Espacios verdes urbanos y diversidad vegetal a diferentes escalas espacio-temporales: el ejemplo de Beijing, China

Beijing, the capital city of China, is one of the largest and most rapidly-urbanizing cities in the world. In this work, we present the main results of one decade’s research on urban vegetation and plant diversity changes in different urban structural units. Urban vegetation/plant diversity has been studied at two different levels: at the landscape level (greening percentage, fragmentation degree) and at the plant species level (structure, composition, and origin). Finally, concerns with the ability to study Beijing’s plant urban ecology are discussed.Pekín, la capital de China, es una de las urbes más pobladas y a la vez con una de las tasas de expansión urbana más rápidas del mundo. En el presente trabajo, se presentan los principales resultados tras una década de estudio de los cambios en la vegetación y diversidad vegetal urbana a lo largo de las diferentes unidades estructurales urbanas. La vegetación y la diversidad vegetal urbana se han estudiado a dos niveles: a nivel de paisaje (porcentaje de zonas verdes, grado de fragmentación) y a nivel de especie (estructura, composición y origen). En último lugar se discuten algunos aspectos relacionados con la metodología de estudio de la ecología urbana en Pekín

A Theory for steady and self-sustained premixed combustion waves

Based on the compressible Navier – Stokes equations for reactive flow problems, an eigenvalue problem for the steady and self-sustained premixed combustion wave propagation is developed. The eigenvalue problem is analytically solved and a set of analytic formulae for description of the wave propagation is found out. The analytic formulae are actually the exact solution of the eigenvalue problem in the form of integration, based on which author develops an iterative and numerical algorithm for calculation of the steady and self-sustained premixed combustion wave propagation and its speed. In order to explore the mathematical model and test the computational method developed in this paper, three groups of combustion wave propagation modes are calculated. The computational results show that the non-trivial modes of the combustion wave propagation exist and their distribution is not continuous but discrete

Finite-temperature ordering in a two-dimensional highly frustrated spin model

We investigate the classical counterpart of an effective Hamiltonian for a strongly trimerized kagome lattice. Although the Hamiltonian only has a discrete symmetry, the classical groundstate manifold has a continuous global rotational symmetry. Two cases should be distinguished for the sign of the exchange constant. In one case, the groundstate has a 120^\circ spin structure. To determine the transition temperature, we perform Monte-Carlo simulations and measure specific heat, the order parameter as well as the associated Binder cumulant. In the other case, the classical groundstates are macroscopically degenerate. A thermal order-by-disorder mechanism is predicted to select another 120^\circ spin-structure. A finite but very small transition temperature is detected by Monte-Carlo simulations using the exchange method.Comment: 11 pages including 9 figures, uses IOP style files; to appear in J. Phys.: Condensed Matter (proceedings of HFM2006

Acute Malnutrition and Under-5 Mortality, Northeastern Part of India.

We assessed the prevalence of childhood acute malnutrition and under-five mortality rate (U5MR) in Darbhanga district, India, using a two-stage 49-cluster household survey. A total of 1379 households comprising 8473 people were interviewed. During a 90-day recall period, U5MR was 0.5 [95% confidence interval (CI), 0.2-1.4] per 10 000 per day. The prevalence of global acute malnutrition among 1405 children aged 6-59 months was 15.4% (NCHS) and 19.4% (2006 WHO references). This survey suggests that in Darbhanga district, the population is in a borderline food crisis with few food resources. Appropriate strategies should be developed to improve the overall nutritional and health status of children

High-Order Coupled Cluster Method Study of Frustrated and Unfrustrated Quantum Magnets in External Magnetic Fields

We apply the coupled cluster method (CCM) in order to study the ground-state properties of the (unfrustrated) square-lattice and (frustrated) triangular-lattice spin-half Heisenberg antiferromagnets in the presence of external magnetic fields. Here we determine and solve the basic CCM equations by using the localised approximation scheme commonly referred to as the `LSUB$m$' approximation scheme and we carry out high-order calculations by using intensive computational methods. We calculate the ground-state energy, the uniform susceptibility, the total (lattice) magnetisation and the local (sublattice) magnetisations as a function of the magnetic field strength. Our results for the lattice magnetisation of the square-lattice case compare well to those results of QMC for all values of the applied external magnetic field. We find a value for magnetic susceptibility of $\chi=0.070$ for the square-lattice antiferromagnet, which is also in agreement with the results of other approximate methods (e.g., $\chi=0.0669$ via QMC). Our estimate for the range of the extent of the ($M/M_s=$)$\frac 13$ magnetisation plateau for the triangular-lattice antiferromagnet is $1.37< \lambda < 2.15$, which is in good agreement with results of spin-wave theory ($1.248 < \lambda < 2.145$) and exact diagonalisations ($1.38 < \lambda < 2.16$). The CCM value for the in-plane magnetic susceptibility per site is $\chi=0.065$, which is below the result of the spin-wave theory (evaluated to order 1/S) of $\chi_{SWT}=0.0794$.Comment: 30 pages, 13 figures, 1 Tabl

Calibration and First light of the Diabolo photometer at the Millimetre and Infrared Testa Grigia Observatory

We have designed and built a large-throughput dual channel photometer, Diabolo. This photometer is dedicated to the observation of millimetre continuum diffuse sources, and in particular, of the Sunyaev-Zel'dovich effect and of anisotropies of the 3K background. We describe the optical layout and filtering system of the instrument, which uses two bolometric detectors for simultaneous observations in two frequency channels at 1.2 and 2.1 mm. The bolometers are cooled to a working temperature of 0.1 K provided by a compact dilution cryostat. The photometric and angular responses of the instrument are measured in the laboratory. First astronomical light was detected in March 1995 at the focus of the new Millimetre and Infrared Testa Grigia Observatory (MITO) Telescope. The established sensitivity of the system is of 7 mK_RJ s^1/2$. For a typical map of at least 10 beams, with one hour of integration per beam, one can achieve the rms values of y_SZ ~ 7 10^-5 and the 3K background anisotropy Delta T/T ~ 7 10^-5, in winter conditions. We also report on a novel bolometer AC readout circuit which allows for the first time total power measurements on the sky. This technique alleviates (but does not forbid) the use of chopping with a secondary mirror. This technique and the dilution fridge concept will be used in future scan--modulated space instrument like the ESA Planck mission project.Comment: 10 pages, LaTeX, 12 figures, accepted for publication in Astronomy and Astrophysics Supplement Serie

Risk Factors for Nosocomial Bacterremia Due to Methicillin-Resistant Staphylococcus Aureus

In a prospective surveillance study (February 1990–December 1991) performed at a 1000-bed teaching hospital to identify risk factors for nosocomial methicillin-resistantStaphylococcus aureus (MRSA) bacteremia, 309 patients were found to be colonized (n=103; 33 %) or infected (n=206; 67 %) by MRSA. Sixty-three of them developed bacteremia. Compared with 114 patients who had nosocomial bacteremia caused by methicillin-sensitiveStaphylococcus aureus during the same period of time, MRSA bacteremic patients had more severe underlying diseases (p<0.01), were more often in intensive care units (p<0.01) and had received prior antibiotic therapy more frequently (p<0.01). To further identify risk factors for MRSA bacteremia, univariate and multivariate analyses of this series of 309 patients were performed using the occurrence of MRSA bacteremia as the dependent variable. Among 14 variables analyzed, intravascular catheterization, defined as one or more intravascular catheters in place for more than 48 h, was the only variable selected by a logistic regression model as an independent risk factor (OR=2.7, CI=1.1–6.6). The results of this study reinforce the concept that recent antibiotic therapy may predispose patients to MRSA infection and suggest that among patients colonized or infected by MRSA, those with intravascular catheters are at high risk of developing MRSA bacteremia