Theory of the quasiparticle excitation in high Tc_{c} cuprates: quasiparticle charge and nodal-antinodal dichotomy

A variational theory is proposed for the quasiparticle excitation in high T$_{c}$ cuprates. The theory goes beyond the usual Gutzwiller projected mean field state description by including the spin-charge recombination effect in the RVB background. The spin-charge recombination effect is found to qualitatively alter the behavior of the quasiparticle charge as a function of doping and cause considerable anisotropy in quasiparticle weight on the Fermi surface.Comment: 10 page

Enhanced voltage generation through electrolyte flow on liquid-filled surfaces.

The generation of electrical voltage through the flow of an electrolyte over a charged surface may be used for energy transduction. Here, we show that enhanced electrical potential differences (i.e., streaming potential) may be obtained through the flow of salt water on liquid-filled surfaces that are infiltrated with a lower dielectric constant liquid, such as oil, to harness electrolyte slip and associated surface charge. A record-high figure of merit, in terms of the voltage generated per unit applied pressure, of 0.043 mV Pa-1 is obtained through the use of the liquid-filled surfaces. In comparison with air-filled surfaces, the figure of merit associated with the liquid-filled surface increases by a factor of 1.4. These results lay the basis for innovative surface charge engineering methodology for the study of electrokinetic phenomena at the microscale, with possible application in new electrical power sources

Refining grain structure and porosity of an aluminium alloy with intensive melt shearing

The official published version of the article can be obtained at the link below.Intensive melt shearing was achieved using a twin-screw machine to condition an aluminium alloy prior to solidification. The results show that intensive melt shearing has a significant grain-refining effect. In addition, the intensive melt shearing reduces both the volume fraction and the size of porosity. It can reduce the density index from 10.50% to 2.87% and the average size of porosity in the samples solidified under partial vacuum from around 1 mm to 100 μm.Financial support was obtained from the EPSRC and the Technology Strategy Board

Cross correlations of Frank sequences and Chu Sequences.

Sets of Frank sequences and Chu sequences are two classes of polyphase sequence with ideal periodic autocorrelation functions, which at the same time have optimum crosscorrelation functions. The authors consider the crosscorrelations of sets of combined Frank/Chu sequences, which contain a larger number of sequences than either of the two constituent sets. It is shown analytically that the crosscorrelations are similar to those of the original sets with one exception, while the autocorrelations remain perfectly impulsiv

Grain refinement of DC cast magnesium alloys with intensive melt shearing

A new direct chill (DC) casting process, melt conditioned DC (MC-DC) process, has been developed for the production of high quality billets/slabs of light alloys by application of intensive melt shearing through a rotor-stator high shear device during the DC casting process. The rotor-stator high shear device provides intensive melt shearing to disperse the naturally occurring oxide films, and other inclusions, while creating a microscopic flow pattern to homogenize the temperature and composition fields in the sump. In this paper, we report the grain refining effect of intensive melt shearing in the MC-DC casting processing. Experimental results on DC casting of Mg-alloys with and without intensive melt shearing have demonstrated that the MC-DC casting process can produce magnesium alloy billets with significantly refined microstructure. Such grain refinement in the MC-DC casting process can be attributed to enhanced heterogeneous nucleation by dispersed naturally occurring oxide particles, increased nuclei survival rate in uniform temperature and compositional fields in the sump, and potential contribution from dendrite arm fragmentation

Should India invest more in less-favored areas?:

Developing countries have to allocate limited government resources for rural areas among different investment activities and regions to achieve the twin goals of productivity growth and poverty alleviation. This is particularly important at a time when many countries are facing severe financial constraints. This paper develops a framework and provides empirical evidence on the impact of government investments in technology, irrigation, education and infrastructure on agricultural productivity growth and rural poverty reduction in rural India. The results reveal that government investments in more favored areas played significant roles during the green revolution period. But the marginal returns from additional government investments in these areas have declined in more recent years. It is now the less-favored areas where marginal returns are higher. This result has important policy implications for where government investments should be targeted in order to achieve further productivity growth and rural poverty reductions.Poverty alleviation India., Investments., Government spending policy India., Agricultural development Asia.,

Buoyant magnetic flux ropes in a magnetized stellar envelope: Idealized numerical 2.5-D MHD simulations

Context: The context of this paper is buoyant toroidal magnetic flux ropes, which is a part of flux tube dynamo theory and the framework of solar-like magnetic activity. Aims: The aim is to investigate how twisted magnetic flux ropes interact with a simple magnetized stellar model envelope--a magnetic "convection zone"--especially to examine how the twisted magnetic field component of a flux rope interacts with a poloidal magnetic field in the convection zone. Method: Both the flux ropes and the atmosphere are modelled as idealized 2.5-dimensional concepts using high resolution numerical magneto-hydrodynamic (MHD) simulations. Results: It is illustrated that twisted toroidal magnetic flux ropes can interact with a poloidal magnetic field in the atmosphere to cause a change in both the buoyant rise dynamics and the flux rope's geometrical shape. The details of these changes depend primarily on the polarity and strength of the atmospheric field relative to the field strength of the flux rope. It is suggested that the effects could be verified observationally.Comment: 8 pages, 5 figures (9 files), accepted by A&