Effects of different seed pretreatments on germination of ten Calligonum species

In order to determine the optimum seed pre??sowing treatments and patterns of germination,a greenhouse experiment was conducted to study the effects of abrasion,sulphuric acid,boiling water,cold stratification and seed exudate treatments on the germination of ten Calligonum species.The results showed that the response of seed germination to the different pretreatments was similar for all ten Calligonum species.The abrasion,sulphuric acid and cold stratification treatments significantly promoted overall germinability.Compared with the control,the exudate treatment significantly decreased the percent germination,hampered the rate of germination and bolstered dormancy for almost all species.The cold stratification treatment can break the dormancy of viable Calligonum seeds and increased the germination,but it has a little lethal effect on viable seeds probably as well as the boiling water treatments.The germinaton patterns performed significant difference between the pre-sowing treatments for all ten Calligonum species,and the speed and percent germination of the Calligonum species can be greatly increased by mechanical scarification or sulphuric acid treatments.The results showed that seeds of C.junceum have strong ability of germinating.

Extraction of Nitraria tangutorum seed oil by supercritical carbon dioxide and determination of free fatty acids by HPLC/APC/IMS with fluorescence detection

The seed oil from Nitraria tangutorum samples was obtained by supercritical carbon dioxide extraction methods. The extraction parameters for this methodology, including pressure, temperature, particle size and extraction time, were optimized. The free fatty acids in the seed oil were separated with a pre-column derivation method and 1,2-benzo-3,4-dihydrocarbazole-9-ethyl-p-toluenesulfonate (BDETS) as a labeling regent, followed by high-performance liquid chromatography (HPLC) with fluorescence detection. The target compounds were identified by mass spectrometry with atmospheric pressure chemical ionization (APCI in positive-ion mode). HPLC analysis shows that the main compositions of the seed oil samples were free fatty acids (FFAs) in high to low concentrations as follows: linoleic acid, oleic acid, hexadecanoic acid and octadecanoic acid. The assay detection limits (at signal-to-noise of 3:1) were 3.378-6.572 nmol/L. Excellent linear responses were observed, with correlation coefficients greater than 0.999. The facile BDETS derivatization coupled with mass spectrometry detection allowed the development of a highly sensitive method for analyzing free fatty acids in seed oil by supercritical CO2 extraction. The established method is highly efficient for seed oil extraction and extremely sensitive for fatty acid profile determination. (C) 2007 Elsevier B.V. All rights reserved.

Effect of a laser pre-quenched steel substrate surface on the crack driving force in a coating-steel substrate system

A mechanical model of a coating/laser pre-quenched steel substrate specimen with a crack oriented perpendicular to the interface between the coating and the hardened layer is developed to quantify the effects of the residual stress and hardness gradient on the crack driving force in terms of the J-integral. It is assumed that the crack tip is in the middle of the hardened layer of the pre-quenched steel substrate. Using a composite double cantilever beam model, analytical solutions can be derived, and these can be used to quantify the effects of the residual stress and the hardness gradient resulting from the pre-quenched steel substrate surface on the crack driving force. A numerical example is presented to investigate how the residual compressive stress, the coefficient linking microhardness and yield strength and the Young's modulus ratio of the hardened layer to the coating influence the crack driving force for a given crack length. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.