1,409 research outputs found
Daisy
Daisy was a very earnest worker. To Mrs. Dreger, who was out of the house most of the day, all that mattered was that Daisy seemed to get on with the baby, and so all was well with the world
Strong ExB shear flows in the pedestal region in H-mode plasma
We report the first experimental observation of stationary zonal flows in the
pedestal region of the H-mode plasma in the H-1 toroidal heliac. Strong peaks
in E_r shear mark the top and foot of the density pedestal. Strong m=n=0
low-frequency (f < 0.6 kHz) zonal flows are observed in regions of increased
E_r, suggesting substantial contribution of zonal flows to the spatial
modulation of E_r radial profiles. Radial localization of zonal flows is
correlated with a region of zero magnetic shear and low-order (7/5) rational
surfaces.Comment: 4 pages, 5 figure
Self-organization in turbulence as a route to order in plasma and fluids
Transitions from turbulence to order are studied experimentally in thin fluid
layers and magnetically confined toroidal plasma. It is shown that turbulence
self-organizes through the mechanism of spectral condensation. The spectral
redistribution of the turbulent energy leads to the reduction in the turbulence
level, generation of coherent flow, reduction in the particle diffusion and
increase in the system's energy. The higher order state is sustained via the
nonlocal spectral coupling of the linearly unstable spectral range to the
large-scale mean flow. The similarity of self-organization in two-dimensional
fluids and low-to-high confinement transitions in plasma suggests the
universality of the mechanism.Comment: 5 pages, 4 figure
Action minimizing fronts in general FPU-type chains
We study atomic chains with nonlinear nearest neighbour interactions and
prove the existence of fronts (heteroclinic travelling waves with constant
asymptotic states). Generalizing recent results of Herrmann and Rademacher we
allow for non-convex interaction potentials and find fronts with non-monotone
profile. These fronts minimize an action integral and can only exists if the
asymptotic states fulfil the macroscopic constraints and if the interaction
potential satisfies a geometric graph condition. Finally, we illustrate our
findings by numerical simulations.Comment: 19 pages, several figure
Generalized Action Invariants for Drift Waves-Zonal Flow Systems
Generalized action invariants are identified for various models of drift wave turbulence in the presence of the mean shear flow. It is shown that the wave kinetic equation describing the interaction of the small scale turbulence and large scale shear flow can be naturally written in terms of these invariants. Unlike the wave energy, which is conserved as a sum of small- and large- scale components, the generalized action invariant is shown to correspond to a quantity which is conserved for the small scale component alone. This invariant can be used to construct canonical variables leading to a different definition of the wave action (as compared to the case without shear flow). It is suggested that these new canonical action variables form a natural basis for the description of the drift wave turbulence with a mean shear flow
Radiotherapy for GIST progressing during or after tyrosine kinase inhibitor therapy : A prospective study
Purpose: Gastrointestinal stromal tumor (GIST) has been considered radiation-resistant, and radiotherapy is recommended only for palliation of bone metastases in current treatment guidelines. No registered prospective trial has evaluated GIST responsiveness to radiotherapy. Patients and methods: Patients with GIST progressing at intra-abdominal sites or the liver were entered to this prospective Phase II multicenter study (identifier NCT00515931). Metastases were treated with external beam radiotherapy using either conformal 3D planning or intensity modulated radiotherapy and conventional fractionation to a cumulative planning target volume dose of approximately 40 Gy. Systemic therapy was maintained unaltered during the study. Results: Of the 25 patients entered, 19 were on concomitant tyrosine kinase inhibitor therapy, most often imatinib. Two (8%) patients achieved partial remission, 20 (80%) had stable target lesion size for >= 3 months after radiotherapy with a median duration of stabilization of 16 months, and 3 (12%) progressed. The median time to radiotherapy target lesion progression was 4-fold longer than the median time to GIST progression at any site (16 versus 4 months). Radiotherapy was generally well tolerated. Conclusions: Responses to radiotherapy were infrequent, but most patients had durable stabilization of the target lesions. GIST patients with soft tissue metastases benefit frequently from radiotherapy. (C) 2015 The Authors. Published by Elsevier Ireland Ltd.Peer reviewe
Magneto-optical Kerr Effect Studies of Square Artificial Spin Ice
We report a magneto-optical Kerr effect study of the collective magnetic
response of artificial square spin ice, a lithographically-defined array of
single-domain ferromagnetic islands. We find that the anisotropic inter-island
interactions lead to a non-monotonic angular dependence of the array coercive
field. Comparisons with micromagnetic simulations indicate that the two
perpendicular sublattices exhibit distinct responses to island edge roughness,
which clearly influence the magnetization reversal process. Furthermore, such
comparisons demonstrate that disorder associated with roughness in the island
edges plays a hitherto unrecognized but essential role in the collective
behavior of these systems.Comment: Physical Review B, Rapid Communications (in press
Ruled Laguerre minimal surfaces
A Laguerre minimal surface is an immersed surface in the Euclidean space
being an extremal of the functional \int (H^2/K - 1) dA. In the present paper,
we prove that the only ruled Laguerre minimal surfaces are up to isometry the
surfaces R(u,v) = (Au, Bu, Cu + D cos 2u) + v (sin u, cos u, 0), where A, B, C,
D are fixed real numbers. To achieve invariance under Laguerre transformations,
we also derive all Laguerre minimal surfaces that are enveloped by a family of
cones. The methodology is based on the isotropic model of Laguerre geometry. In
this model a Laguerre minimal surface enveloped by a family of cones
corresponds to a graph of a biharmonic function carrying a family of isotropic
circles. We classify such functions by showing that the top view of the family
of circles is a pencil.Comment: 28 pages, 9 figures. Minor correction: missed assumption (*) added to
Propositions 1-2 and Theorem 2, missed case (nested circles having nonempty
envelope) added in the proof of Pencil Theorem 4, missed proof that the arcs
cut off by the envelope are disjoint added in the proof of Lemma
Absence of Complex I Is Associated with Diminished Respiratory Chain Function in European Mistletoe
Parasitism is a life history strategy found across all domains of life whereby nutrition is obtained from a host. It is often associated with reductive evolution of the genome, including loss of genes from the organellar genomes [1, 2]. In some unicellular parasites, the mitochondrial genome (mitogenome) has been lost entirely, with far-reaching consequences for the physiology of the organism [3, 4]. Recently, mitogenome sequences of several species of the hemiparasitic plant mistletoe (Viscum sp.) have been reported [5, 6], revealing a striking loss of genes not seen in any other multicellular eukaryotes. In particular, the nad genes encoding subunits of respiratory complex I are all absent and other protein-coding genes are also lost or highly diverged in sequence, raising the question what remains of the respiratory complexes and mitochondrial functions. Here we show that oxidative phosphorylation (OXPHOS) in European mistletoe, Viscum album, is highly diminished. Complex I activity and protein subunits of complex I could not be detected. The levels of complex IV and ATP synthase were at least 5-fold lower than in the non-parasitic model plant Arabidopsis thaliana, whereas alternative dehydrogenases and oxidases were higher in abundance. Carbon flux analysis indicates that cytosolic reactions including glycolysis are greater contributors to ATP synthesis than the mitochondrial tricarboxylic acid (TCA) cycle. Our results describe the extreme adjustments in mitochondrial functions of the first reported multicellular eukaryote without complex I
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