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We apply a recently developed measurement technique for methane (CH 4 ) isotopologues * (isotopic variants of CH 4 - 13 CH 4 , 12 CH 3 D, 13 CH 3 D, and 12 CH 2 D 2 ) to identify contributions to the atmospheric burden from fossil fuel and microbial sources. The aim of this study is to constrain factors that ultimately control the concentration of this potent greenhouse gas on global, regional, and local levels. While predictions of atmospheric methane isotopologues have been modeled, we present direct measurements that point to a different atmospheric methane composition and to a microbial flux with less clumping (greater deficits relative to stochastic) in both 13 CH 3 D and 12 CH 2 D 2 than had been previously assigned. These differences make atmospheric isotopologue data sufficiently sensitive to variations in microbial to fossil fuel fluxes to distinguish between emissions scenarios such as those generated by different versions of EDGAR (the Emissions Database for Global Atmospheric Research), even when existing constraints on the atmospheric CH 4 concentration profile as well as traditional isotopes are kept constant.

A large volume of freshwater is incorporated in the relatively fresh (salinity ~32-33) Pacific Ocean waters that are transported north through the Bering Strait relative to deep Atlantic salinity in the Arctic Ocean (salinity ~34.8). These freshened waters help maintain the halocline that separates cold Arctic surface waters from warmer Arctic Ocean waters at depth. The stable oxygen isotope composition of the Bering Sea contribution to the upper Arctic Ocean halocline was established as early as the late 1980's as having a δ18OV-SMOW value of approximately -1.1‰. More recent data indicates a shift to an isotopic composition that is more depleted in 18O (mean δ18O value ~-1.5‰). This shift is supported by a data synthesis of >1400 water samples (salinity from 32.5 to 33.5) from the northern Bering and Chukchi seas, from the years 1987-2020, which show significant year-to-year, seasonal and regional variability. This change in the oxygen isotope composition of water in the upper halocline is consistent with observations of added freshwater in the Canada Basin, and mooring-based estimates of increased freshwater inflows through Bering Strait. Here, we use this isotopic time-series as an independent means of estimating freshwater flux changes through the Bering Strait. We employed a simple end-member mixing model that requires that the volume of freshwater (including runoff and other meteoric water, but not sea ice melt) flowing through Bering Strait has increased by ~40% over the past two decades to account for a change in the isotopic composition of the 33.1 salinity water from a δ18O value of approximately -1.1‰ to a mean of -1.5‰. This freshwater flux change is comparable with independent published measurements made from mooring arrays in the Bering Strait (freshwater fluxes rising from 2000-2500 km3 in 2001 to 3000-3500 km3 in 2011)., Competing Interests: The first author (Cooper) is a section editor for PLOS One. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Carbon dioxide (CO 2 ) and methane (CH 4 ) are natural and anthropogenic products that play a central role in the global carbon cycle and regulating Earth's climate. Applications utilizing laser absorption spectroscopy, which continuously measure concentrations and stable isotope ratios of these greenhouse gases, are routinely employed to measure the source and magnitude of atmospheric inputs. We developed a discrete sample introduction module (DSIM) to enable measurements of methane and CO 2 concentrations and δ 13 C values from limited volume (5-100 mL) gas samples when interfaced with a commercially available cavity ring-down spectroscopy (CRDS) analyzer. The analysis has a dynamic range that spans six orders of magnitude from 100% analyte to the lower limit of instrument detection (2 ppm). We demonstrate system performance for methane by comparing concentrations and δ 13 C results from the DSIM-CRDS system and traditional methods for a variety of sample types, including low concentration (nanomolar CH 4 ) seawater and high concentration (>90% CH 4 ) natural gas. The expansive concentration range of the field-portable DSIM-CRDS system can measure enhances analytical performance for investigating methane and CO 2 dynamics and, potentially, other gases measured by laser absorption spectroscopy.

The expected reduction of ice algae with declining sea ice may prove to be detrimental to the Pacific Arctic ecosystem. Benthic organisms that rely on sea ice organic carbon (iPOC) sustain benthic predators such as the Pacific walrus (Odobenus rosmarus divergens). The ability to track the trophic transfer of iPOC is critical to understanding its value in the food web, but prior methods have lacked the required source specificity. We analyzed the H-Print index, based on biomarkers of ice algae versus phytoplankton contributions to organic carbon in marine predators, in Pacific walrus livers collected in 2012, 2014 and 2016 from the Northern Bering Sea (NBS) and Chukchi Sea. We paired these measurements with stable nitrogen isotopes (δ15N) to estimate trophic position. We observed differences in the contribution of iPOC in Pacific walrus diet between regions, sexes, and age classes. Specifically, the contribution of iPOC to the diet of Pacific walruses was higher in the Chukchi Sea (52%) compared to the NBS (30%). This regional difference is consistent with longer annual sea ice persistence in the Chukchi Sea. Within the NBS, the contribution of iPOC to walrus spring diet was higher in females (~45%) compared to males (~30%) for each year (p < 0.001), likely due to specific foraging behavior of females to support energetic demands associated with pregnancy and lactation. Within the Chukchi Sea, the iPOC contribution was similar between males and females, yet higher in juveniles than in adults. Despite differences in the origin of organic carbon fueling the system (sea ice versus pelagic derived carbon), the trophic position of adult female Pacific walruses was similar between the NBS and Chukchi Sea (3.2 and 3.5, respectively), supporting similar diets (i.e. clams). Given the higher quality of organic carbon from ice algae, the retreat of seasonal sea ice in recent decades may create an additional vulnerability for female and juvenile Pacific walruses and should be considered in management of the species., Competing Interests: The authors have declared that no competing interests exist.

Background: Harm reduction (HR) interventions are essential to reduce human immunodeficiency virus (HIV) and hepatitis C virus (HCV) transmission in people who inject drugs (PWID). Preliminary testing of the Individually Tailored Support and Education for Safer Injection (ITSESI) evidence-based educational intervention for PWID was performed in France in 2011. We created the Eurosider project to implement and evaluate ITSESI at a wider European level, with a view to its future pan-European diffusion., Methods: We performed a mixed-methods study involving quantitative (a 6-month before-after study with PWID) and qualitative (focus groups with field workers) components. The study was conducted in 2018-2019 with 307 eligible PWID participating in four existing HR programmes in Bulgaria, Greece, Portugal, and Romania. ITSESI consists in trained field workers observing PWID injection practices and providing an educational exchange. For the present study, PWID participants were allocated to either the control group (i.e., they continued receiving only the current HR services) or the intervention group (i.e., current HR services plus ITSESI). We used the RE-AIM QuEST framework to assess the effectiveness of ITSESI and its acceptability by field workers. Effectiveness was defined as a reduction in both syringe sharing - the highest HIV/HCV transmission risk practice - and in cutaneous abscesses. We used a multivariable mixed logit model to analyse both effectiveness outcomes and to provide adjusted odds ratios (aOR) and 95% confidence intervals (CI). Field workers' acceptability of the intervention was described using a thematic analysis of the qualitative data., Results: Of the 307 PWID, 55% received ITSESI. Syringe sharing and cutaneous abscesses decreased during follow-up in the intervention group (from 25 to 16% and from 27 to 14%, respectively). Reductions were smaller in the control group (from 29 to 24% and from 23 to 18%, respectively). The multivariable analyses confirmed the effect of the intervention on both of these outcomes (aOR [95% CI]: 0.38 [0.17, 0.85]) and (aOR [95% CI]: 0.38 [0.16, 0.90], respectively). Our qualitative data on acceptability showed the feasibility of involving field workers as proactive research partners in making ITSESI more accessible and acceptable across Europe., Conclusions: We demonstrated both the effectiveness of ITSESI in reducing syringe sharing and cutaneous abscesses in four European countries, and a high level of intervention acceptability by field workers. Our findings provide important insights into how ITSESI can be adapted for pan-European implementation., Competing Interests: Declaration of Interests The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Golden and Blueline Tilefish ( Lopholatilus chamaeleonticeps and Caulolatilus microps ) are keystone taxa in northwest (NW) Atlantic continental shelf-edge environments due to their biotic (trophic-mediated) and abiotic (ecosystem engineering) functional roles combined with high-value fisheries. Despite this importance, the ecological niche dynamics (i.e., those relating to trophic behavior and food-web interactions) of these sympatric species are poorly understood, knowledge of which may be consequential for maintaining both ecosystem function and fishery sustainability. We used stable isotope ratios of carbon (δ 13 C) and nitrogen (δ 15 N) to build realized ecological niche hypervolumes to serve as proxies for diet and production use patterns of L .  chamaeleonticeps and C. microps . We hypothesized that: (a) species exhibit ontogenetic shifts in diet and use of production sources; (b) species acquire energy from spatially distinct resource pools that reflect a sedentary life-history and differential use of the continental shelf-edge; and (c) species exhibit differentiation in one or more measured niche axes. We found evidence for ontogenetic shifts in diet (δ 15 N) but not production source (δ 13 C) in both species, suggesting a subtle expansion of measured ecological niche axes. Spatial interpolation of stable isotope ratios showed distinct latitudinal gradients; for example, individuals were 13 C enriched in northern and 15 N enriched in southern regions, supporting the assertion that tilefish species acquire energy from regional resource pools. High isotopic overlap was observed among species (≥82%); however, when hypervolumes included depth and region of capture, overlap among species substantially decreased to overlap estimates of 15%-77%. This suggests that spatial segregation could alleviate potential competition for resources among tilefish species inhabiting continental shelf-edge environments. Importantly, our results question the consensus interpretation of isotopic overlap estimates as representative of direct competition among species for shared resources or habitats, instead identifying habitat segregation as a possible mechanism for coexistence of tilefish species in the NW Atlantic., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

Invasive species management can be a victim of its own success when decades of effective control cause memories of past harm to fade and raise questions of whether programs should continue. Economic analysis can be used to assess the efficiency of investing in invasive species control by comparing ecosystem service benefits to program costs, but only if appropriate data exist. We used a case study of water hyacinth ( Eichhornia crassipes (Mart.) Solms), a nuisance floating aquatic plant, in Louisiana to demonstrate how comprehensive record-keeping supports economic analysis. Using long-term data sets, we developed empirical and spatio-temporal simulation models of intermediate complexity to project invasive species growth for control and no-control scenarios. For Louisiana, we estimated that peak plant cover would be 76% higher without the substantial growth rate suppression (84% reduction) that appeared due primarily to biological control agents. Our economic analysis revealed that combined biological and herbicide control programs, monitored over an unusually long time period (1975-2013), generated a benefit-cost ratio of about 34:1 derived from the relatively modest costs of $124 million ($2013) compared to the $4.2 billion ($2013) in benefits to anglers, waterfowl hunters, boating-dependent businesses, and water treatment facilities over the 38-year analysis period. This work adds to the literature by: (1) providing evidence of the effectiveness of water hyacinth biological control; (2) demonstrating use of parsimonious spatio-temporal models to estimate benefits of invasive species control; and (3) incorporating activity substitution into economic benefit transfer to avoid overstating benefits. Our study suggests that robust and cost-effective economic analysis is enabled by good record keeping and generalizable models that can demonstrate management effectiveness and promote social efficiency of invasive species control., Competing Interests: Al Cofrancesco is a director at the US Army Engineer Research and Development Center that funded this work. The remaining authors declare that they have no competing interests.

Anaerobic ammonium oxidizing (anammox) bacteria own a central position in the global N-cycle, as they have the ability to oxidize NH 4 + to N 2 under anoxic conditions using NO 2 - . They are responsible for up to 50% of all N 2 released from marine ecosystems into the atmosphere and are thus indispensible for balancing the activity of N-fixing bacteria and completing the marine N-cycle. The contribution, diversity, and impact of anammox bacteria in freshwater ecosystems, however, is largely unknown, confounding assessments of their role in the global N-cycle. Here we report the activity and diversity of anammox bacteria in the world's largest freshwater lake-Lake Superior. We found that anammox performed by previously undiscovered bacteria is an important contributor to sediment N 2 production. We observed striking differences in the anammox bacterial populations found at different locations within Lake Superior and those described from other locations. Our data thus reveal that novel anammox bacteria underpin N-loss from Lake Superior, and if more broadly distributed across inland waters would play an important role in continental N-cycling and mitigation of fixed nitrogen transfer from land to the sea.

The community-based management of acute malnutrition treatment model was introduced to respond to the limited coverage of the inpatient model. Yet until the introduction of quick and low-cost approaches to measuring coverage, its reach was unknown. Once the Coverage Monitoring Network (CMN) had been created to roll out the routine measurement of direct coverage estimates to implementers, they found that programs were reaching only a third of cases. The barriers found to be limiting coverage were the result of the limited perceived value, and therefore focus, on the community. Therefore, the Network used the coverage assessment methodology as a way to encourage implementers to engage more fully with the community. By introducing small changes to the project cycle, specifically a participatory approach to assessments, program design and implementation, the CMN has changed the way implementers engage with the community. Instead of viewing them as passive receivers of services, they have shifted their perspective to view them as service delivery partners. The process provides implementers with a deeper understanding of the context while allowing the community to better understand the program, its challenges, and the identification of solutions. The Network observed implementers from Ministries of Health, and non-governmental organizations, adjusted their understanding and approach to service provision, which is critical if we are to see sustainable increases in program coverage. These experiences show that there is an appetite from implementers in multiple contexts for these practical and simple tools for re-engaging the community.

The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap and carries great potential to impact areas such as data storage, sensing, and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nm by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic nonplanar nanodevices.

In this work the position-controlled growth of GaN nanowires (NWs) on diamond by means of molecular beam epitaxy is investigated. In terms of growth, diamond can be seen as a model substrate, providing information of systematic relevance also for other substrates. Thin Ti masks are structured by electron beam lithography which allows the fabrication of perfectly homogeneous GaN NW arrays with different diameters and distances. While the wurtzite NWs are found to be Ga-polar, N-polar nucleation leads to the formation of tripod structures with a zinc-blende core which can be efficiently suppressed above a substrate temperature of 870 °C. A variation of the III/V flux ratio reveals that both axial and radial growth rates are N-limited despite the globally N-rich growth conditions, which is explained by the different diffusion behavior of Ga and N atoms. Furthermore, it is shown that the hole arrangement has no effect on the selectivity but can be used to force a transition from nanowire to nanotube growth by employing a highly competitive growth regime.

We report on the synthesis and optical gain properties of regularly shaped lead iodide (PbI2) platelets with thickness ranging from 10-500 nm synthesized by chemical vapor deposition methods. The as-prepared single crystalline platelets exhibit a near band edge emission of ∼ 500 nm. Whispering gallery mode (WGM) lasing from individual hexagonal shaped PbI2 platelets is demonstrated in the temperature-range of 77-210 K, where the lasing modes are supported by platelets as thin as 45 nm. The finite-difference time-domain simulation and the edge-length dependent threshold confirm the planar WGM lasing mechanism in such hexagonal shaped PbI2 platelet. Through a comprehensive study of power-dependent photoluminescence (PL) and time-resolved PL spectroscopy, we ascribe the WGM lasing to be biexcitonic in nature. Moreover, for different thicknesses of platelet, the lowest lasing threshold occurs in platelets of ∼ 120 nm, which attributes to the formation of a good Fabry-Pérot resonance cavity in the vertical direction between the top and bottom platelet surfaces that enhances the reflection. Our present study demonstrates the feasibility of planar light sources based on layered semiconductor materials and that their thickness-dependent threshold characteristic is beneficial for the optimization of layered material based optoelectronic devices.

As an incommensurate epitaxy, van der Waals epitaxy allows defect-free crystals to grow on substrates even with a large lattice mismatch. Furthermore, van der Waals epitaxy is proposed as a universal platform where heteroepitaxy can be achieved irrespective of the nature of the overlayer material and the method of crystallization. Here we demonstrate van der Waals epitaxy in solution phase synthesis for seedless and catalyst-free growth of ZnO wire arrays on phlogopite mica at low temperature. A unique incommensurate interface is observed even with the incomplete initial wetting of ZnO onto the substrate. Interestingly, the imperfect contacting layer does not affect the crystalline and optical properties of other parts of the wires. In addition, we present patterned growth of a well-ordered array with hexagonal facets and in-plane alignment. We expect our seedless and catalyst-free solution phase van der Waals epitaxy synthesis to be widely applicable in other materials and structures.

Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-in-nanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.

We present a novel approach for self-assembled growth of GaN quantum wires (QWRs) exhibiting strong confinement in two spatial dimensions. The GaN QWRs are formed by selective nucleation on {112[combining macron]0} (a-plane) facets formed at the six intersections of {11[combining macron]00} (m-plane) sidewalls of AlN/GaN nanowires used as a template. Based on microscopy observations we have developed a 3D model explaining the growth mechanism of QWRs. We show that the QWR formation is governed by self-limited pseudomorphic growth on the side facets of the nanowires (NWs). Quantum confinement in the QWRs is confirmed by the observation of narrow photoluminescence lines originating from individual QWRs with emission energies up to 4.4 eV. Time-resolved photoluminescence studies reveal a short decay time (~120 ps) of the QWR emission. Capping of the QWRs with AlN allows enhancement of the photoluminescence, which is blue-shifted due to compressive strain. The emission energies from single QWRs are modelled assuming a triangular cross-section resulting from self-limited growth on a-plane facets. Comparison with the experimental results yields an average QWR diameter of about 2.7 nm in agreement with structural characterization. The presented results open a new route towards controlled realization of one-dimensional semiconductor quantum structures with a high potential both for fundamental studies and for applications in electronics and in UV light generation.

The optical response of multibranched gold nanoparticles is studied by means of electron energy-loss spectroscopy (EELS) in aberration corrected STEM mode. In every case the plasmon response is constant and variations in the maxima positions were found to be dependent on the branches aspect ratio. The good spatial resolution combined with the high energy resolution (0.18 eV) of the monochromated electron beam allows mapping the different plasmonic modes along the entire nanoparticles ranging from 0.7 eV up to 2.25 eV.

The paper describes a novel and straightforward wet-chemical synthetic route to produce biocompatible single-crystalline gold tabular nanoparticles, herein called nanoprisms (NPRs) due to their characteristic shape. Besides the novelty of the method to produce NPRs with an unprecedented high yield, the synthesis avoids the use of highly toxic cetyltrimethylammonium bromide (CTAB), the most widely used surfactant for the synthesis of gold anisotropic nanoparticles such as nanorods or nanoprisms. The method presented here allows for tuning the edge length of NPRs in the range of 100-170 nm by adjusting the final concentration/molar ratio of gold salt and reducing agent (thiosulfate), while the thickness of NPRs remained constant (9 nm). Thus, the surface plasmon band of NPRs can be set along the near-infrared (NIR) range. The resulting NPRs were derivatized with heterobifunctional polyethylene glycol (PEG) and 4-aminophenyl β-D-glucopyranoside (glucose) chains to improve their stability and cellular uptake, respectively. The heating properties of colloidal solutions of NPRs upon 1064 nm light illumination were evaluated. As a proof of concept, the biocompatibility and suitability of functional NPRs as photothermal agents were studied in cell cultures. Due to their biocompatibility (avoiding CTAB), ease of production, ease of functionalization, and remarkable heating features, the NPRs discussed herein represent a significant advance in the biocompatibility of nanoparticles and serve as an attractive alternative to those currently in use as plasmonic photothermal agents.

Aberration corrected scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging and the newly developed annular bright field (ABF) imaging are used to define a new guideline for the polarity determination of semiconductor nanowires (NWs) from binary compounds in two extreme cases: (i) when the dumbbell is formed with atoms of similar mass (GaAs) and (ii) in the case where one of the atoms is extremely light (N or O: ZnO and GaN/AlN). The theoretical fundaments of these procedures allow us to overcome the main challenge in the identification of dumbbell polarity. It resides in the separation and identification of the constituent atoms in the dumbbells. The proposed experimental via opens new routes for the fine characterization of nanostructures, e.g., in electronic and optoelectronic fields, where the polarity is crucial for the understanding of their physical properties (optical and electronic) as well as their growth mechanisms.

The requirement of lattice matching between a material and its substrate for the growth of defect-free heteroepitaxial crystals can be circumvented with van der Waals epitaxy (vdWE). However, the utilization and characteristics of vdWE in nonlamellar/nonplanar nanoarchitectures are still not very well-documented. Here we establish the characteristics of vdWE in nanoarchitectures using a case study of ZnO nanowire (NW) array on muscovite mica substrate without any buffer/seed layer. With extensive characterizations involving electron microscopy, diffractometry, and the related analyses, we conclude that the NWs grown via vdWE exhibit an incommensurate epitaxy. The incommensurate vdWE allows a nearly complete lattice relaxation at the NW-substrate heterointerface without any defects, thus explaining the unnecessity of lattice matching for well-crystallized epitaxial NWs on muscovite mica. We then determine the polarity of the NW via a direct visualization of Zn-O dumbbells using the annular bright field scanning transmission electron miscroscopy (ABF-STEM) in order to identify which atoms are at the base of the NWs and responsible for the van der Waals interactions. The information from the ABF-STEM is then used to construct the proper atomic arrangement at the heterointerface with a 3D atomic modeling to corroborate the characteristics of the incommensurate vdWE. Our findings suggest that the vdWE might be extended for a wider varieties of compounds and epitaxial nanoarchitectures to serve as a universal epitaxy strategy., (© 2012 American Chemical Society)

Multiple seed formation by three-dimensional twinning at the initial stages of growth explains the manifold of orientations found when self-catalyzed GaAs nanowires grow on silicon. This mechanism can be tuned as a function of the growth conditions by changing the relative size between the GaAs seed and the Ga droplet. We demonstrate how growing under high V/III ratio results in a 100% yield of vertical nanowires on silicon(111). These results open up the avenue towards the efficient integration of III-V nanowire arrays on the silicon platform.

Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centres immobilizing quantized vortices at high temperature and magnetic fields. Here we demonstrate a highly effective mechanism of artificial pinning centres in solution-derived high-temperature superconductor nanocomposites through generation of nanostrained regions where Cooper pair formation is suppressed. The nanostrained regions identified from transmission electron microscopy devise a very high concentration of partial dislocations associated with intergrowths generated between the randomly oriented nanodots and the epitaxial YBa(2)Cu(3)O(7) matrix. Consequently, an outstanding vortex-pinning enhancement correlated to the nanostrain is demonstrated for four types of randomly oriented nanodot, and a unique evolution towards an isotropic vortex-pinning behaviour, even in the effective anisotropy, is achieved as the nanostrain turns isotropic. We suggest a new vortex-pinning mechanism based on the bond-contraction pairing model, where pair formation is quenched under tensile strain, forming new and effective core-pinning regions.

This paper reports the decoration of single wall carbon nanotubes (SWCNTs) with platinum (Pt) nanoparticles using an electrochemical technique, rotating disk slurry electrode (RoDSE). Pt/SWCNTs were electrochemically characterized by cyclic voltammetry technique (CV) and physically characterized through the use of transmission electron microscopy (TEM), energy dispersive spectroscopy - X-ray florescence (EDS-XRF) and X-ray diffraction (XRD). After characterization it was found that electrodeposited nanoparticles had an average particle size of 4.1 ± 0.8 nm. Pt/SWCNTs were used as sensing material for methane (CH 4 ) detection and showed improved sensing properties in a range of concentration from 50 ppm to 200 ppm parts per million (ppm) at room temperature, when compared to other Pt/CNTs-based sensors. The use of this technique for the preparation of Pt/SWCNTs opens a new possibility in the bulk preparation of samples using an electrochemical method and thus their potential use in a wide variety of applications in chemical sensing, fuel cell and others.

Strain engineering enables modification of the properties of thin films using the stress from the substrates on which they are grown. Strain may be relaxed, however, and this can also modify the properties thanks to the coupling between strain gradient and polarization known as flexoelectricity. Here we have studied the strain distribution inside epitaxial films of the archetypal ferroelectric PbTiO(3), where the mismatch with the substrate is relaxed through the formation of domains (twins). Synchrotron X-ray diffraction and high-resolution scanning transmission electron microscopy reveal an intricate strain distribution, with gradients in both the vertical and, unexpectedly, the horizontal direction. These gradients generate a horizontal flexoelectricity that forces the spontaneous polarization to rotate away from the normal. Polar rotations are a characteristic of compositionally engineered morphotropic phase boundary ferroelectrics with high piezoelectricity; flexoelectricity provides an alternative route for generating such rotations in standard ferroelectrics using purely physical means.

Long multi-branched gold nanoparticles have been synthesized in a very high yield through a facile synthesis combining two different capping agents. The stability of these materials with the time has been tested and their characterization have been performed by diverse advanced electron microscopy techniques, paying special attention to aberration corrected transmission electron microscopy in order to unambiguously analyze the surface structure of the branches and provide insights for the formation of stellated gold nanoparticles.

In this paper we introduce a new paradigm for nanowire growth that explains the unwanted appearance of parasitic nonvertical nanowires. With a crystal structure polarization analysis of the initial stages of GaAs nanowire growth on Si substrates, we demonstrate that secondary seeds form due to a three-dimensional twinning phenomenon. We derive the geometrical rules that underlie the multiple growth directions observed experimentally. These rules help optimizing nanowire array devices such as solar or water splitting cells or of more complex hierarchical branched nanowire devices.

In Lake Matano, Indonesia, the world's largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr)oxides in the lake sediments. Biogenic CH₄ accumulates to high concentrations (up to 1.4 mmol L⁻¹) in the anoxic bottom waters, which contain a total of 7.4 × 10⁵ tons of CH₄. Profiles of dissolved inorganic carbon (ΣCO₂) and carbon isotopes (δ¹³C) show that CH₄ is oxidized in the vicinity of the persistent pycnocline and that some of this CH₄ is likely oxidized anaerobically. The dearth of NO₃⁻ and SO₄²⁻ in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn) (hydr)oxides. Thermodynamic considerations reveal that CH₄ oxidation coupled to Fe(III) or Mn(III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH₄. 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe-rich environment. Such Fe-rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem., (© 2010 Blackwell Publishing Ltd.)

Considerable discussion surrounds the potential role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce (<20 micromol x liter(-1)), and it is completely removed by sulfate reduction within the deep, Fe(II)-rich chemocline. The sulfide produced is efficiently scavenged by the formation and precipitation of FeS, thereby maintaining very low sulfide concentrations within the chemocline and the deep ferruginous bottom waters. Low productivity in the surface water allows sunlight to penetrate to the >100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lake's euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity.

The onset of a Griffiths-like phase has been observed in Tb5Si2Ge2 (TC=110 K) by means of magnetic susceptibility and small-angle neutron scattering experiments. We show the growth of a ferromagnetic cluster system characterized by an inverse susceptibility exponent lower than unity at TC

Effects of temperature and pressure on magnetic, elastic, structural, and thermal properties of Tb5Si2Ge2 have been studied by means of macroscopic (thermal expansion and magnetization) and microscopic (neutron powder diffraction) techniques. We present evidence that the high-temperature second-order ferromagnetic transition can be coupled with the low-temperature first-order structural phase change into a single first-order magnetic-crystallographic transformation at and above a tricritical point in the vicinity of 8.6 kbar. This pressure-induced coupling has a remarkable effect on the magnetocaloric effect, transforming Tb5Si2Ge2 from an ordinary into a giant magnetocaloric effect material.

The giant magnetocaloric compound Gd5Ge4 is the only member of the Gd5(SixGe1-x)4 family where three-dimensional exchange interactions between two-dimensional correlated layers of the crystallographic structure are so weak that spontaneous ferromagnetism does not set in at any temperature. In this Letter we explore the possibility to reach the ferromagnetic state by application of hydrostatic pressure. Linear thermal expansion and magnetic measurements under pressure reveal that the reduction of the unit cell volume induces a spatially phase-segregated ground state below 10 kbar.