A field test of a linear stability model for crescentic bars

A morphodynamical linear stability analysis is used to predict the natural development of crescentic bed patterns and rip channels. The purpose is to investigate whether this technique, which is useful for understanding the physics of emerging bed-forms, can be used to make quantitative predictions in the field, which may then be of use for coastal engineers.     

Agricultural land use dynamics in the Brazilian Amazon based on remote sensing and census data

The potential impact of deforestation in the Brazilian Amazon on greenhouse gas emissions to the atmosphere calls for policies that take account of changes in forest cover. Although much research has focused on the location and effects of deforestation, little is known about the distribution and reasons for the agricultural uses that replace forest cover. We used Landsat TM-based deforestation and agricultural census data to generate maps of the distribution and proportion of four major agricultural land uses throughout the Brazilian Amazon in 1997 and 2007. We built linear and spatial regression models to assess the determinant factors of deforestation and those major agricultural land uses - pasture, temporary agriculture and permanent agriculture - for the states of Pará, Rondônia, and Mato Grosso. The data include 30 determinant factors that were grouped into two years (1996 and 2006) and in four categories: accessibility to markets, public policies, agrarian structure, and environment. We found an overall expansion of the total agricultural area between 1997 and 2007, and notable differences between the states of Pará, Rondônia, and Mato Grosso in land use changes during this period. Regression models for deforestation and pasture indicated that determinant factors such as distance to roads were more influential in 1997 than in 2007. The number of settled families played an important role in the deforestation and pasture, the effect was stronger in 2007 than 1997. Indigenous lands were significant in preventing deforestation in high-pressure areas in 2007. For temporary and permanent agricultures, our results show that in 1997 the effect of small farms was stronger than in 2007. The mapped land use time series and the models explain empirically the effects of land use changes across the region over one decade.     

Seismicity, seismic input and site effects in the Sahel—Algiers region (North Algeria)

Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this Capital city, a realistic modelling of the seismic ground motion (SGM) is conducted by using the hybrid method that combines the finite differences method and the modal summation. For this purpose, a complete database of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone [2.25°E–3.50°E, 36.50°N–37.00°N] is performed and an earthquake list, for the period 1359–2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross sections have been built up to model the SGM in the city, caused by the 1989 Mont-Chenoua and the 1924 Douéra earthquakes. Synthetic seismograms and response spectral ratio is produced for Algiers, and they show that the soft sediments in Algiers centre are responsible of the noticed amplification of the SGM.     

Granitic plutonism as an indicator of microplates in the Palaeozoic of central and eastern Maine

Oxygen and strontium isotope ratios have been used to characterize source regions for granitic magmas for a transect across the northern Appalachian orogen in central and eastern Maine. The northwestern plutons (Katahdin and Seboeis) have δ¹⁸O values of 10.3–13.3 and initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7083 and 0.7066, respectively. The central plutons (Bottle Lake and Center Pond) have lower δ¹⁸O values (8.2–9.9) and initial ⁸⁷Sr/⁸⁶Sr ratios (0.7043–0.7055). The southeastern plutons (Lucerne and Deblois) have δ¹⁸O values (9.0–11.0) but initial ⁸⁷Sr/⁸⁶Sr ratios (0.7077 and 0.7041, respectively) which are intermediate between the northwestern and central plutons.Source models derived from these results and other petrological and geochemical data reflect the juxtaposition of discrete source regions by transcurrent faulting, which may be related to oblique plate motions. This model illustrates the importance of microplate accretion in the Palaeozoic history of the northern Appalachian orogen.     

An analytical solution for rainfall infiltration into an unsaturated infinite slope and its application to slope stability analysis

Surficial slope failures in residual soils are common in tropical and subtropical regions as a result of rainfall infiltration. This study develops an analytical solution for simulating rainfall infiltration into an infinite unsaturated soil slope. The analytical solution is based on the general partial differential equation for water flow through unsaturated soils. It can accept soil–water characteristic curve and unsaturated permeability function of the exponential form into account. Numerical simulations are conducted to verify the assumptions of the analytical solution and demonstrate that the proposed analytical solution is acceptable for the coarse soils with low air entry values. The pore‐water pressure (pwp) distributions obtained from the analytical solution can be incorporated into a limit equilibrium method to do infinite slope stability analysis for a rain‐induced shallow slip. The analysis method takes into account the influence of the water content change on unit weight and hence on factor of safety. A series of analytical parametric analyses have been performed using the developed model. The analyses indicate that when the residual soil slope, consisting of a completely decomposed granite layer underlain by a less permeable layer, is subjected to a continuous heavy rainfall, the loss of negative pwp and the reduction in factor of safety were found to be most significant for the shallow soil layer and during the first 12 h. The antecedent and subsequent rainfall intensity, depth of a less permeable layer and slope angle all have a significant influence on the pwp response and hence the slope stability. Copyright © 2012 John Wiley & Sons, Ltd.     

Zircon geochronology reveals polyphase magmatism and crustal anatexis in the Buchan Block,NE Scotland: Implications for the Grampian Orogeny

The type locality for high-temperature,low-pressure regional metamorphism,the Buchan Block in NE Scotland,exhibits profound differences to the rest of the Grampian Terrane.These differences have led some to regard the Buchan Block as an exotic crustal fragment comprising Precambrian basement gneisses and cover rocks thrust into their current position during Grampian orogenesis.Although rocks of the Buchan Block are now generally correlated with Dalradian strata elsewhere,the origin of the gneisses and the cause of the high heat flow and associated magmatism is debated.We report SIMS U-Pb and LA-ICPMS Hf isotopic data in zircon from high-grade rocks from the northeast(Inzie Head Gneiss)and northwest(Portsoy)corners of the Buchan Block.Around Inzie Head,upper amphibolite to granulite facies metasedimentary gneisses coexist with diorite sheets that were emplaced contemporaneously with partial melting of their host rocks,at least locally.U-Pb geochronology indicates a crystallisation age for the diorite of 486±9 Ma.Highly-deformed diorites within the Portsoy Gabbro have a crystallisation age of 493±8 Ma.Ages of ca.490 Ma for magmatism and high-grade metamorphism,which are broadly contemporaneous with ophiolite obduction and the onset of orogenesis,are significantly older than the established peak of Grampian metamorphism(ca.470 Ma).We propose a new model for the Grampian Orogeny involving punctuated tectonothermal activity due to tectonic switching during accretionary orogenesis.Rollback of a NW-dipping subduction zone at ca.490 Ma produced a back-arc environment(the Buchan Block)with associated arc magmatism and high dT/dP metamorphism.Arrival of an outboard arc resulted in shortening(the initial phase of the Grampian Orogeny)at ca.488 Ma.Rollback of a NW-dipping subduction zone to the SE of the ca.488 Ma suture began at 473 Ma and led to lithospheric-scale extension,decompression melting and advective heating of the middle crust,producing the widespread ca.470 Ma Grampian(classic Barrovian and Buchan)regional metamorphism.Resumed hinge advance and the final phase of shortening cut off the heat supply at ca.465 Ma,marking the end of the Grampian Orogeny.     

The partial molal volume of silicic acid in 0.725 m NaCl

The partial molal volume ($\text{V}\text{?}$) of silicic acid in 0.725 m NaCl at 20°C has been calculated from (1) direct volume changes due to the dissolution of anhydrous sodium silicate and (2) some literature values for the partial molal volumes of NaOH and water. , unconnected for electrostriction effects, was found to be 53 ± 2 ml mole^?1. , corrected for volume changes due to solvent electrostriction by charged Si species, was estimated to be in the range 58–62 ml mole^?1; this range is 7–11 ml mole^?1 greater than the calculated from Willey's (Mar. Chem. 2, 239–250, 1974) solubility data obtained from the dissolution, in seawater, of amorphous silica subjected to hydrostatic pressure. Our does, however, agree within experimental error with the calculated from Jones and Pytkowicz's (Bull. Soc. Roy. Sci. Liege 42, 118–120, 1973) data for the solubility of amorphous silica in seawater at high pressure and is nearly in agreement with Willey's (Ph.D. thesis, Dalhousie University, 1975) solubility data for amorphous silica in 0.6 m NaCl.     

World Cities in the Pacific Rim: A New Global Test of Regional Coherence

A new evaluation of the Pacific Rim concept is presented. The originality of this test for regional coherence is to be found in the basic units being analysed: cities instead of states. Based on a theoretical framework that identifies world city and world city network formation in terms of the office networks of advanced producer service firms, we use a principal components analysis to analyse a data set of 28 Pacific Rim cities and 46 global service firms. This identifies five main groupings of cities in terms of similar mixes of corporate service firms: a western Rim group; a group of ‘old Commonwealth’ cities; a market communist group of cities; Tokyo as a global city; and US cities as a specific separate group. These results confirm numerous earlier studies that were sceptical of the existence of a coherent Pacific Rim region. However, the particular approach adopted here allows us to identify the Pacific Rim generically as a particularly pernicious construct. We conclude that the Pacific Rim is a geographical chaotic conception.     

Development of two novel CYP-antibodies and their use in a PCB exposure experiment with Mytilus edulis

In an attempt to learn more about the cytochrome P450 (CYP) system of mussels, we used protein databases and alignment software to extract highly conserved CYP sequences. From these alignments synthetic peptides were produced and used for rabbit immunisation, which yielded polyclonal antibodies against the CYP families 2 and 4. The antibodies were evaluated with Western Blot and ELISA assays, using digestive gland microsomal samples from the mussel Mytilus edulis. Western Blots revealed immunoreactions for both antibodies. The anti-CYP2 sequence rendered one major immunopositive protein of approximately 49 kDa size, and weak signals for proteins of approximately 41 and 56 kDa size. The anti-CYP4 sequence rendered two major bands of approximately 56 and 59 kDa size, and also a weak immunoreaction with a protein of approximately 43 kDa size. ELISA rendered only weak signals even with a 1:50 dilution of IgG-purified serum. A 10-day exposure to Aroclor 1254 did not appear to affect any of the immunopositive proteins, while total PCBs in soft bodies increased from 14-40 ng/g DW in controls to 373-638 ng/g DW in exposed mussels.