Automatic Metadata Generation using Associative Networks

In spite of its tremendous value, metadata is generally sparse and incomplete, thereby hampering the effectiveness of digital information services. Many of the existing mechanisms for the automated creation of metadata rely primarily on content analysis which can be costly and inefficient. The automatic metadata generation system proposed in this article leverages resource relationships generated from existing metadata as a medium for propagation from metadata-rich to metadata-poor resources. Because of its independence from content analysis, it can be applied to a wide variety of resource media types and is shown to be computationally inexpensive. The proposed method operates through two distinct phases. Occurrence and co-occurrence algorithms first generate an associative network of repository resources leveraging existing repository metadata. Second, using the associative network as a substrate, metadata associated with metadata-rich resources is propagated to metadata-poor resources by means of a discrete-form spreading activation algorithm. This article discusses the general framework for building associative networks, an algorithm for disseminating metadata through such networks, and the results of an experiment and validation of the proposed method using a standard bibliographic dataset

Method of studying the Bogoliubov-de Gennes equations for the superconducting vortex lattice state

In this paper, we present a method to construct the eigenspace of the normal-state electrons moving in a 2D square lattice in presence of a perpendicular uniform magnetic field which imposes (quasi)-periodic boundary conditions for the wave functions in the magnetic unit cell. An exact unitary transformations are put forward to correlate the discrete eigenvectors of the 2D electrons with those of the Harper's equation. The cyclic-tridiagonal matrix associated with the Harper's equation is then tridiagonalized by another unitary transformation. The obtained eigenbasis is utilized to expand the Bogoliubov-de Gennes equations for the superconducting vortex lattice state, which showing the merit of our method in studying the large-sized system. To test our method, we have applied our results to study the vortex lattice state of an s-wave superconductor.Comment: 8 pages; 3 figure

An experimental evaluation of the consistency of competitive ability and agonistic dominance in different social contexts in captive bonobos

Bonobos have been described as a relatively egalitarian and female dominant species. The exact nature and quality of their dominance relationships and the existence of female dominance are current topics of dispute. We investigated the consistency across social contexts, the stability in time, and the degree of expression of the competitive feeding ability and agonistic dominance in a captive group of bonobos. First, we examined whether the competitive feeding ranks and agonistic ranks differed in different dyadic contexts, triadic contexts and the whole group context. For some pairs of animals the dominance relationships with respect to competitive feeding altered with different group compositions. The agonistic dominance relationships changed accordingly. The competitive feeding ranks and agonistic ranks in the experiments correlated strongly with each other. The alpha position was occupied by a female, but not all females outranked all males. We suggest that females can profit from each others presence to gain inter-sexual dominance. Second, although the agonistic rank order in the whole group remained the same over at least five years, some dyadic competitive feeding ranks changed over time, resulting in a stronger female intersexual dominance. Third, the degree of expression of the behaviors used to quantify dyadic competitive and agonistic dominance was not high, in line with the popular egalitarian epithet. Notwithstanding its low consistency across contexts, the dominance hierarchy in the whole group has a strong predictive value for other social relationships such as grooming. Given this strong effect of rank on other behaviours and given the strong dependency of rank on social context, the choice of the right party members may be a crucial factor in the fission-fusion processes of free-ranging bonobos

The pivotal role of rank in grooming and support behaviour in a captive group of bonobos (Pan paniscus)

We investigated dyadic grooming relationships in a captive group of bonobos (Pan paniscus) and questioned what social function grooming fulfils in the market of services and favors. Hereto we examined which of two theoretical models - grooming for support (Seyfarth, 1977, 1980) or grooming according to the similarity principle (de Waal & Luttrell, 1986) - best accounted for the observed grooming distribution. Similarity in traits did not correlate with increased grooming or close proximity among the individuals. Therefore, the similarity hypothesis was rejected. Seyfarths model of rank-related grooming was largely confirmed. The animals distributed their grooming according to the rank of the receivers. We found an exchange between grooming and receipt of support. There was more grooming up than down the hierarchy. However, not all predictions about rank-related competition over grooming were confirmed. We found that dyadic grooming reciprocity indeed increased with decreasing rank distance. Yet, there was no increase of grooming within the dyad with decreasing rank distance and high ranking individuals were not competed over at the highest rates. The observed correlation between grooming and support received represents an important fit with Seyfarths prediction, but does not allow for conclusions about underlying causal processes. Other causal explanations, besides the groom to receive support hypothesis, that could explain a similar correlation are discussed

Decision Problems For Convex Languages

In this paper we examine decision problems associated with various classes of convex languages, studied by Ang and Brzozowski (under the name "continuous languages"). We show that we can decide whether a given language L is prefix-, suffix-, factor-, or subword-convex in polynomial time if L is represented by a DFA, but that the problem is PSPACE-hard if L is represented by an NFA. In the case that a regular language is not convex, we prove tight upper bounds on the length of the shortest words demonstrating this fact, in terms of the number of states of an accepting DFA. Similar results are proved for some subclasses of convex languages: the prefix-, suffix-, factor-, and subword-closed languages, and the prefix-, suffix-, factor-, and subword-free languages.Comment: preliminary version. This version corrected one typo in Section 2.1.1, line

Quasiperiodic Modulated-Spring Model

We study the classical vibration problem of a chain with spring constants which are modulated in a quasiperiodic manner, {\it i. e.}, a model in which the elastic energy is $\sum_j k_j( u_{j-1}-{u_j})^2$, where $k_j=1+\Delta cos[2\pi\sigma(j-1/2)+\theta]$ and $\sigma$ is an irrational number. For $\Delta < 1$, it is shown analytically that the spectrum is absolutely continuous, {\it i.e.}, all the eigen modes are extended. For $\Delta=1$, numerical scaling analysis shows that the spectrum is purely singular continuous, {\it i.e.}, all the modes are critical.Comment: REV TeX fil

Thickness dependence of unidirectional spin-Hall magnetoresistance in metallic bilayers

A nonlinear magnetoresistance - called unidirectional spin-Hall magnetoresistance - is recently experimentally discovered in metallic bilayers consisting of a heavy metal and a ferromagnetic metal. To study the fundamental mechanism of the USMR, both ferromagnetic and heavy metallic layer thickness dependence of the USMR are presented in a Pt/Co/AlOx trilayer at room temperature. To avoid ambiguities, second harmonic Hall measurements are used for separating spin-Hall and thermal contributions to the non-linear magnetoresistance. The experimental results are fitted by using a drift-diffusion theory, with parameters extracted from an analysis of longitudinal resistivity of the Co layer within the framework of the Fuchs-Sondheimer model. A good agreement with the theory is found, demonstrating that the USMR is governed by both the spin-Hall effect in the heavy metallic layer and the metallic diffusion process in the ferromagnetic layer

Green's Function Approach to the Edge Spectral Density

It is shown that the conventional many-body techniques to calculate the Green's functions can be applied to the wide, compressible edge of a quantum Hall bar. The only ansatz we need is the existence of stable density modes that yields a simple equation of motion of the density operators. We derive the spectral density at a finite temperature and show how the tunneling characteristics of a sharp edge can be deduced as a limiting case.Comment: Revised and Enlarged. Submitted to Phys. Rev.

Polycation-siRNA nanoparticles can disassemble at the kidney glomerular basement membrane

Despite being engineered to avoid renal clearance, many cationic polymer (polycation)-based siRNA nanoparticles that are used for systemic delivery are rapidly eliminated from the circulation. Here, we show that a component of the renal filtration barrier—the glomerular basement membrane (GBM)—can disassemble cationic cyclodextrin-containing polymer (CDP)-based siRNA nanoparticles and, thereby, facilitate their rapid elimination from circulation. Using confocal and electron microscopies, positron emission tomography, and compartment modeling, we demonstrate that siRNA nanoparticles, but not free siRNA, accumulate and disassemble in the GBM. We also confirm that the siRNA nanoparticles do not disassemble in blood plasma in vitro and in vivo. This clearance mechanism may affect any nanoparticles that assemble primarily by electrostatic interactions between cationic delivery components and anionic nucleic acids (or other therapeutic entities)

Discrete transverse superconducting modes in nano-cylinders

Spatial variation in the superconducting order parameter becomes significant when the system is confined at dimensions well below the typical superconducting coherence length. Motivated by recent experimental success in growing single-crystal metallic nanorods, we study quantum confinement effects on superconductivity in a cylindrical nanowire in the clean limit. For large diameters, where the transverse level spacing is smaller than superconducting order parameter, the usual approximations of Ginzburg-Landau theory are recovered. However, under external magnetic field the order parameter develops a spatial variation much stronger than that predicted by Ginzburg-Landau theory, and gapless superconductivity is obtained above a certain field strength. At small diameters, the discrete nature of the transverse modes produces significant spatial variations in the order parameter with increased average magnitude and multiple shoulders in the magnetic response.Comment: 10 pages, 8 figure