Variation saisonnière de la composition chimique de carraghénophyte, Gymnogongrus patens (J. Agardh) de la côte atlantique marocaine

Les compositions chimiques du carraghénophyte, Gymnogongrus patens ont été analysées sur des échantillons d’algues récoltées mensuellement pendant un cycle annuel, d’avril 2002 à mars 2003, sur la plage de Méhdia (Nord ouest de la côte atlantique marocaine). L’analyse de la composition chimique des thalles montre que la teneur en matière sèche (MS), en carraghénanes, en azote total et en cendres présente des variations saisonnières. La teneur moyenne en matière sèche est de 19,7% de la matière fraîche du thalle. Ainsi, celle-ci varie de 16% en automne-hiver à 22,5% en période printanière et estivale. L’étude de la production des carraghénanes par Gymnogongrus patens montre que les meilleurs rendements sont obtenus en été (30,2 % en août), les plus faibles en hiver (8,4% en janvier). Ceci montre que la meilleure période de récolte de l’espèce en vue de son exploitation est l’été. Les teneurs en azote total sont comprises entre un maximum noté en février (3,61% MS) et un minimum enregistré en août (2,57 % MS). Les taux moyens en cendres sont légèrement élevés, ils sont de l’ordre de 35% MS. Le maximum est obtenu en janvier (46,34% MS) et le minimum pendant le mois de septembre (28,77% MS). L’analyse des taux en cendres au cours de l’année montre que cette espèce est capable d’accumuler des concentrations élevées en sels minéraux et peut donc être utilisées pour l’épuration des eaux.Mots-clés : Gymnogongrus patens, composition chimique, carraghénanes, azote total, cendres, Maroc. Seasonal varaition in the Chimical composition of Gymnogongrus patens Agardh on Moroccan Atlantic caost The chimical composition of Gymnogongrus patens J. Agardh (Rhodophyta, Phyllophoracea) has been analyzed on samples collected monthly on a one year cycle from April 2002 to March 2003 on Méhdia beach (North west Atlantic caost of Morocco). The analysis of chemical composition of thallus shows that the content of dry matter, of carrageenan, of nitrogen and of ash present also a seasonal variations. The study of carrageenan production from Gymnogongrus patens shows that the best yields were obtained In summer (30,2% in August) and the lowest ones in winter (8,4% in January). This shows that the best period of harvest of this species in order to its exploitation is a summer. The contents of total nitrogen are between a maximum in February (3,62%) and a minimum registered in August (2,57%). The medium rates of ash are highers little bite, they arrived to 35%. The maximum is observed in January (46.34% MS) and the minimum during September (28,77% MS). This important variation of ash rates during a year show that this species can accumulate high concentrations of minerals salt, therefore it can be used like an also for the epurification of waters.Keywords : Gymnogongrus patens, chimical composition, carrageenans, nitrogen, ash, Morocco

Contribution à la connaissance des micromycètes du Maroc. Cas des espèces en survie dans un milieu aquatique

Cette étude présente les premiers résultats concernant l’analyse quantitative et qualitative des micromycètes d’origine terrestre de la région de Rabat (Maroc). Les espèces fongiques décrites ont été isolées de l’eau d’un lac-réservoir ; elles ont été entraînées dans le milieu aquatique par différents moyens de transport. L’analyse fongique des échantillons d’eau prélevés du rivage et du large du lac, ainsi que de l’écume et d’autres matériaux immergés dans l’eau a montré que l’eau du lac est riche en champignons (10 250 UFC/litre). Sa charge fongique n’est pas uniformément répartie ; c’est l’eau du rivage qui est la plus chargée.Les souches isolées sont identifiées en se basant sur la morphologie de  leurs appareils végétatif et reproducteur. Cinquante espèces de micromycètes ont été obtenues ; elles appartiennent principalement aux genres Penicillium, Fusarium, Aspergillus et Trichoderma. Ce sont surtout des champignons telluriques, en survie dans l’eau et à large répartition géographique. Six de ces espèces sont inventoriées pour la première fois au Maroc.Mots-clés : Fusarium, Penicillium, micromycètes, champignons terrestres, lac-réservoir, Maro

Synthesis analysis of the free form curves and surfaces parametrical models

Parametrical models have become an important mathematical tool for free form curves and surface description. they allow the use of state-of-the-art computers to do the various processing and analysis with respect to shape (calculation of the volume and surface area, vibration analysis, NC programs preparation, etc.). Without these models, the current product design and manufacturing would be difficult. The paper presents an analysis study for the most important parametrical models of free form curves and surfaces description (Ferguson, Coons, Bezier, B-Spline and rational models). Firstly, it emphasises external and mathematical properties of each model. Secondly, it gives the most interesting interfaces between models. Thus the process of complex surface design and manufacturing would be more efficient in view this analysis. Finally for validation, the study is ended by an application to the design of a car bonnet.Parametrical models have become an important mathematical tool for free form curves and surface description. they allow the use of state-of-the-art computers to do the various processing and analysis with respect to shape (calculation of the volume and surface area, vibration analysis, NC programs preparation, etc.). Without these models, the current product design and manufacturing would be difficult. The paper presents an analysis study for the most important parametrical models of free form curves and surfaces description (Ferguson, Coons, Bezier, B-Spline and rational models). Firstly, it emphasises external and mathematical properties of each model. Secondly, it gives the most interesting interfaces between models. Thus the process of complex surface design and manufacturing would be more efficient in view this analysis. Finally for validation, the study is ended by an application to the design of a car bonnet

System multilayered applied to the radiative cooling

In applied optics, the multilayered structures (MLS) take an important place in many instrumental and industrial devices. The aim of this work is to study the MLS in order to optimize the inverse greenhouse effect; it is made by a survey on theoretical formalism of the energy exchange phenomena. This optimization requires that the window materials (MLS) are good reflectors in the visible range and assuring a total transmission in the infrared zone (8-13 µm); One of the support elements, of the window, answering to these criterions is germanium, for which we have studied the thickness influence and have found that the equilibrium temperature reached by the absorber has a minimal value between 0.01 µm and 0.06 µm. However, only with germanium, the window can not products the inverse greenhouse effect. Indeed, the germanium must include other layers in order to increase the visible reflectance and the infrared transmittance (8-13µm); what forms a multilayered structure. Several system have been used, only 7 of them have been kept for this work: S1, S2, …, S7 systems. Only the following systems: S2/S1, S3/S2/S1 and MgO/S3/S2/S1 give a radiative cooling effect, with a very good result of 15 °C below ambient temperature in the case of the S6 system. To approach of the real conditions of this system realization (S6), we simulated the effects of such imperfections, as presence of air, that would be due to the quality of the layers deposition. This study is made in the case of the S7 system. As results, we found that, for zenithal angles ≤ 60°, the layers of air, for which the thickness is lower than 0.5 µm, don't present any influence on the absorber's equilibrium temperature.In applied optics, the multilayered structures (MLS) take an important place in many instrumental and industrial devices. The aim of this work is to study the MLS in order to optimize the inverse greenhouse effect; it is made by a survey on theoretical formalism of the energy exchange phenomena. This optimization requires that the window materials (MLS) are good reflectors in the visible range and assuring a total transmission in the infrared zone (8-13 µm); One of the support elements, of the window, answering to these criterions is germanium, for which we have studied the thickness influence and have found that the equilibrium temperature reached by the absorber has a minimal value between 0.01 µm and 0.06 µm. However, only with germanium, the window can not products the inverse greenhouse effect. Indeed, the germanium must include other layers in order to increase the visible reflectance and the infrared transmittance (8-13µm); what forms a multilayered structure. Several system have been used, only 7 of them have been kept for this work: S1, S2, …, S7 systems. Only the following systems: S2/S1, S3/S2/S1 and MgO/S3/S2/S1 give a radiative cooling effect, with a very good result of 15 °C below ambient temperature in the case of the S6 system. To approach of the real conditions of this system realization (S6), we simulated the effects of such imperfections, as presence of air, that would be due to the quality of the layers deposition. This study is made in the case of the S7 system. As results, we found that, for zenithal angles ≤ 60°, the layers of air, for which the thickness is lower than 0.5 µm, don't present any influence on the absorber's equilibrium temperature

Croissance et capacité réproductive de Gymnogongrus patens (J. Agardh) (Rhodophyceae, Gigartinale) de la côte atlantique marocaine

L’algue carraghénophyte Gymnogongrus patens présente une large distribution sur le littoral marocain, sa valorisation et son exploitation ont été précédées par l’étude de sa biologie en milieu naturel. Le site étudié est la plage de Méhdia situé au nord de la côte atlantique marocaine. L’influence des facteurs environnementaux (température, salinité, nitrates et phosphates) sur l’évolution de la croissance a été étudiée par d’analyse en composantes principales (ACP). La croissance de l’espèce présente une variation saisonnière, ainsi deux périodes de croissance ont été déterminées : une période de forte croissance fin printemps et été et une période de faible croissance en automne et en hiver. L’ACP a confirmé cette saisonnalité de la croissance, en précisant que le gain en poids de thalles est principalement lié à l’augmentation de nombre de ramification total. La période active de croissance est caractérisée par l’élévation de la température, de la salinité et de l’intensité lumineuse principalement. L’étude de la capacité reproductive de G. patens a permis de montrer que l’espèce est fertile toute l’année avec une dominance de la génération tétrasporophytiques. Le maximum de fertilité a été obtenu en été.Mots-clés : Gymnogongrus patens, croissance, reproduction, ACP, Maroc.Growth and reproductuive capacity of Gymnogongrus patens (Rhodophyceae, Gigartinale) on the Morccan Atlantic coastGymnogongrus patens represent an important biomass along the Atlantic coast of Morocco, the first step befor exploitation is gather information about the biology and growth of this species in naturel environment. The studied site is the beach of Mehdia located at the north of the Moroccan Atlantic Coast. The influence of environmental parametres (temperature, salinty, nitrates and phosphates) on growth has been studied using Principal Components Analysis (ACP). The monthly survey of its growth did sow seasonal variations. G. Patens has 2 periods of growth: period’s active growth at the ending of spring and summer and period’s weak growth in automn and winter. ACP showed a seaonal variation of the species growth. The active growth periods of G. Patens are characterized by important temperature and salinty and light intensities. The species was fertil almost all along the year and tetrasporophyte pahse predominated. The maximum of fertility was obtained in summer.Keywords : gymnogongrus patens, growth, reproduction, ACP, Morocco

Conformational flexibility of the oncogenic protein LMO2 primes the formation of the multi-protein transcription complex

LMO2 was discovered via chromosomal translocations in T-cell leukaemia and shown normally to be essential for haematopoiesis. LMO2 is made up of two LIM only domains (thus it is a LIM-only protein) and forms a bridge in a multi-protein complex. We have studied the mechanism of formation of this complex using a single domain antibody fragment that inhibits LMO2 by sequestering it in a non-functional form. The crystal structure of LMO2 with this antibody fragment has been solved revealing a conformational difference in the positioning and angle between the two LIM domains compared with its normal binding. This contortion occurs by bending at a central helical region of LMO2. This is a unique mechanism for inhibiting an intracellular protein function and the structural contusion implies a model in which newly synthesized, intrinsically disordered LMO2 binds to a partner protein nucleating further interactions and suggests approaches for therapeutic targeting of LMO2