Dynamic attentional modulation of vision across space and time after right hemisphere stroke and in ageing

This article is available open access and is shared under a Creative Commons licence (http://creativecommons.org/licenses/by/3.0/). Copyright @ 2012 Elsevier Ltd.Introduction - Attention modulates the availability of sensory information to conscious perception. In particular, there is evidence of pathological, spatial constriction of the effective field of vision in patients with right hemisphere damage when a central task exhausts available attentional capacity. In the current study we first examined whether this constriction might be modulated across both space and time in right hemisphere stroke patients without neglect. Then we tested healthy elderly people to determine whether non-pathological ageing also leads to spatiotemporal impairments of vision under conditions of high attention load. Methods - Right hemisphere stroke patients completed a task at fixation while attempting to discriminate letters appearing in the periphery. Attentional load of the central task was modulated by increasing task difficulty. Peripheral letters appeared simultaneously with the central task or at different times (stimulus onset asynchronies, SOAs) after it. In a second study healthy elderly volunteers were tested with a modified version of this paradigm. Results - Under conditions of high attention load right hemisphere stroke patients have a reduced effective visual field, over a significantly extended ‘attentional blink’, worse for items presented to their left. In the second study, older participants were unable to discriminate otherwise salient items across the visual field (left or right) when their attention capacity was loaded on the central task. This deficit extended temporally, with peripheral discrimination ability not returning to normal for up to 450 msec. Conclusions - Dynamically tying up attention resources on a task at fixation can have profound effects in patient populations and in normal ageing. These results demonstrate that items can escape conscious detection across space and time, and can thereby impact significantly on visual perception in these groups.The European Commission, Brunel University and the Wellcome Trust

On the nature of rainfall intermittency as revealed by different metrics and sampling approaches

A general consensus on the concept of rainfall intermittency has not yet been reached, and intermittency is often attributed to different aspects of rainfall variability, including the fragmentation of the rainfall support (i.e., the alternation of wet and dry intervals) and the strength of intensity fluctuations and bursts. To explore these different aspects, a systematic analysis of rainfall intermittency properties in the time domain is presented using high-resolution (1-min) data recorded by a network of 201 tipping-bucket gauges covering the entire island of Sardinia (Italy). Four techniques, including spectral and scale invariance analysis, and computation of clustering and intermittency exponents, are applied to quantify the contribution of the alternation of dry and wet intervals (i.e., the rainfall support fragmentation), and the fluctuations of intensity amplitudes, to the overall intermittency of the rainfall process. The presence of three ranges of scaling regimes between 1 min to ~ 45 days is first demonstrated. In accordance with past studies, these regimes can be associated with a range dominated by single storms, a regime typical of frontal systems, and a transition zone. The positions of the breaking points separating these regimes change with the applied technique, suggesting that different tools explain different aspects of rainfall variability. Results indicate that the intermittency properties of rainfall support are fairly similar across the island, while metrics related to rainfall intensity fluctuations are characterized by significant spatial variability, implying that the local climate has a significant effect on the amplitude of rainfall fluctuations and minimal influence on the process of rainfall occurrence. In addition, for each analysis tool, evidence is shown of spatial patterns of the scaling exponents computed in the range of frontal systems. These patterns resemble the main pluviometric regimes observed on the island and, thus, can be associated with the corresponding synoptic circulation patterns. Last but not least, we demonstrate how the methodology adopted to sample the rainfall signal from the records of the tipping instants can significantly affect the intermittency analysis, especially at smaller scales. The multifractal scale invariance analysis is the only tool that is insensitive to the sampling approach. Results of this work may be useful to improve the calibration of stochastic algorithms used to downscale coarse rainfall predictions of climate and weather forecasting models, as well as the parameterization of intensity-duration-frequency curves, adopted for land planning and design of civil infrastructures

Meteorological forecasting for the European Southern observatory in Chile

The potential of numerical weather prediction to supply a useful support to flexible scheduling of astronomical observations is investigated. We applied some common tools presently used in numerical meteorology at regional scale in order to evaluate the ability to forecast local meteorological conditions (cloud cover, air temperature and wind speed) at Cerro Paranal and Cerro La Silla in Chile, where telescopes of ESO (the European Southern Observatory) are sited. The first part of this paper is devoted to evaluating the accuracy of analysis and forecasts of the ECMWF (European Center for Medium-range Weather Forecast) general circulation model for ESO needs. With this aim, analysis and 24-48 hour forecasts from ECMWF are systematically compared with observations at the ground meteorological stations of Paranal and La Silla, and with vertical profiles of radiosounding launches at Antofagasta and Quintero. The second part of this paper is aimed at improving the ECMWF forecasts at telescope sites by means of Kalman filter statistical post-processing and meteorological limited area modeling. Encouraging results are obtained concerning temperature, whereas much less satisfactory results are obtained for wind field and cloud cover. The most critical aspects of atmospheric dynamics affecting the local forecast are discussed within the limits of available information

Modelling a cell tower using SFM: automated detection of structural elements from skeleton extraction on a point cloud

The surveying and management of telecommunication towers poses a series of engineering challenges. Not only they must be regularly inspected for the purpose of checking for issues that require maintenance interventions, but they are often sub-let by their owners to communication companies, requiring a survey of the many (several thousand per company) installed appliances to check that they respect the established contracts. This requires a surveying methodology that is fast and possibly automated. Photogrammetric techniques using UAV-mounted cameras seem to offer a solution that is both suitable and economical. Our research team was asked to evaluate whether, from the information acquired by small drones it was possible to obtain geometric information on the structure, with what degree of accuracy and what level of detail. The workflow of this process is naturally articulated in three steps: the acquisition, the construction of the point cloud, and the extraction of geometries. The case study is a tower carrying antennas owned by several operators and placed in the industrial district of Cagliari. The article examines the problems found in modelling such structures using point clouds derived from the Structure-from-Motion technique, in order to obtain a model of nodes and beams suitable for the reconstruction of the structure's geometric elements, and possibly for a finite elements analysis or for populating GIS and BIM, either automatically or with minimal user intervention. In order to achieve this, we have used voxelization and skeleton extraction algorithms to obtain a 3D graph of the structure. The analysis of the results was carried out by varying the parameters relating to the voxel size, which defines the resolution, and the density of the points contained inside each voxel

Design and construction of earth dams.

This thesis deals with the design and construction of rolled-fill earth dams with the standard methods of practice, taking the Hirakud Dam as the basis. The field operations of the investigation to obtain observational information and to secure samples for the laboratory testing include observation of rain gauge and river gauge readings, taking river water samples, digging test pits, drilling grout holes, opening drifts, digging borrow pits and conducting detailed topographical surveys. Laboratory tests are conducted on the samples and the results are plotted in graphs. Rainfall and run-off statistics are plotted in graphs. Observational information of geology is plotted in log sheets and the field data of survey works is made use of for the preparation of the topographical maps. From the results of the investigation it is found that the Hirakud Dam has a firm foundation and there is sufficient quantity of material for the embankment at site. The annual rainfall is 47.49 inches yielding a run-off of 50 million sore feet over a catchment area of 32,200 square miles. The stability of the embankment is computed by the slip circle method and the seepage water from the flow net method. The dam is designed for 100 years with a reservoir capacity of 5.98 million acre feet at the maximum water level elevation 625 feet, the bed level being elevation 500 feet. The dead storage is 2.24 million acre feet corresponding to elevation 590 feet, and the maximum submerged area corresponding elevation 625 feet is 150,380 acres. The minimum factor of safety for the upstream slope is 1.68 and that for the downstream slope is 1.19. The seepage water is 0.264 cubic feet per lineal foot per year. The dam is to be constructed as per the design and the specifications. The compaction is attained by the mechanical effort at the optimum moisture content. The mechanical effort is influenced by the type of roller, its weight and the number of passes. Field control is affected by vigilant supervision, needle penetration, ring test and sand test. The construction is to be carried out according to a plan of seven stages. A comparison and contrast is drawn between the U.S.A. and India to bring out the inherent difficulties of construction operations of large dams in India. Importance is given to the sequence of the subject matter since no text book gives all the relevant portions as used in practice. Reference is given to the text books from which the formulas are taken so that a student who is interested in theory, derivation and explanation of the formulas may study the available literature. The procedures employed and the conclusions drawn are based on the experience, observation and the research study of the author both in India and the United States of America

Distributed hydrologic modeling of a sparsely monitored basin in Sardinia, Italy, through hydrometeorological downscaling

The water resources and hydrologic extremes in Mediterranean basins are heavily influenced by climate variability. Modeling these watersheds is difficult due to the complex nature of the hydrologic response as well as the sparseness of hydrometeorological observations. In this work, we present a strategy to calibrate a distributed hydrologic model, known as TIN-based Real-time Integrated Basin Simulator (tRIBS), in the Rio Mannu basin (RMB), a medium-sized watershed (472.5 km2) located in an agricultural area in Sardinia, Italy. In the RMB, precipitation, streamflow and meteorological data were collected within different historical periods and at diverse temporal resolutions. We designed two statistical tools for downscaling precipitation and potential evapotranspiration data to create the hourly, high-resolution forcing for the hydrologic model from daily records. Despite the presence of several sources of uncertainty in the observations and model parameterization, the use of the disaggregated forcing led to good calibration and validation performances for the tRIBS model, when daily discharge observations were available. The methodology proposed here can be also used to disaggregate outputs of climate models and conduct high-resolution hydrologic simulations with the goal of quantifying the impacts of climate change on water resources and the frequency of hydrologic extremes within medium-sized basins

Durum wheat productivity today and tomorrow: A review of influencing factors and climate change effects

Durum wheat is a crucial staple crop in many arid and semi-arid regions around the world, significantly contributing to local food security. This review paper aims to explore the current status of durum wheat productivity and the potential impacts of future climatic conditions on its cultivation. Various drivers and constraints affecting durum wheat yield are examined, including biotic and abiotic stressors, CO2 concentrations and agronomic practices. Drought and heat stress were identified as the primary yield limiting factors. Furthermore, the influence of climate change on durum wheat is evaluated, focusing on altered precipitation patterns, temperature extremes, and increased atmospheric CO2 levels. Most prominent quantification methods for climate change impact on yields are explored. The paper provides a summary of the current state of research, which reveals some contradictory results for future durum wheat yields. On the one hand, significant increases in productivity due to the fertilization effect of higher CO2 levels are predicted. On the other hand, the crop failures are foreseen as consequence of elevated heat and drought stress as part of climate change. Overall, this paper underlines the importance of understanding the complex interactions between climate change and durum wheat productivity and highlights the urgency to explore sustainable adaptation strategies to ensure future food security

Dietary Nitrate: Effects on the health of weaning pigs and Antimicrobial activity on seven probiotic Bifidobacterium spp. strains

The potential role of nitrite as an antimicrobial substance in the stomach may be of some importance in the ecology of the gastrointestinal tract and in host physiology. It has been shown that nitrite, under the acidic conditions of the stomach, may kill gut pathogens like Salmonella enteritidis, Escherichia coli, Salmonella typhimurium, and Yersinia enterocolitica, whereas acid alone has only a bacteriostatic effect. An in vivo study was conducted in order to assess the effects of dietary nitrate on microbiota and on the health of the gut (particularly in the stomach and small intestine). 96 weaning pigs were fed a diet containing high nitrate levels (15 mg and 150 mg) and then challenged with Salmonella enterica serovar typhimurium. Differences in composition of the gut microbiota were assessed by analysing samples from the pigs: To date analysis of 48 pigs has been completed.. Preliminary results demonstrated no effect on the population densities of microbial groups either from the challenge or from nitrate intake. However, increasing the time from challenge decreased either the counts of LAB in the stomach and jejunum or of clostridia in the stomach. Bifidobacteria also decreased in the stomach contents as nitrate supplementation increased. Supplementing the feedstuff with high dietary nitrate intake and then challenging with Salmonella did not affect the gastric pH or the degree of ulceration in the pigs. The synergistic bactericidal effects of pH, nitrite and thiocyanate on seven probiotic Bifidobacterium spp. strains were also investigated in an in vitro study. The results of the in vitro study demonstrated that an inhibitory effect exists on the seven probiotic bifidobacteria investigated with an exposure longer than 2 hours and pH values < 5.0. Addition of thiocyanate also increased the susceptibility of the tested strains. In this in vitro study, the most resistant strains at all conditions were B. animalis subsp. lactis Ra 18 and P32 and B. choerinum Su 877, Su 837 and Su 891

Investigating parameter transferability across models and events for a Semiarid Mediterranean Catchment

Physically based distributed hydrologic models (DHMs) simulate watershed processes by applying physical equations with a variety of simplifying assumptions and discretization approaches. These equations depend on parameters that, in most cases, can be measured and, theoretically, transferred across different types of DHMs. The aim of this study is to test the potential of parameter transferability in a real catchment for two contrasting periods among three DHMs of varying complexity. The case study chosen is a small Mediterranean catchment where the TIN-based Real-time Integrated Basin Simulator (tRIBS) model was previously calibrated and tested. The same datasets and parameters are used here to apply two other DHMs-the TOPographic Kinematic Approximation and Integration model (TOPKAPI) and CATchment HYdrology (CATHY) models. Model performance was measured against observed discharge at the basin outlet for a one-year period (1930) corresponding to average wetness conditions for the region, and for a much drier two-year period (1931-1932). The three DHMs performed comparably for the 1930 period but showed more significant differences (the CATHY model in particular for the dry period. In order to improve the performance of CATHY for this latter period, an hypothesis of soil crusting was introduced, assigning a lower saturated hydraulic conductivity to the top soil layer. It is concluded that, while the physical basis for the three models allowed transfer of parameters in a broad sense, transferability can break down when simulation conditions are greatly altered