Band Suppression Research Articles

Deep brain stimulation for Parkinson's disease modulates high-frequency evoked and spontaneous neural activity

Deep brain stimulation is an established therapy for Parkinson's disease; however, its effectiveness is hindered by limited understanding of therapeutic mechanisms and the lack of a robust feedback signal for tailoring stimulation. We recently reported that subthalamic nucleus deep brain stimulation evokes a neural response resembling a decaying high-frequency (200-500 Hz) oscillation that typically has a duration of at least 10 ms and is localizable to the dorsal sub-region. As the morphology of this response suggests a propensity for the underlying neural circuitry to oscillate at a particular frequency, we have named it evoked resonant neural activity. Here, we determine whether this evoked activity is modulated by therapeutic stimulation – a critical attribute of a feedback signal. Furthermore, we investigated whether any related changes occurred in spontaneous local field potentials. Evoked and spontaneous neural activity was intraoperatively recorded from 19 subthalamic nuclei in patients with Parkinson's disease. Recordings were obtained before therapeutic stimulation and during 130 Hz stimulation at increasing amplitudes (0.67–3.38 mA), ‘washout’ of therapeutic effects, and non-therapeutic 20 Hz stimulation. Therapeutic efficacy was assessed using clinical bradykinesia and rigidity scores. The frequency and amplitude of evoked resonant neural activity varied with the level of 130 Hz stimulation (p < .001). This modulation coincided with improvement in bradykinesia and rigidity (p < .001), and correlated with spontaneous beta band suppression (p < .001). Evoked neural activity occupied a similar frequency band to spontaneous high-frequency oscillations (200-400 Hz), both of which decreased to around twice the 130 Hz stimulation rate. Non-therapeutic stimulation at 20 Hz evoked, but did not modulate, resonant activity. These results indicate that therapeutic deep brain stimulation alters the frequency of evoked and spontaneous oscillations recorded in the subthalamic nucleus that are likely generated by loops within the cortico-basal ganglia-thalamo-cortical network. Evoked resonant neural activity therefore has potential as a tool for providing insight into brain network function and has key attributes of a dynamic feedback signal for optimizing therapy.

Performance Analysis of 80 GHz-Millimeter Wave Radio over Dispersive Fiber

Abstract The generation of 80 GHz millimeter wave (mm-wave) signal and its transmission over single mode fiber (SMF) is presented. The mm-wave signal is generated with dual parallel dual drive Mach Zehnder modulators using frequency quadrupling of 20 GHz radio frequency signal. Transmission of generated mm-wave signal over SMF has been investigated. The impact of varying modulation depth on optical side band suppression ratio and radio frequency spurious suppression ratio for different extinction ratios (ER) is studied. Further, the impact of dispersion, on received power is also analyzed. Error analysis between analytical and simulation results is carried out. It has been observed, that increasing ER leads to reduction in both peak error and mean error and the received power is reduced under the combined effect of second and third order dispersion at very high modulation depth.

Optimal design for high-performance passive dynamic vibration absorbers under random vibration

This work is motivated to determinate the optimal design for various types of Dynamic Vibration Absorbers (DVAs) under the effect of random loads. These devices are the following: DVAs connected in parallel or series; two degree-of-freedom traditional dynamic vibration absorber (2dof-TVA) with translational and rotational motion; and inerter-based DVAs (IDVA-C6, C4, and C3). These types of DVAs were selected by their high effectiveness for suppressing vibration however a comparative study on their dynamic performance has not yet been performed. Two different excitation sources of random loads are studied in this paper which are random ground motion and force excitation. An optimum design for majority of these devices has not yet been computed when subjected to random ground motion excitation, and therefore in this paper are computed. For random force excitation, some numerical solutions for the optimal design of these devices have not yet reported which in this paper are computed in order to compare the dynamic performance for each device with respect to that of the classic DVA. For both random excitation cases, the H2 optimization criteria is used to analytically compute the variance of squared modulus of frequency response of the undamped primary structure, and then nonlinear unconstrained optimization problems are formulated in order to obtain the optimal design. Numerical solutions revealed that the IDVA-C6, C3, and DVAs connected in series presents more than 13% and 10% improvement with respect to the classic DVA for random ground motion and force excitation cases, respectively. These devices can widen the suppression band (SB) from 30% to 40% for mass ratios values from 1% to 10%. It means that devices are more effective and robust for mitigating vibration than the classic DVA. In addition, the rotational inertial double tuned mass damper (IDVA-C6) has the same relative dynamic performance (RDP) and suppression band index (SB) than the double-mass dynamic vibration absorber arranged in series. For practical application where the mounting space of the DVA is extremely reduced, the DVAs connected in series could be more convenient to use than IDVA-C6. The concept of equivalent mass ratio is introduced in order to explain the superiority of these devices with respect to the classic DVA. Finally, in H∞ optimization criteria, the IDVA-C6 presents the same vibration amplitudes at all excitation frequency range and suppression band than DVAs connected in series.

Influence of the La3+, Eu3+, and Er3+ Doping on Structural, Optical, and Electrical Properties of BiFeO3 Nanoparticles Synthesized by Microwave-Assisted Solution Combustion Method

In this study, nanocrystalline (18–28 nm) perovskite-like bismuth ferrite rare earth-doped powders (Bi0.9RE0.1FeO3, where RE = La (BLaFO), Eu (BEuFO), and Er (BErFO)) were obtained by microwave-assisted modification of solution combustion synthesis (SCS). The influence of high load La3+, Eu3+, and Er3+ doping on structural, optical, and electrical properties of BiFeO3 was investigated. It was found that rare earth doping along with fast phase formation and quenching significantly distorts the crystal cells of the obtained materials, which results in the formation of mixed rhombohedral- (R3c-) orthorhombic (Pbnm) crystal structures with decreased lengths of Bi-O and Fe-O bonds along with a decreasing radius size of doping ions. This promotes reduction of the optical band gap energy and suppression of ionic polarization at high frequencies and results in enhanced dielectric permittivity of the materials at 1 MHz.

Design of bicontinuous metallic nanocomposites for high-strength and plasticity

We demonstrate design of Cu/Mo nanocomposite thin films with bicontinuous intertwined morphologies for high strength and plastic deformability. Through co-sputtering Cu and Mo at different temperatures, nanocomposites with lateral and random concentration modulations (LCMs and RCMs) were fabricated. Ligament size and coherency of the Cu/Mo interfaces was also controlled via the deposition conditions. It was discovered that nanocomposites with LCM structure and coherent interfaces have high strength but limited deformability. Enhanced deformability was achieved when the interface was altered to semi-coherent, although plasticity was localized in kink bands. The RCM structure design with semi-coherent interfaces showed an excellent combination of high flow strength and plastic deformability due to suppression of shear and kink bands.

A novel EBG structure with spiral line bridges for radiation suppression in marine VHF band

The very high frequency (VHF) marine communication band (156–165 MHZ) is consequential for ship navigation safety, having the radiation limitation of 24dB·μV/m in this band and 54dB·μV/m in the adjacent band. The existing technologies are not enough to achieve targeted suppression of the radiation disturbance in this frequency band at PCB-level, which is equivalent to imposing strict limits on the whole test frequency band, making it necessary to pay an extra cost to achieve electromagnetic compatibility of marine electronic equipment. A spiral line bridged electromagnetic band gap (SL-EBG) is proposed for the radiation suppression of the marine VHF band. Based on the calculation of parasitic parameter, the equivalent circuit of SL-EBG is modeled; simulation and measurement are also performed to analyze the characteristic of SL-EBG. The stopband of the proposed EBG structure is 100MHz–300MHz, which S21 parameter is −27dB for two units, −59dB for four units and −72dB for five units at 160MHz.

A Compact LTCC Decoupling-Network Based on Coupled-Resonator for Antenna Interference Suppression of Adjacent Frequency Bands

A low-temperature co-fired ceramic (LTCC) coupled resonator decoupling network (CRDN) with asymmetric input/output (I/O) couplings for suppressing interference between two adjacent frequency bands is proposed in this paper. Based on LTCC multilayer technology, a second-order CRDN module is realized by strongly coupled semi-lumped LC resonators in a very small volume of 3.2 mm $\times2.5$ mm $\times1.2$ mm. A wide range of mutual admittance and different self-admittances of the CRDN can be realized by adjusting the asymmetric I/O couplings. Thus, a satisfactory decoupling performance covering two contiguous bands, as well as good matching in each band, can be realized without additional matching networks. To prove the concept, two planar inverted-F antennas working in TD-LTE and Wi-Fi frequency bands, along with the corresponding decoupling network, are designed, fabricated, and tested. The measured results have demonstrated that more than 15-dB isolation improvement can be achieved within the two operating bands, showing the feasibility of this ”one-fit-all” integrated solution. More importantly, the design methodology and circuit topology presented in this paper are general and can be applied to practical multi-input multi-output system applications.

High‐Frequency Communications Response to Solar Activity in September 2017 as Observed by Amateur Radio Networks

AbstractNumerous solar flares and coronal mass ejection‐induced interplanetary shocks associated with solar active region AR12673 caused disturbances to terrestrial high‐frequency (HF, 3–30 MHz) radio communications from 4–14 September 2017. Simultaneously, Hurricanes Irma and Jose caused significant damage to the Caribbean Islands and parts of Florida. The coincidental timing of both the space weather activity and hurricanes was unfortunate, as HF radio was needed for emergency communications. This paper presents the response of HF amateur radio propagation as observed by the Reverse Beacon Network and the Weak Signal Propagation Reporting Network to the space weather events of that period. Distributed data coverage from these dense sources provided a unique mix of global and regional coverage of ionospheric response and recovery that revealed several features of storm time HF propagation dynamics. X‐class flares on 6, 7, and 10 September caused acute radio blackouts during the day in the Caribbean with recovery times of tens of minutes to hours, based on the decay time of the flare. A severe geomagnetic storm with Kpmax = 8+ and SYM‐Hmin = −146 nT occurring 7–10 September wiped out ionospheric communications first on 14 MHz and then on 7 MHz starting at ∼1200 UT 8 September. This storm, combined with affects from additional flare and geomagnetic activity, contributed to a significant suppression of effective HF propagation bands both globally and in the Caribbean for a period of 12 to 15 days.

Effect of constraint and latent hardening ratio on the plastic flow around a crack tip in a hardening FCC single crystal

In this work, the crack tip fields in the neighborhood of a stationary mode I crack in a hardening Cu single crystal, under tensile load was investigated. A modified boundary layer (MBL) simulation was performed with the implementation of Bassani and Wu (1991) hardening model while taking into account the crystal elastic anisotropy. The effect of latent hardening ratio (LHR) on the stress and strain fields was studied by considering three different values of LHR, q, viz. diagonal hardening (q=0) and latent hardening (q=1,1.4). In addition, the effect of crack tip constraint representing different test specimens and load conditions was examined with the inclusion of T-stress through the imposed displacement boundary condition. Important observations from this work include the suppression of kink band, presence of elastic sectors, and the occurrence of triple slip near the crack tip. The increase of T-stress suppressed the plastic strain accumulation and showed a decrease in the number of triple slip sectors near the crack tip. Whereas, the increase in q made the triple slip regions slightly prominent with wider angular spread for non-negative T. But, for negative T case, rise in q caused a suppression in the angular spread of triple slip regions. Also, the implementation of T-stress allowed for a correlation between full 3D and 2D plane strain simulations in the analysis of crack tip fields for hardening single crystals. The present study offers a comprehensive investigation of the effect of crack tip constraint and latent hardening ratio on the crack tip fields for hardening FCC single crystals.

Enhanced photoelectric performance of rutile SnO2 by double-hole-assisted coupling of carbon and sulfur

Photoelectric performance of (C, S) co-doped SnO2 was explored by an integrated strategy combining first principle calculation with experimental measurement. The exploration began with theoretical calculation upon geometry characteristic and electronic structure of pure and (C, S) co-doped SnO2, then follow by experimental measurement. Namely, pure and different ratios of (C, S) co-doped SnO2 were prepared and characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). And photoelectric performance of the prepared pure and (C, S) co-doped SnO2 electrodes was studied. Theoretical calculation result indicate that carbon and sulfur atom interact intensely to each other by lattice distortion. Fully filled energy levels are introduced to the top of the valence band, resulting effective reduction of band gap value and suppression of charged defects. Consequently, the photoelectric performance of SnO2 is improved. Double-hole-assisted coupling mechanism of dopants in SnO2 is interpreted to reveal the interaction of C and S. Besides, experimental results indicate that all samples are rutile phase with the dopants carbon and sulfur entered into SnO2 crystal by substituting oxygen. 5% co-doped sample shows the most homogeneous spherical shape and dispersed character, which is provided with the maximum photocurrent value (6.8 μA/cm2) and minimum electrochemical impedance. Theoretical calculation and experiment jointly indicate that (C, S) co-doped SnO2 possess superior photoelectric performance. The doping method of double-hole-assisted coupling may contribute to the design of highly active tin oxide-based photoelectric materials, and also pave the way for modification of other congener materials.

Passivation of yellow luminescence of MOCVD grown InGaN/GaN heterostructures by Nitrogen - ion implantation

Abstract The effect of Nitrogen - ion implantation and post annealing treatment on Metal Organic Chemical Vapor Deposited (MOCVD) InGaN/GaN heterostructured samples were studied using structural, optical, morphological and electrical characterizations. Three samples with various implantation dosage (1 × 1015, 3 × 1015 and 5 × 1015 ions/cm2) has been studied. A clear increase in crystallinity was observed for post annealed implanted samples from HRXRD. The roughness of the sample increases from 1.3 nm to 5.8 nm when fluency of N - ion increases but is reduced after annealing. The PL spectra for our ion implanted sample shows that there is a remarkable suppression of the YL bands (∼500 nm–650 nm) as the dosage of ions are increased due to the passivation of the YL centers. Hall Effect Measurement shows N+ implanted samples offers high resistance which is reduced on annealing.

Structural, Optical, and Luminescent Properties of ZnO:Ga and ZnO:In Ceramics

Zinc oxide optical ceramics were prepared by the hot uniaxial pressing technique. Nominally undoped and gallium- and indium-doped ceramics were studied. Undoped ceramics with a thickness of 0.5 mm had a total transmittance of about 65% in the visible range and exhibited mainly deep level luminescence at 600 nm. Doping of the ceramics resulted in the appearance of free charge carriers, suppression of the defect emission band, and enhancement of the excitonic luminescence intensity. The typical concentration of donor centers in doped ceramics was on the order of 1019 cm−1. Admixture of the dopants also decreased the average grain size of the ceramics and, in the case of indium-doped ceramics, affected their morphology. With respect to the excitonic emission intensity, the optimal concentration of dopants was 0.028 at% of Ga3+ and 0.045 at% of In3+. The maximum intensity of excitonic luminescence in indium-doped ceramics was about 1.5 times higher than that in gallium-doped ones. Luminescence decay curves of the ceramics with suppressed defect emission had a main decay time constant of 0.7 ns.

Suppression of the green emission, texturing, solute-atom diffusion and increased electron-phonon coupling induced by Ni in sol-gel ZnNiO thin films

Zn1−xNixO thin films (nominal x = 0, 0.01, 0.02, 0.04, 0.1 and 0.2) were synthesized on silicon substrates through a sol-gel/dip-coating technique. Samples were studied by X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, Rutherford backscattering spectrometry and depth-profiling X-ray photoelectron spectroscopy. The results from X-ray diffraction show growth in the wurtzite crystal structure for all samples, with cubic NiO being detected as a secondary phase for x = 0.2. While for x = 0 (pure ZnO) no texture is present, for 0 ≤ x ≤ 0.1 strong preferential crystallization along the c-axis is observed. A tendency for Ni diffusion towards the film/Si substrate interface was observed. The formation of substitutional ZnxNi1−xO solid solution for 0.01 ≤ x ≤ 0.04 is suggested by the results. Photoluminescence spectra exhibit strong near band edge UV emission and suppression of deep defect-related emission in the visible upon Ni+2 incorporation into the ZnO lattice. As in pure ZnO, the UV emission in ZnNiO at room temperature is dominated by the first two phonon replica of the excitonic emission, however the LO phonon energy (ħωLO) is reduced by up to ∼15 meV in the 0 ≤ x ≤ 0.04 range. Due to this reduction of ħωLO, the exciton-phonon coupling increases, in consistency with a corresponding expected increase of the Fröhlich coupling constant with decreasing ħωLO.

Asymmetric Substrate Integrated Waveguide Leaky Wave Antenna with Open Stop Band Suppression and Radiation Efficiency Equalization through Broadside

Asymmetric Substrate Integrated Waveguide Leaky Wave Antenna with Open Stop Band Suppression and Radiation Efficiency Equalization through Broadside

Optical millimeter wave signal generation with frequency 16-tupling using cascaded MZMs and no optical filtering for radio over fiber system

BackgroundAn optical Millimeter Wave (MM-Wave) generation with high frequency multiplication factor is very attractive solution to avoid the use of high frequency local oscillators at the central station. MethodsIn this paper, a frequency 16 tupling technique is demonstrated with the use of four cascaded MZMs. With the proper adjustment of DC bias of the Mach-Zehnder Modulators (MZM), amplitude and phases of the RF Local oscillators, MM-Wave with a frequency 16 times the input RF LO is demonstrated. ResultsThe cascaded structure has resulted very low modulation index of 2.827 and 54 dB and 42 dB of OSSR and RFSSR respectively. Analysis of both optical and RF sided band suppression ratios under non-ideal cases are also simulated and presented. Further, 10 Gbps NRZ data transmission performance over 50 km Single Mode Fiber (SMF) is also evaluated. ConclusionsThe proposed structure can tolerate up to few degrees of non-ideal parameter variation and is very simple to realize.

Theory and Experiment of Two-Section Two-Resistor Wilkinson Power Divider With Two Arbitrary Frequency Bands

In this paper, a novel design theory of two-section two-resistor Wilkinson power divider (WPD) is introduced. By selecting two different physical lengths of two-section transmission lines (TLs), two arbitrary frequency band WPD can be achieved. Compared with the former work, the designable frequency ratio range $u$ can be extremely extended from $1 to $1 , general design equations for characteristic impedances, physical lengths, absorption resistors, and frequency ratio ranges are newly derived and proved from even- and odd-mode analysis. Because of no capacitors or inductors, the proposed WPD can be used for high-frequency applications. Spurious band of $S_{21}$ appears between two passbands under the condition of two different physical lengths; therefore, a $\Pi$ -type dual-band transformer is newly introduced to replace single TL for spurious band suppression. We proved that $\Pi$ -type structure could effectively suppress spurious band of $S_{11}$ , maintain two arbitrary frequency passband of $S_{21}$ , and provide an extra isolation band of $S_{32}$ at center frequency. Finally, three proposed WPD examples with $\Pi$ -type structure are selected with different frequency ratios, where frequency ratio $u = 4$ in Example A, $u = 6$ in Example B, and $u = 20$ in Example C are designed and fabricated in the experiment. Measured results show good agreement with the theoretical results.

Design of 6-gon-Shaped Notch Filter for Cognitive Radio Applications

This paper presents a 6-gon-shaped bandpass and notch filters for Cognitive Radio (CR) applications. The bandpass filter consists of a 6-gon-shaped multiple mode resonator with interdigital coupling at both ends. The notch filter is derived from bandpass filter by embedding four identical Embedded Open Stubs (EOS) nearby the multiple mode resonators that introduce narrow band suppression in the desired passband. Such bandpass filter with notching band is required in practical CR systems in order to effectively sense the spectrum and avoid the interference between the systems working in same environment with the same frequency. The filter is simulated using an electromagnetic solver, IE3D. The group delay obtained for bandpass filter is below 0.2[Formula: see text]ns. With the above structural features, the overall dimension of the filter is [Formula: see text][Formula: see text]mm2 and the fractional bandwidth (FBW) of the proposed bandpass filter is more than 100% with optimal performances in terms of insertion loss, return loss, group delay and phase.

Neurophysiology underlying influence of stimulus reliability on audiovisual integration.

We tested the predictions of the dynamic reweighting model (DRM) of audiovisual (AV) speech integration, which posits that spectrotemporally reliable (informative) AV speech stimuli induce a reweighting of processing from low-level to high-level auditory networks. This reweighting decreases sensitivity to acoustic onsets and in turn increases tolerance to AV onset asynchronies (AVOA). EEG was recorded while subjects watched videos of a speaker uttering trisyllabic nonwords that varied in spectrotemporal reliability and asynchrony of the visual and auditory inputs. Subjects judged the stimuli as in-sync or out-of-sync. Results showed that subjects exhibited greater AVOA tolerance for non-blurred than blurred visual speech and for less than more degraded acoustic speech. Increased AVOA tolerance was reflected in reduced amplitude of the P1-P2 auditory evoked potentials, a neurophysiological indication of reduced sensitivity to acoustic onsets and successful AV integration. There was also sustained visual alpha band (8-14Hz) suppression (desynchronization) following acoustic speech onsets for non-blurred vs. blurred visual speech, consistent with continuous engagement of the visual system as the speech unfolds. The current findings suggest that increased spectrotemporal reliability of acoustic and visual speech promotes robust AV integration, partly by suppressing sensitivity to acoustic onsets, in support of the DRM's reweighting mechanism. Increased visual signal reliability also sustains the engagement of the visual system with the auditory system to maintain alignment of information across modalities.

Systematic Optical Design of Constituting Layers to Realize High‐Performance Red‐Selective Thin‐Film Organic Photodiodes

AbstractA high‐performance red‐selective thin‐film organic photodiode (OPD) is designed. Dual‐band absorbing poly[(2,5‐bis(2‐hexyldecyloxy)phenylene)‐alt‐(5,6‐difluoro‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]‐thiadiazole)] (PPDT2FBT) is introduced as the photoactive donor layer of a planar heterojunction OPD in conjunction with a sol–gel synthesized ZnO acceptor layer. The active layer thickness is systematically controlled to suppress band II absorption (λmax = 420 nm) of PPDT2FBT without sacrificing band I absorption (λmax = 650 nm). The optimal PPDT2FBT thickness is 320 nm to realize red‐selective absorption while maintaining the low dark current density of the OPD (predicted by optical simulation conducted using the transfer matrix method). In addition, the introduction of ZnO (with a strategically determined thickness) as an acceptor layer in front of PPDT2FBT in an illumination pathway enables further suppression of band II absorption because of the blue color filter effect. Consequently, the resulting OPD with a device architecture of indium tin oxide/ZnO/PPDT2FBT/MoO3/Ag shows an outstanding red‐selective photodiode performance with peak detectivity up to 3.04 × 1012 Jones and a high linear dynamic range of 116 dB.

High Performance Microstrip Low Pass Filter for Wireless Communications

A microstrip low-pass filter using T-shaped resonators is designed to achieve an ultra-sharp transition band and high suppression level. The performance of the resonators is investigated based on an LC equivalent circuit and a transfer function to compute the equations of the transmission zeros. This filter has an acceptable stopband with high insertion loss (28 dB) by adopting a rectangular suppressor. Also, the width of the transition band is 0.09 GHz (with – 3 and − 40 dB attenuation levels), that exhibits a very high sharpness (ξ = 411 dB/GHz). The proposed filter with a 3 dB cut-off frequency (fc) of 1.32 GHz presents a high return loss in the passband (17 dB) and high figure of merit of 57,073. The designed filter is fabricated and measured, demonstrating sufficient agreement between the simulation and experimental results.