| 1. |
- Andrén, Daniel, 1991, et al.
(författare)
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Probing Photothermal Effects on Optically Trapped Gold Nanorods by Simultaneous Plasmon Spectroscopy and Brownian Dynamics Analysis
- 2017
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 11:10, s. 10053-10061
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic gold nanorods are prime candidates for a variety of biomedical, spectroscopy, data storage, and sensing applications. It was recently shown that gold nanorods optically trapped by a focused circularly polarized laser beam can function as extremely efficient nanoscopic rotary motors. The system holds promise for-applications ranging from nanofluidic flow control and nanorobotics to biomolecular actuation and analysis. However, to fully exploit this potential, one needs to be able to control and understand heating effects associated with laser trapping. We investigated photothermal heating of individual rotating gold nanorods by simultaneously probing their localized surface plasmon resonance spectrum and rotational Brownian dynamics over extended periods of time. The data reveal an extremely slow nanoparticle reshaping process, involving migration of the order of a few hundred atoms per minute, for moderate laser powers and a trapping wavelength close to plasmon resonance. The plasmon spectroscopy and Brownian analysis allows for separate temperature estimates based on the refractive index and the viscosity of the water surrounding a trapped nanorod. We show that both measurements yield similar effective temperatures, which correspond to the actual temperature at a distance of the order 10-15 nm from the particle surface. Our results shed light on photothermal processes on the nanoscale and will be useful in evaluating the applicability and performance of nanorod motors and optically heated nanoparticles for a variety of applications.
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| 2. |
- Andrén, Daniel, 1991, et al.
(författare)
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Surface Interactions of Gold Nanoparticles Optically Trapped against an Interface
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:26, s. 16406-16414
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Tidskriftsartikel (refereegranskat)abstract
- Particles that diffuse in close proximity to a surface are expected to behave differently than in free solution because the surface interaction will influence a number of physical properties, including the hydrodynamic, optical, and thermal characteristics of the particle. Understanding the influence of such effects is particularly important in view of the increasing interest in laser tweezing of colloidal resonant nanoparticles for applications such as nanomotors and optical printing and for investigations of unconventional optical forces. Therefore, we used total internal reflection microscopy to probe the interaction between a glass surface and individual ∼100 nm gold nanoparticles trapped by laser tweezers. The results show that particles can be optically confined at controllable distances ranging between ∼30 and ∼90 nm from the surface, depending on the radiation pressure of the trapping laser and the ionic screening of the surrounding liquid. Moreover, the full particle-surface distance probability distribution can be obtained for single nanoparticles by analyzing temporal signal fluctuations. The experimental results are in excellent agreement with Brownian dynamics simulations that take the full force field and photothermal heating into account. At the observed particle-surface distances, translational friction coefficients increase by up to 60% compared to freely diffusing particles, whereas the rotational friction and thermal dissipation are much less affected. The methodology used here is general and can be adapted to a range of single nanoparticle-surface interaction investigations.
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| 3. |
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| 4. |
- Holmberg, Nils, et al.
(författare)
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Hjälpmedel för syntolkningsutbildningar
- 2016
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Ingår i: Syntolkning - forskning och praktik : Lund University Cognitive Studies - Lund University Cognitive Studies. - 9789198106091 - 9789198106091 ; 166, s. 79-84
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Bokkapitel (refereegranskat)
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| 5. |
- Jakobsson, Martin, et al.
(författare)
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Reconstructing the Younger Dryas ice dammed lake in the Baltic Basin: Bathymetry, area and volume
- 2007
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 57:3-4, s. 355-370
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Tidskriftsartikel (refereegranskat)abstract
- A digital 3D-reconstruction of the Baltic Ice Lake's (BIL) configuration during the termination of the Younger Dryas cold phase (ca. 11700 cal. yr BP) was compiled using a combined bathymetric-topographic Digital Terrain Model (DTM), Scandinavian ice sheet limits, Baltic Sea Holocene bottom sediment thickness information, and a paleoshoreline database maintained at the Lund University. The bathymetric-topographic DTM, assembled from publicly available data sets, has a resolution of 500 X 500 m on Lambert Azimuthal Equal Area projection allowing area and volume calculations of the BIL to be made with an unprecedented accuracy. When the damming Scandinavian ice sheet margin eventually retreated north of Mount Billingen, the high point in terrain of Southern central Sweden bordering to lower terrain further to the north, the BIL was catastrophically drained resulting in a 25 m drop of the lake level. With our digital reconstruction, we estimate that approximately 7800 km(3) of water drained during this event and that the ice dammed lake area was reduced by ca. 18%. Building on previous results suggesting drainage over 1 to 2 years, our lake volume calculations imply that the freshwater flux to the contemporaneous sea in the west was between about 0.12 and 0.25 Sv. The BIL reconstruction provides new detailed information on the paleogeography in the area of southern Scandinavia, both before and after the drainage event, with implications for interpretations of geological records concerning the post-glacial environmental development. (c) 2007 Elsevier B.V All rights reserved.
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| 6. |
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| 7. |
- Månsson, Johan, et al.
(författare)
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Spatial and temporal predictions of moose winter distribution
- 2012
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 170, s. 411-419
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Tidskriftsartikel (refereegranskat)abstract
- Herbivores are usually distributed unevenly across the landscape often because of variation in resource availability. We used zero-inflated generalised additive models (to account for data with a high number of zeros) that include georeferences to predict winter distribution of a large herbivore (moose Alces alces). Moose distribution was analysed in relation to forage availability and distance to neighbouring sites. Our results showed that the ability to explain moose distribution indexed by pellet count data at a local scale increased when spatial information (longitude and latitude) was added to the model compared to the model only including food availability. By using the relationship between moose and forage distribution, and the spatial information, we predicted patch choice by moose reasonably well in 2 out of 4 years. However, the distribution of moose was also influenced by weather conditions, as it was most clumped in the year with most snow. In conclusion, our study lends support for a non-linear approach using georeferences for a comprehensive understanding of herbivore distribution at a small scale. This result also indicates that the use of a certain patch by moose not only depends on the selected patch itself but is also influenced by the neighbouring patch and factors at a larger spatial scale, such as moose management influencing the density above moose home range level. The relatively high proportion of unexplained variation suggests that the use of a certain patch is also influenced by other factors such as topography, predation, competition, weather conditions, and wildlife management strategies.
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| 8. |
- Rönnberg, Sten, et al.
(författare)
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Sprutbyte för personer med intravenöst missbruk
- 1992
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Verksamheten med att intravenösa narkotikamissbrukare får byta ut sina använda sprutor mot nya har pågått vid infektionsklinikerna i Lund sedan 1978 och Malmö sedan 1989. Verksamheten inrättades för att minska risken för ytterligare utbredning av HIV. Det har diskuterats livligt för och emot denna sprututbytesverksamhet i Sverige. Den här rapporten ger stoff för en mer nyanserad diskussion i frågan. Den innehåller intervjuer med personal som arbetar med verksamheten, med forskare och andra personer som ägnat sig åt frågan. Den ger inblick i lagstiftning som berör området. Forskningen på området refereras och diskuteras. En empirisk undersökning som ger data om hur verksamheten fungerar redovisas också. För den som vill veta mera om sprututbytesverksamheten och dess roll i narkotikabehandling och narkotikapolitik är denna rapport starkt att rekommendera.
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| 9. |
- Sipova, Hana, 1983, et al.
(författare)
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Photothermal DNA Release from Laser-Tweezed Individual Gold Nanomotors Driven by Photon Angular Momentum
- 2018
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:6, s. 2168-2175
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticles offer a unique possibility for contact-free bioanalysis and actuation with high spatial resolution that increases their potential for bioapplications such as affinity-based biosensing, drug delivery, and cancer treatment. Here we demonstrate an ultrasensitive optomechanical method for probing and releasing DNA cargo from individual gold nanoparticles trapped and manipulated by laser tweezers. Single nanorods are operated as rotational nanomotors, driven and controlled by circularly polarized laser light in aqueous solution. By rotational dynamics analysis, we resolve differences in the thickness of adsorbed ultrathin molecular layers, including different DNA conformations, with nanometer resolution. We then utilize photothermal heating to release DNA from single nanomotors while measuring the temperature-dependent kinetics and activation energy of the DNA melting process. The method opens new possibilities for optomechanical quantification and application of thermally induced molecular transitions in strongly confined geometries, such as inside microfluidic devices and single cells.
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| 10. |
- Verre, Ruggero, 1985, et al.
(författare)
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High index dielectric metasurfaces and colloidal solutions: From fabrication to application
- 2018
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1092
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Konferensbidrag (refereegranskat)abstract
- High index dielectric nanoparticles and meta-materials have been proposed for many different applications, including light harvesting, sensing and metalenses. However, widespread utilization in practice also requires large-scale fabrication methods able to produce homogeneous structures with engineered optical properties in a cost effective manner. Here, it is presented a facile fabrication method for silicon nanoparticles which is scalable to 4-inch wafers and can produce a wide range of nanoparticle shapes on demand. We also show that the fabricated nanoparticles can be detached from their support using a simple substrate removal technique and then transferred to colloidal suspension. We will finally discuss some uses of the fabricated systems. For the metasurfaces, we will demonstrate complete absorption due to far field interference effects. For the nanoparticles colloids we will show the possibility of realizing an intrinsically chiral structure composed of a low-loss dielectric resonator and we will study optical trapping phenomena for different particle sizes and shapes.
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