Permanent gullies are common features in many landscapes and quite often they represent the dominant soil erosion process. Once a gully has initiated, field evidence shows that gully channel ...formation and headcut migration rapidly occur. In order to prevent the undesired effects of gullying, there is a need to predict the places where new gullies might initiate. From detailed field measurements, studies have demonstrated strong inverse relationships between slope gradient of the soil surface (S) and drainage area (A) at the point of channel initiation across catchments in different climatic and morphological environments. Such slope–area thresholds (S–A) can be used to predict locations in the landscape where gullies might initiate. However, acquiring S–A requires detailed field investigations and accurate high resolution digital elevation data, which are usually difficult to acquire. To circumvent this issue, we propose a two-step method that uses published S–A thresholds and a logistic regression analysis (LR). S–A thresholds from the literature are used as proxies of field measurement. The method is calibrated and validated on a watershed, close to the town of Algiers, northern Algeria, where gully erosion affects most of the slopes. The gullies extend up to several kilometres in length and cover 16% of the study area. First we reconstruct the initiation areas of the existing gullies by applying S–A thresholds for similar environments. Then, using the initiation area map as the dependent variable with combinations of topographic and lithological predictor variables, we calibrate several LR models. It provides relevant results in terms of statistical reliability, prediction performance, and geomorphological significance. This method using S–A thresholds with data-driven assessment methods like LR proves to be efficient when applied to common spatial data and establishes a methodology that will allow similar studies to be undertaken elsewhere.
•A two-step method to predict susceptibility to gully initiation in data-poor regions•Published slope-area thresholds (S–A) are used as field measurement proxies•Initiation areas of the current gullies are reconstructed from the S–A thresholds•Logistic regression analysis to predict the spatial occurrence of initiation areas•Susceptibility models are geomorphologically sound
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In many landslide-prone regions, data on landslide characteristics remain poor or inexistent. This is also the case for the Rwenzori Mountains, located on the border of Uganda and the DR Congo. ...There, landslides frequently occur and cause fatalities and substantial damage to private property and infrastructure. In this paper, we present the results of a field inventory performed in three representative study areas covering 114 km2. A total of 371 landslides were mapped and analyzed for their geomorphological characteristics and their spatial distribution. The average landslide areas varied from less than 0.3 ha in the gneiss-dominated highlands to >1 ha in the rift alluvium of the lowlands. Large landslides (>1.5 ha) are well represented while smaller landslides (<1.5 ha) are underrepresented. The degrees of completeness of the field inventories are comparable to those of similar historical landslide inventories. The diversity of potential mass movements in the Rwenzori is large and depends on the dominant lithological and topographic conditions. A dominance of shallow translational soil slides in gneiss and of deep rotational soil slides in the rift alluvium is observed. Slope angle is the main controlling topographic factor for landslides with the highest landslide concentrations for slope angles above 25–30° in the highlands and 10–15° in the lowlands. The undercutting of slopes by rivers and excavations for construction are important preparatory factors. Rainfall-triggered landslides are the most common in the area, however in the zones of influence of the last two major earthquakes (1966: Mw = 6.6 and 1994: Mw = 6.2), 12 co-seismic landslides were also observed.
•A first systematic landslide inventory for the Rwenzori Mountains is presented.•Slope steepness and lithology are key controlling factors for landslides.•Most landslides are rainfall-triggered but co-seismic slides also occur.•Preparatory factors for landslides are often human-induced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
Spatio-temporal inventory of natural hazards is a challenging task especially in rural or remote areas in the Global South where data collection at regional scale is difficult. Citizen ...science, i.e. involvement of no-experts in collecting information and co-creation of knowledge with experts to solve societal and environmental problems, has been suggested as a viable approach to tackle this bottleneck, although the reliability of the resulting data is often questioned. Here we analyse an inventory of geo-hydrological hazards (landslides and floods) reported by a network of citizen scientists in the Rwenzori Mountains, Uganda, established since 2017. We assess the precision, sensitivity and potential biases affecting this citizen science-based hazard inventory. We compare the citizen science-based records with two independent inventories, one collected through systematic fieldwork and another by PlanetScope satellite imagery mapping for the period between May 2019 and May 2020. The precision of the geo-observer data is higher (99% and 100% for landslides and floods, respectively) than that of satellite-based data (44% and 84%, respectively) indicative of fewer false positives in the former inventory. Also, citizen scientists have a higher sensitivity in reporting landslides (51%) compared to satellite imagery (39%) in addition to being able to report the events a few days after the occurrence. In contrast, the sensitivity of satellite-based flood detection is higher than that of citizen scientists. The probability of landslide events being reported by citizen scientists depends both on citizen scientists and hazard specific features (impact, landslide-citizen scientist home distance, landslide-road access distance and altitude). Although satellite imagery mapping could result in a spatially less biased inventory, small landslides are often missed while shallow ones can easily be confused with freshly cleared vegetation. Also, in a dominantly cloudy environment, it can take several days to weeks before a cloud-free satellite image can be obtained. In summary, the typically rapid response time of citizen scientists can result in faster information with high reliability at the risk of missing out almost half of the occurrences. Citizen scientists also provide more data on impact and type of land use, something difficult to achieve using satellite imagery. Working with farmers at village level as citizen scientists can facilitate covering a wider geographical area while reducing the area monitored by each citizen scientist at the same time.
Determining rainfall thresholds for landsliding is crucial in landslide hazard evaluation and early warning system development, yet challenging in data-scarce regions. Using freely available ...satellite rainfall data in a reproducible automated procedure, the bootstrap-based frequentist threshold approach, coupling antecedent rainfall (AR) and landslide susceptibility data as proposed by Monsieurs et al., has proved to provide a physically meaningful regional AR threshold equation in the western branch of the East African Rift. However, previous studies could only rely on global- and continental-scale rainfall and susceptibility data. Here, we use newly available regional-scale susceptibility data to test the robustness of the method to different data configurations. This leads us to improve the threshold method through using stratified data selection to better exploit the data distribution over the whole range of susceptibility. In addition, we discuss the effect of outliers in small data sets on the estimation of parameter uncertainties and the interest of not using the bootstrap technique in such cases. Thus improved, the method effectiveness shows strongly reduced sensitivity to the used susceptibility data and is satisfyingly validated by new landslide occurrences in the East African Rift, therefore successfully passing first transferability tests.
Abstract
Brain hypoxia can occur after non-traumatic subarachnoid hemorrhage (SAH), even when levels of intracranial pressure (ICP) remain normal. Brain tissue oxygenation (PbtO
2
) can be measured ...as a part of a neurological multimodal neuromonitoring. Low PbtO
2
has been associated with poor neurologic recovery. There is scarce data on the impact of PbtO
2
guided-therapy on patients’ outcome. This single-center cohort study (June 2014–March 2020) included all patients admitted to the ICU after SAH who required multimodal monitoring. Patients with imminent brain death were excluded. Our primary goal was to assess the impact of PbtO
2
-guided therapy on neurological outcome. Secondary outcome included the association of brain hypoxia with outcome. Of the 163 patients that underwent ICP monitoring, 62 were monitored with PbtO
2
and 54 (87%) had at least one episode of brain hypoxia. In patients that required treatment based on neuromonitoring strategies, PbtO
2
-guided therapy (OR 0.33 CI 95% 0.12–0.89) compared to ICP-guided therapy had a protective effect on neurological outcome at 6 months. In this cohort of SAH patients, PbtO
2
-guided therapy might be associated with improved long-term neurological outcome, only when compared to ICP-guided therapy.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Pathophysiology of brain dysfunction due to sepsis remains poorly understood. Cerebral microcirculatory alterations may play a role; however, experimental data are scarce. This study sought to ...investigate whether the cerebral microcirculation is altered in a clinically relevant animal model of septic shock.
Fifteen anesthetized, invasively monitored, and mechanically ventilated female sheep were allocated to a sham procedure (n = 5) or sepsis (n = 10), in which peritonitis was induced by intra-abdominal injection of autologous faeces. Animals were observed until spontaneous death or for a maximum of 20 hours. In addition to global hemodynamic assessment, the microcirculation of the cerebral cortex was evaluated using Sidestream Dark-Field (SDF) videomicroscopy at baseline, 6 hours, 12 hours and at shock onset. At least five images of 20 seconds each from separate areas were recorded at each time point and stored under a random number to be analyzed, using a semi-quantitative method, by an investigator blinded to time and condition.
All septic animals developed a hyperdynamic state associated with organ dysfunction and, ultimately, septic shock. In the septic animals, there was a progressive decrease in cerebral total perfused vessel density (from 5.9 ± 0.9 at baseline to 4.8 ± 0.7 n/mm at shock onset, P = 0.009), functional capillary density (from 2.8 ± 0.4 to 2.1 ± 0.7 n/mm, P = 0.049), the proportion of small perfused vessels (from 95 ± 3 to 85 ± 8%, P = 0.02), and the total number of perfused capillaries (from 22.7 ± 2.7 to 17.5 ± 5.2 n/mm, P = 0.04). There were no significant changes in microcirculatory flow index over time. In sham animals, the cerebral microcirculation was unaltered during the study period.
In this model of peritonitis, the cerebral microcirculation was impaired during sepsis, with a significant reduction in perfused small vessels at the onset of septic shock. These alterations may play a role in the pathogenesis of septic encephalopathy.
•In Uganda, decentralised platforms are used as spatial tactics to centralise power for the ruling party.•Decentralised platforms may co-produce unequal risk through blame dissolution and scale ...jumping.•A problematic implementation of decentralised platforms prevents competent disaster governance.
The international agenda for disaster risk reduction, through the Hyogo Framework for Action and the Sendai Framework for disaster risk reduction, promotes decentralised platforms as an indispensable strategy to achieve effective and efficient disaster risk management. Based on empirical data from the Rwenzori Mountains region, we question the implications of this type of network governance for disaster risk management. We embed our observations in an analytical framework that combines literature on network governance with insights from politics of disaster, notably scale and blame theories. In this study, we investigate the implications for disaster risk reduction through the analysis of three processes of scale structuration observed in contemporary West Uganda: (i) incomplete decentralisation, (ii) blame dissolution, and (iii) scale jumping. We argue that decentralised platforms in Uganda co-produce unequal risk, as they are used as spatial tactics to centralise power for the ruling party and enable blame dissolution and scale jumping. From our analysis we draw broader conclusions on drivers and implications of the implementation of disaster network governance in countries that are primarily governed hierarchically and that endorse the international frameworks of disaster risk reduction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Neurological outcome and mortality of patients suffering from poor grade subarachnoid hemorrhage (SAH) may have changed over time. Several factors, including patients' characteristics, the presence ...of hydrocephalus and intraparenchymal hematoma, might also contribute to this effect. The aim of this study was to assess the temporal changes in mortality and neurologic outcome in SAH patients and identify their predictors.
We performed a single center retrospective cohort study from 2004 to 2018. All non-traumatic SAH patients with poor grade on admission (WFNS score of 4 or 5) who remained at least 24 h in the hospital were included. Time course was analyzed into four groups according to the years of admission (2004-2007; 2008-2011; 2012-2015 and 2016-2018).
A total of 353 patients were included in this study: 202 patients died (57 %) and 260 (74 %) had unfavorable neurological outcome (UO) at 3 months. Mortality tended to decrease in in 2008-2011 and 2016-2018 periods (HR 0.55 0.34-0.89 and HR 0.33 0.20-0.53, respectively, when compared to 2004-2007). The proportion of patients with UO remained high and did not vary significantly over time. Patients with WFNS 5 had higher mortality (68 % vs. 34 %, p = 0.001) and more frequent UO (83 % vs. 54 %, p = 0.001) than those with WFNS 4. In the multivariable analysis, WFNS 5 was independently associated with mortality (HR 2.12 1.43-3.14) and UO (OR 3.23 1.67-6.25). The presence of hydrocephalus was associated with a lower risk of mortality (HR 0.60 0.43-0.84).
Both hospital mortality and UO remained high in poor grade SAH patients. Patients with WFNS 5 on admission had worse prognosis than others; this should be taken into consideration for future clinical studies.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recombinant adeno‐associated virus (rAAV) vectors mediating long term transgene expression are excellent gene therapy tools for chronic neurological diseases. While rAAV2 was the first serotype ...tested in the clinics, more efficient vectors derived from the rh10 serotype are currently being evaluated and other serotypes are likely to be tested in the near future. In addition, aside from the currently used stereotaxy‐guided intraparenchymal delivery, new techniques for global brain transduction (by intravenous or intra‐cerebrospinal injections) are very promising.
Various strategies for therapeutic gene delivery to the central nervous system have been explored in human clinical trials in the past decade. Canavan disease, a genetic disease caused by an enzymatic deficiency, was the first to be approved. Three gene transfer paradigms for Parkinson's disease have been explored: converting L‐dopa into dopamine through AADC gene delivery in the putamen; synthesizing GABA through GAD gene delivery in the overactive subthalamic nucleus and providing neurotrophic support through neurturin gene delivery in the nigro‐striatal pathway.
These pioneer clinical trials demonstrated the safety and tolerability of rAAV delivery in the human brain at moderate doses. Therapeutic effects however, were modest, emphasizing the need for higher doses of the therapeutic transgene product which could be achieved using more efficient vectors or expression cassettes. This will require re‐addressing pharmacological aspects, with attention to which cases require either localized and cell‐type specific expression or efficient brain‐wide transgene expression, and when it is necessary to modulate or terminate the administration of transgene product. The ongoing development of targeted and regulated rAAV vectors is described.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Accurate and detailed multitemporal inventories of landslides and their process characterization are crucial for the evaluation of landslide hazards and the implementation of disaster risk reduction ...strategies in densely-populated mountainous regions. Such investigations are, however, rare in many regions of the tropical African highlands, where landslide research is often in its infancy and not adapted to the local needs. Here, we have produced a comprehensive multitemporal investigation of the landslide processes in the hillslopes of Bujumbura, situated in the landslide-prone East African Rift. We inventoried more than 1200 landslides by combining careful field investigation and visual analysis of satellite images, very-high-resolution topographic data, and historical aerial photographs. More than 20% of the hillslopes of the city are affected by landslides. Recent landslides (post-1950s) are mostly shallow, triggered by rainfall, and located on the steepest slopes. The presence of roads and river quarrying can also control their occurrence. Deep-seated landslides typically concentrate in landscapes that have been rejuvenated through knickpoint retreat. The difference in size distributions between old and recent deep-seated landslides suggests the long-term influence of potentially changing slope-failure drivers. Of the deep-seated landslides, 66% are currently active, those being mostly earthflows connected to the river system. Gully systems causing landslides are commonly associated with the urbanization of the hillslopes. Our results provide a much more accurate record of landslide processes and their impacts in the region than was previously available. These insights will be useful for land management and disaster risk reduction strategies.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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