Introduction

Rosita Di Peri and Daniel Meier At the start of the Arab uprisings, Lebanon was facing a critical political situation: In January 2011, the Lebanese government collapsed after Hizbullah and its allied ministers had made the decision to resign. This act was the result of tension between the Shi'a Islamic party Hizbullah and the March 8 coalition on the one hand and the rival March 14 coalition, led by al-mustaqbal, the Saad Hariri-led Sunni party, on the other. One of the bones of contention between the two coalitions was the United Nations' Special Tribunal for Lebanon charged with investigating the 2005 assassination of then-Prime Minister Rafic Hariri. The subsequent indictment of four Hizbullah militants required approval by the state, but the Shi'i party was ready to do everything in order to preserve its image, including overturning the government led by the late Hariri's son Saad. In June 2011, when the Arab uprisings spread across the Middle East and North Africa, Lebanon formed a new cabinet headed by Sunni politician Najib Mikati and dominated by Hizbullah. This small country in the Middle East was facing internal power struggles and seemed oblivious to the development of regional events.

In early 2011, however, simultaneously with the country's turbulent political events, several protests broke out in numerous cities in Lebanon. The protesters adopted the slogan of the Tunisian and Egyptian uprisings, "the people want to topple the regime", but changed it slightly to "the people want to topple the sectarian regime" (Lebanon Wire 2011). The protests succeeded in bringing out only a small number of participants. They lacked strong coordination and consequently failed to have a major impact, including on the international media [START_REF] Fakhoury | Lebanon against the Backdrop of the 2011 Arab Uprisings: Which Revolution in Sight?[END_REF]. During the summer of 2015, after a period of relative calm, the eruption of popular protests over the halt in garbage collection and of protesters calling for greater accountability of sectarian leaders echoed the protests in the region at large and gave a glimpse of the internal damage the Syrian crisis had caused. Besides the rift between the two main political coalitions, an even wider crack has opened up within a vivid civil society whose mobilisation spread because of a growing distrust of political leadership and produced a profound crisis in the political system. There are numerous internal and external hazards, but so far both the system and the society has managed to adapt.

In the field of social sciences, the 2011 protests in Lebanon (and Lebanon in general) did not make for "marketable news". Moreover, in the post-uprising period, scholars and analysts have increasingly focused on the regional dimension and attempts to find links and connections between the events of different countries and tried to understand why nobody was able to predict such major political changes. The role and the impact of the domestic dimension and the specific local features were strongly overlooked. The spasmodic need to find common explanations of the paths and trajectories of states in the Middle East has concealed the role of domestic politics, actors, and local decision making. One of the most investigated topics at the regional level has been the sectarian issue by means of a broader culturalist reading of the social and political process in the Middle East under the label of the whole region's "sectarianization" (Abdo 2013; Byman 2014). According to these scholars, a never-ending conflict between Sunnis and Shia was simply a "natural" consequence of this state of affairs. This view has unfortunately become an all-encompassing meta-narrative producing simplistic readings of the regional processes and, at the same time, considering the role of domestic politics and actors to be irrelevant and giving room to pervasive geopolitical analysis.

This argument is of particular consequence to the case of Lebanon. Most of the analysis of that period, especially after the beginning of the civil war in Syria, has focused on Hizbullah's involvement in the war [START_REF] Alagha | Hizbullah's DNA and the Arab Spring[END_REF][START_REF] Alagha | Hezbollah and the Arab Spring[END_REF][START_REF] Spyer | Hizballah and the Arab Revolutions: The Contradiction Made Apparent?[END_REF], the Syrian refugee problem [START_REF] Knudsen | Violence et déplacement : La crise des r fugi s Syriens au Liban[END_REF][START_REF] Dot-Pouillard | Les réfugiés syriens au Liban: l' mergence progressive d'un discours de neutralit[END_REF], Lebanon's broader regional context [START_REF] Heydemann | Syria's uprisings: Sectarianism, regionalization and State Order in the Levant[END_REF][START_REF] Osoegawa | Syria and Lebanon. International Relations and Diplomacy in the Middle East[END_REF], or the role of the movements/parties that could affect the region's geopolitical circumstancesfor example, Hizbullah, Salafist movements, Palestinian refugees, etc. (see [START_REF] Omayma | Lebanon's Sunni Islamists -A Growing Force[END_REF][START_REF] Salloukh | The Arab uprisings and the geopolitics of Middle East[END_REF][START_REF] Rabil | Salafism in Lebanon. From Apoliticism to transnational Jihadis[END_REF]. The impact of the war in Syria and more generally of the regional turmoil on Lebanon, however, is only a lens through which to observe how the state and society may adapt in order to cope with this situation [START_REF] Peri | Islamist Actors from An Anti-System Perspective: the Case of Hizbullah[END_REF]Meier 2015b).

At present, the political scene in Lebanon is characterised by many constraints: a political vacuum caused by an inability to find agreement on the election of a new president; social mobilisation for waste management, which calls into question the accountability of decision makers; political bargaining between the two main political coalitions about the problems relating to the influx of Syrian refugees; and any other issue that can be politically divisive.

All these constraints have revealed a picture of a country that cannot be reduced to being a mere proxy of Iran or Saudi Arabia. By contrast, the internal debate, the vitality of Lebanese political life, the multiplicity of its actors, and the variety of its topics -from women's rights to election lawsshow a country in transition that displays a capacity for continuous adaptation. The actors' "path of resilience" (their capacity to face the many dangers threatening the country) goes to the heart of the questioning that led to this volume. How do the various sectors of Lebanese society manage external and internal threats, and how did this managementwhich can sometimes appear chaotic and uncontrolledresult in a form of adaptation and resistance to the local and regional constraints?

Assuming that the domestic dimension is crucial in order to understand the resonance and impact of external issues, this book provides an intimate picture of the country after 2011.

The picture is based upon micro-transformations occurring inside Lebanese society (at different levels and from various starting points, including communities, social movements, and the Lebanese Armed Forces) or by reflecting upon issues that, even if they have a regional impact, are analysed from the perspective of their influence on the domestic sphere (Hizbullah, Syrian refugees, consociational system, etc.). Lebanon's "exceptional" capacity to cope with a blurred and dangerous environment raises issues at the levels of identity, order, and the nation state. An examination of these issues forms the basis for the three main research questions in this book: What kind of identifications and identity resources do the actors' practices reveal? How do political actors and social groups re-order interactions and norms in order to cope with recent changes? And how does Lebanon's "nationhoodness" still make sense (or not) for actors with regard to their actions and state symbols?

New lenses for old problems

Thanks to empirically grounded research that delves into recent events, the book explores several dimensions of Lebanon's post-uprising "exceptionalism" from different angles in order to renew perspectives on classical topics that include mobilisation, army, political movements, and refugees. At the core of those processes is the production of a collective identity that is currently affecting the entire region, which is worthy of exploration with respect to Lebanon as it covers most of the themes investigated in this volume. In so doing, we also acknowledge that Lebanon's socio-political trend can shed new light on developments and dynamics in the region. The book's chapters focus on the post-2011 era in Lebanon and question history, at many levels, by proposing lenses at different scales through which to read historical facts and sectarianism in order to reshape the boundaries of society. All the chapters' narratives make sense and practices related to them for each case studied. The narratives can differ from the one to the next, they can have parallel discourses, or the practices can diverge. Furthermore, the facts on the ground will raise doubts about old categories, concepts, narratives, and common boundaries. To this aim, three main transversal "identity incubators" will be considered.

First of all, there is what we call "identity in practices". This label refers to personal, sectarian, or multiple belongings. Instead of identity, the notion of identification is more accurate to describe what we mean, as it underlines an ongoing process [START_REF] Brubaker | Au-delà de l'identit[END_REF].

Beyond "sectarianism" (a term commonly used to explain the Lebanese context), social classes, regional belonging, and other identity factors play a crucial role, and class community [START_REF] Picard | De la 'communaut -classe' à la r sistance 'nationale'. Pour une analyse du rôle des Chi'ites dans le système politique libanais (1970-1985)[END_REF]) may be useful to re-assess the situation that some groups are currently facing.

Secondly, there is a major issue that we identify as the "social order". It links identity with norms and values at the scale of a social community (groups) seeking to (re-)organise sociopolitical and mental spaces (of movement to carry out actions). The theoretical frame can be linked with the (b)ordering or re-ordering processes currently going on at different locations and levels of society (Meier 2015a) and regarded as a way for people to fix or re-arrange interactions in order to cope with a changing situation (Syrian refugees, socio-economic constraints, political vacuum, Salafist threats, etc.).

The third "identity incubator" is the issue of nation fabricationi.e. Lebanon's "nationhood" and therefore its failure in both Lebanon and the Middle East, as revealed by the Arab uprisings and underscored by many commentators since the rise of the Islamic State organisation [START_REF] Cheterian | Failure of the Modern Middle East Nation State. Roll up the Map[END_REF][START_REF] Daguzan | La fin de l'Etat-nation? De Barcelone à Bagdad[END_REF]. How does "identity in practices" refer or relate to the state? In which narrative or ideology? After 2011, what kind of relationship exists between the state and (communal, class, regional, civil, or military) society? What about the nation today in Lebanon? "Nationhoodness" requires an examination of how people recognise themselves in the nation state: through classical symbols of the state (army, welfare, borders, or other institutions) or through the existence of powerful actors able to provide alternative identity structures (Hizbullah, Islamic or non-sectarian belonging).

The book is divided into two parts totalling seven chapters: "From identification to social (dis)order" and "From ordering to nationhood". Each chapter incorporates the three "identity incubators" mentioned above that are strongly interrelated and ultimately serve to counter the prevailing arguments used to describe Lebanon before and after 2011.

From identification to social (dis)order

The result of the Arab uprisings in Lebanon, especially after the outbreak of the war in Syria, is that they seem to have brought identities to the surface. At the levels of parties, groups, communities, neighbours, coreligionists, and others, the Lebanese have overcome many difficulties to transcend appurtenance and challenge old legacies. On the one hand, because of a sectarian reading of the regional context, the narrative of sectarianism has blocked the "identities in practices" with the skilful use of rhetoric and repertoires. On the other hand, by contrast, it has offered a stimulus to re-think and re-imagine a new social dis(order). The upheaval inside and between the parties and communities, as well as the transformations in some regions and disputed border areas, have effectively brought to the foreground those processes that contrast with the catastrophic reading of the Lebanese context and shown, instead, its flexibility and adaptability: its "path of resilience". This first part of the book, which resonates with the three "identity incubators", mainly discusses these processes of resilience at many different levels.

With a focus on the border regions, Lorenzo Trombetta argues that local actors in Lebanon have been playing a crucial role by ensuring the exceptional flexibility of the Lebanese system. By analysing three different cases, Wadi Khalid, Tall 'Abbas and Marj al Khawkh, the chapter presents how communities struggle to maintain social order in the midst of a precarious status, adapt their social interactions, and adjust their physical, cultural, and political spaces. It also emphasises that the concept of class community, beyond pure sectarianism, is able to describe the process of an elaboration of (local or supranational) identities by Syrians and host communities that goes beyond physical and mental borders.

Daniel Meier and Rosita Di Peri look at the Sunni community's paths of transformation and adaptability and focus on the post-2011 era in particular. The identity-building process, which led to the consolidation of Lebanon's Sunni community, especially after the end of the Civil War, and gave birth to the phenomenon of "Harirism", was challenged by the assassination of Rafic Hariri in 2005. From this moment on, Sunni "identities in practice" have emerged and underscored the crisis of "Harirism"an entirely unexpected development in Lebanon. This shift paved the way for the rise of radical Sunni movements, such as that of Sheikh al-'Asîr between 2011 and 2013. These movements display a clearly antisystemic stance capable of altering the social order, challenging the Sunni community itself.

Another case of "identity in practice" is analysed by looking at Hizbullah, which is at the core of Francesco Mazzuccotelli's chapter. Here, the focus on possible dissent inside the Shi'i movement, especially after its involvement in the Syrian war, shows how Hizbullah's inability to listen to its internal disagreements can offer a fresh perspective to look at the party's political dynamics. Hizbullah is not a monolithic bloc but composed of multiple identities that can challenge the internal and the external social order and simultaneously have an impact on the nationhood consciousness.

From (re)-ordering to nationhood

The second part deals with the process of (re-)ordering that is affecting Lebanon as it faces new challenges and problems and how this process relates to nationhood via narrative or ideology. Ways of belonging can sometimes be identified through social mobilisation at the start of and during the Arab uprisings.

Myriam Catusse, Marie-Noëlle AbiYaghi, and Mariam Younes call attention to the concept of "sectarian shadow" as part of their reflection on identities during mobilisation. As a means to take distance with "identity in practices", the "sectarian shadow" underlines the nonconscious categories of thoughts strongly marked by sectarianism that continue to shape the social order, even among antisectarian groups of Lebanese citizens. It highlights the difficulties of going beyond those norms that bind together and rule actors' social lives in Lebanon.

One of the ways that the citizens of Lebanon have found to express their collective belonging and their concern for nationhood lies in the popular empowerment of the national army. This institution, as Vincent Geisser clearly shows, functions as a symbol during times of trouble and deep uncertainty and a means to discredit political and sectarian actors. This return to the state is also shaped by a professional communication sector in the army that plays a role in identifying it as a guarantor of civility, situated far above the corrupt political scene and able to come to the defence of citizens and state borders.

Another means to establish a link between social order and nationhood can be found in Estella Carpi's chapter, which explores the effect of humanitarian technocracy on the welfare state system. She explains how welfare regimes have been experienced across Lebanon in the wake of internal and regional displacements.

Towards new challenges

Between 2011 and 2015, Lebanon experienced a severe political crisis, one of the longer and more delicate ones since the end of the Civil War. Instead of falling into a new cycle of violence, this small country in the Middle East showed a rare, somewhat "unexpected" flexibility and capacity to adapt, especially considering the turbulent regional environment. This flexibility, however, is not without consequences: As the analysis developed by this book's various contributions points out, Lebanon, its institutions, and population have been directly affected by the transformations that occurred during this critical period. New protests erupted and new actors emerged to challenge the state and its institutions, while old confessional legacies have remained and become stronger. All these factors shape the boundaries of the identity fabrication process and their connections between the nationhood legacies, questioning the (re)production of the social order. This tendency is not something new in Lebanon, a country capable of reinventing itself even after violent and dramatic events.

However, despite the many ways that social actors have found to adapt to the challenging (local and regional) environment, Lebanon appears to be walking a tightrope. Its capacity to cope with several types of danger, which some describe as the power of the weak, can also be a trap, a sort of self-confident illusion. Playing with fire, as the sectarian leaderships seem to be used to doing by threatening and weakening state institutions as well as state legitimacy, may provoke unpredictable and unintentional results. While there is no doubt about the renewed or reproduced powers of the zu'ama [START_REF] Kingston | Reproducing sectarianism: Advocacy networks and the politics of civil society in postwar Lebanon[END_REF][START_REF] Cammett | Compassionate communalism: welfare and sectarianism in Lebanon[END_REF][START_REF] Salloukh | The politics of sectarianism in postwar Lebanon[END_REF], the sprawling presence of sectarianism is something discussed by all of the authors in this bookwhether in relation to garbage protests, the army, Syrian refugees, or humanitarianismfrom the variable perspective of "identity incubators". This lens has been adopted to shed new light on actors' capacities at the scale of their daily life, in such changing times, as well as on the dynamic aspect of identity-building processes. This volume has sought to illuminate a few visible (and some less visible) social processes at stake in Lebanon but concludes with the paradoxical result of mixed feelings: On the one hand, the state is constantly downgraded and its capacity to act threatened by powerful actors on the political scene. On the other hand, social actors seem to act as moral guardians of a sinking ship called Lebanon when they build new relationships between each other or with the old and new refugees. Many challenges remain and are immediately visible: electing a new president, setting up a new legislative electoral process, and more broadly re-legitimising politics in the eyes of the country's citizens. But the highest priority may be a return to normality. When abnormal times become "normal", what is taken for granted needs to be reshaped, rethought, and rebuilt together. Contrary to the end of the Civil War in 1990, the next step for Lebanon will be to put opposing views of the nation and the state around the same table. Thus, there may be an opportunity to reconfigure the Lebanese Republic after the end of the war in Syria. Sadly, in any realistic scenario, this will only happen after a slow return to sectarian "business as usual", like what happened with the "national dialogue" gatherings after the popular protests of 2005 and the Doha Agreement in 2008. Therefore, the question is not whether another social movement will clamour for political leaders to be accountable or for the protesters to be represented in a new deal but when exactly this "second" uprising will take place.

Bibliography

Abdo, Genevieve. 2013. The New Sectarianism: The Arab Uprisings and the Rebirth of the Shi'a-Sunni Divide. Analysis Paper, 29, The Saban Center For Middle East Policy, Brookings Institution.

  Thanks to the example of Beirut's southern suburb in the aftermath of the Israeli bombing campaign in 2006 and the issue of Syrian refugees since 2011, she shows how the postwar internationalisation of local welfare has created a management crisis because of the cycle of prioritising new emergencies. But welfare and aid appear to pursue differing social orders and curb cohesion and feelings of seamlessness, which generally define nationhood.Finally, Are Knudsen's study of Lebanon's sectarianism in the face of the Syrian refugee crisis highlights the process of re-ordering national politics from another point of view. The lens of the state's non-camp policy with respect to the more than 1 million Syrian refugees in Lebanon reveals the chaotic political scene. The polarisation regarding the war in Syria provides an original tool to assess the contradictory visions of nationhood in Lebanon.

Acknowledgements

The editors would like to thank the Italian Society for Middle Eastern Studies (SeSaMO)in particular, President Matteo Legrenzi and General Secretary Paola Rivettifor enabling us to bring together a group of researchers on a panel called "Lebanon facing the Arab uprisings:

between internal challenges and external constraints" during its annual conference held in Venice in January 2015. We are also indebted to the Institut français du Proche-Orient (IFPO) in Beirut and to Myriam Catusse, the director of its "Etudes contemporaines" department, for giving us the opportunity to set up a workshop in Lebanon a few months later thanks to the European Research Council's WAFAW programme. We were privileged to receive a warm welcome at the Orient-Institut Beirut (OIB) and would like to convey our warmest thanks to its director, Stefan Leder. Our gratitude also goes out to Sarah Roughley and Jennifer Timmins at Palgrave for their patience and kindness throughout the process. We were fortunate to receive the support of the University of Turin's Department of Culture, Politics and Society, and of the PACTE Laboratoire in Grenoble to fund the outstanding copy-editing carried out by André Crous, and we wish to express our gratitude to all of them. Warm regards to Anne-Laure Amilhat-Szary, the EUBORDERSCAPES programme, and the " nderstanding the Middle East" summer school project for funding Daniel Meier's trips to Venice, Catania and Turin in 2015, which led to discussions and eventually this collaborative project with Rosita Di Peri.

We also want to acknowledge the help of a few individuals in particular who assisted us at various stages during the preparation of this book. Thanks to Nicolas Dot-Pouillard, Elizabeth Longuenesse, and Bruno Lefort for actively taking part in our workshop in Beirut and helping us to frame the topic and strengthen our arguments. Thanks to Helen for correcting several drafts and to Khalil in Beirut for his friendly support at the workshop. Last but not least, we are indebted to all the contributors for their active participation in the project, their insightful comments and suggestions both during and after the seminars, and the patience they showed at all times during the review and finalisation process of their chapters.


in Martin Wählisch and Maximilian Felsch (eds), In the Eye of the Hurricane:

Lebanon and the Arab Uprisings, London, Routledge, 2016 (forthcoming)

The Blind Spot: Palestinian Refugees from Syria in Lebanon Daniel Meier -CNRS, PACTE, F-38000 Grenoble -France

Several studies have been produced about the impact of the massive influx of Syrian refugees on neighbourhood states. This is also true for Lebanon where the amount of refugees from Syria now reaches the level of one quarter of the population [START_REF]Apart from international agencies' reports, see for instance Paul Salem[END_REF] . Much less has been said about the Palestinian refugees in Syria of which many have fled to Lebanon. On two occasions their dramatic fate became visible on local TV screens. The first occasion was in December 2012 when thousands of them were fleeing the shelling of their houses in the Yarmouk camp in the suburbs of Damascus. Twenty months later, in the fall of 2013, starving Palestinian children showed up on the world's TV screens as the Syrian regime blockaded the Yarmouk camp in order to pressure the insurgents to leave the part of the camp they controlled. From a few thousands in late 2012 the Palestinian refugees from Syria in Lebanon numbered 44.000 people registered early 2015 according to United Nations relief and Works Agency for Palestine Refugees (UNRWA) [START_REF]See UNRWA's website[END_REF] . These figures, however, disregard those entering without registering and those leaving Lebanon, or returning to Syria. In a summer 2014 census, conducted in a door-to-door inquiry, UNRWA reached another figure of 42.000 actually living in Lebanon 3 . Most of the Palestinian refugees from Syria initially settled in overcrowded camps or informal settlements where they found relatives or friends. UNRWA started to assist them in such difficult circumstances although some could not receive any assistance as they entered Lebanon for political reasons illegally. The Lebanese immigration policy towards Palestinian refugees from Syria has changed several times. Initially they were allowed to enter Lebanon with a Syrian authorization. However, but in May 2014 Lebanon has closed its border for them without any official explanation.

In the light of the long and troubled history of the Palestinian refugees in Lebanon and the political divide among the Palestinian factions in Syria due to the uprising, this chapter examines the impact of the influx of the Palestinians from Syria on the Lebanese social and political environment as well as on the Palestinian refugee community in Lebanon.

At first sight, the arrival of this contingent from Syria shed a crude light on the social and humanitarian conditions of the Palestinian refugee community in Lebanon compared with the one in Syria prior to the uprising. The specific situation they face in Lebanon has been analyzed as a "state of exception" 4 . This chapter argues first that this "state of exception" expands to those refugees arriving from Syria due to the limit of UN's mandate but also due to Lebanon's lack of investment in the improvement of their living conditions as an inherited aspect of the troubled history of the Lebanese-Palestinian relationships. Second, I will contend that the Syrian crisis was a catalyst for a rapprochement of rival Palestinian factions and that all of them rather opted for a neutral position towards the Syrian crisis. Both the relative weakness of the Hamas, the post-Syrian Lebanon context after 2005 and the low politicisation of the refugees arriving from Syria can explain this posture when it is put in relation to the collective trauma faced by the Palestinians in Lebanon with the brutal destruction of the camp of Nahr el-Bared by the Lebanese army in 2007 [START_REF]): Qu'est-ce que le salafisme?[END_REF] .

The chapter is divided into two parts. The first deals with humanitarian aspects regarding the Palestinian refugees from Syria (PRS). With the help of UNRWA information and statistics, their social and economical conditions can be related to Lebanon's restrictive refugee policy. Both aspects are showing how PRS inherited the "state of exception". The second part addresses the security issue related to the arrival of thousands of PRS. It evaluates the impact on the internal equilibrium among the Palestinian factions as well as in the balance of their relationship with the Lebanese political parties.

Palestinian refugees from Syria: inheriting the "state of exception"

The nakba in 1948 had caused an influx of 75.000 to 100.000 Palestinian refugees in Syria. Most of them settled down in five camps in Damascus and three unofficial ones near the Damascus, Aleppo and Latakia. By the time of the Syrian uprising in 2011, this refugee community has grown to nearly half a million. A significant part of them were living in the camps as well as in informal gatherings. Palestinians in Syria received UNRWA services and were entitled to almost the same restricted civil rights as Syrian nationals and became relatively well integration into the Syrian socioeconomic structure. [START_REF] Anaheed | The Right of Return Movement in Syria: Building a Culture of Return, Mobilizing Memories for the Return[END_REF] Inserted in secondary and third economic sectors, most of them were located in urban cities.

When the Syrian uprising began in spring 2011, PRS were more often exposed to violence than Syrians. Although some PRS have joined the governmental forces and some others the opposition, the bulk of the Palestinians in Syria chose to carefully follow a neutral and distanced posture towards both sides. Despite this neutral position, two thirds (270.000 people) of PRS have been displaced by early 2014, of which 75.000 have left the country. [START_REF]UNRWA's website[END_REF] During an initial period of several months following December 2012 when the war affected them most intensively, they mainly sought refuge in Turkey, Jordan and Lebanon. When both Turkey and Jordan unilaterally decided to close their borders for PRS, Lebanon remained the last haven.

Facing the impacts of the huge Syrian refugee community, which grow to more than one million, the Lebanese authorities seem to regard PRS as the sole responsibility of UNRWA and the international community. In May 2014, the General Security of State even decided to shut down the Lebanese borders to Palestinian refugees without any official decision or justification. In order to understand such behaviour, one can refer to the specific and tensed situation which Palestinians in Lebanon are facing. To conceptualise their Lebanese environment, Sari Hanafi and Taylor Long 8 borrowed the concept of "state of exception" from Giorgio Agamben. Understood as a "zone of indistinction between exception and rule, licit and illicit" 9 the term can be applied to the Palestinian refugees as "the suspension of the law by the sovereign state, usually in the name of national defence or security" [START_REF] Sari Hanafi | Governance, Governmentalities, and the State of Exception in the Palestinian refugee Camps of Lebanon[END_REF] . But the authors add the suspension of the law and the practice of measures of exception involve all institutional actors related to the Palestinian refugees issue namely, the Lebanese state, the NGOs, and the PLO. All of them are part of a system of interactions where the Palestinians are treated within a state of exception because of the lack of political will to deal with their situation in Lebanon.

The situation PRS are facing in Lebanon is by most described as bad. Only 7% among those fleeing Syria have found a job in Lebanon and most of the refugees are traumatised by direct exposure to violencea fifth have lost a close relative or friend. [START_REF]For instance, see the 2013 mid-summer[END_REF] The bulk of the PRS arrived after the Yarmouk camp attack by the end of 2012 and continued to seek refuge in Lebanon in 2013 and 2014 despite the poor living conditions they will experience in Lebanon. [START_REF]For example[END_REF] There are several reasons why Palestinian refugees from Syria flew to Lebanon: their concentration in Damascus neighbourhood (which is close to Lebanon), kinship, intermarriages, labour ties, and the fact that the Turkish and Jordanian borders have been closed. Contrary to those two countries, Lebanon left its doors open for those refugees from Syriaprovided they paid an individual entry fee of 25.000 Lebanese Pounds (17$) for a seven-day entrance visa 13until May 2014. [START_REF] Cf | Syrian refugees in Jordan and Lebanon: a Snapshot from Summer 2013[END_REF] Since then, the Lebanese authorities have blocked the process sine die. Syrian travel documents or ID cards were required for Palestinians to leave Syria and an exit visa costs 1.500 Syrian Pounds (approx 32$) for an entire family. For some refugees it was difficult to leave the country, like for those who stayed in Yarmouk camp because they were suspected to have sided with the insurgents. The same problem occurred to men who had not done their military service in the Palestinian Liberation Army (PLA)the Palestinian corpse of the Syrian Army. Thus, the illegal crossing of the porous Lebanese border became the last option for many.

When arrived in Lebanon, the PRS faced harsh living conditions. UNRWA provided them at least with basic health care, social service and education as well as some other direct material help. However, as the Beirut based Palestinian NGO "Tatwir Study Center" stated, the main challenges for the refugees were to find accommodation and to get legal residences. The NGO also mentioned the limited health services, as UNRWA reimburses only 50% of any emergency surgery, compared to a full support in Syria. [START_REF] Tatwir | [END_REF] In terms of shelter, UNRWA's insufficient assistance is partly compensated by programs of the Palestinian Authority.

In 2013, the number of Palestinian refugees arriving from Syria rose from 10.000 to more than 80.000, an approximate figure that includes those not registered. 16 UNRWA's Director 17 explained that half of them joined Palestinian camps in Lebanon after having been displaced more than once within Syria. The other half of them stayed outside camps, in gatherings, or spread in main cities. These refugees are equally located in the South of Lebanon, in the North of Lebanon and in the Beqaa Valley. No more than a few thousand PRS settled in Beirut due to pricy renting and overcrowded spaces. In the South, as mentioned by Kamel Dorai 18 , Palestinian refugees who possess houses (acquired prior to the 2001 law that has banned such acquisition) eased the stay of some relatives from Syria there and also provided them with connections to Europe and the U.S. thanks to earlier migrations. In July 2013, an international pledge of $45 mio was made to finance assistance in terms of sheltering, health, education and cash distributions. Main donors are the EU, the US, the United Kingdom, France, Germany, Kuwait, and Saudi Arabia. [START_REF]Refugees and Lebanese after the Lebanese Civil War[END_REF] Still, an additional influx of refugees will strain already encumbered refugee communities. For 2015, the projection of UNRWA's urgent assistance estimates their number up to 44.000 people in Lebanon and the agency required $415,4 mio for the year, affecting US$ 63,5 mio to Lebanon's Palestine refugees only.

In spring 2014, UNRWA succeeded to provide a monthly cash distribution by ATM card for individuals and families of respectively 30$/each person a month and 100$/each family for the renting 20 . UNRWA's financial assistance is nevertheless insufficient, given the high living costs in Lebanon. A second issue related to the residence permit also appeared after the first year of residence as the General Security Office required from refugees to pay a 200$ fee for the renewal of the permit in order to stay in Lebanon another year. As most of them cannot afford such a sum of money, the refugees end up staying inside overcrowded refugee camps as they face forced repatriation if the Internal Security Forces catch them 21 . This illegal status prevents them from leaving the camp, even to withdraw their cash assistance by ATM as there are no ATMs within Palestinian camps in Lebanon.

More serious implications of their illegality slowly appear as time passes: death, birth and marriages happen but cannot be recorded legally as no legal civil registration is possible without a legal status. Among them, the lack of birth registration is probably the most severe consequence as without a legal status those children become stateless people without any civil rights. How UNRWA tries to find solutions for this issue is described by its PR officer: "UNRWA tries to keep a record of these births but in order to make them official, we have discussed the possibility to have an official authorization from the Lebanese Republic to register them. A project is now trying to put a control ahead of the birth process with a medical certificate that should be delivered to every pregnant woman at 7 and 9 months pregnancy in order to avoid the void of registration with an approx birth ratio of 100 births per months" 22 .

Observing the effects of the PRS presence in the camp of Shatila, Diana Allan described a social tension and sharper boundaries between PRS and local Palestinian inhabitants of this camp, one of the most heterogeneous in Lebanon 23 . Memories of the war of the camps are vivid here: people of Shatila keep in mind the brutal siege they faced during three years (1985-1988) when the Syrian Army was helping the Amal militia to shell the camp that killed hundreds of its residents. 24 In such environment, the PRS are perceived as intruders and small differences between the two communities are seen as major differences that render any cohabitation difficult. However, for a short time during demonstrations and mobilizations in the context of the 2014 Gaza war in August 2014, a feeling of unity and collective belonging was shared by most Palestinians. 25 On the other hand, division between the two Palestinian communities continued to exist in the field of education. UNRWA even had to organise different classes for two thirds of the 7,530 students enrolled in UNRWA schools because of the difference in their school backgrounds as PRS are mostly only Arabic speakers.

PRS in Lebanon as well as Jordan and Turkey are also struggling for their human rights, as stated by the Geneva Convention, to be respected. Human Rights Watch criticises the deportations of Palestinian refugees from Syria by both Jordan and Egypt. 26 In line with such cases, Lebanon is playing the same game as illustrated by the deportation the General Security organized in May 2014. More than 40 Palestinian refugees either from Syria or from Lebanon were caught by the security as they tried to embark on flights for Libya or Egypt with fraudulent visas. The case was divulgated once the refugees had been expelled to Syria but among them three men succeeded to get out of the bus in the transit zone after the Masnaa border crossing. 27 Claiming they would surely be tortured and killed in Syria, they chose to stay in this no man's land for nearly two months with sandwiches they purchased from a kiosk and also thanks to the occasional help of people passing by and providing with blankets or material to ease their stay. Eventually, the Palestinian Embassy in Beirut and the Lebanese General Security negotiated an agreement according to which the three individuals will not be arrested on their return to Lebanon.

To better understand Lebanon's harsh treatment of PRS one has to look at the history of the Palestinian presence in Lebanon as their arrival unveiled old demons of the civil war time (1975-1990). Lebanon's collective memory agrees on the guilt of the Palestinians for having dragged Lebanon into the Arab-Israeli turmoil and ruined their country by triggering a civil war, although this recount of the civil war is clearly partial, the social and political effects of this vision structured the post-civil war era. 28 Since the end of the civil war, the Syrian tutelage over Lebanon used this mindset to keep the Palestinian refugees as a marginalized group. Most of the Lebanese parties and political actors were happy to have found a scapegoat instead of doing the work of memory, which left scars open deep inside the society and did not allow any improvement of the Lebanese perceptions about the Palestinian refugees living in Lebanon. This explains the institutionalisation of the marginalisation of the Palestinians in Lebanon that enforces a state of exception in the way the Lebanese state operates with the Palestinian refugees living in Lebanon.

A good illustration of this lack of consideration for Palestinian refugee's fate is given through the repeated rejection of the "implantation" (al-tawteen), by which any kind of social and economic integration of the Palestinian community is meant. In fact, such an attitude prevents any serious effort to improve the living conditions of the refugees in Lebanon and contributes to raising fear of a "Palestinian burden" among the Lebanese. [START_REF]The danger of their implantation resides in the perspective of the subversion of the sectarian balance in the country and the subsequent shift[END_REF] In the post-Syrian era, after the military withdrawal of 2005, the Lebanese government set up a Lebanese-Palestinian body to build a bilateral relationship after the Lebanese Siniora government had recognized the legitimacy of a Palestinian diplomatic representation in Beirut in 2006. This committee, labelled the Lebanese Palestinian Dialogue Committee (LPDC) turned to be inefficient and political turmoil and military confrontations slowed down its work. More largely, LPDC's action during all these years gives the impression its margin of manoeuvre is generally narrow. 30 LPDC policy should be questioned as their only answer when facing the influx of Palestinian Refugees from Syria was to minimise the problem. The lack of serious policy to cope with this situation reveals the low level of importance the fate of Palestinian refugees living in Lebanon have for the Lebanese state.

The security impact: mapping the Palestinian forces

Considering the current Syrian civil war as the main effect of the Arab uprising that has deeply affected Lebanon so far, the Lebanese state took some unilateral decisions about the refugees from Syria. One year after their first massive arrival in December 2012, the General Security decided to slow down the admission of Palestinian refugees at the border and it finally shut it down in May 2014. Since then, the only authorized persons among PRS to enter Lebanon are minors under the age of eight, Palestinian refugees with a Lebanese mother or relatives in Lebanon or a valid visa for three months. Another possibility is to have an appointment with the Palestinian Embassy for a visa to travel to a foreign country. In the latter case, the General Security allows PRS to enter Lebanon no more than nine hours before their flight departure. In addition, the Ministry of Interior has decided not to extend visas for PRS anymore. Current negotiations between the Lebanese state and UNRWA tend to secure that no PRS will be deported to Syria.

The Lebanese media usually exaggerates the security threat posed by PSR. They stated one should fear internal troubles from internecine feud Palestinian refugees would bring to Lebanon. It is a fact that a divide exits among them as Hamas took side with the uprising while some other Palestinians factions like Palestinian Front for the Liberation of Palestine -General Command (PFLP-GC) stood along the Syrian regime. This worry is linked with the perception of Palestinian camps as sanctuaries or training camps for jihadists. There is a palpable fear linked to a strong belief among a significant segment of the Lebanese society of a Palestinian "security issue" when seeing the "extra-judicial" spaces refuge camps constitute. [START_REF]common fear often heard about of the "extra-judicial" spaces that Palestinian camps are[END_REF] This fear is linked to the symbol of power the Palestinian resistance represented in the pre-civil war period and refers more specifically to the Cairo agreement signed in November 1969 between the Lebanese army and Yasser Arafat as the head of Fateh, at the time the leading group of the Palestinian resistance. Regarding the camps, the Cairo agreement granted Palestinian refugees of Lebanon with freedom of organisation in the camps. The intelligence services of the Lebanese army then withdrew from the camps putting an end to a bleak period of bad treatment of Palestinians in Lebanon. Then camps became the symbol of a powerful Palestinian identity. The cleavage that divided the Lebanese society led to a contradictory perception of what the camps were, alongside with their perception of the political meaning of the 'Palestinian resistance'. For the Leftists and the National Movement (LNM) [START_REF]The LNM gathered several leftists groups and pro-Palestinian factions headed by the Progressist Socialist Party (PSP) under the lead of Kamal Jumblatt. The Movement disbanded after the assassination of its leader in[END_REF] , camps were the symbol of the struggle for liberating Palestine and an internal ally to bring revolution within the Lebanese political scene. For the rightists and the Lebanese Front 33 in general, the camps incarnated dangerous military strongholds and were seen as the vectors for a destabilisation of the Lebanese state, an undermining of its sovereignty and a peril regarding their control over the State. With the weakening of the military wing of the Palestinians after the 1982 Israeli invasion, this second vision became preeminent. Although the Lebanese parliament abrogated the Cairo Agreement in 1987, the camps stayed autonomous partly due to a lack of state capacity to impose its authority over the various Palestinian militias that would fight against for their autonomy. The origin of the discourse on the Palestinian camps as 'security islands' (juzzur amniyyat) is also clearly linked to the Syrian tutelage policy over Lebanon. This Syrian hegemony over the post-civil war state tended to use the "Palestinian card" as a common scapegoat amongst various Lebanese groups, in line with the fear of "implantation" already mentioned.

Palestinian groups toward the Syrian uprising

The Syrian uprising and war have caused deep divisions among Palestinian refugees in Syria. During the initial conflict period, in early December 2012, the Palestinians were fighting on both sides: with Assad's government as well as with the rebels. The PFLP-GC on the government side and the Storm Brigade (Liwaa al-Asifa) on the insurgents' side have even fought against each other causing casualties mainly on the pro-government side. 34 In this fierce battle, the oppositional Free Syrian Army and allied Islamists were able to take control of the Yarmouk camp which provoked the Syrian army to attack the camp by airstrike bombing. [START_REF] Anas Zarzar | [END_REF] As a direct spill-over of these clashes and violence, fights occurred few months later in Lebanon's Ain el-Hilweh camp near Sidon between Islamists of Osbat al-Ansar that joined Al-Nusra Front, one of the strongest jihadist militia of the Syrian battlefield, and the pro-Bashar PFLP-GC. 36 In March 2013, other clashes happened between Fatah and Osbat al-Ansar. Although the latest fight seems related to an older issue [START_REF]Everyday Jihad. The Rise of Militant Islam Among Palestinians in Lebanon[END_REF] , these tensions must have rung the bell among the factions of the camp, in fear of any renewal of Nahr el-Bared scenario. [START_REF]This camp was destroyed after a 3-month battle between the Lebanese Army and the jihadi-led group Fatah al-Islam, causing an immense distrust among Lebanese citizens towards the Palestinian refugees. For details on this case, see Adam Ramadan[END_REF] A general agreement to bring back a quiet and safe environment in Ain el-Hilweh emerged as a means to undermine any scenario of a new Islamist stronghold. [START_REF]Interview with a leading figure of the Democratic Front for Liberation of Palestine (DFLP)[END_REF] This does not mean that all conflicts and controversies have disappeared but rather that they will be discussed by the local committee of the camp. [START_REF]Camps committee are local institutions gathering the residents' representatives and armed groups of the camp. For details about their history and difference between camps, see Daniel Meier[END_REF] A good example of this behaviour happened in June 2013 when few dozens of young Sunnis radical Palestinians from Jund al-Sham and Osbat al-Ansar tried to counter attack the Lebanese Army Forces in order to support the Lebanese Salafist Sheikh Assir and his militiamen during the confrontation that erupted near Sidon. 41 .The unified forces of the camp succeeded in pressuring the young Palestinians to pull back from this battle as their involvement could do harm to the whole Palestinian community. [START_REF]Interview with a Palestinian security officer in Ain el-Hilweh[END_REF] Despite the massive influx of PRS in Lebanon, Palestinian factions surprisingly stayed neutral. In fact, as seen above, the fear of new tensions with the Lebanese army leading to a "new Nahr el-Bared" is probably a key element explaining such collective behaviour. But one also has to take into account the fact that Palestinians from Syria are far less politicised than their Lebanese brothers [START_REF] Interview With A Jaber Suleiman | [END_REF] , an aspect that is congruent with the whole process of de-politicisation of the society under the Assad regime. 44 Another aspect of such Palestinian neutral policy is a long and harmful experience of internal divide among Palestinian factions in Lebanon nurtured by the Syrian power. From its intervention in Lebanon's turmoil in 1976 onward, the Syrian regime tended to oppose the Arafat wing of the PLO and to nurture an internal divide that eventually turned to a success in 1983 with the formation and dissidence of a new Palestinian militia "Fateh-Intifada" that obviously defied the authority of the Fateh over Palestinian refugees. Lebanon was then a vantage ground for Syria to develop clientelistic Palestinian organisations like Fatah-Intifada or PFLP-GCa dissident branch of the PFLP in 1968 under the lead of Ahmad Jibril.

The Oslo Agreement in 1993 deepened the rift between Arafat and the Syrian authorities and in 2001 Hamas chose to settle down in Damascus as Syria appeared as a strong political ally in its opposition to Oslo. The Syrian withdrawal from Lebanon in 2005 led to a new trade-off between Palestinian factions and the Lebanese State that carried out a more homogeneous policy between the pro-Syrian factions (Saiqa, PFLP-GC, Hamas) and the pro-Arafat factions (mainly Fateh, PFLP, DFLP) in Lebanon. In addition, following the Hamas move to Damascus in 2001, a clear "axis of resistance" emerged aggregating Hizbullah and Hamas around the Syrian/Iranian alliance. 45 Today the Syrian popular uprising disturbs this "resistance" in contesting the Syrian regime with a "revolution" discourse that transforms the "resistants" into oppressors. 46 During the first year of the Syrian uprising (2011-2012), Palestinian refugee camps stayed away from the mobilisation against the Syrian regime. The Palestinians were still mobilized against Israel. At that time, Hamas had a distinct position from the PFLP-GC's towards the regime: it tried to mediate between Assad and its opponents. Things changed in June 2011, during the naksa commemoration under the guidance of the Syrian regime 47 when 23 young Palestinians demonstrators were killed by the Israeli army on the Golan border. During the funeral in the Yarmouk camp, a PFLP-GC office was vandalised by Palestinian refugees accusing this group and the Syrian regime of using the Palestinian cause for its ideological profits. 48 This first warning calmed down all the factions who did not want the Syrian crisis to become an internal divider among Palestinians. Nevertheless, in July 2011 an attack launched by the Syrian Army on a Palestinian refugee camp in Latakia increased the tension between Syria and the PLO.

For Hamas, the neutral posture slowly broke down in the Spring of 2012 during the siege of the Syrian city of Homs. Ismael Haniyeh, the Hamas prime minister in Gaza, took side with the Muslim Brotherhood in Cairo and in Syria disregarding Hamas' strategic alliance with Syria and Hizbullah in the "axis of resistance". Fateh, the leftists and the Islamic Jihad movement, on the other hand, tried to diminish the tension during the December fight between the Syrian army and the opposition in Yarmouk camp by staying neutral. Only the PFLP-GC took side with the Syrian army but also faced an internal division leading to the defection of some of its members. On the opposite side of the political spectrum, Hamas took part in the Turkish AKP congress that led Damascus to accusing Khaled Mechaal of being a traitor. On the ground, several militants from Gaza enrolled in the Syrian opposition movements, Hamas being more and more sympathetic with the figure of the revolutionary (al-tha'ir) and less with the resistant one (al-muqawim). For its part, the Islamic Jihad in Palestine did not make the same calculation as its own story is marked by an exclusion of the Egyptian Muslim Brotherhood when the leader of the movement took side for the Iranian Revolution in 1979. The nationalist and third-world paradigms seem to have a bigger weight in regional politics than Sunni belonging or religious orientation.

Facing this tension among Palestinians in Syria, Hizbullah, Hamas, Islamic Jihad, Tawhid movement and Jamaa Islamiyya held common gatherings during the year 2012 with the purpose of preventing the conflicts in Syria from spreading to Lebanon and its Palestinian refugee camps. It is significant that even in 2013, when Hizbullah was facing several bombings of its strongholds and when investigations put the blame on Hamas members, the "Party of God" issued a statement explaining the continual meetings the party organised with Hamas. For its part, Hamas expressed its will to cooperate and immediately mentioned the importance of its alliance with Hizbullah against Israel. 49 This behaviour shows that due to its weakness in Lebanon, Hamas tries to keep a multiple alliance system to stay on the safe side in order to deal with the unpredictable evolution of the Syrian uprising, after the Egyptian military coup against the Muslim Brotherhood.

The Gaza war in summer 2014 reinforced the Hamas-Hizbullah links when, for the first time since 2012, Ali Baraka, the Hamas political official in Lebanon appeared publicly alongside with Mahmoud Qomati, the vice president of Hizbullah's political office. In this context, Hamas was useful for Hizbullah to show its solidarity with Gaza. It also allowed Hizbullah to assume a different policy towards the Palestinian movement from the one of the Syrian authorities. Although some interlocutors saw the move as a means for Hizbullah to keep the movement close to its axis of power when Lebanon was facing the rising threat of ISIL, it is also possible to read it as Iran's interests in keeping a Palestinian card in the Arab-Israeli conflict. 50 Although the rising tension in Lebanon because of Syrian Jihadi groups and especially ISIL and despite the rumours about ISIL recruiting within Palestinian camps, there is a very low probability of significant collusion. 51 The changing evolution of the Hamas-Hizbullah relationship tend to show the key importance of strong strategic alliances and ideological values in the quite volatile environment in the Middle East.

Hamas continues to share with Islamic Jihad main political opinions like their opposition to the Palestine Authority or the definition of Israel as an enemy; and both movements are using the same Islamic discourse. For their parts, explained Dot-Pouillard, leftist groups tend to stay neutral and have more fears of the Islamisation of the uprising 52 . They are also defiant towards the Syrian regime. Surprisingly, leftist groups are also allied with Hizbullah and Islamic Jihadtwo radical Islamic formationswhich is understandable regarding their anti-Imperialistic ideology. Fateh, for its part, seems to be ambivalent: Fateh and the Palestinian Authority condemned the Syrian regime for its behaviour towards the Palestinian refugees, but they seemed to have shifted their position when Hamas left Damascus as the victory of the insurgents on Assad could bring new political opportunities for Hamas. In this perspective, a new "rapprochement" seemed to occur with Hizbullah, the closest ally of the Syrian regime in Lebanon, during the year of 2013. One should also mention the interest for Hizbullah to gather non-Shi'a political forces to aggregate new loyalties among the Lebanese and Palestinians. In this perspective, the "Party of God" seems to have expanded the recruitment of young jobless Palestinian refugees in its non-Shi'a battalion known as Al-Saraya al-Muqawama. 53 The siege of the Yarmouk camp by the Syrian government forces in December 2013 with the cruel strategy of starving its inhabitants progressively united all the Palestinian forces. Fateh was prompt to pay attention and to denounce the siege; other groups did not take long to make statements upon it and to collect donations. Soon, many rallies and protests were organized in different countries of the Middle East, from Lebanon to the Gulf with fund-raising campaigns. UNRWA has set up its own campaign to help the besieged camp. Images of poor people becoming refugees once again and seeking for shelter after having been exiled since 1948 were like a shock, as was one of the first images UNRWA displayed on the front page of its website picturing food delivery early February 2014 in Yarmouk camp. 54 Nevertheless the timing for the Yarmouk campaign was convenient for many Palestinian groups to mobilise. The best example is given by Fateh that took this opportunity to show its leading role in the Palestinian national movement, reminding basic rights for refugees and advocating for the right of return. As Fateh stayed more neutral towards the Assad regime than Hamas, PLO happened to be more successful at getting food into the camp which counts now less than 50.000 people (originally 150.000). 55

Conclusion

This chapter examined the impacts of the PRS in Lebanon from both the humanitarian and security perspective. It was shown that contemporary issues of the PRS in Lebanon cannot be detached from historical events as the Lebanese-Palestinian relationship is strongly influences by civil war memory. It was argued that the "state of exception" in which most Palestinian refugees in Lebanon live is the result of a tense and complex Lebanese-Palestinian coexistence. This mode of governance, which is based on arbitrariness and lack of clear rules for the Palestinian refugees, is now affecting those Palestinians who have fled from the war in Syria.

From a humanitarian perspective, PRS are facing harsh difficulties in Lebanon due to the traumatic events they lived before seeking refuge in Lebanon. This country appeared as the easiest destination from Damascus the moment their camp in Yarmouk, a Damascus suburb, was bombed in December 2012. Although some of the PRS found relatives in Lebanon, many men had to cross illegally the Lebanese border either because they were not able to pay the entrance fees in Lebanon or because they feared to be enrolled in the Syrian military or put in jail. While UNRWA eased their living conditions in Lebanon including cash distribution since 2014, the institution was unable to provide shelter to PRS families. On the highest estimation including non-registered people, PRS numbered 80.000 and dispersed for half of them in Palestinian camps in Lebanon. Since the closure of the Lebanese border for PRS during the summer 2014, this figure stabilized around 44.000, not including illegal PRS residents. This number increased year after year as the Lebanese General Security Office required from refugees to pay a 200$ fee to renew their residence permit. This could have severe repercussion on newborn babies of illegal parents: they could become stateless and rightless refugees as no legal civil registration is possible without a legal status. Finally, the PRS situation in Lebanon mirror the lack of interest Lebanese State historically pay for them. The perception of Palestinian refugees as a burden for the Lebanese society is not helping to improve the current fate of the PRS.

Such a residence policy continues to feed the myth of camps as "violent" or "dangerous" spaces as most of the illegal PRS are seeking refuge there due to their fear of being deported to Syria. Palestinian refugee camps are becoming the subject of all types of rumours about security issues. The Palestinians from Lebanon know that these places can even be destroyed if the Lebanese security is thretened as it was the case in 2007 with Nahr el-Bared camp. In consequence, the Palestinian factions have expended lots of efforts in security coordination within campsand the case of Ain el-Hilweh is probably an interesting case to follow with the implementation of a new security plan last Spring. 56 Thanks to a post-Syrian era that saw new collaborations between Palestinian factions in Lebanon, the policy followed today in camps tends to promote neutrality towards the current Syrian civil war. In the meantime, the effect of the general context helped the Islamic radical movements among Palestinian camps to mobilise segments of the Palestinian youth. But so far neither the radical Sheikh Ahmad al-Assir nor the Islamic State has succeeded in building up a radical front in the Palestinian environment. And if it happens in the future, nothing seems to significantly relate the PRS with such a mobilisation. After all, the internecine fights among Palestinian radicals or with Fateh have a long story in Lebanon clearly pre-dating the arrival of the current refugees from Syria. 57 In addition, the ideological and strategic link between Hamas and Hizbullah seem strong enough to keep Palestinian Sunni radicals away from possible Sunni-Shia clashes.

Disregarding this overall positive outlook, there are still some unsolved critical issues that could cause serious problems for the Palestinians in Lebanon. The main problem is that the security coordination in camps is not prepared to face what could be the next challenge in this Palestinian refugees' environment: tensions between Palestinians from Syria and Lebanon and a growing resentment among PRS against what they perceive as a lack of dignity in their treatment in Lebanon. In light of the difficult Lebanese-Palestinian relations, any terrorist action committed by a Palestinian individual could once again turn the Lebanese anger against the "usual suspect", the scapegoat that helps to hide an internal lack of national cohesion among the Lebanese.

See Lina Blin (2011): "Entre ici et là: Intégration et comportement politique des réfugiés palestiniens de Syrie", in Jalal Al Husseini & Aude Signoles (eds), Les Palestiniens entre Etat et diaspora (Paris: Karthala): 211-33.


Gregoire Cattan

Anton Andreev

Bastien Maureille

Marco Congedo

I. Introduction

Event-related potentials (ERPs) are very small voltage potentials produced by the brain in response to external stimulation and are measured with an electroencephalogram (EEG). Differences in the onset time and amplitude of ERPs reflect different sensory and high-level brain processing functions, such as the recognition of symbols (e.g., words or figures) or of the correctness of presented information, or changes in a subject's attention [START_REF] Luck | Event-related potentials[END_REF]. For these reasons, ERPs are a useful tool for describing the processing of information inside the brain, with practical applications, for example, in the domain of brain-computer interfaces (BCIs), which allow for direct communication between the brain and an electronic device, bypassing the usual muscular and peripheral nerve pathways [START_REF] Wolpaw | Brain-Computer Interfaces: Principles and Practice[END_REF]. The first BCI was designed by Vidal in the late 1970s [START_REF] Vidal | Real-time detection of brain events in EEG[END_REF] and allowed control of a cursor on a computer screen using an EEG signal. Recent improvements in EEG signal processing [START_REF] Congedo | Spatio-temporal common pattern: A companion method for ERP analysis in the time domain[END_REF][START_REF] Congedo | EEG Source Analysis[END_REF] have made the detection of ERPs more reliable, opening a promising field of BCI applications for people with disabilities (6-8) as well as for the general public (e.g., 9,10). In order to detect and evaluate an ERP in an ongoing electroencephalogram (EEG), it is necessary to tag the EEG with the exact onset time of the stimulus. A fixed latency engenders a constant offset which can be easily removed. Variance in latency, referred to as jitter, is more problematic, since it invalidates common operations such as trial averaging. Failing to control sequencing in the tagging pipeline causes problems when interpreting latency and can lead to contradictory conclusions [START_REF] Amin | Evaluation of passive polarized stereoscopic 3D display for visual amp;amp; mental fatigues[END_REF][START_REF] Pegna | Effects of stereoscopic disparity on early ERP components during classification of three-dimensional objects[END_REF][START_REF] Käthner | Rapid P300 brain-computer interface communication with a head-mounted display[END_REF]. In this work, we present number of technical aspects which can influence latency.

The remainder of this report is organised as it follows: Section II describes a model for estimating latency. It contains A) the description of the tagging pipelines, B) an estimation of the latency for each tagging pipeline, and C) these estimations applied to the particular case of stimuli displayed in a matrix. Section III contains specific considerations on the case of a stimulus rendered by multiple cameras. Section IV reports on an example experiment. Section V presents our conclusions and recommendations.

II. Model for estimating latency A. Tagging pipelines

On most platforms, we separate software rendering (SoR) from screen rendering (ScR). In the first case, the software is drawing the stimulus to display on a texture (via the GPU/CPU); in the second case, the pre-rendered texture is being displayed on the screen. Tagging rarely occurs after ScR, since this would require observing the colour of the pixels on the screen by means of a hardware or software component to ensure that the texture is displayed. More likely it would take place before or after SoR:

Pipeline A SoR  Tagging  ScR  Observation Pipeline B Tagging  SoR  ScR  Observation
Once the stimulus is displayed on the screen, it can be observed by a photodiode. The response time of the photodiode is nearly instantaneous, less than one millisecond (ms). We define the latency (L) as the delay between the time the tagging command is sent and the detection of the stimulus by the photodiode.

B. Latency of tagging pipelines

In pipeline A, L is mainly due to ScR, which is a linear function of the height h of the stimulus on the screen, with the LCD screen refreshing from top to bottom. On a screen with a refresh rate (RR) of 60 Hz, ScR typically finishes within 20 ms:

ScR(h) = a * h + b, where
h is the position of the stimulus in screen height percentage, a is the time taken to update the screen (16 ms by default), and b is the time taken by a pixel to switch its colour (about 6 ms, Figure 1). Figure 1. LCD refreshes from top to bottom in linear time [START_REF]LCD Screen Refresh in 1000 FPS[END_REF].

Time (ms) taken by a pixel to switch its colour as a function of its height (%) on the screen

ScR does not depend on SoR, but SoR does influence the perceived ScR (PScR). Ideally, when the number of frames per second (FPS) is equal to RR, a texture is displayed each time the screen is refreshed. However, when FPS is lower than RR, the time between two textures may be higher than 20 ms. In contrast, when FPS is higher than RR, this may cause screen tearing, that is, two frames rendering at the same time [START_REF] Fedorov | Frame Rate (FPS) vs Refresh Rate (Hz)[END_REF]. Ideally, a stimulus should be drawn within a single frame and then displayed during ScR. This is generally the case when just one camera is rendering a virtual scene. However, it is not always so when the stimulus is rendered by more than one camera, as is the case in virtual reality (VR).

In pipeline B, the latency is due to both SoR and PScR.

L(h) of Pipeline A PScR(h) + e L(h) of Pipeline B SoR + PScR(h) + e

In both conditions, e stands for hardly measurable delays, due to software and screen drivers, between the moment when the texture is ready and the moment when it is displayed. When estimating the latency with a photodiode, e also includes delays due to the sampling rate of the acquisition unit, the threshold used to detect the peaks of the photodiode and tagging signals, and the method used to remove the drift of the photodiode signal. We assume e and SoR to finish in near-constant time.

C. Matrix of stimuli

When multiple stimuli are displayed, they are regrouped in a matrix (e.g. ( 16)). Thus, we can refer to a stimulus S using its position (i, j) in the matrix I x J rather than its height h on the screen. Therefore, we need to express PScR as a function of (i, j). The size of the screen is defined by W x H, corresponding to the actual width and height of the screen in pixels. PScR (i, j) may be seen as a compound of three functions:

1. P: i, j  x, y is the position of the stimulus in screen percentage, where (Figure 2) 𝑥 = (𝑚 𝑗 + 𝑗𝑢 𝑗 ) 𝑊 and 𝑦 = (𝑚 𝑖 + 𝑖𝑢 𝑖 ) 𝐻 , 0 < 𝑖 < 𝐼 and 0 < 𝑗 < 𝐽 ;

2. H: x, y  h is the height of the stimulus on the screen, where h = x if the screen is turned 90° (as is the case for smartphone-based VR) and h = y otherwise; and 3. PScR(h) already defined such that

PScR(i, j) = PScR(h) o H(x, y) o P(i, j)
with the following property (P), which corresponds to the delay between the observation of two stimuli

III. Multiple display of a stimulus

As explained in section II.B, the PScR is probably modified when a stimulus is rendered by multiple cameras. This is always the case when using VR, for example, since it requires the display of two images for stereoscopic vision (Figure 3). To avoid having a single stimulus being perceived as multiple stimuli, the delay between multiple appearances of the same stimulus on screen has to be as short as possible; that is, ideally PScR ~ ScR.

In practice, this is only the case if single-pass rendering is implemented. For instance, frameworks such as Unity (Unity, San Francisco, US), starting from version 2017.3, help to render the content of two stereoscopic cameras within a single frame [START_REF]Unity -Manual: Single Pass Stereo rendering (Double-Wide rendering)[END_REF].

Whenever this feature is not available, a solution is to take into account the ScR of just one camera, a camera being a priori rendered within a frame. However, it is not clear which camera has to be considered. At this point, we propose the latency-of-first-appearance principle (LOFAP); that is, the first appearance of the stimulus on screen induces the ERP, and thus the latency of this first appearance should be used to correct the offset of the ERP.

Under single-pass rendering or the LOFAP, the property (P) is simplified as follows: Notice that at this point the latency between two stimuli depends only on the orientation of the screen (turned or not).

Nevertheless, the LOFAP does not correct for differences in amplitude which may result from multiple-pass rendering. Indeed, a high latency between the rendered content of the cameras may cause the stimulus to stay longer on the screen. In the case of visual stimulation such as the P300, however, this effect is minimal [START_REF] Lu | The Effects of Stimulus Timing Features on P300 Speller Performance[END_REF].

IV. Experiment

We conducted an experiment to compare the ERPs produced by a user under two conditions: when the stimulus was displayed within a traditional PC application using a flat-panel display refreshing from top to bottom (condition 1), and when it was displayed on a smartphone-based VR immersion screen refreshing from left to right (condition 2). We used pipelines A and B for conditions 1 and 2, respectively. Pipeline A introduced less variability since it depended only on ScR. Unexpectedly, pipeline B gave better results (in terms of jitter) in condition 2. This can be attributed to the tagging method, which was partially asynchronous (Figure 4). Clearly this explanation has to be investigated further and the relationship between tagging pipelines and asynchronous tagging clarified. We measured the latency between the tag and the appearance of a centred stimulus on the screen for each experimental condition. In condition 1, the latency was around 38 ms (standard deviation, or SD, = 5.3 ms). In condition 2, the stimulus appeared at two different locations on the screen, with latencies of 117 ms (SD = 5.8 ms) and 143 ms (SD = 6.6 ms) for the left and right parts of the smartphone screen, respectively. It was clear that the latency was higher in condition 1 than in condition 2. This was partially explained by the computation time due to the SoR, which was not present in pipeline A. Moreover, in VR two images are rendered at the same time, resulting in an extended computation time for the SoR in comparison to a traditional application. This impacted the PScR, as it became greater than 20 ms (143 ms -117 ms > 20 ms), thus we applied the LOFAP and retained only the shorter latency (117 ms).

Having different latencies is a problem when comparing averaged ERPs in two conditions, since there is no way to know whether the difference in latency is physiological or is due to the tagging process. A solution is to subtract the estimated latencies we found in the two conditions from their respective ERPs. This removes the latency due to SoR, but not the latency due to PScR. In fact, the latency due to PScR in the averaged ERP depends on the location of the stimuli on the screen. If the distribution of the stimuli is uniform, their barycentre should be at the same location as the centred stimulus we used for estimating the latency. In practice, a centred stimulus in the matrix may differ from the barycentre if the matrix is even and/or if the number of stimuli is low (Figure 5).

Figure 5. Distance between the barycentre of the stimuli and the location of the photodiode.

In this example, the photodiode was placed under the stimulus at position (2, 2) in a 6 x 6 matrix (indices start from zero). The Y axis represents the number of stimuli between the barycentre and the photodiode. The X axis represents the number of stimuli displayed the experiment.

In such case, the latency between the barycentre (𝑖̅ , 𝑗 ̅) and the centred stimulus (𝑖 0 , 𝑗 0 ) can be estimated with the following: The values of u, H, and W were computed by measuring on the screens, and we used a = a' = 16 ms. Twelve stimuli were used for this experiment, with mean (N = 10,000) row and column distance to photodiode of 0 ms (SD = 0.4) and 0.2 ms (SD = 0.4), respectively, leading to (P) |𝐿(𝑖̅ , 𝑗 ̅) -𝐿(𝑖 0 , 𝑗 0 )| = 0.54(1.23) ms in VR and 0.00(0.87) ms in PC with 𝐿(𝑖̅ , 𝑗 ̅) ≥ 𝐿(𝑖 0 , 𝑗 0 ) in the two conditions.

The average variability under the two conditions was reduced since we used the same stimulus for the photodiode. A maximum difference in latency of 0.9 ms (0.54 ms + 1.23 ms -0 ms -0.87 ms) between the two conditions can be observed due to the variability in the location of the barycentre. If the uniform hypothesis is fulfilled (as it is in the case using 12 stimuli) but the location of the photodiode is not known, the maximum difference in latency is about 2.6 ms for the matrix we used. Mean barycentre distance (in number of stimuli) to photodiode as a function of the number of displayed stimuli

V. Conclusion

In summary, tagging latency depends on the location of all stimuli on screen. This latency causes variability in the position of ERPs and can introduce a shift when averaging ERPs because not all stimuli have the same position on the screen. This variability is high when the number of stimuli is low. For a 6 x 6 matrix and 12 stimuli, the variability is only about 1 ms. Additional variability is introduced by positioning the photodiode at different locations when estimating latency. These errors can be corrected for if the location is known. When either the barycentre (of all the stimuli) or the photodiode location is not known, the maximum latency between two pixels on the screen should be lower than the refresh time of the screen, which is around 20 ms when the screen RR is 60 Hz. Uncertainty being cumulative, the maximum uncertainty is then in the range 30-40 ms when comparing two averaged ERPs (2 x 20 ms for a screen with RR of 60 Hz).

The subjects themselves are a source of variability [START_REF] Humes | The effects of age on sensory thresholds and temporal gap detection in hearing, vision, and touch[END_REF][START_REF] Hagström | Frames That Matter : The Importance of Frames per Second in Games[END_REF]. In fact, [START_REF] Hagström | Frames That Matter : The Importance of Frames per Second in Games[END_REF] reported that aircraft pilots were able to perceived between 12 and 220 FPS. The variability of the subject's perception of FPS is a priori negligible if the number of subjects is high and the experiment is paired (i.e., the paired ERPs in the two conditions are produced by the same subjects).

In conclusion, we recommend the following guidelines: 1) Use pipeline A with synchronous tagging when possible. With asynchronous tagging, pipeline B may lead to better performance. 2) The higher the RR, the better: whenever possible use a modern gaming monitor with a refresh rate of 140 FPS. 3) Use the VSync or, preferably, the NVIDIA GSync method. VSync allows the graphic card to match its FPS to the RR of the screen. Ideally GSync also lets the monitor vary its RR according to the FPS of the graphic card. 4) When multiple cameras are rendering, try to enable single-pass rendering. This helps to draw all cameras within a single frame [START_REF]Unity -Manual: Single Pass Stereo rendering (Double-Wide rendering)[END_REF]. Otherwise, use the latency of the first displayed camera. 5) Make sure stimuli are uniformly distributed on the screen or that the barycentre of the displayed stimuli can easily be predicted. 6) Use the same photodiode location in all experimental conditions, close to the barycentre of the displayed stimuli. 7) Each subject has to be assessed under both conditions. Employ a substantial number of subjects to prevent variability in the perception of FPS by the human eye (increasing the sample size lower the variance). Exclude from the study subjects having trained vision, such as pilots or hard-core gamers.

ScR

  (P) |𝐿(𝑖 1 , 𝑗 1 ) -𝐿(𝑖 0 , 𝑗 0 )| = |𝑃𝑆𝑐𝑅(𝑖 1 , 𝑗 1 ) -𝑃𝑆𝑐𝑅(𝑖 0 , 𝑗 0 )| .

Figure 2 .

 2 Figure 2. Example of a matrix of stimuli with J stimuli in a row and I stimuli in a column. Ui is the distance between two adjacent stimuli in the same column. Uj is the distance between two adjacent stimuli in the same row. Mi and Mj are, respectively, the top or bottom and left or right margins.

Figure 3 .

 3 Figure 3. Example of matrix of stimuli in VR having J stimuli in a line and I stimuli in a column.

(

  P) |𝐿(𝑖 1 , 𝑗 1 ) -𝐿(𝑖 0 , 𝑗 0 )| =|𝑆𝑐𝑅(𝑖 1 , 𝑗 1 ) -𝑆𝑐𝑅(𝑖 0 , 𝑗 0 )

Figure 4 .

 4 Figure 4. Model for explaining the impact of asynchronous tagging: By moving asynchronous tagging before SoR, it finishes before ScR. Thus, the stimulus is observable subsequent to the tagging.

(

  𝑖̅ | (condition 2).Notice that the latency depends only on the orientation of the screen-top-to-bottom (flat-panel display) or left-to-right (smartphone).


Dr Elodie Decuypere

Dr Sabrina Bernard

Minghao Feng

Karine Porte

Dr Margaux Riomet

Pierre Thuéry

Dr Davide Audisio

Frédéric Taran

Copper-Catalyzed Aza-Iminosydnone-Alkyne Cycloaddition Reaction Discovered by Screening

Keywords: Mesoionics, Screening, Triazoles, Cycloaddition, Copper

published or not. The documents may come

Mesoionics are an old, intriguing class of dipoles often considered as exotic structures, even within the heterocyclic community. As a consequence, their chemistry and reactivity have been only sporadically explored; a rapid survey of literature indicates that less than 5% of the possible mesoionic structures have been described. [START_REF] Lopchuk | For reviews on mesoionics[END_REF] These compounds were originally defined as dipolar five-membered heterocycles with multiple aromatic resonances that cannot be satisfactorily represented without charge separation. Pioneering investigations into this class of compounds began in the early 1930s [START_REF] Earl | The Action of Acetic Anhydride on N-nitrosophenylglycine and Some of its Derivatives[END_REF] and were significantly furthered by Huisgen in the 1960s who worked extensively on sydnones and münchnones. [START_REF] Huisgen | 1,3-Dipolar Additions of Sydnones to Alkynes. A New Route into the Pyrazoles Series[END_REF] These two mesoionics are still the most described in the literature and have been essentially used as dipoles in non-catalyzed, thermal cycloaddition reactions. [4] Recently, we reported that copper salts are able to catalyze the 1,3-dipolar cycloaddition of sydnones with terminal alkynes leading to 1,4-pyrazoles under mild conditions and with complete control over regioselectivity. [5] The reaction involves the copper-controlled [3+2] cycloaddition followed by a retro-Diels Alder (rDA) step leading to pyrazole with the concomitant extrusion of CO2 (Figure 1). Given that the reactivity of mesoionic compounds is still largely unexplored, we questioned whether other mesoionics would react under copper catalysis in presence of terminal alkynes. In this contribution, we designed and used a MS-screening approach to explore the capability of a library of selected mesoionics to undergo the [3+2]/rDA sequence with terminal alkynes under copper-catalysis. The screening allowed the identification of the unprecedented ligand dependent reactivity of aza-iminosydnones to access N-2-aryl-1,2,3-triazoles and hydrazineylidene-propanal derivatives. The screening method consists in attaching a MS-tag to the alkyne molecule to allow rapid and specific detection of tagged molecules by ESI-MS. [6] After reaction in the presence of mesoionics and copper catalysts, the MS-tagged products can be directly detected without work-up (Figure 1b). The core experiment was conducted with a series of 24 designed mesoionics 1-24 (Figure 2b) which were mixed with the tris (2,4,6,-trimethoxyphenyl)-phosphonium TMPP-tagged terminal alkyne. Most of these mesoionics are known to undergo thermal cycloaddition with alkynes at elevated temperatures. [1a] Each combination was then exposed to one set of reaction conditions in presence of a copper complex obtained after addition of CuSO4, sodium ascorbate and one of the nine selected ligands A-I. The corresponding 216 reactions were run overnight at room temperature and screened in few hours by direct MS analysis of the crude reactions. The results, indicated in Figure 2d, confirmed the reactivity of N-phenyl-sydnones 2 and 3 but also revealed new mesoionics 4, 8, 11, 13, 18 and 19, which were able to react with terminal alkynes in the presence of copper salts. However, only two, the iminosydnone 4 and the aza-iminosydnone 13 afforded reasonable yields under the tested conditions and were therefore the subject of our attention. Both reactions were reproduced in flask, on mmol scale with phenylbutyne as model alkyne, to isolate and identify the products.

Reaction of 4 with one equivalent of phenylbutyne, copper and ligand B gave two products, a pyrazole together with an urea product, in low yields at room temperature and moderate yields upon heating at 60 °C (Scheme 1a). Attempts to improve the reaction efficiency were unsuccessful. (Scheme 1b). In both cases, iPr-isocyanate R2 was formed as released product. To our delight, we found that the reaction was still efficient with only catalytic amounts of copper at room temperature (for optimization studies see Tables S1 andS2); attempts to improve the catalytic system by MSscreening of a library of 11 metals (including Au, Ag, Ru, Zn and Ni salts) and 29 ligands (used with 1:1 and 1:5 ratios compared to metal) were unsuccessful (Figures S9 andS10). We next investigated the influence of substrate structures and found that the reaction is highly dependent on the structure of both the mesoionic and the alkyne substrate. (Table 1).

Scheme 1.

Interesting reactions revealed by MS-screening.

[a] isolated yields, [b] ratio determined by NMR of the crude reaction mixture.

Table 1. Influence of Cu-ligands and substrates on the reaction [a] Entry R R' Ligand Yield [b] C2 : C3 [c] [a] Experiments were carried out overnight at 0.1 M with 0.2 equiv. of copper and ligand, 1.5 equiv. mesoionic, 1 equiv. of triethanolamine and Na. Asc. [b] Global (C2 + C3) isolated yields.

[c] C2/C3 ratios were determined by NMR on crude reaction mixture.

Bulky tert-butyl substitution on the hexocyclic nitrogen atom of the mesoionic was found particularly important for the efficiency of the process and no reaction took place when an aryl or a benzoyl is linked at this position (entries 1-6 in Table 1). Alkynes bearing a heteroatom in propargylic position and the use of ligand E favoured the formation of product C3 (compare entries 7-9 and 10-12 in Table 1) whereas regular alkynes and ligand A favoured the formation of triazoles C2 in good yields and selectivity. With this information in our hands, we looked at the scope of the reactions under the optimized conditions. As illustrated in Scheme 2, the reactions showed good function tolerances and the desired triazoles or hydrazono-aldehydes products were obtained as the major products when using the proper copper ligand.

Scheme 2. Scope of the reactions. Reactions were carried out at 0.1 M with 0.2 equiv. of copper and ligand, 1.5 equiv. of mesoionic, 1 equiv. of triethanolamine (TEA) and 1 equiv. of sodium ascorbate (Na. Asc.). % values correspond to isolated yields of the major product. C2/C3 ratios were determined by NMR on the crude reaction mixtures.

In general, the use of ligand A allowed the formation of the desired triazole with excellent selectivity. The presence of substituents on the aromatic moiety of the mesoionic did not affect reactivity. On the other hand, the presence of ligand E and an oxygen or nitrogen atom in propargylic position highly favored the formation of the corresponding aldehyde C3, suggesting a possible internal coordination with the copper center. In addition, the peculiar structures of C2-14

and C3-8 were unambiguously confirmed by X-ray crystallography. Both reactions proceeded well with multi-functionalized substrates such as sugars (C2-16, C3-5 and C3-6) and peptides (C2-15 and C3-2), derivatization of the nonsteroidal anti-inflammatory drug indomethacin was also effective (C3-7). However, the reactions showed also some limitations in term of alkyne substrate scope: disubstituted alkynes were found inactive and ynamides, hindered or sulfur containing alkynes were poor substrates for the reaction (Figures S11-12). With the exception of these types of alkynes, the reaction was found quite effective on a large panel of substrates. It is worth noting that the development of practical and efficient methods for both N-2-substitued-1,2,3-triazoles C2 [7] and aldehydes derivatives C3 [8] received only limited attention. Compared to these known methodologies, the described reaction presents milder conditions and better functional group tolerance therefore representing an interesting alternative method to prepare these products known for their photo-physical and biological properties. [9] Interestingly, we then found that aza-iminosydnones are not reactive toward activated or strained alkynes: no reaction took place when mixing aza-iminosydnones with the cyclooctyne bicyclo-[6.1.0]-nonyne (BCN) or with dimethylacetylene dicarboxylate (DMAD) even at elevated temperatures. We therefore designed and synthesized the bifunctional compound 25 bearing azide and aza-iminosydnone moieties (Scheme 3). Reaction of 25 with BCN was very clean and afforded quantitatively the corresponding triazole without affecting the mesoionic structure demonstrating the perfect orthogonality of the Cucatalyzed aza-iminosydnone/alkyne reaction towards the strained-promoted azide/alkyne cycloaddition reaction (SPAAC). [START_REF] For Reviews On | From Mechanism to Mouse: A Tale of Two Bioorthogonal Reactions[END_REF] After this SPAAC step, the product was successfully converted to either bis-triazole C2-17 using the Cu-Ligand A system or to the aldehyde product using the Cu-Ligand E system which was subsequently derivatised by oxime ligation to afford C3-10. Although the obtained yield was moderate (25% for 3 steps), this experiment showed the possibility to use the Cu-catalyzed azaiminosydnone/alkyne reaction for triple ligation reactions.

To investigate the mechanism of the reaction we performed a series of experiments using isotopically enriched substrates (see supporting information for their synthesis). As shown in Scheme 4a, the use of 15 N-enriched aza-iminosydnones and 13 C-enriched heptyn-1-ol proved that the copper-catalyzed reactions are completely regioselective. In all cases, only one single labeled product was obtained demonstrating that a C-N bond is formed between the terminal sp-carbon of the alkyne and the nitrogen atom in position 4 of the mesoionic, the second formed C-N bond involving the nitrogen in position 2. The results indicated also that the formation of products C3 involves a loss of nitrogen in position 4 while experiments conducted in presence of D2O or H2 18 O suggest hydrolysis of an intermediate to form products C3 (Scheme 4a). Based on these results and on established mechanisms involving copper(I) acetylide species, [START_REF] Fokin | Enhanced Reactivity of Dinuclear Copper(I) Acetylides in Dipolar Cycloadditions[END_REF] we postulated a Reactions were carried out at 0.1 M with 0.2 equiv. of copper and ligand, 1 equiv. of TEA and 1 equiv. of Na. Asc.; IE = isotopic enrichment; b) Proposed mechanism for the Cu-catalyzed azaiminosydone-alkyne reactions.

In summary, we described in this paper the first example of a Cu-catalyzed reaction allowing both ligation of two substrates and release of a fragment molecule. The reaction involves azaiminosydnones, a family of mesoionic compounds rarely described in literature, [START_REF] Finnegan | L. 1-(Alkylamino)-guanidines[END_REF] which generate 1,2,3-triazoles or 2-hydrazineylidene-propanal derivatives depending on the Cu-ligand and the alkyne used, together with an isocyanate release product. The reaction is wide in scope, uses mild conditions and shows very good function tolerance. Besides its synthetic interest, the excellent orthogonality of the reaction with the SPAAC reaction may also find nice applications in the field of ligation reactions. Mesoionic ring systems represent a fascinating and still under-exploited collection of putative 1,3-dipoles useful for cycloaddition chemistry. This study showed how the exploration of this chemical space using high-throughput screening conducted to interesting discoveries.

Figure 1 .

 1 Figure 1. Cu-catalyzed alkyne-mesoionic reactions, a) Cu-catalyzed sydnone-alkyne reaction;

Figure 2 .

 2 Figure 2. Parallel reactions were carried out at 25 °C in 40 µL total volume of DMSO : H2O (60 :

Scheme 3 .

 3 Scheme 3. Application of the reaction to double and triple ligations. *isolated yield after

  Scheme 4. Mechanistic investigations. a) Experiments with isotopically labelled substrates.

ACKNOWLEDGMENT

The authors thank Elodie Marcon and David-Alexandre Buisson for excellent analytical support and Dr. Philippe Dauban (CNRS, ICSN) for helpful discussions.

Funding Sources

This work was supported by the French Research National Agency (ANR-14-CE06-0004).

Notes

The authors declare no competing financial interest.

AUTHOR INFORMATION

Corresponding Author E-mail: frederic.taran@cea.fr Author Contributions ‡These authors contributed equally.

SUPPORTING INFORMATION

Screening data, optimization data, additional experimental data on substrate scope, synthetic procedures and analytical data of reactants and products.