On products in algebraic K-theory

This paper investigates the product structure in algebraic K-theory of rings. The first objective is to understand the relationships between products and the kernel of the Hurewicz homomorphism relating the algebraic K-theory of any ring to the integral homology of its linear groups. The second part of the paper is devoted to the ring of integers . Using recent results of V. Voevodsky we completely determine the products in tensored with the ring of 2-adic integers. Received: January 3, 1999.     

On the cohomology of highly connected covers of finite Hopf spaces

Relying on the computation of the André-Quillen homology groups for unstable Hopf algebras, we prove that if the mod p cohomology of both the fiber and the base in an H-fibration is finitely generated as algebra over the Steenrod algebra, then so is the mod p cohomology of the total space. In particular, the mod p cohomology of the n-connected cover of a finite H-space is always finitely generated as algebra over the Steenrod algebra.     

Color cyclic homology and Steinberg Lie color algebras

The present paper contains two interrelated developments. First, the basic properties of the construction theory over the Steinberg Lie color algebras are developed in analogy with Steinberg Lie algebra case. This is done on the example of the central closed of the Steinberg Lie color algebras. The second development is that we define the first ?-cyclic homology group HC₁(R, ?) of the Γ-graded associative algebra R (which could be seemed as the generalization of cyclic homology group and the ?/2?-graded version of cyclic homology that was introduced by Kassel) to calculate the universal central extension of Steinberg Lie color algebras.     

The Antagonist pGlu-βGlu-Pro-NH2 Binds to an Allosteric Site of the Thyrotropin-Releasing Hormone Receptor

After we identified pGlu-βGlu-Pro-NH₂ as the first functional antagonist of the cholinergic central actions of the thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH₂), we became interested in finding the receptor-associated mechanism responsible for this antagonism. By utilizing a human TRH receptor (hTRH-R) homology model, we first refined the active binding site within the transmembrane bundle of this receptor to enhance TRH’s binding affinity. However, this binding site did not accommodate the TRH antagonist. This directed us to consider a potential allosteric binding site in the extracellular domain (ECD). Searches for ECD binding pockets prompted the remodeling of the extracellular loops and the N-terminus. We found that different trajectories of ECDs produced novel binding cavities that were then systematically probed with TRH, as well as its antagonist. This led us to establish not only a surface-recognition binding site for TRH, but also an allosteric site that exhibited a selective and high-affinity binding for pGlu-βGlu-Pro-NH₂. The allosteric binding of this TRH antagonist is more robust than TRH’s binding to its own active site. The findings reported here may shed light on the mechanisms and the multimodal roles by which the ECD of a TRH receptor is involved in agonist and/or antagonist actions.     

SiCl4浓度对微晶硅薄膜生长及光电特性的影响

研究了SiCl4浓度对等离子体增强化学气相沉积(PECVD)系统中以SiCl4/H2为反应气体的微晶硅薄膜生长及光电特性的影响.结果表明,微晶硅薄膜的沉积速率和晶化率均随SiCl4浓度的增加而增大,而晶粒平均尺寸在SiCl4浓度小于65;时呈增大趋势,在SiCl4浓度大于65;时呈减小趋势;此外,光照实验表明制备的微晶硅薄膜具有较稳定的微观结构,具有类稳恒光电导效应,且样品的电导率依赖于SiCl4浓度的变化.此外,还讨论了Cl基基团在微晶硅薄膜生长过程中所起的作用.     

Anomalous Kondo-Switching Effect of a Spin-Flip Quantum Dot Embedded in an Aharonov-Bohm Ring

We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm （AIR） ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current （PC） sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering （R）. In the small AB ring, the PC is suppressed due to the enhancing R weakening the Kondo resonance. On the contrary, in the large AB ring, with R increasing, the peak of PC firstly moves up to max-peak and then down. Especially, the PC phase shift of π appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a carldidate for quantum switch.     

Curvature and Zeeman effects on persistent currents in a multi-walledcarbon nanotorus

Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown that in the absence of the Zeeman effect, the intrinsic curvature induces some dramatic changes in energy spectra and thus changes in the shape of the flux-dependent current. A paramagnetism--diamagnetism transition is observed. With consideration of the Zeeman splitting energy, the period of persistent current is destroyed, and a diamagnetism--paramagnetism transition is obtained at high magnetic field. In addition, we further explore the effect of external electric field energy (E_ef) on persistent current, indicating that it changes unmonotonously with E_ef.     

Anomalous Kondo-Switching Effect of a Spin-Flip Quantum Dot Embedded in an Aharonov-Bohm Ring

We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm (AB) ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current (PC) sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering (R). In the small AB ring, the PC issuppressed due to the enhancing R weakening the Kondo resonance.On the contrary, in the large AB ring, with R increasing, the peakof PC firstly moves up to max-peak and then down. Especially, the PCphase shift of ø appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a candidate for quantum switch.     

基于前处理的色谱联动检测多氯联苯的技术研究

研究了对多氯联苯（PCBs）进行检测分析过程中的关键技术.重点介绍固相微萃取（SPME）前处理技术及在富集、分离PCBs阶段的研究情况.并在此基础上,提出了提高气相色谱-电子捕获检测（GC-ECD）方法的灵敏度、提高固相微萃取柱对PCBs的吸附效率和速度、实现GC对不同极性的共面PCBs分离效率等的技术研究方向,对于研究PCBs检测技术的发展具有一定的指导作用.     

A Metal–Organic Supramolecular Box as a Universal Reservoir of UV,WL, and NIR Light for Long‐Persistent Luminescence

Long persistent luminescence (LPL) materials have a unique photophysical mechanism to store light radiation energy for subsequent release. However, in comparison to the common UV source, white‐light (WL) and near‐infrared (NIR) excited LPL is scarce. Herein we report a metal–organic supramolecular box based on a D–π–A‐type ligand. Owing to the integrated one‐photon absorption (OPA) and two‐photon absorption (TPA) attributes of the ligand, the heavy‐atom effect of the metal center, as well as π‐stacking and J‐aggregation states in the supramolecular assembly, LPL can be triggered by all wavebands from the UV to the NIR region. This novel designed supramolecular kit to afford LPL by both OPA and TPA pathways provides potential applications in anti‐counterfeiting, camouflaging, decorating, and displaying, among others.