ABSTRACT
A polarized differential-phase laser scanning microscope, which combines a polarized optical heterodyne Mach-Zehnder interferometer and a differential amplifier to scan the topographic image of a surface, is proposed. In the experiment the differential amplifier, which acts as a PM-AM converter in the experiment, converting phase modulation (PM) into amplitude modulation (AM). Then a novel, to our knowledge, phase demodulator was proposed and implemented for the differential-phase laser scanning microscope. An optical grating (1800 lp/mm) was imaged. The lateral and the depth resolutions of the imaging system were 0.5 mum and 1 nm, respectively. The detection accuracy, which was limited by the reflectivity variation of the test surface, is discussed.
ABSTRACT
A novel Zeeman laser-scanning confocal microscope (ZLSCM) is proposed. It has the same configuration as the conventional laser-scanning confocal microscope (LSCM) in which a Zeeman laser in conjunction with a Glan-Thompson analyzer is used. In our system, the analyzer with the bandpass filter, which act simultaneously as a polarization gate and a coherence gate, enhance the collection efficiency of the weak-scattering photons and simultaneously suppress the multiple-scattering photons. The improvement in depth resolution of a ZLSCM in a scattering medium compared with that of a conventional LSCM is discussed and demonstrated experimentally.
ABSTRACT
A method that uses a Zeeman laser in conjunction with a Glan-Thompson analyzer to image an object in a turbid medium is proposed. A heterodyne signal is generated only when the scattering photons are partially polarized, and the spatial coherence is not seriously degraded after the signal propagates in the turbid medium. A system combining polarization discrimination with optical coherence detection to image the object in a scattering medium is successfully demonstrated. The medium is a solution of polystyrene microspheres measuring 1.072 mum in diameter suspended in distilled water contained in a 10-mm-thick quartz cuvette. The advantages of this optical system, including better selectivity of the weak partially polarized scattering photons and better imaging ability in higher-scattering media, are discussed.
ABSTRACT
Children in low-income families may have high exposures to polycyclic aromatic hydrocarbons (PAH). Such exposures could result from household proximity to heavy traffic or industrial sources, environmental tobacco smoke, contaminated house dust or soil, among others. The objectives of this study were: to establish methods for measuring total PAH exposure of children in low-income families, to estimate the PAH exposures of these children, and to estimate the relative importance of the environmental pathways for PAH exposure. Analytical methods to determine PAH in air, dust, soil, and food and to determine hydroxy-PAH in urine samples were evaluated and validated. A two-home pilot study was conducted in downtown Durham, North Carolina (NC) during February 1994. One smoker's and one nonsmoker's household, which had preschool children and income at or below the official U.S. poverty level, participated. A nine-home winter and a nine-home summer study were conducted in Durham and the NC Piedmont area during February 1995 and August 1995, respectively. A summer study in four smokers' homes was also conducted. In each of these studies, multimedia samples were collected and analyzed for PAH or hydroxy-PAH. Summary statistics, Pearson correlations, and analysis of variance were performed on the combined data from these four field studies. An effective screening method was established for recruiting low-income families. The field protocol involved measurements of three homes in 2-day periods. This protocol should be suitable for large-scale studies. The results showed that indoor PAH levels were generally higher than outdoor PAH levels. Higher indoor PAH levels were observed in the smokers' homes compared to nonsmokers' homes. Higher outdoor PAH levels were found in inner city as opposed to rural areas. The relative concentration trend for PAH in dust and soil was: house dust > entryway dust > pathway soil. The PAH concentrations in adults' food samples were generally higher than those in children's food samples. Children's potential daily doses of PAH were higher than those of adults in the same household, when intakes were normalized to body weights. Inhalation is an important pathway for children's exposure to total PAH because of the high levels of naphthalene present in both indoor and outdoor air. Dietary ingestion and nondietary ingestion pathways became more important for children's exposure to the B2 PAH (ranked as probable human carcinogens, B2 by the U.S. EPA's Integrated Risk System), most of which are of low volatility. The analysis of variance results showed that inner city participants had higher total exposure to B2 PAH than did rural participants.
