A micropillar for cavity optomechanics

We present a new micromechanical resonator designed for cavity optomechanics. We have used a micropillar geometry to obtain a high-frequency mechanical resonance with a low effective mass and a very high quality factor. We have coated a 60-$\mu$m diameter low-loss dielectric mirror on top of the pillar and are planning to use this micromirror as part of a high-finesse Fabry-Perot cavity, to laser cool the resonator down to its quantum ground state and to monitor its quantum position fluctuations by quantum-limited optical interferometry

Mapping the cellular electrophysiology of rat sympathetic preganglionic neurones to their roles in cardiorespiratory reflex integration:A whole cell recording study in situ

Sympathetic preganglionic neurones (SPNs) convey sympathetic activity flowing from the CNS to the periphery to reach the target organs. Although previous in vivo and in vitro cell recording studies have explored their electrophysiological characteristics, it has not been possible to relate these characteristics to their roles in cardiorespiratory reflex integration. We used the working heart–brainstem preparation to make whole cell patch clamp recordings from T3–4 SPNs (n = 98). These SPNs were classified by their distinct responses to activation of the peripheral chemoreflex, diving response and arterial baroreflex, allowing the discrimination of muscle vasoconstrictor-like (MVC(like), 39%) from cutaneous vasoconstrictor-like (CVC(like), 28%) SPNs. The MVC(like) SPNs have higher baseline firing frequencies (2.52 ± 0.33 Hz vs. CVC(like) 1.34 ± 0.17 Hz, P = 0.007). The CVC(like) have longer after-hyperpolarisations (314 ± 36 ms vs. MVC(like) 191 ± 13 ms, P < 0.001) and lower input resistance (346 ± 49  MΩ vs. MVC(like) 496 ± 41 MΩ, P < 0.05). MVC(like) firing was respiratory-modulated with peak discharge in the late inspiratory/early expiratory phase and this activity was generated by both a tonic and respiratory-modulated barrage of synaptic events that were blocked by intrathecal kynurenate. In contrast, the activity of CVC(like) SPNs was underpinned by rhythmical membrane potential oscillations suggestive of gap junctional coupling. Thus, we have related the intrinsic electrophysiological properties of two classes of SPNs in situ to their roles in cardiorespiratory reflex integration and have shown that they deploy different cellular mechanisms that are likely to influence how they integrate and shape the distinctive sympathetic outputs

High-sensitivity optical monitoring of a micro-mechanical resonator with a quantum-limited optomechanical sensor

We experimentally demonstrate the high-sensitivity optical monitoring of a micro-mechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10^-19 m/rootHz level, and cooled the resonator down to 5K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator.Comment: 4 pages, 5 figure

Estudio sistemático, morfométrico y biogeográfico de <i>Blainia gregaria</i> Walcott, trilobite cámbrico medio de la Precordillera argentina

Se reconoce por primera vez en la Precordillera argentina el trilobite Blainia gregaria Walcott, del Cámbrico medio (Series 3). Los ejemplares estudiados fueron hallados en el tramo superior de la Formación La Laja, con litofacies de plataforma carbonática, aflorante en la Precordillera Oriental de San Juan. El presente trabajo se basa en dos perfiles ubicados en el cerro Tres Marías (sierra de Marquesado), y en la quebrada de Zonda (sierra Chica de Zonda). Los trilobites coleccionados están compuestos por 1.202 ejemplares (632 de la quebrada de Zonda y 570 del cerro Tres Marías) integrados por 563 pigidios y 639 cranidios. El estudio biométrico realizado en los especímenes precordilleranos de Blainia gregaria se basó en la colección del cerro Tres Marías (205 cranidios y 365 pigidios), hallada en 22 niveles estratigráficos distribuidos a lo largo de 155m de espesor columnar (15m cuspidales del Miembro Soldano, 100m del Miembro Rivadavia y 40m basales del Miembro Juan Pobre). El análisis morfométrico muestra relaciones bivariables que dan una nube de puntos muy similares, con rectas de regresión únicas, con los coeficientes de correlación bajos, que son compatibles con la idea de variabilidad intraespecífica. Se reconocen 6 morfotipos (3 cranidios y 3 pigidios) que aparecen juntos en la misma colección. Esto evidencia que es una especie extraordinariamente polimórfica, y nos lleva a proponer una extensa lista sinonímica con más de 30 especies de América del Norte, anteriormente agrupadas en los géneros Blainia Walcott y Glyphaspis Poulsen. La distribución biogeográfica de Blainia gregaria, así redefinida, muestra que esta especie poseía una amplia tolerancia ecológica a los diversos ambientes de las plataformas carbonáticas que rodeaban a Laurentia durante el Cámbrico medio. Su presencia en Precordillera es una evidencia de la estrecha relación que tiene el Terrane Precordillera con Laurentia.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorFacultad de Ciencias Naturales y Muse

Radiation-pressure cooling and optomechanical instability of a micro-mirror

Recent experimental progress in table-top experiments or gravitational-wave interferometers has enlightened the unique displacement sensitivity offered by optical interferometry. As the mirrors move in response to radiation pressure, higher power operation, though crucial for further sensitivity enhancement, will however increase quantum effects of radiation pressure, or even jeopardize the stable operation of the detuned cavities proposed for next-generation interferometers. The appearance of such optomechanical instabilities is the result of the nonlinear interplay between the motion of the mirrors and the optical field dynamics. In a detuned cavity indeed, the displacements of the mirror are coupled to intensity fluctuations, which modifies the effective dynamics of the mirror. Such "optical spring" effects have already been demonstrated on the mechanical damping of an electromagnetic waveguide with a moving wall, on the resonance frequency of a specially designed flexure oscillator, and through the optomechanical instability of a silica micro-toroidal resonator. We present here an experiment where a micro-mechanical resonator is used as a mirror in a very high-finesse optical cavity and its displacements monitored with an unprecedented sensitivity. By detuning the cavity, we have observed a drastic cooling of the micro-resonator by intracavity radiation pressure, down to an effective temperature of 10 K. We have also obtained an efficient heating for an opposite detuning, up to the observation of a radiation-pressure induced instability of the resonator. Further experimental progress and cryogenic operation may lead to the experimental observation of the quantum ground state of a mechanical resonator, either by passive or active cooling techniques

Comparison of Bundle and Classical Column Generation

An updated version of this paper has appeared in : Math. Program., Ser. A, 2006 DOI 10.1007/s10107-006-0079-zWhen a column generation approach is applied to decomposable mixed integer programming problems, it is standard to formulate and solve the master problem as a linear program. Seen in the dual space, this results in the algorithm known in the nonlinear programming community as the cutting-plane algorithm of Kelley and Cheney-Goldstein. However, more stable methods with better theoretical convergence rates are known and have been used as alternatives to this standard. One of them is the bundle method; our aim is to illustrate its differences with Kelley's method. In the process we review alternative stabilization techniques used in column generation, comparing them from both primal and dual points of view. Numerical comparaisons are presented for five applications: cutting stock (which includes bin packing), vertex coloring, capacitated vehicle routing, multi-item lot sizing, and traveling salesman

Increased intrinsic excitability of muscle vasoconstrictor preganglionic neurons may contribute to the elevated sympathetic activity in hypertensive rats

Hypertension is associated with pathologically increased sympathetic drive to the vasculature. This has been attributed to increased excitatory drive to sympathetic preganglionic neurons (SPN) from brainstem cardiovascular control centers. However, there is also evidence supporting increased intrinsic excitability of SPN. To test this hypothesis, we made whole cell recordings of muscle vasoconstrictor-like (MVC(like)) SPN in the working-heart brainstem preparation of spontaneously hypertensive (SH) and normotensive Wistar-Kyoto (WKY) rats. The MVC(like) SPN have a higher spontaneous firing frequency in the SH rat (3.85 ± 0.4 vs. 2.44 ± 0.4 Hz in WKY; P = 0.011) with greater respiratory modulation of their activity. The action potentials of SH SPN had smaller, shorter afterhyperpolarizations (AHPs) and showed diminished transient rectification indicating suppression of an A-type potassium conductance (I(A)). We developed mathematical models of the SPN to establish if changes in their intrinsic properties in SH rats could account for their altered firing. Reduction of the maximal conductance density of I(A) by 15–30% changed the excitability and output of the model from the WKY to a SH profile, with increased firing frequency, amplified respiratory modulation, and smaller AHPs. This change in output is predominantly a consequence of altered synaptic integration. Consistent with these in silico predictions, we found that intrathecal 4-aminopyridine (4-AP) increased sympathetic nerve activity, elevated perfusion pressure, and augmented Traube-Hering waves. Our findings indicate that I(A) acts as a powerful filter on incoming synaptic drive to SPN and that its diminution in the SH rat is potentially sufficient to account for the increased sympathetic output underlying hypertension

The burden of cardiovascular diseases in Ethiopia from 1990 to 2017: evidence from the Global Burden of Disease Study

In Ethiopia, evidence on the national burden of cardiovascular diseases (CVDs) is limited. To address this gap, this systematic analysis estimated the burden of CVDs in Ethiopia using the Global Burden of Disease (GBD) 2017 study data. The age-standardized CVD prevalence, disability-adjusted life years (DALYs) and mortality rates in Ethiopia were 5534 (95% uncertainty interval [UI] 5310.09 - 5774.0), 3549.6 (95% UI 3229.0 - 3911.9) and 182.63 (95% UI 165.49 - 203.9) per 100 000 population, respectively. Compared with 1990, the age-standardized CVD prevalence rate in 2017 showed no change. But significant reductions were observed in CVD mortality (54.7%), CVD DALYs (57.7%) and all-cause mortality (53.4%). The top three prevalent CVDs were ischaemic heart disease, rheumatic heart disease and stroke in descending order. The reduction in the mortality rate due to CVDs is slower than for communicable, maternal, neonatal and nutritional disease mortalities. As a result, CVDs are the leading cause of mortality in Ethiopia. These findings urge Ethiopia to consider CVDs as a priority public health problem.publishedVersio

Dynamics of gravity driven three-dimensional thin films on hydrophilic-hydrophobic patterned substrates

We investigate numerically the dynamics of unstable gravity driven three-dimensional thin liquid films on hydrophilic-hydrophobic patterned substrates of longitudinal stripes and checkerboard arrangements. The thin film can be guided preferentially on hydrophilic longitudinal stripes, while fingers develop on adjacent hydrophobic stripes if their width is large enough. On checkerboard patterns, the film fingering occurs on hydrophobic domains, while lateral spreading is favoured on hydrophilic domains, providing a mechanism to tune the growth rate of the film. By means of kinematical arguments, we quantitatively predict the growth rate of the contact line on checkerboard arrangements, providing a first step towards potential techniques that control thin film growth in experimental setups.Comment: 30 pages, 12 figure

Free-space cavity optomechanics in a cryogenic environment

International audienceWe present a free-space optomechanical system operating in the 1-K range. The device is made ofa high mechanical quality factor micropillar with a high-reflectivity optical coating atop, combinedwith an ultra-small radius-of-curvature coupling mirror to form a high-finesse Fabry-Perot cavityembedded in a dilution refrigerator. The cavity environment as well as the cryostat have beendesigned to ensure low vibrations and to preserve micron-level alignment from room temperatur