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71.
The geographical position of the island of New Guinea suggests that it may have been an early staging post in the Pleistocene settlement of Australia from the Indonesia-Indochina region. Previous data have not supported this, as archaeological sites 35,000 to 40,000 years old occur in southern Australia, whereas the earliest previously known in Papua New Guinea is 26,000 years old. We now report evidence that the north coast of Papua New Guinea was occupied at least 40,000 years ago. Sahuland, which is the greater land area of Australia and New Guinea plus their connecting continental shelf exposed as land when Pleistocene sea levels were lower than now, was occupied by humans in several widely separated areas at that time. A distinctive 'waisted axe' culture appears to have existed in New Guinea and probably in Australia in the Late Pleistocene, but antecedents are not yet known from east and southeast Asia. There is evidence for hafting of these tools at a date which is earlier than known elsewhere in the world. 相似文献
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The relation between mechanical and electrical relaxation in polymer/lithium-salt complexes is a fascinating and still unresolved problem in condensed-matter physics, yet has an important bearing on the viability of such materials for use as electrolytes in lithium batteries. At room temperature, these materials are biphasic: they consist of both fluid amorphous regions and salt-enriched crystalline regions. Ionic conduction is known to occur predominantly in the amorphous fluid regions. Although the conduction mechanisms are not yet fully understood, it is widely accepted that lithium ions, coordinated with groups of ether oxygen atoms on single or perhaps double polymer chains, move through re-coordination with other oxygen-bearing groups. The formation and disruption of these coordination bonds must be accompanied by strong relaxation of the local chain structure. Here we probe the relaxation on a nanosecond timescale using quasielastic neutron scattering, and we show that at least two processes are involved: a slow process with a translational character and one or two fast processes with a rotational character. Whereas the former reflects the slowing-down of the translational relaxation commonly observed in polyethylene oxide and other polymer melts, the latter appears to be unique to the polymer electrolytes and has not (to our knowledge) been observed before. A clear picture emerges of the lithium cations forming crosslinks between chain segments and thereby profoundly altering the dynamics of the polymer network. 相似文献
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Biological scaling: does the exception prove the rule? 总被引:1,自引:0,他引:1
Enquist BJ Allen AP Brown JH Gillooly JF Kerkhoff AJ Niklas KJ Price CA West GB 《Nature》2007,445(7127):E9-10; discussion E10-1
Reich et al. report that the whole-plant respiration rate, R, in seedlings scales linearly with plant mass, M, so that R=C(R)M(theta) when theta approximately 1, in which c(R) is the scaling normalization and theta is the scaling exponent. They also state that because nitrogen concentration (N) is correlated with c(R), variation in N is a better predictor of R than M would be. Reich et al. and Hedin incorrectly claim that these "universal" findings question the central tenet of metabolic scaling theory, which they interpret as predicting theta = (3/4), irrespective of the size of the plant. Here we show that these conclusions misrepresent metabolic scaling theory and that their results are actually consistent with this theory. 相似文献
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Payne BA Wilson IJ Hateley CA Horvath R Santibanez-Koref M Samuels DC Price DA Chinnery PF 《Nature genetics》2011,43(8):806-810
There is emerging evidence that people with successfully treated HIV infection age prematurely, leading to progressive multi-organ disease, but the reasons for this are not known. Here we show that patients treated with commonly used nucleoside analog anti-retroviral drugs progressively accumulate somatic mitochondrial DNA (mtDNA) mutations, mirroring those seen much later in life caused by normal aging. Ultra-deep re-sequencing by synthesis, combined with single-cell analyses, suggests that the increase in somatic mutation is not caused by increased mutagenesis but might instead be caused by accelerated mtDNA turnover. This leads to the clonal expansion of preexisting age-related somatic mtDNA mutations and a biochemical defect that can affect up to 10% of cells. These observations add weight to the role of somatic mtDNA mutations in the aging process and raise the specter of progressive iatrogenic mitochondrial genetic disease emerging over the next decade. 相似文献
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V. Hemleben K. Bachmann H. J. Price 《Cellular and molecular life sciences : CMLS》1978,34(11):1452-1453
Summary 8 species of the subtribe Microseridinae contain between 1100 and 3400 genes for 25 and 18 S ribosomal RNA. The gene numbers seem to evolve by discrete steps. Their trend follows a general reduction in genome size during the evolution of the annual species ofMicroseris, but numbers remain high in one of them and inAgoseris grandiflora. 2 species ofPyrrhopappus differ by a duplication of the ribosomal gene numbers; 5 S ribosomal RNA genes in 4 species are repeated roughly 10,000 times.We thank Miss S. Werner, Miss A. Roth and Miss U. Krehan for help with some of the experiments. This paper is part of a project supported by grant Ba 536/1-5 from the Deutsche Forschungsgemeinschaft. 相似文献
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Distribution of menaquinones in aerobic Micrococcaceae 总被引:4,自引:0,他引:4