Nonequilibrium Evolution of Correlation Functions: A Canonical Approach

We study nonequilibrium evolution in a self-interacting quantum field theory invariant under space translation only by using a canonical approach based on the recently developed Liouville-von Neumann formalism. The method is first used to obtain the correlation functions both in and beyond the Hartree approximation, for the quantum mechanical analog of the $\phi^{4}$ model. The technique involves representing the Hamiltonian in a Fock basis of annihilation and creation operators. By separating it into a solvable Gaussian part involving quadratic terms and a perturbation of quartic terms, it is possible to find the improved vacuum state to any desired order. The correlation functions for the field theory are then investigated in the Hartree approximation and those beyond the Hartree approximation are obtained by finding the improved vacuum state corrected up to ${\cal O}(\lambda^2)$. These correlation functions take into account next-to-leading and next-to-next-to-leading order effects in the coupling constant. We also use the Heisenberg formalism to obtain the time evolution equations for the equal-time, connected correlation functions beyond the leading order. These equations are derived by including the connected 4-point functions in the hierarchy. The resulting coupled set of equations form a part of infinite hierarchy of coupled equations relating the various connected n-point functions. The connection with other approaches based on the path integral formalism is established and the physical implications of the set of equations are discussed with particular emphasis on thermalization.Comment: Revtex, 32 pages; substantial new material dealing with non-equilibrium evolution beyond Hartree approx. based on the LvN formalism, has been adde

Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue

The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere–biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997–1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources

History of clinical transplantation

How transplantation came to be a clinical discipline can be pieced together by perusing two volumes of reminiscences collected by Paul I. Terasaki in 1991-1992 from many of the persons who were directly involved. One volume was devoted to the discovery of the major histocompatibility complex (MHC), with particular reference to the human leukocyte antigens (HLAs) that are widely used today for tissue matching.1 The other focused on milestones in the development of clinical transplantation.2 All the contributions described in both volumes can be traced back in one way or other to the demonstration in the mid-1940s by Peter Brian Medawar that the rejection of allografts is an immunological phenomenon.3,4 © 2008 Springer New York

Sex, age, and population density affect aggressive behaviors in Island lizards promoting cannibalism

Island populations may evolve distinct behavioral repertoires as a response to the conditions of insular life. Strong intraspecific competition is typical in insular lizards and may include cannibalism. In this study, we investigated sexual and age patterns of aggression in two populations of the Skyros wall lizard (Podarcis gaigeae), one from the main island of Skyros (Aegean Sea, Greece) and another from the satellite islet Diavates. The latter is terrestrial predator-free biotope, hosting a dense population of large-bodied lizards that have been reported to exert cannibalism. In staged encounters, we examined the aggressive propensities of adult male and female lizards against their age-peers and juveniles. Males from both populations were much more aggressive than females toward juveniles and other adults. Males from Diavates were more frequently aggressive to juveniles and other male lizards than males from Skyros. Diavates cannibals also captured their targets at shorter latency. We ascribe this distinct behavioral pattern to the high population density. Infanticide and intramale aggressiveness confer two great advantages to cannibals: food and elimination of future rivals. © 2014 Blackwell Verlag GmbH

Foraging modes of cordyliform lizards

The first quantitative data on foraging mode in the cordyliform lizards reveal different foraging behaviours between and within families. All species of cordylids studied (four Cordylus, two Pseudocordylus, and one Platysaurus) are ambush foragers. However, the species of Cordylus and Pseudocordylus microlepidotus are the most extreme ambushers. These species spent a significantly lower per cent time moving than did all of the other species studied and made significantly fewer movements per minute than Platysaurus capensis and gerrhosaurids. In addition, P. microlepidotus made significantly fewer movements per minute than did its congener Pseudocordylus capensis. Possible reasons for the high number of movements per minute in Platysaurus capensis are discussed. Very limited observations of two gerrhosaurid species show that Cordylosaurus subtessellatus is an active forager and Gerrhosaurus validus forages actively at least some of the time. A tentative hypothesis of the evolution of cordyliform foraging behaviour based on very limited data hints that active foraging is plesiomorphic in the Gerrhosaurini and further that gerrhosaurids may have retained active foraging from the common ancestor of Scincidae and Cordyliformes. Somewhat stronger data suggest that ambush foraging arose in the common ancestor of Cordylidae or Cordylinae. Further study is needed to trace inter- and intrageneric changes in foraging mode in cordylids.Articl

Discrimination between self-produced pheromones and those produced by individuals of the same sex in the lizard Cordylus cordylus

Male and female Cordylus cordylus can discriminate between tiles labeled by their own pheromones and tiles labeled by individuals of the same sex, as shown by elevated tongue-flick rates in which the tongue contacts only air above the tiles labeled by other individuals and tongue-flicks in which the tongue contacts the tiles themselves. Potential pheromone sources for these discriminations are the femoral glands, cloacal glands, generation glands, ventral skin, and excretory products. Although studied in few species, pheromonal discriminations between self and other individuals, familiar and unfamiliar individuals, and kin and unrelated individuals appear to be broadly distributed in lizards, occurring in Iguania and in both Gekkonoidea and Scincomorpha within Scleroglossa. Both sexes of C. cordylus defend territories against both sexes. An ability to distinguish pheromones of other individuals of the same sex from self-produced pheromones would allow detection of intruders, but pheromonal discriminations among individuals would be more useful. Adaptive functions of pheromonal discriminations for residents and nonresidents and discriminatory abilities required are discussed. Tongue-flicks touching labeled tiles differed between experimental conditions, suggesting vomerolfactory discrimination, but the interpretation of a similar difference for tongue-flicks that contacted no substrate is problematical. Such air tongue-flicks might indicate sampling of volatile molecules for delivery to the vomeronasal organs. Experiments are needed to conclusively determine the sensory bases of the discriminations and the role of air tongue-flicks.Articl

Fish and amphibians

from IIb - Escape decisions prior to pursui

Atmospheric measurements using a scanning, solar-blind Raman Lidar

The study of the water cycle by Lidar has many applications. Because micro-scale structures can be identified by their water content, the technique offers new opportunities to visualize and study the phenomena. There are applications to many practical problems in agricultural and water management as well as at waste storage sites. Conventional point sensors are limited and are inappropriate for use in complex terrain or varied vegetation and cannot be extrapolated over even modest ranges. To this end, techniques must be developed to measure the variables associated with evapotranspirative processes over large areas and varied surface conditions. A scanning water-Raman Lidar is an ideal tool for this task in that it can measure the water vapor concentration rapidly with high spatial resolution without influencing the measurements by the presence of the sensor. 3 refs., 5 figs., 1 tab