Crawling Water Beetles of Wisconsin (Coleoptera: Haliplidae)

(excerpt) Haliplidae are smail water beetles, less than 5 mm long, that frequently occur in abundance in ponds, marshes, sloughs, and swamps and also along the margins of slow streams or lakes where there is not severe wave action. Adults are readily recognized by their yelloa- to orange ground color with black maculations on the elytra and sometimes on the head and pronotum (Figs. 1,3,4). They have a distinctive shape, being broadest at the basss of the elytra and tapered toward the posterior end. The metacoxae are covered by dis~ctive plates that are unique among water beetles (Fig. 2). The tarsi and tibiae of the adults are modified for swimming, and the beetles can swim quite well, although they mostly crawl among the vegetation. Adults and larvae are found among vegetation upon which they feed, filamentous algae being the primary source of food for most species, but detrims and animal material may form a portion of the diet in some species. In Wisconsin most species probably have a one-year life cycle and overwinter as adults. Eggs are laid during spring and early summer, usually in or upon algae. There are three larval instars, and pupation takes place in moist soil above the water line. Larvae have been derrihd for only a few species, so identification is based upon adult characteristics

Pinwheel patterns and powder diffraction

Pinwheel patterns and their higher dimensional generalisations display continuous circular or spherical symmetries in spite of being perfectly ordered. The same symmetries show up in the corresponding diffraction images. Interestingly, they also arise from amorphous systems, and also from regular crystals when investigated by powder diffraction. We present first steps and results towards a general frame to investigate such systems, with emphasis on statistical properties that are helpful to understand and compare the diffraction images. We concentrate on properties that are accessible via an alternative substitution rule for the pinwheel tiling, based on two different prototiles. Due to striking similarities, we compare our results with the toy model for the powder diffraction of the square lattice.Comment: 7 pages, 4 figure

Chapter 9: Aquatic Macroinvertebrates, Section A: Aquatic Macroinvertebrates (Exclusive of Mosquitoes)

Final Report. Excerpt (Chapter 9, Section A) from The Des Plaines River Wetlands Demonstration Project, Volume II, Baseline Survey, edited by Donald L. Hey and Nancy S. PhilippiReport issued on: October 1985INHS Technical Report prepared for Wetlands Research, Inc

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

The [4+2]‐cycloadditions of α‐nitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styryl‐substituted 4H‐1,5,2‐oxathiazines in moderate to good yields. Of the eight conceivable hetero‐Diels–Alder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the α‐nitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bis‐heterocyclic [4+2]‐cycloadducts. The experiments are supported by high‐level DFT calculations that were also extended to related hetero‐Diels–Alder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2‐dithiin and 2H‐thiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process

Monte Carlo Simulation of Lyman Alpha Scattering and Application to Damped Lyman Alpha Systems

A Monte Carlo code to solve the transfer of Lyman alpha (Lya) photons is developed, which can predict the Lya image and two-dimensional Lya spectra of a hydrogen cloud with any given geometry, Lya emissivity, neutral hydrogen density distribution, and bulk velocity field. We apply the code to several simple cases of a uniform cloud to show how the Lya image and emitted line spectrum are affected by the column density, internal velocity gradients, and emissivity distribution. We then apply the code to two models for damped Lya absorption systems: a spherical, static, isothermal cloud, and a flattened, axially symmetric, rotating cloud. If the emission is due to fluorescence of the external background radiation, the Lya image should have a core corresponding to the region where hydrogen is self-shielded. The emission line profile has the characteristic double peak with a deep central trough. We show how rotation of the cloud causes the two peaks to shift in wavelength as the slit is perpendicular to the rotation axis, and how the relative amplitude of the two peaks is changed. In reality, damped Lya systems are likely to have a clumpy gas distribution with turbulent velocity fields, which should smooth the line emission profile, but should still leave the rotation signature of the wavelength shift across the system.Comment: 19 pages, 17 eps figures. One panel is added in Fig.1 to show the recoil effect. Revisions are made in response to the referee's comments. Accepted for publication in Ap