9,810 research outputs found
Diffusion of muonium and hydrogen in diamond
Jump rates of muonium and hydrogen in diamond are calculated by quantum
transition-state theory, based on the path-integral centroid formalism. This
technique allows us to study the influence of vibrational mode quantization on
the effective free-energy barriers Delta F for impurity diffusion, which are
renormalized respect to the zero-temperature classical calculation. For the
transition from a tetrahedral (T) site to a bond-center (BC) position, Delta F
is larger for hydrogen than for muonium, and the opposite happens for the
transition from BC to T. The calculated effective barriers decrease for rising
temperature, except for the muonium transition from T to BC sites. Calculated
jump rates are in good agreement to available muon spin rotation data.Comment: 4 pages, 3 figure
Non-integrability of the Armbruster-Guckenheimer-Kim quartic Hamiltonian through Morales-Ramis theory
We show the non-integrability of the three-parameter
Armburster-Guckenheimer-Kim quartic Hamiltonian using Morales-Ramis theory,
with the exception of the three already known integrable cases. We use
Poincar\'e sections to illustrate the breakdown of regular motion for some
parameter values.Comment: Accepted for publication in SIAM Journal on Applied Dynamical
Systems. Adapted version for arxiv with 19 pages and 11 figure
Comment on "Two Phase Transitions in the Fully frustrated XY Model"
The conclusions of a recent paper by Olsson (Phys. Rev. Lett. 75, 2758
(1995), cond-mat/9506082) about the fully frustrated XY model in two dimensions
are questioned. In particular, the evidence presented for having two separate
chiral and U(1) phase transitions are critically considered.Comment: One page one table, to Appear in Physical Review Letter
Unveiling interactions between DNA and cytotoxic 2-arylpiperidinyl-1,4-naphthoquinone derivatives: A combined electrochemical and computational study
Indexación: Scopus.Three 2-arylpiperidinyl-1,4-naphthoquinone derivatives were synthesized and evaluated in vitro to determine their cytotoxicity on cancer and normal cell lines. In order to establish their possible action mechanism, the electrochemical behaviour of these quinones was examined using cyclic voltammetry (CV) as technique by using a three-electrode setup: a glassy carbon, Ag/AgCl (in 3 M KCl), and platinum wire as working, reference, and counter electrodes, respectively. Kinetic studies were done to determine the control of the reduction reaction and the number of transferred electrons in the process. Furthermore, the addition of dsDNA to the quinone solutions allowed for the observation of an interaction between each quinone and dsDNA as the current-peaks became lower in presence of dsDNA. Otherwise, motivated to support the aforementioned results, electronic structure calculations at the TPSS-D3/6-31+G(d,p) level of theory were carried out in order to find the most favourable noncovalently bonded complexes between quinones and DNA. Noncovalent complexes formed between DNA and 2-arylpiperidinyl-1,4-naphthoquinones and stabilized by π-stacking interactions along with the well-known hydrogen-bonded complexes were found, with the former being more stable than the latter. These results suggest that the intercalation of these quinone derivatives in DNA is the most likely action mechanism. © 2018 King Saud Universityhttps://www.sciencedirect.com/science/article/pii/S1878535218300893?via%3Dihu
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