Connectivity Restoration Research Articles

Assessing the effect of recovery programs for salmon (Salmo salar Linnaeus, 1758) at its Southern limit in Europe: application of segmented regression models to long-term data from the Ulla River

The abundance of Atlantic salmon in Europe has declined throughout its native range. One of the main causes is low marine survival, which has been mainly attributed to overexploitation at sea, but global warming, decreased zooplankton abundance in the North Atlantic and local changes in freshwater conditions have been also blamed. It has been also pointed out that Southern populations experience the greatest decline, but information from these areas in Europe is scarce, and also in Spain there are few long-term data series related with the salmon recovery programs carried out. In this paper, we analyse a long-term data set (1992-2018) provided by a fish-trap located in the Ulla River (Galicia, NW Spain), at the southern limit of the salmon distribution range. Salmon restocking programs have been carried out in this river from 2000, and although this management technique is widely accepted, it is necessary to document the fate of those individuals to evaluate their success. Segmented regression models (or piecewise regression) are applied here for the first time to estimate the value of the explanatory variable (the so called break-point) which can indicate the potential success of the recovery program in this river. Data analysis suggest a gradual population increase to the early 1990s, then remained relatively stable until 2007 and increased thereafter due to an increase in the number of wild salmon entering the river. An increase in the frequency of appearance of 3SW salmon since 2009 was detected, both including previous spawners and individuals at its first spawning migration after three consecutive winters at sea. Data suggest an increase in number of wild salmon entering the river. Restoring river connectivity has also helped to enhance this population. We finally consider that the increase in the number of returning salmons in the Ulla River achieved over this period is due not only to the good management and conservation practices related to salmon stocking, but also to the connectivity restoration in the river and to a higher marine survival rate.

Energy-Aware Connectivity Restoration Mechanism for Cyber-Physical Systems of Networked Sensors and Robots

This article focuses on cyber-physical systems involving a set of robots and sensors that are interconnected through wireless links. In applications that operate in harsh environments, wireless sensors and robot networks (WSRNs) may suffer simultaneous failures, which lead to partitioning the WSRN into unconnected subnetworks. The loss of connectivity often leads to degrade performance and inability to fulfill the application mission. To address this issue, several proposals have been made in the literature where node mobility is exploited to re-establish connectivity. These proposals, however, focus on minimizing the number of mobile nodes and the traveled distance cost while ignoring important factors, such as robot battery level, network lifetime, and environmental conditions, that may limit or hinder the whole recovery process. To overcome these limitations, we present a distributed node repositioning algorithm based on fuzzy logic. We evaluate our approach via extensive simulations and prototype experiments using Khepera IV robots. The results demonstrate superior performance to that of contemporary approaches.

Функциональные сети головного мозга: от восстановления связей до динамической интеграции

Функциональные сети головного мозга: от восстановления связей до динамической интеграции

Are national barrier inventories fit for stream connectivity restoration needs? A test of two catchments

AbstractCatchment‐scale river reconnection programmes require barrier inventories for restoration planning, yet barrier inventories are variable in extent and quality internationally. To test the degree to which barrier databases, in this case for England, are fit for purpose, we made a comparison of the national database (mostly originating from desk‐study) for two catchments, the Wear and the Tees, against detailed walkover surveys. We surveyed 701 km (32.8%) of stream length, stratified by stream order, altitude and subcatchment and recorded natural and artificial barriers. Only 22.7% of barriers identified in the walkover survey were present in the national database, including low‐head (<5 m) artificial structures (32.3% representation), artificial barriers ≥5 m (14.3% representation) and culverts (0% representation). About 18.9% of artificial barriers in the national database were found, during a field survey, to have been breached naturally. Mean densities of artificial barriers were 0.68 barriers km−1 and 0.45 barriers km−1 in the Wear and Tees, respectively, significantly higher than in the national database. Stream connectivity restoration in England may be hampered by the incomplete national barrier inventory; we recommend careful checks of barrier inventories as they are developed internationally.

Fault Node Detection and Connectivity Restoration with Mobile Relay Node in Wireless Sensor Networks

In Wireless Sensor Network (WSN), node failure is an imperative concern in a hostile environment. These node failures create disjoints in the network and leads to a network partitioning problem. It is important for the nodes to be alive and communicate with each other to check the network connectivity. Replacement of Mobile Relay Nodes (MRN) in the location of faulty nodes is the best solutions to reestablish the network connectivity. In this paper, a diverse mechanism is proposed to restore the network connectivity, in the first approach the gateway node takes the responsibility of identifying the faulty node and corresponding communication is to be given to MRN. In the second approach, the residual energy of each node will play a major role in determining the faulty node. Further, performance analysis was performed using a hardware setup with Node MCU and Raspberry Pi3, which proves that this work is mainly suitable for resource constrained devices and provides better results in restoring network connectivity. The performance was validated using experimental analysis and better performance was achieved.

A potential engineering solution to facilitate upstream movement of fish in mountain rivers with weirs: Southern Carpathians, the Azuga River

An important aspect in the restoration of longitudinal connectivity in rivers and streams is the implementation of fish migration systems at the upstream of the functional hydraulic structures (weirs, drop structures or river sills). The diversity of these existing structures as well as the different locations of these weirs within the river, watershed and riparian zone challenge the design engineers to find new holistic solutions for fish migration systems. The Azuga River study area requires a new synergistic fish migration design system. Being a mountain area, rapid increase in water level is quite frequent, especially after heavy or prolonged rainfalls and during spring snow melt. Therefore, it is necessary to design a specific system for fish migration to meet this locations requirements. Due to the characteristics in this location of the Azuga river, the classic fish migration systems would not be functional. The indigenous/mountain trout is considered as the target species in this paper. Although this is a good swimming species, the use of classical systems could, due to exhaustion, prevent and/or reduce the movement of fish upstream of the two weirs (also known as river sills). This new, comprehensive solution, presented in this paper includes: (i) the restoration and stabilization works of the right bank in the weir study area by using biotechnical measures and (ii) the upstream migration system itself - for supporting the migration of fish on the Azuga River.

Trade‐offs among road–stream crossing upgrade prioritizations based on connectivity restoration and erosion risk control

AbstractPrioritizing projects to improve cost‐effectiveness has become a common practice in natural resources management, especially in selecting sites for river restoration work. Previous studies for prioritizing road–stream crossing upgrade projects focused on either restoring river connectivity or reducing sedimentation, even though crossings can affect connectivity and sedimentation simultaneously. In this study, we simulated site selection to maximize the improvement of connectivity restoration and sedimentation reduction of three prioritization schemes targeting (a) river connectivity, (b) erosion risk, or (c) both objectives concurrently and compared the results. Furthermore, we examined the relationships between the cost‐effectiveness of prioritizations and watershed characteristics. We found significant differences among the effectiveness of prioritization objectives; thus, trade‐offs should be taken into consideration when prioritizing crossings. The incorporation of spatial interdependency among crossings and weighting objectives could significantly change the cost‐effectiveness. We also found that splitting the budget and using a portion to individually prioritize each objective could be more cost‐effective than using the whole budget to achieve concurrent objectives. Watershed characteristics like size and connectivity‐ and sedimentation‐related factors could be used to help identify effective management for both connectivity restoration and sedimentation control.

River-floodplain restoration and hydrological effects on GHG emissions: Biogeochemical dynamics in the parafluvial zone.

The parafluvial zone is frequently exposed to drying-rewetting cycles with critical consequences for the biogeochemistry of soil and sediment in river-floodplain landscapes. Upon restoration of the hydrological connectivity, substantial changes in biogeochemical processes are expected. The effects of water fluctuation on the magnitude of GHG emissions were investigated in the parafluvial zone of a restored river floodplain in Austria. Sediment composition, DOM quality and N2O, CO2, CH4 fluxes were quantified during distinct hydrological periods (intermittent, desiccation and post flood) and along a hydrological gradient. The hydrological gradient ranged from non-flooded plots in the floodplain soil (used as reference plots after restoration), to rarely-flooded and frequently flooded sediment plots in the parafluvial zone. Enhanced biogeochemical turnover rates were identified during the intermittent period, when N2O and CO2 emissions peaked. In particular, the frequently flooded plots showed significantly higher CO2 and CH4 emissions compared to non-flooded and rarely-flooded plots. This indicates a strong effect of water level fluctuation on GHG emissions, with higher emissions occurring during transitional stages of drying and rewetting. Strong positive relationships were found between individual GHG fluxes, suggesting a tight link between C and N cycles. Both the C and N cycles are dependent on similar substrate characteristics that are governed by the quality of the DOM pool. Interestingly, drier sediments in the rarely-flooded plots were also active areas for emissions. This highlights the importance to include dry phases and sites in the overall C and N emission estimates of riverine landscapes. From the restoration point of view, N2O emissions in the parafluvial zone did not differ significantly from the emissions in the reference plots, whereas CO2 and CH4 fluxes did. When making management decisions to restore connectivity, one needs to carefully consider the interplay between nutrient removal from water versus GHG emissions, to reach maximum environmental benefits.

An indicator system for assessing the impact of human activities on river structure

The impact of human activities on river systems has reached a state in which they can no longer be considered to be controlled only by natural processes of the Earth but also by anthropogenic forces in many regions of world. However, most approaches for assessing the impact still consider human activities to be an external influence in the study of feedback mechanisms between human activities and river systems, and they are usually complicated and specialized. This paper aims to develop an indicator system that includes the artificial water surface ratio (AWSR), artificial water surface density ratio (AWSDR), disruption of longitudinal connectivity ratio (DLCR), artificial river ratio (ARR), sinuosity of artificial cutoff (SAC), channelization ratio (CR), artificial levee ratio (ALR), road along river ratio (RARR), artificial sediment transport ratio (ASTR) and the integrated river structure impact index (IRSII) to quantitatively assess the impact of human activities on river structure by comparing natural and anthropogenic forces in a river system. The Nanliu River basin under the dramatic impact of human activities was selected to validate the indicator system. The case results showed the Nanliu River has become an anthropogenic river according to its high IRSII value (greater than 0.49). The artificialwater surface area and artificialsediment discharge were 2.96 (AWSR = 2.96) and 2.51 (ASTR = 2.51) times of the outcome of natural process. The river was dramatically blocked by human-made buildings (DLCR = 68.63) and artificialchannel accounts for 54.23% of total length of natural river (ARR = 0.54). Within the river basin, upper and lower sub-basins in areas with a higher economic level were more affected by human activities. Future management of the Nanliu River basin should focus on restoration of river connectivity, sand mining and irrigation issues. Unlike most previous assessment methods, the approach developed in this study is simple and readily comprehensible by the public and decision makers, cost-effective for long-term monitoring and not subject to the reference condition.

A Machine Learning Based Connectivity Restoration Strategy for Industrial IoTs

The connectivity restoration has significance for Industrial IoTs (IIoTs). If the connectivity is compromised, mobile data collectors can be deployed to restore the connectivity. The aggregation ratio, which is the proportion of data successfully delivered to the sink over all data, is considered as a crucial index. However, previous works only consider the travel distance, the load balance, the latency and the energy cost over the aggregation ratio. In this paper, a machine learning based connectivity restoration strategy CRrbf, that utilizes a Radial Basis Function Neural Network (RBFNN) along with an Unscented Kalman Filter (UKF), is proposed to maximize the aggregation ratio meanwhile reduce the energy cost. The theoretical analysis and simulation results indicate that CRrbf outperforms both distance based strategies and terrain based strategies in the aggregation ratio, the network latency and the network throughput. And the energy cost of CRrbf is less than that of distance based strategies.

Conservation Status and Challenges of the Atlantic Forest Birds of Paraguay

The Atlantic Forest, one of the most biodiverse biomes in the world, is also one of the most endangered. In Paraguay, its remnants are mostly fragmented and isolated. The Paraguay Biodiversity Corridor is an initiative that is being developed to generate and maintain connectivity of the main conservation areas. With the objective to analyze the bird richness and occurrence in each of the core areas of this corridor, we gathered published data, details of the management plans, and bird surveys recorded during 2015 and 2017 in these areas. In total, 557 bird species occur in the core areas of the Corridor, representing more than 80% of the birds of the country. San Rafael National Park and Mbaracayú Forest Nature Reserve are the richest areas, with 427 (70) and 408 (61) bird species (Atlantic forest endemics), respectively. These two areas also harbor more than 30 bird species of global conservation concern. Only 24% of the Corridor area is protected or sustainably managed, with only 10% under strict protection. The Corridor situated within this endangered biome encompasses some of the most important areas for bird conservation, but the situation of many of these areas is alarming as they are not protected or effectively managed to conserve their biodiversity. Restoration of connectivity, legal enforcement, and strengthening of authorities to combat deforestation on core areas, along with research focused on the impact contributed by human activities (selective logging, ecotoxicity exposure to agrochemicals) are key actions prioritized for the Upper Parana Atlantic forest (UPAF) Corridor.

A Novel Hybrid Optimization Scheme on Connectivity Restoration Processes for Large Scale Industrial Wireless Sensor and Actuator Networks

In the wireless sensor and actuator networks (WSANs) of industrial field monitoring, maintaining network connectivity with coverage perception plays a decisive role in many industrial process scenarios. The mobile actuator node is responsible for collecting data from the sensing nodes and performing diverse specific collaborative operation tasks. However, the failure of the nodes usually causes coverage vulnerability and partition of the network. Urgent and time-sensitive applications expect a minimum coverage loss to complete an instant connectivity restoration. This paper presents a hybrid coverage perception-based connectivity restoration algorithm, which is designed to restore network connectivity with minimal coverage area loss. The algorithm uses a backup node, which is selected nearby the critical node, to ensure a timely restoration when the critical node encounters failure. In the process of backup node migration, the optimal destination will be reselected to maintain the best network coverage after network connectivity recovery. The effectiveness of the proposed algorithm was verified by some simulation experiments.

Restoring Connectivity of Damaged Sensor Networks for Long-Term Survival in Hostile Environments

Connectivity restoration plays an important role in maintaining the long-term operation in wireless sensor networks (WSNs), especially, in environment-harsh cases. However, current solutions lack the ability to handle the second damages and the capacity of designing requirement-different connectivity approaches according to different needs. In this article, we propose a durability-based connectivity establishment (DBCE) scheme for disjoint segments of WSNs. This scheme includes three approaches regarding segment evaluation or segment selection: 1) a segment shape evaluation approach; 2) a region different connectivity approach; and 3) a data traffic transfer approach, for their respective objectives. The unique characteristics of this article are twofold. On the one hand, this is the first attempt to investigate segment shapes, which we demonstrate have great impact on the robustness of the network. On the other hand, distinguished from the existing networks with uniform connectivity rule, the network is divided into two parts and different connectivity sequences and connectivity approaches are designed according to disparate features and requirements of the network. The performance of DBCE is validated through extensive simulation experiments.

Management measures for the restoration of degraded ecosystems in order to increase biodiversity conservation in the Târnava Mică catchment area. Case study Bălăuşeri section, Târnava Mică River, Romania

The paper examines the possibilities of maintaining the longitudinal connectivity of the Târnava Mică R water courses in the context of hydrotechnical works execution. The main reason why the longitudinal connectivity needs to be analysed is that the transverse obstacles may prevent the migration of upstream fish species in order to reproduce the species concerned. In this way, the state of aquatic ecosystems is affected, which the Water Framework Directive aims to protect. The European Commission has launched two infringement procedures against Romania due to the destruction of unique habitats by not ensuring the longitudinal connectivity. The current methodology for the restoration of longitudinal connectivity provides that the longitudinal connectivity of a water body is ensured if there are no transverse obstacles on the river, or if these obstacles meet certain criteria which make the pressure given by them insignificant. In addition, longitudinal connectivity is an important criterion for defining the natural water bodies and heavily modified water bodies. The most widespread measure is the fish scale. The advantage is given by the lowest cost compared to the other variants and the fact that in many cases, it can be applied to the already existing constructions. However, there is a construction height limit for which it is recommended. In the National Administration of Romanian Waters methodology, the height limit is 15 m. The case study in this paper will also present the numerical modelling (1d) for a fish scale at Bălăuşeri on the Târnava Mică water stream from the Mureş River catchment area. The purpose of the case study of the longitudinal connectivity of the Târnava Mică River was to restore water connectivity to ensure favourable conditions for aquatic species dependent on riparian habitats.

Puma genomes from North and South America provide insights into the genomic consequences of inbreeding

Pumas are the most widely distributed felid in the Western Hemisphere. Increasingly, however, human persecution and habitat loss are isolating puma populations. To explore the genomic consequences of this isolation, we assemble a draft puma genome and a geographically broad panel of resequenced individuals. We estimate that the lineage leading to present-day North American pumas diverged from South American lineages 300–100 thousand years ago. We find signatures of close inbreeding in geographically isolated North American populations, but also that tracts of homozygosity are rarely shared among these populations, suggesting that assisted gene flow would restore local genetic diversity. The genome of a Florida panther descended from translocated Central American individuals has long tracts of homozygosity despite recent outbreeding. This suggests that while translocations may introduce diversity, sustaining diversity in small and isolated populations will require either repeated translocations or restoration of landscape connectivity. Our approach provides a framework for genome-wide analyses that can be applied to the management of similarly small and isolated populations.

Quasi-synchronization of heterogeneous nonlinear multi-agent systems subject to DOS attacks with impulsive effects

This paper is concerned with the quasi-synchronization of heterogeneous nonlinear multi-agent systems under DOS attacks with impulsive effects. The impulsive effects play either a positive role (impulsive control) or a negative role (impulsive disturbance) in the synchronization problem. The communication topology subjected to DOS attacks is considered, which destroys the communication channel among agents. A connectivity restoration mechanism is assumed. Only considering the positive impulsive effect, the controller does not need to operate constantly, which will reduce the controller resource consumption. Only taking the negative impulsive effect into account, a feedback controller is designed to counteract with the impulsive disturbance and DOS attacks. By using the concept of ‘average impulsive interval’, the criterion of quasi-synchronization with two impulsive effects is unified. Based on the impulsive theorem, the relationship among attack strength, control gain and average impulsive interval is analyzed. The results are illustrated by a simulation example.

The Prenylflavonoid ENDF1 Overrules Central Nervous System Growth Inhibitors and Facilitates Regeneration of DRG Neurons.

Restoration of neuronal connectivity after lesion of the central nervous system, such as spinal cord injury, is one of the biggest challenges in modern medicine. In particular, the accumulation of axon growth inhibitory factors at the site of injury constitutes a major obstacle to structural and thus functional repair. We previously investigated a group of prenylflavonoids derived from hops for their capacity to promote neuroregeneration. We identified a molecule called ENDF1 that was very potent to enhance regrowth and branching of neurites from dorsal root ganglion neurons in culture on growth promoting substrates. In the present study, we investigated ENDF1’s capacity to promote regeneration of rat dorsal root ganglion neurons in vitro in the presence of three main components of the extracellular matrix acting as axon growth inhibitors: Semaphorin 3A, Ephrin A4 and mixed chondroitin sulfate proteoglycans. We report that ENDF1 application significantly promoted the percentages of sensory neurons able to regrow their neurites regardless of the presence of those inhibitors, and this to an extent similar to the one obtained after NGF treatment. Moreover, ENDF1 strongly enhanced the total neurite length and the complexity of neurites extending from neurons challenged with axon growth inhibitors. Although the impact of NGF and ENDF1 on the regeneration of neurons was similar, the activity of ENDF1 was not mediated by signaling through the TrkA receptor, indicating that each molecule act through different signaling pathways. In addition, ENDF1 did not decrease the phosphorylation of cofilin, a downstream effector of the regeneration-associated RhoA/ROCK signaling pathway. Hence, ENDF1 is a potent pro-neuroregenerative factors that could help in identifying new efficient targets for regenerative therapies of the nervous system.

MR imaging central thalamic deep brain stimulation restored autistic-like social deficits in the rat

BackgroundSocial deficit is a core symptom in autism spectrum disorder (ASD). Although deep brain stimulation (DBS) has been proposed as a potential treatment for ASD, an ideal target nucleus is yet to be identified. DBS at the central thalamic nucleus (CTN) is known to alter corticostriatal and limbic circuits, and subsequently increase the exploratory motor behaviors, cognitive performance, and skill learning in neuropsychiatric and neurodegenerative disorders. ObjectiveWe first investigated the ability of CTN-DBS to selectively engage distinct brain circuits and compared the spatial distribution of evoked network activity and modulation. Second, we investigated whether CTN-DBS intervention improves social interaction in a valproic acid–exposed ASD rat offspring model. MethodsBrain regions activated through CTN-DBS by using a magnetic resonance (MR)-compatible neural probe, which is capable of inducing site-selective microstimulations during functional MRI (fMRI), were investigated. We then performed functional connectivity MRI, the three-chamber social interaction test, and Western blotting analyses to evaluate the therapeutic efficacy of CTN-DBS in an ASD rat offspring model. ResultsThe DBS-evoked fMRI results indicated that the activated brain regions were mainly located in cortical areas, limbic-related areas, and the dorsal striatum. We observed restoration of brain functional connectivity (FC) in corticostriatal and corticolimbic circuits after CTN-DBS, accompanied with increased social interaction and decreased social avoidance in the three-chamber social interaction test. The dopamine D2 receptor decreased significantly after CTN-DBS treatment, suggesting changes in synaptic plasticity and alterations in the brain circuits. ConclusionsApplying CTN-DBS to ASD rat offspring increased FC and altered the synaptic plasticity in the corticolimbic and the corticostriatal circuits. This suggests that CTN-DBS could be an effective treatment for improving the social behaviors of individuals with ASD.

Mitochondrial Dysfunction Leads to Cortical Under-Connectivity and Cognitive Impairment

Under-connectivity between cerebral cortical association areas may underlie cognitive deficits in neurodevelopmental disorders, including the 22q11.2 deletion syndrome (22q11DS). Using the LgDel 22q11DS mouse model, we assessed cellular, molecular, and developmental origins of under-connectivity and its consequences for cognitive function. Diminished 22q11 gene dosage reduces long-distance projections, limits axon and dendrite growth, and disrupts mitochondrial and synaptic integrity in layer 2/3 but not 5/6 projection neurons (PNs). Diminished dosage of Txnrd2, a 22q11 gene essential for reactive oxygen species catabolism in brain mitochondria, recapitulates these deficits in WT layer 2/3 PNs; Txnrd2 re-expression in LgDel layer 2/3 PNs rescues them. Anti-oxidants reverse LgDel- or Txnrd2-related layer 2/3 mitochondrial, circuit, and cognitive deficits. Accordingly, Txnrd2-mediated oxidative stress reduces layer 2/3 connectivity and impairs cognition in the context of 22q11 deletion. Anti-oxidant restoration of mitochondrial integrity, cortical connectivity, and cognitive behavior defines oxidative stress as a therapeutic target in neurodevelopmental disorders.

Science and Practice in NRM: Insights from connectivity restoration in the south west slopes of NSW

Interactions between landholders, practitioners and research scientists have greatly influenced landscape restoration activities in South‐eastern Australia. Vegetation connectivity projects undertaken by Holbrook Landcare Network in the Slopes to Summit (S2S) region of South‐eastern Australia have benefitted from the input of both scientists and practitioners. This paper explores what factors support an evidence‐informed restoration outcome, what constrains this and what we can learn from this case.