| 1. |
|
|
| 2. |
- Dahlin, Andreas, 1980
(författare)
-
Nanoplasmonic Biosensors compatible with Artificial Cell Membranes
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within life science, there is currently an intense search for novel techniques that enable efficient and reliable analysis of biomolecular interactions. Such methods have future applications within medical diagnostics and drug development, as well as within proteomic research in general. Lately, several concepts have emerged that are based on monitoring molecular binding to surfaces via optical, mechanical or electrical signal transduction. In particular, the plasmons associated with metallic nanoparticles are of interest since they offer a convenient way to monitor biomolecular interactions, also in a miniaturized format, by optical spectroscopy.This thesis describes the development of a biosensor based on the optical properties of nanoscale apertures in continuous metal films. The fabrication and characterization of the nanostructure is described, as well as surface modification protocols based on thiol chemistry for material-specific functionalization. In addition, an experimental setup for spectroscopy is presented together with data analysis algorithms for minimizing noise.It is emphasized that, from an experimental sensing perspective, nanoholes and nanoparticles have essentially the same plasmonic properties. However, the nanoholes offer several advantages because of the fact that the structure is physically different. In particular, it is shown how various artificial cell membranes can be spontaneously formed inside nanoholes. This makes the sensor compatible with studies of processes related to biological membranes. In this context, membrane-bound proteins are of special interest since they constitute a third of our genome and represent the target of half of the most common medical drugs. Potential future applications of the artificial membranes on the plasmonic nanostructures are discussed, with focus on probing transport across the membrane.
|
|
| 3. |
- Wågberg, Lars, et al.
(författare)
-
The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes
- 2008
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:3, s. 784-795
-
Tidskriftsartikel (refereegranskat)abstract
- A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 mu m. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = similar to 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.
|
|
| 4. |
- Bengtsson, Lars, 1963
(författare)
-
Signalbehandling
- 2003
-
Ingår i: Tabeller och Formler. - Stockholm : Liber AB. - 9147050926 ; , s. 355-360
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Denna formel- och tabellsamling innehåller grundläggande definitioner, tabeller och formler inom det naturvetenskapliga och tekniska området. Boken är lämplig för högskoleingenjörsutbildning och grundläggande utbildningar för civilingenjörer. Författarnas inriktning har varit att ge boken en sådan bredd att den också kan användas som referenslitteratur på gymnasiet.
|
|
| 5. |
- Fredenberg, Erik, 1979-
(författare)
-
Spectral Mammography with X-Ray Optics and a Photon-Counting Detector
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Early detection is vital to successfully treating breast cancer, and mammography screening is the most efficient and wide-spread method to reach this goal. Imaging low-contrast targets, while minimizing the radiation exposure to a large population is, however, a major challenge. Optimizing the image quality per unit radiation dose is therefore essential. In this thesis, two optimization schemes with respect to x-ray photon energy have been investigated: filtering the incident spectrum with refractive x-ray optics (spectral shaping), and utilizing the transmitted spectrum with energy-resolved photon-counting detectors (spectral imaging). Two types of x-ray lenses were experimentally characterized, and modeled using ray tracing, field propagation, and geometrical optics. Spectral shaping reduced dose approximately 20% compared to an absorption-filtered reference system with the same signal-to-noise ratio, scan time, and spatial resolution. In addition, a focusing pre-object collimator based on the same type of optics reduced divergence of the radiation and improved photon economy by about 50%. A photon-counting silicon detector was investigated in terms of energy resolution and its feasibility for spectral imaging. Contrast-enhanced tumor imaging with a system based on the detector was characterized and optimized with a model that took anatomical noise into account. Improvement in an ideal-observer detectability index by a factor of 2 to 8 over that obtained by conventional absorption imaging was found for different levels of anatomical noise and breast density. Increased conspicuity was confirmed by experiment. Further, the model was extended to include imaging of unenhanced lesions. Detectability of microcalcifications increased no more than a few percent, whereas the ability to detect large tumors might improve on the order of 50% despite the low attenuation difference between glandular and cancerous tissue. It is clear that inclusion of anatomical noise and imaging task in spectral optimization may yield completely different results than an analysis based solely on quantum noise.
|
|
| 6. |
|
|
| 7. |
- Bengtsson, Magnus, et al.
(författare)
-
Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators
- 2005
-
Ingår i: Optics and Lasers in Engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 43:6, s. 624-632
-
Tidskriftsartikel (refereegranskat)abstract
- Remote fluorescence imaging of fungal growth on polymeric high-voltage insulators was performed using a mobile lidar system with a laser wavelength of 355 nm. Insulator areas contaminated by fungal growth could be distinguished from clean surfaces and readily be imaged. The experiments were supported by detailed spectral studies performed in laboratory using a fibre-optic fluorosensor incorporating an optical multi-channel analyser system (OMA) and a nitrogen laser emitting radiation at 33 7 nm.
|
|
| 8. |
|
|
| 9. |
- Ferdos, Fariba, 1966
(författare)
-
InAS Quantum Dots for Laser Applications and Pedogogical, Gender, and Multicultural Aspects in Engineering Education
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis builds on new cross-disciplinary research between engineering and educational sciences. Recently, two other theses that combine research in physics and education (Åke Ingerman, 2002, and Tom Adawi, 2002) have been completed in Sweden. This thesis consolidates a trend that can benefit both disciplines. It is similar to the other theses in that it focuses on engineering education and investigates knowledge formation in a scientific subject. It differs in that the scientific study concerns a different area of physics. Its original contribution is that it focuses on the pedagogical, socio-cultural and gendered context in which learning in engineering education takes place and does so by means of a cross cultural, autobiographical case study and three action research projects. These projects deal with a pedagogy of e-learning (paper E), developing generic capabilities in online learning (papers C and E), learning in groups (papers B and G) and gender equity in physics (paper D). The thesis is divided into two parts. The study in engineering science (photonics) was successfully defended at the licentiate level and is reported in appended paper A and in published articles (papers H to M). The pedagogical study in engineering education is reported in the following chapters and in papers B to G.The scientific engineering study concerns the development of InAs Quantum Dot (QD) structures on GaAs substrate for 1.3 μm laser applications and investigations of how structural and optical properties of InAs QDs depend on the growth conditions and the choice of pre-layer and cap materials. Growth conditions for the best luminance intensity and line width were found for substrate temperatures (500-520oC) and nominal InAs layer thickness (3.3-3.7 monolayers). It was found that the QD size was considerably reduced during initial GaAs capping, resulting in a blue-shift of the emission wavelength. The density of the QDs also reduces significantly during GaAs capping. Using an Al-containing cap layer the size reduction can be suppressed, and therefore a longer emission wavelength can be obtained. The density of QDs can also be increased. Furthermore, introducing a thin InAlAs cap layer resulted in 1.3 μm emission with a large energy separation between the ground and the first excited state transmission. A record transition energy separation of 108 meV was demonstrated.
|
|
| 10. |
|
|
