344 research outputs found
Self-consistent predictions for LIER-like emission lines from post-AGB stars
Early type galaxies (ETGs) frequently show emission from warm ionized gas.
These Low Ionization Emission Regions (LIERs) were originally attributed to a
central, low-luminosity active galactic nuclei. However, the recent discovery
of spatially-extended LIER emission suggests ionization by both a central
source and an extended component that follows a stellar-like radial
distribution. For passively-evolving galaxies with old stellar populations, hot
post-Asymptotic Giant Branch (AGB) stars are the only viable extended source of
ionizing photons. In this work, we present the first prediction of LIER-like
emission from post-AGB stars that is based on fully self-consistent stellar
evolution and photoionization models. We show that models where post-AGB stars
are the dominant source of ionizing photons reproduce the nebular emission
signatures observed in ETGs, including LIER-like emission line ratios in
standard optical diagnostic diagrams and H equivalent widths of order
0.1-3 angstroms. We test the sensitivity of LIER-like emission to the details
of post-AGB models, including the mass loss efficiency and convective mixing
efficiency, and show that line strengths are relatively insensitive to post-AGB
timescale variations. Finally, we examine the UV-optical colors of the models
and the stellar populations responsible for the UV-excess observed in some
ETGs. We find that allowing as little as 3% of the HB population to be
uniformly distributed to very hot temperatures (30,000 K) produces realistic UV
colors for old, quiescent ETGs.Comment: ApJ accepted. 20 pages, 8 figure
Parametric and sensitivity analysis for a proposed filtered tailings storage facility in challenging topography
Parametric and sensitivity analyses were performed for a proposed filtered tail-
ings storage facility in challenging topography from the Southern Peru region. The purpose was to identify elements which are likely to dictate performance and stability, and to understand the risk profile for the facility. The analyses were performed varying: foundation material physical and hydraulic properties, tailings physical and hydraulic properties, foundation configuration, seismicity, and staged construction. The physical properties of the foundation material were
varied by changing the Mohr-Coulomb strength parameters c’ and φ’, whereas the hydraulic properties were varied by moving the groundwater table upwards or saturating a larger amount of the foundation material. A similar approach was adopted in order to vary the physical and hydraulic properties of the tailings. The foundation configuration was varied by hypothetically moving the starter buttress closer to the edge of steep slopes further downhill from the facility. Staged construction stability analyses were simulated by analyzing filtered tailings fill configurations, which followed the overall design slope but varied in height. All analyses presented herein were conducted for the most critical failure mode for each scenario. The results from these parametric analyses showed that the design of the facility was highly sensitive to tailings potential saturation. In the simulation scenarios, saturation of the tailings caused instability in both static and seismic conditions. This sensitivity to moisture conditions highlighted the importance of properly defining the unsaturated filtered tailings parameters and simulating water
infiltration processes through the vadose zone.Fil: Preciado, H. F. AMEC S.A; PerĂş.Fil: Ale, J. AMEC S.A; PerĂş.Fil: Byler, B. AMEC Englewood; USA.Fil: Perez, F. AMEC S.A; PerĂş.Fil: MejĂa, V. AMEC S.A; PerĂş.Fil: McIver, D. Minera IRL SA; PerĂş.Otras IngenierĂa Civi
Regional action plan for the conservation of western chimpanzees (Pan troglodytes verus) 2020–2030
This is the final version. Available from IUCN via the DOI in this recordIn 2016, IUCN uplisted the western chimpanzee, Pan troglodytes verus, from “Endangered” to “Critically Endangered”, reflecting the subspecies’ increasingly dire conservation status. Of the four recognised chimpanzee subspecies, Pan troglodytes verus is under the greatest threat. The current plan presents the status and threats to P. t. verus, based on expert evaluation of the best scientific knowledge available to date. A considerable amount of new data has improved our knowledge of the distribution and status patterns of this subspecies since the first action plan was published in 2003, and an analysis of the threats to chimpanzee populations highlights the need to address these threats and their drivers. This action plan highlights how concerned stakeholders can harmonise their efforts, emphasising the critical role of regional coordination and inter- and multidisciplinary approaches in conserving the western chimpanzee. Finally, this plan also seeks to be dynamic, embedded in a monitoring and evaluation framework that will keep priorities and strategies relevant, updating objectives and information on threats as anthropogenic and ecological pressures evolve across West Africa.Arcus FoundationUnited States Fish & Wildlife Servic
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering
Effective models focused on pertinent low-energy degrees of freedom have
substantially contributed to our qualitative understanding of quantum
materials. An iconic example, the Kondo model, was key to demonstrating that
the rich phase diagrams of correlated metals originate from the interplay of
localized and itinerant electrons. Modern electronic structure calculations
suggest that to achieve quantitative material-specific models, accurate
consideration of the crystal field and spin-orbit interactions is imperative.
This poses the question of how local high-energy degrees of freedom become
incorporated into a collective electronic state. Here, we use resonant
inelastic x-ray scattering (RIXS) on CePd to clarify the fate of all
relevant energy scales. We find that even spin-orbit excited states acquire
pronounced momentum-dependence at low temperature - the telltale sign of
hybridization with the underlying metallic state. Our results demonstrate how
localized electronic degrees of freedom endow correlated metals with new
properties, which is critical for a microscopic understanding of
superconducting, electronic nematic, and topological states
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering
Effective models focused on pertinent low-energy degrees of freedom have substantially contributed to our qualitative understanding of quantum materials. An iconic example, the Kondo model, was key to demonstrating that the rich phase diagrams of correlated metals originate from the interplay of localized and itinerant electrons. Modern electronic structure calculations suggest that to achieve quantitative material-specific models, accurate consideration of the crystal field and spin-orbit interactions is imperative. This poses the question of how local high-energy degrees of freedom become incorporated into a collective electronic state. Here, we use resonant inelastic x-ray scattering (RIXS) on CePd to clarify the fate of all relevant energy scales. We find that even spin-orbit excited states acquire pronounced momentum-dependence at low temperature—the telltale sign of hybridization with the underlying metallic state. Our results demonstrate how localized electronic degrees of freedom endow correlated metals with new properties, which is critical for a microscopic understanding of superconducting, electronic nematic, and topological states
Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure
We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.
Grifonin-1: A Small HIV-1 Entry Inhibitor Derived from the Algal Lectin, Griffithsin
Background:
Griffithsin, a 121-residue protein isolated from a red algal Griffithsia sp., binds high mannose N-linked glycans of virus surface glycoproteins with extremely high affinity, a property that allows it to prevent the entry of primary isolates and laboratory strains of T- and M-tropic HIV-1. We used the sequence of a portion of griffithsin's sequence as a design template to create smaller peptides with antiviral and carbohydrate-binding properties.
Methodology/Results:
The new peptides derived from a trio of homologous β-sheet repeats that comprise the motifs responsible for its biological activity. Our most active antiviral peptide, grifonin-1 (GRFN-1), had an EC50 of 190.8±11.0 nM in in vitro TZM-bl assays and an EC50 of 546.6±66.1 nM in p24gag antigen release assays. GRFN-1 showed considerable structural plasticity, assuming different conformations in solvents that differed in polarity and hydrophobicity. Higher concentrations of GRFN-1 formed oligomers, based on intermolecular β-sheet interactions. Like its parent protein, GRFN-1 bound viral glycoproteins gp41 and gp120 via the N-linked glycans on their surface.
Conclusion:
Its substantial antiviral activity and low toxicity in vitro suggest that GRFN-1 and/or its derivatives may have therapeutic potential as topical and/or systemic agents directed against HIV-1
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Establishment report : permanent plots to evaluate the effects of Armillaria root disease in precommercially thinned stands
Methods used to establish permanent plots in precommercially thinned and unthinned stands to monitor root disease development are described. Plots were established in 22 Armillaria-infested stands in northern Idaho and western Montana. The proportion of trees dead and infected was significantly higher for planted than for natural regeneration at the time of plot establishment
Rice and rice bran from different cultivars: physicochemical, spectroscopic, and thermal analysis characterization.
Várias cultivares de arroz tem sido desenvolvida no intuito de obter grĂŁos com caracterĂsticas de cultivo e composição apropriadas, que sĂŁo responsáveis pela indicação de uso/consumo dos grĂŁos. Assim, justifica-se a necessidade de caracterização das diferentes cultivares de arroz. No presente estudo, o arroz branco e o farelo de arroz das cultivares BRS AG, BRS Pampa, e BRS 358, cedidas pela EMBRAPA, foram caracterizadas a partir de análises fĂsico-quĂmicas, espectroscopia no infravermelho (FTIR-ATR) e análises tĂ©rmicas. Nas amostras de arroz branco, o conteĂşdo de umidade, lipĂdios e cinzas nĂŁo diferiu entre as cultivares. A BRS Pampa teve o maior teor de proteĂnas e o menor teor de carboidratos. A BRS Pampa e BRS 358 tiveram maior teor de ácido fĂtico. O maior conteĂşdo de carboidratos observado no arroz branco da cultivar BRS AG confirma sua indicação de uso na produção de bioetanol. Nas amostras de farelo de arroz, a BRS teve maior teor de lipĂdios, proteĂnas e ácido fĂtico, e o menor de carboidratos totais. A análise por FTIR-ATR e análise tĂ©rmica permitiram correlacionar as propriedades fĂsico-quĂmicas do farelo de arroz e arroz branco com a composição quĂmica dentro de cada cultivar estudada. O arroz branco e o farelo de arroz exibiram degradação tĂ©rmica a 300 °C. O conteĂşdo de lipĂdios, proteĂnas, cinzas e ácido fĂtico foram superiores no farelo em comparação ao arroz branco para todas as cultivares, o que demonstra a importância do uso desse subproduto.TĂtulo em portuguĂŞs: Arroz e farelo de arroz de diferentes cultivares: caracterização fĂsico-quĂmica, por espectroscopia e análise tĂ©rmica
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