No abstract

In this study we aimed to elucidate the validity and usefulness of the oxygen uptake efficiency slope (OUES) in the evaluation of adult cardiac patients. Cardiopulmonary exercise tests were performed on a treadmill by 50 adult patients with chronic heart failure. The OUES was calculated from data for the first 75%, 90%, and 100% of exercise duration. The OUES is derived from the following equation: VO(2)=ax logV(E)+b, where VO(2) is oxygen uptake (ml/kg/min), V(E) is minute ventilation (l/kg/min), and the constant "a" represents OUES. We also determined the ventilatory anaerobic threshold (VAT). The correlation coefficient of the logarithmic curve-fitting model was [mean (SD)] 0.986 (0.009). The OUES could be used to discriminate effectively between New York Heart Association functional classes (P < 0.001). OUES and maximum VO(2) were significantly correlated (r=0.78, P < 0.01). Agreement between the OUES values for the first 90%, 75%, and 100% of the exercise was excellent (intraclass correlation coefficient = 0.99). Our results suggest that OUES is applicable to adult cardiac patients as an objective, effort-independent estimation of cardiorespiratory functional reserve.

The etch rate, chemical reactions and etched surface of -silicon carbide are studied in detail using chlorine trifluoride gas. The etch rate is greater than 10 mm min À1 at 723 K with a flow rate of 0.1 ' min À1 at atmospheric pressure in a horizontal reactor. The maximum etch rate at a substrate temperature of 773 K is 40 mm min À1 with a flow rate of 0.25 ' min À1 . The steplike pattern that initially exists on the -silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 mm to 1 mm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large etch rate for -silicon carbide associated with making a rough surface smooth.

The silicon etching rate by chlorine trifluoride gas is systematically studied using a reactor having a very small cross section above the silicon substrate and achieving a very high efficiency of etchant gas consumption and very large etching rate, larger than 20 m min Ϫ1 . The silicon etching rate is shown to be proportional to the flow rate of the chlorine trifluoride gas. However, this rate is, for the first time, found to be independent of the initial silicon substrate temperature. This study shows that the silicon substrate is automatically heated to the temperature determined by the balance of the reaction heat and the heat transport in the reactor. Since this temperature increment processes an extremely large-surface chemical reaction rate, the etching rate is governed by the transport rate of the chlorine trifluoride gas. This study concludes that a high efficiency silicon etching by chlorine trifluoride gas is possible without any supplemental heating.Chlorine trifluoride (ClF 3 ) gas has a very high reactivity for various materials. 1-5 This gas is especially suitable for plasmaless etching 2,6-10 near room temperature at atmospheric and reduced pressures. In silicon crystal technology, chlorine trifluoride gas has been known to be used for the in situ cleaning 2,11,12 of a chemical vapor deposition ͑CVD͒ reactor in order to remove any polysilicon film deposited on the susceptor and on the inner wall of the chamber.For the further development of new industrial etching and cleaning processes using chlorine trifluoride gas, its chemical reaction should be systematically studied. For this purpose, our previous study 13 reported the chemical reaction between a silicon surface and chlorine trifluoride gas in ambient nitrogen at atmospheric pressure. It also reported that chlorine trifluoride gas has been shown to work as a source of active fluorine atoms to form inorganic fluorides, for example, silicon tetrafluoride for silicon etching. However, this previous study was performed only to evaluate the overall chemical reaction and the produced gas species. The other fundamental properties of the chemical reaction by chlorine trifluoride gas, such as the etching rate and the rate-determining parameters, have, unfortunately, not been studied.Therefore, in this study using the chlorine trifluoride gas in the CVD reactor designed for achieving the industrially applicable highperformance process, the silicon etching rate and its ratedetermining parameters are experimentally evaluated. ExperimentalIn order to etch silicon by chlorine trifluoride gas, the horizontal cold-wall CVD reactor shown in Fig. 1 was used. This reactor consists of a gas supply system, a quartz chamber, and infrared lamps. A 30 ϫ 50 mm silicon substrate is horizontally held on the bottom wall of the quartz chamber. The silicon substrate is cut from the n-type ͑100͒ 200 mm diam semiconductor silicon wafer, which was grown using the Chzochralski method.The silicon substrate is heated by infrared rays from the infrared lamps through the transpar...

No abstract