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1
Gainsford, Graeme J. y Mark E. Bowden. "Propylamine–borane". Acta Crystallographica Section E Structure Reports Online 65, n.º 6 (23 de mayo de 2009): o1395. http://dx.doi.org/10.1107/s160053680901887x.
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Behrndt, Jussi, Pavel Exner, Markus Holzmann y Vladimir Lotoreichik. "On the spectral properties of Dirac operators with electrostatic δ -shell interactions". Journal de Mathématiques Pures et Appliquées 111 (marzo de 2018): 47–78. http://dx.doi.org/10.1016/j.matpur.2017.07.018.
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Behrndt, Jussi, Markus Holzmann, Andrea Mantile y Andrea Posilicano. "Limiting absorption principle and scattering matrix for Dirac operators with δ-shell interactions". Journal of Mathematical Physics 61, n.º 3 (1 de marzo de 2020): 033504. http://dx.doi.org/10.1063/1.5123289.
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Hassan, Ahlam Hussein y Muhsen Abood Muhsen Al-Ibadi. "Study the Chemical Bonding of Heterometallic Trinuclear Cluster Containing Cobalt and Ruthenium: [(Cp*Co) (CpRu)2 (μ3-H) (μ-H)3] using QTAIM Approach". Baghdad Science Journal 20, n.º 3(Suppl.) (20 de junio de 2023): 1078. http://dx.doi.org/10.21123/bsj.2023.7937.
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The topological parameters of the metal-metal and metal-ligand bonding interactions in a trinuclear tetrahydrido cluster [(Cp*Co) (CpRu)2 (μ3-H) (μ-H)3]1 (Cp* = η5 -C5Me4Et), (Cp = η5 -C5Me5), was explored by using the Quantum Theory of Atoms-in-Molecules (QTAIM). The properties of bond critical points such as the bond delocalization indices δ (A, B), the electron density ρ(r), the local kinetic energy density G(r), the Laplacian of the electron density ∇2ρ(r), the local energy density H(r), the local potential energy density V(r) and ellipticity ε(r) are compared with data from earlier organometallic system studies. A comparison of the topological processes of different atom-atom interactions has become possible thanks to these results. In the core of the heterometallic tetrahydrido cluster, the Ru2CoH4 part, the calculations show no existence of any bond critical points (BCP) or identical bond paths (BPs) between Ru-Ru and Ru-Co. Electron densities are determined by the position of bridging hydride atoms coordinated to Ru-Ru and Ru-Co, which significantly affects the bonds between these transition metal atoms. On the other hand, the results confirm that the cluster under study contains a 7c–11e bonding interaction delocalized over M3H4, as shown by the non-negligible delocalization index calculations. The small values for electron density ρ(b) above zero, together with the small values, again above zero, for Laplacian ∇2ρ(b) and the small positive values for total energy density H(b), are shown by the Ru-H and Co-H bonds in this cluster is typical for open-shell interactions. Also, the topological data for the bond interactions between Co and Ru metal atoms with the C atoms of the cyclopentadienyl Cp ring ligands are similar. They show properties very identical to open-shell interactions in the QTAIM classification.
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Tzeng, Y., T. T. S. Kuo y T.-S. H. Lee. "The effect of the Δ excitation on the nucleon–nucleon effective interactions in the nuclear shell-model". Physica Scripta 53, n.º 3 (1 de marzo de 1996): 300–305. http://dx.doi.org/10.1088/0031-8949/53/3/004.
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Behrndt, Jussi, Pavel Exner, Markus Holzmann y Vladimir Lotoreichik. "On Dirac operators in $$\mathbb {R}^3$$ R 3 with electrostatic and Lorentz scalar $$\delta $$ δ -shell interactions". Quantum Studies: Mathematics and Foundations 6, n.º 3 (2 de marzo de 2019): 295–314. http://dx.doi.org/10.1007/s40509-019-00186-6.
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MODARRES, M., N. RASEKHINEJAD y H. MARIJI. "THE DENSITY-DEPENDENT Av18 EFFECTIVE INTERACTION AND GROUND STATE OF CLOSED SHELL NUCLEI". International Journal of Modern Physics E 20, n.º 03 (marzo de 2011): 679–703. http://dx.doi.org/10.1142/s0218301311018162.
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The ground state properties of light closed shell nuclei, i.e. 4He, 12C, 16O, 28Si, 32S, 40Ca and 56Ni are studied by using the channel-dependent effective two-body interactions (CDEI's). The CDEI's are generated through the lowest-order constrained variational (LOCV) calculation for asymmetric nuclear matter with the charge-dependent Av18 bare nucleon–nucleon potential. The work is performed on the harmonic oscillator basis, and the local density approximation is applied to create the relative and the center of mass dependent effective two-body potential. Unlike nuclear matter, and similar to our previous calculations with the Reid68 interaction, while the Av18 potential under binds above nuclei up J max = 2 channel, it gives ground state binding energies closer to the experimental data with respect to the Δ- Reid68 and the Reid68 potentials. There are not much difference between the results of Av18 interaction with J max = 5, and those of Reid68Day potential which has been define up to J max = 5. The different CDEI's up to J max = 5 are discussed and the results of our calculations are compared with the other theoretical approaches and experimental data. Finally, it is shown that the contributions of higher partial waves (J>2) are not very important and the two-body kinetic energy in J = 1 channel is roughly twice as that of J = 0 which is not the case for the two-body potential energy.
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Pazur, Richard J., D. Lee, F. J. Walker y Maxim Kasai. "LOW FIELD 1H NMR INVESTIGATION OF PLASTICIZER AND FILLER EFFECTS IN EPDM". Rubber Chemistry and Technology 85, n.º 2 (1 de junio de 2012): 295–312. http://dx.doi.org/10.5254/rct.12.88944.
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Abstract A series of compounds based on peroxide-cured EPDM were prepared with varying amounts of paraffinic plasticizer and carbon black. Modeling of the NMR relaxation signal was successfully carried out by either a biexponential or triexponential fitting procedure. It was found the degree of plasticization correlated directly with the average molar mass between chain entanglements (Me) calculated from the short decay constant T21. Values of Me correlated to the dynamic properties (storage modulus and tan δ) in the unvulcanized state, thus providing a measure of processability. An increase in carbon black concentration brought about a decrease in Me because of increased interactions between the filler and the polymer chain. A new parameter Mchain–filler is introduced to estimate the average molar mass between polymer chains and fillers. Compared with the chain entanglement density, the overall magnitude of this interaction appears to be weak in the mobile zone of the compound matrix. As in the case of plasticization, a relatively good correlation is obtained between Me and the dynamical properties in the unvulcanized state. Compression-set resistance is shown to directly follow the average molar mass between cross-links (Mc) before and after aging. The carbon black study results can be understood within the context of a morphological model containing different zones of chain mobility—a thin shell of immobilized chains, an intermediate zone of limited mobility, and a dominant mobile phase consisting mainly of entangled and cross-linked polymer chains.
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Nissen, P. E., J. S. Silva-Cabrera y W. J. Schuster. "G 112-43/44: A metal-poor binary star with a unique chemical composition and Helmi stream kinematics". Astronomy & Astrophysics 651 (julio de 2021): A57. http://dx.doi.org/10.1051/0004-6361/202140826.
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Context. Correlations between high-precision elemental abundance ratios and the kinematics of halo stars provide interesting information about the formation and early evolution of the Galaxy. Aims. Element abundances of G 112-43/44, a metal-poor wide-orbit binary star with extreme kinematics, are revisited. Methods. High-precision studies of the chemical compositions of 94 metal-poor dwarf stars in the solar neighbourhood are used to compare abundance ratios for G 112-43/44 with ratios for stars that have similar metallicities, taking into account the effect of deviations from local thermodynamic equilibrium on the derived abundances. Gaia EDR3 data are used to compare the kinematics. Results. The X/Fe abundance ratios of the two components of G 112-43/44 agree within ±0.05 dex for nearly all elements, but there is a hint of a correlation between the difference in [X/H] and the elemental condensation temperature, which may be due to planet-star interactions. The Mg/Fe, Si/Fe, Ca/Fe, and Ti/Fe ratios of G 112-43/44 agree with the corresponding ratios for accreted (Gaia-Enceladus) stars, but Mn/Fe, Ni/Fe, Cu/Fe, and Zn/Fe are significantly enhanced, with Δ [Zn/Fe] reaching 0.25 dex. The kinematics show that G 112-43/44 belongs to the Helmi streams in the solar neighbourhood. In view of this, we discuss if the abundance peculiarities of G 112-43/44 can be explained by chemical enrichment from supernova events in the progenitor dwarf galaxy of the Helmi streams. Interestingly, yields calculated for a helium shell detonation Type Ia supernova model can explain the enhancement of Mn/Fe, Ni/Fe, Cu/Fe, and Zn/Fe in G 112-43/44 and three other α-poor stars in the Galactic halo with abundances from the literature, one of which has Helmi stream kinematics. However, the helium shell detonation model also predicts enhanced abundance ratios of Ca/Fe, Ti/Fe, and Cr/Fe, in disagreement with the observed ratios.
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Exner, P. "Dirac Operators with a δ-Shell Interaction". Physics of Particles and Nuclei 51, n.º 4 (julio de 2020): 405–9. http://dx.doi.org/10.1134/s1063779620040255.
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KIENAST, ARNE, LUTZ GALICH, KEITH S. MURRAY, BOUJEMA MOUBARAKI, GEORGE LAZAREV, JOHN D. CASHION y HEINER HOMBORG. "μ-Carbido Diporphyrinates and Diphthalocyaninates of Iron and Ruthenium". Journal of Porphyrins and Phthalocyanines 01, n.º 02 (abril de 1997): 141–57. http://dx.doi.org/10.1002/(sici)1099-1409(199704)1:2<141::aid-jpp18>3.0.co;2-m.
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μ-Carbido diporphyrinates and diphthalocyaninates of general formula [{ Mp 2−}2(μ- C )] ( p 2− = tpp ( M = Fe ), oep ( Fe ), pc ( Fe , Ru ); H 2 tpp : 21H,23H-5,10,15,20-tetraphenylporphine; H 2 oep : 21H,23H-2,3,4,8,12,13,17,18-octaethylporphine; H 2 pc : 29H,31H-phthalocyanine) of formally Fe IV and Ru IV are prepared by a new and improved ‘one-pot’ synthesis. The corresponding chloro complexes of the tervalent metal ions react successively with potassium hydroxide in boiling 2-propanol and then with trichloromethane. Potassium hydroxide is proven to be a very versatile and powerful reductant in tetrapyrrolic chemistry. As evidenced from electron spin resonance and UV vis spectral measurements, the precursor is reduced primarily to an ate-complex of type [ M I p 2−]− of a formally monovalent metal ion. This active species is assumed to react with trichloromethane via a dichlorocarbene complex of type [ M II( CCl 2) p 2−] to yield the actual -carbido complex. [{ Feoep 2−}2(μ- C )] is crystallographically characterized. It is monoclinic, space group C12/c1 (15), with a = 18.279(3) Å, b = 15.005(2) Å, c = 23.392(7) Å, β = 107.12(2)°, Z = 4, R1 = 0.0773. The iron atom is displaced by 0.192(3) Å out of the centre ( Ct ) of the ( N p )4 plane toward the (μ- C ) atom. Average d ( Fe - N p ) is 1.986(5) Å; d ( Fe -(μ- C )) is 1.6638(9) Å. The Fe - C - Fe skeleton is linear (179.5(3)°). The two slightly waving porphyrinato cores are in a staggered conformation, the ( N p - Fe - Fe ″- N p ″) torsion angle being 21.0(3)°. Solutions of each μ-carbido complex in pyridine/dichloromethane show four distinct quasi-reversible redox processes in their differential-pulse voltammograms and these are assigned to the successive one-electron reduction and oxidation of the macrocyclic ligands. 13 C CP MAS NMR spectra indicate effective four-fold symmetry within the series of the μ-carbido complexes with isotropic shifts occurring at similar fields to those of the corresponding macrocyclic complex of a closed-shell metal ion. Resonances of the bridging carbon atom are not detected. A characteristic increase of line broadening within the series tpp 2− > oep 2− > pc 2− may be due to Fermi contact interactions with the strongly coupled low-spin M IV centres. The magnetic susceptibility studies show that the complexes all display non-zero μ values at 295 K increasing from pc 2− to tpp 2−. Mössbauer spectra confirm the low-spin Fe IV oxidation state for the iron centres. Isomer shift, δ, and quadrupole splitting, ΔE Q , for [{ Fepc 2−}2(μ- C )] and [{ Fetpp 2−}2(μ- C )] are identical to those previously reported. Data for [{ Feoep 2−}2(μ- C )] are essentially the same as for the pc and tpp complex. Thus the order of δ is tpp ≈ oep > pc whilst that of Δ E Q is pc >> oep > tpp . Small impurity lines are observed which help explain the magnetic data. UV vis/NIR spectra of the μ-carbido complexes show the characteristic π-π* transitions. These are shifted with respect to the corresponding mononuclear complexes to higher energy because of excitonic interactions. Vibrational spectra are discussed in detail ν as ( M - C - M ) (in cm−1) is at 937 ( M = Fe ; tpp ) < 976 ( Fe / oep ) < 997 ( Fe / pc ) < 1050 ( Ru / pc ), ν s ( M - C - M ) (in cm−1 at 433 ( Fe / tpp ) < 460 ( Fe / oep ) < 477 ( Fe / pc ). Hence, valence force constants increase significantly in the order tpp < oep < pc . ν s ( Fe - C - Fe ) of [{ Fepc 2−}2(μ- C )] is selectively resonance Raman enhanced. As evidenced from the excitation profile a C → Fe charge transfer, not detected in the vis spectrum, is assumed to be present at 22 000 > ν > 25 000 cm −1.
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Črnivec, Nina y Bernhard Mayer. "The incorporation of the Tripleclouds concept into the <i>δ</i>-Eddington two-stream radiation scheme: solver characterization and its application to shallow cumulus clouds". Atmospheric Chemistry and Physics 20, n.º 17 (14 de septiembre de 2020): 10733–55. http://dx.doi.org/10.5194/acp-20-10733-2020.
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Abstract. The treatment of unresolved cloud–radiation interactions in weather and climate models has considerably improved over the recent years, compared to conventional plane-parallel radiation schemes, which previously persisted in these models for multiple decades. One such improvement is the state-of-the-art Tripleclouds radiative solver, which has one cloud-free and two cloudy regions in each vertical model layer and is thereby capable of representing cloud horizontal inhomogeneity. Inspired by the Tripleclouds concept, primarily introduced by Shonk and Hogan (2008), we incorporated a second cloudy region into the widely employed δ-Eddington two-stream method with the maximum-random overlap assumption for partial cloudiness. The inclusion of another cloudy region in the two-stream framework required an extension of vertical overlap rules. While retaining the maximum-random overlap for the entire layer cloudiness, we additionally assumed the maximum overlap of optically thicker cloudy regions in pairs of adjacent layers. This extended overlap formulation implicitly places the optically thicker region towards the interior of the cloud, which is in agreement with the core–shell model for convective clouds. The method was initially applied on a shallow cumulus cloud field, evaluated against a three-dimensional benchmark radiation computation. Different approaches were used to generate a pair of cloud condensates characterizing the two cloudy regions, testing various condensate distribution assumptions along with global cloud variability estimate. Regardless of the exact condensate setup, the radiative bias in the vast majority of Tripleclouds configurations was considerably reduced compared to the conventional plane-parallel calculation. Whereas previous studies employing the Tripleclouds concept focused on researching the top-of-the-atmosphere radiation budget, the present work applies Tripleclouds to atmospheric heating rate and net surface flux. The Tripleclouds scheme was implemented in the comprehensive libRadtran radiative transfer package and can be utilized to further address key scientific issues related to unresolved cloud–radiation interplay in coarse-resolution atmospheric models.
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OTSUKA, TAKAHARU. "HADRONIC INTERACTION AND STRUCTURE OF EXOTIC NUCLEI". International Journal of Modern Physics E 18, n.º 10 (noviembre de 2009): 1981–85. http://dx.doi.org/10.1142/s0218301309014123.
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I will overview recent studies on the evolution of the shell structure in stable and exotic nuclei, and will show its relevance to hadronic interaction, including nuclear forces. This shell evolution is primarily due to the tensor force. The robust mechanism and some examples will be presented. Such examples include the disappearance of existing magic numbers and the appearance of new ones. The shell structure and existing limit of nuclei depend also on the three-body interaction in a specific way. I will sketch how the Δ-hole excitation induced three-body force (Fujita-Miyazawa force) modifies them.
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Dittrich, J., P. Exner y P. Šeba. "Dirac operators with a spherically symmetric δ‐shell interaction". Journal of Mathematical Physics 30, n.º 12 (diciembre de 1989): 2875–82. http://dx.doi.org/10.1063/1.528469.
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Mas, Albert y Fabio Pizzichillo. "Klein’s paradox and the relativistic δ-shell interaction in ℝ3". Analysis & PDE 11, n.º 3 (1 de enero de 2018): 705–44. http://dx.doi.org/10.2140/apde.2018.11.705.
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ARENHÖVEL, H., E. M. DARWISH, A. FIX y M. SCHWAMB. "PRESENT STATUS OF ELECTROMAGNETIC REACTIONS ON THE DEUTERON ABOVE PION THRESHOLD". Modern Physics Letters A 18, n.º 02n06 (28 de febrero de 2003): 190–99. http://dx.doi.org/10.1142/s0217732303010235.
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The present status of the theoretical description of electromagnetic reactions on the deuteron above pion threshold is reviewed. Three major topics are considered: (i) retardation effects in π-meson exchange contributions to NN-interaction and meson exchange currents in deuteron photodisintegration above π-threshold in the Δ-resonance region, (ii) off-shell effects in the one-body current treated in a simple pion cloud model in, deuteron photodisintegration in and above the Δ-resonance region, and (iii) final state interaction effects in photoproduction of π and η mesons on the deuteron.
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Maung, Khin Maung, P. A. Deutchman y R. L. Buvel. "Theoretical shell-model signatures in heavy-ion, coherent pion production". Canadian Journal of Physics 70, n.º 4 (1 de abril de 1992): 202–15. http://dx.doi.org/10.1139/p92-035.
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A comprehensive summary of a many-body, microscopic, particle–hole formalism is presented that describes coherent, subthreshold, pion production in peripheral, heavy-ion collisions. The formalism uses a new separable model transition interaction that produces Δ-hole states in either the projectile or target nucleus. Shell-model states described by harmonic oscillator functions are used in the calculation of Δ formation and decay and Lorentz-contraction effects of the nucleus not at rest are included. An analytical expression to lowest multipole order for the differential cross section is examined. The sensitivity of the theoretical results to the shell-model states is determined with preliminary shape results compared with data. The effects of higher multipoles are examined with attention paid to the second-order multipole value.
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POMORSKI, KRZYSZTOF, BOŻENA NERLO-POMORSKA y JOHANN BARTEL. "MICROSCOPIC ENERGY CORRECTIONS AT THE SCISSION CONFIGURATION". International Journal of Modern Physics E 20, n.º 02 (febrero de 2011): 316–24. http://dx.doi.org/10.1142/s0218301311017673.
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The Strutinsky shell correction and the pairing correlations at deformations close to scission point are studied. It is shown that the shell correction energy of the nuclear system at scission is simply the sum of the shell-correction energies of the two nascent fragments while this is not the case for the pairing corrections when the reflection symmetry of the system is broken. To study this effect the use of a δ-pairing force or of the Gogny interaction is recommended. It is also shown that the strength of the pairing correlations should grow with increasing deformation of the fissioning nucleus in order to obtain the correct properties of the fragments.
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Mas, Albert y Fabio Pizzichillo. "The relativistic spherical δ -shell interaction in R 3 : Spectrum and approximation". Journal of Mathematical Physics 58, n.º 8 (agosto de 2017): 082102. http://dx.doi.org/10.1063/1.5000381.
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KABIR, K., T. K. DATTA, MUSLEMA PERVIN y L. M. NATH. "THE ROLE OF Δ(1232) IN TWO-PION EXCHANGE THREE-NUCLEON POTENTIAL". International Journal of Modern Physics E 09, n.º 02 (abril de 2000): 157–68. http://dx.doi.org/10.1142/s021830130000009x.
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In this paper we have studied the two-pion exchange three-nucleon potential (2πE-3NP) using an approximate SU(2)×SU(2) chiral symmetry of the strong interaction. The off-shell pion-nucleon scattering amplitudes obtained from the Weinberg Lagrangian are supplemented with contributions from the well-known σ-term and the Δ(1232) exchange. It is the role of the Δ-resonance in 2πE-3NP, which we have investigated in detail in the framework of the Lagrangian field theory. The Δ-contribution is quite appreciable and, more significantly, it is dependent on a parameter Z which is arbitrary but has the empirical bounds |Z|≤1/2. We find that the Δ-contribution to the important parameters of the 2πE-3NP depends on the choice of a value for Z, although the correction to the binding energy of triton is not expected to be very sensitive to the variation of Z within its bounds.
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MISHRA, SUNIL K. y V. SUBRAHMANYAM. "SIZE-DEPENDENT MAGNETIZATION FLUCTUATIONS IN NiO NANOPARTICLES". International Journal of Modern Physics B 25, n.º 18 (20 de julio de 2011): 2507–24. http://dx.doi.org/10.1142/s0217979211100035.
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The finite size and surface roughness effects on the magnetization of NiO nanoparticles is investigated. A large magnetic moment arises for an antiferromagnetic nanoparticle due to these effects. The magnetic moment without the surface roughness has a nonmonotonic and oscillatory dependence on R, the size of the particles, with the amplitude of the fluctuations varying linearly with R. The geometry of the particle also matters a lot in the calculation of the net magnetic moment. An oblate spheroid shape particle shows an increase in net magnetic moment by increasing oblateness of the particle. However, the magnetic moment values thus calculated are very small compared to the experimental values for various sizes, indicating that the bulk antiferromagnetic structure may not hold near the surface. We incorporate the surface roughness in two different ways; an ordered surface with surface spins inside a surface roughness shell aligned due to an internal field, and a disordered surface with randomly oriented spins inside surface roughness shell. Taking a variational approach we find that the core interaction strength is modified for nontrivial values of Δ which is a signature of multi-sublattice ordering for nanoparticles. The surface roughness scale Δ is also showing size-dependent fluctuations, with an envelope decay Δ~R-1/5. The net magnetic moment values calculated using spheroidal shape and ordered surface are close to the experimental values for different sizes.
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ALEXA, PETR, JAN KVASIL y RAYMOND K. SHELINE. "NEUTRON-PROTON INTERACTION IN ODD-ODD SPHERICAL NUCLEI NEAR 208PB". International Journal of Modern Physics E 08, n.º 04 (agosto de 1999): 337–46. http://dx.doi.org/10.1142/s0218301399000240.
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A total of 74 levels from 21 multiplets of the nuclei 206 Tl , 208 Tl , 208 Bi , and 210 Bi have been calculated with a Generalized Intermediate Coupling Model, with Gaussian and delta potentials with and without an interaction between octupole phonon and odd nucleons. The goodness of fit is compared with that of other calculations of Molinari et al. and Schiffer and True. It is quite clear that the calculations work well in spite of the fact that they are required to fit simultaneously odd-odd nuclei with neutron and proton shells which differ by principal harmonic oscillator quantum numbers Δ N = +1.
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Hosokawa, Saburo, Yudai Oshino, Toyokazu Tanabe, Hiroaki Koga, Kosuke Beppu, Hiroyuki Asakura, Kentaro Teramura, Teruki Motohashi, Mitsutaka Okumura y Tsunehiro Tanaka. "Strong Metal–Support Interaction in Pd/Ca2AlMnO5+δ: Catalytic NO Reduction over Mn-Doped CaO Shell". ACS Catalysis 11, n.º 13 (17 de junio de 2021): 7996–8003. http://dx.doi.org/10.1021/acscatal.1c01559.
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Mikhailov, G. P. "Quantum-chemical study of еhe binding energy of lithium ion endofullerene li<sup>+</sup>@C<sub>60</sub> with anion". Журнал общей химии 93, n.º 6 (15 de junio de 2023): 978–84. http://dx.doi.org/10.31857/s0044460x23060173.
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The optimal geometry, binding energy Δ E ion pairs of type Li+@C60·A- (A = BF4, AsF6, PF6, FSI, TFSI, 4F-BB) in vacuum and chlorobenzene medium were calculated using the method of density functional theory. ΔE values were found to decrease significantly in chlorobenzene medium depending on the nature of the anion. In the structures of Li+@C60·A-, various contacts C···F, C···O, C···C, C···N and Li···C were established, which, within the framework of Bader’s theory, “atoms in molecules” were assigned to interactions of closed shells, and their energy is calculated.
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Gómez de Santiago, Miguel, Péter Gurin, Szabolcs Varga y Gerardo Odriozola. "Extended law of corresponding states: square-well oblates". Journal of Physics: Condensed Matter 34, n.º 10 (21 de diciembre de 2021): 104002. http://dx.doi.org/10.1088/1361-648x/ac3fd8.
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Abstract The vapour–liquid coexistence collapse in the reduced temperature, T r = T/T c , reduced density, ρ r = ρ/ρ c , plane is known as a principle of corresponding states, and Noro and Frenkel have extended it for pair potentials of variable range. Here, we provide a theoretical basis supporting this extension, and show that it can also be applied to short-range pair potentials where both repulsive and attractive parts can be anisotropic. We observe that the binodals of oblate hard ellipsoids for a given aspect ratio (κ = 1/3) with varying short-range square-well interactions collapse into a single master curve in the Δ B 2 * –ρ r plane, where Δ B 2 * = ( B 2 ( T ) − B 2 ( T c ) ) / v 0 , B 2 is the second virial coefficient, and v 0 is the volume of the hard body. This finding is confirmed by both REMC simulation and second virial perturbation theory for varying square-well shells, mimicking uniform, equator, and pole attractions. Our simulation results reveal that the extended law of corresponding states is not related to the local structure of the fluid.
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PARTHASARATHY, R. "NEUTRINO NEUTRAL CURRENT EXCITATION OF 12C*(1+; T=1; 15.1 MeV)". International Journal of Modern Physics E 03, n.º 04 (diciembre de 1994): 1195–202. http://dx.doi.org/10.1142/s021830139400036x.
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We report here the total cross-sections for [Formula: see text][Formula: see text], for incident neutrino energies from 16 MeV to 54 MeV, so as to provide theoretical values for comparison with the recent Karlsruhe-Rutherford Medium Energy Neutrino Experiment (KARMEN). The effects of the isospin mixing from the 1+; T=0; 12.7 MeV level of 12C are taken into account. The effect of the only strong interaction induced weak magnetism form factor is studied, as well as that of the isovector axial coupling. The nuclear models used are the combination of general 1p-shell wave functions of Cohen-Kurath for the 15.1 MeV level, and Gillet-VinhMau particle-hole wave functions with 2ħω excitations for 12.7 MeV level. The neutrino (antineutrino) flux averaged sum [Formula: see text] is found to be 9.86×10−42 cm2without isospin mixing and 9.83×10−42 cm2with isospin mixing (δ=0.05) to be compared with the KARMEN result for the sum as [10.8±1.1(stat)±1.2(syst)]×10−42 cm2.
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Ray, Santanu Kr. "Influence of Intrinsic Solidification Behaviour on Quality of Stainless Steel Cast and Rolled Products". Advanced Materials Research 794 (septiembre de 2013): 63–74. http://dx.doi.org/10.4028/www.scientific.net/amr.794.63.
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Recent advances in continuous casting have facilitated remarkable improvement in the quality of cast steel. The focus of the present paper is directed towards understanding of the influence of chemistry and intrinsic solidification behaviour on the different quality issues of stainless steel. An attempt has been made, wherever possible in quantitative terms , to correlate the chemistry and the process parameters with the quality factors. The relevant theoretical background has been touched upon. Understanding has been developed on the role of the ratio of nickel equivalent and chromium equivalent. This factor can be used to represent the chemistry of any stainless steel grade. Under similar casting conditions, specific problem of mould sticking , strand bulging , or depression formation has been explained invoking this chemistry factor. Each quality issue owes its genesis to interaction between the high-temperature strength and ductility of the solidifying shell during casting. The important roles of micro-segregation , the effective shell thickness during the early stage of casting , and the temperature range of transformation for δ-ferrite to austenite have been highlighted. An approach of grade-specific casting practice has been suggested to formulate the specific casting parameters. The developed understanding has been utilised to address specific quality problems in continuously cast slabs and rolled products of different stainless steel grades. This integrated understanding can be useful for ensuring the quality of stainless steel of any chemistry.
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TREVISANI, MARCELLO, ALESSANDRA DE CESARE, SILVA VITALI, ROCCO MANCUSI, FEDERICA BOVO y GERARDO MANFREDA. "Growth Potential of Listeria monocytogenes in Chef-Crafted Ready-to-Eat Fresh Cheese-Filled Pasta Meal Stored in Modified Atmosphere Packaging". Journal of Food Protection 82, n.º 9 (19 de agosto de 2019): 1546–52. http://dx.doi.org/10.4315/0362-028x.jfp-18-590.
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ABSTRACT This study evaluated the growth of lactic acid bacteria (LAB) in a fresh, filled-pasta meal, stored in modified atmosphere packaging and the influence of lactic acid (LA) and pH on the growth of Listeria monocytogenes (Lm). Samples were taken from three lots manufactured by a local catering company and stored at both 6 and 14°C. LAB numbers, LA concentration, pH, and the presence of Lm were evaluated at 1, 4, 6, 8, 10, 12, and 14 days of shelf life and the undissociated LA concentration ([LA]) was calculated. The LAB maximum cell density was greater in the products stored at 14°C than those stored at 6°C (10.1 ± 1.1 versus 5.6 ± 1.5 log CFU/g) and [LA] at 14 days was 9 to 21 ppm at 6°C and 509 to 1,887 ppm at 14°C. Challenge tests were made to evaluate the interference of LAB and [LA] on Lm growth. Aliquots of the samples (25 g) were inoculated at 1 to 10 days of shelf life and incubated at 9°C for 7 days, and the difference between Lm numbers at the end and at the beginning of the test (δ) was calculated. Logistic regression was used to model the probability of growth of Lm as a function of LAB and [LA]. The products inoculated at 1 day of shelf life had δ values between 4.2 and 5.6 log CFU/g, but the growth potential was progressively reduced during the shelf life. Lm growth was never observed in the products stored at 14°C. In those stored at 6°C, it grew only in the samples with LAB <5.7 log CFU/g. LAB interaction might thus inhibit the growth of Lm in temperature-abused products and limit its growth in refrigerated products. Logistic regression estimated that the probability of Lm growth was <10% if LAB was >6.6 log CFU/g or log[LA] was >2.2 ppm. The growth or inactivation kinetic of Lm was investigated with a homogenate of three samples with LAB numbers close to the maximum population density. After an initial growth, a subsequent reduction in the number of Lm was observed. This means that the maximum numbers of Lm might not be detected at the end of the product shelf life.
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TAKATSUKA, TATSUYUKI. "EFFECTS OF HYPERON MIXING ON NEUTRON STAR PROPERTIES". International Journal of Modern Physics E 17, n.º 09 (octubre de 2008): 1739–52. http://dx.doi.org/10.1142/s021830130801074x.
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From a serious inconsistency between theory and observations for the mass of hyperon-mixed neutron stars (NSs), it is stressed that some "extra repulsion" is missing in hypernuclear systems and three-body force repulsion is tested for the cases with phenomenological Illinoi's type, 2π-exchange via Δ-excitation type(2πΔ) and string-junction quark model(SJM). It is remarked that the "extra repulsion" should have a nature to act universally, i.e., independent of baryon species. The SJM three-body repulsion can meet the condition because of flavor-independence and {2πΔ+ SJM } scheme is shown to be a promising candidate for the "extra repulsion". Occurence of Λ and Σ- superfluidities are shown also by a realistic approach, which importantly supports the idea of nonstandard fast "hyperon cooling" scenario to explain colder class NSs. However, less attractive ΛΛ interaction suggested by the "NAGARA event" [Formula: see text] leads to the disappearance of Λ superfluidity and the breaking down of the scenario. In this connection, the revival of "Λ superfluidity" due to ΛΣ- pairing instead of ΛΛ one is discussed in a new scheme of "bubble shell" hypothesis where the matching of two different Fermi surfaces is forced.
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Goharpey, F., A. A. Katbab y H. Nazockdast. "Formation of Rubber Particle Agglomerates During Morphology Development in Dynamically Crosslinked EPDM/PP Thermoplastic Elastomers. Part 1: Effects of Processing and Polymer Structural Parameters". Rubber Chemistry and Technology 76, n.º 1 (1 de marzo de 2003): 239–52. http://dx.doi.org/10.5254/1.3547737.
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Abstract Formation of agglomerate structure by the rubber particles through flocculation or networking mechanism during dynamic crosslinking of thermoplastic elastomers based on EPDM rubber and polypropylene has been evidenced. Scanning electron microscopy (SEM) examination performed on the crosslinked blend samples which had been etched by hot xylene suggested that agglomeration occurs mainly through a joint shell mechanism. Reduction of the mixing torque after passing the peak maximum at the dynamic crosslinking stage was concluded to be due to the shear induced breaking down of agglomerates leading to a more defined morphology. Samples removed after the maximum mixing torque showed higher dynamic loss tangent (tan δ) above the PP glass transition. This is attributed to the broadening of the retardation time spectra for the PP matrix in the blend system. Higher mixing torque, higher tensile strength, as well as better extensibility were found for the blend samples based on PP with low MFI value as a result of higher density of aggregates and more extent of their interfacial adhesion with the PP matrix. More defined morphology and higher rate of network breakdown was observed at high mixing shear rate. Mixing torque increased significantly with increasing the rubber content of the blend system from 40% to 60% (W : W) as a consequence of higher interaction of rubber aggregates with the PP matrix. Based on the obtained results, the structure of the rubber aggregates and associated networks as well as extent of interaction between the two phases play an important role in controlling the final morphology, processing behavior and therefore mechanical properties of the dynamically cured blend system.
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Zaprivoda, Vitaliy, Vitalii Ploskyi, Olga Krivenko y Andrey Zaprivoda. "Definition of the daily model of distribution of solar radiation on the curved surfaces of buildings". EUREKA: Physics and Engineering, n.º 6 (29 de noviembre de 2022): 24–32. http://dx.doi.org/10.21303/2461-4262.2022.002640.
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The development of the integration of renewable energy into the energy supply of buildings leads to the formulation of the problem of efficient placement of solar thermal devices on surfaces of complex shapes (shells). An urgent task is the development of tools that can justify the decision-making by designers about the advisability of placing solar thermal devices and their implementation in the energy-efficient design of buildings. The study solves the problem of finding zones on the surface of the envelope, receiving the maximum amount of solar radiation during a given period of time – an epoch. A method is applied based on discrete geometric modeling of solar radiation input to curved surfaces of buildings. In this case, the interaction of a set of design parameters is taken into account: parameters of the shape of a curved surface and parameters of variable sunlight for the characteristic dates of September 21, March 21 – the solar equinox and December 21, June 21 – the winter and summer solstices. In the course of the study, N is determined – the optimal number of fixed positions of the Sun on the solar trajectory for different angles of solar declination (for June 22 N=17, for September 21, March 21 N=11, for December 21 N=8), for a given geographical location. One of the examples of modeling the amount of solar radiation entering the surface of a hyperbolic paraboloid during the day at the geographical latitude δ=52° (Kyiv, Ukraine) is shown. The simulation results in a family of lines of the same level of solar radiation on a curved surface during the day. Using the values of the averaged daily model, it is possible to proceed to obtaining averaged daily models for the estimated time interval at the stage of pre-project proposals to predict the efficiency of using the solar system
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Hou, Qiu-Yu, Hao-Yi Guan, Yu-Lu Huang, Shi-Lin Chen, Ming Yang y Ming-Jie Wan. "Electronic structures and transition properties of AsH<sup>+</sup> cation". Acta Physica Sinica 71, n.º 21 (2022): 213101. http://dx.doi.org/10.7498/aps.71.20221104.
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<sec>Potential energy curves (PECs), dipole moments (DMs) and transition dipole moments (TDMs) of the X<sup>2</sup>Π, a<sup>4</sup>Σ<sup>–</sup>, A<sup>2</sup>Σ<sup>–</sup>, b<sup>4</sup>Π, B<sup>2</sup>Δ, C<sup>2</sup>Σ<sup>+</sup>, D<sup>2</sup>Π, 2<sup>2</sup>Σ<sup>+</sup> states correlating with the three lowest dissociation channels of AsH<sup>+</sup> cation are calculated by using the multireference configuration interaction (MRCI) method. The Davidson correction, core-valence (CV) correlation, and spin-orbit coupling (SOC) effect are all considered. The aug-cc-pV5Z all-electron basis set of H atom and the aug-cc-pwCV5Z-PP pseudopotential basis set of As atom are both selected in the calculation.</sec><sec>In the complete active space self-consistent field (CASSCF) calculation, H (1 s) and As (4s4p) shell are selected as active orbitals, As (3p3d) shells are selected as closed orbitals, which keeps doubly occupation, the remaining electrons are in the frozen orbitals. In the MRCI calculation, As (3p3d) shells are used for CV correlation, and the calculation accuracy can be improved. The SOC effects are considered with Breit-Pauli operators.</sec><sec>All calculated states are bound states. The X<sup>2</sup>Π is the ground state, which is a deep potential well, the dissociation energy is 3.100 eV. The b<sup>4</sup>Π, C<sup>2</sup>Σ<sup>+</sup> and D<sup>2</sup>Π are weakly bound states. The spectroscopic parameters are obtained by solving radial Schrodinger equation. To the best of our knowledge, there has been no study of the spectroscopy of AsH<sup>+</sup> cation so far. Comparing with Ⅴ-hydride cations <i>M</i>H<sup>+</sup> (<i>M</i> = N, P, As), the orders of the energy levels of the low-lying states for three ions are identical. The dissociation energy and harmonic frequency both decrease with the increase of the atomic weight of <i>M</i>.</sec><sec>At spin-free level, the PEC of b<sup>4</sup>Π state and the PEC of B<sup>2</sup>Δ state cross at about 1.70 Å. When SOC effects are taken into account, according to the rule of avoid-crossing, the <inline-formula><tex-math id="M5">\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M5.png"/></alternatives></inline-formula>state and <inline-formula><tex-math id="M6">\begin{document}$ {{{\rm{B}}^2}}{\Delta _{5/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M6.png"/></alternatives></inline-formula>state change to the double potential wells, and the avoided crossing between the <inline-formula><tex-math id="M7">\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M7.png"/></alternatives></inline-formula> (<inline-formula><tex-math id="M8">\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M8.png"/></alternatives></inline-formula>) state and <inline-formula><tex-math id="M9">\begin{document}$ {b^4}{\Pi _{3/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M9.png"/></alternatives></inline-formula> (<inline-formula><tex-math id="M10">\begin{document}$ {b^4}{\Pi _{5/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M10.png"/></alternatives></inline-formula>) state is observed. The transition dipole moment (TDM) of the <inline-formula><tex-math id="M11">\begin{document}$ {{{\rm{A}}^2}}{\Sigma ^ - } \to {{{\rm{X}}^2}}\Pi $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M11.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M12">\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M12.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M13">\begin{document}$ {{{\rm{A}}^2}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M13.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M13.png"/></alternatives></inline-formula> transition are also calculated. The TDM at the equilibrium distance of the <inline-formula><tex-math id="M14">\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M14.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M14.png"/></alternatives></inline-formula> spin-forbidden reaches 0.036 Debye, therefore, the SOC effect plays an important role. Based on the accurate PECs and PDMs, the Franck-Condon factors, spontaneous radiative coefficients, and spontaneous radiative lifetimes of the <inline-formula><tex-math id="M15">\begin{document}$ {{{\rm{A}}^2}}{\Sigma ^ - } \to {{{\rm{X}}^2}}\Pi $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M15.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M15.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M16">\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M16.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M16.png"/></alternatives></inline-formula>, and <inline-formula><tex-math id="M17">\begin{document}$ {{{\rm{A}}^2}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M17.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M17.png"/></alternatives></inline-formula> transition are also calculated.</sec>
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Behrndt, Jussi, Markus Holzmann y Matej Tusek. "Two-dimensional Dirac operators with general δ-shell interactions supported on a straight line". Journal of Physics A: Mathematical and Theoretical, 3 de enero de 2023. http://dx.doi.org/10.1088/1751-8121/acafaf.
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Abstract In this paper the two-dimensional Dirac operator with a general hermitian δ-shell interaction supported on a straight line is introduced as a self-adjoint operator and its spectral properties are investigated in detail. In particular, it is demonstrated that the singularly continuous spectrum is always empty and that by switching a certain δ-shell interaction on, it is possible to generate an eigenvalue in the gap of the spectrum of the free operator or to partially or even fully close the gap. This suggests that the studied operators may serve as interesting continuum toy-models for Dirac materials. Finally, approximations by Dirac operators with regular potentials are presented.
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Holzmann, Markus. "The nonrelativistic limit of Dirac operators with Lorentz scalar δ‐shell interactions". PAMM 19, n.º 1 (8 de octubre de 2019). http://dx.doi.org/10.1002/pamm.201900126.
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Hassan, Ahlam Hussein y Muhsen Abood Muhsen Al-Ibadi. "A Theoretical Investigation of Chemical Bonding of a Heterometallic Trinuclear Cluster Containing Iridium and Ruthenium: [(Cp*Ir) (CpRu)2 (μ3-H) (μ-H)3] by QTAIM Approach". Baghdad Science Journal, 20 de mayo de 2023. http://dx.doi.org/10.21123/bsj.2023.7945.
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Numerous integral and local electron density’s topological parameters of significant metal-metal and metal-ligand bonding interactions in a trinuclear tetrahydrido cluster [(Cp* Ir) (Cp Ru)2 (μ3-H) (μ-H)3]1 (Cp = η5 -C5Me5), (Cp* = η5 -C5Me4Et) were calculated and interpreted by using the quantum theory of atoms in molecules (QTAIM). The properties of bond critical points such as the delocalization indices δ (A, B), the electron density ρ(r), the local kinetic energy density G(r), the Laplacian of the electron density ∇2ρ(r), the local energy density H(r), the local potential energy density V(r) and ellipticity ε(r) are compared with data from earlier organometallic system studies. A comparison of the topological processes of different atom-atom interactions has become possible thanks to these results. In the core of the heterometallic tetrahydrido cluster, the Ru2IrH4 part, the calculations showed that there are no bond critical points (BCPs) or identical bond paths (BPs) between Ru-Ru and Ru-Ir. The distribution of electron densities is determined by the position of bridging hydride atoms coordinated to Ru-Ru and Ru-Ir, which significantly affects the bonds between these transition metal atoms. On the other hand, the results confirm that the cluster under study contains a 7c–11e bonding interaction delocalized over M3H4, as shown by the non-negligible delocalization index calculations. The small values for ρ(b) above zero, together with the small values, again above zero, for Laplacian ∇2ρ(b) and the small positive values for total energy density H(b), are shown by the Ru-H and Ir-H bonds in this cluster is typical for open-shell interactions. Also, the topological data for the bond interactions between Ir and Ru metal atoms with the C atoms of the cyclopentadienyl Cp ring ligands are similar. They show properties very identical to open-shell interactions in the QTAIM classification.
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Britzger, Daniel, Max Klein y Hubert Spiesberger. "Electroweak physics in inclusive deep inelastic scattering at the LHeC". European Physical Journal C 80, n.º 9 (septiembre de 2020). http://dx.doi.org/10.1140/epjc/s10052-020-8367-y.
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AbstractAt the proposed electron-proton collider LHeC electroweak interactions can be uniquely studied in a largely unexplored kinematic region of spacelike momentum transfer. We simulate inclusive neutral- and charged-current deep-inelastic lepton proton scattering cross section data at center-of-mass energies of 1.2 and 1.3 TeV, and estimate the uncertainties of Standard Model parameters as well as of parameters describing physics beyond the Standard Model. A precision at sub-percent level is expected for the measurement of the weak neutral-current couplings of the light-quarks to the Z boson, $$g_{A/V}^{u/d}$$ g A / V u / d , improving their present precision by more than an order of magnitude. The weak mixing angle can be determined with a precision of about $$\Delta \sin ^2\theta _\text {W}=\pm \,0.00015$$ Δ sin 2 θ W = ± 0.00015 , and its scale dependence can be studied in the range between about 25 and 700 GeV. An indirect determination of the W-boson mass in the on-shell scheme is possible with an experimental uncertainty down to $$\Delta m_{W}=\pm \,6\,\text {MeV}$$ Δ m W = ± 6 MeV . We discuss how measurements in deep-inelastic scattering compare with those in the timelike domain, and which aspects are unique, for instance electroweak parameters in charged-current interactions. We conclude that the LHeC will determine electroweak physics parameters, in the spacelike region, with unprecedented precision leading to thorough tests of the Standard Model and possibly beyond.
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Jin, Bo, Hai-Ru Li, Zhihong Wei, Miao Yan, Caixia Yuan, Yan-Bo Wu y Si-Dian Li. "Prediction of heptagonal bipyramidal nonacoordination in highly viable [OB-M©B7O7-BO]− (M = Fe, Ru, Os) complexes". Communications Chemistry 5, n.º 1 (10 de enero de 2022). http://dx.doi.org/10.1038/s42004-021-00620-0.
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AbstractNon-spherical distributions of ligand atoms in coordination complexes are generally unfavorable due to higher repulsion than for spherical distributions. To the best of our knowledge, non-spherical heptagonal bipyramidal nonacoordination is hitherto unreported, because of extremely high repulsion among seven equatorial ligand atoms. Herein, we report the computational prediction of such nonacoordination, which is constructed by the synergetic coordination of an equatorial hepta-dentate centripetal ligand (B7O7) and two axial mono-dentate ligands (-BO) in the gear-like mono-anionic complexes [OB-M©B7O7-BO]– (M = Fe, Ru, Os). The high repulsion among seven equatorial ligand B atoms has been compensated by the strong B–O bonding. These complexes are the dynamically stable (up to 1500 K) global energy minima with the HOMO-LUMO gaps of 7.15 to 7.42 eV and first vertical detachment energies of 6.14 to 6.66 eV (being very high for anions), suggesting their high probability for experimental realization in both gas-phase and condensed phases. The high stability stems geometrically from the surrounded outer-shell oxygen atoms and electronically from meeting the 18e rule as well as possessing the σ + π + δ triple aromaticity. Remarkably, the ligand-metal interactions are governed not by the familiar donation and backdonation interactions, but by the electrostatic interactions and electron-sharing bonding.
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Tumino, Aurora, Giuseppe G. Rapisarda, Marco La Cognata, Alessandro Oliva, Alejandro Kievsky, Carlos A. Bertulani, Giuseppe D’Agata et al. "Coulomb-free 1S0 p − p scattering length from the quasi-free p + d → p + p + n reaction and its relation to universality". Communications Physics 6, n.º 1 (18 de mayo de 2023). http://dx.doi.org/10.1038/s42005-023-01221-0.
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AbstractThe Coulomb-free 1S0 proton-proton (p-p) scattering length relies heavily on numerous and distinct theoretical techniques to remove the Coulomb contribution. Here, it has been determined from the half-off-the-energy-shell p-p scattering cross section measured at center-of-mass energies below 1 MeV using the quasi-free p + d → p + p + n reaction. A Bayesian data-fitting approach using the expression of the s-wave nucleon-nucleon scattering cross section returned a p-p scattering length $${a}_{pp}=-18.1{7}_{-0.58}^{+0.52}{| }_{stat}\pm 0.0{1}_{syst}$$ a p p = − 18.1 7 − 0.58 + 0.52 ∣ s t a t ± 0.0 1 s y s t fm and effective range r0 = 2.80 ± 0.05stat ± 0.001syst fm. A model based on universality concepts has been developed to interpret this result. It accounts for the short-range interaction as a whole, nuclear and residual electromagnetic, according to what the s-wave phase-shift δ does in the description of low-energy nucleon-nucleon scattering data. We conclude that our parameters are representative of the short-range physics and propose to assess the charge symmetry breaking of the short-range interaction instead of just the nuclear interaction. This is consistent with the current understanding that the charge dependence of nuclear forces is due to different masses of up-down quarks and their electromagnetic interactions. This achievement suggests that these properties have a lesser than expected impact in the context of the charge symmetry breaking.
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Szczęśniak, Małgorzata M. y Grzegorz Chałasinski. "Reassessing the Role of σ Holes in Noncovalent Interactions: It is Pauli Repulsion that Counts". Frontiers in Chemistry 10 (7 de abril de 2022). http://dx.doi.org/10.3389/fchem.2022.858946.
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A number of prototypical weak electron donor–electron acceptor complexes are investigated by the Symmetry Adapted Perturbation Theory, some of which belong to novel classes of weak bonds such as halogen and chalcogen bonds. Also included are complexes involving strong Lewis acids such as BeO and AuF. The common view in the literature is to associate these novel bonds with a variety of “holes”, σ, π, δ, or positive areas in their electrostatic potential maps. The presumption is that these positive areas of the electrostatic potential are indicative of the electrostatic nature of these noncovalent bonds. The electrostatic view extends to the explanations of the directionality of approaches between the subsystems forming these bonds. This work demonstrates that one common feature of these electrostatic potential “holes” is the local depletion of electron density of which the best detector is the first-order Pauli repulsion. The minimization of this repulsion determines the bond directionality and its relative angular rigidity. In relatively strong complexes of BeO with rare gases, where BeO shows a clear cavity in electron density—an ultimate “σ hole”—the electrostatic effect does not control the bending potential—the exchange repulsion does. In halogen bonds, the halogen atom is nonspherical, displaying an axial “σ hole” in its electrostatic potential. However, in no examined case, from rare gas acting as an electron donor to a polar donor to an anionic donor, is the electrostatic energy responsible for the directionality of the halogen bond. In fact, it is not even maximized in the direction of the σ hole in N2-ClF and NH3-ClF. Yet, in all the cases, the exchange repulsion is minimized in the direction of the σ hole. The minimized exchange repulsion associated with the subtle and less subtle depletions of the electron density occur on the nodal planes or on the intersections thereof in the highest occupied molecular orbitals of Lewis acids, provided that the systems are closed-shell. The role of nodal planes in covalent and coordinate covalent bonds is well recognized. This work points to their similarly equal importance in certain types of donor–acceptor noncovalent interactions.
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Angelopoulos, V., X. J. Zhang, A. V. Artemyev, D. Mourenas, E. Tsai, C. Wilkins, A. Runov et al. "Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective". Space Science Reviews 219, n.º 5 (11 de julio de 2023). http://dx.doi.org/10.1007/s11214-023-00984-w.
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AbstractWe review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or $\Delta L\sim 0.56$ Δ L ∼ 0.56 ) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at $L\sim 5-7$ L ∼ 5 − 7 at dusk, while a smaller subset exists at $L\sim 8-12$ L ∼ 8 − 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an $L$ L -shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of $\sim 1.45$ ∼ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.
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Behrndt, Jussi, Markus Holzmann y Matěj Tušek. "Spectral Transition for Dirac Operators with Electrostatic $$\delta $$-Shell Potentials Supported on the Straight Line". Integral Equations and Operator Theory 94, n.º 3 (30 de agosto de 2022). http://dx.doi.org/10.1007/s00020-022-02711-6.
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AbstractIn this note the two dimensional Dirac operator $$A_\eta $$ A η with an electrostatic $$\delta $$ δ -shell interaction of strength $$\eta \in {\mathbb {R}}$$ η ∈ R supported on a straight line is studied. We observe a spectral transition in the sense that for the critical interaction strengths $$\eta =\pm 2$$ η = ± 2 the continuous spectrum of $$A_\eta $$ A η inside the spectral gap of the free Dirac operator $$A_0$$ A 0 collapses abruptly to a single point.
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Adapa, Sai y Ateeque Malani. "Cation hydration by confined water and framework-atoms have crucial role on thermodynamics of clay swelling". Scientific Reports 12, n.º 1 (24 de octubre de 2022). http://dx.doi.org/10.1038/s41598-022-21349-3.
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AbstractThe swelling capacity and stability of clay play a crucial role in various areas ranging from cosmetics to oil extraction; hence change in their swelling behaviour after cation exchange with the surrounding medium is important for their efficient utilisation. Here we focus on understanding the role of different hydration properties of cation on the thermodynamics of clay swelling by water adsorption. We have used mica as the reference clay, Na$$^+$$ + , Li$$^+$$ + , and H$$^+$$ + ions as the interstitial cations, and performed grand canonical Monte Carlo simulations of water adsorption in mica pores (of widths $$d = 4-40$$ d = 4 - 40 Å). The disjoining pressure ($$\Pi$$ Π ), swelling free energy ($$\Delta \Omega ^{ex}$$ Δ Ω ex ), and several structural properties of confined water and ions were calculated to perform a thermodynamic analysis of the system. We expected higher water density in H-mica pores ($$\rho_{ \hbox{H}}$$ ρ H ) due to the smaller size of $$\hbox {H}^+$$ H + ions having higher hydration energy. However, the counter-intuitive trend of $$\rho _{\hbox{Li}}> \rho _{\hbox{Na}} > \rho_b$$ ρ Li > ρ Na > ρ b (bulk density) $$> \rho_{\hbox{H}}$$ > ρ H was observed due to adsorption energy, where the interaction of water with mica framework atoms was also found to be significant. All three mica systems exhibited oscillatory behaviour in the $$\Pi$$ Π and $$\Delta \Omega ^{ex}$$ Δ Ω ex profiles, diminishing to zero for $$d \ge 11$$ d ≥ 11 Å. The $$\Delta \Omega ^{ex}$$ Δ Ω ex for Na-mica is characterised by global minima at $$d=6 {\hbox {\AA}}$$ d = 6 Å corresponding to crystalline swelling with significant and multiple barriers for crystalline swelling to osmotic swelling ($$d > 12$$ d > 12 Å). A shift in the location of global minima of $$\Delta \Omega ^{ex}$$ Δ Ω ex towards the higher d values and $$\Delta \Omega ^{ex}$$ Δ Ω ex becoming more repulsive is observed in the increasing order of hydration energy of $$\hbox {Na}^+$$ Na + , $$\hbox {Li}^+$$ Li + , and $$\hbox {H}^+$$ H + ions. The $$\Delta \Omega ^{ex} > 0$$ Δ Ω ex > 0 for all d in the H-mica system thus favours osmotic swelling. We found that the Na$$^+$$ + ions hydrate more surface oxygens, act as anchors, and hold the mica pore together (at smaller d), by sharing hydrating water with ions of the opposite side, forming an electrostatically connected mica-Na-water-Na-mica bridge. The Li$$^+$$ + ions do hydrate surface oxygen atoms, albeit in lesser numbers, and sharing of hydration shell with nearby Li$$^+$$ + ions is also minimum. Hydration by surface atoms and water sharing, both, are minimum in the H$$^+$$ + ion case, as they are mostly present in the center of the pore as diffusive ions, thus exerting a consistent osmotic pressure on the mica frameworks, favouring swelling.
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Trivedi, Ravi Kumar y Pritam Bhattacharyya. "A theoretical study of Ferrocene using combined configuration interaction single (CIS) and time-dependent density functional theory (TDDFT) approach". Physica Scripta, 12 de diciembre de 2023. http://dx.doi.org/10.1088/1402-4896/ad14da.
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Abstract The state-of-the art density functional theory (DFT) is used to clearly resolve the two parallel cyclopentadienyl rings of ferrocene, which are either staggered (D5d symmetry) or eclipsed (D5h symmetry), in their ground-state conformation. Present result revealed that the eclipsed conformer with D5h point group represents the true minimum ground state structure of ferrocene. Natural population analysis is used to determine how atomic charge is distributed across different atoms of ferrocene D5h conformer and also the distribution of electrons in the core, valence, and Rydberg sub-shells. It is further investigated in potential energy scan that the rotation of the dihedral angle δ from 0◦ to 3π/5 will reproduce three times D5h or D5d conformers periodically as the period of 2π/5 due to the pentagonal structure of the CP ring. Further to examine optical spectra in the ultraviolet-visible (UV-vis) range, configuration interaction single (CIS) and time-dependent density functional theory (TDDFT) have conducted which help in locating the significant electronic shifts between different energy levels. Absorption spectra for high spin states were also generated in order to comprehend the characteristics of low-lying spin excitation. According to our estimates, the greatest absorption intensity is restricted to an energy range of 4-6 eV. Knowledge of ferrocene conformers will improve the research on other metallocenes and their derivatives, which have applications in biotechnology, nanotechnology, and solar technology.
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Hou Qiu-Yu, Guan Hao-Yi, Huang Yu-Lu, Chen Shi-Lin, Yang Ming y Wan Ming-Jie. "The electronic structures and transition properties of AsH<sup>+</sup> cation". Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.7120221104.
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Potential energy curves (PECs), dipole moments (DMs) and transition dipole moments (TDMs) of the X<sup>2</sup>Π, a<sup>4</sup>Σ<sup>-</sup>, A<sup>2</sup>Σ<sup>-</sup>, b<sup>4</sup>Π, B<sup>2</sup>ΣΔ, C<sup>2</sup>Σ<sup>+</sup>, D<sup>2</sup>Π, 2<sup>2</sup>Σ<sup>+</sup> states correlating with the three lowest dissociation channels of AsH<sup>+</sup>cation are calculated by using the multireference configuration interaction (MRCI) method. The Davidson corrections, core-valence (CV) correlation and spin-orbit coupling (SOC) effects are considered. The aug-cc-pV5Z all-electron basis set of H atom and the aug-cc-pwCV5Z-PP pseudopotential basis set of As atom is selected in the calculation.<br>In the complete active space self-consistent field (CASSCF) calculation, H (1s) and As (4s4p) shell are selected as active orbital, As (3p3d) shells are selected as closed orbital, which keeps doubly occupation, the rest electrons are in the frozen orbital. In the MRCI calculation, As (3p3d) shells are used for CV correlation, the calculation accuracy can be improved. SOC effects are considered with Breit-Pauli operators.<br>All calculated states are bound states. The X<sup>2</sup>Π is the ground state, which is a depth potential well, the dissociation energy is 3.100 eV. The b<sup>4</sup>Π, C<sup>2</sup>Σ<sup>+</sup> and D<sup>2</sup>Π are weakly bound states. The spectroscopic parameters are obtained by solving radial Schrodinger equation. To the best of our knowledge, there have not any study on the spectroscopy of AsH<sup>+</sup> cation. Compared with Ⅴ-hydride cations MH<sup>+</sup> (M = N, P, As), the order of the energy levels of the low-lying states for three ions are same. The dissociation energy and harmonic frequency both decreases with increase the atomic weight of M.<br>At spin-free level, the PECs of b<sup>4</sup>Π and B<sup>2</sup>Δ states cross at about 1.70 Å. When SOC effects are taken into account, according to the rule of avoid-crossing, the <i>B</i><sup>2</sup>Δ<sub>3/2</sub> and <i>B</i><sup>2</sup>Δ<sub>5/2</sub> states change to the double potential wells, and the avoided crossing between the <i>B</i><sup>2</sup>Δ<sub>3/2</sub> (<i>B</i><sup>2</sup>Δ<sub>3/2</sub>) and <i>b</i><sup>4</sup>Π<sub>3/2</sub> (<i>b</i><sup>4</sup>Π<sub>5/2</sub>) states is observed, respectively. The transition dipole moments (TDMs) of the <i>A</i><sup>2</sup>Σ<sup>-</sup>→<i>X</i><sup>2</sup>Π,<i>a</i><sup>4</sup>Σ<sub>1/2</sub><sup>-</sup>,<i>X</i><sup>2</sup>Π<sub>1/2</sub> and <i>A</i><sup>2</sup>Σ<sub>1/2</sub><sup>-</sup>→<i>X</i><sup>2</sup>Π<sub>1/2</sub> transitions are also calculated. The TDM at equilibrium distance of the <i>a</i><sup>4</sup>Σ<sub>1/2</sub><sup>-</sup>→<i>X</i><sup>2</sup>Π<sub>1/2</sub> spin-forbidden reaches 0.036 Debye, therefore, the SOC effect plays an important role. Based on the accurately PECs and PDMs, the Franck-Condon factors, spontaneous radiative coefficients and spontaneous radiative lifetimes of the <i>A</i><sup>2</sup>Σ<sup>-</sup>→<i>X</i><sup>2</sup>Π,<i>a</i><sup>4</sup>Σ<sub>1/2</sub><sup>-</sup>→和<i>X</i><sup>2</sup>Π<sub>1/2</sub> and <i>A</i><sup>2</sup>Σ<sub>1/2</sub><sup>-</sup>→<i>X</i><sup>2</sup>Π<sub>1/2</sub> transitions are also calculated.
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Dumoulin, J.-P., C. Rabouille, S. Pourtout, B. Bombled, B. Lansard, I. Caffy, S. Hain et al. "IDENTIFICATION IN PORE WATERS OF RECYCLED SEDIMENT ORGANIC MATTER USING THE DUAL ISOTOPIC COMPOSITION OF CARBON (δ13C AND Δ14C): NEW DATA FROM THE CONTINENTAL SHELF INFLUENCED BY THE RHÔNE RIVER". Radiocarbon, 2 de diciembre de 2022, 1–11. http://dx.doi.org/10.1017/rdc.2022.71.
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ABSTRACT Estuaries and deltas are crucial zones to better understand the interactions between continents and oceans, and to characterize the mineralization and burial of different sources of organic matter (OM) and their effect on the carbon cycle. In the present study, we focus on the continental shelf of the northwest Mediterranean Sea near the Rhône river delta. Sediment cores were collected and pore waters were sampled at different depths at one station (Station E) located on this shelf. For each layer, measurements of dissolved inorganic carbon concentration (DIC) and its isotopic composition (δ13C and Δ14C) were conducted and a mixing model was applied to target the original signature of the mineralized OM. The calculated δ13C signature of the mineralized organic matter is in accordance with previous results with a δ13COM of marine origin that is not significantly impacted by the terrestrial particulate inputs from the river. The evolution with depth of Δ14C shows two different trends indicating two different Δ14C signatures for the mineralised OM. In the first 15 cm, the mineralized OM is modern with a Δ14COM = 100 ± 17‰ and corresponds to the OM produced during the nuclear period of the last 50 years. Deeper in the sediment, the result is very different with a depleted value Δ14COM = –172 ± 60‰ which corresponds to the pre-nuclear period. In these two cases, the marine substrate was under the influence of the local marine reservoir effect with more extreme Δ14C results. These differences can be largely explained by the influence of the river plume on the local marine DIC during these two periods.