Kirsten Koop

Pierre-Antoine Landel

Bernard Pecqueur

Pourquoi croire au modèle du développement territorial au Maghreb ? Une approche critique

Introduction 1

Depuis la décolonisation 1 , les politiques de développement économique des pays du Maghreb, ont été fortement déterminées par des modèles extérieurs (occidentaux ou socialistes), axés principalement sur la croissance et supposés être mis en oeuvre par les Etats avec l'appui des dispositifs de coopération. Après une phase où étaient préconisées planification centralisée et industrialisation (Maroc, Algérie, Tunisie), vint celle du « développement local ». Nous assistons actuellement au transfert du modèle français de « développement territorial » vers ses anciennes colonies.

2

Dans le contexte contemporain des processus de la mondialisation, les sciences régionales des pays industrialisés (économie régionale et géographie économique notamment) semblent avoir découvert le « territoire » 2 à l'échelle infranationale, comme « noeud des processus critiques de développement et de croissance » [START_REF] Scott | La poussée régionale : vers une géographie de la croissance dans les pays en développement[END_REF]. Le territoire est désormais considéré comme le gabarit adéquat à la conception du développement et devient ainsi le cadre de l'action publique. Cela implique la mutation du rôle de l'Etat, moins régulateur, et l'amplification de la décentralisation. En France, le concept de « projet de territoire » est devenu référent incontournable de l'action publique. Depuis le milieu des années 2000, la DATAR 3 a développé des actions de coopération avec les pays du Maghreb, d'abord au Maroc, puis en Tunisie, et enfin en Algérie, pour accompagner une profonde mutation des politiques publiques, reposant sur l'affirmation du « territoire de projet » comme espace et mode pertinent du développement. Au vu des difficultés, voire de l'échec des transferts antécédents de modèles de développement occidentaux, il semble de bon sens de questionner les conditions et limites de la « transférabilité » de ce nouveau modèle vers des pays du Sud. Si les programmes de coopération mis en oeuvre par les Etats attestent cette possibilité de transfert, la réalité concrète de leur mise en oeuvre, dans des contextes qui diffèrent considérablement des cadres de référence français, souligne la difficulté de l'exercice.

L'évolution des visions françaises de développement et leurs applications au Maghreb

Le rattrapage industriel

Les programmes et plans de développement conçus par et pour les pays maghrébins depuis leur indépendance n'ont pas échappé à l'inscription, directe ou indirecte, dans la vision et le modèle français de développement. Le référentiel dominant des politiques nationales, aussi variables furent-elles 4 , était celui du rattrapage du retard par rapport aux pays industrialisés. Les gouvernements des différents pays du Maghreb fondaient leurs politiques de développement sur l'industrialisation et la planification centralisée et nationale [START_REF] Dresch | Industrialisation au Mahgreb[END_REF]. Tous les éléments de base de la vision moderniste du développement peuvent être retrouvés : le « développement » fut pensé comme une rupture avec le « sous-développement », il était supposé être réalisé à travers la croissance du secteur économique moderne, les particularités politiques, les réalités socioculturelles diverses et le potentiel du secteur informel grandissant étant négligés par principe.

Certes, ce fond commun dans les conceptions du développement se décline de façons différentes dans ces pays. Les programmes nationaux successifs des années 1960 et 1970 montrent une forte préoccupation pour le renforcement des pôles de croissance 5 , dans une approche sectorielle, le gabarit d'application étant la nation entière (Scott, Storper, 1991, p. 8). De cette approche du développement découlaient aussi les modalités du découpage régional : celui-ci fut réalisé sur la base d'un ensemble de critères largement dominés par les aspects économiques et dans une démarche administrative, servant surtout à permettre l'application des politiques nationales (voir, par exemple, Bellaoui, 2009).

Le développement local

Le bilan de l'application de ces stratégies modernistes au Maghreb audébut des années 1980 est connu : des chiffres de croissance économique parfois négatifs (Algérie), un fort endettement, la persistance de la pauvreté de masse, surtout en milieu rural. Les pôles de croissance manquaient de dynamisme, les effets d'entraînement se laissaient attendre. Les causes de l'échec seront tantôt cherchés dans les facteurs internes aux pays (régimes de dictature, corruption, clientélisme), tantôt dans les facteurs externes, comme l'échange inégal entre pays industrialisés et pays en développement. Des économistes, s'inscrivant dans les théories de la dépendance, découvrent les surcoûts de l'industrialisation liés à la dépendance des transferts financiers et du savoir-faire occidental (Courlet, Gaulet, 1973). Ils critiquent l'image statique que les analyses modernistes aussi bien que marxistes ont des sociétés « traditionnelles », leur vision ahistorique et découvrent la petite production artisanale et le secteur informel non comme « arriéré » et « obstacle » au développement, mais comme son potentiel (Courlet, Judet, 1986, p. 522).

Ainsi émerge au sein des sciences économiques un courant scientifique se penchant sur le potentiel économique des régions maghrébines (Bouchara, 1987 ;Courlet 1989, etc.). Il est intéressant de noter que les auteurs de ce nouveau type d'études régionales analysent, en parallèle, la reconversion réussie de certaines régions industrielles occidentales en crise, notamment de l'Italie du Nord [START_REF] Judet | Quand la Ruhr entre au Musée[END_REF][START_REF] Garofoli | Le développement périphérique en Italie[END_REF] ainsi que le succès des petits tigres asiatiques [START_REF] Judet | Les nouveaux pays industriels[END_REF]. Dans ce va-et-vient entre études au Nord et aux Suds commence à se dessiner une nouvelle vision du développement : celui du « développement endogène ». Rapidement qualifié de développement local [START_REF] Pecqueur | Le développement local[END_REF]Colettis et al. 1990), il donne toute sa place aux dynamiques locales, aux acteurs locaux, à leur initiative et aux stratégies endogènes ayant échappé à la planification dite « d'en haut », a-spatiale dans son approche. Cette découverte des dynamiques locales s'inscrit, certes, dans un courant plus vaste, international, travaillant aussi bien sur les pays du Nord dans le contexte post-fordiste qui se dessine, que sur les pays des Suds. Elle trouve des fondements théoriques dans les travaux internationalement reconnus de Stöhr et Tödling (1971[START_REF] Friedmann | Territory and Function[END_REF][START_REF] Stöhr | Development from Above or Below ? The Dialectics of Regional Planning in Developing Countries[END_REF].Au Maghreb, elle sera particulièrement diffusée à partir de la conférence fondatrice sur le « développement endogène », organisée par l'Institut de Recherche Economique et de Planification (IREP) à Tunis en 1987.

Ce changement de perspective scientifique trouve son application concrète aussi bien en France que dans les pays du Maghreb. Pourtant, ses formes et dimensions varient fortement. En France, en réaction à la crise du modèle fordiste, émerge, à la fin des années 1980, le « projet de territoire », outil qui permet à des acteurs coordonnés d'apporter des solutions à des problèmes productifs inédits à l'échelle infra-nationale (Pecqueur, 1989, p. 15). Cette approche définit le territoire « comme le résultat d'un processus de construction par les acteurs » (Pecqueur, 2005, p. 299). Les relations sont placées au coeur du système d'innovation et développées à des échelles intermédiaires qui se situent entre l'individu et les systèmes productifs nationaux. Le cadre de l'Etat nation, comme espace de développement et de mise en oeuvre des politiques macro-économiques, est ainsi remplacé par un espace méso-économique. Celui-ci est appréhendé selon deux modes : celui de la coordination sectorielle, entre acteurs d'une même filière [START_REF] Gillard | Le secteur comme concept théorique, essai de méso-analyse[END_REF] et celui du regroupement partiel d'acteurs ou d'agents économiques, dans des logiques de coopération [START_REF] Gilly | Gouvernance et proximité[END_REF]. En réaction aux dépendances financières et organisationnelles, l'autonomie est au coeur des notions de « self-reliance » ou de développement autocentré, qui repose sur « l'utilisation prioritaire des facteurs de production disponibles localement » (Rist, 2007, p. 219).

Contrairement à l'application en France dece changement de vision sur les conditions du développement dans une partie du monde académique, il n'influençait guère les politiques nationales maghrébines. Des projets participatifs de « développement d'en bas » émergent cependant timidement dans le milieu de la coopération et des associations à partir de la fin des années 1980. Alors que les processus de décentralisation, base indispensable pour la réalisation du « développement local », s'approfondissent en France, ils sont encore loin de s'affirmer au Maghreb.

Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro...

EchoGéo, 13 | 2010

A partir du milieu des années 1990, le concept du développement local commence donc à être remplacé, en France, par celui du développement territorial, concept transféré au Maghreb depuis les années 2000 par le biais de programmes bilatéraux de coopération. En quoi consiste le changement d'optique ? Pourquoi assiste-t-on, contrairement au faible succès du modèle de développement local, à une prise en compte réelle par les autorités publiques de ce nouveau modèle ?

France ou Maghreb, Nord ou Sud, pour la première fois depuis l'époque de la colonisation, les pays semblent se trouver face à des dynamiques similaires : celles de la mondialisation. Les défis semblent être les mêmes : adapter les économies et sociétés face à des marchés libéralisés et à la mobilité globale des firmes. Aussi, les réponses au changement fondamental des conditions du développement, au Nord comme au Sud, paraissent-elles être les mêmes : ouverture économique volontaire ou forcée (au Sud, à travers les programmes d'ajustement structurel), retrait de l'Etat par rapport aux logiques du marché et découverte unanime du territoire, à l'échelle infranationale, comme « l'espace d'action publique, de mobilisation politique et de changement économique » (Keating, Loughlin, 1997, p. 11). Un changement fondamental dans la conception du développement, généralisé cette fois-ci et non restreint à une certaine communauté scientifique, comme ce fut le cas pour le développement local, s'est réalisé : celui du rattrapage du retard des nations à « l'intégration des territoires » dans les flux et réseaux mondiaux [START_REF] Koop | Les nouvelles fractures du monde et le défi pour la recherche sur les inégalités de développement[END_REF]. Bien que la notion de développement local continue à être utilisée, certains auteurs et acteurs du développement passent à celle du développement territorial pour des raisons non explicitées, mais consistantes.

Le premier argument à avancer est que le développement local est trop connoté, autour d'un développement économique autocentré. A l'ère de la mondialisation et du libre échange, le développement local doit désormais être pensé en articulation avec d'autres échelles. Cette ouverture aux marchés introduit la nécessité pour les territoires d'être compétitifs en ajustant production et vente sur les marchés extérieurs.

La seconde différence réside dans l'émergence de nouveaux modes de gouvernance. Dans le contexte de la décentralisation et de l'affirmation de la société civile en tant qu'acteur du développement, le territoire n'est plus le monopole de l'Etat ou des acteurs politiques. D'autres acteurs le revendiquent pour régler leurs problèmes, qu'ils soient d'origineéconomique, sociale ou environnementale. Le développement territorial s'appuie sur une double notion de territoire : le territoire « donné », issu de l'histoire administrative des pays, en opposition au territoire « construit » [START_REF] Colletis | Intégration des espaces et quasi intégration des firmes : vers de nouvelles rencontres productives ?[END_REF]. En parallèle à l'émergence de politiques de contractualisation visant à accompagner les processus de développement à l'échelle infranationale, la gouvernance désigne « une production de règles par des acteurs en vue de réguler le système économique, productif, social, etc.». (Angeon, Houédété, 2006). Elle place la coordination au coeur des processus de développement, les acteurs ayant une plus ou moins grande capacité à se grouper pour créer leurs propres organisations, règles et normes, face à des problèmes à résoudre localement.

La troisième différence tient au fait que les acteurs ne visent plus l'allocation optimale de ressources dont seraient dotés initialement les territoires, mais la création de ressources territoriales. Ce processus de création se fait en valorisant les potentiels spécifiques des territoires, c'est-à-dire les avantages relatifs qui distinguent le territoire par rapport à ses concurrents potentiels (ce processus de spécification s'illustre par exemple dans le cas des labellisations de produits agro-alimentaires en appellation d'origine). Ceux-ci vont alors « promouvoir une stratégie haute de développement reposant sur des ressources spécifiques ou latentes produites par des acteurs locaux et dédiées » (Adelmalki, Courlet, 1996, p. 18). C'est à partir de ces ressources spécifiques que les acteurs du territoire vont rechercher une compétitivité par la différenciation, à partir de qualités spécifiques, en parallèle à une mobilisation systématique des patrimoines et identités locales [START_REF] Landel | Invention de patrimoines et créations de territoires[END_REF].

Ainsi, le développement territorial se différencie du développement local au travers de trois traits essentiels : l'ouverture des marchés, la construction de systèmes de gouvernance élargis à d'autres acteurs et la mobilisation de ressources spécifiques. Contrairement aux administrations des pays industrialisés, celles des pays des Suds, et notamment du Maghreb, se retrouvent face à un défi supplémentaire si elles veulent créer des conditions favorables à la réalisation de projets de territoire : elles doivent intégrer les notables et institutions coutumières en tant qu'acteurs stratégiques à part égale dans les politiques territorialisées. Un premier pas dans cette direction est certes la reconnaissance du douar, défini comme un « ensemble de foyers réunis par les liens réels ou fictifs de la parenté, correspondant à une cellule territoriale, comportant ou non des modes d'exploitation communautaire » [START_REF] Mahdi | La tribu au secours du développement pastoral. In La tribu à l'heure de la globalisation[END_REF]

Conclusion : limites et perspectives du développement territorial pour les Suds

Les démarches de transfert de la thématique du développement territorial posent nombre de questions et, en premier lieu, celle du sens de la notion de « territoire » dans les pays du Maghreb. Quelle est l'utilité de ce concept ? Quelles sont les conditions d'acceptation ou de rejet de cette catégorie d'analyse et de stratégie de développement transférée au Sud ?

Les premiers résultats obtenus montrent que les autorités locales ont tendance à ne considérer que le territoire « donné », issu des organisations administratives hérités du colonialisme, au détriment des territoires « construits », au travers de la coordination d'acteurs. Aussi, la notion de ressource territoriale devrait-elle être approfondie pour ces We here question the relevance of the application of the concept of territory in these North African countries -a concept which turned out to be a central one in French regional planning politics. We particularly analyse the two preconditions for the revealing of specific territorial resources: the decentralisation processes of North African public policies and the capacity of local actors to participate at territorial governance systems.

Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro... EchoGéo, 13 | 2010

  , comme un espace d'intervention. Il y a là un lieu de rencontre entre les structures administratives d'une part, et les organisations tribales ou coutumières. C'est à ce niveau que l'Etat algérien a décidé de concentrer ses moyens d'intervention en faveur du développement rural au travers des Plans de Proximité et de développement Rural (P.P.D.R.) mis en oeuvre depuis 2004, pour rapprocher l'Etat des populations qui en sont éloignées. Au final, cette faible « autonomie » territoriale peut être illustrée par le schéma suivant : Schéma 1 -Autonomie du secteur public aux échelles infra nationales et intégration des acteurs non publics : deux processus en cours mais inachevés Auteurs : Kisten Koop, Pierre-Antoine Landel, Bernard PecqueurParallèlement à ces processus administratifs, bien qu'incomplets, ouvrant la voie à la réalisation de projets de territoire, la tendance à la concession(Giraut, 2006, p. 13) s'affirme au travers de l'identification de sites stratégiques pour l'accueil d'investissement étrangers. A titre d'exemples peuvent être citées les zones franches d'exportation Tanger Med au Maroc et de Bizerte en Tunisie. Ces espaces extraterritoriaux, cédés par l'Etat, échappent non seulement aux législations nationales en vigueur, mais aussi au contrôle par les collectivités territoriales et ainsi à toute initiative de développement territorial.

RÉSUMÉS

  Depuis la décolonisation, plusieurs modèles de développement ont fait l'objet de transferts de la France vers les pays du Maghreb. La crise du développement industriel a ouvert la voie au développement local à partir des années 1980, et la puissance du mouvement de mondialisation a vu émerger le développement territorial. Depuis le début des années 2000, différents programmes de coopération ont été développés dans le domaine de l'aménagement sur cette thématique entre la France et le Maroc, puis la Tunisie, enfin l'Algérie.Le concept de territoire apparaît central dans les politiques françaises de développement, sa pertinence mérite d'être discutée dans les pays du Maghreb. Il pose en particulier la question de la décentralisation des politiques publiques, et de la capacité des acteurs locaux à participer à la mise en place de systèmes de gouvernance territoriale, deux conditions indispensables à la construction de ressources territoriales spécifiques.Since decolonisation, a succession of development models has been transferred from France towards North African countries. The failure of the industrial development approach on national level opened the way for local development in the late 1980's, and the power of globalisation dynamics recently gave birth to the "territorial development" model. This new approach towards (economic) development and local governance is actually transferred into regional planning practices of Morocco, Tunisia and Algeria on behalf of several French cooperation programs.

  Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro...

	EchoGéo, 13 | 2010

  Les lois françaises de 1995 (loi Pasqua) et 1999 (loi Voynet) marquent la transformation fondamentale de la politique nationale d'Aménagement du Territoire et traduisent le changement de vision de développement. On passe à une politique décentralisée, au sein de laquelle le projet de territoire intègre le diagnostic de la situation de départ, la construction d'une vision prospective et la définition d'une stratégie au travers de la contractualisation(Gorgeu, Jenkins, 1997, p. 34). Contrairement au concept du développement local, le développement territorial en tant que modèle fait son entrée dans la politique d'aménagement des pays maghrébins. Durant la dernière décennie, trois opérations de transferts ont été décidées puis mises en oeuvre au niveau des Etats. De 2001 et 2007, le Royaume du Maroc a mis en place un programme intitulé « Appui institutionnel à la mise en oeuvre d'une politique d'aménagement du Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro... EchoGéo, 13 | 2010 territoire rénovée au Maroc » avec la participation de l'Etat français, dans le cadre d'un projet du Fonds de Solidarité Prioritaire. La coopération avec la Tunisie s'est inscrite de 2006 à 2009 dans le cadre d'un jumelage, impulsé par la Commission européenne, et associant des partenaires français et italiens. L'objectif affiché est de « renforcer des capacités institutionnelles des organismes de développement régional en matière de promotion de l'investissement privé ». Enfin, l'Algérie bénéficie depuis 2008 d'un nouveau projet du FSP intitulé « Appui institutionnel à la mise en oeuvre de la politique d'aménagement et de développement durable en Algérie ».Il s'agit d'opérations longues, mobilisant des moyens importants, impliquant au niveau français la DATAR.Après l'échec relatif du transfert du modèle de rattrapage industriel, conçu à l'échelle nationale, qu'est-ce qui peut justifier cette nouvelle ingérence occidentale dans ses excolonies? Tout comme celui du développement local, il paraît évident que cette approche dispose d'un atout majeur par rapport aux stratégies sectorielles et nationales : elle permet la prise en compte des acteurs locaux et des logiques socioculturelles et endogènes (souvent dites « informelles »), si longtemps négligés par les politiques publiques. Il s'agit donc de profiter d'opportunités nouvelles, en élargissant le champ des possibles en matière de ressources. Même s'il s'agit d'un modèle universel d'adaptation à la mondialisation, l'application de la stratégie du développement territorial paraît particulièrement séduisante pour les Suds, car elle ouvre une voie pour échapper à la lourdecontrainte de la compétitivité globale, en mettant en avant des ressources spécifiques localisées. Ce modèle paraît donc potentiellement bien adapté aux régions en marge.Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro... EchoGéo, 13 | 2010 éventuellement de planification, mais en aucun cas de décision. L'autonomie financière des collectivités locales reste très limitée. L'organisation administrative s'inscrit dans des systèmes très fortement hiérarchisés qui limitent les possibilités d'initiatives et de coordinations propres aux territoires. Enfin, la culture administrative centralisée limite la possibilité pour les acteurs de définir leurs propres principes et règles d'organisation.Concernant la démarche d'intégration d'acteurs non étatiques dans le développement territorial, permettant potentiellement de construire des ressources spécifiques intégrant la réalité socioculturelle et l'histoire locale, deux constats peuvent être faits.Au Maghreb, les associations et les ONG se sont partiellement substituées à l'Etat là où il faisait défaut, à partir des années 1980. Différents indicateurs permettent de représenter cette évolution. A titre d'exemple, l'Algérie a vu le nombre d'associations passer de 11 000 à 57 000 entre 1987 et 1997, puis à 73 000 en 2004. Au Maroc, après une longue période où elles étaient suspectées, et face aux exigences des bailleurs de fonds internationaux, les associations ont pu se développer quelque peu. Une étude comparative réalisée au niveau local montre l'émergence d'associations de vallées, de corporations, à côté des structures traditionnelles intervenant au niveau des douars. Les partenariats se nouent avec des structures nationales et internationales. En Tunisie, à côté de la reconnaissance de la société civile au travers des conseils locaux de développement, différents types d'organisation, telles que les coopératives de service agricole, les groupements d'intérêt collectif pour la gestion des ressources naturelles ou des groupements de développement voient le jour à différentes échelles territoriales. Affichant leur orientation vers un développement participatif, les ONG suscitent elles aussi la création d'associations au niveau local, en intégrant de façon croissante des exigences de durabilité. Il s'agit là d'acteurs potentiellement déterminants des projets de territoire. L'intégration de ces dynamiques de la société civile par les autorités publiques est encore très loin d'être systématique. Aussi, les programmes de transfert de compétences éludent la question : les associations n'ont été que rarement impliquées dans la formation, et les outils et méthodes d'animation permettant leur implication font largement défaut.

	De surcroît, les modalités de transfert de compétences dans les trois programmes de
	coopération cités, ne semblaient pas en mesure de compenser ce manque d'autonomie :
	les échelles décentralisées ne furent pas impliquées, à l'exception de l'expérimentation
	d'un diagnostic stratégique de territoire développée en 2009 sur le gouvernorat de
	Tozeur, pilotée par un comité composé d'administrations de l'Etat, d'élus, de chefs
	d'entreprises et d'associations 7 .
	L'intégration des acteurs non publics
	Tableau 1 -Du Développement local au développement territorial
	Développement local	Développement territorial
	Renforcement de circuits locaux	Intégration dans marchés à diverses échelles
	Identités et échanges mono scalaires	Identité et échanges multi scalaires
	Mobilisation de ressources locales en	Compétitivité (locale, nationale, mondiale) par la
	réponse aux besoins locaux	génération de ressources spécifiques
	Rôle déterminant de l'Etat dans le dispositif de contractualisation Les limites du transfert	Intégration de nouveaux acteurs dans la gouvernance
	Auteurs : Kirsten Koop, Pierre-Antoine-Landel, Bernard Pecqueur
	Les modalités de transfert contemporain du modèle
	du développement territorial dans les politiques
	publiques
	Pourquoi le transfert du modèle de développement
	territorial français ?
	Un processus de décentralisation inachevé
	La comparaison des processus de déconcentration/décentralisation dans les trois pays du
	Maghreb montre que le processus de déconcentration y est largement avancé. Il se
	déploie jusqu'au niveau des communes, voire au niveau infra communal, avec au Maroc,
	la représentation du Ministère de l'Intérieur au niveau des quartiers et des douars au
	travers du « Moqaddem ». Mais la décentralisation reste incomplète. Les exécutifs des
	assemblées restent largement dominés par l'omniprésence du représentant de l'Etat, qui
	exerce un contrôle a priori sur l'ensemble des décisions, et ce à tous les niveaux. La
	régionalisation, comme transfert des compétences d'aménagement et de planification à

Cette approche du développement met en évidence la nécessité d'une organisation administrative permettant l'émergence de ces projets de territoire à différentes échelles. Elle implique notamment l'autonomie administrative ainsi que l'intégration d'acteurs locaux non publics dans les processus de décision et de réalisation de projets de territoire. Un rapprochement avec la réalité des tendances d'évolution des dispositifs nationaux s'avère ainsi intéressant. Depuis 2006, une approche comparative des processus de territorialisation est engagée dans les pays méditerranéens

6

. Une première synthèse des travaux permet de souligner différentes dynamiques, susceptibles d'être mises en rapport avec les transferts organisés dans le champ du développement territorial. un échelon intermédiaire entre l'Etat et les municipalités et instauration de l'autonomie des services d'administration aux échelles sous-nationales, reste embryonnaire. Cela est particulièrement le cas en Algérie et en Tunisie, où elle reste un niveau d'étude et

  Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro...EchoGéo, 13 | 2010 pays. Si les premières études ont été engagées au Maroc(Courlet, 2006), d'autres situations méritent d'être analysées. Cela pose l'importance des travaux de recherche comparatifs sur ces questions, impliquant les universités et équipes de recherche de chacun des pays.Ces interrogations épistémologiques sous-tendent un questionnement sur les pratiques politiques et aménagistes : quelles peuvent être les définitions de « politiques de développement territorial » dans des pays où le sens même de territoire n'est souvent pas partagé, et où l'autonomie des acteurs territoriaux fait souvent défaut ? La question est alors de savoir si le processus de transfert du modèle de « projet de territoire » peut favoriser l'autonomie nécessaire aux processus de construction et de mobilisation des ressources territoriales spécifiques.La perspective essentielle réside dans un changement de culture, en passant des systèmes hiérarchisés à des systèmes publics, publics-privés, ou mixtes, hybrides ou coopératifs, traduisant une nouvelle capacité organisationnelle. Il s'agit en particulier d'accompagner la mise en place d' «opérateurs territorialisés » susceptibles de réaliser différents types d'opérations sur la ressource : révélation, protection, spécification, articulation avec d'autres ressources. Dans le champ des modes de transfert, un certain nombre de conditions minimales peuvent être proposées pour mieux accompagner le développement territorial. En tout premier lieu, l'échelle du transfert doit être interrogée. Les transferts d'Etat à Etat doivent évoluer vers des coopérations décentralisées portant sur le champ du développement territorial, à partir d'expériences concrètes développées par des collectivités territoriales. Pour ce faire, la définition d'un cadre d'intervention intégrant des appuis financiers et organisationnels serait nécessaire. Il pourrait prévoir en particulier des modalités d'implication des Universités et des équipes de recherche locales dans les transferts, en favorisant le développement des formations. Cette dynamique contribuerait à la mise en réseau des acteurs du développement territorial, dans des dispositifs de recherche action définis au niveau local, national et international. Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro... EchoGéo, 13 | 2010 dans le cadre du réseau RAFAC (Réseau Agriculture Familiale Comparée en méditerranée), sous la direction de Pierre Campagne et Bernard Pecqueur. Pour les pays du Maghreb, 3 équipes sont intervenues : Pour l'Algérie, celle de Slimane Bedrani, Directeur du CREAD, pour le Maroc, celle de Mohamed Mahdi, de l'école Supérieure d'Agronomie de Mekhnès, et pour la Tunisie, celle de Mohammed Elloumi, de l'Institut National d'Agronomie de Tunis. 7. En effet, le partenariat impliquait les Ministères maghrébins de l'Aménagement du Territoire, au travers d'une Direction chargée d'assurer le pilotage des opérations. Les publics concernés sont prioritairement des cadres de l'Etat. De l'échelle centrale aux échelons déconcentrés, ils constituent la cible essentielle des programmes. Les transferts impliquent des experts français, fonctionnaires d'administrations centrales, enseignants chercheurs et cadres des collectivités territoriales. Des séminaires réguliers ont été organisés autour de quatre thématiques : le diagnostic de territoire, la prospective, la contractualisation et l'évaluation.

	BIBLIOGRAPHIE
	Abdelmalki L., Courlet C., 1996. Les nouvelles logiques du développemenT. Paris, L'harmattan,
	Logiques économiques. 415 p.
	Angeon V., Houédété T., 2006. Le développement entre gouvernement et gouvernance : réflexion
	critique sur le rôle des institutions dans le développement. In Ferguène A. (éd.), Gouvernance locale
	et développement territorial. Le cas des pays du Sud. Paris, L'harmattan. 407 p.
	Bouchrara M., 1987. L'industrialisation rampante, ampleur, mécanismes et portée. Exemples
	tunisiens. Economie et humanisme, n° 296.

Bellaoui A., 2009

. L'organisation régionales au Maroc : vers une plus grande artificialisation de l'espace géographique. In Boujrouf S., Antheaume B, Giraut F., Landel P.A., 2009, Les territoires à l'épreuve des normes : et référents et innovations. Contributions croisées sud africaines, françaises et

Pourquoi croire au modèle du développement territorial au Maghreb ? Une appro...EchoGéo, 13 | 2010


Yashank Gupta
email: yahsank.gupta@gipsa-lab.fr

Jonathan Dumon
email: jonathan.dumon@gipsa-lab.fr

Ahmad Hably
email: ahmad.hably@gipsa-lab.fr

Power Curve Analysis Of On-ground Airborne Wind Energy Systems

Keywords: Airborne wind energy system, On-ground system, pumping system, Power curve, Ground station design, Magnus effect, Static modeling, High-level control, Hydraulic stage

In this paper, an algorithm is proposed to control parameters of an on-ground airborne wind energy system for the operational wind speed range, considering different winch configurations and the related saturation of its components, including electrical and hydraulic devices. Coupled with a static model, this leads to a tool that can easily calculate expected power curves for on-ground airborne wind energy system as a function of design parameters. The paper also presents the numerical examples of the power curve for a Magnus-based system and draws a comparison with the power curves of horizontal axis wind turbines.

I. INTRODUCTION

Airborne wind energy systems (AWE) aims at proposing a complementary solution to the conventional wind turbines. AWE systems harness the energy of high altitude winds by using an airborne platform connected to the ground by tethers or conducting cables. AWE systems have attracted a lot of interest in the last few decades (see [START_REF] Ahmed | High altitude wind power systems: A survey on flexible power kites[END_REF] for a survey on soft kites and [START_REF] Cherubini | Airborne wind energy systems: A review of the technologies[END_REF] for AWE systems in general).

Depending on the location of energy production, AWE systems can be divided into two main classes: On-ground production and On-board production AWE systems. On-ground production systems consist of a ground-based generator connected to an airborne platform by tethers. Whereas in the on-board production systems, the turbine is mounted on the airborne platform. Currently, in the research community, there are many innovative designs regarding the airborne platform. The choice of the platform depends on the lifting capabilities of the aerodynamic surface. Classically, kites and unmanned aerial vehicles (UAV) have been used as the airborne platform. But with an increased interest in AWE usage of many innovative concepts are being explored such as Magnus cylinders, rotary kites, balloons etc.

Power curves serve as a tool to analyze the economic feasibility of any type of wind turbine. In literature, there are many studies discussing the power curves of conventional wind turbines. Over the years, the power curves have been validated and improved by incorporating the on-field data from the installed wind turbines. To evaluate the economic viability of airborne wind energy systems, and to draw valid comparisons with the conventional turbines, there is a need to develop accurate power curves for AWE systems. Currently, there are very few working prototypes of AWE systems and none of them is a fully functioning commercial unit. Thus, the power curves for AWE systems are still an open topic of discussion in the research community. In [START_REF] Ranneberg | Fast power curve and yield estimation of pumping airborne wind energy systems[END_REF] a study is presented discussing the family of power curves for different altitudes derived from a model presented in [START_REF] Loyd | Crosswind kite power[END_REF]. The study also compares the power curves with the dynamic simulations of the Enerkite AWE prototype EK30 and it concludes that the significant confidence can be placed on the approach presented in the work for estimating the power curves for AWE systems. In [START_REF] Bauer | Drag power kite with very high lift coefficient[END_REF] a simplified model is analyzed to estimate the maximum feasible drag power for an on-board production system. In [START_REF] Schutter | Optimal control of a rigidwing rotary kite system for airborne wind energy[END_REF] an optimal control problem is discussed which is then used to obtain power curves for a rotary kite AWE system. In the authors' previous work [START_REF] Hably | Control of an airborne wind energy system with a Magnus effect[END_REF], a strategy to control the power production of a Magnusbased AWE system is proposed. In [START_REF] Gupta | Modeling and control of a magnus effect-based airborne wind energy system in crosswind maneuvers[END_REF], the authors propose a 6-DOF mathematical model for the Magnus based AWE system validated by simulation, controlling the system in crosswind trajectories. A static model of the full cycle is presented and compared to the dynamic simulation. In this present study, based on a static model proposed and validated in [START_REF] Gupta | Modeling and control of a magnus effect-based airborne wind energy system in crosswind maneuvers[END_REF] and a structural analysis of ground station structure, including electrical and hydraulic solutions, a generic static model of onground AWES is proposed. A high-level algorithm is the developed to maximize the net output power of the system, taking into consideration the necessary saturation of the system. This fast model can then be used to calculate power curves of on-ground AWES in function of different design parameters. As authors are working specifically on Magnusbased on-ground AWE systems, numerical application for these type of systems is done to draw comparisons with conventional horizontal axis wind turbines. The power curves calculated in this paper give a valuable insight into the potential of AWE systems and expose some advantages over conventional wind turbines.

The paper is organized as follows. Section II focuses on the modeling of the different parts of the system. In section III, the control and the optimization of the output power are presented. A numerical application follows in section IV. The paper ends with some conclusions in section V.

II. MODELLING

A. Model of Wind Profile

In this paper, wind profile power law is considered to describe the evolution of horizontal mean wind speed with altitude. This theoretical model is discussed in detail in literature [START_REF] Archer | An introduction to meteorology for airborne wind energy[END_REF] and provides a good approximation of the wind speed for the altitudes between 100 to 2000 m. According to this model, the wind speed Vw at any altitude z can be given by:

Vw(z) = Vw(z0)( z z0 ) α (1)
Where, z0 represents the operating altitude, Vw(z0) is the known wind speed at altitude z0, and α is an empirically derived coefficient that characterizes the surface. It depends on the stability of the atmosphere and is generally assumed to be equal to 0.143. To take into account the constant variation of the wind speed and to calculate the mean wind speed at a particular site throughout the year, the well know Weibull distribution is used in this paper. The distribution basically tells at a particular site how often the wind blows and how strong it is. Thus, it is a good way to describe the wind speed variations and it is given by:

f (v) = k a v A k-1 e -v A k (2)
Where, f (v) is a probability to have v wind speed over the year, A is the Weibull scale parameter expressed in m/s and is proportional to mean wind speed, and k is the Weibull form parameter describing the shape of the Weibull distribution with its value between 1 and 3. Smaller values of k show very variable winds while larger values show constant winds. Finally, v is the wind speed series whose probability distribution is calculated.

B. Model of a Horizontal axis wind turbine (HAWT)

For conventional wind turbines, the power produced depends on the kinetic energy of the air and Cp the power coefficient of the turbine which is smaller than its theoretical Betz limit 16/27:

PHAW T = 1 2 ρCpAsweptV 3 w (3)
Where, Aswept is the total surface swept by the blades. Power produced, PHAW T , is generally divided into four phases characterized by the design constraints of the system. The first phase is from zero wind speed to cut-in wind speed Vci, where a conventional turbine does not produce any energy. The second phase is from Vci to the nominal wind speed Vnom, where the maximum wind power extraction occurs by maximizing Cp coefficient. The third phase is from Vnom to the cutoff wind speed Vco, and during this phase power is curtailed to nominal power Pnom by reducing Cp coefficient. Finally, for any wind speed beyond Vco, the wind turbine is switched-off to avoid its mechanical and electrical degradation. Therefore, the power curves of a HAWT can be produced by the following set of equations:

PHAW T =            1 2 ρCpmaxAsweptV 3 w if Vci < Vw ≤ Vnom Pnom if Vnom < Vw < Vco 0 if Vw ≥ Vco or Vw ≤ Vci (4)

C. Static Model of Ground-based Airborne Wind Energy System

The production cycle for any on-ground AWE system is divided into two phases, namely, the production phase and the recovery phase. The production phase is characterized by reeling out the tether from the onground station while following a crosswind trajectory in the air. As a result, a traction force is produced in the tether attached to the airborne platform which is then used to generate electricity. In the recovery phase, the airborne platform is pulled back to the on-ground station. Thus, a part of the power produced during the production phase is consumed during the recovery phase. In order to minimize the energy consumption during this phase, the traction force has to be minimized.

Aerodynamic lift and drag forces acting on any classical airborne platform (such as kite, rigid wing, UAV or Magnus cylinder etc.) can be expressed as:

L = 1 2 ρSV 2 a CL, D = 1 2 ρSV 2 a CDeq (5)
Where, ρ is the air density, Va is the apparent wind velocity, S is the projected surface of the airborne platform, CL is its aerodynamic lift coefficient, and CDeq is equivalent aerodynamic drag coefficient of the system including the drag due to the tether and any other structural components of the airborne platform. Note that CDeq has to be expressed in function of tether length to consider additional drag effect for each additional tether length. The component of the wind in the direction parallel to the tether, as experienced by the platform, can be expressed as:

Vt = Vw cos(θT ) cos(φT ) (6)
Where, θT and φT represents the elevation and the azimuthal angle of the tether with respect to the inertial frame. Figure 1 presents a 3D model of a Magnus-based AWE system described using two frames of references. Inertial frame, (xi, yi, zi), centered at the ground station O, and a body frame, (x b , y b , z b ), centered at the center of gravity Cg of the system. The tether length is presented by variable r which can be expressed as:

r = x 2 + y 2 + z 2 (7)
Where, (x, y, z) are the coordinates of Cg in the inertial frame. In the static analysis of [START_REF] Gupta | Modeling and control of a magnus effect-based airborne wind energy system in crosswind maneuvers[END_REF], assuming straight taut tether, the traction force Fr developed in the tether is directly proportional to the resultant aerodynamic force acting on the Magnus cylinder. Thus, the total mechanical energy available at the winch of the on-ground station is given by P = Fr ṙ. Where, ṙ represents the reel-in or reel-out speed of the tether.

1) Production phase:

The power produced by any AWE during a production phase is given by:

P prod = Fr ṙprod (8)
Where, ṙprod refers to the reeling-out speed of the tether from the winch.

Fr refers to the traction force developed in the tether due to the resultant aerodynamic forces. Considering the reel-out speed ṙprod , the power produced during the production phase is given by:

P prod = 1 2 ρS(Vt -ṙprod ) 2 CL( CL CDeq ) 2 ṙprod ( 9
)
Here it is important to note that this static power equation first derived in [START_REF] Loyd | Crosswind kite power[END_REF] and further refined in [START_REF] Argatov | Estimation of the mechanical energy output of the kite wind generator[END_REF] is obtained by using equilibrium motion theory for crosswind maneuver. It does not take into account the contribution of the centrifugal force acting on the airborne platform.

In addition, it is assumed that the wind is parallel to the tether and the AWE system is assumed in the static state. Thus, a detailed analysis considering all the effects may yield a better expression for power produced by an AWE system. For the production phase, the maximum possible theoretical mechanical power that can be produced for a given set of lift and drag coefficients CL and CDeq is studied in [START_REF] Loyd | Crosswind kite power[END_REF]. In [START_REF] Argatov | Estimation of the mechanical energy output of the kite wind generator[END_REF] it is proved that for maximum power the reel-out speed of the tether, ṙprod , should be equivalent to Vw 3 while the AWE system follows a crosswind trajectory such as circles or eight-like figures perpendicular to the wind direction. Thus, following this assumption the maximum theoretical mechanical power produced can be expressed by:

P prod = 1 2 ρ 4 27 SVt 3 CL( CL CDeq ) 2 (10)
However, this maximizes only the production phase and not the total power produced during the full cycle, as discussed later in section III.

2) Recovery phase: In the recovery phase, the airborne platform is returned to its initial position .i.e. the tether length is brought to its initial value. In this maneuver, a portion of the energy produced during the production phase is consumed. The power consumed can be calculated as the product of the winding speed of the tether ṙrec and the resulting drag force of the system through the tether F drag :

Prec = F drag ṙrec (11) Prec = 1 2 ρS(Vt + ṙrec) 2 CDrec ṙrec (12)
Where, CDrec is the resulting drag coefficient during the recovery phase. Note that in this formulation, as ṙrec is negative and F drag is positive, so Prec is negative.

There are several operational strategies proposed in the literature to minimize the energy consumption during the recovery phase for different types of AWE system. For instance, in case of soft kites based AWE systems to minimize the energy consumption, generally, the kite is flown to the zenith to the limits of the wind window before commencing the reel-in of the tether.

In case of a Magnus-based system, in order to minimize the power consumption, the rotational speed of the Magnus cylinder, ω cyl is simply set to zero, leading to lift coefficient CL zero. Thus, minimizing the resulting drag. In [START_REF] Gupta | Modeling and control of a magnus effect-based airborne wind energy system in crosswind maneuvers[END_REF], this type of maneuvers is performed in dynamic simulations.

Depending on the choice of airborne platform and recovery strategy, Prec might have to be modified to incorporate all the effects and variables arising due to maneuvers performed for the recovery phase. This model is adapted to a platform that can be configured with no or very low lift coefficient during the recovery phase. It can be replaced by another static model of the recovery phase, such as the one proposed in [START_REF] Ranneberg | Fast power curve and yield estimation of pumping airborne wind energy systems[END_REF] that includes a given set of lift and drag coefficients and a necessary additional transition time.

D. Ground-based Airborne Wind Energy System design constraints

The ground station is a reversible winch that produces energy when the airborne platform is pulling the tether, and during the recovery phase, it produces a retraction force to reel-in the tether to the drum. Actuators to be used will have saturations that are chosen to represent the following parameters:

• The nominal rotational speed ωnom • The nominal torque Γnom • The efficiency η which depends on the actuator's rotational speed ω and torque Γ The saturation on traction force, Fmax, and reel-out and reel-in speed, ṙmax, are dependant on the design of the ground station. They have to be considered in the control algorithm. Note that the system must be designed in such a way that Fmax = R d Γnom, and ṙmax = R d ωnom, where R d is the radius of winch's drum. On the other hand, the tether and the airborne platform must be able to withstand the maximum traction force Fmax. In this work, two configurations for the ground station architecture are considered. In the first one, an electrical motorgenerator is used for both the phases .i.e. production and recovery phase. In the second configuration, each phase uses a separate device .i.e. an electrical generator with a gearbox optimized for production phase and an electrical motor with a gearbox optimized for the recovery phase. In this case, saturation for the each phases has to be differentiated as F prod max , ṙprod max , Frec max and ṙrecmax . Note that the same differentiation has to be done if a single motor is coupled with two different gearboxes.

The winch-generator system then can be directly connected either to the grid or to a local storage device which can be used to provide the power required during the recovery phase and the mean power to the grid. The system is then able to provide a constant power during all the cycle. In this case, no power is taken from the grid, thus, ensuring a unidirectional connection to the grid. Figure 2 presents the configuration with two separate electric actuators for the two phases and a local storage device. In an another approach, proposed in [START_REF] Tattersfield | Method and system for harnessing wind energy using a tethered airfoil[END_REF], use of a hydraulic stage between the drum and the grid connection is considered. Figure 3 shows the configuration with a variable speed hydraulic motor/pump coupled with a hydraulic accumulator and a fixed speed motor which produces electricity which is then fed directly to the grid. Thanks to the emerging high efficiency digital hydraulic devices, the authors expect substantial cost reductions in the cost of both actuators and storage devices. From a control point of view, as the same actuator is used for both the phases, this leads to F prodmax = Frec max and ṙprod max = ṙrecmax . As Fig. 3. Ground Station using hydraulic stage electrical as well as hydraulic actuators has a yield that can vary with operating speed and torque, we can define for all theses configurations common parameters ηp, yield of the generator (or pump) used during production phase, ηr yield of the motor used during recovery phase, ηs yield of the storage device and ηg yield of the grid connection. For hydraulic case, yield of grid connection includes hydraulic motor, electrical generator and grid connection itself.

1) Full production cycle:

A given power cycle is thus defined by one complete production and recovery phase. The transitional phase between the production and the recovery phase is neglected in this formulation. The time for each phase can then be expressed as:

t1 = rmax -rmin ṙprod = ∆r ṙprod (13) t2 = rmax -rmin ṙrec = ∆r ṙrec (14)
Where, t1 and t2 represent the duration of the production and recovery phase respectively. Thus, the total time, t taken for one complete production cycle is:

t = t1 + t2 (15)
The net output power provided to the grid P cycle can then be calculated by the sum of power produced affected by its yield, power consumed also affected by the inverse of its yield and the yield of storage device, and additional power loss in the storage device P loss . This is due to the storage of the necessary energy that has to be provided to the grid during recovery phase. Its expression is given in equation ( 16).

P loss = P cycle t2(η -1 s -1) t1 + t2 (16)
Hence, the mean power produced during one full production cycle can be computed as:

P cycle = ηg ηpP prod t1 + η -1 r η -1 s Prect2 -P cycle t2(η -1 s -1) t1 + t2
(17) Where, replacing the values of t1 and t2 from equations ( 13) and ( 14) into (17), the power produced in one complete cycle can be expressed as:

P cycle = ηg ηpP prod ṙrec + η -1 r η -1 s Prec ṙprod ṙrec + η -1 s ṙprod (18)
Note that from equation (18) it can be observed that in order to obtain maximum power from one complete cycle, there is a trade-off between ṙrec and ṙprod . Hence, the augmentation of ṙrec not only increases the contribution of the production phase but also increases the value of the power consumed Prec as given by equation (12). Similarly, increasing ṙprod not only increases the power produced as expressed by equation ( 9) but also the power consumed.

III. CONTROL AND OPTIMIZATION OF OUTPUT POWER

As explained in the section II, for a ground-based AWE system, the net power produced in one cycle depends on physical parameters, design parameters, and controllable parameters. All controllable parameters of P prod described in equation ( 9) must maximize P prod , except reelout speed ṙprod which also influences the whole cycle through Prec.

This leads to maximization of cos(θT ) cos(φT ) and CL

C L C D eq 2 .
Similarly, all controllable parameters of Prec described in equation ( 12) has to minimize it, except reel-in speed ṙrec which also influences the whole cycle through P prod . In this phase, cos(θT ) cos(φT ) and CDrec has to be minimized. Thus, to obtain the maximum mean power, it is necessary to obtain optimal values of ṙprod and ṙrec. In this section, a high level algorithm is described, using all control parameters available for on-ground AWE systems in presence of saturation. An optimization technique is discussed for three separate situations which characterizes different typical constraints due to on-ground winch and airborne platform design, namely:

• Optimize both ṙrec and ṙprod • Optimize ṙprod when ṙrec is set • Optimize ṙrec when ṙprod is set

A. No saturation on actuators: Optimization of reel-in and reel-out speeds

To maximize the net power production during one complete cycle, ṙprod and ṙrec has to be optimized simultaneously. In the considered optimization procedure, P cycle is derived with respect to each ṙrec and ṙprod while considering the other variables as constant.

∂P cycle ∂ ṙrec = f (Vw, ṙrec, ṙprod , M ) (19)
while considering ṙprod , Vw and the vector of parameters M as constant. Vector M is given by: M = [CL, CDeq, CDrec, φT , θT , ηp, ηr, ηs, ηg, ρ, S]

Similarly,

∂P cycle ∂ ṙprod = f (Vw, ṙrec, ṙprod , M ) (21)
while considering this time that ṙrec as constant. The first order partial derivative results in a polynomial function, and solving the system of equation gives the optimal values of ṙrec and ṙprod :

ṙrec opt = fs(Vw, ṙprod , M ) ṙprod opt = gs(Vw, ṙrec, M ) (22)

B. Optimization of reel-in speed when reel-out speed is set

As presented before, the power produced by an AWE system in production phase is given by:

P prod = Fr ṙprod (23)
Due to design and structural constraints, there exists an upper limit for traction force Fr denoted by Fmax. This limit can be attributed to tether, winch and/or kite structural limitations. When this limit is reached during the production phase, and if cos(θT ) cos(φT ) and CL( C L C D eq ) 2 are set at their maximum value, then ṙprod has to be set such that Fr = Fmax, and it can be calculated using equation ( 9):

ṙprodf = Vt - Fmax 1 2 ρSCL( C L C Deq ) 2 (24)
In this case, if ṙprod reaches ṙprodmax then it can be saturated, but Fr has to be maintained equal to Fmax. This can be done by reducing other parameters such as cos(θT ) cos(φT ) or

CL C L C D eq 2
. Thus, in this case in order to maximize P cycle the reel-in speed has to be optimized for Fr = Fmax and ṙprod given by equation ( 24). The optimal reel-in speed ṙrec opt1 can be found by:

∂P cycle ∂ ṙrec = f1(Vw, ṙprod , rrec, Fr, M ) (25)
where, P cycle is calculated from equation ( 18) with a saturation on traction force and is calculated as:

P cycle = ηg ηpFmax ṙprod ṙrec + η -1 r η -1 s Prec ṙprod ṙrec + η -1 s ṙprod (26)
and, the optimal reel-in speed ṙrec opt1 is given by:

ṙrec opt1 = fs1(Vw, ṙprod , Fr, M ) (27)
Similarly, if ṙprod reaches ṙprodmax before the saturation of traction force Fr then ṙrec opt1 is calculated from equation ( 27), using ṙprod = ṙprodmax and Fr are calculated from eqs. ( 8) and [START_REF] Archer | An introduction to meteorology for airborne wind energy[END_REF].

C. Optimization of reel-out speed when reel-in speed is set

In some situations, reel-in speed is required to be saturated to ṙrecmax , before other variables like traction force or reel-out speed reach their upper limit. As optimal reel-in speed can be several times higher than the reel-out speed, especially in the case when the ground station uses the same actuator for production and recovery phases .i.e. without a two-stage gearbox. In such situations, the reel-in speed can reach its upper limit before the traction force. Thus, in this case the optimal ṙprod opt2 has to be calculated using equation ( 22) and ṙrecmax :

ṙprod opt2 = gs 2 (Vw, ṙrecmax , M ) (28)
Here it is important to note that in this case it is mandatory to check other variables for saturation. Thus, if ṙprod opt > ṙprod max then ṙprod opt has to be set to ṙprodmax . On the other hand, by using equation ( 9) if the traction force is found to be greater than its maximum i.e. F r > Fmax.

Then ṙprod has to be calculated by using equation (24).

D. Control by using altitude

Control of working altitude can be done by controlling rmin and rmax parameters i.e. minimum and maximum tether length. This can be done in order to find an altitude that maximizes power produced or to curtail production by lowering wind speed when it is necessary. Thus, there is a maximal effective wind speed Vt max beyond which P cycle starts to decrease despite of the augmentation of wind speed. This is due to the fact that at Vt max , due to all the design constraints, the production phase saturates while the power required for the recovery phase continues to grow with the increase in wind speed. Seeking an altitude where the wind is lower is useful when the wind is greater than the optimal wind speed of the system.

E. Control of elevation angle θ T or azimuthal angle φ T

To curtail output power or reduce effective wind speed, the trajectory of the airborne platform can be controlled, in order to modify elevation angle θT or azimuthal angle φT . This gives an additional control variable in order to operate on-ground AWES.

F. Summary Of The High-Level control algorithm

A high-level control strategy to maximize net power production P cycle in presence of multiple actuator saturation for all operating wind speed range presented in this section can be summed as the following. Reel-in and reel-out speed has to be optimized, taking into account system saturations. With both reel-in and reel-out are saturated, control of altitude z, elevation angle θT , and/or azimuthal angle φT can be used to maintain output power to its nominal value.

IV. NUMERICAL APPLICATION

In this section, different set of parameters of Magnus-based onground airborne wind energy system (MGAWES) are considered. Power curves, annual production, and capacity factor are compared with those of similar size horizontal axis wind turbine (HAWT).

A. HAWT parameters

VESTAS V 150 -4.2M W T M , designed for IEC IIIB wind class, is chosen as HAWT system to be compared with on-ground AWES. Corresponding parameters presented in table are taken from [12] or deduced from power curve data set in [13].

B. Wind parameters

Wind is considered at an altitude at the tower height i.e. 160m with mean annual wind speed 7.5m/s. For annual production, Weibull distribution is used with parameters A = 8, 47m/s and k = 2, which leads to class IIIB.

C. 90m span MGAWES parameters

The parameters considered are listed in table II. Aerodynamical parameters are taken from [START_REF] Milutinović | Operating cycle optimization for a magnus effect-based airborne wind energy system[END_REF], and for the sake of comparison, some other parameters are designed to get the same power curve as for the considered HAWT for wind speeds varying from Vci to Vnom. Also, for the same reason same cut-in and cut-out wind speeds are used. Two types of ground stations as described in section II-D are considered. One with two separate electrical actuators, and other with hydraulic stage with their apecifications also listed in table II

D. Results

Power curves of HAWT V150 both with theoretical model and dataset are plotted in figure [START_REF] Loyd | Crosswind kite power[END_REF]. Power curves derived using P cycle for a 90m span MGAWES for case 1 and case 2 ground station configuration are also plotted in figure [START_REF] Loyd | Crosswind kite power[END_REF]. As case 1 represents a more relevant example of different configurations of saturation expressed in section III, thus, for this case P prod and Prec are also plotted in figure [START_REF] Loyd | Crosswind kite power[END_REF]. To describe the 4 different phases of the power curve, denoted by I to IV, reel-in and reel-out speed, traction forces and elevation angle are shown on figure [START_REF] Bauer | Drag power kite with very high lift coefficient[END_REF]. As it can be observed from figure (4) phase II of HAWT and MGAWES are very similar. This is because in this phase, just like HAWT, MGAWES is a function of V 3 w , and an optimal amount of kinematic energy is extracted from the wind. During phase III, the traction force is saturated, but P prod continues to increase as reel-out speed increases with an increasing wind speed. In phase IV, once the maximum P prod is reached then only Prec increases as with an increase in the wind speed the drag also increase. Thus, more and more power is required to recover the airborne platform. This leads to a reduction in the net power output P cycle as represented by dotted line in figures (4) and [START_REF] Bauer | Drag power kite with very high lift coefficient[END_REF]. Finally, solid lines in phase IV shows the use of elevation angle θT control, to maintain the effective wind Vt at its maximal value in order to the maintain output power at its maximum. In table II, case 2 represents the case when there are no set limitations on the winch actuators. This set of parameters are chosen to illustrate hydraulic configuration because for both the phases actuator is same. So, the winch actuators have to at least produce the high force Fmax and high speed ṙrecmax in the same time. This extends the phase III to maximum cut-out value Vco. The maximum output power is then produced at this maximum wind speed, and has to be used to size the grid connection P grid . Note that the same power curve can be produced with a single 40M W electric motor/generator coupled with a single gearbox. Using these theoretical power curves and wind distribution described in subsection IV-B, the theoretically expected energy produced during one year can be computed for HAWT V150 and different ground-station configurations for the same 90m span Magnus effect kite. In particular, it is interesting to note that just for the sake of comparison, using figure (4), the use of a generator and a motor that saturates at the same wind speed as HAWT (i.e. P prodmax = 6.7M W and Prec max = 4M W ) will lead to a similar power curve and similar annual production. This configuration is considered as case 0. In this work, a static model is proposed as a simple tool that can be used to predict the performance of the on-ground AWES in relation to the main design parameters. The proposed algorithm gives a strategy to maximize the energy produced by this kind of system for different configurations of actuator saturation under the static assumption. By coupling the static model with the high-level algorithm, a way to calculate power curves is presented. This approach is used to study the effects of design parameters on performances and can be used directly to control a system in real-time. The resulting power curves consist of different phases, each phase corresponding to the different control variables, and illustrates the high flexibility of on-ground airborne wind energy system. The strategy presented can be used to evaluate other types of AWE systems and draw some valid comparisons with conventional wind turbines.

Fig. 1 .

 1 Fig. 1. Magnus-based AWE system.

Fig. 2 .

 2 Fig. 2. Ground station using two separate electrical actuators and a storage device

Fig. 4 .

 4 Fig. 4. Power curves: Power production comparison between HAWT Vestas V150 and case 1 and case 2 of MW-size MGAWES. P cycle is decomposed into production and recovery contributions for case 1. Dotted line denotes P cycle when control of elevation angle is not used

Fig. 5 .

 5 Fig. 5. High level control variables of case 1, 90m span MGAWES. Top: reelout speed during production phase (black) and reel-in speed during recovery phase (red) in function of wind speed. Dotted line represents variables when control of elevation angle is not used. Down: Traction force during production (black) and recovery (red) phases.

  .

	Kite parameters			Variable	Value
	Span [m]			L		90
	Radius [m]			R		9
	Magnus Surface [m 2 ]		S		1620
		2			2
	Maximum C L	C L C Deq	for X = 3.6	C L	C L C Deq	69.44
	Minimum drag coefficient		C Drec	0.5
	Minimum elevation angle [deg]	θ T		25
	Cut-in wind speed [m/s]		V ci		3
	Cut-out wind speed [m/s]		Vco		22.5
	Maximal traction force [kN]	Fmax		2405
	Maximal strength [N/m 2 ]		σ		1485
	Working altitude [m]		z		160
	Aspect ratio			AR		5
	Reynolds number for Va = 10m/s	Re		10.9e6
	Case 1: Ground station with 2 electrical actuators
	Electric generator nominal power [MW]	P prodmax	10
	Nominal Power for grid connection [MW]	P grid		5.91
	Electric motor nominal power [MW]	Prec max	5.56
	Yield of generator		ηp		0.92
	Yield of motor			ηr		0.88
	Yield of storage device		ηs		1
	Yield of grid connection		ηg		0.98
	Maximal reel-in speed [m/s]	ṙrecmax	14.7
	Maximal reel-out speed [m/s]	ṙprodmax	4.16
	Case 2 : Ground station with hydraulic stage
	Electric generator nominal power [MW]	P grid		10.9
	Hydraulic motor/pump nom. power [MW]	Pmax		40
	Yield of motor/Pump for production	ηp		0.92
	Yield of motor/Pump for recovery	ηr		0.88
	Yield of storage device		ηs		1
	Yield of grid connection		ηg		0.98
	Maximal reel-in and reel-out speed [m/s]	ṙmax		16.65
			TABLE II
	PARAMETERS OF THE 90M SPAN MGAWES.

  Table III summarizes the different systems considered and associated size of actuators. It also gives the corresponding theoretical annual production and capacity factor, computed by annual production divided by 8760P grid .

	System	P Grid	Generator	Motor Prod.	Capacity
		[MW]	[MW]	[MW]	[GWh/yr] factor
	V150	4.2	4.2	-	18.2	0.49
	AWES Case 0 4.2	6.7	4	18.2	0.49
	AWES Case 1 5.9	10	5.56	21.9	0.42
	AWES Case 2 10.9	40	-	24.8	0.26
			TABLE III
	CONSIDERED ACTUATORS CONFIGURATIONS AND CORRESPONDING
	THEORETICAL ANNUAL PRODUCTION AND CAPACITY FACTOR


Katrine M Johannesen

Elena Gardella

Tarja Linnankivi

Carolina Courage

Anne De Saint

Anna-Elina Lehesjoki

Cyril Mignot

Alexandra Afenjar

Gaetan Lesca

Marie-Thérèse Abi-Warde

Anne De Saint Martin

Marie-Th Er Ese Abi-Warde

Jamel Chelly

| Am

Elie Piton

| J Lawrence Merritt

| Lance

H Rodan

Wen-Hann Tan

Lynne M Bird

Mark Nespeca

Joseph G Gleeson

Yongjin Yoo

| Murim Choi

Jong-Hee Chae

Desiree Czapansky-Beilman

| Sara

Chadwick Reichert

Manuela Pendziwiat

Judith S Verhoeven

| Helenius

J Schelhaas

Orrin Devinsky

Jakob Christensen

Nicola Specchio

Marina Trivisano

Yvonne G Weber

Caroline Nava

Boris Keren

Diane Doummar

Elise Schaefer

Sarah Hopkins

| Holly Dubbs

Jessica E Shaw

Laura Pisani

Candace T Myers

Shan Tang

Deb K Pal

| John

J Millichap

Gemma L Carvill

Kathrine L Helbig

Oriano Mecarelli

Pasquale Striano

Ingo Helbig

| Guido Rubboli

Heather C Mefford

| Rikke

S Møller

Rikke S Møller

Pasquale Orcid

Striano

Guido Rubboli

Defining the phenotypic spectrum of SLC6A1 mutations

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Funding information

Deutsche Forschungsgemeinschaft, Grant/ Award Number: We4896/3-1, He5415/6-1; Ambry Genetics; SNSF Early Postdoc fellowship Summary Objective: Pathogenic SLC6A1 variants were recently described in patients with myoclonic atonic epilepsy (MAE) and intellectual disability (ID). We set out to define the phenotypic spectrum in a larger cohort of SCL6A1-mutated patients. Methods: We collected 24 SLC6A1 probands and 6 affected family members.

Four previously published cases were included for further electroclinical description. In total, we reviewed the electroclinical data of 34 subjects. Results: Cognitive development was impaired in 33/34 (97%) subjects; 28/34 had mild to moderate ID, with language impairment being the most common feature. Epilepsy was diagnosed in 31/34 cases with mean onset at 3.7 years.

Cognitive assessment before epilepsy onset was available in 24/31 subjects and was normal in 25% (6/24), and consistent with mild ID in 46% (11/24) or moderate ID in 17% (4/24). Two patients had speech delay only, and 1 had severe ID. After epilepsy onset, cognition deteriorated in 46% (11/24) of cases. The most common seizure types were absence, myoclonic, and atonic seizures. Sixteen cases fulfilled the diagnostic criteria for MAE. Seven further patients had different forms of generalized epilepsy and 2 had focal epilepsy. Twenty of 31 patients became seizure-free, with valproic acid being the most effective drug. There was no clear-cut correlation between seizure control and cognitive outcome. Electroencephalography (EEG) findings were available in 27/31 patients showing irregular bursts of diffuse 2.5-3.5 Hz spikes/polyspikes-and-slow waves in 25/31. Two patients developed an EEG pattern resembling electrical status epilepticus during sleep. Ataxia was observed in 7/34 cases. We describe 7 truncating and 18 missense variants, including 4 recurrent variants (Gly232Val, Ala288Val, Val342Met, and Gly362Arg). Significance: Most patients carrying pathogenic SLC6A1 variants have an MAE phenotype with language delay and mild/moderate ID before epilepsy onset. However, ID alone or associated with focal epilepsy can also be observed.

K E Y W O R D S
epilepsy, epilepsy genetics, MAE, SLC6A1

| INTRODUCTION

The voltage-dependent c-aminobutyric acid (GABA) transporter 1 (GAT-1), encoded by SLC6A1, is one of the major GABA transporters of the human central nervous system. [START_REF] Madsen | The subcellular localization of GABA transporters and its implication for seizure management[END_REF] GAT-1 is expressed primarily in the nerve terminals of GABAergic interneurons but can also be found in astrocytes, and has been shown to be crucial for the reuptake of GABA from the synapses and for its clearing from the extracellular space. [START_REF] Zhou | GABA and glutamate transporters in brain[END_REF] In addition to the neocortex, GAT-1 is found in abundance in the cerebellum. [START_REF] Scimemi | Structure, function, and plasticity of GABA transporters[END_REF] GAT-1 knockout mice exhibit spontaneous spike-wave discharges (SWDs) and absence seizures. [START_REF] Cope | Enhanced tonic GABAA inhibition in typical absence epilepsy[END_REF] In 2014, Dikow et al., [START_REF] Dikow | 3p25.3 microdeletion of GABA transporters SLC6A1 and SLC6A11 results in intellectual disability, epilepsy and stereotypic behavior[END_REF] described 3 patients with intellectual disability (ID), epilepsy/electroencephalography (EEG) abnormalities, ataxia and stereotypic hand movements, and a microdeletion at 3p25.3, including the 2 GABA transporter genes, SLC6A1 and SLC6A11. Recently, de novo SLC6A1 variants discovered by large exome sequencing studies were reported in 3 patients with ID, myoclonic atonic (MA) seizures, delayed speech and delayed walking, autism spectrum disorders, and absence seizures, as well as in a patient with epileptic encephalopathy. [START_REF] Rauch | Range of genetic mutations associated with severe non-syndromic sporadic intellectual disability: an exome sequencing study[END_REF][START_REF] Sanders | De novo mutations revealed by whole-exome sequencing are strongly associated with autism[END_REF][START_REF] Halvorsen | Mosaic mutations in early-onset genetic diseases[END_REF] In 2015, we reported de novo inactivating variants in SLC6A1 in up to 4% of patients with myoclonic atonic epilepsy (MAE), suggesting that pathogenic SLC6A1 variants might be specific for MAE. [START_REF] Carvill | Mutations in the GABA transporter SLC6A1 cause epilepsy with myoclonic-atonic seizures[END_REF] MAE is a syndrome characterized by the presence of myoclonic-atonic seizures, usually in an otherwise normal child, which may typically develop cognitive impairment after seizure onset (reviewed in Guerrini and Aicardi). [START_REF] Guerrini | Epileptic encephalopathies with myoclonic seizures in infants and children (severe myoclonic epilepsy and myoclonic-astatic epilepsy)[END_REF] Extensive searches in other epileptic encephalopathy cohorts, such as epileptic spasms or Lennox-Gastaut syndrome, failed to detect pathogenic variants in this gene.

Here we aim to better characterize the clinical presentation and electroencephalographic features associated with pathogenic SLC6A1 variants.

| MATERIAL AND METHODS

Patients with presumed pathogenic variants in SLC6A1 were collected through an international collaboration between epilepsy genetics centers worldwide. The cohorts included for screening consisted primarily of patients with ID or childhood epilepsies including childhood encephalopathies, without a previously identified genetic cause. Probands and families, when available, underwent clinical, neurophysiological, and genetic examinations. All the available EEG data were collected and reviewed by a single epileptologist (EG). Seizures were classified according to the International League Against Epilepsy (ILAE) classification. [START_REF] Scheffer | ILAE classification of the epilepsies: position paper of the ILAE Commission for Classification and Terminology[END_REF] Atypical absences were defined as absence seizures with additional clinical features (eg, myoclonic jerks) and with an EEG pattern of diffuse spike-wave <3 c/s with a slower onset and offset compared to typical absence seizures. [START_REF] Fisher | Operational classification of seizure types by the International League Against Epilepsy: position paper of the ILAE Commission for Classification and Terminology[END_REF] Cognitive development was based mainly on the assessment of the psychomotor development by the referring physicians; only in a few cases was a formal neuropsychological testing performed.

For the diagnosis of MAE, we adopted the following diagnostic criteria: (1) usually normal development before epilepsy onset and absence of brain structural abnormali-

Key Points

• SLC6A1 mutations cause a wider phenotype than solely MAE

• The SLC6A1 phenotype consists of absence sei- zures and mild-to-moderate intellectual disability

• The common EEG pattern comprises irregular, high ample, and generalized spike-and-waves ties; (2) onset of myoclonic, myoclonic-atonic, or atonic seizures between 7 months and 6 years of age; (3) EEG: 2-3 Hz generalized spike/polyspikes-and-slow waves; (4) diagnoses of benign myoclonic epilepsy of infancy (BMEI), severe myoclonic epilepsy of infancy (SMEI), and Lennox-Gastaut syndrome (LGS) have been excluded. (https://www.epilepsydiagnosis.org/syndrome/epilepsy-myo clonic-atonic-overview.html).

All probands and/or their parents or legal guardians signed an informed consent form. The study was approved by the local ethics committees.

Variants were classified as pathogenic if they were (1) nonsynonymous, splice-site altering, or truncating changes;

(2) predicted damaging by one or more prediction software programs (PolyPhen-2 [http://genetics.bwh.harvard.ed u/pph2/], SIFT [http://sift.jcvi.org], and MutationTaster [http://www.mutationtaster.org]); (3) not present in >60 000 of nonepileptic controls in the ExAC browser (the exome aggregation consortium browser, see Web Resources); and (4) were either de novo changes, inherited from an unaffected mosaic parent, or inherited from an affected parent. We used Sanger sequencing to confirm all variants and to perform segregation analysis.

| RESULTS

We identified 30 unpublished patients with a pathogenic SCL6A1 variant (24 probands and 6 affected family members). Moreover, we included additional clinical information of 4 previously published cases. One (Patient 25) had only briefly been described previously and the 3 remaining cases were included for electroencephalographic characterization (Patients 5, 28, and 34) (Table 1). In total, we studied 34 SLC6A1-positive patients. Gender ratio was 19 female to 15 male patients.

| Genetics

We report on a cohort of 24 previously unpublished probands with pathogenic SLC6A1 variants. Twenty variants occurred de novo in the affected proband, and 2 variants segregated in a dominant manner with the phenotype in the affected family (Figure 1). In 2/24 probands (Patients 12 and 24), segregation analysis could not be performed, and the inheritance mode remained unclear. However, both probands had missense variants identical to those found in other affected probands in this study. We found 18 missense variants, 2 splice-site variants, 1 frameshift variant, 3 nonsense variants, and 1 in-frame deletion. The 18 missense variants all affect highly conserved nucleotides and are absent from control databases (Figure 2). Overall, the variants suggest that loss of function of GAT-1 is the likely disease mechanism, as reported previously. All subjects but 1 (Patient 17) had cognitive impairment at the time of the inclusion in the study.

| Cognitive development

Sixteen of 34 patients had mild ID, 12 had moderate ID, 3 had severe ID, and 2 had learning disabilities. The most common feature was language delay, described in 16/ 34, whereas 4 probands presented mainly nonverbal deficits (Patients 1, 25, 27, and 29). There was no apparent correlation between seizure control and cognitive profile.

A large proportion of the 34 SLC6A1 mutation carriers had behavioral problems, such as aggressive behavior/irritability (Patients 4, 10, 12, 14, 16, and 29), attention deficit disorders (Patients 10, 13, 15, 21, 30, and 31), stereotypies/automatisms (Patients 12, 20, 23, 27, and 29), and autistic features (Patients 4, 5, 12, 16, 20, 22, 26, and 27).

| Other clinical features

Neurological examination revealed mild ataxia (Patients 4, 7, 13, 22, and 31) or unsteady gait (Patients 23, 26, 27, and 28) in 9/34 patients, hypotonia in 3 cases (Patients 1, 4, and 16), and impairment of fine motor skills (Patients 21 and 32) and tremor (Patients 15 and 33) in 2 probands each. One patient each had chorea (4), verbal dyspraxia (21) and dyskinesia (31). No consistent dysmorphisms or malformations were present.

| Epilepsy phenotype

Thirty-one of 34 individuals had epilepsy, namely 27 of 28 probands (27 unpublished and 4 previously published cases) and 4 of 6 family members. Mean age at seizure onset was 3.7 years (range 0.5-7 years); 2 probands had epilepsy onset before the age of 1 year. Mean age at follow-up was 11.3 years (range 2-21 years).

Affected individuals presented with a variety of seizure types: absences not further specified (14/31), atypical absences (10/31), atonic seizures (14/31), and myoclonic or myoclonic-atonic seizures (12/31) were the most common. A few subjects (5/31) also had generalized tonic-clonic seizures (GTCS) (Table 1). At the time of diagnosis, epilepsy syndromes were described as MAE in 16 patients and LGS in 1 patient (Patient 25), early onset absence epilepsy (EOAE) in its atypical form (Patient 1), eyelid myoclonia with absences (Patient 22), and childhood absence epilepsy (CAE) (Patients 17 and 33). Seven further patients presented with a generalized epilepsy difficult to classify because of inconsistencies of the electroclinical picture such as absence seizures (up to 100/day), atypical EEG pattern, or because further clinical details and EEG data were not available. Finally, 3 patients were diagnosed with focal epilepsy: 1 had temporal lobe epilepsy (Patient 24) and the other 2 had atypical childhood epilepsy with centrotemporal spikes (aBECTS) (Patients 6 and 28). The diagnosis of aBECTS was based on the description of focal motor seizures during sleep and on the presence of centrotemporal spikes on EEG, together with several atypical features (ID with autistic features or mild neurological deficits, the epilepsy history, and the topography of the EEG abnormalities).

Twenty of 31 patients with epilepsy became seizurefree. Ten of them were treated with valproic acid (VPA), either as monotherapy or in combination with clonazepam (CLZ), lamotrigine (LTG), or levetiracetam (LEV). The remaining 10 subjects became seizure-free on LTG, ethosuximide (ESM), LEV, and LTG or CLZ, alone or in combination. Five further patients were treated with VPA, all achieving partial seizure control. Vagus nerve stimulation (VNS) was attempted in 1 patient with LGS (Patient 25) without benefit. None of the patients reported herein has tried a ketogenic diet, recently described as potentially effective for MAE.

| Neurophysiological and imaging characteristics

EEG data were available in 27/34 SLC6A1-positive patients, all with epilepsy (23 novel cases and 4 previously published), and were abnormal in all cases. A slowing of the background activity was observed in 11/28 subjects and bursts of irregular generalized 2.5-3.5 Hz spikes/polyspikes and slow waves with a gradual onset in the occipital regions were present in 25/28 patients (Figure 3). In some instances, these epileptic discharges correlated with staring and loss of consciousness with or without a myoclonic or atonic component, in different combinations, resulting in atypical absences, myoclonic-atonic seizures, atonic seizures/drop attacks, or myoclonic seizures. Two further probands had focal epileptiform abnormalities in the centrotemporal (Patient 12) or frontotemporal (Patient 23) regions (the latter occasionally presenting generalized spike and slow waves during the hyperpnea). Of interest, in Patient 12, epilepsy evolved presenting generalized spike and slow waves and atypical absences at the latest observations. Two patients (6 and 28) initially presenting with an MAE-like phenotype and irregular generalized spikes and slow waves, transitioned to showing only focal epileptiform abnormalities in the centro-parietotemporal regions at the time of the inclusion in this study (school age). In both cases, the epileptiform abnormalities were markedly enhanced by sleep, as it occurs in encephalopathy with status epilepticus during sleep (ESES). In 1 patient, the spike-wave index during non-rapid eye movement (NREM) sleep was 82% (Figure 4) and in the other, the EEG was reported as "almost continuous epileptic activity" during NREM sleep. In neither patient was this EEG pattern associated with cognitive/behavioral deterioration as seen in ESES.

Brain magnetic resonance imaging (MRI) was unremarkable in the majority of SLC6A1 mutation carriers for whom data were available (14/19). Five cases had nonspecific MRI abnormalities, such as mild vermian hypoplasia or enlarged frontal spaces.

In the present study, we describe the clinical features of 34 patients with pathogenic variants in SLC6A1 (24 probands, 6 family members, as well as 4 cases previously published [START_REF] Halvorsen | Mosaic mutations in early-onset genetic diseases[END_REF][START_REF] Carvill | Mutations in the GABA transporter SLC6A1 cause epilepsy with myoclonic-atonic seizures[END_REF] ) and the EEG features of 28 of them.

The identified variants include several truncating variants supporting loss of function of GAT-1 as a disease mechanism, as reported previously. [START_REF] Rauch | Range of genetic mutations associated with severe non-syndromic sporadic intellectual disability: an exome sequencing study[END_REF] Within this study, we found 4 recurring missense variants (Gly232Val, Ala288-Met, Val342Met, and Gly362Arg), suggesting possible mutational "hot spots" in SLC6A1.

In contrast to the previously published cases with SLC6A1 variants, this cohort displays a broader phenotypic spectrum sharing some common key features.

| Cognitive and behavioral deficits

The clinical hallmark of the SCL6A1 variant carriers is cognitive impairment. Almost all subjects (33/34) presented certain degrees of cognitive deficits at the time of observation, consisting of mild-to-moderate ID in 82% of the cases (28/ 34). Speech difficulties were a common feature, as reported previously, present in 17/34 of patients, whereas pure nonverbal deficits were uncommon. In half of the cases (17/34), we also observed behavioral problems, namely, attention deficit, hyperactivity, aggressive behavior, hand stereotypies, and autistic features in different combinations. This observation is supported by the data in the Scl6a1 mouse model. [START_REF] Chen | Hyperactivity and impaired attention in Gamma aminobutyric acid transporter subtype 1 gene knockout mice[END_REF] Recently, a study found that selected SLC6A1 variants may correlate with a higher risk of Attention-deficit/hyperactivity disorder (ADHD) in humans. [START_REF] Yuan | SLC6A1 gene involvement in susceptibility to attention-deficit/hyperactivity disorder: A casecontrol study and gene-environment interaction[END_REF] Of interest, 3/34 SLC6A1 variant carriers never had epileptic seizures, but manifested only learnings disabilities or mild ID with or without autistic features, which represent a previously undescribed phenotype associated with SLC6A1. Two of these individuals had relatives, carrying the same variant, with an MAE phenotype, suggesting variable expressivity possibly due to either genetic or environmental modifying factors, and indicating that genotype-phenotype correlations are not straightforward.

F I G U R E 2 The SLC6A1 gene with the missense variants found in this study. Recurrent variants are highlighted

| Epilepsy

Thirty-one of 34 patients had epilepsy, with a mean age at onset of 3.7 years. The majority (24/30) of the patients displayed absences as the main seizure type, in agreement with studies in mice, that have shown an electroclinical phenotype consistent with atypical absence seizures. [START_REF] Cope | Enhanced tonic GABAA inhibition in typical absence epilepsy[END_REF] We identified 16 subjects classified as MAE. Doose et al. stated that MAE usually begins in previously normally developing children. [START_REF] Doose | Myoclonic-astatic epilepsy[END_REF] However, he did not propose a "rigid" syndrome, but rather a condition with unifying features plus a recognized phenotypic variability attributed to a multifactorial background. In our cohort, the most common phenotype associated with SLC6A1 could indeed be classified as MAE, associated in most of the patients with various degrees of ID before epilepsy onset, as also observed previously. [START_REF] Carvill | Mutations in the GABA transporter SLC6A1 cause epilepsy with myoclonic-atonic seizures[END_REF] Five patients were diagnosed as having a variety of other generalized epilepsy syndromes, including phenotypes resembling CAE (Patient 25) and EOAE (Patient 1), in both cases associated with mild-to-moderate ID. The phenotypes of CAE and EOAE have previously been observed in SLC2A1, GABRB3, and CACNA1H, [START_REF] Larsen | The role of SLC2A1 mutations in myoclonic astatic epilepsy and absence epilepsy, and the estimated frequency of GLUT1 deficiency syndrome[END_REF][START_REF] Tanaka | Hyperglycosylation and reduced GABA currents of mutated GABRB3 polypeptide in remitting childhood absence epilepsy[END_REF][START_REF] Liang | Common polymorphisms in the CACNA1H gene associated with childhood absence epilepsy in Chinese Han population[END_REF] but we now extend the genetic etiology of these 2 epilepsy phenotypes to include SLC6A1. Finally, in 4 patients, diagnosed as "unclassified generalized," the inconsistencies between the clinical features and the EEG findings did not allow a syndromic classification.

Two patients presented with a phenotype resembling aBECTS, although with atypical electroclinical features (Patients 6 and 28), and 1 had temporal lobe epilepsy (Patient 24). This has not been described in any of the Slc6a1 animal models or human SLC6A1 variant carriers. [START_REF] Oguni | Myoclonic-astatic epilepsy of early childhood-clinical and EEG analysis of myoclonicastatic seizures, and discussions on the nosology of the syndrome[END_REF] The subjects with aBECTS presented an extreme activation of the Data about cognition before epilepsy onset were available in 24/31 patients. Only 5 had normal cognitive development, whereas 64% of the subjects (16/24) presented mild-to-moderate ID. After epilepsy onset, cognition deteriorated in 44% of cases (11/24) and did not improve after seizure control was achieved. Therefore, the contribution of epilepsy to the development of the cognitive impairment in patients with a pathogenic SLC6A1 variant is uncertain.

| EEG data

Most patients exhibited a similar EEG pattern consisting of irregular, generalized 2.5-3.5 Hz spike/polyspikes-and-waves, providing a neurophysiological link to the animal studies. The clinical correlate of these EEG discharges could be an absence seizure, in most cases with atypical features, and with atonic and/or myoclonic components (16/28 cases). In our cohort, differences in the EEG pattern and in the associated clinical manifestations led to different phenotypical classification such as MAE, LGS, EOAE, or CAE. In 3 patients, the epileptiform abnormalities transitioned from generalized to strictly focal in the centro-parietotemporal regions (Patients 6 and 28) and vice versa (Patient 12) during the disease.

| Epilepsy treatment

The limited data thus far available suggest a good response to VPA, either as monotherapy or in combination with other antiepileptic drugs (AEDs). Ten of 15 patients treated with VPA became seizure-free, and the remaining 5 had a partial benefit. VPA is thought to have a positive effect on the GABA system (possibly increasing the GABA concentration in the human brain. [START_REF] Chateauvieux | Molecular and Therapeutic Potential and Toxicity of Valproic Acid[END_REF] ), which could be part of the explanation for the favorable response to this drug.

| Neurological signs

Electroclinical studies in mice have suggested that the tonic inhibition in the brain also leads to motor disturbances, such as ataxia, which correlates well with the observation that the GABA transporters are highly present in the cerebellum as well as in cortical neurons. [START_REF] Madsen | The subcellular localization of GABA transporters and its implication for seizure management[END_REF] We found that 29% (9/31) of the patients had mild ataxia or unsteady gait. A few patients displayed other cerebellar signs such as mild hypotonia, tremor, and fine-motor impairment, in accordance with the hypothesis of a slight perturbation of motor control in animal models. [START_REF] Cope | Enhanced tonic GABAA inhibition in typical absence epilepsy[END_REF] Overall, we can conclude that humans carrying pathogenic SLC6A1 variants do not seem to display severe neurological symptoms.

These data combined with those of Carvill et al. [START_REF] Carvill | Mutations in the GABA transporter SLC6A1 cause epilepsy with myoclonic-atonic seizures[END_REF] suggest that typically SLC6A1-positive patients have mild-tomoderate ID, with language delay being one of the major features, preceding the onset of an epilepsy with an MAE phenotype. Therefore, in children with ID with or without behavioral disturbances, developing polymorphic seizure types, including absences, myoclonic and atonic seizures, and rare or no GTCS, screening for SLC6A1 should be undertaken. In addition, we describe cases never developing epilepsy. Because most patients described to date are children or young adults, longitudinal follow-up will be important to understand how seizures and cognition may change with age.

With this study, we define the phenotypic spectrum of clinical manifestations associated with SLC6A1 variants to include different forms of generalized epilepsies, but also a few cases of focal epilepsies as well as cases with ID without epilepsy. We confirm that the predominant epilepsy phenotype is MAE with preexisting mild-to-moderate ID with or without behavioral symptoms. Further studies are needed to confirm the phenotypic spectrum and to investigate the functional consequences of pathogenic variants in SLC6A1.

F

  I G U R E 3 Similar EEG pattern in 3 different patients diagnosed as MAE-like (Patient 20), unclassified generalized (Patient 2), and typical MAE (Patient 31). The EEG abnormalities consisted of prolonged bursts of irregular generalized 2.5-3.5 Hz slow waves with and without prominent spikes/polyspikes component, typically starting gradually in the occipital regions. In Patient 20, roughly the same EEG pattern can give rise to clinical manifestations consisting of atypical absence (to the left), or to a seizure with a brief atonic and myoclonic component (to the right). EEG parameters are the following. Patient 20: band pass filter 1-35 Hz, time constant 0.1 s, sensitivity 20 lV/mm; Patient 2: band pass filter 1-70 Hz time constant 0.3 s, sensitivity 10 lV/mm; Patient 31: band pass filter 1-30, time constant 0.16 s, sensitivity 10 lV/mm epileptiform abnormalities during NREM sleep resembling an ESES pattern. Surprisingly, both subjects developed aBECTS as an evolution of an MAE-like phenotype. A third subject presenting with aBECTS at epilepsy onset (Patient 12), evolved into a generalized epilepsy difficult to classify later, suggesting that the electroclinical features of SLC6A1-related epilepsy are variable and can change over time. Finally, 1 patient (25) was diagnosed with an epileptic encephalopathy of the LGS type.

F

  I G U R E 4 Nocturnal sleep EEG in Patient 26 at the age of 4 y and 5 mo. During NREM sleep (to the left) the EEG is characterized by almost continuous spike and slow waves in the right hemisphere, with occasional spreading diffuse (spike-wave index 82%). During REM sleep (to the right) the epileptiform abnormalities are less frequent and more focal in the temporocentral region. This EEG picture strongly resembles hemispheric ESES, although the clinical correlate is vague. In the right upper corner, the amplitude map corresponding to the pick of the spike shows a radial orientation of the dipole. EEG parameters: band pass filter 1-70 Hz, time constant 0.1 s

  Patient 29),. After epilepsy onset, cognition deteriorated in 11 of them (Patients 3, 8, 10, 13, 15, 16, 22, 24, 26, 30, and 32).

	Data on cognitive performance before epilepsy onset were
	available in 24/31 patients with epilepsy. Cognition before
	epilepsy onset was normal in 5/24 (Patients 8, 15, 17, 26,
	and 30), mildly impaired in 12/24 (Patients 2, 5, 6, 11, 13,
	14, 16, 22, 24, 28, and 21), and moderately impaired in 4/
	24 (Patients 20, 21, 23, and27); 2 Patients had speech
	delay (3 and 10) and 1 had severe ID (

  Prev.publ., previously published; aBECTs, atypical benign childhood epilepsy with centrotemporal spikes; Ab, absence seizures; A, atonic seizures; AA, atypical absence seizures; ADD, attention deficit disorder; ADHD, attention-deficit/hyperactivity disorder; BG, background; CAE, childhood absence epilepsy; CLZ, clonazepam; ESES, electrical status epilepticus during sleep; rep., repeated; ESM, ethosuximide; EOAE, early onset absence

				Mutation	3p25.3 del.	including	SLC6A11	and SLC6A1	(exon 1)	de novo
				Effective AED	Sz free with	VPA, LEV
			Neurological	findings	Normal
			Behavioral	problems	None
		Cognition	after seizure	onset	Mild/moderate	ID
		Epilepsy syn-	drome at	diagnosis	MAE
				EEG	BG slowing	Generalized delta	activity and SW
				Seizure type	Absences,	myoclonic	atonic
		Age at	epilepsy	onset	3 y
	Cognition	before	epilepsy	onset	NA
			Family	history	None
		Gender/	age at	inclusion	F/7 y
				Patient no.	34	Prev.publ. in	Carvill	et al. 9

T A B L E 1 (Continued) epilepsy; F, female; GTC, generalized tonic-clonic; ID, intellectual disability; LEV, levetiracetam; LTG, lamotrigine; MAE, myoclonic atonic epilepsy; M, Male; m, months; NA, not available; NREM, non-rapid eye movement; Sz, seizure; SW, spike wave; TPM, topiramate; VPA, valproic acid; VNS, vagus nerve stimulation; y, years; ZSM, zonisamide; del., deletion.

F I G U R E 1 Pedigrees of families 1 and 2

ACKNOWLEDGMENT

We thank the patients and their families for the participation in this study.

DISCLOSURE OF CONFLICT OF INTEREST

ST and KLH are employed by Ambry Genetics. CC was funded by the SNSF Early Postdoc fellowship. YW and IH were funded by DFG We4896/3-1; He5415/6-1. The remaining authors have no conflicts of interest to disclose. added. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

WEB RESOURCES

The ExAC browser: http://exac.broadinstitute.org; SIFT: http://sift.jcvi.org; Poly-Phen2: http://genetics.bwh.harva rd.edu/pph2/; MutationTaster: http://www.mutationtaster.org