The use of simulated whole effluents in toxicity assessments: A review of case studies from reverse osmosis desalination plants

Seawater desalination is an increasingly common means to meet the demand for freshwater. Resulting wastewater discharges can, however, impact biota of the surrounding environment. Concern exists that interactive effects specific to the outputs of each desalination plant may result in unique impacts difficult to predict by studying existing plants or assessing the effects of individual chemicals found in waste streams. Given this, we highlight an alternative approach to assess potential toxicity of desalination outfalls. Specifically, we review three recent case studies from Australia in which simulated whole effluents were used in toxicity assessments before desalination plants were constructed. This approach enabled potential toxic effects of wastewater to be considered before the plants became operational and, in one case, even facilitated consideration of potential effects of different treatment processes and suppliers. As in many whole effluent toxicity assessments, the time required for testing and restricted range of species considered were limitations. Given the benefits of this method, however, the use of simulated whole effluents is a development that could facilitate an improved capacity to forecast impacts of proposed desalination plants

Simple and efficient way of speeding up transmission calculations with kk-point sampling

The transmissions as functions of energy are central for electron or phonon transport in the Landauer transport picture. We suggest a simple and computationally "cheap" post-processing scheme to interpolate transmission functions over $k$-points to get smooth well-converged average transmission functions. This is relevant for data obtained using typical "expensive" first principles calculations where the leads/electrodes are described by periodic boundary conditions. We show examples of transport in graphene structures where a speed-up of an order of magnitude is easily obtained.Comment: 6 pages, 4 figure

The role of E+A and post-starburst galaxies – I. Models and model results

‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14416.xDifferent compositions of galaxy types in the field in comparison to galaxy clusters as described by the morphology–density relation in the local universe are interpreted as a result of transformation processes from late- to early-type galaxies. This interpretation is supported by the Butcher–Oemler effect. We investigate E+A galaxies as an intermediate state between late-type galaxies in low-density environments and early-type galaxies in high-density environment to constrain the possible transformation processes. For this purpose, we model a grid of post-starburst galaxies by inducing a burst and/or a halting of star formation on the normal evolution of spiral galaxies with our galaxy evolution code galev. From our models, we find that the common E+A criteria exclude a significant number of post-starburst galaxies, and propose that comparing their spectral energy distributions leads to a more sufficient method to investigate post-starburst galaxies. We predict that a higher number of E+A galaxies in the early universe cannot be ascribed solely to a higher number of starburst, but is a result of a lower metallicity and a higher burst strength due to more gas content of the galaxies in the early universe. We find that even galaxies with a normal evolution without a starburst have an Hδ-strong phase at early galaxy ages.Peer reviewe

Evolving information systems: meeting the ever-changing environment

To meet the demands of organizations and their ever-changing environment, information systems are required which are able to evolve to the same extent as organizations do. Such a system has to support changes in all time-and application-dependent aspects. In this paper, requirements and a conceptual framework for evolving information systems are presented. This framework includes an architecture for such systems and a revision of the traditional notion of update. Based on this evolutionary notion of update (recording, correction and forgetting) a state transition-oriented model on three levels of abstraction (event level, recording level, correction level) is introduced. Examples are provided to illustrate the conceptual framework for evolving information systems

Optimizing Organic Solar Cells: Transparent Electron Transport Materials for Improving the Device Performance

This thesis deals with the characterization and implementation of transparent electron transport materials (ETM) in vacuum deposited p-i-n type organic solar cells (OSC) for substituting the parasitically absorbing standard ETM composed of n-doped C60. In addition to transparency in the visible range of the sun spectrum, the desired material properties include high electron mobility and conductivity, thermal and morphological stability, as well as good energy level alignment relative to the adjacent acceptor layer which is commonly composed of intrinsic C60. In this work, representatives of three different material classes are evaluated with regard to the above mentioned criteria. HATCN (hexaazatriphenylene hexacarbonitrile) is a small discoid molecule with six electron withdrawing nitrile groups at its periphery. It forms smooth thin films with an optical energy gap of 3.3eV, thus being transparent in the visible range of the sun spectrum. Doping with either 5wt% of the cationic n-dopant AOB or 7wt% of the proprietary material NDN1 effectively increases the conductivity to 7.6*10^-6 S/cm or 2.2*10^-4 S/cm, respectively. However, the fabrication of efficient OSC is impeded by the exceptionally high electron affinity (EA ) of approximately 4.8eV that causes the formation of an electron injection barrier between n-HATCN and intrinsic C60 (EA=4.0eV). This work presents a strategy to remove the barrier by introducing doped and undoped C60 intermediate layers, thus demonstrating the importance of energy level matching in a multi-layer structure and the advantages of Fermi level control by doping. Next, a series of six Bis-Fl-NTCDI (N,N-bis(fluorene-2-yl)-naphthalenetetracarboxylic diimide) compounds, which only differ by the length of the alkyl chains attached to the C9 positions of the fluorene side groups, is examined. When increasing the chain length from 0 to 6 carbon atoms, the energy levels remain nearly unchanged: We find EA=3.5eV as estimated from cyclic voltammetry, an ionization potential (IP ) in the range between 6.45eV and 6.63eV, and Eg,opt=3.1eV which means that all compounds form transparent thin films. Concerning thin film morphology, the addition of side chains results in the formation of amorphous layers with a surface roughness <1nm on room temperature glass substrates, and (1.5+/-0.5)nm for deposition onto glass substrates heated to 100°C. In contrast, films composed of the side chain free compound Bis-HFl-NTCDI exhibit a larger surface roughness of (2.5+/-0.5)nm and 9nm, respectively, and are nanocrystalline already at room temperature. Moreover, the conductivity achievable by n-doping is very sensitive to the side chain length: Whereas doping of Bis-HFl-NTCDI with 7wt% NDN1 results in a conductivity in the range of 10^-4 S/cm, the attachment of alkyl chains causes a conductivity which is more than three orders of magnitude smaller despite equal or slightly higher doping concentrations. The insufficient transport properties of the alkylated derivatives lead to the formation of pronounced s-kinks in the jV -characteristics of p-i-n type OSC while the use of n-Bis-HFl-NTCDI results in well performing devices. The last material, HATNA-Cl6 (2,3,8,9,14,15- hexachloro-5,6,11,12,17,18-hexaazatrinaphthylene), exhibits Eg,opt=2.7eV and is therefore not completely transparent in the visible range of the sun spectrum. However, its energy level positions of EA=4.1eV and IP=7.3eV are well suited for the application as ETM in combination with i-C60 as acceptor. The compound is dopable with all available n-dopants, resulting in maximum conductivities of sigma=1.6*10^-6, 3.5*10^-3, and 7.5*10^-3 S/cm at 7.5wt% AOB, Cr2(hpp)4, and NDN1, respectively. Applying n-HATNA-Cl6 instead of the reference ETM n-C60 results in a comparable or improved photocurrent density at an ETM thickness d(ETM)=40nm or 120nm, respectively. At d(ETM)=120nm, the efficiency eta is more than doubled as it increases from eta(n-C60)=0.4% to eta(n-HATNA-Cl6)=0.9% . Optical simulations show that the replacement of n-C60 by n-Bis-HFl-NTCDI, n-HATNA-Cl6, or the previously studied n-NTCDA (naphthalenetretracarboxylic dianhydride) in p-i-n or n-i-p type device architectures is expected to result in an increased photocurrent due to reduced parasitic absorption. For quantifying the gain, the performance of p-i-n type OSC with varying ETM type and thickness is evaluated. Special care has to be taken when analyzing devices comprising the reference ETM n-C60 as its conductivity is sufficiently large to extend the area of the aluminum cathode and thus the effective device area which may lead to distorted results. Overall, the experiment is able to confirm the trends predicted by the optical simulation. At large ETM thickness in the range between 60 and 120nm, the window layer effect of the ETM is most pronounced. For instance, at d(ETM)=120nm, eta(C60) is more than doubled using n-HATNA-Cl6 and even more than tripled using n-Bis-HFl-NTCDI or n-NTCDA. At optimized device geometry the photocurrent gain is slightly less than expected but nonetheless, the efficiency is improved from eta(max)=2.1% for n-C60 and n-HATNA-Cl6 solar cells to eta(max)=2.3, and 2.4% for n-Bis-HFl-NTCDI and n-NTCDA devices, respectively. This development is supported by generally higher Voc and FF in solar cells with transparent ETM. Finally, p-i-n type solar cells with varying ETM are aged at a temperature of 50°C and an illumination intensity of approximately 2 suns. Having extrapolated lifetimes t(80) of 36, 500, and 14000h and nearly unchanged jV-characteristics after 2000h, n-C60 and n-Bis-HFl-NTCDI devices exhibit the best stability. In contrast, n-NTCDA devices suffer from a constant decrease in Isc while n-HATNA-Cl6 solar cells show a rapid dscegradation of both Isc and FF associated with a decomposition of the material or a complete de-doping of the ETM. Here, lifetimes of only 4500h and 445hare achieved

Efficient Machine-type Communication using Multi-metric Context-awareness for Cars used as Mobile Sensors in Upcoming 5G Networks

Upcoming 5G-based communication networks will be confronted with huge increases in the amount of transmitted sensor data related to massive deployments of static and mobile Internet of Things (IoT) systems. Cars acting as mobile sensors will become important data sources for cloud-based applications like predictive maintenance and dynamic traffic forecast. Due to the limitation of available communication resources, it is expected that the grows in Machine-Type Communication (MTC) will cause severe interference with Human-to-human (H2H) communication. Consequently, more efficient transmission methods are highly required. In this paper, we present a probabilistic scheme for efficient transmission of vehicular sensor data which leverages favorable channel conditions and avoids transmissions when they are expected to be highly resource-consuming. Multiple variants of the proposed scheme are evaluated in comprehensive realworld experiments. Through machine learning based combination of multiple context metrics, the proposed scheme is able to achieve up to 164% higher average data rate values for sensor applications with soft deadline requirements compared to regular periodic transmission.Comment: Best Student Paper Awar