Search

• ADHD persisters showed widespread anomalies in microstate and spectral features. • The neural features in remitters exhibited multiple patterns, including normalization, compensation, and fixed abnormalities. • Microstate dynamics and spectral components may be potential markers of distinct ADHD outcomes. We leveraged microstate characteristics and power features to examine temporal and spectral deviations underlying persistent and remittent attention-deficit/hyperactivity disorder (ADHD). 50 young adults with childhood ADHD (28 persisters, 22 remitters) and 28 demographically similar healthy controls (HC) were compared on microstates features and frequency principal components (f-PCs) of eye-closed resting state. Support vector machine model with sequential forward selection (SVM-SFS) was utilized to discriminate three groups. Four microstates and four comparable f-PCs were identified. Compared to HC, ADHD persisters showed prolonged duration in microstate C, elevated power of the delta component (D), and compromised amplitude of the two alpha components (A1 and A2). Remitters showed increased duration and coverage of microstate C, together with decreased activity of D, relatively intact amplitude of A1, and amplitude reduction in A2. The SVM-SFS algorithm achieved an accuracy of 93.59% in classifying persisters, remitters and controls. The most discriminative features selected were those exhibiting group differences. We found widespread anomalies in ADHD persisters in brain dynamics and intrinsic EEG components. Meanwhile, the neural features in remitters exhibited multiple patterns. This study underlines the use of microstate dynamics and spectral components as potential markers of persistent and remittent ADHD. [ABSTRACT FROM AUTHOR]

Background. This article presents an analysis of the physical qualities of asphalt concrete pavement samples and their own resonant characteristics affecting the reliability and durability of the roadway. The relevance and practical significance of the issue considered in the article is determined by the fact that the analysis of the spectral resonance of asphalt concrete can answer the question of the cause of the cause of the destruction of the road and help to make a decision on the repair or replacement of the roadway. Materials and/or methods. Methods of experiment, system analysis, comparison were used. Asphalt concrete samples of road surfaces with various fillers, which are widely used for paving, were taken as the material. A resonant frequency receiver and a camera were used as the research equipment. Results. The paper presents an analysis of the physical properties of various asphalt concrete pavement compositions and their own resonant characteristics can be used for express diagnostics of the condition of the roadway in order to make a decision on its repair or replacement. Conclusion. The article defines the main elements of the asphalt mixture and evaluates the quality of the asphalt mixture at the manufacturing stage and determines the main physical indicators.

Directivity patterns of terahertz emission by femtosecond laser filament plasma in air after radiation propagation in hollow tubes with metal and dielectric (polypropylene) walls are experimentally studied. It is shown that narrow directed radiation can be obtained using quasi-waveguide propagation in a tube with dielectric walls, while the terahertz pulse duration is not affected significantly. [ABSTRACT FROM AUTHOR]

The angular distributions of various spectral components of terahertz radiation generated by filament plasma are measured in a wide range of numerical apertures NA of the laser beam from 0.003 to 0.1. It is shown that propagation angles of terahertz radiation are inversely proportional to the square root of the terahertz frequency. It is shown that an increase in the numerical aperture of the laser beam leads to an increase in propagation angles of terahertz radiation in the entire range of observed frequencies. [ABSTRACT FROM AUTHOR]

The method of measuring bearing (azimuth) of a moving surface (underwater) object in the passive sonar is described. This method is considered to be a modification of signals phase comparing method. It is based on the measurement of the delay time between signals received at different signal reception point. A distinctive feature of this method is the use for signal processing method of coherent accumulation of the spectral components of the received signal, developed by the authors. This method provides increase signal/noise ratio in the reception channels, therefore decrease errors of measuring bearing in the passive sonar.

Corona current is an important parameter to characterise the corona discharge on high‐voltage direct current (HVDC) transmission lines. The spectral components of corona current are closely related to a variety of corona effects, such as audible noise. It is of great significance to study the frequency‐domain characteristics of corona current. Here, the relationship between DC component and spectral components of corona current on HVDC transmission lines in the band of 2–20 kHz was analysed. First, a lot of corona current data were measured in two HVDC experiment bases. Then, the expression representing the correlation between DC component and spectral components of corona current within 2–20 kHz was established with the maximum surface nominal electric field intensity of conductor as an intermediate variable. Finally, the correctness and universality of the relationship found were verified. The research results here not only reveal the characteristics of corona discharge but can also provide a new way for obtaining the spectral components of corona current in 2–20 kHz with its DC component, and can lay the foundation to provide a new way to get audible noise indirectly based on the DC component of corona current in the future.

The Dirac combs of primitive Pisot–Vijayaraghavan (PV) inflations on the real line or, more generally, in R d are analysed. We construct a mean-orthogonal splitting for such Dirac combs that leads to the classic Eberlein decomposition on the level of the pair correlation measures, and thus to the separation of pure point versus continuous spectral components in the corresponding diffraction measures. This is illustrated with two guiding examples, and an extension to more general systems with randomness is outlined. [ABSTRACT FROM AUTHOR]

Corona current is an important parameter to characterise the corona discharge on high‐voltage direct current (HVDC) transmission lines. The spectral components of corona current are closely related to a variety of corona effects, such as audible noise. It is of great significance to study the frequency‐domain characteristics of corona current. Here, the relationship between DC component and spectral components of corona current on HVDC transmission lines in the band of 2–20 kHz was analysed. First, a lot of corona current data were measured in two HVDC experiment bases. Then, the expression representing the correlation between DC component and spectral components of corona current within 2–20 kHz was established with the maximum surface nominal electric field intensity of conductor as an intermediate variable. Finally, the correctness and universality of the relationship found were verified. The research results here not only reveal the characteristics of corona discharge but can also provide a new way for obtaining the spectral components of corona current in 2–20 kHz with its DC component, and can lay the foundation to provide a new way to get audible noise indirectly based on the DC component of corona current in the future. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of a parametric study of irregular wave run-up over fringing reefs using the shock-capturing Boussinesq wave model Funwave-TVD to better understand the role of fringing reefs in the mitigation of wave-driven flooding. Laboratory experiments were newly performed with a typical fringing reef profile and typical hydrodynamic conditions to validate the model. Experimental data shows irregular wave run-ups are dominated by the low-frequency motions and confirms the run-up resonant phenomenon over the back-reef slope, which has been revealed in previous numerical studies. It is demonstrated that irregular wave evolution and run-up over fringing reefs are reasonably reproduced by the present model with a proper grid size. However, the infragravity run-up height and highest 2% run-up height over the back-reef slope are under-predicted due to the underestimation of the infragravity wave height over the reef flat. The validated model was then utilized to model irregular wave transformations and run-ups under different conditions. Through a series of numerical experiments, the effects of key hydrodynamic and reef geometry parameters, including the reef flat width, water depth over the reef flat, fore-reef slope angle and back-reef slope angle, on the irregular wave run-up were investigated. Variations of spectral components of irregular wave run-ups were examined to better understand the physical process underlying the effect of each parameter. [ABSTRACT FROM AUTHOR]

Night-time changes in bioluminescence intensity in the coastal area of the Black Sea were recorded. It was noted that the biomass of luminous organisms is closely correlated with the biomass of plankton and other pelagic organisms, including commercial pelagic fish. The parameters of plankton communities' basic biological rhythms were determined using the discrete Fourier transform method. These rhythms were manifest as spatial and temporal changes in the bioluminescence intensity. It was shown that changes in the bioluminescence intensity over a 14.0-h period were due to the duration of the light/dark cycles. By contrast, changes in bioluminescence intensity with periods of 4.7 and 2.8 h were due to the endogenous rhythms of the plankton community (feeding and cell division). An original method for evaluating of errors in the calculated periods of the biological rhythms was proposed. A strong correlation ( r = 0.906) was observed between the measured and calculated values for the bioluminescence intensity, which provided support for the assumptions made. [ABSTRACT FROM AUTHOR]

The Head Bay of Bengal is highly vulnerable to flooding events caused due to monsoons, cyclones and sea-level rise, owing to its funnel-like shape, high tidal range, presence of numerous river drainage systems, low-lying topography, and shallow bathymetry. Tides dominate the hydrodynamic behaviour and coastal processes in this region and its propagation is quite distinct. The present study uses ADCIRC hydrodynamic model customized for the Head Bay of Bengal, discretized using unstructured finite elements and validated against limited available observations in this data sparse region. The water-level elevations derived from ADCIRC simulation was used to understand the pattern of non-linear tidal propagation with respect to complex coastal geomorphology prevalent in this region. The study finds a marginal amplification of diurnal tide, nearly double amplification of semi-diurnal components, and existence of a degenerate amphidromic point near Meghna delta consistent with previous studies. The spatial and temporal variability of tidal spectral components were examined by applying the techniques of wavelet, harmonic, and time-series analysis at various locations. Maximum amplification of tides occurs at the head of the bay, along a zone enclosing the mouth of tidal inlets; and for regions northward, the tides decay with progressively increasing phase lags. The study signifies dominance of a forced fortnightly tide and tidal asymmetry leading to flood-dominance in the rivers Hooghly, Meghna, and Tetulia. The non-linear properties of tides have been elucidated, and their origin and spatio-temporal variability in these riverine systems were further investigated. Shallow depth and sharp depth gradients were discerned to be the important conditions for the origin of non-linear components. It has been deduced that non-linear tides are generated in regions where propagating tides are accumulated, and amplified in regions where they are funneled. A study of tidal energetics show that maximum rate of tidal energy dissipation is deep inside the rivers at head of the bay. The spatial variability analysis of tidal form factor shows an overall semi-diurnal dominance in the Head Bay. [ABSTRACT FROM AUTHOR]

The method of dynamic analysis for the wave packet parameters is considered. The method involves selection and evaluation of the amplitudes and phases of the separate monochromatic components of a wave packet. Positions of the intensity maximum of the wave packet can be determined using initial phases of monochromatic components estimated by nonlinear discrete Kalman filter.

An algorithm and a technique are developed for finding the maximum values of the target current components in a MOS transistor with an n-type built-in channel depending on the submicron and nanoscale topological norms for a frequency transformer in the presence of intensive noise at its input. The spectral making components of the intermediate frequency are evaluated and analyzed for the given amplitudes of the generator, signal, and handicap. The behavior of the n-MOS transistors designed according to the GPDK045 and GPDK0990 technological norms is investigated. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of experimental positron lifetime spectra in polymer materials by using various algorithms of neural networks. A method based on the use of artificial neural networks for unfolding the mean lifetime and intensity of the spectral components of simulated positron lifetime spectra was previously suggested and tested on simulated data [Pžzsitetal, Applied Surface Science, 149 (1998), 97]. In this work, the applicability of the method to the analysis of experimental positron spectra has been verified in the case of spectra from polymer materials with three components. It has been demonstrated that the backpropagation neural network can determine the spectral parameters with a high accuracy and perform the decomposi-tion of lifetimes which differ by 10% or more. The backpropagation network has not been suitable for the identification of both the parameters and the number of spectral components. Therefore, a separate artificial neural network module has been designed to solve the classification problem. Module types based on self-organizing map and learning vector quantization algorithms have been tested. The learning vector quantization algorithm was found to have better performance and reliability. A complete artificial neural network analysis tool of positron lifetime spectra has been constructed to include a spectra classification module and parameter evaluation modules for spectra with a different number of components. In this way, both flexibility and high resolution can be achieved.

Methods of decomposing the IR spectra of coal and related materials are considered-specifically, methods based on baselines, reference spectra, difference spectra, and decomposition by Gaussian functions. Their advantages and disadvantages are identified. A method of spectral decomposition by polynomial components is proposed, on the basis of approximation by minimization of a nonquadratic cost function. For the example of Zh coal and coal pitch, the new method is shown to be a promising means of increasing the available spectral information. [ABSTRACT FROM AUTHOR]

Considering that spectral components of one random process are not necessarily independent for all types of signals, this paper defines a generalized auto-spectral coherence function (GAS-CF) to measure this spectral correlation. The GAS-CF is a generalization of the temporal coherence function and the spectral coherence function, where they have already been successfully applied to detect howling components and transient noise components, respectively. After defining the GAS-CF, this paper studies its statistical properties in detail. Simulation results show that the proposed GAS-CF can be applied to detect different types of signals, including transient noise, howling frequency and chirp signal, in a simple way. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports fast crack profile reconstruction methods using transient slices and spectral components of pulsed eddy current (PEC) signals after a review of the state-of-the-art and current challenges. These methods provide initial approximate profiles for crack shape reconstruction, and have potential to reduce the computing time. Experimental samples, results, and reconstructions have been presented and discussed. Comparative studies of different profile reconstructions using different PEC signals such as amplitude, phase, real and imaginary values of spectral components, transient slices, have also been conducted using reconstruction Mean Square Errors (MSE). The results show that the profiles estimation using the imaginary values of spectral components is more stable and accurate than the others. [Copyright &y& Elsevier]

The aim of the present work was to demonstrate the possibility of selective detection of nanoparticle contrast agents (NPCAs) on diagnostic echographic images by exploiting the second harmonic component they introduce in the spectra of corresponding ultrasound signals, as a consequence of nonlinear distortion during ultrasound propagation. We employed silica nanospheres (SiNSs) of variable diameter (160 nm, 330 nm, and 660 nm) dispersed in different volume concentrations (range 0.07-0.8%) in agarose gel samples that were automatically scanned through a digital ecograph using narrow-band ultrasound pulses at 6.6 MHz and variable mechanical index (MI range 0.2-0.6). In the first part of the study, the intensity peaks of four different spectral components of the backscattered signal were considered: fundamental (detected in correspondence of the incident ultrasound frequency), subharmonic (detected at half of the fundamental frequency), ultra harmonic (detected at 1.5 times the fundamental frequency), and second harmonic (detected at twice the fundamental frequency). Subsequently, based on the experimental results of the first part of the study and on our recently reported findings, the focus was moved to a detailed comparison between subharmonic and second harmonic trend, which were determined as a function of nanoparticle composition, sample concentration, and MI. The experiments were also repeated on different agarose samples, containing SiNSs covered by an outer shell of smaller magnetic nanoparticles, made of either iron oxide (IO) or FePt-IO nanocrystals. Obtained results show that this new ultrasound-based method for NPCA imaging has a detection sensitivity similar to that of our previously introduced subharmonic-based technique in the presence of 330-nm SiNSs, but performs significantly better in the detection of both the types of “dual mode” NPCAs. The fact that the reported detection method was optimized for identification of 330-nm SiNSs (a sort of “ideal” size for the development of novel tumor-targeting NPCAs) and that the magnetically coated particles are detectable also through magnetic resonance imaging makes the presented second harmonic ultrasound method a valuable solution for the introduction of new protocols for multimodal molecular diagnoses employing only nonionizing radiations. [ABSTRACT FROM PUBLISHER]

Abstract: Absorption spectra of liquid water at various temperatures in the whole IR region () are obtained from ATR spectra recorded in the mid-IR region combined with absorption spectra measured in the FIR region. They can be accurately decomposed over two independent spectra. The spectra of the two kinds of H2O (D2O) molecules they suppose are defined as fulfilling spectroscopic constraints and as being in accordance with thermodynamic values. Their enthalpy difference He − Hg is found equal to 11.8kJmol−1 for ordinary water and 12.2kJmol−1 for heavy water. H2O (D2O) molecules of lower enthalpies Hg , greater than the enthalpy of H2O or D2O molecules in ices by 1.3kJmol−1, display vibrations that resemble those of H2O (D2O) molecules in ice. Molecules with enthalpies He reorient without breaking their H-bonds as He appears greater than the potential barrier for rotations around their symmetry axes. [Copyright &y& Elsevier]

Amplitudes of spectral geomagnetic field components and signal/noise ratios are estimated at frequencies of lunar and solar tides based on the data registered at the experimental site of Vladimir State University (VlSU) and Japanese geomagnetic stations Kakioka (1913-2006) and Memambetsu (1950-1999). The influence of thermal solar tides S1, S2, S3, and S4 and lunar gravitational tides O1, M2, and N2 on the geomagnetic field of the surface layer of the atmosphere is reliably distinguished. [ABSTRACT FROM AUTHOR]

Abstract: Photoprotein obelin, the enzyme–substrate complex of polypeptide with 2-hydroperoxycoelenterazine, is responsible for bioluminescence of marine hydroid Obelia longissima. Addition of Ca2+ to the photoprotein triggers the bioluminescent reaction with light emission. The product of the bioluminescent reaction – enzyme-bound coelenteramide – is a fluorescent protein called ‘discharged’ obelin. It is stable and highly fluorescent. The paper considers dependence of its light-induced fluorescence on Ca2+ concentration. Increase of Ca2+ concentration enhanced the fluorescence intensity of discharged obelin; the dependence was found as linear in double logarithmic coordinates at Ca2+ concentration range 10−7–10−6 М, both in excitation and emission spectra. The spectra were divided into components; contributions of the components to experimental excitation and emission spectra depended on Ca2+ concentration. The data suggest enzymatic conformational transition in discharged obelin at ∼5×10−7 M of Ca2+ concentration. Spectra variations were attributed to acidity changes of discharged obelin chromophore (coelenteramide) in its fluorescent state . [ABSTRACT FROM AUTHOR]

Abstract: Complex bioluminescence spectra of photoproteins from marine coelenterates – jellyfish Aequorea victoria and hydroid Obelia longissima, and photoluminescence spectra of the bioluminescent reaction products (Ca2+-discharged photoproteins) were deconvolved into components. The bioluminescence spectra of aequorin were found to include three, the bioluminescence spectra of obelin – four, and the photoluminescence spectra of the Ca2+-discharged photoproteins – only two components. The spectral components were assigned to one unionized and three ionized forms of coelenteramide. The changes in acidity of the excited coelenteramide molecule are discussed. The differences in bioluminescence and photoluminescence spectra are considered, with protonic environment of coelenteramide taken into account. [Copyright &y& Elsevier]

The chemical composition of surface and underneath layers of WO3 thin films, deposited by thermal evaporation and annealed in air at different temperatures, has been studied by means of soft X-ray and X-ray photoemission spectroscopies. Both the W 4f and valence band spectra have been analyzed. The analysis has been performed on samples as inserted and after an annealing process in an ultra high vacuum. The results have shown that the surface always presents a nonstoichiometric WO3 compound, whose spectral components do not depend on the sample preparation. Instead, the study of the underneath layers has shown that the WO3 films annealed in air at 500°C are highly stoichiometric and stable, while the samples heated in air at 300°C are much more sensitive to the vacuum thermal treatment showing the presence of reduced WOx phases, whose intensity and chemical states change after the in vacuum annealing procedure. [ABSTRACT FROM PUBLISHER]

This paper discusses the improvement in the third-order intermodulation product (IM3) performance obtainable from RF and microwave amplifiers by two alternative injection techniques. The first is the addition to the amplifier input of the second harmonics of the input spectrum and the second is the addition to the amplifier input of the difference frequencies between the spectral components of the input signal. Both techniques are considered in theory, by simulation and in practice. Both techniques give useful improvements in two-tone IM3 performance. The second harmonic technique reduced the IM3 level by 43 dB in an amplifier at 835 MHz. The difference-frequency technique gave a reduction of 48 dB in an amplifier at 880 MHz. The difference-frequency technique also gives a greater improvement for complex spectra signals [ABSTRACT FROM PUBLISHER]

Linear combination is a common feature of most methods designed to aggregate a set of time series into a composite index. In this paper the principal components approach is utilized by means of spectral techniques to improve the variance explained by the first principal component. The optimality criterion resorts to the alignment of the elements of the vector time series. [ABSTRACT FROM AUTHOR]

Coherent relations between EEG signals of five frequency ranges recorded from different cortical sites were evaluated in 8- to 12-year-old children with congenital and acquired visual dysfunctions; the results were compared with those observed in children with normal vision. In visual dysfunctions, the coherence was, in general, higher for slow-wave ranges and weaker for the alpha EEG range. These facts are indicative of probable intensification of brainstem influences of the cortex. Specific features of the coherence dependent on the time of development of visual dysfunctions were identified. [ABSTRACT FROM AUTHOR]

Incoherent broadband light sources are used in interferometric fibre optic gyroscopes (IFOGs) to mitigate the deleterious effects of Kerr and polarisation nonreciprocity, and backscattering effects in gyroscopes. However, incoherent broadband sources suffer from excess noise or relative intensity noise (RIN), caused by the beating of different spectral components on the photodetector. Unless RIN noise is suppressed, IFOG performance cannot be improved once light on the photodetector exceeds one photon per coherence time (∼μW's). Demonstrated is a low RIN light source capable of significantly improving angle random walk of an IFOG by 12 dB. [ABSTRACT FROM AUTHOR]

Abstract: We report a new optical sensor exploiting the innovative operation principle developed for the selective registration of UV and visible radiations. The operation is based on the mutual influence of depletion regions in the photovoltaic structure composed by Schottky barrier and n−p junction. The important feature of this structure is that the depletion regions expand over the whole base so that they contact each other. We have shown that the position of the contact point in the base is a function of voltage applied to the structure. Also absorption spectrum for each of the depletion regions and the photoresponse of the structure are functions of the applied voltage. We have revealed that the change induced by the applied voltage in the photoresponse, ΔI, is proportional to the change Δλ induced in the spectrum, Δλ∼ΔI. This linear correlation between ΔI and Δλ is a very important spectrophotometric property required for the precise selective registration of bio signals in dynamic and static biological processes. [Copyright &y& Elsevier]

An approximate strong injection perturbation mathematical model to analyze the frequency pulling and non-linear dynamics in radio frequency (RF) signal driven optoelectronic microwave oscillator (OEO) is presented here. The formulas regarding the lock-range, the beat frequency and the average frequency are derived, which help to estimate the amount of phase perturbation in pulled (unlocked-driven) OEO more accurately considering both weak and strong RF signal injection. The analytical expressions for the spectral components of the pulled OEO are also given to predict the frequency pulling phenomenon of the pulled OEO. It is presented that our proposed analytical model has the capability to accurately determine the phase-locking and assessing the frequency pulling of RF driven single-loop OEO when injected by weak and strong RF signal. The verification of the accuracy of the proposed model is also done by the experiments. [ABSTRACT FROM AUTHOR]