Necrodols: Anti-insectan terpenes from defensive secretion of carrion beetle (Necrodes surinamensis)

Two compounds recently isolated from the defensive gland ofNecrodes surinamensis, -and -necrodol, first representatives of a new category of monoterpenes (the necrodanes), are shown to be repellent to ants and other insects and irritating to cockroaches and flies. The compounds doubtless play a defensive role inNecrodes. The possible long-range applied significance of research on insect repellents is discussed.Paper No. 80 of the seriesDefense Mechanisms of Arthropods. Paper No. 79 is T. Eisner et al., Experientia 42:204–207 (1986).     

Lightweight dynamic symmetry breaking

Symmetries in constraint problems present an opportunity for reducing search. This paper presents Lightweight Dynamic Symmetry Breaking, an automatic symmetry breaking method that is efficient enough to be used as a default, since it never yields a major slowdown while often giving major performance improvements. This is achieved by automatically exploiting certain kinds of symmetry that are common, can be compactly represented, easily and efficiently processed, automatically detected, and lead to large reductions in search. Moreover, the method is easy to implement and integrate in any constraint system. Experimental results show the method is competitive with the best symmetry breaking methods without risking poor performance.     

Preparation of nano-sized silicon carbide powder using thermal plasma

Nano-sized silicon carbide (SiC) powder was prepared by thermal plasma process using silicon tetrachloride (SiCl₄) and methane (CH₄). The synthesized powder was characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and particle size analyzer. The powder was dominated by β-SiC including some of α-SiC and free carbon species. The quality of the powder was varied with process conditions such as the molar ratio of H/Si and C/Si, and collecting positions. It was known that the conversion to SiC was mainly affected by the addition of hydrogen gas because it promoted the decomposition and reduction of SiCL. CH₄ was easily decomposed to carbon species for the formation of SiC as well as removal of impure oxygen, but excessive carbon suppressed the formation of crystalline SiC and resulted in the solid carbon contamination. The optimum ratio of H/Si was approx. 26 and that of C/Si was 1.1. For collecting positions, the powder collected at the vessel and filter was preferable to that at the reaction tube. The average size of the powder synthesized was estimated to be below 100 nm and uniform in distribution.     

Terrain‐inclination‐based Three‐dimensional Localization for Mobile Robots in Outdoor Environments

A new terrain‐inclination‐based localization technique is proposed in this paper to enable a robot to identify its three‐dimensional location relative to measurable terrain inclinations. Given a topographical map and a planned path, a robot‐terrain‐inclination model (RTI model) is extracted along the path on the terrain upon which the robot is operating. A particle filter is then used to fuse the measurement data with the robot motion based on the extracted RTI model for either a three‐wheeled or a four‐wheeled mobile robot. Experiments were carried out in four outdoor scenarios: one short path with different initial conditions and map resolution, another short path with different surface roughness and sensor accuracy, and two long paths with different types of rigid terrains and multiple loops. Experimental results show that the proposed method could achieve good localization performance on inclined outdoor terrains.     

The hitchhiker’s guide to ubicomp: using techniques from literary and critical theory to reframe scientific agendas

Literary criticism places fictional work in historical, social and psychological contexts to offer insights about the way that texts are produced and consumed. Critical theory offers a range of strategies for analysing what a text says and just as importantly, what it leaves unsaid. Literary analyses of scientific writing can also produce insights about how research agendas are framed and addressed. This paper provides three readings of a seminal ubiquitous computing scenario by Marc Weiser. Three approaches from literary and critical theory are demonstrated in deconstructive, psychoanalytic and feminist readings of the scenario. The deconstructive reading suggests that alongside the vision of convenient and efficient ubiquitous computing is a complex set of fears and anxieties that the text cannot quite subdue. A psychoanalytic reading considers what the scenario is asking us to desire and identifies the dream of surveillance without intrusion. A final feminist reading discusses gender and collapsing distinctions between public and private, office and home, family and work life. None of the readings are suggested as the final truth of what Weiser was “really” saying. Rather they articulate a set of issues and concerns that might frame design agendas differently. The scenario is then re-written in two pastiches that draw on source material with very different visions of ubiquitous computing. The Sal scenario is first rewritten in the style of Douglas Adams’ Hitchhiker’s Guide to the Galaxy. In this world, technology is broken, design is poor and users are flawed, fallible and vulnerable. The second rewrites the scenarios in the style of Philip K Dick’s novel Ubik. This scenario serves to highlight what is absent in Weiser’s scenario and indeed most design scenarios: money. The three readings and two pastiches underline the social conflict and struggle more often elided or ignored in the stories told in ubicomp literature. It is argued that literary forms of reading and writing can be useful in both questioning and reframing scientific writing and design agendas.     

Damage Mechanisms and the Mechanical Properties of a Laminated 0/90 Ceramic/Matrix Composite

The tensile properties of a 0/90 laminated CAS matrix composite reinforced with Nicalon fibers have been measured. Some effects of notches have also been explored. Changes in modulus and permanent strain caused by matrix cracking have been measured and compared with available models. For this comparison, independent measurements have been made of the constituent properties and the residual stress. The ultimate tensile strength has also been measured and compared with a global load-sharing model. It is concluded that lower-bound matrix cracking models provide good predictability of the stresses at which various matrix cracking mechanisms first operate. Also, the ultimate tensile strength is found to be consistent with a global load-sharing model, based on the in situ strength properties of the fibers. Conversely, the evolution of matrix cracks at stresses above the lower bound has yet to be adequately modeled. In addition, a need is identified for improved models relating elastic properties and permanent strains to matrix crack spacing.     

Applications of laser Raman microprobe spectroscopy to the characterization of coals and cokes

Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions.     

Model for the effects of water on the cationic UV-curing of cyclohexyl epoxides

The effect of relative humidity on the photoin-duced curing kinetics of cyclohexyl epoxide and epoxide/polyol coating formulations was investigated in real-time using FTIR spectroscopy. In total, five formulations were used in this study, including a cyclohexyl epoxide without polyol, and four with polyols. The polyol formulations were varied with respect to ratio of epoxide to polyol, and molar functionality of the hydroxyl group. The formulations were exposed to a maximum of seven different relative humidities (6, 16, 20, 30, 51, 62, 75 RH). The curing speed and overall conversion of the epoxy group passed through a maxima for all the formulations. The polyol had an effect on the hydrophilicity of the overall formulation. It was also found that water and polyols had a synergistic effect on the UV-curing kinetics, in effect lowering the relative humidity to achieve a maxima. A model for UV-curing mechanisms at low, medium, and high relative humidity was proposed for both systems with and without the polyols. Part of this work was done at the Polymers and Coatings Dept., North Dakota State University, Fargo, ND 58105. Presented at the 80th Annual Meeting of the Federation of Societies for Coatings Technology, Oct. 30–Nov. 1, 2002, in New Orelans, LA. Dept. of Polymer Engineering, Akron, OH 44325-0301.     

Neutral sterols of sawflies (symphyta): Their relationship to other hymenoptera

To investigate sterol utilization in sawflies, the neutral sterols of four species of sawflies were determined by gas-liquid chromatography and mass spectrometry, and compared to the respective dietary plant material. Cholesterol was the predominant (55–76%) sterol in all species and stages of sawflies examined. Host plants, however, contained primarily sitosterol (50–88%), along with other 24-alkylsterols and only 0.5–5.9% cholesterol, indicating that the sawflies examined are capable of dealkylating the C₂₈ and C₂₉ phytosterols in their diet to cholesterol. Comparative sterol metabolism in Hymenoptera is discussed.     

Comparison of microwave and thermal cure of epoxy resins

Stoichiometric mixtures of DGEBA (diglycidyl ether of bisphenol A)/DDS (diaminodiphenyl sulfone) and DGEBA/mPDA (meta phenylene diamine) have been isothermally cured by electromagnetic radiation and conventional heating using thin film sample configurations. Fourier transform infrared spectroscopy (FTIR) was used to measure the extent of cure. Thermal mechanical analysis (TMA) was used to determine the glass transition temperatures directly from the cured thin film samples. Well-defined glass transitions were observed in the TMA thermograph for both thermal and microwave cured samples. Significant increases in the reaction rates have been observed in the microwave cured DGEBA/DDS samples. Only slight increases in the reaction rates have been observed in the microwave cured DGEBA/mPDA samples. Higher glass transition temperatures were obtained in microwave cured samples compared to those of thermally cured ones after gelation. The magnitude of increases of glass transition temperature is much larger for the DGEBA/DDS system than DGEBA/mPDA system. The microwave radiation effect was much more significant in DGEBA/DDS system than in DGEBA/mPDA system. DiBenedetto's model was used to fit the experimental T_g data of both thermal and microwave cured epoxy resins.