Basic Aspects of the Quantum Theory of Solids: Order and Elementary Excitations,by Daniel I. Khomskii

This article briefly surveys the wide variety of applications of radar in meteorology. Microwave radars are used to provide information about the distribution, type and intensity of precipitation in the atmosphere and about wind patterns and turbulence. VHF and UHF radars are used to provide wind profiles. Advances in information technology are enabling the information derived from radars to be processed and made available to users in a timely and convenient fashion. The detailed patterns of precipitation-intensity given by networks of radars are proving to be valuable to weather forecasters and hydrologists alike. Doppler radar enables tornadoes to be detected and aviation will be able to benefit from the detection of other hazardous wind conditions, such as wind shear and microbursts. For the research meteorologist, Doppler radar provides one of the best tools for measuring detailed 3-D fields of air motion within convective storms and frontal weather systems as well as within the planetary boundary layer.     

Understanding Quantum Phase Transitions,edited by Lincoln Carr

The concept of the superdeformed shape is first introduced classically as the most stable configuration of a rapidly rotating deformable body and is then applied to nuclei. The shape of nuclei are determined by a competition between the collective energy of the core, to which classical considerations apply quite well, and the quantal energies of the valence nucleons, which may be evaluated by the Nilsson model. The result of this competition is that slowly rotating nuclei can be either oblate or prolate but rapidly rotating nuclei can have a superdeformed prolate shape, with a 2:1 ratio of axes particularly favoured.

The evidence for superdeformation in nuclei is described under four headings. Firstly, some light nuclei are superdeformed in their ground state or in an excited state. Secondly, some nuclei pass through a well defined superdeformed shape on the way to fission. Thirdly, studies of the excitation functions of elastic and inelastic scattering of identical heavy ions provide evidence of a nuclear molecule in a superdeformed shape. Finally, recent analyses of gamma rays from nuclei formed in a very high spin state by a heavy ion collision provide conclusive evidence for superdeformation.     

Technical Report: UV and VUV Radiometry Programs at the Synchrotron Ultraviolet Radiation Facility (SURF III)

The fourth international workshop on Adaptive and Active X-ray &; XUV Optics (ACTOP11) was held on April 4–5, 2011, at Diamond Light Source in Oxfordshire, UK. This workshop follows on from earlier, successful active optic events at SOLEIL (2006), Elettra (2008), and Osaka (2009).     

THE PLACE OF EXPERIMENTAL TASKS IN GEOMETRY TEACHING: LEARNING FROM THE TEXTBOOK DESIGNS OF THE EARLY 20th CENTURY

The dual nature of geometry, in that it is a theoretical domain and an area of practical experience, presents mathematics teachers with opportunities and dilemmas. Opportunities exist to link theory with the everyday knowledge of pupils but the dilemmas are that learners very often find the dual nature of geometry a chasm that is very difficult to bridge. With research continuing to focus on understanding the nature of this problem, with a view to developing better pedagogical techniques, this paper examines the place of experimental tasks in the process of learning geometry. In particular, the paper provides some results from an analysis of innovative geometry textbooks designed in the early part of the 20^th Century, a time when significant efforts were being made to improve the teaching and learning of geometry. The analysis suggests that experimental tasks have a vital role to play and that a potent tool for informing the design of such tasks, so that they build effectively on pupils' geometrical intuition, is the notion of the geometrical eye, a term coined by Charles Godfrey in 1910 as "the power of seeing geometrical properties detach themselves from a figure".     

A New F Approximation for the Pillai—Bartlett Trace Under H 0

Abstract

Pillai suggested two approximations for the Pillai-Bartlett trace statistic in the null case. The first one matches one moment of a β₁ random variable, and corresponds to an F random variable, and the second matches four moments in the Pearson system. Although intuitively appealing and widely used in current statistical packages, the first lacks accuracy even with moderate sample size. The second matches two moment ratios in the Pearson system and provides much greater accuracy. Two new approximations match two moments of a β₁ random variable, and hence correspond to an F random variable, yet achieve most of the accuracy of Pillai's second approximation. The second of the two new approximations provides the best combination of logical properties and numerical accuracy.     

A system for encoding and searching markush structures

The encoding and searching of generic chemical structures, so-called Markush structures, have received little attention in the literature of late. The ability to encode and search these complex entities is of use in various branches of chemoinformatics. We describe a general language for encoding Markush structures and algorithms for searching them and give three examples of the utility of such a system: development of general Free-Wilson analyses of chemical series, detection of controlled substances within a large database of molecular structures, and searching of large databases of virtual compounds.     

An easy test for congruence modularity

We describe an easy way to determine whether the realization of a set of idempotent identities guarantees congruence modularity or the satisfaction of a nontrivial congruence identity. Our results yield slight strengthenings of Day’s Theorem and Gumm’s Theorem, which each characterize congruence modularity.     

Ultrafast photovoltaic response in ferroelectric nanolayers

We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond time scales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.     

Photorefractive control of surface plasmon polaritons in a hybrid liquid crystal cell

We present a photorefractive hybrid liquid crystal system that allows strong photorefractive effects on surface plasmon polaritons. We demonstrate its capability to couple energy between two 1.03 eV surface plasmon polariton modes with an efficiency of 25.3±2.3%. We present the energy and grating pitch dependence of the diffraction and a model that can qualitatively explain them.