Lateral Mode Research Articles

(Invited) Recent Progress on Selective Area Regrowth and Doping for Vertical GaN Power Transistors

Wide bandgap semiconductor GaN is a very promising candidate for efficient power conversion applications due to its large bandgap energy and high critical electric field. Vertical GaN power devices grown on bulk substrates are enabling the next-generation power electronics with higher efficiency, higher power density and smaller form factor. However, selective area doping in GaN is far from mature, which is limiting the realization of many advanced GaN power devices such as vertical junction effect transistors (VJFETs), junction barrier Schottky (JBS), superjunction, and junction termination extension (JTE). Epitaxial regrowth or selective area regrowth has been regarded as one of the most promising routes to selective area doping.Currently, the regrown p-n junctions suffer from large leakage currents and premature breakdown. To understand this phenomena, the regrowth experiments were carried out by metalorganic chemical vapor deposition via an etching-then-regrowth process. The etching was performed by inductively coupled plasma (ICP) etching. The regrowth dynamics with different trench widths and depths was revealed, where basal plane and lateral growth modes were identified. It was also found that shallow trenches for selective area regrowth was beneficial for reducing the reverse leakage currents of regrown p-n junctions.The regrowth interface plays a critical role in understating the leakage mechanism of regrown p-n junctions. With developed material characterization techniques, the regrown structures and interface were analyzed in detail. Cathodoluminescence (CL) and secondary electrons (SEs) were used to realize both lateral and vertical dopant profiling at a sub-micron scale [1]. The regrowth interface by dry etching accumulated lots of impurities and charges, contributing to the formation of a p+-n+ tunneling junction. This was further confirmed by the electrostatic potential profile at the regrowth interface using electron holography [2]. This tunneling junction is likely to be the major contributor to the large reverse leakage currents and low breakdown voltages in regrown junctions. To improve the regrowth interface, novel etching technologies were demonstrated. It was found that low-power dry etching significantly reduced the interfacial charges and the reverse leakage currents of regrown p-n junctions [3]. Atomic layer etching (ALE) was also successfully developed for GaN, which uses self-limiting chemical processes, thus removing the damaged layers without inducing further etching damage. The tertiarybutylchloride (TBCl) based in situ etching may serve as an alternative etching method to dry etching with reduced etching damage [4]. In terms of devices, regrown p-n junctions with low leakage currents [3] and the first normally-off VJFETs were demonstrated. Further improvements in selective area regrowth and associated devices can be expected via regrowth optimization and regrowth interface engineering via surface treatments and low-damage etching. These results represent an important step towards realizing selective area doping for GaN power transistors. H. Liu et al., Appl. Phys. Lett., 114, 082102 (2019)S. Alugubelli, et al., Appl. Phys. Lett., 115, 201602 (2019)K. Fu et al., IEEE Electron Device Lett. 40, 1728 (2019)B. Li et al., Appl. Phys. Lett., 115, 162101 (2019)

Maneuver mode analysis and parametric modeling for hypersonic glide vehicles

The maneuver modes in the glide phase are explored from the perspective of hypersonic vehicle defense in this study, and a novel maneuver mode description approach is proposed. The longitudinal and lateral maneuver modes' mechanisms and evolution laws are explored. And, the focus of this research is on the evolution laws of complex lateral maneuver modes in real scenarios. To solve the maneuver mode description problems, a novel maneuver mode parametric analyzing and modeling method is proposed based on the Vector Auto-regressive model. Firstly, the Granger causality test is adopted to verify whether there are causal correlations between the maneuver characteristic parameter series, which have a high level of regularity and are taken as modeling variables. Then, the Vector Auto-regressive method is employed to model the coupling relationship between the maneuver characteristic parameters, as well as to provide a precise description method with simple structure and uniform form for various maneuver modes. Moreover, the model coefficients estimation and model order selection methods are presented. This study helps to deepen the understanding of the target's maneuver modes in hypersonic vehicle defense. Simulation results demonstrate that the proposed modeling method can greatly improve modeling accuracy.

Doublet-Singlet-Doublet Transition in a Single Organic Molecule Magnet On-Surface Constructed with up to 3 Aluminum Atoms.

Starting from a long aza-starphene neutral and nonmagnetic organic molecule, a single-molecule magnet is on-surface constructed using up to 3 light nonmagnetic aluminum (Al) atoms. Seldom observed in solution with transition-metal atoms and going from 1 to 3 Al coordinated atoms, the doublet-singlet-doublet transition is easily on-surface accessible using the scanning tunneling microscope single-atom and single-molecule manipulations on a gold(111) surface. With 3 coordinated Al atoms, the lateral vibration modes of the Al3-aza-starphene molecule magnet are largely frozen. Using the Kondo states, this opens the observation of the in-phase Al vertical atom vibrations and out-of-phase central phenyl vibrations.

Comparative dynamic flight stability of insect-inspired flapping-wing micro air vehicles in hover: Longitudinal and lateral motions

In this paper, we compare the characteristics of hovering stability for two insect-inspired flapping-wing micro air vehicles (FW-MAVs) with different strategies to generate control moments for the longitudinal and lateral attitude controls. The two robots were named according to their control mechanisms, i.e., the Stroke-Plane-Change (SPC), and the Trailing-Edge-Change (TEC). The forces and moments produced by flapping wings were computed by the computational fluid dynamics (CFD) method. The longitudinal and lateral flight characteristics were identified as one fast subsidence mode, one slow subsidence mode, and one divergence oscillation mode. The results revealed that the fast and slow subsidence modes in the longitudinal and lateral motions of the SPC were stabilized faster than those of the TEC, while both of the lateral and longitudinal divergence modes of the SPC were more unstable than those of the TEC. Moreover, the effect of the longitudinal and lateral derivatives on the system poles of the SPC were investigated. The results showed that the major source of instability in the longitudinal motion was the pitching derivative with respect to the horizontal speed, Mu+. Meanwhile, that in the lateral motion was the rolling derivative with respect to the horizontal side speed, Lv+. Overall, the time response of the SPC, when the body was disturbed by an external force, was relatively faster than that of the TEC. Therefore, using the SPC mechanism can give the FW-MAV more agility to operate in highly cluttered spaces with obstacles.

The investigation on flight quality of tilt-rotor aircraft

Purpose This paper aims to present an investigation on flight quality analysis and design of tilt-rotor aircraft combined with corresponding flight quality specifications. Design/methodology/approach From the perspective of modal characteristics of tilt-rotor aircraft, it focuses on the analysis of the change rules of the longitudinal short-term motion mode, lateral roll convergence mode, spiral mode and Dutch roll mode. Then, the flight quality design research is carried out using the explicit model tracking control method. The quantitative relationship between flight quality requirements and explicit model is established. Accordingly, the closed-loop flight quality of XV-15 tilt-rotor aircraft is evaluated. Findings The stability of spiral mode is the result of the interaction of various aerodynamic derivatives and spiral instability occurs in helicopter mode. The other motion modes are stable in full flight mode and meet the requirements of level 1 specified in ADS-33E-PRF and MIL-F-8785C flight quality specifications. There is a quantitative relationship between flight quality requirements and explicit model, and the flight quality of tilt-rotor aircraft is improved through the explicit model tracking control method. Practical implications The presented analysis results showed the influence of motion modes and flight quality and the effectiveness of explicit model tracking control method in flight quality improvement, which could be considered as new information for further flight quality design of tilt-rotor aircraft. Originality/value The originality of the paper lies in the proposed design and analysis method of the flight quality of tilt-rotor aircraft from the direction of the influence of its aerodynamic derivatives and motion modes.

Near-Infrared Photoresponse in Ge/Si Quantum Dots Enhanced by Photon-Trapping Hole Arrays.

Group-IV photonic devices that contain Si and Ge are very attractive due to their compatibility with integrated silicon photonics platforms. Despite the recent progress in fabrication of Ge/Si quantum dot (QD) photodetectors, their low quantum efficiency still remains a major challenge and different approaches to improve the QD photoresponse are under investigation. In this paper, we report on the fabrication and optical characterization of Ge/Si QD pin photodiodes integrated with photon-trapping microstructures for near-infrared photodetection. The photon traps represent vertical holes having 2D periodicity with a feature size of about 1 μm on the diode surface, which significantly increase the normal incidence light absorption of Ge/Si QDs due to generation of lateral optical modes in the wide telecommunication wavelength range. For a hole array periodicity of 1700 nm and hole diameter of 1130 nm, the responsivity of the photon-trapping device is found to be enhanced by about 25 times at μm and by 34 times at μm relative to a bare detector without holes. These results make the micro/nanohole Ge/Si QD photodiodes promising to cover the operation wavelength range from the telecom O-band (1260–1360 nm) up to the L-band (1565–1625 nm).

Growth Mechanisms and Morphology Engineering of Atomic Layer-Deposited WS2.

Transition-metal dichalcogenides (TMDs) have attracted intense research interest for a broad range of device applications. Atomic layer deposition (ALD), a CMOS compatible technique, can enable the preparation of high-quality TMD films on 8 to 12 in. wafers for large-scale circuit integration. However, the ALD growth mechanisms are still not fully understood. In this work, we systematically investigated the growth mechanisms for WS2 and found them to be strongly affected by nucleation density and film thickness. Transmission electron microscope imaging reveals the coexistence and competition of lateral and vertical growth mechanisms at different growth stages, and the critical thicknesses for each mechanism are obtained. The in-plane lateral growth mode dominates when the film thickness remains less than 5.6 nm (8 layers), while the vertical growth mode dominates when the thickness is greater than 20 nm. From the resulting understanding of these growth mechanisms, the conditions for film deposition were optimized and a maximum grain size of 108 nm was achieved. WS2-based field-effect transistors were fabricated with electron mobility and on/off current ratio up to 3.21 cm2 V-1 s-1 and 105, respectively. Particularly, this work proves the capability of synthesis of TMD films in a wafer scale with excellent controllability of thickness and morphology, enabling many potential applications other than transistors, such as nanowire- or nanosheet-based supercapacitors, batteries, sensors, and catalysis.

Static Elastoplastic Analysis of Turbine House under Different Lateral Loading MoDES in Conventional Island of Nuclear Power Plant

Nuclear island in nuclear power plant requires that under the extreme safety shutdown earthquake action, the collapse of the turbine house of conventional island shall not affect the safety of nuclear island, so as to ensure the functional integrity of nuclear island. At present, the way to meet this requirement is to carry out elastoplastic analysis on the turbine house of the regular island under the action of the ultimate safe earthquake to ensure that it does not collapse and its deformation meets the deformation requirements of the standard rare earthquake. Structure elastic-plastic analysis method with static analysis and dynamic elastic-plastic time history analysis, in this paper, the ci turbine room nappe analyzed, and compared the five kinds of lateral load loading mode of static elastoplastic analysis results, the seismic performance of the structure, puts forward the layer shear lateral loading mode suitable for ci turbine room structure static elastoplastic analysis.

Data-Driven Retrospective Cost Adaptive Control for Flight Control Applications

Unlike fixed-gain robust control, which trades off performance with modeling uncertainty, direct adaptive control uses partial modeling information for online tuning. The present paper combines retrospective cost adaptive control (RCAC), a direct adaptive control technique for sampled-data systems, with online system identification based on recursive least squares (RLS) with variable-rate forgetting (VRF). The combination of RCAC and RLS-VRF constitutes data-driven RCAC (DDRCAC), where the online system identification is used to construct the target model, which defines the retrospective performance variable. This paper investigates the ability of RLS-VRF to provide the modeling information needed for the target model, especially non-minimum-phase (NMP) zeros. DDRCAC is applied to single-input, single-output and multiple-input, multiple-output numerical examples with unknown NMP zeros, as well as several flight control problems, namely, unknown transition from minimum phase to NMP lateral dynamics, flexible modes, flutter, and nonlinear planar missile dynamics.

Perfectly-reflecting guided-mode-resonant photonic lattices possessing Mie modal memory.

Resonant periodic nanostructures provide perfect reflection across small or large spectral bandwidths depending on the choice of materials and design parameters. This effect has been known for decades, observed theoretically and experimentally via one-dimensional and two-dimensional structures commonly known as resonant gratings, metamaterials, and metasurfaces. The physical cause of this extraordinary phenomenon is guided-mode resonance mediated by lateral Bloch modes excited by evanescent diffraction orders in the subwavelength regime. In recent years, hundreds of papers have declared Fabry-Perot or Mie resonance to be the basis of the perfect reflection possessed by periodic metasurfaces. Treating a simple one-dimensional cylindrical-rod lattice, here we show clearly and unambiguously that Mie resonance does not cause perfect reflection. In fact, the spectral placement of the Bloch-mode-mediated zero-order reflectance is primarily controlled by the lattice period by way of its direct effect on the homogenized effective-medium refractive index of the lattice. In general, perfect reflection appears away from Mie resonance. However, when the lateral leaky-mode field profiles approach the isolated-particle Mie field profiles, the resonance locus tends towards the Mie resonance wavelength. The fact that the lattice fields "remember" the isolated particle fields is referred here as "Mie modal memory." On erasure of the Mie memory by an index-matched sublayer, we show that perfect reflection survives with the resonance locus approaching the homogenized effective-medium waveguide locus. The results presented here will aid in clarifying the physical basis of general resonant photonic lattices.

Shaking table testing of groin vaults made by 3D printers

A novel experimental study of the dynamic and seismic response of a 2 m × 2 m in plan - 0.7 m in height groin vault model, involving 266 tests conducted on the shaking table of EQUALS laboratory, University of Bristol, UK, is reported. The experimental rig consists of blocks formed by a 3D-printed plastic skin to provide stiffness and strength, filled with mortar. Dry joints between the voussoirs are formed for ease of testing and vault reconstruction. No investigations of this kind and size have been attempted in the past. Two support boundary conditions involving four lateral confinement modes, leading to various vault configurations, were tested. White-noise, sinusoidal and earthquake motions were imposed in one horizontal direction, with progressively increasing amplitude and different frequencies, up to collapse. The model exhibited a strong non-linear behaviour, characterised by decreasing fundamental frequency and increasing damping with increasing table acceleration. Failure mechanisms and collapse accelerations were found to mainly depend on base restraint conditions.

Vocal fold vibration mode changes due to cricothyroid and thyroarytenoid muscle interaction in a three-dimensional model of the canine larynx.

Using a continuum model based on magnetic resonance imaging of a canine larynx, parametric simulations of the vocal fold vibration during phonation were conducted with the cricothyroid muscle (CT) and the thyroarytenoid muscle (TA) independently activated from zero to full activation. The fundamental frequency (f0) first increased and then experienced a downward jump as TA activity gradually increased under moderate to high CT activation. Proper orthogonal decomposition analysis revealed that the vocal fold vibrations were dominated by two modes representing a lateral motion and rotational motion, respectively, and the f0 drop was associated with a switch on the order of the two modes. In another parametric set where only the vocalis was active, f0 increased monotonically with both TA and CT activity and the mode switch did not occur. The results suggested that the active stress in the TA, which causes large stress differences between the body and cover, is essential for the occurrence of the rotational mode and mode switch. Relatively greater TA activity tends to promote the rotational mode, while relatively greater CT activity tends to promote the lateral mode. The results also suggested that the vibration modes affected f0 by affecting the contribution of the TA stress to the effective stiffness. The switch in the dominant mode caused the non-monotonic change of f0.

Resting-State Functional Connectivity of the Ageing Female Brain-Differences Between Young and Elderly Female Adults on Multislice Short TR rs-fMRI.

Introduction: Age-related brain changes are one of the most important world health problems due to the rising lifespan and size of the elderly populations. The aim of the study was to assess the effect of ageing in women on coordinated brain activity between eight resting-state networks.Material and Methods: The study group comprised 60 healthy female volunteers who were divided into two age groups: younger women (aged 20–30 n = 30) and older women (aged 55–80 n = 30). Resting-state data were collected during a 15 min scan in the eyes-closed condition using a 3T MR scanner. Data were preprocessed and analysed using the CONN toolbox version 19.c. The large-scale network analysis included a priori selected regions of interest of the default mode, the sensorimotor, the visual, the salience, the dorsal attention, the fronto-parietal, the language, and the cerebellar network.Results: Within the visual, the default mode, the salience, and the sensorimotor network, the intra-network resting-state functional connectivity (RSFC) was significantly higher with increasing age. There was also a significant increase in the inter-network RSFC in older females compared to young females found in the following networks: sensorimotor lateral and salience, salience and language, salience and fronto-parietal, cerebellar anterior and default mode, cerebellar posterior and default mode, visual and sensorimotor lateral, visual and sensorimotor, visual lateral and default mode, language and cerebellar anterior, language and cerebellar posterior, fronto-parietal and cerebellar anterior, dorsal attention and sensorimotor, dorsal attention and default mode, sensorimotor superior, and salience. Compared to young females, elderly women presented bilaterally significantly lower inter-network RSFC of the salience supramarginal gyrus and cerebellar posterior, sensorimotor lateral, and cerebellar anterior network, and sensorimotor lateral and cerebellar posterior as well as sensorimotor superior and cerebellar posterior network.Conclusion: Increased RSFC between some brain networks including the visual, the default mode, the salience, the sensorimotor, the language, the fronto-parietal, the dorsal attention, and the cerebellar networks in elderly females may function as a compensation mechanism during the ageing process of the brain. To the best of our knowledge, this study is the first to report the importance of increase of cerebellar networks RSFC during healthy female ageing.

Mechanical properties and acoustic emission data analyses of crumb rubber concrete under biaxial compression stress states

Crumb rubber concrete (CRC) is increasingly becoming one of the environmental protection ways to solve the problem of waste rubber tires. This paper mainly analyzes the mechanical properties and acoustic emission (AE) parameters under biaxial compression stress states of CRC with different rubber contents (0%, 5% and 10%). Two biaxial loading modes, constant lateral pressure loading mode (LPM) and proportional loading mode (PM), were used to determine the failure modes, strength characteristics and peak strain of the concrete under different stress ratio conditions. The experiment results show that the compressive strength and peak strain of CRC are improved under biaxial stress like plain concrete (PC), but due to the weak bond between rubber and cement-based materials, the strength growth rate of CRC is not as much as PC. Therefore, the modified Kupfer failure criterions are proposed to describe its strength growth laws. Meanwhile, under the uniaxial loading mode and LPM, the initiation and growth of concrete cracks were monitored based on AE technology. The analysis used various AE statistical parameters, including the AE ringing counts, cumulative energy, amplitude distribution, b-value and RA-AF value analyses. Based on the above AE parameters can be related to the mechanical characteristics of the concrete, and the similarities and differences between CRC and PC are analyzed in the whole failure stage. The results show that CRC has better integrity in main collapse stage with mainly microcracks, which means the plastic failure characteristics. This paper provides experimental and theoretical foundations for the strength analyses and failure characteristics of CRC structures under complex stress states.

Impacts of load distribution and lane width on pavement rutting performance for automated vehicles

ABSTRACT Over the recent years, considerable attention has been drawn to intelligent driving technologies and particularly to automated vehicles (AVs). The deployment of AVs would provide the opportunity to have more control over the dynamics of the vehicle, including its lateral movement, which can affect the pavement's long-term rutting performance. The controlled lateral movement of the AVs may also imply a reduced lane width. This paper evaluates the impacts of dedicating a reduced lane width to AVs on pavement rutting performance, considering two lateral movement modes for AVs; zero-wander and uniform-wander. A finite element model was developed using ABAQUS software. The rutting simulation results of this study showed that the abrupt changes in the loading schemes of the zero- and uniform-wander modes cause considerable accumulated rutting in the edges of the loading areas. This is significantly greater than the total rutting induced by the human-driven vehicles (HDVs) following the normal-wander mode, which causes a compensated rutting behaviour by a gradual increase in loading time. Furthermore, the comparison between rutting depths in different lane widths reveals that when dedicating the narrower lane for AVs with a uniform-wander distribution, the pavement's total rutting depth would remarkably increase compared to the wider lanes.

FtsZ induces membrane deformations via torsional stress upon GTP hydrolysis

FtsZ is a key component in bacterial cell division, being the primary protein of the presumably contractile Z ring. In vivo and in vitro, it shows two distinctive features that could so far, however, not be mechanistically linked: self-organization into directionally treadmilling vortices on solid supported membranes, and shape deformation of flexible liposomes. In cells, circumferential treadmilling of FtsZ was shown to recruit septum-building enzymes, but an active force production remains elusive. To gain mechanistic understanding of FtsZ dependent membrane deformations and constriction, we design an in vitro assay based on soft lipid tubes pulled from FtsZ decorated giant lipid vesicles (GUVs) by optical tweezers. FtsZ filaments actively transform these tubes into spring-like structures, where GTPase activity promotes spring compression. Operating the optical tweezers in lateral vibration mode and assigning spring constants to FtsZ coated tubes, the directional forces that FtsZ-YFP-mts rings exert upon GTP hydrolysis can be estimated to be in the pN range. They are sufficient to induce membrane budding with constricting necks on both, giant vesicles and E.coli cells devoid of their cell walls. We hypothesize that these forces result from torsional stress in a GTPase activity dependent manner.

Bulk-surface coupling identifies the mechanistic connection between Min-protein patterns in vivo and in vitro

Self-organisation of Min proteins is responsible for the spatial control of cell division in Escherichia coli, and has been studied both in vivo and in vitro. Intriguingly, the protein patterns observed in these settings differ qualitatively and quantitatively. This puzzling dichotomy has not been resolved to date. Using reconstituted proteins in laterally wide microchambers with a well-controlled height, we experimentally show that the Min protein dynamics on the membrane crucially depend on the micro chamber height due to bulk concentration gradients orthogonal to the membrane. A theoretical analysis shows that in vitro patterns at low microchamber height are driven by the same lateral oscillation mode as pole-to-pole oscillations in vivo. At larger microchamber height, additional vertical oscillation modes set in, marking the transition to a qualitatively different in vitro regime. Our work reveals the qualitatively different mechanisms of mass transport that govern Min protein-patterns for different bulk heights and thus shows that Min patterns in cells are governed by a different mechanism than those in vitro.

Modeling and Analysis of a Generic Internal Cargo Airdrop System for a Tandem Helicopter

This article describes the results of modeling and analysis of a generic internal cargo system using a discretization method of the vector mechanics. The model can be easily incorporated into a tandem helicopter model and is intended for use of simulation and investigating the problems of flight dynamics, control, etc., both in flight operation loading a cargo and flight operation in the process of airdrops. The model is derived by considering the main descriptions of the cargo, including the linear and rotational dynamics, the kinematics, and the forces and moments acting on the helicopter. A simulation method embedded with a numerical trim algorithm is developed for the complete coupling helicopter/cargo nonlinear dynamics system. The simulation application of the model is illustrated, including the case of flight operation loading a cargo by considering three mass configurations of 3000, 4500, and 6000 kg, and the case of flight operation in the process of airdrops at velocities of 0, 40, 80, 120, and 160 knots. Stabilities of the helicopter in the process of airdrops are also analyzed. The major conclusions drawn are: (i) the tandem helicopter has a good attitude maintaining ability in the whole flight velocity envelope when it conducts a flight operation loading a cargo; (ii) in the process of airdrops, the increase in flight velocity will constantly decrease the helicopter pitching attitude and increases the total airdrop time and decreases the backward moving velocity of the cargo, and helicopter flying at a velocity between 80 and 120 knots might be acceptable; (iii) the stabilities of both the longitudinal and lateral periodic modes are continuing to decrease during the backward movement of the cargo.

Study on human-induced vibration of a cable-stayed bridge without backstays located in abrupt valley

This research aims to assess the pedestrian comfort and to control human-induced vibration of an arch tower cable-stayed bridge without backstays located in canyon. Dynamic simulations of human-induced vibration were carried out with a mode-by-mode approach, and the results indicated that a total of seven lateral and vertical modes of the bridge may suffer from excessive vibrations at the design crowd density. Based on the periodic walking force, the structure response under pedestrian loads was evaluated performing dynamic analyses with two Finite Element models of the footbridge. A single tuned mass damper (STMD) control system was developed for control of human-induced vibration, which consisted of four tuned mass dampers mounted on the mid-span of bridge to enhance damping ratios of lively modes. The results indicate that the maximum acceleration for the first-order lateral and second-order vertical vibration at the design crowd density exceed the associated threshold values referring to the comfort level 1 (CL1) Criteria. The critical pedestrian number of lateral dynamic instability estimated by the Dallard’s empirical formula is much smaller than the dynamic design pedestrian number; and the Dallard’s empirical formula is applicable to estimate the critical pedestrian number of lateral dynamic instability for this bridge by comparing with Pedroe Inês footbridge. The damping ratios for both the vertical and lateral modes increase appreciably after installing the tuned mass dampers and no evidence of large-amplitude vibrations has been observed, leading to the realization of satisfactory comfort levels, which can provide reference for vibration reduction design of this kind of bridge.

Alpha-Helical Protein KfrC Acts as a Switch between the Lateral and Vertical Modes of Dissemination of Broad-Host-Range RA3 Plasmid from IncU (IncP-6) Incompatibility Group.

KfrC proteins are encoded by the conjugative broad-host-range plasmids that also encode alpha-helical filament-forming KfrA proteins as exemplified by the RA3 plasmid from the IncU incompatibility group. The RA3 variants impaired in kfrA, kfrC, or both affected the host’s growth and demonstrated the altered stability in a species-specific manner. In a search for partners of the alpha-helical KfrC protein, the host’s membrane proteins and four RA3-encoded proteins were found, including the filamentous KfrA protein, segrosome protein KorB, and the T4SS proteins, the coupling protein VirD4 and ATPase VirB4. The C-terminal, 112-residue dimerization domain of KfrC was involved in the interactions with KorB, the master player of the active partition, and VirD4, a key component of the conjugative transfer process. In Pseudomonas putida, but not in Escherichia coli, the lack of KfrC decreased the stability but improved the transfer ability. We showed that KfrC and KfrA were involved in the plasmid maintenance and conjugative transfer and that KfrC may play a species-dependent role of a switch between vertical and horizontal modes of RA3 spreading.