Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling

Carbon-based semiconductors such as conjugated organic polymers are of potential use in the development of spintronic devices and spin-based information processing. In particular, these materials offer a low spin-orbit coupling strength due to their relatively light constituent chemical elements, which should, in principle, favour long spin diffusion lengths. However, organic polymers are relatively disordered materials and typically have a carrier mobility that is orders of magnitude lower than crystalline inorganic materials. As a result, small spin diffusion lengths of around 50 nm have typically been measured using vertical organic spin valves. Here, we report measuring spin diffusion lengths in doped conjugated polymers using a lateral spin transport device architecture, which is based on spin pumping injection and inverse spin Hall detection. The approach suggests that long spin diffusion lengths of more than 1 mu m and fast spin transit times of around 10 ns are possible in conjugated polymer systems when they have a sufficiently high spin density (around 10(20)cm(-3)). We explain these results in terms of an exchangebased spin diffusion regime in which the exchange interactions decouple spin and charge transport.N

From the soil to the seeds: the long journey of nitrate in plants

Under temperate climates and in cultivated soils, nitrate is the most important source of nitrogen (N) available for crops and, before its reduction and assimilation into amino acids, must enter the root cells and then move in the whole plant. The aim of this review is to provide an overall picture of the numerous membrane proteins that achieve these processes by being localized in different compartments and in different tissues. Nitrate transporters (NRT) from the NRT1 and NRT2 families ensure the capacity of root cells to take up nitrate, through high- and low-affinity systems (HATS and LATS) depending on nitrate concentrations in the soil solution. Other members of the NRT1 family are involved subsequently in loading and unloading of nitrate to and from the xylem vessels, allowing its distribution to aerial organs or its remobilization from old leaves. Once in the cell, nitrate can be stored in the vacuole by passing through the tonoplast, a step that involves chloride channels (CLC) or a NRT2 member. Finally, with the exception of one NRT1 member, the transport of nitrite towards the chloroplast is still largely unknown. All these fluxes are controlled by key factors, the 'major tour operators' like the internal nutritional status of the plant but also by external abiotic factors.Julie Dechorgnat, Chi Tam Nguyen, Patrick Armengaud, Mathieu Jossier, Eugene Diatloff, Sophie Filleur, and Françoise Daniel-Vedel

Nitrate transporters in plants : structure, function and regulation.

Physiological studies have established that plants acquire their NO−3 from the soil through the combined activities of a set of high- and low-affinity NO−3 transport systems, with the influx of NO−3 being driven by the H+ gradient across the plasma membrane. Some of these NO−3 transport systems are constitutively expressed, while others are NO−3-inducible and subject to negative feedback regulation by the products of NO−3 assimilation. Here we review recent progress in the characterisation of the two families of NO−3 transporters that have so far been identified in plants, their structure and their regulation, and consider the evidence for their roles in NO−3 acquisition. We also discuss what is currently known about the genetic basis of NO−3 induction and feedback repression of the NO−3 transport and assimilatory pathway in higher plants