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  • 1
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    Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions (2017)
    Royal Society
    Details
    Publication Date: 2017-02-10
    Description: If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of the sun based on the orientation of the two observed brushes. This method has been suggested to have been used on the open sea by Viking navigators to determine the position of the invisible sun occluded by cloud or fog. Furthermore, Haidinger's brushes can also be used to locate the sun when it is below the horizon or occluded by objects on the horizon. To determine the position of the sun using the celestial polarization pattern, the d of the portion of the sky used must be greater than the viewer's degree of polarization threshold d * for perception of Haidinger's brushes. We studied under which sky conditions the prerequisite d 〉 d * is satisfied. Using full-sky imaging polarimetry, we measured the d -pattern of skylight in the blue (450 nm) spectral range for 1296 different meteorological conditions with different solar elevation angles and per cent cloud cover . From the measured d -patterns of a given sky we determined the proportion P of the sky for which d 〉 d *. We obtained that P is the largest at low solar elevations 0° and under totally or nearly clear skies with cloud coverage = 0%, when the sun's position is already easily determined. If the sun is below the horizon (–5° ≤ 〈 0°) during twilight, P = 76.17 ± 4.18% for dmin * =23% under clear sky conditions. Consequently, the sky-polarimetric Viking navigation based on Haidinger's brushes is most useful after sunset and prior to sunrise, when the sun is not visible and large sky regions are bright, clear and polarized enough for perception of Haidinger's brushes.
    Keywords: atmospheric science, meteorology, optics
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 2
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    Heterogeneity of carbon loss and its temperature sensitivity in East-European subarctic tundra soils (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-07
    Description: Arctic peatlands store large stocks of organic carbon which are vulnerable to the climate change but their fate is uncertain. There is increasing evidence that a part of it will be lost as a result of faster microbial mineralization. We studied the vulnerability of 3500–5900 years old bare peat uplifted from permafrost layers by cryogenic processes to the surface of an arctic peat plateau. We aimed to find biotic and abiotic drivers of C LOSS from old peat and compare them with those of adjacent, young vegetated soils of the peat plateau and mineral tundra. The soils were incubated in laboratory at three temperatures (4°C, 12°C and 20°C) and two oxygen levels (aerobic, anaerobic). C LOSS was monitored and soil parameters (organic carbon quality, nutrient availability, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools) were determined. We found that C LOSS from the old peat was constrained by low microbial biomass representing only 0.22% of organic carbon. C LOSS was only slightly reduced by the absence of oxygen and exponentially increased with temperature, showing the same temperature sensitivity under both aerobic and anaerobic conditions. We conclude that carbon in the old bare peat is stabilized by a combination of physical, chemical and biological controls including soil compaction, organic carbon quality, low microbial biomass and the absence of plants.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    Mechanism of ribosomal peptide bond formation (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-02-24
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barta, A -- Dorner, S -- Polacek, N -- New York, N.Y. -- Science. 2001 Jan 12;291(5502):203.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Medical Biochemistry, University of Vienna, Dr. Bohrgasse 9/3, A-1030, Vienna, Austria.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11209070" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine/chemistry/*metabolism ; Catalysis ; Catalytic Domain ; *Peptide Biosynthesis ; RNA, Ribosomal/chemistry/metabolism ; Ribosomes/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    A chloroplast retrograde signal regulates nuclear alternative splicing (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-04-26
    Description: Light is a source of energy and also a regulator of plant physiological adaptations. We show here that light/dark conditions affect alternative splicing of a subset of Arabidopsis genes preferentially encoding proteins involved in RNA processing. The effect requires functional chloroplasts and is also observed in roots when the communication with the photosynthetic tissues is not interrupted, suggesting that a signaling molecule travels through the plant. Using photosynthetic electron transfer inhibitors with different mechanisms of action, we deduce that the reduced pool of plastoquinones initiates a chloroplast retrograde signaling that regulates nuclear alternative splicing and is necessary for proper plant responses to varying light conditions.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4382720/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4382720/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petrillo, Ezequiel -- Godoy Herz, Micaela A -- Fuchs, Armin -- Reifer, Dominik -- Fuller, John -- Yanovsky, Marcelo J -- Simpson, Craig -- Brown, John W S -- Barta, Andrea -- Kalyna, Maria -- Kornblihtt, Alberto R -- BB/G024979/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- P 26333/Austrian Science Fund FWF/Austria -- Biotechnology and Biological Sciences Research Council/United Kingdom -- New York, N.Y. -- Science. 2014 Apr 25;344(6182):427-30. doi: 10.1126/science.1250322. Epub 2014 Apr 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratorio de Fisiologia y Biologia Molecular, Departamento de Fisiologia, Biologia Molecular y Celular, IFIBYNE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon 2, C1428EHA Buenos Aires, Argentina.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24763593" target="_blank"〉PubMed〈/a〉
    Keywords: *Alternative Splicing ; Arabidopsis/*genetics/metabolism ; Arabidopsis Proteins/genetics/metabolism ; Cell Nucleus/genetics ; Chloroplasts/*metabolism ; Circadian Clocks ; Dibromothymoquinone/pharmacology ; Diuron/pharmacology ; Electron Transport/drug effects ; *Gene Expression Regulation, Plant ; Light ; Models, Biological ; Oxidation-Reduction ; Photosynthesis/drug effects ; Plant Leaves/metabolism ; Plant Roots/metabolism ; Plants, Genetically Modified ; Plastoquinone/*metabolism ; RNA Stability ; RNA, Messenger/genetics/metabolism ; RNA, Plant/genetics/metabolism ; Seedlings/genetics/metabolism ; Signal Transduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
    Electronic Resource
    Electronic Resource
    Ethanol synthesis and loss from flooded roots of Medicago sativa L. and Lotus corniculatus L. (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Field flooding of established alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) for up to 12 d resulted in a significant increase in alcohol dehydrogenase activity (ADH) and an increase in the Km of ADH in both species. Root concentration of ethanol increased throughout the flooding regime in alfalfa roots. No ethanol was detected in any trefoil root samples. Alfalfa plants which had shoots removed 5 d prior to flooding accumulated significantly higher levels of root ethanol and showed flooding injury sooner, indicating a significant effect of shoots on development of flooding injury.Alfalfa and trefoil plants grown in the greenhouse were flooded and ethanol in the transpiration effluent was trapped and measured. Alfalfa transpired measurable quantities of ethanol which peaked just prior to development of shoot injury symptoms. No ethanol was detected in the transpiration effluent from trefoil shoots. Flooded roots of both alfalfa and trefoil excreted ethanol but alfalfa roots synthesized more total ethanol and retained a larger proportion in the roots than did trefoil.While the ethanol accumulation response in alfalfa and trefoil are consistent with the ethanol ‘self-poisoning’ hypothesis of flooding injury, the very small quantities of ethanol found in these roots still raises questions as to its absolute effect in the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11614629
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  • 6
    Electronic Resource
    Electronic Resource
    Supply and partitioning of assimilates to roots of Medicago sativa L. and Lotus corniculatus L. under anoxia (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A current explanation of the mechanism of flooding injury to roots suggests that oxygen deficiency depresses the supply of respirable carbohydrates sufficiently to inhibit fermentation. However, even though it has been shown that phloem transport of assimilate is sharply reduced to anaerobic roots, inhibition of assimilate metabolism has also been suggested to be an important factor. This study examines these hypotheses by relating assimilate supply and metabolic activity in anoxic roots of alfalfa (Medicago sativa L.), a flood-intolerant species, and birdsfoot trefoil (Lotus corniculatus L.), a flood-tolerant plant. Roots were made anoxic (severe O2 deficiency) for 2, 4 or 6 d and shoots were labelled with 14CO2. Assimilate transport to the roots and metabolism to structural components were significantly decreased in both species in response to anoxia. Trefoil exhibited significantly greater 14C incorporation into the residue fraction at 4 d anoxia than did alfalfa, and this was consistent with the greater flooding tolerance of trefoil. When assimilate supply to O2-deficient roots was decreased by shoot shading, shoot fresh weight was reduced by both anoxia and light treatments. Root-soluble sugars were significantly decreased by shading but were greatly increased in response to anoxia. Root starch concentration also increased under anoxia. Root K+ concentration was reduced by anoxia only. The energy status (ATP/ADP) of roots was significantly decreased by shading; however, anoxia reduced the energy status only in unshaded plants. The data indicate that carbohydrate supply to anaerobic roots does not appear to be a limiting factor in the metabolic response of alfalfa roots. Alternatively, metabolism of assimilate in anoxic roots may be an important determinant of survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11602103
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  • 7
    Electronic Resource
    Electronic Resource
    Photoaffinity labelling of 23 S RNA at the donor-site of the Escherichia coli ribosome
    Amsterdam : Elsevier
    FEBS Letters 56 (1975), S. 170-174 
    Details
    ISSN: 0014-5793
    Keywords: BP-Phe-tRNA ; p-benzophenone-propionylphenylalanyl-transfer ribonucleic acid.
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(75)80134-7
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  • 8
    Electronic Resource
    Electronic Resource
    Integrated analytical scheme for the development of an atactic polypropylene-based olefin-polymer producing technology
    Amsterdam : Elsevier
    Journal of Chromatography A 241 (1982), S. 121-128 
    Details
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0021-9673(00)82396-1
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  • 9
    Electronic Resource
    Electronic Resource
    Part of the 23S RNA located in the 11S RNA fragment is a constituent of the ribosomal peptidyltransferase centre
    Amsterdam : Elsevier
    FEBS Letters 163 (1983), S. 319-323 
    Details
    ISSN: 0014-5793
    Keywords: 23S RNA ; Benzophenone derivative ; Cross-link ; E. coli ribosome ; Peptidyltransferase ; Photoaffinity labelling
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(83)80844-8
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  • 10
    Electronic Resource
    Electronic Resource
    Transport and Distribution of 14CO2 Assimilate in Lolium perenne in Response to Varying Nitrogen Supply to Halves of a Divided Root System (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 38 (1976), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The movement of 14C assimilate from shoots to roots and its subsequent metabolism in the root of Lolium perenne L. was studied using variable N nutrition supplied to halves of a divided root system. Half of the N-deficient root system was supplied with either high NO3-N or high NH4-N for 16 hours or 6 days before 14CO2 labeling of the shoots.The distribution of 14C in sugars, ethanol-soluble nitrogen and organic acids in roots appeared to be related to the N content of the tissue. Supply of high NO3-N for 6 days resulted in significant internal translocation of N into the low N supplied root half. Both root halves also had similar patterns of 14C distribution among soluble and insoluble metabolites. However, NH4-N supply for 6 days did not result in a significant increase of N in the low N supplied roots, thus only the high NH4-N supplied roots displayed stimulated sugar metabolism, similar to that in both root halves in the high NO3-N supply treatment.Percent transport of 14C assimilates from shoot to root was influenced by form and level of N supplied to root halves. Root halves supplied with either high N source for 6 days accumulated greater amounts of 14C assimilate than the corresponding low N root half. However NH4-N supply appeared to make roots stronger sinks since NH4 supply resulted in significantly greater 14C accumulation in both the high NH4 supplied and the low N root halves than did NO3-N supply in corresponding root halves.The data suggest that factors other than root metabolism, such as N mediated metabolism in the shoot, may also influence the percent transport of assimilates to the root. Internal distribution of the incoming assimilate within the root system could be regulated by the metabolic activity or assimilate demand of the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1976.tb04856.x
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