Flow Structure and Channel Stability at the Site of a Deep Scour Hole, Mackenzie Delta, Canada

Unusually deep scour holes in distributary channels of the Mackenzie Delta are of concern for oil and gas resource development, particularly with respect to buried pipeline crossings. Surveys of one such hole, carried out in 1985 and 1992, indicated vertical stability and slight lateral movement. The present study examines how the hole may have changed by the mid-2000s and documents the complex local velocity field and related bed material properties. Small discrepancies between isobaths of different years suggest a dynamic stability that involves short-term fluctuations in erosion and deposition. This suggestion was corroborated by detailed measurements of the highly three-dimensional velocity field, which revealed major eddy structures and flow reversals that help maintain sizeable velocity magnitudes despite low mean velocities. The composition of the bed material suggests cohesive behaviour, but the literature indicates a range of critical shear stresses that spans two orders of magnitude. The more probable lower end of this range is consistent with the observed dynamic stability of the scour hole.Des fosses d’affouillement exceptionnellement profondes se trouvant dans les effluents du delta du Mackenzie risquent de poser des problèmes en matière de mise en valeur des ressources pétrolières et gazières, surtout en ce qui a trait aux pipelines enfouis. Selon les levés d’une de ces fosses effectués en 1985 et en 1992, cette fosse serait verticalement stable et aurait un léger mouvement latéral. La présente étude se penche sur la façon dont la fosse pourrait avoir changé une fois rendu vers le milieu des années 2000 et documente le champ de vitesse local complexe de même que les propriétés des matériaux de fond connexes. De petits écarts entre les isobathes de différentes années laissent entrevoir une stabilité dynamique assortie de fluctuations à court terme sur le plan de l’érosion et de la déposition. Cette suggestion a été corroborée à l’aide de mesures détaillées du champ de vitesse hautement tridimensionnel, qui a révélé d’importantes structures à grands tourbillons et des écoulements de retour qui favorisent le maintien d’intensités de vitesse appréciables malgré des vélocités moyennes faibles. Bien que la composition des matériaux de fond suggère un comportement cohésif, la documentation indique une gamme de contraintes de cisaillement critique qui s’étend sur deux ordres de grandeur. Le bas de cette gamme plus probable est conforme à la stabilité dynamique observée à l’égard de la fosse d’affouillement

Rare chondrosarcoma of the breast treated with quadrantectomy instead of mastectomy. A case report

Breast chondrosarcoma is a rare sarcoma that mainly occurs in females >50 years old. To the best of our knowledge, only 16 cases were reported in the literature prior to 2013 and all patients were surgically treated by mastectomy, with or without lymphadenectomy, which was occasionally preceded by neoadjuvant chemotherapy. However, the literature does not report the benefit of mastectomy compared with a more conservative surgery. The present study reports a novel case of extraskeletal chondrosarcoma of the breast. A 63‑year‑old female patient presented with a neoplasm localized in the upper‑outer quadrant of the right breast. The palpable lesion with sharp margins was a firm parenchymatous mass, which was confirmed by ultrasonography and mammography. The patient underwent conservative quadrantectomy instead of mastectomy, followed by post‑surgical chemotherapy. A positron emission tomography scan performed five months subsequent to the surgery revealed no remnants of the disease. The patient underwent a strict clinical and instrumental follow‑up, and two and half years after surgery, there are no signs of recurrent disease. In conclusion, the present case is currently one of the two cases in which a more conservative quadrantectomy was performed, instead of mastectomy. This surgical approach did not lead to metastasis and resulted in a good follow‑up for the patient

The W_N minimal model classification

We first rigourously establish, for any N, that the toroidal modular invariant partition functions for the (not necessarily unitary) W_N(p,q) minimal models biject onto a well-defined subset of those of the SU(N)xSU(N) Wess-Zumino-Witten theories at level (p-N,q-N). This permits considerable simplifications to the proof of the Cappelli-Itzykson-Zuber classification of Virasoro minimal models. More important, we obtain from this the complete classification of all modular invariants for the W_3(p,q) minimal models. All should be realised by rational conformal field theories. Previously, only those for the unitary models, i.e. W_3(p,p+1), were classified. For all N our correspondence yields for free an extensive list of W_N(p,q) modular invariants. The W_3 modular invariants, like the Virasoro minimal models, all factorise into SU(3) modular invariants, but this fails in general for larger N. We also classify the SU(3)xSU(3) modular invariants, and find there a new infinite series of exceptionals.Comment: 25 page

Experimental study of curvature effects on jet impingement heat transfer on concave surfaces

Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects. The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters: jet Reynolds number from 27,000 to 130,000, relative nozzle to surface distance from 3.3 to 30, and relative surface curvature from 0.005 to 0.030. Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics. On one hand, an increase of relative nozzle to surface distance (increasing jet diameter in fact) enhances the average heat transfer around the surface for the same curved surface. On the other hand, the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter. Finally, experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect. This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces, which is of high importance to the design of the aircraft anti-icing system