Développement durable et rapports Nord-Sud dans un modèle à générations imbriquées : Interroger le futur pour éclairer le présent

Nous présentons un modèle « prospectif » avec deux économies. Le Nord a stabilisé son stock de gaz à effet de serre, alors que le Sud continue d'émettre des polluants sans moyen de lutter contre. Ces externalités ont un impact sur la production du Sud et sont source de désutilité au Nord. On montre alors que le Nord est conduit à les internaliser en investissant dans le patrimoine écologique du Sud. Ceci lui permet de converger vers un état stationnaire sur un sentier de croissance équilibrée le long duquel on vérifie un critère de soutenabilité, alors que ces « investissements verts » s'avèrent insuffisants pour que le Sud connaisse une telle issue.Développement durable, Rapports Nord-Sud, Générations imbriquées

Pollution as a source of endogenous fluctuations and periodic welfare inequality in OLG economies.

This article examines the conditions under which endogenous fluctuations and periodic welfare inequality can emerge in OLG economies having an environmental dimension.Endogenous fluctuations; Environmental quality; Intergenerational equity

Aléa moral et politiques d'audit optimales dans le cadre de la pollution d'origine agricole de l'eau.

Compte tenu de l'information incomplète dont on dispose quant aux pratiques culturales des exploitants agricoles, il n'est pas toujours optimal de baser les politiques de lutte contre la pollution d'origine agricole exclusivement sur un mode de taxation. Symétriquement, un système entièrement assis sur des subventions "vertes" se justifie mal dans le cadre de certaines cultures déjà largement subventionnées au niveau européen. Dans cet article, nous montrons qu'une alternative possible consiste à établir un contrat entre l'agriculteur et les instances environnementales qui combine un système de vérification aléatoire des pratiques culturales avec une menace crédible de pénalisation si l'effort environnemental n'est pas suffisant compte tenu des conditions initiales ou, dans le cas contraire, une promesse crédible de versement de subvention. Ce système d'audit, dont l'originalité tient à son caractère aléatoire, doit reposer sur des indicateurs fiables des caractéristiques hydrologiques, pédologiques et agronomiques des parcelles étudiées. Les différentes études effectuées sur la plaine d'Alsace par des équipes pluridisciplinaires montrent qu'il est possible d'établir des cartographies fiables de vulnérabilité de la nappe et des indicateurs permettant une bonne mesure de la pollution due aux intrants (engrais, pesticides, ...).Pollution agricole, nitrates, aléa moral, incitations, audit, contrat optimal.

Critique of network management systems and their practicality

Networks have become an integral part of the computing landscape, forming a global interconnection of a staggering number of heterogeneous systems and services. Current research focuses on policy based management and autonomous systems and involves the utilisation of very different languages and technologies in concert. This paper examines four current proposals for autonomous network management and analyses them using architectural modelling, against a measure of practicality, as expressed by scalability, reliability and maintainability. © 2010 IEEE

Advances and Challenges in Islet Transplantation: Islet Procurement Rates and Lessons Learned from Suboptimal Islet Transplantation

The initial step in successful islet transplantation is procurement of healthy donor islets. Given the limited number of donor pancreata selected for islet isolation and that islets from multiple donors are typically required to obtain insulin independence, it is critical to improve pancreas procurement rates and yield of islets for transplantation. Islets are delicate microorgans that are susceptible to apoptosis, hypoxia, and ischemia during isolation, culture, and the peritransplant period. Once the islets are engrafted, both prompt revascularization and protection from beta-cell death and graft rejection are key to secure long-term survival and function. To facilitate the engraftment of more robust islets suitable for combating the challenging isolation period and proinflammatory transplantation milieu, numerous approaches have been employed to prevent beta-cell dysfunction and death including immune modulation, prevention of apoptosis and hypoxia, as well as stimulation of growth factors, angiogenesis, and reinnervation. In addition to briefly discussing islet isolation procedures, procurement rates, and islet transplantation, the relevant literature pertaining to successful suboptimal islet transplantation is reviewed to provide insight into potential approaches to balance the limited supply of available donor islets

Time-resolved studies define the nature of toxic IAPP intermediates, providing insight for anti-amyloidosis therapeutics

Islet amyloidosis by IAPP contributes to pancreatic β-cell death in diabetes, but the nature of toxic IAPP species remains elusive. Using concurrent time-resolved biophysical and biological measurements, we define the toxic species produced during IAPP amyloid formation and link their properties to induction of rat INS-1 β-cell and murine islet toxicity. These globally flexible, low order oligomers upregulate pro-inflammatory markers and induce reactive oxygen species. They do not bind 1-anilnonaphthalene-8-sulphonic acid and lack extensive β-sheet structure. Aromatic interactions modulate, but are not required for toxicity. Not all IAPP oligomers are toxic; toxicity depends on their partially structured conformational states. Some anti-amyloid agents paradoxically prolong cytotoxicity by prolonging the lifetime of the toxic species. The data highlight the distinguishing properties of toxic IAPP oligomers and the common features that they share with toxic species reported for other amyloidogenic polypeptides, providing information for rational drug design to treat IAPP induced β-cell death

Pollution diffuse de l’eau en milieu rural et marché des permis d’émission : les enseignements de l’expérience américaine

Cet article s’interroge sur l’emploi de marchés de permis dans la lutte contre la pollution diffuse de l’eau en milieu rural. Après avoir expliqué les problèmes particuliers posés par cette pollution, le fonctionnement des marchés de permis appliqués à ce type de pollutions est exposé, avant de livrer la synthèse de deux expériences mises en œuvre aux Etats-Unis. Une revue des conditions qui peuvent favoriser le succès d’un tel mode de régulation permet de conclure, étant entendu que les cas de réussite restent à ce jour minoritaires.This article deals with marketable permits applied to water protection from non-point source pollution (NPS) in rural areas. We explain the challenges that this pollution represents for public authorities before presenting the general principle of maketable permits applied to NPS pollution. We then expose two experiences encountered in the United States and we conclude by reviewing the main conditions to raise the probability of success of such public regulation, still in minority

Dynamic-threshold-based pre-relaying for enhanced key allocation in quantum-secured networks

Quantum key distribution (QKD) is experiencing a rapid increase of interest due to its security advantages in the face of quantum computers. However, typical QKD deployments are point-to-point and limited in terms of distance, which significantly restricts their utilization for end-user applications. To overcome these restrictions, trusted relays are adopted as intermediate nodes to allow the transition to QKD networks (QKDNs), where one of the hallmarks is the key management system. In this work, we investigate different key allocation strategies as a method to enhance the performance of key management systems in QKDN from the perspective of key allocation success rate and key delivery delay. We first describe an upgrade model from classical to QKDN at three distinct network layers—quantum, key management, and service. Then, we propose a novel, to our knowledge, key allocation strategy leveraging the benefits of key storage and relaying as a solution to improve the QKDN performance. To achieve this, our method makes use of end-to-end virtual quantum key pools (VQKPs) implemented between non-adjacent nodes requesting key material. We introduce static and dynamic upper and lower threshold limits at the VQKP level, with the dynamic thresholds adapted according to application demand, to control the key distribution in the network and fill the pools ahead of end-user requests. We demonstrate through simulations that the introduction of thresholds achieves performance enhancement and explain the trade-off between the key allocation success rate and key delivery delay evaluation metrics in comparison with different on-demand key allocation strategies.</p

Resource Allocation Strategies in Quantum Key Distribution Networks

Quantum key distribution (QKD) is a symmetric key exchange mechanism designed to enhance the security of current communication systems. Although QKD provides unconditional security, it also comes with deployment challenges. One challenge is the distance limitation between the transmitter and receiver, which restricts the large-scale adoption of QKD. To overcome this, trusted relays are used as intermediate nodes, allowing QKD to evolve from distance-limited point-to-point connections to unlimited QKD networks (QKDN). With an increasing deployment of QKD and a growing number of applications requesting keys, quality of service (QoS) constraints must be set for efficient key resource management to alleviate the risk of rejecting application requests. In this work, we integrate key delivery delay and maximum requested key size as QoS constraints in a novel key allocation algorithm built on three QKDN layers - quantum, key management and service. Moreover, we design key relaying using quantum key pools and virtual quantum key pools as storage mechanisms. We use static and dynamic weights for relay path computation and evaluate their impact on the proposed key allocation strategies with QoS constraints and find that static weights show a good overall performance for QKDN, while performance with dynamic weights varies based on historical key consumption data.</p