THE EFFECT OF IMPREGNATED GLASS FIBERS ON THE FLEXURAL STRENGTH OF ACRYLIC AND COMPOSITE RESIN: AN IN-VITRO STUDY

Objective: The aim of this in-vitro study is to compare flexural strength of polymethyl methacrylate (PMMA) and bis-acryl composite (BAC) resin material reinforced with impregnated glass fibers. Materials and Methods: Two groups of rectangular test specimens (n=20) were fabricated. One group contained PMMA acrylic and the other contained bis-acryl composite resin material. The experimental groups contained impregnated glass fiber reinforcement and the non-reinforced group served as the control. Flexural strength of the specimens was measured by a universal testing machine until fracture. The mean flexural strength (N) was compared by a two way ANOVA test and followed by a simple main effect, using a significance level of 0.05. Results: For reinforced groups, the mean flexural strength of PMMA resin increased from 349.4N (+/- 23.4) to 613.6N (+/-54.2). For BAC resin, the mean flexural strength increased from 513.6N (+/-103.1) to 603.5N (+/-50.5). Reinforced PMMA resin was highly significant (p<0.001) compared to BAC resin (p=0.150). At the non-reinforced control groups, the flexural strength BAC resin was significantly higher than PMMA resin group (p=0.036). Conclusion: Although impregnated glass fiber increased the flexural strength of both PMMA and BAC groups, it was significantly higher for PMMA resin. At the non-reinforced control groups, the flexural strength of BAC resin was significantly higher than PMMA

Field Analytical Technology Verification: The ETV Site Characterization Program

Innovative field characterization and monitoring technologies are often slow to be adopted by the environmental engineering/consulting community because of concerns that their performance has not been proven by an independent testing body, and/or they have not received the EPA`s blessing on a regional or national level. The purpose of the EPA Environmental Technology Verification (ETV) Site Characterization Pilot, a joint effort between EPA and DOE, is to accelerate the acceptance of technologies that reduce the cost and increase the speed of environmental clean-up and monitoring. Technology verifications that have been completed or are underway include: in situ technologies for the characterization of sub-surface hydrocarbon plumes, field-portable GC/MS systems, field-portable X-ray fluorescence analyzers, soil sampling technologies, field-portable PCB analyzers, analyzers for VOC analysis at the wellhead, and decision support software systems to aid site sample collection and contaminant plume definition. The verification process follows a somewhat generic pathway. A user-community need is identified, the vendor community is canvassed, and relevant, interested companies are selected. A demonstration plan is prepared by the verification organization and circulated to participants prior to the field activities. Field trials are normally held at two geologically or environmentally different sites and typically require one week at each site. Samples (soil, soil gas, water, surface wipe etc.) provided to the vendor at the demonstration include site-specific samples and standards or performance evaluation samples. Sample splits are sent to a pre-selected laboratory for analysis using a reference method. Laboratory data are used for comparison with field technology results during the data analysis phase of the demonstration

Spatial scaling of forest soil microbial communities across a temperature gradient.

Temperature is an important correlate of global patterns of biodiversity, yet the mechanisms driving these relationships are not well understood. Taxa-area relationships (TARs) have been intensively examined, but the effects of temperature on TARs, particularly for microbial communities, are largely undocumented. Here we present a continental-scale description of temperature-dependent nested TARs of microbial communities (bacteria and archaea) from soils of six forest sites spanning a temperature gradient from subalpine Colorado to tropical Panama. Our results revealed that spatial scaling rates (z-values) of microbial communities varied with both taxonomic resolutions and phylogenetic groups. Additionally, microbial TAR z-values increased with temperature (r = 0.739, P &lt; 0.05), but were not correlated with other environmental variables tested (P &gt; 0.05), indicating that microbial spatial scaling rate is temperature-dependent. Understanding how temperature affects the spatial scaling of microbial biodiversity is of fundamental importance for preservation of soil biodiversity and management of ecosystems

Scientific Opinion addressing the state of the science on risk assessment of plant protection products for in-soil organisms

Following a request from EFSA, the Panel on Plant Protection Products and their Residues developed an opinion on the science behind the risk assessment of plant protection products for in-soil organisms. The current risk assessment scheme is reviewed, taking into account new regulatory frameworks and scientific developments. Proposals are made for specific protection goals for in-soil organisms being key drivers for relevant ecosystem services in agricultural landscapes such as nutrient cycling, soil structure, pest control and biodiversity. Considering the time-scales and biological processes related to the dispersal of the majority of in-soil organisms compared to terrestrial non-target arthropods living above soil, the Panel proposes that in-soil environmental risk assessments are made at in- and off-field scale considering field boundary levels. A new testing strategy which takes into account the relevant exposure routes for in-soil organisms and the potential direct and indirect effects is proposed. In order to address species recovery and long-term impacts of PPPs, the use of population models is also proposed