Observed Deep Cyclonic Eddies around Southern Greenland

Recent mooring measurements from the Overturning in the Subpolar North Atlantic Program have revealed abundant cyclonic eddies at both sides of Cape Farewell, the southern tip of Greenland. In this study, we present further observational evidence, from both Eulerian and Lagrangian perspectives, of deep cyclonic eddies with intense rotation (𝜁/f > 1) around southern Greenland and into the Labrador Sea. Most of the observed cyclones exhibit strongest rotation below the surface (700-1000 dbar), where maximum azimuthal velocities are ~30 cm/s at radii of ~10 km, with rotational periods of 2-3 days. The cyclonic rotation can extend to the deep overflow water layer (below 1800 dbar), albeit with weaker azimuthal velocities (~10 cm/s) and longer rotational periods of about one week. Within the mid-depth rotation cores, the cyclones are in near solid-body rotation and have the potential to trap and transport water. The first high-resolution hydrographic transect across such a cyclone indicates that it is characterized by a local (both vertically and horizontally) potential vorticity maximum in its core and cold, fresh anomalies in the overflow water layer, suggesting its source as the Denmark Strait outflow. Additionally, the propagation and evolution of the cyclonic eddies are illustrated with deep Lagrangian floats, including their detachments from the boundary currents to the basin interior. Taken together, the combined Eulerian and Lagrangian observations have provided new insights on the boundary current variability and boundary-interior exchange over a geographically large scale near southern Greenland, calling for further investigations on the (sub)mesoscale dynamics in the region.

The Invariance of Recognition to the Stretching of Faces is Not Explained by Familiarity or Warping to an Average Face

Stretching (or compressing) a face by a factor of two has no effect on its recognition as assessed by the speed and accuracy of judging whether the face is that of a celebrity (Hole, 2002). This invariance has stood as a challenge to all contemporary accounts of the relation between neurocomputational measures of face similarity and face recognition. We extend the documentation of strong invariance over compression to a factor of four and show that the deformation so produced is sufficiently great that the resultant image is as similar to markedly different faces—even those differing in race, sex, and expression-- as it is to the original face. The invariance to face compression is readily witnessed with less familiar celebrities and unfamiliar faces ruling out a role of exposure to transformed images of particular faces through depth rotation or viewing pictures at varied viewing angles. We additionally discount the possibility that faces are “un-stretched” by warping them to an average face. Instead, we suggest that the percept of an elongated face provides a signal for the shrink-wrapping of receptive fields to conform to an attended object, a phenomenon witnessed in single unit activity in the macaque by Moran and Desimone (1985) which may serve, more generally, as the underlying neural mechanism for object-based attention.

Experimental investigation of the weldability of high strength aluminium using friction spot welding

Friction spot welding is a technique for joining lightweight aluminium and magnesium alloys in the overlap configuration by means of frictional heat and mechanical work and has a high potential for industrial applications. As this is a very recent technique, little information is available regarding the evaluation and optimisation of process parameters for specific material combinations. The process has been used to investigate the weldability of the high strength aluminium alloy EN AW-7475-T761, aiming to produce high quality joints in terms of mechanical performance and microstructure. More specific, the influence of the plunge depth, rotation speed and welding time was investigated. The paper first shortly describes the process and continues with the results of the microhardness, static tensile and optical microscopy tests.