Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

     

Protein binding sites on Escherichia coli 16S ribosomal RNA; RNA regions that are protected by proteins S7, S9 and S19, and by proteins S8, S15 and S17.

Selected groups of isolated 14C-labelled proteins from E. coli 30S ribosomal subunits were reconstituted with 32P-labelled 16S RNA, and the reconstituted complexes were partially digested with ribonuclease A. RNA fragments protected by the proteins were separated by gel electrophoresis and subjected to sequence analysis. Complexes containing proteins S7 and S19 protected an RNA region comprising helices 29 to 32, part of helix 41, and helices 42 and 43 of the 16S RNA secondary structure. Addition of protein S9 had no effect. When compared with previous data for proteins S7, S9, S14 and S19, these results suggest that S14 interacts with helix 33, and that S9 and S14 together interact with the loop-end of helix 41. Complexes containing proteins S8, S15 and S17 protected helices 7 to 10 as well as the "S8-S15 binding site" (helices 20, 22 and parts of helices 21 and 23). When protein S15 was omitted, S8 and S18 showed protection of part of helix 44 in addition to the latter regions. The results are discussed in terms of our model for the detailed arrangement of proteins and RNA in the 30S subunit.     

Relationship Between Structural Properties and Electrochemical Characteristics of Monolithic Carbon Xerogel‐Based Electrochemical Double‐Layer Electrodes in Aqueous and Organic Electrolytes

The impact of the micropore width, external surface area, and meso‐/macropore size on the charging performance of electrochemical double‐layer capacitor (EDLC) electrodes is systematically investigated. Nonactivated carbon xerogels are used as model electrodes in aqueous and organic electrolytes. Monolithic porous model carbons with different structural parameters are prepared using a resorcinol‐formaldehyde‐based sol–gel process and subsequent pyrolysis of the organic precursors. Electrochemical properties are characterized by utilizing them as EDLC half‐cells operated in aqueous and organic electrolytes, respectively. Experimental data derived for organic electrolytes reveals that the respective ions cannot enter the micropores within the skeleton of the meso‐ and macroporous carbons. Therefore the total capacitance is limited by the external surface formed by the interface between the meso‐/macropores and the microporous carbon particles forming the xerogel skeleton. In contrast, for aqueous electrolytes the total capacitance solely depends on the total surface area, including interfaces at the micropore scale. For both types of electrolytes the charging rate of the electrodes is systematically enhanced when increasing the diameter of the carbon xerogel particles from 10 to 75 nm and the meso‐/macropore size from 10 to 121 nm.     

Genetic variation in the bovine myostatin gene in UK beef cattle: allele frequencies and haplotype analysis in the South Devon

Work on Belgian Blue cattle revealed that an 11 base pair (bp) deletion within the bovine myostatin gene (GDF8) is associated with the double-muscled phenotype seen in this breed. Investigations focusing on other European breeds known to show double-muscling identified several mutations within the coding region of the gene associated with the double-muscled phenotype in different breeds. The number of mutations found suggest that myostatin is highly variable within beef cattle. Variations that alter the structure of the gene product such that the protein is inactivated are associated with the most pronounced form of double-muscling as seen in the Belgian Blue. However, other mutations may have a less extreme affect on muscle development. While overt double-muscling gives rise to a high incidence of dystocia (calving difficulty), it is possible that some variants may give enhanced muscling, but with limited calving problems. We describe sequence analysis of the myostatin gene in ten beef breeds commonly used in the UK and show that the 11-bp deletion responsible for double-muscling in the Belgian Blue is also present in the South Devon cattle population. Allele frequencies and haplotypes in the South Devon and a polymerase chain reaction (PCR) based test for the deletion are described. PCR amplification across the deleted region provides a quick and effective test with clear identification of heterozygous individuals. We discuss our results with regard to the effect of genotype on phenotype and differences observed between the Belgian Blue and the South Devon.     

Model based decoding of spike trains

Reliably decoding neuronal responses requires knowing what aspects of neuronal responses are stimulus related, and which aspects act as noise. Recent work shows that spike trains can be viewed as stochastic samples from the rate variation function, as estimated by the time dependent spike density function (or normalized peristimulus time histogram). Such spike trains are exactly described by order statistics, and can be decoded millisecond-by-millisecond by iterative application of order statistics.     

Population genetics of chimpanzee blood groups

A series of 60 chimpanzees (Pan troglodytes) were tested for their human-type A-B-O blood groups and for ten simian-type blood factors. Of the 60 chimpanzees four were group O and 56 group A; combining this with our previous results, among 274 chimpanzees there were 36 group O and 238 group A. Gene frequency analysis of the V-A-B types (determined by three antisera, anti- V ^c, anti- A ^c and anti- B ^c) of the 60 chimpanzees indicated inheritance by four allelic genes, namely, the amorphic gene v and the three additional alleles v^A, v^B and V. This theory allows for the existence of ten genotypes but only seven V-A-B phenotypes, since the type V.AB is excluded. Gene frequency analysis confirmed that C^c and c^c are contrasting antigens determined by corresponding allelic genes. The distribution of the C-c-E-F types among the 60 chimpanzees, as well as among 133 chimpanzees previously tested, is compatible with the postulation of five allelic genes, namely, the amorph c, and the alleles C^E, C^F, C^EF and the very rare allele C. The blood factor G ^c appears to define a separate blood group system, independent of the V-A-B and C-E-F systems. The newly defined blood factor Lindsay appears to be related to the V-A-B system, while factor H ^c may be related to the C-E-F system.     

Movements of myelin sheath particles in a weak electric field

When a weak electric field is applied to longitudinal sections of myelinated nerve, myelin material migrates out of the tissue edges towards both poles. the materials migrating from the anodal and cathodal edges seem to be chemically similar but differ in physical properties. at the anodal edge the bimolecular lipid layers rearrange into spherical micelles forming an “oil in water” emulsion, and at the cathodal edge into micelles forming a “water in oil” emulsion. the latter is unstable in water and is rapidly transformed into an “oil in water” emulsion. these findings have physiological and structural implications for the study of biological membranes.