Delta Scuti Network observations of XX Pyx: detection of 22 pulsation modes and of short-term amplitude and frequency variations     

G. Handler  T. Arentoft  R. R. Shobbrook  M. A. Wood  L. A. Crause  P. Crake  F. Podmore  A. Habanyama  T. Oswalt  P. V. Birch  G. Lowe  C. Sterken  P. Meintjes  J. Brink  C. F. Claver  R. Medupe  J. A. Guzik  T. E. Beach  P. Martinez  E. M. Leibowitz  P. A. Ibbetson  T. Smith  B. N. Ashoka  N. E. Raj  D. W. Kurtz  L. A. Balona  D. O'donoghue  J. E. S. Costa §  M. Breger 《Monthly notices of the Royal Astronomical Society》2000,318(2):511-525

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Halo occupation numbers and galaxy bias     

J. A. Peacock  R. E. Smith 《Monthly notices of the Royal Astronomical Society》2000,318(4):1144-1156

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The US Southern Ocean Joint Global Ocean Flux Study: an introduction to AESOPS     

Walker O. Smith  Jr.  Robert F. Anderson  J. Keith Moore  Louis A. Codispoti  John M. Morrison 《Deep Sea Research Part II: Topical Studies in Oceanography》2000,47(15-16)

The United States Southern Ocean Joint Global Ocean Flux Study (JGOFS), also known as AESOPS (Antarctic Environment and Southern Ocean Process Study), focused on two distinct regions. The first was the Ross-Sea continental shelf, where a series of six cruises collected a variety of data from October 1996 through February 1998. The second area was the southwest Pacific sector of the Southern Ocean, spanning the Antarctic Circumpolar Current (ACC) at 170°W. Data were collected within this region during five cruises from September 1996 through March 1998, as well as during selected transits between New Zealand and the Ross Sea. The first results of these cruses are described in this issue. The Ross-Sea investigation extensively sampled the area along 76°30′S to elucidate the temporal patterns and processes that contribute to making this one of the Antarctic's most productive seas. Hydrographic distributions confirm that stratification is initiated early in October within the polynya, generating an environment that is favorable for phytoplankton growth. Significant spatial variations in mixed-layer depths, the timing of the onset of stratification, and the strength of the stratification existed throughout the growing season. Nutrient concentrations reflected phytoplankton uptake, and reached their seasonal minimal in early February. Chlorophyll concentrations were maximal in early January, whereas productivity was maximal in late November, which reflects the temporal uncoupling between growth and biomass accumulation in the region. Independent estimates of biogenic export suggest that majority of the flux occurred in late summer and was strongly uncoupled from phytoplankton growth. The ACC region exhibited seasonal changes that in some cases were greater than those observed in the Ross Sea. Sea ice covered much of the region south of the Polar Front in winter, and retreated rapidly in late spring and early summer. Mixed layers throughout the region shoaled in summer due to surface heating, while the addition of freshwater from melting sea ice enhanced stratification in the Seasonal Ice Zone, creating conditions favorable for phytoplankton growth. For example, silicic acid concentrations decreased from initial values as high as 65 to less than 2 μM within approximately 100 km (from 65.7 to 64.8°S). Fluorescence values, however, showed less than a two-fold variation over the same distance. The vertical flux of carbon in the Polar Front area is substantial, and marked variations in the composition of exported material exited over the region. The results provide a means whereby the controls of phytoplankton growth and organic matter flux and remineralization can be analyzed in great detail. Additional results of the AESOPS project are discussed.  相似文献   

Nutrient and carbon removal ratios and fluxes in the Ross Sea, Antarctica     

Colm Sweeney  Walker O. Smith  Burke Hales  Robert R. Bidigare  Craig A. Carlson  L. A. Codispoti  Louis I. Gordon  Dennis A. Hansell  Frank J. Millero  Mi-OK Park  Taro Takahashi 《Deep Sea Research Part II: Topical Studies in Oceanography》2000,47(15-16)

Net community production (NCP) and nutrient deficits (Def(X)) were calculated using decreases in dissolved CO₂ and nutrient concentrations due to biological removal in the upper 200 m of the water column during four cruises in the Ross Sea, Antarctica along 76°30′S in 1996 and 1997. A comparison to excess dissolved and particulate organic carbon showed close agreement between surplus total organic carbon (TOC) and NCP during bloom initiation and productivity maximum; however, when TOC values had returned to low wintertime values NCP was still significantly above zero. This seasonal NCP, 3.9±1 mol C m⁻², must be equivalent to the particle export to depths greater than 200 m over the whole productive season. We estimate that the annual export was 55±22% of the seasonal maximum in NCP. The fraction of the seasonal maximum NCP that is exported through 200 m is significantly higher than that measured by moored sediment traps at a depth of 206 m. The removal of carbon, nitrate and phosphate (based on nutrient disappearance since early spring) and their ratios showed significant differences between regions dominated by diatoms and regions dominated by the haptophyte Phaeocystis antarctica. While the ΔC/ΔN removal ratio was similar (7.8±0.2 for diatoms and 7.2±0.1 for P. antarctica), the ΔN/ΔP and ΔC/ΔP removal ratios for diatoms (10.1±0.3 and 80.5±2.3) were significantly smaller than those of P. antarctica (18.6±0.4 and 134.0±4.7). The similarity in ΔC/ΔN removal ratios of the two assemblages suggests that preferential uptake of phosphate by diatoms caused the dramatic differences in ΔC/ΔP and ΔN/ΔP removal ratios. In contrast to low ΔC/ΔP and ΔN/ΔP removal ratio in diatom-dominated areas early in the growing season, deficit N/P and C/P ratios in late autumn indicate that the elemental stochiometry of exported organic matter did not deviate significantly from traditional Redfield ratios. Changes in biologically utilized nutrient and carbon ratios over the course of the growing season indicated either a substantial remineralization of phosphate or a decrease in phosphate removal relative to carbon and total inorganic nitrogen over the bloom period. The species dependence in C/P ratios, and the relative constancy in the C/N ratios, makes N a better proxy of biological utilization of CO₂.  相似文献   

High-resolution near-infrared observations of Herbig–Haro flows – II. Echelle spectroscopy     

Christopher J. Davis  Aaron Berndsen  Michael D. Smith  Antonio Chrysostomou  Jason Hobson 《Monthly notices of the Royal Astronomical Society》2000,314(2):241-255

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Evidence for different scaling of earthquake source parameters for large earthquakes depending on faulting mechanism   总被引：2，自引：0，他引：2  

Christian Stock  Euan G. C. Smith 《Geophysical Journal International》2000,143(1):157-162

Scaling relationships between seismic moment, rupture length, and rupture width have been examined. For this purpose, the data from several previous studies have been merged into a database containing more than 550 events. For large earthquakes, a dependence of scaling on faulting mechanism has been found. Whereas small and large dip-slip earthquakes scale in the same way, the self-similarity of earthquakes breaks down for large strike-slip events. Furthermore, no significant differences in scaling could be found between normal and reverse earthquakes and between earthquakes from different regions. Since the thickness of the seismogenic layer limits fault widths, most strike-slip earthquakes are limited to rupture widths of between 15 and 30 km while the rupture length is not limited. The aspect ratio of dip-slip earthquakes is similar for all earthquake sizes. Hence, the limitation in rupture width seems to control the maximum possible rupture length for these events. The different behaviour of strike-slip and dip-slip earthquakes can be explained by rupture dynamics and geological fault growth. If faults are segmented, with the thickness of the seismogenic layer controlling the length of each segment, strike-slip earthquakes might rupture connected segments more easily than dip-slip events, and thus could produce longer ruptures than dip-slip events of the same width  相似文献   

Intraplate volcanism influenced by distal subduction tectonics at Jeju Island,Republic of Korea     

Marco Brenna  Shane J. Cronin  Gábor Kereszturi  Young Kwan Sohn  Ian E. M. Smith  Jan Wijbrans 《Bulletin of Volcanology》2015,77(1):1-16

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Cross‐cutting moraines reveal evidence for North Atlantic influence on glaciers in the tropical Andes     

Jacqueline A. Smith  Donald T. Rodbell 《第四纪科学杂志》2010,25(3):243-248

Surface exposure dating of boulders on an exceptionally well‐preserved sequence of moraines in the Peruvian Andes reveals the most detailed record of glaciation heretofore recognised in the region. The high degree of moraine preservation resulted from dramatic changes in the flow path of piedmont palaeoglaciers at the southern end of the Cordillera Blanca (10° 00′ S, 77° 16′ W), which, in turn, generated a series of cross‐cutting moraines. Sixty ¹⁰Be surface exposure ages indicate at least four episodes of palaeoglacier stabilisation (>65, ca. 65, ca. 32 and ca. 18–15 ka) and several minor advances or stillstands on the western side of the Nevado Jeulla Rajo massif. The absence of ages close to the global Last Glacial Maximum (ca. 21 ka) suggests that if an advance culminated at that time any resulting moraines were subsequently overridden. The timing of expanded ice cover in the central Peruvian Andes correlates broadly with the timing of massive iceberg discharge (Heinrich) events in the North Atlantic Ocean, suggesting a possible causal connection between southward migration of the Intertropical Convergence Zone during Heinrich events and a resultant increase in precipitation in the tropical Andes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Hunter‐gatherer response to late Holocene climatic variability in northern and central Australia     

Alan N. Williams  Sean Ulm  Ian D. Goodwin  Mike Smith 《第四纪科学杂志》2010,25(6):831-838

Sum probability analysis of 1275 radiometric ages from 608 archaeological sites across northern and central Australia demonstrates a changing archaeological signature that can be closely correlated with climate variability over the last 2 ka. Results reveal a marked increase in archaeological records across northern and central Australia over the last 2 ka, with notable declines in western and northern Australia between ca. AD 700 and 1000 and post‐AD 1500 – two periods broadly coeval with the Medieval Climatic Anomaly and the Little Ice Age as they have been documented in the Asia–Pacific region. Latitudinal and longitudinal analysis of the dataset suggests the increase in archaeological footprint was continent wide, while the declines were greatest from 9 to 20° S, 110 to 135° E and 143 to 150° E. The change in the archaeological data suggests that, combined with an increase in population over the late Holocene, a disruption or reorganisation of pre‐European resource systems occurred across Australia between ca. AD 700 and 1000 and post‐AD 1500. These archaeological responses can be broadly correlated with transitions of the El Niño–Southern Oscillation (ENSO) mean state on a multi‐decadal to centennial timescale. The latter involve a shift towards the La Niña‐like mean state with wetter conditions in the Australian region between AD 700 and 1150. A transition period in ENSO mean state occurred across Australia during AD 1150–1300, with persistent El Niño‐like and drier conditions to ca. AD 1500, and increasing ENSO variability post‐AD 1500 to the present. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Early Devensian (MIS 5d–5b) occupation at Dartford,southeast England     

Francis F. Wenban‐Smith  Martin R. Bates  Jean‐Luc Schwenninger 《第四纪科学杂志》2010,25(8):1193-1199

A deeply buried horizon containing mint‐condition flint artefacts was discovered in 2006 during archaeological investigations in advance of major roadworks near Dartford, Kent, in southeast England. The context of the artefacts and the freshness of their condition suggest this horizon represents a buried occupation surface. Optically stimulated luminescence dating places this horizon in the period Marine Isotope Stage 5d–5b, early in the British Devensian glaciation. This paper describes details of the artefacts, their context and dates, and outlines how this apparent occupation fits in with the wider pattern of Neanderthal settlement in Britain and northwest Europe in the later Pleistocene. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献