Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?

The STEREO/WAVES instrument has detected a very large number of intense voltage pulses. We suggest that these events are produced by impact ionisation of nanoparticles striking the spacecraft at a velocity of the order of magnitude of the solar wind speed. Nanoparticles, which are half-way between micron-sized dust and atomic ions, have such a large charge-to-mass ratio that the electric field induced by the solar wind magnetic field accelerates them very efficiently. Since the voltage produced by dust impacts increases very fast with speed, such nanoparticles produce signals as high as do much larger grains of smaller speeds. The flux of 10-nm radius grains inferred in this way is compatible with the interplanetary dust flux model. The present results may represent the first detection of fast nanoparticles in interplanetary space near Earth orbit.Comment: In press in Solar Physics, 13 pages, 5 figure

An Optical Survey for mm-Sized Interstellar Meteoroids

We report high resolution multi-station observations of meteors by the Canadian Automated Meteor Observatory (CAMO) recorded from June 2009 to August 2010. Our survey has a limiting detection magnitude of +5 mag in R-band, equivalent to a limiting meteoroid mass of ~2*E-7 kg. The high metric trajectory accuracy (of the order of 30 m perpendicular to the solution and 200 m along-track) allows us to determine velocities with average uncertainty of < 1.5% in speed and ~0.4 degr in radiant direction. A total of 1739 meteors had measured orbits. The data has been searched for meteors in hyperbolic orbits, which are potentially of interstellar origin. We found 22 potential hyperbolic meteors among our sample, with only two of them having a speed at least three sigma above the hyperbolic limit. For our one year survey we find no clear evidence of interstellar meteoroids at mm-sizes in a weighted time-area product of ~1*E4 km^2*h. Backward integrations performed for these 22 potentially hyperbolic meteors to check for close encounters with planets show no considerable changes in their orbits. Detailed examination leads us to conclude that our few identified events are most likely the result of measurement error. We find an upper limit of f_ISP < 2*E-4/(km^2*h) for the flux of interstellar meteoroids at Earth with a limiting mass of m > 2*E-7 kg.Comment: 15 pages, 2 figures, accepted by Ap

The Effect of Calcium Ions on Mechanosensation and Neuronal Activity in Proprioceptive Neurons

Proprioception of all animals is important in being able to have coordinated locomotion. Stretch activated ion channels (SACs) transduce the mechanical force into electrical signals in the proprioceptive sensory endings. The types of SACs vary among sensory neurons in animals as defined by pharmacological, physiological and molecular identification. The chordotonal organs within insects and crustaceans offer a unique ability to investigate proprioceptive function. The effects of the extracellular environment on neuronal activity, as well as the function of associated SACs are easily accessible and viable in minimal saline for ease in experimentation. The effect of extracellular [Ca2+] on membrane properties which affect voltage-sensitivity of ion channels, threshold of action potentials and SACs can be readily addressed in the chordotonal organ in crab limbs. It is of interest to understand how low extracellular [Ca2+] enhances neural activity considering the SACs in the sensory endings could possibly be Ca2+ channels and that all neural activity is blocked with Mn2+. It is suggested that axonal excitability might be affected independent from the SAC activity due to potential presence of calcium activated potassium channels (K(Ca)) and the ability of Ca2+ to block voltage gated Na+ channels in the axons. Separating the role of Ca2+ on the function of the SACs and the excitability of the axons in the nerves associated with chordotonal organs is addressed. These experiments may aid in understanding the mechanisms of neuronal hyperexcitability during hypocalcemia within mammals

Identification of β-meteoroids from measurements of the dust detector on board the Ulysses spacecraft, Astron

Abstract. We investigate the detection of β-meteoroids (i.e. dust particles that leave the Solar system in unbound orbits from the direction of the Sun) in the data set of the Ulysses dust experiment. Analysis of the detection geometry of the experiment for the time span from launch until the end of 1995 shows that the detection of β-meteoroids is possible during 3 phases of the mission: in the first 100 days in the beginning of the mission in the ecliptic part of the orbit at heliocentric distances smaller than 1.6 AU, during the south polar passage, and at a time interval of approximately 150 days around the north polar passage. For these three intervals we can identify 48 particles in hyperbolic orbits with perihelion distances smaller than about 0.5 AU which may be classified as β-meteoroids. The mass distribution of the detected β-meteoroids covers a relatively small interval in the ecliptic path, but for the high latitude path it shows no significant difference from the mass distribution of other detected particles of presumably interplanetary origin. The flux of β-meteoroids derived from the data amounts to 1.5 ± 0.3 · 10 −4 m −2 s −1 between 1.0 and 1.6 AU in the ecliptic plane, and amounts to 9.0 ± 6.3 · 10 −5 m −2 s −1 between 1.8 and 2.7 AU at solar ecliptic latitudes between 67 ◦ and 79 ◦ during the north polar passage. Key words: inteplanetary medium – meteoroids 1

Le diagnostic biologique du paludisme dans un centre de soins à Port-Harcourt (Nigéria) (étude compraée d'une méthode classique avec une méthode de concentration)

Le diagnostic du paludisme est important quant à la lutte contre cette maladie qui sévit surtout dans les pays en voie de développement. Différentes techniques sont disponibles, mais beaucoup d'entre elles ne sont pas adaptées en raison de leur coûts économiques. Une étude menée au Nigéria sur une période de six semaines utilisant une méthode de frottis classiques et une méthode de concentration permet d'aborder le problème de d'observer un coefficient de concentration entre 10 et 20, ce qui présente un grand avantage dans les infections à très faibles parasitémies. Les parasites observés sur les frottis obtenus par la méthode de concentration, présentent de plus l'avantage de ne pas subir de déformation contrairement à la technique de la goutte épaisse.CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF