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151.
Downtowns are responding to decades of decline through a variety of revitalization strategies. The progression and success of downtown renewal efforts are largely rooted in asset-based, mixed-use approaches to revitalization that mirror the evolving economic functions of downtowns. While contemporary economic revitalization strategies provide opportunities, their complexity also creates potential challenges for community organizations tasked with determining the highest and best uses for downtown properties. Accordingly, this article examines how the evolution of downtown economic revitalization strategies has influenced the capacity and expertise required by organizations engaged in the endeavor of downtown market analysis. In particular, we identify applied market analysis challenges arising from organizational deficiencies in expertise, credibility, scope, and technology adoption and propose capacity building opportunities for overcoming these deficits. 相似文献
152.
Matthew J. Wooller John W. Pohlman Benjamin V. Gaglioti Peter Langdon Miriam Jones Katey M. Walter Anthony Kevin W. Becker Kai-Uwe Hinrichs Marcus Elvert 《Journal of Paleolimnology》2012,48(1):27-42
Atmospheric contributions of methane from Arctic wetlands during the Holocene are dynamic and linked to climate oscillations. However, long-term records linking climate variability to methane availability in Arctic wetlands are lacking. We present a multi-proxy ~12,000?year paleoecological reconstruction of intermittent methane availability from a radiocarbon-dated sediment core (LQ-West) taken from a shallow tundra lake (Qalluuraq Lake) in Arctic Alaska. Specifically, stable carbon isotopic values of photosynthetic biomarkers and methane are utilized to estimate the proportional contribution of methane-derived carbon to lake-sediment-preserved benthic (chironomids) and pelagic (cladocerans) components over the last ~12,000?years. These results were compared to temperature, hydrologic, and habitat reconstructions from the same site using chironomid assemblage data, oxygen isotopes of chironomid head capsules, and radiocarbon ages of plant macrofossils. Cladoceran ephippia from ~4,000?cal?year BP sediments have ??13C values that range from ~?39 to ?31??, suggesting peak methane carbon assimilation at that time. These low ??13C values coincide with an apparent decrease in effective moisture and development of a wetland that included Sphagnum subsecundum. Incorporation of methane-derived carbon by chironomids and cladocerans decreased from ~2,500 to 1,500?cal?year BP, coinciding with a temperature decrease. Live-collected chironomids with a radiocarbon age of 1,640?cal?year BP, and fossil chironomids from 1,500?cal?year BP in the core illustrate that ??old?? carbon has also contributed to the development of the aquatic ecosystem since ~1,500?cal?year BP. The relatively low ??13C values of aquatic invertebrates (as low as ?40.5??) provide evidence of methane incorporation by lake invertebrates, and suggest intermittent climate-linked methane release from the lake throughout the Holocene. 相似文献
153.
A multimodel comparison of centennial Atlantic meridional overturning circulation variability 总被引:1,自引:1,他引:0
Matthew B. Menary Wonsun Park Katja Lohmann Michael Vellinga Matthew D. Palmer Mojib Latif Johann H. Jungclaus 《Climate Dynamics》2012,38(11-12):2377-2388
A mechanism contributing to centennial variability of the Atlantic Meridional Overturning Circulation (AMOC) is tested with multi-millennial control simulations of several coupled general circulation models (CGCMs). These are a substantially extended integration of the 3rd Hadley Centre Coupled Climate Model (HadCM3), the Kiel Climate Model (KCM), and the Max Plank Institute Earth System Model (MPI-ESM). Significant AMOC variability on time scales of around 100?years is simulated in these models. The centennial mechanism links changes in the strength of the AMOC with oceanic salinities and surface temperatures, and atmospheric phenomena such as the Intertropical Convergence Zone (ITCZ). 2 of the 3 models reproduce all aspects of the mechanism, with the third (MPI-ESM) reproducing most of them. A comparison with a high resolution paleo-proxy for Sea Surface Temperatures (SSTs) north of Iceland over the last 4,000?years, also linked to the ITCZ, suggests that elements of this mechanism may also be detectable in the real world. 相似文献
154.
Linking Inuit knowledge and meteorological station observations to understand changing wind patterns at Clyde River,Nunavut 总被引:1,自引:1,他引:0
Shari Gearheard Matthew Pocernich Ronald Stewart Joelie Sanguya Henry P. Huntington 《Climatic change》2010,100(2):267-294
Connecting indigenous and scientific observations and knowledge has received much attention in the Arctic, not least in the
area of climate change. On some levels, this connection can be established relatively easily, linking observations of similar
phenomena or of various effects stemming from the same cause. Closer examinations of specific environmental parameters, however,
can lead to far more complex and difficult attempts to make those connections. In this paper we examine observations of wind
at Clyde River, Nunavut, Canada. For Inuit, many activities are governed by environmental conditions. Wind, in particular,
is identified by Inuit as one of the most important environmental variables, playing a key role in driving sea ice, ocean,
and weather conditions that can either enable or constrain hunting, travel, or other important activities. Inuit observe wind
patterns closely, and through many means, as a result of their close connection to the land and sea. Inuit in many parts of
Nunavut are reporting changes in wind patterns in recent years. At Clyde River, a community on the eastern coast of Baffin
Island, Inuit have observed that at least three key aspects of wind have changed over the last few decades: wind variability,
wind speed, and wind direction. At the same time, wind observations are also available from an operational weather station
located at Clyde River. An analysis of this information shows little change in wind parameters since the mid-1970s. Though
the station data and Inuit observations correspond in some instances, overall, there is limited agreement. Although the differences
in the two perspectives may point to possible biases that may exist from both sources—the weather station data may not be
representative of the region, Inuit observations or explanations may be inaccurate, or the instrumental and Inuit observations
may not be of the same phenomena—they also raise interesting questions about methods for observing wind and the nature of
Arctic winds. 相似文献
155.
Lisa M. Baldini Frank McDermott James U. L. Baldini Matthew J. Fischer Martin Möllhoff 《Climate Dynamics》2010,35(6):977-993
This two-year study investigates the relative influence of meteorological variables (precipitation amount and temperature),
atmospheric circulation, air mass history, and moisture source region on Irish precipitation oxygen isotopes (δ18Op) on event and monthly timescales. Single predictor correlations reveal that on the event scale, 20% of δ18Op variability is attributable to the amount effect and 7% to the temperature effect while on the monthly timescale the North
Atlantic Oscillation accounts for up to 20% of δ18Op variability and the amount and temperature effects are not significant. In comparison, multivariate linear regression reveals
that the interaction of temperature and precipitation amount explains up to 40% of δ18Op variance at event and monthly timescales. Five-day kinematic back trajectories suggest that the amount-weighted mean δ18Op value of southerly- and northerly-derived events are lower by 2‰ relative to events derived from the west. Because air mass
history and atmospheric circulation appear to influence δ18Op in Ireland, Irish paleo-δ18Op proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall. 相似文献
156.
157.
Chris Blake Russell J. Jurek Sarah Brough Matthew Colless Warrick Couch Scott Croom Tamara Davis Michael J. Drinkwater Duncan Forbes Karl Glazebrook Barry Madore Chris Martin Kevin Pimbblet Gregory B. Poole Michael Pracy Rob Sharp Todd Small David Woods 《Monthly notices of the Royal Astronomical Society》2009,395(1):240-254
158.
Epimetheus, a small moon of Saturn, has a rotational libration (an oscillation about synchronous rotation) of 5.9°±1.2°, placing Epimetheus in the company of Earth’s Moon and Mars’ Phobos as the only natural satellites for which forced rotational libration has been detected. The forced libration is caused by the satellite’s slightly eccentric orbit and non-spherical shape.Detection of a moon’s forced libration allows us to probe its interior by comparing the measured amplitude to that predicted by a shape model assuming constant density. A discrepancy between the two would indicate internal density asymmetries. For Epimetheus, the uncertainties in the shape model are large enough to account for the measured libration amplitude. For Janus, on the other hand, although we cannot rule out synchronous rotation, a permanent offset of several degrees between Janus’ minimum moment of inertia (long axis) and the equilibrium sub-Saturn point may indicate that Janus does have modest internal density asymmetries.The rotation states of Janus and Epimetheus experience a perturbation every 4 years, as the two moons “swap” orbits. The sudden change in the orbital periods produces a free libration about synchronous rotation that is subsequently damped by internal friction. We calculate that this free libration is small in amplitude (<0.1°) and decays quickly (a few weeks, at most), and is thus below the current limits for detection using Cassini images. 相似文献
159.
Sarah J. Morrison Peter C. Thomas Matthew S. Tiscareno Joseph A. Burns Joseph Veverka 《Icarus》2009,204(1):262-270
High-resolution images from the Cassini Imaging Science Subsystem (ISS) show parallel sets of grooves on Epimetheus and Pandora. Grooves have previously been observed on other satellites and asteroids, including Phobos, Gaspra, Ida, Eros, and minor occurrences on Phoebe. Sets of parallel grooves are so far observed only on satellites known or likely to be subject to significant tidal stresses, such as forced librations. Grooves on asteroids and on satellites not subject to significant forced librations occur in more globally disorganized patterns that may reflect impacts, varying internal structures, or even thermal stresses. The patterns and individual morphologies of grooves on the tidally-affected satellites suggest fracturing in weak materials due to tidal stresses and forced librations. 相似文献
160.
Jorge Peñarrubia Matthew G. Walker Gerard Gilmore 《Monthly notices of the Royal Astronomical Society》2009,399(3):1275-1292
We use N -body simulations to study the tidal evolution of globular clusters (GCs) in dwarf spheroidal (dSph) galaxies. Our models adopt a cosmologically motivated scenario in which the dSph is approximated by a static Navarro, Frenk & White halo with a triaxial shape. We apply our models to five GCs spanning three orders of magnitude in stellar density and two in mass, chosen to represent the properties exhibited by the five GCs of the Fornax dSph. We show that only the object representing Fornax's least dense GC (F1) can be fully disrupted by Fornax's internal tidal field – the four denser clusters survive even if their orbits decay to the centre of Fornax. For a large set of orbits and projection angles, we examine the spatial and velocity distribution of stellar debris deposited during the complete disruption of an F1-like GC. Our simulations show that such debris appears as shells, isolated clumps and elongated overdensities at low surface brightness (≥26 mag arcsec−2 ), reminiscent of substructure observed in several Milky Way dSphs. Such features arise from the triaxiality of the galaxy potential and do not dissolve in time. The kinematics of the debris depends strongly on the progenitor's orbit. Debris associated with box and resonant orbits does not display stream motions and may appear 'colder'/'hotter' than the dSph's field population if the viewing angle is perpendicular/parallel to the progenitor's orbital plane. In contrast, debris associated with loop orbits shows a rotational velocity that may be detectable out to a few kpc from the galaxy centre. Chemical tagging that can distinguish GC debris from field stars may reveal whether the merger of GCs contributed to the formation of multiple stellar components observed in dSphs. 相似文献