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991 result(s) for "Gomez, Christopher"
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UAV- based Photogrammetry and Geocomputing for Hazards and Disaster Risk Monitoring – A Review
Background The unraveling of the human-induced climate-change crisis has put to the forth the ability of human-beings to impact the planet as a whole, but the discourse of politics has also emphasized the ability of the human race to adapt and counterweigh the environmental change, in turn increasing the public expectation that one should be able to control nature and its affects. Such cozy and reassured society consequently puts an increasing amount of pressure on hazards assessors, emergency and disaster managers “to get it right”, and not only to save the majority, but to save all. To reach such level of competency, emergency relief teams and disaster managers have to work always faster with an increasing need of high quality, high-resolution geospatial data. This need is being partly resolved with the usage of UAV (Unmanned Autonomous Vehicles), both on the ground and airborne. Results In this contribution, we present a review of this field of research that has increased exponentially in the last few years. The rapid democratization of the tool has lead to a significant price reduction and consequently a broad scientific usage that have resulted in thousands of scientific contributions over the last decade. The main usages of UAVs are the mapping of land features and their evolution over time, the mapping of hazards and disasters as they happen, the observation of human activity during an emergency or a disaster, the replacement of telecommunication structures impacted by a natural hazards and the transport of material to isolated groups. Conclusion Those usages are mostly based on the use of single UAVs or UAVs as single agents eventually collaborating. The future is most certainly in the ability to accomplish complex tasks by leveraging the multiple platforms possibilities. As an example, we presented an experiment showing how multiple UAV platforms taking imagery together at the same time could provide true 4D (3D in time) of geo-processes such as river-bed evolution, or rockfalls, etc.
Loss-of-function BK channel mutation causes impaired mitochondria and progressive cerebellar ataxia
Despite a growing number of ion channel genes implicated in hereditary ataxia, it remains unclear how ion channel mutations lead to loss-of-function or death of cerebellar neurons. Mutations in the gene KCNMA1, encoding the α-subunit of the BK channel have emerged as responsible for a variety of neurological phenotypes. We describe a mutation (BKG354S) in KCNMA1, in a child with congenital and progressive cerebellar ataxia with cognitive impairment. The mutation in the BK channel selectivity filter dramatically reduced single-channel conductance and ion selectivity. The BKG354S channel trafficked normally to plasma, nuclear, and mitochondrial membranes, but caused reduced neurite outgrowth, cell viability, and mitochondrial content. Small interfering RNA (siRNA) knockdown of endogenous BK channels had similar effects. The BK activator, NS1619, rescued BKG354S cells but not siRNA-treated cells, by selectively blocking the mutant channels. When expressed in cerebellum via adenoassociated virus (AAV) viral transfection in mice, the mutant BKG354S channel, but not the BKWT channel, caused progressive impairment of several gait parameters consistent with cerebellar dysfunction from 40- to 80-d-old mice. Finally, treatment of the patient with chlorzoxazone, a BK/SK channel activator, partially improved motor function, but ataxia continued to progress. These studies indicate that a loss-of-function BK channel mutation causes ataxia and acts by reducing mitochondrial and subsequently cellular viability.
The autosomal dominant spinocerebellar ataxias: emerging mechanistic themes suggest pervasive Purkinje cell vulnerability
The spinocerebellar ataxias are a genetically heterogeneous group of disorders with clinically overlapping phenotypes arising from Purkinje cell degeneration, cerebellar atrophy and varying degrees of degeneration of other grey matter regions. For 22 of the 32 subtypes, a genetic cause has been identified. While recurring themes are emerging, there is no clear correlation between the clinical phenotype or penetrance, the type of genetic defect or the category of the disease mechanism, or the neuronal types involved beyond Purkinje cells. These phenomena suggest that cerebellar Purkinje cells may be a uniquely vulnerable neuronal cell type, more susceptible to a wider variety of genetic/cellular insults than most other neuron types.
Deposits’ Morphology of the 2018 Hokkaido Iburi-Tobu Earthquake Mass Movements from LiDAR & Aerial Photographs
On 6 September at 03:08 a.m. local time, a 33 km deep earthquake underneath the Iburi mountains triggered more than 7000 co-seismic mass movements within 25 km of the epicenter. Most of the mass movements occurred in complex terrain and became coalescent. However, a total of 59 mass movements occurred as discrete events and stopped on the semi-horizontal valley floor. Using this case study, the authors aimed to define planar and vertical parameters to (1) compare the geometrical parameters with rain-triggered mass movements and (2) to extend existing datasets used for hazards and disaster risk purposes. To reach these objectives, the methodology relies on LiDAR data flown in the aftermath of the earthquake as well as aerial photographs. Using a Geographical Information System (GIS), planform and vertical parameters were extracted from the DEM in order to calculate the relationship between areas and volume, between the Fahrböschung and the volume of the deposits, and to discuss the relationship between the deposit slope surface and the effective stress of the deposit. Results have shown that the relation S=k[Vd]2/3 (where S is the surface area of a deposit and Vd the volume, and k a scalar that is function of S) is k = 2.1842ln(S) − 10.167 with a R2 of 0.52, with less variability in deposits left by valley-confined processes compared to open-slope processes. The Fahrböschung for events that started as valley-confined mass-movements was Fc = −0.043ln(D) + 0.7082, with a R2 of 0.5, while for open-slope mass-movements, the Fo = −0.046ln(D) + 0.7088 with a R2 of 0.52. The “T-values”, as defined by Takahashi (2014), are displaying values as high as nine times that of the values for experimental rainfall debris-flow, signifying that the effective stress is higher than in rain-triggered counterparts, which have an increased pore pressure due to the need for further water in the material to be moving. For co-seismic debris-flows and other co-seismic mass movements it is the ground acceleration that “fluidizes” the material. The maxima found in this study are as high as 3.75.
Multi-scale topographic analysis of Merbabu and Merapi volcanoes using wavelet decomposition
With the increasing availability of data, geo-sciences have experienced deep changes in handling and processing it. One of the presently explored research directions concerns the systematic decomposition and understanding of topographical features, without the subjective interactions of humans. This can eventually lead to fully automated algorithms for topographic analysis and understanding. This paper aims at being a contribution to this broad research area for the specific cases of stratovolcanoes, whose general geometry are very similar to a perfect cone. More specifically, this paper addresses two issues: (1) is it possible to separate erosion features (local variations) from structural features (large variations) on stratovolcanoes, through mathematical expression; (2) can information on volcanic activity—intensity, age, etc.—be retrieved from a topographic analysis? The study has been conducted from two volcanoes in Central Java (Indonesia): the Merapi and the Merbabu. The DEM of these volcanoes has been sampled using concentric circles with a radius ranging from 500 to 5,000 m (horizontal distance) to the summit. The data conversion and sampling was performed in ArcMap®, while the data analysis was carried out with Matlab®, using Discrete Meyer wavelet decomposition. Results provide an insight on large-scale topographic variations (long-wave wavelet) that have been separated from rapidly varying topographic features such as lahar channels (short-wave wavelets). Observations proved that flanks where the most recent volcanic activity occur—like at Merapi Volcano on the S-SE flank—present a very low variability of long-wave variations, whereas short-wave variations are important. The author argues that this feature is due to highly erosive lahars that dig the valleys combined with a recent production of material and volcanic growth keeping the overall structure regular. Flanks with lesser activity are characterized at the two volcanoes by important long-wave variations—most certainly due to long-term differential erosion—and different level of short-waves variations. Comparing the two volcanoes, results show that the valleys of Merapi and Merbabu volcanoes are deeply incised, indicating recent periods of high activity, with reworkable material eroded by lahars and other channels deepening processes. The topography of the summit area of Merapi Volcano is smoother than at Merbabu Volcano, where deep erosion features extend up to the summit area. This difference is most certainly due by the material production at the summit of Merapi Volcano. Developing such classification is important for automated mapping and computer recognition of volcanic past activities and their impacts on landscapes. It is the based for the development of decision trees that assist computer assisted and automated computer vision.
Pontine stroke in a patient with Chronic Progressive External Ophthalmoplegia (CPEO): a case report
Background Chronic progressive external ophthalmoplegia (CPEO) is a mitochondrial disease with slowly progressive bilateral ptosis and symmetric ophthalmoplegia due to a genetic mutation that results in defective oxidative phosphorylation. Common genes that are implicated in CPEO include POLG , RRM2B , ANT1 and PEO1 / TWNK . Here, we report a case of a patient diagnosed with CPEO caused by a novel mutation in PEO / TWNK after suffering a right pontine stroke. Case presentation A 70-year-old man with history of chronic progressive bilateral ptosis and ophthalmoplegia, as well as similar ocular symptoms in his father and grandfather, presented with acute onset of right hemifacial weakness and dysarthria. Brain MRI revealed an acute ischemic stroke in the right dorsal pons. The patient did not experience diplopia due to severe baseline ophthalmoplegia. Creatine kinase was elevated to 6,080 U/L upon admission and normalized over the course of one week; electromyography revealed a myopathic process. Genetic testing revealed a novel mutation c.1510G > A (p. Ala504Thr) in a pathogenic “hot spot” of the C10ORF2 gene ( TWNK / PEO1 ), which is associated with CPEO. The mutation appears to be deleterious using several pathogenicity prediction tools. Conclusions This case report describes a patient with late-onset CPEO caused by a novel, likely pathogenic, mutation in the TWNK gene. Although the patient presented with a pontine stroke, it manifested with solely new onset facial palsy, as he had a severe underlying ophthalmoplegia secondary to his CPEO.
SARA captures disparate progression and responsiveness in spinocerebellar ataxias
Background The Scale for Assessment and Rating of Ataxia (SARA) is a widely used clinical scale to assess cerebellar ataxia but faces some criticisms about the relevancy of all its items. Objectives To prepare for future clinical trials, we analyzed the progression of SARA and its items in several polyQ spinocerebellar ataxias (SCA) from various cohorts. Methods We included data from patients with SCA1, SCA2, SCA3, and SCA6 from four cohorts (EUROSCA, RISCA, CRC-SCA, and SPATAX) for a total of 850 carriers and 3431 observations. Longitudinal progression of the SARA and its items was measured. Cohort, stage and genetic effects were tested. We looked at the respective contribution of each item to the total scale. Sensitivity to change of the scale and the impact of item removal was evaluated by calculating sample sizes needed in various scenarios. Results Longitudinal progression was significantly different between cohorts in SCA1, SCA2 and SCA3, the EUROSCA cohort having the fastest progression. Advanced-stage patients were progressing slower in SCA2 and SCA6. Items were not contributing equally to the full scale through ataxia severity: gait, stance, hand movement, and heel-shin contributed the most in the early stage, and finger-chase, nose-finger, and sitting in later stages. Few items drove the sensitivity to the change of SARA, but changes in the scale structure could not improve its sensitivity in all populations. Conclusion SARA and its item’s progression pace showed high heterogeneity across cohorts and SCAs. However, no combinations of items improved the responsiveness in all SCAs or populations taken separately.
Quantitative Gait and Balance Outcomes for Ataxia Trials: Consensus Recommendations by the Ataxia Global Initiative Working Group on Digital-Motor Biomarkers
With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid, finely granulated, digital health measures are highly warranted to augment clinical and patient-reported outcome measures. Gait and balance disturbances most often present as the first signs of degenerative cerebellar ataxia and are the most reported disabling features in disease progression. Thus, digital gait and balance measures constitute promising and relevant performance outcomes for clinical trials. This narrative review with embedded consensus will describe evidence for the sensitivity of digital gait and balance measures for evaluating ataxia severity and progression, propose a consensus protocol for establishing gait and balance metrics in natural history studies and clinical trials, and discuss relevant issues for their use as performance outcomes.
The Transcription Factor, α1ACT, Acts Through a MicroRNA Network to Regulate Neurogenesis and Cell Death During Neonatal Cerebellar Development
MicroRNAs, a class of small RNA regulators, function throughout neurodevelopment, from neural stem cell neurogenesis to neuronal maturation, synaptic formation, and plasticity. α1ACT, a transcription factor (TF), plays a critical role in neonatal cerebellar development by regulating an ensemble of genes. Of these, ChIP-seq analysis matched near 50% genes directly regulated by α1ACT. Yet, more than half the regulated transcripts lacked direct interaction with α1ACT. To investigate whether α1ACT acts through a microRNA network, we studied α1ACT-associated simultaneous miRNA:mRNA transcriptome profiles, using miRNA-seq paired with RNA-seq. Thirty-one differentially expressed miRNAs (DEMs) associated with α1ACT-regulated differentially expressed genes (DEGs) were profiled in α1ACT-overexpressing PC12 cells and were further validated in neonatal transgenic mouse cerebellum overexpressing α1ACT in a context-dependent manner. Here, we also demonstrated that α1ACT facilitates neurogenesis and development of dendritic synapses and is partially a result of the downregulation of the miR-99 cluster, miR-143, miR-23, miR-146, miR-363, and miR-484. On the other hand, the miR-181, miR-125, and miR-708 clusters were upregulated by α1ACT, which inhibit MAPK signaling and cell death pathways by targeting Ask1, Odc1, Atf4, and Nuf2 for decreased expression. MiR-181a-5p was verified as the most abundant DEM in neonatal cerebellum, which was further induced by α1ACT. Overall, under α1ACT modulation, up-/downregulated miRNA clusters with their paired target genes may form a regulatory network controlling the balance between the neuronal proliferation, differentiation, and cell death in the cerebellum to promote neonatal development. Our findings concerning the α1ACT-related miRNA/mRNA expression profiles in neonatal cerebellum may inform future investigations for cerebellar development.