A Symmetrical Diester as the Sex Attractant Pheromone of the North American Click Beetle Parallelostethus attenuatus (Say) (Coleoptera: Elateridae)

Hexanoic acid, 1-octanol, 1,8-octanediol, octyl hexanoate, 1,8-octanediol monohexanoate, and 1,8-octanediol dihexanoate were identified in headspace volatiles collected from the crushed abdomen of a female click beetle of the species Parallelostethus attenuatus (Say) (Elaterinae, tribe Elaterini). In field trials carried out in Illinois, South Carolina, North Carolina, and Virginia, adult male beetles were strongly attracted to 1,8-octanediol dihexanoate alone. Blends of the dihexanoate with one or more of the other compounds proved to be less attractive than the dihexanoate alone, suggesting that the pheromone of this species may consist of a single compound. The symmetrical diester structure of the pheromone is a novel natural product and appears to be structurally unique among insect pheromones.

     

Cognitive and affective processes for learning science in immersive virtual reality

As immersive virtual reality (IVR) systems proliferate in classrooms, it is important to understand how they affect learning outcomes and the underlying affective and cognitive processes that may cause these outcomes. Proponents argue that IVR could improve learning by increasing positive affective and cognitive processing, thereby supporting improved performance on tests of learning outcome, whereas opponents of IVR contend that it could hurt learning by increasing distraction, thereby disrupting cognitive learning processes and leading to poorer learning outcomes. In a media comparison study, students viewed a biology lesson either as an interactive animated journey in IVR or as a slideshow on a desktop monitor. Those who viewed the IVR lesson performed significantly worse on transfer tests, reported higher emotional arousal, reported more extraneous cognitive load and showed less engagement based on EEG measures than those who viewed the slideshow lesson, with or without practice questions added to the lessons. Mediational analyses showed that the lower retention scores for the IVR lesson were related to an increase in self-reported extraneous cognitive load and emotional arousal. These results support the notion that immersive environments create high affective and cognitive distraction, which leads to poorer learning outcomes than desktop environments.     

Use of mass loading to operate a thin film ultrasonic transducer in the 300 kHz–10 MHz frequency range

Thin film ultrasonic transducers have been designed which operate over an important frequency range, 300 kHz to 10 MHz. The transducers were made using piezoelectric aluminium nitride films a few microns thick. The films would have a fundamental thickness mode resonance at 1–3 GHz if fabricated as an unsupported film, however operation at much lower frequencies has been demonstrated when the transducers are fabricated on bulk substrates. This would enables them to be used in ultrasonic non-destructive testing in circumstances where the film can be deposited directly onto the object under test. We have found that the major factors influencing the below-resonance operation of the thin film transducers are the device impedance, the spectrum of the excitation pulse, and any mechanical (mass) loading applied to the back face of the transducer. Results are presented showing that the evolution of device impedance as a function of device area could be predicted using a PSpice model of the thin film transducer. The ability of the transducer to generate longitudinal mode pulses rather than shear wave pulses was found to depend on increasing the mechanical loading at the back face of the transducer. This mechanism for pulse generation was confirmed by Finite Element Modelling using PZFlex.     

Modeling with blocks

This paper presents a simple and general modeling primitive, called a block, based on a generalized cuboid shape. Blocks are laid out and connected together to constitute the base shape of complex objects, from which is extracted a control mesh that can contain both smooth and sharp edges. The volumetric nature of the blocks allows for easy topology specification, as well as CSG operations between blocks. The surface parameterization inherited from the block faces provides support for texturing and displacement functions to apply surface details. A?variety of examples illustrate the generality of our blocks in both interactive and procedural modeling contexts.     

Defect analysis and excitons diffusion in undoped homoepitaxial diamond films after polishing and oxygen plasma etching

Several 65 μm thick epitaxial diamond films prepared on (100) Ib substrates by high power pulsed microwave plasma assisted chemical vapour deposition (HP-MPCVD) are studied as a function of surface treatments by cathodoluminescence (CL) and photoluminescence (PL) spectroscopies. They are either asgrown, or polished, or etched by a microwave oxygen plasma, or after applying subsequently the two last processes. In CL spectra, bands due to defects occur at 2.3 eV, 3.07 eV, 3.7 eV and 4.7 eV, the last one being specific of polished surfaces, with nearly no contrast in the luminescence image. A fundamental result consists in demonstrating that the defects induced by polishing can be removed by oxygen plasma etching. Additionally, in order to assess how luminescence spectra originate from a peculiar depth or not, a bevelled sample is studied. PL spectra are acquired on the sample side while CL spectra are measured at several points on the bevel top side till to the Ib substrate. Comparison of the two sets of result show that the H3 signal originates from the Ib substrate even if it is present in the CL spectra of the film. An analysis of the change in the intensity of the TO free exciton line, defect bands and H3 signal, along decreasing photon energies, as a function of the thickness of the remaining HP-PMPCVD film, is performed with the help of a model taking the diffusion of the unrecombined excitonic pairs and the re-excited photoluminescence into account. CL images recorded at specific wavelengths, which do not show inverted contrast, are also assessed. From these data, the exciton diffusion length is evaluated to 11 μm in the major part of the epitaxial layer except for the first 20 μm close to the Ib substrate where it decreases down to 2 μm. This study sheds light on the interpretation of luminescence spectra excited by an electron beam in undoped diamond layers. Defects bands due to damages induced by polishing and etching processes are also documented.