Academic literature on the topic 'Onde de Rossby'
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Journal articles on the topic "Onde de Rossby"
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Seo, Kyong-Hwan, and Seok-Woo Son. "The Global Atmospheric Circulation Response to Tropical Diabatic Heating Associated with the Madden–Julian Oscillation during Northern Winter." Journal of the Atmospheric Sciences 69, no. 1 (January 1, 2012): 79–96. http://dx.doi.org/10.1175/2011jas3686.1.
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Abstract The detailed dynamical mechanisms of the upper-tropospheric circulation response to the Madden–Julian oscillation (MJO) convection are examined by integrating a primitive equation model. A series of initial-value calculations with the climatological boreal winter background flow forced by the MJO-like thermal forcing successfully capture the key aspects of the observed circulation response to the MJO convection. This suggests that a large fraction of MJO-related circulation anomalies are direct responses to tropical heating in both the tropics and extratropics and can be largely explained by linear dynamics. It is found that MJO-like dipole heatings not only intensify tropical upper-tropospheric anomalies but also weaken them at certain regions because of the interaction between equatorial Kelvin and Rossby waves. The Rossby wave train primarily excited by horizontal divergence of upper-level perturbation flow propagates northeastward and then heads back to the equator. In this way, Rossby wave activity once generated over the subtropical Indian Ocean tends to enhance the equatorial upper-tropospheric anomalies over the tropical Atlantic and West Africa that have already been created by the zonally propagating equatorial Rossby and Kelvin waves. A ray path tracing reveals that a successive downstream development of Rossby wave train mostly results from the large-scale waves with zonal wavenumbers 2–3 in the Northern Hemisphere and 3–5 in the Southern Hemisphere. The sensitivity tests show that the overall results are quite robust. It is found, however, that the detailed circulation response to the MJO-like forcing is somewhat sensitive to the background flow. This suggests that MJO-related circulation anomalies may have nonnegligible long-term variability and change as background flow varies.
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Takaya, Koutarou, and Hisashi Nakamura. "Mechanisms of Intraseasonal Amplification of the Cold Siberian High." Journal of the Atmospheric Sciences 62, no. 12 (December 1, 2005): 4423–40. http://dx.doi.org/10.1175/jas3629.1.
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Abstract Mechanisms of intraseasonal amplification of the Siberian high are investigated on the basis of composite anomaly evolution for its strongest events at each of the grid points over Siberia. At each location, the amplification of the surface high is associated with formation of a blocking ridge in the upper troposphere. Over central and western Siberia, what may be called “wave-train (Atlantic-origin)” type is common, where a blocking ridge forms as a component of a quasi-stationary Rossby wave train propagating across the Eurasian continent. A cold air outbreak follows once anomalous surface cold air reaches the northeastern slope of the Tibetan Plateau. It is found through the potential vorticity (PV) inversion technique that interaction between the upper-level stationary Rossby wave train and preexisting surface cold anomalies is essential for the strong amplification of the surface high. Upper-level PV anomalies associated with the wave train reinforce the cold anticyclonic anomalies at the surface by inducing anomalous cold advection that counteracts the tendency of the thermal anomalies themselves to migrate eastward as surface thermal Rossby waves. The surface cold anomalies thus intensified, in turn, act to induce anomalous vorticity advection aloft that reinforces the blocking ridge and cyclonic anomalies downstream of it that constitute the propagating wave train. The baroclinic development of the anomalies through this vertical coupling is manifested as a significant upward flux of wave activity emanating from the surface cold anomalies, which may be interpreted as dissipative destabilization of the incoming external Rossby waves.
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Page, Michael A. "Separation and free-streamline flows in a rotating fluid at low Rossby number." Journal of Fluid Mechanics 179 (June 1987): 155–77. http://dx.doi.org/10.1017/s0022112087001472.
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The flow past a circular cylinder in a rotating frame is examined when the Rossby number Ro is O(E½), where E is the Ekman number. Previous studies of the configuration have shown that, provided the ratio Ro/E½ is less than a certain critical value, the flow around the cylinder is determined by the classical potential-flow solution. However, once Ro/E½ is greater than that critical value the E1/4 layer on the surface of the cylinder, which is rather like a boundary layer in a high-Reynolds-number non-rotating fluid, can separate from the cylinder and distort the potential flow. In this study the form of the flow once separation has occurred is examined using a method analogous to the Kirchhoff free-streamline theory in a non-rotating fluid. The results are compared with published experimental and numerical data on the flow for various values of Ro/E½.
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David, Trevor J., Ruth Angus, Jason L. Curtis, Jennifer L. van Saders, Isabel L. Colman, Gabriella Contardo, Yuxi Lu, and Joel C. Zinn. "Further Evidence of Modified Spin-down in Sun-like Stars: Pileups in the Temperature–Period Distribution." Astrophysical Journal 933, no. 1 (July 1, 2022): 114. http://dx.doi.org/10.3847/1538-4357/ac6dd3.
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Abstract We combine stellar surface rotation periods determined from NASA’s Kepler mission with spectroscopic temperatures to demonstrate the existence of pileups at the long-period and short-period edges of the temperature–period distribution for main-sequence stars with temperatures exceeding ∼5500 K. The long-period pileup is well described by a curve of constant Rossby number, with a critical value of Rocrit ≲ Ro⊙. The long-period pileup was predicted by van Saders et al. as a consequence of weakened magnetic braking, in which wind-driven angular momentum losses cease once stars reach a critical Rossby number. Stars in the long-period pileup are found to have a wide range of ages (∼2–6 Gyr), meaning that, along the pileup, rotation period is strongly predictive of a star’s surface temperature but weakly predictive of its age. The short-period pileup, which is also well described by a curve of constant Rossby number, is not a prediction of the weakened magnetic braking hypothesis but may instead be related to a phase of slowed surface spin-down due to core-envelope coupling. The same mechanism was proposed by Curtis et al. to explain the overlapping rotation sequences of low-mass members of differently aged open clusters. The relative dearth of stars with intermediate rotation periods between the short- and long-period pileups is also well described by a curve of constant Rossby number, which aligns with the period gap initially discovered by McQuillan et al. in M-type stars. These observations provide further support for the hypothesis that the period gap is due to stellar astrophysics, rather than a nonuniform star formation history in the Kepler field.
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Shaman, Jeffrey, and Eli Tziperman. "The Effect of ENSO on Tibetan Plateau Snow Depth: A Stationary Wave Teleconnection Mechanism and Implications for the South Asian Monsoons." Journal of Climate 18, no. 12 (June 15, 2005): 2067–79. http://dx.doi.org/10.1175/jcli3391.1.
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Abstract An atmospheric stationary wave teleconnection mechanism is proposed to explain how ENSO may affect the Tibetan Plateau snow depth and thereby the south Asian monsoons. Using statistical analysis, the short available record of satellite estimates of snow depth, and ray tracing, it is shown that wintertime ENSO conditions in the central Pacific may produce stationary barotropic Rossby waves in the troposphere with a northeastward group velocity. These waves reflect off the North American jet, turning equatorward, and enter the North African–Asian jet over the eastern Atlantic Ocean. Once there, the waves move with the jet across North Africa, South Asia, the Himalayas, and China. Anomalous increases in upper-tropospheric potential vorticity and increased wintertime snowfall over the Tibetan Plateau are speculated to be associated with these Rossby waves. The increased snowfall produces a larger Tibetan Plateau snowpack, which persists through the spring and summer, and weakens the intensity of the south Asian summer monsoons.
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Mittag, M., J. H. M. M. Schmitt, and K. P. Schröder. "Revisiting the connection between magnetic activity, rotation period, and convective turnover time for main-sequence stars." Astronomy & Astrophysics 618 (October 2018): A48. http://dx.doi.org/10.1051/0004-6361/201833498.
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The connection between stellar rotation, stellar activity, and convective turnover time is revisited with a focus on the sole contribution of magnetic activity to the Ca II H&K emission, the so-called excess flux, and its dimensionless indicator R+HK in relation to other stellar parameters and activity indicators. Our study is based on a sample of 169 main-sequence stars with directly measured Mount Wilson S-indices and rotation periods. The R+HK values are derived from the respective S-indices and related to the rotation periods in various B–V-colour intervals. First, we show that stars with vanishing magnetic activity, i.e. stars whose excess flux index R+HK approaches zero, have a well-defined, colour-dependent rotation period distribution; we also show that this rotation period distribution applies to large samples of cool stars for which rotation periods have recently become available. Second, we use empirical arguments to equate this rotation period distribution with the global convective turnover time, which is an approach that allows us to obtain clear relations between the magnetic activity related excess flux index R+HK, rotation periods, and Rossby numbers. Third, we show that the activity versus Rossby number relations are very similar in the different activity indicators. As a consequence of our study, we emphasize that our Rossby number based on the global convective turnover time approaches but does not exceed unity even for entirely inactive stars. Furthermore, the rotation-activity relations might be universal for different activity indicators once the proper scalings are used.
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Karami, K., P. Braesicke, M. Kunze, U. Langematz, M. Sinnhuber, and S. Versick. "Modelled thermal and dynamical responses of the middle atmosphere to EPP-induced ozone changes." Atmospheric Chemistry and Physics Discussions 15, no. 22 (November 25, 2015): 33283–329. http://dx.doi.org/10.5194/acpd-15-33283-2015.
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Abstract. Energetic particles including protons, electrons and heavier ions, enter the Earth's atmosphere over the polar regions of both hemispheres, where they can greatly disturb the chemical composition of the upper and middle atmosphere and contribute to ozone depletion in the stratosphere and mesosphere. The chemistry–climate general circulation model EMAC is used to investigate the impact of changed ozone concentration due to Energetic Particle Precipitation (EPP) on temperature and wind fields. The results of our simulations show that ozone perturbation is a starting point for a chain of processes resulting in temperature and circulation changes over a wide range of latitudes and altitudes. In both hemispheres, as winter progresses the temperature and wind anomalies move downward with time from the mesosphere/upper stratosphere to the lower stratosphere. In the Northern Hemisphere (NH), once anomalies of temperature and zonal wind reach the lower stratosphere, another signal develops in mesospheric heights and moves downward. Analyses of Eliassen and Palm (EP) flux divergence show that accelerating or decelerating of the stratospheric zonal flow is in harmony with positive and negative anomalies of the EP flux divergences, respectively. This results suggest that the oscillatory mode in the downwelling signal of temperature and zonal wind in our simulations are the consequence of interaction between the resolved waves in the model and the mean stratospheric flow. Therefore, any changes in the EP flux divergence lead to anomalies in the zonal mean zonal wind which in turn feed back on the propagation of Rossby waves from the troposphere to higher altitudes. The analyses of Rossby waves refractive index show that the EPP-induced ozone anomalies are capable of altering the propagation condition of the planetary-scale Rossby waves in both hemispheres. It is also found that while ozone depletion was confined to mesospheric and stratospheric heights, but it is capable to alter Rossby wave propagation down to tropospheric heights. In response to an accelerated polar vortex in the Southern Hemisphere (SH) late wintertime, we found almost two weeks delay in the occurrence of mean dates of Stratospheric Final Warming (SFW). These results suggest that the stratosphere is not merely a passive sink of wave activity from below, but it plays an active role in determining its own budget of wave activity.
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Nakamura, Noboru, Jonathan Falk, and Sandro W. Lubis. "Why Are Stratospheric Sudden Warmings Sudden (and Intermittent)?" Journal of the Atmospheric Sciences 77, no. 3 (February 25, 2020): 943–64. http://dx.doi.org/10.1175/jas-d-19-0249.1.
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Abstract This paper examines the role of wave–mean flow interaction in the onset and suddenness of stratospheric sudden warmings (SSWs). Evidence is presented that SSWs are, on average, a threshold behavior of finite-amplitude Rossby waves arising from the competition between an increasing wave activity A and a decreasing zonal-mean zonal wind u¯. The competition puts a limit to the wave activity flux that a stationary Rossby wave can transmit upward. A rapid, spontaneous vortex breakdown occurs once the upwelling wave activity flux reaches the limit, or equivalently, once u¯ drops below a certain fraction of uREF, a wave-free, reference-state wind inverted from the zonalized quasigeostrophic potential vorticity. This fraction is 0.5 in theory and about 0.3 in reanalyses. We propose r≡u¯/uREF as a local, instantaneous measure of the proximity to vortex breakdown (i.e., preconditioning). The ratio r generally stays above the threshold during strong-vortex winters until a pronounced final warming, whereas during weak-vortex winters it approaches the threshold early in the season, culminating in a precipitous drop in midwinter as SSWs form. The essence of the threshold behavior is captured by a semiempirical 1D model of SSWs, similar to the “traffic jam” model of Nakamura and Huang for atmospheric blocking. This model predicts salient features of SSWs including rapid vortex breakdown and downward migration of the wave activity/zonal wind anomalies, with analytical expressions for the respective time scales. The model’s response to a variety of transient wave forcing and damping is discussed.
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CENEDESE, C., and P. F. LINDEN. "Stability of a buoyancy-driven coastal current at the shelf break." Journal of Fluid Mechanics 452 (February 10, 2002): 97–121. http://dx.doi.org/10.1017/s0022112001006668.
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Buoyancy-driven surface currents were generated in the laboratory by releasing buoyant fluid from a source adjacent to a vertical boundary in a rotating container. Different bottom topographies that simulate both a continental slope and a continental ridge were introduced in the container. The topography modified the flow in comparison with the at bottom case where the current grew in width and depth until it became unstable once to non-axisymmetric disturbances. However, when topography was introduced a second instability of the buoyancy-driven current was observed. The most important parameter describing the flow is the ratio of continental shelf width W to the width L* of the current at the onset of the instability. The values of L* for the first instability, and L*−W for the second instability were not influenced by the topography and were 2–6 times the Rossby radius. Thus, the parameter describing the flow can be expressed as the ratio of the width of the continental shelf to the Rossby radius. When this ratio is larger than 2–6 the second instability was observed on the current front. A continental ridge allowed the disturbance to grow to larger amplitude with formation of eddies and fronts, while a gentle continental slope reduced the growth rate and amplitude of the most unstable mode, when compared to the continental ridge topography. When present, eddies did not separate from the main current, and remained near the shelf break. On the other hand, for the largest values of the Rossby radius the first instability was suppressed and the flow was observed to remain stable. A small but significant variation was found in the wavelength of the first instability, which was smaller for a current over topography than over a flat bottom.
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Parés-Sierra, A. "Remote and local forcing of Rossby wave variability in the midlatitude Pacific Ocean." Geofísica Internacional 30, no. 3 (July 1, 1991): 121–34. http://dx.doi.org/10.22201/igeof.00167169p.1991.30.3.598.
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Un modelo de gravedad reducida se utilizó para investigar la variabilidad de baja frecuencia en el Pacífico Nororiental. El dominio del modelo abarca desde los 18°N hasta los 50°N y desde 155°O hasta la costa oeste de Norteamérica. En un primer experimento, el modelo es forzado por el esfuerzo del viento (COADS). Un segundo experimento consiste en forzar el modelo a través de su frontera austral usando los resultados de un modelo ecuatorial de gravedad reducida. Encontrarnos que los espectros de número de onda-frecuencia calculados a partir de los resultados de nuestro modelo son congruentes con los calculados a partir de observaciones. La mayor parte de la energía de baja frecuencia en el interior del océano modelado consiste en ondas de Rossby propagándose hacia el oeste. El análisis de la respuesta del modelo a los dos forzamientos (forzamiento local por el viento y forzamiento remoto a través de la frontera) nos muestra que ambos mecanismos son capaces de generar el tipo de ondas que determina la variabilidad en el interior del océano. En los resultados del modelo forzado por el viento se observa la existencia de una latitud crítica alrededor de los 35° N. La respuesta del modelo al norte y sur de esta latitud es marcadamente diferente, principalmente en cuanto a las características de propagación de las ondas predominantes: se observa un fuerte componente de decaimiento al norte y de propagación al sur de dicha latitud.
Dissertations / Theses on the topic "Onde de Rossby"
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Ben, Jelloul Mahdi. "Tourbillons et fronts dans l'océan et l'atmosphère : dynamique, stabilité et interactions avec les ondes d'inertie-gravité." Paris 6, 2001. http://www.theses.fr/2001PA066016.
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Vergara, Oscar. "Ventilation de la circulation océanique dans le Pacifique sud-est par les ondes de Rossby et l'activité méso-échelle : téléconnexions d'ENSO." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30356/document.
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L'objectif principal de cette thèse est l'étude de la connexion entre la variabilité dans l'océan Pacifique équatorial et la circulation de subsurface le long des côtes du Pérou et du Chili, à des échelles de temps interannuelles à décennales. Les diagnostiques menés dans ce travail se basent sur un modèle régional océanique. L'accent est mis sur l'interprétation de la propagation verticale de la variabilité dans les couches intermédiaires de l'océan, où l'on trouve une intense zone de minimum d'oxygène (OMZ ; de l'anglais Oxygen Minimum Zone), et la relation de cette propagation verticale avec les processus advectifs et diffusifs. La propagation verticale est diagnostiquée à travers le flux vertical d'énergie associé à la propagation verticale de l'onde de Rossby extratropicale (ETRW; de l'anglais Extra-Tropical Rossby Wave). Aux échelles de temps interannuelles, les résultats montrent que 80% du flux vertical d'énergie dans l'océan Pacifique Sud-Est (SEP ; de l'anglais South-Eastern Pacific) est associé aux événements El Niño extraordinaires. Ce flux d'énergie s'étend vers l'Ouest en suivant les rayons théoriques WKB, avec une pente plus prononcée au fur et à mesure que la latitude augmente. Les analyses du flux d'énergie mettent aussi en évidence l'existence d'une modulation du flux d'énergie interannuel à l'échelle décennale, qui serait liée aux fluctuations décennales et inter-décennales dans le Pacifique équatorial. Une décomposition de la stratification en modes verticaux montre que le flux d'énergie associé à El Niño et aux fluctuations décennales se projette sur les trois premiers modes baroclines, ce qui confirme l'interprétation du flux d'énergie comme la propagation de l'onde de Rossby. Des tests de sensibilité menés avec un modèle linéaire ajusté aux conditions de la simulation montrent que la propagation d'énergie verticale pendant les événements El Niño est aussi impactée par la contribution des modes baroclines supérieurs. La variabilité méridienne/verticale du flux d'énergie vertical met en évidence une atténuation de l'amplitude le long de la trajectoire de l'onde, ce qui est interprété comme un flux diffusif de chaleur induit par la dissipation de l'onde. La variabilité de subsurface de la circulation à l'échelle saisonnière est aussi étudiée dans cette région à travers la ventilation de l'OMZ. Les résultats montrent que la variabilité saisonnière de l'OMZ en dessous de 400 m de profondeur possède des caractéristiques de propagation similaires à celles du flux d'énergie associé à l'ETRW annuelle, ce qui indique que l'ETRWpourrait influencer la variabilité de l'OMZ profonde, du moins à l'échelle saisonnière. Au-dessus de 400 m de profondeur, le processus dominant qui influence la ventilation de l'OMZ à l'échelle saisonnière est le transport d'oxygène par les tourbillons de méso-échelle. Dans ce travail, nous mettons en évidence la nature complexe de la variabilité de la circulation de subsurface dans le SEP. Nous montrons en particulier la connexion entre la circulation sous la thermocline extratropicale et les modes climatiques de variabilité du Pacifique équatorialThe oceanic circulation in the subthermocline of the South Eastern Pacific remains poorly documented although this region is thought to play a key role in the climate variability owed to, in particular, the presence of an extended oxygen minimum zone (OMZ) that intervenes in the carbon and nitrogen cycle. The subthermocline in this region is also largely unmonitored and historical estimates of ocean heat content are mostly limited to the upper 500 m. In this thesis we document various oceanic processes at work in the subthermocline based on a regional modeling approach that is designed to take in account the efficient oceanic teleconnection from the equatorial region to the mid-latitudes, in particular at ENSO (El Niño Southern Oscillation) timescales. The focus is on two aspects: (1) the seasonality of the turbulent flow and its role in modulating the OMZ volume off Peru, and (2) the planetary wave fluxes associated with interannual to decadal timescales. It is first shown that the vertical energy flux at interannual timescales can be interpreted as resulting from the vertical propagation of extra-tropical Rossby waves remotely forced from the equatorial region. This flux primarily results from extreme Eastern Pacific El Niño events, despite that a significant fraction of interannual Sea Surface Temperature (SST) variability in the tropical Pacific is also associated with Central Pacific El Niño events and La Niña events. Vertically propagating energy flux at decadal timescales is also evidenced in the model, which, like for the interannual flux, is marginally impacted by mesoscale activity. On the other hand, the wave energy beams experience a marked dissipation in the deep-ocean ( 2000 m) which is interpreted as resulting from vertical diffusivity. While the oxygen field within the OMZ appears to be influenced by the vertical propagation of isopycnals height anomalies, induced by the seasonal Rossby waves, the seasonality of the OMZ is shown to be dominantly associated with the seasonal change in the eddy flux at its boundaries. Implications of the results for the study of both the low-frequency variability of the OMZ and the Earth's energy budget are discussed
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Gula, Jonathan. "Instabilités agéostrophiques des écoulements baroclines dans l'amosphère et dans l'océan et leur évoluton non-linéaire." Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-00443696.
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Les instabilités agéostrophiques procurent un mécanisme capable de coupler les mouvements équilibrés et non-équilibrés dans l'atmosphère et dans l'océan. Leur étude est effectuée par des analyses de stabilité linéaire dans le modèle de l'eau peu profonde. L'instabilité Rossby-Kelvin (RK) est mise en évidence dans un canal et dans un anneau et des instabilités frontales dans le cas de courants côtiers. Le développement non-linéaire de ces instabilités est étudié par une méthode numérique aux volumes finis et à l'aide d'un modèle méso-échelle. Ces simulations montrent que ces instabilités ont un développement non-linéaire marqué par une croissance à amplitude finie et une saturation. Le déferlement de l'onde de Kelvin conduit à la formation d'une zone localisée de mélange et de dissipation, à l'émission d'ondes d'inertie-gravité et à la réorganisation de l'écoulement moyen qui peut être suivie du développement d'une instabilité secondaire et de la formation et du détachement de vortex.
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Vautard, Robert. "Les echelles de temps de la circulation atmospherique : couplage interne et approches de la parametrisation des modes rapides." Paris 6, 1987. http://www.theses.fr/1987PA066657.
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Les interactions entre les modes lents et les modes rapides de la circulation atmospherique sont examinees a travers deux problemes. Le premier concerne le couplage entre les ondes de gravite et les ondes de rossby. En raison des erreurs d'observation, les modeles de prevision numerique engendrent des ondes de gravite rapides irrealistes. Ces modes doivent donc etre initialement filtres. Le probleme est aborde de maniere theorique par l'etude de l'existence et des proprietes d'une variete invariante de l'espace des phases, appelee "variete lente", qui est sensee contenir l'attracteur du systeme atmospherique. Nous montrons au moyen d'exemples et de theoremes mathematiques qu'une telle variete peut exister, mais que les algorithmes actuels ne convergent pas vers elle. Le deuxieme probleme concerne la generation de la variabilite basse-frequence de l'atmosphere. Nous montrons que la dynamique lente de grande echelle est largement gouvernee par le forcage qu'induisent les transitoires rapides de petite echelle. L'existence de plusieurs structures de grande echelle associees a des regimes de temps, maintenues par les ondes baroclines rapides venant se superposer, est demontree dans le cadre d'un modele quasi-geostrophique. L'alternance entre ces regimes contribue a l'essentiel de la variabilite basse-frequence aux latitudes temperees. Cette notion de "regime de temps", jusqu'ici definie de maniere vague, est abordee de facon quantitative et objective au moyen d'une methode variationnelle statistico-dynamique. Celle-ci permet la reconnaissance de plusieurs types de circulation persistante dont l'une constitue le phenomene de "blocage". Dans ce phenomene, nous montrons que les transitoires ont un effet positif et important pour le maintien de la structure de l'anomalie
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Gula, Jonathan. "Instabilités agéostrophiques des écoulements baroclines dans l'atmosphère et dans l'océan et leur évolution non-linéaire." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00443696.
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Les écoulements atmosphériques et océaniques sont habituellement séparés en une partie lente, proche de l'équilibre géostrophique, et une partie rapide qui interagissent faiblement. Les instabilités agéostrophiques procurent néanmoins un mécanisme capable de coupler les mouvements équilibrés et non-équilibrés. L'étude de tels mécanismes dans cette thèse est d'abord effectuée par des études systématiques de stabilité linéaire dans le modèle de l'eau peu profonde. L'instabilité de Rossby-Kelvin (RK), issue du couplage barocline d'une onde de Rossby (équilibrée) et d'une onde de Kelvin ou de Poincaré (non-équilibrées), est mise en évidence dans un canal. Ces résultats sont étendus à un anneau en géométrie cylindrique et montrent que dans les configurations proches des dispositifs expérimentaux il peut y avoir une compétition entre l'instabilité RK et l'instabilité barocline classique. Les instabilités des courants côtiers, caractérisés par la présence d'un bord vertical et d'un "outcropping", sont ensuite étudiées de manière exhaustive. Les instabilités dues à l'interaction d'un mode frontal et d'une onde de Kelvin (KF) ou d'une onde de Rossby (RF) sont mises en évidence. Le développement non-linéaire de ces instabilités est étudié dans le modèle de l'eau peu profonde par une méthode numérique aux volumes finis et dans un fluide continument stratifié à l'aide d'un modèle méso-échelle. Ces simulations montrent que les instabilités RK et KF ont un développement non-linéaire marqué par une croissance à amplitude finie et une saturation. Le déferlement de l'onde de Kelvin conduit alors à la formation d'un front de Kelvin, zone localisée de mélange et de dissipation, à l'émission d'ondes d'inertie-gravité et à la réorganisation de l'écoulement moyen. Dans le cas des courants côtiers cette réorganisation est suivie du développement d'une instabilité secondaire qui conduit à la formation et au détachement de vortex.
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Leroux, Marie-Dominique. "Intensification rapide des cyclones tropicaux du sud-ouest de l’océan Indien (SWIO) : dynamique interne et influences externes." Thesis, La Réunion, 2012. http://www.theses.fr/2012LARE0014/document.
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Dans un contexte international, la prévision d'intensité des cyclones tropicaux connaît encore de graves déficiences tandis que la prévision de trajectoire de ces phénomènes météorologiques extrêmes s'est grandement améliorée ces dernières décennies. Une source d'erreur pour la prévision d'intensité est le manque de connaissance des processus physiques qui régissent l'évolution de la structure et de l'intensité des cyclones. Cette thèse, proposée dans le cadre des responsabilités du Centre Météorologique Régional Spécialisé (CMRS) de la Réunion et des axes de recherche du LACy et du CNRM, a pour but d'améliorer la prévision numérique et la compréhension des mécanismes de changement de structure et d'intensité des cyclones dans le sud-ouest de l'océan Indien. On observe statistiquement dans le bassin de fréquents déferlements d'ondes de Rossby qui correspondent à une intrusion des talwegs d'altitude depuis les moyennes latitudes vers les régions où évoluent les cyclones. Ces déferlements advectent dans la troposphère tropicale de l'air d'origine stratosphérique à fort tourbillon potentiel (PV). Le cœur d'un cyclone tropical étant caractérisé par un vortex cyclonique de fort PV, il est donc légitime de se demander si de tels talwegs sont capables de « nourrir » un cyclone en déferlant jusqu'à lui, et l'intensifier par superposition de PV. D'un autre côté, l'approche d'un talweg est associée à d'autres facteurs pouvant jouer en défaveur d'une intensification, comme un fort cisaillement vertical de vent. L'étude de processus est réalisée sur le cyclone Dora (2007) avec le modèle opérationnel du CMRS sur le bassin, Aladin-Réunion. Ce modèle hydrostatique à aire limitée bénéficie d'une résolution horizontale de 8 km et de son propre schéma d'assimilation 3Dvar avec bogus de vent. Un tel bogus permet d'affiner la structure du cyclone à l'instant initial en ajoutant des observations de vent déduites d'un profil analytique et des paramètres de structure du cyclone estimés par les images satellites. Des diagnostiques sur les variables thermodynamiques en sortie de modèle montrent que la phase d'intensification rapide de Dora est bien associée à l'advection de tourbillon potentiel (PV) en provenance du talweg. Bien que fortement cisaillé, le système parvient à s'intensifier grâce à la forte inclinaison du talweg qui advecte du PV au cœur du cyclone en 2 temps et à 2 niveaux (haute et moyenne troposphère). Lorsque le talweg est au plus proche du cyclone, il force un processus dynamique interne appelé « cycle de remplacement du mur de l'œil ». On observe une inclinaison et un renforcement des vitesses verticales à l'extérieur du mur de l'œil principal, associé à une accélération de la circulation cyclonique tangentielle par advection de moment angulaire sur toute l'épaisseur de la troposphère dans cette zone annulaire (mis en évidence par les flux d'Eliassen-Palm). Un second maximum de vent relatif apparaît alors et une deuxième phase d'intensification rapide s'ensuit avec la contraction du mur secondaire. Le forçage de processus internes par une influence externe (un talweg) semble donc être le moteur de l'intensification rapide de Dora dans un environnement cisaillé, et potentiellement celui d'autres cyclones dans le bassin qui sont approchés par des talwegs d'altitude. Les prévisionnistes du CMRS sont invités à surveiller les champs de PV de tels systèmes, en attendant que de plus amples diagnostiques soient réalisés avec l'outil d'inversion du tourbillon potentiel développé sur le modèle global ArpègeDespite significant improvements in Tropical Cyclone (TC) track forecasts over the past few decades, anticipating the sudden intensity changes of TCs remains a major operational issue. The main purpose of this thesis is to analyze TC rapid intensification processes in relation with external forcing induced by upper-level troughs originating from the mid-latitudes. The impact of initial storm structure on storm evolution and prediction is also documented. An objective definition for rapid intensification in the southwest Indian Ocean is first proposed. The location and frequency of TC-trough interactions are identified, as well as TC-trough arrangements conducive to TC intensification. An interesting study case, TC Dora (2007), is chosen to run numerical simulations initialized with synthetic TC observations blended in a global analysis. The simulated TC-trough interaction is intricate with potential vorticity (PV) advection from the trough into the TC core at mid and upper levels. Vortex intensification first occurs inside the eyewall and results from PV superposition. Further intensification is associated with a subsequent secondary eyewall formation triggered by external forcing from the trough. The numerical model is able to reproduce the main features associated with outer eyewall spin-up, inner eyewall spin-down, and their effects on vortex intensity changes. Another numerical study examines typhoons in the northwest Pacific and demonstrates the critical role played by initial vortex structure in TC track and intensity prediction. Upgrading the initial specification of a TC inner-core structure in numerical models is recommended for future TC prediction improvements
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Pantillon, Florian. "Transition extra-tropicale d'ouragans en Atlantique Nord et impact sur la prévisibilité d'événements extrêmes en Méditerranée." Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00755220.
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La transition extra-tropicale est la transformation d'un cyclone tropical en cyclone extra-tropical lors de sa migration vers les latitudes moyennes. Au cours de son interaction avec son nouvel environnement barocline, le cyclone peut se réintensifier par des processus dynamiques et diabatiques complexes. Il peut également avoir un impact en aval par le renforcement d'un train d'ondes de Rossby, qui se propage rapidement et dont le déferlement est souvent à l'origine d'événements extrêmes. La complexité des processus dynamiques et diabatiques de la transition extra-tropicale conduit alors à une réduction de la prévisibilité en aval. Les ouragans Florence et Hélène en Atlantique Nord ont ainsi contribué au déclenchement des événements extrêmes de septembre 2006 en Méditerranée, respectivement un épisode de précipitations intenses et un phénomène plus rare, un méditerragan (ouragan méditerranéen). Hélène s'est distinguée de Florence par des processus diabatiques prépondérants au cours de sa réintensification sur un océan plus chaud, ce qui lui a permis de conserver des caractéristiques tropicales. Ses trois réintensifications en trois jours induites par l'étirement de trois filaments de tourbillon potentiel, ajoutées au développement du méditerragan en aval, font d'Hélène un cas exceptionnel. Les deux événements extrêmes en Méditerranée étaient absents de la prévision déterministe à moyen terme. L'incertitude dans la représentation des processus diabatiques a été examinée car ceux-ci contrôlent l'impact des ouragans sur les ondes de Rossby. Pour la première fois, des simulations ont été réalisées avec le modèle Méso-NH sur un grand domaine avec une résolution explicite de la convection profonde, tirant parti de la parallélisation massive du modèle. Une faible sensibilité à la résolution horizontale du modèle a été trouvée dans les précipitations des ouragans, donc dans leur impact sur les ondes de Rossby et sur les événements extrêmes en Méditerranée. La trajectoire d'Hélène a par contre montré une forte sensibilité à sa synchronisation avec le train d'ondes de Rossby, influencée par la résolution horizontale du modèle. Cette forte sensibilité a été retrouvée dans les prévisions d'ensemble du Centre Européen pour la Prévision Météorologique à Moyen Terme, où le développement du méditerragan a requis la synchronisation d'Hélène avec le train d'ondes de Rossby. La perturbation ciblée des conditions initiales autour d'Hélène et du thalweg en amont a suffi à prévoir le méditerragan à une échéance de 108 h dans une simulation Méso-NH. Ces résultats montrent l'impact possible de transitions extra-tropicales en Atlantique Nord, qui surviennent à la même saison que la plupart des épisodes de précipitations intenses en Méditerranée. La réduction de l'incertitude dans la prévision de la transition extra-tropicale est donc un des enjeux de l'amélioration de la prévision d'événements extrêmes d'automne en Méditerranée.
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Pantillon, Florian. "Transition extra-tropicale d'ouragans en Atlantique Nord et impact sur la prévisibilité d'événements extrêmes en Méditerranée." Phd thesis, Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1770/.
Full textAbstract:
La transition extra-tropicale est la transformation d'un cyclone tropical en cyclone extra-tropical lors de sa migration vers les latitudes moyennes. Au cours de son interaction avec son nouvel environnement barocline, le cyclone peut se réintensifier par des processus dynamiques et diabatiques complexes. Il peut également avoir un impact en aval par le renforcement d'un train d'ondes de Rossby, qui se propage rapidement et dont le déferlement est souvent à l'origine d'événements extrêmes. La complexité des processus dynamiques et diabatiques de la transition extra-tropicale conduit alors à une réduction de la prévisibilité en aval. Les ouragans Florence et Hélène en Atlantique Nord ont ainsi contribué au déclenchement des événements extrêmes de septembre 2006 en Méditerranée, respectivement un épisode de précipitations intenses et un phénomène plus rare, un méditerragan (ouragan méditerranéen). Hélène s'est distinguée de Florence par des processus diabatiques prépondérants au cours de sa réintensification sur un océan plus chaud, ce qui lui a permis de conserver des caractéristiques tropicales. Ses trois réintensifications en trois jours induites par l'étirement de trois filaments de tourbillon potentiel, ajoutées au développement du méditerragan en aval, font d'Hélène un cas exceptionnel. Les deux événements extrêmes en Méditerranée étaient absents de la prévision déterministe à moyen terme. L'incertitude dans la représentation des processus diabatiques a été examinée car ceux-ci contrôlent l'impact des ouragans sur les ondes de Rossby. Pour la première fois, des simulations ont été réalisées avec le modèle Méso-NH sur un grand domaine avec une résolution explicite de la convection profonde, tirant parti de la parallélisation massive du modèle. Une faible sensibilité à la résolution horizontale du modèle a été trouvée dans les précipitations des ouragans, donc dans leur impact sur les ondes de Rossby et sur les événements extrêmes en Méditerranée. La trajectoire d'Hélène a par contre montré une forte sensibilité à sa synchronisation avec le train d'ondes de Rossby, influencée par la résolution horizontale du modèle. Cette forte sensibilité a été retrouvée dans les prévisions d'ensemble du Centre Européen pour la Prévision Météorologique à Moyen Terme, où le développement du méditerragan a requis la synchronisation d'Hélène avec le train d'ondes de Rossby. La perturbation ciblée des conditions initiales autour d'Hélène et du thalweg en amont a suffi à prévoir le méditerragan à une échéance de 108 h dans une simulation Méso-NH. Ces résultats montrent l'impact possible de transitions extra-tropicales en Atlantique Nord, qui surviennent à la même saison que la plupart des épisodes de précipitations intenses en Méditerranée. La réduction de l'incertitude dans la prévision de la transition extra-tropicale est donc un des enjeux de l'amélioration de la prévision d'événements extrêmes d'automne en MéditerranéeThe extratropical transition is the transformation of a tropical cyclone into an extratropical cyclone during its migration towards the midlatitudes. During its interaction with its new baroclinic environment, the cyclone can reintensify through complex dynamical and diabatic processes. It can also have a impact downstream from the strengthening of a Rossby wave train, which quickly propagates and of which the breaking is often the trigger of extreme weather events. The complexity of dynamical and diabatic processes lead then to a reduction of the downstream predictability. Hurricanes Florence and Helene over the North Atlantic contributed that way to the triggering of extreme weather events in September 2006 in the Mediterranean, respectively, an intense precipitation event and a rarer phenomenon, a Medicane (Mediterranean hurricane). Helene was distinguished from Florence by its predominant diabatic processes during the reintensification over a warmer ocean, from which it maintained tropical characteristics. Helene was an exceptional case from its three reintensifications in three days, induced by the elongation of three filaments of potential vorticity, in addition to the development of the Medicane downstream. Both extreme weather events in the Mediterranean were missed from the midrange deterministic forecast. As diabatic processes control the impact of the hurricanes on the Rossby wave trains, the uncertainty in their description was investigated. For the first time, numerical simulations were performed with the Meso-NH model over a large domain with an explicit resolution of deep convection, taking advantage of the massive parallel computing capabilities of the model. A weak sensitivity to the horizontal resolution of the model was found in the precipitation of the hurricanes, thus in their impact on the Rossby wave trains and in the extreme weather events in the Mediterranean. The track of Helene showed instead a high sensitivity to its phasing with the Rossby wave train, that was influenced by the horizontal resolution of the model. This high sensitivity was found again in the ensemble forecasts from the European Centre for Medium-Range Weather Forecasts, where the developement of the Medicane required the phasing of Helene with the Rossby wave train. Targeted perturbation of initial conditions around Helene and the upstream trough were sufficient to predict the Medicane at 108-h lead time in a Meso-NH simulation. The results show the possible impact of extratropical transitions over the North Atlantic, which take place during the same season as most high precipitation episodes in the Mediterranean. A reduction in the uncertainty of the forecast of an extratropical transition is therefore one of the issues for an improvement of the forecast of extreme weather events in the Autumn season, over the Mediterranean region
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Treguier, Anne-Marie. "Effets des vents fluctuants et de la topographie sur la turbulence océanique à moyenne échelle." Brest, 1987. http://www.theses.fr/1987BRES2003.
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Les fluctuations du vent sont un des mecanismes pouvant generer la variabilite oceanique d'echelle moyenne, observee notamment dans l'atlantiuqe nord-est. La reponse de l'ocean est calculee par un modele numerique spectral, qui resout les equations quasi-geostrophiques dans le cas non lineaire et stratifie. Dans une premiere partie, nous decrivons la turbulence d'echelle moyenne generee par les fluctuations du vent dans un ocean a fond plat. L'energie de la reponse se partage entre un regime lineaire constitue d'ondes de rossby barotropes a grande echelle, et un regime non lineaire. Nous etudions la sensibilite de la reponse a tous les parametres physiques (echelle et energie du vent, frottement, rotation de la terre,stratification). Nos resulats montrent que le parametre cle est le rapport de la plus grande echelle forcee au rayon de rossby. Dans une seconde partie, nous etudions lm'influence d'une topographie aleatoire de faible hauteur sur la dynamique des tourbillons forces par le vent. La generation de courants moyens correles a la topographie est mise en evidence, ainsi qu'une diminution importante des echelles spatiales au fond. Enfin, nous montrons que la presence de topographie induit une intensification au fond dans le cas de la turbulence libre, et par contre une plus grande intensification en surface dans le cas de la turbulence forcee. La reponse de notre modele, surtout en presence de topographie, presente des caracteristiques proches de la variabilite observee dans l'atlantique nord-est, ce qui confirme l'importance des fluctuations du vent pour la generation de cette variabilite
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Bonhomme, Céline. "Turbulences et ondes en milieu naturel stratifié : deux études de cas : étude du mélange turbulent et des ondes internes du lac Pavin (Auvergne, France) ; influence des ondes de Rossby sur la concentration en chlorophylle de surface dans l'upwelling du Pérou." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00558713.
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Dans les milieux aquatiques, les facteurs liés à l'hydrodynamique et au mélange aux échelles de la turbulence sont déterminants pour le transport des substances chimiques et des micro-organismes. Ce travail s'intéresse à ces phénomènes physiques et se situe à la frontière entre la limnologie physique et l'océanographie physique, au travers de l'étude de deux cas : le lac Pavin (Auvergne, France) et la région d'upwelling au large du Pérou. Un des intérêts de ce travail réside dans le changement d'échelle de l'observation de milieux naturels aquatiques allant de l'échelle millimétrique (étude de la microstructure dans le Lac Pavin) à l'échelle de la centaine de kilomètres (étude des ondes de Rossby). Le Lac Pavin est le seul lac méromictique français, ce qui signifie que le compartiment inférieur du lac ne se mélange pas annuellement. La méromicticité concerne pourtant bien d'autres bassins, plus connus et plus vastes comme la Mer Noire, la Mer Caspienne, le lac Baïkal, d'où son importance écologique. Sa méromicticité lui confère des propriétés physiques particulières, étudiées dans le cadre de cette thèse. L'étude de la variabilité du mélange diapycnal à différentes échelles de temps et d'espace dans le lac Pavin au travers de mesures de microstructure et de surveillance en continu des principaux paramètres physiques a conduit à mettre en évidence la variabilité de la stabilité de la colonne d'eau à l'échelle interannuelle. Par ailleurs, les propagations d'ondes internes de gravité sont étudiées dans ce cadre particulier à l'aide d'un modèle linéaire bidimensionnel. Elles génèrent des mouvements advectifs verticaux importants dans toute la colonne d'eau dont il faut tenir compte dans les protocoles d'échantillonnage chimiques ou biologiques. Enfin, une intrusion sous lacustre semble avoir une grande importance dans la détermination de la profondeur du mélange hivernal et le maintien de la méromicticité. La zone de l'upwelling du Pérou est parmi les plus poissonneuses au monde. Elle est caractérisée par une forte productivité primaire, observable par satellite. L'observation des ondes de Rossby a permis de mettre en évidence qu'elles génèrent plus de 50% de la variabilité observée à l'échelle intra saisonnière sur la concentration en chlorophylle de surface, à distance des côtes. Les ondes transportent la chlorophylle vers le large et participent à la détermination de l'extension de la zone de forte productivité primaire. A travers des mesures variées allant de la microstructure à l'observation satellite et grâce à l'utilisation de modèles conceptuels, la thèse met en évidence l'influence certaine des facteurs hydrodynamiques sur l'organisation des paramètres biogéochimiques de ces deux écosystèmes
Books on the topic "Onde de Rossby"
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Broderick, Virginia. The Scriptural Rosary: A modern version of the way the Rosary was once prayed throughout Western Europe in the late Middle Ages. Glenview, IL: Christianica (America), 1989.
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Morris, Gilbert. One by One: Dani Ross Mystery #1. Thorndike, Me: Thorndike Press, 2001.
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Winston, Kimberly. Bead one, pray, too: A guide to making and using prayer beads. Harrisburg, [Pa.]: Morehouse Pub., 2008.
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Arcangeli, Letizia, and Marco Gentile, eds. Le signorie dei Rossi di Parma tra XIV e XVI secolo. Florence: Firenze University Press, 2008. http://dx.doi.org/10.36253/978-88-8453-684-6.
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This volume is devoted to one of the major aristocratic lineages of northern Italy in the later middle ages. The Rossi, whose political and social eminence dates back to the communal age, built in the Parmense a powerful lordship, based both on their estates and fortresses and on a vast patronage network spread over the territory and in the town: and the power of the family, though diminished after the crisis in the relations with the Sforza in 1482, was restored on partially different foundations during the Italian Wars. The essays collected in this book explore the complexity of the Rossi "little seignorial state", focusing on its internal constitution, on its exterior relations and on its artistic and cultural features between the mid-fourteenth and the early sixteenth century.
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Pavlova, R. Vladivostok: Poltora veka na karte Rossii = Vladivostok : one and a half centuries on a Russia map. Vladivostok: Dalʹpress, 2010.
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Assotsiat︠s︡ii︠a︡ Ukrainy s Evropeĭskim soi︠u︡zom: Posledstvii︠a︡ dli︠a︡ Rossii : informat︠s︡sionno-analiticheskiĭ doklad. Moskva: IMĖMO RAN, 2014.
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United States. Congress. Senate. Committee on the Judiciary. Subcommittee on Antitrust, Monopolies, and Business Rights. Competitive issues in infant formula pricing: Hearing before the Subcommittee on Antitrust, Monopolies, and Business Rights of the Committee on the Judiciary, United States Senate, One Hundred First Congress, second session, on the pricing behavior of infant formula companies, May 29, 1990. Washington: U.S. G.P.O., 1990.
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Mahan, Jeffrey H. A long way from solving that one: Psycho/social and ethical implications of Ross Macdonald's Lew Archer tales. Lanham: University Press of America, 1990.
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Quenum, Gandome Mayeul L. D., Nana A. B. Klutse, Eric A. Alamou, Emmanuel A. Lawin, and Philip G. Oguntunde. "Precipitation Variability in West Africa in the Context of Global Warming and Adaptation Recommendations." In African Handbook of Climate Change Adaptation, 1533–54. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_85.
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AbstractIt is commonly accepted that the Earth’s climate is changing and will continue to change in the future. Rising temperatures are one of the direct indicators of global climate change. To investigate how the rising global temperature will affect the spatial pattern of rainfall in West Africa, the precipitation and potential evapotranspiration variables from ten Global Climate Models (GCMs) under the RCP8.5 scenario were driven by the Rossby Centre regional atmospheric model (RCA4) from the COordinated Regional Climate Downscaling EXperiment (CORDEX) and analyzed at four specific global warming levels (GWLs) (i.e., 1.5 °C, 2.0 °C, 2.5 °C, and 3.0 °C) above the preindustrial level. This study utilized three indices, the precipitation concentration index (PCI), the precipitation concentration degree (PCD), and the precipitation concentration period (PCP) over West Africa to explore the spatiotemporal variations in the characteristics of precipitation concentrations. Besides, the analysis of the effect of the specified GWLs on the Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), and frequency of the intense rainfall events allowed to a better understanding of the spatial and temporal patterns of extreme precipitation in West Africa. Results reveal that, for the projections simulations and at each GWL, the rainfall onset starts one month earlier in the Gulf of Guinea in response to the control period. To encourage adaptation to the various changes in climate in general, and particularly in respect of rainfall, this study proposes several adaptation methods that can be implemented at the local (country) level, as well as some mitigation and adaptation strategies at the regional (West African) level.
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Anderson, John B., and Louis R. Bartek. "Cenozoic glacial history of the Ross Sea revealed by intermediate resolution seismic reflection data combined with drill site information." In The Antarctic Paleoenvironment: A Perspective on Global Change: Part One, 231–63. Washington, D. C.: American Geophysical Union, 1992. http://dx.doi.org/10.1029/ar056p0231.
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Yang, Weiyu. "A Competitor Smells Fishy but a Friend Smells Rosy: Social Identity Influences Psychological Well-Being During One-Person Social Exclusion." In Proceedings of the 2022 6th International Seminar on Education, Management and Social Sciences (ISEMSS 2022), 3321–28. Paris: Atlantis Press SARL, 2022. http://dx.doi.org/10.2991/978-2-494069-31-2_391.
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"One. Double Bayou." In Ross Sterling, Texan, 5–13. University of Texas Press, 2007. http://dx.doi.org/10.7560/714427-003.
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Davidson, P. A. "Zonal (East–West) Winds and Rossby-Wave Turbulence." In The Dynamics of Rotating Fluids, 455–71. Oxford University PressOxford, 2024. http://dx.doi.org/10.1093/9780191994272.003.0021.
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Abstract One of the most striking features of the weather layers on Jupiter and Saturn are the bands of intense east–west winds that alternate in direction with latitude. It has long been appreciated that these east–west winds are a result of an interplay between turbulence and Rossby waves, although the precise details of that interplay are still disputed. These zonal winds, and their relationship to Rossby waves, are discussed in some detail in this chapter. This remains an area of intense research, as increasingly accurate astrophysical measurements fuels an ongoing debate.
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Dancy, Jonathan. "Prichard on Duty and Lgnorance Of Fact." In Ethical lntuitionism: Re-evaluations, 229–47. Oxford University PressOxford, 2002. http://dx.doi.org/10.1093/oso/9780198250999.003.0011.
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Abstract I am contributing this paper to a volume intended to re-evaluate ethical intuitionism for two reasons, one historical and the other not. The historical reason is that Prichard’s paper ‘Duty and Ignorance of Fact’ caused a complete volte-face in Ross. Ross’s first book, The Right and the Good, expounded the view that Prichard’s paper was intended to undermine, and Ross was so completely persuaded by Prichard that he included in The Foundations of Ethics a ten-page summary of Prichard’s argument, often word for word. (Nonetheless, he managed, as I will suggest below, to make a couple of significant errors.) This interesting example of the influence that Prichard had over Ross is worth re-examination. I suggest that Prichard’s arguments were not really as powerful as Ross supposed.
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"Twenty-one. Martial Law’s Finale." In Ross Sterling, Texan, 218–25. University of Texas Press, 2007. http://dx.doi.org/10.7560/714427-023.
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Kirk, Neville. "World War I and its Aftermath." In Transnational Radicalism and the Connected Lives of Tom Mann and Robert Samuel Ross. Liverpool University Press, 2017. http://dx.doi.org/10.5949/liverpool/9781786940094.003.0008.
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The final chapter considers the ways in which Mann’s and Ross’s commitments to labour-movement unity and wider working-class solidarity fared in the face of the highly divisive issues of war, militarism, imperialism, peace, patriotism, loyalism, internationalism, conscription, revolution and counter-revolution surrounding the period of World War One and its aftermath. It shows that while Mann and Ross continued to preach peace, opposition to the ‘imperialist’ war and conscription, Ross was far more active and outspoken in his anti-war activities than Mann and as a consequence suffered imprisonment and declining health. The pacifism of Ross, indeed, is to be contrasted with Mann’s commitment to taking the war to a successful conclusion against ‘Prussianism’. In 1917 both Mann and Ross welcomed the ‘emancipatory’ Russian Revolution and staunchly opposed the politics of counter-revolution and ‘loyalism’. Yet while Mann embraced communism, Ross found a home in the radicalised Australian Labor Party and rejected the Bolshevik model for democratic Australia. The case of Mann and Ross casts important new light upon the general issues of labour’s and workers’ attitudes to war and peace, revolution and reaction, patriotism and loyalism and communism and social democracy.
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Reiner Jr., Robert C., and David L. Smith. "Heterogeneity, Stochasticity and Complexity in the Dynamics and Control of Mosquito-Borne Pathogens." In Population Biology of Vector-Borne Diseases, 13–28. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198853244.003.0002.
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A theory for the transmission dynamics and control of malaria was developed around a set of concepts, quantities, and mathematical models introduced by Ronald Ross. Decades later, Macdonald linked Ross's models to epidemiological and entomological data, developed the concept of the basic reproductive number, R0, and proposed a rudimentary theory of control based on sensitivity to parameters. Here, we review development of the Ross–Macdonald model, present one simple version, and provide an eclectic critique of the theory based on studies conducted more recently. While mosquito populations are logically necessary for mosquito-borne pathogen transmission, the study of transmission since then shows it is noisy, heterogeneous, and complex. Heterogeneity, stochasticity, and complexity represent important challenges for applying theory in context.
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Smullyan, Raymond M. "Rosser Systems." In Gödel's Incompleteness Theorems. Oxford University Press, 1992. http://dx.doi.org/10.1093/oso/9780195046724.003.0009.
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Our first proof of the incompleteness of P.A. was based on the assumption that P.A. is correct. Gödel’s proof of the last chapter was based on the metamathematically weaker assumption that P.A. is ω-consistent. Rosser [1936] subsequently showed that P.A. can be proved incomplete under the still weaker metamathematical assumption that P.A. is simply consistent! Now, Rosser did not show that the Gödel sentence G of the last chapter is undecidable on the weaker assumption of simple consistency. He constructed another sentence (a more elaborate one) which he showed undecidable on the basis of simple consistency. Our first proof of the incompleteness of P.A. boils down to finding a formula that expresses the set P̃* (or alternatively one that expresses R*). Gödel’s proof, which we gave in the last chapter, boils down to representing one of the sets P* and R* in P.A. and the only way known in Gödel’s time of doing this involved the assumption of ω-consistency. [This assumption was not needed to show that the sets P* and R* are enumerable in P.A.—it was in passing from the enumerability of these sets to their representability that ω-consistency stepped in.] Now, Rosser did not achieve incompleteness by representing either of the sets P* and R*, but rather by representing some superset of R* disjoint from P*—this can be done under the weaker assumption of simple consistency—and it also serves to establish incompleteness, as we will see. The axiom schemes Ω4 and Ω5 of the system (R) will play a key role in this and the next chapter. We shall say that a system S is an extension of Ω4 and Ω5 if all formulas of Ω4 and Ω5 are provable in S. We will prove the following theorem and its corollaries. Theorem R. Every simply consistent axiomatizable extension of Ω4 and Ω5 in which all Σ1-sets are enumerable must be incomplete. Corollary 1. Every simply consistent axiomatizable extension of Ω4 and Ω5 in which all true Σ0-sentences are provable must be incomplete. Corollary 2. Every simply consistent axiomatizable extension of the system (R) is incomplete.
Conference papers on the topic "Onde de Rossby"
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Iacovides, H., and B. E. Launder. "Parametric and Numerical Study of Fully-Developed Flow and Heat Transfer in Rotating Rectangular Ducts." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-024.
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This work is concerned with fully-developed constant-density turbulent flow through rectangular straight ducts rotating in an orthogonal mode. Ducts of both square and 2:1 aspect ratio cross-sections have been examined. For the square duct, predictions have been performed for Reynolds numbers of 33,500 and 97,000 and for the 2:1 aspect ratio duct the computations were carried out for a Reynolds number of 33,500. Values of the inverse Rossby number (Ro = ΩD/Wb) ranged from 0.005 to 0.2. Except in the immediate vicinity of the wall, the standard high-Reynolds-number version of the k-ε model is used to account for the effects of turbulence. Across the near-wall sublayer the damping of turbulence is modelled through a low-Reynolds-number one-equation model. Low rotational speeds cause the formation of a pair of symmetric streamwise vortices. At higher rotational speeds, flow instabilities on the pressure side lead to transition to a more complex four-vortex structure. The transition point depends on both the cross-sectional geometry and the flow Reynolds number. Moreover, over a range of Rossby number, either two- or four-vortex solutions are possible depending upon initial conditions. The rotation leads to significant differences between the values of friction factor and Nusselt number on the suction and pressure surfaces of the duct. The degree of heat transfer augmentation on the pressure side is found to depend on the Reynolds number as well as on Rossby number. In contrast, heat-transfer attenuation on the suction side is only Rossby-number dependent.
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Chen, Y. N., U. Seidel, J. Chen, U. Haupt, and M. Rautenberg. "Experimental Investigation of the Flow Field of Deep Rotating Stall in a Centrifugal Compressor." In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-160.
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The pressure field of deep rotating stall of a centrifugal compressor with two stall cells is analysed by means of the two-dimensional pressure pattern in the impeller determined by Chen et al. (1993). These authors transferred the pressure pattern measured on the shroud surface (i.e. in the absolute frame) to that related to the rotating blade channels. The transferred pressure pattern is thus a two-dimensional one. The existence of the low and high pressure vortices according to the Rossby wave theory is confirmed by this experiment. The development stages of the two vortices, in combination with the Rossby wave that steers the rotating stall, can be evaluated very well. The vortex low is developed from the front between the reverse flow (with high temperature and entropy) and the forward flow (with low temperature and entropy) due to baroclinic instability. Its center is situated within the channel of the splitter blade. This front is accompanied by a squall line of small-scaled eddies. This is the same phenomenon as can be observed on the meteorological polar front. The vortex high is induced by the vortex low. Its embryo starts on the pressure surface. Its center is situated behind the inlet edge of the splitter blade. It can be further verified that the stall cell is caused by the backflows of the induction fields of the two vortices (low and high).
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Chen, Y. N., U. Seidel, U. Haupt, and M. Rautenberg. "The Vortex Behaviour of the Rotating-Stall Cell of a Centrifugal Compressor With Vaned Diffuser." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-066.
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The aerodynamic behaviour of the rotating-stall cell of a centrifugal compressor with radial blading and vaned diffuser is investigated experimentally using two stagnation pressure transducers located parallel to each other on the opposing walls of the semi-vaneless annular space between the impeller and the diffuser. The transducers are turned simultaneously step by step through an angle of 360° during the measurement, so that the flow field of both the forward and reverse flows and the swirl flow components can be detected in the stalled and the unstalled regions. It was shown in the previous papers of the authors (1991 b) that the jet and wake in the flow of the blade channel in the normal operating range are cores of longitudinal vortices with opposite rotational sense. During rotating stall, the jet of a blade channel bends over the outlet edge of the blade and is converted into the wake of the neighbouring one to form a vortex loop around the blade in question. The swirling speed of this vortex loop (the vorticity) is measured to be about twice impeller speed for the present case. The vortex loops of the adjacent blades then join together to form a bubble, the stall cell, embodying the region of the stalled blades. The outer reach of the vortex bubble forms the border of the outer lobe of the Rossby waves associated with the vortex pair “high” (H) and “low” (L) guiding the stall cell. The longitudinal-vortex-nature of the jet stream along the flank of the Rossby wave, as determined recently in a vaneless diffuser by the authors (1991a), is confirmed in the present investigation. Its intensity reaches a velocity of about 20% u2 when measured in the absolute frame, or 120% u2 when measured in the rotating impeller frame, superimposed by a swirling component of (1 to 4) x ωimp (u2 = tangential velocity of the impeller outlet. ωimp = angular velocity of the impeller).
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Yuan, Shuaihang, and Yi Fang. "ROSS: Robust Learning of One-Shot 3D Shape Segmentation." In 2020 IEEE Winter Conference on Applications of Computer Vision (WACV). IEEE, 2020. http://dx.doi.org/10.1109/wacv45572.2020.9093604.
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Cooper, Cortis K., James D. Stear, Douglas A. Mitchell, Wensu Wang, David B. Driver, John Heideman, and Michael Vogel. "Development of Gulf of Mexico Deepwater Currents for Reference by API Recommended Practices." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29588.
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The metocean conditions contained in the 21st edition of API RP2A, last updated in 1993, are in the process of being revised to account for: the effects of recent major hurricanes, the shift of production to deeper water, and improvements in our understanding of metocean conditions in US waters. As the Oil Industry has moved into the deeper Gulf of Mexico waters, it has become exposed to strong currents generated by the Loop Current, its associated eddies, and by topographic Rossby waves. This paper describes the basis for the draft extreme conditions we have developed for these strong deepwater ocean currents. Further work is underway to develop conditions for extreme near-bottom currents on the continental slope and for joint hurricane-Loop currents. Once accepted by API, the conditions will ultimately be published as part of a stand-alone API recommended practice (RP) which will in turn be referenced by other API recommended practices such as those addressing shallow-water fixed platforms, jack-ups, deepwater platforms, and floating MODUs. The Metocean RP will also include hurricane-generated conditions the development of which is documented in a separate paper (Berek, et al. 2007).
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Chen, Y. N., D. Hagelstein, U. Haupt, and M. Rautenberg. "Excitation Mechanism for Standing Stall of Centrifugal Compressors." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-245.
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The standing stall of the centrifugal compressors appears with pulsating or switching pattern at operating points slightly away from the stall line. It is a weak form of the rotating stall and stands still in the absolute frame. The reverse flow of the compressed warm fluid travelling from the impeller’s outlet along the shroud surface towards the inlet is not yet powerful enough to generate rotating stall. The experimental investigations revealed that in the low-flow-rate off-design region, the inlet flow to the impeller has a large positive incidence angle. Nose bubbles are formed on the suction surface of the blade after the leading edge. Once the reverse flow as a pressure wave reaches the inlet of the blades, the nose bubble is stagnated to an enlarged size. The corresponding disturbance sends a rarefaction wave in the forward direction into the impeller. This wave of cool fluid meets the reverse pressure wave of the warm fluid at a circular front around the circumference of the impeller. Since this circular front has a weak baroclinicity, it cannot develop into Rossby waves which initiate the rotating stall. Instead it will either pulsate concentrically or switch linearly. We then experience a standing stall with the corresponding pattern.
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Jackson, Richard W., Hui Tang, James A. Scobie, Oliver J. Pountney, Carl M. Sangan, J. Michael Owen, and Gary D. Lock. "Unsteady Pressure Measurements in a Heated Rotating Cavity." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59090.
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Abstract The flow in the heated rotating cavity of an aero-engine compressor is driven by buoyancy forces, which result in pairs of cyclonic and anticyclonic vortices. The resultant cavity flow field is three-dimensional, unsteady and unstable, which makes it challenging to model the flow and heat transfer. In this paper, properties of the vortex structures are determined from novel unsteady pressure measurements collected on the rotating disc surface over a range of engine-representative parameters. These measurements are the first of their kind with practical significance to the engine designer and for validation of computational fluid dynamics. One cyclonic/anticyclonic vortex pair was detected over the experimental range, despite the measurement of harmonic modes in the frequency spectra at low Rossby numbers. It is shown that these modes were caused by unequal size vortices, with the cyclonic vortex the larger of the pair. The structures slipped relative to the discs at a speed typically around 10% to 15% of that of the rotor, but the speed of precession was often unsteady. The coherency, strength and slip of the vortex pair increased with the buoyancy parameter, due to the stronger buoyancy forces, but they were largely independent of the rotational Reynolds number.
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Kim, Young-Ju, Nam-Sub Woo, and Young-Kyu Hwang. "Flow of Newtonian and Non-Newtonian Fluids in a Concentric Annulus With Rotation of the Inner Cylinder." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45791.
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This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0∼600 rpm. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. In all flow regime, the skin friction coefficient is increased by the inner cylinder rotation. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and, then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Rec decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.
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Farthing, P. R., C. A. Long, J. M. Owen, and J. R. Pincombe. "Rotating Cavity With Axial Throughflow of Cooling Air: Flow Structure." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-017.
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A rotating cavity with an axial throughflow of cooling air is used to provide a simplified model for the flow that occurs between adjacent corotating compressor discs inside a gas-turbine engine. Flow visualization and laser-Doppler anemometry are employed to study the flow structure inside isothermal and heated rotating cavities for a wide range of axial-gap ratios. G. rotational. Reynolds numbers, Reφ, axial Reynolds numbers, Rez, and temperature distributions. For the isothermal case, the superposed axial flow of air generates a powerful toroidal vortex inside cavities with large gap ratios (G > 0.400) and weak counter-rotating toroidal vortices for cavities with small gap ratios. Depending on the gap ratio and the Rossby number, ε (where ε ∝ Rez/Reφ), axisymmetric and nonaxisymmetric vortex breakdown can occur, but circulation inside the cavity becomes weaker as ε is reduced. For the case where one or both discs of the cavity are heated, the flow becomes nonaxisymmetric: cold air enters the cavity in a “radial arm” on either side of which is a vortex. The cyclonic and anti-cyclonic circulations inside the two vortices are presumed to create the circumferential pressure gradient necessary for the air to enter the cavity (in the radial arm) and to leave (in Ekman layers on the discs). The core of fluid between the Ekman layers precesses with an angular speed close to that of the discs, and vortex breakdown appears to reduce the relative speed of precession.
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Ushakov, E. A. "СОЦИАЛЬНО-ЭКОНОМИЧЕСКОЕ ПОЛОЖЕНИЕ НОВЫХ СУБЪЕКТОВ ДВФО ПРИ СРАВНЕНИИ С ДРУГИМИ СУБЪЕКТАМИ ФЕДЕРАЛЬНОГО ОКРУГА." In Geosistemy vostochnyh raionov Rossii: osobennosti ih struktur i prostranstvennogo razvitiia. ИП Мироманова Ирина Витальевна, 2019. http://dx.doi.org/10.33833/tig.2019.12.22.003.
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Аннотация. Республика Бурятия и Забайкальский край указом президента Российской Федерации 3 ноября 2018 года вошли в состав Дальневосточного федерального округа. Эти субъекты имеют свою социальноэкономическую специфику по отношению к другим субъектам по структуре экономики, уровню жизни населения, экономикогеографическому положению. Одна из главных целей работы была сравнить новые субъекты с другими субъектами Дальневосточного федерального округа по структуре экономики и социальноэкономическому положению и его динамики. Оба региона как было установлено имеют схожие структуры экономики с приграничными субъектами юга Дальнего Востока. Они имеют довольно низкие социальноэкономические показатели по отношению к подавляющему большинству субъектов Российской Федерации, так и в особенности среди субъектов Дальневосточного региона находясь наряду с Еврейской автономной областью в числе аутсайдеров. Это было подсчитано на примере одного из коэффициентов сравнения, который показывает степень социальноэкономического развития между субъектами федерального округа. Также на примере этого коэффициента выявлено, что рассматриваемые регионы также уступают значительной части других регионов по динамике социальноэкономических показателей. Оба региона имеют небольшую долю в социально экономических показателях округа, прежде всего за счет слабого развития регионов. Это вызывает и снижение этих показателей в расчете на 1 человека по округу. Был выявлен ряд экономических особенностей и географических факторов характерных для причинноследственной связи низкого социальноэкономического положения и развития Республики Бурятия и Забайкальского края по отношению к другим субъектам федерального округа. На примере структуре экономики регионов указано, что наибольшие социальноэкономические показатели имеют регионы с высокой долей промышленности за счет добычи полезных ископаемых. Обозначен ряд факторов, которые сказываются или должны сказываться положительно на развитии новых субъектов в будущем в составе нового федерального округа. Были подсчитаны изменения социальноэкономических показателей для Дальневосточного федерального округа в результате произошедшего изменения его границ. By a decree of the President of the Russian Federation on November 3, the Republic of Buryatia and the TransBaikal Territory became a part of the Far Eastern Federal District. These subjects have their own socioeconomic specifics relatively to other subjects by the structure of economy, the standard of living of the population, and the economic geographical position. One of the main goals of the work was to compare new subjects with other subjects of the Far Eastern Federal District in terms of the economic structure, a socioeconomic situation, and its dynamics. Both regions were found to have similar economic structures with the border regions of the south of the Far East. They have rather low socioeconomic indicators relatively to the overwhelming majority of the subjects of the Russian Federation, and especially among the subjects of the Far Eastern region, being together with the Jewish Autonomous Region among the outsiders. This was calculated by example of one of the comparison coefficients, which shows the degree of socioeconomic development between the subjects of the Federal district. Besides, by example of this coefficient, it was revealed that the regions under consideration conceded a significant part of other regions in the dynamics of socioeconomic indicators. Both regions have a small share in the socioeconomic indicators of the district, primarily because of weak development of the regions. This causes a decrease in these indicators per 1 person in the district. A number of economic features and geographical factors typical of a causal relationship of a low socioeconomic status and development of the Republic of Buryatia and the TransBaikal Territory relatively to other subjects of the Federal district were identified. By example of the structure of regional economy, it is indicated that, the regions with the highest share of industry have the highest socioeconomic indicators at the expense of mining. A number of factors are indicated that affect or should have a positive effect on the development of new subjects in future as part of a new federal district. The changes in socioeconomic indicators for the Far Eastern Federal District that occurred as a result of the change in its borders have been calculated.
Reports on the topic "Onde de Rossby"
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Willis, Larkin, and Monica R. Martinez. Authentic Student Work in College Admissions: Lessons From the Ross School of Business. Learning Policy Institute, January 2023. http://dx.doi.org/10.54300/756.774.
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To develop holistic review processes, admission professionals are changing the ways they structure applications for undergraduate admissions. This study examines how the Stephen M. Ross School of Business (Ross School) at the University of Michigan requests, collects, and reviews portfolios of student work along with traditional application materials. The first section presents the rationale for the new holistic review process, the second shares insights it provides the Ross School, and the third details how admission professionals at the Ross School built it. The case illuminates the use of student-generated portfolios as one possible model for other higher education systems seeking to evolve their holistic admission processes.
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Sela, Shlomo, and Michael McClelland. Investigation of a new mechanism of desiccation-stress tolerance in Salmonella. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7598155.bard.
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Low-moisture foods (LMF) are increasingly involved in foodborne illness. While bacteria cannot grow in LMF due to the low water content, pathogens such as Salmonella can still survive in dry foods and pose health risks to consumer. We recently found that Salmonella secretes a proteinaceous compound during desiccation, which we identified as OsmY, an osmotic stress response protein of 177 amino acids. To elucidate the role of OsmY in conferring tolerance against desiccation and other stresses in Salmonella entericaserovarTyphimurium (STm), our specific objectives were: (1) Characterize the involvement of OsmY in desiccation tolerance; (2) Perform structure-function analysis of OsmY; (3) Study OsmY expression under various growth- and environmental conditions of relevance to agriculture; (4) Examine the involvement of OsmY in response to other stresses of relevance to agriculture; and (5) Elucidate regulatory pathways involved in controlling osmY expression. We demonstrated that an osmY-mutant strain is impaired in both desiccation tolerance (DT) and in long-term persistence during cold storage (LTP). Genetic complementation and addition of a recombinantOsmY (rOsmY) restored the mutant survival back to that of the wild type (wt). To analyze the function of specific domains we have generated a recombinantOsmY (rOsmY) protein. A dose-response DT study showed that rOsmY has the highest protection at a concentration of 0.5 nM. This effect was protein- specific as a comparable amount of bovine serum albumin, an unrelated protein, had a three-time lower protection level. Further characterization of OsmY revealed that the protein has a surfactant activity and is involved in swarming motility. OsmY was shown to facilitate biofilm formation during dehydration but not during bacterial growth under optimal growth conditions. This finding suggests that expression and secretion of OsmY under stress conditions was potentially associated with facilitating biofilm production. OsmY contains two conserved BON domains. To better understand the role of the BON sites in OsmY-mediated dehydration tolerance, we have generated two additional rOsmY constructs, lacking either BON1 or BON2 sites. BON1-minus (but not BON2) protein has decreased dehydration tolerance compared to intact rOsmY, suggesting that BON1 is required for maximal OsmY-mediated activity. Addition of BON1-peptide at concentration below 0.4 µM did not affect STm survival. Interestingly, a toxic effect of BON1 peptide was observed in concentration as low as 0.4 µM. Higher concentrations resulted in complete abrogation of the rOsmY effect, supporting the notion that BON-mediated interaction is essential for rOsmY activity. We performed extensive analysis of RNA expression of STm undergoing desiccation after exponential and stationary growth, identifying all categories of genes that are differentially expressed during this process. We also performed massively in-parallel screening of all genes in which mutation caused changes in fitness during drying, identifying over 400 such genes, which are now undergoing confirmation. As expected OsmY is one of these genes. In conclusion, this is the first study to identify that OsmY protein secreted during dehydration contributes to desiccation tolerance in Salmonella by facilitating dehydration- mediated biofilm formation. Expression of OsmY also enhances swarming motility, apparently through its surfactant activity. The BON1 domain is required for full OsmY activity, demonstrating a potential intervention to reduce pathogen survival in food processing. Expression and fitness screens have begun to elucidate the processes of desiccation, with the potential to uncover additional specific targets for efforts to mitigate pathogen survival in desiccation.
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Campbell, Seth, Zoe Courville, Samantha Sinclair, and Joel Wilner. Brine, englacial structure and basal properties near the terminus of McMurdo Ice Shelf, Antarctica. Engineer Research and Development Center (U.S.), September 2022. http://dx.doi.org/10.21079/11681/45303.
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We collected ∼1300 km of ground-penetrating radar profiles over McMurdo Ice Shelf, Antarctica, using frequencies between 40 and 400 MHz to determine extent, continuity and depth to the brine. We also used profiles to determine meteoric ice thickness and locate englacial features, which may suggest ice shelf instability. The brine extends 9–13 km inland from the ice shelf terminus and covers the entire region between Ross, White and Black Islands. Jump unconformities and basal fractures exist in the brine and ice shelf, respectively, suggesting prior fracturing and re-suturing. One 100 MHz profile, the most distal from the ice shelf edge while still being situated over the brine, simultaneously imaged the brine and bottom of meteoric ice. This suggests a negative brine salinity gradient moving away from the terminus. The meteoric ice bottom was also imaged in a few select locations through blue ice in the ablation zone near Black Island. We suggest that brine, sediment-rich ice and poor antenna coupling on rough ice attenuates the signal in this area. When combined with other recent mass-balance and structural glaciology studies of MIS, our results could contribute to one of the most high-resolution physical models of an ice shelf in Antarctica.
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Clement, Timothy, and Brett Vaughan. Evaluation of a mobile learning platform for clinical supervision. University of Melbourne, 2021. http://dx.doi.org/10.46580/124369.
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Context: This report details a formative evaluation of the Clinical Supervision Online (CSO) course, a fee-paying, fully online ‘light touch’ program of study for clinical supervisors offered by the Melbourne Medical School, which was developed in conjunction with the University’s Mobile Learning Unit. The course requires between six to ten hours of self-directed study and is designed for any clinicians who teach. Methods: Evaluation of the course was guided by Rossi, Lipsey and Freeman’s (2004) approach to program evaluation, addressing the need for the course, its design, implementation, impact, and return on investment. Data were collected through interviews with key informants, document analysis, an embedded student survey, learning analytics data, financial data, and an audit against ‘best practice’ standards for online course design. Findings: The findings suggest that course development was driven by both a financial imperative and genuine concern to meet training needs of clinical supervisors. Two hundred and four students enrolled on the course in its first 18 months. This has been enough to cover its developmental costs. In relation to 64 quality standards for online course design, the level of performance was rated as ‘meets’ for 44 items; ‘exceeds’ for one item; ‘developing for 13 items’; and, ‘non-existent’ for six items. An additional 33 items were identified as ‘not applicable’ for the ‘light touch’ course design. Significance: From a learning design perspective there is much to like about the CSO course and the outcome of assessing it against the standards for ‘best practice’ online course design suggests that an evolutionary approach - making incremental changes - could improve the course whilst retaining its existing ‘light touch’ format. The CSO course on its own is unlikely to realise the depth of achievement implied in the course aims and learning outcomes. The CSO course may best be seen as an entrée into the art of clinical supervision.