Academic literature on the topic 'Algerian Gyres'

Abstract. The presence of two large-scale cyclonic gyres in the Algerian Basin influences the general and eddy circulation, but their effects on water mass transfer remain poorly characterized. Our study has confirmed the presence of these gyres using the first direct current measurements of the whole water column collected during the SOMBA-GE2014 cruise, specifically designed to investigate these gyres. Using cruise sections and a climatology from 60 years of in situ measurements, we have also shown the effect of these gyres on the distribution at intermediate depth of Levantine Intermediate Water (LIW) with warmer (∼ 0.15 ∘C) and saltier (∼ 0.02) characteristics in the Algerian Basin than in the Provençal Basin. The Algerian Gyres, combined with the effect of anticyclonic Algerian Eddies, also impact horizontal density gradients with sinking of the isopycnals at the gyres' centers. Temporal cross-correlation of LIW potential temperature referenced to a signal observed southwest of Sardinia reveals a timescale of transit of 4 months to get to the center of the Algerian Basin. The LIW potential temperature and salinity trends, on average in the basin interior, are estimated to be +0.0022 ± 0.0002 ∘Cyr-1 and +0.0022 ± 0.0001 yr−1, respectively, over the 1968–2017 period and accelerating to +0.048 ± 0.003 ∘Cyr-1 and +0.0076 ± 0.0009 yr−1 over the 2013–2017 period.

Abstract Drifter observations and satellite-derived sea surface height data are used to quantitatively study the surface geostrophic circulation of the entire Mediterranean Sea for the period spanning 1992–2010. After removal of the wind-driven components from the drifter velocities and low-pass filtering in bins of 1° × 1° × 1 week, maps of surface geostrophic circulation (mean flow and kinetic energy levels) are produced using the drifter and/or satellite data. The mean currents and kinetic energy levels derived from the drifter data appear stronger/higher with respect to those obtained from satellite altimeter data. The maps of mean circulation estimated from the drifter data and from a combination of drifter and altimeter data are, however, qualitatively similar. In the western basin they show the main pathways of the surface waters flowing eastward from the Strait of Gibraltar to the Sicily Channel and the current transporting waters back westward along the Italian, French, and Spanish coasts. Intermittent and long-lived subbasin-scale eddies and gyres abound in the Tyrrhenian and Algerian Seas. In the eastern basin, the surface waters are transported eastward by several currents but recirculate in numerous eddies and gyres before reaching the northward coastal current off Israel, Lebanon, and Syria and veering westward off Turkey. In the Ionian Sea, the mean geostrophic velocity maps were also produced separately for the two extended seasons and for multiyear periods. Significant variations are confirmed, with seasonal reversals of the currents in the south and changes of the circulation from anticyclonic (prior to 1 July 2007) to cyclonic and back to anticyclonic after 31 December 2005.

Background: Alzheimer’s disease (AD) is a progressive and irreversible neurodegenerative disorder. It is characterized by a gradual decrease in cognitive function and is considered a disorder in which the intensifying neuronal loss. The autopsy is considered the gold standard for the diagnosis of AD and non-AD dementia. Objective: Our study aims to clarify the involvement of neuroinflammation processes in brain lesions of AD. Methods: The defunct was admitted to the forensic medicine department of Issad Hassani Hospital (Algeria). In order to recover the brain, an autopsy was performed within 24 hours of death and then immediately fixed in formaldehyde to maintain structural brain integrity for histological and immunohistochemical analysis. Results: Our findings indicate the presence of tissue lesions in the specific brain regions: right middle frontal gyrus, right cingulate gyrus, right putamen and globus pallidus, right caudate nucleus, right hippocampus, inferior parietal lobule, left parahippocampal gyrus, and left hippocampus. Notably, there is a predominant occurrence of lesions: granulovacuolar degeneration, Hirano bodies, cotton-wool, and neuritic plaques. The causes of neurodegenerative processes are probably related to TNF-α, IL-1β, and TGF-β production and iNOS expression by the NF-κB activation pathway in the R-HP, inducing necroptosis. Conclusions: The occurrence of neuroinflammatory responses is linked to tissue lesions in AD. The production of inflammatory cytokines is the basis of this process, which ultimately leads to the necroptosis, which is triggered by neuroinflammation amplification. The inhibition of neuroinflammation by targeting TNF-α/iNOS could stop tissue damage, this may be a promising therapeutic pathway.

ABSTRACT The Algerian Space Agency has been active in the field of microsatellite engineering for more than 15 years and has successfully developed microsatellites under several know-how transfer technology programs, six to date. This paper presents the flight results and lessons learned from the attitude determination and control system (ADCS) flown on the ALSAT-2B satellite, an Earth observation microsatellite, by analysing the behaviour of the satellite from the initial attitude acquisition through the coarse pointing mode then the nominal mode, where the payload is first tested, and finally the orbit control mode. The spacecraft was launched on 26 September 2016 and placed into a 670km Sun-synchronous orbit with a solar local time at an ascending node of 22:15. The ADCS performance presented here mainly focuses on the launch and early operation results. ALSAT-2B includes four reaction wheels in a pyramidal configuration, three gyros, three Sun sensors, three magneto-torquers, one magnetometer, and one star tracker for agile and accurate attitude control. In addition, a propulsion system based on four 1N hydrazine thrusters is also used on board the microsatellite. The main new development in this platform compared with previous ones of the same type is the fusion of the star tracker and measurements by the three gyroscopes into one gyrostellar estimator that was implemented for the first time on ALSAT-2B, and the pyramidal configuration of the wheels, aiming to increase the angular momentum. The results obtained from the early launch operations for different ADCS modes are very encouraging and fulfil all the requirements set during design and testing. Currently, the satellite has accomplished its fourth year in orbit and is still operational and producing high-quality images.

Les données de la campagne océanographique SOMBA-GE2014, nous ont permis de mettre en évidence la présence des gyres algériens via des mesures de courant. Les radiales de température et salinité obtenues à travers le bassin ont permis la visualisation de l'influence des gyres algériens sur la répartition hydrologique. En effet des eaux levantines intermédiaires jeunes s'étendent depuis la veine d'eau remontant le plateau sarde vers l'intérieur du bassin algérien, sous forme de patchs. Des climatologies du cœur de la LIW et de WIW couvrant la période 1960 à 2017 dans le bassin Algéro-Provençal, ont été produites grâce à la base de données Méditerranéenne de profils de température et salinité et des nouvelles méthodes de détection. Un transport de LIW vers l'ouest, depuis la veine sud de la Sardaigne vers l'intérieur du bassin algérien en suivant la périphérie des gyres algériens est mis en évidence par cette climatologie et confirmé par la corrélation croisée du signal de refroidissement observé durant les années 80. L'estimation des tendances des caractéristiques de la LIW et WIW contribuent à documenter leur évolution. L'accélération du réchauffement observée dans tout le bassin à partir de 2010 est alarmante. Les observations par les gliders ont permis d'appuyer nos conclusions quant à l'efficacité des structures de méso et de sous-méso échelle pour le transport des masses d'eaux vers l'intérieur du bassin Algérien. En effet nous avons observé des parcelles de WIW, LIW et WMDW à l'intérieur du bassin Algérien dont les caractéristiques sont plus marquées que les eaux adjacentes
Data from the SOMBA-GE2014 oceanographic cruise, allowed us to highlight the presence of Algerian gyres via current measurements. The temperature and salinity sections obtained across the basin allowed the visualization of the influence of the Algerian gyres on the hydrological distribution. Indeed, young intermediate Levantine waters extend from Saridinian LIW vein towards the interior of the Algerian basin, in the form of patches. LIW and WIW core climatologies covering the period 1960 to 2017 in the Algerian-Provençal basin were produced using the Mediterranean database of temperature and salinity profiles and new detection methods. A westward transport of LIW from the southern vein of Sardinia to the interior of the Algerian basin following the periphery of the Algerian gyres is highlighted by this climatology and confirmed by the cross-correlation of the cooling signal observed during the 1980s. The estimation of trends of LIW and WIW characteristics help to document their evolution. The acceleration of warming observed throughout the basin from 2010 is alarming. Glider observations have supported our conclusions regarding the effectiveness of mesoscale and submesoscale structures for the transport of water masses into the interior of the Algerian basin. Indeed, we observed WIW, LIW, and WMDW parcels within the Algerian Basin with more pronounced characteristics than adjacent waters

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