Towards Intelligent Databases

This article is a presentation of the objectives and techniques of deductive databases. The deductive approach to databases aims at extending with intensional definitions other database paradigms that describe applications extensionaUy. We first show how constructive specifications can be expressed with deduction rules, and how normative conditions can be defined using integrity constraints. We outline the principles of bottom-up and top-down query answering procedures and present the techniques used for integrity checking. We then argue that it is often desirable to manage with a database system not only database applications, but also specifications of system components. We present such meta-level specifications and discuss their advantages over conventional approaches

Forward-looking solvency contagion

Solvency contagion risk is a key channel through which systemic risk can come about. We introduce a model that accounts not only for losses transmitted after banks default, but also for losses due to the fact that creditors revalue their exposures when probabilities of default of their counterparties change. We apply the model to run a series of simplified stress tests of the UK banking system from 2008 to 2016, based on two datasets of real interbank exposures between the seven major UK banks. We show that risks due to solvency contagion decrease markedly from the peak of the crisis, to the point of becoming negligible. We also characterise the distributions of both vulnerabilities and systemic importances of individual banks, thereby tracking the evolution of risk concentration

The Survey of HI in Extremely Low-mass Dwarfs: New Results from VLA Imaging

We present new HI spectral line imaging of 19 galaxies in the “Survey of HI in Extremely Low-mass Dwarfs” (SHIELD) acquired for Large Program VLA/ 20A-330. Using the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array (VLA) in the C configuration, we produce images of the neutral interstellar medium (HI) on angular scales of 15 to 20 arcseconds (corresponding to physical resolutions of 200 to 1100 parsecs). The three-dimensional cubes probe the morphology and kinematics of the gas at a range of spatial and spectral resolutions. The cubes were collapsed to produce two-dimensional moment maps (representing HI mass surface density and intensity weighted HI velocity). The HI gas was directly compared to the stellar component by comparison against optical and infrared imaging. In most cases, the gas and stars are co-spatial, with the exception of dwarfs with companion galaxies. The SHIELD galaxies are important to our understanding of galaxies’ properties at the low end of the mass spectrum

Acumulación de Cu y Zn por célular microalgales marinas de Nannochloropsis gaditana (Eustigmatophyceae) inmovilizadas en alginato de calcio

13 páginas, 5 figuras, 2 tablas.[EN] Different experiments about the accumulation capacity for copper and zinc were carried out on the marine microalgae Nannochloropsis gaditana Lubián (Eustigmatophyceae). A 24-hour study of the evolution of accumulated metal in the beads revealed two possible accumulation phases. Accumulation differences between free and immobilized microalgal cells were investigated finding no differences for copper, and little differences for zinc. Free cells accumulated practically 100% Cu or Zn in the media under experimental conditions. Experiments in order to compare the accumulation capacity of living vs. dead cells were designed too, obtaining the largest accumulation levels for both metals in the beads containing immobilized living microalgae. In experiments carried out in continuous-flow reactors, beads with entrapped cells showed to be more efficient removing Cu and Zn than beads without cells. In all the experiments, the calcium alginate beads showed strong affinity for Cu. Similar results were obtained when accumulation by packed beads in columns was tested, but efficacy was higher if this design was used (beads with cells retain 80% of Cu introduced in the column).[ES] Se han realizado distintos experimentos sobre la capacidad de acumulación de cobre y zinc por parte de la microalga marina Nannochloropsis gaditana Lubián (Eustigmatophyceae). Un estudio de la evolución del metal acumulado durante 24 horas reveló la existencia de dos posibles fases de acumulación. Se investigaron las diferentes capacidades de acumulación de células microalgales libres e inmovilizadas, no encontrándose diferencias para el cobre y pequeñas diferencias para el zinc. Las células libres acumularon prácticamente el 100% del Cu o Zn presentes en el medio, en las condiciones experimentales. Se desarrollaron experimentos encaminados a determinar la capacidad de acumulación de estos metales por parte de algas inmovilizadas vivas frente a la de algas inmovilizadas muertas, encontrándose los niveles acumulativos más altos para ambos metales en las gotas de alginato que contenían algas vivas. En experimentos realizados en reactores de flujo continuo, las gotas de alginato con células inmovilizadas en su interior demostraron ser más eficientes en cuanto a la retirada de Cu y Zn del medio que las gotas sin algas. En todos los experimentos realizados se observa una fuerte afinidad del Cu por el alginato de calcio. Se obtuvieron resultados similares cuando se ensayó la acumulación de metales en gotas de alginato dispuestas en columnas llenas, aunque la eficacia fue mayor cuando se usó este último diseño (las gotas de alginato con células retuvieron el 80% del Cu introducido en la columna).Peer reviewe

Shift-Symmetric Configurations in Two-Dimensional Cellular Automata: Irreversibility, Insolvability, and Enumeration

The search for symmetry as an unusual yet profoundly appealing phenomenon, and the origin of regular, repeating configuration patterns have long been a central focus of complexity science and physics. To better grasp and understand symmetry of configurations in decentralized toroidal architectures, we employ group-theoretic methods, which allow us to identify and enumerate these inputs, and argue about irreversible system behaviors with undesired effects on many computational problems. The concept of so-called configuration shift-symmetry is applied to two-dimensional cellular automata as an ideal model of computation. Regardless of the transition function, the results show the universal insolvability of crucial distributed tasks, such as leader election, pattern recognition, hashing, and encryption. By using compact enumeration formulas and bounding the number of shift-symmetric configurations for a given lattice size, we efficiently calculate the probability of a configuration being shift-symmetric for a uniform or density-uniform distribution. Further, we devise an algorithm detecting the presence of shift-symmetry in a configuration. Given the resource constraints, the enumeration and probability formulas can directly help to lower the minimal expected error and provide recommendations for system's size and initialization. Besides cellular automata, the shift-symmetry analysis can be used to study the non-linear behavior in various synchronous rule-based systems that include inference engines, Boolean networks, neural networks, and systolic arrays.Comment: 22 pages, 9 figures, 2 appendice

Effects of size at birth, childhood growth patterns and growth hormone treatment on leukocyte telomere length

__Background__ Small size at birth and rapid growth in early life are associated with increased risk of cardiovascular disease in later life. Short children born small for gestational age (SGA) are treated with growth hormone (GH), inducing catch-up in length. Leukocyte telomere length (LTL) is a marker of biological age and shorter LTL is associated with increased risk of cardiovascular disease. __Objectives__ To investigate whether LTL is influenced by birth size, childhood growth and long-term GH treatment. __Methods__ We analyzed LTL in 545 young adults with differences in birth size and childhood growth patterns. Previously GH-treated young adults born SGA (SGA-GH) were compared to untreated short SGA (SGA-S), SGA with spontaneous catch-up to a normal body size (SGA-CU), and appropriate for gestational age with a normal body size (AGA-NS). LTL was measured using a quantitative PCR assay. __Results__ We found a positive association between birth length and LTL (p = 0.04), and a trend towards a positive association between birth weight and LTL (p = 0.08), after adjustments for gender, age, gestational age and adult body size. Weight gain during infancy and childhood and fat mass percentage were not as

A complementary view on the growth of directory trees

Trees are a special sub-class of networks with unique properties, such as the level distribution which has often been overlooked. We analyse a general tree growth model proposed by Klemm {\em et. al.} (2005) to explain the growth of user-generated directory structures in computers. The model has a single parameter $q$ which interpolates between preferential attachment and random growth. Our analysis results in three contributions: First, we propose a more efficient estimation method for $q$ based on the degree distribution, which is one specific representation of the model. Next, we introduce the concept of a level distribution and analytically solve the model for this representation. This allows for an alternative and independent measure of $q$. We argue that, to capture real growth processes, the $q$ estimations from the degree and the level distributions should coincide. Thus, we finally apply both representations to validate the model with synthetically generated tree structures, as well as with collected data of user directories. In the case of real directory structures, we show that $q$ measured from the level distribution are incompatible with $q$ measured from the degree distribution. In contrast to this, we find perfect agreement in the case of simulated data. Thus, we conclude that the model is an incomplete description of the growth of real directory structures as it fails to reproduce the level distribution. This insight can be generalised to point out the importance of the level distribution for modeling tree growth.Comment: 16 pages, 7 figure