Scientific Mapping of Research on Nature-based Solutions for Sustainable Water Management

Nature-based solutions (NBS), including the protection and restoration of ecosystems, can provide a major contribution to global sustainable water resources management (WRM) in both urban and rural areas, yet the knowledge base essential for facilitating widespread uptake is lacking. The objective of this paper is to identify the main developments and trends in NBS-related research over time, including areas for future research. A bibliometric approach is used to quantitatively analyze relevant publications indexed in the Web of Science database from 1990 to 2018. The study identifies five thematic hotspots within the research landscape and several areas for future research, including the evaluation of ecosystem services provided, design and implementation at the landscape scale and consideration of cultural aspects, to push forward operationalization.

     

Microstructure Control of Silicon Nitride by Seeding with Rodlike β-Silicon Nitride Particles

The effect of seeding on microstructure development and mechanical properties of silicon nitride was investigated by the use of morphologically regulated rodlike β-Si₃N₄ singlecrystal particles with a diameter of 1 μm and a length of 4 μm as seed crystals. Silicon nitride with a bimodal microstructure was fabricated under a relatively low nitrogen gas pressure of 0.9 MPa owing to the epitaxial growth of β-silicon nitride from the seed particles. Grain growth from seeds followed the empirical equation D ⁿ–D₀ⁿ= kt , with growth exponents of 3 and 5 for the c -axis direction and the a -axis direction, respectively, being analogous to the kinetics of matrix grain growth. By seeding morphologically regulated particles, fracture toughness of silicon nitride was improved from 6.3 to 8.4–8.7 MPa·m^1/2, retaining high strength levels of about 1 GPa.     

The CO-catalyzed conversion of H2S to H2 + sulfur part 2. The thermal decomposition of COS

The pyrolysis of COS has been studied over the temperature range 300 to 750°C using a variety of catalysts. The observed product distribution confirmed that two parallel reaction paths: 2 COS → 2 CO S₂ (2) and 2 COS → CO₂ + CS₂ (4) are involved in the decomposition. The decomposition yield increased with rising temperature, accompanied with a shift in selectivity. At temperatures lower than ～700°C the disproportionation reaction 4 was predominant, whereas at temperatures higher than 700°C, reaction 2 was favoured. In the high-temperature region (700 to 750°C) it was possible to achieve full suppression of reaction 4 with added CS₂. The pyrolysis of COS was also studied in a reactor packed with quartz chips without catalysts at high temperatures. Between 800 and 900°C, up to 99% conversion (with respect to the thermodynamic limit) could be achieved, with the almost complete absence of the disproportionation reaction 4. The results point to the commercial potential in the two-step reaction sequence: for the economic conversion of hydrogen sulfide to hydrogen and sulfur.     

Margarine's trans-fatty acid composition: modifications during the last decades and new trends

Trans fatty acids isomers are formed during the hydrogenation process used in the food industry to harden oils. In the last decades there has been a great controversy about the consumption of margarine due to the levels of trans fatty acids they contain. While in the eighties consumption of margarines was considered healthy, during the nineties several studies indicated that consumption of 18:1t increased LDL-cholesterol levels and decreased HDL-cholesterol level, and was related with an increased risk of coronary heart disease. The publicity about the unfavourable effects of trans fatty acid consumption seems to have influenced margarine producers to reduce the trans fatty acid content of margarines. Meanwhile USA has adopted a new legislation about trans fatty acid labelling. In Europe, Dinamarca has limited the maximum level of trans fatty acids allowed in food products.     

Virtual Blocks: a serious game for spatial ability improvement on mobile devices

This paper presents a novel spatial instruction system for improving spatial abilities of engineering students. A 3D mobile game application called Virtual Blocks has been designed to provide a 3D virtual environment to build models with cubes that help students to perform visualization tasks to promote the development of their spatial ability during a short remedial course. A validation study with 26 freshman engineering students at La Laguna University (Spain) has concluded that the training had a measurable and positive impact on students’ spatial ability. In addition, the results obtained using a satisfaction questionnaire show that Virtual Blocks is considered an easy to use and stimulating application.     

The influence of different sensory cues as selection feedback and co-location in presence and task performance

For some applications based on virtual reality technology, presence and task performance are important factors to validate the experience. Different approaches have been adopted to analyse the extent to which certain aspects of a computer-generated environment may enhance these factors, but mainly in 2D graphical user interfaces. This study explores the influence of different sensory modalities on performance and the sense of presence experienced within a 3D environment. In particular, we have evaluated visual, auditory and active haptic feedback for indicating selection of virtual objects. The effect of spatial alignment between proprioceptive and visual workspaces (co-location) has also been analysed. An experiment has been made to evaluate the influence of these factors in a controlled 3D environment based on a virtual version of the Simon game. The main conclusions obtained indicate that co-location must be considered in order to determine the sensory needs during interaction within a virtual environment. This study also provides further evidence that the haptic sensory modality influences presence to a higher extent, and that auditory cues can reduce selection times. Conclusions obtained provide initial guidelines that will help designers to set out better selection techniques for more complex environments, such as training simulators based on VR technology, by highlighting different optimal configurations of sensory feedback.     

Correlation between Transport and Occurrence of Dengue Cases in Bahia

Dengue is a public health problem that presents complexity in its dissemination. The physical means of spreading and the dynamics of the spread between the municipalities need to be analyzed to guide effective public policies to combat this problem. This study shows a correlation between the exponent of criticality present in SOC （self-organized criticality） and the number of buses per week, identifying municipalities that exert important roles in the spread of dengue in Bahia, confirming transport as a physical means for the diffusion of dengue.     

Alterations in the complex refractive index of copper oxide thin films as sensing effect for hydrogen sulfide monitoring

Throughout the last three decades cuprous (Cu₂O) and cupric oxide (CuO) have been subject of extensive investigations of their material properties. This research was mainly driven by potential applicability as a photovoltaic or doping material. However, CuO/Cu₂O layers show a specific reaction towards hydrogen sulfide (H₂S), making it a good candidate as highly selective gas sensor material. On this account thin film samples of CuO and Cu₂O have been investigated with regard to their specific surface interactions with H₂S gas. Changes in morphology, chemical composition, and alterations in the complex refractive index have been thoroughly examined in order to understand possible sensing effects. Raman spectroscopy was used for verifying the films composition after heat treatment. Transmission and reflection characteristics in the extended UV/Vis regime (350–1,100 nm) of initially prepared samples and after exposure to well-defined doses of H₂S were recorded. A distinct increase in transmissivity was observed for Cu₂O films in the wavelength region λ = 550–900 nm. An initial conditioning effect was observed from consecutive measurements. Absorptivity characteristics and optical band gaps were derived, showing an absorptivity shift of CuO thin films after exposure towards H₂S. A specific optical read-out based on total internal reflection was set-up, offering a transient monitoring of the materials surface interactions with the gas phase. Changes in the response, in terms of intensity variations, were reproducibly shown for low concentrations of 5 ppm of H₂S.     

Nanofiltration of a clarified fermentation broth

Membrane technology has a growing role in downstream processing of biopharmaceuticals showing greater performances than the traditional processes. Concerning the use of membrane technology for the isolation of clavulanic acid from fermentation broths, the major drawback is the severe flux decline observed during concentration by nanofiltration (NF) of the clarified broth. This work addresses the study of the NF, aiming the achievement of high fluxes and high clavulanic acid rejections. A suitable NF membrane is chosen and the main causes of flux decline are searched.The tested membranes (NFT50, Desal DL and Desal DK) were characterized, evidencing significant differences concerning their molecular weight cut-off (MWCO), hydraulic permeability, roughness (atomic force microscopy measurements) and rejection to clavulanic acid. However, for high volumetric concentrations of clarified broth, their fluxes were identical. Taking into account the average permeation fluxes and clavulanic acid retention, the membrane Desal DK was considered the most appropriate for carrying the clavulanic acid concentration.Throughout experiments with model solutions of increasing complexity, glucose and clavulanic acid were identified as the major contributors to flux decline due to concentration polarization together with enhanced osmotic pressures. Considering these mechanisms, a simplified approach was used aiming the modelling of the observed flux decline of both model and real solutions.     

Mixture of Merged Gaussian Algorithm using RTDENN

Computer vision has been a widely developed research area in the last years, and it has been used for a broad range of applications, including surveillance systems. In the pursuit of an autonomous and smart motion detection system, a reliable segmentation algorithm is required. The main problems of present segmentation solutions are their high execution time and the lack of robustness against changes in the environment due to variations in lighting, shadows, occlusions or the movement of secondary objects. This paper proposes a new algorithm named Mixture of Merged Gaussian Algorithm (MMGA) that aims to achieve a substantial improvement in execution speed to enable real-time implementation, without compromising the reliability and accuracy of the segmentation. The MMGA is based on the combination of a probabilistic model for the background, similar to the Mixture of Gaussian Model (MGM), with the learning processes of Real-Time Dynamic Ellipsoidal Neural Networks (RTDENN) for the update of the model. The proposed algorithm has been tested for different videos and compared to the MGM and SDGM algorithms. Results show a reduction of 30 to 50 % in execution times. Furthermore, the segmentation is more robust against the effect of noise and adapts faster to lighting changes.