Breakdown of adiabatic invariance in spherical tokamaks

Thermal ions in spherical tokamaks have two adiabatic invariants: the magnetic moment and the longitudinal invariant. For hot ions, variations in magnetic-field strength over a gyro period can become sufficiently large to cause breakdown of the adiabatic invariance. The magnetic moment is more sensitive to perturbations than the longitudinal invariant and there exists an intermediate regime, super-adiabaticity, where the longitudinal invariant remains adiabatic, but the magnetic moment does not. The motion of super-adiabatic ions remains integrable and confinement is thus preserved. However, above a threshold energy, the longitudinal invariant becomes non-adiabatic too, and confinement is lost as the motion becomes chaotic. We predict beam ions in present-day spherical tokamaks to be super-adiabatic but fusion alphas in proposed burning-plasma spherical tokamaks to be non-adiabatic.Comment: 6 pages, 8 figure

Mind the Gap: A Study in Global Development through Persistent Homology

The Gapminder project set out to use statistics to dispel simplistic notions about global development. In the same spirit, we use persistent homology, a technique from computational algebraic topology, to explore the relationship between country development and geography. For each country, four indicators, gross domestic product per capita; average life expectancy; infant mortality; and gross national income per capita, were used to quantify the development. Two analyses were performed. The first considers clusters of the countries based on these indicators, and the second uncovers cycles in the data when combined with geographic border structure. Our analysis is a multi-scale approach that reveals similarities and connections among countries at a variety of levels. We discover localized development patterns that are invisible in standard statistical methods

Congenital thumb anomalies and the consequences for daily life : patients’ long-term experience after corrective surgery. A qualitative study

Purpose: The aim of the study was to explore patients’ long-term experience of a congenital hand problem, and the consequences for daily life. Method: Fifteen participants with a median age 24 years (17–55 years), born with thumb hypoplasia/aplasia or thumb duplication were interviewed using a semi-structured interview guide. The interviews were subjected to qualitative content analysis. Results: Although the mobility and strength in the thumb/hand(s) varied within the group, hand function was generally described as good. Compensatory strategies were used to overcome practical obstacles. The emotional reactions to being visibly different from peers in early life varied from total acceptance and a sense of pride in being special, to deep distress and social withdrawal. Support from parents, teachers and others was important in facing emotional challenges and practical consequences. Conclusion: The present study highlights the importance of healthcare professionals addressing appearance-related concerns which may have long-term emotional and social consequences for patients born with a thumb anomaly. Implications for RehabilitationAppearance-related concerns and need for emotional support should be fully considered throughout the rehabilitation process to prevent distress and social withdrawal.Effective problem-solving strategies, such as compensation, change in occupational performance and support from others may reduce activity limitations and participation restriction

Relation between cardiac dimensions and peak oxygen uptake

<p>Abstract</p> <p>Background</p> <p>Long term endurance training is known to increase peak oxygen uptake (<inline-formula><graphic file="1532-429X-12-8-i1.gif"/></inline-formula>) and induce morphological changes of the heart such as increased left ventricular mass (LVM). However, the relationship between <inline-formula><graphic file="1532-429X-12-8-i1.gif"/></inline-formula> and the total heart volume (THV), considering both the left and right ventricular dimensions in both males and females, is not completely described. Therefore, the aim of this study was to test the hypothesis that THV is an independent predictor of <inline-formula><graphic file="1532-429X-12-8-i1.gif"/></inline-formula> and to determine if the left and right ventricles enlarge in the same order of magnitude in males and females with a presumed wide range of THV.</p> <p>Methods and Results</p> <p>The study population consisted of 131 subjects of whom 71 were athletes (30 female) and 60 healthy controls (20 female). All subjects underwent cardiovascular MR and maximal incremental exercise test. Total heart volume, LVM and left- and right ventricular end-diastolic volumes (LVEDV, RVEDV) were calculated from short-axis images. <inline-formula><graphic file="1532-429X-12-8-i1.gif"/></inline-formula> was significantly correlated to THV, LVM, LVEDV and RVEDV in both males and females. Multivariable analysis showed that THV was a strong, independent predictor of <inline-formula><graphic file="1532-429X-12-8-i1.gif"/></inline-formula> (R²= 0.74, p < 0.001). As LVEDV increased, RVEDV increased in the same order of magnitude in both males and females (R²= 0.87, p < 0.001).</p> <p>Conclusion</p> <p>Total heart volume is a strong, independent predictor of maximal work capacity for both males and females. Long term endurance training is associated with a physiologically enlarged heart with a balance between the left and right ventricular dimensions in both genders.</p

Solid-Liquid Phase Diagrams for Binary Metallic Alloys: Adjustable Interatomic Potentials

We develop a new approach to determining LJ-EAM potentials for alloys and use these to determine the solid-liquid phase diagrams for binary metallic alloys using Kofke's Gibbs-Duhem integration technique combined with semigrand canonical Monte Carlo simulations. We demonstrate that it is possible to produce a wide-range of experimentally observed binary phase diagrams (with no intermetallic phases) by reference to the atomic sizes and cohesive energies of the two elemental materials. In some cases, it is useful to employ a single adjustable parameter to adjust the phase diagram (we provided a good choice for this free parameter). Next, we perform a systematic investigation of the effect of relative atomic sizes and cohesive energies of the elements on the binary phase diagrams. We then show that this approach leads to good agreement with several experimental binary phase diagrams. The main benefit of this approach is not the accurately reproduction of experimental phase diagrams, but rather to provide a method by which material properties can be continuously changed in simulations studies. This is one of the keys to the use of atomistic simulations to understand mechanisms and properties in a manner not available to experiment

Direct Improvement of Hamiltonian Lattice Gauge Theory

We demonstrate that a direct approach to improving Hamiltonian lattice gauge theory is possible. Our approach is to correct errors in the Kogut-Susskind Hamiltonian by incorporating additional gauge invariant terms. The coefficients of these terms are chosen so that the order $a^2$ classical errors vanish. We conclude with a brief discussion of tadpole improvement in Hamiltonian lattice gauge theory.Comment: 9 page

Density functional study of the adsorption of K on the Ag(111) surface

Full-potential gradient corrected density functional calculations of the adsorption of potassium on the Ag(111) surface have been performed. The considered structures are Ag(111) (root 3 x root 3) R30degree-K and Ag(111) (2 x 2)-K. For the lower coverage, fcc, hcp and bridge site; and for the higher coverage all considered sites are practically degenerate. Substrate rumpling is most important for the top adsorption site. The bond length is found to be nearly identical for the two coverages, in agreement with recent experiments. Results from Mulliken populations, bond lengths, core level shifts and work functions consistently indicate a small charge transfer from the potassium atom to the substrate, which is slightly larger for the lower coverage.Comment: to appear in Phys Rev

The Quiet-Sun Photosphere and Chromosphere

The overall structure and the fine structure of the solar photosphere outside active regions are largely understood, except possibly important roles of a turbulent near-surface dynamo at its bottom, internal gravity waves at its top, and small-scale vorticity. Classical 1D static radiation-escape modelling has been replaced by 3D time-dependent MHD simulations that come closer to reality. The solar chromosphere, in contrast, remains ill-understood although its pivotal role in coronal mass and energy loading makes it a principal research area. Its fine structure defines its overall structure, so that hard-to-observe and hard-to-model small-scale dynamical processes are the key to understanding. However, both chromospheric observation and chromospheric simulation presently mature towards the required sophistication. The open-field features seem of greater interest than the easier-to-see closed-field features.Comment: Accepted for special issue "Astrophysical Processes on the Sun" of Phil. Trans. Royal Soc. A, ed. C. Parnell. Note: clicking on the year in a citation opens the corresponding ADS abstract page in the browse

Solar polarimetry through the K I lines at 770 nm

We characterize the K I D1 & D2 lines in order to determine whether they could complement the 850 nm window, containing the Ca II infrared triplet lines and several Zeeman sensitive photospheric lines, that was studied previously. We investigate the effect of partial redistribution on the intensity profiles, their sensitivity to changes in different atmospheric parameters, and the spatial distribution of Zeeman polarization signals employing a realistic magnetohydrodynamic simulation. The results show that these lines form in the upper photosphere at around 500 km and that they are sensitive to the line of sight velocity and magnetic field strength at heights where neither the photospheric lines nor the Ca II infrared lines are. However, at the same time, we found that their sensitivity to the temperature essentially comes from the photosphere. Then, we conclude that the K I lines provide a complement to the lines in the 850 nm window for the determination of atmospheric parameters in the upper photosphere, especially for the line of sight velocity and the magnetic field.Comment: 10 pages, 9 figures, main journal publicatio