Methods to Determine Node Centrality and Clustering in Graphs with Uncertain Structure

Much of the past work in network analysis has focused on analyzing discrete graphs, where binary edges represent the "presence" or "absence" of a relationship. Since traditional network measures (e.g., betweenness centrality) utilize a discrete link structure, complex systems must be transformed to this representation in order to investigate network properties. However, in many domains there may be uncertainty about the relationship structure and any uncertainty information would be lost in translation to a discrete representation. Uncertainty may arise in domains where there is moderating link information that cannot be easily observed, i.e., links become inactive over time but may not be dropped or observed links may not always corresponds to a valid relationship. In order to represent and reason with these types of uncertainty, we move beyond the discrete graph framework and develop social network measures based on a probabilistic graph representation. More specifically, we develop measures of path length, betweenness centrality, and clustering coefficient---one set based on sampling and one based on probabilistic paths. We evaluate our methods on three real-world networks from Enron, Facebook, and DBLP, showing that our proposed methods more accurately capture salient effects without being susceptible to local noise, and that the resulting analysis produces a better understanding of the graph structure and the uncertainty resulting from its change over time.Comment: Longer version of paper appearing in Fifth International AAAI Conference on Weblogs and Social Media. 9 pages, 4 Figure

Telemetry downlink interfaces and level-zero processing

The technical areas being investigated are as follows: (1) processing of space to ground data frames; (2) parallel architecture performance studies; and (3) parallel programming techniques. Additionally, the University administrative details and the technical liaison between New Mexico State University and Goddard Space Flight Center are addressed

Direct innervation of capillary endothelial cells in the lamina propria of the ferret stomach

Direct innervation of capillary endothelial cells in lamina propria of ferret stomac

On the Invariants of the Cohomology of Complements of Coxeter Arrangements

We refine Brieskorn's study of the cohomology of the complement of the reflection arrangement of a finite Coxeter group $W$. As a result we complete the verification of a conjecture by Felder and Veselov that gives an explicit basis of the space of $W$-invariants in this cohomology ring.Comment: 12 pages, 3 figures; final versio

Compact Binary Waveform Center-of-Mass Corrections

We present a detailed study of the center-of-mass (c.m.) motion seen in simulations produced by the Simulating eXtreme Spacetimes (SXS) collaboration. We investigate potential physical sources for the large c.m. motion in binary black hole simulations and find that a significant fraction of the c.m. motion cannot be explained physically, thus concluding that it is largely a gauge effect. These large c.m. displacements cause mode mixing in the gravitational waveform, most easily recognized as amplitude oscillations caused by the dominant (2,$\pm$2) modes mixing into subdominant modes. This mixing does not diminish with increasing distance from the source; it is present even in asymptotic waveforms, regardless of the method of data extraction. We describe the current c.m.-correction method used by the SXS collaboration, which is based on counteracting the motion of the c.m. as measured by the trajectories of the apparent horizons in the simulations, and investigate potential methods to improve that correction to the waveform. We also present a complementary method for computing an optimal c.m. correction or evaluating any other c.m. transformation based solely on the asymptotic waveform data.Comment: 20 pages, 15 figure

Open-closed TQFTs extend Khovanov homology from links to tangles

We use a special kind of 2-dimensional extended Topological Quantum Field Theories (TQFTs), so-called open-closed TQFTs, in order to extend Khovanov homology from links to arbitrary tangles, not necessarily even. For every plane diagram of an oriented tangle, we construct a chain complex whose homology is invariant under Reidemeister moves. The terms of this chain complex are modules of a suitable algebra A such that there is one action of A or A^op for every boundary point of the tangle. We give examples of such algebras A for which our tangle homology theory reduces to the link homology theories of Khovanov, Lee, and Bar-Natan if it is evaluated for links. As a consequence of the Cardy condition, Khovanov's graded theory can only be extended to tangles if the underlying field has finite characteristic. In all cases in which the algebra A is strongly separable, i.e. for Bar-Natan's theory in any characteristic and for Lee's theory in characteristic other than 2, we also provide the required algebraic operation for the composition of oriented tangles. Just as Khovanov's theory for links can be recovered from Lee's or Bar-Natan's by a suitable spectral sequence, we provide a spectral sequence in order to compute our tangle extension of Khovanov's theory from that of Bar-Natan's or Lee's theory. Thus, we provide a tangle homology theory that is locally computable and still strong enough to recover characteristic p Khovanov homology for links.Comment: 56 pages, LaTeX2e with xypic and pstricks macro

Charge metastability and hysteresis in the quantum Hall regime

We report simultaneous quasi-dc magnetotransport and high frequency surface acoustic wave measurements on bilayer two-dimensional electron systems in GaAs. Near strong integer quantized Hall states a strong magnetic field sweep hysteresis in the velocity of the acoustic waves is observed at low temperatures. This hysteresis indicates the presence of a metastable state with anomalously high conductivity in the interior of the sample. This non-equilibrium state is not revealed by conventional low frequency transport measurements which are dominated by dissipationless transport at the edge of the 2D system. We find that a field-cooling technique allows the equilibrium charge configuration within the interior of the sample to be established. A simple model for this behavior is discussed.Comment: 8 pages, 4 postscript figure

Optimizing crop loading of apples and pears - results 2004-2006 (foliar fertilizers, thinning)

Main topics of the research-project FuE 03OE088 of “Bundesprogramm Ökologischer Landbau” (30.04.2004-31.12.2006) were the testing of foliar fertilizers in organic apples and pears, optimizing lime sulphur for blossom thinning, looking for alternatives to lime sulphur for blossom thinning and looking at different combinations of thinning measures. Only the results of testing foliar fertilizers (carried out by KoGa Ahrweiler and OVB/ÖON Jork) and combinations of thinning measures (carried out by LVWO Weinsberg) are described in this article. Over three years only a small increase in yield was evaluated for the fertilizers Aminosol PS and Wuxal Ascofol (site Ahrweiler, apple variety ‘Elstar’). In Jork (apple variety ‘Holsteiner Cox’) yield could only be judged in 2005 and 2006. Wuxal Ascofol showed some advantage in comparison to the control. At pear variety ‘Conference’ no clear tendencies could be seen, the control had the highest yield. In 2005 the fruitsetting of ‘Conference’ was very low because of bad conditions during blossom

Field-induced resonant tunneling between parallel two-dimensional electron systems

Resonant tunneling between two high-mobility two-dimensional (2D) electron systems in a double quantum well structure has been induced by the action of an external Schottky gate field. Using one 2D electron gas as source and the other as drain, the tunnel conductance between them shows a strong resonance when the gate field aligns the ground subband edges of the two quantum wells