106 research outputs found
Interaction-induced adiabatic non-linear transport
We calculate the time-dependent non-linear transport current through an
interacting quantum dot in the single-electron tunneling regime (SET). We show
that an additional dc current is generated by the electron-electron interaction
by adiabatic out-of-phase modulation of the gate and bias voltage. This current
can arise only when two SET resonance conditions are simultaneously satisfied.
We propose an adiabatic transport spectroscopy where lock-in measurement of a
"time-averaged stability diagram" probes interactions, tunnel asymmetries and
changes in the ground state spin-degeneracy.Comment: 4 pages, 2 figure
Flow sorting in aquatic ecology
Flow sorting can be a very helpful tool in revealing phytoplankton and bacterial community structure and elaborating specific physiological parameters of isolated species. Droplet sorting has been the most common technique. Despite the high optical and hydro-dynamic stress for the cells to be sorted, many species grow in culture subsequent to sorting. To date, flow sorting has been applied to post-incubation separation in natural water samples to account for group-specific physiological parameters (radiotracer-uptake rates), to the production of clonal or non-clonal cultures from mixtures, to the isolaton of cell groups from natural assemblages for molecular analyses, and for taxonomic identification of sorted cells by microscopy. The application of cell sorting from natural water samples from the Wadden Sea, including different cryptophytes, cyanobacteria and diatoms, is shown, as well as the establishment of laboratory cultures from field samples. The optional use of a red laser to account for phycocyanine-rich cells is also discussed.No disponibl
Dealing with Diversity in English Children's Books in the Heterogeneous EFL Classroom
The use of children’s literature in language teaching is very common. However, in view of heterogeneous English as a foreign language (EFL) classrooms with learners of different interests, abilities, preferences, competences, identities, beliefs, etc., approaches to dealing with literature need to be supplemented by carefully selected scaffolds to cater to individual learner needs. Yet, it is not just the teaching methods that need to be (re)considered with regards to teaching a heterogeneous learner group, but also the topics that are covered in class should be carefully selected. Children’s books offer a wide range of topics that are commonly dealt with in the EFL classroom with younger learners. Some books, classic as well as recent ones, also depict different aspects of diversity. Such pieces of literature offer the potential to discuss diversity with learners in the EFL classroom and can serve as a basis for negotiations of diversity at the content-level. Therefore, this article deals with a two-fold question on aspects of diversity: (1) How do selected English children’s books represent or mirror diversity? (2) Can such books be used successfully in the heterogeneous EFL classroom
Transport signature of pseudo-Jahn-Teller dynamics in a single-molecule transistor
We calculate the electronic transport through a molecular dimer, in which an
excess electron is delocalized over equivalent monomers, which can be locally
distorted. In this system the Born-Oppenheimer approximation breaks down
resulting in quantum entanglement of the mechanical and electronic motion. We
show that pseudo Jahn-Teller (pJT) dynamics of the molecule gives rise to
conductance peaks that indicate this violation. Their magnitude, sign and
position sharply depend on the electro-mechanical properties of the molecule,
which can be varied in recently developed three-terminal junctions with
mechanical control. The predicted effect depends crucially on the degree of
intramolecular delocalization of the excess electron, a parameter which is also
of fundamental importance in physical chemistry.Comment: 6 pages, 3 figure
Phaeocystis blooming enhanced by copepod predation on protozoa: evidence from incubation experiments
Laboratory experiments were carried out to investigate the effect of protozoan, copepod and combined grazing on Phaeocystis biomass. Phaeocystis cf. globosa single cells were offered to 3 different protozoan species, to the calanoid copepod Temora longicornis, as well as to mixtures of both grazer types. The heterotrophic dinoflagellate Oxyrrhis marina and the oligotrich ciliate Strombidinopsis acuminatum ingested Phaeocystis at much higher rates than did the copepod. Nevertheless, protozoan growth and ingestion rates were submaximal, indicating Phaeocystis to be suboptimal food.
The oligotrich ciliate Strombidium elegans did not feed on Phaeocystis. In grazing experiments with mixtures of both predator types, the decline of Phaeocystis single cells could be explained by protozoan grazing alone, implying no grazing by the copepods on Phaeocystis. Instead, copepods ingested the protozoans at high rates. Predation on 0. marina and S. acuminatum by T. longicornis resulted in a
reduction of the total grazing pressure on Phaeocystis of 21 and 67 % respectively. We conclude that mesozooplankton predation on herbivorous ciliates and heterotrophic dinoflagellates, which consumed Phaeocystis cells, can considerably reduce the overall grazing pressure and may enhance Phaeocystis
bloomng
Vibrational detection and control of spin in mixed-valence molecular transistors
We investigate electron transport through a mixed-valence molecular complex
in which an excess electron can tunnel between hetero-valent transition metal
ions, each having a fixed localized spin. We show that in this class of
molecules the interplay of the spins and the vibrational breathing modes of the
ionic ligand-shells allows the total molecular spin to be detected as well as
controlled by nonequilibrium transport. Due to a spin-dependent pseudo
Jahn-Teller effect electronic transitions with different spin values can be
distinguished by their vibronic conductance side peaks, without using an
external magnetic field. Conversely, we show that the spin state of the entire
molecule can also be controlled via the nonequilibrium quantized molecular
vibrations due to a vibration-induced spin-blockade.Comment: 6 pages, 3 figure
Heat, molecular vibrations, and adiabatic driving in non-equilibrium transport through interacting quantum dots
In this article we review aspects of charge and heat transport in interacting
quantum dots and molecular junctions under stationary and time-dependent
non-equilibrium conditions due to finite electrical and thermal bias. In
particular, we discuss how a discrete level spectrum can be beneficial for
thermoelectric applications, and investigate the detrimental effects of
molecular vibrations on the efficiency of a molecular quantum dot as an energy
converter. In addition, we consider the effects of a slow time-dependent
modulation of applied voltages on the transport properties of a quantum dot and
show how this can be used as a spectroscopic tool complementary to standard
dc-measurements. Finally, we combine time-dependent driving with
thermoelectrics in a double-quantum dot system - a nanoscale analogue of a
cyclic heat engine - and discuss its operation and the main limitations to its
performance.Comment: Review article submitted to PSS (b) for the special issue "Quantum
transport at the molecular scale
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