Process mechanism in ultrasonic cavitation assisted fluid jet polishing

Material removal rate in fluid jet polishing is significantly enhanced when ultrasonic cavitation bubbles are introduced at the nozzle outlet. In this paper, two theories are put forward to explain the process mechanism: a micro-scale hypothesis in which the surface is micro-jetted by collapsing bubbles, and a macro-scale hypothesis in which vibration of the fluid in the impingement region increases abrasive particle erosive action. Experimental investigation suggests the higher likelihood of the macro-scale phenomenon, and a material removal model is proposed accordingly. Process footprints simulated by this model were found to agree well with experimental measurements.     

Flame-retardant properties of cellulose phenylthiophosphonate

The effects of sulfur atoms on the thermal degradation and flammability of cellulose phenylthiophosphonate were investigated using thermogravimetry, IR spectrometry, and limiting oxygen index flammability tester. Introduction of sulfur atoms instead of oxygen atoms in the phosphonyl groups had little influence on the thermal degradation of cellulose. The thermal reactions were altered by ion exchange with sodium ions, and degradation of the cellulose chains was retarded. Cellulose phenylthiophosphonate was self-extinguishing above 4.64% phosphorus content. The flame-retardant properties remained when the cellulose phosphorus ester was ion exchanged with sodium ions. It was concluded that introduction of sulfur atoms into phosphorus esters of cellulose was effective in preventing the decrease in flame-retardant properties by ion exchange in laundering.     

Flame-retardant action of chlorine compounds and antimony trioxide on cellulose fabric

Chemical research on the flame-retardant action of halogen compounds and antimony trioxide on cellulose fabric was carried out by thermogravimetry, infrared spectrum analysis, and x-ray diffraction analysis. The following results and conclusion were drawn: (1) Independently of the type of chlorine atoms introduced, that is, whether chlorine atoms are chemically bonded with cellulose chains or not, the introduction of chlorine atoms alone has little flame-retardant effect, while combination of chlorine atoms with antimony trioxide is more effective. (2) Addition of only antimony trioxide to samples obtained from the dechlorination of chlordeoxycellulose is as effective as the combination of chlorine compounds and antimony trioxide, in spite of a trace of chlorine in the DCDC samples. (3) Introduction of chlorine compounds yielded the formation of carbonyl and double bond groups in the cellulose chains. The formation of the latter groups was accelerated by the combination of antimony trioxide; that of the former groups was inhibited. Most of the introduced chlorine atoms were missing in the condensed phase even at 300°C while a large portion of the initially added antimony trioxide remained in the condensed phase at least up to 400°C. One mode of flame-retardant action of the combination of chlorine compounds and antimony trioxide was assumed to be the catalytic effect on the dehydration of cellulose to yield a thermostable polyene structure in the cellulose chains.     

Electrical properties of polymer films prepared from mixture of tetramethylsilane and oxygen by glow discharge polymerization

Summary The electrical properties of polymer films prepared from tetramethylsilane (TMS) and the mixture of TMS and oxygen by glow discharge polymerization were investigated in connection with the chemical structure of the polymers. The polymer films showed two different electrical properties which depended on the strength of electrical field. Under the electrical field of less than 10⁴ V/cm, the polymers showed ohmic behaviour, and their resistivity was approximately 10¹⁴ · cm being independent of the chemical structure of the polymers. Under the electrical field of above 10⁴ V/cm, non-ohmic behaviour was observed, and the current increased exponentially with increasing of the applied field. To explain this enhanced current the contribution of the Poole-Frenkel emission was assumed. The dielectric breakdown of the polymer films (1000–5000 angstroms) occured at the electrical field as high as 3 MV/cm. This indicates that these thin films may be deposited on substrates without pinhole.     

Preliminary experiment of surface hardening of polymers by glow discharge polymerization

Polymers including polyethylene, polycarbonate, and polytetrafluoroethylene were modified by glow discharge polymerization to enhance surface hardness. The surface hardness of the polymer substrates could be improved by glow discharge polymerizations of silicon-containing compounds. The mixture of tetramethylsilane (TMS) and oxygen was more effective than tetramethoxysilane to improve the surface hardness. The surface hardness improved by the glow discharge polymerization strongly depended on the nature of the polymer substrates to be modified. The adhesion between polymer films prepared from the TMS/O₂ mixture by glow discharge polymerization and the polymer substrates was good.     

Upregulation of HIV-1 replication in chronically infected cells by ingenol derivatives

We have previously reported that ingenol derivatives are highly potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in acutely infected cells. In this study, however, we have found that some ingenol derivatives strongly enhance the replication of HIV-1 in chronically infected cells at nanomolar concentrations. One of the derivatives could activate nuclear factor kappa B (NF-kappa B), a potent inducer of HIV-1 replication, through the activation of protein kinase C (PKC). Whereas another derivative, which affected neither PKC nor NF-kappa B, significantly enhanced HIV-1 replication, suggesting that a PKC-independent mechanism may also exist in ingenol derivative-induced HIV-1 upregulation.