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- Zamora, Juan Carlos, et al.
(författare)
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Considerations and consequences of allowing DNA sequence data as types of fungal taxa
- 2018
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Ingår i: IMA Fungus. - : INT MYCOLOGICAL ASSOC. - 2210-6340 .- 2210-6359. ; 9:1, s. 167-185
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Tidskriftsartikel (refereegranskat)abstract
- Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
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- Fuger, C., et al.
(författare)
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Influence of Ta on the oxidation resistance of WB2-z coatings
- 2021
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 864
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Tidskriftsartikel (refereegranskat)abstract
- Ternary W1-x TaxB2-z is a promising protective coating material possessing enhanced ductile character and phase stability compared to closely related binaries. Here, the oxidation resistance of W1-xTaxB2-z thin films was experimentally investigated at temperatures up to 700 degrees C. Ta alloying in sputter deposited WB2-z coatings led to decelerated oxide scale growth and a changed growth mode from paralinear to a more linear (but retarded) behavior with increasing Ta content. The corresponding rate constants decrease from k(p)* = 6.3.10(-4) mu m(2)/s for WB2-z to k(p)* = 1.1.10(-4) mu m(2)/s for W0.66Ta0.34B2-z as well as k(1) = 2.6.10(-5) mu m/s for TaB2-z, underlined by decreasing scale thicknesses ranging from 1170 nm (WB2-z), over 610 nm (W0.66Ta0.34B2-z) to 320 nm (TaB2-z) after 10 min at 700 degrees C. Dense and adherent scales exhibit an increased tantalum content (columnar oxides), which suppresses the volatile character of tungsten-rich as well as boron oxides, hence being a key-factor for enhanced oxidation resistance. Thus, adding Ta (in the range of x = 0.2-0.3) to a-structured WB2-z does not only positively influence the ductile character and thermal stability but also drastically increases the oxidation resistance.
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- Moraes, V., et al.
(författare)
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Substoichiometry and tantalum dependent thermal stability of alpha-structured W-Ta-B thin films
- 2018
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 155, s. 5-10
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Tidskriftsartikel (refereegranskat)abstract
- Physical vapor deposited (PVD) WB2 thin films crystallize in the alpha-AIB(2)-prototype structure rather than in their thermodynamically stable (omega-W2B5-z-prototype structure. Contrary to the majority of alpha-AlB2-type transition metal diborides (TMB2), alpha-WB2 exhibits a more ductile character. Combining density functional theory and sophisticated experiments, we show that the stability of alpha-WB2 thin films is basically influenced by point defects such as vacancies present in PVD materials. With the help of alpha-TaB2 (one of the most ductile TMB2 with high preference for alpha-AlB2-type), the thermally driven decomposition and phase transformation of alpha-W1-xTaxB2-z to the omega-W2B5-z-type can be shifted to temperatures above 1200 degrees C.
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- Resl, P., et al.
(författare)
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Large differences in carbohydrate degradation and transport potential in the genomes of lichen fungal symbionts
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Lichen symbioses are thought to be stabilized by the transfer of fixed carbon from a photosynthesizing symbiont to a fungus. In other fungal symbioses, carbohydrate subsidies correlate with reductions in plant cell wall-degrading enzymes, but whether this is true of lichen fungal symbionts (LFSs) is unknown. Here, we predict genes encoding carbohydrate-active enzymes (CAZymes) and sugar transporters in 46 genomes from the Lecanoromycetes, the largest extant clade of LFSs. All LFSs possess a robust CAZyme arsenal including enzymes acting on cellulose and hemicellulose, confirmed by experimental assays. However, the number of genes and predicted functions of CAZymes vary widely, with some fungal symbionts possessing arsenals on par with well-known saprotrophic fungi. These results suggest that stable fungal association with a phototroph does not in itself result in fungal CAZyme loss, and lends support to long-standing hypotheses that some lichens may augment fixed CO2 with carbon from external sources.
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- Hahn, R., et al.
(författare)
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Unraveling the superlattice effect for hexagonal transition metal diboride coatings
- 2023
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Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- Superlattice structures enable the simultaneous enhancement in hardness (H) and fracture toughness (KIC) of ceramic-like coatings. While a deeper understanding of this effect has been gained for fcc-structured transition metal nitrides (TMN), hardly any knowledge is available for hexagonal diborides (TMB2). Here we show that superlattices can-similarly to nitrides-increase the hardness and toughness of diboride films. For this purpose, we deposited TiB2/WB2 and TiB2/ZrB2 superlattices with different bilayer periods (?) by non-reactive sputtering. Nanoindentation and in-situ microcantilever bending tests yield a distinct H peak for the TiB2/WB2 system (45.5 & PLUSMN; 1.3 GPa for ? = 6 nm) but no increase in KIC related to a difference in shear moduli (112 GPa). Contrary, the TiB2/ZrB2 system shows no peak in H, but for KIC with 3.70 & PLUSMN; 0.26 MPa & BULL;m1/2 at ? = 4 nm originating from differences in lattice spacing (0.14 & ANGS;), hence causing coherent stresses retarding crack growth.
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