Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle

The time-frequency uncertainty principle states that the product of the temporal and frequency extents of a signal cannot be smaller than $1/(4\pi)$. We study human ability to simultaneously judge the frequency and the timing of a sound. Our subjects often exceeded the uncertainty limit, sometimes by more than tenfold, mostly through remarkable timing acuity. Our results establish a lower bound for the nonlinearity and complexity of the algorithms employed by our brains in parsing transient sounds, rule out simple "linear filter" models of early auditory processing, and highlight timing acuity as a central feature in auditory object processing.Comment: 4 pages, 2 figures; Accepted at PR

The problem of antenna array calibration for radar applications

The objective of this paper is to present the problem of antenna array calibration for radar applications. In the first part, the nature of the data is described, with special emphasis on their specificity compared to the general antenna situation . The need for array calibration is then analyzed, depending on the signal processing effectively used. Finally, the causes of the perturbations are studied, and a coarse modelization is given .L'objet de cet article est de présenter les problèmes de calibrations d'antennes dans le cas de réseaux d'antennes radar. L'objectif de cette partie est de préciser, dans un premier temps, la nature des données caractéristiques du problème, dans le cadre de l'application radr, en insistant sur leurs spécificités vis-à-vis du problème générique du traitement d'antenne. La nécessité d'une calibration du réseau est analysée, dans une deuxième étape, en fonction de la nature des traitements appliquées aux signaux reçus. Enfin, les causes de perturbation sont analysées dans un dernier paragraphe, et une esquise de leur modélisation est fourni

Movement exploitation and elimination for radar imaging and detection

The relative movement between the radar and the observed targets and background is primarily used by radars to isolate and detect moving targets by Doppler filtering techniques. Movement is also used for imaging targets (radar holography, ISAR) : these techniques take advantage of the movement to analyse the scene, and correct it to allow a correct imaging of the target (focusing) . Radar platform movement is also used for cartogaphy (synthetic aperture) and fast moving targets detection, or canceled for slow targets detection . This article is a survey of methods allowing exploitation, correction, or cancellation of movement in radar, especially for movin g targets imaging and slow moving targets detection with airborne radars . In a first part, radar imaging using radar holography is reviewed an applied to Inverse Synthetic Aperture Radar (ISAR), and a n original technique for automatic focusing is presented . In a second part, after a summary of spectral properties of clutter echoes in airborne radars, ground imaging techniques with fas t and slow moving targets detection are examined, and an original automatic calibration technique on ground echoes is describe d for a receiver with two or more channels . These techniques, relying on a precise analysis and correction of the phase of the received signals, are under evaluation o r implementation on radar demonstrators .Le mouvement relatif entre le porteur radar et le paysage ou les cibles qu'il observe est d'abord utilisé classiquement en radar pour séparer et détecter les cibles mobiles par les techniques de filtrage Doppler. Hormis cet emploi, le mouvement est également utilisé - ou éliminé - en radar pour faire une image de la cible (holographie radar, ISAR) : ces procédés permettent à la fois une utilisation du mouvement pour analyser la scène, et une correction ou régularisation du mouvement pour permettre une imagerie correcte (focalisation). Le mouvement du porteur est également utilisé pour réaliser une cartographie du paysage (antenne synthétique) et détecter les cibles rapides, ou éliminé, pour permettre la détection des cibles lentes. Cet article effectue un survol des méthodes permettant d'exploiter, de corriger, ou d'éliminer le mouvement en radar, en particulier pour l'imagerie de cibles en mouvement et la détection des cibles lentes par radar aéroporté. Dans une première partie, les principes d'imagerie par holographie radar sont d'abord rappelés, puis appliqués à l'imagerie par « radar à antenne synthétique inverse » (Inverse Synthetic Aperture Radar, ISAR), et une procédure originale de focalisation automatique en ISAR est exposée. Dans une deuxième partie, après avoir rappelé les particularités spectrales des échos de fouillis vus par un radar aéroporté, on examine les techniques permettant de réaliser une imagerie du terrain en détectant les cibles rapides ou lentes, et on décrit une procédure originale de calibration automatique sur l'image du terrain pour un récepteur comprenant deux ou plusieurs voies de réception. Ces techniques, reposant sur une analyse fine et une correction de la phase des signaux reçus, sont actuellement en cours d'implantation sur des démonstrateurs radar. Radar, imagerie, holographie, antenne synthétique, détection, calibration, fouillis, clutter, traitement spatio-temporel, Formation de Faisceaux par le Calcul (FFC)

Influence of the molding pressure on the magnetic properties of soft ferrite composite materials

International audienceExperimental studies on the complex susceptibility of soft magnetic composite materials (Ni and Ni-Zn spinels and YIG) in their region of spin resonance (SR) show that the SR frequency is a decreasing function of the magnetic concentration (demagnetising effects) which moreover tends to the natural spin resonance (NSR) frequency of the bulk material much before the unit concentration is reached. We take benefit of this remarkable property to show how powders could advantageously replace sintered materials to measure with no ambiguity (screening effects of domain wall oscillations) the NSR frequencies. Since composite materials are achieved by moulding processes under pressures, particular care of the technological stresses has been taken

Influence of arrays errors on the performances of radar adaptive antenna processing

The purpose of ibis chapter is to present some results concerning the impact of array errors residuals, after calibration of the antenna, on the performances of adoptive array processing in radar applications . Adoptive array processing is a means for detecting targets in presence of jammers, e.g. in presence of spatially coloured noise. The processing concept is recalled, and indexes of performance examined. Some models of array errors are presented concerning for instance, complex gains différences, or transfert function différences, from channel to channel . Two examples illustrate the influence of the various types of error on the processing performancesL'objet de ce chapitre est de présenter quelques élements d'analyse relatifs à l'influence des imperfections de calibration d'antenne sur les performances de traitements de formation de voies adaptives en radar. Ce type de traitement est mis en place pour détecter les cibles en présence de brouillage, ce qui se traduit par une coloration spatiale du bruit de réception. On rappelle dans un premier temps les caractéristiques générales des traitements considérés et les critères de performances examiné

Spin resonance in soft magnetic composite materials : a surprising effect of the magnetic load.

International audienceThe paper shows a successful extension to the high frequencies, namely in the spin resonance regions, of an analytical law firstly proposed to interpret the magnetic properties of soft magnetic composite materials in low fields and in the quasistatic domain. During the first investigations where the frequency did not yet taken into account, it was shown that the effective susceptibility of powder materials was only dependent on three parameters : The magnetic load, the chemical nature of the magnetic compound (through the intrinsic susceptibility) and the internal demagnetizing fields (through the effective shape factor). Dynamic effects were then examined by introducing in the intrinsic susceptibility parameter the dynamic model of Landau and Lifshitz. Experiments carried on soft ferrimagnetic powders (YIG and Ni-Zn spinels) between 10kHz and 20GHz, have led to a total agreement with the analytical law mentioned above

Phase II trial of raltitrexed ('Tomudex') in advanced small-cell lung cancer.

Raltitrexed, a thymidylate synthase inhibitor, was given to 21 patients with advanced small-cell lung cancer, at a dose of 3 mg m(-2) as a 15-min intravenous infusion at 21-day intervals. All of the patients had extensive disease and 17 had received prior therapy. Patients with disease refractory to primary chemotherapy were excluded. Forty-one treatment cycles were given (median two, range one to four). The drug was well tolerated. No objective tumour response was documented. The patients had chemoresistant disease, as shown by a response in only one of ten patients who went on to receive alternative cytotoxic regimens. We conclude that raltitrexed given in this schedule is inactive as second line therapy for small-cell lung cancer

Brain metastases at the time of presentation of non-small cell lung cancer: a multi-centric AERIO analysis of prognostic factors

A multi-centre retrospective study involving 4 French university institutions has been conducted in order to identify routine pre-therapeutic prognostic factors of survival in patients with previously untreated non-small cell lung cancer and brain metastases at the time of presentation. A total of 231 patients were recorded regarding their clinical, radiological and biological characteristics at presentation. The accrual period was January 1991 to December 1998. Prognosis was analysed using both univariate and multivariate (Cox model) statistics. The median survival of the whole population was 28 weeks. Univariate analysis (log-rank), showed that patients affected by one of the following characteristics proved to have a shorter survival in comparison with the opposite status of each variable: male gender, age over 63 years, poor performance status, neurological symptoms, serum neuron-specific enolase (NSE) level higher than 12.5 ng ml−1, high serum alkaline phosphatase level, high serum LDH level and serum sodium level below 132 mmol l−1. In the Cox's model, the following variables were independent determinants of a poor outcome: male gender: hazard ratio (95% confidence interval): 2.29 (1.26–4.16), poor performance status: 1.73 (1.15–2.62), age: 1.02 (1.003–1.043), a high serum NSE level: 1.72 (1.11–2.68), neurological symptoms: 1.63 (1.05–2.54), and a low serum sodium level: 2.99 (1.17–7.62). Apart from 4 prognostic factors shared in common with other stage IV NSCLC patients, whatever the metastatic site (namely sex, age, gender, performance status and serum sodium level) this study discloses 2 determinants specifically resulting from brain metastasis: i.e. the presence of neurological symptoms and a high serum NSE level. The latter factor could be in relationship with the extent of normal brain tissue damage caused by the tumour as has been demonstrated after strokes. Additionally, the observation of a high NSE level as a prognostic determinant in NSCLC might reflect tumour heterogeneity and understimated neuroendocrine differentiation. © 2001 Cancer Research Campaignhttp://www.bjcancer.co

Effect of grain orientation and magnesium doping on β-tricalcium phosphate resorption behavior

The efficiency of calcium phosphate (CaP) bone substitutes can be improved by tuning their resorption rate. The influence of both crystal orientation and ion doping on resorption is here investigated for beta-tricalcium phosphate (β-TCP). Non-doped and Mg-doped (1 and 6 mol%) sintered β-TCP samples were immersed in acidic solution (pH 4.4) to mimic the environmental conditions found underneath active osteoclasts. The surfaces of β-TCP samples were observed after acid-etching and compared to surfaces after osteoclastic resorption assays. β-TCP grains exhibited similar patterns with characteristic intra-crystalline pillars after acid-etching and after cell-mediated resorption. Electron BackScatter Diffraction analyses, coupled with Scanning Electron Microscopy, Inductively Coupled Plasma–Mass Spectrometry and X-Ray Diffraction, demonstrated the influence of both grain orientation and doping on the process and kinetics of resorption. Grains with c-axis nearly perpendicular to the surface were preferentially etched in non-doped β-TCP samples, whereas all grains with simple axis (a, b or c) nearly normal to the surface were etched in 6 mol% Mg-doped samples. In addition, both the dissolution rate and the percentage of etched surface were lower in Mg-doped specimens. Finally, the alignment direction of the intra-crystalline pillars was correlated with the preferential direction for dissolution. Statement of significance: The present work focuses on the resorption behavior of calcium phosphate bioceramics. A simple and cost-effective alternative to osteoclast culture was implemented to identify which material features drive resorption. For the first time, it was demonstrated that crystal orientation, measured by Electron Backscatter Diffraction, is the discriminating factor between grains, which resorbed first, and grains, which resorbed slower. It also elucidated how resorption kinetics can be tuned by doping β-tricalcium phosphate with ions of interest. Doping with magnesium impacted lattice parameters. Therefore, the crystal orientations, which preferentially resorbed, changed, explaining the solubility decrease. These important findings pave the way for the design of optimized bone graft substitutes with tailored resorption kinetics