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Electric double-layer structure at the electrode interface has been studied by using molecular dynamics simulation on four quaternary ammonium-based ionic liquids (QaILs) to investigate the effect of switching the alkyl chain length of the Qa cation. These four QaILs are composed of a common anion, bis(trifluoromethanesulfonyl)- amide (TFSA⁻) and different cations: butyltrimethylammonium (N₁₁₁₄⁺, k = 1), dibutyldimethylammonium (N₁₁₄₄⁺, k = 2), tributylmethylammonium (N₁₄₄₄⁺, k = 3), and tetrabutylammonium (N₄₄₄₄⁺, k = 4), where k represents the number of butyl chains. The difference in k affects the potential dependence for the composition of the first ionic layer and the orientation of butyl chains in the layer. For the case of k = 1, 2, 3, the butyl chains parallel to the interface increases as the potential becomes negative, but further negative potential results in the increase in perpendicular ones. In the case of k = 1, all the cations in the first ionic layer show the perpendicular orientation at the negative potentials, forming a honeycomb lattice consisting of only cations. On the other hand, in the case of k = 4, no change in orientation has been observed due to the geometrical restrictions. The difference in k also affects the differential capacitance. The potential dependence of differential capacitance shows bell shape for the smaller two (k = 1, 2) and camel shape for the larger two (k = 3, 4). The camel shape for larger IL cations agrees with the prediction from the mean-field lattice gas model and recent experimental results. The differential capacitance at negative potentials deviated to the values higher than the model prediction and the discrepancy becomes greater for smaller k. The results indicate that the potential dependence of ionic orientation significantly affects the differential capacitance. Even for k = 4, which does not show the orientational change, the discrepancy has been observed, indicating that not only the orientational change but also the densification of ions in the first ionic layer are the factors we should take into account beyond the lattice gas model.

本稿では、SNS(ソーシャルネットワークサービス)の流行を記述する数理モデルのダイナミクスを考察する。SNSの流行モデルは、SIR型感染症モデルを基に、非線形な常微分方程式で定式化されており、その解挙動も類似なものとなっている。解の極限が満たす方程式(最終規模方程式)を導出する。この最終規模方程式を解析すると、最初期にSNSの利用や参加に消極的な人口の数が少ないほど、最終的にSNSの利用を止めたユーザー数は多くなることが示される。

application/pdf, Journal Article, 雪室貯蔵は雪を冷却源として食品の保存に用いる貯蔵方法であり、豪雪地域を中心に古くから行われている。この雪室貯蔵は二酸化炭素を排泄しない冷却方法として見直されつつあり、近年ではまたその優れた品質保持効果と食味向上効果に注目した取り組みがなされている。本研究では、夏期の高温による品質低下が大きいソバを試料とし、その品質保持における雪室貯蔵の効果を検証した。収穫直後の玄ソバを常温、冷蔵庫、雪室のそれぞれの条件で2.5 ヶ月、5 ヶ月、7.5 ヶ月間貯蔵し、貯蔵条件の違いが脂質過酸化と香気成分の保持に及ぼす影響を検討した。その結果、5 ヶ月までの貯蔵では、常温貯蔵した玄ソバと比較した場合、冷蔵貯蔵では過酸化脂質の生成が抑制されるとともに、多くの香気成分が残存しており、雪室貯蔵では、冷蔵保存と比較してもさらに良好な成績を示した。製麺したそばの官能評価では、常温貯蔵のそばと雪室貯蔵のそばは3 点識別法で有意に識別されており、また5 点評価法では有意差はみられなかったものの、雪室貯蔵で好まれる傾向が示された。香気成分の保持に関するモデル実験では、疑似雪室で保存した試料は常温保存および冷蔵保存と比較して、高級脂肪族アルコールを中心に多くの香気成分を保持していたが、不快臭の原因となる短鎖アルデヒド類に対する保持効果はみられなかった。これらの結果から、ソバの雪室貯蔵はその品質と香気成分を保持する上で有効であることが示され、またこの効果は低温のみならず高湿度の条件が寄与していることが示唆された。, “Yukimuro (i.e., snow room)” storage is an old-fashioned food preservation method in heavy snowfall areas of Japan. Yukimuro uses a room filled with snow for the cooling system without external energy source and so that contributes to reduce emissions of CO2. Additionally, high-humid and lowtemperature conditions (nearly 100% and 0˚C, respectively) in the yukimuro enable to keep vegetables fresh for a long time, or rather, improve the quality by increasing the taste and flavor components. In the present study, we investigated the efficacy of the yukimuro storage for the preservation of buckwheat grain, which is easy to diminish the quality during the storage under high temperature. In the study,buckwheat grains were immediately stored after the harvest under different three conditions: at room temperature, refrigerator, and Yukimuro storages, for 2.5, 5, and 7 months. At each end of the storage periods, samples were pulled out and provided for analyses of the quality evaluation. At both 2.5 and 5 months periods, the samples stored in yukimuro showed lower lipid peroxidation index and retained high amount of flavor components than those stored at room temperature or in the refrigerator. By organoleptic evaluation, it was confirmed that the noodle prepared from buckwheat grains stored in the yukimuro is significantly distinguishable from that prepared from buckwheat grains stored at room temperature. Furthermore, a model experiment using a low-temperature chamber filled with crushed ice and starch that added 12 flavor components of buckwheat demonstrated that the high-humid and lowtemperature conditions in yukimuro could retain higher fatty alcohols, but not undesirable off-flavor aldehydes. These results indicate that yukimuro storage is effective to keep the quality and flavor of buckwheat grain, and that results from the conditions of both cold and high humidity in the yukimuro.

application/pdf, Journal Article