Visual Stability and the Motion Aftereffect: A Psychophysical Study Revealing Spatial Updating

Eye movements create an ever-changing image of the world on the retina. In particular, frequent saccades call for a compensatory mechanism to transform the changing visual information into a stable percept. To this end, the brain presumably uses internal copies of motor commands. Electrophysiological recordings of visual neurons in the primate lateral intraparietal cortex, the frontal eye fields, and the superior colliculus suggest that the receptive fields (RFs) of special neurons shift towards their post-saccadic positions before the onset of a saccade. However, the perceptual consequences of these shifts remain controversial. We wanted to test in humans whether a remapping of motion adaptation occurs in visual perception

Angle-resolved resonant Auger electron spectroscopy of CO after vibrationally resolved C 1s→nlλ1s \to nl\lambda excitations

Angle-resolved resonant electron spectra following vibrationally resolved C 1srightarrow nllambda (nu = 0,1) excitations in CO have been measured. The observed groups of resonant Auger lines exhibit great similarity in shape to the C-KVV group of non-resonant Auger lines and the observed angular distribution behaviour reflects the symmetry-dependent anisotropies of the excitation process. The molecular progressions in the C 1srightarrowpi* resonant Auger spectrum could be clearly identified due to their different angular distribution behaviour. Furthermore, it could be shown that the screening energies for spectator electrons over binding energy have a linear dependence between 3ppi, 4ppi and threshold as was expected for the higher p-symmetry Rydberg orbitals

Universit"at Karlsruhe

Abstract This paper presents an analysis of the performance potential and limitation of the so-called small-space scheme, where several logical address spaces are securely multiplexed onto a single hardware address space. This can be achieved on the IA-32 architecture by using the segment registers to relocate address spaces transparently to the applications. Our results show that the scheme can provide significant performance improvements in cases where processes with small working sets interact frequently, as is often the case in client-server applications, and particularly in microkernel-based systems. We also investigate how potentially costly revocation of mappings can be prevented by clustering communicating processes. 1 Introduction The gap between processor and memory speed continues to widen in modern architectures. As a result, the dependence of system performance on high hit rates in the CPU caches is increasing. Computer architects achieve these high hit rates by increasing cache capacity, and increasing the depth of the cache hierarchy. A large cache implies that there is a significant probability of finding part of the cache still hot after a context switch, and thus a possibility of reducing the indirect context switch costs resulting from a cold cache. This potential always exists when switchin

Probing the transition from non-localization to localization by K-shell photoemission from isotope-substituted N2N_{2}

In homonuclear diatomic molecules such as N_2, the inversion symmetry of the system causes non-local, coherent behavior of the otherwise localized core holes. The non-locality of the electron emission and the remaining core hole changes in a continuous way into partially localized behaviour if a gradual breakdown of the inversion symmetry is induced by isotope substitution. This is reflected by a loss of interference and a parity mixing of the outgoing photoelectron waves. Our results represent the first experimentally observed isotope effect on the electronic structure of a diatomic molecule

Localization and loss of coherence in molecular double-slit experiments

In molecular double-slit experiments, the interference between emitted core electrons of diatomic molecules gives rise to oscillations in the observed electron intensity. Here, we explore this behaviour for photoelectrons emitted from CO and N_2 by soft X-ray ionization in the molecular frame, and we argue that in addition to the undisturbed emission process, intramolecular scattering can lead to electron interference between the scattered and unscattered wave in two ways: two-centre interference between two spatially coherent emitters and one-centre self-interference. The latter is the signature of a loss of spatial coherence. The spatial scale over which the transition from two-centre to one-centre coherence occurs is the de Broglie wavelength of the scattered photoelectron in units of the bond length. These results highlight the fact that the molecular double slit is based on two independent uncertainty principles, Δp_xΔx and ΔEΔt, the second of which causes ongoing tunnelling between the two centres, even after the collapse of the electron wavefunction in real space

Isotope-induced partial localization of core electrons in the homonuclear molecule N2

Because of inversion symmetry and particle exchange, all constituents of homonuclear diatomic molecules are in a quantum mechanically non-local coherent state; this includes the nuclei and deep-lying core electrons. Hence, the molecular photoemission can be regarded as a natural double-slit experiment: coherent electron emission originates from two identical sites, and should give rise to characteristic interference patterns. However, the quantum coherence is obscured if the two possible symmetry states of the electronic wavefunction ('gerade' and 'ungerade') are degenerate; the sum of the two exactly resembles the distinguishable, incoherent emission from two localized core sites. Here we observe the coherence of core electrons in N(2) through a direct measurement of the interference exhibited in their emission. We also explore the gradual transition to a symmetry-broken system of localized electrons by comparing different isotope-substituted species--a phenomenon analogous to the acquisition of partial 'which-way' information in macroscopic double-slit experiments