Superconductors from Superstrings

We establish that in a large class of strongly coupled 3+1 dimensional N=1 quiver conformal field theories with gravity duals, adding a chemical potential for the R-charge leads to the existence of superfluid states in which a chiral primary operator of the schematic form O = \lambda\lambda + W condenses. Here \lambda is a gluino and W is the superpotential. Our argument is based on the construction of a consistent truncation of type IIB supergravity that includes a U(1) gauge field and a complex scalar.Comment: 5 pages, 2 figures; v2 improved figure, small change

Obesity and vulnerability of the CNS

AbstractThe incidence of obesity is increasing worldwide, and is especially pronounced in developed western countries. While the consequences of obesity on metabolic and cardiovascular physiology are well established, epidemiological and experimental data are beginning to establish that the central nervous system (CNS) may also be detrimentally affected by obesity and obesity-induced metabolic dysfunction. In particular, data show that obesity in human populations is associated with cognitive decline and enhanced vulnerability to brain injury, while experimental studies in animal models confirm a profile of heightened vulnerability and decreased cognitive function. This review will describe findings from human and animal studies to summarize current understanding of how obesity affects the brain. Furthermore, studies aimed at identifying key elements of body–brain dialog will be discussed to assess how various metabolic and adipose-related signals could adversely affect the CNS. Overall, data suggest that obesity-induced alterations in metabolism may significantly synergize with age to impair brain function and accelerate age-related diseases of the nervous system. Thus, enhanced understanding of the effects of obesity and obesity-related metabolic dysfunction on the brain are especially critical as increasing numbers of obese individuals approach advanced age

Stopping to food can reduce intake. Effects of stimulus-specificity and individual differences in dietary restraint

types: JOURNAL ARTICLECopyright © 2014 The Authors. Published by Elsevier Ltd.Overeating in our food-rich environment is a key contributor to obesity. Computerised response-inhibition training could improve self-control in individuals who overeat. Evidence suggests that training people to inhibit motor responses to specific food pictures can reduce the subsequent choice and consumption of those foods. Here we undertook three experiments using the stop-signal task to examine the effects of food and non-food related stop-training on immediate snack food consumption. The experiments examined whether training effects were stimulus-specific, whether they were influenced by the comparator (control) group, and whether they were moderated by individual differences in dietary restraint. Experiment 1 revealed lower intake of one food following stop- vs. double- (two key-presses) response training to food pictures. Experiment 2 offered two foods, one of which was not associated with stopping, to enable within- and between-subjects comparisons of intake. A second control condition required participants to ignore signals and respond with one key-press to all pictures. There was no overall effect of training on intake in Experiment 2, but there was a marginally significant moderation by dietary restraint: Restrained eaters ate significantly less signal-food following stop- relative to double-response training. Experiment 3 revealed that stop- vs. double-response training to non-food pictures had no effect on food intake. Taken together with previous findings, these results suggest some stimulus-specific effects of stop-training on food intake that may be moderated by individual differences in dietary restraint.Wales Institute of Cognitive NeuroscienceBBSRCESRCERCThe UK Experimental Psychology Societ

Narrow heavy-hole cyclotron resonances split by the cubic Rashba spin-orbit interaction in strained germanium quantum wells

The spin-orbit interaction was found to split the cyclotron resonance of heavy holes confined in high-mobility, compressively strained germanium quantum wells. The interference between coherent spin-split cyclotron resonances was tracked on picosecond time scales using terahertz time-domain spectroscopy. Analysis in the time domain, or using a time-frequency decomposition based on the Gabor-Morlet wavelet, was necessary when the difference between cyclotron frequencies was comparable to the linewidth. The cubic Rashba spin-orbit coefficient β was determined via two methods: (i) the magnetic-field dependence of the cyclotron frequencies, and (ii) the spin-resolved subband densities. An enhanced β and spin polarization was created by tailoring the strain to enhance the spin-orbit interaction. The amplitude modulation of the narrow, interfering cyclotron resonances is a signature of spin coherences persisting for more than 10 ps

Magnetically driven dielectric and structural behavior in Bi0.5La0.5FeO3

The authors would like to thank the Royal Society for a University Research Fellowship (FDM), Engineering and Physical Sciences Research Council for a studentship (CMK), and the Science and Technology Facilities Council for access to neutron facilities.A detailed structural analysis of the antiferromagnetic (Gz-type) lanthanum doped bismuth ferrite - Bi0.5La0.5FeO3 (Pn′ma′) – using variable-temperature powder neutron diffraction is reported. The analysis highlights a structural link between changes in the relative dielectric permittivity and changes in the FeO6 octahedral tilt magnitudes, accompanied by a structural distortion of the octahedra with corresponding A-site displacement along the c-axis; this behavior is unusual due to an increasing in-phase tilt mode with increasing temperature. The anomalous orthorhombic distortion is driven by magnetostriction at the onset of antiferromagnetic ordering resulting in an Invar effect along the magnetic c-axis and anisotropic displacement of the A-site Bi3+ and La3+ along the a-axis.PostprintPeer reviewe

Structural, magnetic, and electrical properties of Bi1-xLaxMnO3 (x=0.0, 0.1, and 0.2) solid solutions

Possible ferromagnetic and ferroelectric orders in ceramic Bi1–xLaxMnO3 (x = 0.0, 0.1, and 0.2) samples prepared under 3–6 GPa pressure have been investigated. Rietveld fits to powder neutron diffraction data show that BiMnO3 and Bi0.9La0.1MnO3 adopt a monoclinic C2/c perovskite superstructure whereas Bi0.8La0.2MnO3 has orthorhombic Pnma symmetry. Both structural analysis and Curie–Weiss fits to magnetic susceptibility data show that high spin d4 Mn3+ is present with no significant Bi deficiency or Mn4+ content apparent. La substitution suppresses the magnetic Curie temperature of the monoclinic phase from 105 K for x = 0 to 94 K at x = 0.1, but the x = 0.2 material shows antiferromagnetic order similar to that of LaMnO3. Impedance spectroscopy and dielectric measurements on the x = 0.1 and 0.2 materials show modest bulk permittivity values (45–80) down to 50 K, and there is no strong evidence for ferroelectric behavior. The two samples have thermally activated conductivities with activation energies of 0.21–0.24 eV.PostprintPeer reviewe

Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO3

CALD and CMK were supported by EPSRC DTA studentships (EP/L505079/1).The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO3 has been studied in detail by powder neutron diffraction in the temperature range 25<T<1285 K. A conventional bond length/bond angle analysis, combined with an analysis in terms of symmetry-adapted modes, allows key aspects of the thermal behavior to be understood. In particular, the largest-amplitude symmetry modes (viz. in-phase and out-of-phase octahedral tilts, and A-site cation displacements) are shown to display relatively ‘normal’ behavior, increasing with decreasing temperature, which contrasts with the anomalous behavior previously shown by the derivative Bi0.5La0.5FeO3. However, an unexpected behavior is seen in the nature of the intra-octahedral distortion, which is used to rationalize the unique occurrence of a temperature dependent crossover of the a and c unit cell metrics in this compound.PostprintPeer reviewe