Estimation Of Temporal Variability Research Articles

Water supply of the population in the cyanobacteria mass development conditions at the Volga reservoirs

The results of the monitoring data analysis of the Kuibyshev reservoir as a source of drinking water supply for the period 2000-2018 are presented. The observations were carried out monthly in the water area and in the closing section of the reservoir, located in the Zhigulevsky dam area. The estimation of temporal variability and spatial heterogeneity of the reservoir water quality is given. It was established that in the summer, during the period of cyanobacteria mass development, biological pollution of the reservoir is observed, the water quality deteriorates by smell, color, pH, and dissolved oxygen content. The content of dissolved organic and toxic substances increases, and the concentration of nutrients, on the contrary, decreases. With a limited concentration of phosphates in the water of the reservoir, the cyanobacteria mass development process stops. In the period of water quality deterioration in the source of water supply in large Volga cities, the problems in the purification of natural water to the requirements of drinking water supply for the population arise. To solve the problem, the recommendations to improve the technological scheme of purification of the Volga water from organic and toxic substances were developed. Organic pollution can be reduced using ozone or activated carbon. Membrane technologies being capable of filtering water and cyanobacterial cells without mechanical damage can serve as a barrier against toxic substances entering drinking water.

Variability of Hydroacoustic Noise Probability Density Function at the Output of Automatic Gain Control System

This research presents results of the estimation of temporal variability of the hydroacoustic noise probability density function (PDF) in shallow waters within the frequency band of 0.03–3.3 kHz; the studies were conducted near the Primorsky Aquarium on Russky Island, Vladivostok, Russia. Signals were received via unidirectional hydrophone and automatic gain control of the received signals. The hydrophone was attached to a drifting buoy via an elastic suspension; the received signals were transmitted by cable to a boat drifting with the buoy. The results of the comparison of the sea noise probability density function (PDF) estimates at the output of a system with automatic gain control (AGC) with similar results for a white Gaussian noise in the same frequency band are described.

The Surface-Forced Overturning of the North Atlantic: Estimates from Modern Era Atmospheric Reanalysis Datasets

Abstract Estimates of the recent mean and time varying water mass transformation rates associated with North Atlantic surface-forced overturning are presented. The estimates are derived from heat and freshwater surface fluxes and sea surface temperature fields from six atmospheric reanalyses—the Japanese 25-yr Reanalysis (JRA), the NCEP–NCAR reanalysis (NCEP1), the NCEP–U.S. Department of Energy (DOE) reanalysis (NCEP2), the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-I), the Climate Forecast System Reanalysis (CFSR), and the Modern-Era Reanalysis for Research and Applications (MERRA)—together with sea surface salinity fields from two globally gridded datasets (World Ocean Atlas and Met Office EN3 datasets). The resulting 12 estimates of the 1979–2007 mean surface-forced streamfunction all depict a subpolar cell, with maxima north of 45°N, near σ = 27.5 kg m−3, and a subtropical cell between 20° and 40°N, near σ = 26.1 kg m−3. The mean magnitude of the subpolar cell varies between 12 and 18 Sv (1 Sv ≡ 106 m3 s−1), consistent with estimates of the overturning circulation from subsurface observations. Analysis of the thermal and haline components of the surface density fluxes indicates that large differences in the inferred low-latitude circulation are largely a result of the biases in reanalysis net heat flux fields, which range in the global mean from −13 to 19 W m−2. The different estimates of temporal variability in the subpolar cell are well correlated with each other. This suggests that the uncertainty associated with the choice of reanalysis product does not critically limit the ability of the method to infer the variability in the subpolar overturning. In contrast, the different estimates of subtropical variability are poorly correlated with each other, and only a subset of them captures a significant fraction of the variability in independently estimated North Atlantic Subtropical Mode Water volume.

Precision of light intensity measurement in biological optical microscopy

Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high-content screening technology. The proper interpretation of data from high-content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi-step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide-field microscope.

Recruitment rates exhibit high elasticity and high temporal variation in populations of a short‐lived perennial herb

Empirical studies for different life histories have shown an inverse relationship between elasticity (i.e. the proportional contribution to population growth rate) and temporal variation in vital rates. It is accepted that this relationship indicates the effect of selective pressures in reducing variation in those life‐history traits with a major impact on fitness. In this paper, we sought to determine whether changes in environmental conditions affect the relationship between elasticity of vital rates and their temporal variation, and whether vital rates with simultaneously large elasticity and temporal variation might represent a characteristic life‐history strategy. We used demographic data on 13 populations of the short‐lived Hypericum cumulicola over 5–6 years, in three time‐since‐fire classes. For each population of each time‐since‐fire, we computed the mean matrix over years and its respective elasticity matrix, and the coefficients of variation in matrix entries over study years as an estimate of temporal variability. We found that mean elasticity negatively significantly correlated with temporal variation in vital rates in populations (overall eight out of 13) included in each time‐since‐fire. However, seedling recruitment exhibited both high elasticity and high temporal variation in almost all study populations. These results indicated that (1) the general relationship between elasticity and temporal variation in vital rates was not modified by environmental changes due to time‐since‐fire, and (2) high elasticity and high temporal variation in seedling recruitment in H. cumulicola is a particular trait of the species' life history. After seed survival in the soil seed bank, seedling recruitment represents the most important life‐history trait influencing H. cumulicola population growth rate (and fitness). The high temporal variability in seedling recruitment suggests that this trait is determined by environmental cues, leading to an increase in population size and subsequent replenishment of the seed bank in favorable years.

Estimation of Temporal Variability of Survival in Animal Populations

Estimation of Temporal Variability of Survival in Animal Populations

Estimation of Temporal Variability in Populations

A common measure of the temporal variability of a population is the standard deviation of the logarithms of successive estimated population sizes, ln(Dt). This measure overestimates true temporal variability (the standard deviation of the logarithms of true population density, ln[Δt]) because it is contaminated by spatial variance (variability among samples taken on the same date). The random error in Dt causes an overestimation of temporal variance, both directly and also indirectly, by causing ln(Dt) to underestimate ln(Δt). Both problems are more severe if spatial variance is large or the sample size, on a date, is small. We develop an alternative estimator, which uses an estimate of spatial variance to correct for both problems. To evaluate it, we sampled from simulated populations with a wide range of clumping. The results show that the standard estimate can be badly biased. The new estimator is much better and is quite accurate over a broad range of conditions. Our results suggest a reanalysis of some ecological studies that have estimated temporal variability to attack theoretically important questions. In particular, the apparently greater average temporal variability of terrestrial arthropods compared with terrestrial vertebrates could be an artifact caused by the fact that, typically, clumping is weaker and density estimates are more accurate in vertebrates.

Relationship of body temperature stability to mortality in aging mice

An age-related decline in the capacity for thermoregulation among homeothermic animals has been observed frequently under conditions of extreme ambient temperatures. We investigated the temporal stability of the internal body temperature of 69 C57BL/6J mice from 25 months of age until death in a controlled, neutral thermal environment. Estimates of temporal variability were calculated over consecutive 1-month intervals using (colonic) body temperature data collected weekly. The results of this longitudinal analysis indicated that the regulation of body temperature, as measured by its temporal stability, became increasingly less precise with advancing age. Body temperature exhibited a significant decline as the animal approached death. Individual differences in body temperature and the temporal regulation of body temperature were significantly correlated with lifespan, although the direction of the relations were opposite. Body temperature correlated positively with lifespan, whereas the temporal stability of body temperature correlated negatively with lifespan. Thus, animals exhibiting higher body temperatures and greater temporal stability also tended to liver longer than their cohorts.