The Generalized Reflect-Thru-Line (GTRL) calibration technique is used for the measurement of a waveguide devices operating in a multioctave band region, where waveguides are multimodal. In this ...contribution some preliminary results are shown concerning measurements up to the third harmonic of a WR75 reduced height rectangular waveguide, where up to four modes are above cutoff.
Equilibrium ultracentrifuge and circular dichroism (CD) studies of a retropeptide of a GCN4-like leucine zipper in neutral saline buffer are reported as functions of temperature. Ultracentrifuge ...results indicate the presence of three oligomeric species: monomer, dimer, and tetramer, in quantifiable amounts, and the data provide values for the standard Δ
G, Δ
H, and Δ
S for interconversion. CD at 222
nm displays the strong concentration dependence characteristic of dissociative unfolding, but also shows a helicity far below that of the parent propeptide. Remarkably enough, the CD at 222
nm shows an extremum in the region between 0 and 20°C. At higher
T, the usual cooperative unfolding is observed. Comparable data are presented for a mutant retropeptide, in which a single asparagine residue is restored to the characteristic heptad position it occupies in the propeptide. The mutant shows marked differences from its unmutated relative in both thermodynamic properties and CD, although the oligomeric ensemble also comprises monomers, dimers, and tetramers. The mutant is closer in helicity to the parent propeptide but is less stable. These findings do not support either of the extant views on retropeptides. The behavior seen is consistent neither with the view that retropeptides should have the same structure as propeptides nor with the view that they should have the same structure but opposite chirality. The simultaneous availability of oligomeric population data and CD allows the latter to be dissected into individual contributions from monomers, dimers, and tetramers. This dissection yields explanations for the observed extrema in curves of CD (222
nm) versus
T and reveals that the dimer population in both retropeptides undergoes “cold denaturation.”
Abstract
Fifty-four Enterococcus faecalis and 20 Enterococcus faecium isolates from clinical and non-human sources in Rome, Italy, were characterized by antibiotic resistance and pulsed field gel ...electrophoresis (PFGE). Resistance to vancomycin, teicoplanin, ampicillin, and ciprofloxacin was more frequent in E. faecium than in E. faecalis, whereas high-level resistance to aminoglycoside was found primarily in E. faecalis. Multi-resistance was found primarily among clinical isolates, but was also observed among environmental isolates. Common genotypes shared among clinical and environmental isolates were observed, however, the majority of isolates occurred as unique, source-specific clones. Several PFGE types were associated with shared features in their antibiotic resistance patterns; evidences of clonal spread between and within wards were also noted. This is the first report indicating clonal relatedness between human and environmental enterococci isolated in Italy.
The authors studied the correlation and agreement of commercially available assays in detection and quantification of the HIV-1 intersubtype A/G circulating recombinant form CRF02. The assays under ...comparison were Bayer Versant HIV-1 RNA, version 3.0; Roche Amplicor HIV-1 Monitor, version 1.5 (standard procedure); and Organon Teknika NucliSens HIV-1 RNA QT. Plasma samples from 114 patients infected with CRF02 were tested by the three assays under standard conditions. Although correlation among the assays was high and statistically significant for subtype B and CRF02, in the latter instance, NucliSens measured average viral load values (3.29 ± 0.71 log10 copies/mL) about 4 and >8 times lower than those obtained by Versant (3.90 ± 0.90 log10 copies/mL) and Amplicor (4.22 ± 1.05 log10 copies/mL), respectively. Furthermore, in a statistically significant percentage of CRF02-harboring samples, NucliSens produced viral load values undetectable or 1 log10 lower than those obtained in Versant and Amplicor assays. Altogether, these data underline a low performance of NucliSens in detecting and quantifying viremia in plasma samples harboring the CRF02. These results are potentially important as global distribution of new HIV-1 subtypes is expanding, and recombinant strains, particularly CRF02, are emerging and becoming highly prevalent.
Since the discovery of tubulin as the major component of microtubules over 40 years ago, its diversity of forms has raised a continuum of fundamental questions about its regulation and functions in a ...variety of organisms across phyla. Its high abundance in the brain or in specialized organelles such as cilia has allowed early characterization of this important target for anticancer drugs. However, it was only when matrix-assisted laser desorption ionization and electrospray ionization mass spectrometry technologies became available in the late 1980's that the full complexity of tubulin expression patterns became more obvious. This contributed in a major way to the idea that due to increasing and conserved tubulin heterogeneity during evolution, a tubulin code read by microtubule associated proteins might exist and be of functional significance. We review here the merging of recent genetic and cell biology studies with proteomics to decipher this code and illustrate some of the tubulin proteomic approaches with new data generated in our laboratories.
La perception est le moyen par lequel nous connaissons le monde extérieur. C’est grâce à nos perceptions que nous sommes capables d’interagir avec notre environnement et d’accomplir de nombreuses ...actions du quotidien comme se repérer, se déplacer, reconnaître des objets et autres. Cette perception n’est pas juste passive comme peut l’être une sensation, elle comporte des aspects actifs. En particulier, elle peut être orientée dans un but précis, permettant de filtrer les données pour ne traiter que les plus pertinentes. Si la perception humaine est particulièrement efficace, la perception artificielle, elle, demeure un problème complexe qui se heurte à de nombreuses difficultés. Ainsi, les changements de conditions de perception comme des modifications de l’illumination ou des occultations partielles de l’objet à percevoir doivent pouvoir être gérées efficacement. Pour résoudre ces difficultés, s’inspirer de la perception humaine semble être une piste intéressante. Ce manuscrit propose un système de perception polyvalent et générique reposant sur une stratégie de perception active. Pour ce faire, nous proposons un algorithme Top-Down utilisant un modèle en parties. Le problème de perception est transformé en un problème d’estimation d’un vecteur de caractéristiques. La détection des différentes parties permet de réaliser cette estimation. Le système de perception proposé est un algorithme itératif multi-capteurs. À chaque itération, il sélectionne au mieux, en fonction des objectifs fixés par l’application, la partie à détecter ainsi que les meilleurs capteur et détecteur compatibles. Un réseau bayésien est utilisé pour prendre en compte les événements incertains pouvant survenir lors de ce processus comme la défaillance d’un détecteur ou la non existence potentielle d’une partie donnée. Un processus de focalisation à la fois spatiale et de caractéristiques permet d’améliorer la détection en augmentant le rapport signal sur bruit, en restreignant la zone de recherche pour une partie et en éliminant certains des candidats trouvés. Ce processus de focalisation permet aussi de réduire les temps de calcul et de restreindre l’influence des distracteurs. L’ajout de nouveaux capteurs, détecteurs ou parties se fait simplement. De plus, l’utilisation d’un réseau bayésien permet une grande flexibilité au niveau de la modélisation des événements pris en compte : il est facile de rajouter de nouveaux événements pour obtenir une modélisation plus réaliste. L’algorithme proposé a été utilisé pour plusieurs applications incluant de la reconnaissance d’objets, de l’estimation fine de pose et de la localisation.
Perception is the way by which we know the outside world. Thanks to our perceptions we are able to interact with our environment and to achieve various everyday life actions as locating or moving in an environment, or recognizing objects. Perception is not passive whereas sensations are, it has active components. In particular, perception can be oriented for a specific purpose allowing to filter data and to take care only of the most relevant. If human perception is particularly effective, artificial perception remains a complex problem with a lot of non solved difficulties. For example, changes of perception conditions as modification of illumination or partial occultation of the searched object must be effectively managed. This thesis proposes a system of perception based on a strategy of active perception which can adapt itself to various applications. To do it, we propose an algorithm Top-Down using a part-based model. The problem of perception is transformed into a problem of estimation of a characteristics vector. The detection of the different parts constituting the searched object allows to realize this estimation. The proposed perceptive system is an iterative and multi-sensors algorithm. In every iteration, it selects, at best, according to the application objectives, the part to detect and the best compatible sensor and detector. A bayesian network is used to take into account uncertain events which can arise during this process as detector failure or potential non existing part. A focus process consisting of a spatial focus and of a characteristics focus, improves the detection by restricting the search area, by improving the signal to noise ratio and by eliminating some erroneous candidates. This focus process also allows to reduce computation time and to restrict influence of distractors. Adding a part, a sensor or a detector is simple. Furthermore, the use of a bayesian network allows to be flexible in the events modelisation : it is easy to add new events to obtain a more realistic modelisation. The proposed algorithm has been used for several applications including object’s recognition, fine pose estimation and localization. So, it is multi-purpose and generic.
Antiquité, Moyen Âge, Renaissance, Trente Glorieuses… Les époques structurent notre imaginaire temporel et notre appréhension du présent. Catégorie centrale des sciences humaines et sociales, ...l’époque régit aussi l’expérience ordinaire des acteurs et peut servir de fondement à l’action politique. Elle reste pourtant remarquablement peu interrogée. Au fond, qu’est-ce qu’une époque ? Comment en arrêter les contours ? De quoi est-on contemporain ? Et que produisent les tentatives de périodisation sur notre rapport au temps et à l’histoire ? C’est à l’étude de ces questionnements qu’est consacré ce numéro de Tracés. À travers l’examen d’objets aussi divers que la naissance du capitalisme, l’historiographie du Moyen Âge, la place des femmes dans la Renaissance, la critique du temps présent dans le théâtre des XVe et XVIe siècles, les révolutions caribéennes de la fin du XVIIIe siècle, la périodisation des relations internationales, le sens du temps à l’ère capitaliste, la crise financière de 2008, ou les époques du futur imaginées par la science-fiction, les différentes contributions de ce numéro viennent chacune éclairer un pan de ce phénomène que nous appelons époque. Ce numéro montre ainsi la pluralité des manières de « faire époque », en s’intéressant aux conditions parfois conflictuelles de la genèse des époques, ainsi qu’aux soubassements épistémologiques et politiques de leurs usages. Antiquity, Middle Ages, Renaissance… Historical epochs structure our imagination and our ways of understanding the present. If epochs are a central category in human and social sciences, they also play a structuring role in the ordinary experience of social actors, and can lead to political action. Yet, epochs remain an understudied phenomenon. What is an epoch ? How to decide where one starts and ends ? What are we the contemporaries of ? And what are the consequences of periodizing attempts on our relationship to time and history ? This special issue of Tracés is precisely dedicated to these questions. The papers gathered in this special issue enlighten the implications of epoch-making through the study of various topics, such as the birth of capitalism, the historiography of Middle Ages, the place of women in the Renaissance, the critique of present time in 15th and 16th centuries’ theater, the Caribbean revolutions at the end of the 18th century, the periodization of international relations, the sense of time in the capitalist epoch, the financial crisis of 2008, or the future epochs depicted by science fiction. Thereby, this special issue shows the multiple ways to conceive an epoch, by studying the conditions of their emergence as well as the epistemological and political implications of their uses.
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