| 1. |
- Fortuna, E., et al.
(author)
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Plasma-induced damage of tungsten coatings on graphite limiters
- 2007
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In: Physica Scripta. - 0031-8949 .- 1402-4896. ; T128, s. 162-165
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Journal article (peer-reviewed)abstract
- Vaccum plasma sprayed tungsten coatings with an evaporated sandwich Re - W interlayer on graphite limiter blocks were studied after the experimental campaign in the TEXTOR tokamak. The coating morphology was modified by high-heat loads and co-deposition of species from the plasma. Co-deposits contained fuel species, carbon, boron and silicon. X-ray diffractometer phase analysis indicated the coexistence of metallic tungsten and its carbides (WC and W2C) and boride (W2B). In the Re - W layer the presence of carbon was detected in a several micrometres thick zone. In the overheated part of the limiter, the Re - W layer was transformed into a sigma phase.
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| 2. |
- Fortuna, E., et al.
(author)
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Properties of co-deposited layers on graphite high heat flux components at the TEXTOR tokamak
- 2007
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In: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 367:B, s. 1507-1511
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Journal article (peer-reviewed)abstract
- The objective of this work was to examine the structure, composition and properties of co-deposited films from the TEXTOR tokamak. Hydrogenated films formed on the toroidal belt pump limiter (ALT-II), and on the ICRF antenna grill were studied using a set of material analysis techniques. Plasma edge diagnostics were used to assess the parameters influencing the film formation during discharges auxiliary heated by ICRF. The essential results are summarized as follows: (i) the distribution of plasma impurities co-deposited in the films is non-uniform and (ii) the surface topography, crystallographic structure, fuel retention and composition (i.e., content of re-deposited plasma impurities) of the films show significant diversity depending on the location where they were formed. These differences are associated with the local geometry, the tokamak operation scenarios and the resulting plasma edge properties.
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| 3. |
- Ivanov, A G, et al.
(author)
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Iron stress restricts photosynthetic intersystem electron transport in Synechococcus sp, PCC 7942
- 2000
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In: FEBS Letters. - 0014-5793 .- 1873-3468. ; 485:2-3, s. 173-177
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Journal article (peer-reviewed)abstract
- Although exposure of Synechococcus sp. PCC 7942 to iron stress induced the accumulation of the isiA gene product (CP43') compared with non-stressed controls, immunodetection of the N-terminus of cytochrome (Cyt) f indicated that iron stress not only reduced the content of the 40 kDa, heme-binding, Cyt f polypeptide by 32% but it also specifically induced the accumulation of a new, 23 kDa, non-heme-binding, putative Cyt f polypeptide, Concomitantly, iron stress restricted intersystem electron transport based on the in vivo reduction of P700(+), monitored as DeltaA(820)/A(820) in the presence and absence of electron transport inhibitors, as well as the inhibition of the Emerson enhancement effect on O-2 evolution. However, iron stress appeared to be associated with enhanced rates of PS I cyclic electron transport, low rates of PS I-driven photoreduction of NADP(+) but comparable rates for PS II+PS I photoreduction of NADP(+) relative to controls. We hypothesize that Synechococcus sp, PCC 7942 exhibits a dynamic capacity to uncouple PS II and PS I electron transport, which may allow for the higher than expected growth rates observed during iron stress. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.
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| 4. |
- Miskiewicz, E, et al.
(author)
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Photosynthetic acclimation of the Filamentous Cyanobacterium Plectonema boryanum UTEX 485 to Temperature and Light.
- 2000
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In: Plant and Cell Physiology. - 0032-0781 .- 1471-9053. ; 41:6, s. 767-775
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Journal article (peer-reviewed)abstract
- Photosynthetic acclimation to temperature and irradiance was studied in the filamentous, non-heterocystous cyanobacterium Plectonema boryanum UTEX 485. Growth rates of this cyanobacterium measured at ambient CO2 were primarily influenced by temperature with minimal effects of irradiance. Both growth temperature and irradiance affected linolenic (18:3) and linoleic acid (18:2) levels in the four major lipid classes in an independent but additive manner. In contrast, photosynthetic acclimation was not due to either growth temperature or irradiance per se, but rather, due to the interaction of these environmental factors. P. boryanum grown at low temperature and moderate irradiance mimicked cells grown at high light. Compared to cells grown at either 29°C/150 μmol m-2 s-1 (29/150) or 15/10, P. boryanum grown at either 15/150 or 29/750 exhibited: (1) reduced cellular levels of Chl a and phycobilisomes (PBS), and concomitantly higher content of an orange-red carotenoid, myxoxanthophyll; (2) higher light saturated rates (Pmax) when expressed on a Chl a basis but lower apparent quantum yields of oxygen evolution and (3) enhanced resistance to high light stress. P. boryanum grown at 15/150 regained normal blue-green pigmentation within 16 h after a temperature shift to 29°C at a constant irradiance of 150 μmol m-2 s-1. DBMIB and KCN but not DCMU and atrazine partially inhibited the change in myxoxanthophyll/Chl a ratio following the shift from 15 to 29°C. We conclude that P boryanum responds to either varying growth temperature or varying growth irradiance by adjusting the ability to absorb light through decreasing the cellular contents of Chl a and light-harvesting pigments and screening of excessive light by myxoxanthophyll predominantly localized in the cell wall/cell membrane to protect PSII from over-excitation. The possible role of redox sensing/signalling for photosynthetic acclimation of cyanobacteria to either temperature or irradiance is discussed.
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