Probabilistic Motion Estimation Based on Temporal Coherence

We develop a theory for the temporal integration of visual motion motivated by psychophysical experiments. The theory proposes that input data are temporally grouped and used to predict and estimate the motion flows in the image sequence. This temporal grouping can be considered a generalization of the data association techniques used by engineers to study motion sequences. Our temporal-grouping theory is expressed in terms of the Bayesian generalization of standard Kalman filtering. To implement the theory we derive a parallel network which shares some properties of cortical networks. Computer simulations of this network demonstrate that our theory qualitatively accounts for psychophysical experiments on motion occlusion and motion outliers.Comment: 40 pages, 7 figure

Alien Registration- Macelveny, Marie L. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/24099/thumbnail.jp

Autoimmunity Overlaps Primary Biliary Cirrhosis: a Not Straightforward Diagnosis

info:eu-repo/semantics/publishedVersio

Imaging of electron potential landscapes on Au(111)

The Hohenberg-Kohn theorem states that the ground state electron density completely determines the external potential acting on an electron system. Inspired by this fundamental theorem, we developed a novel approach to map directly the electron potential in surface systems: linear response theory applied to the total electron density as measured with scanning tunneling microscopy determines the external potential. Potential imaging is demonstrated for the s-p derived surface state on Au(111), where the "herringbone" reconstruction induces a periodic potential modulation, the details of which are revealed by our technique

Noble metal surface states: deviations from parabolic dispersion

Dispersion relations of the s-p derived surface state on (111) surfaces of silver and copper have been measured using low-temperature scanning tunneling microscopy and spectroscopy. For silver as well as for copper we find a significant deviation from a parabolic dispersion characteristic of free-electron-like systems. A simple tight-binding model accounts for the trends in the measured dispersions. (C) 2000 Elsevier Science B.V. All rights reserved

Dynamic origin of chirality transfer between chiral surface and achiral ligand in Au38 clusters

The transfer of chirality between nanomolecules is at the core of several applications in chiral technology such as sensing and catalysis. However, the origin of this phenomenon and how exactly nanoscale objects transfer chirality to molecules in their vicinity remain largely obscure. Here, we show that the transfer of chirality for the intrinsically chiral gold cluster Au38(SR)24 is site dependent; that is, it differs depending on the ligand-binding sites. This is closely related to the dynamic nature of the ligands on the cluster surface. Using a combination of NMR techniques and molecular dynamics simulations, we could assign the four symmetry- unique ligands on the cluster. The study reveals largely different conformational dynamics of the bound ligands, explaining the diverse diastereotopicities observed for the CH2 protons of the ligands. Although chirality is a structural property, our study reveals the importance of dynamics for the transfer of chirality

Probing hot-electron dynamics at surfaces with a cold scanning tunneling microscope

We report on a novel approach to measure the phase relaxation length and femtosecond lifetime of hot quasiparticles on metal surfaces. A 4 K scanning tunneling microscope has been used to study the spatial decay of interference patterns in the local density of states for surface state electrons on Ag(111) and Cu(111). This decay is governed by inelastic; electron-electron scattering. We find a (E - E-F)(-2) energy dependence of the lifetimes for both Ag and Cu, and our values are comparable to the corresponding bulk electron lifetimes. This indicates that electron-electron interaction of hot surface state electrons with the Fermi sea is dominated by the underlying bulk electrons. [S0031-9007(99)09260-1]

Quantum coherence and lifetimes of surface-state electrons

We discuss a novel approach to measure the electron phase-relaxation length and femtosecond lifetimes at surfaces. It relies on the study of the spatial decay of quantum interference patterns in the local density of states (LDOS) with the STM. The method has been applied to s-p derived surface-state electrons on Cu(111) and Ag(111). The characteristic decay length of the LDOS oscillations is influenced by the finite lifetime, and thus reveals information about inelastic scattering in the two-dimensional (2D) electron gas. After an introduction in Section 1, we present a model describing the decay of Friedel oscillations off from straight steps in Section 2. Energy dependent lifetime measurements of hot electrons are presented in Section 3 and interpreted in terms of electron-electron scattering. The temperature dependent lifetime measurements of low-energy quasiparticles discussed in Section 4 give insight into the interaction of these 2D electrons with phonons. Our results on inelastic lifetimes are discussed in comparison with high-resolution angle-resolved photoemission and femtosecond two-photon photoemission measurements. (C) 2000 Elsevier Science B.V. All rights reserved