A comparative study of Brans-Dicke and general relativistic cosmologies in terms of observationally measurable quantities

A comparison between general relativistic and Brans-Dicke cosmologies is made in terms of quantities measurable by an observational astronomer. Numerical integration of the Brans-Dicke field equations was employed to find the relationships of the mean density of cosmic matter, the age, and the time derivative of the gravitational constant to the Hubble constant and deceleration parameter. The difference between general relativistic and Brans-Dicke apparent magnitude-redshift diagrams was found to be negligible even at large redshifts under the assumption of no galactic evolution in absolute magnitude.     

Source and tectonic implications of tonalite-trondhjemite magmatism in the Klamath Mountains

 In the Klamath Mountains, voluminous tonalite-trondhjemite magmatism was characteristic of a short period of time from about 144 to 136 Ma (Early Cretaceous). It occurred about 5 to 10 m.y. after the ∼165 to 159 Ma Josephine ophiolite was thrust beneath older parts of the province during the Nevadan orogeny (thrusting from ∼155 to 148 Ma). The magmatism also corresponds to a period of slow or no subduction. Most of the plutons crop out in the south-central Klamath Mountains in California, but one occurs in Oregon at the northern end of the province. Compositionally extended members of the suite consist of precursor gabbroic to dioritic rocks followed by later, more voluminous tonalitic and trondhjemitic intrusions. Most plutons consist almost entirely of tonalite and trondhjemite. Poorly-defined concentric zoning is common. Tonalitic rocks are typically of the low-Al type but trondhjemites are generally of the high-Al type, even those that occur in the same pluton as low-Al tonalite. The suite is characterized by low abundances of K₂O, Rb, Zr, and heavy rare earth elements. Sr contents are generally moderate (∼450 ppm) by comparison with Sr-rich arc lavas interpreted to be slab melts (up to 2000 ppm). Initial ⁸⁷Sr/⁸⁶Sr, δ ¹⁸O, and ɛ _Nd are typical of mantle-derived magmas or of crustally-derived magmas with a metabasic source. Compositional variation within plutons can be modeled by variable degrees of partial melting of a heterogeneous metabasaltic source (transitional mid-ocean ridge to island arc basalt), but not by fractional crystallyzation of a basaltic parent. Melting models require a residual assemblage of clinopyroxene+garnet±plagioclase±amphibole; residual plagioclase suggests a deep crustal origin rather than melting of a subducted slab. Such models are consistent with the metabasic part of the Josephine ophiolite as the source. Because the Josephine ophiolite was at low T during Nevadan thrusting, an external heat source was probably necessary to achieve significant degrees of melting; heat was probably extracted from mantle-derived basaltic melts, which were parental to the mafic precursors of the tonalite-trondhjemite suite. Thus, under appropriate tectonic and thermal conditions, heterogeneous mafic crustal rocks can melt to form both low- and high-Al tonalitic and trondhjemitic magmas; slab melting is not necessary. Received: 1 September 1994 / Accepted: 28 August 1995     

Relocating resource peripheries to the core of economic geography's theorizing: rationale and agenda

Theorizing in economic geography has focused on core regions, industrial and non-industrial, old and new. Indeed, contemplation of the idea of globalization has reinforced this quest. This paper disputes this blinkered thinking that peripheralizes resource peripheries, and seeks to re-position and emphasize resource peripheries within economic geography's theoretical agenda, specifically that associated with the new 'institutional' approach. A truly 'global' economic geography cannot afford to ignore resource peripheries. In particular, we argue that characterizing resource peripheries, and making them distinct from cores, is the intersection of four sets of institutional values or dimensions which we summarize in terms of industrialism (economic dimension), environmentalism (environmental dimension), aboriginalism (cultural dimension) and imperialism (geopolitical dimension). This admittedly preliminary framework underlies our hypothesis that resource peripheries around the world have become deeply contested spaces, much more so than those found in cores.     

Modelling Access with GIS in Urban Systems (MAGUS): capturing the experiences of wheelchair users

Access and mobility are important dimensions of quality of life. For wheelchair users, everyday trips are often fraught with problems, with many barriers imperceptible to the able-bodied, hindering or totally restricting movement. This paper describes a project undertaken with wheelchair users, which has developed, tested and applied a Geographic Information System model. This model acts both as a navigational device for wheelchairs users – enabling them to make informed route choices through urban places – and as a decision support and planning tool for urban planners – making visible the ways in which built environments are often distorted and hostile spaces for wheelchair users.     

The new X-ray universe

Phil Charles and Andy Fabian review the changes brought to X-ray astronomy by the two orbiting observatories, XMM-Newton and Chandra.
We describe here the changes to X-ray astronomy that are being brought about by the two new orbiting X-ray observatories, NASA's Chandra and ESA's XMM-Newton. Between them they bring a dramatic gain in sensitivity, spatial resolution (now comparable to ground-based optical and infrared telescopes) and spectral resolution. The superb Chandra mirrors rapidly resolved the diffuse X-ray background and have produced stunning detailed images of a wide variety of cosmic objects. Large gains have been made by both missions in spectroscopic performance, with individual X-ray emission lines now detectable in hot stellar coronae, supernova remnants, X-ray binaries, active galactic nuclei and galaxy clusters.     

Frontal accretion and thrust wedge evolution under very oblique plate convergence: Fiordland Basin, New Zealand

A thrust wedge with unusual geometry has developed under very oblique (50–60°) convergence between the Pacific and Australian Plates, along the 240‐km length of the Fiordland margin, New Zealand. The narrow (25 km‐wide) wedge comprises three overlapping components, lying west of the offshore section of the Alpine Fault, and straddles a change of > 30° in the regional strike of the plate boundary. Swath bathymetry, marine seismic reflection profiles, and dated samples together reveal the stratigraphy, structure, and evolution of the wedge and the underthrusting, continental, Caswell High (Australian Plate). Lateral variations in the composition and structure of the accretionary wedge, and the depth of the décollement thrust, result partly from variations in crustal structure and basement relief of the underthrust plate, and from associated variations in the thickness of turbidites available for frontal accretion. In the southern Fiordland Basin the underthrust plate is undergoing flexural uplift and extension, and a thick turbidite section is available for accretion. Along‐strike, a structurally elevated portion of the underthrust plate is very obliquely colliding with the central part of the accretionary wedge, the turbidite section available for accretion is condensed, and structural inversion occurs in the underthrust plate. Growth of the thrust wedge is inferred to have commenced in the Pliocene prior to 3 ± 1 Ma, but much of the wedge developed in the Quaternary. The spatial distribution of thrusting has varied through time, with most late Quaternary shortening occurring on structures within 10 km of the right‐stepping deformation front. Estimates of the magnitude and rates of deformation indicate that the wedge accommodates a significant component of the oblique convergence between the Pacific and Australian Plates. Shortening of up to 7.3 ± 1.4 km and 9.1 ± 1.8 km within the southern and central parts of the wedge, respectively, represent about 5–15% of the total 70–140 km of shortening predicted across the plate boundary since 6.4 Ma, and about 10–30% since 3 Ma. Late Quaternary shortening rates of the order of 1–5 mm yr^?1, estimated across both the northern and southern parts of the wedge, represent about 10–50 and 5–21% of the total NUVEL‐1 A shortening across the plate boundary at these respective latitudes, implying that most shortening is occurring onshore. Furthermore, possible oblique‐slip thrusting within the wedge may be accommodating boundary‐parallel displacement of 0–6 mm yr^?1, representing 0–17% of the total predicted within the plate boundary.     

Adding bounds to kriging

The ordinary kriging interpolation algorithm is extended by the inclusion of explicit lower and upper bounds on the estimate. The associated estimation variance is written as the ordinary kriging variance plus a non-negative correction term.