Special report: silent disasters.

Disasters occur not only in war and conflict or after natural events, such as earthquakes or floods. In fact, the death of hundreds of thousands of children in Niger every year, often for treatable conditions, could just as well qualify as a disaster situation. A lack of funding for health care and health-care staff and user fee policies for health care in very poor or unstable settings challenge international agreements that make statements about the right to health and access to health care for all people. This paper argues that although sustainable development is important, today many are without essential health care and die in the silent disasters of hunger and poverty. In other words, the development of health care appears to be stalled for the sake of sustainability

Coeficientes culturais de consórcio milho-feijão e milho-braquiária.

Para estabelecer os riscos climáticos para consórcios milho-feijão e milho-pastagens, é necessário que se conheça os seus respectivos coeficientes culturais. Objetivando determinar esses coeficientes, foram instalados, em três épocas, ensaios de campo onde determinou-se, o consumo de água pelas cultura no consórcio por meio do balanço hídrico do solo e a demanda potencial de água por meio da metodologia proposta por Penman-Monteith. Os resultados mostraram que os coeficiente culturais dos consórcios foram muito maiores que das culturas isoladamente, o que permite concluir que o consórcio demanda maior disponibilidade de água no solo. Portanto, a implantação do consorcio dependente grandemente da distribuição das chuvas na região e da a capacidade de retenção de umidade do solo. Assim sendo haverá restrição da época e da área a ser plantada por esse sistema produtivo comparado com a cultura isolada

Mean-Field-Theory for Polymers in Mixed Solvents Thermodynamic and Structural Properties

Theoretical aspects of polymers in mixed solvents are considered using the Edwards Hamiltonian formalism. Thermodynamic and structural properties are investigated and some predictions are made when the mixed solvent approaches criticality. Both the single and the many chain problems are examined. When the pure mixed solvent is near criticality, addition of a small amount of polymers shifts the criticality towards either enhanced compatibility or induced phase separation depending upon the value of the parameter describing the interaction asymmetry of the solvents with respect to the polymer. The polymer-solvent effective interaction parameter increases strongly when the solvent mixture approaches criticality. Accordingly, the apparent excluded volume parameter decreases and may vanish or even become negative. Consequently, the polymer undergoes a phase transition from a swollen state to an unperturbed state or even take a collapsed configuration. The effective potential acting on a test chain in strong solutions is calculated and the concept of Edwards screening discussed. Structural properties of ternary mixtures of polymers in mixed solvents are investigated within the Edwards Hamiltonian model. It is shown that the effective potential on a test chain in strong solutions could be written as an infinite series expansion of terms describing interactions via one chain, two chains etc. This summation can be performed following a similar scheme as in the Ornstein-Zernike series expansion.Comment: accepted in Macromol. Theory Simu

Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2

The magnetic response of antiferromagnetic CsO2, coming from the p-orbital S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic resonance across the structural phase transition occuring at Ts1=61 K on cooling. Above Ts1, where spins form a square magnetic lattice, we observe a huge, nonmonotonic temperature dependence of the exchange coupling originating from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic spin chains are formed as a result of p-orbital ordering, we observe a spin Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting phenomena, which provide rare simple manifestations of the coupling between spin, lattice and orbital degrees of freedom, establish CsO2 as a model system for molecular solids.Comment: 9 pages, 5 figures (with Supplemental Material), to appear in Physical Review Letter

One-dimensional quantum antiferromagnetism in the p−p-orbital CsO2_2 compound revealed by electron paramagnetic resonance

Recently it was proposed that the orbital ordering of $\pi_{x,y}^*$ molecular orbitals in the superoxide CsO$_2$ compound leads to the formation of spin-1/2 chains below the structural phase transition occuring at $T_{\rm{s1}}=61$~K on cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR) study of this phase in CsO$_2$ powder. The EPR signal appears as a broad line below $T_{\rm{s1}}$, which is replaced by the antiferromagnetic resonance below the N\'{e}el temperature $T_{\rm N}=8.3$~K. The temperature dependence of the EPR linewidth between $T_{\rm{s1}}$ and $T_{\rm{N}}$ agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of $S=1/2$ spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR lineshape, linewidth and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent $K=0.48$. Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO$_2$, which is, therefore, a unique $p-$orbital system where such a state could be studied.Comment: 6 pages, 3 figure