| 1651. |
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| 1652. |
- da Silva, Humberto, Jr., et al.
(författare)
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Multiple electron capture, excitation, and fragmentation in C6+-C-60 collisions
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 90:3, s. 032701-
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental and theoretical results on single- and multiple-electron capture, and fragmentation, in C6+ + C-60 collisions at velocities in the v(col) = 0.05 - 0.4 a.u. range. We use time-of-flight mass spectrometry and coincidence detection of charged fragments to separate pure target ionization from processes in which the C-60 target is both ionized and fragmented. The coincidence technique allows us to identify different types of fragmentation processes such as C-60(q+) -> C-58(q+) + C-2 and C-60(q+) -> C-58((q-1)+) + C-2(+). A quasimolecular approach is employed to calculate charge transfer and target excitation cross sections. First-order time-dependent perturbation and statistical methods are used to treat the postcollisional processes: the calculated rate constants for C-2 and C-2(+) emission from the excited and charged fullerene are then used to evaluate the fragmentation dynamics. We show that the target ionization cross section decreases with the induced target charge state and the impact energy. C-2 emission from C-60(q+) is found to dominate when q <= 2 while C-2(+) emission dominates when q >= 5, in agreement with the present and previous experimental results.
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| 1653. |
- Dale, Virginia H., et al.
(författare)
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Status and prospects for renewable energy using wood pellets from the southeastern United States
- 2017
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Ingår i: Global Change Biology Bioenergy. - : Wiley-Blackwell. - 1757-1693 .- 1757-1707. ; 9:8, s. 1296-1305
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Tidskriftsartikel (refereegranskat)abstract
- The ongoing debate about costs and benefits of wood-pellet based bioenergy production in the southeastern United States (SE USA) requires an understanding of the science and context influencing market decisions associated with its sustainability. Production of pellets has garnered much attention as US exports have grown from negligible amounts in the early 2000s to 4.6 million metric tonnes in 2015. Currently, 98% of these pellet exports are shipped to Europe to displace coal in power plants. We ask, 'How is the production of wood pellets in the SE USA affecting forest systems and the ecosystem services they provide?' To address this question, we review current forest conditions and the status of the wood products industry, how pellet production affects ecosystem services and biodiversity, and what methods are in place to monitor changes and protect vulnerable systems. Scientific studies provide evidence that wood pellets in the SE USA are a fraction of total forestry operations and can be produced while maintaining or improving forest ecosystem services. Ecosystem services are protected by the requirement to utilize loggers trained to apply scientifically based best management practices in planning and implementing harvest for the export market. Bioenergy markets supplement incomes to private rural landholders and provide an incentive for forest management practices that simultaneously benefit water quality and wildlife and reduce risk of fire and insect outbreaks. Bioenergy also increases the value of forest land to landowners, thereby decreasing likelihood of conversion to nonforest uses. Monitoring and evaluation are essential to verify that regulations and good practices are achieving goals and to enable timely responses if problems arise. Conducting rigorous research to understand how conditions change in response to management choices requires baseline data, monitoring, and appropriate reference scenarios. Long-term monitoring data on forest conditions should be publicly accessible and utilized to inform adaptive management.
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| 1654. |
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| 1655. |
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| 1656. |
- de la Hera, Ivan, et al.
(författare)
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How much variation in the molt duration of passerines can be explained by the growth rate of tail feathers?
- 2011
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Ingår i: The Auk. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 128:2, s. 321-329
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Tidskriftsartikel (refereegranskat)abstract
- In birds, molt duration is an important trait that can affect plumage functionality and, consequently, the fitness of individuals. However, knowledge about the factors that affect variation in molt speed is sparse, mostly because of the methodological difficulties of studying avian molt. We used a ptilochronology-based approach to estimate the rate at which tail feathers were produced during molt to shed light on the relationship between molt duration and feather growth rate. For that purpose, we used three data sets. First, we tested whether the average molt durations of 22 passerine species were correlated with the mean growth rates of their feathers, using both conventional and phylogenetically corrected statistical procedures. Second, we explored this same association among captive Great Tits (Pants major). And third, we took advantage of the biannual complete molt of Willow Warblers (Phylloscopus trochilus) to examine whether the feathers synthesized during their short summer molt grew faster than those produced during their long winter molt. Feather growth rates were negatively correlated with molt duration in all analyses, revealing that molt duration can be estimated from the growth rate of a single feather. However, predictive power was limited by the fact that molt duration is modulated mainly by molt intensity, which seems to be correlated with ecological constraints in our interspecific approach. We also discuss the implications of our results for the evolution of molt duration, and the potential application of ptilochronology in its study. Received 2 August 2010, accepted 21 December 2010.
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| 1657. |
- Diaz, A., et al.
(författare)
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Second-best urban tolling with distributive concerns
- 2014
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Ingår i: Economics of Transportation. - : Elsevier BV. - 2212-0122 .- 2212-0130. ; 3:4, s. 257-269
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Tidskriftsartikel (refereegranskat)abstract
- This paper analyzes the optimal urban congestion toll in a second-best setting where only one road in a network can be tolled. Both heterogeneity in labor productivity and income distribution concerns are considered. The optimal toll balances two types of considerations. The first consideration is the correction of the congestion externality on the tolled road given the distortion on the non-tolled roads, while the second is the equity consideration that takes into account which income group uses the tolled road and how toll revenues are spent. Both separating and pooling equilibria are analyzed for two alternative uses of toll revenues: poll transfers and labor-tax cuts. Using numerical simulations, we show that equity concerns can lead a government to prefer inefficient toll levels and recycling via poll transfers rather than via labor tax reductions.
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| 1658. |
- Diaz-Barreiro, A., et al.
(författare)
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The SLE variant Ala71Thr of BLK severely decreases protein abundance and binding to BANK1 through impairment of the SH3 domain function
- 2016
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Ingår i: Genes and Immunity. - : Springer Science and Business Media LLC. - 1466-4879 .- 1476-5470. ; 17:2, s. 128-138
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Tidskriftsartikel (refereegranskat)abstract
- The B-lymphocyte kinase (BLK) gene is associated genetically with several human autoimmune diseases including systemic lupus erythematosus. We recently described that the genetic risk is given by two haplotypes: one covering several strongly linked single-nucleotide polymorphisms within the promoter of the gene that correlated with low transcript levels, and a second haplotype that includes a rare nonsynonymous variant (Ala71Thr). Here we show that this variant, located within the BLK SH3 domain, is a major determinant of protein levels. In vitro analyses show that the 71Thr isoform is hyperphosphorylated and promotes kinase activation. As a consequence, BLK is ubiquitinated, its proteasomal degradation enhanced and the average life of the protein is reduced by half. Altogether, these findings suggest that an intrinsic autoregulatory mechanism previously unappreciated in BLK is disrupted by the 71Thr substitution. Because the SH3 domain is also involved in protein interactions, we sought for differences between the two isoforms in trafficking and binding to protein partners. We found that binding of the 71Thr variant to the adaptor protein BANK1 is severely reduced. Our study provides new insights on the intrinsic regulation of BLK activation and highlights the dominant role of its SH3 domain in BANK1 binding.
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| 1659. |
- Díaz Baso, Carlos José, et al.
(författare)
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Bayesian Stokes inversion with normalizing flows
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
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Tidskriftsartikel (refereegranskat)abstract
- Stokes inversion techniques are very powerful methods for obtaining information on the thermodynamic and magnetic properties of solar and stellar atmospheres. In recent years, highly sophisticated inversion codes have been developed that are now routinely applied to spectro-polarimetric observations. Most of these inversion codes are designed to find an optimum solution to the nonlinear inverse problem. However, to obtain the location of potentially multimodal cases (ambiguities), the degeneracies and the uncertainties of each parameter inferred from the inversions algorithms – such as Markov chain Monte Carlo (MCMC) – require evaluation of the likelihood of the model thousand of times and are computationally costly. Variational methods are a quick alternative to Monte Carlo methods, and approximate the posterior distribution by a parametrized distribution. In this study, we introduce a highly flexible variational inference method to perform fast Bayesian inference, known as normalizing flows. Normalizing flows are a set of invertible, differentiable, and parametric transformations that convert a simple distribution into an approximation of any other complex distribution. If the transformations are conditioned on observations, the normalizing flows can be trained to return Bayesian posterior probability estimates for any observation. We illustrate the ability of the method using a simple Milne-Eddington model and a complex non-local thermodynamic equilibrium (NLTE) inversion. The method is extremely general and other more complex forward models can be applied. The training procedure need only be performed once for a given prior parameter space and the resulting network can then generate samples describing the posterior distribution several orders of magnitude faster than existing techniques.
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| 1660. |
- Díaz Baso, Carlos José, et al.
(författare)
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Diagnostic potential of the Ca II 8542 Ångstrom line for solar filaments
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 623
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Tidskriftsartikel (refereegranskat)abstract
- Aims. In this study we explore the diagnostic potential of the chromospheric Ca II line at 8542 angstrom for studying the magnetic and dynamic properties of solar filaments. We have acquired high spatial resolution spectropolarimetric observations in the Ca II 8542 angstrom line using the CRISP instrument at the Swedish 1 m Solar Telescope. Methods. We used the NICOLE inversion code to infer physical properties from observations of a solar filament. We discuss the validity of the results due to the assumption of hydrostatic equilibrium. We have used observations from other telescopes such as CHROTEL and SDO, in order to study large scale dynamics and the long term evolution of the filament. Results. We show that the Ca II 8542 angstrom line encodes information of the temperature, line-of-sight velocity and magnetic field vector from the region where the filament is located. The current noise levels only allow us to estimate an upper limit of 260 G for the total magnetic field of the filament. Our study also reveals that if we consider information from the aforementioned spectral line alone, the geometric height, the temperature and the density could be degenerated parameters outside the hydrostatic equilibrium approach.
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