DC Domain Research Articles

DCX Uses Distinct Domains to Sequentially Nucleate and Stabilize Microtubules

Doublecortin (DCX) is a microtubule associated protein essential for brain development. Mutations in DCX cause severe mental disability or epilepsy due to unsuccessful neuronal migration. Previous studies have shown that DCX facilitates the formation of new microtubules and increases their lifetimes. The tertiary structure of DCX consists of two globular microtubule binding domains, an N-terminal DC domain (DC-1) and a C-terminal DC domain (DC-2). However, it remains unclear how these domains modulate microtubule dynamics.

Resonant controller of single‐stage off‐board EV charger in G2V and V2G modes

This study presents the control design and implementation of a three-phase single-stage off-board electric vehicle (EV) charger. The charger is controlled to perform four quadrants operation in active–reactive (P–Q) power plane. Generally, the control of the EV charger consists of two control loops, i.e. exterior (slow) loop and fast-acting interior loop. Since the signals to be regulated in outer loop are DC in nature, they can be easily handled by regular proportional plus integral regulators. The inner loop control may also be performed in the DC domain, but inaccuracy involved in determining the parameter-dependent decoupling terms and difficulty in setting the gain for fast-acting inner loops make it unfavourable. Therefore, the inner control is performed in AC domain, where the signals are periodic. The proportional plus resonant controller is found to be very useful in tracking such type of periodic signals of fixed frequency, and accordingly, it has been designed and successfully implemented for the proposed work. The proposed methodology has been tested for eight different modes in the P–Q-plane. The system is simulated in MATLAB/Simulink environment and implemented in real time with a scaled-down hardware prototype.

DC Hard Faults Detection and Localization in Analog Circuits Using Fuzzy Logic Techniques

This paper demonstrates a novel technique based on the use of a fuzzy logic system and the simulation before test (SBT) approach for hard faults detection and localization in analog electronic circuits comprising bipolar transistors. For this purpose, first, simulations of the circuit under test (CUT) are performed before the test stage by investigating the response of the circuit under test in faulty and fault-free conditions. Following this, two signatures parameters—output voltage and supply current—are observed and used for the fault diagnosis; the CUT is simulated using the OrCAD/PSpice software, and the output is analyzed in the DC domain. This method is validated through an inverter amplifier based on the uA741 operational amplifier. Then the results of different experiments are presented to demonstrate the applicability of the proposed method by increasing its efficiency.

Microtubule Nucleation and Stabilization by Doublecortin

Doublecortin (DCX) is a microtubule (MT)-associated protein indispensable for migrating neurons during brain development. DCX nucleates and stabilises MTs via homologous DC domains. The C-terminal DC domain (C-DC) is separated from the N-terminal counterpart (N-DC) by a 42-residue linker. Intellectual disability (smooth brain) and epilepsy-causing mutations cluster around both DC domains. Thus, both domains are thought to interact with MTs, but their exact roles remain obscure. For MT nucleation, the naturally bent tubulin dimers associating longitudinally and laterally need to straighten up to form cylindrical lattice. Stabilization of such lattice relies on counteracting the natural tendency of tubulin to curl outward. The DCX binding site on the MT lattice is at the vertex of four tubulin dimers, so DCX binding stabilizes both longitudinal and lateral lattice contacts. But it is neither clear which of the two DC domains mediates this MT-stabilizing interaction nor which is involved in MT nucleation. We found that the construct in which C-DC was replaced with another N-DC showed much lower MT-nucleating activity and – in contrast to wild-type DCX – it produced not only the physiological 13-protofilament (PF) MT architecture, but also 14-PF MTs. Near-atomic resolution cryo-EM reconstructions enabled visualisation of the structural differences between the DC domains suggesting that N-DC has higher affinity for the mature MT lattice while the newly-formed lattice is predominantly decorated with C-DC. Molecular modelling suggests that C-DC can bind between moderately curved PFs, whereas N-DC cannot. The predicted C-DC binding mode largely overlaps with patient mutations. Taken together, the data suggest that C-DC facilitates nucleation of physiological 13-PF MTs, while N-DC gradually replaces C-DC along the lattice, ensuring robust stabilisation of the straight polymer.

Exploring a Novel Methodology for DC Analysis in Memristive Circuits with Multiple Operating Points

The memristor and the memristive systems have represented a challenge to be incorporated into a simulation procedure in order to carry out novel applications. The discovery of the physical memristor by the HP Labs has caused widespread interest for modeling the memristive behavior in order to combine this new fundamental circuit element with traditional devices. DC domain analysis represents a fundamental stage in the circuit simulators because the DC operating points are used as starting points in other analysis domains. In this work, the DC response of mathematical memristive systems is explored in order to recognize different scenarios according to the nature of the memristive variable. The piecewise linear formulation has been used in order to establish the memristive phenomenon in the device. As a result of this exploration, a novel DC modeling methodology for memristive systems is introduced. This methodology is capable of generating current–voltage branch relationships that represent the memristive behavior of the device. The memristive model proposed is characterized in order to determinate the impact of the variables on the memristive behavior. Moreover, the existence of multiple DC operation points (MOPs) is treated and the conditions for the occurrence of MOPs are established by two cases of study. Finally, the new contributions of this work compared to previous work are presented and discussed.

A Novel Method Towards Time-Efficient Fault Analysis of Analog and Mixed-Signal Circuits

A novel method of nodal impedance calculation is presented in this paper. This method is capable of time-efficient calculation of arbitrary two-point complex impedance in an analog and mixed-signal circuit and could improve the development time of impedance-based tests both in DC and AC domain. A fault simulation methodology based on the proposed method is described in detail. Several experiments are provided that prove the time efficiency of the method. Experimental application showing the benefits of the method on a real circuit is provided as well.

A droop control incorporated dc equivalent power flow method for distribution and low voltage systems

Rapid growth in the use of distributed generations in low voltage (LV) and medium voltage (MV) network is attributed the distribution systems ‘active’, which has made distribution power flow analysis a hot area of research. In this paper, a droop control based distribution power flow formulation is proposed and realized in the dc domain, which is independent of the various assumptions made in existing distribution power flow methods, e.g., unconstrained slack bus capacity, fixed power loads and generations, low R/X ratio etc. And, these assumptions are ill-suited to low and medium voltage systems in both autonomous and grid-connected topology, usually powered by small generators, intermittent renewable sources and also considering the high-resistance interconnecting power lines. The proposed method ensures performance enhancement with better load sharing among sources within the allowable limit. An optimization based numerical solution approach is used for solving the proposed technique. The performance of the system is investigated using a 10-bus low voltage microgrid system and on three IEEE distribution networks, viz., 12-bus, 33-bus, and 69-bus systems. The effectiveness of the proposed method is investigated and compared with existing literature works in terms of reduced power losses, improved voltage profile, R/X sensitivity, and maximum loading point.

Self-Heat Characterizations and Modeling of Multifinger nMOSFETs for RF-CMOS Applications

The purpose of this paper is to characterize and model the self-heating effect (SHE) of multifinger n-channel MOSFETs (nMOSFETs). The amount of SHE is small enough not to be analyzed for single-finger bulk CMOS devices. However, SHE should be considered for multifinger nMOSFETs that are mainly used for RF-CMOS applications. The SHE mechanism was analyzed based on a 2-D device simulator. SHE model equations are derived and implemented in the BSIM6 model with Verilog-A language used in a SPICE simulator. The model improves speed and accuracy of multifinger nMOSFETs simulations. To extract thermal resistance and capacitance, an advanced ac conductance method using a vector network analyzer is developed to obtain $I_{{\textrm {ds}}}$ – $V_{{\textrm {ds}}}$ measurement without increasing temperatures with the proposed model and extracted parameters, excellent agreement has been obtained between measurements and simulations in dc and S-parameter domain, whereas the original BSIM6 shows inconsistency between the static dc and the small signal ac simulations due to the lack of SHE. Unlike the widely used subcircuits-based SHE models, including Silicon-On-Insulator MOSFET and power MOSFET models, the proposed SHE model can converge in large-scale circuits even for transient simulations.

Role of the Dc domain of the bacterial hook protein FlgE in hook assembly and function.

The bacterial flagellar hook acts as a universal joint to smoothly transmit torque produced by the motor to the filament. The hook protein FlgE assembles into a 55 nm tubular structure with the help of the hook cap (FlgD). FlgE consists of four domains, D0, Dc, D1 and D2, arranged from the inner to the outer part of the tubular structure of the hook. The Dc domain contributes to the structural stability of the hook, but it is unclear how this Dc domain is responsible for the universal joint mechanism. Here, we carried out a deletion analysis of the FlgE Dc domain. FlgEΔ4/5 with deletion of residues 30 to 49 was not secreted into the culture media. FlgEΔ5 and FlgEΔ6 with deletions of residues 40 to 49 and 50 to 59, respectively, still formed hooks, allowing the export apparatus to export the hook-filament junction proteins FlgK and FlgL and flagellin FliC. However, these deletions inhibited the replacement of the FlgD hook cap by FlgK at the hook tip, thereby abolishing filament formation. Deletion of residues 50 to 59 significantly affected hook morphology. These results suggest that the Dc domain is responsible not only for hook assembly but also for FlgE export, the interaction with FlgK, and the polymorphic supercoiling mechanism of the hook.

Simultaneous fusion, compression, and encryption of multiple images

We report a new spectral multiple image fusion analysis based on the discrete cosine transform (DCT) and a specific spectral filtering method. In order to decrease the size of the multiplexed file, we suggest a procedure of compression which is based on an adapted spectral quantization. Each frequency is encoded with an optimized number of bits according its importance and its position in the DC domain. This fusion and compression scheme constitutes a first level of encryption. A supplementary level of encryption is realized by making use of biometric information. We consider several implementations of this analysis by experimenting with sequences of gray scale images. To quantify the performance of our method we calculate the MSE (mean squared error) and the PSNR (peak signal to noise ratio). Our results consistently improve performances compared to the well-known JPEG image compression standard and provide a viable solution for simultaneous compression and encryption of multiple images.

Auto Correction Feedback for Ripple Suppression in a Chopper Amplifier

This paper proposes a local feedback, named Auto Correction Feedback (ACFB), for a chopper amplifier to suppress its offset related ripple. It nulls out the amplifier's initial offset in DC domain which would otherwise become modulated ripple at the chopper amplifier's output, instead of filtering the ripple with a post filter. The proposed ACFB has been implemented as a stand alone chopper operational amplifier fabricated in 0.64 mm2 die area with a 0.35 μm standard CMOS process. It achieves 10 μV maximum input offset voltage and 95 nV/rt(Hz) input voltage noise spectrum density flat down to 0.1 Hz, with a 1.8-5.5 V supply voltage range and 13 μA supply current dissipation. When configured in unity-gain, the typical magnitude of the input referred ripple at the chopping frequency is 9.4 μVrms, as a result of 45 dB ripple attenuation obtained by the ACFB. The analysis, the simulation, and the measurement prove there is no noise penalty due to the addition of ACFB.

Structural basis of the autolysis of AaHIV suggests a novel target recognizing model for ADAM/reprolysin family proteins

AaHIV, a P-III-type snake venom metalloproteinase (SVMP), consists of metalloproteinase/disintegrin/cysteine-rich (MDC) domains and is homologous to a disintegrin and metalloproteinase (ADAM) family proteins. Similar to brevilysin H6 and jararhagin, AaHIV can easily autolyse to release a stable protein named acucetin, which contains disintegrin-like and cysteine-rich domains. In this study, we determined the crystal structure of AaHIV and investigated the autolysis mechanism. Based on the structure of AaHIV and the results from docking experiments, we present a new model for target recognition in which two protein molecules form a functional unit, and the DC domain of one molecule is used for target recognition while the M-domain of the other is used for target proteolysis. Our results shed new light on the mechanism of target recognition and processing in ADAM/reprolysin family proteins.

Analogue electronic circuit diagnosis based on ANNs

Feed-forward artificial neural networks (ANNs) have been applied to the diagnosis of nonlinear dynamic analogue electronic circuits. Using the simulation-before-test (SBT) approach, a fault dictionary was first created containing responses observed at all inputs and outputs of the circuit. The ANN was considered as an approximation algorithm to capture mapping enclosed within the fault dictionary and, in addition, as an algorithm for searching the fault dictionary in the diagnostic phase. In the example given DC and small signal frequency domain measurements were taken as these data are usually given in device’s data-sheets. A reduced set of data per fault (DC output values, the nominal gain and the 3 dB cut-off frequency, measured at one output terminal) was recorded. Soft (parametric) and catastrophic (shorts and opens) defects were introduced and diagnosed simultaneously and successfully. Large representative set of faults was considered, i.e., all possible catastrophic transistor faults and qualified representatives of soft transistor faults were diagnosed in an integrated circuit. The generalization property of the ANNs was exploited to handle noisy measurement signals.

Pragmatic Circuits: Signals and Filters

Pragmatic Circuits: Signals and Filters is built around the processing of signals. Topics include spectra, a short introduction to the Fourier series, design of filters, and the properties of the Fourier transform. The focus is on signals rather than power. But the treatment is still pragmatic. For example, the author accepts the work of Butterworth and uses his results to design filters in a fairly methodical fashion. This third of three volumes finishes with a look at spectra by showing how to get a spectrum even if a signal is not periodic. The Fourier transform provides a way of dealing with such non-periodic signals. The two other volumes in the Pragmatic Circuits series include titles on DC and Time Domain and Frequency Domain. These short lecture books will be of use to students at any level of electrical engineering and for practicing engineers, or scientists, in any field looking for a practical and applied introduction to circuits and signals. The author's “pragmatic” and applied style gives a unique and helpful “non-idealistic, practical, opinionated” introduction to circuits

Magnesium and Phosphate Ions Enable NAD Binding to Methylenetetrahydrofolate Dehydrogenase-Methenyltetrahydrofolate Cyclohydrolase

The mitochondrial NAD-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase (NMDMC) is believed to have evolved from a trifunctional NADP-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase-synthetase. It is unique in its absolute requirement for inorganic phosphate and magnesium ions to support dehydrogenase activity. To enable us to investigate the roles of these ions, a homology model of human NMDMC was constructed based on the structures of three homologous proteins. The model supports the hypothesis that the absolutely required Pi can bind in close proximity to the 2'-hydroxyl of NAD through interactions with Arg166 and Arg198. The characterization of mutants of Arg166, Asp190, and Arg198 show that Arg166 is primarily responsible for Pi binding, while Arg198 plays a secondary role, assisting in binding and properly orienting the ion in the cofactor binding site. Asp190 helps to properly position Arg166. Mutants of Asp133 suggest that the magnesium ion interacts with both Pi and the aspartate side chain and plays a role in positioning Pi and NAD. NMDMC uses Pi and magnesium to adapt an NADP binding site for NAD binding. This adaptation represents a novel variation of the classic Rossmann fold.

Doublecortin Kinase-2, a Novel Doublecortin-related Protein Kinase Associated with Terminal Segments of Axons and Dendrites

The microtubule (MT)-associated DCX protein plays an essential role in the development of the mammalian cerebral cortex. We report on the identification of a protein kinase, doublecortin kinase-2 (DCK2), with a domain (DC) highly homologous to DCX. DCK2 has MT binding activity associated with its DC domain and protein kinase activity mediated by a kinase domain, organized in a structure in which the two domains are functionally independent. Overexpression of DCK2 stabilizes the MT cytoskeleton against cold-induced depolymerization. Autophosphorylation of DCK2 strongly reduces its affinity for MTs. DCK2 and DCX mRNAs are nervous system-specific and are expressed during the period of cerebrocortical lamination. DCX is down-regulated postnatally, whereas DCK2 persists in abundance into adulthood, suggesting that the DC sequence has previously unrecognized functions in the mature nervous system. In sympathetic neurons, DCK2 is localized to the cell body and to the terminal segments of axons and dendrites. DCK2 may represent a phosphorylation-dependent switch for the reversible control of MT dynamics in the vicinity of neuronal growth cones.

Ferrielectricity in Chiral Smectic Cβ of an Antiferroelectric Liquid Crystal

The switching current behavior and the complex dielectric constant under DC electric bias field and domain structures ofan antiferroelectric liquid crystal, 4-(1-methylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), wereinvestigated as a function of optical purity and cell thickness, and the ferrielectricity of the chiral smectic Cβ phase (SmCβ*) was discussed. Optically pure samples show two-step decrease in the real part of complex dielectric constant with increasing DC bias field. The first decrease corresponds to the suppression of the ferroelectric Goldstone mode, which is also suppressed by decreasing cell thickness. The second step, which is observed even in the chiral smectic Cα phase (SmCα*), corresponds to the suppression of a new relaxation mode induced by DC electric bias field. Three peaks of the switching current were observed in SmCβ* and also in the lower-temperature region of SmCα*. Temperature dependence curves of the peak positionsare continuously connected together at the phase transition temperature between SmCβ* and SmCα*. It can be said that the antiferroelectricity of SmCα* is conserved in SmCβ*, and that the ferrielectricity of SmCβ* may consist of the ferroelectricityof SmC* and the antiferroelectricity of SmCα*. Striped domains observed in SmCβ* after removing the DC electric bias field can be considered to be the SmCα* phase.

Expression and chromosomal localization of KIAA0369, a putative kinase structurally related to Doublecortin.

Neuropathy in vertebrates can be a consequence of failure of genes involved in the nervous system to be expressed at the correct times and levels during embryonic life. Recently, a brain specific gene, Doublecortin, was cloned and was shown to have mutations in X-linked lissencephaly and double cortex syndrome. KIAA0369 is a putative kinase that is structurally related to Doublecortin. We compared the expression of KIAA0369 with that of Doublecortin, both of which were expressed specifically or predominantly in fetal brain among 20 different tissues examined. The deduced products of both genes contain a unique domain (the Doublecortin [DC] domain), but KIAA0369 also contains a calmodulin-dependent kinase (CaM kinase)-like domain following the DC domain. We found at least four splicing variants of KIAA0369: KIAA0369-AS (type A, short version), KIAA0369-AL (type A, long version), KIAA0369-BS (type B, short version), and KIAA0369-BL (type B, long version). KIAA0369-B, which lacked the DC domain and maintained the kinase domain, was expressed in adult as well as fetal brain, but the variants that included the DC domain, KIAA0369-A, were expressed predominantly in fetal brain. These results suggest that the DC domain plays an important role in the development of the nervous system. In the adult brain, KIAA0369 was expressed in all 15 different regions examined, more intensely in cerebral cortex, occipital pole, frontal lobe, amygdala, and hippocampus, and less intensely in corpus callosum and thalamus. The murine homologs of Doublecortin and KIAA0369 were not detectable in 7-day mouse embryos, but both genes were expressed extensively in 11-day embryos. Human KIAA0369 was mapped by fluorescence in situ hybridization (FISH) to chromosome 13q13-q14.1. The presence of genes related to neuropathy has been reported in this locus.

Crystallization of the bifunctional methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase domain of the human trifunctional enzyme.

Methylenetetrahydrofolate([H4] folate) dehydrogenase (D) and methenyl[H4] folate cyclohydrolase (C) coexist as a bifunctional enzyme (DC) or as the amino-terminal domain of a trifunctional enzyme (DCS) where the third activity is 10-formyl[H4]folate synthetase (S). Two crystal forms of the DC domain of the human cytosolic DCS enzyme have been grown from polyethyleneglycol solution. The monoclinic P2(1) crystals diffract to 2.8 A with a = 72.5 A, b = 68.5 A, c = 125.2 A, and beta = 91.8 degrees but were found to be twinned. The orthorhombic P2(1)2(1)2(1) crystals diffract to 2.5 A with a = 67.7 A, b = 135.9 A, c = 61.6 A, and contain two molecules per asymmetric unit.

Simulation and modeling-new macro model for Zeners

A macro model of the 6.2-V 1N5920B Zener diode which very accurately represents the measured characteristics both in the DC and AC domain is presented. For users who do not have access to optimization software, the model can still be easily customised for other Zener diodes by replacing the emission coefficients (N), saturation currents (Is) and series resistance (Rs) under forward and reverse bias. One would also need to modify the temperature coefficient and measure the capacitance (CIO) at V/sub d/=0 V bias, to have a functional model of the Zener diode. However, there is no easy technique to extract the TT parameter without going through an extraction process. Therefore, without modification to the T1 parameter, one has to be careful when using the customized model for switching applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>