407 research outputs found
Possibility of Concentration of Non-volatile Species near the Surface of Comet 67P/Churyumov-Gerasimenko
The cometary materials are thought to be the reservoir of primitive materials
in the Solar System. The recent detection of glycine and CHNH by the
ROSINA mass spectrometer in the coma of 67P/Churyumov-Gerasimenko suggests that
amino acids and their precursors may have been formed in an early evolutionary
phase of the Solar System. We investigate the evolution of cometary interior
considering the evaporation process of water followed by the concentration of
non-volatile species. We develop a Simplified Cometary Concentration Model
(SCCM) to simulate the evaporation and concentration processes on the cometary
surface.We use 67P/Churyumov-Gerasimenko as the benchmark of SCCM. We
investigate the depth of the layer where non-volatile species concentrate after
the numerous passages of perihelion after the formation of the Solar System. As
a result, the SCCM explains the observed production rates of water and
CHNH at 100 comet years. SCCM results suggest that the non-volatile
species would concentrate at depths between 0 and 100cm of comet surface within
10 comet years. Our results also suggest that the non-volatile species would
concentrate several meters beneath the surface before it hit the early Earth.
This specific mass of non-volatile species may provide unique chemical
condition to the volcanic hot spring pools.Comment: accepted to A&
Trans-complemented hepatitis C virus particles as a versatile tool for study of virus assembly and infection
AbstractIn this study, we compared the entry processes of trans-complemented hepatitis C virus particles (HCVtcp), cell culture-produced HCV (HCVcc) and HCV pseudoparticles (HCVpp). Anti-CD81 antibody reduced the entry of HCVtcp and HCVcc to almost background levels, and that of HCVpp by approximately 50%. Apolipoprotein E-dependent infection was observed with HCVtcp and HCVcc, but not with HCVpp, suggesting that the HCVtcp system is more relevant as a model of HCV infection than HCVpp. We improved the productivity of HCVtcp by introducing adapted mutations and by deleting sequences not required for replication from the subgenomic replicon construct. Furthermore, blind passage of the HCVtcp in packaging cells resulted in a novel mutation in the NS3 region, N1586D, which contributed to assembly of infectious virus. These results demonstrate that our plasmid-based system for efficient production of HCVtcp is beneficial for studying HCV life cycles, particularly in viral assembly and infection
Simulations of Surface X-ray Diffraction from a Monolayer 4He Film Adsorbed on Graphite
We carried out simulations of crystal truncation rod (CTR) scatterings, i.e.,
one of the surface X-ray diffraction techniques with atomic resolution, from a
monolayer He film adsorbed on graphite. Our simulations reveal that the 00L rod
scatterings from the He monolayer exhibit notable intensity modifications for
those from a graphite surface in the ranges of approximately L = 0.6 - 1.7 and
L = 2.2 - 3.5. The height of the He monolayer from the graphite surface largely
affects the CTR scattering profiles, indicating that CTR scatterings have
enough sensitivities to determine the surface structure of the various phases
in the He layer. In particular, in the incommensurate solid phase, our
preliminary experimental data show the intensity modulations that are expected
from the present simulations.Comment: 6 pages, 4 figures, to be published in JPS Conf. Pro
Comparative transcriptomic characterization of aluminum, sodium chloride, cadmium and copper rhizotoxicities in Arabidopsis thaliana
Abstract Background Rhizotoxic ions in problem soils inhibit nutrient and water acquisition by roots, which in turn leads to reduced crop yields. Previous studies on the effects of rhizotoxic ions on root growth and physiological functions suggested that some mechanisms were common to all rhizotoxins, while others were more specific. To understand this complex system, we performed comparative transcriptomic analysis with various rhizotoxic ions, followed by bioinformatics analysis, in the model plant Arabidopsis thaliana. Results Roots of Arabidopsis were treated with the major rhizotoxic stressors, aluminum (Al) ions, cadmium (Cd) ions, copper (Cu) ions and sodium (NaCl) chloride, and the gene expression responses were analyzed by DNA array technology. The top 2.5% of genes whose expression was most increased by each stressor were compared with identify common and specific gene expression responses induced by these stressors. A number of genes encoding glutathione-S-transferases, peroxidases, Ca-binding proteins and a trehalose-synthesizing enzyme were induced by all stressors. In contrast, gene ontological categorization identified sets of genes uniquely induced by each stressor, with distinct patterns of biological processes and molecular function. These contained known resistance genes for each stressor, such as AtALMT1 (encoding Al-activated malate transporter) in the Al-specific group and DREB (encoding dehydration responsive element binding protein) in the NaCl-specific group. These gene groups are likely to reflect the common and differential cellular responses and the induction of defense systems in response to each ion. We also identified co-expressed gene groups specific to rhizotoxic ions, which might aid further detailed investigation of the response mechanisms. Conclusion In order to understand the complex responses of roots to rhizotoxic ions, we performed comparative transcriptomic analysis followed by bioinformatics characterization. Our analyses revealed that both general and specific genes were induced in Arabidopsis roots exposed to various rhizotoxic ions. Several defense systems, such as the production of reactive oxygen species and disturbance of Ca homeostasis, were triggered by all stressors, while specific defense genes were also induced by individual stressors. Similar studies in different plant species could help to clarify the resistance mechanisms at the molecular level to provide information that can be utilized for marker-assisted selection.</p
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