Microstructure and tensile strength of grade 2 titanium processed by equal-channel angular pressing and by rolling

Commercially pure titanium strengthened by severe plastic deformation constitutes an alternative to the use of complex Ti alloys in many medical or industrial applications. In this research, rods of grade 2 Ti were processed by up to six passes using Equal-channel angular pressing (ECAP) at 573 K followed by cold rolling at room or subzero temperatures. After four passes of ECAP, the grain size was refined down to the submicrometer scale and subsequent rolling led to further refinement. The microstructure was characterized by taking Vickers microhardness measurements and tensile testing was performed both at room temperature and in the temperature range of 573–773 K. The results show that at all temperatures the tensile strength is significantly improved by means of these processing techniques. At room temperature, the ultimate tensile strength of pure Ti after ECAP plus subzero rolling is close to that of the traditional Ti-6Al-4V alloy while maintaining adequate levels of elongation to failure.     

An evaluation of the shearing patterns introduced by different anvil alignments in high-pressure torsion

A two-phase duplex stainless steel was used to investigate the influence of different amounts of anvil misalignment on the shearing patterns produced during high-pressure torsion (HPT) and subsequently on the hardness distributions across the disc upper surfaces. The results show that for a perfect alignment of the anvils, to within <25 μm, the discs exhibit regular flow patterns as anticipated from conventional analysis whereas for anvil misalignments of 100 or 200 μm the discs develop double-swirl patterns on the upper surfaces. These double swirls increase in size with increasing anvil misalignments and decrease in size with increasing numbers of torsional turns. The origin of these double swirls is investigated by examining a model based on a buckling theory for loaded beams and the development of instabilities within the discs during HPT processing. It is demonstrated that this model provides a satisfactory explanation for the reports of swirls and vortices in samples processed by HPT.     

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

Fracture sealing by precipitation is known to occur in high-strength and ultra-low-permeability concrete (HSULPC) immersed in water. Because a high ability to retard radionuclide migration is required for HSULPC, understanding both the sealing process and the composition of sealing deposits is important to identify optimum conditions for significant sealing. In this study, sealing of a macro-fractured HSULPC specimen with initial aperture of approximately 0.1 mm was investigated in simulated seawater over 49 days. The composition of sealing deposits at 49 days after immersion was clarified by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX), and the progress of sealing during the 49 days was clarified by image analysis with micro-focus X-ray computed tomography (X-rayCT). Both the SEM/EDX and X-rayCT results showed that significant sealing was attained only near the outermost part of the specimen. The SEM/EDX results showed that a thin brucite layer formed on the entire specimen surface over which significant precipitation of calcium carbonate occurred and sealed the macro-fracture only near the outermost part of the specimen. The X-rayCT results indicated that the amount of sealing deposits in the macro-fracture ( \(P_\mathrm{seal})\) reached 70 % in the mostly sealed region at 49 days and the rate of change in \(P_\mathrm{seal}\) became maximum \((3.7\,\% \hbox { day}^{-1})\) during 7–21 days after immersion, then decreased. In conclusion, the findings in this study represent an important clue in the search for optimum conditions to achieve fracture sealing in HSUPLC.     

Direct observation of X-ray induced atomic motion using scanning tunneling microscope combined with synchrotron radiation

X-ray induced atomic motion on a Ge(111)-c(2 x 8) clean surface at room temperature was directly observed with atomic resolution using a synchrotron radiation (SR)-based scanning tunneling microscope (STM) system under ultra high vacuum condition. The atomic motion was visualized as a tracking image by developing a method to merge the STM images before and after X-ray irradiation. Using the tracking image, the atomic mobility was found to be strongly affected by defects on the surface, but was not dependent on the incident X-ray energy, although it was clearly dependent on the photon density. The atomic motion can be attributed to surface diffusion, which might not be due to core-excitation accompanied with electronic transition, but a thermal effect by X-ray irradiation. The crystal surface structure was possible to break even at a lower photon density than the conventionally known barrier. These results can alert X-ray studies in the near future about sample damage during measurements, while suggesting the possibility of new applications. Also the obtained results show a new availability of the in-situ SR-STM system.     

Numerical analysis on the optical role of nano-randomness on the Morpho butterfly's scale

The blue coloration of Morpho butterflies has anomalously low angular dependence despite the production of color with a selected wavelength based on an interference effect. A key to the mechanism of the specific Morpho-color was suggested to be the randomness of its scale. Using finite-difference time-domain (FDTD) analysis, the role of different kinds of randomness in the structure of the Morpho butterfly's scale was investigated, which was impossible by conventional analytical calculations. The results revealed that incoherence in the incident light plays an essential role, which cannot be realized only by structural randomness. On the other hand, the lateral and vertical randomness, and the number of random components were found each to have an independent role to realize the specific Morpho-color preventing the sharp reflective angular dependence. The direction obtained by the numerical simulations to analyze optically complex random structures will serve not only to understand the scientific principles, but also to design the optical properties of artificial materials.     

STM-induced light emission from thin films of perylene derivatives on the HOPG and Au substrates

We have investigated the emission properties of N,N'-diheptyl-3,4,9,10-perylenetetracarboxylic diimide thin films by the tunneling-electron-induced light emission technique. A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules. The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes. The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.     

Probabilistic Dynamic Framed Slotted ALOHA for RFID Tag Identification

In this paper, we study radio frequency identification tag identification problems using framed slotted ALOHA protocol. Each tag will be assumed to participate in the contention with a certain probability. Then, the frame size and the probability will be dynamically controlled by the reader in every reading round so that all the tags can be detected in a short period of time. Moreover, we propose a practical way of controlling the probability in terms of transmit power control, assuming Additive White Gaussian Noise channel or flat Rayleigh fading channel. Computer simulation results demonstrate the effectiveness of the proposed method.     

Effects of Chronic Intracerebroventricular Infusion of RFamide-Related Peptide-3 on Energy Metabolism in Male Mice

RFamide-related peptide-3 (RFRP-3), the mammalian ortholog of avian gonadotropin-inhibitory hormone (GnIH), plays a crucial role in reproduction. In the present study, we explored the other functions of RFRP-3 by investigating the effects of chronic intracerebroventricular infusion of RFRP-3 (6 nmol/day) for 13 days on energy homeostasis in lean male C57BL/6J mice. The infusion of RFRP-3 increased cumulative food intake and body mass. In addition, the masses of brown adipose tissue (BAT) and the liver were increased by the administration of RFRP-3, although the mass of white adipose tissue was unchanged. On the other hand, RFRP-3 decreased O₂ consumption, CO₂ production, energy expenditure, and core body temperature during a short time period in the dark phase. These results suggest that the increase in food intake and the decrease in energy expenditure contributed to the gain of body mass, including the masses of BAT and the liver. The present study shows that RFRP-3 regulates not only reproductive function, but also energy metabolism, in mice.