Preparation of telechelic oligomers by controlled thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene)

It was found that telechelic isotactic oligo(1-butene) and telechelic oligo(propylene-ran-1-butene) could be isolated as nonvolatile oligomers from polymer residues resulting from the thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene), respectively. Their structures were determined by ¹H and ¹³C NMR with attention being paid to their reactive end groups. The maximum average number of terminal vinylidene groups per molecule (f_TVD) was 1.8, indicating that about 80 mol% were α,ω-diene oligomers having two terminal vinylidene groups. This useful new telechelic oligomer had a lower polydispersity than the original polymer, in spite of its lower molecular weight and T_m. The composition of end groups of nonvolatile oligomers obtained by thermal degradation of poly(propylene-ran-1-butene) could be explained by the differences in bond dissociation energy and activation energy of elementary reactions during thermal degradation, based on the monomer composition of the original polymer.     

Ladderlike ferromagnetic spin coupling network on a pi-conjugated pendant polyradical

A poly(9,10-anthryleneethynylene)-based polyradical with two pendant stable phenoxyls in one anthracene skeleton was newly synthesized via polymerization of the corresponding bromoethynylanthracene monomer using a Pd(0) catalyst. The average molecular weight of the polymer reached M(n) = 5 x 10(3) and was soluble in common organic solvents. The polyradical was prepared from the corresponding hydroxyl precursor polymer and was appropriately stable at room temperature. The ESR spectrum of the corresponding monomeric radical suggested an effectively delocalized spin density distribution on the backbone anthracene. The magnetization and the static magnetic susceptibility of the polyradical were measured using a SQUID magnetometer. The large average spin quantum number (S = (5)/(2)) of the polyradical indicated that the ferromagnetic spin coupling network of the polyradical had spread throughout the pi-conjugated chain and that it was considerably insensitive to spin defects.     

Reductive coupling of carbonyl compounds using lanthanum metal

We found that lanthanum metal was an excellent agent for the reduction of carbonyl compounds in the presence of a catalytic amount of iodine. When carbonyl compounds were treated with lanthanum metal in the presence of a catalytic amount of iodine, the reductive coupling of the carbonyl compounds proceeded efficiently to afford the corresponding vic‐diols in moderate to good yields. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:81–85, 2000     

Stability radius of linear parameter-varying systems and applications

In this paper, we present a unifying approach to the problems of computing of stability radii of positive linear systems. First, we study stability radii of linear time-invariant parameter-varying differential systems. A formula for the complex stability radius under multi perturbations is given. Then, under hypotheses of positivity of the system matrices, we prove that the complex, real and positive stability radii of the system under multi perturbations (or affine perturbations) coincide and they are computed via simple formulae. As applications, we consider problems of computing of (strong) stability radii of linear time-invariant time-delay differential systems and computing of stability radii of positive linear functional differential equations under multi perturbations and affine perturbations. We show that for a class of positive linear time-delay differential systems, the stability radii of the system under multi perturbations (or affine perturbations) are equal to the strong stability radii. Next, we prove that the stability radii of a positive linear functional differential equation under multi perturbations (or affine perturbations) are equal to those of the associated linear time-invariant parameter-varying differential system. In particular, we get back some explicit formulas for these stability radii which are given recently in [P.H.A. Ngoc, Strong stability radii of positive linear time-delay systems, Internat. J. Robust Nonlinear Control 15 (2005) 459-472; P.H.A. Ngoc, N.K. Son, Stability radii of positive linear functional differential equations under multi perturbations, SIAM J. Control Optim. 43 (2005) 2278-2295]. Finally, we give two examples to illustrate the obtained results.     

Holographic Three Dimensional Printer Using Galvanometer Scanners

To make holograms from computer graphic (CG) in a short time, a new holographic three dimensional (3D) printer is proposed here. This printer consists of galvanometer scanners, a micro computer and a laser, and uses a holographic contact duplicating method. Experiments have shown that a hologram of 39 × 41 mm can be obtained in 4 min.Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994.     

Low‐voltage,high‐gain,and high‐mobility organic complementary inverters based on N,N′‐ditridecyl‐3,4,9,10‐perylenetetracarboxylic diimide and pentacene

The authors describe an organic complementary inverter with N,N′‐ditridecyl‐3,4,9,10‐perylenetetracarboxylic diimide as an n‐type semiconductor and pentacene as a p‐type semiconductor. Each transistor of the inverter exhibited high carrier mobility: 1.62 cm²/Vs for an n‐type drive transistor and 0.57 cm²/Vs for a p‐type switch transistor. The gain of the inverter reached 125. Another inverter using Ta₂O₅ as a high κ gate dielectric performed well with a gain of 500 and an operation voltage of only 5 V.

     

Conical support for double-stage diamond anvil apparatus

ABSTRACT

Both micro-paired and conical support type double-stage diamond anvil cells (ds-DAC) were tested using a newly synthesized ultra-fine nano-polycrystalline diamond (NPD). Well-focused X-ray sub-micron beam and the conically supported 2nd stage anvils (micro-anvils) with 10?μm culet enable us to obtain good quality X-ray diffraction peaks from the sample at around 400?GPa. The relationship between confining pressure and sample pressure depends heavily on the initial height (thickness) of micro-anvils, the difference of a few micrometers leads to a quite different compression path. The conical support type is a solution to retain both enough thickness and strength of micro-anvils at higher confining pressure conditions. All conical support ds-DAC experiments terminated by the failure of the 1st stage anvil instead of 2nd one. The combination of ultra-fine NPD 2nd stage anvil and NPD 1st stage anvil opens a new frontier for measurement of the X-ray absorption spectrum above 300?GPa.     

Atomic correlation between adjacent graphene layers in double-wall carbon nanotubes

Atomic correlation between adjacent graphene layers was elucidated for double-wall carbon nanotubes (DWNTs) through a chiral index assignment of two nested nanotubes by high-resolution transmission electron microscopy. Our analysis provides a rather constant diameter difference close to 0.75 nm but no chiral angle correlation between the constituent nanotubes in the concentric DWNTs. The local atomic correlation as a commensurate graphene stacking was repeatedly found in eccentric DWNTs and circumscribed nanotubes, which should lead to elastic deformation and bundling of nanotubes.