Extra Loop Research Articles

Designing of a Functional Chimeric Protein for Production of Nanobodies Against Human CD20: Molecular Dynamics Simulation and In Vitro Verification

One major issue in cancer immunotherapy is the large size of mAbs (150 kDa) which usually causes limitation in tumor penetration. Camel nanobodies (< 15 kDa) could be used as an alternative for this problem. Here in, using molecular modeling we designed a novel recombinant chimeric protein containing the extra membrane loop of human CD20 which was fused to the FC region of camel with proper potential for production of camel derived nanobodies. Molecular dynamics simulation showed that the recombinant chimera can interact specifically with therapeutic antibody Rituximab Fab and the interaction site was the residue 164IYNCEPANPSE174. The recombinant chimeric protein was successfully expressed in HEK293-T cells and evaluated in vitro using western blotting analysis. In agreement with simulation results, western blotting analysis also confirmed the interactions between Rituximab and hCD20. The results of this paper show that protein engineering with the help of molecular modelling tools can be promising and efficient approach in developing new nanobodies for caner immunotherapy.

Arabidopsis MAP-Kinase 3 Phosphorylates UDP-Glucose Dehydrogenase: a Key Enzyme Providing UDP-Sugar for Cell Wall Biosynthesis

The enzyme UDP-glucose dehydrogenase (UGD) competes with sucrose-phosphate synthase for the common photosynthesis product UDP-glucose. Sucrose-phosphate synthase is part of a pathway for the export of sucrose from source leaves to neighboring cells or the phloem. UGD is a central enzyme in a pathway for many nucleotide sugars used in local cell wall biosynthesis. Here, we identify a highly conserved phosphorylation site in UGD which is readily phosphorylated by MAP-kinase 3 in Arabidopsis. Phosphorylation occurs at a surface-exposed extra loop in all plant UGDs that is absent in UGDs from bacteria or animals. Phosphorylated sucrose-phosphate synthase is shifted to an inactive form which we did not measure for phosphorylated UGD. Plant UGDs have an extra loop which is phosphorylated by AtMPK3. Phosphorylation is not causing a reduction of UGD activity as found for the competitor enzymes and thus sets a preference for maintaining UDP-sugars at a constant level to prioritize cell wall biosynthesis.

A novel missense mutation of GJA8 causes congenital cataract in a large Mauritanian family.

Inborn lens opacity is the most frequent cause of childhood blindness. In this study, we aimed to define the presumed genetic cause of a congenital cataract present in a Mauritanian family over the last nine generations. A family history of the disease and eye examination were carried out for the family members. Next-generation sequencing using a panel of 116 cataract underlying genes was selectively conducted on the proband's DNA. Nucleotide and amino acid changes and their impact on the phenotype were evaluated using various data analyzing software. Congenital nuclear cataract, with autosomal dominant mode, was observed in the family. All patients had consequences on their vision in the first 2 years of life. Genetic screening revealed a new mutation c.166A>C (p.Thr56Pro) in GJA8, encoding the Cx50 α-connexin protein. This mutation co-segregated in all patients and was not observed in the unaffected family members and controls. The predicted secondary structure impacted by p.Thr56Pro revealed a localized disruption, in the first extra membrane loop of the wild-type sheet, which is replaced in the mutant protein by a turn then a coil. This conformational change was functionally predicted as probably damaging. A new mutation (c.166A>C) in GJA8 underlying a nuclear congenital cataract was identified in this study. Its segregation with the phenotype might be useful as a predicting marker of the disease.

Robust MPC-based current controller against grid impedance variations for single-phase grid-connected inverters

Recently, LCL filters have been widely used in the output of single phase inverters. Since, the grid side inductor in these filters is in series with the grid impedance at the Point of Common Coupling (PCC), it may create new resonances. This phenomena may take the control loop toward instability. In this case, in order to have a reliable operation, the current controller should be insensitive to the grid impedance variation. In order to damp these resonances, researchers have presented some methods using active or passive damping. These methods added an extra loop to the control loop, an extra passive component in the filter or extra sensor in the control process. But in most of them, the complexity and the cost of controller have been increased. Therefore, presenting a simple control method without extra sensor, passive component or extra arrangement can be a promising approach. This paper presents an MPC-based current controller, which is simple and robust against the grid impedance variation and even the variation of the LCL filter parameters. In contrast to classical multi-loop controller like Proportional-Resonant (PR) controllers, the proposed control method does not need any parameter tuning. In the proposed controller, the switching plan and duty cycles are determined by a cost function and a switching table. Therefore, at the same time with any variation in grid impedance, the proposed controller changes the next switching state and duty cycle. Operating performance like look-up table, searching in all possible switching states to find the best state for the next switching period, makes the controller adaptive and robust against the variation of LCL filter parameters. In order to confirm the effectiveness of the proposed controller, simulations and experimental results of the proposed controller are compared with a classical PR controller.

When underwater degraded images meet logical stochastic resonance

Owing to light attenuation and high background noise, underwater images are significantly degraded, which hiders the development of underwater exploration. However, noise itself can be used to counter noise. In this paper, we apply logical stochastic resonance (LSR) to help detect weak objects from low-quality underwater images. On the basis of analysis of the physical character of underwater images, three models, namely basic dynamical system driven by Gaussian noise, basic dynamical system driven by Ornstein–Uhlenbeck (OU) noise, and dynamical system with extra delay loop, are chosen to study the performance of LSR-based object detection. The main workflow of LSR-based object detection is introduced. To analyze the performance of LSR, we perform explicit experiments and systematically discuss the interplay of additional noise with the system parameters. LSR is proven to be helpful in detecting weak objects from low-quality underwater images. Both OU noise and extra delay loop will help the whole system to maintain stability in a higher noisy background.

Impact of Organic Hole Transporting Material and Doping on the Electrical Response of Perovskite Solar Cells

The hole transport material (HTM) layer is a key component of the perovskite solar cells (PSCs) that must be optimized to reach high efficiency. The development of new HTMs alternative to Spiro-OMeTAD and the understanding of the role of doping agents on these layers are important research axes in the field. It requires the use of appropriate characterization tools enabling us to discriminate the bulk and interface effects. In the present paper, we fully analyze the effect of HTM doping and of the material on the impedance response of PSCs. The approach has been implemented on two different molecular HTMs, Spiro-OMeTAD and a new molecular carbazole HTM, called B186, and with various doping levels. We show that limitations by poor doping are characterized by an extra high frequency impedance loop for which capacitance and resistance analysis gives the dielectric constant and conductivity of the material, respectively. However, the low-frequency part of the spectra provides important information on the char...

Small-signal stability improvement of an islanded microgrid with electronically-interfaced distributed energy resources in the presence of parametric uncertainties

This paper deals with the concept of small signal stability (SSS) issue in an electronically-interfaced microgrid with large penetration of distributed energy resources (DERs) subjected to the parametric uncertainties. Utilizing a method to enhance SSS of the system stemmed from industrial experiences is the first achievement of this study, which is realized by employing two extra feed-forward loops in the power controller section of DER unit. This control structure damps the active and reactive power oscillations by shifting the dominant eigenvalues to the left half-plane (LHP) in case of any changes in the operating point or droop coefficients. For investigating the impacts of parametric uncertainties on the overall stability, the basic theorem of the proposed robust control strategy, frequency-domain modeling of the microgrid, robustness and close-loop stability analyses are outlined. This method shows that improving the power control section topology results in higher stability margins in case of uncertain load perturbations. Furthermore, it demonstrates how much load variations are allowed to preserve SSS of the system in the frequency-domain which is a more convenient approach and takes less time than time-domain simulations. Finally, time-domain simulations conducted in MATLAB/Simulink on the sample test system will show proper results of the frequency-domain findings.

Lead-free Ba(1-x)SrxTiO3 ceramics for room-temperature pyroelectric energy conversion

Lead-free Ba(1-x)SrxTiO3 (BST) ceramics were fabricated to convert near-room-temperature waste heat to electric energy for creating self-powered and ‘battery-less’ systems. In comparison to thermoelectrics that are specifically used for harvesting heat with stable temperature span, pyroelectric converters based on Olsen cycle mechanism can harvest heat with temperature-vibration environment. Large energy conversion density (ND) was obtained in BST ceramics within the narrower temperature gradient (< 60 °C). In terms of the diffused phase transition (DPT) in BST ceramics, the extra slim hysteresis loops processed relatively low coercive field (Ec) and hysteresis loss, which can effectively enhance the ND owing to the wider electrical field interval. The effect of Curie temperature (Tc) tuned by the ratios of Ba/Sr on ND and applicable range of temperature were also systematically examined. At the same electrical field difference (07 MV/m), the optimal energy conversion properties were gained around the Tc, e.g., 0.36 J/cm3 for BST66/34 (Tc = 23 °C) within a temperature range between 25 °C and 65 °C, and 0.48 J/cm3 for BST72/28 (Tc = 43 °C) between 25 °C and 85 °C.

Two Degrees-of-Freedom Fractional-Order Proportional–Integral–Derivative-Based Temperature Control of Fermentation Process

Temperature is one of the essential parameter in a fermentation process, which affects the thermal movement of cells. The temperature range for such processes is very tight and must be maintained precisely for efficient operation. Therefore, in this work combination of fractional calculus and two degrees-of-freedom proportional–integral–derivative (2DOF-PID) controller is proposed for desired temperature control of bioreactor. The 2DOF-PID controller incorporates an extra control loop, whereas fractional operator offers additional tractability for alteration in system dynamics. In order to achieve efficient execution of the control strategies, design parameters are optimized with the help of nondominated sorted genetic algorithm-II (NSGA-II) and Cuckoo search algorithm (CSA). NSGA-II-tuned controllers perform better than the CSA-tuned controllers. Further, the results show that the proposed controller regulates the temperature of bioreactor in a more robust and efficient manner in comparison to other designed controllers.

Dolichocolon revisited: An inborn anatomic variant with redundancies causing constipation and volvulus.

The objective of this review is to examine whether a redundant colon gives rise to symptoms like constipation and volvulus. In 1820, Monterossi made drawings of colons with displacements and elongation of the colon found during autopsy. In 1912, Kienböeck first visualized a redundant colon using bismuth, and Lardennois and Auborg named the anatomic variant dolichocolon in 1914. The criteria were later: A sigmoid loop rising over the line between the iliac crests, a transverse colon below the same line and extra loops at the flexures. The incidence of dolichocolon is 1.9%-28.5%. Dolichocolon seems to be congenital, as fetuses, newborns, and infants exhibit colonic redundancies. Studies have identified a triade of constipation, abdominal pain, and distension. Colon transit time was recently shown to increase significantly with increased number of redundancies, which increases abdominal pain, bloating and infrequent defecation. The diagnosis of dolichocolon is established by barium enema or CT-colonography. Treatment is conservative, or surgical in case of volvulus or refractory constipation.

A Decentralized Current-Sharing Controller Endows Fast Transient Response to Parallel DC–DC Converters

This paper proposes a decentralized current-sharing control strategy to endow fast transient response to paralleled dc–dc converters systems, such as dc microgrids or distributed power systems. The proposed controller consist of two main control loops: an external voltage droop control for current-sharing proposes and an internal current loop. The external droop control loop is designed as a voltage loop with embedded virtual impedance, which avoids the use of a slow voltage loop and a separate extra virtual impedance loop that may limit the system bandwidth. The internal current loop, thanks to the external control loop simplification, plays a major role in the system bandwidth, so that an adaptive proportional-integral (PI) controller is proposed for this matter. In the paper, two different droop control methods have been modeling, designed, simulated, and tested: The conventional virtual-impedance-loop based V–I droop and the proposed embedded-virtual-impedance based I–V droop. In order to compare the dynamic response performances between two droop controllers, their state-space models have been developed and analyzed in this paper. The results show that the dynamic response of the I–V droop control is faster than that of the conventional V–I droop control. Furthermore, by analyzing the effects from I–V droop control parameters, the errors can be reduced faster by enlarging the proportional terms, but with no fluctuations, and then completely eliminated by restoring back to small proportional values. Meanwhile, there exists a tradeoff phenomenon between the fast dynamic response and good steady-state performance; thus, an adaptive PI controller is proposed to both improve dynamic response and guarantee good steady-state performance simultaneously. Experimental results are shown to verify the accuracy of the models and the effectiveness of the proposed control framework.

An Improved Coordinated Control Strategy for PV System Integration with VSC-MVDC Technology

The rapid development of renewable energy calls for feasible and reliable technologies to transmit and integrate power into grids. Voltage Source Converter (VSC)- Direct Current (DC) technology is considered as a promising solution for its independent control of active and reactive power. Modeling and coordinated control of a large-scale concentrating photovoltaic integration system with VSC-MVDC (Voltage Source Converter-Medium Voltage Direct Current) technology have been investigated in this paper. The average controlled-source model of PhotoVoltaic (PV) integration system is firstly established. Then, a novel control strategy without fast communication is proposed to improve the reliability of the coordinated control system. An extra voltage loop is added to the basic control block, which is able to assure stable operation of the PV system in various conditions. Finally, the proposed control strategy is verified with simulation results.

Dynamic stability of rolling missiles with angle-of-attack feedback three-loop autopilot considering parasitic effect

This paper focuses on the dynamic stability of rolling missiles equipped with angle-of-attack feedback three-loop autopilot considering parasitic effect induced by radar radome slope. By analyzing the parasitic effect, it is found that an extra feedback loop occurs in the guidance and control system. This undesired loop will strongly affect the dynamic stability of rolling missile. Based on the differential equations expressed in the complex form, the sufficient and necessary stability condition for rolling missiles with angle-of-attack feedback three-loop autopilot considering parasitic effect is obtained. Numerical simulations and theoretical discussions are conducted to demonstrate the validity of stability condition. The results indicated that the rolling effect and parasitic effect will deteriorate the stability of autopilot designed in conventional method.

Optimized guide RNA structure for genome editing via Cas9.

The genome editing tool Cas9-gRNA (guide RNA) has been successfully applied in different cell types and organisms with high efficiency. However, more efforts need to be made to enhance both efficiency and specificity. In the current study, we optimized the guide RNA structure of Streptococcus pyogenes CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas (CRISPR-associated) system to improve its genome editing efficiency. Comparing with the original functional structure of guide RNA, which is composed of crRNA and tracrRNA, the widely used chimeric gRNA has shorter crRNA and tracrRNA sequence. The deleted RNA sequence could form extra loop structure, which might enhance the stability of the guide RNA structure and subsequently the genome editing efficiency. Thus the genome editing efficiency of different forms of guide RNA was tested. And we found that the chimeric structure of gRNA with original full length of crRNA and tracrRNA showed higher genome editing efficiency than the conventional chimeric structure or other types of gRNA we tested. Therefore our data here uncovered the new type of gRNA structure with higher genome editing efficiency.

Crystal Structure and Substrate Specificity Modification of Acetyl Xylan Esterase from Aspergillus luchuensis.

Acetyl xylan esterase (AXE) catalyzes the hydrolysis of the acetyl bonds present in plant cell wall polysaccharides. Here, we determined the crystal structure of AXE from Aspergillus luchuensis (AlAXEA), providing the three-dimensional structure of an enzyme in the Esterase_phb family. AlAXEA shares its core α/β-hydrolase fold structure with esterases in other families, but it has an extended central β-sheet at both its ends and an extra loop. Structural comparison with a ferulic acid esterase (FAE) from Aspergillus niger indicated that AlAXEA has a conserved catalytic machinery: a catalytic triad (Ser119, His259, and Asp202) and an oxyanion hole (Cys40 and Ser120). Near the catalytic triad of AlAXEA, two aromatic residues (Tyr39 and Trp160) form small pockets at both sides. Homology models of fungal FAEs in the same Esterase_phb family have wide pockets at the corresponding sites because they have residues with smaller side chains (Pro, Ser, and Gly). Mutants with site-directed mutations at Tyr39 showed a substrate specificity similar to that of the wild-type enzyme, whereas those with mutations at Trp160 acquired an expanded substrate specificity. Interestingly, the Trp160 mutants acquired weak but significant type B-like FAE activity. Moreover, the engineered enzymes exhibited ferulic acid-releasing activity from wheat arabinoxylan.IMPORTANCE Hemicelluloses in the plant cell wall are often decorated by acetyl and ferulic acid groups. Therefore, complete and efficient degradation of plant polysaccharides requires the enzymes for cleaving the side chains of the polymer. Since the Esterase_phb family contains a wide array of fungal FAEs and AXEs from fungi and bacteria, our study will provide a structural basis for the molecular mechanism of these industrially relevant enzymes in biopolymer degradation. The structure of the Esterase_phb family also provides information for bacterial polyhydroxyalkanoate depolymerases that are involved in biodegradation of thermoplastic polymers.

Highly Tunable Triangular Wave UWB Baseband Pulse Generator With Amplitude Stabilization in 40-nm CMOS

This brief introduces a highly configurable ultrawideband triangular wave baseband pulse generator designed in 40-nm complementary metal-oxide-semiconductor technology. The baseband pulse width is adjustable between 660 ps and 3.8 ns. An extra amplitude compensation loop is implemented to prevent amplitude changes when the pulse width varies. The amplitude variations are limited to 13% compared with the maximum amplitude over the entire pulse width range. The amplitude compensation loop allows a pulse amplitude tuning range between 280 and 640 mV, whereas the pulse width only varies 80 ps over this entire range. The pulse generator has a maximum simulated signal-to-noise ratio of 59 dB and a measured maximum power consumption of 6.2 pJ/pulse from a 0.9-V power supply and a 100-MHz pulse repetition frequency.

A Simple Sensorless Current Sharing Technique for Multiphase DC–DC Buck Converters

Multiphase buck converters are widely used to power up low-voltage high-current loads, such as microprocessors, battery chargers, hybrid vehicles, among others. For this converter, topology is necessary to guarantee a correct distribution of the total output current among phases in order to ensure proportionality in electrical losses and thermal stresses. So, a current sharing scheme is a desirable part in a multiphase buck converter. Most of the proposed current distribution schemes include sensing circuitry and a current loop for each phase. Nevertheless, by using sensors, control complexity and assembly costs increases proportionally to the number of phases. This paper presents a simple sensorless current sharing algorithm for multiphase buck converters. The proposed technique is based on simple one-time tests by turning-on each phase in order to estimate the parasitic resistance for the turned-on phase. Once the parasitic resistances are known, the duty cycles, which allow for adequate current sharing among phases, are calculated. An extra control algorithm ensures that the compensated duty cycle is applied at the switching node. This extra control loop does not require analog-to-digital converters. Analysis and experimental results of proposed control technique are shown using a five-phase dc-dc buck converter. The proposed algorithm exhibits an adequate distribution of the load current between phases.

Bioreactor temperature control using modified fractional order IMC-PID for ethanol production

The product quality of a fermentation process depends on a number of factors such as temperature, pH, nutrient balance, dilution rate, dissolved oxygen and CO2 concentration etc. The present work focuses on the precise temperature control of the process and to achieve desired product quality. Therefore a novel control algorithm, which is an amalgamation of fractional mathematics and IMC-PID, having less design parameters is proposed. A fractional order IMC-PID is designed and then modified (MFOIMC-PID) by incorporating an extra control loop with proportional gain to reduce the offset error. A nature inspired optimization technique i.e. water cycle algorithm is utilized for estimation of optimum design parameters of proposed controller which leads to WMFOIMC-PID controller. Fractional order PID (FOPID) and conventional PID are also designed for comparative study. Simulation results show that the proposed controller reduces integral absolute error (IAE) by 57% and 72% in comparison to FOPID and PID respectively for set-point tracking. Similar reduction of IAE is observed for disturbance rejection and noise suppression. Thus WMFOIMC-PID proves to be more robust and efficient in comparison to the other designed controllers.

A 10-b Fourth-Order Quadrature Bandpass Continuous-Time $\Sigma \Delta $ Modulator With 33-MHz Bandwidth for a Dual-Channel GNSS Receiver

A fourth-order quadrature bandpass continuous-time sigma–delta modulator for a dual-channel global navigation satellite system (GNSS) receiver is presented. With a bandwidth (BW) of 33 MHz, the modulator is able to digitalize the downconverted GNSS signals in two adjacent signal bands simultaneously, realizing dual-channel GNSS reception with one receiver channel instead of two independent receiver channels. To maintain the loop-stability of the high-order architecture, any extra loop phase shifting should be minimized. In the system architecture, a feedback and feedforward hybrid architecture is used to implement the fourth-order loop-filter, and a return-to-zero (RZ) feedback after the discrete-time differential operation is introduced into the input of the final integrator to realize the excess loop delay compensation, saving a spare summing amplifier. In the circuit implementation, power-efficient amplifiers with high-frequency active feedforward and antipole-splitting techniques are employed in the active RC integrators, and self-calibrated comparators are used to implement the low-power 3-b quantizers. These power saving techniques help achieve superior figure of merit for the presented modulator. With a sampling rate of 460 MHz, current-steering digital–analog converters are chosen to guarantee high conversion speed. Implemented in only 180-nm CMOS, the modulator achieves 62.1-dB peak signal to noise and distortion ratio, 64-dB dynamic range, and 59.3-dB image rejection ratio, with a BW of 33 MHz, and consumes 54.4 mW from a 1.8 V power supply.

Offset-Free Direct Power Control of DFIG Under Continuous-Time Model Predictive Control

This paper presents a robust continuous-time model predictive direct power control for doubly fed induction generator (DFIG). The proposed approach uses Taylor series expansion to predict the stator current in the synchronous reference frame over a finite time horizon. The predicted stator current is directly used to compute the required rotor voltage in order to minimize the difference between the actual stator currents and their references over the predictive time. However, as the proposed strategy is sensitive to parameter variations and external disturbances, a disturbance observer is embedded into the control loop to remove the steady-state error of the stator current. It turns out that the steady-state and the transient performances can be identified by simple design parameters. In this paper, the reference of the stator current is directly calculated from the desired stator active and reactive powers without encompassing the parameters of the machine itself. Hence, no extra power control loop is required in the control structure to ensure smooth operation of the DFIG. The feasibility of the proposed strategy is verified by the experimental results of the grid-connected DFIG and satisfactory performances are obtained.