96 research outputs found
Chemistry with Photons, Protons, and Electrons
This is an account of the research activities of our group during the first two years of its existence. First results from our work on proton-coupled electron transfer and long-range charge tunneling reactions are presented. This includes a hydrogen-bonded cation–anion pair in
which a proton-coupled electron transfer process can be phototriggered and followed by simple optical spectroscopic means, as well as a series of rigid rod-like donor-bridge-acceptor molecules which we use to investigate physical phenomena associated with the tunneling of electrons or holes.
A unifying feature of this research is the use of light (photons) to induce proton and/or electron transfer
Robust excitation of C-band quantum dots for quantum communication
Building a quantum internet requires efficient and reliable quantum hardware,
from photonic sources to quantum repeaters and detectors, ideally operating at
telecommunication wavelengths. Thanks to their high brightness and
single-photon purity, quantum dot (QD) sources hold the promise to achieve high
communication rates for quantum-secured network applications. Furthermore, it
was recently shown that excitation schemes, such as longitudinal acoustic
phonon-assisted (LA) pumping, provide security benefits by scrambling the
coherence between the emitted photon-number states. In this work, we
investigate further advantages of LA-pumped quantum dots with emission in the
telecom C-band as a core hardware component of the quantum internet. We
experimentally demonstrate how varying the pump energy and spectral detuning
with respect to the excitonic transition can improve quantum-secured
communication rates and provide stable emission statistics regardless of
network-environment fluctuations. These findings have significant implications
for general implementations of QD single-photon sources in practical quantum
communication networks
Suspended core subwavelength fibers: practical designs for the low-loss terahertz guidance
In this work we report two designs of subwavelength fibers packaged for
practical terahertz wave guiding. We describe fabrication, modeling and
characterization of microstructured polymer fibers featuring a
subwavelength-size core suspended in the middle of a large porous outer
cladding. This design allows convenient handling of the subwavelength fibers
without distorting their modal profile. Additionally, the air-tight porous
cladding serves as a natural enclosure for the fiber core, thus avoiding the
need for a bulky external enclosure for humidity-purged atmosphere. Fibers of 5
mm and 3 mm in outer diameters with a 150 \mu m suspended solid core and a 900
\mu m suspended porous core respectively, were obtained by utilizing a
combination of drilling and stacking techniques. Characterization of the fiber
optical properties and the near-field imaging of the guided modes were
performed using a terahertz near-field microscopy setup. Near-field imaging of
the modal profiles at the fiber output confirmed the effectively single-mode
behavior of such waveguides. The suspended core fibers exhibit broadband
transmission from 0.10 THz to 0.27 THz (larger core), and from 0.25 THz to 0.51
THz (smaller core). Due to the large fraction of power that is guided in the
holey cladding, fiber propagation losses as low as 0.02 cm-1 are demonstrated.
Low-loss guidance combined with the core isolated from environmental
perturbations make these all-dielectric fibers suitable for practical terahertz
imaging and sensing applications.Comment: 13 pages, 7 figure
Quantum Acoustics with Surface Acoustic Waves
It has recently been demonstrated that surface acoustic waves (SAWs) can
interact with superconducting qubits at the quantum level. SAW resonators in
the GHz frequency range have also been found to have low loss at temperatures
compatible with superconducting quantum circuits. These advances open up new
possibilities to use the phonon degree of freedom to carry quantum information.
In this paper, we give a description of the basic SAW components needed to
develop quantum circuits, where propagating or localized SAW-phonons are used
both to study basic physics and to manipulate quantum information. Using
phonons instead of photons offers new possibilities which make these quantum
acoustic circuits very interesting. We discuss general considerations for SAW
experiments at the quantum level and describe experiments both with SAW
resonators and with interaction between SAWs and a qubit. We also discuss
several potential future developments.Comment: 14 pages, 12 figure
Imidazole propionate is increased in diabetes and associated with dietary patterns and altered microbial ecology
Microbiota-host-diet interactions contribute to the development of metabolic diseases. Imidazole propionate is a novel microbially produced metabolite from histidine, which impairs glucose metabolism. Here, we show that subjects with prediabetes and diabetes in the MetaCardis cohort from three European countries have elevated serum imidazole propionate levels. Furthermore, imidazole propionate levels were increased in subjects with low bacterial gene richness and Bacteroides 2 enterotype, which have previously been associated with obesity. The Bacteroides 2 enterotype was also associated with increased abundance of the genes involved in imidazole propionate biosynthesis from dietary histidine. Since patients and controls did not differ in their histidine dietary intake, the elevated levels of imidazole propionate in type 2 diabetes likely reflects altered microbial metabolism of histidine, rather than histidine intake per se. Thus the microbiota may contribute to type 2 diabetes by generating imidazole propionate that can modulate host inflammation and metabolism
The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases
The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article
Elaboration de complexes porphyrines/C60 : Vers la synthèse de modèles des antennes collectrices d'énergie lumineuse et du centre réactionnel du système photosynthétique.
To modelize the antenna effect and to obtain a charge-separated system, the two first steps of photosynthesis, we have associated porphyrins and fullerenes. Porphyrins have structural and photophysical properties similar than those of the chlorophyll.To obtain an antenna-effect, we have realized several assemblies of porphyrins, with always a free-base porphyrin. Then, we have seen an energy-transfer from metallated porphyrins to the free-base porphyrin.To obtain a charge-separated system, we have synthetised complexes between multiporphyrinic assemblies, with a free-base porphyrin bearing a crown-ether moity and a C60-derivative.It was possible to observe high stability constants in those complexes, coming from association of H-bonds and π− π interactions between the porphyrin-core and the C60 surface, having then a molecular cup-and-ball.These complexes very stable in solution afford us to obtain strong quenching of the porphyrin light-emission by the C60, either by electron-transfer or by energy-transfer.Pour modéliser l'effet d'antenne et l'obtention d'un système à charges séparées, les deux étapes primordiales de la photosynthèse, nous avons associé des porphyrines et des fullerènes. Les porphyrines ont des propriétés structurelles et photophysiques proches de la chlorophylle.Pour obtenir un effet d'antenne, nous avons réalisé plusieurs ensembles de porphyrines, avec toujours une porphyrine base-libre. Nous avons alors pu observer un transfert d'énergie des porphyrines métallées vers la porphyrine base-libre.Pour obtenir un système à charges séparées, nous avons synthétisé des complexes entre ces ensembles multiporphyriniques, avec une porphyrine base-libre portant un éther-couronne et un dérivé de fullerène C60.Il a été possible d'observer de fortes constantes d'association dans ces complexes, résultant de l'association d'interactions de type liaisons-H et d'interactions π− π entre le cœur de la porphyrine et la surface du C60, obtenant ainsi un bilboquet moléculaire.Ces complexes, très stables, en solution nous ont permis d'obtenir de forts piégeages de l'énergie lumineuse de la porphyrine par le C60, soit par transfert d'électron, soit par transfert d'énergie
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