Split Junctions Research Articles

Structure determination and optimization of a cysteine-less intein with NMR spectroscopy and molecular dynamics simulations

Inteins are a unique class of proteins that are capable of stitching other proteins together in a process known as protein splicing. Inteins are valuable tools for protein chemists as they allow for selective isotopic labelling in NMR experiments and the assembly of proteins with novel properties. Most efficient inteins to date rely on cysteine chemistry to carry out the splicing reaction. This means that a key cysteine residue has to be present at the desired protein's split site. As cysteines are relatively rare in proteins, this often requires mutagenesis at the split junction.

High-performance near-infrared photodetectors based on gate-controlled graphene-germanium Schottky junction with split active junction.

The structure of a gate-controlled graphene/germanium hybrid photodetector was optimized by splitting the active region to achieve highly sensitive infrared detection capability. The strengthened internal electric field in the split active junctions enabled efficient collection of photocarriers, resulting in a responsivity of 2.02AW-1 and a specific detectivity of 5.28×1010 Jones with reduced dark current and improved external quantum efficiency; these results are more than doubled compared with the responsivity of 0.85AW-1 and detectivity of 1.69×1010 Jones for a single active junction device. The responsivity of the optimized structure is 1.7, 2.7, and 39 times higher than that of previously reported graphene/Ge with Al2O3 interfacial layer, gate-controlled graphene/Ge, and simple graphene/Ge heterostructure photodetectors, respectively.

A dynamic model for engineering change propagations in multiple product development stages

Abstract To accurately predict propagation dynamics for single or multiple change propagations across different product development stages in a sequential or concurrent way is critical for decision-making of implementing change requests. In this paper, a change propagation dynamic model is built based on the compartmentalization of engineering entities into susceptible engineering entities and affected engineering entities (SA), the ordinary differential equations for describing the rate of affected entities with respect to the total ones and the duration for resolving all the changes for every moment are presented by combining the calculations of change impacts with different split and joint junctions. Considering the difficulty of finding analytical solutions to the differential equations, algorithms for sequential and concurrent simulations of change propagations across different development stages, and random and GA (Genetic Algorithm)-based optimal selections of feasible propagation paths are developed to obtain numerical solutions for single and multiple change requests. Simulation results show that change ripples and blossoms can be observed in both sequential and concurrent change propagations, and these propagation patterns are not sensitive to the initial change effect and the threshold value for propagations, while critical change propagation paths and the number of initiated changes have important effects on both concurrent and sequential change propagation process. It is also demonstrated that concurrent propagation strategy is advantageous for processing single or few of initiated changes since it can shorten product redevelopment time, sequential propagation strategy has an advantage of robustness for handling multiple initiated change requests.

An approach for support design in depillaring panels of coal mines

Among different methods of underground mining technology adopted for coal extraction, bord and pillar mining is the most popular and predominant method of underground mining in India. This method is characterised with small capital investment and faster rate of return on capital. Varying geomining conditions demand scientific approach for design of supports in depillaring panels. In view, this there is a decisive lack of judgement on support design, given the geomining conditions. Support design methods in vogue for depillaring districts do not takes into account, among other parameters, the inclination of the coal seam and direction of in situ stress. Thus, there exists a need for research work aimed at investigating the effective role, inter-alia, of direction of in situ horizontal stress and inclination of coal seams to ensure a better condition of roof and efficient design of effective support system. The authors through this paper intend to address similar problems being faced by the industry. Detailed numerical models for one depillaring panel in Thesgora Mine and in two depillaring panels of Kakatiya Khani (KTK)-KTK-1 and KTK-5 Incline mines respectively of Bhupalpalli area under study have been developed. The models are then calibrated using the empirical relations of pillar strength. Stage-wise extraction in the models is carried out to simulate the change in stress and displacement as the mining activity progresses. Based on the geo-mining data and the numerical models, the rock load heights at four strategic locations namely split gallery, slice, junction and goaf edge have been evaluated in all the depillaring panels under study. Generalised equations for rock load height at different strategic locations in a depillaring panel have been developed. The said empirical relations for rock load height have been derived using parametric study of the numerical models developed for depillaring panels of the selected mines. The equations so developed have a correlation coefficient of maximum 87.8 % and a minimum of 80.5%.

Modeling of dual material surrounding split gate junctionless transistor as biosensor

In this paper an analytical model of dual material surrounding split gate junctionless transistor for application as a biosensor is introduced. The simulation results show fair compatibility with the analytical models developed for the channel center potential and threshold voltage at channel length of 45 nm and 20 nm. For the detection of the bio-molecules, concept of dielectric modulation has been used. The model shows a satisfactory value of sensitivity in the range of 0–0.27 and 0–0.8 for relative permittivity of biomolecules varying from 1 to 9 at channel length of 45 nm and 20 nm respectively, thus making it an attractive option for use as biosensor. This model has been demonstrated with the aid of TCAD device simulations. • Present work includes modelling of dual material surrounding split gate junction less transistor for bio-sensing application. • The model for channel centre potential and threshold voltage has been developed. • Sensitivity is defined in terms of change in threshold voltage of the device. • Decent sensitivity in the range of 0–0.27 and 0–0.8 for 45 nm and 20 nm technology respectively is observed for relative permittivity varying from 1–9.

Surrogate‐assisted design of microstrip corporate feeds integrated with linear microstrip array apertures for required sidelobe levels

AbstractA systematic computer‐aided design of low‐sidelobe linear microstrip antenna arrays is proposed. It starts from identifying the corporate feed architecture which is optimal for a given excitation taper under constrains imposed on the power splits within the feed. The novelty of the approach includes utilization of a numerically efficient simulation‐based kriging model of unequal split microstrip junctions for implementation of the optimal microstrip feed, and simulation‐based tuning of the excitation taper. The tuning is carried out with surrogate‐assisted optimization which is based on the electromagnetic simulations of an integrated array circuit comprising the aperture and the feed. Additionally, in‐phase excitation of the array aperture radiators is ensured with a simulation‐based correction of the corporate feed microstrip branches. The approach is implemented iteratively to realize the nominal sidelobe level. The approach is demonstrated with design of a 12‐element H‐plane 25‐dB sidelobe level Tschebyscheff array. Experimental validation is provided.

On Alternative Approaches to Design of Corporate Feeds for Low-Sidelobe Microstrip Linear Arrays

Two design approaches, illustrated by simulations and measurements, aiming at a systematic computer-aided design of printed circuit feeds for low-sidelobe microstrip antenna arrays are described. The novelty of these approaches resides in identification of the optimal feed architectures with subsequent simulation-based optimization of the feed and array aperture dimensions. In this communication, we consider microstrip corporate feeds (CFs) realizing nonuniform amplitude excitation of linear arrays of microstrip patch antennas. Two types of the microstrip CFs are considered: with equal power split junctions and with unequal power split junctions. For each feed type, we identify candidate prototypes of feed architectures using numerical optimization of the corresponding fast feed models. Subsequently, the architectures are implemented as microstrip subcircuits within the antenna array electromagnetic (EM) models. For the sake of comparison, the antenna array circuits are defined with the same linear array of microstrip patch antennas featuring the half-wavelength element spacing, and implemented on the same microstrip substrates. Finally, the EM models are tuned—using simulation-based optimization techniques—to ensure an appropriate input reflection coefficient and minimum sidelobe levels. Selected optimal designs of antenna array circuits with 12 microstrip patches and different feeds are manufactured and measured.

Droplet breakup in an asymmetric bifurcation with two angled branches

Droplet breakup in an asymmetric bifurcation with two angled branches is studied experimentally and theoretically in this paper. In order to tune the droplet size and droplet velocity separately, a diluting channel is added and its influence on droplet generation is confirmed to be negligible. The underlying physics of the droplet generation is revealed as compared with other works. Effects of the droplet parameters, including the initial droplet length and the droplet velocity, on breakup characteristics are analyzed. The regime diagram of the droplet breakup and the critical conditions between different regimes are provided. It is found that the splitting ratio is largely influenced by the initial droplet length and the droplet velocity, which indicates that the breakup process is an inter-dependent process between the splitting junction and droplets themselves. At last, a simple but effective prediction model is constructed by considering the hydrodynamic resistance of the branches with the presence of the daughter droplets, which also proves the similar motion of the droplets with low viscosity ratio of the two liquids and the bubble.

Transverse and Longitudinal Stress Analysis in Reinforced Welded Oil Branched Pipes

Welding process results in the non-uniform distribution of heat. Combined with thermal strain, plastic deformation and welding-induced distortion, it causes important problems such as failure. This study models welding process in a 12×16 split tee junction using finite element. This junction is a reinforcing branch used in the hot taping of oil pipe line. The model is studied in 3D state. This zone, i.e. heat affected zone (HAZ) is of high importance due to the existence of a severe temperature gradient and stress in the vicinity of HAZ. This study analyses single pass butt welding with a cooling time of 2700 seconds. In order to apply boundary conditions to the model, the studied structure should be in Free State according to practical procedure. The main aim of this simulation is to analyse Longitudinal and transverse residual stresses originated from co-directional and opposite-directional welding. This joint is formed of two semicircles welded to each other as linear single pass welding. Two welders simultaneously welded both sides of the pipe.

Tunability of Andreev levels via spin-orbit coupling in Zeeman-split Josephson junctions

We study Andreev reflection and Andreev levels $\ensuremath{\varepsilon}$ in Zeeman-split superconductor/Rashba wire/Zeeman split superconductor junctions by solving the Bogoliubov--de Gennes equation. We theoretically demonstrate that the Andreev levels $\ensuremath{\varepsilon}$ can be controlled by tuning either the strength of Rashba spin-orbit interaction or the relative direction of the Rashba spin-orbit interaction and the Zeeman field. In particular, it is found that the magnitude of the band splitting is tunable by the strength of the Rashba spin-orbit interaction and the length of the wire, which can be interpreted by a spin precession in the Rashba wire. We also find that if the Zeeman field in the superconductor has the component parallel to the direction of the junction, the $\ensuremath{\varepsilon}\ensuremath{-}\ensuremath{\phi}$ curve becomes asymmetric with respect to the superconducting phase difference $\ensuremath{\phi}$. Whereas the Andreev reflection processes associated with each pseudospin band are sensitive to the relative orientation of the spin-orbit field and the exchange field, the total electric conductance interestingly remains invariant.

Optimization of Y-splitting antiresonant reflecting optical waveguides-based rib waveguides.

Antiresonant reflecting optical waveguide power splitters, designed for use around the 635-nm wavelength, are characterized for multiple split angles ranging from 0.5 deg to 9 deg. Theoretical expectations and simulations predict lowest transmission losses at this split junction for the lowest angles. This is confirmed by the experimental structures built in SiO2 films on silicon substrates. A fabrication nonideality affects the achievable splitting angle. Design considerations are discussed based on tradeoffs between loss and the required length for a Y-splitter.

Minimal circuit for a flux-controlled Majorana qubit in a quantum spin-Hall insulator

We construct a minimal circuit, based on the top-transmon design, to rotate a qubit formed out of four Majorana zero-modes at the edge of a two-dimensional topological insulator. Unlike braiding operations, generic rotations have no topological protection, but they do allow for a full characterization of the coherence times of the Majorana qubit. The rotation is controlled by variation of the flux through a pair of split Josephson junctions in a Cooper pair box, without any need to adjust gate voltages. The Rabi oscillations of the Majorana qubit can be monitored via oscillations in the resonance frequency of the microwave cavity that encloses the Cooper pair box.

Design for energy: Modeling of spectrum, temperature and device structure dependences of solar cell energy production

Solar photovoltaic energy generation can benefit from high efficiency, environment specific design. In this work, a model is developed to assess the electrical energy produced by concentrator solar cells during specific time frames with varying realistic weather conditions and cell temperatures. The model is applied to a comparative study of the spectral and temperature sensitivities of efficiency and energy production for tandem junction and spectrally split parallel junction solar cell structures. Direct normal solar spectra in a representative sunny site, Tucson, Arizona are calculated using the SPCTRAL2 model at 15-minute intervals throughout a year with real-time meteorological data input. The corresponding efficiencies of the two devices under 500 times concentration at cell temperatures deduced from thermal modeling with real-time ambient temperatures are computed. Both device structures comprise the same materials, InGaP, GaAs and Ge, and each device design is optimized to standard operating conditions (AM1.5D spectrum and a cell temperature of 25°C). The two devices are compared for their efficiencies and power/energy output at (i) 15min intervals (instantaneous values), (ii) daily and (iii) yearly time spans. Despite efficiency loss due to series resistance that is three times as high as that for the tandem junction, the parallel junction has a higher daily averaged efficiency every single day, and its yearly averaged efficiency is 1.2% absolute higher, meaning an additional annual energy production of 19.2MWh per m2 cell area. Besides energy forecast and assessment, the developed method can be used to obtain optimum solar cell designs for maximum energy production under varying geographical and climatic conditions.

Reactant recirculation in electrochemical co-laminar flow cells

Co-laminar electrochemical cells utilize hydrodynamic engineering rather than a physical separator to prevent mixing of reactants. Commonly known as microfluidic fuel cells and batteries, these cells are based on stratified laminar flow of reactants in a microfluidic channel. The objective of the present work is to evaluate the feasibility and effectiveness of reactant recirculation in co-laminar flow cells with flow-through porous electrodes. Two representative device architectures are fabricated with separate outlets for reactant recirculation in Y-junction and dual-pass configurations. It is found that crossover at the electrodes reduces the open circuit potential of both cells and serves as a useful diagnostic method for assessing the degree of crossover at the outlets. Outlet concentration is monitored at a range of flow rates and indicates that asymmetric splitting of the co-laminar interface can lead to a constant 2% loss of state of charge, while the loss due to diffusion ranges from 0-40%. The dual-pass cell is shown to have greater diffusive loss due to deceleration at the splitting junction but also demonstrates better performance due to its higher convective velocity through the porous electrodes. These effects are observed during a series of discharge operations with recirculating reactants, in which the dual-pass cell results in greater reactant utilization despite its higher crossover rates. Overall, the present results demonstrate reactant recirculation as a useful strategy to combine high reactant utilization and high power density in membraneless co-laminar flow cells.

Split intein mediated ultra‐rapid purification of tagless protein (SIRP)

Rapid and efficient tag removal remains a significant problem in recombinant protein purification. Using an engineered DnaE intein from Nostoc punctiforme, we developed a split intein mediated ultra-rapid purification (SIRP) method for the purification of tagless recombinant protein from E. coli lysate in less than 1 h. This system exhibits extraordinarily rapid thio-induced C-terminal cleavage with about 50% completion within 30 s at both 22°C and 6°C. This is the fastest C-terminal cleavage activity reported to date for inteins. Although the reaction kinetics slow down after the first minute, >90% cleavage completion is achieved within 30 min at 22°C, or within 3 h at 6°C. The ultra-rapid cleavage kinetics are made possible by the positioning of the purification tag at the split junction to the C-terminus of the intein N-fragment, thus avoiding potential steric hindrance of the critical interaction between the N- and C-extein. Target proteins are cleaved to >72% completion after 1 h of intein reaction regardless of the identity of the N-terminal amino acid except in the cases of threonine (50% cleavage) and proline. The C-terminal cleavage reaction can be effectively inhibited by divalent Zn(2+) under non-reducing conditions. Importantly, the association of the intein N- and C-fragments is reversible, enabling the column-bound intein N-fragment bait protein to be regenerated for multiple usages and further reducing the cost of protein purification. SIRP technology should provide a useful tool for the purification of tagless proteins and peptides.

A simple silica-on-silicon technology-compatible design of 1×8 optical splitter based on field matching Y-branch with S-bend sine taper and arc waveguide

A simple technology-compatible design of silica-on-silicon based 1×8 optical power splitter is proposed. The device is based on symmetric Y-branch comprising of S-bend sine taper and S-bend sine arc waveguide. Initially, a symmetric Y-junction based 1×8 optical power splitter is designed, which can deliver the best result in simulated performance. The design is, however, not technology-compatible to be fabricated in silica-on-silicon, and therefore, the design is modified by incorporating a finite gap at the splitting junction, instead of zero-gap. Inclusion of this gap in the design slightly deteriorates the simulated performance of the splitter, however, a relatively better post-fabrication performance is expected in terms of total insertion loss, non-uniformity and the polarization dependent loss. Beam propagation method is applied for this work, where S-bend sine taper and arc waveguides are designed for optimal field matching in each Y-branch section of the optical splitter.

International Society of Blood Transfusion Committee on Terminology for Red Cell Surface Antigens: Cape Town report

International Society of Blood Transfusion Committee on Terminology for Red Cell Surface Antigens: Cape Town report

Distribution of Two-Phase Flow across 2.7-mm Vertically Split U-Type Junctions

A visual observation of the two-phase flow across vertically split U-type junctions and its flow redistribution inside two 2.7-mm diameter smooth tubes with curvature ratios (2R/D) of 3 and 7, respectively, are reported. The range of mass flux is between 100 and 700 kg/m2s and quality (x) ranges from 0.001 to 0.5. The ratio of liquid distribution between the upper and lower outlet legs is related to the inlet flow pattern, but its influence is reduced at higher mass flux. The difference in liquid flow rates in the lower and upper legs is significantly affected by gravity at a small inlet mass flux, but this difference becomes less profound when the inlet mass flux is increased. The difference between the liquid flux in the upper and lower leg is reduced for the smaller curvature radius due to the reduced effect of gravity between the upper and lower legs. However, there is no consistent trend of gas flow distribution across the U-type junction as compared to liquid flow distribution. The air mass flux in the upper and lower legs always increase with an increase in both gas quality and the total mass flux.

Visualization of mode transformation in a planar waveguide splitter by near-field optical phase imaging

The gradual transformation of a guided TM00 mode into an “intermediate” double mode by a splitting junction has been investigated with a phase-sensitive photon scanning tunneling microscope. Field profiles and wave vectors of the modes have been directly determined from the phase information. Via a Fourier analysis of the measured phase and amplitude maps the decay of the TM00 mode and buildup of the intermediate mode have been directly visualized. Phase singularities and phase jumps in the transition region underline the mode transformation process. Finally, a partial polarization conversion of the TM modes to TE-polarized modes has been observed.

Electron Crystallographic Methods for Investigating Gap Junction Structure

Gap junctions are clusters of closely packed intercellular membrane channels embedded in the plasma membranes of two adjoining cells. The central pore of the membrane channels serves as a conduit between cell cytoplasms for molecules less than 1000 Da in size. Advances in the purification of gap junctions and electron cryocrystallography and computer reconstruction techniques have produced new insights into the intercellular channel structure. Methods are described here for the purification of gap junction membranes, biochemical treatments to produce hemichannel layers (“split junctions”), assessment of the purity of gap junction preparations, electron cryomicroscopy, image processing and reconstruction, three-dimensional visualization, and interpretation. The critical step in electron crystallographic structure determination remains the isolation of crystalline material in sufficient and pure quantities for recording of electron microscope images. Along with sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Western blotting, the quality of gap junction purification is assessed using electron microscopy of negatively stained preparations. Electron microscopy is also used to assess the crystallinity of the purified gap junctions and split junctions. Electron cryocrystallography is a powerful technique for high-resolution structural characterization. Image processing is used to combine and enhance two-dimensional images. Electron crystallographic analysis is used to generate a three-dimensional structure from a set of electron micrographs. This three-dimensional information is extracted from a set of images recorded after tilting the specimen in the electron microscope stage and recombined using Fourier analysis techniques analogous to those used in X-ray crystallography. Computer modeling of the three-dimensional gap junction structures is a useful tool for analyzing hemichannel docking.