Probing the Nature and the Structure of Pores in Silica Xerogels by Water Sorption: The Tetramethyl Orthosilicate-Hydrogen Chloride/Fluoride System

A series of silica xerogels were synthesized in a closed system by hydrolyzing tetramethyl orthosilicate (TMOS) with various concentrations of hydrochloric acid solution but without the addition of alcohol. The molar ratio of H₂O to TMOS was fixed at 4.96. The gels were characterized by water and nitrogen sorption measurements. The gelation time peaked at 50 to 80 h with 5 × 10⁻² to 10⁻¹ M HCl, apparently a consequence of the isoelectric point of silica. Surface area, pore size, and sorption capacity were, however, at a minimum for samples prepared with 5 × 10⁻² to 10⁻¹ M HCl. The BET c constant and hence the net heats of sorption were at a maximum for these samples. Although water sorption of all the samples prepared with HCl exhibited moderate Type I isotherms, the concavity of the isotherms to the P/P ₀ axis increased with increasing concentrations of HCl up to 10⁻¹ M in accordance with the decreased pore size and increased heat of sorption. Addition of F⁻ ions (HF or NaF) in the presence of 10⁻¹ M HCl steadily decreased the gelation time. Addition of F⁻ in the absence of HCl, however, caused rapid gelation and an increase in pore size, nitrogen BET surface area, and hydrophobicity. Consequently, the shape of water isotherms gradually converted to Type IV and/or Type V. Adsorption and desorption measurements on differently activated gels exhibited various types of hystereses as a result of development of hydrophobie sites at as low as 200°C, inelastic distortion induced by adsorption, and chemical reaction and aging of gels when exposed to water vapor.     

Hydroxyapatite coating by dipping method,and bone bonding strength

Hydroxyapatite (HA) was coated onto titanium rods by a dip coating method using HA sol. The HA sols were prepared by dispersing HA crystals less than 100 nm length in distilled water or physiological salt solution using an ultrasonic homogenizer. The surface of the HA coating was homogeneous as determined by scanning electron microscopy (SEM). After implantation of uncoated and HA dip coated titanium rods in dog femurs, new bone formation was observed only around the coated material. The bone bonding strength to HA coated rods was 1.0, 1.5, 2.0 and 2.5 Mpa after 1,2,3 and 4 weeks implantation, respectively, as determined by pull-out testing. These values were over twice that of the uncoated titanium rods at 1–4 weeks after implantation. The dip coated titanium exhibited superior biocompatibility to the uncoated implant and may be of great value for bone repacement applications.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

RGM1, a cell line derived from normal gastric mucosa of rat

Brainstem evoked potentials (BAEPs) were determined in three groups of male prisoners of war (POWs) released from detention camps and a control group. The first group comprised 21 POWs in whom BAEPs were determined 10-60 days after release (group I). The second group comprised 24 POWs in whom BAEPs were determined 6-9 months after release (group II), and the third group comprised 22 POWs in whom BAEPs were determined 12-18 months after release (group III). The control group comprised 32 subjects. The following changes were found in relation to the control group: in group I significantly longer interpeak latencies (IPLs) P1-P3; in group II significantly longer IPLs P1-P3 and P3-P5; and in group III significantly longer IPLs P1-P3. The subjective symptomatology of the POWs and the results of a routine examination indicate subclinical functional changes of the central nervous system, reflecting the dynamics of these changes. It is suggested that the basis of these changes may be a demyelinization intrathecal process, which occurred as a result of immunological changes during prolonged and intensive post-traumatic stress syndrome.     

Absolute and relative nonlinear optical coefficients of KDP, KD*P,BaB2O4, LiIO3, MgO:LiNbO3,and KTP measured by phase-matched second-harmonic generation

Both absolute and relative nonlinear optical coefficients of six nonlinear materials measured by second-harmonic generation are discussed. A single-mode, injection-seeded, Q-switched Nd:YAG laser with spatially filtered output was used to generate the 1.064-μm fundamental radiation. The following results were obtained: d₃₆(KD*P)=0.38 pm/V, d₃₆(KD*P)=0.37 pm/V, |d₂₂(BaB ₂O₄)|=2.2 pm/V, d₃₁(LiIO₃ )=-4.1 pm/V, d₃₁(5%MgO:MgO LiNbO₃)=-4.7 pm/V, and d_eff(KTP)=3.2 pm/V. The accuracy of these measurements is estimated to be better than 10%     

Development of New Water Tree Suppressive XLPE Cable

With a view to develop a new water tree suppressive XLPE cable, the authors have investigated the effect of introducing polar groups into crosslinked polyethylene (XLPE) dielectrics. An aliphatic carboxylic acid derivative was found to be the best additive as a water tree suppressor. New cables insulated with XLPE dielectrics containing this aliphatic carboxylic acid derivative were developed. It was confirmed that the cables, having the same physical and electrical properties as those of conventional XLPE cables, showed an excellent water tree suppressive effect and long term performance.     

Involvement of hydrogen peroxide production in erbstatin-induced apoptosis in human small cell lung carcinoma cells

Tyrosine kinase inhibitor, erbstatin, induced morphological apoptosis and DNA fragmentation in human small cell lung carcinoma (SCLC) cells. Erbstatin-induced apoptosis was inhibited by antioxidants, whereas erbstatin-inhibited tyrosine phosphorylation was not affected by them. Erbstatin was shown by means of flow cytometry to induce hydrogen peroxide generation. Furthermore, hydrogen peroxide induced morphological apoptosis and DNA fragmentation in the SCLC cells. We also demonstrated that erbstatin-induced hydrogen peroxide production and DNA fragmentation were partially suppressed by inhibition of protein synthesis. Thus, erbstatin-induced apoptosis would be due to hydrogen peroxide generation via newly synthesized protein.     

Planning model — airport

A leading Japanese multidisciplinary design practice, Nikken Sekkei of Osaka has developed a micro computer simulation system. System engineer, Kazunori Wachi and planner, Yoshihko Masuda, discuss the theoretical composition of the simulation model, input conditions for executing a simulation and simulation application examples.     

Effect of electrical field on crazing test of enameled wire in water

We investigated the tendency to crazing to enameled wire under applying DC voltage in an electrolyte in the different conductivity. Crazing occurred in the enameled wire film in the case of connecting the wire to the negative pole, but did not occur in the film in the case of connecting the wire to the positive pole. It was found that the penetration of H₃O⁺ ion, due to electroosmosis, is the major factor for crazing.     

Zinc oxide particles connected by nano-sheets and their heat treatment

Particulate films of crystalline ZnO connected by nano-sheets were fabricated in an aqueous solution. This study focused on the annealing behavior of the particulate films, especially the morphology change of the nano-sheets. The nano-sheets had a thickness of 10 nm to 50 nm and width of 1 μm to 10 μm. They were connected to particles closely with no clearance. Their morphology was changed to nanoparticles and porous particulate films of crystalline ZnO by annealing at 500 °C for 1 h in air. The morphology of the sheets changed due to their slimness and/or phase transformation. Crystallization and morphology control of crystalline ZnO at low temperature can be applied to a wide variety of devices supported by low-heat resistant polymer films and would contribute to the environmentally friendly fabrication of oxide devices.