Thermal evolution of the moon     

M. Nafi Toksőz  Sean C. Solomon  John W. Minear  David H. Johnston 《Earth, Moon, and Planets》1972,4(1-2):190-213

The thermal history and current state of the lunar interior are investigated using constraints imposed by recent geological and physical data. Theoretical temperature models are computed taking into account different initial conditions, heat sources, differentiation and simulated convection. To account for the early formation of the lunar highlands, the time duration of magmatism and presentday temperatures estimated from lunar electrical conductivity profiles, it is necessary to restrict initial temperatures and abundances of radioactivie elements. Successful models require that the outer half of the Moon initially heated to melting temperatures, probably due to rapid accretion. Differentiation of radioactive heat sources toward the lunar surface occurred during the first 1.6 billion years. Temperatures in the outer 500 km are currently low, while the deep interior (radius less than 700 to 1000 km) is warmer than 1000°C, and is of primordial material. In some models there is a partially melted core. The calculated surface heat flux is between 25 and 30 erg/cm² s.Presently at the Research Triangle Institute, Research Triangle, North Carolina 27709, U.S.A.  相似文献   

The Alaskan shelf: Hydrographic,sedimentary and geochemical environment | G.D. Sharma, 1979. Springer-Verlag,Berlin, 498 pp., DM 59.00     

Robert E. Burns 《Earth》1982,18(1):80-81

  相似文献   

Stochastic inversion of thermal data in a sedimentary basin: resolving spatial variability     

Sean D. Willett 《Geophysical Journal International》1990,103(2):321-339

  相似文献   

“An oasis for us”: ‘in-between’ spaces of training for people with mental health problems in the Scottish Highlands     

Chris Philo  Hester Parr  Nicola Burns 《Geoforum》2005,36(6):778-791

Training and Guidance (TAG) units in the Scottish Highlands are sites that people with mental health problems can access for training and learning activities designed to prepare them for (re-)entry into the labour market. These units also perform other, perhaps more intangible, roles in assisting trainees to cope with their mental health problems, thereby offering a supportive setting with therapeutic dimensions (albeit one not explicitly configured as delivering therapy). In this paper we explore the ‘in-between’ quality of the TAG units as spaces that might be said to possess dual economic and social roles. Using primarily qualitative evidence, we investigate both sets of roles, debating the extent to which the economic and social imperatives complement or contradict one another. The paper contributes to critical commentary on how ‘workfare’ initiatives articulate with the experiences and concerns of disabled trainees, the novelty arising in part from centralising the material spaces at the heart of such initiatives.  相似文献   

Stable isotope study of cave percolation waters in subtropical Brazil: Implications for paleoclimate inferences from speleothems     

Francisco W. Cruz  Jr.  Ivo Karmann  Oduvaldo Viana  Jr.  Stephen J. Burns  Jos A. Ferrari  Mathias Vuille  Alcides N. Sial  Marcelo Z. Moreira 《Chemical Geology》2005,220(3-4):245-262

We analyze the interannual monthly variability of oxygen isotope ratios in data from IAEA stations along the Atlantic coast of South America between 23° and 34° S to evaluate the influence of parameters such as temperature, rainfall amount and moisture source contribution on meteoric water recharging two karst systems in subtropical Brazil. In addition, a 2 year monitoring program performed on soil and cave drip and rimstone pool waters from sampling sites with contrasting discharge values and located at 100 and 300 m below the surface in the Santana Cave System (24°31′ S; 48°43′ W), is used to test the influence of hydrologic and geologic features on the temporal variations of seepage water δ¹⁸O.

Interannual monthly variations in δ¹⁸O of rainfall reflect primarily regional changes in moisture source contribution related to seasonal shifts in atmospheric circulation from a more monsoonal regime in summer (negative values of δ¹⁸O) to a more extratropical regime in winter (positive values of δ¹⁸O). Variations in groundwater δ¹⁸O indicate that the climatic signal of recent rainfall events is rapidly transmitted through the relatively deep karst aquifer to the cave drip waters, regardless of location of collection in the cave. In addition, the data also suggest that water replenishment in the system is triggered by the increase in hydraulic head during periods when recharge exceeds the storage capacity of the soil and epikarst reservoirs. Significant perturbations in the groundwater composition, characterized by more positive values of δ¹⁸O, are probably connected to an increased Atlantic moisture contribution associated with extratropical precipitation. This implies that the δ¹⁸O of speleothems from caves in this region may be a suitable proxy for studying tropical–extratropical interactions over South America, a feature that is intrinsically related to the global atmospheric circulation.  相似文献   

The protection of groundwater dependent ecosystems in Otago, New Zealand   总被引：1，自引：0，他引：1  

Gabor Bekesi  Sean Hodges 《Hydrogeology Journal》2006,14(8):1696-1701

Surface waters (streams, rivers, and wetlands) are the most important groundwater dependent ecosystems (GDEs) in Otago, New Zealand. Pumping wells in the vicinity can deplete water in the GDE. In Otago, most of the surface water resources are allocated and a method, which would assist in the implementation of water management policy, is needed to acknowledge the strong hydraulic link between surface and shallow groundwater. A simplified method has been developed which derives a numerical relationship between the bore pumping rate and the distance between the bore and surface water body beyond which depletion is considered insignificant. A range of GDE depletion scenarios are examined at various combinations of hydraulic parameters to find a minimum distance for a given pumping rate, at which 90% of the modelled surface water depletion scenarios become less than a threshold GDE depletion after a specified time. A buffer zone, based on the minimum distance is placed around GDEs, and groundwater abstraction rights within the buffer are subject to stricter rules. Applicants wishing to abstract from bores within the buffer zone will need to address the environmental impact of the proposed activity on the GDE.  相似文献   

Bioenergetics modeling to investigate habitat use by the nonindigenous crab,Carcinus maenas, in Willapa Bay, Washington     

P. Sean McDonald  Kirstin K. Holsman  David A. Beauchamp  Brett R. Dumbauld  David A. Armstrong 《Estuaries and Coasts》2006,29(6):1132-1149

A bioenergetics model was developed and applied to questions of habitat use and migration behavior of nonindigenous European green crab (Carcinus maenas) in Willapa Bay, Washington, USA. The model was parameterized using existing data from published studies on the ecology and physiology ofC. maenas and allied brachyuran crabs., Simulations of the model were run describing four scenarios of habitat use and behavior during a 214-d simulation period (April–October) including crabs occupying mid littoral habitat, high littoral habitat, sublittoral habitat, and sublittoral habitat but undertaking intertidal migrations. Monthly trapping was done along an intertidal gradient in Willapa Bay to determine the actual distribution of crabs for the same time interval as the simulation period, and model results were compared to the observed pattern. Model estimates suggest no intrinsic energetic incentive for crabs to occupy littoral habitats since metabolic costs were c. 6% higher for these individuals than their sublittoral counterparts. Crabs in the littoral simulations were also less efficient than sublittoral crabs at converting consumed energy into growth. Monthly trapping revealed thatC. maenas are found predominantly in mid littoral habitats of Willapa Bay and there is no evidence of resident sublittoral populations. The discrepancy intimates the significance of other factors, including interspecific interactions, that are not incorporated into the model but nonetheless increase metabolic demand. Agonistic encounters with native Dungeness crabs (Cancer magister) may be chief among these additional costs, andC. maenas may largely avoid interactions by remaining in littoral habitats neglected by native crabs, such as meadows of nonindigenous smooth cordgrass (Spartina alterniflora). AdultC. maenas in Willapa Bay may occupy tidal elevations that minimize such encounters, and metabolic costs, while simultaneously maximizing submersion time and foraging opportunities.  相似文献   

Shallow Drainage Flows   总被引：1，自引：1，他引：0  

L. Mahrt  Dean Vickers  Reina Nakamura  M. R. Soler  Jielun Sun  Sean Burns  D.H. Lenschow 《Boundary-Layer Meteorology》2001,101(2):243-260

Two-dimensional sonic anemometers and slowresponse thermistors were deployedacross a shallow gully during CASES99. Weak gully flow of a few tenths of m s^-1 anda depth of a few metres develops in the earlyevening on most nights with clear skies.Flow down the gully developed sometimes evenwhen the opposing ambient wind exceeded10 m s^-1 at the top of the60–m tower. Cold air drainage fromlarger-scale slopes flows over the top ofthe colder gully flow. The gully flowand other drainage flows are generally eliminated in the middle of the night in conjunctionwith flow acceleration abovethe surface inversion layer and downwardmixing of warmer air and highermomentum. As the flow decelerates later inthe night, the gully flow may re-form.The thin drainage flows decouple standard observational levels of3–10 m from the surface.Under such common conditions, eddy correlationflux measurements cannot be used toestimate surface fluxes nor even detect thethin gully and drainage flows. The gentlegully system in this field program is typical ofmuch of the Earths land surface.  相似文献   

Survey of tar,hydrocarbon and metal pollution in the coastal waters of Oman     

K.A. Burns  J.P. Villeneuve  V.C. Anderlin  S.W. Fowler 《Marine pollution bulletin》1982,13(7):240-247

Quantitative beach sampling conducted after the S. W. monsoon season yielded average standing stocks of tar ranging from 5 to 2325 g m^?1 of shoreline with overall average of 224 g m^?1. Values are among the highest reported for any world area and show a trend of increasing levels of oil residues close to the Strait of Hormuz. Data support the premise that tanker deballasting is a major source of oil pollution on the Omani coast. Locally high levels were seen near offshore tanker loading facilities. Petroleum hydrocarbons in rock oysters increased in a south to north gradient consistent with beach tar observations. But relatively low hydrocarbon levels in biota coupled with observations of very little floating tar suggests that oil released in Omani coastal waters aggregates, sinks, and reaches the coast as heavy tar lumps. Except for elevated levels of Cd at two stations, heavy metal and chlorinated hydrocarbon concentrations were low compared to more industrialized world areas. Suggestions are made to improve the effectiveness of future pollution studies in the Gulf Region.  相似文献   

Critical Data,Critical Technology in Theory and Practice     

Ryan Burns  Craig M. Dalton  Jim E. Thatcher 《The Professional geographer》2018,70(1):126-128

  相似文献