There is provided a method for determining a signal transfer characteristic along a light path between a first point and a second point in an optical network. A majority of the colorants has a maximum haze of about 10% and exhibits an absorbance peak in the visible spectrum wherein at least about 50% of the total absorbance in the visible spectrum occurs at wavelengths within about 50 nm of the wavelength of the peak absorbance. The ACU limits execution of DMA transfer by the DMAC based on access control information set in a controlstatus register by a privileged process, and disables the DMAC from accessing any memory area other than the memory area that can be accessed by the user process. The present invention further provides Candida albicans genes that are demonstrated to be essential and are potential targets for drug screening.