| 1. |
- Bengtsson, Martin, et al.
(författare)
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Acoustic Streaming - Ultrasonic Agitation in Microchannels
- 2003
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Ingår i: [Host publication title missing]. - 1545-8288. ; 2, s. 939-942
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Konferensbidrag (refereegranskat)abstract
- This paper describes an acoustic method to induce rotating vortexflows in microchannels. The method is tested on two different systems, a mixing channel with two paralell flows and a porous silicon microreactor for protein digestion. A significant increase of the mixing ratio is detected in both cases.
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| 2. |
- Bengtsson, Martin, et al.
(författare)
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Influence of Nonuniform Channel Width Distribution in Porous Silicon High Aspect Ratio Parallel Channel Micro Reactors
- 2005
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Ingår i: [Host publication title missing]. - 0854046437 ; 1, s. 629-631
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Konferensbidrag (refereegranskat)abstract
- The paper focuses on the fact that, since the flow rate in parallel channels relies strongly on the channel width, the combination may lead to inaccurate results if errors in the fabrication process lead to an uneven distribution of channel widths. Parallel channel enzyme reactors were designed with channel widths distributed normally with different degrees of standard deviation. The reactors were then evaluated with regard to dispersion and to catalytic effect of the immobilised enzyme. It was shown that for lower concentrations the catalytic efficiency decreased significantly even for small variations in the distribution of channel widths and reactors with poor homogeneity in channel widths also diluted the sample more than the others.
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| 3. |
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| 4. |
- Evander, Mikael, et al.
(författare)
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Acoustic trapping of cells in a microfluidic format
- 2005
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Ingår i: Proceedings of µTAS 2005 Conference. ; 1, s. 515-517
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Konferensbidrag (refereegranskat)abstract
- This paper presents, for the first time, non-contact acoustic trapping of cells in a microfluidic format. The employed acoustic force maintains the cells in the center of a fluidic channel while allowing for perfusion of e.g. nutrients or drugs as well as optical monitoring of the cells. Neural stem cells have been acoustically trapped and tested for viability after 15 minutes of ultrasonic radiation. It is also shown that it is possible to grow yeast cells suspended in an acoustic standing wave while perfusing with cell media.
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| 5. |
- Hantson, Stijn, et al.
(författare)
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The status and challenge of global fire modelling
- 2016
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 13:11, s. 3359-3375
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Tidskriftsartikel (refereegranskat)abstract
- Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.
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| 6. |
- Harrison, Sandy P., et al.
(författare)
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Development and testing scenarios for implementing land use and land cover changes during the Holocene in Earth system model experiments
- 2020
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Ingår i: Geoscientific Model Development. - : Copernicus Gesellschaft MBH. - 1991-959X .- 1991-9603. ; 13:2, s. 805-824
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic changes in land use and land cover (LULC) during the pre-industrial Holocene could have affected regional and global climate. Existing scenarios of LULC changes during the Holocene are based on relatively simple assumptions and highly uncertain estimates of population changes through time. Archaeological and palaeoenvironmental reconstructions have the potential to refine these assumptions and estimates. The Past Global Changes (PAGES) LandCover6k initiative is working towards improved reconstructions of LULC globally. In this paper, we document the types of archaeological data that are being collated and how they will be used to improve LULC reconstructions. Given the large methodological uncertainties involved, both in reconstructing LULC from the archaeological data and in implementing these reconstructions into global scenarios of LULC, we propose a protocol to evaluate the revised scenarios using independent pollen-based reconstructions of land cover and climate. Further evaluation of the revised scenarios involves carbon cycle model simulations to determine whether the LULC reconstructions are consistent with constraints provided by ice core records of CO2 evolution and modern-day LULC. Finally, the protocol outlines how the improved LULC reconstructions will be used in palaeoclimate simulations in the Palaeoclimate Modelling Intercomparison Project to quantify the magnitude of anthropogenic impacts on climate through time and ultimately to improve the realism of Holocene climate simulations.
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| 7. |
- Johansson, Linda, et al.
(författare)
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Temperature evaluation of soft and hard PZT transducers for ultrasonic
- 2005
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Ingår i: Proceedings of µTAS 2005 Conference. ; 2, s. 1428-1430
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Konferensbidrag (refereegranskat)abstract
- This paper reports a comparison of soft and hard piezoceramic transducer materials used for ultrasonic particle trapping in a microfluidic bioanalytical platform. The investigation is made with the objective to obtain high acoustic forces with a minimum of temperature increase. Themperature is a critical parameter for bioassays and most often need to be kept below a certain level to allow handling of e.g. temperature sensitive proteins. The main conclusion in this paper is that it is possible to get efficieint trapping with a temperature increase of only a few degrees using a hard type III transducer material.
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| 8. |
- Lenshof, Andreas, et al.
(författare)
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Improved design and performance of an acoustically operated multi channel particle separation chip
- 2005
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Ingår i: [Host publication title missing]. ; 1, s. 575-577
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Konferensbidrag (refereegranskat)abstract
- An improved design for acoustic particle separation in multichannel chips is presented. By wavelength matching of the microfluidic channel widths and the width of the interlacing bulk silicon, a well tuned resonating multilayer system can be accomplished. The acoustically tuned microchip offers considerable improvements in regards to particle focusing performance, i.e. separation efficiency, at fixed ultrasonic input power.
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| 9. |
- Lilliehorn, Tobias, et al.
(författare)
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Bioassays on ultrasonically trapped microbead clusters in microfluidic systems
- 2004
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Ingår i: Micro Total Analysis Systems 2004. - 0854048960 ; 2, s. 327-329
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Konferensbidrag (refereegranskat)abstract
- The handling of biochemically functionalised beads or particles is becoming increasingly important in µTAS. Bead-based analysis of e.g. proteins can be made sensitive due to the large active surface area and flexible by chemical design of the bead surface. We have developed a microfluidic device utilising an array of integrated and individually controlled ultrasonic microtransducers for particle trapping [1]. Particles inserted in the device are subjected to acoustic radiation forces [2] confining them at localised trapping sites. We would now, for the first time at an international conference, like to present a technique for performing bioassays on such ultrasonically trapped beads in microfluidic systems. The microfluidic device is shown in Fig. 1, where the piezoceramic ultrasonic transducers can be seen in the channel crossings in the insert. The device is designed as an acoustic resonator, to obtain localised standing acoustic waves at each transducer with essentially one pressure node in the middle of the 72 µm deep channel when operated near 10 MHz. This configuration is chosen to keep trapped particles away from the interior surfaces of the device, thus enabling fast switching of beads with a minimum in carry-over between assays. The fluidic chip, shown in Fig. 2, is designed to allow injection of microbeads, washing fluid and sample to the three trapping sites. It has been shown that the microbead clusters, as shown in Fig. 3, can be trapped at considerably high perfusion rates, up to 10 µl/min, Fig 4. As a model bioassay, 6.7 µm biotin-covered beads (PC-B-6.0, Gerlinde Kisker, Germany) were injected and transported to one tapping site using washing fluid (water). Activating the transducer trapped the beads. A solution of FITC-tagged avidin was perfused over the bead bed at 3 µl/min, using the corresponding orthogonal sample channel. After 100 s the sample flow was turned off and the bead trap was washed by perfusing water at 3 µl/min. The fluorescence response from the trapped bead clusters was monitored during the assay, and the result is shown in Fig. 5. After excess avidin was washed from the bead trap, a measured step response . indicated that avidin had bound to the beads. Finally the possibility of moving trapped microbeads between the individually controlled trapping sites in the device is shown in Fig. 6, where the transducers are activated sequentially while keeping the bead carrying washing fluid at 3 µl/min during the experiment. Work in the near future will be focused on optimising the device with respect to the bioassay performance, and in a longer perspective on expanding the concept to two dimensions to enable a new dynamic mode of generating bioanalytical arrays.
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| 10. |
- Morrison, Kathleen D., et al.
(författare)
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Mapping past human land use using archaeological data : A new classification for global land use synthesis and data harmonization
- 2021
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- In the 12,000 years preceding the Industrial Revolution, human activities led to significant changes in land cover, plant and animal distributions, surface hydrology, and biochemical cycles. Earth system models suggest that this anthropogenic land cover change influenced regional and global climate. However, the representation of past land use in earth system models is currently oversimplified. As a result, there are large uncertainties in the current understanding of the past and current state of the earth system. In order to improve representation of the variety and scale of impacts that past land use had on the earth system, a global effort is underway to aggregate and synthesize archaeological and historical evidence of land use systems. Here we present a simple, hierarchical classification of land use systems designed to be used with archaeological and historical data at a global scale and a schema of codes that identify land use practices common to a range of systems, both implemented in a geospatial database. The classification scheme and database resulted from an extensive process of consultation with researchers worldwide. Our scheme is designed to deliver consistent, empirically robust data for the improvement of land use models, while simultaneously allowing for a comparative, detailed mapping of land use relevant to the needs of historical scholars. To illustrate the benefits of the classification scheme and methods for mapping historical land use, we apply it to Mesopotamia and Arabia at 6 kya (c. 4000 BCE). The scheme will be used to describe land use by the Past Global Changes (PAGES) LandCover6k working group, an international project comprised of archaeologists, historians, geographers, paleoecologists, and modelers. Beyond this, the scheme has a wide utility for creating a common language between research and policy communities, linking archaeologists with climate modelers, biodiversity conservation workers and initiatives.
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