Exurbia from the bottom-up: Confronting empirical challenges to characterizing a complex system   总被引：2，自引：0，他引：2  

Daniel G. Brown  Derek T. Robinson  Li An  Moira Zellner  William Rand  Rick Riolo  Bobbi Low 《Geoforum》2008,39(2):805-818

We describe empirical results from a multi-disciplinary project that support modeling complex processes of land-use and land-cover change in exurban parts of Southeastern Michigan. Based on two different conceptual models, one describing the evolution of urban form as a consequence of residential preferences and the other describing land-cover changes in an exurban township as a consequence of residential preferences, local policies, and a diversity of development types, we describe a variety of empirical data collected to support the mechanisms that we encoded in computational agent-based models. We used multiple methods, including social surveys, remote sensing, and statistical analysis of spatial data, to collect data that could be used to validate the structure of our models, calibrate their specific parameters, and evaluate their output. The data were used to investigate this system in the context of several themes from complexity science, including have (a) macro-level patterns; (b) autonomous decision making entities (i.e., agents); (c) heterogeneity among those entities; (d) social and spatial interactions that operate across multiple scales and (e) nonlinear feedback mechanisms. The results point to the importance of collecting data on agents and their interactions when producing agent-based models, the general validity of our conceptual models, and some changes that we needed to make to these models following data analysis. The calibrated models have been and are being used to evaluate landscape dynamics and the effects of various policy interventions on urban land-cover patterns.  相似文献   

Rate constants for the reactions of the NO3 radical with HCOOH/HCOO− and CH3COOH/CH3COO− in aqueous solution between 278 and 328 K     

M. Exner  H. Herrmann  R. Zellner 《Journal of Atmospheric Chemistry》1994,18(4):359-378

The kinetics of the aqueous phase reactions of NO₃ radicals with HCOOH/HCOO^– and CH₃COOH/CH₃COO^– have been investigated using a laser photolysis/long-path laser absorption technique. NO₃ was produced via excimer laser photolysis of peroxodisulfate anions (S₂O ₈ ^2– ) at 351 nm followed by the reactions of sulfate radicals (SO ₄ ^– ) with excess nitrate. The time-resolved detection of NO₃ was achieved by long-path laser absorption at 632.8 nm. For the reactions of NO₃ with formic acid (1) and formate (2) rate coefficients ofk ₁=(3.3±1.0)×10⁵ l mol^–1 s^–1 andk ₂=(5.0±0.4)×10⁷ l mol^–1 s^–1 were found atT=298 K andI=0.19 mol/l. The following Arrhenius expressions were derived:k ₁(T)=(3.4±0.3)×10¹⁰ exp[–(3400±600)/T] l mol^–1 s^–1 andk ₂(T)=(8.2±0.8)×10¹⁰ exp[–(2200±700)/T] l mol^–1 s^–1. The rate coefficients for the reactions of NO₃ with acetic acid (3) and acetate (4) atT=298 K andI=0.19 mol/l were determined as:k ₃=(1.3±0.3)×10⁴ l mol^–1 s^–1 andk ₄=(2.3±0.4)×10⁶ l mol^–1 s^–1. The temperature dependences for these reactions are described by:k ₃(T)=(4.9±0.5)×10⁹ exp[–(3800±700)/T] l mol^–1 s^–1 andk ₄(T)=(1.0±0.2)×10¹² exp[–(3800±1200)/T] l mol^–1 s^–1. The differences in reactivity of the anions HCOO^– and CH₃COO^– compared to their corresponding acids HCOOH and CH₃COOH are explained by the higher reactivity of NO₃ in charge transfer processes compared to H atom abstraction. From a comparison of NO₃ reactions with various droplets constituents it is concluded that the reaction of NO₃ with HCOO^– may present a dominant loss reaction of NO₃ in atmospheric droplets.  相似文献   

Photometric properties of outer planetary satellites     

J. Degewij  L.E. Andersson  B. Zellner 《Icarus》1980,44(2):520-540

We present optical broadband photometry for the satellites J6, J7, J8, S7, S9, U3, U4, N1, and polarimetry for J6, obtained between 1970 and 1979. The outer Jovian satellites resemble C-type asteroids; J6 has a rotational lightcurve with period ～9.5 hr. The satellites beyond Jupiter also show C-like colors with the exception of S7 Hyperion. S9 Phoebe has a rotational lightcurve with period near either 11.25 or 21.1 hr. For U4 and N1 there is evidence for a lightcurve synchronous with the orbital revolution. The seven brighter Saturnian satellites show a regular relation between the ultraviolet dropoff and distance to the planet, probably related with differences in the rock component on their surfaces.  相似文献   

Surface texture of Vesta from optical polarimetry     

T. Le Bertre  B. Zellner 《Icarus》1980,43(2):172-180

Polarimetric, photometric, and reflectance spectroscopic properties of asteroid 44 Vesta are simulated in the laboratory by a preparation of eucrite Bereba consisting oof a broad mixture of particle sizes (mainly greater than 50-μm) mixed and partially coated with particles of size 10 μm and less. Coarse grains are necessary for producing the same albedo and a very fine dust coating is necessary for producing the same polarization inversion angle as observed for Vesta. There are less small grains and fine dust in this sample than in lunar soils. Photometrically, if coating a sphere, this sample shows a constant brightness on the sunward half of the observed hemisphere, the brightness being given on the other half by the Minnaert reciprocity principle. With such a photometric behavior, the global geometric albedo and the sub-Earth point geometric albedo differ by no more than 5%. The microscopic phase coefficient β is 0.021 magnitude per degree for the sample; the larger value, β = 0.025, observed telescopically for Vesta indicates that large-scale roughness is present on this asteroid.  相似文献   

Surface properties of asteroids: A synthesis of polarimetry,radiometry, and spectrophotometry     

Clark R. Chapman  David Morrison  Ben Zellner 《Icarus》1975,25(1):104-130

The surface compositions of 110 asteroids are analyzed from statistically representative data sets of polarimetry as a function of phase angle, broad-band radiometry near 10 and 20 μm, and visible and near-infrared spectrophotometry. A comparison of albedos and diameters determined by polarimetry and radiometry shows that a modest upward revision of the radiometric albedo scale is needed and that a single law relating the slope of the polarization-phase curve to geometric albedo may not hold for very dark asteroids. We present reliable adopted albedos and diameters for 56 objects. Roughdi ameters for 52 additional objects are obtained from spectrophotometry using a correlation between albedo and color. Corrections for sampling bias permit investigation of asteroid compositions as a function of diameter, orbit, and other parameters.More than 90% of the minor planets fall into two broad compositional groups, defined by several optical parameters, designated by the symbols C and S. Comparisons with meteorite spectral albedo curves suggest that the two groups are compositionally similar to carbonaceous and stony-metallic meteorites, respectively. C-type asteroids predominate in the belt, especially in the outer half. An unusual distribution of compositions is found between 2.77 and 3.0 AU. Many S-type objects have diameters of 100–200 km; C-type objects are much more common at both larger and smaller sizes. Vesta is unique, being apparently the only differentiated asteroid remaining intact in the belt. The largest C-type objects are compositionally distinct from smaller ones and possibly are metamorphosed. We sketch some implications for meteoritics and for the early history of the solar system and point to the need for further systematic sampling of smaller and fainter objects by these three observational techniques.  相似文献   

Surface complexation of neodymium at the rutile-water interface: A potentiometric and modeling study in NaCl media to 250°C     

Moira K. Ridley  Michael L. Machesky  Donald A. Palmer 《Geochimica et cosmochimica acta》2005,69(1):63-81

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Methoxy formation in the reaction of CH3O2 radicals with NO     

R. Zellner  B. Fritz  K. Lorenz 《Journal of Atmospheric Chemistry》1986,4(2):241-251

Formation of methoxy (CH₃O) radicals in the reaction (1) CH₃O₂+NOCH₃O+NO₂ at 298 K has been observed directly using time resolved LIF. The branching ratio % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqOXdyMaae% 4qaiaabIeadaWgaaWcbaGaae4maaqabaGccaqGpbGaaeiiaiaabIca% ieqacaWF9aGaa8hiaiaa-nbicaWFGaGaeuiLdqKaai4waiaaboeaca% qGibWaaSbaaSqaaiaabodaaeqaaOGaae4taiaac2facaWFVaGaeuiL% dqKaai4waiaaboeacaqGibWaaSbaaSqaaiaabodaaeqaaOGaae4tam% aaBaaaleaacaqGYaaabeaakiaac2facaqGPaaaaa!4E31!\[\phi {\rm{CH}}_{\rm{3}} {\rm{O (}} = -- \Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}]/\Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}_{\rm{2}} ]{\rm{)}}\] has been determined by quantitative cw-UV-laser absorption at 257 nm of CH₃O₂ and CH₃ONO, the product of the consecutive methoxy trapping reaction (2) % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4qaiaabI% eadaWgaaWcbaGaae4maaqabaGccaqGpbacbeGaa83kaiaa-bcaieaa% caGFobGaa43taiaa+bcacaGFOaGaa83kaiaa+1eacaGFPaGaa4hiai% abgkziUkaabccacaqGdbGaaeisamaaBaaaleaacaqGZaaabeaakiaa% b+eacaqGGaGaaeOtaiaab+eacaqGGaGaa4hkaiaa-TcacaGFnbGaa4% xkaiaa+5cacaGFGaGaa4hiaiabeA8aMnaaBaaajqwaacqaaiaaboea% caqGibWaaSbaaKazcaiabaGaae4maaqabaqcKfaGaiaab+eaaSqaba% aaaa!55AC!\[{\rm{CH}}_{\rm{3}} {\rm{O}} + NO ( + M) \to {\rm{ CH}}_{\rm{3}} {\rm{O NO }}( + M). \phi _{{\rm{CH}}_{\rm{3}} {\rm{O}}} \] is found to be (1.0±0.2). The rate constant k ₁ is (7±2) 10^-12 cm³/molecule · s in good agreement with previous results.  相似文献   

Chemical Mechanism Development: Laboratory Studies and Model Applications     

Harald Geiger  Ian Barnes  Karl H. Becker  Birger Bohn  Theo Brauers  Birgit Donner  Hans-Peter Dorn  Manfred Elend  Carlos M. Freitas Dinis  Dirk Grossmann  Heinz Hass  Holger Hein  Axel Hoffmann  Lars Hoppe  Frank Hülsemann  Dieter Kley  Björn Klotz  Hans G. Libuda  Tobias Maurer  Djuro Mihelcic  Geert K. Moortgat  Romeo Olariu  Peter Neeb  Dirk Poppe  Lars Ruppert  Claudia G. Sauer  Oleg Shestakov  Holger Somnitz  William R. Stockwell  Lars P. Thüner  Andreas Wahner  Peter Wiesen  Friedhelm Zabel  Reinhard Zellner  Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357

Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.  相似文献   

CAPRAM2.3: A Chemical Aqueous Phase Radical Mechanism for Tropospheric Chemistry     

H. Herrmann  B. Ervens  H.-W. Jacobi  R. Wolke  P. Nowacki  R. Zellner 《Journal of Atmospheric Chemistry》2000,36(3):231-284

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Mesozooplankton biomass and grazing responses to Cyclone Opal, a subtropical mesoscale eddy     

Michael R. Landry  Moira Decima  Melinda P. Simmons  Cecelia C.S. Hannides  Emy Daniels 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1378

As part of E-Flux III cruise studies in March 2005, plankton net collections were made to assess the effects of a cyclonic cold-core eddy (Cyclone Opal) on the biomass and grazing of mesozooplankton. Mesozooplankton biomass in the central region of Cyclone Opal, an area of uplifted nutricline and a subsurface diatom bloom, averaged 0.80±0.24 and 1.51±0.59 g DW m⁻², for day and night tows, respectively. These biomass estimates were about 80% higher than control (OUT) stations, with increases more or less proportionately distributed among size classes from 0.2 to >5 mm. Though elevated relative to surrounding waters south of the Hawaiian Islands (Hawai’i lee), total biomass and size distribution in Cyclone Opal were almost exactly the same as contemporary measurements made at Stn. ALOHA, 100 km north of the islands, by the HOT (Hawaii Ocean Time-series) Program. Mesozooplankton biomass and community composition at the OUT stations were also similar to ALOHA values from 1994 to 1996, preceding a recent decadal increase. These comparisons may therefore provide insight into production characteristics or biomass gradients associated with decadal changes at Stn. ALOHA. Gut fluorescence estimates were higher in Opal than in ambient waters, translating to grazing impacts of 0.11±0.02 d⁻¹ (IN) versus 0.03±0.01 d⁻¹ (OUT). Over the depth-integrated euphotic zone, mesozooplankton accounted for 30% of the combined grazing losses of phytoplankton to micro- and meso-herbivores in Opal, as compared to 13% at control stations. Estimates of active export flux by migrating zooplankton averaged 0.81 mmol C m⁻² d⁻¹ in Cyclone Opal and 0.37 mmol C m⁻² d⁻¹ at OUT stations, 53% and 24%, respectively, of the carbon export measured by passive sediment traps. Migrants also exported 0.18 mmol N m⁻² d⁻¹ (117% of trap N flux) in Cyclone Opal compared to 0.08 mmol N m⁻² d⁻¹ (51% of trap flux) at control stations. Overall, the food-web importance of mesozooplankton increased in Cyclone Opal both in absolute and relative terms. Diel migrants provided evidence for enhanced export flux in the eddy that was missed by sediment trap and ²³⁴Th techniques, and migrant-mediated flux was the major export term in the observed bloom-perturbation response and N mass balance of the eddy.  相似文献