Signatures of quantum phase transitions in parallel quantum dots: Crossover from local moment to underscreened spin-1 Kondo physics

We study a strongly interacting "quantum dot 1" and a weakly interacting "dot 2" connected in parallel to metallic leads. Gate voltages can drive the system between Kondo-quenched and non-Kondo free-moment phases separated by Kosterlitz-Thouless quantum phase transitions. Away from the immediate vicinity of the quantum phase transitions, the physical properties retain signatures of first-order transitions found previously to arise when dot 2 is strictly noninteracting. As interactions in dot 2 become stronger relative to the dot-lead coupling, the free moment in the non-Kondo phase evolves smoothly from an isolated spin-one-half in dot 1 to a many-body doublet arising from the incomplete Kondo compensation by the leads of a combined dot spin-one. These limits, which feature very different spin correlations between dot and lead electrons, can be distinguished by weak-bias conductance measurements performed at finite temperatures.

Detection of human T-cell lymphotropic virus type 1 in plasma samples

Human T-cell lymphotropic virus type 1 (HTLV-1) is-an RNA virus responsible for diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATL). Cell-to-cell contact and Tax-induced clonal expansion of infected cells are the main modes of virus replication, making virus detection during the viremic stage difficult. Consequently, the proviral load is the current virologic marker for disease monitoring, but the mechanisms of progression have not been established yet. Thus, this study investigated the presence of virus in plasma from asymptomatic HTLV-1 carriers and from HAM/TSP patients. Real-time PCR was performed on DNA from 150 plasma samples; 12(8%) had detectable DNA amplification, including 6(4%) asymptomatic HTLV-1 carriers and 14(26%) HAM/TSP patients (p < 0.005). Of the 33 samples submitted for nested PCR, six (18%, p = 0.02) were positive for HTLV-1 RNA in the plasma. Additionally, 26 plasma samples were treated with DNAse enzyme to eliminate any DNA contamination before RNA extraction. Two of them (8%) showed amplification for HTLV-1 (p = 0.5). Therefore, this study described for the first time the detection of free HTLV-1 RNA in plasma from HTLV-1-infected subjects, regardless of their clinical status. Thus, HTLV-1 viral replication does occur in plasma, and other transmission pathways for HTLV-1 should be investigated further. (C) 2011 Elsevier B.V. All rights reserved.

Age-Related Expansion of Tim-3 Expressing T Cells in Vertically HIV-1 Infected Children

As perinatally HIV-1-infected children grow into adolescents and young adults, they are increasingly burdened with the long-term consequences of chronic HIV-1 infection, with long-term morbidity due to inadequate immunity. In progressive HIV-1 infection in horizontally infected adults, inflammation, T cell activation, and perturbed T cell differentiation lead to an "immune exhaustion'', with decline in T cell effector functions. T effector cells develop an increased expression of CD57 and loss of CD28, with an increase in co-inhibitory receptors such as PD-1 and Tim-3. Very little is known about HIV-1 induced T cell dysfunction in vertical infection. In two perinatally antiretroviral drug treated HIV-1-infected groups with median ages of 11.2 yr and 18.5 yr, matched for viral load, we found no difference in the proportion of senescent CD28(-)CD57(+)CD8(+) T cells between the groups. However, the frequency of Tim-3(+)CD8(+) and Tim-3(+)CD4(+) exhausted T cells, but not PD-1(+) T cells, was significantly increased in the adolescents with longer duration of infection compared to the children with shorter duration of HIV-1 infection. PD-1(+)CD8(+) T cells were directly associated with T cell immune activation in children. The frequency of Tim-3(+)CD8(+) T cells positively correlated with HIV-1 plasma viral load in the adolescents but not in the children. These data suggest that Tim-3 upregulation was driven by both HIV-1 viral replication and increased age, whereas PD-1 expression is associated with immune activation. These findings also suggest that the Tim-3 immune exhaustion phenotype rather than PD-1 or senescent cells plays an important role in age-related T cell dysfunction in perinatal HIV-1 infection. Targeting Tim-3 may serve as a novel therapeutic approach to improve immune control of virus replication and mitigate age related T cell exhaustion.

Divertor map with freedom of geometry and safety factor profile

An explicit, area-preserving and integrable magnetic field line map for a single-null divertor tokamak is obtained using a trajectory integration method to represent equilibrium magnetic surfaces. The magnetic surfaces obtained from the map are capable of fitting different geometries with freely specified position of the X-point, by varying free model parameters. The safety factor profile of the map is independent of the geometric parameters and can also be chosen arbitrarily. The divertor integrable map is composed of a nonintegrable map that simulates the effect of external symmetry-breaking resonances, so as to generate a chaotic region near the separatrix passing through the X-point. The composed field line map is used to analyze escape patterns (the connection length distribution and magnetic footprints on the divertor plate) for two equilibrium configurations with different magnetic shear profiles at the plasma edge.

Bifurcation effects on the plasma edge of tokamaks with ergodic limiter.

In the present paper, we solve a twist symplectic map for the action of an ergodic magnetic limiter in a large aspect-ratio tokamak. In this model, we study the bifurcation scenarios that occur in the remnants regular islands that co-exist with chaotic magnetic surfaces. The onset of atypical local bifurcations created by secondary shearless tori are identified through numerical profiles of internal rotation number and we observe that their rupture can reduce the usual magnetic field line escape at the tokamak plasma edge.

Tokamak TCABR: Acquisition system, data analysis, and remote participation using MDSplus

Each plasma physics laboratory has a proprietary scheme to control and data acquisition system. Usually, it is different from one laboratory to another. It means that each laboratory has its own way to control the experiment and retrieving data from the database. Fusion research relies to a great extent on international collaboration and this private system makes it difficult to follow the work remotely. The TCABR data analysis and acquisition system has been upgraded to support a joint research programme using remote participation technologies. The choice of MDSplus (Model Driven System plus) is proved by the fact that it is widely utilized, and the scientists from different institutions may use the same system in different experiments in different tokamaks without the need to know how each system treats its acquisition system and data analysis. Another important point is the fact that the MDSplus has a library system that allows communication between different types of language (JAVA, Fortran, C, C++, Python) and programs such as MATLAB, IDL, OCTAVE. In the case of tokamak TCABR interfaces (object of this paper) between the system already in use and MDSplus were developed, instead of using the MDSplus at all stages, from the control, and data acquisition to the data analysis. This was done in the way to preserve a complex system already in operation and otherwise it would take a long time to migrate. This implementation also allows add new components using the MDSplus fully at all stages. (c) 2012 Elsevier B.V. All rights reserved.

Shearless transport barriers in magnetically confined plasmas

Shearless transport barriers appear in confined plasmas due to non-monotonic radial profiles and cause localized reduction of transport even after they have been broken. In this paper we summarize our recent theoretical and experimental research on shearless transport barriers in plasmas confined in toroidal devices. In particular, we discuss shearless barriers in Lagrangian magnetic field line transport caused by non-monotonic safety factor profiles. We also discuss evidence of particle transport barriers found in the TCABR Tokamak (University of Sao Paulo) and the Texas Helimak (University of Texas at Austin) in biased discharges with non-monotonic plasma flows.

Anthropometric, physiological, performance, and nutritional profile of the Brazil National Canoe Polo Team

The purpose of this study was to determine the physiological, anthropometric, performance, and nutritional characteristics of the Brazil Canoe Polo National Team. Ten male canoe polo athletes (age 26.7 +/- 4.1 years) performed a battery of tests including assessments of anthropometric parameters, upper-body anaerobic power (Wingate), muscular strength, aerobic power, and nutritional profile. In addition, we characterized heart rate and plasma lactate responses and the temporal pattern of the effort/recovery during a simulated canoe polo match. The main results are as follows: body fat, 12.3 +/- 4.0%; upper-body peak and mean power, 6.8 +/- 0.5 and 4.7 +/- 0.4 W . kg(-1), respectively; 1-RM bench press, 99.1 +/- 11.7 kg; peak oxygen uptake, 44.3 +/- 5.8 mL . kg(-1) . min(-1); total energy intake, 42.8 +/- 8.6 kcal . kg(-1); protein, carbohydrate, and fat intakes, 1.9 +/- 0.1, 5.0 +/- 1.5, and 1.7 +/- 0.4 g . kg(-1), respectively; mean heart rate, 146 +/- 11 beats . min(-1); plasma lactate, 5.7 +/- 3.8 mmol . L-1 at half-time and 4.6 +/- 2.2 mmol . L-1 at the end of the match; effort time (relative to total match time), 93.1 +/- 3.0%; number of sprints, 9.6 +/- 4.4. The results of this study will assist coaches, trainers, and nutritionists in developing more adequate training programmes and dietary interventions for canoe polo athletes.

Equilibrium topology for plasmas with reversed current density.

Actually, transition from positive to negative plasma current and quasi-steady-state alternated current (AC) operation have been achieved experimentally without loss of ionization. The large transition times suggest the use of MHD equilibrium to model the intermediate magnetic field configurations for corresponding current density reversals. In the present work we show, by means of Maxwell equations, that the most robust equilibrium for any axisymmetric configuration with reversed current density requires the existence of several nonested families of magnetic surfaces inside the plasma. We also show that the currents inside the nonested families satisfy additive rules restricting the geometry and sizes of the axisymmetric magnetic islands; this is done without restricting the equilibrium through arbitrary functions. Finally, we introduce a local successive approximations method to describe the equilibrium about an arbitrary reversed current density minimum and, consequently, the transition between different nonested topologies is understood in terms of the eccentricity of the toroidal current density level sets.

Analysis of Electrostatic Turbulence Drive in Texas Helimak.

Plasma turbulence and particle transport in Texas Helimak change with the radial electric field profile modified by an external voltage bias. When the bias is positive, the turbulence shows enhanced level and broadband spectra with extreme events, similar to the turbulence in tokamak scrape-���off layer. However, negative bias reduces the turbulence level and decreases the spectrum widths. Moreover, for negative biased shots, the particle transport is strongly affected by a wave particle resonant interaction. On the other hand, for positive bias values, the plasma presents a transport barrier in the reversed shear flow region.

Multiple Island Chains in Primary Resonances.

We analyse the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a stationary electrostatic wave. We show that a pulsed wave produces an infinite number of perturbing terms with the same winding number. The perturbation coupling alters the number of island chains as a function of the parameters of the wave. We also observe that the number of chains in is always even if the number of islands in each chain is odd.

Scaling of Spontaneous Rotation with Temperature and Plasma Current in Tokamaks

Using theoretical arguments, a simple scaling law for the size of the intrinsic rotation observed in tokamaks in the absence of a momentum injection is found: The velocity generated in the core of a tokamak must be proportional to the ion temperature difference in the core divided by the plasma current, independent of the size of the device. The constant of proportionality is of the order of 10 km . s(-1) . MA . keV(-1). When the intrinsic rotation profile is hollow, i.e., it is countercurrent in the core of the tokamak and cocurrent in the edge, the scaling law presented in this Letter fits the data remarkably well for several tokamaks of vastly different size and heated by different mechanisms.

Pb0.90Ba0.10Zr0.40Ti0.60O3 Nanostructured Ferroelectric Ceramics Prepared by Spark Plasma Sintering

Nanostructured Pb0.90Ba0.10Zr0.40Ti0.60O3 dense ceramics presenting an average grain size of 62 +/- 5 nm was prepared by the polymeric precursor method and using the spark plasma sintering technique. The dielectric permittivity curves versus temperature exhibit broad anomaly, indicative of a diffuse phase transition. This result can be explained by the spread of Curie temperatures which are expected to depend on the degree of tetragonality related to the grain size distribution. A pronounced decrease in the maximum of the dielectric permittivity value is attributed to the existence of a large amount of grain boundaries which are non-ferroelectric regions.

H-1 low- and high-field NMR study of the effects of plasma treatment on the oil and water fractions in crude heavy oil

The chemical and physical properties of a Brazilian heavy oil submitted to plasma treatment were investigated by H-1 low-and high-field nuclear magnetic resonance (NMR) combined to the characterization of rheological properties, thermogravimetry and measurement of basic sediments and water (BSW) content. The crude oil was treated in a dielectric barrier discharge plasma reactor, using natural gas, CO2 or H-2 as working gas. The results indicated a large drop in the water content of the plasma-treated samples as compared to the crude oil, giving rise to a reduction in the viscosity. No significant chemical change was produced in the oil portion itself, as observed by H-1 NMR. The water contents determined by H-1 low-field NMR analyses agreed well with those obtained by BSW, indicating the low-field NMR methods as a useful tool for following the effects of plasma treatments on heavy oils, allowing the separation of the effects caused on the water and oil fractions. (C) 2011 Elsevier Ltd. All rights reserved.

Drag force in a strongly coupled anisotropic plasma

We calculate the drag force experienced by an in finitely massive quark propagating at constant velocity through an anisotropic, strongly coupled N = 4 plasma by means of its gravity dual. We find that the gluon cloud trailing behind the quark is generally misaligned with the quark velocity, and that the latter is also misaligned with the force. The drag coefficient mu can be larger or smaller than the corresponding isotropic value depending on the velocity and the direction of motion. In the ultra-relativistic limit we find that generically mu proportional to p. We discuss the conditions under which this behaviour may extend to more general situations.