Influence du substrat sur la répartition des macroinvertébrés benthiques dans un système lotique : cas des rivières Gombe, Kinkusa et Mangengenge

La répartition géographique des espèces dans un écosystème est liée à leurs habitats. L’influence du substrat sur la distribution des macroinvertébrés benthiques de trois hydrosystèmes de la ville de Kinshasa (Gombe, Kinkusa et Mangengenge) était étudiée de mai en début septembre 2014. L’échantillonnage des  macroinvertébrés était effectué grâce au filet troubleau dans chaque type de substrat. Douze types de substrats étaient regroupés en deux grandes catégories : la vase et le sable. Le gravier ayant été présent en faible proportion. Cinq mille huit cent quatre-vingt et un macroinvertébrés appartenant à trente deux familles ont été récoltés : seize familles ont été récoltés respectivement dans la Gombe et dans la Kinkusa; et vingt quatre dans la Mangengenge. Seize familles étaient  localisées dans le sable et le gravier, quinze dans la vase et cinq étaient concomitamment présentes dans le sable et la vase. La présence des Trichoptères dans la Mangengenge associée aux valeurs indiciaires de Shannon et Weaver (3,6) et à la note de l’Indice Biologique Général Normalisé (IBGN) (14/20), montre que l’eau de cet hydrosystème est de bonne qualité par rapport à celles des rivières Gombe et Kinkusa qui sont polluées et similaires à 73%.Mots clés : Kinshasa, rivières, substrat, influence, macroinvertébrés benthiques

An application of the theory of reasoned action: Assessing success factors of engineering students

© 2016 TEMPUS Publications. Student attrition in engineering is of concern. This study investigated motivational factors necessary to succeed in engineering. The Theory of Reasoned Action (TRA) model was used to guide the suggested paths from learning strategy, interest, and intention to academic performance. Participants were 135 Malaysian and 132 Australian engineering undergraduates who had completed the Study Process Questionnaire (R-SPQ-2F) scale and the Learner Autonomy Profile (LAP-SF) scale. The correlation coefficient analysis showed strong interrelationships between learning strategy, interest and intention. The findings of the structural equation modelling (SEM) revealed unexpected but interesting findings between the two countries. Two different pathways were established for the Malaysian and Australian data suggesting that the TRA model is best suited to the Australian learning context. The findings of this study could help identify a suitable model for explaining success factors in engineering

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

The formation of cold air pools in valleys under stable conditions represents an important challenge for numerical weather prediction (NWP). The challenge is increased when the valleys that dominate cold pool formation are on scales unresolved by NWP models, which can lead to substantial local errors in temperature forecasts. In this study a 2-month simulation is presented using a nested model con- figuration with a finest horizontal grid spacing of 100 m. The simulation is compared with observations from the recent COLd air Pooling Experiment (COLPEX) project and the model’s ability to represent cold pool formation, and the surface energy balance is assessed. The results reveal a bias in the model long-wave radiation that results from the assumptions made about the sub-grid variability in humidity in the cloud parametrization scheme. The cloud scheme assumes relative humidity thresholds below 100 % to diagnose partial cloudiness, an approach common to schemes used in many other models. The biases in radiation, and resulting biases in screen temperature and cold pool properties are shown to be sensitive to the choice of critical relative humidity, suggesting that this is a key area that should be improved for very high-resolution modeling

A case‐study of cold‐air pool evolution in hilly terrain using field measurements from COLPEX

A case‐study investigation of cold‐air pool (CAP) evolution in hilly terrain is conducted using field measurements made during IOP 16 of the COLd‐air Pool EXperiment (COLPEX). COLPEX was designed to study cold‐air pooling in small‐scale valleys typical of the UK (∼100–200 m deep, ∼1 km wide). The synoptic conditions during IOP 16 are typical of those required for CAPs to form during the night, with high pressure, clear skies and low ambient winds. Initially a CAP forms around sunset and grows uninterrupted for several hours. However, starting 4 hr after sunset, a number of interruptions to this steady cooling rate occur. Three episodes are highlighted from the observations and the cause of disruption attributed to (a) wave activity, in the form of gravity waves and/or Kelvin–Helmholtz (KH) instability, (b) increases in the above‐valley winds resulting from the development of a nocturnal low‐level jet (NLLJ), (c) shear‐induced mixing resulting from instability of the NLLJ. A weakly stable residual layer provides the conditions for wave activity during Episode 1. This residual layer is eroded by a developing NLLJ from the top down during Episode 2. The sustained increase in winds at hill‐top levels – attributed to the NLLJ – continue to disrupt the CAP through Episode 3. Although cooling is interrupted, the CAP is never completely eroded during the night. Complete CAP break‐up occurs some 3.5 hr after local sunrise. This case‐study highlights a number of meteorological phenomena that can disrupt CAP evolution even in ideal CAP conditions. These processes are unlikely to be sufficiently represented by current operational weather forecast models and can be challenging even for high‐resolution research models

Reversible change in electrical and optical properties in epitaxially grown Al-doped ZnO thin films

Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01× 10-4 Ω cm. However, after annealing at 450 °C in air, the electrical resistivity of the AZO films increased to 1.97× 10-1 Ω cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H2 recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H2 annealing. A photoluminescence study showed that oxygen interstitial (Oi′) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films. © 2008 American Institute of Physics

Regulating synchronous oscillations of cerebellar granule cells by different types of inhibition

Synchronous oscillations in neural populations are considered being controlled by inhibitory neurons. In the granular layer of the cerebellum, two major types of cells are excitatory granular cells (GCs) and inhibitory Golgi cells (GoCs). GC spatiotemporal dynamics, as the output of the granular layer, is highly regulated by GoCs. However, there are various types of inhibition implemented by GoCs. With inputs from mossy fibers, GCs and GoCs are reciprocally connected to exhibit different network motifs of synaptic connections. From the view of GCs, feedforward inhibition is expressed as the direct input from GoCs excited by mossy fibers, whereas feedback inhibition is from GoCs via GCs themselves. In addition, there are abundant gap junctions between GoCs showing another form of inhibition. It remains unclear how these diverse copies of inhibition regulate neural population oscillation changes. Leveraging a computational model of the granular layer network, we addressed this question to examine the emergence and modulation of network oscillation using different types of inhibition. We show that at the network level, feedback inhibition is crucial to generate neural oscillation. When short-term plasticity was equipped on GoC-GC synapses, oscillations were largely diminished. Robust oscillations can only appear with additional gap junctions. Moreover, there was a substantial level of cross-frequency coupling in oscillation dynamics. Such a coupling was adjusted and strengthened by GoCs through feedback inhibition. Taken together, our results suggest that the cooperation of distinct types of GoC inhibition plays an essential role in regulating synchronous oscillations of the GC population. With GCs as the sole output of the granular network, their oscillation dynamics could potentially enhance the computational capability of downstream neurons

Constrained analytical interrelations in neutrino mixing

Hermitian squared mass matrices of charged leptons and light neutrinos in the flavor basis are studied under general additive lowest order perturbations away from the tribimaximal (TBM) limit in which a weak basis with mass diagonal charged leptons is chosen. Simple analytical expressions are found for the three measurable TBM-deviants in terms of perturbation parameters appearing in the neutrino and charged lepton eigenstates in the flavor basis. Taking unnatural cancellations to be absent and charged lepton perturbation parameters to be small, interrelations are derived among masses, mixing angles and the amount of CP-violation.Comment: To be published in the Springer Proceedings in the Physics Series under the heading of the XXI DAE-BRNS Symposium (Guwahati, India

The temperature dependence of C-H⋯F-C interactions in benzene:hexafluorobenzene

The evolution of the structure of the four solid phases of the prototype binary-adduct C6H6:C6F6 as a function of temperature has been investigated using X-ray and neutron diffraction. An explanation is proposed concerning changes in the arrangements of the molecules at each of the three phase transitions and the dynamics in C6H6:C6F6 are briefly compared with those of the adduct formed between mesitylene and C6F6. The observations are rationalised using simple models of intermolecular electrostatics

Diverse role of NMDA receptors for dendritic integration of neural dynamics

Neurons, represented as a tree structure of morphology, have various distinguished branches of dendrites. Different types of synaptic receptors distributed over dendrites are responsible for receiving inputs from other neurons. NMDA receptors (NMDARs) are expressed as excitatory units, and play a key physiological role in synaptic function. Although NMDARs are widely expressed in most types of neurons, they play a different role in the cerebellar Purkinje cells (PCs). Utilizing a computational PC model with detailed dendritic morphology, we explored the role of NMDARs at different parts of dendritic branches and regions. We found somatic responses can switch from silent, to simple spikes and complex spikes, depending on specific dendritic branches. Detailed examination of the dendrites regarding their diameters and distance to soma revealed diverse response patterns, yet explain two firing modes, simple and complex spike. Taken together, these results suggest that NMDARs play an important role in controlling excitability sensitivity while taking into account the factor of dendritic properties. Given the complexity of neural morphology varying in cell types, our work suggests that the functional role of NMDARs is not stereotyped but highly interwoven with local properties of neuronal structure

Enhancing Visual Coding Through Collaborative Perception

A central challenge facing the nature human-computer interaction involves understanding how neural circuits process visual perceptual information to improve the user’s operation ability under complex tasks. Visual coding models aim to explore the biological characteristics of retinal ganglion cells to provide quantitative predictions of responses to a range of visual stimuli. The existing visual coding models lack adaptability in natural and complex scenes. Therefore this paper proposes an enhanced visual coding model through collaborative perception. Our model first extracts the multi-modal spatiotemporal features of the input video to simulate the retinal response characteristics adaptively. Secondly, it uses the basis function to compile the input stimulus into a multi-modal stimulus matrix. Afterward, the upstream and downstream filters reform the stimulus matrix to generate the spike sequence. Experiments show that the proposed model reproduces the physiological characteristics of ganglion cells in the biological retina, leading to the high accuracy, good adaptability, and biological interpretability in comparison with its rivals