Effect of Germanium Oxide (GeO2) Additive on the Anatase-to-Rutile Phase Transition

The effect of germanium oxide (GeO₂) addition on the anatase-to-rutile phase transition was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). TiO₂ xerogels containing up to 20 mol% GeO₂ were prepared by refluxing and hydrolyzing titanium tetraisopropoxide (TTIP) and germanium butoxide (GB) using nitric acid as a catalyst. The following occurred with increasing amounts of GeO₂ in the xerogels: (i) the crystallization temperature of anatase increased from 410° to 565°C and the DTA temperature of the anatase-to-rutile phase transition increased from 676° to 977°C in 20 mol% GeO₂-containing xerogel; (ii) the crystallite size of anatase became smaller; (iii) the lattice a-parameter of the anatase showed little change, but the c-parameter decreased up to 20 mol% GeO₂; (iv) both the lattice a- and c-parameters of the rutile decreased monotonically. From these results, the added GeO₂ is considered to become incorporated into the anatase structure. The following occurred with increasing anatase heating temperature: (i) the lattice c-parameter of the anatase increased gradually and approached the value of pure anatase; and (ii) the chemical composition of the xerogel surfaces, measured by XPS, showed an increase in GeO₂ content, indicating the expulsion of GeO₂ from the anatase to form an amorphous surface layer. The formation of this amorphous GeO₂ surface layer is thought to play an important role in retarding the anatase-to-rutile phase transition by suppressing diffusion between the anatase particles in direct contact, and limiting their ability to act as surface nucleation sites for rutile, as in the case of SiO₂ additions. However, GeO₂ addition is less effective than SiO₂ in retarding the phase transition.     

Photoconductivity of poly(vinyl alcohol) films with Fe3+ complexes and ESR study of their structures

We have studied whether photoconductivity is observed in polymer films containing the first transition metal complexes. Polymers investigated were poly(vinyl alcohol) (PVA), polyacrylamide, poly(acrylic acid), poly(vinyl pyrrolidone), and polyethylene glycol. Transition metal salts used were CrCl₃, MnCl₂, FeCl₃, CoCl₂, NiCl₂, FeBr₃, Fe(NO₃)₃, Fe₂(SO₄)₃, and Fe(ClO₄)₃. Only in the PVA–FeCl₃ film was relatively large photoconductivity due to the photoreduction of Fe³⁺ observed. ESR spectra indicate that an Fe³⁺ ion is chelated with two in-plane OH residues of PVA and coordinated with three Cl^?ions on the meridian. UV irradiation causes an electron transfer from Cl^? to Fe³⁺. The produced chlorine atom extracts an electron from the oxygen of a neighboring OH residue. The unpaired electron thus formed can move from one oxygen to another through hydrogen bonding. In other words, the photoconductivity is due to holes produced in the network of PVA hydrogen bonding by the reduction of Fe³⁺. Finally, we have tried to explain why the photoconductivity is observed only in the PVA–FeCl₃ film.     

STEM tomography for thick biological specimens

Scanning transmission electron microscopy (STEM) tomography was applied to biological specimens such as yeast cells, HEK293 cells and primary culture neurons. These cells, which were embedded in a resin, were cut into 1-microm-thick sections. STEM tomography offers several important advantages including: (1) it is effective even for thick specimens, (2) 'dynamic focusing', (3) ease of using an annular dark field (ADF) mode and (4) linear contrasts. It has become evident that STEM tomography offers significant advantages for the observation of thick specimens. By employing STEM tomography, even a 1-microm-thick specimen (which is difficult to observe by conventional transmission electron microscopy (TEM)) was successfully analyzed in three dimensions. The specimen was tilted up to 73 degrees during data acquisition. At a large tilt angle, the specimen thicknesses increase dramatically. In order to observe such thick specimens, we introduced a special small condenser aperture that reduces the collection angle of the STEM probe. The specimen damage caused by the convergent electron beam was expected to be the most serious problem; however, the damage in STEM was actually smaller than that in TEM. In this study, the irradiation damage caused by TEM- and STEM-tomography in biological specimens was quantitatively compared.     

Locating congested segments over the Internet by clustering the delay performance of multiple paths

Delay variation-based detection and location of congestion in a large network is considered. Since the Internet is still highly prone to performance deterioration due to transient large delays, locating a part of the network (segments) responsible is vital to ensure that Internet Service Providers can mitigate or prevent such performance deterioration. In the proposed method, the end-to-end packet delays from multiple origins to multiple destinations are actively and continuously measured. By analyzing those data on delay variation along each monitored path, congestion is detected by finding a delay performance deterioration worse than a predefined criteria and a congested segment responsible could be inferred by finding a set of paths among which delay variations are strongly correlated. This is a network tomographic approach based on a clustering technique that effectively tackles the correlation among packet delay variation along individual paths. The proposed method was evaluated through a real-world long-term experiment on the Japan’s commercial Internet, and was shown to have considerable potential to promptly locate congested segments through various analyses on the experimental results.     

Semi‐synthesis and Structure–Activity Relationship of Neuritogenic Oleanene Derivatives

(3S,4R)‐23,28‐Dihydroxyolean‐12‐en‐3‐yl (2E)‐3‐(3,4‐dihydroxyphenyl)acrylate ( 1 a ), which possesses significant neuritogenic activity, was isolated from the traditional Chinese medicine (TCM) plant, Desmodium sambuense. To confirm the structure and to assess biological activity, we semi‐synthesized 1 a from commercially available oleanolic acid. A series of novel 1 a derivatives was then designed and synthesized for a structure–activity relationship (SAR) study. All synthetic derivatives were characterized by analysis of spectral data, and their neuritogenic activities were evaluated in assays with PC12 cells. The SAR results indicate that the number and position of the hydroxy groups on the phenyl ring and the triterpene moiety, as well as the length of the (saturated or unsaturated) alkyl chain that links the phenyl ring with the triterpene critically influence neuritogenic activity. Among all the tested compounds, 1 e [(3S,4R)‐23,28‐dihydroxyolean‐12‐en‐3‐yl (2E)‐3‐(3,4,5‐trihydroxyphenyl)acrylate] was found to be the most potent, inducing significant neurite outgrowth at 1 μm .     

Review of Topographic and Soil Conditions for Liquefaction-Related Damage Induced by the 2007 Off Mid-Niigata Earthquake

The 2007 Niigata-ken Chuetsu-oki (Off Mid-Niigata) earthquake caused the liquefaction of the sandy soil distributed near the coast of the Japan Sea in the middle of Niigata Prefecture. The liquefaction-induced damage occurring in many residential areas was investigated in detail by means of victim interviews, visual inspections, Swedish Weight Sounding tests, Standard Penetration Tests, old topographical map examinations, etc. Based on in situ soil investigations, the liquefied soil layers were estimated for each area. As a result, it was confirmed that the liquefied areas were mainly sand dune hinterlands, flood plains, reclaimed old river channels and sandy fills with high groundwater table. Among them, damage was especially serious on land having an inclined ground surface due to the flow of foundations, on the cut-fill borders of artificially developed land due to landslides and at the toes of sand dune slopes due to the thrust of the sliding soil and/or the collision of the sliding soil with objects. These investigation results also revealed that soil improvement by cement mixed columns is an effective countermeasure against liquefaction-induced damage unless lateral spreading of the subsoil arises.     

Formation of Apatite Coatings on an Artificial Ligament Using a Plasma- and Precursor-Assisted Biomimetic Process

A plasma- and precursor-assisted biomimetic process utilizing plasma and alternate dipping treatments was applied to a Leed-Keio artificial ligament to produce a thin coating of apatite in a supersaturated calcium phosphate solution. Following plasma surface modification, the specimen was alternately dipped in calcium and phosphate ion solutions three times (alternate dipping treatment) to create a precoating containing amorphous calcium phosphate (ACP) which is an apatite precursor. To grow an apatite layer on the ACP precoating, the ACP-precoated specimen was immersed for 24 h in a simulated body fluid with ion concentrations approximately equal to those in human blood plasma. The plasma surface modification was necessary to create an adequate apatite coating and to improve the coating adhesion depending on the plasma power density. The apatite coating prepared using the optimized conditions formed a thin-film that covered the entire surface of the artificial ligament. The resulting apatite-coated artificial ligament should exhibit improved osseointegration within the bone tunnel and possesses great potential for use in ligament reconstructions.