The strength and dynamics of magnetoelastic coupling through the paramagnetic (PM) – antiferromagnetic (AFM) – ferrimagnetic (FIM) transitions in multiferroic hexagonal ErMnO3 have been investigated by Resonant Ultrasound Spectroscopy. Elastic stiffening by up to 2% below the PM – AFM transition at 80 K arises from biquadratic coupling between strain and the magnetic order parameter with relaxation times longer than ∼ 10-6 s for the response of spins to changes in strain. In contrast with YMnO3, the PM – AFM transition in ErMnO3 is accompanied by a peak in acoustic loss immediately below the Néel point which is interpreted in terms of strain relaxation accompanying ordering of spins of Er3+ at 4b sites. Changes in the magnetic ordering scheme at the AFM – FIM transition near 3 K are accompanied by elastic softening of ∼ 0.03 %. During poling of the low temperature ferrimagnetic structure round magnetic hysteresis loops, small changes in elastic stiffness which arise due to the contribution of piezomagnetic and/or piezoelectric moduli are detected. Contributions of piezoelectric moduli to acoustic resonance frequencies also permit changes in the configuration of ferroelectric domains to be detected in response both to cycling through this transition and to application of a magnetic field. A peak in acoustic loss in the vicinity of 250 K is attributed to strain-mediated pinning/freezing of some aspect of the domain microstructure with an activation energy of ∼ 0.25–0.3 eV. A return to the original elastic properties on heating to temperatures above ∼ 250 K is interpreted in terms of backswitching of domains to the configuration they had at the start. These observations confirm the existence of subtle variations in magnetoelastic coupling behaviour relating to both the magnetic order parameters and magnetic domain structures.

Collisional electron drift wave turbulence generates drift wave packet structures with density and vorticity fluctuations in the central plasma pressure gradient region of a linear plasma device. Tracking these packets reveals that they follow an outward directed spiral-shaped trajectory in the (r,θ) plane, are azimuthally stretched, and develop anisotropy as they approach an axisymmetric, radially sheared azimuthal flow located at the plasma boundary. Nonlinear energy transfer measurements and time-delay analysis confirm that structure absorption amplifies the sheared flow. Similar mechanisms likely operate at the edge of confined toroidal plasmas and should lead to the amplification of sheared flows at the boundary of these devices as well.

© Zhang et al.Defecation allows the body to eliminate waste, an essential step in food processing for animal survival. In contrast to the extensive studies of feeding, its obligate counterpart, defecation, has received much less attention until recently. I

An azimuthally symmetric radially sheared azimuthal flow is driven by a nondiffusive, or residual, turbulent stress localized to a narrow annular region at the boundary of a cylindrical magnetized helicon plasma device. A no-slip condition, imposed by ion-neutral flow damping outside the annular region, combined with a diffusive stress arising from turbulent and collisional viscous damping in the central plasma region, leads to net plasma rotation in the absence of momentum input.

We investigate the effect of chemical doping on the electric and magnetic domain pattern in multiferroic hexagonal ErMnO3. Hole- and electron doping are achieved through the growth of Er1-xCaxMnO3 and Er1-xZrxMnO3 single crystals, which allows for a controlled introduction of divalent and tetravalent ions, respectively. Using conductance measurements, piezoresponse force microscopy and nonlinear optics we study doping-related variations in the electronic transport and image the corrsponding ferroelectric and antiferromagnetic domains. We find that moderate doping levels allow for adjusting the electronic conduction properties of ErMnO3 without destroying its characteristic domain patterns. Our findings demonstrate the feasibility of chemical doping for nonperturbative property-engineering of intrinsic domain states in this important class of multiferroics.

A dimensionless collisionality scan has been performed in H-mode plasmas on DIII-D tokamak, with detailed measurements of intermediate-to-high wavenumber turbulence using Doppler backscattering systems. It is found that the shorter wavelength turbulence develops into spatially asymmetric turbulent structures with a long-radial-range correlation (LRRC) in the mid-radius region of high collisionality discharges. Linear cgyro simulations indicate that the underlying turbulence is likely driven by the electron-temperature-gradient mode. The LRRC transport events are highly intermittent and show a power spectrum of Sñ(k⊥)∝k⊥−1 for density fluctuations, which is often associated with self-organized criticality. The magnitude and the radial scale of those turbulent structures increase significantly when the Er×B mean flow shearing rate decreases at higher collisionality. The enhanced LRRC transport events appear to be correlated with the degraded energy confinement time. The emergence of such LRRC transport events may serve as a candidate explanation for the degrading nature of H-mode core plasma confinement at high collisionality.

Background: Malaria around the China-Myanmar border is a serious health problem in the countries of South-East Asia. An. minimus is a principle malaria vector with a wide geographic distribution in this area. Malaria is endemic along the boundary between Yunnan province in China and the Kachin State of Myanmar where the local Anopheles community (species composition) and the malaria transmission vectors have never been clarified. Methods. Adult Anopheles specimens were collected using CDC light traps in four villages along the border of China and Myanmar from May 2012 to April 2013. Morphological and molecular identification of mosquito adults confirmed the species of Anopheles. Blood-meal identification using the female abdomens was conducted using multiplex PCR. For sporozoite detection in An. minimus, sets of 10 female salivary glands were pooled and identified with SSU rDNA using nested PCR. Monthly abundance of An. minimus populations during the year was documented. The diversity of Anopheles and the role of An. minimus on malaria transmission in this border area were analyzed. Results: 4,833 adult mosquitoes in the genus Anopheles were collected and morphologically identified to species or species complex. The Anopheles community is comprised of 13 species, and 78.83% of our total specimens belonged to An. minimus s.l., followed by An. maculatus (5.55%) and the An. culicifacies complex (4.03%). The quantity of trapped An. minimus in the rainy season of malaria transmission was greater than during the non-malarial dry season, and a peak was found in May 2012. An. minimus fed on the blood of four animals: humans (79.8%), cattle (10.6%), pigs (5.8%) and dogs (3.8%). 1,500 females of An. minimus were pooled into 150 samples and tested for sporozoites: only 1 pooled sample was found to have sporozoites of Plasmodium vivax. Conclusion: Anopheles is abundant with An. minimus being the dominant species and having a high human blood index along the China-Myanmar border. The sporozoites in An. minimus were determined to be Plasmodium vivax with a 0.07-0.7% infection rate. © 2013Yu et al.; licensee BioMed Central Ltd.

Low-temperature X-ray photoemission electron microscopy (X-PEEM) is used to measure the electric potential at domain walls in improper ferroelectric Er0.99Ca0.01MnO3. By combining X-PEEM with scanning probe microscopy and theory, we develop a model that relates the detected X-PEEM contrast to the emergence of uncompensated bound charges, explaining the image formation based on intrinsic electronic domain-wall properties. In contrast to previously applied low-temperature electrostatic force microscopy (EFM), X-PEEM readily distinguishes between positive and negative bound charges at domain walls. Our study introduces an X-PEEM-based approach for low-temperature electrostatic potential mapping, facilitating nanoscale spatial resolution and data acquisition times on the order of 0.1-1 s.

The spontaneous transformations associated with symmetry-breaking phase transitions generate domain structures and defects that may be topological in nature. The formation of these defects can be described according to the Kibble-Zurek mechanism, which provides a generic relation that applies from cosmological to interatomic length scales. Its verification is challenging, however, in particular at the cosmological scale where experiments are impractical. While it has been demonstrated for selected condensed-matter systems, major questions remain regarding, e.g., its degree of universality. Here, we develop a global Kibble-Zurek picture from the condensed-matter level. We show theoretically that a transition between two fluctuation regimes (Ginzburg and mean field) can lead to an intermediate region with reversed scaling, and we verify experimentally this behavior for the structural transition in the series of multiferroic hexagonal manganites. Trends across the series allow us to identify additional intrinsic features of the defect formation beyond the original Kibble-Zurek paradigm.

Understanding the physics of the L-H transition power threshold scaling dependencies on toroidal field and density is critical to operating and optimizing the performance of ITER. Measurements of long-wavelength (k ρI < 1) turbulent eddy dynamics, characteristics, flows, and flow shear in the near edge region of DIIID plasmas have been obtained during an ion gyroradius scan (varying toroidal field and current) and density scan in a favourable geometry (ion ∇B drifts towards the X-point), in order to determine the underlying mechanisms that influence the macroscopic L-H power threshold scaling relations. It is found that the normalized integrated long wavelength density fluctuation amplitudes (ñ/n) in the pedestal increases with ρ* approaching the L-H transition. The turbulence poloidal flow spectrum evolves from geodesic acoustic mode dominant at lower power to low-frequency zonal flow (LFZF) dominant near the L-H transition, and the effective shearing rate correspondingly increases. An inferred Reynolds stress, , from BES velocimetry (inferring velocity field from imaging) measurements is found to significantly increase near the L-H transition. At lower electron density, a clear increase of the LFZF is observed prior to the L-H transition, which is not evident at higher density. Taken together, these results are qualitatively consistent with the electron density and toroidal field scaling of the L-H transition power threshold. © 2013 IAEA, Vienna.