RESUMEN
Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOx) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOx. We show that NOx suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOx. By illustrating how NOx affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOx level in forest regions around the globe.
RESUMEN
Using a CO(2), cw, coherent lidar, we have measured the surface roughness of diffuse targets through 1000 m of turbulent atmosphere. The technique measures the phase fluctuations of the speckle field at the receiver and relates the measured phase variance to the surface roughness. Measurements were made with aluminum targets that had been sandblasted with 8-, 16-, and 30-grit material and also with a flame-sprayed aluminum target. It was found that a linear relationship exists between the standard deviation (SD) of the unwrapped phase fluctuations and the SD of the target surface-height fluctuations. Good results were obtained with modest transmitter power and small receiver optics in just a few seconds of averaging time.
RESUMEN
A model for the unwrapped phase of a speckle field that propagates through clear air turbulence is proposed, and a formulation for the probability density function of the unwrapped phase is developed. A method is given to obtain the parameters of the unwrapped density function from parameters of the diffuse target, the laser source, and the atmosphere. Unwrapped-phase measurements at an atmospheric test site with a CO(2) laser show agreement with the model.
RESUMEN
This study investigated the magnitude of the asymmetrical tonic neck reflex (ATNR) response in forty preschool children, grouped by age (3 years and 5 years) and sex. The ATNR response was measured by electrogoniometers at the head and elbows and recorded graphically on an X-Y plotter. Change scores indicating the difference in degrees of elbow flexion before and after head rotation were analyzed. Repetition of the stimulus (head turning) to the left and to the right occurred under two test postures (supine, quadrupedal) with the effect of a blindfold nested within quadruped trials and the effect of added tension nested within supine, totaling 16 trials per child. The magnitude of the ATNR decreased significantly with age, but sex differences were not significant. The quadrupedal test posture produced significant increases in the supine posture. The blindfold did not produce significant main effects. Electrogoniometric measurement consistently demonstrated the magnitude of the ATNR in normal preschool children, which decreases with age, is dependent upon test posture and can provide numerical guides in clinical tests of central nervous system integration.
