Detection and extraction of signals from the epoch of reionization using higher-order one-point statistics

Detecting redshifted 21-cm emission from neutral hydrogen in the early Universe promises to give direct constraints on the epoch of reionization (EoR). It will, though, be very challenging to extract the cosmological signal (CS) from foregrounds and noise which are orders of magnitude larger. Fortunately, the signal has some characteristics which differentiate it from the foregrounds and noise, and we suggest that using the correct statistics may tease out signatures of reionization. We generate mock data cubes simulating the output of the Low Frequency Array (LOFAR) EoR experiment. These cubes combine realistic models for Galactic and extragalactic foregrounds and the noise with three different simulations of the CS. We fit out the foregrounds, which are smooth in the frequency direction, to produce residual images in each frequency band. We denoise these images and study the skewness of the one-point distribution in the images as a function of frequency. We find that, under sufficiently optimistic assumptions, we can recover the main features of the redshift evolution of the skewness in the 21-cm signal. We argue that some of these features – such as a dip at the onset of reionization, followed by a rise towards its later stages – may be generic, and give us a promising route to a statistical detection of reionization.     

An analysis of v sin (i) correlations in early-type binaries

We use information on the   v sin ( i )  values of early-type binaries in order to search for correlations which may constrain the relative orientation of the stellar spin axes in binary systems. We find correlations in the case of close binaries which suggest that tidal synchronization is effective for binaries whose separation exceeds the stellar radius by more than an order of magnitude, in line with the theoretical predictions of Goldreich & Nicholson and the previous observational analysis of Giuricin et al. In the case of wide binaries, the   v sin ( i )  values are not well correlated, which requires that the magnitude of the spin speeds is not tightly correlated. Under this assumption, we then find that the data provide no significant constraints on the degree of alignment of spin axes. The data are therefore compatible with scenarios (such as disc fragmentation or capture) which differ widely in the expected degree of spin alignment.     

Stuart H. Perry's contributions to meteorite collection and research, 1927–1957

Abstract— Stuart H. Perry (1874–1957), an influential Michigan newspaper editor and publisher and a vice president of the Associated Press, developed a passionate interest in collecting and studying meteorites in the 1920s and 1930s. Firmly believing that meteorites belong in great museums where they can be properly investigated, he generously donated his meteorites to various museums after he finished his own study of them. He had a sincere interest in the National Collection of Meteorites, and donated 192 specimens–‐mostly irons–‐to the U.S. National Museum; these constituted some of the most important meteorites in its collection, and moved iron meteorites to center stage, a position still occupied. By applying current metallographic methods to the study of iron meteorites, Perry directed scientists to a powerful new research tool, which led to major advances in our understanding of meteoritic irons and helped give rise to a new field within planetary sciences. His groundbreaking monograph The metallography of meteoric iron served as a standard reference collection of metallographic photomicrographs of iron meteorites for more than 30 years. It remained an insightful and useful work on the structure of meteoritic iron until improved binary and ternary phase diagrams in the Fe‐Ni(‐P) system allowed a more detailed treatment of the formation of iron meteorites. Perry received many honors for his work, and held office in the Meteoritical Society, serving as a councilor from 1941–1950, and as a vice president from 1950–1957.     

Eccentricity growth of planetesimals in a self-gravitating protoplanetary disc

We investigate the orbital evolution of planetesimals in a self-gravitating circumstellar disc in the size regime (∼1–5000 km) where the planetesimals behave approximately as test particles in the disc's non-axisymmetric potential. We find that the particles respond to the stochastic, regenerative spiral features in the disc by executing large random excursions (up to a factor of 2 in radius in ∼1000 yr), although typical random orbital velocities are of the order of one tenth of the Keplerian speed. The limited time frame and small number of planetesimals modelled do not permit us to discern any net direction of planetesimal migration. Our main conclusion is that the high eccentricities (∼0.1) induced by interaction with spiral features in the disc is likely to be highly unfavourable to the collisional growth of planetesimals in this size range while the disc is in the self-gravitating regime. Thus if , as recently argued by Rice et al., the production of planetesimals gets under way when the disc is in the self-gravitating regime (either at smaller planetesimal size scales, where gas drag is important, or via gravitational fragmentation of the solid component), the planetesimals thus produced would not be able to grow collisionally until the disc ceases to be self-gravitating. It is unclear, however, given the large amplitude excursions undergone by planetesimals in the self-gravitating disc, whether they would be retained in the disc throughout this period, or whether they would instead be lost to the central star.     

Microbially induced calcite precipitation along a circular flow channel under a constant flow condition

Biogrouting is a new ground improvement method that has been studied in recent years. This method involves mainly the use of a microbially induced calcite precipitation process to bind soil particles to increase the strength or to fill in the pores of soil or joints of rock for seepage control. There are two major challenges in the use of biogrout for seepage control through rock joints. The first is how to inject the biogrout solutions, and the second is to understand the mechanisms for the formation of calcite under seepage flow. In this paper, a study on the injection of biogrout solution and the formation of precipitates along a circular 1D flow channel is presented. To minimize the influence of flow, a new one-phase injection method to inject bacterial solution and cementation agents simultaneously was adopted in this study. Factors affecting the formation and distribution of precipitates along the flow channel such as flow velocity, flow rate, and aperture of flow channel were investigated. The experimental results indicated that less calcite was precipitated at locations further away from the injection point due to depletion of the reactants’ concentrations along the flow path. Using the one-phase injection method, the bacterial activity had a major effect on the accumulation of the calcite on the inner surface of the flow channel. The total calcite precipitated on the surface of the flow channel increased slightly with increasing bacterial activity or flow rate. An equation to predict the distance travelled by the biosolution has been derived based on the testing results.

     

Clitellate worms (Annelida) in lateglacial and Holocene sedimentary DNA records from the Polar Urals and northern Norway

While there are extensive macro‐ and microfossil records of a range of plants and animals from the Quaternary, earthworms and their close relatives amongst annelids are not preserved as fossils and therefore the knowledge of their past distributions is limited. This lack of fossils means that clitellate worms (Annelida) are currently underused in palaeoecological research, even though they can provide valuable information about terrestrial and aquatic environmental conditions. Their DNA might be preserved in sediments, which offers an alternative method for detection. Here we analyse lacustrine sediments from lakes in the Polar Urals, Arctic Russia, covering the period 24 000–1300 cal. a BP, and NE Norway, covering 10 700–3300 cal. a BP, using a universal mammal 16S rDNA marker. While mammals were recorded using the marker (reindeer was detected twice in the Polar Urals core at 23 000 and 14 000 cal. a BP, and four times in the Norwegian core at 11 000 cal. a BP and between 3600–3300 cal. a BP), worm extracellular DNA ‘bycatch’ was rather high. In this paper we present the first reported worm detection from ancient DNA. Our results demonstrate that both aquatic and terrestrial clitellates can be identified in late‐Quaternary lacustrine sediments, and the ecological information retrievable from this group warrants further research with a more targeted approach.     

The evolution of zircon during low‐P partial melting of metapelitic rocks: theoretical predictions and a case study from Mt Stafford,central Australia

Palaeoproterozoic metasedimentary migmatite reflects the highest temperature parts of a regional aureole at Mt Stafford, central Australia, comprising rocks that experienced 500–800 °C at ≈3 kbar. Whole‐rock major element concentrations are correlated with Zr content, psammitic compositions having nearly twice the Zr content of pelitic compositions. Zirconium is concentrated in mesosome compared with leucosome. Zircon is largely detrital, mostly lacking any overgrowth contemporary with migmatite formation. Comparatively small proportions of micro‐zircon (<10 μm) in sub‐solidus rocks are mostly hosted by quartz and plagioclase. Much higher proportions (three to five times) of micro‐zircon in migmatite are hosted by prograde K‐feldspar, cordierite and biotite. T–X and P–T NCKFMASHTZr pseudosections constructed using thermocalc model the distribution of Zr between solid and silicate liquid phases. Half of the detrital zircon (~100 ppm Zr) is predicted to be dissolved into silicate liquid at ≈800 °C and all dissolved by 850 °C, if all zircon is involved in the equilibration volume. Melt segregation at relatively low temperature is predicted to enrich the residuum in Zr, consistent with the observed distribution of Zr between mesosome and leucosome. The limited development of metamorphic zircon rims or overgrowths at Mt Stafford is explained by three concurrent processes: (i) Zr liberated during prograde metamorphism formed micro‐zircon, rather than following the prediction that Zr will partition into silicate liquid; (ii) some detrital zircon was probably armoured by other rock‐forming minerals, reducing Zr content in the effective bulk rock composition; and (iii) small proportions of melt loss during migmatization removed Zr that otherwise would have been available to form metamorphic rims.     

Optimizing GPS-guidance transit route for cable crane collision avoidance using artificial immune algorithm

GPS Solutions - A cable crane collision accident usually causes serious damage to workers, equipment and materials. Owing to the emergence of global position system (GPS), some new collision...     

Modeling the environmental susceptibility of landfill sites in California

??The proper management of solid waste (SW) is a global environmental challenge. A major issue is the proper disposal of SW while balancing a wide range of criteria and working with different spatial data. In this study, we used geographic information system as a tool to perform multi-criteria decision analysis with an analytical hierarchy process to develop an environmental impact susceptibility model (EISM) for landfills. The model was applied to the state of California, USA and results are presented herein. In particular, the EISM considers factors such as geology, pedology, geomorphology, water resources, and climate as represented by 13 associated environmental indicators. The results of the EISM indicate that more than 75% of California’s territory is situated in areas with very low, low, and medium environmental impact susceptibility categories. However, in the remaining 25% of the state’s land, 61 landfills are located in the high and very high categories. These results are alarming because during the period from 2000 to 2015, these 61 landfills received approximately 308 million tons of SW, which corresponds to more than 57% of all SW disposed in California. The model results can be used toward mitigating the environmental impacts of these facilities.