We developed a sequential injection analysis (SIA) method for the determination of iron in coastal, ground, and surface fresh waters using two different reagents (ferrozine and 1,10-phenathroline). The methodology uses a double-line SIA system to improve mixing conditions between sample and reagent solutions. A liquid waveguide capillary cell (LWCC) with 1.0 m pathlength, 550 μm i.d., and 250 μ...

A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 10(9), by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an o...

Current methods for measuring cerebral blood volume (CBV) in newborn infants are unsatisfactory. A new method is described in which the effect of a small change (5-10%) in arterial oxygen saturation (SaO2) on cerebral oxyhemoglobin [HbO2] and deoxyhemoglobin [Hb] concentration is observed by near-infrared (NIR) spectroscopy. Previous experiments in which the NIR absorption characteristics of Hb...

A linear motion device was designed and built to move small sample cells within the confined space of a liquid nitrogen Dewar cryostat. Instead of the often-used methods of flowing or rotating samples to generate motion, this cryostat insert simply translates the sample cell while maintaining atmospheric isolation. Accurate, repeatable and rapid translation over a 5 cm range with peak linear ve...

Background—Previous studies suggest that the antifibrillatory action of class I and III drugs is due to prolongation of the atrial wavelength. The aim of the present study was to directly evaluate the electrophysiological action of antifibrillatory drugs in a goat model of chronic atrial fibrillation (AF). Methods and Results—Six goats were instrumented with multiple atrial electrodes, and sust...

Cytoplasmic pH in single living specimens of Chaos carolinensis is determined microfluorometrically by measuring the ratio of fluorescence intensity of microinjected fluorescein-thiocarbamyl (FTC)-ovalbumin at two different excitation wavelengths. The probe is evenly distributed throughout, and confined to, the cytoplasm, and the fluorescence intensity ratio depends only upon pH. It is independ...

We have developed a simple, specific, and sensitive reversed-phase liquid-chromatographic method for accurate and simultaneous analysis of corticosterone and cortisol in human plasma. We achieved a detection limit of 300 ng/L for both steroids by modifying the old solid-phase extraction method to make use of "Tef Elutor" C18 columns, using a minibore (100 x 2 mm) analytical column, and using an...

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure...

A method of interrogating a free-space Fabry–Perot sensing interferometer (FPI) by angle tuning the incident beam in order to vary the optical pathlength is described. A system based on a PC controlled precision galvanometer and a 1–1 beam expander that enabled the angle of incidence to be rapidly and continuously varied without translation is described. This system was used to demonstrate that...

It is clear that continuous light affords a very limited window of opportunity for quantitative spectrophotometry of brain tissue. However, the number of qualitative applications which are available exemplify how this extremely simple technique can be applied to important medical problems. The development of devices which can measure directly the oxygen saturation of the brain is more complicat...