Tetra- and pentacyclic alkanes in the Cretaceous/Tertiary boundary sediments at Kawaruppu, Hokkaido, Japan

Twenty two steranes and 17 triterpanes were detected in the Cretaceous-Tertiary (K/T) boundary sediments at Kawaruppu, Hokkaido, Japan. These steranes and triterpanes were detected at a concentration level of 0.001-0.1nmol g-1. Their concentrations were smaller within the K/T boundary claystone than in the sediments above and below the claystone, which are likely related to the large biomass extinction event at the end of the Cretaceous. The concentrations of 5α-cholestane and the relative ones of 17α,21β-hopane in the sediments above the boundary claystone were about a half of those in the sediments below the claystone, whereas those of 5α-ergostane, 5α-stigmastane, and oleanane in the sediments above were less than a half abundance level of those in the sediments below the claystone. Diastereomer ratios of steranes and triterpanes were nearly constant over the sediments. No tricyclic alkanes were detected in the sediments.This work was supported by the Grant-in-Aid for ScientificResearch (B) No.11440166 from the Ministry of Education, Science, Sports and Culture, Japan and the Research Grant for Fellowship No.00007064 to H. Y. from Japanese Society for the Promotion of Science

Deciphering Elapsed Time and Predicting Action Timing from Neuronal Population Signals

The proper timing of actions is necessary for the survival of animals, whether in hunting prey or escaping predators. Researchers in the field of neuroscience have begun to explore neuronal signals correlated to behavioral interval timing. Here, we attempt to decode the lapse of time from neuronal population signals recorded from the frontal cortex of monkeys performing a multiple-interval timing task. We designed a Bayesian algorithm that deciphers temporal information hidden in noisy signals dispersed within the activity of individual neurons recorded from monkeys trained to determine the passage of time before initiating an action. With this decoder, we succeeded in estimating the elapsed time with a precision of approximately 1 s throughout the relevant behavioral period from firing rates of 25 neurons in the pre-supplementary motor area. Further, an extended algorithm makes it possible to determine the total length of the time-interval required to wait in each trial. This enables observers to predict the moment at which the subject will take action from the neuronal activity in the brain. A separate population analysis reveals that the neuronal ensemble represents the lapse of time in a manner scaled relative to the scheduled interval, rather than representing it as the real physical time

Recent increase of genetic diversity in Plasmodium vivax population in the Republic of Korea

<p>Abstract</p> <p>Background</p> <p>The reemergence of <it>Plasmodium vivax </it>in South Korea since 1993 represents a serious public health concern. Despite the importance in understanding genetic diversity for control strategies, however, studies remain inconclusive with the general premise that due to low rate of malaria transmission, there is generally low genetic diversity with very few strains involved. In this study, the genetic diversity and population structure of <it>P. vivax </it>in South Korea were explored by analysing microsatellite polymorphism.</p> <p>Methods</p> <p>Sequences for 13 microsatellite loci distributed across the twelve chromosomes of <it>P. vivax </it>were obtained from 58 South Korean isolates collected during two sampling periods, namely 1997-2000 and 2007. The sequences were used for the analysis of expected heterozygosity and multilocus genotype diversity. Population structure was evaluated using STRUCTURE version 2.3.2. Linkage disequilibrium was also analysed to investigate the extent of outbreeding in the <it>P. vivax </it>population.</p> <p>Results</p> <p>Mean expected heterozygosity significantly increased from 0.382 in 1997-2000 to 0.545 in 2007 (<it>P </it>< 0.05). The number of multilocus genotypes was 7 and 27; and genotype diversity was statistically significant (<it>P </it>< 0.01) at 0.661 and 0.995 in 1997-2000 and 2007, respectively. Analysis by STRUCTURE showed a more complex population structure in 2007 than in 1997-2000. Linkage disequilibrium between 13 microsatellites, although significant in both time points, was notably lower in 2007.</p> <p>Conclusions</p> <p>The present microsatellite analysis clearly showed recent increase of genetic diversity and recent relaxation of the strong population structure observed in 1997-2000. These results suggest that multiple genotypes not present previously recently migrated into South Korea, accompanied by substantial outbreeding between different genotypes.</p

H, C, and N isotopic compositions of Hayabusa category 3 organic samples

Since isotopic ratios of H, C, and N are sensitive indicators for determining extraterrestrial organics, we have measured these isotopes of Hayabusa category 3 organic samples of RB-QD04-0047-02, RA-QD02-0120, and RB-QD04-0001 with ion imaging using a NanoSIMS ion microprobe. All samples have H, C, and N isotopic compositions that are terrestrial within errors (approximately ±50‰ for H, approximately ±9‰ for C, and approximately ±2‰ for N). None of these samples contain micrometer-sized hot spots with anomalous H, C, and N isotopic compositions, unlike previous isotope data for extraterrestrial organic materials, i.e., insoluble organic matters (IOMs) and nano-globules in chondrites, interplanetary dust particles (IDPs), and cometary dust particles. We, therefore, cannot conclude whether these Hayabusa category 3 samples are terrestrial contaminants or extraterrestrial materials because of the H, C, and N isotopic data. A coordinated study using microanalysis techniques including Fourier transform infrared spectrometry (FT-IR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), NanoSIMS ion microprobe, Raman spectroscopy, X-ray absorption near edge spectroscopy (XANES), and transmission electron microscopy/scanning transmission electron microscopy (TEM/STEM) is required to characterize Hayabusa category 3 samples in more detail for exploring their origin and nature.This research was supported by the JSPS Strategic Fund for Strengthening Leading-edge Research and Development to the JAMSTEC

ToF-SIMS analysis of carbonaceous particles in the sample catcher of the Hayabusa spacecraft

Three carbonaceous category 3 particles (RA-QD02-0180, RB-QD04-0037-01, and RB-QD04-0047-02) returned in the sample catcher from the Hayabusa spacecraft were analyzed by time of flight-secondary ion mass spectrometry (ToF-SIMS) to establish an analytical procedure for determination of their origins. By the different analytical schemes, the three particles gave distinct elemental and molecular ions, in which the organic carbons commonly appear to be associated with nitrogen, silicon, and/or fluorine. The particles could be debris of silicon rubber and fluorinated compounds and are therefore man-made artifacts rather than natural organic matter