Fast interrogation wavelength tuning for all-optical photoacoustic imaging

Optical detection of ultrasound for photoacoustic imaging provides large bandwidth and high sensitivity at high acoustic frequencies. Higher spatial resolutions can therefore be achieved using Fabry-P\'erot cavity sensors, as compared to conventional piezoelectric detection. However, fabrication constraints during deposition of the sensing polymer layer require a precise control of the interrogation beam wavelength to provide optimal sensitivity. This is commonly achieved by employing slowly tunable narrowband lasers as interrogation sources, hence limiting the acquisition speed. We propose instead to use a broadband source and a fast tunable acousto-optic filter to adjust the interrogation wavelength at each pixel within a few microseconds. We demonstrate the validity of this approach by performing photoacoustic imaging with a highly inhomogeneous Fabry-P\'erot sensor.Comment: 9 pages, 4 figure

Cloning, characterization and chromosomal localization of a repeated sequence in Crypthecodinium cohnii, a marine dinoflagellate

Genomic DNA of Crypthecodinium cohnii has been extracted in the presence of cetylmethylammonium bromide and hydrolysed by 13 restriction enzymes. No typical ladder-like pattern or isolated band of satellite sequences were found with any of these enzymes. A “mini” genomic DNA library had been made and screened by reverse hybridization to isolate highly repeated sequences. Seven such DNA fragments were sequenced. The copy number of one of them (Cc18), 226 bp long, was estimated at around 25,000, representing 0.06% of the total genome. Cc18 was found to be included in a higher fragment of 3.0 kb by Southern blot analysis after cleavage by PstI. This higher molecular weight fragment could be composed either of tandemly repeated Cc18 sequences, or by only one or a very low copy number of Cc18. In this latter case, these fragments, also repeated 25,000 times would represent 1 to 2% of the total genome. Genomic localization of Cc18 by in situ hybridization on squashed C. cohnii cells showed that it was widely distributed on the different chromosomes. All the chromosomes observed displayed Cc18 labeling, which appeared homogeneously distributed. The ability of Cc18 to be a specific molecular marker to distinguish sibling C. cohnii species is discussed

Design and assessment of an electrodynamic loudspeaker used in a variable acoustic lining concept

The acoustic impedance at the diaphragm of an electroacoustic transducer can be modified using a range of active control strategies, amongst which is “direct impedance control”. This technique employs a combination of feedbacks, one on the acoustic pressure and the other on the diaphragm velocity, to the loudspeaker electric terminals, allowing significant modifications of the acoustic resonator properties of the diaphragm within a specified range. This concept has been specifically developed for a novel concept of active acoustic liners for aircraft engines within the European project OPENAIR. One of the objectives of active acoustic liners is the achievement of real‐time modifications of the acoustic impedance of a 1 degree of freedom resonator. These properties should then match variable target impedances, specified by phases of flight. The paper presents the development of a specific electrodynamic loudspeaker for use as active liners, with an emphasis on integration issues, as well as acoustic performances. The general concept of direct impedance control is first introduced, followed by design considerations on the loudspeakers side, and then experimental assessments of performances are presented

Reduced parathyroid functional mass after successful kidney transplantation

Reduced parathyroid functional mass after successful kidney transplantation.BackgroundChronic uremia is responsible for secondary hyperparathyroidism (HPT II). Parathyroid secretion usually tends to normalize after kidney transplantation (KT), but the parameters of the reversibility of HPT II remain poorly defined, particularly the intrinsic mechanisms underlying the improvement of parathyroid function.MethodsThe kinetic functional parameters of the ionized calcium (iCa)/parathormone (PTH) relationship curve were studied in 11 patients with mild to moderate HPT II one and six months after successful KT. Hypercalcemia and hypocalcemia were induced, respectively, by CaCl2 and Na2-ethylenediaminetetraacetic acid (Na2-EDTA) infusions.ResultsThe mean glomerular filtration rate remained stable during follow-up. Basal PTH decreased from 195 ± 54 pg/ml before KT to 70 ± 12 pg/ml six months later (P < 0.005). During the tests, mean PTH levels decreased significantly between the two measured times for all iCa levels, indicating an improved parathyroid function. An analysis of the kinetic parameters of the curves showed significant decreases of the mean maximal and minimal PTH levels, respectively, from 340 ± 91 to 220 ± 30 pg/ml (P = 0.03) and from 25 ± 6 to 15 ± 5 pg/ml (P = 0.005). On the other hand, no change was noted in the parathyroid-cell calcium-sensitivity parameters (slope, set point) assessed using two different approaches, either the entire curve or the limited calcium-mediated suppression curve.ConclusionImprovement of the parathyroid function between the first and sixth months post-KT seems mainly attributable to a reduction of the parathyroid functional mass

Design of Acoustic Metamaterials based on the Concept of Dual Transmission Line

Within the last years, an increasing number of studies have been carried out in the field of acoustic metamaterials. These artificial composite materials aim at achieving new macroscopic properties, like negative refraction, that are not readily present in nature. In analogy to electromagnetics, where such concepts are more mature, a novel concept of artificial acoustic transmission line has recently been reported, which presents such artificial behavior. In this article, the design of the proposed transmission line is presented and a validation is made with the help of a finite element model. Moreover, these results are compared to a usual circuit description of the problem. One cell and 10-cell long structures are implemented in Comsol Multiphysics® and confirm the good performances of the different models, in terms of dispersion diagram, Bloch impedance, as well as reflection and transmission coefficients

Optimisation d'un absorbeur électroacoustique par plans d'expériences : approche expérimentale et numérique

Dans cet article le processus d'optimisation d'absorbeurs électroacoustiques est étudié à l'aide de la méthode des surfaces de réponses. Un absorbeur électroacoustique est un système haut-parleur dont l'impédance acoustique peut être ajustée électriquement, de manière passive ou bien active. Un modèle mathématique est établi par plans d'expériences pour analyser l'effet de certains paramètres de conception sur les performances acoustiques de l'absorbeur. Pour quantifier la sensibilité d'un tel système soumis à différentes contraintes physiques, la méthode de surface de réponse a été choisie pour développer un modèle multivariable. Ces contraintes ont été choisies de manière à représenter les différents mécanismes dissipatifs mis en jeu au sein de l'absorbeur électroacoustique : dissipation par effet résonateur mécanique, dissipation par viscosité de l'air sollicitée par la pénétration des ondes sonores dans un milieu poreux, et dissipation par effet Joule induite par la charge résistive branchée aux bornes du haut-parleur. En vue d'évaluer la contribution de ces différents mécanismes sur les performances d'un absorbeur électroacoustique, notre étude à retenu les quatre paramètres d'entrée suivants : la masse de l'équipage mobile, la compliance induite par le volume de l'enceinte close, le taux de remplissage en matériaux poreux et la résistance électrique de shunt. Une étude préliminaire, réalisée par une double approche expérimentale et numérique, illustre les possibilités du processus d'optimisation développé. Le résultat obtenu est une mise en équation du facteur d'absorption permettant de piloter des réglages et de trouver un optimum en fonction de la fréquence

Prasinovirus distribution in the Northwest Mediterranean Sea is affected by the environment and particularly by phosphate availability

AbstractNumerous seawater lagoons punctuate the southern coastline of France. Exchanges of seawater between these lagoons and the open sea are limited by narrow channels connecting them. Lagoon salinities vary according to evaporation and to the volume of freshwater arriving from influent streams, whose nutrients also promote the growth of algae. We compared Prasinovirus communities, whose replication is supported by microscopic green algae, in four lagoons and at a coastal sampling site. Using high-throughput sequencing of DNA from a giant virus-specific marker gene, we show that the environmental conditions significantly affect the types of detectable viruses across samples. In spatial comparisons between 5 different sampling sites, higher levels of phosphates, nitrates, nitrites, ammonium and silicates tend to increase viral community richness independently of geographical distances between the sampling sites. Finally, comparisons of Prasinovirus communities at 2 sampling sites over a period of 10 months highlighted seasonal effects and the preponderant nature of phosphate concentrations in constraining viral distribution

An improved genome of the model marine alga Ostreococcus tauri unfolds by assessing Illumina de novo assemblies

Background: Cost effective next generation sequencing technologies now enable the production of genomic datasets for many novel planktonic eukaryotes, representing an understudied reservoir of genetic diversity. O. tauri is the smallest free-living photosynthetic eukaryote known to date, a coccoid green alga that was first isolated in 1995 in a lagoon by the Mediterranean sea. Its simple features, ease of culture and the sequencing of its 13 Mb haploid nuclear genome have promoted this microalga as a new model organism for cell biology. Here, we investigated the quality of genome assemblies of Illumina GAIIx 75 bp paired-end reads from Ostreococcus tauri, thereby also improving the existing assembly and showing the genome to be stably maintained in culture. Results: The 3 assemblers used, ABySS, CLCBio and Velvet, produced 95% complete genomes in 1402 to 2080 scaffolds with a very low rate of misassembly. Reciprocally, these assemblies improved the original genome assembly by filling in 930 gaps. Combined with additional analysis of raw reads and PCR sequencing effort, 1194 gaps have been solved in total adding up to 460 kb of sequence. Mapping of RNAseq Illumina data on this updated genome led to a twofold reduction in the proportion of multi-exon protein coding genes, representing 19% of the total 7699 protein coding genes. The comparison of the DNA extracted in 2001 and 2009 revealed the fixation of 8 single nucleotide substitutions and 2 deletions during the approximately 6000 generations in the lab. The deletions either knocked out or truncated two predicted transmembrane proteins, including a glutamate-receptor like gene. Conclusion: High coverage (>80 fold) paired-end Illumina sequencing enables a high quality 95% complete genome assembly of a compact ~13 Mb haploid eukaryote. This genome sequence has remained stable for 6000 generations of lab culture

Immunological markers after long-term treatment interruption in chronically HIV-1 infected patients with CD4 cell count above 400 x 10(6) cells/l.

OBJECTIVE: To analyse immunological markers associated with CD4+ lymphocyte T-cell count (CD4+) evolution during 12-month follow-up after treatment discontinuation. METHOD: Prospective observational study of chronically HIV-1 infected patients with CD4+ above 400 x 10(6) cells/l. RESULTS: CD4+ changes took place in two phases: an initial rapid decrease in the first month (-142 x 10(6) cells/l on average), followed by a slow decline (-17 x 10(6) cells/l on average) The second slope of CD4+ decline was not correlated with the first and only baseline plasma HIV RNA was associated with it. The decline in CD4+ during the first month was steeper in patients with higher CD4+ and weaker plasma HIV RNA baseline levels. Moreover, the decline was less pronounced (P < 10(-4)) in patients with CD4+ nadir above 350 x 10(6) cells/l (-65 x 10(6) cells/l per month) in comparison with those below 350 x 10(6) cells/l (-200 x 10(6) cells/l per month). A high number of dendritic cells (DCs) whatever the type was associated with high CD4+ at the time of treatment interruption and its steeper decline over the first month. Moreover, the myeloid DC level was stable whereas the lymphoid DC count, which tended to decrease in association with decrease in CD4+, was negatively correlated with the HIV RNA load slope. CONCLUSIONS: The results support the use of the CD4+ nadir to predict the CD4+ dynamic after treatment interruption and consideration of the CD4+ count after 1-month of interruption merely reflects the 12-month level of CD4+. Although DCs seem to be associated with the CD4+ dynamic, the benefit of monitoring them has still to be defined

Genes of the most conserved WOX clade in plants affect root and flower development in Arabidopsis

Background: The Wuschel related homeobox (WOX) family proteins are key regulators implicated in the determination of cell fate in plants by preventing cell differentiation. A recent WOX phylogeny, based on WOX homeodomains, showed that all of the Physcomitrella patens and Selaginella moellendorffii WOX proteins clustered into a single orthologous group. We hypothesized that members of this group might preferentially share a significant part of their function in phylogenetically distant organisms. Hence, we first validated the limits of the WOX13 orthologous group (WOX13 OG) using the occurrence of other clade specific signatures and conserved intron insertion sites. Secondly, a functional analysis using expression data and mutants was undertaken. Results: The WOX13 OG contained the most conserved plant WOX proteins including the only WOX detected in the highly proliferating basal unicellular and photosynthetic organism Ostreococcus tauri. A large expansion of the WOX family was observed after the separation of mosses from other land plants and before monocots and dicots have arisen. In Arabidopsis thaliana, AtWOX13 was dynamically expressed during primary and lateral root initiation and development, in gynoecium and during embryo development. AtWOX13 appeared to affect the floral transition. An intriguing clade, represented by the functional AtWOX14 gene inside the WOX13 OG, was only found in the Brassicaceae. Compared to AtWOX13, the gene expression profile of AtWOX14 was restricted to the early stages of lateral root formation and specific to developing anthers. A mutational insertion upstream of the AtWOX14 homeodomain sequence led to abnormal root development, a delay in the floral transition and premature anther differentiation. Conclusion: Our data provide evidence in favor of the WOX13 OG as the clade containing the most conserved WOX genes and established a functional link to organ initiation and development in Arabidopsis, most likely by preventing premature differentiation. The future use of Ostreococcus tauri and Physcomitrella patens as biological models should allow us to obtain a better insight into the functional importance of WOX13 OG genes