Low-TT Phononic Thermal Conductivity in Superconductors with Line Nodes

The phonon contribution to the thermal conductivity at low temperature in superconductors with line nodes is calculated assuming that scattering by both nodal quasiparticles and the sample boundaries is significant. It is determined that, within the regime in which the quasiparticles are in the universal limit and the phonon attenuation is in the hydrodynamic limit, there exists a wide temperature range over which the phonon thermal conductivity varies as $T^2$. This behaviour comes from the fact that transverse phonons propagating along certain directions do not interact with nodal quasiparticles and is thus found to be required by the symmetry of the crystal and the superconducting gap, independent of the model used for the electron-phonon interaction. The $T^2$-dependence of the phonon thermal conductivity occurs over a well-defined intermediate temperature range: at higher $T$ the temperature-dependence is found to be linear while at lower $T$ the usual $T^3$ (boundary-limited) behaviour is recovered. Results are compared to recent measurements of the thermal conductivity of Tl2201, and are shown to be consistent with the data.Comment: 4 page

Direct thrust measurement of a 30-cm ion thruster

A direct thrust measurement of a 30-cm diameter ion thruster was accomplished by means of a laser interferometer thrust stand. The thruster was supported in a pendulum manner by three 3.65-m long wires. Electrical power was provided by means of 18 mercury filled pots. A movable 23-button planar probe rake was used to determine thrust loss due to ion beam divergence. Values of thrust, thrust loss due to ion beam divergence, and thrust loss due to multiple ionization were measured for ion beam currents ranging from 0.5 A to 2.5 A. Measured thrust values indicate an accuracy of approximately 1% and are in good agreement with thrust values calculated by indirect measurements

Methodology of measuring internal contamination in spacecraft hardware Final report

Methodology of measuring internal contamination in spacecraft hardwar

Symmetry of the order parameter in superconducting ZrZn_2

We apply symmetry considerations to study the possible superconducting order parameters in ferromagnetic ZrZn_2. We predict that the presence and the location of the superconducting gap nodes depend on the direction of magnetization M. In particular, if M is directed along the z axis, then the order parameter should always have zeros. We also discuss how to determine the gap symmetry in ZrZn_2 using ultrasound attenuation measurements.Comment: 6 pages, submitted to PRB; some corrections and discussion adde

Climate or rural development policy?

Being heavily energy dependent, it is not much of a surprise that Europe pays special attention to reducing the use of fossil fuels. Each one of the ten new member states is characterized by relatively low per capita energy consumption and relatively low energy efficiency, and the share of renewables in their energy mix tends to be low, too. The paper examines the problem when policy measures create a decrease in environmental capital instead of an increase. In this case it hardly seems justified to talk about environmental protection. The authors describe a case of a Hungarian rapeseed oil mill which would not be of too much interest on its own but given that almost all similar plants went bankrupt, there are some important lessons to learn from its survival. The enterprise the authors examined aimed at establishing a micro-regional network. They completed a brown-field development to establish a small plant on the premises of a former large agricultural cooperative. By partnering with the former employees and suppliers of the sometime cooperative, they enjoyed some benefits which all the other green-field businesses focusing on fuel production could not. The project improved food security, energy security and population retention as well

Displacement and the public interest in Nigeria: contesting developmental rationales for displacement

The displacement of urban households and livelihoods by state institutions is typically justified on the basis of the developmental purposes of land clearance, purportedly in the public interest. However, conflicts around such displacement highlight both the contested nature of the “public interest” and the unequal position that different urban actors are into shape consensus about what this should constitute. This article draws on research into the relationship between urban infrastructure development and displacement in Nigeria, to explore how actors negotiate their positions vis-a-vis displacement and contest its developmental rationale

Growth of Epitaxial Oxide Thin Films on Graphene

The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridgepillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices

Non-Abelian Flat Directions in a Minimal Superstring Standard Model

Recently, by studying exact flat directions of non-Abelian singlet fields, we demonstrated the existence of free fermionic heterotic-string models in which the SU(3)_C x SU(2)_L x U(1)_Y-charged matter spectrum, just below the string scale, consists solely of the MSSM spectrum. In this paper we generalize the analysis to include VEVs of non-Abelian fields. We find several, MSSM-producing, exact non-Abelian flat directions, which are the first such examples in the literature. We examine the possibility that hidden sector condensates lift the flat directions.Comment: 14 pages. Standard Late