Rheometry for large-particulated fluids: analysis of the ball measuring system and comparison to debris flow rheometry

For large-particulated fluids encountered in natural debris flow, building materials, and sewage treatment, only a few rheometers exist that allow the determination of yield stress and viscosity. In the present investigation, we focus on the rheometrical analysis of the ball measuring system as a suitable tool to measure the rheology of particulated fluids up to grain sizes of 10mm. The ball measuring system consists of a sphere that is dragged through a sample volume of approximately 0.5l. Implemented in a standard rheometer, torques exerted on the sphere and the corresponding rotational speeds are recorded within a wide measuring range. In the second part of this investigation, six rheometric devices to determine flow curve and yield stress of fluids containing large particles with maximum grain sizes of 1 to 25mm are compared, considering both rheological data and application in practical use. The large-scale rheometer of Coussot and Piau, the building material learning viscometer of Wallevik and Gjorv, and the ball measuring system were used for the flow curve determination and a capillary rheometer, the inclined plane test, and the slump test were used for the yield stress determination. For different coarse and concentrated sediment-water mixtures, the flow curves and the yield stresses agree well, except for the capillary rheometer, which exhibits much larger yield stress values. Differences are also noted in the measuring range of the different devices, as well as for the required sample volume that is crucial for applicatio

Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges

Citation: Ruiz-Villanueva, V., Piégay, H., Gurnell, A. A., Marston, R. A., & Stoffel, M. (2016). Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges. Reviews of Geophysics. doi:10.1002/2015RG000514Large wood is an important physical component of woodland rivers and significantly influences river morphology. It is also a key component of stream ecosystems. However, large wood is also a source of risk for human activities as it may damage infrastructure, block river channels, and induce flooding. Therefore, the analysis and quantification of large wood and its mobility are crucial for understanding and managing wood in rivers. As the amount of large-wood-related studies by researchers, river managers, and stakeholders increases, documentation of commonly used and newly available techniques and their effectiveness has also become increasingly relevant as well. Important data and knowledge have been obtained from the application of very different approaches and have generated a significant body of valuable information representative of different environments. This review brings a comprehensive qualitative and quantitative summary of recent advances regarding the different processes involved in large wood dynamics in fluvial systems including wood budgeting and wood mechanics. First, some key definitions and concepts are introduced. Second, advances in quantifying large wood dynamics are reviewed; in particular, how measurements and modeling can be combined to integrate our understanding of how large wood moves through and is retained within river systems. Throughout, we present a quantitative and integrated meta-analysis compiled from different studies and geographical regions. Finally, we conclude by highlighting areas of particular research importance and their likely future trajectories, and we consider a particularly underresearched area so as to stress the future challenges for large wood research. ©2016. American Geophysical Union

Multi- and unisensory decoding of words and nonwords result in differential brain responses in dyslexic and nondyslexic adults

The present functional magnetic resonance imaging (fMRI) study was designed, in order to investigate the neural substrates involved in the audiovisual processing of disyllabic German words and pseudowords. Twelve dyslexic and 13 nondyslexic adults performed a lexical decision task while stimuli were presented unimodally (either aurally or visually) or bimodally (audiovisually simultaneously). The behavioral data collected during the experiment evidenced more accurate processing for bimodally than for unimodally presented stimuli irrespective of group. Words were processed faster than pseudowords. Notably, no group differences have been found for either accuracy or for reaction times. With respect to brain responses, nondyslexic compared to dyslexic adults elicited stronger hemodynamic responses in the leftward supramarginal gyrus (SMG), as well as in the right hemispheric superior temporal sulcus (STS). Furthermore, dyslexic compared to nondyslexic adults showed reduced responses to only aurally presented signals and enhanced hemodynamic responses to audiovisual, as well as visual stimulation in the right anterior insula. Our behavioral results evidence that the two groups easily identified the two-syllabic proper nouns that we provided them with. Our fMRI results indicate that dyslexics show less neuronal involvement of heteromodal and extrasylvian regions, namely, the STS, SMG, and insula when decoding phonological information. We posit that dyslexic adults evidence deficient functioning of word processing, which could possibly be attributed to deficits in phoneme to grapheme mapping. This problem may be caused by impaired audiovisual processing in multimodal areas

Climate change and mine reclamation in British Columbia

Since the mid-1900s, mining projects have progressively increased in disturbance area, leading to larger project footprints, and mines with longer lifespans or project durations. Some of the major mines operating in British Columbia began modern mining in the 1960s and are anticipated to be active for as long as eighty years. Local, regional, and global climates have already changed since the inception of such long-term projects, and will continue to change as mines approach closure. Historically, reclamation and closure plans for these mines have been designed with the assumption that abiotic environmental conditions and biological communities are static, but these assumptions are no longer considered valid, and there may be additional risks to mining operations and closure if the influence of a changing climate is not explicitly considered in reclamation planning. With the cumulative area of disturbance caused by major mines in British Columbia over 50,000 hectares, it is necessary to ensure that reclamation approaches, regulations, policies, and objectives consider the implications of climate change, and are directed by quantitative and ecologically relevant metrics of success. The BC Ministry of Energy, Mines and Low Carbon Innovation is in the process of developing reclamation guidance with a focus on the design of end land use and capability objectives based on pre-mining and reference conditions as well as future climatic scenarios, supporting the integration of climate adaptation into reclamation planning. This paper presents information on current tools and approaches available to support reclamation practitioners in designing for a changing climate. In addition, we discuss some of the key challenges—and potential solutions—that climate change introduces to reclamation practice, including, but not limited to, designing and planning prescriptions with shifting climates in mind as well as the inclusion of ecological and climate relevant metrics-of-success within ecosystem capability objectives for closure.Non UBCUnreviewedOthe

Reliability and statistical power analysis of cortical and subcortical FreeSurfer metrics in a large sample of healthy elderly

FreeSurfer is a tool to quantify cortical and subcortical brain anatomy automatically and noninvasively. Previous studies have reported reliability and statistical power analyses in relatively small samples or only selected one aspect of brain anatomy. Here, we investigated reliability and statistical power of cortical thickness, surface area, volume, and the volume of subcortical structures in a large sample (N = 189) of healthy elderly subjects (64 + years). Reliability (intraclass correlation coefficient) of cortical and subcortical parameters is generally high (cortical: ICCs > 0.87, subcortical: ICCs > 0.95). Surface-based smoothing increases reliability of cortical thickness maps, while it decreases reliability of cortical surface area and volume. Nevertheless, statistical power of all measures benefits from smoothing. When aiming to detect a 10% difference between groups, the number of subjects required to test effects with sufficient power over the entire cortex varies between cortical measures (cortical thickness: N = 39, surface area: N = 21, volume: N = 81; 10 mm smoothing, power = 0.8, α = 0.05). For subcortical regions this number is between 16 and 76 subjects, depending on the region. We also demonstrate the advantage of within-subject designs over between-subject designs. Furthermore, we publicly provide a tool that allows researchers to perform a priori power analysis and sensitivity analysis to help evaluate previously published studies and to design future studies with sufficient statistical power

The relevance of cortical lesions in patients with multiple sclerosis

BACKGROUND: Recent studies suggest that cortical lesions in multiple sclerosis (MS) substantially contribute to clinical disease severity. The present study aimed at investigating clinical, neuroanatomical, and cognitive correlates of these cortical lesions with a novel approach, i.e. by comparing two samples of relapsing-remitting multiple sclerosis (RRMS) patients, one group with and the other without cortical lesions. METHODS: High-resolution structural MRI was acquired from 42 RRMS patients and 43 controls (HC). The patient group was dichotomized based on the presence versus absence of DIR-hyperintense cortex-involving lesions, resulting in a cortical lesion group (CL, n = 32) and a non-cortical lesion group (nCL, n =10). Cognitive functioning was assessed in all participants with a comprehensive neuropsychological battery, covering mnestic, executive, and attentional functions. RESULTS: Highest densities of cortical lesions in the CL group were observed in the bilateral parahippocampal gyrus. Relative to HC, patients with cortical lesions - but not those without - showed significant global cortical thinning and mnestic deficits. The two patient groups did not differ from each other regarding demographic and basic disease characteristics such as EDSS scores. CONCLUSION: The appearance of cortical lesions in MS patients is associated with cortical thinning as well as mnestic deficits, which might be key characteristics of a 'cortically dominant' MS subtype