ATMOSPHERIC DEPOSITION OF CHEMICAL SPECIES TO POLAR SNOW

Particles and gases can deposit from the atmosphere to polar snow by several mechanisms. Dry deposition can be considered to consist of three steps: aerodynamic transport from the free atmosphere to the viscous sublayer near the surface, boundary layer transport across the sublayer, and interactions with the surface. The particle dry deposition mass flux is dominated by the largest particles present in a size distribution. Wet deposition includes in-cloud and below-cloud scavenging, where the former refers to uptake of particles during nucleation of cloudwater as well as scavenging of particles and gases by existing droplets and ice crystals. Of all the wet deposition mechanisms, nucleation scavenging is often the most important mechanism for particles in the polar regions. Finally, incorporation of particles and gases into fog droplets and subsequent settling of the fog to the snow surface can be an important removal process in regions of frequent fog. For Summit, Greenland, the total deposition of MSA, SO₄^2-, Na⁺, K⁺, and Ca²⁺ during May 24-July 13, 1993 was dominated by wet deposition: this mechanism accounted for an average of 62% of the total deposition for these species. Fog and dry deposition accounted for 21% and 17% of the total, respectively. These results suggest that all three mechanisms may need to be considered when estimating total deposition of certain chemical species to polar snow.     

An overview of the Real-Time CORBA specification

A growing class of real-time systems require end-to-end support for various quality-of-service (QoS) aspects, including bandwidth, latency, jitter and dependability. Applications include command and control, manufacturing process control, videoconferencing, large-scale distributed interactive simulation, and testbeam data acquisition. These systems require support for stringent QoS requirements. To meet this challenge, developers are turning to distributed object computing middleware, such as the Common Object Request Broker Architecture, an Object Management Group (OMG) industry standard. In complex real-time systems, DOC middleware resides between applications and the underlying operating systems, protocol stacks and hardware. CORBA helps decrease the cycle time and effort required to develop high-quality systems by composing applications using reusable software component services rather than building them entirely from scratch. The Real-Time CORBA specification includes features to manage CPU, network and memory resources. The authors describe the key Real-Time CORBA features that they feel are the most relevant to researchers and developers of distributed real-time and embedded systems     

Eucalyptol is an Attractant of the Redbay Ambrosia Beetle,Xyleborus Glabratus

The redbay ambrosia beetle, Xyleborus glabratus, is an invasive wood-boring beetle that has become established in the southeastern United States. The beetle transmits the causal pathogen of lethal laurel wilt to susceptible host trees, which include redbay, an important forest community species, and avocado, a valuable food crop. By examining odors of redbay wood, we developed an artificial lure that captured X. glabratus in redbay forests. Eucalyptol was a critical component of the blend for beetle attraction, and eucalyptol alone in large quantities attracted X. glabratus. Furthermore, eucalyptol stimulated boring by X. glabratus into paper arenas. The results suggest that eucalyptol contributes to host selection behavior of X. glabratus and may be useful for management of this pathogen vector.     

Use of quantitative assays for hepatitis B e antigen and IgM antibody to hepatitis B core antigen to monitor therapy in chronic hepatitis B

OBJECTIVES: We evaluated the clinical utility of IgM antibody to the hepatitis B (HB) core antigen (anti-HBc) and HB e antigen (HBeAg) serum levels in patients with chronic HB receiving interferon alfa. METHODS: Stored serum from 47 patients with chronic HB participating in a controlled trial of interferon alfa therapy (10 million U three times a week for 16 wk) were analyzed. All were seropositive for HB surface Ag, HBeAg, and HB virus (HBV) DNA before entry. IgM anti-HBc index values and HBeAg standard values were determined by automated microparticle enzyme immunoassay on samples drawn just before therapy and 6 months later. Ten normal subjects were tested as controls. IgM anti-HBc and HBeAg levels were compared to initial serum HBV DNA, DNA polymerase, serum aminotransferase levels, and demographic features. Serial IgM anti-HBc levels were also obtained during and after therapy in 10 responders and five nonresponders, and serial HBeAg levels were also obtained during and after therapy in four responders and four nonresponders. RESULTS: Neither IgM anti-HBc nor HBeAg levels correlated significantly with values for serum HBV DNA, DNA polymerase, aminotransferases, or demographic features. The initial mean IgM anti-HBc level among the 15 responders to therapy (loss of HBeAg and HBV DNA from serum) was no different from that in nonresponders (mean 1.15 vs 1.27, p = not significant). However, the initial mean HBeAg level was significantly lower in responders than in nonresponders (749.4 vs 1356.4, p = 0.019). Among 10 responders, IgM anti-HBc levels decreased progressively over time, so that at latest follow-up (1.5-4 yr later, mean 2.6 yr), the mean had decreased from 1.325 to 0.312 (p = < 0.001). Among five nonresponders, the mean did not change significantly over 1.5-3 yr (mean 2.2 yr) (1.26 vs 1.08, p = not significant). HBeAg values fell in parallel with HBV DNA and DNA polymerase values in four responders tested but remained elevated in four nonresponders. CONCLUSIONS: HBeAg levels, but not IgM anti-HBc levels, are useful in predicting response to interferon alfa, with responders tending to have lower pretreatment HBeAg levels than nonresponders. HBeAg levels may be used to monitor response to interferon alfa in patients with chronic HB.     

Fiberoptic transillumination: a new tool for the pediatric surgeon

Transillumination (TI) is a safe and reliable technique for evaluating masses or the presence of free air in the thorax or abdomen. TI can also be of help in the accurate placement of catheters or needles in the chest, abdomen, bladder, or vessels. Its use in several hundred cases has been documented by this report.     

Disruption of Vector Host Preference with Plant Volatiles May Reduce Spread of Insect-Transmitted Plant Pathogens

Plant pathogens can manipulate the odor of their host; the odor of an infected plant is often attractive to the plant pathogen vector. It has been suggested that this odor-mediated manipulation attracts vectors and may contribute to spread of disease; however, this requires further broad demonstration among vector-pathogen systems. In addition, disruption of this indirect chemical communication between the pathogen and the vector has not been attempted. We present a model that demonstrates how a phytophathogen (Candidatus Liberibacter asiaticus) can increase its spread by indirectly manipulating the behavior of its vector (Asian citrus psyllid, Diaphorina citri Kuwayama). The model indicates that when vectors are attracted to pathogen-infected hosts, the proportion of infected vectors increases, as well as, the proportion of infected hosts. Additionally, the peak of infected host populations occurs earlier as compared with controls. These changes in disease dynamics were more important during scenarios with higher vector mortality. Subsequently, we conducted a series of experiments to disrupt the behavior of the Asian citrus psyllid. To do so, we exposed the vector to methyl salicylate, the major compound released following host infection with the pathogen. We observed that during exposure or after pre-exposure to methyl salicylate, the host preference can be altered; indeed, the Asian citrus psyllids were unable to select infected hosts over uninfected counterparts. We suggest mechanisms to explain these interactions and potential applications of disrupting herbivore host preference with plant volatiles for sustainable management of insect vectors.     

Comparison of Automated Image-Based Grain Sizing to Standard Pebble-Count Methods

This study explores the use of an automated image-based method for characterizing grain-size distributions (GSDs) of exposed open-framework gravels by comparing the GSDs measured with the image-based method to distributions obtained with two pebble-count methods. Selection of grains for the two pebble-count methods was carried out using a gridded sampling frame and the heel-to-toe Wolman walk method at six field sites. At each site, 500-particle pebble-count samples were collected with each of the two pebble-count methods and digital images were systematically collected over the same sampling area. For the methods used, pebble counts collected with the gridded sampling frame were assumed to be the most accurate representations of the true grain-size population. Therefore, results from the image-based method were compared to the grid-derived GSDs for accuracy estimates; comparisons between the grid and Wolman walk methods were conducted to give an indication of possible variation between commonly used methods for the particular field sites used in the study. The grain-size comparisons were made at two spatial scales. At the larger scale, results from the image-based method were integrated over the sampling area required to collect the 500-particle pebble-count samples. At the smaller sampling scale, the image derived GSDs were compared to those from 100-particle, pebble-count samples obtained with the gridded sampling frame. The comparison shows that the image-based method performed reasonably well on five of the six study sites. For those five sites, the image-based method slightly underestimated all grain-size percentiles relative to the pebble counts collected with the gridded sampling frame, but the method performed well in estimating the median grain size (the average bias for ψ5, ψ50, and ψ95 was 0.07ψ, 0.04ψ, and 0.19ψ, respectively). The Wolman pebble-counts yielded coarser results than the pebble counts obtained with the gridded sampling frame, especially for the smaller percentiles (the average bias for ψ5, ψ50, and ψ95 was 0.20ψ, 0.16ψ, and 0.04ψ, respectively). Oversegmentation of large pitted grains in the image-analysis procedures was identified as a leading cause for failure of the image-based method at one of the sites. It is likely that lower degrees of oversegmentation and physical particle orientation contributed to the slight underestimation of all grain-size percentiles in the image-based method.     

Inhibition of aflatoxin production inAspergillus flavus infected cotton bolls after treatment with neem (Azadirachta indica) leaf extracts

In separate treatments, a spore suspension ofA. flavus (control), an aqueous leaf extract of the subtropical neem tree plus a spore suspension ofA. flavus, or an aqueous neem leaf extract followed by anA. flavus spore suspension were injected 48 hr later onto the surfaces of locks of developing cotton bolls (30-day post anthesis). Thirteen days after the treatments, the seeds from the locules were harvested and both fungal growth and aflatoxin production were determined. Fungal growth was unaffected by the treatments but the seeds from locules receiving both neem leaf extracts andA. flavus simultaneously exhibited 16% inhibition of aflatoxin production, while the seeds in locules receivingA. flavus spores 48 hr after neem extract was added exhibited >98% inhibition in aflatoxin production. Neem leaf extracts contain an aflatoxin inhibiting factor, however, the neem leaf extract may need to translocate from the fibrous locule surface to the seed, prior to the fungal inoculation, for maximal effect.