It has been indicated that low-luminosity active galactic nuclei (LLAGNs) are accelerating high-energy cosmic-ray (CR) protons in their radiatively inefficient accretion flows (RIAFs). If this is the case, Sagittarius A* (Sgr A*) should also be generating CR protons, because Sgr A* is a LLAGN. Based on this scenario, we calculate a production rate of CR protons in Sgr A* and their diffusion in the central molecular zone (CMZ) around Sgr A*. The CR protons diffusing in the CMZ create gamma-rays through pp interaction. We show that the gamma-ray luminosity and spectrum are consistent with observations if Sgr A* was active in the past.

Half-Heusler MNiSn (M=Ti, Zr, Hf) compounds are well-known, excellent n-type thermoelectric materials. The n-type Seebeck coefficients of ZrNiSn are reduced because of the precipitation of the metallic Heusler ZrNi2Sn phase. An excellent n-type Seebeck coefficient can be converted to p-type based on the vacancy site occupation by the solute Co atoms in the half-Heusler TiNiSn phase as well as ZrNiSn. The Heusler phase precipitates, including their precursor nano-structure in the half-Heusler matrix and the vacancy site occupation of the half-Heusler phase, are regarded as lattice defects based on the crystallographically and thermodynamically close relationship between half-Heusler and Heusler phases.

Since the occlusion of hydrogen and carbonic oxide by palladium and iron was first discovered by Graham, many similar effects have been discovered. Prof. Knott has investigated in considerable detail the very peculiar changes in the thermo-electric position and in the electrical resistance of palladium when variously charged with hydrogen. With respect to iron, Dr Monckman has experimented on the resistance of iron occluding carbonic oxide, but, in regard to hydrogen, he came to the conclusion that no change in the thermo-electric properties could be detected.

The hexagonal domain suppression-effects in cubic-GaNAs grown by metalorganic chemical-vapor deposition (MOCVD) is reported. A thin buffer layer (20 nm) was first grown on a substrate at 853 K using trimethylgallium and dimethylhydrazine (DMHy), and GaNAs samples were grown at different AsH3 flow rates (0 ∼ 450 μmol/min) at 1193 K. As a result, three types of surface morphologies were obtained: the first was a smooth surface (AsH3 = 0 μmol/min); the second was a mirrorlike surface having small and isotropic grains (AsH3 : 45 ∼ 225 μmol/min ); and the third involved three-dimensional surface morphologies (above 450 μmol/min of AsH3 flow rate). Furthermore, it was confirmed using X-ray diffraction that the mixing ratio of hexagonal GaNAs in cubic GaNAs decreased with an increase of the AsH3 flow rate. We could obtain GaNAs having a cubic component of above 85% at AsH3 flow rates above 20 μmol/min. Therefore, the MOCVD growth method using AsH3 and DMHy was mostly effective for suppressing hexagonal GaNAs. It was observed that the photoluminescence intensity of GaNAs was decreased with increase of arsine flow rate.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Mucosal mast cells (MMC) play a crucial role in the expulsion of Strongyloides ratti adults from the small intestine of mice. We reported the large intestinal parasitism of S. ratti in rats, and there has been no report on MMC in the large intestine of the natural host. We studied kinetics of MMC, together with eosinophils, in the upper and lower small intestines, caecum and colon of infected rats. Two distinct phases of mastocytosis were revealed: one in the upper small intestine triggered by stimulation of ‘ordinary’ adults, and the other in the colon stimulated by ‘immune-resistant’ adults that started parasitizing the colon around 19 days post-infection. In all 4 intestinal sites, the MMC peaks were observed 5–7 days after the number of adult worms became the maximum and the height of MMC peaks appeared to be dependent on the number of parasitic adults, suggesting an important role played by worms themselves in the MMC buildup.

Single crystals of E21 (L12) Ni3AlC1-x were prepared by the unidirectional solidification using the optical floating zone melting method to determine their mechanical properties. Particularly the effects of interstitial carbon atoms on mechanical properties were evaluated by compression tests at room temperature. Operative slip system of E21 Ni3AlC is {111}<011> type which is the same as that of L12 Ni3Al. Strength of Ni3AlC single crystals increases with carbon concentration due to the solid solution effect, though the stress relief of yielding behavior is enhanced at the intermediate carbon content at around 3at%. A large gap appears in the carbon concentration dependence of critical resolved shear stress (as well as yield stress) at almost the same carbon content. This discontinuity in strengthening is attributed to the interaction between multiple solute carbon atoms and mobile dislocations.

The hexagonal domain suppression-effects in cubic-GaNAs grown by metalorganic chemical-vapor deposition (MOCVD) is reported. A thin buffer layer (20 nm) was first grown on a substrate at 853 K using trimethylgallium and dimethylhydrazine (DMHy), and GaNAs samples were grown at different AsH3 flow rates (0 ∼ 450 µmol/min) at 1193 K. As a result, three types of surface morphologies were obtained: the first was a smooth surface (AsH3 = 0 µmol/min); the second was a mirrorlike surface having small and isotropic grains (AsH3 : 45 ∼ 225 µmol/min ); and the third involved threedimensional surface morphologies (above 450 µmol/min of AsH3 flow rate). Furthermore, it was confirmed using X-ray diffraction that the mixing ratio of hexagonal GaNAs in cubic GaNAs decreased with an increase of the AsH3 flow rate. We could obtain GaNAs having a cubic component of above 85% at AsH3 flow rates above 20 µmol/min. Therefore, the MOCVD growth method using AsH3 and DMHy was mostly effective for suppressing hexagonal GaNAs. It was observed that the photoluminescence intensity of GaNAs was decreased with increase of arsine flow rate.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-x C x alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1-x C x solid solutions were formed up to x = 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1-x ,C x alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ∼28% for E i , = 100 eV and ∼18% for E i = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

We have investigated characteristic ferroelectric and structural antiphase domain structures in single crystals of hexagonal RMnO3 (R=Y, Ho, Lu, and Yb) by obtaining various electron diffraction patterns, dark-filed images and high-resolution lattice images. In the ferroelectric phase of RMnO3 characteristic domain structures consisting of six ferroelectric and structural antiphase domains, which can be identified as the “cloverleaf” pattern, is found in the (110) plane, in addition to the (001) plane, and are inherent to the ferroelectric phase of hexagonal RMnO3. In domain configuration with the cloverleaf pattern in the (110) plane, the structural antiphase boundaries are inclined to be parallel to the [001] direction.

We have investigated microstructures in both the antiferroelectric (AFE) and relaxor states of Pb(In1/2Nb1/2)O3 (PIN) with the perovskite structure by a transmission electron microscopy (TEM). Electron diffraction (ED) experiments revealed that the AFE state is characterized as the modulated structure with the modulation vector of q =1/4 1/4 0. High-resolution TEM images clearly show the coexistence of two types of domains consisting of the modulated and the nonmodulated structures with the 100 ∼ 200 nm size. On the other hand, in the relaxor state there appear two types of diffuse scatterings in the ED patterns. One is diffuse spots at the 1/2 1/2 0-type reciprocal positions and the other is diffuse streaks elongating along the <110> direction around the fundamental spots. The real-space TEM images clearly demonstrate the presence of nanodomains with the average size of ∼ 5 nm. These nanodomains in the relaxor state should be responsible for the characteristic dielectric properties.

Strongyloides ratti (Nagoya strain) is unique in that a portion of adults parasitizing the small intestine withstands ‘worm expulsion’, which starts at around day 8 post-infection (p.i.) by host immunity, and establishes in the large intestine after day 19 p.i. To investigate the mechanism, adults obtained from the small intestine at day 7 or 19 p.i. were transplanted into the colon of infection-primed immune rats. Adults obtained at day 7 p.i. were rejected quickly, whereas those obtained at day 19 p.i. could establish infection. Moreover, the body length and the number of intrauterine eggs increased in the large intestine. In a separate experiment, large intestinal parasitism was abolished by the treatment of host rats with an anti-oxidant, butylated hydroxyanisole. These results indicate that small intestinal adults between days 7 and 19 p.i. acquired the ability to parasitize the large intestine of immune rats, and that free radicals produced by the host may have played a significant role in the process.

Temperature dependence of thermoelectric power and resistivity was measured for the β-FeSi2 based cast alloys on which n-type Co doping was performed with or without Cu addition. The Cu-free alloy shows a homogeneous eutectic microstructure consisting of metallic phases α-FeSi2 and ε-FeSi, while the Cu-doped alloy has a quite heterogeneous microstructure dominated by coarse ε-FeSi dendrites in the α-FeSi2 matrix. Adequate heat treatment condition for the semiconductor β-FeSi2 phase formation has been evaluated as annealing at 923 K for less than 50 h, which is lower in temperature and shorter in duration than previously reported for alloys prepared by powder metallurgy. The resistivity measurement with the aid of microstructure observation has revealed that the β-FeSi2 formation takes place and almost finishes at very early stage of annealing process. Addition of Cu effectively promotes the β-FeSi2 formation rate of the present cast alloys.

In the present work, we investigate microstructures and thermoelectric power of the binary higher manganese silicide (hereafter denoted as HMS) base alloys prepared by ingot metallurgy, i.e., arc-melting in an Ar gas atmosphere. Alloys with 63.5, 64.0 and 64.5 at% Si have a small amount of second phase, either the primary metallic MnSi phase or Si solid solution (hereafter denoted as (Si)). A slight revision is thereby made on the HMS single phase region of the Mn-Si binary phase diagram. The presence of MnSi seems to reduce the thermoelectric power of the HMS, while that of (Si) enhances it. An alloy having the HMS/(Si) eutectic microstructure, 67.9at%Si, shows the highest thermoelectric power in the Mn-Si binary alloys examined. Moreover, effect of doping the p-type elements, Fe and Cr, on the thermoelectric power and microstructural features is also investigated for a 63.5at%Si alloy which consists mostly of HMS phase with a small amount of (Si) phase. It is shown that both elements, especially 0.5 at% Cr addition, enhance the thermoelectric power of the alloys.

In view of the possibility of the E21-type intermetallic compound as a strengthener in austenitic alloys at high temperatures, mechanical properties and microstructures of the γ / κ two-phase alloys in the Fe-Mn-Al-C system were investigated. Alloy compositions with more than 1.5wt% C were selected in order to stabilize the γ / κ two-phase microstructure in the high temperature regime exceeding 873K. During furnace cooling after the homogenization treatment, κ phase precipitates on the γ grain boundary, which results in the poor tensile ductility. In these alloys, tensile yield strength at 873K and 1073K increases with increasing κ phase volume fraction. Applying ageing treatment at 1073K after the solid solution treatment followed by water quenching causes the formation of a uniform γ / κ lamellar microstructure, and the remarkable improvement of ductility was achieved. The addition of Cr, which is expected to improve the oxidation resistance, reduces the phase stability of κ phase, and leads to the formation of Cr7C3 carbide and β-Mn phase with more than 5.5wt.% Cr addition.

C11b/C40 fully lamellar microstructures, similar to the well-known TiAl/Ti3Al lamellae, were obtained in Ta- and Nb-added MoSi2 polycrystalline alloys in a previous work. In the present study, the crystallography of the lamellar structure is investigated in a MoSi2-15mol%TaSi2 pseudo-binary alloy after homogenized at 1400°C for 168h, in order to provide some useful parameters for microstructural control to improve mechanical properties. The orientation relationship between C11b and C40 phases and its three distinct variants were identified. Coherency of the lamellar interface is analyzed in comparison with the TiAl/Ti3Al lamellae. Approach to modify the C11b/C40 lamellar microstructure to increase its coherency is discussed based on the results obtained.

Icosahedral quasicrystals Al71.5Pd20.3Mn8.2, Al70.7Pd21.34Re7.96, Al62.5Cu25.5Fe12.5, and α-Al68.31Mn21.21Si10.48 1/1- approximant were investigated by using a monoenergetic slow positron beam. The structural vacancy densities in the first three samples were determined to be 5.0×1020, 7.7×1020, and 4.7×1020 cm−3, respectively, by analyzing the measured S-parameter.

The materials used for the SO3 decomposer in Iodine-Sulfur (IS) cycle for Nuclear Hydrogen Production System require excellent mechanical properties as well as a high corrosion resistance in SO2/SO3 environment at an elevated temperature up to 950°C. So far, no metallic materials have been suggested to be useful in such an environment. A surface modification of Hastelloy X by a SiC coating processed by an electron beam evaporative deposition has been studied in combination with an ion beam mixing (IBM) and an ion beam hammering (IBH). The simply deposited SiC film on the Hastelloy X substrate is easily peeled-off during an annealing at a high temperature due to a huge difference in their coefficients of thermal expansion (CTE), however the SiC coating on Hastelloy X prepared with IBM is sustained above 900 °C when the heating rate is less than 10 °C/min. The process of coating and IBM consists of a thin SiC film deposition, a subsequent N ion beam bombardment, and then an additional deposition of the film to the designed thickness. IBM plays a role of fastening the SiC film on the Hastelloy X substrate until the interfacial reaction takes place. Once the reaction takes place, new phases are developed at the interface under the consumption of the film and the substrate materials, producing a buffer layer. Without IBM, the SiC film tends to be easily detached during an annealing before the interfacial reaction initiates. The SiC film prepared with IBM requires a post-deposition annealing in vacuum for the interfacial reaction. However, the sublimation of SiC film prepared by an electron beam evaporative deposition occurs at the temperature above 900 °Cdecreasing the thickness of the deposited film. The sublimation of the SiC film can be prevented by IBH in which ion beams are bombarded onto the deposited film. This may be attributed to an ion beam bombardment induced densification of the deposited film. The resultant SiC coated Hastelloy X prepared by IBM and IBH exhibits a high corrosion resistance in a sulfuric acid at 300 °C, suggesting a possible application for the IS cycle.