Reconstructions of eolian dust accumulation in northwest African margin sediments

Reconstructions of eolian dust accumulation in northwest African margin sediments provide important continuous records of past changes in atmospheric circulation and aridity in the region. Existing records indicate dramatic changes in North African dust emissions over the last 20 ka, but the limited spatial extent of these records and the lack of high-resolution flux data do not allow us to determine whether changes in dust deposition occurred with similar timing, magnitude and abruptness throughout northwest Africa. Here we present new records from a meridional transect of cores stretching from 31°N to 19°N along the northwest African margin. By combining grain size endmember modeling with 230Th-normalized fluxes for the first time, we are able to document spatial and temporal changes in dust deposition under the North African dust plume throughout the last 20 ka. Our results provide quantitative estimates of the magnitude of dust flux changes associated with Heinrich Stadial 1, the Younger Dryas, and the African Humid Period (AHP; ~11.7-5 ka), offering robust targets for model-based estimates of the climatic and biogeochemical impacts of past changes in North African dust emissions. Our data suggest that dust fluxes between 8 and 6 ka were a factor of ~5 lower than average fluxes during the last 2 ka. Using a simple model to estimate the effects of bioturbation on dust input signals, we find that our data are consistent with abrupt, synchronous changes in dust fluxes in all cores at the beginning and end of the AHP. The mean ages of these transitions are 11.8±0.2 ka (1Sigma) and 4.9±0.2 ka, respectively.

Grain size distribution and bulk chemistry of eolian dust

Atmospheric dust samples collected along a transect off the West African coast have been investigated for their physical (grain-size distribution), mineralogical, and chemical (major elements) composition. On the basis of these data the samples were grouped into sets of samples that most likely originated from the same source area. In addition, shipboard-collected atmospheric meteorological data, modeled 4-day back trajectories for each sampling day and location, and Total Ozone Mapping Spectrometer aerosol index data for the time period of dust collection (February-March 1998) were combined and used to reconstruct the sources of the groups of dust samples. On the basis of these data we were able to determine the provenance of the various dust samples. It appears that the bulk of the wind-blown sediments that are deposited in the proximal equatorial Atlantic Ocean are transported in the lower level (>~900 hPa) NE trade wind layer, which is a very dominant feature north of the Intertropical Convergence Zone (ITCZ). However, south of the surface expression of the ITCZ, down to 5°S, where surface winds are southwesterly, we still collected sediments that originated from the north and east, carried there by the NE trade wind layer, as well as by easterly winds from higher altitudes. The fact that the size of the wind-blown dust depends not only on the wind strength of the transporting agent but also on the distance to the source hampers a direct comparison of the dust's size distributions and measured wind strengths. However, a comparison between eolian dust and terrigenous sediments collected in three submarine sediment traps off the west coast of NW Africa shows that knowledge of the composition of eolian dust is a prerequisite for the interpretation of paleorecords obtained from sediment cores in the equatorial Atlantic.

In situ d18O and Mg/Ca analyses of ODP Site 143-865 samples

We report d18O and minor element (Mg/Ca, Sr/Ca) data acquired by high-resolution, in situ secondary ion mass spectrometry (SIMS) from planktic foraminiferal shells and 100-500 µm sized diagenetic crystallites recovered from a deep-sea record (ODP Site 865) of the Paleocene-Eocene thermal maximum (PETM). The d18O of crystallites (~1.2 per mil Pee Dee Belemnite (PDB)) is ~4.8 per mil higher than that of planktic foraminiferal calcite (-3.6 per mil PDB), while crystallite Mg/Ca and Sr/Ca ratios are slightly higher and substantially lower than in planktic foraminiferal calcite, respectively. The focused stratigraphic distribution of the crystallites signals an association with PETM conditions; hence, we attribute their formation to early diagenesis initially sourced by seafloor dissolution (burndown) ensued by reprecipitation at higher carbonate saturation. The Mg/Ca ratios of the crystallites are an order of magnitude lower than those predicted by inorganic precipitation experiments, which may reflect a degree of inheritance from "donor" phases of biogenic calcite that underwent solution in the sediment column. In addition, SIMS d18O and electron microprobe Mg/Ca analyses that were taken within a planktic foraminiferal shell yield parallel increases along traverses that coincide with muricae blades on the chamber wall. The parallel d18O and Mg/Ca increases indicate a diagenetic origin for the blades, but their d18O value (-0.5 per mil PDB) is lower than that of crystallites suggesting that these two phases of diagenetic carbonate formed at different times. Finally, we posit that elevated levels of early diagenesis acted in concert with sediment mixing and carbonate dissolution to attenuate the d18O decrease signaling PETM warming in "whole-shell" records published for Site 865.

Enviromagnetic, major element, and grain-size analyses of surface sediment samples along the continental margin between East Brazil and Patagonia

Continental margin sediments of SE South America originate from various terrestrial sources, each conveying specific magnetic and element signatures. Here, we aim to identify the sources and transport characteristics of shelf and slope sediments deposited between East Brazil and Patagonia (20°-48°S) using enviromagnetic, major element, and grain-size data. A set of five source-indicative parameters (i.e., chi-fd%, ARM/IRM, S0.3T, SIRM/Fe and Fe/K) of 25 surface samples (16-1805 m water depth) was analyzed by fuzzy c-means clustering and non-linear mapping to depict and unmix sediment-province characteristics. This multivariate approach yields three regionally coherent sediment provinces with petrologically and climatically distinct source regions. The southernmost province is entirely restricted to the slope off the Argentinean Pampas and has been identified as relict Andean-sourced sands with coarse unaltered magnetite. The direct transport to the slope was enabled by Rio Colorado and Rio Negro meltwaters during glacial and deglacial phases of low sea level. The adjacent shelf province consists of coastal loessoidal sands (highest hematite and goethite proportions) delivered from the Argentinean Pampas by wave erosion and westerly winds. The northernmost province includes the Plata mudbelt and Rio Grande Cone. It contains tropically weathered clayey silts from the La Plata Drainage Basin with pronounced proportions of fine magnetite, which were distributed up to ~24° S by the Brazilian Coastal Current and admixed to coarser relict sediments of Pampean loessoidal origin. Grain-size analyses of all samples showed that sediment fractionation during transport and deposition had little impact on magnetic and element source characteristics. This study corroborates the high potential of the chosen approach to access sediment origin in regions with contrasting sediment sources, complex transport dynamics, and large grain-size variability.

Compte rendu de Resche, Catherine (dir.) 2015. Terminologie et domaines spécialisés. Approches plurielles. Paris : Classiques Garnier, Rencontres 143, Série linguistique 2. 264 p.

Paru dans ASp 70, p. 127-132

Expressions and clinic significance of miRNA-143, miRNA- 34A, miRNA-944, miRNA-101 and miRNA-218 in cervical cancer tissues

Purpose: To search for novel biomarkers for early diagnosis of cervical cancer, as well as novel therapeutic target for cervical cancer. Methods: A total of 96 cervical tissue specimens were collected from patients in the Second Affiliated Hospital of Zhengzhou University, out of which 10 were normal control. The remaining specimens (86) were cervical cancer specimens and were divided into 4 groups (A - D) based on tumor-biomarker levels of CA125 and SCC. Quantitative real-time polymerase chain reaction technology (qRT-PCR) was used to detect the expressions of miRNA-143, miRNA-34A, miRNA-944, miRNA-101 and miRNA-218 in the cervical cancer tissues. Results: The levels of CA125 (U/mL) and SCC (ug/L) expressed in normal control group and groups A - D were 11.75 and 0.73 (n = 10), 382 and 2.72 (n = 25), 912.9 and 3.93 (n = 21), 1675 and 5.87 (n = 29), and 2120 and 6.66 (n = 11), respectively. Furthermore, qRT-PCR results showed that the expressions of miRNA-944 and miRNA-218 in cervical cancer tissues were markedly up-regulated compared to normal control tissues (p < 0.01). In contrast, the expression level of miRNA-143, miRNA-34A, and miRNA-101 were significantly decreased (p < 0.01). Conclusion: The biomarkers, miRNA-143, miRNA-34A, miRNA-944, miRNA-101 and miRNA-218, can be considered novel for early diagnosis of cervical cancer.

Condensed phase combustion travelling waves with sequential exothermic or endothermic reactions

The one-dimensional propagation of a combustion wave through a premixed solid fuel for two-stage kinetics is studied. We re-examine the analysis of a single reaction travelling-wave and extend it to the case of two-stage reactions. We derive an expression for the travelling wave speed in the limit of large activation energy for both reactions. The analysis shows that when both reactions are exothermic, the wave structure is similar to the single reaction case. However, when the second reaction is endothermic, the wave structure can be significantly different from single reaction case. In particular, as might be expected, a travelling wave does not necessarily exist in this case. We establish conditions in the limiting large activation energy limit for the non-existence, and for monotonicity of the temperature profile in the travelling wave.

Uses of YouTube : digital literacy and the growth of knowledge

I invented YouTube. Well, not YouTube exactly, but something close – something called YIRN; and not by myself exactly, but with a team. In 2003-5 I led a research project designed to link geographically dispersed young people, to allow them to post their own photos, videos and music, and to comment on the same from various points of view – peer to peer, author to public, or impresario to audience. We wanted to find a way to take the individual creative productivity that is associated with the Internet and combine it with the easy accessibility and openness to other people’s imagination that is associated with broadcasting; especially, in the context of young people, listening to the radio. So we called it the Youth Internet Radio Network, or YIRN.

Full-time is a given here : part-time versus full-time job quality

This study explores full-time workers' understanding of and assumptions about part-time work against six job quality components identified in recent literature. Forty interviews were conducted with employees in a public sector agency in Australia, a study context where part-time work is ostensibly 'good quality' and is typically long term, voluntary, involving secure contracts (i.e. permanent rather than casual) and having predictable hours distributed evenly over the week and year. Despite strong collective bargaining arrangements as well as substantial legal and industrial obligations, the findings revealed some serious concerns for part-time job quality. These concerns included reduced responsibilities and lesser access to high status roles and projects, a lack of access to promotion opportunities, increased work intensity and poor workplace support. The highly gendered, part-time labour market also means that it is women who disproportionately experience this disadvantage. To foster equity, greater attention needs to focus on monitoring and enhancing job quality, regardless of hours worked.

From mass communication to mass conversation : why 1984 wasn't like 1984

Marketers and commercial media alike are confronted by shifts in the social relations of media production and consumption in the global services economy, including the challenge of capturing, managing and commercialising media-user productivity. This trajectory of change in media cultures and economies is described here as ‘mass conversation’. Two media texts and a new media object provide a starting point for charting the ascendance and social impact of mass conversation. Apple’s 1984 television commercial, which launched the Macintosh computer, inverted George Orwell’s dystopian vision of the social consequences of panoptic communications systems. It invoked a revolutionary rhetoric to anticipate the social consequences of a new type of interactivity since theorised as ‘intercreativity’. This television commercial is contrasted with another used in Nike’s 2006 launch of its Nike+ (Apple iPod) system. The Nike+ online brand community is also used to consider how a multiplatform brand channel is seeking to manage the changing norms and practices of consumption and end-user agency. This analysis shows that intercreativity modifies the operations of ‘Big Brother’ but serves the more mundane than revolutionary purpose of generating commercial value from the affective labour of end-users.

The world of science education : handbook of research in Australasia

The focus of this Handbook is on Australasia (a region loosely recognized as that which includes Australia and New Zealand plus nearby Pacific nations such as Papua New Guinea, Solomon Islands, Fiji, Tonga, Vanuatu, and the Samoan islands) science education and the scholarship that most closely supports this program. The reviews of the research situate what has been accomplished within a given field in Australasian rather than international context. The purpose therefore is to articulate and exhibit regional networks and trends that produced specific forms of science education. The thrust lies in identifying the roots of research programs and sketching trajectories—focusing the changing façade of problems and solutions within regional contexts. The approach allows readers review what has been done and accomplished, what is missing, and what might be done next.

Introduction : science education research in Australasia : an overview

This chapter overviews the major themes of research reviewed and justifies the selection of topics.