| 1. |
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| 2. |
- Alves, Joao S., et al.
(författare)
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Experimental investigation on performance improvement by mid-plane guide-vanes in a biplane-rotor Wells turbine for wave energy conversion
- 2021
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- The Wells turbine is the most frequently used or proposed self-rectifying air turbine for oscillating-water column wave-energy converter application, largely because of its conceptual and mechanical simplicity. Biplane Wells turbines allow a higher total blade solidity to be attained than monoplane turbines do, but this results in larger aerodynamic losses associated with the swirl kinetic energy loss at turbine exit. This may be overcome by the presence of a row of guide vanes between the two rotor planes, a solution that had been proposed and investigated theoretically or by numerical modelling. Results of turbine overall performance and flow details are reported from laboratory tests of a biplane Wells turbine without guide vanes and with specially designed guide vanes. The presence of the guide vanes was found to increase the peak efficiency by seven percentual points, while reducing (for fixed rotational speed) the damping provided by the turbine. Measured losses in the guide vane row were much smaller than in the rotors. Experimental results are compared with previously published numerical results. A stochastic theoretical transform was applied to obtain averaged results for the turbine performance subject to the irregular bidirectional air flow induced by real sea waves.
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| 3. |
- Williams, James Henty, et al.
(författare)
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Roadmap for action on the environmental risk assessment of chemicals for insect pollinators (IPol-ERA)
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Approaches integrating interdisciplinary perspectives are necessary to address current and future health and environmental challenges. Many policy initiatives have embraced more holistic approaches to tackle these challenges, e.g., the One Health concept, the Farm to Fork (F2F), Biodiversity and Chemical strategies within the European Green Deal and the global Sustainable Development Goals (SDGs). Insect pollinators are an excellent example of the One Health concept and have gained renewed focus through the EU Pollinator Initiative. Insect pollinators are essential for healthy diets by providing pollination services and maintaining biodiversity and healthy ecosystem functions. For this reason, they are part of the Environmental Risk Assessment (ERA) of chemicals, such as plant protection products (PPPs). However, an ERA of PPPs can align with and embrace these more holistic concepts and strategies by evolving towards a systems-based approach that recognises the diversity and the important role played by insect pollinators (e.g., pollination services for food security), as well as the variety of habitats and contexts they live in with their multiple stressors, and where PPPs may be used. A roadmap has been developed to determine the steps and actions needed to progress ERA methodologies and tools for insect pollinators. This roadmap is based on a review of the latest scientific knowledge, determining key areas for development to advance ERA, and identifying expertise and networks needed to foster progressive dialogue and public acceptance. The roadmap proposes several actions to generate the necessary knowledge to advance methodologies and tools within the current ERA framework, initially for chemical PPPs but extendable to other regulated chemicals. In addition, it outlines the actions needed to build the framework and the collaborative activities required to realise the transition to a systems-based ERA for insect pollinators by 2030.
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| 4. |
- Gomes, João, et al.
(författare)
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Evaluation of the impact of stagnation temperatures in different prototypes of low concentration PVT solar panels
- 2015
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Ingår i: ISES Solar World Congress 2015, Conference Proceedings. - Freiburg, Germany : International Solar Energy Society. - 9783981465952 ; , s. 993-1004
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Konferensbidrag (refereegranskat)abstract
- Photovoltaic thermal (PVT) solar panels produce both thermal and electric power from the some area. This paper concerns a PVT design where the series connected strings of cells are laminated using silicone to an aluminium receiver where the heat transfer fluid flows. An evaluation of the impact of reaching high temperatures in the cell structural integrity and performance is presented. Eight small test receivers were made in which the following properties were varied: Size of the PV cells, type of silicone used to encapsulate the PV cells, existence of a strain relief between the cells, size of the gap between cells and type of cell soldering (line or point soldering). These test receivers were placed in an oven for one hour, under eight different monitored temperatures. The temperature of the last round was set at 220°C which well exceeds the highest temperature the panel design can reach. Before and after each round in the oven, the following tests were conducted to the receivers: Electroluminescence (EL) test, IV-curve, diode function, and visual inspection. The test results showed that the receivers made with the transparent silicone and strain relief between cells experienced less micro-cracks and lower degradation in maximum power. No prototype test receiver lost more than 30% of its initial power, despite the large cell breakage shown in some receivers. Prototype receivers with transparent (softer) silicone showed much far less cracks and power decrease when compared to red (harder) silicone receivers. As expected, larger cells are more prone to develop micro-cracks after exposure to thermal stress. Additionally, existing micro-cracks tend to grow in size into larger micro-cracks relatively fast with thermal stress. The EL imaging taken during our experiment leads us to observe that it seems far easier for existing cracks to expand than for new cracks to appear.
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| 5. |
- Henriques, Joao, et al.
(författare)
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A coarse-grained model for flexible (phospho)proteins: Adsorption and bulk properties
- 2015
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 43, s. 473-480
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Tidskriftsartikel (refereegranskat)abstract
- Protein adsorption is a complex process that it controlled by several different mechanisms, for example: (i) electrostatic interactions between the protein and the surface, and (ii) between adsorbed proteins; (iii) dispersion interactions; (iv) hydration effects; and (v) structural rearrangements of the protein to balance conformational chain entropy with energetics. The aim of this study was to develop a simple model for the adsorption of intrinsically disordered proteins onto surfaces at a mesoscopic level of detail, while retaining protein integrity. Monte Carlo simulations were used in order to study the thermodynamical and structural properties of the flexible phosphoprotein beta-casein, in bulk and adsorbed to hydrophilic silica surfaces, in order to evaluate the effect of varying pH, monovalent salt concentration, and degree of serine phosphorylation. Experimental evidence from our previous study, published in this Journal, was used to set up and tune the Hamiltonian of the model. Our simulations show that protein-surface electrostatic interactions are, indeed, not the main driving force behind adsorption under the simulated conditions. Despite its importance, when taken alone, this type of interaction is not enough to promote the adsorption of beta-casein at any salt concentration. Adsorption is only possible through the inclusion of a protein-surface short-ranged attractive interaction potential with a minimum interaction strength of 2.25 k(B)T. This represents the lowest interaction strength required to mimic experimental adsorption results. An equally important finding is that considerable protein net charge fluctuations, due to phosphorylated serine saturation, have a negligible contribution to the free energy of adsorption. (C) 2014 Elsevier Ltd. All rights reserved.
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| 6. |
- Henriques, Joao
(författare)
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Modeling and simulation of intrinsically disordered proteins
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work is primarily about the development, validation and application of computer simulation models for intrinsically disordered proteins, both in solution and in the presence of uniformly charged, ideal surfaces. The models in question are either coarse-grained or atomistic in nature, and their applications are dependent on the specific purpose of each study. Both, Metropolis Monte Carlo and molecular dynamics simulations were employed to execute them.In regard to the coarse-grained models, it was found that a simple physical model can be used to mimic the properties of flexible proteins, helping to understand how and why these proteins adsorb to surfaces under certain conditions. The same model later shown that two disordered proteins from different sources (saliva and milk) possess similar structural and thermodynamic properties in solution and when adsorbed to surfaces, thus being hypothesized that it may be possible to use one of them as a substitute for the other under a pharmaceutical context.After a first indication that the atomistic models used until recently for the simulation of well-folded proteins may not be applicable to their disordered counterparts, it was then confirmed - by evaluating several such models against experimental evidence - that these models do indeed produce overly collapsed IDP conformational ensembles. New models, favoring protein–water over protein–protein interactions, were then shown to effectively produce more extended conformations, which are in much better agreement with each other and with experimental evidence. One of the new atomistic models was then used to perform the structural characterization of a disordered peptide conjugated to a small molecule, which has been shown to possess promising therapeutical applications. The value of computer simulations is well illustrated in this study, as the insight obtainable from experiment was limited and it was only through the analysis of the simulations that a possible link between the average conjugate structure and its increased antifungal activity is established.
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| 7. |
- Henriques, Joao, et al.
(författare)
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Molecular Dynamics Simulations of Intrinsically Disordered Proteins: Force Field Evaluation and Comparison with Experiment
- 2015
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 11:7, s. 3420-3431
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of studies using molecular dynamics (MD) simulations of unfolded and intrinsically disordered proteins (IDPs) suggest that current force fields sample conformations that are overly collapsed. Here, we study the applicability of several state-of-the-art MD force fields, of the AMBER and GROMOS variety, for the simulation of Histatin 5, a short (24 residues) cationic salivary IDP with antimicrobial and antifungal properties. The quality of the simulations is assessed in three complementary analyses: (i) protein shape and Size comparison with recent experimental small-angle X-ray scattering data; (ii) secondary structure prediction; (iii) energy landscape exploration and conformational Class analysis. Our results show that, indeed, standard force fields sample conformations that are too compact, being systematically unable to reproduce experimental evidence such as the scattering function, the shape of the protein as compared with the Kratky plot, and intrapeptide distances obtained through the pair distance distribution function, p(r). The consistency of this deviation suggests that the problem is not mainly due to protein-protein or water-water interactions, whose parametrization varies the most between force fields and water models. In fact, as originally proposed in [Best et al. J. Chem. Theory Comput. 2014, 10, 5113-5124.], balanced protein-water interactions may be the key to solving this problem. Our simulations using this approach produce results in very good agreement with experiment.
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| 8. |
- Henriques, Joao, et al.
(författare)
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Molecular Dynamics Simulations of Intrinsically Disordered Proteins: On the Accuracy of the TIP4P‐D Water Model and the Representativeness of Protein Disorder Models
- 2016
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 12:7, s. 3407-3415
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Tidskriftsartikel (refereegranskat)abstract
- Here, we first present a follow-up to a previous work by our group on the problematic of molecular dynamics simulations of intrinsically disordered proteins (IDPs) [Henriques et al. J. Chem. Theory Comput. 2015, 11, 3420−3431], using the recently developed TIP4P-D water model. When used in conjunction with the standard AMBER ff99SB-ILDN force field and applied to the simulation of Histatin 5, our IDP model, we obtain results which are in excellent agreement with the best performing IDP-suitable force field from the earlier study and with experiment. We then assess the representativeness of the IDP models used in these and similar studies, finding that most are too short in comparison to the average IDP and contain a bias toward hydrophilic amino acid residues. Moreover, several key order- and disorder-promoting residues are also found to be misrepresented. It seems appropriate for future studies to address these issues.
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| 9. |
- Henriques, João, et al.
(författare)
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On the Calculation of SAXS Profiles of Folded and Intrinsically Disordered Proteins from Computer Simulations
- 2018
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836. ; 430:16, s. 2521-2539
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Tidskriftsartikel (refereegranskat)abstract
- Solution techniques such as small-angle X-ray scattering (SAXS) play a central role in structural studies of intrinsically disordered proteins (IDPs); yet, due to low resolution, it is generally necessary to combine SAXS with additional experimental sources of data and to use molecular simulations. Computational methods for the calculation of theoretical SAXS intensity profiles can be separated into two groups, depending on whether the solvent is modeled implicitly as continuous electron density or considered explicitly. The former offers reduced computational cost but requires the definition of a number of free parameters to account for, for example, the excess density of the solvation layer. Overfitting can thus be an issue, particularly when the structural ensemble is unknown. Here, we investigate and show how small variations of the contrast of the hydration shell, δρ, severely affect the outcome, analysis and interpretation of computed SAXS profiles for folded and disordered proteins. For both the folded and disordered proteins studied here, using a default δρ may, in some cases, result in the calculation of non-representative SAXS profiles, leading to an overestimation of their size and a misinterpretation of their structural nature. The solvation layer of the different IDP simulations also impacts their size estimates differently, depending on the protein force field used. The same is not true for the folded protein simulations, suggesting differences in the solvation of the two classes of proteins, and indicating that different force fields optimized for IDPs may cause expansion of the polypeptide chain through different physical mechanisms.
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| 10. |
- Jephthah, Stephanie, et al.
(författare)
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Structural Characterization of Histatin 5-Spermidine Conjugates : A Combined Experimental and Theoretical Study
- 2017
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Ingår i: Journal of Chemical Information and Modeling. - : American Chemical Society (ACS). - 1549-9596 .- 1549-960X. ; 57:6, s. 1330-1341
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Tidskriftsartikel (refereegranskat)abstract
- Histatin 5 (Hst5) is a naturally occurring antimicrobial peptide that acts as the first line of defense against oral candidiasis. It has been shown that conjugation of the active Hst5 fragment, Hst54-15, and the polyamine spermidine (Spd) improves the candidacidal effect. Knowledge about the structure of these conjugates is, however, very limited. Thus, the aim of this study was to characterize the structural properties of the Hst54-15-Spd conjugates by performing atomistic molecular dynamics simulations in combination with small-angle X-ray scattering. It was shown that the Hst54-15-Spd conjugates adopt extended and slightly rigid random coil conformations without any secondary structure in aqueous solution. It is hypothesized that the increased fungal killing potential of Hst54-15-Spd, in comparison with the Spd-Hst54-15 conjugate, is due to the more extended conformations of the former, which cause the bonded Spd molecule to be more accessible for recognition by polyamine transporters in the cell.
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| 11. |
- Kristan, Matej, et al.
(författare)
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The Sixth Visual Object Tracking VOT2018 Challenge Results
- 2019
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Ingår i: Computer Vision – ECCV 2018 Workshops. - Cham : Springer Publishing Company. - 9783030110086 - 9783030110093 ; , s. 3-53
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2018 is the sixth annual tracker benchmarking activity organized by the VOT initiative. Results of over eighty trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis and a “real-time” experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. A long-term tracking subchallenge has been introduced to the set of standard VOT sub-challenges. The new subchallenge focuses on long-term tracking properties, namely coping with target disappearance and reappearance. A new dataset has been compiled and a performance evaluation methodology that focuses on long-term tracking capabilities has been adopted. The VOT toolkit has been updated to support both standard short-term and the new long-term tracking subchallenges. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website (http://votchallenge.net).
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| 12. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2014 Challenge Results
- 2015
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Ingår i: COMPUTER VISION - ECCV 2014 WORKSHOPS, PT II. - Cham : Springer. - 9783319161808 - 9783319161815 ; , s. 191-217
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge 2014, VOT2014, aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 38 trackers are presented. The number of tested trackers makes VOT 2014 the largest benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the appendix. Features of the VOT2014 challenge that go beyond its VOT2013 predecessor are introduced: (i) a new VOT2014 dataset with full annotation of targets by rotated bounding boxes and per-frame attribute, (ii) extensions of the VOT2013 evaluation methodology, (iii) a new unit for tracking speed assessment less dependent on the hardware and (iv) the VOT2014 evaluation toolkit that significantly speeds up execution of experiments. The dataset, the evaluation kit as well as the results are publicly available at the challenge website (http://votchallenge.net).
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| 13. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2016 Challenge Results
- 2016
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Ingår i: COMPUTER VISION - ECCV 2016 WORKSHOPS, PT II. - Cham : SPRINGER INT PUBLISHING AG. - 9783319488813 - 9783319488806 ; , s. 777-823
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2016 aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 70 trackers are presented, with a large number of trackers being published at major computer vision conferences and journals in the recent years. The number of tested state-of-the-art trackers makes the VOT 2016 the largest and most challenging benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the Appendix. The VOT2016 goes beyond its predecessors by (i) introducing a new semi-automatic ground truth bounding box annotation methodology and (ii) extending the evaluation system with the no-reset experiment.
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| 14. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2017 challenge results
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2017). - : IEEE. - 9781538610343 ; , s. 1949-1972
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2017 is the fifth annual tracker benchmarking activity organized by the VOT initiative. Results of 51 trackers are presented; many are state-of-the-art published at major computer vision conferences or journals in recent years. The evaluation included the standard VOT and other popular methodologies and a new "real-time" experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The VOT2017 goes beyond its predecessors by (i) improving the VOT public dataset and introducing a separate VOT2017 sequestered dataset, (ii) introducing a realtime tracking experiment and (iii) releasing a redesigned toolkit that supports complex experiments. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 15. |
- Kurut Sabanoglu, Anil, et al.
(författare)
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Role of histidine for charge regulation of unstructured peptides at interfaces and in bulk.
- 2014
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Ingår i: Proteins. - : Wiley. - 0887-3585. ; 82:4, s. 657-667
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Tidskriftsartikel (refereegranskat)abstract
- Histidine rich, unstructured peptides adsorb to charged interfaces such as mineral surfaces and microbial cell membranes. At a molecular level, we investigate the adsorption mechanism as a function of pH, salt, and multivalent ions showing that (1) proton charge fluctuations are - in contrast to the majority of proteins - optimal at neutral pH, promoting electrostatic interactions with anionic surfaces through charge regulation, and (2) specific zinc(II)-histidine binding competes with protons and ensures an unusually constant charge distribution over a broad pH interval. In turn this further enhances surface adsorption. Our analysis is based on atomistic molecular dynamics simulations, coarse grained Metropolis Monte Carlo, and classical polymer density functional theory. This multi-scale modelling provides a consistent picture in good agreement with experimental data on Histatin 5, an antimicrobial salivary peptide. Biological function is discussed and we suggest that charge regulation is a significant driving force for the remarkably robust activity of histidine rich antimicrobial peptides.
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| 16. |
- Mantei, Franz, et al.
(författare)
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The night cooling effect on a C-PVT solar collector
- 2015
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Ingår i: ISES Solar World Congress 2015, Conference Proceedings. - Freiburg, Germany : International Solar Energy Society. - 9783981465952 ; , s. 1167-1175
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Konferensbidrag (refereegranskat)abstract
- Night cooling consists in running a fluid through a solar panel during the night in order to reduce the fluid temperature which can be used for cooling applications. Radiative heat losses can allow the fluid to reach temperatures below ambient while conduction and convection works to equalize the collector with the ambient temperature. This paper analyzes the possibility of using an asymmetric concentrating photovoltaic thermal solar collector (C-PVT) for cooling applications during the night by losing heat through convection, conduction and irradiation. The cooling performance of the C-PVT collector has been measured during the night at different inlet temperatures in the interval of 13 to 38°C which corresponded to a AT (between the collector average and the ambient) from 6 to 28°C. The performance of the tested C-PVT collector has been measured at different inlet temperatures in an interval of 13 to 38°C. During all performed measurements, the radiation losses did not drive the collector temperature below ambient temperature. With high AT (between the inlet and the ambient) of 30°C, a 1,85°C temperature decrease in the fluid was obtained. For AT of 14°C, the temperature decrease was only 0,88°C. The measurements showed a night U-value for the Solarus C-PVT of 4,2 W/m2K This correlates well with previous papers showing measurements taken during the day. Heat losses seem to be dominated by convection and conduction due to the existence of the glass in the collector. Despite this, a measurable relation between heat losses and cloudiness factor exists. This shows that the irradiance losses are not negligible. Only very specific applications can be suited for night cooling with this collector design, since it is not so common to have applications that require low grade cooling during the night time or justify storing this energy. However, if the C-PVT design was made without a glass cover, the results could potentially be very different for locations with many clear nights.
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| 17. |
- Martins Mattos, Marina, et al.
(författare)
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Analysis of voltage control using V2G technology to support low voltage distribution networks
- 2024
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Ingår i: IET Generation, Transmission & Distribution. - : John Wiley & Sons. - 1751-8687 .- 1751-8695. ; 18:6, s. 1133-1157
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Tidskriftsartikel (refereegranskat)abstract
- The decarbonization of the power generation and transport sector encourage the analysis of connection of distributed energy resources (DER), such as electric vehicles (EVs), to the electrical system, as well as the evaluation of their impact on smart cities. A better understanding of the negative impacts on the power systems will lead to propose mitigation measures and eventually revolutionize the way distributed generation works. This paper aims at modelling and evaluating the impact of EVs on a real distribution network. The energy system chosen operates at 60 Hz, 34.5 kV (medium voltage) and 0.208 kV (low voltage) and it is simulated using PSCAD/EMTDC. To reproduce realistic user consumption profiles, dynamic load profiles based on EV owners behaviour have been simulated. The vehicle-to-grid (V2G) technology is modelled to mitigate the impacts of high penetration of EVs by supporting the network from undervoltage. The results show the importance of active management in modern power systems, especially considering the increase in DER penetration expected for the coming years. This work shows the benefits of implementing V2G technology while highlighting the challenges involved in a real case. This paper aims at modelling and evaluating the impact of EVs on a real distribution network. The V2G technology is modelled to mitigate the impacts of high penetration of EVs by supporting the network from undervoltage. This work shows the benefits of implementing V2G technology while highlighting the challenges involved in a real case.image
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| 18. |
- Proletov, Ian, et al.
(författare)
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Primary and secondary glomerulonephritides 1.
- 2014
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Ingår i: Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association. - : Oxford University Press (OUP). - 1460-2385. ; 29 Suppl 3:May, s. 186-200
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Tidskriftsartikel (refereegranskat)
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| 19. |
- Santangelo, James S., et al.
(författare)
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Global urban environmental change drives adaptation in white clover
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 375
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Tidskriftsartikel (refereegranskat)abstract
- Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural dines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.
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