Diffusion of probe polymer in gellan gum solutions during gelation process studied by gradient NMR

The diffusion coefficients of pullulan added in gellan gum solutions as a probe polymer were measured using pulsed-field-gradient stimulated-spin-echo (PFG-Ste) ¹H NMR in order to investigate the gelation mechanism and gel structure. The echo intensity of gellan was steeply decreased at around the gelling temperature T_gel indicating stiffening of the gellan chains upon aggregation and formation of the network. The diffusion coefficient of pullulan D_pull increased with decreasing temperature below T_gel. This result suggests that the decrease in concentration of solute gellan in the interspaces of the network below T_gel, as evidenced by the decrease in its echo intensity, leads to an overall decrease of hydrodynamic interactions between gellan and pullulan. The characteristic hydrodynamic shielding length ξ was calculated from the relation D_pull/D_pull,0 = exp(−R_h/ξ), where D_pull,0 is D_pull in dilute solution and R_h is the hydrodynamic radius of pullulan. The temperature dependence of ξ, which was investigated for varying concentrations of several cations, was found to follow closely the gelling temperature, and in particular, showing a very similar thermal hysteresis.     

Monitoring growth and movement of Ralstonia solanacearum cells harboring plasmid pRSS12 derived from bacteriophage ϕRSS1

We monitored growth and movement of Ralstonia solanacearum harboring the plasmid pRSS12 in tomato seedlings. The plasmid contains a gene for green fluorescent protein (GFP) and is stably maintained in R. solanacearum cells without selection pressure. Bacteria harboring the plasmid can be tracked in planta by visualizing GFP fluorescence. Stems of seedlings were infected with R. solanacearum cells transformed with pRSS12, and bacterial growth and movement, particularly around the vascular bundles, were monitored for more than 7 days. Our results showed that vascular bundles are independent of each other within the stem, and that it takes a long time for R. solanacearum cells to migrate from one vascular bundle to another. For real-time monitoring of bacteria in planta, tomato seedlings were grown on agar medium and bacterial suspension was applied to the root apex. The bacterial invasion process was monitored by fluorescent microscopy. Bacteria invaded taproots within 6 h, and movement of the bacteria was observed until 144 h after inoculation. In susceptible tomato cultivars, strong GFP fluorescence was observed in hypocotyls and lateral roots as well as the taproot. In resistant cultivars, however, GFP fluorescence was rarely observed on lateral roots. Our results show that this monitoring system can be used to assess bacterial pathogenicity efficiently.     

Identification and characterization of a novel l-amino acid ligase from Photorhabdus luminescens subsp. laumondii TT01

l-Amino acid ligase catalyzes dipeptide synthesis from unprotected l-amino acids in an ATP-dependent manner. We recently identified a new member of l-amino acid ligase, the plu1440 protein, from Photorhabdus luminescens subsp. laumondii TT01 by in silico analysis. This protein was found to synthesize dipeptides containing l-asparagine at the N-terminus, which is a novel substrate specificity.     

Domain wall observation and dielectric anisotropy in PZN–PT by SPM

The voltage drops on the surfaces in PZN–20% PT and PZN–30% PT were investigated using the electrostatic force microscopy (EFM). It was found that the voltage drop per unit length in the a-domain is larger than the one in the c-domains on the sample surface with the ferroelastic domain wall structure, implying that the dielectric constant perpendicular to the spontaneous polarization is larger than the one parallel to the spontaneous polarization in the vicinity of the morphotropic phase boundary (MPB). Dielectric anisotropy in the vicinity of the MPB was discussed.     

Composite structure composed of overlapped fibre bundles,thermoplastic resin and metal plate for secondary forming process

A simple shape of a composite is preferable in mass production, while a curved or stretched shape is sometimes preferable for final products. High formability would enable the composite to deform into a preferable shape by secondary forming. In this paper, a structure for a composite is proposed to enhance formability. The composite is composed of reinforcing fibre bundles, thermoplastic resin as the matrix and metal plates. The reinforcing fibre bundles are discontinuous, and are intentionally overlapped in the longitudinal direction. The resin including fibre bundles is sandwiched between the metal plates. As the thermoplastic resin is melted at an adequate temperature, heating would enhance the mobility of thermoplastic resin resulting in high formability at the secondary forming. If the overlapped length is adequately designed, the composite would still maintain high strength after the secondary formation. The validity of the concept was checked by finite element analyses and experiments.     

Xanthine Oxidase Inhibitory Activity and Hypouricemic Effect of Aspalathin from Unfermented Rooibos

Rooibos is rich in flavonoids such as aspalathin, which is a unique C‐glycosyl dihydrochalcone, that is used as a traditional herbal tea. This study was designed to evaluate the in vitro xanthine oxidase (XOD) inhibitory activity of the aspalathin‐rich fraction (ARF) and purified aspalathin from rooibos. The hypouricemic effects of the ARF and aspalathin on hyperuricemic mice were also assessed. The ARF was prepared from aqueous extract of unfermented rooibos leaves and stems, and it was collected by column chromatography; the aspalathin content in this fraction was 21.4%. The ARF and aspalathin inhibited XOD in a dose‐dependent manner. The concentrations of the ARF and aspalathin required to inhibit XOD at 50% (IC₅₀) were 20.4 μg/mL (4.4 μg/mL aspalathin equivalents) and 4.5 μg/mL, respectively. Lineweaver–Burk plot analysis indicated that aspalathin was a competitive inhibitor of XOD, and the inhibition constant (Ki) was 3.1 μM. In hyperuricemic mice induced by inosine‐5’‐monophosphate, treatment with the ARF and aspalathin significantly suppressed the increased plasma uric acid level in a dose‐dependent manner. The suppressed plasma uric acid level in mice could be attributed to the XOD inhibitory activity of the ARF and aspalathin. Further study is required to determine the effect of aspalathin or its metabolites on XOD activity in vivo.     

Discovering the efficient organization structure: horizontal versus vertical

Structure analysis is one of the most important issues in corporate management. The pyramid structure, which is a well-known vertical structure, plays an important part in corporate organizations. Most structures of traditional organizations, such as the functional structure and the divisional structure, are vertical. Recently, owing to the development of information technology, a new horizontal structure instead of the vertical one has received considerable attention. In this article, we review organizational structures and find that there are two efficient structures, a vertical structure and a horizontal structure, depending on the different abilities of each member in any organization with a comprehensive evaluation measurement. The line structure of a vertical organization is efficient when the ability of all members is small. While if the ability of all members is large, the star structure of a horizontal organization will be efficient. Therefore, this article provides a theoretical proof of the efficiency of the structures of organizations and their required conditions.     

Spin Turbulence Made by the Oscillating Magnetic Field in a Spin-1 Spinor Bose-Einstein Condensate

We numerically study spin turbulence made by the oscillating magnetic field in a two-dimensional homogeneous spin-1 spinor Bose-Einstein condensate. We confine ourselves to the case of the ferromagnetic interaction, where the ground state is ferromagnetic. By the oscillating magnetic field along some direction makes the system unstable. At first, the spin density vector revolves in the plane perpendicular to the magnetic field, exciting long-wavelength modes. Secondly, appear some vector components along the magnetic field. Finally, the system becomes spin turbulence. In terms of the energy spectrum of the spin-dependent interaction energy, the peak appears first at low wave number region. Gradually, the peak shifts from low to high wave number region. Eventually, the spectrum exhibits the ?7/3 power law. The ?7/3 power law is confirmed by the scaling analysis using the hydrodynamic equation of the spinor Bose-Einstein condensate.     

Characteristic of an AC chopper circuit with LC filters in the input and output side

LC filters are connected to both the input and output side of the AC chopper circuit in order to remove the switching ripple and harmonics. Characteristics of THD and input power factor are examined by simulation and experiments. When the load is resistive, characteristics are minimally influenced by the filters. In the case of an inductive load, since two poles exist owing to the input and output filters, waveform distortion becomes large. This paper shows that THD can be improved by reducing input filter capacitance. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(2): 45–52, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20304