Deterioration of Graphene Nanocoated Optical Taper Saturable Absorber at High Power

We experimentally investigate the loss of nonlinear transmission of graphene nanocoated optical taper (GNOT) saturable absorber at high input average power. Above a certain threshold of incident average power, the component experiences an irreversible modification of its nonlinear properties. This leads to a permanent deterioration of saturable absorption characteristics of this component. Such behavior is discussed and analyzed

High power passively mode-locked fiber laser based on graphene nanocoated optical taper

We experimentally demonstrate a passively mode-locked Er:Yb doped double-clad fiber laser usinga graphene nanocoated optical taper. Averaging 20lm of clad diameter with a length of 6 mm,such a saturable absorber enables a strong light–graphene interaction owing to the evanescent fieldof the excited cladding mode. With the highest pump power of 5 W, the 326th harmonic mode lock-ing of soliton bunches with an average output power of 520 mW was obtained in a fiber ring cavitythat has a fundamental frequency of 1.67 MHz. This is the highest average output power yetreported in graphene-based passively mode-locked fiber lasers

Limitations of graphene nanocoated optical tapers for high-power nonlinear applications

In this letter, we investigate the limitations of graphene as a saturable absorber for high-power nonlinear optical applications. The response of graphene nanocoated optical tapers against the average optical power injected is tested. We point out that the power handled by such components is limited and their nonlinear properties are strongly and permanently modified when exposed to high optical power. The origin of the degradation of the components is discussed

Optical Spectroscopy of Active Galactic Nuclei in SA57

The cosmological evolution of X-ray-selected and optically selected Active Galactic Nuclei (AGNs) show different behaviours interpreted in terms of two different populations. The difference is evident mainly for low luminosity AGNs (LLAGNs), many of which are lost by optical photometric surveys. We are conducting a spectroscopical study of a composite sample of AGN candidates selected in SA57 following different searching techniques, to identify low luminosity AGNs and break down the sample into different classes of objects. AGN candidates were obtained through optical variability and/or X-ray emission. Of special interest are the extended variable objects, which are expected to be galaxies hosting LLAGNs. Among the 26 classified objects a fair number (9) show typical AGN spectra. 10 objects show Narrow Emission Line Galaxy spectra, and in most of them (8/10) optical variability suggests the presence of LLAGNs.Comment: 7 pages, 8 figures, to appear in A&

Analyse amibienne et fongique des boues résiduaires d'une station d'épuration d'Industrie laitière

Nous avons, pendant 19 mois consécutifs, avec deux mois d'interruption en avril et mai de la deuxième année, suivi une station d'épuration d'eaux usées provenant d'une industrie laitière. Ce suivi a été centré exclusivement sur les boues, après addition de polyélectrolytes, et au sortir de la presse à boues, et avait pour objectif de vérifier le rôle pathogène potentiel de ce type de boues lors de leur emploi en agriculture. Nos résultats qui devront être confirmés pour d'autres types de station d'épuration d'eaux usées agro-alimentaires, sont en faveur de l'inocuité des boues sur le double point de vue des amibes libres et des champignons kératinophiles. Il existes certes une double faune amibienne et fongique abondante, mais cette faune est dépourvue d'amibes libres thermophiles potentiellement pathogènes, et quant aux champignons microscopiques retrouvés, il s'agissait quasi exclusivement de Mucorales, avec dans de rares cas quelques Aspergillus niger et A. fumigatus, Candida tropicalis et Keratinomyces ajelloi

Review of climate, landscape, and viral genetics as drivers of the Japanese encephalitis virus ecology

The Japanese encephalitis virus (JEV), an arthropod-born Flavivirus, is the major cause of viral encephalitis, responsible for 10,000-15,000 deaths each year, yet is a neglected tropical disease. Since the JEV distribution area has been large and continuously extending toward new Asian and Australasian regions, it is considered an emerging and reemerging pathogen. Despite large effective immunization campaigns, Japanese encephalitis remains a disease of global health concern. JEV zoonotic transmission cycles may be either wild or domestic: the first involves wading birds as wild amplifying hosts; the second involves pigs as the main domestic amplifying hosts. Culex mosquito species, especially Cx. tritaeniorhynchus, are the main competent vectors. Although five JEV genotypes circulate, neither clear-cut genotype-phenotype relationship nor clear variations in genotype fitness to hosts or vectors have been identified. Instead, the molecular epidemiology appears highly dependent on vectors, hosts' biology, and on a set of environmental factors. At global scale, climate, land cover, and land use, otherwise strongly dependent on human activities, affect the abundance of JEV vectors, and of wild and domestic hosts. Chiefly, the increase of rice-cultivated surface, intensively used by wading birds, and of pig production in Asia has provided a high availability of resources to mosquito vectors, enhancing the JEV maintenance, amplification, and transmission. At fine scale, the characteristics (density, size, spatial arrangement) of three landscape elements (paddy fields, pig farms, human habitations) facilitate or impede movement of vectors, then determine how the JEV interacts with hosts and vectors and ultimately the infection risk to humans. If the JEV is introduced in a favorable landscape, either by live infected animals or by vectors, then the virus can emerge and become a major threat for human health. Multidisciplinary research is essential to shed light on the biological mechanisms involved in the emergence, spread, reemergence, and genotypic changes of JEV

Direct Synthesis of Cyclopropanes from gem-Dialkyl Groups through Double CH Activation

Cyclopropanes are important structural motifs found in numerous bioactive molecules, and a number of methods are available for their synthesis. However, one of the simplest cyclopropanation reactions involving the intramolecular coupling of two C-H bonds on gem-dialkyl groups has remained an elusive transformation. We demonstrate herein that this reaction is accessible using aryl bromide or triflate precursors and the 1,4-Pd shift mechanism. The use of pivalate as the base was found to be crucial to divert the mechanistic pathway toward the cyclopropane instead of the previously obtained benzocyclobutene product. Stoichiometric mechanistic studies allowed the identification of aryl- and alkylpalladium pivalates, which are in equilibrium via a five-membered palladacycle. With pivalate, a second C(sp3)-H activation leading to the four-membered palladacycle intermediate and the cyclopropane product is favored. A catalytic reaction was developed and showed a broad scope for the generation of diverse arylcyclopropanes, including valuable bicyclo[3.1.0] systems. This method was applied to a concise synthesis of lemborexant, a recently approved anti-insomnia drug

Human-associated Staphylococcus aureus strains within great ape populations in Central Africa (Gabon)

The risk of serious infections caused by Staphylococcus aureus is well-known. However, most studies regarding the distribution of (clinically relevant) S.aureus among humans and animals took place in the western hemisphere and only limited data are available from (Central) Africa. In this context, recent studies focused on S.aureus strains in humans and primates, but the question of whether humans and monkeys share related S.aureus strains or may interchange strains remained largely unsolved. In this study we aimed to evaluate the distribution and spread of human-like S.aureus strains among great apes living in captivity. Therefore, a primate facility at the International Centre for Medical Research of Franceville (Gabon) was screened. We detected among the primates a common human S.aureus strain, belonging to the spa-type t148. It was isolated from three different individuals of the western lowland gorilla (Gorilla gorilla gorilla), of which one individual showed a large necrotizing wound. This animal died, most probably of a staphylococcal sepsis. Additionally, we discovered the t148 type among chimpanzees (Pan troglodytes) that were settled in the immediate neighbourhood of the infected gorillas. A detailed analysis by pulsed field gel electrophoresis showed that the gorilla and chimpanzee isolates represented two closely related strains. To our knowledge, this is the first report of a human-associated S.aureus strain causing disease in great apes. The simultaneous detection in gorillas and chimpanzees indicated an interspecies transmission of this S.aureus strain. Our results recommend that protection of wild animals must not only be based on habitat conservation, but also on the assessment of the risk of contact with human pathogens