The return of subducted continental crust in Samoan lavas

Substantial quantities of terrigenous sediments are known to enter the mantle at subduction zones, but little is known about their fate in the mantle. Subducted sediment may be entrained in buoyantly upwelling plumes and returned to the Earth's surface at hotspots, but the proportion of recycled sediment in the mantle is small, and clear examples of recycled sediment in hotspot lavas are rare. Here we report remarkably enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures in Samoan lavas from three dredge locations on the underwater flanks of Savai'i island, Western Samoa. The submarine Savai'i lavas represent the most extreme 87Sr/86Sr isotope compositions reported for ocean island basalts to date. The data are consistent with the presence of a recycled sediment component (with a composition similar to the upper continental crust) in the Samoan mantle. Trace-element data show affinities similar to those of the upper continental crust--including exceptionally low Ce/Pb and Nb/U ratios--that complement the enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures. The geochemical evidence from these Samoan lavas significantly redefines the composition of the EM2 (enriched mantle 2; ref. 9) mantle endmember, and points to the presence of an ancient recycled upper continental crust component in the Samoan mantle plume.     

Formation of stable epialleles and their paramutation-like interaction in tetraploid Arabidopsis thaliana

Polyploidization is found frequently in plants, and species previously considered to be diploid may show remnants of earlier polyploidization events on closer inspection of their genomes. The success of polyploids may lie in increased genetic redundancy supporting subsequent genetic diversification. Although doubling the genome does not generate diversity per se, recent studies show that rapid genomic rearrangements and changes in DNA modification and gene expression patterns are associated with polyploid formation. But recessive modifications will not become phenotypically apparent in early polyploid generations. Here we show that epialleles in tetraploid plants (but not in diploids) interact in trans and lead to heritable gene silencing persisting after segregation from the inactivating allele. This mechanism, resembling paramutation, leads to the establishment of functional epigenetic homozygosity and, thus, to conversion of new recessive alleles into traits expressed in early polyploid generations. Such interactions probably contribute to rapid adaptation and evolution of polyploid plant species.     

Bioinspired and hydrophobic alkyl-silanized protective polymer coating for Mg alloy

The modification of silica coating surfaces by trimethylsilylation has contributed to enhanced hydrophobicity(θ_w~o90°)against fluid permeation and corrosion in Na Cl.These alkyl-silanized coatings were deployed to protect Mg alloy after reinforcing their internal structures with nanosilica powder.The reduced wetness of coating surfaces is attributed to their chemically-modified surface morphology,and this has been compared to the reticulate leaf structures of lotus plant.The optimum amount of silylating additive(hexamethyldisilazane)required to prepare a hydrophobic coating with minimum water adhesion has been established.Barrier performance of coatings were examined by electrochemical and surface analyses in 5 wt%Na Cl.The corrosion resistance of these coatings is a result of the direct contribution of their bulk stability and surface hydrophobicity,and this is expressed in terms of the variation of electrochemical parameters with exposure time.These coatings may have emerging industrial applications,including a future in metal surface treatments and anticorrosion paints.     

The Social Construction of Mind and the Future of Cognitive Science

Cognitive activity, which essentially consistsof the use of signs, does not only depend onthe internal (mental, or brain) processes. Thefirst part of the paper presents severalversions of the idea of the external andcultural organization of individual's mentalprocesses. The second part of the paperconsiders a future development of cognitivescience as a science of the extended andsocially constructed mind. KazimierzTwardowski's theory of intentionality and histheory of actions and products provide theconceptual framework of the undertaken analysis.     

Mining incomplete data—A rough set approach

Many reallife data sets are incomplete, or in different words, are affected by missing attribute values.Three interpretations of missing attribute values are discussed in the paper: lost values (erased values), attributeconcept values(such a value may be replaced by any value from the attribute domain restricted to the concept), and “do not care” conditions (a missing attribute value may be replaced by any value from the attribute domain).For incomplete data sets three definitions of lower and upper approximations are discussed.Experiments were conducted on six typical data sets with missing attribute values, using three different interpretations of missing attribute values and the same definition of concept lower and upper approximations.The conclusion is that the best approach to missing attribute values is the lost value type.     

The sulfur metabolism regulator MetR is a global regulator controlling phytochrome-dependent light responses in Aspergillus nidulans

Phytochrome-dependent light signaling has been studied in several fungi.In Aspergillus nidulans light-stimulated phytochrome activates the high-osmolarity glyce...