Control of Oxidation State of Eu Ions in Na2O–Al2O3–SiO2 Glasses

Glasses doped with well‐controlled Eu³⁺ and Eu²⁺ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their ⁵D₀→⁷F_j and 5d–4f electron transitions. Glasses were prepared to dope Eu³⁺ ions in a Na₂O–Al₂O₃–SiO₂ system, and the changes in the valence state of Eu³⁺ ions and the glass structure surrounding the Eu atoms during heating under H₂ atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and ²⁷Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu³⁺ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al³⁺ ions formed the AlO₄ network structure accompanied by the Na⁺ ions as charge compensators; the Eu³⁺ ions occupied the interstitial positions in the SiO₄ network structure and were not reduced even under heating in H₂ gas. On the other hand, in the glasses containing Al₂O₃ with the Al/Na ratio exceeding unity, the Eu³⁺ ions commenced to be coordinated by the AlO₄ units in addition to the SiO₄ network structure. When heated in H₂ gas, H₂ gas molecules reacted with the AlO₄ units surrounding Eu³⁺ ions to form AlO₆ units terminated with OH bonds, and reduced Eu³⁺ ions to Eu²⁺ via the extracted electrons.     

Adsorption Desalination Quenches Global Thirst

The search for fresh or potable water remains a pressing concern throughout many regions of the world. Although most of the Earth's surface is covered by oceans, the effort to provide for the world's inhabitants with fresh or potable water seems to be insurmountable; at least one billion people do not have access to clean and fresh water. The World Health Organization (WHO) reported that about 41% of the Earth's population lives in water-stressed areas, and the number of people in the water scarce regions may climb to 3.5 billion by the year 2025. Thus, innovative and cost-effective desalination technologies for producing fresh water are needed to provide practical solutions.     

Preparation of resins having various phosphonium groups and their adsorption and elution behavior for anionic surfactants

Resins containing phosphonium groups were prepared by reaction of chlorohydroxylated glycidylmethacrylate–divinylbenzene macroreticular resins with three trialkylphosphines. Triethylphosphine, tributylphosphine, and trioctylphosphine were used as trialkylphosphines. Adsorption and elution behavior of sodium benzenesulfonate (SBS) and sodium dodecylbenzenesulfonate (SDBS) on the resins were studied. Adsorption of SBS and SDBS increased with increasing the alkyl chain length of phosphonium groups in the resins. The adsorption of SBS decreased with increasing ionic strength of the solution, while the adsorption of SDBS increased with increasing ionic strength of the solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 371–378, 1999     

The role of Mn2+-rich hydrous manganese oxide in the accumulation of arsenic in lake sediments

Arsenic is present at high concentrations in the upper layer of Lake Biwa sediments and shows a depth profile similar to that of Mn. Adsorption experiments of As onto synthetic hydrous Mn oxide (HMO) in the presence of Mn²⁺ and the speciation of Mn in the sediment cores, suggest that the accumulation of As at the sediment surface results from post-depositional migration of arsenite in the sediment pore water followed by oxidation to arsenate at the sediment surface and adsorption onto Mn²⁺-rich HMO.     

Ion-implanted and permalloy hybrid magnetic bubble memory devices

Hybrid bubble memory devices have been proposed and operated with the memory density of 4 Mbit/cm². In the hybrid bubble memory devices, minor loops are composed of ion-implanted tracks with 4-µm period, and major lines and functional parts including block-replicate and swap gates are composed of Permalloy tracks with a longer period of 12 µm. Passive junctions between ion-implanted and Permalloy tracks have been developed, introducing the tapered ion-implantation technique. Improving the characteristics of the functional parts composed of Permalloy tracks, the hybrid bubble memory devices with block-replicate and swap gates have been operated, and the feasibility of the devices has been confirmed. In addition, the possibility of higher memory density has been shown.     

GaInAs-GaInNAs-GaInAs intermediate layer structure for longwavelength lasers

Proposes two new structures, the GaInAs-GaInNAs intermediate layer (IML) and the GaInN_xAs graded wells, which show better optical properties than the commonly used GaInNAs-GaAs rectangular quantum-wells. A 1240-nm emitting IML laser has been achieved with a low-threshold current density (200 A/cm²/well) and a relatively high characteristic temperature (T_o=100 K). The IML structure is very promising for long wavelength GaAs-based laser applications     

In vivo immunological toxicity in mice of carbon nanotubes with impurities

The longstanding question as to whether carbon nanotubes are intrinsically toxic hinders their widespread industrial application. Here, we clarify the effect of impurities within such tubes through systemic studies of immunological responses in mice by monitoring and examining changes in peripheral T-cell subset and peripheral cytokine levels and histology. Contaminated and clean tubes were subcutaneously implanted in mice. The implanted tubes with impurities clearly induced immunological toxicity and localized alopecia, whereas extremely pure implanted tubes showed good biocompatibility. Our studies suggest that such high-temperature thermal treatment is an effective way to improve the biocompatibility of carbon nanotube.     

A 250-Mb/s/pin, 1-Gb double-data-rate SDRAM with a bidirectionaldelay and an interbank shared redundancy scheme

This paper describes three circuit technologies indispensable for high-bandwidth multibank DRAM's. (1) A clock generator based on a bidirectional delay (BDD) eliminates the output skew. The BDD measures the cycle time as the quantity charged or discharged of an analog quantity, and replicates it in the next cycle. This achieves a 0.18-mm ², two-cycle-lock clock generator operating from 25 to 167 MHz with a 30-ps resolution. (2) A quad-coupled receiver eliminates the internal skew caused by the difference between a rise input and a fall input by 40%. (3) An interbank shared redundancy scheme (ISR) with a variable unit redundancy (VUR) efficiently increases yield in multibank DRAM's. The ISR allows redundancy match circuits to be shared with two or more banks. The VUR allows the number of units replaced to be variable. These circuit technologies achieved a 250-Mb/s/pin, 8-bank, 1-Gb double-data-rate synchronous DRAM