371 research outputs found
Closeup: Utah\u27s Course on Women and Education
The telephone rang before my alarm clock could sound its bell. Hello, have you seen the morning paper? The cover story on your class in women\u27s studies has just been released! announced my excited secretary. A second call extended an invitation to be an immediate guest on a party-line hookup with Two-way Radio, and before lunch an additional interview had been taped for airing the following morning. This startling reaction opened the way for a hectic two weeks. During this time I would be referred to as a heretic and a corrupter of youth, and my husband would be accused of abnegating his priestly authority. (Ecclesiastical offices in our church are held by lay members.) What lit the proverbial fire in the kitchen was my public statement that it was a frustrating experience to be a woman in Utah; that our religious subculture put blinders on women and effectively bound her to the home. If women were allowed to grow individually, I commented, it wouldn\u27t come as such a crushing blow when she discovered in later years that she was not the perfect mother
Thorium nanochemistry: The solution structure of the Th(iv)-hydroxo pentamer
Tetravalent thorium exhibits a strong tendency towards hydrolysis and subsequent polymerization. Polymeric species play a crucial role in understanding thorium solution chemistry, since their presence causes apparent solubility several orders of magnitude higher than predicted by thermodynamic data bases. Although electrospray mass spectrometry (ESI MS) identifies Th(iv) dimers and pentamers unequivocally as dominant species close to the solubility limit, the molecular structure of Th 5(OH) y polymers was hitherto unknown. In the present study, X-ray absorption fine structure (XAFS) spectroscopy, high energy X-ray scattering (HEXS) measurements, and quantum chemical calculations are combined to solve the pentamer structure. The most favourable structure is represented by two Th(iv) dimers linked by a central Th(iv) cation through hydroxide bridges. © 2012 The Royal Society of Chemistry
Rapid deglaciation during the Bølling-Allerød Interstadial in the Central Pyrenees and associated glacial and periglacial landforms
The Central Pyrenees hosted a large ice cap during the Late Pleistocene. The cirques under relatively low-altitude peaks (2200-2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. Here, we focus on the headwaters of the Garonne River, namely on the low-altitude Bacivèr Cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. We reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. Ice thickness in the Bacivèr Cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the Garonne paleoglacier. However, by ~15 ka, during the Bølling-Allerød (B-A) Interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the Garonne paleoglacier. Glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debriscovered and rock glaciers in their final stages. Climate conditions prevailing at the transition between the B-A and the Younger Dryas (YD) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the B-A or the YD. The melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. These remained active throughout the Early Holocene until at least ~7 ka. Since then, the landscape of the Bacivèr Cirque has seen a period of relative stability. A similar chronological sequence of deglaciation has been also detected in other cirques of the Pyrenees below 3000 m. As in other mid-latitude mountain regions, the B-A triggered the complete deglaciation of the Garonne paleoglacier and promoted the development of the wide variety of glacial and periglacial landforms existing in the Bacivèr cirque
Autoantibodies against NMDAR subunit NR1 disappear from blood upon anesthesia
Anesthetics penetrate the blood-brain-barrier (BBB) and - as confirmed preclinically – transiently disrupt it. An analogous consequence in humans has remained unproven. In mice, we previously reported that upon BBB dysfunction, the brain acts as ‘immunoprecipitator’ of autoantibodies against N-methyl-D-aspartate-receptor subunit-NR1 (NMDAR1-AB). We thus hypothesized that during human anesthesia, pre-existing NMDAR1-AB will specifically bind to brain. Screening of N = 270 subjects undergoing general anesthesia during cardiac surgery for serum NMDAR1-AB revealed N = 25 NMDAR1-AB seropositives. Only N = 14 remained positive post-surgery. No changes in albumin, thyroglobulin or CRP were associated with reduction of serum NMDAR1-AB. Thus, upon anesthesia, BBB opening likely occurs also in humans
Holocene glacial oscillations in the Tyroler Valley (NE Greenland)
Although the spatiotemporal oscillations of the Greenland Ice Sheet (GrIS) during the last millennia have played a prominent role in global environmental changes, its glacial response to the natural variability still needs to be better constrained. Here, we focused on the reconstruction of the glacial behavior and deglaciation process along the Tyroler Valley (74° N, 22° E), within the Northeast Greenland National Park. This NW-SE valley connects with the GrIS via the Pasterze Glacier and divides two ice caps (A.P. Olsen Land and Payer Land), this last one feeding two piedmont glaciers (Copeland and Kløft glaciers). For this study, we combined the interpretation of the spatial pattern of geomorphological features and the chronological framework defined by a new dataset of 15 Be cosmic-ray exposure (CRE) ages from glacially polished bedrock surfaces and moraine boulders together with one optically stimulated luminescence (OSL) age of a glaciolacustrine deposit. CRE ages indicate that the deglaciation of the lowest parts of the valley and the exposure of the highest slopes took place during the Early Holocene, at ca. 10–8.5 ka (ka = thousand year [BP]). Furthermore, this ice thinning also favored the disconnection of the valley tributary glaciers. Samples from the moraines of the two tributary glaciers indicate that the deglaciation was not continuous, but it was interrupted by at least three phases of glacial advance during the Neoglacial cooling (before ca. 5.9 ka), and the Little Ice Age (LIA, 0.6, and 0.3 ka). The larger piedmont glacier (Copeland Glacier) occupied the valley floor during these major advances, damming the river and allowing the formation of a proglacial glacial lake upvalley, as confirmed by the OSL date of lacustrine sediments that yielded an age of 0.53 ± 0.06 ka. In short, our study provides new evidence of the relative stability of GrIS and the regional ice caps in the area, in which glacial fronts have been rather stable since their advances during the Neoglacial and the LIA.This study was funded by the NEOGREEN (PID2020‐113798GB‐C31) and PALEOGREEN (CTM2017‐87976‐P) projects of the Spanish Ministerio de Economía y Competitividad. Field research was also supported by the research group ANTALP (Antarctic, Arctic, Alpine Environments; 2017‐SGR‐1102) funded by the Agència de Gestió d'Ajuts Universitaris i de Recerca of the Government of Catalonia. Julia Garcia‐Oteyza was supported by an FPI fellowship from the Spanish Ministry of Science, Innovation and Universities, and Marcelo Fernandes by a PhD fellowship of the Fundação para a Ciência e Tecnologia of Portugal (UIDB/00295/2020). The Be measurements were performed at the ASTER AMS national facility (CEREGE, Aix‐en‐Provence), which is supported by the INSU/CNRS and the ANR through the “Projets thématiques d'excellence” programme for the “Equipements d'excellence” ASTER‐CEREGE action and IRD
Tris‐{hydridotris(1‐pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour
The isostructural compounds of the trivalent actinides uranium, neptunium, plutonium, americium, and curium with the hydridotris(1-pyrazolyl)borato (Tp) ligand An[η-HB(NCH)] (AnTp) have been obtained through several synthetic routes. Structural, spectroscopic (absorption, infrared, laser fluorescence) and magnetic characterisation of the compounds were performed in combination with crystal field, density functional theory (DFT) and relativistic multiconfigurational calculations. The covalent bonding interactions were analysed in terms of the natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) models
Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory
Here, we review the historical development, current status, and prospects of
Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only
theory.Comment: 15 page
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