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Silk fibroin films in the random‐coil and β‐form conformations were immersed in water at temperatures from 2 to 130°C, and conformational changes were followed by x‐ray diffraction, infrared spectroscopy and differential scanning calorimetry. On treatment with water below 60°C, the random‐coil conformation is converted to the α form and above 70°C to mixtures of the α and β conformations. The β‐form content increases as the immersion temperature is raised. The β form is not affected by immersion in water in the temperature range studied.

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The reactions of 2H-heptafluoropropane (CF 3 CHFCF 3 , HFC-227ea) with O( 3 P) and H atoms have been studied at high temperatures by using a shock tube technique coupled with atomic resonance absorption spectroscopy. Electronically ground-state oxygen and hydrogen atoms were produced by the laser photolysis of sulfur dioxide and the thermal decomposition of ethyl iodide, respectively. The rate coefficients for the reactions CF 3 -CHFCF 3 + O( 3 P) f i-C 3 F 7 + OH (1a) and CF 3 CHFCF 3 + H f i-C 3 F 7 + H 2 (2a) were experimentally determined from the decay of O( 3 P) and H atoms as k 1a ) 10 -10.27(0.67 exp[-(56 ( 13) kJ mol -1 /RT] cm 3 molecule -1 s -1 (880-1180 K) and k 2a ) 10 -9.15(0.66 exp [-(63 ( 14) kJ mol -1 /RT] cm 3 molecule -1 s -1 (1000-1180 K). These results showed that reaction 2a was faster than reaction 1a by a factor of 7-8 over the present experimental temperature range. Both rate coefficients were much smaller than the previous kinetic data for the reactions of propane with O( 3 P) and H atoms, because of an electron-attracting effect of fluorine atoms. To compare the reactivities between isomers, the rate coefficients for the reactions of 1Hheptafluoropropane, CHF 2 CF 2 CF 3 + O( 3 P) f n-C 3 F 7 + OH (3a) and CHF 2 CF 2 CF 3 + H f n-C 3 F 7 + H 2 (4a), were also determined by using the same technique as k 3a ) 10 -10.13(0.52 exp[-(55 ( 10) kJ mol -1 /RT] cm 3 molecule -1 s -1 (880-1180 K) and k 4a ) 10 -9.44(0.32 exp[-(57 ( 7) kJ mol -1 /RT] cm 3 molecule -1 s -1 (1000-1180 K). Furthermore, the rate coefficients for reactions 1a and 2a were calculated with the transitionstate theory (TST). Structural parameters and vibrational frequencies of the reactants and the transition states required for the TST calculation were obtained from the MP2(full)/6-31G(d) ab initio molecular orbital (MO) calculation. The energy barrier, E 0 q , was adjusted until the TST rate coefficient most closely matched the observed one. The fitting results of E 0 q (1a) ) 51 kJ mol -1 and E 0 q (2a) ) 41 kJ mol -1 were in agreement with the G2(MP2) energy barriers, within the expected uncertainty.

A phenomenological model has been developed to simulate the feature profile evolution of polycrystalline silicon (poly-Si) gate etching in Cl 2 /O 2 plasmas. The model takes into account the deposition of etch products, surface oxidation, and the forward reflection of energetic ions on feature sidewalls. To describe the formation of multilayer SiCl x or SiCl x O y on feature surfaces during etching, the substrates consist of a number of small cells or lattices of atomic size in the computational domain; this model provides a nanometer-scale representation of the feature geometry and the chemical constituents therein. The inelastic or nonspecular reflection of incoming ions from feature surfaces and the penetration of ions into substrates are incorporated into the model by calculating the trajectory of ions through successive binary collisions with substrate atoms. Etching experiments were performed to evaluate and improve the accuracy of the model. To analyze the effects of the control variables of a plasma reactor on profile evolution, the simulated profiles for different gas flow ratios and incident ion energies were compared with the etched profiles obtained in the experiments. The numerical results reproduced the behaviors of profile anomalies such as sidewall tapering and microtrenches at the corner of the feature bottom, upon varying the incident fluxes of O neutrals and etch by-products, and the incident energy of ions. Moreover, the simulated profiles exhibited passivation layers deposited on feature sidewalls, which is a similar geometry to those obtained in the experiments.

We have developed a cylindrical RF plasma source by the inductive coupling of multiple low-inductance antenna (LIA) units and analyzed the plasma density profile of this source using fluid simulation. Experiments using four LIA units showed a stable source operation even at 2000 W RF power, attaining plasma densities as high as 1011–1012 cm-3 in an argon pressure range of 0.67–2.6 Pa. The amplitude of antenna RF voltage was measured to be less than 600 V, which is considerably smaller than those obtained using conventional ICP antennas. The radial distribution of plasma density sustained using four LIA units showed excellent agreement with profiles numerically predicted using a fluid-simulation code.

Cold atmospheric pressure plasma (CAP) does not cause thermal damage or generate toxic residues; hence, it is projected as an alternative agent for sterilization in food and pharmaceutical industries. The fungicidal effects of CAP have not yet been investigated as extensively as its bactericidal effects. We herein examined the effects of CAP on yeast proteins using a new CAP system with an improved processing capacity. We demonstrated that protein ubiquitination and the formation of protein aggregates were induced in the cytoplasm of yeast cells by the CAP treatment. GFP-tagged Tsa1 and Ssa1, an HO-responsive molecular chaperone and constitutively expressed Hsp70, respectively, formed cytoplasmic foci in CAP-treated cells. Furthermore, Tsa1 was essential for the formation of Ssa1-GFP foci. These results indicate that the denaturation of yeast proteins was caused by CAP, at least partially, in a HO-dependent manner. Furthermore, misfolded protein levels in the endoplasmic reticulum (ER) and the oligomerization of Ire1, a key sensor of ER stress, were enhanced by the treatment with CAP, indicating that CAP causes ER stress in yeast cells as a specific phenomenon to eukaryotic cells. The pretreatment of yeast cells at 37 °C significantly alleviated cell death caused by CAP. Our results strongly suggest that the induction of protein denaturation is a primary mechanism of the fungicidal effects of CAP.