Consequences of deviatoric normality in plasticity with isotropic strain hardening

For many soils experimental evidence suggests that deviation from normality between the plastic strain increments and the yield function is exhibited mainly in the volumetric behaviour, whereas the deviatoric behaviour exhibits normality. An analysis of the consequence of this observation is presented, and it leads to an expression for the plastic potential function as composed of two functions, a yield function and another dependent only on the hydrostatic pressure; the latter is considered to constitute the concept of correction functions presented recently by Desai and Siriwardane¹³.     

Remineralization Ratios in the Subtropical North Pacific Gyre

Based on a new mixing model of two end-members, the water column remineralization ratios of P/N/C_org - O₂ = 1/13 ± 1/135 ± 18/170 ± 9 are obtained for the Hawaii Ocean Time-series (HOT) data set at station ALOHA. The traditional Redfield ratios of P/N/C_org/–O₂ = 1/16/106/138 have standard deviations of more than 50%, when they are based on the average composition of phytoplankton. Apparently, the remineralization processes in the water column have smoothed out the observed large variability of plankton compositions. A new molar formula for the remineralized plankton may be written as ₁₃₅H₂₈₀O₁₀₅N₁₃P or C₂₅(CH₂O)₁₀₁(CH₄)₉(NH₃)₁₃(H₃PO₄). Oxidation of this formula results inC₂₅(CH₂O)₁₀₁(CH₄)₉(NH₃)₁₃(H₃PO₄) + 170O₂ 135CO₂ + 132H₂O + 13NO₃ ^- + H₂PO₄ ^- + 14H⁺.For comparison, remineralization using Redfield's formula gives:(CH₂O)₁₀₆(NH₃)₁₆(H₃PO₄) + 138O₂ 106CO₂ + 122H₂O + 16NO₃ ^-+ H₂PO₄ ^- + 17H⁺     

Drastic shift in lava geochemistry in the volcanic-front to rear-arc region of the Southern Kamchatkan subduction zone: Evidence for the transition from slab surface dehydration to sediment melting

The shift of lava geochemistry between volcanic front to rear-arc volcanoes in active subduction zones is a widespread phenomenon. It is somehow linked to an increase of the slab surface depth of the subducting oceanic lithosphere and increasing thickness of the mantle wedge and new constraints for its causes may improve our understanding of magma generation and element recycling in subduction zones in general. As a case study, this paper focuses on the geochemical composition of lavas from two adjacent volcanic centres from the volcanic front (VF) to rear-arc (RA) transition of the Southern Kamchatkan subduction zone, with the aim to examine whether the shift in lava geochemistry is associated with processes in the mantle wedge or in the subducted oceanic lithosphere or both. The trace element and O-Sr-Nd-Hf-Pb (double-spike)-isotopic composition of the mafic Mutnovsky (VF) and Gorely (RA) lavas in conjunction with geochemical modelling provides constraints for the degree of partial melting in the mantle wedge and the nature of their slab components. Degrees of partial melting are inferred to be significantly higher beneath Mutnovsky (∼18%) than Gorely (∼10%). The Mutnovsky (VF) slab component is dominated by hydrous fluids, derived from subducted sediments and altered oceanic crust, eventually containing minor but variable amounts of sediment melts. The composition of the Gorely slab component strongly points to a hydrous silicate melt, most likely mainly stemming from subducted sediments, although additional fluid-contribution from the underlying altered oceanic crust (AOC) is likely. Moreover, the Hf-Nd-isotope data combined with geochemical modelling suggest progressive break-down of accessory zircon in the melting metasediments. Therefore, the drastic VF to RA shift in basalt chemistry mainly arises from the transition of the nature of the slab component (from hydrous fluid to melt) in conjunction with decreasing degrees of partial melting within ∼15 km across-arc. Finally, systematic variations of key inter-element with high-precision Pb-isotope ratios provide geochemical evidence for a pollution of the Mutnovsky mantle source with Gorely melt components but not vice versa, most likely resulting from trench-ward mantle wedge corner flow. We also present a geodynamic model integrating the location of the Mutnovsky and Gorely volcanic centres and their lava geochemistry with the recently proposed thermal structure of the southern Kamchatkan arc and constraints about phase equilibria in subducted sediments and AOC. Herein, the slab surface hosting the subducted sediments suffers a transition from dehydration to melting above a continuously dehydrating layer of AOC. Wider implications of this study are that an onset of (flush-) sediment melting may ultimately be the main trigger for the VF to RA transition of lava geochemistry in subduction zones.     

The Green Revolution re-assessed: Insider perspectives on agrarian change in Bulandshahr District, Western Uttar Pradesh, India

In spite of raising Asian per capita food production by 27% and making India food self-sufficient, the Green Revolution has received much criticism for its environmental and socio-economic impacts. Taking on board post-development critiques of ‘speaking for’ Third World ‘others’, this paper seeks to examine the Green Revolution from the points of view of people directly affected by it. Comparative, historically-informed research in three villages for which 1972 baseline data exist reveal that the Green Revolution has ensured, in the words of one marginal farmer that ‘nobody sleeps with an empty stomach nowadays’. Most villagers associate the Green Revolution with increases in living standards and weakening community-based wealth hierarchies. Nevertheless, socio-economic inequalities between certain Scheduled Castes and other villagers are still very apparent.     

Geobotanical and biogeochemical reconnaissance of the ultramafics of Central Iran

In Iran, ultramafic rocks cover substantial areas at many locations in the country. These rocks consist predominantly of peridotite which has been serpentinized to some degree. Anarak and Nain are two ultramafic areas in Central Iran comprising about 180 and 270 km², respectively, located in a coloured melange zone. There is little information available regarding the geobotany and biogeochemistry of these areas. They have a dry climate, with low rainfall and high temperatures in summer which encourages mostly annual and perennial herbaceous types of plants. In this paper, we report a reconnaissance study of these two ultramafic areas of Iran. Soil analysis of total elements indicates that typical concentrations of Ni, Cr, Co, Mn, Fe, Mg and Ca are about 1500, 300, 75, 800, 45.000 150.000 and 2000 μg g^− 1, respectively. During this study 176 plant species were collected, belonging to 29 families. The species diversity at Anarak is more than at Nain, possibly due to microclimatic differences and a greater precipitation. The number of plants endemic to ultramafic soils of these two areas is very low. The herb Cleome heratensis (Capparaceae) appears to be an indicator of ultramafics in Central Iran. Populations of this plant cover quite extensive areas during summer and autumn when there is no rainfall. Analysis of the dry matter of the leaves of all plants collected did not reveal any hyperaccumulator of nickel or any other ‘serpentine’ metals. The ultramafic endemic plant C. heratensis contained low concentrations of all metals and thus it possesses exclusion mechanisms to restrict excessive metal uptake. The Mg/Ca ratio for some plants collected is high—up to 4.9. This initial survey suggests that a more complete investigation of the ultramafic areas of Iran would be valuable.     

A Sociodemographic and Partisan Analysis of Voting in Three Anti-Gay Rights Referenda in Oregon

Since 1988, three separate anti-gay rights referenda have been placed on the ballot in the state of Oregon. While in 1988 Oregon voters passed the first measure (subsequently found unconstitutional), they rejected similar referenda in 1992 and 1994. This paper examines the electoral geography of these three referenda both cartographically and quantitatively. It finds patterns of support for the referenda were closely associated with voting patterns for the Republican Party in gubernatorial and presidential elections, and with sociodemographic indicators reflective of traditionalist areas.     

On the properties of strange modes

Properties of the so-called strange modes occurring in linear stability calculations of stellar models are discussed. The behaviour of these modes is compared for two different sets of stellar models, for very massive zero-age main-sequence stars and for luminous hydrogen-deficient stars, both with high luminosity-to-mass ratios. We have found that the peculiar behaviour of the frequencies of the strange modes with the change of a control parameter is caused by the pulsation amplitude of a particular eigenmode being strongly confined to the outer part of the envelope, around the density inversion zone. The frequency of a strange mode changes because the depth of the confinement zone changes with the control parameter. Weakly non-adiabatic strange modes tend to be overstable because the amplitude confinement quenches the effect of radiative damping. On the other hand, extremely non-adiabatic strange modes become overstable because the perturbation of radiation force (gradient of radiation pressure) provides a restoring force that can be out of phase with the density perturbation. We discuss this mechanism by using a plane-parallel two-zone model.     

Vertical migration ofcentropages typicus (copepoda) in Chesapeake Bay,with some thoughts on migration studies

Centropages typicus was collected at two hour intervals over a diel cycle at a station near the Chesapeake Bay mouth. The species migrated upward at dusk and downward at dawn. Neither light, temperature, salinity, nor density appeared to cue the migration. Attention is drawn to the need for information on the extent and regularity of migration by individual organisms, and how the lack of such information may lead to poor interpretations of migration data.