Social Mix and the `Balanced Community' in British housing policy – a tale of two epochs

In Britain, concepts of `social mix' and the `balanced community' provide an example of how policy discourses have adapted to changing conceptions of the role of the state in public provision, forms of social division and inequality, and housing market transformations. The recent development of a policy agenda by the Labour government in Britain devised to promote more socially balanced neighbourhoods is not new, and its lineage may be traced back to the origins of housing and urban policy. However, the manner in which this objective has been framed and the intervention it has provoked have varied considerably over time. One is struck more by the episodic and discontinuous nature of the application of mix and balance in British policy than any sense of a coherent set of strategies pursued through changing times. This paper contrasts the place of social mix and balance in the discourses of the immediate post-war period in Britain with the renewed emphasis on such ideas in the policies of the New Labour government elected in 1997. In the first period, the claims of social mix were infused with the language of national reconstruction and the post-war settlement and the development of universal state provision. More recently, interest in social balance has arisen partly as a response to increased management difficulties and the process of `residualisation' in social housing and partly in response to new concepts of the underclass, social exclusion and social capital. The promotion of social mix and balance in contemporary policy has been shaped by notions of the underclass, social exclusion and the development of social capital in poorer communities. Policy intervention is overtly premised on the assumption that more mixed communities will promote more positive social interaction for residents, despite the lack of evidence for this claim. In practice, much of the discourse has now taken on a stronger sense of discipline and control in order to manage social housing estates. The meaning of social balance remains confused, however, and the achievement of this objective through policy intervention is likely to remain fraught with problems.     

Preservation of near-solar neon isotopic ratios in Icelandic basalts

Neon isotopic ratios measured in olivine and basaltic glass from Iceland are the most primitive observed so far in terrestrial mantle-derived samples. Ratios were measured in gas released from olivine and basaltic glass from a total of 10 samples from the Reykjanes Peninsula, Iceland, and one sample from central Iceland. The neon isotopic ratios include solar-like, mid-ocean ridge basalt (MORB)-like and atmospheric compositions. Neon isotopic ratios near the air–solar mixing line were obtained from the total gas released from glass separates from five samples. MORB-like neon isotopic compositions were measured in the total gas released from olivine and glass separates from four samples. Although there is clear evidence for a solar neon component in some of the Icelandic samples, there is no corresponding evidence for a solar helium ratio (320R_a>³He/⁴He>100R_a). Instead, ³He/⁴He ratios are mainly between 12±2(R_a) and 29±3(R_a), similar to the range observed in ocean island basalts, indicating that the He–Ne isotopic systematics are decoupled. The mantle source of Icelandic basalts is interpreted to be highly heterogeneous on a local scale to explain the range in observed helium and neon isotopic ratios. The identification of solar-like neon isotopic ratios in some Icelandic samples implies that solar neon trapped within the Earth has remained virtually unchanged over the past 4.5 Ga. Such preservation requires a source with a high [Ne_solar]/[U+Th] ratio so that the concentration of solar neon overwhelms the nucleogenic ²¹Ne* produced from the decay of U and Th in the mantle over time. High [Ne_solar]/[U+Th] ratios are unlikely to be preserved in the mantle if it has experienced substantial melting. An essentially undegassed primitive mantle component is postulated to be the host of the solar neon in the Icelandic plume source. Relatively small amounts of this primitive mantle component are likely to mix with more depleted and degassed mantle such that the primitive mantle composition is not evident in other isotopic systems (e.g. strontium and neodymium). The lower mantle plume source is inferred to be relatively heterogeneous owing to being more viscous and less well stirred than the upper mantle. This discovery of near-solar neon isotopic ratios suggests that relatively primitive mantle may be preserved in the Icelandic plume source.     

Millimetre-scale variation in metamorphic permeability of marbles during transient fluid flow: an example from the Reynolds Range, central Australia

Fluid inclusions from a biotite-garnet schist in the Southern Aravalli Mountain Belt (India) give information on both peak metamorphic conditions and post-peak metamorphic processes during uplift. A combination of careful petrography, microthermometry and Raman spectroscopy reveals the presence of at least five generations of enclosed fluids. Lower amphibolite-facies pressure-temperature conditions of the growth of garnet rims are reproduced by the highest fluid density of the relatively oldest inclusion type of CO₂ (±N₂)-rich compositions. A calculated fluid composition in the COH system, in equilibrium with the graphite buffer corresponds to a CO₂-rich fluid at metamorphic conditions. However, the results of these calculations are very sensitive to small fluctuations in oxygen fugacity and the accuracy of thermodynamic properties of mineral equilibria. Re-equilibration, conceived by specific size-density distribution and the absence of an aqueous phase in inclusions that contain nahcolite crystals, is monitored in these inclusions as post-peak metamorphic processes, like partial decrepitation and preferential leakage. The other fluid types represent heterogeneous fluid trapping of coexisting aqueous NaCl-bearing solutions with CO₂-CH₄-rich vapour bubbles in healed cracks, and probably the introduction of external fluids containing high salinity aqueous CaCl₂-rich solutions in nearly pure N₂ vapour bubbles, at lower P-T conditions. This study illustrates that fluid inclusions remain a valuable database of peak metamorphic conditions, moreover, alterations of the entrapped fluids and surrounding crystals are illustrative for specific exhumation evolutions. Received: 24 March 1999 / Accepted: 13 January 2000     

美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续)

(接第 1期第 1 6页 )3　富矿分带与控制因素贝茨金矿中不同矿石矿物组合和蚀变类型的分布与构造背景、围岩岩石及在矿体中的位置有关。根据形态、矿物组成和地质背景可分出几种空间形式截然不同的矿石类型 ,彼此之间由废石或低含金量的岩石所分隔。富矿体的地球化学、矿物学、地质及冶金方面的分带在三维空间上是连续的。富矿体的形状和定位与 Peters向斜构造的特征 ,沉积岩的岩石组成以及闪长岩接触带的几何形态和厚度有关 (图 6 A,B)。根据对不同的矿石类型和围岩类型的研究结果 ,对不同的富矿体进行了分类和判别。 Pe-ters( 1 996 ,1 9…     

The diversity of SCUBA-selected galaxies

We present extensive observations of a sample of distant, submillimetre (submm) galaxies detected in the field of the massive cluster lens Abell 1835, using the Submm Common-User Bolometer Array (SCUBA). Taken in conjunction with earlier observations of other submm-selected sources, we now have detailed, multiwavelength observations of seven examples of the submm population, having exploited the combination of achromatic amplification by cluster lenses and lavish archival data sets. These sources, all clearly at z ≳1, illustrate the wide range in the radio and optical properties of distant submm-selected galaxies. We include detailed observations of the first candidate 'pure' starburst submm galaxy at high redshift, a z =2.56 interacting galaxy which shows no obvious sign of hosting an AGN. The remaining sources have varying degrees of inferred AGN activity (three out of seven of the most luminous show some evidence of the presence of an AGN), although even when an AGN is obviously present it is still not apparent whether reprocessed radiation from this source dominates the submm emission. In contrast with the variation in the spectral properties, we see relatively homogeneous morphologies for the population, with a large fraction of merging or interacting systems. Our study shows that virtually identical spectral energy distributions are seen for galaxies that exhibit strikingly different optical/UV spectral-line characteristics. We conclude that standard optical/UV spectral classifications are misleading when applied to distant, highly obscured galaxies, and that we must seek other means of determining the various contributions to the overall energy budget of submm galaxies and hence to the far-infrared extragalactic background.     

Crystal‐bearing lunar spherules: Impact melting of the Moon's crust and implications for the origin of meteoritic chondrules

Abstract— Crystal‐bearing lunar spherules (CLSs) in lunar breccia (14313, 14315, 14318), soil (68001, 24105), and impact‐melt rock (62295) samples can be classified into two types: feldspathic and olivine‐rich. Feldspathic CLSs contain equant, tabular, or acicular plagioclase grains set in glass or a pyroxene‐olivine mesostasis; the less common olivine‐rich CLSs contain euhedral or skeletal olivine set in glass, or possess a barred‐olivine texture. Bulk‐chemical and mineral‐chemical data strongly suggest that feldspathic CLSs formed by impact melting of mixtures of ferroan anorthosite and Mg‐suite rocks that compose the feldspathic crust of the Moon. It is probable that olivine‐rich CLSs also formed by impact melting, but some appear to have been derived from distinctively magnesian lunar materials, atypical of the Moon's crust. Some CLSs contain reversely‐zoned “relic” plagioclase grains that were not entirely melted during CLS formation, thin (≤5 μm thick) rims of troilite or phosphate, and chemical gradients in glassy mesostases attributed to metasomatism in a volatile‐rich (Na‐K‐P‐rich) environment. Crystal‐bearing lunar spherules were rimmed and metasomatized prior to brecciation. Compound CLS objects are also present; these formed by low‐velocity collisions in an environment, probably an ejecta plume, that contained numerous melt droplets. Factors other than composition were responsible for producing the crystallinity of the CLSs. We agree with previous workers that relatively slow cooling rates and long ballistic travel times were critical features that enabled these impact‐melt droplets to partially or completely crystallize in free‐flight. Moreover, incomplete melting of precursor materials formed nucleation sites that aided subsequent crystallization. Clearly, CLSs do not resemble meteoritic chondrules in all ways. The two types of objects had different precursors and did not experience identical rimming processes, and vapor fractionation appears to have played a less important role in establishing the compositions of CLSs than of chondrules. However, the many detailed similarities between CLSs and chondrules indicate that it is more difficult to rule out an origin for some chondrules by impact melting than some have previously argued. Differences between CLSs, chondrules, and their host rocks possibly can be reconciled with an impact‐melt origin for some chondrules when different precursors, the higher gravity of the Moon compared to chondrite parent bodies, and the likely presence of nebular gas during chondrule formation are taken into account.     

Sea Surface Height Variability in the Indian Ocean from TOPEX/POSEIDON Altimetry and Model Simulations

Sea Surface Height (SSH) variability in the Indian Ocean during 1993-1995 is studied using TOPEX/POSEIDON (T/P) altimetry data. Strong interannual variability is seen in the surface circulation of the western Arabian Sea, especially in the Somali eddy structure. During the Southwest (SW) monsoon, a weak monsoon year is characterized by a single eddy system off Somalia, a strong or normal monsoon year by several energetic eddies. The Laccadive High (LH) and Laccadive Low (LL) systems off southwest India are observed in the altimetric SSH record. The variability of the East India Coastal Current (EICC), the western boundary current in the Bay of Bengal, is also detected. Evidence is found for the propagation of Kelvin and Rossby waves across the northern Indian Ocean; these are examined in the context of energy transfer to the western boundary currents, and associated eddies. A simple wind-driven isopycnal model having three active layers is implemented to simulate the seasonal changes of surface and subsurface circulation in the North Indian Ocean and to examine the response to different wind forcing. The wind forcing is derived from the ERS-1 scatterometer wind stress for the same period as the T/P altimeter data, enabling the model response in different (active/weak) monsoon conditions to be tested. The model output is derived in 10-day snapshots to match the time period of the T/P altimeter cycles. Complex Principal Component Analysis (CPCA) is applied to both altimetric and model SSH data. This confirms that long Rossby waves are excited by the remotely forced Kelvin waves off the southwest coast of India and contribute substantially to the variability of the seasonal circulation in the Arabian Sea.