Channel Filter Research Articles

Binding modes of two scorpion toxins to the voltage-gated potassium channel kv1.3 revealed from molecular dynamics.

Molecular dynamics (MD) simulations are used to examine the binding modes of two scorpion toxins, margatoxin (MgTx) and hongotoxin (HgTx), to the voltage gated K+ channel, Kv1.3. Using steered MD simulations, we insert either Lys28 or Lys35 of the toxins into the selectivity filter of the channel. The MgTx-Kv1.3 complex is stable when the side chain of Lys35 from the toxin occludes the channel filter, suggesting that Lys35 is the pore-blocking residue for Kv1.3. In this complex, Lys28 of the toxin forms one additional salt bridge with Asp449 just outside the filter of the channel. On the other hand, HgTx forms a stable complex with Kv1.3 when the side chain of Lys28 but not Lys35 protrudes into the filter of the channel. A survey of all the possible favorable binding modes of HgTx-Kv1.3 is carried out by rotating the toxin at 3° intervals around the channel axis while the position of HgTx-Lys28 relative to the filter is maintained. We identify two possible favorable binding modes: HgTx-Arg24 can interact with either Asp433 or Glu420 on the vestibular wall of the channel. The dissociation constants calculated from the two binding modes of HgTx-Kv1.3 differ by approximately 20 fold, suggesting that the two modes are of similar energetics.

Multi-layered mesh generation and user subroutine development based on an Eulerian–Eulerian approach for soot filtration visualization in a three-dimensional particulate filter model

A three-dimensional model is developed for computational fluid dynamics analysis of soot filtration processes in a wall flow–type particulate filter based on an Eulerian–Eulerian numerical approach. The primary objective of this study is to accurately capture the local values of filtration parameters, such as volume porosity, collection efficiency, and soot mass deposited, through isotropically discretized computational grids within the multi-layered porous wall regions. Most commercial computational fluid dynamics codes do not have the ability to generate structured mesh with ordered cell index or allow expressing mathematical recursive operation or handling time array through defined user field functions. For these reasons, it is difficult to utilize the code in situations where complex algorithms and mathematical treatments are required. Therefore, custom-build user subroutines, written with C++ programming language, are developed and integrated with the model to calculate localized soot mass distributions in each layer of porous wall. New recursive and computationally efficient algorithms are developed utilizing the functional attributes of the computational fluid dynamics code and coupled with the modified unit collector mechanism in order to obtain temporal and local filtration efficiency. Simulations enabled quantitative visualization of the detailed filtration processes along the filter wall and channel, including the time evolution of filtration parameters, which is difficult to detect experimentally. The model revealed correlations between wall flow pattern and rearrangement behaviors of filtration parameters and provided insights into the soot cake layer profiles with respect to both the length and the width of the channel.

Analysis of time delay difference due to parametric mismatch in matched filter channels

SummaryThis paper presents an analysis of the time delay difference between the outputs of two matched filter channels, in the presence of parametric mismatch. A theorem for computing the cross‐correlation value between two signals is developed. From the cross‐correlation theorem, expressions are developed that estimate the effect of parametric mismatch in the differential time delay (DTD) for filters of arbitrary type and order and input signals of arbitrary form. The accuracy of these expressions is simulated and then demonstrated experimentally using a carefully designed setup. Filter design considerations that attempt to minimize spurious DTD in high‐precision time delay estimation systems are presented. Copyright © 2014 John Wiley & Sons, Ltd.

The conserved potassium channel filter can have distinct ion binding profiles: structural analysis of rubidium, cesium, and barium binding in NaK2K.

Potassium channels are highly selective for K(+) over the smaller Na(+). Intriguingly, they are permeable to larger monovalent cations such as Rb(+) and Cs(+) but are specifically blocked by the similarly sized Ba(2+). In this study, we used structural analysis to determine the binding profiles for these permeant and blocking ions in the selectivity filter of the potassium-selective NaK channel mutant NaK2K and also performed permeation experiments using single-channel recordings. Our data revealed that some ion binding properties of NaK2K are distinct from those of the canonical K(+) channels KcsA and MthK. Rb(+) bound at sites 1, 3, and 4 in NaK2K, as it does in KcsA. Cs(+), however, bound predominantly at sites 1 and 3 in NaK2K, whereas it binds at sites 1, 3, and 4 in KcsA. Moreover, Ba(2+) binding in NaK2K was distinct from that which has been observed in KcsA and MthK, even though all of these channels show similar Ba(2+) block. In the presence of K(+), Ba(2+) bound to the NaK2K channel at site 3 in conjunction with a K(+) at site 1; this led to a prolonged block of the channel (the external K(+)-dependent Ba(2+) lock-in state). In the absence of K(+), however, Ba(2+) acts as a permeating blocker. We found that, under these conditions, Ba(2+) bound at sites 1 or 0 as well as site 3, allowing it to enter the filter from the intracellular side and exit from the extracellular side. The difference in the Ba(2+) binding profile in the presence and absence of K(+) thus provides a structural explanation for the short and prolonged Ba(2+) block observed in NaK2K.

Approximate pressure drop and filtration efficiency expressions for semi‐open wall‐flow channels

AbstractSemi‐open wall‐flow channels are conventional filter channels with missing plugs either in the frontal or rear side. This configuration has lately become an interesting modelling issue with respect to partial filters designed for the emerging markets and as a special case of wall‐flow filters, that have suffered damage due to regeneration. This paper presents the development of approximate analytical expressions for the estimation of pressure drop and filtration efficiency of semi‐open channels. In order to facilitate the derivation, realistic assumptions are employed and the results are extensively validated using a commercial simulation software, able to solve the differential equations system of the 1D channel model. The validation covers important design parameters and operational conditions, namely filter permeability, length, mass flow rate and soot loading. It is shown that the analytical expressions can predict all trends and moreover offer clear physical explanations. The pressure drop calculation does not exceed 6% of the numerical prediction, while the filtration efficiency absolute error lies within 6% except for specific cases. Finally, a partially failed DPF is simulated using the developed expressions and a commercial CFD package in order to estimate the failure effect on filtration and pressure drop performance. In this way, the usability of the proposed modelling approach is demonstrated.

Embolic Activity During In Vivo Cardiopulmonary Bypass

Neurologic injury after cardiac surgery is principally associated with emboli. Although much work has focused on surgical sources of emboli, less attention has been focused on emboli associated with the heart–lung machine. We tested whether emboli are associated with discrete processes during cardiopulmonary bypass (CPB). One hundred patients undergoing cardiothoracic surgery were enrolled between April 2008 and May 2011 at a single medical center. During each surgical procedure, emboli were counted in three CPB locations: the venous side (Channel 1), before the arterial line filter (Channel 2), and after the arterial line filter (Channel 3). We used prespecified event markers to identify perfusionist interventions. Identical circuits were used on all patients. Of the 100 patients enrolled, 62 underwent isolated coronary artery bypass grafting (CABG), 17 underwent isolated valve operations, and 21 underwent CABG plus valve. Median counts across Channels 1, 2, and 3 were 69,853, 3,017, and 1,251, respectively. The greatest contributor to emboli in Channels 1, 2, and 3, respectively, were achieving the calculated CPB flow, opening of the electronic arterial line clamp, and introducing a hemofilter. The circuit technology was efficient in reducing total emboli counts from Channels 1–2 irrespective of the size of the emboli. Nearly 71% of all emboli 30–100 mm in size were removed from the circuit between Channels 2 and 3. No significant association was found between emboli counts and S100B release. Emboli occur frequently during CPB and are predominantly associated with the initiation of bypass, operation of the electronic arterial line clamp, and the initiation of a hemofilter. Continued work to reduce the occurrence of emboli is warranted.

CeO2-based catalysts with engineered morphologies for soot oxidation to enhance soot-catalyst contact.

As morphology plays a relevant role in solid/solid catalysis, where the number of contact points is a critical feature in this kind of reaction, three different ceria morphologies have been investigated in this work as soot oxidation catalysts: ceria nanofibers, which can become organized as a catalytic network inside diesel particulate filter channels and thus trap soot particles at several contact points but have a very low specific surface area (4 m2/g); solution combustion synthesis ceria, which has an uncontrolled morphology but a specific surface area of 31 m2/g; and three-dimensional self-assembled (SA) ceria stars, which have both high specific surface area (105 m2/g) and a high availability of contact points. A high microporous volume of 0.03 cm3/g and a finer crystallite size compared to the other morphologies suggested that self-assembled stars could improve their redox cycling capability and their soot oxidation properties. In this comparison, self-assembled stars have shown the best tendency towards soot oxidation, and the temperature of non-catalytic soot oxidation has dropped from 614°C to 403°C in tight and to 552°C in loose contact conditions, respectively. As far as the loose contact results are concerned, this condition being the most realistic and hence the most significant, self-assembled stars have exhibited the lowest T10% onset temperature of this trio (even after ageing), thus proving their higher intrinsic activity. Furthermore, the three-dimensional shape of self-assembled stars may involve more of the soot cake layer than the solution combustion synthesis or nanofibers of ceria and thus enhance the total number of contact points. The results obtained through this work have encouraged our efforts to understand soot oxidation and to transpose these results to real diesel particulate filters.

A Narrowband Superconducting Quadruplexer With High Isolation

A manifold-coupled microstrip superconducting quadruplexer with high isolation for S-band communications systems is presented. The problems of channel isolation and common-port impedance matching in the design of the quadruplexer are addressed and studied. An equivalent circuit model for a trial diplexer is built to analyze the isolation between two channel filters with Chebyshev responses. Analyses and simulations show that channel isolation is mainly determined by the resonators that are closest to the noncommon ports. A circuit layout is proposed for the quadruplexer to obtain high isolation. Moreover, a binary matching network is designed to minimize the undesired interactions between the four channel filters in the quadruplexer. The quadruplexer is successfully designed with the proposed methods and fabricated. The measured results show high performance and match well with the simulations.

Design of Compact Superconducting Diplexer With Spiral Short-Circuited Stubs

Three types of impedance-matching structures for diplexer design are analyzed and calculated in this paper. Calculations show that different matching structures should be selected for size reduction, depending on the input impedance of the channel filters in the diplexer. Two channel filters in the superconducting microstrip diplexer at the P-band are designed with spiral resonators and capacitively coupled feedlines. The diplexer is then constructed with an impedance-matching structure of spiral short-circuited stubs. The compact diplexer has a size of 22.9 mm × 21.7 mm on an MgO substrate, which amounts to only 0.101 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> ×0.096 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> is the guided wavelength of the 50- Ω line on the substrate at the midband frequency. The fabricated device exhibits high performance, and its measurements match the simulations well. The experimental insertion loss of both channels is less than 0.13 dB. The common-port return loss is greater than 18.9 dB, and the isolation between the two channels is greater than 60 dB.

Auditory-inspired pitch extraction using a synchrony capture filterbank for speech signals

The question of how harmonic sounds produce strong, low pitches at their fundamental frequencies, F0s, has been of theoretical and practical interest to scientists and engineers for many decades. Currently the best auditory models for F0 pitch, [e.g., Meddis and Hewitt, J. Acoust. Soc. Am. 89(6), 2866–2894 (1991)] are based on bandpass filtering (cochlear mechanics), half-wave rectification and low-pass filtering (haircell transduction and synaptic transmission), channel autocorrelations (all-order interspike interval statistics) aggregated into a summary autocorrelation, and an analysis that determines the most prevalent interspike intervals. As a possible alternative to autocorrelation computations, we propose an alternative model that uses an adaptive Synchrony Capture Filterbank (SCFB) in which groups of filter channels in a spectral neighborhood are driven exclusively (captured) by dominant frequency components that are closest to them. The channel outputs (for frequencies below 1500 Hz) are then adaptively phase aligned with respect to a common time reference to compute a Summary Phase Aligned Function (SPAF), aggregated across all channels, from which F0 is easily extracted.

Compact microstrip loop resonator-based bandstop filters for sub-GHz channels

This article presents two microwave bandstop filters based on microstrip loop resonators with capacitors. The filters have steep band edges, are compact and easy to fabricate. They are applicable for protection against strong signals in nearby channels. Construction of filters, capabilities of band shift compensation, and tuning are discussed. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:993–997, 2014

Investigation of the effect of biodiesel blends on the performance of a fuel additive-assisted diesel filter system

The results of full-scale regeneration tests with a unit silicon carbide diesel particulate filter installed on a single-cylinder diesel engine are presented. Two sets of transient regeneration experiments, one for each fuel used, with high level of exhaust gas flow rate (normalized per filter volume) and markedly different levels of soot loading were performed. The test fuels were conventional diesel (denoted as B0) and B20 biodiesel blend. The effect of the biodiesel on filter regeneration was further investigated by means of infrared thermography. The main objective was to investigate the catalytic soot ignition and regeneration propagation when the engine is fueled by biodiesel blends. Special focus was on the temperature distribution across the filter channels and the evolution of the regeneration at the central and peripheral part of the filter. The results indicated a faster evolution of the regeneration with lower overall filter wall temperatures with favorable effects on the filter durability, when the engine is fueled by B20.

Modeling and effect of distortion product generated by harmonic complex tones

To study deeply the effect of distortion product on auditory perception, a functional model is proposed to generate distortion products at frequencies below those of primary stimuli. The operations include calculating different power of the stimuli, low pass filtering, searching optimum weights, and summing the weighted signals across all filtering channels. The model uses simulate annealing and genetic algorithm to search the globally optimum weights. Moreover, this paper studies the effect of distortion products on pitch perception for unresolved harmonics based on the proposed model. Results find that distortion products could enhance the resolvability and temporal information of the harmonics. Thus, it is suggested to use background noise with appropriate sound levels to mask distortion products to reduce the effect on pitch perception.

Kalman filter and semi-blind technique-based channel estimation for coded STBC multi-antenna set-ups in faded wireless channels

Alamouti's space-time block coding STBC with diversity gains provide improved performance in faded channels. Alamouti's transmit diversity scheme, however, relies on the availability of accurate channel state information CSI. If the assistance of channel estimation is considered, the overall performance can be further enhanced. In this work, we report the performance of three separate approaches to deal with coded multi-antenna setups. These are STBC Coded MISO-MIMO Set-up with BPSK and QPSK, pilot assisted channel estimation with Walsh-Hadamard code and semi-blind channel estimation using Kalman filter KF. The first two proposed techniques are able to obtain an error performance closer to a known CSI in severely faded channel. The semi-blind estimation technique using KF with Walsh-Hadamard coded pilot symbols incorporates orthogonality to facilitate decoupling of multiple data blocks after STBC decoding. The simulated results prove the effectiveness of the channel estimators in time varying Rayleigh faded channel.

Design and Optimization of a Compact Superconducting Quadruplexer at VHF-Band With an Accurate Equivalent Circuit Model

This paper presents the modeling and optimization of a manifold-coupled superconducting quadruplexer at VHF-band. The quadruplexer consists of four individually designed channel filters with a bandwidth of 400 kHz centered at 216, 224, 232, and 240 MHz, respectively, connected to a common manifold. The complex interactions between the channel filters make the design and optimization of the quadruplexer difficult and even impossible. An equivalent circuit for the manifold and the capacitive external couplings of the four channel filters in the quadruplexer is presented. The parameters of the equivalent circuit are accurately extracted from electromagnetic simulations. Afterward, the equivalent circuit is optimized to compensate for the interactions between the channel filters and obtain a good common-port return loss and channel transfer characteristics. Thereafter, the design of the individual channel filters is improved according to the optimized parameters of the equivalent circuit. The superconducting quadruplexer is successfully designed and fabricated. The measurements show high performance and match well with the simulations. The experimental insertion losses of the four channels are less than 0.45 dB, the center frequency discrepancies of the four channels are less than 40 kHz, the common-port return loss is greater than 16.3 dB, and the out-of-band rejection is higher than 90 dB. Moreover, a high isolation greater than 75 dB between the channels is achieved.

Optimal Transmit Filters for ISI Channels under Channel Shortening Detection

We consider channels affected by intersymbol interference with reduced-complexity, mutual information optimized, channel-shortening detection. For such settings, we optimize the transmit filter, taking into consideration the reduced receiver complexity constraint. As figure of merit, we consider the achievable information rate of the entire system and with functional analysis, we establish a general form of the optimal transmit filter, which can then be optimized by standard numerical methods. As a corollary to our main result, we obtain some insight of the behavior of the standard waterfilling algorithm for intersymbol interference channels. With only some minor changes, the general form we derive can be applied to multiple-input multiple-output channels with intersymbol interference. To illuminate the practical use of our results, we provide applications of our theoretical results by deriving the optimal shaping pulse of a linear modulation transmitted over a bandlimited additive white Gaussian noise channel which has possible applications in the faster-than-Nyquist/time packing technique.

Sodium and potassium competition in potassium-selective and non-selective channels

Potassium channels selectively conduct K+, primarily to the exclusion of Na+, despite the fact that both ions can bind within the selectivity filter. Here we perform crystallographic titration and single-channel electrophysiology to examine the competition of Na+ and K+ binding within the filter of two NaK channel mutants; one is the potassium-selective NaK2K mutant and the other is the non-selective NaK2CNG, a CNG channel pore mimic. With high-resolution structures of these engineered NaK channel constructs, we explicitly describe the changes in K+ occupancy within the filter upon Na+ competition by anomalous diffraction. Our results demonstrate that the non-selective NaK2CNG still retains a K+-selective site at equilibrium, whereas the NaK2K channel filter maintains two high-affinity K+ sites. A double-barrier mechanism is proposed to explain K+ channel selectivity at low K+ concentrations.

A 40-MHz-to-1-GHz Fully Integrated Multistandard Silicon Tuner in 80-nm CMOS

To address a worldwide market, silicon tuners have to support a wide range of frequencies and standards, motivating the use of architectures inspired by the software-defined-radio paradigm. DVB-T, DVB-C, ATSC-A/74 as well as cable modems (DOCSIS) and analog TV require low-noise, high-linearity front-ends with high-performance local oscillators. Integrability and cost dictate minimization of external components. Unlike common approaches [1,2], the silicon tuner presented in this paper features one single-ended RF input for the entire 40MHz-to-1GHz band, requires no external SAW filters or balun, and supports channel bandwidths from 5 to 8MHz. The analog IF output is programmable from 5MHz to 44MHz, supporting both modern digital demodulators and legacy analog demodulators. The receiver uses a low-IF architecture and is able to process the broadband input spectrum through the combination of a low-noise programmable RF filter, a digitally calibrated harmonic-rejection mixer, and a wide dynamic range ADC, whose intrinsic filtering nature and large SNDR make the tuner compatible with the very demanding ATSC A/74 standard. The chip's sophisticated digital back-end provides channel filtering and image rejection for the signal path, runs the RF and IF AGCs, and controls a variety of calibration schemes used to improve performance and robustness toward PVT variations. The chip has been designed in a scaled 90nm CMOS technology, requires a 1.8V analog supply and a 1.0V digital supply, and dissipates <450mW during normal operation and <10mW in standby mode. The BoM is limited to a single LNA bias inductor and a 40MHz crystal, thus minimizing the required footprint and cost.

원전 증기발생기 와전류검사 장치의 전기적 특성 측정

원전 증기발생기는 원자로 냉각재 계통에서 발생한 열에너지를 터빈 계통의 주급수에 전달하여 터빈을 회전시키기 위한 증기를 생산하는 일종의 열교환기이다. 증기발생기 전열관의 손상은 증기발생기의 구조적 및 누설 건전성 유지 능력을 저해시키기 때문에 주기적으로 와전류검사를 수행하여 전열관의 건전성을 평가한다. 증기발생기 전열관의 건전성 평가는 보통 원자로 연료 재장전 기간 중에 수행된다. 현재 국내 증기발생기 전열관에 적용되는 와전류검사는 KEPIC 및 ASME 코드 요건에 따라 수행되며, 와전류검사 수행에 필요한 검사 시스템은 와전류검사 장치와 수집된 신호를 평가하기 위한 평가 프로그램으로 구성된다. 검사에 적용되는 와전류검사 시스템을 구성하는 핵심기기인 와전류검사 장치는 ASME 및 KEPIC 코드에서 총 고조파 왜곡율, 입출력 임피던스, 증폭기 직선성 및 안정성, 위상 직선성, 대역폭 및 복조필터 응답, 디지털 변환, 채널 간섭 등과 같은 전기적 특성을 측정하도록 규정하고 있다. 이에 따라 본 논문에서는 국내 최초로 개발한 원전 증기발생기 와전류검사 장치의 전기적 특성 측정을 위한 ASME 및 KEPIC 코드 요건을 설명하고, 이 요건에 따른 증기발생기 와전류검사 장치의 전기적 특성의 측정 결과를 제시하였다. A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

Ostéotomie pelvienne percutanée chez l’enfant paralysé cérébral non marchant : 22 hanches opérées avec des résultats préliminaires encourageants

A diverse range of molecular interactions can occur between engineered nanomaterials (ENM) and biomembranes, some of which could lead to toxic outcomes following human exposure to ENM. In this study, we adapted electrophysiology methods to investigate the ability of 20 nm polystyrene nanoparticles (PNP) to induce pores in model bilayer lipid membranes (BLM) that mimic biomembranes. PNP charge was varied using PNP decorated with either positive (amidine) groups or negative (carboxyl) groups, and BLM charge was varied using dioleoyl phospholipids having cationic (ethylphosphocholine), zwitterionic (phosphocholine), or anionic (phosphatidic acid) headgroups. Both positive and negative PNP induced BLM pores for all lipid compositions studied, as evidenced by current spikes and integral conductance. Stable PNP-induced pores exhibited ion selectivity, with the highest selectivity for K+ (PK/PCl ~ 8.3) observed when both the PNP and lipids were negatively charged, and the highest selectivity for Cl− (PK/PCl ~ 0.2) observed when both the PNP and lipids were positively charged. This trend is consistent with the finding that selectivity for an ion in channel proteins is imparted by oppositely charged functional groups within the channel's filter region. The PK/PCl value was unaffected by the voltage-ramp method, the pore conductance, or the side of the BLM to which the PNP were applied. These results demonstrate for the first time that PNP can induce ion-selective pores in BLM, and that the degree of ion selectivity is influenced synergistically by the charges of both the lipid headgroups and functional groups on the PNP.