1 We present a method for determining streambed seepage rates using time series thermal data. The new method is based on quantifying changes in phase and amplitude of temperature variations between ...pairs of subsurface sensors. For a reasonable range of streambed thermal properties and sensor spacings the time series method should allow reliable estimation of seepage rates for a range of at least +/-10 m d(-1) (+/-1.2 x 10(-2) m s(-1)), with amplitude variations being most sensitive at low flow rates and phase variations retaining sensitivity out to much higher rates. Compared to forward modeling, the new method requires less observational data and less setup and data handling and is faster, particularly when interpreting many long data sets. The time series method is insensitive to streambed scour and sedimentation, which allows for application under a wide range of flow conditions and allows time series estimation of variable streambed hydraulic conductivity. This new approach should facilitate wider use of thermal methods and improve understanding of the complex spatial and temporal dynamics of surface water-groundwater interactions.
Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and ...theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths ~2 x 10 super(8) G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs.
ABSTRACT
1. This paper reviews and compares the effects of forest fire and timber harvest on mammalian abundance and diversity, throughout successional time in the boreal forest of North America.
2. ...Temporal trends in mammal abundance and diversity are generally similar for both harvested and burned stands, with some differences occurring in the initiation stage (0–10 years post disturbance).
3. Small mammals and ungulates are most abundant immediately post disturbance, and decrease as stands age. Lynxes and hares utilize mid‐successional stands, but are rare in young and old stands. Bats, arboreal sciurids and mustelids increase in abundance with stand age, and are most abundant in old growth.
4. Substantial gaps in the data exist for carnivores; the response of these species to fire and harvest requires research, as predator–prey interactions can affect mammal community structure in both early and late successional stages.
5. The lack of explicit treatment of in‐stand forest structure post disturbance, in the reviewed literature made comparisons difficult. Where forest structure was considered, the presence of downed woody material, live residual trees and standing dead wood were shown to facilitate convergence of mammal communities to a pre‐disturbance state for both disturbance types.
6. Mammalian assemblages differed considerably between successional stages, emphasizing the importance of maintaining stands of each successional stage on the landscape when implementing forest management strategies.
We report a unique process for rapid synthesis of few-layer graphene films on Cu foil by microwave plasma chemical vapor deposition (MPCVD). We show that the plasma/metal interaction can be ...advantageous for a rapid synthesis of such thin films. The process can produce films of controllable quality from amorphous to highly crystalline by adjusting plasma conditions during growth processes of ∼100
s duration and with no supplemental substrate heating. Films have been characterized using Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results help to identify the stages involved in the MPCVD deposition of thin carbon films on Cu foil, and the findings open new pathways for a rapid growth of few-layer graphene films.
Chemical hydrides have been identified as a potential medium for on-board hydrogen storage, one of the most challenging technical barriers to the prospective transition from gasoline to ...hydrogen-powered vehicles. Systematic study of the feasibility of the sodium borohydride systems, and chemical-hydride systems more generally, requires detailed kinetic studies of the reaction for use in reactor modeling and system-level experiments. This work reports an experimental study of the kinetics of sodium borohydride hydrolysis with a Ru-on-carbon catalyst and a Langmuir-Hinshelwood kinetic model developed based on experimental data. The model assumes that the reaction consists of two important steps: the equilibrated adsorption of sodium borohydride on the surface of the catalyst and the reaction of the adsorbed species. The model successfully captures both the reaction's zero-order behavior at low temperatures and the first-order behavior at higher temperatures. Reaction rate constants at different temperatures are determined from the experimental data, and the activation energy is found to be 66.9
kJ
mol
−1 from an Arrhenius plot.
One of the most important applications for porous material with high surface area is the supercapacitor. For supercapacitors, power density and energy density are the most significant metrics. ...However, currently no dominant, established standard exists, and research papers often report these two metrics differently. A standard for reporting power and energy density is proposed here for objective comparison. This paper also discusses a common flaw in current supercapacitor power density calculations.
In many areas of the world, groundwater resources are increasingly stressed, and unsustainable use has become common. Where existing mechanisms for governing groundwater are ineffective or ...nonexistent, new ones need to be developed. Local level groundwater governance provides an intriguing alternative to top-down models, with the promise of enabling management to better match the diversity of physical and social conditions in groundwater basins. One such example is emerging in California, USA, where new state law requires new local agencies to self-organize and act to achieve sustainable groundwater management. In this article, we draw on insights from research on common pool resource management and natural resources governance to develop guidelines for institutional design for local groundwater governance, grounded in California’s developing experience. We offer nine criteria that can be used as principles or standards in the evaluation of institutional design for local level groundwater governance: scale, human capacity, funding, authority, independence, representation, participation, accountability, and transparency. We assert that local governance holds promise as an alternative to centralized governance in some settings but that its success will depend heavily on the details of its implementation. Further, for local implementation to achieve its promise, there remain important complementary roles for centralized governance. California’s developing experience with local level groundwater management in dozens of basins across the state provides a unique opportunity to test and assess the importance and influence of these criteria.
► Pulmonary neuroepithelial bodies (NEBs) are polymodal airway sensors. ► NEBs respond to hypoxia/hypercarbia/acidosis/and mechanical stretch stimuli. ► NEB signaling to the CNS occurs via extensive ...innervation. ► Alternatively, NEBs function as mechanosensors involved in lung vagal reflexes.
Pulmonary neuroepithelial bodies are polymodal sensors widely distributed within the airway mucosa of mammals and other species. Neuroepithelial body cells store and most likely release serotonin and peptides as transmitters. Neuroepithelial bodies have a complex innervation that includes vagal sensory afferent fibers and dorsal root ganglion fibers. Neuroepithelial body cells respond to a number of intraluminal airway stimuli, including hypoxia, hypercarbia, and mechanical stretch. This article reviews recent findings in the cellular and molecular biology of neuroepithelial body cells and their potential role as airway sensors involved in the control of respiration, particularly during the perinatal period. Alternate hypotheses and areas of controversy regarding potential function as mechanosensory receptors involved in pulmonary reflexes are discussed.
Cystic fibrosis (CF) is a recessive disease that affects multiple organs. It is caused by mutations in CFTR. Animal modeling of this disease has been challenging, with species- and strain-specific ...differences in organ biology and CFTR function influencing the emergence of disease pathology. Here, we report the phenotype of a CFTR-knockout ferret model of CF. Neonatal CFTR-knockout ferrets demonstrated many of the characteristics of human CF disease, including defective airway chloride transport and submucosal gland fluid secretion; variably penetrant meconium ileus (MI); pancreatic, liver, and vas deferens disease; and a predisposition to lung infection in the early postnatal period. Severe malabsorption by the gastrointestinal (GI) tract was the primary cause of death in CFTR-knockout kits that escaped MI. Elevated liver function tests in CFTR-knockout kits were corrected by oral administration of ursodeoxycholic acid, and the addition of an oral proton-pump inhibitor improved weight gain and survival. To overcome the limitations imposed by the severe intestinal phenotype, we cloned 4 gut-corrected transgenic CFTR-knockout kits that expressed ferret CFTR specifically in the intestine. One clone passed feces normally and demonstrated no detectable ferret CFTR expression in the lung or liver. The animals described in this study are likely to be useful tools for dissecting CF disease pathogenesis and developing treatments.
Emotions have long been regarded as a central component of the entertainment media experience. The present study combines computational analysis and quantitative content analysis to analyze the ...emotional arcs of inspirational media content and associated elicitors of self-transcendent emotions in order to develop a more comprehensive understanding of inspirational media. Results demonstrate that inspirational movies can be characterized by a positive shift in sentiment at the end of the narrative and multiple shifts between relatively negative and relatively positive sentiment throughout the story. Furthermore, the "peaks" and "valleys" in the emotional arcs are associated with the presence of differing inspirational elicitors, and the presence of certain elicitors (such as kindness/moral goodness) within a scene predicted positive shifts in the emotional arcs in the scenes following the elicitor.
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