Showing papers by "Chalmers University of Technology published in 2011"
TL;DR: The dynamical Casimir effect is observed in a superconducting circuit consisting of a coplanar transmission line with a tunable electrical length and two-mode squeezing in the emitted radiation is detected, which is a signature of the quantum character of the generation process.
Abstract: One of the most surprising predictions of modern quantum theory is that the vacuum of space is not empty. In fact, quantum theory predicts that it teems with virtual particles flitting in and out of existence. Although initially a curiosity, it was quickly realized that these vacuum fluctuations had measurable consequences-for instance, producing the Lamb shift of atomic spectra and modifying the magnetic moment of the electron. This type of renormalization due to vacuum fluctuations is now central to our understanding of nature. However, these effects provide indirect evidence for the existence of vacuum fluctuations. From early on, it was discussed whether it might be possible to more directly observe the virtual particles that compose the quantum vacuum. Forty years ago, it was suggested that a mirror undergoing relativistic motion could convert virtual photons into directly observable real photons. The phenomenon, later termed the dynamical Casimir effect, has not been demonstrated previously. Here we observe the dynamical Casimir effect in a superconducting circuit consisting of a coplanar transmission line with a tunable electrical length. The rate of change of the electrical length can be made very fast (a substantial fraction of the speed of light) by modulating the inductance of a superconducting quantum interference device at high frequencies (>10 gigahertz). In addition to observing the creation of real photons, we detect two-mode squeezing in the emitted radiation, which is a signature of the quantum character of the generation process.
864 citations
TL;DR: In this paper, an empirical model for the stoichiometry of biomass pyrolysis is presented, where empirical parameters are introduced to close the conservation equations describing the process, and the prediction capability of the model is briefly addressed, with the results showing that the yields of volatiles released from a specific biomass are predicted with a reasonable accuracy.
671 citations
TL;DR: It is demonstrated that increasing the Pd concentration to 8% leads to an increase of the electrocatalytic H( 2)O(2) production selectivity up to nearly 95%, when the nanoparticles are placed in an environment compatible with that of a proton exchange membrane.
Abstract: A novel strategy to direct the oxygen reduction reaction to preferentially produce H2O2 is formulated and evaluated The approach combines the inertness of Au nano-particles towards oxidation, with the improved O2 sticking probability of isolated transition metal “guest” atoms embedded in the Au “host” DFT modeling was employed to screen for the best alloy candidates Modeling indicates that isolated alloying atoms of Pd, Pt or Rh placed within the Au surface should enhance the H2O2 production relative to pure Au Consequently, Au1-xPdx nanoalloys with variable Pd content supported on Vulcan XC-72 were prepared to investigate the predicted selectivity towards H2O2 production for Au alloyed with Pd It is demonstrated that increasing of Pd concentration to 8% leads to an increase of the electrocatalytic H2O2 production selectivity up to nearly 95%, when the nanoparticles are placed in an environment compatible with that of a proton exchange membrane Further increase of Pd content leads to a drop of H2O2 selectivity, below 10% for x = 05 It is proposed that the enhancement in H2O2 selectivity is caused by the presence of individual surface Pd atoms surrounded by gold whereas surface ensembles of contiguous Pd atoms support H2O formation The results are discussed in the context of exergonic electrocatalytic H2O2 synthesis in Polymer Electrolyte Fuel Cells for the simultaneous cogeneration of chemicals and electricity, the latter a credit to production costs
533 citations
TL;DR: The analysis of microbial communities in river sediments exposed to waste water from the production of antibiotics in India identified very high levels of several classes of resistance genes as well as elements for horizontal gene transfer, including integrons, transposons and plasmids.
Abstract: The high and sometimes inappropriate use of antibiotics has accelerated the development of antibiotic resistance, creating a major challenge for the sustainable treatment of infections world-wide. Bacterial communities often respond to antibiotic selection pressure by acquiring resistance genes, i.e. mobile genetic elements that can be shared horizontally between species. Environmental microbial communities maintain diverse collections of resistance genes, which can be mobilized into pathogenic bacteria. Recently, exceptional environmental releases of antibiotics have been documented, but the effects on the promotion of resistance genes and the potential for horizontal gene transfer have yet received limited attention. In this study, we have used culture-independent shotgun metagenomics to investigate microbial communities in river sediments exposed to waste water from the production of antibiotics in India. Our analysis identified very high levels of several classes of resistance genes as well as elements for horizontal gene transfer, including integrons, transposons and plasmids. In addition, two abundant previously uncharacterized resistance plasmids were identified. The results suggest that antibiotic contamination plays a role in the promotion of resistance genes and their mobilization from environmental microbes to other species and eventually to human pathogens. The entire life-cycle of antibiotic substances, both before, under and after usage, should therefore be considered to fully evaluate their role in the promotion of resistance.
487 citations
TL;DR: In this article, the authors argue that technology-specific policies are necessary if we are to meet the climate challenge and that a main contribution of innovation system (IS) analysis to the study of sustainability transitions is that it allows policy makers to identify the processes and components in a system where intervention is likely to matter most.
Abstract: This paper argues (1) that technology-specific policies are necessary if we are to meet the climate challenge and (2) that a main contribution of innovation system (IS) analysis to the study of sustainability transitions is that it allows policy makers to identify the processes and components in a system where intervention is likely to matter most. We demonstrate that an IS framework can identify a diverse set of system weaknesses in the field of environmental innovation and identify five venues for further research that can help strengthen the framework and improve its application to environmental innovations.
476 citations
TL;DR: The current state of understanding of bacterial cellulose, known methods for controlling its physical and chemical structure, biomedical applications for which it is currently being used, or investigated for use, challenges yet to be overcome, and future possibilities for BC are reviewed.
Abstract: Bacterial cellulose (BC) is a unique and promising material for use as implants and scaffolds in tissue engineering. It is composed of a pure cellulose nanofiber mesh spun by bacteria. It is remarkable for its strength and its ability to be engineered structurally and chemically at nano-, micro-, and macroscales. Its high water content and purity make the material biocompatible for multiple medical applications. Its biocompatibility, mechanical strength, chemical and morphologic controllability make it a natural choice for use in the body in biomedical devices with broader application than has yet been utilized. This paper reviews the current state of understanding of bacterial cellulose, known methods for controlling its physical and chemical structure (e.g., porosity, fiber alignment, etc.), biomedical applications for which it is currently being used, or investigated for use, challenges yet to be overcome, and future possibilities for BC.
432 citations
TL;DR: In this work, the radiative and nonradiative damping contributions to the LSPR line width over a broad nanoparticle size range (40-500 nm) for a selection of three metals with fundamentally different bulk dielectric properties are explored experimentally and theoretically.
Abstract: Localized surface plasmon resonances (LSPR) are collective electronic excitations in metallic nanoparticles. The LSPR spectral peak position, as a function of nanoparticle size and material, is known to depend primarily on dynamic depolarization and electron structure related effects. The former gives rise to the well-known spectral red shift with increasing nanoparticle size. A corresponding understanding of the LSPR spectral line width for a wide range of nanoparticle sizes and different metals does, however, not exist. In this work, the radiative and nonradiative damping contributions to the LSPR line width over a broad nanoparticle size range (40−500 nm) for a selection of three metals with fundamentally different bulk dielectric properties (Au, Pt, and Al) are explored experimentally and theoretically. Excellent agreement was obtained between the observed experimental trends and the predictions based on electrostatic spheroid theory (MLWA), and the obtained results were successfully related to the sp...
420 citations
TL;DR: In this paper, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation format independence, and nearly 6dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links.
Abstract: Optical phase-sensitive amplifiers (PSAs) are known to be capable, in principle, of realizing noiseless amplification and improving the signal-to-noise-ratio of optical links by 3 dB compared to conventional, phase-insensitively amplified links. However, current state-of-the-art PSAs are still far from being practical, lacking e.g. significant noise performance improvement, broadband gain and modulation-format transparency. Here we demonstrate experimentally, for the first time, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation-format independence, and nearly 6-dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links. The PSA has a record-low 1.1-dB NF, and can be extended to work with multiple wavelength channels with modest system complexity. This concept can also be realized in other materials with third-order nonlinearities, and is useful in any attenuation-limited optical link.
419 citations
TL;DR: In this paper, a plasmonic binary NOR gate, a "universal logic gate", can be realized through cascaded OR and NOT gates in four-terminal PLASMIC nanowire networks, which provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies.
Abstract: Optical computing has been pursued for decades as a potential strategy for advancing beyond the fundamental performance limitations of semiconductor-based electronic devices, but feasible on-chip integrated logic units and cascade devices have not been reported. Here we demonstrate that a plasmonic binary NOR gate, a 'universal logic gate', can be realized through cascaded OR and NOT gates in four-terminal plasmonic nanowire networks. This finding provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies.
398 citations
TL;DR: In this paper, the ridge gap waveguide is used to verify the large bandwidth and low losses of the quasi-transverse electromagnetic (TEM) mode propagating along the guiding ridge.
Abstract: This study describes the design and experimental verification of the ridge gap waveguide, appearing in the gap between parallel metal plates. One of the plates has a texture in the form of a wave-guiding metal ridge surrounded by metal posts. The latter posts, referred to as a pin surface or bed of nails, are designed to give a stopband for the normal parallel-plate modes between 10 and 23 GHz. The hardware demonstrator includes two 90 bends and two capacitive coupled coaxial transitions enabling measurements with a vector network analyser (VNA). The measured results verify the large bandwidth and low losses of the quasi-transverse electromagnetic (TEM) mode propagating along the guiding ridge, and that 90 bends can be designed in the same way as for microstrip lines. The demonstrator is designed for use around 15 GHz. Still, the ridge gap waveguide is more advantageous for frequencies above 30 GHz, because it can be realised entirely from metal using milling or moulding, and there are no requirements for conducting joints between the two plates that otherwise is a problem when realising conventional hollow waveguides.
377 citations
TL;DR: This work demonstrates the great potential of isoindigo moieties as electron-deficient units for building donor-acceptor-type polymers for high-performance polymer solar cells.
Abstract: A new, low-band-gap alternating copolymer consisting of terthiophene and isoindigo has been designed and synthesized. Solar cells based on this polymer and PC71BM show a power conversion efficiency of 6.3%, which is a record for polymer solar cells based on a polymer with an optical band gap below 1.5 eV. This work demonstrates the great potential of isoindigo moieties as electron-deficient units for building donor–acceptor-type polymers for high-performance polymer solar cells.
TL;DR: This work embedded an artificial atom, a superconducting transmon qubit, in an open transmission line and investigated the strong scattering of incident microwave photons, using two-tone spectroscopy to study scattering from excited states and electromagnetically induced transparency (EIT).
Abstract: We have embedded an artificial atom, a superconducting transmon qubit, in an open transmission line and investigated the strong scattering of incident microwave photons (similar to 6 GHz). When an input coherent state, with an average photon number N << 1 is on resonance with the artificial atom, we observe extinction of up to 99.6% in the forward propagating field. We use two-tone spectroscopy to study scattering from excited states and we observe electromagnetically induced transparency (EIT). We then use EIT to make a single-photon router, where we can control to what output port an incoming signal is delivered. The maximum on-off ratio is around 99% with a rise and fall time on the order of nanoseconds, consistent with theoretical expectations. The router can easily be extended to have multiple output ports and it can be viewed as a rudimentary quantum node, an important step towards building quantum information networks.
TL;DR: A nanophotonic structure built from pairs of closely spaced gold and silver disks that show phase accumulation through material-dependent plasmon resonances that can be fabricated on a wafer scale and offer a versatile platform for manipulating optical response through polarization, choice of materials and geometrical parameters.
Abstract: Recent progress in nanophotonics includes demonstrations of meta-materials displaying negative refraction at optical frequencies, directional single photon sources, plasmonic analogies of electromagnetically induced transparency and spectacular Fano resonances. The physics behind these intriguing effects is to a large extent governed by the same single parameter-optical phase. Here we describe a nanophotonic structure built from pairs of closely spaced gold and silver disks that show phase accumulation through material-dependent plasmon resonances. The bimetallic dimers show exotic optical properties, in particular scattering of red and blue light in opposite directions, in spite of being as compact as similar to lambda(3)/100. These spectral and spatial photon-sorting nanodevices can be fabricated on a wafer scale and offer a versatile platform for manipulating optical response through polarization, choice of materials and geometrical parameters, thereby opening possibilities for a wide range of practical applications.
TL;DR: Enlarged adipocytes and reduced serum adiponectin, together with a large waistline, rather than androgen excess, may be central factors in the pathogenesis/maintenance of insulin resistance in PCOS.
Abstract: Context: Comprehensive characterization of the adipose tissue in women with polycystic ovary syndrome (PCOS), over a wide range of body mass indices (BMIs), is lacking. Mechanisms behind insulin resistance in PCOS are unclear. Objective: To characterize the adipose tissue of women with PCOS and controls matched pair-wise for age and BMI, and to identify factors, among adipose tissue characteristics and serum sex steroids, that are associated with insulin sensitivity in PCOS. Design/Outcome Measures: Seventy-four PCOS women and 31 controls were included. BMI was 18-47 (PCOS) and 19-41 kg/m(2) (controls). Anthropometric variables, volumes of subcutaneous/visceral adipose tissue (magnetic resonance imaging; MRI), and insulin sensitivity (clamp) were investigated. Adipose tissue biopsies were obtained to determine adipocyte size, lipoprotein lipase (LPL) activity, and macrophage density. Circulating testosterone, free testosterone, free 17β-estradiol, SHBG, glycerol, adiponectin, and serum amyloid A were measured/calculated. Results: Comparison of 31 pairs revealed lower insulin sensitivity, hyperandrogenemia, and higher free 17β-estradiol in PCOS. Abdominal adipose tissue volumes/distribution did not differ in the groups, but PCOS women had higher waist-to-hip ratio, enlarged adipocytes, reduced adiponectin, and lower LPL activity. In regression analysis, adipocyte size, adiponectin, and waist circumference were the factors most strongly associated with insulin sensitivity in PCOS (R(2)=0.681, P < 0.001). Conclusions: In PCOS, adipose tissue has aberrant morphology/function. Increased waist-to-hip ratio indicates abdominal/visceral fat accumulation, but this is not supported by MRI. Enlarged adipocytes and reduced serum adiponectin, together with a large waistline, rather than androgen excess, may be central factors in the pathogenesis/maintenance of insulin resistance in PCOS.
University of Manchester1, ASTRON2, University of Amsterdam3, University of Oxford4, Max Planck Society5, University of Southampton6, University of Sheffield7, Radboud University Nijmegen8, University of Orléans9, University of California, Berkeley10, Curtin University11, University of Bonn12, Centre national de la recherche scientifique13, Kapteyn Astronomical Institute14, University of Edinburgh15, Jacobs University Bremen16, Australian National University17, Chalmers University of Technology18, Ruhr University Bochum19, Leiden University20, Rutherford Appleton Laboratory21, Leibniz Institute for Neurobiology22, Center for Information Technology23
TL;DR: The LOw Frequency ARray (LOFAR) as mentioned in this paper is a radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240 MHz, that will greatly facilitate observing pulsars at low radio frequencies.
Abstract: Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR.
Proceedings Article•
01 Jan 2011TL;DR: This paper presents and discusses the development and views of three terms: knowledge transfer, knowledge sharing and knowledge barriers and highlights the effects on the terms when two different knowledge perspectives, knowledge as an object (or the K-O view) and knowledge as a subjective contextual construction are applied.
Abstract: In the knowledge management world there are many different terms flying around. Some are more important and frequently used than others. In this paper, we present and discuss the development and views of three terms: knowledge transfer, knowledge sharing and knowledge barriers. Knowledge transfer and knowledge sharing are sometimes used synonymously or have overlapping content. Several authors have pointed out this confusion while other authors have attempted to clarify the differences and define the terms. Knowledge barriers in themselves seem to have a more obvious content although the borders between knowledge barriers and connecting terms, such as 'barriers to knowledge sharing', seem to blur discussions and views. Our aim is to make a contribution to finding appropriate demarcations between these concepts. After reviewing Knowledge Management literature, we can state that the three terms, knowledge transfer, knowledge sharing and knowledge barriers, are somewhat blurred. For knowledge transfer and knowledge sharing, the blurriness is linked mainly to the fact that the analytical level each term is related to has come and gone and come back again. For knowledge barriers, the blurriness comes from the development of the term. The mere existence of the many different categorizations of knowledge barriers implies that the concept itself is blurry. The concept seems clear cut and focuses on knowledge although it is also broad and later sources have included much more than knowledge. This paper concludes by highlighting the effects on the terms when two different knowledge perspectives, knowledge as an object (or the K-O view) and knowledge as a subjective contextual construction (or the K-SCC view) are applied. The clarifications are supported by examples from companies in different industries (such as Cargotec and IKEA) and the public sector (police, fire brigade, ambulance and other emergency services).
TL;DR: Results show effects in ambient air in 18 European countries from Sweden in the north to Greece in the south are shown, with the POD3gen model for clover fitting the clover effects data better than that for a generic crop.
Abstract: Records of effects of ambient ozone pollution on vegetation have been compiled for Europe for the years 1990–2006. Sources include scientific papers, conference proceedings, reports to research funders, records of confirmed ozone injury symptoms and an international biomonitoring experiment coordinated by the ICP Vegetation. The latter involved ozone-sensitive (NC-S) and ozone-resistant (NC-R) biotypes of white clover (Trifolium repens L.) grown according to a common protocol and monitored for ozone injury and biomass differences in 17 European countries, from 1996 to 2006. Effects were separated into visible injury or growth/yield reduction. Of the 644 records of visible injury, 39% were for crops (27 species), 38.1% were for (semi-) natural vegetation (95 species) and 22.9% were for shrubs (49 species). Owing to inconsistencies in reporting effort from year to year it was not possible to determine geographical or temporal trends in the data. Nevertheless, this study has shown effects in ambient air in 18 European countries from Sweden in the north to Greece in the south. These effects data were superimposed on AOT40 (accumulated ozone concentrations over 40 ppb) and POD3gen (modelled accumulated stomatal flux over a threshold of 3 nmol m−2 s−1) maps generated by the EMEP Eulerian model (50 km × 50 km grid) that were parameterized for a generic crop based on wheat and NC-S/NC-R white clover. Many effects were found in areas where the AOT40 (crops) was below the critical level of 3 ppm h. In contrast, the majority of effects were detected in grid squares where POD3gen (crops) were in the mid-high range (>12 mmol m−2). Overall, maps based on POD3gen provided better fit to the effects data than those based on AOT40, with the POD3gen model for clover fitting the clover effects data better than that for a generic crop.
TL;DR: The model is applied and validated in a comprehensive systematic literature review of evaluations of requirements engineering technologies published in software engineering journals and shows that the model can be applied to characterize evaluations in requirements engineering.
Abstract: One of the main goals of an applied research field such as software engineering is the transfer and widespread use of research results in industry. To impact industry, researchers developing technologies in academia need to provide tangible evidence of the advantages of using them. This can be done trough step-wise validation, enabling researchers to gradually test and evaluate technologies to finally try them in real settings with real users and applications. The evidence obtained, together with detailed information on how the validation was conducted, offers rich decision support material for industry practitioners seeking to adopt new technologies and researchers looking for an empirical basis on which to build new or refined technologies. This paper presents model for evaluating the rigor and industrial relevance of technology evaluations in software engineering. The model is applied and validated in a comprehensive systematic literature review of evaluations of requirements engineering technologies published in software engineering journals. The aim is to show the applicability of the model and to characterize how evaluations are carried out and reported to evaluate the state-of-research. The review shows that the model can be applied to characterize evaluations in requirements engineering. The findings from applying the model also show that the majority of technology evaluations in requirements engineering lack both industrial relevance and rigor. In addition, the research field does not show any improvements in terms of industrial relevance over time.
01 Jan 2011
TL;DR: Since the 1970s, environmental problems have risen on the political agenda as mentioned in this paper and many environmental problems (such as water pollution, local air pollution, acid rain) have since been solved or substantiated.
Abstract: Since the 1970s, environmental problems have risen on the political agenda. Many environmental problems (such as water pollution, local air pollution, acid rain) have since been solved or substanti...
TL;DR: It is concluded that progress has been made in understanding fluidized-bed dynamics by extracting the relevant information from pressure fluctuation data, but the picture is still incomplete.
TL;DR: A molecule consisting of three linked photochromes that can be configured as AND, XOR, INH, half-adder,half-subtractor, multiplexer, demultiplexers, encoder, decoder, keypad lock, and logically reversible transfer gate logic devices, all with a common initial state are reported.
Abstract: Photochromes are photoswitchable, bistable chromophores which, like transistors, can implement binary logic operations. When several photochromes are combined in one molecule, interactions between them such as energy and electron transfer allow design of simple Boolean logic gates and more complex logic devices with all-photonic inputs and outputs. Selective isomerization of individual photochromes can be achieved using light of different wavelengths, and logic outputs can employ absorption and emission properties at different wavelengths, thus allowing a single molecular species to perform several different functions, even simultaneously. Here, we report a molecule consisting of three linked photochromes that can be configured as AND, XOR, INH, half-adder, half-subtractor, multiplexer, demultiplexer, encoder, decoder, keypad lock, and logically reversible transfer gate logic devices, all with a common initial state. The system demonstrates the advantages of light-responsive molecules as multifunctional, reconfigurable nanoscale logic devices that represent an approach to true molecular information processing units.
TL;DR: In this paper, four commercial steels with carbon contents in the range 1-05 wt% have been examined in the as-quenched condition using electron microscopy, X-ray diffraction and atom probe tomography.
TL;DR: Application of white-rot fungi capabilities can offer environmentally friendly processes for utilising lignocelluloses over physical or chemical pretreatment, and the effect of biological pretreatment on biomass characteristics, and factors affecting biological pret treatment are reviewed.
Abstract: Lignocellulosic carbohydrates, i.e. cellulose and hemicellulose, have abundant potential as feedstock for production of biofuels and chemicals. However, these carbohydrates are generally infiltrated by lignin. Breakdown of the lignin barrier will alter lignocelluloses structures and make the carbohydrates accessible for more efficient bioconversion. White-rot fungi produce ligninolytic enzymes (lignin peroxidase, manganese peroxidase, and laccase) and efficiently mineralise lignin into CO2 and H2O. Biological pretreatment of lignocelluloses using white-rot fungi has been used for decades for ruminant feed, enzymatic hydrolysis, and biopulping. Application of white-rot fungi capabilities can offer environmentally friendly processes for utilising lignocelluloses over physical or chemical pretreatment. This paper reviews white-rot fungi, ligninolytic enzymes, the effect of biological pretreatment on biomass characteristics, and factors affecting biological pretreatment. Application of biological pretreatment for enzymatic hydrolysis, biofuels (bioethanol, biogas and pyrolysis), biopulping, biobleaching, animal feed, and enzymes production are also discussed.
TL;DR: In this paper, the magnetic field of the nearby galaxy M51 on scales from 200 pc to several kpc was studied using multi-wavelength radio observations, made with the VLA and Effelsberg telescopes, and the authors compared the spatial distribution of radio emission with observations of the neutral gas, derived radio spectral index and Faraday depolarization maps, and model the large-scale variation in Faraday rotation in order to deduce the structure of the regular magnetic field.
Abstract: We use new multiwavelength radio observations, made with the VLA and Effelsberg telescopes, to study the magnetic field of the nearby galaxy M51 on scales from 200 pc to several kpc. Interferometric and single-dish data are combined to obtain new maps at lambda lambda 3, 6 cm in total and polarized emission, and earlier lambda 20 cm data are rereduced. We compare the spatial distribution of the radio emission with observations of the neutral gas, derive radio spectral index and Faraday depolarization maps, and model the large-scale variation in Faraday rotation in order to deduce the structure of the regular magnetic field. We find that the lambda 20 cm emission from the disc is severely depolarized and that a dominating fraction of the observed polarized emission at lambda 6 cm must be due to anisotropic small-scale magnetic fields. Taking this into account, we derive two components for the regular magnetic field in this galaxy; the disc is dominated by a combination of azimuthal modes, m = 0 + 2, but in the halo only an m = 1 mode is required to fit the observations. We discuss how the observed arm-interarm contrast in radio intensities can be reconciled with evidence for strong gas compression in the spiral shocks. In the inner spiral arms, the strong arm-interarm contrasts in total and polarized radio emission are roughly consistent with expectations from shock compression of the regular and turbulent components of the magnetic field. However, the average arm-interam contrast, representative of the radii r > 2 kpc where the spiral arms are broader, is not compatible with straightforward compression: lower arm-interarm contrasts than expected may be due to resolution effects and decompression of the magnetic field as it leaves the arms. We suggest a simple method to estimate the turbulent scale in the magneto-ionic medium from the dependence of the standard deviation of the observed Faraday rotation measure on resolution. We thus obtain an estimate of 50 pc for the size of the turbulent eddies.
TL;DR: In this paper, the bandwidth of gap waveguide is determined by the cut-off bandwidth of a parallel-plate waveguide where one surface has such a texture and no ridges or strips.
Abstract: Recently it has been shown that so-called gap waveguides can be generated in the gap between parallel metal plates The gap waveguides are formed by metal ridges or strips along which local waves propagate, and parallel plate modes are prohibited from propagating by providing one of the surfaces with a texture that generates an artificial magnetic conductor (AMC) or an electromagnetic bandgap (EBG) surface on both sides of the ridges or strips The bandwidth of the gap waveguide is determined by the cut-off bandwidth of a parallel-plate waveguide where one surface has such a texture (and no ridges or strips) This paper studies the bandwidths (or stop bands) of such parallel-plate cut-offs when the AMC or EBG is realised by a metal pin surface, corrugations or a mushroom surface It is shown that cut-off bandwidths of up to 4:1 are potentially available, and thereby similar bandwidths should be achievable also for gap waveguides
TL;DR: In this article, an inferential network of 55 sites throughout Europe for atmospheric reactive nitrogen (N-r) was established in 2007, providing ambient concentrations of gaseous NH3, NO2, HNO3 and HONO and aerosol NH4+ and NO3- as part of the NitroEurope Integrated Project.
Abstract: Inferential models have long been used to determine pollutant dry deposition to ecosystems from measurements of air concentrations and as part of national and regional atmospheric chemistry and transport models, and yet models still suffer very large uncertainties. An inferential network of 55 sites throughout Europe for atmospheric reactive nitrogen (N-r) was established in 2007, providing ambient concentrations of gaseous NH3, NO2, HNO3 and HONO and aerosol NH4+ and NO3- as part of the NitroEurope Integrated Project. Network results providing modelled inorganic Nr dry deposition to the 55 monitoring sites are presented, using four existing dry deposition routines, revealing inter-model differences and providing ensemble average deposition estimates. Dry deposition is generally largest over forests in regions with large ambient NH3 concentrations, exceeding 30-40 kg N ha(-1) yr(-1) over parts of the Netherlands and Belgium, while some remote forests in Scandinavia receive less than 2 kg N ha(-1) yr(-1). Turbulent Nr deposition to short vegetation ecosystems is generally smaller than to forests due to reduced turbulent exchange, but also because NH3 inputs to fertilised, agricultural systems are limited by the presence of a substantial NH3 source in the vegetation, leading to periods of emission as well as deposition. Differences between models reach a factor 2-3 and are often greater than differences between monitoring sites. For soluble Nr gases such as NH3 and HNO3, the non-stomatal pathways are responsible for most of the annual uptake over many surfaces, especially the non-agricultural land uses, but parameterisations of the sink strength vary considerably among models. For aerosol NH4+ and NO3-, discrepancies between theoretical models and field flux measurements lead to much uncertainty in dry deposition rates for fine particles (0.1-0.5 mu m). The validation of inferential models at the ecosystem scale is best achieved by comparison with direct long-term micrometeorological Nr flux measurements, but too few such datasets are available, especially for HNO3 and aerosol NH4+ and NO3-.
TL;DR: In this paper, a series of pure, highly porous titanium dioxide films with identical grain sizes, surface areas, and crystallinity, but varying polymorph compositions, were used to investigate the influence of the anatase-to-rutile ratio on the photoreactivity.
Abstract: In 1991, Bickley et al. proposed a synergetic effect between anatase and rutile in Degussa P25. Since then, there has been an intensive debate about the correctness of this proposal, the origin of the synergism, and the right polymorph composition. However, a comparison of pure titanium dioxide samples with various anatase-to-rutile ratios, but otherwise identical properties, is missing. In this paper, we report about a series of utterly pure, highly porous titanium dioxide films with identical grain sizes, surface areas, and crystallinity, but varying polymorph compositions. Photocatalytic oxidation of methylene blue was utilized to investigate the influence of the anatase-to-rutile ratio on the photoreactivity. We clearly observe the synergetic effect within a well-defined range of anatase-to-rutile ratios. A film with ∼60% anatase and ∼40% rutile exhibits optimal performance at a 50% improved activity compared with pure anatase.
TL;DR: The effluent from a commercially available silver nanowashing machine was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water.
TL;DR: In this paper, the authors assess the emission mitigation potential of GHG weighted consumption taxes on animal food products in the EU and also estimate the decrease in agricultural land area through the related changes in food production and the additional mitigation potential in devoting this land to bioenergy production.
Abstract: Agriculture is responsible for 25–30% of global anthropogenic greenhouse gas (GHG) emissions but has thus far been largely exempted from climate policies. Because of high monitoring costs and comparatively low technical potential for emission reductions in the agricultural sector, output taxes on emission-intensive agricultural goods may be an efficient policy instrument to deal with agricultural GHG emissions. In this study we assess the emission mitigation potential of GHG weighted consumption taxes on animal food products in the EU. We also estimate the decrease in agricultural land area through the related changes in food production and the additional mitigation potential in devoting this land to bioenergy production. Estimates are based on a model of food consumption and the related land use and GHG emissions in the EU. Results indicate that agricultural emissions in the EU27 can be reduced by approximately 32 million tons of CO2-eq with a GHG weighted tax on animal food products corresponding to €60 per ton CO2-eq. The effect of the tax is estimated to be six times higher if lignocellulosic crops are grown on the land made available and used to substitute for coal in power generation. Most of the effect of a GHG weighted tax on animal food can be captured by taxing the consumption of ruminant meat alone.
TL;DR: This Review provides an overview of methods developed for chemical analysis of single cells over the last two years, and suggests that the development of extremely sensitive measurements, down to single cells, may provide the best ability for diagnoses.
Abstract: In this Review, we provide an overview of methods developed for chemical analysis of single cells over the last two years. Many biological systems contain an ensemble of cells with heterogeneous chemistry; therefore, it is important to analyze them on an individual basis in order to elucidate the role each cell plays in the function of these systems. In clinical diagnostics, the development of extremely sensitive measurements, down to single cells, may provide the best ability for diagnoses. Single cell analysis has, in fact, been present for quite some time. Investigators in life sciences consider the cell as the unit of life and so the pursuit to quantify, image, and modulate the cell has been ongoing for decades.