Damage Spreading and Criticality in Finite Random Dynamical Networks

We systematically study and compare damage spreading at the sparse percolation (SP) limit for random boolean and threshold networks with perturbations that are independent of the network size $N$. This limit is relevant to information and damage propagation in many technological and natural networks. Using finite size scaling, we identify a new characteristic connectivity $K_s$, at which the average number of damaged nodes $\bar d$, after a large number of dynamical updates, is independent of $N$. Based on marginal damage spreading, we determine the critical connectivity $K_c^{sparse}(N)$ for finite $N$ at the SP limit and show that it systematically deviates from $K_c$, established by the annealed approximation, even for large system sizes. Our findings can potentially explain the results recently obtained for gene regulatory networks and have important implications for the evolution of dynamical networks that solve specific computational or functional tasks.Comment: 4 pages, 4 eps figure

Molecular dynamics simulations of reflection and adhesion behavior in Lennard-Jones cluster deposition

We conduct molecular dynamics simulations of the collision of atomic clusters with a weakly-attractive surface. We focus on an intermediate regime, between soft-landing and fragmentation, where the cluster undergoes deformation on impact but remains largely intact, and will either adhere to the surface (and possibly slide), or be reflected. We find that the outcome of the collision is determined by the Weber number, We i.e. the ratio of the kinetic energy to the adhesion energy, with a transition between adhesion and reflection occurring as We passes through unity. We also identify two distinct collision regimes: in one regime the collision is largely elastic and deformation of the cluster is relatively small but in the second regime the deformation is large and the adhesion energy starts to depend on the kinetic energy. If the transition between these two regimes occurs at a similar kinetic energy to that of the transition between reflection and adhesion, then we find that the probability of adhesion for a cluster can be bimodal. In addition we investigate the effects of the angle of incidence on adhesion and reflection. Finally we compare our findings both with recent experimental results and with macroscopic theories of particle collisions.Comment: 18 pages, 13 figure

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

Annual, semiannual and seasonal variations of the Vertical Total Electron Content (VTEC) have been investigated during high solar activity in 2000. In this work we use Global IGS VTEC maps and Principal Component Analysis to study spatial and temporal ionospheric variability. The behavior of VTEC variations at two-hour periods, at noon and at night is analyzed. Particular characteristics associated with each period and the geomagnetic regions are highlighted. <br><br> The variations at night are smaller than those obtained at noon. At noon it is possible to see patterns of the seasonal variation at high latitude, and patterns of the semiannual anomaly at low latitudes with a slow decrease towards mid latitudes. At night there is no evidence of seasonal or annual anomaly for any region, but it was possible to see the semiannual anomaly at low latitudes with a sudden decrease towards mid latitudes. In general, the semiannual behavior shows March–April equinox at least 40 % higher than September one. Similarities and differences are analyzed also with regard to the same analysis done for a period of low solar activity

Towards semantic software engineering environments

Software tools processing partially common set of data should share an understanding of what these data mean. Since ontologies have been used to express formally a shared understanding of information, we argue that they are a way towards Semantic SEEs. In this paper we discuss an ontology-based approach to tool integration and present ODE, an ontology-based SEE

Temporal and diffraction effects in entanglement creation in an optical cavity

A practical scheme for entanglement creation between distant atoms located inside a single-mode optical cavity is discussed. We show that the degree of entanglement and the time it takes for the entanglement to reach its optimum value is a sensitive function the initial conditions and the position of the atoms inside the cavity mode. It is found that the entangled properties of the two atoms can readily be extracted from dynamics of a simple two-level system. Effectively, we engineer two coupled qubits whose the dynamics are analogous to that of a driven single two-level system. It is found that spatial variations of the coupling constants actually help to create transient entanglement which may appear on the time scale much longer than that predicted for the case of equal coupling constants. When the atoms are initially prepared in an entangled state, they may remain entangled for all times. We also find that the entanglement exhibits an interesting phenomenon of diffraction when the the atoms are located between the nodes and antinodes of the cavity mode. The diffraction pattern of the entanglement varies with time and we explain this effect in terms of the quantum property of complementarity, which is manifested as a tradeoff between the knowledge of energy of the exchanged photon versus the evolution time of the system.Comment: Phys. Rev. A75, 042307 (2007

Syphilis iridocyclitis in a patient with type 1 diabetes

We present a rare cause of iridocyclitis in a patient with vitiligo and type 1 diabetes who showed poor metabolic control, and suffered from remitting fever, weight loss, fatigue, diffuse arthralgias and reduced visual acuity. Mild systemic symptoms coupled with increased cholestasis enzymes, insulin resistance, mild inflammation and a functioning adrenal gland focused our clinical work-up on granulomatous causes of iridocyclitis. Specific tests confirmed syphilis, with no involvement of the central nervous system. Ocular syphilis, despite being unusual, can be the only manifestation of the disease. The work-up of any unexplained ocular inflammation should include testing for syphilis so as to not delay the diagnosis

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

Annual, semiannual and seasonal variations of theVertical Total Electron Content (VTEC) have been investigatedduring high solar activity in 2000. In this work we useGlobal IGS VTEC maps and Principal Component Analysisto study spatial and temporal ionospheric variability. The behaviorof VTEC variations at two-hour periods, at noon andat night is analyzed. Particular characteristics associated witheach period and the geomagnetic regions are highlighted.The variations at night are smaller than those obtained atnoon. At noon it is possible to see patterns of the seasonalvariation at high latitude, and patterns of the semiannualanomaly at low latitudes with a slow decrease towards midlatitudes. At night there is no evidence of seasonal or annualanomaly for any region, but it was possible to see the semiannualanomaly at low latitudes with a sudden decrease towardsmid latitudes. In general, the semiannual behavior showsMarch–April equinox at least 40% higher than Septemberone. Similarities and differences are analyzed also with regardto the same analysis done for a period of low solar activity.Fil: Natali, Maria Paula. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Meza, A.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Collaborators, Collaboration, and the Problems of Empire in Napoleonic Italy, The Oppizzoni Affair, 1805-1807

The recent bicentennial commemorations of the Napoleonic empire have witnessed a proliferation of new studies. Scholars now possess much more sophisticated conceptual tools than in past decades with which to gauge the problems faced by French imperial administrators throughout Europe. Well-trodden concepts, like centre/periphery or collaboration/resistance, have been reinvigorated by more sophisticated understandings of how rulers and ruled interacted in the early nineteenth century. This article argues that, while much progress has been made in understanding problems of ‘resistance’, there is more to be said about the other side of the same coin, namely: ‘collaboration’. Using the micro/local history of a scandal in Napoleonic Bologna, this article wishes to reaffirm that collaboration was an active agent that shaped, and often shook, the French imperial project. The biggest problem remained that, despite ‘good intentions’, collaborators sometimes simply did not collaborate with each other. After all, imperial clients were determined to benefit from the experience of empire. The centre was often submerged by local petty squabbles. This article will use a specific micro-history in Bologna to highlight the extent to which Napoleonic empire builders had to thread a fine line between the impracticalities of direct control and the dangers of ‘going native’