Search

In this study, the distribution of colloidal nano-gold particles on the nanoporous surfaces of FeAl single crystals was investigated. Colloidal nano-gold particles were dropped onto the nanoporous surface, and their distribution was observed by TEM. Some of nano-gold particles located at the edges of nanopores. A few additional attempts to improve the wettability of the surfaces were made using surface treatments. As a result, the frequency of nano-gold particles put into nanopores was achieved up to 98.3%.

The apparent activation energy for rupture life sometimes changes from a high value of short term creep to a low value of long term creep. This change results in overestimation of rupture life recognized recently in advanced high Cr ferritic steels. The present study examined how to detect the decrease of activation energy in 9-12 %Cr steels with tempered martensitic lath microstructure. During aging without stress hardness of the tempered martensite microstructures remains almost constant in short term, whereas it decreases with increasing time after long term exposure. The onset of hardness drop can be a good measure of the decrease of activation energy. Causes of the hardness drop and the decrease of activation energy are discussed.

The aims of this research are to investigate the effect of Sm addition in Mg-Al-Ca alloys on microstructure and mechanical properties. Sm addition to Mg-5Al-3Ca based alloys results in the change from dendritic to equiaxed grain morphorlogy and formation of Al-Sm rich itermetallic compounds at grain boundary and α-Mg matrix. And these Al-Sm rich intermetallic compounds were dispersed homogeously and stabilized at high temperature. And maximum yield and ultimate strength value was obtained at Mg-5Al-3Ca-2Sm alloys at elevated temperature because of homogeneous dispersion of stable Al-Sm rich intermetallic compound at high temperature.

Recent researches have shown the premature breakdown of creep rupture strength in long term creep region of advanced high Cr ferritic steels. As safe operation of power plants becomes a serious problem we should be able to detect and predict the breakdown transition of creep rupture strength. Some methods for detecting the breakdown transition have been presented till now like the measurement of reduction of area after creep rupture and particle size of laves phase. However it will be more economic if we make use of non-destructive tests, for example, hardness testing. In this paper 3 types of ferritic steels with different Cr concentration have been studied. The results suggest that the hardness of aged structures is constant independently of exposure time in short term region, whereas the hardness breaks down in long term region. The boundary of breakdown in hardness coincides with that of breakdown in creep rupture strength.

Mg97Zn1Y2 alloy powders were prepared from gas atomization process, followed by consolidation using spark plasma sintering (SPS) process. The atomized Mg97Zn1Y2 alloy particles were entirely spherical in shape and dendrite microstructure. The compacts sintered by SPS process have values more than 99% of theoretical density. The compressive yield strength was decreased as sintering temperature increased. It is found that the compressive strength showed the maximum value of 303MPa at the sintered specimen under load of 250MPa at 350°C.

As samarium addition was increased, α- Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased from 101.6㎛ to 39.3㎛. Samarium addition to Mg-5Al-3Ca based alloys resulted in the formation of Mg-Al-Sm thernary intermetallic compounds at grain boundarys and α-Mg matrix grains. In these alloys, two kinds of eutectic structure were observed; coarse irregular-shape structure at grain boundary and fine needle-shape structure in the α-Mg matrix grain. It is found that the yield strength and ultimate strength showed the maximum value of 109.1MPa and 139.3 at Mg-5Al-3Ca-2Sm alloy, respectively.

A thixomoulded magnesium alloy containing thermally stable Al2Ca phase was friction stir processed, and its microstructure and mechanical property were investigated. In friction stir zone, the cast structure of the base metal is replaced by fine magnesium grains containing fine dispersoides of Al2Ca. Due to the refined grain size of 0.8-1 μm, hardness of friction stir zone is higher than that of base metal. Texture was developed at top and bottom surfaces, (0002) being parallel to the plate surface, whereas (0001) plane is randomly oriented in the center of friction stir zone.

THERMEC 2006 From 7/4/2006 To 7/8/2006, Vancouver, Canada, available, unclassified, unlimited

We propose here a novel interpretation of the embryonic origin of cells of diencephalic sensory relay nuclei in teleosts based on our recent studies of gene expression patterns in the medaka (Oryzias latipes) embryonic brain and comparative hodological studies. It has been proposed that the diencephalic sensory relay system in teleosts is unique among vertebrates. Teleost relay nuclei, the preglomerular complex (PG), have been assumed to originate from the basal plate (the posterior tuberculum) of the diencephalon, whereas relay nuclei in mammals are derived from the alar plate (dorsal thalamus) of the diencephalon. Our results using in situ hybridization show, however, that many pax6- or dlx2-positive cells migrate laterally and ventrocaudally from the diencephalic alar plate to the basal plate during development. Massive clusters of the migrated alar cells become localized in the mantle layer lateral to the posterior tubercular neuroepithelium, from which main nuclei of the PG appear to differentiate. We therefore consider most if not all neurons in the PG to be of alar, not basal, origin. Thus, the teleost PG, at least in part, can be regarded as migrated alar nuclei. Developmental and hodological data strongly suggest that the teleost PG is homologous to a part of the mammalian dorsal thalamus. The organization and origin of the diencephalic sensory relay system might have been conserved across vertebrates.

Exposure to ionizing radiation (IR) could induce deleterious effects including cancer. Diet, as one of the major factors to influence susceptibility to many diseases, plays a critical role in maintaining human heath. It is known that unbalanced diet could result in health consequences, for example, high-calorie diet could lead to obesity, which could increase the risk of diabetes, heart disease, fatty liver, and some forms of cancer. Although the impact of diet on susceptibility to IR is thought to be big, the evidence is not clear due to lack of study. In this work, effects from dietary fat on modulation of mouse responses to total-body-irradiation (TBI) were studied. The mice were fed after weaning at postnatal age of 4 weeks with a standard diet (MB-1), a very high-fat diet (HFD32), and a very low-fat diet (CE-2 Low Fat), containing of 4.4%, 32.0%, and 0.4% of crude fat, respectively. A mouse model for radiation-induced adaptive response (AR) was applied to this work. The priming low-dose TBI at a dose of 0.5 Gy from X-rays was given at postnatal age of 6 weeks, and the challenge high dose of TBI was given at postnatal age of 8 weeks. The mouse response to low dose of TBI was evaluated by the efficacy of the priming low dose to rescue the animals from bone marrow death induced by the challenge high dose in the 30-day survival test. The mouse response to high dose of TBI was evaluated by comparing the LD50 in the 30day survival test. In addition, dietary modulation of the residual (late) genotoxic effect from TBI was also evaluated by comparing the incidence of micronucleated erythro‐ cytes in bone marrow using micronucleus test. Results showed that for the mice fed with the MB-1, a successful AR was demonstrated. While for the mice fed with either HFD32 or CE-2 Low Fat, no AR was observed, and all the animals died within 15 days after TBI with the challenge high dose at 7.5 Gy regardless the priming low dose at © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 0.5 Gy. When comparing the LD50 in the 30-day survival test, the LD50 values for the animals fed with the MB-1, HFD32 diet, and CE-2 Low Fat were 7.1 Gy, 6.0 Gy, and 6.2 Gy, respectively. As to the micronucleus test, for the mice fed with MB-1, the priming low dose at 0.5 Gy could significantly reduce the incidence of micronucleated erythrocytes in bone marrow that were caused by a challenge high dose at 4.0 Gy, while for the mice fed with either HFD32 or CE-2 Low Fat no such effect was observed. These findings indicated that under an unbalanced diet, namely, either of very high fat or of very low fat, alterations in mouse responses to TBI were induced. These findings confirmed that diet played a pivotal role in the response of the animals to radiation exposure, and suggested the possibility to modulate radiosensitivity through diet intervention in humans.

After the accident at the Fukushima Daiichi Nuclear Power Plant (F1NPP) in March 2011, much attention has been paid to the biological consequences of the released radionuclides into the surrounding area. We investigated the morphological changes in Japanese fir, a Japanese endemic native conifer, at locations near the F1NPP. Japanese fir populations near the F1NPP showed a significantly increased number of morphological defects, involving deletions of leader shoots of the main axis, compared to a control population far from the F1NPP. The frequency of the defects corresponded to the radioactive contamination levels of the observation sites. A significant increase in deletions of the leader shoots became apparent in those that elongated after the spring of 2012, a year after the accident. These results suggest possibility that the contamination by radionuclides contributed to the morphological defects in Japanese fir trees in the area near the F1NPP.

Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding (FSW) was investigated through pole figure measurement and X-ray diffraction (XRD) pattern analysis. It was found that at the top and bottom surfaces of friction stir zone (FSZ), (0002) basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and (0002) basal planes showed a random distribution.

available, unclassified, unlimited

Premature breakdown of creep strength is a serious problem to be solved in long-term creep of advanced high Cr ferritic steels. The material studied was ASTM grade 92 steel crept at 550–650 °C for up to 63 151 h. Stress exponent for rupture life decreases from 17 in short-term creep to 8 in long-term creep, confirming the breakdown in the steel. The steel shows ductile to brittle transition with increasing rupture life, and the breakdown accords with the onset of brittle intergranular fracture. Creep cavities are nucleated at coarse precipitates of Laves phase along grain boundaries. These findings suggest the following story of the breakdown of creep strength. Laves phase precipitates and grows during creep exposure. Coarsening of Laves phase particles over a critical size triggers the cavity formation and the consequent brittle intergranular fracture. The brittle fracture causes the breakdown. The coarsening of Laves phase can be detected non-destructively by means of hardness testing of the steel exposed to elevated temperature without stress.

Long-term creep rupture life is usually evaluated from short-term data by a time-temperature parameter (TTP) method. The allowable stress of Gr.122 steel listed in the ASME code has been evaluated by this method and is recognized to be overestimated. The objective of the present study is to understand the causes of the overestimation and propose appropriate methodology for avoiding the overestimation. The apparent activation energy Q for rupture life of the steel changes from a high value of short-term creep to a low value of long-term creep. However, the decrease in Q is ignored in the conventional TTP analyses, resulting in the overestimation of rupture life. A multiregion analysis of creep rupture data is employed to avoid the overestimation; in the analysis creep rupture data are divided into a couple of regions so that the Q value is unique in each divided region. The multiregion analysis provides a good fit to the data and the lowest value of 105h creep rupture strength among the three ways of data analysis examined. A half of 0.2% proof stress cannot provide an appropriate boundary for dividing data to be used in the multiregion analysis. In the 2001 edition of the ASME code an F average concept has been proposed as a substitution for the safety factor of 2∕3 for average rupture stress. The allowable stress of Gr.122 steel changes significantly depending on the allowable stress criteria as well as the methods of rupture data analysis: i.e., from 74MPato48MPa.

Finer lamellar spacing in the lamellar structure of a Ti–45Al–2Nb–2Mn + 0.8 vol.%TiB 2 (45XD) alloy does improve the primary creep resistance. However, the unstable nature of the fine plate contributes largely to the degradation of the lamellar structure and a rapid increase in the tertiary creep rate, indicating that a fine lamellar structure has a detrimental effect on the long-term creep.

The microstructure and material properties of continuous cast 5052 alloy sheet in as-received condition (as-received sheet) and laboratory cold rolled condition (lab-processed sheet) were investigated after annealing treatment. Microstructural examinations show that the cold rolling process increases the extent of centerline segregation of second-phase particles. The increase in rolling reduction results in a decrease of grain size and a more random distribution of crystallite orientations. Tensile test results indicate that all the sheets exhibit two-stage strain-hardening behavior. Cold rolling increases the total elongation and n2-value in the transverse direction of the lab-processed sheet with a thickness of 1.6 mm. However, further increase in the rolling reduction leads to an increase of UTS with a decrease of elongation and n2-value. Furthermore, from the determined forming limit curves (FLCs), it is found that the 1.6 mm thick lab-processed sheet has better stretchability than the as-received sheet, whereas further cold rolling reduces the level of FLC. The effects of cold rolling on the mechanical property and formability are discussed in terms of the microstructural changes.

In a fully lamellar Ti–48Al + W alloy, β phase precipitated by aging lowers the primary creep rate significantly. However, dynamic precipitation of the β phase during long-term creep reduces the steady-state creep rate of the unaged alloy close to that of the alloy in the aged condition.

Developmental neurotoxicity/Brain/X-rays/Cell death/Medaka. Medaka ( Oryzias latipes ) embryos at 25‐26 and 28‐30 stages were irradiated with a single acute dose of 10 Gy of X-ray, which is lower than the LD 50 of the embryos. The effects on developing brains were examined under a stereomicroscope in living embryos until hatching. All the irradiated embryos survived; however, from 6 to 35 h after X-ray irradiation, massive clusters of optically opaque and round cells were observed either in the entire brain region (when irradiated at 25‐26 stages) or mainly in the optic tectum (when irradiated at 28‐30 stages). Histological examination and TUNEL showed that these cells are clusters of dead cells. These dead cell clusters disappeared thereafter, and the irradiated embryos continued to develop apparently normally. The grown irradiated embryos, however, had smaller brains and eyes than the nonirradiated control embryos. At hatching, the irradiated embryos exhibited histological abnormalities in the brain, particularly in the torus longitudinalis, and in the retina, although most of them hatched normally and survived. The results indicate that brain cell death and a reduced brain size can be observed in living irradiated embryos, and suggest that the medaka embryo is useful for screening the developmental neurotoxicity effects of various hazardous factors.

We compared the newly developed heat resistant magnesium alloy with conventional ones by Thixomolding® and aluminum alloy by die casting. Tensile properties at elevated temperatures of AXEJ6310 were equal to those of ADC12. In particular, elongation tendency of AXEJ6310 at higher temperature was better than those of the other alloys. Creep resistance of AXEJ6310 was larger than that of AE42 by almost 3 orders and smaller than that of ADC12 by almost 2 orders of magnitude. Fatigue limits at room temperature and 423K of AXEJ6310 was superior among conventional magnesium alloys.

Lamellar microstructures of a Ti-48 mol.% Al alloy were varied by changing heating rate in the α + γ dual phase field, and their creep properties were investigated at 1150 K and 316 MPa. The minimum creep rate of the alloy first decreases and then increases with increasing the heating rate. Average spacing of α2 lamellae decreases and density of γ/α2-lamellar boundaries increases with increasing the heating rate. The high density of γ/α2 boundaries stabilizes the lamellar microstructure during creep, resulting in the decrease in the minimum creep rate. With increasing the heating rate, α2 lamellae are discontinuous and γ/α2 boundaries become less efficient in retarding recovery. This microstructural degradation results in the increase in creep rate at high heating rate. A reduction of creep rate by one order of magnitude from as-grown lamellar microstructure is achieved at the optimal heating rate.

n/a, available, unclassified, unlimited

Microstructures of a heat-resistant magnesium alloy prepared by friction stir welding were investigated. In the friction stir zone, the microstructure of the thixomoulded parent material is replaced by fine magnesium grains and small particles of intermetallic compounds (Al 2 Ca). Due to microstructural refinement, the microhardness of the friction stir zone is higher than that of the base material.

The fully lamellar structure of a Ti–48Al alloy was subjected to secondary annealing heat treatments with controlled heating rates in the α + γ dual phase field to produce various lamellar structures. The effects of heating rate on the microstructure and creep property were investigated. It was found that the α 2 lamellar spacing, length and thickness decrease with increasing heating rate. The decrease of α 2 lamellar spacing is most effective at lower heating rate, and minimum creep rate decreases with increasing heating rate, since a high density of γ/α 2 boundaries stabilizes the lamellar microstructure. Secondary γ precipitation in thick α 2 laths may also contribute to the decrease of the minimum creep rate at the lower heating rate. On the other hand, creep rate increases at high heating rate since α 2 laths become discontinuous with increasing heating rate. A reduction of creep rate by one order of magnitude was achieved at the optimum heating rate providing the best combination of narrow spacing and sufficiently long length of α 2 lamellae.

Hard oriented PST crystals of a Ti-48 mol%Al alloy, in which lamellar boundaries are aligned parallel or perpendicular to stress axis, were creep tested. PST crystals of different α2 spacing were used: one has the equilibrium amount of α2 phase and the other contains an excess amount. Activation energy for creep rate of the former is 350 kJ/mol, being close to that of self-diffusion. The other crystal having fine α2 spacing provides lower creep rate due to its more significant strain hardening in the primary creep stage. This crystal shows substantially high activation energy of 510 kJ/mol. The superior creep resistance of the fine α2 spacing and its high activation energy is discussed in conjunction with the characteristics and degradation of lamellar structure in the material having the fine initial α2 spacing.

Superplasticity and superplastic diffusion bonding in a TiAl alloy with a fine-grained duplex microstructure have been investigated in order to fabricate TiAl alloy products using a combination process of superplastic forming with diffusion bonding. Superplastic tensile tests were carried out at temperatures ranging from 1000 to 1100 � C, and at strain rates ranging from 10 � 5 to 10 � 3 s � 1 . A low superplastic flow stress of less than 25 MPa was observed at 1100 � C and at a strain rate of 8:3 � 10 � 5 s � 1 . Under this condition, a tensile elongation of 300% and a strain rate sensitivity coefficient of over 0.5 were obtained. Furthermore, superplastic diffusion bonding under a low pressure of 10 MPa was conducted. Defect-free bonds were achieved at 1100 � C for holding 1 h. It is suggested that the low superplastic flow stress at 1100 � C allows a significant plastic flow between the two contacted surfaces, resulting in a full contact of the surfaces, which is necessary for the sound bonds. Finally, a twosheet part of spherical dome was successfully produced from this alloy.

Compressive Creep behavior of a hot-rolled Mg–Y binary alloy and Mg–Y–Zn ternary alloys was investigated at 650 K. Creep strength of Mg–Y alloys was significantly improved by the addition of zinc. In Mg–Y–Zn alloys, many “planar faults” were formed on (0 0 0 1) matrix planes at high temperatures even with small addition of 0.02 mol% zinc. The stacking fault energy decreased by the simultaneous addition of yttrium (Y) and zinc and many a -dislocations on basal planes were extended. The separation width of the extended dislocations is stabilized by the segregation of yttrium and zinc and the separation width significantly increases under the interaction of partial dislocations on different basal planes. The excellent creep strength in Mg–Y–Zn was explained by the decrease of the mobility of these widely extended dislocations.

Hard oriented PST crystals of a Ti–48 mol% Al alloy, in which the stress axis is parallel or normal to lamellar boundaries, were creep tested. The lamellar structures contain γ/α 2 boundaries and three types of γ/γ boundaries. Changes of lamellar structures in the PST crystals were examined during high-temperature exposure with (creep) or without applied stress (annealing). Coarsening and spheroidization of the lamellar structures are typical degradation processes observed experimentally. γ/γ lamellar boundaries migrate and coalesce with other γ/γ boundaries and α 2 lamellae dissolve during the high-temperature exposure. These events result in the coarsening and the spheroidization. Thermal stability of each lamellar boundary depends on its boundary type. A higher density of γ/α 2 lamellar boundaries is recommended for retarding the coarsening and the spheroidization, and thereby making a thermally stable lamellar structure. The high density of γ/α 2 boundaries is confirmed experimentally to provide good creep resistance.

Strengthening by refinement of lamellar thickness was studied at room temperature on dual phase Ti–39.4mol%Al alloy over a wide range of average lamellar thickness λ from 850 to 20 nm. The relation between yield stress σy and λ was examined, paying special attention to the change in lamellar boundary structure. The γ/α2 lamellar boundaries in the alloy are found to be perfectly coherent in thin lamellar structure formed at low aging temperatures. In thick lamellar structure formed at high aging temperatures, misfit dislocations were introduced to relieve the lattice misfit and are found on the lamellar boundaries. Both thin lamellae with coherent boundaries and thick lamellae with dislocated ones are present in a lamellar structure formed at an intermediate aging temperature. The critical thickness of γ lamella for the introduction of misfit dislocations is about 50 nm. The dislocated boundaries render a high resistance to dislocation motion across the boundaries. A Hall–Petch relation holds in the range of λ > 170 nm, and the Hall–Petch slope takes a large value corresponding to the high boundary resistance. The coherent boundaries provide a relatively low resistance. Another σy–λ correlation typical of the coherent boundary appears in the range of λ < 100 nm. The yield stress saturates to an upper limit of 1 GPa at λ = 70 nm. The transition from the property of dislocated boundary to that of coherent boundary proceeds with an increase in the density of the coherent boundaries within the range of λ = 170–100 nm.

Recently we cloned two globin gene clusters from the genome of medaka (Oryzias latipes): one designated the embryonic globin gene cluster (E1; (5')alpha0(3')-(3')beta1(5')-(5')alpha1(3')-(5')beta2(3')-(5')alpha2(3')-(3')alpha3(5')-(5')beta3(3')-(3')beta4(5')-(5')alpha4(3')-(3')psialpha(5')-(5')psibeta(3')) and the other the adult globin gene cluster (A1; (3')ad.alpha1(5')-(5')ad.beta1(3')-(3')ad.alpha2(5')). The E1 and A1 clusters map to linkage groups 8 and 19, respectively. The genes beta1/alpha1, alpha3/beta3, beta4/alpha4, psialpha/psibeta and ad.alpha1/ad.beta1 are organized in head-to-head orientation with respect to transcriptional polarity. The genes alpha0, alpha1 and alpha2 are arranged in tandem with the same orientation. The results suggest that a variety of events occurred in globin gene evolution such as chromosomal translocation, duplication of alpha/beta-paired genes, tandem duplication of single alpha genes and the transformation of one pair of alpha/beta-paired genes into pseudogenes (psialpha/psibeta). Amino acid sequences predicted from the genes were compared with those of 42 alpha and 55 beta teleostean globins using the neighbor-joining or maximum likelihood methods. The phylogenetic trees that were generated classified the teleostean globins into at least four groups, tentatively named 'Embryonic Hb Group (I)', 'Notothenioid Major Adult Hb Group (II)', 'Anodic Adult Hb Group (III)' and 'Cathodic Adult Hb Group (IV)'. The medaka genes alpha0, beta1, alpha1, alpha2, alpha3, beta3, beta4 and alpha4 belong to group I, and ad.alpha1 and ad.beta1 to group II. Further analysis suggests that psialpha/psibeta and beta2/ad.alpha2 belong to groups III and IV, respectively. Thus, globin genes in the medaka probably were diversified from four ancestral genes, one for each group. On the basis of the gene comparisons, we present a hypothetical pathway for globin gene evolution in the medaka.

We isolated globin genes from a genomic DNA library of the drR strain of medaka Oryzias latipes, and walked on chromosome. The present study is the first demonstration of the full-length structure of globin gene locus in the teleosts. Two gene clusters were found. One cluster of 36 kbp consisted of nine globin genes and two pseudogenes. Based on structural and phylogenetic similarity of amino acid sequences, the cluster was named embryonic globin gene cluster (E1). The orientation of the genes was in (5')alpha0(3')-(3')beta1(5')-(5')alpha1(3')-(5')beta2(3')-(5')alpha2(3')-(3')alpha3(5')-(5')beta3(3')-(3')beta4(5')-(5')alpha4(3')-(3')psialpha(5')-(5')psibeta(3'). The other cluster of 20 kbp contained three globin genes ((3')ad.alpha1(5')-(5')ad.beta1(3')-(3')ad.alpha2(5')), and was named adult globin gene cluster (A1). Genetic linkage analysis clarified that E1 and A1 were mapped on linkage groups 8 and 19, respectively. The E1 cluster included other genes homologous to human EST clone KIAA0172, Sushi-1 retrotransposon, and protein 14 gene-like gene, while the A1 cluster linked to aquaporin-8 gene-like gene. The expression patterns of the genes were classified into four types: embryo-specific expression (alpha3, beta3, alpha4 and beta4), expression in embryo to young fish (alpha0, beta1, alpha1 and ad.alpha2), expression in young to adult fish (alpha2 and ad.alpha1) and successive expression in embryo to adult (ad.beta1).

We isolated seven cDNA clones from embryos of the Japanese eel Anguilla japonica. Each deduced amino acid sequence consisted of a signal peptide, a propeptide and a mature enzyme portion belonging to the astacin protease family. A phylogenetic analysis showed that the eel enzymes resembled the high choriolytic enzyme (HCE) of medaka Oryzias latipes, and the hatching enzymes of the zebra fish Danio rerio and masu salmon Oncorhynchus masou. Hatching enzymes of these teleosts belonged to the group of the medaka HCE, and not the medaka low choriolytic enzyme (LCE), another hatching enzyme of medaka. Southern blot analysis showed that the genes of the eel hatching enzymes were multicopy genes like the medaka HCE genes. However, one of the eel hatching enzyme genes comprised eight exons and seven introns, and the exon-intron organization was similar to the medaka LCE gene, which is a single-copy gene. The molecular evolution of the fish hatching enzyme genes is discussed. In addition, whole-mount in situ hybridization and immunocytochemistry showed that the eel hatching enzyme was first expressed in the pillow anterior to the forebrain of early neurula, and finally in the cell mass on the yolk sac of later stage embryos. The early differentiation profile of eel hatching gland cells was similar to that of medaka, masu salmon and zebrafish, whereas the final location of the gland cells was different among fishes.

Extruded and subsequently rolled sheets of AZ61 (Mg-6Al-1Zn in mass%) were tensile tested at room temperature at an initial strain rate of 1×10-3s-1. The effects of extrusion ratio and tensile direction on fracture elongation were investigated. Extrusion ratios were 3.4/100 and 1.0/100 in area reduction. Tensile direction was chosen to be 0, 45 and 90° with respect to the rolling direction. Texture change with strain was also investigated in order to understand a major dislocation slip system.We found that the magnitude of basal-plane tilt with respect to the tensile axis was a controlling factor for a major slip system and for fracture elongation. When the basal planes were tilted by more than approximately 16° from the normal direction towards the tensile direction, a major slip system was basal a dislocation slip and poor ductility was obtained. In contrast, with less tilting than 16°, a major slip system changed to non-basal a dislocation slip, which leads to better ductility. The present results indicated an importance of texture control in tensile ductility of Mg alloys.

In order to know the general pattern of axonogenesis in vertebrates, we examined axonogenesis in the embryonic brain of a teleost fish, medaka (Oryzias latipes), and the results were compared with previous studies in zebrafish and mouse. The axons and somata were stained immunocytochemically using antibodies to a cell surface marker (HNK-1) and acetylated tubulin and visualized by retrograde and anterograde labeling with a lipophilic dye. The fiber systems developed correlating with the organization of the longitudinal and transverse subdivisions of the embryonic brain. The first axons extended from the synencephalic tegmentum, forming the first fiber tract (fasciculus longitudinalis medialis) in the ventral longitudinal zone of the neural rod, 38 hours after fertilization. In the neural tube, throughout the entire brain two pairs of longitudinal fiber systems, one ventral series and one dorsal or intermediate series, and four pairs of transverse fiber tracts in the rostral brain were formed sequentially during the first 16 hours of axon production. In one of the dorsal longitudinal tracts, its branch retracted and disappeared at later stages. One of the transverse tracts was found to course in the telencephalon and hypothalamus. The overall pattern of the longitudinal fiber systems in medaka brain is similar to that in mouse, but apparently different from that in zebrafish. We propose that a ventral tract reported in zebrafish partially belongs to the dorsal fiber system, and that the longitudinal fiber systems in all vertebrate brains pass through a common layout defined by conserved genetic and developmental programs.

A near lamellar microstructure and two fine-grained fully lamellar (FGFL) microstructures in Ti-45Al-2Nb-2Mn+0.8 vol%TiB 2 alloy were prepared by selected heat treatments, and the fully lamellar microstructures were aged for stabilizing the lamellar plates. Microstructural examination and tensile creep tests at 760°C showed that the near lamellar microstructure possessed inferior creep resistance due to its coarse lamellar spacing and its larger amount of equiaxed y grains at colony boundaries. The fine lamellar spacing as well as the fine lamellar colony size gave a major contribution to make the minimum creep rates smaller in the fully lamellar TiAl alloys. Since aging treatments stabilized the lamellar microstructures and delayed the degradation process during creep deformation, the aged samples exhibited lower minimum creep rate and longer creep life than the corresponding samples without the aging treatment. These results suggest that a fine as well as stabilized fully lamellar structure is a critical factor to improve the creep resistance of TiAl alloys in terms of short and long-term creep.

Three kinds of microstructures with different grain boundary morphologies and their creep properties of a Ti-47Al-2Nb-2Mn+0.8 vol%TiB 2 alloy are investigated. Tensile creep tests and microstructural examinations indicatethat a stabilized fine-grained fully lamellar (FGFL) microstructure with relatively smooth grain boundaries shows inferior creep resistance. A stabilized fully lamellar (FL) microstructure with well-interlocked grain boundaries and wider lamellar spacing yields reduced minimum strain rate and extended creep rupture life. Furthermore, a nearly lamellar microstructure (NL) with well-interlocked grain boundaries exhibits better creep resistance than the stabilized FGFL microstructure though it has four times wider lamellar spacing and 15 vol% equiaxed y grains at the grain boundaries, but worse creep resistance than the stabilized FL microstructure. Examinations to the deformed microstructures show that grain boundary instability involving spheroidization of the lamellae is a major microstructural degradation process, resulting in fine globular regions at the grain boundaries. Voids develop along the grain boundaries, particularly in the fine globular regions, leading to intergranual fracture. It is suggested that grain boundary sliding (GBS) is operating in the stabilized FGFL microstructure, and promotes mutually with the grain boundary instability during subsequent creep deformation, resulting in increased minimum strain rate and shortened tertiary stage. The well-interlocked grain boundary inhibits the onset of GBS and enhances the grain boundary stability effectively. These results demonstrated that the grain boundary stability has a great effect on creep behavior of TiAl Alloys.

We have developed a technique for estimating 3D motion of knee prosthesis from its 2D perspective projections. Our primary studies of computer model simulation and experiments on the CCD images of prosthesis demonstrated sufficient accuracies of position/orientation estimation for knee prosthesis. Then we changed over our project from the basic analyses and experiments to the countermeasurements against various problems which could possibly happen at clinical application. Among them, the following problems and their solutions are stated in this paper : Miss estimation for an orientations of a tibial compartment due to its symmetry-like shape, effects of image quality on the estimation accuracies. It is also ahown an idea how to improve the estimation accuracy of translation along the direction perpendicular to the image plane.

Simulations of magnetized [or magnetically enhanced reactive ion etch (MERIE)] plasma sources are increasingly in demand with the advent of 300 mm technology in which plasma sources (like MERIE tools) are believed will play a prominent role. Resolving locality issues and understanding how electrons relax in electric and magnetic fields are important in the understanding of electron heating and the resolution of numerical issues associated with the simulations of these phenomena. In this paper describing Monte Carlo simulations of electron swarms, it is shown that electron swarms in crossed electric and magnetic fields have appreciable relaxation times related to their evolution to steady-state mean electron energy. These times are correlated to relaxation lengths that are on the order of 0.1 cm to 10 cm and increase with increasing reduced magnetic field. The times and distances are parameterized over the ranges of 100–106 G/Torr and 28–1415 Td. Finally, parallelization through Java-based remote method invocation and distributed computing is presented as a successful approach for solving large-particle-number Monte Carlo simulations, the type of which are employed in this study.

The addition of zinc is effective in improving creep strength of Mg–Y solid solution alloys at temperatures 550–650 K because zinc suppresses the non-basal slip that operates predominantly at such temperatures. This suppression is caused by the formation of planar defects on the (0 0 0 1) plane and confinement of dislocations in the basal plane due to a decrease in stacking fault energy.

Rolled sheets of AZ31 Mg alloys were subjected to tensile testing at temperatures ranging from room temperature to 523K. The occurrence of grain-boundary sliding (GBS) at room temperature was demonstrated by the displacement of scribed lines across grain boundaries of deformed samples. Surface relief of deformed samples was measured by use of a scanning laser microscope. GBS strain was calculated from the measured surface step height, and its temperature dependence was analyzed by a Dorn-type constitutive equation. GBS above 423K was found to be pure GBS that was activated by resolved applied shear stress acting on grain boundaries. The activation energy for GBS was found to be 80 kJ/mol, which is in agreement with the activation energy for grain boundary diffusion. Meanwhile, GBS below 373K was found to be slipinduced GBS, and its extent was found to be significantly greater than that expected from extrapolation of high-temperature values. The slipinduced GBS is considered to occur by plastic compatibility conditions in the presence of plastic strain anisotropy and by absorption and dissociation of lattice dislocations at grain boundaries.

Using the teleost Oryzias latipes (medaka), we isolated three embryonic globin cDNAs (em.alpha-0, em.alpha-1, and em.beta-1) from the embryos 5 days after fertilization (at 30 degrees C) and two adult globin cDNAs (ad.alpha-1 and ad.beta-1) from the kidney of the fully-grown adult fish, and predicted their amino acid sequences. Molecular phylogenetic analysis showed that the embryonic globins were highly homologous in amino acid sequence to the embryonic globins previously identified in rainbow trout and zebrafish, and that they formed a monophyletic group among the teleostean globin molecules. They were clearly discriminated from the adult globin of the medaka. RT-PCR analysis showed that the embryonic globin mRNAs were intensely expressed in stage 30 and 38 embryos and in young fish 30 days after hatching. The level of expression decreased drastically after the young fish stage, and was low in fully-grown adult fish. The adult alpha globin mRNA ad.alpha-1 was scarcely expressed in the embryos, and the level of expression gradually increased in young to fully-grown adult fish. Unexpectedly, the adult beta globin mRNA ad.beta-1 was expressed throughout life, from the early embryonic stage to the fully-grown adult stage. This expression profile was quite different from that of the rainbow trout previously investigated. Some globins of the medaka were expressed both in primitive hematopoiesis and in definitive hematopoiesis.