Differences In Temporal Behavior Research Articles

Spatiotemporal variation and provincial scale differences of the AOD across China during 2000–2021

The spatiotemporal variation of the aerosol optical depth (AOD) over China was studied using MODIS data retrieved with the MAIAC algorithm. Time series were extended to July 2021. The study area is defined as the mainland of South-Eastern China Below the Hu line, with Hebei as the most northerly province (in short SECBH) and includes 16 provinces, 4 central government-controlled municipalities and one autonomous region, all referred to here as provinces. The extended time series and provincial-scale averaging of the AOD provide more detailed and new information on the spatiotemporal variation across the SECBH. Differences in temporal behaviour are observed between the north, central-south and south of the SEBCH. The AOD increased in southern China before it increased in the northern provinces. The AOD was high between 2006 and 2014, with strong interannual fluctuations in response to the emission reduction policy opposed by economic developments, and decreased significantly from 2013/2014, in response to the Clean Air Action Plan (2013–2017). However, during the period 2017–2020 the AOD stabilized and fluctuated within 10% of the average value for these years which was similar to, and in part of the study area lower than, the AOD in 2000. Exceptions are Guangxi, Guangdong, Jiangxi and part of Shandong, where the AOD in 2020 was slightly higher than in 2000. The extension of the AOD time series until July 2021 shows that earlier derived trends do not continue and the emission reduction policy needs to be extended to achieve the earlier air quality goals.

Effects of Shell Thickness on Cross-Helicity Generation in Convection-Driven Spherical Dynamos

The relative importance of the helicity and cross-helicity electromotive dynamo effects for self-sustained magnetic field generation by chaotic thermal convection in rotating spherical shells is investigated as a function of shell thickness. Two distinct branches of dynamo solutions are found to coexist in direct numerical simulations for shell aspect ratios between 0.25 and 0.6—a mean-field dipolar regime and a fluctuating dipolar regime. The properties characterising the coexisting dynamo attractors are compared and contrasted, including differences in temporal behaviour and spatial structures of both magnetic fields and rotating thermal convection. The helicity α-effect and the cross-helicity γ-effect are found to be comparable in intensity within the fluctuating dipolar dynamo regime, where their ratio does not vary significantly with the shell thickness. In contrast, within the mean-field dipolar dynamo regime the helicity α-effect dominates by approximately two orders of magnitude and becomes stronger with decreasing shell thickness.

Impact flash evolution of CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets

AbstractThe wavelength dependence and temporal evolution of the hypervelocity impact self‐luminous plume (or “flash”) from CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets have been investigated using the Kent two‐stage light‐gas gun. An array of 10 band‐pass filtered photodiodes and a digital camera monitored changes in the impact flash intensity during the different phases of the emitting ejecta. Early‐time emission spectra were also recorded to examine short‐lived chemical species within the ejecta. Analyses of the impact flash from the varied frozen targets show considerable differences in temporal behavior, with a strong wavelength dependence observed within monitored near‐UV to near‐IR spectral regions. Emission spectra showed molecular bands across the full spectral range observed, primarily due to AlO from the projectile, and with little or no contribution from vaporized metal oxides originating from frozen regolith simulant targets. Additional features within the impact flash decay profiles and emission spectra indicate an inhomogeneity in the impact ejecta composition. A strong correlation between the density of water ice‐containing targets and the impact flash rate of decay was shown for profiles uninfluenced by significant atomic/molecular emission, although the applicability to other target materials is currently unknown. Changes in impact speed resulted in considerable differences in the temporal evolution of the impact flash, with additional variations observed between recorded spectral regions. A strong correlation between the impact speed and the emission decay rate was also shown for CO2 ice targets. These results may have important implications for future analyses of impact flashes both on the lunar/Martian surface and on other frozen bodies within the solar system.

Observation of the TESPEL-injected impurities behaviour by the PHA system at Wendelstein 7-X

The Pulse Height Analysis (PHA) system at Wendelstein 7-X (W7-X) is a broad energy range spectrometer dedicated to the observation of impurity behaviour during the plasma discharges. The system measures spectra in the range between 0.5 and 20 keV, from integrated signals along three lines of sight that pass close to the plasma center. During the recent operational phase of W7-X, the TESPEL (Tracer-Encapsulated Solid PELlet) injector has been commissioned. By this injector, polystyrene pellets with a single tracer impurity as well as multiple tracer impurities have been injected into the W7-X plasmas. The multiple tracer impurities injection allows studying the behavior of various impurities in the same plasma condition. The time resolution of the PHA system in the order of 60–100 ms, is smaller than typical confinement times and sufficient to observe differences in temporal behaviour of injected impurities. The collected PHA spectra consist of Kα lines of vanadium, manganese and nickel in case of the triple tracers, and of iron or copper in case of the single tracer. The temporal evolution of these Kα lines has been obtained in various plasma conditions, which will be presented and discussed in this paper.

The spectral structure of acoustic time series can predict the perceptual assessment of urban soundscapes

The field of soundscape studies considers sound environments as perceived, in context, and has recently focussed on understanding the potential of physical acoustical features, including temporal characteristics, for predicting human perception. This study investigates the presence of a 1/f structure in the power spectrum slope of six (psycho)acoustical parameters of 30-s recordings of urban acoustic environments. The acoustical parameters were calculated as time series throughout the recording period, then the power spectrum of the time series was calculated and plotted on a log-log scale, with the x-axis ranging from 30 s/10-1.5 Hz to 0.01 s/102 Hz. The slope of the best-fitted straight line through the power spectrum was calculated and compared to the corresponding perceptual attribute ratings of the soundscape collected on site during the recording. The dataset includes 300 + recording-response pairs. An overall 1/f structure was not found for any of the parameters. Differences in temporal behaviour are indicated at different time scales, with a deviation in slope typically occurring at ∼2 s/0.5 Hz, reflecting differences in temporal behaviour among within-sound-event time scales and between-sound-event time scales. An ordinal logistic regression model is developed which predicts the perceptual attributes of urban soundscapes based on the spectral slopes of the acoustic time series.

Line scanning fMRI reveals earlier onset of optogenetically evoked BOLD response in rat somatosensory cortex as compared to sensory stimulation

The combination of optogenetic control and fMRI readout in the brain is increasingly used to assess neuronal networks and underlying signal processing. However, how exactly optogenetic activation or inhibition reproduces normal physiological input has not been fully unraveled. To assess details of temporal dynamics of the hemodynamic response, temporal resolution in rodent fMRI is often not sufficient. Recent advances in human fMRI using faster acquisition schemes cannot be easily translated to small animals due to smaller dimensions, fast physiological motion, and higher sensitivity to artefacts. Here, we applied a one dimensional line scanning acquisition with 50ms temporal resolution in rat somatosensory cortex. We observed that optogenetic activation reproduces the hemodynamic response upon sensory stimulation, but shows a 160 to 340ms earlier onset of the response. This difference is explained by direct activation of all opsin-expressing and illuminated cortical layers, while hemodynamic response to sensory stimulation is delayed during intracortical transmission between cortical layers. Our results confirm that optogenetic activation is a valid model for physiological neuronal input, and that differences in temporal behavior of only a few hundred milliseconds can be resolved in rodent fMRI.

A DISCRETE TIME VARIABLE INDEX FOR SUPPORTING DYNAMIC MULTI-CRITERIA DECISION MAKING

While Multi-Criteria Decision Making (MCDM) models are focused on selecting the best alternative from a finite number of feasible solutions according to a set of criteria, in Dynamic Multi-Criteria Decision Making (DMCDM) the selection process also takes into account the temporal performance of such alternatives during different time periods. In this paper a new discrete time variable index is proposed, to handling differences in temporal behavior of alternatives, which are not discriminated in preceding dynamic approaches, also considering rating-based perspectives for discrimination of the decision maker by modeling different attitudes to deal with the rating changes along different time periods. Moreover a DMCDM for supplier selection example is provided to illustrate the feasibility and effectiveness of the proposed index.

Ultrafast luminescence kinetics of metallic single-walled carbon nanotubes: Possible evidence for excitonic luminescence

In metallic systems, strong screening of the Coulomb interaction between an electron and a hole by free electrons largely prevents the formation of an exciton. In one-dimensional metallic systems, however, the screening effect is significantly reduced. Recent theoretical and experimental studies suggest that an exciton state can be realized in metallic single-walled carbon nanotubes (SWNTs) due to their ideal one-dimensional structure. Here, we experimentally investigate photoluminescence in both metallic-SWNT-enriched and semiconducting-SWNT-enriched samples using femtosecond time-resolved photoluminescence measurements. By comparing luminescence kinetics and time-integrated spectra between the two samples, the observed signal in the metallic-SWNT-enriched sample is attributed to the luminescence from metallic SWNTs. We also show complementary data of photoabsorption signals in the metallic-SWNT-enriched sample measured by transient absorption spectroscopy. A difference in temporal behavior between the luminescence and absorption signals strongly suggests that the luminescence is excitonic in nature, and the exciton lifetime is found to be $40\ifmmode\pm\else\textpm\fi{}10$ fs. This long lifetime indicates that a large exciton binding energy leads to a relatively stable exciton state in the presence of metallic electrons.

Electroluminescence of single CdSe nanocrystals induced by scanning tunneling microscope

Electroluminescence intensity of single CdSe nanocrystals (NCs) excited by the tunnel current of a scanning tunneling microscope (STM) was measured. Samples with NCs do not exhibit plasmon emission. This enables one to measure pure emission from a single NC. Electroluminescence, measured in time, differs considerably from that of photoluminescence in similar NCs. This difference in temporal behavior results from the difference in physical conditions of experiments on photo- and electroluminescence.

Temporal evolution of inverse spin Hall effect voltage in a magnetic insulator-nonmagnetic metal structure

It is demonstrated that the temporal evolution of a spin-wave induced inverse spin Hall effect voltage in a magnetic insulator–nonmagnetic metal structure is distinctly different from that of the directly excited (microwave pulse driven) spin-wave mode from which it originates. The differences in temporal behavior provide compelling evidence that incoherent secondary spin-wave modes, having a range of different characteristic lifetimes, make an important contribution to spin pumping at the insulator-metal interface.

Temporal dynamics of ocular aberrations: monocular vs binocular vision

The temporal dynamics of ocular aberrations are important for the evaluation of, e.g. the accuracy of aberration estimates, the correlation to visual performance, and the requirements for real-time correction with adaptive optics. Traditionally, studies on the eye's dynamic behavior have been performed monocularly, which might have affected the results. In this study we measured aberrations and their temporal dynamics both monocularly and binocularly in the relaxed and accommodated state for six healthy subjects. Temporal frequencies up to 100 Hz were measured with a fast-acquisition Hartmann-Shack wavefront sensor having an open field-of-view configuration which allowed fixation to real targets. Wavefront aberrations were collected in temporal series of 5 s duration during binocular and monocular vision with fixation targets at 5 m and 25 cm distance. As expected, a larger temporal variability was found in the root-mean-square wavefront error when the eye accommodated, mainly for frequencies lower than 30 Hz. A statistically-significant difference in temporal behavior between monocular and binocular viewing conditions was found. However, on average it was too small to be of practical importance, although some subjects showed a notably higher variability for the monocular case during near vision. We did find differences in pupil size with mono- and binocular vision but the pupil size temporal dynamics did not behave in the same way as the aberrations' dynamics.

Temporal properties of responses to broadband noise in the auditory nerve.

Temporal information in the responses of auditory neurons to sustained sounds has been studied mostly with periodic stimuli, using measures that are based on Fourier analysis. Less information is available on temporal aspects of responses to nonperiodic wideband sounds. We recorded responses to a reference Gaussian noise and its polarity-inverted version in the auditory nerve of barbiturate-anesthetized cats and used shuffled autocorrelograms (SACs) to quantify spike timing. Two metrics were extracted from the central peak of autocorrelograms: the peak-height and the width at halfheight. Temporal information related to stimulus fine-structure was isolated from that to envelope by subtracting or adding responses to the reference and inverted noise. Peak-height and halfwidth generally behaved as expected from the existing body of data on phase-locking to pure tones and sinusoidally amplitude-modulated tones but showed some surprises as well. Compared with synchronization to low-frequency tones, SACs reveal large differences in temporal behavior between the different classes of nerve fibers (based on spontaneous rate) as well as a strong dependence on characteristic frequency (CF) throughout the phase-locking range. SACs also reveal a larger temporal consistency (i.e., tendency to discharge at the same point in time on repeated presentation of the same stimulus) in the responses to the stochastic noise stimulus than in the responses to periodic tones. Responses at high CFs reflect envelope phase-locking and are consistent with previous reports using sinusoidal AM. We conclude that the combined use of broadband noise and SAC analysis allow a more general characterization of temporal behavior than periodic stimuli and Fourier analysis.

Near-IR Luminescent Rare Earth Ion–Sensitizer Complexes

Rare earth ions, with relatively long luminescence lifetimes, have significant advantages for application in fields as varied as diagnostics and optical amplification. In diagnostics the long luminescence lifetimes allow for extremely sensitive time-gated detection, where the difference in temporal behavior of scatter and background fluorescence and the long-lived rare earth luminescence is utilized. In optical amplification the long excited-state lifetime makes it easier to obtain population inversion, a requirement for effective stimulated emission. Unfortunately the absorption cross section of rare earth ion transitions is extremely low. However, via sensitized excitation by means of a suitable organic molecule, efficient excitation is obtained. It is shown that excitation in the visible part of the spectrum can be used to excite rare earth ions which luminesce in the near-IR, such as ytterbium, neodymium, and erbium, via a fluorescein-derivative as sensitizer. The advantages of this approach are manifold. Low-cost light sources are available for the visible part of the spectrum, and interferences from the matrix (scatter, absorption) are minimal. Detection in the near-IR is almost interference-free. For optical amplification the wavelength regions around 1300 and 1550 nm, which can be covered with the neodymium and erbium complexes, respectively, are the most important for applications in optical telecommunication.

Application of phase-sensitive photoreflectance spectroscopy to a study of undoped AlGaAs/GaAs quantum well structures

Phase-sensitive photoreflectance (PR) has been used here to study undoped AlGaAs/GaAs single and multiple quantum well structures. The PR features of these structures exhibited a phase detection angle dependence as a function of spectral energy at the output of the lock-in amplifier, which was attributed to the differences in temporal behavior of the PR features from different layers within these structures.

Shallow equatorial jets

When zonal velocity profiles from the central equatorial Pacific are expanded into sums of vertical normal modes, the peak amplitudes occur consistently near modes 1, 5, 12, and 18. The first two of these peaks sum to a recognizable equatorial undercurrent profile. The two higher‐mode peaks blunt and thicken the equatorial undercurrent (EUC) and add a westward extremum near 340 m. During the 1982–1983 El Niño, the low‐mode component of the flow (modes 1–10) was more variable than the residual component, which was dominated by the modes near 12 and 18. The residuals below 120 m persisted as alternating westward and eastward current bands (the “shallow jets”) through the disappearance of the EUC in the second half of 1982 and its reappearance in 1983. The shallow jets were nearly constant in depth until late 1982 and then gradually rose through the end of the time series in June 1983. Differences in temporal behavior among the mode amplitude peaks indicate that these peaks are describing dynamically separate components of the flow which are not tightly coupled on time scales shorter than a few months.

Human temporal behavior and discrimination-reversal learning.

The present study demonstrates that a relationship exists between individual differences in temporal behavior and individual differences in human discrimination-reversal learning behavior. When the results of performance on a time-estimation task employing the method of reproduction are compared with the results of acquisition performance on a complex form of discrimination-reversal learning task is can be demonstrated that underestimation of time is associated with faster learning and overestimation of time is associated with slower learning of the discrimination task. The experimental design was based on the historical fact that the Sechenov-Pavlov and Spence-Hull formulations assigned a primary role in learning to excitation and inhibition as intervening variables between the input of stimulation and output of response. The present study also used the tasks of time estimation and discrimination learning as dependent variables; and the concept that underestimation of time is associated with and underlying predominance of excitatory processes as a hypothetical construct. The conclusion was reached that one of the many theoretical processes which may be used to explain discrimination learning is the concept that acquisition of the correct response may be viewed as a function of the individual rates at which excitatory processes come to be conditioned to a predominance over existing inhibitory processes.