Symmetry breaking orbital anisotropy on detwinned Ba(Fe1-xCox)2As2 above the spin density wave transition

Nematicity, defined as broken rotational symmetry, has recently been observed in competing phases proximate to the superconducting phase in the cuprate high temperature superconductors. Similarly, the new iron-based high temperature superconductors exhibit a tetragonal to orthorhombic structural transition (i.e. a broken C4 symmetry) that either precedes or is coincident with a collinear spin density wave (SDW) transition in undoped parent compounds, and superconductivity arises when both transitions are suppressed via doping. Evidence for strong in-plane anisotropy in the SDW state in this family of compounds has been reported by neutron scattering, scanning tunneling microscopy, and transport measurements. Here we present an angle resolved photoemission spectroscopy study of detwinned single crystals of a representative family of electron-doped iron-arsenide superconductors, Ba(Fe1-xCox)2As2 in the underdoped region. The crystals were detwinned via application of in-plane uniaxial stress, enabling measurements of single domain electronic structure in the orthorhombic state. At low temperatures, our results clearly demonstrate an in-plane electronic anisotropy characterized by a large energy splitting of two orthogonal bands with dominant dxz and dyz character, which is consistent with anisotropy observed by other probes. For compositions x>0, for which the structural transition (TS) precedes the magnetic transition (TSDW), an anisotropic splitting is observed to develop above TSDW, indicating that it is specifically associated with TS. For unstressed crystals, the band splitting is observed close to TS, whereas for stressed crystals the splitting is observed to considerably higher temperatures, revealing the presence of a surprisingly large in-plane nematic susceptibility in the electronic structure.Comment: final version published in PNAS, including supplementary informatio

Cost and impact of policies to remove and reduce fees for obstetric care in Benin, Burkina Faso, Mali and Morocco.

BACKGROUND: Across the Africa region and beyond, the last decade has seen many countries introducing policies aimed at reducing financial barriers to obstetric care. This article provides evidence of the cost and effects of national policies focussed on improving financial access to caesarean and facility deliveries in Benin, Burkina Faso, Mali and Morocco. METHODS: The study uses a comparative case study design with mixed methods, including realist evaluation components. This article presents results across 14 different data collection tools, used in 4-6 research sites in each of the four study countries over 2011-13. The methods included: document review; interviews with key informants; analysis of secondary data; structured extraction from medical files; cross-sectional surveys of patients and staff; interviews with patients and observation of care processes. RESULTS: The article finds that the policies have contributed to continued increases in skilled birth attendance and caesarean sections and a narrowing of inequalities in all four countries, but these trends were already occurring so a shift cannot be attributed solely to the policies. It finds a significant reduction in financial burdens on households after the policy, suggesting that the financial protection objectives may have been met, at least in the short term, although none achieved total exemption of targeted costs. Policies are domestically financed and are potentially sustainable and efficient, and were relatively thoroughly implemented. Further, we find no evidence of negative effects on technical quality of care, or of unintended negative effects on untargeted services. CONCLUSIONS: We conclude that the policies were effective in meeting financial protection goals and probably health and equity goals, at sustainable cost, but that a range of measures could increase their effectiveness and equity. These include broadening the exempted package (especially for those countries which focused on caesarean sections alone), better calibrated payments, clearer information on policies, better stewardship of the local health system to deal with underlying systemic weaknesses, more robust implementation of exemptions for indigents, and paying more attention to quality of care, especially for newborns

Effect of Disorder on Fermi surface in Heavy Electron Systems

The Kondo lattice model with substitutional disorder is studied with attention to the size of the Fermi surface and the associated Dingle temperature. The model serves for understanding heavy-fermion Ce compounds alloyed with La according to substitution Ce{x}La{1-x}. The Fermi surface is identified from the steepest change of the momentum distribution of conduction electrons, and is derived at low enough temperature by the dynamical mean-field theory (DMFT) combined with the coherent potential approximation (CPA). The Fermi surface without magnetic field increases in size with decreasing x from x=1 (Ce end), and disappears at such x that gives the same number of localized spins as that of conduction electrons. From the opposite limit of x=0 (La end), the Fermi surface broadens quickly as x increases, but stays at the same position as that of the La end. With increasing magnetic field, a metamagnetic transition occurs, and the Fermi surface above the critical field changes continuously across the whole range of x. The Dingle temperature takes a maximum around x=0.5. Implication of the results to experimental observation is discussed.Comment: 5 pages, 5 figure

Cost and impact of policies to remove and reduce fees for obstetric care in Benin, Burkina Faso, Mali and Morocco

Background: Across the Africa region and beyond, the last decade has seen many countries introducing policies aimed at reducing financial barriers to obstetric care. This article provides evidence of the cost and effects of national policies focussed on improving financial access to caesarean and facility deliveries in Benin, Burkina Faso, Mali and Morocco. Methods: The study uses a comparative case study design with mixed methods, including realist evaluation components. This article presents results across 14 different data collection tools, used in 4-6 research sites in each of the four study countries over 2011-13. The methods included: document review; interviews with key informants; analysis of secondary data; structured extraction from medical files; cross-sectional surveys of patients and staff; interviews with patients and observation of care processes. Results: The article finds that the policies have contributed to continued increases in skilled birth attendance and caesarean sections and a narrowing of inequalities in all four countries, but these trends were already occurring so a shift cannot be attributed solely to the policies. It finds a significant reduction in financial burdens on households after the policy, suggesting that the financial protection objectives may have been met, at least in the short term, although none achieved total exemption of targeted costs. Policies are domestically financed and are potentially sustainable and efficient, and were relatively thoroughly implemented. Further, we find no evidence of negative effects on technical quality of care, or of unintended negative effects on untargeted services. Conclusions: We conclude that the policies were effective in meeting financial protection goals and probably health and equity goals, at sustainable cost, but that a range of measures could increase their effectiveness and equity. These include broadening the exempted package (especially for those countries which focused on caesarean sections alone), better calibrated payments, clearer information on policies, better stewardship of the local health system to deal with underlying systemic weaknesses, more robust implementation of exemptions for indigents, and paying more attention to quality of care, especially for newborns.sch_iih15pub4430pub

Preparation of stable magnetic nanofluids containing Fe3O4@PPy nanoparticles by a novel one-pot route

Stable magnetic nanofluids containing Fe3O4@Polypyrrole (PPy) nanoparticles (NPs) were prepared by using a facile and novel method, in which one-pot route was used. FeCl3·6H2O was applied as the iron source, and the oxidizing agent to produce PPy. Trisodium citrate (Na3cit) was used as the reducing reagent to form Fe3O4 NPs. The as-prepared nanofluid can keep long-term stability. The Fe3O4@PPy NPs can still keep dispersing well after the nanofluid has been standing for 1 month and no sedimentation is found. The polymerization reaction of the pyrrole monomers took place with Fe3+ ions as the initiator, in which these Fe3+ ions remained in the solution adsorbed on the surface of the Fe3O4 NPs. Thus, the core-shell NPs of Fe3O4@PPy were obtained. The particle size of the as-prepared Fe3O4@PPy can be easily controlled from 7 to 30 nm by the polymerization reaction of the pyrrole monomers. The steric stabilization and weight of the NPs affect the stability of the nanofluids. The as-prepared Fe3O4@PPy NPs exhibit superparamagnetic behavior

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

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed