Tuning the Correlation Decay in the Resistance Fluctuations of Multi-Species Networks

A new network model is proposed to describe the $1/f^\alpha$ resistance noise in disordered materials for a wide range of $\alpha$ values ($0< \alpha < 2$). More precisely, we have considered the resistance fluctuations of a thin resistor with granular structure in different stationary states: from nearly equilibrium up to far from equilibrium conditions. This system has been modelled as a network made by different species of resistors, distinguished by their resistances, temperature coefficients and by the energies associated with thermally activated processes of breaking and recovery. The correlation behavior of the resistance fluctuations is analyzed as a function of the temperature and applied current, in both the frequency and time domains. For the noise frequency exponent, the model provides $0< \alpha < 1$ at low currents, in the Ohmic regime, with $\alpha$ decreasing inversely with the temperature, and $1< \alpha <2$ at high currents, in the non-Ohmic regime. Since the threshold current associated with the onset of nonlinearity also depends on the temperature, the proposed model qualitatively accounts for the complicate behavior of $\alpha$ versus temperature and current observed in many experiments. Correspondingly, in the time domain, the auto-correlation function of the resistance fluctuations displays a variety of behaviors which are tuned by the external conditions.Comment: 26 pages, 16 figures, Submitted to JSTAT - Special issue SigmaPhi200

Growing monitoring in sea cages: TS measurements issues

Hydroacoustic monitoring of fish growing in sea cages needs of an accurate relationship between fish size and target strength (TS) for every species of commercial interest. We discuss the conditions for TS measurement in near range conditions in sea cages for the case of the dorsal and ventral aspects of gilthead sea bream and bluefin tuna. Gilthead sea bream dorsal and ventral TS distributions, obtained with a split beam echosounder, are unimodal and the same results are derived for single beam data analysis when specific processing threshold criteria are applied. The expected linear relationship between the average TS and the logarithm of fish length is only found for the ventral case, being more accurate the uncompensated TS single beam analysis, probably due to near range errors. Bluefin tuna dorsal measurements performed in a fattening farm from February to July did not show a significant variation of TS distributions, and we propose a synchronized system of echosounder and video recordings, in order to relate target strength and orientation and size of specific tuna in the acoustic beam. Preliminary results indicate that only ventral TS values correlate properly with tuna size

Dual community assembly processes in dryland biocrust communities

1. Biocrusts are critical components of drylands where they regulate a wide range of ecosystem functions, however, their response to the world‐wide phenomenon of shrub encroachment and to livestock grazing, the most extensive land use in drylands, is not well studied. Grazing by livestock and increases in shrub cover could influence biocrust communities directly via trampling or shading, or indirectly, by altering biotic interactions amongst biocrust taxa. The extent of these changes in biocrust cover, diversity and composition are poorly known. 2. We used linear models and structural equation modelling to examine the direct effects of grazing and shrubs on biocrust community composition and the indirect effects mediated by changes in species interactions. 3. Biocrust richness and cover increased with increasing shrub cover at the site level. This pattern occurred despite the negative response we found (lower cover and richness) under shrub patches versus open areas, which was consistent irrespective of the grazing level. Functional diversity and evenness were similar between shrubs and open at low grazing intensity, but at high grazing functional diversity was greater in the open. Competition between biocrust species was an important driver of their community assembly irrespective of shrub cover, grazing intensity or patch type. Structural equation models showed that the effects of grazing and shrub cover on functional evenness, functional diversity and richness were controlled by biotic interactions within the shrub microsites. In the open, however, these effects were either direct or mediated by changes in cover. 4. Biocrust cover, species richness and functional diversity increase with shrub cover at the site scale, despite the negative effects at the microsite level. We demonstrate here that drivers of community assembly differ markedly at small spatial scales. Though biocrust communities were directly driven by environmental filtering in the open, biotic interactions played a fundamental role in their assembly when growing beneath shrubs.Both authors acknowledge support from the Hermon Slade Foundation Grant no. HSF13/1. S.S. was supported by the Spanish Government under the Ramón y Cajal contract (RYC-2016-20604)

Fracturas de radio distal. ¿Progresa el desplazamiento entre la segunda y la sexta semana?.

Las fracturas de radio distal son las más frecuentes en nuestra especialidad. El tratamiento conservador con inmovilización, basado en una serie de parámetros radiológicos, sigue siendo el más utilizado hoy en día. El objetivo de nuestro estudio ha sido evaluar el desplazamiento secundario de estas fracturas entre la segunda y sexta semana de evolución. Para ello hemos evaluado las fracturas de radio distal tratadas de forma conservadora en nuestro Servicio, durante el año 2016. De un total de 53 fracturas de muñeca tratadas de forma conservadora, un 49% de los casos presentó algún tipo de desplazamiento, si bien la mayor parte de estos tuvieron lugar antes de la segunda semana. Nuestros resultados fueron similares a los revisados en la literatura, en cuanto a datos demográficos y tasa de desplazamiento. Por lo que recomendamos intercalar algunos controles radiográficos semanales en aquellas fracturas que presenten desde el inicio algún parámetro de inestabilidad

Estudio de las lesiones en el judo

Judo is a martial art whose origins come from jujutsu, created in 1882 by the master Jigoro Kano, who proposed a method that was based on techniques that could be applied in real combat, as well as practiced with the partner without risk of injury .The objective of the present study is to assess the prevalence, type and distribution of the injuries suffered. Check whether sex or sports performance influences the appearance of injuries, determine which technique intervenes more frequently, assess whether they occur mostly in training or competition, and analyze how they act.This is a descriptive crosssectional observational study, in which four clubs were asked to participate, in which they had to answer an anonymous survey.Regarding the results, a total of 652 injuries were registered, in 63 men and 38 women. The most commonly injured body regions were the upper limbs 254 (38.95 %%). Contusions and sprains were the most frequent injuries and the most frequently associated technique was Seoi Nage. The number of injuries was higher during the competition if we take into account time. Most of the injuries (74.1%) were of slight characteristics, with a sports rest of less than a week and only 38.95% forced the judoka to interrupt the sport.After the study carried out, we can conclude that the results obtained are comparable to the bibliography, confirming the stated objective

Redefining ecosystem multifunctionality

Recent years have seen a surge of interest in ecosystem multifunctionality, a concept that has developed in the largely separate fields of biodiversity-ecosystem function and land management research. Here we discuss the merit of the multifunctionality concept, the advances it has delivered, the challenges it faces and solutions to these challenges. This involves the redefinition of multifunctionality as a property that exists at two levels: ecosystem function multifunctionality and ecosystem service multifunctionality. The framework presented provides a road map for the development of multifunctionality measures that are robust, quantifiable and relevant to both fundamental ecological science and ecosystem management

Wide Contact Structures for Low-Noise Nanochannel Devices Based on a Carbon Nanotube Network

We have developed a wide contact structure for low-noise nanochannel devices based on a carbon nanotube (CNT) network. This low-noise CNT network-based device has a dumbbell-shaped channel, which has wide CNT/electrode contact regions and, in effect, reduces the contact noise. We also performed a systematic analysis of structured CNT networks and established an empirical formula that can explain the noise behavior of arbitrary-shaped CNT network-based devices including the effect of contact regions and CNT alignment. Interestingly, our analysis revealed that the noise amplitude of aligned CNT networks behaves quite differently compared with that of randomly oriented CNT networks. Our results should be an important guideline in designing low-noise nanoscale devices based on a CNT network for various applications such as a highly sensitive low-noise sensor

Defining the functional traits that drive bacterial decomposer community productivity

Microbial communities are essential to a wide range of ecologically and industrially important processes. To control or predict how these communities function, we require a better understanding of the factors which influence microbial community productivity. Here, we combine functional resource use assays with a biodiversity–ecosystem functioning (BEF) experiment to determine whether the functional traits of constituent species can be used to predict community productivity. We quantified the abilities of 12 bacterial species to metabolise components of lignocellulose and then assembled these species into communities of varying diversity and composition to measure their productivity growing on lignocellulose, a complex natural substrate. A positive relationship between diversity and community productivity was caused by a selection effect whereby more diverse communities were more likely to contain two species that significantly improved community productivity. Analysis of functional traits revealed that the observed selection effect was primarily driven by the abilities of these species to degrade β-glucan. Our results indicate that by identifying the key functional traits underlying microbial community productivity we could improve industrial bioprocessing of complex natural substrates

A dominant dwarf shrub increases diversity of herbaceous plant communities in a Trans-Himalayan rangeland

Plant communities are structured by both competition and facilitation. The interplay between the two interactions can vary depending on environmental factors, nature of stress, and plant traits. But, whether positive or negative interactions dominate in regions of high biotic and abiotic stress remains unclear.We studied herbaceous plant communities associated with a dwarf shrub Caragana versicolor in semi-arid, high altitude Trans Himalayan rangelands of Spiti, India. We surveyed 120 pairs of plots (within and outside shrub canopies) across four watersheds differing in altitude, aspect and dominant herbivores. Herbaceous communities within shrub canopies had 25% higher species richness, but similar abundance when compared to communities outside the canopy, with the shrub edge having higher diversity than the center of the canopy. Grasses and erect forbs showed positive associations with the shrub, while prostrate plants occurred at much lower abundance within the canopy. Rare species showed stronger positive associations with Caragana than abundant species. Experimental removal of herbaceous vegetation from within shrub canopies led to 42% increase in flowering in Caragana, indicating a cost to the host shrubs. Our study indicates a robust pattern of a dwarf shrub facilitating local community diversity across this alpine landscape, increasing diversity at the plot level, facilitating rare species, and yet incurring a cost to hosts from the presence of herbaceous plants. Given these large influences of this shrub on vegetation of these high altitude rangelands, we suggest that the shrub microhabitat be explicitly considered in any analyses of ecosystem health in such rangelands

An excess of niche differences maximizes ecosystem functioning

Ecologists have long argued that higher functioning in diverse communities arises from the niche differences stabilizing species coexistence and from the fitness differences driving competitive dominance. However, rigorous tests are lacking. We couple field-parameterized models of competition between 10 annual plant species with a biodiversity-functioning experiment under two contrasting environmental conditions, to study how coexistence determinants link to biodiversity effects (selection and complementarity). We find that complementarity effects positively correlate with niche differences and selection effects differences correlate with fitness differences. However, niche differences also contribute to selection effects and fitness differences to complementarity effects. Despite this complexity, communities with an excess of niche differences (where niche differences exceeded those needed for coexistence) produce more biomass and have faster decomposition rates under drought, but do not take up nutrients more rapidly. We provide empirical evidence that the mechanisms determining coexistence correlate with those maximizing ecosystem functioning. It is unclear how biodiversity-ecosystem functioning and species coexistence mechanisms are linked. Here, Godoy and colleagues combine field-parameterised competition models with a BEF experiment to show that mechanisms leading to more stable species coexistence lead to greater productivity, but not necessarily to enhanced functions other than primary production