5,656 research outputs found

    Book Review: Hsieh Liang-tso and the Analects of Confucius: Humane Learning as a Religious Quest

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    Hsieh Liang-tso is the first volume to explore Chinese traditions in the Academy Series sponsored by Oxford and the American Academy of Religion. Most previous titles in the series focus on Christianity, which perhaps explains Selover’s attention to the perspectives of comparative religions and comparative theology in his introduction. There he briefly traces the history of the issues concerning the religious dimensions of the Chinese literati tradition and outlines a comparative framework for approaching eleventh-century Chinese thought. Inspired by Robert Neville’s Beyond the Masks of God, Selover focuses in the introduction on four themes—scripture, tradition, reason, and experience. This framework, however, does not figure prominently until the conclusion. [excerpt

    Discovery of large scale shock fronts correlated with the radio halo and radio relic in the A2163 galaxy cluster

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    Imprints of galaxy cluster formation processes are visible in the intracluster medium and can arise in shock fronts, which are detectable via discontinuities in e.g. the gas temperature and density profiles. In this study, we investigate the X-ray properties of the intracluster gas and the radio morphology of the extraordinary cluster A2163. This cluster shows an irregular morphology in various wavelengths and has one of the most luminous and extended known radio halos. Additionally, it is one of the hottest clusters known. We analyze two Suzaku observations of A2163, one in the north-east (NE) and one in the south-west (SW) direction, and use archival XMM-Newton data to remove point sources in the field of view. To compare our findings in the X-ray regime with the radio emission, we obtain radio images of the cluster from an archival VLA observation at 20cm. We identify three shock fronts in A2163 in our spectral X-ray study. A clear shock front lies in the NE direction at a distance of 1.4Mpc from the center, with a Mach number of M=1.70.2+0.3M=1.7_{-0.2}^{+0.3}, estimated from the temperature discontinuity. This shock coincides with the position of a known radio relic. We identify two additional shocks in the SW direction, one with M=1.50.3+0.5M=1.5_{-0.3}^{+0.5} at a distance of 0.7Mpc, which is likely related to a cool core remnant, and a strong shock with M=3.20.7+0.6M=3.2_{-0.7}^{+0.6} at a distance of 1.3Mpc, which also closely matches the radio contours. The complex structure of A2163 as well as the different Mach numbers and shock velocities suggest a merging scenario with two unequal merging constituents, where two shock fronts emerged in an early stage of the merger and traveled outwards while an additional shock front developed in front of the merging cluster cores.Comment: 9 pages, 7 figures, accepted by A&

    Linking foraging strategies of marine calanoid copepods to patterns of nitrogen stable isotope signatures in a mesocosm study

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    The foraging modes of calanoid copepods differ in that stationary suspension-feeding is more easily detected by prey with strong escape responses (ciliates) than is ‘cruising’ or ‘ambushing’ feeding. Thus, the ability of a copepod to include heterotrophic prey in its diet may be associated with its foraging mode and, further, with its nitrogen stable isotope signature (δ15N). This is because a more carnivorous diet may be expected to result in a higher δ15N. We tested this hypothesis in a mesocosm study using a density gradient (0 to 80 ind. l-1) of calanoid copepods. We expected copepod δ15N to generally increase with decreasing copepod density because of increased food availability, and predicted stronger increases for cruising than for stationary suspension-feeding species. As an assemblage, copepods had a pronounced impact on the food web: diatoms and ciliates decreased, whereas nanoflagellates increased with increasing copepod density. As expected, Centropages hamatus, a cruising species, showed the strongest isotopic increase and also highest population growth at low copepod density, suggesting that it was the most efficient species in capturing ciliates. Temora longicornis, a stationary suspension-feeder, showed a uniform isotopic increase in all mesocosms, which we believe resulted from nutritional stress arising from poor feeding on both ciliates (too fast for ingestion by T. longicornis) and nanoflagellates (too small). However, Pseudocalanus elongatus, a species equally categorised as a stationary suspension-feeder, showed increases in its δ15N similar to those for C. hamatus. While this may indicate potential switching in its foraging mode, alternative explanations cannot be ruled out, partly because qualitative and quantitative aspects of trophic enrichment in our experiment could not be clearly separated. This study shows that consumer δ15N are difficult to interpret, even if potential food sources and aspects of the species’ biology are known, and thus emphasises the necessity for further laboratory studies to help better interpret zooplankton δ15N in the field

    Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory

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    We demonstrate that ground state energies approaching chemical accuracy can be obtained by combining the adiabatic connection fluctuation-dissipation theorem (ACFDT) with time-dependent density functional theory (TDDFT). The key ingredient is a renormalization scheme, which eliminates the divergence of the correlation hole characteristic of any local kernel. This new class of renormalized kernels gives a significantly better description of the short-range correlations in covalent bonds compared to the random phase approximation (RPA) and yields a four fold improvement of RPA binding energies in both molecules and solids. We also consider examples of barrier heights in chemical reactions, molecular adsorption and graphene interacting with metal surfaces, which are three examples where RPA has been successful. In these cases, the renormalized kernel provides results that are of equal quality or even slightly better than RPA, with a similar computational cost.Comment: Accepted for publication in Phys. Rev. Lett. Supplementary material included as appendi

    Improved description of metal oxide stability:Beyond the random phase approximation with renormalized kernels

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    The renormalized adiabatic PBE (rAPBE) method has recently been shown to comprise a significant improvement over the random phase approximation (RPA) for total energy calculations of simple solids and molecules. Here we consider the formation energies of 19 group I and II metal oxides and a few transition-metal oxides. The mean absolute error relative to experiments is 0.21 eV and 0.38 eV per oxygen atom for rAPBE and RPA, respectively, and thus the rAPBE method greatly improves the description of metal-oxygen bonds across a wide range of oxides. The failure of the RPA can be partly attributed to the lack of error cancellation between the correlation energy of the oxide on the one hand and the bulk metal and oxygen molecule on the other hand, which are all separately predicted much too negative by the RPA. We ascribe the improved performance of the rAPBE to its significantly better description of absolute correlation energies which reduces the need for error cancellation. The rAPBE is just one out of an entire class of renormalized exchange-correlation kernels which should be further investigated.The authors acknowledge support from the Danish Council for Independent Research’s Sapere Aude Program, Grant No. 11-1051390. The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation, Project DNRF58. T.B. thanks DOE-BES for funding to SUNCAT.Peer reviewe
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