Research on the geography of agricultural change: redundant or revitalized?   总被引：2，自引：0，他引：2  

C Morris  N J Evans† 《Area》1999,31(4):349-358

Summary Future research directions for agricultural geography were the subject of debate in Area in the late 1980s, and the subsequent application of political economy ideas undoubtedly revived interest in agricultural research. This paper argues that agricultural geography contains greater diversity than the dominant political economy discourse would suggest. It reviews 'other' areas of agricultural research such as policy, post- productivism, people, culture and animals, presenting future suggestions which should ensure that agricultural research continues revitalized rather than redundant into the next millennium.  相似文献   

The association between gas and galaxies – II. The two-point correlation function     

R. J. Wilman  S. L. Morris  B. T. Jannuzi  R. Davé  A. M. Shone 《Monthly notices of the Royal Astronomical Society》2007,375(2):735-744

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Searching for hidden Wolf–Rayet stars in the Galactic plane – 15 new Wolf–Rayet stars     

L. J. Hadfield  S. D. Van Dyk  P. W. Morris  J. D. Smith  A. P. Marston  D. E. Peterson 《Monthly notices of the Royal Astronomical Society》2007,376(1):248-262

We report the discovery of 15 previously unknown Wolf–Rayet (WR) stars found as part of an infrared (IR) broad-band study of candidate WR stars in the Galaxy. We have derived an empirically based selection algorithm which has selected ∼5000 WR candidate stars located within the Galactic plane drawn from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (mid-IR) and Two-Micron All-Sky Survey (near-IR) catalogues. Spectroscopic follow-up of 184 of these reveals 11 nitrogen-rich (WN) and four carbon-rich (WC) WR stars. Early WC subtypes are absent from our sample and none shows evidence for circumstellar dust emission. Of the candidates which are not WR stars, ∼120 displayed hydrogen emission-line features in their spectra. Spectral features suggest that the majority of these are in fact B supergiants/hypergiants, ∼40 of these are identified Be/B[e] candidates.
Here, we present the optical spectra for six of the newly detected WR stars, and the near-IR spectra for the remaining nine of our sample. With a WR yield rate of ∼7 per cent and a massive star detection rate of ∼65 per cent, initial results suggest that this method is one of the most successful means for locating evolved, massive stars in the Galaxy.  相似文献   

The stellar mass content of distant galaxy groups     

Michael L. Balogh  Dave Wilman  Robert D. E. Henderson  Richard G. Bower  David Gilbank  Richard Whitaker  Simon L. Morris  George Hau  J. S. Mulchaey  A. Oemler  Jr    R. G. Carlberg 《Monthly notices of the Royal Astronomical Society》2007,374(3):1169-1180

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Resolved spectroscopy of a gravitationally lensed L* Lyman-break galaxy at z∼ 5     

A. M. Swinbank  R. G. Bower  Graham P. Smith  R. J. Wilman  Ian Smail  R. S. Ellis  S. L. Morris  J.-P. Kneib 《Monthly notices of the Royal Astronomical Society》2007,376(2):479-491

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Residential Location,Ambient Air Lead Pollution And Lead Absorption In Children*     

Raphael J. Caprio  Harry L. Margulis  Morris M. Joselow 《The Professional geographer》1975,27(1):37-42

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Possible impact melt and debris flows at Tooting Crater, Mars     

Aisha R. Morris  Peter J. Mouginis-Mark 《Icarus》2010,209(2):369-181

Candidate examples of impact melt flows and debris flows have been identified at Tooting crater, an extremely young (<2 Myr), 29 km diameter impact crater in Amazonis Planitia, Mars. Using HiRISE and CTX images, and stereo-derived digital elevation models derived from these images, we have studied the rim and interior wall of Tooting crater to document the morphology and topography of several flow features in order to constrain the potential flow formation mechanisms. Four flow types have been identified; including possible impact melt sheets and three types of debris flows. The flow features are all located within 2 km of the rim crest on the southern rim or lie on the southern interior wall of the crater ∼1500 m below the rim crest. Extensive structural failure has modified the northern half of the crater inner wall and we interpret this to have resulted in the destruction of any impact melt emplaced, as well as volatile-rich wall rock. The impact melt flows are fractured on the meter to decameter scale, have ridged, leveed lobes and flow fronts, and cover an area >6 km × 5 km on the southern rim. The debris flows are found on both the inner wall and rim of the crater, are ∼1-2 km in length, and vary from a few tens of meters to >300 m in width. These flows exhibit varying morphologies, from a channelized, leveed flow with arcuate ridges in the channel, to a rubbly flow with a central channel but no obvious levees. The flows indicate that water existed within the target rocks at the time of crater formation, and that both melt and fluidized sediment was generated during this event.  相似文献   

The fate of technetium in reduced estuarine sediments: Combining direct and indirect analyses     

Ian T. Burke  Francis R. Livens  Jonathan R. Lloyd  Andrew P. Brown  Gareth T.W. Law  Joyce M. McBeth  Beverley L. Ellis  Richard S. Lawson  Katherine Morris 《Applied Geochemistry》2010

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Trends in Canadian Short‐Duration Extreme Rainfall: Including an Intensity–Duration–Frequency Perspective     

Mark W. Shephard  Eva Mekis  Robert J. Morris  Yang Feng  Xuebin Zhang  Karen Kilcup 《大气与海洋》2014,52(5):398-417

Short-duration (5 minutes to 24 hours) rainfall extremes are important for a number of purposes, including engineering infrastructure design, because they represent the different meteorological scales of extreme rainfall events. Both single location and regional analyses of the changes in short-duration extreme rainfall amounts across Canada, as observed by tipping bucket rain gauges from 1965 to 2005, are presented. The single station analysis shows a general lack of a detectable trend signal, at the 5% significance level, because of the large variability and the relatively short period of record of the extreme short-duration rainfall amounts. The single station 30-minute to 24-hour durations show that, on average, 4% of the total number of stations have statistically significant increasing amounts of rainfall, whereas 1.6% of the cases have significantly decreasing amounts. However, regional spatial patterns are apparent in the single station trend results. Thus, for the same durations regional trends are presented by grouping the single station trend statistics across Canada. This regional trend analysis shows that at least two-thirds of the regions across Canada have increasing trends in extreme rainfall amounts, with up to 33% being significant (depending on location and duration). Both the southwest and the east (Newfoundland) coastal regions generally show significant increasing regional trends for 1- and 2-hour extreme rainfall durations. For the shortest durations of 5–15 minutes, the general overall regional trends in the extreme amounts are more variable, with increasing and decreasing trends occurring with similar frequency; however, there is no evidence of statistically significant decreasing regional trends in extreme rainfall amounts. The decreasing regional trends for the 5- to 15-minute duration amounts tend to be located in the St. Lawrence region of southern Quebec and in the Atlantic provinces. Additional analysis using criteria specified for traditional water management practice (e.g., Intensity-Duration-Frequency (IDF)) shows that fewer than 5.6% and 3.4% of the stations have significant increasing and decreasing trends, respectively, in extreme annual maximum single location observation amounts. This indicates that at most locations across Canada the traditional single station IDF assumption that historical extreme rainfall observations are stationary (in terms of the mean) over the period of record for an individual station is not violated. However, the trend information is still useful complementary information that can be considered for water management purposes, especially in terms of regional analysis.  相似文献   

Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times     

M. Bencsik  M. F. Shamim  R. H. Morris  M. I. Newton 《International Journal of Environmental Science and Technology》2014,11(5):1189-1196

Horizontal sub-surface flow wetlands are essentially a bed of porous material in which suitable plants are grown to facilitate the removal of organic matter and particulates from wastewater. The aim of this study is to assess the reliability and accuracy of magnetic resonance transverse relaxation time for monitoring clogging development in a constructed wetland. In this study, three different horizontal sub-surface flow constructed wetland models have been produced using tubes packed with different sizes of glass beads with diameter 3, 8 and 14 mm. Accelerated clogging has been achieved by pumping sludge extracted from a real clogged wetland through the bead pack. A desktop MRI tomography system has been used to monitor the transverse relaxation rate as a function of position along the tube and hydraulic conductivity. To corroborate the clogging with magnetic resonance measurements, the head loss was monitored to determine the hydraulic conductivity. Using a bi-exponential fit to the spin echo train data, the slow relaxation rate contribution shows good correlation with the changing hydraulic conductivity. Both fast and slow contributions map well to the expected clog patterns for a constructed wetland. We have demonstrated that there is a linear correlation between the hydraulic conductivity and both parameters of a bi-exponential fit to R ₂ ^eff , but particularly for the case of the short T ₂ component.  相似文献