A Birkhoff connection between quantum circuits and linear classical reversible circuits

Birkhoff's theorem tells how any doubly stochastic matrix can be decomposed as a weighted sum of permutation matrices. Similar theorems on unitary matrices reveal a connection between quantum circuits and linear classical reversible circuits. It triggers the question whether a quantum computer can be regarded as a superposition of classical reversible computers

Age-related microvascular degeneration in the human cerebral periventricular white matter

Clinical studies have identified white matter (WM) lesions as hyperintensive regions in the MRI images of elderly patients. Since a cerebrovascular origin was attributed to such lesions, the present analysis set out to define the microvascular histopathologic changes in the periventricular WM in the aged. Post-mortem samples of the frontal, parietal, and occipital periventricular WM of 40-90-year-old subjects were prepared for quantitative light and electron microscopy. Light microscopic examination revealed microvascular fibrohyalinosis as the most common type of microvascular damage in the elderly. Ultrastructural analysis identified the microvascular thickening as collagen deposits affecting the basement membrane. The vascular density did not correlate with the age. The basement membrane pathology significantly increased, while the number of intact microvessels gradually decreased, with advancing age in the frontal and occipital WM. Finally, peripheral atherosclerosis coincided with massive microvascular fibrosis, particularly in the frontal WM. Our results demonstrate an age-related microvascular degeneration in the periventricular WM, which may contribute to the development of WM lesions by hindering a sufficient supply of nutrients to the affected WM sites. Furthermore, the data accord with previous observations identifying the frontal lobe as the site at which WM vulnerability is most pronounced. Finally, atherosclerosis in large, peripheral vessels is considered to be a predictive marker of microvascular pathology in the WM.</p

Cosmic rays studied with a hybrid high school detector array

The LORUN/NAHSA system is a pathfinder for hybrid cosmic ray research combined with education and outreach in the field of astro-particle physics. Particle detectors and radio antennae were mainly setup by students and placed on public buildings. After fully digital data acquisition, coincidence detections were selected. Three candidate events confirmed a working prototype, which can be multiplied to extend further particle detector arrays on high schools.Comment: 10 pages, 6 figures. Nigl, A., Timmermans, C., Schellart, P., Kuijpers, J., Falcke, H., Horneffer, A., de Vos, C. M., Koopman, Y., Pepping, H. J., Schoonderbeek, G., Cosmic rays studied with a hybrid high school detector array, Europhysics News (EPN), Vol. 38, No. 5, accepted on 22/08/200

The chemical potential of the electron gas on a one dimensional lattice

The chemical potential of the electron gas on a one-dimensional lattice is determined within the discrete Hubbard model. The result will have applications in studies of transport properties of quasi one-dimensional organic conductors such as the Bechgaard salts.Comment: 4 pages,plain TeX,presented at the 9 National Congress of Yugoslav Physicists,held in May 1995.,and published in the proceedings.The author can be contacted at: [email protected]

Automatic Configuration of Multi-Agent Model Predictive Controllers based on Semantic Graph World Models

We propose a shared semantic map architecture to construct and configure Model Predictive Controllers (MPC) dynamically, that solve navigation problems for multiple robotic agents sharing parts of the same environment. The navigation task is represented as a sequence of semantically labeled areas in the map, that must be traversed sequentially, i.e. a route. Each semantic label represents one or more constraints on the robots' motion behaviour in that area. The advantages of this approach are: (i) an MPC-based motion controller in each individual robot can be (re-)configured, at runtime, with the locally and temporally relevant parameters; (ii) the application can influence, also at runtime, the navigation behaviour of the robots, just by adapting the semantic labels; and (iii) the robots can reason about their need for coordination, through analyzing over which horizon in time and space their routes overlap. The paper provides simulations of various representative situations, showing that the approach of runtime configuration of the MPC drastically decreases computation time, while retaining task execution performance similar to an approach in which each robot always includes all other robots in its MPC computations