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排序方式: 共有1304条查询结果,搜索用时 15 毫秒
91.
Cold acclimation of Lolium L. and Zoysia Willd. Grass cultivars significantly increased regrowth of cryopreserved meristems. One wk of cold acclimation improved recovery following cryopreservation but extended acclimation (4-8 wk) resulted in the best regrowth. Cold acclimation also significantly increased the dehydration tolerance of both Zoysia and Lolium meristems. Lolium apices cold acclimated for 4 wk produced 60-100% regrowth following cryopreservation by slow freezing or encapsulation-dehydration. Cold-acclimated Zoysia had greater than 60% regrowth following encapsulation-dehydration when beads were dehydrated to less than 22% water content. Non-acclimated meristems of both genera had little or no regrowth. Thawed meristems grew quickly without callus formation and the plantlets produced were transplanted to pots in the greenhouse after 4 to 6 wk. Samples of each cultivar were stored in liquid nitrogen as part of the U.S. National Plant Germplasm System. 相似文献
92.
Leary SM Brex PA MacManus DG Parker GJ Barker GJ Miller DH Thompson AJ 《Magnetic resonance imaging》2000,18(4):455-459
1H magnetic resonance spectroscopy (MRS) provides a unique tool to detect and quantify brain metabolites. In multiple sclerosis it can be used to investigate axonal loss or dysfunction through measurement of N-acetyl aspartate (NAA), a neuronal marker. Previous studies in adults have reported variable effects of aging on metabolite concentrations but have predominantly focused on changes in the elderly. This study has examined a younger adult age group to provide a reference database more applicable to the multiple sclerosis population. Single voxel (1)H MRS was carried out in 44 subjects between 22 and 62 years of age. Sixteen subjects underwent repeat examination after one year. Absolute concentrations of NA (the sum of NAA and N-acetyl aspartate glutamate), NAA, creatine/phosphocreatine (Cr), choline containing compounds (Cho) and myo-inositol (mI) were measured. NA, NAA and mI concentrations did not correlate with age but there were significant correlations between age and Cr (r = 0.43, p = 0.004) and Cho (r = 0.38, p = 0. 011) concentrations. No significant differences in metabolite concentrations were seen over one year. This study provides evidence that age-related changes of metabolite concentrations occur even in a young to middle aged adult population. This emphasizes the need to perform absolute quantification of metabolite concentrations rather than ratios and the importance of age-matching in (1)H MRS studies of multiple sclerosis. 相似文献
93.
Busayamas Pimpunchat Winston L. Sweatman Graeme C. Wake Wannapong Triampo Aroon Parshotam 《Applied Mathematics Letters》2009,22(3):304-308
We present a simple mathematical model for river pollution and investigate the effect of aeration on the degradation of pollutant. The model consists of a pair of coupled reaction–diffusion–advection equations for the pollutant and dissolved oxygen concentrations, respectively. The coupling of these equations occurs because of reactions between oxygen and pollutant to produce harmless compounds. Here we consider the steady-state case in one spatial dimension. For simplified cases the model is solved analytically. We also present a numerical approach to the solution in the general case. The extension to the transient spatial model is relatively straightforward. The study is motivated by the crucial problem of water pollution in many countries and specifically within the Tha Chin River in Thailand. For such real situations, simple models can provide decision support for planning restrictions to be imposed on farming and urban practices. 相似文献
94.
Tim Kemmitt Graeme J. Gainsford Najeh I. Al‐Salim 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):m42-m43
The title compound, octa‐tert‐butoxybis[μ3‐2,2′‐(N‐methylimino)diethanolato]di‐μ‐oxo‐tetratitanium(IV), [Ti2O{(OCH2CH2)2(NCH3)}{(CH3)3CO}4]2 or [Ti4(C5H11NO2)2(C4H9O)8O2], lies about an inversion centre, and displays the less usual zigzag configuration. One O atom of the N‐methyldiethoxoamine ligand bridges the symmetry‐related Ti atoms, while the other bridges the two independent Ti atoms, with the N atom binding to give a facial configuration. Four tBuO− ligands and a bridging oxide complete the respective five‐ and sixfold coordination of the two Ti atoms. The Ti—O bond lengths range in a self‐consistent fashion from 1.7624 (17) to 2.0878 (18) Å, while the Ti—N bond length is 2.374 (2) Å. 相似文献
95.
Cornelis Lensink Graeme J. Gainsford Neville I. Baxter 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):366-367
The title compound, [Ti(CF3O3S)2(C14H15NO2S)(C4H8O)], contains a unique ligand system in which the Ti ion is bound to the N and O atoms of a 2‐p‐toluenesulfonamide ligand, which is linked by an ethyl group to a coordinated cyclopentadiene moiety. The distorted octahedral geometry about the Ti ion is completed by two trifluoromethanesulfonate ligands and a tetrahydrofuran molecule. Comparison with related compounds shows that both the Ti—N and Ti—O bonds of the sulfonamide, although longer than normal values, indicate significant bonding interactions. 相似文献
96.
97.
R. J. Barker 《International Journal of Infrared and Millimeter Waves》1989,10(10):1213-1222
Selected basic research efforts currently sponsored by the U.S. Department of Defense (DOD) and the National Science Foundation (NSF) are reviewed. Major achievements are highlighted and remaining obstacles are discussed. Future advances are suggested. Opinions expressed are solely those of the author. 相似文献
98.
This paper describes measurements undertaken on an isothermal facility to study the effects of acoustic excitation on the
flow field issuing from gas turbine style fuel injectors. The highly swirling and turbulent flow field is excited with plane
acoustic waves generated by loudspeakers. Emphasis is placed on the accuracy of the measured response, over the range of excitation
frequencies (50–1,500 Hz), and its possible contamination by the background turbulence. Simulated data are used to assess
the experimental accuracy and the established errors, using this technique, are compared with an example set of results. 相似文献
99.
N. Stratford W. V. Stubbings F. Henesey W. F. Barker S. G. Shuttleworth C. W. Davies und R. F. Innes 《Fresenius' Journal of Analytical Chemistry》1942,124(7-8):315-316
Ohne Zusammenfassung 相似文献
100.