The Suburbanization of Food Insecurity: An Analysis of Projected Trends in the Atlanta Metropolitan Area     

Jerry Shannon  Mathew E. Hauer  Alexis Weaver  Sarah Shannon 《The Professional geographer》2018,70(1):84-93

Although general patterns of food insecurity in the United States are known, few studies have attempted to estimate small area food security or account for ongoing socioeconomic changes. Here we address these issues by producing small area estimates of food insecurity in the Atlanta metropolitan area using two methodologies: fixed effects modeling and demographic metabolism. In both cases, we use county-level data from the Current Population Survey to determine the association between food insecurity and demographic predictors. These associations are then applied to tract-level data from the 2009 to 2013 American Community Survey and projected data for 2020 to create small area estimates of food insecurity. We find broad consensus between our two methods. For both time periods, food insecurity is highest in southern sections of the city of Atlanta and its neighboring suburbs. Projections to 2020, however, show that food insecurity rates are projected to increase in outer-ring suburbs east and west of the city while decreasing in the urban core. These results highlight the need to further adapt antihunger efforts for often sprawling suburban communities, where poverty rates are increasing but spatial mismatch combined with poor transit access might hinder access to food assistance.  相似文献   

Lacustrine wave-dominated clastic shorelines: modern to ancient littoral landforms and deposits from the Lake Turkana Basin (East African Rift System,Kenya)     

Mathieu Schuster  Alexis Nutz 《Journal of Paleolimnology》2018,59(2):221-243

This paper presents an overview of some of the most significant, recent to ancient, littoral morpho-sedimentary structures and deposits from the Lake Turkana Basin. We highlight the importance of wave-related sedimentary processes in lakes, and more specifically in rift lakes. In the published literature, references to wave-dominated shorelines are mainly in regards to coastal marine environments. However, numerous modern lakes exhibit typical wave-dominated littoral landforms, and related sedimentary deposits are known from several paleolake successions in the geological record. Wave-related processes are often of relatively minor importance in depositional models for lacustrine environments. Classical models emphasize clastics transported by rivers, which are then distributed by fan-deltas and/or deltas into a water body of fluctuating depth, where reworking of clastics is limited in the littoral domain, and episodic in deep waters. Modern processes in Lake Turkana and the exposed paleolake deposits of the Turkana Basin demonstrate that this view is incomplete. Wave-dominated shorelines are evident (1) for modern Lake Turkana based on prominent and active littoral landforms (e.g., beach ridges, sand spits, washover fans, and arcuate-cuspate deltas); (2) for the Holocene (African Humid Period) climate-driven highstand of Megalake Turkana and its subsequent forced regression based on conspicuous raised beach ridges and spits; and (3) for the Pliocene–Pleistocene (Omo Group, Nachukui Formation) from typical nearshore sedimentary facies and stratigraphic architectures associated with paleolake Turkana. These examples from the Turkana Basin coupled with examples from other lacustrine settings, suggest that wave-dominated clastic shorelines represent significant portions of existing and ancient lake-shores. As this view contrasts with classic depositional models for lakes, notably for those found in rift setting, we also present examples of wave-influenced littoral landforms from other lakes of the East African Rift System. Identifying lacustrine paleoshorelines from typical clastic landforms and deposits is the key to the spatial reconstruction of lakes over time, and to determine transgressive–regressive cycles. Waves action is an important agent in lakes for the erosion, transport, and deposition of clastics at the basin-scale, an aspect that needs to be integrated in sedimentary models.  相似文献   

A model for pore‐fluid‐sensitive rock behavior using a weathering state parameter     

R. J. Hickman  M. S. Gutierrez  V. De Gennaro  P. Delage 《国际地质力学数值与分析法杂志》2008,32(16):1927-1953

Chalk and other porous rocks are known to behave differently when saturated with different pore fluids. The behavior of these rocks varies with different pore fluids and additional deformation occurs when the pore fluid composition changes. In this article, we review the evidence that behavior in porous rocks is pore‐fluid‐dependent, present a constitutive model for pore‐fluid‐dependent porous rocks, and present a compilation of previously published data to develop quantitative relationships between various pore fluids and mechanical behavior. The model proposed here is based on a state parameter approach for weathering and has similarities to models previously proposed for weathering‐sensitive rocks in that the values for parameters that characterize material behavior vary as a function of weathering. Comparisons with published experimental data indicate that the model is capable of reproducing observed behavior of chalk under a variety of loading conditions and changes in pore fluid composition. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Formulation of a three‐dimensional rate‐dependent constitutive model for chalk and porous rocks     

R. J. Hickman  M. S. Gutierrez 《国际地质力学数值与分析法杂志》2007,31(4):583-605

Rate‐dependent behaviour of chalk and other porous rocks has undergone widespread study in geomechanics due to its implications on the performance of engineering structures. We present a rate‐dependent constitutive model for chalk and other porous rocks with several new features. The model formulation is based on a viscoplastic rate‐lines approach in which the axial strain rate depends on the proximity of the stress point to an elliptical reference surface. A non‐associated viscoplastic potential surface and an axial scaling algorithm are used to determine the viscoplastic strain components. The model predicts that axial yields stress varies as a power function of applied axial strain rate, as shown by published laboratory data. Comparisons with published experimental data indicate that the model is capable of reproducing observed rate‐dependent behaviour of chalk under a variety of loading conditions. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Comment on the postulate of three plane strain mechanisms     

Marte Gutierrez  Suzanne Lacasse 《国际地质力学数值与分析法杂志》1991,15(11):809-816

This note discusses the inconsistencies that are inherent in the postulate of three plane strain mechanisms. It is shown that this postulate violates the principle of invariance and one obtains different results depending on the choice of the reference axes. If formulated in the principal stress space, this postulate requires that the principal stress and principal plastic strain increment directions be coaxial. Constitutive models based on this postulate cannot be used for general loading situations involving principal stress rotation where significant non-coaxiality is obtained.  相似文献   

CCD Photometry of KZ Hya using the 45-CM Telescope in Paraguay     

Fredy Doncel  Alexis Troche  Takeshi Noguchi 《Astrophysics and Space Science》2004,290(3-4):399-408

A SX Phe-type pulsating variable KZ Hya (HD94033) was observed with CCD set attached to the 45-cm reflector at Asuncion Astronomical Observatory in Paraguay. In the present work, 12 maximum phases were covered. A new ephemeris has been obtained, and the result suggests a probable change of the pulsation period of KZ Hya.  相似文献   

The Effect of Fluid Content on the Mechanical Behaviour of Fractures in Chalk   总被引：7，自引：0，他引：7  

M. Gutierrez  L. E. Øino  K. Høeg 《Rock Mechanics and Rock Engineering》2000,33(2):93-117

Summary ?The paper presents an experimental study on the effects of fluid content on the mechanical behaviour of natural fractures in chalk. The aims of the study are to provide better understanding of the mechanisms of chalk-fluid interaction, in general, and to explain the behaviour of petroleum chalk reservoirs during water injection, in particular. The experiments were carried out on L?gerdorf chalk using the direct shear apparatus. Two types of fluids were used in the tests: 1) water, and 2) synthetic oil. L?gerdorf chalk is a water-wet material which will develop capillary pressures upon contact with water. Initially saturating the chalk with oil will enhance the water wettability by inducing additional capillary forces between water and the non-wetting oil. In addition to the tests on fractured chalk samples, unconfined compression and direct shear tests on intact chalk samples were performed. The results showed significant differences in the strength and deformation characteristics of intact chalk initially saturated with different fluids. Intact water-saturated chalk showed lower deformation modulus (about 50%) and lower peak (also about 50%) and residual shear strength than the oil-saturated chalk. Water injection in initially oil-saturated fractures resulted in significant normal deformation under constant effective normal stress and shear stress relaxation under fixed shear displacement. The water-induced deformation occurred almost instantaneously after only a few cm³ of water had been injected into the fracture, and further injection of water did not increase the water-induced deformation. After water injection, fractures in initially oil-saturated chalk showed significantly lower normal and shear stiffnesses and lower shear strength. The weakening in shear is attributed partly to the reduction in the basic friction angle, φ_b, and this reduction was verified in a series of tilt tests to measure the frictional resistance between smooth edges of core samples of chalk. The reduction in the basic friction angle implies that the interaction of chalk with water is governed not only by capillary forces, as postulated in several previous studies, but also by chemical and/or physio-chemical effects.  相似文献   

How much does dry‐season fog matter? Quantifying fog contributions to water balance in a coastal California watershed          下载免费PDF全文

Michaella Chung  Alexis Dufour  Rebecca Pluche  Sally Thompson 《水文研究》2017,31(22):3948-3961

The seasonally‐dry climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. Frequently during summer, the only water inputs occur as non‐rainfall water, in the form of fog and dew. However, due to spatially heterogeneous fog interaction within a watershed, estimating fog water fluxes to understand watershed‐scale hydrologic effects remains challenging. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems, in a San Francisco Peninsula watershed. To monitor fog occurrence, intensity, and spatial extent, we focused on the mechanisms through which fog can affect the water balance: throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables. A stratified sampling design was used to capture the watershed's spatial heterogeneities in relation to fog events. We developed a novel spatial averaging scheme to upscale local observations of throughfall inputs and evapotranspiration suppression and make watershed‐scale estimates of fog water fluxes. Inputs from fog water throughfall (10–30 mm/year) and fog suppression of evapotranspiration (125 mm/year) reduced dry‐season water deficits by 25% at watershed scales. Evapotranspiration suppression was much more important for this reduction in water deficit than were direct inputs of fog water. The new upscaling scheme was analyzed to explore the sensitivity of its results to the methodology (data type and interpolation method) employed. This evaluation suggests that our combination of sensors and remote sensing allows an improved incorporation of spatially‐averaged fog fluxes into the water balance than traditional interpolation approaches.  相似文献   

Quantifying and monetizing potential climate change policy impacts on terrestrial ecosystem carbon storage and wildfires in the United States     

David Mills  Russell Jones  Karen Carney  Alexis St. Juliana  Richard Ready  Allison Crimmins  Jeremy Martinich  Kate Shouse  Benjamin DeAngelo  Erwan Monier 《Climatic change》2015,131(1):163-178

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Transgressive dunefield landforms and vegetation associations,Doña Juana,Veracruz, Mexico     

Patrick Hesp  Marisa Martinez  Graziela Miot da Silva  Natalia Rodríguez‐Revelo  Erika Gutierrez  Adriana Humanes  Daniela Laínez  Irene Montaño  Verónica Palacios  Agustín Quesada  Lorena Storero  Gabriela González Trilla  Carolina Trochine 《地球表面变化过程与地形》2011,36(3):285-295

Transgressive dune fields often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefield located in the central Gulf of Mexico, in order to assess the relationships between dunefield habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefield. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefield: deflation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fish‐scale shaped) dunefields and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (deflation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial‐tolerant species were dominant in the most mobile areas (blowouts and aklé dunefield and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献