Adapting visual methods: action research with Kampala street children   总被引：3，自引：0，他引：3  

Lorraine Young  & Hazel Barrett 《Area》2001,33(2):141-152

The paper examines the use of four visual 'action' methods for eliciting information from street children about their interactions with the socio-spatial environment. These methods were adapted and used to encourage child-led activities and minimize researcher input. The advantages and constraints associated with the successful implementation of visual methods with children are examined, followed by a brief examination of the 'real' and ethical considerations surrounding their use. The paper concludes that visual methods allow a high level of child-led participation in research, as well as providing a stimulus for eliciting further oral material.  相似文献   

Elemental concentrations and their distribution in two bituminous coals of different paleoenvironments     

L.A. Harris  H.E. Barrett  O.C. Kopp 《International Journal of Coal Geology》1981,1(3):175-193

The vertical distributions of major and minor elements in two high-volatile bituminous coals of Eastern Tennessee are compared. The coals studied are the Pewee, deposited in a fresh-water environment, and the Upper Grassy Spring, previously thought to be influenced by a late incursion of marine water.X-ray fluorescence analyses were performed on a continuous series of specimens obtained from full-face channel samples representing the entire thickness of each seam. Correlation coefficients (r) for all element pairs show high positive correlations for element pairs normally associated with clay minerals. Equally good correlations were observed for (Si, Ti) and (Al, Ti), suggesting that titanium is associated with clay minerals in both coals. Strontium and phosphorous showed a high positive r factor for both the Upper Grassy Spring and the Pewee.Major differences were found to exist in the concentrations and distributions of sulfur, iron, and arsenic in the Upper Grassy Spring and Pewee seams. The Upper Grassy Spring contains an order of magnitude more sulfur than the Pewee as well as several times as much iron and arsenic. The element concentrations and especially their distributions in the Upper Grassy Spring suggest an earlier time for the marine incursion than previously reported. In fact, there is evidence that this coal deposit may have been influenced by marine conditions from its inception.  相似文献   

Strontium and oxygen isotopic composition of some basalts from Hole 504B,Costa Rica Rift,DSDP Legs 69 and 70     

T.J. Barrett  H. Friedrichsen 《Earth and Planetary Science Letters》1982,60(1):27-38

Seventeen whole-rock samples, generally taken at 25–50 m intervals from 5 to 560 m sub-basement in Hole 504B, drilled in 6.2 m.y. old crust, were analysed for⁸⁷Sr/⁸⁶Sr ratios, Sr and Rb concentrations, and¹⁸O/¹⁶O ratios. Sr isotope ratios for 8 samples from the upper 260 m of the hole range from 0.70287 to 0.70377, with a mean of 0.70320. In the 330–560 m interval, 5 samples have a restricted range of 0.70255–0.70279, with a mean of 0.70266, the average value for fresh mid-ocean ridge basalts (MORB). In the 260–330 m interval, approximately intermediate Sr isotopic ratios are found.δ¹⁸O values (‰) range from 6.4 to 7.8 in the upper 260 m, 6.2–6.4 in the 270–320 m interval, and 5.8–6.2 in the 320–560 m interval. The values in the upper 260 m are typical for basalts which have undergone low-temperature seawater alteration, whereas the values for the 320–560 m interval correspond to MORB which have experienced essentially no oxygen isotopic alteration.The higher⁸⁷Sr/⁸⁶Sr and¹⁸O/¹⁶O ratios in the upper part of the hole can be interpreted as the result of a greater overall water/rock ratio in the upper part of the Hole 504B crust than in the lower part. Interaction of basalt with seawater(⁸⁷Sr/⁸⁶Sr=0.7091) increased basalt⁸⁷Sr/⁸⁶Sr ratios and produced smectitic alteration products which raised whole-rock δ¹⁸O values. Seawater circulation in the lower basalts may have been partly restricted by the greater number of relatively impermeable massive lava flows below about 230 m sub-basement. These flows may have helped to seal off lower basalts from through-flowing seawater.  相似文献   

REPLY TO the preceding Discussion by Göksel Türk of "Interpretation of Hydrochemical Facies by Factor Analysis"     

Sam B. Upchurch 《Ground water》1979,17(2):213-215

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Multivariate analysis of sedimentary environments using grain-size frequency distributions     

Richard L. Chambers  Sam B. Upchurch 《Mathematical Geosciences》1979,11(1):27-43

Multivariate statistics were used to characterize and test the effectiveness of grain-size frequencies as environmental discriminators. Sediment from the following two depositional systems along eastern Lake Michigan were studied: (1) a closed system with respect to available grain sizes (Little Sable Point), and (2) an open system (Sleeping Bear Point-Manitou Passage). Principal components analysis shows that grain-size distributions are composed of two or more subgroups that reflect surface creep bedload, mixed suspension bedload, and uniform suspension. Discriminant function and principal latent vector analyses of the Little Sable Point environments show that, when available sediment is limited with respect to grain size (0.5 φto 3.0 φ), similar size distributions can occur in environments supposedly characterized by different energy conditions. Sediment in the Sleeping Bear Point-Manitou Passage system is not restricted to available grain sizes and the environments discriminated very well (α < 0.001). The grain-size distributions are such that they reflect differences in energy conditions within the environments. It is apparent that the grain sizes available to a depositional system control to a great extent the effectiveness of environmental discrimination.  相似文献   

Bottom sediment contamination in the Bay of Naples,Italy     

G.B. Griggs  Sam Johnson 《Marine pollution bulletin》1978,9(8):208-214

The nearshore sediments in the Bay of Naples show a buildup of organic carbon and increased levels of lead, copper and chromium as a result of discharge of domestic and industrial waste water. Twenty to twenty-five square kilometres of bottom area have been contaminated by the buildup of anoxic muds with elevated heavy metal concentrations.  相似文献   

Geological setting of the Rapu Rapu gold-rich volcanogenic massive sulfide deposits,Albay Province,Philippines     

Ross?L.?SherlockEmail author  Timothy?J.?Barrett  Peter?D.?Lewis 《Mineralium Deposita》2004,39(1):122-122

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The role of “excess” CO₂ in the formation of trona deposits     

Sam Earman  Fred M. Phillips  Brian J.O.L. McPherson 《Applied Geochemistry》2005,20(12):2217-2232

The prevailing theory for the formation of trona [Na₃(CO₃)(HCO₃) · 2(H₂O)] relies on evaporative concentration of water produced by silicate hydrolysis of volcanic rock or volcaniclastic sediments. Given the abundance of closed drainage basins dominated by volcanics, it is puzzling that there are so few trona deposits and present-day lakes that would yield dominantly Na–CO₃ minerals upon evaporation. Groundwater in the San Bernardino Basin (southeastern Arizona, USA and northeastern Sonora, Mexico) would yield mainly Na–CO₃ minerals upon evaporation, but waters in the surrounding basins would not. Analysis of the chemical evolution of this groundwater shows that the critical difference from the surrounding basins is not lithology, but the injection of magmatic CO₂. Many major deposits of trona and Na–CO₃-type lakes appear to have had “excess” CO₂ input, either from magmatic sources or from the decay of organic matter. It is proposed that, along with the presence of volcanics, addition of “excess” CO₂ is an important pre-condition for the formation of trona deposits.  相似文献   

Detection of model voids by identifying reverberation phenomena in GPR records   总被引：2，自引：1，他引：2  

Lev Kofman  Amit Ronen  Sam Frydman   《Journal of Applied Geophysics》2006,59(4):284-299

In order to improve the reliability of the ground penetrating radar (GPR) method in identifying subsurface sinkholes and karst cavities, laboratory investigations have been performed. The main objective of this work was to examine the relationship between horizontal/vertical voids dimensions and wavelengths of various antennas, and the corresponding GPR responses. Emphasis was given to the investigation of the factors that cause the appearance of reverberation phenomena in the signal pattern.The tests were conducted in 5 m × 10 m area by 2-m-deep trench filled with homogenous, dry sand. The voids models (empty fiberglass cylinders in diameters of 0.6 m, 1.0 m, 1.5 m and 2.4 m, with various heights) were buried vertically with their tops at depths of between 0.7 and 1.5 m. Investigations were performed for the various model conditions by towing 500, 300 and 100 MHz antennas along a pre-established grid, for the various model conditions.The GPR data collected using the 500 MHz bistatic antenna above the 1.0-m- and the 1.5-m-diameter cylinders, and using the 300 MHz bistatic antenna above the 1.5-m-diameter cylinder, confirmed the presence of a reverberation phenomenon, i.e. a strong convex signal pattern, containing a series of high amplitude extending oscillations with reduced frequency.Based on past practical GPR experience of void detection and presently obtained experimental data, two rules of thumbs may be adopted for the prediction of the appearance of resonant radar pictures:

1. The void diameter larger than the wavelength in air of the antenna used.

2. The vertical size of the empty void not significantly smaller than its horizontal dimension.

The strong reverberations generated by the inner surface of the void targets were found to approximate standing waves generated in cylindrical waveguides and waveguide resonators. The theoretical, experimental and practical results obtained concur.  相似文献   

Inversion of Thick-Target Bremsstrahlung Spectra from Nonuniformly Ionised Plasmas     

Brown  John C.  McArthur  Guillian K.  Barrett  Richard K.  McIntosh  Scott W.  Emslie  A. Gordon 《Solar physics》1998,179(2):379-404

The effects of non-uniform plasma target ionisation on the spectrum of thick-target HXR bremsstrahlung from a non-thermal electron beam are analysed. In particular the effect of the target ionisation structure on beam collisional energy losses, and hence on inversion of an observed photon spectrum to yield the electron injection spectrum, is considered and results compared with those obtained under the usual assumption of a fully ionised target.The problem is formulated and solved in principle for a general target ionisation structure, then discussed in detail for the case of a step function distribution of ionisation with column depth as an approximation to the sharp coronal–chromospheric step structure in solar flare plasmas. It is found that such ionisation structure has very dramatic effects on derivation of the thick-target electron injection spectrum F₀(E₀) as compared with the result F*₀(E ₀) obtained under the usual assumption of a fully ionised target: (a) Inferred F*₀ contain more electrons than F ₀ and in some cases include electrons at energies where none are actually present. Although the total (energy-integrated) beam fluxes in the two cases do not differ by a factor of more than A_ee/A_eH, the spectral shapes can differ greatly over finite energy intervals resulting in the danger of misleading results for total fluxes obtained by extrapolation. (b) The unconstrained mathematical solution for F₀ for any photon spectrum is never unique, while that for F*₀ is unique. When the physical constraint F₀ 0 is added, for some photon spectra solutions for F₀ may not exist or may not be unique. (This is not an effect of noise but of real analytic ambiguity.) (c) For data corresponding to F*₀ with a low-energy cut-off, or a cut-off or rapid enough exponential decline at high energies, a unique solution F₀ does exist and we obtain a recursive summation for its evaluation.Consequently, in future work on the inversion of HXR bremsstrahlung spectra it will be vital for algorithms to include the effects of target ionisation if spurious results on thick-target electron spectra are not to be inferred. Finally it is pointed out that the depth of the transition zone, and its evaporative evolution during flares may be derivable from its effect on the HXR spectrum.  相似文献