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.

Sorption and desorption of pesticides by clay minerals and humic acid-clay complexes

Abstract: In soils, organic matter and minerals are often associated such that it is unclear how the presence of the former component influences the sorptive properties of the latter one. In this study, sorption and desorption of the herbicides 4,6-dinitro-o-cresol (C 7 H 6 N 2 O 5 ) and dichlobenil (C 7 H 3 Cl 2 N) by Ca 2+ -, K + -smectites, and humic acid-smectite complexes, was investigated using batch-equilibrations and x-ray diffraction (XRD). Greater sorption of 4,6-dinitro-o-cresol compared with dichlobenil was observed for both smectites and humic acid-smectite complexes. For both pesticides, K + smectites were more effective sorbents than Ca 2+ smectites, with the lower charge-density day (SWy-2) displaying a greater sorption capacity than the higher charge-density day (SAz-1). The presence of humic add did not impact pesticide sorption by K + clays, but could enhance or suppress pesticide sorption by Ca 2+ -clays. A composite model for estimating pesticide sorption, which assumes mineral and organic matter function individually as sorbent phases, predicted sorption within a factor of 0.8 to 1.5 times the measured values. Humic add did not contribute to pesticide desorption hysteresis in K + -humic add-day complexes, but was a source of hysteresis in the corresponding Ca 2+ complexes. The basal spacings of K-SWy-2 and humic add-modified K-SWy-2 increased gradually from approximately 10.4 to 12.2 A with increasing 4,6-dinitro-o-cresol loadings. Also, XRD patterns of humic acid-modified and unmodified K-SWy-2 smectite days were found identical. These results demonstrate the Intercalation of 4,6-dinitro-o-cresol and suggest that humic adds are restricted to the external surfaces of day tactoids. Together, these results indicate that clay mineral fractions in soils, including those with organic coatings, may play an important role in the retention of certain pesticides.

Emotional dissonance and the information technology professional

Abstract: The information technology professional is regularly expected to work with colleagues in both IT and other areas of the organization. During these interactions, the IT employee is expected to conform to occupational or organizational norms regarding the display of emotion. How do these display norms affect the IT professional? This study examines an IT professional's emotional dissonance, the conflict between norms of emotional display and an employee's felt emotion. Emotional dissonance is studied as a factor of IT professionals' work exhaustion, job satisfaction, and turnover intention, modeled as an extension to the work of Moore (2000a). The results indicate emotional dissonance predicts work exhaustion better than do perceived workload, role conflict, or role ambiguity, constructs which have long been associated with work exhaustion. Job satisfaction is influenced directly by role ambiguity and work exhaustion. In turn, job satisfaction influences employee turnover intention. We discuss implications of these findings for both IT management and future research.

Recent Directions and Developments in Geographical Information Systems

Abstract: Geographical information systems (GIS) are tools for handling and processing spatially referenced information that have permeated all facets of archaeology, frequently revolutionizing research by allowing easy access to vast amounts of information, new ways of data visualization that promote insight through pattern recognition, and unique methodologies that allow entirely new approaches to the study of the past. This comprehensive review examines and critiques recent advances achieved through GIS in regional and within-site databases, locational analysis and modeling, regional simulation, studies of landscape perception through intervisibility analysis, and models of spatial allocation, territoriality, and site access. The future prospects of GIS are enormous with the growth of the Internet, the resultant linking of databases, expected enhancements in satellite remote sensing, and the increasing pervasiveness of global positioning systems for spatial data capture.

Major Mesoamerican droughts of the past millennium

Abstract: [1] Ancient Montezuma baldcypress (Taxodium mucronatum) trees found in Barranca de Amealco, Queretaro, have been used to develop a 1,238-year tree-ring chronology that is correlated with precipitation, temperature, drought indices, and crop yields in central Mexico. This chronology has been used to reconstruct the spring-early summer soil moisture balance over the heartland of the Mesoamerican cultural province, and is the first exactly dated, annually resolved paleoclimatic record for Mesoamerica spanning the Late Classic, Post Classic, Colonial, and modern eras. The reconstruction indicates that the Terminal Classic drought extended into central Mexico, supporting other sedimentary and speleothem evidence for this early 10th century drought in Mesoamerica. The reconstruction also documents severe and sustained drought during the decline of the Toltec state (1149–1167) and during the Spanish conquest of the Aztec state (1514–1539), providing a new precisely dated climate framework for Mesoamerican cultural change.

An overview of molecular layer deposition for organic and organic–inorganic hybrid materials: mechanisms, growth characteristics, and promising applications

Abstract: It has been a strong desire for researchers to control material growth at the molecular and atomic levels. Molecular and atomic layer deposition (MLD and ALD) are two such techniques. In comparison to a huge amount of studies invested on ALD, the research on MLD is still relatively limited due to the difficulty in finding suitable coupling precursors, but the recently successful applications of MLD are very encouraging in many areas such as surface engineering, new energies, and catalysis. In order to further stimulate more research enthusiasm and educate beginners, we contribute this thorough survey on the progress of MLD. This review is a comprehensive account of MLD processes for organic and organic–inorganic materials, covering precursors, surface chemistry, growth characteristics, film properties, and promising applications. The work provides a complete summary of over 80 MLD processes for growing over 20 types of pure polymeric and metal-based hybrid polymeric materials. Given their similarities in mechanisms, we made a comparative description between ALD and MLD, and discussed the uncountable possibilities to combine both ALD and MLD for advanced materials with desirable properties. To feature and highlight the significance of MLD, this review specially gives some detailed discussions on MLD's applications in several important areas, including novel nanostructured materials, surface engineering, new energies (i.e., batteries, supercapacitors, solar cells, and water splitting), catalysis, and rewritable data storage. With this work, we expect to boost research interest and attempts at advanced materials using MLD as well as ALD.