Microvertebrates preserved in mammal burrows from the Holocene of the Argentine Pampas: a taphonomic and paleoecological approach

Microvertebrates are a major component of many assemblages recovered from the Quaternary of the Argentine Pampas. The main goal of this paper is to analyse the taphonomic history of a Holocene microfossil bonebed, recovered from the infilling of a burrow. Evidences suggest the plains vizcacha Lagostomus maximus as the putative producer of the burrow. The assemblage includes individuals belonging to different taxa of mammals (marsupials and rodents) and reptiles (snakes). Taphonomic features suggest that the accumulation inside the burrow was related to flooding processes in the plain. The burrow was a natural trap that favoured the accumulation and preservation of remains corresponding to individuals from different sources. According to the taphonomic evidence, some individuals (Lagostomus maximus, Lestodelphys halli and Serpentes indet.) died inside the burrow, whereas others (Microcavia australis, Reithrodon auritus and Ctenomys sp.) died outside the burrow, and after a time of being exposed on the surface their remains were transported by surface run-offs into the burrow. The record of Lestodelphys halli and Serpentes indet. in the burrow produced by Lagostomus maximus could be related to a circumstantial use. Mammal burrows are a significant taphonomic mode for the late Cenozoic of the Argentine Pampas

Climate Change and American Bullfrog Invasion: What Could We Expect in South America?

BACKGROUND: Biological invasion and climate change pose challenges to biodiversity conservation in the 21(st) century. Invasive species modify ecosystem structure and functioning and climatic changes are likely to produce invasive species' range shifts pushing some populations into protected areas. The American Bullfrog (Lithobates catesbeianus) is one of the hundred worst invasive species in the world. Native from the southeast of USA, it has colonized more than 75% of South America where it has been reported as a highly effective predator, competitor and vector of amphibian diseases. METHODOLOGY/PRINCIPAL FINDINGS: We modeled the potential distribution of the bullfrog in its native range based on different climate models and green-house gases emission scenarios, and projected the results onto South America for the years of 2050 and 2080. We also overlaid projected models onto the South American network of protected areas. Our results indicate a slight decrease in potential suitable area for bullfrog invasion, although protected areas will become more climatically suitable. Therefore, invasion of these sites is forecasted. CONCLUSION/SIGNIFICANCE: We provide new evidence supporting the vulnerability of the Atlantic Forest Biodiversity Hotspot to bullfrog invasion and call attention to optimal future climatic conditions of the Andean-Patagonian forest, eastern Paraguay, and northwestern Bolivia, where invasive populations have not been found yet. We recommend several management and policy strategies to control bullfrog invasion and argue that these would be possible if based on appropriate articulation among government agencies, NGOs, research institutions and civil society

Pressure-temperature phase diagram of SeO2. Characterization of new phases

We have investigated SeO2 at high pressures and high temperatures. Two new phases (beta-SeO2 and gamma-SeO2) and the boundary separating them have been found, following experimental runs performed at pressures tip to 15 GPa and temperatures up to 820degreesC. The two phases crystallize in the orthorhombic system in space group Pmc2(1) (no. 26) with a = 5.0722(1) Angstrom, b = 4.4704(1) Angstrom, c = 7.5309(2) Angstrom, V = 170.760(9) Angstrom(3) and Z = 4 for the beta-phase, and with a = 5.0710(2) Angstrom, b = 4.4832(2) Angstrom, c = 14.9672(6) Angstrom, V = 340.27(3) Angstrom(3) and Z = 8 for the gamma-phase. Both phases are stable at ambient pressure and temperature below -30degreesC. At ambient temperature the phases return to the starting phase (alpha-SeO2) in a few days. We discuss our findings in relation to a previous report of in-situ measurements at high pressures and ambient temperature. (C) 2004 Elsevier Inc. All rights reserved

Triple Co-II,Co- (III,) (IV) charge ordering and spin states in modular cobaltites: a systematization through experimental and virtual compounds

International audienceThe series of modular compounds [BanCo2+nO3n+2][BaCo6O9] (n = 1 to 3) including experimental and hypothetical terms, was investigated using DFT calculations and several experimental results. A systematic evolution of the electronic and magnetic states was evidenced along the series leading to ordered Co-II/Co-III versus mixed Co-III/IV charge segregation in two distinct structural motifs. In essence, using different packing modes within the labile [BanCo2+nO3n+2] block, we have systematized the spin state dependence on the CoO6 connectivity, i.e. corner-sharing (HS states) against face-sharing (LS states). We also show that the electronic and magnetic features of the [BaCo6O9] blocks do not vary trough the series, (i.e. HS-Co-II and LS-Co-III charge ordering) whereas the [BanCo2+nO3n+2] blocks hold drastic changes from n = 1 to 3. In particular, the later carries a mixed III/IV cobalt charge for n >= 2. It leads to a triple valence cobalt state. For n = 2, we experimentally observe at 4 K a superstructure (2a, 2c) superstructure accompanied by a perfect Co-II/Co-III/Co-IV charge ordering. The charge ordering occurs at Tt = 160 K and is accompanied by a transition in the electronic transport leading to a 2D-VRH behaviour below Tt

Triple Co-II,Co- (III,) (IV) charge ordering and spin states in modular cobaltites: a systematization through experimental and virtual compounds

International audienceThe series of modular compounds [BanCo2+nO3n+2][BaCo6O9] (n = 1 to 3) including experimental and hypothetical terms, was investigated using DFT calculations and several experimental results. A systematic evolution of the electronic and magnetic states was evidenced along the series leading to ordered Co-II/Co-III versus mixed Co-III/IV charge segregation in two distinct structural motifs. In essence, using different packing modes within the labile [BanCo2+nO3n+2] block, we have systematized the spin state dependence on the CoO6 connectivity, i.e. corner-sharing (HS states) against face-sharing (LS states). We also show that the electronic and magnetic features of the [BaCo6O9] blocks do not vary trough the series, (i.e. HS-Co-II and LS-Co-III charge ordering) whereas the [BanCo2+nO3n+2] blocks hold drastic changes from n = 1 to 3. In particular, the later carries a mixed III/IV cobalt charge for n >= 2. It leads to a triple valence cobalt state. For n = 2, we experimentally observe at 4 K a superstructure (2a, 2c) superstructure accompanied by a perfect Co-II/Co-III/Co-IV charge ordering. The charge ordering occurs at Tt = 160 K and is accompanied by a transition in the electronic transport leading to a 2D-VRH behaviour below Tt

Symptom variability in patients with severe COPD: a pan-European cross-sectional study

In between exacerbations, chronic obstructive pulmonary disease (COPD) is usually regarded as a stable condition, but there is increasing recognition of variability in this state. This cross-sectional study assessed patients' perception of symptom variability. Participants were outpatients > 45 yrs old with COPD, current or ex-smokers, forced expiratory volume in 1 s (FEV₁) <50% predicted, FEV₁/forced vital capacity < 0.7 and no exacerbation leading to therapeutic intervention in the previous 3 months. Patients' perceptions of COPD symptoms and their impact on daily life activities were recorded. Alterations in therapy use in response to COPD worsening were also recorded. COPD symptoms were experienced by 2,258 (92.5%) out of 2,441 patients during the 7 days before interview. Breathlessness was the most common symptom (72.5%). Daily and/or weekly symptom variability was reported by 62.7% of symptomatic patients; the morning was the worst time of day. Factors associated with perception of variability of breathlessness included younger age, symptom severity and recruitment to the study by general practitioners. The perception of variability was significantly different between European countries or regions. Patient-perceived COPD symptoms vary over the day and the week, and impact on daily activities; morning being the worst time of day. The majority of patients appear not to adjust treatment when symptoms worsen