Elderly co-residence and the household responsibilities hypothesis: evidence from Nanjing,China     

Jianxi Feng  Martin Dijst  Bart Wissink  Jan Prillwitz 《Urban geography》2013,34(5):757-776

In this paper, we analyze the effects of co-residence with elderly parents on gender differences in travel. The Household Responsibility Hypothesis (HRH) explains differences in the role of women regarding household responsibilities. However, research so far has studied “Western” household types while excluding households with co-residing elderly parents. Furthermore, research has paid exclusive attention to gender differences in commuting trips, and has neglected the effects of built environment characteristics. In view of these shortcomings, we pose the following research questions: what are the determinants of gendered differences in travel behavior, and specifically, what are the effects of elderly co-residence in households and land use on gender differences in trip frequency and travel distance? In addition to the HRH, we introduce the Elderly Co-residence Hypothesis, which suggests that co-residing elderly parents take over household responsibilities from adult women, resulting in diminishing gender differences in working-age travel patterns. We present the results of empirical research in Nanjing, China, that support this hypothesis.  相似文献   

Generic query tool for spatio-temporal data     

Peter Van Oosterom  Bart Maessen  Wilko Quak 《International journal of geographical information science》2013,27(8):713-748

Geographical information systems are more and more based on a DBMS with spatial extensions, which is also the case for the system described in this paper. The design and implementation of a generic geographical query tool, a platform for querying multiple spatio-temporal data sets and associated thematic data, is presented. The system is designed to be generic, that is without one specific application in mind. It supports ad-hoc queries covering both the spatial and the thematic part of the data. The generic geographic query tool will be illustrated with spatial and thematic Cadastral data. Special attention will be given to the temporal aspects: a spatio-temporal data model will be described together with a set of views for easy querying. DBMS views play an important role in the architecture of the system: integration of models, aggregation of information, presentation of temporal data, and so on. The current production version of the geographic query tool within the Dutch Cadastre is based on GeoICT products with a relatively small market share (Ingres and GEO++). A new prototype version is being developed using mainstream Geo-ICT products (Oracle and MapInfo). First results and open issues with respect to this prototype are presented.  相似文献   

Diversity and conservation status of large branchiopods (Crustacea) in ponds of western Poland     

Bartłomiej Gołdyn  Rafał Bernard  Michał Jan Czyż  Anna Jankowiak 《Limnologica》2012,42(4):264-270

A survey on temporary ponds has been conducted in search for large branchiopod crustaceans (Anostraca, Notostraca, Spinicaudata and Laevicaudata) in Wielkopolska province (western Poland). 728 pools have been studied and large branchiopods have been found in 221 of them. Seven species have been recorded, including three anostracans: Branchipus schaefferi, Chirocephalus shadini and Eubranchipus grubii; two notostracans: Lepidurus apus and Triops cancriformis; one spinicaudatan, Cyzicus tetracerus and one laevicaudatan, Lynceus brachyurus. According to the analysis of co-occurrence, the species form three groups, differing in habitat preferences and conservation status. The number of species shows that the diversity of globally threatened large branchiopods is still relatively high in the region. On the other hand, their conservation status is highly diverse and in most species unfavourable. Distribution of all species is highly clustered: large branchiopods have been generally found in 33 UTM squares (10 × 10 km) of 96 squares studied. However, only two species, i.e. E. grubii and L. apus occurred in more than five such squares and could be assessed as moderately widespread. Most water bodies inhabited by large branchiopods occur in groups forming patches of suitable habitats which are dispersed among prevailing seemingly unsuitable areas. Sustaining the existence of large metapopulations seems, therefore, to be essential for conservation of branchiopod species diversity. Field observations also bring some examples of human activities unintentionally supporting the branchiopod conservation.  相似文献   

Evaluating competing hypotheses for the origin and dynamics of river anastomosis     

M. G. Kleinhans  T. de Haas  E. Lavooi  B. Makaske 《地球表面变化过程与地形》2012,37(12):1337-1351

Anastomosing rivers have multiple interconnected channels that enclose flood basins. Various theories potentially explain this pattern, including an increased discharge conveyance and sediment transport capacity of multiple channels, deltaic branching, avulsion forced by base‐level rise, or a tendency to avulse due to upstream sediment overloading. The former two imply a stable anabranching channel pattern, whereas the latter two imply disequilibrium and evolution towards a single‐channel pattern in the absence of avulsion. Our objective is to test these hypotheses on morphodynamic scenario modelling and data of a well‐documented case study: the upper Columbia River. Proportions of channel and floodplain sediments along the river valley were derived from surface mapping. Initial and boundary conditions for the modelling were derived from field data. A 1D network model was built based on gradually varied flow equations, sediment transport prediction, mass conservation, transverse slope and spiral meander flow effects at the bifurcations. The number of channels and crevasse splays decreases in a downstream direction. Also, measured sediment transport is higher at the upstream boundary than downstream. These observations concur with bed sediment overloading from upstream, which can have caused channel aggradation above the surrounding floodplain and subsequent avulsion. The modelling also indicates that avulsion was likely caused by upstream overloading. In the model, multi‐channel systems inevitably evolve towards single‐channel systems within centuries. The reasons are that symmetric channel bifurcations are inherently unstable, while confluenced channels have relatively less friction than two parallel channels, so that more discharge is conveyed through the path with more confluences and less friction. Furthermore, the present longitudinal profile curvature of the valley could only be reproduced in the model by temporary overfeeding. We conclude that this anastomosing pattern is the result of time‐varying sediment overloading and is not an equilibrium pattern feature, and suggest this is valid for many anastomosing rivers. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Contrasting sorption behaviours affecting groundwater arsenic concentration in Kandal Province,Cambodia   总被引：1，自引：1，他引：0  

Laura A.Richards  Maria J.Casanueva-Marenco  Daniel Magnone  Chansopheaktra Sovann  Bart E.van Dongen  David A.Polya 《地学前缘(英文版)》2019,10(5):1701-1713

Natural arsenic(As)contamination of groundwater which provides drinking water and/or irrigation supplies remains a major public health issue,particularly in South and Southeast Asia.A number of studies have evaluated various aspects of the biogeochemical controls on As mobilization in aquifers typical to this region,however many are predicated on the assumption that key biogeochemical processes may be deduced by sampled water chemistry.The validity of this assumption has not been clearly established even though the role of sorption/desorption of As and other heavy metals onto Fe/Mn(hydr)oxides is an important control in As mobilization.Here,selective chemical extractions of sand-rich and clay-rich sediments from an As-affected aquifer in Kandal Province,Cambodia,were undertaken to explore the potential role of partial re-equilibrium through sorption/desorption reactions of As and related solutes(Fe,Mn and P)between groundwater and the associated solid aquifer matrix.In general,groundwater As is strongly affected by both pH and Eh throughout the study area.However,contrasting sorption behaviour is observed in two distinct sand-dominated(T-Sand)and clay dominated(T-Clay)transects,and plausibly attributed to differing dominant lithologies,biogeochemical and/or hydrogeological conditions.Sorption/desorption processes appear to be re-setting groundwater As concentrations in both transects,but to varying extents and in different ways.In T-Sand,which is typically highly reducing,correlations suggest that dissolved As may be sequestered by sorption/re-adsorption to Fe-bearing mineral phases and/or sedimentary organic matter;in T-Clay Eh is a major control on As mobilization although binding/occlusion of Fe-bearing minerals to sedimentary organic matter may also occur.Multiple linear regression analysis was conducted with groups categorised by transect and by Eh,and the output correlations support the contrasting sorption behaviours encountered in this study area.Irrespective of transect,however,the key biogeochemical processes which initially control As mobilization in such aquifers,may be "masked" by the re-setting of As concentrations through in-aquifer sorption/desorption processes.  相似文献   

Reconstruction of floodplain sedimentation rates: a combination of methods to optimize estimates     

Noortje Hobo  Bart Makaske  Hans Middelkoop  Jakob Wallinga 《地球表面变化过程与地形》2010,35(13):1499-1515

Reconstruction of overbank sedimentation rates over the past decades gives insight into floodplain dynamics, and thereby provides a basis for efficient and sustainable floodplain management. We compared the results of four independent reconstruction methods – optically stimulated luminescence (OSL) dating, caesium‐137 (¹³⁷Cs) dating, heavy metal analysis, and flood bed interpretation – applied at three embanked floodplain sites along lower Rhine River distributaries in the Netherlands. All methods indicate significant sedimentation rates on the floodplains, varying between 2–7 mm/a in the distal zones and 3–9 mm/a in the proximal zones. On a rapidly developing sand bar along a natural levee sedimentation rates of 9 to 25 mm/a were found. Except for some minor inconsistencies in ¹³⁷Cs dating results, all methods show decreasing sedimentation rates with increasing distance from the river channel. Intercomparison of the results of the different dating methods revealed the potential errors associated with each method, particularly where disagreement among the results were found. Uncertainties may arise due to (1) grain‐size dependent downward migration of ¹³⁷Cs, (2) smoothing of the vertical heavy metal and ¹³⁷Cs profiles, (3) delayed sediment‐associated input of ¹³⁷Cs in addition to direct atmospheric fall‐out, (4) overestimation of the burial age in OSL dating due to incomplete resetting of the OSL signal, or (5) non‐linear relationships between sediment deposition and flood magnitude in the count‐from‐the‐top correlation between sediment lamination and past observed flood records. Still, taking the uncertainties associated with each method into account, the results are generally in good agreement. Using the results we indicate the optimal spatial range of application of each method, depending on sediment texture and sedimentation rate. The optimal spatial and temporal ranges differ for each method, but show significant overlap. A combination of the methods will thus provide maximum information for accurate estimation of sedimentation rates on a decadal time scale. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The Phase A study of the ESA M4 mission candidate ARIEL     

Ludovic Puig  Göran Pilbratt  Astrid Heske  Isabel Escudero  Pierre-Elie Crouzet  Bram de Vogeleer  Kate Symonds  Ralf Kohley  Pierre Drossart  Paul Eccleston  Paul Hartogh  Jeremy Leconte  Giusi Micela  Marc Ollivier  Giovanna Tinetti  Diego Turrini  Bart Vandenbussche  Paulina Wolkenberg 《Experimental Astronomy》2018,46(1):211-239

ARIEL, the Atmospheric Remote sensing Infrared Exoplanet Large survey, is one of the three M-class mission candidates competing for the M4 launch slot within the Cosmic Vision science programme of the European Space Agency (ESA). As such, ARIEL has been the subject of a Phase A study that involved European industry, research institutes and universities from ESA member states. This study is now completed and the M4 down-selection is expected to be concluded in November 2017. ARIEL is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. ARIEL targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to warm zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own Solar System in the context of other planetary systems in the Milky Way. A technical and programmatic review of the ARIEL mission was performed between February and May 2017, with the objective of assessing the readiness of the mission to progress to the Phase B1 study. No critical issues were identified and the mission was deemed technically feasible within the M4 programmatic boundary conditions. In this paper we give an overview of the final mission concept for ARIEL as of the end of the Phase A study, from scientific, technical and operational perspectives.  相似文献   

Large wood clogging during floods in a gravel‐bed river: the Długopole bridge in the Czarny Dunajec River,Poland          下载免费PDF全文

Virginia Ruiz‐Villanueva  Bartłomiej Wyżga  Paweł Mikuś  Maciej Hajdukiewicz  Markus Stoffel 《地球表面变化过程与地形》2017,42(3):516-530

During floods, large quantities of wood can be mobilized and transported downstream. At critical sections, such as bridges, the transported wood might be entrapped and a quick succession of backwater effects can occur as a result of the reduction of the cross‐sectional area. The aim of this work is to explore large wood‐related hazards during floods in the gravel‐bed river Czarny Dunajec (Polish Carpathians), where the river flows through the village of D?ugopole. This work is based on the numerical modelling of large wood transport together with flow dynamics in which inlet and boundary conditions were designed based on field observations. The exploratory approach developed in this study uses multiple scenarios (193) to analyse the factors controlling bridge clogging: wood size, wood supply, flow conditions, morphology and obstacles in the riverbed. Results highlighted the strong control of log length (stronger than that of log diameter) on potential blockage probability; however, according to our results the main factor controlling bridge clogging was the flood discharge. River morphology and wood supply play an important role as well. The river morphology may reduce bridge blockage, as it influences flow velocity and depth, and creates natural retention zones for wood. In addition, the impacts of bridge blockage were analysed in terms of afflux depth and length, and flooded area. Results showed that bridge blockage may result in a significant increase in water depth (up to 0.7 m) and flooded area (up to 33% more), therefore increasing flood risk in the village. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure     

Olek  Bartłomiej Szczepan 《Acta Geotechnica》2020,15(12):3571-3591

Acta Geotechnica - Consolidation rate has significant influence on the settlement of structures founded on soft fine-grained soil. This paper presents the results of a series of small-scale and...  相似文献   

Critical tissue copper residues for marine bivalve (Mytilus galloprovincialis) and echinoderm (Strongylocentrotus purpuratus) embryonic development: conceptual, regulatory and environmental implications     

Rosen G  Rivera-Duarte I  Chadwick DB  Ryan A  Santore RC  Paquin PR 《Marine environmental research》2008,66(3):327-336

Critical tissue copper (Cu) residues associated with adverse effects on embryo-larval development were determined for the Mediterranean mussel (Mytilus galloprovincialis) and purple sea urchin (Strongylocentrotus purpuratus) following laboratory exposure to Cu-spiked seawater collected from San Diego Bay, California, USA. Whole body no-observed-effect-residues (NOER) were similar, with means of 21 and 23mugg(-1)dw, for M. galloprovincialis and S. purpuratus, respectively. Mean whole body median effect residues (ER50) were 49 and 142mugg(-1)dw for M. galloprovincialis and S. purpuratus, respectively. The difference in ER50s between species was reduced to a factor of <2 when expressed as soft tissue residues. Coefficients of variation among whole body-ER50s were 3-fold lower than median waterborne effect concentrations (EC50) for both species exposed to samples varying in water quality characteristics. This suggests that tissue concentrations were a better predictor of toxicity than water concentrations. The CBRs described herein do not differentiate between the internal Cu concentrations that are metabolically available and those that are accumulated and then detoxified. They do appear, however, to be well enough related to the level of accumulation at the site of action of toxicity that they serve as useful surrogates for the copper concentration that affects embryonic development of the species tested. Results presented have potentially important implications for a variety of monitoring and assessment strategies. These include regulatory approaches for deriving saltwater ambient water quality criteria for Cu, contributions towards the development of a saltwater biotic ligand model, the conceptual approach of using CBRs, and ecological risk assessment.  相似文献