A polymer deformation process is studied by numerical simulations and the results are compared with the related experimental results in nanoimprint lithography. The imprint pressures required for successful imprinting and the filling rate into the mold grooves are studied as the aspect ratio of the pattern, initial thickness of the polymer, and the duty ratio of the pattern are changed. The required pressure increases not only for high aspect ratio pattern but also low aspect ratio pattern. Also, the pressure increases when the initial thickness of the polymer decreases to less than about two times that of the groove depth of the mold. These results are explained by the deformation mechanism of the polymer and agree well with the related experimental results. Based on these theoretical and experimental studies, fabrication of a high aspect ratio pattern having 100 nm width and 860 nm height is successfully demonstrated using thick polymer by nanoimprint lithography.

The fracture defect of the polymer in thermal nanoimprint lithography is studied based on numerical simulation and experiments. Hot pressing, cooling, and releasing steps in nanoimprint lithography are investigated in detail by a numerical simulation study. The applied pressure after the polymer deformation below the glass transition temperature will induce a stress concentration at the corner of the polymer pattern. On the other hand, the difference of the thermal expansion coefficients between the mold and the substrate causes lateral strain, and the strain is concentrated at the corner of the pattern. These strains induce defects and cause fracture defects at the base part of the pattern during the mold releasing step. To eliminate the defects, the applied pressure is released below the glass transition temperature, and slow cooling is introduced to relax the stress concentration. The result shows successful fabrication of fine patterns with a high aspect ratio.

Numerical simulations and experimental studies are carried out to understand the deformation process of thin polymer film in nanoimprint lithography. Deformation of a thin polymer above its glass transition temperature is studied for various imprinting conditions such as the aspect ratios of a mold pattern, initial thickness of the polymer, and imprinting pressure. Cross-sectional profiles of the deformed polymers are simulated by the finite element method based on a rubber elastic model. The results are compared with experimental data. The areal penetration ratio of the polymer into the recessed groove of the mold and residual thickness underneath the mold are quantitatively evaluated. The simulations and the experimental results agree well with each other.

Physiological aspects of acidity stress in plants (synonymous with H(+) rhizotoxicity or low-pH stress) have long been a focus of research, in particular with respect to acidic soils where aluminium and H(+) rhizotoxicities often co-occur. However, toxic H(+) and Al(3+) elicit different response mechanisms in plants, and it is important to consider their effects separately. The primary aim of this review was to provide the current state of knowledge regarding the genetics of the specific reactions to low-pH stress in growing plants. A comparison of the results gleaned from quantitative trait loci analysis and global transcriptome profiling of plants in response to high proton concentrations revealed a two-stage genetic response: (i) in the short-term, proton pump H(+)-ATPases present the first barrier in root cells, allocating an excess of H(+) into either the apoplast or vacuole; the ensuing defence signaling system involves auxin, salicylic acid, and methyl jasmonate, which subsequently initiate expression of STOP and DREB transcription factors as well as chaperone ROF; (2) the long-term response includes other genes, such as alternative oxidase and type II NAD(P)H dehydrogenase, which act to detoxify dangerous reactive oxygen species in mitochondria, and help plants better manage the stress. A range of transporter genes including those for nitrate (NTR1), malate (ALMT1), and heavy metals are often up-regulated by H(+) rhizotoxicity. Expansins, cell-wall-related genes, the γ-aminobutyric acid shunt and biochemical pH-stat genes also reflect changes in cell metabolism and biochemistry in acidic conditions. However, the genetics underlying the acidity stress response of plants is complicated and only fragmentally understood.

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