Cytoskeleton abnormalities in axonopathies of unknown aetiology: correlations with morphometry

To determine if specific axonal cytoskeleton abnormalities could be demonstrated in axonopathies without aetiology, nerve biopsies from five controls and nine cases were analyzed by morphometry and immunocytochemistry with anti-neurofilament (NF, subunits L, M, H) and anti-beta tubulin (TUB) antibodies. Morphometry revealed either large fiber atrophy (decrease in large fiber density with increased density in small fibers), degeneration of large fibers (decrease in large fiber density and in total density of fibers) or of all diameter fibers. NF immunostaining density decreased (by 21-89%) only in cases with fiber loss, in parallel to myelinated fiber density as determined by morphometry. On the contrary, the density of fibers labelled for TUB increased significantly in all except two cases by 52-102% over controls. Nevertheless, in these two cases--with a severe loss of fibers--as well as in other cases, the ratio of the density of fibers labelled for TUB and NFL (TUB/NFL) increased by 48-404%. Thus, the total density of myelinated fibers was always inversely correlated with the TUB/NFL ratio. Similar abnormalities have been described only after axotomy; our cases could thus be compared to

The catalog of radial velocity standard stars for the Gaia RVS: status and progress of the observations

A new full-sky catalog of Radial Velocity standard stars is being built for the determination of the Radial Velocity Zero Point of the RVS on board of Gaia. After a careful selection of 1420 candidates matching well defined criteria, we are now observing all of them to verify that they are stable enough over several years to be qualified as reference stars. We present the status of this long-term observing programme on three spectrographs : SOPHIE, NARVAL and CORALIE, complemented by the ELODIE and HARPS archives. Because each instrument has its own zero-point, we observe intensively IAU RV standards and asteroids to homogenize the radial velocity measurements. We can already estimate that ~8% of the candidates have to be rejected because of variations larger than the requested level of 300 m/s.Comment: Proceedings of SF2A2010, S. Boissier, M. Heydari-Malayeri, R. Samadi and D. Valls-Gabaud (eds), 3 pages, 2 figure

Electrode Selection for Noninvasive Fetal Electrocardiogram Extraction using Mutual Information Criteria

International audienceBlind source separation (BSS) techniques have revealed to be promising approaches for the noninvasive extraction of fetal cardiac signals from maternal abdominal recordings. From previous studies, it is now believed that a carefully selected array of electrodes well-placed over the abdomen of a pregnant woman contains the required 'information' for BSS, to extract the complete fetal components. Based on this idea, previous works have involved array recording systems and sensor selection strategies based on the Mutual Information (MI) criterion. In this paper the previous works have been extended, by considering the 3-dimensional aspects of the cardiac electrical activity. The proposed method has been tested on simulated and real maternal abdominal recordings. The results show that the new sensor selection strategy together with the MI criterion, can be effectively used to select the channels containing the most 'information' concerning the fetal ECG components from an array of 72 recordings. The method is hence believed to be useful for the selection of the most informative channels in online applications, considering the different fetal positions and movements

Transmission Properties of the oscillating delta-function potential

We derive an exact expression for the transmission amplitude of a particle moving through a harmonically driven delta-function potential by using the method of continued-fractions within the framework of Floquet theory. We prove that the transmission through this potential as a function of the incident energy presents at most two real zeros, that its poles occur at energies $n\hbar\omega+\varepsilon^*$ ($0<Re(\varepsilon^*)<\hbar\omega$), and that the poles and zeros in the transmission amplitude come in pairs with the distance between the zeros and the poles (and their residue) decreasing with increasing energy of the incident particle. We also show the existence of non-resonant "bands" in the transmission amplitude as a function of the strength of the potential and the driving frequency.Comment: 21 pages, 12 figures, 1 tabl

Affine convex body semigroups

In this paper we present a new kind of semigroups called convex body semigroups which are generated by convex bodies of R^k. They generalize to arbitrary dimension the concept of proportionally modular numerical semigroup of [7]. Several properties of these semigroups are proven. Affine convex body semigroups obtained from circles and polygons of R^2 are characterized. The algorithms for computing minimal system of generators of these semigroups are given. We provide the implementation of some of them

Terahertz master-oscillator power-amplifier quantum cascade lasers

We report on the realization of a monolithically integrated master-oscillator power-amplifier architecture in a terahertz quantum cascade laser (THz-QCL) with a metal-metal waveguide. The master-oscillator section is a first-order distributed feedback (DFB) laser. Instead of using a thick anti-reflection coating, we exploit a diffraction grating together with an absorbing boundary in the power-amplifier section to efficiently extract the laser radiation and suppress the self-lasing in it. The devices demonstrate a stable generation and power amplification of single-mode emission. The amplification factor is about 5, and the output power is approximately twice that of the standard second-order DFB lasers fabricated from the same material. Emission beam pattern with a divergence angle of ∼18 × 40° is achieved. Our work provides an avenue for the realization of single-mode THz-QCLs with high output power and good beam quality

High contrast dual-mode optical and 13C magnetic resonance imaging in diamond particles

Multichannel imaging -- the ability to acquire images of an object through more than one imaging mode simultaneously -- has opened interesting new perspectives in areas ranging from astronomy to medicine. Visible optics and magnetic resonance imaging (MRI) offer complementary advantages of resolution, speed and depth of penetration, and as such would be attractive in combination. In this paper, we take first steps towards marrying together optical and MR imaging in a class of biocompatible particulate materials constructed out of diamond. The particles are endowed with a high density of quantum defects (Nitrogen Vacancy centers) that under optical excitation fluoresce brightly in the visible, but also concurrently electron spin polarize. This allows the hyperpolarization of lattice 13C nuclei to make the particles over three-orders of magnitude brighter than in conventional MRI. Dual-mode optical and MR imaging permits immediate access to improvements in resolution and signal-to-noise especially in scattering environments. We highlight additional benefits in background-free imaging, demonstrating lock-in suppression by factors of 2 and 5 in optical and MR domains respectively. Ultimate limits could approach as much as two orders of magnitude in each domain. Finally, leveraging the ability of optical and MR imaging to simultaneously probe Fourier-reciprocal domains (real and k-space), we elucidate the ability to employ hybrid sub-sampling in both conjugate spaces to vastly accelerate dual-image acquisition, by as much as two orders of magnitude in practically relevant sparse-imaging scenarios. This is accompanied by a reduction in optical power by the same factor. Our work suggests interesting possibilities for the simultaneous optical and low-field MR imaging of targeted diamond nanoparticles

Prioritization of fish communities with a view to conservation and restoration on a large scale European basin, the Loire (France)

The hierarchical organization of important sites for the conservation or the restoration of fish communities is a great challenge for managers, especially because of financial or time constraints. In this perspective, we developed a methodology, which is easy to implement in different locations. Based on the fish assemblage characteristics of the Loire basin (France), we created a synthetic conservation value index including the rarity, the conservation status and the species origin. The relationship between this new synthetic index and the Fish-Based Index allowed us to establish a classification protocol of the sites along the Loire including fish assemblages to be restored or conserved. Sites presenting disturbed fish assemblages, a low rarity index, few threatened species, and a high proportion of non-native species were considered as important for the restoration of fish biodiversity. These sites were found mainly in areas where the assemblages are typical of the bream zone, e.g. with a higher number of eurytopic and limnophilic species. On the contrary, important sites for conservation were defined as having an important conservation potential (high RI, a lot of threatened species, and few nonnatives fish species) and an undisturbed fish assemblage similar to the expected community if habitats are undisturbed. Important sites for conservation were found in the Loire basin’s medium reaches which host assemblages typical for the grayling and the barbell zones, e.g. with a higher number of rheophilic species. The synthetic conservation value index could be adapted and completed with other criteria according to management priorities and capacities

Computer simulation of diffusion processes in tilt spatio-periodic potentials

Нещодавно було показано, що в істотно нерівноважних системах коефіцієнт дифузії може вести себе немонотонно з температурою. Одним із прикладів таких систем з аномальною температурної залежністю є рух броунівських часток в просторово-періодичних структурах. Метою статті було дослідження зміни температурної залежності дифузії в недодемпфованих системах з низьким коефіцієнтом тертя. В роботі методами комп'ютерного моделювання вивчено зміна коефіцієнта дифузії частинок в широкому діапазоні температур в нахилених просторово-періодичних потенціалах для різних значень коефіцієнта тертя. Показано, що дифузія досягає максимуму при певній величині зовнішньої сили. Її значення залежить від величини коефіцієнта тертя. Показано, що на відміну від звичайної залежності Аррениуса, в разі нахиленого періодичного потенціалу, максимальний коефіцієнт дифузії зростає, а не зменшується з пониженням температури експоненціальним чином. Встановлено, що така залежність характерна для всіх недодемпфованих систем. Показано, що для просторово-періодичних структур існує обмежена ділянка сил, в якому спостерігається зростання коефіцієнта дифузії зі зменшенням температури. Це область так званої температурно-аномальної дифузії (ТАД). Визначено ширина і положення області ТАД в залежності від коефіцієнта тертя γ і параметрів системи. Показано, що зі зменшенням γ, ширина області ТАД зменшується пропорційно γ. При цьому коефіцієнт дифузії в області ТАД, навпаки зростає ~γ. Отримані дані про температурно-аномальної дифузії мають важливе значення для різних областей фізики і техніки та відкривають перспективи створення новітніх технологій управління процесами дифузії.It was recently shown that in essentially nonequilibrium systems, the diffusion coefficient can behave nonmonotonically with temperature. One example of such systems with anomalous temperature dependence is the motion of Brownian particles in spatially periodic structures. The aim of the article was to study the change in the temperature dependence of diffusion in underdamped systems with a low coefficient of friction. In this paper, computer simulation methods are used to study the change in the diffusion coefficient of particles in a wide range of temperatures in oblique spatially periodic potentials for different values of the friction coefficient. It is shown that diffusion reaches a maximum at a certain external force. Its value depends on the coefficient of friction. It is shown that, in contrast to the usual Arrhenius dependence, in the case of an inclined periodic potential, the maximum diffusion coefficient increases while temperature is decreasing exponentially. It is established that such a dependence is common to all underdamped systems. It is shown that for spatially periodic structures there is a limited portion of forces in which an increase in the diffusion coefficient while decreasing temperature is observed. This is the area of the so-called temperature-anomalous diffusion (TAD). The width and position of the TAD region are determined depending on the friction coefficient γ and the system parameters. It has been shown that a decrease in γ, width TAD region decreases proportionally γ. In this case, the diffusion coefficient in the TAD region, on the contrary, increases ~γ. The data obtained on the temperature and the anomalous diffusion are important for various fields of physics and engineering, and opens new prospects for a diffusion process control technology