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排序方式: 共有289条查询结果,搜索用时 15 毫秒
101.
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103.
Racková L Jancinová V Petríková M Drábiková K Nosál R Stefek M Kostálová D Prónayová N Kovácová M 《Natural product research》2007,21(14):1234-1241
The antiradical activity, protective effect against lipid peroxidation of liposomal membrane, and inhibitory effect on whole blood reactive oxygen species (ROS) liberation of Glycyrrhiza glabra crude extract and glycyrrhizin, its major compound, were assessed. The liquorice extract showed significant activity in all the three assay systems used in a dose dependent manner. It displayed remarkable reactivity with free stable 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, inhibitory efficacy in peroxidatively damaged unilamellar dioleoyl phosphatidylcholine (DOPC) liposomes, and inhibition of ROS chemiluminescence, generated by whole blood, induced by both receptor-bypassing stimuli (PMA) and receptor operating stimuli (Opz) in the ranking order of stimuli PMA> Opz. These activities may be attributed to phenolic antioxidants involving isoflavan derivatives, coumarins and chalcones. Nonetheless, triterpene saponin glycyrrhizin exhibited no efficacy in the system of DPPH reaction and peroxidation of liposomal membrane, and negligible inhibition of chemiluminescence generated by inflammatory cells. These results indicate that the mechanism of anti-inflammatory effect of glycyrrhizin most probably does not involve ROS and this major constituent is not responsible for the inhibition effects of liquorice extract on neutrophil functions. 相似文献
104.
A simple and rapid method for morphine detection is described based on PEDOT electrode in the presence of SDS. The electrochemistry of morphine is investigated by CV, LSV and SWV. The effect of common interferences on the current response of morphine namely AA and UA is studied. The electrode is applied to the selective determination of morphine in urine samples in the linear ranges 0.3–8 µmol L?1 and 10–60 µmol L?1, with low detection limits of 50 and 68 nmol L?1, respectively and recovery of 96.4 %. The application of PEDOT is realized in determination of morphine in tablets successfully. 相似文献
105.
A promising composite‐modified glassy carbon electrode is fabricated by electrodeposition of mono‐dispersed gold nanoparticles onto carbon nanotubes (AuNPs/CNTs/GCE). The electroanalysis of Tramadol (TRA) was achieved by different electrochemical techniques. The effect of different parameters including pH, concentration and potential scan on the oxidation current signal of TRA was investigated. Large excess of ascorbic acid (AA) and uric acid (UA) with a maximum molar ratio of 1/1000 and 1/100, respectively, did not interfere with the response of TRA. The detection limit with high sensitivity is 68 nM. TRA was successfully determined in pharmaceutical dosage forms, without any pretreatment of the samples. 相似文献
106.
Correlation between radionuclides associated with zircon and monazite in beach sand of Rosetta,Egypt
A. Nada T. M. Abd EL-Maksoud H. Abu Zeid I. E. El-Asy S. M. I. Mostafa S. A. Abd El-Azeem 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):601-610
The study aims to evaluate the activity concentrations of 238U, 232Th, 40K and 137Cs along Rosetta beach, Egypt. Non-destructive assay techniques were carried out using HP-Ge spectrometer and binocular microscope.
The results of this study serve as a database for radioactivity levels of the mineral sand deposits of Rosetta area. The activity
concentrations of 238U, 232Th and 40K ranged from 5.39 to 134.2, 6.6 to 160.8 and 57.6 to 492 Bqkg−1 respectively. The range of activity concentrations of 137Cs is between 0.05 and 0.91 Bqkg−1. The total gamma absorbed dose rates varied from 11.59 to 160.01 nGyh−1 with a mean value of 50.53 nGyh−1. These values correspond to an annual effective dose equivalent of 0.01–0.2 mSvy−1 with a mean of 0.07 mSvy−1, which is in agreement with the worldwide average. Also, a correlation between the calculated zircon and monazite radioactive
mineral contents with the measured radioactive isotopes was carried out to determine the contribution of each mineral for
radioactivity. These correlations predicted that both zircon and monazite minerals are the main contributors for radioactivity
in the Egyptian beach black sands. Also the present study ensured that area under investigation is to be safe for public. 相似文献
107.
Tatjana Tomić Sandra Babić Nada Uzorinac Nasipak Maja Fabulić Ruszkowski Livijana Škrobonja Marija Kaštelan-Macan 《Journal of chromatography. A》2009,1216(18):3819-3824
Alkene content determinations in fluid catalytic cracking (FCC) liquid products were performed by means of normal-phase high-performance liquid chromatography (NP-HPLC) with diode array detection (UV/DAD). Separation of alkenes from aromatic hydrocarbons was performed on amino-modified silica gel column with n-heptane as mobile phase. The column has a little affinity to alkenes and saturated hydrocarbons and a pronounced affinity to aromatic compounds. The problem of alkenes and saturates co-elution on this column type was overcome with the detection system, UV/DAD, sensitive and selective to alkenes, while saturates are inactive in UV field. Total alkene content was determined as a sum of mono- and dialkene groups quantified by external standard method. Validation and verification of the developed method proved their applicability. The following criteria were used to validate the HPLC–DAD method: selectivity, linearity, precision, limits of detection and quantification. Alkene contents were quantified with the external standard method of wide calibration range, so both low and high alkene contents can be determined by the single calibration. Correlation coefficients were higher than 0.99. Precision was evaluated as repeatability and intermediary precision with relative standard deviations less than 5%. Some structural investigation of alkene groups was performed to confirm the assumption. Proposed method was compared with certified NMR method. Six commercial motor gasoline samples were analyzed by these two methods. Obtained results indicate good agreement between alkene content determined by both methods. The developed method was applied to the determination of alkene content in liquid FCC products in the boiling range from 70 °C to 190 °C. 相似文献
108.
A Nag DS Chung DS Dolzhnikov NM Dimitrijevic S Chattopadhyay T Shibata DV Talapin 《Journal of the American Chemical Society》2012,134(33):13604-13615
Colloidal semiconductor nanocrystals (NCs) provide convenient "building blocks" for solution-processed solar cells, light-emitting devices, photocatalytic systems, etc. The use of inorganic ligands for colloidal NCs dramatically improved inter-NC charge transport, enabling fast progress in NC-based devices. Typical inorganic ligands (e.g., Sn(2)S(6)(4-), S(2-)) are represented by negatively charged ions that bind covalently to electrophilic metal surface sites. The binding of inorganic charged species to the NC surface provides electrostatic stabilization of NC colloids in polar solvents without introducing insulating barriers between NCs. In this work we show that cationic species needed for electrostatic balance of NC surface charges can also be employed for engineering almost every property of all-inorganic NCs and NC solids, including photoluminescence efficiency, electron mobility, doping, magnetic susceptibility, and electrocatalytic performance. We used a suite of experimental techniques to elucidate the impact of various metal ions on the characteristics of all-inorganic NCs and developed strategies for engineering and optimizing NC-based materials. 相似文献
109.
Dhesi SS Mirone A De Nadaï C Ohresser P Bencok P Brookes NB Reutler P Revcolevschi A Tagliaferri A Toulemonde O van der Laan G 《Physical review letters》2004,92(5):056403
Orbital ordering (OO) in the layered perovskite La0.5Sr1.5MnO4 has been investigated using the enhanced sensitivity of soft x-ray resonant diffraction at the Mn L edges. The energy dependence of an OO diffraction peak over the L(2,3) edges is compared to ligand-field calculations allowing a distinction between the influences of Jahn-Teller distortions and spin correlations. The energy dependence of the diffraction peak at the Mn L1 edge is remarkably different from that observed at the Mn K edge. 相似文献
110.
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of four groups of s-triazine derivatives (14 compounds) has been studied by TLC on silica gel... 相似文献