The room temperature magnetic susceptibilities of human and carp oxy-and carbonmonoxyhemoglobin solutions were measured in a 30-gauss (1 G = 10-4 T) field with a superconducting magnetometer. To within experimental uncertainty, the susceptibility was the same for both the oxy and carbonmonoxy forms, and salt concentration did not affect it. A variety of sample preparations were used; the iron chemical state was verified by Mossbauer spectroscopy. A value of -0.580 ± 0.010 x 10-6 centimeter-gram-second (cgs) system was obtained for the mass susceptibility of the protein.We attribute the paramagnetism sometimes observed in oxyhemoglobin solutions to the presence of a small amount of the deoxy form.A controversy has recently grown over the magnetic susceptibility of oxy-and carbonmonoxyhemoglobin under various solution conditions. The data of Pauling and Coryell (1), Taylor and Coryell (2), and Havemann et al. (3) indicate that both forms of the protein are totally diamagnetic at room temperature. Recent work (4, 5) shows spin unpairing in oxyhemoglobin with a singlet-triplet separation of 144 cm'1. Further evidence for an excited state was the observation of temperature-dependent quadrupole splittings and linewidths in the Mossbauer spectra of oxyhemoglobins (6). The diamagnetism of carbonmonoxyhemoglobin came under question with reports of salt-dependent effects (7). Most recently, one researcher has again found oxyhemoglobin to be diamagnetic (8) but in solution conditions vastly different from those in which paramagnetism was seen.The resolution of this conflict is imperative for the development of valid electronic models of reversible oxygen binding to hemes. Therefore, we have constructed a superconducting magnetometer to measure the magnetic susceptibilities of oxy-and carbonmonoxyhemoglobin at room temperature and have attempted to reproduce the conditions of the work which showed paramagnetism (4, 5, 7) as closely as possible. MATERIALS AND METHODSA superconducting magnetometer built in our laboratory was used to make the measurements. Fig. 1). These samples proved to be more paramagnetic than water. A Mossbauer spectrum of one of these, frozen to 77 K immediately after the susceptibility measurement, indicated about 9% deoxyhemoglobin, a spin 2 compound. After this discovery, Mossbauer spectra were taken immediately after all susceptibility measurements. Mossbauer measurements, although less sensitive than optical spectroscopy, avoid dilution and the consequent risk of changing the oxy/deoxy equilibrium.We found that it was difficult to prepare samples free of deoxyhemoglobin by exposing concentrated solutions (15 mM in heme) to air. If a concentrated, mostly oxygenated sample were exposed to CO, all deoxyhemoglobin would be replaced by carbonmonoxyhemoglobin, but a significant fraction of the protein remained in the oxygenated form. By diluting a sample to about 5 mM in heme, we could reliably prepare pure oxy or carbonmonoxy proteins. More concentrated solutions were then obtained through the u...

A dielectric hemisphere of refractive index N can act as an N(2) concentrator of isotropic diffuse radiation under appropriate conditions. We give an analytic expression for the gain of a concentrator of arbitrary radius, neglecting surface reflections, and numerical methods for calculating the gain when the surface transmissivity is an arbitrary function of incidence angle. The theory is applied to the design of multilayer spectral filters for hemispherical concentrators. When an appropriate wavelength shift is incorporated into the design process, an 11-layer, coupled-cavity spectral filter on the surface of a hemisphere of index 1.5 shows excellent bandpass performance with a concentrator radius as small as 3 times the sensor radius. This concentrator-filter combination shows a peak response of 97% of the ideal N(2) response at 950 nm, together with a FWHM of 55 nm.

Abstmct -Rednet provides portable computers with an incxpensivc wireless network connection. It is designed to support seamless end-to-end communication using the Asynchronous Transfer Mode (ATM). Rednet uses a Iowpower infrared transceiver operating at 2-5 Mbps over a distance of 4 meters. The link layer protocol supports link sharing and transport of ATM cells over the link. Ceiling mounted base stalions in each room act as gateways between the infrared link and rhe wired network. Rednet is designed to support user mobility, so that users can roam from room to room and access network services in a location independent manner. The paper describes our infrared physical layer and link layer protocols, presents an ovcrview of protocols for dynamic address assignment and conncction management, and summarizes the status of the work.

Conducting tubes threading the pick-up coils in SQUID magnetometers may generate magnetic flux noise larger than the intrinsic SQUID noise. A method for calculating the level of this noise is presented which can aid in the design of low noise systems. Application to a system in this lab predicts a noise level of 0.001 fluxoids rms/(Hz)1/2, in good agreement with the observed level of 0.001 fluxoids rms in a 1-Hz bandwidth.

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