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Georgiana Daian Alexander Taube Amikam Birnboim Mihai Daian Yury Shramkov 《Wood Science and Technology》2006,40(3):237-246
A method for calculating the complex dielectric permittivity of an anisotropic wood structure at microwave frequencies is
presented. A numerical model for describing the 3D wood structure containing fibers, rays, vessels and cracks with changeable
dimensions and material composition is built. This model is introduced into an efficient solver that calculates the effective
dielectric constant of any 3D structure of dielectric materials. Using our numerical model we succeeded in theoretically reproducing
the results of recent measurements of the dielectric permittivity of wood, in various directions and various moisture contents.
The qualitative agreement is realistic, reproducing all the trends of the changes in ɛ as the direction of the electric field
and the moisture content are varied. The quantitative agreement is practical and reliable for engineering calculations with
an average deviation of ±10% in ɛ′ and ±5% in ɛ′′. As microwave processing of wood involves internal temperatures as high
as 150°C and pressures of up to 5 atm, the dielectric properties of wood were also calculated with the same numerical model
by simulating high internal temperature and pressure. A comparison between the calculated and measured values shows once again
how accurate the model reproduces the empirical study. 相似文献
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Hall IM Shankaranarayana GD Noma K Ayoub N Cohen A Grewal SI 《Science (New York, N.Y.)》2002,297(5590):2232-2237
The higher-order assembly of chromatin imposes structural organization on the genetic information of eukaryotes and is thought to be largely determined by posttranslational modification of histone tails. Here, we study a 20-kilobase silent domain at the mating-type region of fission yeast as a model for heterochromatin formation. We find that, although histone H3 methylated at lysine 9 (H3 Lys9) directly recruits heterochromatin protein Swi6/HP1, the critical determinant for H3 Lys9 methylation to spread in cis and to be inherited through mitosis and meiosis is Swi6 itself. We demonstrate that a centromere-homologous repeat (cenH) present at the silent mating-type region is sufficient for heterochromatin formation at an ectopic site, and that its repressive capacity is mediated by components of the RNA interference (RNAi) machinery. Moreover, cenH and the RNAi machinery cooperate to nucleate heterochromatin assembly at the endogenous mat locus but are dispensable for its subsequent inheritance. This work defines sequential requirements for the initiation and propagation of regional heterochromatic domains. 相似文献
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