Auto‐Initiating Performance of Styrene on Surface Photografting Polymerization

Investigating the surface photografting polymerization of styrene (St), it was found that in the absence of photoinitiator and at high temperatures, a remarkable amount of St‐grafted polymer is formed. The initiation performance of St was further confirmed by surface photografting polymerization of acrylic acid, where St was used as the photoinitiator. This finding is useful to investigate the reaction mechanism of aromatic compounds under UV radiation and develop photoinitiator‐free polymerization systems.     

微波作用下2,3,5-三取代噻吩的合成及光电性质的研究

含硫芳香化合物可用于有机半导体、电致发光器件,电致变色器件和场效应管。噻吩是一种富电子的五元芳杂环,电子的流动性大,有望成为较好的电子注入／传输材料。我们利用微波辐射在噻吩环的2,3,5位引入了芳基,产物的结构经元素分析、质谱、^1H NMR表征,采     

Synthesis and Cytotoxicity Evaluation of Certain α‐Methylidene‐ γ‐butyrolactones Bearing Coumarin,Flavone, Xanthone,Carbazole, and Dibenzofuran Moieties

The cytotoxicities of α‐methylidene‐γ‐butyrolactones, which are linked to coumarins (see 15 and 16 ) and to potential DNA‐intercalating carriers such as flavones, xanthones, carbazole, and dibenzofuran (see 9a – e , 10a – e , 11 , and 12 ), were studied. These compounds were synthesized via alkylation of their hydroxy precursors followed by a Reformatsky‐type condensation (Scheme). These α‐methylidene‐γ‐butyralactones were evaluated in vitro against 60 human tumor cell lines derived from nine cancer cell types and demonstrated a strong growth‐inhibitory activity against leukemia cancer cells (Tables 1 and 2). For flavone‐ and xanthone‐containing α‐methylidene‐γ‐butyrolactones 9a – e and 10a – e , respectively, the overall potency (mean value) decreased on introduction of an electron‐withdrawing substituent at the γ‐phenyl substituent and increased with an electron‐donating substituent. Comparing the different chromophores established the following order of decreasing potency (log GI₅₀): dibenzofuran ( 12 , −6.17) > flavone ( 9a , −5.96) > carbazole ( 11 , −5.80) and xanthone ( 10a , −5.77) > coumarin ( 15 , −5.60; 16 , −5.65). Among them, the dibenzofuran derivative 12 showed not only strong inhibitory activities against leukemia cancer cell lines with an average log GI₅₀ value of −7.22, but also good inhibitory activities against colon, melanoma, and breast cancer cells with average log GI₅₀ values of −6.23, −6.31, and −6.39, respectively.     

STUDY ON POLYMERIZATION OF OILLESS ALKYD RESIN WITH PHENYLTRIETHOXYSILANE

Oilless alkyd resin modified with the silicoorganic compounds has been obtainedsuccessfully by polymerization.At appropriate proportion of silicoorganic compounds,thepolymerized product has higher hardness and lustre than that of oilless alkyd resin.     

A bilinear form of the variational principle with vanishing parameter

Summary  A variational principle whose Lagrangian function generates a hyperbolic heat conduction equation is exhibited. The main characteristic of this principle is that it contains two temperature fields that enter bilinearly into the Lagrangian function. These two fields are interpreted as two mutually independent approximate temperature profiles which are potentially competent to describe rationally the real physical temperature distribution. The proposed variational principle is used as a starting point for finding approximate solutions of the classical, i.e. Fourier's, heat conduction theory, by employing the vanishing parameter technique and the direct methods of variational calculus. Received 4 June 1997; accepted for publication 1 July 1997     

Comparison of optimization methods in planar chromatography

Summary The optimisation of chromatographic parameters is studied. The Window Diagram and Overlapping Resolution Map (ORM) methods are compared. The latter is developed to take into account the spot diameter and the average plate height variations with the development distance, in order to improve the reliability of the method.     

Transoral laryngeal surgeryunder flexible laryngovideostroboscopy

Although direct microlaryngoscopic surgery is universally accepted as the standard procedure for endolaryngeal surgery, general anesthesia and direct laryngoscopy are necessary during the procedure. Suspended laryngeal position also impedes intraoperative functional monitoring. Transoral laryngeal surgery under indirect laryngeal mirror or telescope has the advantage of sparing general anesthesia and direct laryngoscopy, but lower precision, difficult manipulation, and a high patient cooperation requirement make the procedure of limited application. Trying to overcome the above shortcomings, transoral laryngeal surgery under flexible laryngovideostroboscopy (FLVS) is undertaken at our institute. The surgery is performed at an outpatient office under topical anesthesia, with the help of high-resolution fiberoptic stroboscopy, high-quality CCD videocamera, and monitor. From October, 1993 to March, 1996, 157 patients with selected laryngeal problems were operated upon using this technique, and 150 patients smoothly completed the procedure with satisfactory results. The technique is highly effective, especially for limited-manipulation, lower precision procedures and for patients who are not candidates for general anesthesia. With proper patient selection, this is a cost-effective surgery of low invasiveness and high applicability.     

Synthesis of New β-Cyclodextrin Dimers Bridged by Schiff Base

Thecyclodextrindimerisaveryinterestingsupramolecularhostthatcanrecognizeditopicgueststoformvarioussignificantsupramolecularstructures.Althoughmanycyclodextrindimershavebeensuccessfullyprepared',theirsynthesisisstilldifficultandrequirescontinuousefforttoovercome.Sincethepropertiesofacyclodextrindimeraredecideddomnantlybythebridge,itiscriticaltochoosealinkerthathassignificanceandavailability.ConsideringtheinterestingbindingandchromophoricpropertiesoftheSchiffbasemoiety,aswellastheconvenienceofin…