Short-term variations

There are considerable geographic, seasonal, and short-term variations in all parameters of the Na layer, that should be taken into account by the LGS system design. The average height of the layer is at 92 km and is usually... 

Performance data have been published on most of the S02 oxidation flow reversal plants operating in Russia (Matros, 1989 Bunimovich et al, 1990). These are summarized in Table VII. More than 14 years of operating data has been collected on the Krasnouralsk plant. The S02 concentration in the feed has varied considerably. Typically, during a working shift the variation is between 1 and 3%, but short-term variations have been much... 

With this arrangement, the output of one controller is used to adjust the set point of another. Cascade control can give smoother control in situations where direct control of the variable would lead to unstable operation. The slave controller can be used to compensate for any short-term variations in, say, a service stream flow, which would upset the controlled variable the primary (master) controller controlling long-term variations. Typical examples are shown in Figure 5.22c (see p. 235) and 5.23 (see p. 235). 

Repeatability is a measure of the short-term variation in measurement results and is the precision that can be most easily determined. It is often used to establish compliance with method performance criteria. While repeatability is a... 

The temperature in a sewer depends on a number of different conditions, e.g., climate, source of wastewater and system characteristics. The microbial community developed in a sewer is typically subject to annual temperature variations and, to some extent, a daily variability. Different microbial systems may be developed under different temperature conditions, and process rates relevant for the microorganisms vary considerably with temperature. Long-term variations may affect which microbial population will develop in a sewer, whereas short-term variations have impacts on microbial processes in the cell itself as well as on the diffusion rate of substrates. 

Knowledge about the isotopic variations in precipitation is increased when single rain events are analyzed from local stations. Especially under mid-latitude weather conditions, such short-term variations arise from varying contributions of tropical, polar, marine, and continental air masses. 

There will also be a temporal mean concentration. If there is a source or sink in the flow, or transport across the boundaries as in Figure 5.1, then the temporal mean concentration profile will eventually reach a value such as that given in Figure 5.1. This flux of compound seems to be from the bottom toward the top of the flow. Superimposed on this temporal mean concentration profile will be short-term variations in concentration caused by turbulent transport. The concentration profile is flatter in the middle of the flow because the large turbulent eddies that transport mass quickly are not as constrained by the flow boundaries in this region. Now, if we put a concentration-velocity probe into the flow at one location, the two traces of velocity and concentration versus time would look something like that shown in Figure 5.2. 

A slightly modified approach has also been used in a number of studies in which the sum of (03 + N02) is plotted against NOz (e.g., St. John et al., 1998). This minimizes the effects of short-term variations in 03 caused by its rapid reaction with NO. Thus, when 03 is titrated by the NO reaction, the measured 03 concentrations will be small however, the N02 generated is a source of 03 through its subsequent photolysis. Flence the sum of (03 + N02) is sometimes chosen as a measure of the ultimate formation of ozone. The ozone production efficiency determined from slopes of plots of (03 + N02) against NOz in the Nashville, Tennessee, area was measured to be typically 5-6 if it was assumed that NOr is not removed by other processes. The production efficiency appeared to be about the same for the general urban plume and for an air mass in which a plume from a power plant was also embedded. Including other losses for NOy such as deposition lowers the estimated production efficiency by about a factor of two (St. John et al., 1998 Nunnermacker et al., 1998). 

Ion suppression is so far mainly considered in the context of sensitivity and the lower limit of quantification of an assay. But it has to be emphasized that short term variations in ion yields—particularly due to matrix components—can compromise the accuracy of analyses Whenever the variation of ion yield has a differential impact on target analyte and internal standard, accuracy is compromised. This means that the reliability of LC-MS/MS analyses critically depends on (1) how similar the impact of ion suppression or ion enhancement on target analyte and internal standard compound is and on (2) how similar the matrices of calibrator samples and actual patients samples are with respect to the modulation of ionization efficacy. This problem can be of relevance for an entire measuring series—if systematic differences in the ionization modulation properties of calibration materials and actual patients samples are present—or it may non-systematically affect individual patients samples as well. 

Plants such as mung bean seedlings can be used as bioindicators for toxic elements such as As [267]. Analysis of tree rings can provide information on short-term variations in pollution sources [268]. Elemental fingerprints have also been used to identify sources of plants, including cannabis [269]. 

The location of the mixing zone depends on the river water runoff, the pattern of the nearshore zone (deep, shallow, wide, narrow), the range and phase of tide, wind direction and force, and sea level fluctuations. Therefore, this zone undergoes both seasonal and short-term variations. 

Though in general the IP and EP DON release rates are similar, short-term variations in the atom % enrichment of the intracellular ON pool can cause some variations between them (Bronk, 1999 Mulholland et al., 2004). The IP DON release rate is also very labor intensive and requires a host of assumptions, and therefore is less robust than the EP DON release method. The IP and EP distinctions are only necessary when both types of rates are being discussed (Bronk and Ward, 2000). 

RockmannT., BrenninkmeijerC. A. M., Crutzen P. J., and Platt U. (1999) Short term variations in the 13C/12C ratio of CO as a measure of Cl activation during tropospheric ozone depletion events in the Arctic. J. Geophys. Res. 104, 1691-1697. 

There has been growing emphasis on the development and use of on-line measurements, which provide an abundance of data in real time. Short-term variations in aerosol composition can reveal great detail, as shown in Figure 12, which illustrates marked differences in the composition of the aerosol at an urban site over periods as short as tens of minutes. The mass concentration was measured by an oscillating microbalance whose frequency was altered by deposition of material. Ionic species were measured by subjecting the aerosol to supersaturation, which greatly increased particle sizes and permitted... 

Ryan, M., and Meiman, J., 1996, An examination of short-term variations in water quality at a karst spring in Kentucky, Ground Water, 34 23-30. 

The naturally occurring radioisotopes that were measured, Be and Pb, continue to be detected in most air filter samples. Variations in the annual mean concentrations of Be at many of the sites appear to result primarily from changes in the atmospheric production rate of this cosmogenic radionuclide. Short-term variations in the concentrations of Be and °Pb continued to be observed at many sites at which weekly air filter samples were analyzed. These short-term fluctuations probably resulted from variations in meteorological factors. The data from quality control samples indicate that in general the reliability of the air filter measurements are acceptable for their intended application. 

Pethidine 50 mg plus promethazine 25 mg given intravenously to 14 mothers in labor caused a significant change in fetal heart rate indices 40 minutes after administration (18). There were significant changes in fetal heart rate acceleration of at least 10 beats/minute, acceleration of at least 15 beats/minute, time spent in episodes of high variation, and short-term variation. 

Since the influence of ambient air humidity is very significant, we extended this study. Two tests were carried out on boards that were first fully conditioned in a chamber at 23°C and 55% RH First, short term variations were studied over a period of 1 week, and, second, continuous measurements were taken during sudden moisture uptakes. The results are as follows ... 

J. Marra (1978). Effect of short-term variation in light intensity on photosynthesis of a marine phytoplankter a laboratory simulation study. Mar. Biol., 46,191-202. 

Some of the first modeling efforts to quantify the effects of ozone depletion on aquatic ecosystems were with phytoplankton photosynthesis in Antarctica where the close proximity of regions of high and low ozone facilitated intercomparisons [97,98]. These studies indicated that inhibition of phytoplankton photosynthesis related to ozone depletion was <5%. In more recent years enough information has accumulated on BWFs for photosynthesis in phytoplankton that comparative summaries are possible. Work on the Rhode River, a sub-estuary of the Chesapeake Bay, has demonstrated short-term variation in the BWFs for phytoplankton, but no significant patterns of seasonal variation [99]. Comparisons among systems in this same study demonstrated striking similarities for the BWFs from the Rhode River and Antarctic phytoplankton. 

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