1,302 research outputs found
A reactive-transport model for examining tectonic and climatic controls on chemical weathering and atmospheric CO(2) consumption in granitic regolith
No full textAbstract not availableDarcy D. Li, Andrew D. Jacobson, David J. McInerne
Controls on the solute geochemistry of subglacial discharge from the Russell Glacier, Greenland Ice Sheet determined by radiogenic and stable Sr isotope ratios
No full textWe used radiogenic and stable Sr isotope ratios (87Sr/86Sr and δ88/86Sr) to examine controls on solute acquisition in subglacial discharge from the Russell Glacier, a land-terminating lobe of the Greenland Ice Sheet (GrIS) located in western Greenland. The study focused on two melt seasons in 2014 and 2015. Subglacial discharge 87Sr/86Sr ratios are 13,000 ppm higher than those measured for bedload and suspended sediment digests, and are more similar to those of bedload sediment leachates. These results point to the preferential dissolution of minerals with high 87Sr/86Sr ratios. Analyses of mineral separates from bulk rocks demonstrate that biotite, chlorite, hornblende, and K-feldspar have relatively high 87Sr/86Sr ratios. Subglacial discharge δ88/86Sr values are ∼0.10‰ higher than those for bedload and suspended sediment digests. Isotope fractionation during secondary mineral formation and/or adsorption cannot account for the difference between subglacial discharge and bedrock δ88/86Sr values, as suspended and bedload sediment leachates and digests produced similar δ88/86Sr values and are within the range for bulk silicate Earth. Consistent with the interpretation of 87Sr/86Sr ratios, we attribute the difference to the preferential dissolution of minerals with high δ88/86Sr values. Mineral separates display a wide range of δ88/86Sr values (∼0.40‰). Those having high δ88/86Sr values include hornblende and K-feldspar, as well as apatite and titanite. Taken together, the preferential weathering of predominately silicate minerals explains the Sr isotope geochemistry of subglacial discharge.Subglacial discharge from the Russell Glacier feeds the proglacial Akuliarusiarsuup Kuua River (AKR). Along a 32 km transect of the AKR from the GrIS margin toward the coast, riverine 87Sr/86Sr ratios increase from ∼0.722 to ∼0.747 in an approximately step-wise pattern that corresponds to point-source inputs of additional subglacial discharge. Major cation concentrations and 87Sr/86Sr ratios minimally vary along lengths of the transect with no hydrological inputs. This suggests that proglacial chemical weathering is negligible and likely does not contribute significantly to GrIS solute fluxes.In general, this study supports the recent contention that silicate mineral weathering dominates the solute geochemistry of GrIS subglacial discharge in contrast to valley glaciers, which typically show substantial contributions from carbonate and sulfide weathering regardless of primary bedrock composition. Ice sheet subglacial chemical weathering may therefore have a greater impact on long-term atmospheric CO2 drawdown than previously realized
Silicate versus carbonate weathering in Iceland: New insights from Ca isotopes
No full text) to trace sources of Ca in Icelandic rivers. We report elemental and Ca isotope data for rivers, high- and low-temperature groundwater, basalt, hydrothermal calcite (including Iceland Spar), and stilbite and heulandite, which are two types of zeolites commonly formed during low-grade metamorphism of basalt. In agreement with previous research, we find that rivers have higher ?44/40Ca values than basalt, with a maximum difference of ?0.40‰. This difference may reflect isotope fractionation in the weathering zone, i.e., preferential uptake of 40Ca during clay mineral formation, adsorption, and other geochemical processes that cycle Ca. However, calcite ?44/40Ca values are also up to ?0.40‰?higher than bedrock values, and on a diagram of ?44/40Ca versus Sr/Ca, nearly all waters plot within a plausible mixing domain bounded by the measured compositions of basalt and calcite, with glacial rivers plotting closer to calcite than non-glacial rivers. Calcite and heulandite form during hydrothermal alteration of basalt in the deep lava pile and often occur together in metabasalts now exposed at the surface. Because heulandite ?44/40Ca values are ?1–2‰?lower than basalt, we suggest that 40Ca uptake by heudlandite explains the relatively high ?44/40Ca values of calcite and that calcite weathering in turn elevates riverine ?44/40Ca values. High mechanical erosion rates are known to facilitate the exposure and weathering of calcite, which explains the isotopic contrast between glacial and non-glacial watersheds. Using a mixing model, we find that calcite weathering provides ?0–65% of the Ca in non-glacial rivers and ?25–90% of the Ca in glacial rivers, with silicate weathering providing the remainder. Icelandic hydrothermal calcite contains mantle carbon. Noting that zeolite facies metamorphism and hydrothermal fluid circulation are ubiquitous characteristics of basaltic eruptions and assuming that hydrothermal calcite in other basaltic settings also contains mantle carbon, we suggest that the contribution of basalt weathering to long-term CO2 drawdown and climate regulation may be less significant than previously realized
Aggressive behavior in adolescents with fetal alcohol spectrum disorders
No full textIncludes bibliographical references.Behavioral studies of fetal alcohol spectrum disorders (FASD) have indicated that aggression is common amongst alcohol-exposed adolescents, and that it appears to become more prevalent with age in that population. Such studies have documented the presence of aggression as a behavioral outcome, but have not provided detailed information regarding its presentation, including whether it is proactive or reactive in nature and under which circumstances it arises. Consequently, there is a lack of a theoretical framework within which to understand aggression in FASD. The current research comprised two studies. In Study 1, comorbid developmental disorders that are typically associated with aggression were examined in alcohol-exposed and non-exposed boys and girls. The results indicated a higher prevalence of disruptive behavior disorders, and conduct disorder in particular, amongst the alcohol-exposed boys, and highlighted a significant association between prenatal alcohol exposure and an aggressive subtype of conduct disorder. Based on these findings, Study 2, a multiple-case study, examined the aggressive behaviors of 6 alcohol-exposed and nonexposed adolescents and their classmates
Manipulate energy transport via fluorinated spacers towards record-efficiency 2D Dion-Jacobson CsPbI<sub>3</sub> solar cells
No full textTwo-dimensional (2D) Dion-Jacobson (D-J)-type cesium lead iodide CsPbI 3 perform remarkably in terms of stability. However, the complex interactions between spacer and inorganic layers limit its excellent progress in perovskite solar cells (PSCs). Herein, starting from the considerable structural diversity of organic spacers, we engineer 2D CsPbI 3 with fine-tuning functionalities. Specifically, for the first time we embedded fluorinated aromatic cations in 2D D-J CsPbI 3, and successfully applied it into construction of high-performance PSCs. Compared with constitutive 1,4-diaminobenzene (PDA), the fluorinated 2-fluorobenzene-1,4-diamine (F-PDA) component greatly expands the dipole moment from 0.59D to 3.47D, which reduces the exciton binding energy of the system. A theoretical study shows that the spacer layer and inorganic plane are more enriched with charge accumulation in (F-PDA)Cs n– 1Pb nI 3 n+ 1. The results show that (F-PDA)Cs n– 1Pb nI 3 n+ 1 demonstrates more significant charge transfer between organic and inorganic layers than (PDA)Cs n– 1Pb nI 3 n+ 1, and it is confirmed in the femtosecond transient absorption experiment. Moreover, the interactions of the fluorinated spacer with the [PbI 6] 4 – plane effectively manipulate the crystallization quality, and thus the ion migration and defect formation of target 2D CsPbI 3 are inhibited. As a result, we obtained a record power conversion efficiency (PCE) beyond 15% for 2D D-J (F-PDA)Cs 3Pb 4I 13 (n = 4) PSCs with significantly improved environmental stability compared with the three-dimensional (3D) counterparts. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Photovoltaic Materials and Device
Forms of the generic norm of a separable Jordan algebra
No full textAbstractThe purpose of this note is to show that the type of problem considered by Professor Waterhouse in the preceding paper has its natural setting in the theory of generic norms of finite-dimensional Jordan algebras. Using this approach the results can be obtained on forms of the determinant and considerably more by invoking well-known results on Jordon algebras. The most general class of Jordan algebras that shall be considered is that of the separable ones. The key fact, which is easily established, is that forms of the generic norm of such an algebra are algebra forms of isotopes of the algebra. The algebra forms of the important algebras in our class are well known. Perhaps the most important of these were determined in 1949 by F. D. Jacobson and the author by a method based on special universal envelopes. This circumvented the use of Galois descent that had been used earlier for the analogous problems for Lie algebras by W. Landherr and by the author. Another known Jordan result is that similarity of generic norms of separable Jordan algebras holds if and only if the algebras are isotopic. Thus the determination of the forms and conditions for similarity can be derived from the Jordan theory
Experience and Outcomes of a Pharmaceutical Care Leadership Residency Program
No full textThe University of Minnesota College of Pharmacy’s Ambulatory Care Residency Program has graduated 22 residents from its Leadership Emphasis program from 1999 to 2014. The Leadership Emphasis program is unique in its design, providing a set of experiences over two years focused on developing leadership skills in practice development, establishing personal influence, advocacy in the profession, and teaching. The program’s design has focused on bringing value to three distinct audiences: pharmacists enrolled in the program, the local pharmacy practice community, and the College of Pharmacy. This paper explores the program’s contributions in each of these areas.
Program graduates from 1999-2009 were interviewed and cited the independent, yet mentored, activities of the program as instrumental to their professional and personal development. The program has provided significant value to the College of Pharmacy, primarily in the form of instructional support, service to faculty practice sites and development of new practice sites for APPEs. Teaching and precepting hours offset the salary of the residents, resulting in financial benefits for the College. In the second year of the program, residents pursue development of new practice sites, 15 of which have been sustained to provide at least a half-time pharmacist position, having a direct impact on pharmacy practice development in the region.
The program provides a win-win-win situation for all the stakeholders involved. Schools and colleges of pharmacy are encouraged to consider whether a similar program may assist in achieving its own goals in practitioner development, teaching and learning, and community engagement.Bartelme, Kassandra M.; Bzowyckyj, Andrew; Frueh, Janice; Speedie, Marilyn; Jacobson, Gerald; Sorenson, Todd D.. (2014). Experience and Outcomes of a Pharmaceutical Care Leadership Residency Program. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/171820
Pb isotopic ratios and aluminum normalized elemental concentrations from different sediment cores of the Pacific Ocean
No full textPb isotopic ratios and aluminum normalized elemental concentrations for samples of the Pacific Ocean. These samples were from the upper 10 cm of the sediment column, excluding the upper 2 cm to limit anthropogenic contamination. While undated, they are presumed to be Quaternary in age, though this is a source of error discussed in the manuscript
Pb isotopic ratios and aluminum normalized elemental concentrations from different sediment cores of the Eastern Equatorial Pacific
No full textPb isotopic ratios and aluminum normalized elemental concentrations for samples from the Eastern Equatorial Pacific. These samples were from the upper 10 cm of the sediment column, excluding the upper 2 cm to limit anthropogenic contamination. While undated, they are presumed to be Quaternary in age, though this is a source of error discussed in the manuscript
Pb isotopic ratios and selected elemental concentrations from dust source regions to the Pacific Ocean
No full textPb isotopic ratios and selected elemental concentrations from both bulk samples and geochemically isolated detrital fractions from likely dust source regions to the Pacific Ocean. The samples were obtained from collaborators utilizing clean sampling techniques, sampling below the surface to minimize anthropogenic contamination. While samples were not dated, they are presumed to represent Holocene deposition based on sample depth and geological context
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