Shape control of anatase TiO2 nanoparticles by amino acids in a gel-sol system

Ellipsoidal anatase TiO2 nanoparticles of different aspect ratios were obtained by the gel-sol method in the presence of amino acids in which the resulting particles were basically single crystals, but highly rough surfaces or partly polycrystalline structures were observed with a high concentration of glutamic acid or aspartic acid.     

Dynamic axial-position control of a laser-trapped particle by wave-front modification

The axial position of a laser-trapped particle has been controlled by modification of the wave front by means of a membrane deformable mirror. The mirror gives wave-front modulation in terms of Zernike polynomials. By modulation of the Zernike defocus term we can modulate the particle position under conditions of laser trapping. A polystyrene particle of 1-microm diameter was moved along the optical axis direction for a distance of 2370 nm in minimum steps of 55.4 nm. We also demonstrated particle oscillation along the optical axis by changing the focal position in a sinusoidal manner. From the frequency dependency of the amplitude of particle oscillation we determined the spring constant as 91.7 nN/m.     

Influence of superimposed steady shear flow on the dynamic properties of polyethylene melts

Experiments in which an oscillatory shear flow is superimposed on a steady state shear flow were performed on polyethylene melts by the use of a cone and plate type rheogoniometer. The phase difference between oscillatory shear stress and shear strain increases in all cases and for all frequencies with the increase of the superimposed shear rate. Between ω₀, the frequency at which the phase difference is π/2 and the steady shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}, as found by Booij for polymer solution, the relation ω₀ = 1/2 \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma$\end{document}. holds also for polyethylene melts. The significance of this relation is discussed briefly from the viewpoint that the entanglement density decreases with the increase of the imposed shear rate.     

Mössbauer spectra at 77 K of products formed during transformation of iron(II) hydroxide containing zinc(II) ion to Zn-bearing ferrite in aqueous suspension by air oxidation

At pH 7.0, lower crystalline iron (II) hydroxide, “green rust II” (the Fe^II:Fe^III mol ratios and the electron diffraction measurements do not indicate the tendency for Zn²⁺ ion to be incorporated in place of the Fe²⁺ ion) and Zn-bearing ferrite are formed from aqueous iron (II) hydroxide suspensions containing the zinc (II) ion at a Zn: Fe_tot. mol ratio of 1.00:2.00. At pH 9.0 and 10.0, higher and lower crystalline iron (II) hydroxides and Zn-bearing ferrite are formed. The ratios of higher to lower crystalline iron (II) hydroxide are approximately constant during oxidation at pH 9.0. The oxidation reactions are divided into two classes according to the Zn: Fe_tot. mol ratios. At pH 7.0, lower crystalline iron (II) hydroxide is formed at the early stages of oxidation and dissolved iron (II) species are formed during the oxidation at a Zn:Fe_tot. mol ratio of 0.20:2.80. Iron (II) hydroxide is formed during oxidation and dissolved iron (II) species are formed at an early stage of the oxidation at Zn:Fe_tot. mol ratios of 0.60:2.40 and higher. At pH 9.0 and 10.0, both higher and lower crystalline iron (II) hydroxides are formed at Zn: Fe_tot. mol ratios of 0.60:2.40 and higher, and 1.00:2.00, respectively. However, at a Zn:Fe_tot. mol ratio of 0.20:2.80, iron (II) hydroxide with a large quadrupole splitting value and dissolved iron (II) species with large isomer shifts and quadrupole splitting values are formed before and during oxidation at pH 7.0, and the formation of Zn-bearing ferrite is depressed (-FeO(OH) is formed) at pH 10.0.