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A new method was developed for the determination of trace compounds in water samples using ultrasonic-enhanced hollow fiber liquid-phase microextraction (U-HF-LPME). The ultrasonic radiation, which produces mechanical vibration and ultrasonic cavitation, could be used for accelerating the diffusion mass transfer process. Thus, ultrasonic was introduced into the HF-LPME procedure to enhance the mass-transfer rate during the aqueous and extraction solvent phases. Experimental parameters such as the extraction solvent, the extraction time, the ultrasonic frequency and power, the extractant volume, and ionic strength of the sample were assessed and optimized. Under optimal conditions, HF-LPME was achieved within 10 min. The high enrichment factor in the range of 120-666 and a good relative recovery in the range of 97-103% were evaluated with the relative standard deviations (RSDs, n = 5) of 0.3-7.0%. The limit of detection was in the range of 0.8-3.0 μg/L. The method was applied to the analysis of groundwater, lake water, and seawater. The results showed that the method can determine trace benzene derivatives in real samples with RSD values of 1.1-4.2%. The results demonstrated that U-HF- LPME is a rapid, accurate, and effective sample preparation method, and could be successfully applied for the determination of trace compounds in analytical chemistry. 相似文献
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Chao Huangfu Liang Fu Yuzhi Li Xueling Li Haijun Du Jianshan Ye 《Electroanalysis》2013,25(9):2238-2243
In the present work, a sensitive, facile and disposable sensing platform for trace analysis of heavy metal ions was developed at the Bi modified graphene‐poly(sodium 4‐styrenesulfonate) composite film screen printed electrode (GR/PSS/Bi/SPE). The GR/PSS/Bi/SPE improved sensitivity and linearity due to the functionalization of graphene with negatively charged PSS providing more absorbing sites. The detection limit of the GR/PSS/Bi/SPE is found to be 0.042 µg L?1 for Cd2+ and 0.089 µg L?1 for Pb2+ with linear responses of Cd2+ and Pb2+ in the range of 0.5–120 µg L?1. Finally, the practical application was confirmed in real water with satisfactory results. 相似文献
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Study of total ionizing dose radiation effects on enclosed gate transistors in a commercial CMOS technology 下载免费PDF全文
This paper studies the total ionizing dose radiation effects on MOS
(metal-oxide-semiconductor) transistors with normal and enclosed gate
layout in a standard commercial CMOS (compensate MOS) bulk process.
The leakage current, threshold voltage shift, and transconductance of
the devices were monitored before and after $\gamma $-ray
irradiation. The parameters of the devices with different layout
under different bias condition during irradiation at different total
dose are investigated. The results show that the enclosed layout not
only effectively eliminates the leakage but also improves the
performance of threshold voltage and transconductance for NMOS
(n-type channel MOS) transistors. The experimental results also
indicate that analogue bias during irradiation is the worst case for
enclosed gate NMOS. There is no evident different behaviour observed
between normal PMOS (p-type channel MOS) transistors and enclosed
gate PMOS transistors. 相似文献
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Single-pulse chaos are studied for a functionally graded materials rectangular plate. By means of the global perturbation method, explicit conditions for the existence of a Silnikov-type homoclinic orbit are obtained for this system, which suggests that chaos are likely to take place. Then, numerical simulations are given to test the analytical predictions. And from our analysis, when the chaotic motion occurs, there are a quasi-period motion in a two-dimensional subspace and chaos in another two-dimensional supplementary subspace. 相似文献
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Wang D Li Y Zhang Y Liu Y Shi G 《Combinatorial chemistry & high throughput screening》2012,15(3):232-241
G protein-coupled receptors (GPCRs) which constitute one of the largest and most versatile families of cell surface receptors are involved in a wide spectrum of physiological functions, such as, neuronal transmission, chemotaxis, pacemaker activity and embryonic development. Therefore, in the past a few years GPCR families have become very important targets in pharmaceutical design. However, according to the human genome project, there are approximately 1000 genes encoding GPCRs, only about 200 of GPCRs have known ligands and functions. Searching for ligands of the unknown GPCRs and better modulators of known GPCRs are currently attracting lots of interest. High throughput screening (HTS), which is commonly defined as an automatic process of testing potential drug candidates efficiently, is widely used in drug discovery. In this review, the use of high throughput screening (HTS) in studying GPCRs and the choice of screening technology in different G-protein signaling pathways were summarized. 相似文献
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Wang K Stringfellow S Dong S Jiao Y Yu H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(12):2595-2603
The fluorescence spectroscopy of 7-azaindole (7aIn) incorporated in DNA oligonucleotides is investigated. Incorporation of 7aIn into DNA oligonucleotides is accomplished through standard solid-phase phosphoramidite chemistry. Fluorescence emission of the 7aIn chromophore shifts slightly to the red (from 386 nm to 388 nm) upon glycosylation at the N-1 position, but its relative fluorescence quantum yield increases 23 times, from 0.023 to 0.53. Upon incorporation into DNA, the fluorescence emission of 7aIn is greatly quenched with fluorescence quantum yields of 0.020 and 0.016 in single and double strand DNA, respectively. The fluorescence emission for 7aIn in DNA oligonucleotides shifts to the blue with an emission maximum at 379 nm. Both the strong fluorescence quenching and the blue shift of the emission spectrum signify that 7aIn is stacked with neighboring DNA bases in both single and double strand DNA. As the duplex DNA melts due to temperature increase, the fluorescence of the 7aIn chromophore increases, indicating the transition from the less fluorescent duplex DNA to the more fluorescent single strand DNA. Since this fluorescent 7aIn is a structural analog of purine, its fluorescence property may be utilized as a probe for studying nucleic acid structure and dynamics. 相似文献
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The global bifurcations in mode of a nonlinear forced dynamics of suspended cables are investigated with the case of the 1:1
internal resonance. After determining the equations of motion in a suitable form, the energy phase method proposed by Haller
and Wiggins is employed to show the existence of the Silnikov-type multi-pulse orbits homoclinic to certain invariant sets
for the two cases of Hamiltonian and dissipative perturbation. Furthermore, some complex chaos behaviors are revealed for
this class of systems. 相似文献
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This study describes an ultrasound-accelerated hollow-fiber liquid-phase microextraction (U-HF-LPME) method for the simultaneous trace analysis of benzene and toluene in beverages. Sample preparation was followed by analysis using gas chromatography–flame ionization detection. Experimental parameters such as extraction solvent, extraction time, ultrasonic power and frequency, extractant volume and ionic strength of the sample were assessed and optimized. Finally, the enrichment factor (EF), limit of quantitation (LOQ) and precision of the method for benzene and toluene were evaluated. The relative standard deviations (RSD, n = 5) were found to be 0.11 and 1.07% with good relative recovery of 98.2 and 99.6%, respectively. High EF of 105 and 308, and LOQ of 0.34 and 0.18 μg L?1 were obtained within 10 min. The results demonstrated that the proposed method was suitable for trace analysis of beverage samples. 相似文献