894 resultados para Bivalent transitions metals


Relevância:

20.00% 20.00%

Publicador:

Resumo:

In the aftermath of the 2011 Arab uprisings in the southern and eastern Mediterranean, the region has reached a turning point in its history, presenting as many opportunities as challenges. The European Union itself is facing challenging conditions following the financial and economic crises that have hit its periphery. This MEDPRO Policy Paper examines and assesses various possible scenarios that could play out in EU-Mediterranean relations over the next two decades and offers recommendations towards long-term sustainable socio-economic development in the region.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Algeria is so far the only country in North Africa not to have experienced sustained mass protests calling for political change. The government in Algiers has by no means remained indifferent to the groundbreaking events in neighbouring countries, but it is responding to this sweeping wave of change at its own pace. This paper argues that, despite its apparent stability, the Algerian polity suffers from underlying currents of instability that risk undermining the long-term sustainability of the state. It identifies the failure of the country’s political and economic transitions and its implications as the most serious challenge confronting the Algerian state today. Unless a) the process of democratic transition that was initiated in 1989 is refined and put back on track, leading to the advent and consolidation of the rule of law, popular enfranchisement and total civilian control of the military; and b) the efforts to diversify the economy away from hydrocarbons are intensified and made more coherent, Algeria will remain susceptible to future instability. This is all the more pertinent given that the country is heading towards a crossroads where the issue of generational transition will also become imperative for the current leadership to deal with.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Policies and politics are an integral part of socio-technical transitions but have not received much attention in the transitions literature so far. Drawing on the advocacy coalition framework, our paper addresses this gap with a study on actors and coalitions in Swiss energy policy. Our results show that advocacy coalitions in Switzerland have largely remained stable despite the Fukushima shock. However, heterogeneity of beliefs has increased and in 2013, even a majority of actors expressed their support for the energy transition – an indication that major policy change might be ahead. It seems that in socio-technical transitions, changes in the policy issue and in the actor base also work toward policy change, next to changes in core beliefs. We make suggestions how the advocacy coalition framework can inform analysis and theory building in transition studies. We also present first ideas about the interplay of socio-technical systems and policy systems.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We determined the sedimentary concentrations of phosphorus (P), barium (Ba), manganese (Mn), titanium (Ti), aluminum (Al), and uranium (U) for sediment samples from the southeast Pacific Nazca Ridge, Ocean Drilling Program Site 1237. This unique record extends to 31 Ma over 360 meters composite depth (mcd), recording depositional history as the site progressed eastward over its paleohistory. We sampled with a temporal resolution of ~0.2 m.y. throughout the sequence, equivalent to an average spacing of 1.63 m/sample. Concentrations of sequentially extracted components of P (oxide-associated, authigenic, organic, and detrital) increase toward the modern. Al/Ti ratios indicate that the background detrital source material is consistent with upper continental crust. U enrichment factors (U EFs) generally exceed crustal values and indicate slightly reducing environments. However, authigenic U precipitation can also be influenced by the organic carbon rain rate and may not be solely an indicator of redox conditions. Dramatic changes in Mn EFs at ~162 mcd, from values between 12 and 93 to values <12 after this depth, and a sharp color contact boundary lead us to believe that a paleoredox boundary from an oxygenated to a more reducing depositional environment occurred near this depth. Estimates of biogenic barite concentrations from a total sediment digestion technique (Ba excess) are greater than those from a barite extraction (Ba barite) for selected samples across the entire depth range. Applying a range of Ba/Ti ratios from different source materials to correct for detrital inputs does not change the lack of agreement with Ba barite concentrations. Reactive P (P reactive) concentrations (the sum of oxide-associated, authigenic, and organic P concentrations) increase toward the modern with values typically <12 µmol P/g from the base of our record through ~100 mcd, with a gradual increase to concentrations >15 µmol P/g. Ba excess follows the same general trends as Preactive, with concentrations <14 µmol Ba/g in the lower portion of the record to values >15 µmol Ba/g. Accumulation rate records of these proxies will be needed to infer paleoproductivity. P reactive/Ba excess ratios, an indicator of the relative burial of the nutrient P to organic carbon export, exhibit higher values, similar to modern, from the base of our record through ~180 mcd. The remainder of the record exhibits values lower than modern, indicating that organic carbon export to the sediments was higher relative to nutrient burial.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

"July 1960 [OTI Issuance Date]."

Relevância:

20.00% 20.00%

Publicador:

Resumo:

"August 1979."

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Mode of access: Internet.