1,166 research outputs found
Does river restoration work? Taxonomic and functional trajectories at two restoration schemes
Rivers and their floodplains have been severely degraded with increasing global activity and expenditure undertaken on restoration measures to address the degradation. Early restoration schemes focused on habitat creation with mixed ecological success. Part of the lack of ecological success can be attributed to the lack of effective monitoring. The current focus of river restoration practice is the restoration of physical processes and functioning of systems. The ecological assessment of restoration schemes may need to follow the same approach and consider whether schemes restore functional diversity in addition to taxonomic diversity. This paper examines whether two restoration schemes, on lowland UK rivers, restored macroinvertebrate taxonomic and functional (trait) diversity and relates the findings to the Bradshaw's model of ecological restoration. The study schemes are considered a success in terms of restoring physical processes, longitudinal connectivity and the resulting habitat composition. However, the rehabilitation of macroinvertebrate community structure and function was limited and inconsistent, varying over time, depending on the restoration measure applied and the taxonomic or functional index considered. Resampling of species pools at each site revealed a role for functional redundancy, meaning that increases in functional diversity are more difficult to achieve than outcomes based on taxonomic analyses. Our results highlight the usefulness of applying functional traits alongside taxonomic indices in evaluating river restoration projects
Discovery of Associated Absorption Lines in an X-Ray Warm Absorber: Hubble Space Telescope Faint Object Spectrograph Observations of MR 2251–178
The presence of a "warm absorber" was first suggested to explain spectral variability in an X-ray spectrum of the radio-quiet quasi-stellar object (QSO) MR 2251-178. A unified picture, in which X-ray warm absorbers and "intrinsic" UV absorbers are the same, offers the opportunity to probe the nuclear environment of active galactic nuclei. To test this scenario and understand the physical properties of the absorber, we obtained a UV spectrum of MR 2251-178 with the Faint Object Spectrograph on board the Hubble Space Telescope (HST). The HST spectrum clearly shows absorption due to Lyα, N V, and C IV, blueshifted by 300 km s^-1 from the emission redshift of the QSO. The rarity of both X-ray and UV absorbers in radio-quiet QSOs suggests these absorbers are physically related, if not identical. Assuming the unified scenario, we place constraints on the physical parameters of the absorber and conclude the mass outflow rate is essentially the same as the accretion rate in MR 2251-178
The Hydrodynamics of River Ecosystems: Towards an Objective and Ecologically Relevant Classification of Mesohabitats
Time Use during Activities and Trips – Potentials for Analyzing Future Travel and Activity Behavior
We carried out a survey with students on time use during activities and trips with upcoming fully automated vehicles (AV). Compared to current time used in public transit, in AV more attention-demanding activities will be undertaken. Shorter trips lead to use the time with less attention-demanding activities. Time use differences originate in the current mode. Using time in the vehicle for activities, people save time outside it. This is mostly done to extend previously existing activities or to spend more time at home. However, around 15% of the students will perform new activities, which leads to an increase of travel demand
The Case for Optically-Thick High Velocity Broad Line Region Gas in Active Galactic Nuclei
A combined analysis of the profiles of the main broad quasar emission lines
in both Hubble Space Telescope and optical spectra shows that while the
profiles of the strong UV lines are quite similar, there is frequently a strong
increase in the Ly-alpha/H-alpha ratio in the high-velocity gas. We show that
the suggestion that the high velocity gas is optically-thin presents many
problems. We show that the relative strengths of the high velocity wings arise
naturally in an optically-thick BLR component. An optically-thick model
successfully explains the equivalent widths of the lines, the Ly-alpha/H-alpha
ratios and flatter Balmer decrements in the line wings, the strengths of CIII]
and the lambda 1400 blend, and the strong variability of high-velocity,
high-ionization lines (especially HeII and HeI).Comment: 34 pages in AASTeX, including 10 pages of figures. Submitted to
Astrophysical Journa
Pre-service teachers' evidence-informed reasoning: do attitudes, subjective norms, and self-efficacy facilitate the use of scientific theories to analyze teaching problems?
Using the theory of planned behavior, we investigated whether attitudes, subjective norms, and
self-efficacy facilitate pre-service teachers’ engagement in evidence-informed reasoning about
classroom problems. N=157 pre-service teachers were asked about these motivationally relevant
antecedents to engaging in evidence-informed reasoning about classroom-related challenges and
analyzed case scenarios of problematic teaching situations. Results revealed that self-reported evidence-informed reasoning was directly predicted by intention to engage in evidence-informed reasoning, self-efficacy, and attitude toward evidence-informed reasoning. However, the objectively
coded quality of teachers’ evidence-informed reasoning was seemingly negatively predicted by perceived costs and self-efficacy. Thus, the theory of planned behavior partly explained selfreported evidence-informed reasoning, but not objectively observed reasoning. Pre-service teachers might not be skilled enough to assess their own competency accurately and might be
unaware of external conditions facilitating or hindering evidence-informed reasoning. Thus, interventions aiming to foster pre-service teachers’ motivation to engage in evidence-informed reasoning might not be effective until such teachers gain the necessary skills
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