130,506 research outputs found
molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: density functional theory data
No full text<p>Provided here are density functional theory research datasets generated using the Vienna Ab Initio Simulation Package. Data relates to publication in Chemical Geology, entitled, Molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: A computational investigation. By Scott D Midgley, James O Taylor, Dominik Fleitmann, Ricardo Grau-Crespo. </p>
<p>We include here final geometries in .cif format, as well as full OUTCAR files generated in VASP. Using this file, readers can access all details of the DFT simulations reported. </p>
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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Late Holocene onset of intensive cultivation and introduction of the falaj irrigation system in the Salut oasis (Sultanate of Oman)
No full textThis paper discusses the time and steps of the introduction of intensive agriculture and evolution of irrigation systems to sustain crops in the palaeo-oasis of Salut in the northern Sultanate of Oman. Various geoarchaeological methods allow reconstructing the exploitation of the natural resources of the region and technological development of irrigation methods since the Mid-Holocene. Intensive agriculture started during the Bronze Age and continued with some spatial and intensity fluctuations up to the Islamic period. Cultivations were initially sustained by surface irrigation systems and later replaced by a dense net of aflaj, the typical surface/underground system adopted in the Levant, Arabian Peninsula and western Asia to collect water from deep piedmont aquifers and redistribute it to the fields located in the lowlands. Our results indicate that the aflaj were in use for a long period in the palaeo-oasis formed along Wadi Sayfam and surrounding the citadel of Salut. Uranium-Thorium dating of calcareous tufa formed in the underground tunnels of the aflaj suggests that they were used between ∼540 BCE and ∼1150 CE. After ∼1150 CE Wadi Sayfam were abandoned and the size of the oasis shrank substantially. During the late Islamic period, a surface aqueduct descending from the piedmont of Jabal Shams secured water supply. Our work confirms that in arid lands archaeological and historical communities were able to actively modulate their response to climate changes by using a variety of technological strategies
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
sulphate and molybdate incorporation at calcite-water interface - ab initio molecular dynamics data
No full textProvided here are ab initio molecular dynamics data files generated in CP2K, relating to the publication entitled
Sulphate and Molybdate Incorporation at the Calcite-Water Interface: Insights from Ab Initio Molecular Dynamics. By Scott D. Midgley, Devis Di Tommaso, Dominik Fleitmann, Ricardo Grau-Crespo.
We have provided the CP2K input file (.inp), the CP2K energy file (.ener), and a single geometry snapshot from the simulation (.xyz).
It is not possible to share the fully dynamics trajectory, because each file is extremely large.
N.B. for the sulphate ion in water, a corruption in the .ener file meant that it was not possible to share. Instead a list of MD energies are given as a .txt file, with energies in eV
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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Inverse modelling of the 14C bomb pulse in stalagmites to constrain the dynamics of soil carbon cycling at selected European cave sites
No full textThe decomposition of soil organic matter (SOM) is temperature dependent, but its response to a future warmer climate remains equivocal. Enhanced rates of decomposition of SOM under increased global temperatures might cause higher CO2 emissions to the atmosphere, and could therefore constitute a strong positive feedback. The magnitude of this feedback however remains poorly understood, primarily because of the difficulty in quantifying the temperature sensitivity of stored, recalcitrant carbon that comprises the bulk (>90%) of SOM in most soils. In this study we investigated the effects of climatic conditions on soil carbon dynamics using the attenuation of the 14C ‘bomb’ pulse as recorded in selected modern European speleothems. These new data were combined with published results to further examine soil carbon dynamics, and to explore the sensitivity of labile and recalcitrant organic matter decomposition to different climatic conditions. Temporal changes in 14C activity inferred from each speleothem was modelled using a three pool soil carbon inverse model (applying a Monte Carlo method) to constrain soil carbon turnover rates at each site. Speleothems from sites that are characterised by semi-arid conditions, sparse vegetation, thin soil cover and high mean annual air temperatures (MAATs), exhibit weak attenuation of atmospheric 14C ‘bomb’ peak (a low damping effect, D in the range: 55–77%) and low modelled mean respired carbon ages (MRCA), indicating that decomposition is dominated by young, recently fixed soil carbon. By contrast, humid and high MAAT sites that are characterised by a thick soil cover and dense, well developed vegetation, display the highest damping effect (D = c. 90%), and the highest MRCA values (in the range from 350 ± 126 years to 571 ± 128 years). This suggests that carbon incorporated into these stalagmites originates predominantly from decomposition of old, recalcitrant organic matter. SOM turnover rates cannot be ascribed to a single climate variable, e.g. (MAAT) but instead reflect a complex interplay of climate (e.g. MAAT and moisture budget) and vegetation development
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Orbital- and millennial-scale environmental changes between 64 and 20 ka BP recorded in Black Sea sediments
No full textHigh-resolution pollen and dinoflagellate cyst records from sediment core
M72/5-25-GC1 were used to reconstruct vegetation dynamics in northern
Anatolia and surface conditions of the Black Sea between 64 and 20 ka BP.
During this period, the dominance of Artemisia in the pollen record indicates a
steppe landscape and arid climate conditions. However, the concomitant
presence of temperate arboreal pollen suggests the existence of glacial
refugia in northern Anatolia. Long-term glacial vegetation dynamics reveal
two major arid phases ~64–55 and 40–32 ka BP, and two major
humid phases ~54–45 and 28–20 ka BP, correlating with higher
and lower summer insolation, respectively. Dansgaard–Oeschger (D–O) cycles
are clearly indicated by the 25-GC1 pollen record. Greenland interstadials
are characterized by a marked increase in temperate tree pollen, indicating
a spread of forests due to warm/wet conditions in northern Anatolia,
whereas Greenland stadials reveal cold and arid conditions as indicated by
spread of xerophytic biomes. There is evidence for a phase lag of
~500 to 1500 yr between initial warming and forest expansion,
possibly due to successive changes in atmospheric circulation in the North
Atlantic sector. The dominance of Pyxidinopsis psilata and
Spiniferites cruciformis in the dinocyst record indicates
brackish Black Sea conditions during the entire glacial period. The decrease
of marine indicators (marine dinocysts, acritarchs) at ~54 ka
BP and increase of freshwater algae (Pediastrum, Botryococcus) from 32 to 25 ka BP reveals
freshening of the Black Sea surface water. This freshening is possibly
related to humid phases in the region, to connection between Caspian Sea and
Black Sea, to seasonal freshening by floating ice, and/or to closer position
of river mouths due to low sea level. In the southern Black Sea, Greenland
interstadials are clearly indicated by high dinocyst concentrations and
calcium carbonate content, as a result of an increase in primary
productivity. Heinrich events show a similar impact on the environment in the
northern Anatolia/Black Sea region as Greenland stadials
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