Single point aerosol sampling: Evaluation of mixing and probe performance in a nuclear stack

Alternative Reference Methodologies (ARMS) have been developed for sampling of radionuclide; from stacks and ducts that differ from the methods required by the US EPA. The EPA methods are prescriptive in selection of sampling locations and in design of sampling probes whereas the alternative methods are performance driven. Tests were conducted in a stack at Los Alamos National Laboratory to demonstrate the efficacy of the ARMS. Coefficients of variation of the velocity tracer gas, and aerosol particle profiles were determined at three sampling locations. Results showed numerical criteria placed upon the coefficients of variation by the ARMs were met at sampling stations located 9 and 14 stack diameters from flow entrance, but not at a location that is 1.5 diameters downstream from the inlet. Experiments were conducted to characterize the transmission of 10 {mu}m aerodynamic equivalent diameter liquid aerosol particles through three types of sampling probes. The transmission ratio (ratio of aerosol concentration at the probe exit plane to the concentration in the free stream) was 107% for a 113 L/min (4-cfm) an isokinetic shrouded probe, but only 20% for an isokinetic probe that follows the EPA requirements. A specially designed isokinetic probe showed a transmission ratio of 63%. The shrouded probe performance would conform to the ARM criteria; however, the isokinetic probes would not

Trail Marking by Caterpillars of the Silverspot Butterfly Dione Juno Huascuma

A pheromone is implicated in the trail marking behavior of caterpillars of the nymphalid silverspot butterfly, Dione juno huascuma (Reakirt) (Lepidoptera: Heliconiinae) that feed gregariously on Passiflora (Malpighiales: Passifloraceae) vines in Mexico. Although they mark pathways leading from one feeding site to another with silk, this study shows that the silk was neither adequate nor necessary to elicit trail following behavior. Caterpillars marked trails with a long-lived pheromone that was deposited when they brushed the ventral surfaces of the tips of their abdomens along branch pathways. The caterpillars distinguished between pathways deposited by different numbers of siblings and between trails of different ages. Caterpillars also preferentially followed the trails of conspecifics over those of another nymphalid, Nymphalis antiopa L., the mourning cloak butterfly

External Morphology and Ultra-Structure of Eggs and First Instar of Prepona Laertes Laertes (Hübner, [1811]), with Notes on Host Plant use and Taxonomy

The external morphology and the tegument ultra-structure of Prepona laertes laertes (Hübner, [1811]) (Lepidoptera: Nymphalidae: Charaxinae) eggs and first instar larvae feeding on Inga spp. (Fabaceae) in a forest fragment in Joinville, Santa Catarina, Brazil, are described. Descriptions of the morphology with illustrations are presented, based upon observations through scanning electron microscopy and stereoscopic and optic microscopes attached to a camera lucida. Descriptions and illustrations of the head capsule, chaetotaxy, tegument, and setae are presented. The taxonomy, morphological characters, and host plant use of Prepona laertes immature stages are discussed

Is avian predation so important in keeping down butterfly populations?

Volume: 88Start Page: 283End Page: 28

Notes on Caligo memnon Felder and Caligo atreus Kollar (Lepidoptera: Nymphalidae: Brassolinae) in Costa Rica and El Salvador

Volume: 24Start Page: 154End Page: 17

Modeling of transient ionizing radiation effects in bipolar devices at high dose-rates

To optimally design circuits for operation at high intensities of ionizing radiation, and to accurately predict their a behavior under radiation, precise device models are needed that include both stationary and dynamic effects of such radiation. Depending on the type and intensity of the ionizing radiation, different degradation mechanisms, such as photoelectric effect, total dose effect, or single even upset might be dominant. In this paper, the authors consider the photoelectric effect associated with the generation of electron-hole pairs in the semiconductor. The effects of low radiation intensity on p-II diodes and bipolar junction transistors (BJTs) were described by low-injection theory in the classical paper by Wirth and Rogers. However, in BJTs compatible with modem integrated circuit technology, high-resistivity regions are often used to enhance device performance, either as a substrate or as an epitaxial layer such as the low-doped n-type collector region of the device. Using low-injection theory, the transient response of epitaxial BJTs was discussed by Florian et al., who mainly concentrated on the effects of the Hi-Lo (high doping - low doping) epilayer/substrate junction of the collector, and on geometrical effects of realistic devices. For devices with highly resistive regions, the assumption of low-level injection is often inappropriate, even at moderate radiation intensities, and a more complete theory for high-injection levels was needed. In the dynamic photocurrent model by Enlow and Alexander. p-n junctions exposed to high-intensity radiation were considered. In their work, the variation of the minority carrier lifetime with excess carrier density, and the effects of the ohmic electric field in the quasi-neutral (q-n) regions were included in a simplified manner. Later, Wunsch and Axness presented a more comprehensive model for the transient radiation response of p-n and p-i-n diode geometries. A stationary model for high-level injection in p-n junctions was developed by Isaque et al. They used a more complete ambipolar transport equation, which included the dependencies of the transport parameters (ambipolar diffusion constant, mobility, and recombination rate) on the excess minority carrier concentration. The expression used for the recombination rate was that of Shockley-Reed-Hall (SRH) recombination which is dominant for low to mid-level radiation intensities. However, at higher intensities, Auger recombination becomes important eventually dominant. The complete ambipolar transport equation including the complicated dependence of transport parameters on the radiation intensity, cannot be solved analytically. This solution is obtained for each of the regimes where a given recombination mechanism dominates, and then by joining these solutions using appropriate smoothing functions. This approach allows them to develop a BJT model accounting for the photoelectric effect of the ionizing radiation that can be implemented in SPICE