共查询到9条相似文献,搜索用时 0 毫秒
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Amanda Sheely 《政策研究杂志》2018,46(3):651-673
Under devolution, state and local governments are expected to use the greater authority granted to them to design new and innovative programs that are tailored to local needs. Existing research on the devolution of welfare programs has reported substantial variation in the policies adopted by states in the wake of welfare reform. However, under second‐order devolution, local governments also gained discretion over welfare services. Some have argued that, while devolution should increase flexibility, local governments face constraints that limit their functional discretion. Using California as an example, I assess whether there is variation in the service priorities adopted by local governments and whether these priorities translate to frontline practices. I show differences in the service priorities of local governments; however, these priorities are not associated with differences in sanctioning or time‐limit exemptions. Thus, while local governments may formally adopt different priorities, state and federal policy choices, as well as client characteristics, may restrict priorities from translating into differences in caseworker behavior. 相似文献
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Prior research considers the extent to which public assistance recipients' charitable activity differs from the habits of the general population. Although receiving public assistance is negatively associated with donating money, the relationship to volunteering is unclear. In response to challenges overcoming selection bias, we conducted a multivariate cluster‐based subgroup analysis to reduce bias in our claims about the ways in which public assistance receipt affects charitable activity. This innovative approach to dealing with the problem of selection bias has implications and applications across the social sciences. 相似文献
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Samuel Mark 《International Journal of Nautical Archaeology》2012,41(1):84-93
A review of the Khufu I vessel (c.2566 BC) and contemporary Egyptian iconography (c.2613–2345 BC) suggest this vessel was originally fitted with six pairs of quarter‐rudders, instead of one pair. Furthermore, quarter‐rudders may have been mounted on knob‐shaped thole‐pins, instead of crossbeams. The iconography also suggests that each quarter‐rudder was fitted with a loom‐line and specialized grommet, and rowers may have used a similar system to mount their oars. Finally, a recently published depiction of Sahure sailing a boat may show an anchor secured on the stern deck. © 2011 The Author 相似文献
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L. M. CATHLES 《Geofluids》2007,7(2):209-226
A fundamental change in the nature of sub‐water table fluid flow occurred at roughly the Proterozoic–Phanerozoic boundary when organic matter began to be buried in sufficient quantities that nonaqueous fluids could occupy a significant fraction of the pore space. This allowed the formation of remarkably durable capillary seals that could trap gas in large portions (hundreds of kilometers) of a basin for hundreds of millions of years. Gas loss from these gas zones can be highly dynamic, especially during gas generation. Under the right circumstances, hundreds of cubic kilometers of gas can be rapidly discharged into adjacent permeable aquifers. In Pennsylvanian/Permian time, the Arkoma Basin may have repeatedly discharged such volumes of gas into the very permeable Cambrian sandstone and karstic carbonate aquifers of the mid‐continent of the United States. This could have displaced brines rapidly enough to form the Mississippi Valley‐type (MVT) lead–zinc deposits of this age that are associated with the Arkoma Basin, heating them only briefly as required by maturity indicators. Sea level rise accompanying the melting of Permian continental glaciers may have triggered the gas expulsion events. This radically new mechanism for the formation of MVT deposits is just one example of the nonlinear dynamics of gas accumulations that are possible since Late Proterozoic time. 相似文献
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Andy Viduka 《International Journal of Nautical Archaeology》2020,49(1):87-106
UCH managers are increasingly aware of the limitations of excluding public participation in heritage management both in terms of their own limited resources and need for wide public political support. This article assesses a pilot project in South Australia to train citizen scientists to record and monitor underwater cultural heritage sites. The results reinforced the need to ensure the data collected is robust and meaningful, and that citizen scientists know their contribution is valid; the need to help citizen scientists interpret data and foster peer‐to‐peer learning, and highlighted the importance of open source data for site conditions. 相似文献
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The Pine Point region is a classic metallogenic mining camp that produced over 58 million short tons of Zn–Pb ore from approximately 40 base‐metal mineralized deposits hosted by Middle Devonian carbonates. The ore deposits are localized in paleokarstic features found in the epigenetic ‘Presqu'ile’ dolomite that preferentially replaced some of the upper barrier limestones. The main ore‐stage sulfides include galena, sphalerite, marcasite, and pyrite. A bulk fluid inclusion chemistry study was carried out on sulfide, coarse non‐saddle and saddle dolomite and calcite samples from the Pine Point and Great Slave Reef deposits, and unmineralized coarse non‐saddle and saddle dolomite samples from Hay West, Windy Point and Qito areas. Molar Cl/Br ratio data from Pine Point indicate the presence of four fluids at different stages of the paragenesis. The fluids trapped in sulfides and ore‐stage dolomites predominately consist of a Br‐rich fluid with a composition similar to that of evaporated seawater (fluid A), and a very Br‐enriched fluid of unknown origin (fluid B). Both these fluids are CaCl2–NaCl (Na to Ca ratios of 1:10)‐rich brines and have compositions unlike the modern formation waters in the Devonian aquifers in the basin today. A third, relatively Cl‐rich (or Br‐poor), fluid (fluid C) was identified in two samples and may have acquired some chlorinity by dissolving halide minerals. Mixing between the Br‐rich fluid A and a dilute fluid also occurred in the later stages of the paragenesis, resulting in the formation of calcite and native sulfur. Saddle and coarse dolomites not associated with significant sulfide mineralization have a narrow range of halogen compositions similar to fluid A. There is no evidence of fluid B or C in the unmineralized samples. Relative to a modern‐day seawater compositions all the fluids have had some modification of their cation compositions. There is some weak evidence for interactions with clastic units or crystalline basement rocks. It is also possible however, that the evaporative brines could have formed from a relatively CaCl2‐rich, NaCl‐depleted Devonian seawater, unlike the composition of modern‐day seawater. 相似文献
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Petrography, Eh‐pH calculations and the stable isotope composition of oxygen are used to interpret geochemical processes that occurred during iron oxide mineralization and dolomitization along the Menuha Ridge segment of the Paran Fault, southern Israel, adjacent to the Dead Sea Transform (DST). Iron mineralization is strongly localized in the fault zone as ferruginous lenses, whereas Fe dolomitization spreads laterally into the Cenomanian‐Turonian carbonate host rock as stratabound beds. The average oxygen isotope fractionation between syngenetic quartz and iron oxides in the ferruginous lenses gives a temperature of 50 ± 10°C and δ18O SMOW water = ?3.5‰; consistent with an origin from metalliferous groundwater flow in the sedimentary basin. Ferroan dolomite initially formed under strongly reducing conditions, but this was followed by oxidation and pseudomorphic replacement of the dolomite by a mesh of fine‐grained iron oxides (simple zoned dolomites). This cycle of ferroan dolomite formation and replacement by iron oxides was repeated in complex zoned dolomites. Dolomite oxygen isotope compositions fall into two groups: a high δ18O group corresponding to the simple zoned dolomites and non‐ferroan dolomites and a low δ18O group corresponding to the complex zoned dolomites. Water‐rock calculations suggest that the epignetic dolomites formed under fluid‐buffered conditions: the high δ18O group are indicated to have formed at temperatures of ca. 25°C for waters with δ18O = ?4 to 0‰; the low δ18O complex zoned dolomites at 50–75°C for waters with the same isotopic composition. A kinetic calculation for a complex zoned dolomite‐bearing bed indicates that dolomitization must have occurred at high values of the dolomite saturation index. This requirement for high Mg supersaturation and the indication that epigenetic dolomitization is more protracted in stratigraphically deeper formations located closer to the DST is consistent with models proposing that Mg‐rich solutions originated in the Dead Sea Rift. 相似文献