322,968 research outputs found
Online Similarity Prediction of Networked Data from Known and Unknown Graphs
No full textWe consider online similarity prediction problems over networked data. We begin by relating this task to the more standard class prediction problem, showing that, given an arbitrary algorithm for class prediction, we can construct an algorithm for similarity prediction with "nearly" the same mistake bound, and vice versa. After noticing that this general construction is computationally infeasible, we target our study to {\em feasible} similarity prediction algorithms on networked data. We initially assume that the network structure is {\em known} to the learner. Here we observe that Matrix Winnow \cite{w07} has a near-optimal mistake guarantee, at the price of cubic prediction time per round. This motivates our effort for an efficient implementation of a Perceptron algorithm with a weaker mistake guarantee but with only poly-logarithmic prediction time. Our focus then turns to the challenging case of networks whose structure is initially {\em unknown} to the learner. In this novel setting, where the network structure is only incrementally revealed, we obtain a mistake-bounded algorithm with a quadratic prediction time per round
Combined effects of salinity and chlorpyrifos on the earthworm Eisenia andrei
No full textSoil salinization could represent a threat for earthworms, affecting their general health status, reproduction and survival. This stressing condition could be worsened by the presence of further anthropic factors, like pesticides, whose effect may be exacerbated in a climate change scenario. Hence the goal of this study was to evaluate the effects of salinity (SAL), chlorpyrifos (CP) and their combination on the earthworm Eisenia andrei. Five different SAL conditions (0.1 ÷ 12 g/L), and five different CP concentrations (3.16 ÷ 316 mg/kg) were tested in “single stressor” experiments. Seventeen different combinations (SAL 2.5 ÷ 10 g/L; CP 5 ÷ 80 mg/kg) were tested in the following “combination” experiment. The endpoints considered were mortality, growth, reproduction and acetylcholinesterase (AChE) activity. Exposure to SAL decreased growth, survival and reproduction of earthworms, especially at the highest salt concentrations, where no cocoons were found at the end of the experiment. CP affected survival and growth only at the highest concentration, where 100% mortality was observed. Contrariwise, reproduction was affected also at lower concentrations of CP. AChE activity was drastically inhibited by increasing CP concentrations. In the combination experiment, neither SAL nor CP affected worm survival. Growth and number of laid cocoons were reduced by both stress factors, with no interactive effects. Number of juveniles showed a hormetic response to CP in the absence of SAL. Interestingly, SAL eliminated the hormesis. AChE activity was affected only by CP, and not by SAL. In conclusion, combination experiments showed that E. andrei life cycle traits were negatively affected by soil SAL, and also by CP at high concentrations. AChE activity was very sensitive to CP, while it was not affected by SAL. The number of juveniles was the only endpoint showing interactive effects between the two stress factors
Efectos de la transición nutricional en adolescentes escolarizados de nivel secundario de Córdoba (Argentina)
No full textFil: Pasteris, María Victoria. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Carrera de Ciencias Biológicas; Argentina.El sobrepeso y la obesidad han sido definidos por la OMS como la acumulación anormal o
excesiva de grasa que puede ser perjudicial para la salud, y es reconocida actualmente como la
pandemia más importante, en términos sanitarios, del siglo XXI. Para este estudio se
seleccionaron 4 colegios de nivel secundario, de la ciudad de Córdoba, Argentina, de diferentes
niveles socioeconómicos. Se realizaron comparaciones entre ellos y con las referencias
nacionales (SAP) e internacionales (OMS), en cuanto a talla/edad e IMC/edad; también se
realizaron comparaciones entre los establecimientos para determinar similitudes y diferencias
en cuanto al estado nutricional y analizar la relación entre este y los patrones de alimentación,
condiciones socio económicas y estilos de vida. Además, se utilizó el método LMS para ajustar
datos antropométricos y obtener estándares de percentilos normalizados teniendo en cuenta el
coeficiente de curtosis (L), la mediana (M) y el coeficiente de variación (S). Los datos de
talla/edad e IMC/edad, se ajustan a lo establecido por las referencias nacionales e
internacionales. Si bien los mayores niveles de obesidad se presentan en los colegios con nivel
socioeconómico bajo y medio bajo, el exceso de peso (sobrepeso y obesidad) está presente en
todos los colegios, más allá del nivel socioeconómico. La variable ambiental que estaría más
asociada al exceso de peso es la exposición a pantallas en un rango de 4 a 6 horas diarias.Fil: Pasteris, María Victoria. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Carrera de Ciencias Biológicas; Argentina
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Survey of microarthropods and biological quality of soils of San Vitale pinewood (Ravenna, Italy): first results / Etude sur les microarthropodes et sur la qualite biologique des sols de la pinede de San Vitale (Ravenna, Italie): premiers resultats / Indagine sui microartropodi e sulla qualità biologica dei suoli della pineta di San Vitale (Ravenna, Italia): primi risultati
No full textSono riportati i primi risultati di uno studio condotto nella Pineta di San Vitale (Ravenna). L'obiettivo è valutare la qualità biologica dei suoli mediante l’analisi del popolamento dei microartropodi edafici, in relazione al pedotipo ed in particolare alla salinizzazione. La Qualità Biologica del Suolo è valutata con l’indice QBS-ar.
La Pineta è stata campionata nella zona Est, maggiormente influenzata dall’ingressione salina e nella zona Ovest, dove tale fenomeno è meno rilevante. Il campionamento è stato svolto in primavera e in estate. I risultati del campionamento primaverile, confermano che le caratteristiche chimiche e fisiche variano secondo il gradiente sommità dunali - bassure interdunali. Per quanto riguarda la struttura del popolamento di microartropodi e il QBS-ar, si riconoscono alcune caratteristiche comuni alla maggior parte delle stazioni con il medesimo pedotipo. Non si evidenzia uno stress sul popolamento attribuibile alla salinizzazione. Il QBS-ar è nel complesso abbastanza elevato
Toxicity of hexavalent chromium to the earthworm Eisenia andrei: linking effects at different levlels of biological organization
No full textLiving organisms respond to chemicals at all the levels of biological organization, from molecules to ecosystems. In general, biochemical and physiological responses (molecules, cells, tissues) are triggered at low concentrations and after short exposure times, while ecological responses (life cycle traits, populations, communities, ecosystems) can be evidenced only at higher concentrations and after longer exposures. On the other hand, responses at the higher levels of organization are considered more relevant from an environmental point of view, as they often result in irreversible severe damage to ecological systems. It is important to clarify the relationship between low-level and high-level responses to different toxicants, particularly considering the increasing application of biomarkers as early warning systems to assess environmental pollution.
In accordance with this view, effects of exposure to hexavalent chromium, Cr(VI), on life cycle endpoints were compared to effects on a battery of eight biomarkers in the earthworm Eisenia andrei. In spite of the importance of Cr(VI) as an environmental contaminant, its toxicity to earthworms, a major component of soil fauna, has received little attention; in particular almost no data are available on biochemical and physiological responses.
A natural clayey soil was spiked at six Cr(VI) concentrations, from 6.25 to 200 mg/kg. Adult worms were exposed in laboratory to the spiked soils and to a control treatment (unspiked soil). Two sets of experimental containers were prepared: the first to measure lysosomal membrane stability, lysosomal lipofuscins and neutral lipids accumulation, metallothionein content, Ca2+ ATPase, catalase, glutathione S-transferase and acyl CoA oxydase activities, after 10 d of exposure; the second to asses survival, growth and chromium bioaccumulation after 28 d, and reproduction after 56 d of exposure.
All the biological effects were significantly affected by Cr(VI) exposure and showed a clear concentration-effect relationship, except for the content of metallothioneins. Biomarkers showed different trends at increasing Cr(VI) concentrations, that could be classified as typical “increasing responses” (neutral lipids), “decreasing responses” (lysosomal membrane stability, Ca2+-ATPase and acyl Co-A oxydase activities) and “bell-shaped responses” (catalase and glutathione S-transferase activities). Biomarkers were more sensitive to Cr(VI) than life-cycle endpoints; among these, reproduction was the most responsive
The effect factor for nano TiO2: preliminary toxicity tests on Daphnia magna and future developments
No full textNanotechnologies are being developed for application in a large variety of sectors, from food industry to environmental remediation technology. However, numerous uncertainties exist regarding their possible impacts on the environment and human health. The Life Cycle Assessment (LCA) methodology could be a tool to evaluate, analyze and manage the environmental and health effects for the emerging technologies. The evaluation of the environmental performance of nanotechnologies trough LCA is not always possible due to the lack of data regarding the environmental pathway of NPs. The focus of the present research is to evaluate the freshwater ecotoxicological Effect Factor (EF) for TiO2 nanoparticles (which are widely used in different applications as sunscreens, solar cells, ecc.), following the framework of the USEtox model. This model is used for the Life Cycle Impact Assessment (LCIA) phase and is aimed to provide the Characterization Factor (CF) for the ecotoxicity impact category. The CF is quantified trough the evaluation of the Fate Factor (FF) and Effect Factor (EF). The latter is based on chronic or acute toxicity value as EC50. In order to establish the acute EC50 for nano TiO2, two preliminary toxicity tests on Daphnia magna (72h) have been performed. The particles were prepared following two different treatments. In the first case the nano TiO2 suspensions were stirred for 24 h only before the test; in the second case the particles were maintained in agitation also for the whole duration of the bioassay. No adverse effects have been observed for the concentration applied, this contrasts with the findings of other studies that reported effects of nano TiO2 on D. magna. The future developments of our research are to conduct other toxicity tests on D. magna, following different treatments of the sample (example: irradiation with UV-A, filtration etc), and to conduct toxicity test on different trophic level (algae, crustaceans, fish) as suggested by USEtox framework. The research is intended to identify suitable treatments for nanoparticles to be used in toxicity test, taking into account their tendency to aggregate and precipitate and that this could influence the results of the tests. The suitable treatment should also reproduce the actual exposure modality of the organisms in the field
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