On the Surface Circulation in Some Channels of the Canadian Arctic Archipelago

This paper advances an explanation for the presence of surface currents in opposite directions on facing sides of some of the main channels of the Canadian Arctic Archipelago. It is found that geostrophic dynamics coupled with geometrical constraints and the general direction of surface drift through the archipelago can readily account for the existence, if not all the properties, of the observed flow patterns

Internal wave propagation normal to a geostrophic current

It is shown that (i) internal gravity waves propagating along a horizontal density gradient in a uniformly rotating ocean can exist for a range of slightly smaller frequencies than is possible in the absence of such a gradient, (ii) such waves exhibit a phase difference from top to bottom, and (iii) they exchange energy with the geostrophic current, which balances the density-induced pressure gradient...

Can Regulation of Freshwater Runoff in Hudson Bay Affect the Climate of the North Atlantic?

A sequence of phenomena links anthropogenic changes in the timing of freshwater runoff in Hudson Bay to a possible impact on the North Atlantic thermohaline circulation. The chain of events starts with the spreading of estuarine plumes under ice and continues with the effect of lowered salinity on the rate of ice formation, regional effects on the scale of Hudson Bay, the export of freshwater to the Labrador Sea, its impact on deep convection in that area, and the relative importance of such changes to the North Atlantic circulation. At each step we compare anthropogenic effects with other factors and place them within the perspective of natural variability. Our conclusion does not support the contention that freshwater runoff regulation, even of all rivers in the basins of Hudson and James Bays, could have a significant or even a detectable effect on the climate of the North Atlantic.Une séquence de phénomènes relie des changements anthropiques dans le moment où les eaux douces commencent à s'écouler dans la baie d'Hudson à leur répercussion possible sur les courants thermiques des eaux marines. La séquence débute par la formation d'un panache estuarien sous la glace et se poursuit avec l'effet de la baisse de salinité sur la vitesse de formation de la glace, des répercussions régionales affectant toute la baie d'Hudson, l'exportation d'eau douce vers la mer du Labrador et ses retombées sur la convection profonde dans cette zone, ainsi qu'avec l'importance relative de tels changements sur les courants nord-atlantiques. À chaque étape, on compare les influences anthropiques avec d'autres facteurs pour les situer dans un contexte de variabilité. Notre conclusion n'appuie pas la thèse que la régulation de l'écoulement des eaux douces, même si elle s'étendait à tous les cours d'eau des bassins de la baie d'Hudson et de la baie James, pourrait avoir des répercussions notables ou même détectables sur le climat nord-atlantique

Interaction of internal waves and mean flow observed near a coast

Vortex stretching has been proposed as a possible mechanism by which internal waves can extract energy from the mean flow. Relationships between the slowly varying (ω \u3c 0.25 cpd) and rapidly varying (0.13 cph \u3c ω \u3c 0.5 cph) components of the flow have been examined in a 4-month-long data set taken off the coast of British Columbia. The rapidly varying component of horizontal velocity generally rotates clockwise, and is in rough agreement with internal wave dynamics. It is horizontally incoherent within a distance of 10 km and is vertically coherent across the water column with a nearly 180° phase change. Scatter plots show that the wavefield is anisotropic, with the Reynolds stresses generally obeying uv \u3c 0, vw \u3c 0 and uw \u3e 0, where (u, v, w) are the fluctuating velocity components in the (onshore, alongshore, upward) directions. Instances have been found in which time variations of uv and the mean horizontal shear rate Vx are negatively correlated, with an implied horizontal viscosity of VH ∼ (3 ± 2) × 105 cm2/s. No correlation of vw and the mean vertical shear Vz is found. It is suggested that nonlocal behavior is important because propagation times in the vertical are smaller than the interaction times of the wave packets. With the observed shear rates and the wave energy levels, the vertical viscosity is unlikely to be beyond the range ± 20 cm2/s

Minimum-Uncertainty Angular Wave Packets and Quantized Mean Values

Uncertainty relations between a bounded coordinate operator and a conjugate momentum operator frequently appear in quantum mechanics. We prove that physically reasonable minimum-uncertainty solutions to such relations have quantized expectation values of the conjugate momentum. This implies, for example, that the mean angular momentum is quantized for any minimum-uncertainty state obtained from any uncertainty relation involving the angular-momentum operator and a conjugate coordinate. Experiments specifically seeking to create minimum-uncertainty states localized in angular coordinates therefore must produce packets with integer angular momentum.Comment: accepted for publication in Physical Review

Case report: an unexpected link between partial deletion of the SHANK3 gene and Heller’s dementia infantilis, a rare subtype of autism spectrum disorder

International audienceAbstractBackgroundDeletions and mutations involving the SHANK3 gene lead to a nonspecific clinical presentation with moderate to profound intellectual disability, severely delayed or absent speech, and autism spectrum disorders (ASD).Better knowledge of the clinical spectrum of SHANK3 haploinsufficiency is useful to facilitate clinical care monitoring and to guide molecular diagnosis, essential for genetic counselling.Case presentationHere, we report a detailed clinical description of a 10-year-old girl carrying a pathogenic interstitial 22q13.3 deletion encompassing only the first 17 exons of SHANK3.The clinical features displayed by the girl strongly suggested the diagnosis of dementia infantilis, described by Heller in 1908, also known as childhood disintegrative disorder.ConclusionOur present case confirms several observations according to which regression may be part of the clinical phenotype of SHANK3 haploinsufficiency. Therefore, we think it is crucial to look for mutations in the gene SHANK3 in patients diagnosed for childhood disintegrative disorder or any developmental disorder with a regressive pattern involving social and communicative skills as well as cognitive and instinctual functions, with onset around 3 years

Light-cone M5 and multiple M2-branes

We present the light-cone gauge fixed Lagrangian for the M5-brane; it has a residual `exotic' gauge invariance with the group of 5-volume preserving diffeomorphisms, SDiff(5), as gauge group. For an M5-brane of topology R2 x M3, for closed 3-manifold M3, we find an infinite tension limit that yields an SO(8)-invariant (1+2)-dimensional field theory with `exotic' SDiff(3) gauge invariance. We show that this field theory is the Carrollian limit of the Nambu bracket realization of the `BLG' model for multiple M2-branes.Comment: 21 pages, revised to clarify some points, to include a discussion of SDiff gauge invariance, and to add two reference

Über den Einfluß von Reibung und Vermischung auf interne Wellen

Es wird gezeigt, daß interne Wellen in einer inkompressiblen Flüssigkeit mit innerer Reibung und Vermischung nur existieren können, wenn die Schichtung Γ größer als eine minimale Schichtung Γmin ist und daß ihr Auftreten dann auf einen endlichen Wellenlängenbereich beschränkt ist. Die maximale Frequenz ist kleiner als im Fall einer idealen Flüssigkeit (Väisäläfrequenz). Eine Flüssigkeit der obigen Art verhält sich internen Wellen gegenüber wie ein Filter, dessen Bandbreite von den Flüssigkeitseigenschaften und der Schichtung abhängt und dessen maximale Durchlässigkeit bei Wellen liegt, deren horizontale Wellenlänge doppelt so groß wie die vertikale ist. Alle Abweichungen der Eigenschaften interner Wellen (mit Ausnahme des Dämpfungsfaktors) gegenüber denen in einer idealen Flüssigkeit lassen sich als Funktion des Verhältnisses Γ/Γmin darstellen. lt is shown that in an incompressible fluid where viscosity and mixing are present internal waves can exist only when the stratification, Γ, is larger than a minimum value, Γmin, and then only for a finite band of wave lengths. The maximum frequency is smaller than in ideal fluids (Väisälä frequency). Such an incompressible fluid is seen to behave as a filter for internal waves, the band-width of which depends on fluid properties and on stratification, and which has its maximum response for waves having a wave length twice as long in the horizontal as in the vertical direction. All deviations ( except for the damping factor) from the theory of ideal fluids can be expressed as functions of the ratio Γ/Γmin, so that the results can be written in a generalized form which applies to all fluids