Study on high voltage generation using flame column and DC power supply

A theory for generating an ultra-high voltage using a flame column (weakly ionized plasma) and a normal high-voltage (HV) power supply is presented. A high-voltage generator adapted based on this theory was fabricated, and experiments on high voltage generation were carried out. As a result, high voltages were observed between an electron cloud in front of the flame column and the positive electrode in the experiment, and highly positive charges were stored efficiently on the large positive electrode. The experimental results proved that the output voltage is three times higher than that of the output voltage of the HV power supply whenever the gas flow velocity is close to 0. A maximum output voltage was obtained for the output voltage of the HV power supply, which was 15 times higher than the output voltage of the HV power supply. The generated voltage and the output current for the output voltage of the HV power supply were investigated, and the temporal dependence of the charging current was also measured. The use of this method made it possible to obtain a high voltage and high electric field in a large space. Furthermore, the realistic possibility of achieving a 10-MV using this method was shown.     

Link-wise artificial compressibility method

The artificial compressibility method (ACM) for the incompressible Navier–Stokes equations is (link-wise) reformulated (referred to as LW-ACM) by a finite set of discrete directions (links) on a regular Cartesian mesh, in analogy with the lattice Boltzmann method (LBM). The main advantage is the possibility of exploiting well established technologies originally developed for LBM and classical computational fluid dynamics, with special emphasis on finite differences (at least in the present paper), at the cost of minor changes. For instance, wall boundaries not aligned with the background Cartesian mesh can be taken into account by tracing the intersections of each link with the wall (analogously to LBM technology). LW-ACM requires no high-order moments beyond hydrodynamics (often referred to as ghost moments) and no kinetic expansion. Like finite difference schemes, only standard Taylor expansion is needed for analyzing consistency. Preliminary efforts towards optimal implementations have shown that LW-ACM is capable of similar computational speed as optimized (BGK-) LBM. In addition, the memory demand is significantly smaller than (BGK-) LBM. Importantly, with an efficient implementation, this algorithm may be among the few which are compute-bound and not memory-bound. Two- and three-dimensional benchmarks are investigated, and an extensive comparative study between the present approach and state of the art methods from the literature is carried out. Numerical evidences suggest that LW-ACM represents an excellent alternative in terms of simplicity, stability and accuracy.     

Magnetically recoverable osmium catalysts for dihydroxylation of olefins

We prepared magnetically recoverable osmium catalysts by use of magnetite, quaternary ammonium salts, and potassium osmate(VI), and applied them to the dihydroxylation of olefins. By employing 2 mol% of the magnetic osmium catalyst, the dihydroxylation reaction proceeded smoothly to provide the corresponding vicinal diol in a good chemical yield. The osmium catalyst was readily recovered by use of an external magnet, and was reused repeatedly.     

Iron‐ and Bismuth‐Catalyzed Asymmetric Mukaiyama Aldol Reactions in Aqueous Media

We have developed asymmetric Mukaiyama aldol reactions of silicon enolates with aldehydes catalyzed by chiral Fe^II and Bi^III complexes. Although previous reactions often required relatively harsh conditions, such as strictly anhydrous conditions, very low temperatures (?78 °C), etc., the reactions reported herein proceeded in the presence of water at 0 °C. To find appropriate chiral water‐compatible Lewis acids for the Mukaiyama aldol reaction, many Lewis acids were screened in combination with chiral bipyridine L1 , which had previously been found to be a suitable chiral ligand in aqueous media. Three types of chiral catalysts that consisted of a Fe^II or Bi^III metal salt, a chiral ligand ( L1 ), and an additive have been discovered and a wide variety of substrates (silicon enolates and aldehydes) reacted to afford the desired aldol products in high yields with high diastereo‐ and enantioselectivities through an appropriate selection of one of the three catalytic systems. Mechanistic studies elucidated the coordination environments around the Fe^II and Bi^III centers and the effect of additives on the chiral catalysis. Notably, both Brønsted acids and bases worked as efficient additives in the Fe^II‐catalyzed reactions. The assumed catalytic cycle and transition states indicated important roles of water in these efficient asymmetric Mukaiyama aldol reactions in aqueous media with the broadly applicable and versatile catalytic systems.     

Oligo(ethylene glycol)/alkyl‐modified Chromophore Assemblies for Photon Upconversion in Water

Molecular self‐assembly is a powerful means to construct nanoscale materials with advanced photophysical properties. Although the protection of the photo‐excited states from oxygen quenching is a critical issue, it still has been in an early phase of development. In this work, we demonstrate that a simple and typical molecular design for aqueous supramolecular assembly, modification of the chromophoric unit with hydrophilic oligo(ethylene glycol) chains and hydrophobic alkyl chains, is effective to avoid oxygen quenching of triplet–triplet annihilation‐based photon upconversion (TTA‐UC). While a TTA‐UC emission is completely quenched when the donor and acceptor are molecularly dispersed in chloroform, their aqueous co‐assemblies exhibit a clear upconverted emission in air‐saturated water even under extremely low chromophore concentrations down to 40 μm . The generalization of this nano‐encapsulation approach offers new functions and applications using oxygen‐sensitive species for supramolecular chemistry.     

A Chemo-Enzymatic Expeditious Route to Racemic Dihexanoyl (2R*,3R*,4R*)-Dehydroxymethylepoxyquinomycin (DHMEQ), the Precursor for Lipase-Catalyzed Synthesis of the Potent Nuclear Factor-κB Inhibitor, (2S,3S,4S)-DHMEQ

In order to synthesize the potent nuclear factor (NF)-κB inhibitor, (2S,3S,4S)-dehydroxymethylepoxyquinomycin (DHMEQ), in a large scale, a new route for its corresponding racemic precursor, dihexanoyl (2R*,3R*,4R*)-DHMEQ, was developed. By employing both hydroquinone and benzoquinone intermediates, the total yield, reproducibility, and synthetic steps were improved and the synthetic cost was reduced.     

Preparation of soluble and fusible poly(2,5-dimethoxy-1,4-phenylene)

Poly(2,5-dimethoxy-1,4-phenylene) was prepared by oxidative polymerization of p-dimethoxybenzene with aluminum chloride and copper(II) chloride in nitrobenzene under reduced pressure. The polymers obtained were soluble in sulfuric acid and fusible at 320°C. The intrinsic viscosity of the polymer was ca. 0.07 in sulfuric acid. Demethylation of methoxy groups did not occur during the polymerization.     

Isolation of heptadepsin, a novel bacterial cyclic depsipeptide that inhibits lipopolysaccharide activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.     

Chimeric (alpha/beta + alpha)-peptide ligands for the BH3-recognition cleft of Bcl-XL: critical role of the molecular scaffold in protein surface recognition

Molecules that bind to specific surface sites on proteins are of great interest from both fundamental and practical perspectives. We are exploring a ligand development strategy that is based on oligomers with discrete folding propensities ("foldamers"); we target a specific cleft on the cancer-associated protein Bcl-xL because this system is well characterized structurally. In vivo, this cleft binds to alpha-helical segments (BH3 domains) of other proteins. We evaluated several types of helical foldamer, built entirely from beta-amino acid residues or from mixtures of alpha- and beta-amino acid residues, and ultimately identified foldamers in the latter class that bind very tightly to Bcl-xL. Our results suggest that combining different types of foldamer backbones will be an effective and general strategy for creating high-affinity and specific ligands for protein surface sites.     

Chemoenzymatic synthesis of (2S,3S,4S)-form, the physiologically active stereoisomer of dehydroxymethylepoxyquinomicin (DHMEQ), a potent inhibitor on NF-κB

A new route for (2S,3S,4S)-form, the physiologically active stereoisomer of dehydroxymethylepoxyquinomicin (DHMEQ), a potent NF-κB inhibitor, was established by chemoenzymatic approach. Elaboration on the asymmetric epoxidation of a p-benzoquinone monoketal with benzylcinchonidinium tert-butylhydroperoxide yielded an epoxyenone, in 79.8% ee and 57% yield in reproducible manner. By way of the transformation of this key intermediate to enantiomerically pure (2S,3S,4S)-DHMEQ, the contaminating undesired enantiomer could be effectively removed by applying Burkholderia cepacia lipase-catalyzed hydrolysis of diacylated precursor. The above integrated combination of chemical asymmetric synthesis and enzyme-catalyzed kinetic resolution enabled us to prepare active DHMEQ in a large-scale.