Influence of Ag on Kinetics of Solid-State Reactive Diffusion between Pd and Sn

The influence of Ag on the kinetics of the solid-state reactive diffusion between Pd and Sn was experimentally examined using Sn/ (Pd-Ag)/Sn diffusion couples with a Ag concentration of 75 at% in the present study. The diffusion couples were isothermally annealed at temperatures of 433, 453 and 473 K for various periods up to 1365 h. During annealing, a compound layer dominantly consisting of polycrystalline PdSn 4 and Ag 3 Sn lamellae is formed at the (Pd-Ag)/Sn interface in the diffusion couple. The square of the thickness of the compound layer increases in proportion to the annealing time. This relationship is called the parabolic relationship. On the other hand, the interlamellar spacing in the compound layer is proportional to a power function of the annealing time, and thus grain growth occurs in the compound layer. The exponent of the power function is close to 1/3. The parabolic relationship of the layer growth and the occurrence of the grain growth guarantee that the growth of the compound layer is controlled by volume diffusion. The addition of Ag with 75 at% into Pd decreases the parabolic coefficient by 93, 88 and 78% at 433, 453 and 473 K, respectively. Hence, Ag works as an effective suppressant against the growth of the compound during the solid-state reactive diffusion between Pd and Sn

Evaluation of interdiffusion in liquid phase during reactive diffusion between Cu and

Using Cu/Al diffusion couples initially composed of pure Cu and Al, the reactive diffusion in the binary Cu-Al system was experimentally examined in a previous study. The diffusion couple was isothermally annealed in the temperature range of T ¼ 973{1073 K. Due to annealing, compound layers of the , and " phases are formed between the Cu-rich solid () phase and the Al-rich liquid (L) phase, and the L=" interface migrates towards the " phase. At each annealing time, the migration distance of the L=" interface is much greater than the total thickness of the compound layers. Furthermore, there exists the parabolic relationship between the migration distance and the annealing time. This means that the migration of the interface is controlled by the volume diffusion in the L phase. The mathematical model for the interface migration controlled by volume diffusion was used in order to analyze quantitatively the migration rate of the interface. Through the analysis, the interdiffusion coefficient D of the L phase was evaluated to be 1:24 Â 10 À9 , 2:91 Â 10 À9 and 3:62 Â 10 À9 m 2 /s at T ¼ 973, 1023 and 1073 K, respectively. Expressing the temperature dependence of À4 m 2 /s and Q ¼ 93:5 kJ/mol were obtained by the least-squares method. According to the analysis, the interdiffusion coefficient is much greater for the L phase than for the solid phases. Consequently, the L=" interface migrates towards the " phase, and the migration rate of the interface is much greater than the overall growth rate of the compound layers

Significance of ethnic values in the process of the youth self-definition in Northern Caucasus

В статье выявляются факторы, воздействующие на этническую социализацию в поликультурном пространстве Северного Кавказа. Рассматривается специфичность этнической идентичности юности.In this paper factors, affecting the increasing significance of ethnic socialization in policultural space of North Caucasus are considered. The specificity of the youth ethnic identity forming is shown and the necessity of other identity kinds development, allowing to develop constructive forms of intergroup reciprocity is demonstrated

Atomic dynamics in fluids studied by inelastic x-ray scattering

1990年代半ばにmeVオーダーのエネルギー分解能を達成したX線非弾性散乱実験技術により，高温高圧下の極端条件下にある超臨界流体の原子，分子ダイナミクス研究は大きく進展した。本稿では，著者らが独自の高温高圧実験技術を用いてSPring-8のBL35XUビームラインで行った，高温高圧下で膨張した流体水銀のX線非弾性散乱実験を中心に，液体，流体の原子ダイナミクスの理論的背景と，超臨界流体特有のダイナミクスについて紹介する。中でも，流体水銀の金属-非金属転移近傍で観察された，音響モードのエネルギーが超音波を用いて観測された音速よりも3倍大きい分散を示す速い音波の解明は，原子が凝集して金属が形成される素過程を理解する上で重要な現象と考えられる。本稿の結びでは，この分野の近い将来についても展望する。Studies on atomic dynamics in supercritical fluids at high temperature and high pressure have remarkably been advanced by using an inelastic x-ray scattering technique that achieved a meV-energy resolution in the middle of 1990's. In this article, we describe a brief review of the theoretical background on liquid dynamics, our own high-temperature high-pressure technique and recent results of atomic dynamics in supercritical fluids. In particular, we report the results of inelastic x-ray scattering measurements for expanding fluid Hg at high temperature and high pressure, which were conducted at BL35XU/SPring-8. We found that in the metal-nonmetal transition in Fluid Hg, the excitation energy of the acoustic mode disperses three times faster than the adiabatic sound velocity obtained by ultrasonic measurements. This phenomenon must be crucial to understand how a metallic state is formed during atomic condensation accurately. Finally we put a future development of this field in perspective

Molecular Phylogeny of the Genus Nipponnemertes (Nemertea: Monostilifera: Cratenemertidae) and Descriptions of 10 New Species, With Notes on Small Body Size in a Newly Discovered Clade

Nemerteans, or ribbon worms, have been reported from intertidal to hadal depths, often showing bathymetrically wide distribution in genus levels. Although current nemertean systematics practices require to provide DNA sequences and infer phylogenetic relationships with suitable molecular markers, previous molecular systematics on nemerteans are mostly biased toward shallow-water species. Members in the genus Nipponnemertes occur worldwide, from tropical to polar waters and intertidal to bathyal waters. Molecular phylogenetic studies are scarce for the genus; only six shallow-water species of 18 species in the genus were subject to molecular phylogeny. Thus, Nipponnemertes is one candidate that needs to be assessed by genetic approaches. In this study, we performed molecular phylogenetic analyses using 59 specimens in 23 species based on partial sequences of two mitochondrial (16S rRNA and cytochrome c oxidase subunit I) and three nuclear gene markers (18S rRNA, 28S rRNA, and histone H3). Our extensive sampling from intertidal to bathyal waters in the Northwest Pacific significantly updated the fauna of Nipponnemertes in this region from four to 17 species. We herein establish 10 new species and provide an updated species list concisely summarizing all the congeners known from the world. Our phylogenetic tree indicated three major lineages within the genus (herein referred to as “Clade A, B, and C”), each presumably characterized by the combination of morphological characters in the head region. Members in Clade A are: Nipponnemertes pulchra (Johnston, 1837), Nipponnemertes ogumai (Yamaoka, 1947), and several unidentified congeners, characterized by having demarcated head without cephalic patches; members in Clade B are: Nipponnemertes crypta sp. nov., Nipponnemertes jambio sp. nov., Nipponnemertes neonilae sp. nov., and Nipponnemertes ojimaorum sp. nov., species having demarcated head with cephalic patches; members in Clade C are: Nipponnemertes ganahai sp. nov., Nipponnemertes kozaensis sp. nov., Nipponnemertes lactea sp. nov., Nipponnemertes notoensis sp. nov., Nipponnemertes ornata sp. nov., Nipponnemertes sugashimaensis sp. nov., and two unidentified forms collected off Jogashima (Japan) and Guam (USA), species with non-demarcated head lacking cephalic patches. Furthermore, we discuss the evolution of remarkably small body size retained among Clade C

Asymmetrical bonding in liquid Bi disentangled by inelastic X-ray scattering

The structure of liquid Bi has been debated in relationship with the Peierls distortion, as crystalline Bi takes A7 structure. A recent ab initio molec- ular dynamics simulation for liquid Bi predicted a flat-topped profile of the acoustic dispersion curve. To confirm the prediction, we have carried out inelas- tic x-ray scattering (IXS) for liquid Bi. The dynamic structure factor obtained by the IXS exhibits a distinct inelastic excitation of the longitudinal acoustic mode up to 14 nm−1 and the dispersion curve of the excitation energy obtained by the memory function analysis becomes a flat-topped one. We found that a linear chain model including the interatomic interaction with the second near- est neighbors can explain the flat-topped profile. The result suggests that the anomalous dispersion curve in liquid Bi arises from local anisotropy related to the Peierls distortion in the crystalline phase.