Compact Configuration Research Articles

Scalable membrane-less microbial electrolysis cell with multiple compact electrode assemblies for high performance hydrogen production

Bioelectrochemical hydrogen production via microbial electrolysis cells (MECs) is a promising method for sustainable energy production and decarbonization of energy systems. However, the application of MECs is limited by the electrochemical performance, scalability, and the cost associated with expensive materials. In this study, a scalable MEC (500 mL) with novel compact electrode assemblies and high electrode surface area to volume ratio (160 m2/m3) was designed and constructed. The use of membranes, precious metal catalyst, and current collectors with high costs was avoided. A high current density at the steady state of 49.5 ± 5.3 A/m2 was achieved using acetate as the substrate with phosphate buffer under the applied voltage of 1.01 V. The corresponding volumetric current density was 3948 ± 422 A/m3. The compact electrode assembly design limited methane production rate to 3.9 ± 0.2 L/L/D, while achieving a hydrogen production rate of 33.7 ± 1.7 L/L/D. With the suppression of microbial hydrogen consumption, the hydrogen production rate was 39.8 ± 1.9 L/L/D, higher by almost one order of magnitude than those of MECs with scaling up attempts. The compact electrode configuration reduced internal resistance to 88.5 ± 4.4 Ω cm2. The energy efficiency based on input electricity was 146 ± 7 % to 189 ± 9 % within the applied voltage range of 0.71 to 1.05 V. The results in this study demonstrated successful scaling up of high performance small MECs and offered a new possible approach of scaling up MECs by stacking high-performance subunits, with no trade-offs on electrochemical performance.

Lipid nanoparticles for antisense oligonucleotide gene interference into brain border-associated macrophages.

A colloidal synthesis' proof-of-concept based on the Bligh-Dyer emulsion inversion method was designed for integrating into lipid nanoparticles (LNPs) cell-permeating DNA antisense oligonucleotides (ASOs), also known as GapmeRs (GRs), for mRNA interference. The GR@LNPs were formulated to target brain border-associated macrophages (BAMs) as a central nervous system (CNS) therapy platform for silencing neuroinflammation-related genes. We specifically aim at inhibiting the expression of the gene encoding for lipocalin-type prostaglandin D synthase (L-PGDS), an anti-inflammatory enzyme expressed in BAMs, whose level of expression is altered in neuropsychopathologies such as depression and schizophrenia. The GR@LNPs are expected to demonstrate a bio-orthogonal genetic activity reacting with L-PGDS gene transcripts inside the living system without interfering with other genetic or biochemical circuitries. To facilitate selective BAM phagocytosis and avoid subsidiary absorption by other cells, they were functionalized with a mannosylated lipid as a specific MAN ligand for the mannose receptor presented by the macrophage surface. The GR@LNPs showed a high GR-packing density in a compact multilamellar configuration as structurally characterized by light scattering, zeta potential, and transmission electronic microscopy. As a preliminary biological evaluation of the mannosylated GR@LNP nanovectors into specifically targeted BAMs, we detected in vivo gene interference after brain delivery by intracerebroventricular injection (ICV) in Wistar rats subjected to gene therapy protocol. The results pave the way towards novel gene therapy platforms for advanced treatment of neuroinflammation-related pathologies with ASO@LNP nanovectors.

Fully Planar 2-D Multibeam Millimeter-Wave Antenna With Via-Based Phase Shifters

For fifth-generation (5G) millimeter-wave (mmWave) beamforming, a fully planar 2 × 2 2-D multibeam antenna operating at 24–28 GHz is proposed. The proposed antenna is fed by a compact dual-layer 4 × 4 Butler matrix in substrate-integrated waveguide (SIW). In this fully planar and compact configuration, SIW coupling slot is used to facilitate the output ports of the Butler matrix on the same planar layer, and the via-based phase shifters are designed to generate wideband phase performance with compact size. The measured impedance bandwidth is 15.4%, and the measured maximum beam pointing angle is 55°. These results are in good agreement with simulation. The proposed configuration can be extended with more radiating elements for higher gain, and it is promising for beamforming scenarios, including communications.

Global dynamics and architecture of the Kepler-444 system

Context. S-type planets, which orbit one component of multiple-star systems, place strong constraints on planet formation and evolution models. A notable case study is Kepler-444, a triple-star system whose primary is orbited by five planets smaller than Venus in a compact configuration, and for which the stellar binary companion revolves around the primary on a highly eccentric orbit. Aims. Several open questions remain about the formation and evolution of Kepler-444. Having access to the most precise up-to-date masses and orbital parameters is highly valuable when tackling those questions. We provide the first full dynamical exploration of this system, with the goal being to refine those parameters. Methods. We apply orbital stability arguments to refine the system parameters on models with and without the stellar binary companion in order to understand the origin of the dynamical constraints. This approach makes use of the numerical analysis of fundamental frequencies fast chaos indicator. We also explore potential two- and three-planet mean-motion resonances (MMRs) in the system. Prior to investigating the dynamics of a model that includes the binary companion, we update its orbital parameters and mass using new observational constraints from both HIRES radial velocity and Gaia astrometric data, as well as archival imaging of the system. Results. The planetary system does not appear in any of the low-order two- or three-planet MMRs. We provide the most precise up-to-date dynamical parameters for the planets and the stellar binary companion. The orbit of the latter is constrained by the new observations, and also by the stability analysis. This update further challenges the planets formation processes. We also test the dynamical plausibility of a sixth planet in the system, following hints found in HST data. We find that this putative planet could exist over a broad range of masses, and with an orbital period of between roughly 12 and 20 days. Conclusions. We note the overall good agreement of the system with short-term orbital stability. This suggests that a diverse range of planetary system architectures could be found in multiple-star systems, potentially challenging the planet formation models further.

Design a Multistub Array Antenna at 28 GHz with Beam Switching Ability

In this paper, a Millimeter Wave antenna is designed which has a compact, lightweight and planar configuration. The frequency band is 27–29.5 GHz as a candidate band for 5G/millimeter Wave (mmW) systems. The antenna structure is similar to Quasi Yagi antenna which has driver, director, feeding part, and reflector. Substrate Integrated Waveguide used for feeding part of single element antenna and Wilkinson power divider used for antenna array feeding network. The proposed antenna has been simulated, fabricated, and measured (S11, E, and H pattern). The simulation and measurement values showed good similarity. The switched line phase shifter used to consider the beam steering (rotation) ability of the designed antenna which is important in (mmW) systems such as RADARs and mobile handsets. To evaluate this ability, for 0 ° , 30 ° , 45 ° , and 90 ° phase differences, the beam steering angle ( θ ) simulated and also for − 90 ° and 90 ° implemented. The results showed that the efficiency, S11, and E patterns in the rotated beam is suitable and without degradation in antenna operation. To simulate and evaluate the designed antenna HFSS and CST Software are used.

Compact Wide-Beam Circularly Polarized End-Fire Antenna Combining Ground Radiation Mode and Vertically Polarized Mode

A compact wide-beam endfire antenna with ground radiation mode and vertically polarized mode for circular polarization (CP) is presented in this article. The antenna is constructed based on a configuration of coupled-mode patch antenna (CMPA), which consists of two coupling cavities with a shorting wall, and can generate vertically polarized modes. The CP is realized through a pair of orthogonally polarized modes of horizontal and vertical polarizations. Meanwhile, rendering them acquires an equal amplitude and a 90° phase difference. The horizontally polarized radiation mode is realized through inserting a crossed ground slot. Offset probe feed is used to excite all the radiation modes and introduce an additional phase shift for the CP. A set of offset ground slots (OGSs) are then applied to perturb the electromagnetic coupling of the modes and adjust the phase and magnitude of the radiating electric fields (E-fields). Several effects are synthesized, which results in a wide-beam circularly polarized (CP) endfire radiation. Aiming to improve the radiation performances, a cavity-backed planar reflector was applied in the experiment. Simulated and measured results are detailed and analyzed, which demonstrate that the measured 3 dB axial ratio (AR < 3 dB) bandwidth (ARBW) ranges from 3.385 to 3.428 GHz (1.2%), and the peak gain can be up to 3.4 dBi if the planar reflector is added. The measured half-power beamwidth (HPBW) and 3 dB ARBW can be up to 88°/114° and 53°/112° at 3.4 GHz, respectively. The antenna size (excluding the reflector) is maintained at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.49\lambda _{0}\times 0.25\lambda _{0}\times 0.017\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the wavelength in free space, performing a compact configuration.

Narrow bandgap ferroelectric [KNbO3](1-x)-[BaCo1/2Nb1/2O3-δ]x solid solution for bulk photovoltaic cell

We report a stable bulk photovoltaic effect in [KNbO3]0.9-[BaCo1/2Nb1/2O3–δ]0.1 (KBCNO-91) solid solution as a result of the light-induced electric field in the orthorhombic phase of KBCNO. Introducing Ba2+ and Co3+ ions in the host lattice of perovskite solid solution, the bandgap can be tuned from 3.2 to 1.59 eV. A photovoltaic cell consists of a 43 nm thin KBCNO-91 perovskite oxide semiconductor sandwiched between the metal electrodes evoke open-circuit voltage (VOC) of >1.9 V, above the bandgap with short-circuit current of ∼1 nA at no external bias (0 V). The fabrication of a two-dimensional ferroelectric solid solution semiconductor with a narrow bandgap of ∼1.59 eV enables the conversion of visible photons into electrical energy in a compact electrode configuration. The device retains its stability for over one year and is expected to be a potential candidate for the next generation of photovoltaic cells.

Theoretical and practical guide for an axial superresolved focus via Gouy phase steering

Achieving an axial superresolved focus with a single lens by simply inserting a modulation mask in the pupil plane is preferred due to its compact configuration and general applicability. However, lack of a universal theoretical model to manifest the superresolved focusing mechanism vastly complicates the mask design and hinders optimal resolution. Here we establish an interference model and find out that the axial resolution closely relates to the Gouy phase gradient (GPG) at the focal point. Using a GPG tuning-based optimization approach, the axial resolution of a ring-mask-modulated beam is readily improved to attain superresolved focal depth for multiple types of pupil function and polarization. In experiment, a focus with an axial resolution of 27% improved from the diffraction limit and 11% finer than the previously reported record is demonstrated for the radially polarized beam. In simulations, a spherical focus with 3D isotropic resolution and a superoscillation-like axial modulation behavior toward extremely high axial resolution is also presented. This approach can be applied for varied types of pupil function, wavelength, and polarization, and can be easily transferred to other traditional or superresolution microscopes to upgrade their axial resolution.

D2-Filled Hollow-Core Fiber Gas Raman Laser at 2.15 μm

Fiber lasers around 2 µm band have attractive applications, such as coherent detecting, material processing, pump source for mid-IR lasers based on nonlinear frequency shift, etc. Fiber gas Raman lasers (FGRLs) based on the stimulated Raman scattering of the gas molecules filled in the hollow-core fibers (HCFs) have been proved an efficient method to enrich the wavelengths of fiber lasers. In this paper, we demonstrated a deuterium-filled fiber gas Raman laser working at 2147 nm. The pump laser is directly coupled into the HCF through the fusion splice between the HCF and the solid-core fiber. By adjusting the pressure, fiber length as well as the repetition frequency of the 1971 nm pump laser, a maximum average Raman power of ~2.57 W was obtained, with corresponding efficiency of ~40%. This work provides a simple and compact configuration for 2.1 µm fiber lasers, which is significant for their application.

Shadows of boson and Proca stars with thin accretion disks

In this work, we obtain the shadow images of spherically symmetric scalar boson and Proca stars using analytical fittings of numerical solutions, when illuminated by a geometrically thin accretion disk. We chose a sample of four boson and four Proca stars with radii ranging from more compact configurations with $R\sim 9M$ to more dilute configurations with $R\sim 20M$, where $M$ is the total mass of the bosonic star. In these configurations, the absence of the photon sphere (the locus of unstable bound geodesics) makes the optical appearance of these stars to be dominated by a single luminous ring enclosing a central brightness depression, and no further light rings are available. We show that if one considers face-on observations and a disk model whose emission is truncated at some finite radius at which the luminosity attains its maximum value, both the size of the shadow, as well as the luminosity and depth of the bright region, are heavily influenced by the emission profile, with the choice of the type and parameters of the bosonic stars in our samples having a sub-dominant influence. These differences are nonetheless significantly magnified when one allows the accretion disk to extend close enough to the center of the star. Our results point out that even though bosonic stars are horizonless and do not have a photon sphere, some of them may be able to produce conventional black hole shadow-like images provided that their compactness is large enough, thus being potentially consistent with current and future observations.

Synthetic Next Generation Very Large Array line observations of a massive star-forming cloud

Context. Studies of the interstellar medium and the pre-stellar cloud evolution require spectral line observations that have a high sensitivity and high angular and velocity resolution. Regions of high-mass star formation are particularly challenging because of line-of-sight confusion, inhomogeneous physical conditions, and potentially very high optical depths. Aims. We wish to quantify to what accuracy the physical conditions within a massive star-forming cloud can be determined from observations. We are particularly interested in the possibilities offered by the Next Generation Very Large Array (ngVLA) interferometer. Methods. We used data from a magnetohydrodynamic simulation of star formation in a high-density environment. We concentrated on the study of a filamentary structure that has physical properties similar to a small infrared-dark cloud. We produced synthetic observations for spectral lines observable with the ngVLA and analysed these to measure column density, gas temperature, and kinematics. Results were compared to ideal line observations and the actual 3D model. Results. For a nominal cloud distance of 4kpc, ngVLA provides a resolution of ~0.01 pc even in its most compact configuration. For abundant molecules, such as HCO+, NH3, N2H+, and CO isotopomers, cloud kinematics and structure can be mapped down to subarcsecond scales in just a few hours. For NH3, a reliable column density map could be obtained for the entire 15″ × 40″ cloud, even without the help of additional single-dish data, and kinetic temperatures are recovered to a precision of ~1 K. At higher frequencies, the loss of large-scale emission becomes noticeable. The line observations are seen to accurately trace the cloud kinematics, except for the largest scales, where some artefacts appear due to the filtering of low spatial frequencies. The line-of-sight confusion complicates the interpretation of the kinematics, and the usefulness of collapse indicators based on the expected blue asymmetry of optically thick lines is limited. Conclusions. The ngVLA will be able to provide accurate data on the small-scale structure and the physical and chemical state of star-forming clouds, even in high-mass star-forming regions at kiloparsec distances. Complementary single-dish data are still essential for estimates of the total column density and the large-scale kinematics.

A high efficiency and high power L-band relativistic magnetron with all-cavity extraction

Relativistic magnetron (RM) is a promising high-power microwave source, whose advantages include high efficiency, high power, and compact configuration. Enhancing power efficiency and output power are the most important two development directions for RM. Based on the two targets, a high efficiency and high power RM is presented and investigated numerically and experimentally in this paper. When the diode voltage is 485kV, the beam current is 6.9kA, and the magnetic field is 0.34T, and high power microwave is generated with the power of 1.35 GW, frequency of 1.47GHz, and power efficiency of 40.3% in the experiments.

A Mini-Marx Generator Powered by a Cockcroft–Walton Voltage Multiplier

A Marx generator generates a high-voltage (HV) pulse by charging two or more capacitors in parallel and then suddenly connecting them in series. In principles, a comparatively lower voltage dc power supply has to be used for the charging to achieve the desired HV. However, a moderate dc HV power supply is still quite expensive and bulky but not in full-time usage. In this work, a mini-Marx generator powered by a Cockcroft–Walton (CW) voltage multiplier has been proposed to form a more efficient, compact, but affordable configuration of pulsed HV power sources. For generating an HV in a range of 20–150 kV with the mini-Marx generator consisting of eight stages, a CW multiplier operating up to 3–20 kV is required. Numerical simulations using PSpice have been performed for validating the concept. For demonstration, a prototype of the 22-stage CW-powered four-stage mini-Marx has been built and tested with an ac voltage of 110 V at 60 Hz. In the experiment, the CW generator can reach 3.6 kV to power the mini-Marx, delivering an HV of 12.7 kV, consistent with the PSpice modeling. With an ac household voltage of 220 V at 60 Hz, a dc voltage of 5.2 kV can be obtained from the CW to charge an eight-stage mini-Marx generator, achieving an output voltage of 33 kV to drive a field emission-based X-ray source. The proposed CW powered mini-Marx generator is general and can be used as a compact pulsed voltage supply for some portable devices.

VDTA and DO-CCII based incremental/decremental floating memductance/meminductance simulator: A novel realization

The meminductor element is useful just like the memristor element due to the similar kind of hysteresis property found in its transient characteristics. This study presents a floating memelement emulator to realize the dual memelement function (memristor and meminductor) using a VDTA (Voltage Differencing Transconductance Amplifier) and a DO-CCII (Dual Output Second Generation Current Conveyor) based compact circuit configuration. The developed emulator architecture requires only three passive elements (all in the grounded state) with just two active elements to realize the floating meminductor and memristor suitable for both incremental as well as decremental modes of operation. The tuning of the proposed circuit to provide desired memelement behavior realization (memristor or meminductor) can be obtained by selecting an employed grounded impedance as a capacitor and resistor respectively. No use of any floating passive element and external memristor emulator is a remarkable design feature along with the feature of tunability found in the proposed emulator circuit enriching the superiority of its design. The circuit analysis also shows that the selection of the grounded impedance as an inductor can also lead to the realization of a non-linear capacitor, which is the dual of a memcapacitor element. The workability of the presented emulator circuit is validated through the simulations generated for the 0.18μm CMOS technology in the PSPICE environment. The application examples of both the realized floating elements have been presented and verified through the presented simulation results. Also, the reported memelement emulator has been implemented and verified by using commercially available ICs; AD844 and LM13700.

Palmitoylation of A-kinase anchoring protein 79/150 modulates its nanoscale organization, trafficking, and mobility in postsynaptic spines.

A-kinase anchoring protein 79-human/150-rodent (AKAP79/150) organizes signaling proteins to control synaptic plasticity. AKAP79/150 associates with the plasma membrane and endosomes through its N-terminal domain that contains three polybasic regions and two Cys residues that are reversibly palmitoylated. Mutations abolishing palmitoylation (AKAP79/150 CS) reduce its endosomal localization and association with the postsynaptic density (PSD). Here we combined advanced light and electron microscopy (EM) to characterize the effects of AKAP79/150 palmitoylation on its postsynaptic nanoscale organization, trafficking, and mobility in hippocampal neurons. Immunogold EM revealed prominent extrasynaptic membrane AKAP150 labeling with less labeling at the PSD. The label was at greater distances from the spine membrane for AKAP150 CS than WT in the PSD but not in extra-synaptic locations. Immunogold EM of GFP-tagged AKAP79 WT showed that AKAP79 adopts a vertical, extended conformation at the PSD with its N-terminus at the membrane, in contrast to extrasynaptic locations where it adopts a compact or open configurations of its N- and C-termini with parallel orientation to the membrane. In contrast, GFP-tagged AKAP79 CS was displaced from the PSD coincident with disruption of its vertical orientation, while proximity and orientation with respect to the extra-synaptic membrane was less impacted. Single-molecule localization microscopy (SMLM) revealed a heterogeneous distribution of AKAP150 with distinct high-density, nano-scale regions (HDRs) overlapping the PSD but more prominently located in the extrasynaptic membrane for WT and the CS mutant. Thick section scanning transmission electron microscopy (STEM) tomography revealed AKAP150 immunogold clusters similar in size to HDRs seen by SMLM and more AKAP150 labeled endosomes in spines for WT than for CS, consistent with the requirement for AKAP palmitoylation in endosomal trafficking. Hidden Markov modeling of single molecule tracking data revealed a bound/immobile fraction and two mobile fractions for AKAP79 in spines, with the CS mutant having shorter dwell times and faster transition rates between states than WT, suggesting that palmitoylation stabilizes individual AKAP molecules in various spine subpopulations. These data demonstrate that palmitoylation fine tunes the nanoscale localization, mobility, and trafficking of AKAP79/150 in dendritic spines, which might have profound effects on its regulation of synaptic plasticity.

Essential oil-in-water microemulsions for topical application: structural study, cytotoxic effect and insect repelling activity

Essential oils (EOs) extracted from aromatic plants have been well recognized for their insect repellent properties. Although EOs are effective when freshly applied, their protective effect usually dissipates quickly due to low chemical stability and rapid volatilization of their ingredients. To address this issue, encapsulation in protective carrier materials at the nanoscale is proposed. In this study, oil-in-water (O/W) microemulsions containing geraniol or Citrepel® 75 (citrepel) as the oil phase, a mixture of water and diethylene glycol monoethyl ether (DEGEE) as the aqueous phase and caprylocaproyl polyoxyl-8 glycerides as surfactant were formulated and structurally characterized. DLS analysis showed that the emulsified oil droplets had low polydispersity (PdI<0.3) and average hydrodynamic diameter ranging from 13.7 ± 0.7–35.2 ± 2.7 nm, depending on composition. Mean viscosity of all prepared microemulsions was from 15.7 ± 0.3 cP to 23.8 ± 0.2 cP indicating the suitability of all preparations for topical application. EPR spectroscopy using spin probes gave information about the rigidity of the surfactants’ monolayer. In all cases an outer compact configuration of the interfacial layer and a more flexible inner one was observed. SAXS measurements revealed significant changes in the low q values related to the impact of geraniol and citrepel in microemulsion formulations. Looking at the high q region of the spectra, the curves were affected by the presence of the compounds in a concentration depended manner. Cytotoxicity studies on normal human epidermal keratinocytes (NHKs) confirmed that the sub-toxic dosage for geraniol-in-water and citrepel-in-water microemulsions is 56.25 μg active ingredient per cm2 of cell monolayer. Finally, diluted geraniol-in-water microemulsions were evaluated for repellence action against the Asian tiger mosquito (Aedes albopictus) showing activity for 3 h at a dose of 190 μg/cm2 active ingredient. Gaining a comprehensive understanding from all the results, promising candidates for topical application of geraniol as insect repellent based on safe microemulsions were proposed.

Forceless folding of thin annular strips

Thin strips or sheets with in-plane curvature have a natural tendency to adopt highly symmetric shapes when forced into closed structures and to spontaneously fold into compact multi-covered configurations under feed-in of more length or change of intrinsic curvature. This disposition is exploited in nature as well as in the design of everyday items such as foldable containers. We formulate boundary-value problems (for an ODE) for symmetric equilibrium solutions of unstretchable circular annular strips and present sequences of numerical solutions that mimic different folding modes. Because of the high-order symmetry, closed solutions cannot have an internal force, i.e., the strips are forceless. We consider both wide and narrow (strictly zero-width) strips. Narrow strips cannot have inflections, but wide strips can be either inflectional or non-inflectional. Inflectional solutions are found to feature stress localisations, with divergent strain energy density, on the edge of the strip at inflections of the surface. ‘Regular’ folding gives these singularities on the inside of the annulus, while ‘inverted’ folding gives them predominantly on the outside of the annulus. No new inflections are created in the folding process as more length is inserted. We end with a discussion of an intriguing apparent connection with a deep result on the topology of curves on surfaces.

Enhanced-Stopband Dual-Polarized Filtenna Without Extra Circuit for Tile Array Applications

In this communication, a dual polarized (DP) stacked patch filtenna (filtering antenna) with a wide stopband is developed for tile array applications. The bandpass filtering property is realized by improving the feeding network and patch without adding extra bandpass circuit or size. An elaborate feeding structure with complementary pair of a short-circuited stub and an open-circuited stub (CSSOS) is developed, which generates two transmission nulls effectively enhancing the selectivity and suppressing the harmonic. Moreover, CSSOS has a small size and broadens the impedance bandwidth apparently by introducing an in-band resonance. By properly etching four U-shaped slots on the driven patch, a radiation null in the upper stopband is also generated. The nulls generated by the two approaches can be adjusted independently in wide ranges. For further harmonic suppression, bandstop striplines (BSSs) with ultralow insertion loss are developed. Measured results show that the filtenna performs a wide operating band (3.10–3.95 GHz) and a wide stopband up to 8 GHz with a rejection level higher than 16 dB. Besides, a 32-element tile phased array employing the filtennas is also fabricated and measured. A compact configuration, high selectivity, and good beam steering capacity are exhibited.

A general stability-driven approach for the refinement of multi-planet systems

Context. Over recent years, the number of detected multi-planet systems has grown significantly. An important subclass of these are the compact configurations. Precise knowledge of this subclass is crucial for understanding the conditions in which planetary systems form and evolve. However, observations often leave these systems with large uncertainties, notably on the orbital eccentricities. This is especially prominent for systems with low-mass planets detected with radial velocities, and increasing numbers of these are being discovered in the exoplanet population. Refining these parameters with the help of orbital stability arguments is becoming a common approach. Aims. Such dynamical techniques can be computationally expensive. In this work, we use an alternative procedure that is orders of magnitude faster than classical N-body integration approaches, and has the potential to narrow down parameter uncertainties. Methods. We coupled a reliable exploration of the parameter space with the precision of the Numerical Analysis of Fundamental Frequencies (Laskar, J. 1990, Icarus, 88, 266) fast chaos indicator. We also propose a general procedure to calibrate the NAFF indicator on any multi-planet system without additional computational cost. This calibration strategy is illustrated using the compact multiplanet system HD 45364, in addition to yet-unpublished measurements obtained with the HARPS and CORALIE high-resolution spectrographs. We validate the calibration approach by a comparison with long integrations performed on HD 202696. We test the performances of this stability-driven approach on two systems with different architectures: first we study HD 37124, a three-planet system composed of planets in the Jovian regime; then, we analyse the stability constraints on HD 215152, a compact system of four low-mass planets. Results. We revise the planetary parameters for HD 45364, HD 202696, HD 37124, and HD 215152, and provide a comprehensive view of the dynamical state these systems are in. Conclusions. We demonstrate the potential of the NAFF stability-driven approach to refine the orbital parameters and planetary masses. We stress the importance of undertaking systematic global dynamical analyses on every new multi-planet system discovered.

A new type-γ′/γ′′ coprecipitation behavior and its evolution mechanism in wrought Ni-based ATI 718Plus superalloy

In the precipitation-hardened Ni-based superalloy, typified by ATI 718Plus, the nano-scale γ′ and γ′′ phase in duplet or triple coprecipitate morphology can provide superior high-temperature strength. Thus, it is of great sense to study the evolution of γ′/γ′′ coprecipitate during long term service at elevated temperature. In this study, the new-type γ′/γ′′ coprecipitates with a sandwich or compact configuration were found firstly in wrought ATI 718Plus superalloy during long term thermal exposure at 705 °C. These co-structure of the γ′/γ′′ precipitates evidently inhibit the coarsening of γ′ phase. The increase of thermal exposure time evidently leads to the increase of the volume fraction of γ′/γ′′ coprecipitate and transformation of sandwich-type γ′/γ′′ coprecipitate to compact-type γ′/γ′′ coprecipitate, which is characterized as γ′′ phase precipitate at several faces of the γ′ phase. The main evolution mechanism of γ′/γ′′ coprecipitates is element segregation, especially the composition variations of Al + Ti and Nb and their ratio of Al+Ti/Nb. In addition, the interfacial energy between γ′′ phase and γ matrix also plays a key role on the γ′/γ′′ coprecipitates evolution. The calculated results show that the longer thermal exposure time leads to the higher interfacial energy, which is beneficial for nucleation and precipitation of γ′′ phase on the faces of γ′ phase.