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Soil life revolves around microorganisms that are crucial for soil ecosystems and health. In megacities, the combined exposure of multiple pollutants exerts a significant impact on the structures and functions of soil microorganisms; however, there is a lack of empirical studies on this topic. Hence, we conducted a study including urban parks in Beijing, China. The results indicate that bacteria were abundant in the soils of Beijing parks, showing the same dominant groups but different rare groups. The dominant groups included Actinobacteria and Proteobacteria. Candidate phyla radiation bacteria, a large evolutionary radiation of bacterial lineages whose members remain mostly uncultivated, were the main specialists. Under the combined exposure of multiple pollutants, the structures of soil microbial communities in different parks were similar. Community change due to pollutants (31%) was greater than that due to natural factors (2.4%). Among multipollutants, organophosphate esters, led by dibutyl phosphate, had the highest influence on microbial abundance and distribution. An increase in dibutyl phosphate concentration decreased the abundance of Firmicutes, while the abundance of Synergistota was increased. The interactions among pollutants affecting the bacteria were different. Bis(2-chloroethyl) phosphate, nickel and benzo[g,h,i]perylene influenced microorganisms by working with organophosphate esters. High-molecular-weight polycyclic aromatic hydrocarbons, such as benzo[a]pyrene and benzo[g,h,i]perylene, mainly acted on the functional genes and thus affected multiple biogeochemical cycles. Benzo[a]anthracene, bis(2-chloroethyl) phosphate, and arsenic were the primary pollutants affecting metabolic pathways. Our research helps to better understand the impacts of urban environmental pollution on soil microorganisms.

Taking the BTA deep hole boring bar as the object of axial flow and axial feed movement, the dynamic characteristics of the fluid-structure coupling boring bar are systematically studied. The influence of complex deformation (bending, torsion, tension, and compression) factors are considered in the derivation of dynamic characteristics. According to the force situation of the BTA deep hole boring bar, the transverse vibration equation of the BTA deep hole boring bar is established. The transverse vibration equation is discretized by Galerkin method, and then its characteristic root, response variance, and spectral density are solved to realize the transverse vibration analysis of the boring bar. Research has found that the correlation between system stability and boring bar speed is no longer monotonous. System stability is positively correlated with the equivalent stiffness and the equivalent shear modulus. There is a negative correlation between system stability and axial force, but it is not significant. [ABSTRACT FROM AUTHOR]

In this study, the effects of large geometric mistuning on blade response are investigated considering the change of mistuning properties and excitation characteristics. The response variations because of large mistuning are negligible under white noise excitations and are highly significant under narrow band excitations. For the different excitation correlations, the responses are represented using non-dimensional variables in order for the results to be comparable to each other. It is shown that the ratio of the modal frequency between the tuned and large mistuned blades determines the propagation direction of the natural frequencies of the mistuned system, therefore, the responses of large mistuned blades depend primarily on their level of modal frequency. [ABSTRACT FROM AUTHOR]

In this study, vibration analysis of a cantilever pipe conveying fluid under distributed random excitation was performed using stochastic approach. The equation of motion was first discretized by means of the Galerkin method. Next, the classic flutter analysis of the pipe conveying fluid was performed in absence of random excitation. Then, the random load was taken into account as a white noise excitation. Spectral density of response and response variance were calculated versus the velocity of internal flow in the pipe. The velocity of the maximum of the response variance in case of white noise excitation was regarded as flutter speed. The effects of viscoelastic dissipation, mass ratio and damping ratio of surrounding environment were investigated for the pipe under random excitation and results showed a good agreement with other studies. The spectral density of response was used to obtain the flutter frequency. Random time history and probability density function were exploited to study the pipe's random behavior near the flutter speed. This novel approach for pipe conveying fluid was also used to investigate all possible flutter speeds. The results provided a better understanding of dynamical behavior of pipes conveying fluid under random excitation. [ABSTRACT FROM AUTHOR]

In robust parameter design, a compound noise experiment has been frequently used for reducing the number of experimental runs compared to a product array experiment. However, the results obtained by the compound noise experiment and the product array experiment are often much different. This paper derives an expression of the correlation coefficient of response variances in the compound noise and the product array experiments, which gives an explanation of that difference. [ABSTRACT FROM PUBLISHER]

In this study, the effects of excitation correlation on the mistuned bladed disk assembly are investigated. Base correlation patterns are used to generate a general correlated excitation. An example of a mistuned system is investigated to examine the interaction between excitation correlations and resembled natural modes. It is shown that the blade responses are very sensitive to the correlation of excitations. [ABSTRACT FROM AUTHOR]

For optimal action planning, the gain/loss associated with actions and the variability in motor output should both be considered. A number of studies make conflicting claims about the optimality of human action planning but cannot be reconciled due to their use of different movements and gain/loss functions. The disagreement is possibly because of differences in the experimental design and differences in the energetic cost of participant motor effort. We used a coincident timing task, which requires decision making with constant energetic cost, to test the optimality of participant’s timing strategies under four configurations of the gain function. We compared participant strategies to an optimal timing strategy calculated from a Bayesian model that maximizes the expected gain. We found suboptimal timing strategies under two configurations of the gain function characterized by asymmetry, in which higher gain is associated with higher risk of zero gain. Participants showed a risk-seeking strategy by responding closer than optimal to the time of onset/offset of zero gain. Meanwhile, there was good agreement of the model with actual performance under two configurations of the gain function characterized by symmetry. Our findings show that human ability to make decisions that must reflect uncertainty in one’s own motor output has limits that depend on the configuration of the gain function.

Neural encoding of sensory stimuli is typically studied by averaging neural signals across repetitions of the same stimulus. However, recent work has suggested that the variance of neural activity across repeated trials can also depend on sensory inputs. Here we characterize how intertrial variance of the local field potential (LFP) in primary auditory cortex of awake ferrets is affected by continuous natural sound stimuli. We find that natural sounds often suppress the intertrial variance of low-frequency LFP (<16 Hz). However, the amount of the variance reduction is not significantly correlated with the amplitude of the mean response at the same recording site. Moreover, the variance changes occur with longer latency than the mean response. Although the dynamics of the mean response and intertrial variance differ, spectro-temporal receptive field analysis reveals that changes in LFP variance have frequency tuning similar to multiunit activity at the same recording site, suggesting a local origin for changes in LFP variance. In summary, the spectral tuning of LFP intertrial variance and the absence of a correlation with the amplitude of the mean evoked LFP suggest substantial heterogeneity in the interaction between spontaneous and stimulus-driven activity across local neural populations in auditory cortex. [ABSTRACT FROM AUTHOR]

Robust parameter design has been widely used to improve the quality of products and processes. Although a product array, in which an orthogonal array for control factors is crossed with an orthogonal array for noise factors, is commonly used for parameter design experiments, this may lead to an unacceptably large number of experimental runs. The compound noise strategy proposed by Taguchi [30] can be used to reduce the number of experimental runs. In this strategy, a compound noise factor is formed based on the directionality of the effects of noise factors. However, the directionality is usually unknown in practice. Recently, Singhet al.[28] proposed a random compound noise strategy, in which a compound noise factor is formed by randomly selecting a setting of the levels of noise factors. The present paper evaluates the random compound noise strategy in terms of the precision of the estimators of the response mean and the response variance. In addition, the variances of the estimators in the random compound noise strategy are compared with those in then-replication design. The random compound noise strategy is shown to have smaller variances of the estimators than the 2-replication design, especially when the control-by-noise-interactions are strong. [ABSTRACT FROM AUTHOR]

Abstract: In this study a new analytical method for analyzing flutter speed of aeroelastic systems is presented. In this method, apart from the aerodynamic lift and moment deduced from the aerodynamic theories, one Gaussian white noise force was also added to the lift force. Then the spectral density of response was calculated with respect to the frequency response of the system as well as the spectral density of the excitation. The variance of the response was determined with respect to the airspeed. The flutter speed was obtained by investigating the variation of the response-variance against the airspeed. The maximum of the variance of response represented the flutter speed. To verify this new approach, two case studies were considered. The first case study was a 2-D airfoil under unsteady subsonic flow and the second one was a slender wing in an unsteady incompressible flow with Goland wing properties. The results of the proposed method showed a good agreement with the results of the conventional flutter analysis. One of the major advantages of this approach over the other numerical methods such as the p–k method was that no convergence of reduced frequency was needed so the computational cost was reduced dramatically. [Copyright &y& Elsevier]

Abstract: Sensitivity to 6-n-propylthiouracil (PROP) for a group of 180 naïve consumers was related to their perception of 16 commercially available vanilla custard desserts. Rated intensities of taste and texture attributes varied moderately and inconsistently with PROP sensitivity. In contrast, discriminative ability increased with PROP sensitivity resulting in higher numbers of significant differences between pairs of custards. In terms of signal/noise theory, the results indicate that PROP sensitivity enhances the separation of the response signals but does not reduce their noise. The naïve consumers were also compared with highly trained panelists to test whether effects of PROP sensitivity resemble the effects of experience and training. Naïve consumers and trained panelists responded similarly with respect to taste and texture sensations such as creaminess and thickness, but were clearly different with respect to others such as heterogeneity and fattiness. Trained panelists demonstrated even stronger discriminative abilities than consumers with high PROP sensitivities for some attributes but weaker abilities for others. A practical implication of these findings is that selection criteria for participation in sensory panels should include PROP sensitivity, if the panel is aimed at maximum discriminative performance. [Copyright &y& Elsevier]

Skip sequencing in surveys reduces costs but also acts as a mechanism of contagion in transmitting error from one survey item to subsequent items. The error process as modeled as a contagious, stochastic one in which both the initiating and reduced errors follow the Poisson distribution. The resulting compound distribution, first used by Thomas in 1949, is then used as the basis of a discrete contagious regression model in which characteristics of respondents, subject individuals, and interviewers are allowed to affect the intensity of both initiating and induced errors. The model is applied to data from the 1984 Survey of Income and Program Participation (SIPP) Reinterview Program. The results suggest that reduced-sequencing errors are at least as important a source of losses in reliability as are initiating-response or spontaneous-procedural errors. The relative importance of reduced-sequencing errors is directly proportional to the sequence length. Because the relationships between individual characteristics and the various types of error differ significantly conclusions based on narrow definitions of response errors do not necessarily generalize when sequencing errors are included. The regression estimates suggest that older and less educated respondents provide less reliable data. Older female interviewers, however, are found to obtain more reliable data. [ABSTRACT FROM AUTHOR]

Fellegi's (1974) improved method for estimating the interviewer component of correlated response variance is extended to I groups of k interviewer assignments for general multistage survey designs. Using a linear models approach suggestive of Hartley and Rao's (1978), the independence of the two estimators of interviewer variance is established and the forms of the variances of the estimators are derived. Then using 1980 census data to compute terms in the estimator variances, (a) the optimal design of interviewer variance studies is considered, (b) the improvement of the composite estimator is demonstrated, and (c) some principles of efficient study design are developed. [ABSTRACT FROM AUTHOR]

We studied the response of single units to moving random dot patterns in areas V1 and MT of the alert macaque monkey. Most cells could be driven by such patterns; however, many cells in V1 did not give a consistent response but fired at a particular point during stimulus presentation. Thus different dot patterns can produce a markedly different response at any particular time, though the time averaged response is similar. A comparison of the directionality of cells in both V1 and MT using random dot patterns shows the cells of MT to be far more directional. In addition our estimates of the percentage of directional cells in both areas are consistent with previous reports using other stimuli. However, we failed to find a bimodality of directionality in V1 which has been reported in some other studies. The variance associated with response was determined for individual cells. In both areas the variance was found to be approximately equal to the mean response, indicating little difference between extrastriate and striate cortex. These estimates are in broad agreement (though the variance appears a little lower) with those of V1 cells of the anesthetized cat. The response of MT cells was simulated on a computer from the estimates derived from the single unit recordings. While the direction tuning of MT cells is quite wide (mean half-width at half-height approximately 50°) it is shown that the cells can reliably discriminate much smaller changes in direction, and the performance of the cells with the smallest discriminanda were comparable to thresholds measured with human subjects using the same stimuli (approximately 1.1°). Minimum discriminanda for individual cells occurred not at the preferred direction, that is, the peak of their tuning curves, but rather on the steep flanks of their tuning curves. This result suggests that the cells which may mediate the discrimination of motion direction may not be the cells most sensitive to that direction. [ABSTRACT FROM AUTHOR]

The activity of pairs of neurons in the visual cortex (area 17) of anaesthetized, paralysed cats was recorded using two independently manipulated micropipettes. The number of spikes in the evoked responses of pairs of single neurons were analyzed for response covariance. Responses of the majority of cell pairs (83%) did not covary. Covariance was restricted to closeby neurons with distances of less than 150 μm and with identical orientation and ocular dominance preference. [ABSTRACT FROM AUTHOR]

For neurones in the cat's striate cortex, we examined the dependence of response on the contrast of moving sinusoidal gratings. Most neurones showed a clear threshold contrast below which no response was elicited. Such thresholds presumably contribute to the animal's behavioural threshold, which should not be accounted for solely in terms of the detection of a signal in the presence of spontaneous 'noise'. Above threshold, the response amplitude usually increased linearly with contrast until it began to saturate at the highest contrasts. The variance of the response increased with its amplitude; this finding perhaps underlies the Weber-Fechner relation for psychophysical contrast discrimination. [ABSTRACT FROM AUTHOR]

Neural encoding of sensory stimuli is typically studied by averaging neural signals across repetitions of the same stimulus. However, recent work has suggested that the variance of neural activity across repeated trials can also depend on sensory inputs. Here we characterize how intertrial variance of the local field potential (LFP) in primary auditory cortex of awake ferrets is affected by continuous natural sound stimuli. We find that natural sounds often suppress the intertrial variance of low-frequency LFP (<16 Hz). However, the amount of the variance reduction is not significantly correlated with the amplitude of the mean response at the same recording site. Moreover, the variance changes occur with longer latency than the mean response. Although the dynamics of the mean response and intertrial variance differ, spectro-temporal receptive field analysis reveals that changes in LFP variance have frequency tuning similar to multiunit activity at the same recording site, suggesting a local origin for changes in LFP variance. In summary, the spectral tuning of LFP intertrial variance and the absence of a correlation with the amplitude of the mean evoked LFP suggest substantial heterogeneity in the interaction between spontaneous and stimulus-driven activity across local neural populations in auditory cortex., (Copyright © 2016 the American Physiological Society.)

For optimal action planning, the gain/loss associated with actions and the variability in motor output should both be considered. A number of studies make conflicting claims about the optimality of human action planning but cannot be reconciled due to their use of different movements and gain/loss functions. The disagreement is possibly because of differences in the experimental design and differences in the energetic cost of participant motor effort. We used a coincident timing task, which requires decision making with constant energetic cost, to test the optimality of participant's timing strategies under four configurations of the gain function. We compared participant strategies to an optimal timing strategy calculated from a Bayesian model that maximizes the expected gain. We found suboptimal timing strategies under two configurations of the gain function characterized by asymmetry, in which higher gain is associated with higher risk of zero gain. Participants showed a risk-seeking strategy by responding closer than optimal to the time of onset/offset of zero gain. Meanwhile, there was good agreement of the model with actual performance under two configurations of the gain function characterized by symmetry. Our findings show that human ability to make decisions that must reflect uncertainty in one's own motor output has limits that depend on the configuration of the gain function.