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- Karpinska, B., et al.
(författare)
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MYB transcription factors are differentially expressed and regulated during secondary vascular tissue development in hybrid aspen
- 2004
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Ingår i: Plant Molecular Biology. - : Springer Science and Business Media LLC. - 0167-4412 .- 1573-5028. ; 56:2, s. 255-270
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Tidskriftsartikel (refereegranskat)abstract
- More than 120,000 poplar ESTs have been sequenced from 20 different cDNA libraries by the Swedish Centre for Tree Functional Genomics. We screened this EST collection for MYB transcription factors involved in secondary vascular tissue formation, and genes assigned as PttMYB3Ra, PttMYB4a and PttMYB21a were selected for further characterisation. Three MYB genes showed different expression patterns in various organs, tissues and stem sub-sections representing different developmental stages of vascular tissue formation. Furthermore, the analysis showed that PttMYB21a expression was much higher in secondary cell wall formation zone of xylem and phloem fibers than in other developmental zones. Transgenic hybrid aspen plants, expressing the 3'-part of the PttMYB21a gene in antisense orientation were generated to assess the function of PttMYB21a gene in vascular tissue formation and lignification. All transgenic lines showed reduced growth and had fewer internodes compared to the wild-type. The analysis of selected lines showed that acid soluble lignin present in the bark was higher in transgenic lines as compared to wild-type plants. Moreover a higher transcript level of caffeoyl-CoA 3-O-methyltransferase [CCoAOMT];EC2.1.1.104) was found in the phloem of the transgenic plants, suggesting that PttMYB21a might function as a transcriptional repressor.
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| 2. |
- Ernst, Thomas, 1960-
(författare)
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A new method q-calculus
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In q-calculus we are looking for q-analogues of mathematical objects, which have the original object as limits when q tends to 1. q-Calculus has wide-ranging applications in analytic number theory and theoretical physics. The main topic of the thesis is the invention of the tilde operator and the renaissance of the q-addition. There are two types of q-addition, the Ward-AlSalam q-addition and the Hahn q-addition. The first is both commutative and associative, while the second is neither. This is one of the reasons why sometimes more than one q-analogue exist. These two operators form the basis of the method which unites hypergeometric series and q-hypergeometric series and which gives many formulas of q-calculus a natural form reminding directly of their classical origin. This method is reminiscent of Heine, who mentioned the case where one parameter in a q-hypergeometric series is plus infinity. The q-addition is the natural way to extend addition to the q-case as is shown when restating addition formulas for q-trigonometric functions.We give a more lucid definition of the q-difference operator. A new notation for powers of q reminding of the exponential function is given. A q-Taylor formula with remainder term expressed as q-integral is proved.We present a new expression for generalized Vandermonde determinants, and thus for the Schur function. We also obtain an equivalence relation on the set of all generalized Vandermonde determinants. We find a more general expression for the Vandermonde determinant. We show the connection to a determinant of Flowe and Harris and to the solution of difference and q-difference equations with constant coefficients.
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| 6. |
- Saravanan, P., et al.
(författare)
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Influence of spraying variables on structure and properties of plasma sprayed alumina coatings
- 2000
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Ingår i: British Ceramic Transactions. - London, United Kingdom : Inst of Materials. - 0967-9782 .- 1743-2766. ; 99:6, s. 241-247
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Tidskriftsartikel (refereegranskat)abstract
- An experimental statistical design study on the plasma spraying of alumina powder has been carried out.Coating experiments were conducted, using a Taguchi full factorial L16 design parametric approach, to study the effect of four key plasma processing variables on the coating quality, namely, primary gas flow rate, arc current, powder feed rate, and spray distance. Optical microscopy, scanning electron microscopy, XRD, image analysis, and hardness testing were used for characterization. The resulting as sprayed coating characteristics were quantified with respect to roughness, microhardness, porosity, and microstructure. Through statistical calculation (analysis of variance), the parameters that have significant influence on the structure and properties of the coatings were identified and their relative importance and contribution ratios to overall variance were studied. The Taguchi evaluation employed in the present investigation showed that an improvement in the coating properties could be achieved using an optimum combination of variables.
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| 7. |
- Saravanan, P., et al.
(författare)
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Study of plasma- and detonation gun-sprayed alumina coatings using Taguchi experimental design
- 2000
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Ingår i: Journal of thermal spray technology (Print). - Materials Park, OH, United States : ASM International. - 1059-9630 .- 1544-1016. ; 9:4, s. 505-512
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al2O3) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al2O3 coatings deposited using the above techniques by using Taguchi experimental design. Alumina coating experiments were conducted using a Taguchi fractional-factorial (L8) design parametric study to optimize the spray process parameters for both APS and D-gun. The Taguchi design evaluated the effect of four APS and D-gun spray variables on the measured coating attributes. The coating qualities evaluated were surface roughness, porosity, microhardness, abrasion, and sliding wear. The results show that the coating quality is directly related to the corresponding coating microstructure, which is significantly influenced by the spray parameters employed. Though it is evident that the D-gun-sprayed coatings consistently exhibit dense and uniform microstructure, higher hardness, and superior tribological performance, the attainment of suitable plasma-sprayed coatings can be improved by employing the Taguchi analysis.
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