Discovery of 10 pulsars in an Arecibo drift-scan survey     

D. R. Lorimer  K. M. Xilouris  A. S. Fruchter  I. H. Stairs  F. Camilo  A. M. Vazquez  J. A. Eder  M. A. McLaughlin  M. S. E. Roberts  J. W. T. Hessels  S. M. Ransom 《Monthly notices of the Royal Astronomical Society》2005,359(4):1524-1530

We present the results of a 430-MHz survey for pulsars conducted during the upgrade to the 305-m Arecibo radio telescope. Our survey covered a total of 1147 deg² of sky using a drift-scan technique. We detected 33 pulsars, 10 of which were not known prior to the survey observations. The highlight of the new discoveries is PSR J0407+1607, which has a spin period of 25.7 ms, a characteristic age of 1.5 Gyr and is in a 1.8-yr orbit about a low-mass  (>0.2 M_⊙)  companion. The long orbital period and small eccentricity  ( e = 0.0009)  make the binary system an important new addition to the ensemble of binary pulsars suitable to test for violations of the strong equivalence principle. We also report on our initially unsuccessful attempts to detect optically the companion to J0407+1607, which imply that its absolute visual magnitude is >12.1. If, as expected on evolutionary grounds, the companion is an He white dwarf, our non-detection implies a cooling age of least 1 Gyr.  相似文献   

Chandra temperature and metallicity maps of the Perseus cluster core     

R. W. Schmidt  A. C. Fabian  J. S. Sanders 《Monthly notices of the Royal Astronomical Society》2002,337(1):71-78

We present temperature and metallicity maps of the Perseus cluster core obtained with the Chandra X-ray Observatory. We find an overall temperature rise from  ∼3.0 keV  in the core to  ∼5.5 keV  at 120 kpc and a metallicity profile that rises slowly from  ∼0.5  solar to  ∼0.6  solar inside 60 kpc, but drops to  ∼0.4  solar at 120 kpc. Spatially resolved spectroscopy in small cells shows that the temperature distribution in the Perseus cluster is not symmetrical. There is a wealth of structure in the temperature map on scales of  ∼10  arcsec (5.2 kpc) showingswirliness and a temperature rise that coincides with a sudden surface brightness drop in the X-ray image. We obtain a metallicity map of the Perseus cluster core and find that the spectra extracted from the two central X-ray holes as well as the western X-ray hole are best-fit by gas with higher temperature and higher metallicity than is found in the surroundings of the holes. A spectral deprojection analysis suggests, however, that this is due to a projection effect; for the northern X-ray hole we find tight limits on the presence of an isothermal component in the X-ray hole, ruling out volume-filling X-ray gas with temperatures below 11 keV at 3σ.  相似文献   

Elimination of Swimming Pool Water Disinfection By‐products with Advanced Oxidation Processes (AOPs)     

Thomas Glauner  Fabian Kunz  Christian Zwiener  Fritz H. Frimmel 《洁净——土壤、空气、水》2005,33(6):585-594

Ozonation is a treatment step which was first applied in the 1960s in pool water treatment for disinfection as well as for oxidation of pool water contaminants. Contact time between ozone and pool water was identified to be of significance with an increased elimination efficiency regarding chloramines, trihalogenmethane formation potential and the permanganate index for longer reaction times. Oxidation via OH radicals might be the dominating pathway. In this study ozonation was compared with the ozone based advanced oxidation processes ozone/UV and ozone/hydrogen peroxide regarding the elimination efficiency of both disinfection by‐products (DBPs) and DBP precursors. It was observed that AOPs in comparison to ozonation showed an increased elimination efficiency regarding total organic carbon (TOC), the organically bound halogens adsorbable on activated carbon (AOX) and AOX formation potential. A contact time of 3 minutes between pool water and oxidant turned out to be practically sufficient. Just for the trihalomethane (THM) formation potential ozonation showed a slight advantage compared to the AOPs because ozonation is a highly selective oxidant and OH radical reactions are known to produce small reactive molecules which are easier transformed to THMs. Combination of membrane filtration and AOPs resulted in an elimination of 10 to 90 % of the DBPs and their precursors. The ozone/hydrogen peroxide process is suggested for pool water treatment because of the higher elimination rates compared to ozonation and of economic reasons compared to the ozone/UV process.  相似文献   

A stratigraphic network across the Subtropical Front in the central South Atlantic: Multi-parameter correlation of magnetic susceptibility, density, X-ray fluorescence and δO records     

Daniela I. Hofmann  Karl Fabian  Frank Schmieder  Barbara Donner  Ulrich Bleil 《Earth and Planetary Science Letters》2005,240(3-4):694-709

Computer aided multi-parameter signal correlation is used to develop a common high-precision age model for eight gravity cores from the subtropical and subantarctic South Atlantic. Since correlations between all pairs of multi-parameter sequences are used, and correlation errors between core pairs (A, B) and (B, C) are controlled by comparison with (A, C), the resulting age model is called a stratigraphic network. Precise inter-core correlation is achieved using high-resolution records of magnetic susceptibility κ, wet bulk density ρ and X-ray fluorescence scans of elemental composition. Additional δ¹⁸O records are available for two cores. The data indicate nearly undisturbed sediment series and the absence of significant hiatuses or turbidites. After establishing a high-precision common depth scale by synchronously correlating four densely measured parameters (Fe, Ca, κ, ρ), the final age model is obtained by simultaneously fitting the aligned δ¹⁸O and κ records of the stratigraphic network to orbitally tuned oxygen isotope [J. Imbrie, J. D. Hays, D. G. Martinson, A. McIntyre, A. C. Mix, J. J. Morley, N. G. Pisias, W. L. Prell, N. J. Shackleton, The orbital theory of Pleistocene climate: support from a revised chronology of the marine δ¹⁸O record, in: A. Berger, J. Imbrie, J. Hays, G. Kukla, B. Saltzman (Eds.), Milankovitch and Climate: Understanding the Response to Orbital Forcing, Reidel Publishing, Dordrecht, 1984, pp. 269-305; D. Martinson, N. Pisias, J. Hays, J. Imbrie, T. C. Moore Jr., N. Shackleton, Age dating and the orbital theory of the Ice Ages: development of a high-resolution 0 to 300.000-Year chronostratigraphy, Quat. Res. 27 (1987) 1-29.] or susceptibility stacks [T. von Dobeneck, F.Schmieder, Using rock magnetic proxy records for orbital tuning and extended time series analyses into the super-and sub-Milankovitch Bands, in: G. Fischer, G. Wefer (Eds.), Use of proxies in paleoceanography: Examples from the South Atlantic, Springer-Verlag, Berlin (1999), pp. 601-633.]. Besides the detection and elimination of errors in single records, the stratigraphic network approach allows to check the intrinsic consistency of the final result by comparing it to the outcome of more restricted alignment procedures. The final South Atlantic stratigraphic network covers the last 400 kyr south and the last 1200 kyr north of the Subtropical Front (STF) and provides a highly precise age model across the STF representing extremely different sedimentary regimes. This allows to detect temporal shifts of the STF by mapping δMn / Fe. It turns out that the apparent STF movements by about 200 km are not directly related to marine oxygen isotope stages.  相似文献   

Meridional distribution of tropospheric ozone from ground-based registrations between Norway and South Africa     

Fabian  P.  Pruchniewicz  P. G. 《Pure and Applied Geophysics》1973,106(1):1027-1035

By means of a meridional chain of 19 stations between Tromso, Norway, and Hermanus, South Africa, a permanent registration of ozone near the ground has been obtained since 1970. From the first year of operation surprisingly systematic annual variations come out, which agree with theoretical calculations on stratospheric-tropospheric exchange.  相似文献   

Uncertainty in an emissions-constrained world     

Matthias Jonas  Gregg Marland  Volker Krey  Fabian Wagner  Zbigniew Nahorski 《Climatic change》2014,124(3):459-476

Our study focuses on uncertainty in greenhouse gas (GHG) emissions from anthropogenic sources, including land use and land-use change activities. We aim to understand the relevance of diagnostic (retrospective) and prognostic (prospective) uncertainty in an emissions-temperature setting that seeks to constrain global warming and to link uncertainty consistently across temporal scales. We discuss diagnostic and prognostic uncertainty in a systems setting that allows any country to understand its national and near-term mitigation and adaptation efforts in a globally consistent and long-term context. Cumulative emissions are not only constrained and globally binding but exhibit quantitative uncertainty; and whether or not compliance with an agreed temperature target will be achieved is also uncertain. To facilitate discussions, we focus on two countries, the USA and China. While our study addresses whether or not future increase in global temperature can be kept below 2, 3, or 4 °C targets, its primary aim is to use those targets to demonstrate the relevance of both diagnostic and prognostic uncertainty. We show how to combine diagnostic and prognostic uncertainty to take more educated (precautionary) decisions for reducing emissions toward an agreed temperature target; and how to perceive combined diagnostic and prognostic uncertainty-related risk. Diagnostic uncertainty is the uncertainty contained in inventoried emission estimates and relates to the risk that true GHG emissions are greater than inventoried emission estimates reported in a specified year; prognostic uncertainty refers to cumulative emissions between a start year and a future target year, and relates to the risk that an agreed temperature target is exceeded.  相似文献   

High precision triple oxygen isotope composition of small size urban micrometeorites indicating constant influx composition in the early geologic past     

Fabian Zahnow  Tido Stracke  Tommaso di Rocco  Thilo Hasse  Andreas Pack 《Meteoritics & planetary science》2023,58(11):1567-1579

In this study, we present a method for high precision Δ′¹⁷O (Δ′¹⁷O_RL = ln(δ¹⁷O + 1) – λ_RL ln(δ¹⁸O + 1)) analysis of small mass silicate and oxide materials. The analyses were conducted by laser fluorination in combination with gas chromatography and continuous flow isotope ratio monitoring gas spectrometry. We could analyze the oxygen isotope composition of samples down to 1 μg, which corresponded to about 13 nmol O₂. The analytical error (we report the 1σ external reproducibility of a single analysis) in δ¹⁸O increases with decreasing sample sizes from ~0.2‰ for ~20 μg samples to ~0.9‰ for 1 μg samples. For Δ′¹⁷O, we achieved an external reproducibility of 0.04‰ for a sample mass range between 1 and 27 μg. The uncertainty in Δ′¹⁷O is smaller than the uncertainty in δ¹⁸O due to the correlated errors in δ¹⁷O and δ¹⁸O. We applied the method to urban micrometeorites, that is, small meteorites (<2 mm) that were sampled from a rooftop in Berlin, Germany. A total of 10 melted micrometeorites (S-type cosmic spherules, masses between 11 and 22 μg) were analyzed. The oxygen isotope compositions are comparable to that of modern Antarctic collections, indicating that the urban micrometeorites sample the same population. No indication for terrestrial weathering had been identified in the studied set of urban micrometeorites making them suitable materials for the study of micrometeorite origins.  相似文献   

X-ray reverberation around accreting black holes     

P.?UttleyEmail author  E.?M.?Cackett  A.?C.?Fabian  E.?Kara  D.?R.?Wilkins 《Astronomy and Astrophysics Review》2014,22(1):72

Luminous accreting stellar mass and supermassive black holes produce power–law continuum X-ray emission from a compact central corona. Reverberation time lags occur due to light travel time delays between changes in the direct coronal emission and corresponding variations in its reflection from the accretion flow. Reverberation is detectable using light curves made in different X-ray energy bands, since the direct and reflected components have different spectral shapes. Larger, lower frequency, lags are also seen and are identified with propagation of fluctuations through the accretion flow and associated corona. We review the evidence for X-ray reverberation in active galactic nuclei and black hole X-ray binaries, showing how it can be best measured and how it may be modelled. The timescales and energy dependence of the high-frequency reverberation lags show that much of the signal is originating from very close to the black hole in some objects, within a few gravitational radii of the event horizon. We consider how these signals can be studied in the future to carry out X-ray reverberation mapping of the regions closest to black holes.  相似文献   

Coherent Structures at a Forest Edge: Properties, Coupling and Impact of Secondary Circulations   总被引：1，自引：1，他引：0  

Fabian Eder  Andrei Serafimovich  Thomas Foken 《Boundary-Layer Meteorology》2013,148(2):285-308

Little is known about the influence of coherent structures on the exchange process, mainly in the case of forest edges. Thus, in the framework of the ExchanGE processes in mountainous Regions (EGER) project, measurements of atmospheric turbulence were taken at different heights between a forest and an adjacent clear cutting using sonic anemometers and high-frequency optical gas analyzers. From these turbulence data, dominant coherent structures were extracted using an already existing wavelet methodology, which was developed for homogeneous forest canopies. The aim of this study is to highlight differences in properties of coherent structures between a forest and a clear cutting. Distinct features of coherent exchange at the forest edge are presented and a careful investigation of vertical and horizontal coupling by coherent structures around the surface heterogeneity is made. Within the forest, coherent structures are less frequent but possess larger time scales, indicating that only the largest coherent motions can penetrate through the forest canopy. At the forest edge, there is no crown layer that can hinder the vertical exchange of coherent structures, because these exhibit similar time scales at all heights. In contradiction to that, no improved vertical coupling was detected at the forest edge. This is mainly because the structures captured by the applied routine contribute less to total turbulent fluxes at the edge than within the forest. Thus, coherent structures with time scales between 10 and 40 s are not the dominant exchange mechanism at the forest edge. With respect to the horizontal direction, a consistent picture of coherent transport could be derived: along the forest edge there is mainly good coupling by coherent structures, whereas perpendicular to the forest edge there is mainly decoupling. Finally, it was found that there is a systematic modulation of coherent structures directly at the forest edge: strong ejection motions appear in all time series during the daytime, whereas strong sweeps dominate at night. An effect of wind direction relative to the forest edge is excluded. Consequently, it is hypothesized that this might be an indication of a quasi-stationary secondary circulation above the clear cutting that develops due to differences in surface temperature and roughness. Such circulations might be a relevant turbulent transport mechanism for ecosystem-atmosphere exchange in heterogeneous landscapes.  相似文献   

Twinned calcite as an indicator of high differential stresses and low shock pressure conditions during impact cratering     

Lina Seybold  Claudia A. Trepmann  Stefan Hölzl  Kilian Pollok  Falko Langenhorst  Fabian Dellefant  Melanie Kaliwoda 《Meteoritics & planetary science》2023,58(9):1287-1305

Shock-related calcite twins are characterized in calcite-bearing metagranite cataclasites within crystalline megablocks of the Ries impact structure, Germany, as well as in cores from the FBN1973 research drilling. The calcite likely originates from pre-impact veins within the Variscan metagranites and gneisses, while the cataclasis is due to the Miocene impact. Quartz in the metagranite components does not contain planar deformation features, indicating low shock pressures (<7 GPa). Calcite, however, shows a high density (>1/μm) of twins with widths <100 nm. Different types of twins (e-, f-, and r-twins) crosscutting each other can occur in one grain. Interaction of r- and f-twins results in a-type domains characterized by a misorientation relative to the host with a misorientation angle of 35°–40° and a misorientation axis parallel to an a-axis. Such a-type domains have not been recorded from deformed rocks in nature before. The high twin density and activation of different twin systems in one grain require high differential stresses (on the order of 1 GPa). Twinning of calcite at high differential stresses is consistent with deformation during impact cratering at relatively low shock pressure conditions. The twinned calcite microstructure can serve as a valuable low shock barometer.  相似文献