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International audience; Pt nanoparticles in a Al2O3 dielectric matrix thin films are elaborated by means of atomic layer deposition. These nanostructured thin films are integrated in vertical and planar test structures in order to assess both their in-plane and out-of-plane electrical properties. A shadow edge evaporation process is used to develop planar devices with electrode separation distances in the range of 30 nm. Both vertical and planar test structures show a Poole–Frenkel conduction mechanism. Low trap energy levels (

Volume is a basic physical property of cells; however, it has been poorly investigated in cell biology so far, mostly because it is difficult to measure it precisely. Recently, large efforts were made to experimentally measure mammalian cell size and used mass, density, or volume as proxies for cell size. Here, we describe a method enabling cell volume measurements for single living cells. The method is based on the principle of fluorescent dye exclusion and can be easily implemented in cell biology laboratories. As this method is very versatile, it can be used for cells of different sizes, adherent or growing in suspension, over several cell cycles and is independent of cell shape changes. The method is also compatible with traditional cell biology tools such as epifluorescence imaging or drug treatments.

Volume is a basic physical property of cells; however, it has been poorly investigated in cell biology so far, mostly because it is difficult to measure it precisely. Recently, large efforts were made to experimentally measure mammalian cell size and used mass, density, or volume as proxies for cell size. Here, we describe a method enabling cell volume measurements for single living cells. The method is based on the principle of fluorescent dye exclusion and can be easily implemented in cell biology laboratories. As this method is very versatile, it can be used for cells of different sizes, adherent or growing in suspension, over several cell cycles and is independent of cell shape changes. The method is also compatible with traditional cell biology tools such as epifluorescence imaging or drug treatments.

International audience; Platinum nanoparticle-based strain gauges are elaborated by means of atomic layer deposition on flexible polyimide substrates. Their electro-mechanical response is tested under mechanical bending in both buckling and conformational contact configurations. A maximum gauge factor of 70 is reached at a strain level of 0.5%. Although the exponential dependence of the gauge resistance on strain is attributed to the tunneling effect, it is shown that the majority of the junctions between adjacent Pt nanoparticles are in a short circuit state. Finally, we demonstrate the feasibility of an all-plastic pressure sensor integrating Pt nanoparticle-based strain gauges in a Wheatstone bridge configuration.

Summary Objectives To prospectively study the predictive value (PV) of urine nitrite (NIT) dipstick testing against urine cultures during antibiotic treatment for urinary tract infection (UTI), and other situations, in patients with spinal cord injury (SCI). Methods Inpatients with SCI on intermittent catheterisation (IC) or a Foley indwelling catheter (FC) were included. Urine specimens were collected in patients without symptoms (routine), with symptoms of UTI (suspicion), and on day 4 of a 5-day antibiotic treatment (ATB + 3). Results A total of 157 urine samples were collected in 61 patients: 34 were on IC (95 samples) and 27 on FC (62 samples). The prevalence of asymptomatic bacteriuria in the urine cultures was 89% in routine (70 samples). At ATB + 3, microbiological cure was found in 27/30 specimens (IC group) and 2/6 (FC group). In the routine condition, the specificity and positive PV of the NIT tests was 1.00 and sensitivity 0.63. The negative PV was low in both groups. In suspicion of UTI, the sensitivity was between 0.69 and 0.55, the positive PV was 1.00 and the negative PV 0.00 for both groups. At ATB + 3, the negative PV and sensitivity was 1.00, specificity 0.85 and positive PV 0.43 in the IC group, and in the FC group, specificity was 1.00, negative PV 0.33 and sensitivity 0.00. Conclusion In the SCI population on intermittent or indwelling catheters with high prevalence of bacteriuria, dipstick testing helped assess the eradication of germs during antibiotic treatment, but showed no value in the decision making process for UTI. Level of evidence 3.

We derive scaling laws for the steady spectrum of wind excited waves, neglecting surface tension and taking air and water as inviscid, an approximation valid at large wind speed. Independently of the wind speed, there exists an unique (small) dimensionless parameter ϵ, the ratio of the mass densities of the two fluids (air and water). The smallness of ϵ allows to derive some important average properties of the wave system. The average square slope of the waves is, as observed, a small but not very small quantity, because it is of order |ln(ϵ 2)|-1. This supports the often used assumption of small nonlinearity in the wave-wave interaction. We introduce an equation to be satisfied by the two-point correlation of the height fluctuations. Lastly we reconsider the formation of swell, that is the relationship between the randomness of waves and the observation of quasi monochromatic water waves.

A small population of Alpine marmots was introduced near the top of the Mezenc Massif (France) in 1980 and reinforced 7 times until 1991. An annual monitoring was performed since 1988. It took 12 years to the population size to reach the number of marmots released. Afterwards the population doubled every 7 years, despite several population crashes (in 1997 and 2001). The currently censused 492 marmots were distributed into 86 sites on an area of about 200 km2 in 2007. A Multiple Correspondence Analysis of demographic and environmental parameters of each site showed that marmots preferred, these last years, anthropogenic sites (meadows, dry stone walls, elevation under 1200 m) where reproduction rate was highest. Thus, marmots are now competing with farmers for space. In the same time, tourism increased strongly, especially tourism related to marmot spotting. The interactions between the presence of marmots in this agricultural environment and human activities are described, and their consequences are cons...

Crystallization is one of the key steps for the determination of a protein structure by X-ray diffraction. Microfluidics offers new perspectives for high throughput screening of the crystallization conditions with much reduced cost. In particular, fast prototyping of microfluidic devices by soft-lithography using PDMS has lead to successful demonstrations of both on chip crystallisation and large scale integration. However, PDMS, which is gas permeable, can lead irreversibly to the liquid evaporation in microfluidic chambers. Because of the fragility of the protein crystals, this is clearly undesirable for post-crystallization experiments. We describe here a simple but yet efficient approach to solve this problem, where the PDMS device is placed inside a small tight box having two compartments separated with a thin membrane. Inside the box, a good control of humidity can be achieved and protein crystals could be conserved over a long period without dehydratation.

We report on a micro-fabrication method based on micro-aspiration assisted lithography (MAAL). Unlike nanoimprint lithography where a mould is pressed into a resist layer spin coated on a substrate, MAAL uses aspiration forces to guide the resist material in the mould cavities. By suing this technique, the limit of capillary based lithography techniques has been extended. Double layer PDMS moulds were fabricated using multi-layer soft-lithography in which a micro-aspiration network could be introduced close to the pattern layer of the mould. As a result, high resolution patterning could be obtained with a UV curable resist. We also show the results of patterning of a thin layer of PDMS, nano-particles as well as agar gels. We have also provided a semi-quantitative analysis in order to understand the limitation of different approaches.

This paper deals with a novel and flexible method for microfluidic device assembling. In general, microfluidic device assembly is obtained by irreversible sealing with anodic, thermal or chemical bonding. Reversible assembly can be obtained by aspiration through a crossing channel network (CCN) between the two pieces of microfluidic device (channels and substrate). In this way, relatively high injection pressure can be achieved in microfluidic channels without leakage. We describe the principle and the fabrication of such PDMS devices and also show two examples of the described assembly method applied to surface functionalization.

Electrocapillary force can be used to displace a mercury droplet confined in microfluidic channels. When the plug is moved into an area of a thin membrane of low Young's module, the surface tension of the confined mercury droplet provides a force to deform the membrane. We show that this effect, together with the electrocapillary force controlled movement, can be used for the actuation of microfluidic elements. We applied this technique to micro valves obtained by using multilayer soft-lithography techniques. Fabrication of integrated microelectrodes as well as single and multiple mercury plugs using microfluidic techniques has also been shown, thereby providing a set of technology for more detailed investigations.

Protein immobilization is of great importance for the development of biosensors, immunoassays and microfluidic devices. In this work, we study the in situ bio-functionalization and cell adhesion in microfluidic channels. A way of covalently linking antibodies on the channel surface while keeping their bio-functionality and its application for efficient cell adhesion were shown. Soft lithography has been used to fabricate simple microfluidic devices and all chemical and biologic materials were injected into microfluidic channels for the in situ bio-functionalization and cell adhesion. Our results show that the established bio-processing protocol significantly enhances the protein immobilization on both glass and poly-dimethylsiloxane surfaces, thereby allowing one to develop a large number of applications.

Thin films of Yttrium Iron Garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system on quartz and Gadolinium Gallium Garnet (GGG) for optical applications or alumina substrates for microwave applications. A post deposition annealing is needed to obtain the crystallization of YIG films and the magnetic properties which are correlated with the magneto-optical properties. Their crystallographic, morphologic and magnetic properties are explored. The variation of Faraday rotation is studied versus the wavelength. For both optical substrates, quartz and GGG, results are comparable with the literature for bulk material. A microwave isolator was realized with YIG thin film on alumina substrate in a coplanar configuration. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ferrites have magnetic properties suitable for electronic applications, especially in the microwave range (circulators and isolators). Hexagonal ferrite, such as barium ferrite (BaFe12O19 or BaM), are of great interest for microwave device applications because of their large resistivity and high permeability at high frequencies. BaM films, 1–10 μm thick, were deposited under optimized conditions by RF magnetron sputtering on alumina and silicon substrates. After deposition, films were amorphous and needed a post-deposition annealing at 800 °C to crystallize and to present magnetic properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that BaM films deposited on alumina and silicon substrates presented a good crystallization, a smooth surface and no cracks. Ba, Fe and O depth profiles obtained by secondary ion mass spectroscopy (SIMS) showed that the films have a good in-depth uniformity. The film residual stress was evaluated using curvature measurements. Whatever the substrate type, the films are in compression after deposition. Upon annealing and crystallization, a tensile stress adds up in relation with crystalline arrangements. Finally, regarding the magnetic properties measured using a vibrating sample magnetometer (VSM), the optimized saturation magnetization of such films reached 500 mT and the coercive force 325 kA/m. These values are close to that of the bulk BaM.

For near the first lasing threshold, we give a detailed derivation of a real order parameter equation for the degenerate optical parametric oscillator with a saturable absorber. For this regime, we study analytically the role of the quasi-homogeneous neutral mode in the pattern formation process. We show that this effect stabilized the hexagonal patterns below the lasing threshold. More importantly, we find numerically that when Turing and Hopf bifurcations interact, a stable moving asymmetric localized structure with a constant transverse velocity is generated. The formation of the moving localized structures is analysed for both the propagation and the mean field models. A quantitative confrontation of the two models is discussed.

An experimental investigation was conducted to determine the thermal behaviour of micro heat pipe (MHP) arrays micromachined in silicon wafers. Two types of MHP arrays were tested, one with triangular channels, 230 μm wide, 170 μm deep, and the other with triangular channels, 500 μm wide, 340 μm deep, coupled with arteries. Both types of arrays were fabricated using an anisotropic etching process. Once fabricated, a plain Si wafer was used to seal the pipe array hermetically. Two working fluids were tested, ethanol and methanol. A polysilicon heater was used to supply the heat input, and cooling water flowing through the condenser was used as a heat sink. Fill charges from 0% up to 66% were tested. The axial temperature variation along the length of the pipe was measured using T-type thermocouples connected to a data acquisition system. The effective thermal conductivity was evaluated using the experimental temperature profiles and 3D thermal modelling. The results show a maximum improvement of 300% in effective thermal conductivity at high heat flux, which demonstrates enhanced heat transfer in a prototype with liquid arteries.

Introduction La scoliose idiopathique de l’adolescent (SIA) est une deformation tridimentionnelle du rachis, d’etiologie inconnue. Nous posons l’hypothese pathogenique suivante : la SIA s’accompagne d’une representation centrale erronee de la verticalite a l’origine d’une adaptation posturale du tronc dans les 3 plans de l’espace. Pour le verifier, nous avons debute une etude dont l’objectif est d’evaluer le sens de la verticalite dans la SIA, a la fois dans ses composantes top down et bottom up . Materiel et methodes Trois types de mesure ont ete realisees : – Verticale visuelle subjective (VVS) realisee en conditions visuelles statique et dynamique (stimulation optocinetique 40°/sec) chez 83 SIA versus 15 controles non scoliotiques ; – Verticale posturale subjective (VPS) chez 12 SIA ; – evaluation de l’image du tronc deforme par le Spinal Appareance Questionnaire (SAQ) chez 19 SIA versus 5 hypercyphoses thoraciques. Resultats Exactement 51,8 % des SIA ont une VVS anormale, surtout en condition visuelle dynamique versus 0 % dans le groupe controle. Les valeurs de VPS dans la SIA sont proches de celles trouvees chez les hemiplegiques pusher (exemple : tilt droit = 8,28°4,05). Les SIA avec une scoliose majeure ont un SAQ significativement deteriore par rapport aux hypercyphoses thoraciques. Discussion–conclusion Un sous-groupe de patients SIA presente une perturbation du sens de la verticalite. Cette anomalie peut etre secondaire a la deformation scoliotique mais peut egalement etre un facteur d’evolutivite de la SIA.

La formation de structures localisees intenses dans le profil transverse du faisceau signal transmis par un oscillateur parametrique degenere (DOPO), presente un regime transitoire de coalescence pendant lequel la taille des domaines correspondants a des solutions de signes opposes s'agrandit selon une loi de puissance t 1/3 .

The ring cavity device with large diffraction path in the free-space of the cavity cannotbe described within the mean-field model. It is shown to generate a large variety of monoconicaland multiconical patterns with wave and/or Turing modes, for anonlinear medium either made of two-level atoms or with a χ (2) crystal.Even in the limit of a single-longitudinal mode operation, monoconical structures can be differentfrom those predicted by the mean-field model. For instance, chaotic localized structures with anatomic medium and square patterns with a DOPO are presented.

A family of circular and striped domain walls with oscillatory tails have been observed with the propagation model for the DOPO that is more general than the mean-field model. The same structures are observed with diffraction inside or outside the cell, showing that diffraction and nonlinearity may be decoupled. They result from the switching of the signal amplitude, from the positive to the negative solution. They are formed for positive and negative signal detunings of order unity, in a wide range of input pump amplitude. A second-order MacLaurin expansion mapping model is found to agree well with the propagation model.

International audience; We present a thermo-resistance based micro-calorimeter using a glass/platinum/PDMS prototyping technology which is more flexible than the existing silicon based technology for lab on a chip device integration. Resistance monitoring and fluid injection techniques are optimized in order to reduce thermal noises and improve the detection sensibility. We used neutralization acid-base reaction to evaluate the device capability in determination of both reagent concentration and reaction enthalpy. We also performed a glucose/glucose oxy-dase enzymatic reaction to illustrate the advantage of using PDMS device for the studies of aerobic reaction.

The hippopotamus (Hippopotamus amphibius) spends more than 12 h a day in the water. Hippos are often submitted to water temperatures that vary with the seasons. We hypothesize that this difference between cool and warm water temperatures leads to variations in behavioural thermoregulation. We recorded the exposure of hippos to sunshine at the beginning and at the end of the dry season. Our results show that (1) sunshine exposure lasted much longer in cool water and (2) sun-bathing occurred during the hottest hours. It is therefore likely that in cool water hippos were cold and expressed an original behaviour of search for heat.

Investigations of the thermal drifts of the resistivity and gauge factors of polysilicon are needed to extend its use as a transducing material for high temperature piezoresistive microsensor applications. Longitudinal gauge factors of LPCVD B-doped and rapid thermal-annealed polysilicon films, patterned onto oxidized silicon using a clamped beam technique, have been measured in the 20–200 °C temperature range as a function of the doping concentration between 8 × 10 18 and 10 20 cm −3 . The gauge factors have been simulated as a function of the B-concentration and the temperature, starting from experimental data for the polysilicon resistivity and literature data for the hole resistivity and the piezoresistive effect in monocrystalline silicon. Only a model involving a significant piezoresistive effect at grain boundaries can adequately fit the temperature dependent gauge factors of polysilicon.

Silicon on insulator (SOI) pressure sensors show potential applications in high temperature environment. However, as a result of thermal mismatch, large stresses usually exist in the composite SiO 2 /Si membranes which would provide an otherwise promising substrate for such sensors. These stresses can significantly influence the long term reliability of such membranes. In this work a high spatial resolution (10 μm 2 ) Raman spectroscopy method has been used to measure the localized stresses over an oxidized membrane, thus yielding stress maps. The method is based on the frequency shift of the Raman line at 520 cm −1 . Shift between 0.05 and 1 cm −1 are observed. A three-dimensional commercially available finite element modeling (FEM) software (ANSYS) has been used to modelize the thermal stress distribution over the complete micromachined bilayer membrane. Its validity has been checked out through optical profilometer deflection measurements. The experimental Raman shifts were compared with those calculated using stresses from FEM and a biaxial stress hypothesis. Finally, the sensitivity of Raman stress mapping method for high temperature SOI pressure sensors is discussed.

At the third order of the order parameter expansion, the system under study is variational, and for some range of parameters, a two-mode structure may occur. Both a square pattern and a 48\ifmmode^\circ\else\textdegree\fi{} rhombic pattern are shown to minimize the free energy, while the numerical simulations of the full equations display only the squares. The expansion at the nontrivial fifth order removes the degeneracy between the two different patterns and predicts squares.

In the absence of environmental cues, a migrating cell performs an isotropic random motion. Recently, the breaking of this isotropy has been observed when cells move in the presence of asymmetric adhesive patterns. However, up to now the mechanisms at work to direct cell migration in such environments remain unknown. Here, we show that a non-adhesive surface with asymmetric micro-geometry consisting of dense arrays of tilted micro-pillars can direct cell motion. Our analysis reveals that most features of cell trajectories, including the bias, can be reproduced by a simple model of active Brownian particle in a ratchet potential, which we suggest originates from a generic elastic interaction of the cell body with the environment. The observed guiding effect, independent of adhesion, is therefore robust and could be used to direct cell migration both in vitro and in vivo., Comment: To appear in PRL. Supplementary Information file available on request

The stability of the 8-fold orientational order quasipattern is studied both analytically and numerically. Close to the intensity threshold, the sequence, that minimizes the free energy, displays structures built up with four, two and one modes, successively, as the linear refractive index decreases. Differently, when increasing the intensity above the threshold, the 8-fold orientational order quasipattern bifurcates to a three mode quasiperiodic pattern, followed by a robust rhombic pattern. A multiconical emission process is invoked to explain the occurrence of the rhombuses.

Near-field patterns with three to fifteen petals set on a single circle are numerically observed in the ring cavity device. Three to six petal daisies result from usual finite size effects. We point out the non-trivial formation of seven to fifteen petal daisies, with a top-hat input, and a small diffusion term that controls this daisy-type pattern formation, preventing the usual hexagonal structure to be formed.

A bounded spatio-temporal period-doubling sequence is shown to occur in the Ahkmanov et al. non-linear interferometer. This happens when the pattern is a rotating 2k-armed spiral. First, all arms are identical and the period is the time required for any arm to rotate by the angle 2 pi /2k. As the control parameter increases, the time trace at some location on the pattern displays period doubling as the arms develop progressively distinct spatial modulations. Period 2 behaviour occurs when the nearest patterns similar to arm 'i' are arms 'i+or-2', period 4 behaviour occurs when arm 'i' has arms 'i+or-4' as its nearest similar neighbours, and so on until period 2k when all arms are distinct and the pattern must complete a full revolution for the time series to repeat. Such a cascade is shown to be qualitatively modelled by a mapping.

Flower-like patterns are numerically investigated when the schematic Rb four-level relevant transition is reduced to the lower two Zeeman sub-levels via the adiabatic elimination of the upper states. These flower-like patterns are the signature of small aspect ratio while typical patterns like squares are displayed in the opposite limit. Depending on the relative weights of diffraction effects and nonlinearities, they display, or not, self-similar shapes in the near and the far field.

A general method is presented for determining the average tensorial components of a physical quantity for a polycrystalline sample with random crystallite orientation, when this tensor is known for a monocrystal. The technique, based on the determination of the rotationally invariant part of the tensor, is very convenient and provides analytical results. Explicit expressions are given for symmetrical 4th rank and 8th rank tensors and are applied to calculate piezoresistive effects in polycrystalline silicon.

The Swift-Hohenberg diffusion-type equation is shown to be the normal form of the purely diffraction-type Ginzburg-Landau equation for the passive and saturable ring cavity in the vicinity of nascent hysteresis.

The structural, electrical, and piezoresistive properties of in situ boron‐doped thin silicon layers deposited by plasma‐enhanced chemical‐vapor deposition at 320 °C on oxidized silicon substrates and subjected to a rapid thermal anneal (1100 °C for 20 s) have been investigated. Macroscopic electrical parameters derived from resistivity and Hall‐effect measurements were compared to microscopic characteristics deduced from optical data to explain the low‐temperature coefficients of resistance measured on this polycrystalline material. Finally, the piezoresistivity gauge factors of these heavily doped layers are discussed in view of their internal stress state and of other structural characteristics.

The formation of multi-petals and multi-spirals is analysed with the help of a generalized dispersion relation, taking advantage of the invariance of the rotation frequency of a pattern. It results in an eigenvalue problem, which allows us to predict the rotation frequency and the radial curvature of the pattern, in good agreement with exact calculations: A stationary pattern is predicted to look like petals, while a uniform rotating pattern is predicted to have some curvature, leading to a spiral shape.

We present numerical simulations of a simplified model for the ring cavity device in the case of round-trip time equal to the atomic radiative lifetime. Real pattern effects are of primordial importance, especially in small systems where the boundary conditions seem the key for the pattern selection. For a plane-wave input, our system displays not only hexagons, as in the mean-field model, but also stationary rolls, squares and octagons with a weakly chaotic structure. All these structures are also obtained in the case of bell-shaped input profile with large aspect ratio; they even appear regular and wonderful, as if boundary effects stabilize them.

The potential locomotor performances of four Saharan species of rodents were tested in laboratory conditions, using three experimental situations. Two questions were investigated: Is each of these species able to use the vertical dimension when it is available? Does each of these species behave efficiently in a new environment? We tested the performances of Acomys cahirinus (Desmarest 1819) and Gerbillus campestris (Le Vaillant 1867) that are found in rocky environments in the wild and of Gerbillus pyramidum (I. Geoffroy 1825) and Meriones shaivi (Rozet 1833), that are found in sandy environments. Climbing performance of the species was tested on a horizontal platform, a thread and a tree-branch. From our data, we concluded that Acomys and G. campestris showed an efficient behaviour in these three tasks. M. shawi and to a lesser extent G. pyramidum were unable to behave efficiently in the test situations.

This work focuses on the properties of 10–15 μm thick barium M-type hexaferrite (BaFe 12 O 19 or BaM) films deposited by non-reactive RF magnetron sputtering on alumina substrates. High deposition rates were achieved through deposition at room temperature and operation at an RF power of 100 W. By varying sputtering gas pressure, the dc magnetic properties were correlated with structural, morphological and compositional properties obtained by X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS), respectively. A deposition pressure of P =3 Pa enables one to reach the best compromise between high deposition rate (0.75 μm/h) and adequate crystallographic, stoichiometric and magnetostatic properties. Finally the gyromagnetic properties at high frequency were assessed through the characterization of coplanar isolator up to 60 GHz. As such, hexaferrite films prepared using this technique may offer opportunities for the next generation of self-biased planar microwave devices.

The attractive properties of coplanar waveguides with or without ferrite thin films are presented in this article.The microwave characteristics are measured from 1 to 55 GHz. Also, analytical calculations and simulations are performed. The influence of ferrite thin film with remanent magnetization in-plane or out-of-plane is studied. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2007–2010, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25393

International audience; The preparation of Yttrium Iron Garnet films (YIG) presenting controlled magnetic properties is of great interest for miniaturization of RF passive components. The present work deals with the integration of YIG ferrite sputtered films for coplanar circulators. These components must work at frequencies above 10GHz, and they must be compatible with mass-production and low-cost process. The YIG films (of thickness 15 μm) are deposited on an alumina substrate by RF magnetron sputtering. Their structural mechanical and magnetic properties in the millimetre wave range are optimised to enable the film's integration. A circulator is fabricated using such prepared film, and its properties in the microwave range are characterised using a network analyzer and a probing system.

The instability threshold characteristics are derived for the ring cavity with passive weakly absorbing two-level atoms cell. Emission of several conical shells is predicted, depending on the optical arrangement, and on the buffer gas pressure. In the case of pure vapor, each conical shell has its own frequency, while all the conical shells display the same frequency in case of large buffer gas pressure.

Wave-breaking is studied analytically first and the results are compared with accurate numerical simulations of 3D wave-breaking. We focus on the time dependence of various quantities becoming singular at the onset of breaking. The power laws derived from general arguments and the singular behavior of solutions of nonlinear hyperbolic differential equations are in excellent agreement with the numerical results. This shows the power of the analysis by methods using generic concepts of nonlinear science.

International audience; The development of telecommunications networks requires low-cost microwave and millimeter waves integrated devices. Among the microwave devices based on the non-reciprocity of ferrites, circulators are the most important. A typical use of circulators is in communication equipment (mobile phone and low power radar detection). Their operation allows to combine emission and detection using the same antenna. This work concerns the characterization of barium hexaferrite sputtered films and the device integration for the development of an integrated circulator working at a frequency of 40 GHz.

Periodic instabilities which occur in the output beam of a ring cavity containing a short cell of passive homogeneously broadened two-level atoms are studied as a function of the atomic detuning and the mode spacing in a high-finesse cavity. The output characteristics are found to be very sensitive to the round-trip time of the light through the cavity and to the refractive index. Conditions for the occurrence of large-amplitude self-oscillation are given in terms of these two parameters. >

International audience

The development of passive devices using a ferrite is a major focus of current research for electronic applications in the microwave range (circulators and isolators). Hexagonal ferrite, such as barium ferrite (BaFe12O19 or BaM), which has a large resistivity and high permeability at high frequencies are indeed of great interest for microwave device applications. In this work we developed an integrated and self-biased coplanar isolator using BaM sputtered films. BaM films, 1-36 mum thick, were deposited under optimized conditions by radio frequency magnetron sputtering on alumina substrates. The films were crystallized using a 800degC thermal annealing. Isolators were then realized using patterning of coplanar waveguides (CPW) with standard lift-off technique. The slots and the central width were 300 mum wide and gold was used for the conductor lines. We evaluated the influence of various parameters on the device performances: the magnetic film's thickness, the positioning of the magnetic film (CPW deposited onto the magnetic film or directly on the substrate), the CPW metallic thickness and the polarizing field. As standard design, the CPW were deposited on the top of the magnetic film. At the remanent magnetization (no polarizing field applied), the transmission coefficients then showed a non reciprocal effect, which reached 5.4 dB per cm of line length at 50 GHz for a 26.5 mum thick BaM film. Both the insertion losses and the non-reciprocal effect measured increased with the magnetic film thickness with a saturation effect. In the second design where the CPW is deposited directly on the substrate after a selective etching of the BaM film, we measured that the non reciprocal effect reached higher values for lower BaM thicknesses than for the first design and that the insertion losses also decreased. The interaction between the field lines created by the conductors and the magnetic film was indeed favored in the second case. Finally, we show the tunability of the isolator with the polarizing field.

We report on a new method to handle fluids in microfluidic systems by using both micro- aspiration and PDMS valves. Multilayer soft lithography technique has been used to fabricate microfluidic circuit and micro-aspiration network. We introduced micro-aspiration areas to locally create vacuum in the microfluidic network. The induced pressure differences can drive confined liquid into motion. This allowed us to fill chambers, form droplets and displace droplets in channels without any other external injection apparatus. We describe the principle and the operation of this method. Finally, we discuss a possible application of this method in the field of protein crystallization.