Diterpene resin acids: Major active principles in tall oil against Variegated cutworm,Peridroma saucia (Lepidoptera: Noctuidae)

Tall oil, a by-product of the kraft process for pulping softwood, has been shown to have insecticidal properties. In the present study, the active principles in tall oil against the variegated cutworm,Peridroma saucia Hübner, were investigated. GC-MS analysis showed that abietic, dehydroabietic, and isopimaric acids were major resin acid components of crude tall oil and depitched tall oil. When crude tall oil samples of differing resin acid composition were incorporated into artificial diet at a concentration of 2.0% fresh weight, they suppressed larval growth by 45–60% compared to controls. This suppression was significantly (P0.05) correlated with the equivalent contents of abietic, dehydroabietic, isopimaric, and total resin acids. These results were also evident from a diet choice test, showing that the second-instar larvae obviously selected diets with low levels of resin acids when different diets were randomly arranged in a Petri dish. Bioassays with pure resin acids (abietic, dehydroabietic, and isopimaric acids) demonstrated that all individual chemicals have similar bioactivity against this insect. Comparison of the bioactivities of depitched tall oil and an equivalent mixture of pure resin acids in thePeridroma chronic growth bioassay indicated that pure resin acids and depitched tall oil share a common mode of action to this insect. This study confirms that resin acids are major active principles in tall oil against the variegated cutworm, but other chemicals likely also contribute to the bioactivity of tall oil.     

Use of a sex attractant and an inhibitor for monitoring winter moth and bruce spanworm populations

A single sex pherormone component was isolated from abdominal tip extracts of female Bruce spanworm.Operophtera bruceata (Hulst). This was identified as (Z,Z,Z)-1,3,6,9-nonadecatetraene by capillary gas chromatography (GC), electroantennography, and mass spectrometry. In addition, hexane extracts of female abdominal tips from Bruce spanworm and the winter moth.O. brumata L., were analyzed by GC coupled to an electroantennographic detector (GC-EAD). The extracts ofO. bruceata andO. brumata females elicited only a single response, at the same retention time, from antennae of their conspecific and reciprocal males. In field tests conducted in Saskatchewan, traps baited with the synthetic tetraene captured Bruce spanworm males. In tests carried out on Vancouver Island, British Columbia, where the two species coexist, both Bruce spanworm and winter moth males were captured. The attractancy of lures containing the synthetic pheromone alone and in combination with several structurally related analogs was field tested at both locations. One of these, an isomer of the natural pheromone, (E,Z,Z)-1,3,6,9-nonadecatetraene, inhibited the capture of Bruce spanworm males but had no effect upon the number of winter moth males which were taken. Thus, populations of these two very similar species can be distinguished by employing traps baited with pheromone ± the inhibitor. Coneorifice Hara traps were found useful for field trapping males of both species.Issued as NRCC No. 26107     

Adhesion-Delamination Mechanics of a Prestressed Circular Film Adhered onto a Rigid Substrate

A thin circular film clamped at the periphery is adhered to the planar surface of a rigid cylindrical punch. An external tensile load is applied to the punch, causing the film to delaminate from the substrate and the circular contact edge to contract. The film spontaneously separates from the punch, or pulls off, when the contact radius reduces to a range between 0.1758 and 0.3651 of the film radius, depending on the magnitude of the residual membrane stress. The mechanical delamination process is derived by a thermodynamic energy balance based on a coupled interfacial adhesion and residual membrane stress. The theoretical model has significant implications in nanoforce measurement, microelectromechanical systems (MEMS) comprising active moveable films, and biological cell adhesion.     

Heat capacity of copolymers of chlorotrifluoroethylene and vinylidene fluoride

The heat capacities of two copolymers of chlorotrifluorethylene and vinylidene fluoride, one 30:70 mol % and the other 44:56 mol % in composition, were measured in an adiabatic calorimeter from 80 to 340 K. The glass-transition points T_g observed at 256 and 269 K for the 30:70 and 44:56 samples, respectively, closely agree with the prediction of the theory of Flory and Fox; the accompanying jump of heat capacities at these points was found to be 2.2 cal/K ‘per bead’ for both samples, in fair agreement with the ‘constant ΔC_p rule’. A small peak was observed immediately above T_g, and interpreted as a time-dependent effect arising from the lack of equilibrium in the region. The data of the heat capacities were analysed in detail in the framework of the Tarasov model and the principle of additivity, and were found to agree well ( 1–3%) with theory up to the respective glass-transition points in all cases, thus giving support to the validity of the previously published segmental values of heat capacity and of characteristic temperature θ₁.     

Sex attractants for Geometrid and Noctuid moths

Male moths belonging to 17 species of Geometridae and nine species of Noctuidae were captured in traps baited with synthetic chemicals as part of a field screening program. The compounds tested were the C₁₈-C₂₂ homologs of: (1) (3Z,6Z,9Z)-triene hydrocarbons; (2) mixtures containing equal quantities of (3Z,6Z)-cis-9,10-expoxydienes, (3Z,92Z)-cis-6,7-epoxydienes, and (6Z,9Z)-cis-3,4-epoxydienes; (3) (3Z,6Z)-9S,10R-epoxydienes; (4) (3Z,6Z)-9R,10S-epoxydienes; and (5) (3Z,6Z,9Z,11E)-nonadecatetraene. Field captures and electroantennographic assays revealed a high degree of specificity in the responses of many species to the synthetic chemicals. In several species the ability of males to discriminate between the 9S,10R and 9R,10S enantiomers of the monoepoxydiene isomers was clearly shown. Synergists and inhibitors were discovered for several of the reported attractants, some of which were not previously known to have semiochemical activity. The geometrid moths captured includedEpirrhoe sperryi (Herbulot),Mesoleuca ruficillata (Guenée),Triphosa haesitata (Guenée),Metanema inatomaria (Guenée),Prochoerodes transversata (Drury),Cabera erythemaria (Guenée),Synaxis jubararia (Hulst),Dysstroma brunneata ethela (Hulst),Eulithes testata (Linnaeus),Sicya macularia (Harris),Xanthorhoe iduata (Guenée),X. abrasaria aquilonaria (Herrich-Schäffer),X. munitata (Hübner),Itame loricaria (Eversmann),Eupithecia annulata (Hulst),E. rovocastaliata (Packard) andE. satyrata dodata (Taylor). The noctuid moths captured includedBleptina caradrinalis (Guenée),Idia américalis (Guenée),I. aemula (Hübner),Rivula propinqualis (Guenée),Lomanaltes eductalis (Walker),Spargaloma sexpunctata (Grote),Caenurgina distincta (Neumuller),Euclidia cuspidea (Hübner), andZale duplicata (Bethune). Six of the nine noctuid species captured belong to three subfamilies for which sex attractants had not been reported previously. Details for the stereospecific synthesis of (3Z,6Z)-cis-9,10-epoxydienes are also reported.Issued as NRCC No. 24314.     

Investigations of fluid dynamics in mechanically stirred aerated slurry reactors

The fluid dynamics of stirred aerated slurry reactors with A-310® propeller, 4-blade 45° pitch turbine and 6-blade Rushton disc turbine were studied over a wide range of gas flow rates. With respect to power consumption, gas hold-up, and fluid dynamically limiting cases, viz., suspension and flooding, the Rushton disc turbine was found to be the best in stirred aerated slurry reactors. The influence of particle density, shape and mass fraction and of liquid properties on gassed critical stirrer speed, N_jsg, and of gassed power input per unit volume, P_jsg, on particle suspension and gas dispersion, were investigated. Empircal correlations in combination with that of Zwietering were established for scale-up design in three-phase slurry reactors.     

Investigation of microstructure of laser cladding Ni-WC layer on Al-Si alloy

A plasma-sprayed Ni-WC layer was deposited on an Al-Si cast alloy surface, and then it was further melted by a 5 kW CO₂ laser. The microstructure and chemical composition of the laser-melted zone were investigated, and the microhardness in different parts was measured. Experimental results showed that the chemical composition of the sample was not uniform. Compositional segregation in the laser-melted zone was found. Some amorphous structure appeared in the nickel-rich locations after laser melting. Owing to the thermal effect of the laser scanning, an intermediate-phase Ni₃Al segregated from this region and formed Ni₃Al grains and amorphous grains. Some WC particles melted in the matrix, and chromium carbide Cr2;|C6 and (Cr,W)C separated during the cooling process. The highest microhardness (1027HV) was found in the high-nickel region.     

Tool wear detection and fault diagnosis based on cutting force monitoring

In metal cutting processes, an effective monitoring system, which depends on a suitably developed scheme or set of algorithms can maintain machine tools in good condition and delay the occurrence of tool wear. In this paper, an approach is developed for fault detection and diagnosis based on an observer model of an uncertain linear system. A robust observer is designed, using the derived uncertain linear model, to yield the necessary and key information from the system. Subsequently, it is used as a state (tool wear) estimator, and fault detection is carried out by using the observed variables and cutting force. The developed approach is applied to milling machine center. Several linear models are identified based on different working conditions. A dominant model plus uncertain terms is derived from these model set and used as an observer. Threshold values are proposed for detecting the fault of the milling machine. Examples taken from experimental tests shown that the developed approach is effective for the fault detection. The approach can be used for fault detection of failures arising from sensor or actuator malfunction.     

Investigation of micro-EDM material removal characteristics using single RC-pulse discharges

Similar to EDM, in micro-EDM, intense heat is generated between the workpiece and tool electrode by the discharge through a dielectric medium to result in the formation of a microcrater that is much smaller in size. In this study, a single-spark generator has been developed to study the erosion characteristics from the microcrater size. Using a simple heat transfer model, the efficiency at different discharge condition is also deduced. It is found that at lower-energy (<50 μJ) discharges, the energy required to remove the unit volume of material, defined as the specific energy, is found to be much less than that at higher-energy discharges. Additionally, the ratio of the standard deviation to the measured microcrater size is found to be lower at lower discharge energy, indicating greater consistency in shape and size when the discharge occurs at lower energy. The fundamental erosion mechanism of material is discussed by considering melting and evaporation phenomena using theoretical modeling. The average efficiency of erosion, when estimated to be due primarily to melting or evaporation alone, is found to be up to an order of magnitude higher at lower-energy discharges than that at higher-energy discharges.     

Spatial navigation model based on chaotic attractor networks

We present a model of spatial navigation based on the non-convergent dynamics of brain activity. The system includes a hippocampal module that processes global spatial information and a cortical module that deals with local sensory information. We test the model using several spatial navigation paradigms: goal finding, shortcutting and detouring. Computer simulations show that the performance of the agent qualitatively matches that of animals and related models. This new approach provides a novel interpretation of how the brain accomplishes spatial navigation.