Direct manipulation of wave amplitude and phase through inverse design of isotropic media

In this article we propose a new design methodology to control both amplitude and phase of electromagnetic waves from cylindrical incidence, which utilizes engineered media that does not resort to transformation optics or its quasi-conformal approximations. This method can lead to two-dimensional isotropic, inhomogeneous material profiles of permittivity and permeability, to which a general class of scattering-free wave solutions arise. Our design is based on the separation of the complex wave solution into amplitude and phase. We give two types of examples to validate our methodology.We are supported by the Engineering and Physical Sciences Research Council (EPSRC) of UK [grant number EP/I034548/1]. L Y benefits from EPSRC Durham Symposium 104, LMS Caring Supplementary Grant [Ref. CC-15/16-09] and Antennas group travel grant [EECSRC2/4a], and wants to thank Patrick Bradley, Flynn Castle and Fang Yanlong for inspiring conversations to improve this manuscript

A class of invisible inhomogeneous media and the control of electromagnetic waves

We propose a general method to arbitrarily manipulate an electromagnetic wave propagating in a two-dimensional medium, without introducing any scattering. This leads to a whole class of isotropic spatially varying permittivity and permeability profiles that are invisible while shaping the field magnitude and/or phase. In addition, we propose a metamaterial structure working in the infrared that demonstrates deep sub-wavelength control of the electric field amplitude and strong reduction of the scattering. This work offers an alternative strategy to achieve invisibility with isotropic materials and paves the way for tailoring the propagation of light at the nanoscal

A game theoretic approach for optimizing density of remote radio heads in user centric cloud-based radio access network

In this paper, we develop a game theoretic formulation for empowering cloud enabled HetNets with adaptive Self Organizing Network (SON) capabilities. SON capabilities for intelligent and efficient radio resource management is a fundamental design pillar for the emerging 5G cellular networks. The C-RAN system model investigated in this paper consists of ultra-dense remote radio heads (RRHs) overlaid by central baseband units that can be collocated with much less densely deployed overlaying macro base-stations (BSs). It has been recently demonstrated that under a user centric scheduling mechanism, C-RAN inherently manifests the trade-off between Energy Efficiency (EE) and Spectral Efficiency (SE) in terms of RRH density. The key objective of the game theoretic framework developed in this paper is to dynamically optimize the trade-off between the EE and the SE of the C- RAN. More specifically, for an ultra-dense C- RAN based HetNet, the density of active RRHs should be carefully dimensioned to maximize the SE. However, the density of RRHs which maximizes the SE may not necessarily be optimal in terms of the EE. In order to strike a balance between these two performance determinants, we develop a game theoretic formulation by employing a Nash bargaining framework. The two metrics of interest, SE and EE, are modeled as virtual players in a bargaining problem and the Nash bargaining solution for RRH density is determined. In the light of the optimization outcome we evaluate corresponding key performance indicators through numerical results. These results offer insights for a C-RAN designer on how to optimally design a SON mechanism to achieve a desired trade-off level between the SE and the EE in a dynamic fashion

Earlier versus later start of antiretroviral therapy in HIV-infected adults with tuberculosis.

Tuberculosis remains an important cause of death among patients infected with the human immunodeficiency virus (HIV). Robust data are lacking with regard to the timing for the initiation of antiretroviral therapy (ART) in relation to the start of antituberculosis therapy

The Universal One-Loop Effective Action

We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.Comment: 30 pages, v2 contains additional comments and corrects typos, version accepted for publication in JHE

Decoherence-protected quantum gates for a hybrid solid-state spin register

Protecting the dynamics of coupled quantum systems from decoherence by the environment is a key challenge for solid-state quantum information processing. An idle qubit can be efficiently insulated from the outside world via dynamical decoupling, as has recently been demonstrated for individual solid-state qubits. However, protection of qubit coherence during a multi-qubit gate poses a non-trivial problem: in general the decoupling disrupts the inter-qubit dynamics, and hence conflicts with gate operation. This problem is particularly salient for hybrid systems, wherein different types of qubits evolve and decohere at vastly different rates. Here we present the integration of dynamical decoupling into quantum gates for a paradigmatic hybrid system, the electron-nuclear spin register. Our design harnesses the internal resonance in the coupled-spin system to resolve the conflict between gate operation and decoupling. We experimentally demonstrate these gates on a two-qubit register in diamond operating at room temperature. Quantum tomography reveals that the qubits involved in the gate operation are protected as accurately as idle qubits. We further illustrate the power of our design by executing Grover's quantum search algorithm, achieving fidelities above 90% even though the execution time exceeds the electron spin dephasing time by two orders of magnitude. Our results directly enable decoherence-protected interface gates between different types of promising solid-state qubits. Ultimately, quantum gates with integrated decoupling may enable reaching the accuracy threshold for fault-tolerant quantum information processing with solid-state devices.Comment: This is original submitted version of the paper. The revised and finalized version is in print, and is subjected to the embargo and other editorial restrictions of the Nature journa

Methane production and energy partition in sheep fed timothy silage- or hay-based diets

Methane is produced as a result of anaerobic fermentation of the soluble and structural carbohydrates by methanogens in the rumen of ruminant animals. Removal of methane from rumen represents a loss of approximately 7.22% of gross energy intake.  Four ruminally fistulated Cheviot wethers were used in a crossover design to determine methane production and energy partition in sheep fed timothy silage- or hay-based diets. The experimental diets consisted of either timothy silage or timothy hay and a commercial concentrate (85:15, on DM basis). Variables measured were nutrients digestibility, energy balance and methane production. Apparent digestibilities of DM, OM, CP, NDF, ADF, cellulose and hemicellulose were significantly higher (P0.05) on sheep fed silage-based diet than those fed hay-based diet. Sheep fed silage-based diet had greater (P0.01) urinary energy loss, methane and heat production, but lower (P0.05) fecal energy loss. Methane production, either expressed as g kg-1 dry matter intake or g day-1 was markedly lower (P0.05) in hay-based diet as compared to silage-based diet. There was a strong relationship between methane production (g day-1) and NDF digested (g day-1) (R2 = 88.4%, P0.001). Methane production expressed as g kg-1 NDF digested in silage-based diet was higher (P0.05) than in hay-based diet (66.44 vs 62.70). These results indicate that methane release by sheep increased with increasing NDF digested. Key Words : Methane, Silage, Hay, Neutral detergent fiber, Shee

Implications of a High-Mass Diphoton Resonance for Heavy Quark Searches

Heavy vector-like quarks coupled to a scalar $S$ will induce a coupling of this scalar to gluons and possibly (if electrically charged) photons. The decay of the heavy quark into $Sq$, with $q$ being a Standard Model quark, provides, if kinematically allowed, new channels for heavy quark searches. Inspired by naturalness considerations, we consider the case of a vector-like partner of the top quark. For illustration, we show that a singlet partner can be searched for at the 13$\,$TeV LHC through its decay into a scalar resonance in the $2\gamma+\ell + X$ final states, especially if the diphoton branching ratio of the scalar $S$ is further enhanced by the contribution of non coloured particles. We then show that conventional heavy quark searches are also sensitive to this new decay mode, when $S$ decays hadronically, by slightly tightening the current selection cuts. Finally, we comment about the possibility of disentangling, by scrutinising appropriate kinematic distributions, heavy quark decays to $St$ from other standard decay modes.Comment: 8 pages, 3 figures and 1 table; v3: typos fixed. Matches published versio

Soil acidity and the liming of Iowa soils

Whether or not their lands will give better crop yields if lime1 is applied has become a live question with Iowa farmers. They have written many letters of inquiry upon this point to the Iowa Agricultural Experiment Station and hundreds of soil samples have been analyzed to make satisfactory answer. To provide more complete information relative to this important question of soil acidity and the use of lime in Iowa, the agronomy section of the experiment station gathered many soil samples from well scattered localities in the principal soil areas. These were analyzed and the results are now presented and discussed in this bulletin. These analyses show that liming is likely to be profitable in the Mississippi loess, the Southern Iowa loess and the Iowan drift areas because those soils are very apt to be more or less acid; also, that the soils of the Wisconsin drift are only occasionally in need of liming, and those of the Missouri loess only very rarely