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201.
Abduljelil Iliyas Kelly Hawboldt Faisal Khan 《Journal of Thermal Analysis and Calorimetry》2011,106(1):53-61
Thermal methods of analysis such as DSC and TGA provide a powerful methodology for the study of solid reactions. This paper
proposes an improved thermal analysis methodology for thermal stability and safety investigation of complex solid-state reactions.
The proposed methodology is based on differential iso-conversional approach and involves peak separation and individual peak
analysis for kinetic analysis and safety prediction. The proposed thermal analysis method was coupled with Mineral Libration
Analysis (MLA) to investigate self-heating of sulfide mineral ores. The influence of sample’s mineralogy on thermal degradation
was examined and discussed. The information gained from the advanced kinetic analysis of DSC/TGA measurements were up-scaled
for TMR and SADT determination. The described thermal analysis method provides not only an understanding of sulfide mineral
self-heating, but also aids the design of effective mitigation measures for their adverse environmental and safety effects. 相似文献
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Herein, the reaction between CO2 and piperidine, as well as commercially available functionalised piperidine derivatives, for example, those with methyl‐, hydroxyl‐ and hydroxyalkyl substituents, has been investigated. The chemical reactions between CO2 and the functionalised piperidines were followed in situ by using attenuated total reflectance (ATR) FTIR spectroscopy. The effect of structural variations on CO2 absorption was assessed in relation to the ionic reaction products identifiable by IR spectroscopy, that is, carbamate versus bicarbonate absorbance, CO2 absorption capacity and the mass‐transfer coefficient at zero loading. On absorption of CO2, the formation of the carbamate derivatives of the 3‐ and 4‐hydroxyl‐, 3‐ and 4‐hydroxymethyl‐, and 4‐hydroxyethyl‐substituted piperidines were found to be kinetically less favourable than the carbamate derivatives of piperidine and the 3‐ and 4‐methyl‐substituted piperidines. As the CO2 loading of piperidine and the 3‐ and 4‐methyl‐ and hydroxyalkyl‐substituted piperidines exceeded 0.5 moles of CO2 per mole of amine, the hydrolysis of the carbamate derivative of these amines was observed in the IR spectra collected. From the subset of amines analysed, the 2‐alkyl‐ and 2‐hydroxyalkyl‐substituted piperidines were found to favour bicarbonate formation in the reaction with CO2. Based on IR spectral data, the ability of these amines to form the carbamate derivatives was also established. Computational calculations at the B3LYP/6‐31+G** and MP2/6‐31+G** levels of theory were also performed to investigate the electronic/steric effects of the substituents on the reactivity (CO2 capture performance) of different amines, as well as their carbamate structures. The theoretical results obtained for the 2‐alkyl‐ and 2‐hydroxyalkyl‐substituted piperidines suggest that a combination of both the electronic effect exerted by the substituent and a reduction in the exposed area of the nitrogen atom play a role in destabilising the carbamate derivative and increasing its susceptibility to hydrolysis. A theoretical investigation into the structure of the carbamate derivatives of these amines revealed shorter N? C bond lengths and a less‐delocalised electron distribution in the carboxylate moiety. 相似文献
204.
da Silva JK Andrade EH Kato MJ Carreira LM Guimarães EF Maia JG 《Natural product communications》2011,6(9):1361-1366
The leaves and twigs of Piper krukoffii, collected in the Carajás National Forest, north Brazil, yielded essential oils (2.0% and 0.8%), the main constituents of which were myristicin (40.3% and 26.7%), apiole (25.4% and 34.1%) and elemicin (2.8% and 3.0%). The antioxidant activities of the oils, methanol extract and its sub-fractions were evaluated. The DPPH EC50 values varied from the ethyl acetate sub-fraction (73.4 +/- 3.7 microg/mL) to the methanol extract (24.9 +/- 0.8 microg/mL), and the ABTS TEAC values ranged in the same order from 265.7 to 349.2 microMol TE/g. These results indicated a significant antioxidant activity for the plant. The lignans (-)-kusunokin, yatein, (-)-hinokin and cubebin were identified in the methanol extract. The hydro-methanolic sub-fraction showed a high value for total phenol content (106.5 +/- 0.7 mg GAE/g), as well as 1H NMR signals for sugar moieties. Crude extracts and sub-fractions were also able to inhibit beta-carotene bleaching, varying from 22.4 to 47.1%. The oils from the leaves and twigs showed strong larvicidal (21.4 and 3.6 microg/mL) and fungicide (0.5 and 0.1 microg/mL) activities. 相似文献
205.
Kelly A. Davidson 《Journal of organometallic chemistry》2007,692(10):1871-1874
PhGeCl3 reacts with Na{[OP(OEt)2]3CoCp} to give the six-coordinate complex PhCl2Ge{[OP(OEt)2]3CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge-O 1.973(2) Å]. 相似文献
206.
A regioselective synthesis of 2,4,6-trisubstituted pyridine is described starting from 2,6-dibromo-4-nitropyridine. All three different regioisomers of the 2,4,6-triamino substituted pyridine have been synthesized in four to five steps. The method described is a general route to unsymmetrical 2,4,6-trisubstituted amino pyridines. 相似文献
207.
The Optical Fourier Transform (OFT) is one of the most fundamental operations in analogue Optical Signal Processing (OSP). There are many optical arrangements for implementing the OFT, however one which is particularly popular is the Scaled Optical Fourier Transform (SOFT) because it offers the user the ability to scale the output Fourier distribution. In this paper we study some of the practical limits introduced by using a converging spherical lens of finite aperture to produce the illuminating field in the implementation of the SOFT. By deriving simple rules of thumb, based on examining phase and intensity deviations from the ideal unapertured case, we define an area inside the geometric shadow, which we refer to as a sub-geometric shadow. Inside this sub-geometric shadow we show that the worst-case errors in the resulting SOFT, arising due to diffraction, can be quantified and avoided. 相似文献
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209.
We present an introductory review of recent work on the control of open queueing networks. We assume that customers of different types arrive at a network and pass through the system via one of several possible routes; the set of routes available to a customer depends on its type. A route through the network is an ordered set of service stations: a customer queues for service at each station on its route and then leaves the system. The two methods of control we consider are the routing of customers through the network, and the sequencing of service at the stations, and our aim is to minimize the number of customers in the system. We concentrate especially on the insights which can be obtained from heavy traffic analysis, and in particular from Harrison's Brownian network models. Our main conclusion is that in many respects dynamic routingsimplifies the behaviour of networks, and that under good control policies it may well be possible to model the aggregate behaviour of a network quite straightforwardly.Supported by SERC grant GR/F 94194. 相似文献
210.