990 research outputs found
Using coherent dynamics to quantify spin-coupling within triplet-exciton/polaron complexes in organic diodes
Quantifying the spin-spin interactions which influence electronic transitions
in organic semiconductors is crucial for understanding their
magneto-optoelectronic properties. By combining a theoretical model for three
spin interactions in the coherent regime with pulsed electrically detected
magnetic resonance experiments on MEH-PPV diodes, we quantify the spin-coupling
within complexes comprising three spin-half particles. We determine that these
particles form triplet-exciton:polaron pairs, where the polaron:exciton
exchange is over 5 orders of magnitude weaker (less than 170 MHz) than that
within the exciton. This approach providing a direct spectroscopic approach for
distinguishing between coupling regimens, such as strongly bound trions, which
have been proposed to occur in organic devices.Comment: 5 pages, 4 figure
Slow Hopping and Spin Dephasing of Coulombically Bound Polaron Pairs in an Organic Semiconductor at Room Temperature
Polaron pairs are intermediate electronic states that are integral to the optoelectronic conversion process in organic semiconductors. Here, we report on electrically detected spin echoes arising from direct quantum control of polaron pair spins in an organic light-emitting diode at room temperature. This approach reveals phase coherence on a microsecond time scale, and offers a direct way to probe charge recombination and dissociation processes in organic devices, revealing temperature-independent intermolecular carrier hopping on slow time scales. In addition, the long spin phase coherence time at room temperature is of potential interest for developing quantum-enhanced sensors and information processing systems which operate at room temperature
Strengthening Europe's Capability in Biological Ocean Observations
This publication is primarily aimed at stakeholders involved in ocean observing, spanning diverse roles from commissioning,
managing, funding and coordinating, to developing, implementing, or advising on, ocean observation programmes.
Such programmes will have strategic and policy drivers but their main purpose may vary from predominantly researchdriven
scientific purposes to environmental monitoring for providing data and reporting to legally-binding regulations or
directives. The main focus is on European capabilities but set in a global context with the various actors spanning a variety
of geographical scales from national to regional and European. Key stakeholder organizations include environmental or
other agencies; marine research institutions, their researchers and operators; international and regional ocean observing
initiatives and programmes; national, regional and European policy makers and their advisors; national stations for
observations; etc.). It will also be of interest to the wider marine and maritime research and policy community.
The main aim of the publication is to increase the relevance of current (and future) European biological ocean observation
capacity to strengthen global efforts towards our understanding of the ocean and enhance marine biodiversity
conservation, for maintaining a healthy ocean for healthy societies.
This document explains why biological ocean observations are needed to assess progress against national and international
conservation targets, the Sustainable Development Goals (SDGs), the Blue Growth agenda and to contribute to key EU
directives including the Marine Strategy Framework Directive (MSFD). To achieve this, the publication highlights the need
of biological ocean observations to reflect clearly defined hypotheses about potential causes of change, including the
combined impacts of local and global drivers, and to support the management of our impacts on the ocean. Additionally,
it calls for flexible biological ocean observing programmes to capture the relevant drivers operating at multiple spatial
scales, by networking and integration of ongoing monitoring programmes, methodological standardization and
appropriate policies of data integration and dissemination. It then presents key variables, elements and information
products to inform on the status and trends of marine biodiversity
The importance of Southern Ocean frontal systems for the improvement of body condition in southern elephant seals
Funding: Natural Environment Research Council, Grant/Award Numbers: NE/E018289/1, NE/L501852/1 NER/D/S/2002/00426; Scottish Funding Council, Grant/Award Number: HR09011.1. As top predators, it has been suggested that southern elephant seals serve as sentinels of ecosystem status to inform management and conservation.2. This is because southern elephant seals annually undertake two largeâscale foraging migrations for 2â3 and 7â8 months to replenish resources after fasting during breeding and moulting and often rely on dynamic macroscale latitudinal fronts to provide favourable foraging through aggregating prey.3. Yet it is largely unknown whether southern elephant seals respond to changes in frontal systems over the years, whether their foraging success is associated with specific frontal systems shifts, and how flexible southern elephant seals populations are in behaviourally adapting to changes in frontal systems.4. This study examines the relationship between frontal systems and the resource acquisition of 64 southern elephant seals during four postâmoult and three postâbreeding migrations between 2005 and 2010.5. Satelliteârelayâdataâloggers provided in situ measurements concurrent with >27,500 dive profiles to define fronts and interfrontal zones between the Subtropical Frontal Zone and the Southern Boundary of the Antarctic Circumpolar Current. For >430,000 in situ measurements water mass properties could be identified.6. Generally, southern elephant seals associate more frequently with more southerly, higherâlatitude fronts/zones. Body condition improvements related to a given frontal system or water mass vary strongly according to year, season, month and sex.7. The variability in body condition improvements is higher in some frontal systems than in others, probably owing to shifts in the Subantarctic and Polar Front.8. During a migration, some individuals stay within â€3 frontal systems, whilst others change between several frontal systems and primarily improve their body condition in upper ocean waters.9. Southern elephant seals do not trace particular water masses across frontal systems, and both surface and deep foraging strategies are used.10. This suggests that southern elephant seals do not target particular water masses but adjust foraging and movement strategies to exploit boundary areas at which mixing and prey aggregation is high.11. The large behavioural plasticity towards the spatioâtemporal variability in the different oceanographic regions they encounter could indicate resilience against environmental changes.PostprintPeer reviewe
Non-Bloch-Siegert-type power-induced shift of two-photon electron paramagnetic resonances of charge-carrier spin states in an OLED
We present Floquet theory-based predictions and electrically detected
magnetic resonance (EDMR) experiments scrutinizing the nature of two-photon
magnetic resonance shifts of charge-carrier spin states in the perdeuterated
-conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene
vinylene] (d-MEH-PPV) under strong magnetic resonant drive conditions
(radiation amplitude ~ Zeeman field ). Numerical calculations show
that the two-photon resonance shift with power is nearly drive-helicity
independent. This is in contrast to the one-photon Bloch-Siegert shift that
only occurs under non-circularly polarized strong drive conditions. We
therefore treated the Floquet Hamiltonian analytically under arbitrary
amplitudes of the co- and counter-rotating components of the radiation field to
gain insight into the nature of the helicity dependence of multi-photon
resonance shifts. In addition, we tested Floquet-theory predictions
experimentally by comparing one-photon and two-photon charge-carrier spin
resonance shifts observed through room-temperature EDMR experiments on
d-MEH-PPV-based bipolar injection devices [i.e., organic light emitting diode
structures (OLEDs)]. We found that under the experimental conditions of strong,
linearly polarized drive, our observations consistently agree with theory,
irrespective of the magnitude of , and therefore underscore the robustness
of Floquet theory in predicting nonlinear magnetic resonance behaviors.Comment: 22 pages, 5 figure
Early and efficient detection of Mycobacterium tuberculosis in sputum by microscopic observation of broth cultures.
Early, efficient and inexpensive methods for the detection of pulmonary tuberculosis are urgently needed for effective patient management as well as to interrupt transmission. These methods to detect M. tuberculosis in a timely and affordable way are not yet widely available in resource-limited settings. In a developing-country setting, we prospectively evaluated two methods for culturing and detecting M. tuberculosis in sputum. Sputum samples were cultured in liquid assay (micro broth culture) in microplate wells and growth was detected by microscopic observation, or in Löwenstein-Jensen (LJ) solid media where growth was detected by visual inspection for colonies. Sputum samples were collected from 321 tuberculosis (TB) suspects attending Bugando Medical Centre, in Mwanza, Tanzania, and were cultured in parallel. Pulmonary tuberculosis cases were diagnosed using the American Thoracic Society diagnostic standards. There were a total of 200 (62.3%) pulmonary tuberculosis cases. Liquid assay with microscopic detection detected a significantly higher proportion of cases than LJ solid culture: 89.0% (95% confidence interval [CI], 84.7% to 93.3%) versus 77.0% (95% CI, 71.2% to 82.8%) (pâ=â0.0007). The median turn around time to diagnose tuberculosis was significantly shorter for micro broth culture than for the LJ solid culture, 9 days (interquartile range [IQR] 7-13), versus 21 days (IQR 14-28) (p<0.0001). The cost for micro broth culture (labor inclusive) in our study was US 11.35 per sample for the LJ solid culture. The liquid assay (micro broth culture) is an early, feasible, and inexpensive method for detection of pulmonary tuberculosis in resource limited settings
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