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Antsiranana, Madagascar

Fenoradosoa T.A.,University Blaise Pascal | Fenoradosoa T.A.,University of Antsiranana | Ali G.,University Blaise Pascal | Delattre C.,University Blaise Pascal | And 4 more authors.
Journal of Applied Phycology | Year: 2010

Matrix polysaccharide from the brown algae Sargassum turbinarioides collected in the coastal waters of Nosy Be (Madagascar) in the Indian Ocean was isolated and its structure was studied by 1H-NMR spectroscopy, FT-IR, SEC-MALLS and HPAEC. An alginate with a molecular weight of 5.528 × 105 g mol-1 was identified as sole polysaccharide. Values of the M/G ratio, FGG, FMM and FGM (or FGM) blocks were measured at respectively 0.94, 0.39, 0.36 and 0.25 and compared with those of alginates from other Sargassum species. This sodium alginate appeared similar to some of the other Sargassum alginates with M/G > 1, high values of homopolymeric blocks (η > 1) and significant polyguluronic block content. © 2009 Springer Science+Business Media B.V.

Macron C.,University of Burgundy | Richard Y.,University of Burgundy | Garot T.,French National Center for Scientific Research | Bessafi M.,University of Reunion Island | And 3 more authors.
Monthly Weather Review | Year: 2016

Using daily rain gauge records for Madagascar and nearby islands, this paper investigates rainfall intraseasonal variability at local and regional scales during the austral summer season (November-February), as well as the respective influences of recurrent convective regimes over the southwest Indian Ocean (SWIO) and the Madden-Julian oscillation (MJO). The results show a general consistency between local-scale rainfall variability in Madagascar and regional-scale features of climate variability. The influence of tropical temperate troughs in their mature phase and/or their easternmost locations is first underlined. The development of such systems over southern Africa and the Mozambique Channel can be considered as precursors for Malagasy wet spells, especially over the southern part of the island. Regional and local effects of the MJO are weaker on average, and only concern the northwest of the island and the north of the Mozambique Channel. MJO and convective regimes are finally shown to explain distinct fractions of regional rainfall variability. © 2016 American Meteorological Society.

David Razafimahefa T.,French National Center for Scientific Research | David Razafimahefa T.,University of Antsiranana | Heraud N.,Institute Superieur Of Technology | Sambatra E.J.R.,French National Center for Scientific Research
Proceedings of the 18th Mediterranean Electrotechnical Conference: Intelligent and Efficient Technologies and Services for the Citizen, MELECON 2016 | Year: 2016

Most cases of electrical machines are connected directly to the low voltage power system without inverter, which can be subjected to a harmonic pollution at any time. The presence of these harmonics can compromise the reliability of the fault detection. In this paper, we present the winding fault diagnosis of induction machine connected to a harmonically polluted low voltage power system. The detection method is based on the Hilbert transform. This proposed approach allows the suppression of the harmonics from the network while keeping all possible clues to the presence of winding fault in the induction machine. The proposed approach is tested experimentally to an induction machine subjected to a 2.5% of inter-turns short circuit fault. © 2016 IEEE.

Menard F.,IRD Montpellier | Benivary H.D.,University of Antsiranana | Bodin N.,IRD Montpellier | Coffineau N.,IRD Montpellier | And 4 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2014

We measured the stable carbon (δ13C) and nitrogen (δ15N) isotopic composition of tissues of micronektonic organisms (fishes, squids, crustaceans and gelatinous organisms) collected in the Mozambique Channel during two scientific cruises in 2008 and 2009. The oceanic circulation in the Mozambique Channel is dominated by mesoscale cyclonic and anticyclonic eddies which play a key role in biological processes of less-productive deep-sea ecosystems. We investigated the potential impact of mesoscale features on the δ13C and δ15N values of 32 taxa of micronekton. Fishes, squids, crustaceans and gelatinous organisms encompassed a wide range of isotopic niches, with large overlaps among species. Our results showed that mesoscale features did not really influence the isotopic signatures of the sampled organisms, although cyclonic eddies can occasionally impact the nitrogen signatures of micronekton. We show that δ13C values were intermediate between standard offshore and nearshore signatures, suggesting that pelagic production in the Mozambique Channel could be partly supported by the transport and export of inorganic and organic particles from the Mozambican coast toward the offshore area. Trophic levels calculated from δ15N values ranged from 2.6 to 4.2, showing that micronekton taxa can be tertiary consumers in the Mozambique Channel. Our findings evidenced clusters of micronektonic organisms according to their δ15N or δ13C isotopic signatures, but variations in stable isotope values reflect a complex set of embedded processes linked to physical mesoscale dynamics (rotational dynamics of eddies) and basic biology and ecology of micronektonic organisms (vertical habitat, migration pattern, dietary habits, body length) that are discussed with regard to the stable isotope method based on time-integrated assimilated food. © 2013 Elsevier Ltd.

Nematchoua M.K.,University of Yaounde I | Raminosoa C.R.R.,University of Antsiranana | Mamiharijaona R.,University of Antsiranana | Rene T.,University of Dschang | And 3 more authors.
Renewable and Sustainable Energy Reviews | Year: 2015

In Cameroon, these last centuries, an increase in energy demand for cooling and heating in buildings has been witnessed all over the world. Solutions must be proposed by researchers and specialists of buildings to remedy this situation. In this study, a literature review on the thermal insulation applications to external walls of buildings was presented, and a case was investigated in a tropical wet and hot climate. The economic model including the cost of insulation material and the present value of energy consumption and the cost over a lifetime of 22 years of the building, were used to find the optimum insulation thickness, energy saving, and payback period, for buildings in Cameroon. Materials that extruded polystyrene were chosen and used for two typical wall structures (Concrete block (HCB) and compressed stabilized earth block wall (CSEB)). The yearly cooling transmission loads, according to wall orientations and percentage of radiation blocked were calculated using the explicit finite-difference method under steady periodic conditions. As a result, it was found that the lowest value of optimum insulation thickness (0.09 m) and energy savings (79.80%) were obtained for the south-oriented wall, while the payback period (4.73years) was the highest on the same face compared to all wall orientations. Insulation optimum thickness was higher in the HCB wall (0.0983 m) than in CSEB wall (0.0958 m), however, the payback period was the weakest for the HCB wall compared to the other wall type. © 2015 Elsevier Ltd. All rights reserved.

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