The phenomenon and mechanism of germanium (hereinafter Ge) dissolution in sulfuric acid based solutions were studied. The sulfuric acid concentration, the presence of an oxidizer and the treatment time were varied as parameters of these tests. It was clarified that Ge surface is covered by two layers: germanium dioxide (hereinafter GeO2) and germanium monoxide (hereinafter GeO). GeO2 dissolves easily in water and in the sulfuric acid solutions with high water fraction. On the other hand, the dissolution of GeO and Ge is influenced strongly by the sulfuric acid concentration in the solution and the treatment time when oxidizer is present in the solution.

Ultrapure water contains dilute hydrogen peroxide as an impurity. In order to clarify an impact of the dilute hydrogen peroxide on cleaning processes, a SiGe epitaxial layer was deposited on a Si(100) wafer which surface was treated by HF last process with hydrogen peroxide contained UPW or hydrogen peroxide removed UPW. The defect in the SiGe epitaxial layer was reduced when the hydrogen peroxide removed UPW was used.

We studied the spontaneous increase in the fluorescence intensity of 4,5-diaminofluorescein. A slow, steady increase in fluorescence continued for at least 125 h, and this increase was accompanied by ca. 2 nm red shift in the peak of emission spectrum. The spontaneous increase also occurred to diaminorhodamine-4M and a fluorinated form of diaminofluorescein, which has been also used for the detection of nitric oxide (NO). We found that several factors (excitation light, pH etc.) did not alter the time course of this increase. Moreover, we found that this spontaneous increase can produce false-positive results when measuring low-rate nitric oxide production in human umbilical vein endothelial cells, and may confound the interpretation of results of NO production. We show that this adverse effect can be avoided by careful grouping of samples during measurement.Key words nitric oxide; 4,5-diaminofluorescein; human umbilical cord endothelial cell Nitric oxide (NO) production in cells, such as macrophages and endothelial cells was often measured using Griess reagent.1-3) Recently, a fluorescent indicator 4,5-diaminofluorescein (DAF-2) and its analogs have been introduced, 4,5) and are now widely used.6-9) Upon nitrosation in the presence of dissolved oxygen DAF-2 is converted to the triazole form, DAF-2T 10) ( Fig. 1), and the quantum yield increases by >100-fold. 4,5) Before the nitrosation, the fluorescence of DAF-2 arising from a fluorescein moiety is quenched due to electron donation from the diaminobenzene moiety, but nitrosation releases the quenching effect.4) The detection limit of NO with DAF-2 is 5 nM.4) Thus, DAF-2 is highly sensitive to the presence of NO.The high sensitivity of DAF-2 is especially advantageous when it is used with endothelial cells because these cells produce NO at rates much lower than those of activated macrophages. The low rate of NO production in endothelial cells results in very small increases in the fluorescence intensity, because most DAF-2 remains un-reacted, producing background fluorescence. Thus, these small increases require careful, accurate measurement of the level of fluorescence intensity. [11][12][13] In this situation, the stability of the fluorescence intensity of un-reacted DAF-2 is extremely important.We are investigating the effect of magnetic fields on NO production in human umbilical vein endothelial cells (HUVECs) 6) using DAF-2. During our study, we noticed a spontaneous increase in the fluorescence intensity of DAF-2 and its analogs in the absence of exogenous NO. Although the degree of the spontaneous increase is small compared with the large increase in the presence of sufficient amounts of NO (e.g., from NO releasing reagent), we realized that this spontaneous increase can lead to an erroneous conclusion if the amount of produced NO is small. Here, we report the results of phenomenological study of the spontaneous increase and evaluation of the effects of these increases on the measurement of NO production by HUVECs. MATERIALS AND METHODS Fluorescent Reagen...

This paper focuses on the mechanism and methodology of the dissolution of Alternative Dipole Material (ADM) and its inhibition through the use of functional waters. The study investigates the etching behavior of ADM in different solutions, examines the surface state of ADM before and after cleaning, and evaluates the impact of the functional water process on its electrical properties.