Electron-dependent thermoelectric properties in Si/Si_(1_x)Ge_(x) heterostructures and Si_(1-x)Ge_(x) alloys from first-principles

Unlike phononic thermal conductivity (which is shown in the literature to be reduced due to alloying and has a nearly constant value over a range of compositional variations), electron-dependent thermoelectric properties are shown here, from first-principles, to vary nonlinearly with composition. Of the Si/Si_(1_x)Ge_(x) systems considered, the maximum thermopower observed, which is 10% higher than that of crystalline Si, is obtained for a Si_(0.875)Ge_(0.125) alloy. Also, heterostructuring is shown to reduce thermopower, electrical conductivity, and electron thermal conductivity. Additionally, neither Lorenz number nor Seebeck coefficient shows oscillations for heterostructures, regardless of electron/hole energies, contradicting the conclusions obtained with miniband approximations

Miniature oxygen resuscitator

Miniature, portable resuscitation system is used during evacuation of patients to medical facilities. A carrying case contains a modified resuscitator head, cylinder of oxygen, two-stage oxygen regulator, low pressure tube, and a mask for mouth and nose

Centre-of-mass and internal symmetries in classical relativistic systems

The internal symmetry of composite relativistic systems is discussed. It is demonstrated that Lorentz-Poincar\'e symmetry implies the existence of internal moments associated with the Lorentz boost, which are Laplace-Runge-Lenz (LRL) vectors. The LRL symmetry is thus found to be the internal symmetry universally associated with the global Lorentz transformations, in much the same way as internal spatial rotations are associated with global spatial rotations. Two applications are included, for an interacting 2-body system and for an interaction-free many-body system of particles. The issue of localizability of the relativistic CM coordinate is also discussed

Non-Markovianity of local dephasing channels and time-invariant discord

We study non-Markovianity and information flow for qubits experiencing local dephasing with an Ohmic class spectrum. We demonstrate the existence of a temperature-dependent critical value of the Ohmicity parameter s for the onset of non-Markovianity and give a physical interpretation of this phenomenon by linking it to the form of the reservoir spectrum. We demonstrate that this link holds also for more general spectra. We unveil a class of initial states for which discord is forever frozen at a positive value. We connect time invariant discord to non-Markovianity and propose a physical system in which it could be observed

Probing the dynamic structure factor of a neutral Fermi superfluid along the BCS-BEC crossover using atomic impurity qubits

We study an impurity atom trapped by an anharmonic potential, immersed within a cold atomic Fermi gas with attractive interactions that realizes the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC). Considering the qubit comprising the lowest two vibrational energy eigenstates of the impurity, we demonstrate that its dynamics probes the equilibrium density fluctuations encoded in the dynamic structure factor of the superfluid. Observing the impurity's evolution is thus shown to facilitate nondestructive measurements of the superfluid order parameter and the contact between collective and single-particle excitation spectra. Our setup constitutes a novel model of an open quantum system interacting with a thermal reservoir, the latter supporting both bosonic and fermionic excitations that are also coupled to each other.Comment: Updated to final author version. 9+7 pages, 18 figure

Improved fiberglass-to-metal joint produces lighter stronger fiberglass strut

Axial tension and compression are transmitted between end fittings and fiberglass tube without depending on glass-to-metal bonding, conventional fasteners or combination of these things. Joint design significantly reduces both structural weight of strut and its cross-sectional area

Direct gaze modulates face recognition in young infants

From birth, infants prefer to look at faces that engage them in direct eye contact. In adults, direct gaze is known to modulate the processing of faces, including the recognition of individuals. In the present study, we investigate whether direction of gaze has any effect on face recognition in four-month-old infants. Four-month infants were shown faces with both direct and averted gaze, and subsequently given a preference test involving the same face and a novel one. A novelty preference during test was only found following initial exposure to a face with direct gaze. Further, face recognition was also generally enhanced for faces with both direct and with averted gaze when the infants started the task with the direct gaze condition. Together, these results indicate that the direction of the gaze modulates face recognition in early infancy

Fine Details of the Nodal Electronic Excitations in Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta}

Very high energy resolution photoemission experiments on high quality samples of optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ show new features in the low-energy electronic excitations. A marked change in the binding energy and temperature dependence of the near-nodal scattering rates is observed near the superconducting transition temperature, $T_C$. The temperature slope of the scattering rate measured at low energy shows a discontinuity at ~$T_C$. In the superconducting state, coherent excitations are found with the scattering rates showing a cubic dependence on frequency and temperature. The superconducting gap has a d-wave magnitude with negligible contribution from higher harmonics. Further, the bi-layer splitting has been found to be finite at the nodal point.Comment: 5 pages, 4 figure