4,035 research outputs found
Entanglement sharing in Jahn-Teller model in the presence of a magnetic field
We discuss the ground state entanglement of the
Jahn-Teller model in the presence of a strong transverse magnetic field as a
function of the vibronic coupling strength. A complete characterization is
given of the phenomenon of entanglement sharing in a system composed by a qubit
coupled to two bosonic modes. Using the residual -tangle, we find that
three-partite entanglement is significantly present in the system in the
parameter region near the bifurcation point of the corresponding classical
model
Compact relaxations for polynomial programming problems
Reduced RLT constraints are a special class of Reformulation- Linearization Technique (RLT) constraints. They apply to nonconvex (both continuous and mixed-integer) quadratic programming problems subject to systems of linear equality constraints. We present an extension to the general case of polynomial programming problems and discuss the derived convex relaxation. We then show how to perform rRLT constraint generation so as to reduce the number of inequality constraints in the relaxation, thereby making it more compact and faster to solve. We present some computational results validating our approach
Nuclear halo and the coherent nuclear interaction
The unusual structure of Li11, the first halo nucleus found, is analyzed by
the Preparata model of nuclear structure. By applying Coherent Nucleus Theory,
we obtain an interaction potential for the halo-neutrons that rightly
reproduces the fundamental state of the system.Comment: 9 pages Submitted to International Journal of Modern Physics E
(IJMPE
Square-planar vs. Trigonal bipyramidal geometry in Pt(II) complexes containing triazole-based glucose ligands as potential anticancer agents
This article describes the synthesis, characterization, and biological activity of novel square-planar cationic platinum(II) complexes containing glucoconjugated triazole ligands and a comparison with the results obtained from the corresponding five-coordinate complexes bearing the same triazole ligands. Stability in solution, reactivity with DNA and small molecules of the new compounds were evaluated by NMR, fluorescence, and UV–vis absorption spectroscopy, together with their cytotoxic action against pairs of immortalized and tumorigenic cell lines. The results show that the square-planar species exhibit greater stability than the corresponding five-coordinate ones. Furthermore, although the square-planar complexes are less cytotoxic than the latter ones, they exhibit a certain selectivity. These results simultaneously demonstrate that overall stability is a fundamental prerequisite for preserving the performance of the agents and that coordinative saturation constitutes a point in favor of their biological action
Coherent QED, Giant Resonances and Pairs in High Energy Nucleus-Nucleus Collisions
We show that the coherent oscillations of the e.m. field induced by the
collective quantum fluctuations of the nuclear matter field associated with the
giant resonances, with frequencies MeV, give
rise to a significant pair production in high energy Heavy Ion
collisions. The approximate parameterless calculation of such yield is in good
agreement with recent experimental observations.Comment: 27 pages, 13 figure
Mesoscopic patterns of neural activity support songbird cortical sequences
Time-locked sequences of neural activity can be found throughout the vertebrate forebrain in various species and behavioral contexts. From time cells in the hippocampus of rodents to cortical activity controlling movement, temporal sequence generation is integral to many forms of learned behavior. However, the mechanisms underlying sequence generation are not well known. Here, we describe a spatial and temporal organization of the songbird premotor cortical microcircuit that supports sparse sequences of neural activity. Multi-channel electrophysiology and calcium imaging reveal that neural activity in premotor cortex is correlated with a length scale of 100 microm. Within this length scale, basal-ganglia-projecting excitatory neurons, on average, fire at a specific phase of a local 30 Hz network rhythm. These results show that premotor cortical activity is inhomogeneous in time and space, and that a mesoscopic dynamical pattern underlies the generation of the neural sequences controlling song
An algorithm to enumerate all possible protein conformations verifying a set of distance constraints
International audienceBackground: The determination of protein structures satisfying distance constraints is an important problem in structural biology. Whereas the most common method currently employed is simulated annealing, there have been other methods previously proposed in the literature. Most of them, however, are designed to find one solution only. Results: In order to explore exhaustively the feasible conformational space, we propose here an interval Branch-and-Prune algorithm (iBP) to solve the Distance Geometry Problem (DGP) associated to protein structure determination. This algorithm is based on a discretization of the problem obtained by recursively constructing a search space having the structure of a tree, and by verifying whether the generated atomic positions are feasible or not by making use of pruning devices. The pruning devices used here are directly related to features of protein conformations. Conclusions: We described the new algorithm iBP to generate protein conformations satisfying distance constraints, that would potentially allows a systematic exploration of the conformational space. The algorithm iBP has been applied on three α-helical peptides
Optimization of RPCs read-out panel with electromagnetic simulation
With the upgrade of the RPCs [1]-[2] and the increase of its performances,
the study and the optimization of the read-out panel is necessary in order to
maintain the signal integrity and to reduce the intrinsic crosstalk. Through
Electromagnetic Simulation, performed with CST Studio Suite, new panels design
are tested and their crosstalk property are studied. The behavior of different
type of panel is shown, in particular a panel with the decoupling strip
connected through their characteristic impedance to the ground plane is
simulated
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