PVA unveiled the actual role of starch in the Briggs-Rauscher reaction
The Briggs Rauscher reaction (BR reaction) is one of the famous oscillating reactions; the aqueous mixture of KIO3, H2SO4, H2O2, C3H4O4, MnSO4, and starch exhibit color change between yellow and blue-purple repeatedly. The blue-purple color formation is due to the iodine test reaction caused by inclusions of polyiodides such as I3- and I5- in the helical structure of starch. Therefore, starch has been regarded as only an indicator in the BR reaction. But our seniors have found that the oscillation did not last without starch. They hypothesized that starch’s linear helical framework is necessary to elongate the lifetime of the oscillating reaction. If this hypothesis is correct, similar BR-type oscillations must be observed when other polymers with helical structures are used instead of starch. We found the literature which reports that polyvinyl alcohol (PVA) forms a helical structure and indicates the iodine test reaction. In our research, we studied the BR reactions using PVA, with different saponification degrees and viscosities. First, we studied the correlation between the structural features of PVA and the iodine color reaction by spectroscopic approach, exhibiting that PVA with low saponification form helical structures and show the iodine color reactions, which gives red color solutions. Second, we found that additions of the helical-structured PVA to the reaction solution instead of starch induces the BR-type oscillating reactions, while PVA without helical structure induces only a few numbers of oscillations. This is the world-first example of the oscillating reaction using PVA. The oscillation that lasted for 6 minutes with 23 oscillations was almost the same as that of the general BR reaction using starch. We concluded that the polymers with helical structures are intrinsic to elongate the lifetime of the BR reaction. Furthermore, we found that the addition of K3[Fe(CN)6], which has a high redox activity, in the reaction solution with PVA drastically elongated the lifetime (50 min) and increased the numbers of the oscillations (nearly 100 times). This result suggests that the oxidation-reduction reactions by the ferricyanide ion promotes the redox process of iodine and iodide ions.
Limited Query Black-box Adversarial Attacks in the Real World
We study the creation of physical adversarial examples, which are robust to real-world transformations, using a limited number of queries to the target black-box neural networks. We observe that robust models tend to be especially susceptible to foreground manipulations, which motivates our novel Foreground attack. We demonstrate that gradient priors are a useful signal for black-box attacks and therefore introduce an improved version of the popular SimBA. We also propose an algorithm for transferable attacks that selects the most similar surrogates to the target model. Our black-box attacks outperform state-of-the-art approaches they are based on and support our belief that the concept of model similarity could be leveraged to build strong attacks in a limited-information setting.
傅立葉轉換於奈米螢光鑽石超微量偵測之研究
螢光奈米鑽石(Fluorescent Nanodiamond, FND)主要應用於生物定位，其結構中與一個氮原子相鄰的晶格缺陷部分(Nitrogen-Vacancy, NV^-)照射波長532nm的雷射會發出637nm的螢光，對FND施加磁場會使螢光強度減弱。由於在低濃度溶液中螢光訊號會被溶液的背景雜訊掩蓋而難以偵測，因此設計實驗對FND施加穩定變換的磁場，此動作能夠使螢光強度也進行相同週期的變化。針對此週期進行快速傅立葉轉換(Fast Fourier Transformation, FFT)得出的數值會與螢光強度呈正比，進而推知FND濃度，有效排除不隨磁場變動的背景雜訊。研究結果顯示，施加磁場並使用FFT能夠成功排除牛血清蛋白(Bovine Serum Albumin, BSA)、碘化丙啶(Propidium Iodide, PI)、水、血液的背景輻射，且FND在高離子濃度溶液中會沉澱，在表層包覆BSA則可以有效地改善此現象。FND不易受到血液的背景輻射干擾螢光測定。