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Search Results: 1 - 10 of 208440 matches for " L. Korecz "
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Highly 13C isotope enriched azafullerene, C59N, for nuclear spin labelling
F. Simon,F. Fulop,A. Rockenbauer,L. Korecz,H. Kuzmany
Physics , 2004, DOI: 10.1016/j.cplett.2005.01.056
Abstract: Synthesis of highly $^{13}$C isotope enriched azafullerene, C$_{59}$N embedded in C$_{60}$ is reported. $^{13}$C enriched fullerenes, produced with the Kr\"{a}tschmer-Huffmann process, were subject to a N$_{2}$ discharge that produces C$_{59}$N with a low probability. Raman spectroscopy indicates a homogeneous $^{13}$C distribution. Electron spin resonance measurement (ESR) proves that the C$_{59}$N concentration, 0.2 %, is similar as in non-enriched fullerenes. The ESR spectrum is simulated accurately with the known $^{14}$N and $^{13}$C hyperfine coupling constants. The material enables the nuclear spin-labelling of heterofullerene complexes with a potential for biological applications. It might also find applications as a building element for quantum computation.
Enhanced thermal stability and spin-lattice relaxation rate of N@C60 inside carbon nanotubes
S. Toth,D. Quintavalle,B. Nafradi,L. Korecz,L. Forro,F. Simon
Physics , 2008, DOI: 10.1103/PhysRevB.77.214409
Abstract: We studied the temperature stability of the endohedral fullerene molecule, N@C60, inside single-wall carbon nanotubes using electron spin resonance spectroscopy. We found that the nitrogen escapes at higher temperatures in the encapsulated material as compared to its pristine, crystalline form. The temperature dependent spin-lattice relaxation time, T_1, of the encapsulated molecule is significantly shorter than that of the crystalline material, which is explained by the interaction of the nitrogen spin with the conduction electrons of the nanotubes.
Testing the Elliott-Yafet spin-relaxation mechanism in KC8; a model system of biased graphene
Gábor Fábián,Balázs Dóra,ágnes Antal,Lénárd Szolnoki,László Korecz,Antal Rockenbauer,Norbert M. Nemes,László Forró,Ferenc Simon
Physics , 2012, DOI: 10.1103/PhysRevB.85.235405
Abstract: Temperature dependent electron spin resonance (ESR) measurements are reported on stage 1 potassium doped graphite, a model system of biased graphene. The ESR linewidth is nearly isotropic and although the g-factor has a sizeable anisotropy, its majority is shown to arise due to macroscopic magnetization. Albeit the homogeneous ESR linewidth shows an unusual, non-linear temperature dependence, it appears to be proportional to the resistivity which is a quadratic function of the temperature. These observations suggests the validity of the Elliott-Yafet relaxation mechanism in KC8 and allows to place KC8 on the empirical Beuneu-Monod plot among ordinary elemental metals.
Magnetic fullerenes inside single-wall carbon nanotubes
F. Simon,H. Kuzmany,B. Nafradi,T. Feher,L. Forro,F. Fulop,A. Janossy,L. Korecz,A. Rockenbauer,F. Hauke,A. Hirsch
Physics , 2006, DOI: 10.1103/PhysRevLett.97.136801
Abstract: C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A hindered, anisotropic rotation of C59N was deduced from the temperature dependence of the electron spin resonance spectra near room temperature. Shortening of spin-lattice relaxation time, T_1, of C59N indicates a reversible charge transfer toward the host nanotubes above $\sim 350$ K. Bound C59N-C60 heterodimers are formed at lower temperatures when C60 is co-encapsulated with the functionalized C59N. In the 10-300 K range, T_1 of the heterodimer shows a relaxation dominated by the conduction electrons on the nanotubes.
Low temperature fullerene encapsulation in single wall carbon nanotubes: synthesis of N@C$_{60}$@SWCNT
F. Simon,H. Kuzmany,H. Rauf,T. Pichler,J. Bernardi,H. Peterlik,L. Korecz,F. Fül?p,A. Jánossy
Physics , 2003, DOI: 10.1016/j.cplett.2003.11.039
Abstract: High filling of single wall carbon nanotubes (SWCNT) with C$_{60}$ and C$_{70}$ fullerenes in solvent is reported at temperatures as low as 69 $^{o}$C. A 2 hour long refluxing in n-hexane of the mixture of the fullerene and SWCNT results in a high yield of C$_{60}$,C$_{70}$@SWCNT, fullerene peapod, material. The peapod filling is characterized by TEM, Raman and electron energy loss spectroscopy and X-ray scattering. We applied the method to synthesize the temperature sensitive (N@C$_{60}$:C$_{60}$)@SWCNT as proved by electron spin resonance spectroscopy. The solvent prepared peapod samples can be transformed to double walled nanotubes enabling a high yield and industrially scalable production of DWCNT.
Computing Reachable Sets as Capture-Viability Kernels in Reverse Time  [PDF]
No?l Bonneuil
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.311219
Abstract: The set SF(x0;T) of states y reachable from a given state x0 at time T under a set-valued dynamic x’(t)∈F(x (t)) and under constraints x(t)∈K where K is a closed set, is also the capture-viability kernel of x0 at T in reverse time of the target {x0} while remaining in K. In dimension up to three, Saint-Pierre’s viability algorithm is well-adapted; for higher dimensions, Bonneuil’s viability algorithm is better suited. It is used on a large-dimensional example.
Three Dimensional Evolution of SN 1987A in a Self-Gravitating Disk  [PDF]
L. Zaninetti
International Journal of Astronomy and Astrophysics (IJAA) , 2013, DOI: 10.4236/ijaa.2013.32010
Abstract:

The introduction of an exponential or power law gradient in the interstellar medium (ISM) allows to produce an asymmetric evolution of the supernova remnant (SNR) when the framework of the thin layer approximation is adopted. Unfortunately both the exponential and power law gradients for the ISM do not have a well defined physical meaning. The physics conversely is well represented by an isothermal self-gravitating disk of particles whose velocity is everywhere Maxwellian. We derived a law of motion in the framework of the thin layer approximation with a control parameter of the swept mass. The photon’s losses, which are often neglected in the thin layer approximation, are modeled trough velocity dependence. The developed framework is applied to SNR 1987A and the three observed rings are simulated.

The Luminosity Function of Galaxies as Modeled by a Left Truncated Beta Distribution  [PDF]
L. Zaninetti
International Journal of Astronomy and Astrophysics (IJAA) , 2014, DOI: 10.4236/ijaa.2014.41013
Abstract: A first new luminosity function of galaxies can be built starting from a left truncated beta probability density function, which is characterized by four parameters. In the astrophysical conversion, the number of parameters increases by one, due to the addition of the overall density of galaxies. A second new galaxy luminosity function is built starting from a left truncated beta probability for the mass of galaxies once a simple nonlinear relationship between mass and luminosity is assumed; in this case the number of parameters is six because the overall density of galaxies and a parameter that regulates mass and luminosity are added. The two new galaxy luminosity functions with finite boundaries were tested on the Sloan Digital Sky Survey (SDSS) in five different bands; the results produce a better fit than the Schechter luminosity function in two of the five bands considered. A modified Schechter luminosity function with four parameters has been also analyzed.
On the Dark Matter’s Halo Theoretical Description  [PDF]
L. M. L. M. Chechin
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.35052
Abstract: We argued that the standard field scalar potential couldn’t be widely used for getting the adequate galaxies’ curve lines and determining the profiles of dark matter their halo. For discovering the global properties of scalar fields that can describe the observable characteristics of dark matter on the cosmological space and time scales, we propose the simplest form of central symmetric potential celestial-mechanical type, i.e. U(φ) = –μ/φ. It was shown that this potential allows get rather satisfactorily dark matter profiles and rotational curves lines for dwarf galaxies. The good agreement with some previous results, based on the N-body simulation method, was pointed out. A new possibility of dwarf galaxies’ masses estimation was given, also.
Analytical Approximation to the Dynamics of a Binary Stars System with Time Depending Mass Variation  [PDF]
Gustavo V. López, Elkin L. López
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.63053
Abstract: We study the classical dynamics of binary stars when there is an interchange of mass between them. Assuming that one of the stars is more massive than others, the dynamics of the lighter one is analyzed as a function of its time depending mass variation. Within our approximations and models for mass transference, we obtain a general result which establishes that if the lightest star looses mass, its period increases. If the lightest star wins mass, its period decreases.
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