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1. The dynamic response of neurons sensitive to knee joint rotation in the cat somatosensory thalamus was studied during sinusoidal variation of joint angle. The input sine waves were applied with a precise voltage-controlled, electromechanical actuator. The average rate of discharge of a single cell was considered as the output parameter. Describing functions of the sensory system were extracted by correlation and spectral analysis techniques. The effects of anesthetic, bias angle, and excursion angle were investigated. Discrete and swept sinusoidal waveforms between 0.1 and 7.0 Hz were used as inputs.2. The majority of joint cells in the thalamus were rapidly adapting and had frequency-response curves that were characterized as highpass filters. Although the major features of the response curves for individual cells were very similar, they could not all be fit with a single transfer function. The describing function of all the rapidly adapting cells averaged together was well fit by a transfer function that could be termed velocity sensitive in the bandwidth between 0.1 and 6.5 Hz. Most of these phasic cells showed a phase-locking tendency, particularly at high frequencies.3. The dynamics of the response for the rapidly adapting cells was relatively independent of anesthetic, bias angle, and excursion angle. Threshold and saturation effects were exhibited by some cells for very small (less than 1 degree) and large (greater than 10 degrees) input amplitudes, respectively. In addition a few (17%) showed a bidirectional response, i.e., responded at both flexion and extension of the limb. The anesthetic had a strong effect in depressing the spontaneous discharge of the cells and seemed to change the character of the tonic response by introducing a bursting component.4. The transfer characteristic of the thalamic cells was found to be a single-pole low-pass filter plus a time delay. The optimized value for the filter was found to have a corner frequency of 6.0 Hz with a time delay of 6 ms.5. Of the knee joint sensitive cells, 17% were slowly adapting or tonic, and more tonic cells were found in the unanesthetized animals. Only one tonic cell was studied in detail, and its dynamic characteristics were similar to that of the slowly adapting joint receptors at low frequencies. In this respect the rapidly adapting and slowly adapting joint cells in the thalamus have strikingly different frequency-response curves, the former curves have a much steeper slope in the magnitude.6. The functional implications of these results and of other recent findings in relation to the probable role of joint receptors in mediating proprioception are discussed.

Soft agar culture CFU-C (colony-forming units in culture) are rapidly classified in situ as eosinophil, macrophage, and neutrophil-monocyte types by whole culture staining with luxol fast blue for eosinophil specific granules and acetoorcein for nuclei. Stained colonies may be picked and examined individually as wet mount cover slip preparations, or the agar culture may be air dried and mounted permanently. The whole culture stain has been variously modified for the enzyme markers alpha-naphthyl acetate esterase and peroxidase and for nuclear staining alone with acetoorcein.

Observations of absorption of solar radiation by atmospheric nitric acid obtained on different balloon flights are presented. This absorption occurs in three different wavelength intervals. The use of the very long paths, occurring near sunset, for enhancing weak absorption is discussed.

The stratospheric water vapor mixing ratio altitude profile has been derived from spectral observations of the downward night emission from the pure rotation water vapor lines in the 24–29-μm region of the spectrum. The data were obtained during two balloon flights, made on 22 February 1971 and on 29 June 1971, using a balloon-borne spectral radiometer with ~2 cm^−1 resolution. The observed radiances have been fitted to line-by-line, layer-by-layer radiance calculations, from which the water vapor mixing ratio between 10 km and 30 km has been derived. The resulting mixing ratio altitude profiles from both flights show a broad minimum around 15 km and a broad maximum around 25 km with a range of values of 6 × 10^−7g/g to 4 × 10^−6 g/g.

The variation with altitude of the infrared solar spectrum in the 4.5-µm region was observed with a balloon-borne spectrometer. Line-by-line–layer-by-layer analysis of the N_2O absorption lines in this region yields a detailed N_2O mixing-ratio altitude profile up to ~20 km. The results show a nearly constant mixing ratio of ~0.33 ppm from 3 to 12 km followed by a gradual decrease to ~0.15 ppm near 19 km. The mixing ratio is estimated to be <0.01 ppm above 20 km.

A balloon-borne spectrometer was used to measure the atmospheric absorption of solar radiation in the 9–10-μ region as a function of altitude. Among the numerous spectra recorded, several were made with very long optical paths above the troposphere obtained from floating altitude (~30 km) while the sun set. When the experimental results are compared with calculated spectra, based on line by line parameters of the ν_3 and ν_1 fundamentals of ordinary ozone, ^16O_3, combined with the Curtis-Godson approximation, large discrepancies are found for the long path spectra. It is shown that the hot bands ν_3 + ν_2 − ν_2 and ν_3 + ν_3 − ν_3 of the ^16O_3, and the ν_3 fundamentals of the isotopic species ^16O^18O^16O and ^16O^16O^18O, can contribute significant absorption for long paths such as obtained in this experiment. Such long paths also give rise to significant absorptions by the ν_3 − ν_1 and the ν_3 − 2ν_2° bands of CO_2. Including these weak bands in the calculated spectra leads to good agreement with the observed data.

A grating spectrometer with a Ge Cu detector was flown on three balloon flights. Spectra in the 4–14.3-μ region were obtained at various altitudes from the ground through 30 km with a resolution considerably better than that achieved in previous flights. Some of the spectra were obtained over long paths at float altitude, during the sunset. Data from these flights are presented with a discussion of the significant features of the observed absorptions. Special emphasis is put on the new features observed during the sunset.