The large-scale extraction of microvertebrate fossils from sediment residues using Interfacial Methods     

Eric F. Freeman 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(1):4-12

The wet-sieving of sediments on the tonne scale has been used, probably since the mid-1800s, to search for Mesozoic mammal teeth and other microvertebrate fossils. Unfortunately, more sediment can usually be washed than can be searched, because of the very laborious nature of hand-picking non-enriched sediment residues.Such residues can be enriched cheaply and effectively using Interfacial Methods, which exploit differential wetting phenomena. Placed in a suspension of kerosene in water, microvertebrate fossils become wetted preferentially with the kerosene, which then allows them to adhere to granules of paraffin wax; these are removed and melted to release the fossils.One experiment is described where 8.92 kg of a quartz-rich residue (from 13 tonnes of raw sediment) was processed using apparatus centred on a cement mixer.Smaller scale ‘low tech’ apparatus designed for use in the field and improvised from various items of household waste, etc., were used to enrich various sediment residues weighing between 500 g and 1582 g.Theoretical aspects of the process were investigated experimentally with an eye to their practical significance.  相似文献   

Testing the nature of S0 galaxies using planetary nebula kinematics in NGC 1023     

E. Noordermeer †  M. R. Merrifield  L. Coccato  M. Arnaboldi  M. Capaccioli  N. G. Douglas  K. C. Freeman  O. Gerhard  K. Kuijken  F. De Lorenzi  N. R. Napolitano  A. J. Romanowsky 《Monthly notices of the Royal Astronomical Society》2008,384(3):943-952

We investigate the manner in which lenticular galaxies are formed by studying their stellar kinematics: an S0 formed from a fading spiral galaxy should display similar cold outer disc kinematics to its progenitor, while an S0 formed in a minor merger should be more dominated by random motions. In a pilot study, an attempt to distinguish between these scenarios, we have measured the planetary nebula (PN) kinematics of the nearby S0 system NGC 1023. Using the Planetary Nebula Spectrograph, we have detected and measured the line-of-sight velocities of 204 candidate planetary nebulae (PNe) in the field of this galaxy. Out to intermediate radii, the system displays the kinematics of a normal rotationally supported disc system. After correction of its rotational velocities for asymmetric drift, the galaxy lies just below the spiral galaxy Tully–Fisher relation, as one would expect for a fading system. However, at larger radii the kinematics undergo a gradual but major transition to random motion with little rotation. This transition does not seem to reflect a change in the viewing geometry or the presence of a distinct halo component, since the number counts of PNe follow the same simple exponential decline as the stellar continuum with the same projected disc ellipticity out to large radii. The galaxy's small companion, NGC 1023A, does not seem to be large enough to have caused the observed modification either. This combination of properties would seem to indicate a complex evolutionary history in either the transition to form an S0 or in the past life of the spiral galaxy from which the S0 formed. More data sets of this type from both spirals and S0s are needed in order to definitively determine the relationship between these types of system.  相似文献   

Is the sky falling? Searching for stellar streams in the local Milky Way disc in the CORAVEL and RAVE surveys     

G. M. Seabroke  G. Gilmore  A. Siebert  O. Bienaymé  J. Binney  J. Bland-Hawthorn  R. Campbell  K. C. Freeman  B. Gibson  E. K. Grebel  A. Helmi  U. Munari  J. F. Navarro  Q. A. Parker  A. Siviero  M. Steinmetz  F. G. Watson  R. F. G. Wyse  T. Zwitter  J. Peñarrubia  M. C. Smith  M. Williams 《Monthly notices of the Royal Astronomical Society》2008,384(1):11-32

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Archaeal lipids record paleosalinity in hypersaline systems   总被引：2，自引：0，他引：2  

Courtney Turich  Katherine H. Freeman 《Organic Geochemistry》2011,42(9):1147-1157

We present an ecologically based biomarker method for estimating past salinity, especially in hypersaline conditions. The relative amounts of acyclic diether and tetraether membrane lipids synthesized by Archaea correlate with salinity from 0–250 practical salinity units (psu) in modern settings. We examined the preservation of this lipid biomarker–salinity relationship in ancient sedimentary organic matter using samples from two sequences of marls and diatomites deposited just prior to the Messinian Salinity Crisis. Salinity estimates were consistent with expected absolute salinity, as well as the amplitude of variations leading up to the Messinian Salinity Crisis. This lipid biomarker approach to salinity reconstruction complements existing paleosalinity proxies because (i) Archaea survive and thrive over a broad salinity range, well beyond that of haptophyte algae and other plankton which form the microfossil record and (ii) it provides fine salinity resolution for the wide range broadly defined as hypersaline. With the proxy, there is the potential to provide novel insights into salinity variation within desiccating basins in climatically sensitive seas (e.g. Dead Sea, Permian Delaware Basin), evolution of brines, timing of onset of hypersaline conditions and evaporite deposition.  相似文献   

Verification of model simulated mass balance, flow fields and tabular calving events of the Antarctic ice sheet against remotely sensed observations     

Diandong Ren  Lance M. Leslie  Mervyn J. Lynch 《Climate Dynamics》2013,40(11-12):2617-2636

The Antarctic ice sheet (AIS) has the greatest potential for global sea level rise. This study simulates AIS ice creeping, sliding, tabular calving, and estimates the total mass balances, using a recently developed, advanced ice dynamics model, known as SEGMENT-Ice. SEGMENT-Ice is written in a spherical Earth coordinate system. Because the AIS contains the South Pole, a projection transfer is performed to displace the pole outside of the simulation domain. The AIS also has complex ice-water-granular material-bedrock configurations, requiring sophisticated lateral and basal boundary conditions. Because of the prevalence of ice shelves, a ‘girder yield’ type calving scheme is activated. The simulations of present surface ice flow velocities compare favorably with InSAR measurements, for various ice-water-bedrock configurations. The estimated ice mass loss rate during 2003–2009 agrees with GRACE measurements and provides more spatial details not represented by the latter. The model estimated calving frequencies of the peripheral ice shelves from 1996 (roughly when the 5-km digital elevation and thickness data for the shelves were collected) to 2009 compare well with archived scatterometer images. SEGMENT-Ice’s unique, non-local systematic calving scheme is found to be relevant for tabular calving. However, the exact timing of calving and of iceberg sizes cannot be simulated accurately at present. A projection of the future mass change of the AIS is made, with SEGMENT-Ice forced by atmospheric conditions from three different coupled general circulation models. The entire AIS is estimated to be losing mass steadily at a rate of ~120 km³/a at present and this rate possibly may double by year 2100.  相似文献   

The Northern HIPASS catalogue – data presentation, completeness and reliability measures     

O. I. Wong  E. V. Ryan-Weber  D. A. Garcia-Appadoo  R. L. Webster  L. Staveley-Smith  M. A. Zwaan  M. J. Meyer  D. G. Barnes  V. A. Kilborn  R. Bhathal  W. J. G. de Blok  M. J. Disney  M. T. Doyle  M. J. Drinkwater  R. D. Ekers  K. C. Freeman  B. K. Gibson  S. Gurovich  J. Harnett  P. A. Henning  H. Jerjen  M. J. Kesteven  P. M. Knezek  B. S. Koribalski  S. Mader  M. Marquarding  R. F. Minchin  J. O'Brien  M. E. Putman  S. D. Ryder  E. M. Sadler  J. Stevens  I. M. Stewart  F. Stootman  M. Waugh 《Monthly notices of the Royal Astronomical Society》2006,371(4):1855-1864

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Improved absorption cross-sections of oxygen in the wavelength region 205–240 nm of the Herzberg continuum     

K. Yoshino  A.S.-C. Cheung  J.R. Esmond  W.H. Parkinson  D.E. Freeman  S.L. Guberman  A. Jenouvrier  B. Coquart  M.F. Merienne 《Planetary and Space Science》1988,36(12):1469-1475

The laboratory values of the Herzberg continuum absorption cross-section of oxygen at room temperature from Cheung et al. (1986, Planet. Space Sci. 34, 1007), Jenouvrier et al. (1986a, Planet. Space Sci. 34, 253) and Jenouvrier et al. (1986, J. quant. Spectrosc. radiat. Transfer 36, 349) have been compared and re-analyzed. There is no discrepancy between the absolute values of these two sets of independent measurements. These values have been combined together in a linear least-squares fit to obtain improved values of the Herzberg continuum cross-section of oxygen at room temperature throughout the wavelength region 205–240 nm. Agreement with in situ and other laboratory measurements is discussed.  相似文献   

High resolution absorption cross-section measurements of N₂O at 295–299 K in the wavelength region 170–222 nm     

K. Yoshino  D.E. Freeman  W.H. Parkinson 《Planetary and Space Science》1984,32(10):1219-1222

High resolution absorption cross-section measurements of N₂O at 295–299 K have been performed in the wavelength region 170–222 nm with a 6.65 m scanning spectrometer/spectrograph of sufficient resolution to yield cross-sections that are independent of the instrumental function. The measured cross-sections are presented graphically and are available throughout the region 44925–58955 cm^?1 at intervals of 0.1–0.2 cm^?1 as a numerical tabulation stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Previously unresolved details of the banded structure which is superposed on the continuous absorption in the region 174–190 nm are observed.  相似文献   

The Effect of Small, Aspherical Perturbations on Travel Times and a Re-examination of the Corrections for Ellipticity   总被引：6，自引：0，他引：6  

Adam M. Dziewonski  Freeman Gilbert 《Geophysical Journal International》1976,44(1):7-17

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Lunar surface electric potential changes associated with traversals through the Earth's foreshock     

Michael R. Collier  H. Kent Hills  Timothy J. Stubbs  Jasper S. Halekas  Gregory T. Delory  Jared Espley  William M. Farrell  John W. Freeman  Richard Vondrak 《Planetary and Space Science》2011,59(14):1727-1743

We report an analysis of one year of Suprathermal Ion Detector Experiment (SIDE) Total Ion Detector (TID) “resonance” events observed between January 1972 and January 1973. The study includes only those events during which upstream solar wind conditions were readily available. The analysis shows that these events are associated with lunar traversals through the dawn flank of the terrestrial magnetospheric bow shock. We propose that the events result from an increase in lunar surface electric potential effected by secondary electron emission due to primary electrons in the Earth's foreshock region (although primary ions may play a role as well). This work establishes (1) the lunar surface potential changes as the Moon moves through the terrestrial bow shock, (2) the lunar surface achieves potentials in the upstream foreshock region that differ from those in the downstream magnetosheath region, (3) these differences can be explained by the presence of energetic electron beams in the upstream foreshock region and (4) if this explanation is correct, the location of the Moon with respect to the terrestrial bow shock influences lunar surface potential.  相似文献