An alternative to common envelope evolution     

Martin E. Beer  Lynnette M. Dray  rew R. King  Graham A. Wynn 《Monthly notices of the Royal Astronomical Society》2007,375(3):1000-1008

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Temporal Evolution of the Solar-Wind Electron Core Density at Solar Minimum by Correlating SWEA Measurements from STEREO A and B     

A. Opitz  J.-A. Sauvaud  A. Fedorov  P. Wurz  J. G. Luhmann  B. Lavraud  C. T. Russell  P. Kellogg  C. Briand  P. Henri  D. M. Malaspina  P. Louarn  D. W. Curtis  E. Penou  R. Karrer  A. B. Galvin  D. E. Larson  I. Dandouras  P. Schroeder 《Solar physics》2010,266(2):369-377

The twin STEREO spacecraft provide a unique tool to study the temporal evolution of the solar-wind properties in the ecliptic since their longitudinal separation increases with time. We derive the characteristic temporal variations at ～?1 AU between two different plasma parcels ejected from the same solar source by excluding the spatial variations from our datasets. As part of the onboard IMPACT instrument suite, the SWEA electron experiment provides the solar-wind electron core density at two different heliospheric vantage points. We analyze these density datasets between March and August 2007 and find typical solar minimum conditions. After adjusting for the theoretical time lag between the two spacecraft, we compare the two density datasets. We find that their correlation decreases as the time difference increases between two ejections. The correlation coefficient is about 0.80 for a time lag of a half day and 0.65 for two days. These correlation coefficients from the electron core density are somewhat lower than the ones from the proton bulk velocity obtained in an earlier study, though they are still high enough to consider the solar wind as persistent after two days. These quantitative results reflect the variability of the solar-wind properties in space and time, and they might serve as input for solar-wind models.  相似文献   

A submillimetre survey of the kinematics of the Perseus molecular cloud – I. Data     

Emily I. Curtis  John S. Richer  Jane V. Buckle 《Monthly notices of the Royal Astronomical Society》2010,401(1):455-472

We present submillimetre observations of the   J = 3 → 2  rotational transition of ¹²CO, ¹³CO and C¹⁸O across over 600 arcmin² of the Perseus molecular cloud, undertaken with the Heterodyne Array Receiver Programme (HARP), a new array spectrograph on the James Clerk Maxwell Telescope. The data encompass four regions of the cloud, containing the largest clusters of dust continuum condensations: NGC 1333, IC348, L1448 and L1455. A new procedure to remove striping artefacts from the raw HARP data is introduced. We compare the maps to those of the dust continuum emission mapped with the Submillimetre Common-User Bolometer Array (SCUBA; Hatchell et al.) and the positions of starless and protostellar cores (Hatchell et al.). No straightforward correlation is found between the masses of each region derived from the HARP CO and SCUBA data, underlining the care that must be exercised when comparing masses of the same object derived from different tracers. From the ¹³CO/C¹⁸O line ratio the relative abundance of the two species  ([¹³CO]/[C¹⁸O]∼ 7)  and their opacities (typically τ is 0.02–0.22 and 0.15–1.52 for the C¹⁸O and ¹³CO gas, respectively) are calculated. C¹⁸O is optically thin nearly everywhere, increasing in opacity towards star-forming cores but not beyond  τ₁₈∼ 0.9  . Assuming the ¹²CO gas is optically thick, we compute its excitation temperature, T _ex (around 8–30 K), which has little correlation with estimates of the dust temperature.  相似文献   

Climate and cultural history of the Northeastern Yucatan Peninsula, Quintana Roo, Mexico     

D. A. Hodell  M. Brenner  J. H. Curtis 《Climatic change》2007,83(1-2):215-240

We inferred the Holocene paleoclimate history of the northeastern Yucatan Peninsula, Mexico, by studying stratigraphic variations in stable isotopes (δ ¹⁸O and δ ¹³C) and lithologic properties (organic matter and carbonate content) in sediment cores taken in 6.3 and 16.2 m of water from Lake Punta Laguna. We present a simple model to explain the lithologic and isotopic variations, and discuss the inferred paleoclimate history in terms of its relation to ancient Maya cultural development. We find evidence for lower lake level and drier climate at about the same time as each major discontinuity in Maya cultural history: Preclassic Abandonment (150–250 A.D.), Maya Hiatus (534 to 593 A.D.), Terminal Classic Collapse (750–1050 A.D.), and Postclassic Abandonment (mid-fifteenth century). Although these broad temporal correlations suggest climate played a role in Maya cultural evolution, chronological uncertainties preclude a detailed analysis of climate changes and archaeologically documented cultural transformations.  相似文献   

Two rapid assays for screening of patulin biodegradation     

S. A. I. Wright  D. V. de Felice  G. Ianiri  C. Pinedo-Rivilla  F. De Curtis  R. Castoria 《International Journal of Environmental Science and Technology》2014,11(5):1387-1398

The mycotoxin patulin is produced by the blue mould pathogen Penicillium expansum in rotting apples during postharvest storage. Patulin is toxic to a wide range of organisms, including humans, animals, fungi and bacteria. Wash water from apple packing and processing houses often harbours patulin and fungal spores, which can contaminate the environment. Ubiquitous epiphytic yeasts, such as Rhodosporidium kratochvilovae strain LS11 which is a biocontrol agent of P. expansum in apples, have the capacity to resist the toxicity of patulin and to biodegrade it. Two non-toxic products are formed. One is desoxypatulinic acid. The aim of the work was to develop rapid, high-throughput bioassays for monitoring patulin degradation in multiple samples. Escherichia coli was highly sensitive to patulin, but insensitive to desoxypatulinic acid. This was utilized to develop a detection test for patulin, replacing time-consuming thin layer chromatography or high-performance liquid chromatography. Two assays for patulin degradation were developed, one in liquid medium and the other in semi-solid medium. Both assays allow the contemporary screening of a large number of samples. The liquid medium assay utilizes 96-well microtiter plates and was optimized for using a minimum of patulin. The semi-solid medium assay has the added advantage of slowing down the biodegradation, which allows the study and isolation of transient degradation products. The two assays are complementary and have several areas of utilization, from screening a bank of microorganisms for biodegradation ability to the study of biodegradation pathways.  相似文献   

Measurement and implication of "effective" viscosity for rhyolite flow emplacement   总被引：1，自引：0，他引：1  

Richard J. Stevenson †  Donald B. Dingwell  Nikolai S. Bagdassarov  Curtis R. Manley 《Bulletin of Volcanology》2001,63(4):227-237

Hazardous explosive activity may sporadically accompany the extrusion of silicic lava domes. Modelling of the emplacement of silicic domes is therefore an important task for volcanic hazard assessment. Such modelling has been hampered by a lack of a sufficiently accurate rheological database for silicic lavas with crystals and vesicles. In the present study, the parallel-plate viscometry method was applied to determine the shear viscosity of five natural rhyolitic samples from a vertical section through the Ben Lomond lava dome, Taupo Volcanic Centre, New Zealand. Rheological measurements were performed at volcanologically relevant temperatures (780-950°C) and strain rates (10^-5-10^-7 s^-1). Although these samples are in the metastable state, viscosity determinations, melt composition, as well as water and crystal contents of samples were demonstrably stable during experiments. For samples containing up to 5 vol.% microlites, the composition of the melt, rather than the physical effect of suspended crystals, had greater influence on the effective viscosity of the silicic magma. Samples with 10 vol.% microlites and containing a flow banding defined by microlites show no significant orientational effects on apparent viscosity. The rheological measurements were used together with a simple cooling model to construct thermal and viscosity profiles revealing conditions during the emplacement of the Ben Lomond lava dome.  相似文献   

Galaxy–galaxy weak lensing in the Sloan Digital Sky Survey: intrinsic alignments and shear calibration errors     

Christopher M. Hirata  Rachel Mandelbaum  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Jonathan Brinkmann  Tamas Budávari  rew Connolly  Istvan Csabai  Ryan Scranton  Alexander S. Szalay 《Monthly notices of the Royal Astronomical Society》2004,353(2):529-549

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The RHESSI Spectrometer   总被引：2，自引：0，他引：2  

Smith  D.M.  Lin  R.P.  Turin  P.  Curtis  D.W.  Primbsch  J.H.  Campbell  R.D.  Abiad  R.  Schroeder  P.  Cork  C.P.  Hull  E.L.  Landis  D.A.  Madden  N.W.  Malone  D.  Pehl  R.H.  Raudorf  T.  Sangsingkeow  P.  Boyle  R.  Banks  I.S.  Shirey  K.  Schwartz  Richard 《Solar physics》2002,210(1-2):33-60

RHESSI observes solar photons over three orders of magnitude in energy (3 keV to 17 MeV) with a single instrument: a set of nine cryogenically cooled coaxial germanium detectors. With their extremely high energy resolution, RHESSI can resolve the line shape of every known solar gamma-ray line except the neutron capture line at 2.223 MeV. High resolution also allows clean separation of thermal and non-thermal hard X-rays and the accurate measurement of even extremely steep power-law spectra. Detector segmentation, fast signal processing, and two sets of movable attenuators allow RHESSI to make high-quality spectra and images of flares across seven orders of magnitude in intensity. Here we describe the configuration and operation of the RHESSI spectrometer, show early results on in-flight performance, and discuss the principles of spectroscopic data analysis used by the RHESSI software.  相似文献   

Acknowledgment of referees     

Antonio C. da Silva  Scott T. Kay  rew R. Liddle  Peter A. Thomas 《Monthly notices of the Royal Astronomical Society》2004,355(4):1401-1408

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The power spectrum of galaxies in the 2dF 100k redshift survey     

Max Tegmark †  rew J. S. Hamilton †  Yongzhong Xu 《Monthly notices of the Royal Astronomical Society》2002,335(4):887-908

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