In situ observations of domain wall motion in Mn–Zn and Ni–Zn ferrites by Lorentz microscopy and electron holography

Domain wall motion in Mn–Zn and Ni–Zn ferrites with applied magnetic fields is investigated by in situ observations with Lorentz microscopy and electron holography. It is found that both Mn–Zn and Ni–Zn ferrites have a mean grain size of approximately 10 μm and several pores with sizes ranging from 0.2 to 1.1 μm. In situ observations by Lorentz microscopy with an applied magnetic field reveals that in Mn–Zn ferrite, the domain walls move easily across the grain boundary, while in Ni–Zn ferrite, the domain walls move along the grain boundary but are pinned at the grain boundary and pores. From in situ observations of Ni–Zn ferrite by electron holography, it is clarified that domain wall pinning at the grain boundary retards a sensitive increase in magnetic flux parallel to the applied field direction, which is considered to result in high hysteresis loss.     

Micro-phase sorbent extraction for trace analysis via in situ sorbent formation: application to the spectrophotometric determination of nitrite in environmental waters.

A micro-phase sorbent in situ formation from an aqueous solution was proposed for the sensitive spectrophotometric determination of nitrite in environmental waters. Nitrite in a 10 mL sample solution was converted into a cationic azo dye by the reaction with 4-trifluoromethylanilinium ion and N-1-naphthylethylenediammonium ion in an acidic medium. Addition of dodecylbenzenesulfonate ion caused the formation of a suspension of ion associate in the solution. Centrifugation of the solution led to the isolation of a liquid organic phase that extracted the azo dye at the bottom of the centrifuge tube. The volume of the new phase was ca. 5 microL. After the aqueous phase was discarded, the organic phase was dissolved with 1 mL of 2-methoxyethanol to measure the absorbance. Nitrogen as NO2- at concentrations from 1.5 to 30 microg L(-1) was determined with sufficient precision. When 0.2 mL of 2-methoxyethanol was applied to dissolve the organic phase, 0.3-4.8 microg NO2--N L(-1) was determined. The recovery tests for nitrite added to some river water and seawater were satisfactory. This method is very simple and rapid. It takes only 30 min from the dye formation to the measurement of the absorbance.     

Analysis of tetracycline antibiotics using HPLC with pulsed amperometric detection.

The analysis of tetracycline, oxytetracyline, chlortetracycline and doxycycline by high-performance liquid chromatography with pulsed amperometric detection using an anodized boron-doped diamond thin film (BDD) electrode is originally reported. The analyses were carried out using the mobile phase, phosphate buffer (0.01 M, pH 2.5)-acetonitrile (80:20; v/v), on a C18 column (250 x 4.6 mm i.d., 5 microm) at a flow rate of 1.0 mL/min. The optimal PAD waveform parameters at the anodized BDD were 1.5 V (versus Ag/AgCl) detection potential (E(det)) for 290 ms (200 ms delay time and 90 ms integration time), 2.0 V (versus Ag/AgCl) oxidation potential (E(oxd)) for 200 ms oxidation time (t(oxd)) and 0.4 V (versus Ag/AgCI) reduction potential (E(red)) for 200 ms reduction time (t(red)). The proposed method showed the simultaneous determination of tetracycline, oxytetracyline, chlortetracycline and doxycycline with a linear range of 0.1 - 100 microg/mL, detection limits of 0.05 - 0.1 microg/mL and recoveries of 70.8 - 96.0%. The application of this method to real samples was demonstrated and validated using a shrimp sample.     

Polymorphy in the stereostructure of periodic polymer backbones

We theoretically investigated the polymorphy of the stereostructures of a periodic polymer. Using the polymer's internal conformation parameters of bond lengths, bond angles, and internal rotation angles, we extended the mathematical treatment for designing polymer backbones. We considered those periodic polymers whose unit cell consists of one (m = 1), two (m = 2), or three (m = 3) kinds of atoms. Moreover, for these three types of polymers, we supposed two catenation types for the skeleton atoms; one is a “homorotatory” sequence and the other is a “heterorotatory” one. To specify the backbone's stereostructure, we introduced several conformation parameters such as the helical pitch number n, the translation distance d, and the inclination angle of the skeleton plane Θ. By combining these parameters, we can systematically understand the variety and the possible polymorphy in the stereostructure of a periodic polymer backbone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2829–2849, 2003     

A Pseudo-Random Frequency Modulation Continuous Wave Coherent Lidar Using an Optical Field Correlation Detection Method

We propose a new detection method for a pseudo-random frequency modulation continuous wave (RM-CW) coherent lidar. The feature of this method is modulation of local beam with a time delayed pseudo-random sequence. Heterodyne detection and correlation detection between the received beam and the local beam are simultaneously carried out in an optical field. In the RM-CW coherent lidar using the optical field correlation detection method, the received equipment is greatly simplified. We carried out preliminary experiments and demonstrated that the new method is effective for detection of a CW coherent lidar.     

Lightness Change as Perceived in Relation to the Size of Recognized Visual Space of Illumination

According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators.     

Frequency measuring system using mirror gap stabilized Fabry-Perot interferometer

The mirror gap of a Fabry-Perot interferometer was stabilized with two laser diodes; one locked to the line frequency 385,243,555.14445 MHz of the F=3<--1 in 5D(3/2)<--5S(1/2) (87Rb) and the other to the 385,284,566.3663 MHz of the F=4<--2 in 5D(5/2)<--5S(1/2) (87Rb) [Opt. Commun. 102 (1993) 432]. The length of the mirror gap was adjusted to generate the zero-cross points simultaneously at both of the two line positions. The fringe signals obtained from an interferometer thus stabilized can be used as frequency markers having accuracies of the order of 10(10) depending on the finesse of the interferometer used. Based on measurement using Cs D1 hyperfine lines reported by Udem et al. [Phys. Rev. Lett. 82 (1999) 3568], the uncertainty of markers in the region 50 THz apart from the reference lines is +/- 5 MHz.     

Cation binding properties of crown ether-modified polyethylenimines

Crown ether-modified polyethylenimines (PEI-CR) were prepared to elucidate their cation binding efficiency and selectivity by liquid-liquid and solid-liquid extraction methods. With alkali metal cations it was found that polyethylenimines containing benzo-15-crown-5 moieties (Ia and Ib) extracted all cations examined more efficiently than their monomeric analogs, especially in the cases of K⁺ and Rb⁺ cations. The solid-liquid extraction revealed clearly that the polymers complexed with K⁺ and Rb⁺ cations according to a 1:2 cation-to-crown stoichiometry. The high selectivities of the polymers for K⁺ and Rb⁺ were interpreted in terms of the favourable conformation of the polymer chain for the formation of intramolecular 1:2 complexes. On the contrary, these polymers bound alkali earth cations less effectively with low selectivities.