New Symmetries in Crystals and Handed Structures

For over a century, the structure of materials has been described by a combination of rotations, rotation-inversions and translational symmetries. By recognizing the reversal of static structural rotations between clockwise and counterclockwise directions as a distinct symmetry operation, here we show that there are many more structural symmetries than are currently recognized in right- or left-handed handed helices, spirals, and in antidistorted structures composed equally of rotations of both handedness. For example, though a helix or spiral cannot possess conventional mirror or inversion symmetries, they can possess them in combination with the rotation reversal symmetry. Similarly, we show that many antidistorted perovskites possess twice the number of symmetry elements as conventionally identified. These new symmetries predict new forms for "roto" properties that relate to static rotations, such as rotoelectricity, piezorotation, and rotomagnetism. They also enable symmetry-based search for new phenomena, such as multiferroicity involving a coupling of spins, electric polarization and static rotations. This work is relevant to structure-property relationships in all material structures with static rotations such as minerals, polymers, proteins, and engineered structures.Comment: 15 Pages, 4 figures, 3 Tables; Fig. 2b has error

Bounding the pseudogap with a line of phase transitions in YBCO cuprate superconductors

Close to optimal doping, the copper oxide superconductors show 'strange metal' behavior, suggestive of strong fluctuations associated with a quantum critical point. Such a critical point requires a line of classical phase transitions terminating at zero temperature near optimal doping inside the superconducting 'dome'. The underdoped region of the temperature-doping phase diagram from which superconductivity emerges is referred to as the 'pseudogap' because evidence exists for partial gapping of the conduction electrons, but so far there is no compelling thermodynamic evidence as to whether the pseudogap is a distinct phase or a continuous evolution of physical properties on cooling. Here we report that the pseudogap in YBCO cuprate superconductors is a distinct phase, bounded by a line of phase transitions. The doping dependence of this line is such that it terminates at zero temperature inside the superconducting dome. From this we conclude that quantum criticality drives the strange metallic behavior and therefore superconductivity in the cuprates

Component-based approach in the development of a knowledge-based planning support system (KBPSS). Part 1: The architecture of KBPSS

Urban planners need to have a flexible, interactive, and intelligent computer-based tool to support their use of analytical models and to structure their planning process. Existing spatial information systems have not developed appropriate procedures and mechanisms to enable easy construction and manipulation of models within their system environment, and to allow various information resources to be shared by different application systems and platforms. Recent research and development of planning support systems (PSS) provide a range of interesting concepts and frameworks that can be adopted by system developers to design a multifunctional and planning-specific decision support system to meet the multifaceted needs of the planning process. In this paper we aim to go beyond the current approaches of PSS and spatial decision support systems (SDSS) in designing a knowledge-based PSS (KBPSS) that uses the component-based software development (CBSD) approach. We introduce the features of CBSD and its technical advantages in the design of a multifunctional PSS. An architecture of a component-based KBPSS is subsequently proposed which incorporates four essential component systems: MapObjects GIS, Database Manager database management system, ModelObjects model-management system, and KBSAgents knowledge-based system. The first two components are based on proprietary components systems and can be easily adapted into the KBPSS environment. The ModelObjects and KBSAgents components were developed by the authors. Based on these components and their associated information layers, two application subsystems are constructed: a Model and Knowledge Development System and an Intelligent Model Selection System. These application systems can be used to assist users and model developers to build new models or to select predefined models from an existing model library for their problems. In order to implement these functions, we propose and define a number of procedures and techniques for component communication and model and knowledge development.link_to_subscribed_fulltex