Particle growth of magnesium alkoxide as a carrier material for polypropylene polymerization catalyst

Images from scanning electron microscopy, transmission electron microscopy and X-ray diffraction profiles of typical magnesium diethoxide (MGE) particles obtained by the reaction of ethanol, metal magnesium and iodine showed the round MGE particle (tertiary particle) had a layer structure consisting of many crystalline fragments (secondary particles) comprising many minute crystals (primary particles). It was clearly shown that each precipitated secondary particle had not agglomerated, but had repeatedly grown and combined with others. From the investigation of the course of a reaction, it was suggested the MGE crystals grown on Mg metal exfoliated as “lump-like” seeds, and crystal growth on seeds proceeded such that the shapes of the final MGE particles were more spherical than those of their seeds. It was presumed from a model reaction that the enhancement of MGE solubility by I₂ addition to form the quasi-stable complex nMg(OEt)₂·MgI₂·mEtOH was the key process in the formation of plate crystals. The relationship between the size of crystalline fragments and crystallization rate (reaction rate, MGE solubility) was discussed.The catalyst, when prepared using MGE as the carrier material, exhibited exceptionally high polymerization activity than when it was prepared with MgCl₂ alcohol complex (MgCl₂·ROH). We presume that this is because particles of the MGE-based catalyst are porous, and because the formation of active species of the supported Ti and monomer diffusion progressed adequately from the surface of the particle to its internal parts.     

Production of recombinant human lysosomal acid lipase in Schizosaccharomyces pombe: development of a fed-batch fermentation and purification process

A fed-batch fermentation process has been developed to enable the production of large quantities of recombinant human lysosomal acid lipase (hLAL; EC 3.1.1.13), in Schizosaccharomyces pombe, for preclinical studies as a potential enzyme therapy drug. Recombinant S. pombe, clone ASP397-21, expressed enzymatically active hLAL in the secreted form. A feedback fed-batch system was used to determine the optimal feed rate of a 50% glucose solution used as the carbon source. The feed rate of the glucose solution was calculated by a computer-aided system according to the equation; F=q(sf)(VX)/S(in) (q(sf), specific substrate feed rate [gram substrate/gram dry cell weight/h]; V, volume of culture broth [l]; X, cell density [gram dry cell weight/l]; S(in), concentration of growth limiting substrate in feed solution [gram substrate/gram feed solution]). At the time of the initial consumption of glucose in the batch-phase culture, the nutrient supply was automatically initiated by means of monitoring the respiratory quotient change. The obtained profile of the feed rate was applied to the feed forward control fermentation. Finally, the cells were grown up to >50 g dry cell weight/l, and the hLAL expression level was approximately 16,000 U/l. Expressed hLAL protein was purified in a two-step process by hydrophobic interaction and anion exchange chromatographies. Purified recombinant hLAL exhibited a 90-150 kDa broad band upon SDS-PAGE with specific activity of about 300 U/mg. After endoglycosidase H treatment, the band converged to 45 kDa, equal to the calculated molecular weight, suggesting that hLAL produced in S. pombe was hyper-glycosylated. N-terminal analysis of de-glycosylated hLAL revealed that the signal sequence of hLAL was correctly processed in S. pombe.     

Vibration-assisted upconversion of molecular luminescence induced by scanning tunneling microscopy

We investigate the effects of coupling between a molecular exciton, which consists of an electron and a hole in a molecule, and a surface plasmon (exciton-plasmon coupling) on the electron transitions of the molecule using nonequilibrium Green’s function method. Due to the exciton-plasmon coupling, excitation channels of the molecule arise in the energy range lower than the electronic excitation energy of the molecule. It is found that the electron transitions via these excitation channels give rise to the molecular luminescence and the vibrational excitations at the bias voltage lower than the electronic excitation energy of the molecule. Our results also indicate that the vibrational excitations assist the emission of photons, whose energy exceeds the product of the elementary charge and the bias voltage, (upconverted luminescence).     

Evaluating uncertainty in accident rate estimation at hydrogen refueling station using time correlation model

Hydrogen, as a future energy carrier, is receiving a significant amount of attention in Japan. From the viewpoint of safety, risk evaluation is required in order to increase the number of hydrogen refueling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However, in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability, which increases over long operation period due to decrease in number of stations. In this paper, a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data, which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.     

Nickel volatilization phenomenon on the Ni-CGO anode in a cathode-supported SOFC operated at low concentrations of H2

Rapid degradation phenomenon is generally occurred when Ni-based anode on a cathode-supported SOFC is operated in low concentrations of hydrogen at high current density. In order to clarify this phenomenon, homogenous NiO-Ce_0.8Gd_0.2O_1.9 (CGO) composites powder with fixed weight ratio of Ni:Ce was synthesized using a nitric-citrate sol-gel method, and coated on LSM-CGO cathode-supported SOFC using slurry coating method. As-prepared fuel cells exhibited good performance when they were operated at pure H₂. However, rapid degradation phenomenon on Ni-CGO anode usually happened when low concentration of H₂ was used as fuel at high current density. Obvious microstructure damage and sintering of Ni were observed in SEM micrographs of Ni-CGO anode after repeated degradation process in 5.66% of H₂ at high current density. Furthermore, the decrease in Ni amount in Ni-CGO anode was also found via EDX analysis when this degradation process was repeated for several times. It is inferred that the volatilization of nickel hydroxide should happen at triple-phase boundaries of Ni-CGO anode when high partial pressure ratio of H₂O and H₂ appeared in this case.     

The origin of hypersaline liquid in the quaternary kakkonda granite, sampled from well WD-1a, kakkonda geothermal system, Japan

Hypersaline metal-rich liquid (ca. 40 wt% total chloride species) was obtained from a depth of 3708 m in the Kakkonda geothermal system. Sampling of well WD-1a was conducted by reverse circulation after a standing time of about 196 hours (with temperature recovering to >500°C). Tritium content and the relationship between δD and δ¹⁸O showed that the river water that was circulated in the well had mixed with an isotopically heavy fluid during the standing time. Phase separation occurred during temperature recovery, concentrating the hypersaline liquid in the bottom of the well. This original hypersaline liquid has a salinity of about 55 wt% NaCl eq., consisting of Na–Fe–K–Mn–Ca chloride, rich in Zn and Pb but poor in Cu, Au and Ag. The fluid originates from the Kakkonda granite and mixed with circulating water from the well in a zone of fine fractures induced by thermal stress during drilling.     

800 Mbit/s Digital Transmission System Over Coaxial Cable

800 Mbit/s digital transmission systems, using nonredundant three-level and four-level codes, have been studied as a means of providing an economically attractive digital transmission system. These systems have been designed to be compatible with a 60 MHz analog system in repeater spacing and repeater size, so as to be easily introduced into the existing network. These systems with 11 520 telephone channels, exceed the 60 MHz analog system in both capacity and economy. Due to repeater construction factors, it became clear that the three-level code is more suitable. This paper describes the design and performance of 800 Mbit/s digital transmission systems and repeaters.     

A convenient method for the preparation of asialo-GM1

A convenient and efficient procedure has been devised for the large-scale preparation of asialo-G_M1 from bovine brain gangliosides. The procedure relies on the complete desialylation of brain ganglio-sides, consisting primarily of G_M1, G_D1a, G_D1b and G_T1b, by mild formic acid hydrolysis (0.1 N, 100 C; 2 hr). Following the hydrolysis step, asialo-G_M1 can be isolated and purified by Folch partitioning and Iatrobeads column chromatography, with an overall yield of more than 50%. The ganglioside nomenclature used is that of Svennerholm (1).     

Effects of contact‐dehydrating sheets on preference for fried food and deterioration of frying oil

The purpose of this study was to investigate the effects of contact‐dehydrating sheets on preferences for fried food and the deterioration of frying oil. Mackerel or chicken breast were dehydrated by wrapping with the contact‐dehydrating sheets at 4°C for 1.5 h and subsequently fried at 180°C for 3 min; those were referred to as the dehydrated samples. The same fried materials not wrapped with the contact‐dehydrating sheets were referred to as the control. The frying procedure was repeated 15 times under the above conditions and the amount of frying oil was adjusted to 1000 g by addition of new oil each time. Sensory analysis showed that the dehydrated samples were preferred to the control. Acidic values, anisidine values and ΔE values of the frying oil used for the dehydrated mackerel were significantly lower than for that used for preparing the control. These results indicate that the use of contact‐dehydrating sheets for the dehydration of the frying materials was effective in both significantly increased preference for the fried food and the retardation of the deterioration of the frying oil. Copyright © 2004 Society of Chemical Industry