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We study the field dependence of the antiferromagnetic spin-1/2 Heisenberg model on the square lattice by means of exact diagonalizations. In the first part, we calculate the spin-wave velocity c, the spin stiffness rho(s), and the magnetic susceptibility ...
We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)(2)CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in t ...
To investigate synaptic events underlying sensory perception, we made whole-cell membrane potential recordings of barrel cortex neurons in awake mice while recording whisker-related behavior. During quiet periods, we recorded slow, large-amplitude membrane ...
Internal brain states form key determinants for sensory perception, sensorimotor coordination and learning. A prominent reflection of different brain states in the mammalian central nervous system is the presence of distinct patterns of cortical synchrony, ...
Synchrotron light is usually treated with a rather complicated electrodynamics formalism. However. its basic properties can be easily understood with a simple approach based on the classical emission of electromagnetic radiation by an accelerated charge in ...
We present an inelastic neutron scattering study of the spin dynamics in the mixed phase of the high-T-c superconductor La2-xSrxCuO4, In the overdoped regime (x = 0. 17, T-c = 37 K) the application of a magnetic field induces a spectral weight redistributi ...
We present a study of the kinetics of electron injection in ruthenium(II) cis-(2,2‘-bipyridyl-4,4‘-dicarboxylate)2(NCS)2-sensitized nanocrystalline TiO2 films as a function of electrical potential applied to the TiO2 film and as a function of the compositi ...
In this PhD thesis we deal with two mathematical problems arising from quantum mechanics. We consider a spinless non relativistic quantum particle whose configuration space is a two dimensional surface S. We also suppose that the particle feels the effect ...
The water-soluble endohedral gadofullerene derivatives, Gd@C60(OH)x and Gd@C60[C(COOH)2]10, have been characterized with regard to their MRI contrast agent properties. Water-proton relaxivities have been measured in aqueous solution at variable temperature ...
Several formulations of correlation-based Hebbian learning are reviewed. On the presynaptic side, activity is described either by a firing rate or by presynaptic spike arrival. The state of the postsynaptic neuron can be described by its membrane potential ...
