Diastereoselective dl-hydrocoupling of benzalacetones by electroreduction

Electroreduction of benzalacetones with an undivided cell in Et(4)NOTs/acetonitrile gave cyclized dl-hydrodimers as mixtures of two diastereomers. The hydrodimerization proceeded stereoselectively to afford linear dl-hydrodimers, and the following cyclization led to two thermodynamically stable diasteromers of cyclopentanols.     

Fluoride complexation of element 104, rutherfordium

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.     

Ultrathin hollow nanoshells of manganese oxide

Novel hollow nanoshells of Mn(2)O(3) with controllable ultrathin shell thickness have been fabricated through layer-by-layer assembly of exfoliated MnO(2) nanosheets and polyelectrolytes on polymer bead templates, followed by removal of the polymer cores via calcination.     

Holographic manipulation of nanoparticle distribution morphology in nanoparticle-dispersed photopolymers

We report on experimental verification of mass transfer of nanoparticles during holographic recording in nanoparticle-dispersed photopolymers. Through direct observations of the microscopic structure of recorded holograms as well as optical measurements of the phase shift between the light interference pattern and a recorded hologram we find that holographic exposure causes nanoparticles to be redistributed from bright to dark regions, leading to periodic assembly of nanoparticles and thereby to formation of high-contrast holograms.     

Identification of a set of genes involved in the formation of the substrate for the incorporation of the unusual "glycolate" chain extension unit in ansamitocin biosynthesis

The unusual "glycolate" extender unit at C-9/C-10 of ansamitocin is not derived from 2-hydroxymalonyl-CoA or 2-methoxymalonyl-CoA, as demonstrated by feeding experiments with the corresponding 1-13C-labeled N-acetylcysteamine thioesters but is formed from an acyl carrier protein (ACP)-bound substrate, possibly 2-methoxymalonyl-ACP, elaborated by enzymes encoded by a subcluster of five genes, asm12-17, from the ansamitocin bisosynthetic gene cluster.     

Synthetic Chemistry and Function of Bacterial Cell Surface Glycoconjugates

Typical bacterial glycoconjugates are known to stimulate immunological systems of higher animals and thereby play important roles in the primary defense of animals against bacterial infection. Lipopolysaccharide (LPS) of gram‐negative bacteria is a representative of such glycoconjugates. LPS was first discovered as a potent bacterial toxin and named endotoxin but was soon found to exhibit immunostimulating activity. By the use of our synthetic pure preparations, the lipophilic partial structure of LPS, designated lipid A, proved to be the active entity responsible for both endotoxic and immunostimulating activities of LPS. This paper deals with our recent chemical synthesis and functional study of lipid A and related compounds. Synthesis is described of its various structural analogues, radio‐labeled compound and Re‐type LPS that contains two additional sugar moieties linked to lipid A.     

Sparse coding for layered neural networks

We investigate storage capacity of two types of fully connected layered neural networks with sparse coding when binary patterns are embedded into the networks by a Hebbian learning rule. One of them is a layered network, in which a transfer function of even layers is different from that of odd layers. The other is a layered network with intra-layer connections, in which the transfer function of inter-layer is different from that of intra-layer, and inter-layered neurons and intra-layered neurons are updated alternately. We derive recursion relations for order parameters by means of the signal-to-noise ratio method, and then apply the self-control threshold method proposed by Dominguez and Bollé to both layered networks with monotonic transfer functions. We find that a critical value _C of storage capacity is about 0.11|a ln a|⁻¹ (a1) for both layered networks, where a is a neuronal activity. It turns out that the basin of attraction is larger for both layered networks when the self-control threshold method is applied.     

Dependence of viscosity of concentrated polymer solutions upon molecular weight and concentration

Molecular weight M and concentration c dependencies of the zero-shear viscosity (η) were measured over wide ranges of M and c for concentrated solutions of linear and branched poly(vinyl acetate) as well as of polystyrene under θ conditions. The log η versus log M and log η versus log c curves for a given system can be superposed by the horizontal shift along the abscissa, giving smooth master curves. From the shift factors the ratio of two exponents β and α, which appear in the following equation, can be evaluated: η = K′(cρ)^αM^β, where ρ is the density of the solution and K′ is a constant at constant temperature. The evaluated values of β/α for the systems under θ conditions are equal to or very close to 0.50 as was anticipated from the previous work. The above superposition method was also applied to available viscosity data, and it was found that β/α had a good correlation with a in [η] = KM^a. This indicates that the individual molecules in concentrated solutions maintain the same individuality as in dilute solutions, and might be a positive support to the packed sphere model proposed previously by the authors. The effect of solvent on the molecular weight and the concentration dependencies of viscosity was also discussed.     

Calderón-Zygmund Operators on the Predual of a Morrey Space

We consider the boundedness of Calderón-Zygmund operators from H ^{p ,ϕ} (R ⁿ )(the predual of a Morrey space) to h ^{p ,ϕ} (R ⁿ )(the local version of H ^{p ,ϕ} ). We show that Calderón's commutator is bounded from H ^{p ,ϕ} to h ^{p ,ϕ} .