On Krugman's model of economic geography

This essay evaluates the evolution of Paul Krugman's ideas about economic geography between 1989 and 1996, focusing on the scope and intention of his work. While Krugman's geographical writings have acknowledged diverse research traditions, he has increasingly focused his efforts on formal spatial models that embody the methods of mainstream economic modeling. This emphasis reflects Krugman's view that formal modeling holds the most promise for understanding spatial aspects of urbanization. Krugman's interventions into economic geography have in turn allowed him to develop and articulate his own view of the future of social science: that is, the explanation of self-organizing behaviour should be the focal point of research, and formal modelling is the key means of advancing this agenda.     

Influence of a spatial structure of precipitates on polarization characteristics of the outgoing microwave radiation of the atmosphere

Issues of the formation and recording of the spatial and angular distributions of thermal radio radiation of rainfall in the microwave range are discussed. The thermal radio-frequency radiative transfer in a threedimensional rain cell is simulated numerically with a different rainfall rate, taking into account the nonspherical shape of falling raindrops and their size distribution. The role of the three-dimensional inhomogeneity of rainfall fields in the formation of a field of their inherent thermal radio radiation in the microwave range is revealed.     

Macrobenthos relative to the oxygen minimum zone on the East Indian margin,Bay of Bengal

The Bay of Bengal remains one of the least studied of the world's oxygen minimum zones (OMZs). Here we offer a detailed investigation of the macrobenthos relative to oxygen minimum zone [OMZ – DO (dissolved oxygen), concentration <0.5 ml·1^?1] at 110 stations off the North East Indian margin (16⁰ and 20⁰ N) featuring coastal, shelf and slope settings (10–1004 m). Macrobenthos (>0.5 mm) composition, abundance and diversity were studied in relation to variations in depth, dissolved oxygen, sediment texture and organic carbon. Using multivariate procedures powered by SIMPROF analysis we identified distinct OMZ core sites (depth 150–280 m; DO 0.37 ml·1^?1) that exhibited dense populations of surface‐feeding polychaetes (mean 2188 ind. m^?2) represented by spionids and cossurids (96%). Molluscs and crustaceans were poorly represented except for ampeliscid amphipods. The lower OMZ sites (DO > 0.55 ml·l^?1) supported a different assemblage of polychaetes (cirratulids, amphinomids, eunicids, orbinids, paraonids), crustaceans and molluscs, albeit with low population densities (mean 343 ind. m^?2). Species richness [E(S₁₀₀)], diversity (Margalef d; H’) and evenness (J’) were lower and dominance was higher within the OMZ core region. Multiple regression analysis showed that a combination of sand, clay, organic carbon, and dissolved oxygen explained 62–78% of the observed variance in macrobenthos species richness and diversity: E(S₁₀₀) and H’. For polychaetes, clay and oxygen proved important. At low oxygen sites (DO <1 ml·l^?1), depth accounted for most variance. Residual analysis (after removing depth effects) revealed that dissolved oxygen and sediment organic matter influenced 50–62% of residual variation in E(S₁₀₀), H’ and d for total macrofauna. Of this, oxygen alone influenced up to ~50–62%. When only polychaetes were evaluated, oxygen and organic matter explained up to 58–63%. For low oxygen sites, organic matter alone had the explanatory power when dominance among polychaetes was considered. Overall, macrobenthic patterns in the Bay of Bengal were consistent with those reported for other upwelling margins. However, the compression of faunal gradients at shallower depths was most similar to the Chile/Peru margin, and different from the Arabian Sea, where the depth range of the OMZ is two times greater. The Bay of Bengal patterns may take on added significance as OMZs shoal globally.     

Perceptions of climate engineering in the South Pacific,Sub-Saharan Africa,and North American Arctic

Nearly all research on public perceptions of climate engineering has been conducted in wealthy, developed countries. However, understanding perspectives from vulnerable populations is critical to inclusive, democratic debate on both research and governance. This study utilized in-depth interviews to explore the perspectives of vulnerable populations in the South Pacific, Sub-Saharan Africa, and the North American Arctic. Interviewees in this study were desperate for solutions to climate change and therefore willing to consider climate engineering. However, their willingness to consider climate engineering could be characterized as both deeply reluctant and highly conditional. Interviewees expressed a number of concerns about potential social and political implications of engineering the climate. They also described conditions that may need to be met to ensure that future climates (engineered or otherwise) are more equitable.     

Prediction of SST anomalies of east Pacific Ocean (Nino 3 region) using a statistical model

Summary  Average SST anomalies of OCT-DEC months for Nino-3 region are predicted using the following parameters – (i) April rain over Himachal Pradesh, (ii) Darwin pressure change (January–April), (iii) Southern Oscillation Index (Tahiti–Darwin) and (iv) SST anomalies of Nino-3 region in the month of May. Principal component analysis is used to orthogonalise the predictors before using them in the regression equation. The first two principal components, which explain nearly 73% of the variance, are used to fit a regression line. The period 1951–1985 is used as the calibration period for the model and the period 1986–1997 as the verification period for the forecast. The Brier score with respect to a reference forecast (persistence) for the independent period is found to be 0.82 which is indicative of good forecast skill. Received April 1, 1999 Revised January 17, 2000     

Calcium carbonate dissolution in deep sea sediments: reconciling microelectrode, pore water and benthic flux chamber results

We report the benthic fluxes of O₂, titration alkalinity (TA), Ca²⁺, NO₃⁻, PO₄³⁻, and Si(OH)₄ from in situ benthic flux chamber incubations on the Ceara Rise and Cape Verde Plateau and compare them to previously published results. We find within analytical uncertainty that the TA flux is twice the calcium flux, suggesting that dissolution/precipitation of CaCO₃ is the principal mechanism controlling benthic TA and Ca²⁺ fluxes. At sites where the sediments contain significant (>35%) CaCO₃ and the overlying waters are supersaturated with respect to CaCO₃, the ratios of the total dissolution rate to the remineralization rate are significantly less than at all other study sites. We propose that these observations can be explained by precipitation of fresh CaCO₃ at the supersaturated sediment surface followed by redissolution deeper in the sediments because of metabolically-produced CO₂. A numerical simulation is presented to demonstrate the feasibility of this explanation. In addition, surface exchange reactions in high-CaCO₃ sediments coupled with high rates of particle mixing may also impact rates of metabolic dissolution and depress chamber-derived estimates of carbonate alkalinity and calcium benthic fluxes. These results suggest that at supersaturated, high CaCO₃ locations, previous models of sediment diagenesis may have overestimated the impact of metabolic dissolution on the preservation of CaCO₃ deposited on the sea floor.     

Geological structure of the Ubinka River valley (Northwestern Caucasus)

A thick olistostrome strata of late Paleocene-early Eocene age is outlined in the northern flank of the Northwestern Caucasus folded structure in the Ubinka river valley, which shows the significant role of earlier Cenozoic tectonic movements in forming the alpine structure of the region. The largest part of the strata is composed of dark weakly calcareous clays, which were earlier recognized as Lower Cretaceous deposits. Olistoliths and large olistoplaques are mostly of light calcareous rocks in which microfauna of Cenomanian and Maastrichtian ages were discovered in dark clays. A poor series of foraminifers was recognized in the dark clays hosting these olistoliths; this series do not enable one to determine with certainty the age of the strata (of approximately the late Paleocene-early Eocene). Small structural forms were recognized in olistoliths and olistoplaques, which are not traced in the matrix, this indicates that a series of folded and fissured structures were formed before these olistoliths and olistoplaques appeared in the olistostrome strata.     

Geochemistry of the volcanoplutonic association of the Shaw massif (East Antarctica): Composition,genesis, and geodynamic interpretation

This paper reports the first petrological and geochemical evidence for the Meso-Neoproterozoic metamorphic and metaintrusive rocks of the Shaw Mountain massif (Prince Charles Mountains, East Antarctica). It was shown that the orthogneisses (plagiogneisses) and metabasites of the massif were formed as constituents of a volcanoplutonic complex, which included a variety of igneous rocks of normal and subalkaline groups, from ultrabasic to silicic and was assigned to the volcanic tholeiite basalt-andesite-rhyolite, plutonic peridotite-gabbro, and late (?) calc-alkaline gabbro-diorite-plagiogranite associations. The distribution of major and compatible trace elements indicates the fractionation of the primary melts that produced the volcanoplutonic association of the Shaw massif. With respect to the distribution of REE and trace elements and some trace element ratios, the metabasic rocks of the Shaw massif correspond mainly to enriched and normal basalts of mid-ocean ridges, continental rifts, and ocean islands, which suggests a contribution from a plume mantle source. It was found that the region of the Shaw massif is a high-grade metamorphosed margin of the Fisher volcanoplutonic complex, a Mesoproterozoic structure of single geodynamic nature. This is supported by the spatial proximity of the Shaw and Fisher regions, the similar behaviors of most major elements and distribution patterns of trace elements and REE in comparable magmatic associations, and the similar ages of some plutonic associations. Based on the petrological and geochemical data, an alternative geotectonic model was proposed for this region. According to this model, the Fisher complex was formed in a setting of continental rifting coupled with the processes of mantle diapirism, which was subsequently changed by the compression stage. During rifting, the structure could experience significant opening accompanied by ultrabasic-basic tholeiitic magmatism with a significant contribution of mantle material. A subsequent inversion resulted in that the rift structure underwent considerable horizontal compression accompanied by calc-alkaline magmatism and the formation of narrow intracratonic fold zones. The cyclic character of rifting processes and superposition of young rift systems on older ones was also established in the Phanerozoic geotectonic history of the region of the Prince Charles Mountains.     

Quantifying fracture geometry with X-ray tomography: Technique of Iterative Local Thresholding (TILT) for 3D image segmentation

This paper presents a new method—the Technique of Iterative Local Thresholding (TILT)—for processing 3D X-ray computed tomography (xCT) images for visualization and quantification of rock fractures. The TILT method includes the following advancements. First, custom masks are generated by a fracture-dilation procedure, which significantly amplifies the fracture signal on the intensity histogram used for local thresholding. Second, TILT is particularly well suited for fracture characterization in granular rocks because the multi-scale Hessian fracture (MHF) filter has been incorporated to distinguish fractures from pores in the rock matrix. Third, TILT wraps the thresholding and fracture isolation steps in an optimized iterative routine for binary segmentation, minimizing human intervention and enabling automated processing of large 3D datasets. As an illustrative example, we applied TILT to 3D xCT images of reacted and unreacted fractured limestone cores. Other segmentation methods were also applied to provide insights regarding variability in image processing. The results show that TILT significantly enhanced separability of grayscale intensities, outperformed the other methods in automation, and was successful in isolating fractures from the porous rock matrix. Because the other methods are more likely to misclassify fracture edges as void and/or have limited capacity in distinguishing fractures from pores, those methods estimated larger fracture volumes (up to 80 %), surface areas (up to 60 %), and roughness (up to a factor of 2). These differences in fracture geometry would lead to significant disparities in hydraulic permeability predictions, as determined by 2D flow simulations.