Chirality‐Sensing Binaphthocrown Ether–Polythiophene Conjugate

An enantiomeric binaphthyl unit was tethered to adjacent thiophenes with oxyethylene linkers to give a chiral polythiophene with binaphthocrown ether cavities. Upon inclusion of a chiral cationic guest in the cavity of the chiral crown ether–polythiophene conjugate, the bithiophene unit was twisted to shorten the effective conjugation length of polythiophene backbone, enabling us to sense the guest binding by reading out the amplified optical signal gains arising from the backbone structure change. This strategy allowed us to discriminate the guest chirality without using chiroptical signals or a circular dichroism spectrometer to achieve the highest enantioselectivity of 7.3 for valine methyl ester with a 40‐fold enhanced sensitivity compared with the corresponding monomeric sensor.     

Separation of zeros for source signature identification under reverberant path conditions

This paper presents an approach to distinguishing the zeros representing a sound source from those representing the transfer function on the basis of Lyon's residue-sign model. In machinery noise diagnostics, the source signature must be separated from observation records under reverberant path conditions. In numerical examples and an experimental piano-string vibration analysis, the modal responses could be synthesized by using clustered line-spectrum modeling. The modeling error represented the source signature subject to the source characteristics being given by a finite impulse response. The modeling error can be interpreted as a remainder function necessary for the zeros representing the source signature.     

A birational construction of projective compactifications of ℂ3 with second Betti number equal to onewith second Betti number equal to one

We give an explicit construction of all projective compactifications of ℂ³ with second Betti number equal to one. Dedicated to K.-N. Hatsue Entrata in Redazione il 30 novembre 1998.     

Neutron scattering of fragile antiferromagnetic phases in heavy fermion compounds

Results of neutron scattering and specific heat measurements are reported for two kinds of weak antiferromagnetic compounds corresponding to (i) the situation at the quantum critical point and (ii) the double magnetic transition observed in CeRu₂Ge₂.     

Stokesian dynamics simulation of the role of hydrodynamic interactions on the behavior of a single particle suspending in a Newtonian fluid. Part 1. 1D flexible and rigid fibers

As seen in textbooks of polymer physics, a linear polymer chain can be modeled as a filament of connected beads. This concept can also be adapted to fibers and, for example, flexible fibers can be modeled by considering a stretch force, bending and torsion torques with a non-slip condition between adjacent beads, following the particle simulation method. In predicting fiber motions and their relating rheological properties, the importance of hydrodynamic interactions should be analyzed, so in this work we study the effect of hydrodynamic interactions on the behavior of a single flexible fiber under shear using Stokesian dynamics simulation with a 11N × 11N mobility matrix, where N is the aspect ratio of the fiber. Our results indicate that hydrodynamic interaction becomes significant when the fiber is highly flexible.     

Synthesis, chemical properties and mutagenicity of 1,6- and 3,6-dinitrobenzo[a]pyrenes

Nitration of benzo[a]pyrene (BaP) with HNO3 (d = 1.38) produced a mixture of dinitroBaPs (1,6- and 3,6-isomers) and mononitroBaPs (1-, 3- and 6-isomers). Pure 1,6-dinitroBaP and 3,6-dinitroBaP were obtained by the reduction of the dinitroBaPs mixture with NaSH to yield the separable products 1-amino-6-nitroBaP and 3-amino-6-nitroBaP, followed by conversion to dinitroBaPs via the the diazonium salts. The half-wave potentials (E1/2) corresponding to the one-electron reduction of dinitroBaPs were measured and the relationship of these values to the mutagenicity is discussed.     

Crystal structure of methyl endo-8-cyano-exo-8-methyl-3-oxo-2-oxabicyclo[2.2.2]oct-5-ene-6-carboxylate.

A photochemical cycloaddition reaction of methyl 2-pyrone-5-carboxylate with methacrylonitrile mainly gave a [4 + 2] cycloadduct, assigned as methyl endo-8-cyano-exo-8-methyl-3-oxo-2-oxabicyclo[2.2.2]oct-5-ene-6-carboxylate, whose structure was determined by an X-ray diffraction study. The formation of the cycloadduct was reasonably explained by considering a biradical intermediate having a less steric hindrance between the methoxycarbonyl group and the cyano group.     

Low temperature dependence of elastic moduli and internal friction for the glassy alloy Zr55Cu30Al10Ni5

Longitudinal and transverse wave velocities, eight kinds of elastic parameters, and dilational and shear internal frictions of Zr₅₅Cu₃₀Al₁₀Ni₅ glassy alloy were simultaneously measured as a function of temperature in the range from 77 to 373 K, using an ultrasonic pulse method. The inflections at around 150 K for wave velocities, anisotropy factor and Poisson's ratio, and the 150 K peak of shear friction seem to correspond to one topological change (pseudo‐transition) associated with an interatomic readjustment or vacancy rearrangements. The behaviors from 77 to 125 K and 125 to 373 K are due to thermal relaxation of squeezed free volumes and entropy elasticity associated with vibrational motions of clusters, respectively, accompanied by an increase in atomic distance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of highly dispersible and tumor-accumulative, iron oxide nanoparticles Multi-point anchoring of PEG-b-poly(4-vinylbenzylphosphonate) improves performance significantly

This paper describes the preparation of iron oxide nanoparticles, surface of which was coated with extremely high immobilization stability and relatively higher density of poly(ethylene glycol) (PEG), which are referred to as PEG protected iron oxide nanoparticles (PEG-PIONs). The PEG-PIONs were obtained through alkali coprecipitation of iron salts in the presence of the PEG-poly(4-vinylbenzylphosphonate) block copolymer (PEG-b-PVBP). In this system, PEG-b-PVBP served as a surface coating that was bound to the iron oxide surface via multipoint anchoring of the phosphonate groups in the PVBP segment of PEG-b-PVBP. The binding of PEG-b-PVBP onto the iron oxide nanoparticle surface and the subsequent formation of a PEG brush layer were proved by FT-IR, zeta potential, and thermogravimetric measurements. The surface PEG-chain density of the PEG-PIONs varied depending on the [PEG-b-PVBP]/[iron salts] feed-weight ratio in the coprecipitation reaction. PEG-PIONs prepared at an optimal feed-weight ratio in this study showed a high surface PEG-chain surface density (≈0.8 chainsnm(-2)) and small hydrodynamic diameter (<50 nm). Furthermore, these PEG-PIONs could be dispersed in phosphate-buffered saline (PBS) that contains 10% serum without any change in their hydrodynamic diameters over a period of one week, indicating that PEG-PIONs would provide high dispersion stability under in vivo physiological conditions as well as excellent anti-biofouling properties. In fact we have confirmed the prolong blood circulation time and facilitate tumor accumulation (more than 15% IDg(-1) tumor) of PEG-PIONs without the aid of any target ligand in mouse tumor models. The majority of the PEG-PIONs accumulated in the tumor by 96 h after administration, whereas those in normal tissues were smoothly eliminated by 96 h, proving the enhancement of tumor selectivity in the PEG-PION localization. The results obtained here strongly suggest that originally synthesized PEG-b-PVBP, having multipoint anchoring character by the phosphonate groups, is rational design for improvement in nanoparticle as in vivo application. Two major points, viz., extremely stable anchoring character and dense PEG chains tethered on the nanoparticle surface, worked simultaneously to become PEG-PIONs as an ideal biomedical devices intact for prolonged periods in harsh biological environments.