Comparison of 13CO line and far-infrared continuum emission as a diagnostic of dust and molecular gas physical conditions – I. Motivation and modelling

Determining temperatures in molecular clouds from ratios of CO rotational lines or from ratios of continuum emission in different wavelength bands suffers from reduced temperature sensitivity in the high-temperature limit. In theory, the ratio of far-infrared (FIR), submillimetre or millimetre continuum to that of a ¹³CO (or C¹⁸O) rotational line can place reliable upper limits on the temperature of the dust and molecular gas. Consequently, FIR continuum data from the COBE /Diffuse Infrared Background Experiment (DIRBE) instrument and Nagoya 4-m  ¹³CO  J = 1 → 0  spectral line data were used to plot  240 μm/¹³CO  J = 1 → 0  intensity ratios against 140/240 μm dust colour temperatures, allowing us to constrain the multiparsec-scale physical conditions in the Orion A and B molecular clouds.
The best-fitting models to the Orion clouds consist of two components: a component near the surface of the clouds that is heated primarily by a very large scale (i.e. ∼1 kpc) interstellar radiation field and a component deeper within the clouds. The former has a fixed temperature and the latter has a range of temperatures that vary from one sightline to another. The models require a dust–gas temperature difference of 0 ± 2 K and suggest that 40–50 per cent of the Orion clouds are in the form of dust and gas with temperatures between 3 and 10 K. The implications are discussed in detail in later papers and include stronger dust–gas thermal coupling and higher Galactic-scale molecular gas temperatures than are usually accepted, and an improved explanation for the N (H₂)/ I (CO) conversion factor. It is emphasized that these results are preliminary and require confirmation by independent observations and methods.     

Experimental investigation and application of garnet granulite equilibria

Two mineralogic geobarometers based on the assemblages olivine-plagioclase-garnet and orthopyroxeneplagioclase-garnet-quartz have been calibrated from the reaction (1) fayalite+anorthite?garnet (Gr₁Alm₂). The reaction boundary has been determined to within 0.2 kbar using piston-cylinder apparatus. It is located at 4.7, 5.1, 5.5, 5.8, 6.2, 6.6, and 7.0 kbar at 750, 800, 850, 900, 950, 1,000, and 1,050° C, respectively. Summation of ΔG for reaction (1) and fayalite +quartz?ferrosilite locates to within 0.3 kbar the following model garnet-forming reaction for quartz-saturated granulites: (2) ferrosilite+ anorthite?garnet(Gr₁ Alm₂) + quartz. Geobarometers based on (1) and (2) are widely applicable in granulite terranes and yield precise pressures that are in agreement with other well-calibrated barometers. Pressures of 7–10 kbar are inferred for many granulite terranes requiring the widespread development of 60–70 km thick continental crust by mid-Proterozoic.     

Tube-like schlieren structures in the Fürstenstein Intrusive Complex (Bavarian Forest,Germany): Evidence for melt segregation and magma flow at intraplutonic contacts

Tube-like schlieren structures occur at the boundary between two units of the Fürstenstein Intrusive Complex, the Tittling and the Saldenburg granites. We have analysed the magnetic fabrics, petrographic variation and geochemistry of key examples of these structures in order to test the hypothesis that they originated as granitic microdiapirs. The rims of the schlieren structures have high magnetic susceptibility compared to their interiors and surrounding granite due to the enrichment of biotite ± opaques. The low anisotropy that characterizes the AMS fabric is probably caused by magmatic flow. Hypersolidus microfabrics support this interpretation. Magnetic fabric orientation within the schlieren structures differs significantly from the NE–SW-trending magnetic foliation generally observed within the hosting Tittling granite. A steeply plunging magnetic lineation and a NNE–SSW girdle distribution of the magnetic foliation poles within the schlieren structures are consistent with the conical geometry of the schlieren structures evolved during the rise of the magma. Based on geochemistry, granite in the schlieren structures is interpreted to be differentiated melt expelled from the Tittling granite mush that formed after early crystallization of plagioclase. We suggest that the schlieren structures are pockets of residual melt of the Tittling granite that were mobilized buoyantly due to a thermal input from the neighbouring Saldenburg granite. The mafic rims of the schlieren structures formed as a result of early crystallization and subsequent accumulation due of the Bagnold effect. The results of the magnetic and geochemical investigations allow us to interpret the schlieren structures as diapiric in nature and consequently as “within-chamber diapirs” (sensu Weinberg et al., 2001).     

Continental rift-setting and evolution of Neoproterozoic Sindreth Basin in NW-India

The Neoproterozoic Sindreth Basin, NW India, and its surrounding area represent a half graben structure situated between the undeformed Malani Igneous Suite (MIS) in the west and a corridor of coeval Cryogenian ductile deformation, anatexis and granite intrusion in the east. The main lithologies observed in the basin are conglomerate, fanglomerate, debris flow and lake deposits derived from a nearby continental provenance, intercalated with concurrent mafic and felsic lava flows. Based on geological traverses across the strike of the basin, we propose a three-fold classification comprising Lower Clastic Unit and an Upper Clastic Unit and a Bimodal (basalt–rhyolite) Volcanic Unit separating the two. Tilting due to basin inversion and faulting has been observed; however, the rocks are unmetamorphosed and show undisturbed primary sedimentary features. The stratigraphic record of the basin is characteristic for deposition and magmatism in a fault-related continental setting. Implications of the findings have been discussed in the context of Neoproterozoic crustal dynamics in NW India. This study provides conclusive evidence for a continental setting for Sindreth Basin evolution and contests the recent models of active subduction setting (either back-arc basin or accretionary sediments over a subduction zone).     

Reflections Upon the State of Asian Tourism

This paper addresses the implications of the Asian economic crisis for tourism. The nature of the crisis is discussed briefly and its occurrence at a time of previously rapid regional growth in tourism is pointed out. It is argued that effective demand diminished at a time when supply was increasing. In the short term, reductions in regional travel and spending have been widespread and not confined to Southeast Asia. In the longer term, reduced real prices will make Asian destinations highly competitive in long-haul markets provided that the quality of products is maintained. The crisis emphasises the need to examine tourism planning initiatives, to acknowledge that the tourism product consists of more than the provision of quality accommodation, and to give greater attention to product differentiation.     

Modelling of the thermal dependence of structural and elastic properties of calcite, CaCO3

A computational method, based on the quasiharmonic approximation, has been computer-coded to calculate the temperature dependence of elastic constants and structural features of crystals. The model is applied to calcite, CaCO₃; an interatomic potential based on a C-O Morse function and Ca-O and O-O Borntype interactions, including a shell model for O, has been used. Equilibrations in the range 300–800 K reproduce the experimental unit-cell edges and bond lengths within 1%. The simulated thermal expansion coefficients are 22.3 (//c) and 2.6 (⊥ c), against 25.5 and-3.7×10^?6K^?1 experimental values, respectively. The thermal coefficients of elastic constants tend to be underestimated; for the bulk modulus, -2.3 against-3.7×10^?4K^?1 is obtained.     

CLIMATE CHANGE AND THE BATHURST CARIBOU HERD IN THE NORTHWEST TERRITORIES, CANADA

The Bathurst barren-ground caribou herd was chosen as the focus of a study of the possible effects of a changed climate on hunting of a caribou herd in the Northwest Territories. Four climate change scenarios representing conditions under a doubling of atmospheric carbon dioxide concentrations were used in the study. The locations of the Bathurst herd throughout the year were determined, and the 1951 to 1980 average monthly temperatures and total monthly precipitation amounts were ascertained at those locations. The four climate change scenarios were applied, with changes in average monthly temperatures and in total monthly precipitation amounts noted. Analyses indicate a possible increase in winter snowfall, and increased insect harassment of caribou in the summer, due to an increase in average monthly temperatures. The reduced accessibility and health of caribou in the Bathurst herd suggest a reduced hunting potential. Management options are briefly discussed.     

The Use of Field Dependence of Magnetic Susceptibility for Monitoring Variations in Titanomagnetite Composition - A Case Study on Basanites from the Vogelsberg 1996 Drillhole,Germany

In high Ti basanites from the Vogelsberg 1996 drillhole distinct variations in the field dependence of AC magnetic susceptibility correlate with compositional variations of titanomagnetite, as determined by temperature dependence of magnetic susceptibility. Curie temperatures for the basanites are in the range of 240 to 525°C. The field dependence reaches up to 20% for measurements in 30 A/m and 300 A/m AC field amplitude. It is demonstrated that two-field magnetic susceptibility measurements can prevail information about compositional changes of titanomagnetite and therefore support the interpretation of magnetic susceptibility logs from drillcores of basaltic rock suites.     

Rapid urbanization in a transitional economy in China: The case of Hainan Island

The outcomes and forms of urbanization and modernization in China following the reform and opening of the late 1970s have attracted extensive attention and competing interpretations in scholarly documentation. This paper focuses on Hainan Island, established in 1988 as the biggest special economic zone in China. Since then, considerable inflows of human as well as speculative capital have led to rapid real estate, in particular tourism-related, development. While urban expansion and improvements have been encouraged, the ongoing over-building, unregulated conversion of land use and degradation of the urban environment present serious social and economic problems. This paper summarizes the trajectory, causal factors and outcomes of this urban growth and consequent planning problems that make the island an atypical case in China's urbanization experience. We argue that the establishment of a practical framework combining socioeconomic planning, land use planning, and the management of both, is crucial to achieve sustainable growth for this transitional economy.     

Interactive analysis of the spatial distribution of disease using a geographic information systems

Geographic information systems (GIS) provide a variety of tools for the manipulation and display of public health data. Few, however, enable users to interactively evaluate hypotheses on spatial trends in disease risk that may be suggested by maps of measures of disease impact. We addressed this limitation by developing a seamless interface between a commercial GIS and a suite of spatial analysis algorithms. Users of the system can utilize the GIS's capability to interactively select and manipulate geographically referenced data and, through a series of pull-down menus, apply a variety of exploratory analysis methods to this information. In the presented application, we illustrate this capability by including algorithms for the reduction of random noise in observed incidence rates, for the detection of unusual aggregations of disease events, and for the statistical evaluation of inferences drawn from spatial trends. We demonstrate this application by examining lung cancer mortality in the state of Ohio. Received: 22 September 1999 / Accepted: 8 March 2000