Environmental controls of wood entrapment in upper Midwestern streams     

Eric Christopher Merten  Jacques Finlay  Lucinda Johnson  Raymond Newman  Heinz Stefan  Bruce Vondracek 《水文研究》2011,25(4):593-602

Wood deposited in streams provides a wide variety of ecosystem functions, including enhancing habitat for key species in stream food webs, increasing geomorphic and hydraulic heterogeneity and retaining organic matter. Given the strong role that wood plays in streams, factors that influence wood inputs, retention and transport are critical to stream ecology. Wood entrapment, the process of wood coming to rest after being swept downstream at least 10 m, is poorly understood, yet important for predicting stream function and success of restoration efforts. Data on entrapment were collected for a wide range of natural wood pieces (n = 344), stream geomorphology and hydraulic conditions in nine streams along the north shore of Lake Superior in Minnesota. Locations of pieces were determined in summer 2007 and again following an overbank stormflow event in fall 2007. The ratio of piece length to effective stream width (length ratio) and the weight of the piece were important in a multiple logistic regression model that explained 25% of the variance in wood entrapment. Entrapment remains difficult to predict in natural streams, and often may simply occur wherever wood pieces are located when high water recedes. However, this study can inform stream modifications to discourage entrapment at road crossings or other infrastructure by applying the model formula to estimate the effective width required to pass particular wood pieces. Conversely, these results could also be used to determine conditions (e.g. pre‐existing large, stable pieces) that encourage entrapment where wood is valued for ecological functions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

First ENA observations at Mars: ENA emissions from the martian upper atmosphere     

Y. Futaana  S. Barabash  M. Holmström  E. Kallio  H. Gunell  R. Lundin  M. Yamauchi  J.D. Winningham  J.R. Sharber  A.J. Coates  D.O. Kataria  P. Riihelä  H. Koskinen  J. Luhmann  D. Williams  C.C. Curtis  B.R. Sandel  M. Carter  A. Fedorov  S. Orsini  M. Maggi  P. Bochsler  N. Krupp  M. Fränz  C. Dierker 《Icarus》2006,182(2):424-430

The neutral particle detector (NPD) on board Mars Express has observed energetic neutral atoms (ENAs) from a broad region on the dayside of the martian upper atmosphere. We show one such example for which the observation was conducted at an altitude of 570 km, just above the induced magnetosphere boundary (IMB). The time of flight spectra of these ENAs show that they had energies of 0.2-2 keV/amu, with an average energy of ∼1.1 keV/amu. Both the spatial distribution and the energy of these ENAs are consistent with the backscattered ENAs, produced by an ENA albedo process. This is the first observation of backscattered ENAs from the martian upper atmosphere. The origin of these ENAs is considered to be the solar wind ENAs that are scattered back by collision processes in the martian upper atmosphere. The particle flux and energy flux of the backscattered ENAs are and , respectively.  相似文献   

Negative ion chemistry in Titan's upper atmosphere     

V. Vuitton  P. Lavvas  M. Galand  G.R. Lewis  A.J. Coates  J.-E. Wahlund 《Planetary and Space Science》2009,57(13):1558-662

The Electron Spectrometer (ELS), one of the sensors making up the Cassini Plasma Spectrometer (CAPS) revealed the existence of numerous negative ions in Titan's upper atmosphere. The observations at closest approach (∼1000 km) show evidence for negatively charged ions up to ∼10,000 amu/q, as well as two distinct peaks at 22±4 and 44±8 amu/q, and maybe a third one at 82±14 amu/q. We present the first ionospheric model of Titan including negative ion chemistry. We find that dissociative electron attachment to neutral molecules (mostly HCN) initiates the formation of negative ions. The negative charge is then transferred to more acidic molecules such as HC₃N, HC₅N or C₄H₂. Loss occurs through associative detachment with radicals (H and CH₃). We attribute the three low mass peaks observed by ELS to CN⁻, C₃N⁻/C₄H⁻ and C₅N⁻. These species are the first intermediates in the formation of the even larger negative ions observed by ELS, which are most likely the precursors to the aerosols observed at lower altitudes.  相似文献   

Negative ions in the Enceladus plume     

A.J. Coates  G.H. Jones  G.R. Lewis  A. Wellbrock  D.T. Young  R.E. Johnson  T.W. Hill 《Icarus》2010,206(2):618-622

During Cassini’s Enceladus encounter on 12th March 2008, the Cassini Electron Spectrometer, part of the CAPS instrument, detected fluxes of negative ions in the plumes from Enceladus. It is thought that these ions include negatively charged water group cluster ions associated with the plume and forming part of the ‘plume ionosphere’. In this paper we present our observations, argue that these are negative ions, and present preliminary mass identifications. We also suggest mechanisms for production and loss of the ions as constrained by the observations. Due to their short lifetime, we suggest that the ions are produced in or near the water vapour plume, or from the extended source of ice grains in the plume. We suggest that Enceladus now joins the Earth, Comet Halley and Titan as locations in the Solar System where negative ions have been directly observed although the ions observed in each case have distinctly different characteristics.  相似文献   

Downhole Weir for Measuring Flow Rate in RecirculationWellsWells     

Tyler Gilmore  John Davis  James Coates 《Ground Water Monitoring & Remediation》1998,18(3):146-150

Recirculating wells are increasingly being used for ground water remediation and aquifer characterization investigations. Determination of flow rate is required for proper design and spacing of recirculation wells. The measurement of flow rate, however, can be difficult using standard equipment. To overcome some of the flow measurement problems associated with more common measurement systems, a new device in the form of a downhole weir was developed for recirculating wells that use a two-casing design. The weir was designed to measure flow rates between 10 and 40 gpm. In this flow range, the weir had an accuracy of ±2.8 gpm. This accuracy may be improved with some modifications.  相似文献   

The Development of the Chagas' Online Data Entry System (CODES-GIS)     

Jason K Blackburn  rew Curtis  Frances Currin Mujica  Farrell Jones  Patricia Dorn  Rosamond Coates 《Transactions in GIS》2008,12(2):249-265

This article describes a web‐based data entry and GIS‐driven mapping system designed for an ethnographic and entomological survey of Chagas’ disease, an emerging zoonotic disease, and Triatoma dimidiata, a primary vector, in the Los Tuxtlas region of Veracruz, Mexico. To better understand this disease in the region, a collaborative, multi‐disciplinary study was initiated to conduct a spatial investigation of T. dimidiata and a community‐by‐community survey of local perceptions of the disease. In order to facilitate such a collaborative effort the CODES‐GIS was developed. This system allows for (near) real‐time mapping, analyses, disease reporting, and results sharing. CODES‐GIS provides a framework for a research team working in a remote area with limited technology, software, or GIS expertise to benefit from (near) real‐time spatial analyses performed at collaborating institutions. The system is bi‐directional, where field personnel can upload data to the system for field‐based map production. Likewise, laboratory personnel can upload diagnostics data for viewing by field personnel. In this way, the system provides a virtual link between the field and the laboratory to increase the speed at which results are returned to the local community. The CODES‐GIS is described along with a selection of study results.  相似文献   

Observations of magnetic anomaly signatures in Mars Express ASPERA-3 ELS data     

Y. Soobiah  A.J. Coates  D.O. Kataria  R.A. Frahm  J.R. Scherrer  R. Lundin  H. Andersson  A. Grigoriev  H. Koskinen  T. Säles  W. Schmidt  J. Luhmann  D. Williams  C.C. Curtis  B.R. Sandel  M. Carter  A. Fedorov  S. McKenna-Lawler  R. Cerulli-Irelli  P. Wurz  N. Krupp  M. Fränz  C. Dierker 《Icarus》2006,182(2):396-405

Mars Express (MEX) Analyser of Space Plasmas and Energetic Atoms (ASPERA-3) data is providing insights into atmospheric loss on Mars via the solar wind interaction. This process is influenced by both the interplanetary magnetic field (IMF) in the solar wind and by the magnetic ‘anomaly’ regions of the martian crust. We analyse observations from the ASPERA-3 Electron Spectrometer near to such crustal anomalies. We find that the electrons near remanent magnetic fields either increase in flux to form intensified signatures or significantly reduce in flux to form plasma voids. We suggest that cusps intervening neighbouring magnetic anomalies may provide a location for enhanced escape of planetary plasma. Initial statistical analysis shows that intensified signatures are mainly a dayside phenomenon whereas voids are a feature of the night hemisphere.  相似文献   

First ENA observations at Mars: Subsolar ENA jet     

Y. Futaana  S. Barabash  M. Holmström  E. Kallio  H. Gunell  R. Lundin  M. Yamauchi  J.D. Winningham  J.R. Sharber  A.J. Coates  D.O. Kataria  P. Riihelä  H. Koskinen  J. Luhmann  D. Williams  C.C. Curtis  B.R. Sandel  M. Carter  A. Fedorov  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):413-423

The Neutral Particle Detector (NPD), an Energetic Neutral Atom (ENA) sensor of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) on board Mars Express, detected intense fluxes of ENAs emitted from the subsolar region of Mars. The typical ENA fluxes are (4-7) × 10⁵ cm⁻² sr⁻¹ s⁻¹ in the energy range 0.3-3 keV. These ENAs are likely to be generated in the subsolar region of the martian exosphere. As the satellite moved away from Mars, the ENA flux decreased while the field of view of the NPD pointed toward the subsolar region. These decreases occurred very quickly with a time scale of a few tens of seconds in two thirds of the orbits. Such a behavior can be explained by the spacecraft crossing a spatially constrained ENA jet, i.e., a highly directional ENA emission from a compact region of the subsolar exosphere. This ENA jet is highly possible to be emitted conically from the subsolar region. Such directional ENAs can result from the anisotropic solar wind flow around the subsolar region, but this can not be explained in the frame of MHD models.  相似文献   

Solar wind plasma protrusion into the martian magnetosphere: ASPERA-3 observations     

E. Dubinin  D. Winningham  J. Woch  S. Barabash  R. Frahm  A.J. Coates  J.-A. Sauvaud  H. Andersson  A. Grigoriev  K. Asamura  K.S. Hsieh  H. Koskinen  P. Riihelä  T. Säles  J. Luhmann  R. Cerulli-Irelli  M. Maggi  D. Williams  P. Wurz  C. Dierker  M. Carter 《Icarus》2006,182(2):343-349

The ASPERA-3 experiment onboard the Mars Express spacecraft revealed, near the wake boundary of Mars, a spatially narrow, strip-like plasma structure composed of magnetosheath-like electrons and planetary ions. The peak electron energy often exceeds the peak energy at the bow shock that indicates a significant heating (acceleration) during the structure formation. It is shown that this structure is formed during efficient plasma penetration into the martian magnetosphere in the region near the terminator. The penetration of sheath electrons and their gradual heating (acceleration) is accompanied by a change of the ion composition from a solar wind plasma to a planetary plasma dominated by oxygen ions. A possible mechanism of plasma inflow to the magnetosphere is discussed.  相似文献   

First ENA observations at Mars: Solar-wind ENAs on the nightside     

K. Brinkfeldt  H. Gunell  P. C:son Brandt  R.A. Frahm  E. Kallio  Y. Futaana  R. Lundin  M. Yamauchi  J.R. Sharber  A.J. Coates  D.O. Kataria  T. Säles  W. Schmidt  J. Luhmann  D. Williams  C.C. Curtis  B.R. Sandel  M. Carter  A. Fedorov  S. McKenna-Lawler  R. Cerulli-Irelli  P. Wurz  N. Krupp  M. Fränz  C. Dierker 《Icarus》2006,182(2):439-447

We present measurements with an Energetic Neutral Atom (ENA) imager on board Mars Express when the spacecraft moves into Mars eclipse. Solar wind ions charge exchange with the extended Mars exosphere to produce ENAs that can spread into the eclipse of Mars due to the ions' thermal spread. Our measurements show a lingering signal from the Sun direction for several minutes as the spacecraft moves into the eclipse. However, our ENA imager is also sensitive to UV photons and we compare the measurements to ENA simulations and a simplified model of UV scattering in the exosphere. Simulations and further comparisons with an electron spectrometer sensitive to photoelectrons generated when UV photons interact with the spacecraft suggest that what we are seeing in Mars' eclipse are ENAs from upstream of the bow shock produced in charge exchange with solar wind ions with a non-zero temperature. The measurements are a precursor to a new technique called ENA sounding to measure solar wind and planetary exosphere properties in the future.  相似文献