Preparation and magnetometric characterization of iron oxide-containing alginate/poly(vinyl alcohol) networks

Alginate-based magnetic gels were prepared in a sequence of procedures for in situ synthesis of iron oxides: crosslinking of alginate in ferrous salt aqueous solution, immersion of the resulting gels into alkaline-earth metallic hydroxide solution, and treatment of the partially cation-exchanged gels with hydrogen peroxide. Magnetometry measurements revealed that the lyophilized gels showed superparamagnetism or ferromagnetism at room temperature, depending on the sort of the metallic cation employed in the alkali treatment. An interpenetrating network (IPN) type of alginate/poly(vinyl alcohol) (Alg/PVA) gels containing iron oxides was also designed and fabricated from mixed polymer solutions by a modified preparation method; the gelation and alkali treatment were carried out with the aid of a metallic borate. Viscoelasticity of the magnetic IPN composites in the gelatinous state was controllable by changing the mixing ratio of the compatible carbohydrate/viny polymer pair. Magnetization versus magnetic field curves were constructed at different temperatures for the IPNs freeze-dried. Their magnetic character was variable according to alterations of the Alg/PVA composition, alkaline reagent adopted, and measurement temperature.     

Highly sensitive elemental analysis for Cd and Pb by liquid electrode plasma atomic emission spectrometry with quartz glass chip and sample flow

This paper describes the development of a highly sensitive liquid-electrode plasma atomic emission spectrometry (LEP-AES) by combination of quartz glass chip and sample flow system. LEP-AES is an ultracompact elemental analysis method, in which the electroconductive sample solution is put into a microfluidic channel whose center is made narrower (～100 μm in width). When high voltage pulses (1500 V) are applied at both ends of the channel, the sample evaporates locally at the narrow part and generates plasma. By the emission from the plasma, elemental concentration is analyzed. In this paper, the limits of detection (LODs) were investigated in various conditions of accumulation time, material of the chip, and the sample flow. It was found that the long accumulation using the quartz chip with sample flow was effective to improve LOD. Authors suggested that this was because bubbles remaining after each plasma pulse were removed from the narrow channel by sample flow, resulting in highly reproducible plasma generation, to enable a high accumulation effect. Finally, LODs were calculated from a calibration curve, to be 0.52 μg/L for Cd and 19.0 μg/L for Pb at optimized condition. Sub-ppb level LOD was achieved for Cd.     

Characterization of rpoH in Acetobacter pasteurianus NBRC3283

The RpoH in Acetobacter pasteurianus NBRC3283 was characterized. It was revealed that the rpoH controls the expression of groEL, dnaKJ, grpE, and clpB to different extents. In addition, the rpoH disruption mutant became apt to be affected by heat, ethanol, and acetic acid, indicating its importance in acetic acid fermentation.     

Low methanol crossover and high performance of DMFCs achieved with a pore-filling polymer electrolyte membrane

We compared the performance of the membrane electrode assembly for direct methanol fuel cells (DMFCs) composed of a pore-filling polymer electrolyte membrane (PF membrane) with that composed of a commercial Nafion-117 membrane. In DMFC tests, the methanol crossover flux was 23% lower in the PF membrane than in the Nafion-117 membrane even though the thickness of the PF membrane was 43% that of Nafion-117. This led to a higher DMFC performance and the lower overpotential of the cathode of the PF membrane. Feeding an aqueous 10 M methanol solution at 50 °C produced a low cathode overpotential, as low as 0.40 V at 0.2 A in the PF membrane, whereas the potential was 0.65 V at 0.2 A in the Nafion-117 membrane. In contrast, the ohmic loss and anode overpotential were almost the same in the two membranes. We confirmed that a reduction in methanol crossover using the PF membrane results in lower cathode overpotential and higher DMFC performance. In addition, the electro-osmotic coefficient was estimated as 1.3 in the PF membrane and 2.6 in Nafion-117, based on a water mass-balance model and values showing that the PF membrane prevents the flooding of the cathode at a low gas flow rate using. A highly concentrated methanol solution can be applied as a fuel without decreasing DMFC performance using PF membranes.     

Transformation of oil-producing fungus, Mortierella alpina 1S-4, using Zeocin, and application to arachidonic acid production

The arachidonic acid-producing fungus Mortierella alpina 1S-4, an industrial strain, was endowed with Zeocin resistance by integration of the Zeocin-resistance gene at the rDNA locus of genomic DNA. Plasmid DNA was introduced into spores by microprojectile bombardment. Twenty mg/ml Zeocin completely inhibited the germination of M. alpina 1S-4 spores, and decreased the growth rate of fungal filaments to some extent. It was suggested that preincubation period and temperature had a great influence on transformation efficiency. Four out of 26 isolated transformants were selected. Molecular analysis of these stable transformants showed that the plasmid DNA was integrated into the rDNA locus of the genomic DNA. We expect that this system will be applied for useful oil production by gene manipulation of M. alpina 1S-4 and its derivative mutants. On the basis of the fundamental transformation system, we also tried to overexpress a homologous polyunsaturated fatty acid elongase gene, which has been reported to be included in the rate-limiting step for arachidonic acid production, thereby leading to increased arachidonic acid production.     

Dietary n-3 Fatty Acid Deficiency in Mice Enhances Anxiety Induced by Chronic Mild Stress

Docosahexaenoic acid (DHA), is the major polyunsaturated fatty acid in the brain and is important for both the structure and the function of the nervous system. Mice were fed either an n-3 fatty acid deficient (n-3 Def) or adequate (n-3 Adq) diet for two generations. The mice were housed under two conditions, as a group or in isolation and the major point of the study was to determine whether n-3 fatty acid deficiency would enhance isolation-induced anxiety. Isolation stress was assessed using the novelty suppressed feeding paradigm (NSF) after a 3-week period and the test lasted a maximal duration of 10 min. The number of successful mice consuming food pellets within 5 min in the n-3 Def diet group was low in both housing conditions (group housing, 33% and isolated, 30%), but was 92% in the group housed and 50% in the isolated group when fed the n-3 Adq diet. In the subsequent 5 min period, the isolated housing group consuming the n-3 Adq diet increased up to 79% and the group housed animals fed the n-3 Def diet increased to 67%. However, those that consumed the n-3 deficient diet combined with isolation stress exhibited no increase. These results suggested that the n-3 deficient mice had increased anxiety that was enhanced by the chronic mild stress of social isolation.