Urban landscape as mirror of ethnicity: trees of the South Plains

The literatures on urban forestry, environmental justice, and Marxist urban political ecology are considered through empirical attention to the localized racial and ethnic politics which spatially differentiate urban socio-natural landscapes. In the American Southwest, urban landscapes reflect a history in which Anglo Whites were able to distance themselves from spaces of production while gaining access to superior residences and environmental amenities in spaces of reproduction; ethnoracially marginalized Others were treated as necessary yet disfavored populations, thus constituting a segregated mode of production. In this study, we investigate the association between tree canopy cover and the location of urban ethnic minority populations with a focus on the arid Southern High Plains city of Lubbock, Texas. Using data from color infrared aerial photography and block-group demographic indicators from the 2010 US Census, we analyze the city’s arboreal landscape with a mix of methods—hierarchical regression, archival research, and field observation. Results confirm that a lack of tree cover in minority neighborhoods is a symptom of broader environmental inequalities in which contemporary segregation patterns reflect a history of residential and land-use zoning with the socio-natural relations of planting and sustaining urban trees.     

ASSURE: a model for the simulation of urban expansion and intra-urban social segregation

Numerous cities in developing regions worldwide are expanding at a tremendous rate. This requires adequate strategies to address the needs of these growing cities with diverse populations. Nonetheless, the development of urban policies is often hampered by the lack of reliable data or insight in the socio-spatial dynamics of this urban expansion. This paper therefore presents ASSURE, a spatially and temporally explicit model that can simulate urban growth and intra-urban social segregation, taking into account alternative policy strategies and expected social dynamics. The model has a flexible structure that allows incorporating specific city conditions that influence residential decision-making and adapting the simulation to the data available. This, in combination with the transparent model structure, makes ASSURE a potentially valuable decision support tool for urban planning. The potential is demonstrated with an example where the urban growth of and social segregation in Kampala (Uganda) is simulated based on (semi-)quantitative and qualitative data for ca. 800 households collected through interviews. The results of the simulations show that depending on the scenario, the spatial segregation and accessibility problems will evolve highly differently.     

Stellar contents and star formation in the young cluster Stock 18

We have carried out deep (V ∼ 21 mag) UBVRI photometric study of the star cluster Stock 18. These along with archival Infrared data have been used to derive the basic cluster parameters and also to study the star formation processes in and around the cluster region. The distance to the cluster is derived as 2.8 ± 0.2 kpc while its age is estimated as 6.0 ± 2.0 Myr. Present study indicates that interstellar reddening is normal in the direction of the cluster. The mass function slope is found to be −1.37 ± 0.27 for the mass range 1 < M/M_⊙ < 11.9. There is no evidence found for the effect of mass segregation in main-sequence stars of the cluster. A young stellar population with age between 1-2 Myr have been found in and around the cluster region. The presence of IRAS and AKARI sources with MSX intensity map also show the youth of the Sh2-170 region.     

Large-scale melt-depletion in granulite terranes: an example from the Archean Ashuanipi Subprovince of Quebec

This study uses field, petrographic and geochemical methods to estimate how much granitic melt was formed and extracted from a granulite facies terrane, and to determine what the grain‐ and outcrop‐scale melt‐flow paths were during the melt segregation process. The Ashuanipi subprovince, located in the north‐eastern Superior Province of Quebec, is a large (90 000 km²) metasedimentary terrane, in which > 85% of the metasediments are of metagreywacke composition, that was metamorphosed at mid‐crustal conditions (820–900 °C and 6–7 kbar) in a late Archean dextral, transpressive orogen. Decrease in modal biotite and quartz as orthopyroxene and plagioclase contents increase, together with preserved former melt textures indicate that anatexis was by the biotite dehydration reaction: biotite + quartz + plagioclase = melt + orthopyroxene + oxides. Using melt/orthopyroxene ratios for this reaction derived from experimental studies, the modal orthopyroxene contents indicate that the metagreywacke rocks underwent an average of 31 vol% partial melting. The metagreywackes are enriched in MgO, CaO and FeO_t and depleted in SiO₂, K₂O, Rb, Cs, and U, have lower Rb/Sr, higher Rb/Cs and Th/U ratios and positive Eu anomalies compared to their likely protolith. These compositions are modelled by the extraction of between 20 and 40 wt %, granitic melt from typical Archean low‐grade metagreywackes. A simple mass balance indicates that about 640 000 km³ of granitic melt was extracted from the depleted granulites. The distribution of relict melt at thin section‐ and outcrop‐scales indicates that in layers without leucosomes melt extraction occurred by a pervasive grain boundary (porous) flow from the site of melting, across the layers and into bedding planes between adjacent layers. In other rocks pervasive grain boundary flow of melt occurred along the layers for a few, to tens of centimetres followed by channelled flow of melt in a network of short interconnected and structurally controlled conduits, visible as the net‐like array of leucosomes in some outcrops. The leucosomes contain very little residual material (< 5% biotite + orthopyroxene) indicating that the melt fraction was well separated from the residuum left in situ as melt‐depleted granulite. Only 1–3 vol percentage melt remained in the melt‐depleted granulites, hence, the extraction of melt generated by biotite dehydration melting in these granulites, was virtually complete under conditions of natural melting and strain rates in a contractional orogen.     

Socio-spatial differentiation and residential segregation in Delhi: a question of scale?

This paper focuses on the pattern of social-spatial differentiation and segmentation of the metropolitan area of Delhi. The main objective is to analyse the mechanisms of residential segregation and the factors that explain it both at the micro- and macro-level. In the context of the Indian society and its caste system traditionally associated with strong social and spatial segregation, we try to appraise the extent to which the metropolitanization process in Delhi engenders original forms of spatial segmentation or perpetuates and strengthens the traditional forms of socio-spatial divisions. At the level of the global spatial organization of the urban agglomeration, our objective is twofold: to analyse the factors that shaped the urban landscape and introduced spatial discontinuity, from physical barriers to the different historic periods and the impact of town planning; to analyse the residential pattern of different segments of the urban population, in order to detect whether certain economic and socio-cultural attributes generate a pattern of segregation. We then pursue a more detailed investigation at the level of a zone, based on the case study of Mayur Vihar-Trilokpuri in east Delhi. We analyse the residential practices developed by different socio-economic groups, their strategies as regards the occupation of the geographical and economic space, their tendency to residential clustering that leads to a pattern of social segregation at the level of the neighbourhood. In this perspective, the links between the urban policies at the macro-level and the individuals’ residential practices at the micro-level are also examined.     

Compositional Continuity and Discontinuity in the Horoman Peridotite, Japan, and its Implication for Melt Extraction Processes in Partially Molten Upper Mantle

A hypothetical model is proposed to explain the origin of compositionaldiscontinuities in the layering observed in orogenic lherzolites.The observed collinearity of the whole-rock peridotite compositionsis best explained in terms of partial melting and melt segregation.The presence of chemical discontinuities implies that melt segregationincludes an abrupt and discontinuous process. A key conceptin the model is the topological transformation of melt geometryin partially molten rocks responding to the equality and inequalityof the fluid pressure and solid pressure, which may be realizedin a gravitational field. It is emphasized that the percolationthreshold is a critical boundary, beyond which a rapid microstructuralchange occurs in response to the change of local fluid pressure,thus causing a rapid increase of permeability. The model impliesthat the mode of melting is closer to batch melting than tofractional melting in the upper mantle. KEY WORDS: critical phenomenon; partial melting; percolation threshold; Horoman peridotite; melt segregation     

与花岗岩有关的成矿流体与成矿金属研究

虽然分异结晶和热重力扩散对花岗质岩浆结晶过程中成矿元素的相对富集有重要的影响，但在此过程中富水流体相的分离却显得更加重要，温度、压力、流体成分及水的绝对含量决定着亲花岗岩类元亲从熔浆中分离出来的量．流体中成矿元素主要以Ｃｌ￣－、Ｆ￣－、ＯＨ￣－、ＨＳ￣－等的络合物形式迁移，而其沉淀环境则介于岩石缓冲及流体缓冲条件之间。     

Prediction of magnetite segregation in dense medium cyclone using computational fluid dynamics technique

Multi-phase simulations of turbulent driven flow in a dense medium cyclone with magnetite medium have been conducted in Fluent, using the Algebraic Slip Mixture model to model the dispersed phases and the air-core, and both the Large Eddy Simulation turbulence model (LES) and Reynolds Stress Models (RSM) for turbulence closure. The predicted air-core shape and diameter were found to be close to the experimental results measured by gamma ray tomography. It is possible to use the LES turbulence model with ASM multi-phase model to predict the air/slurry interface accurately. Multi-phase simulations (air/water/medium) show appropriate medium segregation effects but over-predict the level of segregation compared to that measured by gamma ray tomography near the wall. This is believed to be because of unaccounted back-mixing of the dispersed phase due to turbulence in the basic Algebraic Slip Mixture model. The predictions of accurate axial segregation of magnetite medium are investigated using the LES turbulence model in conjunction with the multi-phase mixture model and viscosity corrections according to the feed particle loading factor. At higher feed densities the agreement between the Dunglison [Dunglison, M.E., 1999, A general model of the dense medium cylone, PhD thesis, JKMRC, University of Queensland] correlations and experimental measurements and the CFD is reasonably good, but the overflow density is lower than the model predictions. It is believed that the excessive underflow volumetric flow rates are responsible for under prediction of the overflow density. The effect of size distribution of the magnetite has been fully studied. As expected, the ultra-fine magnetite sizes (i.e. 2 and 7 microns) are distributed uniformly throughout the cyclone. As the size of magnetite increases, more segregation of magnetite occurs close to the wall.