| 1. |
- Casolino, M., et al.
(författare)
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Cosmic ray measurements with Pamela experiment
- 2009
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Konferensbidrag (refereegranskat)abstract
- PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature hi a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of 10(-8)). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15(th) 2006 in a 350 X 600 km orbit with an inclination of 70 degrees. In this work we describe the scientific objectives awl the performance of PAMELA in its first two years of operation. Data oil protons of trapped, secondary and galactic nature - as well as measurements of the December 13(th) 2006 Solar Particle Event - are also provided.
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| 2. |
- Lappalainen, Hanna K., et al.
(författare)
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Pan-Eurasian Experiment (PEEX) : towards a holistic understanding of the feedbacks and interactions in the land-atmosphere-ocean-society continuum in the northern Eurasian region
- 2016
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:22, s. 14421-14461
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Tidskriftsartikel (refereegranskat)abstract
- The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-atmosphereaquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context.
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| 3. |
- Bramsen, Jesper B., et al.
(författare)
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A large-scale chemical modification screen identifies design rules to generate siRNAs with high activity, high stability and low toxicity
- 2009
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Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 37:9, s. 2867-2881
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Tidskriftsartikel (refereegranskat)abstract
- The use of chemically synthesized short interfering RNAs (siRNAs) is currently the method of choice to manipulate gene expression in mammalian cell culture, yet improvements of siRNA design is expectably required for successful application in vivo. Several studies have aimed at improving siRNA performance through the introduction of chemical modifications but a direct comparison of these results is difficult. We have directly compared the effect of 21 types of chemical modifications on siRNA activity and toxicity in a total of 2160 siRNA duplexes. We demonstrate that siRNA activity is primarily enhanced by favouring the incorporation of the intended antisense strand during RNA-induced silencing complex (RISC) loading by modulation of siRNA thermodynamic asymmetry and engineering of siRNA 3'-overhangs. Collectively, our results provide unique insights into the tolerance for chemical modifications and provide a simple guide to successful chemical modification of siRNAs with improved activity, stability and low toxicity.
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| 4. |
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| 5. |
- Kukushkin, I V, et al.
(författare)
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Miniature quantum-well microwave spectrometer operating at liquid-nitrogen temperatures
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:4, s. 044101-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that a two-dimensional electron system fabricated from a GaAs/AlGaAs quantum well in the presence of a magnetic field B possesses the ability to detect electromagnetic radiation in a broad frequency range. Irradiation of the sample with microwaves produces a dc-photovoltage which oscillates as a function of B. The amplitude and the period of the oscillations are proportional to the radiation power and the wavelength, respectively. Successful operation of such a detector/spectrometer is reported for microwave frequencies up to similar to150 GHz and temperatures up to similar to80 K. We do not anticipate any principal difficulties in extending the operation frequency further into the terahertz region.
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| 6. |
- Kukushkin, I. V., et al.
(författare)
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New type of B-periodic magneto-oscillations in a two-dimensional electron system induced by microwave irradiation
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:23, s. 236803-1
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Tidskriftsartikel (refereegranskat)abstract
- A B-periodic magnetotransport oscillation in GaAs/AlGaAs quantum wells was reported. The oscillations were induced by microwave radiation and were periodic in magnetic field. The period was determined by the electron density, the microwave frequency and the distance between potential probes. It was found that the phenomenon was accounted for by interference of coherently excited edge magnetoplasmons in the contact regions and offers perspectives for developing new tunable microwave and terahertz detection schemes and spectroscopic techniques.
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| 7. |
- Mikhailov, Sergey A
(författare)
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Microwave-induced magnetotransport phenomena in two-dimensional electron systems : Importance of electrodynamic effects
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:16, s. 165311-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss possible origins of recently discovered microwave induced photoresistance oscillations in very-high-electron-mobility two-dimensional electron systems. We show that electrodynamic effects-the radiative decay, plasma oscillations, and retardation effects-are important under the experimental conditions, and that their inclusion in the theory is essential for understanding the discussed and related microwave induced magnetotransport phenomena.
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| 8. |
- Mikhailov, Sergey A, et al.
(författare)
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Microwave response of a two-dimensional electron stripe
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71§:3, s. 035320-
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Tidskriftsartikel (refereegranskat)abstract
- Electromagnetic response of a finite-width two-dimensional electron stripe is theoretically studied. It is shown that retardation and radiative effects substantially modify the absorption spectrum of the system at microwave frequencies, leading to a nontrivial zigzag behavior of the magnetoplasmon-polariton modes in magnetic fields, similar to that recently observed by Kukushkin [Phys. Rev. Lett. 90, 156801 (2003)].
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| 9. |
- Mikhailov, Sergey
(författare)
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Edge magnetoplasmons for a new type of quantum-well microwave detector
- 2007
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Ingår i: International Journal of Modern Physics B. - 0217-9792. ; 21:8-9, s. 1491-1496
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically study the wavelength and the propagation length of the edge magnetoplasmons (EMP's), running along the edge of a two-dimensional (2D) electron layer in a semiconductor quantum-well structure with and without metallic gates. We show that the metallic gate suppresses the propagation of the EMP's, but the quality factor of the wave (q'/q '', where q' and q '' are the real and imaginary parts of the complex EMP wavevector) can be larger in the gated structures as compared to the structures without the gate. The results may be useful for analysis of operation of the recently discovered microwave detectors and spectrometers operating at liquid nitrogen temperatures (Kukushkin et al., Appl. Phys. Lett. 86, 044101 (2005)).
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| 10. |
- Mikhailov, Sergey, et al.
(författare)
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Influence of contacts on the microwave response of a two-dimensional electron stripe
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:4
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Tidskriftsartikel (refereegranskat)abstract
- Electromagnetic response of a finite-width two-dimensional electron stripe with attached metallic side contacts is theoretically studied. It is shown that contacts substantially influence the position, the linewidth, and the amplitude of plasmon-polariton resonances in the stripe. In finite magnetic fields, absorption of the wave with the inactive circular polarization (which is not absorbed in an infinite system without contacts) may become larger than that of the wave with the active polarization. The results are discussed in view of recent microwave experiments in two-dimensional electron systems.
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