CONTEXTUALIZING LEARNING OBJECTS USING ONTOLOGIES

Educational research over the past three years has intensified such that the context of learning resources needs to be properly modeled. Many researchers have described and even mandated the use of ontologies in the research being conducted, yet the process of actually connecting one or more ontologies to a learning object has not been extensively discussed. This paper describes a practical model for associating multiple ontologies with learning objects while making full use of the IEEE LOM specification. The model categorizes these ontologies according to five major categories of context based on the most popular fields of study actively being pursued by the educational research community: Thematic context, Pedagogical context, Learner context, Organizational context, and Historical/Statistical context.     

The application of the polyaromatic sulfonates as tracers in geothermal reservoirs

Five polyaromatic sulfonate compounds, 1,3,6,8-pyrene tetrasulfonate, 1,5-naphthalene disulfonate, 1,3,6-naphthalene trisulfonate, 2-naphthalene sulfonate, and 2,7-naphthalene disulfonate, were tested for use as geothermal tracers. They were subjected to a simulated hydrothermal environment in batch autoclave reactors in order to determine their thermal decay kinetics. The decay kinetics study indicated that all of the compounds are suitable for use in reservoirs having temperatures up to 310 °C, whereas some are suitable for use in reservoirs as hot as 350 °C. Methods were developed for the chemical analysis of the polyaromatic sulfonates and their detection limits were shown to be approximately 200 parts per trillion by conventional high-performance liquid chromatography. The tracers were successfully tested in a series of field studies at Dixie Valley, Nevada; Steamboat Springs, Nevada; Ohaaki, New Zealand; and Awibengkok, Indonesia.     

Molecular characterization of low-level vancomycin-resistant enterococci found in coastal water of Thermaikos Gulf, Northern Greece

Enterococcus includes species that may pose emerging health risks and has been used as biomarkers for environmental contamination while little is known concerning their occurrence in marine water. Classification of enterococci in environmental samples can be problematic and requires polyphasic taxonomy. In this study, we investigated the presence of vancomycin-resistant enterococci (VRE) in the inner bay of Thermaikos Gulf in Northern Greece. Based on physiological and biochemical criteria, 121 presumptive enterococcal strains were identified. High-level VRE were undetectable in seawater and only 35 vancomycin gene-negative strains possessed low-level vancomycin resistance. Genotyping by pulsed field gel electrophoresis (PFGE) proved to be more reliable for marine enterococcal discrimination and revealed distinguished characteristics of the seawater enterococci, indicating high genetic diversity. Random amplified polymorphic DNA-PCR (RAPD-PCR) was unable to separate distinct species analyzed in this study. This study indicates the need of polyphasic taxonomy for seawater enterococcal species' identification and provides information for future biomonitoring programs of Thermaikos Gulf.     

Hydrofluorocarbons as geothermal vapor-phase tracers

Two hydrofluorocarbons, R-134a and R-23, have been developed for use as a vapor-phase tracer in geothermal systems. These low molecular weight compounds are volatile, electrically neutral, nontoxic, relatively inexpensive, and have detection limits as low as 10⁻⁵ ppm. Data from laboratory and field tests indicate that they are stable enough to be used as tracers in vapor-dominated systems such as The Geysers. However, these compounds have a higher volatility than water, which affects the rate of transfer of the tracer from the liquid injectate to reservoir steam during boiling. Simple analytic models of boiling were used to estimate the effects of the high tracer volatilities on the outcome of tracer tests in vapor-dominated systems. The results imply that the effects of volatility are exaggerated under conditions of high superheat, which promote the continuous removal of steam from the vicinity of the boiling interface. In contrast, low to moderate superheat reduces the effects of volatility to the extent that the volatile-tracer test results qualitatively resemble those in which tritiated water is used as a tracer. Thus, volatile tracers can be used with confidence to qualitatively describe the distribution of injected water in vapor-dominated systems where superheat is low to moderate.