A model for upper kHz QPO coherence of accreting neutron star

{We investigate the coherence of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in the low-mass X-ray binary (LMXB) theoretically. The profile of upper kHz QPO, interpreted as Keplerian frequency, is ascribed to the radial extent of the kHz QPO emission region, associated with the transitional layer at the magnetosphere-disk boundary, which corresponds to the coherence of upper kHz QPO. The theoretical model for Q-factor of upper kHz QPO is applied to the observational data of five Atoll and five Z sources, and the consistence is implied.Comment: accepted by A&

The correlations between the spin frequencies and kHz QPOs of Neutron Stars in LMXBs

We studied the correlations between spin frequencies and kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low mass X-ray binaries. The updated data of kHz QPOs and spin frequencies are statistically analyzed. We found that when two simultaneous kHz QPOs are present in the power spectrum, the minimum frequency of upper kHz QPO is at least 1.3 times larger than the spin frequency, i.e. \nu_{s}<\nu_{2min}/1.3. We also found that the average kHz QPO peak separation in 6 Atoll sources anti-correlates with the spin frequency in the form \lan\dn\ran = -(0.19\pm0.05)\ns+(389.40\pm21.67)Hz. If we shifted this correlation in the direction of the peak separation by a factor of 1.5, this correlation matches the data points of the two accretion powered millisecond X-ray pulsars, SAX J1808.4-3658 and XTE J1807-294.Comment: 4 pages, 2 figures, accepted for publication in A&

Selective Reagent Ion Mass Spectrometric Investigations of the Nitroanilines

This paper presents an investigation of proton and charge transfer reactions to 2-, 3- and 4-nitroanilines (C6H6N2O2) involving the reagent ions H3O+·(H2O)n (n=0, 1 and 2) and O2+, respectively, as a function of reduced electric field (60-240 Td), using Selective Reagent Ion-Time-of-Flight-Mass Spectrometry (SRI-ToF-MS). To aid in the interpretation of the H3O+·(H2O)n experimental data, the proton affinities and gas-phase basicities for the three nitroaniline isomers have been determined using density functional theory. These calculations show that proton transfer from both the H3O+ and H3O+·H2O reagent ions to the nitroanilines will be exoergic and hence efficient, with the reactions proceeding at the collisional rate. For proton transfer from H3O+ to the NO2 sites, the exoergicities are 171 kJ mol-1 (1.8 eV), 147 kJ mol-1 (1.5 eV) and 194 kJ mol-1 (2.0 eV) for 2-, 3- and 4-nitroanilines, respectively. Electron transfer from all three of the nitroanilines is also significantly exothermic by approximately 4 eV. Although a substantial transfer of energy occurs during the ion/molecule reactions, the processes are found to predominantly proceed via non-dissociative pathways over a large reduced electric field range. Only at relatively high reduced electric fields (>180 Td) is dissociative proton and charge transfer observed. Differences in fragment product ions and their intensities provide a means to distinguish the isomers, with proton transfer distinguishing 2-nitroaniline (2-NA) from 3- and 4-NA, and charge transfer distinguishing 4-NA from 2- and 3-NA, thereby providing a means to enhance selectivity using SRI-ToF-MS.(VLID)4826158Version of recor

Patterning total mercury distribution in coastal podzolic soils from an Atlantic area: influence of pedogenetic processes and soil components

Soils are the main Hg reservoir in the terrestrial ecosystems where it is deposited via wet or dry deposition and litterfall. Once on the soil surface, different biogeochemical routes will determine the fate of Hg and the role of terrestrial ecosystems as a Hg source or sink. The specific chemical and physical characteristics of Podzols and podzolic soils contribute to the accumulation of Hg in their illuvial horizons, avoiding its leaching to groundwater. The geographical location, state of pedogenesis, soil age, abundance of carrier phases and physical properties can affect the presence and distribution of Hg in soils. Therefore, understand and relate these factors with the behavior of Hg in Podzols and podzolic soils is key to define the role of this type of soil in the terrestrial Hg cycle. In this work, ten podzolic soil profiles were collected in an Atlantic coastal forest area of Portugal and analyzed for the main physico-chemical properties and Hg content to assess the influence of the intensity of podzolization in the Hg depth distribution. Three different patterns of Hg distribution in the studied Podzols, depending on the predominance of atmospheric deposition or the intensity of podzolization, have been defined. The pattern I showed the maximum Hg contents in the surface A horizons (12.9–23.5 μg kg 1), pattern II exhibited the highest peaks in the subsurface illuvial horizons (2.3–17.3 μg kg 1) and pattern III presented an even distribution of Hg through the soil profile. We found that dissolved organic matter (DOM) is the main carrier of Hg in the A and E horizons, whereas metal(Al, Fe)-humus complexes and/or oxyhydroxides contribute to immobilizing Hg in the illuvial horizons (Bh, Bs and Bhs). The principal component regression (PCR) analysis predicted satisfactorily the Hg distribution through soil organic matter and Al and Fe oxyhydroxides. The Hg immobilized in the subsurface layers of Podzols is retained in the long term, avoiding its migration to other components of terrestrial ecosystems where it could cause serious environmental damage such as groundwater and superficial watersinfo:eu-repo/semantics/publishedVersio

Strain- and Adsorption-Dependent Electronic States and Transport or Localization in Graphene

The chapter generalizes results on influence of uniaxial strain and adsorption on the electron states and charge transport or localization in graphene with different configurations of imperfections (point defects): resonant (neutral) adsorbed atoms either oxygen- or hydrogen-containing molecules or functional groups, vacancies or substitutional atoms, charged impurity atoms or molecules, and distortions. To observe electronic properties of graphene-admolecules system, we applied electron paramagnetic resonance technique in a broad temperature range for graphene oxides as a good basis for understanding the electrotransport properties of other active carbons. Applied technique allowed observation of possible metal-insulator transition and sorption pumping effect as well as discussion of results in relation to the granular metal model. The electronic and transport properties are calculated within the framework of the tight-binding model along with the Kubo-Greenwood quantum-mechanical formalism. Depending on electron density and type of the sites, the conductivity for correlated and ordered adsorbates is found to be enhanced in dozens of times as compared to the cases of their random distribution. In case of the uniaxially strained graphene, the presence of point defects counteracts against or contributes to the band-gap opening according to their configurations. The band-gap behaviour is found to be nonmonotonic with strain in case of a simultaneous action of defect ordering and zigzag deformation. The amount of localized charge carriers (spins) is found to be correlated with the content of adsorbed centres responsible for the formation of potential barriers and, in turn, for the localization effects. Physical and chemical states of graphene edges, especially at a uniaxial strain along one of them, play a crucial role in electrical transport phenomena in graphene-based materials.Comment: 16 pages, 10 figure

Modeling photosynthetically active radiation from satellite-derived estimations over mainland Spain

A model based on the known high correlation between photosynthetically active radiation (PAR) and global horizontal irradiance (GHI) was implemented to estimate PAR from GHI measurements in this present study. The model has been developed using satellite-derived GHI and PAR estimations. Both variables can be estimated using Kato bands, provided by Satellite Application Facility on Climate Monitoring (CM-SAF), and its ratio may be used as the variable of interest in order to obtain the model. The study area, which was located in mainland Spain, has been split by cluster analysis into regions with similar behavior, according to this ratio. In each of these regions, a regression model estimating PAR from GHI has been developed. According to the analysis, two regions are distinguished in the study area. These regions belong to the two climates dominating the territory: an Oceanic climate on the northern edge; and a Mediterranean climate with hot summer in the rest of the study area. The models obtained for each region have been checked against the ground measurements, providing correlograms with determination coefficients higher than 0.99This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) [Project CGL2016-79284-P AEI/FEDER/UE]S

Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038

Transitional millisecond pulsars are an emerging class of sources that link low-mass X-ray binaries to millisecond radio pulsars in binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray to optical pulsations are observed only during the high mode. The root cause of this puzzling behaviour remains elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar prototype, PSR J1023+0038, covering from the radio to X-rays. The campaign was carried out over two nights in June 2021 and involved 12 different telescopes and instruments, including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA, and FAST. By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with ALMA at the high-to-low mode switch. The pulsar is subsequently re-enshrouded, completing our picture of the mode switches.</p