Hot Dates

The results of an analytic investigation on the influence of the thermal conductance of a sorption element (adsorber/desorber), evaporator, and condenser on the performance of a three-bed silica-gel-water adsorption chiller are presented with consideration given to the thermal capacitance ratio of the adsorbent and metal of the adsorber/desorber heat exchanger. The analysis was performed by using a cycle-simulation model developed by the authors. The chiller is driven by exploiting waste heat at a temperature 60 and 95°C with a cooling source at 30°C for air conditioning purpose. The results show that the cycle performance is strongly affected by the thermal capacitance ratio and sorption element thermal conductance due to several sensible heating/cooling requirements resulting from batched cycle operation. The model is somewhat sensitive to the thermal conductance of the evaporator, and the thermal conductance of the condenser is the least sensitive parameter.     

Center of excellence for atomically controlled fabrication technology

This short review aims to show the introduction of the educational and research program of "Center of excellence of atomically controlled fabrication technology" supported ministry of education, culture, sports, science and technology--Japan. We would like to introduce research activity and a unique trait of educational system.     

Airflow and thermal conductance in a totally enclosed induction motor

Heat transfer coefficients of air‐cooled fins located on the outer surface of a totally enclosed induction motor were measured. It was found that the heat transfer coefficient decreases in the downstream direction in relation to the outer fins. It was also found that increasing the axial length of the fan cover (i.e., so that the fan cover overlaps the fin) increases the average heat transfer coefficient of the outer fins. Internal airflow induced by the rotor fan inside the motor end‐bracket coincides with the rotational speed of the rotor fan. Airflow velocity between the stator coil end and the housing in the motor is low, so a cooling structure with an inside ventilation passage for airflow was introduced to increase the heat transfer of the stator coil. By using an actual motor, the effect of resin (varnish) between the stator and the motor housing on the thermal‐contact conductance was determined; the thermal‐contact conductance of a motor with resin was 1.58 times higher than that of one without resin. © 2001 Scripta Technica, Heat Trans Asian Res, 31(1): 7–20, 2002     

Solubilization of Myofibrils and Inhibition of Autolysis of Squid Mantle Muscle by Sodium Citrate

ABSTRACT:  The effects of organic salts (sodium (Na)-citrate, Na-gluconate, and Na-succinate) on the solubilization of myofibrillar proteins and the inhibition of autolysis of squid mantle muscle were investigated. All of the organic compounds dissolved myofibrils as NaCl did. Na-citrate showed the strongest ability with half dissolving at 0.06 M. Half dissolving by Na-gluconate, Na-succinate, and NaCl were 0.27, 0.21, and 0.27 M, respectively. Dissolving myofibrils by Na-citrate was not accompanied by the acceleration of autolysis. Na-citrate above 0.25 M almost completely inhibited the autolysis. The inhibition of autolysis by Na-gluconate and Na-succinate was much less than that of Na-citrate. Consequently, it was concluded that Na-citrate was the organic salt to dissolve squid myofibrils without inducing autolysis.     

Electrochemical polymerization of aniline in the presence of poly(acrylic acid) and characterization of the resulting films

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of PAA. The PAA content in the films (PANI/PAA films) was controlled by the concentration of PAA in polymerization solution, and the properties of the films were investigated in relation to the PAA content. It was demonstrated by means of scanning electron microscopy and cyclic voltammetry that the surface morphology and electrochemical property of the films were affected significantly by the PAA content. In contrast, the conductivity of the films was found hardly dependent on the PAA content up to 18 wt %. The cyclic voltammetry gave an interesting result that the PANI/PAA films showed an electroactivity in neutral solution, which was not observed for the PANI film without PAA, and the electroactivity was closely related to the PAA content in the PANI/PAA films.     

Synthesis of zeolite from steel slag and its application as a support of nano-sized TiO2 photocatalyst

Steel slag, commercial waste material containing silica and alumina which are the chemical components elements of zeolite, was used as a source for synthesis of FAU zeolite (Y-zeolite, X-zeolite). Through acid-treatment to remove CaO species from steel slag and hydrothermal treatment, well-crystallized Na type FAU zeolite was obtained. Furthermore the synthesized FAU zeolite was applied as a support of photocatalyst. It was found that hydrophobic surface property of zeolite enhances photocatalytic activity for decomposition of organic pollutants and the zeolite synthesized from steel slag would be applicable as promising support of TiO₂ photocatalyst.     

Importance of the Ca2+-binding sites in the N-catalytic domain of a family I.3 lipase for activity and stability

A family I.3 lipase from Pseudomonas sp. MIS38 (PML) contains three Ca(2+)-binding sites (Ca1-Ca3) in the N-catalytic domain. Of them, the Ca1 site is formed only in an open conformation. To analyze the role of these Ca(2+)-binding sites, three mutant proteins D157A-PML, D275A-PML and D337A-PML, which are designed to remove the Ca1, Ca2 and Ca3 sites, respectively, were constructed. Of them, the crystal structures of D157A-PML and D337A-PML in a closed conformation were determined. Both structures are nearly identical to that of the wild-type protein, except that the Ca3 site is missing in the D337A-PML structure. D157A-PML was as stable as the wild-type protein. Nevertheless, it exhibited little lipase and very weak esterase activities. D275A-PML was less stable than the wild-type protein by approximately 5 degrees C in T(1/2). It exhibited weak but significant lipase and esterase activities when compared with the wild-type protein. D337A-PML was also less stable than the wild-type protein by approximately 5 degrees C in T(1/2) but was fully active. These results suggest that the Ca1 site is required to make the active site fully open by anchoring lid 1. The Ca2 and Ca3 sites contribute to the stabilization of PML. The Ca2 site is also required to make PML fully active.     

Effect of soy protein isolate on gel properties of Alaska pollock and common carp surimi at different setting conditions

The effects of soy protein isolate (SPI) on the gel properties of different grade Alaska pollock and common carp surimi at different setting conditions were evaluated and compared. Breaking force and distance of gels decreased with increasing SPI concentrations in direct cook (85 °C for 30 min) and in cook after setting at 30 °C for 60 min conditions. The effect of SPI on gel strength of common carp surimi was less than in Alaska pollock surimi. The breaking force obtained for addition of 10% SPI to Alaska pollock surimi was higher than for surimi alone when cooked after incubation at 50 °C for 60 min. Addition of SPI decreased the whiteness and increased the yellowness of the gel. The gel structure showed that the addition of SPI modified the microstructure of the fish protein gel, thus resulting in surimi with different gelling properties. Copyright © 2004 Society of Chemical Industry     

Year-round high arachidonic acid levels in herbivorous rabbit fish Siganus fuscescens tissues

To identify a stable resource of 20∶4 n−6 (arachidonic acid, AA) in marine fish tissues, the lipid profiles of Siganus fuscescens organs (muscle, liver, and other viscera) and stomach contents were examined throughout the year. Crude total lipid (TL) contents in respective organs showed seasonal variations and were high in winter and low in summer. The main FA in TL were 16∶0, 18∶0, 16∶1n−7, 18∶1n−9, AA, and 22∶6n−3 (DHA). These FA were those generally observed in marine fish lipids, except for comparatively high levels of AA. In TL of muscle and liver, AA showed relatively high values during the period from late May to August (muscle, 4.6–13.1%; liver, 4.5–9.1%), compared with other seasons (muscle, 4.3–9.5%; liver, 3.6–8.4%). The AA levels in TL of other viscera and stomach contents fluctuated (other viscera, 2.0–10.7%; stomach contents, 7.6–26.7%). Regardless of the fishing season, each organ contained a higher level of AA in polar lipids (PL) than in neutral lipids. It was concluded that the fish contain comparatively high levels of AA in their TL throughout the year, and they accumulate AA characteristically in their tissue PL, probably from dietary food sources. Moreover, it was suggested that S. fuscescens has potential utility as a natural marine source of nutritional lipids, because the fish contain comparatively high levels of DHA and AA.     

Extracellular secretion of Escherichia coli alkaline phosphatase with a C-terminal tag by type I secretion system: purification and biochemical characterization

Type I secretion system (TISS) of Gram-negative bacteria permits proteins to be secreted directly from the cytoplasm to the external medium by a single, energy-coupled step. To examine whether this system can be used as an extracellular production system of recombinant proteins, Escherichia coli alkaline phosphatase (AP) was fused to a C-terminal region of Pseudomonas sp. MIS38 lipase (PML) and examined for secretion using the E.coli cells carrying the heterologous TISS. PML is one of the passenger proteins of TISS and contains 12 repetitive sequences and a secretion signal at the C-terminal region. The fusion protein was efficiently secreted to the extracellular medium, while AP was not secreted at all, indicating that the secretion of AP is promoted by a secretion signal of PML. The repetitive sequences were not so important for secretion of the fusion protein, because the secretion level of the fusion protein containing entire repeats ( approximately 10 mg/l culture) was only 2-fold higher than that of the fusion protein without repeats. The fusion protein purified from the culture supernatant existed as a homodimer, like AP, and was indistinguishable from AP in enzymatic properties and stability.