Estimation of off-track visits in a nature reserve: a case study in central Belgium

Equilibrium has to be found between maximizing social profit and minimizing ecological disturbance in open (accessible) nature reserves. Because the probability of disturbance grows with increasing visit density and frequency, some nature reserves tend to lose their specific quality. The aim of this study, concentrated on the ‘Demerbroeken’, 45 km east of Brussels in central Belgium, is to estimate the probability of off-track visits in any location of the nature reserve at specific times and terrain conditions, by means of a GIS-based friction model. Research was based on a detailed land survey, interviews with visitors, performance of walking experiments and determination of friction values of specific terrain units. Data from interviews and walking experiments were collected to validate the model. The output from this study is of potential help to design an impact assessment and management tool.     

Mechanistic study of drying of alkyd resins using (Z,Z)- and (E,E)-3,6-nonadiene as model substances

The cobalt-catalysed autoxidative drying of alkyd resins was studied using (Z,Z)-3,6-nonadiene and (E,E)-3,6-nonadiene as model compounds. A large number of reaction products were isolated from the autoxidation mixture using HPLC and preparative size exclusion chromatography and identified with ¹H- and ¹³C-NMR. The identified compounds comprised C₉ hydroperoxides, endoperoxides, epoxides, aldehydes and ketones and some other oxidation products. Their chemical structures pointed to three different types of oxidation processes taking place. Besides the main radical autoxidation reaction, evidence was found for photo-sensitized oxidation involving singlet oxygen. Thirdly, epoxidation occurs via peracids or hydroperoxides formed as intermediates. Because of the large number of possible isomers having very similar physical properties, isolation of dimers required considerable effort. Nevertheless, two dimers were isolated and characterized. Their structures indicate crosslinking to occur by recombination of radicals as termination reaction.     

A low-power transmission-gate-based 16-bit multiplier for digital hearing aids

The most widespread 16-bit multiplier architectures are compared in terms of area occupation, dissipated energy, and EDP (Energy-Delay Product) in view of low-power low-voltage signal processing for digital hearing aids and similar applications. Transistor-level simulations including back-annotated wire parasitics confirm that the propagation of glitches along uneven and re-convergent paths results in large unproductive node activity. Because of their shorter full-adder chains, Wallace-tree multipliers indeed dissipate less energy than the carry-save (CSM) and other traditional array multipliers (6.0 µW/MHz versus 10.9 µW/MHz and more for 0.25 µm CMOS technology at 0.75 V). By combining the Wallace-tree architecture with transmission gates (TGs), a new approach is proposed to improve the energy efficiency further (3.1 µW/MHz), beyond recently published low-power architectures. Besides the reduction of the overall capacitance, minimum-sized transmission gate full-adders act as RC-low-pass filters that attenuate undesired switching. Finally, minimum size TGs increase the V _dd to ground resistance, hence decreasing leakage dissipation (0.55 nW versus 0.84 nW in CSM and 0.94 nW in Wallace).     

A high power solid-state medium wave broadcast transmitter

The factors leading to the choice of an all-solid-state 50-kW medium-wave broadcast transmitter are examined, and its advantages over vacuum-tube-type transmitters of the same power are discussed. The installation and operation of the transmitter are described. The transmitter has demonstrated high levels of performance and reliability. Energy savings and reduction of maintenance times have been achieved     

Assessing biological control of Acarus siro by Cheyletus malaccensis under laboratory conditions: Effect of temperatures and prey density

In stored grain, the predatory mite Cheyletus spp. may be used to control the pest mite Acarus siro. The efficiency of control depends on many factors, particularly ambient temperature. In this study we investigated the effects of temperature and initial prey density on the prey–predator system under laboratory conditions. Ratio–response models were fitted to estimate the efficiency of control for three temperatures. At 15 °C a 90% reduction of A. siro was achieved by releasing nine Cheyletus malaccensis individuals into a population of 100 A. siro individuals in 1 kg of grain. At 20 °C, 90% reduction required seven C. malaccensis individuals and at 25 °C, it required three C. malaccensis individuals. Without the predator the intrinsic rates of increase of A. siro populations increased with temperature and were highest for an initial density of 100 individuals, revealing some form of positive interaction among A. siro individuals during food processing. The intrinsic rates of increase of C. malaccensis populations also increased with temperature and decreased with increasing density of the predator, presumably as a result of interference competition among predators.At 15 °C the rate of increase for A. siro was higher than that for C. malaccensis, while at higher temperatures it was the other way around. Lower developmental thresholds were 10 °C for A. siro and 13.6 °C for C. malaccensis. In order to find when an artificial release of C. malaccensis is most efficient we simulated a population increase of A. siro using temperature records from one grain store. In Central Europe this type of biological control can be efficient only when the predator is released at the beginning of storage, i.e. in September and October.     

The TASSO vertex detector

The design, construction and performance of a small pressurized drift chamber of low mass and high wire density is described. The chamber forms part of the TASSO experiment at the PETRA e⁺e⁻ storage ring of the DESY Laboratory. First physics results obtained with the chamber are also briefly discussed.     

Underrated transformations in the open space—The case of an urbanized and multifunctional area

The open space in Flanders is subjected to different transformation processes. These processes are related to dynamic interactions within an urbanizing society and to competition for space by an increasing number of functions. Despite the acknowledgement of dynamic land use demands, the current categorizations of land use and land cover are not always able to catch transformations related to e.g. newcomers in land use, ecosystem services and multifunctionality in mixed urban–rural areas. Remote sensing tools and census data are insufficient when studying a complex and intensively used space. This research therefore aims to identify underrated transformations in the study area Flanders (the northern part of Belgium) using two main sources: (i) open expert interviews and (ii) three case studies. The interviews serve to formulate a renewed framework that can be used to describe transformations in the open space. The transformation processes that emerge from the interviews and case studies are compared to those defined and recognized in the current spatial planning policy and in existing monitoring data, in order to identify bottlenecks and options for future spatial planning policy. The major conclusions of this paper are (i) a critical view on the analysis and categorization of functions and open space as it is currently practiced in land use monitoring and land use planning programs, (ii) additional data needs to encompass transformation processes in the open space and (iii) the need for a more integral vision for open space.     

The flavour of cape gooseberry (Physalis peruviana L.)

European Food Research and Technology - The volatile constituents of cape gooseberry (Physalis peruviana L.) were characterized using liquid/liquid extraction and fractionation of the flavour...     

Measuring the impregnation of an out-of-autoclave prepreg by micro-CT

Resin flow into dry reinforcement regions is the main microstructural change during the processing of out-of-autoclave prepregs and influences air evacuation and void suppression. Such impregnation flow was investigated experimentally during the processing of a second-generation out-of-autoclave prepreg. First, laminates were partially processed to different stages of a simple cure cycle. Then, samples from each laminate were scanned using X-ray microtomography (micro-CT) to obtain 3D microstructural data. This data was used to investigate the initial microstructure of the material and measure the extent of impregnation at each processing stage, the rate of impregnation, and the evolution of macro-porosity within the material.