聚硅烷研究进展 (1)聚硅烷的合成及应用

聚硅烷的合成及应用因可溶性聚硅烷的发现而成为聚合物研究的又一热点。本文综述了聚硅烷合成与应用的近期发展。     

All-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity

A novel scheme for all-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity is proposed and investigated numerically. The results show, for a 2.5 GHz driving pulse train, it can be generated 5-25 GHz repetition rate pulse trains with low clock amplitude jitter, polarization independence and high peak power. Furthermore, the extraction of the clock signal from a pseudorandom bit sequence signal can be realized based on the proposed scheme.     

Ring expansion of 5- to 6-member zirconacycles by carbenoid insertion

A wide range of carbenoids (1-lithio-1-halo species), including those with α-SiR₃, OEt, SPh, SO₂Ph, P(O)(OEt)₂, and CN substituents, insert into 5-member zirconacycles (saturated and unsaturated, mono- and bi-cyclic) to afford functionalized 6-member zirconacycles. 1-Lithio-1-haloalkenes insert to afford 6-member zirconacycles with an alkylidene substituent next to the metal. Unexpected double insertion of some carbenoids, and evidence for endocylic β-hydride transfer processes provide additional mechanistic interest.     

INJECTIVE PRECOVERS AND MODULES OF GENERALIZED INVERSE POLYNOMIALS

Let (S,≤) be an ordered set. Recall that (S,≤) is artinian if every strictly decreasingsequence of elements of S is ?nite, and that (S,≤) is narrow if every subset of pairwiseorder-incomparable elements of S is ?nite. Let S be a commutative monoid. Unl…     

Synthetic studies toward the immunosuppressant FR901483. Facile construction of the azatricyclic skeleton

A concise synthesis of the azatricyclic core structure of FR901483, a potent immunosuppressant, has been accomplished. The key elements of the approach involve a nucleophilic addition to an acyl iminium ion, a ring closing metathesis and a lactone-lactam rearrangement to provide the tricyclic structure.     

Total synthesis of malayamycin A and analogues

The total synthesis of the bicyclic C-nucleoside malayamycin A is described starting with d-ribonolactone. A new method was developed to obtain preparatively important quantities of β-pseudouridine, which was used as an intermediate. The synthesis of a carba N-nucleoside analogue of malayamycin A is also described.     

Concise asymmetric synthesis of (−)-halosaline and (2R,9aR)-(+)-2-hydroxy-quinolizidine by ruthenium-catalyzed ring-rearrangement metathesis

A ruthenium-catalyzed ring opening-ring closing metathesis reaction serves as the key step in the stereoselective synthesis of a new enantiopure 2-substituted-4,5-dehydropiperidine skeleton, a valuable intermediate for the synthesis of piperidine alkaloids (such as (−)-halosaline) and of hydroxylated quinolizidines (such as (2R,9aR)-(+)-2-hydroxy-quinolizidine).     

集合环

本文用集环来表现模糊集，得到了表现定理的新形式，并证明了这种表现可以有限化，即用有限个经典集近似刻划模糊集并且这样的刻划是同态的。最后，证明了集对方法是集环表现的特殊情形。     

Complete Surjections and Complete Epimorphisms over Completely Distributive Lattices

Generators and lattice properties of the poset of complete homomorphisic images of a completely distributive lattice are exploited via the localic methods. Some intrinsic and extrinsic conditions about this poset to be a completely distributive lattice are given. It is shown that the category of completely distributive lattices is co-well-powered,and complete epimorphisms on completely distributive lattice are not necessary to be surjections. Finally, some conditions about complete epimorphisms to be surjections are given.     

Recognition of ring pairs in the data analysis of Cherenkov detectors

We present a new algorithm for the identification of ring pairs in Cherenkov detectors. The approach combines linear regression methods for the construction of an appropriate reference quantity, methods from statistics for the evaluation of hypotheses and Monte Carlo simulation runs for the tuning of threshold levels.