Control of mesoporous and crystalline structures in turbostratic carbon derived from Fe- or Ni-doped phenolic resin

A technique to control the mesoporous structure and crystallites present in turbostratic carbon (Ts-carbon) derived from Fe- and Ni-doped phenolic resin is described. To eliminate the effect of heat treatment temperature, all of the Fe- and Ni-doped phenolic resins are carbonized at a fixed temperature of 1000 °C. The catalyst content in the obtained Ts-carbon varies from 0.001 to 5 mmol/g. Mesopores and turbostratic crystallites are formed in the Ts-carbon samples, and these increase in size as the catalyst content and its particle size increases. The turbostratic crystallites assemble to form carbon aggregates with a cup-stacked, thin tube-like, or coil-like structure. The mesopore surface area increases proportionally with the amount of turbostratic crystallites rather than the type of carbon aggregate. It is proposed that the mesopore is surrounded by turbostratic crystallites. Altering the size of the turbostratic crystallites in Ts-carbon has revealed an effective method for controlling the size and volume of its mesopores.     

Radiation safety management of residual long-lived radioactivity distributed in an inner concrete wall of a medical cyclotron room

The depth distribution of residual long-lived radioactivity in the inner concrete wall of a medical cyclotron room was measured by assaying concrete cores. Seven long-lived radioactive nuclides ((46)Sc, (60)Co, (65)Zn, (134)Cs, (152)Eu, (22)Na and (54)Mn) were identified by gamma-ray spectrometry of the concrete samples. It was confirmed that the gamma-ray-emitting radionuclides induced by thermal neutrons through the (n, γ) reaction are dominant, and that the activity induced by thermal neutrons is greater at a depth of 10-30 cm, rather than at the surface of the concrete, and decreased exponentially beyond a depth of ~40 cm. Although the specific activity at the surface was greater than the clearance level for radioactive waste indicated in IAEA RS-G-1.7, the mean specific activities in the walls and floor were less than the clearance level.     

Efficient hydrogen generation from organic chemical hydrides by using catalytic reactor on the basis of superheated liquid-film concept

Under boiling and refluxing conditions for catalytic dehydrogenation of organic chemical hydrides (decalin, methylcyclohexane and others) in a batch-wise reactor, either suspended states with excess amounts of substrate or sand-bath states with its scarce amounts were found to be inferior generally to the so-called “liquid-film states” with adequate amount ratios of substrate to catalyst, where the catalyst-layer temperatures were superheated or raised higher than the boiling point, and, consequently, reactivities became more favorable at higher heating temperatures in contrast to the boiling suspended states.Equilibrium shifts due to reactive distillation were well demonstrated under boiling and refluxing conditions in naphthene dehydrogenation. Moreover, desorption of hydrogen from the active sites to the bubble space was enhanced in the superheated liquid-film states, with large translational entropy endowed.Provided the extents of equilibrium deviation were large enough (Prigogine's approach), thermodynamic couplings among irreversible processes would be realized between heat transfer and mass transfer as an example of the extended De Donder's equation. Restriction of chemical equilibrium could be removed under temperature gradient conditions, as the consequence that its Gibbs energy change became more negative than that under iso-temperature conditions.Within the framework of irreversible thermodynamics, the decreased retardation constant K in the superheated liquid-film states was interpreted in terms of a vector-level coupling between temperature gradient and desorption. Moreover, vigorous bubble formation would give additional favor to the reaction rates owing to enlarged repeating frequencies of sequential non-microreversible processes in dehydrogenation catalysis.Organic chemical hydrides are attractive from the viewpoints of safe, economical, exergy-saving and large hydrogen contents for hydrogen storage and distribution. Their main defects have been pointed out hitherto that the endothermic reaction temperatures are too high. In this paper, a new concept on superheated liquid-film catalysis is explored for dehydrogenation temperatures to decrease, which would result in not only saving exergy for external heating but also avoiding catalyst deactivation due to carbon deposit.     

Multi-grooved cutting tool to reduce cutting force and temperature during bone machining

The cutting temperature of a cutting tool are required to be low during bone machining for preventing damage to bone cells. However, conventional tools are practically the same as those used for metal cutting, and many operational limitations have been reported. In this study, a dedicated cutting tool was designed for reducing cutting force and temperature. A short contact between the workpiece and the cutting edge leads to a reduction in the cutting force. Furthermore, a straight-line edge improves surface roughness. The effectiveness was evaluated using bovine bone, and the cutting force was found to be decreased by about 40%.     

Model-based tomographic reconstruction of objects containing known components

The likelihood of finding manufactured components (surgical tools, implants, etc.) within a tomographic field-of-view has been steadily increasing. One reason is the aging population and proliferation of prosthetic devices, such that more people undergoing diagnostic imaging have existing implants, particularly hip and knee implants. Another reason is that use of intraoperative imaging (e.g., cone-beam CT) for surgical guidance is increasing, wherein surgical tools and devices such as screws and plates are placed within or near to the target anatomy. When these components contain metal, the reconstructed volumes are likely to contain severe artifacts that adversely affect the image quality in tissues both near and far from the component. Because physical models of such components exist, there is a unique opportunity to integrate this knowledge into the reconstruction algorithm to reduce these artifacts. We present a model-based penalized-likelihood estimation approach that explicitly incorporates known information about component geometry and composition. The approach uses an alternating maximization method that jointly estimates the anatomy and the position and pose of each of the known components. We demonstrate that the proposed method can produce nearly artifact-free images even near the boundary of a metal implant in simulated vertebral pedicle screw reconstructions and even under conditions of substantial photon starvation. The simultaneous estimation of device pose also provides quantitative information on device placement that could be valuable to quality assurance and verification of treatment delivery.     

Programmable self-assembly of metal ions inside artificial DNA duplexes

The ultimate bottom-up approach for the construction of functional nanosystems requires the precise arrangement of atoms and molecules in three dimensions. DNA is currently one of the most prominent molecules able to self-assemble into complex networks and is therefore regarded as the 'silicon of the nano-world'. Metals and metal ions, in contrast, are the atomic building-blocks needed in such materials to establish functions such as electrical conductivity or magnetism. Here we report a new concept, which efficiently combines metal ions and DNA. The DNA structure is used as a matrix to program robustly the complexation of different metal ions under precise control with regard to element, number and composition.     

Temperature phase-matching properties for harmonic generation in GdCa4O(BO3)3 and Gd(x)Y(1-x)Ca4O(BO3)3

GdCa4O(BO3)3 has been found to have phase-matching points where the temperature variations of the phase-matching angles become zero for type-1 sum-frequency generation in the zx plane. We also found that the temperature sensitivities of the phase-matching conditions in the zx plane are different along the phi = 0 degrees and phi = 180 degrees directions in this material. In addition, the thermo-optic dispersion formula of this material that reproduces the temperature phase-matching properties of GdCa4O(BO3)3 and Gd(x)Y(1-x)Ca4O(BO3)3 is presented.     

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of ¹³¹I in brown algae was 0.37 ± 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of ¹³¹I and ¹³⁷Cs in these seaweeds. The specific activity of ¹³⁷Cs ranged from 0.0034 ± 0.00075 to 0.090 ± 0.014 Bq/kg-wet. Low specific activity and minimal variability of ¹³⁷Cs in brown algae indicated that past nuclear weapon tests were the source of ¹³⁷Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of ¹³¹I, there was no relationship between the sites where ¹³¹I was detected and the locations of nuclear power facilities. Most of the sites where ¹³¹I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of ¹³¹I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.     

Change in bulk and surface structure of mixed MoO3-ZnO oxide by heat treatment in air and in hydrogen

The mixed MoO₃-ZnO oxides with various mole fraction of Mo, X _Mo, obtained by the impregnation method were heated in air and in hydrogen. As for the mixed oxide heated in air, MoO₃ reactedstoichiometrically with ZnO to give ZnMoO₄ at X _Mo < 0.5, while at X _Mo > 0.5, the reaction did not proceed completely. On the other hand, for the mixed oxide heated in hydrogen, at X _Mo < 0.5 ZnMoO₄ was reduced to ZnMoO₃ with the anion vacancy, while at X _Mo > 0.5, MoO₃ was reduced to MoO₂ and ZnMoO₄ was difficult to be reduced to ZnMoO₃. The structure of the surface and/or near the surface was different from the bulk structure.