Broken rotational symmetry in the pseudogap phase of a high-Tc superconductor

The nature of the pseudogap phase is a central problem in the quest to understand high-Tc cuprate superconductors. A fundamental question is what symmetries are broken when that phase sets in below a temperature T*. There is evidence from both polarized neutron diffraction and polar Kerr effect measurements that time- reversal symmetry is broken, but at temperatures that differ significantly. Broken rotational symmetry was detected by both resistivity and inelastic neutron scattering at low doping and by scanning tunnelling spectroscopy at low temperature, but with no clear connection to T*. Here we report the observation of a large in-plane anisotropy of the Nernst effect in YBa2Cu3Oy that sets in precisely at T*, throughout the doping phase diagram. We show that the CuO chains of the orthorhombic lattice are not responsible for this anisotropy, which is therefore an intrinsic property of the CuO2 planes. We conclude that the pseudogap phase is an electronic state which strongly breaks four-fold rotational symmetry. This narrows the range of possible states considerably, pointing to stripe or nematic orders.Comment: Published version. Journal reference and DOI adde

Algebraic charge liquids

High temperature superconductivity emerges in the cuprate compounds upon changing the electron density of an insulator in which the electron spins are antiferromagnetically ordered. A key characteristic of the superconductor is that electrons can be extracted from them at zero energy only if their momenta take one of four specific values (the `nodal points'). A central enigma has been the evolution of the zero energy electrons in the metallic state between the antiferromagnet and the superconductor, and recent experiments yield apparently contradictory results. The oscillation of the resistance in this metal as a function of magnetic field indicate that the zero energy electrons carry momenta which lie on elliptical `Fermi pockets', while ejection of electrons by high intensity light indicates that the zero energy electrons have momenta only along arc-like regions. We present a theory of new states of matter, which we call `algebraic charge liquids', which arise naturally between the antiferromagnet and the superconductor, and reconcile these observations. Our theory also explains a puzzling dependence of the density of superconducting electrons on the total electron density, and makes a number of unique predictions for future experiments.Comment: 6+8 pages, 2 figures; (v2) Rewritten for broader accessibility; (v3) corrected numerical error in Eq. (5

Background risk of breast cancer and the association between physical activity and mammographic density

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The pseudogap: friend or foe of high Tc?

Although nineteen years have passed since the discovery of high temperature superconductivity, there is still no consensus on its physical origin. This is in large part because of a lack of understanding of the state of matter out of which the superconductivity arises. In optimally and underdoped materials, this state exhibits a pseudogap at temperatures large compared to the superconducting transition temperature. Although discovered only three years after the pioneering work of Bednorz and Muller, the physical origin of this pseudogap behavior and whether it constitutes a distinct phase of matter is still shrouded in mystery. In the summer of 2004, a band of physicists gathered for five weeks at the Aspen Center for Physics to discuss the pseudogap. In this perspective, we would like to summarize some of the results presented there and discuss its importance in the context of strongly correlated electron systems.Comment: expanded version, 20 pages, 11 figures, to be published, Advances in Physic

Recurrent Modification of a Conserved Cis-Regulatory Element Underlies Fruit Fly Pigmentation Diversity

The development of morphological traits occurs through the collective action of networks of genes connected at the level of gene expression. As any node in a network may be a target of evolutionary change, the recurrent targeting of the same node would indicate that the path of evolution is biased for the relevant trait and network. Although examples of parallel evolution have implicated recurrent modification of the same gene and cis-regulatory element (CRE), little is known about the mutational and molecular paths of parallel CRE evolution. In Drosophila melanogaster fruit flies, the Bric-à-brac (Bab) transcription factors control the development of a suite of sexually dimorphic traits on the posterior abdomen. Female-specific Bab expression is regulated by the dimorphic element, a CRE that possesses direct inputs from body plan (ABD-B) and sex-determination (DSX) transcription factors. Here, we find that the recurrent evolutionary modification of this CRE underlies both intraspecific and interspecific variation in female pigmentation in the melanogaster species group. By reconstructing the sequence and regulatory activity of the ancestral Drosophila melanogaster dimorphic element, we demonstrate that a handful of mutations were sufficient to create independent CRE alleles with differing activities. Moreover, intraspecific and interspecific dimorphic element evolution proceeded with little to no alterations to the known body plan and sex-determination regulatory linkages. Collectively, our findings represent an example where the paths of evolution appear biased to a specific CRE, and drastic changes in function were accompanied by deep conservation of key regulatory linkages. © 2013 Rogers et al

Radiative contribution to neutrino masses and mixing in μν\mu\nuSSM

In an extension of the minimal supersymmetric standard model (popularly known as the $\mu\nu$SSM), three right handed neutrino superfields are introduced to solve the $\mu$-problem and to accommodate the non-vanishing neutrino masses and mixing. Neutrino masses at the tree level are generated through $R-$parity violation and seesaw mechanism. We have analyzed the full effect of one-loop contributions to the neutrino mass matrix. We show that the current three flavour global neutrino data can be accommodated in the $\mu\nu$SSM, for both the tree level and one-loop corrected analyses. We find that it is relatively easier to accommodate the normal hierarchical mass pattern compared to the inverted hierarchical or quasi-degenerate case, when one-loop corrections are included.Comment: 51 pages, 14 figures (58 .eps files), expanded introduction, other minor changes, references adde

Magnetic-field-induced charge-stripe order in the high temperature superconductor YBa2Cu3Oy

Electronic charges introduced in copper-oxide planes generate high-transition temperature superconductivity but, under special circumstances, they can also order into filaments called stripes. Whether an underlying tendency of charges to order is present in all cuprates and whether this has any relationship with superconductivity are, however, two highly controversial issues. In order to uncover underlying electronic orders, magnetic fields strong enough to destabilise superconductivity can be used. Such experiments, including quantum oscillations in YBa2Cu3Oy (a notoriously clean cuprate where charge order is not observed) have suggested that superconductivity competes with spin, rather than charge, order. Here, using nuclear magnetic resonance, we demonstrate that high magnetic fields actually induce charge order, without spin order, in the CuO2 planes of YBa2Cu3Oy. The observed static, unidirectional, modulation of the charge density breaks translational symmetry, thus explaining quantum oscillation results, and we argue that it is most likely the same 4a-periodic modulation as in stripe-ordered cuprates. The discovery that it develops only when superconductivity fades away and near the same 1/8th hole doping as in La2-xBaxCuO4 suggests that charge order, although visibly pinned by CuO chains in YBa2Cu3Oy, is an intrinsic propensity of the superconducting planes of high Tc cuprates.Comment: For a final version, see http://www.nature.com/nature/journal/v477/n7363/full/nature10345.htm

Phenomenology and physical origin of shear-localization and shear-banding in complex fluids

We review and compare the phenomenological aspects and physical origin of shear-localization and shear-banding in various material types, namely emulsions, suspensions, colloids, granular materials and micellar systems. It appears that shear-banding, which must be distinguished from the simple effect of coexisting static-flowing regions in yield stress fluids, occurs in the form of a progressive evolution of the local viscosity towards two significantly different values in two adjoining regions of the fluids in which the stress takes slightly different values. This suggests that from a global point of view shear-banding in these systems has a common physical origin: two physical phenomena (for example, in colloids, destructuration due to flow and restructuration due to aging) are in competition and, depending on the flow conditions, one of them becomes dominant and makes the system evolve in a specific direction.Comment: The original publication is available at http://www.springerlink.co

Violent aggression predicted by multiple pre-adult environmental hits

Early exposure to negative environmental impact shapes individual behavior and potentially contributes to any mental disease. We reported previously that accumulated environmental risk markedly decreases age at schizophrenia onset. Follow-up of matched extreme group individuals (≤1 vs. ≥3 risks) unexpectedly revealed that high-risk subjects had >5 times greater probability of forensic hospitalization. In line with longstanding sociological theories, we hypothesized that risk accumulation before adulthood induces violent aggression and criminal conduct, independent of mental illness. We determined in 6 independent cohorts (4 schizophrenia and 2 general population samples) pre-adult risk exposure, comprising urbanicity, migration, physical and sexual abuse as primary, and cannabis or alcohol as secondary hits. All single hits by themselves were marginally associated with higher violent aggression. Most strikingly, however, their accumulation strongly predicted violent aggression (odds ratio 10.5). An epigenome-wide association scan to detect differential methylation of blood-derived DNA of selected extreme group individuals yielded overall negative results. Conversely, determination in peripheral blood mononuclear cells of histone-deacetylase1 mRNA as 'umbrella mediator' of epigenetic processes revealed an increase in the high-risk group, suggesting lasting epigenetic alterations. Together, we provide sound evidence of a disease-independent unfortunate relationship between well-defined pre-adult environmental hits and violent aggression, calling for more efficient prevention

The association between misperceptions around weight status and quality of life in adults in Australia

Objective: Limited evidence supports a possible association between a person’s perception of their weight status and their quality of life (QoL). This study evaluates whether misperception around weight status is associated with QoL and the impact of gender on this association. Methods: A cross-sectional survey of Australian adults (n=1,905 analysed) collected selfreported height and weight (used to estimate BMI), gender and QoL (described using the AQoL-8D). Participants reported whether they perceived their weight status to be ‘underweight’, ‘healthy weight’, ‘overweight’ or ‘obese’. Misperception around weight status was categorised based on perceived weight status and self-reported BMI. Ordinary least squares regression was used to test associations between self-reported overall, physical and psychosocial QoL, misperception of weight status, and gender, across different BMI categories, after controlling for income, education, relationship status and health conditions. Results: Compared to accurate perception, underestimation of weight status was associated with higher overall QoL for obese males and females and for overweight males. Overestimation of weight status was associated with higher overall QoL for underweight females and lower overall QoL for healthy weight males and females. The same pattern was seen for psychosocial QoL. Physical QoL was less sensitive to misperception than psychosocial QoL. Conclusions: Self-reported misperception around weight status is associated with overall, psychosocial and to a lesser extent physical QoL in Australian adults, although its role depends on BMI category and gender. Generally misperception in the direction of “healthy weight” is associated with higher QoL and overestimation of weight status by those who are of healthy weight is associated with lower QoL. Findings should be confirmed in datasets that contain measured as opposed to self-report height and weight