Resonance Capture Research Articles

Resonant electron capture by 5-Br-2'-deoxyuridine.

The results of the study of resonant electron capture by molecules of 5-Br-2'-deoxyuridine (BrdUrd) over the range of electron energies from near zero to 14eV are described. In the thermal energy range, long-lived molecular negative ions, unstable with respect to autoneutralization and dehalogenation, have been registered. Examination of the kinetics of these decay processes led us to the conclusion that the most probable structure for molecular negative ions is that with an extended C-Br bond, which was predicted earlier using quantum-chemical calculations. Estimates have shown that the BrdUrd molecule owns a significant electronic affinity of 0.93-1.38eV. The most intense fragmentation channel leads to the abundant formation of Br- ions. The dissociative electron attachment cross section for Br- ions formation was estimated to amount to no less than 1.65 × 10-15cm2, indirectly implying a fairly intense formation of complementary highly reactive deoxyuridine-5-yl particles. These particles are known to be responsible for the radiosensitizing properties of BrdUrd.

SDS coated Fe3O4@MoS2 with NIR-enhanced photothermal-photodynamic therapy and antibiotic resistance gene dissemination inhibition functions

Infection caused by antibiotic-resistant bacteria is serious threat for public health, and calls for novel antibacterial agents with versatile functions. In particular, nanomaterial is one of promising candidates to fight the increasing antibiotic resistance crisis. Here, we synthesized distinct Fe3O4@MoS2@SDS nanocomposites by ultrasonication assisted SDS coating on the Fe3O4@MoS2. Photothermal investigation indicated that the Fe3O4@MoS2@SDS showed excellent and stable photothermal performance and could be a NIR-induced photothermal reagent. It also displayed superior disinfection ability of Escherichia coli (E. coli), Methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa (P. aeruginosa) and in vivo wound healing ability with the help of NIR irradiation. According to the results of electron paramagnetic resonance (EPR) and radical capture tests, plenty of superoxide, hydroxyl radicals, singlet oxygen and living cell reactive oxygen species can be observed under NIR irradiation. Besides, the synergistic effect Fe3O4@MoS2@SDS and NIR irradiation eradicated almost all the biofilms of MRSA, so this kind of function enhanced the disinfection ability of Fe3O4@MoS2@SDS under NIR irradiation. Furthermore, its inhibition effect on antibiotic resistance gene dissemination was also investigated. As expected, the Fe3O4@MoS2@SDS could efficiently and broadly block the horizontal transfer of antibiotic resistance genes which mediated by conjugative plasmids, and its blocking effect was better than that we have reported Fe3O4@MoS2. Overall, our findings revealed that the Fe3O4@MoS2@SDS could be a potential candidate for photothermal-photodynamic therapy and antibiotic resistance gene dissemination inhibition.

Metal-Organic Framework-Encapsulated Anthraquinone for Efficient Photocatalytic Hydrogen Atom Transfer.

Anthraquinone (AQ) as an effective hydrogen atom transfer catalyst was limited in photocatalysis application due to the dimerization of reduced AQ. Sr-NDI@AQ, encapsulating AQ into the channel of Sr-NDI, paved a new way for solving the problem of dimerization of reduced AQ and improving the catalytic efficiency owing to the fast electron transfer from reduced AQ to the ligand through host-guest interaction. The structure of Sr-NDI@AQ was determined by single-crystal X-ray diffraction, and the value for distance and torsion angle between the ligand and AQ was calculated. The photochemical and electrochemical properties for Sr-NDI@AQ were characterized through a series of experiments. The coupling reaction between aldehyde and phenyl vinyl sulfone and photoacetalization reaction were carried out, displaying the improving catalytic efficiency of Sr-NDI@AQ compared to Sr-NDI and AQ. The reaction mechanisms were proposed through radical capture and electron paramagnetic resonance experiments.

S-scheme BiVO4/CQDs/β-FeOOH photocatalyst for efficient degradation of ofloxacin: Reactive oxygen species transformation mechanism insight

Photocatalysis technology exhibited promising application for advanced treatment of wastewater. Nevertheless, the design of efficient photocatalyst and the mechanism of free radicals in pollutant degradation still remained to be further investigated. Herein, BiVO4/CQDs/β-FeOOH photocatalyst was fabricated by electrostatic self-assembly method, which exhibited the excellent photocatalytic performance. Under visible-light irradiation, the removal rate of ofloxacin by BiVO4/CQDs/β-FeOOH (0.25 min−1) was 1.93 times than pristine BiVO4, and the removal efficiency in 15 min reached 99.21%. The perfect reusability of BiVO4/CQDs/β-FeOOH was ascribed to the persistent catalytic active centers provided by the renewable surface oxygen vacancies on the β-FeOOH. As electron transfer channels, CQDs facilitated the transfer of BiVO4 photogeneration electrons. The matched band structure allowed the construction of S-scheme heterojunctions, and the higher conduction band position was retained while the carrier separation was promoted. More importantly, this work firstly reported the phenomenon that the main reactive groups in the photocatalysis process would be directionally transformed with the change of pH conditions. Based on the analysis of capture and electron paramagnetic resonance experiments, ·O2− was the main free radicals to photodegrade OFL in neutral and alkaline conditions. However, when the solution pH turned into acidic, the photodegradation of OFL was dominated by 1O2. This innovative phenomenon was due to that acidic condition accelerated the reaction kinetics of spontaneous transformation of ·O2− to 1O2 and inhibited the direct oxidation of pollutants by ·O2−. Accordingly, this research could inspire theoretical study of free radical reaction and the design of S-scheme heterojunction photocatalysts.

Novel Tb2O3/Ag2Mo2O7 heterojunction photocatalyst for excellent photocatalytic activity: In-built Tb4+/Tb3+ redox center, proliferated hydroxyl radical yield and promoted charge carriers separation

The novel Tb2O3/Ag2Mo2O7 heterojunction photocatalyst was designed and synthesized successfully. X-ray diffraction and scanning electron microscope illustrated the crystalline phase and morphology of as-synthesized hybrid. X-ray photoelectron spectroscopy analysis displayed the element composite of Tb2O3/Ag2Mo2O7 photocatalyst and proved the existent of Tb4+/Tb3+ redox center in the heterojunction structure. Significantly, Tb2O3/Ag2Mo2O7 composite presented splendid photocatalytic performance under visible light irradiation, and the degradation rate of optimal Tb2O3/Ag2Mo2O7 composite is 3.2 times for methylene blue and 2.3 times for tetracycline compared to Ag2Mo2O7, respectively. Photoluminescence and photocurrent measurement results revealed that Tb2O3/Ag2Mo2O7 sample exhibited higher photoexited carries separation than Ag2Mo2O7. Moreover, the results of electron spin resonance test and capture experiment showed that the construction of Tb2O3/Ag2Mo2O7 heterojunction structure effectively boosted the production of powerful hydroxyl radials. The good stability and repeatability of Tb2O3/Ag2Mo2O7 heterojunction photocatalyst were illustrated by systematic experiments. This finding proposes an original strategy for modifying Ag2Mo2O7, and boosts the development of photocatalyst modification technology.

Running the gauntlet – survival of small circumbinary planets migrating through destabilizing resonances

ABSTRACT All of the known circumbinary planets are large (Rp ≥ 3 R⊕). Whilst observational biases may account for this dearth of small planets, in this paper we propose a theoretical explanation. Most of the known planets are near the stability limit, interspersed between potentially unstable 5:1, 6:1, and 7:1 mean motion resonances with the binary. It is believed that these planets did not form in situ, but rather migrated from farther out in the disc, and hence passed through these resonances. Planets are expected to migrate at a speed proportional to their mass, and a slower rate makes resonant capture and subsequent ejection more likely. Therefore, whilst large planets may be able to successfully ‘run the gauntlet’, small planets may be imperilled. This hypothesis is tested using N-body integrations of migration in a truncated and turbulent disc. We discover that surprisingly none of the known planets exist interior to a fully unstable resonance. We demonstrate that resonant ejection of migrating planets may occur in nature, and that it does indeed disproportionately affect small planets, but it requires a highly turbulent disc and its efficiency is likely too low to fully explain a dearth of Rp < 3 R⊕ planets.

Compensation effect of growth of the lifetime of charged carriers in semiconductors at a magnetic field

The condition of regulation of increasing of carrier lifetime by recombination processes in semiconductors at low temperatures (1-10) K and classical "strong" magnetic fields (3·102-3·104) Gs are analyzed. The values of carrier concentrations (1010-1014) cm-3 correspond to conditions of manifestation as cascade as resonant capture. It is indicated on necessarily to take into account of scattering of electrons on acoustic phonons along with electron-electron collisions, by it cascade capture on cuolomb centers. As showed (on the basis of concrete estimates) namely scattering on acoustic phonons at cascade capture, stabilities of lifetime and controls of dynamics it increases in the presence of "strong" magnetic field. Keywords: effective coefficient of capture, cascade capture, recombination, classical "strong" magnetic field, "shallow" acoustic phonons, electron-electron collisions, lifetime.

Эффект компенсации роста времени жизни носителей заряда в полупроводниках в магнитном поле

The condition of regulation of increasing of carrier lifetime by recombination processes in semiconductors at low temperatures (1-10) K and classical "strong" magnetic fields (300-30000) Gs are analyzed. The values of carrier concentrations (10^10-10^14) cm^-3 correspond to conditions of manifestation as cascade as resonant capture. It is indicated on necessarily to take into account of scattering of electrons on acoustic phonons along with electron-electron collisions, by it cascade capture on cuolomb centers. As showed (on the basis of concrete estimates) namely scattering on acoustic phonons at cascade capture, stabilities of lifetime and controls of dynamics it increases in the presence of "strong" magnetic field.

New capability for indirect neutron capture measurements: The DICER instrument at LANSCE

The Device for Indirect Capture on Radionuclides (DICER) implements a new indirect technique for (n,γ) studies in which the neutron capture rate is determined from analysis of resonance neutron transmission data. The DICER instrument and associated radionuclide production at the Isotope Production Facility (IPF), both at the Los Alamos Neutron Science Center (LANSCE), as well radioactive sample fabrication, have been under development in the last few years. First measurements on a radioactive sample (88Zr, t½=83.4 days), which was recently reported to have an extremely large thermal neutron capture cross section and resonance integral [1, 2], are planned for the winter of 2021. A performance overview, brief details on the 88Zr fabrication and proof of good operation results will be presented.

Attempting to Capture Resonance during Co-Creation with Biosignal Indicators

Attempting to Capture Resonance during Co-Creation with Biosignal Indicators

Determination of the Characteristics of the Molecular Structure of Trialkyl Phosphates by the Joint Application of Electronic Ionization Mass Spectra with Registration of Positive Ions and Negative Ions of Resonance Coupling

Trialkylphosphates are of considerable interest from the military-chemical point of view as precursors of highly toxic organophosphorus toxicants, possible products of their decontamination, complexing agents in processes of reprocessing of used nuclear fuel, etc. Meanwhile, the development of ways to identify these substances is still in its infancy. In addition, trialkylphosphates are an interesting subject for the search of a solution to the analytical problem of establishing the structure of O-alkyl fragments in molecules of M(O) (OR) n esters of multibasic acids, where M is the central atom (central core), n is the basicity of the acid, R are alkyl radicals with an unknown and in general case different number of carbon atoms in each of them. No general solution to this problem could be found in the book sources. The aim of this work is to develop an algorithm for in-depth identification of trialkyl phosphates, which includes establishing the belonging of the investigated substance to this class, as well as a general and reliable method for determining the number of carbon atoms in each of the O-alkyl radicals of the investigated substances. On the basis of the revealed regularities of the decay of positive molecular ions of trialkyl phosphates, as well as negative ions of resonant capture of electrons of the same compound obtained under conditions of electron ionization, an algorithm for in-depth identification of trialkyl phosphates is proposed, which includes establishing the belonging of the investigated substance to this class, as well as a general and reliable method determining the number of carbon atoms in each of the O-alkyl radicals of the substance molecule

Exciting Mutual Inclination in Planetary Systems with a Distant Stellar Companion: The Case of Kepler-108

Abstract We study the excitation of mutual inclination between planetary orbits by a novel secular-orbital resonance in multi-planet systems perturbed by binary companions, which we call “ivection.” The ivection resonance happens when the nodal precession rate of the planet matches a multiple of the orbital frequency of the binary, and its physical nature is similar to the previously studied evection resonance. Capture into an ivection resonance requires encountering the resonance with slowly increasing nodal precession rate, and it can excite the mutual inclination of the planets without affecting their eccentricities. We discuss the possible outcomes of ivection resonance capture, and we use simulations to illustrate that it is a promising mechanism for producing the mutual inclination in systems where planets have significant mutual inclination but modest eccentricity, such as Kepler-108. We also find an apparent deficit of multi-planet systems that would have a nodal precession period comparable to the binary orbital period, suggesting that ivection resonance may inhibit formation of or destablize multi-planet systems with an external binary companion.

Application of non-destructive neutron resonance capture analysis for investigation of women’s Old Believer cross dating back to the second half of the 17th century

Neutron Resonance Capture Analysis (NRCA) is presently being developed at the Frank Laboratory of Neutron Physics (FLNP) to determine the elemental composition of samples. The NRCA is a nondestructive method that allows measuring objects’ bulk composition. The procedure is based on detecting neutron resonances in radiative capture and the measurement of the yield of reaction products in these resonances. The experiments are carried out at the Intense REsonance Neutron source (IREN). In this study, we applied the NRCA to investigate an archaeological object provided by the Museum and Exhibition Complex (MVK) "Volokolamsk Kremlin". The object was a women’s Old Believer cross (second half of the 17th century) found in the Moscow region, Volokolamsk district, the village of Chubarovo.

Исследование вакантных электронных состояний активаторов хемилюминесценции на примере молекул 2-кумаранона

2-coumaranone molecules were studied by the method of mass spectrometry of negative ions of resonant capture of low (0-15 eV) electrons. This substance is widely used as a platform on which chemiluminescent probes are built. The analysis of the decay channels of molecular negative ions (OI) into stable fragments using the results of quantum chemical calculations in the approximation of the density functional theory allowed us to determine the most probable structures of fragmentation ions ([M – H]–, [M – 2H]–, [M – CO]–).

Lossy mode resonances in photonic crystal fibers

The interaction effect of the fundamental mode in a special photonic crystal fiber (PCF) with a thin-film absorbing coating deposited on a surface of a fiber cladding on the optical transmission of the PCF is theoretically studied. It is shown that the transmission has a multi-peak spectrum that is determined by the resonance capture of the fundamental PCF mode energy by the coating. In some cases, this capture is explained by a resonance coupling between the fundamental core mode and leaky modes of the coating, or between the fundamental PCF mode and cladding modes located between PCF air channels and the coating. Examples are presented of using this effect to develop fiber-optic sensors of refractive index or pressure, and to sense a nanoscale adsorption layer of ammonia molecules deposited on a coating surface contacting air.

Dynamics of Colombo’s top: tidal dissipation and resonance capture, with applications to oblique super-Earths, ultra-short-period planets and inspiraling hot Jupiters

ABSTRACT We present a comprehensive theoretical study on the spin evolution of a planet under the combined effects of tidal dissipation and gravitational perturbation from an external companion. Such a ‘spin + companion’ system (called Colombo’s top) appears in many [exo]planetary contexts. The competition between the tidal torque (which drives spin-orbit alignment and synchronization) and the gravitational torque from the companion (which drives orbital precession of the planet) gives rise to two possible spin equilibria (‘tidal Cassini Equilibria’, tCE) that are stable and attracting: the ‘simple’ tCE1, which typically has a low spin obliquity, and the ‘resonant’ tCE2, which can have a significant obliquity. The latter arises from a spin-orbit resonance and can be broken when the tidal alignment torque is stronger than the precessional torque from the companion. We characterize the long-term evolution of the planetary spin (both magnitude and obliquity) for an arbitrary initial spin orientation, and develop a new theoretical method to analytically obtain the probability of resonance capture driven by tidal dissipation. Applying our general theoretical results to exoplanetary systems, we find that a super-Earth (SE) with an exterior companion can have a substantial probability of being trapped in the high-obliquity tCE2, assuming that SEs have a wide range of primordial obliquities. We also evaluate the recently proposed ‘obliquity tide’ scenarios for the formation of ultra-short-period Earth-mass planets and for the orbital decay of hot Jupiter WASP-12b. We find in both cases that the probability of resonant capture into tCE2 is generally low and that such a high-obliquity state can be easily broken by the required orbital decay.

Relic neutrinos at accelerator experiments

We present a new technique for observing low energy neutrinos with the aim of detecting the cosmic neutrino background using ion storage rings. Utilising high energy targets exploits the quadratic increase in the neutrino capture cross section with beam energy, and with sufficient beam energy, enables neutrino capture through inverse-beta decay processes from a stable initial state. We also show that there exist ion systems admitting resonant neutrino capture, capable of achieving larger capture cross sections at lower beam energies than their non-resonant counterparts. We calculate the neutrino capture rate and the optimal experimental runtime for a range of different resonant processes and target ions and we demonstrate that the resonant capture experiment can be performed with beam energies as low as $\mathcal{O}(10\,\mathrm{TeV})$ per target nucleon. Unfortunately, none of the ion systems discussed here can provide sufficient statistics to discover the cosmic neutrino background with current technology. We address the challenges associated with realising this experiment in the future, taking into account the uncertainty in the beam and neutrino momentum distributions, synchrotron radiation, as well as the beam stability.

First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV 25Mg(p, [formula omitted])26Al resonance

The 25Mg(p, γ)26Al reaction plays an important role in the study of cosmic 1.809 MeV γ-ray as a signature of ongoing nucleosynthesis in the Galaxy. At astrophysical temperature around 0.1 GK, the 25Mg(p, γ)26Al reaction rates are dominated by the 92 keV resonance capture process. We report a precise measurement of the 92 keV 25Mg(p, γ)26Al resonance in the day-one experiment at Jinping Underground Nuclear Astrophysics experiment (JUNA) facility in the China Jinping Underground Laboratory (CJPL). The resonance strength and ground state feeding factor are determined to be 3.8±0.3 ×10−10 eV and 0.66±0.04, respectively. The results are in agreement with those reported in the previous direct underground measurement within uncertainty, but with significantly reduced uncertainties. Consequently, we recommend new 25Mg(p, γ)26Al reaction rates which are by a factor of 2.4 larger than those adopted in REACLIB database at the temperature around 0.1 GK. The new results indicate higher production rates of 26gAl and the cosmic 1.809 MeV γ-ray. The implication of the new rates for the understanding of other astrophysical situations is also discussed.

A Short Note on Synchrosqueezed Transforms for Resonant Capture, Sommerfeld Effect and Nonlinear Jump Characterization in Mechanical Systems

A Short Note on Synchrosqueezed Transforms for Resonant Capture, Sommerfeld Effect and Nonlinear Jump Characterization in Mechanical Systems

Resonance-Averaged Solar Torque Dynamics for Tumbling Satellites

Observations indicate that the spin states of retired and otherwise defunct satellites are diverse and can change significantly over time. Understanding defunct satellite spin state evolution is important for solar radiation pressure modeling, active debris removal, satellite servicing, and space situational awareness. Research has shown that many defunct satellites in geosynchronous earth orbit (GEO) are primarily driven by solar radiation torques via the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. Recent exploration of YORP-driven nonprincipal axis tumbling has uncovered rich dynamic behavior, including tumbling cycles, spin–orbit coupling, and tumbling period resonances. Radar and optical observations of the defunct Geostationary Operational Environmental Satellite (GOES) 8 strongly suggest that it has been captured in a tumbling resonance at least once since 2018. Motivated by these findings, we develop a numerical resonance-averaged dynamic model to understand YORP-driven resonance capture, building on our earlier nonresonant averaging framework. This resonance-averaged model illuminates resonance capture mechanisms. Also, by averaging over the satellite’s rotation, this model is roughly 20 times faster to propagate than the full (Euler) dynamics. Overall, this allows for rapid, broad exploration to determine resonance capture durations, spin states changes, and the influence of initial spin rate and resonance order on resonance strength. This resonance-averaged model can be easily applied to other environmental perturbations.