Should energy labels for washing machines be expanded to include a durability rating?

Washing machines are a key household appliance that can be found in the majority of UK homes. Over 2.5 million are sold in the UK every year and account for one of the highest material and production impacts of householder products in the UK (WRAP, 2011). Energy efficiency ratings are provided as a method for consumers to make an informed purchasing decision and were brought in by EU legislation to reduce energy use and enable users to reduce running costs, as it is known that the greater environmental impact of a washing machine is during use. From 2014, all washing machines sold must be at a minimum A rated, with ratings increasing to A+++. However, under this current labelling system the embodied impacts and durability of the machines are ignored. Through semi-structured interviews with consumers, manufacturers and distributors, this paper explores different perceptions of longevity and expectations of performance and durability. The paper explores whether energy labels should be expanded to include durability information, as this could enable consumers to make a decision based not only on cost and energy efficiency but also on expected lifespan. Existing manufacturer’s guarantees may give an indication of the expected durability of the product and this is investigated to explore if there is a positive correlation. The findings will further discuss the potential impacts of providing durability information and how this could enable manufacturers and consumers to shift towards a low material and energy future

First principle electronic, structural, elastic, and optical properties of strontium titanate

We report self-consistent ab-initio electronic, structural, elastic, and optical properties of cubic SrTiO$_{3}$ perovskite. Our non-relativistic calculations employed a generalized gradient approximation (GGA) potential and the linear combination of atomic orbitals (LCAO) formalism. The distinctive feature of our computations stem from solving self-consistently the system of equations describing the GGA, using the Bagayoko-Zhao-Williams (BZW) method. Our results are in agreement with experimental ones where the later are available. In particular, our theoretical, indirect band gap of 3.24 eV, at the experimental lattice constant of 3.91 \AA{}, is in excellent agreement with experiment. Our predicted, equilibrium lattice constant is 3.92 \AA{}, with a corresponding indirect band gap of 3.21 eV and bulk modulus of 183 GPa.Comment: 11 pages, 6 figures,Accepted for publication in AIP Advances (2012

Anomalous Dynamic Arrest in a Mixture of Big and Small Particles

We present molecular dynamics simulations on the slow dynamics of a mixture of big and small soft-spheres with a large size disparity. Dynamics are investigated in a broad range of temperature and mixture composition. As a consequence of large size disparity, big and small particles exhibit very different relaxation times. As previously reported for simple models of short-ranged attractive colloids and polymer blends, several anomalous dynamic features are observed: i) sublinear behavior for mean squared displacements, ii) concave-to-convex crossover for density-density correlators, by varying temperature or wavevector, iii) logarithmic decay for specific wavevectors of density-density correlators. These anomalous features are observed over time intervals extending up to four decades, and strongly resemble predictions of the Mode Coupling Theory (MCT) for state points close to higher-order MCT transitions, which originate from the competition between different mechanisms for dynamic arrest. For the big particles we suggest competition between soft-sphere repulsion and depletion effects induced by neighboring small particles. For the small particles we suggest competition between bulk-like dynamics and confinement, respectively induced by neighboring small particles and by the slow matrix of big particles. By increasing the size disparity, a new relaxation scenario arises for the small particles. Self-correlators decay to zero at temperatures where density-density correlations are frozen. The behavior of the latters resembles features characteristic of type-A MCT transitions, defined by a zero value of the critical non-ergodicity parameter.Comment: Version 2. Added major new result

Bipartite all-versus-nothing proofs of Bell's theorem with single-qubit measurements

If we distribute n qubits between two parties, which quantum pure states and distributions of qubits would allow all-versus-nothing (or Greenberger-Horne-Zeilinger-like) proofs of Bell's theorem using only single-qubit measurements? We show a necessary and sufficient condition for the existence of these proofs for any number of qubits, and provide all distinct proofs up to n=7 qubits. Remarkably, there is only one distribution of a state of n=4 qubits, and six distributions, each for a different state of n=6 qubits, which allow these proofs.Comment: REVTeX4, 4 pages, 2 figure

Quantum Criticality and Incipient Phase Separation in the Thermodynamic Properties of the Hubbard Model

Transport measurements on the cuprates suggest the presence of a quantum critical point hiding underneath the superconducting dome near optimal hole doping. We provide numerical evidence in support of this scenario via a dynamical cluster quantum Monte Carlo study of the extended two-dimensional Hubbard model. Single particle quantities, such as the spectral function, the quasiparticle weight and the entropy, display a crossover between two distinct ground states: a Fermi liquid at low filling and a non-Fermi liquid with a pseudogap at high filling. Both states are found to cross over to a marginal Fermi-liquid state at higher temperatures. For finite next-nearest-neighbor hopping t' we find a classical critical point at temperature T_c. This classical critical point is found to be associated with a phase separation transition between a compressible Mott gas and an incompressible Mott liquid corresponding to the Fermi liquid and the pseudogap state, respectively. Since the critical temperature T_c extrapolates to zero as t' vanishes, we conclude that a quantum critical point connects the Fermi-liquid to the pseudogap region, and that the marginal-Fermi-liquid behavior in its vicinity is the analogous of the supercritical region in the liquid-gas transition.Comment: 18 pages, 9 figure

Using off-diagonal confinement as a cooling method

In a recent letter [Phys. Rev. Lett. 104, 167201 (2010)] we proposed a new confining method for ultracold atoms on optical lattices, based on off-diagonal confinement (ODC). This method was shown to have distinct advantages over the conventional diagonal confinement (DC) that makes use of a trapping potential, including the existence of pure Mott phases and highly populated condensates. In this paper we show that the ODC method can also lead to temperatures that are smaller than with the conventional DC method, depending on the control parameters. We determine these parameters using exact diagonalizations for the hard-core case, then we extend our results to the soft-core case by performing quantum Monte Carlo (QMC) simulations for both DC and ODC systems at fixed temperatures, and analysing the corresponding entropies. We also propose a method for measuring the entropy in QMC simulations.Comment: 6 pages, 6 figure

Re-examining the electronic structure of germanium: A first-principle study

We report results from an efficient, robust, ab-initio method for self-consistent calculations of electronic and structural properties of Ge. Our non-relativistic calculations employed a generalized gradient approximation (GGA) potential and the linear combination of atomic orbitals (LCAO) formalism. The distinctive feature of our computations stem from the use of Bagayoko-Zhao-Williams-Ekuma-Franklin (BZW-EF) method. Our results are in agreement with experimental ones where the latter are available. In particular, our theoretical, indirect band gap of 0.65 eV, at the experimental lattice constant of 5.66 \AA{}, is in excellent agreement with experiment. Our predicted, equilibrium lattice constant is 5.63 \AA{}, with a corresponding indirect band gap of 0.65 eV and a bulk modulus of 80 GPa. We also calculated the effective masses in various directions with respect to the $\Gamma$ point.Comment: 10 Pages, 3 Figures, and 1 tabl

Free Form of the Foldy-Wouthuysen Transformation in External Electromagnetic Fields

We derive the exact Foldy-Wouthuysen transformation for Dirac fermions in a time independent external electromagnetic field in the basis of the Ritus eigenfunctions, namely the eigenfunctions of the operator $(\gamma \cdot \Pi)^2$, with $\Pi^\mu = p^\mu - e A^\mu$. In this basis, the transformation acquires a free form involving the dynamical quantum numbers induced by the field.Comment: 8 pages. Accepted in J. Phys. A: Math. and Theo. (Fast Track Communication