Marginal gaps and voids of three root-end filling materials: A microcomputed tomographic study

A root-end filling material is required to fill the root-end cavity without gaps or voids, to prevent root canal reinfection and to provide periapical healing. Thus, this study evaluated the volume of marginal gaps and voids of three root-end filling materials using microcomputed tomography (micro-CT). Thirty maxillary incisors were prepared and filled with gutta-percha and endodontic sealer. The specimens were scanned using micro-CT and distributed into three groups (n = 10): White MTA, MTA Repair HP, and Bio-C Repair. The root tips were resected at 90° to the longitudinal axis and the cavity (3 mm depth) was prepared with an ultrasonic tip. The materials were handled, and the cavities were filled. The specimens were rescanned and the percentual volume of gaps and voids were analyzed. The data were analyzed using Kruskal–Wallis and Dunn tests (p < .05). No statistical difference was found in the percentage of gaps among the tested materials (p > .05). White MTA presented less voids than Bio-C and MTA Repair HP (p < .05). The materials presented a similar percentual volume of gaps and White MTA presented less voids than other tested materials.     

Immuno‐detection of mRNA‐binding protein complex in human cells under transmission electron microscopy

Transit from the nuclear complex to the cytoplasm through the nuclear pore complex permits modification of mRNA, including processing such as splicing, capping, and polyadenylation, etc. At each of these events, mRNA interacts with various proteins to form mRNA‐protein complex. Visualizing the mRNA is crucial for understanding the mechanisms underlying mRNA processing and elucidating its structure and recent advances in mRNA imaging allow detection of real‐time mRNA localization in living cells. However, these techniques revealed only the location of mRNA but cannot visualize the conformation of mRNA‐protein complex in cells. On the other hand, transmission electron microscopy has been used to visualize the structure of the Balbiani ring‐derived large mRNA, but their observations were limited to the insect cells. In this study, we visualized the structure of mRNA‐protein complex in human culture cells by using immuno‐electron microscopy. Through immuno‐detection, an mRNA exon junction binding complex Y14, and its binding protien Upf2, different gold particle patterns were imaged with transmission electron microscopy and analyzed. Characteristic linear and stacked particle orientation were observed. Across the nuclear membrane, only linear aggregation pattern was observed, whereas the stacked aggregation pattern was detected in the cytoplasm. Our method is able to visualize mRNA‐conformation and applicable to many cell types, including mammalian cells, where genes can easily be manipulated.     

Reduction of temperature fluctuation within low temperature region using a cryocooler

Modeling and experiments are performed to decrease temperature fluctuation generated by the periodic motion of the displacer in a Gifford-McMahon (GM) type cryocooler within the low-temperature region. The one-dimensional heat equation allows us to show that thermal diffusivity is an essential factor to achieve much smaller temperature fluctuation, and fiber-reinforced plastic (FRP) with low thermal diffusivity makes it possible to reduce the temperature fluctuation dramatically. Based on the model, experiments are performed to vary the thickness of two FRP dampers, on the cryohead of the cryocooler and on the sample stage. As a result, the FRP dampers enable us to achieve the temperature fluctuations of only 0.7 mK, corresponding to a standard deviation of 0.25 mK, when the sample stage is maintained at 4.2000 K, even if a GM cryocooler is utilized for cooling the temperature, which introduces an initial temperature fluctuation of 282 mK at the cryohead.     

Methanol synthesis over a Zn-deposited copper model catalyst

Methanol synthesis by the hydrogenation of CO₂ over Zn-deposited polycrystalline Cu was studied using surface science techniques. The Zn sub-monolayer was oxidized by the reaction mixture during the reaction at 523 K, leading to the formation of ZnO species. The kinetic results definitely showed that the ZnO species on the Cu surface promoted the catalytic activity of methanol formation, where the activity of Cu increased by a factor of 6 at the Zn coverage of 0.17. A volcano-shaped curve was obtained for the correlation between the Zn coverage and the catalytic activity, which was very similar to the correlation curve between the oxygen coverage and the specific activity for methanol formation previously obtained for the Cu powder catalysts. The role of ZnO in Cu/ZnO based catalysts was ascribed to the stabilization of Cu⁺ species by the ZnO moieties on the Cu surface.     

Monohexosylceramides of larval and adult forms of the tapeworm,spirometra erinacei

The occurrence of glycosphingolipids with unique carbohydrate structures in different species of cestode, Platyhelminth, which had been shown, previously, prompted us to study the molecular species of the monohexosylceramides (cerebrosides) in the pseudophyllidean cestode,Spirometra erinacei. The purpose of the study was to obtain a basis for future investigations of the physiological role of glycolipids in parasitism. Cerebrosides were isolated froms. erinacei at two growth stages, i.e., from the larval form (plerocercoid) and from the adult tapeworms (intestinal form). The cerebrosides were separated into four subfractions by silica gel column chromatography, and their constituents were analyzed by gasliquid chromatography, gas chromatography/mass spectrometry, and high-performance liquid chromatography/mass spectrometry. The hexoses of the cerebrosides consisted primarily of galactose in both growth stages, while only a small amount of glucose was detected. The ceramides were composed of sphinganine (d18∶0) and phytosphingosine (t18∶0) as sphingoid bases, and of nonhydroxy fatty acids ranging from C₁₆ to C₃₀ and hydroxy stearic acid (18h∶0). The cerebrosides of adult tapeworms contained more 18h∶0 than those of plerocercoids. The combination of hexoses and ceramides in the cerebroside molecules was slightly different in the two growth stages: the glucocerebrosides of plerocercoids contained only d18∶0-nonhydroxy fatty acids in their ceramide moieties, whereas those of adult tapeworms contained varying ceramide moieties. Our data indicate that the molecular species of glycolipids present were essentially homeostatic throughout growth in spite of the entirely different environmental conditions, although there were slight differences in the hexose distribution in the two growth stages.     

Novel tools for coating developers: a solution to the inverse problem in formulation

The inverse problem in coating formulation, i.e., that of finding a formulation that will satisfy a given set of performance properties, is much more difficult than the direct problem of finding the properties of a given formula. While the latter case may be labor intensive and time-consuming, we have at hand a wealth of test methods that make the solution straightforward. By contrast, the former case calls for experienced formulators plus intensive trial-and-testing work. In this work we describe a way to use intelligent systems in the form of artificial neural networks and genetic algorithms to tackle the more difficult inverse problem. It is applied to a set of five different families of alkyd enamels. In the direct mode, we are able to predict performance of a formulation with 90% efficiency. Through a sensitivity analysis, we can also obtain those variables to which a given property responds more strongly. In the inverse mode, we can obtain enamel formulations that will satisfy a given set of performance requirements. On the whole, it constitutes a powerful lab tool for coating developers. Computer-proposed formulations with some prescribed characteristics and their laboratory tests are discussed. Presented at the 2006 FutureCoat! conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006. Javier E. Vitela On Sabbatical Leave from Instituto de Ciencias Nucleares, UNAM, 04510 México D.F., México     

Control of pit initiation sites on aluminum foil using colloidal crystals as mask

The electrochemical etching of aluminum foils using a physical mask of colloidal spheres was studied to directly control the initiation sites of pits independent of the surface activation state of the substrate. A two-dimensional array of colloidal spheres used as a mask was prepared by self-assembly on an aluminum substrate. The transfer of the hexagonally ordered pattern of self-assembled colloidal spheres to the aluminum substrate could be achieved by the selective electrochemical etching of an exposed aluminum surface. That is, etch pits were generated only in the triangular void space among the three spheres on the aluminum surface. Based on this process, the dispersibility of the initiation sites of pits was improved clearly in comparison with that for the conventional method. The density of pits could also be controlled by changing the diameter of spheres used as a mask.     

Relation between thermal conductivity and network formation with polymerizable liquid crystals

The molecules with the mono‐ and bi‐function at the sides in the acrylic PLC mixtures were aligned by the rubbing method. The alignment was immobilized by the photo polymerization to result the homogeneous acrylic films, which have good alignment with the higher order parameters. The thermal conductivity along the molecular long axis direction showed the larger magnitude of 0.62 W/m · K, which is independent on ratio of the main chain and the side chain fractions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3169–3174, 2007     

Apatite Coating on Organic Polymers by a Biomimetic Process

Dense and uniform layers of a biologically active carbonate-containing hydroxyapatite can be formed on various kinds of organic polymers by the following biomimetic method. First, a substrate is set in contact with particles of CaO–SiO₂-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma for forming the apatite nuclei on the substrate. Second, the substrate is soaked in another solution highly supersaturated with respect to the apatite, e.g, with ion concentrations 1.5 times those of SBF (1.5SBF) for making the apatite nuclei grow on the substrate in situ. The induction period for the apatite nucleation, which is defined as the time of the first treatment required for forming enough of the apatite nuclei to make the continuous layer after the second treatment, was almost 24 h for most of the examined polymers. The adhesive strength of the formed apatite layer to the polymers was as high as 3 to 4 M Pa for poly(ethylene terephthalate), poly-ether sulfone, and poly (vinyl alcohol) hydrogel. This type of apatite–organic polymer composite is expected to be useful for repairing not only living hard tissues but also soft ones.     

Effect of calcination temperature on the catalytic activity of Au colloids mechanically mixed with TiO2 powder for CO oxidation

In order to elucidate the role of the contact structure between gold and metal oxide support in low-temperature CO oxidation, a mechanical mixture of colloidal gold with TiO₂ powder was prepared and calcined at different temperatures. The sample calcined at 473 K, which is composed of spherical gold particles with a mean diameter of 5.1 nm and TiO₂ powder, is poorly active for CO oxidation at temperatures up to 473 K. The catalytic activity appreciably increases with an increase in calcination temperature up to 873 K even though gold particles grow to larger ones, reaching a level with almost the same turnover frequency as that of Au/TiO₂ prepared by a deposition–precipitation method. This revised version was published online in July 2006 with corrections to the Cover Date.