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Summary This paper describes a simplified model which links the sedimentary concentration of selected biomarkers to their export primary production, their stability during transit to the anoxic sediment layer and the sediment bulk sedimentation rate. Manipulation of the biomarker data permits the individual effects of these processes to be separated. Examples demonstrate the use of this strategy in the evaluation of environmentally significant parameters. 相似文献
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This paper describes the results of the experimental verification of the idea of wave-like aquatic propulsion of autonomous and man-inhabited vessels first published about 10 years ago by one of the present authors (V.V.K.). The idea is based on employing the unique type of localised flexural elastic waves propagating along edges of wedge-like structures immersed in water (wedge elastic waves). Such wedge-like structures supporting localised elastic waves can be attached like fish fins to a body of a small ship or a submarine and used for their propulsion. The proposed principle of employing localised flexural waves as a source of aquatic propulsion has been biologically inspired by the specific swimming mode used in nature by stingrays. To verify the idea experimentally, the first working prototype of a small catamaran using the above-mentioned wave-like propulsion via the attached rubber keel has been build and tested in Loughborough University. The tests have been carried out in two phases, in a water tank and then in open water. The test results have shown that the catamaran was propelled very efficiently and could achieve the speed of 36 cm/s, i.e., about one vehicle length per second, thus demonstrating that the idea of wave-like propulsion of small man-inhabited craft is viable. The reported proof of the viability of this idea may open new opportunities for marine craft propulsion, which can have far reaching implications. 相似文献
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Paul V. Bernhardt Dr. Geoffrey A. Lawrance Brian W. Skelton Allan H. White 《无机化学与普通化学杂志》2007,633(7):1036-1039
Cations derived by protonation of the ligand title compound (L1) have been structurally characterized in their di‐ and tetra‐ protonated forms in the salts [H2L1][ClO4]2·2H2O and [H4L1][ZnCl4]2·4H2O. In both structures, one half of the formula unit comprises the asymmetric unit of the structure, the macrocycle being centrosymmetric, with the two macrocycles adopting similar conformations. In both salts, a pair of diagonally opposed macrocyclic secondary amine groups are protonated; in the [H4L1]4+ salt, the additional pair of protons are accommodated on the exocyclic pendant amine groups. The dispositions of the pendent amines differ between the two structures, being ‘equatorial’ with respect to the macrocyclic ring in the [H2L1]2+ salt, and ‘axial’ in the [H4L1]4+ salt. In other structurally characterized compounds containing [H4L1]4+ the equatorial disposition was found in the ferricyanide adduct, while in the tetraperchlorate salt the axial disposition was identified. The differences in disposition of the exocyclic groups are ascribed to the extensive H‐bonding in the lattices. 相似文献
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J. G. Pritchard 《Journal of mass spectrometry : JMS》1974,8(1):103-108
The metastable ion spectra of ethylene oxide, acetaldehyde, acetaldehyde-d4, propylene oxide, propionaldehyde and trimethylene oxide are presented. They reveal no reason to suppose that electron-impact-induced isomerisation of oxide to aldehyde structure occurs, although many spectral features are common to various members of this set. The spectra of phenylacetaldehyde and styrene oxide are compared, and the more plausible possibility of partial isomerisation in this case is discussed. 相似文献
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The molecular geometry of perfluoro(methyloxirane) has been studied using gas-phase electron diffraction data, effective least-squares refinement of the structure being achieved with the aid of constraints to limit the number of variable parameters. With the CCF3 bond constrained to be 0.078 Å longer than the ring CC, the refined bond- length values CF (av.) = 1.323(2), CO (av.) = 1.410(8), and CC (ring) = 1.467(7) Å (g values, with e.s.d. in parentheses) were obtained; the angles between ring bonds and substituent CF bonds were CCF (av.) 121(1) and OCF (av.) 114(1)o, the corresponding parameters involving the bulkier CCF3 fragment being larger by 3o in each case [∠CCCF3 124(1)o∠OCCF3 117(2)o]. The remaining refined parameters were ∠CCF(of CF3) = 110.6(4)o and τ , a torsion angle defining the orientation of the CF bonds of the CF3 group with respect to ring bonds, = 29(2)o. Dependent bond angles possessed the values 62.7 (COC), 58.7 [OCC (ring)], 108.3 [FCF (CF3 group)], 114 [FCF (ring CF2)], and 111o (FCCF3). 相似文献