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  • Space Sciences (General)  (2)
  • Blastomere  (1)
  • Chemical Engineering  (1)
  • 1
    Publication Date: 2019-07-13
    Description: Highly promising locales for biosignature prospecting on Mars are ancient hydrothermal deposits, formed by the interaction of surface water with heat from volcanism or impacts. On Earth, they occur throughout the geological record (to at least approx. 3.5 Ga), preserving robust mineralogical, textural and compositional evidence of thermophilic microbial activity. Hydrothermal systems were likely present early in Mars' history, including at two of the three finalist candidate landing sites for M2020, Columbia Hills and NE Syrtis Major. Hydrothermal environments on Earth's surface are varied, constituting subaerial hot spring aprons, mounds and fumaroles; shallow to deep-sea hydrothermal vents (black and white smokers); and vent mounds and hot-spring discharges in lacustrine and fluvial settings. Biological information can be preserved by rapid, spring-sourced mineral precipitation, but also could be altered or destroyed by postdepositional events. Thus, field observations need to be followed by detailed laboratory analysis to verify potential biosignatures. See Attachment
    Keywords: Space Sciences (General)
    Type: JSC-E-DAA-TN52589 , International Mars Sample Return Conference; Apr 25, 2018 - Apr 27, 2018; Berlin; Germany
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 1097-1102 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper is a sequel to an earlier one on the applicability of classical nucleation theory to second-order transitions in the Ehrenfest sense (1). In each case the approach was to obtain the critical size rc and energy barrier ΔGc for the growth of a nucleus of β-phase in an α-phase matrix by a Maclaurin series expansion of the free-energy-density g = (Gβ - Gα)/vβ as a function of θ (in BC-I) and of ΔP and Δσ in this paper where θ = (T - Tt) is the degree of undercooling and ΔP and Δσ are analogous terms for the hydrostatic pressure shift and tensile stress shift away from the equilibrium transition. The expansion coefficients were determined by the use of thermodynamic relationships. For second-order transitions, rc = 4γvβ Tt/ΔCpθ2, rc = 4γ/Δβ(Δp)2, and rc = 4γ/YαYβ(Δσ)2, respectively, for the three cases. The terms ΔCp, Δβ, and ΔY denote the differences in heat capacity, compressibility, and Young's modulus, e.g., ΔY = Yβ - Yα. The interfacial energy γαβ is denoted by γ. The activation energy barriers for the cases developed in this paper were ΔGc = (16π/3)γ3/(Δβ)2 (Δp)4 and ΔGc = (64π/3)γ3Yα2Yβ2/(ΔY)2(Δσ)4. More complicated expressions are given in the paper for the rc and ΔGc for first-order transitions. In the long run, these expressions may prove more useful than the ones for second-order because of the modifications expressions for the kinetics of transformations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 39 (1994), S. 147-152 
    ISSN: 1040-452X
    Keywords: Mitosis ; Synchronization ; Mice ; Blastomere ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Mouse 2-, 4-, 8-, and 16-cell embryos were exposed to nocodazole in M16 culture medium. The effect of different concentrations and exposure times on the efficiency of cell cycle synchronization and the development of the treated embyros after release from the drug was determined. The minimum effective concentration (95% of arrested nuclei) for 4-, 8-, and 16-cell embryos was 5μM nocodazole. The effect upon subsequent development of mouse embryos depended upon both the stage of development of the embryo at treatment (P 〈 0.001) and the length of exposure to nocodazole (P 〈 0.001). Exposure to any concentration of nocodazole within the range 2.5-10 μM for 12 hr caused a reduction in the proportion of embryos that formed blastocysts. As the period of exposure to 5μM nocodazole increased from 12 to 24 hr, the proportion of embryos developing to the blastocyst stage decreased. The lower proportion of embyros developing to the blastocyst stage and to term (P 〈 0.01) suggests that the more advanced stages were more susceptible to damage as a result of exposure to nocodazole. The rate of development of 4-cell embryos to blastocysts was not affected when an exposure time of 9 hr was used. Together these results show that it is possible to use nocodazole to arrest mouse embryonic cells in mitosis but that it is not appropriate to culture the embryos in the presence of this drug for prolonged periods. Individual blastomeres completed mitosis at 60-90 min and started DNA synthesis at 120-150 min after release from nocodazole. Nuclei from blastomeres thus synchronized were used to conduct studies on the effect of the cell cycle on nuclear transfer. A signficant effect was found. When nuclei from 8-cell embryos in G1 or S-phase were used as nuclei donors, development to blastocyst was respectively 27% and none. ©Wiley-Liss, Inc.
    Additional Material: 6 Tab.
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  • 4
    Publication Date: 2019-07-13
    Description: Seeking the signs of life on Mars is often considered the "first among equal" objectives for any potential Mars Sample Return (MSR) campaign. Among the geological settings considered to have the greatest potential for recording evidence of ancient life or its pre-biotic chemistry on Mars are lacustrine (and marine, if ever present) sedimentary depositional environments. This potential, and the possibility of returning samples that could meaningfully address this objective, have been greatly enhanced by investigations of an ancient redox stratified lake system in Gale crater by the Curiosity rover.
    Keywords: Space Sciences (General)
    Type: JSC-E-DAA-TN52615 , International Mars Sample Return Conference; Apr 25, 2018 - Apr 27, 2018; Berlin; Germany
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