Topochemistry. Part XXXIX. The Solid-state Photochemistry of some 2′-Nitrochalcones

It is shown that the specific pathway of a complex photochemical reaction in the solid state is governed by the molecular conformation and its retention, and by the molecular packing. 2′-Nitrochalcone and those of its derivatives which are isomorphous with it display the s-trans conformation in the solid state and yield indigos upon irradiation. However, this conformation is not sufficient to ensure photoreactivity: thus the s-trans-4-bromo-derivative does not yield indigo. The same derivative in the s-cis conformation (in a second crystal form) has a crystal structure similar to that of the parent compound, and also does not yield indigo.     

A study of machine-level software profile

The instruction mix of a CDC CYBER/74 computer in a university environment was monitored, and in this paper frequencies of execution for the most commonly used instructions are given. From these measurements we make a number of observations about several aspects of computing patterns. One observation is the fact that if we exclude the idle loop of the operating system, the percentage of occurrences for each type of instruction over various time intervals is constant. This fact is used to define a machine-level software profile (MLSP) for the type of machine operations in the given computing environment. It is shown that the MLSP could be used to find machine utilization and the extent to which software takes advantage of machine architecture, and as a consistent method to improve the performance of a machine configuration.     

Control design for suppressing transversal patterns in reaction–(convection)–diffusion systems

The stabilization of planar stationary fronts solutions in a two-dimensional rectangular or cylinder domain, in which a diffusion–convection–reaction process occurs, is studied by reducing the original two-variable PDEs model to an approximate one-dimensional model that describes the behavior of the front line. We consider the control strategy based on sensors placed at the designed front line position and actuators that are spatially-uniform or space dependent. We present a systematic control design that determines the number of required sensors and actuators, their position and their form. The control used linear analysis of a lumped truncated model and concepts of finite and infinite zeros of linear multidimensional systems.     

Correlates of employee lateness: Some theoretical considerations.

Using hypothesis-driven meta-analytic procedures on 30 samples containing 118 correlations, researchers examined competing models of the relationship between lateness and assorted work-related variables. Consistent with a progression withdrawal model, the mean corrected lateness-absence correlation, .40, was found to be higher than the lateness-turnover correlation, .27. Hypotheses regarding the relationships between lateness and attitudes, performance, and demographics were generally supported. Methodological issues, including the need for longitudinal designs in the field and the inclusion of other moderators such as organizational and personality variables, were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A note on lossless database decompositions

It is known that under a wide variety of assumptions a database decomposition is lossless if and only if the database scheme has a lossless join. Biskup, Dayal and Bernstein (1979) have shown that when the given dependencies are functional, the database scheme has a lossless join if and only if one of the relation schemes is a key for the universal scheme. In this note we supply an alternative proof of that characterization. The proof uses tools from the theory of embedded join dependencies and the theory of tuple and equality generating dependencies, but is, nevertheless, much simpler than the previously published proof.     

Thermal energy storage in columns packed with crosslinked polyethylene tubes

An energy storage system based on solid-solid phase transition of crosslinked polyethylene was constructed and tested. The energy storage unit consisted of a column packed with crosslinked polyethylene tubes. The solid-solid phase transition enables heat transfer by direct contact between the form-stable polymer and the hot (cold) fluid. A theoretical model for the simulation of this system was developed. The heating-cooling characteristics of the energy storage system were simulated by the model, using measured thermodynamic properties of the crosslinked polyethylene. The potential of various crosslinked polyethylene materials for energy storage applications will depend on sufficient high-temperature stability.     

Alternative Modes of Addition of Electrophilic Olefins to the Vinylcyclopropane Systems in 2,2-Ethano-1-Methylene-1,2,3,4-Tetrahydronaphthalene and 1,1-Ethano-2-Methylene-1,2,3,4-Tetrahydronaphthalene

The title compounds 2,2-ethano-1-methylene and 1,1-ethano-2-methylene-1,2,3,4-tetrahydronaphthalene ( 13 and 14 respectively) were synthesized by the Wittig reaction from the corresponding ethano-tetralones ( 16 ) and ( 19 ) which were, in turn, prepared from the respective α- and β-tetralones ( 15 ) and ( 18 ). It is shown that the reaction of ( 13 ) with TCNE at 0° yields the corresponding [2 + 2] cycloaddition adduct ( 20 ), isomerizing thermally to the formal [2 + 5] cycloaddition adduct ( 21 ). Compound ( 13 ) reacts with N-tosylisocyanate (TIC) and with N-phenylsulfonylisocyanate (PSI) to a 4:1-isomeric mixture of (Z)- and (E)-acryloamides ( 24 ) and ( 26 ), respectively. The reaction of ( 14 ) with TCNE at 0° leads to the [2 + 5] cycloadduct ( 30 ), while with (TIC) and (PSI) the corresponding tricyclic adducts ( 28a ) and ( 28b ) result. Bromination of ( 16 ) with NBS yielded the respective 4-bromo-2,2-ethano-1-tetralone ( 31 ) which gave, upon dehydrobromination with the aid of DBU, the naphtho-dihydrofurane derivative ( 34 ). The latter was formed most likely via facile cyclopropylketone upon dihydrofurane rearrangement of an initially formed 2,2-ethano-1-oxo-1,2-dihydronaphthalene ( 32 ) which was desired for the formation of ( 33 ). Structures of all new compounds were assigned on basis of analytical and spectroscopic data (IR, UV, mass spectra, ¹H-NMR).     

Feeding Responses of Free-flying Honeybees to Secondary Compounds Mimicking Floral Nectars

The role of secondary compounds (SC) in deterring herbivores and pathogens from vegetative parts of plants is well established, whereas their role in plant reproductive organs such as floral nectar is unclear. The present study aimed to reveal the response of free-flying honeybees to naturally occurring concentrations of four SC in floral nectar. We selected nicotine, anabasine, caffeine, and amygdalin, all of which are found in nectar of various plants. In repeated paired-choice experiments, we offered 20% sucrose solution as control along with test solutions of 20% sucrose with various concentrations of the above SC. Except for anabasine, naturally occurring concentrations of SC did not have a deterring effect. Furthermore, low concentrations of nicotine and caffeine elicited a significant feeding preference. SC can, therefore, be regarded as postingestive stimulants to pollinators, indicating that the psychoactive alkaloids in nectar may be a part of their mutualistic reward. Further studies are needed to test our hypothesis that psychoactive alkaloids in nectar impose dependence or addiction effects on pollinators.