Organocatalytic Lewis base functionalisation of carboxylic acids, esters and anhydrides via C1-ammonium or azolium enolates

This tutorial review highlights the organocatalytic Lewis base functionalisation of carboxylic acids, esters and anhydrides via C1-ammonium/azolium enolates. The generation and synthetic utility of these powerful intermediates is highlighted through their application in various methodologies including aldol-lactonisations, Michael-lactonisations/lactamisations and [2,3]-rearrangements.Publisher PDFPeer reviewe

Exact Quantum States for all Two-Dimensional Dilaton Gravity Theories

It is shown that the recently obtained quantum wave functionals in terms of the CJZ variables for generic 2d dilaton gravity are equivalent to the previously reported exact quantum wave functionals in geometrical variables. A third representation of these exact quantum states is also presented

Interface Collisions

We provide a theoretical framework to analyze the properties of frontal collisions of two growing interfaces considering different short range interactions between them. Due to their roughness, the collision events spread in time and form rough domain boundaries, which defines collision interfaces in time and space. We show that statistical properties of such interfaces depend on the kinetics of the growing interfaces before collision, but are independent of the details of their interaction and of their fluctuations during the collision. Those properties exhibit dynamic scaling with exponents related to the growth kinetics, but their distributions may be non-universal. These results are supported by simulations of lattice models with irreversible dynamics and local interactions. Relations to first passage processes are discussed and a possible application to grain boundary formation in two-dimensional materials is suggested.Comment: Paper with 12 pages and 2 figures; supplemental material with 4 pages and 3 figure

Spinning Relativistic Particle in an External Electromagnetic Field

The Hamiltonian formulation of the motion of a spinning relativistic particle in an external electromagnetic field is considered. The approach is based on the introduction of new coordinates and their conjugated momenta to describe the spin degrees of freedom together with an appropriate set of constraints in the Dirac formulation. For particles with gyromagnetic ratio $g=2$, the equations of motion do not predict any deviation from the standard Lorentz force, while for $g \neq 2$ an additional force, which corresponds to the magnetic dipole force, is obtained.Comment: Latex file, 11 page

Abundance of Cereal Aphids (Homoptera: Aphididae) and Their Predators in Spring Wheat-Alfalfa Intercrops Under Different Crop Management Intensities

Natural infestations of cereal aphids and abundance of their predators were compared from 1990 through 1993 among plots of intercropped spring wheat and alfalfa grown under high, intermediate, or low crop management intensity (CMI). CMI treatments differed in the amount of nitrogen fertilizer applied and herbicide used and in the rigor of tillage operations. Cereal aphids (primarily Rhopalosiphum padi, Sitobion avenae, and Schizaphis graminum) collectively infested a mean of 0 to 5.9 of 15 wheat tillers sam­pled per plot on various dates from 1990 through 1993, but aphid infestation did not vary by CM!. Seven taxa of aphid predators predominated: Nabis spp., Chrysoperla spp., Coleomegilla maculata, Hippodamia convergens, H. tredecimpunctata tibialis, H. parenthesis, and Coccinella septempunctata. Coccinella transversoguttata richardsoni, a species in decline in eastern South Dakota, was not collected. Nabids were generally the most abundant predatory taxon. In 1992, coccinellid adults were more abundant in high than low CMI plots. In 1993, H. tredecimpunctata tibialis adults were significantly more abundant in high CMI plots on the first three sampling dates but became more abundant in the low and intermediate CMI plots by the fifth sampling date. Regressions between the number of aphid-infested tillers and abundance of some predator taxa were significant in 1990, 1991, and 1992. In 1990, most regressions showed that counts of predators (except Chrysoperla spp. adults) were inversely proportional to aphid infestation levels, whereas significant regressions in 1991 and 1992 showed that the abundances of predators were weakly proportional to aphid infestation levels. Adjusted r2 values for all significant regressions ranged from 0.07 to 0.27. Relationships between crop management, cereal aphid infestation, and aphidophagous predators are discussed

Impact of the Redheaded Pine Sawfly (Hymenoptera: Diprionidae) on Young Red Pine Plantations

The ecology of the redheaded pine sawfly was studied relative to its impact on red pine plantations. An ecological model, which formed the basis for socioeconomic analysis, was constructed. Because the sawfly prefers trees under moisture stress, damage is most severe in stands growing on sand blows, where there is competition for moisture from bracken fern and hardwoods, and where soils are too moist, too shallow, or too compacted. Outbreaks also appear to be related to dry years. The sawfly has a variable impact on multiple-use values. Because it injures the least productive trees in a stand, timber is only indirectly affected. Small openings created by tree mortality after an outbreak may provide edge \u27Wildlife habitat. The sawfly has both negative and positive effects on recreationists, depending upon the type of recreation; it may be a nuisance to campers, but may positively influence hunting. Preventive sawfly management involves proper site selection for red pine