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91.
92.
The polarographic currents of lincomycin in the absence and the presence of persulfate are studied by linear potential scan polarography and cyclic voltammetry. The reduction wave of lincomycin in phosphate buffer is a catalytic hydrogen wave, which is the reduction of the proton combined with lincomycin in nature. When S2O82− is present, the atomic hydrogen as intermediate product from the reduction of the combined proton is oxidized by both S2O82− and its reduction intermediate, sulfate radical anion SO4−, to regenerate the original proton, producing the parallel catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave, a novel method for the determination of lincomycin is proposed. In 0.48 mol l−1 KH2PO4-Na2HPO4 (pH 7.4)-8.0×10−3 mol l−1 K2S2O8 supporting electrolyte, the peak potential of the parallel catalytic hydrogen wave is −1.82 V (vs. SCE). The second-order derivative peak current is rectilinear to the lincomycin concentration in the range of 8.5×10−8-9.0×10−5 mol l−1 and the detection limit is 4×10−8 mol l−1. The parallel catalytic hydrogen wave is three orders in magnitude higher than that of the corresponding catalytic hydrogen wave in analytical sensitivity. The proposed method is applied to the rapid determination of lincomycin hydrochloride in eye drops without previous separation. 相似文献
93.
本文探究了MRI增强扫描(DCE-MRI)联合磁共振扩散加权成像(DWI)检测对乳腺癌的诊断效果。回顾性分析2015年8月~2017年8月本院收治的经手术病理证实的乳腺癌患者81例,术前均行DCE-MRI和DWI检查,根据数据绘制时间-信号强度曲线(TIC),并计算扩散系数(ADC)值。以病理结果为金标准,计算单一检测及联合检测的诊断准确率,并采用ROC分析ADC值诊断乳腺癌良/恶性的效能。结果显示,81例患者经手术病理诊断显示良性37例、恶性44例;DCE-MRI与DWI联合检测的敏感度与准确度显著高于单一检测(P<0.05);良、恶性病灶的TIC分型分布比较,差异具有统计学意义(P<0.05);恶性病灶ADC值较良性病灶低(P<0.05);ADC值诊断乳腺癌良/恶性最佳界限值为1.28×10-3 mm 2/s,灵敏度和特异度分别为86.5%和90.9%。因此,DCE-MRI与DWI联合检测可明显提高乳腺癌良/恶性病变诊断的准确度,为临床诊断提供可靠影像学依据。 相似文献
94.
A series of 10 new poly(heteroarylene methylenes) containing one pyrrole or thiophene ring alternating with a carbon atom in the main chain were synthesized and characterized. The polymers which were synthesized in the air were found to be partially dehydrogenated by the oxygen, that is, the bridge carbon atoms between pyrrole or thiophene rings were partially sp3 atoms and partially sp2 atoms. However the polymers which were synthesized in the flowing nitrogen atmosphere were found to be deoxidized, that is the bridge atoms were sp3 atoms. The deoxidized polymers could be oxidatively dehydrogenated with tetrchlorobenzoquinone. These polymers are useful model systems to investigate the effect of conjugation length on the electronic and optical properties of conjugated polymers. Third‐order optical non‐linearities of the reulting polymers were studied by z‐scan techniques. The results show that the reulting polymers exhibited large third‐order optical non‐linear susceptibilities as large as 10?8 esu. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
95.
N. Blidi Boukamel A. Krallafa D. Bormann L. Caron M. Canipelle S. Tilloy E. Monflier 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(3-4):269-274
Quantum mechanical calculations on the (4-tert-butylphenyl)(3-sulfonatophenyl) (phenyl) phosphine/-cyclodextrin inclusion complex werecarried out using semi-empirical calculations. Inclusion process pathways are describedand the most probable structures of the 1:1 complex are sought through a global potentialenergy scan. The calculations suggest that the most stable structure is obtained whenthe aromatic ring bearing the tert-butyl group is includedinto the hydrophobic cavity of the -cyclodextrin from theside of the primary hydroxyl groups. 相似文献
96.
Chemically modified steroids (designer steroids), including tetrahydrogestrinone and norbolethone, pose a threat to the integrity of the sport community. These compounds have recently been detected in urine specimens from athletes, resulting in temporary or permanent suspension from amateur and/or professional competition. Triple quadrupole mass spectrometers enable doping control laboratories to screen for unknown, anabolic, androgenic steroids utilizing precursor ion scans. On the basis of common dissociation patterns of steroids with common structural features, characteristic product ions were selected to serve as diagnostic markers for previously unidentified drugs or drug metabolites in human urine samples. An assay was established to complement standard screening procedures. Urine specimens were enzymically hydrolyzed, partitioned into ether, concentrated, and analyzed by precursor ion scanning. Spectra from samples fortified with eight standard compounds (methyltestosterone, ethyltestosterone, 1-testosterone, gestrinone, dihydrogestrinone, tetrahydrogestrinone, norbolethone, and propyltrenbolone) and one deuterium-labeled analog (d(4)-tetrahydrogestrinone) at 50 ng/ml of urine, had precursor ion peaks other than those from common endogenous steroids. Subsequent product ion scan experiments on precursor ions of peaks of unknown origin provided structural identification of the unknown compounds. 相似文献
97.
98.
Scanning the beta-globin gene for mutations in large populations by denaturing capillary and gel electrophoresis 总被引:1,自引:0,他引:1
Separation of mutant from nonmutant DNA sequences of 100 bp may be accomplished by using defined denaturing conditions of chemical denaturant and/or elevated temperature during electrophoresis on either polyacrylamide slab gels (denaturing gradient gel electrophoresis, DGGE) or capillary gels (constant denaturant capillary electrophoresis, CDCE). In analysis of mutant directly from a polymerase chain reaction (PCR) product mixture, both have detection sensitivities of approximately 1%. CDCE that facilitates an intermediate mutant enrichment step permits detection of mutants at fractions as low as 2 x 10(-6). Here we report the successful application of both approaches to scan for mutations of the human beta-globin gene (HBB) in two human population samples of approximately 5000 persons in the HBB. Using DGGE, the coding region and flanking intronic splice sites of HBB were scanned in a population of 4949 Han Chinese individuals in pool sizes of 48 individual DNA samples. Four point mutations ranging in mutant frequency from 0.5 to 0.0002 were identified. Using CDCE with a mutant enrichment step, these same sequences were scanned in a population of 5028, predominantly African-American juveniles (<9 years) as a single pooled DNA sample. Three point mutations were identified ranging in mutant frequency from 0.13 to 0.0005. This study shows that both the DGGE/small pool and the CDCE/large pool approaches offer the means to define the fine structure map of genetic variation in large population samples, and with appropriately engineered facilities to provide high throughput, should be useful in pangenomic scans to discover genes carrying casual mutations for common diseases. 相似文献
99.
100.
The ability to analyse complex multi-component mixtures without resorting to tedious separation procedures is extremely useful for routine analysis. Single-wavelength fluorescence measurement is limited in its ability to analyse complicated multi-component samples when they have severely overlapping emission and/or excitation spectra. This can be overcome by using synchronous fluorescence scan (SFS), where overlapping of spectra can be minimized. The selectivity of SFS can still be increased by taking derivative spectrum, applying different multivariate methods, selective fluorescence quenching, three-dimensional synchronous measurement or using some of these procedures in combination. Recent developments in various synchronous fluorescence methods for analysis of multi-component systems are discussed in this review. 相似文献