A catchment-scale carbon and greenhouse gas budget of a subarctic landscape

This is the first attempt to budget average current annual carbon (C) and associated greenhouse gas (GHG) exchanges and transfers in a subarctic landscape, the Lake Tornetr?sk catchment in northern Sweden. This is a heterogeneous area consisting of almost 4000 km2 of mixed heath, birch and pine forest, and mires, lakes and alpine ecosystems. The magnitudes of atmospheric exchange of carbon in the form of the GHGs, CO2 and CH4 in these various ecosystems differ significantly, ranging from little or no flux in barren ecosystems over a small CO2 sink function and low rates of CH4 exchange in the heaths to significant CO2 uptake in the forests and also large emissions of CH4 from the mires and small lakes. The overall catchment budget, given the size distribution of the individual ecosystem types and a first approximation of run-off as dissolved organic carbon, reveals a landscape currently with a significant sink capacity for atmospheric CO2. This sink capacity is, however, extremely sensitive to environmental changes, particularly those that affect the birch forest ecosystem. Climatic drying or wetting and episodic events such as insect outbreaks may cause significant changes in the sink function. Changes in the sources of CH4 through increased permafrost melting may also easily change the sign of the current radiative forcing, due to the stronger impact per gram of CH4 relative to CO2. Hence, to access impacts on climate, the atmospheric C balance alone has to be weighed in a radiative forcing perspective. When considering the emissions of CH4 from the mires and lakes as CO2 equivalents, the Tornetr?sk catchment is currently a smaller sink of radiative forcing, but it can still be estimated as representing the equivalent of approximately 14000 average Swedish inhabitants' emissions of CO2. This can be compared with the carbon emissions of less than 200 people who live permanently in the catchment, although this comparison disregards substantial emissions from the non-Swedish tourism and transportation activities.     

Constructing cities,deconstructing scaling laws

Cities can be characterized and modelled through different urban measures. Consistency within these observables is crucial in order to advance towards a science of cities. Bettencourt et al. have proposed that many of these urban measures can be predicted through universal scaling laws. We develop a framework to consistently define cities, using commuting to work and population density thresholds, and construct thousands of realizations of systems of cities with different boundaries for England and Wales. These serve as a laboratory for the scaling analysis of a large set of urban indicators. The analysis shows that population size alone does not provide us enough information to describe or predict the state of a city as previously proposed, indicating that the expected scaling laws are not corroborated. We found that most urban indicators scale linearly with city size, regardless of the definition of the urban boundaries. However, when nonlinear correlations are present, the exponent fluctuates considerably.     

The wake of hovering flight in bats

Hovering means stationary flight at zero net forward speed, which can be achieved by animals through muscle powered flapping flight. Small bats capable of hovering typically do so with a downstroke in an inclined stroke plane, and with an aerodynamically active outer wing during the upstroke. The magnitude and time history of aerodynamic forces should be reflected by vorticity shed into the wake. We thus expect hovering bats to generate a characteristic wake, but this has until now never been studied. Here we trained nectar-feeding bats, Leptonycteris yerbabuenae, to hover at a feeder and using time-resolved stereoscopic particle image velocimetry in conjunction with high-speed kinematic analysis we show that hovering nectar-feeding bats produce a series of bilateral stacked vortex loops. Vortex visualizations suggest that the downstroke produces the majority of the weight support, but that the upstroke contributes positively to the lift production. However, the relative contributions from downstroke and upstroke could not be determined on the basis of the wake, because wake elements from down- and upstroke mix and interact. We also use a modified actuator disc model to estimate lift force, power and flap efficiency. Based on our quantitative wake-induced velocities, the model accounts for weight support well (108%). Estimates of aerodynamic efficiency suggest hovering flight is less efficient than forward flapping flight, while the overall energy conversion efficiency (mechanical power output/metabolic power) was estimated at 13%.     

Relaxation of Alternating Iterative Algorithms for the Cauchy Problem Associated with the Modified Helmholtz Equation

We propose two algorithms involving the relaxation of either the given Dirichlet data or the prescribed Neumann data on the over-specified boundary, in the case of the alternating iterative algorithm of Kozlov, Maz'ya and Fomin(1991) applied to Cauchy problems for the modified Helmholtz equation. A convergence proof of these relaxation methods is given, along with a stopping criterion. The numerical results obtained using these procedures, in conjunction with the boundary element method (BEM), show the numerical stability, convergence, consistency and computational efficiency of the proposed methods.     

Textural and hydrogen sulphide adsorption behaviour of double metal–silica modified with potassium permanganate

A new MgCa–silica material with bimodal pore size is impregnated with KMnO₄ for dynamic adsorption of H₂S. The MgCa–silica was synthesized using sodium silicate and calcium and magnesium salts as precipitating agents. The KMnO₄ impregnation onto MgCa–silica was obtained through either direct addition into MgCa–silica wet coagulum or doping of dried MgCa–silica pellets into KMnO₄ solution. These chemisorbents were characterized by nitrogen physisorption, spectrophotometer, microscopy and dynamic H₂S adsorption test setup similar to ASHRAE standard I45.I. The results show that impregnation route and KMnO₄ wt% cause a reduction of surface area and total pore volume. The decrease in pore volume was slightly more in chemisorbents obtained via post doping compared to direct impregnation. Regardless of pore volume reduction the pore size range, 1–32 nm, was as in the parent MgCa–silica with micro and meso-pore diameter centered at 1.4 and 5.4 nm respectively. Thus obtained chemisorbents have their pore entrances neither blocked nor shifted. The MgCa–silica/KMnO₄ chemisorbents exhibits good H₂S uptake performance. The chemisorbent with 11.4 wt% KMnO₄ and obtained via direct impregnation possesses the highest uptake capacity. The lowest capacity was observed for chemisorbent with 8 wt% KMnO₄ and made by direct impregnation. The variations in uptake capacity are likely due to impregnation route, the KMnO₄ content and its location in the pore system. The results suggest that the MgCa–silica/KMnO₄ chemisorbents can remove H₂S from indoor air at room temperature.     

Glycopeptide Dendrimers with High Affinity for the Fucose‐Binding Lectin LecB from Pseudomonas aeruginosa

Dendritic antibacterial agents : Glycopeptide dendrimer biofilm inhibitors were synthesized combinatorially and optimized for binding to the fucose‐specific lectin LecB, which has high affinity of fucose. These dendritic ligands are potential antibacterial agents against Pseudomonas aeruginosa, an antibiotic resistant human pathogen.

     

The effect of fatty acid methyl esters on the curing performance and final properties of thermally cured solvent-borne coil coatings

The solvent content of a thermally cured coil-coating paint may be reduced by introducing a reactive diluent derived from a vegetable oil and thereby producing a coating partly based on a renewable resource. A reactive diluent acts as a solvent in the liquid paint, lowering the viscosity, and is then incorporated into the film during cure. In the present study, rape seed methyl ester (RME) has been evaluated as reactive diluent in a thermally cured hydroxyl-functional polyester/melamine system. RME has suitable diluting properties and functionality to be incorporated into the dry coating. Dynamic mechanical analysis of free standing films shows that the final film properties are affected by presence of reactive diluent, oven temperature, choice of co-solvent, and flash-off period.     

The content and composition of sterols and sterol esters in sunflower and poppy seed oils

The composition and proportion of free sterols and sterol esters in crude sunflower and poppy seed oils were determined, using preparative thin layer chromatography followed by gas chromatography with cholesterol as an internal standard. Free sterols and sterol esters were also isolated in a liquid fraction obtained by low temperature crystallization (−80 C) of the oils and enriched with minor lipid classes. This enrichment procedure provided a liquid fraction suitable for studies of minor components in the oils. However, selectivity towards sterol esters was observed since sterols esterified to very long chain fatty acids (C₂₀–C₂₄) were preferentially retained in the precipitate. The proportions of free and esterified sterols were found to be 0.34 and 0.28%, respectively, in the sunflower oil, whereas the corresponding figures for poppy seed oil were 0.33% and 0.05%. Sunflower oil was characterized by a relatively high percentage of Δ7-sterols, preferentially obtained in the esterified fraction, and by very long chain saturated fatty acids of sterol esters. The sterols in poppy seed oil were composed almost entirely of campesterol, stigmasterol, sitosterol and Δ5-avenasterol, although their percentage distributions were remarkably different in the free and esterified fraction.     

Neutron induced single-word multiple-bit upset in SRAM

The single-word multiple-bit upset (SMU) frequency for nine commercial static random access memories (SRAM) have been evaluated at eight different neutron energies; 0-11 MeV, 14 MeV, 22 MeV, 35 MeV, 45 MeV, 75 MeV, 96 MeV, 160 MeV. The SRAM types used at these experiments have sizes from 256 Kbit up to 1 Mbit, with date-codes ranging from 9209 up to 9809. The result showed a slightly rising dependence on the neutron energy. Also experiments at two neutron energies, 45 MeV and 96 MeV, were performed where the supply voltage influence on the SMU-rate was studied. Five device types were used at 96 MeV and the supply voltage was changed between 5 V, 3.3 V and 2.5 V. At 45 MeV three devices at 5 V and 3.3 V were irradiated. The experiments showed a relation between the amount of total upset and SMU that indicates no clear supply voltage dependence     

Piecewise quadratic stability of fuzzy systems

Presents an approach to stability analysis of fuzzy systems. The analysis is based on Lyapunov functions that are continuous and piecewise quadratic. The approach exploits the gain-scheduling nature of fuzzy systems and results in stability conditions that can be verified via convex optimization over linear matrix inequalities. Examples demonstrate the many improvements over analysis based on a single quadratic Lyapunov function. Special attention is given to the computational aspects of the approach and several methods to improve the computational efficiency are described