Two-cell Systems Research Articles

Biosynthesis of C12 Fatty Alcohols by Whole Cell Biotransformation of C12 Derivatives Using Escherichia coli Two-cell Systems Expressing CAR and ADH

Biosynthesis of C12 Fatty Alcohols by Whole Cell Biotransformation of C12 Derivatives Using Escherichia coli Two-cell Systems Expressing CAR and ADH

Analysis of Drone Placement Strategies for Complete Interference Cancellation in Two-Cell NOMA CoMP Systems

The use of unmanned aerial vehicles (UAV) as flying base stations is rapidly growing in the field of wireless communications to leverage the capacity of congested cells. This study considers a two-cell system where one of the cells is saturated, i.e. can no longer serve its users, and is supported by a UAV. The UAV positioning problem is investigated specifically to benefit from the interference cancellation properties available through the introduction of power-domain non-orthogonal multiple access (NOMA) techniques in coordinated multipoint (CoMP) systems. Indeed, adequate placement of the UAV can enable triple mutual successive interference cancellation (TMSIC) between a triplet of users, including a cell-edge and a cell-center user in each cell, to maximize system throughput or a mixture of throughput and TMSIC probability. The random line-of-sight/non-line-of-sight realizations of air-to-ground links between users and UAV are taken into account in the problem modeling, showing a significant improvement in performance compared to the conventional mean path loss model. The performance evaluation highlights the existing trade-offs between system capacity, fairness, and computational complexity of the investigated approaches.

Performance of Multi-Cell Massive MIMO Systems With Interference Decoding

We consider a multi-cell massive MIMO system where a time-division duplex protocol is used to estimate the channel state information via uplink pilots. When maximum ratio combining (MRC) is used at the BSs, the re-use of pilots across cells causes the pilot contamination effect which yields interference components that do not vanish as the number of base-station (BS) antennas $M \rightarrow \infty$. When treating interference as noise (TIN), this phenomenon limits the performance of multi-cell massive MIMO systems. In this paper, we analyze more advanced schemes based on simultaneous unique decoding (SD) as well as simultaneous non-unique decoding (SND) of the interference that can provide unbounded rate as $M \rightarrow \infty$. We also establish a worst-case uncorrelated noise technique for multiple-access channels to derive achievable rate expressions for finite $M$. Furthermore, we study a much simpler subset of SND (called S-SND) which provides a lower bound to SND and achieves unbounded rate as $M \rightarrow \infty$, and also outperforms SD for finite $M$. For the special cases of two-cell and three-cell systems, using a maximum symmetric rate allocation policy we compare the performance of different interference decoding schemes with that of TIN. Finally, we numerically illustrate the improved performance of the proposed schemes.

Hydrothermal Aging Factor Estimation for Two-Cell Diesel-Engine SCR Systems via a Dual Time-Scale Unscented Kalman Filter

Selective catalytic reduction (SCR) systems have been widely used to meet the emission regulations and two-cell SCR systems have shown the advantages of high NO $_{x}$ conversion efficiency and low NH $_{3}$ slip simultaneously. However, it is noteworthy that the catalyst performance of SCR device would degrade over the service time gradually. If the performance degrading is not well-compensated, the NO $_{x}$ conversion efficiency would reduce significantly. Different from detecting the aging issue in the laboratory, a practical method is to design an observer to estimate the aging factor online such that the urea injection can be modified accordingly. In this paper, we aim to construct an aging-factor observer for two-cell SCR systems. In order to reduce the algorithm computational load and guarantee the implementation performance, we propose a dual time-scale algorithm based on two-cell SCR model and unscented Kalman filter. There is a fast time scale and a slow time scale in the algorithm. Two simulation studies of constant aging factor and time-varying aging factor are investigated in the simulation environment of MATLAB/SIMULINK. The simulation results indicate that the proposed dual time-scale observer works well under different conditions and the calculational load is reduced significantly.

Reduction of SINR Fluctuation in Indoor Multi-Cell VLC Systems Using Optimized Angle Diversity Receiver

Due to severe inter-cell interference (ICI), the signal-to- interference-and-noise ratio (SINR) suffers from very significant fluctuation in indoor multi-cell visible light communication (VLC) systems, which greatly limits the overall system performance. In this paper, we propose and evaluate a generalized angle diversity receiver (ADR) structure to reduce SINR fluctuation in indoor multi-cell VLC systems. The generalized ADR consists of one top detector and multiple inclined side detectors. In an indoor multi-cell VLC system using the generalized ADR, the inclination angle of the side detectors is optimized in order to minimize the SINR fluctuation over the receiving plane, where the impact of receiver random rotation is considered. An optimized ADR with different numbers of detectors is analyzed with different LED layouts and diversity combining techniques in a typical indoor environment. Analytical results show that the SINR fluctuation is gradually reduced when more detectors are equipped in the optimized ADR. In an indoor two-cell VLC system, much more significant SINR fluctuation reduction is achieved by using select-best combining (SBC). However, nearly the same SINR fluctuations are obtained in an indoor four-cell VLC system when using SBC and maximal-ratio combining (MRC). By applying the optimized ADR, up to 15.9 and 32.4-dB SINR fluctuation reductions can be achieved in comparison to a conventional single-element receiver (SER) in indoor two-cell and four-cell VLC systems, respectively.

Improving Performance of Treatment Wetlands: Evaluation of Supplemental Aeration, Varying Flow Direction, and Phosphorus Removing Filters

Pollutant removal was compared among subsurface flow constructed wetland (CW) mesocosms used for dairy farm wastewater treatment. Supplemental aeration, flow direction, and the use of phosphorus-reducing filters (PRFs) were varied among the CWs. The following were compared: (1) vertical flow CWs with and without supplemental aeration, (2) aerated CWs with horizontal and vertical flow directions, (3) single-cell and two-cell treatment systems, and (4) wetland-wetland systems (two CWs in series) and wetland-PRF systems (a CW followed by a PRF). The results from this investigation showed that, first, nearly all treatment strategies, either singly or in pairs, substantially reduced almost all the contaminants we tested. Second, supplemental aeration resulted in higher ammonium-nitrogen (NH4-N) removal efficiencies in aerated vertical flow CWs, compared to unaerated CWs. However, it caused no further improvement in dissolved reactive phosphorus (DRP), total suspended solids (TSS), E. coli, or BOD5 removal. Third, there was no difference between aerated horizontal and aerated vertical flow CWs in removal of any of the tested contaminants. Fourth, adding a second stage of treatment significantly improved DRP, TSS, E. coli, and NH4-N removal, but not BOD5. Finally, treatment systems with PRFs showed superior performance in DRP and E. coli removal.

A fuzzy logic urea dosage controller design for two-cell selective catalytic reduction systems

Diesel engines have dominated in the heavy-duty vehicular and marine power source. However, the induced air pollution is a big problem. As people's awareness of environmental protection increasing, the emission regulations of diesel-engine are becoming more stringent. In order to achieve the emission regulations, the after-treatment system is a necessary choice. Specifically, the selective catalytic reduction (SCR) system has been widely applied to reduce the NOX emissions of diesel engine. Different from single-cell SCR systems, the two-cell systems have various benefits from the modeling and control perspective. In this paper, the urea dosage controller design for two-cell SCR systems was investigated. Firstly, the two-cell SCR modeling was introduced. Based on the developed model, the design procedure for the fuzzy logic urea dosage controller was well addressed. Secondly, simulations and comparisons were employed via an experimental verification of the whole vehicle simulator. And the results showed that the designed controller simultaneously achieved high NOX reduction rate and low tail-pipe ammonia slip.

Integrated Study of Inland-Vessel Diesel Engine Two-Cell SCR Systems With Dynamic References

In this paper, we investigate the integrated study of closed-loop control for two-cell selective catalytic reduction (SCR) systems with application to diesel engine-powered small inland vessels. For two-cell SCR systems, the first catalyst cell is mainly used to reduce the nitrogen oxide (NO x ) emissions and the second cell aims to adsorb the ammonia from the first cell. Therefore, the ammonia coverage ratios for the first and second SCR cells may be different, and their values affect both the SCR NO x conversion efficiency and tailpipe ammonia slip. Based on the optimization results, several dynamic ammonia-coverage-ratio reference generators are designed and implemented to online produce the references for the two SCR cells. With the generated references, an adaptive backstepping controller is adopted to control the two-cell SCR system. Experimental tests are carried out based on the US06 test cycle. It infers from the test results that the control performance with the designed dynamic reference generators has certain advantages over the performance with selected constant references and the lumped cases.

Development of a robust reporter gene assay to measure the bioactivity of anti-PD-1/anti-PD-L1 therapeutic antibodies

Being regarded as the ‘cancer panacea’, the anti-PD-1/anti-PD-L1 monoclonal antibodies (mAbs) have become the R&D focus of biopharmaceutical industries. Several marketed such mAbs have been proved particularly effective in treating various cancers. However, the cell-based bioassay to measure the biological activities of the anti-PD-1/anti-PD-L1 mAbs as the lot release or stability test has been a great challenge to quality control laboratories due to the immunomodulating nature of the mAbs. Here, we describe the development and validation of a reporter gene assay consisting of two-cell systems to measure the bioactivity of the anti-PD-1/anti-PD-L1 mAbs. We have generated two cell lines, the CHO-PD-L1-CD3L cell line that stably expresses PD-L1 and the membrane-anchored anti-CD3 single chain antibody fragment (scFv) named CD3L and the Jurkat-PD-1-NFAT cell line that stably expresses PD-1 and the luciferase gene under the control of the NFAT response elements from the IL-2 promoter. The results show good dose-dependent responsiveness to the mAbs and excellent performance characteristics including specificity, accuracy and precision. The biological relevance of the assay, the passage stability of the two cell lines, and the capability of measuring various anti-PD-1/anti-PD-L1 mAbs render this assay applicable not only in lot release and stability test but also in characterization and development of new anti-PD1/anti-PD-L1 mAbs.

Dynamics of two-cell systems with discrete delays

We consider the system of delay differential equations (DDE) representing the models containing two cells with time-delayed connections. We investigate global, local stability and the bifurcations of the trivial solution under some generic conditions on the Taylor coefficients of the DDE. Regarding eigenvalues of the connection matrix as bifurcation parameters, we obtain codimension one bifurcations (including pitchfork, transcritical and Hopf bifurcation) and Takens-Bogdanov bifurcation as a codimension two bifurcation. For application purposes, this is important since one can now identify the possible asymptotic dynamics of the DDE near the bifurcation points by computing quantities which depend explicitly on the Taylor coefficients of the original DDE. Finally, we show that the analytical results agree with numerical simulations.

Optimal Dosing and Sizing Optimization for a Ground-Vehicle Diesel-Engine Two-Cell Selective Catalytic Reduction System

In this paper, we investigate the cycle-based sizing optimization for diesel-engine two-cell selective catalytic reduction (SCR) systems. In modeling the SCR system, it is generally assumed that the states inside the catalyst can are homogeneous to simplify the modeling work. However, the actual states are not homogeneous, and the modeling error becomes large if the catalyst length is long. To reduce the modeling error, the states are assumed piecewise homogeneous, i.e., the catalyst is sliced into multicells and the states for each cell are assumed homogeneous. In this paper, we focus on the two-cell SCR systems where the two cells are connected in series and where the chemical reaction rates are assumed identical for the two cells. Considering the main chemical reactions and assuming that each cell is a continuous stirred tank reactor, a nonlinear system model with six states is obtained. To simultaneously reduce the tailpipe $\mbox{NO}_{x}$ and ammonia slip, it is quite interesting to study the optimal control of the urea dosing such that the $\mbox{NO}_{x}$ emissions can be maximally converted and where the ammonia slip is constrained. A dynamic programming (DP) algorithm that has a tolerable computational load is proposed. Since the whole catalyst is sliced into two cells, the next motivation is how to divide the catalyst such that the $\mbox{NO}_{x}$ conversion efficiency can be maximized while meeting the tailpipe ammonia constraint. The best sizing ratio of the SCR system in our application for the US06 test cycle is found to be 60%–40%.

Estimation and adaptive nonlinear model predictive control of selective catalytic reduction systems in automotive applications

The demands of high NOx conversion efficiency and low tailpipe ammonia slip for urea-based selective catalytic reduction (SCR) systems have been substantially increased in the past decade, as NOx emission legislations for Diesel engines are becoming more stringent than ever before. Since catalyst aging has a significant impact on SCR performance, robust and adaptive SCR control has been preferred for degraded SCR systems to realize emission control objectives. The purpose of this paper is twofold. Firstly, a robust ammonia coverage ratio observer was designed for estimating the ammonia coverage ratio reference for catalysts with different aging levels. An ammonia storage capacity observer was developed for estimating the actual ammonia storage capacity which can be reduced due to catalyst aging. An adaptive ammonia coverage ratio reference design was then developed to estimate the desired ammonia coverage ratio ranges at each instantaneous engine operating point for both single-cell and two-cell SCR systems at different aging levels based on a singular perturbation method. Secondly, to ensure the estimated ammonia coverage ratio falls in the desired ranges for most of engine operating conditions, robust nonlinear model predictive control (NMPC) algorithms were designed for both single-cell and two-cell SCR systems. Experimental data over US06 cycle were collected from a Diesel engine and aftertreatment system platform for controller verification. Simulation results under US06 test cycle demonstrate that the proposed NMPC algorithms were capable of consistently achieving high NOx conversion efficiency (>95.6%) and constrained tailpipe ammonia slip (<10ppm on average and <12ppm on the peak) for both fresh catalyst and aged catalyst with 30% loss of ammonia storage capacity.

Cycle-based ammonia-coverage-ratio reference generator design for Diesel engine two-cell selective catalytic reduction systems via a fuzzy approach

In this paper, we investigate the cycle-based ammonia-coverage-ratio reference generator design for Diesel engine two-cell selective catalytic reduction (SCR) systems. Since the dynamic programming algorithm is time-consuming, the motivation of this research is to develop the ammonia-coverage-ratio reference generator which has the capacity to produce the optimal desired ammonia coverage ratios onboard. With the sizing optimization results obtained from the dynamic programming algorithm, we propose an ammonia-coverage-ratio reference generator by using the adaptive-network-based fuzzy inference system (ANFIS). In the generator, the inputs include the engine-out NOx concentration, the ammonia concentration between the two cans, and the ammonia concentration in the tailpipe. The performance of the generator is comparable to the optimized results using the dynamic programming algorithm.

Sliding-mode observers for urea selective catalytic reduction system state estimations based on nitrogen oxide sensor measurements

The state estimations for urea-based selective catalytic reduction systems have received growing interest in the past few years because of their importance to selective catalytic reduction controls and onboard diagnostics, as well as the high cost and difficulties of direct sensor measurements. Most of the existing estimation techniques suffer because of the ammonia cross-sensitivity from the nitrogen oxide sensor and require an ammonia sensor to be available downstream of the selective catalytic reduction, which may increase the costs of production urea-based selective catalytic reduction systems. The purpose of this study is to design observers for estimating the key states (the nitrogen oxide concentration, the ammonia concentration, and the ammonia coverage ratio) of the urea-based selective catalytic reduction system at the selective catalytic reduction outlet in various situations, using only a nitrogen oxide sensor. The sliding-mode observers were designed to ensure high robustness against the ammonia cross-sensitivity from the nitrogen oxide sensor and uncertainties from the selective catalytic reduction inputs. Simulation verification results under the Federal Test Procedure 75 test cycle showed that the proposed observers were able to estimate the states accurately, in hot and cold exhaust conditions, for both single-cell selective catalytic reduction systems and two-cell selective catalytic reduction systems. The proposed observer-based estimation technique has the potential for reducing the cost of advanced selective catalytic reduction control systems and for applying it to onboard diagnostics.

Novel in vitro respiratory models to study lung development, physiology, pathology and toxicology

Detailed studies of lung pathology in patients during the course of development of acute lung injury or respiratory distress are limited, and in the past information related to lung-specific responses has been derived from the study of lungs from patients who died at autopsy or from animal models. Development of good in vitro human tissue models would help to bridge the gap in our current knowledge of lung responses and provide a better understanding of lung development, physiology and pathology. In vitro models of simple one-cell or two-cell culture systems as well as complex multicellular lung analogs that reproduce defined components of specific human lung responses have already been realized. A benefit of current in vitro lung models is that hypotheses generated from review of data from human or animal disease studies can be tested directly in engineered human tissue models. Results of studies done using simple in vitro lung systems or more complex three-dimensional models have already been used to examine cell-based responses, physiologic functions, pathologic changes and even drug toxicity or drug responses. In the future we will create models with specific genetic profiles to test the importance of single gene products or pathways of significance. Recent development of microfluidics-based models that support high-throughput screening will allow early-stage toxicity testing in human systems and faster development of new and innovative medical products. Model design in the future will also allow for evaluation of multiple organ systems at once, providing a more holistic or whole-body approach to understanding human physiology and responses.

Reliability and Security Analysis on Two-Cell Dynamic Redundant System

Based on analysis on reliability and security on three types of two-cell dynamic redundant systems which has been widely applied in modern railway signal system, whose isomorphic Markov model was established in this paper. During modeling several important factors, including common-cause failure, coverage of diagnostic systems, online maintainability, and periodic inspection maintenance, and as well as many failure modes, were considered, which made the established model more credible. Through analysis and calculation on reliability and security indexes of the three types of two-module dynamic redundant structures, the paper acquires a significant conclusion, i.e., the safety and reliability of the kind of structure possesses an upper limit, and can not be inordinately improved through the hardware and software comparison methods under the failure and repairing rate fixed. Finally, the paper performs the simulation investigations, and compares the calculation results of the three redundant systems, and analysis each advantages and disadvantages, and gives out each application scope, which provides a theoretical technical support for the railway signal equipments selection. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2492

Simulation of alloy thermodynamics: From an atomic to a mesoscale Hamiltonian

Starting from an atomic interaction model of an alloy with a clustering tendency, a mesoscopic thermodynamic simulation method is developed. The alloy is represented by a mesoscopic rigid lattice of cells characterized by the number of solute atoms they contain and a discrete cellular Monte Carlo (CMC) algorithm is designed to perform simulations at this scale. The central quantity is a mesoscopic free energy, whose components (local free energy and stiffness parameter) are extracted from the equilibrium properties of single-cell and two-cell systems. Particular attention has been paid to properly incorporate, at mesoscale, the correlations between neighboring cells with identical concentrations. Finally, the ability of the CMC method to compute thermodynamic properties such as phase diagrams, interface profiles, and equilibrium fluctuation spectra is illustrated on a model alloy as well as on an Ising model with interactions up to the second-nearest neighbors, previously developed for body-centered-cubic Fe-Cu alloys. The very good agreement between the CMC calculation results for different cell sizes and direct computations at the atomic scale indicate that the proposed scale change is thermodynamically consistent.

Weighted sum throughput maximisation for downlink multicell orthogonal frequency-division multiple access systems by intercell interference limitation

This study addresses resource allocation for weighted sum throughput maximisation (WSTM) in a sectorised two-cell downlink orthogonal frequency-division multiple access systems impaired by multicell interference. It is well known that the optimisation problem for this scenario is NP-hard and combinational, which is here converted to a novel WSTM problem based on the intercell interference limitation. In the new problem, we use a lower bound of throughout as a cost function which is convex, and so it simplifies the power allocation algorithm and offers a better convergence. Then, two subclasses of this new problem are solved based on the dual Lagrange framework. By the first subclass, on the assumption that subcarrier allocation parameters are fixed, an algorithm for optimal power allocation (OPA) is obtained. However, the optimal resource allocation requires an exhaustive search, including the OPA which cannot be implemented in practice because of its high complexity. By the second subclass, the joint subcarrier allocation and power distribution for two adjacent cells as a general problem is solved. Here, the algorithm allocates simultaneously the subcarriers and the power of the considered two cells while the resource allocation parameters of both cells are coupled mutually. After that, we propose a new centralised algorithm which combines the proposed power allocation with the non-convex subcarrier allocation without increase in the complexity. Simulation results show that the proposed algorithms achieve efficient performance in many practical situations.

Rescue effects in radiobiology: Unirradiated bystander cells assist irradiated cells through intercellular signal feedback

Mammalian cells respond to ionization radiation by sending out extracellular signals to affect non-irradiated neighboring cells, which is referred to as radiation induced bystander effect. In the present paper, we described a phenomenon entitled the “rescue effects”, where the bystander cells rescued the irradiated cells through intercellular signal feedback. The effect was observed in both human primary fibroblast (NHLF) and cancer cells (HeLa) using two-cell co-culture systems. After co-culturing irradiated cells with unirradiated bystander cells for 24 h, the numbers of 53BP1 foci, corresponding to the number of DNA double-strand breaks in the irradiated cells were less than those in the irradiated cells that were not co-cultured with the bystander cells (0.78 ± 0.04 foci/cell vs. 0.90 ± 0.04 foci/cell) at a statistically significant level. Similarly, both micronucleus formation and extent of apoptosis in the irradiated cells were different at statistically significant levels if they were co-cultured with the bystander cells. Furthermore, it was found that unirradiated normal cells would also reduce the micronucleus formation in irradiated cancer cells. These results suggested that the rescue effects could participate in repairing the radiation-induced DNA damages through a media-mediated signaling feedback, thereby mitigating the cytotoxicity and genotoxicity of ionizing radiation.

Membrane redistributions through multi-intercellular exchanges and serial trogocytosis

Trogocytosis is a rapid transfer between cells of membranes and associated proteins. Trogocytic exchanges have been investigated between different cell types, mainly in two-cell systems, involving one donor and one acceptor cell type. Here, we studied trogocytosis in a more complex system, involving not only several immune cell subsets but also multiple tumor cells. We show that CD4(+) T cells, CD8(+) T cells and monocytes can acquire membrane patches and the intact proteins they contain from different tumor cells by multiple simultaneous trogocytoses. The trogocytic capabilities of CD4(+) and CD8(+) T cells were found to be similar, but inferior to that of autologous monocytes. Activated peripheral-blood mononuclear cells (PBMCs) may also exchange membranes between themselves in an all-autologous system. For this reason, monocytes are capable of acquiring membranes from multiple tumor cell sources, and transfer them again to autologous T cells, along with some of their own membranes (serial trogocytosis). Our data illustrate the extent of membrane exchanges between autologous activated immune effector cells and their environment, and how the cellular content of the local environment, including "bystander" cells, may impact the functions of immune effector cells.