We examined the effect of coffee on conjugation reactions in the human colon carcinoma cell line, Caco-2. After supplementing Caco-2 cultures with both 1-naphthol (200 m mM) and various concentrations of coffee, the accumulation of 1-naphthyl sulfate and glucuronide in the growth medium was determined by analytical HPLC over a 24-h period. A strong reduction in sulfo-conjugation (Ͻ50% of the control value) was observed in cells treated with coffee (IC 50 ,)%3.4؍ but no effect on glucuronic acid conjugation (glucuronidation) was observed. Coffee was also found to inhibit sulfotransferase (SULT) activity towards 1-naphthol in vitro to a similar extent (IC 50 )%1.5؍ as in intact Caco-2 cells, but exhibited no effect upon UDP-glucuronosyl transferase (UGT) activity in vitro. PCR analyses showed no significant changes in the expression of either SULT genes (SULT1A1 and SULT1A3) or UGT genes (UGT1A1 and UGT1A6) following treatment with coffee solutions of up to 5% in concentration. These results suggest that the consumption of coffee can modify sulfo-conjugation reactions within intestinal epithelial cells, which may possibly affect the bioavailability of therapeutic drugs and the toxicity of environmental chemicals.
ZnS:Mn thin film electroluminescent devices having doubly-stacked insulating layers have been developed. The insulating layer consists of electron-beam evaporated Ta2O5, and rf-magnetron sputtered SiO2 stacked layers. It is concluded that the thick semi-insulating Ta2O5 films (1000 nm) deposited on both sides of the ZnS:Mn active layer act as a carrier injctor for electroluminescence and the thin insulating SiO2 films (80 nm) inserted between the electrodes and Ta2O5 films act as a carrier limiter. The breakdown voltage margin defined by (V
bd-V
th)/V
th was improved from 15% to more than 80% by introducing thick semi-insulating Ta2O5 films.
The effects of annealing on sputtered ZnS:Tb, F thin films is investigated by electron probe microanalysis, secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. It is shown that the annealing decreases the F/Tb atomic ratio from 4 to 1, due to the release of F atoms. It is concluded that many of the F ions not contributing to the formation of luminescent centers with Tb ions exist in as-sputtered film and that efficient Tb-F complex centers are formed by annealing at over 400°C. Luminance is enhanced by increasing the Tb-F complex centers and decreasing the hot-electron scattering centers of the F ions.
We have developed a novel 1200 dot per inch (dpi) light emitting diode (LED) printhead for a high quality digital color printer in the next generation. Performance tests showed that the LED printhead was really suitable for a color printer printhead: an excellent light output uniformity within ±1%, a high contrast light spot of 80%, a high accuracy light spot position within±20μm, and a very high light output efficiency to realize a high-speed printing of 45 pages per minute (PPM). In order to achieve the high performance of the LED printhead, we have developed an original 1200 dpi LED array chip with 8x8 matrix-structured wiring (dubbed as "chip-matrix LED array chip"). The chip-matrix LED (CM LED) array chip was fabricated on a double hetero structured Al x Ga 1-x As epitaxial wafer using our original fabrication techniques and device designs. This is the key for fabricating a super-high resolution array chip with a super-high light output efficiency. Moreover, the CM LED array chip made it possible to reduce an overall super-high-density printhead cost: the number of bonding wires and driver integrated circuit (IC) chips on the LED printhead decreases to one-fourth, and one-half, respectively, compared to the conventional 1200 dpi printhead.
To clarify the difference in ZnS:Tb,F films fabricated by electron-beam evaporation (EB) and by rf magnetron sputtering (SP), the doping condition of Tb and F ions was investigated by electron probe micro analysis and secondary ion mass spectroscopy. The F/Tb atomic ratio of 3 and EL spectra for EB films are found to be hardly affected by annealing. As the model for luminescent centers, it is proposed that the Tb and F ions are substituted for Zn and three S ion sites, respectively, with two Zn vacancies for satisfying charge compensation. For the SP films, interstitial F ions are released from ZnS film and Tb-F complex centers are formed by annealing.
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