Dam removal: Listening in Foley, M. M.; Bellmore, J. R.; O'Connor, J. E. ...
Water resources research,
July 2017, 2017-07-00, 20170701, Letnik:
53, Številka:
7
Journal Article
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Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam‐removal studies over the last few decades ...motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam‐removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad‐scale ecological effects, and gives managers information needed to understand and predict long‐term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam‐removal methods in the U.S.
Key Points
Dam removal is an increasingly common approach to river restoration in the United States
Dam‐removal studies provide insights on key controls influencing the physical and ecological responses to dam removal
Although many aspects of physical and ecological systems react quickly to dam removal, overall response trajectories depend on how and where dams are removed and overall watershed conditions
Summary
A systematic review and meta‐analyses were conducted to evaluate the effects of interventions to reduce sugar‐sweetened beverages (SSB) or increase water intakes and to examine the impact of ...behaviour change techniques (BCTs) in consumption patterns. Randomized and nonrandomized controlled trials published after January 1990 and until December 2016 reporting daily changes in intakes of SSB or water in volumetric measurements (mL d−1) were included. References were retrieved through searches of electronic databases and quality appraisal followed Cochrane principles. We calculated mean differences (MD) and synthesized data with random‐effects models. Forty studies with 16 505 participants were meta‐analysed. Interventions significantly decreased consumption of SSB in children by 76 mL d−1 (95% confidence interval CI −105 to −46; 23 studies, P < 0.01), and in adolescents (−66 mL d−1, 95% CI −130 to −2; 5 studies, P = 0.04) but not in adults (−13 mL d−1, 95% CI −44 to 18; 12 studies, P = 0.16). Pooled estimates of water intakes were only possible for interventions in children, and results were indicative of increases in water intake (MD +67 mL d−1, 95% CI 6 to 128; 7 studies, P = 0.04). For children, there was evidence to suggest that modelling/demonstrating the behaviour helped to reduce SSB intake and that interventions within the home environment had greater effects than school‐based interventions. In conclusion, public health interventions – mainly via nutritional education/counselling – are moderately successful at reducing intakes of SSB and increasing water intakes in children. However, on average, only small reductions in SSBs have been achieved by interventions targeting adolescents and adults. Complementary measures may be needed to achieve greater improvements in both dietary behaviours across all age groups.
An operando electrochemical stage for the transmission electron microscope has been configured to form a “Li battery” that is used to quantify the electrochemical processes that occur at the anode ...during charge/discharge cycling. Of particular importance for these observations is the identification of an image contrast reversal that originates from solid Li being less dense than the surrounding liquid electrolyte and electrode surface. This contrast allows Li to be identified from Li-containing compounds that make up the solid-electrolyte interphase (SEI) layer. By correlating images showing the sequence of Li electrodeposition and the evolution of the SEI layer with simultaneously acquired and calibrated cyclic voltammograms, electrodeposition, and electrolyte breakdown processes can be quantified directly on the nanoscale. This approach opens up intriguing new possibilities to rapidly visualize and test the electrochemical performance of a wide range of electrode/electrolyte combinations for next generation battery systems.
Fracture pattern development has been a challenging area of research in the Earth sciences for more than 100 years. Much has been learned about the spatial and temporal complexity inherent to these ...systems, but severe challenges remain. Future advances will require new approaches. Chemical processes play a larger role in opening‐mode fracture pattern development than has hitherto been appreciated. This review examines relationships between mechanical and geochemical processes that influence the fracture patterns recorded in natural settings. For fractures formed in diagenetic settings (~50 to 200 °C), we review evidence of chemical reactions in fractures and show how a chemical perspective helps solve problems in fracture analysis. We also outline impediments to subsurface pattern measurement and interpretation, assess implications of discoveries in fracture history reconstruction for process‐based models, review models of fracture cementation and chemically assisted fracture growth, and discuss promising paths for future work. To accurately predict the mechanical and fluid flow properties of fracture systems, a processes‐based approach is needed. Progress is possible using observational, experimental, and modeling approaches that view fracture patterns and properties as the result of coupled mechanical and chemical processes. A critical area is reconstructing patterns through time. Such data sets are essential for developing and testing predictive models. Other topics that need work include models of crystal growth and dissolution rates under geological conditions, cement mechanical effects, and subcritical crack propagation. Advances in machine learning and 3‐D imaging present opportunities for a mechanistic understanding of fracture formation and development, enabling prediction of spatial and temporal complexity over geologic timescales. Geophysical research with a chemical perspective is needed to correctly identify and interpret fractures from geophysical measurements during site characterization and monitoring of subsurface engineering activities.
Plain Language Summary
Fracture patterns in rock strongly affect directions, magnitudes, and heterogeneities of both fluid flow and rock strength. Accurate and testable predictions of patterns are essential for understanding many societally important processes in the Earth and for effectively managing subsurface engineering operations. Chemical processes play a larger role in opening‐mode fracture pattern development than has hitherto been appreciated. For fractures formed at depths of ~1–10 km and temperatures of 50–200 °C, new evidence shows chemical reactions are common and more diverse than previously recognized. We describe how viewing fracture formation and evolution from a chemical perspective helps to solve problems in fracture pattern analysis. We outline the main impediments to subsurface fracture pattern measurement and interpretation, assess implications of recent discoveries in fracture history reconstruction for process‐based models of fracture and cement accumulation, review models of fracture cementation and chemically assisted fracture growth, and discuss promising paths for future work. Potential exists for basic scientific investigations to lead to progress on what has been one of the most refractory practical problems in subsurface science. Results suggest that progress in fracture interpretation and prediction can be made using observational, experimental, modeling, and theoretical approaches that view fracture patterns as the result of coupled mechanical and chemical processes.
Key Points
A chemical perspective helps solve challenges to understanding subsurface fractures: inadequate samples, ambiguous analogs, and difficulties determining which models are correct from observations
Many tools of chemical analysis, experiment, modeling, and theory have yet to be brought to bear on understanding how fracture patterns develop at geological timescales
Chemical and mechanical investigations together have great potential to solve challenging practical problems in subsurface science
GOALS: The Great Observatories All-Sky LIRG Survey Armus, L.; Mazzarella, J. M.; Evans, A. S. ...
Publications of the Astronomical Society of the Pacific,
06/2009, Letnik:
121, Številka:
880
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The Great Observatories All-Sky LIRG Survey (GOALS20) combines data from NASA’sSpitzer Space Telescope,
Chandra X-Ray Observatory,
Hubble Space Telescope(HST), andGalaxy Evolution Explorer(GALEX) ...observatories, together with ground-based data, into a comprehensive imaging and spectroscopic survey of over 200 low-redshift (
z < 0.088
z
<
0.088
), Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of theIRASRevised Bright Galaxy Sample (RBGS), which comprises 629 extragalactic objects with 60 μm flux densities above 5.24 Jy, and Galactic latitudes above five degrees. The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams (type-1 and type-2 AGN, LINERs, and starbursts) as well as interaction stages (major mergers, minor mergers, and isolated galaxies). They provide an unbiased picture of the processes responsible for enhanced infrared emission in galaxies in the local Universe. As an example of the analytic power of the multiwavelength GOALS data set, we presentSpitzer, Chandra, HST,andGALEXimages and spectra for the interacting system VV 340 (IRAS
F14547 + 2449
F
14547
+
2449
). TheSpitzerMIPS imaging data indicates that between 80–95% of the total far-infrared emission (or about5 × 1011 L
⊙
5
×
10
11
L
⊙
) originates in VV 340 north. While theSpitzerIRAC colors of VV 340 north and south are consistent with star-forming galaxies, both theSpitzerIRS andChandraACIS data indicate the presence of an AGN in VV 340 north. The observed line fluxes, without correction for extinction, imply that the AGN accounts for less than 10%–20% of the observed infrared emission. The X-ray data are consistent with a heavily absorbed (
N
H
≥1024 cm-2
N
H
≥
10
24
cm
-
2
) AGN. The GALEX far and near-UV fluxes imply a extremely large infrared “excess” (IRX) for the system (FIR/Ffuv ∼ 81
F
IR
/
F
fuv
∼
81
) which is well above the correlation seen in starburst galaxies. Most of this excess is driven by VV 340 N, which has an IR excess of nearly 400. The VV 340 system seems to be comprised of two very different galaxies: an infrared luminous edge-on galaxy (VV 340 north) that dominates the long-wavelength emission from the system, which hosts a buried AGN; and a face-on starburst (VV 340 south) that dominates the short-wavelength emission.
One of the experimental challenges in the study of nanomaterials in liquids in the (scanning) transmission electron microscope ((S)TEM) is gaining quantitative information. A successful experiment in ...the fluid stage will depend upon the ability to plan for sensitive factors such as the electron dose applied, imaging mode, acceleration voltage, beam-induced solution chemistry changes, and the specifics of solution reactivity. In this paper, we make use of a visual approach to show the extent of damage of different instrumental and experimental factors in liquid samples imaged in the (S)TEM. Previous results as well as new insights are presented to create an overview of beam-sample interactions identified for changing imaging and experimental conditions. This work establishes procedures to understand the effect of the electron beam on a solution, provides information to allow for a deliberate choice of the optimal experimental conditions to enable quantification, and identifies the experimental factors that require further analysis for achieving fully quantitative results in the liquid (S)TEM.
An overview of beam-sample interactions identified for changing imaging and experimental conditions using a visual approach.
Thiopurine methyltransferase (TPMT) activity exhibits a monogenic codominant inheritance and catabolizes thiopurines. TPMT variant alleles are associated with low enzyme activity and pronounced ...pharmacologic effects of thiopurines. Loss‐of‐function alleles in the NUDT15 gene are common in Asians and Hispanics and reduce the degradation of active thiopurine nucleotide metabolites, also predisposing to myelosuppression. We provide recommendations for adjusting starting doses of azathioprine, mercaptopurine, and thioguanine based on TPMT and NUDT15 genotypes (updates on www.cpicpgx.org).
Broad absorption signatures from alkali metals, such as the sodium (Na I) and potassium (K I) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated ...gas giant exoplanets
. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles
. Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances
. Here we report an optical transmission spectrum for the 'hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logε
= Formula: see text, and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Z
/Z
= Formula: see text). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets
.
Many global environmental agendas, including halting biodiversity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the ...scale and degree of forest modification remain poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate a globally consistent, continuous index of forest condition as determined by the degree of anthropogenic modification. Globally, only 17.4 million km
of forest (40.5%) has high landscape-level integrity (mostly found in Canada, Russia, the Amazon, Central Africa, and New Guinea) and only 27% of this area is found in nationally designated protected areas. Of the forest inside protected areas, only 56% has high landscape-level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally.
We present an analysis of , O iii88, N ii122, and far-infrared (FIR) fine-structure line observations obtained with Herschel/PACS, for ∼240 local luminous infrared galaxies (LIRGs) in the Great ...Observatories All-sky LIRG Survey. We find pronounced declines ("deficits") of line-to-FIR continuum emission for N ii122, , and as a function of FIR color and infrared luminosity surface density, . The median electron density of the ionized gas in LIRGs, based on the N ii122/N ii205 ratio, is = 41 cm−3. We find that the dispersion in the deficit of LIRGs is attributed to a varying fractional contribution of photodissociation regions (PDRs) to the observed emission, f( ) = / , which increases from ∼60% to ∼95% in the warmest LIRGs. The / ratio is tightly correlated with the PDR gas kinetic temperature in sources where is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, , and intensity of the interstellar radiation field, G, in units of and find G/ ratios of ∼0.1-50 cm3, with ULIRGs populating the upper end of the distribution. There is a relation between G/ and , showing a critical break at 5 × 1010 L kpc−2. Below , G/ remains constant, 0.32 cm3, and variations in are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. Above , G/ increases rapidly with , signaling a departure from the typical PDR conditions found in normal star-forming galaxies toward more intense/harder radiation fields and compact geometries typical of starbursting sources.
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