First order transition between magnetic order and valence-bond order in a 2D frustrated Heisenberg model

We study the competition between magnetic order and valence bond order in a two dimensional (2D) frustrated Heisenberg model introduced some time ago by Shastry and Sutherland ({\sc B. Sriram Shastry} and {\sc Bill Sutherland}, {\em Physica} 108{\bf B},1069 (1981) ) for which a configuration of dimers is known to be the ground state in a certain range of parameters. Using exact diagonalisation of small clusters, linear spin wave theory and Schwinger boson mean field theory, we show that the transition between the two types of order is first-order, and that it takes place inside the domain where magnetic long-range order is stable with respect to quantum fluctuations.Comment: Revtex, 8 pages, 1 latex figure and 2 uuencoded postscript figure

ABJM Wilson loops in the Fermi gas approach

The matrix model of ABJM theory can be formulated in terms of a Fermi gas in an external potential. We show that, in this formalism, vevs of Wilson loops correspond to averages of operators in the statistical-mechanical problem. This makes it possible to calculate these vevs at all orders in 1/N, up to exponentially small corrections, and for arbitrary Chern-Simons coupling, by using the WKB expansion. We present explicit results for the vevs of 1/6 and the 1/2 BPS Wilson loops, at any winding number, in terms of Airy functions. Our expressions are shown to reproduce the low genus results obtained previously in the 't Hooft expansion.Comment: 48 pages, 2 figures, expansion (2.110) and typos corrected, slight improvements of the presentatio

Bead-based assay for spatiotemporal gene expression control in cell-free transcription-translation systems

Cell-free gene expression has applications in synthetic biology, biotechnology and biomedicine. In this technique gene expression regulation plays an important role. Transcription factors do not completely suppress expression while other methods for expression control, for example CRISPR/Cas, often require important biochemical modifications. Here we use an all Escherichia coli-based cell-free expression system and present a bead-based method to instantly start and, at a later stage, completely stop gene expression. Magnetic beads coated with DNA of the gene of interest trigger gene expression. The expression stops if we remove the bead-bound DNA as well as transcribed mRNA by hybridization to bead-bound ssDNA. Our method is a simple way to control expression duration very accurately in time and space

Mindfully Teaching in the Classroom: a Literature Review

The practice of mindfulness is being used with increased frequency in schools around the world. In the current literature review we outline some of the core concepts and practices associated with mindfulness and discuss studies analysing the process of mindfulness teacher training. Preliminary research in this emerging field suggests that mindfulness has the potential to improve classroom management, teacher-student relationships and instructional strategies. Mindfulness instructors recommend that before teachers can feel comfortable and effectively teach mindfulness in the classroom they need to embody and practice mindfulness in their own lives. It is proposed that in order to improve our knowledge base in this area a critical synthesis and analysis of school-based mindfulness programs is required

Mapping Evolving Internal Roles of the Armed Forces

It is widely assumed, at least from a Western perspective, that the armed forces provide national defence against external threats. In reality, within many consolidated Western democracies the armed forces are assuming an increasingly wide range of internal roles and tasks. These can include domestic security roles and the provision of humanitarian assistance in situations of natural or humanitarian catastrophe, often under the command and control of different civilian agencies. This SSR Paper seeks to make sense of this complex reality. Different internal roles of armed forces are analysed, drawing on the cases of Austria, Belgium, Canada, Denmark, Finland, France, Germany, Italy, Luxembourg, Netherlands, Norway, Spain, Sweden, the United Kingdom and the United States of America. Through carefully examining evolving internal roles and identifying patterns and lessons from these experiences, this SSR Paper provides an important contribution to understanding the evolving nature of contemporary armed forces

Operations and Performance of the PACS Instrument 3He Sorption Cooler on board of the Herschel Space Observatory

A 3He sorption cooler produced the operational temperature of 285mK for the bolometer arrays of the Photodetector Array Camera and Spectrometer (PACS) instrument of the Herschel Space Observatory. This cooler provided a stable hold time between 60 and 73h, depending on the operational conditions of the instrument. The respective hold time could be determined by a simple functional relation established early on in the mission and reliably applied by the scientific mission planning for the entire mission. After exhaustion of the liquid 3He due to the heat input by the detector arrays, the cooler was recycled for the next operational period following a well established automatic procedure. We give an overview of the cooler operations and performance over the entire mission and distinguishing in-between the start conditions for the cooler recycling and the two main modes of PACS photometer operations. As a spin-off, the cooler recycling temperature effects on the Herschel cryostat 4He bath were utilized as an alternative method to dedicated Direct Liquid Helium Content Measurements in determining the lifetime of the liquid Helium coolant.Comment: 34 pages, 13 figures, accepted in Experimental Astronom

Gyrokinetic Large Eddy Simulations

The Large Eddy Simulation (LES) approach is adapted to the study of plasma microturbulence in a fully three-dimensional gyrokinetic system. Ion temperature gradient driven turbulence is studied with the {\sc GENE} code for both a standard resolution and a reduced resolution with a model for the sub-grid scale turbulence. A simple dissipative model for representing the effect of the sub-grid scales on the resolved scales is proposed and tested. Once calibrated, the model appears to be able to reproduce most of the features of the free energy spectra for various values of the ion temperature gradient