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61.
62.
Emily C. Hazell Claus Rinner 《International journal of geographical information science》2020,34(8):1648-1681
ABSTRACT Modelling changes in biodiversity have become a necessary component of smart urban planning practices. However, concepts such as biodiversity are often evaluated using area-based composite indices, the results of which are heavily reliant on specific parameters chosen. This paper explores the design and implementation of a butterfly biodiversity index by comparing two widely accepted modelling techniques: principal component analysis and spatial multi-criteria decision analysis (MCDA). A high degree of scale dependency has been demonstrated in previous studies exploring the use of area-based composite measures. To evaluate the impact of scale, each model was assessed at two different spatial resolutions. The outcomes were analyzed, mapped and compared using ordinary least squares, geographically weighted regression and global Moran’s I to evaluate relative biodiversity patterns across the City of Toronto, Canada. Findings indicate that the impact of spatial scale was significant, whereby the coarser resolution models were found to be more highly correlated with biodiversity, compared to the finer resolution models. The results of this study contribute to a growing body of literature that explores key conceptual questions regarding the robustness of GIS-based MCDA, the impact of scale in urban ecology studies, and the use of composite indices to manage spatial ecological data. 相似文献
63.
FIRST RESULTS FROM VIRGO,THE EXPERIMENT FOR HELIOSEISMOLOGY AND SOLAR IRRADIANCE MONITORING ON SOHO 总被引:1,自引:0,他引:1
Fröhlich Claus Andersen Bo N. Appourchaux Thierry Berthomieu Gabrielle Crommelynck Dominique A. Domingo Vicente Fichot Alain Finsterle Wolfgang Gómez Maria F. Gough Douglas Jiménez Antonio Leifsen Torben Lombaerts Marc Pap Judit M. Provost Janine Roca Cortés Teodoro Romero José Roth Hansjörg Sekii Takashi Telljohann Udo Toutain Thierry Wehrli Christoph 《Solar physics》1997,170(1):1-25
First results from the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and Heliospheric Observatory) are reported. The observations started mid-January 1996 for the radiometers and sunphotometers and near the end of March for the luminosity oscillation imager. The performance of all the instruments is very good, and the time series of the first 4–6 months are evaluated in terms of solar irradiance variability, solar background noise characteristics and p-mode oscillations. The solar irradiance is modulated by the passage of active regions across the disk, but not all of the modulation is straightforwardly explained in terms of sunspot flux blocking and facular enhancement. Helioseismic inversions of the observed p-mode frequencies are more-or-less in agreement with the latest standard solar models. The comparison of VIRGO results with earlier ones shows evidence that magnetic activity plays a significant role in the dynamics of the oscillations beyond its modulation of the resonant frequencies. Moreover, by comparing the amplitudes of different components ofp -mode multiplets, each of which are influenced differently by spatial inhomogeneity, we have found that activity enhances excitation. 相似文献
64.
65.
Claus Tappert Boris T. Gänsicke Ronald E. Mennickent Linda Schmidtobreick 《Astrophysics and Space Science》2006,304(1-4):299-301
We present preliminary results on spectroscopic data of the candidate pre-cataclysmic variable LTT 560. A fit to the flux-calibrated spectrum reveals the temperature of the white-dwarf primary to be T
eff=7000–7500 K, and confirms the result of previous studies on the detection of an M5V secondary star. The analysis of radial velocity data from spectral features attributed to the primary and the secondary star show evidence for low-level accretion. 相似文献
66.
Maria I. Velez Jason H. Curtis Mark Brenner Jaime Escobar Barbara W. Leyden Marion Popenoe de Hatch 《Geoarchaeology》2011,26(3):346-364
We inferred the late Holocene environmental history of the Guatemala highlands from multiple lines of evidence in a sediment core from Lake Amatitlán. Inferred environmental changes are generally synchronous with archaeologically documented highland Maya cultural shifts. Population increases in the Middle Preclassic, Early Classic, and Late Postclassic are associated with deforestation and soil erosion. Land abandonment in the Late Preclassic, Late Classic, and Early Postclassic is associated with evidence for reforestation and soil stabilization. Diatoms indicate relatively lower lake level and greater trophic status at times of reduced human impact, from ca. 250 B.C. to A.D. 125 and from ca. A.D. 875 to 1375. Decreased water levels were probably due to drier climate, to reforestation, or both. Lake eutrophication was caused by reduced water volume combined with a legacy of long‐term agricultural activity. Our data contribute to the understanding of relations among ancient Maya culture, climate, and environment. © 2011 Wiley Periodicals, Inc. 相似文献
67.
Raffaella Meffe Gudrun Massmann Claus Kohfahl Thomas Taute Doreen Richter Uwe Dünnbier Asaf Pekdeger 《Environmental Earth Sciences》2012,65(3):861-870
The groundwater downstream of a former sewage irrigation farm in Berlin is contaminated with ammonium (NH4
+) and para-toluenesulfonamide (p-TSA), besides other anthropogenic pollutants. In the field, in situ removal of NH4
+ by gaseous oxygen (O2) and air injection is currently being tested. A laboratory column experiment using aquifer material and groundwater from
the site was performed to determine whether this remediation technology is also feasible to reduce high p-TSA concentrations in the anoxic groundwater. First, the column was operated under anoxic conditions. Later, compressed air
was introduced into the system to simulate oxic conditions. Samples were collected from the column outlet before and after
the addition of compressed air. The experiment revealed that whereas p-TSA was not removed under anoxic conditions, it was almost fully eliminated under oxic conditions. Results were modelled
using a transient one-dimensional solute transport model. The degradation rate constants for p-TSA increased from 2.8E−06 to 7.5E−05 s–1 as a result of microbial adaption to the change of redox conditions. Results show that O2 injection into an anoxic aquifer is a successful strategy for p-TSA remediation. 相似文献
68.
Jaime Escobar Mark Brenner Thomas J. Whitmore William F. Kenney Jason H. Curtis 《Journal of Paleolimnology》2008,40(2):715-731
Fifty-seven surface sediment samples from 35 Florida lakes were collected to study testate amoebae. Seven genera, 17 species,
and 28 strains were identified in the 46 sediment samples from 31 lakes that contained testate rhizopods. Seven species accounted
for ≥90% of the individuals in all samples. Sediment total phosphorus (TPsed), organic matter (OM), and total carbon:total
nitrogen ratio (TC:TN) were measured to assess the effect of these variables on thecamoebian assemblages. OM content was the
only sediment variable that influenced presence/absence of thecamoebians. Samples with <5% OM contained no thecamoebians.
Lakes with multiple surface sediment samples showed high Morisita–Horn similarity values (0.74–0.99), indicating that all
sites at which samples were collected in a lake provided representative thecamoebian assemblages. No relationship was observed
between thecamoebian diversity indices and sediment variables. Lake trophic state and pH were examined to explore potential
water column influences on thecamoebian communities. Highest thecamoebian diversity indices were found in mesotrophic to eutrophic
lakes with pH near 8.0. These results suggest that water column conditions have a greater influence on thecamoebian assemblages
than do sediment variables. We used multivariate analysis to evaluate the relations between water quality variables and testate
rhizopod assemblages. Canonical correspondence analysis (CCA) showed that alkalinity and pH are the water column variables
that most influence the relative abundance of species. Thecamoebians thus hold promise as bioindicators of acidification in
Florida lakes. Thecamoebian remains in lake sediment cores should be useful to infer past anthropogenic shifts in lake pH. 相似文献
69.
70.
Eruptive style of the young high-Mg basaltic-andesite Pelagatos scoria cone,southeast of México City 总被引:1,自引:1,他引:0
The eruption of the Pelagatos scoria cone in the Sierra Chichinautzin monogenetic field near the southern suburbs of Mexico
City occurred less than 14,000 years ago. The eruption initiated at a fissure with an effusive phase that formed a 7-km-long
lava flow, and continued with a phase of alternating and/or simultaneous explosive and effusive activity that built a 50-m-high
scoria cone on the western end of the fissure and formed a compound lava flow-field near the vent. The eruption ended with
the emplacement of a short lava flow that breached the cone and was accompanied by weak explosions at the crater. Products
consist of a microlite-rich high-Mg basaltic andesite. Samples were analyzed to determine the magma’s initial properties as
well as the effects of degassing-induced crystallization on eruptive style. Although distal ash fallout deposits from this
eruption are not preserved, a recent quarry exposes a large section of the scoria cone. Detailed study of exposed layers allows
us to elucidate the mode of cone-building activity. Petrological and textural data, combined with models calibrated by experimental
work and melt-inclusion analyses of similar magmas elsewhere, indicate that the magma was initially hot (>1,200°C), gas-rich
(up to 5 wt.% H2O), crystal-poor (~10 vol.% Fo90 olivine phenocrysts) and thus poorly viscous (40–80 Pa s). During the early phase, low magma ascent velocity at the fissure
vent allowed low-viscosity magma to degas and crystallize during ascent, producing lava flows with elevated crystal contents
at T < 1,100°C, and blocky surfaces. Later, the closure of the fissure by cooling dikes focused the magma flow at a narrow section
of the fissure. This led to an increased magma ascent velocity. Rapid and shallow degassing (<3 km deep) triggered ~40 vol.%
microlite crystallization. Limited times for gas-escape and higher magma viscosity (6 × 105–4 × 106 Pa s) drove strong explosions of highly (60–80 vol.%) and finely vesicular magma. Coarse clasts broke on landing, which implies
brittle behavior due to complete solidification. This requires sufficient time to cool and in turn implies ejection heights
of over 1 km, which is much higher than “normal” Strombolian activity. Hence, magma viscosity significantly impacts eruption style at monogenetic volcanoes because it affects the kinetics
of shallow degassing. The long-lasting eruptions of Jorullo and Paricutin, which produced similar magmas in western México,
were more explosive. This can be related to higher magma fluxes and total erupted volumes. Implications of this study are
important because basaltic andesites are commonly erupted to form monogenetic scoria cones of the Trans-Mexican Volcanic Belt. 相似文献