536 research outputs found
Cu nuclear magnetic resonance study of charge and spin stripe order in LaBaCuO
We present a Cu nuclear magnetic/quadrupole resonance study of the charge
stripe ordered phase of LBCO, with detection of previously unobserved
('wiped-out') signal. We show that spin-spin and spin-lattice relaxation rates
are strongly enhanced in the charge ordered phase, explaining the apparent
signal decrease in earlier investigations. The enhancement is caused by
magnetic, rather than charge fluctuations, conclusively confirming the
long-suspected assumption that spin fluctuations are responsible for the
wipeout effect. Observation of the full Cu signal enables insight into the spin
and charge dynamics of the stripe-ordered phase, and measurements in external
magnetic fields provide information on the nature and suppression of spin
fluctuations associated with charge order. We find glassy spin dynamics, in
agreement with previous work, and incommensurate static charge order with
charge modulation amplitude similar to other cuprate compounds, suggesting that
the amplitude of charge stripes is universal in the cuprates.Comment: 7 pages, 5 figure
Glucose availability and sensitivity to anoxia of isolated rat peripheral nerve
The contrast between resistance to ischemia and ischemic lesions in peripheral nerves of diabetic patients was explored by in vitro experiments. Isolated and desheathed rat peroneal nerves were incubated in the following solutions with different glucose availability: 1) 25 mM glucose, 2) 2.5 mM glucose, and 3) 2.5 mM glucose plus 10 mM 2-deoxy-D-glucose. Additionally, the buffering power of all of these solutions was modified. Compound nerve action potential (CNAP), extracellular pH, and extracellular potassium activity (aKe) were measured simultaneously before, during, and after a period of 30 min of anoxia. An increase in glucose availability led to a slower decline in CNAP and to a smaller rise in aKe during anoxia. This resistance to anoxia was accompanied by an enhanced extracellular acidosis. Postanoxic recovery of CNAP was always complete in 25 mM HCO3(-)-buffered solutions. In 5 mM HCO3- and in HCO3(-)-free solutions, however, nerves incubated in 25 mM glucose did not recover functionally after anoxia, whereas nerves bathed in solutions 2 or 3 showed a complete restitution of CNAP. We conclude that high glucose availability and low PO2 in the combination with decreased buffering power and/or inhibition of HCO3(-)-dependent pH regulation mechanisms may damage peripheral mammalian nerves due to a pronounced intracellular acidosis
Sticking under wet conditions: the remarkable attachment abilities of the torrent frog, staurois guttatus
Tree frogs climb smooth surfaces utilising capillary forces arising from an air-fluid interface around their toe pads, whereas torrent frogs are able to climb in wet environments near waterfalls where the integrity of the meniscus is at risk. This study compares the adhesive capabilities of a torrent frog to a tree frog, investigating possible adaptations for adhesion under wet conditions. We challenged both frog species to cling to a platform which could be tilted from the horizontal to an upside-down orientation, testing the frogs on different levels of roughness and water flow. On dry, smooth surfaces, both frog species stayed attached to overhanging slopes equally well. In contrast, under both low and high flow rate conditions, the torrent frogs performed significantly better, even adhering under conditions where their toe pads were submerged in water, abolishing the meniscus that underlies capillarity. Using a transparent platform where areas of contact are illuminated, we measured the contact area of frogs during platform rotation under dry conditions. Both frog species not only used the contact area of their pads to adhere, but also large parts of their belly and thigh skin. In the tree frogs, the belly and thighs often detached on steeper slopes, whereas the torrent frogs increased the use of these areas as the slope angle increased. Probing small areas of the different skin parts with a force transducer revealed that forces declined significantly in wet conditions, with only minor differences between the frog species. The superior abilities of the torrent frogs were thus due to the large contact area they used on steep, overhanging surfaces. SEM images revealed slightly elongated cells in the periphery of the toe pads in the torrent frogs, with straightened channels in between them which could facilitate drainage of excess fluid underneath the pad
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Unconventional charge order in a co-doped high-Tc superconductor
Charge-stripe order has recently been established as an important aspect of cuprate high-Tc
superconductors. However, owing to the complex interplay between competing phases and
the influence of disorder, it is unclear how it emerges from the parent high-temperature state.
Here we report on the discovery of an unconventional ordered phase between charge-stripe
order and (pseudogapped) metal in the cuprate La1.8xEu0.2SrxCuO4. We use three
complementary experimentsânuclear quadrupole resonance, nonlinear conductivity and
specific heatâto demonstrate that the order appears through a sharp phase transition and
exists in a dome-shaped region of the phase diagram. Our results imply that the new phase is
a state, which preserves translational symmetry: a charge nematic. We thus resolve the
process of charge-stripe development in cuprates, show that this nematic phase is distinct
from high-temperature pseudogap and establish a link with other strongly correlated
electronic materials with prominent nematic order
Rolled-up self-assembly of compact magnetic inductors, transformers and resonators
Three-dimensional self-assembly of lithographically patterned ultrathin films
opens a path to manufacture microelectronic architectures with functionalities
and integration schemes not accessible by conventional two-dimensional
technologies. Among other microelectronic components, inductances,
transformers, antennas and resonators often rely on three-dimensional
configurations and interactions with electromagnetic fields requiring
exponential fabrication efforts when downscaled to the micrometer range. Here,
the controlled self-assembly of functional structures is demonstrated. By
rolling-up ultrathin films into cylindrically shaped microelectronic devices we
realized electromagnetic resonators, inductive and mutually coupled coils.
Electrical performance of these devices is improved purely by transformation of
a planar into a cylindrical geometry. This is accompanied by an overall
downscaling of the device footprint area by more than 50 times. Application of
compact self-assembled microstructures has significant impact on electronics,
reducing size, fabrication efforts, and offering a wealth of new features in
devices by 3D shaping.Comment: 19 pages, 3 figures, 6 supplementary figure
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RolledâUp SelfâAssembly of Compact Magnetic Inductors, Transformers, and Resonators
3D self-assembly of lithographically patterned ultrathin films opens a path to manufacture microelectronic architectures with functionalities and integration schemes not accessible by conventional 2D technologies. Among other microelectronic components, inductances, transformers, antennas, and resonators often rely on 3D configurations and interactions with electromagnetic fields requiring exponential fabrication efforts when downscaled to the micrometer range. Here, the controlled self-assembly of functional structures is demonstrated. By rolling up ultrathin films into cylindrically shaped microelectronic devices, electromagnetic resonators, inductive and mutually coupled coils are realized. Electrical performance of these devices is improved purely by transformation of a planar into a cylindrical geometry. This is accompanied by an overall downscaling of the device footprint area by more than 50 times. Application of compact self-assembled microstructures has significant impact on electronics, reducing size, fabrication efforts, and offering a wealth of new features in devices by 3D shaping
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