Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources

New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.

A case study of the cognitive and behavioral deficits of temporal lobe damage in herpes simplex encephalitis.

Herpes simplex viral encephalitis is a fairly common nonepidemic encephalitis which produces severe neurological sequelae in survivors. Most viral infections of the central nervous system produce diffuse damage, but the herpes simplex virus demonstrates a predilection for localization in the temporal and orbitofrontal regions of the brain. This case study illustrates the highly significant language difficulties, marked memory deficits, and propensity for physical aggression following temporal lobe damage brought about by herpes encephalitis, and presents the usefulness of a new diagnostic measure in delineating such a variable cognitive pattern.

Auditory brain stem evoked responses to bone-conducted signals.

Auditory brain stem evoked responses to air-conducted and bone-conducted signals were recorded in subjects with normal hearing and in subjects with conductive hearing loss. In normal subjects, the latency to wave V for bone-conducted signals was approximately 0.5 ms longer than the latency for air-conducted signals delivered at the same sensation level. In conductive hearing loss, the separation of the latency-intensity functions for air conduction and bone conduction (corrected for the 0.5-ms delay) provided a valid estimate of the behavioral air-bone gap in the 1,000- to 4,000-Hz region.

Activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase in human cerebrospinal fluid.

Activity of the myelin marker enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) was assayed in cerebrospinal fluid samples obtained from patients with multiple sclerosis (MS) and other neurological diseases. The enzyme activity was found to be elevated in acute cases of MS and reduced during remission. It was present in other demyelinating diseases, and no activity was detected in normal CSF. CNP may be released into CSF from any insult to myelin. The level of activity appears to reflect demyelination and the rate of breakdown of the myelin sheath.

Impedance audiometry in the squirrel monkey. Effect of transection of crossed olivocochlear bundle.

Acoustic reflex thresholds in squirrel monkeys did not show any statistically significant change following midline section of the crossed olivocochlear bundle. Lack of agreement with the results reported by Borg in rabbits is most probably due to the species difference.

Impedance audiometry in the squirrel monkey. Sensorineural losses.

Acoustic reflex thresholds for pure tones and broad-band noise were measured before and after treatment of nine squirrel monkeys. Experimental sensorineural hearing loss was created in six monkeys by ototoxic drug administration (gentamicin) and in three monkeys by exposure to intense sound. Extent of cochlear damage was assessed histopathologically, in the case of permanent loss induced by the ototoxic agent, and inferred from exposure history, in the case of the reversible loss induced by exposure to intense sound. Posttreatment changes in relationships among acoustic reflex thresholds (noise-tone difference [NTD]) reflected approximate degree of cochlear damage. Serial measurement of changes in the NTD in acoustic reflex thresholds appears to be a worthwhile and useful technique for monitoring sensorineural levels in the squirrel monkey.

Prediction of sensorineural hearing level from the brain stem evoked response.

Correlational analysis was carried out between the auditory brain stem evoked response (BER) threshold, BER latency, and various audiometric indices in 275 ears with varying degrees and configurations of sensorineural hearing loss. Results confirm the importance of sensitivity in the 1 to 4-kHZ region to the brain stem response. Sensitivity over this frequency region is best predicted as 0.6 of the BER threshold. Brain stem evoked response latency in the 70- to 90-dB hearing level range increases about 0.2 ms for each 30-dB increase in the steepness of the audiometric contour between 1 and 4 kHZ. Finally, audiometric shape appears to be more important than absolute high-frequency sensitivity in determining BER latency.

Impedance audiometry in the squirrel monkey. Effect of middle ear surgery.

The two principal components of impedance audiometry, the tympanogram and acoustic reflexes, were measured preoperatively and postoperatively in seven squirrel monkeys subjected to experimental middle ear surgery. A probe-tone frequency of 1,200 Hz yielded both tympanograms and acoustic reflex thresholds roughly comparable to analogous data in humans at a probe-tone frequency of 220 Hz. Both tympanograms and acoustic reflex thresholds could be obtained reliably and with comparative ease. In general, postoperative data were modified in the expected fashion by the experimental middle ear surgery. Impedance audiometry appears to be a worthwhile and useful technique for monitoring middle ear status in the squirrel monkey.

Temporal summation of the acoustic reflex.

A signal-averaging technique was used to minimize acoustic reflex measurement system noise while preserving temporal fidelity. In normal listeners, the interaction of signal intensity and signal duration was explored at visual detection threshold (VDT) and at varying suprathreshold signal levels. Reflex amplitude increases, with signal intensity, at a rate which changes as a function of signal duration, a finding which complicates the interpretation of temporal summation data based on VDT. A theoretical model is proposed to explain the complex interactions of signal intensity, duration, and band width on the amplitude of the acoustic reflex.