An acoustic model to control an experimental slide flute

International audienceWe consider the problem of modeling and control of a slide flute: a kind of recorder without finger holes but ended by a piston to modify the length of the resonator. To control dynamical systems, it is important to elaborate a realistic model, so that control laws can be tested efficiently before they are implemented on real size prototypes. The dynamical model we have elaborated takes into account the coupling effects between the jet and the pipe which is a linear acoustic resonator. The jet is obtained by blowing through a flue channel and formed by flow separation at the flue exit, and finally directed towards a sharp edge, called the labium. A modal analysis is then performed using the linearized boundary conditions to compute the suitable blowing pressure and the suitable pipe length to obtain a desired pitch. This will constitute the "feedforward" part of our control algorithm. The Proportional-Integral feedback term is then elaborated to regulate the system to the desired set point, using the length of the piston measured by an encoder and the blowing pressure measured by a pressure sensor. First experimental results, obtained on a "mechatronic" prototype developed at Mines ParisTech will be presented

An acoustic model for automatic control of a slide flute

International audienceIn this paper, we consider the problem of modeling and control of a slide flute : a kind of recorder without finger holes but which is ended by a piston mechanism to modify the length of the resonator. A previous study has been done (see [3]), but with a very simple boundary condition for the mouth, corresponding to an ideal situation assuming that the acoustic pressure is zero at the entrance of the resonator. In this work, we have taken into account a more realistic model, describing the coupling effects between the jet and the pipe. The jet is obtained by blowing through a flue channel and formed by flow separation at the flue exit, and finally directed towards a sharp edge, called the labium. The resulting structure can then be seen as a nonlinear oscillator coupled with the pipe which is a linear acoustic resonator. The pressure obtained through this model has been compared to the pressure measured on an actual instrument, a recorder closed at its end. A modal analysis is then performed using the linearized boundary conditions which can also be used to compute the suitable blowing pressure and the suitable pipe length to obtain a desired fundamental frequency or equivalently a desired pitch. This will constitute the basis of our control algorithm. A possible musical application of such a device is to build a flue instrument with a pitch independent of the dynamical level

Klebsiella pneumonia strains moderately resistant to ampicillin and carbenicillin: characterization of a new β-lactamase

Klebsiella pneumoniae strain 11-03, moderately resistant to ampicillin and carbenicillin, produces one constitutive β-lactamase with an isoelectric point of 7.10 and a molecular weight of 20,000±500. The enzymatic activity is directed primarily against the penicillins, ampicillin being the best substrate. Some cephalosporins are also hydrolyzed to some extent but the affinity of the enzyme for these antibiotics is low (high Km values). It has not been possible to determine whether the biogenesis of this β-lactamase is mediated by the bacterial chromosome or by a non-transferable plasmid. This β-lactamase appears to be different, on the basis of isoelectricfocusing, from an enzyme produced by the K pneumoniae strain GN422 (Sawal et al, 1973), but similar to the latter in several propertie

High resolution, on-line identification of strains from the Mycobacterium tuberculosis complex based on tandem repeat typing

BACKGROUND: Currently available reference methods for the molecular epidemiology of the Mycobacterium tuberculosis complex either lack sensitivity or are still too tedious and slow for routine application. Recently, tandem repeat typing has emerged as a potential alternative. This report contributes to the development of tandem repeat typing for M. tuberculosis by summarising the existing data, developing additional markers, and setting up a freely accessible, fast, and easy to use, internet-based service for strain identification. RESULTS: A collection of 21 VNTRs incorporating 13 previously described loci and 8 newly evaluated markers was used to genotype 90 strains from the M. tuberculosis complex (M. tuberculosis (64 strains), M. bovis (9 strains including 4 BCG representatives), M. africanum (17 strains)). Eighty-four different genotypes are defined. Clustering analysis shows that the M. africanum strains fall into three main groups, one of which is closer to the M. tuberculosis strains, and an other one is closer to the M. bovis strains. The resulting data has been made freely accessible over the internet to allow direct strain identification queries. CONCLUSIONS: Tandem-repeat typing is a PCR-based assay which may prove to be a powerful complement to the existing epidemiological tools for the M. tuberculosis complex. The number of markers to type depends on the identification precision which is required, so that identification can be achieved quickly at low cost in terms of consumables, technical expertise and equipment

La catastrophe hydrogéologique du 03 octobre 1988 à Nîmes et dans sa région.

Mémoire HS n° 15 - Géologie Alpine Risques naturels dans le Sud-est de la France - Colloque Association des Géologues du Sud-est - Avignon, 19 et 20 octobre 1989Le 3 octobre 1988, la ville de Nimes était victime d'inondations catastrophiques. Après une présentation rapide du site de la ville mettant en évidence ses dangers potentiels au plan hydrogéologique, sont également résumées les principales caractéristiques des phénomènes hydrogéologiques du 3 octobre 1988 en matière de précipitations et de ruissellement. Une analyse statistique du caractère exceptionnel du phénomène, conduite par trois approches différentes, permet de conclure que les risques d'inondations sérieuses de la ville sont relativement importants et qu'ils ont été aggravés par le développement de l'urbanisation

Dexamethasone enhances constitutive androstane receptor expression in human hepatocytes: consequences on cytochrome P450 gene regulation.

ABSTRACT The barbiturate phenobarbital induces the transcription of cytochromes P450 (CYPs) 2B through the constitutive androstane receptor (CAR; NR1I3). CAR is a member of the nuclear receptor family (NR1) mostly expressed in the liver, which heterodimerizes with retinoid X receptor (RXR) and was shown to transactivate both the phenobarbital responsive element module of the human CYP2B6 gene and the CYP3A4 xenobiotic response element. Because previous studies in rodent hepatocyte cultures have shown that the phenobarbital-mediated induction of CYP2B genes is potentiated by glucocorticoids, we examined the role of activated glucocorticoid receptor in this process. We show that submicromolar concentrations of dexamethasone enhance phenobarbital-mediated induction of CYP3A4, CYP2B6, and CYP2C8 mRNA in cultured human hepatocytes. In parallel, we observed that glucocorticoid agonists, such as dexamethasone, prednisolone, or hydrocortisone, specifically increase human car (hCAR) mRNA expression. Accumulation of hCAR mRNA parallels that of tyrosine aminotransferase: both mRNAs reach a maximum at a concentration of 100 nM dexamethasone and are downregulated by concomitant treatment with the glucocorticoid antagonist RU486. Moreover, the effect of dexamethasone on hCAR mRNA accumulation appears to be of transcriptional origin because the addition of protein synthesis inhibitor cycloheximide has no effect, and dexamethasone does not affect the degradation of hCAR mRNA. Furthermore, dexamethasone increases both basal and phenobarbital-mediated nuclear translocation of CAR immunoreactive protein in human hepatocytes. The up-regulation of CAR mRNA and protein in response to dexamethasone explains the synergistic effect of this glucocorticoid on phenobarbital-mediated induction of CYP2B genes and the controversial role of the glucocorticoid receptor on phenobarbital-mediated CYP gene inductions