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Background. The accessibility of the remineralizing ions in teeth's environment is essential for their incorporation into caries-affected dentin. Novel bioglass-reinforced materials capable of releasing fluoride, calcium and phosphates may be particularly useful in the tissue remineralization process. A novel restorative material, ACTIVA BioActive-Restorative (Pulpdent Corp., Watertown, USA), is a hydrophilic resin-modified glassionomer cement (RMGIC) enriched with bioglass particles and fortified with a patented rubberized polymer resin. Its application in restorative dentistry may be significant, promoting remineralization of carious lesions. Objectives. The aim of the study was to compare the fluoride ion release profiles from a bioglass-reinforced RMGIC, a conventional glass-ionomer cement (GIC) and a nanohybrid restorative polymer resin. Material and methods. The quantity of fluoride ions released from ACTIVA, Ketac Molar Quick Aplicap and Tetric EvoCeram was assessed using a fluoride-specific electrode. The surface characteristics of the preand post-experimental specimens were studied using a scanning electron microscope (SEM) and confocal microscope. An X-ray powder diffraction (XRD) analysis was additionally used to examine the chemical compositions of the dental materials. Results. The greatest quantity of fluoride ions was freed from the GIC specimens (20.698-54.118 ppm), followed by the bioglass-reinforced RMGIC (from 1.236 to 15.552 ppm) and nanohybrid polymer resin (0.370-1.148 ppm). The pre-experimental specimens of the bioglass-reinforced RMGIC were porous, while the post-experimental specimens were smoother with visible micro-cracks. The XRD analysis of the bioglass particles confirmed that the material was composed mainly of fluoride (27.70 mass%), silicon (15.62 mass%), aluminum (5.91 mass%), and calcium (5.40 mass%). Conclusions. The fluoride ion release profile of ACTIVA was lower than the GIC Keta Molar Quick Aplicap, but significantly higher than the nanohybrid restorative polymer resin Tetric EvoCeram. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to compare the effect of diode laser, endoActivator, and passive ultrasonics for smear layer removal at the apical third from root canals with 0.2% chitosan. Materials and Methods: A total of 40 mandibular premolars were decoronated to establish a working length of 12 mm and shaped with ProTaper rotary files up to size F3. In Group A, canals were irrigated with 1 ml of 0.2% chitosan. In Group B, canals were initially irrigated with 0.8 ml of 0.2% chitosan and the remaining 0.2 ml was activated with diode laser. In Group C, canals were irrigated with 1 ml of 0.2% chitosan which was activated with endoActivator. In Group D, canals were irrigated with 0.2% chitosan and activated with passive ultrasonics. All samples were finally flushed with 3 ml of distilled water. The percentage of smear layer removal was analyzed with a scanning electron microscope examination at ×1000 and ×3000. Data were analyzed using Statistical Package for the Social Sciences version 16.0 (SPSS Inc., Chicago, IL, USA) at a significance level of P < 0.05. Results: The mean value for Group B when compared to Group C for the removal of smear layer was higher, but there was no statistically significant difference between the two groups (P < 0.068 and P < 0.295). Both Group B and Group C showed a statistically significant difference (P < 0.001) when compared to Group A and Group D for the removal of smear layer. Conclusion: Diode laser and endoActivator with 0.2% chitosan proved better in the removal of the smear layer when compared to passive ultrasonic irrigation. [ABSTRACT FROM AUTHOR]

Quantitative X-ray microanalysis of thick samples is usually performed by measuring the characteristic X-ray intensities of each element in a sample and in corresponding standards. The ratio of the measured intensities from the unknown material to that from the standard is related to the concentration using the ZAF or φ(ρz) equations. Under optimal conditions, accuracies approaching 1% are possible. However, all the experimental conditions must remain the same during the sample and standard measurements. This is not possible with cold field emission scanning electron microscopes (FE-SEMs) where beam current can fluctuate around 5% in its stable regime. Very little work has been done on variable beam current conditions (Griffin, B.J. & Nockolds, C.E., Scanning 13, 307-312, 1991), and none relating to cold FE-SEM applications. To address this issue, a new method was developed using a single spectral measurement. It is similar in approach to the Cliff-Lorimer method developed for the analytical transmission electron microscope. However, corrections are made for X rays generated from thick specimens using the ratio of the characteristic X-ray intensities of two elements in the same material. The proposed method utilizes the ratio of the intensity of a characteristic X-ray normalized by the sum of X-ray intensities of all the elements measured for the sample, which should also reduce the amplitude of error propagation. Uncertainties in the physical parameters of X-ray generation are corrected using a calibration factor that must be previously acquired or calculated. As an example, when this method was applied to the calculation of the composition of Au-Cu National Institute of Standards and Technology standards measured with a cold field emission source SEM, relative accuracies better than 5% were obtained. [ABSTRACT FROM AUTHOR]

Abrading artifacts made of vesicular (porous) rock are not uncommon at archaeological sites along the Missouri River and adjacent areas. Various terms have been used to describe this material including pumice, scoria, clinker, and floatstone. Each of these terms implies different geologic origins (volcanic vs. non-volcanic) and affects interpretation of the potential modes of transport. Identification of the source area of these materials may provide significant information regarding past human movements and activities. This study focuses on vesicular artifacts in the central Plains and in particular from the Leary site (25RH1) in the southeastern corner of Nebraska. Scanning Electron Microscopy (SEM) was used to identify the chemical compositions of a subset of the Leary artifacts and comparative geologic samples of volcanic and metasedimentary origin. The results imply that the Leary (and likely many other) vesicular artifacts from the central Plains are non-volcanic in origin. The raw material from which these artifacts were made is more properly termed "paralava" and derives from outcrops in the northern Plains. Historical documents suggest that this buoyant material was transported naturally by the Missouri River as "floatstone". [ABSTRACT FROM AUTHOR]

Building and evaluating artifacts specifically for K-12 education, technologists committed to design sciences are needed along with an approach to evaluation increasing the systemic transfer from research and development into school settings. The authors describe THE VIRTUAL LAB scanning electronic microscope simulation, including (a) its development from a design and project management perspective at NASA and (b) the formative evaluation, drawing on a usability study conducted in high school science classrooms by University of Central Florida. The authors offer a four-level assessment that begins with the overarching vision that guided developers. Over time, a team of evaluators (a) verify (the artifact), (b) check variation (of content), (c) verify (in context), and (d) document value (in the field of education). THE VIRTUAL LAB usability study is offered as a specific example in the evaluation process using both quantitative and qualitative data while responding and contributing to an overarching vision for education. [ABSTRACT FROM AUTHOR]

Abstract: Recently, there have been several occurrences of failure in the bolt of the Ml6 rifle at a United States Army installation. Near the failure location, the bolt was subjected to repeated loading as the Ml6 was fired. In order to determine the stress distribution of the bolt due to the firing process, a geometric element analysis was performed using ProMechanica®. The fracture surface was examined using both an optical stereomicroscope and a scanning electron microscope in order to determine failure initiation and failure mode. It was discovered that the fracture initiated at a localized corrosion pit and propagated by fatigue. A controlled experiment was conducted where 1800 and 3600 rounds were fired using new bolts. After 1800 rounds, a region of wear was observed near the site where fracture occurred in the failed bolt. After 3600 rounds, a notch was observed in this wear region. This suggests two possibilities: firstly, exposure of the base metal may have facilitated the formation of the observed corrosion pits; and secondly, the presence of a notch may facilitate the fracture of bolts in general. In addition, Vickers microhardness profiles were taken on cross-sectional areas near the fillet region and 10mm away from the failed locking lug. Disparities between microhardness profiles near the fillet region and 10mm away from this region revealed that the bolt may not have been uniformly case hardened. [Copyright &y& Elsevier]

The National Institute of Standard and Technology (NIST) is developing single-crystal reference materials for use as critical dimension (CD) reference materials. In earlier work, the reference features on these reference materials have been in the device layer of a silicon-on-insulator (SOI) wafers, with the buried oxide providing electrical isolation. This paper describes a new method of Slating the structures from the substrate by mews of a pn junction. The junction isolation technique is expected to provide several advantages over the SOI technique Including minimal susceptibility to charging when imaged in a CD scanning electron microscope (CDSEM), better edge quality, and ease of manufacture. Primary calibration of these reference materials is by imaging the cross-section of the feature with high-resolution transmission electron microscopy (HRTEM) at sufficiently high energy to resolve and count the individual lattice planes while electrical test structure metrology techniques provide the transfer calibration. Secondary calibration is performed with electrical test structure metrology, supplemented by visual techniques to verify that the features meet uniformity requirements. In this paper, we describe results for determining the electrical critical dimensions of these junction-isolated structures. This measurement and data analysis technique is a unique combination of the short-bridge variation of the cross-bridge resistor and the multi-bridge structure. [ABSTRACT FROM AUTHOR]

This article presents technical abstracts and notes related to police science. The article "Forensic Applications of the Scanning Electron Microscope," by I. Covin and O. Jahari, presents the proceedings of a forensic workshop held in May, 1971. The article " The Status of Polygraph Legislation of the Fifty States," by Clarence H.A. Romig, discusses the history of the polygraph, the physiological and psychological aspects involved, and the legal status of the polygraph in the United States; part two of this paper continues with the various uses being discussed and concludes by presenting both sides of the argument over the use of the polygraph. The concluding segment covers legislation affecting the use of the polygraph including licensing legislation in eleven states. The series is concluded with a model set of minimum standards for operator certification and regulation. The article " Ubiquitous Reds: A Local Perspective on Secobarbital Abuse," by Bryan S. Finkle, discusses the social background and results of a study and evaluation of secobarbital abuse in Santa Clara County, California. The study also reports the results of analytical analysis showing great variations of the secobarbital content of capsules and also shows that the blood levels are significantly in excess of therapeutic levels which is a possible explanation for a rapid use in secobarbital fatalities among young people and the drug involvement in road traffic accidents.

This article offers news briefs related to the field of science and technology. For more than 2 decades, photomicroscopist Dee Breger of Drexel University in Philadelphia, Pennsylvania, has used artistic photographs from scanning electron microscopes (SEM) to lure the public into learning about science. Last fall, she offered an hour-long guided session on an SEM as part of an auction to raise money for educational software. The auction, organized by Galaxygoo, a San Francisco nonprofit, featured works of art inspired by science, including Breger's own SEM image of a penguin feather. In 2000, Aristides Patrinos brokered a truce between a U.S. government project to sequence the human genome and a competing, private effort led by J. Craig Venter. Now, the 59-year-old engineer-turned-science administrator is leaving the Department of Energy after 3 decades to run a company founded by Venter. Great Britain's Nicholas Shackleton died on January 24, 2006. He started out studying physics, switched to measuring minuscule isotopic differences in microscopic bits of ocean mud, and ended up establishing the metronomic qualities of climate change.

Polyacrylamide (PAM) is used at rates of 1 to 2 kg ha-1 per irrigation on a half million hectares of United States irrigated farmland to prevent 94% of irrigation-induced erosion and to enhance infiltration by 15% to 50% on medium to fine-textured soils. The polyacrylamides used for this application are large (12 to 15 megagrams per mole), water-soluble anion molecules applied in the irrigation stream. Erosion prevention has been shown to result from stabilized soil structure in the 1 to 5 mm veneer of surface soil that regulates infiltration, runoff, and sediment loss on water application. We hypothesized that this could be confirmed from scanning electron micrographs (SEMs) of PAM-treated soil. Both untreated and PAM-treated soils form surface seals in irrigation furrows, but the stable surface structure of PAM-treated furrows is more pervious. This is thought to result from a greater number of continuous unblocked pores at the soil-water interface. SEMs of PAM-treated and untreated soil microstructures are presented from thin surface samples of Portneuf silt loam, collected from furrows immediately following an irrigation, and freeze-dried. SEMs of PAM-treated soil showed net or web-like microstructural surface coatings about 1 mm thick on soil mineral particles, giving a glue-like porous appearance. Individual strands of PAM were about 0.2 mm in diameter. Strands of PAM aggregated the soil by ensnaring and bridging mineral particles while untreated soil had poorly aggregated, unconnected particles. Thus, microstructural differences between PAM-treated and untreated soil from irrigation furrows were consistent with erosion and infiltration results. [ABSTRACT FROM AUTHOR]