Scalp attached tangential magnetoencephalography using tunnel magneto-resistive sensors

Non-invasive human brain functional imaging with millisecond resolution can be achieved only with magnetoencephalography (MEG) and electroencephalography (EEG). MEG has better spatial resolution than EEG because signal distortion due to inhomogeneous head conductivity is negligible in MEG but serious in EEG. However, this advantage has been practically limited by the necessary setback distances between the sensors and scalp, because the Dewar vessel containing liquid helium for superconducting sensors requires a thick vacuum wall. Latest developments of high critical temperature (high-Tc) superconducting or optically pumped magnetometers have not allowed scalp-attached MEG due to cold or hot temperatures at the sensing point, respectively. Here we applied tunnel magneto-resistive (TMR) sensors that operate at room temperature. Improvement of TMR sensitivity with magnetic flux concentrators enabled scalp-attached and scalp-tangential MEG to target the largest signal component produced by the neural current below. In a healthy subject, our single-channel TMR-MEG system clearly demonstrated the N20m, the initial cortical component of the somatosensory evoked response after median nerve stimulation. Multisite measurement confirmed a spatially and temporally steep peak of N20m, immediately above the source at a latency around 20 ms, indicating a new approach to non-invasive functional brain imaging with millimeter and millisecond resolutions.

A Small Transfer and Distribution System for Liquid Nitrogen

A system for remotely controlled filling of small Dewars with liquid nitrogen from a central storage Dewar vessel is described, consisting of a plunger type pump with an electromechanical driver and electromechanical ball type valves for distribution of liquid nitrogen. The preset nitrogen level in the small Dewars is kept constant by automatic refilling. The delivery is adjustable in steps by frequency change from 2.5 to 25 cm3/s, and delivery height up to 2 meters is assured.

Thermochemical Determination of Glucose in Serum, Plasma, and Whole Blood without Prior Deproteinization

Glucose can be determined by phosphorylatlon in the presence of hexokinase (EC 2.7.1.1) by using Mg2+/ (ATP)2- as the phosphorylating agent. A novel instrumental quantitation method is described, direct injection enthalpimetry, whereby the heat of the enzymatically catalyzed reaction was measured. The reaction was allowed to proceed to virtual completion (99.5+%) in an adiabatic Dewar vessel at 25.00 ± 0.01 °C (range). Samples were sequentially injected into a reaction mixture consisting of hexokinase, ATP, Mg2+, and a tris(hydroxymethyl)aminomethane buffer (pH 8). Single analyses required <2 min for 0-3 g/liter samples. The linear dynamic range was 0.3-10 g/liter, with zero intercept and a precision and accuracy of 2%. Electrical calibration in situ obviated the need for chemical standards, and because protein and color do not interfere, no sample pretreatment was necessary before analysis.