Palaeoclimatology and palaeoceanography from laminated sediments,A.E.S. Kemp(ed.), Geological Society of London,Bath 1996 (258 pp) Special Publication No. 116, $108/?65 (members Geological Society $53/?32) ISBN 1-897799-67-5     

Jaap J.M Van Der Meer 《第四纪科学杂志》1999,14(3):289-289

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Subglacial water-escape structures and till structures,sléttjökull,Iceland     

Jaap J. M Van Der Meer  Kurt H. Kjaer  Johannes Krüger 《第四纪科学杂志》1999,14(3):191-205

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Atmospheric behavior and extreme beginning heights of the thirteen brightest photographic Leonid meteors from the ground‐based expedition to China     

Pavel Spurný  Hans Betlem  Jaap van't Leven  Peter Jenniskens 《Meteoritics & planetary science》2000,35(2):243-249

Abstract— Precise atmospheric trajectories including dynamic and photometric data on thirteen of the brightest Leonid fireballs have been determined from the double‐station photographic observations of Leonid meteors during the ground‐based expedition to China in 1998 November. the expedition was organized as a collaboration between the dutch and chinese academy of sciences and was supported by the leonid multi‐instrument aircraft campaign (mac) program (jenniskens and butow, 1999). All data presented here were taken at Xinglong Observatory and at a remote station, Lin Ting Kou near Beijing, on the night of 1998 November 16/17. At the Xinglong station, photographic cameras were accompanied by an all‐sky television camera equipped with an image intensifier and 15 mm fish‐eye objective in order to obtain precise timings for all observed meteors up to magnitude +2. Whereas beginning heights of photographed meteors are all lower than 130 km, those observed by the all‐sky television system are at ～160 km, and for three brightest events, even > 180 km. Such high beginnings for meteors have never before been observed. We also obtained a precise dynamic single‐body solution for the Leonid meteor 98003, including the ablation coefficient, which is an important material and structural quantity (0.16 s² km^?2). From this and from known photometry, we derived a density of this meteoroid of 0.7 g/cm³. Also, all PE coefficients indicate that these Leonid meteors belonged to the fireball group IIIB, which is typical for the most fragile and weak interplanetary bodies. From a photometric study of the meteor lightcurves, we found two typical shapes of light curves for these Leonid meteors.  相似文献   

New type of radiation of bright Leonid meteors above 130 km     

Pavel SPURNÝ  Hans BETLEM  Klaas JOBSE  Pavel KOTEN  Jaap van't LEVEN 《Meteoritics & planetary science》2000,35(5):1109-1115

Abstract— In this paper, we study the extremely high beginning parts of atmospheric trajectories of seven Leonid meteors recorded by sensitive TV systems equipped with image intensifiers up to apparent magnitude +6.5. For all seven cases, we observed comet‐like diffuse structures with sizes on the order of kilometers that developed quickly during the meteoroids' descent through the atmosphere. For the brightest event with a maximum absolute magnitude of ?12.5, we observed an arc similar to a solar protuberance and producing a jet detectable several kilometers sideways from the brightest parts of the meteor head, and moving with a velocity over 100 km/s. These jets are common features for the seven studied meteors. Precise position in trajectory, velocity, and brightness at each point is available for all seven meteors, because of double‐station records on 85 km base‐line. When these meteoroids reached 130 km height, their diffuse structures of the radiation quickly transformed to the usual meteor appearance resembling moving droplets, and meteor trains started to develop. These meteor phenomena above 130 km were not recognized before our observations, and they cannot be explained by standard ablation theory.  相似文献   

Practical aspects of wavefield separation of two-component surface seismic data based on polarization and slowness estimates     

Sandra Richwalski  Kabir Roy-Chowdhury  Jaap C. Mondt 《Geophysical Prospecting》2000,48(4):697-722

The processing of multicomponent seismic data, carried out individually on the different wavetypes (P-, S- and converted waves), should result in an improved image of the subsurface. We examine the wavefield‐separation method proposed by Cho and Spencer . We discuss practical aspects related to the separation of interfering waves on two-component surface seismic data and illustrate these using synthetic data. A sliding spatial window is used for analysis. The choice of its width represents a trade-off between stabilizing the method in the presence of random noise and ensuring a good spatial resolution. No a priori knowledge of the subsurface is required, but locally, the characteristic parameters of the waves, i.e. horizontal slowness and polarization, are assumed to be constant inside the analysis window. These parameters are estimated at each frequency, but a statistical analysis provides a more robust estimate, especially in the presence of random noise. This approach also solves the problem of eigenvalue sharing and switching. Additional smoothing of the estimates according to a model may further improve the results. The width of the analysis window may be decreased if the waves inside the data window differ significantly in amplitude. The dominant wave in each case is separated from the lower-amplitude waves and subtracted from the data. This novel iterative approach thereby allows for the isolation of low-amplitude events.  相似文献   

Micromorphology of some North Sea till samples,a pilot study     

Jaap J. M. Der Van Meer  Cees Laban 《第四纪科学杂志》1990,5(2):95-101

In a pilot study three samples of diamictons from boreholes in the Dutch sector of the North Sea have been thin sectioned. In the thin sections the granulometry, structure and plasmic fabric of the diamictons have been studied. On the basis of this study two of the samples have been interpreted as flow tills, while one sample has been interpreted as a basal (lodgement) till.  相似文献   

The influence of oxic degradation on the sedimentary biomarker record II. Evidence from Arabian Sea sediments     

Jaap S Sinninghe Damsté  W.Irene C RijpstraGert-jan Reichart 《Geochimica et cosmochimica acta》2002,66(15):2737-2754

Biomarker accumulation rates in nine different time slices in three cores on and at the foot of a submarine high in the northern Arabian Sea (the Murray Ridge) were measured to investigate the influence of oxygen exposure time on the preservation of biomarker signals in the sedimentary record. All three sites experienced the same history of surface water productivity and sediment supply but had different bottom-water redox conditions due to their different positions (in, just below, well below) relative to the present location of the intense oxygen minimum zone (OMZ). Past variations in the intensity and position of the OMZ, known from a wide variety of proxies (TOC content, distribution and abundance of planktonic and benthic foraminifera and pteropods, trace metals, and δ¹⁵N), enabled specific biomarker (i.e., n-alkanes, steroids, alkenones, alkyldiols, C₂₆ fatty acid, loliolide, biphytane diols, and archaeal tetraether lipids) accumulation rates at contrasting oxygen exposure times to be compared. The results indicate that these accumulation rates can vary by more than an order of magnitude for marine biomarkers. In addition, there are significant differences in the degree of oxic degradation of different types of biomarkers: Terrestrial n-alkanes are much more resistant than alkenones and n-alkyl diols, which are more refractory than steroids and biphytane diols. These differences in degree of oxic degradation indicate that biomarker distributions will change on increasing exposure to oxygen. These findings have a significant impact on the application of biomarkers to sedimentary settings in which oxygen exposure time is likely to change significantly.  相似文献   

Intra- and interspecies comparison of energy flow in North Atlantic flatfish species by means of dynamic energy budgets   总被引：1，自引：0，他引：1  

Henk W. van der Veer  Sebastiaan A. L. M. Kooijman  Jaap van der Meer 《Journal of Sea Research》2001,45(3-4)

The quantitative aspects of growth and reproduction in four flatfish species (plaice, flounder, dab, sole) in terms of energy flow are described on the basis of a dynamic energy budget (DEB theory). This theory consists of general assumptions about energy uptake, storage and utilisation and describes an individual by two state variables: structure and reserve, whereby body size exerts its influence through the ratio between surface area and volume. Comparison between model estimates and field data shows that the DEB model successfully describes the energetics of growth and reproduction in a number of flatfish species. Differences between species could be captured in the same model using different parameter values. Intraspecific differences in growth between males and females are mainly caused by differences in maximum surface area-specific ingestion rates. Differences between species are reflected in the surface area-specific maximum ingestion rate, the energy partitioning over growth and reproduction, and in egg volume. According to these parameters at 283 K (10°C), the species could be ranked as follows: surface area-specific maximum ingestion rate (W m⁻²) plaice: 56.6; flounder: 54.5; sole: 45.1 and dab: 36.1 W m⁻². Fraction of energy allocated to reproduction (–): flounder: 0.35; plaice: 0.15; dab: 0.15 and sole 0.10. As a consequence of these differences in surface area-specific maximum ingestion rate and in the fraction of utilised energy allocated to reproduction, the gonad masses (g) of females of 0.5 kg wet mass differ considerably: flounder: 149 g; plaice: 86 g; sole: 70 g; and dab: 69 g. However, due to differences in egg size between species, the potential annual egg production shows a completely different pattern: dab: 2200 10³; flounder: 1560 10³; sole: 343 10³ and plaice: 130 10³ eggs.  相似文献   

Assessment of the molecular composition of particulate organic matter exchanged between the Saeftinghe salt marsh (southwestern Netherlands) and the adjacent water system     

Vincent A. Klap  Jaap J. Boon  Marten A. Hemminga  Jos van Soelen 《Marine Chemistry》1996,54(3-4)

In this study the chemical composition of seston, transported by tidal water between an estuarine salt marsh and the adjacent water system, was assessed. The analytical techniques used are Pyrolysis in combination with Gas Chromatography and/or Mass Spectrometry. Interpretation of the Py-MS data was aided by discriminant analysis.The presented results indicate that throughout the year a dominant refractory fraction is present in the seston, but that seasonal additions can be distinguished. Apart from this seasonal pattern, differences between ebb and flood can be visualized by the use of discriminant analysis. During summertime, flood seston is enriched with lipids and recently synthesized polysaccharides, while during the rest of the year the flood tide samples contain more (remains of) lignin and polysaccharides than their ebb tide counterparts. The lignin markers comprise only fragments with extremely altered (reduced) character.These results, which highlight the molecular composition of the exchanged seston but do not offer exact quantitative budget estimations, provide no evidence for export of lignin-rich particulate halophytic material from the marsh to the water system. On the contrary, based on seston compositions, the water system seems to supply lignin-rich particles to the marsh during a considerable part of the year.  相似文献   

Higher plant vegetation changes during Pliocene sapropel formation     

Diana Menzel  Stefan Schouten  Pim F. van Bergen  Jaap S. Sinninghe Damst 《Organic Geochemistry》2004,35(11-12):1343

The δ¹³C values of higher plant wax C_27–33 n-alkanes were determined in three, time-equivalent Pliocene (2.943 Ma) sapropels and homogeneous calcareous ooze from three different sites forming an east-west transect in the eastern Mediterranean Basin in order to study the composition of the vegetation on the continents surrounding the Mediterranean Sea. A two-end member mixing model transformed the measured δ¹³C values into the contribution of C₄ plants to the terrestrial vegetation. These calculations indicated a high C₄ plant contribution (i.e. 40–50%) in the periods just before and just after sapropel formation. During sapropel deposition the C₄ plant contribution increased by up to 20% at all sites. This is interpreted to record the increased overall plant coverage of the Mediterranean borderlands resulting from the change in formerly barren desert areas into C₄ grass-dominated savannahs as a response to the wetter climate during sapropel deposition. Enhanced accumulation rates (ARs) of long-chain n-alkanes (C_27–33) and n-alkan-1-ols (C_26–30) towards the middle of the sapropel in concert with a decrease in the Ti/Al ratio confirm an increased delivery of terrigenous organic matter at all sites. These biomarkers were probably predominantly fluvially transported to the Mediterranean Sea, not only by the Nile but by fossil wadi river systems on the northern African continent.  相似文献