| 1. |
- Broberg, Martin, et al.
(författare)
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Comparative genomics highlights the importance of drug efflux transporters during evolution of mycoparasitism in Clonostachys subgenus Bionectria (Fungi, Ascomycota, Hypocreales)
- 2021
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Ingår i: Evolutionary applications. - : Wiley. - 1752-4571. ; 14, s. 476-497
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Tidskriftsartikel (refereegranskat)abstract
- Various strains of the mycoparasitic fungal speciesClonostachys roseaare used commercially as biological control agents for the control of fungal plant diseases in agricultural crop production. Further improvements of the use and efficacy ofC. roseain biocontrol require a mechanistic understanding of the factors that determines the outcome of the interaction betweenC. roseaand plant pathogenic fungi. Here, we determined the genome sequences of 11Clonostachysstrains, representing five species inClonostachyssubgenusBionectria, and performed a comparative genomic analysis with the aim to identify gene families evolving under selection for gene gains or losses. Several gene families predicted to encode proteins involved in biosynthesis of secondary metabolites, including polyketide synthases, nonribosomal peptide syntethases and cytochrome P450s, evolved under selection for gene gains (p <= .05) in theBionectriasubgenus lineage. This was accompanied with gene copy number increases (p <= .05) in ATP-binding cassette (ABC) transporters and major facilitator superfamily (MFS) transporters predicted to contribute to drug efflux. MostClonostachysspecies were also characterized by high numbers of auxiliary activity (AA) family 9 lytic polysaccharide monooxygenases, AA3 glucose-methanol-choline oxidoreductases and additional carbohydrate-active enzyme gene families with putative activity (or binding) towards xylan and rhamnose/pectin substrates. Particular features of theC. roseagenome included expansions (p <= .05) of the ABC-B4 multidrug resistance transporters, the ABC-C5 multidrug resistance-related transporters and the 2.A.1.3 drug:H + antiporter-2 MFS drug resistance transporters. The ABC-G1 pleiotropic drug resistance transporter geneabcG6inC. roseawas induced (p <= .009) by exposure to the antifungalFusariummycotoxin zearalenone (1121-fold) and various fungicides. Deletion ofabcG6resulted in mutants with reduced (p < .001) growth rates on media containing the fungicides boscalid, fenhexamid and iprodione. Our results emphasize the role of biosynthesis of, and protection against, secondary metabolites inClonostachyssubgenusBionectria.
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| 2. |
- Agarwal, PK, et al.
(författare)
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Box-trees and R-trees with near-optimal query time
- 2002
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Ingår i: Discrete & Computational Geometry. - : Springer Science and Business Media LLC. - 0179-5376 .- 1432-0444. ; 28:3, s. 291-312
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Tidskriftsartikel (refereegranskat)abstract
- A box-tree is a bounding-volume hierarchy that uses axis-aligned boxes as bounding volumes. The query complexity of a box-tree with respect to a given type of query is the maximum number of nodes visited when answering such a query. We describe several new algorithms for constructing box-trees with small worst-case query complexity with respect to queries with axis-parallel boxes and with points. We also prove lower bounds on the Worst-case query complexity for box-trees, which show that our results are optimal or close to optimal. Finally, we present algorithms to convert box-trees to R-trees, resulting in R-trees with (almost) optimal query complexity.
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| 3. |
- Alerstam, Thomas, et al.
(författare)
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A polar system of intercontinental bird migration
- 2007
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 274:1625, s. 2523-2530
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Tidskriftsartikel (refereegranskat)abstract
- Studies of birdmigration in the Beringia region of Alaska and eastern Siberia are of special interest for revealing the importance of bird migration between Eurasia and North America, for evaluating orientation principles used by the birds at polar latitudes and for understanding the evolutionary implications of intercontinental migratory connectivity among birds as well as their parasites. We used tracking radar placed onboard the ice-breaker Oden to register bird migratory flights from 30 July to 19 August 2005 and we encountered extensive birdmigration in the whole Beringia range from latitude 64 degrees N in Bering Strait up to latitude 75 degrees N far north of Wrangel Island, with eastward flights making up 79% of all track directions. The results from Beringia were used in combination with radar studies from the Arctic Ocean north of Siberia and in the Beaufort Sea to make a reconstruction of a major Siberian-American birdmigration system in a wide Arctic sector between longitudes 1108 E and 130 degrees W, spanning one-third of the entire circumpolar circle. This system was estimated to involve more than 2 million birds, mainly shorebirds, terns and skuas, flying across the Arctic Ocean at mean altitudes exceeding 1 km (maximum altitudes 3-5 km). Great circle orientation provided a significantly better fit with observed flight directions at 20 different sites and areas than constant geographical compass orientation. The long flights over the sea spanned 40-80 degrees of longitude, corresponding to distances and durations of 1400-2600 km and 26-48 hours, respectively. The birds continued from this eastward migration system over the Arctic Ocean into several different flyway systems at the American continents and the Pacific Ocean. Minimization of distances between tundra breeding sectors and northerly stopover sites, in combination with the Beringia glacial refugium and colonization history, seemed to be important for the evolution of this major polar bird migration system.
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| 4. |
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| 5. |
- Alerstam, Thomas, et al.
(författare)
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Great-Circle Migration Of Arctic Passerines
- 2008
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Ingår i: The Auk. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 125:4, s. 831-838
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Tidskriftsartikel (refereegranskat)abstract
- Birds can save distance and time on their migratory journeys by following great circles rather than rhumblines, but great-circle routes require more complex orientation with changing courses. Flight directions at different places along the route and in relation to the destination can be used to test whether birds migrate along great circles or rhumblines. Such data have indicated great-circle migration among shorebirds at high latitudes, but no critical tests have been made for passerines. Using tracking radar on board the icebreaker Oden in August 2005, we recorded westerly flight directions of passerine migrants over the Chukchi Sea. The main sector of migratory directions was 237-311 degrees centered oil a mean heading direction of 274 degrees. The most likely species to participate in this westward trans-Beringia migration, mainly departing from Alaska, were Eastern Yellow Wagtail (Motacilla Ischutschensis), Arctic Warbler (Phylloscopus borealis kennicotti), Northern Wheatear (Oenanthe oenanthe), and Bluethroat (Luscinia svecica); all except the Bluethroat were recorded from the ship. Observed flight directions agreed with predicted great-circle courses but not with rhumbline courses for three of these four species with winter quarters in Southeast Asia; no definite conclusion could be drawn for the Northern Wheatear (wintering in East Africa). These results support great-circle migration among passerines traveling between Alaska and Old World winter quarters, though the long-distance precision and orientation mechanisms are Still unknown. The relative importance of different evolutionary causes-such as circumvention of geographic barriers, retracing of ancient colonization ways, or distance reduction by great-circle migration-to complex bird migration routes with changing courses remains to be understood. Received 24 August 2007, accepted 6 March 2008.
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| 6. |
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| 7. |
- Bohgard, Mats, et al.
(författare)
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Pedagogisk förändring av arbetsvetenskapskurser i några olika utbildningsprogram vid LTH
- 2003
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Ingår i: Pedagogisk inspirationskonferens LTH 27 maj 2003. - Lund : Lunds tekniska högskola, Lunds universitet. ; , s. 14-17
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Konferensbidrag (refereegranskat)abstract
- Vi har genomfört genomgripande förändringar i obligatoriska grundkurser i arbetsvetenskap. Förändringarna har genomförts som en utvecklingsprocess i vilken samtliga lärare som deltagit i kurserna har medverkat. Processen startade med konsulthjälp från Universitetspedagogiskt centrum vid Lunds universitet, fortsatte med kompetensutveckling av oss själva och följdes av några utvecklingsprojekt, varefter från grunden förändrade kurser genomfördes under fyra år. Den nya uppläggningen medförde att vi fick positiva attityder i studentenkäterna när det gällde två av kurserna i årskurs 2 i vilken medodiken genomfördes fullständigt. I en kurs, som gavs i årskurs 1 och i vilken den nya uppläggningen endast delvis genomfördes blev studentattityderna negativa.
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| 8. |
- Dubey, Mukesh, et al.
(författare)
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Evolution and functional characterization of pectate lyase PEL12, a member of a highly expanded Clonostachys rosea polysaccharide lyase 1 family
- 2018
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Ingår i: BMC Microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPectin is one of the major and most complex plant cell wall components that needs to be overcome by microorganisms as part of their strategies for plant invasion or nutrition. Microbial pectinolytic enzymes therefore play a significant role for plant-associated microorganisms and for the decomposition and recycling of plant organic matter. Recently, comparative studies revealed significant gene copy number expansion of the polysaccharide lyase 1 (PL1) pectin/pectate lyase gene family in the Clonostachys rosea genome, while only low numbers were found in Trichoderma species. Both of these fungal genera are widely known for their ability to parasitize and kill other fungi (mycoparasitism) and certain species are thus used for biocontrol of plant pathogenic fungi.ResultsIn order to understand the role of the high number of pectin degrading enzymes in Clonostachys, we studied diversity and evolution of the PL1 gene family in C. rosea compared with other Sordariomycetes with varying nutritional life styles. Out of 17 members of C. rosea PL1, we could only detect two to be secreted at acidic pH. One of them, the pectate lyase pel12 gene was found to be strongly induced by pectin and, to a lower degree, by polygalacturonic acid. Heterologous expression of the PEL12 in a PL1-free background of T. reesei revealed direct enzymatic involvement of this protein in utilization of pectin at pH5 without a requirement for Ca2+. The mutants showed increased utilization of pectin compounds, but did not increase biocontrol ability in detached leaf assay against the plant pathogen Botrytis cinerea compared to the wild type.ConclusionsIn this study, we aimed to gain insight into diversity and evolution of the PL1 gene family in C. rosea and other Sordariomycete species in relation to their nutritional modes. We show that C. rosea PL1 expansion does not correlate with its mycoparasitic nutritional mode and resembles those of strong plant pathogenic fungi. We further investigated regulation, specificity and function of the C. rosea PEL12 and show that this enzyme is directly involved in degradation of pectin and pectin-related compounds, but not in C. rosea biocontrol.
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| 9. |
- Gudmundsson, J, et al.
(författare)
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Higher order Delaunay triangulations
- 2002
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Ingår i: Computational Geometry. - 0925-7721. ; 23:1, s. 85-98
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Tidskriftsartikel (refereegranskat)abstract
- For a set P of points in the plane, we introduce a class of triangulations that is an extension of the Delaunay triangulation. Instead of requiring that for each triangle the circle through its vertices contains no points of P inside, we require that at most k points are inside the circle. Since there are many different higher-order Delaunay triangulations for a point set, other useful criteria for triangulations can be incorporated without sacrificing the well-shapedness too much. Applications include realistic terrain modeling and mesh generation. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 10. |
- Gudmundsson, Mikael, et al.
(författare)
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Kinetic and molecular dynamics study of inhibition and transglycosylation in Hypocrea jecorina family 3 beta-glucosidases
- 2019
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294, s. 3169-3180
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Tidskriftsartikel (refereegranskat)abstract
- -Glucosidases enhance enzymatic biomass conversion by relieving cellobiose inhibition of endoglucanases and cellobiohydrolases. However, the susceptibility of these enzymes to inhibition and transglycosylation at high glucose or cellobiose concentrations severely limits their activity and, consequently, the overall efficiency of enzyme mixtures. We determined the impact of these two processes on the hydrolytic activity of the industrially relevant family 3 -glucosidases from Hypocrea jecorina, HjCel3A and HjCel3B, and investigated the underlying molecular mechanisms through kinetic studies, binding free energy calculations, and molecular dynamics (MD) simulations. HjCel3B had a 7-fold higher specificity for cellobiose than HjCel3A but greater tendency for glucose inhibition. Energy decomposition analysis indicated that cellobiose has relatively weak electrostatic interactions with binding site residues, allowing it to be easily displaced by glucose and free to inhibit other hydrolytic enzymes. HjCel3A is, thus, preferable as an industrial -glucosidase despite its lower activity caused by transglycosylation. This competing pathway to hydrolysis arises from binding of glucose or cellobiose at the product site after formation of the glycosyl-enzyme intermediate. MD simulations revealed that binding is facilitated by hydrophobic interactions with Trp-37, Phe-260, and Tyr-443. Targeting these aromatic residues for mutation to reduce substrate affinity at the product site would therefore potentially mitigate transglycosidic activity. Engineering improved variants of HjCel3A and other structurally similar -glucosidases would have a significant economic effect on enzymatic biomass conversion in terms of yield and production cost as the process can be consequently conducted at higher substrate loadings.
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| 11. |
- Gudmundsson, Mikael, et al.
(författare)
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Structural and Electronic Snapshots during the Transition from a Cu(II) to Cu(I) Metal Center of a Lytic Polysaccharide Monooxygenase by X-ray Photoreduction
- 2014
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 289, s. 18782-18792
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Tidskriftsartikel (refereegranskat)abstract
- Lytic polysaccharide monooxygenases (LPMOs) are a recently discovered class of enzymes that employ a copper-mediated, oxidative mechanism to cleave glycosidic bonds. The LPMO catalytic mechanism likely requires that molecular oxygen first binds to Cu(I), but the oxidation state in many reported LPMO structures is ambiguous, and the changes in the LPMO active site required to accommodate both oxidation states of copper have not been fully elucidated. Here, a diffraction data collection strategy minimizing the deposited x-ray dose was used to solve the crystal structure of a chitin-specific LPMO from Enterococcus faecalis (EfaCBM33A) in the Cu(II)-bound form. Subsequently, the crystalline protein was photoreduced in the x-ray beam, which revealed structural changes associated with the conversion from the initial Cu(II)-oxidized form with two coordinated water molecules, which adopts a trigonal bipyramidal geometry, to a reduced Cu(I) form in a T-shaped geometry with no coordinated water molecules. A comprehensive survey of Cu(II) and Cu(I) structures in the Cambridge Structural Database unambiguously shows that the geometries observed in the least and most reduced structures reflect binding of Cu(II) and Cu(I), respectively. Quantum mechanical calculations of the oxidized and reduced active sites reveal little change in the electronic structure of the active site measured by the active site partial charges. Together with a previous theoretical investigation of a fungal LPMO, this suggests significant functional plasticity in LPMO active sites. Overall, this study provides molecular snapshots along the reduction process to activate the LPMO catalytic machinery and provides a general method for solving LPMO structures in both copper oxidation states.
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| 12. |
- Gudmundsson, Mikael, et al.
(författare)
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Structural and functional studies of the glycoside hydrolase family 3 beta-glucosidase Cel3A from the moderately thermophilic fungus Rasamsonia emersonii
- 2016
-
Ingår i: Acta Crystallographica Section D. - 2059-7983. ; 72:7, s. 860-870
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Tidskriftsartikel (refereegranskat)abstract
- The filamentous fungus Hypocrea jecorina produces a number of cellulases and hemicellulases that act in a concerted fashion on biomass and degrade it into monomeric or oligomeric sugars. beta-Glucosidases are involved in the last step of the degradation of cellulosic biomass and hydrolyse the beta-glycosidic linkage between two adjacent molecules in dimers and oligomers of glucose. In this study, it is shown that substituting the beta-glucosidase from H. jecorina (HjCel3A) with the beta-glucosidase Cel3A from the thermophilic fungus Rasamsonia emersonii (ReCel3A) in enzyme mixtures results in increased efficiency in the saccharification of lignocellulosic materials. Biochemical characterization of ReCel3A, heterologously produced in H. jecorina, reveals a preference for disaccharide substrates over longer gluco-oligosaccharides. Crystallographic studies of ReCel3A revealed a highly N-glycosylated three-domain dimeric protein, as has been observed previously for glycoside hydrolase family 3 beta-glucosidases. The increased thermal stability and saccharification yield and the superior biochemical characteristics of ReCel3A compared with HjCel3A and mixtures containing HjCel3A make ReCel3A an excellent candidate for addition to enzyme mixtures designed to operate at higher temperatures.
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| 13. |
- Gudmundsson, Mikael
(författare)
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Structure and functional studies of plant cell wall degrading enzymes : glycoside hydrolase family 3 β-glucosidases and lytic polysaccharide monooxygenases
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Presently, plant biomass is considered as one of the major future renewable sources for the production of second-generation biofuels. While the first generation biofuels essentially are based on starch and sucrose rich feed stocks and which production may compete with food production, the second-generation biofuels may be based on lignocellulose as feedstock, which is less problematic from an ethical point of view. The degradation of carbohydrates in plant biomass to fermentable sugars requires the concerted action of several diverse classes of carbohydrate active enzymes (CAZymes) for a total and efficient conversion of the plant biomass. Through a carefully balanced synergism mechanistically different CAZymes are able to degrade the stable and recalcitrant pol- ymers in the plant cell walls, such as cellulose, to soluble and fermentable monosaccharides. It is crucial to study the properties and function of these enzymes if we want to strive for a sustainable production of chemicals and biofuels, as they serve as a reservoir of environmentally friendly molecular tools. The main focus of the research work presented in this thesis is biochemical and structure-function characterizations of two classes of CAZymes: fungal glycoside hydrolase family 3 (GH3) β-glucosidases, and bacterial lytic polysaccharide monooxygenases, often referred to as LPMOs. GH3 β- glucosidases catalyse the conversion of disaccharides, produced by other CAZymes e.g. cellulases, to glucose. H. jecorina Cel3A, R. emersonii Cel3A and N. crassa NcGH3-3 are three industrially relevant fungal GH3 β-glucosidases for which the structures have been determined using X-ray crystallographic methods. The H. jecorina Cel3A, R. em- ersonii Cel3A enzymes has also been characterized biochemically. The LPMOs act in the very initial stage of plant cell wall degradation and cleave glycosidic bonds in crys- talline polysaccharides via an oxidative mechanism, which facilitates access to new chain ends for other CAZymes. To elucidate the structural and biochemical properties of LPMOs with bacterial origin, the structure of an AA10 LPMO the LPMO10A from Enterococcus faecalis was determined using X-ray crystallography. Furthermore, structural changes of the active site metal configuration by so-called X-ray induced photoreduction, were determined. During this reduction process, which mimics the active enzyme, the bound active site copper atom is reduced from Cu(I) to Cu(II), which causes changes in the ligation configuration.
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| 14. |
- Gudmundsson, Mikael, et al.
(författare)
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The dissociation mechanism of processive cellulases
- 2019
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116, s. 23061-23067
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Tidskriftsartikel (refereegranskat)abstract
- Cellulase enzymes deconstruct recalcitrant cellulose into soluble sugars, making them a biocatalyst of biotechnological interest for use in the nascent lignocellulosic bioeconomy. Cellobiohydrolases (CBHs) are cellulases capable of liberating many sugar molecules in a processive manner without dissociating from the substrate. Within the complete processive cycle of CBHs, dissociation from the cellulose substrate is rate limiting, but the molecular mechanism of this step is unknown. Here, we present a direct comparison of potential molecular mechanisms for dissociation via Hamiltonian replica exchange molecular dynamics of the model fungal CBH, Trichoderma reesei Cel7A. Computational rate estimates indicate that stepwise cellulose dethreading from the binding tunnel is 4 orders of magnitude faster than a clamshell mechanism, in which the substrate-enclosing loops open and release the substrate without reversing. We also present the crystal structure of a disulfide variant that covalently links substrate-enclosing loops on either side of the substrate-binding tunnel, which constitutes a CBH that can only dissociate via stepwise dethreading. Biochemical measurements indicate that this variant has a dissociation rate constant essentially equivalent to the wild type, implying that dethreading is likely the predominant mechanism for dissociation.
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| 15. |
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| 16. |
- Gudmundsson, Valur, et al.
(författare)
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Characterization of dopant segregated Schottky barrier source/drain contacts
- 2009
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Ingår i: ULIS 2009. - NEW YORK : IEEE. - 9781424437054 ; , s. 73-76
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Konferensbidrag (refereegranskat)abstract
- In this paper, the gate-voltage dependent source/drain (S/D) resistance (R-SD) in dopant segregated (DS) Schottky barrier (SB) junctions is examined by experiment and simulation. The focus is placed on fully depleted UTB-SOI MOSFETs featuring PtSi S/D with As-DS realized at low temperatures. When modeling SB-S/D with DS, it is challenging to determine if the performance enhancement observed is induced by a highly doped shallow layer in Si or by an interfacial dipole causing SB height lowering. The simulation reveals that the gate-voltage dependence of R-SD is stronger for the dipole effect. For the SB-MOSFETs with DS-S/D examined in this work, the simulation gives an excellent fit to the measured data when SBH lowering is combined with high concentration shallow doping.
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| 17. |
- Gudmundsson, Valur, et al.
(författare)
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Direct measurement of sidewall roughness on Si, poly-Si and poly-SiGe by AFM
- 2008
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Ingår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY. - Bristol : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- In this paper the effect of the commonly used HBr/Cl-2 chemistry for dry etching on the line-edge roughness (LER) of photoresist patterned single crystalline Si (sc-Si), polycrystalline Si (poly-Si) and poly-Si0.2Ge0.8 sidewalls was characterized. Measurements were done by means of atomic force microscopy in combination with an elaborated sample preparation technique that allowed the LER at different depths of the sidewall to be measured. Samples were patterned by I-line lithography and etching was performed at an RF power of 200 W using HBr/Cl-2 (30/10 sccm) plasma. For sc-Si the photoresist and Si sidewalls had an LER of 0.8-1.4 nm and 1.5-2 nm, respectively. For poly-Si and poly-SiGe the photoresist sidewall roughness was, respectively, increased to 1.5-3 nm and 2-3.5 nm due to light scattering from the rough surface of the polycrystalline materials. The poly-Si film had a sidewall roughness of 3-4 nm. Poly-SiGe sidewall exhibited larger roughness with an LER of 5-12 nm which was not transferred from the photoresist. The results show that for sc-Si and poly-Si the sidewall roughness mainly originates from the photoresist process and little additional roughening is caused by the HBr/Cl-2 etching. However, for poly-Si0.2Ge0.8 the LER is considerably increased from that of the photoresist indicating that the HBr/Cl-2 etching is the main contributor to the LER.
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| 18. |
- Gudmundsson, Valur, et al.
(författare)
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Effect of Be segregation on NiSi/Si Schottky barrier heights
- 2011
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Ingår i: Solid-State Device Research Conference (ESSDERC). - 9781457707070 - 9781457707063
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Konferensbidrag (refereegranskat)abstract
- The effect of Be segregation on the Schottky barrier heights (SBH) of NiSi/Si is studied. Many elements have been shown to modulate the SBH of NiSi. However, group II elements have, to our knowledge, not been investigated before. Be is a double acceptor in Si, making it interesting for SBH modulation towards the valence band. The results show that Be implantation did not change the silicidation process. The SBH modulation was found to be strongly dependent on the silicidation temperature, with a minimum barrier to the valence band Φbp=0.28±0.02 eV, for diodes formed at 600 °C. SIMS analysis show the Be dose left at the interface is very low. With such a low dose, modulation cannot be caused by an interface dipole. However, the results can be explained assuming a thin (~4-5 nm) layer of activated Be close to the interface.
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| 19. |
- Gudmundsson, Valur, et al.
(författare)
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Error Propagation in Contact Resistivity Extraction Using Cross-Bridge Kelvin Resistors
- 2012
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 59:6, s. 1585-1591
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Tidskriftsartikel (refereegranskat)abstract
- The cross-bridge Kelvin resistor is a commonly used method for measuring contact resistivity (rho(c)). For low rho(c), the measurement has to be corrected for systematic error using measurements of contact resistance, semiconductor sheet resistance, and device dimensions. However, it is not straightforward to estimate the propagation of random measurement error in the measured quantities on the extracted rho(c). In this paper, a method is presented to quantify the effect of random measurement error on the accuracy of rho(c) extraction. This is accomplished by generalized error propagation curves that show the error in rho(c) caused by random measurement errors. Analysis shows that when the intrinsic resistance of the contact is smaller than the semiconductor sheet resistance, it becomes important to consider random error propagation. Comparison of literature data, where rho(c) < 5.10(-8) Omega.cm(2) has been reported, shows that care should be taken since, even assuming precise electrical data, a 1% error in the measurement of device dimensions can lead to up to similar to 50% error in the estimation of rho(c).
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| 20. |
- Gudmundsson, Valur, et al.
(författare)
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Fully Depleted UTB and Trigate N-Channel MOSFETs Featuring Low-Temperature PtSi Schottky-Barrier Contacts With Dopant Segregation
- 2009
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 30:5, s. 541-543
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Tidskriftsartikel (refereegranskat)abstract
- Schottky-barrier source/drain (SB-S/D) presents a promising solution to reducing parasitic resistance for device architectures such as fully depleted UTB, trigate, or FinFET. In this letter, a low-temperature process (<= 700 degrees C) with PtSi-based S/D is examined for the fabrication of n-type UTB and trigate FETs on SOI substrate (t(si) = 30 nm). Dopant segregation with As was used to achieve the n-type behavior at implantation doses of 1 (.) 10(15) and 5. 10(15) cm(-2). Similar results were found for UTB devices with both doses, but trigate devices with the larger dose exhibited higher on currents and smaller process variation than their lower dose counterparts.
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| 21. |
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| 22. |
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| 23. |
- Gudmundsson, Valur, et al.
(författare)
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Simulation of low Schottky barrier MOSFETs using an improved Multi-subband Monte Carlo model
- 2013
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Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 79, s. 172-178
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple and efficient approach to implement Schottky barrier contacts in a Multi-subband Monte Carlo simulator by using the subband smoothening technique to mimic tunneling at the Schottky junction. In the absence of scattering, simulation results for Schottky barrier MOSFETs are in agreement with ballistic Non-Equilibrium Green's Functions calculations. We then include the most relevant scattering mechanisms, and apply the model to the study of double gate Schottky barrier MOSFETs representative of the ITRS 2015 high performance device. Results show that a Schottky barrier height of less than approximately 0.15 eV is required to outperform the doped source/drain structure.
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| 24. |
- Hedenström, Anders, et al.
(författare)
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Radar Observations of Arctic Bird Migration in the Beringia Region
- 2009
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Ingår i: Arctic. - 0004-0843. ; 62:1, s. 25-37
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Tidskriftsartikel (refereegranskat)abstract
- Bird migration was recorded by tracking radar and visual observations in the Beringia region. The data were subdivided into seven areas extending from north of Wrangel Island southeastward toward the Bering Strait and then northwestward off the coast of Alaska to Point Barrow. The studies, which took place during a ship-based expedition between 30 July and 19 August 2005, recorded a total of 557 tracks (average duration 120 seconds) of bird flocks or individuals on post-breeding migration. The dominant eastward-flying flocks were likely composed of shorebirds on their way from breeding areas in central or eastern Siberia to intermediate stopovers and final destinations in North and South America. The courses were more southerly into the Bering Strait, possibly because of topographical influence. At two areas, the Chukchi Sea and Koluchinskaya Bay, there was also a westward component of migrants. At the Chukchi Sea these were almost certainly passerine birds migrating from Alaska to wintering areas in Asia and Africa, while at Koluchinskaya Bay, king ciders on molt migration could represent an important part of the westward component. The overall mean altitude of flights was 1157 m, and flight altitude was positively correlated with latitude. The mean ground speed was 15.9 m/s and the mean airspeed was 14.1 m/s, indicating that on average the birds were experiencing a small tail wind component. The airspeed was a function of the tail wind component and the vertical speed; altitude and the side wind component did not contribute significantly to variation in airspeed in this data set. Comparing these results with similar data obtained from Siberia and Canada, we concluded that Beringia is a migration hotspot where intense bird migration crosses between Asia and Alaska in both directions.
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| 25. |
- Iqbal, Mudassir, et al.
(författare)
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Comparative evolutionary histories of fungal proteases reveal gene gains in the mycoparasitic and nematode-parasitic fungus Clonostachys rosea
- 2018
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Background: The ascomycete fungus Clonostachys rosea (order Hypocreales) can control several important plant diseases caused by plant pathogenic fungi and nematodes. Subtilisin-like serine proteases are considered to play an important role in pathogenesis in entomopathogenic, mycoparasitic, and nematophagous fungi used for biological control. In this study, we analysed the evolutionary histories of protease gene families, and investigated sequence divergence and regulation of serine protease genes in C. rosea.Results: Proteases of selected hypocrealean fungal species were classified into families based on the MEROPS peptidase database. The highest number of protease genes (590) was found in Fusarium solani, followed by C. rosea with 576 genes. Analysis of gene family evolution identified non-random changes in gene copy numbers in the five serine protease gene families S1A, S8A, S9X, S12 and S33. Four families, S1A, S8A, S9X, and S33, displayed gene gains in C. rosea. A gene-tree / species-tree reconciliation analysis of the S8A family revealed that the gene copy number increase in C. rosea was primarily associated with the S08.054 (proteinase K) subgroup. In addition, regulatory and predicted structural differences, including twelve sites evolving under positive selection, among eighteen C. rosea S8A serine protease paralog genes were also observed. The C. rosea S8A serine protease gene prs6 was induced during interaction with the plant pathogenic species F. graminearum.Conclusions: Non-random increases in S8A, S9X and S33 serine protease gene numbers in the mycoparasitic species C. rosea, Trichoderma atroviride and T. virens suggests an involvement in fungal-fungal interactions. Regulatory and predicted structural differences between C. rosea S8A paralogs indicate that functional diversification is driving the observed increase in gene copy numbers. The induction of prs6 expression in C. rosea during confrontation with F. graminearum suggests an involvement of the corresponding protease in fungal-fungal interactions. The results pinpoint the importance of serine proteases for ecological niche adaptation in C. rosea, including a potential role in the mycoparasitic attack on fungal prey.
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| 26. |
- Karkehabadi, Saeid, et al.
(författare)
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Biochemical Characterization and Crystal Structures of a Fungal Family 3 beta-Glucosidase, Cel3A from Hypocrea jecorina
- 2014
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 289, s. 31624-31637
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Tidskriftsartikel (refereegranskat)abstract
- Cellulase mixtures from Hypocrea jecorina are commonly used for the saccharification of cellulose in biotechnical applications. The most abundant beta-glucosidase in the mesophilic fungus Hypocrea jecorina is HjCel3A, which hydrolyzes the beta-linkage between two adjacent molecules in dimers and short oligomers of glucose. It has been shown that enhanced levels of HjCel3A in H. jecorina cellulase mixtures benefit the conversion of cellulose to glucose. Biochemical characterization of HjCel3A shows that the enzyme efficiently hydrolyzes (1,4)-as well as (1,2)-, (1,3)-, and (1,6)-beta-D-linked disaccharides. For crystallization studies, HjCel3A was produced in both H. jecorina (HjCel3A) and Pichia pastoris (Pp-HjCel3A). Whereas the thermostabilities of HjCel3A and Pp-HjCel3A are the same, Pp-HjCel3A has a higher degree of N-linked glycosylation. Here, we present x-ray structures of HjCel3A with and without glucose bound in the active site. The structures have a three-domain architecture as observed previously for other glycoside hydrolase family 3 beta-glucosidases. Both production hosts resulted in HjCel3A structures that have N-linked glycosylations at Asn(208) and Asn(310). In H. jecorina-produced HjCel3A, a single N-acetylglucosamine is present at both sites, whereas in Pp-HjCel3A, the P. pastoris-produced HjCel3A enzyme, the glycan chains consist of 8 or 4 saccharides. The glycosylations are involved in intermolecular contacts in the structures derived from either host. Due to the different sizes of the glycosylations, the interactions result in different crystal forms for the two protein forms.
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| 27. |
- Karkehabadi, Saeid, et al.
(författare)
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Structural studies of a glycoside hydrolase family 3 beta-glucosidase from the model fungus Neurospora crassa
- 2018
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Ingår i: Acta crystallographica. Section F, Structural biology communications. - 2053-230X. ; 74, s. 787-796
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Tidskriftsartikel (refereegranskat)abstract
- The glycoside hydrolase family 3 (GH3) beta-glucosidases are a structurally diverse family of enzymes. Cel3A from Neurospora crassa (NcCel3A) belongs to a subfamily of key enzymes that are crucial for industrial biomass degradation. beta-Glucosidases hydrolyse the beta-1,4 bond at the nonreducing end of cellodextrins. The hydrolysis of cellobiose is of special importance as its accumulation inhibits other cellulases acting on crystalline cellulose. Here, the crystal structure of the biologically relevant dimeric form of NcCel3A is reported. The structure has been refined to 2.25 angstrom resolution, with an R-cryst and R-free of 0.18 and 0.22, respectively. NcCel3A is an extensively N-glycosylated glycoprotein that shares 46% sequence identity with Hypocrea jecorina Cel3A, the structure of which has recently been published, and 61% sequence identity with the thermophilic beta-glucosidase from Rasamsonia emersonii. NcCel3A is a three-domain protein with a number of extended loops that deepen the active-site cleft of the enzyme. These structures characterize this subfamily of GH3 beta-glucosidases and account for the high cellobiose specificity of this subfamily.
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| 28. |
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| 29. |
- Lind, Tekla, et al.
(författare)
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Reduced live-birth rates after IVF/ICSI in women with previous unilateral oophorectomy : results of a multicentre cohort study
- 2018
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Ingår i: Human Reproduction. - : Oxford University Press. - 0268-1161 .- 1460-2350. ; 33:2, s. 238-247
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Tidskriftsartikel (refereegranskat)abstract
- Is there a reduced live-birth rate (LBR) after IVF/ICSI treatment in women with a previous unilateral oophorectomy (UO)? A significantly reduced LBR after IVF/ICSI was found in women with previous UO when compared with women with intact ovaries in this large multicentre cohort, both crudely and after adjustment for age, BMI, fertility centre and calendar period and regardless of whether the analysis was based on transfer of embryos in the fresh cycle only or on cumulative results including transfers using frozen-thawed embryos. Similar pregnancy rates after IVF/ICSI have been previously reported in case-control studies and small cohort studies of women with previous UO versus women without ovarian surgery. In all previous studies multiple embryos were transferred. No study has previously evaluated LBR in a large cohort of women with a history of UO. This research was a multicentre cohort study, including five reproductive medicine centres in Sweden: Carl von Linn, Clinic (A), Karolinska University Hospital (B), Uppsala University Hospital (C), Linkoping University Hospital (D) and A-rebro University Hospital (E). The women underwent IVF/ICSI between January 1999 and November 2015. Single embryo transfer (SET) was performed in approximately 70% of all treatments, without any significant difference between UO exposed women versus controls (68% versus 71%), respectively (P = 0.32), and a maximum of two embryos were transferred in the remaining cases. The dataset included all consecutive treatments and fresh and frozen-thawed cycles. The exposed cohort included 154 women with UO who underwent 301 IVF/ICSI cycles and the unexposed control cohort consisted of 22 693 women who underwent 41 545 IVF/ICSI cycles. Overall, at the five centres (A-E), the exposed cohort underwent 151, 34, 35, 41 and 40 treatments, respectively, and they were compared with controls of the same centre (18 484, 8371, 5575, 4670 and 4445, respectively). The primary outcome was LBR, which was analysed per started cycle, per ovum pick-up (OPU) and per embryo transfer (ET). Secondary outcomes included the numbers of oocytes retrieved and supernumerary embryos obtained, the Ovarian Sensitivity Index (OSI), embryo quality scores and cumulative pregnancy rates. We used a Generalized Estimating Equation (GEE) model for statistical analysis in order to account for repeated treatments. MAIN RESULTS AND THE ROLE OF CHANCE: The exposed (UO) and control women's groups were comparable with regard to age and performance of IVF or ICSI. Significant differences in LBR, both crude and age-adjusted, were observed between the UO and control groups: LBR per started cycle (18.6% versus 25.4%, P = 0.007 and P = 0.014, respectively), LBR/OPU (20.3% versus 27.1%, P = 0.012 and P = 0.015, respectively) and LBR/ET (23.0% versus 29.7%, P = 0.022 and P = 0.025, respectively). The differences in LBR remained significant after inclusion of both fresh and frozen-thawed transfers (both crude and age-adjusted data): LBR/OPU (26.1% versus 34.4%, P = 0.005 and P = 0.006, respectively) and LBR/ET (28.3% versus 37.1%, P = 0.006 and P = 0.006, respectively). The crude cancellation rate was significantly higher among women with a history of UO than in controls (18.9% versus 14.5%, P = 0.034 and age-adjusted, P = 0.178). In a multivariate GEE model, the cumulative odds ratios for LBR (fresh and frozen-thawed)/OPU (OR 0.70, 95% CI 0.52-0.94, P = 0.016) and LBR (fresh and frozen-thawed)/ET (OR 0.68, 95% CI 0.51-0.92, P = 0.012) were approximately 30% lower in the group of women with UO when adjusted for age, BMI, reproductive centre, calendar period and number of embryos transferred when appropriate. The OSI was significantly lower in women with a history of UO than in controls (3.6 versus 6.0) and the difference was significant for both crude and age-adjusted data (P =< 0.001 for both). Significantly fewer oocytes were retrieved in treatments of women with UO than in controls (7.2 versus 9.9, P = < 0.001, respectively). LIMITATIONS, REASONS FOR CAUTION: Due to the nature of the topic, this is a retrospective analysis, with all its inherent limitations. Furthermore, the cause for UO was not possible to obtain in all cases. A diagnosis of endometriosis was also more common in the UO group, i. e. a selection bias in terms of poorer patient characteristics in the UO group cannot be completely ruled out. However, adjustment for all known confounders did not affect the general results. WIDER IMPLICATIONS OF THE FINDINGS: To date, this is the largest cohort investigated and the first study indicating an association of achieving reduced live birth after IVF/ICSI in women with previous UO. These findings are novel and contradict the earlier notion that IVF/ICSI treatment is not affected, or is only marginally affected by previous UO.
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| 30. |
- Ridderström, Christian, et al.
(författare)
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The basic design of the quadruped robot WARP1
- 2000
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Ingår i: International Conference on Climbing and Walking Robots.
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the basic design of a walking robot platform, in terms of its mechanics,electronics and control. The four-legged robot weighs about 60 kilograms, has three actuatorsin each leg and uses a distributed control system over six CAN busses. Basic strength and speedis demonstrated by experiments where the robot performs walking motions and goes down onits knees and then up again. A brief discussion of experiences from designing and implementingthe platform is included.
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| 31. |
- Risberg, Mikael, et al.
(författare)
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Influence from fuel type on the performance of an air-blown cyclone gasifier
- 2014
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 116, s. 751-759
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Tidskriftsartikel (refereegranskat)abstract
- Entrained flow gasification of biomass using the cyclone principle has been proposed in combination with a gas engine as a method for combined heat and power production in small to medium scale (<20 MW). This type of gasifier also has the potential to operate using ash rich fuels since the reactor temperature is lower than the ash melting temperature and the ash can be separated after being collected at the bottom of the cyclone. The purpose of this work was to assess the fuel flexibility of cyclone gasification by performing tests with five different types of fuels; torrefied spruce, peat, rice husk, bark and wood. All of the fuels were dried to below 15% moisture content and milled to a powder with a maximum particle size of around 1 mm. The experiments were carried out in a 500 kWth pilot gasifier with a 3-step gas cleaning process consisting of a multi-cyclone for removal of coarse particles, a bio-scrubber for tar removal and a wet electrostatic precipitator for removal of fine particles and droplets from the oil scrubber (aerosols). The lower heating value (LHV) of the clean producer gas was 4.09, 4.54, 4.84 and 4.57 MJ/Nm3 for peat, rice husk, bark and wood, respectively, at a fuel load of 400 kW and an equivalence ratio of 0.27. Torrefied fuel was gasified at an equivalence ratio of 0.2 which resulted in a LHV of 5.75 MJ/Nm3 which can be compared to 5.50 MJ/Nm3 for wood powder that was gasified at the same equivalence ratio. A particle sampling system was designed in order to collect ultrafine particles upstream and downstream the gasifier cleaning device. The results revealed that the gas cleaning successfully removed >99.9% of the particulate matter smaller than 1 μm.
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| 32. |
- Rodriguez-Wallberg, Kenny A., et al.
(författare)
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Ovarian tissue cryopreservation and transplantation among alternatives for fertility preservation in the Nordic countries - compilation of 20 years of multicenter experience
- 2016
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : WILEY-BLACKWELL. - 0001-6349 .- 1600-0412. ; 95:9, s. 1015-1026
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Tidskriftsartikel (refereegranskat)abstract
- Introduction. The aim of this study is to report the current status of ovarian tissue cryopreservation among alternatives for fertility preservation in the Nordic countries. Material and methods. A questionnaire was sent to 14 Nordic academic reproductive centers with established fertility preservation programs. It covered fertility preservation cases performed up to December 2014, standard procedures for ovarian tissue cryopreservation and oocyte cryopreservation and reproductive outcomes following ovarian tissue transplantation. Results. Among the Nordic countries, Denmark and Norway practice ovarian tissue cryopreservation as a clinical treatment (822 and 164 cases, respectively) and their programs are centralized. In Sweden (457 cases), ovarian tissue cryopreservation is practiced at five of six centers and in Finland at all five centers (145 cases). Nearly all considered ovarian tissue cryopreservation to be experimental. In Iceland, embryo cryopreservation is the only option for fertility preservation. Most centers use slow-freezing methods for ovarian tissue cryopreservation. Most patients selected for ovarian tissue cryopreservation were newly diagnosed with cancer and the tissue was predominantly retrieved laparoscopically by unilateral oophorectomy. Only minor complications were reported. In total, 46 women have undergone ovarian tissue transplantation aiming at recovering fertility, 17 healthy children have been born and several additional pregnancies are currently ongoing. Whenever patients' clinical condition is permissive, oocyte cryopreservation after hormonal stimulation is preferred for fertility preservation. Between 2012 and 2014, a smaller proportion of females have undergone fertility preservation in the Nordic centers, in comparison to males (1: 3). Conclusions. Overall, ovarian tissue cryopreservation was reported to be safe. Slow freezing methods are still preferred. Promising results of recovery of fertility have been reported in Nordic countries that have initiated ovarian tissue transplantation procedures.
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| 33. |
- Schmuck, Benjamin, et al.
(författare)
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Coupled chemistry kinetics demonstrate the utility of functionalized Sup35 amyloid nanofibrils in biocatalytic cascades
- 2019
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294, s. 14966–14977-
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Tidskriftsartikel (refereegranskat)abstract
- Concerns over the environment are a central driver for designing cell-free enzymatic cascade reactions that synthesize non?petrol-based commodity compounds. An often-suggested strategy that would demonstrate the economic competitiveness of this technology is recycling of valuable enzymes through their immobilization. For this purpose, amyloid nanofibrils are an ideal scaffold to realize chemistry-free covalent enzyme immobilization on a material that offers a large surface area. However, in most instances, only single enzyme?functionalized amyloid fibrils have so far been studied. To embark on the next stage, here we displayed xylanase A, ?-xylosidase, and an aldose sugar dehydrogenase on Sup35(1?61) nanofibrils to convert beechwood xylan to xylonolactone. We characterized this enzymatic cascade by measuring the time-dependent accumulation of xylose, xylooligomers, and xylonolactone. Furthermore, we studied the effects of relative enzyme concentrations, pH, temperature, and agitation on product formation. Our investigations revealed that a modular cascade with a mixture of xylanase and ?-xylosidase, followed by product removal and separate oxidation of xylose with the aldose sugar dehydrogenase, is more productive than an enzyme mix containing all of these enzymes together. Moreover, we found that the nanofibril-coupled enzymes do not lose activity compared with their native state. These findings provide proof of concept of the feasibility of functionalized Sup35(1?61) fibrils as a molecular scaffold for biocatalytic cascades consisting of reusable enzymes that can be used in biotechnology.
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| 34. |
- Schmuck, Benjamin, et al.
(författare)
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Production of Ready-To-Use Functionalized Sup35 Nanofibrils Secreted by Komagataella pastoris
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 12, s. 9363-9371
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid nanofibrils are excellent scaffolds for design-able materials that can be endowed with biotechnologically relevant functions. However, most of all excellent ideas and concepts that have been reported in the literature might never see real-world implementation in biotechnological applications. One bottleneck is the large-scale production of these materials. In this paper, we present an attempt to create a generic and scalable platform for producing ready-to-use functionalized nanofibrils directly from a eukaryotic organism. As a model material, we assembled Sup35(1-61) amyloid nanofibrils from Saccharomyces cerevisiae decorated with the Z-domain dimer, which has a high affinity toward antibody molecules. To this end, Komagataella pastoris was engineered by inserting gene copies of Sup35(1-61) and the protein chimera Sup35(1-61)-ZZ into the genome. This strain has the capability to constantly secrete amyloidogenic proteins into the extracellular medium, where the mature functionalized fibrils form, with a production yield of 35 mg/L culture. Another striking feature of this strategy is that the separation of the fibril material from the cells requires only centrifugation and resuspension in saline water. The fast production rates, minimal hands-on time, and high stability of the assembled material are some highlights that make the direct assembly of functionalized fibrils in the extracellular medium an alternative to production methods that are not suitable for large-scale production of designed amyloids.
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| 35. |
- Östling, Mikael, et al.
(författare)
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Integration of metallic source/drain (MSD) contacts in nanoscaled CMOS technology
- 2010
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Ingår i: ICSICT-2010 - 2010 10th IEEE International Conference on Solid-State and Integrated Circuit Technology, Proceedings. - 9781424457984 ; , s. 41-45
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Konferensbidrag (refereegranskat)abstract
- An overview of metallic source/drain (MSD) contacts in nanoscaled MOSFET technology is provided in this paper. MSD contacts offer several benefits for nanoscaled CMOS, i.e., extremely low S/D parasitic resistance, abruptly sharp junctions between S/D and channel and preferably low temperature processing. In order to achieve high performance MSD MOSFETs, many design parameters such as Schottky barrier height (SBH), S/D to gate underlap, top Si layer thickness, oxide thickness and so on should be optimized. Recently, a lot of efforts have been invested in MSD MOSFETs based on Pt- and Ni-silicide implementation and several promising results have been reported in literature. The experimental work as well as the results of Monte Carlo simulations by this research team and by other research teams is discussed in this paper. It will be shown that the present results place MSD MOSFETs as a competitive candidate for future generations of CMOS technology.
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| 36. |
- Östling, Mikael, et al.
(författare)
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Nanoscaling of MOSFETs and the implementation of Schottky barrier S/D contacts
- 2010
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Ingår i: 2010 27th International Conference on Microelectronics, MIEL 2010 - Proceedings. - 9781424472017 ; , s. 9-13
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of metallic source/drain (MSD) Schottky-barrier (SB) MOSFET technology. This technology offers several benefits for scaling CMOS, i.e., extremely low S/D series resistance, sharp junctions from S/D to channel and low temperature processing. A successful implementation of this technology needs to overcome new obstacles such as Schottky barrier height (SBH) engineering and careful control of SALICIDE process. Device design factors such as S/D to gate underlap, Si film thickness and oxide thickness affect device performance owing to their effects on the SB width. Recently, we have invested a lot of efforts on Pt- and Ni-silicide MSD SB-MOSFETs and achieved some promising results. The present work, together with the work of other groups in this field, places silicide MSD SB-MOSFETs as a competitive candidate for future generations of CMOS technology.
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| 37. |
- Östling, Mikael, et al.
(författare)
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Technology challenges in silicon devices beyond the 16 nm node
- 2011
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Ingår i: Proceedings of the 18th International Conference. - 9788393207503 ; , s. 27-31
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Konferensbidrag (refereegranskat)abstract
- An overview of metallic source/drain (MSD) contacts in nano-scaled MOSFET technology is provided in this paper. MSD contacts offer several benefits for nano-scaled CMOS, i.e. extremely low S/D parasitic resistance, abruptly sharp junctions between S/D and channel and preferably low temperature processing. In order to achieve high performance MSD MOSFETs, many design parameters such as Schottky barrier height (SBH), S/D to gate underlap, top Si layer thickness, oxide thickness should be optimized. Recently, efforts have been invested in MSD MOSFETs based on Pt- and Ni-silicide implementation and several promising results have been reported in literature. The experimental work as well as the results of Monte Carlo simulations by several investigators, including the authors, is discussed in this paper. It will be shown that the present results place MSD MOSFETs as a competitive candidate for future generations of CMOS technology.
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| 38. |
- Östling, Mikael, et al.
(författare)
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Towards Schottky-Barrier Source/Drain MOSFETs
- 2008
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Ingår i: 2008 9TH INTERNATIONAL CONFERENCE ON SOLID-STATE AND INTEGRATED-CIRCUIT TECHNOLOGY, VOLS 1-4. - NEW YORK : IEEE. - 9781424421855 ; , s. 146-149
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of metal source/drain (S/D) Schottky-barrier (SB) MOSFET technology. The technology offers several benefits for scaling CMOS, i.e., extremely low source/drain resistance, sharp junctions from S/D to channel and low temperature processing. A successful implementation of the technology needs to overcome new obstacles such as SB height engineering and precise control of silicide growth. Device design factors such as S/D to gate underlap, Si film thickness and oxide thickness affect device performance owing to their effects on the SB width. In the past two years several groups have demonstrated high-performance SB MOSFETs, which places the technology as a promising candidate for future generations of CMOS technology.
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