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By long and intense study I finally found that if the motions of the other planets are correlated with the orbiting of the Earth, not only do their phenomena follow therefrom but also the order and size of all planets and spheres, and Heaven itself is so linked together that in no portion of it can anything be shifted without disturbing the remaining parts and the Universe as a whole.

Spintronic neurons that emit sharp voltage spikes are needed for neural-network hardware, for fast data processing with low power consumption. Conventional spintronic neurons, $i.e.$ spin-torque nano-oscillators (STNOs), emit sinusoidal waveforms, though. The authors suggest how to imitate neuron spiking in STNOs in which both magnetic layers are free and thin enough to be switched by current. Simulations show that the chaotic behavior of these frequency-tunable devices can be adjusted by the magnetic stack and current. The proposed spintronic relaxation oscillator is a promising building block for hardware neuromorphic chips, leveraging nonlinear dynamics for computing.

We first report the synthesis of supraparticles with a mean diameter of 130 nm consisting in a compact self-assembly of colloidal CdSe/CdS/ZnS nanocrystals encapsulated in a silica shell. This provides a system with robust optical properties such as a high quantum efficiency, a stable and Poissonian emission at room temperature. Additionally, enhancement of the photoluminescence decay rate through Förster resonance energy transfer is observed.

International audience; In their letter [1], Karpitschka et al. discuss our claim that the predictions of our theoretical description for the spreading of a droplet on a soft solid layer based on a global-dissipation approach [2] differ from the outcomes of Karpitschka et al.'s model based on a local-force-balance analysis [3]. In particular, Karpitschka et al. claim that our conclusion results from a misstep in our calculation. We explain here the motivations behind our approach and why we think that their model is different from ours, the latter being the only one able to reproduce our extensive set of experimental data. Let us state first that we agree with Karpitschka et al. that "models based on energy dissipation or on force balance" should be "equivalent". However, contrary to their claim, the dissipation power P visc due to viscoelastic stresses cannot be transformed into a contour integral in general. In particular, care must be taken when fields such as strains or stresses present jumps in their value. Such a jump occurs in the elastowetting problem, as the sign of the first derivative of the strain field jumps from negative to positive in the vicinity of the contact line. The solid must be divided in two regions A and B separated by a surface Γ that encompasses the contact line and that is normal to the flat elastomer surface. The dissipation P visc in this system reads: P visc = A B σ ij˙ ij d 2 s = ∂A ∂B/Γ σ ij n jui d + Γ [σ ijui ]n j d (1) where the symbol [f ] denotes the jump of f across Γ. The last term in the equation above does not vanish for arbitrary thickness and rheology. Thus, we conclude that the simple form of the divergence theorem on which Eq. 1 in ref. [1] is based cannot be used here. As a final note, we would like to indicate that current work in our group shows that configurational forces contribute to global dissipation besides Newtonian forces. In our paper [2], instead of calculating the full dissipation, we choose a simpler, approximated route. Indeed, we do not enforce Neumann's force balance at the contact line and we hypothesize that dissipation can be represented by a single term (∼ A B σ zx˙ zx d 2 s). Thus, our model is not equivalent to Karpitschka et al.'s. The remaining dissipative term is then calculated under some approximations, as an effective representation of the full dissipation. The resulting formula provides an excellent fit to the experimental data for the dependence of the dynamic contact angle on the thickness of the elastomer layer, indicating that the approximations underlying our description are reasonable. In contrast, Karpitschka et al.'s model does not capture our data. In other words, our results do not support the hypothesis that the Neumann force balance holds at the tip of a moving contact line, as stated in our paper. We note that our model is only one step among many others that remain to build a thorough and sound description of the dynamics of elastowetting. We agree with Karpitschka et al. that work remains to be done to explain the vast amount of observations that has been reported in the literature on the topic of elastowetting.

The income of the scientists in France during the 17th to the middle of the 19th century is reviewed and compared to the cost of their instruments. Only a small number of scientists received enough public money to be able to do full-time research; this number increased substantially after the Revolution. Most scientists had to have other sources of income, in particular to be able to purchase their instruments. Large research projects, generally decided and financed by the Academy of Sciences, took place during this period, requiring collaborative interdisciplinary efforts and a considerable logistics: they anticipate our present cooperative programs and giant research facilities.

We study the relationship between the mid-IR (5-18 $\mu$m) emission of late-type galaxies and various other star formation tracers in order to investigate the nature of the dust heating sources in this spectral domain. The analysis is carried out using a sample of 123 normal, late-type, nearby galaxies with available data at several frequencies. The mid-IR luminosity (normalized to the H-band luminosity) correlates better with the far-IR luminosity than with more direct tracers of the young stellar population such as the H$\alpha$ and the UV luminosity. The comparison of resolved images reveals a remarkable similarity in the H$\alpha$ and mid-IR morphologies, with prominent HII regions at both frequencies. The mid-IR images, however, show in addition a diffuse emission not associated with HII regions nor with the diffuse H$\alpha$ emission. This evidence indicates that the stellar population responsible for the heating of dust emitting in the mid-IR is similar to that heating big grains emitting in the far-IR, including relatively evolved stars responsible for the non-ionizing radiation. The scatter in the mid-IR vs. H$\alpha$, UV and far-IR luminosity relation is mostly due to metallicity effects, with metal-poor objects having a lower mid-IR emission per unit star formation rate than metal-rich galaxies. Our analysis indicates that the mid-IR luminosity is not an optimal star formation tracer in normal, late-type galaxies., Comment: accepted for publication on A&A

We present ISOCAM imaging data at 6.75 and 15 mum for 145 galaxies in the Virgo cluster and in the Coma/A1367 supercluster. Of these, 99 form a complete, optically-selected, volume-limited sample including galaxies in the core and in the periphery of the Virgo cluster, suitable for statistical analysis. 34 of the Virgo galaxies were resolved by ISOCAM: for these objects we present mid-IR images, radial light and colour profiles, as well as effective and isophotal radii, surface brightness and light concentration indices. The mid-IR colours of the target galaxies show a weak trend with the H band luminosity, with values of F(6.75 mum)/F(15 mum) = 1 found generally in massive objects (L-H greater than or equal to 10(10) L-H.), and F(6.75 mum)/F(15 mum) less than or equal to 1 in low- mass (L-H less than or equal to 10(10) L-H.) dwarf galaxies. All early-type galaxies (type less than or equal to S0a) have F(6.75 mum)/F(15 mum) greater than or equal to 1, as expected when the mid-IR emission is dominated by the photosphere of the cold stellar population. The mid-IR, near-IR and visible light concentration indices of bright galaxies are tightly correlated with one another, indicating that the spatial distribution of the mid-IR emitting sources is, to the first order, similar to that of the stars.

International audience; Bubbles are dynamic objects that grow and rise or shrink and disappear, often on the scale of seconds. This conflicts with their uses in foams where they serve to modify the properties of the material in which they are embedded. Coating the bubble surface with solid particles has been demonstrated to strongly enhance the foam stability, although the mechanisms for such stabilization remain mysterious. In this paper, we reduce the problem of foam stability to the study of the behavior of a single spherical bubble coated with a monolayer of solid particles. The behavior of this armored bubble is monitored while the ambient pressure around it is varied, in order to simulate the dissolution stress resulting from the surrounding foam. We find that above a critical stress, localized dislocations appear on the armor and lead to a global loss of the mechanical stability. Once these dislocations appear, the armor is unable to prevent the dissolution of the gas into the surrounding liquid, which translates into a continued reduction of the bubble volume, even for a fixed overpressure. The observed route to the armor failure therefore begins from localized dislocations that lead to large-scale deformations of the shell until the bubble completely dissolves. The critical value of the ambient pressure that leads to the failure depends on the bubble radius, with a scaling of ΔPcollapse∝R−1, but does not depend on the particle diameter. These results disagree with the generally used elastic models to describe particle-covered interfaces. Instead, the experimental measurements are accounted for by an original theoretical description that equilibrates the energy gained from the gas dissolution with the capillary energy cost of displacing the individual particles. The model recovers the short-wavelength instability, the scaling of the collapse pressure with bubble radius, and the insensitivity to particle diameter. Finally, we use this new microscopic understanding to predict the aging of particle-stabilized foams, by applying classical Ostwald ripening models. We find that the smallest armored bubbles should fail, as the dissolution stress on these bubbles increases more rapidly than the armor strength. Both the experimental and theoretical results can readily be generalized to more complex particle interactions and shell structures.

Rotating mirror and its mechanism built by Louis Breguet in 1844 for Arago. After a few modifications, it was used by Fizeau in 1850 for the comparison of the velocity of light in air and in water. Bibliotheque de l’Observatoire de Paris

A primitive electric motor built by Froment, mid-nineteenth century. Three pairs of coils (a vertical one is barely visible under the axis) successively attract bars of iron located around the rotor. A commutator in front distributes the current to the coils so that the rotor and the attached flywheel turn in the desired direction. Bibliotheque de l’Observatoire de Paris

International audience; Amorphous polymers in their glass transition regime can be described as a tiling of nanometric domains. Each domain exhibits its own relaxation time, which is distributed over at least four decades. These domains are known as dynamical heterogeneities. This article describes the mechanics of amorphous polymers using a stochastic continuum mechanics model that includes their heterogeneous dynamics. Solving this model both by finite elements and by using a self-consistent method, we find a viscoelastic relaxation spectrum quantitatively similar to an experimentally measured spectrum in a polymer. We show evidence that elastic couplings between domains control the stress relaxation after a step strain and result in a narrowing of the long-time region of the viscoelastic spectrum (as compared to that of dynamical heterogeneities).

Spin torque resonance has been used to simultaneously probe the dynamics of a magnetic domain wall and of magnetic domains in a nanostripe magnetic tunnel junction. Due to the large associated resistance variations, we are able to analyze quantitatively the resonant properties of these single nanoscale magnetic objects. In particular, we find that the magnetic damping of both the domains and the domain wall is doubled compared to the damping value of the host magnetic layer. We estimate the contributions to the damping arising from the dipolar couplings between the different layers in the junction and from the intralayer spin pumping effect, and find that they cannot explain the large damping enhancement that we observe. We conclude that the measured increased damping is intrinsic to large amplitudes excitations of spatially localized modes or solitons such as vibrating or propagating domain walls.

We present 12 CO(J= 1-0) line observations of 99 galaxies obtained with the SEST 15 m, the Kitt Peak 12 m and the IRAM 30 m telescopes. The target galaxies were selected from the catalogue of isolated galaxies of Karachentseva (1973). These data are thus representative of the CO properties of isolated late-type galaxies. All objects were observed in their central position, those with large angular sizes were mapped. These new measurements are used to estimate the molecular gas mass of the target galaxies. The molecular gas is on average18% of the atomic gas mass.

Aims. The present high accuracy of stellar positions and proper motions allows us to determine the positional accuracy of old stellar catalogues. This has already been done for the most important catalogues from before the 18th century. Our aim is to extend this study to several 18th century catalogues.Methods. To do this, I studied ten catalogues: those of Flamsteed and Romer, four catalogues of La Caille, and catalogues of Tobias Mayer, Bradley, Piazzi, and Lalande. A comparison with modern data, mostly from Hipparcos, compiled in the Simbad database of the CDS allowed me to determine the position errors of these catalogues. I also compared the stellar visual magnitudes given in eight of these catalogues with photometric V magnitudes.Results. Thanks to novel instruments, the rms positional accuracy improved from thousands to hundreds of arcsec in older catalogues to less than one minute in that of Flamsteed, and to 2−6 arcsec in the other catalogues I examined. These improvements allowed for the first time relatively accurate proper motions to be determined by 19th century astronomers.

Le Verrier: Magnificent and Detestable Astronomer. James Lequeux, translated by Bernard Sheehan, introduction by William Sheehan (Astrophysics and Space Science Library, 397; Springer, New York, 2013). Pp. xvi +337. £117. ISBN 978-1-4614-5564-6.After writing a scientific biography of the celebrated and much-loved astronomer Francois Arago, James Lequeux (in 2009) produced a similar account of the equally celebrated, but much less loved, successor of Arago as Director of the Paris Observatory, Urbain-Jean-Joseph Le Verrier (1811-77). This English version casts a fresh light on Le Verrier - the astronomer who discovered the planet Neptune "at the end of his pen" in September 1846.Regrettably, most English-speaking readers are likely to know of Le Verrier only in the context of the international priority dispute surrounding the discovery of Neptune and whether the Englishman, John Couch Adams, as well as the French astronomer, ought to have been given credit for predicting where the new planet would be found. The inspiring story of the Neptune discovery is covered well in the first two chapters of this book. Le Verrier's long career, however, was full of achievement on many fronts, including astronomical geodesy and meteorology, and this is described with copious illustrations in the remaining chapters. The images in this edition, it must be said, are deployed in a much better way than in the French version.Modem historians customarily avoid being judgemental when dealing with past astronomers, so the book's title is likely to raise eyebrows amongst readers who are unfamiliar with the history of the Paris Observatory. That he was 'detested', however, by a considerable number of those with whom he had dealings was an unfortunate feature of Le Verrier's career and it had a significant impact on what he was able to achieve. In his personal relationships he was often brusque and arrogant. A contemporary quipped, "Le Verrier produces sharp words as naturally as the apple tree bears apples" (p. 131). We read that even a colleague as illustrious as Charles Delaunay, famed for his theory of the Moon's motion, felt oppressed. "Delaunay", observed Leon Foucault, "only thinks of two things: the Moon and Le Verrier. When he is thinking about the Moon, he has a large, expansive face, like the full Moon. On the other hand, if he is thinking of Le Verrier he has the face of a bulldog" (p. 15). At one stage Le Verrier's dictatorial style provoked mass resignations by the staff of the Observatory.Politically, Le Verrier was firmly on the right in French politics, the polar opposite of Arago who had served as provisional head of state during the turbulent events of 1848 and had been instrumental in abolishing slavery in the French colonies. …

Using the Canada-France-Hawaii Telescope we have obtained deep high-resolution CCD images in V and I of a 28'x28' field in the outer disk of M 31 at ~ 116' from the center along the major axis to the south-west, and covering a range of projected galactocentric distance from about 23 to 33 kpc. The field was chosen to correspond with extended HI features recorded near the HI edge of the galaxy. The many tens of thousands of objects detected in this large field have been classified using an automatic algorithm which distinguishes unresolved from resolved structures and provides photometry on them. For the most part the unresolved objects are stars in M 31. The V-I colors of these stars are highly correlated with the column density of HI in the field. Assuming a Galactic extinction law, this yields a minimum extinction/atomic-gas ratio about 1/3 of that in the Solar neighbourhood. The ISM in this outer disk of M 31 therefore contains substantial amounts of dust. We have identified a population of B stars in the field whose distribution is also well correlated with the extended HI distribution. Evidently, star formation is both ongoing and wide spread in the outer disk of M 31. According to the current view of the star formation process, molecular gas is therefore also expected to be present., 24 pages, 15 figures, Accepted for publication in the Astrophysical Journal

We present deep 450 and 850µ m SCUBA images of the nearby spiral galaxy NGC 7331. Using the submillimeter emissivity inferred from COBE observations of Milky Way dust, we convert our SCUBA images into maps of optical depth. The opacity derived in this way is quite low at the visible limit of NGC 7331 (TB

We present ISOCAM images and CVF observations of the centre of the Andromeda Galaxy. The images were taken in the LW1, LW2, LW3 and LW6 filters. They show an elliptical contribution of the stars and the spatial distribution of dust. The dust distribution follows a spiral structure identical to the distribution of absorption at optical wavelengths. The spectrum of the dust as seen from the CVF observations shows only one broad emission band at 11.3 μmwhile other PAH features at 6.2, 7.7 and 8.6 μm are absent or very faint. This seems to correspond to infrared emission of combinations of neutral polycyclic aromatic hydrocarbons.

I review briefly the present understanding of the history of silicate and carbonaceous grains from their formation around stars or in active regions of the interstellar medium to their appearance in objects of the solar system. This review is based mainly on recent observations with the Infrared Space Observatory. Progress has been substantial, but there are still many missing links in the long and complex chain of events which govern the formation, transport, and processing of cosmic grains.

On the basis of new spectroscopic observations of the blue compact dwarf galaxy IZw18 in the narrow spectral range between 4000Å and 4500Å absorption components of Hγ and Hδ lines were discovered. Equivalent widths of Hγ and Hδ lines have been measured. From available data the OB population of IZw18 was analyzed.

28′ x 28′ deep V- and I-band images of the center and of the SE field of M33 have been obtained at the prime focus of the Canada-France-Hawaii 3.6m telescope. They allowed to map separately the young blue stars, the red supergiants, the red giants and the extreme AGB stars. The disk as traced by red giants has a surprisingly sharp edge. The young blue stars trace the spiral structure very well, but the detailed comparison with H I and CO maps does not show a very good correspondence. The simple spiral-shock model of star formation proposed for the South arm of M33 is not confirmed. On the edge of the galaxy, star formation starts at a column density of H I of about 3 x 1020 atom cm−2. The colour-magnitude diagram for the halo stars shows a broadened red giant branch with a mean metallicity [Fe/H] ≃ −1.0. The shape of the red giant branch confirms the distance modulus of 24.82±0.20 for M33.

We have used the 30 m IRAM millimeter radio telescope to search for two low-lying rotational transitions of the CO-H2 dimer in the emission spectra of three Galactic sources and in the absorption spectrum of a low-latitude extragalactic continuum source. We first summarize the structure of this dimer as it can be inferred currently from laboratory infrared spectroscopy. The transitions we have observed and their initial estimated frequencies are the 111-↔000+ line at ~109 GHz and the 110+↔101- line at ~91 GHz. The search targets were the TMC-1 and L134 dark clouds, the L1157 bipolar outflow, and the compact radio continuum source 2013+370. The spectral search covered the frequency ranges from 90.58 to 91.10 GHz and from 108.95 to 109.46 GHz. Several known emission lines were found, including HC3N (12-11), HC3N (10-9), OCS, SO, and HNC, but no other features were seen in the spectra. The rms noise was typically 5 mK per 1 MHz channel (≈ 3 km s-1). Improved laboratory values for the frequencies were obtained after the 30 m observations were made and are also given here for future reference. The frequency of the 111-↔000+ line may now fall outside of our present search range, but the 110+↔101- frequency is likely to be within it. We conclude that the fractional abundance of the CO-H2 dimer with respect to the CO monomer is typically ≤1 × 10-4, if the excitation temperature is at least a few degrees above the cosmic background. This is the most stringent upper limit yet placed on the presence of a dimer in the interstellar medium.

We report observations of emission from molecular clouds in a complex extending ~2 kpc south of 30 Dor in the Large Magellanic Cloud. The observations were taken on the Swedish-ESO Submillimetre Telescope (SEST) as part of the Key Programme: CO in the Magellanic Clouds. This paper presents observations of the emission from the Central and Southern parts of that complex. In both parts, the strongest emission has . This is a factor of to 5 weaker than we would expect for Milky Way GMCs observed at a distance of 50 kpc. In the Central region, the emission is dominated by a 600 pc long, slightly curved feature, which is clearly seen in peak and integrated intensity maps. When we look at this emission in 5 velocity ranges, it breaks into 22 clouds whose sizes and line profiles look like that from Milky Way molecular clouds. The Southern region is clearly separated from the Central region, and its emission can be broken into 5 clouds.

Like all the important primary journals in astronomy, Astronomy & Astrophysics (A&A) is turning to electronic publication. The Board of Directors of A&A has decided on the principle at its last meeting in May 1996, and we are implementing it progressively with the help of our publishing houses, Les Editions de Physique and Springer- Verlag.

We present time-resolved measurements of the displacement of magnetic domain-walls (DWs) driven by vertical spin-polarized currents in track-shaped magnetic tunnel junctions. In these structures we observe very high DW velocities (600 m/s) at current densities below $10^7 A/cm^2$. We show that the efficient spin-transfer torque combined with a short propagation distance allows to avoid the Walker breakdown process, and achieve deterministic, reversible and fast ($\approx$ 1 ns) DW-mediated switching of magnetic tunnel junction elements, which is of great interest to the implementation of fast DW-based spintronic devices.

Formation of Stars from Interstellar Matter Stellar Physics in General Evolution of Isolated Stars Death of Low-Mass Stars Death of High-Mass Stars as Supernovae Close Binaries, Their Evolution Close Binaries as X-ray and Gamma-ray Sources Brown Dwarfs, White Dwarfs, Neutron Stars and Black Holes Stellar Nucleosynthesis Chemical and Photometric Evolution of Galaxies.

We describe a high-resolution, high-sensitivity CO(1-0) survey of a large fraction of the south-west star-forming "ring" 20 kpc in diameter in M31 made with the 14 m FCRAO telescope and its QUARRY receiver array. At the 45'' angular resolution of the telescope, the ring is resolved into giant complexes of molecular gas with typical sizes of a few hundred parsecs and masses in excess to 106 M☉. Most of these delineate a prominent spiral arm coincident with that traced by atomic hydrogen and dust. This arm appears in all respects quite similar to a prominent spiral arm in our Galaxy at about the same Galactic radius: the Carina arm. Closer to the center, a second fainter molecular spiral arm segment with an H I and dust counterpart is also detected. The main OB associations and the UV light define an arm offset from that traced by the gas by about 500 pc. The H II regions are mainly found either along the edge of the prominent gaseous arm which faces the associations, or aligned with the second fainter gaseous arm. They define Baade's arms S4 and S3, respectively.

We present further results of fully-sampled observations in the J =1 ! 0a nd J =2 !1 rotational transitions of 12 CO and 13 CO, obtained with the SEST telescope at 43 00 or 22 00 resolution, toward the Small Magellanic Cloud. These observations concern six molecular clouds with a variety of physical conditions. Maps in the 12 CO(1!0), 12 CO(2!1), and in some cases of 13 CO(1!0) lines are presented, as well as proles of the four lines at the peak positions convolved to the same angular resolution of 43 00 . The line ratio results are interpreted in Paper IV of this

We present $^{12}$CO(J=1--0) line observations of 22 low-luminosity spiral galaxies in the Virgo cluster. These data, together with 244 others available in the literature, allow us to build a large sample that we use to study the molecular gas properties of galaxies spanning a large range of morphological types and luminosities and belonging to different environments (clusters - field). The molecular gas content of the target galaxies is estimated using a luminosity-dependent X = $N(H_2)/I(CO)$ conversion factor that has been calibrated on a sample of nearby galaxies. $X$ spans from $\sim$ 10$^{20}$ mol cm$^{-2}$ (K km s$^{-1})^{-1}$ in giant spirals to $\sim$ 10$^{21}$ mol cm$^{-2}$ (K km s$^{-1})^{-1}$ in dwarf irregulars. The value of the $X$ conversion factor is found consistent with a value derived independently from dust masses estimated from FIR fluxes, with a metallicity-dependent dust to gas ratio. The relationships between X and the UV radiation field (as traced by the $H\alpha+[NII] E.W.$), the metallicity and the H band luminosity are analysed. We show that the molecular gas contained in molecular clouds or complexes is of the order of 15% of the total gas on average whatever the luminosity or the Hubble type of the galaxies. We discuss the relation between the star formation rate and the molecular gas content and estimate the average star formation efficiency of late-type galaxies.

We present a calibration of the massive star formation rate vs. [CII] luminosity relation based on a sample of nearby, late-type galaxies observed with ISO-LWS and imaged in the Halpha+[NII] line. The relation holds for far-IR luminosities 10^8 < L_{FIR} < 10^{10.5} L (solar units). The derived star formation rates have an uncertainty of about a factor of 10. Part of this uncertainty is due to the different mix of contributions to the [CII] emission from the different components of the interstellar medium in individual galaxies, as discussed in an appendix., Accepted for publication on Astronomy & Astrophysics

The goal of spectral synthesis is to determine the characteristics of a stellarpop-ulation (age and Initial Mass function) by comparing its observed spectrum to synthetic spectra built by adding contributions of stars (or star clusters) of various ages. When the population is young, its visible spectrum is dominated by Balmer lines. These lines have rarely been used for spectral synthesis because Balmer lines in emission are superimposed to the corresponding stellar absorption lines if there is gas ionized by the hottest young stars, a very frequent case. Still it is here that the absorption Balmer lines are the most useful. An example of a problem that can be attacked only by observing the Balmer lines is that of the possible existence of a low-mass cutoff in the IMF of an extragalactic starburst. This is a very important problem as it may affect our knowledge of star formation in general and also our ideas about evolution of galaxies. The colors of a young starburst as well as most of its spectral features are relatively unaffected by stars of a few solar masses which contribute little to the integrated luminosity and to the ionization and excitation properties. However, as the Balmer lines are much stronger for those stars than for the more massive, hotter ones, one may hope that the strength of the Balmer lines in the integrated spectrum of the starburst can give information on the presence or absence of those hot stars. It has been suggested by Augarde and Lequeux (1985) that the starburst galaxy Mkr 171 = Arp 299 = NGC 3690/IC 694 contains relatively few stars of a few solar masses as the Balmer lines in absorption seem relatively weak. Separation of the absorption from the emission component of those lines requires a good spectral resolution with a high dynamical range. Modern detectors make this possible. We have thus undertaken a program to study the Balmer lines in absorption in extragalactic starburst galaxies. This program has necessitated a new, systematic calibration of the Balmer lines equivalent widths of 70 well-classified galactic stars from spectral types O3 to G0 and luminosity classes I, III, V obtained with the same instrument and in the same conditions as the extragalactic observations (Cananzi et al.,1993,paper I). The study is limited to the Hδ and Hγ lines as they are easily accessible and less contaminated by emission lines than Hα and Hβ. We present here the model we have computed showing the variation of the equivalent widths of a star cluster as a function of the slope x, the higher mass M up , the lower mass M in f of the IMF for 2 histories of star formation: an instantaneous burst in which all stars are formed at the same time on the ZAMS and subsequently evolve in the HR diagram until 107 years and a constant star formation scenario also lasting up to 107 years. The time step used is 106 years. Because of the non-unicity of the solution inherent to spectral synthesis model, constraints like L Bol , L V, LB, LU, the number of Lyman continuum α photons and the Hβ luminosity (Osterbrock, 1989) have been synthesized as well to compare with what we observe in galaxies (Cananzi et al.,1993: paper II)

We present a time evolution of 1H spin-lattice relaxation rates in the laboratory (1/T(1)) and in the rotating frame (1/T(1rho)) of a synthetic cement paste. The typical results found for both rates allows us to follow the main hydration stages of the cement paste and the refinement of its microporosity. In particular the texturation of the porosity and the structuration of the surface of the material is evidenced.

Living systems are constituted of clusters of monomers which break and stick together at equilibrium. The macroscopic response is calculated. It depends on the aggregates' lifetime and on the response of dead clusters. Levy flight and viscoelastic features which occur in such systems are unified in the same approach.

The relations between the distributions of interstellar gas and young stars in the central parts of the SMC are discussed, based on their distributions over the sky, radial velocities and distances. There are large differences between stars and gas. The existence of two main complexes is confirmed. There is no strong evidence for a distance in depth between these complexes larger than about 10 kpc, although Cepheid observations suggest a large total depth in some regions. Further, more accurate observations of Cepheids, especially of their mean radial velocities, are required for a better understanding of the structure of the SMC.

International audience; The autocorrelation function of the fluorescence intensity of a nanoemitter is measured with the standard Hanbury-Brown and Twiss setup. Time-tagging of the photodetection events during all the experiment has opened new possibilities in terms of post-selection techniques that enable to go beyond the blinking and antibunching characterization. Here, we first present a new method developed to investigate in detail the antibunching of a fluorophore switching between two emitting states. Even if they exhibit the same fluorescence intensity, their respective amount of antibunching can be measured using the gap between their respective decay rates. The method is then applied to a nanoemitter consisting in a colloidal quantum dot coupled to a plasmonic resonator. The relative quantum efficiency of the charged and neutral biexcitons are determined.

We present FUSE spectra of the giant HII region NGC604 in the spiral galaxy M33. Chemical abundances are derived from far-UV absorption lines and are compared to those derived from optical emission lines. We derived the column densities of HI, NI, OI, SiII, PII, ArI, and FeII, fitting the line profiles with either a single component or several components. Our net results, assuming a single component, show that N, O, Si, and Ar are apparently underabundant in the neutral phase by a factor of 10 or more with respect to the ionized phase, while Fe is the same. However, we discuss the possibility that the absorption lines are made of individual unresolved components, and find that only PII, ArI, and FeII lines should not be affected by the presence of hidden saturated components, while NI, OI, and SiII might be much more affected. If N, O, and Si are actually underabundant in the neutral gas of NGC604 with respect to the ionized gas, this would confirm earlier results obtained for the blue compact dwarfs. However, a deeper analysis focused on P, Ar, and Fe mitigates the above conclusion and indicates that the neutral gas and ionized gas could have similar abundances., Comment: Accepted for publication in A&A

We study a kinetically constrained lattice glass model in which continuous local densities are randomly redistributed on neighbouring sites with a kinetic constraint that inhibits the process at high densities, and a random bias accounting for attractive or repulsive interactions. The full steady-state distribution can be computed exactly in any space dimension d. Dynamical heterogeneities are characterized by a length scale that diverges when approaching the critical density. The glassy dynamics of the model can be described as a reaction-diffusion process for the mobile regions. The motion of mobile regions is found to be subdiffusive, for a large range of parameters, due to a self-induced trapping mechanism., 4 pages, 4 figures