Interplay of Kondo effect and strong spin-orbit coupling in multi-hole ultraclean carbon nanotubes

We report on cotunneling spectroscopy magnetoconductance measurements of multi-hole ultraclean carbon nanotube quantum dots in the SU(4) Kondo regime with strong spin-orbit coupling. Successive shells show a gradual weakening of the Kondo effect with respect to the spin-orbital splittings, leading to an evolution from SU(4) to SU(2) symmetry with a suppressed conductance at half shell filling. The extracted energy level spectrum, overally consistent with negligible disorder in the nanotube, shows in the half filled case large renormalizations due to Coulombian effects.Comment: 5 pages, 4 figures, 1 supplementary fil

Gate-tuned high frequency response of carbon nanotube Josephson junctions

Carbon nanotube (CNT) Josephson junctions in the open quantum dot limit exhibit superconducting switching currents which can be controlled with a gate electrode. Shapiro voltage steps can be observed under radiofrequency current excitations, with a damping of the phase dynamics that strongly depends on the gate voltage. These measurements are described by a standard RCSJ model showing that the switching currents from the superconducting to the normal state are close to the critical current of the junction. The effective dynamical capacitance of the nanotube junction is found to be strongly gate-dependent, suggesting a diffusive contact of the nanotube.Comment: 14 pages, 8 figure

Interplay of electromagnetic noise and Kondo effect in quantum dots

We investigate the influence of an electromagnetic environment, characterized by a finite impedance $Z(\omega)$, on the Kondo effect in quantum dots. The circuit voltage fluctuations couple to charge fluctuations in the dot and influence the spin exchange processes transferring charge between the electrodes. We discuss how the low-energy properties of a Kondo quantum dot subject to dynamical Coulomb blockade resemble those of Kondo impurities in Luttinger liquids. Using previous knowledge based on the bosonization of quantum impurity models, we show that low-voltage conductance anomalies appear at zero temperature. The conductance can vanish at low temperatures even in presence of a screened impurity spin. Moreover, the quantitative determination of the corresponding Kondo temperature depends on the full frequency-dependent impedance of the circuit. This is demonstrated by a weak-coupling calculation in the Kondo interaction, taking into account the full distribution $P(E)$ of excited environmental modes.Comment: 10 pages, 4 figures, revised version, new titl

The signature of a splice

We study the behavior of the signature of colored links [6,9] under the splice operation. We extend the construction to colored links in integral homology spheres and show that the signature is almost additive, with a correction term independent of the links. We interpret this correction term as the signature of a generalized Hopf link and give a simple closed formula to compute it. © The Author(s) 2016. Published by Oxford University Press

Quantum Phase Transition in a Resonant Level Coupled to Interacting Leads

An interacting one-dimensional electron system, the Luttinger liquid, is distinct from the "conventional" Fermi liquids formed by interacting electrons in two and three dimensions. Some of its most spectacular properties are revealed in the process of electron tunneling: as a function of the applied bias or temperature the tunneling current demonstrates a non-trivial power-law suppression. Here, we create a system which emulates tunneling in a Luttinger liquid, by controlling the interaction of the tunneling electron with its environment. We further replace a single tunneling barrier with a double-barrier resonant level structure and investigate resonant tunneling between Luttinger liquids. For the first time, we observe perfect transparency of the resonant level embedded in the interacting environment, while the width of the resonance tends to zero. We argue that this unique behavior results from many-body physics of interacting electrons and signals the presence of a quantum phase transition (QPT). In our samples many parameters, including the interaction strength, can be precisely controlled; thus, we have created an attractive model system for studying quantum critical phenomena in general. Our work therefore has broadly reaching implications for understanding QPTs in more complex systems, such as cold atoms and strongly correlated bulk materials.Comment: 11 pages total (main text + supplementary

Metal-insulator transition in the two-orbital Hubbard model at fractional band fillings: Self-energy functional approach

We investigate the infinite-dimensional two-orbital Hubbard model at arbitrary band fillings. By means of the self-energy functional approach, we discuss the stability of the metallic state in the systems with same and different bandwidths. It is found that the Mott insulating phases are realized at commensurate band fillings. Furthermore, it is clarified that the orbital selective Mott phase with one orbital localized and the other itinerant is stabilized even at fractional band fillings in the system with different bandwidths.Comment: 7 pages, 10 figure

Evaluation of HIV and AIDS knowledge in rural Cameroon men with the use of a questionnaire

Introduction: HIV/AIDS, the most important health problem in Africa, is the leading cause of death on the continent. Ignorance on HIV/AIDS status will hamper treatment and prevention. To investigate the level of HIV/AIDS knowledge among men in a rural area, we performed a questionnaire study on HIV/AIDS knowledge in men living in Banga Bakundu, a rural village in Cameroon. Methods: Forty-eight men, aged 17-66 years, were interviewed. They were divided in 2 groups: ≤29 years, being those young enough to be able to have knowledge about HIV/AIDS at the time of their first sexual contact, and those > 29 years who weren't. A semi-structured clinical interview was performed to obtain information about socio-demographic characteristics, sexual activity, knowledge about HIV/AIDS and its prevention. Results: There is an overall good HIV/AIDS knowledge and what should be done about it. Men with a higher level of education and more HIV/AIDS knowledge seem to take less preventive measures. The differentiation per age group showed that age influenced the data on knowledge and behaviour. Conclusion: Our data are consistent with other studies. Remarkable is the difference in HIV/AIDS knowledge between the 2 age groups, and the relation between HIV/AIDS knowledge and sexual habits and prevention. Sufficient HIV/AIDS knowledge did not lead to significant changes in sexual behaviour. The questionnaire showed to provide sufficient information and was easy to use. Further research should be performed

Periodic Anderson model with degenerate orbitals: linearized dynamical mean field theory approach

We investigate a multi-orbital extension of the periodic Anderson model with particular emphasis on electron correlations including orbital fluctuations. By means of a linearized version of the dynamical mean-field theory, we compute the renormalization factor, the density of states, the spectral gap and the local correlation functions for a given set of the intra- and inter-orbital Coulomb interactions as well as the Hund coupling. It is found that when a certain condition is met for the intra- and inter-orbital interactions for $f$ electrons, orbital fluctuations are enhanced, thereby enlarging the Kondo insulating gap. This effect is suppressed in the presence of the Hund coupling. We also clarify how the Kondo insulator is continuously changed to the Mott insulator when electron correlations among conduction electrons are increased.Comment: 7 pages, 10 figure

Calmodulin-like proteins localized to the conoid regulate motility and cell invasion by Toxoplasma gondii

Toxoplasma gondii contains an expanded number of calmodulin (CaM)-like proteins whose functions are poorly understood. Using a combination of CRISPR/Cas9-mediated gene editing and a plant-like auxin-induced degron (AID) system, we examined the roles of three apically localized CaMs. CaM1 and CaM2 were individually dispensable, but loss of both resulted in a synthetic lethal phenotype. CaM3 was refractory to deletion, suggesting it is essential. Consistent with this prediction auxin-induced degradation of CaM3 blocked growth. Phenotypic analysis revealed that all three CaMs contribute to parasite motility, invasion, and egress from host cells, and that they act downstream of microneme and rhoptry secretion. Super-resolution microscopy localized all three CaMs to the conoid where they overlap with myosin H (MyoH), a motor protein that is required for invasion. Biotinylation using BirA fusions with the CaMs labeled a number of apical proteins including MyoH and its light chain MLC7, suggesting they may interact. Consistent with this hypothesis, disruption of MyoH led to degradation of CaM3, or redistribution of CaM1 and CaM2. Collectively, our findings suggest these CaMs may interact with MyoH to control motility and cell invasion

The Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES): progress and next steps

Biodiversity and the services ecosystems provide have built the foundation of human civilization and provide for the welfare of people. With the increase of the human population it has become clearer than ever that the human exploitation of our natural resources leads to detrimental interactions between ecological and sociological systems. Only concerted and global actions will be able to reverse ongoing biodiversity loss. In response to these needs, the United Nations agreed the establishment of the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) in 2010. Here, we report on the progress IPBES has made since its inception, and suggest how the scientific community can engage with this important science-policy interfac