ゼツアツ コウトウ ウンドウ ケイソク システム ニ ヨル パーキンソンビョウ カンジャ ノ エンゲ ドウタイ ヒョウカ

The different forms of flowers in a species have attracted the attention of many evolutionary biologists, including Charles Darwin. In Fagopyrum esculentum (common buckwheat), the occurrence of dimorphic flowers, namely short-styled and long-styled flowers, is associated with a type of self-incompatibility (SI) called heteromorphic SI. The floral morphology and intra-morph incompatibility are both determined by a single genetic locus named the S-locus. Plants with short-styled flowers are heterozygous (S/s) and plants with long-styled flowers are homozygous recessive (s/s) at the S-locus. Despite recent progress in our understanding of the molecular basis of flower development and plant SI systems, the molecular mechanisms underlying heteromorphic SI remain unresolved. By examining differentially expressed genes from the styles of the two floral morphs, we identified a gene that is expressed only in short-styled plants. The novel gene identified was completely linked to the S-locus in a linkage analysis of 1,373 plants and had homology to EARLY FLOWERING 3. We named this gene S-LOCUS EARLY FLOWERING 3 (S-ELF3). In an ion-beam-induced mutant that harbored a deletion in the genomic region spanning S-ELF3, a phenotype shift from short-styled flowers to long-styled flowers was observed. Furthermore, S-ELF3 was present in the genome of short-styled plants and absent from that of long-styled plants both in world-wide landraces of buckwheat and in two distantly related Fagopyrum species that exhibit heteromorphic SI. Moreover, independent disruptions of S-ELF3 were detected in a recently emerged self-compatible Fagopyrum species and a self-compatible line of buckwheat. The nonessential role of S-ELF3 in the survival of individuals and the prolonged evolutionary presence only in the genomes of short-styled plants exhibiting heteromorphic SI suggests that S-ELF3 is a suitable candidate gene for the control of the short-styled phenotype of buckwheat plants

Formation of Al-Ni Intermetallic Layers Lining Microchannels Produced by Powder-Metallurgical Process Using Aluminum Sacrificial Cores

The mechanism of in-situ formation of Al-Ni intermetallic lining layers during microchannel formation in nickel bodies by a powder-metallurgical process has been investigated. Aluminum wire was used as a sacrificial core that gives the shape of the microchannel and supplies the alloying element for the lining layer. Nickel powder compacts with 29(±1)% porosity containing aluminum wires were heated from room temperature and then quenched at various temperatures between 873 K and 1473 K. Porous intermetallic lining layers were clearly recognized at temperatures above 1073 K. Each lining layer was built up from an outward-growing layer and an inward-growing layer. Change in the voidage in the outward-growing layer during heat treatment and the formation of a high-voidage zone around the lining layer were accounted for in terms of phase equilibria and unequal diffusion rates of the alloy elements in the Al-Ni intermetallic compounds and nickel solid solution

Filtration of Ni-Al Alloy Containing By-Product Alumina in Centrifugal Combustion Synthesis

The centrifugal combustion synthesis (CCS) process with a thermite-type combustion synthesis reaction can produce a joint of a cast Ni3Al member and a dissimilar material. We verify effectiveness of filtration of the combustion-synthesized Ni-Al alloy on the distribution of by-product alumina inclusions in the cast member. In the specimen produced without filtration, coarse alumina inclusions were distributed. In contrast, no such a fatal defect was observed in the filtrated specimen

Bonding Strengths of Interfaces between Cast Mg-Al Alloy and Cast-In Inserted Transition Metal Cores

The structures and strengths of the joining interfaces between Mg-10mass%Al alloy and cast-in inserted transition metal cores have been investigated. Three kinds of core materials were examined: S20C carbon steel, SUS304 stainless steel and titanium. The Mg-Al alloy specimen had higher shear strength than the pure Mg specimen for every core material. Molten Mg does not react with these core materials. On the other hand, molten Mg-Al alloy reacts with each core material and produces metallurgical joint with the core. The Ti core provided highest shear strength

Formation Mechanism of Microchannels and Lining Layers in Sintered Iron Powder Compacts with Copper Sacrificial Cores

The formation mechanism of microchannels with Fe-Cu alloy lining layers in iron bodies produced by a powder-metallurgical microchanneling process has been investigated. Copper wire was used as a sacrificial core that gives the shape of the microchannel and supplies the alloying element for the lining layer. An iron powder compact containing the sacrificial core was heated and sintered at temperatures between the melting points of copper and iron. Quenching experiments showed that the microchannel was produced just after melting of copper. In a quenched specimen with a newly-formed microchannel, fine copper-rich regions were observed between the iron powder particles in the lining layer. These results established that infiltration of molten copper into the iron powder is the dominant mechanism for the Fe-Cu microchanneling process. It was also found that the liquid copper infiltrated via preferential flow pathways between the iron powder particles

Formation of Porous Intermetallic Thick Film by Ni-Al Microscopic Reactive Infiltration

Microporous structures of nickel-aluminide thick films lining the inner wall of microchannels have been investigated. The microchannels were produced in metal bodies by a powder metallurgical process utilizing microscopic reactive infiltration. In the experiment, a nickel-powder compact containing shaped aluminum wires was sintered at a temperature between the melting points of nickel and aluminum. Infiltration and diffusion of aluminum into the surrounding nickel powder, accompanied by the reaction between the metals, occurred during the sintering and brought about the formation of microchannels lined with a NiAl intermetallic layer. In this process, nickel powder composed the device body, and the aluminum wires gave the shape of the microchannels. The intermetallic layer had a microporous structure when the diameter of the aluminum wire was 500 μm and the porosity of the compact specimen was 23.6–31.5% within the porosity range examined. When the porosity was 36.0%, such a structure, the porous thick film, was not observed. On the other hand, the porous NiAl thick film was produced in all specimens with an aluminum wire of 200 μm in diameter. The voidage of the porous thick film was maximized when the porosity of the compact specimen was 29.8%, and it reached to 53.8% in the case the diameter of the aluminum wire was 500 μm, and 60.2% in the case that was 200 μm

Precision Casting of Ni-Al Alloy and Simultaneous Joining to Dissimilar Metals by Modified Centrifugal Combustion Synthesis

A modified centrifugal combustion synthesis process has been developed that enables precisely casting synthesized materials and simultaneously joining them to a dissimilar metal. The material to be synthesized was a Ni–25 mol%Al alloy; that to be bonded with the synthesized material was a stainless steel, an ultra-low carbon steel, pure nickel or a Ni–25 mol%Al alloy. The base material to be bonded; a graphite mold; and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, synthesized molten Ni–Al alloy flew into the mold and collided with the base material. This process was successfully applied in joining the synthesized Ni–Al alloy and various base materials. Centrifugal force was also confirmed to assist the molten Ni–Al alloy fill the mold cavity and adhere to the surface of the base materials

Microchanneling and Lining Layer Formation by Spontaneous Infiltration in Fe-Cu System

The influence of the body-metal powder size on the microchanneling behavior and the lining-layer formation in the powder-metallurgical microchanneling process was investigated using the combination of iron powder and copper wire. Iron powders 45 μm and 110 μm in average diameters were examined. Open microchannels and clear lining layers were formed in all specimens. The coarser iron powder tended to reduce the homogenization rate of the composition of the lining layer

Simulation of Peritectic Reaction during Cooling of Iron-Carbon Alloy

The effects of cooling rate on the growth behavior of austenite phase during cooling of an iron-carbon alloy are investigated by means of a numerical simulation . In the cooling process of this alloy, austenite phase nucleates at the interface between δ-ferrite and liquid phases at the peritectic temperature 1768 K and then keeps growing during cooling. The growth mechanisms of austenite phase during cooling are: (1) carbon diffusion from liquid phase through austenite phase into δ-ferrite phase, (2) precipitation from δ-ferrite phase, and (3) crystallization from liquid phase. All these mechanisms induce the growth of austenite phase with increasing cooling rate. The ratio of austenite phase which grows by precipitation and crystallization increases with increasing cooling rate, while that by carbon diffusion decreases. The decrease in the ratio of the diffusional growth is more remarkable for the migration of austenite/liquid interface than for that of δ-ferrite/austenite interface

Fabrication of Microchannels in Metallic Wire Bundles by a Sacrificial-Core Method

We examined a new method for producing a metallic thin rod or band in which a long microchannel ran through its entire length. A tin wire and about 140 copper wires were inserted in a nickel sheath. They were cold rolled to produce a band specimen. It was heated to 1173 K and then furnace-cooled. The band specimens before and after the heat treatment were cast-in inserted in aluminum. In either case, an open microchannel formed at the site initially occupied by the tin wire, and thus the aluminum casting containing the band had the long microchannel in its body