Structural and mechanistic insights into s-block bimetallic catalysis : sodium magnesiate-catalyzed guanylation of amines

To advance the catalytic applications of s-block mixed-metal complexes, sodium magnesiate [NaMg(CH2SiMe3)3] (1) is reported as an efficient precatalyst for the guanylation of a variety of anilines and secondary amines with carbodiimides. First examples of hydrophosphination of carbodiimides by using a Mg catalyst are also described. The catalytic ability of the mixed-metal system is much greater than that of its homometallic components [NaCH2SiMe3 ] and [Mg(CH2SiMe3)2]. Stoichiometric studies suggest that magnesiate amido and guanidinate complexes are intermediates in these catalytic routes. Reactivity and kinetic studies imply that these guanylation reactions occur via (tris)amide intermediates that react with carbodiiimides in insertion steps. The rate law for the guanylation of N,N'-diisopropylcarbodiimide with 4-tert-butylaniline catalyzed by 1 is first order with respect to [amine], [carbodiimide], and [catalyst], and the reaction shows a large kinetic isotopic effect, which is consistent with an amine-assisted rate-determining carbodiimide insertion transition state. Studies to assess the effect of sodium in these transformations denote a secondary role with little involvement in the catalytic cycle

Community change within a Caribbean coral reef Marine Protected Area following two decades of local management

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e54069, doi:10.1371/journal.pone.0054069.Structural change in both the habitat and reef-associated fish assemblages within spatially managed coral reefs can provide key insights into the benefits and limitations of Marine Protected Areas (MPAs). While MPA zoning effects on particular target species are well reported, we are yet to fully resolve the various affects of spatial management on the structure of coral reef communities over decadal time scales. Here, we document mixed affects of MPA zoning on fish density, biomass and species richness over the 21 years since establishment of the Saba Marine Park (SMP). Although we found significantly greater biomass and species richness of reef-associated fishes within shallow habitats (5 meters depth) closed to fishing, this did not hold for deeper (15 m) habitats, and there was a widespread decline (38% decrease) in live hard coral cover and a 68% loss of carnivorous reef fishes across all zones of the SMP from the 1990s to 2008. Given the importance of live coral for the maintenance and replenishment of reef fishes, and the likely role of chronic disturbance in driving coral decline across the region, we explore how local spatial management can help protect coral reef ecosystems within the context of large-scale environmental pressures and disturbances outside the purview of local MPA management.Funding was provided by the Saba Conservation Foundation ((SCF), King Abdullah University of Science and Technology, The Australian National University and Australian Research Council

Redox cycling metals: Pedaling their roles in metabolism and their use in the development of novel therapeutics

Essential metals, such as iron and copper, play a critical role in a plethora of cellular processes including cell growth and proliferation. However, concomitantly, excess of these metal ions in the body can have deleterious effects due to their ability to generate cytotoxic reactive oxygen species (ROS). Thus, the human body has evolved a very well-orchestrated metabolic system that keeps tight control on the levels of these metal ions. Considering their very high proliferation rate, cancer cells require a high abundance of these metals compared to their normal counterparts. Interestingly, new anti-cancer agents that take advantage of the sensitivity of cancer cells to metal sequestration and their susceptibility to ROS have been developed. These ligands can avidly bind metal ions to form redox active metal complexes, which lead to generation of cytotoxic ROS. Furthermore, these agents also act as potent metastasis suppressors due to their ability to up-regulate the metastasis suppressor gene, N-myc downstream regulated gene 1. This review discusses the importance of iron and copper in the metabolism and progression of cancer, how they can be exploited to target tumors and the clinical translation of novel anti-cancer chemotherapeutics

Planck 2015 results: XXV. Diffuse low-frequency Galactic foregrounds

We discuss the Galactic foreground emission between 20 and 100 GHz based on observations by Planck and WMAP. The total intensity in this part of the spectrum is dominated by free-free and spinning dust emission, whereas the polarized intensity is dominated by synchrotron emission. The Commander component-separation tool has been used to separate the various astrophysical processes in total intensity. Comparison with radio recombination line templates verifies the recovery of the free-free emission along the Galactic plane. Comparison of the high-latitude H\u3b1 emission with our free-free map shows residuals that correlate with dust optical depth, consistent with a fraction (\ue2\u2030 30%) of H\u3b1 having been scattered by high-latitude dust. We highlight a number of diffuse spinning dust morphological features at high latitude. There is substantial spatial variation in the spinning dust spectrum, with the emission peak (in I\u3bd) ranging from below 20 GHz to more than 50 GHz. There is a strong tendency for the spinning dust component near many prominent H ii regions to have a higher peak frequency, suggesting that this increase in peak frequency is associated with dust in the photo-dissociation regions around the nebulae. The emissivity of spinning dust in these diffuse regions is of the same order as previous detections in the literature. Over the entire sky, the Commander solution finds more anomalous microwave emission (AME) than the WMAP component maps, at the expense of synchrotron and free-free emission. This can be explained by the difficulty in separating multiple broadband components with a limited number of frequency maps. Future surveys, particularly at 5-20 GHz, will greatly improve the separation by constraining the synchrotron spectrum. We combine Planck and WMAP data to make the highest signal-to-noise ratio maps yet of the intensity of the all-sky polarized synchrotron emission at frequencies above a few GHz. Most of the high-latitude polarized emission is associated with distinct large-scale loops and spurs, and we re-discuss their structure. We argue that nearly all the emission at 40deg > l >-90deg is part of the Loop I structure, and show that the emission extends much further in to the southern Galactic hemisphere than previously recognised, giving Loop I an ovoid rather than circular outline. However, it does not continue as far as the "Fermi bubble/microwave haze", making it less probable that these are part of the same structure. We identify a number of new faint features in the polarized sky, including a dearth of polarized synchrotron emission directly correlated with a narrow, roughly 20deg long filament seen in H\u3b1 at high Galactic latitude. Finally, we look for evidence of polarized AME, however many AME regions are significantly contaminated by polarized synchrotron emission, and we find a 2\u3c3 upper limit of 1.6% in the Perseus region

Ecosystem-based management of coral reefs under climate change

Coral reefs provide food and livelihoods for hundreds of millions of people as well as harbour some of the highest regions of biodiversity in the ocean. However, overexploitation, land-use change and other local anthropogenic threats to coral reefs have left many degraded. Additionally, coral reefs are faced with the dual emerging threats of ocean warming and acidification due to rising CO2 emissions, with dire predictions that they will not survive the century. This review evaluates the impacts of climate change on coral reef organisms, communities and ecosystems, focusing on the interactions between climate change factors and local anthropogenic stressors. It then explores the shortcomings of existing management and the move towards ecosystembased management and resilience thinking, before highlighting the need for climate change-ready marine protected areas (MPAs), reduction in local anthropogenic stressors, novel approaches such as human-assisted evolution and the importance of sustainable socialecological systems. It concludes that designation of climate changeready MPAs, integrated with other management strategies involving stakeholders and participation at multiple scales such as marine spatial planning, will be required to maximise coral reef resilience under climate change. However, efforts to reduce carbon emissions are critical if the long-term efficacy of local management actions is to be maintained and coral reefs are to survive

Un nouvel enjeu international : le Baloutchistan

A new international stake: Baluchistan? by Selig S. Harrison The Soviet occupation of Afghanistan revealed the strategic importance of Baluchistan to the Western world: if the coastal zone of the Baluch national territory were to fall into Soviet hands, the latter would control the sea of Oman and the Straits of Hormuz, which would radically alter the military balance in the region. Pakistani and Iranian leaders, while not ruling out the possibility of direct Soviet aggression in the region, are more concerned that Moscow might help the Baluch nationalist movement by technical and military support in order to obtain the use of Baluch ports for military purposes. Baluch nationalist movement leaders, who are coming up against the traditional hostility of the Punjabi and the uncompromising attitude of Zia in Pakistan, as well as being rejected by the new Iranian Constitution, are exploring the prospects of obtaining foreign help (whether from the Soviet Union, China, the United States, India or the Arab world). Meanwhile they are encouraging nationalist groups in both Iran and Pakistan to build up their organizational strength in preparation for a possible renewal of hostilities. This nationalist movement which has acquired an independent strength, deeply implanted by a tempestuous struggle for survival stretching back for more than 2000 years of history, has nevertheless given rise to a cautious attitude on the part of Moscow: Soviet strategists recognise that although there is a recrudescence of Baluch nationalism, it is not yet ripe. The basic reason for Soviet caution lies in Moscow's overall assessment of short-term prospects in Iran and Pakistan.Un nouvel enjeu international : le Balouchistan ? par Selig S. Harrison L'occupation soviétique de l'Afghanistan a révélé aux Occidentaux l'importance stratégique du Balouchistan : si la zone côtière du territoire national baloutche tombait sous l'emprise des Soviétiques, ceux-ci pourraient contrôler la mer d'Oman et le détroit d'Ormuz, ce qui modifierait profondément l'équilibre militaire de la région. Les dirigeants pakistanais et iraniens, sans exclure l'hypothèse d'une intervention directe de Moscou dans la région, redoutent un éventuel soutien technique et militaire des Soviétiques au mouvement nationaliste baloutche dans le but d'obtenir l'utilisation des ports baloutches à des fins militaires. Les dirigeants du mouvement national baloutche, se heurtant à l'hostilité traditionnelle des Panjabis et l'intransigeance de Zia au Pakistan et rejetés par la nouvelle Constitution iranienne, explorent les perspectives possibles d'aide étrangère (que ce soit celle de l'Union soviétique, de la Chine, des Etats-Unis, de l'Inde ou du monde arabe...) et encouragent les groupes nationalistes en Iran et au Pakistan à s'organiser en vue d'une éventuelle reprise de l'insurrection. Ce mouvement national, qui a acquis une force indépendante au cours d'une histoire sanglante jalonnée de luttes pour la survie pendant plus de 2000 ans, suscite néanmoins une attitude de réserve de la part de Moscou : les stratèges soviétiques conviennent que le nationalisme baloutche connaît un regain mais ne le jugent pas encore mûr... D'autre part, leur prudence est fondée sur une appréciation globale des perspectives à court terme en Iran et au Pakistan.Harrison Selig S. Un nouvel enjeu international : le Baloutchistan. In: Politique étrangère, n°4 - 1980 - 45ᵉannée. pp. 891-903

L'Afghanistan : une solution politique est-elle possible ?

Afghanistan : is there a political solution ?, by Selig S. Harrison Politically as will as mïlitarïly, the stalemate in Afghanistan deepens. On one side, the Soviet-subsidized communist regime is slowly but steadily building a stable Afghan city-state in Kabul and its environs. On the other, scattered groups of dedicated résistance fighters, while better coordinated militarily than in the past, continue to lack the political infrastructure that would be necessary to follow up there military successes. If the present escalation of the Afghan conflict should continue, Moscow woul be likely to intensify its efforts to make Afghanistan a South Asian Mongolia governed by a monolithic communist elite. The security interests of non-communist countries woul be better served by a negotiated seulement based on acceptance of a Finland-style security relationship between the Soviet Union and a less monolithic client regime in Kabul.L'Afghanistan : une solution politique est-elle possible ?, par Selig S. Harrison Tant sur le plan politique que militaire, l'Afghanistan s'enferre chaque jour un peu plus dans une terrible impasse. D'une part, le régime communiste, soutenu par les Soviétiques, édifie lentement mais sûrement une ville-Etat afghane solide à Kaboul et dans ses environs. D'autre part, même s'ils sont mieux coordonnés militairement qu'auparavant, les groupes dispersés de combattants de la résistance ne disposent toujours pas de l'infrastructure politique nécessaire pour asseoir leurs victoires militaires. Si l'actuelle escalade du conflit afghan devait se poursuivre, Moscou intensifierait probablement ses efforts pour faire de l'Afghanistan une Mongolie de l'Asie du Sud, gouvernée par une élite communiste monolithique. La sécurité des pays non communistes serait mieux servie par un accord négocié sur les relations à établir, peut-être sur le modèle finlandais, entre l'Union soviétique et un Etat « satellite » moins monolithique à Kaboul.Harrison Selig S. L'Afghanistan : une solution politique est-elle possible ?. In: Politique étrangère, n°3 - 1984 - 49ᵉannée. pp. 613-622

The Widening Gulf : Asian Nationalism and American Policy

xi.404 hal.;24 c