| 1. |
- Abel, Martin, et al.
(author)
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Collision-induced absorption by supermolecular complexes from a new potential energy and induced dipole surface, suited for calculations up to thousands of kelvin
- 2010
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In: 20th International Conference on Spectral Line Shapes. - Melville, NY : American Institute of Physics (AIP). - 9780735408456 ; , s. 251-257
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Conference paper (peer-reviewed)abstract
- Absorption by pairs of H2 molecules is an important opacity source in the atmospheres of the outer planets, and thus of special astronomical interest. The emission spectra of cool white dwarf stars differ significantly from the expected blackbody spectra, amongst other reasons due to absorption by H2-H2, H2-He, and H2-H collisional complexes in the stellar atmospheres. To model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole (ID) and potential energy surfaces (PES) of such collisional complexes. These come from quantum-chemical calculations with the H2 bonds stretched or compressed far from equilibrium. Laboratory measurements of collision-induced (CI) absorption exist only at much lower temperature. For H2 pairs at room temperature, the calculated spectra of the rototranslational band, the fundamental band, and the first overtone match the experimental data very well. In addition, with the newly obtained IDS it became possible to reproduce the measurements in the far blue wing of the rototranslational spectrum of H2 at 77.5 K, as well as at 300 K. Similarly good agreement between theory and measurement is seen in the fundamental band of molecular deuterium at room temperature. Furthermore, we also show the calculated absorption spectra of H2-He at 600 K and of H2-H2 at 2,000 K, for which there are no experimental data for comparison
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| 2. |
- Coria, Jessica, 1979, et al.
(author)
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The progress of GHG markets : opportunities and risks
- 2010
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Reports (other academic/artistic)abstract
- The climate negotiations at the COP15 in December 2009 did not produce a new international treaty with binding emissions commitments but the Copenhagen Accord for dealing with post-2012 climate change. Given the current climate negotiation process it is unlikely that we will see a global climate agreement soon on a global cap between all Convention members participating in a single carbon market. We may be more likely to see a stepwise process moving towards this scenario, most likely involving linkages between different national policy programs when it comes to mitigation as well as offsetting emissions. In such a process countries will offer commitments based on their domestic abilities, preferences and policies, norms and institutions. National and sub-national policies are thus likely to be the de-facto building blocks of nations' abilities to make and fulfill international commitments. However, also with multilateral mitigation programs without binding commitments, carbon markets will be needed as well as international authorities that support measurement, reporting and verification rules and the international registries. Such markets will necessarily be complicated and temporary in a world without an overarching binding agreement. There will be numerous tradeoffs between different kinds of second-best arrangements. The purpose of this report is to build knowledge about the effects of the development of regional and international carbon markets and the auxiliary technology agreements that might be needed. Among the topics we address are: the evolution and integration of carbon markets, the impacts of policy and technology cost uncertainty on the cost of meeting targets through a carbon market mechanism, the effect of banking, price floors and ceilings, institutional constraints and technological change in the further development of carbon markets and their links to other environmental policy instruments, and the potential of REDD-plus to encourage sustainable forest development and climate mitigation.
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| 3. |
- Frommhold, Lothar, et al.
(author)
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Infrared atmospheric emission and absorption by simple molecular complexes, from first principles
- 2010
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In: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 108:17, s. 2265-2272
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Journal article (peer-reviewed)abstract
- Quantum chemical methods are used to obtain the interaction-induced dipole surfaces (IDS) of complexes of two interacting (i.e. colliding) molecules, for example H2–H2, H2–He, etc., collisional complexes, along with their potential energy surfaces (PES). Eight H2 bond distances, from 0.942 to 2.801 bohr, are chosen for each H2 molecule to account for rotovibrational excitations. Rotovibrational matrix elements of these ID and PE surfaces are computed as necessary for the study of supermolecular (‘collision-induced’) absorption spectra of dense hydrogen gas, and of gaseous mixtures of hydrogen and helium, at temperatures up to several thousand kelvin and for frequencies from 0 to those of several H2 overtone bands. Rotovibrational state to state scattering calculations couple the collisional complex perturbatively to single photons. The absorption process causes rotovibrational transitions in one molecule, or simultaneous transitions in both molecules (when H2–H2 collisional complexes are considered). The spectral profiles of tens of thousands of such transitions are computed from first principles. Individual ‘lines’ are very broad so that they overlap substantially, forming a supermolecular quasi-continuum. The comparison of the computed collision-induced absorption (CIA) spectra with existing laboratory measurements at low temperatures (≤ 300 K) shows close agreement so that our results for higher temperatures, where laboratory experiments do not exist, may be used with confidence. Similar calculations of CIA spectra at high temperatures and frequencies are underway for other collisional systems (e.g. H2–H) of interest in astrophysical applications (e.g. ‘cool’ stellar atmospheres). Collision-induced Raman spectra (CIRS) have been similarly obtained; computed Raman spectra also compare favourably with existing laboratory measurements.
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| 4. |
- Gustafsson, Magnus, et al.
(author)
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Calculation of interaction-induced spectra using complex absorbing potentials
- 2010
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In: 20th International Conference on Spectral Line Shapes. - Melville, NY : American Institute of Physics (AIP). - 9780735408456 ; , s. 240-244
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Conference paper (peer-reviewed)abstract
- A complex absorbing potential method is implemented for calculation of collision-induced spectra. The scheme provides a way to avoid the integration of the Schrödinger equation to very large separations of the collisional pair. The method is tested by reproducing a previously computed absorption spectrum for H-He at two different temperatures.
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| 5. |
- Gustafsson, Magnus
(author)
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Far Wing Asymmetry of Rotational Raman Lines in Hydrogen
- 2010
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In: International Journal of Spectroscopy. - : Hindawi Limited. - 1687-9449 .- 1687-9457. ; 2010
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Journal article (peer-reviewed)abstract
- Depolarized Raman spectra of compressed hydrogen gas have been computed rigorously previously for 36 K and 50 K (Gustafsson et al. (2009)). The far wings of the rotational lines show asymmetry that goes beyond that expected from the theory for intracollisional interference and Fano line shapes. Here we analyze the (0) line for pure hydrogen at 36 K in detail. The added asymmetry stems partly from a shape resonance which adds significant intensity to the higher frequency side of the line profile. The influence of the threshold energy for the rotational transition accounts for the remainder.
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| 6. |
- Hedman, Linnea, 1979-, et al.
(author)
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Good agreement between parental and self-completed questionnaires about allergic diseases and environmental factors in teenagers
- 2010
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In: Journal of Clinical Epidemiology. - : Elsevier BV. - 0895-4356 .- 1878-5921. ; 63:7, s. 783-789
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To study whether the methodological change from parent to index subject as questionnaire respondent affected the prevalence estimates and risk factor patterns for allergic diseases in a longitudinal study.STUDY DESIGN AND SETTING: A prospective study of asthma and allergic diseases among children was begun in 1996 within the Obstructive Lung Disease in Northern Sweden Study. In 2002, about 3,342 (95% of invited) teenagers (13 to 14 years) completed the annual questionnaire. A random sample of 294 (84% of invited) parents also completed the same extended International Study of Asthma and Allergies in Childhood questionnaire. Skin prick tests were performed in 1996 and 2000.RESULTS: There were no significant differences in the prevalence of rhinitis, eczema, or related environmental factors between parental and self-reports, except for the question of having a dog at home. The absolute agreement was high, whereas the kappa values were fair or moderate. Kappa values of questions regarding parental smoking were 0.8-0.9. Allergic sensitization was the major risk factor for both rhinitis and eczema, and the odds ratios were similar regardless of who reported the condition.CONCLUSION: The agreement between the parental and teenagers' reports was good, and the methodological change did not affect the study results.
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| 7. |
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| 8. |
- Li, Xiaoping, et al.
(author)
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The anisotropic polarizability of pairs of hydrogen molecules and the depolarized collision-induced roto-translational Raman light scattering spectra
- 2010
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In: Journal of Computational Methods in Sciences and Engineering. - 1472-7978 .- 1875-8983. ; 10:3-6, s. 367-399
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Journal article (peer-reviewed)abstract
- In earlier work, Li, Ahuja, Harrison, and Hunt have calculated the collision-induced polarizability Δα of a pair of hydrogen molecules at CCSD(T) level with an aug-cc-pV5Z basis, for 178 relative orientations of the pair, with the bond length in each molecule fixed at r=1.449 a.u. Here we present new results from an expansion of the second-rank tensor components of Δα as series in the spherical harmonics of the molecular orientation angles and the orientation angles of the intermolecular vector. The coefficients in this expansion depend on the separation R between the molecules. We compare the ab initio coefficients with predictions from long-range perturbation theory, including the dipole-induced-dipole interactions at first and second order, higher-multipole induction, effects of nonuniform local fields, hyperpolarization, and van der Waals dispersion. Li and Hunt have derived equations for the long-range coefficients complete to order R^{-6}, using spherical-tensor methods developed by Bancewicz, Głaz, and Kielich for collision-induced light scattering by centrosymmetric linear molecules. We also give new results here for the van der Waals dispersion terms in both isotropic and anisotropic polarizability coefficients. We have calculated these coefficients by 64-point Gauss-Legendre quadrature, using the H_{2} polarizabilities and hyperpolarizabilities at imaginary frequencies computed by Bishop and Pipin, with explicitly correlated wave functions for isolated H_{2} molecules. We show that the ab initio values for the larger anisotropic polarizability coefficients converge to the predictions of the long-range theory, as the separation R between the molecules increases. The coefficients computed ab initio have been used by Gustafsson, Frommhold, Li, and Hunt to calculate the depolarized collision-induced roto-translational Raman spectra of hydrogen gas at 36 K and 50 K out to 800~cm^{-1}, and at 296 K out to 300 cm^{-1}. The general features of the experimental spectra are well reproduced, although the calculated intensities are ∼30% too large over much of the frequency range.
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| 9. |
- Ramser, Kerstin, et al.
(author)
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Optical manipulation for single cell studies
- 2010
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In: Journal of Biophotonics. - : Wiley. - 1864-063X .- 1864-0648. ; 3:4, s. 187-206
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Journal article (peer-reviewed)abstract
- In the last decade optical manipulation has evolved from a field of interest for physicists to a versatile tool widely used within life sciences. This has been made possible in particular due to the development of a large variety of imaging techniques that allow detailed information to be gained from investigations of single cells. The use of multiple optical traps has high potential within single-cell analysis since parallel measurements provide good statistics. Multifunctional optical tweezers are, for instance, used to study cell heterogeneity in an ensemble, and force measurements are used to investigate the mechanical properties of individual cells. Investigations of molecular motors and forces on the single-molecule level have led to discoveries that would have been difficult to make with other techniques. Optical manipulation has prospects within the field of cell signalling and tissue engineering. When combined with microfluidic systems the chemical environment of cells can be precisely controlled. Hence the influence of pH, salt concentration, drugs and temperature can be investigated in real time. Fast advancing technical developments of automated and user-friendly optical manipulation tools and cross-disciplinary collaboration will contribute to the routinely use of optical manipulation techniques within the life sciences.
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| 10. |
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