Conditions for requiring nonlinear thermoelectric transport theory in nanodevices

In this paper, we examine the conditions under which the nonlinear transport theory is inescapable, when a correlated quantum dot is symmetrically coupled to two leads submitted to temperature and voltage biases. By detailed numerical comparisons between nonlinear and linear currents, we show that the claimed nonlinear behavior in a temperature gradient for the electric current is not so genuine, and the linear theory made at the operating temperature $\bar{T}= (T_H+T_C)/2$ is unexpectedly robust. This is demonstrated for the single impurity Anderson model, in different regimes: resonant tunneling, Coulomb blockade and Kondo regimes

Hund and pair-hopping signature in transport properties of degenerate nanoscale devices

We investigate the signature of a complete Coulomb interaction in transport properties of double-orbital nanoscale devices. We analyze the specific effects of Hund exchange and pair hopping terms, calculating in particular stability diagrams. It turns out that a crude model, with partial Coulomb interaction, may lead to a misinterpretation of experiments. In addition, it is shown that spectral weight transfers induced by gate and bias voltages strongly influence charge current. The low temperature regime is also investigated, displaying inelastic cotunneling associated with the exchange term, as well as Kondo conductance enhancement.Comment: 5 pages, 4 figure

Kondo physics and orbital degeneracy interact to boost thermoelectrics on the nanoscale

We investigate the transport through a nanoscale device consisting of a degenerate double-orbital Anderson dot coupled to two uncorrelated leads. We determine the thermoelectric transport properties close to the one-electron regime and compare them to a corresponding single-orbital dot. The linear and nonlinear regimes are addressed, the latter via a non-equilibrium generalization of the non-crossing approximation based on the Keldysh formalism. Power output and efficiency in the Kondo regime are shown to be strongly enhanced through the presence of a second orbital. We predict an experimentally relevant optimal operating point which benefits from the concomitant increase of the Kondo temperature in the two-orbital setup. An approximation based on the transport coefficients and fulfilling the thermodynamic balance is proven to remain appropriate even far beyond the expected range of validity of such approaches. Finally, the double-orbital Kondo regime reveals itself as a promising candidate to avoid, at least partially, the generic dilemma between optimal thermoelectric efficiency on one hand, and fair power output on the other.Comment: 5 pages, 2 figure

Evidence That Intracellular Stages of Leishmania major Utilize Amino Sugars as a Major Carbon Source

Intracellular parasites, such as Leishmania spp, must acquire suitable carbon sources from the host cell in order to replicate. Here we present evidence that intracellular amastigote stages of Leishmania exploit amino sugars in the phagolysosome of mammalian macrophages as a source of carbon and energy. L. major parasites are capable of using N-acetylglucosamine and glucosamine as primarily carbon sources and contain key enzymes required for conversion of these sugars to fructose-6-phosphate. The last step in this pathway is catalyzed by glucosamine-6-phosphate deaminase (GND), which was targeted to glycosomes via a canonical C-terminal targeting signal when expressed as a GFP fusion protein. Mutant parasites lacking GND were unable to grow in medium containing amino sugars as sole carbohydrate source and rapidly lost viability, concomitant with the hyper-accumulation of hexosamine-phosphates. Expression of native GND, but not a cytosolic form of GND, in Δgnd parasites restored hexosamine-dependent growth, indicating that toxicity is due to depletion of glycosomal pools of ATP. Non-lethal increases in hexosamine phosphate levels in both Δgnd and wild type parasites was associated with a defect in promastigote metacyclogenesis, suggesting that hexosamine phosphate levels may influence parasite differentiation. Promastigote and amastigote stages of the Δgnd mutant were unable to replicate within macrophages and were either completely cleared or exhibited reduced lesion development in highly susceptible Balb/c mice. Our results suggest that hexosamines are a major class of sugars in the macrophage phagolysosome and that catabolism of scavenged amino sugars is required to sustain essential metabolic pathways and prevent hexosamine toxicity

Monitoring biological wastewater treatment processes: Recent advances in spectroscopy applications

Biological processes based on aerobic and anaerobic technologies have been continuously developed to wastewater treatment and are currently routinely employed to reduce the contaminants discharge levels in the environment. However, most methodologies commonly applied for monitoring key parameters are labor intensive, time-consuming and just provide a snapshot of the process. Thus, spectroscopy applications in biological processes are, nowadays, considered a rapid and effective alternative technology for real-time monitoring though still lacking implementation in full-scale plants. In this review, the application of spectroscopic techniques to aerobic and anaerobic systems is addressed focusing on UV--Vis, infrared, and fluorescence spectroscopy. Furthermore, chemometric techniques, valuable tools to extract the relevant data, are also referred. To that effect, a detailed analysis is performed for aerobic and anaerobic systems to summarize the findings that have been obtained since 2000. Future prospects for the application of spectroscopic techniques in biological wastewater treatment processes are further discussed.The authors thank the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors also acknowledge the financial support to Daniela P. Mesquita and Cristina Quintelas through the postdoctoral Grants (SFRH/BPD/82558/2011 and SFRH/BPD/101338/2014) provided by FCT - Portugal.info:eu-repo/semantics/publishedVersio