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Two species of entomopathogenic nematodes, an ambush forager (Steinernema carpocapsae) and a cruising forager (S. glaseri), were assayed for their responses to volatiles associated with Galleria mellonella (Insecta: Lepidoptera). The responses of entomopathogenic nematodes to six host-associated volatile treatments were assayed. Live G. mellonella, live G. mellonella with the cuticular hydrocarbons removed, live G. mellonella with carbon dioxide removed, dead G. mellonella, dead G. mellonella with the cuticular hydrocarbons removed, and volatiles from S. exiqua feces were assayed in a Y-tube choice aparatus. Steinernema glaseri were attracted only to treatments producing carbon dioxide. Steinernema carpocapsae showed no significant response to any treatments tested. To assess the directionality of the response toward live G. mellonella, net average movement per nematode after 5, 10, and 20 min was measured for both nematode species. The assay method was based on the "quadrant plate" bioassay, with a 9 cm Petri dish containing 2% agar. Steinernema carpocapsae showed little directionality of response, whereas S. glaseri was attracted to carbon dioxide. We conclude that carbon dioxide attracts S. glaseri to areas likely to hold hosts. Ambush foragers are less influenced by cues associated with hosts or their habitat.

SUMMARYSearch behaviour of two entomopathogenic nematode species with different foraging strategies was compared by measuring parameters of unrewarded search after contact with host cues. Steinernema glaseri cruises in search of hosts. Steinernema carpocapsae ambushes hosts. Nematodes should respond to contact with relevant host cues by shifting their search from ranging to localized after contact with them. We predicted that cruising foragers rely on chemical cues more heavily than ambushers. These species were also tested for host affinities. Nematodes were tracked by image analysis after exposure to faeces, cuticle or food of either Popillia japonica or Spodoptera exiqua. Steinernema glaseri responded to selected host cues by shifting from ranging to localized search, characterized by decreased locomotory rate, distance travelled, search area and the proportion of the test period spent moving. Steinernema carpocapsae did not respond to host cues. Steinernema glaseri responds to selected chemical host cues for host location, whereas S. carpocapsae does not.

ZrC and ZrN ceramics are of interest in the application of materials in extreme high temperature environments, particularly for nuclear applications in generation IV reactors. These materials demonstrate desirable characteristics such as high thermal and electrical conductivities along with high hardness and melting temperatures. Data reported in the literature often suffer from scatter due to differences in processing techniques and difficulty determining stoichiometry, which will significantly affect thermophysical properties. This article reviews the current available data for the properties of ZrC, ZrN and mixed carbonitrides phases and identifies causes of scatter in the literature and areas requiring further research.

Transmission electron microscopy (TEM) with in situ He ion irradiation has been used to examine the damage microstructure of W when varying the helium concentration to displacement damage ratio, irradiation temperature and total dose. Irradiations employed 15, 60 or 85 keV He + ions, at temperatures between 500 and 1000°C up to doses of ~3.0 DPA. Once nucleated and grown to an observable size in the TEM, bubble diameter as a function of irradiation dose did not measurably increase at irradiation temperatures of 500°C between 1.0 and 3.0 DPA; this is attributed to the low mobility of vacancies and He/vacancy complexes at these temperatures. Bubble diameter increased slightly for irradiation temperatures of 750°C and rapidly increased when irradiated at 1000°C. Dislocation loops were observed for at irradiation temperature of 500 and 750°C and no loops were observed at 1000°C. Burgers vectors of the dislocations were determined to be b = ±1/2<111> type only and both vacancy and interstitial loops were observed. The proportion of interstitial loops increased with He-appm/DPA ratio and this is attributed to the concomitant increase in bubble areal density, which reduces the vacancy flux for both the growth of vacancy-type loops and the annihilation of interstitial clusters.

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Satellite remote sensing has been used in forest health management as a method for vegetation mapping, fire fuel mapping, fire risk estimation, fire detection, post-fire severity mapping, insect infestation mapping, and relative water stress monitoring. This paper reviews the use of satellite remote sensing in forest health studies, including current research activities; the satellite sensors, methods, and parameters used; and their accuracy. The review concludes that the Moderate Resolution Imaging Spectroradiometer satellite data (MODIS) are more appropriate for most of the remote sensing applications for forest health than other current satellite data when considering temporal and spatial resolutions, cost, and bands. MODIS has a 1-2 day temporal and a 250-1000 m spatial resolution; the data are free and cover more spectral bands than other satellites (up to 36 bands). We recommend that physical and physiological modeling (e.g., evapotranspiration and biomass growth) be developed for remote sensing of forest health. Some additional satellite sensors, such as for high temperature estimates (as high as 1800 K) and sensors of narrow bands, are also needed.

A model was developed to account for the recent observations indicating that type I collagen fibrils assembled in vivo grow from symmetrical pointed tips. The essential features of the model are (i) a distnctive structural nucleus forms at each end of a growing fibril and growth of the fibril then proceeds by propagation ofthe two structural nuclei, METHODSComputer simulations of fibril models were carried out with a Silicon Graphics workstation. Each collagen monomer was represented as a cylinder with a length defined as 4.4 D periods. Models for fibril assembly were simulated by addition of one monomer at a time according to rules for binding through unidirectional 3.4 D-period overlaps or 0.4 D-period overlaps as described in Results. Interactive programs were written so that the models could be rotated in three dimensions after each monomer addition and so that different growth patterns could be explored in two or three dimensions. RESULTSCriteria for the Model. The major criteria for developing a model were that it account for the following observations made on fibrils assembled de novo at 370C (Fig. 1): (i) in cross-section, the a-tips were circular down to a tip of <25 nm (22,24); (ii) axially, the a-tips were near-paraboloidal, as indicated by a decrease in mass toward the tip that was an average of 17 molecular D segments per D period and that was linear over 100 or more D periods (24); (iii) the a-tips on both short and long fibrils were essentially the same (24), an observation implying that the contour remained constant as the fibrils grew; (iv) the (-tips were also near-paraboloidal but were more irregular with slopes that varied from 50 to 200 molecular D segments per D period (24); (v) after the (3-tips appeared, both a-tips and (-tips grew simultaneously on the same fibril (24); (vi) all monomers were oriented so that the N termini were directed toward the tips (22, 24); and (vii) the shafts of all the fibrils formed under the same conditions had about the same diameters (21, 23).Initial Considerations of Alternative Models. Initial considerations indicated that the observations could not be explained in any simple manner by several previous suggestions about fibril growth (Table 1). For example, assembly driven primarily by surface tension and liquid-like forces (see ref.11) cannot readily explain the persistent differences in con§To whom reprint requests should be addressed. 9860The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.