A magnetic map leads juvenile European eels to the Gulf Stream

Migration allows animals to track the environmental conditions that maximize growth, survival, and reproduction [ 1–3 ]. Improved understanding of the mechanisms underlying migrations allows for improved management of species and ecosystems [ 1–4 ]. For centuries, the catadromous European eel (Anguilla anguilla) has provided one of Europe’s most important fisheries and has sparked considerable scientific inquiry, most recently owing to the dramatic collapse of juvenile recruitment [ 5 ]. Larval eels are transported by ocean currents associated with the Gulf Stream System from Sargasso Sea breeding grounds to coastal and freshwater habitats from North Africa to Scandinavia [ 6, 7 ]. After a decade or more, maturing adults migrate back to the Sargasso Sea, spawn, and die [ 8 ]. However, the migratory mechanisms that bring juvenile eels to Europe and return adults to the Sargasso Sea remain equivocal [ 9, 10 ]. Here, we used a “magnetic displacement” experiment [ 11, 12 ] to show that the orientation of juvenile eels varies in response to subtle differences in magnetic field intensity and inclination angle along their marine migration route. Simulations using an ocean circulation model revealed that even weakly swimming in the experimentally observed directions at the locations corresponding to the magnetic displacements would increase entrainment of juvenile eels into the Gulf Stream System. These findings provide new insight into the migration ecology and recruitment dynamics of eels and suggest that an adaptive magnetic map, tuned to large-scale features of ocean circulation, facilitates the vast oceanic migrations of the Anguilla genu

Exploring the phases of 3D artificial spin ice: From Coulomb phase to magnetic monopole crystal

Artificial spin-ices consist of lithographic arrays of single-domain magnetic nanowires organised into frustrated lattices. These geometries are usually two-dimensional, allowing a direct exploration of physics associated with frustration, topology and emergence. Recently, three-dimensional geometries have been realised, in which transport of emergent monopoles can be directly visualised upon the surface. Here we carry out an exploration of the three-dimensional artificial spin-ice phase diagram, whereby dipoles are placed within a diamond-bond lattice geometry. We find a rich phase diagram, consisting of a double-charged monopole crystal, a single-charged monopole crystal and conventional spin-ice with pinch points associated with a Coulomb phase. In our experimental demagnetised systems, broken symmetry forces formation of ferromagnetic stripes upon the surface, a configuration that forbids the formation of the lower energy double-charged monopole crystal. Instead, we observe crystallites of single magnetic charge, superimposed upon an ice background. The crystallites are found to form due to the intricate distribution of magnetic charge around a three-dimensional nanostructured vertex, which locally favours monopole formation. Our work suggests that engineered surface energetics can be used to tune the ground state of experimental three-dimensional ASI systems

Use of microscale coplanar striplines with indium tin oxide windows in optical ferromagnetic resonance measurements

Copyright © 2005 American Institute of PhysicsIt is shown that a coplanar stripline structure containing indium tin oxide windows can be used to perform optical ferromagnetic resonance measurements on a sample grown on an opaque substrate, using a pulsed magnetic field of any desired orientation. The technique is demonstrated by applying it to a thin film of permalloy grown on a Si substrate. The measured precession frequency was found to be in good agreement with macrospin simulations. The phase of the oscillatory Kerr response was observed to vary as the probe spot was scanned across the coplanar stripline structure, confirming that the orientation of the pulsed field varied from parallel to perpendicular relative to the plane of the sample

Epidural Analgesia Provides Better Pain Management After Live Liver Donation: A Retrospective Study

Despite the increase in surgical volumes of live liver donation, there has been very little documentation of the postoperative pain experience. The primary aim of this study was to examine the difference in acute postoperative pain intensity and adverse effects between patients who received intravenous patient-controlled analgesia (IV PCA) or patient-controlled epidural analgesia (PCEA) for pain control after live liver donation surgery. A retrospective chart review was performed of 226 consecutive patients who underwent right living donor hepatic surgery at the Toronto General Hospital, Toronto, Canada. Patients who received as their primary postoperative analgesic modality IV PCA (n = 158) were compared to patients who received PCEA (n = 68). Demographic profiles for the 2 groups were similar with respect to age, sex, and body mass index at the time of surgery. For the first 3 postoperative days, pain intensity was significantly lower in patients who received epidural analgesia (P 4) was reported more frequently in the IV PCA group (P < 0.05) along with increased sedation (P < 0.05). Pruritus was reported more frequently in the PCEA group of patients compared to the IV PCA group (P < 0.05). Significant between-group differences were not found for the incidence of postoperative vomiting, the time at which patients began fluid intake, the time to initial ambulation, or the length of hospital stay. In conclusion, epidural analgesia provides better postoperative pain relief, less sedation, but more pruritus than IV PCA after live liver donation

Topology by Design in Magnetic nano-Materials: Artificial Spin Ice

Artificial Spin Ices are two dimensional arrays of magnetic, interacting nano-structures whose geometry can be chosen at will, and whose elementary degrees of freedom can be characterized directly. They were introduced at first to study frustration in a controllable setting, to mimic the behavior of spin ice rare earth pyrochlores, but at more useful temperature and field ranges and with direct characterization, and to provide practical implementation to celebrated, exactly solvable models of statistical mechanics previously devised to gain an understanding of degenerate ensembles with residual entropy. With the evolution of nano--fabrication and of experimental protocols it is now possible to characterize the material in real-time, real-space, and to realize virtually any geometry, for direct control over the collective dynamics. This has recently opened a path toward the deliberate design of novel, exotic states, not found in natural materials, and often characterized by topological properties. Without any pretense of exhaustiveness, we will provide an introduction to the material, the early works, and then, by reporting on more recent results, we will proceed to describe the new direction, which includes the design of desired topological states and their implications to kinetics.Comment: 29 pages, 13 figures, 116 references, Book Chapte

Manipulating ultracold atoms with a reconfigurable nanomagnetic system of domain walls

The divide between the realms of atomic-scale quantum particles and lithographically-defined nanostructures is rapidly being bridged. Hybrid quantum systems comprising ultracold gas-phase atoms and substrate-bound devices already offer exciting prospects for quantum sensors, quantum information and quantum control. Ideally, such devices should be scalable, versatile and support quantum interactions with long coherence times. Fulfilling these criteria is extremely challenging as it demands a stable and tractable interface between two disparate regimes. Here we demonstrate an architecture for atomic control based on domain walls (DWs) in planar magnetic nanowires that provides a tunable atomic interaction, manifested experimentally as the reflection of ultracold atoms from a nanowire array. We exploit the magnetic reconfigurability of the nanowires to quickly and remotely tune the interaction with high reliability. This proof-of-principle study shows the practicability of more elaborate atom chips based on magnetic nanowires being used to perform atom optics on the nanometre scale.Comment: 4 pages, 4 figure

Multi-Step Ordering in Kagome and Square Artificial Spin Ice

We show that in colloidal models of artificial kagome and modified square ice systems, a variety of ordering and disordering regimes occur as a function of biasing field, temperature, and colloid-colloid interaction strength, including ordered monopole crystals, biased ice rule states, thermally induced ice rule ground states, biased triple states, and disordered states. We describe the lattice geometries and biasing field protocols that create the different states and explain the formation of the states in terms of sublattice switching thresholds. For a system prepared in a monopole lattice state, we show that a sequence of different orderings occurs for increasing temperature. Our results also explain several features observed in nanomagnetic artificial ice systems under an applied field.Comment: 16 pages, 11 postscript figure

Two-photon Lithography for 3D Magnetic Nanostructure Fabrication

Ferromagnetic materials have been utilised as recording media within data storage devices for many decades. Confinement of the material to a two dimensional plane is a significant bottleneck in achieving ultra-high recording densities and this has led to the proposition of three dimensional (3D) racetrack memories that utilise domain wall propagation along nanowires. However, the fabrication of 3D magnetic nanostructures of complex geometry is highly challenging and not easily achievable with standard lithography techniques. Here, by using a combination of two-photon lithography and electrochemical deposition, we show a new approach to construct 3D magnetic nanostructures of complex geometry. The magnetic properties are found to be intimately related to the 3D geometry of the structure and magnetic imaging experiments provide evidence of domain wall pinning at a 3D nanostructured junction