| 1. |
- Frommhold, Lothar, et al.
(författare)
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Infrared atmospheric emission and absorption by simple molecular complexes, from first principles
- 2010
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Ingår i: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 108:17, s. 2265-2272
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Gustafsson, Magnus
(författare)
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Far Wing Asymmetry of Rotational Raman Lines in Hydrogen
- 2010
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Ingår i: International Journal of Spectroscopy. - : Hindawi Limited. - 1687-9449 .- 1687-9457. ; 2010
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Hedman, Linnea, 1979-, et al.
(författare)
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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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Ingår i: Journal of Clinical Epidemiology. - : Elsevier BV. - 0895-4356 .- 1878-5921. ; 63:7, s. 783-789
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Tidskriftsartikel (refereegranskat)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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| 4. |
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| 5. |
- Li, Xiaoping, et al.
(författare)
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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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Ingår i: Journal of Computational Methods in Sciences and Engineering. - 1472-7978 .- 1875-8983. ; 10:3-6, s. 367-399
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Ramser, Kerstin, et al.
(författare)
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Optical manipulation for single cell studies
- 2010
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Ingår i: Journal of Biophotonics. - : Wiley. - 1864-063X .- 1864-0648. ; 3:4, s. 187-206
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Stage, Jesper, 1972-
(författare)
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Economic valuation of climate change adaptation in developing countries
- 2010
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 1185, s. 150-163
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the literature on the economics of climate change adaptation in developing countries, and identifies three key points for consideration in future studies. One key point is that all development policy should be formulated using forecasts from climate science as a baseline. When this is not done, there is risk that a false status quo without climate change is seen as an implicit baseline. Another key point is that authors must be clearer about their behavioral assumptions: Many studies either (problematically) assume profit maximization on the side of farm households, or do not specify behavioral assumptions at all. A third important point is that the allocation of rights is crucial for the results; if households have a right to maintain their current livelihoods, the costs of climate change in developing countries are considerably greater than traditional willingness-to-pay studies would indicate. Thus, costs and benefits of climate change adaptation cannot be analyzed using economic aspects only; climate science, behavioral science, and legal and moral aspects have crucial implications for the outcome of the analysis.
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| 8. |
- Öman, Lisa, et al.
(författare)
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Mobile phone quality vs. direct quality : How the presentation format affects earwitness identification accuracy
- 2010
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Ingår i: The European Journal of Psychology Applied to Legal Context. - : Sociedad Española de Psicología Jurídica y Forense. - 1889-1861 .- 1989-4007. ; 2:2, s. 161-182
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to gain insight into the effect of mobile phone quality on voice identification using an ecologically realistic design. A total of 165 participants were exposed to an unfamiliar voice, either directly recorded or mobile phone recorded, for 40 seconds. After a two week delay, they were asked to identify the target-voice in a 7 voice target-present line-up. We used a between- subjects design, where half of the subjects were exposed to a directly recorded line-up, and the other half to a mobile phone recorded line-up. Data analysis did not show any significant effect of presentation format or line-up format. These results suggest that the detrimental effect on voice recognition suggested by the poorer sound quality of mobile phone recordings is minimal. They also indicate that there is no benefit from conducting a mobile phone recorded line-up, if the voice is originally heard over a mobile phone. More research is needed, however, before definitive conclusions may be drawn. The overall accuracy for correct identifications was 12.7% which is expected by chance. Further, one particular foil attracted 54% of all false identifications. Future research should focus on explaining why earwitnesses perform so poorly and develop methods to improve identification accuracy.
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