Lubrication of Si3N4 and Al2O3 in water with and without addition of silane coupling agents in the range of 0.05–0.10 mol/l

To improve water lubrication of ceramics at a lower sliding velocity, the effect of the addition of silane coupling agents was investigated. Si₃N₄ and Al₂O₃ were slid against themselves in water with and without the addition of silane coupling agents in amounts ranging from 0.05 to 0.10 mol/l. Silane coupling agents containing one or more amino groups were effective in reducing the friction of Si₃N₄ and Al₂O₃ in water. Si₃N₄ also showed significant wear reduction but not Al₂O₃. However, the addition of a silane coupling agent containing an epoxy group increased both friction and wear of Si₃N₄. Improved lubricative characteristics of Si₃N₄ in water and in silane coupling agent solutions were obtained when Si₃N₄ contained smaller amounts of sintering additives. The adsorption behaviour of a silane coupling agent on ceramics was examined using both Fourier transform infrared spectroscopy and thin layer chromatography to clarify the interaction between the silane coupling agent and the ceramics. The role of polysiloxane film formation on ceramics is discussed to demonstrate the lubrication properties of ceramics.     

To Separate a Particular Ln(III) Selectively Using Solvent Extraction

ABSTRACT

Since a particular trivalent lanthanide (Ln(III)) often plays a unique role in different industrial applications, the development of a selective separation method to get only the requisite Ln(III) would be most convenient. Synergistic extraction with β-diketone (HA) and Lewis base (B), which has been extensively used for the separation of lanthanides, relies on two processes: the extraction with HA as LnA₃ into the organic phase and the complexation of LnA₃ with B as LnA₃B in the organic phase. The variation in the pattern of the extraction constants of LnA₃ across the Ln series correlates with the number of CF₃- group in the β-diketones, and with the stability constants of LnA₃B of different Lewis bases. It is seen that the constants with bipyridyl increase with increasing atomic number, while those with POPO (methylenediphosphonate) and MePhPA (methylphenylphenanthroline carboxamide) decrease with increasing Ln atomic number. Using pivaloyltrifluoroacetone as the β-diketone and MePhPA, the best extractability appeared at Sm(III) among the series. As a conclusion, to get only a required Ln(III), the combination of β-diketone and Lewis base is very important. In addition, the separation of Lns(III) from other metals and the use of new extractants developed recently and reported in literature were referred to find out more effective extractants and selective separation methods.     

Culture system for extensive production of CD19+IgM+ cells by human cord blood CD34+ progenitors

We established a co-culture system with a monolayer of the murine bone marrow (BM) stroma cell line, MS-5, in which human cord blood CD34+ cells differentiated to CD19+ cells. The addition of stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) highly enhanced the production of CD19+ cells. The expansion of the cell numbers was over 10(3)-fold. Furthermore, a significant proportion (<45%) of the cells expressed surface IgM (sIgM) after 5 weeks of co-culture. CD34+CD19- cells also showed a similar development of CD19+ cells and CD19+sigM+ cells. Filter separation of MS-5 cells and CD34+ cells did not inhibit the growth of CD19+ cells. However, when further purified CD34+CD19-CD13- CD33- cells were cultured in the presence of MS-5 cells with or without a separation filter, CD19+ cells did not appear in the non-contact setting. This result suggested that the highly purified CD34+CD19-CD13-CD33- progenitors require the cell-cell contact for the development of CD19+ cells, whereas other CD34+ fractions contain progenitors that do not require the contact. This co-culture system should be useful for the study of early human B-lymphopoiesis.     

Production of env-deficient rous sarcoma virus (RSV) early after infection

In this paper we document a case of peripheral T cell lymphoma (PTCL) that exhibited variable T cell histology at presentation and follow-up. Southern blot analysis for T cell receptor (TCR) and immunoglobulin (Ig) receptor gene rearrangements failed to reveal clonal T or B cell populations. TCR gamma (TCRG) and beta (TCRB) chain gene polymerase chain reaction (PCR) amplification of DNA isolated from biopsies was also consistent with polyclonal T cell populations, however Ig PCR revealed clonal Ig rearrangements in follow-up biopsies but not in the presentation biopsy. There was no histological evidence for a neoplastic B cell population in these biopsies although occasional EB virus positive blasts were present. The significance of a cryptic B cell clone is unknown but suggests a relationship with the proliferating polyclonal T cells in this case of PTCL. These data reflect the complexity of PTCL with implications for treatment and patient management.     

Studies on peroxidized lipids. VI. Fluorescent products derived from the reaction of primary amines,malonaldehyde and monofunctional aldehydes

Monofunctional aldehydes such as acetaldehyde,n-propylaldehyde,n-butylaldehyde,n-hexylaldehyde,n-heptylaldehyde and benzaldehyde affected the reaction between primary amines and malonaldehyde. While the reaction of primary amines and malonaldehyde at pH 7 produced fluorescent 4-methyl-1,4-dihydropyridine-3,5-dicarbaldehydesIa-f, the reaction of the primary amines, malonaldehyde and the aldehydes listed above gave fluorescent 4-substituted 1,4-dihydropyridine-3,5-dicarbaldehydesIIa-j. The primary amines used for this reaction included alkylamines, amino acids and alkanolamines. The optimal ratio of the amine, malonaldehyde and the aldehyde was 1:2:1–2, at which compoundsII were produced quantitatively. Peroxidized lipids which may contain malonaldehyde and other aldehydes could react with the primary amines to produce highly fluorescentII. Fluorescence spectra ofII showed excitation maxima at 386–403 nm and emission maxima at 444–465 nm in phosphate similar to those ofI. The spectra of these 1,4-dihydropyridinesI andII were roughly similar to those of lipofuscin pigment, but they exhibited different characteristics in acid and alkaline media from those of lipofuscin pigment. CompoundsII may be useful as model compounds to elucidate the chemical structure of lipofuscin pigment.     

{beta}-sheet folding of fragment (16-36) of bovine pancreatic trypsin inhibitor as predicted by Monte Carlo simulated annealing

A tertiary structure prediction is described using Monte Carlosimulated annealing for the peptide fragment corresponding toresidues 16–36 of bovine pancreatic trypsin inhibitor(BPTI). The simulation starts with randomly chosen initial conformationsand is performed without imposing experimental constraints usingenergy functions given for generic interatomic interactions.Out of 20 simulation trials, seven conformations show a sheet-likestructure—two strands connected by a turn—althoughthis sheet-like structure is not as rigid as that observed innative BPTI. It is also shown that these conformations are mostlylooped and exhibit a native- like right-handed twist. Unlikethe case with the C-peptide of RNase A, no conspicuous -helicalstructure is found in any of the final conformations obtainedin the simulation. However, the lowest-energy conformation doesnot resemble exactly the native structure. This indicates thatthe rigid ß-sheet conformation of native BPTI merelycorresponds to a local minimum of the energy function if thefragment with residues 16–36 is isolated from the nativeprotein. A statistical analysis of all 20 final conformationssuggests that the tendency for the peptide segments to formextended ß-strands is strong for those with residues18–24, and moderate for those with residues 30–35.The segment of residues 25–29 does not tend to form anydefinite structure. In native BPTI, the former segments areinvolved in the ß-sheet and the latter in the turn.A folding scenario is also speculated from this analysis.     

Combined processing of polypropylene film by coextrusion and zone-annealing

In order to improve the mechanical properties of polypropylene film, a new processing combining extrusion and zone-annealing has been applied. It was found that there are suitable conditions for each step in the combined processing. When the coextrusion draw ratio was low, the total draw ratio and modulus could be increased by the zone-annealing subsequently done. The highest modulus was obtained when the film was coextruded at extrusion draw ratio 4 and then zone-annealed at 120°C under 7 kg/mm². The value was 12 GPa in Young's modulus or 17 GPa in dynamic modulus. The peak temperature of α_c dynamic dispersion for the combinedly processed film was 109°C, which is higher by 10°C than that for the as-coextruded film. Four drawing methods were compared in dynamic viscoelasticity. These methods are the coextrusion, zone-drawing/zone-annealing, two-step coextrusion, and the combined processing by coextrusion and zone-annealing. The highest dynamic modulus for each method was arranged in the above order. The combined processing indicated the most effective improvement in mechanical properties, because it is believed that lamellae in the original film were broken by cooperating interaction of shear stress, compression, and tension on coextrusion and then the superstructure with a high crystallinity and a high molecular orientation was formed on zone-annealing.     

Esterification of n‐butyric acid with n‐butyl alcohol and transesterification of (R, S)‐phenylethanol by lipase immobilized on cellulose acetate–TiO2 gel fibre

Lipase (EC 3.1.1.3) was immobilized on cellulose acetate–TiO₂ gel fibre by the sol–gel method. The immobilized lipases were used for esterification of n‐butyric acid with n‐butyl alcohol and enantioselective acylation of (R, S)‐phenylethanol using vinyl acetate as an acyl donor. Compared with native lipase, the activity of the immobilized lipase was stable and relatively unaffected by the water content of the solvent and the substrate concentration. The data indicate that the lipases are immobilized on the fibre surface and that enzyme activity is influenced by bound water. However, the thermal reactivity and enantioselectivity of the immobilized lipase were less than those of native lipase. This may not reflect thermal inactivation of the enzyme but rather significant thermal contraction of the gel fibre by cellulose crystallization, resulting in liberation of bound water and a decrease in the amount of enzyme which is available for the reaction. Copyright © 2001 Society of Chemical Industry     

Effect of surface structure of porous silica microballoons on dynamic mechanical properties of amine cured epoxy resin composites

Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (T_g) of the composites is 12–14°C lower than the T_g of the unfilled epoxy resin. This T_g depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm. Tan δ_c tan δ_m decreases with increasing Hg-surface area.     

An electrochemical oxygen separator using an ion-exchange membrane as the electrolyte

An electrochemical oxygen separator based on oxygen reduction at an air cathode and oxygen evolution at an anode has been developed. The device features use of an ion-exchange membrane (Nafion 117) as the sole electrolyte and an air cathode mainly made of carbon.The anode was formed by chemically plating platinum (3.7 mgcm^–2) on one side of the Nafion 117 membrane. The air cathode was bonded to the other side of the membrane by spraying a slurry of graphitized furnace black loaded with platinum, followed by hot-pressing. The addition of a Nafion solution and a PTFE dispersion to the slurry was essential. The ultimate loading of platinum for the cathode was 0.2 mg cm^–2. An electrochemical oxygen separator with a working area of 100 cm² was constructed. When the separator was used as an oxygen concentrator it could be operated at 200 mA cm^–2 and produced 70.9 cm³ min^–1 of oxygen with a purity of 98.4%. When the separator was used as a circulation-type oxygen removal system it reduced the oxygen concentration of a 10-dm³ chamber to less than 0.02% within 70min. When the separator was used as a flow-through-type oxygen remover, air with an oxygen concentration of 0.02% was produced at 100 cm³ min^–1.