两点边值问题解的存在性

本文讨论两点边值问题解的存在性,在没有孤立性条件下,获得了不动点定理,作为应用实例,给出了反应扩散方程稳态解的存在性证明。     

宽带可调谐掺Yb3+双包层光纤激光器的研究

利用闪耀光栅构成可调谐Littrow外腔,对掺Yb³⁺双包层光纤激光器的波长调谐输出进行了实验研究.激光调谐输出波长范围70nm.针对光纤内的双折射效应对激光的输出功率的影响,实验中使用了在线光纤偏振控制器,从而有效地减小了调谐曲线的起伏及其与荧光谱的差别,并得到了窄线宽、线偏振、宽带调谐的激光输出.     

Regioselective 1,2-Addition of Ti(IV)-enolate to α, β–Unsaturated Compounds

The nucleophilic addition to α, β-unsaturated carbonyl compounds is a fundamental C-C bond forming reaction in organic chemistry1. Since there are two reaction sites in the α, β–unsaturated carbonyl group, the regioselectivity of the nucleophilic addition (1, 2 vs. 1, 4 addition) is of primary importance when applying this type of reaction in organic synthesis. Factors that control the regioselectivity include the softness and hardness of the attacking nucleophiles2, solvent and temperatu…     

A New Alkaloid from Sinomenium acutum

Sinomenium acutum is widely used in East and South Asia for the treatment of many diseases, especially rheumatoid arthritis （RA）. The chemical research on Sinomenium acutum led to the isolation of a new alkaloid compound （1）. On the basis of chemical evidences and spectral analysis, 1 was identified as N-（1, 7-dimethoxylphenanthren-2-yl）acetamide.     

Alcohols＇ Classification by Infrared Spectra Segment Based on Support Vector Machines

This paper studies various classifiers to identify primary, secondary or tertiary alcohols by using segmental spectra and their combinations to support vector machines （SVMs）. The results showed that the O-H in-plane bending absorption contributed most to identification their substitute. This conclusion disagrees with related known research results.     

Electric transport character in the La0.7Ce0.3MnO3-SrTiO3-Nb heterojunction

The electric transport character in heterojunction composed of a La_0.7Ce_0.3MnO₃ film and a 0.5 wt% Nb-doped SrTiO₃ substrate (LCEM/STON) is investigated. It is found that the energy band gap (E_g) between LCEM and STON decreases with increasing temperatures. The most striking observation of present work is that there exists a variation of reverse transport mechanism from ionization to tunneling at the temperature of 175 K. We attribute the temperature dependence of reverse transport mechanism to co-work of E_g and the ferromagnetic (FM) insulting phase in the heterojunction. These results are helpful in configuring artificial devices using manganites.     

Synthesis and antitumor activity of a group of diosgenyl glycosides

Using orthogonal protection-deprotection glycosylation strategy, a series of diosgenyl glycosides with same of monosaccharides component but different in sequence were synthesized. The antitumor activity in vitro of synthesized diosgenyl glycosides was evaluated by standard MTT assay. It was observed that diosgenyl glycosides with a rhamnopyranosyl at C2′ of glucopyranosyl residue show potent antitumor activity in vitro.     

Surface Modification of Silica Gels as Carrier for AminoacylaseImmobilization

IrnmobilisedaIninoacylaseisanotablecatalystforthekineticresolutionofN-acetyl-D,L-aIninoacidsandquitealotofresearchworkhasbeeninvolvedonaminoacylase~bilisationswithitscarriers.lTheauthorshaverePortedthattheaIninosilicagelspreparedbyanlinProvedmethodwereeffechveforchymotryPsininunobilisahon,'l'butitwasnotproperforaIninoacylasetriobilisahon.InordertodevelopasahsfactorysurfacesmictUreofsilicagelsforaIninoacylasetriobilisation,tWokindsofreactivegrouPs,theN,N-diethylaIninogrouPandthehydroxygr…     

Sharp photonic Crystal Defect Modes and Their Response to Ultrashort Optical Pulses

Single photonic crystal defects based on an air-bridge structure were fabricated. We obtained sharp defect modes with quality factors higher than 600 and observed their response to ultrashort optical pulses by utilizing two-photon absorption.