Magnitude Of Rs Research Articles

PAR and UVA composition of global solar radiation at a high altitude Mediterranean forest site

Photosynthetically active (PAR) and ultraviolet-A (UVA) radiation have important effects on plant processes, affecting both health and ecology of the natural ecosystems. Studies dealing with the composition of global solar radiation Rs in PAR and UVA wavelengths are thus important. The present work is aimed at the investigation of the relationships of PAR, UVA with Rs, assessing the key factors that affect the corresponding ratios PAR/Rs and UVA/Rs at a high-altitude mountainous environment. The study was conducted in a protected Natura-2000 forest in Greece at a high altitude (1896 m a.s.l.) site and covers a time period of about 5 years (2014–2019). The analysis was performed on a monthly, seasonal and annual basis using hourly data. Results show that PAR/Rs and UVA/Rs present annual values 0.438 ± 0.031 and 0.034 ± 0.007, respectively with low monthly and seasonal variability. Further, sky clearness was found to have a significant effect on the composition of incident Rs, with PAR/Rs values to increase from 0.417 ± 0.013 to 0.483 ± 0.037 as sky conditions change from clear to overcast. The respective UVA/Rs values were 0.031 ± 0.002 and 0.045 ± 0.011. The hourly ratios become minimum at noon, whereas the magnitude of Rs was found to have a negative effect. In addition, PAR/Rs and UVA/Rs were increasing with relative humidity, optical thickness and relative optical air mass and decreasing with saturation vapor pressure, vapor pressure deficit, and to a less degree with air temperature. Concluding, at the high altitude Mediterranean forest site, Rs composition to PAR and UVA appears to be affected mainly by atmospheric clearness and by the geometric characteristics of the incident radiation rays, whereas atmospheric clearness was affected mainly by air humidity.

Plant community composition alters moisture and temperature sensitivity of soil respiration in semi-arid shrubland.

Soil respiration (Rs) is the second largest carbon (C) flux to the atmosphere and our understanding of how Rs and its components shift with plant-community composition remains an important question. We used high-frequency soil respiration measurements and root exclusion to evaluate how Rs, autotrophic respiration (Ra) and heterotrophic respiration (Rh) vary between a semi-arid perennial shrub community and annual invasive community. Over two growing seasons, total Rs was 40% higher under annual vegetation compared to shrubs. Partitioning revealed consistently higher Ra under annual vegetation which accounted for most of the difference in Rs. Under annual vegetation, Ra increased soon after the first rain events and remained high despite cooling temperatures while shrub Ra increased only when soil temperature began to warm up. The Rh rates were similar between vegetation types when daily soil temperatures were lower than 20°C. As soil temperatures increased and soil moisture dropped below 10%, Rh was consistently higher under annual vegetation than shrubs. Seasonal dynamics of Rs and Rh were best modeled with an interaction term between soil moisture and temperature with significantly different model parameters for each vegetation type. Differences in the timing and magnitude of Rs and Ra between vegetation types are consistent with phenological differences between shrubs and annuals. Under annuals, larger Rh at high temperatures suggests that expansion of annual vegetation and future hotter and drier conditions could lead to greater C losses from this semi-arid shrub system.

EFFECT OF BREATHING PATTERN ON BLOOD PRESSURE AND HEART RATE OSCILLATIONS IN HUMANS

1. The relationships of respiratory sinus arrhythmia (RSA) and respiratory changes in systolic blood pressure (SBP) to tidal volume (VT) and breathing frequency (BF), were quantified during voluntary control of VT and BF in healthy subjects. 2. Respiration was measured non-invasively with a respiratory inductive plethysmograph, which was calibrated prior to each study while breathing through a pneumotachygraph. Finger arterial blood pressure was measured non-invasively by the Finapres. 3. Heart rate (HR) increased during inspiration, with a nearly fixed time delay for most VT and BF approximating 0.9 s. The magnitude of RSA increased with increases in VT and with decreases in BF. SBP decreased during inspiration, with a time delay which increased as BF decreased, resulting in a phase delay approximating 160 degrees. The magnitude of the inspiratory fall in SBP increased with increases in VT. Increased amplitudes of RSA and SBP variation occurred at the lowest BF, consistent with the possibility of interactions between respiratory-related influences and those due to 'slow waves' of vasomotor tone. 4. The present results are consistent with the conclusion that respiratory effects on SBP are caused by a mechanism other that simply changes in HR.

Interrelationships among stabilities of important agronomic traits in sugarcane

The stability-variance statistic, ĝs i (2) , measures the contribution of the i(th) genotype to genotype x environment interaction. In addition to the knowledge of cultivar stability for an agronomic trait, information on whether stability of one trait can be used to predict stability of another should be useful to breeders. Three separate groups of data, respectively involving CP 79 series, CP 80 series, and CP 81 series experimental clones of sugarcane (Saccharum spp.) were used in this study. Rank-correlation coefficients (rs) between ranks of genotypes for ĝs i (2) 's for paired traits indicated in both plant-cane and ratoon crops that stability of tons per hectare of sugar can be predicted from the stability of tons per hectare of cane (THC) and also, to a lesser extent, from the stability of stalk number. The stability of THC also can be reasonably well predicted from the stability of stalk number. Brix stability may give some indication of the stabilities for percentage sucrose and sugar concentration (SC). The ĝs i (2) 's for percentage sucrose and SC were almost identical in the CP 79 and CP 81 series (rs varied from 0.93, P<0.01, in plant-cane crop for CP 79 series to 0.98, P<0.01, in plant-cane crop for CP 81 series). Whether correlations were based on ĝs i (2) 's estimated across locations within crops or across crops, the magnitude of rs was about the same. Means of various traits were not correlated with their respective ĝs i (2) 's (for CP 81 series), indicating that identification and selection of high-yielding sugarcane genotypes with a relatively high degree of stability of performance across test environments should be possible.

Magnetic Anisotropy Effects on the Hall Resistivity of Rare-Earth Metals

Results are presented for the normal and anomalous Hall coefficients R0 and Rs in the rare-earth metals Tb, Dy, Ho, and Er in the paramagnetic temperature range. Above TN the anomalous coefficients are essentially temperature-independent, indicating a dominant spin-disorder scattering mechanism. Measurements with H along 〈0001〉 gave a constant value of R0=−3.6×10−12 Ω-cm/G for all elements of the series; Rs, on the other hand, varied by more than a factor of 8. This variation cannot be explained on the basis of an isotropic theory of spin disorder. The coefficients for H applied in the basal plane showed changes in sign of both R0 and Rs occurring between Dy and Ho and a marked decrease in magnitude of Rs throughout the series. A model is developed to include the effects of the large magnetic anisotropy on the anomalous coefficient. The model includes the contribution from both intrinsic and extrinsic spin-orbit couplings. The magnetic anisotropy has a significant effect on Rs, and leads to better agreement with experiment.