Do so-called multivariate filters have better revision properties? An empirical analysis

The output gap plays a crucial role in thinking and actions of many central banks but real time measurements undergo substantial revisions as more data become available (Orphanides (2001), Orphanides and van Norden (forthcoming)). Some central banks augment, such as the Bank of Canada and the Reserve Bank of New Zealand, the Hodrick and Prescott (1997) filter with conditioning structural information to mitigate the impact of revisions to the output gap estimates. In this paper, we use a state space Kalman filter framework to examine whether the augmented (so-called “multivariate filtersâ€) achieve this objective. We find that the multivariate filters are no better than the Hodrick-Prescott filter for real-time NZ data. The addition of structural equations increase the number of signal equations, but at the same time adds more unobserved trend/equilibrium variables to the system. We find that how these additional trends/equilibrium values are treated matters a lot, and they increase the uncertainty around the estimates. In addition, the revisions from these models can be as large as a univariate Hodrick-Prescott filter.output gap, real time, multivariate filters

Orientation computation of an inclined textured plane: accuracy and performances

The aim of this paper is to present one method for computing the orientation of an inclined textured plane with only one view of this plane. Two steps are used for this computation. First we build a local scales map by a wavelets decomposition of the image of the plane. Then we have to do an interpolation of this map by use the theoretical equation of the local scales variation. So we obtain features values which allow us to compute the tilt and the slant angles. After developing the computation technique, we do a theoretical study in order to know the precision of the method. For the tilt angle, the precision is about one degree, but for the slant angle the precision is only about five degrees, if the slant angle is over forty degrees. But, we have to know the camera parameters for computing the slant angle. If there is some errors about these parameters, so the slant angle will be bad. After this study, we build a data base of one hundred images of real textures with different tilt and slant angles. The camera which has been used for acquiring the images has been calibrated. Results on this data base are agree with the theoretical study.Le but de cet article est de présenter une méthode de calcul de l'orientation d'un plan texturé incliné à partir d'une seule vue de ce plan. Cette méthode est constituée de deux étapes. Dans un premier temps on calcule, à partir de l'image initiale, une carte des échelles locales. Ces échelles sont obtenues au moyen d'une décomposition en ondelettes de l'image d'origine. Puis on interpole cette carte des échelles locales par l'équation théorique de leurs variations. On obtient ainsi des paramètres qui permettent de calculer les angles de tilt et de slant, décrivant l'orientation du plan. Pour valider cette démarche, nous avons mené une étude théorique sur la précision qui pouvait être atteinte par une telle méthode. Nous avons pu mettre en évidence que, si la précision sur l'angle de tilt était assez bonne (de l'ordre de 1°), celle sur l'angle de slant n'excédait pas 5°, à condition que cet angle soit suffisamment important (supérieur à 40°). Mais la précision sur l'angle de slant est conditionnée par la connaissance des paramètres de prise de vue. En effet, nous avons mis en évidence que l'utilisation de valeurs erronées des paramètres de la caméra entraînerait une erreur maximum pour un slant entre 40° et 50°, c'est à dire, a priori, là où la méthode est la meilleure. Cette étude théorique a été validée par des expérimentations sur des images de synthèse et sur des images de textures réelles. Une base de données d'une centaine d'images a été constituée, au moyen d'une caméra préalablement calibrée, pour évaluer la qualité des résultats fournis par notre méthode

HIV-1 group P infection: towards a dead-end infection?

HIV/1 group P (HIV-1/P) is the last HIV/1 group discovered and to date, comprises only two strains. To obtain new insights into this divergent group, we screened for new infections by developing specific tools, and analysed phenotypic and genotypic properties of the prototypic strain RBF168. In addition, the follow-up of the unique patient monitored so far, has raised the knowledge of the natural history of this infection and its therapeutic management. We developed an HIV-1/P specific sero-molecular strategy and screened over 29,498 specimen samples. Infectivity and evolution of the gag-30 position, considered as marker of adaptation to human, were explored by successive passages of RBF168 strain onto human PBMCs. Natural history and immuno-virological responses to combined antiretroviral therapy (cART) were analysed based on CD4 counts and plasmatic viral load evolution. No new infection was detected. Infectivity of RBF168 was found lower, relative to other main HIV groups and the conservative methionine found in the gag-30 position revealed a lack of adaptation to human. The follow-up of the patient during the five-year ART-free period, showed a relative stability of CD4 cell count with a mean of 326 mm. Initiation of cART led to rapid RNA undetectability with a significant increase of CD4, reaching 687 mm after 8 years. Our results showed that HIV-1/P strains remain extremely rare and could be less adapted and pathogenic than other HIV strains. These data lead to the hypothesis that HIV-1/P infection could evolve towards, or even already correspond to, a dead-end infection

Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector

Cosmic rays extensive air showers (EAS) are associated with transient radio emission, which could provide an efficient new detection method of high energy cosmic rays, combining a calorimetric measurement with a high duty cycle. The CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is investigating this phenomenon in the 10^17 eV region. One challenging point is the understanding of the radio emission mechanism. A first observation indicating a linear relation between the electric field produced and the cross product of the shower axis with the geomagnetic field direction has been presented (B. Revenu, this conference). We will present here other strong evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde

Role of nitric oxide synthases in elastase-induced emphysema

Nitric oxide (NO) in combination with superoxide produces peroxynitrites and induces protein nitration, which participates in a number of chronic degenerative diseases. NO is produced at high levels in the human emphysematous lung, but its role in this disease is unknown. The aim of this study was to determine whether the NO synthases contribute to the development of elastase-induced emphysema in mice. nNOS, iNOS, and eNOS were quantified and immunolocalized in the lung after a tracheal instillation of elastase in mice. To determine whether eNOS or iNOS had a role in the development of emphysema, mice bearing a germline deletion of the eNOS and iNOS genes and mice treated with a pharmacological iNOS inhibitor were exposed to elastase. Protein nitration was determined by immunofluorescence, protein oxidation was determined by ELISA. Inflammation and MMP activity were quantified by cell counts, RT-PCR and zymography in bronchoalveolar lavage fluid. Cell proliferation was determined by Ki67 immunostaining. Emphysema was quantified morphometrically. iNOS and eNOS were diffusely upregulated in the lung of elastase-treated mice and a 12-fold increase in the number of 3-nitrotyrosine-expressing cells was observed. Over 80% of these cells were alveolar type 2 cells. In elastase-instilled mice, iNOS inactivation reduced protein nitration and increased protein oxidation but had no effect on inflammation, MMP activity, cell proliferation or the subsequent development of emphysema. eNOS inactivation had no effect. In conclusion, in the elastase-injured lung, iNOS mediates protein nitration in alveolar type 2 cells and alleviates oxidative injury. Neither eNOS nor iNOS are required for the development of elastase-induced emphysema