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The Strelley Pool Formation ( SPF) is widely distributed in the East Pilbara Terrane ( EPT) of the Pilbara Craton, Western Australia, and represents a Paleoarchean shallow-water to subaerial environment. It was deposited ~3.4 billion years ago and displays well-documented carbonate stromatolites. Diverse putative microfossils ( SPF microfossils) were recently reported from several localities in the East Strelley, Panorama, Warralong, and Goldsworthy greenstone belts. Thus, the SPF provides unparalleled opportunities to gain insights into a shallow-water to subaerial ecosystem on the early Earth. Our new micro- to nanoscale ultrastructural and microchemical studies of the SPF microfossils show that large (20-70 μm) lenticular organic-walled flanged microfossils retain their structural integrity, morphology, and chain-like arrangements after acid ( HF- HCl) extraction (palynology). Scanning and transmitted electron microscopy of extracted microfossils revealed that the central lenticular body is either alveolar or hollow, and the wall is continuous with the surrounding smooth to reticulated discoidal flange. These features demonstrate the evolution of large micro-organisms able to form an acid-resistant recalcitrant envelope or cell wall with complex morphology and to form colonial chains in the Paleoarchean era. This study provides evidence of the evolution of very early and remarkable biological innovations, well before the presumed late emergence of complex cells. [ABSTRACT FROM AUTHOR]

The 3.4-Ga Strelley Pool Formation ( SPF) at the informally named 'Waterfall Locality' in the Goldsworthy greenstone belt of the Pilbara Craton, Western Australia, provides deeper insights into ancient, shallow subaqueous to possibly subaerial ecosystems. Outcrops at this locality contain a thin (<3 m) unit of carbonaceous and non-carbonaceous cherts and silicified sandstones that were deposited in a shallow-water coastal environment, with hydrothermal activities, consistent with the previous studies. Carbonaceous, sulfide-rich massive black cherts with coniform structures up to 3 cm high are characterized by diverse rare earth elements ( REE) signatures including enrichment of light [light rare earth elements ( LREE)] or middle rare earth elements and by enrichment of heavy metals represented by Zn. The massive black cherts were likely deposited by mixing of hydrothermal and non-hydrothermal fluids. Coniform structures in the cherts are characterized by diffuse laminae composed of sulfide particles, suggesting that unlike stromatolites, they were formed dominantly through physico-chemical processes related to hydrothermal activity. The cherts yield microfossils identical to previously described carbonaceous films, small and large spheres, and lenticular microfossils. In addition, new morphological types such as clusters composed of large carbonaceous spheroids (20-40 μm across each) with fluffy or foam-like envelope are identified. Finely laminated carbonaceous cherts are devoid of heavy metals and characterized by the enrichment of LREE. This chert locally contains conical to domal structures characterized by truncation of laminae and trapping of detrital grains and is interpreted as siliceous stromatolite formed by very early or contemporaneous silicification of biomats with the contribution of silica-rich hydrothermal fluids. Biological affinities of described microfossils and microbes constructing siliceous stromatolites are under investigation. However, this study emphasizes how diverse the microbial community in Paleoarchean coastal hydrothermal environment was. We propose the diversity is at least partially due to the availability of various energy sources in this depositional environment including reducing chemicals and sunlight. [ABSTRACT FROM AUTHOR]

The Serpens South embedded cluster, which is located in the constricted part of a long, filamentary, infrared dark cloud, is believed to be in a very early stage of cluster formation. We present results of near-infrared (JHKs) polarization observations of the filamentary cloud. Our polarization measurements of near-infrared point sources indicate a well-ordered global magnetic field that is perpendicular to the main filament, implying that the magnetic field is likely to have controlled the formation of the main filament. On the other hand, the sub-filaments, which converge on the central part of the cluster, tend to run along the magnetic field. The global magnetic field appears to be curved in the southern part of the main filament, Such morphology is consistent with the idea that the global magnetic field is distorted by gravitational contraction along the main filament toward the northern part, which contains larger mass. Applying the Chandrasekhar-Fermi method, the magnetic field strength is roughly estimated to be a few × 100 μG, suggesting that the filamentary cloud is close to magnetically critical. [ABSTRACT FROM AUTHOR]

Abstract: Fish CNS neurons can repair their axons following nerve injury, whereas mammalian CNS neurons cannot regenerate, and become apoptotic within 1–2 weeks after the nerve lesion. One explanation for these differences is that one, or several molecules are upregulated in fish CNS neurons during nerve regeneration, and this same molecule is downregulated in mammalian CNS neurons before the development of apoptosis caused by nerve injury. A molecule satisfying these criteria might successfully rescue and repair the mammalian CNS neurons. In this study, we looked for such a candidate molecule from goldfish retinas. Transglutaminase derived from goldfish retina (TGR) was characterized as a regenerating molecule after optic nerve injury. A full-length cDNA for TGR was isolated from the goldfish retinal cDNA library prepared from axotomized retinas. Levels of TGR mRNA and protein increased only in the retinal ganglion cells (RGCs) between 10 and 40 days after optic nerve transection. Recombinant TGR protein enhanced neurite outgrowth from adult fish RGCs in culture. Specific interference RNA and antibodies for TGR inhibited neurite outgrowth both in vitro and in vivo. In contrast, the level of TGR protein decreased in rat RGCs within 1–3 days after nerve injury. Furthermore, the addition of recombinant TGR to retinal cultures induced striking neurite outgrowth from adult rat RGCs. These molecular and cellular data strongly suggest that TGR promotes axonal elongation at the surface of injured RGCs after optic nerve injury. [Copyright &y& Elsevier]

The ca. 3 Ga Farrel Quartzite (FQ, Western Australia) contains possible organic microfossils of unusual spindle-like morphology that are surprisingly large and complex, preserved along with spheroids. The unusual nature of the possible fossils, coupled with their antiquity, makes their interpretation as biogenic difficult and debatable. Here, we report 32 in situ carbon isotopic analyses of 15 individual FQ specimens. The spheroids and the spindle-like forms have a weighted mean δ13C value of -37‰, an isotopic composition that is quite consistent with a biogenic origin. Both the spheroids and the spindle-like structures are isotopically distinct from the background organic matter in the same thin section (weighted mean δ13C value of -33‰), which shows that the preserved microstructures are not pseudofossils formed from physical reprocessing of the bulk sedimentary organic material. When considered along with published morphological and chemical studies, these results indicate that the FQ microstructures are bonafide microfossils, and support the interpretation that the spindles were planktonic. Our results also provide metabolic constraints that imply most of these preserved microorganisms were autotrophic. The existence of similar spindles in the ca. 3.4 Ga Strelley Pool Formation of Australia and the ca. 3.4 Ga Onverwacht Group of South Africa suggests that the spindle-containing microbiota may be one of the oldest, morphologically preserved examples of life. If this is the case, then the FQ structures represent the remains of a cosmopolitan biological experiment that appears to have lasted for several hundred million years, starting in the Paleoarchean. [ABSTRACT FROM AUTHOR]

A systematic investigation on the evolution of a prolate cloud at an H II boundary is conducted using smoothed particle hydrodynamics in order to understand the mechanism for a variety of irregular morphological structures found at the boundaries of various H II regions. The prolate molecular clouds in this investigation are set with their semimajor axes at inclinations between 0° and 90° to a plane-parallel ionizing radiation flux. A set of four parameters, the number density n, the ratio of major to minor axis γ, the inclination angle and the incident flux FEUV, are used to define the initial state of the simulated clouds. The dependence of the evolution of a prolate cloud under radiation-driven implosion (RDI) on each of the four parameters is investigated. It is found that (i) in addition to the well-studied standard type A, B or C bright-rimmed clouds (BRCs), many other types such as asymmetrical BRCs, filamentary structures and irregular horse-head structures could also be developed at H II boundaries with only simple initial conditions; (ii) the final morphological structures are very sensitive to the four initial parameters, especially to the initial density and the inclination; (iii) the previously defined ionizing radiation penetration depth can still be used as a good indicator of the final morphology. Based on the simulation results, the formation time-scales and masses of the early RDI-triggered star formation from clouds of different initial conditions are also estimated. Finally a unified mechanism for the various morphological structures found in many different H II boundaries is suggested. [ABSTRACT FROM AUTHOR]

A systematic investigation on the evolution of a prolate cloud at an HII boundary is conducted using smoothed particle hydrodynamics in order to understand the mechanism for a variety of irregular morphological structures found at the boundaries of various HII regions. The prolate molecular clouds in this investigation are set with their semimajor axes at inclinations between 0° and 90° to a plane-parallel ionizing radiation flux. A set of four parameters, the number density n, the ratio of major to minor axis γ , the inclination angle φ and the incident flux FEUV, are used to define the initial state of the simulated clouds. The dependence of the evolution of a prolate cloud under radiation-driven implosion (RDI) on each of the four parameters is investigated. It is found that (i) in addition to the well-studied standard type A, B or C bright-rimmed clouds (BRCs), many other types such as asymmetrical BRCs, filamentary structures and irregular horse-head structures could also be developed at HII boundaries with only simple initial conditions; (ii) the final morphological structures are very sensitive to the four initial parameters, especially to the initial density and the inclination; (iii) the previously defined ionizing radiation penetration depth can still be used as a good indicator of the final morphology. Based on the simulation results, the formation time-scales and masses of the early RDI-triggered star formation from clouds of different initial conditions are also estimated. Finally a unified mechanism for the various morphological structures found in many different HII boundaries is suggested. [ABSTRACT FROM AUTHOR]

We present the result of a deep near-infrared survey of the newly identified X-ray luminous cluster of galaxies CIZA J1324.7-5736 in the Great Attractor (GA) region. In a 35 × 35 arcmin2 region, 111 galaxy candidates with are identified. Comparison of the extinction-corrected -band luminosity function of CIZA J1324.7-5736 with those of nearby clusters indicates that the richness class of CIZA J1324.7-5736 is almost the same as, or richer than, the Pavo, Centaurus and Hydra clusters but poorer than the Coma, Perseus and Norma clusters. CIZA J1324.7-5736 is possibly the second richest cluster in the GA region following the Norma cluster. The position of CIZA J1324.7-5736 [in the ( l, b, v) space] is close to the Centaurus–Crux cluster and the agglomeration of galaxies detected by the Parkes H i survey. CIZA J1324.7-5736, together with the Centaurus–Crux cluster and the H i galaxy agglomeration, is most likely to be one of the richest local concentrations in the GA overdensity of galaxies. [ABSTRACT FROM AUTHOR]

We present the results of a deep near-infrared survey of aregion centred on the giant elliptical radio galaxy PKS 1343–601, suggested to be the core of an unknown rich cluster located at the low Galactic latitude ofin the Great Attractor (GA) region. 19 obvious galaxies and 38 galaxy candidates have been detected; only three of them were previously identified as a galaxy. The total Galactic extinctionAK towards our survey area is estimated to be 0.6–0.8 mag from theJ− Kcolour of foreground giants. This is systematically lower by about 0.4 mag thanAK taken from the IRAS/DIRBE extinction map. The number density of galaxies brighter than an extinction-correctedKsband magnitude of 13 is 42 galaxies deg−2, five times as high as the overall average in the GA region. However, the number of galaxies within the central 270-kpc radius is less than that of the Norma, Pavo and Centaurus clusters in the GA region. We found no evidence that a rich cluster is associated with PKS 1343–601. [ABSTRACT FROM AUTHOR]

• Archean atmospheric xenon can be retained within kerogens. • New Xe-derived model ages are lower than expected from the age of the host rocks. • Trapped Xe may have been mixed with Xe from younger generations of organics. • Xe isotopes provide a non unequivocal tool for testing the syngenecity of kerogens. • Future investigation of the mechanisms for noble gas mobility in organics is required. Insoluble organic materials (kerogens) isolated from ancient sedimentary rocks provide unique insights into the evolution of early life. However, establishing whether these kerogens are indeed syngenetic with the deposition of associated sedimentary host rocks, or contain contribution from episodes of secondary deposition, is not straightforward. Novel geochemical criterions are therefore required to test the syngenetic origin of Archean organic materials. On the one hand, the occurrence of mass-independent fractionation of sulphur isotopes (MIF-S) provides a tool to test the Archean origin of ancient sedimentary rocks. Determining the isotope composition of sulphur within kerogens whilst limiting the contribution from associated minerals (e.g., nano-pyrites) is however challenging. On the other hand, the Xe isotope composition of the Archean atmosphere has been shown to present enrichments in the light isotopes relative to its modern composition, together with a mono-isotopic deficit in 129Xe. Given that the isotopic composition of atmospheric Xe evolved through time by mass dependent fractionation (MDF) until ~2.5 to 2.0 Ga, the degree of MDF of Xe isotopes trapped in kerogens could provide a time stamp for the last chemical equilibration between organic matter and the atmosphere. However, the extent to which geological processes could affect the signature of Xe trapped in ancient kerogen remains unclear. In this contribution, we present new Ar, Kr and Xe isotopic data for four kerogens isolated from 3.4 to 1.8 Gy-old cherts and confirm that Xe isotopes from the Archean atmosphere can be retained within kerogens. However, new Xe-derived model ages are lower than expected from the ages of host rocks, indicating that initially trapped Xe components were at least partially lost and/or mixed together with some Xe carried out by younger generations of organic materials, therefore complicating the Xe-based dating method. Whilst non-null Δ33S values and 129Xe deficits relative to modern atmosphere constitute reliable imprints from the Archean atmosphere, using Xe isotopes to provide information on the syngenetic origin of ancient organic matter appears to be a promising – but not unequivocal – tool that calls for further analytical development. [ABSTRACT FROM AUTHOR]