An innovative approach for locating and evaluating subsurface pathways for nitrogen loss.

Fundamental watershed-scale processes governing chemical flux to neighboring ecosystems are so poorly understood that effective strategies for mitigating chemical contamination cannot be formulated. Characterization of evapotranspiration, surface runoff, plant uptake, subsurface preferential flow, behavior of the chemicals in neighboring ecosystems, and an understanding of how crop management practices influence these processes are needed. Adequate characterization of subsurface flow has been especially difficult because conventional sampling methods are ineffective for measuring preferential flow of water and solutes. A sampling strategy based on ground-penetrating radar (GPR) mapping of subsurface structures coupled with near real-time soil moisture data, surface topography, remotely sensed imagery, and a geographic information system (GIS) appears to offer a means of accurately identifying subsurface preferential flow pathways. Four small adjacent watersheds draining into a riparian wetland and first-order stream at the USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD are being studied with this protocol. The spatial location of some preferential flow pathways for chemicals exiting these agricultural watersheds to the neighboring ecosystems have been identified. Confirmation of the pathways is via examination of patterns in yield monitor data and remote sensing imagery.

Surface and subsurface nitrate flow pathways on a watershed scale.

Determining the interaction and impact of surface runoff and subsurface flow processes on the environment has been hindered by our inability to characterize subsurface soil structures on a watershed scale. Ground penetrating radar (GPR) data were collected and evaluated in determining subsurface hydrology at four small watersheds in Beltsville, MD. The watersheds have similar textures, organic matter contents, and yield distributions. Although the surface slope was greater on one of the watersheds, slope alone could not explain why it also had a nitrate runoff flux that was 18 times greater than the other three watersheds. Only with knowledge of the subsurface hydrology could the surface runoff differences be explained. The subsurface hydrology was developed by combining GPR and surface topography in a geographic information system. Discrete subsurface flow pathways were identified and confirmed with color infrared imagery, real-time soil moisture monitoring, and yield monitoring. The discrete subsurface flow patterns were also useful in understanding observed nitrate levels entering the riparian wetland and first order stream. This study demonstrated the impact that subsurface stratigraphy can have on water and nitrate (NO3-N) fluxes exiting agricultural lands, even when soil properties, yield distributions, and climate are similar. Reliable protocols for measuring subsurface fluxes of water and chemicals need to be developed.

Impact of a first-order riparian zone on nitrogen removal and export from an agricultural ecosystem.

Riparian zones are reputed to be effective at preventing export of agricultural groundwater nitrogen (N) from local ecosystems. This is one impetus behind riparian zone regulations and initiatives. However, riparian zone function can vary under different conditions, with varying impacts on the regional (and ultimately global) environment. Rates of groundwater delivery to the surface appear to have significant effects on the N-removing capabilities of a riparian zone. Research conducted at a first-order agricultural watershed with a well-defined riparian zone in the Maryland coastal plain indicates that more than 2.5 kg/day of nitrate-N can be exported under moderate-to-high stream baseflow conditions. The total nitrate-N load that exits the system increases with increasing flow not simply because of the greater volume of water export. Stream water nitrate-N concentrations also increase by more than an order of magnitude as flow increases, at least during baseflow. This appears to be largely the result of changes in dominant groundwater delivery mechanisms. Higher rates of groundwater exfiltration lessen the contact time between nitrate-carrying groundwater and potentially reducing riparian soils. Subsurface preferential flow paths, in the wetland and adjacent field, also strongly influence N removal. Simple assumptions regarding riparian zone function may be inadequate because of complexities observed in response to changing hydrologic conditions.

Herpesvirus protease assays.

Herpesviruses encode a serine protease that is essential for the maturation of viral capsids (1,2). The protease is expressed as part of a polyprotein. The catalytic domain is contained within the N-terminal third of the protein, and the remainder comprises a structural "scaffold" protein. The scaffold protein is independently expressed in excess to the polyprotein from an internal initiation codon. The protease cleaves the polyprotein at two sites: one at the c-terminus of the protease catalytic domain, the release or R-site, and the other close to the c-terminus of the scaffold protein, the maturation or M-site (Fig. 1). Cleavage of the M-site follows assembly of the viral procapsids and precedes packaging of the viral DNA. The M-site sequence is conserved among the herpesviruses and has a consensus sequence (V/L)-X-A-S, with cleavage between A-S (3). Structural studies have shown that the herpesvirus proteases have a novel structure, and their essential role in capsid maturation makes them a potential target for antiviral intervention. Fig. 1. Cartoon illustration of the structure of the herpesvirus protease/scaffold polyprotein showing the position of the protease catalytic domain, the scafold protein, and the release and maturation cleavage sites.

Localized juvenile periodontitis: a case analysis and rational approach to treatment.

This case involves a 14-year-old female patient affected with localized juvenile periodontitis. Treatment consisted of periodontal flap surgery in conjunction with tetracycline therapy. A successful result was obtained and maintained. The case depicts the fact that in many instances localized juvenile periodontitis can be treated with confidence and a high degree of predictability. It should also be noted that, like all treatment modalities, the treatment of this disease as discussed in this case is not the panacea and will undergo considerable changes in the future; however, in light of current knowledge, this combined treatment approach appears to be effective in LJP patients.

Use of the PDQ system in a clinical setting.

This pilot study examined the use of PDQ (Physician Data Query)--a user-friendly, full-text, cancer database--as a clinical information resource on an oncology unit. The twenty-nine participants included faculty, hematology-oncology fellows, residents, interns, medical students, pharmacists, and nursing staff. During the one-month study, PDQ was available twenty-four hours a day at the nursing station via a microcomputer. Participants were trained to use PDQ and allowed to search the database as prompted by clinical situations. The project evaluated the use of PDQ, as well as clinicians' perceptions of its usefulness. Results indicate that access to PDQ on an oncology unit provides an excellent educational and clinical resource. Fifty-one percent of the participants used PDQ an average of 2.4 times each. Heaviest users were medical trainees (78%), although 39% of nurses became users. Over half of the PDQ users reported that use of the database affected clinical care.

Issues in consumer mental health information.

Consumer health information as applied to mental health includes areas such as the diagnosis, management, and treatment of mental illness, as well as self-help, emotional wellness, and the relationship between life events, stress, and disease. This paper presents issues specific to the provision of mental health information to the layperson, e.g., confidentiality, literacy, competence, the social stigma of mental illness, the state of the art in psychiatry, popular psychology, and treatment fads. The development of a community education pamphlet illustrates how one organization addressed these issues.