Rare earth element geochemistry of Late Cenozoic alkaline lavas of the McMurdo Volcanic Group, Antarctica

Rare earth element (REE) concentrations were determined in 16 Ross Island and northern Victoria Land alkaline lava samples which were representative of four lava lineages of the McMurdo Volcanic Group, Antarctica. A kaersutite and two feldspar mineral separates were also analysed.

Two of the lava lineages, a basanite to nepheline benmoreite and a basanite to phonolite, have similar chondrite-normalized REE fractionation patterns, with a continuous enrichment of light and heavy REE and depletion of middle REE. The patterns result from the fractionation of olivine, clinopyroxene, spinels, feldspar, kaersutite and apatite. Kaersutite is an important fractionated phase responsible for the middle REE depletion.

Another of the lava lineages is mildly potassic with trachyandesite to peralkaline K-trachyte lavas which have partly overlapping REE fractionation patterns. There is a depletion in REE from tristanite to K-trachyte. Fractionation of olivine, clinopyroxene, feldspar and apatite probably control the REE chemistry of the lineage, greater degrees of apatite fractionation deplete the K-trachyte in REE relative to the tristanite. Feldspar fractionation in the genesis of the peralkaline K-trachyte is shown by a large negative Eu anomaly (Eu/Eu* = 0.10).

A nepheline hawaiite to anorthoclase phonolite lava lineage from the Erebus Centre shows enrichment of REE, although minor overlapping in the middle REE does occur. Anorthoclase phonolite has a positive Eu anomaly (Eu/Eu* = 1.31), indicating possible accumulation of anorthoclase. The lineage resulted from fractionation of olivine, clinopyroxene, magnetite and apatite.     

Individual and integrated pulse properties of PSR B0943+10 involved in the mode-changing phenomenon

The characteristics of the “burst” (B) mode and “quiescent” (Q) mode pulse sequences–long known from studies at or below 103 MHz–are identified at 430 MHz for the first time. An 18-minute, Polarimetrie observation begins with a long Bmode sequence, which has a higher average intensity, regular drifting subpulses, and a preponderance of primary polarisationmode radiation. An abrupt transition to a Q-mode sequence is then marked by a) weaker average intensity, but occasional very bright individual subpulses, b) a complete cessation of drifting subpulses, with disorganized subpulses now being emitted over a much wider longitude interval, and c) near parity between the primary and secondary polarisation modes, resulting in pronounced depolarisation, both of individual pulses and the average profile. Careful study, however, of profile changes before and after this mode change reveals slower variations which both anticipate the abrupt transition and respond to it. A slow attenuation of the intensity level of the dominant component is observed throughout the duration of the B-mode sequence, which then accelerates with the onset of the Q-mode sequence. This slow variation appears to represent a “preswitching transition” process; and the combination of effects on slow and abrupt time scales are finally responsible for the formation of the characteristic B and Q-mode average profiles.     

Contaminant exposure and effects in Baltic ringed and grey seals as assessed by biomarkers

The Baltic Sea ecosystem has suffered from a heavy pollutant load for more than three decades. Persistent organic pollutants (POPs) and heavy metals have been of most concern due to their persistence and toxic properties. Ringed seals (Phoca hispida baltica) and grey seals (Halichoerus grypus) living in the Baltic Sea have been suffering from pathological impairments, including reproductive disturbances, which have resulted in a depressed reproductive capacity. We investigated several biochemical parameters as potential biomarkers for exposure to and effects of the contaminant load in the Baltic seals. Seals from less polluted areas were used as reference material in terms of the pollution load. In both Baltic seal populations, the levels of some biochemical parameters diverged from those in the reference seals, and some of these showed a clear correlation with the individual contaminant load. Of the potential bioindicators, we propose cytochrome P4501A activity and vitamin E levels, in blubber or plasma, as exposure biomarkers for polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in both species. The arylhydrocarbon receptor-mediated chemical-activated luciferase gene expression (CALUX) response reflects the whole PCB and DDT burden in ringed seals. Retinyl palmitate (vitamin A) levels showed a negative correlation with the individual POP load, and is proposed as potential effect biomarkers for the depletion of the vitamin A stores. As the nutritional levels of both vitamin A and E have an impact on the vitamin levels in the seals, more information on the dietary vitamin levels is needed before any conclusions can be drawn. As the relationship between biochemical parameters and contaminants varied between the two species, species-specific characteristics has to be considered when monitoring the health status and possible toxic effects of the contaminant load in ringed and grey seals.     

Manufacturing rural finance in Asia: Institutional assemblages, market societies, entrepreneurial subjects

This paper takes up the proposition that institutions mediate market formation, through a comparative study of rural finance in Nepal and Vietnam. It explores how microfinance, as an iconic institution of ‘roll-out neoliberalism’, articulates political-economic and cultural-political milieux—with particular emphasis given to the ways in which the Vietnamese Party-state has engaged rural finance to further the socialist transition even as it has undergone significant ‘economic renovation’. In so doing, the paper adopts a processual interpretation of institutions not as bounded structures, but as arenas of ongoing debate over culturally constructed meanings and ‘practices of assemblage’ [Li, T.M., 2007a. Practices of assemblage and community forest management. Economy and Society 36 (2), 263–293] that are inextricably linked with wider-scale political-economic and cultural-political formations. A comparative approach is pursued here to emphasize spatio-temporal contingencies in the articulation of a market-led development institution with specific national regulatory frameworks and political cultures. A critical-geographical orientation helps to deepen Polanyi’s proposition that the economy is an instituted process, to challenge the prevailing binary opposition between state- and market-led development, account for the multiple scales at which power and interest reside in the formation of markets, and highlight the variable ways in which markets are embodied and enacted in particular places.     

Pulsar PSR B2303+30: a single system of drifting subpulses, moding and nulling

Analyses of multiple pulse sequences of the pulsar PSR B2303+30 reveal two distinct emission modes. One mode (B) follows a steady even–odd pattern and is more intense. The second mode (Q) is characteristically weak, but has intermittent drift bands with a periodicity of approximately 3 P ₁/cycle, and nulls much more frequently than the B mode. Both modes occur with roughly equal frequency, and their profiles have a similar single-humped form with a slight asymmetry. Our observations and analyses strongly suggest that the subpulse drift rates in both modes are linked in a series of cycles, which can be modelled as relaxing oscillations in the underlying circulation rate.     

On the polarisation and emission geometry of pulsar 1929+10: Does its emission come from a single pole or two poles?

Pulsar B1929+10 is remarkable on a number of grounds. Its narrow primary components exhibit virtually complete and highly stable linear polarisation, which can be detected over most of its rotation cycle. Various workers have been lured by the unprecedented range over which its linear polarisation angle can be determined, and more attempts have been made to model its emission geometry than perhaps for any other pulsar. Paradoxically, there is compelling evidence to interpret the pulsar’s emission geometryboth in terms of an aligned configuration whereby its observed radiation comes from a single magnetic-polar emission regionand in terms of a nearly orthogonal configuration in which we receive emission from regions near each of its two poles. Pulsar 1929+10 thus provides a fascinating context in which to probe the conflict between these lines of interpretation in an effort to deepen our understanding of pulsar radio emission. Least-squares fits to the polarisation-angle traverse fit poorly near the main pulse and interpulse and have an inflection point far from the centre of the main pulse. This and a number of other circumstances suggest that the position-angle traverse is an unreliable indicator of the geometry in this pulsar, possibly in part because its low level ‘pedestal’ emission makes it impossible to properly calibrate a Polarimeter which correlates orthogonal circular polarisations. Taking the interpulse and main-pulse comp. II widths as indicators of the magnetic latitude, it appears that pulsar 1929+10 has anα value near 90‡ and thus has a two-pole interpulse geometry. This line of interpretation leads to interesting and consistent results regarding the geometry of the conal components. Features corresponding to both an inner and outer cone are identified. In addition, it appears that pulsar 1929+10–and a few other stars–have what we are forced to identify as a ‘furtherin’ cone, with a conal emission radius of about2.3‡/P _1/2 Secondarily, 1929+10’s nearly complete linear polarisation provides an ideal opportunity to study how mechanisms of depolarisation function on a pulse-to-pulse basis. Secondary-polarisation-mode emission appears in significant proportion only in some limited ranges of longitude, and the subsequent depolarization is studied using different mode-separation techniques. The characteristics of the two polarisation modes are particularly interesting, both because the primary mode usually dominates the secondary so completely and because the structure seen in the secondary mode appears to bear importantly on the question of the pulsar’s basic emission geometry. New secondary-mode features are detected in the average profile of this pulsar which appear independent of the main-pulse component structure and which apparently constitute displaced modal emission. Individual pulses during which the secondary-mode dominates the primary one are found to be considerably more intense than the others and largely depolarised. Monte-Carlo modeling of the mode mixing in this region, near the boundary of comps. II and III, indicates that the incoherent interference of two fully and orthogonally polarised modes can adequately account for the observed depolarisation. The amplitude distributions of the two polarisation modes are both quite steady: the primary polarisation mode is well fitted by a χ² distribution with about nine degrees of freedom; whereas the secondary mode requires a more intense distribution which is constant, but sporadic.     

A Note on Tree Deaths during the Current (2001–?) Drought in South-eastern Australia

Tree deaths over large areas during droughts are uncommon. In the semi-arid zone of New South Wales (NSW) such events were last reported during the prolonged droughts of 1895–1903 and 1939–45, though whether caused solely by drought is open to question. Anecdotal and quantitative evidence during the current prolonged drought (2001–?) in NSW's sub-humid zone (where deaths are localised) and semi-arid zone (where deaths are more extensive) suggest that climatic conditions are comparable to, and perhaps more severe than, those of the earlier prolonged droughts. It is suggested that lack of access to deep soil moisture due to inherent shallow rooting, or due to site conditions, is the most likely cause; and that this may be associated with higher than optimal tree densities in cohorts of trees that arose from previous regeneration events during periods of well above average rainfall. A more thorough examination of the extent and severity of this event is warranted.     

Gully formation on Mars: Two recent phases of formation suggested by links between morphology, slope orientation and insolation history

The unusual 80 km diameter Noachian-aged Asimov crater in Noachis Terra (46°S, 5°E) is characterized by extensive Noachian-Hesperian crater fill and a younger superposed annulus of valleys encircling the margins of the crater floor. These valleys provide an opportunity to study the relationships of gully geomorphology as a function of changing slope orientation relative to solar insolation. We found that the level of development of gullies was highly correlated with slope orientation and solar insolation. The largest and most complex gully systems, with the most well-developed fluvial landforms, are restricted to pole-facing slopes. In contrast, gullies on equator-facing slopes are smaller, more poorly developed and integrated, more highly degraded, and contain more impact craters. We used a 1D version of the Laboratoire de Météorologie Dynamique GCM, and slope geometries (orientation and angle), driven by predicted spin-axis/orbital parameter history, to assess the distribution and history of surface temperatures in these valleys during recent geological history. Surface temperatures on pole-facing slopes preferential for water ice accumulation and subsequent melting are predicted to occur as recently as 0.5-2.1 Ma, which is consistent with age estimates of gully activity elsewhere on Mars. In contrast, the 1D model predicts that water ice cannot accumulate on equator-facing slopes until obliquities exceed 45°, suggesting they are unlikely to have been active over the last 5 Ma. The correlation of the temperature predictions and the geological evidence for age differences suggests that there were two phases of gully formation in the last few million years: an older phase in which top-down melting occurred on equator-facing slopes and a younger more robust phase on pole-facing slopes. The similarities of small-scale fluvial erosion features seen in the gullies on Mars and those observed in gullies cut by seasonal and perennial snowmelt in the Antarctic Dry Valleys supports a top-down melting origin for these gullies on Mars.