic radicals NO x ( x = 2–6)

Ab initio MO calculations at the UHF and MP2 levels with 6–31G ∗ basis set are carried out to examine the stability and the structure of a series of NO x ( x = 2–6) radicals. We have located a series of exotic but stable radicals with a ring comprised of one nitrogen atom and two to six oxygen atoms. The stability is confirmed by evaluating the harmonic frequencies at both levels. The bonds in the cyclic radicals are discussed by comparing with both lengths and bond stretching vibrational frequencies of the related known molecules. The reaction energy for NO x → NO 2 + ( x − 2)/2 O 2 is evaluated with the MP4SDTQ approximation, and it is shown that the cyclic NO x is a new type of energy-rich molecules. Besides, all the ring radicals of being stable not only on UHF/6–31G ∗ but also on MP2/6–31G ∗ are further investigated by density functional theory with nonlocal corrections (Becke3LYP). Most of them become unstable, except for three-membered NO 2 ring and four-membered NO 3 ring. The different stability for some NO x ring radicals on MP2 and DFT levels are illustrated.

High Rydberg states of the NO molecule studied by two-color four-wave mixing spectroscopy

The ns, np and nf high Rydberg series of NO below the ionization limit are studied by two-color resonant four-wave mixing spectroscopy. The Rydberg states are prepared by two-step excitation through the A 2 Σ + ( v′ = 0, N′ = 2) intermediate state in a supersonic jet. Rotational constants and term values are determined for the ns series ( n = 8−13, v = 0), while only term values are determined for the nf series ( n = 7−10, v = 0). Rotationally resolved structures of the diffuse np series ( n = 8−13, v = 0) are observed.

Rydberg states in quantum crystals NO in solid H2

Fluorescence, excitation and fluorescence depletion spectra of the lowest Rydberg states of NO trapped in H2 matrices are reported. The absorption bands are shifted by about 0.58 eV to the blue of the gas phase energy. They are strongly broadened and exhibit an asymmetry by a blue wing. The fluorescence bands are significantly narrower, with a red wing, and lie very close to the gas phase energy. The absorption lineshape can be accounted for by the large extension of the ground state wavefunction, due to the strong contribution of the zero point motion in the H2 lattice. The absorption–emission Stokes shift is interpreted in terms of ‘bubble’ formation around the Rydberg excited molecule. A moment analysis of the absorption and emission bands in the harmonic approximation shows that most of the absorption–emission Stokes shift is used up as energy to create the ‘bubble’ around the excited molecule. The fluorescence depletion spectrum yields Rydberg–Rydberg transitions very close to the gas phase energy. This, together with the fluorescence spectra, indicates that the molecule is in a quasi-free, gas-phase-like state in the expanded cage. The excitation spectra and the fluorescence depletion spectra indicate a severe compression of the Rydberg series of NO in H2 matrices, which can be accounted for by a large negative electron affinity of solid H2. Concerning the intramolecular energy relaxation in NO, it is found that the Rydberg↔valence relaxation processes follow much the same pattern as observed in rare gas matrices for the lower valence states. For the higher valence states, a photochemical route is suggested. For the vibrational relaxation by Δv=2 in the A state and for the C–A electronic relaxation, intermolecular energy transfer processes between NO molecules are invoked, which occur in the sub-ns timescale.

The dynamics of predissociating high Rydberg states of NO

In this paper we present a theoretical study of the predissociation dynamics of the nf(N+=2) (with the principal quantum numbers n=40–95) and the np(N+=0) (n=70–125) Rydberg series of NO, which exhibit a marked lifetime dilution (lengthening) at n≳65 for the f series and at n≳116 for the p series [M.J.J. Vrakking and Y. T. Lee, J. Chem. Phys. 102, 8818 (1995)]. The multichannel effective Hamiltonian with several doorway (for excitation) and escape (for decay) states was constructed using experimental information on the quantum defects and on the decay width constants incorporating both intramolecular coupling and exterior electric field coupling between high Rydbergs. The analysis of the intramolecular Rydberg electron–core dipole long range coupling (HR-D) in conjunction with the energy gaps between proximal pairs of energy levels, which are subjected to appropriate selection rules, reveals that (i) for low l(≤3) core-penetrating Rydbergs only a small number of accidental near-resonances are exhibited, and (ii) for high l(≳3) nonpenetrating Rydbergs the electron-core dipole coupling decreases fast with increasing l, i.e., (HR-D)∝l−7. The general characteristics of the high l(≳3) manifold establish a bottleneck effect, which precludes intramolecular l mixing, implying that high Rydberg lifetime dilution effects can be induced only by exterior electric field coupling (HSTARK). Parameter-free multichannel effective Hamiltonian calculations were conducted under narrow-band excitation conditions, which interrogate the electric field induced mixing in the energetic vicinity of the doorway state. The electric field induced l mixing model accounts semiquantitatively for the electric field dependence of the energy-resolved line shapes of the nf(N+=2) series and for the n and electric field dependence of the lifetimes of the nf(N+=2) and the np(N+=0) series. Accidental near-resonant simultaneous intramolecular and electric field coupling np(N+=0)↔HR-Dn′d(N+=1)↔HSTARKn′ l(≥3)(N+=1) for two sets of proximal states n=92, n′=80 and n=95, n′=82, result in mediated-sequential mixing, which is manifested by slow decay times below the onset of effective electric field mixing by weak (F0≂0.04–0.08 V/cm) stray electric fields.

Measurement of circular dichroism in rotationally resolved photoelectron angular distributions following the photoionization of NO A 2Σ+

The photoionization process NO A 2Σ+ (v=0, N=22)→NO+ X 1Σ+ (v+=0, N+)+e− is studied with sufficient photoelectron energy resolution that the photoelectron angular distributions (PADs) associated with individual rotational levels N+ of the ion are determined. By ionizing with left and right circularly polarized light and observing the change in the rotationally resolved PADs, we can deduce all dynamical information, including the signs of the relative phase shifts of the photoelectron partial waves. This information constitutes the first complete description of the photoionization of a molecule. We discuss the consistency of our dynamical parameters with the Rydberg series of NO. We present a general formalism for (1+1′) resonance-enhanced multiphoton ionization (REMPI) PADs for rotationally resolved ion states using linearly polarized light for excitation and elliptically polarized light for ionization. Based on the dynamical parameters determined from our fit, we use this formalism to predict the total system state, i.e., three-dimensional PADs and polarization of ion rotational levels following photoionization.