An analysis of debris-flow events in the Sardinia Island (Thyrrenian Sea, Italy)

On 6 December 2004, the Villagrande Strisaili area (middle-east Sardinia), was struck by debris flows; 330 mm of rainfall took place within 3 h with an hourly intensity of 120 mm, which is far more above than normal for the study area. In the urban center stony and driftwood deposits accounted for a total volume estimated as 10,000 m³. The event claimed huge amount of infrastructural loss and two human lives. According to the chronicle reports, the area experienced two debris-flow events in the last century. The present paper is the outcome of an intensive study of such debris-flow events including their physical processes and geomorphological effects through both field survey and laboratory analysis.     

Temporal patterns of deforestation and fragmentation in lowland Bolivia: implications for climate change

The lowlands of eastern and northeastern Bolivia are characterized by a transition between the humid evergreen forests of the Amazon Basin and the deciduous thorn-scrub vegetation of the Gran Chaco. Within this landscape lies one of the world’s best preserved areas: the ecoregion known as the Chiquitano dry forest, where deforestation patterns over a 30 year period were analyzed. Results indicate that the area of the natural cover was reduced from 97.21 % before 1976 to 82.10 % in 2008, causing significant change in the landscape, especially in the spatial configuration of forest cover. The density of forest fragments increased from 0.073 patches per 100 ha before 1976 to 0.509 in 2008, with a mean distance between patches of 151 and 210 m over the same period, leading to a considerable reduction in the fragment sizes, from 1,204 ha before 1976 to a mere 54 in 2008. This pattern, observed in forests, does not occur in the savannas because, on one hand the savanna area is much lower compared to that of forests, and on the other because the deforestation process tended to be concentrated within forested areas. Based on the observed patterns, it is possible that in the future the natural landscapes will be substituted principally by anthropic landscapes, if there is no change in the economic and land distribution policies. If this process continues, it will stimulate the expansion of mechanized agriculture and the colonization of new areas, which will lead to further deforestation and landscape fragmentation.     

Late‐Pleistocene Wedge Structures Along the Patagonian Coast (Argentina): Chronological Constraints and Palaeo‐Environmental Implications

This paper investigates several wedge structures formed in continental deposits covering marine sediments deposited during MIS 5 along the central Patagonian coast of Argentina. The size and surface microtexture characteristics of the infilling sediments are consistent with a depositional environment dominated by aeolian transport. Fragments of Andean volcanic rocks (glass shards) in the wedge‐fill suggest long‐distance transport via a westerly component of wind direction. The wedges are interpreted as products of deep seasonal frost action in frozen ground, which produced open cracks that filled rapidly with partially non‐local aeolian sediments. Many wedges cross cut carbonate crusts that formed under permafrost conditions in coastal Patagonia. The radiocarbon dating of carbonate crusts yielded an age of 25–27 kyr bp , while wedge‐fill sediments are OSL dated to 14 670 ± 750 yr bp . This indicates that ground wedge formation occurred during a cold event (the Antarctic Cold Reversal period) that interrupted the permafrost degradation following the Last Glacial Maximum.     

A two-dimensional pedestrian navigation solution aided with a visual gyroscope and a visual odometer

Integration of different positioning systems such as wireless local area networks (WLAN) and INS has proven to be the most promising approach for navigation in global navigation satellite system challenging environments. However, the integrated solution suffers from the errors induced by the sensors in the INS and the low availability and infrastructure dependency of the WLAN. Visual aiding is a complementary method for augmenting these systems, because it suffers from errors and availability problems of a different nature. We introduce the concept of a “visual gyroscope” and a “visual odometer,” based on recovering user information by tracking the feature motion between consecutive images. All calculations are of sufficiently low complexity to be adoptable for navigation with current smartphones. The camera orientation is observed using the vanishing point locations, and this information is transformed into user heading change information and also used for visual odometer calculations. The visual odometer retrieves the camera translation information based on a special camera configuration and the motion of the matched scale-invariant feature transform features. The performance of both of these tools is evaluated. Experiments in selected environments have proven that visual aiding with a visual gyroscope and visual odometer improves the two-dimensional navigation solution significantly.     

South Central Farmers and Shadow Hills Homeowners: Land Use Policy and Relational Racialization in Los Angeles∗

This article draws from the recent relational turn in geography to develop a model of relational racialization. It argues that racism functions through the legal and discursive production of linked, interdependent, and unequal places. By comparing two social movements in Los Angeles, the South Central Farmers and the Shadow Hills homeowners, I examine two spatial discourses through which race is relationally reproduced: unequal abilities to mobilize the entitlements of “property rights” and unequal claims to represent hegemonic forms of local heritage. When materialized and naturalized in land use policy, these discourses re-create racial disparities in wealth and poverty and reproduce the qualitative nature of the physical places on which racism depends.     

Ethnic Restructuring in Rural America: Migration and the Changing Faces of Rural Communities in the Great Plains

Scholars have long documented widespread aging and depopulation of rural communities in the Great Plains. Paralleling these trends is the emergence, growth, and spatial dispersion of new and longtime non-white populations across the region. The dual processes of population loss in many counties combined with the growth of new, non-white population groups suggest that the ethnic structure of the population is changing. In this article we utilize choropleth maps, Hoover and Simpson indexes, and cluster analysis to assess whether the emergence and growth of ethnic minority groups in the Great Plains between 1970 and 2008 is a localized phenomenon or region-wide shift in the ethnic composition of the population. Results suggest that as depopulation is occurring in many counties of this region, the growth of non-white populations, both immigrant and native born, is changing or restructuring the ethnic composition of the Great Plains.     

User fees and the permeability of public space at municipal pools and bathhouses in New York City, 1870 – present

This paper examines fees for access to New York City’s public swimming and bathing spaces from 1870 to the present. We argue that, beyond generating revenue and rationing space, charges for admission to public bathing spaces have served to condition how permeable those spaces were to various groups of potential users. Municipal actors involved in administering baths and pools have used fees to maintain and order these spaces; to distinguish between deserving and undeserving users; and to include and exclude participants in an ostensibly universal public. Over time, fees have been naturalized, erasing these motivations and giving cause to their outcomes. We problematize the fee in order to address both theoretical questions about the nature of public space and practical ones about how municipal administrators govern amidst competing pressures to serve, develop and regulate urban residents and their communities.     

Retrieving lateral variations from surface wave dispersion curves‡

Surface wave analysis is usually applied as a 1D tool to estimate V_S profiles. Here we evaluate the potential of surface wave analysis for the case of lateral variations. Lateral variations can be characterized by exploiting the data redundancy of the ground roll contained in multifold seismic data. First, an automatic processing procedure is applied that allows stacking dispersion curves obtained from different records and which retrieves experimental uncertainties. This is carried out by sliding a window along a seismic line to obtain an ensemble of dispersion curves associated to a series of spatial coordinates. Then, a laterally constrained inversion algorithm is adopted to handle 2D effects, although a 1D model has been assumed for the forward problem solution. We have conducted different tests on three synthetic data sets to evaluate the effects of the processing parameters and of the constraints on the inversion results. The same procedure, applied to the synthetic data, was then tested on a field case. Both the synthetic and field data show that the proposed approach allows smooth lateral variations to be properly retrieved and that the introduction of lateral constraints improves the final result compared to individual inversions.