scholarly journals Fishery-dependent and -independent data lead to consistent estimations of essential habitats

2016 ◽  
Vol 73 (9) ◽  
pp. 2302-2310 ◽  
Author(s):  
Maria Grazia Pennino ◽  
David Conesa ◽  
Antonio López-Quílez ◽  
Facundo Muñoz ◽  
Angel Fernández ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Survey Design ◽  
Scientific Information ◽  
Marine Species ◽  
Dependent Data ◽  
Independent Data ◽  
Elasmobranch Species ◽  
Spatio Temporal ◽  
Definition Of ◽  
Spatial Locations

Abstract Species mapping is an essential tool for conservation programmes as it provides clear pictures of the distribution of marine resources. However, in fishery ecology, the amount of objective scientific information is limited and data may not always be directly comparable. Information about the distribution of marine species can be derived from two main sources: fishery-independent data (scientific surveys at sea) and fishery-dependent data (collection and sampling by observers in commercial vessels). The aim of this paper is to compare whether these two different sources produce similar, complementary, or different results. We compare them in the specific context of identifying the Essential Fish Habitats of three elasmobranch species (S. canicula, G. melastomus, and E. spinax). Similarity and prediction statistics are used to compare the two different spatial patterns obtained by applying the same Bayesian spatio-temporal modelling approach in the two sources. Results showed that the spatial patterns obtained are similar, although differences are present. In particular, models based on fishery-dependent data are better able to identify temporal relationships between the probability of presence of the species and seasonal environmental variables. In contrast, fishery-independent data better discriminate spatial locations where a species is present or absent. Besides the spatial and temporal differences of the two datasets, the consistency of habitat results highlights the inclusion in each dataset of most of the environmental envelope of each species, both in time and space. Consequently, sampling data should be adapted to each species to reasonably cover their environmental envelope, and a combination of datasets will likely provide a better habitat estimation than using each dataset independently. These findings can be useful in helping fishery managers improve definition of survey design and analyses.

Spatio-temporal variability of zoobenthic communities in a tectonic lagoon (Lake Vouliagmeni, Attika, Greece)

2008 ◽  
Vol 88 (5) ◽  
pp. 873-881 ◽  
Author(s):  
Chariton Chintiroglou ◽  
Chryssanthi Antoniadou ◽  
Panagiotis Damianidis
Keyword(s):  
Multivariate Analyses ◽  
Benthic Communities ◽  
Marine Species ◽  
Trophic Group ◽  
Spatial And Temporal Scales ◽  
Mediterranean Lagoons ◽  
Deposit Feeders ◽  
Spatio Temporal ◽  
Lagoon Lake ◽  
Hard Substrata

Lake Vouliagmeni (Attica, Greece) is a lagoon of great scientific interest due to its endemic fauna, widely used for recreational activities. Understanding the dynamics of this peculiar ecosystem is essential for its conservation. An ecological survey of the benthic communities was carried out, in both spatial and temporal scales. Material was collected with SCUBA diving, by taking off samples from the principal habitats of the lagoon, i.e. meadows, soft and hard substrata. The identification of the collected 61,975 living specimens revealed the presence of 12 floral and 20 faunal species. Multivariate analyses separated the sampling sites according to the four different habitats of the lagoon, whereas no temporal patterns came up. Micrograzers were the dominant trophic group, followed by deposit feeders regardless of the habitat studied. Lake Vouliagmeni is among the less diverse Mediterranean lagoons, mostly due to its isolation from the sea that hinders the entrance of marine species.

scholarly journals Observational evidence in favor of scale-free evolution of sunspot groups

2018 ◽  
Vol 618 ◽  
pp. A183
Author(s):  
A. Shapoval ◽  
J.-L. Le Mouël ◽  
M. Shnirman ◽  
V. Courtillot
Keyword(s):  
Weibull Distribution ◽  
Power Law ◽  
Large Range ◽  
Scale Free ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Spatio Temporal ◽  
Computational Procedures ◽  
Definition Of ◽  
Sunspot Groups

Context. The hypothesis stating that the distribution of sunspot groups versus their size (φ) follows a power law in the domain of small groups was recently highlighted but rejected in favor of a Weibull distribution. Aims. In this paper we reconsider this question, and are led to the opposite conclusion. Methods. We have suggested a new definition of group size, namely the spatio-temporal “volume” (V) obtained as the sum of the observed daily areas instead of a single area associated with each group. Results. With this new definition of “size”, the width of the power-law part of the distribution φ ∼ 1/Vβ increases from 1.5 to 2.5 orders of magnitude. The exponent β is close to 1. The width of the power-law part and its exponent are stable with respect to the different catalogs and computational procedures used to reduce errors in the data. The observed distribution is not fit adequately by a Weibull distribution. Conclusions. The existence of a wide 1/V part of the distribution φ suggests that self-organized criticality underlies the generation and evolution of sunspot groups and that the mechanism responsible for it is scale-free over a large range of sizes.

scholarly journals Spatial pattern evaluation of a calibrated national hydrological model – a remote sensing based diagnostic approach

2017 ◽  
Author(s):  
Gorka Mendiguren ◽  
Julian Koch ◽  
Simon Stisen
Keyword(s):  
Remote Sensing ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Hydrological Model ◽  
Remote Sensing Data ◽  
Driving Mechanism ◽  
Distributed Hydrological Model ◽  
Eof Analysis ◽  
Sensing Data ◽  
Spatio Temporal

Abstract. Distributed hydrological models are traditionally evaluated against discharge stations, emphasizing the temporal and neglecting the spatial component of a model. The present study widens the traditional paradigm by highlighting spatial patterns of evapotranspiration (ET), a key variable at the land-atmosphere interface, obtained from two different approaches at the national scale of Denmark. The first approach is based on a national water resources model (DK-model), using the MIKE-SHE model code, and the second approach utilizes a two source energy balance model (TSEB) driven mainly by satellite remote sensing data. The main hypothesis of the study is that while both approaches are essentially estimates, the spatial patterns of the remote sensing based approach are explicitly driven by observed land surface temperature and therefore represent the most direct spatial pattern information of ET; enabling its use for distributed hydrological model evaluation. Ideally the hydrological model simulation and remote sensing based approach should present similar spatial patterns and driving mechanism of ET. However, the spatial comparison showed that the differences are significant and indicating insufficient spatial pattern performance of the hydrological model. The differences in spatial patterns can partly be explained by the fact that the hydrological model is configured to run in 6 domains that are calibrated independently from each other, as it is often the case for large scale multi-basin calibrations. Furthermore, the model incorporates predefined temporal dynamics of Leaf Area Index (LAI), root depth (RD) and Crop coefficient (Kc) for each land cover type. This zonal approach of model parametrization ignores the spatio-temporal complexity of the natural system. To overcome this limitation, the study features a modified version of the DK-Model in which LAI, RD, and KC are empirically derived using remote sensing data and detailed soil property maps in order to generate a higher degree of spatio-temporal variability and spatial consistency between the 6 domains. The effects of these changes are analyzed by using the empirical orthogonal functions (EOF) analysis to evaluate spatial patterns. The EOF-analysis shows that including remote sensing derived LAI, RD and KC in the distributed hydrological model adds spatial features found in the spatial pattern of remote sensing based ET.

scholarly journals Learning from satellite observations: increased understanding of catchment processes through stepwise model improvement

2021 ◽  
Vol 25 (2) ◽  
pp. 957-982 ◽  
Author(s):  
Petra Hulsman ◽  
Hubert H. G. Savenije ◽  
Markus Hrachowitz
Keyword(s):  
Time Series ◽  
Spatial Patterns ◽  
Temporal Dynamics ◽  
Water Storage ◽  
Remotely Sensed ◽  
Satellite Observations ◽  
Model Structure ◽  
Total Water ◽  
Groundwater Reservoir ◽  
Spatio Temporal

Abstract. Satellite observations can provide valuable information for a better understanding of hydrological processes and thus serve as valuable tools for model structure development and improvement. While model calibration and evaluation have in recent years started to make increasing use of spatial, mostly remotely sensed information, model structural development largely remains to rely on discharge observations at basin outlets only. Due to the ill-posed inverse nature and the related equifinality issues in the modelling process, this frequently results in poor representations of the spatio-temporal heterogeneity of system-internal processes, in particular for large river basins. The objective of this study is thus to explore the value of remotely sensed, gridded data to improve our understanding of the processes underlying this heterogeneity and, as a consequence, their quantitative representation in models through a stepwise adaptation of model structures and parameters. For this purpose, a distributed, process-based hydrological model was developed for the study region, the poorly gauged Luangwa River basin. As a first step, this benchmark model was calibrated to discharge data only and, in a post-calibration evaluation procedure, tested for its ability to simultaneously reproduce (1) the basin-average temporal dynamics of remotely sensed evaporation and total water storage anomalies and (2) their temporally averaged spatial patterns. This allowed for the diagnosis of model structural deficiencies in reproducing these temporal dynamics and spatial patterns. Subsequently, the model structure was adapted in a stepwise procedure, testing five additional alternative process hypotheses that could potentially better describe the observed dynamics and pattern. These included, on the one hand, the addition and testing of alternative formulations of groundwater upwelling into wetlands as a function of the water storage and, on the other hand, alternative spatial discretizations of the groundwater reservoir. Similar to the benchmark, each alternative model hypothesis was, in a next step, calibrated to discharge only and tested against its ability to reproduce the observed spatio-temporal pattern in evaporation and water storage anomalies. In a final step, all models were re-calibrated to discharge, evaporation and water storage anomalies simultaneously. The results indicated that (1) the benchmark model (Model A) could reproduce the time series of observed discharge, basin-average evaporation and total water storage reasonably well. In contrast, it poorly represented time series of evaporation in wetland-dominated areas as well as the spatial pattern of evaporation and total water storage. (2) Stepwise adjustment of the model structure (Models B–F) suggested that Model F, allowing for upwelling groundwater from a distributed representation of the groundwater reservoir and (3) simultaneously calibrating the model with respect to multiple variables, i.e. discharge, evaporation and total water storage anomalies, provided the best representation of all these variables with respect to their temporal dynamics and spatial patterns, except for the basin-average temporal dynamics in the total water storage anomalies. It was shown that satellite-based evaporation and total water storage anomaly data are not only valuable for multi-criteria calibration, but can also play an important role in improving our understanding of hydrological processes through the diagnosis of model deficiencies and stepwise model structural improvement.

African business leadership: Perspectives from aspiring young leaders

2021 ◽  
Vol 19 ◽  
Author(s):  
Matete Lerutla ◽  
Renier Steyn
Keyword(s):  
Content Analysis ◽  
Empirical Research ◽  
Research Study ◽  
Survey Design ◽  
Cross Sectional Survey ◽  
Business Leadership ◽  
Cross Sectional ◽  
Directed Content Analysis ◽  
Sub Saharan ◽  
Definition Of

Orientation: Although a lot is written about leadership in Africa, little empirical research has been conducted and published in prominent academic journals, which comprehensively and specifically define the concept of African business leadership.Research purpose: The goal of the research study was to define the African business leadership comprehensively, tapping into the views of young leaders and making a contribution to the discourse and literature on leadership in Africa.Motivation for the study: Whilst business leadership practices are deemed to be universal by some, others argue that the matter is geographically specific. The latter view is supported by those interested in decolonisation and Africanisation. Although politically inspired and philosophically embedded definitions of African leadership are readily available, definitions stemming from empirical processes seem to be absent.Research approach, design and method: This research focuses on the sub-Saharan region, which accounts for the greater part of the African continent. A total of 121 adult students, representing 14 sub-Saharan countries, participated in this study. The participants were part of the Young African Leaders Initiative, a leadership development programme facilitated by the University of South Africa. A cross sectional survey design was used, as part of which open-ended questions were posed to the young leaders. Summative content analysis (Cohort 1) was uses to identify elements central to African leadership, and directed content analysis was then framed based on inter-relational plots, which include all these identified themes.Method: A cross-sectional survey design was used, as part of which open-ended questions were posed to the young leaders. Summative content analysis (Cohort 1) was used to identify elements central to African business leadership, and directed content analysis (Cohort 2) was applied to verify the themes. A definition of African business leadership was then framed based on inter-relational plots, which include all these identified themes.Main findings: Eight elements typical of African business leadership were identified and, following an analysis of inter-relational plots, a definition incorporating the participants’ inputs was crafted. African business leadership is seen as unique to leaders on the continent (Afrocentric), as an act of service to the community (Ubuntu), operating in challenging and resource-deprived environments (because of the legacy of colonialism) and providing hope for creating a better future. African business leadership is further seen as being dominated by those in positions of (political) authority, who engage in entrepreneurial activities, and yet as still requiring development because many leaders are corrupt (brokenness), which seems to be legitimised by post-colonial sentiments (Afro-centric).Contribution: The research study presents a multidimensional perspective on defining African business leadership, reiterating the admirable community orientation, but also the skill gaps, and therefore, the need for improvement.Practical Implications: The definition crafted from the research study provides a compelling conceptualisation of a phenomenon that is often described from only a philosophical or political perspective. This empirical research study contributes to the leadership debate by providing a multidimensional and comprehensive definition of African business leadership, incorporating both the positive and negative elements.

Manifold Visual Working Memory

2020 ◽  
pp. 311-332
Author(s):  
Nicole Hakim ◽  
Edward Awh ◽  
Edward K. Vogel
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Neural Activity ◽  
Long Term Memory ◽  
Term Memory ◽  
Memory Representations ◽  
Latent Representations ◽  
Definition Of ◽  
Spatial Locations

Visual working memory allows us to maintain information in mind for use in ongoing cognition. Research on visual working memory often characterizes it within the context of its interaction with long-term memory (LTM). These embedded-processes models describe memory representations as existing in three potential states: inactivated LTM, including all representations stored in LTM; activated LTM, latent representations that can quickly be brought into an active state due to contextual priming or recency; and the focus of attention, an active but sharply limited state in which only a small number of items can be represented simultaneously. This chapter extends the embedded-processes framework of working memory. It proposes that working memory should be defined operationally based on neural activity. By defining working memory in this way, the important theoretical distinction between working memory and LTM is maintained, while still acknowledging that they operate together. It is additionally proposed that active working memory should be further subdivided into at least two subcomponent processes that index item-based storage and currently prioritized spatial locations. This fractionation of working memory is based on recent research that has found that the maintenance of information distinctly relies on item-based representations as well as prioritization of spatial locations. It is hoped that this updated framework of the definition of working memory within the embedded-processes model provides further traction for understanding how we maintain information in mind.

A Spatio-Temporal Cache Replacement Policy for Location Dependent Data in Mobile Environments

2010 ◽  
Vol 6 (3) ◽  
pp. 31-48 ◽  
Author(s):  
Mary Magdalene Jane.F ◽  
R. Nadarajan ◽  
Maytham Safar
Keyword(s):  
Data Access ◽  
Data Availability ◽  
Replacement Policy ◽  
Dependent Data ◽  
Access Time ◽  
Cache Replacement ◽  
Cache Replacement Policy ◽  
Active Sets ◽  
Mobile Clients ◽  
Spatio Temporal

Data caching in mobile clients is an important technique to enhance data availability and improve data access time. Due to cache size limitations, cache replacement policies are used to find a suitable subset of items for eviction from the cache. In this paper, the authors study the issues of cache replacement for location-dependent data under a geometric location model and propose a new cache replacement policy RAAR (Re-entry probability, Area of valid scope, Age, Rate of Access) by taking into account the spatial and temporal parameters. Mobile queries experience a popularity drift where the item loses its popularity after the user exhausts the corresponding service, thus calling for a scenario in which once popular documents quickly become cold (small active sets). The experimental evaluations using synthetic datasets for regular and small active sets show that this replacement policy is effective in improving the system performance in terms of the cache hit ratio of mobile clients.

The best available science for the management of anadromous salmonids in the Columbia River Basin

2002 ◽  
Vol 59 (12) ◽  
pp. 1952-1959 ◽  
Author(s):  
Gustavo A Bisbal
Keyword(s):  
River Basin ◽  
Scientific Information ◽  
Columbia River ◽  
Columbia River Basin ◽  
Explicit Definition ◽  
Refinement Process ◽  
Best Available Science ◽  
Definition Of

Reference to the "best available science" is popular among administrators and scientists responsible for the management of anadromous salmonids in the Columbia River Basin. Regional recovery documents explicitly call for the consideration of the best available science during the formulation of policies, but they fail to elaborate on what this phrase means. In the absence of such clarification, the definition of what counts as science, how to recognize the best science from the rest, and a determination of how much of it is available invites a wide array of interpretations. Two possible remedies are proposed to alleviate this ambiguity. The first is to leave this phrase intact, but also to append an explicit definition of what each term means. This should establish sideboards for what is acceptable when compiling scientific information. The second remedy is to discontinue the impulsive use of the phrase best available science and select alternative language that more accurately reflects legislative intent. This refinement process will naturally result in other phrases tailored to the specific preferences and requirements of each situation. A decision to accept any of these alternatives may profoundly affect how science influences the management of anadromous salmonids in the Columbia River Basin.

scholarly journals A MULTIMEDIA MODEL BASED ON STRUCTURED MEDIA AND SUB-ELEMENTS FOR COMPLEX MULTIMEDIA AUTHORING AND PRESENTATION

2002 ◽  
Vol 12 (05) ◽  
pp. 473-500 ◽  
Author(s):  
TRAN_THUONG TIEN ◽  
CECILE ROISIN
Keyword(s):  
New Media ◽  
Significant Advance ◽  
Extended Model ◽  
Multimedia Model ◽  
Multimedia Authoring ◽  
Fine Grained ◽  
Model Based ◽  
Structured Media ◽  
Spatio Temporal ◽  
Definition Of

Declarative definition of multimedia presentation such as provided by SMIL standard can be considered as the most significant advance in the multimedia integration domain. However, the requirements of a model that could express richer scenarios for presentations are always a challenge. The work presented here proposes an extended model based on the concept of structured media and sub-elements that allows a finer granularity and a more semantic specification of significant events and locations inside media fragments. The new media fragments can be composed in multimedia scenarios through the specification of temporal, spatial and spatio-temporal relations. Moreover, we propose an abstract animation model that can be combined with the intra-media temporal structuration to specify animation effects in a flexible, not redundant and easy to maintain way. The underlying model is the Madeus model that is a flexible model based on the structural, interval, region and relative constraints. This paper describes the sub-element and the abstract animation models and shows how they are implemented in the Madeus multimedia framework. A complete schema of the video authoring tool based on this model is also specified. Thanks to that, the fine-grained authoring of multimedia scenarios with video media can be done in an easy and effective way.

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