A gradient index metamaterial

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index-of-refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated

Rhodium Pyrazolate Complexes as Potential CVD Precursors

Reaction of 3,5-(CF3)(2)PzLi with [Rh(mu-Cl)(eta(2)-C2H4)(2)](2) or [Rh(mu-Cl)(PMe3)(2)](2) in Et2O gave the dinuclear complexes [Rh(eta(2)-C2H4)(2)(mu-3,5-(CF3)(2)-Pz)](2) (1) and [Rh-2(mu-Cl)(mu-3,5-(CF3)(2)-Pz) (PMe3)(4)] (2) respectively (3,5-(CF3)(2)Pz = bis-trifluoromethyl pyrazolate). Reaction of PMe3 with [Rh(COD)(mu-3,5-(CF3)(2)-Pz)](2) in toluene gave [Rh(3,5-(CF3)(2)-Pz)(PMe3)(3)] (3). Reaction of 1 and 3 in toluene (1 : 4) gave moderate yields of the dinuclear complex [Rh(PMe3)(2)(mu-3,5-(CF3)(2)-Pz)](2) (4). Reaction of 3,5-(CF3)(2)PzLi with [Rh(PMe3)(4)]Cl in Et2O gave the ionic complex [Rh(PMe3)(4)][3,5-(CF3)(2)-Pz] (5). Two of the complexes, 1 and 3, were studied for use as CVD precursors. Polycrystalline thin films of rhodium (fcc-Rh) and metastable-amorphous films of rhodium phosphide (Rh2P) were grown from 1 and 3 respectively at 170 and 130 degrees C, 0.3 mmHg in a hot wall reactor using Ar as the carrier gas (5 cc min(-1)). Thin films of amorphous rhodium and rhodium phosphide (Rh2P) were grown from 1 and 3 at 170 and 130 degrees C respectively at 0.3 mmHg in a hot wall reactor using H-2 as the carrier gas (7 cc min(-1)).Welch Foundation F-816Petroleum Research Fund 47014-ACSNSF 0741973Chemistr

Energetics and dynamics of simple impulsive solar flares

Flare energetics and dynamics were studied using observations of simple impulsive spike bursts. A large, homogeneous set of events was selected to enable the most definite tests possible of competing flare models, in the absence of spatially resolved observations. The emission mechanisms and specific flare models that were considered in this investigation are described, and the derivations of the parameters that were tested are presented. Results of the correlation analysis between soft and hard X-ray energetics are also presented. The ion conduction front model and tests of that model with the well-observed spike bursts are described. Finally, conclusions drawn from this investigation and suggestions for future studies are discussed

Convergence of the waste and water sectors: risks, opportunities and future trends – discussion paper

The aim of this discussion paper is to bring to light the increasing convergence of the water and waste sectors and the associated risks, benefits, and future trends already on the horizon. Current examples of convergence in managing coal seam gas (CSG), food waste, fats, oils and grease (FOG) and biosolids, provide insights into not only the risks to public and environmental health of waste streams that cross sectoral boundaries but also potential opportunities for the water and waste sectors to seize as business opportunities. What is clear is that convergence between these sectors is already happening and in some cases there are adverse environmental consequences and associated health impacts. A key message from this research is the need to take an integrated and coordinated approach to planning and regulating the convergence of the water and waste sectors. Key recommendations to manage the risks associated with cross sector convergence of the water and waste sectors include facilitating: (1) increased engagement between regulators of each sector, (2) greater communication across sectors (3) a co-ordinated approach and plan to managing waste streams, (4) the development of monitoring and evaluation frameworks that cross sectors and (5) a coordinated approach to the assessment of research needs

New Dimensions for Wound Strings: The Modular Transformation of Geometry to Topology

We show, using a theorem of Milnor and Margulis, that string theory on compact negatively curved spaces grows new effective dimensions as the space shrinks, generalizing and contextualizing the results in hep-th/0510044. Milnor's theorem relates negative sectional curvature on a compact Riemannian manifold to exponential growth of its fundamental group, which translates in string theory to a higher effective central charge arising from winding strings. This exponential density of winding modes is related by modular invariance to the infrared small perturbation spectrum. Using self-consistent approximations valid at large radius, we analyze this correspondence explicitly in a broad set of time-dependent solutions, finding precise agreement between the effective central charge and the corresponding infrared small perturbation spectrum. This indicates a basic relation between geometry, topology, and dimensionality in string theory.Comment: 28 pages, harvmac big. v2: references and KITP preprint number added, minor change

Predictive relation for the α-relaxation time of a coarse-grained polymer melt under steady shear

We examine the influence of steady shear on structural relaxation in a simulated coarse-grained unentangled polymer melt over a wide range of temperature and shear rates. Shear is found to progressively suppress the α-relaxation process observed in the intermediate scattering function, leading ultimately to a purely inertially dominated β-relaxation at high shear rates, a trend similar to increasing temperature. On the basis of a scaling argument emphasizing dynamic heterogeneity in cooled liquids and its alteration under material deformation, we deduce and validate a parameter-free scaling relation for both the structural relaxation time τα from the intermediate scattering function and the “stretching exponent” β quantifying the extent of dynamic heterogeneity over the entire range of temperatures and shear rates that we can simulate

Modularization as a system life cycle management strategy:Drivers, barriers, mechanisms and impacts

This literature-grounded research contributes to a deeper understanding of modularization as a system life cycle management strategy, by providing a comprehensive view of its key barriers, drivers, possible mechanisms of implementation and impact. This comprehensive view, arranged into a decision-making–driven ontology, enables a decision maker to systematically identify modularization implementation opportunities in different industrial and service domains. The proposed ontology transforms modularization into a fully operationalizable strategy and contributes to a paradigm shift in the understanding of modularization, from a pure design option (i.e. modularity) to a fully strategic choice that, by nature, impacts on many of the system’s life cycle phases and involves a number of stakeholders

Thermodynamics, Structure, and Dynamics of Water Confined between Hydrophobic Plates

We perform molecular dynamics simulations of 512 water-like molecules that interact via the TIP5P potential and are confined between two smooth hydrophobic plates that are separated by 1.10 nm. We find that the anomalous thermodynamic properties of water are shifted to lower temperatures relative to the bulk by $\approx 40$ K. The dynamics and structure of the confined water resemble bulk water at higher temperatures, consistent with the shift of thermodynamic anomalies to lower temperature. Due to this $T$ shift, our confined water simulations (down to $T = 220$ K) do not reach sufficiently low temperature to observe a liquid-liquid phase transition found for bulk water at $T\approx 215$ K using the TIP5P potential. We find that the different crystalline structures that can form for two different separations of the plates, 0.7 nm and 1.10 nm, have no counterparts in the bulk system, and discuss the relevance to experiments on confined water.Comment: 31 pages, 14 figure