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Notes: Adult hornets (Vespa orientalis; Hymenoptera, Vespinae) build the brood combs out of organic or mineral matter. The cement that serves to glue the building material together is secreted in their saliva, the latter hardening within seconds to form fibers or plates. This saliva-derived spittle overlies and unites the building particles laminally and vertically. The hornet larvae spin a cocoon within the brood cells, which is largely fastened to and supported by the cell walls and is composed of a network of silk fibers and interlinking flat surfaces. On the outside of the cocoon fibers are spherical button-like structures that are very rich in phosphorus. The chemical composition of the adult salivary cement and the larval cocoon fibers is similar: both contain the elements P, Mg, S, Cl, K, and Ca. The possible biological significance of these findings is discussed.Among social insects belonging to the Hymenoptera, there are three main groups that build a multitude of cells, namely, the paper wasps (Polistinae), the other social wasps or hornets (Vespinae), and the social bees (Apinae). The constructed cells serve mainly for rearing the brood, but in many instances (particularly among various Apinae) they also serve for storing honey and pollen. For building material, Apinae rely primarily on beeswax (a product secreted by the bee itself to which various amounts of plant resins are added). On the other hand, wasps (Polistinae and Vespinae) build mainly from matter collected in the nearby environment, be it organic matter such as tree bark, mineral matter, or a combination of the two.Much information has accumulated on comb and cell building among these insect groups (e.g., Wheeler, '23; Van der Vecht, '57, '65; Lindauer, '61; Michener, '61; Kemper and Döhring, '67; Wilson, '71; Guiglia, '72; Spradbery, '73; Edwards, '80; Brian, '83; Schremmer et al., '85). Species of Polistinae and Vespinae are prevalent in forest areas in Southeast Asia and in central and South America or in the temperate regions in both the northern and southern hemispheres, and they mainly use vegetable matter to build their combs. In contrast, species prevalent in the Mediterranean region, which is dry and relatively unvegetated during the wasp and hornet active season, rely more on nearby mineral than on plant matter. Comb building in the Oriental hornet is well known (Darchen, '64; Ishay et al., '67; Schaudinischky and Ishay, '68; Ishay, '73, '75a, b, '76; Ishay and Sadeh, '75, '76; Ishay and Perna, '79; Ishay et al., '82). Recently Ganor et al. ('86) described the cell wall in the V. orientalis comb, showing it to be composed of mineral particles collected near the subterranean nest, in contrast to the comb of two European species (V. crabro and Vespula) (Paravespula) germanica, which is built primarily of organic matter. Regardless of whether the building material is mineral or organic, the hornets utilize particles of sand or other minerals or pieces of wood wrapped and melded together by saliva. However, nothing is known about the cement or mortar used to glue together these “bricks.” The present investigation was initiated to increase our knowledge of this cementing substance.Combs of V. orientalis were collected from fields in the Tel-Aviv district in 1987 during the active season, which extends over most of the summer months. Because the combs are easily damaged, care was taken to remove them intact from the natural nest. Once removed, the combs were cleared of the existing brood (eggs, larvae, or pupae) and then stored carefully in dry glass vessels until examined. For the present study, combs were collected only from nests in Khamra soil, which is common in the Tel-Aviv district and along the coastal area of Israel. To investigate the morphology of the cement material in the comb, strips of comb wall as well as segments of the pupal silk dome were removed from each comb and prepared for examination. The comb wall strips were cut to a size of 3 × 6 mm and fastened to the stub of a scanning electron microscope (SEM). The silk pieces were processed in two ways: (1)strips of 3 × 4 mm were fastened onto a stub with the convex (outer surface) facing up or (2) with the concave (interior) side upward.Silk strips were boiled for 2 hours in distilled water to remove all impurities, such as foreign matter adhering to the silk secreted by the larvae. Examination of these silk fibres was carried out in the three ways: (1)SEM micrography of the exterior (white portion) of the silk dome; (2) micrography of the interior; (3) micrography of both exterior and interior aspects after boiling for 2 hours in distilled water to remove water-suspended foreign materials that may have clung to the silk dome in the course of ordinary nest activity.The chemical composition of selected specimens was investigated by x-ray analysis. They were done on JEOL 840 Scanning Electron Microscope (SEM) equipped with Link 10,000 Energy-Dispersive System (EDS). (With the EDS System, the spectrometer separates the elements according to energy rather than wavelength). Quantitative analysis was by ZAF4 program. Five strips of comb cell wall were examined from a randomly selected comb, each comb from a different nest. Micrographs were taken of isolated silk samples from each of the examined combs.

Notes: Morphological, mineralogical, and chemical investigations were undertaken to determine the structure and composition of the cell walls of the comb in the nest of Vespa orientalis, Paravespula germanica, and Vespacrabro. Nests of V. orientalis were from three sites having different soil types, namely, Khamra soil, Gramosol soil, and organically rich soil from the city dump in Tel Aviv. Nests of P. germanica were from areas rich in organic matter, and those of V. crabro, shipped from Austria, were similarly comprised of organic matter. Structure and composition of cell walls in the three species differed; furthermore, grain size in the combs differed from that of particles in the surrounding soil.

Notes: Scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDS) have been used to study the internal micromorphology of the frons plate in the Oriental hornet, Vespa orientalis. A conical shaped organ was described which is recessed into the frons plate and projects toward the interior of the acoustic box. The latter is located on the inner side of the frons plate. On the exterior of the conical region are observed aggregates containing Ca and Si, and a thin transparent membrane bearing a hole in its center. The innermost surface of the conical structure terminates bluntly as a convex lentiform tip, bearing a transparent oval-shaped window in its center. The conical organ, excepting the window, is enclosed in several layers of epithelium.The structure of this many-layered conical organ is highly complex; its numerous sub-structures and the possible role as a gravity sense organ are discussed. © 1993 Wiley-Liss, Inc.

Notes: The one-component steady-state permeation of gases through a silicalite-1 zeolite composite membrane as a function of the temperature is studied from 190 to 680 K for light hydrocarbons, noble gases, and some inorganic gases. In general, with increasing temperature the permeance shows a maximum followed by a minimum. For gases weakly adsorbed the permeance has only a minimum and for gases strongly adsorbed only a maximum is observed in the permeance. The permeance for various gases, for a feed pressure of 101 kPa, span four orders of magnitude. The lowest permeation is for i-butane at 300 K: a permeance of 0.07 × 10-8 mol. m-2.s-1.Pa-1. The highest value is observed for methane: a permeance of 70 × 10-8 mol. m-2.s-1.Pa-1 at about 240 K. A comparison between the isobars and the temperature dependence of the steady-state permeance, both at 101 kPa, shows that at the temperature where the amount adsorbed vanishes the permeance starts to increase. The temperature dependence of the steady-state fluxes through the silicalite-1 membrane can be described only if two diffusion mechanisms are taken into account. For high occupancies the mass transport can be described by equilibrium adsorption followed by surface diffusion and for low occupancies the mass transport can be described by activated gaseous diffusion. With increasing temperature the mass-transport mechanism shifts from the surface diffusion regime to the activated gaseous diffusion regime. With these two diffusivities modeling results agree well with experimental results for the one-component flux through the silicalite-1 zeolite membrane.

Notes: Morphological aspects of the evolution of a gas - solid interface during typical CVD processes are presented, as well as a continuum model of CVD growth. A linear stability analysis used determines the effect of reactor conditions on the stability of planar growth. The main focus, however, is numerical solution of governing equations under a wide variety of conditions and with different initial interface shapes as starting point. Simplified solutions under specific deposition conditions and the numerical procedure for solving the complete system of equations are presented. The focuses are on the use of a parametrization that eliminates numerical problems encountered with steep interface gradients and the automatic generation of an adaptive mesh for the domain above the interface. Several examples illustrate the numerical solution procedure. To our knowledge, this is the first attempt to simulate interface evolution during CVD for long deposition times from various initial interface shapes. The simulation revealed several morphological phenomena observed experimentally in previous studies, including the formation of occlusions that contributes to film porosity and was clearly shown by the numerical results. Film uniformity strongly depends on the controlling mechanism of deposition. Severe nonuniformities develop under diffusional limitations, while deposition is very uniform under conditions of kinetics control. Film uniformity could be improved by choosing conditions for which a Damköhler number of deposition, Da, would have the lowest value.

Notes: Sedimentation and consolidation of suspensions of fine particles were analyzed by integrating experimental measurement of properties in a centrifuge with a comprehensive numerical model. The yield stress and settling velocity for tailings from tar sands extraction were determined experimentally as a function of the volume fraction of solids. The evaluated state functions were used to simulate batch settling and consolidation, and the results compare well with long-term settling tube tests. This approach is very attractive where gravity sedimentation may take many years, and it allows prediction of the rate of clear water production, total time for sedimentation and consolidation, and the maximum concentration of solids.Scaling of the sedimentation between centrifuge and field conditions is discussed. Conversion of permeability-void ratio relationships from geotechnical experiments to state functions of hindered settling velocity is demonstrated, allowing the use of data derived from a variety of experimental techniques.

Notes: The oxidation of CO by O2 and N2O over an oxidized 10 wt. % Cu-Cr/Al2O3 catalyst (Cu:Cr=1:1) has been studied by temperature-programmed reactivity measurements (400-550 K) over a wide range of partial reactant pressures, including inhibition by CO2. The CO oxidation rate is zeroth-order in oxygen and has orders between 0-1 in CO and N2O, depending on the gas-phase composition. Mechanistic information from literature combined with the kinetic data resulted in the selection of an Eley-Rideal-type of kinetic model without a priori assumptions on rate-determining processes. The model consists of the oxidation of reduced sites by O2 and/or N2O, followed by a reaction with CO, yielding a surface intermediate that releases CO2 in a consecutive step. CO2 inhibits both by reversible adsorption on oxidized and reduces sites, the latter under formation of the surface reaction intermediate. Apart from the surface oxidation by O2, the reaction rates of all assumed elementary processes are of the same order of magnitude and, therefore, determine the overall rate. The surface oxidation by oxygen is about four orders of magnitude larger, which explains the zeroth-order in oxygen and the observation that oxygen first reacts with CO before N2O is able to oxidize CO. The obtained activation energies of the elementary processes agree with values in the literature for corresponding systems.

Notes: The morphology of the gas-solid interface during typical chemical vapor deposition (CVD) processes is investigated. The dynamic behavior of the interface depends on many factors, including local curvature of the film, reactant diffusion, adsorption equilibrium, surface kinetics, and mobility of adatoms. These factors depend on material properties of the system and reactor conditions, such as the deposition temperature and pressure. A 2-D model proposed describes the evolution of the interface in Cartesian coordinates under the influence of stabilizing and destabilizing effects. A linear stability analysis is used to predict under which conditions a planar interface becomes unstable. Stability criteria of a simplified 1-D analysis is not necessarily valid if the real system has more than one dimension. The substrate temperature and reactor pressure are important factors affecting the stability of film growth and thus the morphology of CVD films. An increase in temperature stabilizes planar film growth if the deposition is diffusion-limited, but destabilizes it if the process is reaction-controlled. The reactor pressure has a destabilizing effect on planar film growth during a typical CVD process.