University of Arkansas

About: University of Arkansas is a education organization based out in Fayetteville, Arkansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17225 authors who have published 33329 publications receiving 941102 citations. The organization is also known as: Arkansas & UA.

Quantum anomalous Hall effect in graphene proximity coupled to an antiferromagnetic insulator

Abstract: We propose realizing the quantum anomalous Hall effect by proximity coupling graphene to an antiferromagnetic insulator that provides both broken time-reversal symmetry and spin-orbit coupling. We illustrate our idea by performing ab initio calculations for graphene adsorbed on the (111) surface of BiFeO3. In this case, we find that the proximity-induced exchange field in graphene is about 70 meV, and that a topologically nontrivial band gap is opened by Rashba spin-orbit coupling. The size of the gap depends on the separation between the graphene and the thin film substrate, which can be tuned experimentally by applying external pressure.

Water-Soluble and Optically pH-Sensitive Single-Walled Carbon Nanotubes from Surface Modification

Abstract: There is great interest in using single-walled carbon nanotubes (SWNTs) as nanoscale probes and sensors in biological electronics and optical devices because the electronic and optical properties of SWNTs are extremely sensitive to the surrounding environments A well-controlled modification of SWNT surfaces may provide unique interfaces that are sensitive to the biological variables such as pH, glucose, various ions and proteins In this paper, we report a facile chemical routine to prepare water-soluble SWNTs that still retain their van Hove singularities after acid oxidative treatment The aqueous solutions (003−015 mg/mL) are stable for more than a month The solubility in water for as-treated SWNTs with surfaces modified by carboxylate groups provides us with a unique opportunity to reveal the relationship of the SWNT electronic and optical properties with pH Here we present the first observation that after surface modification with carboxylate groups, the optical absorption of the first interband

Call for mixed analysis: A philosophical framework for combining qualitative and quantitative approaches

Abstract: We provide a philosophical justification for analyzing qualitative and quantitative data within the same study. First, we present several recent typologies of analyses in social science research th...

A 1,200-year perspective of 21st century drought in southwestern North America

Abstract: A key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity. Instrumental records and paleoclimatic evidence for past prolonged drought in the Southwest that coincide with elevated temperatures can be assessed to provide insights on temperature-drought relations and to develop worst-case scenarios for the future. In particular, during the medieval period, ∼AD 900–1300, the Northern Hemisphere experienced temperatures warmer than all but the most recent decades. Paleoclimatic and model data indicate increased temperatures in western North America of approximately 1 °C over the long-term mean. This was a period of extensive and persistent aridity over western North America. Paleoclimatic evidence suggests drought in the mid-12th century far exceeded the severity, duration, and extent of subsequent droughts. The driest decade of this drought was anomalously warm, though not as warm as the late 20th and early 21st centuries. The convergence of prolonged warming and arid conditions suggests the mid-12th century may serve as a conservative analogue for severe droughts that might occur in the future. The severity, extent, and persistence of the 12th century drought that occurred under natural climate variability, have important implications for water resource management. The causes of past and future drought will not be identical but warm droughts, inferred from paleoclimatic records, demonstrate the plausibility of extensive, severe droughts, provide a long-term perspective on the ongoing drought conditions in the Southwest, and suggest the need for regional sustainability planning for the future.

Effects of solvent and temperature on pressurized liquid extraction of anthocyanins and total phenolics from dried red grape skin.

Abstract: Pressurized liquid extraction (PLE) was used to extract anthocyanins from the freeze-dried skin of a highly pigmented red wine grape with six solvents at 50 °C, 10.1 MPa, and 3 × 5 min extraction cycles. Temperature (from 20 to 140 °C in 20 °C increments) effects on anthocyanin recovery by acidified water and acidified 60% methanol were also studied. Acidified methanol extracted the highest levels of total monoglucosides and total anthocyanins, whereas the solvent mixture (40:40:20:0.1 methanol/acetone/water HCl) extracted the highest levels of total phenolics and total acylated anthocyanins. Acidified water extracts obtained by PLE at 80−100 °C had the highest levels of total monoglucosides, total acylated anthocyanins, total anthocyanins, total phenolics, and ORAC values. Acidified methanol extracts obtained by PLE at 60 °C had the highest levels of total monoglucosides and total anthocyanins, whereas extracts obtained at 120 °C had the highest levels of total phenolics. High-temperature PLE (80−100 °C)...