Band Amplitude Research Articles

Adaptive Sample Reduction Techniques for Continuous Interleaved Sampling Strategy in Multi Channel Cochlear Implant

CIS (Continuous Interleaved Sampling) strategy in which electrodes stimulus is determined based on extracted information from amplitude of different bands of input signal, is a basis in processing methods in cochlear implant systems. In this paper besides implementing this strategy, methods for improving sample reduction and computational efficiency are also presented. In this case adaptive method according to processing parameters and an input signal has been suggested that due to the use of fewer samples to synthesize the signal is better than the other methods and is significantly efficient.

Two-Dimension Fault Line Selection Method Based on Transient Signal Features of Fault Phase

When single-line-to-ground fault happen in neutral non-effectively earthed system, there is a big difference between the fault feeder and un-fault feeder in transient signal energy centralized frequency band and signal amplitude of fault phase. The transient signal energy in fault feeder’s fault phase is bigger, and it centralizes in lower frequency band. But the transient signal in un-fault feeders’ has the contrary features. And this feature is affected little by the fault initial angle. So the paper proposed a method that using the gravity frequency and transient signal energy to form a two-dimension line selection method that using the signal overall distribution characteristics. It can be applied in neutral unearthed and resonant system simultaneously. And the method is effectively to different fault initial angle and fault resistance. The method is proved correctly, effectively and adaptively by actual simulation in different fault cases.

Coupled 100-kyr cycles between 3 and 1 Ma in terrestrial and marine paleoclimatic records

Earth's climate over the last one million years experienced several ∼100-kyr glacial cycles, but no simple forcing mechanism has been identified. Numerous studies have tried to explain strong 100-kyr glacial cycles without recognizable forcing, which has come to be known as the 100-kyr problem. Few studies have examined 100-kyr band paleoclimatic signals before 1 Ma. A recent study has demonstrated that benthic oxygen and carbon isotope records are phase-locked and amplitude-coupled at the 100-kyr band, but that neither is phase-locked to and amplitude-coupled with the 100-kyr eccentricity signal between 3 and 1 Ma. This phasing and amplitude mismatch of the 100-kyr band between 3 and 1 Ma between marine records and the eccentricity forcing signal has been called the “late Pliocene-early Pleistocene 100-kyr problem.” However, it remains unknown whether terrestrial paleoclimate records are consistent with marine records at the 100-kyr band. Here I show that loess monsoon records from China are amplitude-coupled with benthic oxygen and carbon isotope records at the 100-kyr band, but not with the 100-kyr eccentricity forcing between 3 and 1 Ma. This observation provides further evidence in support of a free 100-kyr oscillation as the cause of the 100-kyr band amplitude variability in paleoclimatic records between 3 and 1 Ma. In contrast, benthic oxygen isotope records and loess monsoon records at the 100-kyr band are not amplitude-coupled with 100-kyr benthic carbon isotope records over the last 0.4 million years, indicating that the late Pleistocene 100-kyr climatic cycles may not result exclusively from a free oscillation.

Hybrid coupled-cluster and perturbation method for extended systems of one-dimensional periodicity

A hybrid of the coupled-cluster singles and doubles (CCSD) and second-order Møller-Plesset perturbation (MP2) methods [M. Nooijen, J. Chem. Phys. 111, 10815 (1999); A. D. Bochevarov and C. D. Sherrill, ibid. 122, 234110 (2005); A. D. Bochevarov et al., ibid. 125, 054109 (2006)] is formulated and implemented for one-dimensional periodic extended systems, in which the excitation (T) amplitudes of active bands are determined iteratively by CCSD, while the T amplitudes of mixed active/inactive bands are held fixed at the first-order Møller-Plesset perturbation values. The occupied and virtual bands near the Fermi level, which can cause instability in MP2 when they are (quasi-)degenerate, are selected as active bands to be treated by CCSD, which can, in principle, resist such instability. Two contraction schemes of the T amplitudes (Contractions A and B) are considered. Contraction A is the one proposed for molecules and used also for extended systems because it is efficient for CCSD, but not necessarily so for the hybrid CCSD/MP2. Contraction B is introduced to be more optimally efficient for the hybrid CCSD/MP2 by maximizing the number of intermediate quantities made of the inactive T amplitudes and molecular integrals, which do not vary during CCSD iterations and are computed only once, stored, and reused. In an application to trans-polyacetylene, a smooth transition of the results of the hybrid CCSD/MP2 is observed toward those of CCSD and MP2 by increasing and decreasing, respectively, the number of active bands. With the smallest active space, the hybrid CCSD/MP2 with Contractions A and B achieves a speedup by a factor of 360 and 520, respectively, relative to CCSD. When all of the occupied bands and about half of the virtual bands are active, the hybrid CCSD/MP2 can recover 98% of the CCSD correlation energy or half of the difference between CCSD and MP2 at less than a tenth of the usual CCSD cost.

Car Interior Noise

To analyze the influence of the amplitude of different frequency bands of vehicle interior noise on subjective evaluation, an orthogonal array table was designed with 12 factors and three levels using the design of experiment (DOE) method. Furthermore, the range analysis was presented, and the optimal combinations for different categories were found. The sound quality can be improved by increasing, decreasing, or keeping the sound pressure level (SPL) in a certain frequency band.

Incidental Finding of Retinal Capillary Hemangioma

To better understand ‘when’ and ‘where’ wideband electrophysiological signals are altered by sedation.We generated animation movies showing electrocorticography (ECoG) amplitudes at eight spectral frequency bands across 1.0–116 Hz, every 0.1 s, on three-dimensional surface images of 10 children who underwent epilepsy surgery. We measured the onset, intensity, and variance of each band amplitude change at given nonepileptic regions separately from those at affected regions. We also determined the presence of differential ECoG changes depending on the brain anatomy.Within 20 s following injection of midazolam, beta (16–31.5 Hz) and sigma (12–15.5 Hz) activities began to be multifocally augmented with increased variance in amplitude at each site. Beta-sigma augmentation was most prominent within the association neocortex. Augmentation of low-delta activity (1.0–1.5 Hz) was relatively modest and confined to the somatosensory-motor region. Conversely, injection of midazolam induced attenuation of theta (4.0–7.5 Hz) and high-gamma (64–116 Hz) activities.Our observations support the notion that augmentation beta-sigma and delta activities reflects cortical deactivation or inactivation, whereas theta and high-gamma activities contribute to maintenance of consciousness. The effects of midazolam on the dynamics of cortical oscillations differed across regions.Sedation, at least partially, reflects a multi-local phenomenon at the cortical level rather than global brain alteration homogeneously driven by the common central control structure.

A Dual Effect of Au-Nanoparticles on Nucleic Acid Cholesteric Liquid-Crystalline Particles

Au-nanoparticles (size about 2 nm, but not 5 or 15 nm) are capable of effectively incorporating into quasinematic layers of particles of cholesteric liquid-crystalline dispersion formed by double-stranded nucleic acid molecules of various families (DNA and poly(I)xpoly(C)). This Au-size-dependent process is accompanied by a decrease in amplitudes of abnormal bands in the CD spectra specific to initial cholesteric liquid-crystalline dispersions and simultaneously by an appearance of plasmon resonance band in visible absorption spectrum. The study of properties of particles of cholesteric liquid-crystalline dispersion treated with Au-nanoparticles by means of various physico-chemical methods demonstrates that incorporation of Au-nanoparticles into quasinematic layers of these particles results in two effects: i) it facilitates reorganization of the spatial cholesteric structure of particles, and ii) it induces the formation of Au-clusters in the content of particles. It is not excluded that these effects represent a possible reason for genotoxicity of Au-nanopar- ticles.

Characterization of archeological glasses by micro‐Raman spectroscopy

AbstractThe method based on the deconvolution of the Raman spectra of glasses, proposed for the investigation of glazed ceramics by Colomban, is applied to archeological samples of glass of two different origins in an attempt to characterize the glass composition and the fictive temperature using a contactless, nondestructive spectroscopic technique. The samples investigated are glassy mosaic tesserae of Roman times from Massa Lubrense, Napoli, Italy, and medieval rosary grains found during the excavations in the church of San Martino di Rivosecco, Parma, Italy. The polymerization index, obtained as the ratio of the bending and stretching band amplitudes, suggests firing temperatures not less than 1000–1100 °C for both Roman and medieval glasses. From the wavenumber shift of some stretching bands at about 1050–1100 cm−1, the content of lead was estimated. The medieval samples show a lower Pb content, a result confirmed by elementary energy dispersive X‐ray spectral data. Copyright © 2010 John Wiley & Sons, Ltd.

Annealing of induced absorption in quartz glasses by ArF laser radiation

Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 — 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at λ = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered.

Topographic movie of intracranial ictal high-frequency oscillations with seizure semiology: Epileptic network in Jacksonian seizures

We developed a technique to produce images of dynamic changes in ictal high-frequency oscillations (HFOs) >40 Hz recorded on subdural electroencephalography (EEG) that are time-locked to the ictal EEG and ictal semiology video. We applied this technique to Jacksonian seizures to demonstrate ictal HFO propagation along the homunculus in the primary sensory-motor cortex to visualize the underlying epileptic network. We analyzed intracranial ictal EEGs from two patients with intractable Jacksonian seizures who underwent epilepsy surgery. We calculated the degrees of increase in amplitude within 40-80, 80-200, and 200-300 Hz frequency bands compared to the interictal period and converted them into topographic movies projected onto the brain surface picture. We combined these data with the ictal EEGs and video of the patient demonstrating ictal semiology. The ictal HFOs began in the sensory cortex and appeared concomitantly with the sensory aura. They then propagated to the motor cortex at the same time that focal motor symptoms evolved. As the seizure progressed, the ictal HFOs spread or reverberated in the rolandic region. However, even when the seizure became secondarily generalized, the ictal HFOs were confined to the rolandic region. In both cases, there was increased amplitude of higher frequency bands during seizure initiation compared to seizure progression. This combined movie showed the ictal HFO propagation corresponding to the ictal semiology in Jacksonian seizures and revealed the epileptic network involved in seizure initiation and progression. This method may advance understanding of neural network activities relating to clinical seizure generation and propagation.

Structural and optical properties of the gadolinium–lead–germanate glasses

Glasses in the system xGd 2O 3(100 − x)[7GeO 2·3PbO] with 0 ≤ x ≤ 40 mol% have been prepared from melt quenching method. The influence of gadolinium ions on structural behavior in lead–germanate glasses has been investigated using FTIR, UV-VIS and EPR spectroscopy. The structural changes have been analyzed with increasing rare earth concentration. FTIR data suggest that the glass network modifications has taken place mainly in the germanate part whereas the lead part remained unmodified and its network consists mainly from the [GeO 4], [GeO 6], [Ge 2O 7] structural units and with interconnected through Ge–O–Ge bridges in [GeO 4] structural units. The changes in amplitude and bandwidth of the UV-VIS bands ranging from 200 nm to 350 nm depend on the content of Gd 2O 3. By increasing the Gd 2O 3 content in the glass matrix, the optical band gap energy increases, indicating changes of the lattice parameters and that no non-bridging-oxygens form upon the addition of gadolinium oxide. The decreasing trend has been observed both in optical gap band energy and refractive index of oxide glasses at x = 10 mol% Gd 2O 3 indicating breaks up the [GeO 4] tetrahedral units bonds and create of non-bridging oxygen atoms. For sample with x ≥ 20 mol%, the gadolinium ions having a behavior of network formers ( g ≈ 4.8) will coordinate more with the excess of oxygen. Accordingly, the gadolinium ions are generally suspected to improve their environment of network formers.

Quantitative EEG in Patients With Alcohol‐Related Seizures

To investigate whether quantitative electroencephalography (QEEG) recorded within a few days after a generalized seizure can improve the discrimination between alcohol-related seizures (ARSs), seizures in epilepsy and other seizures. In addition, we wanted to evaluate the influence of various external factors on QEEG, e.g., drug use, time from seizure occurrence, and alcohol intake. An ARS was defined by (i) scores ≥8 in the Alcohol Use Disorders Identification Test (AUDIT) and (ii) no history of epilepsy. Twenty-two ARS patients, 21 epileptic patients with seizures (ES), 30 AUDIT-negative patients with seizures (OS), and 37 well-controlled epileptic outpatients (EPO) were included. EEG from 79 sciatica patients (SC) served as an additional control group. EEG was recorded in relaxed wakefulness with eyes closed. Spectral analysis of ongoing resting EEG activity was performed. For the main analysis, spectral band amplitudes were averaged across 14 electrodes. Major quantitative EEG abnormalities were mainly seen in the ES group. AUDIT score correlated negatively with QEEG band amplitudes in patients with seizures unrelated to alcohol, but not in the ARS group. Recent alcohol intake correlated negatively with delta and theta amplitude. We could not confirm that beta activity is increased in ARS subjects. A QEEG with slightly reduced alpha amplitude supports a clinical diagnosis of ARS. An abnormally slow QEEG profile and asymmetry in the temporal regions indicates ES. QEEG predicted the clinical diagnosis better than standard EEG.

In Situ Studies on the Switching Behavior of Ultrathin Poly(acrylic acid) Polyelectrolyte Brushes in Different Aqueous Environments

The pH-dependent switching of a poly(acrylic acid) (PAA) polyelectrolyte brush was investigated in situ using infrared spectroscopic ellipsometry (IRSE). The brush was synthesized by a "grafting to" procedure on silicon substrate with a native oxide layer. The overall thickness of the PAA brush in the dry state was approximately 5 nm. Reversible switching of the polymer brush was studied at titration from pH 2 to 10 and back in steps of 1 pH unit. The switching process was observed by monitoring the characteristic vibrational bands of the carboxylic groups of the PAA molecules. Decreasing of the C=O vibrational band amplitude and arising of a COO(-) vibrational band proved the chemical changes in the molecular structure of the brushes due to changes of the pH value in the aqueous solution. Due to the strong absorption of these bands in the IR region, the switching process could be monitored clearly. Switching the brush in several cycles with increasing and decreasing pH value showed a hysteresis-like behavior. For the first time, such hysteresis is observed in titration experiments of polyelectrolyte brushes. This behavior is attributed to the complex mechanisms of the ion's mobility in the brush layer which is explained with a suggested simplifying model describing the influence of ions inside the brush layer. In addition to the IRSE measurements, X-ray standing waves (XSW), in situ visible ellipsometry, and contact angle measurements have been performed and were in good agreement with the results from IRSE. Repetition of the in situ measurement cycles proved the good reversibility of the switching process which is highly important for practical applications of polymer brushes.

Implementation of a new fast direct torque control algorithm for induction motor drives

Induction motor (IM) drives based on direct torque control (DTC) allow high dynamic performance to be obtained with very simple control schemes. The conventional DTC has two main drawbacks. The first one is the variation of the switching frequency according to the amplitude of the hysteresis bands and the motor operating speed, whereas the second is that the selection of voltage vectors is not optimised inside the flux hysteresis band to give fast torque response, because of the nature of the hysteresis controllers. This study proposes a new DTC method for IM, which enables fast torque response and constant switching frequency. This is achieved by optimising the selection of the voltage vectors to give maximum rate of torque increase. Simulation and hardware implementation results show that both the torque and speed responses are faster than the old method. In addition, the effect of variation of the IM parameters on the system performance is taken into consideration.

Hypnotizability-related EEG alpha and theta activities during visual and somesthetic imageries

Hypnotizability is a cognitive multidimensional trait that involves peculiar imagery characteristics. Subjects with high- (Highs) and low (Lows)-susceptibilities to hypnosis have shown different levels of skill at visual and somesthetic-guided imageries performed during upright stance. The aim of this experiment is to study the modulation of the EEG alpha and theta band amplitude during guided visual and somesthetic imageries in Highs and Lows, as these rhythms are responsive to the cognitive activities involved in mental imagery. Our results show that, at variance with standing subjects, subjects in both groups in a semi-reclined position report higher vividness and lower effort for visual than for somesthetic imagery. EEG patterns however are different between the two groups. Highs exhibit a more widespread alpha desynchronization and slightly different EEG patterns during visual and somesthetic imageries, while Lows show segregated alpha- and theta-desynchronization, without any difference between the tasks. Our results indicate that different, hypnotizability-related cognitive strategies, that are revealed by differences in EEG modulation, are responsible for the similar subjective experience associated with visual and somesthetic imageries in Highs and Lows. In addition, in both groups higher order mental representation of different sensory modalities might be subserved by a unique integrated neural network.

Now You'll Feel It, Now You Won't: EEG Rhythms Predict the Effectiveness of Perceptual Masking

Do ongoing brain states determine conscious perception of an upcoming stimulus? Using the high temporal resolution of EEG, we investigated the relationship between prestimulus neuronal oscillations and the perceptibility of two competing somatosensory stimuli embedded in a backward masking paradigm. We identified two prestimulus EEG signatures predictive for a suprathreshold yet weak target stimulus to become perceptually resistant against masking by a stronger distractor stimulus: (i) over left frontal cortex a desynchronization of the regional beta rhythm (approximately 20 Hz) 500 msec prior to a perceived target, and (ii) a subsequent additional attenuation of both mu (approximately 10 Hz) and beta "idling" rhythms over those pericentral sensorimotor cortices which are going to process the upcoming target stimulus. Furthermore, across subjects the probability for target perception strongly correlates with the individual absolute level of pre-target amplitudes in these frequency bands and locations. These signatures significantly differed from the EEG characteristics preceding detected and undetected single stimuli. We suggest that the early activation of left frontal areas involved in top-down attentional control is critical for preventing backward masking and leads the preparation of primary sensory cortices: The ensuing prestimulus suppression of sensory idling rhythms warrants an intensified poststimulus processing, and thus, effectively promotes conscious perception of suprathreshold target stimuli embedded into an ecologically relevant condition featuring competing environmental stimuli.

Plasticity changes in the brain in hypnosis and meditation

AbstractNeuroscientific evidence interprets both hypnotic trance induction and different meditation traditions as modified states of consciousness that emphasize attention, concentration and the letting go of thoughts, but they differ in terms of sensory input, processing, memory, and the sense of time. Furthermore, hypnosis is based on the suggestibility of a person and meditation on mindfulness; therefore it is not surprising to find differential brain plasticity changes. We analysed shared and non‐shared neural substrates using electroencephalography (EEG), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI). Most pronounced EEG changes were in deep as compared to light hypnosis (step‐by‐step induction) and in arm levitation where suggested movement was perceived as external. In a within‐subject‐design changes in brain activity during hypnosis and Tibetan Buddhist meditation were compared. High amplitudes in alpha frequency bands were most pronounced with meditation at frontal positions and with hypnosis in central and temporal locations. Significantly greater activity in theta 2 band was observed only with hypnosis in both hemispheres. PET cerebral activation patterns of imagery‐mediated learning were analysed in hypnosis in a within‐subject‐design. Compared with baseline the learning of high‐imagery words was associated with (i) more pronounced bilateral activation in the occipital cortex and prefrontal areas and (ii) improved memory performance. Visual illusion in hypnosis was studied with fMRI, analysed with Granger Causality Mapping, showing changes in the effective connectivity relations of fusiform gyrus, anterior cingulate cortex and intraparietal sulcus. Little is known about the neurobiological basis of the process of enhancing cognitive and emotional traits in meditation. In a longitudinal fMRI study attention abilities through intensive Soto‐Zen meditation were investigated before (baseline), after training (6 months) and at follow‐up (9 months). After six months differences were observed in the left inferior and left superior frontal gyrus; after 9 months activations in the left precuneus. Taken together, the findings advance understanding of the neural mechanisms that underlie hypnosis and meditation. Further studies with a greater sample size are needed to explore the differences and commonalities of hypnosis and different meditation techniques. Copyright © 2009 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.

Negative covariation between task-related responses in alpha/beta-band activity and BOLD in human sensorimotor cortex: An EEG and fMRI study of motor imagery and movements

Similar to the occipital alpha rhythm, electroencephalographic (EEG) signals in the alpha- and beta-frequency bands can be suppressed by movement or motor imagery and have thus been thought to represent the “idling state” of the sensorimotor cortex. A negative correlation between spontaneous alpha EEG and blood-oxygen-level-dependent (BOLD) signals has been reported in combined EEG and fMRI (functional Magnetic Resonance Imaging) experiments when subjects stayed at the resting state or alternated between the resting state and a task. However, the precise nature of the task-induced alpha modulation remains elusive. It was not clear whether alpha/beta rhythm suppressions may co-vary with BOLD when conducting tasks involving varying activations of the cortex. Here, we quantified the task-evoked responses of BOLD and alpha/beta-band power of EEG directly in the cortical source domain, by using source imaging technology, and examined their covariation across task conditions in a mixed block and event-related design. In this study, 13 subjects performed tasks of right-hand, right-foot or left-hand movement and motor imagery when EEG and fMRI data were separately collected. Task-induced increase of BOLD signal and decrease of EEG amplitudes in alpha and beta bands were shown to be co-localized at the somatotopic sensorimotor cortex. At the corresponding regions, the reciprocal changes of the two signals co-varied in the magnitudes across imagination and movement conditions. The spatial correspondence and negative covariation between the two measurements were further shown to exist at somatotopic brain regions associated with different body parts. These results suggest an inverse functional coupling relationship between task-induced changes of BOLD and low-frequency EEG signals.

Educational problems related to quantitative EEG changes in benign childhood epilepsy with centrotemporal spikes

The relationship between educational problems and clinical/electroencephalographic aspects was assessed in 38 children with benign childhood epilepsy with centrotemporal spikes (BECTS). Children were assessed using the School Performance Test; questionnaires on learning difficulties administered to parents and teachers; the Wechsler Intelligence Scale for Children, Third Edition; and EEGs. Absolute and relative amplitudes in the classic bands (quantitative EEG) and characteristics of epileptiform activity on the EEG were examined. Educational problems were observed in 7 (18.4%) children with BECTS. In this subgroup, relative alpha amplitudes at the central and parietal electrodes were lower as compared with those of the BECTS subgroup with normal educational performance and a control group matched for age, gender, and socioeconomic status. The data indicated a possible relationship between alterations in background brain electrical activity and the tendency toward inferior educational performance in children with BECTS. This study suggested that quantitative EEGs are a possible physiological tool in the assessment of cognitive aspects in children with BECTS.

Chemical and Structural Changes in a pH-Responsive Mixed Polyelectrolyte Brush Studied by Infrared Ellipsometry

This work provides direct chemical and structural insight into pH-dependent changes of an ultrathin (d=12 nm) mixed polyelectrolyte brush. In-situ infrared spectroscopic ellipsometry was used for the first time to study the gradual pH-responsive behavior of the brush, constituted of weak anionic and cationic polyelectrolytes, poly(acrylic acid) (PAA) and poly(2-vinylpyridine) (P2VP), respectively. The pH-dependent infrared fingerprints in the mid-infrared spectral range were analyzed as a function of chemical and structural changes in the mixed brush caused by pH changes. Thereby, the IR spectra were directly correlated to different chemical states of the brush, giving previously not accessible new information on the ionization of the thin film. In contrast to other techniques (e.g., classical attenuated total reflection IR spectroscopy) we used almost plane Si-substrates for the IR ellipsometric approach with application of a single reflection mode. The optical path through Si is of minimal length, which makes a large spectral range accessible. For the most pronounced bands of the carboxyl group at 1718 cm(-1) and the carboxylate ion at 1565 cm(-1), the band amplitudes were correlated with the degree of ionization of the carboxylic groups. Interpretation of the pH-dependent changes in the spectral signature reveals gradual changes of the chemical structures of the mixed brush between three distinct switchable states: strongly ionized PAA at pH 10, strongly ionized P2VP at pH 2, and mainly nonionized functional groups in a "dry" PAA-P2VP polyelectrolyte complex in the range from pH=4 to pH=7. At intermediate pH, the IR spectra confirm the previously made hypothesis of the formation of a polyelectrolyte complex between P2VP and PAA in the mixed brush. From IR spectra it is also concluded that the polyelectrolyte complex is formed as a result of a small fraction of ionized functional groups.