Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

International nosocomial infection control consortium (INICC) report, data summary of 36 countries, for 2004-2009

The results of a surveillance study conducted by the International Nosocomial Infection Control Consortium (INICC) from January 2004 through December 2009 in 422 intensive care units (ICUs) of 36 countries in Latin America, Asia, Africa, and Europe are reported. During the 6-year study period, using Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN; formerly the National Nosocomial Infection Surveillance system [NNIS]) definitions for device-associated health care-associated infections, we gathered prospective data from 313,008 patients hospitalized in the consortium's ICUs for an aggregate of 2,194,897 ICU bed-days. Despite the fact that the use of devices in the developing countries' ICUs was remarkably similar to that reported in US ICUs in the CDC's NHSN, rates of device-associated nosocomial infection were significantly higher in the ICUs of the INICC hospitals; the pooled rate of central line-associated bloodstream infection in the INICC ICUs of 6.8 per 1,000 central line-days was more than 3-fold higher than the 2.0 per 1,000 central line-days reported in comparable US ICUs. The overall rate of ventilator-associated pneumonia also was far higher (15.8 vs 3.3 per 1,000 ventilator-days), as was the rate of catheter-associated urinary tract infection (6.3 vs. 3.3 per 1,000 catheter-days). Notably, the frequencies of resistance of Pseudomonas aeruginosa isolates to imipenem (47.2% vs 23.0%), Klebsiella pneumoniae isolates to ceftazidime (76.3% vs 27.1%), Escherichia coli isolates to ceftazidime (66.7% vs 8.1%), Staphylococcus aureus isolates to methicillin (84.4% vs 56.8%), were also higher in the consortium's ICUs, and the crude unadjusted excess mortalities of device-related infections ranged from 7.3% (for catheter-associated urinary tract infection) to 15.2% (for ventilator-associated pneumonia). Copyright © 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved

Effects of interparticle interactions in magnetic Fe/Si3N4 granular systems

An experimental evidence of the progressive modification in the magnetic behavior of granular Fe/ Si3 N4 samples due to interaction effects between particles is reported. Microstructural features and local structure were determined by x-ray absorption spectroscopy and transmission electron microscopy to select granular samples with predetermined cluster size. Fe/ Si3 N4 systems have been characterized by ac- and dc-magnetization measurements to study the gradual evolution of magnetic properties of granular systems, where three different behaviors have been observed. As-deposited samples with Fe thickness layers of 2.5 nm, present a modified superparamagnetic behavior, due to very weak interactions between very small Fe clusters separated by a nonmagnetic FeN phase. An evolution of the average blocking temperature at intermediate fields (TB ∼ H3⊃/2) is observed, similar to noninteracting systems, but first signatures of a frozen spin state at low temperatures appear. Annealed samples exhibit a noticeable modification from the multilayer character to a random three-dimensional organization of Fe clusters embedded in a Si3 N4 matrix. After annealing, samples with initial Fe layer thickness of 0.7 nm provide iron cluster in the range of 1.3 nm and exhibit a superspin-glass state, with a de Almeida-Thouless evolution of the energy barriers (TB ∼ H2⊃/3) that is explained in terms of increasing interparticle interactions. Moreover, annealed samples, with initial layer thickness of 1.3 nm, supply iron cluster of near 3 nm that present stronger interactions and yield a superferromagnetic state, likely provided by residual ultrasmall particles between the blocked clusters. © 2010 The American Physical Society.This work has been supported by Spanish MICINN under Contracts No. MAT2009-08786, No. MAT2008-06517-C02-01, and No. CSD2009-00013 and by CAM under Contract No. S2009/MAT-1756. J.S.M. is grateful to MICINN for the financial support within the JdlC program.Peer Reviewe

Optimization of the Guide Design of MIRACLES, the Neutron Time-of-Flight Backscattering Spectrometer at the European Spallation Source

To boost the science case of MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source (ESS), an optimized neutron guide system, is proposed. This systematic study resulted in an enhancement in the transport of cold neutrons, compared with the previous conceptual design, with wavelengths ranging from λ = 2 Å to 20 Å along the 162.5-m distance from source to sample. This maintained the undisturbed main focus of the instrument, viz, to carry out quasielastic and inelastic neutron scattering (QENS and INS) experiments on a large dynamic range and for both energy-gain and energy-loss sides. To improve the collection of cold neutrons from the source and direct them to the sample position, the vertical geometry was adjusted to an adapted version of a ballistic elliptical profile. Its horizontal geometry was conceived to: (i) keep the high-resolution performance of the instrument, and (ii) minimize the background originating from fast and thermal neutrons. To comply with the first requirement, a narrow guide section at the pulse shaping chopper position has been implemented. To fulfil the second, a curved guide segment has been chosen to suppress neutrons with wavelengths λ < 2 Å. Subsequent tailoring of the phase space provided an efficient transport of cold neutrons along the beamline to reach a 3 × 3 cm2 sample. Finally, additional calculations were performed to present a potential upgrade, with the exchange of the final segment, to focus on samples of approximately 1 × 1 cm2; the proposal anticipates a flux increase of 70% in this 1 cm2 sample area

Gold-coated iron nanoparticles in transparent Si3N4 matrix thin films

A new method to prepare thin films containing gold-coated iron nanoparticles is presented. The ternary Fe–Au–Si3N4 system prepared by sequential sputtering has revealed a progressive variation of microstructures from Au/Fe/Au/Si3N4 multilayers to iron nanoparticles. Microstructural characterization by transmission electron microscopy, analysis of the magnetic properties and probing of the iron short-range order by X-ray absorption spectroscopy confirm the existence of a gold-coated iron nanoparticles of 1–2 nm typical size for a specific range of iron and gold contents per layer in the transparent silicon nitride ceramic matrix.This study was supported by Spanish MICINN under contracts MAT2009-08786 and CSD2009-00013 and by regional government of Madrid though contract S2009/MAT-1756.Peer reviewe

Gold embedding influence on the magnetic behaviour of iron in Fe/Si3N4 multilayers prepared by sputtering

Au/Fe/Au/Si3N4 multilayers have been prepared in order to improve ferromagnetism in Fe/Si3N4 system. A huge enhancement of magnetization is observed when the iron layers are embedded into gold ones, showing saturation magnetization values near the bulk ones. In this paper, a careful microstructural study has been carried out to explain the observed magnetic behaviour of this ferromagnetic system prepared in the transparent silicon nitride matrix. © 2010 Elsevier B.V. All rights reserved.This work has been partially supported under the Spanish MICINN contract MAT2009-08786.Peer Reviewe

Towards a conceptual design for the moderators of ARGITU: A preliminary neutronics study

This work reports on preliminary calculations of potential low-dimensional moderators for the high-current accelerator-driven neutron source (HiCANS) ARGITU. Simulations start with the selection of materials, depending on the neutron energy range to be used for each instrument. Results evaluate the performance of water for thermal moderators to deliver neutrons for thermal instruments, whereas para-H2 and solid methane have been analyzed to deliver cold neutrons. Additionally, alternative concepts like using hybrid moderators (water/liquid methane) or reduced-size cold moderators (reduced-size para-H2) have been scrutinized for their use in bispectral instruments that require a wide range of intermediate neutron energies. The dimensions of the moderators have been refined to improve the neutron yield for the neutron wavelength range selected in each case. After that, a space-efficient layout has been proposed to implement four moderators next to the Be target, linked to a preliminary suite of instruments that these moderators would serve. Although the eventual selection shall consider both the final instrument suite and the phase space volume required for such neutron instruments (that defines their neutron optics features), the results presented here represent a qualitative step towards the conceptual development of the ARGITU neutron source

Indium-tin oxide thin films deposited at room temperature on glass and PET substrates: Optical and electrical properties variation with the H2-Ar sputtering gas mixture

The optical and electrical properties of indium tin oxide (ITO) films deposited at room temperature on glass and polyethylene terephthalate (PET) substrates were investigated. A clear evolution of optical transparency and sheet resistance with the content of H2 in the gas mixture of H2 and Ar during magnetron sputtering deposition is observed. An optimized performance of the transparent conductive properties ITO films on PET was achieved for samples prepared using H2/(Ar + H2) ratio in the range of 0.3–0.6%. Moreover, flexible ITO-PET samples show a better transparent conductive figure of merit, ΦTC = T10/RS, than their glass counterparts. These results provide valuable insight into the room temperature fabrication and development of transparent conductive ITO-based flexible devices.We acknowledge financial support from Spanish MINECO though contracts MAT2012-37276-C03-01 and from the Madrid Regional Government though contract P2013/MIT-2740

Crystal structures and temperature-induced phase transitions of Sr2Mn(2+)W(6+)O6, and of its transformation to Sr2Mn(3+)W(6+)O(6+δ)

10 pages, 9 figures, 3 tables.-- Printed version published Sep 17, 2009.We present a new effective method for synthesizing Sr2MWO6 double perovskite oxides: the co-precipitation route at 1220 K in nitrogen environment. Using conventional X-ray diffraction methods, we have confirmed the room-temperature space group of Sr2Mn(2+)WO6 to be P2(1)/n: Z = 2; a=5.6764(1)Ǻ; b=5.6752(1)Ǻ; c=8.0149(1)Ǻ; β=90.12(1)Ǻ and V=258.18(1)Å3. We show that the compound presents the following temperature induced phase-transition sequence: P2(1)/n -> I4/m -> Fm3m. After a thermal treatment, 24 h at 870 K in air, the Sr2Mn(2+)WO6 compound transforms irreversibly to Sr2Mn(3+)WO(6+δ). This transformation has been confirmed by EPR and XANES measurements. Using conventional X-ray diffraction methods, we have shown the room-temperature space group of Sr2Mn(3+)WO(6+δ) to be I4/m: Z = 2; a=5.6353(1)Ǻ; c=8.0149(1)Ǻ and V=254.53(1)Å3. We show that the compound presents the following temperature induced phase-transition sequence: I4/m(->I4/mmm) -> Fm3m. The tetragonal-to-tetragonal phase transition is suggested to be present, it is not observed as it is very weak; it is attributed to the presence of the Jahn-Teller active Mn3+ cation.This work was done in part under Project Nos.: UPV 0063.310-13564/2001-2007 and MAT2008-05839/MAT. The authors thank the Spanish Ministry of Science for the beamtime allocation and the staff of Spanish CRG beamline (SpLine-BM25) of ESRF for their support during the experiment.Peer reviewe

Elastic properties of boron carbide films via surface acoustic waves measured by Brillouin light scattering

et al.Surface acoustic wave (SAW) velocity has been determined by high resolution Brillouin light scattering to study the mechano-elastic properties of boron carbide films prepared by radio frequency (RF) sputtering. The comparison of experimentally observed elastic behaviour with simulations made by considering film composition obtained from elastic recoil detection analysis-time of flight (ERDA-ToF) spectroscopy allows establishing that elastic properties are determined by that of crystalline boron carbide with a lessening of the SAW velocity values due to surface oxidation.This work has been supported by Spanish MICINN under contracts MAT2009-08786, FIS2008-01431 and CSD2009-00013 as well as by the Madrid regional government though contract S2009/MAT-1756.Peer reviewe