scholarly journals Technical note: Long-term memory loss of urban streams as a metric for catchment classification

2017 ◽  
Author(s):  
Dusan Jovanovic ◽  
Tijana Jovanovic ◽  
Alfonso Mejía ◽  
Jon Hathaway ◽  
Edoardo Daly

Abstract. Urbanisation has been associated with a reduction in the long-term correlation within a streamflow series, quantified by the Hurst exponent (H). This presents an opportunity to use the H exponent as an index for the classification of catchments on a scale from natural to urbanised conditions. However, before using the H exponent as a general index, the relationship between this exponent and level of urbanisation needs to be further examined and verified on catchments with different levels of imperviousness and from different climatic regions. In this study, the H exponent is estimated for 38 (deseasonalized) mean daily runoff time series, 22 from the USA and 16 from Australia, using the traditional rescaled-range statistic (R/S) and the more advanced multi-fractal detrended fluctuation analysis (MF-DFA). Relationships between H and catchment imperviousness, catchment size, annual rainfall and specific mean discharge were investigated. No clear relationship with catchment area was found, and a weak negative relationship with annual rainfall and specific mean streamflow was found only when the R/S method was used. Conversely, both methods showed decreasing values of H as catchment imperviousness increased. The H exponent decreased from around 1.0 for catchments in natural conditions to around 0.6 for highly urbanised catchments. Three significantly different ranges of H exponents were identified, allowing catchments to be parsed into groups with imperviousness lower than 5 % (natural), catchments with imperviousness between 5 and 15 % (peri-urban), and catchments with imperviousness larger than 15 % (urban). The H exponent thus represents a useful metric to quantitatively assess the impact of catchment imperviousness on streamflow regime.

2018 ◽  
Vol 22 (6) ◽  
pp. 3551-3559 ◽  
Author(s):  
Dusan Jovanovic ◽  
Tijana Jovanovic ◽  
Alfonso Mejía ◽  
Jon Hathaway ◽  
Edoardo Daly

Abstract. Urbanisation has been associated with a reduction in the long-term correlation within a streamflow series, quantified by the Hurst exponent (H). This presents an opportunity to use the H exponent as an index for the classification of catchments on a scale from natural to urbanised conditions. However, before using the H exponent as a general index, the relationship between this exponent and level of urbanisation needs to be further examined and verified on catchments with different levels of imperviousness and from different climatic regions. In this study, the H exponent is estimated for 38 (deseasonalised) mean daily runoff time series, 22 from the USA and 16 from Australia, using the traditional rescaled-range statistic (R∕S) and the more advanced multifractal detrended fluctuation analysis (MF-DFA). Relationships between H and catchment imperviousness, catchment size, annual rainfall and specific mean discharge were investigated. No clear relationship with catchment area was found, and a weak negative relationship with annual rainfall and specific mean streamflow was found only when the R∕S method was used. Conversely, both methods showed decreasing values of H as catchment imperviousness increased. The H exponent decreased from around 1.0 for catchments in natural conditions to around 0.6 for highly urbanised catchments. Three significantly different ranges of H exponents were identified, allowing catchments to be parsed into groups with imperviousness lower than 5 % (natural), catchments with imperviousness between 5 and 15 % (peri-urban) and catchments with imperviousness larger than 15 % (urban). The H exponent thus represents a useful metric to quantitatively assess the impact of catchment imperviousness on streamflow regime.


2016 ◽  
pp. 59-70
Author(s):  
Ninh Le Khuong ◽  
Nghiem Le Tan ◽  
Tho Huynh Huu

This paper aims to detect the impact of firm managers’ risk attitude on the relationship between the degree of output market uncertainty and firm investment. The findings show that there is a negative relationship between these two aspects for risk-averse managers while there is a positive relationship for risk-loving ones, since they have different utility functions. Based on the findings, this paper proposes recommendations for firm managers to take into account when making investment decisions and long-term business strategies as well.


2019 ◽  
Vol 98 (10) ◽  
pp. 1068-1073
Author(s):  
Oksana I. Shevchenko ◽  
D. V. Rusanova ◽  
O. L. Lakhman

Introduction. Issues of studying the central origins and development of оccupational pathology in the faces of flight personnel define a need for the application of neurophysiological and neuropsychological methods of research. Material and methods. The levels of constant potential (LCP), characteristics the somatosensory caused potentials (SSVP), neuropsychological features in 95 patients with оccupational neurosensory deafness (ONSD) and 35 cases in a group of comparison are studied. Methods of the statistical analysis with a definition of W-of criterion of Shapiro-Uilka, Mann-Whitney›s U-criterion, coefficient of correlation of Spirmen, the discriminant analysis are applied. Results. in ONSD at patients the quantity of cases with the increased values of average LCP were established to prevail significantly in comparison with those in patients of a group of comparison (39% and 13% respectively, р = 0.03), strengthening of neuropower exchange in right and left frontal, central, left central, left parietal, right temporal assignments, increase in duration of the latent period of N18, N30 components are registered (р < 0.05). The condition of the cognitive sphere was characterized by the easily expressed violations of functions of analytical and synthetic thinking, оral-aural memory, visual, long-term memory, reciprocal coordination, impressive speech. Correlation connection between the index of N13-N20 and indices characterizing a condition of long-term memory, reciprocal coordination, the expressional speech is established (rs=0.45; 0.28; 0.28 at р =0.008; 0.04; 0.03 respectively), an index the between hemispheres of the relations Fd-Fs and latency of P25 and N30 (rs = 0.53 and 0.29 at р =0.009; 0.02 respectively). Diagnostic signs of brain deficiency at patients with ONSD were indices of visual gnosis, reciprocal coordination, LCP in right central, central parietal assignments of a brain, duration of the latent period of N30, N18-N20 (F=9.14; 5.43; 6.08; 4.41 4.77; 4.34 respectively). Conclusions. Violations of power metabolism in the frontal and central and parietal and temporal assignments of a brain, a functional condition of the central carrying-out structures, disorganization of cognitive activity were established to be a consequence of the impact of aviation noise and the reason of brain deficiency.


2020 ◽  
Vol 11 ◽  
Author(s):  
Clémence Nineuil ◽  
Delphine Dellacherie ◽  
Séverine Samson

2002 ◽  
Vol 8 (3) ◽  
pp. 395-409 ◽  
Author(s):  
ALLEN E. THORNTON ◽  
NAFTALI RAZ ◽  
KAREN A. TUCKER

Long-term memory (LTM) is one of the diverse cognitive functions adversely affected by multiple sclerosis (MS). The LTM deficits have often been attributed to failure of retrieval, whereas encoding processes are presumed intact. However, support for this view comes primarily from studies in which encoding and retrieval operations were not investigated systematically. In the current study, we used an encoding specificity paradigm to examine the robustness of encoding in MS and to specifically evaluate the impact of the disease on contextual memory. We hypothesized that persons with MS would exhibit a selective impairment in retrieving items from LTM when required to generate new cue-target associations at encoding, but not when cues held a strong preexisting relationship to the targets. The findings supported the hypotheses. We conclude that the mnemonic deficits associated with MS affect both encoding and retrieval. Specifically, problems with binding of contextual information at encoding impair effective retrieval of memories. Nonetheless, access to these memories can be gained through preexisting associations organized in the semantic network. (JINS, 2002, 8, 395–409.)


Author(s):  
H. Gomes ◽  
A. R. Testera ◽  
N. B. Carvalho ◽  
M. F. Barciela ◽  
K. A. Remley

2011 ◽  
Vol 39 (2) ◽  
pp. 53-54
Author(s):  
Kevin Mccarty

2017 ◽  
Author(s):  
Blanca Marin Bosch ◽  
Aurélien Bringard ◽  
Maria Grazia Logrieco ◽  
Estelle Lauer ◽  
Nathalie Imobersteg ◽  
...  

AbstractRegular physical exercise enhances memory functions and neurogenesis in the hippocampus, an effect partially mediated by BDNF (Brain Derived Neurotrophic Factor). Acute exercise promotes the release of endocannabinoids (especially anandamide, AEA), which enhance BDNF release and improve hippocampal plasticity in rodents. How acute exercise affects BDNF and AEA levels and influences memory performance in humans remains to date unknown. Here we combined blood biomarkers, behavioral and fMRI measurements to assess the impact of acute physical exercise on associative memory and underlying neurophysiological mechanisms. For each participant, memory was tested after three conditions: rest, moderate or high exercise intensity. A long-term memory retest took place 3 months later. At both test and retest, memory performance increased after moderate but not high intensity exercise or rest. We also show that memory benefited from exercise-related increases in both AEA and BNDF levels: AEA boosted hippocampal activity during memory recall, while BDNF enhanced hippocampal memory representations and long-term performance.


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