810 research outputs found
Non-Abelian statistics as a Berry phase in exactly solvable models
We demonstrate how to directly study non-Abelian statistics for a wide class
of exactly solvable many-body quantum systems. By employing exact eigenstates
to simulate the adiabatic transport of a model's quasiparticles, the resulting
Berry phase provides a direct demonstration of their non-Abelian statistics. We
apply this technique to Kitaev's honeycomb lattice model and explicitly
demonstrate the existence of non-Abelian Ising anyons confirming the previous
conjectures. Finally, we present the manipulations needed to transport and
detect the statistics of these quasiparticles in the laboratory. Various
physically realistic system sizes are considered and exact predictions for such
experiments are provided.Comment: 10 pages, 3 figures. To appear in New Journal of Physic
Immune and acute phase markers in exercising adults
Many reports have documented the anti-inflammatory effects of regular exercise in adults. However clinicians and researchers remain uncertain on selecting specific biomarkers that are useful for predicting or monitoring chronic inflammatory states and/or disease. Clearer identification of markers (or clusters of markers) in physically active individuals that vary from established references ranges will indicate the extent of the purported anti-inflammatory effect of regular exercise.
Physically active adults were recruited from the community to participate in a prospective study comparing self-reported health outcomes and exercise activity across 150 days of dietary intervention. Of the 450 participants recruited, 64 males (mean age 37.4 y, mean BMI = 25.3) and 59 females (mean age 40.4y, mean BMI= 23.4) agreed to supply a baseline blood sample taken at rest. A total of 187 analytes were measured by standard techniques on these pre-intervention samples including 11 immune markers (cell-types and immunoglobulins) and 11 acute phase reactants (WCC, albumin, haptoglobin, CRP, C3, C4, IGF-1, transferrin, iron, ferritin & ceruloplasmin). We compared baseline values with relevent hospital reference range (RR) values where these are assumed to be more reflective of a much less physically-active community population.
A total of 5 out of 11 of the acute phase reactants (Hapt, C3, Fer, Trf (for females), and ceruloplasmin (for males)) had \u3e10% of values below the low âcut-off endâ of the relevant RR. Three immune cell-types (CD19, CD8 & CD16/56) had \u3e10% of values below the âlow-cut-off endâ of the relevant RR. In contrast 25% of subjects had an IgE value that exceeded the RR. Collectively our results support the notion that regular exercise or physical activity exerts an anti-inflammatory affect. The results suggest putative roles for a host of exercise associated adaptive mechanisms beyond the generally accepted role for IL-6 derived from skeletal muscle and\or visceral fat.
We conclude that across a host of measures, exercising adults have values for immune and acute phase reactants largely within, but at the non-inflammatory âendâ of clinical reference ranges
Preoperative and perioperative use of levosimendan in cardiac surgery: European expert opinion
In cardiac surgery, postoperative low cardiac output has been shown to correlate with increased rates of organ failure and mortality. Catecholamines have been the standard therapy for many years, although they carry substantial risk for adverse cardiac and systemic effects, and have been reported to be associated with increased mortality. On the other hand, the calcium sensitiser and potassium channel opener levosimendan has been shown to improve cardiac function with no imbalance in oxygen consumption, and to have protective effects in other organs. Numerous clinical trials have indicated favourable cardiac and non-cardiac effects of preoperative and perioperative administration of levosimendan. A panel of 27 experts from 18 countries has now reviewed the literature on the use of levosimendan in on-pump and off-pump coronary artery bypass grafting and in heart valve surgery. This panel discussed the published evidence in these various settings, and agreed to vote on a set of questions related to the cardioprotective effects of levosimendan when administered preoperatively, with the purpose of reaching a consensus on which patients could benefit from the preoperative use of levosimendan and in which kind of procedures, and at which doses and timing should levosimendan be administered. Here, we present a systematic review of the literature to report on the completed and ongoing studies on levosimendan, including the newly commenced LEVO-CTS phase III study (NCT02025621), and on the consensus reached on the recommendations proposed for the use of preoperative levosimendan
Deuterium retention on the tungsten-coated divertor tiles of JET ITER-like wall in 2015-2016 campaign
Tungsten-coated divertor files exposed during the third JET ITER-Like Wall (ILW) campaign in 2015-2016 (ILW-3) were studied with Secondary Ion Mass Spectrometry (SIMS). ILW-3 campaign contained more high-power plasma discharges and longer plasma time than the earlier ILW campaigns. Measurements showed increased beryllium (Be) deposition on the upper inner divertor, whereas on the outer divertor, Be deposition was lower than during the second campaign in 2013-2014 (ILW-2). Increased intensifies of nickel, molybdenum and tungsten were observed at the surface layer of the inner divertor Be dominated deposits. These layers are probably formed during the high-power plasma discharge phase near the end of the ILW-3 campaign. Compared to the earlier campaigns, D retention on the upper inner divertor was observed to on a similar level than after ILW-2, whereas at the lower inner divertor and most parts of the outer divertor, D retention was lower for ILW-3 than ILW-2. D retention was increased at lower part of outer divertor Tile 7, where Be deposition was slightly increased. Probable reason for the reduction is the higher surface temperature of the files due to higher powers used.Peer reviewe
Constrained spin dynamics description of random walks on hierarchical scale-free networks
We study a random walk problem on the hierarchical network which is a
scale-free network grown deterministically. The random walk problem is mapped
onto a dynamical Ising spin chain system in one dimension with a nonlocal spin
update rule, which allows an analytic approach. We show analytically that the
characteristic relaxation time scale grows algebraically with the total number
of nodes as . From a scaling argument, we also show the
power-law decay of the autocorrelation function C_{\bfsigma}(t)\sim
t^{-\alpha}, which is the probability to find the Ising spins in the initial
state {\bfsigma} after time steps, with the state-dependent non-universal
exponent . It turns out that the power-law scaling behavior has its
origin in an quasi-ultrametric structure of the configuration space.Comment: 9 pages, 6 figure
Scenario development for D-T operation at JET
The JET exploitation plan foresees D-T operations in 2020 (DTE2). With respect to the first D-T campaign in 1997 (DTE1), when JET was equipped with a carbon wall, the experiments will be conducted in presence of a beryllium-tungsten ITER-like wall and will benefit from an extended and improved set of diagnostics and higher additional heating power (32 MW neutral beam injection + 8 MW ion cyclotron resonance heating). There are several challenges presented by operations with the new wall: a general deterioration of the pedestal confinement; the risk of heavy impurity accumulation in the core, which, if not controlled, can cause the radiative collapse of the discharge; the requirement to protect the divertor from excessive heat loads, which may damage it permanently. Therefore, an intense activity of scenario development has been undertaken at JET during the last three years to overcome these difficulties and prepare the plasmas needed to demonstrate stationary high fusion performance and clear alpha particle effects. The paper describes the status and main achievements of this scenario development activity, both from an operational and plasma physics point of view.Peer reviewe
Real-time plasma state monitoring and supervisory control on TCV
In ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state arc modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECI I) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation.Peer reviewe
Transport Properties of Random Walks on Scale-Free/Regular-Lattice Hybrid Networks
We study numerically the mean access times for random walks on hybrid
disordered structures formed by embedding scale-free networks into regular
lattices, considering different transition rates for steps across lattice bonds
() and across network shortcuts (). For fast shortcuts () and
low shortcut densities, traversal time data collapse onto an universal curve,
while a crossover behavior that can be related to the percolation threshold of
the scale-free network component is identified at higher shortcut densities, in
analogy to similar observations reported recently in Newman-Watts small-world
networks. Furthermore, we observe that random walk traversal times are larger
for networks with a higher degree of inhomogeneity in their shortcut
distribution, and we discuss access time distributions as functions of the
initial and final node degrees. These findings are relevant, in particular,
when considering the optimization of existing information networks by the
addition of a small number of fast shortcut connections.Comment: 8 pages, 6 figures; expanded discussions, added figures and
references. To appear in J Stat Phy
Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns
Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).Peer reviewe
Overview of the JET ITER-like wall divertor
The work presented draws on new analysis of components removed following the second JET ITER-like wall campaign 2013â14 concentrating on the upper inner divertor, inner and outer divertor corners, lifetime issues relating to tungsten coatings on JET carbon fibre composite divertor tiles and dust/particulate generation. The results show that the upper inner divertor remains the region of highest deposition in the JET-ILW. Variations in plasma configurations between the first and second campaign have altered material migration to the corners of the inner and outer divertor. Net deposition is shown to be beneficial in the sense that it reduces W coating erosion, covers small areas of exposed carbon surfaces and even encapsulates particles.The work presented draws on new analysis of components removed following the second JET ITER-like wall campaign 2013â14 concentrating on the upper inner divertor, inner and outer divertor corners, lifetime issues relating to tungsten coatings on JET carbon fibre composite divertor tiles and dust/particulate generation. The results show that the upper inner divertor remains the region of highest deposition in the JET-ILW. Variations in plasma configurations between the first and second campaign have altered material migration to the corners of the inner and outer divertor. Net deposition is shown to be beneficial in the sense that it reduces W coating erosion, covers small areas of exposed carbon surfaces and even encapsulates particles.Peer reviewe
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