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.

Communication between plants : induced resistance in wild tobacco plants following clipping of neighboring sagebrush

Abstract: The possibility of communication between plants was proposed nearly 20 years ago, although previous demonstrations have suffered from methodological problems and have not been widely accepted. Here we report the first rigorous, experimental evidence demonstrating that undamaged plants respond to cues released by neighbors to induce higher levels of resistance against herbivores in nature. Sagebrush plants that were clipped in the field released a pulse of an epimer of methyl jasmonate that has been shown to be a volatile signal capable of inducing resistance in wild tobacco. Wild tobacco plants with clipped sagebrush neighbors had increased levels of the putative defensive oxidative enzyme, polyphenol oxidase, relative to control tobacco plants with unclipped sagebrush neighbors. Tobacco plants near clipped sagebrush experienced greatly reduced levels of leaf damage by grasshoppers and cutworms during three field seasons compared to unclipped controls. This result was not caused by an altered light regime experienced by tobacco near clipped neighbors. Barriers to soil contact between tobacco and sagebrush did not reduce the difference in leaf damage although barriers that blocked air contact negated the effect.

Sexual dimorphism in primate evolution.

Abstract: Sexual dimorphism is a pervasive phenomenon among anthropoid primates. Comparative analyses over the past 30 years have greatly expanded our understanding of both variation in the expression of dimorphism among primates, and the underlying causes of sexual dimorphism. Dimorphism in body mass and canine tooth size is familiar, as is pelage and “sex skin” dimorphism. More recent analyses are documenting subtle differences in the pattern of skeletal dimorphism among primates. Comparative analyses have corroborated the sexual selection hypotheses, and have provided a more detailed understanding of the relationship between sexual selection, natural selection, and mating systems in primates. A clearer picture is emerging of the relative contribution of various selective and nonselective mechanisms in the evolution and expression of dimorphism. Most importantly, recent studies have shown that dimorphism is the product of changes in both male and female traits. Developmental studies demonstrate the variety of ontogenetic pathways that can lead to dimorphism, and provide additional insight into the selective mechanisms that influence dimorphism throughout the lifetime of an animal. Evidence from the fossil record suggests that dimorphism probably evolved in parallel twice, and the dimorphism in some extinct hominoids probably exceeded that of any living primate. Our advances in understanding the behavioral/ecological correlates of dimorphism in living primates have not improved our ability to reconstruct social systems in extinct species on the basis of dimorphism alone, beyond the inference of polygyny or intense male-male competition. However, our understanding of the behavioral/ecological correlates of growth and development, and of the expression of dimorphism as a function of separate changes in male and female traits, offers great potential for inferring evolutionary changes in behavior over time. Yrbk Phys Anthropol 44:25–53, 2001. © 2001 Wiley-Liss, Inc.

Lateral loading of deep foundations in stiff clay

Abstract: A full-sized drilled shaft, or drilled pier, was constructed in the field in a stratum of stiff clay. The foundation was instrumented so that bending moment could be measured at various depths. A series of lateral loads, both short-term static and cyclic, were applied to the foundation and families of bending moment curves, along with the boundary conditions at the groundline, were obtained. These data were analyzed and sets of curves were developed showing soil resistance p as a function of deflection y for various depths. Rational concepts concerning the behavior of soil around a laterally loaded deep foundation were employed, along with some empirical expressions, and equations are presented for the development of p-y curves for stiff clay, both for short-term static loading and for cyclic loading. The expressions were tested against available experiments and were found to yield satisfactory results.

Aggression and Sexual Behavior in Best-Selling Pornography Videos: A Content Analysis Update

Abstract: This current study analyzes the content of popular pornographic videos, with the objectives of updating depictions of aggression, degradation, and sexual practices and comparing the study's results to previous content analysis studies. Findings indicate high levels of aggression in pornography in both verbal and physical forms. Of the 304 scenes analyzed, 88.2% contained physical aggression, principally spanking, gagging, and slapping, while 48.7% of scenes contained verbal aggression, primarily name-calling. Perpetrators of aggression were usually male, whereas targets of aggression were overwhelmingly female. Targets most often showed pleasure or responded neutrally to the aggression.