Energy-efficient traffic engineering

The energy consumption in telecommunication networks is expected to grow considerably, especially in core networks. In this chapter, optimization of energy consumption is approached from two directions. In a first study, multilayer traffic engineering (MLTE) is used to assign energy-efficient paths and logical topology to IP traffic. The relation with traditional capacity optimization is explained, and the MLTE strategy is applied for daily traffic variations. A second study considers the core network below the IP layer, giving a detailed power consumption model. Optical bypass is evaluated as a technique to achieve considerable power savings over per-hop opticalelectronicoptical regeneration. Document type: Part of book or chapter of boo

Atomic Layer Deposition-Based Synthesis of Photoactive TiO2 Nanoparticle Chains by Using Carbon Nanotubes as Sacrificial Templates

Highly ordered and self supported anatase TiO2 nanoparticle chains were fabricated by calcining conformally TiO2 coated multi-walled carbon nanotubes (MWCNTs). During annealing, the thin tubular TiO2 coating that was deposited onto the MWCNTs by atomic layer deposition (ALD) was transformed into chains of TiO2 nanoparticles (~12 nm diameter) with an ultrahigh surface area (137 cm2 per cm2 of substrate), while at the same time the carbon from the MWCNTs was removed. Photocatalytic tests on the degradation of acetaldehyde proved that these forests of TiO2 nanoparticle chains are highly photo active under UV light because of their well crystallized anatase phase

Deriving soil hydraulic parameters in a high spatial resolution for a heterogeneous agricultural field-site

Providing information about the structure of the subsurface plays an important role for setting up soil hydraulic models, which are in turn an important prerequisite for ecosystem modelling approaches. Because soils often show a high within-field heterogeneity in terms of texture, stone content, and bulk density, they may also exhibit a wide range of hydraulic properties in the field. During water stress periods and especially on agricultural fields, which are characterized by uniform vegetation, the occurrence of a within-field heterogeneity in terms of soil hydraulic properties can be observed as it affects the different water status of the plants. The patterns of visible plant water stress and areas of low apparent electrical conductivities measured by electromagnetic induction measurements (EMI) often coincide, for e.g. within sugar beet cropped fields. Such observations have also been made beforehand at the current study site; an agricultural field (2.7 ha) that is situated in an area developed by fluvial processes. To account for this, the current approach included a sampling campaign on a field with 70 drilling locations for texture and organic carbon analyses. Furthermore, soil water retention functions and saturated hydraulic conductivity were determined at 20 sampling locations. Our approach for ecosystem modelling is based on 4 m² grid cells over the whole study site. To consider within-field heterogeneity in the ecosystem model, soil hydraulic parameters were predicted for each grid cell, whereby different approaches such as spatial interpolation, Miller-Miller scaling, and the use of pedotransfer functions were taken into account to identify the most appropriate approach

Transmissão materno-fetal de diferentes subtipos de HIV-1 entre gestantes infectadas na Nigéria

The rate of mother-to-child transmission (MTCT) of HIV as well as the implications of the circulating multiple subtypes to MTCT in Nigeria are not known. This study was therefore undertaken to determine the differential rates of MTCT of HIV-1 subtypes detected among infected pregnant women before ARV intervention therapy became available in Nigeria. Twenty of the HIV-positive women who signed the informed consent form during pregnancy brought their babies for follow-up testing at age 18-24 months. Plasma samples from both mother and baby were tested for HIV antibody at the Department of Virology, UCH, Ibadan, Nigeria. All positive samples (plasma and peripheral blood mononuclear cells - PBMCs) were shipped to the Institute of Tropical Medicine, Antwerp, Belgium, where the subtype of the infecting virus was determined using the HMA technique. Overall, a mother-to-child HIV transmission rate of 45% was found in this cohort. Specifically, 36.4%, 66.7% and 100% of the women infected with HIV-1 CRF02 (IbNg), G and B, respectively, transmitted the virus to their babies. As far as it can be ascertained, this is the first report on the rate of MTCT of HIV in Nigeria. The findings reported in this paper will form a useful reference for assessment of currently available therapeutic intervention of MTCT in the country.A taxa de transmissão materno-fetal (MTCT) do HIV bem como as implicações dos múltiplos subtipos circulantes para MTCT na Nigéria não são conhecidos. Este estudo foi realizado para determinar as diferentes taxas de MTCT dos subtipos de HIV-1 detectados entre gestantes infectadas antes que a administração da terapia ARV estivesse disponível na Nigéria. Vinte das mulheres HIV positivas que assinaram o consentimento durante a gravidez trouxeram seus filhos para seguimento na idade de 18-24 meses. Amostras de plasma de ambos, mãe e filho foram testadas para anticorpos HIV no Departamento de Virologia, UCH, Ibadan, Nigéria. Todas as amostras positivas (plasma e células mononucleares do sangue periférico - PBMCs) foram enviadas para o Instituto de Medicina Tropical da Antuérpia, Bélgica, onde os subtipos de vírus infectantes foram determinados utilizando-se a técnica HMA. No conjunto, uma taxa de transmissão de HIV, materno-fetal, de 45% foi encontrada neste grupo. Especificamente, 36,4%, 66,7% e 100% das mulheres infectadas com HIV-1 CRF02 (IbNg), G e B, respectivamente, transmitiram o vírus para seus filhos. Até onde pode ser verificado, este é o primeiro relato da taxa de MTCT do HIV na Nigéria. Os achados relatados neste trabalho serão uma útil referência para estimar a qualidade das terapêuticas atuais disponíveis para MTCT neste país

Atmospheric isoprene ozonolysis: impacts of stabilised Criegee intermediate reactions with SO₂, H₂O and dimethyl sulfide

Isoprene is the dominant global biogenic volatile organic compound (VOC) emission. Reactions of isoprene with ozone are known to form stabilised Criegee intermediates (SCIs), which have recently been shown to be potentially important oxidants for SO2 and NO2 in the atmosphere; however the significance of this chemistry for SO2 processing (affecting sulfate aerosol) and NO2 processing (affecting NOx levels) depends critically upon the fate of the SCIs with respect to reaction with water and decomposition. Here, we have investigated the removal of SO2 in the presence of isoprene and ozone, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity, confirming a significant reaction for isoprene-derived SCIs with H2O. Under excess SO2 conditions, the total isoprene ozonolysis SCI yield was calculated to be 0.56 (+/-0.03). The observed SO2 removal kinetics are consistent with a relative rate constant, k (SCI + H2O) = k (SCI + SO2), of 3.1 (+/-0.5) x 10(-5) for isoprene-derived SCIs. The relative rate constant for k (SCI decomposition) = k (SCI + SO2) is 3.0 (+/-3.2) x 10(11) cm(-3). Uncertainties are +/-2 sigma and represent combined systematic and precision components. These kinetic parameters are based on the simplification that a single SCI species is formed in isoprene ozonolysis, an approximation which describes the results well across the full range of experimental conditions. Our data indicate that isoprenederived SCIs are unlikely to make a substantial contribution to gas-phase SO2 oxidation in the troposphere. We also present results from an analogous set of experiments, which show a clear dependence of SO2 removal in the isopreneozone system as a function of dimethyl sulfide concentration. We propose that this behaviour arises from a rapid reaction between isoprene-derived SCIs and dimethyl sulfide (DMS); the observed SO2 removal kinetics are consistent with a relative rate constant, k (SCI + DMS) = k (SCI + SO2), of 3.5 (+/-1.8). This result suggests that SCIs may contribute to the oxidation of DMS in the atmosphere and that this process could therefore influence new particle formation in regions impacted by emissions of unsaturated hydrocarbons and DMS

The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO2 oxidation : experiment, theory and modelling

The gas-phase reaction of alkenes with ozone is known to produce stabilised Criegee intermediates (SCIs). These biradical/zwitterionic species have the potential to act as atmospheric oxidants for trace pollutants such as SO₂, enhancing the formation of sulfate aerosol with impacts on air quality and health, radiative transfer and climate. However, the importance of this chemistry is uncertain as a consequence of limited understanding of the abundance and atmospheric fate of SCIs. In this work we apply experimental, theoretical and numerical modelling methods to quantify the atmospheric impacts, abundance and fate of the structurally diverse SCIs derived from the ozonolysis of monoterpenes, the second most abundant group of unsaturated hydrocarbons in the atmosphere. We have investigated the removal of SO₂ by SCIs formed from the ozonolysis of three atmospherically important monoterpenes (<i>α</i>-pinene, <i>β</i>-pinene and limonene) in the presence of varying amounts of water vapour in large-scale simulation chamber experiments that are representative of boundary layer conditions. The SO₂ removal displays a clear dependence on water vapour concentration, but this dependence is not linear across the range of [H₂O] explored. At low [H₂O] a strong dependence of SO₂ removal on [H₂O] is observed, while at higher [H₂O] this dependence becomes much weaker. This is interpreted as being caused by the production of a variety of structurally (and hence chemically) different SCIs in each of the systems studied, which displayed different rates of reaction with water and of unimolecular rearrangement or decomposition. The determined rate constants, <i>k</i>(SCI+H₂O), for those SCIs that react primarily with H₂O range from 4 to 310  ×  10⁻¹⁵ cm³ s⁻¹. For those SCIs that predominantly react unimolecularly, determined rates range from 130 to 240 s⁻¹. These values are in line with previous results for the (analogous) stereo-specific SCI system of <i>syn</i>-/<i>anti</i>-CH₃CHOO. The experimental results are interpreted through theoretical studies of the SCI unimolecular reactions and bimolecular reactions with H₂O, characterised for <i>α</i>-pinene and <i>β</i>-pinene at the M06-2X/aug-cc-pVTZ level of theory. The theoretically derived rates agree with the experimental results within the uncertainties. A global modelling study, applying the experimental results within the GEOS-Chem chemical transport model, suggests that &gt; 97 % of the total monoterpene-derived global SCI burden is comprised of SCIs with a structure that determines that they react slowly with water and that their atmospheric fate is dominated by unimolecular reactions. Seasonally averaged boundary layer concentrations of monoterpene-derived SCIs reach up to 1.4  ×  10⁴ cm⁻³ in regions of elevated monoterpene emissions in the tropics. Reactions of monoterpene-derived SCIs with SO₂ account for &lt; 1 % globally but may account for up to 60 % of the gas-phase SO₂ removal over areas of tropical forests, with significant localised impacts on the formation of sulfate aerosol and hence the lifetime and distribution of SO₂

Is high-resolution inverse characterization of heterogeneous river bed hydraulic conductivities needed and possible?

River–aquifer exchange fluxes influence local and regional water balances and affect groundwater and river water quality and quantity. Unfortunately, river–aquifer exchange fluxes tend to be strongly spatially variable, and it is an open research question to which degree river bed heterogeneity has to be represented in a model in order to achieve reliable estimates of river–aquifer exchange fluxes. This research question is addressed in this paper with the help of synthetic simulation experiments, which mimic the Limmat aquifer in Zurich (Switzerland), where river–aquifer exchange fluxes and groundwater management activities play an important role. The solution of the unsaturated–saturated subsurface hydrological flow problem including river–aquifer interaction is calculated for ten different synthetic realities where the strongly heterogeneous river bed hydraulic conductivities (L) are perfectly known. Hydraulic head data (100 in the default scenario) are sampled from the synthetic realities. In subsequent data assimilation experiments, where L is unknown now, the hydraulic head data are used as conditioning information, with the help of the ensemble Kalman filter (EnKF). For each of the ten synthetic realities, four different ensembles of L are tested in the experiments with EnKF; one ensemble estimates high-resolution L fields with different L values for each element, and the other three ensembles estimate effective L values for 5, 3 or 2 zones. The calibration of higher-resolution L fields (i.e. fully heterogeneous or 5 zones) gives better results than the calibration of L for only 3 or 2 zones in terms of reproduction of states, stream–aquifer exchange fluxes and parameters. Effective L for a limited number of zones cannot always reproduce the true states and fluxes well and results in biased estimates of net exchange fluxes between aquifer and stream. Also in case only 10 head data are used for conditioning, the high-resolution characterization of L fields with EnKF is still feasible. For less heterogeneous river bed hydraulic conductivities, a high-resolution characterization of L is less important. When uncertainties in the hydraulic parameters of the aquifer are also regarded in the assimilation, the errors in state and flux predictions increase, but the ensemble with a high spatial resolution for L still outperforms the ensembles with effective L values. We conclude that for strongly heterogeneous river beds the commonly applied simplified representation of the streambed, with spatially homogeneous parameters or constant parameters for a few zones, might yield significant biases in the characterization of the water balance. For strongly heterogeneous river beds, we suggest adopting a stochastic field approach to model the spatially heterogeneous river beds geostatistically. The paper illustrates that EnKF is able to calibrate such heterogeneous streambeds on the basis of hydraulic head measurements, outperforming zonation approaches

A new version of the HBSC Family Affluence Scale - FAS III: Scottish qualitative findings from the International FAS Development Study

A critical review of the Family Affluence Scale (FAS) concluded that FAS II was no longer discriminatory within very rich or very poor countries, where a very high or a very low proportion of children were categorised as high FAS or low FAS respectively (Currie et al. 2008). The review concluded that a new version of FAS - FAS III - should be developed to take into account current trends in family consumption patterns across the European region, the US and Canada. In 2012, the FAS Development and Validation Study was conducted in eight countries - Denmark, Greenland, Italy, Norway, Poland, Romania, Slovakia and Scotland. This paper describes the Scottish qualitative findings from this study. The Scottish qualitative fieldwork comprising cognitive interviews and focus groups sampled from 11, 13 and 15 year-old participants from 18 of the most- and least- economically deprived schools. These qualitative results were used to inform the final FAS III recommendations.Publisher PDFPeer reviewe

Photocatalytic acetaldehyde oxidation in air using spacious TiO2 films prepared by atomic layer deposition on supported carbonaceous sacrificial templates

Supported carbon nanosheets and carbon nanotubes served as sacrificial templates for preparing spacious TiO2 photocatalytic thin films. Amorphous TiO2 was deposited conformally on the carbonaceous template material by atomic layer deposition (ALD). Upon calcination at 550{\deg}C, the carbon template was oxidatively removed and the as-deposited continuous amorphous TiO2 layers transformed into interlinked anatase nanoparticles with an overall morphology commensurate to the original template structure. The effect of type of template, number of ALD cycles and gas residence time of pollutant on the photocatalytic activity, as well as the stability of the photocatalytic performance of these thin films was investigated. The TiO2 films exhibited excellent photocatalytic activity towards photocatalytic degradation of acetaldehyde in air as a model reaction for photocatalytic indoor air pollution abatement. Optimized films outperformed a reference film of commercial PC500