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871.
Changes in the extent of glaciers and rates of glacier termini retreat in the eastern Terskey–Alatoo Range, the Tien Shan Mountains, Central Asia have been evaluated using the remote sensing techniques. Changes in the extent of 335 glaciers between the end of the Little Ice Age (LIA; mid-19th century), 1990 and 2003 have been estimated through the delineation of glacier outlines and the LIA moraine positions on the Landsat TM and ASTER imagery for 1990 and 2003 respectively. By 2003, the glacier surface area had decreased by 19% of the LIA value, which constitutes a 76 km2 reduction in glacier surface area. Mapping of 109 glaciers using the 1965 1:25,000 maps revealed that glacier surface area decreased by 12.6% of the 1965 value between 1965 and 2003. Detailed mapping of 10 glaciers using historical maps and aerial photographs from the 1943–1977 period, has enabled glacier extent variations over the 20th century to be identified with a higher temporal resolution. Glacial retreat was slow in the early 20th century but increased considerably between 1943 and 1956 and then again after 1977. The post-1990 period has been marked by the most rapid glacier retreat since the end of the LIA. The observed changes in the extent of glaciers are in line with the observed climatic warming. The regional weather stations have revealed a strong climatic warming during the ablation season since the 1950s at a rate of 0.02–0.03 °C a− 1. At the higher elevations in the study area represented by the Tien Shan meteorological station, the summer warming was accompanied by negative anomalies in annual precipitation in the 1990s enhancing glacier retreat. However, trends in precipitation in the post-1997 period cannot be evaluated due to the change in observational practices at this station. Neither station in the study area exhibits significant long-term trends in precipitation.  相似文献   
872.
When small businesses are impacted by natural hazard events, hazard and sociological researchers may have access to collect data from a sample of open businesses, in hopes of distilling lessons that might help reduce vulnerability to future disasters. Lessons from demised businesses might be more useful in reducing business closure for increasing business sustainability to disasters. Using interviews from a random sample of 371 open and 126 closed businesses’ experiences with Hurricane Katrina, discrete choice methods examine the relationship between the impact of post-disaster damage, loss of lifelines, types of delays in reopening, and cascading damages on business continuity. This unique sample offers the opportunity to determine whether damage to operating businesses was different than that of demised businesses. Respondents provided pre-Katrina data up through the last interviews in 2013. Results demonstrate that damage may have a short-term effect on operating status; it was associated with immediate demise but had much less effect on longer-term recovery. Additionally, it is evident that there is one path to failure. Businesses that did reopen, but later closed, may have been impacted by a cascade of both exogenous and endogenous shocks.  相似文献   
873.

Anthropogenic sinkholes are generally due to the collapse of man-made underground caves and represent a major threat, especially in urban contexts, where they could cause damage to people, buildings and lifelines. The hinterland of Naples (Campania, Southern Italy) is one of the most urbanized areas of Italy and is historically affected by frequent sinkhole phenomena. This study analyzes a database of both man-made caves and sinkholes collected by the authors over several years. The aim is to comprehend the predisposing and triggering factors of sinkholes in order to attempt a zonation of occurrence. The predisposing factor resulted to be the presence of a preexisting network of caves within the Campanian Ignimbrite tuff and their geometric features. Generally, the shallower the depth of the chamber roof and the lower the thickness of the vault, the higher is the frequency of sinkholes. Furthermore, an intrinsic fragility is represented by the access shafts of vertical wells, usually filled in and abandoned. Meanwhile, the main triggering mechanism identified consists in saturation of the subsoil, due to water leaks coming from buried sewage and water pipelines. The macrozonation of sinkhole occurrence shows that the highest class is achieved where the tuff is shallow and both man-made caves and historical sinkholes are present.

  相似文献   
874.
Increasingly, health outcomes are tied to nutritional opportunities based on the availability of foods and cultural patterns of consumption. This paper demonstrates how Esri Community Analyst can help in identifying at-risk communities. The methodology that results argues a means by which national data made available by Esri in a “one-stop shop” can be utilized in a simplified, user-friendly way to identify specific populations with higher prevalence of certain diseases and areas where nutritional needs are likely unmet. For demonstration purposes, this paper presents a case study for South Carolina, USA.  相似文献   
875.
The Mercury Laser Altimeter on the NASA MESSENGER mission has ranged to several ridges and lobate scarps during two equatorial flybys of the planet Mercury. The tectonic features sampled, like others documented by spacecraft imaging and Earth-based radar, are spatially isolated and have vertical relief in excess of 1 km. The profiles also indicate that the faulting associated with their formation penetrated to tens of kilometers depth into the lithosphere and accommodated substantial shortening. To gain insight into the mechanism(s) of strain accommodation across these structures, we perform analytical and numerical modeling of representative dynamic localization mechanisms. We find that ductile localization due to shear heating is not favored, given our current understanding of thermal gradients and shallow thermal structure of Mercury at the time of ridge and scarp formation, and is likely to be of secondary importance at best. Brittle localization, associated with loss of resistance during fault development or with velocity weakening during sliding on mature faults, is weakly localizing but permits slip to accumulate over geological time scales. The range of shallow thermal gradients that produce isolated faults rather than distributed fault sets under the assumption of modest fault weakening is consistent with previous models for Mercury’s early global thermal history. To be consistent with strain rates predicted from thermal history models and the amount of shortening required to account for the underlying large-offset faults, ridges and scarps on Mercury likely developed over geologically substantial time spans.  相似文献   
876.
In the State Archive of Como, Northern Italy, about 15,000 historical maps belonging to different national cadastral productions are preserved. The Web C.A.R.T.E. project was started to enhance the accessibility of this valuable cartographic heritage using FOSS (Free and Open Source Software) technologies. The system, which implements specific web geoservices for cataloguing and visualization, should assist the State Archive of Como in the digital management of its cartographic resources and related information. After the high‐resolution digitization step, maps undergo a georeferencing operation. A special statistical procedure for choosing the best mathematical model was developed, verifying also strengths and weaknesses of georeferencing with a common free and Open Source GIS. Next, metadata consistent with current Italian standards were added to the georeferenced maps using an ad hoc localized version of GeoNetwork Opensource (recently provided as the official Italian version of the software). A dedicated WebGIS system was built for publishing the georeferenced cadastral maps. This system is capable of navigating large raster data in a georeferenced framework and easily retrieving their metadata. The WebGIS system for the State Archive of Como is an important contribution for the preservation of the original historical paper maps and also a great modernization and simplification of the end user's access to this archive.  相似文献   
877.
Jezioro Lake is the only natural lake in southern Poland outside mountainous areas to have existed continuously since the Pleistocene. The record of environmental change in the Late Vistulian (Weichselian) and Holocene is preserved in the deposits and landforms around the lake. This paper presents the results of paleogeographical and paleoecological research that emabled us to reconstruct the history of the Jezioro Lake. At the end of the Vistulian period, the outlet of the lake was blocked by a parabolic dune moving in from the west. Limnic sedimentation was evident in the sediment core at all levels from the Holocene, with remains of Cladocera, Chironomidae larvae, and aquatic plants. The lake did not disappear at that time, although its area decreased by a factor of 12 by the end of the period. Paleobotanical research permitted the reconstruction of sequences of plant communities and changes in nutrient status and water level. An initial oligotrophic lake, as indicated by the presence of Iso?tes lacustris L., changed to a eutrophic lake, as indicated by the presence of Potamogeton natans L. and Nuphar sp., then the lake progressed to the present-day dystrophic lake that is surrounded by a swamp. The profile of organic deposits contains a record of environmental change at least since the Younger Dryas in southern Poland.  相似文献   
878.
Accurate estimates of photosynthetically active radiation (PAR) are critical for the development of realistic models of plant productivity. However, in many areas such as the vast Amazon region of South America, there have been few empirical studies of PAR. Here, we analyzed the relationship between PAR and broadband solar irradiance (R s) and formulated models to estimate PAR in two experimental sites (pasture and forest) in the Brazilian Amazon. Three different models of increasing complexity were developed based on information from R s (model 1), R s and clearness index (k t; model 2), and R s, k t, and water vapor pressure (model 3). Estimates of PAR were generated for each season and for the entire year. All models had very high determination coefficients and indices of agreement for both pasture and forest sites. This strongly supports the use of R s and k t to produce robust estimates of PAR. The results obtained by annual models were close than that found by seasonal models, demonstrating that a single annual model is able to estimate PAR, albeit with lower accuracy.  相似文献   
879.
Microfocus X-ray computed tomography (µCT) is a useful tool for non-destructive analysis of corroded archaeological glass objects and for monitoring restoration and conservation processes for these materials. This was demonstrated by µCT analysis of artificially corroded laboratory-produced glasses and corroded archaeological glasses retrieved from soil environments. Corrosion layers with a thickness of 20 µm or more can be detected as areas with lower X-ray attenuation values than the non-corroded glass. Features that are revealed by µCT analyses include the degree and patterns of corrosion and the presence of various internal structures in the corrosion layers. The study of restored corroded glasses demonstrates that mechanical and laser cleaning can be monitored efficiently. The study of consolidation practices, using test objects, requires the use of additives to increase X-ray attenuation values of the organic compounds that are used.  相似文献   
880.
High resolution multiproxy analysis (microcharcoal, pollen, organic carbon, Neogloboquadrina pachyderma (s), ice rafted debris) of the deep-sea record MD04-2845 (Bay of Biscay) provides new insights for understanding mechanisms of fire regime variability of the last glacial period in western France. Fire regime of western France closely follows Dansgaard–Oeschger climatic variability and presents the same pattern than that of southwestern Iberia, namely low fire regime associated with open vegetation during stadials including Heinrich events, and high fire regime associated with open forest during interstadials. This supports a regional climatic control on fire regime for western Europe through fuel availability for the last glacial period. Additionally, each of Heinrich events 6, 5 and 4 is characterised by three episodes of fire regime, with a high regime bracketed by lower fire regime episodes, related to vegetational succession and complex environmental condition changes.  相似文献   
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