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  • Author or Editor: L. Li x
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Abstract  

This work reported on the thermal decomposition of ammonium perchlorate activated by addition of NiO nanocrystals with different surface areas. NiO samples were characterized by X-ray diffraction (XRD), transition electron microscope (TEM), Brunauer-Emmett-Teller (BET) technique, Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. With increasing annealing temperature, the surface areas of NiO samples reduced from 108.6 to 0.9 m2 g−1. The catalytic activities of NiO nanocrystals on the thermal decomposition of ammonium perchlorate were investigated by thermogravimetric analysis (TG) coupled with differential thermal analysis (DTA). With addition of NiO nanocrystals, thermal decomposition temperature of AP decreased greatly. Larger surface areas of NiO nanocrystals promoted the thermal decomposition of AP.

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CuO nanocrystals in thermal decomposition of ammonium perchlorate

Stabilization, structural characterization and catalytic activities

Journal of Thermal Analysis and Calorimetry
Authors: L.-J. Chen, G.-S. Li and L.-P. Li

Abstract  

CuO nanocrystals of different surface areas were prepared. All samples were characterized by X-ray diffraction, transition electron microscope, thermogravimetry, Brunauer-Emmett-Teller technique, Fourier transform infrared spectroscopy, and Raman spectroscopy. CuO nanocrystals showed a stable monoclinic structure. With increasing surface areas, the surface hydration became significant, which is followed by shifts in infrared frequencies and Raman phonon modes. CuO nanocrystals were explored as an additive to catalytic decomposition of ammonium perchlorate (AP). AP decomposition underwent a two-stage process. Addition of CuO nanocrystals led to a downshift of high-temperature stage towards lower temperatures.

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Summary

Two rapid, sensitive and reproducible methods for the determination of baclofen(BAL) in urine and plasma based on high-performance liquid chromatography (HPLC) with UV-vis and fluorescent detection, respectively, were developed for the first time using a new synthesized fluorescent label, 6-oxy-(N-succinimidylacetate)-9-(2′-methoxycarbonyl) fluorescein (SAMF). The optimal derivatization yield was achieved in borate buffer (pH 8.0) for 15 min at room temperature (25 °C). With a mixture of methanol and water containing 5 mmol L−1 sodium citrate buffer (pH 5.0) as mobile phase, BAL was determined at λ = 455 nm with UV-vis detection and at λ ex/λ em = 488/520 nm with FD detection. The detection limits are 1.065 × 10−3 mg mL−1 and 1.065 × 10−2 mg mL−1 with HPLC-UV-vis and HPLC-FD, respectively. The proposed method has been successfully applied to the analysis of BAL in human urine and plasma samples. The established method is rapid (15 min of derivatization process and 10 min of chromatographic run), reproducible and sensitive.

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Ecological transition zones are believed to be unique in their ability to shed light on the organization of populations and communities. In this paper, we study vegetation dynamics in the Great Plains short-grass steppe and Chihuahuan desert grassland ecotone in New Mexico, USA, using long-term, high resolution transect studies of the Sevilleta Long-Term Ecological Research Program. We focus on spatial pattern and examine this in several ways: patch size distribution, spatial autocorrelation analysis, and fractal scaling. These methods are used to examine patch size distributions in two sites representing distributional limits of the dominant species and for detection of an emergent scaling property. We found no characteristic spatial resolution (quadrat size), but rather a fractal structure of spatial variation in abundance and a trend towards consistency of the pattern in time when species were closer to their distributional limit. In this, we were able to detect a robust power law behaviour (the emergent property), indicating strong spatial organization via anti-persistence. Our investigation was exploratory in nature; we feel the results are highly suggestive of intrinsic organization in ecological dynamics and may also be useful in generating testable hypotheses regarding the behaviour of species along ecotones.

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Summary

A reversed-phase high-performance liquid chromatographic method was developed for the first time to simultaneously determine salicin and eight flavonoids in leaves of Salix matsudana, that is salicin, luteolin-7-O-glucoside, myricetin, apigenin-3′-oxyethyl-7-O-glucoside, rutin, quercetin, luteolin, kaempferol and apigenin. The separation of these compounds was achieved on a reversed phase C18 column (250 × 4.6 mm, 5 μm), with linear gradient of methanol in 0.2% phosphoric acid solution with a flow rate of 1.0 mL/min with UV detection at 246 nm. The calibration curves for the determination of all analytes showed good linearity over the investigated ranges (r > 0.999). The % relative standard deviation (% RSD) values were less than 0.34%, and the recoveries were between 95.79% and 99.94%. The values of luteolin-7-O-glucoside, salicin, myricetin, apigenin-3′-oxyethyl-7-O-glucoside, rutin, quercetin, luteolin, kaempferol, and apigenin were 1.0 μg g−1, 20.0 μg g−1, 32.9 μg g−1, 2.0 μg g−1, 29.5 μg g−1, 6.0 μg g−1, 1.0 μg g−1, 3.5 μg g−1, and apigenin was not found in the sample. This developed method can be used for evaluating the quality of different plant materials.

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Abstract  

Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO2 composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression method. The results show that the kinetic models for the decomposition process of PANI/ZrO2 composite and PANI are all D3, and the corresponding function is ƒ(α)=1.5(1−α)2/3[1−(1-α)1/3]−1. The correlated kinetic parameters are E a=112.7±9.2 kJ mol−1, lnA=13.9 and E a=81.8±5.6 kJ mol−1, lnA=8.8 for PANI/ZrO2 composite and PANI, respectively.

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A rapid and sensitive ultraperformance liquid chromatography-multiple reaction monitoring-multi-stage/mass spectrometry (UPLC-MRM-MS/MS) method has been developed for simultaneous quantification of salvianolic acid B and tanshinone IIA of salvia tropolone tablets in dog plasma. This was achieved by performing quantification using the MRM acquisition with two channels of MRM-MS/MS and MS full scan for more accuracy qualitative results, and the fragmentation transitions of m/z 295→249, 191 for tanshinone IIA and m/z 297→279, 251 for IS in positive mode, m/z 717→519, 321 for salvianolic acid B and m/z 295→267, 239 for IS in negative mode were selected. The UPLC separation was achieved within 3 min in a single UPLC run. Linear calibration curves were obtained over the concentration range of 10 pg/mL−1 ng/mL for tanshinone IIA and 100 pg/mL−1 for salvianolic acid B. Lower limit of quantitation (LLOQ) was 10 pg/mL and 100 pg/mL for tanshinone IIA and salvianolic acid B, respectively. The inter-day and intra-day precision (relative standard deviation, RSD) in all samples were less than 8.21%, and the recoveries were over 85.9% for both tanshinone IIA and salvianolic acid B. The two channels of MRM with MS full scan approach could provide both qualitative and quantitative results without the need for repetitive analyses and resulted in the reduction of further confirmation experiments and analytical time. The pharmacokinetic study of the two active components of salvia tropolone tablets following oral gavage administration of dogs was thus explored with this method.

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Abstract  

The flux of cold neutrons that is obtainable from various high energy netron sources is studied for a particular model of a cold neutron source when the cold moderation region of the apparatus is at 20, 70, and 298K. The maximum flux obtained with a californium-252 source was 2.7·10−3 cold neutron per (cm2·second (source neutron)). This flux was obtained when the cold moderation region of the apparatus was at 20K and when the thermal moderator is either polyethylene or trimethylbenzene and the cold moderator is polyethylene. This flux should allow sensitive prompt and delayed neutron activation analysis measurements.

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Maize seeds from inbred line Mo17, susceptible to Sugarcane mosaic virus (SCMV), were investigated for SCMV seed transmission. The seed quality significantly influenced the seed transmission rate. There were more infected seedlings derived from larger seeds than smaller seeds in both golden (G) and buff (B) seed groups, the proportion of infected seedlings in G1 was similar to G2 and B1, and significantly higher than the others (P < 0.05 or P < 0.01). While the proportion of SCMV seed transmission was higher in golden (3.9%) than buff seeds groups (2.3%), and there were significantly difference (P < 0.05) between the both colors seeds. However the percentage of infected seedlings was closely related to the location of seeds on ears, most infected seedlings were derived from seeds of the middle (Part III) and mid-base regions (Part IV), and the both parts (Parts III and IV) were significantly higher than that of Part I (P < 0.05). Fisher’s exact test indicated that the seed quality was associated significantly with the efficiency of SCMV seed transmission.

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