The reliability of R50 as a measure of vulnerability of food webs to sequential species deletions

Recent studies predict elevated and accelerating rates of species extinctions over the 21st century, due to climate change and habitat loss. Considering that such primary species loss may initiate cascades of secondary extinctions and push systems towards critical tipping points, we urgently need to increase our understanding of if certain sequences of species extinctions can be expected to be more devastating than others Most theoretical studies addressing this question have used a topological (non-dynamical) approach to analyse the probability that food webs will collapse, below a fixed threshold value in species richness, when subjected to different sequences of species loss. Typically, these studies have neither considered the possibility of dynamical responses of species, nor that conclusions may depend on the value of the collapse threshold. Here we analyse how sensitive conclusions on the importance of different species are to the threshold value of food web collapse. Using dynamical simulations, where we expose model food webs to a range of extinction sequences, we evaluate the reliability of the most frequently used index, R<inf>50</inf>, as a measure of food web robustness. In general, we find that R<inf>50</inf> is a reliable measure and that identification of destructive deletion sequences is fairly robust, within a moderate range of collapse thresholds. At the same time, however, focusing on R<inf>50</inf> only hides a lot of interesting information on the disassembly process and can, in some cases, lead to incorrect conclusions on the relative importance of species in food webs.

Brightness variation distributions among main belt asteroids from sparse light curve sampling with Pan-STARRS 1

The rotational state of asteroids is controlled by various physical mechanisms including collisions, internal damping and the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. We have analysed the changes in magnitude between consecutive detections of ∼ 60,000 asteroids measured by the PanSTARRS 1 survey during its first 18 months of operations. We have attempted to explain the derived brightness changes physically and through the application of a simple model. We have found a tendency toward smaller magnitude variations with decreasing diameter for objects of 1 < D < 8 km. Assuming the shape distribution of objects in this size range to be independent of size and composition our model suggests a population with average axial ratios 1: 0.85 ± 0.13: 0.71 ± 0.13, with larger objects more likely to have spin axes perpendicular to the orbital plane.

SN 2011fu: a type IIb supernova with a luminous double-peaked light curve

We present optical and near-infrared observations of the type IIb supernova (SN) 2011fu from a few days to similar to 300 d after explosion. The SN presents a double-peaked light curve (LC) similar to that of SN 1993J, although more luminous and with a longer cooling phase after the primary peak. The spectral evolution is also similar to SN 1993J's, with hydrogen dominating the spectra to similar to 40 d, then helium gaining strength, and nebular emission lines appearing from similar to 60 d post-explosion. The velocities derived from the P-Cygni absorptions are overall similar to those of other type IIb SNe. We have found a strong similarity between the oxygen and magnesium line profiles at late times, which suggests that these lines are forming at the same location within the ejecta. The hydrodynamical modelling of the pseudo-bolometric LC and the observed photospheric velocities suggest that SN 2011fu was the explosion of an extended star (R similar to 450 R-circle dot), in which 1.3 x 10(51) erg of kinetic energy were released and 0.15 M-circle dot of Ni-56 were synthesized. In addition, a better reproduction of the observed early pseudo-bolometric LC is achieved if a more massive H-rich envelope than for other type IIb SNe is considered (0.3 M-circle dot). The hydrodynamical modelling of the LC and the comparison of our late-time spectra with nebular spectral models for type IIb SNe, point to a progenitor for SN 2011fu with a Zero Age Main Sequence (ZAMS) mass of 13-18 M-circle dot.

The Reliability of the Arc-Length Method in the Analysis of Mode-Jumping Problems

The Arc-Length Method is a solution procedure that enables a generic non-linear problem to pass limit points. Some examples are provided of mode-jumping problems solutions using a commercial nite element package, and other investigations are carried out on a simple structure of which the numerical solution can be compared with an analytical one. It is shown that Arc-Length Method is not reliable when bifurcations are present in the primary equilibrium path; also the presence of very sharp snap-backs or special boundary conditions may cause convergence diÆculty at limit points. An improvement to the predictor used in the incremental procedure is suggested, together with a reliable criteria for selecting either solution of the quadratic arc-length constraint. The gap that is sometimes observed between the experimantal load level of mode-jumping and its arc-length prediction is explained through an example.

Possibility of designing catalysts beyond the traditional volcano curve: A theoretical framework for multi-phase surfaces

The current theory of catalyst activity in heterogeneous catalysis is mainly obtained from the study of catalysts with mono-phases, while most catalysts in real systems consist of multi-phases, the understanding of which is far short of chemists' expectation. Density functional theory (DFT) and micro-kinetics simulations are used to investigate the activities of six mono-phase and nine bi-phase catalysts, using CO hydrogenation that is arguably the most typical reaction in heterogeneous catalysis. Excellent activities that are beyond the activity peak of traditional mono-phase volcano curves are found on some bi-phase surfaces. By analyzing these results, a new framework to understand the unexpected activities of bi-phase surfaces is proposed. Based on the framework, several principles for the design of multi-phase catalysts are suggested. The theoretical framework extends the traditional catalysis theory to understand more complex systems.

Repeatability and reliability of new air and water permeability tests for assessing the durability of high-performance concretes

This paper reports on the accuracy of new test methods developed to measure the air and water permeability of high-performance concretes (HPCs). Five representative HPC and one normal concrete (NC) mixtures were tested to estimate both repeatability and reliability of the proposed methods. Repeatability acceptance was adjudged using values of signal-noise ratio (SNR) and discrimination ratio (DR), and reliability was investigated by comparing against standard laboratory-based test methods (i.e., the RILEM gas permeability test and BS EN water penetration test). With SNR and DR values satisfying recommended criteria, it was concluded that test repeatability error has no significant influence on results. In addition, the research confirmed strong positive relationships between the proposed test methods and existing standard permeability assessment techniques. Based on these findings, the proposed test methods show strong potential to become recognized as international methods for determining the permeability of HPCs.

Signal Reliability Improvement Using Selection Combining Based Macro-Diversity for Off-Body Communications At 868 MHz

This paper investigates the potential improvement in signal reliability for outdoor short-range off-body communications channels at 868 MHz using the macro-diversity offered by multiple co-located base stations. In this study, ten identical hypothetical base stations were positioned equidistantly around the perimeter of a rectangle of length 6.67 m and width 3.3 m. A body worn node was placed on the central chest region of an adult male. Five scenarios, each considering different user trajectories, were then analyzed to test the efficacy of using macro-diversity when the desired link is subject to shadowing caused by the human body. A number of selection combining based macro-diversity configurations consisting of four and then ten base stations were considered. It was found that using a macro-diversity system consisting of four base stations (or equivalently signal branches), a maximum diversity gain of 22.5 dB could be obtained while implementing a 10-base station setup this figure could be improved to 25.2 dB.

Reliability of reports of childhood trauma in bipolar disorder: A test–retest study over 18 months

This study aimed to explore the reliability of self-reported trauma histories in a population with a diagnosis of Bipolar Disorder using the Childhood Trauma Questionnaire. Previous studies in other populations suggest high reliability of trauma histories over time and it was postulated that a similar high reliability would be demonstrated in this population. Thirty-nine patients with a confirmed diagnosis (DSM-IV criteria) were followed-up and re-administered the Childhood Trauma Questionnaire after 18 months. Cohen's kappa scores and intraclass correlations suggest reasonable test-retest reliability over the 18-month time period of the study for all types of childhood abuse, namely emotional, physical, sexual, and physical abuse and emotional neglect. Intraclass correlations ranged from r = .50 to (sexual abuse) to r = .96 (physical abuse). Cohen's kappas ranged from .44 (sexual abuse) to .76 (physical abuse). Retrospective reports of childhood trauma can be seen as reliable and are in keeping with results found with other mental health populations.

Reliability and factorial validity of Adolescent Time Inventory-Time Attitude (ATI-TA) Scores in Scottish and Northern Irish adolescents

The contemporary literature investigating the construct broadly known as time perspective is replete with methodological and conceptual concerns. These concerns focus on the reliability and factorial validity of measurement tools, and the sample-specific modification of scales. These issues continue to hamper the development of this potentially useful psychological construct. An emerging body of evidence has supported the six-factor structure of scores on the Adolescent Time Inventory-Time Attitudes Scale, as well as their reliability. The present study utilized data from the first wave of a longitudinal study in the United Kingdom to examine the reliability, validity, and cross-cultural invariance of the scale. Results showed that the hypothesized six-factor model provided the best fit for the data; all alpha and omega estimates were >. .70; scores on ATI-TA factors related meaningfully to self-efficacy scores; and the factor structure was invariant across both research sites. Results are discussed in the context of the extant temporal literature.

Evidence for the reliability and validity, but not the practical utility of the two-factor Consideration of Future Consequences Scale-14

Researchers have proposed 1-factor, 2-factor, and bifactor solutions to the 12-item Consideration of Future Consequences Scale (CFCS-12). In order to overcome some measurement problems and to create a robust and conceptually useful two-factor scale the CFCS-12 was recently modified to include two new items and to become the CFCS-14. Using a University sample, we tested four competing models for the CFCS-14: (a) a 12-item unidimensional model, (b) a model fitted for two uncorrelated factors (CFC-Immediate and CFC-Future), (c) a model fitted for two correlated factors (CFC-I and CFC-F), and (d) a bifactor model. Results suggested that the addition of the two new items has strengthened the viability of a two factor solution of the CFCS-14. Results of linear regression models suggest that the CFC-F factor is redundant. Further studies using alcohol and mental health indicators are required to test this redundancy.

A influência da estimulação auditiva na pessoa em coma

Este estudo teve como finalidade compreender os efeitos da estimulação auditiva com uma voz desconhecida e familiar, na pessoa em coma nos parâmetros e curvas monitorizados em ambiente de cuidados intensivos. A revisão da literatura acerca da comunicação verbal em cuidados intensivos e consequente análise de conteúdo foi utilizada para construir a mensagem estímulo, que foi refinada e validada por um grupo de peritos. Esta mensagem é constituída por três partes: apresentação e orientação, informação e avaliação funcional e estimulação, e serviu como referência para a gravação das mensagens no estudo que se seguiu. Neste estudo também foi traduzida, adaptada para a realidade Portuguesa e convertida em linguagem CIPE® a Coma Recovery Scale – Revised, que deu origem ao Instrumento de Avaliação da Recuperação do Coma da Universidade de Aveiro (IARCUA), que foi sujeito a testes de fiabilidade.Os resultados da análise sugerem que o referido instrumento pode ser utilizado com fiabilidade, mesmo quando existem algumas flutuações no estado clínico das pessoas. A correlação dos scores das subescalas foi elevada e superior aos resultados apresentados para a escala original, indicando que esta escala é um instrumento indicado para a avaliação da função neuro-comportamental. O estudo da influência da estimulação auditiva foi realizado com uma amostra de 10 pessoas em coma internadas no Serviço de Cuidados Intensivos do Hospital de Santo António, no ano de 2009, com total autorização da Comissão de Ética do referido Hospital, sendo a selecção baseada numa avaliação preliminar através do instrumento referido e avaliação dos potenciais evocados auditivos do tronco cerebral. A pessoa significativa foi seleccionada através da aplicação de testes sociométricos. A todos os participantes foram dadas informações escritas acerca do estudo e foi concedido um período de tempo para reflexão e posterior decisão acerca da autorização ou não da aplicação do estudo. O tempo total de recolha de dados foi de 45 minutos distribuídos equitativamente por três períodos: pré-estimulação, estimulação e pós-estimulação. Os valores recolhidos foram os das curvas de ECG, das pressões arteriais e pletismografia de pulso e dos parâmetros de frequência cardíaca, pressão arterial sistólica, diastólica e média, temperatura corporal periférica e saturação parcial de oxigénio, utilizando-se o programa Datex-Ohmeda S/5 Collect para o efeito. A análise estatística e clínica dos dados, foi realizada por períodos de estimulação e fases da mensagem estímulo, aplicando-se testes estatísticos e uma análise baseada em critérios de relevância clínica.Os resultados demonstraram que na estimulação com uma voz desconhecida se verificou um aumento dos valores da frequência cardíaca, dos valores das pressões arteriais sistólicas, diastólicas e médias, na transição entre os períodos de préestimulação e estimulação e que estes valores tendem a normalizar quando termina a estimulação. Estas alterações foram corroboradas pela análise dos intervalos RR e da curva de pressões arteriais. Em relação à estimulação com uma voz familiar, as pessoas também reagiram aquando da estimulação com aumento dos valores da frequência cardíaca e dos valores das pressões arteriais sistólicas, diastólicas e médias. No entanto em alguns casos verificámos que os valores destes parâmetros continuaram a aumentar no período de pós-estimulação, o que revela que os utentes desenvolveram episódios de ansiedade de separação. Relativamente à temperatura corporal periférica e saturação parcial de oxigénio, em ambos os casos, não verificámos alterações aquando da estimulação. Relativamente às fases da mensagem estímulo, durante a estimulação com uma voz desconhecida, os participantes apresentaram uma maior variabilidade nos valores da frequência cardíaca, pressões arteriais sistólica, diastólica e média na fase de avaliação funcional e estimulação. Esta constatação é corroborada pela análise das curvas monitorizadas. Em relação à estimulação com uma voz familiar, além de reagirem nos mesmos parâmetros com maior intensidade na fase de avaliação funcional e estimulação, os participantes também reagiram de forma relevante na fase de apresentação e orientação. Este estudo contribui para a reflexão sobre a prática comunicacional com as pessoas inconscientes, no sentido de sensibilizar os enfermeiros e outros profissionais de saúde para a importância da comunicação nas unidades de cuidados intensivos e contribuir igualmente para a melhoria da qualidade de cuidados.

Impact of antenna choices on the reliability of mobile broadband transmission at millimetre - wave frequencies

This paper deals with the impact of several antenna chices on the radio transmission performance within a cellular Mobile Broaband System (MBS) currently under research in Europe. Several antenna types are considered, namely switchable-beam antennas and adaptive antennas employing a phased array approach.

Impact of antenna choices on the reliability of mobile broadband transmission at mm-wave frequencies

This paper deals with the impact of several antenna choices on the radio transmission performance within a cellular Mobile Broaband System (MBS) currently under research in Europe. Several antenna types are considered, namely switchble-beam antennas and adaptive antennas employing a phased array approach.