Branched/Crosslinked Sulfonated Polyimide Membranes for Polymer Electrolyte Fuel Cells

Summary: Branched/crosslinked sulfonated polyimide membranes incorporating superior mechanical properties, high proton conductivity, and excellent fuel cell performance were successfully developed. The resulting polymer electrolytes displayed conductivity values of about 0.2 S · cm⁻¹ at 120 °C and 100% relative humidity. In a single H₂/O₂ fuel cell system at 90 °C, they exhibited reasonably high fuel cell performances comparable to that of Nafion 112.

The structure of the branched/crosslinked sulfonated polyimide membranes studied here.     

Blind Speech Watermarking Method with Frame Self-Synchronization Based on Spread-Spectrum Using Linear Prediction Residue

State-of-the-art speech watermarking techniques enable speech signals to be authenticated and protected against any malicious attack to ensure secure speech communication. In general, reliable speech watermarking methods must satisfy four requirements: inaudibility, robustness, blind-detectability, and confidentiality. We previously proposed a method of non-blind speech watermarking based on direct spread spectrum (DSS) using a linear prediction (LP) scheme to solve the first two issues (inaudibility and robustness) due to distortion by spread spectrum. This method not only effectively embeds watermarks with small distortion but also has the same robustness as the DSS method. There are, however, two remaining issues with blind-detectability and confidentiality. In this work, we attempt to resolve these issues by developing an approach called the LP-DSS scheme, which takes two forms of data embedding for blind detection and frame synchronization. We incorporate blind detection with frame synchronization into the scheme to satisfy blind-detectability and incorporate two forms of data embedding process, front-side and back-side embedding for blind detection and frame synchronization, to satisfy confidentiality. We evaluated these improved processes by carrying out four objective tests (PESQ, LSD, Bit-error-rate, and accuracy of frame synchronization) to determine whether inaudibility and blind-detectability could be satisfied. We also evaluated all combinations with the two forms of data embedding for blind detection with frame synchronization by carrying out BER tests to determine whether confidentiality could be satisfied. Finally, we comparatively evaluated the proposed method by carrying out ten robustness tests against various processing and attacks. Our findings showed that an inaudible, robust, blindly detectable, and confidential speech watermarking method based on the proposed LP-DSS scheme could be achieved.     

Stereo-controlled anti-hydromagnesiation of aryl alkynes by magnesium hydrides

A concise protocol for anti-hydromagnesiation of aryl alkynes was established using 1 : 1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI₂) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH₂) is responsible for the process.

Anti-hydromagnesiation of aryl alkynes was facilitated solely by magnesium hydride. The resulting alkenylmagnesium intermediates were functionalized with various electrophiles to afford stereochemically defined tri-substituted alkenes.     

Triflumizole as a Novel Lead Compound for Strigolactone Biosynthesis Inhibitor

Strigolactones (SLs) are carotenoid-derived plant hormones involved in the development of various plants. SLs also stimulate seed germination of the root parasitic plants, Striga spp. and Orobanche spp., which reduce crop yield. Therefore, regulating SL biosynthesis may lessen the damage of root parasitic plants. Biosynthetic inhibitors effectively control biological processes by targeted regulation of biologically active compounds. In addition, biosynthetic inhibitors regulate endogenous levels in developmental stage- and tissue-specific manners. To date, although some chemicals have been found as SL biosynthesis inhibitor, these are derived from only three lead chemicals. In this study, to find a novel lead chemical for SL biosynthesis inhibitor, 27 nitrogen-containing heterocyclic derivatives were screened for inhibition of SL biosynthesis. Triflumizole most effectively reduced the levels of rice SL, 4-deoxyorobanchol (4DO), in root exudates. In addition, triflumizole inhibited endogenous 4DO biosynthesis in rice roots by inhibiting the enzymatic activity of Os900, a rice enzyme that converts the SL intermediate carlactone to 4DO. A Striga germination assay revealed that triflumizole-treated rice displayed a reduced level of germination stimulation for Striga. These results identify triflumizole as a novel lead compound for inhibition of SL biosynthesis.     

Concerted Nucleophilic Aromatic Substitution Reactions

Recent developments in experimental and computational chemistry have identified a rapidly growing class of nucleophilic aromatic substitutions that proceed by concerted (cS_NAr) rather than classical, two‐step, S_NAr mechanisms. Whereas traditional S_NAr reactions require substantial activation of the aromatic ring by electron‐withdrawing substituents, such activating groups are not mandatory in the concerted pathways.     

Linear Separability of Positive Self-Dual Logical Filters

The threshold logic filter is an important nonlinear filter class, which is defined by a threshold logic function of binary input values. It is proved in this paper that not all positive self-dual logical functions are threshold functions if the number of input variables is 5 or more. The positive self-dual logical filter is a limited class but includes almost all filters for noise removal. Our result means that not all positive self-dual filters can be expressed by one operation of the threshold logic filters. In the sense of the filter expression by neural networks, the two-layer network cannot always optimize even this limited class.     

Dynamic Interconversion between Boroxine Cages Based on Pyridine Ligation

Dynamic interconversion between large covalent organic cages was achieved simply by heating or acid/base treatment. A mixture of the boroxine cages 12‐mer and 15‐mer was cleanly converted into a pyridine adduct of the 9‐mer boroxine cage upon treatment with pyridine, and the geometry of N‐coordinated boron atoms changed from trigonal to tetrahedral. The reverse reaction was achieved by heating or acid treatment. In this process, the larger boroxine cages 12‐mer and 15‐mer were found to be entropically favored owing to the release of free pyridine molecules from 9‐mer ?6 Py.     

Synergistic N‐Heterocyclic Carbene/Palladium‐Catalyzed Reactions of Aldehyde Acyl Anions with either Diarylmethyl or Allylic Carbonates

Benzylation and allylation of aldehyde acyl anions were enabled by the merger of a thiazolium N‐heterocyclic carbene (NHC) catalyst and a palladium/bisphosphine catalyst in a synergistic manner. Owing to the mildness of the reaction conditions, various functional groups were tolerated in the substrates.     

Preparation of Anti-Glycyrrhetinic Acid Monoclonal Antibody for Application in an Indirect Competitive Enzyme-Linked Immunosorbent Assay

Glycyrrhetinic acid is a major metabolite of glycyrrhizin, which is one of the main components of licorice roots and is considered to be one of the pharmacologically active substances in licorice. A new hybridoma cell line, named G-2A6, was generated by fusing mouse myeloma cells and splenocytes, which were immunized using glycyrrhetinic-acid–keyhole limpet hemocyanin to produce a monoclonal antibody (mAb) against glycyrrhetinic acid. Using the anti-glycyrrhetinic acid mAb, we attempted to develop a simple, rapid, and highly sensitive indirect competitive enzyme-linked immunosorbent assay (icELISA). The developed icELISA had a range from 3.91 to 125?ng/mL with low coefficients of variation (less than 5%) and demonstrated a high recovery rate of glycyrrhetinic acid spiked into licorice powder (average?=?101.76%). In addition, the icELISA could determine the glycyrrhetinic acid concentration in glycyrrhetinic-acid-spiked human serum with simple pretreatment, which suggests that the developed ELISA system using anti-glycyrrhetinic acid mAb would prove to be an effective and useful tool for determining glycyrrhetinic acid in various fields such as the analysis of Glycyrrhiza plants and pharmacokinetic studies of glycyrrhetinic acid during the administration of glycyrrhetinic acid, glycyrrhizin, and/or licorice-based medical agents.     

Structural change in a series of protonated layered perovskite compounds, HLnTiO4 (Ln=La, Nd and Y)

A deuterated n=1 Ruddlesden-Popper compound, DLnTiO₄ (HLnTiO₄, Ln=La, Nd and Y), was prepared by an ion-exchange reaction of Na⁺ ions in NaLnTiO₄ with D⁺ ions, and its structure was analyzed by Rietveld method using powder neutron diffraction data. The structure analyses showed that DLaTiO₄ and DNdTiO₄ crystallized in the space group P4/nmm with a=3.7232(1) and c=12.3088(1) Å, and a=3.7039(1) and c=12.0883(1) Å, respectively. On the other hand, DYTiO₄ crystallized in the space group P2₁/c with a=11.460(1), b=5.2920(4), c=5.3628(5) Å and β=90.441(9)°. The loaded protons were found to statistically occupy the sites around an apical oxygen of TiO₆ octahedron in the interlayer of these compounds, rather than Na atom sites in NaLnTiO₄.