Current sheet formation and nonideal behavior at three-dimensional magnetic null points

The nature of the evolution of the magnetic field, and of current sheet formation, at three-dimensional (3D) magnetic null points is investigated. A kinematic example is presented which demonstrates that for certain evolutions of a 3D null (specifically those for which the ratios of the null point eigenvalues are time-dependent) there is no possible choice of boundary conditions which renders the evolution of the field at the null ideal. Resistive MHD simulations are described which demonstrate that such evolutions are generic. A 3D null is subjected to boundary driving by shearing motions, and it is shown that a current sheet localised at the null is formed. The qualitative and quantitative properties of the current sheet are discussed. Accompanying the sheet development is the growth of a localised parallel electric field, one of the signatures of magnetic reconnection. Finally, the relevance of the results to a recent theory of turbulent reconnection is discussed.Comment: to appear in Phys. Plasmas. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin/ In this replacement version, typos have been corrected, and in addition references and some further discussion adde

Quasi-Dynamic Frame Coordination For Ultra- Reliability and Low-Latency in 5G TDD Systems

The fifth generation (5G) mobile technology features the ultra-reliable and low-latency communications (URLLC) as a major service class. URLLC applications demand a tight radio latency with extreme link reliability. In 5G dynamic time division duplexing (TDD) systems, URLLC requirements become further challenging to achieve due to the severe and fast-varying cross link interference (CLI) and the switching time of the radio frame configurations (RFCs). In this work, we propose a quasi-dynamic inter-cell frame coordination algorithm using hybrid frame design and a cyclic-offset-based RFC code-book. The proposed solution adaptively updates the RFCs in time such that both the average CLI and the user-centric radio latency are minimized. Compared to state-of-the-art dynamic TDD studies, the proposed scheme shows a significant improvement in the URLLC outage latency, i.e., 92% reduction gain, while boosting the cell-edge capacity by 189% and with a greatly reduced coordination overhead space, limited to B-bit

Two-photon Double Ionization of H2_2 in Intense Femtosecond Laser Pulses

Triple-differential cross sections for two-photon double ionization of molecular hydrogen are presented for a central photon energy of 30 eV. The calculations are based on a fully {\it ab initio}, nonperturbative, approach to the time-dependent Schroedinger equation in prolate spheroidal coordinates, discretized by a finite-element discrete-variable-representation. The wave function is propagated in time for a few femtoseconds using the short, iterative Lanczos method to study the correlated response of the two photoelectrons to short, intense laser radiation. The current results often lie in between those of Colgan {\it et al} [J. Phys. B {\bf 41} (2008) 121002] and Morales {\it et al} [J. Phys. B {\bf 41} (2009) 134013]. However, we argue that these individual predictions should not be compared directly to each other, but preferably to experimental data generated under well-defined conditions.Comment: 4 pages, 4 figure

A cross-cultural study of cereal foods' quality perception

Cereal foods' production and use show substantial heterogeneity across Europe. For a category central in most EU diets, cereal foods' quality perception is, nevertheless, surprisingly understudied. With this in mind, 357 Danish, Lithuanian and Portuguese citizens were inquired about the importance of several cues and dimensions in their evaluation of the perceived quality of bread, cookies, breakfast cereals, pasta and vodka. Portuguese and Lithuanians consistently gave a significantly higher average importance to all the cues and quality dimensions considered, for all products, than their Danish counterparts. Nevertheless, respondents in all three samples found expected quality dimensions to be much more important than both extrinsic and intrinsic cues across almost all product categories. Dimensions and cues like taste and country - of- origin were the most relevant to Lithuanians, while taste , label information and price were the most important for Danes. The cues and dimensions Portuguese found relevant were fairly different and more category- dependent. Cues like store type for bread, brand for breakfast cereals, pasta and vodka, country - of- origin for vodka , and price for cookies, pasta and vodka were more often assessed by the Portuguese as relevant for decision- making at the point - of- purchase. This highlights the need for further cross - cultural research on food quality perception.Cereal Foods, Consumer Quality Perception, Total Food Quality Model, Cross - cultural Study, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

On the fundamental theorem of asset pricing: random constraints and bang-bang no-arbitrage criteria

The paper generalizes and refines the Fundamental Theorem of Asset Pricing of Dalang, Morton and Willinger in the following two respects: (a) the result is extended to a model with portfolio constraints; (b) versions of the no-arbitrage criterion based on the bang-bang principle in control theory are developed.no arbitrage criteria, portfolio constraints, supermartingale measures, bang-bang control