Enhanced North American carbon uptake associated with El Niño.

Long-term atmospheric CO2 mole fraction and δ13CO2 observations over North America document persistent responses to the El Niño-Southern Oscillation. We estimate these responses corresponded to 0.61 (0.45 to 0.79) PgC year-1 more North American carbon uptake during El Niño than during La Niña between 2007 and 2015, partially offsetting increases of net tropical biosphere-to-atmosphere carbon flux around El Niño. Anomalies in derived North American net ecosystem exchange (NEE) display strong but opposite correlations with surface air temperature between seasons, while their correlation with water availability was more constant throughout the year, such that water availability is the dominant control on annual NEE variability over North America. These results suggest that increased water availability and favorable temperature conditions (warmer spring and cooler summer) caused enhanced carbon uptake over North America near and during El Niño.

Effects of Respiratory Muscle Strength Training in Classically Trained Singers.

Many voice pedagogy practices revolve around the notion of controlling airflow and lung volumes and focus heavily on the concepts of breath support and breath control. Despite this emphasis, the effects of increased respiratory muscle strength on airflow and phonation patterns in trained singers remain unknown. This study addressed whether singers could increase respiratory muscle strength with progressive threshold training and whether respiratory muscle strength increases had measurable effect on voice outcomes. A single-subject design was used to answer the research questions. Improved breath support was hypothesized to manifest in differences in airflow and phonetogram characteristics. Six graduate-level singing students were recruited to complete the protocol, which consisted of a baseline phase followed by either inspiratory muscle strength training followed by expiratory muscle strength training or vice versa. Results showed that these singers had increased respiratory muscle strength after completing the training program. Consistent changes in measures of aerodynamics and voice were not present among subjects, although some individual changes were noted. Future research may focus on the effects of respiratory muscle strength training in less advanced singers.

Stable isotopic analysis of atmospheric methane by infrared spectroscopy by use of diode laser difference-frequency generation.

An infrared absorption spectrometer has been constructed to measure the stable isotopic composition of atmospheric methane samples. The spectrometer employs periodically poled lithium niobate to generate 15 microW of tunable difference-frequency radiation from two near-infrared diode lasers that probe the nu3 rotational-vibrational band of methane at 3.4 microm. To enhance the signal, methane is extracted from 25 l of air by use of a cryogenic chromatographic column and is expanded into the multipass cell for analysis. A measurement precision of 12 per thousand is demonstrated for both delta13C and deltaD.