Metamorphic petrology and gravity studies of the Archean English River subprovince, western Superior Province, Manitoba and Ontario, Canada

The tectonic development of the English River Subprovince (ERSP) of the Superior Province in Ontario and Manitoba, as with other Archean medium-high grade metasedimentary/gneiss terranes, is an area of active research. Geochemical and geophysical data were collected during this study to determine the metamorphic conditions of formation, and the relationship between surface and subsurface geology. The results of metamorphic studies by Henke (1984), Baumann (1985), Chipera (1985) and Reeb (1987) were also integrated with those of this study. The temperatures and pressures of formation, as well as detailed gravity characteristics, constrain the postulated tectonic model for the ERSP. Chemical data were obtained from the metasedimentary samples collected in the Lac Seul area, using an electron probe micro-analyzer for geothermobarometric calculations. The temperatures and pressures of formation were estimated using garnet-biotite geotherrnometers and garnet-cordieriteplagioclase-quartz geobarometers. Pressure, temperature, isograd and granulite occurrence maps were produced, which included results from all UNO workers in the Lac seul area. Gravity data were collected along Highways 11, 304, 314 and 315 in Manitoba, and reduced to a Bouguer anomaly. The data were divided into five profiles. These profiles, in addition to one profile based on previously existing Bouguer data in Ontario, were modelled using a two dimensional gravity modelling program. The models were developed with a primary focus on the surficial geology. No new isograds or mineral assemblages were identified in the Lac seul area during this study. The index minerals found are garnet, biotite, cordierite, sillimanite and orthopyroxene. The temperatures results ranged from 577 to 751 °c. The highest temperatures were found in the northeast and the lowest in the southwest. Isotherms display a pattern of domes and basins. Pressure results ranged from 2.7 to 5.7 kb, with the highest values in the northeast and lowest in the west. The pressure and temperature values of this study were intermediate compared to the range found by other UNO workers. The gravity models display calculated profiles which closely resemble the observed anomalies. Modelling results indicate that the abundant granitoids at the surface are also pervasive at depth. There is also strong evidence that dense, mafic bodies exist at depth and may be a result of crustal underplating. Determination of the tectonic regime operating during formation of the ERSP and adjacent subprovinces is hampered by the abundant granitoid intrusions. A potential sequence of accretionary tectonic events, distinguishing the northern and southern domains of the ERSP as individual subprovinces, is presented

Natural resources conflicts and the biofuel industry: implications and proposals for Ghana

Africa has become an important target producer of the feedstock, Jatropha curcas L (JCL), for biofuel production. This presents opportunities for transforming production, markets and the well-being of farmers and rural populations in developing countries, if deals are well-structured. The history of natural resource use conflicts in Africa has important implications for understanding current resource ecology and the social and political relationships within it. Ghana has had varying resource management regimes in its history. This paper seeks to relate the history of Ghana's natural resources conflicts to the current rush for lands in Ghana forcultivation of JCL and to discuss its implications and opportunities for a sustainable JCL industry in the countly. The colonial and postcolonial land conflicts and politics and the current and potential conflicts and opportunities associated with the JCL indust1y are presented. The paper offers suggestions not only for a sustainable cultivation of Jatropha, but alsofor a biofuel policy in Ghana.Keywords: Biofuel; natural resources conflicts,- land grabbing; Jatrophacurcas; Ghana

The use of tensiometers to control the irrigation of nursery stock in containers.

End of Project ReportThe use of digital tensiometers to control the irrigation of nursery stock in containers was studied over a three year period. Over this time the tensiometers performed satisfactorily and successfully automated the irrigation of the plants. The results indicate the feasibility of using them to control nursery stock irrigation under Irish conditions. An irrigation tension of 50 hPa to trigger an irrigation period resulted in larger plants than those grown under drier regimes with irrigation tensions of 100 and 200 hPa. Measurements of stomatal resistance indicated that the plants in the drier regimes were growing under greater moisture stress. The drier regimes reduced the number of irrigations and also the overall usage of water. They reduced plant size but did not impair plant appearance. It may be possible to use this approach in the future to control plant growth. There was no difference in performance between plants gown with ebb and flood irrigation and those irrigated via overhead spraylines. The ebb and flood system gave a considerable reduction in water use.European Union Structural Funds (EAGGF

Lithographically and electrically controlled strain effects on anisotropic magnetoresistance in (Ga,Mn)As

It has been demonstrated that magnetocrystalline anisotropies in (Ga,Mn)As are sensitive to lattice strains as small as 10^-4 and that strain can be controlled by lattice parameter engineering during growth, through post growth lithography, and electrically by bonding the (Ga,Mn)As sample to a piezoelectric transducer. In this work we show that analogous effects are observed in crystalline components of the anisotropic magnetoresistance (AMR). Lithographically or electrically induced strain variations can produce crystalline AMR components which are larger than the crystalline AMR and a significant fraction of the total AMR of the unprocessed (Ga,Mn)As material. In these experiments we also observe new higher order terms in the phenomenological AMR expressions and find that strain variation effects can play important role in the micromagnetic and magnetotransport characteristics of (Ga,Mn)As lateral nanoconstrictions.Comment: 11 pages, 4 figures, references fixe

Strain dependence of the Mn anisotropy in ferromagnetic semiconductors observed by x-ray magnetic circular dichroism

We demonstrate sensitivity of the Mn 3d valence states to strain in the ferromagnetic semiconductors (Ga,Mn)As and (Al,Ga,Mn)As, using x-ray magnetic circular dichroism (XMCD). The spectral shape of the Mn $L_{2,3}$ XMCD is dependent on the orientation of the magnetization, and features with cubic and uniaxial dependence are distinguished. Reversing the strain reverses the sign of the uniaxial anisotropy of the Mn $L_3$ pre-peak which is ascribed to transitions from the Mn 2p core level to p-d hybridized valence band hole states. With increasing carrier localization, the $L_3$ pre-peak intensity increases, indicating an increasing 3d character of the hybridized holes.Comment: 4 pages plus 2 figures, accepted for publication in Physical Review