Relative intensity noise and frequency noise of a compact Brillouin laser made of As38Se62 suspended-core chalcogenide fiber

International audienceRelative intensity noise and frequency noise have been measured for the first time for a single-frequency Brillouin chalcogenide As38Se62 fiber laser. This is also the first demonstration of a compact suspended-core fiber Brillouin laser, which exhibits a low threshold power of 22 mW and a slope efficiency of 26% for nonresonant pumping

20 GHz instantaneous bandwidth RF spectrum analyzer with high time-resolution

International audienceWe report on the experimental demonstration of a multi-gigahertz bandwidth RF spectrum analyzer exhibiting a resolution below 20 MHz, based on spectral hole burning in a rare-earth ion-doped crystal. To be compatible with demanding real-time spectrum monitoring applications, our demonstrator is designed to reach a high time resolution. For this purpose, we implemented the so-called "rainbow" architecture in which the spectral components of the incoming signal are angularly separated by the crystal, and are then acquired with a pixelated photodetector. The Tm 3+ :YAG crystal is programmed with a semiconductor DFB laser which frequency scan is servo-controlled and synchronized with the angular scan of a resonant galvanometric mirror, while a high-speed camera is used to acquire the spectra. In the perspective of future implementation within a system, the crystal is cooled below 4 K with a closed-cycle cryostat. With this setup, we have been able to monitor and record the spectrum of complex microwave signals over an instantaneous bandwidth above 20 GHz, with a time resolution below 100 µs, 400 resolvable frequency components and a probability of intercept of 100 %

Anthrax Edema Toxin Modulates PKA- and CREB-Dependent Signaling in Two Phases

Background: Anthrax edema toxin (EdTx) is an adenylate cyclase which operates in the perinuclear region of host cells. However, the action of EdTx is poorly understood, especially at molecular level. The ability of EdTx to modulate cAMPdependent signaling was studied in Jurkat T cells and was compared with that of other cAMP-rising agents: Bordetella pertussis adenylate cyclase toxin, cholera toxin and forskolin. Methodology/Principal Findings: EdTx caused a prolonged increase of the intracellular cAMP concentration. This led to nuclear translocation of the cAMP-dependent protein kinase (PKA) catalytic subunit, phosphorylation of cAMP response element binding protein (CREB) and expression of a reporter gene under control of the cAMP response element. Neither p90 ribosomal S6 kinase nor mitogen- and stress-activated kinase, which mediate CREB phosphorylation during T cell activation, were involved. The duration of phospho-CREB binding to chromatin correlated with the spatio-temporal rise of cAMP levels. Strikingly, EdTx pre-treated T cells were unresponsive to other stimuli involving CREB phosphorylation such as addition of forskolin or T cell receptor cross-linking. Conclusions/Significance: We concluded that, in a first intoxication phase, EdTx induces PKA-dependent signaling, which culminates in CREB phosphorylation and activation of gene transcription. Subsequently CREB phosphorylation is impaired and therefore T cells are not able to respond to cues involving CREB. The present data functionally link the perinuclea

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others

Augmentation de la profondeur de modulation de signaux hyperfréquence sur porteuse optique par effets non linéaires dans les fibres

LA FIBRE OPTIQUE TEND À REMPLACER LE CÂBLE COAXIAL DANS DE NOMBREUX SYSTÈMES DE TRANSPORT ET DE TRAITEMENT DE SIGNAUX HYPERFRÉQUENCE. EN PARTICULIER LES GÉNÉRATIONS FUTURES DE SYSTÈMES RADAR SERONT ÉQUIPÉES DE LAISONS OPTO-ÉLECTRONIQUES UTILISANT AINSI AVEC PROFIT LES AVANTAGES DE LA FIBRE OPTIQUE (FAIBLES PERTES, POIDS, ENCOMBREMENT ET COÛT ET LARGE BANDE-PASSANTE). DANS CES FUTURS SYSTÈMES RADAR, LA TRANSPOSITION LINÉAIRE DE L'INFORMATION HYPERFRÉQUENCE SUR PORTEUSE OPTIQUE AVEC DES MODULATEURS D'INTENSITÉ INTÉGRÉS CLASSIQUES (TYPE MACH-ZEHNDER) EST LIMITÉE EN AMPLITUDE. LE SIGNAL OPTIQUE RÉSULTANT COMPORTE DONC UNE FAIBLE PARTIE MODULÉE CONTENANT L'INFORMATION HYPERFRÉQUENCE ET UNE FORTE COMPOSANTE CONTINUE SUSCEPTIBLE DE SATURER CERTAINS COMPOSANTS DE LA LIAISON OPTO-ÉLECTRONIQUE. DANS CE TRAVAIL NOUS AVONS ÉTUDIÉ DEUX PROCESSUS NON-LINÉAIRES DANS LES FIBRES OPTIQUES PERMETTANT D'ATTÉNUER DE FAÇON SÉLECTIVE ET DYNAMIQUE UNIQUEMENT LA PORTEUSE OPTIQUE DU SIGNAL ET NON L'INFORMATION HYPERFRÉQUENCE QU'ELLE TRANSPORTE. CELA REVIENT À AUGMENTER LE CONTRASTE DU SIGNAL, C'EST-À-DIRE SA PROFONDEUR DE MODULATION. LE PREMIER EFFET ÉTUDIÉ EST LA DIFFUSION BRILLOUIN STIMULÉE DANS LES FIBRES OPTIQUES (Y COMPRIS DANS LES FIBRES OPTIQUES À CRISTAUX PHOTONIQUES). LE SECOND EFFET ÉTUDIÉ EST LE MÉLANGE À DEUX ONDES PAR SATURATION DU GAIN DANS UNE FIBRE OPTIQUE AMPLIFICATRICE. LA FAISABILITÉ DE L'AUGMENTATION DE PROFONDEUR DE MODULATION DU SIGNAL HYPERFRÉQUENE SUR PORTEUSE OPTIQUE PAR CES DEUX TECHNIQUES RESPECTIVEMENT A ÉTÉ DÉMONTRÉE. UNE AUGMENTATION DE LA PROFONDEUR DE MODULATION DU SIGNAL D'UN FACTEUR 10 000 A ÉTÉ DÉMONTRÉE, SANS DÉGRADATION DU SIGNAL HYPERFREQUENCE.OPTICAL FIBRES TEND TO REPLACE COAXIAL CABLES IN MANY SYSTEMS OF TRANSPORT AND PROCESSING OF MICROWAVE SIGNALS. IN PARTICULAR, FUTURE GENERATIONS OF RADAR SYSTEMS WILL BE EQUIPPED WITH OPTO-ELECTRONIC LINKS THUS USING WITH PROFIT THE ADVANTAGES OF OPTICAL FIBRES (WEAK WEIGHT, SIZE, COST AND LARGE BANDWIDTH). IN THESE FUTURE RADAR SYSTEMS, THE LINEAR TRANSPOSITION OF MICROWAVE INFORMATION ON OPTICAL CARRIER WITH TRADITIONAL INTEGRATED INTENSITY MODULATORS (SUCH AS MACH-ZEHNDER) IS AMPLITUDE-LIMITED. THE RESULTING SIGNAL IS THUS COMPOSED OF A WEAK MODULATED PART CONTAINING THE MICROWAVE INFORMATION AND OF A STRONG CONTINUOUS COMPONENT WHICH CAN SATURATE SOME OF THE OPTO-ELECTRONIC LINK COMPONENTS. IN THIS WORK WE STUDIED TWO NON-LINEAR PROCESSES IN OPTICAL FIBRES ALLOWING SELECTIVE AND DYNAMIC ATTENUATION OF THE OPTICAL CARRIER ONLY, WITHOUT ANY ATTENUATION OF THE MICROWAVE SIGNAL. THIS MEANS AN INCREASE OF THE SIGNAL CONTRAST, THAT IS TO SAY AN INCREASE OF ITS MODULATION DEPTH. THE FIRST STUDIED EFFECT IS STIMULATED BRILLOUIN SCATTERING IN OPTICAL FIBRES (INCLUDING IN PHOTONIC CRYSTAL FIBRES). THE SECOND STUDIED EFFECT IS TWO WAVE MIXING BY GAIN SATURATION IN AN AMPLIFYING OPTICAL FIBRE. THE FEASIBILITY OF MODULATION DEPTH INCREASE OF THE MICROWAVE SIGNAL BY THESE TWO TECHNIQUES RESPECTIVELY HAS BEEN PROVEN. AN INCREASE OF THE MODULATION DEPTH OF THE SIGNAL BY A FACTOR 10 000 HAS BEEN DEMONSTRATED.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Phonon-photon interactions for very low noise RF optical links

International audienc