Theoretical connections between mathematical neuronal models corresponding to different expressions of noise

Identifying the right tools to express the stochastic aspects of neural activity has proven to be one of the biggest challenges in computational neuroscience. Even if there is no definitive answer to this issue, the most common procedure to express this randomness is the use of stochastic models. In accordance with the origin of variability, the sources of randomness are classified as intrinsic or extrinsic and give rise to distinct mathematical frameworks to track down the dynamics of the cell. While the external variability is generally treated by the use of a Wiener process in models such as the Integrate-and-Fire model, the internal variability is mostly expressed via a random firing process. In this paper, we investigate how those distinct expressions of variability can be related. To do so, we examine the probability density functions to the corresponding stochastic models and investigate in what way they can be mapped one to another via integral transforms. Our theoretical findings offer a new insight view into the particular categories of variability and it confirms that, despite their contrasting nature, the mathematical formalization of internal and external variability are strikingly similar

Computer-assisted radiographic calculation of spinal curvature in brachycephalic "screw-Tailed" dog breeds with congenital thoracic vertebral malformations: reliability and clinical evaluation

The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009–2013) to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and inter-observer measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35°. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations

Native cellular architecture of Treponema denticola revealed by cryo-electron tomography

Using cryo-electron tomography, we are developing a refined description of native cellular structures in the pathogenic spirochete Treponema denticola. Tightly organized bundles of periplasmic flagella were readily observed in intact plunge-frozen cells. The periplasmic space was measured in both wild-type and aflagellate strains, and found to widen by less than the diameter of flagella when the latter are present. This suggests that a structural change occurs in the peptidoglycan layer to accommodate the presence of the flagella. In dividing cells, the flagellar filaments were found to bridge the cytoplasmic cylinder constriction site. Cytoplasmic filaments, adjacent to the inner membrane, run parallel to the tightly organized flagellar filaments. The cytoplasmic filaments may be anchored by a narrow plate-like structure. The tapering of the cell ends was conserved between cells, with a patella-shaped structure observed in the periplasm at the tip of each cytoplasmic cylinder. Several incompletely characterized structures have been observed in the periplasm between dividing cells, including a cable-like structure linking two cytoplasmic cylinders and complex foil-shaped structures

Identification of areas affected by desertification in Niger using low resolution satellite data

In order to identify areas where desertification may have occurred over the last two decades, 109 stations located in three bioclimatic zones of Niger are analyzed. Time series of remote sensing data are well suited to this task. Here, we use time series of NOAA AVHRR normalized difference vegetation index (NDVI) data and rainfall data. In this study, trend analysis is used to identify areas within the biomes from 1981 to 1999 in Niger with apparent land degradation in semi-arid areas. It appears that most of Niger (98%) recorded increasing rainfall while only 76% experienced increasing maximum NDVI. However, the combination of the two variables through the ratio shows a widespread reduction of the rain-use efficiency with non significant trend for the stations located in northern Sahel (p=0.52), highly significant for those located in central Sahel (p=0.00009) and significant in southern Sahel (p=0.041). Overall, 75.3% of the sample recorded a significant reduction of the NDVIMax/RR ratio. Only one station out of four (24.7%) presented a stability of the ratio. These negative trends suggest a progressive diminution of the vegetation productivity as highlighted by the lowering of the NDVIMax/RR ratio. This situation suggest a consistently environmental degradation and that desertification processes continued during the last two decades over most of the Sahelian belt of Niger.Dans l’optique d’identifier les endroits potentiellement affectés par la désertification au cours des deux dernières décennies, 109 stations réparties dans trois zones bioclimatiques du Niger ont été étudiés. L’analyse conjointe des séries chronologiques de précipitations et d’images satellitales AVHRR de NOAA, transformées en indice de végétation normalisé (NDVI) a permis d’appréhender la dynamique du couvert végétal au sein des biomes considérés de 1981 à 1999. L’évaluation qualitative de la dynamique à long terme du couvert végétal a été réalisée grâce à l’analyse de tendance des valeurs maximales annuelles du NDVI par rapport aux précipitations pendant la période de végétation pour chacun des points étudiés. Sur la période analysée, il ressort que 98% des résultats obtenus pour les précipitations contre 76% des valeurs du NDVIMax/RR montrent une tendance positive allant de modérée à très forte pour l’ensemble des pixels. Par contre, la combinaison des deux variables à travers le rapport NDVIMax/RR montrent un déclin généralisé de l’efficacité de l’utilisation de l’eau par la végétation avec une tendance non significative pour les stations situées dans le Sahel pastoral (p=0,52), hautement significative pour celles localisées dans la zone sahélienne à culture sous pluie (p=0,00009) et significative dans le Sahel méridional (p=0,041). Au total, sur les 109 stations étudiées, 75,3% d’entre elles accusent une baisse du ratio NDVIMax/RR. Seule une station sur quatre (24,7%) révèle une certaine stabilité de ce rapport. Les tendances négatives traduisent une diminution progressive de la productivité végétale qui se reflète dans la baisse du ratio NDVIMax/RR. Cette situation suggère une dégradation environnementale continue et met en lumière que les processus de désertification se sont probablement perpétués au cours des deux dernières décennies sur plus de la moitié de la frange sahélienne du territoire nigérien.Etude de la dynamique environnementale en zone soudanienne et soudano-sahélienne de l’Afrique de l’Ouest : Modifications climatiques et évaluation de la désertification dans le nord Béni

Traitement de polissage par marais épurateur du drainage minier acide

Affiche présentée dans le cadre du Colloque de l'ARC, «La culture de la recherche au collégial», dans le cadre du 82e Congrès de l'Acfas, Université Concordia, Montréal, le 14 mai 2014.Les résidus miniers représentent une source de danger potentiel pour l'environnement, en particulier lorsque ces déchets contiennent des minéraux sulfureux qui peuvent s'oxyder et générer du drainage minier acide (DMA). Ce dernier est caractérisé par un pH faible et des concentrations en sulfates et métaux dissous élevées. Les traitements biologiques constituent une solution moins coûteuse par rapport aux traitements chimiques, en plus de présenter plusieurs avantages dont des taux élevés d’enlèvement des métaux, une réduction du pH, de faibles coûts d’exploitation et une consommation minimale d’énergie. La capacité des marais filtrants à traiter un DMA chargé en fer à l’étape de polissage a été étudiée. Les systèmes consistaient en des marais artificiels à écoulement vertical et horizontal de 0,052 m3, remplis de deux différents substrats et plantés avec des quenouilles (Typha latifolia). Ils étaient alimentés pour traiter 1,5 mL/min d’un DMA ayant une concentration moyenne de 38,0 mg/L de fer, 2,6 mg/L de manganèse, 0,4 mg/L de nickel et 0,9 mg/L de zinc à un pH moyen de 4,2. Après traitement, le pH moyen à l’effluent était de 8,0 pour les marais verticaux et de 7,6 pour les horizontaux. Le taux d’enlèvement du fer et du zinc était respectivement de 95 et 96 % pour les marais à écoulement verticaux et de 87 et 94 % pour les horizontaux. Le traitement du nickel et du manganèse était négligeable

Refugees’ dreams of the past, projected into the future

This article is about refugees’ and migrants’ dreams of home and family and stems from an Australian Research Council Linkage Grant, “A Hand Up: Disrupting the Communication of Intergenerational Welfare Dependency” (LP140100935), with Partner Organisation St Vincent de Paul Society (WA) Inc. (Vinnies). A Vinnies-supported refugee and migrant support centre was chosen as one of the hubs for interviewee recruitment, given that many refugee families experience persistent and chronic economic disadvantage. The de-identified name for the drop-in language-teaching and learning social facility is the Migrant and Refugee Homebase (MARH). At the time of the research, in 2018, refugee and forced migrant families from Syria, Iraq, and Afghanistan constituted MARH’s primary membership base. MARH provided English language classes alongside other educational and financial support. It could also organise provision of emergency food and was a conduit for furniture donated by Australian families. Crucially, MARH operated as a space in which members could come together to build shared community

Native cellular architecture of Treponema denticola revealed by cryo-electron tomography

Using cryo-electron tomography, we are developing a refined description of native cellular structures in the pathogenic spirochete Treponema denticola. Tightly organized bundles of periplasmic flagella were readily observed in intact plunge-frozen cells. The periplasmic space was measured in both wild-type and aflagellate strains, and found to widen by less than the diameter of flagella when the latter are present. This suggests that a structural change occurs in the peptidoglycan layer to accommodate the presence of the flagella. In dividing cells, the flagellar filaments were found to bridge the cytoplasmic cylinder constriction site. Cytoplasmic filaments, adjacent to the inner membrane, run parallel to the tightly organized flagellar filaments. The cytoplasmic filaments may be anchored by a narrow plate-like structure. The tapering of the cell ends was conserved between cells, with a patella-shaped structure observed in the periplasm at the tip of each cytoplasmic cylinder. Several incompletely characterized structures have been observed in the periplasm between dividing cells, including a cable-like structure linking two cytoplasmic cylinders and complex foil-shaped structures

Tox and detox: Are teens\u27 smartphone use and non-use practices fully fungible?

The public sphere includes a range of credible discourses asserting that a proportion of teenagers (“teens”) has an unhealthy dependence upon continuous connection with media devices, and especially smartphones. A review of media discourse (Jaunzems et al.) in Australia, and a critical review of public discourse in Australia and Belgium (Zaman et al.), reveal both positive and negative commentary around screentime. Despite the “emotionally laden, opposing views” expressed in the media, there appears to be a groundswell of concern around young people’s dependence upon digital devices (Zaman et al. 120). Concerns about ‘addiction’ to and dependency on digital media first emerged with the Internet and have been continually represented as technology evolves. One recent example is the 2020 multi-part Massey Lecture series which hooked audiences with the provocative title: “we need to reclaim our lives from our phones” (Deibert). In Sydney, a psychology-based “outpatient addiction treatment centre” offers specialised recovery programs for “Internet addiction”, noting that addicts include school-aged teens, as well as adults (Cabin). Such discourse reflects well-established social anxieties around the disruptive impacts of new technologies upon society (Marvin), while focussing such concern disproportionately upon the lives, priorities, and activities of young people (Tsaliki and Chronaki)

The Red Rectangle: a thin disk with big grains

The Red Rectangle is a nebula surrounding the post-AGB star HD 44179. It is the prototype of a particular class of nebulae associated with post-AGB binaries characterised by the presence of stable circumbinary disks in (quasi-)Keplerian rotation. Here we present the results of new high-resolution (20-50 mas) ALMA observations of continuum and line emissions at 0.9 mm. The continuum maps are analysed through a simple model of dust emission, which can reproduce the observational data. We find that most dust emission in the Red Rectangle is concentrated in the central regions of the rotating disk and that the settlement of dust grains onto the equatorial plane is very significant, particularly in comparison with the much larger scale height displayed by the gas distribution. The diameter of the dust-emitting region is about 250 au, with a total width of about 50 au. This region coincides with the warm PDR where certain molecules (like HCN), CI, and CII are presumably formed, as well as probably PAHs. From the spectral index, we confirm the presence in the disk of large grains, with a typical radius of about 0.150 mm, which supports the long-lived hypothesis for this structure. We also confirm the existence of a compact ionised wind at the centre of the nebula, probably emerging from the accretion disk around the companion, for which we derive an extent of about 10 au and a total flux of 8 mJy. We also briefly present the results on molecular lines of 12CO, 13CO, and other less abundant species.Comment: 6 pages, 4 figures, 1 table, Proceedings IAU Symposium No. 384 "Planetary Nebulae: a Universal Toolbox in the Era of Precision Astrophysics