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141.
This article analyzes the recent growth and configuration of Fair Trade networks connecting South African Rooibos tea producers with American consumer markets. As we demonstrate, Fair Trade’s growth in the Rooibos sector engages key issues of black empowerment, land reform, and sustainable development in post-Apartheid South Africa. Fair Trade networks provide small-scale black Rooibos producers with critical markets. Most significantly, the Wupperthal and Heiveld cooperatives have upgraded into processing and packaging and their jointly owned Fairpackers facility now exports shelf-ready Rooibos tea. Analyzing the nature of US Fair Trade Rooibos buyers and their South African sourcing arrangements, we identify key variations in Fair Trade commitment and engagement between mission-driven and market-driven distributors. While mission-driven buyers engage small-scale Rooibos cooperatives in multifaceted partnership networks, market-driven buyers pursue conventional sourcing strategies favoring purchases from large plantations and exporters. We conclude that tensions between a radical and commercial orientation toward Fair Trade in Rooibos tea networks in many ways mirror those in the broader movement. 相似文献
142.
143.
The data on the species composition, trophic structure, and distribution of macrozoobenthos in Amur Bay obtained in 2001 are presented. Long-term changes in the benthos are analyzed. In 2001, the total benthos biomass significantly increased, although the parameters of the species richness declined as compared to 1986–1989. In 2001, as well as in the 1970s and 1980s, the benthos trophic structure was characterized by the prevalence of deposit feeders. The entire structure of the benthos is evaluated as an eutrophic one. Eutrophication of the bay is considered to be the most probable cause of the negative changes in the benthic communities of the bay in 2001, as well as 15 years ago. 相似文献
144.
T. Radhakrishna 《Journal of the Geological Society of India》2009,73(1):131-142
South Indian granulite terrain had witnessed significant part of Precambrian mafic igneous activity in the form of episodic
mafic dyke intrusions of the Palaeoproterozoic period. Strike trends of these dykes are not uniform over the region and the
dykes are generally fresh, massive, black dolerites except in the Bhavani shear zone bordering the southern fringes of Nilgiri
massif. In Agali-Coimbatore area of our study in the western Bhavani shear zone, the dykes appear to be penecontemporaneous
with shearing. Isotopic data place age of Agali-Coimbatore dyke intrusions at about 2.1 Ga. The age of these dykes is significant
to constrain an early Palaeoproterozoic age for major shearing event in the Bhavani shear zone. Other dyke emplacement ages
are placed at about 1.8 Ga and 1.65 Ga based on the Ar/Ar and K-Ar isotopic results of dykes in Dharmapuri and Tiruvannamalai
areas. Older ages comparable to those of the Dharwar craton are not known and in this respect future isotopic dating is vital.
Geochemically, these dykes are quartz/hypersthene normative subalkalic tholeiites. An attempt is made here to provide insights
into the general petrogenetic history of the Precambrian dykes. Compositional trends are explained by the fractional crystallization
of ferromagnesian phases and plagioclase control is conspicuous at the advanced stages of fractionation. Geochemical characteristics
suggest that the dykes have tapped Fe-rich non-pyrolite mantle sources with LIL and LREE enrichment as in many continental
basalts. The data suggest that role of crustal contamination is limited in petrogenesis; crustal signatures are noticed in
the more mafic end members formed in early stage of evolution suggesting that contamination was temperature controlled with
most primitive high temperature magmas being most vulnerable to the process. Nd-Sr isotopic data, at present restricted to
Agali-Coimbatore dykes, suggest that Palaeoproterozoic magmas tapped subcontinental lithosphere that may have stabilized in
the Archaean times at about 3 Ga during the major crustal building activity in the shield region. Further work coupled with
isotopic and mineral chemistry will improve our knowledge on the petrological evolution of the dyke magmas and mafic magmatism
in general. 相似文献
145.
I. Ya. Azbel L. A. Dmitrieva V. S. Gobarenko T. B. Yanovskaya 《Geophysical Journal International》1984,79(1):199-206
Summary. Numerical modelling is one of the most efficient methods for an investigation of the relationship between structural features and peculiarities of observed wavefields. It is practically the only method for 2-D and 3-D inhomogeneous media.
An algorithm based on ray theory has been developed for calculations of travel times and amplitudes of seismic waves in 3-D inhomogeneous media with curved interfaces. It was applied for numerical modelling of kinematic and dynamic characteristics of seismic waves propagating in laterally inhomogeneous media.
Travel-time and amplitude patterns were studied in the 2-D and 3-D models of a geosyncline, in which velocity distribution was given by an analytical function of the coordinates. For a more complicated model representing a subducting high-velocity lithospheric plate in a transition zone between oceanic and continental upper mantle, the velocity distribution was given by discrete values on a 2-D non-rectangular grid. It was shown that when a source was placed above the lithospheric plate, a shadow zone appeared along a strike of the structure, i.e. in the direction which is perpendicular to a strong lateral velocity gradient. Travel-time residuals were calculated along the seismological profile for a 3-D velocity distribution in the upper mantle beneath Central Asia, obtained as a result of inversion of travel times by the Backus-Gilbert method. They were found to be in a good agreement with the observed data. 相似文献
An algorithm based on ray theory has been developed for calculations of travel times and amplitudes of seismic waves in 3-D inhomogeneous media with curved interfaces. It was applied for numerical modelling of kinematic and dynamic characteristics of seismic waves propagating in laterally inhomogeneous media.
Travel-time and amplitude patterns were studied in the 2-D and 3-D models of a geosyncline, in which velocity distribution was given by an analytical function of the coordinates. For a more complicated model representing a subducting high-velocity lithospheric plate in a transition zone between oceanic and continental upper mantle, the velocity distribution was given by discrete values on a 2-D non-rectangular grid. It was shown that when a source was placed above the lithospheric plate, a shadow zone appeared along a strike of the structure, i.e. in the direction which is perpendicular to a strong lateral velocity gradient. Travel-time residuals were calculated along the seismological profile for a 3-D velocity distribution in the upper mantle beneath Central Asia, obtained as a result of inversion of travel times by the Backus-Gilbert method. They were found to be in a good agreement with the observed data. 相似文献
146.
John F. Bratton John Karl Böhlke Frank T. Manheim David E. Krantz 《Ground water》2004,42(7):1021-1034
147.
The effect of aspect ratio on the mechanical behaviour and micromechanics of two different assemblies during drained triaxial shearing are reported in this paper. Discrete element simulations are done on two different sets of assemblies—first assembly consists of particles with aspect ratio 1.0 and second assembly consists of particles with aspect ratio 1.5. A log normal distribution of particle size is adopted for both the samples. The constitutive behaviour of the assemblies and the evolution of the microstructure of the samples under shearing are closely examined and is related to the aspect ratio of the particles constituting the assembly. The spherical harmonic distributions of contact forces and contact normals along with 3-D histograms are plotted to give quantitative information of the variation of these parameters as the loading progresses. The results indicate that as the aspect ratio increases, there is an increase in the maximum deviatoric stress at the macroscopic level. At the microscopic level, the values of the anisotropic coefficients which are representative of the microparameters also show an increase in the magnitude for the assembly with higher aspect ratio particles. 相似文献
148.
Haverluk T 《The Journal of geography》1997,96(3):134-145
"In 1930, the majority of Hispanics were of Mexican descent and lived in the five Southwestern states of Arizona, California, Colorado, New Mexico, and Texas. After World War II the Latino migrant stream began to diversify and include large numbers of Caribbeans, and Central and South Americans who generally settled in the Eastern states and California.... The U.S. Hispanic population has increased from approximately one million in 1930, to approximately 32 million in 1997. County maps chronicle the changing distribution and numbers of Hispanics from 1850 to 1990." 相似文献
149.
150.
The distribution of plasma density around a metallic cylinder in a collisionfree plasma is determined by the system of Vlassov equations and the Poisson equation. The plasma may have a streaming velocity perpendicular to the cylinder axis producing a wake behind the cylinder. In the region outside a thin double layer at the cylinder surface the problem allows some simplification. Then numerical solutions become possible-even if the streaming velocity is low. Some numerical solutions are presented. A magnetic field produces an asymmetric shape of the wake, if the gyration radius of the ion becomes comparable to the cylinder radius. 相似文献