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| 2. |
- Hoffmann, E. A., et al.
(författare)
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Quantum-dot thermometry
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:25
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for the measurement of a temperature differential across a single quantum dot that has transmission resonances that are separated in energy by much more than the thermal energy. We determine numerically that the method is accurate to within a few percent across a wide range of parameters. The proposed method measures the temperature of the electrons that enter the quantum dot and will be useful in experiments that aim to test theory which predicts that quantum dots are highly efficient thermoelectrics.
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| 3. |
- Jarnac, A., et al.
(författare)
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Communication : Demonstration of a 20 ps X-ray switch based on a photoacoustic transducer
- 2017
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Ingår i: Structural Dynamics. - : AIP Publishing. - 2329-7778. ; 4:5
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Tidskriftsartikel (refereegranskat)abstract
- We have studied an X-ray switch based on a gold coated indium antimonide crystal using time-resolved X-ray diffraction and demonstrated that the switch could reduce the pulse duration of a 100 ps X-ray pulse down to 20 ps with a peak reflectivity of 8%. We have used a dynamical diffraction code to predict the performance of the switch, which was then confirmed experimentally. The experiment was carried out at the FemtoMAX beamline at the short-pulse facility of the MAX IV laboratory. The performance and limitation of the switch are discussed in terms of acoustic transport properties between the two materials and the electron transport properties of gold.
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| 4. |
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| 5. |
- Larsson, Magnus, et al.
(författare)
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In-situ manipulations and electrical measurements of III-V nanowhiskers with TEM-STM
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- A scanning tunnelling microscope (STM) mounted in a sample holder for a transmission electron microscope (TEM), a TEM-STM, have been used for in-situ electrical measurements of semiconductor nano whiskers. The device enables measurements and manipulations of nano structures while observing them in a TEM
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| 6. |
- Müser, M. H., et al.
(författare)
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Meeting the Contact-Mechanics Challenge
- 2017
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Ingår i: Tribology letters. - : Springer New York LLC. - 1023-8883 .- 1573-2711. ; 65:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and substrate, were specified so that diverse quantities of interest, e.g., the distribution of interfacial stresses at a given load or the mean gap as a function of load, could be computed and compared to a reference solution. Many different solution strategies were pursued, ranging from traditional asperity-based models via Persson theory and brute-force computational approaches, to real-laboratory experiments and all-atom molecular dynamics simulations of a model, in which the original assignment was scaled down to the atomistic scale. While each submission contained satisfying answers for at least a subset of the posed questions, efficiency, versatility, and accuracy differed between methods, the more precise methods being, in general, computationally more complex. The aim of this paper is to provide both theorists and experimentalists with benchmarks to decide which method is the most appropriate for a particular application and to gauge the errors associated with each one..
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| 7. |
- Persson, A. I H, et al.
(författare)
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Studies of electron diffusion in photo-excited Ni using time-resolved X-ray diffraction
- 2016
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 109:20
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Tidskriftsartikel (refereegranskat)abstract
- We show that the heat deposition profile in a laser-excited metal can be determined by time-resolved X-ray diffraction. In this study, we investigated the electron diffusion in a 150 nm thick nickel film deposited on an indium antimonide substrate. A strain wave that mimics the heat deposition profile is generated in the metal and propagates into the InSb, where it influences the temporal profile of X-rays diffracted from InSb. We found that the strain pulse significantly deviated from a simple exponential profile, and that the two-temperature model was needed to reproduce the measured heat deposition profile. Experimental results were compared to simulations based on the two-temperature model carried out using commercial finite-element software packages and on-line dynamical diffraction tools. To reproduce the experimental data, the electron-phonon coupling factor was lowered compared to previously measured values. The experiment was carried out at a third-generation synchrotron radiation source using a high-brightness beam and an ultrafast X-ray streak camera with a temporal resolution of 3 ps.
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| 8. |
- Persson, A. I. H.
(författare)
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Time-resolved x-ray diffraction of nanostructured samples
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work presented in this thesis is based on time-resolved x-ray diffraction studies of InSb (111) samples. The experiments were carried out using a pump-probe configuration using short laser pulses as the pump and x-rays as the probe. Laser excitation leads to the formation of a strain pulse that propagates through the sample. The strain pulse gives rise to coherent longitudinal, acoustic phonons, which were probed with the x-rays. By detuning the x-ray energy away from the Bragg reflection, phonon modes could be studied as oscillations in the x-ray reflectivity. The experiments were performed at the, now decommissioned, storage ring MAX-II at the MAX IV Laboratory, with long x-ray pulses (~600 ps). Using a streak camera, time resolutions down to 1 ps could be achieved.An optoacoustic transducer was used to modify the acoustic phonon spectrum. A 150 nm nickel film was deposited on the InSb bulk sample, and a strain pulse was generated in the nickel film by laser excitation. The strain pulse is partially transmitted and partially reflected at the interface between the nickel and indium antimonide. This leads to a train of strain pulses in the indium antimonide, and constructive and destructive interference of the diffracted x-rays.Optoacoustic transducers were also used to study electron diffusion in nickel and gold. The metals were deposited on bulk InSb and excited by short laser pulses. The resulting strain pulse was broadened by electron diffusion. This could be studied in the indium antimonide since the oscillations in x-ray reflectivity mainly occurred when the sharp edge between compression and expansion part of the strain pulse had entered the indium antimonide. The time delay between the strain pulse entering the indium antimonide and the expansion part entering the bulk material can be used to study the shape of the strain pulse. Using InSb nanowires, the generation of coherent acoustic phonons was used to study the speed of sound, which is related to the thermal conductivity of the material. It was found that the speed of sound, and hence the thermal conductivity, is lower in InSb nanowires than in bulk InSb.
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| 9. |
- Persson, A. I., et al.
(författare)
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The fabrication of dense and uniform InAs nanowire arrays
- 2009
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 20:22
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires are important candidates for use in future electronics, photonics and thermoelectrics applications. We focus here in particular on nanowires for use in thermoelectric power generation and present a method of fabricating dense uniform InAs nanowire arrays amenable to future incorporation of advanced heterostructures that could further increase the thermoelectric performance of these nanowires. In these applications it will be important to have the nanowires densely packed in order to give an appreciable amount of power output. Here we present the fabrication of such dense arrays, using metal-particle seeded growth and chemical beam epitaxy, where the metal particles are defined by electron beam lithography, metal evaporation and lift-off. We evaluate the potential of chemical beam epitaxy for the growth of dense, freestanding InAs nanowire arrays and describe the process that enabled us to achieve areal packing densities of up to 19% with a variation of only a few per cent in nanowire diameter and height. We close by discussing how even higher areal packing densities can be achieved.
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| 10. |
- Persson, Lennart, et al.
(författare)
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α-lipoic acid and α-lipoamide prevent oxidant-induced lysosomal rupture and apoptosis
- 2001
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:5, s. 327-334
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Tidskriftsartikel (refereegranskat)abstract
- α-Lipoic acid (LA) and its corresponding derivative, α-lipoamide (LM), have been described as antioxidants, but the mechanisms of their putative antioxidant effects remain largely uncharacterised. The vicinal thiols present in the reduced forms of these compounds suggest that they might possess metal chelating properties. We have shown previously that cell death caused by oxidants may be initiated by lysosomal rupture and that this latter event may involve intralysosomal iron which catalyzes Fenton-type chemistry and resultant peroxidative damage to lysosomal membranes. Here, using cultured J774 cells as a model, we show that both LA and LM stabilize lysosomes against oxidative stress, probably by chelating intralysosomal iron and, consequently, preventing intralysosomal Fenton reactions. In preventing oxidant-mediated apoptosis, LM is significantly more effective than LA, as would be expected from their differing capacities to enter cells and concentrate within the acidic lysosomal compartment. As previously reported, the powerful iron-chelator, desferrioxamine (Des) (which also locates within the lysosomal compartment), also provides protection against oxidant-mediated cell death. Interestingly, although Des enhances the partial protection afforded by LA, it confers no additional protection when added with LM. Therefore, the antioxidant actions of LA and LM may arise from intralysosomal iron chelation, with LM being more effective in this regard.
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| 11. |
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| 12. |
- Sharma, T., et al.
(författare)
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Biomarkers associated with vulnerable plaques
- 2022
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Ingår i: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 43:Suppl. 2, s. 1292-1292
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Cardiovascular heart disease is the leading cause of mortality worldwide, with the rupture or thrombosis of an atherosclerotic plaque being the main reason behind an acute coronary syndrome. It has already been established that the morphology of atherosclerotic plaques determine their stability. A lipid rich lesion with a thin fibrous cap is more prone to rupture compared to solid fibrous lesions. In the PROSPECTII study we used Near infrared spectroscopy (NIRS) and Intravascular ultrasound (IVUS) to identify atherosclerotic plaques in the coronary arteries; NIRS-derived lipid core burden index (LCBI) and IVUS-derived plaque burden (PB) identified plaques that caused adverse cardiovascular events.Purpose: Our aim is to find biomarkers associated with LCBI or PB, to understand the development of vulnerable plaques.Methods: 902 patients were enrolled in this study after successful percutaneous coronary intervention (PCI). A combined NIRS-IVUS catheter was then used to analyze approximately 200m of coronary arteries. Blood samples for biomarker analysis were taken before the PCI procedure and plasma levels of 182 proteins associated with cardiovascular disease were assessed using a novel method for measuring proximity extension assay. Adjusted linear regression models were calculated between the biomarkers and the outcomes of interest, followed by a false discovery rate (FDR) correction.Results: We found 24 proteins associated with plaque burden and 28 proteins associated with LCBI after using a cut off of two tailed P value <0.05. An overlap of 8 biomarkers could be seen between the two groups. After adjusting the P values with FDR, Angiopoeitin like 3 (ANGPTL3) retain edits association to LCBI, and Interleukin 18 receptor 1 (IL18R1) and colony stimulating factor 1 (CSF-1) to plaque burden.Conclusion: We were able to identify different biomarker patterns associated with plaque burden compared to lipid rich vulnerable plaques. ANGPTL3 was shown to only have an association with lipid rich plaques and not with solid fibrous lesions which further supports its role in vulnerable plaques.
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