Investigation of localized deformation in partially saturated sand under triaxial compression using microfocus X-ray CT with digital image correlation

In this paper, localized deformation in partially saturated sand was investigated quantitatively using microfocus X-ray computed tomography (CT) and an image analysis of the CT images. Triaxial compression tests on a partially saturated dense Toyoura sand specimen were carried out under a low confining pressure and under drained conditions for both air and water. The development of localized deformation was observed macroscopically using microfocus X-ray CT, and the displacement field over the entire specimen was quantified by an image analysis of the CT images with the digital image correlation (DIC) technique. The progressive development of shear bands is discussed with reference to these images. In addition, the region of localization was observed microscopically by partial CT scanning on a micron scale with high spatial resolution. Changes in the particulate structures are also discussed herein. The DIC image analysis of the partial CT images provided a microscopic displacement field and indicated that very fine localized shear deformation developed before the shear bands had become visible in the macroscopic investigation.     

On-machine 3D vision system for machining setup modeling

In computer numerical control machine tools, using machining simulation to prevent collision becomes more and more popular due to its efficiency and low cost. However, if the entire digital model of the machining setup does not exist, the simulation is not applicable. As a result, the operator has to manually check the numerical control program, which is a time-consuming and error-prone process. In this paper, an on-machine vision system is presented to quickly construct the digital model based on the actual machining setup. The total construction for a complex setup can be done within a few minutes. Several key technologies have been developed. First, a 2D edge feature detection algorithm has been designed which will extract the edges of the object of interest by processing both the real and virtual images. Second, a stereo vision system is developed which will obtain the three-dimensional (3D) edge data of the object of interest. A new algorithm is presented to solve correspondence, which is the key problem of the stereovision system. Furthermore, the 3D object recognition algorithm is developed to let the system intelligently search for the matched solid model in the database and import it into the virtual environment with an accurate pose. Finally, experiments are carried out to test the developed system.     

Changing Microspatial Patterns of Sulfate-Reducing Microorganisms (SRM) during Cycling of Marine Stromatolite Mats

Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing “non-lithifying” (Type-1) and “lithifying” (Type-2) mats. Our results revealed three major trends: (1) Molecular typing using the dsrA probe revealed a shift in the SRM community composition between Type-1 and Type-2 mats. Fluorescence in-situ hybridization (FISH) coupled to confocal scanning-laser microscopy (CSLM)-based image analyses, and ³⁵SO₄ ²⁻-silver foil patterns showed that SRM were present in surfaces of both mat types, but in significantly (p < 0.05) higher abundances in Type-2 mats. Over 85% of SRM cells in the top 0.5 mm of Type-2 mats were contained in a dense 130 μm thick horizontal layer comprised of clusters of varying sizes; (2) Microspatial mapping revealed that locations of SRM and CaCO₃ precipitation were significantly correlated (p < 0.05); (3) Extracts from Type-2 mats contained acylhomoserine-lactones (C4-, C6-, oxo-C6 C7-, C8-, C10-, C12-, C14-AHLs) involved in cell-cell communication. Similar AHLs were produced by SRM mat-isolates. These trends suggest that development of a microspatially-organized SRM community is closely-associated with the hallmark transition of stromatolite surface mats from a non-lithifying to a lithifying state.     

Qualitative analysis of files of four different rotary systems,before and after being used for the twelfth time

The aim of this study was to make a comparative evaluation of the surface topography of the cervical third and tip of four different rotary systems, before and after being used 12 times, in resin blocks with simulated root canals with standardized 45° curvatures, and analyzed by scanning electronic microscopy (SEM). A total of 1,440 resin blocks with simulated root canals and standardized curvatures were used. The blocks were divided into four groups and prepared by the crown down technique according to the manufacturers' recommendations: Group 1 (G1)—K3®, Group 2 (G2)—Protaper Universal®, Group 3 (G3)—Twisted Files®, and Group 4 (G4)—Biorace®. After each preparation, the instruments were washed and autoclaved. A total of 24 instruments were selected, being three new instruments and three after having been used for the 12th time, from each group. These instruments were analyzed by SEM. To perform the evaluation, 24 micrographs were observed by 12 evaluators who attributed a score to the images according to a template. In the qualitative analysis of the cervical region and tip of new instruments, it was observe that the files of Groups G4 and G2 were the least rough and those of G1, the roughest. In the same manner, the cervical region of the instruments was qualitatively analyzed after the 12th time of using them, and there was no statistically significant difference at a level of 1% (ANOVA P < 0.01) between G2 and G4 as well as between G1 and G3. As regards the tip, it was observed that there was no statistically significant difference, at a level of 1%, between the groups: G1 and G3, G1 and G4, and between G3 and G4, and there was statistically significant difference at a level of 1%, between group G2 and the other groups, with G3 having the greatest roughness (ANOVA P < 0.01). Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.     

Phylogenetic analysis of Rhodococcus erythropolis based on the variation of ribosomal proteins as observed by matrix-assisted laser desorption ionization-mass spectrometry without using genome information

Rhodococcus erythropolis strains characterized as antibiotic producers can be classified into three groups according to their antibiotic spectrum and growth compatibility. Due to their high genotypic similarity, the taxonomic relationship of these strains has not been elucidated. In this study, ribosomal protein profiling using matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) was employed to classify twenty-one strains of R. erythropolis (15 antibiotic producers and 6 non-antibiotic producers). In the first step in this method, a total of 30 intense peaks observed for purified ribosomal subunit proteins of the type strain (R. erythropolis JCM 3201^T) were selected as the reference peaks. The mass spectra observed for the cell lysates of each sample strain were then checked as to whether peaks were observed at the same masses of the reference peaks. The results of peak matching were processed by cluster analysis, generating a dendrogram. Four major clusters of the R. erythropolis strains corresponded to three antibiotic groups and the non-antibiotic group. Furthermore, the topology of the dendrogram was highly comparable with the phylogenetic tree based on DNA gyrase subunit B gene (gyrB) sequencing. These results indicate that our proposed ribosomal protein profiling method using MALDI-MS is a potentially reliable and sufficiently high-throughput technique for the taxonomic analysis of closely related bacterial strains without using DNA sequence information.     

Development of numerical scheme for phase field crystal deformation simulation

The phase field crystal (PFC) method is anticipated as a new multiscale method, because this method can reproduce physical phenomena depending on atomic structures in metallic materials on the diffusion time scale. Although the PFC method has been applied to some phenomena, there are few studies related to evaluations of mechanical behaviors of materials by appropriate PFC simulation. In a previous work using the PFC method, tensile deformation simulations have been performed under conditions where the volume increases during plastic deformation. In this study, we developed a new numerical technique for PFC deformation simulation that can maintain a constant volume during plastic deformation. To confirm that the PFC model with the proposed technique can reproduce appropriate elastic and plastic deformations, we performed a series of deformation simulations in one and two-dimensions. In one- and two-dimensional single-crystal simulations, linear elastic responses were confirmed in a wide strain rate range. In bicrystal simulations, we could observe typical plastic deformations due to the generation, annihilation and movement of dislocations, and the interaction between the grain boundary and dislocations. Moreover, the deformation behaviors of a nanopolycrystalline structure at high temperature were simulated and the intergranular deformations caused by grain rotation and grain boundary migration were reproduced.     

Single-Electron Device With Si Nanodot Array and Multiple Input Gates

We have developed a flexible-logic-gate single-electron device (SED) with an array of nanodots. Although the small size of SEDs is highly advantageous, the size of the nanodots inevitably fluctuates, which causes variations in device characteristics. This variability can be eliminated and high device functionality can be obtained by exploiting the oscillatory characteristics and multigate capability of SEDs. We fabricated, on a silicon-on-insulator wafer, a Si nanodot array device with two input gates and a control gate and investigated its basic operation characteristics experimentally. The device was demonstrated to operate as a logic gate providing six important logic functions ( and, or, nand, nor, xor, and xnor), which are obtained by adjusting the control-gate voltage.     

Ferroelectric properties of ultrathin films of Nylon 11

Ferroelectric properties of ultrathin films of Nylon 11 were investigated. The thickness was in the range of 25 to 55 nm. Ferroelectric response was largely affected by thermal annealing and following cooling conditions. Thermal annealing at higher temperature followed by quenching in liquid nitrogen gave larger remanent polarization and smoother surface, whereas cooling down in an ambient atmosphere caused smaller remanent polarization and rough surface. Surface roughness strongly affected the polarization reversal and remanent polarization. Hydrogen bonding in crystal was also significantly related to the polarization reversal and thus remanent polarization.     

A method to modify coordinates of detectors in positron emission tomography systems

A new method to modify coordinates of detectors in any positron emission tomography (PET) system using a radioactive point source is developed. This method is based on selecting a centered detector in each detector block of PET and measuring coincidence counts between the two centered detectors in opposite detector blocks to find the coordinates of their LOR (Line of Response). Due to slight misalignment of detector positions, measured LORs may not intersect at a single point. Based on the proposed method, the coordinates of detectors can be measured with very high accuracy and the coordinate of the center of the gantry (which is normally the same as the center of field of view) can be defined correctly. The results of the application of our method to a small animal PET system (FinePET), which was recently developed at Tohoku University, Japan, are shown here. The method is expected to contribute to the design and development of PET systems which can realize a very high spatial resolution of less than 1 mm FWHM.