Blindness incidence in Germany - A population-based study from Württemberg-Hohenzollern

Few data on the incidence of blindness in Germany are available. We analysed causes of legal blindness for the region Württemberg-Hohenzollern (population 5.5 million) in order to help fill in this gap. Material and Methods: Population-based investigation on the incidence of legal blindness (visual acuity <1/50) based on materials from the social servies. Age-dependent blindness incidences were modelled via logistic regression models. Results: 647 blind persons were newly registered in 1994 (blindness incidence 11.6/100,000). The blindness incidence is moderate in infants (4.5/100,000) and decreases further during childhood. At the age of 20 years, the incidence again rises to the former level and remains relatively constant. After the age of 60 years, the incidence increases sharply: 5-year odds ratios are 1.76 (CI: 1.68-1.85) in women and 1.72 (CI: 1.60-1.84) in men. The blindness incidence is higher in women, 15.6/100,000, compared to 12.2/100,000 in men. The major causes of blindness are: macular degeneration, 3.92/100,000; diabetic retinopathy, 2.01/100,000; glaucoma, 1.6/100,000; high myopia, 0.77/100,000; optic atrophy, 0.68/100,000; central nervous system-triggered blindness; 0.56/100,000, and tapetoretinal degenerations, 0.52/100,000. Discussion: Due to monetary incentives for the blind persons, social service files offer accurate and complete data. Besides macular degeneration, glaucoma and dia betic retinopathy are major causes of blindness. Thus, this study suggests further blindness prevention activities for diabetic retinopathy and glaucoma

Impact of disorder on dynamics and ordering in the honeycomb-lattice iridate Na2IrO3

Kitaev's honeycomb spin-liquid model and its proposed realization in materials such as α-RuCl3, Li2IrO3, and Na2IrO3 continue to present open questions about how the dynamics of a spin liquid are modified in the presence of non-Kitaev interactions as well as the presence of inhomogeneities. Here we use Na23 nuclear magnetic resonance to probe both static and dynamical magnetic properties in single-crystal Na2IrO3. We find that the NMR shift follows the bulk susceptibility above 30 K but deviates from it below; moreover below TN the spectra show a broad distribution of internal magnetic fields. Both of these results provide evidence for inequivalent magnetic sites at low temperature, suggesting inhomogeneities are important for the magnetism. The spin-lattice relaxation rate is isotropic and diverges at TN, suggesting that the Kitaev cubic axes may control the critical quantum spin fluctuations. In the ordered state, we observe gapless excitations, which may arise from site substitution, emergent defects from milder disorder, or possibly be associated with nearby quantum paramagnetic states distinct from the Kitaev spin liquid

Weak phase separation and the pseudogap in the electron-doped cuprates

We study the quantum transition from an antiferromagnet to a superconductor in a model for electron- and hole-doped cuprates by means of a variational cluster perturbation theory approach. In both cases, our results suggest a tendency towards phase separation between a mixed antiferromagnetic-superconducting phase at low doping and a pure superconducting phase at larger doping. However, in the electron-doped case the energy scale for phase separation is an order of magnitude smaller than for hole doping. We argue that this can explain the different pseudogap and superconducting transition scales in hole- and electron-doped materials.Comment: Final version, accepted for publication in Europhysics Letter

Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho

We report muon spin relaxation measurements on the magnetic structures of RBaCo_2O_5.5 with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co^3+ of CoO_6 octahedra. Phase separation into well separated regions with different spin state order is observed in the antiferromagnetic phases. The unusual strongly anisotropic magnetoresistance and its onset at the FM-AFM phase boundary is explained.Comment: 4 pages, accepted for publication in Phys. Rev. Let

Biodegradable and compostable alternatives to conventional plastics

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Royal Society.Packaging waste forms a significant part of municipal solid waste and has caused increasing environmental concerns, resulting in a strengthening of various regulations aimed at reducing the amounts generated. Among other materials, a wide range of oil-based polymers is currently used in packaging applications. These are virtually all non-biodegradable, and some are difficult to recycle or reuse due to being complex composites having varying levels of contamination. Recently, significant progress has been made in the development of biodegradable plastics, largely from renewable natural resources, to produce biodegradable materials with similar functionality to that of oil-based polymers. The expansion in these bio-based materials has several potential benefits for greenhouse gas balances and other environmental impacts over whole life cycles and in the use of renewable, rather than finite resources. It is intended that use of biodegradable materials will contribute to sustainability and reduction in the environmental impact associated with disposal of oil-based polymers. The diversity of biodegradable materials and their varying properties makes it difficult to make simple, generic assessments such as biodegradable products are all ‘good’ or petrochemical-based products are all ‘bad’. This paper discusses the potential impacts of biodegradable packaging materials and their waste management, particularly via composting. It presents the key issues that inform judgements of the benefits these materials have in relation to conventional, petrochemical-based counterparts. Specific examples are given from new research on biodegradability in simulated ‘home’ composting systems. It is the view of the authors that biodegradable packaging materials are most suitable for single-use disposable applications where the post-consumer waste can be locally composted.EPSR

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

$^{75}$As Nuclear Magnetic (NMR) and Quadrupolar (NQR) Resonance were used, together with M\"{o}ssbauer spectroscopy, to investigate the magnetic state induced by Mn for Fe substitutions in F-doped LaFe$_{1-x}$Mn$_{x}$AsO superconductors. The results show that $0.5$% of Mn doping is enough to suppress the superconducting transition temperature $T_c$ from 27 K to zero and to recover the magnetic structure observed in the parent undoped LaFeAsO. Also the tetragonal to orthorhombic transition of the parent compound is recovered by introducing Mn, as evidenced by a sharp drop of the NQR frequency. The NQR spectra also show that a charge localization process is at play in the system. Theoretical calculations using a realistic five-band model show that correlation-enhanced RKKY exchange interactions between nearby Mn ions stabilize the observed magnetic order, dominated by $Q_1=(\pi,0)$ and $Q_2=(0,\pi)$ ordering vectors. These results give compelling evidence that F-doped LaFeAsO is a strongly correlated electron system at the verge of an electronic instability.Comment: 5 pages, 5 figures and 4 pages of supplemental materia

Ferromagnetism or slow paramagnetic relaxation in Fe-doped Li3_3N?

We report on isothermal magnetization, M\"ossbauer spectroscopy, and magnetostriction as well as temperature-dependent alternating-current (ac) susceptibility, specific heat, and thermal expansion of single crystalline and polycrstalline Li$_2$(Li$_{1-x}$Fe$_x$)N with $x = 0$ and $x \approx 0.30$. Magnetic hysteresis emerges at temperatures below $T \approx 50\,$K with coercivity fields of up to $\mu_0H = 11.6\,$T at $T = 2\,$K and magnetic anisotropy energies of $310\,$K ($27\,$meV). The ac susceptibility is strongly frequency dependent ($f\,=\,10$--$10,000\,$Hz) and reveals an effective energy barrier for spin reversal of $\Delta E \approx 1100\,$K. The relaxation times follow Arrhenius behavior for $T > 25\,$K. For $T < 10\,$K, however, the relaxation times of $\tau \approx 10^{10}\,$s are only weakly temperature-dependent indicating the relevance of a quantum tunneling process instead of thermal excitations. The magnetic entropy amounts to more than $25\,$J mol$^{-1}_{\rm Fe}\,$K$^{-1}$ which significantly exceeds $R$ln2, the value expected for the entropy of a ground state doublet. Thermal expansion and magnetostriction indicate a weak magneto-elastic coupling in accordance with slow relaxation of the magnetization. The classification of Li$_2$(Li$_{1-x}$Fe$_x$)N as ferromagnet is stressed and contrasted with highly anisotropic and slowly relaxing paramagnetic behavior.Comment: 12 pages, 10 figure