The annealing effects on structure and magnetism for Co-doped ZnO films under air, Ar, and Ar/ H 2 atmospheres at 250°C have been systematically investigated. Room-temperature ferromagnetism has been observed for the as-deposited and annealed films. However, the saturation magnetization ͑M s ͒ varied drastically for different annealing processes with M s ϳ 0.5, 0.2, 0.9, and 1.5 B / Co for the as-deposited, air-annealed, Ar-annealed, and Ar/ H 2-annealed films, respectively. The x-ray absorption spectra indicate all these samples show good diluted magnetic semiconductor structures. By comparison of the x-ray near edge spectra with the simulation on Zn K edge, an additional preedge peak appears due likely to the formation of oxygen vacancies. The results show that enhancement ͑suppression͒ of ferromagnetism is strongly correlated with the increase ͑decrease͒ of oxygen vacancies in ZnO. The upper limit of the oxygen vacancy density of the Ar/ H 2-annealed film can be estimated by simulation to be about 1 ϫ 10 21 cm −3 .
Instabilities are common phenomena frequently observed in nature, sometimes leading to unexpected catastrophes and disasters in seemingly normal conditions. One prominent form of instability in a distributed system is its response to a harmonic modulation. Such instability has special names in various branches of physics and is generally known as modulation instability (MI). The MI leads to a growth-decay cycle of unstable waves and is therefore related to Fermi-Pasta-Ulam (FPU) recurrence since breather solutions of the nonlinear Schrödinger equation (NLSE) are known to accurately describe growth and decay of modulationally unstable waves in conservative systems. Here, we report theoretical, numerical and experimental evidence of the effect of dissipation on FPU cycles in a super wave tank, namely their shift in a determined order. In showing that ideal NLSE breather solutions can describe such dissipative nonlinear dynamics, our results may impact the interpretation of a wide range of new physics scenarios.
The ion regulation mechanisms of fishes have been recently studied in zebrafish (Danio rerio), a stenohaline species. However, recent advances using this organism are not necessarily applicable to euryhaline fishes. The euryhaline species medaka (Oryzias latipes), which, like zebrafish, is genetically well categorized and amenable to molecular manipulation, was proposed as an alternative model for studying osmoregulation during acclimation to different salinities. To establish its suitability as an alternative, the present study was conducted to (1) identify different types of ionocytes in the embryonic skin and (2) analyze gene expressions of the transporters during seawater acclimation. Double/triple in situ hybridization and/or immunocytochemistry revealed that freshwater (FW) medaka contain three types of ionocyte: (1) Na(+)/H(+) exchanger 3 (NHE3) cells with apical NHE3 and basolateral Na(+)-K(+)-2Cl(-) cotransporter (NKCC), Na(+)-K(+)-ATPase (NKA) and anion exchanger (AE); (2) Na(+)-Cl(-) cotransporter (NCC) cells with apical NCC and basolateral H(+)-ATPase; and (3) epithelial Ca(2+) channel (ECaC) cells [presumed accessory (AC) cells] with apical ECaC. On the other hand, seawater (SW) medaka has a single predominant ionocyte type, which possesses apical cystic fibrosis transmembrane conductance regulator (CFTR) and NHE3 and basolateral NKCC and NKA and is accompanied by smaller AC cells that express lower levels of basolateral NKA. Reciprocal gene expressions of decreased NHE3, AE, NCC and ECaC and increased CFTR and NKCC in medaka gills during SW were revealed by quantative PCR analysis.
The annealing effects on magnetism, structure, and ac transport for Co:ZnO films have been systematically investigated. The room temperature saturation magnetization ͑M s ͒ varies drastically with Ar or Ar/ H 2 annealing processes. By using the impedance spectra, the change in grain boundary and grain defects of these films can be analyzed. The results demonstrate that Ar annealing produces mainly the grain boundary defects which cause the enhancement of M s. Ar/H 2-annealing creates not only grain boundary defects but also the grain defects, resulting in the stronger enhancement of M s. Ferromagnetism for Co:ZnO films is influenced by both grain boundaries and grain defects.
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