Lembehsterols A and B,novel sulfated sterols inhibiting thymidine phosphorylase,from the marine sponge Petrosia strongylata

Lembehsterols A (1) and B (2), two novel sulfated sterols, were isolated from the marine sponge Petrosia strongylata. Both sterols showed inhibitory activity against thymidine phosphorylase, which is an enzyme related to angiogenesis in solid tumors. The structures of these sulfated sterols were established on the basis of chemical and physicochemical evidence.     

X-ray absorption spectroscopic study on the electronic structure of Li(1)(-)(x)()CoPO(4) electrodes as 4.8 V positive electrodes for rechargeable lithium ion batteries

Changes in the electronic structure of olivine Li(1-x)CoPO(4), 4.8 V positive electrode material for lithium ion batteries, were investigated using the X-ray absorption spectroscopy (XAS) technique. The threshold energy in the Co K-edge increased with electrochemical Li removal, indicating the oxidation of cobalt ions due to charge compensation. Moreover, P and O K-edge XAS showed a slight shift in threshold energy with Li removal. Although it is generally believed that the electrons of PO(4) polyanion do not contribute to the oxidation process, present experimental results indicate changes in the electronic structure around PO(4) units. Such results would be interpreted by the idea of the hybridization effect between the Co 3d and O 2p orbitals and of the polarization effect introduced by Li ions.     

Enzymatic transformation of bacterial polyhydroxyalkanoates into repolymerizable oligomers directed towards chemical recycling

The enzymatic transformation into an oligomer was carried out with the objective of developing the chemical recycling of bacterial polyesters. Poly(R-3-hydroxyalkanoate)s (PHAs), such as poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyhexanoate)] and poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyvalerate)], were degraded by granulated Candida antarctica lipase B immobilized on hydrophilic silica (lipase GCA) in a diluted organic solvent at 70 degrees C. The degradation products were cyclic oligomers having a molecular weight of a few hundreds. The obtained cyclic oligomer was readily repolymerized by the same lipase (lipase GCA) to produce the corresponding polyester in a concentrated solution. The cyclic oligomer was copolymerized with epsilon-caprolactone using lipase to produce the corresponding terpolymers having an Mw of 21,000. This is the first example of the enzymatic chemical recycling of bacterial PHAs using lipase. Poly(R-3-hydroxybutyrate) [P(3HB)] was also degraded into the linear-type R-3HB monomer to trimer by P(3HB)-depolymerase (PHBDP) in phosphate buffer at 37 degrees C. The degradation using PHBDP required a longer reaction time compared with the lipase-catalyzed degradation in organic solvent. The monomer composition of the oligomer depended on the origin of the PHBDP. The R-3HB monomer was predominately produced by PHBDP from Pseudomonas stutzeri, while the R-3HB dimer was produced by PHBDP from Alcaligenes faecalis T1. Repolymerization of these oligomers by lipase in concentrated organic solvent produced a relatively low-molecular-weight P(3HB) (e.g., Mw=2,000). Degradation of P(3HB) by lipase in organic solvent into repolymerizable cyclic oligomer and degradation of P(3HB) by PHBDP in buffer into hydroxy acid type R-3HB dimer.     

Finding any given 2‐factor in sparse pseudorandom graphs efficiently

Given an $n$‐vertex pseudorandom graph $G$ and an $n$‐vertex graph $H$ with maximum degree at most two, we wish to find a copy of $H$ in $G$, that is, an embedding $\phi :V\left(H\right)\to V\left(G\right)$ so that $\phi \left(u\right)\phi \left(v\right)\in E\left(G\right)$ for all $uv\in E\left(H\right)$. Particular instances of this problem include finding a triangle‐factor and finding a Hamilton cycle in $G$. Here, we provide a deterministic polynomial time algorithm that finds a given $H$ in any suitably pseudorandom graph $G$. The pseudorandom graphs we consider are $\left(p,\lambda \right)$‐bijumbled graphs of minimum degree which is a constant proportion of the average degree, that is, $\mathrm{\Omega }\left(pn\right)$. A $\left(p,\lambda \right)$‐bijumbled graph is characterised through the discrepancy property: $|e\left(A,B\right)?p|A||B||<\lambda \sqrt{|A||B|}$ for any two sets of vertices $A$ and $B$. Our condition $\lambda =O(p^{2}n/\log n)$ on bijumbledness is within a log factor from being tight and provides a positive answer to a recent question of Nenadov. We combine novel variants of the absorption‐reservoir method, a powerful tool from extremal graph theory and random graphs. Our approach builds on our previous work, incorporating the work of Nenadov, together with additional ideas and simplifications.     

A Normal Force on the Free Surface of a Coated Material

The three-dimensional theoretical solution of a concentrated normal force acting on the free surface of a coated material has been deduced by applying the reflection method. It is found that all stress functions defined in the local coordinate systems with their origins placed at each mirror point can be deduced from the fundamental solution of a concentrated normal force acting on the free surface of a semi-infinite homogeneous medium. The structure of the elastic solution has been illustrated by numerical analysis. It is found that only the stress functions corresponding to the first few mirror points are influential. It is also found that the effect of material combination on the stress field shall be described by three parameters, the two Dundurs' parameters and one additional parameter.     

A new synthetic approach to aminolycoside antibiotics by use of oxidative decarboxylation and reductive deacetoxylation as key-reactions

By use of a decarboxylation reaction with lead tetraacetate and a deacetoxylation reaction with sodium borohydride as key-reactions, paromamine ($\text{12}$ and tri-N-benzyloxycarbonylparomamine ($\text{12a}$) were synthesized from D-glucosamine.     

Fast and Robust Nanocellulose Width Estimation Using Turbidimetry

The dimensions of nanocelluloses are important factors in controlling their material properties. The present study reports a fast and robust method for estimating the widths of individual nanocellulose particles based on the turbidities of their water dispersions. Seven types of nanocellulose, including short and rigid cellulose nanocrystals and long and flexible cellulose nanofibers, are prepared via different processes. Their widths are calculated from the respective turbidity plots of their water dispersions, based on the theory of light scattering by thin and long particles. The turbidity‐derived widths of the seven nanocelluloses range from 2 to 10 nm, and show good correlations with the thicknesses of nanocellulose particles spread on flat mica surfaces determined using atomic force microscopy.

     

Age-dependent plasticity in the superior temporal sulcus in deaf humans: a functional MRI study

Background  

Sign-language comprehension activates the auditory cortex in deaf subjects. It is not known whether this functional plasticity in the temporal cortex is age dependent. We conducted functional magnetic-resonance imaging in six deaf signers who lost their hearing before the age of 2 years, five deaf signers who were >5 years of age at the time of hearing loss and six signers with normal hearing. The task was sentence comprehension in Japanese sign language.