151 research outputs found
Trilobite-based biostratigraphic model (biofacies and biozonation) for the Middle Cambrian carbonate platform of the Argentine Precordillera
A preliminary biostratigraphic model that combines trilobite biofacies and biozonation is proposed for the early Marjumian (Middle Cambrian) of the Precordillera of western Argentina. This interval involves a variety of paleogeographic–paleoenvironmental settings across the carbonate platform, ranging from its interior to exterior areas beyond the platform margin and including both open-marine and near-shore environments. This model is based on three stratigraphic sections of the basal part of the Alojamiento Formation, which crops out in the Cordón del Alojamiento (Provincia de Mendoza) and Cordón de Santa Clara (Provincia de San Juan); and three sections of the Soldano Member of La Laja Formation in the Sierra Chica de Zonda (Provincia de San Juan). Three biofacies were recognized on the basis of trilobite associations that show a marked environmental distribution: 1) The Ptychagnostidae Biofacies is represented by an assemblage exclusively dominated by agnostoids, most of them belonging to Ptychagnostus; this assemblage occurs in mudstones and calcareous shales deposited below storm wave-base seaward of the platform margin; 2) the Peronopsidae Biofacies also developed in the external areas but it occurs in limestones deposited between fair-weather and storm wave-base; this assemblage is likewise dominated by agnostoids, but instead belonging to Peronopsis, with the rest of the fauna comprising polymeroids (Dolichometopidae, Oryctocephalidae, Zacanthoididae and Alokistocaridae); 3) the Alokistocaridae Biofacies occurs in grainstones, mudstones and calcareous shales deposited between fair-weather and storm wave-base under changeable conditions located near the platform margin and in the interior. It is dominated by alokistocarids whose relative abundance increases landward from 52% to 58% and to 95%. The remaining components belong to Dorypygidae, Zacanthoididae and Oryctocephalidae; Eodiscidae and Peronopsidae comprise minor proportions in the most seaward location. Due to the contrasting, environmentally mediated associations, these sections belong to three essentially synchronous biozones erected previously for the Middle Cambrian of western Laurentia, the Ptychagnostus gibbus, Oryctocephalus and Ehmaniella Biozones
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Workshop report on new directions in soft x-ray photoabsorption
The Workshop Report integrates what was said at the Workshop on New Directions in Soft X-Ray Photoabsorption, which focused on the region from 100 eV to 10 keV. The report clarifies the current state of theory and experiment and identifies the opportunities which new theoretical methods and experimental facilities could be expected to provide. The understanding of photoabsorption (which requires experimental photoabsorption cross section data) is a key to understanding the properties and behavior of atoms, molecules and solids. The Workshop participants were forty-three physicists and quantum chemists, from twenty-four institutions in four countries, all interested in photoabsorption from different perspectives
Contributions of individual reactive biogenic volatile organic compounds to organic nitrates above a mixed forest
Biogenic volatile organic compounds (BVOCs) can react in the atmosphere to form organic nitrates, which serve as reservoirs, impacting ozone and secondary organic aerosol production, the oxidative capacity of the atmosphere, and nitrogen availability to ecosystems. To examine the contributions of biogenic emissions and the formation and fate of organic nitrates in a forest environment, we simulated the oxidation of 57 individual BVOCs emitted from a rural mixed forest in northern Michigan. Key BVOC-oxidant reactions were identified for future laboratory and field investigations into reaction rate constants, yields, and speciation of oxidation products. Of the total simulated organic nitrates, monoterpenes contributed ~70% in the early morning at ~12 m above the forest canopy when isoprene emissions were low. In the afternoon, when vertical mixing and isoprene nitrate production were highest, the simulated contribution of isoprene-derived organic nitrates was greater than 90% at all altitudes, with the concentration of secondary isoprene nitrates increasing with altitude. Notably, reaction of isoprene with leading to isoprene nitrate formation was found to be significant (~8% of primary organic nitrate production) during the daytime, and monoterpene reactions with were simulated to comprise up to ~83% of primary organic nitrate production at night. Lastly, forest succession, wherein aspen trees are being replaced by pine and maple trees, was predicted to lead to increased afternoon concentrations of monoterpene-derived organic nitrates. This further underscores the need to understand the formation and fate of these species, which have different chemical pathways and oxidation products compared to isoprene-derived organic nitrates and can lead to secondary organic aerosol formation
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Controlled English for Reasoning on the Semantic Web
The existing Semantic Web languages have a very technical focus and fail to provide good usability for users with no background in formal methods. We argue that controlled natural languages like Attempto Controlled English (ACE) can solve this problem. ACE is a subset of English that can be translated into various logic based languages, among them the Semantic Web standards OWL and SWRL. ACE is accompanied by a set of tools, namely the parser APE, the Attempto Reasoner RACE, the ACE View ontology and rule editor, the semantic wiki AceWiki, and the Protune policy framework. The applications cover a wide range of Semantic Web scenarios, which shows how broadly ACE can be applied. We conclude that controlled natural languages can make the Semantic Web better understandable and more usable
Biomedical and therapeutic applications of biosurfactants
During the last years, several applications of biosurfactants with medical purposes have been reported. Biosurfactants are considered relevant molecules for applications in combating many diseases and as therapeutic agents due to their antibacterial, antifungal and antiviral activities. Furthermore, their role as anti-adhesive agents against several pathogens illustrate their utility as suitable anti-adhesive coating agents for medical insertional materials leading to a reduction of a large number of hospital infections without the use of synthetic drugs and chemicals. Biomedical and therapeutic perspectives of biosurfactants applications are presented and discussed in this chapter
Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background
The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society
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