| 1. |
- DAWODY, JAZAER, 1959, et al.
(författare)
-
An integrated system for energy-efficient exhaust aftertreatment for heavy-duty vehicles
- 2015
-
Ingår i: Renewable Energy in the Service of Mankind. - Cham : Springer International Publishing. - 9783319177779 - 9783319177762 ; 1, s. 133-143
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- © Springer International Publishing Switzerland 2015. This chapter presents a unique system approach applied in a joint academic- industrial research programme, E4 Mistra, to attain the goals of high energy efficiency and low emissions in an exhaust aftertreatment system for heavy-duty vehicles. The high energy efficiency is achieved by heat recuperation, onboard hydrogen production for NOx reduction, and by finding new solutions for making the aftertreatment system active at low exhaust temperatures. To reach low particulate emissions, a mechanical filter using a sintered metal powder is developed and coated with catalytic material to improve the soot oxidation efficiency. Low NOx emissions are achieved by an efficient NOx reduction catalyst. The integrated E4 Mistra system comprises four technological advances: thermoelectric (TE) materials for heat recuperation, catalytic reduction of NOx over innovative catalyst substrates using either the onboard diesel or biodiesel, H2 from a high-efficiency fuel reformer, and particulate filtration over a porous metal filter. The TE materials are used in a TE generator (TEG) which converts thermal energy into electricity. The TEG is used to recuperate heat from the exhaust-gas recirculation (EGR) circuit of heavy-duty trucks and is expected to generate ~1 kW electric power from 20 kW heat in the exhaust gas. The TEG is integrated in a plate heat exchanger (HEX) designed particularly for this application. Apart from the knowledge and experiences in TEG and heat exchange technologies, a thorough fluid dynamics and TE analysis are performed in this project to understand the governing processes and optimize the system accordingly. The components of the E4 Mistra system are explained in the chapter in addition to test results, which show the system's capacity for H2 production, NOx conversion, particulate matter filtration and soot oxidation, and finally electric power generation via heat recuperation from the exhaust gas using the developed TEG-HEX system.
|
|
| 2. |
- Joffrin, E., et al.
(författare)
-
Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
-
Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
|
|
| 3. |
- Wilkie, George, 1983, et al.
(författare)
-
First principles of modelling the stabilization of microturbulence by fast ions
- 2018
-
Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 58:8
-
Tidskriftsartikel (refereegranskat)abstract
- The observation that fast ions stabilize ion-temperature-gradient-driven microturbulence has profound implications for future fusion reactors. It is also important in optimizing the performance of present-day devices. In this work, we examine in detail the phenomenology of fast ion stabilization and present a reduced model which describes this effect. This model is derived from the high-energy limit of the gyrokinetic equation and extends the existing 'dilution' model to account for nontrivial fast ion kinetics. Our model provides a physically-transparent explanation for the observed stabilization and makes several key qualitative predictions. Firstly, that different classes of fast ions, depending on their radial density or temperature variation, have different stabilizing properties. Secondly, that zonal flows are an important ingredient in this effect precisely because the fast ion zonal response is negligible. Finally, that in the limit of highly-energetic fast ions, their response approaches that of the 'dilution' model; in particular, alpha particles are expected to have little, if any, stabilizing effect on plasma turbulence. We support these conclusions through detailed linear and nonlinear gyrokinetic simulations.
|
|
| 4. |
- Andersson, Anders, 1983-, et al.
(författare)
-
A Framework for Credibility Assessment of a Powertrain Model in Driving Simulator Studies
- 2016
-
Ingår i: Proceedings of the 36th FISITA World Automotive Congress.
-
Konferensbidrag (refereegranskat)abstract
- When performing a driving simulator study, validity of the vehicle model for the intended driving task is of key importance; otherwise, the reliability of the study results might be jeopardized. In this paper a framework for real-time credibility assessment of the simulated longitudinal dynamics by a powertrain model in a moving base driving simulator is presented. The framework consists of the physical system model and a quality model which run in parallel in real time. The developed framework has been evaluated by offline simulations, as well as in real-time in a moving base driving simulator. The evaluation results showed that the developed framework can accurately capture the validity of the powertrain model in different driving conditions and provide the credibility level of the simulation results to the simulator operator in real-time.
|
|
| 5. |
- Andersson, Anders, 1983-
(författare)
-
Distributed Moving Base Driving Simulators : Technology, Performance, and Requirements
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Development of new functionality and smart systems for different types of vehicles is accelerating with the advent of new emerging technologies such as connected and autonomous vehicles. To ensure that these new systems and functions work as intended, flexible and credible evaluation tools are necessary. One example of this type of tool is a driving simulator, which can be used for testing new and existing vehicle concepts and driver support systems. When a driver in a driving simulator operates it in the same way as they would in actual traffic, you get a realistic evaluation of what you want to investigate. Two advantages of a driving simulator are (1.) that you can repeat the same situation several times over a short period of time, and (2.) you can study driver reactions during dangerous situations that could result in serious injuries if they occurred in the real world. An important component of a driving simulator is the vehicle model, i.e., the model that describes how the vehicle reacts to its surroundings and driver inputs. To increase the simulator realism or the computational performance, it is possible to divide the vehicle model into subsystems that run on different computers that are connected in a network. A subsystem can also be replaced with hardware using so-called hardware-in-the-loop simulation, and can then be connected to the rest of the vehicle model using a specified interface. The technique of dividing a model into smaller subsystems running on separate nodes that communicate through a network is called distributed simulation.This thesis investigates if and how a distributed simulator design might facilitate the maintenance and new development required for a driving simulator to be able to keep up with the increasing pace of vehicle development. For this purpose, three different distributed simulator solutions have been designed, built, and analyzed with the aim of constructing distributed simulators, including external hardware, where the simulation achieves the same degree of realism as with a traditional driving simulator. One of these simulator solutions has been used to create a parameterized powertrain model that can be configured to represent any of a number of different vehicles. Furthermore, the driver's driving task is combined with the powertrain model to monitor deviations. After the powertrain model was created, subsystems from a simulator solution and the powertrain model have been transferred to a Modelica environment. The goal is to create a framework for requirement testing that guarantees sufficient realism, also for a distributed driving simulation.The results show that the distributed simulators we have developed work well overall with satisfactory performance. It is important to manage the vehicle model and how it is connected to a distributed system. In the distributed driveline simulator setup, the network delays were so small that they could be ignored, i.e., they did not affect the driving experience. However, if one gradually increases the delays, a driver in the distributed simulator will change his/her behavior. The impact of communication latency on a distributed simulator also depends on the simulator application, where different usages of the simulator, i.e., different simulator studies, will have different demands. We believe that many simulator studies could be performed using a distributed setup. One issue is how modifications to the system affect the vehicle model and the desired behavior. This leads to the need for methodology for managing model requirements. In order to detect model deviations in the simulator environment, a monitoring aid has been implemented to help notify test managers when a model behaves strangely or is driven outside of its validated region. Since the availability of distributed laboratory equipment can be limited, the possibility of using Modelica (which is an equation-based and object-oriented programming language) for simulating subsystems is also examined. Implementation of the model in Modelica has also been extended with requirements management, and in this work a framework is proposed for automatically evaluating the model in a tool.
|
|
| 6. |
- Andersson, Anders, 1983-, et al.
(författare)
-
Framtagning av loktågsmodell för VTI:s tågsimulator
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Genom höjda hastigheter för godståg finns möjligheter till en högre prioritering av trafikslaget hos tågtrafikledningen, vilket i sig är en kapacitetsvinst och bör ge upphov till bättre flöden och högre kapacitet på det svenska järnvägsnätet (framför allt på stambanorna). Simulatorer är ett effektivt och säkert sätt att undersöka effekter av förändringar på både förarbeteende och kapacitet.Syftet med det här projektet var att skapa kapacitetshöjande möjligheter och åtgärder genom att ta fram en loktågssimulator och undersöka möjliga användningsområden för denna. Målet med projektet var att få fram en loktågssimulator, bestående av ett lok och ett antal vagnar, som kan användas i studier för att öka kapaciteten genom till exempel optimerad hastighet, och därmed förändrade bromsprofiler, för loktåg. Projektet har levererat kunskap i form av nya testmetoder, en loktågssimulator samt mjukvaruplattform för ytterligare testverksamhet.Projektet genomfördes i tre successiva etapper. I den första etappen genomfördes en förstudie med lokförare, operatörer och problemägare, som gav forskarna en förståelse för förarmiljön. Här samlades även in en del av det underlag som krävdes för utveckling av loktågsimulatorn. I den andra etappen utvecklades en simulator för loktåg (mjukvara och hårdvara). Etapp tre var en valideringsstudie tillsammans med lokförare.Ett förarbord av modellen Traxx köptes in från en tysk tillverkare. Fordonsmodellen utvecklades från en enstaka enhet, Reginamodell (motorvagnståg), till en kombination av flera enheter. Loktåget i simulatorn består av ett eller flera draglok samt ett antal vagnar med en total längd på maximalt 750 meter. Som draglok används ett lok av modellen Traxx. För varje enhet, lok och vagn, krävs data över enheten: längd, vikt, last, broms-, rull- och luftmotstånd. För lok tillkommer dessutom information om ljud, drivning, broms (återmatande elbroms samt konventionell pneumatisk broms (P-broms)), hyttutrustning med mera. För närvarande finns bansträckningen mellan Falköping–Jönköping–Forserum färdigmodellerad och kommer användas för loktågskörning med ATC. Modellen är konfigurerbar utifrån ett lok (Traxx) och i nuläget fyra olika vagnar. Dessa kan kopplas samman i olika kombinationer.Några användningsområden som diskuterades redan vid projektstart var dels de som naturligt kan kopplas till följder av längre och tyngre tåg, dels de idéer som uppkom som följd av den utrustning som köptes in. Vid Trafikverkets vintermöte genomfördes en workshop där ytterligare användningsområden diskuterades. Några av dessa handlar om utbildning,energieffektiv körning eller projektering. Utbildning och vissa typer av studier går att göra med den nu existerande loktågsmodellen, medan andra kräver antingen validering av parametrar eller viss vidareutveckling av modellen.Projektet har levererat kunskap i form av nya testmetoder, denna forskningsrapport och en produkt i form av en loktågssimulator samt mjukvaruplattform för ytterligare testverksamhet. Projektet har även levererat en nationell resurs i form av simulatormjukvara. Mjukvaran har lagt grunden för en kostnadseffektiv testverksamhet inom loktågsdomänen. En loktågssimulering (simulering av loktåg) har tagits fram, vilken kommer att vara värdefull som ett demonstrationsverktyg samt för utbildning, träning och projektering.
|
|
| 7. |
- Andersson, Anders, 1983-, et al.
(författare)
-
Freight train model for real-time simulation
- 2017
-
Ingår i: Dynamics of Vehicles on Roads and Tracks Vol 2.
-
Konferensbidrag (refereegranskat)abstract
- In an attempt to increse the freight transport capacity in Sweden, introduction of longer and heavier trains is investigated. To aid this investigation, a freight train simulator was designed and constructed. Here, the implemented freight train dynamics model is described, which includes slip control, a modular wagon model structrue and pneumatic brake system. Further, stable real-time performance of the implemented dynamics model is discussed.
|
|
| 8. |
- Andersson, Anders, 1983-, et al.
(författare)
-
Powertrain Model Assesment for Different Driving Tasks through Requirement Verification
- 2016
-
Ingår i: Proceedings of the 9th EUROSIM Congress on Modelling and Simulation.
-
Konferensbidrag (refereegranskat)abstract
- For assessing whether a system model is a good candidate for a particular simulation scenario or choosing the best system model between multiple design alternatives it is important to be able to evaluate the suitability of the system model. In this paper we present a methodology based on finite state machine requirements verifying system behavior in a Modelica environment where the intended system model usage is within a moving base driving simulator. A use case illustrate the methodology with a Modelica powertrain system model using replaceable components and measured data from a Golf V. The achieved results show the importance of context of requirements and how users are assisted in finding system model issues.
|
|
| 9. |
- Andersson, Anders, 1983-, et al.
(författare)
-
Vehicle model quality framework for moving base driving simulators, a powertrain model example
- 2018
-
Ingår i: International Journal of Vehicle Systems Modelling and Testing. - : InderScience Publishers. - 1745-6436 .- 1745-6444. ; 13:2, s. 93-108
-
Tidskriftsartikel (refereegranskat)abstract
- Moving base driving simulators, with an enclosed human driver, are often used to study driver-vehicle interaction or driver behaviour. Reliable results from such a driving simulator study strongly depend on the perceived realism by the driver in the performed driving task. Assuring sufficient fidelity for a vehicle dynamics model during a driving task is currently to a large degree a manual task. Focus here is to automate this process by employing a framework using collected driving data for detection of model quality for different driving tasks. Using this framework, a powertrain model credibility is predicted and assessed. Results show that chosen powertrain model is accurate enough for a driving scenario on rural roads/motorway, but need improvements for city driving. This was expected, considering the complexity of the vehicle dynamics model, and it was accurately captured by the proposed framework which includes real-time information to the simulator operator.
|
|
| 10. |
- Andersson, Emma, 1983-, et al.
(författare)
-
Improved Railway Timetable Robustness for Reduced Traffic Delays – a MILP approach
- 2015
-
Ingår i: 6th International Conference on Railway Operations Modelling and Analysis, Tokyo, Mars 23-26, 2015..
-
Konferensbidrag (refereegranskat)abstract
- Maintaining high on-time performance and at the same time having high capacity utilization is a challenge for several railway traffic systems. The system becomes sensitive to disturbances and delays are easily propagating in the network. One way to handle this problem is to create more robust timetables; timetables that can absorb delays and prevent them from propagating. This paper presents an optimization approach to reduce the propagating of delays with a more efficient margin allocation in the timetable. A Mixed Integer Linear Programming (MILP) model is proposed in which the existing margin time is re-allocated to increase the robustness for an existing timetable. The model re-allocates both runtime margin time and headway margin time to increase the robustness at specific delay sensitive points in a timetable. We illustrate the model’s applicability for a real-world case where an initial, feasible timetable is modified to create new timetables with increased robustness. These new timetables are then evaluated and compared to the initial timetable. We evaluate how the MILP approach affects the initial timetable structure and its capability to handle disturbances by exposing the initial and the modified timetables to some minor initial disturbances of the range 1 up to 7 minutes. The results show that it is possible to reduce the delays by re-allocating margin time, for example, the total delay at end station decreases with 28 % in our real-world example.
|
|
| 11. |
- Aramrattana, Maytheewat, et al.
(författare)
-
Testing cooperative intelligent transport systems in distributed simulators
- 2019
-
Ingår i: Transportation Research Part F. - : Elsevier Ltd. - 1369-8478 .- 1873-5517. ; 65, s. 206-216
-
Tidskriftsartikel (refereegranskat)abstract
- Simulation is often used as a technique to test and evaluate systems, as it provides a cost-efficient and safe alternative for testing and evaluation. A combination of simulators can be used to create high-fidelity and realistic test scenarios, especially when the systems-under-test are complex. An example of such complex systems is Cooperative Intelligent Transport Systems (C-ITS), which include many actors that are connected to each other via wireless communication in order to interact and cooperate. The majority of the actors in the systems are vehicles equipped with wireless communication modules, which can range from fully autonomous vehicles to manually driven vehicles. In order to test and evaluate C-ITS, this paper presents a distributed simulation framework that consists of (a) a moving base driving simulator; (b) a real-time vehicle simulator; and (c) network and traffic simulators. We present our approach for connecting and co-simulating the simulators. We report on limitation and performance that this simulation framework can achieve. Lastly, we discuss potential benefits and feasibility of using the simulation framework for testing of C-ITS.
|
|
| 12. |
- Busch, Susann, et al.
(författare)
-
Cellular organization and molecular differentiation model of breast cancer-associated fibroblasts
- 2017
-
Ingår i: Molecular Cancer. - : Springer Science and Business Media LLC. - 1476-4598. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The role of cancer-associated fibroblasts (CAFs) during tumour progression is obscured by the inherently complex, heterotypic nature of fibroblast cells and behaviours in various subtypes of malignancies. Therefore, we sought to identify distinct fibroblast subpopulations at the single-cell level. Methods: Using single-cell quantitative PCR as a powerful tool to study heterogeneity and rare cell events, in a high-throughput manner a panel of gene targets are run simultaneously on transcripts isolated from single cells obtained by fluorescence-activated cell sort. Assessment of cells with stem-like characteristics was attained by anchorage-independent, anoikis-resistant culture. Results: Single-cell analysis of fibroblasts and their tumour-activated counterparts demonstrated molecularly distinct cell types defined by differential expression of characteristic mesenchymal and fibroblast activation markers. Identified subpopulations presented overlapping gene expression patterns indicating transitional molecular states during fibroblast differentiation. Using single-cell resolution data we generated a molecular differentiation model which enabled the classification of patient-derived fibroblasts, validating our modelling approach. Remarkably, a subset of fibroblasts displayed expression of pluripotency markers, which was enriched for in non-adherent conditions. Yet the ability to form single-cell derived spheres was generally reduced in CAFs and upon fibroblast activation through TGF beta 1 ligand and cancer cell-secreted factors. Hence, our data imply the existence of putative stem/progenitor cells as a physiological feature of undifferentiated fibroblasts. Conclusions: Within this comprehensive study we have identified distinct and intersecting molecular profiles defining fibroblast activation states and propose that underlying cellular heterogeneity, fibroblasts are hierarchically organized. Understanding the molecular make-up of cellular organization and differentiation routes will facilitate the discovery of more specific markers for stromal subtypes and targets for anti-stromal therapies.
|
|
| 13. |
|
|
| 14. |
- Dini, Hoda, 1984-, et al.
(författare)
-
Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn
- 2018
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 710, s. 17-26
-
Tidskriftsartikel (refereegranskat)abstract
- A dislocation density-based constitutive model, including effects of microstructure scale and temperature, was calibrated to predict flow stress of an as-cast AZ91D (Mg-9%Al-1%Zn) alloy. Tensile stress-strain data, for strain rates from 10-4 up to 10-1 s-1 and temperatures from room temperature up to 190 °C were used for model calibration. The used model accounts for the interaction of various microstructure features with dislocations and thereby on the plastic properties. It was shown that the Secondary Dendrite Arm Spacing (SDAS) size was appropriate as an initial characteristic microstructural scale input to the model. However, as strain increased the influence of subcells size and total dislocation density dominated the flow stress. The calibrated temperature-dependent parameters were validated through a correlation between microstructure and the physics of the deforming alloy. The model was validated by comparison with dislocation density obtained by using Electron Backscattered Diffraction (EBSD) technique.
|
|
| 15. |
- Holmgren, Gustav, 1983-, et al.
(författare)
-
Expression Profiling of Human Pluripotent Stem Cell-Derived Cardiomyocytes Exposed to Doxorubicin-Integration and Visualization of Multi-Omics Data
- 2018
-
Ingår i: Toxicological Sciences. - : Oxford University Press (OUP). - 1096-6080 .- 1096-0929. ; 163:1, s. 182-195
-
Tidskriftsartikel (refereegranskat)abstract
- Anthracyclines, such as doxorubicin, are highly efficient chemotherapeutic agents against a variety of cancers. However, anthracyclines are also among the most cardiotoxic therapeutic drugs presently on the market. Chemotherapeutic-induced cardiomyopathy is one of the leading causes of disease and mortality in cancer survivors. The exact mechanisms responsible for doxorubicin-induced cardiomyopathy are not completely known, but the fact that the cardiotoxicity is dose-dependent and that there is a variation in time-to-onset of toxicity, and gender- and age differences suggests that several mechanisms may be involved. In this study, we investigated doxorubicin-induced cardiotoxicity in human pluripotent stem cell-derived cardiomyocytes using proteomics. In addition, different sources of omics data (protein, mRNA, and microRNA) from the same experimental setup were further combined and analyzed using newly developed methods to identify differential expression in data of various origin and types. Subsequently, the results were integrated in order to generate a combined visualization of the findings. In our experimental model system, we exposed cardiomyocytes derived from human pluripotent stem cells to doxorubicin for up to 2 days, followed by a wash-out period of additionally 12 days. Besides an effect on the cell morphology and cardiomyocyte functionality, the data show a strong effect of doxorubicin on all molecular levels investigated. Differential expression patterns that show a linkage between the proteome, transcriptome, and the regulatory microRNA network, were identified. These findings help to increase the understanding of the mechanisms behind anthracycline-induced cardiotoxicity and suggest putative biomarkers for this condition.
|
|
| 16. |
- Holmgren, Gustav, 1983-, et al.
(författare)
-
MicroRNAs as potential biomarkers for doxorubicin-induced cardiotoxicity
- 2016
-
Ingår i: Toxicology in Vitro. - : Elsevier BV. - 0887-2333 .- 1879-3177. ; 34, s. 26-34
-
Tidskriftsartikel (refereegranskat)abstract
- Anthracyclines, such as doxorubicin, are well-established, highly efficient anti-neoplastic drugs used for treatment of a variety of cancers, including solid tumors, leukemia, lymphomas, and breast cancer. The successful use of doxorubicin has, however, been hampered by severe cardiotoxic side-effects. In order to prevent or reverse negative side-effects of doxorubicin, it is important to find early biomarkers of heart injury and drug-induced cardiotoxicity. The high stability under extreme conditions, presence in various body fluids, and tissue specificity, makes,microRNAs very suitable as clinical.biomarkers. The present study aimed towards evaluating the early and late effects of doxorubicin on the microRNA expression in cardiomyocytes derived from human pluripotent stem cells. We report on several microRNAs, including miR-34a, miR-34b, miR-187, miR-199a, miR-199b, miR-146a, miR-15b, miR-130a, miR-214, and miR-424, that are differentially expressed upon, and after, treatment with doxorubicin. Investigation of the biological relevance of the identified microRNAs revealed connections to cardiomyocyte function and cardiotoxicity, thus supporting the findings of these microRNAs as potential biomarkers for drug-induced cardiotoxicity.
|
|
| 17. |
- Karlsson, Johan, 1984, et al.
(författare)
-
Ex vivo alendronate localization at the mesoporous titania implant/bone interface
- 2015
-
Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 26
-
Tidskriftsartikel (refereegranskat)abstract
- An attractive approach in implant technology is local drug delivery, and design of efficient, safe and reliable treatments. Ourhitherto strategy has been to coat Ti implants with a thin mesoporous TiO2 film that in turnis loaded with an osteoporosis drug, such as Alendronate (ALN) that is known to suppress osteoclastic activity. This system has proven highly successful and results in excellent osseointegration. However, more detailed information about drug-release and distribution at the bone/implant interface is needed. In this study, (14)C-ALN loaded titanium implants were placed up to 8weeks into rat tibia and the spatial-temporal distribution of the drug was evaluated. Autoradiography data demonstrated a sustained release of (14)C-ALN and the releaseddrug remained bound to bone in close vicinity, within 500 micrometers,of the implants. Liquid scintillation counting experiments confirmed that the distal transport of released (14)C-ALN was extremely low. The results are favorable as they show that ALN stays for a long time in the vicinity of the implant and may therefore improve for a long time the mechanical fixation of bone anchored implants. Moreover, these findings suggest due to the low systemic spreading a minimal risk of Alendronate related systemic side effects.
|
|
| 18. |
- Karlsson, Johan, 1984, et al.
(författare)
-
Stem cell homing using local delivery of plerixafor and stromal derived growth factor-1alpha for improved bone regeneration around Ti-implants
- 2016
-
Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 104:10, s. 2466-2475
-
Tidskriftsartikel (refereegranskat)abstract
- Triggering of the early healing events, including the recruitment of progenitor cells, has been suggested to promote bone regeneration. In implantology, local drug release technologies could provide an attractive approach to promote tissue regeneration. In this study, we targeted the chemotactic SDF-1a/CXCR4 axis that is responsible e.g. for the homing of stem cells to trauma sites. This was achieved by local delivery of plerixafor, an antagonist to CXCR4, and/or SDF-1a from titanium implants coated with mesoporous titania thin films with a pore size of 7.5 nm. In vitro drug delivery experiments demonstrated that the mesoporous coating provided a high drug loading capacity and controlled release. The subsequent in vivo study in rat tibia showed beneficial effects with respect to bone-implant anchorage and bone-formation along the surface of the implants when plerixafor and SDF-1a were delivered locally. The effect was most prominent by the finding that the combination of the drugs significantly improved the mechanical bone anchorage. These observations suggest that titanium implants with local delivery of drugs for enhanced local recruitment of progenitor cells have the ability to promote osseointegration. This approach may provide a potential strategy for the development of novel implant treatments.
|
|
| 19. |
- Köhncke, Ylva, et al.
(författare)
-
Self-rated intensity of habitual physical activities is positively associated with dopamine D-2/3 receptor availability and cognition
- 2018
-
Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 181, s. 605-616
-
Tidskriftsartikel (refereegranskat)abstract
- Between-person differences in cognitive performance in older age are associated with variations in physical activity. The neurotransmitter dopamine (DA) contributes to cognitive performance, and the DA system deteriorates with advancing age. Animal data and a patient study suggest that physical activity modulates DA receptor availability, but data from healthy humans are lacking. In a cross-sectional study with 178 adults aged 64-68 years, we investigated links among self-reported physical activity, D(2/3)DA receptor (D2/3DR) availability, and cognitive performance. D2/3DR availability was measured with [C-11]raclopride positron emission tomography at rest. We used structural equation modeling to obtain latent factors for processing speed, episodic memory, working memory, physical activity, and D2/3DR availability in caudate, putamen, and hippocampus. Physical activity intensity was positively associated with D2/3DR availability in caudate, but not putamen and hippocampus. Frequency of physical activity was not related to D2/3DR availability. Physical activity intensity was positively related to episodic memory and working memory. D2/3DR availability in caudate and hippocampus was positively related to episodic memory. Taken together, our results suggest that striatal DA availability might be a neurochemical correlate of episodic memory that is also associated with physical activity.
|
|
| 20. |
- Lövdén, Martin, et al.
(författare)
-
Latent-Profile Analysis Reveals Behavioral and Brain Correlates of Dopamine-Cognition Associations
- 2018
-
Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 28:11, s. 3894-3907
-
Tidskriftsartikel (refereegranskat)abstract
- Evidence suggests that associations between the neurotransmitter dopamine and cognition are nonmonotonic and open to modulation by various other factors. The functional implications of a given level of dopamine may therefore differ from person to person. By applying latent-profile analysis to a large (n = 181) sample of adults aged 64-68 years, we probabilistically identified 3 subgroups that explain the multivariate associations between dopamine D2/3R availability (probed with C-11-raclopride-PET, in cortical, striatal, and hippocampal regions) and cognitive performance (episodic memory, working memory, and perceptual speed). Generally, greater receptor availability was associated with better cognitive performance. However, we discovered a subgroup of individuals for which high availability, particularly in striatum, was associated with poor performance, especially for working memory. Relative to the rest of the sample, this subgroup also had lower education, higher body-mass index, and lower resting-state connectivity between caudate nucleus and dorsolateral prefrontal cortex. We conclude that a smaller subset of individuals induces a multivariate non-linear association between dopamine D2/3R availability and cognitive performance in this group of older adults, and discuss potential reasons for these differences that await further empirical scrutiny.
|
|
| 21. |
- Papenberg, Goran, et al.
(författare)
-
Mapping the landscape of human dopamine D2/3 receptors with [11C]raclopride
- 2019
-
Ingår i: Brain Structure and Function. - : Springer Science and Business Media LLC. - 1863-2653 .- 1863-2661. ; 224:8, s. 2871-2882
-
Tidskriftsartikel (refereegranskat)abstract
- The dopamine D2/3 system is fundamental for sensory, motor, emotional, and cognitive aspects of behavior. Small-scale human histopathological and animal studies show high density of D2/3 dopamine receptors (D2/3DR) in striatum, but also demonstrate the existence of such receptors across cortical and limbic regions. Assessment of D2/3DR BPND in the extrastriatal regions with [C-11]raclopride has long been considered unreliable due to the relatively low density of D2/3DR outside the striatum. We describe the distribution and interregional links of D2/3DR availability measured with PET and [C-11]raclopride across the human brain in a large sample (N = 176; age range 64-68 years). Structural equation modeling revealed that D2/3DR availability can be organized according to anatomical (nigrostriatal, mesolimbic, mesocortical) and functional (limbic, associative, sensorimotor) dopamine pathways. D2/3DR availability in corticolimbic functional subdivisions showed differential associations to corresponding striatal subdivisions, extending animal and pharmacological work. Our findings provide evidence on the dimensionality and organization of [C-11]raclopride D2/3DR availability in the living human brain that conforms to known dopaminergic pathways.
|
|
| 22. |
- Rodriguez, Juan, 1983, et al.
(författare)
-
Lack of the brain-specific isoform of apoptosis-inducing factor aggravates cerebral damage in a model of neonatal hypoxia-ischemia.
- 2018
-
Ingår i: Cell Death & Disease. - : Springer Science and Business Media LLC. - 2041-4889. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- Apoptosis-inducing factor (AIF) may contribute to neuronal cell death, and its influence is particularly prominent in the immature brain after hypoxia-ischemia (HI). A brain-specific AIF splice-isoform (AIF2) has recently been discovered, but has not yet been characterized at the genetic level. The aim of this study was to determine the functional and regulatory profile of AIF2 under physiological conditions and after HI in mice. We generated AIF2 knockout (KO) mice by removing the AIF2-specific exon and found that the relative expression of Aif1 mRNA increased in Aif2 KO mice and that this increase became even more pronounced as Aif2 KO mice aged compared to their wild-type (WT) littermates. Mitochondrial morphology and function, reproductive function, and behavior showed no differences between WT and Aif2 KO mice. However, lack of AIF2 enhanced brain injury in neonatal mice after HI compared to WT controls, and this effect was linked to increased oxidative stress but not to caspase-dependent or -independent apoptosis pathways. These results indicate that AIF2 deficiency exacerbates free radical production and HI-induced neonatal brain injury.
|
|
| 23. |
- Salami, Alireza, et al.
(författare)
-
Dopamine D-2/3 Binding Potential Modulates Neural Signatures of Working Memory in a Load-Dependent Fashion
- 2019
-
Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 39:3, s. 537-547
-
Tidskriftsartikel (refereegranskat)abstract
- Dopamine (DA) modulates corticostriatal connections. Studies in which imaging of the DA system is integrated with functional imaging during cognitive performance have yielded mixed findings. Some work has shown a link between striatal DA(measured by PET) and fMRI activations, whereas others have failed to observe such a relationship. One possible reason for these discrepant findings is differences in task demands, such that a more demanding task with greater prefrontal activations may yield a stronger association with DA. Moreover, a potential DA-BOLD association may be modulated by task performance. We studied 155 (104 normal-performing and 51 low-performing) healthy older adults (43% females) who underwent fMRI scanning while performing a working memory (WM) n-back task along with DA D-2/3 PET assessment using [C-11] raclopride. Using multivariate partial-least-squares analysis, we observed a significant pattern revealing positive associations of striatal as well as extrastriatal DA D-2/3 receptors to BOLD response in the thalamo-striatalcortical circuit, which supports WM functioning. Critically, the DA-BOLD association in normal-performing, but not low-performing, individuals was expressed in a load-dependent fashion, with stronger associations during 3-back than 1-/2-back conditions. Moreover, normal-performing adults expressing upregulated BOLD in response to increasing task demands showed a stronger DA-BOLD association during 3-back, whereas low-performing individuals expressed a stronger association during 2-back conditions. This pattern suggests a nonlinear DA-BOLD performance association, with the strongest link at the maximum capacity level. Together, our results suggest that DA may have a stronger impact on functional brain responses during more demanding cognitive tasks.
|
|
| 24. |
|
|
| 25. |
- Torstensson, Peter, 1981-, et al.
(författare)
-
Use of numerical simulation to map and mitigate railway particle emissions
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This feasibility study is an interdisciplinary collaboration between three research institutes (VTI, Chalmers University of Technology and RISE) and a railway brake manufacturer (Faiveley Transport Nordic). Senior researchers specialized on numerical modelling of friction brakes and on particle matters (PM), are combined with expertise in the field of train driving simulation to reduce railway’s impact on environment and human health. The train driving simulator of VTI is further developed to account for the wear generated at the brake blocks and in the wheel‒rail contact. A literature study that focuses on prediction of railway particle emissions is presented
|
|
| 26. |
- Waldén, Katarina, 1983, et al.
(författare)
-
Effects of fibrinogen supplementation on clot formation in blood samples from cardiac surgery patients before and after tranexamic acid administration
- 2019
-
Ingår i: Transfusion Medicine. - : Wiley. - 0958-7578 .- 1365-3148. ; 29:5, s. 319-324
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: To investigate if supplementation with fibrinogen concentrate to blood samples collected after tranexamic acid administration improve clot formation more than what can be achieved with fibrinogen in the absence of tranexamic acid. Background: It is not known if the combination of fibrinogen and tranexamic acid has additional effects than what can be achieved individually. Methods: Four blood samples were collected from 15 coronary artery bypass patients. Two samples were collected before surgery, before and after 2g tranexamic acid was administered. The preoperative samples were diluted to haematocrit 21%. Two samples were collected after surgery, before and after a second dose of 2g tranexamic acid. Fibrinogen concentrate corresponding to a dose of 3g in a 70-kg patient was added to the samples. Platelet-independent clotting time and maximum clot firmness assessed by thromboelastometry (ROTEM-FIBTEM®) were compared between the samples. Results: Administration of tranexamic acid shortened clotting time marginally (−6%) before surgery, P=0·029) but did not influence clot firmness. Fibrinogen concentrate shortened clotting time (−14% before and −12% after surgery, both P=0·003) and increased clot firmness (+51 and +39%, both P<0·001). The effects of fibrinogen did not differ before and after tranexamic acid administration. Fibrinolysis was not detected in any sample. Conclusions: The results of this in vitro study suggest that the enhancing effects of fibrinogen on clot firmness in blood samples from cardiac surgery patients are not further increased in the presence of tranexamic acid. Further studies on patients with ongoing bleeding and/or hyperfibrinolysis are necessary to validate the results. © 2019 British Blood Transfusion Society
|
|
