Quaternary quadratic lattices over number fields

We relate proper isometry classes of maximal lattices in a totally definite quaternary quadratic space (V,q) with trivial discriminant to certain equivalence classes of ideals in the quaternion algebra representing the Clifford invariant of (V,q). This yields a good algorithm to enumerate a system of representatives of proper isometry classes of lattices in genera of maximal lattices in (V,q)

The race to solve the sustainable transport problem via carbon-neutral synthetic fuels and battery electric vehicles

Carbon-neutral synthetic fuels (CNSFs) could offer sustainable alternatives to petroleum distillates that currently dominate the transportation sector, and address the challenge of decarbonising the fuel mix. CNSFs can be divided into synthetic biofuels and 'electrofuels' produced from CO2 and water with electricity. We provide a framework for comparing CNSFs to battery electric vehicles (BEVs) as alternatives to reduce vehicle emissions. Currently, all three options are significantly more expensive than conventional vehicles using fossil fuels, and would require carbon prices in excess of $250/tCO2 or oil prices in excess of$150/bbl to become competitive. BEVs are emerging as a competitive option for short distances, but their competitiveness quickly deteriorates at higher ranges where synthetic biofuels are a lower-cost option. For electrofuels to be viable, the challenge is not simply technological learning, but access to a low-cost ultra-low-carbon electric power system, or to low-carbon electric generators with high annual availability

Determination of the resistivity anisotropy of SrRuO3_{3} by measuring the planar Hall effect

We have measured the planar Hall effect in epitaxial thin films of the itinerant ferromagnet SrRuO3 patterned with their current paths at different angles relative to the crystallographic axes. Based on the results, we have determined that SrRuO3 exhibits small resistivity anisotropy in the entire temperature range of our measurements (between 2 to 300 K); namely, both above and below its Curie temperature (~150 K). It means that in addition to anisotropy related to magnetism, the resistivity anisotropy of SrRuO3 has an intrinsic, nonmagnetic source. We have found that the two sources of anisotropy have competing effects

Quaternion algebras with the same subfields

G. Prasad and A. Rapinchuk asked if two quaternion division F -algebras that have the same subfields are necessarily isomorphic. The answer is known to be "no" for some very large fields. We prove that the answer is "yes" if F is an extension of a global field K so that F /K is unirational and has zero unramified Brauer group. We also prove a similar result for Pfister forms and give an application to tractable fields

Financial stability evaluation of banks of the Russian Federation

In this paper we propose the model for evaluating financial stability of the Russian Federation banks by using discriminatory analysis. The statistical significance of the model was established. Critical value of the resulting was measured. The result of this research can be used in the area of banking

High transport currents in mechanically reinforced MgB2 wires

We prepared and characterized monofilamentary MgB2 wires with a mechanically reinforced composite sheath of Ta(Nb)/Cu/steel, which leads to dense filaments and correspondingly high transport currents up to Jc = 10^5 A/cm^2 at 4.2 K, self field. The reproducibility of the measured transport currents was excellent and not depending on the wire diameter. Using different precursors, commercial reacted powder or an unreacted Mg/B powder mixture, a strong influence on the pinning behaviour and the irreversibility field was observed. The critical transport current density showed a nearly linear temperature dependency for all wires being still 52 kA/cm^2 at 20 K and 23 kA/cm^2 at 30 K. Detailed data for Jc(B,T) and Tc(B) were measured.Comment: 21 pages, 13 figures, revised version, to be published in Supercond. Sci. Techno

Refinement of primary Si in hypereutectic Al-Si alloys by intensive melt shearing

Hypereutectic Al-Si based alloys are gaining popularity for applications where a combination of light weight and high wear resistance is required. The high wear resistance arising from the hard primary Si particles comes at the price of extremely poor machine tool life. To minimize machining problems while exploiting outstanding wear resistance, the primary Si particles must be controlled to a uniform small size and uniform spatial distribution. The current industrial means of refining primary Si chemically by the addition of phosphorous suffers from a number of problems. In the present paper an alternative, physical means of refining primary Si by intensive shearing of the melt prior to casting is investigated. Al-15wt%Si alloy has been solidified under varying casting conditions (cooling rate) and the resulting microstructures have been studied using microscopy and quantitative image analysis. Primary Si particles were finer, more compact in shape and more numerous with increasing cooling rate. Intensive melt shearing led to greater refinement and more enhanced nucleation of primary Si than was achieved by adding phosphorous. The mechanism of enhanced nucleation is discussed.EPSRC (grant EP/H026177/1)

2010 EPRG Public Opinion Survey: Policy Preferences and Energy Saving Measures

This paper presents results of the 2010 Electricity Policy Research Group (EPRG) public opinion survey. The survey examines the energy policy preferences and attitudes of the British public, the potential for consumer engagement and consumer acceptance of various energy demand response activities. Wherever possible, comparisons were made to EPRG public opinion surveys from 2006 and 2008. Since the global financial crisis of 2008, energy and environmental concerns have decreased in priority, and respondents are more sceptical about government interventions in electricity markets. The share of individuals reporting that they are experiencing serious hardship due to energy prices has gone down from the 2008 level. While roughly half of the respondents would agree to have detailed metered consumption information recorded by their energy providers, they are even more wary about making data available to other entities. Local ownership is a potential motivating factor for public support for local small-scale energy plants. Energy efficiency measures had higher uptake than in previous years, but the widespread measures are typically cheaper and easiest to implement. There is scope for shifting discretionary electricity load to off-peak hours through both Time-of-Use tariffs and smart appliances that require limited user intervention.Time-of-use tariff

Band gap bowing of binary alloys: Experimental results compared to theoretical tight-binding supercell calculations for CdZnSe

Compound semiconductor alloys of the type ABC find widespread applications as their electronic bulk band gap varies continuously with x, and therefore a tayloring of the energy gap is possible by variation of the concentration. We model the electronic properties of such semiconductor alloys by a multiband tight-binding model on a finite ensemble of supercells and determine the band gap of the alloy. This treatment allows for an intrinsic reproduction of band bowing effects as a function of the concentration x and is exact in the alloy-induced disorder. In the present paper, we concentrate on bulk CdZnSe as a well-defined model system and give a careful analysis on the proper choice of the basis set and supercell size, as well as on the necessary number of realizations. The results are compared to experimental results obtained from ellipsometric measurements of CdZnSe layers prepared by molecular beam epitaxy (MBE) and photoluminescence (PL) measurements on catalytically grown CdZnSe nanowires reported in the literature.Comment: 7 pages, 6 figure